1 /* 2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/metadataOnStackMark.hpp" 27 #include "classfile/stringTable.hpp" 28 #include "code/codeCache.hpp" 29 #include "code/icBuffer.hpp" 30 #include "gc/g1/bufferingOopClosure.hpp" 31 #include "gc/g1/concurrentG1Refine.hpp" 32 #include "gc/g1/concurrentG1RefineThread.hpp" 33 #include "gc/g1/concurrentMarkThread.inline.hpp" 34 #include "gc/g1/g1AllocRegion.inline.hpp" 35 #include "gc/g1/g1CollectedHeap.inline.hpp" 36 #include "gc/g1/g1CollectorPolicy.hpp" 37 #include "gc/g1/g1ErgoVerbose.hpp" 38 #include "gc/g1/g1EvacFailure.hpp" 39 #include "gc/g1/g1GCPhaseTimes.hpp" 40 #include "gc/g1/g1Log.hpp" 41 #include "gc/g1/g1MarkSweep.hpp" 42 #include "gc/g1/g1OopClosures.inline.hpp" 43 #include "gc/g1/g1ParScanThreadState.inline.hpp" 44 #include "gc/g1/g1RegionToSpaceMapper.hpp" 45 #include "gc/g1/g1RemSet.inline.hpp" 46 #include "gc/g1/g1RootProcessor.hpp" 47 #include "gc/g1/g1StringDedup.hpp" 48 #include "gc/g1/g1YCTypes.hpp" 49 #include "gc/g1/heapRegion.inline.hpp" 50 #include "gc/g1/heapRegionRemSet.hpp" 51 #include "gc/g1/heapRegionSet.inline.hpp" 52 #include "gc/g1/suspendibleThreadSet.hpp" 53 #include "gc/g1/vm_operations_g1.hpp" 54 #include "gc/shared/gcHeapSummary.hpp" 55 #include "gc/shared/gcLocker.inline.hpp" 56 #include "gc/shared/gcTimer.hpp" 57 #include "gc/shared/gcTrace.hpp" 58 #include "gc/shared/gcTraceTime.hpp" 59 #include "gc/shared/generationSpec.hpp" 60 #include "gc/shared/isGCActiveMark.hpp" 61 #include "gc/shared/referenceProcessor.hpp" 62 #include "gc/shared/taskqueue.inline.hpp" 63 #include "memory/allocation.hpp" 64 #include "memory/iterator.hpp" 65 #include "oops/oop.inline.hpp" 66 #include "runtime/atomic.inline.hpp" 67 #include "runtime/orderAccess.inline.hpp" 68 #include "runtime/vmThread.hpp" 69 #include "utilities/globalDefinitions.hpp" 70 #include "utilities/stack.inline.hpp" 71 72 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 73 74 // turn it on so that the contents of the young list (scan-only / 75 // to-be-collected) are printed at "strategic" points before / during 76 // / after the collection --- this is useful for debugging 77 #define YOUNG_LIST_VERBOSE 0 78 // CURRENT STATUS 79 // This file is under construction. Search for "FIXME". 80 81 // INVARIANTS/NOTES 82 // 83 // All allocation activity covered by the G1CollectedHeap interface is 84 // serialized by acquiring the HeapLock. This happens in mem_allocate 85 // and allocate_new_tlab, which are the "entry" points to the 86 // allocation code from the rest of the JVM. (Note that this does not 87 // apply to TLAB allocation, which is not part of this interface: it 88 // is done by clients of this interface.) 89 90 // Local to this file. 91 92 class RefineCardTableEntryClosure: public CardTableEntryClosure { 93 bool _concurrent; 94 public: 95 RefineCardTableEntryClosure() : _concurrent(true) { } 96 97 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 98 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false); 99 // This path is executed by the concurrent refine or mutator threads, 100 // concurrently, and so we do not care if card_ptr contains references 101 // that point into the collection set. 102 assert(!oops_into_cset, "should be"); 103 104 if (_concurrent && SuspendibleThreadSet::should_yield()) { 105 // Caller will actually yield. 106 return false; 107 } 108 // Otherwise, we finished successfully; return true. 109 return true; 110 } 111 112 void set_concurrent(bool b) { _concurrent = b; } 113 }; 114 115 116 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 117 private: 118 size_t _num_processed; 119 120 public: 121 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { } 122 123 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 124 *card_ptr = CardTableModRefBS::dirty_card_val(); 125 _num_processed++; 126 return true; 127 } 128 129 size_t num_processed() const { return _num_processed; } 130 }; 131 132 YoungList::YoungList(G1CollectedHeap* g1h) : 133 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0), 134 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) { 135 guarantee(check_list_empty(false), "just making sure..."); 136 } 137 138 void YoungList::push_region(HeapRegion *hr) { 139 assert(!hr->is_young(), "should not already be young"); 140 assert(hr->get_next_young_region() == NULL, "cause it should!"); 141 142 hr->set_next_young_region(_head); 143 _head = hr; 144 145 _g1h->g1_policy()->set_region_eden(hr, (int) _length); 146 ++_length; 147 } 148 149 void YoungList::add_survivor_region(HeapRegion* hr) { 150 assert(hr->is_survivor(), "should be flagged as survivor region"); 151 assert(hr->get_next_young_region() == NULL, "cause it should!"); 152 153 hr->set_next_young_region(_survivor_head); 154 if (_survivor_head == NULL) { 155 _survivor_tail = hr; 156 } 157 _survivor_head = hr; 158 ++_survivor_length; 159 } 160 161 void YoungList::empty_list(HeapRegion* list) { 162 while (list != NULL) { 163 HeapRegion* next = list->get_next_young_region(); 164 list->set_next_young_region(NULL); 165 list->uninstall_surv_rate_group(); 166 // This is called before a Full GC and all the non-empty / 167 // non-humongous regions at the end of the Full GC will end up as 168 // old anyway. 169 list->set_old(); 170 list = next; 171 } 172 } 173 174 void YoungList::empty_list() { 175 assert(check_list_well_formed(), "young list should be well formed"); 176 177 empty_list(_head); 178 _head = NULL; 179 _length = 0; 180 181 empty_list(_survivor_head); 182 _survivor_head = NULL; 183 _survivor_tail = NULL; 184 _survivor_length = 0; 185 186 _last_sampled_rs_lengths = 0; 187 188 assert(check_list_empty(false), "just making sure..."); 189 } 190 191 bool YoungList::check_list_well_formed() { 192 bool ret = true; 193 194 uint length = 0; 195 HeapRegion* curr = _head; 196 HeapRegion* last = NULL; 197 while (curr != NULL) { 198 if (!curr->is_young()) { 199 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" " 200 "incorrectly tagged (y: %d, surv: %d)", 201 p2i(curr->bottom()), p2i(curr->end()), 202 curr->is_young(), curr->is_survivor()); 203 ret = false; 204 } 205 ++length; 206 last = curr; 207 curr = curr->get_next_young_region(); 208 } 209 ret = ret && (length == _length); 210 211 if (!ret) { 212 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!"); 213 gclog_or_tty->print_cr("### list has %u entries, _length is %u", 214 length, _length); 215 } 216 217 return ret; 218 } 219 220 bool YoungList::check_list_empty(bool check_sample) { 221 bool ret = true; 222 223 if (_length != 0) { 224 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u", 225 _length); 226 ret = false; 227 } 228 if (check_sample && _last_sampled_rs_lengths != 0) { 229 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths"); 230 ret = false; 231 } 232 if (_head != NULL) { 233 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head"); 234 ret = false; 235 } 236 if (!ret) { 237 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty"); 238 } 239 240 return ret; 241 } 242 243 void 244 YoungList::rs_length_sampling_init() { 245 _sampled_rs_lengths = 0; 246 _curr = _head; 247 } 248 249 bool 250 YoungList::rs_length_sampling_more() { 251 return _curr != NULL; 252 } 253 254 void 255 YoungList::rs_length_sampling_next() { 256 assert( _curr != NULL, "invariant" ); 257 size_t rs_length = _curr->rem_set()->occupied(); 258 259 _sampled_rs_lengths += rs_length; 260 261 // The current region may not yet have been added to the 262 // incremental collection set (it gets added when it is 263 // retired as the current allocation region). 264 if (_curr->in_collection_set()) { 265 // Update the collection set policy information for this region 266 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length); 267 } 268 269 _curr = _curr->get_next_young_region(); 270 if (_curr == NULL) { 271 _last_sampled_rs_lengths = _sampled_rs_lengths; 272 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths); 273 } 274 } 275 276 void 277 YoungList::reset_auxilary_lists() { 278 guarantee( is_empty(), "young list should be empty" ); 279 assert(check_list_well_formed(), "young list should be well formed"); 280 281 // Add survivor regions to SurvRateGroup. 282 _g1h->g1_policy()->note_start_adding_survivor_regions(); 283 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */); 284 285 int young_index_in_cset = 0; 286 for (HeapRegion* curr = _survivor_head; 287 curr != NULL; 288 curr = curr->get_next_young_region()) { 289 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset); 290 291 // The region is a non-empty survivor so let's add it to 292 // the incremental collection set for the next evacuation 293 // pause. 294 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr); 295 young_index_in_cset += 1; 296 } 297 assert((uint) young_index_in_cset == _survivor_length, "post-condition"); 298 _g1h->g1_policy()->note_stop_adding_survivor_regions(); 299 300 _head = _survivor_head; 301 _length = _survivor_length; 302 if (_survivor_head != NULL) { 303 assert(_survivor_tail != NULL, "cause it shouldn't be"); 304 assert(_survivor_length > 0, "invariant"); 305 _survivor_tail->set_next_young_region(NULL); 306 } 307 308 // Don't clear the survivor list handles until the start of 309 // the next evacuation pause - we need it in order to re-tag 310 // the survivor regions from this evacuation pause as 'young' 311 // at the start of the next. 312 313 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */); 314 315 assert(check_list_well_formed(), "young list should be well formed"); 316 } 317 318 void YoungList::print() { 319 HeapRegion* lists[] = {_head, _survivor_head}; 320 const char* names[] = {"YOUNG", "SURVIVOR"}; 321 322 for (uint list = 0; list < ARRAY_SIZE(lists); ++list) { 323 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]); 324 HeapRegion *curr = lists[list]; 325 if (curr == NULL) 326 gclog_or_tty->print_cr(" empty"); 327 while (curr != NULL) { 328 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d", 329 HR_FORMAT_PARAMS(curr), 330 p2i(curr->prev_top_at_mark_start()), 331 p2i(curr->next_top_at_mark_start()), 332 curr->age_in_surv_rate_group_cond()); 333 curr = curr->get_next_young_region(); 334 } 335 } 336 337 gclog_or_tty->cr(); 338 } 339 340 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 341 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 342 } 343 344 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 345 // The from card cache is not the memory that is actually committed. So we cannot 346 // take advantage of the zero_filled parameter. 347 reset_from_card_cache(start_idx, num_regions); 348 } 349 350 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 351 { 352 // Claim the right to put the region on the dirty cards region list 353 // by installing a self pointer. 354 HeapRegion* next = hr->get_next_dirty_cards_region(); 355 if (next == NULL) { 356 HeapRegion* res = (HeapRegion*) 357 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 358 NULL); 359 if (res == NULL) { 360 HeapRegion* head; 361 do { 362 // Put the region to the dirty cards region list. 363 head = _dirty_cards_region_list; 364 next = (HeapRegion*) 365 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 366 if (next == head) { 367 assert(hr->get_next_dirty_cards_region() == hr, 368 "hr->get_next_dirty_cards_region() != hr"); 369 if (next == NULL) { 370 // The last region in the list points to itself. 371 hr->set_next_dirty_cards_region(hr); 372 } else { 373 hr->set_next_dirty_cards_region(next); 374 } 375 } 376 } while (next != head); 377 } 378 } 379 } 380 381 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 382 { 383 HeapRegion* head; 384 HeapRegion* hr; 385 do { 386 head = _dirty_cards_region_list; 387 if (head == NULL) { 388 return NULL; 389 } 390 HeapRegion* new_head = head->get_next_dirty_cards_region(); 391 if (head == new_head) { 392 // The last region. 393 new_head = NULL; 394 } 395 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 396 head); 397 } while (hr != head); 398 assert(hr != NULL, "invariant"); 399 hr->set_next_dirty_cards_region(NULL); 400 return hr; 401 } 402 403 // Returns true if the reference points to an object that 404 // can move in an incremental collection. 405 bool G1CollectedHeap::is_scavengable(const void* p) { 406 HeapRegion* hr = heap_region_containing(p); 407 return !hr->is_humongous(); 408 } 409 410 // Private methods. 411 412 HeapRegion* 413 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 414 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 415 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 416 if (!_secondary_free_list.is_empty()) { 417 if (G1ConcRegionFreeingVerbose) { 418 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 419 "secondary_free_list has %u entries", 420 _secondary_free_list.length()); 421 } 422 // It looks as if there are free regions available on the 423 // secondary_free_list. Let's move them to the free_list and try 424 // again to allocate from it. 425 append_secondary_free_list(); 426 427 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 428 "empty we should have moved at least one entry to the free_list"); 429 HeapRegion* res = _hrm.allocate_free_region(is_old); 430 if (G1ConcRegionFreeingVerbose) { 431 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 432 "allocated "HR_FORMAT" from secondary_free_list", 433 HR_FORMAT_PARAMS(res)); 434 } 435 return res; 436 } 437 438 // Wait here until we get notified either when (a) there are no 439 // more free regions coming or (b) some regions have been moved on 440 // the secondary_free_list. 441 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 442 } 443 444 if (G1ConcRegionFreeingVerbose) { 445 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 446 "could not allocate from secondary_free_list"); 447 } 448 return NULL; 449 } 450 451 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 452 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 453 "the only time we use this to allocate a humongous region is " 454 "when we are allocating a single humongous region"); 455 456 HeapRegion* res; 457 if (G1StressConcRegionFreeing) { 458 if (!_secondary_free_list.is_empty()) { 459 if (G1ConcRegionFreeingVerbose) { 460 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 461 "forced to look at the secondary_free_list"); 462 } 463 res = new_region_try_secondary_free_list(is_old); 464 if (res != NULL) { 465 return res; 466 } 467 } 468 } 469 470 res = _hrm.allocate_free_region(is_old); 471 472 if (res == NULL) { 473 if (G1ConcRegionFreeingVerbose) { 474 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 475 "res == NULL, trying the secondary_free_list"); 476 } 477 res = new_region_try_secondary_free_list(is_old); 478 } 479 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 480 // Currently, only attempts to allocate GC alloc regions set 481 // do_expand to true. So, we should only reach here during a 482 // safepoint. If this assumption changes we might have to 483 // reconsider the use of _expand_heap_after_alloc_failure. 484 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 485 486 ergo_verbose1(ErgoHeapSizing, 487 "attempt heap expansion", 488 ergo_format_reason("region allocation request failed") 489 ergo_format_byte("allocation request"), 490 word_size * HeapWordSize); 491 if (expand(word_size * HeapWordSize)) { 492 // Given that expand() succeeded in expanding the heap, and we 493 // always expand the heap by an amount aligned to the heap 494 // region size, the free list should in theory not be empty. 495 // In either case allocate_free_region() will check for NULL. 496 res = _hrm.allocate_free_region(is_old); 497 } else { 498 _expand_heap_after_alloc_failure = false; 499 } 500 } 501 return res; 502 } 503 504 HeapWord* 505 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 506 uint num_regions, 507 size_t word_size, 508 AllocationContext_t context) { 509 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 510 assert(is_humongous(word_size), "word_size should be humongous"); 511 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 512 513 // Index of last region in the series + 1. 514 uint last = first + num_regions; 515 516 // We need to initialize the region(s) we just discovered. This is 517 // a bit tricky given that it can happen concurrently with 518 // refinement threads refining cards on these regions and 519 // potentially wanting to refine the BOT as they are scanning 520 // those cards (this can happen shortly after a cleanup; see CR 521 // 6991377). So we have to set up the region(s) carefully and in 522 // a specific order. 523 524 // The word size sum of all the regions we will allocate. 525 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 526 assert(word_size <= word_size_sum, "sanity"); 527 528 // This will be the "starts humongous" region. 529 HeapRegion* first_hr = region_at(first); 530 // The header of the new object will be placed at the bottom of 531 // the first region. 532 HeapWord* new_obj = first_hr->bottom(); 533 // This will be the new end of the first region in the series that 534 // should also match the end of the last region in the series. 535 HeapWord* new_end = new_obj + word_size_sum; 536 // This will be the new top of the first region that will reflect 537 // this allocation. 538 HeapWord* new_top = new_obj + word_size; 539 540 // First, we need to zero the header of the space that we will be 541 // allocating. When we update top further down, some refinement 542 // threads might try to scan the region. By zeroing the header we 543 // ensure that any thread that will try to scan the region will 544 // come across the zero klass word and bail out. 545 // 546 // NOTE: It would not have been correct to have used 547 // CollectedHeap::fill_with_object() and make the space look like 548 // an int array. The thread that is doing the allocation will 549 // later update the object header to a potentially different array 550 // type and, for a very short period of time, the klass and length 551 // fields will be inconsistent. This could cause a refinement 552 // thread to calculate the object size incorrectly. 553 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 554 555 // We will set up the first region as "starts humongous". This 556 // will also update the BOT covering all the regions to reflect 557 // that there is a single object that starts at the bottom of the 558 // first region. 559 first_hr->set_starts_humongous(new_top, new_end); 560 first_hr->set_allocation_context(context); 561 // Then, if there are any, we will set up the "continues 562 // humongous" regions. 563 HeapRegion* hr = NULL; 564 for (uint i = first + 1; i < last; ++i) { 565 hr = region_at(i); 566 hr->set_continues_humongous(first_hr); 567 hr->set_allocation_context(context); 568 } 569 // If we have "continues humongous" regions (hr != NULL), then the 570 // end of the last one should match new_end. 571 assert(hr == NULL || hr->end() == new_end, "sanity"); 572 573 // Up to this point no concurrent thread would have been able to 574 // do any scanning on any region in this series. All the top 575 // fields still point to bottom, so the intersection between 576 // [bottom,top] and [card_start,card_end] will be empty. Before we 577 // update the top fields, we'll do a storestore to make sure that 578 // no thread sees the update to top before the zeroing of the 579 // object header and the BOT initialization. 580 OrderAccess::storestore(); 581 582 // Now that the BOT and the object header have been initialized, 583 // we can update top of the "starts humongous" region. 584 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(), 585 "new_top should be in this region"); 586 first_hr->set_top(new_top); 587 if (_hr_printer.is_active()) { 588 HeapWord* bottom = first_hr->bottom(); 589 HeapWord* end = first_hr->orig_end(); 590 if ((first + 1) == last) { 591 // the series has a single humongous region 592 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top); 593 } else { 594 // the series has more than one humongous regions 595 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end); 596 } 597 } 598 599 // Now, we will update the top fields of the "continues humongous" 600 // regions. The reason we need to do this is that, otherwise, 601 // these regions would look empty and this will confuse parts of 602 // G1. For example, the code that looks for a consecutive number 603 // of empty regions will consider them empty and try to 604 // re-allocate them. We can extend is_empty() to also include 605 // !is_continues_humongous(), but it is easier to just update the top 606 // fields here. The way we set top for all regions (i.e., top == 607 // end for all regions but the last one, top == new_top for the 608 // last one) is actually used when we will free up the humongous 609 // region in free_humongous_region(). 610 hr = NULL; 611 for (uint i = first + 1; i < last; ++i) { 612 hr = region_at(i); 613 if ((i + 1) == last) { 614 // last continues humongous region 615 assert(hr->bottom() < new_top && new_top <= hr->end(), 616 "new_top should fall on this region"); 617 hr->set_top(new_top); 618 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top); 619 } else { 620 // not last one 621 assert(new_top > hr->end(), "new_top should be above this region"); 622 hr->set_top(hr->end()); 623 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 624 } 625 } 626 // If we have continues humongous regions (hr != NULL), then the 627 // end of the last one should match new_end and its top should 628 // match new_top. 629 assert(hr == NULL || 630 (hr->end() == new_end && hr->top() == new_top), "sanity"); 631 check_bitmaps("Humongous Region Allocation", first_hr); 632 633 assert(first_hr->used() == word_size * HeapWordSize, "invariant"); 634 _allocator->increase_used(first_hr->used()); 635 _humongous_set.add(first_hr); 636 637 return new_obj; 638 } 639 640 // If could fit into free regions w/o expansion, try. 641 // Otherwise, if can expand, do so. 642 // Otherwise, if using ex regions might help, try with ex given back. 643 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 644 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 645 646 verify_region_sets_optional(); 647 648 uint first = G1_NO_HRM_INDEX; 649 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords); 650 651 if (obj_regions == 1) { 652 // Only one region to allocate, try to use a fast path by directly allocating 653 // from the free lists. Do not try to expand here, we will potentially do that 654 // later. 655 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 656 if (hr != NULL) { 657 first = hr->hrm_index(); 658 } 659 } else { 660 // We can't allocate humongous regions spanning more than one region while 661 // cleanupComplete() is running, since some of the regions we find to be 662 // empty might not yet be added to the free list. It is not straightforward 663 // to know in which list they are on so that we can remove them. We only 664 // need to do this if we need to allocate more than one region to satisfy the 665 // current humongous allocation request. If we are only allocating one region 666 // we use the one-region region allocation code (see above), that already 667 // potentially waits for regions from the secondary free list. 668 wait_while_free_regions_coming(); 669 append_secondary_free_list_if_not_empty_with_lock(); 670 671 // Policy: Try only empty regions (i.e. already committed first). Maybe we 672 // are lucky enough to find some. 673 first = _hrm.find_contiguous_only_empty(obj_regions); 674 if (first != G1_NO_HRM_INDEX) { 675 _hrm.allocate_free_regions_starting_at(first, obj_regions); 676 } 677 } 678 679 if (first == G1_NO_HRM_INDEX) { 680 // Policy: We could not find enough regions for the humongous object in the 681 // free list. Look through the heap to find a mix of free and uncommitted regions. 682 // If so, try expansion. 683 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 684 if (first != G1_NO_HRM_INDEX) { 685 // We found something. Make sure these regions are committed, i.e. expand 686 // the heap. Alternatively we could do a defragmentation GC. 687 ergo_verbose1(ErgoHeapSizing, 688 "attempt heap expansion", 689 ergo_format_reason("humongous allocation request failed") 690 ergo_format_byte("allocation request"), 691 word_size * HeapWordSize); 692 693 _hrm.expand_at(first, obj_regions); 694 g1_policy()->record_new_heap_size(num_regions()); 695 696 #ifdef ASSERT 697 for (uint i = first; i < first + obj_regions; ++i) { 698 HeapRegion* hr = region_at(i); 699 assert(hr->is_free(), "sanity"); 700 assert(hr->is_empty(), "sanity"); 701 assert(is_on_master_free_list(hr), "sanity"); 702 } 703 #endif 704 _hrm.allocate_free_regions_starting_at(first, obj_regions); 705 } else { 706 // Policy: Potentially trigger a defragmentation GC. 707 } 708 } 709 710 HeapWord* result = NULL; 711 if (first != G1_NO_HRM_INDEX) { 712 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 713 word_size, context); 714 assert(result != NULL, "it should always return a valid result"); 715 716 // A successful humongous object allocation changes the used space 717 // information of the old generation so we need to recalculate the 718 // sizes and update the jstat counters here. 719 g1mm()->update_sizes(); 720 } 721 722 verify_region_sets_optional(); 723 724 return result; 725 } 726 727 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 728 assert_heap_not_locked_and_not_at_safepoint(); 729 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 730 731 uint dummy_gc_count_before; 732 uint dummy_gclocker_retry_count = 0; 733 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 734 } 735 736 HeapWord* 737 G1CollectedHeap::mem_allocate(size_t word_size, 738 bool* gc_overhead_limit_was_exceeded) { 739 assert_heap_not_locked_and_not_at_safepoint(); 740 741 // Loop until the allocation is satisfied, or unsatisfied after GC. 742 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 743 uint gc_count_before; 744 745 HeapWord* result = NULL; 746 if (!is_humongous(word_size)) { 747 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 748 } else { 749 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 750 } 751 if (result != NULL) { 752 return result; 753 } 754 755 // Create the garbage collection operation... 756 VM_G1CollectForAllocation op(gc_count_before, word_size); 757 op.set_allocation_context(AllocationContext::current()); 758 759 // ...and get the VM thread to execute it. 760 VMThread::execute(&op); 761 762 if (op.prologue_succeeded() && op.pause_succeeded()) { 763 // If the operation was successful we'll return the result even 764 // if it is NULL. If the allocation attempt failed immediately 765 // after a Full GC, it's unlikely we'll be able to allocate now. 766 HeapWord* result = op.result(); 767 if (result != NULL && !is_humongous(word_size)) { 768 // Allocations that take place on VM operations do not do any 769 // card dirtying and we have to do it here. We only have to do 770 // this for non-humongous allocations, though. 771 dirty_young_block(result, word_size); 772 } 773 return result; 774 } else { 775 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 776 return NULL; 777 } 778 assert(op.result() == NULL, 779 "the result should be NULL if the VM op did not succeed"); 780 } 781 782 // Give a warning if we seem to be looping forever. 783 if ((QueuedAllocationWarningCount > 0) && 784 (try_count % QueuedAllocationWarningCount == 0)) { 785 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 786 } 787 } 788 789 ShouldNotReachHere(); 790 return NULL; 791 } 792 793 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 794 AllocationContext_t context, 795 uint* gc_count_before_ret, 796 uint* gclocker_retry_count_ret) { 797 // Make sure you read the note in attempt_allocation_humongous(). 798 799 assert_heap_not_locked_and_not_at_safepoint(); 800 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 801 "be called for humongous allocation requests"); 802 803 // We should only get here after the first-level allocation attempt 804 // (attempt_allocation()) failed to allocate. 805 806 // We will loop until a) we manage to successfully perform the 807 // allocation or b) we successfully schedule a collection which 808 // fails to perform the allocation. b) is the only case when we'll 809 // return NULL. 810 HeapWord* result = NULL; 811 for (int try_count = 1; /* we'll return */; try_count += 1) { 812 bool should_try_gc; 813 uint gc_count_before; 814 815 { 816 MutexLockerEx x(Heap_lock); 817 result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size, 818 false /* bot_updates */); 819 if (result != NULL) { 820 return result; 821 } 822 823 // If we reach here, attempt_allocation_locked() above failed to 824 // allocate a new region. So the mutator alloc region should be NULL. 825 assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here"); 826 827 if (GC_locker::is_active_and_needs_gc()) { 828 if (g1_policy()->can_expand_young_list()) { 829 // No need for an ergo verbose message here, 830 // can_expand_young_list() does this when it returns true. 831 result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size, 832 false /* bot_updates */); 833 if (result != NULL) { 834 return result; 835 } 836 } 837 should_try_gc = false; 838 } else { 839 // The GCLocker may not be active but the GCLocker initiated 840 // GC may not yet have been performed (GCLocker::needs_gc() 841 // returns true). In this case we do not try this GC and 842 // wait until the GCLocker initiated GC is performed, and 843 // then retry the allocation. 844 if (GC_locker::needs_gc()) { 845 should_try_gc = false; 846 } else { 847 // Read the GC count while still holding the Heap_lock. 848 gc_count_before = total_collections(); 849 should_try_gc = true; 850 } 851 } 852 } 853 854 if (should_try_gc) { 855 bool succeeded; 856 result = do_collection_pause(word_size, gc_count_before, &succeeded, 857 GCCause::_g1_inc_collection_pause); 858 if (result != NULL) { 859 assert(succeeded, "only way to get back a non-NULL result"); 860 return result; 861 } 862 863 if (succeeded) { 864 // If we get here we successfully scheduled a collection which 865 // failed to allocate. No point in trying to allocate 866 // further. We'll just return NULL. 867 MutexLockerEx x(Heap_lock); 868 *gc_count_before_ret = total_collections(); 869 return NULL; 870 } 871 } else { 872 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 873 MutexLockerEx x(Heap_lock); 874 *gc_count_before_ret = total_collections(); 875 return NULL; 876 } 877 // The GCLocker is either active or the GCLocker initiated 878 // GC has not yet been performed. Stall until it is and 879 // then retry the allocation. 880 GC_locker::stall_until_clear(); 881 (*gclocker_retry_count_ret) += 1; 882 } 883 884 // We can reach here if we were unsuccessful in scheduling a 885 // collection (because another thread beat us to it) or if we were 886 // stalled due to the GC locker. In either can we should retry the 887 // allocation attempt in case another thread successfully 888 // performed a collection and reclaimed enough space. We do the 889 // first attempt (without holding the Heap_lock) here and the 890 // follow-on attempt will be at the start of the next loop 891 // iteration (after taking the Heap_lock). 892 result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size, 893 false /* bot_updates */); 894 if (result != NULL) { 895 return result; 896 } 897 898 // Give a warning if we seem to be looping forever. 899 if ((QueuedAllocationWarningCount > 0) && 900 (try_count % QueuedAllocationWarningCount == 0)) { 901 warning("G1CollectedHeap::attempt_allocation_slow() " 902 "retries %d times", try_count); 903 } 904 } 905 906 ShouldNotReachHere(); 907 return NULL; 908 } 909 910 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 911 uint* gc_count_before_ret, 912 uint* gclocker_retry_count_ret) { 913 // The structure of this method has a lot of similarities to 914 // attempt_allocation_slow(). The reason these two were not merged 915 // into a single one is that such a method would require several "if 916 // allocation is not humongous do this, otherwise do that" 917 // conditional paths which would obscure its flow. In fact, an early 918 // version of this code did use a unified method which was harder to 919 // follow and, as a result, it had subtle bugs that were hard to 920 // track down. So keeping these two methods separate allows each to 921 // be more readable. It will be good to keep these two in sync as 922 // much as possible. 923 924 assert_heap_not_locked_and_not_at_safepoint(); 925 assert(is_humongous(word_size), "attempt_allocation_humongous() " 926 "should only be called for humongous allocations"); 927 928 // Humongous objects can exhaust the heap quickly, so we should check if we 929 // need to start a marking cycle at each humongous object allocation. We do 930 // the check before we do the actual allocation. The reason for doing it 931 // before the allocation is that we avoid having to keep track of the newly 932 // allocated memory while we do a GC. 933 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 934 word_size)) { 935 collect(GCCause::_g1_humongous_allocation); 936 } 937 938 // We will loop until a) we manage to successfully perform the 939 // allocation or b) we successfully schedule a collection which 940 // fails to perform the allocation. b) is the only case when we'll 941 // return NULL. 942 HeapWord* result = NULL; 943 for (int try_count = 1; /* we'll return */; try_count += 1) { 944 bool should_try_gc; 945 uint gc_count_before; 946 947 { 948 MutexLockerEx x(Heap_lock); 949 950 // Given that humongous objects are not allocated in young 951 // regions, we'll first try to do the allocation without doing a 952 // collection hoping that there's enough space in the heap. 953 result = humongous_obj_allocate(word_size, AllocationContext::current()); 954 if (result != NULL) { 955 return result; 956 } 957 958 if (GC_locker::is_active_and_needs_gc()) { 959 should_try_gc = false; 960 } else { 961 // The GCLocker may not be active but the GCLocker initiated 962 // GC may not yet have been performed (GCLocker::needs_gc() 963 // returns true). In this case we do not try this GC and 964 // wait until the GCLocker initiated GC is performed, and 965 // then retry the allocation. 966 if (GC_locker::needs_gc()) { 967 should_try_gc = false; 968 } else { 969 // Read the GC count while still holding the Heap_lock. 970 gc_count_before = total_collections(); 971 should_try_gc = true; 972 } 973 } 974 } 975 976 if (should_try_gc) { 977 // If we failed to allocate the humongous object, we should try to 978 // do a collection pause (if we're allowed) in case it reclaims 979 // enough space for the allocation to succeed after the pause. 980 981 bool succeeded; 982 result = do_collection_pause(word_size, gc_count_before, &succeeded, 983 GCCause::_g1_humongous_allocation); 984 if (result != NULL) { 985 assert(succeeded, "only way to get back a non-NULL result"); 986 return result; 987 } 988 989 if (succeeded) { 990 // If we get here we successfully scheduled a collection which 991 // failed to allocate. No point in trying to allocate 992 // further. We'll just return NULL. 993 MutexLockerEx x(Heap_lock); 994 *gc_count_before_ret = total_collections(); 995 return NULL; 996 } 997 } else { 998 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 999 MutexLockerEx x(Heap_lock); 1000 *gc_count_before_ret = total_collections(); 1001 return NULL; 1002 } 1003 // The GCLocker is either active or the GCLocker initiated 1004 // GC has not yet been performed. Stall until it is and 1005 // then retry the allocation. 1006 GC_locker::stall_until_clear(); 1007 (*gclocker_retry_count_ret) += 1; 1008 } 1009 1010 // We can reach here if we were unsuccessful in scheduling a 1011 // collection (because another thread beat us to it) or if we were 1012 // stalled due to the GC locker. In either can we should retry the 1013 // allocation attempt in case another thread successfully 1014 // performed a collection and reclaimed enough space. Give a 1015 // warning if we seem to be looping forever. 1016 1017 if ((QueuedAllocationWarningCount > 0) && 1018 (try_count % QueuedAllocationWarningCount == 0)) { 1019 warning("G1CollectedHeap::attempt_allocation_humongous() " 1020 "retries %d times", try_count); 1021 } 1022 } 1023 1024 ShouldNotReachHere(); 1025 return NULL; 1026 } 1027 1028 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1029 AllocationContext_t context, 1030 bool expect_null_mutator_alloc_region) { 1031 assert_at_safepoint(true /* should_be_vm_thread */); 1032 assert(_allocator->mutator_alloc_region(context)->get() == NULL || 1033 !expect_null_mutator_alloc_region, 1034 "the current alloc region was unexpectedly found to be non-NULL"); 1035 1036 if (!is_humongous(word_size)) { 1037 return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size, 1038 false /* bot_updates */); 1039 } else { 1040 HeapWord* result = humongous_obj_allocate(word_size, context); 1041 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1042 g1_policy()->set_initiate_conc_mark_if_possible(); 1043 } 1044 return result; 1045 } 1046 1047 ShouldNotReachHere(); 1048 } 1049 1050 class PostMCRemSetClearClosure: public HeapRegionClosure { 1051 G1CollectedHeap* _g1h; 1052 ModRefBarrierSet* _mr_bs; 1053 public: 1054 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1055 _g1h(g1h), _mr_bs(mr_bs) {} 1056 1057 bool doHeapRegion(HeapRegion* r) { 1058 HeapRegionRemSet* hrrs = r->rem_set(); 1059 1060 if (r->is_continues_humongous()) { 1061 // We'll assert that the strong code root list and RSet is empty 1062 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1063 assert(hrrs->occupied() == 0, "RSet should be empty"); 1064 return false; 1065 } 1066 1067 _g1h->reset_gc_time_stamps(r); 1068 hrrs->clear(); 1069 // You might think here that we could clear just the cards 1070 // corresponding to the used region. But no: if we leave a dirty card 1071 // in a region we might allocate into, then it would prevent that card 1072 // from being enqueued, and cause it to be missed. 1073 // Re: the performance cost: we shouldn't be doing full GC anyway! 1074 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1075 1076 return false; 1077 } 1078 }; 1079 1080 void G1CollectedHeap::clear_rsets_post_compaction() { 1081 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1082 heap_region_iterate(&rs_clear); 1083 } 1084 1085 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1086 G1CollectedHeap* _g1h; 1087 UpdateRSOopClosure _cl; 1088 public: 1089 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1090 _cl(g1->g1_rem_set(), worker_i), 1091 _g1h(g1) 1092 { } 1093 1094 bool doHeapRegion(HeapRegion* r) { 1095 if (!r->is_continues_humongous()) { 1096 _cl.set_from(r); 1097 r->oop_iterate(&_cl); 1098 } 1099 return false; 1100 } 1101 }; 1102 1103 class ParRebuildRSTask: public AbstractGangTask { 1104 G1CollectedHeap* _g1; 1105 HeapRegionClaimer _hrclaimer; 1106 1107 public: 1108 ParRebuildRSTask(G1CollectedHeap* g1) : 1109 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1110 1111 void work(uint worker_id) { 1112 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1113 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1114 } 1115 }; 1116 1117 class PostCompactionPrinterClosure: public HeapRegionClosure { 1118 private: 1119 G1HRPrinter* _hr_printer; 1120 public: 1121 bool doHeapRegion(HeapRegion* hr) { 1122 assert(!hr->is_young(), "not expecting to find young regions"); 1123 if (hr->is_free()) { 1124 // We only generate output for non-empty regions. 1125 } else if (hr->is_starts_humongous()) { 1126 if (hr->region_num() == 1) { 1127 // single humongous region 1128 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous); 1129 } else { 1130 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1131 } 1132 } else if (hr->is_continues_humongous()) { 1133 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1134 } else if (hr->is_old()) { 1135 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1136 } else { 1137 ShouldNotReachHere(); 1138 } 1139 return false; 1140 } 1141 1142 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1143 : _hr_printer(hr_printer) { } 1144 }; 1145 1146 void G1CollectedHeap::print_hrm_post_compaction() { 1147 PostCompactionPrinterClosure cl(hr_printer()); 1148 heap_region_iterate(&cl); 1149 } 1150 1151 bool G1CollectedHeap::do_collection(bool explicit_gc, 1152 bool clear_all_soft_refs, 1153 size_t word_size) { 1154 assert_at_safepoint(true /* should_be_vm_thread */); 1155 1156 if (GC_locker::check_active_before_gc()) { 1157 return false; 1158 } 1159 1160 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1161 gc_timer->register_gc_start(); 1162 1163 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1164 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1165 1166 SvcGCMarker sgcm(SvcGCMarker::FULL); 1167 ResourceMark rm; 1168 1169 G1Log::update_level(); 1170 print_heap_before_gc(); 1171 trace_heap_before_gc(gc_tracer); 1172 1173 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1174 1175 verify_region_sets_optional(); 1176 1177 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1178 collector_policy()->should_clear_all_soft_refs(); 1179 1180 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1181 1182 { 1183 IsGCActiveMark x; 1184 1185 // Timing 1186 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1187 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 1188 1189 { 1190 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id()); 1191 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1192 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1193 1194 g1_policy()->record_full_collection_start(); 1195 1196 // Note: When we have a more flexible GC logging framework that 1197 // allows us to add optional attributes to a GC log record we 1198 // could consider timing and reporting how long we wait in the 1199 // following two methods. 1200 wait_while_free_regions_coming(); 1201 // If we start the compaction before the CM threads finish 1202 // scanning the root regions we might trip them over as we'll 1203 // be moving objects / updating references. So let's wait until 1204 // they are done. By telling them to abort, they should complete 1205 // early. 1206 _cm->root_regions()->abort(); 1207 _cm->root_regions()->wait_until_scan_finished(); 1208 append_secondary_free_list_if_not_empty_with_lock(); 1209 1210 gc_prologue(true); 1211 increment_total_collections(true /* full gc */); 1212 increment_old_marking_cycles_started(); 1213 1214 assert(used() == recalculate_used(), "Should be equal"); 1215 1216 verify_before_gc(); 1217 1218 check_bitmaps("Full GC Start"); 1219 pre_full_gc_dump(gc_timer); 1220 1221 COMPILER2_PRESENT(DerivedPointerTable::clear()); 1222 1223 // Disable discovery and empty the discovered lists 1224 // for the CM ref processor. 1225 ref_processor_cm()->disable_discovery(); 1226 ref_processor_cm()->abandon_partial_discovery(); 1227 ref_processor_cm()->verify_no_references_recorded(); 1228 1229 // Abandon current iterations of concurrent marking and concurrent 1230 // refinement, if any are in progress. We have to do this before 1231 // wait_until_scan_finished() below. 1232 concurrent_mark()->abort(); 1233 1234 // Make sure we'll choose a new allocation region afterwards. 1235 _allocator->release_mutator_alloc_region(); 1236 _allocator->abandon_gc_alloc_regions(); 1237 g1_rem_set()->cleanupHRRS(); 1238 1239 // We should call this after we retire any currently active alloc 1240 // regions so that all the ALLOC / RETIRE events are generated 1241 // before the start GC event. 1242 _hr_printer.start_gc(true /* full */, (size_t) total_collections()); 1243 1244 // We may have added regions to the current incremental collection 1245 // set between the last GC or pause and now. We need to clear the 1246 // incremental collection set and then start rebuilding it afresh 1247 // after this full GC. 1248 abandon_collection_set(g1_policy()->inc_cset_head()); 1249 g1_policy()->clear_incremental_cset(); 1250 g1_policy()->stop_incremental_cset_building(); 1251 1252 tear_down_region_sets(false /* free_list_only */); 1253 g1_policy()->set_gcs_are_young(true); 1254 1255 // See the comments in g1CollectedHeap.hpp and 1256 // G1CollectedHeap::ref_processing_init() about 1257 // how reference processing currently works in G1. 1258 1259 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1260 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1261 1262 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1263 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1264 1265 ref_processor_stw()->enable_discovery(); 1266 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1267 1268 // Do collection work 1269 { 1270 HandleMark hm; // Discard invalid handles created during gc 1271 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1272 } 1273 1274 assert(num_free_regions() == 0, "we should not have added any free regions"); 1275 rebuild_region_sets(false /* free_list_only */); 1276 1277 // Enqueue any discovered reference objects that have 1278 // not been removed from the discovered lists. 1279 ref_processor_stw()->enqueue_discovered_references(); 1280 1281 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 1282 1283 MemoryService::track_memory_usage(); 1284 1285 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1286 ref_processor_stw()->verify_no_references_recorded(); 1287 1288 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1289 ClassLoaderDataGraph::purge(); 1290 MetaspaceAux::verify_metrics(); 1291 1292 // Note: since we've just done a full GC, concurrent 1293 // marking is no longer active. Therefore we need not 1294 // re-enable reference discovery for the CM ref processor. 1295 // That will be done at the start of the next marking cycle. 1296 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1297 ref_processor_cm()->verify_no_references_recorded(); 1298 1299 reset_gc_time_stamp(); 1300 // Since everything potentially moved, we will clear all remembered 1301 // sets, and clear all cards. Later we will rebuild remembered 1302 // sets. We will also reset the GC time stamps of the regions. 1303 clear_rsets_post_compaction(); 1304 check_gc_time_stamps(); 1305 1306 // Resize the heap if necessary. 1307 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); 1308 1309 if (_hr_printer.is_active()) { 1310 // We should do this after we potentially resize the heap so 1311 // that all the COMMIT / UNCOMMIT events are generated before 1312 // the end GC event. 1313 1314 print_hrm_post_compaction(); 1315 _hr_printer.end_gc(true /* full */, (size_t) total_collections()); 1316 } 1317 1318 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1319 if (hot_card_cache->use_cache()) { 1320 hot_card_cache->reset_card_counts(); 1321 hot_card_cache->reset_hot_cache(); 1322 } 1323 1324 // Rebuild remembered sets of all regions. 1325 uint n_workers = 1326 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1327 workers()->active_workers(), 1328 Threads::number_of_non_daemon_threads()); 1329 workers()->set_active_workers(n_workers); 1330 1331 ParRebuildRSTask rebuild_rs_task(this); 1332 workers()->run_task(&rebuild_rs_task); 1333 1334 // Rebuild the strong code root lists for each region 1335 rebuild_strong_code_roots(); 1336 1337 if (true) { // FIXME 1338 MetaspaceGC::compute_new_size(); 1339 } 1340 1341 #ifdef TRACESPINNING 1342 ParallelTaskTerminator::print_termination_counts(); 1343 #endif 1344 1345 // Discard all rset updates 1346 JavaThread::dirty_card_queue_set().abandon_logs(); 1347 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1348 1349 _young_list->reset_sampled_info(); 1350 // At this point there should be no regions in the 1351 // entire heap tagged as young. 1352 assert(check_young_list_empty(true /* check_heap */), 1353 "young list should be empty at this point"); 1354 1355 // Update the number of full collections that have been completed. 1356 increment_old_marking_cycles_completed(false /* concurrent */); 1357 1358 _hrm.verify_optional(); 1359 verify_region_sets_optional(); 1360 1361 verify_after_gc(); 1362 1363 // Clear the previous marking bitmap, if needed for bitmap verification. 1364 // Note we cannot do this when we clear the next marking bitmap in 1365 // ConcurrentMark::abort() above since VerifyDuringGC verifies the 1366 // objects marked during a full GC against the previous bitmap. 1367 // But we need to clear it before calling check_bitmaps below since 1368 // the full GC has compacted objects and updated TAMS but not updated 1369 // the prev bitmap. 1370 if (G1VerifyBitmaps) { 1371 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll(); 1372 } 1373 check_bitmaps("Full GC End"); 1374 1375 // Start a new incremental collection set for the next pause 1376 assert(g1_policy()->collection_set() == NULL, "must be"); 1377 g1_policy()->start_incremental_cset_building(); 1378 1379 clear_cset_fast_test(); 1380 1381 _allocator->init_mutator_alloc_region(); 1382 1383 g1_policy()->record_full_collection_end(); 1384 1385 if (G1Log::fine()) { 1386 g1_policy()->print_heap_transition(); 1387 } 1388 1389 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1390 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1391 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1392 // before any GC notifications are raised. 1393 g1mm()->update_sizes(); 1394 1395 gc_epilogue(true); 1396 } 1397 1398 if (G1Log::finer()) { 1399 g1_policy()->print_detailed_heap_transition(true /* full */); 1400 } 1401 1402 print_heap_after_gc(); 1403 trace_heap_after_gc(gc_tracer); 1404 1405 post_full_gc_dump(gc_timer); 1406 1407 gc_timer->register_gc_end(); 1408 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1409 } 1410 1411 return true; 1412 } 1413 1414 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1415 // do_collection() will return whether it succeeded in performing 1416 // the GC. Currently, there is no facility on the 1417 // do_full_collection() API to notify the caller than the collection 1418 // did not succeed (e.g., because it was locked out by the GC 1419 // locker). So, right now, we'll ignore the return value. 1420 bool dummy = do_collection(true, /* explicit_gc */ 1421 clear_all_soft_refs, 1422 0 /* word_size */); 1423 } 1424 1425 // This code is mostly copied from TenuredGeneration. 1426 void 1427 G1CollectedHeap:: 1428 resize_if_necessary_after_full_collection(size_t word_size) { 1429 // Include the current allocation, if any, and bytes that will be 1430 // pre-allocated to support collections, as "used". 1431 const size_t used_after_gc = used(); 1432 const size_t capacity_after_gc = capacity(); 1433 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1434 1435 // This is enforced in arguments.cpp. 1436 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1437 "otherwise the code below doesn't make sense"); 1438 1439 // We don't have floating point command-line arguments 1440 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1441 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1442 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1443 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1444 1445 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1446 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1447 1448 // We have to be careful here as these two calculations can overflow 1449 // 32-bit size_t's. 1450 double used_after_gc_d = (double) used_after_gc; 1451 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1452 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1453 1454 // Let's make sure that they are both under the max heap size, which 1455 // by default will make them fit into a size_t. 1456 double desired_capacity_upper_bound = (double) max_heap_size; 1457 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1458 desired_capacity_upper_bound); 1459 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1460 desired_capacity_upper_bound); 1461 1462 // We can now safely turn them into size_t's. 1463 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1464 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1465 1466 // This assert only makes sense here, before we adjust them 1467 // with respect to the min and max heap size. 1468 assert(minimum_desired_capacity <= maximum_desired_capacity, 1469 err_msg("minimum_desired_capacity = "SIZE_FORMAT", " 1470 "maximum_desired_capacity = "SIZE_FORMAT, 1471 minimum_desired_capacity, maximum_desired_capacity)); 1472 1473 // Should not be greater than the heap max size. No need to adjust 1474 // it with respect to the heap min size as it's a lower bound (i.e., 1475 // we'll try to make the capacity larger than it, not smaller). 1476 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1477 // Should not be less than the heap min size. No need to adjust it 1478 // with respect to the heap max size as it's an upper bound (i.e., 1479 // we'll try to make the capacity smaller than it, not greater). 1480 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1481 1482 if (capacity_after_gc < minimum_desired_capacity) { 1483 // Don't expand unless it's significant 1484 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1485 ergo_verbose4(ErgoHeapSizing, 1486 "attempt heap expansion", 1487 ergo_format_reason("capacity lower than " 1488 "min desired capacity after Full GC") 1489 ergo_format_byte("capacity") 1490 ergo_format_byte("occupancy") 1491 ergo_format_byte_perc("min desired capacity"), 1492 capacity_after_gc, used_after_gc, 1493 minimum_desired_capacity, (double) MinHeapFreeRatio); 1494 expand(expand_bytes); 1495 1496 // No expansion, now see if we want to shrink 1497 } else if (capacity_after_gc > maximum_desired_capacity) { 1498 // Capacity too large, compute shrinking size 1499 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1500 ergo_verbose4(ErgoHeapSizing, 1501 "attempt heap shrinking", 1502 ergo_format_reason("capacity higher than " 1503 "max desired capacity after Full GC") 1504 ergo_format_byte("capacity") 1505 ergo_format_byte("occupancy") 1506 ergo_format_byte_perc("max desired capacity"), 1507 capacity_after_gc, used_after_gc, 1508 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1509 shrink(shrink_bytes); 1510 } 1511 } 1512 1513 1514 HeapWord* 1515 G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1516 AllocationContext_t context, 1517 bool* succeeded) { 1518 assert_at_safepoint(true /* should_be_vm_thread */); 1519 1520 *succeeded = true; 1521 // Let's attempt the allocation first. 1522 HeapWord* result = 1523 attempt_allocation_at_safepoint(word_size, 1524 context, 1525 false /* expect_null_mutator_alloc_region */); 1526 if (result != NULL) { 1527 assert(*succeeded, "sanity"); 1528 return result; 1529 } 1530 1531 // In a G1 heap, we're supposed to keep allocation from failing by 1532 // incremental pauses. Therefore, at least for now, we'll favor 1533 // expansion over collection. (This might change in the future if we can 1534 // do something smarter than full collection to satisfy a failed alloc.) 1535 result = expand_and_allocate(word_size, context); 1536 if (result != NULL) { 1537 assert(*succeeded, "sanity"); 1538 return result; 1539 } 1540 1541 // Expansion didn't work, we'll try to do a Full GC. 1542 bool gc_succeeded = do_collection(false, /* explicit_gc */ 1543 false, /* clear_all_soft_refs */ 1544 word_size); 1545 if (!gc_succeeded) { 1546 *succeeded = false; 1547 return NULL; 1548 } 1549 1550 // Retry the allocation 1551 result = attempt_allocation_at_safepoint(word_size, 1552 context, 1553 true /* expect_null_mutator_alloc_region */); 1554 if (result != NULL) { 1555 assert(*succeeded, "sanity"); 1556 return result; 1557 } 1558 1559 // Then, try a Full GC that will collect all soft references. 1560 gc_succeeded = do_collection(false, /* explicit_gc */ 1561 true, /* clear_all_soft_refs */ 1562 word_size); 1563 if (!gc_succeeded) { 1564 *succeeded = false; 1565 return NULL; 1566 } 1567 1568 // Retry the allocation once more 1569 result = attempt_allocation_at_safepoint(word_size, 1570 context, 1571 true /* expect_null_mutator_alloc_region */); 1572 if (result != NULL) { 1573 assert(*succeeded, "sanity"); 1574 return result; 1575 } 1576 1577 assert(!collector_policy()->should_clear_all_soft_refs(), 1578 "Flag should have been handled and cleared prior to this point"); 1579 1580 // What else? We might try synchronous finalization later. If the total 1581 // space available is large enough for the allocation, then a more 1582 // complete compaction phase than we've tried so far might be 1583 // appropriate. 1584 assert(*succeeded, "sanity"); 1585 return NULL; 1586 } 1587 1588 // Attempting to expand the heap sufficiently 1589 // to support an allocation of the given "word_size". If 1590 // successful, perform the allocation and return the address of the 1591 // allocated block, or else "NULL". 1592 1593 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1594 assert_at_safepoint(true /* should_be_vm_thread */); 1595 1596 verify_region_sets_optional(); 1597 1598 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1599 ergo_verbose1(ErgoHeapSizing, 1600 "attempt heap expansion", 1601 ergo_format_reason("allocation request failed") 1602 ergo_format_byte("allocation request"), 1603 word_size * HeapWordSize); 1604 if (expand(expand_bytes)) { 1605 _hrm.verify_optional(); 1606 verify_region_sets_optional(); 1607 return attempt_allocation_at_safepoint(word_size, 1608 context, 1609 false /* expect_null_mutator_alloc_region */); 1610 } 1611 return NULL; 1612 } 1613 1614 bool G1CollectedHeap::expand(size_t expand_bytes) { 1615 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1616 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1617 HeapRegion::GrainBytes); 1618 ergo_verbose2(ErgoHeapSizing, 1619 "expand the heap", 1620 ergo_format_byte("requested expansion amount") 1621 ergo_format_byte("attempted expansion amount"), 1622 expand_bytes, aligned_expand_bytes); 1623 1624 if (is_maximal_no_gc()) { 1625 ergo_verbose0(ErgoHeapSizing, 1626 "did not expand the heap", 1627 ergo_format_reason("heap already fully expanded")); 1628 return false; 1629 } 1630 1631 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1632 assert(regions_to_expand > 0, "Must expand by at least one region"); 1633 1634 uint expanded_by = _hrm.expand_by(regions_to_expand); 1635 1636 if (expanded_by > 0) { 1637 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1638 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1639 g1_policy()->record_new_heap_size(num_regions()); 1640 } else { 1641 ergo_verbose0(ErgoHeapSizing, 1642 "did not expand the heap", 1643 ergo_format_reason("heap expansion operation failed")); 1644 // The expansion of the virtual storage space was unsuccessful. 1645 // Let's see if it was because we ran out of swap. 1646 if (G1ExitOnExpansionFailure && 1647 _hrm.available() >= regions_to_expand) { 1648 // We had head room... 1649 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1650 } 1651 } 1652 return regions_to_expand > 0; 1653 } 1654 1655 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1656 size_t aligned_shrink_bytes = 1657 ReservedSpace::page_align_size_down(shrink_bytes); 1658 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1659 HeapRegion::GrainBytes); 1660 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1661 1662 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1663 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1664 1665 ergo_verbose3(ErgoHeapSizing, 1666 "shrink the heap", 1667 ergo_format_byte("requested shrinking amount") 1668 ergo_format_byte("aligned shrinking amount") 1669 ergo_format_byte("attempted shrinking amount"), 1670 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1671 if (num_regions_removed > 0) { 1672 g1_policy()->record_new_heap_size(num_regions()); 1673 } else { 1674 ergo_verbose0(ErgoHeapSizing, 1675 "did not shrink the heap", 1676 ergo_format_reason("heap shrinking operation failed")); 1677 } 1678 } 1679 1680 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1681 verify_region_sets_optional(); 1682 1683 // We should only reach here at the end of a Full GC which means we 1684 // should not not be holding to any GC alloc regions. The method 1685 // below will make sure of that and do any remaining clean up. 1686 _allocator->abandon_gc_alloc_regions(); 1687 1688 // Instead of tearing down / rebuilding the free lists here, we 1689 // could instead use the remove_all_pending() method on free_list to 1690 // remove only the ones that we need to remove. 1691 tear_down_region_sets(true /* free_list_only */); 1692 shrink_helper(shrink_bytes); 1693 rebuild_region_sets(true /* free_list_only */); 1694 1695 _hrm.verify_optional(); 1696 verify_region_sets_optional(); 1697 } 1698 1699 // Public methods. 1700 1701 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 1702 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 1703 #endif // _MSC_VER 1704 1705 1706 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1707 CollectedHeap(), 1708 _g1_policy(policy_), 1709 _dirty_card_queue_set(false), 1710 _into_cset_dirty_card_queue_set(false), 1711 _is_alive_closure_cm(this), 1712 _is_alive_closure_stw(this), 1713 _ref_processor_cm(NULL), 1714 _ref_processor_stw(NULL), 1715 _bot_shared(NULL), 1716 _evac_failure_scan_stack(NULL), 1717 _mark_in_progress(false), 1718 _cg1r(NULL), 1719 _g1mm(NULL), 1720 _refine_cte_cl(NULL), 1721 _full_collection(false), 1722 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1723 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1724 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1725 _humongous_reclaim_candidates(), 1726 _has_humongous_reclaim_candidates(false), 1727 _free_regions_coming(false), 1728 _young_list(new YoungList(this)), 1729 _gc_time_stamp(0), 1730 _survivor_plab_stats(YoungPLABSize, PLABWeight), 1731 _old_plab_stats(OldPLABSize, PLABWeight), 1732 _expand_heap_after_alloc_failure(true), 1733 _surviving_young_words(NULL), 1734 _old_marking_cycles_started(0), 1735 _old_marking_cycles_completed(0), 1736 _concurrent_cycle_started(false), 1737 _heap_summary_sent(false), 1738 _in_cset_fast_test(), 1739 _dirty_cards_region_list(NULL), 1740 _worker_cset_start_region(NULL), 1741 _worker_cset_start_region_time_stamp(NULL), 1742 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1743 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1744 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1745 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1746 1747 _workers = new FlexibleWorkGang("GC Thread", ParallelGCThreads, 1748 /* are_GC_task_threads */true, 1749 /* are_ConcurrentGC_threads */false); 1750 _workers->initialize_workers(); 1751 1752 _allocator = G1Allocator::create_allocator(this); 1753 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2; 1754 1755 int n_queues = (int)ParallelGCThreads; 1756 _task_queues = new RefToScanQueueSet(n_queues); 1757 1758 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1759 assert(n_rem_sets > 0, "Invariant."); 1760 1761 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1762 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC); 1763 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1764 1765 for (int i = 0; i < n_queues; i++) { 1766 RefToScanQueue* q = new RefToScanQueue(); 1767 q->initialize(); 1768 _task_queues->register_queue(i, q); 1769 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1770 } 1771 clear_cset_start_regions(); 1772 1773 // Initialize the G1EvacuationFailureALot counters and flags. 1774 NOT_PRODUCT(reset_evacuation_should_fail();) 1775 1776 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1777 } 1778 1779 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1780 size_t size, 1781 size_t translation_factor) { 1782 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1783 // Allocate a new reserved space, preferring to use large pages. 1784 ReservedSpace rs(size, preferred_page_size); 1785 G1RegionToSpaceMapper* result = 1786 G1RegionToSpaceMapper::create_mapper(rs, 1787 size, 1788 rs.alignment(), 1789 HeapRegion::GrainBytes, 1790 translation_factor, 1791 mtGC); 1792 if (TracePageSizes) { 1793 gclog_or_tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT, 1794 description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size); 1795 } 1796 return result; 1797 } 1798 1799 jint G1CollectedHeap::initialize() { 1800 CollectedHeap::pre_initialize(); 1801 os::enable_vtime(); 1802 1803 G1Log::init(); 1804 1805 // Necessary to satisfy locking discipline assertions. 1806 1807 MutexLocker x(Heap_lock); 1808 1809 // We have to initialize the printer before committing the heap, as 1810 // it will be used then. 1811 _hr_printer.set_active(G1PrintHeapRegions); 1812 1813 // While there are no constraints in the GC code that HeapWordSize 1814 // be any particular value, there are multiple other areas in the 1815 // system which believe this to be true (e.g. oop->object_size in some 1816 // cases incorrectly returns the size in wordSize units rather than 1817 // HeapWordSize). 1818 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1819 1820 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1821 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1822 size_t heap_alignment = collector_policy()->heap_alignment(); 1823 1824 // Ensure that the sizes are properly aligned. 1825 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1826 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1827 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1828 1829 _refine_cte_cl = new RefineCardTableEntryClosure(); 1830 1831 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl); 1832 1833 // Reserve the maximum. 1834 1835 // When compressed oops are enabled, the preferred heap base 1836 // is calculated by subtracting the requested size from the 1837 // 32Gb boundary and using the result as the base address for 1838 // heap reservation. If the requested size is not aligned to 1839 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1840 // into the ReservedHeapSpace constructor) then the actual 1841 // base of the reserved heap may end up differing from the 1842 // address that was requested (i.e. the preferred heap base). 1843 // If this happens then we could end up using a non-optimal 1844 // compressed oops mode. 1845 1846 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1847 heap_alignment); 1848 1849 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1850 1851 // Create the barrier set for the entire reserved region. 1852 G1SATBCardTableLoggingModRefBS* bs 1853 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1854 bs->initialize(); 1855 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1856 set_barrier_set(bs); 1857 1858 // Also create a G1 rem set. 1859 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 1860 1861 // Carve out the G1 part of the heap. 1862 1863 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1864 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1865 G1RegionToSpaceMapper* heap_storage = 1866 G1RegionToSpaceMapper::create_mapper(g1_rs, 1867 g1_rs.size(), 1868 page_size, 1869 HeapRegion::GrainBytes, 1870 1, 1871 mtJavaHeap); 1872 os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(), 1873 max_byte_size, page_size, 1874 heap_rs.base(), 1875 heap_rs.size()); 1876 heap_storage->set_mapping_changed_listener(&_listener); 1877 1878 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1879 G1RegionToSpaceMapper* bot_storage = 1880 create_aux_memory_mapper("Block offset table", 1881 G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize), 1882 G1BlockOffsetSharedArray::heap_map_factor()); 1883 1884 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1885 G1RegionToSpaceMapper* cardtable_storage = 1886 create_aux_memory_mapper("Card table", 1887 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1888 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1889 1890 G1RegionToSpaceMapper* card_counts_storage = 1891 create_aux_memory_mapper("Card counts table", 1892 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1893 G1CardCounts::heap_map_factor()); 1894 1895 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size()); 1896 G1RegionToSpaceMapper* prev_bitmap_storage = 1897 create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1898 G1RegionToSpaceMapper* next_bitmap_storage = 1899 create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1900 1901 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1902 g1_barrier_set()->initialize(cardtable_storage); 1903 // Do later initialization work for concurrent refinement. 1904 _cg1r->init(card_counts_storage); 1905 1906 // 6843694 - ensure that the maximum region index can fit 1907 // in the remembered set structures. 1908 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1909 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1910 1911 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1912 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1913 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1914 "too many cards per region"); 1915 1916 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1917 1918 _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage); 1919 1920 { 1921 HeapWord* start = _hrm.reserved().start(); 1922 HeapWord* end = _hrm.reserved().end(); 1923 size_t granularity = HeapRegion::GrainBytes; 1924 1925 _in_cset_fast_test.initialize(start, end, granularity); 1926 _humongous_reclaim_candidates.initialize(start, end, granularity); 1927 } 1928 1929 // Create the ConcurrentMark data structure and thread. 1930 // (Must do this late, so that "max_regions" is defined.) 1931 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1932 if (_cm == NULL || !_cm->completed_initialization()) { 1933 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 1934 return JNI_ENOMEM; 1935 } 1936 _cmThread = _cm->cmThread(); 1937 1938 // Initialize the from_card cache structure of HeapRegionRemSet. 1939 HeapRegionRemSet::init_heap(max_regions()); 1940 1941 // Now expand into the initial heap size. 1942 if (!expand(init_byte_size)) { 1943 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1944 return JNI_ENOMEM; 1945 } 1946 1947 // Perform any initialization actions delegated to the policy. 1948 g1_policy()->init(); 1949 1950 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1951 SATB_Q_FL_lock, 1952 G1SATBProcessCompletedThreshold, 1953 Shared_SATB_Q_lock); 1954 1955 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 1956 DirtyCardQ_CBL_mon, 1957 DirtyCardQ_FL_lock, 1958 concurrent_g1_refine()->yellow_zone(), 1959 concurrent_g1_refine()->red_zone(), 1960 Shared_DirtyCardQ_lock); 1961 1962 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 1963 DirtyCardQ_CBL_mon, 1964 DirtyCardQ_FL_lock, 1965 -1, // never trigger processing 1966 -1, // no limit on length 1967 Shared_DirtyCardQ_lock, 1968 &JavaThread::dirty_card_queue_set()); 1969 1970 // Initialize the card queue set used to hold cards containing 1971 // references into the collection set. 1972 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code 1973 DirtyCardQ_CBL_mon, 1974 DirtyCardQ_FL_lock, 1975 -1, // never trigger processing 1976 -1, // no limit on length 1977 Shared_DirtyCardQ_lock, 1978 &JavaThread::dirty_card_queue_set()); 1979 1980 // Here we allocate the dummy HeapRegion that is required by the 1981 // G1AllocRegion class. 1982 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1983 1984 // We'll re-use the same region whether the alloc region will 1985 // require BOT updates or not and, if it doesn't, then a non-young 1986 // region will complain that it cannot support allocations without 1987 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1988 dummy_region->set_eden(); 1989 // Make sure it's full. 1990 dummy_region->set_top(dummy_region->end()); 1991 G1AllocRegion::setup(this, dummy_region); 1992 1993 _allocator->init_mutator_alloc_region(); 1994 1995 // Do create of the monitoring and management support so that 1996 // values in the heap have been properly initialized. 1997 _g1mm = new G1MonitoringSupport(this); 1998 1999 G1StringDedup::initialize(); 2000 2001 return JNI_OK; 2002 } 2003 2004 void G1CollectedHeap::stop() { 2005 // Stop all concurrent threads. We do this to make sure these threads 2006 // do not continue to execute and access resources (e.g. gclog_or_tty) 2007 // that are destroyed during shutdown. 2008 _cg1r->stop(); 2009 _cmThread->stop(); 2010 if (G1StringDedup::is_enabled()) { 2011 G1StringDedup::stop(); 2012 } 2013 } 2014 2015 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2016 return HeapRegion::max_region_size(); 2017 } 2018 2019 void G1CollectedHeap::post_initialize() { 2020 CollectedHeap::post_initialize(); 2021 ref_processing_init(); 2022 } 2023 2024 void G1CollectedHeap::ref_processing_init() { 2025 // Reference processing in G1 currently works as follows: 2026 // 2027 // * There are two reference processor instances. One is 2028 // used to record and process discovered references 2029 // during concurrent marking; the other is used to 2030 // record and process references during STW pauses 2031 // (both full and incremental). 2032 // * Both ref processors need to 'span' the entire heap as 2033 // the regions in the collection set may be dotted around. 2034 // 2035 // * For the concurrent marking ref processor: 2036 // * Reference discovery is enabled at initial marking. 2037 // * Reference discovery is disabled and the discovered 2038 // references processed etc during remarking. 2039 // * Reference discovery is MT (see below). 2040 // * Reference discovery requires a barrier (see below). 2041 // * Reference processing may or may not be MT 2042 // (depending on the value of ParallelRefProcEnabled 2043 // and ParallelGCThreads). 2044 // * A full GC disables reference discovery by the CM 2045 // ref processor and abandons any entries on it's 2046 // discovered lists. 2047 // 2048 // * For the STW processor: 2049 // * Non MT discovery is enabled at the start of a full GC. 2050 // * Processing and enqueueing during a full GC is non-MT. 2051 // * During a full GC, references are processed after marking. 2052 // 2053 // * Discovery (may or may not be MT) is enabled at the start 2054 // of an incremental evacuation pause. 2055 // * References are processed near the end of a STW evacuation pause. 2056 // * For both types of GC: 2057 // * Discovery is atomic - i.e. not concurrent. 2058 // * Reference discovery will not need a barrier. 2059 2060 MemRegion mr = reserved_region(); 2061 2062 // Concurrent Mark ref processor 2063 _ref_processor_cm = 2064 new ReferenceProcessor(mr, // span 2065 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2066 // mt processing 2067 (uint) ParallelGCThreads, 2068 // degree of mt processing 2069 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2070 // mt discovery 2071 (uint) MAX2(ParallelGCThreads, ConcGCThreads), 2072 // degree of mt discovery 2073 false, 2074 // Reference discovery is not atomic 2075 &_is_alive_closure_cm); 2076 // is alive closure 2077 // (for efficiency/performance) 2078 2079 // STW ref processor 2080 _ref_processor_stw = 2081 new ReferenceProcessor(mr, // span 2082 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2083 // mt processing 2084 (uint) ParallelGCThreads, 2085 // degree of mt processing 2086 (ParallelGCThreads > 1), 2087 // mt discovery 2088 (uint) ParallelGCThreads, 2089 // degree of mt discovery 2090 true, 2091 // Reference discovery is atomic 2092 &_is_alive_closure_stw); 2093 // is alive closure 2094 // (for efficiency/performance) 2095 } 2096 2097 size_t G1CollectedHeap::capacity() const { 2098 return _hrm.length() * HeapRegion::GrainBytes; 2099 } 2100 2101 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2102 assert(!hr->is_continues_humongous(), "pre-condition"); 2103 hr->reset_gc_time_stamp(); 2104 if (hr->is_starts_humongous()) { 2105 uint first_index = hr->hrm_index() + 1; 2106 uint last_index = hr->last_hc_index(); 2107 for (uint i = first_index; i < last_index; i += 1) { 2108 HeapRegion* chr = region_at(i); 2109 assert(chr->is_continues_humongous(), "sanity"); 2110 chr->reset_gc_time_stamp(); 2111 } 2112 } 2113 } 2114 2115 #ifndef PRODUCT 2116 2117 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2118 private: 2119 unsigned _gc_time_stamp; 2120 bool _failures; 2121 2122 public: 2123 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2124 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2125 2126 virtual bool doHeapRegion(HeapRegion* hr) { 2127 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2128 if (_gc_time_stamp != region_gc_time_stamp) { 2129 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, " 2130 "expected %d", HR_FORMAT_PARAMS(hr), 2131 region_gc_time_stamp, _gc_time_stamp); 2132 _failures = true; 2133 } 2134 return false; 2135 } 2136 2137 bool failures() { return _failures; } 2138 }; 2139 2140 void G1CollectedHeap::check_gc_time_stamps() { 2141 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2142 heap_region_iterate(&cl); 2143 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2144 } 2145 #endif // PRODUCT 2146 2147 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, 2148 DirtyCardQueue* into_cset_dcq, 2149 bool concurrent, 2150 uint worker_i) { 2151 // Clean cards in the hot card cache 2152 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 2153 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq); 2154 2155 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2156 size_t n_completed_buffers = 0; 2157 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2158 n_completed_buffers++; 2159 } 2160 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2161 dcqs.clear_n_completed_buffers(); 2162 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2163 } 2164 2165 2166 // Computes the sum of the storage used by the various regions. 2167 size_t G1CollectedHeap::used() const { 2168 return _allocator->used(); 2169 } 2170 2171 size_t G1CollectedHeap::used_unlocked() const { 2172 return _allocator->used_unlocked(); 2173 } 2174 2175 class SumUsedClosure: public HeapRegionClosure { 2176 size_t _used; 2177 public: 2178 SumUsedClosure() : _used(0) {} 2179 bool doHeapRegion(HeapRegion* r) { 2180 if (!r->is_continues_humongous()) { 2181 _used += r->used(); 2182 } 2183 return false; 2184 } 2185 size_t result() { return _used; } 2186 }; 2187 2188 size_t G1CollectedHeap::recalculate_used() const { 2189 double recalculate_used_start = os::elapsedTime(); 2190 2191 SumUsedClosure blk; 2192 heap_region_iterate(&blk); 2193 2194 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2195 return blk.result(); 2196 } 2197 2198 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2199 switch (cause) { 2200 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2201 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2202 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2203 case GCCause::_g1_humongous_allocation: return true; 2204 case GCCause::_update_allocation_context_stats_inc: return true; 2205 case GCCause::_wb_conc_mark: return true; 2206 default: return false; 2207 } 2208 } 2209 2210 #ifndef PRODUCT 2211 void G1CollectedHeap::allocate_dummy_regions() { 2212 // Let's fill up most of the region 2213 size_t word_size = HeapRegion::GrainWords - 1024; 2214 // And as a result the region we'll allocate will be humongous. 2215 guarantee(is_humongous(word_size), "sanity"); 2216 2217 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2218 // Let's use the existing mechanism for the allocation 2219 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2220 AllocationContext::system()); 2221 if (dummy_obj != NULL) { 2222 MemRegion mr(dummy_obj, word_size); 2223 CollectedHeap::fill_with_object(mr); 2224 } else { 2225 // If we can't allocate once, we probably cannot allocate 2226 // again. Let's get out of the loop. 2227 break; 2228 } 2229 } 2230 } 2231 #endif // !PRODUCT 2232 2233 void G1CollectedHeap::increment_old_marking_cycles_started() { 2234 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2235 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2236 err_msg("Wrong marking cycle count (started: %d, completed: %d)", 2237 _old_marking_cycles_started, _old_marking_cycles_completed)); 2238 2239 _old_marking_cycles_started++; 2240 } 2241 2242 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2243 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2244 2245 // We assume that if concurrent == true, then the caller is a 2246 // concurrent thread that was joined the Suspendible Thread 2247 // Set. If there's ever a cheap way to check this, we should add an 2248 // assert here. 2249 2250 // Given that this method is called at the end of a Full GC or of a 2251 // concurrent cycle, and those can be nested (i.e., a Full GC can 2252 // interrupt a concurrent cycle), the number of full collections 2253 // completed should be either one (in the case where there was no 2254 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2255 // behind the number of full collections started. 2256 2257 // This is the case for the inner caller, i.e. a Full GC. 2258 assert(concurrent || 2259 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2260 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2261 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u " 2262 "is inconsistent with _old_marking_cycles_completed = %u", 2263 _old_marking_cycles_started, _old_marking_cycles_completed)); 2264 2265 // This is the case for the outer caller, i.e. the concurrent cycle. 2266 assert(!concurrent || 2267 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2268 err_msg("for outer caller (concurrent cycle): " 2269 "_old_marking_cycles_started = %u " 2270 "is inconsistent with _old_marking_cycles_completed = %u", 2271 _old_marking_cycles_started, _old_marking_cycles_completed)); 2272 2273 _old_marking_cycles_completed += 1; 2274 2275 // We need to clear the "in_progress" flag in the CM thread before 2276 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2277 // is set) so that if a waiter requests another System.gc() it doesn't 2278 // incorrectly see that a marking cycle is still in progress. 2279 if (concurrent) { 2280 _cmThread->clear_in_progress(); 2281 } 2282 2283 // This notify_all() will ensure that a thread that called 2284 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2285 // and it's waiting for a full GC to finish will be woken up. It is 2286 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2287 FullGCCount_lock->notify_all(); 2288 } 2289 2290 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2291 _concurrent_cycle_started = true; 2292 _gc_timer_cm->register_gc_start(start_time); 2293 2294 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2295 trace_heap_before_gc(_gc_tracer_cm); 2296 } 2297 2298 void G1CollectedHeap::register_concurrent_cycle_end() { 2299 if (_concurrent_cycle_started) { 2300 if (_cm->has_aborted()) { 2301 _gc_tracer_cm->report_concurrent_mode_failure(); 2302 } 2303 2304 _gc_timer_cm->register_gc_end(); 2305 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2306 2307 // Clear state variables to prepare for the next concurrent cycle. 2308 _concurrent_cycle_started = false; 2309 _heap_summary_sent = false; 2310 } 2311 } 2312 2313 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2314 if (_concurrent_cycle_started) { 2315 // This function can be called when: 2316 // the cleanup pause is run 2317 // the concurrent cycle is aborted before the cleanup pause. 2318 // the concurrent cycle is aborted after the cleanup pause, 2319 // but before the concurrent cycle end has been registered. 2320 // Make sure that we only send the heap information once. 2321 if (!_heap_summary_sent) { 2322 trace_heap_after_gc(_gc_tracer_cm); 2323 _heap_summary_sent = true; 2324 } 2325 } 2326 } 2327 2328 G1YCType G1CollectedHeap::yc_type() { 2329 bool is_young = g1_policy()->gcs_are_young(); 2330 bool is_initial_mark = g1_policy()->during_initial_mark_pause(); 2331 bool is_during_mark = mark_in_progress(); 2332 2333 if (is_initial_mark) { 2334 return InitialMark; 2335 } else if (is_during_mark) { 2336 return DuringMark; 2337 } else if (is_young) { 2338 return Normal; 2339 } else { 2340 return Mixed; 2341 } 2342 } 2343 2344 void G1CollectedHeap::collect(GCCause::Cause cause) { 2345 assert_heap_not_locked(); 2346 2347 uint gc_count_before; 2348 uint old_marking_count_before; 2349 uint full_gc_count_before; 2350 bool retry_gc; 2351 2352 do { 2353 retry_gc = false; 2354 2355 { 2356 MutexLocker ml(Heap_lock); 2357 2358 // Read the GC count while holding the Heap_lock 2359 gc_count_before = total_collections(); 2360 full_gc_count_before = total_full_collections(); 2361 old_marking_count_before = _old_marking_cycles_started; 2362 } 2363 2364 if (should_do_concurrent_full_gc(cause)) { 2365 // Schedule an initial-mark evacuation pause that will start a 2366 // concurrent cycle. We're setting word_size to 0 which means that 2367 // we are not requesting a post-GC allocation. 2368 VM_G1IncCollectionPause op(gc_count_before, 2369 0, /* word_size */ 2370 true, /* should_initiate_conc_mark */ 2371 g1_policy()->max_pause_time_ms(), 2372 cause); 2373 op.set_allocation_context(AllocationContext::current()); 2374 2375 VMThread::execute(&op); 2376 if (!op.pause_succeeded()) { 2377 if (old_marking_count_before == _old_marking_cycles_started) { 2378 retry_gc = op.should_retry_gc(); 2379 } else { 2380 // A Full GC happened while we were trying to schedule the 2381 // initial-mark GC. No point in starting a new cycle given 2382 // that the whole heap was collected anyway. 2383 } 2384 2385 if (retry_gc) { 2386 if (GC_locker::is_active_and_needs_gc()) { 2387 GC_locker::stall_until_clear(); 2388 } 2389 } 2390 } 2391 } else { 2392 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2393 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2394 2395 // Schedule a standard evacuation pause. We're setting word_size 2396 // to 0 which means that we are not requesting a post-GC allocation. 2397 VM_G1IncCollectionPause op(gc_count_before, 2398 0, /* word_size */ 2399 false, /* should_initiate_conc_mark */ 2400 g1_policy()->max_pause_time_ms(), 2401 cause); 2402 VMThread::execute(&op); 2403 } else { 2404 // Schedule a Full GC. 2405 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2406 VMThread::execute(&op); 2407 } 2408 } 2409 } while (retry_gc); 2410 } 2411 2412 bool G1CollectedHeap::is_in(const void* p) const { 2413 if (_hrm.reserved().contains(p)) { 2414 // Given that we know that p is in the reserved space, 2415 // heap_region_containing_raw() should successfully 2416 // return the containing region. 2417 HeapRegion* hr = heap_region_containing_raw(p); 2418 return hr->is_in(p); 2419 } else { 2420 return false; 2421 } 2422 } 2423 2424 #ifdef ASSERT 2425 bool G1CollectedHeap::is_in_exact(const void* p) const { 2426 bool contains = reserved_region().contains(p); 2427 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2428 if (contains && available) { 2429 return true; 2430 } else { 2431 return false; 2432 } 2433 } 2434 #endif 2435 2436 // Iteration functions. 2437 2438 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2439 2440 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2441 ExtendedOopClosure* _cl; 2442 public: 2443 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2444 bool doHeapRegion(HeapRegion* r) { 2445 if (!r->is_continues_humongous()) { 2446 r->oop_iterate(_cl); 2447 } 2448 return false; 2449 } 2450 }; 2451 2452 // Iterates an ObjectClosure over all objects within a HeapRegion. 2453 2454 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2455 ObjectClosure* _cl; 2456 public: 2457 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2458 bool doHeapRegion(HeapRegion* r) { 2459 if (!r->is_continues_humongous()) { 2460 r->object_iterate(_cl); 2461 } 2462 return false; 2463 } 2464 }; 2465 2466 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2467 IterateObjectClosureRegionClosure blk(cl); 2468 heap_region_iterate(&blk); 2469 } 2470 2471 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2472 _hrm.iterate(cl); 2473 } 2474 2475 void 2476 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2477 uint worker_id, 2478 HeapRegionClaimer *hrclaimer, 2479 bool concurrent) const { 2480 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2481 } 2482 2483 // Clear the cached CSet starting regions and (more importantly) 2484 // the time stamps. Called when we reset the GC time stamp. 2485 void G1CollectedHeap::clear_cset_start_regions() { 2486 assert(_worker_cset_start_region != NULL, "sanity"); 2487 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2488 2489 for (uint i = 0; i < ParallelGCThreads; i++) { 2490 _worker_cset_start_region[i] = NULL; 2491 _worker_cset_start_region_time_stamp[i] = 0; 2492 } 2493 } 2494 2495 // Given the id of a worker, obtain or calculate a suitable 2496 // starting region for iterating over the current collection set. 2497 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2498 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2499 2500 HeapRegion* result = NULL; 2501 unsigned gc_time_stamp = get_gc_time_stamp(); 2502 2503 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2504 // Cached starting region for current worker was set 2505 // during the current pause - so it's valid. 2506 // Note: the cached starting heap region may be NULL 2507 // (when the collection set is empty). 2508 result = _worker_cset_start_region[worker_i]; 2509 assert(result == NULL || result->in_collection_set(), "sanity"); 2510 return result; 2511 } 2512 2513 // The cached entry was not valid so let's calculate 2514 // a suitable starting heap region for this worker. 2515 2516 // We want the parallel threads to start their collection 2517 // set iteration at different collection set regions to 2518 // avoid contention. 2519 // If we have: 2520 // n collection set regions 2521 // p threads 2522 // Then thread t will start at region floor ((t * n) / p) 2523 2524 result = g1_policy()->collection_set(); 2525 uint cs_size = g1_policy()->cset_region_length(); 2526 uint active_workers = workers()->active_workers(); 2527 2528 uint end_ind = (cs_size * worker_i) / active_workers; 2529 uint start_ind = 0; 2530 2531 if (worker_i > 0 && 2532 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2533 // Previous workers starting region is valid 2534 // so let's iterate from there 2535 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2536 result = _worker_cset_start_region[worker_i - 1]; 2537 } 2538 2539 for (uint i = start_ind; i < end_ind; i++) { 2540 result = result->next_in_collection_set(); 2541 } 2542 2543 // Note: the calculated starting heap region may be NULL 2544 // (when the collection set is empty). 2545 assert(result == NULL || result->in_collection_set(), "sanity"); 2546 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2547 "should be updated only once per pause"); 2548 _worker_cset_start_region[worker_i] = result; 2549 OrderAccess::storestore(); 2550 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2551 return result; 2552 } 2553 2554 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2555 HeapRegion* r = g1_policy()->collection_set(); 2556 while (r != NULL) { 2557 HeapRegion* next = r->next_in_collection_set(); 2558 if (cl->doHeapRegion(r)) { 2559 cl->incomplete(); 2560 return; 2561 } 2562 r = next; 2563 } 2564 } 2565 2566 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2567 HeapRegionClosure *cl) { 2568 if (r == NULL) { 2569 // The CSet is empty so there's nothing to do. 2570 return; 2571 } 2572 2573 assert(r->in_collection_set(), 2574 "Start region must be a member of the collection set."); 2575 HeapRegion* cur = r; 2576 while (cur != NULL) { 2577 HeapRegion* next = cur->next_in_collection_set(); 2578 if (cl->doHeapRegion(cur) && false) { 2579 cl->incomplete(); 2580 return; 2581 } 2582 cur = next; 2583 } 2584 cur = g1_policy()->collection_set(); 2585 while (cur != r) { 2586 HeapRegion* next = cur->next_in_collection_set(); 2587 if (cl->doHeapRegion(cur) && false) { 2588 cl->incomplete(); 2589 return; 2590 } 2591 cur = next; 2592 } 2593 } 2594 2595 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2596 HeapRegion* result = _hrm.next_region_in_heap(from); 2597 while (result != NULL && result->is_humongous()) { 2598 result = _hrm.next_region_in_heap(result); 2599 } 2600 return result; 2601 } 2602 2603 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2604 HeapRegion* hr = heap_region_containing(addr); 2605 return hr->block_start(addr); 2606 } 2607 2608 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2609 HeapRegion* hr = heap_region_containing(addr); 2610 return hr->block_size(addr); 2611 } 2612 2613 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2614 HeapRegion* hr = heap_region_containing(addr); 2615 return hr->block_is_obj(addr); 2616 } 2617 2618 bool G1CollectedHeap::supports_tlab_allocation() const { 2619 return true; 2620 } 2621 2622 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2623 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2624 } 2625 2626 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2627 return young_list()->eden_used_bytes(); 2628 } 2629 2630 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2631 // must be smaller than the humongous object limit. 2632 size_t G1CollectedHeap::max_tlab_size() const { 2633 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment); 2634 } 2635 2636 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2637 // Return the remaining space in the cur alloc region, but not less than 2638 // the min TLAB size. 2639 2640 // Also, this value can be at most the humongous object threshold, 2641 // since we can't allow tlabs to grow big enough to accommodate 2642 // humongous objects. 2643 2644 HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get(); 2645 size_t max_tlab = max_tlab_size() * wordSize; 2646 if (hr == NULL) { 2647 return max_tlab; 2648 } else { 2649 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab); 2650 } 2651 } 2652 2653 size_t G1CollectedHeap::max_capacity() const { 2654 return _hrm.reserved().byte_size(); 2655 } 2656 2657 jlong G1CollectedHeap::millis_since_last_gc() { 2658 // assert(false, "NYI"); 2659 return 0; 2660 } 2661 2662 void G1CollectedHeap::prepare_for_verify() { 2663 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2664 ensure_parsability(false); 2665 } 2666 g1_rem_set()->prepare_for_verify(); 2667 } 2668 2669 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 2670 VerifyOption vo) { 2671 switch (vo) { 2672 case VerifyOption_G1UsePrevMarking: 2673 return hr->obj_allocated_since_prev_marking(obj); 2674 case VerifyOption_G1UseNextMarking: 2675 return hr->obj_allocated_since_next_marking(obj); 2676 case VerifyOption_G1UseMarkWord: 2677 return false; 2678 default: 2679 ShouldNotReachHere(); 2680 } 2681 return false; // keep some compilers happy 2682 } 2683 2684 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 2685 switch (vo) { 2686 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 2687 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 2688 case VerifyOption_G1UseMarkWord: return NULL; 2689 default: ShouldNotReachHere(); 2690 } 2691 return NULL; // keep some compilers happy 2692 } 2693 2694 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 2695 switch (vo) { 2696 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 2697 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 2698 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 2699 default: ShouldNotReachHere(); 2700 } 2701 return false; // keep some compilers happy 2702 } 2703 2704 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 2705 switch (vo) { 2706 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 2707 case VerifyOption_G1UseNextMarking: return "NTAMS"; 2708 case VerifyOption_G1UseMarkWord: return "NONE"; 2709 default: ShouldNotReachHere(); 2710 } 2711 return NULL; // keep some compilers happy 2712 } 2713 2714 class VerifyRootsClosure: public OopClosure { 2715 private: 2716 G1CollectedHeap* _g1h; 2717 VerifyOption _vo; 2718 bool _failures; 2719 public: 2720 // _vo == UsePrevMarking -> use "prev" marking information, 2721 // _vo == UseNextMarking -> use "next" marking information, 2722 // _vo == UseMarkWord -> use mark word from object header. 2723 VerifyRootsClosure(VerifyOption vo) : 2724 _g1h(G1CollectedHeap::heap()), 2725 _vo(vo), 2726 _failures(false) { } 2727 2728 bool failures() { return _failures; } 2729 2730 template <class T> void do_oop_nv(T* p) { 2731 T heap_oop = oopDesc::load_heap_oop(p); 2732 if (!oopDesc::is_null(heap_oop)) { 2733 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2734 if (_g1h->is_obj_dead_cond(obj, _vo)) { 2735 gclog_or_tty->print_cr("Root location "PTR_FORMAT" " 2736 "points to dead obj "PTR_FORMAT, p2i(p), p2i(obj)); 2737 if (_vo == VerifyOption_G1UseMarkWord) { 2738 gclog_or_tty->print_cr(" Mark word: "INTPTR_FORMAT, (intptr_t)obj->mark()); 2739 } 2740 obj->print_on(gclog_or_tty); 2741 _failures = true; 2742 } 2743 } 2744 } 2745 2746 void do_oop(oop* p) { do_oop_nv(p); } 2747 void do_oop(narrowOop* p) { do_oop_nv(p); } 2748 }; 2749 2750 class G1VerifyCodeRootOopClosure: public OopClosure { 2751 G1CollectedHeap* _g1h; 2752 OopClosure* _root_cl; 2753 nmethod* _nm; 2754 VerifyOption _vo; 2755 bool _failures; 2756 2757 template <class T> void do_oop_work(T* p) { 2758 // First verify that this root is live 2759 _root_cl->do_oop(p); 2760 2761 if (!G1VerifyHeapRegionCodeRoots) { 2762 // We're not verifying the code roots attached to heap region. 2763 return; 2764 } 2765 2766 // Don't check the code roots during marking verification in a full GC 2767 if (_vo == VerifyOption_G1UseMarkWord) { 2768 return; 2769 } 2770 2771 // Now verify that the current nmethod (which contains p) is 2772 // in the code root list of the heap region containing the 2773 // object referenced by p. 2774 2775 T heap_oop = oopDesc::load_heap_oop(p); 2776 if (!oopDesc::is_null(heap_oop)) { 2777 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2778 2779 // Now fetch the region containing the object 2780 HeapRegion* hr = _g1h->heap_region_containing(obj); 2781 HeapRegionRemSet* hrrs = hr->rem_set(); 2782 // Verify that the strong code root list for this region 2783 // contains the nmethod 2784 if (!hrrs->strong_code_roots_list_contains(_nm)) { 2785 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" " 2786 "from nmethod "PTR_FORMAT" not in strong " 2787 "code roots for region ["PTR_FORMAT","PTR_FORMAT")", 2788 p2i(p), p2i(_nm), p2i(hr->bottom()), p2i(hr->end())); 2789 _failures = true; 2790 } 2791 } 2792 } 2793 2794 public: 2795 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo): 2796 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {} 2797 2798 void do_oop(oop* p) { do_oop_work(p); } 2799 void do_oop(narrowOop* p) { do_oop_work(p); } 2800 2801 void set_nmethod(nmethod* nm) { _nm = nm; } 2802 bool failures() { return _failures; } 2803 }; 2804 2805 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure { 2806 G1VerifyCodeRootOopClosure* _oop_cl; 2807 2808 public: 2809 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl): 2810 _oop_cl(oop_cl) {} 2811 2812 void do_code_blob(CodeBlob* cb) { 2813 nmethod* nm = cb->as_nmethod_or_null(); 2814 if (nm != NULL) { 2815 _oop_cl->set_nmethod(nm); 2816 nm->oops_do(_oop_cl); 2817 } 2818 } 2819 }; 2820 2821 class YoungRefCounterClosure : public OopClosure { 2822 G1CollectedHeap* _g1h; 2823 int _count; 2824 public: 2825 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 2826 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 2827 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 2828 2829 int count() { return _count; } 2830 void reset_count() { _count = 0; }; 2831 }; 2832 2833 class VerifyKlassClosure: public KlassClosure { 2834 YoungRefCounterClosure _young_ref_counter_closure; 2835 OopClosure *_oop_closure; 2836 public: 2837 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 2838 void do_klass(Klass* k) { 2839 k->oops_do(_oop_closure); 2840 2841 _young_ref_counter_closure.reset_count(); 2842 k->oops_do(&_young_ref_counter_closure); 2843 if (_young_ref_counter_closure.count() > 0) { 2844 guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", p2i(k))); 2845 } 2846 } 2847 }; 2848 2849 class VerifyLivenessOopClosure: public OopClosure { 2850 G1CollectedHeap* _g1h; 2851 VerifyOption _vo; 2852 public: 2853 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 2854 _g1h(g1h), _vo(vo) 2855 { } 2856 void do_oop(narrowOop *p) { do_oop_work(p); } 2857 void do_oop( oop *p) { do_oop_work(p); } 2858 2859 template <class T> void do_oop_work(T *p) { 2860 oop obj = oopDesc::load_decode_heap_oop(p); 2861 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 2862 "Dead object referenced by a not dead object"); 2863 } 2864 }; 2865 2866 class VerifyObjsInRegionClosure: public ObjectClosure { 2867 private: 2868 G1CollectedHeap* _g1h; 2869 size_t _live_bytes; 2870 HeapRegion *_hr; 2871 VerifyOption _vo; 2872 public: 2873 // _vo == UsePrevMarking -> use "prev" marking information, 2874 // _vo == UseNextMarking -> use "next" marking information, 2875 // _vo == UseMarkWord -> use mark word from object header. 2876 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 2877 : _live_bytes(0), _hr(hr), _vo(vo) { 2878 _g1h = G1CollectedHeap::heap(); 2879 } 2880 void do_object(oop o) { 2881 VerifyLivenessOopClosure isLive(_g1h, _vo); 2882 assert(o != NULL, "Huh?"); 2883 if (!_g1h->is_obj_dead_cond(o, _vo)) { 2884 // If the object is alive according to the mark word, 2885 // then verify that the marking information agrees. 2886 // Note we can't verify the contra-positive of the 2887 // above: if the object is dead (according to the mark 2888 // word), it may not be marked, or may have been marked 2889 // but has since became dead, or may have been allocated 2890 // since the last marking. 2891 if (_vo == VerifyOption_G1UseMarkWord) { 2892 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 2893 } 2894 2895 o->oop_iterate_no_header(&isLive); 2896 if (!_hr->obj_allocated_since_prev_marking(o)) { 2897 size_t obj_size = o->size(); // Make sure we don't overflow 2898 _live_bytes += (obj_size * HeapWordSize); 2899 } 2900 } 2901 } 2902 size_t live_bytes() { return _live_bytes; } 2903 }; 2904 2905 class VerifyRegionClosure: public HeapRegionClosure { 2906 private: 2907 bool _par; 2908 VerifyOption _vo; 2909 bool _failures; 2910 public: 2911 // _vo == UsePrevMarking -> use "prev" marking information, 2912 // _vo == UseNextMarking -> use "next" marking information, 2913 // _vo == UseMarkWord -> use mark word from object header. 2914 VerifyRegionClosure(bool par, VerifyOption vo) 2915 : _par(par), 2916 _vo(vo), 2917 _failures(false) {} 2918 2919 bool failures() { 2920 return _failures; 2921 } 2922 2923 bool doHeapRegion(HeapRegion* r) { 2924 if (!r->is_continues_humongous()) { 2925 bool failures = false; 2926 r->verify(_vo, &failures); 2927 if (failures) { 2928 _failures = true; 2929 } else { 2930 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 2931 r->object_iterate(¬_dead_yet_cl); 2932 if (_vo != VerifyOption_G1UseNextMarking) { 2933 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 2934 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] " 2935 "max_live_bytes "SIZE_FORMAT" " 2936 "< calculated "SIZE_FORMAT, 2937 p2i(r->bottom()), p2i(r->end()), 2938 r->max_live_bytes(), 2939 not_dead_yet_cl.live_bytes()); 2940 _failures = true; 2941 } 2942 } else { 2943 // When vo == UseNextMarking we cannot currently do a sanity 2944 // check on the live bytes as the calculation has not been 2945 // finalized yet. 2946 } 2947 } 2948 } 2949 return false; // stop the region iteration if we hit a failure 2950 } 2951 }; 2952 2953 // This is the task used for parallel verification of the heap regions 2954 2955 class G1ParVerifyTask: public AbstractGangTask { 2956 private: 2957 G1CollectedHeap* _g1h; 2958 VerifyOption _vo; 2959 bool _failures; 2960 HeapRegionClaimer _hrclaimer; 2961 2962 public: 2963 // _vo == UsePrevMarking -> use "prev" marking information, 2964 // _vo == UseNextMarking -> use "next" marking information, 2965 // _vo == UseMarkWord -> use mark word from object header. 2966 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 2967 AbstractGangTask("Parallel verify task"), 2968 _g1h(g1h), 2969 _vo(vo), 2970 _failures(false), 2971 _hrclaimer(g1h->workers()->active_workers()) {} 2972 2973 bool failures() { 2974 return _failures; 2975 } 2976 2977 void work(uint worker_id) { 2978 HandleMark hm; 2979 VerifyRegionClosure blk(true, _vo); 2980 _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer); 2981 if (blk.failures()) { 2982 _failures = true; 2983 } 2984 } 2985 }; 2986 2987 void G1CollectedHeap::verify(bool silent, VerifyOption vo) { 2988 if (SafepointSynchronize::is_at_safepoint()) { 2989 assert(Thread::current()->is_VM_thread(), 2990 "Expected to be executed serially by the VM thread at this point"); 2991 2992 if (!silent) { gclog_or_tty->print("Roots "); } 2993 VerifyRootsClosure rootsCl(vo); 2994 VerifyKlassClosure klassCl(this, &rootsCl); 2995 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false); 2996 2997 // We apply the relevant closures to all the oops in the 2998 // system dictionary, class loader data graph, the string table 2999 // and the nmethods in the code cache. 3000 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo); 3001 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl); 3002 3003 { 3004 G1RootProcessor root_processor(this, 1); 3005 root_processor.process_all_roots(&rootsCl, 3006 &cldCl, 3007 &blobsCl); 3008 } 3009 3010 bool failures = rootsCl.failures() || codeRootsCl.failures(); 3011 3012 if (vo != VerifyOption_G1UseMarkWord) { 3013 // If we're verifying during a full GC then the region sets 3014 // will have been torn down at the start of the GC. Therefore 3015 // verifying the region sets will fail. So we only verify 3016 // the region sets when not in a full GC. 3017 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3018 verify_region_sets(); 3019 } 3020 3021 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3022 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3023 3024 G1ParVerifyTask task(this, vo); 3025 workers()->run_task(&task); 3026 if (task.failures()) { 3027 failures = true; 3028 } 3029 3030 } else { 3031 VerifyRegionClosure blk(false, vo); 3032 heap_region_iterate(&blk); 3033 if (blk.failures()) { 3034 failures = true; 3035 } 3036 } 3037 3038 if (G1StringDedup::is_enabled()) { 3039 if (!silent) gclog_or_tty->print("StrDedup "); 3040 G1StringDedup::verify(); 3041 } 3042 3043 if (failures) { 3044 gclog_or_tty->print_cr("Heap:"); 3045 // It helps to have the per-region information in the output to 3046 // help us track down what went wrong. This is why we call 3047 // print_extended_on() instead of print_on(). 3048 print_extended_on(gclog_or_tty); 3049 gclog_or_tty->cr(); 3050 gclog_or_tty->flush(); 3051 } 3052 guarantee(!failures, "there should not have been any failures"); 3053 } else { 3054 if (!silent) { 3055 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet"); 3056 if (G1StringDedup::is_enabled()) { 3057 gclog_or_tty->print(", StrDedup"); 3058 } 3059 gclog_or_tty->print(") "); 3060 } 3061 } 3062 } 3063 3064 void G1CollectedHeap::verify(bool silent) { 3065 verify(silent, VerifyOption_G1UsePrevMarking); 3066 } 3067 3068 double G1CollectedHeap::verify(bool guard, const char* msg) { 3069 double verify_time_ms = 0.0; 3070 3071 if (guard && total_collections() >= VerifyGCStartAt) { 3072 double verify_start = os::elapsedTime(); 3073 HandleMark hm; // Discard invalid handles created during verification 3074 prepare_for_verify(); 3075 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 3076 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 3077 } 3078 3079 return verify_time_ms; 3080 } 3081 3082 void G1CollectedHeap::verify_before_gc() { 3083 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:"); 3084 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 3085 } 3086 3087 void G1CollectedHeap::verify_after_gc() { 3088 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:"); 3089 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 3090 } 3091 3092 class PrintRegionClosure: public HeapRegionClosure { 3093 outputStream* _st; 3094 public: 3095 PrintRegionClosure(outputStream* st) : _st(st) {} 3096 bool doHeapRegion(HeapRegion* r) { 3097 r->print_on(_st); 3098 return false; 3099 } 3100 }; 3101 3102 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3103 const HeapRegion* hr, 3104 const VerifyOption vo) const { 3105 switch (vo) { 3106 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 3107 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 3108 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); 3109 default: ShouldNotReachHere(); 3110 } 3111 return false; // keep some compilers happy 3112 } 3113 3114 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3115 const VerifyOption vo) const { 3116 switch (vo) { 3117 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 3118 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 3119 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); 3120 default: ShouldNotReachHere(); 3121 } 3122 return false; // keep some compilers happy 3123 } 3124 3125 void G1CollectedHeap::print_on(outputStream* st) const { 3126 st->print(" %-20s", "garbage-first heap"); 3127 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3128 capacity()/K, used_unlocked()/K); 3129 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 3130 p2i(_hrm.reserved().start()), 3131 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 3132 p2i(_hrm.reserved().end())); 3133 st->cr(); 3134 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3135 uint young_regions = _young_list->length(); 3136 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3137 (size_t) young_regions * HeapRegion::GrainBytes / K); 3138 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3139 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3140 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3141 st->cr(); 3142 MetaspaceAux::print_on(st); 3143 } 3144 3145 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3146 print_on(st); 3147 3148 // Print the per-region information. 3149 st->cr(); 3150 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), " 3151 "HS=humongous(starts), HC=humongous(continues), " 3152 "CS=collection set, F=free, TS=gc time stamp, " 3153 "PTAMS=previous top-at-mark-start, " 3154 "NTAMS=next top-at-mark-start)"); 3155 PrintRegionClosure blk(st); 3156 heap_region_iterate(&blk); 3157 } 3158 3159 void G1CollectedHeap::print_on_error(outputStream* st) const { 3160 this->CollectedHeap::print_on_error(st); 3161 3162 if (_cm != NULL) { 3163 st->cr(); 3164 _cm->print_on_error(st); 3165 } 3166 } 3167 3168 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3169 workers()->print_worker_threads_on(st); 3170 _cmThread->print_on(st); 3171 st->cr(); 3172 _cm->print_worker_threads_on(st); 3173 _cg1r->print_worker_threads_on(st); 3174 if (G1StringDedup::is_enabled()) { 3175 G1StringDedup::print_worker_threads_on(st); 3176 } 3177 } 3178 3179 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3180 workers()->threads_do(tc); 3181 tc->do_thread(_cmThread); 3182 _cg1r->threads_do(tc); 3183 if (G1StringDedup::is_enabled()) { 3184 G1StringDedup::threads_do(tc); 3185 } 3186 } 3187 3188 void G1CollectedHeap::print_tracing_info() const { 3189 // We'll overload this to mean "trace GC pause statistics." 3190 if (TraceYoungGenTime || TraceOldGenTime) { 3191 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3192 // to that. 3193 g1_policy()->print_tracing_info(); 3194 } 3195 if (G1SummarizeRSetStats) { 3196 g1_rem_set()->print_summary_info(); 3197 } 3198 if (G1SummarizeConcMark) { 3199 concurrent_mark()->print_summary_info(); 3200 } 3201 g1_policy()->print_yg_surv_rate_info(); 3202 } 3203 3204 #ifndef PRODUCT 3205 // Helpful for debugging RSet issues. 3206 3207 class PrintRSetsClosure : public HeapRegionClosure { 3208 private: 3209 const char* _msg; 3210 size_t _occupied_sum; 3211 3212 public: 3213 bool doHeapRegion(HeapRegion* r) { 3214 HeapRegionRemSet* hrrs = r->rem_set(); 3215 size_t occupied = hrrs->occupied(); 3216 _occupied_sum += occupied; 3217 3218 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT, 3219 HR_FORMAT_PARAMS(r)); 3220 if (occupied == 0) { 3221 gclog_or_tty->print_cr(" RSet is empty"); 3222 } else { 3223 hrrs->print(); 3224 } 3225 gclog_or_tty->print_cr("----------"); 3226 return false; 3227 } 3228 3229 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3230 gclog_or_tty->cr(); 3231 gclog_or_tty->print_cr("========================================"); 3232 gclog_or_tty->print_cr("%s", msg); 3233 gclog_or_tty->cr(); 3234 } 3235 3236 ~PrintRSetsClosure() { 3237 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum); 3238 gclog_or_tty->print_cr("========================================"); 3239 gclog_or_tty->cr(); 3240 } 3241 }; 3242 3243 void G1CollectedHeap::print_cset_rsets() { 3244 PrintRSetsClosure cl("Printing CSet RSets"); 3245 collection_set_iterate(&cl); 3246 } 3247 3248 void G1CollectedHeap::print_all_rsets() { 3249 PrintRSetsClosure cl("Printing All RSets");; 3250 heap_region_iterate(&cl); 3251 } 3252 #endif // PRODUCT 3253 3254 G1CollectedHeap* G1CollectedHeap::heap() { 3255 CollectedHeap* heap = Universe::heap(); 3256 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 3257 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 3258 return (G1CollectedHeap*)heap; 3259 } 3260 3261 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3262 // always_do_update_barrier = false; 3263 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3264 // Fill TLAB's and such 3265 accumulate_statistics_all_tlabs(); 3266 ensure_parsability(true); 3267 3268 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) && 3269 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 3270 g1_rem_set()->print_periodic_summary_info("Before GC RS summary"); 3271 } 3272 } 3273 3274 void G1CollectedHeap::gc_epilogue(bool full) { 3275 3276 if (G1SummarizeRSetStats && 3277 (G1SummarizeRSetStatsPeriod > 0) && 3278 // we are at the end of the GC. Total collections has already been increased. 3279 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) { 3280 g1_rem_set()->print_periodic_summary_info("After GC RS summary"); 3281 } 3282 3283 // FIXME: what is this about? 3284 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3285 // is set. 3286 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(), 3287 "derived pointer present")); 3288 // always_do_update_barrier = true; 3289 3290 resize_all_tlabs(); 3291 allocation_context_stats().update(full); 3292 3293 // We have just completed a GC. Update the soft reference 3294 // policy with the new heap occupancy 3295 Universe::update_heap_info_at_gc(); 3296 } 3297 3298 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3299 uint gc_count_before, 3300 bool* succeeded, 3301 GCCause::Cause gc_cause) { 3302 assert_heap_not_locked_and_not_at_safepoint(); 3303 g1_policy()->record_stop_world_start(); 3304 VM_G1IncCollectionPause op(gc_count_before, 3305 word_size, 3306 false, /* should_initiate_conc_mark */ 3307 g1_policy()->max_pause_time_ms(), 3308 gc_cause); 3309 3310 op.set_allocation_context(AllocationContext::current()); 3311 VMThread::execute(&op); 3312 3313 HeapWord* result = op.result(); 3314 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3315 assert(result == NULL || ret_succeeded, 3316 "the result should be NULL if the VM did not succeed"); 3317 *succeeded = ret_succeeded; 3318 3319 assert_heap_not_locked(); 3320 return result; 3321 } 3322 3323 void 3324 G1CollectedHeap::doConcurrentMark() { 3325 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3326 if (!_cmThread->in_progress()) { 3327 _cmThread->set_started(); 3328 CGC_lock->notify(); 3329 } 3330 } 3331 3332 size_t G1CollectedHeap::pending_card_num() { 3333 size_t extra_cards = 0; 3334 JavaThread *curr = Threads::first(); 3335 while (curr != NULL) { 3336 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3337 extra_cards += dcq.size(); 3338 curr = curr->next(); 3339 } 3340 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3341 size_t buffer_size = dcqs.buffer_size(); 3342 size_t buffer_num = dcqs.completed_buffers_num(); 3343 3344 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3345 // in bytes - not the number of 'entries'. We need to convert 3346 // into a number of cards. 3347 return (buffer_size * buffer_num + extra_cards) / oopSize; 3348 } 3349 3350 size_t G1CollectedHeap::cards_scanned() { 3351 return g1_rem_set()->cardsScanned(); 3352 } 3353 3354 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 3355 private: 3356 size_t _total_humongous; 3357 size_t _candidate_humongous; 3358 3359 DirtyCardQueue _dcq; 3360 3361 // We don't nominate objects with many remembered set entries, on 3362 // the assumption that such objects are likely still live. 3363 bool is_remset_small(HeapRegion* region) const { 3364 HeapRegionRemSet* const rset = region->rem_set(); 3365 return G1EagerReclaimHumongousObjectsWithStaleRefs 3366 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 3367 : rset->is_empty(); 3368 } 3369 3370 bool is_typeArray_region(HeapRegion* region) const { 3371 return oop(region->bottom())->is_typeArray(); 3372 } 3373 3374 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 3375 assert(region->is_starts_humongous(), "Must start a humongous object"); 3376 3377 // Candidate selection must satisfy the following constraints 3378 // while concurrent marking is in progress: 3379 // 3380 // * In order to maintain SATB invariants, an object must not be 3381 // reclaimed if it was allocated before the start of marking and 3382 // has not had its references scanned. Such an object must have 3383 // its references (including type metadata) scanned to ensure no 3384 // live objects are missed by the marking process. Objects 3385 // allocated after the start of concurrent marking don't need to 3386 // be scanned. 3387 // 3388 // * An object must not be reclaimed if it is on the concurrent 3389 // mark stack. Objects allocated after the start of concurrent 3390 // marking are never pushed on the mark stack. 3391 // 3392 // Nominating only objects allocated after the start of concurrent 3393 // marking is sufficient to meet both constraints. This may miss 3394 // some objects that satisfy the constraints, but the marking data 3395 // structures don't support efficiently performing the needed 3396 // additional tests or scrubbing of the mark stack. 3397 // 3398 // However, we presently only nominate is_typeArray() objects. 3399 // A humongous object containing references induces remembered 3400 // set entries on other regions. In order to reclaim such an 3401 // object, those remembered sets would need to be cleaned up. 3402 // 3403 // We also treat is_typeArray() objects specially, allowing them 3404 // to be reclaimed even if allocated before the start of 3405 // concurrent mark. For this we rely on mark stack insertion to 3406 // exclude is_typeArray() objects, preventing reclaiming an object 3407 // that is in the mark stack. We also rely on the metadata for 3408 // such objects to be built-in and so ensured to be kept live. 3409 // Frequent allocation and drop of large binary blobs is an 3410 // important use case for eager reclaim, and this special handling 3411 // may reduce needed headroom. 3412 3413 return is_typeArray_region(region) && is_remset_small(region); 3414 } 3415 3416 public: 3417 RegisterHumongousWithInCSetFastTestClosure() 3418 : _total_humongous(0), 3419 _candidate_humongous(0), 3420 _dcq(&JavaThread::dirty_card_queue_set()) { 3421 } 3422 3423 virtual bool doHeapRegion(HeapRegion* r) { 3424 if (!r->is_starts_humongous()) { 3425 return false; 3426 } 3427 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3428 3429 bool is_candidate = humongous_region_is_candidate(g1h, r); 3430 uint rindex = r->hrm_index(); 3431 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 3432 if (is_candidate) { 3433 _candidate_humongous++; 3434 g1h->register_humongous_region_with_cset(rindex); 3435 // Is_candidate already filters out humongous object with large remembered sets. 3436 // If we have a humongous object with a few remembered sets, we simply flush these 3437 // remembered set entries into the DCQS. That will result in automatic 3438 // re-evaluation of their remembered set entries during the following evacuation 3439 // phase. 3440 if (!r->rem_set()->is_empty()) { 3441 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 3442 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 3443 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 3444 HeapRegionRemSetIterator hrrs(r->rem_set()); 3445 size_t card_index; 3446 while (hrrs.has_next(card_index)) { 3447 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 3448 // The remembered set might contain references to already freed 3449 // regions. Filter out such entries to avoid failing card table 3450 // verification. 3451 if (!g1h->heap_region_containing(bs->addr_for(card_ptr))->is_free()) { 3452 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 3453 *card_ptr = CardTableModRefBS::dirty_card_val(); 3454 _dcq.enqueue(card_ptr); 3455 } 3456 } 3457 } 3458 r->rem_set()->clear_locked(); 3459 } 3460 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 3461 } 3462 _total_humongous++; 3463 3464 return false; 3465 } 3466 3467 size_t total_humongous() const { return _total_humongous; } 3468 size_t candidate_humongous() const { return _candidate_humongous; } 3469 3470 void flush_rem_set_entries() { _dcq.flush(); } 3471 }; 3472 3473 void G1CollectedHeap::register_humongous_regions_with_cset() { 3474 if (!G1EagerReclaimHumongousObjects) { 3475 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 3476 return; 3477 } 3478 double time = os::elapsed_counter(); 3479 3480 // Collect reclaim candidate information and register candidates with cset. 3481 RegisterHumongousWithInCSetFastTestClosure cl; 3482 heap_region_iterate(&cl); 3483 3484 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 3485 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 3486 cl.total_humongous(), 3487 cl.candidate_humongous()); 3488 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3489 3490 // Finally flush all remembered set entries to re-check into the global DCQS. 3491 cl.flush_rem_set_entries(); 3492 } 3493 3494 void 3495 G1CollectedHeap::setup_surviving_young_words() { 3496 assert(_surviving_young_words == NULL, "pre-condition"); 3497 uint array_length = g1_policy()->young_cset_region_length(); 3498 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC); 3499 if (_surviving_young_words == NULL) { 3500 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR, 3501 "Not enough space for young surv words summary."); 3502 } 3503 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t)); 3504 #ifdef ASSERT 3505 for (uint i = 0; i < array_length; ++i) { 3506 assert( _surviving_young_words[i] == 0, "memset above" ); 3507 } 3508 #endif // !ASSERT 3509 } 3510 3511 void 3512 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) { 3513 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3514 uint array_length = g1_policy()->young_cset_region_length(); 3515 for (uint i = 0; i < array_length; ++i) { 3516 _surviving_young_words[i] += surv_young_words[i]; 3517 } 3518 } 3519 3520 void 3521 G1CollectedHeap::cleanup_surviving_young_words() { 3522 guarantee( _surviving_young_words != NULL, "pre-condition" ); 3523 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words); 3524 _surviving_young_words = NULL; 3525 } 3526 3527 #ifdef ASSERT 3528 class VerifyCSetClosure: public HeapRegionClosure { 3529 public: 3530 bool doHeapRegion(HeapRegion* hr) { 3531 // Here we check that the CSet region's RSet is ready for parallel 3532 // iteration. The fields that we'll verify are only manipulated 3533 // when the region is part of a CSet and is collected. Afterwards, 3534 // we reset these fields when we clear the region's RSet (when the 3535 // region is freed) so they are ready when the region is 3536 // re-allocated. The only exception to this is if there's an 3537 // evacuation failure and instead of freeing the region we leave 3538 // it in the heap. In that case, we reset these fields during 3539 // evacuation failure handling. 3540 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3541 3542 // Here's a good place to add any other checks we'd like to 3543 // perform on CSet regions. 3544 return false; 3545 } 3546 }; 3547 #endif // ASSERT 3548 3549 uint G1CollectedHeap::num_task_queues() const { 3550 return _task_queues->size(); 3551 } 3552 3553 #if TASKQUEUE_STATS 3554 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3555 st->print_raw_cr("GC Task Stats"); 3556 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3557 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3558 } 3559 3560 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3561 print_taskqueue_stats_hdr(st); 3562 3563 TaskQueueStats totals; 3564 const uint n = num_task_queues(); 3565 for (uint i = 0; i < n; ++i) { 3566 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 3567 totals += task_queue(i)->stats; 3568 } 3569 st->print_raw("tot "); totals.print(st); st->cr(); 3570 3571 DEBUG_ONLY(totals.verify()); 3572 } 3573 3574 void G1CollectedHeap::reset_taskqueue_stats() { 3575 const uint n = num_task_queues(); 3576 for (uint i = 0; i < n; ++i) { 3577 task_queue(i)->stats.reset(); 3578 } 3579 } 3580 #endif // TASKQUEUE_STATS 3581 3582 void G1CollectedHeap::log_gc_header() { 3583 if (!G1Log::fine()) { 3584 return; 3585 } 3586 3587 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id()); 3588 3589 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) 3590 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)") 3591 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : ""); 3592 3593 gclog_or_tty->print("[%s", (const char*)gc_cause_str); 3594 } 3595 3596 void G1CollectedHeap::log_gc_footer(double pause_time_sec) { 3597 if (!G1Log::fine()) { 3598 return; 3599 } 3600 3601 if (G1Log::finer()) { 3602 if (evacuation_failed()) { 3603 gclog_or_tty->print(" (to-space exhausted)"); 3604 } 3605 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3606 g1_policy()->phase_times()->note_gc_end(); 3607 g1_policy()->phase_times()->print(pause_time_sec); 3608 g1_policy()->print_detailed_heap_transition(); 3609 } else { 3610 if (evacuation_failed()) { 3611 gclog_or_tty->print("--"); 3612 } 3613 g1_policy()->print_heap_transition(); 3614 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3615 } 3616 gclog_or_tty->flush(); 3617 } 3618 3619 bool 3620 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3621 assert_at_safepoint(true /* should_be_vm_thread */); 3622 guarantee(!is_gc_active(), "collection is not reentrant"); 3623 3624 if (GC_locker::check_active_before_gc()) { 3625 return false; 3626 } 3627 3628 _gc_timer_stw->register_gc_start(); 3629 3630 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3631 3632 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3633 ResourceMark rm; 3634 3635 G1Log::update_level(); 3636 print_heap_before_gc(); 3637 trace_heap_before_gc(_gc_tracer_stw); 3638 3639 verify_region_sets_optional(); 3640 verify_dirty_young_regions(); 3641 3642 // This call will decide whether this pause is an initial-mark 3643 // pause. If it is, during_initial_mark_pause() will return true 3644 // for the duration of this pause. 3645 g1_policy()->decide_on_conc_mark_initiation(); 3646 3647 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3648 assert(!g1_policy()->during_initial_mark_pause() || 3649 g1_policy()->gcs_are_young(), "sanity"); 3650 3651 // We also do not allow mixed GCs during marking. 3652 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity"); 3653 3654 // Record whether this pause is an initial mark. When the current 3655 // thread has completed its logging output and it's safe to signal 3656 // the CM thread, the flag's value in the policy has been reset. 3657 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause(); 3658 3659 // Inner scope for scope based logging, timers, and stats collection 3660 { 3661 EvacuationInfo evacuation_info; 3662 3663 if (g1_policy()->during_initial_mark_pause()) { 3664 // We are about to start a marking cycle, so we increment the 3665 // full collection counter. 3666 increment_old_marking_cycles_started(); 3667 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3668 } 3669 3670 _gc_tracer_stw->report_yc_type(yc_type()); 3671 3672 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 3673 3674 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3675 workers()->active_workers(), 3676 Threads::number_of_non_daemon_threads()); 3677 workers()->set_active_workers(active_workers); 3678 3679 double pause_start_sec = os::elapsedTime(); 3680 g1_policy()->phase_times()->note_gc_start(active_workers, mark_in_progress()); 3681 log_gc_header(); 3682 3683 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3684 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3685 3686 // If the secondary_free_list is not empty, append it to the 3687 // free_list. No need to wait for the cleanup operation to finish; 3688 // the region allocation code will check the secondary_free_list 3689 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3690 // set, skip this step so that the region allocation code has to 3691 // get entries from the secondary_free_list. 3692 if (!G1StressConcRegionFreeing) { 3693 append_secondary_free_list_if_not_empty_with_lock(); 3694 } 3695 3696 assert(check_young_list_well_formed(), "young list should be well formed"); 3697 3698 // Don't dynamically change the number of GC threads this early. A value of 3699 // 0 is used to indicate serial work. When parallel work is done, 3700 // it will be set. 3701 3702 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3703 IsGCActiveMark x; 3704 3705 gc_prologue(false); 3706 increment_total_collections(false /* full gc */); 3707 increment_gc_time_stamp(); 3708 3709 verify_before_gc(); 3710 3711 check_bitmaps("GC Start"); 3712 3713 COMPILER2_PRESENT(DerivedPointerTable::clear()); 3714 3715 // Please see comment in g1CollectedHeap.hpp and 3716 // G1CollectedHeap::ref_processing_init() to see how 3717 // reference processing currently works in G1. 3718 3719 // Enable discovery in the STW reference processor 3720 ref_processor_stw()->enable_discovery(); 3721 3722 { 3723 // We want to temporarily turn off discovery by the 3724 // CM ref processor, if necessary, and turn it back on 3725 // on again later if we do. Using a scoped 3726 // NoRefDiscovery object will do this. 3727 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3728 3729 // Forget the current alloc region (we might even choose it to be part 3730 // of the collection set!). 3731 _allocator->release_mutator_alloc_region(); 3732 3733 // We should call this after we retire the mutator alloc 3734 // region(s) so that all the ALLOC / RETIRE events are generated 3735 // before the start GC event. 3736 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 3737 3738 // This timing is only used by the ergonomics to handle our pause target. 3739 // It is unclear why this should not include the full pause. We will 3740 // investigate this in CR 7178365. 3741 // 3742 // Preserving the old comment here if that helps the investigation: 3743 // 3744 // The elapsed time induced by the start time below deliberately elides 3745 // the possible verification above. 3746 double sample_start_time_sec = os::elapsedTime(); 3747 3748 #if YOUNG_LIST_VERBOSE 3749 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:"); 3750 _young_list->print(); 3751 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3752 #endif // YOUNG_LIST_VERBOSE 3753 3754 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3755 3756 double scan_wait_start = os::elapsedTime(); 3757 // We have to wait until the CM threads finish scanning the 3758 // root regions as it's the only way to ensure that all the 3759 // objects on them have been correctly scanned before we start 3760 // moving them during the GC. 3761 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3762 double wait_time_ms = 0.0; 3763 if (waited) { 3764 double scan_wait_end = os::elapsedTime(); 3765 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3766 } 3767 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3768 3769 #if YOUNG_LIST_VERBOSE 3770 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:"); 3771 _young_list->print(); 3772 #endif // YOUNG_LIST_VERBOSE 3773 3774 if (g1_policy()->during_initial_mark_pause()) { 3775 concurrent_mark()->checkpointRootsInitialPre(); 3776 } 3777 3778 #if YOUNG_LIST_VERBOSE 3779 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:"); 3780 _young_list->print(); 3781 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3782 #endif // YOUNG_LIST_VERBOSE 3783 3784 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info); 3785 3786 register_humongous_regions_with_cset(); 3787 3788 assert(check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3789 3790 _cm->note_start_of_gc(); 3791 // We call this after finalize_cset() to 3792 // ensure that the CSet has been finalized. 3793 _cm->verify_no_cset_oops(); 3794 3795 if (_hr_printer.is_active()) { 3796 HeapRegion* hr = g1_policy()->collection_set(); 3797 while (hr != NULL) { 3798 _hr_printer.cset(hr); 3799 hr = hr->next_in_collection_set(); 3800 } 3801 } 3802 3803 #ifdef ASSERT 3804 VerifyCSetClosure cl; 3805 collection_set_iterate(&cl); 3806 #endif // ASSERT 3807 3808 setup_surviving_young_words(); 3809 3810 // Initialize the GC alloc regions. 3811 _allocator->init_gc_alloc_regions(evacuation_info); 3812 3813 // Actually do the work... 3814 evacuate_collection_set(evacuation_info); 3815 3816 free_collection_set(g1_policy()->collection_set(), evacuation_info); 3817 3818 eagerly_reclaim_humongous_regions(); 3819 3820 g1_policy()->clear_collection_set(); 3821 3822 cleanup_surviving_young_words(); 3823 3824 // Start a new incremental collection set for the next pause. 3825 g1_policy()->start_incremental_cset_building(); 3826 3827 clear_cset_fast_test(); 3828 3829 _young_list->reset_sampled_info(); 3830 3831 // Don't check the whole heap at this point as the 3832 // GC alloc regions from this pause have been tagged 3833 // as survivors and moved on to the survivor list. 3834 // Survivor regions will fail the !is_young() check. 3835 assert(check_young_list_empty(false /* check_heap */), 3836 "young list should be empty"); 3837 3838 #if YOUNG_LIST_VERBOSE 3839 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:"); 3840 _young_list->print(); 3841 #endif // YOUNG_LIST_VERBOSE 3842 3843 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3844 _young_list->first_survivor_region(), 3845 _young_list->last_survivor_region()); 3846 3847 _young_list->reset_auxilary_lists(); 3848 3849 if (evacuation_failed()) { 3850 _allocator->set_used(recalculate_used()); 3851 for (uint i = 0; i < ParallelGCThreads; i++) { 3852 if (_evacuation_failed_info_array[i].has_failed()) { 3853 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3854 } 3855 } 3856 } else { 3857 // The "used" of the the collection set have already been subtracted 3858 // when they were freed. Add in the bytes evacuated. 3859 _allocator->increase_used(g1_policy()->bytes_copied_during_gc()); 3860 } 3861 3862 if (g1_policy()->during_initial_mark_pause()) { 3863 // We have to do this before we notify the CM threads that 3864 // they can start working to make sure that all the 3865 // appropriate initialization is done on the CM object. 3866 concurrent_mark()->checkpointRootsInitialPost(); 3867 set_marking_started(); 3868 // Note that we don't actually trigger the CM thread at 3869 // this point. We do that later when we're sure that 3870 // the current thread has completed its logging output. 3871 } 3872 3873 allocate_dummy_regions(); 3874 3875 #if YOUNG_LIST_VERBOSE 3876 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:"); 3877 _young_list->print(); 3878 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3879 #endif // YOUNG_LIST_VERBOSE 3880 3881 _allocator->init_mutator_alloc_region(); 3882 3883 { 3884 size_t expand_bytes = g1_policy()->expansion_amount(); 3885 if (expand_bytes > 0) { 3886 size_t bytes_before = capacity(); 3887 // No need for an ergo verbose message here, 3888 // expansion_amount() does this when it returns a value > 0. 3889 if (!expand(expand_bytes)) { 3890 // We failed to expand the heap. Cannot do anything about it. 3891 } 3892 } 3893 } 3894 3895 // We redo the verification but now wrt to the new CSet which 3896 // has just got initialized after the previous CSet was freed. 3897 _cm->verify_no_cset_oops(); 3898 _cm->note_end_of_gc(); 3899 3900 // This timing is only used by the ergonomics to handle our pause target. 3901 // It is unclear why this should not include the full pause. We will 3902 // investigate this in CR 7178365. 3903 double sample_end_time_sec = os::elapsedTime(); 3904 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3905 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info); 3906 3907 MemoryService::track_memory_usage(); 3908 3909 // In prepare_for_verify() below we'll need to scan the deferred 3910 // update buffers to bring the RSets up-to-date if 3911 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3912 // the update buffers we'll probably need to scan cards on the 3913 // regions we just allocated to (i.e., the GC alloc 3914 // regions). However, during the last GC we called 3915 // set_saved_mark() on all the GC alloc regions, so card 3916 // scanning might skip the [saved_mark_word()...top()] area of 3917 // those regions (i.e., the area we allocated objects into 3918 // during the last GC). But it shouldn't. Given that 3919 // saved_mark_word() is conditional on whether the GC time stamp 3920 // on the region is current or not, by incrementing the GC time 3921 // stamp here we invalidate all the GC time stamps on all the 3922 // regions and saved_mark_word() will simply return top() for 3923 // all the regions. This is a nicer way of ensuring this rather 3924 // than iterating over the regions and fixing them. In fact, the 3925 // GC time stamp increment here also ensures that 3926 // saved_mark_word() will return top() between pauses, i.e., 3927 // during concurrent refinement. So we don't need the 3928 // is_gc_active() check to decided which top to use when 3929 // scanning cards (see CR 7039627). 3930 increment_gc_time_stamp(); 3931 3932 verify_after_gc(); 3933 check_bitmaps("GC End"); 3934 3935 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3936 ref_processor_stw()->verify_no_references_recorded(); 3937 3938 // CM reference discovery will be re-enabled if necessary. 3939 } 3940 3941 // We should do this after we potentially expand the heap so 3942 // that all the COMMIT events are generated before the end GC 3943 // event, and after we retire the GC alloc regions so that all 3944 // RETIRE events are generated before the end GC event. 3945 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 3946 3947 #ifdef TRACESPINNING 3948 ParallelTaskTerminator::print_termination_counts(); 3949 #endif 3950 3951 gc_epilogue(false); 3952 } 3953 3954 // Print the remainder of the GC log output. 3955 log_gc_footer(os::elapsedTime() - pause_start_sec); 3956 3957 // It is not yet to safe to tell the concurrent mark to 3958 // start as we have some optional output below. We don't want the 3959 // output from the concurrent mark thread interfering with this 3960 // logging output either. 3961 3962 _hrm.verify_optional(); 3963 verify_region_sets_optional(); 3964 3965 TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats()); 3966 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3967 3968 print_heap_after_gc(); 3969 trace_heap_after_gc(_gc_tracer_stw); 3970 3971 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3972 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3973 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3974 // before any GC notifications are raised. 3975 g1mm()->update_sizes(); 3976 3977 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3978 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3979 _gc_timer_stw->register_gc_end(); 3980 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3981 } 3982 // It should now be safe to tell the concurrent mark thread to start 3983 // without its logging output interfering with the logging output 3984 // that came from the pause. 3985 3986 if (should_start_conc_mark) { 3987 // CAUTION: after the doConcurrentMark() call below, 3988 // the concurrent marking thread(s) could be running 3989 // concurrently with us. Make sure that anything after 3990 // this point does not assume that we are the only GC thread 3991 // running. Note: of course, the actual marking work will 3992 // not start until the safepoint itself is released in 3993 // SuspendibleThreadSet::desynchronize(). 3994 doConcurrentMark(); 3995 } 3996 3997 return true; 3998 } 3999 4000 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) { 4001 _drain_in_progress = false; 4002 set_evac_failure_closure(cl); 4003 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true); 4004 } 4005 4006 void G1CollectedHeap::finalize_for_evac_failure() { 4007 assert(_evac_failure_scan_stack != NULL && 4008 _evac_failure_scan_stack->length() == 0, 4009 "Postcondition"); 4010 assert(!_drain_in_progress, "Postcondition"); 4011 delete _evac_failure_scan_stack; 4012 _evac_failure_scan_stack = NULL; 4013 } 4014 4015 void G1CollectedHeap::remove_self_forwarding_pointers() { 4016 double remove_self_forwards_start = os::elapsedTime(); 4017 4018 G1ParRemoveSelfForwardPtrsTask rsfp_task(this); 4019 workers()->run_task(&rsfp_task); 4020 4021 // Now restore saved marks, if any. 4022 assert(_objs_with_preserved_marks.size() == 4023 _preserved_marks_of_objs.size(), "Both or none."); 4024 while (!_objs_with_preserved_marks.is_empty()) { 4025 oop obj = _objs_with_preserved_marks.pop(); 4026 markOop m = _preserved_marks_of_objs.pop(); 4027 obj->set_mark(m); 4028 } 4029 _objs_with_preserved_marks.clear(true); 4030 _preserved_marks_of_objs.clear(true); 4031 4032 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 4033 } 4034 4035 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) { 4036 _evac_failure_scan_stack->push(obj); 4037 } 4038 4039 void G1CollectedHeap::drain_evac_failure_scan_stack() { 4040 assert(_evac_failure_scan_stack != NULL, "precondition"); 4041 4042 while (_evac_failure_scan_stack->length() > 0) { 4043 oop obj = _evac_failure_scan_stack->pop(); 4044 _evac_failure_closure->set_region(heap_region_containing(obj)); 4045 obj->oop_iterate_backwards(_evac_failure_closure); 4046 } 4047 } 4048 4049 oop 4050 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, 4051 oop old) { 4052 assert(obj_in_cs(old), 4053 err_msg("obj: "PTR_FORMAT" should still be in the CSet", 4054 p2i(old))); 4055 markOop m = old->mark(); 4056 oop forward_ptr = old->forward_to_atomic(old); 4057 if (forward_ptr == NULL) { 4058 // Forward-to-self succeeded. 4059 assert(_par_scan_state != NULL, "par scan state"); 4060 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure(); 4061 uint queue_num = _par_scan_state->queue_num(); 4062 4063 _evacuation_failed = true; 4064 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size()); 4065 if (_evac_failure_closure != cl) { 4066 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag); 4067 assert(!_drain_in_progress, 4068 "Should only be true while someone holds the lock."); 4069 // Set the global evac-failure closure to the current thread's. 4070 assert(_evac_failure_closure == NULL, "Or locking has failed."); 4071 set_evac_failure_closure(cl); 4072 // Now do the common part. 4073 handle_evacuation_failure_common(old, m); 4074 // Reset to NULL. 4075 set_evac_failure_closure(NULL); 4076 } else { 4077 // The lock is already held, and this is recursive. 4078 assert(_drain_in_progress, "This should only be the recursive case."); 4079 handle_evacuation_failure_common(old, m); 4080 } 4081 return old; 4082 } else { 4083 // Forward-to-self failed. Either someone else managed to allocate 4084 // space for this object (old != forward_ptr) or they beat us in 4085 // self-forwarding it (old == forward_ptr). 4086 assert(old == forward_ptr || !obj_in_cs(forward_ptr), 4087 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" " 4088 "should not be in the CSet", 4089 p2i(old), p2i(forward_ptr))); 4090 return forward_ptr; 4091 } 4092 } 4093 4094 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) { 4095 preserve_mark_if_necessary(old, m); 4096 4097 HeapRegion* r = heap_region_containing(old); 4098 if (!r->evacuation_failed()) { 4099 r->set_evacuation_failed(true); 4100 _hr_printer.evac_failure(r); 4101 } 4102 4103 push_on_evac_failure_scan_stack(old); 4104 4105 if (!_drain_in_progress) { 4106 // prevent recursion in copy_to_survivor_space() 4107 _drain_in_progress = true; 4108 drain_evac_failure_scan_stack(); 4109 _drain_in_progress = false; 4110 } 4111 } 4112 4113 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) { 4114 assert(evacuation_failed(), "Oversaving!"); 4115 // We want to call the "for_promotion_failure" version only in the 4116 // case of a promotion failure. 4117 if (m->must_be_preserved_for_promotion_failure(obj)) { 4118 _objs_with_preserved_marks.push(obj); 4119 _preserved_marks_of_objs.push(m); 4120 } 4121 } 4122 4123 void G1ParCopyHelper::mark_object(oop obj) { 4124 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet"); 4125 4126 // We know that the object is not moving so it's safe to read its size. 4127 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id); 4128 } 4129 4130 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) { 4131 assert(from_obj->is_forwarded(), "from obj should be forwarded"); 4132 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee"); 4133 assert(from_obj != to_obj, "should not be self-forwarded"); 4134 4135 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet"); 4136 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet"); 4137 4138 // The object might be in the process of being copied by another 4139 // worker so we cannot trust that its to-space image is 4140 // well-formed. So we have to read its size from its from-space 4141 // image which we know should not be changing. 4142 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id); 4143 } 4144 4145 template <class T> 4146 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) { 4147 if (_g1->heap_region_containing_raw(new_obj)->is_young()) { 4148 _scanned_klass->record_modified_oops(); 4149 } 4150 } 4151 4152 template <G1Barrier barrier, G1Mark do_mark_object> 4153 template <class T> 4154 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) { 4155 T heap_oop = oopDesc::load_heap_oop(p); 4156 4157 if (oopDesc::is_null(heap_oop)) { 4158 return; 4159 } 4160 4161 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 4162 4163 assert(_worker_id == _par_scan_state->queue_num(), "sanity"); 4164 4165 const InCSetState state = _g1->in_cset_state(obj); 4166 if (state.is_in_cset()) { 4167 oop forwardee; 4168 markOop m = obj->mark(); 4169 if (m->is_marked()) { 4170 forwardee = (oop) m->decode_pointer(); 4171 } else { 4172 forwardee = _par_scan_state->copy_to_survivor_space(state, obj, m); 4173 } 4174 assert(forwardee != NULL, "forwardee should not be NULL"); 4175 oopDesc::encode_store_heap_oop(p, forwardee); 4176 if (do_mark_object != G1MarkNone && forwardee != obj) { 4177 // If the object is self-forwarded we don't need to explicitly 4178 // mark it, the evacuation failure protocol will do so. 4179 mark_forwarded_object(obj, forwardee); 4180 } 4181 4182 if (barrier == G1BarrierKlass) { 4183 do_klass_barrier(p, forwardee); 4184 } 4185 } else { 4186 if (state.is_humongous()) { 4187 _g1->set_humongous_is_live(obj); 4188 } 4189 // The object is not in collection set. If we're a root scanning 4190 // closure during an initial mark pause then attempt to mark the object. 4191 if (do_mark_object == G1MarkFromRoot) { 4192 mark_object(obj); 4193 } 4194 } 4195 4196 if (barrier == G1BarrierEvac) { 4197 _par_scan_state->update_rs(_from, p, _worker_id); 4198 } 4199 } 4200 4201 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p); 4202 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p); 4203 4204 class G1ParEvacuateFollowersClosure : public VoidClosure { 4205 protected: 4206 G1CollectedHeap* _g1h; 4207 G1ParScanThreadState* _par_scan_state; 4208 RefToScanQueueSet* _queues; 4209 ParallelTaskTerminator* _terminator; 4210 4211 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4212 RefToScanQueueSet* queues() { return _queues; } 4213 ParallelTaskTerminator* terminator() { return _terminator; } 4214 4215 public: 4216 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4217 G1ParScanThreadState* par_scan_state, 4218 RefToScanQueueSet* queues, 4219 ParallelTaskTerminator* terminator) 4220 : _g1h(g1h), _par_scan_state(par_scan_state), 4221 _queues(queues), _terminator(terminator) {} 4222 4223 void do_void(); 4224 4225 private: 4226 inline bool offer_termination(); 4227 }; 4228 4229 bool G1ParEvacuateFollowersClosure::offer_termination() { 4230 G1ParScanThreadState* const pss = par_scan_state(); 4231 pss->start_term_time(); 4232 const bool res = terminator()->offer_termination(); 4233 pss->end_term_time(); 4234 return res; 4235 } 4236 4237 void G1ParEvacuateFollowersClosure::do_void() { 4238 G1ParScanThreadState* const pss = par_scan_state(); 4239 pss->trim_queue(); 4240 do { 4241 pss->steal_and_trim_queue(queues()); 4242 } while (!offer_termination()); 4243 } 4244 4245 class G1KlassScanClosure : public KlassClosure { 4246 G1ParCopyHelper* _closure; 4247 bool _process_only_dirty; 4248 int _count; 4249 public: 4250 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty) 4251 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {} 4252 void do_klass(Klass* klass) { 4253 // If the klass has not been dirtied we know that there's 4254 // no references into the young gen and we can skip it. 4255 if (!_process_only_dirty || klass->has_modified_oops()) { 4256 // Clean the klass since we're going to scavenge all the metadata. 4257 klass->clear_modified_oops(); 4258 4259 // Tell the closure that this klass is the Klass to scavenge 4260 // and is the one to dirty if oops are left pointing into the young gen. 4261 _closure->set_scanned_klass(klass); 4262 4263 klass->oops_do(_closure); 4264 4265 _closure->set_scanned_klass(NULL); 4266 } 4267 _count++; 4268 } 4269 }; 4270 4271 class G1ParTask : public AbstractGangTask { 4272 protected: 4273 G1CollectedHeap* _g1h; 4274 RefToScanQueueSet *_queues; 4275 G1RootProcessor* _root_processor; 4276 ParallelTaskTerminator _terminator; 4277 uint _n_workers; 4278 4279 Mutex _stats_lock; 4280 Mutex* stats_lock() { return &_stats_lock; } 4281 4282 public: 4283 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 4284 : AbstractGangTask("G1 collection"), 4285 _g1h(g1h), 4286 _queues(task_queues), 4287 _root_processor(root_processor), 4288 _terminator(n_workers, _queues), 4289 _n_workers(n_workers), 4290 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true) 4291 {} 4292 4293 RefToScanQueueSet* queues() { return _queues; } 4294 4295 RefToScanQueue *work_queue(int i) { 4296 return queues()->queue(i); 4297 } 4298 4299 ParallelTaskTerminator* terminator() { return &_terminator; } 4300 4301 // Helps out with CLD processing. 4302 // 4303 // During InitialMark we need to: 4304 // 1) Scavenge all CLDs for the young GC. 4305 // 2) Mark all objects directly reachable from strong CLDs. 4306 template <G1Mark do_mark_object> 4307 class G1CLDClosure : public CLDClosure { 4308 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure; 4309 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure; 4310 G1KlassScanClosure _klass_in_cld_closure; 4311 bool _claim; 4312 4313 public: 4314 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure, 4315 bool only_young, bool claim) 4316 : _oop_closure(oop_closure), 4317 _oop_in_klass_closure(oop_closure->g1(), 4318 oop_closure->pss(), 4319 oop_closure->rp()), 4320 _klass_in_cld_closure(&_oop_in_klass_closure, only_young), 4321 _claim(claim) { 4322 4323 } 4324 4325 void do_cld(ClassLoaderData* cld) { 4326 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim); 4327 } 4328 }; 4329 4330 void work(uint worker_id) { 4331 if (worker_id >= _n_workers) return; // no work needed this round 4332 4333 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, os::elapsedTime()); 4334 4335 { 4336 ResourceMark rm; 4337 HandleMark hm; 4338 4339 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4340 4341 G1ParScanThreadState pss(_g1h, worker_id, rp); 4342 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp); 4343 4344 pss.set_evac_failure_closure(&evac_failure_cl); 4345 4346 bool only_young = _g1h->g1_policy()->gcs_are_young(); 4347 4348 // Non-IM young GC. 4349 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp); 4350 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl, 4351 only_young, // Only process dirty klasses. 4352 false); // No need to claim CLDs. 4353 // IM young GC. 4354 // Strong roots closures. 4355 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp); 4356 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl, 4357 false, // Process all klasses. 4358 true); // Need to claim CLDs. 4359 // Weak roots closures. 4360 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp); 4361 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl, 4362 false, // Process all klasses. 4363 true); // Need to claim CLDs. 4364 4365 OopClosure* strong_root_cl; 4366 OopClosure* weak_root_cl; 4367 CLDClosure* strong_cld_cl; 4368 CLDClosure* weak_cld_cl; 4369 4370 bool trace_metadata = false; 4371 4372 if (_g1h->g1_policy()->during_initial_mark_pause()) { 4373 // We also need to mark copied objects. 4374 strong_root_cl = &scan_mark_root_cl; 4375 strong_cld_cl = &scan_mark_cld_cl; 4376 if (ClassUnloadingWithConcurrentMark) { 4377 weak_root_cl = &scan_mark_weak_root_cl; 4378 weak_cld_cl = &scan_mark_weak_cld_cl; 4379 trace_metadata = true; 4380 } else { 4381 weak_root_cl = &scan_mark_root_cl; 4382 weak_cld_cl = &scan_mark_cld_cl; 4383 } 4384 } else { 4385 strong_root_cl = &scan_only_root_cl; 4386 weak_root_cl = &scan_only_root_cl; 4387 strong_cld_cl = &scan_only_cld_cl; 4388 weak_cld_cl = &scan_only_cld_cl; 4389 } 4390 4391 pss.start_strong_roots(); 4392 4393 _root_processor->evacuate_roots(strong_root_cl, 4394 weak_root_cl, 4395 strong_cld_cl, 4396 weak_cld_cl, 4397 trace_metadata, 4398 worker_id); 4399 4400 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss); 4401 _root_processor->scan_remembered_sets(&push_heap_rs_cl, 4402 weak_root_cl, 4403 worker_id); 4404 pss.end_strong_roots(); 4405 4406 { 4407 double start = os::elapsedTime(); 4408 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator); 4409 evac.do_void(); 4410 double elapsed_sec = os::elapsedTime() - start; 4411 double term_sec = pss.term_time(); 4412 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 4413 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 4414 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, pss.term_attempts()); 4415 } 4416 _g1h->g1_policy()->record_thread_age_table(pss.age_table()); 4417 _g1h->update_surviving_young_words(pss.surviving_young_words()+1); 4418 4419 if (PrintTerminationStats) { 4420 MutexLocker x(stats_lock()); 4421 pss.print_termination_stats(worker_id); 4422 } 4423 4424 assert(pss.queue_is_empty(), "should be empty"); 4425 4426 // Close the inner scope so that the ResourceMark and HandleMark 4427 // destructors are executed here and are included as part of the 4428 // "GC Worker Time". 4429 } 4430 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 4431 } 4432 }; 4433 4434 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 4435 private: 4436 BoolObjectClosure* _is_alive; 4437 int _initial_string_table_size; 4438 int _initial_symbol_table_size; 4439 4440 bool _process_strings; 4441 int _strings_processed; 4442 int _strings_removed; 4443 4444 bool _process_symbols; 4445 int _symbols_processed; 4446 int _symbols_removed; 4447 4448 public: 4449 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 4450 AbstractGangTask("String/Symbol Unlinking"), 4451 _is_alive(is_alive), 4452 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 4453 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 4454 4455 _initial_string_table_size = StringTable::the_table()->table_size(); 4456 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 4457 if (process_strings) { 4458 StringTable::clear_parallel_claimed_index(); 4459 } 4460 if (process_symbols) { 4461 SymbolTable::clear_parallel_claimed_index(); 4462 } 4463 } 4464 4465 ~G1StringSymbolTableUnlinkTask() { 4466 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 4467 err_msg("claim value %d after unlink less than initial string table size %d", 4468 StringTable::parallel_claimed_index(), _initial_string_table_size)); 4469 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 4470 err_msg("claim value %d after unlink less than initial symbol table size %d", 4471 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size)); 4472 4473 if (G1TraceStringSymbolTableScrubbing) { 4474 gclog_or_tty->print_cr("Cleaned string and symbol table, " 4475 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, " 4476 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed", 4477 strings_processed(), strings_removed(), 4478 symbols_processed(), symbols_removed()); 4479 } 4480 } 4481 4482 void work(uint worker_id) { 4483 int strings_processed = 0; 4484 int strings_removed = 0; 4485 int symbols_processed = 0; 4486 int symbols_removed = 0; 4487 if (_process_strings) { 4488 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 4489 Atomic::add(strings_processed, &_strings_processed); 4490 Atomic::add(strings_removed, &_strings_removed); 4491 } 4492 if (_process_symbols) { 4493 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 4494 Atomic::add(symbols_processed, &_symbols_processed); 4495 Atomic::add(symbols_removed, &_symbols_removed); 4496 } 4497 } 4498 4499 size_t strings_processed() const { return (size_t)_strings_processed; } 4500 size_t strings_removed() const { return (size_t)_strings_removed; } 4501 4502 size_t symbols_processed() const { return (size_t)_symbols_processed; } 4503 size_t symbols_removed() const { return (size_t)_symbols_removed; } 4504 }; 4505 4506 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 4507 private: 4508 static Monitor* _lock; 4509 4510 BoolObjectClosure* const _is_alive; 4511 const bool _unloading_occurred; 4512 const uint _num_workers; 4513 4514 // Variables used to claim nmethods. 4515 nmethod* _first_nmethod; 4516 volatile nmethod* _claimed_nmethod; 4517 4518 // The list of nmethods that need to be processed by the second pass. 4519 volatile nmethod* _postponed_list; 4520 volatile uint _num_entered_barrier; 4521 4522 public: 4523 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 4524 _is_alive(is_alive), 4525 _unloading_occurred(unloading_occurred), 4526 _num_workers(num_workers), 4527 _first_nmethod(NULL), 4528 _claimed_nmethod(NULL), 4529 _postponed_list(NULL), 4530 _num_entered_barrier(0) 4531 { 4532 nmethod::increase_unloading_clock(); 4533 // Get first alive nmethod 4534 NMethodIterator iter = NMethodIterator(); 4535 if(iter.next_alive()) { 4536 _first_nmethod = iter.method(); 4537 } 4538 _claimed_nmethod = (volatile nmethod*)_first_nmethod; 4539 } 4540 4541 ~G1CodeCacheUnloadingTask() { 4542 CodeCache::verify_clean_inline_caches(); 4543 4544 CodeCache::set_needs_cache_clean(false); 4545 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 4546 4547 CodeCache::verify_icholder_relocations(); 4548 } 4549 4550 private: 4551 void add_to_postponed_list(nmethod* nm) { 4552 nmethod* old; 4553 do { 4554 old = (nmethod*)_postponed_list; 4555 nm->set_unloading_next(old); 4556 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 4557 } 4558 4559 void clean_nmethod(nmethod* nm) { 4560 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 4561 4562 if (postponed) { 4563 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 4564 add_to_postponed_list(nm); 4565 } 4566 4567 // Mark that this thread has been cleaned/unloaded. 4568 // After this call, it will be safe to ask if this nmethod was unloaded or not. 4569 nm->set_unloading_clock(nmethod::global_unloading_clock()); 4570 } 4571 4572 void clean_nmethod_postponed(nmethod* nm) { 4573 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 4574 } 4575 4576 static const int MaxClaimNmethods = 16; 4577 4578 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) { 4579 nmethod* first; 4580 NMethodIterator last; 4581 4582 do { 4583 *num_claimed_nmethods = 0; 4584 4585 first = (nmethod*)_claimed_nmethod; 4586 last = NMethodIterator(first); 4587 4588 if (first != NULL) { 4589 4590 for (int i = 0; i < MaxClaimNmethods; i++) { 4591 if (!last.next_alive()) { 4592 break; 4593 } 4594 claimed_nmethods[i] = last.method(); 4595 (*num_claimed_nmethods)++; 4596 } 4597 } 4598 4599 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 4600 } 4601 4602 nmethod* claim_postponed_nmethod() { 4603 nmethod* claim; 4604 nmethod* next; 4605 4606 do { 4607 claim = (nmethod*)_postponed_list; 4608 if (claim == NULL) { 4609 return NULL; 4610 } 4611 4612 next = claim->unloading_next(); 4613 4614 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 4615 4616 return claim; 4617 } 4618 4619 public: 4620 // Mark that we're done with the first pass of nmethod cleaning. 4621 void barrier_mark(uint worker_id) { 4622 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4623 _num_entered_barrier++; 4624 if (_num_entered_barrier == _num_workers) { 4625 ml.notify_all(); 4626 } 4627 } 4628 4629 // See if we have to wait for the other workers to 4630 // finish their first-pass nmethod cleaning work. 4631 void barrier_wait(uint worker_id) { 4632 if (_num_entered_barrier < _num_workers) { 4633 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4634 while (_num_entered_barrier < _num_workers) { 4635 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 4636 } 4637 } 4638 } 4639 4640 // Cleaning and unloading of nmethods. Some work has to be postponed 4641 // to the second pass, when we know which nmethods survive. 4642 void work_first_pass(uint worker_id) { 4643 // The first nmethods is claimed by the first worker. 4644 if (worker_id == 0 && _first_nmethod != NULL) { 4645 clean_nmethod(_first_nmethod); 4646 _first_nmethod = NULL; 4647 } 4648 4649 int num_claimed_nmethods; 4650 nmethod* claimed_nmethods[MaxClaimNmethods]; 4651 4652 while (true) { 4653 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 4654 4655 if (num_claimed_nmethods == 0) { 4656 break; 4657 } 4658 4659 for (int i = 0; i < num_claimed_nmethods; i++) { 4660 clean_nmethod(claimed_nmethods[i]); 4661 } 4662 } 4663 } 4664 4665 void work_second_pass(uint worker_id) { 4666 nmethod* nm; 4667 // Take care of postponed nmethods. 4668 while ((nm = claim_postponed_nmethod()) != NULL) { 4669 clean_nmethod_postponed(nm); 4670 } 4671 } 4672 }; 4673 4674 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 4675 4676 class G1KlassCleaningTask : public StackObj { 4677 BoolObjectClosure* _is_alive; 4678 volatile jint _clean_klass_tree_claimed; 4679 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 4680 4681 public: 4682 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 4683 _is_alive(is_alive), 4684 _clean_klass_tree_claimed(0), 4685 _klass_iterator() { 4686 } 4687 4688 private: 4689 bool claim_clean_klass_tree_task() { 4690 if (_clean_klass_tree_claimed) { 4691 return false; 4692 } 4693 4694 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 4695 } 4696 4697 InstanceKlass* claim_next_klass() { 4698 Klass* klass; 4699 do { 4700 klass =_klass_iterator.next_klass(); 4701 } while (klass != NULL && !klass->oop_is_instance()); 4702 4703 return (InstanceKlass*)klass; 4704 } 4705 4706 public: 4707 4708 void clean_klass(InstanceKlass* ik) { 4709 ik->clean_implementors_list(_is_alive); 4710 ik->clean_method_data(_is_alive); 4711 4712 // G1 specific cleanup work that has 4713 // been moved here to be done in parallel. 4714 ik->clean_dependent_nmethods(); 4715 } 4716 4717 void work() { 4718 ResourceMark rm; 4719 4720 // One worker will clean the subklass/sibling klass tree. 4721 if (claim_clean_klass_tree_task()) { 4722 Klass::clean_subklass_tree(_is_alive); 4723 } 4724 4725 // All workers will help cleaning the classes, 4726 InstanceKlass* klass; 4727 while ((klass = claim_next_klass()) != NULL) { 4728 clean_klass(klass); 4729 } 4730 } 4731 }; 4732 4733 // To minimize the remark pause times, the tasks below are done in parallel. 4734 class G1ParallelCleaningTask : public AbstractGangTask { 4735 private: 4736 G1StringSymbolTableUnlinkTask _string_symbol_task; 4737 G1CodeCacheUnloadingTask _code_cache_task; 4738 G1KlassCleaningTask _klass_cleaning_task; 4739 4740 public: 4741 // The constructor is run in the VMThread. 4742 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 4743 AbstractGangTask("Parallel Cleaning"), 4744 _string_symbol_task(is_alive, process_strings, process_symbols), 4745 _code_cache_task(num_workers, is_alive, unloading_occurred), 4746 _klass_cleaning_task(is_alive) { 4747 } 4748 4749 // The parallel work done by all worker threads. 4750 void work(uint worker_id) { 4751 // Do first pass of code cache cleaning. 4752 _code_cache_task.work_first_pass(worker_id); 4753 4754 // Let the threads mark that the first pass is done. 4755 _code_cache_task.barrier_mark(worker_id); 4756 4757 // Clean the Strings and Symbols. 4758 _string_symbol_task.work(worker_id); 4759 4760 // Wait for all workers to finish the first code cache cleaning pass. 4761 _code_cache_task.barrier_wait(worker_id); 4762 4763 // Do the second code cache cleaning work, which realize on 4764 // the liveness information gathered during the first pass. 4765 _code_cache_task.work_second_pass(worker_id); 4766 4767 // Clean all klasses that were not unloaded. 4768 _klass_cleaning_task.work(); 4769 } 4770 }; 4771 4772 4773 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 4774 bool process_strings, 4775 bool process_symbols, 4776 bool class_unloading_occurred) { 4777 uint n_workers = workers()->active_workers(); 4778 4779 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 4780 n_workers, class_unloading_occurred); 4781 workers()->run_task(&g1_unlink_task); 4782 } 4783 4784 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 4785 bool process_strings, bool process_symbols) { 4786 { 4787 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 4788 workers()->run_task(&g1_unlink_task); 4789 } 4790 4791 if (G1StringDedup::is_enabled()) { 4792 G1StringDedup::unlink(is_alive); 4793 } 4794 } 4795 4796 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 4797 private: 4798 DirtyCardQueueSet* _queue; 4799 public: 4800 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { } 4801 4802 virtual void work(uint worker_id) { 4803 G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4804 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 4805 4806 RedirtyLoggedCardTableEntryClosure cl; 4807 _queue->par_apply_closure_to_all_completed_buffers(&cl); 4808 4809 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed()); 4810 } 4811 }; 4812 4813 void G1CollectedHeap::redirty_logged_cards() { 4814 double redirty_logged_cards_start = os::elapsedTime(); 4815 4816 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set()); 4817 dirty_card_queue_set().reset_for_par_iteration(); 4818 workers()->run_task(&redirty_task); 4819 4820 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 4821 dcq.merge_bufferlists(&dirty_card_queue_set()); 4822 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 4823 4824 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 4825 } 4826 4827 // Weak Reference Processing support 4828 4829 // An always "is_alive" closure that is used to preserve referents. 4830 // If the object is non-null then it's alive. Used in the preservation 4831 // of referent objects that are pointed to by reference objects 4832 // discovered by the CM ref processor. 4833 class G1AlwaysAliveClosure: public BoolObjectClosure { 4834 G1CollectedHeap* _g1; 4835 public: 4836 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4837 bool do_object_b(oop p) { 4838 if (p != NULL) { 4839 return true; 4840 } 4841 return false; 4842 } 4843 }; 4844 4845 bool G1STWIsAliveClosure::do_object_b(oop p) { 4846 // An object is reachable if it is outside the collection set, 4847 // or is inside and copied. 4848 return !_g1->obj_in_cs(p) || p->is_forwarded(); 4849 } 4850 4851 // Non Copying Keep Alive closure 4852 class G1KeepAliveClosure: public OopClosure { 4853 G1CollectedHeap* _g1; 4854 public: 4855 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4856 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 4857 void do_oop(oop* p) { 4858 oop obj = *p; 4859 assert(obj != NULL, "the caller should have filtered out NULL values"); 4860 4861 const InCSetState cset_state = _g1->in_cset_state(obj); 4862 if (!cset_state.is_in_cset_or_humongous()) { 4863 return; 4864 } 4865 if (cset_state.is_in_cset()) { 4866 assert( obj->is_forwarded(), "invariant" ); 4867 *p = obj->forwardee(); 4868 } else { 4869 assert(!obj->is_forwarded(), "invariant" ); 4870 assert(cset_state.is_humongous(), 4871 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state.value())); 4872 _g1->set_humongous_is_live(obj); 4873 } 4874 } 4875 }; 4876 4877 // Copying Keep Alive closure - can be called from both 4878 // serial and parallel code as long as different worker 4879 // threads utilize different G1ParScanThreadState instances 4880 // and different queues. 4881 4882 class G1CopyingKeepAliveClosure: public OopClosure { 4883 G1CollectedHeap* _g1h; 4884 OopClosure* _copy_non_heap_obj_cl; 4885 G1ParScanThreadState* _par_scan_state; 4886 4887 public: 4888 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4889 OopClosure* non_heap_obj_cl, 4890 G1ParScanThreadState* pss): 4891 _g1h(g1h), 4892 _copy_non_heap_obj_cl(non_heap_obj_cl), 4893 _par_scan_state(pss) 4894 {} 4895 4896 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4897 virtual void do_oop( oop* p) { do_oop_work(p); } 4898 4899 template <class T> void do_oop_work(T* p) { 4900 oop obj = oopDesc::load_decode_heap_oop(p); 4901 4902 if (_g1h->is_in_cset_or_humongous(obj)) { 4903 // If the referent object has been forwarded (either copied 4904 // to a new location or to itself in the event of an 4905 // evacuation failure) then we need to update the reference 4906 // field and, if both reference and referent are in the G1 4907 // heap, update the RSet for the referent. 4908 // 4909 // If the referent has not been forwarded then we have to keep 4910 // it alive by policy. Therefore we have copy the referent. 4911 // 4912 // If the reference field is in the G1 heap then we can push 4913 // on the PSS queue. When the queue is drained (after each 4914 // phase of reference processing) the object and it's followers 4915 // will be copied, the reference field set to point to the 4916 // new location, and the RSet updated. Otherwise we need to 4917 // use the the non-heap or metadata closures directly to copy 4918 // the referent object and update the pointer, while avoiding 4919 // updating the RSet. 4920 4921 if (_g1h->is_in_g1_reserved(p)) { 4922 _par_scan_state->push_on_queue(p); 4923 } else { 4924 assert(!Metaspace::contains((const void*)p), 4925 err_msg("Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p))); 4926 _copy_non_heap_obj_cl->do_oop(p); 4927 } 4928 } 4929 } 4930 }; 4931 4932 // Serial drain queue closure. Called as the 'complete_gc' 4933 // closure for each discovered list in some of the 4934 // reference processing phases. 4935 4936 class G1STWDrainQueueClosure: public VoidClosure { 4937 protected: 4938 G1CollectedHeap* _g1h; 4939 G1ParScanThreadState* _par_scan_state; 4940 4941 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4942 4943 public: 4944 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4945 _g1h(g1h), 4946 _par_scan_state(pss) 4947 { } 4948 4949 void do_void() { 4950 G1ParScanThreadState* const pss = par_scan_state(); 4951 pss->trim_queue(); 4952 } 4953 }; 4954 4955 // Parallel Reference Processing closures 4956 4957 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4958 // processing during G1 evacuation pauses. 4959 4960 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4961 private: 4962 G1CollectedHeap* _g1h; 4963 RefToScanQueueSet* _queues; 4964 FlexibleWorkGang* _workers; 4965 uint _active_workers; 4966 4967 public: 4968 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4969 FlexibleWorkGang* workers, 4970 RefToScanQueueSet *task_queues, 4971 uint n_workers) : 4972 _g1h(g1h), 4973 _queues(task_queues), 4974 _workers(workers), 4975 _active_workers(n_workers) 4976 { 4977 assert(n_workers > 0, "shouldn't call this otherwise"); 4978 } 4979 4980 // Executes the given task using concurrent marking worker threads. 4981 virtual void execute(ProcessTask& task); 4982 virtual void execute(EnqueueTask& task); 4983 }; 4984 4985 // Gang task for possibly parallel reference processing 4986 4987 class G1STWRefProcTaskProxy: public AbstractGangTask { 4988 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4989 ProcessTask& _proc_task; 4990 G1CollectedHeap* _g1h; 4991 RefToScanQueueSet *_task_queues; 4992 ParallelTaskTerminator* _terminator; 4993 4994 public: 4995 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4996 G1CollectedHeap* g1h, 4997 RefToScanQueueSet *task_queues, 4998 ParallelTaskTerminator* terminator) : 4999 AbstractGangTask("Process reference objects in parallel"), 5000 _proc_task(proc_task), 5001 _g1h(g1h), 5002 _task_queues(task_queues), 5003 _terminator(terminator) 5004 {} 5005 5006 virtual void work(uint worker_id) { 5007 // The reference processing task executed by a single worker. 5008 ResourceMark rm; 5009 HandleMark hm; 5010 5011 G1STWIsAliveClosure is_alive(_g1h); 5012 5013 G1ParScanThreadState pss(_g1h, worker_id, NULL); 5014 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5015 5016 pss.set_evac_failure_closure(&evac_failure_cl); 5017 5018 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5019 5020 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5021 5022 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5023 5024 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5025 // We also need to mark copied objects. 5026 copy_non_heap_cl = ©_mark_non_heap_cl; 5027 } 5028 5029 // Keep alive closure. 5030 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss); 5031 5032 // Complete GC closure 5033 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator); 5034 5035 // Call the reference processing task's work routine. 5036 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 5037 5038 // Note we cannot assert that the refs array is empty here as not all 5039 // of the processing tasks (specifically phase2 - pp2_work) execute 5040 // the complete_gc closure (which ordinarily would drain the queue) so 5041 // the queue may not be empty. 5042 } 5043 }; 5044 5045 // Driver routine for parallel reference processing. 5046 // Creates an instance of the ref processing gang 5047 // task and has the worker threads execute it. 5048 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 5049 assert(_workers != NULL, "Need parallel worker threads."); 5050 5051 ParallelTaskTerminator terminator(_active_workers, _queues); 5052 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator); 5053 5054 _workers->run_task(&proc_task_proxy); 5055 } 5056 5057 // Gang task for parallel reference enqueueing. 5058 5059 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 5060 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 5061 EnqueueTask& _enq_task; 5062 5063 public: 5064 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 5065 AbstractGangTask("Enqueue reference objects in parallel"), 5066 _enq_task(enq_task) 5067 { } 5068 5069 virtual void work(uint worker_id) { 5070 _enq_task.work(worker_id); 5071 } 5072 }; 5073 5074 // Driver routine for parallel reference enqueueing. 5075 // Creates an instance of the ref enqueueing gang 5076 // task and has the worker threads execute it. 5077 5078 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 5079 assert(_workers != NULL, "Need parallel worker threads."); 5080 5081 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 5082 5083 _workers->run_task(&enq_task_proxy); 5084 } 5085 5086 // End of weak reference support closures 5087 5088 // Abstract task used to preserve (i.e. copy) any referent objects 5089 // that are in the collection set and are pointed to by reference 5090 // objects discovered by the CM ref processor. 5091 5092 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 5093 protected: 5094 G1CollectedHeap* _g1h; 5095 RefToScanQueueSet *_queues; 5096 ParallelTaskTerminator _terminator; 5097 uint _n_workers; 5098 5099 public: 5100 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, uint workers, RefToScanQueueSet *task_queues) : 5101 AbstractGangTask("ParPreserveCMReferents"), 5102 _g1h(g1h), 5103 _queues(task_queues), 5104 _terminator(workers, _queues), 5105 _n_workers(workers) 5106 { } 5107 5108 void work(uint worker_id) { 5109 ResourceMark rm; 5110 HandleMark hm; 5111 5112 G1ParScanThreadState pss(_g1h, worker_id, NULL); 5113 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5114 5115 pss.set_evac_failure_closure(&evac_failure_cl); 5116 5117 assert(pss.queue_is_empty(), "both queue and overflow should be empty"); 5118 5119 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5120 5121 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5122 5123 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5124 5125 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5126 // We also need to mark copied objects. 5127 copy_non_heap_cl = ©_mark_non_heap_cl; 5128 } 5129 5130 // Is alive closure 5131 G1AlwaysAliveClosure always_alive(_g1h); 5132 5133 // Copying keep alive closure. Applied to referent objects that need 5134 // to be copied. 5135 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss); 5136 5137 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 5138 5139 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 5140 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 5141 5142 // limit is set using max_num_q() - which was set using ParallelGCThreads. 5143 // So this must be true - but assert just in case someone decides to 5144 // change the worker ids. 5145 assert(worker_id < limit, "sanity"); 5146 assert(!rp->discovery_is_atomic(), "check this code"); 5147 5148 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 5149 for (uint idx = worker_id; idx < limit; idx += stride) { 5150 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 5151 5152 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 5153 while (iter.has_next()) { 5154 // Since discovery is not atomic for the CM ref processor, we 5155 // can see some null referent objects. 5156 iter.load_ptrs(DEBUG_ONLY(true)); 5157 oop ref = iter.obj(); 5158 5159 // This will filter nulls. 5160 if (iter.is_referent_alive()) { 5161 iter.make_referent_alive(); 5162 } 5163 iter.move_to_next(); 5164 } 5165 } 5166 5167 // Drain the queue - which may cause stealing 5168 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator); 5169 drain_queue.do_void(); 5170 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 5171 assert(pss.queue_is_empty(), "should be"); 5172 } 5173 }; 5174 5175 // Weak Reference processing during an evacuation pause (part 1). 5176 void G1CollectedHeap::process_discovered_references() { 5177 double ref_proc_start = os::elapsedTime(); 5178 5179 ReferenceProcessor* rp = _ref_processor_stw; 5180 assert(rp->discovery_enabled(), "should have been enabled"); 5181 5182 // Any reference objects, in the collection set, that were 'discovered' 5183 // by the CM ref processor should have already been copied (either by 5184 // applying the external root copy closure to the discovered lists, or 5185 // by following an RSet entry). 5186 // 5187 // But some of the referents, that are in the collection set, that these 5188 // reference objects point to may not have been copied: the STW ref 5189 // processor would have seen that the reference object had already 5190 // been 'discovered' and would have skipped discovering the reference, 5191 // but would not have treated the reference object as a regular oop. 5192 // As a result the copy closure would not have been applied to the 5193 // referent object. 5194 // 5195 // We need to explicitly copy these referent objects - the references 5196 // will be processed at the end of remarking. 5197 // 5198 // We also need to do this copying before we process the reference 5199 // objects discovered by the STW ref processor in case one of these 5200 // referents points to another object which is also referenced by an 5201 // object discovered by the STW ref processor. 5202 5203 uint no_of_gc_workers = workers()->active_workers(); 5204 5205 G1ParPreserveCMReferentsTask keep_cm_referents(this, 5206 no_of_gc_workers, 5207 _task_queues); 5208 5209 workers()->run_task(&keep_cm_referents); 5210 5211 // Closure to test whether a referent is alive. 5212 G1STWIsAliveClosure is_alive(this); 5213 5214 // Even when parallel reference processing is enabled, the processing 5215 // of JNI refs is serial and performed serially by the current thread 5216 // rather than by a worker. The following PSS will be used for processing 5217 // JNI refs. 5218 5219 // Use only a single queue for this PSS. 5220 G1ParScanThreadState pss(this, 0, NULL); 5221 5222 // We do not embed a reference processor in the copying/scanning 5223 // closures while we're actually processing the discovered 5224 // reference objects. 5225 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL); 5226 5227 pss.set_evac_failure_closure(&evac_failure_cl); 5228 5229 assert(pss.queue_is_empty(), "pre-condition"); 5230 5231 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL); 5232 5233 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL); 5234 5235 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5236 5237 if (g1_policy()->during_initial_mark_pause()) { 5238 // We also need to mark copied objects. 5239 copy_non_heap_cl = ©_mark_non_heap_cl; 5240 } 5241 5242 // Keep alive closure. 5243 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss); 5244 5245 // Serial Complete GC closure 5246 G1STWDrainQueueClosure drain_queue(this, &pss); 5247 5248 // Setup the soft refs policy... 5249 rp->setup_policy(false); 5250 5251 ReferenceProcessorStats stats; 5252 if (!rp->processing_is_mt()) { 5253 // Serial reference processing... 5254 stats = rp->process_discovered_references(&is_alive, 5255 &keep_alive, 5256 &drain_queue, 5257 NULL, 5258 _gc_timer_stw, 5259 _gc_tracer_stw->gc_id()); 5260 } else { 5261 // Parallel reference processing 5262 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5263 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5264 5265 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5266 stats = rp->process_discovered_references(&is_alive, 5267 &keep_alive, 5268 &drain_queue, 5269 &par_task_executor, 5270 _gc_timer_stw, 5271 _gc_tracer_stw->gc_id()); 5272 } 5273 5274 _gc_tracer_stw->report_gc_reference_stats(stats); 5275 5276 // We have completed copying any necessary live referent objects. 5277 assert(pss.queue_is_empty(), "both queue and overflow should be empty"); 5278 5279 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5280 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 5281 } 5282 5283 // Weak Reference processing during an evacuation pause (part 2). 5284 void G1CollectedHeap::enqueue_discovered_references() { 5285 double ref_enq_start = os::elapsedTime(); 5286 5287 ReferenceProcessor* rp = _ref_processor_stw; 5288 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5289 5290 // Now enqueue any remaining on the discovered lists on to 5291 // the pending list. 5292 if (!rp->processing_is_mt()) { 5293 // Serial reference processing... 5294 rp->enqueue_discovered_references(); 5295 } else { 5296 // Parallel reference enqueueing 5297 5298 uint n_workers = workers()->active_workers(); 5299 5300 assert(rp->num_q() == n_workers, "sanity"); 5301 assert(n_workers <= rp->max_num_q(), "sanity"); 5302 5303 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, n_workers); 5304 rp->enqueue_discovered_references(&par_task_executor); 5305 } 5306 5307 rp->verify_no_references_recorded(); 5308 assert(!rp->discovery_enabled(), "should have been disabled"); 5309 5310 // FIXME 5311 // CM's reference processing also cleans up the string and symbol tables. 5312 // Should we do that here also? We could, but it is a serial operation 5313 // and could significantly increase the pause time. 5314 5315 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5316 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5317 } 5318 5319 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) { 5320 _expand_heap_after_alloc_failure = true; 5321 _evacuation_failed = false; 5322 5323 // Should G1EvacuationFailureALot be in effect for this GC? 5324 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5325 5326 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5327 5328 // Disable the hot card cache. 5329 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5330 hot_card_cache->reset_hot_cache_claimed_index(); 5331 hot_card_cache->set_use_cache(false); 5332 5333 const uint n_workers = workers()->active_workers(); 5334 5335 init_for_evac_failure(NULL); 5336 5337 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5338 double start_par_time_sec = os::elapsedTime(); 5339 double end_par_time_sec; 5340 5341 { 5342 G1RootProcessor root_processor(this, n_workers); 5343 G1ParTask g1_par_task(this, _task_queues, &root_processor, n_workers); 5344 // InitialMark needs claim bits to keep track of the marked-through CLDs. 5345 if (g1_policy()->during_initial_mark_pause()) { 5346 ClassLoaderDataGraph::clear_claimed_marks(); 5347 } 5348 5349 // The individual threads will set their evac-failure closures. 5350 if (PrintTerminationStats) G1ParScanThreadState::print_termination_stats_hdr(); 5351 5352 workers()->run_task(&g1_par_task); 5353 end_par_time_sec = os::elapsedTime(); 5354 5355 // Closing the inner scope will execute the destructor 5356 // for the G1RootProcessor object. We record the current 5357 // elapsed time before closing the scope so that time 5358 // taken for the destructor is NOT included in the 5359 // reported parallel time. 5360 } 5361 5362 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 5363 5364 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5365 phase_times->record_par_time(par_time_ms); 5366 5367 double code_root_fixup_time_ms = 5368 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5369 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 5370 5371 // Process any discovered reference objects - we have 5372 // to do this _before_ we retire the GC alloc regions 5373 // as we may have to copy some 'reachable' referent 5374 // objects (and their reachable sub-graphs) that were 5375 // not copied during the pause. 5376 process_discovered_references(); 5377 5378 if (G1StringDedup::is_enabled()) { 5379 double fixup_start = os::elapsedTime(); 5380 5381 G1STWIsAliveClosure is_alive(this); 5382 G1KeepAliveClosure keep_alive(this); 5383 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times); 5384 5385 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 5386 phase_times->record_string_dedup_fixup_time(fixup_time_ms); 5387 } 5388 5389 _allocator->release_gc_alloc_regions(n_workers, evacuation_info); 5390 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5391 5392 // Reset and re-enable the hot card cache. 5393 // Note the counts for the cards in the regions in the 5394 // collection set are reset when the collection set is freed. 5395 hot_card_cache->reset_hot_cache(); 5396 hot_card_cache->set_use_cache(true); 5397 5398 purge_code_root_memory(); 5399 5400 finalize_for_evac_failure(); 5401 5402 if (evacuation_failed()) { 5403 remove_self_forwarding_pointers(); 5404 5405 // Reset the G1EvacuationFailureALot counters and flags 5406 // Note: the values are reset only when an actual 5407 // evacuation failure occurs. 5408 NOT_PRODUCT(reset_evacuation_should_fail();) 5409 } 5410 5411 // Enqueue any remaining references remaining on the STW 5412 // reference processor's discovered lists. We need to do 5413 // this after the card table is cleaned (and verified) as 5414 // the act of enqueueing entries on to the pending list 5415 // will log these updates (and dirty their associated 5416 // cards). We need these updates logged to update any 5417 // RSets. 5418 enqueue_discovered_references(); 5419 5420 redirty_logged_cards(); 5421 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 5422 } 5423 5424 void G1CollectedHeap::free_region(HeapRegion* hr, 5425 FreeRegionList* free_list, 5426 bool par, 5427 bool locked) { 5428 assert(!hr->is_free(), "the region should not be free"); 5429 assert(!hr->is_empty(), "the region should not be empty"); 5430 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 5431 assert(free_list != NULL, "pre-condition"); 5432 5433 if (G1VerifyBitmaps) { 5434 MemRegion mr(hr->bottom(), hr->end()); 5435 concurrent_mark()->clearRangePrevBitmap(mr); 5436 } 5437 5438 // Clear the card counts for this region. 5439 // Note: we only need to do this if the region is not young 5440 // (since we don't refine cards in young regions). 5441 if (!hr->is_young()) { 5442 _cg1r->hot_card_cache()->reset_card_counts(hr); 5443 } 5444 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 5445 free_list->add_ordered(hr); 5446 } 5447 5448 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5449 FreeRegionList* free_list, 5450 bool par) { 5451 assert(hr->is_starts_humongous(), "this is only for starts humongous regions"); 5452 assert(free_list != NULL, "pre-condition"); 5453 5454 size_t hr_capacity = hr->capacity(); 5455 // We need to read this before we make the region non-humongous, 5456 // otherwise the information will be gone. 5457 uint last_index = hr->last_hc_index(); 5458 hr->clear_humongous(); 5459 free_region(hr, free_list, par); 5460 5461 uint i = hr->hrm_index() + 1; 5462 while (i < last_index) { 5463 HeapRegion* curr_hr = region_at(i); 5464 assert(curr_hr->is_continues_humongous(), "invariant"); 5465 curr_hr->clear_humongous(); 5466 free_region(curr_hr, free_list, par); 5467 i += 1; 5468 } 5469 } 5470 5471 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, 5472 const HeapRegionSetCount& humongous_regions_removed) { 5473 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) { 5474 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5475 _old_set.bulk_remove(old_regions_removed); 5476 _humongous_set.bulk_remove(humongous_regions_removed); 5477 } 5478 5479 } 5480 5481 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 5482 assert(list != NULL, "list can't be null"); 5483 if (!list->is_empty()) { 5484 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 5485 _hrm.insert_list_into_free_list(list); 5486 } 5487 } 5488 5489 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 5490 _allocator->decrease_used(bytes); 5491 } 5492 5493 class G1ParCleanupCTTask : public AbstractGangTask { 5494 G1SATBCardTableModRefBS* _ct_bs; 5495 G1CollectedHeap* _g1h; 5496 HeapRegion* volatile _su_head; 5497 public: 5498 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 5499 G1CollectedHeap* g1h) : 5500 AbstractGangTask("G1 Par Cleanup CT Task"), 5501 _ct_bs(ct_bs), _g1h(g1h) { } 5502 5503 void work(uint worker_id) { 5504 HeapRegion* r; 5505 while (r = _g1h->pop_dirty_cards_region()) { 5506 clear_cards(r); 5507 } 5508 } 5509 5510 void clear_cards(HeapRegion* r) { 5511 // Cards of the survivors should have already been dirtied. 5512 if (!r->is_survivor()) { 5513 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 5514 } 5515 } 5516 }; 5517 5518 #ifndef PRODUCT 5519 class G1VerifyCardTableCleanup: public HeapRegionClosure { 5520 G1CollectedHeap* _g1h; 5521 G1SATBCardTableModRefBS* _ct_bs; 5522 public: 5523 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs) 5524 : _g1h(g1h), _ct_bs(ct_bs) { } 5525 virtual bool doHeapRegion(HeapRegion* r) { 5526 if (r->is_survivor()) { 5527 _g1h->verify_dirty_region(r); 5528 } else { 5529 _g1h->verify_not_dirty_region(r); 5530 } 5531 return false; 5532 } 5533 }; 5534 5535 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 5536 // All of the region should be clean. 5537 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5538 MemRegion mr(hr->bottom(), hr->end()); 5539 ct_bs->verify_not_dirty_region(mr); 5540 } 5541 5542 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 5543 // We cannot guarantee that [bottom(),end()] is dirty. Threads 5544 // dirty allocated blocks as they allocate them. The thread that 5545 // retires each region and replaces it with a new one will do a 5546 // maximal allocation to fill in [pre_dummy_top(),end()] but will 5547 // not dirty that area (one less thing to have to do while holding 5548 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 5549 // is dirty. 5550 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5551 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 5552 if (hr->is_young()) { 5553 ct_bs->verify_g1_young_region(mr); 5554 } else { 5555 ct_bs->verify_dirty_region(mr); 5556 } 5557 } 5558 5559 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 5560 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5561 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 5562 verify_dirty_region(hr); 5563 } 5564 } 5565 5566 void G1CollectedHeap::verify_dirty_young_regions() { 5567 verify_dirty_young_list(_young_list->first_region()); 5568 } 5569 5570 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 5571 HeapWord* tams, HeapWord* end) { 5572 guarantee(tams <= end, 5573 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, p2i(tams), p2i(end))); 5574 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end); 5575 if (result < end) { 5576 gclog_or_tty->cr(); 5577 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT, 5578 bitmap_name, p2i(result)); 5579 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT, 5580 bitmap_name, p2i(tams), p2i(end)); 5581 return false; 5582 } 5583 return true; 5584 } 5585 5586 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) { 5587 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap(); 5588 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap(); 5589 5590 HeapWord* bottom = hr->bottom(); 5591 HeapWord* ptams = hr->prev_top_at_mark_start(); 5592 HeapWord* ntams = hr->next_top_at_mark_start(); 5593 HeapWord* end = hr->end(); 5594 5595 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end); 5596 5597 bool res_n = true; 5598 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window 5599 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap 5600 // if we happen to be in that state. 5601 if (mark_in_progress() || !_cmThread->in_progress()) { 5602 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end); 5603 } 5604 if (!res_p || !res_n) { 5605 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT, 5606 HR_FORMAT_PARAMS(hr)); 5607 gclog_or_tty->print_cr("#### Caller: %s", caller); 5608 return false; 5609 } 5610 return true; 5611 } 5612 5613 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) { 5614 if (!G1VerifyBitmaps) return; 5615 5616 guarantee(verify_bitmaps(caller, hr), "bitmap verification"); 5617 } 5618 5619 class G1VerifyBitmapClosure : public HeapRegionClosure { 5620 private: 5621 const char* _caller; 5622 G1CollectedHeap* _g1h; 5623 bool _failures; 5624 5625 public: 5626 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) : 5627 _caller(caller), _g1h(g1h), _failures(false) { } 5628 5629 bool failures() { return _failures; } 5630 5631 virtual bool doHeapRegion(HeapRegion* hr) { 5632 if (hr->is_continues_humongous()) return false; 5633 5634 bool result = _g1h->verify_bitmaps(_caller, hr); 5635 if (!result) { 5636 _failures = true; 5637 } 5638 return false; 5639 } 5640 }; 5641 5642 void G1CollectedHeap::check_bitmaps(const char* caller) { 5643 if (!G1VerifyBitmaps) return; 5644 5645 G1VerifyBitmapClosure cl(caller, this); 5646 heap_region_iterate(&cl); 5647 guarantee(!cl.failures(), "bitmap verification"); 5648 } 5649 5650 class G1CheckCSetFastTableClosure : public HeapRegionClosure { 5651 private: 5652 bool _failures; 5653 public: 5654 G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { } 5655 5656 virtual bool doHeapRegion(HeapRegion* hr) { 5657 uint i = hr->hrm_index(); 5658 InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i); 5659 if (hr->is_humongous()) { 5660 if (hr->in_collection_set()) { 5661 gclog_or_tty->print_cr("\n## humongous region %u in CSet", i); 5662 _failures = true; 5663 return true; 5664 } 5665 if (cset_state.is_in_cset()) { 5666 gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i); 5667 _failures = true; 5668 return true; 5669 } 5670 if (hr->is_continues_humongous() && cset_state.is_humongous()) { 5671 gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i); 5672 _failures = true; 5673 return true; 5674 } 5675 } else { 5676 if (cset_state.is_humongous()) { 5677 gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i); 5678 _failures = true; 5679 return true; 5680 } 5681 if (hr->in_collection_set() != cset_state.is_in_cset()) { 5682 gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u", 5683 hr->in_collection_set(), cset_state.value(), i); 5684 _failures = true; 5685 return true; 5686 } 5687 if (cset_state.is_in_cset()) { 5688 if (hr->is_young() != (cset_state.is_young())) { 5689 gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u", 5690 hr->is_young(), cset_state.value(), i); 5691 _failures = true; 5692 return true; 5693 } 5694 if (hr->is_old() != (cset_state.is_old())) { 5695 gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u", 5696 hr->is_old(), cset_state.value(), i); 5697 _failures = true; 5698 return true; 5699 } 5700 } 5701 } 5702 return false; 5703 } 5704 5705 bool failures() const { return _failures; } 5706 }; 5707 5708 bool G1CollectedHeap::check_cset_fast_test() { 5709 G1CheckCSetFastTableClosure cl; 5710 _hrm.iterate(&cl); 5711 return !cl.failures(); 5712 } 5713 #endif // PRODUCT 5714 5715 void G1CollectedHeap::cleanUpCardTable() { 5716 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5717 double start = os::elapsedTime(); 5718 5719 { 5720 // Iterate over the dirty cards region list. 5721 G1ParCleanupCTTask cleanup_task(ct_bs, this); 5722 5723 workers()->run_task(&cleanup_task); 5724 #ifndef PRODUCT 5725 if (G1VerifyCTCleanup || VerifyAfterGC) { 5726 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 5727 heap_region_iterate(&cleanup_verifier); 5728 } 5729 #endif 5730 } 5731 5732 double elapsed = os::elapsedTime() - start; 5733 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 5734 } 5735 5736 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) { 5737 size_t pre_used = 0; 5738 FreeRegionList local_free_list("Local List for CSet Freeing"); 5739 5740 double young_time_ms = 0.0; 5741 double non_young_time_ms = 0.0; 5742 5743 // Since the collection set is a superset of the the young list, 5744 // all we need to do to clear the young list is clear its 5745 // head and length, and unlink any young regions in the code below 5746 _young_list->clear(); 5747 5748 G1CollectorPolicy* policy = g1_policy(); 5749 5750 double start_sec = os::elapsedTime(); 5751 bool non_young = true; 5752 5753 HeapRegion* cur = cs_head; 5754 int age_bound = -1; 5755 size_t rs_lengths = 0; 5756 5757 while (cur != NULL) { 5758 assert(!is_on_master_free_list(cur), "sanity"); 5759 if (non_young) { 5760 if (cur->is_young()) { 5761 double end_sec = os::elapsedTime(); 5762 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5763 non_young_time_ms += elapsed_ms; 5764 5765 start_sec = os::elapsedTime(); 5766 non_young = false; 5767 } 5768 } else { 5769 if (!cur->is_young()) { 5770 double end_sec = os::elapsedTime(); 5771 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5772 young_time_ms += elapsed_ms; 5773 5774 start_sec = os::elapsedTime(); 5775 non_young = true; 5776 } 5777 } 5778 5779 rs_lengths += cur->rem_set()->occupied_locked(); 5780 5781 HeapRegion* next = cur->next_in_collection_set(); 5782 assert(cur->in_collection_set(), "bad CS"); 5783 cur->set_next_in_collection_set(NULL); 5784 clear_in_cset(cur); 5785 5786 if (cur->is_young()) { 5787 int index = cur->young_index_in_cset(); 5788 assert(index != -1, "invariant"); 5789 assert((uint) index < policy->young_cset_region_length(), "invariant"); 5790 size_t words_survived = _surviving_young_words[index]; 5791 cur->record_surv_words_in_group(words_survived); 5792 5793 // At this point the we have 'popped' cur from the collection set 5794 // (linked via next_in_collection_set()) but it is still in the 5795 // young list (linked via next_young_region()). Clear the 5796 // _next_young_region field. 5797 cur->set_next_young_region(NULL); 5798 } else { 5799 int index = cur->young_index_in_cset(); 5800 assert(index == -1, "invariant"); 5801 } 5802 5803 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 5804 (!cur->is_young() && cur->young_index_in_cset() == -1), 5805 "invariant" ); 5806 5807 if (!cur->evacuation_failed()) { 5808 MemRegion used_mr = cur->used_region(); 5809 5810 // And the region is empty. 5811 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 5812 pre_used += cur->used(); 5813 free_region(cur, &local_free_list, false /* par */, true /* locked */); 5814 } else { 5815 cur->uninstall_surv_rate_group(); 5816 if (cur->is_young()) { 5817 cur->set_young_index_in_cset(-1); 5818 } 5819 cur->set_evacuation_failed(false); 5820 // The region is now considered to be old. 5821 cur->set_old(); 5822 _old_set.add(cur); 5823 evacuation_info.increment_collectionset_used_after(cur->used()); 5824 } 5825 cur = next; 5826 } 5827 5828 evacuation_info.set_regions_freed(local_free_list.length()); 5829 policy->record_max_rs_lengths(rs_lengths); 5830 policy->cset_regions_freed(); 5831 5832 double end_sec = os::elapsedTime(); 5833 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5834 5835 if (non_young) { 5836 non_young_time_ms += elapsed_ms; 5837 } else { 5838 young_time_ms += elapsed_ms; 5839 } 5840 5841 prepend_to_freelist(&local_free_list); 5842 decrement_summary_bytes(pre_used); 5843 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 5844 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 5845 } 5846 5847 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 5848 private: 5849 FreeRegionList* _free_region_list; 5850 HeapRegionSet* _proxy_set; 5851 HeapRegionSetCount _humongous_regions_removed; 5852 size_t _freed_bytes; 5853 public: 5854 5855 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 5856 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) { 5857 } 5858 5859 virtual bool doHeapRegion(HeapRegion* r) { 5860 if (!r->is_starts_humongous()) { 5861 return false; 5862 } 5863 5864 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 5865 5866 oop obj = (oop)r->bottom(); 5867 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 5868 5869 // The following checks whether the humongous object is live are sufficient. 5870 // The main additional check (in addition to having a reference from the roots 5871 // or the young gen) is whether the humongous object has a remembered set entry. 5872 // 5873 // A humongous object cannot be live if there is no remembered set for it 5874 // because: 5875 // - there can be no references from within humongous starts regions referencing 5876 // the object because we never allocate other objects into them. 5877 // (I.e. there are no intra-region references that may be missed by the 5878 // remembered set) 5879 // - as soon there is a remembered set entry to the humongous starts region 5880 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 5881 // until the end of a concurrent mark. 5882 // 5883 // It is not required to check whether the object has been found dead by marking 5884 // or not, in fact it would prevent reclamation within a concurrent cycle, as 5885 // all objects allocated during that time are considered live. 5886 // SATB marking is even more conservative than the remembered set. 5887 // So if at this point in the collection there is no remembered set entry, 5888 // nobody has a reference to it. 5889 // At the start of collection we flush all refinement logs, and remembered sets 5890 // are completely up-to-date wrt to references to the humongous object. 5891 // 5892 // Other implementation considerations: 5893 // - never consider object arrays at this time because they would pose 5894 // considerable effort for cleaning up the the remembered sets. This is 5895 // required because stale remembered sets might reference locations that 5896 // are currently allocated into. 5897 uint region_idx = r->hrm_index(); 5898 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 5899 !r->rem_set()->is_empty()) { 5900 5901 if (G1TraceEagerReclaimHumongousObjects) { 5902 gclog_or_tty->print_cr("Live humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length %u with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d reclaim candidate %d type array %d", 5903 region_idx, 5904 (size_t)obj->size() * HeapWordSize, 5905 p2i(r->bottom()), 5906 r->region_num(), 5907 r->rem_set()->occupied(), 5908 r->rem_set()->strong_code_roots_list_length(), 5909 next_bitmap->isMarked(r->bottom()), 5910 g1h->is_humongous_reclaim_candidate(region_idx), 5911 obj->is_typeArray() 5912 ); 5913 } 5914 5915 return false; 5916 } 5917 5918 guarantee(obj->is_typeArray(), 5919 err_msg("Only eagerly reclaiming type arrays is supported, but the object " 5920 PTR_FORMAT " is not.", 5921 p2i(r->bottom()))); 5922 5923 if (G1TraceEagerReclaimHumongousObjects) { 5924 gclog_or_tty->print_cr("Dead humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length %u with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d reclaim candidate %d type array %d", 5925 region_idx, 5926 (size_t)obj->size() * HeapWordSize, 5927 p2i(r->bottom()), 5928 r->region_num(), 5929 r->rem_set()->occupied(), 5930 r->rem_set()->strong_code_roots_list_length(), 5931 next_bitmap->isMarked(r->bottom()), 5932 g1h->is_humongous_reclaim_candidate(region_idx), 5933 obj->is_typeArray() 5934 ); 5935 } 5936 // Need to clear mark bit of the humongous object if already set. 5937 if (next_bitmap->isMarked(r->bottom())) { 5938 next_bitmap->clear(r->bottom()); 5939 } 5940 _freed_bytes += r->used(); 5941 r->set_containing_set(NULL); 5942 _humongous_regions_removed.increment(1u, r->capacity()); 5943 g1h->free_humongous_region(r, _free_region_list, false); 5944 5945 return false; 5946 } 5947 5948 HeapRegionSetCount& humongous_free_count() { 5949 return _humongous_regions_removed; 5950 } 5951 5952 size_t bytes_freed() const { 5953 return _freed_bytes; 5954 } 5955 5956 size_t humongous_reclaimed() const { 5957 return _humongous_regions_removed.length(); 5958 } 5959 }; 5960 5961 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 5962 assert_at_safepoint(true); 5963 5964 if (!G1EagerReclaimHumongousObjects || 5965 (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) { 5966 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5967 return; 5968 } 5969 5970 double start_time = os::elapsedTime(); 5971 5972 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5973 5974 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5975 heap_region_iterate(&cl); 5976 5977 HeapRegionSetCount empty_set; 5978 remove_from_old_sets(empty_set, cl.humongous_free_count()); 5979 5980 G1HRPrinter* hrp = hr_printer(); 5981 if (hrp->is_active()) { 5982 FreeRegionListIterator iter(&local_cleanup_list); 5983 while (iter.more_available()) { 5984 HeapRegion* hr = iter.get_next(); 5985 hrp->cleanup(hr); 5986 } 5987 } 5988 5989 prepend_to_freelist(&local_cleanup_list); 5990 decrement_summary_bytes(cl.bytes_freed()); 5991 5992 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5993 cl.humongous_reclaimed()); 5994 } 5995 5996 // This routine is similar to the above but does not record 5997 // any policy statistics or update free lists; we are abandoning 5998 // the current incremental collection set in preparation of a 5999 // full collection. After the full GC we will start to build up 6000 // the incremental collection set again. 6001 // This is only called when we're doing a full collection 6002 // and is immediately followed by the tearing down of the young list. 6003 6004 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 6005 HeapRegion* cur = cs_head; 6006 6007 while (cur != NULL) { 6008 HeapRegion* next = cur->next_in_collection_set(); 6009 assert(cur->in_collection_set(), "bad CS"); 6010 cur->set_next_in_collection_set(NULL); 6011 clear_in_cset(cur); 6012 cur->set_young_index_in_cset(-1); 6013 cur = next; 6014 } 6015 } 6016 6017 void G1CollectedHeap::set_free_regions_coming() { 6018 if (G1ConcRegionFreeingVerbose) { 6019 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6020 "setting free regions coming"); 6021 } 6022 6023 assert(!free_regions_coming(), "pre-condition"); 6024 _free_regions_coming = true; 6025 } 6026 6027 void G1CollectedHeap::reset_free_regions_coming() { 6028 assert(free_regions_coming(), "pre-condition"); 6029 6030 { 6031 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6032 _free_regions_coming = false; 6033 SecondaryFreeList_lock->notify_all(); 6034 } 6035 6036 if (G1ConcRegionFreeingVerbose) { 6037 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6038 "reset free regions coming"); 6039 } 6040 } 6041 6042 void G1CollectedHeap::wait_while_free_regions_coming() { 6043 // Most of the time we won't have to wait, so let's do a quick test 6044 // first before we take the lock. 6045 if (!free_regions_coming()) { 6046 return; 6047 } 6048 6049 if (G1ConcRegionFreeingVerbose) { 6050 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6051 "waiting for free regions"); 6052 } 6053 6054 { 6055 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6056 while (free_regions_coming()) { 6057 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 6058 } 6059 } 6060 6061 if (G1ConcRegionFreeingVerbose) { 6062 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6063 "done waiting for free regions"); 6064 } 6065 } 6066 6067 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 6068 _young_list->push_region(hr); 6069 } 6070 6071 class NoYoungRegionsClosure: public HeapRegionClosure { 6072 private: 6073 bool _success; 6074 public: 6075 NoYoungRegionsClosure() : _success(true) { } 6076 bool doHeapRegion(HeapRegion* r) { 6077 if (r->is_young()) { 6078 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young", 6079 p2i(r->bottom()), p2i(r->end())); 6080 _success = false; 6081 } 6082 return false; 6083 } 6084 bool success() { return _success; } 6085 }; 6086 6087 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 6088 bool ret = _young_list->check_list_empty(check_sample); 6089 6090 if (check_heap) { 6091 NoYoungRegionsClosure closure; 6092 heap_region_iterate(&closure); 6093 ret = ret && closure.success(); 6094 } 6095 6096 return ret; 6097 } 6098 6099 class TearDownRegionSetsClosure : public HeapRegionClosure { 6100 private: 6101 HeapRegionSet *_old_set; 6102 6103 public: 6104 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 6105 6106 bool doHeapRegion(HeapRegion* r) { 6107 if (r->is_old()) { 6108 _old_set->remove(r); 6109 } else { 6110 // We ignore free regions, we'll empty the free list afterwards. 6111 // We ignore young regions, we'll empty the young list afterwards. 6112 // We ignore humongous regions, we're not tearing down the 6113 // humongous regions set. 6114 assert(r->is_free() || r->is_young() || r->is_humongous(), 6115 "it cannot be another type"); 6116 } 6117 return false; 6118 } 6119 6120 ~TearDownRegionSetsClosure() { 6121 assert(_old_set->is_empty(), "post-condition"); 6122 } 6123 }; 6124 6125 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 6126 assert_at_safepoint(true /* should_be_vm_thread */); 6127 6128 if (!free_list_only) { 6129 TearDownRegionSetsClosure cl(&_old_set); 6130 heap_region_iterate(&cl); 6131 6132 // Note that emptying the _young_list is postponed and instead done as 6133 // the first step when rebuilding the regions sets again. The reason for 6134 // this is that during a full GC string deduplication needs to know if 6135 // a collected region was young or old when the full GC was initiated. 6136 } 6137 _hrm.remove_all_free_regions(); 6138 } 6139 6140 class RebuildRegionSetsClosure : public HeapRegionClosure { 6141 private: 6142 bool _free_list_only; 6143 HeapRegionSet* _old_set; 6144 HeapRegionManager* _hrm; 6145 size_t _total_used; 6146 6147 public: 6148 RebuildRegionSetsClosure(bool free_list_only, 6149 HeapRegionSet* old_set, HeapRegionManager* hrm) : 6150 _free_list_only(free_list_only), 6151 _old_set(old_set), _hrm(hrm), _total_used(0) { 6152 assert(_hrm->num_free_regions() == 0, "pre-condition"); 6153 if (!free_list_only) { 6154 assert(_old_set->is_empty(), "pre-condition"); 6155 } 6156 } 6157 6158 bool doHeapRegion(HeapRegion* r) { 6159 if (r->is_continues_humongous()) { 6160 return false; 6161 } 6162 6163 if (r->is_empty()) { 6164 // Add free regions to the free list 6165 r->set_free(); 6166 r->set_allocation_context(AllocationContext::system()); 6167 _hrm->insert_into_free_list(r); 6168 } else if (!_free_list_only) { 6169 assert(!r->is_young(), "we should not come across young regions"); 6170 6171 if (r->is_humongous()) { 6172 // We ignore humongous regions, we left the humongous set unchanged 6173 } else { 6174 // Objects that were compacted would have ended up on regions 6175 // that were previously old or free. 6176 assert(r->is_free() || r->is_old(), "invariant"); 6177 // We now consider them old, so register as such. 6178 r->set_old(); 6179 _old_set->add(r); 6180 } 6181 _total_used += r->used(); 6182 } 6183 6184 return false; 6185 } 6186 6187 size_t total_used() { 6188 return _total_used; 6189 } 6190 }; 6191 6192 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6193 assert_at_safepoint(true /* should_be_vm_thread */); 6194 6195 if (!free_list_only) { 6196 _young_list->empty_list(); 6197 } 6198 6199 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 6200 heap_region_iterate(&cl); 6201 6202 if (!free_list_only) { 6203 _allocator->set_used(cl.total_used()); 6204 } 6205 assert(_allocator->used_unlocked() == recalculate_used(), 6206 err_msg("inconsistent _allocator->used_unlocked(), " 6207 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT, 6208 _allocator->used_unlocked(), recalculate_used())); 6209 } 6210 6211 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6212 _refine_cte_cl->set_concurrent(concurrent); 6213 } 6214 6215 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6216 HeapRegion* hr = heap_region_containing(p); 6217 return hr->is_in(p); 6218 } 6219 6220 // Methods for the mutator alloc region 6221 6222 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6223 bool force) { 6224 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6225 assert(!force || g1_policy()->can_expand_young_list(), 6226 "if force is true we should be able to expand the young list"); 6227 bool young_list_full = g1_policy()->is_young_list_full(); 6228 if (force || !young_list_full) { 6229 HeapRegion* new_alloc_region = new_region(word_size, 6230 false /* is_old */, 6231 false /* do_expand */); 6232 if (new_alloc_region != NULL) { 6233 set_region_short_lived_locked(new_alloc_region); 6234 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6235 check_bitmaps("Mutator Region Allocation", new_alloc_region); 6236 return new_alloc_region; 6237 } 6238 } 6239 return NULL; 6240 } 6241 6242 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6243 size_t allocated_bytes) { 6244 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6245 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 6246 6247 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6248 _allocator->increase_used(allocated_bytes); 6249 _hr_printer.retire(alloc_region); 6250 // We update the eden sizes here, when the region is retired, 6251 // instead of when it's allocated, since this is the point that its 6252 // used space has been recored in _summary_bytes_used. 6253 g1mm()->update_eden_size(); 6254 } 6255 6256 // Methods for the GC alloc regions 6257 6258 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6259 uint count, 6260 InCSetState dest) { 6261 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6262 6263 if (count < g1_policy()->max_regions(dest)) { 6264 const bool is_survivor = (dest.is_young()); 6265 HeapRegion* new_alloc_region = new_region(word_size, 6266 !is_survivor, 6267 true /* do_expand */); 6268 if (new_alloc_region != NULL) { 6269 // We really only need to do this for old regions given that we 6270 // should never scan survivors. But it doesn't hurt to do it 6271 // for survivors too. 6272 new_alloc_region->record_timestamp(); 6273 if (is_survivor) { 6274 new_alloc_region->set_survivor(); 6275 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6276 check_bitmaps("Survivor Region Allocation", new_alloc_region); 6277 } else { 6278 new_alloc_region->set_old(); 6279 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6280 check_bitmaps("Old Region Allocation", new_alloc_region); 6281 } 6282 bool during_im = g1_policy()->during_initial_mark_pause(); 6283 new_alloc_region->note_start_of_copying(during_im); 6284 return new_alloc_region; 6285 } 6286 } 6287 return NULL; 6288 } 6289 6290 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6291 size_t allocated_bytes, 6292 InCSetState dest) { 6293 bool during_im = g1_policy()->during_initial_mark_pause(); 6294 alloc_region->note_end_of_copying(during_im); 6295 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6296 if (dest.is_young()) { 6297 young_list()->add_survivor_region(alloc_region); 6298 } else { 6299 _old_set.add(alloc_region); 6300 } 6301 _hr_printer.retire(alloc_region); 6302 } 6303 6304 // Heap region set verification 6305 6306 class VerifyRegionListsClosure : public HeapRegionClosure { 6307 private: 6308 HeapRegionSet* _old_set; 6309 HeapRegionSet* _humongous_set; 6310 HeapRegionManager* _hrm; 6311 6312 public: 6313 HeapRegionSetCount _old_count; 6314 HeapRegionSetCount _humongous_count; 6315 HeapRegionSetCount _free_count; 6316 6317 VerifyRegionListsClosure(HeapRegionSet* old_set, 6318 HeapRegionSet* humongous_set, 6319 HeapRegionManager* hrm) : 6320 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm), 6321 _old_count(), _humongous_count(), _free_count(){ } 6322 6323 bool doHeapRegion(HeapRegion* hr) { 6324 if (hr->is_continues_humongous()) { 6325 return false; 6326 } 6327 6328 if (hr->is_young()) { 6329 // TODO 6330 } else if (hr->is_starts_humongous()) { 6331 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index())); 6332 _humongous_count.increment(1u, hr->capacity()); 6333 } else if (hr->is_empty()) { 6334 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index())); 6335 _free_count.increment(1u, hr->capacity()); 6336 } else if (hr->is_old()) { 6337 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index())); 6338 _old_count.increment(1u, hr->capacity()); 6339 } else { 6340 ShouldNotReachHere(); 6341 } 6342 return false; 6343 } 6344 6345 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) { 6346 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length())); 6347 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6348 old_set->total_capacity_bytes(), _old_count.capacity())); 6349 6350 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length())); 6351 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6352 humongous_set->total_capacity_bytes(), _humongous_count.capacity())); 6353 6354 guarantee(free_list->num_free_regions() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count.length())); 6355 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6356 free_list->total_capacity_bytes(), _free_count.capacity())); 6357 } 6358 }; 6359 6360 void G1CollectedHeap::verify_region_sets() { 6361 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6362 6363 // First, check the explicit lists. 6364 _hrm.verify(); 6365 { 6366 // Given that a concurrent operation might be adding regions to 6367 // the secondary free list we have to take the lock before 6368 // verifying it. 6369 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6370 _secondary_free_list.verify_list(); 6371 } 6372 6373 // If a concurrent region freeing operation is in progress it will 6374 // be difficult to correctly attributed any free regions we come 6375 // across to the correct free list given that they might belong to 6376 // one of several (free_list, secondary_free_list, any local lists, 6377 // etc.). So, if that's the case we will skip the rest of the 6378 // verification operation. Alternatively, waiting for the concurrent 6379 // operation to complete will have a non-trivial effect on the GC's 6380 // operation (no concurrent operation will last longer than the 6381 // interval between two calls to verification) and it might hide 6382 // any issues that we would like to catch during testing. 6383 if (free_regions_coming()) { 6384 return; 6385 } 6386 6387 // Make sure we append the secondary_free_list on the free_list so 6388 // that all free regions we will come across can be safely 6389 // attributed to the free_list. 6390 append_secondary_free_list_if_not_empty_with_lock(); 6391 6392 // Finally, make sure that the region accounting in the lists is 6393 // consistent with what we see in the heap. 6394 6395 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm); 6396 heap_region_iterate(&cl); 6397 cl.verify_counts(&_old_set, &_humongous_set, &_hrm); 6398 } 6399 6400 // Optimized nmethod scanning 6401 6402 class RegisterNMethodOopClosure: public OopClosure { 6403 G1CollectedHeap* _g1h; 6404 nmethod* _nm; 6405 6406 template <class T> void do_oop_work(T* p) { 6407 T heap_oop = oopDesc::load_heap_oop(p); 6408 if (!oopDesc::is_null(heap_oop)) { 6409 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6410 HeapRegion* hr = _g1h->heap_region_containing(obj); 6411 assert(!hr->is_continues_humongous(), 6412 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT 6413 " starting at "HR_FORMAT, 6414 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()))); 6415 6416 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 6417 hr->add_strong_code_root_locked(_nm); 6418 } 6419 } 6420 6421 public: 6422 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6423 _g1h(g1h), _nm(nm) {} 6424 6425 void do_oop(oop* p) { do_oop_work(p); } 6426 void do_oop(narrowOop* p) { do_oop_work(p); } 6427 }; 6428 6429 class UnregisterNMethodOopClosure: public OopClosure { 6430 G1CollectedHeap* _g1h; 6431 nmethod* _nm; 6432 6433 template <class T> void do_oop_work(T* p) { 6434 T heap_oop = oopDesc::load_heap_oop(p); 6435 if (!oopDesc::is_null(heap_oop)) { 6436 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6437 HeapRegion* hr = _g1h->heap_region_containing(obj); 6438 assert(!hr->is_continues_humongous(), 6439 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT 6440 " starting at "HR_FORMAT, 6441 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()))); 6442 6443 hr->remove_strong_code_root(_nm); 6444 } 6445 } 6446 6447 public: 6448 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6449 _g1h(g1h), _nm(nm) {} 6450 6451 void do_oop(oop* p) { do_oop_work(p); } 6452 void do_oop(narrowOop* p) { do_oop_work(p); } 6453 }; 6454 6455 void G1CollectedHeap::register_nmethod(nmethod* nm) { 6456 CollectedHeap::register_nmethod(nm); 6457 6458 guarantee(nm != NULL, "sanity"); 6459 RegisterNMethodOopClosure reg_cl(this, nm); 6460 nm->oops_do(®_cl); 6461 } 6462 6463 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 6464 CollectedHeap::unregister_nmethod(nm); 6465 6466 guarantee(nm != NULL, "sanity"); 6467 UnregisterNMethodOopClosure reg_cl(this, nm); 6468 nm->oops_do(®_cl, true); 6469 } 6470 6471 void G1CollectedHeap::purge_code_root_memory() { 6472 double purge_start = os::elapsedTime(); 6473 G1CodeRootSet::purge(); 6474 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 6475 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 6476 } 6477 6478 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 6479 G1CollectedHeap* _g1h; 6480 6481 public: 6482 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 6483 _g1h(g1h) {} 6484 6485 void do_code_blob(CodeBlob* cb) { 6486 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 6487 if (nm == NULL) { 6488 return; 6489 } 6490 6491 if (ScavengeRootsInCode) { 6492 _g1h->register_nmethod(nm); 6493 } 6494 } 6495 }; 6496 6497 void G1CollectedHeap::rebuild_strong_code_roots() { 6498 RebuildStrongCodeRootClosure blob_cl(this); 6499 CodeCache::blobs_do(&blob_cl); 6500 }