1 /* 2 * Copyright (c) 2001, 2019, 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/atomic.hpp" 55 #include "runtime/java.hpp" 56 #include "runtime/prefetch.inline.hpp" 57 #include "runtime/thread.inline.hpp" 58 #include "utilities/align.hpp" 59 #include "utilities/copy.hpp" 60 #include "utilities/globalDefinitions.hpp" 61 #include "utilities/stack.inline.hpp" 62 63 // 64 // DefNewGeneration functions. 65 66 // Methods of protected closure types. 67 68 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) { 69 assert(_young_gen->kind() == Generation::DefNew, "Expected the young generation here"); 70 } 71 72 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 73 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded(); 74 } 75 76 DefNewGeneration::KeepAliveClosure:: 77 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 78 _rs = GenCollectedHeap::heap()->rem_set(); 79 } 80 81 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 82 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 83 84 85 DefNewGeneration::FastKeepAliveClosure:: 86 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 87 DefNewGeneration::KeepAliveClosure(cl) { 88 _boundary = g->reserved().end(); 89 } 90 91 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 92 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 93 94 DefNewGeneration::FastEvacuateFollowersClosure:: 95 FastEvacuateFollowersClosure(SerialHeap* heap, 96 FastScanClosure* cur, 97 FastScanClosure* older) : 98 _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older) 99 { 100 } 101 102 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 103 do { 104 _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older); 105 } while (!_heap->no_allocs_since_save_marks()); 106 guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan"); 107 } 108 109 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) : 110 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 111 { 112 _boundary = _g->reserved().end(); 113 } 114 115 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 116 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 117 { 118 _boundary = _g->reserved().end(); 119 } 120 121 void CLDScanClosure::do_cld(ClassLoaderData* cld) { 122 NOT_PRODUCT(ResourceMark rm); 123 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s", 124 p2i(cld), 125 cld->loader_name_and_id(), 126 cld->has_modified_oops() ? "true" : "false"); 127 128 // If the cld has not been dirtied we know that there's 129 // no references into the young gen and we can skip it. 130 if (cld->has_modified_oops()) { 131 if (_accumulate_modified_oops) { 132 cld->accumulate_modified_oops(); 133 } 134 135 // Tell the closure which CLD is being scanned so that it can be dirtied 136 // if oops are left pointing into the young gen. 137 _scavenge_closure->set_scanned_cld(cld); 138 139 // Clean the cld since we're going to scavenge all the metadata. 140 cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true); 141 142 _scavenge_closure->set_scanned_cld(NULL); 143 } 144 } 145 146 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 147 _g(g) 148 { 149 _boundary = _g->reserved().end(); 150 } 151 152 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 153 size_t initial_size, 154 size_t min_size, 155 size_t max_size, 156 const char* policy) 157 : Generation(rs, initial_size), 158 _preserved_marks_set(false /* in_c_heap */), 159 _promo_failure_drain_in_progress(false), 160 _should_allocate_from_space(false) 161 { 162 MemRegion cmr((HeapWord*)_virtual_space.low(), 163 (HeapWord*)_virtual_space.high()); 164 GenCollectedHeap* gch = GenCollectedHeap::heap(); 165 166 gch->rem_set()->resize_covered_region(cmr); 167 168 _eden_space = new ContiguousSpace(); 169 _from_space = new ContiguousSpace(); 170 _to_space = new ContiguousSpace(); 171 172 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) { 173 vm_exit_during_initialization("Could not allocate a new gen space"); 174 } 175 176 // Compute the maximum eden and survivor space sizes. These sizes 177 // are computed assuming the entire reserved space is committed. 178 // These values are exported as performance counters. 179 uintx size = _virtual_space.reserved_size(); 180 _max_survivor_size = compute_survivor_size(size, SpaceAlignment); 181 _max_eden_size = size - (2*_max_survivor_size); 182 183 // allocate the performance counters 184 185 // Generation counters -- generation 0, 3 subspaces 186 _gen_counters = new GenerationCounters("new", 0, 3, 187 min_size, max_size, &_virtual_space); 188 _gc_counters = new CollectorCounters(policy, 0); 189 190 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 191 _gen_counters); 192 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 193 _gen_counters); 194 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 195 _gen_counters); 196 197 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 198 update_counters(); 199 _old_gen = NULL; 200 _tenuring_threshold = MaxTenuringThreshold; 201 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 202 203 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer(); 204 } 205 206 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 207 bool clear_space, 208 bool mangle_space) { 209 // If the spaces are being cleared (only done at heap initialization 210 // currently), the survivor spaces need not be empty. 211 // Otherwise, no care is taken for used areas in the survivor spaces 212 // so check. 213 assert(clear_space || (to()->is_empty() && from()->is_empty()), 214 "Initialization of the survivor spaces assumes these are empty"); 215 216 // Compute sizes 217 uintx size = _virtual_space.committed_size(); 218 uintx survivor_size = compute_survivor_size(size, SpaceAlignment); 219 uintx eden_size = size - (2*survivor_size); 220 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 221 222 if (eden_size < minimum_eden_size) { 223 // May happen due to 64Kb rounding, if so adjust eden size back up 224 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment); 225 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 226 uintx unaligned_survivor_size = 227 align_down(maximum_survivor_size, SpaceAlignment); 228 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment); 229 eden_size = size - (2*survivor_size); 230 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 231 assert(eden_size >= minimum_eden_size, "just checking"); 232 } 233 234 char *eden_start = _virtual_space.low(); 235 char *from_start = eden_start + eden_size; 236 char *to_start = from_start + survivor_size; 237 char *to_end = to_start + survivor_size; 238 239 assert(to_end == _virtual_space.high(), "just checking"); 240 assert(Space::is_aligned(eden_start), "checking alignment"); 241 assert(Space::is_aligned(from_start), "checking alignment"); 242 assert(Space::is_aligned(to_start), "checking alignment"); 243 244 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 245 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 246 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 247 248 // A minimum eden size implies that there is a part of eden that 249 // is being used and that affects the initialization of any 250 // newly formed eden. 251 bool live_in_eden = minimum_eden_size > 0; 252 253 // If not clearing the spaces, do some checking to verify that 254 // the space are already mangled. 255 if (!clear_space) { 256 // Must check mangling before the spaces are reshaped. Otherwise, 257 // the bottom or end of one space may have moved into another 258 // a failure of the check may not correctly indicate which space 259 // is not properly mangled. 260 if (ZapUnusedHeapArea) { 261 HeapWord* limit = (HeapWord*) _virtual_space.high(); 262 eden()->check_mangled_unused_area(limit); 263 from()->check_mangled_unused_area(limit); 264 to()->check_mangled_unused_area(limit); 265 } 266 } 267 268 // Reset the spaces for their new regions. 269 eden()->initialize(edenMR, 270 clear_space && !live_in_eden, 271 SpaceDecorator::Mangle); 272 // If clear_space and live_in_eden, we will not have cleared any 273 // portion of eden above its top. This can cause newly 274 // expanded space not to be mangled if using ZapUnusedHeapArea. 275 // We explicitly do such mangling here. 276 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 277 eden()->mangle_unused_area(); 278 } 279 from()->initialize(fromMR, clear_space, mangle_space); 280 to()->initialize(toMR, clear_space, mangle_space); 281 282 // Set next compaction spaces. 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 } 289 290 void DefNewGeneration::swap_spaces() { 291 ContiguousSpace* s = from(); 292 _from_space = to(); 293 _to_space = s; 294 eden()->set_next_compaction_space(from()); 295 // The to-space is normally empty before a compaction so need 296 // not be considered. The exception is during promotion 297 // failure handling when to-space can contain live objects. 298 from()->set_next_compaction_space(NULL); 299 300 if (UsePerfData) { 301 CSpaceCounters* c = _from_counters; 302 _from_counters = _to_counters; 303 _to_counters = c; 304 } 305 } 306 307 bool DefNewGeneration::expand(size_t bytes) { 308 MutexLocker x(ExpandHeap_lock); 309 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 310 bool success = _virtual_space.expand_by(bytes); 311 if (success && ZapUnusedHeapArea) { 312 // Mangle newly committed space immediately because it 313 // can be done here more simply that after the new 314 // spaces have been computed. 315 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 316 MemRegion mangle_region(prev_high, new_high); 317 SpaceMangler::mangle_region(mangle_region); 318 } 319 320 // Do not attempt an expand-to-the reserve size. The 321 // request should properly observe the maximum size of 322 // the generation so an expand-to-reserve should be 323 // unnecessary. Also a second call to expand-to-reserve 324 // value potentially can cause an undue expansion. 325 // For example if the first expand fail for unknown reasons, 326 // but the second succeeds and expands the heap to its maximum 327 // value. 328 if (GCLocker::is_active()) { 329 log_debug(gc)("Garbage collection disabled, expanded heap instead"); 330 } 331 332 return success; 333 } 334 335 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate, 336 size_t new_size_before, 337 size_t alignment) const { 338 size_t desired_new_size = new_size_before; 339 340 if (NewSizeThreadIncrease > 0) { 341 int threads_count; 342 size_t thread_increase_size = 0; 343 344 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'. 345 threads_count = Threads::number_of_non_daemon_threads(); 346 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) { 347 thread_increase_size = threads_count * NewSizeThreadIncrease; 348 349 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'. 350 if (new_size_candidate <= max_uintx - thread_increase_size) { 351 new_size_candidate += thread_increase_size; 352 353 // 3. Check an overflow at 'align_up'. 354 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1)); 355 if (new_size_candidate <= aligned_max) { 356 desired_new_size = align_up(new_size_candidate, alignment); 357 } 358 } 359 } 360 } 361 362 return desired_new_size; 363 } 364 365 void DefNewGeneration::compute_new_size() { 366 // This is called after a GC that includes the old generation, so from-space 367 // will normally be empty. 368 // Note that we check both spaces, since if scavenge failed they revert roles. 369 // If not we bail out (otherwise we would have to relocate the objects). 370 if (!from()->is_empty() || !to()->is_empty()) { 371 return; 372 } 373 374 GenCollectedHeap* gch = GenCollectedHeap::heap(); 375 376 size_t old_size = gch->old_gen()->capacity(); 377 size_t new_size_before = _virtual_space.committed_size(); 378 size_t min_new_size = initial_size(); 379 size_t max_new_size = reserved().byte_size(); 380 assert(min_new_size <= new_size_before && 381 new_size_before <= max_new_size, 382 "just checking"); 383 // All space sizes must be multiples of Generation::GenGrain. 384 size_t alignment = Generation::GenGrain; 385 386 int threads_count = 0; 387 size_t thread_increase_size = 0; 388 389 size_t new_size_candidate = old_size / NewRatio; 390 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease 391 // and reverts to previous value if any overflow happens 392 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment); 393 394 // Adjust new generation size 395 desired_new_size = clamp(desired_new_size, min_new_size, max_new_size); 396 assert(desired_new_size <= max_new_size, "just checking"); 397 398 bool changed = false; 399 if (desired_new_size > new_size_before) { 400 size_t change = desired_new_size - new_size_before; 401 assert(change % alignment == 0, "just checking"); 402 if (expand(change)) { 403 changed = true; 404 } 405 // If the heap failed to expand to the desired size, 406 // "changed" will be false. If the expansion failed 407 // (and at this point it was expected to succeed), 408 // ignore the failure (leaving "changed" as false). 409 } 410 if (desired_new_size < new_size_before && eden()->is_empty()) { 411 // bail out of shrinking if objects in eden 412 size_t change = new_size_before - desired_new_size; 413 assert(change % alignment == 0, "just checking"); 414 _virtual_space.shrink_by(change); 415 changed = true; 416 } 417 if (changed) { 418 // The spaces have already been mangled at this point but 419 // may not have been cleared (set top = bottom) and should be. 420 // Mangling was done when the heap was being expanded. 421 compute_space_boundaries(eden()->used(), 422 SpaceDecorator::Clear, 423 SpaceDecorator::DontMangle); 424 MemRegion cmr((HeapWord*)_virtual_space.low(), 425 (HeapWord*)_virtual_space.high()); 426 gch->rem_set()->resize_covered_region(cmr); 427 428 log_debug(gc, ergo, heap)( 429 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 430 new_size_before/K, _virtual_space.committed_size()/K, 431 eden()->capacity()/K, from()->capacity()/K); 432 log_trace(gc, ergo, heap)( 433 " [allowed " SIZE_FORMAT "K extra for %d threads]", 434 thread_increase_size/K, threads_count); 435 } 436 } 437 438 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) { 439 assert(false, "NYI -- are you sure you want to call this?"); 440 } 441 442 443 size_t DefNewGeneration::capacity() const { 444 return eden()->capacity() 445 + from()->capacity(); // to() is only used during scavenge 446 } 447 448 449 size_t DefNewGeneration::used() const { 450 return eden()->used() 451 + from()->used(); // to() is only used during scavenge 452 } 453 454 455 size_t DefNewGeneration::free() const { 456 return eden()->free() 457 + from()->free(); // to() is only used during scavenge 458 } 459 460 size_t DefNewGeneration::max_capacity() const { 461 const size_t reserved_bytes = reserved().byte_size(); 462 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment); 463 } 464 465 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 466 return eden()->free(); 467 } 468 469 size_t DefNewGeneration::capacity_before_gc() const { 470 return eden()->capacity(); 471 } 472 473 size_t DefNewGeneration::contiguous_available() const { 474 return eden()->free(); 475 } 476 477 478 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); } 479 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 480 481 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 482 eden()->object_iterate(blk); 483 from()->object_iterate(blk); 484 } 485 486 487 void DefNewGeneration::space_iterate(SpaceClosure* blk, 488 bool usedOnly) { 489 blk->do_space(eden()); 490 blk->do_space(from()); 491 blk->do_space(to()); 492 } 493 494 // The last collection bailed out, we are running out of heap space, 495 // so we try to allocate the from-space, too. 496 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 497 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc(); 498 499 // If the Heap_lock is not locked by this thread, this will be called 500 // again later with the Heap_lock held. 501 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread())); 502 503 HeapWord* result = NULL; 504 if (do_alloc) { 505 result = from()->allocate(size); 506 } 507 508 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s", 509 size, 510 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 511 "true" : "false", 512 Heap_lock->is_locked() ? "locked" : "unlocked", 513 from()->free(), 514 should_try_alloc ? "" : " should_allocate_from_space: NOT", 515 do_alloc ? " Heap_lock is not owned by self" : "", 516 result == NULL ? "NULL" : "object"); 517 518 return result; 519 } 520 521 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 522 bool is_tlab, 523 bool parallel) { 524 // We don't attempt to expand the young generation (but perhaps we should.) 525 return allocate(size, is_tlab); 526 } 527 528 void DefNewGeneration::adjust_desired_tenuring_threshold() { 529 // Set the desired survivor size to half the real survivor space 530 size_t const survivor_capacity = to()->capacity() / HeapWordSize; 531 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 532 533 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size); 534 535 if (UsePerfData) { 536 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters(); 537 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold); 538 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize); 539 } 540 541 age_table()->print_age_table(_tenuring_threshold); 542 } 543 544 void DefNewGeneration::collect(bool full, 545 bool clear_all_soft_refs, 546 size_t size, 547 bool is_tlab) { 548 assert(full || size > 0, "otherwise we don't want to collect"); 549 550 SerialHeap* heap = SerialHeap::heap(); 551 552 _gc_timer->register_gc_start(); 553 DefNewTracer gc_tracer; 554 gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start()); 555 556 _old_gen = heap->old_gen(); 557 558 // If the next generation is too full to accommodate promotion 559 // from this generation, pass on collection; let the next generation 560 // do it. 561 if (!collection_attempt_is_safe()) { 562 log_trace(gc)(":: Collection attempt not safe ::"); 563 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 564 return; 565 } 566 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 567 568 init_assuming_no_promotion_failure(); 569 570 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause()); 571 572 heap->trace_heap_before_gc(&gc_tracer); 573 574 // These can be shared for all code paths 575 IsAliveClosure is_alive(this); 576 ScanWeakRefClosure scan_weak_ref(this); 577 578 age_table()->clear(); 579 to()->clear(SpaceDecorator::Mangle); 580 // The preserved marks should be empty at the start of the GC. 581 _preserved_marks_set.init(1); 582 583 heap->rem_set()->prepare_for_younger_refs_iterate(false); 584 585 assert(heap->no_allocs_since_save_marks(), 586 "save marks have not been newly set."); 587 588 FastScanClosure fsc_with_no_gc_barrier(this, false); 589 FastScanClosure fsc_with_gc_barrier(this, true); 590 591 CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier, 592 heap->rem_set()->cld_rem_set()->accumulate_modified_oops()); 593 594 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 595 FastEvacuateFollowersClosure evacuate_followers(heap, 596 &fsc_with_no_gc_barrier, 597 &fsc_with_gc_barrier); 598 599 assert(heap->no_allocs_since_save_marks(), 600 "save marks have not been newly set."); 601 602 { 603 // DefNew needs to run with n_threads == 0, to make sure the serial 604 // version of the card table scanning code is used. 605 // See: CardTableRS::non_clean_card_iterate_possibly_parallel. 606 StrongRootsScope srs(0); 607 608 heap->young_process_roots(&srs, 609 &fsc_with_no_gc_barrier, 610 &fsc_with_gc_barrier, 611 &cld_scan_closure); 612 } 613 614 // "evacuate followers". 615 evacuate_followers.do_void(); 616 617 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 618 ReferenceProcessor* rp = ref_processor(); 619 rp->setup_policy(clear_all_soft_refs); 620 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues()); 621 const ReferenceProcessorStats& stats = 622 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 623 NULL, &pt); 624 gc_tracer.report_gc_reference_stats(stats); 625 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 626 pt.print_all_references(); 627 628 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set."); 629 630 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 631 632 // Verify that the usage of keep_alive didn't copy any objects. 633 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set."); 634 635 if (!_promotion_failed) { 636 // Swap the survivor spaces. 637 eden()->clear(SpaceDecorator::Mangle); 638 from()->clear(SpaceDecorator::Mangle); 639 if (ZapUnusedHeapArea) { 640 // This is now done here because of the piece-meal mangling which 641 // can check for valid mangling at intermediate points in the 642 // collection(s). When a young collection fails to collect 643 // sufficient space resizing of the young generation can occur 644 // an redistribute the spaces in the young generation. Mangle 645 // here so that unzapped regions don't get distributed to 646 // other spaces. 647 to()->mangle_unused_area(); 648 } 649 swap_spaces(); 650 651 assert(to()->is_empty(), "to space should be empty now"); 652 653 adjust_desired_tenuring_threshold(); 654 655 // A successful scavenge should restart the GC time limit count which is 656 // for full GC's. 657 AdaptiveSizePolicy* size_policy = heap->size_policy(); 658 size_policy->reset_gc_overhead_limit_count(); 659 assert(!heap->incremental_collection_failed(), "Should be clear"); 660 } else { 661 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 662 _promo_failure_scan_stack.clear(true); // Clear cached segments. 663 664 remove_forwarding_pointers(); 665 log_info(gc, promotion)("Promotion failed"); 666 // Add to-space to the list of space to compact 667 // when a promotion failure has occurred. In that 668 // case there can be live objects in to-space 669 // as a result of a partial evacuation of eden 670 // and from-space. 671 swap_spaces(); // For uniformity wrt ParNewGeneration. 672 from()->set_next_compaction_space(to()); 673 heap->set_incremental_collection_failed(); 674 675 // Inform the next generation that a promotion failure occurred. 676 _old_gen->promotion_failure_occurred(); 677 gc_tracer.report_promotion_failed(_promotion_failed_info); 678 679 // Reset the PromotionFailureALot counters. 680 NOT_PRODUCT(heap->reset_promotion_should_fail();) 681 } 682 // We should have processed and cleared all the preserved marks. 683 _preserved_marks_set.reclaim(); 684 // set new iteration safe limit for the survivor spaces 685 from()->set_concurrent_iteration_safe_limit(from()->top()); 686 to()->set_concurrent_iteration_safe_limit(to()->top()); 687 688 // We need to use a monotonically non-decreasing time in ms 689 // or we will see time-warp warnings and os::javaTimeMillis() 690 // does not guarantee monotonicity. 691 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 692 update_time_of_last_gc(now); 693 694 heap->trace_heap_after_gc(&gc_tracer); 695 696 _gc_timer->register_gc_end(); 697 698 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 699 } 700 701 void DefNewGeneration::init_assuming_no_promotion_failure() { 702 _promotion_failed = false; 703 _promotion_failed_info.reset(); 704 from()->set_next_compaction_space(NULL); 705 } 706 707 void DefNewGeneration::remove_forwarding_pointers() { 708 RemoveForwardedPointerClosure rspc; 709 eden()->object_iterate(&rspc); 710 from()->object_iterate(&rspc); 711 restore_preserved_marks(); 712 } 713 714 void DefNewGeneration::restore_preserved_marks() { 715 SharedRestorePreservedMarksTaskExecutor task_executor(NULL); 716 _preserved_marks_set.restore(&task_executor); 717 } 718 719 void DefNewGeneration::handle_promotion_failure(oop old) { 720 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size()); 721 722 _promotion_failed = true; 723 _promotion_failed_info.register_copy_failure(old->size()); 724 _preserved_marks_set.get()->push_if_necessary(old, old->mark_raw()); 725 // forward to self 726 old->forward_to(old); 727 728 _promo_failure_scan_stack.push(old); 729 730 if (!_promo_failure_drain_in_progress) { 731 // prevent recursion in copy_to_survivor_space() 732 _promo_failure_drain_in_progress = true; 733 drain_promo_failure_scan_stack(); 734 _promo_failure_drain_in_progress = false; 735 } 736 } 737 738 oop DefNewGeneration::copy_to_survivor_space(oop old) { 739 assert(is_in_reserved(old) && !old->is_forwarded(), 740 "shouldn't be scavenging this oop"); 741 size_t s = old->size(); 742 oop obj = NULL; 743 744 // Try allocating obj in to-space (unless too old) 745 if (old->age() < tenuring_threshold()) { 746 obj = (oop) to()->allocate_aligned(s); 747 } 748 749 // Otherwise try allocating obj tenured 750 if (obj == NULL) { 751 obj = _old_gen->promote(old, s); 752 if (obj == NULL) { 753 handle_promotion_failure(old); 754 return old; 755 } 756 } else { 757 // Prefetch beyond obj 758 const intx interval = PrefetchCopyIntervalInBytes; 759 Prefetch::write(obj, interval); 760 761 // Copy obj 762 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 763 764 // Increment age if obj still in new generation 765 obj->incr_age(); 766 age_table()->add(obj, s); 767 } 768 769 // Done, insert forward pointer to obj in this header 770 old->forward_to(obj); 771 772 return obj; 773 } 774 775 void DefNewGeneration::drain_promo_failure_scan_stack() { 776 while (!_promo_failure_scan_stack.is_empty()) { 777 oop obj = _promo_failure_scan_stack.pop(); 778 obj->oop_iterate(_promo_failure_scan_stack_closure); 779 } 780 } 781 782 void DefNewGeneration::save_marks() { 783 eden()->set_saved_mark(); 784 to()->set_saved_mark(); 785 from()->set_saved_mark(); 786 } 787 788 789 void DefNewGeneration::reset_saved_marks() { 790 eden()->reset_saved_mark(); 791 to()->reset_saved_mark(); 792 from()->reset_saved_mark(); 793 } 794 795 796 bool DefNewGeneration::no_allocs_since_save_marks() { 797 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 798 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 799 return to()->saved_mark_at_top(); 800 } 801 802 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 803 size_t max_alloc_words) { 804 if (requestor == this || _promotion_failed) { 805 return; 806 } 807 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation"); 808 809 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 810 if (to_space->top() > to_space->bottom()) { 811 trace("to_space not empty when contribute_scratch called"); 812 } 813 */ 814 815 ContiguousSpace* to_space = to(); 816 assert(to_space->end() >= to_space->top(), "pointers out of order"); 817 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 818 if (free_words >= MinFreeScratchWords) { 819 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 820 sb->num_words = free_words; 821 sb->next = list; 822 list = sb; 823 } 824 } 825 826 void DefNewGeneration::reset_scratch() { 827 // If contributing scratch in to_space, mangle all of 828 // to_space if ZapUnusedHeapArea. This is needed because 829 // top is not maintained while using to-space as scratch. 830 if (ZapUnusedHeapArea) { 831 to()->mangle_unused_area_complete(); 832 } 833 } 834 835 bool DefNewGeneration::collection_attempt_is_safe() { 836 if (!to()->is_empty()) { 837 log_trace(gc)(":: to is not empty ::"); 838 return false; 839 } 840 if (_old_gen == NULL) { 841 GenCollectedHeap* gch = GenCollectedHeap::heap(); 842 _old_gen = gch->old_gen(); 843 } 844 return _old_gen->promotion_attempt_is_safe(used()); 845 } 846 847 void DefNewGeneration::gc_epilogue(bool full) { 848 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 849 850 assert(!GCLocker::is_active(), "We should not be executing here"); 851 // Check if the heap is approaching full after a collection has 852 // been done. Generally the young generation is empty at 853 // a minimum at the end of a collection. If it is not, then 854 // the heap is approaching full. 855 GenCollectedHeap* gch = GenCollectedHeap::heap(); 856 if (full) { 857 DEBUG_ONLY(seen_incremental_collection_failed = false;) 858 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 859 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 860 GCCause::to_string(gch->gc_cause())); 861 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 862 set_should_allocate_from_space(); // we seem to be running out of space 863 } else { 864 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 865 GCCause::to_string(gch->gc_cause())); 866 gch->clear_incremental_collection_failed(); // We just did a full collection 867 clear_should_allocate_from_space(); // if set 868 } 869 } else { 870 #ifdef ASSERT 871 // It is possible that incremental_collection_failed() == true 872 // here, because an attempted scavenge did not succeed. The policy 873 // is normally expected to cause a full collection which should 874 // clear that condition, so we should not be here twice in a row 875 // with incremental_collection_failed() == true without having done 876 // a full collection in between. 877 if (!seen_incremental_collection_failed && 878 gch->incremental_collection_failed()) { 879 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 880 GCCause::to_string(gch->gc_cause())); 881 seen_incremental_collection_failed = true; 882 } else if (seen_incremental_collection_failed) { 883 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 884 GCCause::to_string(gch->gc_cause())); 885 assert(gch->gc_cause() == GCCause::_scavenge_alot || 886 !gch->incremental_collection_failed(), 887 "Twice in a row"); 888 seen_incremental_collection_failed = false; 889 } 890 #endif // ASSERT 891 } 892 893 if (ZapUnusedHeapArea) { 894 eden()->check_mangled_unused_area_complete(); 895 from()->check_mangled_unused_area_complete(); 896 to()->check_mangled_unused_area_complete(); 897 } 898 899 if (!CleanChunkPoolAsync) { 900 Chunk::clean_chunk_pool(); 901 } 902 903 // update the generation and space performance counters 904 update_counters(); 905 gch->counters()->update_counters(); 906 } 907 908 void DefNewGeneration::record_spaces_top() { 909 assert(ZapUnusedHeapArea, "Not mangling unused space"); 910 eden()->set_top_for_allocations(); 911 to()->set_top_for_allocations(); 912 from()->set_top_for_allocations(); 913 } 914 915 void DefNewGeneration::ref_processor_init() { 916 Generation::ref_processor_init(); 917 } 918 919 920 void DefNewGeneration::update_counters() { 921 if (UsePerfData) { 922 _eden_counters->update_all(); 923 _from_counters->update_all(); 924 _to_counters->update_all(); 925 _gen_counters->update_all(); 926 } 927 } 928 929 void DefNewGeneration::verify() { 930 eden()->verify(); 931 from()->verify(); 932 to()->verify(); 933 } 934 935 void DefNewGeneration::print_on(outputStream* st) const { 936 Generation::print_on(st); 937 st->print(" eden"); 938 eden()->print_on(st); 939 st->print(" from"); 940 from()->print_on(st); 941 st->print(" to "); 942 to()->print_on(st); 943 } 944 945 946 const char* DefNewGeneration::name() const { 947 return "def new generation"; 948 } 949 950 // Moved from inline file as they are not called inline 951 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 952 return eden(); 953 } 954 955 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 956 // This is the slow-path allocation for the DefNewGeneration. 957 // Most allocations are fast-path in compiled code. 958 // We try to allocate from the eden. If that works, we are happy. 959 // Note that since DefNewGeneration supports lock-free allocation, we 960 // have to use it here, as well. 961 HeapWord* result = eden()->par_allocate(word_size); 962 if (result != NULL) { 963 if (_old_gen != NULL) { 964 _old_gen->sample_eden_chunk(); 965 } 966 } else { 967 // If the eden is full and the last collection bailed out, we are running 968 // out of heap space, and we try to allocate the from-space, too. 969 // allocate_from_space can't be inlined because that would introduce a 970 // circular dependency at compile time. 971 result = allocate_from_space(word_size); 972 } 973 return result; 974 } 975 976 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 977 bool is_tlab) { 978 HeapWord* res = eden()->par_allocate(word_size); 979 if (_old_gen != NULL) { 980 _old_gen->sample_eden_chunk(); 981 } 982 return res; 983 } 984 985 size_t DefNewGeneration::tlab_capacity() const { 986 return eden()->capacity(); 987 } 988 989 size_t DefNewGeneration::tlab_used() const { 990 return eden()->used(); 991 } 992 993 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 994 return unsafe_max_alloc_nogc(); 995 }