1 /* 2 * Copyright (c) 2001, 2021, 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/serialGcRefProcProxyTask.hpp" 28 #include "gc/serial/serialHeap.inline.hpp" 29 #include "gc/serial/serialStringDedup.inline.hpp" 30 #include "gc/serial/tenuredGeneration.hpp" 31 #include "gc/shared/adaptiveSizePolicy.hpp" 32 #include "gc/shared/ageTable.inline.hpp" 33 #include "gc/shared/cardTableRS.hpp" 34 #include "gc/shared/collectorCounters.hpp" 35 #include "gc/shared/gcArguments.hpp" 36 #include "gc/shared/gcHeapSummary.hpp" 37 #include "gc/shared/gcLocker.hpp" 38 #include "gc/shared/gcPolicyCounters.hpp" 39 #include "gc/shared/gcTimer.hpp" 40 #include "gc/shared/gcTrace.hpp" 41 #include "gc/shared/gcTraceTime.inline.hpp" 42 #include "gc/shared/generationSpec.hpp" 43 #include "gc/shared/genOopClosures.inline.hpp" 44 #include "gc/shared/preservedMarks.inline.hpp" 45 #include "gc/shared/referencePolicy.hpp" 46 #include "gc/shared/referenceProcessorPhaseTimes.hpp" 47 #include "gc/shared/space.inline.hpp" 48 #include "gc/shared/spaceDecorator.inline.hpp" 49 #include "gc/shared/strongRootsScope.hpp" 50 #include "gc/shared/weakProcessor.hpp" 51 #include "logging/log.hpp" 52 #include "memory/iterator.inline.hpp" 53 #include "memory/resourceArea.hpp" 54 #include "oops/instanceRefKlass.hpp" 55 #include "oops/oop.inline.hpp" 56 #include "runtime/java.hpp" 57 #include "runtime/prefetch.inline.hpp" 58 #include "runtime/thread.inline.hpp" 59 #include "utilities/align.hpp" 60 #include "utilities/copy.hpp" 61 #include "utilities/globalDefinitions.hpp" 62 #include "utilities/stack.inline.hpp" 63 64 // 65 // DefNewGeneration functions. 66 67 // Methods of protected closure types. 68 69 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) { 70 assert(_young_gen->kind() == Generation::DefNew, "Expected the young generation here"); 71 } 72 73 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 74 return cast_from_oop<HeapWord*>(p) >= _young_gen->reserved().end() || p->is_forwarded(); 75 } 76 77 DefNewGeneration::KeepAliveClosure:: 78 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 79 _rs = GenCollectedHeap::heap()->rem_set(); 80 } 81 82 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 83 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 84 85 86 DefNewGeneration::FastKeepAliveClosure:: 87 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 88 DefNewGeneration::KeepAliveClosure(cl) { 89 _boundary = g->reserved().end(); 90 } 91 92 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 93 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 94 95 DefNewGeneration::FastEvacuateFollowersClosure:: 96 FastEvacuateFollowersClosure(SerialHeap* heap, 97 DefNewScanClosure* cur, 98 DefNewYoungerGenClosure* older) : 99 _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older) 100 { 101 } 102 103 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 104 do { 105 _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older); 106 } while (!_heap->no_allocs_since_save_marks()); 107 guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan"); 108 } 109 110 void CLDScanClosure::do_cld(ClassLoaderData* cld) { 111 NOT_PRODUCT(ResourceMark rm); 112 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s", 113 p2i(cld), 114 cld->loader_name_and_id(), 115 cld->has_modified_oops() ? "true" : "false"); 116 117 // If the cld has not been dirtied we know that there's 118 // no references into the young gen and we can skip it. 119 if (cld->has_modified_oops()) { 120 121 // Tell the closure which CLD is being scanned so that it can be dirtied 122 // if oops are left pointing into the young gen. 123 _scavenge_closure->set_scanned_cld(cld); 124 125 // Clean the cld since we're going to scavenge all the metadata. 126 cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true); 127 128 _scavenge_closure->set_scanned_cld(NULL); 129 } 130 } 131 132 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 133 _g(g) 134 { 135 _boundary = _g->reserved().end(); 136 } 137 138 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 139 size_t initial_size, 140 size_t min_size, 141 size_t max_size, 142 const char* policy) 143 : Generation(rs, initial_size), 144 _preserved_marks_set(false /* in_c_heap */), 145 _promo_failure_drain_in_progress(false), 146 _should_allocate_from_space(false), 147 _string_dedup_requests() 148 { 149 MemRegion cmr((HeapWord*)_virtual_space.low(), 150 (HeapWord*)_virtual_space.high()); 151 GenCollectedHeap* gch = GenCollectedHeap::heap(); 152 153 gch->rem_set()->resize_covered_region(cmr); 154 155 _eden_space = new ContiguousSpace(); 156 _from_space = new ContiguousSpace(); 157 _to_space = new ContiguousSpace(); 158 159 // Compute the maximum eden and survivor space sizes. These sizes 160 // are computed assuming the entire reserved space is committed. 161 // These values are exported as performance counters. 162 uintx size = _virtual_space.reserved_size(); 163 _max_survivor_size = compute_survivor_size(size, SpaceAlignment); 164 _max_eden_size = size - (2*_max_survivor_size); 165 166 // allocate the performance counters 167 168 // Generation counters -- generation 0, 3 subspaces 169 _gen_counters = new GenerationCounters("new", 0, 3, 170 min_size, max_size, &_virtual_space); 171 _gc_counters = new CollectorCounters(policy, 0); 172 173 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 174 _gen_counters); 175 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 176 _gen_counters); 177 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 178 _gen_counters); 179 180 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 181 update_counters(); 182 _old_gen = NULL; 183 _tenuring_threshold = MaxTenuringThreshold; 184 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 185 186 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer(); 187 } 188 189 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 190 bool clear_space, 191 bool mangle_space) { 192 // If the spaces are being cleared (only done at heap initialization 193 // currently), the survivor spaces need not be empty. 194 // Otherwise, no care is taken for used areas in the survivor spaces 195 // so check. 196 assert(clear_space || (to()->is_empty() && from()->is_empty()), 197 "Initialization of the survivor spaces assumes these are empty"); 198 199 // Compute sizes 200 uintx size = _virtual_space.committed_size(); 201 uintx survivor_size = compute_survivor_size(size, SpaceAlignment); 202 uintx eden_size = size - (2*survivor_size); 203 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 204 205 if (eden_size < minimum_eden_size) { 206 // May happen due to 64Kb rounding, if so adjust eden size back up 207 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment); 208 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 209 uintx unaligned_survivor_size = 210 align_down(maximum_survivor_size, SpaceAlignment); 211 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment); 212 eden_size = size - (2*survivor_size); 213 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 214 assert(eden_size >= minimum_eden_size, "just checking"); 215 } 216 217 char *eden_start = _virtual_space.low(); 218 char *from_start = eden_start + eden_size; 219 char *to_start = from_start + survivor_size; 220 char *to_end = to_start + survivor_size; 221 222 assert(to_end == _virtual_space.high(), "just checking"); 223 assert(Space::is_aligned(eden_start), "checking alignment"); 224 assert(Space::is_aligned(from_start), "checking alignment"); 225 assert(Space::is_aligned(to_start), "checking alignment"); 226 227 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 228 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 229 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 230 231 // A minimum eden size implies that there is a part of eden that 232 // is being used and that affects the initialization of any 233 // newly formed eden. 234 bool live_in_eden = minimum_eden_size > 0; 235 236 // If not clearing the spaces, do some checking to verify that 237 // the space are already mangled. 238 if (!clear_space) { 239 // Must check mangling before the spaces are reshaped. Otherwise, 240 // the bottom or end of one space may have moved into another 241 // a failure of the check may not correctly indicate which space 242 // is not properly mangled. 243 if (ZapUnusedHeapArea) { 244 HeapWord* limit = (HeapWord*) _virtual_space.high(); 245 eden()->check_mangled_unused_area(limit); 246 from()->check_mangled_unused_area(limit); 247 to()->check_mangled_unused_area(limit); 248 } 249 } 250 251 // Reset the spaces for their new regions. 252 eden()->initialize(edenMR, 253 clear_space && !live_in_eden, 254 SpaceDecorator::Mangle); 255 // If clear_space and live_in_eden, we will not have cleared any 256 // portion of eden above its top. This can cause newly 257 // expanded space not to be mangled if using ZapUnusedHeapArea. 258 // We explicitly do such mangling here. 259 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 260 eden()->mangle_unused_area(); 261 } 262 from()->initialize(fromMR, clear_space, mangle_space); 263 to()->initialize(toMR, clear_space, mangle_space); 264 265 // Set next compaction spaces. 266 eden()->set_next_compaction_space(from()); 267 // The to-space is normally empty before a compaction so need 268 // not be considered. The exception is during promotion 269 // failure handling when to-space can contain live objects. 270 from()->set_next_compaction_space(NULL); 271 } 272 273 void DefNewGeneration::swap_spaces() { 274 ContiguousSpace* s = from(); 275 _from_space = to(); 276 _to_space = s; 277 eden()->set_next_compaction_space(from()); 278 // The to-space is normally empty before a compaction so need 279 // not be considered. The exception is during promotion 280 // failure handling when to-space can contain live objects. 281 from()->set_next_compaction_space(NULL); 282 283 if (UsePerfData) { 284 CSpaceCounters* c = _from_counters; 285 _from_counters = _to_counters; 286 _to_counters = c; 287 } 288 } 289 290 bool DefNewGeneration::expand(size_t bytes) { 291 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 292 bool success = _virtual_space.expand_by(bytes); 293 if (success && ZapUnusedHeapArea) { 294 // Mangle newly committed space immediately because it 295 // can be done here more simply that after the new 296 // spaces have been computed. 297 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 298 MemRegion mangle_region(prev_high, new_high); 299 SpaceMangler::mangle_region(mangle_region); 300 } 301 302 // Do not attempt an expand-to-the reserve size. The 303 // request should properly observe the maximum size of 304 // the generation so an expand-to-reserve should be 305 // unnecessary. Also a second call to expand-to-reserve 306 // value potentially can cause an undue expansion. 307 // For example if the first expand fail for unknown reasons, 308 // but the second succeeds and expands the heap to its maximum 309 // value. 310 if (GCLocker::is_active()) { 311 log_debug(gc)("Garbage collection disabled, expanded heap instead"); 312 } 313 314 return success; 315 } 316 317 size_t DefNewGeneration::calculate_thread_increase_size(int threads_count) const { 318 size_t thread_increase_size = 0; 319 // Check an overflow at 'threads_count * NewSizeThreadIncrease'. 320 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) { 321 thread_increase_size = threads_count * NewSizeThreadIncrease; 322 } 323 return thread_increase_size; 324 } 325 326 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate, 327 size_t new_size_before, 328 size_t alignment, 329 size_t thread_increase_size) const { 330 size_t desired_new_size = new_size_before; 331 332 if (NewSizeThreadIncrease > 0 && thread_increase_size > 0) { 333 334 // 1. Check an overflow at 'new_size_candidate + thread_increase_size'. 335 if (new_size_candidate <= max_uintx - thread_increase_size) { 336 new_size_candidate += thread_increase_size; 337 338 // 2. Check an overflow at 'align_up'. 339 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1)); 340 if (new_size_candidate <= aligned_max) { 341 desired_new_size = align_up(new_size_candidate, alignment); 342 } 343 } 344 } 345 346 return desired_new_size; 347 } 348 349 void DefNewGeneration::compute_new_size() { 350 // This is called after a GC that includes the old generation, so from-space 351 // will normally be empty. 352 // Note that we check both spaces, since if scavenge failed they revert roles. 353 // If not we bail out (otherwise we would have to relocate the objects). 354 if (!from()->is_empty() || !to()->is_empty()) { 355 return; 356 } 357 358 GenCollectedHeap* gch = GenCollectedHeap::heap(); 359 360 size_t old_size = gch->old_gen()->capacity(); 361 size_t new_size_before = _virtual_space.committed_size(); 362 size_t min_new_size = initial_size(); 363 size_t max_new_size = reserved().byte_size(); 364 assert(min_new_size <= new_size_before && 365 new_size_before <= max_new_size, 366 "just checking"); 367 // All space sizes must be multiples of Generation::GenGrain. 368 size_t alignment = Generation::GenGrain; 369 370 int threads_count = Threads::number_of_non_daemon_threads(); 371 size_t thread_increase_size = calculate_thread_increase_size(threads_count); 372 373 size_t new_size_candidate = old_size / NewRatio; 374 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease 375 // and reverts to previous value if any overflow happens 376 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, 377 alignment, thread_increase_size); 378 379 // Adjust new generation size 380 desired_new_size = clamp(desired_new_size, min_new_size, max_new_size); 381 assert(desired_new_size <= max_new_size, "just checking"); 382 383 bool changed = false; 384 if (desired_new_size > new_size_before) { 385 size_t change = desired_new_size - new_size_before; 386 assert(change % alignment == 0, "just checking"); 387 if (expand(change)) { 388 changed = true; 389 } 390 // If the heap failed to expand to the desired size, 391 // "changed" will be false. If the expansion failed 392 // (and at this point it was expected to succeed), 393 // ignore the failure (leaving "changed" as false). 394 } 395 if (desired_new_size < new_size_before && eden()->is_empty()) { 396 // bail out of shrinking if objects in eden 397 size_t change = new_size_before - desired_new_size; 398 assert(change % alignment == 0, "just checking"); 399 _virtual_space.shrink_by(change); 400 changed = true; 401 } 402 if (changed) { 403 // The spaces have already been mangled at this point but 404 // may not have been cleared (set top = bottom) and should be. 405 // Mangling was done when the heap was being expanded. 406 compute_space_boundaries(eden()->used(), 407 SpaceDecorator::Clear, 408 SpaceDecorator::DontMangle); 409 MemRegion cmr((HeapWord*)_virtual_space.low(), 410 (HeapWord*)_virtual_space.high()); 411 gch->rem_set()->resize_covered_region(cmr); 412 413 log_debug(gc, ergo, heap)( 414 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 415 new_size_before/K, _virtual_space.committed_size()/K, 416 eden()->capacity()/K, from()->capacity()/K); 417 log_trace(gc, ergo, heap)( 418 " [allowed " SIZE_FORMAT "K extra for %d threads]", 419 thread_increase_size/K, threads_count); 420 } 421 } 422 423 424 size_t DefNewGeneration::capacity() const { 425 return eden()->capacity() 426 + from()->capacity(); // to() is only used during scavenge 427 } 428 429 430 size_t DefNewGeneration::used() const { 431 return eden()->used() 432 + from()->used(); // to() is only used during scavenge 433 } 434 435 436 size_t DefNewGeneration::free() const { 437 return eden()->free() 438 + from()->free(); // to() is only used during scavenge 439 } 440 441 size_t DefNewGeneration::max_capacity() const { 442 const size_t reserved_bytes = reserved().byte_size(); 443 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment); 444 } 445 446 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 447 return eden()->free(); 448 } 449 450 size_t DefNewGeneration::capacity_before_gc() const { 451 return eden()->capacity(); 452 } 453 454 size_t DefNewGeneration::contiguous_available() const { 455 return eden()->free(); 456 } 457 458 459 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); } 460 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 461 462 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 463 eden()->object_iterate(blk); 464 from()->object_iterate(blk); 465 } 466 467 468 void DefNewGeneration::space_iterate(SpaceClosure* blk, 469 bool usedOnly) { 470 blk->do_space(eden()); 471 blk->do_space(from()); 472 blk->do_space(to()); 473 } 474 475 // The last collection bailed out, we are running out of heap space, 476 // so we try to allocate the from-space, too. 477 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 478 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc(); 479 480 // If the Heap_lock is not locked by this thread, this will be called 481 // again later with the Heap_lock held. 482 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread())); 483 484 HeapWord* result = NULL; 485 if (do_alloc) { 486 result = from()->allocate(size); 487 } 488 489 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s", 490 size, 491 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 492 "true" : "false", 493 Heap_lock->is_locked() ? "locked" : "unlocked", 494 from()->free(), 495 should_try_alloc ? "" : " should_allocate_from_space: NOT", 496 do_alloc ? " Heap_lock is not owned by self" : "", 497 result == NULL ? "NULL" : "object"); 498 499 return result; 500 } 501 502 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, bool is_tlab) { 503 // We don't attempt to expand the young generation (but perhaps we should.) 504 return allocate(size, is_tlab); 505 } 506 507 void DefNewGeneration::adjust_desired_tenuring_threshold() { 508 // Set the desired survivor size to half the real survivor space 509 size_t const survivor_capacity = to()->capacity() / HeapWordSize; 510 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 511 512 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size); 513 514 if (UsePerfData) { 515 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters(); 516 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold); 517 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize); 518 } 519 520 age_table()->print_age_table(_tenuring_threshold); 521 } 522 523 void DefNewGeneration::collect(bool full, 524 bool clear_all_soft_refs, 525 size_t size, 526 bool is_tlab) { 527 assert(full || size > 0, "otherwise we don't want to collect"); 528 529 SerialHeap* heap = SerialHeap::heap(); 530 531 _gc_timer->register_gc_start(); 532 DefNewTracer gc_tracer; 533 gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start()); 534 535 _old_gen = heap->old_gen(); 536 537 // If the next generation is too full to accommodate promotion 538 // from this generation, pass on collection; let the next generation 539 // do it. 540 if (!collection_attempt_is_safe()) { 541 log_trace(gc)(":: Collection attempt not safe ::"); 542 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 543 return; 544 } 545 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 546 547 init_assuming_no_promotion_failure(); 548 549 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause()); 550 551 heap->trace_heap_before_gc(&gc_tracer); 552 553 // These can be shared for all code paths 554 IsAliveClosure is_alive(this); 555 ScanWeakRefClosure scan_weak_ref(this); 556 557 age_table()->clear(); 558 to()->clear(SpaceDecorator::Mangle); 559 // The preserved marks should be empty at the start of the GC. 560 _preserved_marks_set.init(1); 561 562 assert(heap->no_allocs_since_save_marks(), 563 "save marks have not been newly set."); 564 565 DefNewScanClosure scan_closure(this); 566 DefNewYoungerGenClosure younger_gen_closure(this, _old_gen); 567 568 CLDScanClosure cld_scan_closure(&scan_closure); 569 570 set_promo_failure_scan_stack_closure(&scan_closure); 571 FastEvacuateFollowersClosure evacuate_followers(heap, 572 &scan_closure, 573 &younger_gen_closure); 574 575 assert(heap->no_allocs_since_save_marks(), 576 "save marks have not been newly set."); 577 578 { 579 StrongRootsScope srs(0); 580 581 heap->young_process_roots(&scan_closure, 582 &younger_gen_closure, 583 &cld_scan_closure); 584 } 585 586 // "evacuate followers". 587 evacuate_followers.do_void(); 588 589 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 590 ReferenceProcessor* rp = ref_processor(); 591 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues()); 592 SerialGCRefProcProxyTask task(is_alive, keep_alive, evacuate_followers); 593 const ReferenceProcessorStats& stats = rp->process_discovered_references(task, pt); 594 gc_tracer.report_gc_reference_stats(stats); 595 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 596 pt.print_all_references(); 597 598 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set."); 599 600 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 601 602 // Verify that the usage of keep_alive didn't copy any objects. 603 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set."); 604 605 _string_dedup_requests.flush(); 606 607 if (!_promotion_failed) { 608 // Swap the survivor spaces. 609 eden()->clear(SpaceDecorator::Mangle); 610 from()->clear(SpaceDecorator::Mangle); 611 if (ZapUnusedHeapArea) { 612 // This is now done here because of the piece-meal mangling which 613 // can check for valid mangling at intermediate points in the 614 // collection(s). When a young collection fails to collect 615 // sufficient space resizing of the young generation can occur 616 // an redistribute the spaces in the young generation. Mangle 617 // here so that unzapped regions don't get distributed to 618 // other spaces. 619 to()->mangle_unused_area(); 620 } 621 swap_spaces(); 622 623 assert(to()->is_empty(), "to space should be empty now"); 624 625 adjust_desired_tenuring_threshold(); 626 627 // A successful scavenge should restart the GC time limit count which is 628 // for full GC's. 629 AdaptiveSizePolicy* size_policy = heap->size_policy(); 630 size_policy->reset_gc_overhead_limit_count(); 631 assert(!heap->incremental_collection_failed(), "Should be clear"); 632 } else { 633 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 634 _promo_failure_scan_stack.clear(true); // Clear cached segments. 635 636 remove_forwarding_pointers(); 637 log_info(gc, promotion)("Promotion failed"); 638 // Add to-space to the list of space to compact 639 // when a promotion failure has occurred. In that 640 // case there can be live objects in to-space 641 // as a result of a partial evacuation of eden 642 // and from-space. 643 swap_spaces(); // For uniformity wrt ParNewGeneration. 644 from()->set_next_compaction_space(to()); 645 heap->set_incremental_collection_failed(); 646 647 // Inform the next generation that a promotion failure occurred. 648 _old_gen->promotion_failure_occurred(); 649 gc_tracer.report_promotion_failed(_promotion_failed_info); 650 651 // Reset the PromotionFailureALot counters. 652 NOT_PRODUCT(heap->reset_promotion_should_fail();) 653 } 654 // We should have processed and cleared all the preserved marks. 655 _preserved_marks_set.reclaim(); 656 657 heap->trace_heap_after_gc(&gc_tracer); 658 659 _gc_timer->register_gc_end(); 660 661 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 662 } 663 664 void DefNewGeneration::init_assuming_no_promotion_failure() { 665 _promotion_failed = false; 666 _promotion_failed_info.reset(); 667 from()->set_next_compaction_space(NULL); 668 } 669 670 void DefNewGeneration::remove_forwarding_pointers() { 671 assert(_promotion_failed, "precondition"); 672 673 // Will enter Full GC soon due to failed promotion. Must reset the mark word 674 // of objs in young-gen so that no objs are marked (forwarded) when Full GC 675 // starts. (The mark word is overloaded: `is_marked()` == `is_forwarded()`.) 676 struct ResetForwardedMarkWord : ObjectClosure { 677 void do_object(oop obj) override { 678 if (obj->is_forwarded()) { 679 #ifdef _LP64 680 oop forwardee = obj->forwardee(); 681 markWord header = forwardee->mark(); 682 if (header.has_displaced_mark_helper()) { 683 header = header.displaced_mark_helper(); 684 } 685 assert(UseCompressedClassPointers, "assume +UseCompressedClassPointers"); 686 narrowKlass nklass = header.narrow_klass(); 687 obj->set_mark(markWord::prototype().set_narrow_klass(nklass)); 688 #else 689 obj->init_mark(); 690 #endif 691 } 692 } 693 } cl; 694 eden()->object_iterate(&cl); 695 from()->object_iterate(&cl); 696 697 restore_preserved_marks(); 698 } 699 700 void DefNewGeneration::restore_preserved_marks() { 701 _preserved_marks_set.restore(NULL); 702 } 703 704 void DefNewGeneration::handle_promotion_failure(oop old) { 705 log_debug(gc, promotion)("Promotion failure size = " SIZE_FORMAT ") ", old->size()); 706 707 _promotion_failed = true; 708 _promotion_failed_info.register_copy_failure(old->size()); 709 _preserved_marks_set.get()->push_if_necessary(old, old->mark()); 710 // forward to self 711 old->forward_to_self(); 712 713 _promo_failure_scan_stack.push(old); 714 715 if (!_promo_failure_drain_in_progress) { 716 // prevent recursion in copy_to_survivor_space() 717 _promo_failure_drain_in_progress = true; 718 drain_promo_failure_scan_stack(); 719 _promo_failure_drain_in_progress = false; 720 } 721 } 722 723 oop DefNewGeneration::copy_to_survivor_space(oop old) { 724 assert(is_in_reserved(old) && !old->is_forwarded(), 725 "shouldn't be scavenging this oop"); 726 size_t s = old->size(); 727 oop obj = NULL; 728 729 // Try allocating obj in to-space (unless too old) 730 if (old->age() < tenuring_threshold()) { 731 obj = cast_to_oop(to()->allocate(s)); 732 } 733 734 bool new_obj_is_tenured = false; 735 // Otherwise try allocating obj tenured 736 if (obj == NULL) { 737 obj = _old_gen->promote(old, s); 738 if (obj == NULL) { 739 handle_promotion_failure(old); 740 return old; 741 } 742 new_obj_is_tenured = true; 743 } else { 744 // Prefetch beyond obj 745 const intx interval = PrefetchCopyIntervalInBytes; 746 Prefetch::write(obj, interval); 747 748 // Copy obj 749 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s); 750 751 // Increment age if obj still in new generation 752 obj->incr_age(); 753 age_table()->add(obj, s); 754 } 755 756 // Done, insert forward pointer to obj in this header 757 old->forward_to(obj); 758 759 if (SerialStringDedup::is_candidate_from_evacuation(obj, new_obj_is_tenured)) { 760 // Record old; request adds a new weak reference, which reference 761 // processing expects to refer to a from-space object. 762 _string_dedup_requests.add(old); 763 } 764 return obj; 765 } 766 767 void DefNewGeneration::drain_promo_failure_scan_stack() { 768 while (!_promo_failure_scan_stack.is_empty()) { 769 oop obj = _promo_failure_scan_stack.pop(); 770 obj->oop_iterate(_promo_failure_scan_stack_closure); 771 } 772 } 773 774 void DefNewGeneration::save_marks() { 775 eden()->set_saved_mark(); 776 to()->set_saved_mark(); 777 from()->set_saved_mark(); 778 } 779 780 781 void DefNewGeneration::reset_saved_marks() { 782 eden()->reset_saved_mark(); 783 to()->reset_saved_mark(); 784 from()->reset_saved_mark(); 785 } 786 787 788 bool DefNewGeneration::no_allocs_since_save_marks() { 789 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 790 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 791 return to()->saved_mark_at_top(); 792 } 793 794 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 795 size_t max_alloc_words) { 796 if (requestor == this || _promotion_failed) { 797 return; 798 } 799 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation"); 800 801 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 802 if (to_space->top() > to_space->bottom()) { 803 trace("to_space not empty when contribute_scratch called"); 804 } 805 */ 806 807 ContiguousSpace* to_space = to(); 808 assert(to_space->end() >= to_space->top(), "pointers out of order"); 809 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 810 if (free_words >= MinFreeScratchWords) { 811 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 812 sb->num_words = free_words; 813 sb->next = list; 814 list = sb; 815 } 816 } 817 818 void DefNewGeneration::reset_scratch() { 819 // If contributing scratch in to_space, mangle all of 820 // to_space if ZapUnusedHeapArea. This is needed because 821 // top is not maintained while using to-space as scratch. 822 if (ZapUnusedHeapArea) { 823 to()->mangle_unused_area_complete(); 824 } 825 } 826 827 bool DefNewGeneration::collection_attempt_is_safe() { 828 if (!to()->is_empty()) { 829 log_trace(gc)(":: to is not empty ::"); 830 return false; 831 } 832 if (_old_gen == NULL) { 833 GenCollectedHeap* gch = GenCollectedHeap::heap(); 834 _old_gen = gch->old_gen(); 835 } 836 return _old_gen->promotion_attempt_is_safe(used()); 837 } 838 839 void DefNewGeneration::gc_epilogue(bool full) { 840 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 841 842 assert(!GCLocker::is_active(), "We should not be executing here"); 843 // Check if the heap is approaching full after a collection has 844 // been done. Generally the young generation is empty at 845 // a minimum at the end of a collection. If it is not, then 846 // the heap is approaching full. 847 GenCollectedHeap* gch = GenCollectedHeap::heap(); 848 if (full) { 849 DEBUG_ONLY(seen_incremental_collection_failed = false;) 850 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 851 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 852 GCCause::to_string(gch->gc_cause())); 853 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 854 set_should_allocate_from_space(); // we seem to be running out of space 855 } else { 856 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 857 GCCause::to_string(gch->gc_cause())); 858 gch->clear_incremental_collection_failed(); // We just did a full collection 859 clear_should_allocate_from_space(); // if set 860 } 861 } else { 862 #ifdef ASSERT 863 // It is possible that incremental_collection_failed() == true 864 // here, because an attempted scavenge did not succeed. The policy 865 // is normally expected to cause a full collection which should 866 // clear that condition, so we should not be here twice in a row 867 // with incremental_collection_failed() == true without having done 868 // a full collection in between. 869 if (!seen_incremental_collection_failed && 870 gch->incremental_collection_failed()) { 871 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 872 GCCause::to_string(gch->gc_cause())); 873 seen_incremental_collection_failed = true; 874 } else if (seen_incremental_collection_failed) { 875 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 876 GCCause::to_string(gch->gc_cause())); 877 assert(gch->gc_cause() == GCCause::_scavenge_alot || 878 !gch->incremental_collection_failed(), 879 "Twice in a row"); 880 seen_incremental_collection_failed = false; 881 } 882 #endif // ASSERT 883 } 884 885 if (ZapUnusedHeapArea) { 886 eden()->check_mangled_unused_area_complete(); 887 from()->check_mangled_unused_area_complete(); 888 to()->check_mangled_unused_area_complete(); 889 } 890 891 // update the generation and space performance counters 892 update_counters(); 893 gch->counters()->update_counters(); 894 } 895 896 void DefNewGeneration::record_spaces_top() { 897 assert(ZapUnusedHeapArea, "Not mangling unused space"); 898 eden()->set_top_for_allocations(); 899 to()->set_top_for_allocations(); 900 from()->set_top_for_allocations(); 901 } 902 903 void DefNewGeneration::update_counters() { 904 if (UsePerfData) { 905 _eden_counters->update_all(); 906 _from_counters->update_all(); 907 _to_counters->update_all(); 908 _gen_counters->update_all(); 909 } 910 } 911 912 void DefNewGeneration::verify() { 913 eden()->verify(); 914 from()->verify(); 915 to()->verify(); 916 } 917 918 void DefNewGeneration::print_on(outputStream* st) const { 919 Generation::print_on(st); 920 st->print(" eden"); 921 eden()->print_on(st); 922 st->print(" from"); 923 from()->print_on(st); 924 st->print(" to "); 925 to()->print_on(st); 926 } 927 928 929 const char* DefNewGeneration::name() const { 930 return "def new generation"; 931 } 932 933 // Moved from inline file as they are not called inline 934 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 935 return eden(); 936 } 937 938 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 939 // This is the slow-path allocation for the DefNewGeneration. 940 // Most allocations are fast-path in compiled code. 941 // We try to allocate from the eden. If that works, we are happy. 942 // Note that since DefNewGeneration supports lock-free allocation, we 943 // have to use it here, as well. 944 HeapWord* result = eden()->par_allocate(word_size); 945 if (result == NULL) { 946 // If the eden is full and the last collection bailed out, we are running 947 // out of heap space, and we try to allocate the from-space, too. 948 // allocate_from_space can't be inlined because that would introduce a 949 // circular dependency at compile time. 950 result = allocate_from_space(word_size); 951 } 952 return result; 953 } 954 955 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 956 bool is_tlab) { 957 return eden()->par_allocate(word_size); 958 } 959 960 size_t DefNewGeneration::tlab_capacity() const { 961 return eden()->capacity(); 962 } 963 964 size_t DefNewGeneration::tlab_used() const { 965 return eden()->used(); 966 } 967 968 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 969 return unsafe_max_alloc_nogc(); 970 }