1 /* 2 * Copyright (c) 2001, 2020, 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 "gc/serial/defNewGeneration.inline.hpp" 27 #include "gc/serial/serialHeap.inline.hpp" 28 #include "gc/serial/tenuredGeneration.hpp" 29 #include "gc/shared/adaptiveSizePolicy.hpp" 30 #include "gc/shared/ageTable.inline.hpp" 31 #include "gc/shared/cardTableRS.hpp" 32 #include "gc/shared/collectorCounters.hpp" 33 #include "gc/shared/gcArguments.hpp" 34 #include "gc/shared/gcHeapSummary.hpp" 35 #include "gc/shared/gcLocker.hpp" 36 #include "gc/shared/gcPolicyCounters.hpp" 37 #include "gc/shared/gcTimer.hpp" 38 #include "gc/shared/gcTrace.hpp" 39 #include "gc/shared/gcTraceTime.inline.hpp" 40 #include "gc/shared/genOopClosures.inline.hpp" 41 #include "gc/shared/generationSpec.hpp" 42 #include "gc/shared/preservedMarks.inline.hpp" 43 #include "gc/shared/referencePolicy.hpp" 44 #include "gc/shared/referenceProcessorPhaseTimes.hpp" 45 #include "gc/shared/space.inline.hpp" 46 #include "gc/shared/spaceDecorator.inline.hpp" 47 #include "gc/shared/strongRootsScope.hpp" 48 #include "gc/shared/weakProcessor.hpp" 49 #include "logging/log.hpp" 50 #include "memory/iterator.inline.hpp" 51 #include "memory/resourceArea.hpp" 52 #include "oops/instanceRefKlass.hpp" 53 #include "oops/oop.inline.hpp" 54 #include "runtime/java.hpp" 55 #include "runtime/prefetch.inline.hpp" 56 #include "runtime/thread.inline.hpp" 57 #include "utilities/align.hpp" 58 #include "utilities/copy.hpp" 59 #include "utilities/globalDefinitions.hpp" 60 #include "utilities/stack.inline.hpp" 61 62 // 63 // DefNewGeneration functions. 64 65 // Methods of protected closure types. 66 67 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) { 68 assert(_young_gen->kind() == Generation::DefNew, "Expected the young generation here"); 69 } 70 71 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 72 return cast_from_oop<HeapWord*>(p) >= _young_gen->reserved().end() || p->is_forwarded(); 73 } 74 75 DefNewGeneration::KeepAliveClosure:: 76 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 77 _rs = GenCollectedHeap::heap()->rem_set(); 78 } 79 80 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 81 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 82 83 84 DefNewGeneration::FastKeepAliveClosure:: 85 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 86 DefNewGeneration::KeepAliveClosure(cl) { 87 _boundary = g->reserved().end(); 88 } 89 90 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 91 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 92 93 DefNewGeneration::FastEvacuateFollowersClosure:: 94 FastEvacuateFollowersClosure(SerialHeap* heap, 95 FastScanClosure* cur, 96 FastScanClosure* older) : 97 _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older) 98 { 99 } 100 101 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 102 do { 103 _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older); 104 } while (!_heap->no_allocs_since_save_marks()); 105 guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan"); 106 } 107 108 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) : 109 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 110 { 111 _boundary = _g->reserved().end(); 112 } 113 114 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 115 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 116 { 117 _boundary = _g->reserved().end(); 118 } 119 120 void CLDScanClosure::do_cld(ClassLoaderData* cld) { 121 NOT_PRODUCT(ResourceMark rm); 122 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s", 123 p2i(cld), 124 cld->loader_name_and_id(), 125 cld->has_modified_oops() ? "true" : "false"); 126 127 // If the cld has not been dirtied we know that there's 128 // no references into the young gen and we can skip it. 129 if (cld->has_modified_oops()) { 130 if (_accumulate_modified_oops) { 131 cld->accumulate_modified_oops(); 132 } 133 134 // Tell the closure which CLD is being scanned so that it can be dirtied 135 // if oops are left pointing into the young gen. 136 _scavenge_closure->set_scanned_cld(cld); 137 138 // Clean the cld since we're going to scavenge all the metadata. 139 cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true); 140 141 _scavenge_closure->set_scanned_cld(NULL); 142 } 143 } 144 145 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 146 _g(g) 147 { 148 _boundary = _g->reserved().end(); 149 } 150 151 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 152 size_t initial_size, 153 size_t min_size, 154 size_t max_size, 155 const char* policy) 156 : Generation(rs, initial_size), 157 _preserved_marks_set(false /* in_c_heap */), 158 _promo_failure_drain_in_progress(false), 159 _should_allocate_from_space(false) 160 { 161 MemRegion cmr((HeapWord*)_virtual_space.low(), 162 (HeapWord*)_virtual_space.high()); 163 GenCollectedHeap* gch = GenCollectedHeap::heap(); 164 165 gch->rem_set()->resize_covered_region(cmr); 166 167 _eden_space = new ContiguousSpace(); 168 _from_space = new ContiguousSpace(); 169 _to_space = new ContiguousSpace(); 170 171 // Compute the maximum eden and survivor space sizes. These sizes 172 // are computed assuming the entire reserved space is committed. 173 // These values are exported as performance counters. 174 uintx size = _virtual_space.reserved_size(); 175 _max_survivor_size = compute_survivor_size(size, SpaceAlignment); 176 _max_eden_size = size - (2*_max_survivor_size); 177 178 // allocate the performance counters 179 180 // Generation counters -- generation 0, 3 subspaces 181 _gen_counters = new GenerationCounters("new", 0, 3, 182 min_size, max_size, &_virtual_space); 183 _gc_counters = new CollectorCounters(policy, 0); 184 185 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 186 _gen_counters); 187 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 188 _gen_counters); 189 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 190 _gen_counters); 191 192 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 193 update_counters(); 194 _old_gen = NULL; 195 _tenuring_threshold = MaxTenuringThreshold; 196 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 197 198 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer(); 199 } 200 201 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 202 bool clear_space, 203 bool mangle_space) { 204 // If the spaces are being cleared (only done at heap initialization 205 // currently), the survivor spaces need not be empty. 206 // Otherwise, no care is taken for used areas in the survivor spaces 207 // so check. 208 assert(clear_space || (to()->is_empty() && from()->is_empty()), 209 "Initialization of the survivor spaces assumes these are empty"); 210 211 // Compute sizes 212 uintx size = _virtual_space.committed_size(); 213 uintx survivor_size = compute_survivor_size(size, SpaceAlignment); 214 uintx eden_size = size - (2*survivor_size); 215 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 216 217 if (eden_size < minimum_eden_size) { 218 // May happen due to 64Kb rounding, if so adjust eden size back up 219 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment); 220 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 221 uintx unaligned_survivor_size = 222 align_down(maximum_survivor_size, SpaceAlignment); 223 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment); 224 eden_size = size - (2*survivor_size); 225 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 226 assert(eden_size >= minimum_eden_size, "just checking"); 227 } 228 229 char *eden_start = _virtual_space.low(); 230 char *from_start = eden_start + eden_size; 231 char *to_start = from_start + survivor_size; 232 char *to_end = to_start + survivor_size; 233 234 assert(to_end == _virtual_space.high(), "just checking"); 235 assert(Space::is_aligned(eden_start), "checking alignment"); 236 assert(Space::is_aligned(from_start), "checking alignment"); 237 assert(Space::is_aligned(to_start), "checking alignment"); 238 239 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 240 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 241 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 242 243 // A minimum eden size implies that there is a part of eden that 244 // is being used and that affects the initialization of any 245 // newly formed eden. 246 bool live_in_eden = minimum_eden_size > 0; 247 248 // If not clearing the spaces, do some checking to verify that 249 // the space are already mangled. 250 if (!clear_space) { 251 // Must check mangling before the spaces are reshaped. Otherwise, 252 // the bottom or end of one space may have moved into another 253 // a failure of the check may not correctly indicate which space 254 // is not properly mangled. 255 if (ZapUnusedHeapArea) { 256 HeapWord* limit = (HeapWord*) _virtual_space.high(); 257 eden()->check_mangled_unused_area(limit); 258 from()->check_mangled_unused_area(limit); 259 to()->check_mangled_unused_area(limit); 260 } 261 } 262 263 // Reset the spaces for their new regions. 264 eden()->initialize(edenMR, 265 clear_space && !live_in_eden, 266 SpaceDecorator::Mangle); 267 // If clear_space and live_in_eden, we will not have cleared any 268 // portion of eden above its top. This can cause newly 269 // expanded space not to be mangled if using ZapUnusedHeapArea. 270 // We explicitly do such mangling here. 271 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 272 eden()->mangle_unused_area(); 273 } 274 from()->initialize(fromMR, clear_space, mangle_space); 275 to()->initialize(toMR, clear_space, mangle_space); 276 277 // Set next compaction spaces. 278 eden()->set_next_compaction_space(from()); 279 // The to-space is normally empty before a compaction so need 280 // not be considered. The exception is during promotion 281 // failure handling when to-space can contain live objects. 282 from()->set_next_compaction_space(NULL); 283 } 284 285 void DefNewGeneration::swap_spaces() { 286 ContiguousSpace* s = from(); 287 _from_space = to(); 288 _to_space = s; 289 eden()->set_next_compaction_space(from()); 290 // The to-space is normally empty before a compaction so need 291 // not be considered. The exception is during promotion 292 // failure handling when to-space can contain live objects. 293 from()->set_next_compaction_space(NULL); 294 295 if (UsePerfData) { 296 CSpaceCounters* c = _from_counters; 297 _from_counters = _to_counters; 298 _to_counters = c; 299 } 300 } 301 302 bool DefNewGeneration::expand(size_t bytes) { 303 MutexLocker x(ExpandHeap_lock); 304 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 305 bool success = _virtual_space.expand_by(bytes); 306 if (success && ZapUnusedHeapArea) { 307 // Mangle newly committed space immediately because it 308 // can be done here more simply that after the new 309 // spaces have been computed. 310 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 311 MemRegion mangle_region(prev_high, new_high); 312 SpaceMangler::mangle_region(mangle_region); 313 } 314 315 // Do not attempt an expand-to-the reserve size. The 316 // request should properly observe the maximum size of 317 // the generation so an expand-to-reserve should be 318 // unnecessary. Also a second call to expand-to-reserve 319 // value potentially can cause an undue expansion. 320 // For example if the first expand fail for unknown reasons, 321 // but the second succeeds and expands the heap to its maximum 322 // value. 323 if (GCLocker::is_active()) { 324 log_debug(gc)("Garbage collection disabled, expanded heap instead"); 325 } 326 327 return success; 328 } 329 330 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate, 331 size_t new_size_before, 332 size_t alignment) const { 333 size_t desired_new_size = new_size_before; 334 335 if (NewSizeThreadIncrease > 0) { 336 int threads_count; 337 size_t thread_increase_size = 0; 338 339 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'. 340 threads_count = Threads::number_of_non_daemon_threads(); 341 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) { 342 thread_increase_size = threads_count * NewSizeThreadIncrease; 343 344 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'. 345 if (new_size_candidate <= max_uintx - thread_increase_size) { 346 new_size_candidate += thread_increase_size; 347 348 // 3. Check an overflow at 'align_up'. 349 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1)); 350 if (new_size_candidate <= aligned_max) { 351 desired_new_size = align_up(new_size_candidate, alignment); 352 } 353 } 354 } 355 } 356 357 return desired_new_size; 358 } 359 360 void DefNewGeneration::compute_new_size() { 361 // This is called after a GC that includes the old generation, so from-space 362 // will normally be empty. 363 // Note that we check both spaces, since if scavenge failed they revert roles. 364 // If not we bail out (otherwise we would have to relocate the objects). 365 if (!from()->is_empty() || !to()->is_empty()) { 366 return; 367 } 368 369 GenCollectedHeap* gch = GenCollectedHeap::heap(); 370 371 size_t old_size = gch->old_gen()->capacity(); 372 size_t new_size_before = _virtual_space.committed_size(); 373 size_t min_new_size = initial_size(); 374 size_t max_new_size = reserved().byte_size(); 375 assert(min_new_size <= new_size_before && 376 new_size_before <= max_new_size, 377 "just checking"); 378 // All space sizes must be multiples of Generation::GenGrain. 379 size_t alignment = Generation::GenGrain; 380 381 int threads_count = 0; 382 size_t thread_increase_size = 0; 383 384 size_t new_size_candidate = old_size / NewRatio; 385 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease 386 // and reverts to previous value if any overflow happens 387 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment); 388 389 // Adjust new generation size 390 desired_new_size = clamp(desired_new_size, min_new_size, max_new_size); 391 assert(desired_new_size <= max_new_size, "just checking"); 392 393 bool changed = false; 394 if (desired_new_size > new_size_before) { 395 size_t change = desired_new_size - new_size_before; 396 assert(change % alignment == 0, "just checking"); 397 if (expand(change)) { 398 changed = true; 399 } 400 // If the heap failed to expand to the desired size, 401 // "changed" will be false. If the expansion failed 402 // (and at this point it was expected to succeed), 403 // ignore the failure (leaving "changed" as false). 404 } 405 if (desired_new_size < new_size_before && eden()->is_empty()) { 406 // bail out of shrinking if objects in eden 407 size_t change = new_size_before - desired_new_size; 408 assert(change % alignment == 0, "just checking"); 409 _virtual_space.shrink_by(change); 410 changed = true; 411 } 412 if (changed) { 413 // The spaces have already been mangled at this point but 414 // may not have been cleared (set top = bottom) and should be. 415 // Mangling was done when the heap was being expanded. 416 compute_space_boundaries(eden()->used(), 417 SpaceDecorator::Clear, 418 SpaceDecorator::DontMangle); 419 MemRegion cmr((HeapWord*)_virtual_space.low(), 420 (HeapWord*)_virtual_space.high()); 421 gch->rem_set()->resize_covered_region(cmr); 422 423 log_debug(gc, ergo, heap)( 424 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 425 new_size_before/K, _virtual_space.committed_size()/K, 426 eden()->capacity()/K, from()->capacity()/K); 427 log_trace(gc, ergo, heap)( 428 " [allowed " SIZE_FORMAT "K extra for %d threads]", 429 thread_increase_size/K, threads_count); 430 } 431 } 432 433 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) { 434 assert(false, "NYI -- are you sure you want to call this?"); 435 } 436 437 438 size_t DefNewGeneration::capacity() const { 439 return eden()->capacity() 440 + from()->capacity(); // to() is only used during scavenge 441 } 442 443 444 size_t DefNewGeneration::used() const { 445 return eden()->used() 446 + from()->used(); // to() is only used during scavenge 447 } 448 449 450 size_t DefNewGeneration::free() const { 451 return eden()->free() 452 + from()->free(); // to() is only used during scavenge 453 } 454 455 size_t DefNewGeneration::max_capacity() const { 456 const size_t reserved_bytes = reserved().byte_size(); 457 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment); 458 } 459 460 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 461 return eden()->free(); 462 } 463 464 size_t DefNewGeneration::capacity_before_gc() const { 465 return eden()->capacity(); 466 } 467 468 size_t DefNewGeneration::contiguous_available() const { 469 return eden()->free(); 470 } 471 472 473 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); } 474 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 475 476 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 477 eden()->object_iterate(blk); 478 from()->object_iterate(blk); 479 } 480 481 482 void DefNewGeneration::space_iterate(SpaceClosure* blk, 483 bool usedOnly) { 484 blk->do_space(eden()); 485 blk->do_space(from()); 486 blk->do_space(to()); 487 } 488 489 // The last collection bailed out, we are running out of heap space, 490 // so we try to allocate the from-space, too. 491 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 492 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc(); 493 494 // If the Heap_lock is not locked by this thread, this will be called 495 // again later with the Heap_lock held. 496 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread())); 497 498 HeapWord* result = NULL; 499 if (do_alloc) { 500 result = from()->allocate(size); 501 } 502 503 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s", 504 size, 505 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 506 "true" : "false", 507 Heap_lock->is_locked() ? "locked" : "unlocked", 508 from()->free(), 509 should_try_alloc ? "" : " should_allocate_from_space: NOT", 510 do_alloc ? " Heap_lock is not owned by self" : "", 511 result == NULL ? "NULL" : "object"); 512 513 return result; 514 } 515 516 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 517 bool is_tlab, 518 bool parallel) { 519 // We don't attempt to expand the young generation (but perhaps we should.) 520 return allocate(size, is_tlab); 521 } 522 523 void DefNewGeneration::adjust_desired_tenuring_threshold() { 524 // Set the desired survivor size to half the real survivor space 525 size_t const survivor_capacity = to()->capacity() / HeapWordSize; 526 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 527 528 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size); 529 530 if (UsePerfData) { 531 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters(); 532 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold); 533 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize); 534 } 535 536 age_table()->print_age_table(_tenuring_threshold); 537 } 538 539 void DefNewGeneration::collect(bool full, 540 bool clear_all_soft_refs, 541 size_t size, 542 bool is_tlab) { 543 assert(full || size > 0, "otherwise we don't want to collect"); 544 545 SerialHeap* heap = SerialHeap::heap(); 546 547 _gc_timer->register_gc_start(); 548 DefNewTracer gc_tracer; 549 gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start()); 550 551 _old_gen = heap->old_gen(); 552 553 // If the next generation is too full to accommodate promotion 554 // from this generation, pass on collection; let the next generation 555 // do it. 556 if (!collection_attempt_is_safe()) { 557 log_trace(gc)(":: Collection attempt not safe ::"); 558 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 559 return; 560 } 561 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 562 563 init_assuming_no_promotion_failure(); 564 565 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause()); 566 567 heap->trace_heap_before_gc(&gc_tracer); 568 569 // These can be shared for all code paths 570 IsAliveClosure is_alive(this); 571 ScanWeakRefClosure scan_weak_ref(this); 572 573 age_table()->clear(); 574 to()->clear(SpaceDecorator::Mangle); 575 // The preserved marks should be empty at the start of the GC. 576 _preserved_marks_set.init(1); 577 578 heap->rem_set()->prepare_for_younger_refs_iterate(false); 579 580 assert(heap->no_allocs_since_save_marks(), 581 "save marks have not been newly set."); 582 583 FastScanClosure fsc_with_no_gc_barrier(this, false); 584 FastScanClosure fsc_with_gc_barrier(this, true); 585 586 CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier, 587 heap->rem_set()->cld_rem_set()->accumulate_modified_oops()); 588 589 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 590 FastEvacuateFollowersClosure evacuate_followers(heap, 591 &fsc_with_no_gc_barrier, 592 &fsc_with_gc_barrier); 593 594 assert(heap->no_allocs_since_save_marks(), 595 "save marks have not been newly set."); 596 597 { 598 // DefNew needs to run with n_threads == 0, to make sure the serial 599 // version of the card table scanning code is used. 600 // See: CardTableRS::non_clean_card_iterate_possibly_parallel. 601 StrongRootsScope srs(0); 602 603 heap->young_process_roots(&srs, 604 &fsc_with_no_gc_barrier, 605 &fsc_with_gc_barrier, 606 &cld_scan_closure); 607 } 608 609 // "evacuate followers". 610 evacuate_followers.do_void(); 611 612 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 613 ReferenceProcessor* rp = ref_processor(); 614 rp->setup_policy(clear_all_soft_refs); 615 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues()); 616 const ReferenceProcessorStats& stats = 617 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 618 NULL, &pt); 619 gc_tracer.report_gc_reference_stats(stats); 620 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 621 pt.print_all_references(); 622 623 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set."); 624 625 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 626 627 // Verify that the usage of keep_alive didn't copy any objects. 628 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set."); 629 630 if (!_promotion_failed) { 631 // Swap the survivor spaces. 632 eden()->clear(SpaceDecorator::Mangle); 633 from()->clear(SpaceDecorator::Mangle); 634 if (ZapUnusedHeapArea) { 635 // This is now done here because of the piece-meal mangling which 636 // can check for valid mangling at intermediate points in the 637 // collection(s). When a young collection fails to collect 638 // sufficient space resizing of the young generation can occur 639 // an redistribute the spaces in the young generation. Mangle 640 // here so that unzapped regions don't get distributed to 641 // other spaces. 642 to()->mangle_unused_area(); 643 } 644 swap_spaces(); 645 646 assert(to()->is_empty(), "to space should be empty now"); 647 648 adjust_desired_tenuring_threshold(); 649 650 // A successful scavenge should restart the GC time limit count which is 651 // for full GC's. 652 AdaptiveSizePolicy* size_policy = heap->size_policy(); 653 size_policy->reset_gc_overhead_limit_count(); 654 assert(!heap->incremental_collection_failed(), "Should be clear"); 655 } else { 656 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 657 _promo_failure_scan_stack.clear(true); // Clear cached segments. 658 659 remove_forwarding_pointers(); 660 log_info(gc, promotion)("Promotion failed"); 661 // Add to-space to the list of space to compact 662 // when a promotion failure has occurred. In that 663 // case there can be live objects in to-space 664 // as a result of a partial evacuation of eden 665 // and from-space. 666 swap_spaces(); // For uniformity wrt ParNewGeneration. 667 from()->set_next_compaction_space(to()); 668 heap->set_incremental_collection_failed(); 669 670 // Inform the next generation that a promotion failure occurred. 671 _old_gen->promotion_failure_occurred(); 672 gc_tracer.report_promotion_failed(_promotion_failed_info); 673 674 // Reset the PromotionFailureALot counters. 675 NOT_PRODUCT(heap->reset_promotion_should_fail();) 676 } 677 // We should have processed and cleared all the preserved marks. 678 _preserved_marks_set.reclaim(); 679 // set new iteration safe limit for the survivor spaces 680 from()->set_concurrent_iteration_safe_limit(from()->top()); 681 to()->set_concurrent_iteration_safe_limit(to()->top()); 682 683 // We need to use a monotonically non-decreasing time in ms 684 // or we will see time-warp warnings and os::javaTimeMillis() 685 // does not guarantee monotonicity. 686 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 687 update_time_of_last_gc(now); 688 689 heap->trace_heap_after_gc(&gc_tracer); 690 691 _gc_timer->register_gc_end(); 692 693 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 694 } 695 696 void DefNewGeneration::init_assuming_no_promotion_failure() { 697 _promotion_failed = false; 698 _promotion_failed_info.reset(); 699 from()->set_next_compaction_space(NULL); 700 } 701 702 void DefNewGeneration::remove_forwarding_pointers() { 703 RemoveForwardedPointerClosure rspc; 704 eden()->object_iterate(&rspc); 705 from()->object_iterate(&rspc); 706 restore_preserved_marks(); 707 } 708 709 void DefNewGeneration::restore_preserved_marks() { 710 _preserved_marks_set.restore(NULL); 711 } 712 713 void DefNewGeneration::handle_promotion_failure(oop old) { 714 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size()); 715 716 _promotion_failed = true; 717 _promotion_failed_info.register_copy_failure(old->size()); 718 _preserved_marks_set.get()->push_if_necessary(old, old->mark_raw()); 719 // forward to self 720 old->forward_to(old); 721 722 _promo_failure_scan_stack.push(old); 723 724 if (!_promo_failure_drain_in_progress) { 725 // prevent recursion in copy_to_survivor_space() 726 _promo_failure_drain_in_progress = true; 727 drain_promo_failure_scan_stack(); 728 _promo_failure_drain_in_progress = false; 729 } 730 } 731 732 oop DefNewGeneration::copy_to_survivor_space(oop old) { 733 assert(is_in_reserved(old) && !old->is_forwarded(), 734 "shouldn't be scavenging this oop"); 735 size_t s = old->size(); 736 oop obj = NULL; 737 738 // Try allocating obj in to-space (unless too old) 739 if (old->age() < tenuring_threshold()) { 740 obj = (oop) to()->allocate_aligned(s); 741 } 742 743 // Otherwise try allocating obj tenured 744 if (obj == NULL) { 745 obj = _old_gen->promote(old, s); 746 if (obj == NULL) { 747 handle_promotion_failure(old); 748 return old; 749 } 750 } else { 751 // Prefetch beyond obj 752 const intx interval = PrefetchCopyIntervalInBytes; 753 Prefetch::write(obj, interval); 754 755 // Copy obj 756 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s); 757 758 // Increment age if obj still in new generation 759 obj->incr_age(); 760 age_table()->add(obj, s); 761 } 762 763 // Done, insert forward pointer to obj in this header 764 old->forward_to(obj); 765 766 return obj; 767 } 768 769 void DefNewGeneration::drain_promo_failure_scan_stack() { 770 while (!_promo_failure_scan_stack.is_empty()) { 771 oop obj = _promo_failure_scan_stack.pop(); 772 obj->oop_iterate(_promo_failure_scan_stack_closure); 773 } 774 } 775 776 void DefNewGeneration::save_marks() { 777 eden()->set_saved_mark(); 778 to()->set_saved_mark(); 779 from()->set_saved_mark(); 780 } 781 782 783 void DefNewGeneration::reset_saved_marks() { 784 eden()->reset_saved_mark(); 785 to()->reset_saved_mark(); 786 from()->reset_saved_mark(); 787 } 788 789 790 bool DefNewGeneration::no_allocs_since_save_marks() { 791 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 792 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 793 return to()->saved_mark_at_top(); 794 } 795 796 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 797 size_t max_alloc_words) { 798 if (requestor == this || _promotion_failed) { 799 return; 800 } 801 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation"); 802 803 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 804 if (to_space->top() > to_space->bottom()) { 805 trace("to_space not empty when contribute_scratch called"); 806 } 807 */ 808 809 ContiguousSpace* to_space = to(); 810 assert(to_space->end() >= to_space->top(), "pointers out of order"); 811 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 812 if (free_words >= MinFreeScratchWords) { 813 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 814 sb->num_words = free_words; 815 sb->next = list; 816 list = sb; 817 } 818 } 819 820 void DefNewGeneration::reset_scratch() { 821 // If contributing scratch in to_space, mangle all of 822 // to_space if ZapUnusedHeapArea. This is needed because 823 // top is not maintained while using to-space as scratch. 824 if (ZapUnusedHeapArea) { 825 to()->mangle_unused_area_complete(); 826 } 827 } 828 829 bool DefNewGeneration::collection_attempt_is_safe() { 830 if (!to()->is_empty()) { 831 log_trace(gc)(":: to is not empty ::"); 832 return false; 833 } 834 if (_old_gen == NULL) { 835 GenCollectedHeap* gch = GenCollectedHeap::heap(); 836 _old_gen = gch->old_gen(); 837 } 838 return _old_gen->promotion_attempt_is_safe(used()); 839 } 840 841 void DefNewGeneration::gc_epilogue(bool full) { 842 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 843 844 assert(!GCLocker::is_active(), "We should not be executing here"); 845 // Check if the heap is approaching full after a collection has 846 // been done. Generally the young generation is empty at 847 // a minimum at the end of a collection. If it is not, then 848 // the heap is approaching full. 849 GenCollectedHeap* gch = GenCollectedHeap::heap(); 850 if (full) { 851 DEBUG_ONLY(seen_incremental_collection_failed = false;) 852 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 853 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 854 GCCause::to_string(gch->gc_cause())); 855 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 856 set_should_allocate_from_space(); // we seem to be running out of space 857 } else { 858 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 859 GCCause::to_string(gch->gc_cause())); 860 gch->clear_incremental_collection_failed(); // We just did a full collection 861 clear_should_allocate_from_space(); // if set 862 } 863 } else { 864 #ifdef ASSERT 865 // It is possible that incremental_collection_failed() == true 866 // here, because an attempted scavenge did not succeed. The policy 867 // is normally expected to cause a full collection which should 868 // clear that condition, so we should not be here twice in a row 869 // with incremental_collection_failed() == true without having done 870 // a full collection in between. 871 if (!seen_incremental_collection_failed && 872 gch->incremental_collection_failed()) { 873 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 874 GCCause::to_string(gch->gc_cause())); 875 seen_incremental_collection_failed = true; 876 } else if (seen_incremental_collection_failed) { 877 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 878 GCCause::to_string(gch->gc_cause())); 879 assert(gch->gc_cause() == GCCause::_scavenge_alot || 880 !gch->incremental_collection_failed(), 881 "Twice in a row"); 882 seen_incremental_collection_failed = false; 883 } 884 #endif // ASSERT 885 } 886 887 if (ZapUnusedHeapArea) { 888 eden()->check_mangled_unused_area_complete(); 889 from()->check_mangled_unused_area_complete(); 890 to()->check_mangled_unused_area_complete(); 891 } 892 893 if (!CleanChunkPoolAsync) { 894 Chunk::clean_chunk_pool(); 895 } 896 897 // update the generation and space performance counters 898 update_counters(); 899 gch->counters()->update_counters(); 900 } 901 902 void DefNewGeneration::record_spaces_top() { 903 assert(ZapUnusedHeapArea, "Not mangling unused space"); 904 eden()->set_top_for_allocations(); 905 to()->set_top_for_allocations(); 906 from()->set_top_for_allocations(); 907 } 908 909 void DefNewGeneration::ref_processor_init() { 910 Generation::ref_processor_init(); 911 } 912 913 914 void DefNewGeneration::update_counters() { 915 if (UsePerfData) { 916 _eden_counters->update_all(); 917 _from_counters->update_all(); 918 _to_counters->update_all(); 919 _gen_counters->update_all(); 920 } 921 } 922 923 void DefNewGeneration::verify() { 924 eden()->verify(); 925 from()->verify(); 926 to()->verify(); 927 } 928 929 void DefNewGeneration::print_on(outputStream* st) const { 930 Generation::print_on(st); 931 st->print(" eden"); 932 eden()->print_on(st); 933 st->print(" from"); 934 from()->print_on(st); 935 st->print(" to "); 936 to()->print_on(st); 937 } 938 939 940 const char* DefNewGeneration::name() const { 941 return "def new generation"; 942 } 943 944 // Moved from inline file as they are not called inline 945 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 946 return eden(); 947 } 948 949 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 950 // This is the slow-path allocation for the DefNewGeneration. 951 // Most allocations are fast-path in compiled code. 952 // We try to allocate from the eden. If that works, we are happy. 953 // Note that since DefNewGeneration supports lock-free allocation, we 954 // have to use it here, as well. 955 HeapWord* result = eden()->par_allocate(word_size); 956 if (result != NULL) { 957 if (_old_gen != NULL) { 958 _old_gen->sample_eden_chunk(); 959 } 960 } else { 961 // If the eden is full and the last collection bailed out, we are running 962 // out of heap space, and we try to allocate the from-space, too. 963 // allocate_from_space can't be inlined because that would introduce a 964 // circular dependency at compile time. 965 result = allocate_from_space(word_size); 966 } 967 return result; 968 } 969 970 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 971 bool is_tlab) { 972 HeapWord* res = eden()->par_allocate(word_size); 973 if (_old_gen != NULL) { 974 _old_gen->sample_eden_chunk(); 975 } 976 return res; 977 } 978 979 size_t DefNewGeneration::tlab_capacity() const { 980 return eden()->capacity(); 981 } 982 983 size_t DefNewGeneration::tlab_used() const { 984 return eden()->used(); 985 } 986 987 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 988 return unsafe_max_alloc_nogc(); 989 }