1 /* 2 * Copyright (c) 2001, 2015, 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/shared/cardTableRS.hpp" 28 #include "gc/shared/collectorCounters.hpp" 29 #include "gc/shared/gcHeapSummary.hpp" 30 #include "gc/shared/gcLocker.inline.hpp" 31 #include "gc/shared/gcPolicyCounters.hpp" 32 #include "gc/shared/gcTimer.hpp" 33 #include "gc/shared/gcTrace.hpp" 34 #include "gc/shared/gcTraceTime.inline.hpp" 35 #include "gc/shared/genCollectedHeap.hpp" 36 #include "gc/shared/genOopClosures.inline.hpp" 37 #include "gc/shared/generationSpec.hpp" 38 #include "gc/shared/referencePolicy.hpp" 39 #include "gc/shared/space.inline.hpp" 40 #include "gc/shared/spaceDecorator.hpp" 41 #include "gc/shared/strongRootsScope.hpp" 42 #include "logging/log.hpp" 43 #include "memory/iterator.hpp" 44 #include "oops/instanceRefKlass.hpp" 45 #include "oops/oop.inline.hpp" 46 #include "runtime/atomic.inline.hpp" 47 #include "runtime/java.hpp" 48 #include "runtime/prefetch.inline.hpp" 49 #include "runtime/thread.inline.hpp" 50 #include "utilities/copy.hpp" 51 #include "utilities/globalDefinitions.hpp" 52 #include "utilities/stack.inline.hpp" 53 #if INCLUDE_ALL_GCS 54 #include "gc/cms/parOopClosures.hpp" 55 #endif 56 57 // 58 // DefNewGeneration functions. 59 60 // Methods of protected closure types. 61 62 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) { 63 assert(_young_gen->kind() == Generation::ParNew || 64 _young_gen->kind() == Generation::DefNew, "Expected the young generation here"); 65 } 66 67 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 68 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded(); 69 } 70 71 DefNewGeneration::KeepAliveClosure:: 72 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 73 _rs = GenCollectedHeap::heap()->rem_set(); 74 } 75 76 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 77 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 78 79 80 DefNewGeneration::FastKeepAliveClosure:: 81 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 82 DefNewGeneration::KeepAliveClosure(cl) { 83 _boundary = g->reserved().end(); 84 } 85 86 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 87 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 88 89 DefNewGeneration::EvacuateFollowersClosure:: 90 EvacuateFollowersClosure(GenCollectedHeap* gch, 91 ScanClosure* cur, 92 ScanClosure* older) : 93 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older) 94 {} 95 96 void DefNewGeneration::EvacuateFollowersClosure::do_void() { 97 do { 98 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older); 99 } while (!_gch->no_allocs_since_save_marks()); 100 } 101 102 DefNewGeneration::FastEvacuateFollowersClosure:: 103 FastEvacuateFollowersClosure(GenCollectedHeap* gch, 104 FastScanClosure* cur, 105 FastScanClosure* older) : 106 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older) 107 { 108 assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew"); 109 _young_gen = (DefNewGeneration*)_gch->young_gen(); 110 } 111 112 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 113 do { 114 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older); 115 } while (!_gch->no_allocs_since_save_marks()); 116 guarantee(_young_gen->promo_failure_scan_is_complete(), "Failed to finish scan"); 117 } 118 119 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) : 120 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 121 { 122 _boundary = _g->reserved().end(); 123 } 124 125 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); } 126 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); } 127 128 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 129 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 130 { 131 _boundary = _g->reserved().end(); 132 } 133 134 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); } 135 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); } 136 137 void KlassScanClosure::do_klass(Klass* klass) { 138 NOT_PRODUCT(ResourceMark rm); 139 log_develop_trace(gc, scavenge)("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s", 140 p2i(klass), 141 klass->external_name(), 142 klass->has_modified_oops() ? "true" : "false"); 143 144 // If the klass has not been dirtied we know that there's 145 // no references into the young gen and we can skip it. 146 if (klass->has_modified_oops()) { 147 if (_accumulate_modified_oops) { 148 klass->accumulate_modified_oops(); 149 } 150 151 // Clear this state since we're going to scavenge all the metadata. 152 klass->clear_modified_oops(); 153 154 // Tell the closure which Klass is being scanned so that it can be dirtied 155 // if oops are left pointing into the young gen. 156 _scavenge_closure->set_scanned_klass(klass); 157 158 klass->oops_do(_scavenge_closure); 159 160 _scavenge_closure->set_scanned_klass(NULL); 161 } 162 } 163 164 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 165 _g(g) 166 { 167 _boundary = _g->reserved().end(); 168 } 169 170 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); } 171 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); } 172 173 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); } 174 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); } 175 176 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure, 177 KlassRemSet* klass_rem_set) 178 : _scavenge_closure(scavenge_closure), 179 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {} 180 181 182 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 183 size_t initial_size, 184 const char* policy) 185 : Generation(rs, initial_size), 186 _promo_failure_drain_in_progress(false), 187 _should_allocate_from_space(false) 188 { 189 MemRegion cmr((HeapWord*)_virtual_space.low(), 190 (HeapWord*)_virtual_space.high()); 191 GenCollectedHeap* gch = GenCollectedHeap::heap(); 192 193 gch->barrier_set()->resize_covered_region(cmr); 194 195 _eden_space = new ContiguousSpace(); 196 _from_space = new ContiguousSpace(); 197 _to_space = new ContiguousSpace(); 198 199 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) { 200 vm_exit_during_initialization("Could not allocate a new gen space"); 201 } 202 203 // Compute the maximum eden and survivor space sizes. These sizes 204 // are computed assuming the entire reserved space is committed. 205 // These values are exported as performance counters. 206 uintx alignment = gch->collector_policy()->space_alignment(); 207 uintx size = _virtual_space.reserved_size(); 208 _max_survivor_size = compute_survivor_size(size, alignment); 209 _max_eden_size = size - (2*_max_survivor_size); 210 211 // allocate the performance counters 212 GenCollectorPolicy* gcp = gch->gen_policy(); 213 214 // Generation counters -- generation 0, 3 subspaces 215 _gen_counters = new GenerationCounters("new", 0, 3, 216 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space); 217 _gc_counters = new CollectorCounters(policy, 0); 218 219 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 220 _gen_counters); 221 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 222 _gen_counters); 223 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 224 _gen_counters); 225 226 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 227 update_counters(); 228 _old_gen = NULL; 229 _tenuring_threshold = MaxTenuringThreshold; 230 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 231 232 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer(); 233 } 234 235 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 236 bool clear_space, 237 bool mangle_space) { 238 uintx alignment = 239 GenCollectedHeap::heap()->collector_policy()->space_alignment(); 240 241 // If the spaces are being cleared (only done at heap initialization 242 // currently), the survivor spaces need not be empty. 243 // Otherwise, no care is taken for used areas in the survivor spaces 244 // so check. 245 assert(clear_space || (to()->is_empty() && from()->is_empty()), 246 "Initialization of the survivor spaces assumes these are empty"); 247 248 // Compute sizes 249 uintx size = _virtual_space.committed_size(); 250 uintx survivor_size = compute_survivor_size(size, alignment); 251 uintx eden_size = size - (2*survivor_size); 252 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 253 254 if (eden_size < minimum_eden_size) { 255 // May happen due to 64Kb rounding, if so adjust eden size back up 256 minimum_eden_size = align_size_up(minimum_eden_size, alignment); 257 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 258 uintx unaligned_survivor_size = 259 align_size_down(maximum_survivor_size, alignment); 260 survivor_size = MAX2(unaligned_survivor_size, alignment); 261 eden_size = size - (2*survivor_size); 262 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 263 assert(eden_size >= minimum_eden_size, "just checking"); 264 } 265 266 char *eden_start = _virtual_space.low(); 267 char *from_start = eden_start + eden_size; 268 char *to_start = from_start + survivor_size; 269 char *to_end = to_start + survivor_size; 270 271 assert(to_end == _virtual_space.high(), "just checking"); 272 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment"); 273 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment"); 274 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment"); 275 276 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 277 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 278 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 279 280 // A minimum eden size implies that there is a part of eden that 281 // is being used and that affects the initialization of any 282 // newly formed eden. 283 bool live_in_eden = minimum_eden_size > 0; 284 285 // If not clearing the spaces, do some checking to verify that 286 // the space are already mangled. 287 if (!clear_space) { 288 // Must check mangling before the spaces are reshaped. Otherwise, 289 // the bottom or end of one space may have moved into another 290 // a failure of the check may not correctly indicate which space 291 // is not properly mangled. 292 if (ZapUnusedHeapArea) { 293 HeapWord* limit = (HeapWord*) _virtual_space.high(); 294 eden()->check_mangled_unused_area(limit); 295 from()->check_mangled_unused_area(limit); 296 to()->check_mangled_unused_area(limit); 297 } 298 } 299 300 // Reset the spaces for their new regions. 301 eden()->initialize(edenMR, 302 clear_space && !live_in_eden, 303 SpaceDecorator::Mangle); 304 // If clear_space and live_in_eden, we will not have cleared any 305 // portion of eden above its top. This can cause newly 306 // expanded space not to be mangled if using ZapUnusedHeapArea. 307 // We explicitly do such mangling here. 308 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 309 eden()->mangle_unused_area(); 310 } 311 from()->initialize(fromMR, clear_space, mangle_space); 312 to()->initialize(toMR, clear_space, mangle_space); 313 314 // Set next compaction spaces. 315 eden()->set_next_compaction_space(from()); 316 // The to-space is normally empty before a compaction so need 317 // not be considered. The exception is during promotion 318 // failure handling when to-space can contain live objects. 319 from()->set_next_compaction_space(NULL); 320 } 321 322 void DefNewGeneration::swap_spaces() { 323 ContiguousSpace* s = from(); 324 _from_space = to(); 325 _to_space = s; 326 eden()->set_next_compaction_space(from()); 327 // The to-space is normally empty before a compaction so need 328 // not be considered. The exception is during promotion 329 // failure handling when to-space can contain live objects. 330 from()->set_next_compaction_space(NULL); 331 332 if (UsePerfData) { 333 CSpaceCounters* c = _from_counters; 334 _from_counters = _to_counters; 335 _to_counters = c; 336 } 337 } 338 339 bool DefNewGeneration::expand(size_t bytes) { 340 MutexLocker x(ExpandHeap_lock); 341 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 342 bool success = _virtual_space.expand_by(bytes); 343 if (success && ZapUnusedHeapArea) { 344 // Mangle newly committed space immediately because it 345 // can be done here more simply that after the new 346 // spaces have been computed. 347 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 348 MemRegion mangle_region(prev_high, new_high); 349 SpaceMangler::mangle_region(mangle_region); 350 } 351 352 // Do not attempt an expand-to-the reserve size. The 353 // request should properly observe the maximum size of 354 // the generation so an expand-to-reserve should be 355 // unnecessary. Also a second call to expand-to-reserve 356 // value potentially can cause an undue expansion. 357 // For example if the first expand fail for unknown reasons, 358 // but the second succeeds and expands the heap to its maximum 359 // value. 360 if (GC_locker::is_active()) { 361 log_debug(gc)("Garbage collection disabled, expanded heap instead"); 362 } 363 364 return success; 365 } 366 367 void DefNewGeneration::compute_new_size() { 368 // This is called after a GC that includes the old generation, so from-space 369 // will normally be empty. 370 // Note that we check both spaces, since if scavenge failed they revert roles. 371 // If not we bail out (otherwise we would have to relocate the objects). 372 if (!from()->is_empty() || !to()->is_empty()) { 373 return; 374 } 375 376 GenCollectedHeap* gch = GenCollectedHeap::heap(); 377 378 size_t old_size = gch->old_gen()->capacity(); 379 size_t new_size_before = _virtual_space.committed_size(); 380 size_t min_new_size = initial_size(); 381 size_t max_new_size = reserved().byte_size(); 382 assert(min_new_size <= new_size_before && 383 new_size_before <= max_new_size, 384 "just checking"); 385 // All space sizes must be multiples of Generation::GenGrain. 386 size_t alignment = Generation::GenGrain; 387 388 // Compute desired new generation size based on NewRatio and 389 // NewSizeThreadIncrease 390 size_t desired_new_size = old_size/NewRatio; 391 int threads_count = Threads::number_of_non_daemon_threads(); 392 size_t thread_increase_size = threads_count * NewSizeThreadIncrease; 393 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment); 394 395 // Adjust new generation size 396 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size); 397 assert(desired_new_size <= max_new_size, "just checking"); 398 399 bool changed = false; 400 if (desired_new_size > new_size_before) { 401 size_t change = desired_new_size - new_size_before; 402 assert(change % alignment == 0, "just checking"); 403 if (expand(change)) { 404 changed = true; 405 } 406 // If the heap failed to expand to the desired size, 407 // "changed" will be false. If the expansion failed 408 // (and at this point it was expected to succeed), 409 // ignore the failure (leaving "changed" as false). 410 } 411 if (desired_new_size < new_size_before && eden()->is_empty()) { 412 // bail out of shrinking if objects in eden 413 size_t change = new_size_before - desired_new_size; 414 assert(change % alignment == 0, "just checking"); 415 _virtual_space.shrink_by(change); 416 changed = true; 417 } 418 if (changed) { 419 // The spaces have already been mangled at this point but 420 // may not have been cleared (set top = bottom) and should be. 421 // Mangling was done when the heap was being expanded. 422 compute_space_boundaries(eden()->used(), 423 SpaceDecorator::Clear, 424 SpaceDecorator::DontMangle); 425 MemRegion cmr((HeapWord*)_virtual_space.low(), 426 (HeapWord*)_virtual_space.high()); 427 gch->barrier_set()->resize_covered_region(cmr); 428 429 log_debug(gc, heap, ergo)( 430 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 431 new_size_before/K, _virtual_space.committed_size()/K, 432 eden()->capacity()/K, from()->capacity()/K); 433 log_trace(gc, heap, ergo)( 434 " [allowed " SIZE_FORMAT "K extra for %d threads]", 435 thread_increase_size/K, threads_count); 436 } 437 } 438 439 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) { 440 assert(false, "NYI -- are you sure you want to call this?"); 441 } 442 443 444 size_t DefNewGeneration::capacity() const { 445 return eden()->capacity() 446 + from()->capacity(); // to() is only used during scavenge 447 } 448 449 450 size_t DefNewGeneration::used() const { 451 return eden()->used() 452 + from()->used(); // to() is only used during scavenge 453 } 454 455 456 size_t DefNewGeneration::free() const { 457 return eden()->free() 458 + from()->free(); // to() is only used during scavenge 459 } 460 461 size_t DefNewGeneration::max_capacity() const { 462 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment(); 463 const size_t reserved_bytes = reserved().byte_size(); 464 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment); 465 } 466 467 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 468 return eden()->free(); 469 } 470 471 size_t DefNewGeneration::capacity_before_gc() const { 472 return eden()->capacity(); 473 } 474 475 size_t DefNewGeneration::contiguous_available() const { 476 return eden()->free(); 477 } 478 479 480 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); } 481 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 482 483 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 484 eden()->object_iterate(blk); 485 from()->object_iterate(blk); 486 } 487 488 489 void DefNewGeneration::space_iterate(SpaceClosure* blk, 490 bool usedOnly) { 491 blk->do_space(eden()); 492 blk->do_space(from()); 493 blk->do_space(to()); 494 } 495 496 // The last collection bailed out, we are running out of heap space, 497 // so we try to allocate the from-space, too. 498 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 499 bool should_try_alloc = should_allocate_from_space() || GC_locker::is_active_and_needs_gc(); 500 501 // If the Heap_lock is not locked by this thread, this will be called 502 // again later with the Heap_lock held. 503 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread())); 504 505 HeapWord* result = NULL; 506 if (do_alloc) { 507 result = from()->allocate(size); 508 } 509 510 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s", 511 size, 512 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 513 "true" : "false", 514 Heap_lock->is_locked() ? "locked" : "unlocked", 515 from()->free(), 516 should_try_alloc ? "" : " should_allocate_from_space: NOT", 517 do_alloc ? " Heap_lock is not owned by self" : "", 518 result == NULL ? "NULL" : "object"); 519 520 return result; 521 } 522 523 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 524 bool is_tlab, 525 bool parallel) { 526 // We don't attempt to expand the young generation (but perhaps we should.) 527 return allocate(size, is_tlab); 528 } 529 530 void DefNewGeneration::adjust_desired_tenuring_threshold() { 531 // Set the desired survivor size to half the real survivor space 532 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->collector_policy()->counters(); 533 _tenuring_threshold = 534 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, gc_counters); 535 } 536 537 void DefNewGeneration::collect(bool full, 538 bool clear_all_soft_refs, 539 size_t size, 540 bool is_tlab) { 541 assert(full || size > 0, "otherwise we don't want to collect"); 542 543 GenCollectedHeap* gch = GenCollectedHeap::heap(); 544 545 _gc_timer->register_gc_start(); 546 DefNewTracer gc_tracer; 547 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start()); 548 549 _old_gen = gch->old_gen(); 550 551 // If the next generation is too full to accommodate promotion 552 // from this generation, pass on collection; let the next generation 553 // do it. 554 if (!collection_attempt_is_safe()) { 555 log_trace(gc)(":: Collection attempt not safe ::"); 556 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 557 return; 558 } 559 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 560 561 init_assuming_no_promotion_failure(); 562 563 GCTraceTime(Trace, gc) tm("DefNew", NULL, gch->gc_cause()); 564 565 gch->trace_heap_before_gc(&gc_tracer); 566 567 // These can be shared for all code paths 568 IsAliveClosure is_alive(this); 569 ScanWeakRefClosure scan_weak_ref(this); 570 571 age_table()->clear(); 572 to()->clear(SpaceDecorator::Mangle); 573 574 gch->rem_set()->prepare_for_younger_refs_iterate(false); 575 576 assert(gch->no_allocs_since_save_marks(), 577 "save marks have not been newly set."); 578 579 // Not very pretty. 580 CollectorPolicy* cp = gch->collector_policy(); 581 582 FastScanClosure fsc_with_no_gc_barrier(this, false); 583 FastScanClosure fsc_with_gc_barrier(this, true); 584 585 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier, 586 gch->rem_set()->klass_rem_set()); 587 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure, 588 &fsc_with_no_gc_barrier, 589 false); 590 591 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 592 FastEvacuateFollowersClosure evacuate_followers(gch, 593 &fsc_with_no_gc_barrier, 594 &fsc_with_gc_barrier); 595 596 assert(gch->no_allocs_since_save_marks(), 597 "save marks have not been newly set."); 598 599 { 600 // DefNew needs to run with n_threads == 0, to make sure the serial 601 // version of the card table scanning code is used. 602 // See: CardTableModRefBSForCTRS::non_clean_card_iterate_possibly_parallel. 603 StrongRootsScope srs(0); 604 605 gch->gen_process_roots(&srs, 606 GenCollectedHeap::YoungGen, 607 true, // Process younger gens, if any, 608 // as strong roots. 609 GenCollectedHeap::SO_ScavengeCodeCache, 610 GenCollectedHeap::StrongAndWeakRoots, 611 &fsc_with_no_gc_barrier, 612 &fsc_with_gc_barrier, 613 &cld_scan_closure); 614 } 615 616 // "evacuate followers". 617 evacuate_followers.do_void(); 618 619 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 620 ReferenceProcessor* rp = ref_processor(); 621 rp->setup_policy(clear_all_soft_refs); 622 const ReferenceProcessorStats& stats = 623 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 624 NULL, _gc_timer); 625 gc_tracer.report_gc_reference_stats(stats); 626 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 627 628 if (!_promotion_failed) { 629 // Swap the survivor spaces. 630 eden()->clear(SpaceDecorator::Mangle); 631 from()->clear(SpaceDecorator::Mangle); 632 if (ZapUnusedHeapArea) { 633 // This is now done here because of the piece-meal mangling which 634 // can check for valid mangling at intermediate points in the 635 // collection(s). When a young collection fails to collect 636 // sufficient space resizing of the young generation can occur 637 // an redistribute the spaces in the young generation. Mangle 638 // here so that unzapped regions don't get distributed to 639 // other spaces. 640 to()->mangle_unused_area(); 641 } 642 swap_spaces(); 643 644 assert(to()->is_empty(), "to space should be empty now"); 645 646 adjust_desired_tenuring_threshold(); 647 648 // A successful scavenge should restart the GC time limit count which is 649 // for full GC's. 650 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); 651 size_policy->reset_gc_overhead_limit_count(); 652 assert(!gch->incremental_collection_failed(), "Should be clear"); 653 } else { 654 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 655 _promo_failure_scan_stack.clear(true); // Clear cached segments. 656 657 remove_forwarding_pointers(); 658 log_debug(gc)("Promotion failed"); 659 // Add to-space to the list of space to compact 660 // when a promotion failure has occurred. In that 661 // case there can be live objects in to-space 662 // as a result of a partial evacuation of eden 663 // and from-space. 664 swap_spaces(); // For uniformity wrt ParNewGeneration. 665 from()->set_next_compaction_space(to()); 666 gch->set_incremental_collection_failed(); 667 668 // Inform the next generation that a promotion failure occurred. 669 _old_gen->promotion_failure_occurred(); 670 gc_tracer.report_promotion_failed(_promotion_failed_info); 671 672 // Reset the PromotionFailureALot counters. 673 NOT_PRODUCT(gch->reset_promotion_should_fail();) 674 } 675 // set new iteration safe limit for the survivor spaces 676 from()->set_concurrent_iteration_safe_limit(from()->top()); 677 to()->set_concurrent_iteration_safe_limit(to()->top()); 678 679 // We need to use a monotonically non-decreasing time in ms 680 // or we will see time-warp warnings and os::javaTimeMillis() 681 // does not guarantee monotonicity. 682 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 683 update_time_of_last_gc(now); 684 685 gch->trace_heap_after_gc(&gc_tracer); 686 687 _gc_timer->register_gc_end(); 688 689 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 690 } 691 692 class RemoveForwardPointerClosure: public ObjectClosure { 693 public: 694 void do_object(oop obj) { 695 obj->init_mark(); 696 } 697 }; 698 699 void DefNewGeneration::init_assuming_no_promotion_failure() { 700 _promotion_failed = false; 701 _promotion_failed_info.reset(); 702 from()->set_next_compaction_space(NULL); 703 } 704 705 void DefNewGeneration::remove_forwarding_pointers() { 706 RemoveForwardPointerClosure rspc; 707 eden()->object_iterate(&rspc); 708 from()->object_iterate(&rspc); 709 710 // Now restore saved marks, if any. 711 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(), 712 "should be the same"); 713 while (!_objs_with_preserved_marks.is_empty()) { 714 oop obj = _objs_with_preserved_marks.pop(); 715 markOop m = _preserved_marks_of_objs.pop(); 716 obj->set_mark(m); 717 } 718 _objs_with_preserved_marks.clear(true); 719 _preserved_marks_of_objs.clear(true); 720 } 721 722 void DefNewGeneration::preserve_mark(oop obj, markOop m) { 723 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj), 724 "Oversaving!"); 725 _objs_with_preserved_marks.push(obj); 726 _preserved_marks_of_objs.push(m); 727 } 728 729 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) { 730 if (m->must_be_preserved_for_promotion_failure(obj)) { 731 preserve_mark(obj, m); 732 } 733 } 734 735 void DefNewGeneration::handle_promotion_failure(oop old) { 736 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size()); 737 738 _promotion_failed = true; 739 _promotion_failed_info.register_copy_failure(old->size()); 740 preserve_mark_if_necessary(old, old->mark()); 741 // forward to self 742 old->forward_to(old); 743 744 _promo_failure_scan_stack.push(old); 745 746 if (!_promo_failure_drain_in_progress) { 747 // prevent recursion in copy_to_survivor_space() 748 _promo_failure_drain_in_progress = true; 749 drain_promo_failure_scan_stack(); 750 _promo_failure_drain_in_progress = false; 751 } 752 } 753 754 oop DefNewGeneration::copy_to_survivor_space(oop old) { 755 assert(is_in_reserved(old) && !old->is_forwarded(), 756 "shouldn't be scavenging this oop"); 757 size_t s = old->size(); 758 oop obj = NULL; 759 760 // Try allocating obj in to-space (unless too old) 761 if (old->age() < tenuring_threshold()) { 762 obj = (oop) to()->allocate_aligned(s); 763 } 764 765 // Otherwise try allocating obj tenured 766 if (obj == NULL) { 767 obj = _old_gen->promote(old, s); 768 if (obj == NULL) { 769 handle_promotion_failure(old); 770 return old; 771 } 772 } else { 773 // Prefetch beyond obj 774 const intx interval = PrefetchCopyIntervalInBytes; 775 Prefetch::write(obj, interval); 776 777 // Copy obj 778 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 779 780 // Increment age if obj still in new generation 781 obj->incr_age(); 782 age_table()->add(obj, s); 783 } 784 785 // Done, insert forward pointer to obj in this header 786 old->forward_to(obj); 787 788 return obj; 789 } 790 791 void DefNewGeneration::drain_promo_failure_scan_stack() { 792 while (!_promo_failure_scan_stack.is_empty()) { 793 oop obj = _promo_failure_scan_stack.pop(); 794 obj->oop_iterate(_promo_failure_scan_stack_closure); 795 } 796 } 797 798 void DefNewGeneration::save_marks() { 799 eden()->set_saved_mark(); 800 to()->set_saved_mark(); 801 from()->set_saved_mark(); 802 } 803 804 805 void DefNewGeneration::reset_saved_marks() { 806 eden()->reset_saved_mark(); 807 to()->reset_saved_mark(); 808 from()->reset_saved_mark(); 809 } 810 811 812 bool DefNewGeneration::no_allocs_since_save_marks() { 813 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 814 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 815 return to()->saved_mark_at_top(); 816 } 817 818 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ 819 \ 820 void DefNewGeneration:: \ 821 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ 822 cl->set_generation(this); \ 823 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \ 824 to()->oop_since_save_marks_iterate##nv_suffix(cl); \ 825 from()->oop_since_save_marks_iterate##nv_suffix(cl); \ 826 cl->reset_generation(); \ 827 save_marks(); \ 828 } 829 830 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN) 831 832 #undef DefNew_SINCE_SAVE_MARKS_DEFN 833 834 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 835 size_t max_alloc_words) { 836 if (requestor == this || _promotion_failed) { 837 return; 838 } 839 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation"); 840 841 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 842 if (to_space->top() > to_space->bottom()) { 843 trace("to_space not empty when contribute_scratch called"); 844 } 845 */ 846 847 ContiguousSpace* to_space = to(); 848 assert(to_space->end() >= to_space->top(), "pointers out of order"); 849 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 850 if (free_words >= MinFreeScratchWords) { 851 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 852 sb->num_words = free_words; 853 sb->next = list; 854 list = sb; 855 } 856 } 857 858 void DefNewGeneration::reset_scratch() { 859 // If contributing scratch in to_space, mangle all of 860 // to_space if ZapUnusedHeapArea. This is needed because 861 // top is not maintained while using to-space as scratch. 862 if (ZapUnusedHeapArea) { 863 to()->mangle_unused_area_complete(); 864 } 865 } 866 867 bool DefNewGeneration::collection_attempt_is_safe() { 868 if (!to()->is_empty()) { 869 log_trace(gc)(":: to is not empty ::"); 870 return false; 871 } 872 if (_old_gen == NULL) { 873 GenCollectedHeap* gch = GenCollectedHeap::heap(); 874 _old_gen = gch->old_gen(); 875 } 876 return _old_gen->promotion_attempt_is_safe(used()); 877 } 878 879 void DefNewGeneration::gc_epilogue(bool full) { 880 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 881 882 assert(!GC_locker::is_active(), "We should not be executing here"); 883 // Check if the heap is approaching full after a collection has 884 // been done. Generally the young generation is empty at 885 // a minimum at the end of a collection. If it is not, then 886 // the heap is approaching full. 887 GenCollectedHeap* gch = GenCollectedHeap::heap(); 888 if (full) { 889 DEBUG_ONLY(seen_incremental_collection_failed = false;) 890 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 891 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 892 GCCause::to_string(gch->gc_cause())); 893 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 894 set_should_allocate_from_space(); // we seem to be running out of space 895 } else { 896 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 897 GCCause::to_string(gch->gc_cause())); 898 gch->clear_incremental_collection_failed(); // We just did a full collection 899 clear_should_allocate_from_space(); // if set 900 } 901 } else { 902 #ifdef ASSERT 903 // It is possible that incremental_collection_failed() == true 904 // here, because an attempted scavenge did not succeed. The policy 905 // is normally expected to cause a full collection which should 906 // clear that condition, so we should not be here twice in a row 907 // with incremental_collection_failed() == true without having done 908 // a full collection in between. 909 if (!seen_incremental_collection_failed && 910 gch->incremental_collection_failed()) { 911 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 912 GCCause::to_string(gch->gc_cause())); 913 seen_incremental_collection_failed = true; 914 } else if (seen_incremental_collection_failed) { 915 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 916 GCCause::to_string(gch->gc_cause())); 917 assert(gch->gc_cause() == GCCause::_scavenge_alot || 918 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 919 !gch->incremental_collection_failed(), 920 "Twice in a row"); 921 seen_incremental_collection_failed = false; 922 } 923 #endif // ASSERT 924 } 925 926 if (ZapUnusedHeapArea) { 927 eden()->check_mangled_unused_area_complete(); 928 from()->check_mangled_unused_area_complete(); 929 to()->check_mangled_unused_area_complete(); 930 } 931 932 if (!CleanChunkPoolAsync) { 933 Chunk::clean_chunk_pool(); 934 } 935 936 // update the generation and space performance counters 937 update_counters(); 938 gch->collector_policy()->counters()->update_counters(); 939 } 940 941 void DefNewGeneration::record_spaces_top() { 942 assert(ZapUnusedHeapArea, "Not mangling unused space"); 943 eden()->set_top_for_allocations(); 944 to()->set_top_for_allocations(); 945 from()->set_top_for_allocations(); 946 } 947 948 void DefNewGeneration::ref_processor_init() { 949 Generation::ref_processor_init(); 950 } 951 952 953 void DefNewGeneration::update_counters() { 954 if (UsePerfData) { 955 _eden_counters->update_all(); 956 _from_counters->update_all(); 957 _to_counters->update_all(); 958 _gen_counters->update_all(); 959 } 960 } 961 962 void DefNewGeneration::verify() { 963 eden()->verify(); 964 from()->verify(); 965 to()->verify(); 966 } 967 968 void DefNewGeneration::print_on(outputStream* st) const { 969 Generation::print_on(st); 970 st->print(" eden"); 971 eden()->print_on(st); 972 st->print(" from"); 973 from()->print_on(st); 974 st->print(" to "); 975 to()->print_on(st); 976 } 977 978 979 const char* DefNewGeneration::name() const { 980 return "def new generation"; 981 } 982 983 // Moved from inline file as they are not called inline 984 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 985 return eden(); 986 } 987 988 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 989 // This is the slow-path allocation for the DefNewGeneration. 990 // Most allocations are fast-path in compiled code. 991 // We try to allocate from the eden. If that works, we are happy. 992 // Note that since DefNewGeneration supports lock-free allocation, we 993 // have to use it here, as well. 994 HeapWord* result = eden()->par_allocate(word_size); 995 if (result != NULL) { 996 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 997 _old_gen->sample_eden_chunk(); 998 } 999 } else { 1000 // If the eden is full and the last collection bailed out, we are running 1001 // out of heap space, and we try to allocate the from-space, too. 1002 // allocate_from_space can't be inlined because that would introduce a 1003 // circular dependency at compile time. 1004 result = allocate_from_space(word_size); 1005 } 1006 return result; 1007 } 1008 1009 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 1010 bool is_tlab) { 1011 HeapWord* res = eden()->par_allocate(word_size); 1012 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1013 _old_gen->sample_eden_chunk(); 1014 } 1015 return res; 1016 } 1017 1018 size_t DefNewGeneration::tlab_capacity() const { 1019 return eden()->capacity(); 1020 } 1021 1022 size_t DefNewGeneration::tlab_used() const { 1023 return eden()->used(); 1024 } 1025 1026 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1027 return unsafe_max_alloc_nogc(); 1028 }