1 /* 2 * Copyright (c) 2001, 2016, 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 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate, 368 size_t new_size_before, 369 size_t alignment) const { 370 size_t desired_new_size = new_size_before; 371 372 if (NewSizeThreadIncrease > 0) { 373 int threads_count; 374 size_t thread_increase_size = 0; 375 376 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'. 377 threads_count = Threads::number_of_non_daemon_threads(); 378 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) { 379 thread_increase_size = threads_count * NewSizeThreadIncrease; 380 381 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'. 382 if (new_size_candidate <= max_uintx - thread_increase_size) { 383 new_size_candidate += thread_increase_size; 384 385 // 3. Check an overflow at 'align_size_up'. 386 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1)); 387 if (new_size_candidate <= aligned_max) { 388 desired_new_size = align_size_up(new_size_candidate, alignment); 389 } 390 } 391 } 392 } 393 394 return desired_new_size; 395 } 396 397 void DefNewGeneration::compute_new_size() { 398 // This is called after a GC that includes the old generation, so from-space 399 // will normally be empty. 400 // Note that we check both spaces, since if scavenge failed they revert roles. 401 // If not we bail out (otherwise we would have to relocate the objects). 402 if (!from()->is_empty() || !to()->is_empty()) { 403 return; 404 } 405 406 GenCollectedHeap* gch = GenCollectedHeap::heap(); 407 408 size_t old_size = gch->old_gen()->capacity(); 409 size_t new_size_before = _virtual_space.committed_size(); 410 size_t min_new_size = initial_size(); 411 size_t max_new_size = reserved().byte_size(); 412 assert(min_new_size <= new_size_before && 413 new_size_before <= max_new_size, 414 "just checking"); 415 // All space sizes must be multiples of Generation::GenGrain. 416 size_t alignment = Generation::GenGrain; 417 418 int threads_count = 0; 419 size_t thread_increase_size = 0; 420 421 size_t new_size_candidate = old_size / NewRatio; 422 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease 423 // and reverts to previous value if any overflow happens 424 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment); 425 426 // Adjust new generation size 427 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size); 428 assert(desired_new_size <= max_new_size, "just checking"); 429 430 bool changed = false; 431 if (desired_new_size > new_size_before) { 432 size_t change = desired_new_size - new_size_before; 433 assert(change % alignment == 0, "just checking"); 434 if (expand(change)) { 435 changed = true; 436 } 437 // If the heap failed to expand to the desired size, 438 // "changed" will be false. If the expansion failed 439 // (and at this point it was expected to succeed), 440 // ignore the failure (leaving "changed" as false). 441 } 442 if (desired_new_size < new_size_before && eden()->is_empty()) { 443 // bail out of shrinking if objects in eden 444 size_t change = new_size_before - desired_new_size; 445 assert(change % alignment == 0, "just checking"); 446 _virtual_space.shrink_by(change); 447 changed = true; 448 } 449 if (changed) { 450 // The spaces have already been mangled at this point but 451 // may not have been cleared (set top = bottom) and should be. 452 // Mangling was done when the heap was being expanded. 453 compute_space_boundaries(eden()->used(), 454 SpaceDecorator::Clear, 455 SpaceDecorator::DontMangle); 456 MemRegion cmr((HeapWord*)_virtual_space.low(), 457 (HeapWord*)_virtual_space.high()); 458 gch->barrier_set()->resize_covered_region(cmr); 459 460 log_debug(gc, heap, ergo)( 461 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 462 new_size_before/K, _virtual_space.committed_size()/K, 463 eden()->capacity()/K, from()->capacity()/K); 464 log_trace(gc, heap, ergo)( 465 " [allowed " SIZE_FORMAT "K extra for %d threads]", 466 thread_increase_size/K, threads_count); 467 } 468 } 469 470 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) { 471 assert(false, "NYI -- are you sure you want to call this?"); 472 } 473 474 475 size_t DefNewGeneration::capacity() const { 476 return eden()->capacity() 477 + from()->capacity(); // to() is only used during scavenge 478 } 479 480 481 size_t DefNewGeneration::used() const { 482 return eden()->used() 483 + from()->used(); // to() is only used during scavenge 484 } 485 486 487 size_t DefNewGeneration::free() const { 488 return eden()->free() 489 + from()->free(); // to() is only used during scavenge 490 } 491 492 size_t DefNewGeneration::max_capacity() const { 493 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment(); 494 const size_t reserved_bytes = reserved().byte_size(); 495 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment); 496 } 497 498 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 499 return eden()->free(); 500 } 501 502 size_t DefNewGeneration::capacity_before_gc() const { 503 return eden()->capacity(); 504 } 505 506 size_t DefNewGeneration::contiguous_available() const { 507 return eden()->free(); 508 } 509 510 511 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); } 512 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 513 514 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 515 eden()->object_iterate(blk); 516 from()->object_iterate(blk); 517 } 518 519 520 void DefNewGeneration::space_iterate(SpaceClosure* blk, 521 bool usedOnly) { 522 blk->do_space(eden()); 523 blk->do_space(from()); 524 blk->do_space(to()); 525 } 526 527 // The last collection bailed out, we are running out of heap space, 528 // so we try to allocate the from-space, too. 529 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 530 bool should_try_alloc = should_allocate_from_space() || GC_locker::is_active_and_needs_gc(); 531 532 // If the Heap_lock is not locked by this thread, this will be called 533 // again later with the Heap_lock held. 534 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread())); 535 536 HeapWord* result = NULL; 537 if (do_alloc) { 538 result = from()->allocate(size); 539 } 540 541 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s", 542 size, 543 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 544 "true" : "false", 545 Heap_lock->is_locked() ? "locked" : "unlocked", 546 from()->free(), 547 should_try_alloc ? "" : " should_allocate_from_space: NOT", 548 do_alloc ? " Heap_lock is not owned by self" : "", 549 result == NULL ? "NULL" : "object"); 550 551 return result; 552 } 553 554 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 555 bool is_tlab, 556 bool parallel) { 557 // We don't attempt to expand the young generation (but perhaps we should.) 558 return allocate(size, is_tlab); 559 } 560 561 void DefNewGeneration::adjust_desired_tenuring_threshold() { 562 // Set the desired survivor size to half the real survivor space 563 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->collector_policy()->counters(); 564 _tenuring_threshold = 565 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, gc_counters); 566 } 567 568 void DefNewGeneration::collect(bool full, 569 bool clear_all_soft_refs, 570 size_t size, 571 bool is_tlab) { 572 assert(full || size > 0, "otherwise we don't want to collect"); 573 574 GenCollectedHeap* gch = GenCollectedHeap::heap(); 575 576 _gc_timer->register_gc_start(); 577 DefNewTracer gc_tracer; 578 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start()); 579 580 _old_gen = gch->old_gen(); 581 582 // If the next generation is too full to accommodate promotion 583 // from this generation, pass on collection; let the next generation 584 // do it. 585 if (!collection_attempt_is_safe()) { 586 log_trace(gc)(":: Collection attempt not safe ::"); 587 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 588 return; 589 } 590 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 591 592 init_assuming_no_promotion_failure(); 593 594 GCTraceTime(Trace, gc) tm("DefNew", NULL, gch->gc_cause()); 595 596 gch->trace_heap_before_gc(&gc_tracer); 597 598 // These can be shared for all code paths 599 IsAliveClosure is_alive(this); 600 ScanWeakRefClosure scan_weak_ref(this); 601 602 age_table()->clear(); 603 to()->clear(SpaceDecorator::Mangle); 604 605 gch->rem_set()->prepare_for_younger_refs_iterate(false); 606 607 assert(gch->no_allocs_since_save_marks(), 608 "save marks have not been newly set."); 609 610 // Not very pretty. 611 CollectorPolicy* cp = gch->collector_policy(); 612 613 FastScanClosure fsc_with_no_gc_barrier(this, false); 614 FastScanClosure fsc_with_gc_barrier(this, true); 615 616 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier, 617 gch->rem_set()->klass_rem_set()); 618 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure, 619 &fsc_with_no_gc_barrier, 620 false); 621 622 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 623 FastEvacuateFollowersClosure evacuate_followers(gch, 624 &fsc_with_no_gc_barrier, 625 &fsc_with_gc_barrier); 626 627 assert(gch->no_allocs_since_save_marks(), 628 "save marks have not been newly set."); 629 630 { 631 // DefNew needs to run with n_threads == 0, to make sure the serial 632 // version of the card table scanning code is used. 633 // See: CardTableModRefBSForCTRS::non_clean_card_iterate_possibly_parallel. 634 StrongRootsScope srs(0); 635 636 gch->gen_process_roots(&srs, 637 GenCollectedHeap::YoungGen, 638 true, // Process younger gens, if any, 639 // as strong roots. 640 GenCollectedHeap::SO_ScavengeCodeCache, 641 GenCollectedHeap::StrongAndWeakRoots, 642 &fsc_with_no_gc_barrier, 643 &fsc_with_gc_barrier, 644 &cld_scan_closure); 645 } 646 647 // "evacuate followers". 648 evacuate_followers.do_void(); 649 650 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 651 ReferenceProcessor* rp = ref_processor(); 652 rp->setup_policy(clear_all_soft_refs); 653 const ReferenceProcessorStats& stats = 654 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 655 NULL, _gc_timer); 656 gc_tracer.report_gc_reference_stats(stats); 657 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 658 659 if (!_promotion_failed) { 660 // Swap the survivor spaces. 661 eden()->clear(SpaceDecorator::Mangle); 662 from()->clear(SpaceDecorator::Mangle); 663 if (ZapUnusedHeapArea) { 664 // This is now done here because of the piece-meal mangling which 665 // can check for valid mangling at intermediate points in the 666 // collection(s). When a young collection fails to collect 667 // sufficient space resizing of the young generation can occur 668 // an redistribute the spaces in the young generation. Mangle 669 // here so that unzapped regions don't get distributed to 670 // other spaces. 671 to()->mangle_unused_area(); 672 } 673 swap_spaces(); 674 675 assert(to()->is_empty(), "to space should be empty now"); 676 677 adjust_desired_tenuring_threshold(); 678 679 // A successful scavenge should restart the GC time limit count which is 680 // for full GC's. 681 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); 682 size_policy->reset_gc_overhead_limit_count(); 683 assert(!gch->incremental_collection_failed(), "Should be clear"); 684 } else { 685 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 686 _promo_failure_scan_stack.clear(true); // Clear cached segments. 687 688 remove_forwarding_pointers(); 689 log_debug(gc)("Promotion failed"); 690 // Add to-space to the list of space to compact 691 // when a promotion failure has occurred. In that 692 // case there can be live objects in to-space 693 // as a result of a partial evacuation of eden 694 // and from-space. 695 swap_spaces(); // For uniformity wrt ParNewGeneration. 696 from()->set_next_compaction_space(to()); 697 gch->set_incremental_collection_failed(); 698 699 // Inform the next generation that a promotion failure occurred. 700 _old_gen->promotion_failure_occurred(); 701 gc_tracer.report_promotion_failed(_promotion_failed_info); 702 703 // Reset the PromotionFailureALot counters. 704 NOT_PRODUCT(gch->reset_promotion_should_fail();) 705 } 706 // set new iteration safe limit for the survivor spaces 707 from()->set_concurrent_iteration_safe_limit(from()->top()); 708 to()->set_concurrent_iteration_safe_limit(to()->top()); 709 710 // We need to use a monotonically non-decreasing time in ms 711 // or we will see time-warp warnings and os::javaTimeMillis() 712 // does not guarantee monotonicity. 713 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 714 update_time_of_last_gc(now); 715 716 gch->trace_heap_after_gc(&gc_tracer); 717 718 _gc_timer->register_gc_end(); 719 720 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 721 } 722 723 class RemoveForwardPointerClosure: public ObjectClosure { 724 public: 725 void do_object(oop obj) { 726 obj->init_mark(); 727 } 728 }; 729 730 void DefNewGeneration::init_assuming_no_promotion_failure() { 731 _promotion_failed = false; 732 _promotion_failed_info.reset(); 733 from()->set_next_compaction_space(NULL); 734 } 735 736 void DefNewGeneration::remove_forwarding_pointers() { 737 RemoveForwardPointerClosure rspc; 738 eden()->object_iterate(&rspc); 739 from()->object_iterate(&rspc); 740 741 // Now restore saved marks, if any. 742 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(), 743 "should be the same"); 744 while (!_objs_with_preserved_marks.is_empty()) { 745 oop obj = _objs_with_preserved_marks.pop(); 746 markOop m = _preserved_marks_of_objs.pop(); 747 obj->set_mark(m); 748 } 749 _objs_with_preserved_marks.clear(true); 750 _preserved_marks_of_objs.clear(true); 751 } 752 753 void DefNewGeneration::preserve_mark(oop obj, markOop m) { 754 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj), 755 "Oversaving!"); 756 _objs_with_preserved_marks.push(obj); 757 _preserved_marks_of_objs.push(m); 758 } 759 760 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) { 761 if (m->must_be_preserved_for_promotion_failure(obj)) { 762 preserve_mark(obj, m); 763 } 764 } 765 766 void DefNewGeneration::handle_promotion_failure(oop old) { 767 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size()); 768 769 _promotion_failed = true; 770 _promotion_failed_info.register_copy_failure(old->size()); 771 preserve_mark_if_necessary(old, old->mark()); 772 // forward to self 773 old->forward_to(old); 774 775 _promo_failure_scan_stack.push(old); 776 777 if (!_promo_failure_drain_in_progress) { 778 // prevent recursion in copy_to_survivor_space() 779 _promo_failure_drain_in_progress = true; 780 drain_promo_failure_scan_stack(); 781 _promo_failure_drain_in_progress = false; 782 } 783 } 784 785 oop DefNewGeneration::copy_to_survivor_space(oop old) { 786 assert(is_in_reserved(old) && !old->is_forwarded(), 787 "shouldn't be scavenging this oop"); 788 size_t s = old->size(); 789 oop obj = NULL; 790 791 // Try allocating obj in to-space (unless too old) 792 if (old->age() < tenuring_threshold()) { 793 obj = (oop) to()->allocate_aligned(s); 794 } 795 796 // Otherwise try allocating obj tenured 797 if (obj == NULL) { 798 obj = _old_gen->promote(old, s); 799 if (obj == NULL) { 800 handle_promotion_failure(old); 801 return old; 802 } 803 } else { 804 // Prefetch beyond obj 805 const intx interval = PrefetchCopyIntervalInBytes; 806 Prefetch::write(obj, interval); 807 808 // Copy obj 809 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 810 811 // Increment age if obj still in new generation 812 obj->incr_age(); 813 age_table()->add(obj, s); 814 } 815 816 // Done, insert forward pointer to obj in this header 817 old->forward_to(obj); 818 819 return obj; 820 } 821 822 void DefNewGeneration::drain_promo_failure_scan_stack() { 823 while (!_promo_failure_scan_stack.is_empty()) { 824 oop obj = _promo_failure_scan_stack.pop(); 825 obj->oop_iterate(_promo_failure_scan_stack_closure); 826 } 827 } 828 829 void DefNewGeneration::save_marks() { 830 eden()->set_saved_mark(); 831 to()->set_saved_mark(); 832 from()->set_saved_mark(); 833 } 834 835 836 void DefNewGeneration::reset_saved_marks() { 837 eden()->reset_saved_mark(); 838 to()->reset_saved_mark(); 839 from()->reset_saved_mark(); 840 } 841 842 843 bool DefNewGeneration::no_allocs_since_save_marks() { 844 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 845 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 846 return to()->saved_mark_at_top(); 847 } 848 849 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ 850 \ 851 void DefNewGeneration:: \ 852 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ 853 cl->set_generation(this); \ 854 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \ 855 to()->oop_since_save_marks_iterate##nv_suffix(cl); \ 856 from()->oop_since_save_marks_iterate##nv_suffix(cl); \ 857 cl->reset_generation(); \ 858 save_marks(); \ 859 } 860 861 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN) 862 863 #undef DefNew_SINCE_SAVE_MARKS_DEFN 864 865 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 866 size_t max_alloc_words) { 867 if (requestor == this || _promotion_failed) { 868 return; 869 } 870 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation"); 871 872 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 873 if (to_space->top() > to_space->bottom()) { 874 trace("to_space not empty when contribute_scratch called"); 875 } 876 */ 877 878 ContiguousSpace* to_space = to(); 879 assert(to_space->end() >= to_space->top(), "pointers out of order"); 880 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 881 if (free_words >= MinFreeScratchWords) { 882 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 883 sb->num_words = free_words; 884 sb->next = list; 885 list = sb; 886 } 887 } 888 889 void DefNewGeneration::reset_scratch() { 890 // If contributing scratch in to_space, mangle all of 891 // to_space if ZapUnusedHeapArea. This is needed because 892 // top is not maintained while using to-space as scratch. 893 if (ZapUnusedHeapArea) { 894 to()->mangle_unused_area_complete(); 895 } 896 } 897 898 bool DefNewGeneration::collection_attempt_is_safe() { 899 if (!to()->is_empty()) { 900 log_trace(gc)(":: to is not empty ::"); 901 return false; 902 } 903 if (_old_gen == NULL) { 904 GenCollectedHeap* gch = GenCollectedHeap::heap(); 905 _old_gen = gch->old_gen(); 906 } 907 return _old_gen->promotion_attempt_is_safe(used()); 908 } 909 910 void DefNewGeneration::gc_epilogue(bool full) { 911 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 912 913 assert(!GC_locker::is_active(), "We should not be executing here"); 914 // Check if the heap is approaching full after a collection has 915 // been done. Generally the young generation is empty at 916 // a minimum at the end of a collection. If it is not, then 917 // the heap is approaching full. 918 GenCollectedHeap* gch = GenCollectedHeap::heap(); 919 if (full) { 920 DEBUG_ONLY(seen_incremental_collection_failed = false;) 921 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 922 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 923 GCCause::to_string(gch->gc_cause())); 924 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 925 set_should_allocate_from_space(); // we seem to be running out of space 926 } else { 927 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 928 GCCause::to_string(gch->gc_cause())); 929 gch->clear_incremental_collection_failed(); // We just did a full collection 930 clear_should_allocate_from_space(); // if set 931 } 932 } else { 933 #ifdef ASSERT 934 // It is possible that incremental_collection_failed() == true 935 // here, because an attempted scavenge did not succeed. The policy 936 // is normally expected to cause a full collection which should 937 // clear that condition, so we should not be here twice in a row 938 // with incremental_collection_failed() == true without having done 939 // a full collection in between. 940 if (!seen_incremental_collection_failed && 941 gch->incremental_collection_failed()) { 942 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 943 GCCause::to_string(gch->gc_cause())); 944 seen_incremental_collection_failed = true; 945 } else if (seen_incremental_collection_failed) { 946 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 947 GCCause::to_string(gch->gc_cause())); 948 assert(gch->gc_cause() == GCCause::_scavenge_alot || 949 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 950 !gch->incremental_collection_failed(), 951 "Twice in a row"); 952 seen_incremental_collection_failed = false; 953 } 954 #endif // ASSERT 955 } 956 957 if (ZapUnusedHeapArea) { 958 eden()->check_mangled_unused_area_complete(); 959 from()->check_mangled_unused_area_complete(); 960 to()->check_mangled_unused_area_complete(); 961 } 962 963 if (!CleanChunkPoolAsync) { 964 Chunk::clean_chunk_pool(); 965 } 966 967 // update the generation and space performance counters 968 update_counters(); 969 gch->collector_policy()->counters()->update_counters(); 970 } 971 972 void DefNewGeneration::record_spaces_top() { 973 assert(ZapUnusedHeapArea, "Not mangling unused space"); 974 eden()->set_top_for_allocations(); 975 to()->set_top_for_allocations(); 976 from()->set_top_for_allocations(); 977 } 978 979 void DefNewGeneration::ref_processor_init() { 980 Generation::ref_processor_init(); 981 } 982 983 984 void DefNewGeneration::update_counters() { 985 if (UsePerfData) { 986 _eden_counters->update_all(); 987 _from_counters->update_all(); 988 _to_counters->update_all(); 989 _gen_counters->update_all(); 990 } 991 } 992 993 void DefNewGeneration::verify() { 994 eden()->verify(); 995 from()->verify(); 996 to()->verify(); 997 } 998 999 void DefNewGeneration::print_on(outputStream* st) const { 1000 Generation::print_on(st); 1001 st->print(" eden"); 1002 eden()->print_on(st); 1003 st->print(" from"); 1004 from()->print_on(st); 1005 st->print(" to "); 1006 to()->print_on(st); 1007 } 1008 1009 1010 const char* DefNewGeneration::name() const { 1011 return "def new generation"; 1012 } 1013 1014 // Moved from inline file as they are not called inline 1015 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 1016 return eden(); 1017 } 1018 1019 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 1020 // This is the slow-path allocation for the DefNewGeneration. 1021 // Most allocations are fast-path in compiled code. 1022 // We try to allocate from the eden. If that works, we are happy. 1023 // Note that since DefNewGeneration supports lock-free allocation, we 1024 // have to use it here, as well. 1025 HeapWord* result = eden()->par_allocate(word_size); 1026 if (result != NULL) { 1027 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1028 _old_gen->sample_eden_chunk(); 1029 } 1030 } else { 1031 // If the eden is full and the last collection bailed out, we are running 1032 // out of heap space, and we try to allocate the from-space, too. 1033 // allocate_from_space can't be inlined because that would introduce a 1034 // circular dependency at compile time. 1035 result = allocate_from_space(word_size); 1036 } 1037 return result; 1038 } 1039 1040 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 1041 bool is_tlab) { 1042 HeapWord* res = eden()->par_allocate(word_size); 1043 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1044 _old_gen->sample_eden_chunk(); 1045 } 1046 return res; 1047 } 1048 1049 size_t DefNewGeneration::tlab_capacity() const { 1050 return eden()->capacity(); 1051 } 1052 1053 size_t DefNewGeneration::tlab_used() const { 1054 return eden()->used(); 1055 } 1056 1057 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1058 return unsafe_max_alloc_nogc(); 1059 }