1 /* 2 * Copyright (c) 2001, 2017, 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 "classfile/symbolTable.hpp" 29 #include "code/codeCache.hpp" 30 #include "code/icBuffer.hpp" 31 #include "gc/g1/bufferingOopClosure.hpp" 32 #include "gc/g1/concurrentMarkThread.inline.hpp" 33 #include "gc/g1/g1Allocator.inline.hpp" 34 #include "gc/g1/g1CollectedHeap.inline.hpp" 35 #include "gc/g1/g1CollectionSet.hpp" 36 #include "gc/g1/g1CollectorPolicy.hpp" 37 #include "gc/g1/g1CollectorState.hpp" 38 #include "gc/g1/g1ConcurrentRefine.hpp" 39 #include "gc/g1/g1ConcurrentRefineThread.hpp" 40 #include "gc/g1/g1EvacStats.inline.hpp" 41 #include "gc/g1/g1FullCollector.hpp" 42 #include "gc/g1/g1GCPhaseTimes.hpp" 43 #include "gc/g1/g1HeapSizingPolicy.hpp" 44 #include "gc/g1/g1HeapTransition.hpp" 45 #include "gc/g1/g1HeapVerifier.hpp" 46 #include "gc/g1/g1HotCardCache.hpp" 47 #include "gc/g1/g1OopClosures.inline.hpp" 48 #include "gc/g1/g1ParScanThreadState.inline.hpp" 49 #include "gc/g1/g1Policy.hpp" 50 #include "gc/g1/g1RegionToSpaceMapper.hpp" 51 #include "gc/g1/g1RemSet.hpp" 52 #include "gc/g1/g1RootClosures.hpp" 53 #include "gc/g1/g1RootProcessor.hpp" 54 #include "gc/g1/g1StringDedup.hpp" 55 #include "gc/g1/g1YCTypes.hpp" 56 #include "gc/g1/g1YoungRemSetSamplingThread.hpp" 57 #include "gc/g1/heapRegion.inline.hpp" 58 #include "gc/g1/heapRegionRemSet.hpp" 59 #include "gc/g1/heapRegionSet.inline.hpp" 60 #include "gc/g1/vm_operations_g1.hpp" 61 #include "gc/shared/gcHeapSummary.hpp" 62 #include "gc/shared/gcId.hpp" 63 #include "gc/shared/gcLocker.inline.hpp" 64 #include "gc/shared/gcTimer.hpp" 65 #include "gc/shared/gcTrace.hpp" 66 #include "gc/shared/gcTraceTime.inline.hpp" 67 #include "gc/shared/generationSpec.hpp" 68 #include "gc/shared/isGCActiveMark.hpp" 69 #include "gc/shared/preservedMarks.inline.hpp" 70 #include "gc/shared/suspendibleThreadSet.hpp" 71 #include "gc/shared/referenceProcessor.inline.hpp" 72 #include "gc/shared/taskqueue.inline.hpp" 73 #include "gc/shared/weakProcessor.hpp" 74 #include "logging/log.hpp" 75 #include "memory/allocation.hpp" 76 #include "memory/iterator.hpp" 77 #include "memory/resourceArea.hpp" 78 #include "oops/oop.inline.hpp" 79 #include "prims/resolvedMethodTable.hpp" 80 #include "runtime/atomic.hpp" 81 #include "runtime/init.hpp" 82 #include "runtime/orderAccess.inline.hpp" 83 #include "runtime/threadSMR.hpp" 84 #include "runtime/vmThread.hpp" 85 #include "utilities/align.hpp" 86 #include "utilities/globalDefinitions.hpp" 87 #include "utilities/stack.inline.hpp" 88 89 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 90 91 // INVARIANTS/NOTES 92 // 93 // All allocation activity covered by the G1CollectedHeap interface is 94 // serialized by acquiring the HeapLock. This happens in mem_allocate 95 // and allocate_new_tlab, which are the "entry" points to the 96 // allocation code from the rest of the JVM. (Note that this does not 97 // apply to TLAB allocation, which is not part of this interface: it 98 // is done by clients of this interface.) 99 100 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 101 private: 102 size_t _num_dirtied; 103 G1CollectedHeap* _g1h; 104 G1SATBCardTableLoggingModRefBS* _g1_bs; 105 106 HeapRegion* region_for_card(jbyte* card_ptr) const { 107 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 108 } 109 110 bool will_become_free(HeapRegion* hr) const { 111 // A region will be freed by free_collection_set if the region is in the 112 // collection set and has not had an evacuation failure. 113 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 114 } 115 116 public: 117 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 118 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 119 120 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 121 HeapRegion* hr = region_for_card(card_ptr); 122 123 // Should only dirty cards in regions that won't be freed. 124 if (!will_become_free(hr)) { 125 *card_ptr = CardTableModRefBS::dirty_card_val(); 126 _num_dirtied++; 127 } 128 129 return true; 130 } 131 132 size_t num_dirtied() const { return _num_dirtied; } 133 }; 134 135 136 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 137 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 138 } 139 140 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 141 // The from card cache is not the memory that is actually committed. So we cannot 142 // take advantage of the zero_filled parameter. 143 reset_from_card_cache(start_idx, num_regions); 144 } 145 146 147 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 148 MemRegion mr) { 149 return new HeapRegion(hrs_index, bot(), mr); 150 } 151 152 // Private methods. 153 154 HeapRegion* 155 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 156 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 157 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 158 if (!_secondary_free_list.is_empty()) { 159 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 160 "secondary_free_list has %u entries", 161 _secondary_free_list.length()); 162 // It looks as if there are free regions available on the 163 // secondary_free_list. Let's move them to the free_list and try 164 // again to allocate from it. 165 append_secondary_free_list(); 166 167 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 168 "empty we should have moved at least one entry to the free_list"); 169 HeapRegion* res = _hrm.allocate_free_region(is_old); 170 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 171 "allocated " HR_FORMAT " from secondary_free_list", 172 HR_FORMAT_PARAMS(res)); 173 return res; 174 } 175 176 // Wait here until we get notified either when (a) there are no 177 // more free regions coming or (b) some regions have been moved on 178 // the secondary_free_list. 179 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 180 } 181 182 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 183 "could not allocate from secondary_free_list"); 184 return NULL; 185 } 186 187 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 188 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 189 "the only time we use this to allocate a humongous region is " 190 "when we are allocating a single humongous region"); 191 192 HeapRegion* res; 193 if (G1StressConcRegionFreeing) { 194 if (!_secondary_free_list.is_empty()) { 195 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 196 "forced to look at the secondary_free_list"); 197 res = new_region_try_secondary_free_list(is_old); 198 if (res != NULL) { 199 return res; 200 } 201 } 202 } 203 204 res = _hrm.allocate_free_region(is_old); 205 206 if (res == NULL) { 207 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 208 "res == NULL, trying the secondary_free_list"); 209 res = new_region_try_secondary_free_list(is_old); 210 } 211 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 212 // Currently, only attempts to allocate GC alloc regions set 213 // do_expand to true. So, we should only reach here during a 214 // safepoint. If this assumption changes we might have to 215 // reconsider the use of _expand_heap_after_alloc_failure. 216 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 217 218 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 219 word_size * HeapWordSize); 220 221 if (expand(word_size * HeapWordSize)) { 222 // Given that expand() succeeded in expanding the heap, and we 223 // always expand the heap by an amount aligned to the heap 224 // region size, the free list should in theory not be empty. 225 // In either case allocate_free_region() will check for NULL. 226 res = _hrm.allocate_free_region(is_old); 227 } else { 228 _expand_heap_after_alloc_failure = false; 229 } 230 } 231 return res; 232 } 233 234 HeapWord* 235 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 236 uint num_regions, 237 size_t word_size, 238 AllocationContext_t context) { 239 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 240 assert(is_humongous(word_size), "word_size should be humongous"); 241 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 242 243 // Index of last region in the series. 244 uint last = first + num_regions - 1; 245 246 // We need to initialize the region(s) we just discovered. This is 247 // a bit tricky given that it can happen concurrently with 248 // refinement threads refining cards on these regions and 249 // potentially wanting to refine the BOT as they are scanning 250 // those cards (this can happen shortly after a cleanup; see CR 251 // 6991377). So we have to set up the region(s) carefully and in 252 // a specific order. 253 254 // The word size sum of all the regions we will allocate. 255 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 256 assert(word_size <= word_size_sum, "sanity"); 257 258 // This will be the "starts humongous" region. 259 HeapRegion* first_hr = region_at(first); 260 // The header of the new object will be placed at the bottom of 261 // the first region. 262 HeapWord* new_obj = first_hr->bottom(); 263 // This will be the new top of the new object. 264 HeapWord* obj_top = new_obj + word_size; 265 266 // First, we need to zero the header of the space that we will be 267 // allocating. When we update top further down, some refinement 268 // threads might try to scan the region. By zeroing the header we 269 // ensure that any thread that will try to scan the region will 270 // come across the zero klass word and bail out. 271 // 272 // NOTE: It would not have been correct to have used 273 // CollectedHeap::fill_with_object() and make the space look like 274 // an int array. The thread that is doing the allocation will 275 // later update the object header to a potentially different array 276 // type and, for a very short period of time, the klass and length 277 // fields will be inconsistent. This could cause a refinement 278 // thread to calculate the object size incorrectly. 279 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 280 281 // Next, pad out the unused tail of the last region with filler 282 // objects, for improved usage accounting. 283 // How many words we use for filler objects. 284 size_t word_fill_size = word_size_sum - word_size; 285 286 // How many words memory we "waste" which cannot hold a filler object. 287 size_t words_not_fillable = 0; 288 289 if (word_fill_size >= min_fill_size()) { 290 fill_with_objects(obj_top, word_fill_size); 291 } else if (word_fill_size > 0) { 292 // We have space to fill, but we cannot fit an object there. 293 words_not_fillable = word_fill_size; 294 word_fill_size = 0; 295 } 296 297 // We will set up the first region as "starts humongous". This 298 // will also update the BOT covering all the regions to reflect 299 // that there is a single object that starts at the bottom of the 300 // first region. 301 first_hr->set_starts_humongous(obj_top, word_fill_size); 302 first_hr->set_allocation_context(context); 303 // Then, if there are any, we will set up the "continues 304 // humongous" regions. 305 HeapRegion* hr = NULL; 306 for (uint i = first + 1; i <= last; ++i) { 307 hr = region_at(i); 308 hr->set_continues_humongous(first_hr); 309 hr->set_allocation_context(context); 310 } 311 312 // Up to this point no concurrent thread would have been able to 313 // do any scanning on any region in this series. All the top 314 // fields still point to bottom, so the intersection between 315 // [bottom,top] and [card_start,card_end] will be empty. Before we 316 // update the top fields, we'll do a storestore to make sure that 317 // no thread sees the update to top before the zeroing of the 318 // object header and the BOT initialization. 319 OrderAccess::storestore(); 320 321 // Now, we will update the top fields of the "continues humongous" 322 // regions except the last one. 323 for (uint i = first; i < last; ++i) { 324 hr = region_at(i); 325 hr->set_top(hr->end()); 326 } 327 328 hr = region_at(last); 329 // If we cannot fit a filler object, we must set top to the end 330 // of the humongous object, otherwise we cannot iterate the heap 331 // and the BOT will not be complete. 332 hr->set_top(hr->end() - words_not_fillable); 333 334 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 335 "obj_top should be in last region"); 336 337 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 338 339 assert(words_not_fillable == 0 || 340 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 341 "Miscalculation in humongous allocation"); 342 343 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 344 345 for (uint i = first; i <= last; ++i) { 346 hr = region_at(i); 347 _humongous_set.add(hr); 348 _hr_printer.alloc(hr); 349 } 350 351 return new_obj; 352 } 353 354 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 355 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 356 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 357 } 358 359 // If could fit into free regions w/o expansion, try. 360 // Otherwise, if can expand, do so. 361 // Otherwise, if using ex regions might help, try with ex given back. 362 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 363 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 364 365 _verifier->verify_region_sets_optional(); 366 367 uint first = G1_NO_HRM_INDEX; 368 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 369 370 if (obj_regions == 1) { 371 // Only one region to allocate, try to use a fast path by directly allocating 372 // from the free lists. Do not try to expand here, we will potentially do that 373 // later. 374 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 375 if (hr != NULL) { 376 first = hr->hrm_index(); 377 } 378 } else { 379 // We can't allocate humongous regions spanning more than one region while 380 // cleanupComplete() is running, since some of the regions we find to be 381 // empty might not yet be added to the free list. It is not straightforward 382 // to know in which list they are on so that we can remove them. We only 383 // need to do this if we need to allocate more than one region to satisfy the 384 // current humongous allocation request. If we are only allocating one region 385 // we use the one-region region allocation code (see above), that already 386 // potentially waits for regions from the secondary free list. 387 wait_while_free_regions_coming(); 388 append_secondary_free_list_if_not_empty_with_lock(); 389 390 // Policy: Try only empty regions (i.e. already committed first). Maybe we 391 // are lucky enough to find some. 392 first = _hrm.find_contiguous_only_empty(obj_regions); 393 if (first != G1_NO_HRM_INDEX) { 394 _hrm.allocate_free_regions_starting_at(first, obj_regions); 395 } 396 } 397 398 if (first == G1_NO_HRM_INDEX) { 399 // Policy: We could not find enough regions for the humongous object in the 400 // free list. Look through the heap to find a mix of free and uncommitted regions. 401 // If so, try expansion. 402 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 403 if (first != G1_NO_HRM_INDEX) { 404 // We found something. Make sure these regions are committed, i.e. expand 405 // the heap. Alternatively we could do a defragmentation GC. 406 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 407 word_size * HeapWordSize); 408 409 _hrm.expand_at(first, obj_regions, workers()); 410 g1_policy()->record_new_heap_size(num_regions()); 411 412 #ifdef ASSERT 413 for (uint i = first; i < first + obj_regions; ++i) { 414 HeapRegion* hr = region_at(i); 415 assert(hr->is_free(), "sanity"); 416 assert(hr->is_empty(), "sanity"); 417 assert(is_on_master_free_list(hr), "sanity"); 418 } 419 #endif 420 _hrm.allocate_free_regions_starting_at(first, obj_regions); 421 } else { 422 // Policy: Potentially trigger a defragmentation GC. 423 } 424 } 425 426 HeapWord* result = NULL; 427 if (first != G1_NO_HRM_INDEX) { 428 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 429 word_size, context); 430 assert(result != NULL, "it should always return a valid result"); 431 432 // A successful humongous object allocation changes the used space 433 // information of the old generation so we need to recalculate the 434 // sizes and update the jstat counters here. 435 g1mm()->update_sizes(); 436 } 437 438 _verifier->verify_region_sets_optional(); 439 440 return result; 441 } 442 443 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 444 assert_heap_not_locked_and_not_at_safepoint(); 445 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 446 447 uint dummy_gc_count_before; 448 uint dummy_gclocker_retry_count = 0; 449 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 450 } 451 452 HeapWord* 453 G1CollectedHeap::mem_allocate(size_t word_size, 454 bool* gc_overhead_limit_was_exceeded) { 455 assert_heap_not_locked_and_not_at_safepoint(); 456 457 // Loop until the allocation is satisfied, or unsatisfied after GC. 458 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 459 uint gc_count_before; 460 461 HeapWord* result = NULL; 462 if (!is_humongous(word_size)) { 463 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 464 } else { 465 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 466 } 467 if (result != NULL) { 468 return result; 469 } 470 471 // Create the garbage collection operation... 472 VM_G1CollectForAllocation op(gc_count_before, word_size); 473 op.set_allocation_context(AllocationContext::current()); 474 475 // ...and get the VM thread to execute it. 476 VMThread::execute(&op); 477 478 if (op.prologue_succeeded() && op.pause_succeeded()) { 479 // If the operation was successful we'll return the result even 480 // if it is NULL. If the allocation attempt failed immediately 481 // after a Full GC, it's unlikely we'll be able to allocate now. 482 HeapWord* result = op.result(); 483 if (result != NULL && !is_humongous(word_size)) { 484 // Allocations that take place on VM operations do not do any 485 // card dirtying and we have to do it here. We only have to do 486 // this for non-humongous allocations, though. 487 dirty_young_block(result, word_size); 488 } 489 return result; 490 } else { 491 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 492 return NULL; 493 } 494 assert(op.result() == NULL, 495 "the result should be NULL if the VM op did not succeed"); 496 } 497 498 // Give a warning if we seem to be looping forever. 499 if ((QueuedAllocationWarningCount > 0) && 500 (try_count % QueuedAllocationWarningCount == 0)) { 501 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count); 502 } 503 } 504 505 ShouldNotReachHere(); 506 return NULL; 507 } 508 509 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 510 AllocationContext_t context, 511 uint* gc_count_before_ret, 512 uint* gclocker_retry_count_ret) { 513 // Make sure you read the note in attempt_allocation_humongous(). 514 515 assert_heap_not_locked_and_not_at_safepoint(); 516 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 517 "be called for humongous allocation requests"); 518 519 // We should only get here after the first-level allocation attempt 520 // (attempt_allocation()) failed to allocate. 521 522 // We will loop until a) we manage to successfully perform the 523 // allocation or b) we successfully schedule a collection which 524 // fails to perform the allocation. b) is the only case when we'll 525 // return NULL. 526 HeapWord* result = NULL; 527 for (int try_count = 1; /* we'll return */; try_count += 1) { 528 bool should_try_gc; 529 uint gc_count_before; 530 531 { 532 MutexLockerEx x(Heap_lock); 533 result = _allocator->attempt_allocation_locked(word_size, context); 534 if (result != NULL) { 535 return result; 536 } 537 538 if (GCLocker::is_active_and_needs_gc()) { 539 if (g1_policy()->can_expand_young_list()) { 540 // No need for an ergo verbose message here, 541 // can_expand_young_list() does this when it returns true. 542 result = _allocator->attempt_allocation_force(word_size, context); 543 if (result != NULL) { 544 return result; 545 } 546 } 547 should_try_gc = false; 548 } else { 549 // The GCLocker may not be active but the GCLocker initiated 550 // GC may not yet have been performed (GCLocker::needs_gc() 551 // returns true). In this case we do not try this GC and 552 // wait until the GCLocker initiated GC is performed, and 553 // then retry the allocation. 554 if (GCLocker::needs_gc()) { 555 should_try_gc = false; 556 } else { 557 // Read the GC count while still holding the Heap_lock. 558 gc_count_before = total_collections(); 559 should_try_gc = true; 560 } 561 } 562 } 563 564 if (should_try_gc) { 565 bool succeeded; 566 result = do_collection_pause(word_size, gc_count_before, &succeeded, 567 GCCause::_g1_inc_collection_pause); 568 if (result != NULL) { 569 assert(succeeded, "only way to get back a non-NULL result"); 570 return result; 571 } 572 573 if (succeeded) { 574 // If we get here we successfully scheduled a collection which 575 // failed to allocate. No point in trying to allocate 576 // further. We'll just return NULL. 577 MutexLockerEx x(Heap_lock); 578 *gc_count_before_ret = total_collections(); 579 return NULL; 580 } 581 } else { 582 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 583 MutexLockerEx x(Heap_lock); 584 *gc_count_before_ret = total_collections(); 585 return NULL; 586 } 587 // The GCLocker is either active or the GCLocker initiated 588 // GC has not yet been performed. Stall until it is and 589 // then retry the allocation. 590 GCLocker::stall_until_clear(); 591 (*gclocker_retry_count_ret) += 1; 592 } 593 594 // We can reach here if we were unsuccessful in scheduling a 595 // collection (because another thread beat us to it) or if we were 596 // stalled due to the GC locker. In either can we should retry the 597 // allocation attempt in case another thread successfully 598 // performed a collection and reclaimed enough space. We do the 599 // first attempt (without holding the Heap_lock) here and the 600 // follow-on attempt will be at the start of the next loop 601 // iteration (after taking the Heap_lock). 602 result = _allocator->attempt_allocation(word_size, context); 603 if (result != NULL) { 604 return result; 605 } 606 607 // Give a warning if we seem to be looping forever. 608 if ((QueuedAllocationWarningCount > 0) && 609 (try_count % QueuedAllocationWarningCount == 0)) { 610 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() " 611 "retries %d times", try_count); 612 } 613 } 614 615 ShouldNotReachHere(); 616 return NULL; 617 } 618 619 void G1CollectedHeap::begin_archive_alloc_range(bool open) { 620 assert_at_safepoint(true /* should_be_vm_thread */); 621 if (_archive_allocator == NULL) { 622 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open); 623 } 624 } 625 626 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 627 // Allocations in archive regions cannot be of a size that would be considered 628 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 629 // may be different at archive-restore time. 630 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 631 } 632 633 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 634 assert_at_safepoint(true /* should_be_vm_thread */); 635 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 636 if (is_archive_alloc_too_large(word_size)) { 637 return NULL; 638 } 639 return _archive_allocator->archive_mem_allocate(word_size); 640 } 641 642 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 643 size_t end_alignment_in_bytes) { 644 assert_at_safepoint(true /* should_be_vm_thread */); 645 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 646 647 // Call complete_archive to do the real work, filling in the MemRegion 648 // array with the archive regions. 649 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 650 delete _archive_allocator; 651 _archive_allocator = NULL; 652 } 653 654 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 655 assert(ranges != NULL, "MemRegion array NULL"); 656 assert(count != 0, "No MemRegions provided"); 657 MemRegion reserved = _hrm.reserved(); 658 for (size_t i = 0; i < count; i++) { 659 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 660 return false; 661 } 662 } 663 return true; 664 } 665 666 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, 667 size_t count, 668 bool open) { 669 assert(!is_init_completed(), "Expect to be called at JVM init time"); 670 assert(ranges != NULL, "MemRegion array NULL"); 671 assert(count != 0, "No MemRegions provided"); 672 MutexLockerEx x(Heap_lock); 673 674 MemRegion reserved = _hrm.reserved(); 675 HeapWord* prev_last_addr = NULL; 676 HeapRegion* prev_last_region = NULL; 677 678 // Temporarily disable pretouching of heap pages. This interface is used 679 // when mmap'ing archived heap data in, so pre-touching is wasted. 680 FlagSetting fs(AlwaysPreTouch, false); 681 682 // Enable archive object checking used by G1MarkSweep. We have to let it know 683 // about each archive range, so that objects in those ranges aren't marked. 684 G1ArchiveAllocator::enable_archive_object_check(); 685 686 // For each specified MemRegion range, allocate the corresponding G1 687 // regions and mark them as archive regions. We expect the ranges 688 // in ascending starting address order, without overlap. 689 for (size_t i = 0; i < count; i++) { 690 MemRegion curr_range = ranges[i]; 691 HeapWord* start_address = curr_range.start(); 692 size_t word_size = curr_range.word_size(); 693 HeapWord* last_address = curr_range.last(); 694 size_t commits = 0; 695 696 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 697 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 698 p2i(start_address), p2i(last_address)); 699 guarantee(start_address > prev_last_addr, 700 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 701 p2i(start_address), p2i(prev_last_addr)); 702 prev_last_addr = last_address; 703 704 // Check for ranges that start in the same G1 region in which the previous 705 // range ended, and adjust the start address so we don't try to allocate 706 // the same region again. If the current range is entirely within that 707 // region, skip it, just adjusting the recorded top. 708 HeapRegion* start_region = _hrm.addr_to_region(start_address); 709 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 710 start_address = start_region->end(); 711 if (start_address > last_address) { 712 increase_used(word_size * HeapWordSize); 713 start_region->set_top(last_address + 1); 714 continue; 715 } 716 start_region->set_top(start_address); 717 curr_range = MemRegion(start_address, last_address + 1); 718 start_region = _hrm.addr_to_region(start_address); 719 } 720 721 // Perform the actual region allocation, exiting if it fails. 722 // Then note how much new space we have allocated. 723 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 724 return false; 725 } 726 increase_used(word_size * HeapWordSize); 727 if (commits != 0) { 728 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 729 HeapRegion::GrainWords * HeapWordSize * commits); 730 731 } 732 733 // Mark each G1 region touched by the range as archive, add it to 734 // the old set, and set the allocation context and top. 735 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 736 HeapRegion* last_region = _hrm.addr_to_region(last_address); 737 prev_last_region = last_region; 738 739 while (curr_region != NULL) { 740 assert(curr_region->is_empty() && !curr_region->is_pinned(), 741 "Region already in use (index %u)", curr_region->hrm_index()); 742 curr_region->set_allocation_context(AllocationContext::system()); 743 if (open) { 744 curr_region->set_open_archive(); 745 } else { 746 curr_region->set_closed_archive(); 747 } 748 _hr_printer.alloc(curr_region); 749 _old_set.add(curr_region); 750 HeapWord* top; 751 HeapRegion* next_region; 752 if (curr_region != last_region) { 753 top = curr_region->end(); 754 next_region = _hrm.next_region_in_heap(curr_region); 755 } else { 756 top = last_address + 1; 757 next_region = NULL; 758 } 759 curr_region->set_top(top); 760 curr_region->set_first_dead(top); 761 curr_region->set_end_of_live(top); 762 curr_region = next_region; 763 } 764 765 // Notify mark-sweep of the archive 766 G1ArchiveAllocator::set_range_archive(curr_range, open); 767 } 768 return true; 769 } 770 771 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 772 assert(!is_init_completed(), "Expect to be called at JVM init time"); 773 assert(ranges != NULL, "MemRegion array NULL"); 774 assert(count != 0, "No MemRegions provided"); 775 MemRegion reserved = _hrm.reserved(); 776 HeapWord *prev_last_addr = NULL; 777 HeapRegion* prev_last_region = NULL; 778 779 // For each MemRegion, create filler objects, if needed, in the G1 regions 780 // that contain the address range. The address range actually within the 781 // MemRegion will not be modified. That is assumed to have been initialized 782 // elsewhere, probably via an mmap of archived heap data. 783 MutexLockerEx x(Heap_lock); 784 for (size_t i = 0; i < count; i++) { 785 HeapWord* start_address = ranges[i].start(); 786 HeapWord* last_address = ranges[i].last(); 787 788 assert(reserved.contains(start_address) && reserved.contains(last_address), 789 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 790 p2i(start_address), p2i(last_address)); 791 assert(start_address > prev_last_addr, 792 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 793 p2i(start_address), p2i(prev_last_addr)); 794 795 HeapRegion* start_region = _hrm.addr_to_region(start_address); 796 HeapRegion* last_region = _hrm.addr_to_region(last_address); 797 HeapWord* bottom_address = start_region->bottom(); 798 799 // Check for a range beginning in the same region in which the 800 // previous one ended. 801 if (start_region == prev_last_region) { 802 bottom_address = prev_last_addr + 1; 803 } 804 805 // Verify that the regions were all marked as archive regions by 806 // alloc_archive_regions. 807 HeapRegion* curr_region = start_region; 808 while (curr_region != NULL) { 809 guarantee(curr_region->is_archive(), 810 "Expected archive region at index %u", curr_region->hrm_index()); 811 if (curr_region != last_region) { 812 curr_region = _hrm.next_region_in_heap(curr_region); 813 } else { 814 curr_region = NULL; 815 } 816 } 817 818 prev_last_addr = last_address; 819 prev_last_region = last_region; 820 821 // Fill the memory below the allocated range with dummy object(s), 822 // if the region bottom does not match the range start, or if the previous 823 // range ended within the same G1 region, and there is a gap. 824 if (start_address != bottom_address) { 825 size_t fill_size = pointer_delta(start_address, bottom_address); 826 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 827 increase_used(fill_size * HeapWordSize); 828 } 829 } 830 } 831 832 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 833 uint* gc_count_before_ret, 834 uint* gclocker_retry_count_ret) { 835 assert_heap_not_locked_and_not_at_safepoint(); 836 assert(!is_humongous(word_size), "attempt_allocation() should not " 837 "be called for humongous allocation requests"); 838 839 AllocationContext_t context = AllocationContext::current(); 840 HeapWord* result = _allocator->attempt_allocation(word_size, context); 841 842 if (result == NULL) { 843 result = attempt_allocation_slow(word_size, 844 context, 845 gc_count_before_ret, 846 gclocker_retry_count_ret); 847 } 848 assert_heap_not_locked(); 849 if (result != NULL) { 850 dirty_young_block(result, word_size); 851 } 852 return result; 853 } 854 855 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 856 assert(!is_init_completed(), "Expect to be called at JVM init time"); 857 assert(ranges != NULL, "MemRegion array NULL"); 858 assert(count != 0, "No MemRegions provided"); 859 MemRegion reserved = _hrm.reserved(); 860 HeapWord* prev_last_addr = NULL; 861 HeapRegion* prev_last_region = NULL; 862 size_t size_used = 0; 863 size_t uncommitted_regions = 0; 864 865 // For each Memregion, free the G1 regions that constitute it, and 866 // notify mark-sweep that the range is no longer to be considered 'archive.' 867 MutexLockerEx x(Heap_lock); 868 for (size_t i = 0; i < count; i++) { 869 HeapWord* start_address = ranges[i].start(); 870 HeapWord* last_address = ranges[i].last(); 871 872 assert(reserved.contains(start_address) && reserved.contains(last_address), 873 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 874 p2i(start_address), p2i(last_address)); 875 assert(start_address > prev_last_addr, 876 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 877 p2i(start_address), p2i(prev_last_addr)); 878 size_used += ranges[i].byte_size(); 879 prev_last_addr = last_address; 880 881 HeapRegion* start_region = _hrm.addr_to_region(start_address); 882 HeapRegion* last_region = _hrm.addr_to_region(last_address); 883 884 // Check for ranges that start in the same G1 region in which the previous 885 // range ended, and adjust the start address so we don't try to free 886 // the same region again. If the current range is entirely within that 887 // region, skip it. 888 if (start_region == prev_last_region) { 889 start_address = start_region->end(); 890 if (start_address > last_address) { 891 continue; 892 } 893 start_region = _hrm.addr_to_region(start_address); 894 } 895 prev_last_region = last_region; 896 897 // After verifying that each region was marked as an archive region by 898 // alloc_archive_regions, set it free and empty and uncommit it. 899 HeapRegion* curr_region = start_region; 900 while (curr_region != NULL) { 901 guarantee(curr_region->is_archive(), 902 "Expected archive region at index %u", curr_region->hrm_index()); 903 uint curr_index = curr_region->hrm_index(); 904 _old_set.remove(curr_region); 905 curr_region->set_free(); 906 curr_region->set_top(curr_region->bottom()); 907 if (curr_region != last_region) { 908 curr_region = _hrm.next_region_in_heap(curr_region); 909 } else { 910 curr_region = NULL; 911 } 912 _hrm.shrink_at(curr_index, 1); 913 uncommitted_regions++; 914 } 915 916 // Notify mark-sweep that this is no longer an archive range. 917 G1ArchiveAllocator::set_range_archive(ranges[i], false); 918 } 919 920 if (uncommitted_regions != 0) { 921 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 922 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 923 } 924 decrease_used(size_used); 925 } 926 927 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 928 uint* gc_count_before_ret, 929 uint* gclocker_retry_count_ret) { 930 // The structure of this method has a lot of similarities to 931 // attempt_allocation_slow(). The reason these two were not merged 932 // into a single one is that such a method would require several "if 933 // allocation is not humongous do this, otherwise do that" 934 // conditional paths which would obscure its flow. In fact, an early 935 // version of this code did use a unified method which was harder to 936 // follow and, as a result, it had subtle bugs that were hard to 937 // track down. So keeping these two methods separate allows each to 938 // be more readable. It will be good to keep these two in sync as 939 // much as possible. 940 941 assert_heap_not_locked_and_not_at_safepoint(); 942 assert(is_humongous(word_size), "attempt_allocation_humongous() " 943 "should only be called for humongous allocations"); 944 945 // Humongous objects can exhaust the heap quickly, so we should check if we 946 // need to start a marking cycle at each humongous object allocation. We do 947 // the check before we do the actual allocation. The reason for doing it 948 // before the allocation is that we avoid having to keep track of the newly 949 // allocated memory while we do a GC. 950 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 951 word_size)) { 952 collect(GCCause::_g1_humongous_allocation); 953 } 954 955 // We will loop until a) we manage to successfully perform the 956 // allocation or b) we successfully schedule a collection which 957 // fails to perform the allocation. b) is the only case when we'll 958 // return NULL. 959 HeapWord* result = NULL; 960 for (int try_count = 1; /* we'll return */; try_count += 1) { 961 bool should_try_gc; 962 uint gc_count_before; 963 964 { 965 MutexLockerEx x(Heap_lock); 966 967 // Given that humongous objects are not allocated in young 968 // regions, we'll first try to do the allocation without doing a 969 // collection hoping that there's enough space in the heap. 970 result = humongous_obj_allocate(word_size, AllocationContext::current()); 971 if (result != NULL) { 972 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 973 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 974 return result; 975 } 976 977 if (GCLocker::is_active_and_needs_gc()) { 978 should_try_gc = false; 979 } else { 980 // The GCLocker may not be active but the GCLocker initiated 981 // GC may not yet have been performed (GCLocker::needs_gc() 982 // returns true). In this case we do not try this GC and 983 // wait until the GCLocker initiated GC is performed, and 984 // then retry the allocation. 985 if (GCLocker::needs_gc()) { 986 should_try_gc = false; 987 } else { 988 // Read the GC count while still holding the Heap_lock. 989 gc_count_before = total_collections(); 990 should_try_gc = true; 991 } 992 } 993 } 994 995 if (should_try_gc) { 996 // If we failed to allocate the humongous object, we should try to 997 // do a collection pause (if we're allowed) in case it reclaims 998 // enough space for the allocation to succeed after the pause. 999 1000 bool succeeded; 1001 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1002 GCCause::_g1_humongous_allocation); 1003 if (result != NULL) { 1004 assert(succeeded, "only way to get back a non-NULL result"); 1005 return result; 1006 } 1007 1008 if (succeeded) { 1009 // If we get here we successfully scheduled a collection which 1010 // failed to allocate. No point in trying to allocate 1011 // further. We'll just return NULL. 1012 MutexLockerEx x(Heap_lock); 1013 *gc_count_before_ret = total_collections(); 1014 return NULL; 1015 } 1016 } else { 1017 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1018 MutexLockerEx x(Heap_lock); 1019 *gc_count_before_ret = total_collections(); 1020 return NULL; 1021 } 1022 // The GCLocker is either active or the GCLocker initiated 1023 // GC has not yet been performed. Stall until it is and 1024 // then retry the allocation. 1025 GCLocker::stall_until_clear(); 1026 (*gclocker_retry_count_ret) += 1; 1027 } 1028 1029 // We can reach here if we were unsuccessful in scheduling a 1030 // collection (because another thread beat us to it) or if we were 1031 // stalled due to the GC locker. In either can we should retry the 1032 // allocation attempt in case another thread successfully 1033 // performed a collection and reclaimed enough space. Give a 1034 // warning if we seem to be looping forever. 1035 1036 if ((QueuedAllocationWarningCount > 0) && 1037 (try_count % QueuedAllocationWarningCount == 0)) { 1038 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() " 1039 "retries %d times", try_count); 1040 } 1041 } 1042 1043 ShouldNotReachHere(); 1044 return NULL; 1045 } 1046 1047 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1048 AllocationContext_t context, 1049 bool expect_null_mutator_alloc_region) { 1050 assert_at_safepoint(true /* should_be_vm_thread */); 1051 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1052 "the current alloc region was unexpectedly found to be non-NULL"); 1053 1054 if (!is_humongous(word_size)) { 1055 return _allocator->attempt_allocation_locked(word_size, context); 1056 } else { 1057 HeapWord* result = humongous_obj_allocate(word_size, context); 1058 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1059 collector_state()->set_initiate_conc_mark_if_possible(true); 1060 } 1061 return result; 1062 } 1063 1064 ShouldNotReachHere(); 1065 } 1066 1067 class PostCompactionPrinterClosure: public HeapRegionClosure { 1068 private: 1069 G1HRPrinter* _hr_printer; 1070 public: 1071 bool doHeapRegion(HeapRegion* hr) { 1072 assert(!hr->is_young(), "not expecting to find young regions"); 1073 _hr_printer->post_compaction(hr); 1074 return false; 1075 } 1076 1077 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1078 : _hr_printer(hr_printer) { } 1079 }; 1080 1081 void G1CollectedHeap::print_hrm_post_compaction() { 1082 if (_hr_printer.is_active()) { 1083 PostCompactionPrinterClosure cl(hr_printer()); 1084 heap_region_iterate(&cl); 1085 } 1086 1087 } 1088 1089 void G1CollectedHeap::abort_concurrent_cycle() { 1090 // Note: When we have a more flexible GC logging framework that 1091 // allows us to add optional attributes to a GC log record we 1092 // could consider timing and reporting how long we wait in the 1093 // following two methods. 1094 wait_while_free_regions_coming(); 1095 // If we start the compaction before the CM threads finish 1096 // scanning the root regions we might trip them over as we'll 1097 // be moving objects / updating references. So let's wait until 1098 // they are done. By telling them to abort, they should complete 1099 // early. 1100 _cm->root_regions()->abort(); 1101 _cm->root_regions()->wait_until_scan_finished(); 1102 append_secondary_free_list_if_not_empty_with_lock(); 1103 1104 // Disable discovery and empty the discovered lists 1105 // for the CM ref processor. 1106 ref_processor_cm()->disable_discovery(); 1107 ref_processor_cm()->abandon_partial_discovery(); 1108 ref_processor_cm()->verify_no_references_recorded(); 1109 1110 // Abandon current iterations of concurrent marking and concurrent 1111 // refinement, if any are in progress. 1112 concurrent_mark()->abort(); 1113 } 1114 1115 void G1CollectedHeap::prepare_heap_for_full_collection() { 1116 // Make sure we'll choose a new allocation region afterwards. 1117 _allocator->release_mutator_alloc_region(); 1118 _allocator->abandon_gc_alloc_regions(); 1119 g1_rem_set()->cleanupHRRS(); 1120 1121 // We may have added regions to the current incremental collection 1122 // set between the last GC or pause and now. We need to clear the 1123 // incremental collection set and then start rebuilding it afresh 1124 // after this full GC. 1125 abandon_collection_set(collection_set()); 1126 1127 tear_down_region_sets(false /* free_list_only */); 1128 collector_state()->set_gcs_are_young(true); 1129 } 1130 1131 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1132 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1133 assert(used() == recalculate_used(), "Should be equal"); 1134 _verifier->verify_region_sets_optional(); 1135 _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull); 1136 _verifier->check_bitmaps("Full GC Start"); 1137 } 1138 1139 void G1CollectedHeap::prepare_heap_for_mutators() { 1140 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1141 ClassLoaderDataGraph::purge(); 1142 MetaspaceAux::verify_metrics(); 1143 1144 // Prepare heap for normal collections. 1145 assert(num_free_regions() == 0, "we should not have added any free regions"); 1146 rebuild_region_sets(false /* free_list_only */); 1147 abort_refinement(); 1148 resize_if_necessary_after_full_collection(); 1149 1150 // Rebuild the strong code root lists for each region 1151 rebuild_strong_code_roots(); 1152 1153 // Start a new incremental collection set for the next pause 1154 start_new_collection_set(); 1155 1156 _allocator->init_mutator_alloc_region(); 1157 1158 // Post collection state updates. 1159 MetaspaceGC::compute_new_size(); 1160 } 1161 1162 void G1CollectedHeap::abort_refinement() { 1163 if (_hot_card_cache->use_cache()) { 1164 _hot_card_cache->reset_hot_cache(); 1165 } 1166 1167 // Discard all remembered set updates. 1168 JavaThread::dirty_card_queue_set().abandon_logs(); 1169 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1170 } 1171 1172 void G1CollectedHeap::verify_after_full_collection() { 1173 check_gc_time_stamps(); 1174 _hrm.verify_optional(); 1175 _verifier->verify_region_sets_optional(); 1176 _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull); 1177 // Clear the previous marking bitmap, if needed for bitmap verification. 1178 // Note we cannot do this when we clear the next marking bitmap in 1179 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1180 // objects marked during a full GC against the previous bitmap. 1181 // But we need to clear it before calling check_bitmaps below since 1182 // the full GC has compacted objects and updated TAMS but not updated 1183 // the prev bitmap. 1184 if (G1VerifyBitmaps) { 1185 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1186 _cm->clear_prev_bitmap(workers()); 1187 } 1188 _verifier->check_bitmaps("Full GC End"); 1189 1190 // At this point there should be no regions in the 1191 // entire heap tagged as young. 1192 assert(check_young_list_empty(), "young list should be empty at this point"); 1193 1194 // Note: since we've just done a full GC, concurrent 1195 // marking is no longer active. Therefore we need not 1196 // re-enable reference discovery for the CM ref processor. 1197 // That will be done at the start of the next marking cycle. 1198 // We also know that the STW processor should no longer 1199 // discover any new references. 1200 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1201 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1202 ref_processor_stw()->verify_no_references_recorded(); 1203 ref_processor_cm()->verify_no_references_recorded(); 1204 } 1205 1206 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1207 // Post collection logging. 1208 // We should do this after we potentially resize the heap so 1209 // that all the COMMIT / UNCOMMIT events are generated before 1210 // the compaction events. 1211 print_hrm_post_compaction(); 1212 heap_transition->print(); 1213 print_heap_after_gc(); 1214 print_heap_regions(); 1215 #ifdef TRACESPINNING 1216 ParallelTaskTerminator::print_termination_counts(); 1217 #endif 1218 } 1219 1220 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1221 bool clear_all_soft_refs) { 1222 assert_at_safepoint(true /* should_be_vm_thread */); 1223 1224 if (GCLocker::check_active_before_gc()) { 1225 // Full GC was not completed. 1226 return false; 1227 } 1228 1229 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1230 collector_policy()->should_clear_all_soft_refs(); 1231 1232 G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs); 1233 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1234 1235 collector.prepare_collection(); 1236 collector.collect(); 1237 collector.complete_collection(); 1238 1239 // Full collection was successfully completed. 1240 return true; 1241 } 1242 1243 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1244 // Currently, there is no facility in the do_full_collection(bool) API to notify 1245 // the caller that the collection did not succeed (e.g., because it was locked 1246 // out by the GC locker). So, right now, we'll ignore the return value. 1247 bool dummy = do_full_collection(true, /* explicit_gc */ 1248 clear_all_soft_refs); 1249 } 1250 1251 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1252 // Capacity, free and used after the GC counted as full regions to 1253 // include the waste in the following calculations. 1254 const size_t capacity_after_gc = capacity(); 1255 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes(); 1256 1257 // This is enforced in arguments.cpp. 1258 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1259 "otherwise the code below doesn't make sense"); 1260 1261 // We don't have floating point command-line arguments 1262 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1263 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1264 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1265 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1266 1267 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1268 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1269 1270 // We have to be careful here as these two calculations can overflow 1271 // 32-bit size_t's. 1272 double used_after_gc_d = (double) used_after_gc; 1273 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1274 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1275 1276 // Let's make sure that they are both under the max heap size, which 1277 // by default will make them fit into a size_t. 1278 double desired_capacity_upper_bound = (double) max_heap_size; 1279 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1280 desired_capacity_upper_bound); 1281 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1282 desired_capacity_upper_bound); 1283 1284 // We can now safely turn them into size_t's. 1285 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1286 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1287 1288 // This assert only makes sense here, before we adjust them 1289 // with respect to the min and max heap size. 1290 assert(minimum_desired_capacity <= maximum_desired_capacity, 1291 "minimum_desired_capacity = " SIZE_FORMAT ", " 1292 "maximum_desired_capacity = " SIZE_FORMAT, 1293 minimum_desired_capacity, maximum_desired_capacity); 1294 1295 // Should not be greater than the heap max size. No need to adjust 1296 // it with respect to the heap min size as it's a lower bound (i.e., 1297 // we'll try to make the capacity larger than it, not smaller). 1298 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1299 // Should not be less than the heap min size. No need to adjust it 1300 // with respect to the heap max size as it's an upper bound (i.e., 1301 // we'll try to make the capacity smaller than it, not greater). 1302 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1303 1304 if (capacity_after_gc < minimum_desired_capacity) { 1305 // Don't expand unless it's significant 1306 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1307 1308 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1309 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1310 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1311 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio); 1312 1313 expand(expand_bytes, _workers); 1314 1315 // No expansion, now see if we want to shrink 1316 } else if (capacity_after_gc > maximum_desired_capacity) { 1317 // Capacity too large, compute shrinking size 1318 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1319 1320 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1321 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1322 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1323 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio); 1324 1325 shrink(shrink_bytes); 1326 } 1327 } 1328 1329 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1330 AllocationContext_t context, 1331 bool do_gc, 1332 bool clear_all_soft_refs, 1333 bool expect_null_mutator_alloc_region, 1334 bool* gc_succeeded) { 1335 *gc_succeeded = true; 1336 // Let's attempt the allocation first. 1337 HeapWord* result = 1338 attempt_allocation_at_safepoint(word_size, 1339 context, 1340 expect_null_mutator_alloc_region); 1341 if (result != NULL) { 1342 assert(*gc_succeeded, "sanity"); 1343 return result; 1344 } 1345 1346 // In a G1 heap, we're supposed to keep allocation from failing by 1347 // incremental pauses. Therefore, at least for now, we'll favor 1348 // expansion over collection. (This might change in the future if we can 1349 // do something smarter than full collection to satisfy a failed alloc.) 1350 result = expand_and_allocate(word_size, context); 1351 if (result != NULL) { 1352 assert(*gc_succeeded, "sanity"); 1353 return result; 1354 } 1355 1356 if (do_gc) { 1357 // Expansion didn't work, we'll try to do a Full GC. 1358 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1359 clear_all_soft_refs); 1360 } 1361 1362 return NULL; 1363 } 1364 1365 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1366 AllocationContext_t context, 1367 bool* succeeded) { 1368 assert_at_safepoint(true /* should_be_vm_thread */); 1369 1370 // Attempts to allocate followed by Full GC. 1371 HeapWord* result = 1372 satisfy_failed_allocation_helper(word_size, 1373 context, 1374 true, /* do_gc */ 1375 false, /* clear_all_soft_refs */ 1376 false, /* expect_null_mutator_alloc_region */ 1377 succeeded); 1378 1379 if (result != NULL || !*succeeded) { 1380 return result; 1381 } 1382 1383 // Attempts to allocate followed by Full GC that will collect all soft references. 1384 result = satisfy_failed_allocation_helper(word_size, 1385 context, 1386 true, /* do_gc */ 1387 true, /* clear_all_soft_refs */ 1388 true, /* expect_null_mutator_alloc_region */ 1389 succeeded); 1390 1391 if (result != NULL || !*succeeded) { 1392 return result; 1393 } 1394 1395 // Attempts to allocate, no GC 1396 result = satisfy_failed_allocation_helper(word_size, 1397 context, 1398 false, /* do_gc */ 1399 false, /* clear_all_soft_refs */ 1400 true, /* expect_null_mutator_alloc_region */ 1401 succeeded); 1402 1403 if (result != NULL) { 1404 assert(*succeeded, "sanity"); 1405 return result; 1406 } 1407 1408 assert(!collector_policy()->should_clear_all_soft_refs(), 1409 "Flag should have been handled and cleared prior to this point"); 1410 1411 // What else? We might try synchronous finalization later. If the total 1412 // space available is large enough for the allocation, then a more 1413 // complete compaction phase than we've tried so far might be 1414 // appropriate. 1415 assert(*succeeded, "sanity"); 1416 return NULL; 1417 } 1418 1419 // Attempting to expand the heap sufficiently 1420 // to support an allocation of the given "word_size". If 1421 // successful, perform the allocation and return the address of the 1422 // allocated block, or else "NULL". 1423 1424 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1425 assert_at_safepoint(true /* should_be_vm_thread */); 1426 1427 _verifier->verify_region_sets_optional(); 1428 1429 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1430 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1431 word_size * HeapWordSize); 1432 1433 1434 if (expand(expand_bytes, _workers)) { 1435 _hrm.verify_optional(); 1436 _verifier->verify_region_sets_optional(); 1437 return attempt_allocation_at_safepoint(word_size, 1438 context, 1439 false /* expect_null_mutator_alloc_region */); 1440 } 1441 return NULL; 1442 } 1443 1444 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1445 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1446 aligned_expand_bytes = align_up(aligned_expand_bytes, 1447 HeapRegion::GrainBytes); 1448 1449 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1450 expand_bytes, aligned_expand_bytes); 1451 1452 if (is_maximal_no_gc()) { 1453 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1454 return false; 1455 } 1456 1457 double expand_heap_start_time_sec = os::elapsedTime(); 1458 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1459 assert(regions_to_expand > 0, "Must expand by at least one region"); 1460 1461 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers); 1462 if (expand_time_ms != NULL) { 1463 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1464 } 1465 1466 if (expanded_by > 0) { 1467 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1468 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1469 g1_policy()->record_new_heap_size(num_regions()); 1470 } else { 1471 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1472 1473 // The expansion of the virtual storage space was unsuccessful. 1474 // Let's see if it was because we ran out of swap. 1475 if (G1ExitOnExpansionFailure && 1476 _hrm.available() >= regions_to_expand) { 1477 // We had head room... 1478 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1479 } 1480 } 1481 return regions_to_expand > 0; 1482 } 1483 1484 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1485 size_t aligned_shrink_bytes = 1486 ReservedSpace::page_align_size_down(shrink_bytes); 1487 aligned_shrink_bytes = align_down(aligned_shrink_bytes, 1488 HeapRegion::GrainBytes); 1489 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1490 1491 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1492 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1493 1494 1495 log_debug(gc, ergo, heap)("Shrink the heap. requested shrinking amount: " SIZE_FORMAT "B aligned shrinking amount: " SIZE_FORMAT "B attempted shrinking amount: " SIZE_FORMAT "B", 1496 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1497 if (num_regions_removed > 0) { 1498 g1_policy()->record_new_heap_size(num_regions()); 1499 } else { 1500 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1501 } 1502 } 1503 1504 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1505 _verifier->verify_region_sets_optional(); 1506 1507 // We should only reach here at the end of a Full GC which means we 1508 // should not not be holding to any GC alloc regions. The method 1509 // below will make sure of that and do any remaining clean up. 1510 _allocator->abandon_gc_alloc_regions(); 1511 1512 // Instead of tearing down / rebuilding the free lists here, we 1513 // could instead use the remove_all_pending() method on free_list to 1514 // remove only the ones that we need to remove. 1515 tear_down_region_sets(true /* free_list_only */); 1516 shrink_helper(shrink_bytes); 1517 rebuild_region_sets(true /* free_list_only */); 1518 1519 _hrm.verify_optional(); 1520 _verifier->verify_region_sets_optional(); 1521 } 1522 1523 // Public methods. 1524 1525 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1526 CollectedHeap(), 1527 _young_gen_sampling_thread(NULL), 1528 _collector_policy(collector_policy), 1529 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1530 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1531 _g1_policy(create_g1_policy(_gc_timer_stw)), 1532 _collection_set(this, _g1_policy), 1533 _dirty_card_queue_set(false), 1534 _is_alive_closure_cm(this), 1535 _is_alive_closure_stw(this), 1536 _ref_processor_cm(NULL), 1537 _ref_processor_stw(NULL), 1538 _bot(NULL), 1539 _hot_card_cache(NULL), 1540 _g1_rem_set(NULL), 1541 _cr(NULL), 1542 _g1mm(NULL), 1543 _preserved_marks_set(true /* in_c_heap */), 1544 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1545 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1546 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1547 _humongous_reclaim_candidates(), 1548 _has_humongous_reclaim_candidates(false), 1549 _archive_allocator(NULL), 1550 _free_regions_coming(false), 1551 _gc_time_stamp(0), 1552 _summary_bytes_used(0), 1553 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1554 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1555 _expand_heap_after_alloc_failure(true), 1556 _old_marking_cycles_started(0), 1557 _old_marking_cycles_completed(0), 1558 _in_cset_fast_test() { 1559 1560 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1561 /* are_GC_task_threads */true, 1562 /* are_ConcurrentGC_threads */false); 1563 _workers->initialize_workers(); 1564 _verifier = new G1HeapVerifier(this); 1565 1566 _allocator = G1Allocator::create_allocator(this); 1567 1568 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1569 1570 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1571 1572 // Override the default _filler_array_max_size so that no humongous filler 1573 // objects are created. 1574 _filler_array_max_size = _humongous_object_threshold_in_words; 1575 1576 uint n_queues = ParallelGCThreads; 1577 _task_queues = new RefToScanQueueSet(n_queues); 1578 1579 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1580 1581 for (uint i = 0; i < n_queues; i++) { 1582 RefToScanQueue* q = new RefToScanQueue(); 1583 q->initialize(); 1584 _task_queues->register_queue(i, q); 1585 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1586 } 1587 1588 // Initialize the G1EvacuationFailureALot counters and flags. 1589 NOT_PRODUCT(reset_evacuation_should_fail();) 1590 1591 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1592 } 1593 1594 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1595 size_t size, 1596 size_t translation_factor) { 1597 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1598 // Allocate a new reserved space, preferring to use large pages. 1599 ReservedSpace rs(size, preferred_page_size); 1600 G1RegionToSpaceMapper* result = 1601 G1RegionToSpaceMapper::create_mapper(rs, 1602 size, 1603 rs.alignment(), 1604 HeapRegion::GrainBytes, 1605 translation_factor, 1606 mtGC); 1607 1608 os::trace_page_sizes_for_requested_size(description, 1609 size, 1610 preferred_page_size, 1611 rs.alignment(), 1612 rs.base(), 1613 rs.size()); 1614 1615 return result; 1616 } 1617 1618 jint G1CollectedHeap::initialize_concurrent_refinement() { 1619 jint ecode = JNI_OK; 1620 _cr = G1ConcurrentRefine::create(&ecode); 1621 return ecode; 1622 } 1623 1624 jint G1CollectedHeap::initialize_young_gen_sampling_thread() { 1625 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread(); 1626 if (_young_gen_sampling_thread->osthread() == NULL) { 1627 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread"); 1628 return JNI_ENOMEM; 1629 } 1630 return JNI_OK; 1631 } 1632 1633 jint G1CollectedHeap::initialize() { 1634 CollectedHeap::pre_initialize(); 1635 os::enable_vtime(); 1636 1637 // Necessary to satisfy locking discipline assertions. 1638 1639 MutexLocker x(Heap_lock); 1640 1641 // While there are no constraints in the GC code that HeapWordSize 1642 // be any particular value, there are multiple other areas in the 1643 // system which believe this to be true (e.g. oop->object_size in some 1644 // cases incorrectly returns the size in wordSize units rather than 1645 // HeapWordSize). 1646 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1647 1648 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1649 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1650 size_t heap_alignment = collector_policy()->heap_alignment(); 1651 1652 // Ensure that the sizes are properly aligned. 1653 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1654 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1655 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1656 1657 // Reserve the maximum. 1658 1659 // When compressed oops are enabled, the preferred heap base 1660 // is calculated by subtracting the requested size from the 1661 // 32Gb boundary and using the result as the base address for 1662 // heap reservation. If the requested size is not aligned to 1663 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1664 // into the ReservedHeapSpace constructor) then the actual 1665 // base of the reserved heap may end up differing from the 1666 // address that was requested (i.e. the preferred heap base). 1667 // If this happens then we could end up using a non-optimal 1668 // compressed oops mode. 1669 1670 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1671 heap_alignment); 1672 1673 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1674 1675 // Create the barrier set for the entire reserved region. 1676 G1SATBCardTableLoggingModRefBS* bs 1677 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1678 bs->initialize(); 1679 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1680 set_barrier_set(bs); 1681 1682 // Create the hot card cache. 1683 _hot_card_cache = new G1HotCardCache(this); 1684 1685 // Carve out the G1 part of the heap. 1686 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1687 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1688 G1RegionToSpaceMapper* heap_storage = 1689 G1RegionToSpaceMapper::create_mapper(g1_rs, 1690 g1_rs.size(), 1691 page_size, 1692 HeapRegion::GrainBytes, 1693 1, 1694 mtJavaHeap); 1695 os::trace_page_sizes("Heap", 1696 collector_policy()->min_heap_byte_size(), 1697 max_byte_size, 1698 page_size, 1699 heap_rs.base(), 1700 heap_rs.size()); 1701 heap_storage->set_mapping_changed_listener(&_listener); 1702 1703 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1704 G1RegionToSpaceMapper* bot_storage = 1705 create_aux_memory_mapper("Block Offset Table", 1706 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1707 G1BlockOffsetTable::heap_map_factor()); 1708 1709 G1RegionToSpaceMapper* cardtable_storage = 1710 create_aux_memory_mapper("Card Table", 1711 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1712 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1713 1714 G1RegionToSpaceMapper* card_counts_storage = 1715 create_aux_memory_mapper("Card Counts Table", 1716 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1717 G1CardCounts::heap_map_factor()); 1718 1719 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1720 G1RegionToSpaceMapper* prev_bitmap_storage = 1721 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1722 G1RegionToSpaceMapper* next_bitmap_storage = 1723 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1724 1725 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1726 g1_barrier_set()->initialize(cardtable_storage); 1727 // Do later initialization work for concurrent refinement. 1728 _hot_card_cache->initialize(card_counts_storage); 1729 1730 // 6843694 - ensure that the maximum region index can fit 1731 // in the remembered set structures. 1732 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1733 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1734 1735 // Also create a G1 rem set. 1736 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache); 1737 _g1_rem_set->initialize(max_capacity(), max_regions()); 1738 1739 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1740 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1741 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1742 "too many cards per region"); 1743 1744 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1745 1746 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1747 1748 { 1749 HeapWord* start = _hrm.reserved().start(); 1750 HeapWord* end = _hrm.reserved().end(); 1751 size_t granularity = HeapRegion::GrainBytes; 1752 1753 _in_cset_fast_test.initialize(start, end, granularity); 1754 _humongous_reclaim_candidates.initialize(start, end, granularity); 1755 } 1756 1757 // Create the G1ConcurrentMark data structure and thread. 1758 // (Must do this late, so that "max_regions" is defined.) 1759 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1760 if (_cm == NULL || !_cm->completed_initialization()) { 1761 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1762 return JNI_ENOMEM; 1763 } 1764 _cmThread = _cm->cm_thread(); 1765 1766 // Now expand into the initial heap size. 1767 if (!expand(init_byte_size, _workers)) { 1768 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1769 return JNI_ENOMEM; 1770 } 1771 1772 // Perform any initialization actions delegated to the policy. 1773 g1_policy()->init(this, &_collection_set); 1774 1775 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1776 SATB_Q_FL_lock, 1777 G1SATBProcessCompletedThreshold, 1778 Shared_SATB_Q_lock); 1779 1780 jint ecode = initialize_concurrent_refinement(); 1781 if (ecode != JNI_OK) { 1782 return ecode; 1783 } 1784 1785 ecode = initialize_young_gen_sampling_thread(); 1786 if (ecode != JNI_OK) { 1787 return ecode; 1788 } 1789 1790 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1791 DirtyCardQ_FL_lock, 1792 (int)concurrent_refine()->yellow_zone(), 1793 (int)concurrent_refine()->red_zone(), 1794 Shared_DirtyCardQ_lock, 1795 NULL, // fl_owner 1796 true); // init_free_ids 1797 1798 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1799 DirtyCardQ_FL_lock, 1800 -1, // never trigger processing 1801 -1, // no limit on length 1802 Shared_DirtyCardQ_lock, 1803 &JavaThread::dirty_card_queue_set()); 1804 1805 // Here we allocate the dummy HeapRegion that is required by the 1806 // G1AllocRegion class. 1807 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1808 1809 // We'll re-use the same region whether the alloc region will 1810 // require BOT updates or not and, if it doesn't, then a non-young 1811 // region will complain that it cannot support allocations without 1812 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1813 dummy_region->set_eden(); 1814 // Make sure it's full. 1815 dummy_region->set_top(dummy_region->end()); 1816 G1AllocRegion::setup(this, dummy_region); 1817 1818 _allocator->init_mutator_alloc_region(); 1819 1820 // Do create of the monitoring and management support so that 1821 // values in the heap have been properly initialized. 1822 _g1mm = new G1MonitoringSupport(this); 1823 1824 G1StringDedup::initialize(); 1825 1826 _preserved_marks_set.init(ParallelGCThreads); 1827 1828 _collection_set.initialize(max_regions()); 1829 1830 return JNI_OK; 1831 } 1832 1833 void G1CollectedHeap::stop() { 1834 // Stop all concurrent threads. We do this to make sure these threads 1835 // do not continue to execute and access resources (e.g. logging) 1836 // that are destroyed during shutdown. 1837 _cr->stop(); 1838 _young_gen_sampling_thread->stop(); 1839 _cmThread->stop(); 1840 if (G1StringDedup::is_enabled()) { 1841 G1StringDedup::stop(); 1842 } 1843 } 1844 1845 void G1CollectedHeap::safepoint_synchronize_begin() { 1846 SuspendibleThreadSet::synchronize(); 1847 } 1848 1849 void G1CollectedHeap::safepoint_synchronize_end() { 1850 SuspendibleThreadSet::desynchronize(); 1851 } 1852 1853 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1854 return HeapRegion::max_region_size(); 1855 } 1856 1857 void G1CollectedHeap::post_initialize() { 1858 ref_processing_init(); 1859 } 1860 1861 void G1CollectedHeap::ref_processing_init() { 1862 // Reference processing in G1 currently works as follows: 1863 // 1864 // * There are two reference processor instances. One is 1865 // used to record and process discovered references 1866 // during concurrent marking; the other is used to 1867 // record and process references during STW pauses 1868 // (both full and incremental). 1869 // * Both ref processors need to 'span' the entire heap as 1870 // the regions in the collection set may be dotted around. 1871 // 1872 // * For the concurrent marking ref processor: 1873 // * Reference discovery is enabled at initial marking. 1874 // * Reference discovery is disabled and the discovered 1875 // references processed etc during remarking. 1876 // * Reference discovery is MT (see below). 1877 // * Reference discovery requires a barrier (see below). 1878 // * Reference processing may or may not be MT 1879 // (depending on the value of ParallelRefProcEnabled 1880 // and ParallelGCThreads). 1881 // * A full GC disables reference discovery by the CM 1882 // ref processor and abandons any entries on it's 1883 // discovered lists. 1884 // 1885 // * For the STW processor: 1886 // * Non MT discovery is enabled at the start of a full GC. 1887 // * Processing and enqueueing during a full GC is non-MT. 1888 // * During a full GC, references are processed after marking. 1889 // 1890 // * Discovery (may or may not be MT) is enabled at the start 1891 // of an incremental evacuation pause. 1892 // * References are processed near the end of a STW evacuation pause. 1893 // * For both types of GC: 1894 // * Discovery is atomic - i.e. not concurrent. 1895 // * Reference discovery will not need a barrier. 1896 1897 MemRegion mr = reserved_region(); 1898 1899 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1); 1900 1901 // Concurrent Mark ref processor 1902 _ref_processor_cm = 1903 new ReferenceProcessor(mr, // span 1904 mt_processing, 1905 // mt processing 1906 ParallelGCThreads, 1907 // degree of mt processing 1908 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 1909 // mt discovery 1910 MAX2(ParallelGCThreads, ConcGCThreads), 1911 // degree of mt discovery 1912 false, 1913 // Reference discovery is not atomic 1914 &_is_alive_closure_cm); 1915 // is alive closure 1916 // (for efficiency/performance) 1917 1918 // STW ref processor 1919 _ref_processor_stw = 1920 new ReferenceProcessor(mr, // span 1921 mt_processing, 1922 // mt processing 1923 ParallelGCThreads, 1924 // degree of mt processing 1925 (ParallelGCThreads > 1), 1926 // mt discovery 1927 ParallelGCThreads, 1928 // degree of mt discovery 1929 true, 1930 // Reference discovery is atomic 1931 &_is_alive_closure_stw); 1932 // is alive closure 1933 // (for efficiency/performance) 1934 } 1935 1936 CollectorPolicy* G1CollectedHeap::collector_policy() const { 1937 return _collector_policy; 1938 } 1939 1940 size_t G1CollectedHeap::capacity() const { 1941 return _hrm.length() * HeapRegion::GrainBytes; 1942 } 1943 1944 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const { 1945 return _hrm.total_free_bytes(); 1946 } 1947 1948 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 1949 hr->reset_gc_time_stamp(); 1950 } 1951 1952 #ifndef PRODUCT 1953 1954 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 1955 private: 1956 unsigned _gc_time_stamp; 1957 bool _failures; 1958 1959 public: 1960 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 1961 _gc_time_stamp(gc_time_stamp), _failures(false) { } 1962 1963 virtual bool doHeapRegion(HeapRegion* hr) { 1964 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 1965 if (_gc_time_stamp != region_gc_time_stamp) { 1966 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 1967 region_gc_time_stamp, _gc_time_stamp); 1968 _failures = true; 1969 } 1970 return false; 1971 } 1972 1973 bool failures() { return _failures; } 1974 }; 1975 1976 void G1CollectedHeap::check_gc_time_stamps() { 1977 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 1978 heap_region_iterate(&cl); 1979 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 1980 } 1981 #endif // PRODUCT 1982 1983 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 1984 _hot_card_cache->drain(cl, worker_i); 1985 } 1986 1987 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 1988 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 1989 size_t n_completed_buffers = 0; 1990 while (dcqs.apply_closure_during_gc(cl, worker_i)) { 1991 n_completed_buffers++; 1992 } 1993 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 1994 dcqs.clear_n_completed_buffers(); 1995 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 1996 } 1997 1998 // Computes the sum of the storage used by the various regions. 1999 size_t G1CollectedHeap::used() const { 2000 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2001 if (_archive_allocator != NULL) { 2002 result += _archive_allocator->used(); 2003 } 2004 return result; 2005 } 2006 2007 size_t G1CollectedHeap::used_unlocked() const { 2008 return _summary_bytes_used; 2009 } 2010 2011 class SumUsedClosure: public HeapRegionClosure { 2012 size_t _used; 2013 public: 2014 SumUsedClosure() : _used(0) {} 2015 bool doHeapRegion(HeapRegion* r) { 2016 _used += r->used(); 2017 return false; 2018 } 2019 size_t result() { return _used; } 2020 }; 2021 2022 size_t G1CollectedHeap::recalculate_used() const { 2023 double recalculate_used_start = os::elapsedTime(); 2024 2025 SumUsedClosure blk; 2026 heap_region_iterate(&blk); 2027 2028 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2029 return blk.result(); 2030 } 2031 2032 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2033 switch (cause) { 2034 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2035 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2036 case GCCause::_update_allocation_context_stats_inc: return true; 2037 case GCCause::_wb_conc_mark: return true; 2038 default : return false; 2039 } 2040 } 2041 2042 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2043 switch (cause) { 2044 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2045 case GCCause::_g1_humongous_allocation: return true; 2046 default: return is_user_requested_concurrent_full_gc(cause); 2047 } 2048 } 2049 2050 #ifndef PRODUCT 2051 void G1CollectedHeap::allocate_dummy_regions() { 2052 // Let's fill up most of the region 2053 size_t word_size = HeapRegion::GrainWords - 1024; 2054 // And as a result the region we'll allocate will be humongous. 2055 guarantee(is_humongous(word_size), "sanity"); 2056 2057 // _filler_array_max_size is set to humongous object threshold 2058 // but temporarily change it to use CollectedHeap::fill_with_object(). 2059 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2060 2061 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2062 // Let's use the existing mechanism for the allocation 2063 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2064 AllocationContext::system()); 2065 if (dummy_obj != NULL) { 2066 MemRegion mr(dummy_obj, word_size); 2067 CollectedHeap::fill_with_object(mr); 2068 } else { 2069 // If we can't allocate once, we probably cannot allocate 2070 // again. Let's get out of the loop. 2071 break; 2072 } 2073 } 2074 } 2075 #endif // !PRODUCT 2076 2077 void G1CollectedHeap::increment_old_marking_cycles_started() { 2078 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2079 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2080 "Wrong marking cycle count (started: %d, completed: %d)", 2081 _old_marking_cycles_started, _old_marking_cycles_completed); 2082 2083 _old_marking_cycles_started++; 2084 } 2085 2086 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2087 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2088 2089 // We assume that if concurrent == true, then the caller is a 2090 // concurrent thread that was joined the Suspendible Thread 2091 // Set. If there's ever a cheap way to check this, we should add an 2092 // assert here. 2093 2094 // Given that this method is called at the end of a Full GC or of a 2095 // concurrent cycle, and those can be nested (i.e., a Full GC can 2096 // interrupt a concurrent cycle), the number of full collections 2097 // completed should be either one (in the case where there was no 2098 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2099 // behind the number of full collections started. 2100 2101 // This is the case for the inner caller, i.e. a Full GC. 2102 assert(concurrent || 2103 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2104 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2105 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2106 "is inconsistent with _old_marking_cycles_completed = %u", 2107 _old_marking_cycles_started, _old_marking_cycles_completed); 2108 2109 // This is the case for the outer caller, i.e. the concurrent cycle. 2110 assert(!concurrent || 2111 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2112 "for outer caller (concurrent cycle): " 2113 "_old_marking_cycles_started = %u " 2114 "is inconsistent with _old_marking_cycles_completed = %u", 2115 _old_marking_cycles_started, _old_marking_cycles_completed); 2116 2117 _old_marking_cycles_completed += 1; 2118 2119 // We need to clear the "in_progress" flag in the CM thread before 2120 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2121 // is set) so that if a waiter requests another System.gc() it doesn't 2122 // incorrectly see that a marking cycle is still in progress. 2123 if (concurrent) { 2124 _cmThread->set_idle(); 2125 } 2126 2127 // This notify_all() will ensure that a thread that called 2128 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2129 // and it's waiting for a full GC to finish will be woken up. It is 2130 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2131 FullGCCount_lock->notify_all(); 2132 } 2133 2134 void G1CollectedHeap::collect(GCCause::Cause cause) { 2135 assert_heap_not_locked(); 2136 2137 uint gc_count_before; 2138 uint old_marking_count_before; 2139 uint full_gc_count_before; 2140 bool retry_gc; 2141 2142 do { 2143 retry_gc = false; 2144 2145 { 2146 MutexLocker ml(Heap_lock); 2147 2148 // Read the GC count while holding the Heap_lock 2149 gc_count_before = total_collections(); 2150 full_gc_count_before = total_full_collections(); 2151 old_marking_count_before = _old_marking_cycles_started; 2152 } 2153 2154 if (should_do_concurrent_full_gc(cause)) { 2155 // Schedule an initial-mark evacuation pause that will start a 2156 // concurrent cycle. We're setting word_size to 0 which means that 2157 // we are not requesting a post-GC allocation. 2158 VM_G1IncCollectionPause op(gc_count_before, 2159 0, /* word_size */ 2160 true, /* should_initiate_conc_mark */ 2161 g1_policy()->max_pause_time_ms(), 2162 cause); 2163 op.set_allocation_context(AllocationContext::current()); 2164 2165 VMThread::execute(&op); 2166 if (!op.pause_succeeded()) { 2167 if (old_marking_count_before == _old_marking_cycles_started) { 2168 retry_gc = op.should_retry_gc(); 2169 } else { 2170 // A Full GC happened while we were trying to schedule the 2171 // initial-mark GC. No point in starting a new cycle given 2172 // that the whole heap was collected anyway. 2173 } 2174 2175 if (retry_gc) { 2176 if (GCLocker::is_active_and_needs_gc()) { 2177 GCLocker::stall_until_clear(); 2178 } 2179 } 2180 } 2181 } else { 2182 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2183 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2184 2185 // Schedule a standard evacuation pause. We're setting word_size 2186 // to 0 which means that we are not requesting a post-GC allocation. 2187 VM_G1IncCollectionPause op(gc_count_before, 2188 0, /* word_size */ 2189 false, /* should_initiate_conc_mark */ 2190 g1_policy()->max_pause_time_ms(), 2191 cause); 2192 VMThread::execute(&op); 2193 } else { 2194 // Schedule a Full GC. 2195 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2196 VMThread::execute(&op); 2197 } 2198 } 2199 } while (retry_gc); 2200 } 2201 2202 bool G1CollectedHeap::is_in(const void* p) const { 2203 if (_hrm.reserved().contains(p)) { 2204 // Given that we know that p is in the reserved space, 2205 // heap_region_containing() should successfully 2206 // return the containing region. 2207 HeapRegion* hr = heap_region_containing(p); 2208 return hr->is_in(p); 2209 } else { 2210 return false; 2211 } 2212 } 2213 2214 #ifdef ASSERT 2215 bool G1CollectedHeap::is_in_exact(const void* p) const { 2216 bool contains = reserved_region().contains(p); 2217 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2218 if (contains && available) { 2219 return true; 2220 } else { 2221 return false; 2222 } 2223 } 2224 #endif 2225 2226 // Iteration functions. 2227 2228 // Iterates an ObjectClosure over all objects within a HeapRegion. 2229 2230 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2231 ObjectClosure* _cl; 2232 public: 2233 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2234 bool doHeapRegion(HeapRegion* r) { 2235 if (!r->is_continues_humongous()) { 2236 r->object_iterate(_cl); 2237 } 2238 return false; 2239 } 2240 }; 2241 2242 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2243 IterateObjectClosureRegionClosure blk(cl); 2244 heap_region_iterate(&blk); 2245 } 2246 2247 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2248 _hrm.iterate(cl); 2249 } 2250 2251 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl, 2252 HeapRegionClaimer *hrclaimer, 2253 uint worker_id) const { 2254 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id)); 2255 } 2256 2257 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl, 2258 HeapRegionClaimer *hrclaimer) const { 2259 _hrm.par_iterate(cl, hrclaimer, 0); 2260 } 2261 2262 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2263 _collection_set.iterate(cl); 2264 } 2265 2266 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2267 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2268 } 2269 2270 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2271 HeapRegion* hr = heap_region_containing(addr); 2272 return hr->block_start(addr); 2273 } 2274 2275 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2276 HeapRegion* hr = heap_region_containing(addr); 2277 return hr->block_size(addr); 2278 } 2279 2280 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2281 HeapRegion* hr = heap_region_containing(addr); 2282 return hr->block_is_obj(addr); 2283 } 2284 2285 bool G1CollectedHeap::supports_tlab_allocation() const { 2286 return true; 2287 } 2288 2289 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2290 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2291 } 2292 2293 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2294 return _eden.length() * HeapRegion::GrainBytes; 2295 } 2296 2297 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2298 // must be equal to the humongous object limit. 2299 size_t G1CollectedHeap::max_tlab_size() const { 2300 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2301 } 2302 2303 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2304 AllocationContext_t context = AllocationContext::current(); 2305 return _allocator->unsafe_max_tlab_alloc(context); 2306 } 2307 2308 size_t G1CollectedHeap::max_capacity() const { 2309 return _hrm.reserved().byte_size(); 2310 } 2311 2312 jlong G1CollectedHeap::millis_since_last_gc() { 2313 // See the notes in GenCollectedHeap::millis_since_last_gc() 2314 // for more information about the implementation. 2315 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2316 _g1_policy->collection_pause_end_millis(); 2317 if (ret_val < 0) { 2318 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2319 ". returning zero instead.", ret_val); 2320 return 0; 2321 } 2322 return ret_val; 2323 } 2324 2325 void G1CollectedHeap::prepare_for_verify() { 2326 _verifier->prepare_for_verify(); 2327 } 2328 2329 void G1CollectedHeap::verify(VerifyOption vo) { 2330 _verifier->verify(vo); 2331 } 2332 2333 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2334 return true; 2335 } 2336 2337 const char* const* G1CollectedHeap::concurrent_phases() const { 2338 return _cmThread->concurrent_phases(); 2339 } 2340 2341 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2342 return _cmThread->request_concurrent_phase(phase); 2343 } 2344 2345 class PrintRegionClosure: public HeapRegionClosure { 2346 outputStream* _st; 2347 public: 2348 PrintRegionClosure(outputStream* st) : _st(st) {} 2349 bool doHeapRegion(HeapRegion* r) { 2350 r->print_on(_st); 2351 return false; 2352 } 2353 }; 2354 2355 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2356 const HeapRegion* hr, 2357 const VerifyOption vo) const { 2358 switch (vo) { 2359 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2360 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2361 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr); 2362 default: ShouldNotReachHere(); 2363 } 2364 return false; // keep some compilers happy 2365 } 2366 2367 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2368 const VerifyOption vo) const { 2369 switch (vo) { 2370 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2371 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2372 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj); 2373 default: ShouldNotReachHere(); 2374 } 2375 return false; // keep some compilers happy 2376 } 2377 2378 void G1CollectedHeap::print_heap_regions() const { 2379 LogTarget(Trace, gc, heap, region) lt; 2380 if (lt.is_enabled()) { 2381 LogStream ls(lt); 2382 print_regions_on(&ls); 2383 } 2384 } 2385 2386 void G1CollectedHeap::print_on(outputStream* st) const { 2387 st->print(" %-20s", "garbage-first heap"); 2388 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2389 capacity()/K, used_unlocked()/K); 2390 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")", 2391 p2i(_hrm.reserved().start()), 2392 p2i(_hrm.reserved().end())); 2393 st->cr(); 2394 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2395 uint young_regions = young_regions_count(); 2396 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2397 (size_t) young_regions * HeapRegion::GrainBytes / K); 2398 uint survivor_regions = survivor_regions_count(); 2399 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2400 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2401 st->cr(); 2402 MetaspaceAux::print_on(st); 2403 } 2404 2405 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2406 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2407 "HS=humongous(starts), HC=humongous(continues), " 2408 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2409 "AC=allocation context, " 2410 "TAMS=top-at-mark-start (previous, next)"); 2411 PrintRegionClosure blk(st); 2412 heap_region_iterate(&blk); 2413 } 2414 2415 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2416 print_on(st); 2417 2418 // Print the per-region information. 2419 print_regions_on(st); 2420 } 2421 2422 void G1CollectedHeap::print_on_error(outputStream* st) const { 2423 this->CollectedHeap::print_on_error(st); 2424 2425 if (_cm != NULL) { 2426 st->cr(); 2427 _cm->print_on_error(st); 2428 } 2429 } 2430 2431 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2432 workers()->print_worker_threads_on(st); 2433 _cmThread->print_on(st); 2434 st->cr(); 2435 _cm->print_worker_threads_on(st); 2436 _cr->print_threads_on(st); 2437 _young_gen_sampling_thread->print_on(st); 2438 if (G1StringDedup::is_enabled()) { 2439 G1StringDedup::print_worker_threads_on(st); 2440 } 2441 } 2442 2443 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2444 workers()->threads_do(tc); 2445 tc->do_thread(_cmThread); 2446 _cm->threads_do(tc); 2447 _cr->threads_do(tc); 2448 tc->do_thread(_young_gen_sampling_thread); 2449 if (G1StringDedup::is_enabled()) { 2450 G1StringDedup::threads_do(tc); 2451 } 2452 } 2453 2454 void G1CollectedHeap::print_tracing_info() const { 2455 g1_rem_set()->print_summary_info(); 2456 concurrent_mark()->print_summary_info(); 2457 } 2458 2459 #ifndef PRODUCT 2460 // Helpful for debugging RSet issues. 2461 2462 class PrintRSetsClosure : public HeapRegionClosure { 2463 private: 2464 const char* _msg; 2465 size_t _occupied_sum; 2466 2467 public: 2468 bool doHeapRegion(HeapRegion* r) { 2469 HeapRegionRemSet* hrrs = r->rem_set(); 2470 size_t occupied = hrrs->occupied(); 2471 _occupied_sum += occupied; 2472 2473 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2474 if (occupied == 0) { 2475 tty->print_cr(" RSet is empty"); 2476 } else { 2477 hrrs->print(); 2478 } 2479 tty->print_cr("----------"); 2480 return false; 2481 } 2482 2483 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2484 tty->cr(); 2485 tty->print_cr("========================================"); 2486 tty->print_cr("%s", msg); 2487 tty->cr(); 2488 } 2489 2490 ~PrintRSetsClosure() { 2491 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2492 tty->print_cr("========================================"); 2493 tty->cr(); 2494 } 2495 }; 2496 2497 void G1CollectedHeap::print_cset_rsets() { 2498 PrintRSetsClosure cl("Printing CSet RSets"); 2499 collection_set_iterate(&cl); 2500 } 2501 2502 void G1CollectedHeap::print_all_rsets() { 2503 PrintRSetsClosure cl("Printing All RSets");; 2504 heap_region_iterate(&cl); 2505 } 2506 #endif // PRODUCT 2507 2508 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2509 2510 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2511 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2512 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2513 2514 size_t eden_capacity_bytes = 2515 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2516 2517 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2518 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2519 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2520 } 2521 2522 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2523 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2524 stats->unused(), stats->used(), stats->region_end_waste(), 2525 stats->regions_filled(), stats->direct_allocated(), 2526 stats->failure_used(), stats->failure_waste()); 2527 } 2528 2529 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2530 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2531 gc_tracer->report_gc_heap_summary(when, heap_summary); 2532 2533 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2534 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2535 } 2536 2537 G1CollectedHeap* G1CollectedHeap::heap() { 2538 CollectedHeap* heap = Universe::heap(); 2539 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2540 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2541 return (G1CollectedHeap*)heap; 2542 } 2543 2544 void G1CollectedHeap::gc_prologue(bool full) { 2545 // always_do_update_barrier = false; 2546 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2547 2548 // This summary needs to be printed before incrementing total collections. 2549 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2550 2551 // Update common counters. 2552 increment_total_collections(full /* full gc */); 2553 if (full) { 2554 increment_old_marking_cycles_started(); 2555 reset_gc_time_stamp(); 2556 } else { 2557 increment_gc_time_stamp(); 2558 } 2559 2560 // Fill TLAB's and such 2561 double start = os::elapsedTime(); 2562 accumulate_statistics_all_tlabs(); 2563 ensure_parsability(true); 2564 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2565 } 2566 2567 void G1CollectedHeap::gc_epilogue(bool full) { 2568 // Update common counters. 2569 if (full) { 2570 // Update the number of full collections that have been completed. 2571 increment_old_marking_cycles_completed(false /* concurrent */); 2572 } 2573 2574 // We are at the end of the GC. Total collections has already been increased. 2575 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2576 2577 // FIXME: what is this about? 2578 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2579 // is set. 2580 #if COMPILER2_OR_JVMCI 2581 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2582 #endif 2583 // always_do_update_barrier = true; 2584 2585 double start = os::elapsedTime(); 2586 resize_all_tlabs(); 2587 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2588 2589 allocation_context_stats().update(full); 2590 2591 MemoryService::track_memory_usage(); 2592 // We have just completed a GC. Update the soft reference 2593 // policy with the new heap occupancy 2594 Universe::update_heap_info_at_gc(); 2595 } 2596 2597 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2598 uint gc_count_before, 2599 bool* succeeded, 2600 GCCause::Cause gc_cause) { 2601 assert_heap_not_locked_and_not_at_safepoint(); 2602 VM_G1IncCollectionPause op(gc_count_before, 2603 word_size, 2604 false, /* should_initiate_conc_mark */ 2605 g1_policy()->max_pause_time_ms(), 2606 gc_cause); 2607 2608 op.set_allocation_context(AllocationContext::current()); 2609 VMThread::execute(&op); 2610 2611 HeapWord* result = op.result(); 2612 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2613 assert(result == NULL || ret_succeeded, 2614 "the result should be NULL if the VM did not succeed"); 2615 *succeeded = ret_succeeded; 2616 2617 assert_heap_not_locked(); 2618 return result; 2619 } 2620 2621 void 2622 G1CollectedHeap::doConcurrentMark() { 2623 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2624 if (!_cmThread->in_progress()) { 2625 _cmThread->set_started(); 2626 CGC_lock->notify(); 2627 } 2628 } 2629 2630 size_t G1CollectedHeap::pending_card_num() { 2631 size_t extra_cards = 0; 2632 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) { 2633 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2634 extra_cards += dcq.size(); 2635 } 2636 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2637 size_t buffer_size = dcqs.buffer_size(); 2638 size_t buffer_num = dcqs.completed_buffers_num(); 2639 2640 return buffer_size * buffer_num + extra_cards; 2641 } 2642 2643 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2644 private: 2645 size_t _total_humongous; 2646 size_t _candidate_humongous; 2647 2648 DirtyCardQueue _dcq; 2649 2650 // We don't nominate objects with many remembered set entries, on 2651 // the assumption that such objects are likely still live. 2652 bool is_remset_small(HeapRegion* region) const { 2653 HeapRegionRemSet* const rset = region->rem_set(); 2654 return G1EagerReclaimHumongousObjectsWithStaleRefs 2655 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2656 : rset->is_empty(); 2657 } 2658 2659 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2660 assert(region->is_starts_humongous(), "Must start a humongous object"); 2661 2662 oop obj = oop(region->bottom()); 2663 2664 // Dead objects cannot be eager reclaim candidates. Due to class 2665 // unloading it is unsafe to query their classes so we return early. 2666 if (heap->is_obj_dead(obj, region)) { 2667 return false; 2668 } 2669 2670 // Candidate selection must satisfy the following constraints 2671 // while concurrent marking is in progress: 2672 // 2673 // * In order to maintain SATB invariants, an object must not be 2674 // reclaimed if it was allocated before the start of marking and 2675 // has not had its references scanned. Such an object must have 2676 // its references (including type metadata) scanned to ensure no 2677 // live objects are missed by the marking process. Objects 2678 // allocated after the start of concurrent marking don't need to 2679 // be scanned. 2680 // 2681 // * An object must not be reclaimed if it is on the concurrent 2682 // mark stack. Objects allocated after the start of concurrent 2683 // marking are never pushed on the mark stack. 2684 // 2685 // Nominating only objects allocated after the start of concurrent 2686 // marking is sufficient to meet both constraints. This may miss 2687 // some objects that satisfy the constraints, but the marking data 2688 // structures don't support efficiently performing the needed 2689 // additional tests or scrubbing of the mark stack. 2690 // 2691 // However, we presently only nominate is_typeArray() objects. 2692 // A humongous object containing references induces remembered 2693 // set entries on other regions. In order to reclaim such an 2694 // object, those remembered sets would need to be cleaned up. 2695 // 2696 // We also treat is_typeArray() objects specially, allowing them 2697 // to be reclaimed even if allocated before the start of 2698 // concurrent mark. For this we rely on mark stack insertion to 2699 // exclude is_typeArray() objects, preventing reclaiming an object 2700 // that is in the mark stack. We also rely on the metadata for 2701 // such objects to be built-in and so ensured to be kept live. 2702 // Frequent allocation and drop of large binary blobs is an 2703 // important use case for eager reclaim, and this special handling 2704 // may reduce needed headroom. 2705 2706 return obj->is_typeArray() && is_remset_small(region); 2707 } 2708 2709 public: 2710 RegisterHumongousWithInCSetFastTestClosure() 2711 : _total_humongous(0), 2712 _candidate_humongous(0), 2713 _dcq(&JavaThread::dirty_card_queue_set()) { 2714 } 2715 2716 virtual bool doHeapRegion(HeapRegion* r) { 2717 if (!r->is_starts_humongous()) { 2718 return false; 2719 } 2720 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2721 2722 bool is_candidate = humongous_region_is_candidate(g1h, r); 2723 uint rindex = r->hrm_index(); 2724 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2725 if (is_candidate) { 2726 _candidate_humongous++; 2727 g1h->register_humongous_region_with_cset(rindex); 2728 // Is_candidate already filters out humongous object with large remembered sets. 2729 // If we have a humongous object with a few remembered sets, we simply flush these 2730 // remembered set entries into the DCQS. That will result in automatic 2731 // re-evaluation of their remembered set entries during the following evacuation 2732 // phase. 2733 if (!r->rem_set()->is_empty()) { 2734 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2735 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2736 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 2737 HeapRegionRemSetIterator hrrs(r->rem_set()); 2738 size_t card_index; 2739 while (hrrs.has_next(card_index)) { 2740 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 2741 // The remembered set might contain references to already freed 2742 // regions. Filter out such entries to avoid failing card table 2743 // verification. 2744 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 2745 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 2746 *card_ptr = CardTableModRefBS::dirty_card_val(); 2747 _dcq.enqueue(card_ptr); 2748 } 2749 } 2750 } 2751 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2752 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2753 hrrs.n_yielded(), r->rem_set()->occupied()); 2754 r->rem_set()->clear_locked(); 2755 } 2756 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2757 } 2758 _total_humongous++; 2759 2760 return false; 2761 } 2762 2763 size_t total_humongous() const { return _total_humongous; } 2764 size_t candidate_humongous() const { return _candidate_humongous; } 2765 2766 void flush_rem_set_entries() { _dcq.flush(); } 2767 }; 2768 2769 void G1CollectedHeap::register_humongous_regions_with_cset() { 2770 if (!G1EagerReclaimHumongousObjects) { 2771 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2772 return; 2773 } 2774 double time = os::elapsed_counter(); 2775 2776 // Collect reclaim candidate information and register candidates with cset. 2777 RegisterHumongousWithInCSetFastTestClosure cl; 2778 heap_region_iterate(&cl); 2779 2780 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2781 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2782 cl.total_humongous(), 2783 cl.candidate_humongous()); 2784 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2785 2786 // Finally flush all remembered set entries to re-check into the global DCQS. 2787 cl.flush_rem_set_entries(); 2788 } 2789 2790 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2791 public: 2792 bool doHeapRegion(HeapRegion* hr) { 2793 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2794 hr->verify_rem_set(); 2795 } 2796 return false; 2797 } 2798 }; 2799 2800 uint G1CollectedHeap::num_task_queues() const { 2801 return _task_queues->size(); 2802 } 2803 2804 #if TASKQUEUE_STATS 2805 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2806 st->print_raw_cr("GC Task Stats"); 2807 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2808 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2809 } 2810 2811 void G1CollectedHeap::print_taskqueue_stats() const { 2812 if (!log_is_enabled(Trace, gc, task, stats)) { 2813 return; 2814 } 2815 Log(gc, task, stats) log; 2816 ResourceMark rm; 2817 LogStream ls(log.trace()); 2818 outputStream* st = &ls; 2819 2820 print_taskqueue_stats_hdr(st); 2821 2822 TaskQueueStats totals; 2823 const uint n = num_task_queues(); 2824 for (uint i = 0; i < n; ++i) { 2825 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2826 totals += task_queue(i)->stats; 2827 } 2828 st->print_raw("tot "); totals.print(st); st->cr(); 2829 2830 DEBUG_ONLY(totals.verify()); 2831 } 2832 2833 void G1CollectedHeap::reset_taskqueue_stats() { 2834 const uint n = num_task_queues(); 2835 for (uint i = 0; i < n; ++i) { 2836 task_queue(i)->stats.reset(); 2837 } 2838 } 2839 #endif // TASKQUEUE_STATS 2840 2841 void G1CollectedHeap::wait_for_root_region_scanning() { 2842 double scan_wait_start = os::elapsedTime(); 2843 // We have to wait until the CM threads finish scanning the 2844 // root regions as it's the only way to ensure that all the 2845 // objects on them have been correctly scanned before we start 2846 // moving them during the GC. 2847 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2848 double wait_time_ms = 0.0; 2849 if (waited) { 2850 double scan_wait_end = os::elapsedTime(); 2851 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2852 } 2853 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2854 } 2855 2856 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2857 private: 2858 G1HRPrinter* _hr_printer; 2859 public: 2860 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2861 2862 virtual bool doHeapRegion(HeapRegion* r) { 2863 _hr_printer->cset(r); 2864 return false; 2865 } 2866 }; 2867 2868 void G1CollectedHeap::start_new_collection_set() { 2869 collection_set()->start_incremental_building(); 2870 2871 clear_cset_fast_test(); 2872 2873 guarantee(_eden.length() == 0, "eden should have been cleared"); 2874 g1_policy()->transfer_survivors_to_cset(survivor()); 2875 } 2876 2877 bool 2878 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2879 assert_at_safepoint(true /* should_be_vm_thread */); 2880 guarantee(!is_gc_active(), "collection is not reentrant"); 2881 2882 if (GCLocker::check_active_before_gc()) { 2883 return false; 2884 } 2885 2886 _gc_timer_stw->register_gc_start(); 2887 2888 GCIdMark gc_id_mark; 2889 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2890 2891 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2892 ResourceMark rm; 2893 2894 g1_policy()->note_gc_start(); 2895 2896 wait_for_root_region_scanning(); 2897 2898 print_heap_before_gc(); 2899 print_heap_regions(); 2900 trace_heap_before_gc(_gc_tracer_stw); 2901 2902 _verifier->verify_region_sets_optional(); 2903 _verifier->verify_dirty_young_regions(); 2904 2905 // We should not be doing initial mark unless the conc mark thread is running 2906 if (!_cmThread->should_terminate()) { 2907 // This call will decide whether this pause is an initial-mark 2908 // pause. If it is, during_initial_mark_pause() will return true 2909 // for the duration of this pause. 2910 g1_policy()->decide_on_conc_mark_initiation(); 2911 } 2912 2913 // We do not allow initial-mark to be piggy-backed on a mixed GC. 2914 assert(!collector_state()->during_initial_mark_pause() || 2915 collector_state()->gcs_are_young(), "sanity"); 2916 2917 // We also do not allow mixed GCs during marking. 2918 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 2919 2920 // Record whether this pause is an initial mark. When the current 2921 // thread has completed its logging output and it's safe to signal 2922 // the CM thread, the flag's value in the policy has been reset. 2923 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 2924 2925 // Inner scope for scope based logging, timers, and stats collection 2926 { 2927 EvacuationInfo evacuation_info; 2928 2929 if (collector_state()->during_initial_mark_pause()) { 2930 // We are about to start a marking cycle, so we increment the 2931 // full collection counter. 2932 increment_old_marking_cycles_started(); 2933 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 2934 } 2935 2936 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 2937 2938 GCTraceCPUTime tcpu; 2939 2940 FormatBuffer<> gc_string("Pause "); 2941 if (collector_state()->during_initial_mark_pause()) { 2942 gc_string.append("Initial Mark"); 2943 } else if (collector_state()->gcs_are_young()) { 2944 gc_string.append("Young"); 2945 } else { 2946 gc_string.append("Mixed"); 2947 } 2948 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 2949 2950 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 2951 workers()->active_workers(), 2952 Threads::number_of_non_daemon_threads()); 2953 workers()->update_active_workers(active_workers); 2954 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 2955 2956 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 2957 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 2958 2959 // If the secondary_free_list is not empty, append it to the 2960 // free_list. No need to wait for the cleanup operation to finish; 2961 // the region allocation code will check the secondary_free_list 2962 // and wait if necessary. If the G1StressConcRegionFreeing flag is 2963 // set, skip this step so that the region allocation code has to 2964 // get entries from the secondary_free_list. 2965 if (!G1StressConcRegionFreeing) { 2966 append_secondary_free_list_if_not_empty_with_lock(); 2967 } 2968 2969 G1HeapTransition heap_transition(this); 2970 size_t heap_used_bytes_before_gc = used(); 2971 2972 // Don't dynamically change the number of GC threads this early. A value of 2973 // 0 is used to indicate serial work. When parallel work is done, 2974 // it will be set. 2975 2976 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 2977 IsGCActiveMark x; 2978 2979 gc_prologue(false); 2980 2981 if (VerifyRememberedSets) { 2982 log_info(gc, verify)("[Verifying RemSets before GC]"); 2983 VerifyRegionRemSetClosure v_cl; 2984 heap_region_iterate(&v_cl); 2985 } 2986 2987 _verifier->verify_before_gc(collector_state()->yc_type() == Mixed ? G1HeapVerifier::G1VerifyMixed : G1HeapVerifier::G1VerifyYoung); 2988 2989 _verifier->check_bitmaps("GC Start"); 2990 2991 #if COMPILER2_OR_JVMCI 2992 DerivedPointerTable::clear(); 2993 #endif 2994 2995 // Please see comment in g1CollectedHeap.hpp and 2996 // G1CollectedHeap::ref_processing_init() to see how 2997 // reference processing currently works in G1. 2998 2999 // Enable discovery in the STW reference processor 3000 if (g1_policy()->should_process_references()) { 3001 ref_processor_stw()->enable_discovery(); 3002 } else { 3003 ref_processor_stw()->disable_discovery(); 3004 } 3005 3006 { 3007 // We want to temporarily turn off discovery by the 3008 // CM ref processor, if necessary, and turn it back on 3009 // on again later if we do. Using a scoped 3010 // NoRefDiscovery object will do this. 3011 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3012 3013 // Forget the current alloc region (we might even choose it to be part 3014 // of the collection set!). 3015 _allocator->release_mutator_alloc_region(); 3016 3017 // This timing is only used by the ergonomics to handle our pause target. 3018 // It is unclear why this should not include the full pause. We will 3019 // investigate this in CR 7178365. 3020 // 3021 // Preserving the old comment here if that helps the investigation: 3022 // 3023 // The elapsed time induced by the start time below deliberately elides 3024 // the possible verification above. 3025 double sample_start_time_sec = os::elapsedTime(); 3026 3027 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3028 3029 if (collector_state()->during_initial_mark_pause()) { 3030 concurrent_mark()->checkpoint_roots_initial_pre(); 3031 } 3032 3033 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 3034 3035 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3036 3037 // Make sure the remembered sets are up to date. This needs to be 3038 // done before register_humongous_regions_with_cset(), because the 3039 // remembered sets are used there to choose eager reclaim candidates. 3040 // If the remembered sets are not up to date we might miss some 3041 // entries that need to be handled. 3042 g1_rem_set()->cleanupHRRS(); 3043 3044 register_humongous_regions_with_cset(); 3045 3046 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3047 3048 // We call this after finalize_cset() to 3049 // ensure that the CSet has been finalized. 3050 _cm->verify_no_cset_oops(); 3051 3052 if (_hr_printer.is_active()) { 3053 G1PrintCollectionSetClosure cl(&_hr_printer); 3054 _collection_set.iterate(&cl); 3055 } 3056 3057 // Initialize the GC alloc regions. 3058 _allocator->init_gc_alloc_regions(evacuation_info); 3059 3060 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3061 pre_evacuate_collection_set(); 3062 3063 // Actually do the work... 3064 evacuate_collection_set(evacuation_info, &per_thread_states); 3065 3066 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3067 3068 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3069 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 3070 3071 eagerly_reclaim_humongous_regions(); 3072 3073 record_obj_copy_mem_stats(); 3074 _survivor_evac_stats.adjust_desired_plab_sz(); 3075 _old_evac_stats.adjust_desired_plab_sz(); 3076 3077 double start = os::elapsedTime(); 3078 start_new_collection_set(); 3079 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 3080 3081 if (evacuation_failed()) { 3082 set_used(recalculate_used()); 3083 if (_archive_allocator != NULL) { 3084 _archive_allocator->clear_used(); 3085 } 3086 for (uint i = 0; i < ParallelGCThreads; i++) { 3087 if (_evacuation_failed_info_array[i].has_failed()) { 3088 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3089 } 3090 } 3091 } else { 3092 // The "used" of the the collection set have already been subtracted 3093 // when they were freed. Add in the bytes evacuated. 3094 increase_used(g1_policy()->bytes_copied_during_gc()); 3095 } 3096 3097 if (collector_state()->during_initial_mark_pause()) { 3098 // We have to do this before we notify the CM threads that 3099 // they can start working to make sure that all the 3100 // appropriate initialization is done on the CM object. 3101 concurrent_mark()->checkpoint_roots_initial_post(); 3102 collector_state()->set_mark_in_progress(true); 3103 // Note that we don't actually trigger the CM thread at 3104 // this point. We do that later when we're sure that 3105 // the current thread has completed its logging output. 3106 } 3107 3108 allocate_dummy_regions(); 3109 3110 _allocator->init_mutator_alloc_region(); 3111 3112 { 3113 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3114 if (expand_bytes > 0) { 3115 size_t bytes_before = capacity(); 3116 // No need for an ergo logging here, 3117 // expansion_amount() does this when it returns a value > 0. 3118 double expand_ms; 3119 if (!expand(expand_bytes, _workers, &expand_ms)) { 3120 // We failed to expand the heap. Cannot do anything about it. 3121 } 3122 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3123 } 3124 } 3125 3126 // We redo the verification but now wrt to the new CSet which 3127 // has just got initialized after the previous CSet was freed. 3128 _cm->verify_no_cset_oops(); 3129 3130 // This timing is only used by the ergonomics to handle our pause target. 3131 // It is unclear why this should not include the full pause. We will 3132 // investigate this in CR 7178365. 3133 double sample_end_time_sec = os::elapsedTime(); 3134 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3135 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards); 3136 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3137 3138 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3139 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3140 3141 if (VerifyRememberedSets) { 3142 log_info(gc, verify)("[Verifying RemSets after GC]"); 3143 VerifyRegionRemSetClosure v_cl; 3144 heap_region_iterate(&v_cl); 3145 } 3146 3147 _verifier->verify_after_gc(collector_state()->yc_type() == Mixed ? G1HeapVerifier::G1VerifyMixed : G1HeapVerifier::G1VerifyYoung); 3148 _verifier->check_bitmaps("GC End"); 3149 3150 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3151 ref_processor_stw()->verify_no_references_recorded(); 3152 3153 // CM reference discovery will be re-enabled if necessary. 3154 } 3155 3156 #ifdef TRACESPINNING 3157 ParallelTaskTerminator::print_termination_counts(); 3158 #endif 3159 3160 gc_epilogue(false); 3161 } 3162 3163 // Print the remainder of the GC log output. 3164 if (evacuation_failed()) { 3165 log_info(gc)("To-space exhausted"); 3166 } 3167 3168 g1_policy()->print_phases(); 3169 heap_transition.print(); 3170 3171 // It is not yet to safe to tell the concurrent mark to 3172 // start as we have some optional output below. We don't want the 3173 // output from the concurrent mark thread interfering with this 3174 // logging output either. 3175 3176 _hrm.verify_optional(); 3177 _verifier->verify_region_sets_optional(); 3178 3179 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3180 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3181 3182 print_heap_after_gc(); 3183 print_heap_regions(); 3184 trace_heap_after_gc(_gc_tracer_stw); 3185 3186 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3187 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3188 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3189 // before any GC notifications are raised. 3190 g1mm()->update_sizes(); 3191 3192 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3193 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3194 _gc_timer_stw->register_gc_end(); 3195 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3196 } 3197 // It should now be safe to tell the concurrent mark thread to start 3198 // without its logging output interfering with the logging output 3199 // that came from the pause. 3200 3201 if (should_start_conc_mark) { 3202 // CAUTION: after the doConcurrentMark() call below, 3203 // the concurrent marking thread(s) could be running 3204 // concurrently with us. Make sure that anything after 3205 // this point does not assume that we are the only GC thread 3206 // running. Note: of course, the actual marking work will 3207 // not start until the safepoint itself is released in 3208 // SuspendibleThreadSet::desynchronize(). 3209 doConcurrentMark(); 3210 } 3211 3212 return true; 3213 } 3214 3215 void G1CollectedHeap::remove_self_forwarding_pointers() { 3216 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3217 workers()->run_task(&rsfp_task); 3218 } 3219 3220 void G1CollectedHeap::restore_after_evac_failure() { 3221 double remove_self_forwards_start = os::elapsedTime(); 3222 3223 remove_self_forwarding_pointers(); 3224 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3225 _preserved_marks_set.restore(&task_executor); 3226 3227 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3228 } 3229 3230 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3231 if (!_evacuation_failed) { 3232 _evacuation_failed = true; 3233 } 3234 3235 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3236 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3237 } 3238 3239 bool G1ParEvacuateFollowersClosure::offer_termination() { 3240 G1ParScanThreadState* const pss = par_scan_state(); 3241 start_term_time(); 3242 const bool res = terminator()->offer_termination(); 3243 end_term_time(); 3244 return res; 3245 } 3246 3247 void G1ParEvacuateFollowersClosure::do_void() { 3248 G1ParScanThreadState* const pss = par_scan_state(); 3249 pss->trim_queue(); 3250 do { 3251 pss->steal_and_trim_queue(queues()); 3252 } while (!offer_termination()); 3253 } 3254 3255 class G1ParTask : public AbstractGangTask { 3256 protected: 3257 G1CollectedHeap* _g1h; 3258 G1ParScanThreadStateSet* _pss; 3259 RefToScanQueueSet* _queues; 3260 G1RootProcessor* _root_processor; 3261 ParallelTaskTerminator _terminator; 3262 uint _n_workers; 3263 3264 public: 3265 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3266 : AbstractGangTask("G1 collection"), 3267 _g1h(g1h), 3268 _pss(per_thread_states), 3269 _queues(task_queues), 3270 _root_processor(root_processor), 3271 _terminator(n_workers, _queues), 3272 _n_workers(n_workers) 3273 {} 3274 3275 void work(uint worker_id) { 3276 if (worker_id >= _n_workers) return; // no work needed this round 3277 3278 double start_sec = os::elapsedTime(); 3279 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3280 3281 { 3282 ResourceMark rm; 3283 HandleMark hm; 3284 3285 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3286 3287 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3288 pss->set_ref_processor(rp); 3289 3290 double start_strong_roots_sec = os::elapsedTime(); 3291 3292 _root_processor->evacuate_roots(pss->closures(), worker_id); 3293 3294 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3295 // treating the nmethods visited to act as roots for concurrent marking. 3296 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3297 // objects copied by the current evacuation. 3298 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, 3299 pss->closures()->weak_codeblobs(), 3300 worker_id); 3301 3302 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3303 3304 double term_sec = 0.0; 3305 size_t evac_term_attempts = 0; 3306 { 3307 double start = os::elapsedTime(); 3308 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3309 evac.do_void(); 3310 3311 evac_term_attempts = evac.term_attempts(); 3312 term_sec = evac.term_time(); 3313 double elapsed_sec = os::elapsedTime() - start; 3314 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3315 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3316 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3317 } 3318 3319 assert(pss->queue_is_empty(), "should be empty"); 3320 3321 if (log_is_enabled(Debug, gc, task, stats)) { 3322 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3323 size_t lab_waste; 3324 size_t lab_undo_waste; 3325 pss->waste(lab_waste, lab_undo_waste); 3326 _g1h->print_termination_stats(worker_id, 3327 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3328 strong_roots_sec * 1000.0, /* strong roots time */ 3329 term_sec * 1000.0, /* evac term time */ 3330 evac_term_attempts, /* evac term attempts */ 3331 lab_waste, /* alloc buffer waste */ 3332 lab_undo_waste /* undo waste */ 3333 ); 3334 } 3335 3336 // Close the inner scope so that the ResourceMark and HandleMark 3337 // destructors are executed here and are included as part of the 3338 // "GC Worker Time". 3339 } 3340 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3341 } 3342 }; 3343 3344 void G1CollectedHeap::print_termination_stats_hdr() { 3345 log_debug(gc, task, stats)("GC Termination Stats"); 3346 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3347 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3348 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3349 } 3350 3351 void G1CollectedHeap::print_termination_stats(uint worker_id, 3352 double elapsed_ms, 3353 double strong_roots_ms, 3354 double term_ms, 3355 size_t term_attempts, 3356 size_t alloc_buffer_waste, 3357 size_t undo_waste) const { 3358 log_debug(gc, task, stats) 3359 ("%3d %9.2f %9.2f %6.2f " 3360 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3361 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3362 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3363 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3364 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3365 alloc_buffer_waste * HeapWordSize / K, 3366 undo_waste * HeapWordSize / K); 3367 } 3368 3369 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3370 private: 3371 BoolObjectClosure* _is_alive; 3372 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3373 3374 int _initial_string_table_size; 3375 int _initial_symbol_table_size; 3376 3377 bool _process_strings; 3378 int _strings_processed; 3379 int _strings_removed; 3380 3381 bool _process_symbols; 3382 int _symbols_processed; 3383 int _symbols_removed; 3384 3385 bool _process_string_dedup; 3386 3387 public: 3388 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3389 AbstractGangTask("String/Symbol Unlinking"), 3390 _is_alive(is_alive), 3391 _dedup_closure(is_alive, NULL, false), 3392 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3393 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3394 _process_string_dedup(process_string_dedup) { 3395 3396 _initial_string_table_size = StringTable::the_table()->table_size(); 3397 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3398 if (process_strings) { 3399 StringTable::clear_parallel_claimed_index(); 3400 } 3401 if (process_symbols) { 3402 SymbolTable::clear_parallel_claimed_index(); 3403 } 3404 } 3405 3406 ~G1StringAndSymbolCleaningTask() { 3407 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3408 "claim value %d after unlink less than initial string table size %d", 3409 StringTable::parallel_claimed_index(), _initial_string_table_size); 3410 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3411 "claim value %d after unlink less than initial symbol table size %d", 3412 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3413 3414 log_info(gc, stringtable)( 3415 "Cleaned string and symbol table, " 3416 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3417 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3418 strings_processed(), strings_removed(), 3419 symbols_processed(), symbols_removed()); 3420 } 3421 3422 void work(uint worker_id) { 3423 int strings_processed = 0; 3424 int strings_removed = 0; 3425 int symbols_processed = 0; 3426 int symbols_removed = 0; 3427 if (_process_strings) { 3428 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3429 Atomic::add(strings_processed, &_strings_processed); 3430 Atomic::add(strings_removed, &_strings_removed); 3431 } 3432 if (_process_symbols) { 3433 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3434 Atomic::add(symbols_processed, &_symbols_processed); 3435 Atomic::add(symbols_removed, &_symbols_removed); 3436 } 3437 if (_process_string_dedup) { 3438 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3439 } 3440 } 3441 3442 size_t strings_processed() const { return (size_t)_strings_processed; } 3443 size_t strings_removed() const { return (size_t)_strings_removed; } 3444 3445 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3446 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3447 }; 3448 3449 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3450 private: 3451 static Monitor* _lock; 3452 3453 BoolObjectClosure* const _is_alive; 3454 const bool _unloading_occurred; 3455 const uint _num_workers; 3456 3457 // Variables used to claim nmethods. 3458 CompiledMethod* _first_nmethod; 3459 CompiledMethod* volatile _claimed_nmethod; 3460 3461 // The list of nmethods that need to be processed by the second pass. 3462 CompiledMethod* volatile _postponed_list; 3463 volatile uint _num_entered_barrier; 3464 3465 public: 3466 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3467 _is_alive(is_alive), 3468 _unloading_occurred(unloading_occurred), 3469 _num_workers(num_workers), 3470 _first_nmethod(NULL), 3471 _claimed_nmethod(NULL), 3472 _postponed_list(NULL), 3473 _num_entered_barrier(0) 3474 { 3475 CompiledMethod::increase_unloading_clock(); 3476 // Get first alive nmethod 3477 CompiledMethodIterator iter = CompiledMethodIterator(); 3478 if(iter.next_alive()) { 3479 _first_nmethod = iter.method(); 3480 } 3481 _claimed_nmethod = _first_nmethod; 3482 } 3483 3484 ~G1CodeCacheUnloadingTask() { 3485 CodeCache::verify_clean_inline_caches(); 3486 3487 CodeCache::set_needs_cache_clean(false); 3488 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3489 3490 CodeCache::verify_icholder_relocations(); 3491 } 3492 3493 private: 3494 void add_to_postponed_list(CompiledMethod* nm) { 3495 CompiledMethod* old; 3496 do { 3497 old = _postponed_list; 3498 nm->set_unloading_next(old); 3499 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old); 3500 } 3501 3502 void clean_nmethod(CompiledMethod* nm) { 3503 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3504 3505 if (postponed) { 3506 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3507 add_to_postponed_list(nm); 3508 } 3509 3510 // Mark that this thread has been cleaned/unloaded. 3511 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3512 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3513 } 3514 3515 void clean_nmethod_postponed(CompiledMethod* nm) { 3516 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3517 } 3518 3519 static const int MaxClaimNmethods = 16; 3520 3521 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3522 CompiledMethod* first; 3523 CompiledMethodIterator last; 3524 3525 do { 3526 *num_claimed_nmethods = 0; 3527 3528 first = _claimed_nmethod; 3529 last = CompiledMethodIterator(first); 3530 3531 if (first != NULL) { 3532 3533 for (int i = 0; i < MaxClaimNmethods; i++) { 3534 if (!last.next_alive()) { 3535 break; 3536 } 3537 claimed_nmethods[i] = last.method(); 3538 (*num_claimed_nmethods)++; 3539 } 3540 } 3541 3542 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first); 3543 } 3544 3545 CompiledMethod* claim_postponed_nmethod() { 3546 CompiledMethod* claim; 3547 CompiledMethod* next; 3548 3549 do { 3550 claim = _postponed_list; 3551 if (claim == NULL) { 3552 return NULL; 3553 } 3554 3555 next = claim->unloading_next(); 3556 3557 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim); 3558 3559 return claim; 3560 } 3561 3562 public: 3563 // Mark that we're done with the first pass of nmethod cleaning. 3564 void barrier_mark(uint worker_id) { 3565 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3566 _num_entered_barrier++; 3567 if (_num_entered_barrier == _num_workers) { 3568 ml.notify_all(); 3569 } 3570 } 3571 3572 // See if we have to wait for the other workers to 3573 // finish their first-pass nmethod cleaning work. 3574 void barrier_wait(uint worker_id) { 3575 if (_num_entered_barrier < _num_workers) { 3576 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3577 while (_num_entered_barrier < _num_workers) { 3578 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3579 } 3580 } 3581 } 3582 3583 // Cleaning and unloading of nmethods. Some work has to be postponed 3584 // to the second pass, when we know which nmethods survive. 3585 void work_first_pass(uint worker_id) { 3586 // The first nmethods is claimed by the first worker. 3587 if (worker_id == 0 && _first_nmethod != NULL) { 3588 clean_nmethod(_first_nmethod); 3589 _first_nmethod = NULL; 3590 } 3591 3592 int num_claimed_nmethods; 3593 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3594 3595 while (true) { 3596 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3597 3598 if (num_claimed_nmethods == 0) { 3599 break; 3600 } 3601 3602 for (int i = 0; i < num_claimed_nmethods; i++) { 3603 clean_nmethod(claimed_nmethods[i]); 3604 } 3605 } 3606 } 3607 3608 void work_second_pass(uint worker_id) { 3609 CompiledMethod* nm; 3610 // Take care of postponed nmethods. 3611 while ((nm = claim_postponed_nmethod()) != NULL) { 3612 clean_nmethod_postponed(nm); 3613 } 3614 } 3615 }; 3616 3617 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3618 3619 class G1KlassCleaningTask : public StackObj { 3620 BoolObjectClosure* _is_alive; 3621 volatile int _clean_klass_tree_claimed; 3622 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3623 3624 public: 3625 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3626 _is_alive(is_alive), 3627 _clean_klass_tree_claimed(0), 3628 _klass_iterator() { 3629 } 3630 3631 private: 3632 bool claim_clean_klass_tree_task() { 3633 if (_clean_klass_tree_claimed) { 3634 return false; 3635 } 3636 3637 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0; 3638 } 3639 3640 InstanceKlass* claim_next_klass() { 3641 Klass* klass; 3642 do { 3643 klass =_klass_iterator.next_klass(); 3644 } while (klass != NULL && !klass->is_instance_klass()); 3645 3646 // this can be null so don't call InstanceKlass::cast 3647 return static_cast<InstanceKlass*>(klass); 3648 } 3649 3650 public: 3651 3652 void clean_klass(InstanceKlass* ik) { 3653 ik->clean_weak_instanceklass_links(_is_alive); 3654 } 3655 3656 void work() { 3657 ResourceMark rm; 3658 3659 // One worker will clean the subklass/sibling klass tree. 3660 if (claim_clean_klass_tree_task()) { 3661 Klass::clean_subklass_tree(_is_alive); 3662 } 3663 3664 // All workers will help cleaning the classes, 3665 InstanceKlass* klass; 3666 while ((klass = claim_next_klass()) != NULL) { 3667 clean_klass(klass); 3668 } 3669 } 3670 }; 3671 3672 class G1ResolvedMethodCleaningTask : public StackObj { 3673 BoolObjectClosure* _is_alive; 3674 volatile int _resolved_method_task_claimed; 3675 public: 3676 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) : 3677 _is_alive(is_alive), _resolved_method_task_claimed(0) {} 3678 3679 bool claim_resolved_method_task() { 3680 if (_resolved_method_task_claimed) { 3681 return false; 3682 } 3683 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0; 3684 } 3685 3686 // These aren't big, one thread can do it all. 3687 void work() { 3688 if (claim_resolved_method_task()) { 3689 ResolvedMethodTable::unlink(_is_alive); 3690 } 3691 } 3692 }; 3693 3694 3695 // To minimize the remark pause times, the tasks below are done in parallel. 3696 class G1ParallelCleaningTask : public AbstractGangTask { 3697 private: 3698 G1StringAndSymbolCleaningTask _string_symbol_task; 3699 G1CodeCacheUnloadingTask _code_cache_task; 3700 G1KlassCleaningTask _klass_cleaning_task; 3701 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task; 3702 3703 public: 3704 // The constructor is run in the VMThread. 3705 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3706 AbstractGangTask("Parallel Cleaning"), 3707 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3708 _code_cache_task(num_workers, is_alive, unloading_occurred), 3709 _klass_cleaning_task(is_alive), 3710 _resolved_method_cleaning_task(is_alive) { 3711 } 3712 3713 // The parallel work done by all worker threads. 3714 void work(uint worker_id) { 3715 // Do first pass of code cache cleaning. 3716 _code_cache_task.work_first_pass(worker_id); 3717 3718 // Let the threads mark that the first pass is done. 3719 _code_cache_task.barrier_mark(worker_id); 3720 3721 // Clean the Strings and Symbols. 3722 _string_symbol_task.work(worker_id); 3723 3724 // Clean unreferenced things in the ResolvedMethodTable 3725 _resolved_method_cleaning_task.work(); 3726 3727 // Wait for all workers to finish the first code cache cleaning pass. 3728 _code_cache_task.barrier_wait(worker_id); 3729 3730 // Do the second code cache cleaning work, which realize on 3731 // the liveness information gathered during the first pass. 3732 _code_cache_task.work_second_pass(worker_id); 3733 3734 // Clean all klasses that were not unloaded. 3735 _klass_cleaning_task.work(); 3736 } 3737 }; 3738 3739 3740 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3741 bool class_unloading_occurred) { 3742 uint n_workers = workers()->active_workers(); 3743 3744 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3745 workers()->run_task(&g1_unlink_task); 3746 } 3747 3748 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3749 bool process_strings, 3750 bool process_symbols, 3751 bool process_string_dedup) { 3752 if (!process_strings && !process_symbols && !process_string_dedup) { 3753 // Nothing to clean. 3754 return; 3755 } 3756 3757 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3758 workers()->run_task(&g1_unlink_task); 3759 3760 } 3761 3762 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3763 private: 3764 DirtyCardQueueSet* _queue; 3765 G1CollectedHeap* _g1h; 3766 public: 3767 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3768 _queue(queue), _g1h(g1h) { } 3769 3770 virtual void work(uint worker_id) { 3771 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3772 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3773 3774 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3775 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3776 3777 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3778 } 3779 }; 3780 3781 void G1CollectedHeap::redirty_logged_cards() { 3782 double redirty_logged_cards_start = os::elapsedTime(); 3783 3784 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3785 dirty_card_queue_set().reset_for_par_iteration(); 3786 workers()->run_task(&redirty_task); 3787 3788 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 3789 dcq.merge_bufferlists(&dirty_card_queue_set()); 3790 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3791 3792 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3793 } 3794 3795 // Weak Reference Processing support 3796 3797 // An always "is_alive" closure that is used to preserve referents. 3798 // If the object is non-null then it's alive. Used in the preservation 3799 // of referent objects that are pointed to by reference objects 3800 // discovered by the CM ref processor. 3801 class G1AlwaysAliveClosure: public BoolObjectClosure { 3802 G1CollectedHeap* _g1; 3803 public: 3804 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3805 bool do_object_b(oop p) { 3806 if (p != NULL) { 3807 return true; 3808 } 3809 return false; 3810 } 3811 }; 3812 3813 bool G1STWIsAliveClosure::do_object_b(oop p) { 3814 // An object is reachable if it is outside the collection set, 3815 // or is inside and copied. 3816 return !_g1->is_in_cset(p) || p->is_forwarded(); 3817 } 3818 3819 // Non Copying Keep Alive closure 3820 class G1KeepAliveClosure: public OopClosure { 3821 G1CollectedHeap* _g1; 3822 public: 3823 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3824 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3825 void do_oop(oop* p) { 3826 oop obj = *p; 3827 assert(obj != NULL, "the caller should have filtered out NULL values"); 3828 3829 const InCSetState cset_state = _g1->in_cset_state(obj); 3830 if (!cset_state.is_in_cset_or_humongous()) { 3831 return; 3832 } 3833 if (cset_state.is_in_cset()) { 3834 assert( obj->is_forwarded(), "invariant" ); 3835 *p = obj->forwardee(); 3836 } else { 3837 assert(!obj->is_forwarded(), "invariant" ); 3838 assert(cset_state.is_humongous(), 3839 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3840 _g1->set_humongous_is_live(obj); 3841 } 3842 } 3843 }; 3844 3845 // Copying Keep Alive closure - can be called from both 3846 // serial and parallel code as long as different worker 3847 // threads utilize different G1ParScanThreadState instances 3848 // and different queues. 3849 3850 class G1CopyingKeepAliveClosure: public OopClosure { 3851 G1CollectedHeap* _g1h; 3852 OopClosure* _copy_non_heap_obj_cl; 3853 G1ParScanThreadState* _par_scan_state; 3854 3855 public: 3856 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3857 OopClosure* non_heap_obj_cl, 3858 G1ParScanThreadState* pss): 3859 _g1h(g1h), 3860 _copy_non_heap_obj_cl(non_heap_obj_cl), 3861 _par_scan_state(pss) 3862 {} 3863 3864 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3865 virtual void do_oop( oop* p) { do_oop_work(p); } 3866 3867 template <class T> void do_oop_work(T* p) { 3868 oop obj = oopDesc::load_decode_heap_oop(p); 3869 3870 if (_g1h->is_in_cset_or_humongous(obj)) { 3871 // If the referent object has been forwarded (either copied 3872 // to a new location or to itself in the event of an 3873 // evacuation failure) then we need to update the reference 3874 // field and, if both reference and referent are in the G1 3875 // heap, update the RSet for the referent. 3876 // 3877 // If the referent has not been forwarded then we have to keep 3878 // it alive by policy. Therefore we have copy the referent. 3879 // 3880 // If the reference field is in the G1 heap then we can push 3881 // on the PSS queue. When the queue is drained (after each 3882 // phase of reference processing) the object and it's followers 3883 // will be copied, the reference field set to point to the 3884 // new location, and the RSet updated. Otherwise we need to 3885 // use the the non-heap or metadata closures directly to copy 3886 // the referent object and update the pointer, while avoiding 3887 // updating the RSet. 3888 3889 if (_g1h->is_in_g1_reserved(p)) { 3890 _par_scan_state->push_on_queue(p); 3891 } else { 3892 assert(!Metaspace::contains((const void*)p), 3893 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 3894 _copy_non_heap_obj_cl->do_oop(p); 3895 } 3896 } 3897 } 3898 }; 3899 3900 // Serial drain queue closure. Called as the 'complete_gc' 3901 // closure for each discovered list in some of the 3902 // reference processing phases. 3903 3904 class G1STWDrainQueueClosure: public VoidClosure { 3905 protected: 3906 G1CollectedHeap* _g1h; 3907 G1ParScanThreadState* _par_scan_state; 3908 3909 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3910 3911 public: 3912 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3913 _g1h(g1h), 3914 _par_scan_state(pss) 3915 { } 3916 3917 void do_void() { 3918 G1ParScanThreadState* const pss = par_scan_state(); 3919 pss->trim_queue(); 3920 } 3921 }; 3922 3923 // Parallel Reference Processing closures 3924 3925 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3926 // processing during G1 evacuation pauses. 3927 3928 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3929 private: 3930 G1CollectedHeap* _g1h; 3931 G1ParScanThreadStateSet* _pss; 3932 RefToScanQueueSet* _queues; 3933 WorkGang* _workers; 3934 uint _active_workers; 3935 3936 public: 3937 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3938 G1ParScanThreadStateSet* per_thread_states, 3939 WorkGang* workers, 3940 RefToScanQueueSet *task_queues, 3941 uint n_workers) : 3942 _g1h(g1h), 3943 _pss(per_thread_states), 3944 _queues(task_queues), 3945 _workers(workers), 3946 _active_workers(n_workers) 3947 { 3948 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 3949 } 3950 3951 // Executes the given task using concurrent marking worker threads. 3952 virtual void execute(ProcessTask& task); 3953 virtual void execute(EnqueueTask& task); 3954 }; 3955 3956 // Gang task for possibly parallel reference processing 3957 3958 class G1STWRefProcTaskProxy: public AbstractGangTask { 3959 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 3960 ProcessTask& _proc_task; 3961 G1CollectedHeap* _g1h; 3962 G1ParScanThreadStateSet* _pss; 3963 RefToScanQueueSet* _task_queues; 3964 ParallelTaskTerminator* _terminator; 3965 3966 public: 3967 G1STWRefProcTaskProxy(ProcessTask& proc_task, 3968 G1CollectedHeap* g1h, 3969 G1ParScanThreadStateSet* per_thread_states, 3970 RefToScanQueueSet *task_queues, 3971 ParallelTaskTerminator* terminator) : 3972 AbstractGangTask("Process reference objects in parallel"), 3973 _proc_task(proc_task), 3974 _g1h(g1h), 3975 _pss(per_thread_states), 3976 _task_queues(task_queues), 3977 _terminator(terminator) 3978 {} 3979 3980 virtual void work(uint worker_id) { 3981 // The reference processing task executed by a single worker. 3982 ResourceMark rm; 3983 HandleMark hm; 3984 3985 G1STWIsAliveClosure is_alive(_g1h); 3986 3987 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3988 pss->set_ref_processor(NULL); 3989 3990 // Keep alive closure. 3991 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 3992 3993 // Complete GC closure 3994 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 3995 3996 // Call the reference processing task's work routine. 3997 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 3998 3999 // Note we cannot assert that the refs array is empty here as not all 4000 // of the processing tasks (specifically phase2 - pp2_work) execute 4001 // the complete_gc closure (which ordinarily would drain the queue) so 4002 // the queue may not be empty. 4003 } 4004 }; 4005 4006 // Driver routine for parallel reference processing. 4007 // Creates an instance of the ref processing gang 4008 // task and has the worker threads execute it. 4009 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4010 assert(_workers != NULL, "Need parallel worker threads."); 4011 4012 ParallelTaskTerminator terminator(_active_workers, _queues); 4013 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4014 4015 _workers->run_task(&proc_task_proxy); 4016 } 4017 4018 // Gang task for parallel reference enqueueing. 4019 4020 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4021 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4022 EnqueueTask& _enq_task; 4023 4024 public: 4025 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4026 AbstractGangTask("Enqueue reference objects in parallel"), 4027 _enq_task(enq_task) 4028 { } 4029 4030 virtual void work(uint worker_id) { 4031 _enq_task.work(worker_id); 4032 } 4033 }; 4034 4035 // Driver routine for parallel reference enqueueing. 4036 // Creates an instance of the ref enqueueing gang 4037 // task and has the worker threads execute it. 4038 4039 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4040 assert(_workers != NULL, "Need parallel worker threads."); 4041 4042 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4043 4044 _workers->run_task(&enq_task_proxy); 4045 } 4046 4047 // End of weak reference support closures 4048 4049 // Abstract task used to preserve (i.e. copy) any referent objects 4050 // that are in the collection set and are pointed to by reference 4051 // objects discovered by the CM ref processor. 4052 4053 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4054 protected: 4055 G1CollectedHeap* _g1h; 4056 G1ParScanThreadStateSet* _pss; 4057 RefToScanQueueSet* _queues; 4058 ParallelTaskTerminator _terminator; 4059 uint _n_workers; 4060 4061 public: 4062 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4063 AbstractGangTask("ParPreserveCMReferents"), 4064 _g1h(g1h), 4065 _pss(per_thread_states), 4066 _queues(task_queues), 4067 _terminator(workers, _queues), 4068 _n_workers(workers) 4069 { 4070 g1h->ref_processor_cm()->set_active_mt_degree(workers); 4071 } 4072 4073 void work(uint worker_id) { 4074 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4075 4076 ResourceMark rm; 4077 HandleMark hm; 4078 4079 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4080 pss->set_ref_processor(NULL); 4081 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4082 4083 // Is alive closure 4084 G1AlwaysAliveClosure always_alive(_g1h); 4085 4086 // Copying keep alive closure. Applied to referent objects that need 4087 // to be copied. 4088 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4089 4090 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4091 4092 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4093 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4094 4095 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4096 // So this must be true - but assert just in case someone decides to 4097 // change the worker ids. 4098 assert(worker_id < limit, "sanity"); 4099 assert(!rp->discovery_is_atomic(), "check this code"); 4100 4101 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4102 for (uint idx = worker_id; idx < limit; idx += stride) { 4103 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4104 4105 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4106 while (iter.has_next()) { 4107 // Since discovery is not atomic for the CM ref processor, we 4108 // can see some null referent objects. 4109 iter.load_ptrs(DEBUG_ONLY(true)); 4110 oop ref = iter.obj(); 4111 4112 // This will filter nulls. 4113 if (iter.is_referent_alive()) { 4114 iter.make_referent_alive(); 4115 } 4116 iter.move_to_next(); 4117 } 4118 } 4119 4120 // Drain the queue - which may cause stealing 4121 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4122 drain_queue.do_void(); 4123 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4124 assert(pss->queue_is_empty(), "should be"); 4125 } 4126 }; 4127 4128 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4129 // Any reference objects, in the collection set, that were 'discovered' 4130 // by the CM ref processor should have already been copied (either by 4131 // applying the external root copy closure to the discovered lists, or 4132 // by following an RSet entry). 4133 // 4134 // But some of the referents, that are in the collection set, that these 4135 // reference objects point to may not have been copied: the STW ref 4136 // processor would have seen that the reference object had already 4137 // been 'discovered' and would have skipped discovering the reference, 4138 // but would not have treated the reference object as a regular oop. 4139 // As a result the copy closure would not have been applied to the 4140 // referent object. 4141 // 4142 // We need to explicitly copy these referent objects - the references 4143 // will be processed at the end of remarking. 4144 // 4145 // We also need to do this copying before we process the reference 4146 // objects discovered by the STW ref processor in case one of these 4147 // referents points to another object which is also referenced by an 4148 // object discovered by the STW ref processor. 4149 double preserve_cm_referents_time = 0.0; 4150 4151 // To avoid spawning task when there is no work to do, check that 4152 // a concurrent cycle is active and that some references have been 4153 // discovered. 4154 if (concurrent_mark()->cm_thread()->during_cycle() && 4155 ref_processor_cm()->has_discovered_references()) { 4156 double preserve_cm_referents_start = os::elapsedTime(); 4157 uint no_of_gc_workers = workers()->active_workers(); 4158 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4159 per_thread_states, 4160 no_of_gc_workers, 4161 _task_queues); 4162 workers()->run_task(&keep_cm_referents); 4163 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4164 } 4165 4166 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4167 } 4168 4169 // Weak Reference processing during an evacuation pause (part 1). 4170 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4171 double ref_proc_start = os::elapsedTime(); 4172 4173 ReferenceProcessor* rp = _ref_processor_stw; 4174 assert(rp->discovery_enabled(), "should have been enabled"); 4175 4176 // Closure to test whether a referent is alive. 4177 G1STWIsAliveClosure is_alive(this); 4178 4179 // Even when parallel reference processing is enabled, the processing 4180 // of JNI refs is serial and performed serially by the current thread 4181 // rather than by a worker. The following PSS will be used for processing 4182 // JNI refs. 4183 4184 // Use only a single queue for this PSS. 4185 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4186 pss->set_ref_processor(NULL); 4187 assert(pss->queue_is_empty(), "pre-condition"); 4188 4189 // Keep alive closure. 4190 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4191 4192 // Serial Complete GC closure 4193 G1STWDrainQueueClosure drain_queue(this, pss); 4194 4195 // Setup the soft refs policy... 4196 rp->setup_policy(false); 4197 4198 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4199 4200 ReferenceProcessorStats stats; 4201 if (!rp->processing_is_mt()) { 4202 // Serial reference processing... 4203 stats = rp->process_discovered_references(&is_alive, 4204 &keep_alive, 4205 &drain_queue, 4206 NULL, 4207 pt); 4208 } else { 4209 uint no_of_gc_workers = workers()->active_workers(); 4210 4211 // Parallel reference processing 4212 assert(no_of_gc_workers <= rp->max_num_q(), 4213 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4214 no_of_gc_workers, rp->max_num_q()); 4215 4216 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4217 stats = rp->process_discovered_references(&is_alive, 4218 &keep_alive, 4219 &drain_queue, 4220 &par_task_executor, 4221 pt); 4222 } 4223 4224 _gc_tracer_stw->report_gc_reference_stats(stats); 4225 4226 // We have completed copying any necessary live referent objects. 4227 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4228 4229 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4230 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4231 } 4232 4233 // Weak Reference processing during an evacuation pause (part 2). 4234 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4235 double ref_enq_start = os::elapsedTime(); 4236 4237 ReferenceProcessor* rp = _ref_processor_stw; 4238 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4239 4240 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4241 4242 // Now enqueue any remaining on the discovered lists on to 4243 // the pending list. 4244 if (!rp->processing_is_mt()) { 4245 // Serial reference processing... 4246 rp->enqueue_discovered_references(NULL, pt); 4247 } else { 4248 // Parallel reference enqueueing 4249 4250 uint n_workers = workers()->active_workers(); 4251 4252 assert(n_workers <= rp->max_num_q(), 4253 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4254 n_workers, rp->max_num_q()); 4255 4256 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4257 rp->enqueue_discovered_references(&par_task_executor, pt); 4258 } 4259 4260 rp->verify_no_references_recorded(); 4261 assert(!rp->discovery_enabled(), "should have been disabled"); 4262 4263 // If during an initial mark pause we install a pending list head which is not otherwise reachable 4264 // ensure that it is marked in the bitmap for concurrent marking to discover. 4265 if (collector_state()->during_initial_mark_pause()) { 4266 oop pll_head = Universe::reference_pending_list(); 4267 if (pll_head != NULL) { 4268 _cm->mark_in_next_bitmap(pll_head); 4269 } 4270 } 4271 4272 // FIXME 4273 // CM's reference processing also cleans up the string and symbol tables. 4274 // Should we do that here also? We could, but it is a serial operation 4275 // and could significantly increase the pause time. 4276 4277 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4278 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4279 } 4280 4281 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4282 double merge_pss_time_start = os::elapsedTime(); 4283 per_thread_states->flush(); 4284 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4285 } 4286 4287 void G1CollectedHeap::pre_evacuate_collection_set() { 4288 _expand_heap_after_alloc_failure = true; 4289 _evacuation_failed = false; 4290 4291 // Disable the hot card cache. 4292 _hot_card_cache->reset_hot_cache_claimed_index(); 4293 _hot_card_cache->set_use_cache(false); 4294 4295 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4296 _preserved_marks_set.assert_empty(); 4297 4298 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4299 4300 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4301 if (collector_state()->during_initial_mark_pause()) { 4302 double start_clear_claimed_marks = os::elapsedTime(); 4303 4304 ClassLoaderDataGraph::clear_claimed_marks(); 4305 4306 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4307 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4308 } 4309 } 4310 4311 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4312 // Should G1EvacuationFailureALot be in effect for this GC? 4313 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4314 4315 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4316 4317 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4318 4319 double start_par_time_sec = os::elapsedTime(); 4320 double end_par_time_sec; 4321 4322 { 4323 const uint n_workers = workers()->active_workers(); 4324 G1RootProcessor root_processor(this, n_workers); 4325 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4326 4327 print_termination_stats_hdr(); 4328 4329 workers()->run_task(&g1_par_task); 4330 end_par_time_sec = os::elapsedTime(); 4331 4332 // Closing the inner scope will execute the destructor 4333 // for the G1RootProcessor object. We record the current 4334 // elapsed time before closing the scope so that time 4335 // taken for the destructor is NOT included in the 4336 // reported parallel time. 4337 } 4338 4339 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4340 phase_times->record_par_time(par_time_ms); 4341 4342 double code_root_fixup_time_ms = 4343 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4344 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4345 } 4346 4347 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4348 // Process any discovered reference objects - we have 4349 // to do this _before_ we retire the GC alloc regions 4350 // as we may have to copy some 'reachable' referent 4351 // objects (and their reachable sub-graphs) that were 4352 // not copied during the pause. 4353 if (g1_policy()->should_process_references()) { 4354 preserve_cm_referents(per_thread_states); 4355 process_discovered_references(per_thread_states); 4356 } else { 4357 ref_processor_stw()->verify_no_references_recorded(); 4358 } 4359 4360 G1STWIsAliveClosure is_alive(this); 4361 G1KeepAliveClosure keep_alive(this); 4362 4363 { 4364 double start = os::elapsedTime(); 4365 4366 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 4367 4368 double time_ms = (os::elapsedTime() - start) * 1000.0; 4369 g1_policy()->phase_times()->record_ref_proc_time(time_ms); 4370 } 4371 4372 if (G1StringDedup::is_enabled()) { 4373 double fixup_start = os::elapsedTime(); 4374 4375 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4376 4377 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4378 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4379 } 4380 4381 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4382 4383 if (evacuation_failed()) { 4384 restore_after_evac_failure(); 4385 4386 // Reset the G1EvacuationFailureALot counters and flags 4387 // Note: the values are reset only when an actual 4388 // evacuation failure occurs. 4389 NOT_PRODUCT(reset_evacuation_should_fail();) 4390 } 4391 4392 _preserved_marks_set.assert_empty(); 4393 4394 // Enqueue any remaining references remaining on the STW 4395 // reference processor's discovered lists. We need to do 4396 // this after the card table is cleaned (and verified) as 4397 // the act of enqueueing entries on to the pending list 4398 // will log these updates (and dirty their associated 4399 // cards). We need these updates logged to update any 4400 // RSets. 4401 if (g1_policy()->should_process_references()) { 4402 enqueue_discovered_references(per_thread_states); 4403 } else { 4404 g1_policy()->phase_times()->record_ref_enq_time(0); 4405 } 4406 4407 _allocator->release_gc_alloc_regions(evacuation_info); 4408 4409 merge_per_thread_state_info(per_thread_states); 4410 4411 // Reset and re-enable the hot card cache. 4412 // Note the counts for the cards in the regions in the 4413 // collection set are reset when the collection set is freed. 4414 _hot_card_cache->reset_hot_cache(); 4415 _hot_card_cache->set_use_cache(true); 4416 4417 purge_code_root_memory(); 4418 4419 redirty_logged_cards(); 4420 #if COMPILER2_OR_JVMCI 4421 double start = os::elapsedTime(); 4422 DerivedPointerTable::update_pointers(); 4423 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4424 #endif 4425 g1_policy()->print_age_table(); 4426 } 4427 4428 void G1CollectedHeap::record_obj_copy_mem_stats() { 4429 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4430 4431 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4432 create_g1_evac_summary(&_old_evac_stats)); 4433 } 4434 4435 void G1CollectedHeap::free_region(HeapRegion* hr, 4436 FreeRegionList* free_list, 4437 bool skip_remset, 4438 bool skip_hot_card_cache, 4439 bool locked) { 4440 assert(!hr->is_free(), "the region should not be free"); 4441 assert(!hr->is_empty(), "the region should not be empty"); 4442 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4443 assert(free_list != NULL, "pre-condition"); 4444 4445 if (G1VerifyBitmaps) { 4446 MemRegion mr(hr->bottom(), hr->end()); 4447 concurrent_mark()->clear_range_in_prev_bitmap(mr); 4448 } 4449 4450 // Clear the card counts for this region. 4451 // Note: we only need to do this if the region is not young 4452 // (since we don't refine cards in young regions). 4453 if (!skip_hot_card_cache && !hr->is_young()) { 4454 _hot_card_cache->reset_card_counts(hr); 4455 } 4456 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4457 free_list->add_ordered(hr); 4458 } 4459 4460 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4461 FreeRegionList* free_list, 4462 bool skip_remset) { 4463 assert(hr->is_humongous(), "this is only for humongous regions"); 4464 assert(free_list != NULL, "pre-condition"); 4465 hr->clear_humongous(); 4466 free_region(hr, free_list, skip_remset); 4467 } 4468 4469 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4470 const uint humongous_regions_removed) { 4471 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4472 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4473 _old_set.bulk_remove(old_regions_removed); 4474 _humongous_set.bulk_remove(humongous_regions_removed); 4475 } 4476 4477 } 4478 4479 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4480 assert(list != NULL, "list can't be null"); 4481 if (!list->is_empty()) { 4482 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4483 _hrm.insert_list_into_free_list(list); 4484 } 4485 } 4486 4487 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4488 decrease_used(bytes); 4489 } 4490 4491 class G1ParScrubRemSetTask: public AbstractGangTask { 4492 protected: 4493 G1RemSet* _g1rs; 4494 HeapRegionClaimer _hrclaimer; 4495 4496 public: 4497 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) : 4498 AbstractGangTask("G1 ScrubRS"), 4499 _g1rs(g1_rs), 4500 _hrclaimer(num_workers) { 4501 } 4502 4503 void work(uint worker_id) { 4504 _g1rs->scrub(worker_id, &_hrclaimer); 4505 } 4506 }; 4507 4508 void G1CollectedHeap::scrub_rem_set() { 4509 uint num_workers = workers()->active_workers(); 4510 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers); 4511 workers()->run_task(&g1_par_scrub_rs_task); 4512 } 4513 4514 class G1FreeCollectionSetTask : public AbstractGangTask { 4515 private: 4516 4517 // Closure applied to all regions in the collection set to do work that needs to 4518 // be done serially in a single thread. 4519 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4520 private: 4521 EvacuationInfo* _evacuation_info; 4522 const size_t* _surviving_young_words; 4523 4524 // Bytes used in successfully evacuated regions before the evacuation. 4525 size_t _before_used_bytes; 4526 // Bytes used in unsucessfully evacuated regions before the evacuation 4527 size_t _after_used_bytes; 4528 4529 size_t _bytes_allocated_in_old_since_last_gc; 4530 4531 size_t _failure_used_words; 4532 size_t _failure_waste_words; 4533 4534 FreeRegionList _local_free_list; 4535 public: 4536 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4537 HeapRegionClosure(), 4538 _evacuation_info(evacuation_info), 4539 _surviving_young_words(surviving_young_words), 4540 _before_used_bytes(0), 4541 _after_used_bytes(0), 4542 _bytes_allocated_in_old_since_last_gc(0), 4543 _failure_used_words(0), 4544 _failure_waste_words(0), 4545 _local_free_list("Local Region List for CSet Freeing") { 4546 } 4547 4548 virtual bool doHeapRegion(HeapRegion* r) { 4549 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4550 4551 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4552 g1h->clear_in_cset(r); 4553 4554 if (r->is_young()) { 4555 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4556 "Young index %d is wrong for region %u of type %s with %u young regions", 4557 r->young_index_in_cset(), 4558 r->hrm_index(), 4559 r->get_type_str(), 4560 g1h->collection_set()->young_region_length()); 4561 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4562 r->record_surv_words_in_group(words_survived); 4563 } 4564 4565 if (!r->evacuation_failed()) { 4566 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4567 _before_used_bytes += r->used(); 4568 g1h->free_region(r, 4569 &_local_free_list, 4570 true, /* skip_remset */ 4571 true, /* skip_hot_card_cache */ 4572 true /* locked */); 4573 } else { 4574 r->uninstall_surv_rate_group(); 4575 r->set_young_index_in_cset(-1); 4576 r->set_evacuation_failed(false); 4577 // When moving a young gen region to old gen, we "allocate" that whole region 4578 // there. This is in addition to any already evacuated objects. Notify the 4579 // policy about that. 4580 // Old gen regions do not cause an additional allocation: both the objects 4581 // still in the region and the ones already moved are accounted for elsewhere. 4582 if (r->is_young()) { 4583 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4584 } 4585 // The region is now considered to be old. 4586 r->set_old(); 4587 // Do some allocation statistics accounting. Regions that failed evacuation 4588 // are always made old, so there is no need to update anything in the young 4589 // gen statistics, but we need to update old gen statistics. 4590 size_t used_words = r->marked_bytes() / HeapWordSize; 4591 4592 _failure_used_words += used_words; 4593 _failure_waste_words += HeapRegion::GrainWords - used_words; 4594 4595 g1h->old_set_add(r); 4596 _after_used_bytes += r->used(); 4597 } 4598 return false; 4599 } 4600 4601 void complete_work() { 4602 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4603 4604 _evacuation_info->set_regions_freed(_local_free_list.length()); 4605 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4606 4607 g1h->prepend_to_freelist(&_local_free_list); 4608 g1h->decrement_summary_bytes(_before_used_bytes); 4609 4610 G1Policy* policy = g1h->g1_policy(); 4611 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4612 4613 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4614 } 4615 }; 4616 4617 G1CollectionSet* _collection_set; 4618 G1SerialFreeCollectionSetClosure _cl; 4619 const size_t* _surviving_young_words; 4620 4621 size_t _rs_lengths; 4622 4623 volatile jint _serial_work_claim; 4624 4625 struct WorkItem { 4626 uint region_idx; 4627 bool is_young; 4628 bool evacuation_failed; 4629 4630 WorkItem(HeapRegion* r) { 4631 region_idx = r->hrm_index(); 4632 is_young = r->is_young(); 4633 evacuation_failed = r->evacuation_failed(); 4634 } 4635 }; 4636 4637 volatile size_t _parallel_work_claim; 4638 size_t _num_work_items; 4639 WorkItem* _work_items; 4640 4641 void do_serial_work() { 4642 // Need to grab the lock to be allowed to modify the old region list. 4643 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4644 _collection_set->iterate(&_cl); 4645 } 4646 4647 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4648 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4649 4650 HeapRegion* r = g1h->region_at(region_idx); 4651 assert(!g1h->is_on_master_free_list(r), "sanity"); 4652 4653 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4654 4655 if (!is_young) { 4656 g1h->_hot_card_cache->reset_card_counts(r); 4657 } 4658 4659 if (!evacuation_failed) { 4660 r->rem_set()->clear_locked(); 4661 } 4662 } 4663 4664 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4665 private: 4666 size_t _cur_idx; 4667 WorkItem* _work_items; 4668 public: 4669 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4670 4671 virtual bool doHeapRegion(HeapRegion* r) { 4672 _work_items[_cur_idx++] = WorkItem(r); 4673 return false; 4674 } 4675 }; 4676 4677 void prepare_work() { 4678 G1PrepareFreeCollectionSetClosure cl(_work_items); 4679 _collection_set->iterate(&cl); 4680 } 4681 4682 void complete_work() { 4683 _cl.complete_work(); 4684 4685 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4686 policy->record_max_rs_lengths(_rs_lengths); 4687 policy->cset_regions_freed(); 4688 } 4689 public: 4690 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4691 AbstractGangTask("G1 Free Collection Set"), 4692 _cl(evacuation_info, surviving_young_words), 4693 _collection_set(collection_set), 4694 _surviving_young_words(surviving_young_words), 4695 _serial_work_claim(0), 4696 _rs_lengths(0), 4697 _parallel_work_claim(0), 4698 _num_work_items(collection_set->region_length()), 4699 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4700 prepare_work(); 4701 } 4702 4703 ~G1FreeCollectionSetTask() { 4704 complete_work(); 4705 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4706 } 4707 4708 // Chunk size for work distribution. The chosen value has been determined experimentally 4709 // to be a good tradeoff between overhead and achievable parallelism. 4710 static uint chunk_size() { return 32; } 4711 4712 virtual void work(uint worker_id) { 4713 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4714 4715 // Claim serial work. 4716 if (_serial_work_claim == 0) { 4717 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4718 if (value == 0) { 4719 double serial_time = os::elapsedTime(); 4720 do_serial_work(); 4721 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4722 } 4723 } 4724 4725 // Start parallel work. 4726 double young_time = 0.0; 4727 bool has_young_time = false; 4728 double non_young_time = 0.0; 4729 bool has_non_young_time = false; 4730 4731 while (true) { 4732 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4733 size_t cur = end - chunk_size(); 4734 4735 if (cur >= _num_work_items) { 4736 break; 4737 } 4738 4739 double start_time = os::elapsedTime(); 4740 4741 end = MIN2(end, _num_work_items); 4742 4743 for (; cur < end; cur++) { 4744 bool is_young = _work_items[cur].is_young; 4745 4746 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4747 4748 double end_time = os::elapsedTime(); 4749 double time_taken = end_time - start_time; 4750 if (is_young) { 4751 young_time += time_taken; 4752 has_young_time = true; 4753 } else { 4754 non_young_time += time_taken; 4755 has_non_young_time = true; 4756 } 4757 start_time = end_time; 4758 } 4759 } 4760 4761 if (has_young_time) { 4762 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4763 } 4764 if (has_non_young_time) { 4765 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time); 4766 } 4767 } 4768 }; 4769 4770 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4771 _eden.clear(); 4772 4773 double free_cset_start_time = os::elapsedTime(); 4774 4775 { 4776 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4777 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4778 4779 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4780 4781 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4782 cl.name(), 4783 num_workers, 4784 _collection_set.region_length()); 4785 workers()->run_task(&cl, num_workers); 4786 } 4787 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4788 4789 collection_set->clear(); 4790 } 4791 4792 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4793 private: 4794 FreeRegionList* _free_region_list; 4795 HeapRegionSet* _proxy_set; 4796 uint _humongous_objects_reclaimed; 4797 uint _humongous_regions_reclaimed; 4798 size_t _freed_bytes; 4799 public: 4800 4801 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4802 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4803 } 4804 4805 virtual bool doHeapRegion(HeapRegion* r) { 4806 if (!r->is_starts_humongous()) { 4807 return false; 4808 } 4809 4810 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4811 4812 oop obj = (oop)r->bottom(); 4813 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap(); 4814 4815 // The following checks whether the humongous object is live are sufficient. 4816 // The main additional check (in addition to having a reference from the roots 4817 // or the young gen) is whether the humongous object has a remembered set entry. 4818 // 4819 // A humongous object cannot be live if there is no remembered set for it 4820 // because: 4821 // - there can be no references from within humongous starts regions referencing 4822 // the object because we never allocate other objects into them. 4823 // (I.e. there are no intra-region references that may be missed by the 4824 // remembered set) 4825 // - as soon there is a remembered set entry to the humongous starts region 4826 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4827 // until the end of a concurrent mark. 4828 // 4829 // It is not required to check whether the object has been found dead by marking 4830 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4831 // all objects allocated during that time are considered live. 4832 // SATB marking is even more conservative than the remembered set. 4833 // So if at this point in the collection there is no remembered set entry, 4834 // nobody has a reference to it. 4835 // At the start of collection we flush all refinement logs, and remembered sets 4836 // are completely up-to-date wrt to references to the humongous object. 4837 // 4838 // Other implementation considerations: 4839 // - never consider object arrays at this time because they would pose 4840 // considerable effort for cleaning up the the remembered sets. This is 4841 // required because stale remembered sets might reference locations that 4842 // are currently allocated into. 4843 uint region_idx = r->hrm_index(); 4844 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4845 !r->rem_set()->is_empty()) { 4846 log_debug(gc, humongous)("Live humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d", 4847 region_idx, 4848 (size_t)obj->size() * HeapWordSize, 4849 p2i(r->bottom()), 4850 r->rem_set()->occupied(), 4851 r->rem_set()->strong_code_roots_list_length(), 4852 next_bitmap->is_marked(r->bottom()), 4853 g1h->is_humongous_reclaim_candidate(region_idx), 4854 obj->is_typeArray() 4855 ); 4856 return false; 4857 } 4858 4859 guarantee(obj->is_typeArray(), 4860 "Only eagerly reclaiming type arrays is supported, but the object " 4861 PTR_FORMAT " is not.", p2i(r->bottom())); 4862 4863 log_debug(gc, humongous)("Dead humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d", 4864 region_idx, 4865 (size_t)obj->size() * HeapWordSize, 4866 p2i(r->bottom()), 4867 r->rem_set()->occupied(), 4868 r->rem_set()->strong_code_roots_list_length(), 4869 next_bitmap->is_marked(r->bottom()), 4870 g1h->is_humongous_reclaim_candidate(region_idx), 4871 obj->is_typeArray() 4872 ); 4873 4874 // Need to clear mark bit of the humongous object if already set. 4875 if (next_bitmap->is_marked(r->bottom())) { 4876 next_bitmap->clear(r->bottom()); 4877 } 4878 _humongous_objects_reclaimed++; 4879 do { 4880 HeapRegion* next = g1h->next_region_in_humongous(r); 4881 _freed_bytes += r->used(); 4882 r->set_containing_set(NULL); 4883 _humongous_regions_reclaimed++; 4884 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ ); 4885 r = next; 4886 } while (r != NULL); 4887 4888 return false; 4889 } 4890 4891 uint humongous_objects_reclaimed() { 4892 return _humongous_objects_reclaimed; 4893 } 4894 4895 uint humongous_regions_reclaimed() { 4896 return _humongous_regions_reclaimed; 4897 } 4898 4899 size_t bytes_freed() const { 4900 return _freed_bytes; 4901 } 4902 }; 4903 4904 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4905 assert_at_safepoint(true); 4906 4907 if (!G1EagerReclaimHumongousObjects || 4908 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4909 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4910 return; 4911 } 4912 4913 double start_time = os::elapsedTime(); 4914 4915 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4916 4917 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4918 heap_region_iterate(&cl); 4919 4920 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4921 4922 G1HRPrinter* hrp = hr_printer(); 4923 if (hrp->is_active()) { 4924 FreeRegionListIterator iter(&local_cleanup_list); 4925 while (iter.more_available()) { 4926 HeapRegion* hr = iter.get_next(); 4927 hrp->cleanup(hr); 4928 } 4929 } 4930 4931 prepend_to_freelist(&local_cleanup_list); 4932 decrement_summary_bytes(cl.bytes_freed()); 4933 4934 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4935 cl.humongous_objects_reclaimed()); 4936 } 4937 4938 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4939 public: 4940 virtual bool doHeapRegion(HeapRegion* r) { 4941 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4942 G1CollectedHeap::heap()->clear_in_cset(r); 4943 r->set_young_index_in_cset(-1); 4944 return false; 4945 } 4946 }; 4947 4948 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4949 G1AbandonCollectionSetClosure cl; 4950 collection_set->iterate(&cl); 4951 4952 collection_set->clear(); 4953 collection_set->stop_incremental_building(); 4954 } 4955 4956 void G1CollectedHeap::set_free_regions_coming() { 4957 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 4958 4959 assert(!free_regions_coming(), "pre-condition"); 4960 _free_regions_coming = true; 4961 } 4962 4963 void G1CollectedHeap::reset_free_regions_coming() { 4964 assert(free_regions_coming(), "pre-condition"); 4965 4966 { 4967 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 4968 _free_regions_coming = false; 4969 SecondaryFreeList_lock->notify_all(); 4970 } 4971 4972 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 4973 } 4974 4975 void G1CollectedHeap::wait_while_free_regions_coming() { 4976 // Most of the time we won't have to wait, so let's do a quick test 4977 // first before we take the lock. 4978 if (!free_regions_coming()) { 4979 return; 4980 } 4981 4982 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 4983 4984 { 4985 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 4986 while (free_regions_coming()) { 4987 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 4988 } 4989 } 4990 4991 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 4992 } 4993 4994 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 4995 return _allocator->is_retained_old_region(hr); 4996 } 4997 4998 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 4999 _eden.add(hr); 5000 _g1_policy->set_region_eden(hr); 5001 } 5002 5003 #ifdef ASSERT 5004 5005 class NoYoungRegionsClosure: public HeapRegionClosure { 5006 private: 5007 bool _success; 5008 public: 5009 NoYoungRegionsClosure() : _success(true) { } 5010 bool doHeapRegion(HeapRegion* r) { 5011 if (r->is_young()) { 5012 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5013 p2i(r->bottom()), p2i(r->end())); 5014 _success = false; 5015 } 5016 return false; 5017 } 5018 bool success() { return _success; } 5019 }; 5020 5021 bool G1CollectedHeap::check_young_list_empty() { 5022 bool ret = (young_regions_count() == 0); 5023 5024 NoYoungRegionsClosure closure; 5025 heap_region_iterate(&closure); 5026 ret = ret && closure.success(); 5027 5028 return ret; 5029 } 5030 5031 #endif // ASSERT 5032 5033 class TearDownRegionSetsClosure : public HeapRegionClosure { 5034 private: 5035 HeapRegionSet *_old_set; 5036 5037 public: 5038 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5039 5040 bool doHeapRegion(HeapRegion* r) { 5041 if (r->is_old()) { 5042 _old_set->remove(r); 5043 } else if(r->is_young()) { 5044 r->uninstall_surv_rate_group(); 5045 } else { 5046 // We ignore free regions, we'll empty the free list afterwards. 5047 // We ignore humongous regions, we're not tearing down the 5048 // humongous regions set. 5049 assert(r->is_free() || r->is_humongous(), 5050 "it cannot be another type"); 5051 } 5052 return false; 5053 } 5054 5055 ~TearDownRegionSetsClosure() { 5056 assert(_old_set->is_empty(), "post-condition"); 5057 } 5058 }; 5059 5060 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5061 assert_at_safepoint(true /* should_be_vm_thread */); 5062 5063 if (!free_list_only) { 5064 TearDownRegionSetsClosure cl(&_old_set); 5065 heap_region_iterate(&cl); 5066 5067 // Note that emptying the _young_list is postponed and instead done as 5068 // the first step when rebuilding the regions sets again. The reason for 5069 // this is that during a full GC string deduplication needs to know if 5070 // a collected region was young or old when the full GC was initiated. 5071 } 5072 _hrm.remove_all_free_regions(); 5073 } 5074 5075 void G1CollectedHeap::increase_used(size_t bytes) { 5076 _summary_bytes_used += bytes; 5077 } 5078 5079 void G1CollectedHeap::decrease_used(size_t bytes) { 5080 assert(_summary_bytes_used >= bytes, 5081 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5082 _summary_bytes_used, bytes); 5083 _summary_bytes_used -= bytes; 5084 } 5085 5086 void G1CollectedHeap::set_used(size_t bytes) { 5087 _summary_bytes_used = bytes; 5088 } 5089 5090 class RebuildRegionSetsClosure : public HeapRegionClosure { 5091 private: 5092 bool _free_list_only; 5093 HeapRegionSet* _old_set; 5094 HeapRegionManager* _hrm; 5095 size_t _total_used; 5096 5097 public: 5098 RebuildRegionSetsClosure(bool free_list_only, 5099 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5100 _free_list_only(free_list_only), 5101 _old_set(old_set), _hrm(hrm), _total_used(0) { 5102 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5103 if (!free_list_only) { 5104 assert(_old_set->is_empty(), "pre-condition"); 5105 } 5106 } 5107 5108 bool doHeapRegion(HeapRegion* r) { 5109 if (r->is_empty()) { 5110 // Add free regions to the free list 5111 r->set_free(); 5112 r->set_allocation_context(AllocationContext::system()); 5113 _hrm->insert_into_free_list(r); 5114 } else if (!_free_list_only) { 5115 5116 if (r->is_humongous()) { 5117 // We ignore humongous regions. We left the humongous set unchanged. 5118 } else { 5119 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 5120 // We now move all (non-humongous, non-old) regions to old gen, and register them as such. 5121 r->move_to_old(); 5122 _old_set->add(r); 5123 } 5124 _total_used += r->used(); 5125 } 5126 5127 return false; 5128 } 5129 5130 size_t total_used() { 5131 return _total_used; 5132 } 5133 }; 5134 5135 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5136 assert_at_safepoint(true /* should_be_vm_thread */); 5137 5138 if (!free_list_only) { 5139 _eden.clear(); 5140 _survivor.clear(); 5141 } 5142 5143 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5144 heap_region_iterate(&cl); 5145 5146 if (!free_list_only) { 5147 set_used(cl.total_used()); 5148 if (_archive_allocator != NULL) { 5149 _archive_allocator->clear_used(); 5150 } 5151 } 5152 assert(used_unlocked() == recalculate_used(), 5153 "inconsistent used_unlocked(), " 5154 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5155 used_unlocked(), recalculate_used()); 5156 } 5157 5158 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5159 HeapRegion* hr = heap_region_containing(p); 5160 return hr->is_in(p); 5161 } 5162 5163 // Methods for the mutator alloc region 5164 5165 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5166 bool force) { 5167 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5168 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 5169 if (force || should_allocate) { 5170 HeapRegion* new_alloc_region = new_region(word_size, 5171 false /* is_old */, 5172 false /* do_expand */); 5173 if (new_alloc_region != NULL) { 5174 set_region_short_lived_locked(new_alloc_region); 5175 _hr_printer.alloc(new_alloc_region, !should_allocate); 5176 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5177 return new_alloc_region; 5178 } 5179 } 5180 return NULL; 5181 } 5182 5183 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5184 size_t allocated_bytes) { 5185 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5186 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5187 5188 collection_set()->add_eden_region(alloc_region); 5189 increase_used(allocated_bytes); 5190 _hr_printer.retire(alloc_region); 5191 // We update the eden sizes here, when the region is retired, 5192 // instead of when it's allocated, since this is the point that its 5193 // used space has been recored in _summary_bytes_used. 5194 g1mm()->update_eden_size(); 5195 } 5196 5197 // Methods for the GC alloc regions 5198 5199 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 5200 if (dest.is_old()) { 5201 return true; 5202 } else { 5203 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 5204 } 5205 } 5206 5207 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 5208 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5209 5210 if (!has_more_regions(dest)) { 5211 return NULL; 5212 } 5213 5214 const bool is_survivor = dest.is_young(); 5215 5216 HeapRegion* new_alloc_region = new_region(word_size, 5217 !is_survivor, 5218 true /* do_expand */); 5219 if (new_alloc_region != NULL) { 5220 // We really only need to do this for old regions given that we 5221 // should never scan survivors. But it doesn't hurt to do it 5222 // for survivors too. 5223 new_alloc_region->record_timestamp(); 5224 if (is_survivor) { 5225 new_alloc_region->set_survivor(); 5226 _survivor.add(new_alloc_region); 5227 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5228 } else { 5229 new_alloc_region->set_old(); 5230 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5231 } 5232 _hr_printer.alloc(new_alloc_region); 5233 bool during_im = collector_state()->during_initial_mark_pause(); 5234 new_alloc_region->note_start_of_copying(during_im); 5235 return new_alloc_region; 5236 } 5237 return NULL; 5238 } 5239 5240 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5241 size_t allocated_bytes, 5242 InCSetState dest) { 5243 bool during_im = collector_state()->during_initial_mark_pause(); 5244 alloc_region->note_end_of_copying(during_im); 5245 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5246 if (dest.is_old()) { 5247 _old_set.add(alloc_region); 5248 } 5249 _hr_printer.retire(alloc_region); 5250 } 5251 5252 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5253 bool expanded = false; 5254 uint index = _hrm.find_highest_free(&expanded); 5255 5256 if (index != G1_NO_HRM_INDEX) { 5257 if (expanded) { 5258 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5259 HeapRegion::GrainWords * HeapWordSize); 5260 } 5261 _hrm.allocate_free_regions_starting_at(index, 1); 5262 return region_at(index); 5263 } 5264 return NULL; 5265 } 5266 5267 // Optimized nmethod scanning 5268 5269 class RegisterNMethodOopClosure: public OopClosure { 5270 G1CollectedHeap* _g1h; 5271 nmethod* _nm; 5272 5273 template <class T> void do_oop_work(T* p) { 5274 T heap_oop = oopDesc::load_heap_oop(p); 5275 if (!oopDesc::is_null(heap_oop)) { 5276 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5277 HeapRegion* hr = _g1h->heap_region_containing(obj); 5278 assert(!hr->is_continues_humongous(), 5279 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5280 " starting at " HR_FORMAT, 5281 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5282 5283 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5284 hr->add_strong_code_root_locked(_nm); 5285 } 5286 } 5287 5288 public: 5289 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5290 _g1h(g1h), _nm(nm) {} 5291 5292 void do_oop(oop* p) { do_oop_work(p); } 5293 void do_oop(narrowOop* p) { do_oop_work(p); } 5294 }; 5295 5296 class UnregisterNMethodOopClosure: public OopClosure { 5297 G1CollectedHeap* _g1h; 5298 nmethod* _nm; 5299 5300 template <class T> void do_oop_work(T* p) { 5301 T heap_oop = oopDesc::load_heap_oop(p); 5302 if (!oopDesc::is_null(heap_oop)) { 5303 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5304 HeapRegion* hr = _g1h->heap_region_containing(obj); 5305 assert(!hr->is_continues_humongous(), 5306 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5307 " starting at " HR_FORMAT, 5308 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5309 5310 hr->remove_strong_code_root(_nm); 5311 } 5312 } 5313 5314 public: 5315 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5316 _g1h(g1h), _nm(nm) {} 5317 5318 void do_oop(oop* p) { do_oop_work(p); } 5319 void do_oop(narrowOop* p) { do_oop_work(p); } 5320 }; 5321 5322 // Returns true if the reference points to an object that 5323 // can move in an incremental collection. 5324 bool G1CollectedHeap::is_scavengable(oop obj) { 5325 HeapRegion* hr = heap_region_containing(obj); 5326 return !hr->is_pinned(); 5327 } 5328 5329 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5330 guarantee(nm != NULL, "sanity"); 5331 RegisterNMethodOopClosure reg_cl(this, nm); 5332 nm->oops_do(®_cl); 5333 } 5334 5335 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5336 guarantee(nm != NULL, "sanity"); 5337 UnregisterNMethodOopClosure reg_cl(this, nm); 5338 nm->oops_do(®_cl, true); 5339 } 5340 5341 void G1CollectedHeap::purge_code_root_memory() { 5342 double purge_start = os::elapsedTime(); 5343 G1CodeRootSet::purge(); 5344 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5345 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5346 } 5347 5348 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5349 G1CollectedHeap* _g1h; 5350 5351 public: 5352 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5353 _g1h(g1h) {} 5354 5355 void do_code_blob(CodeBlob* cb) { 5356 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5357 if (nm == NULL) { 5358 return; 5359 } 5360 5361 if (ScavengeRootsInCode) { 5362 _g1h->register_nmethod(nm); 5363 } 5364 } 5365 }; 5366 5367 void G1CollectedHeap::rebuild_strong_code_roots() { 5368 RebuildStrongCodeRootClosure blob_cl(this); 5369 CodeCache::blobs_do(&blob_cl); 5370 }