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