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