1 /* 2 * Copyright (c) 2001, 2020, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "gc/serial/defNewGeneration.inline.hpp" 27 #include "gc/serial/serialHeap.inline.hpp" 28 #include "gc/serial/tenuredGeneration.hpp" 29 #include "gc/shared/adaptiveSizePolicy.hpp" 30 #include "gc/shared/ageTable.inline.hpp" 31 #include "gc/shared/cardTableRS.hpp" 32 #include "gc/shared/collectorCounters.hpp" 33 #include "gc/shared/gcArguments.hpp" 34 #include "gc/shared/gcHeapSummary.hpp" 35 #include "gc/shared/gcLocker.hpp" 36 #include "gc/shared/gcPolicyCounters.hpp" 37 #include "gc/shared/gcTimer.hpp" 38 #include "gc/shared/gcTrace.hpp" 39 #include "gc/shared/gcTraceTime.inline.hpp" 40 #include "gc/shared/genOopClosures.inline.hpp" 41 #include "gc/shared/generationSpec.hpp" 42 #include "gc/shared/preservedMarks.inline.hpp" 43 #include "gc/shared/referencePolicy.hpp" 44 #include "gc/shared/referenceProcessorPhaseTimes.hpp" 45 #include "gc/shared/space.inline.hpp" 46 #include "gc/shared/spaceDecorator.inline.hpp" 47 #include "gc/shared/strongRootsScope.hpp" 48 #include "gc/shared/weakProcessor.hpp" 49 #include "logging/log.hpp" 50 #include "memory/iterator.inline.hpp" 51 #include "memory/resourceArea.hpp" 52 #include "oops/instanceRefKlass.hpp" 53 #include "oops/oop.inline.hpp" 54 #include "runtime/java.hpp" 55 #include "runtime/prefetch.inline.hpp" 56 #include "runtime/thread.inline.hpp" 57 #include "utilities/align.hpp" 58 #include "utilities/copy.hpp" 59 #include "utilities/globalDefinitions.hpp" 60 #include "utilities/stack.inline.hpp" 61 62 // 63 // DefNewGeneration functions. 64 65 // Methods of protected closure types. 66 67 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) { 68 assert(_young_gen->kind() == Generation::DefNew, "Expected the young generation here"); 69 } 70 71 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 72 return cast_from_oop<HeapWord*>(p) >= _young_gen->reserved().end() || p->is_forwarded(); 73 } 74 75 DefNewGeneration::KeepAliveClosure:: 76 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 77 _rs = GenCollectedHeap::heap()->rem_set(); 78 } 79 80 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 81 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 82 83 84 DefNewGeneration::FastKeepAliveClosure:: 85 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 86 DefNewGeneration::KeepAliveClosure(cl) { 87 _boundary = g->reserved().end(); 88 } 89 90 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 91 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 92 93 DefNewGeneration::FastEvacuateFollowersClosure:: 94 FastEvacuateFollowersClosure(SerialHeap* heap, 95 FastScanClosure* cur, 96 FastScanClosure* older) : 97 _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older) 98 { 99 } 100 101 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 102 do { 103 _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older); 104 } while (!_heap->no_allocs_since_save_marks()); 105 guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan"); 106 } 107 108 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) : 109 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 110 { 111 _boundary = _g->reserved().end(); 112 } 113 114 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 115 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 116 { 117 _boundary = _g->reserved().end(); 118 } 119 120 void CLDScanClosure::do_cld(ClassLoaderData* cld) { 121 NOT_PRODUCT(ResourceMark rm); 122 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s", 123 p2i(cld), 124 cld->loader_name_and_id(), 125 cld->has_modified_oops() ? "true" : "false"); 126 127 // If the cld has not been dirtied we know that there's 128 // no references into the young gen and we can skip it. 129 if (cld->has_modified_oops()) { 130 if (_accumulate_modified_oops) { 131 cld->accumulate_modified_oops(); 132 } 133 134 // Tell the closure which CLD is being scanned so that it can be dirtied 135 // if oops are left pointing into the young gen. 136 _scavenge_closure->set_scanned_cld(cld); 137 138 // Clean the cld since we're going to scavenge all the metadata. 139 cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true); 140 141 _scavenge_closure->set_scanned_cld(NULL); 142 } 143 } 144 145 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 146 _g(g) 147 { 148 _boundary = _g->reserved().end(); 149 } 150 151 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 152 size_t initial_size, 153 size_t min_size, 154 size_t max_size, 155 const char* policy) 156 : Generation(rs, initial_size), 157 _preserved_marks_set(false /* in_c_heap */), 158 _promo_failure_drain_in_progress(false), 159 _should_allocate_from_space(false) 160 { 161 MemRegion cmr((HeapWord*)_virtual_space.low(), 162 (HeapWord*)_virtual_space.high()); 163 GenCollectedHeap* gch = GenCollectedHeap::heap(); 164 165 gch->rem_set()->resize_covered_region(cmr); 166 167 _eden_space = new ContiguousSpace(); 168 _from_space = new ContiguousSpace(); 169 _to_space = new ContiguousSpace(); 170 171 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) { 172 vm_exit_during_initialization("Could not allocate a new gen space"); 173 } 174 175 // Compute the maximum eden and survivor space sizes. These sizes 176 // are computed assuming the entire reserved space is committed. 177 // These values are exported as performance counters. 178 uintx size = _virtual_space.reserved_size(); 179 _max_survivor_size = compute_survivor_size(size, SpaceAlignment); 180 _max_eden_size = size - (2*_max_survivor_size); 181 182 // allocate the performance counters 183 184 // Generation counters -- generation 0, 3 subspaces 185 _gen_counters = new GenerationCounters("new", 0, 3, 186 min_size, max_size, &_virtual_space); 187 _gc_counters = new CollectorCounters(policy, 0); 188 189 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 190 _gen_counters); 191 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 192 _gen_counters); 193 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 194 _gen_counters); 195 196 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 197 update_counters(); 198 _old_gen = NULL; 199 _tenuring_threshold = MaxTenuringThreshold; 200 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 201 202 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer(); 203 } 204 205 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 206 bool clear_space, 207 bool mangle_space) { 208 // If the spaces are being cleared (only done at heap initialization 209 // currently), the survivor spaces need not be empty. 210 // Otherwise, no care is taken for used areas in the survivor spaces 211 // so check. 212 assert(clear_space || (to()->is_empty() && from()->is_empty()), 213 "Initialization of the survivor spaces assumes these are empty"); 214 215 // Compute sizes 216 uintx size = _virtual_space.committed_size(); 217 uintx survivor_size = compute_survivor_size(size, SpaceAlignment); 218 uintx eden_size = size - (2*survivor_size); 219 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 220 221 if (eden_size < minimum_eden_size) { 222 // May happen due to 64Kb rounding, if so adjust eden size back up 223 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment); 224 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 225 uintx unaligned_survivor_size = 226 align_down(maximum_survivor_size, SpaceAlignment); 227 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment); 228 eden_size = size - (2*survivor_size); 229 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 230 assert(eden_size >= minimum_eden_size, "just checking"); 231 } 232 233 char *eden_start = _virtual_space.low(); 234 char *from_start = eden_start + eden_size; 235 char *to_start = from_start + survivor_size; 236 char *to_end = to_start + survivor_size; 237 238 assert(to_end == _virtual_space.high(), "just checking"); 239 assert(Space::is_aligned(eden_start), "checking alignment"); 240 assert(Space::is_aligned(from_start), "checking alignment"); 241 assert(Space::is_aligned(to_start), "checking alignment"); 242 243 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 244 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 245 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 246 247 // A minimum eden size implies that there is a part of eden that 248 // is being used and that affects the initialization of any 249 // newly formed eden. 250 bool live_in_eden = minimum_eden_size > 0; 251 252 // If not clearing the spaces, do some checking to verify that 253 // the space are already mangled. 254 if (!clear_space) { 255 // Must check mangling before the spaces are reshaped. Otherwise, 256 // the bottom or end of one space may have moved into another 257 // a failure of the check may not correctly indicate which space 258 // is not properly mangled. 259 if (ZapUnusedHeapArea) { 260 HeapWord* limit = (HeapWord*) _virtual_space.high(); 261 eden()->check_mangled_unused_area(limit); 262 from()->check_mangled_unused_area(limit); 263 to()->check_mangled_unused_area(limit); 264 } 265 } 266 267 // Reset the spaces for their new regions. 268 eden()->initialize(edenMR, 269 clear_space && !live_in_eden, 270 SpaceDecorator::Mangle); 271 // If clear_space and live_in_eden, we will not have cleared any 272 // portion of eden above its top. This can cause newly 273 // expanded space not to be mangled if using ZapUnusedHeapArea. 274 // We explicitly do such mangling here. 275 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 276 eden()->mangle_unused_area(); 277 } 278 from()->initialize(fromMR, clear_space, mangle_space); 279 to()->initialize(toMR, clear_space, mangle_space); 280 281 // Set next compaction spaces. 282 eden()->set_next_compaction_space(from()); 283 // The to-space is normally empty before a compaction so need 284 // not be considered. The exception is during promotion 285 // failure handling when to-space can contain live objects. 286 from()->set_next_compaction_space(NULL); 287 } 288 289 void DefNewGeneration::swap_spaces() { 290 ContiguousSpace* s = from(); 291 _from_space = to(); 292 _to_space = s; 293 eden()->set_next_compaction_space(from()); 294 // The to-space is normally empty before a compaction so need 295 // not be considered. The exception is during promotion 296 // failure handling when to-space can contain live objects. 297 from()->set_next_compaction_space(NULL); 298 299 if (UsePerfData) { 300 CSpaceCounters* c = _from_counters; 301 _from_counters = _to_counters; 302 _to_counters = c; 303 } 304 } 305 306 bool DefNewGeneration::expand(size_t bytes) { 307 MutexLocker x(ExpandHeap_lock); 308 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 309 bool success = _virtual_space.expand_by(bytes); 310 if (success && ZapUnusedHeapArea) { 311 // Mangle newly committed space immediately because it 312 // can be done here more simply that after the new 313 // spaces have been computed. 314 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 315 MemRegion mangle_region(prev_high, new_high); 316 SpaceMangler::mangle_region(mangle_region); 317 } 318 319 // Do not attempt an expand-to-the reserve size. The 320 // request should properly observe the maximum size of 321 // the generation so an expand-to-reserve should be 322 // unnecessary. Also a second call to expand-to-reserve 323 // value potentially can cause an undue expansion. 324 // For example if the first expand fail for unknown reasons, 325 // but the second succeeds and expands the heap to its maximum 326 // value. 327 if (GCLocker::is_active()) { 328 log_debug(gc)("Garbage collection disabled, expanded heap instead"); 329 } 330 331 return success; 332 } 333 334 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate, 335 size_t new_size_before, 336 size_t alignment) const { 337 size_t desired_new_size = new_size_before; 338 339 if (NewSizeThreadIncrease > 0) { 340 int threads_count; 341 size_t thread_increase_size = 0; 342 343 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'. 344 threads_count = Threads::number_of_non_daemon_threads(); 345 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) { 346 thread_increase_size = threads_count * NewSizeThreadIncrease; 347 348 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'. 349 if (new_size_candidate <= max_uintx - thread_increase_size) { 350 new_size_candidate += thread_increase_size; 351 352 // 3. Check an overflow at 'align_up'. 353 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1)); 354 if (new_size_candidate <= aligned_max) { 355 desired_new_size = align_up(new_size_candidate, alignment); 356 } 357 } 358 } 359 } 360 361 return desired_new_size; 362 } 363 364 void DefNewGeneration::compute_new_size() { 365 // This is called after a GC that includes the old generation, so from-space 366 // will normally be empty. 367 // Note that we check both spaces, since if scavenge failed they revert roles. 368 // If not we bail out (otherwise we would have to relocate the objects). 369 if (!from()->is_empty() || !to()->is_empty()) { 370 return; 371 } 372 373 GenCollectedHeap* gch = GenCollectedHeap::heap(); 374 375 size_t old_size = gch->old_gen()->capacity(); 376 size_t new_size_before = _virtual_space.committed_size(); 377 size_t min_new_size = initial_size(); 378 size_t max_new_size = reserved().byte_size(); 379 assert(min_new_size <= new_size_before && 380 new_size_before <= max_new_size, 381 "just checking"); 382 // All space sizes must be multiples of Generation::GenGrain. 383 size_t alignment = Generation::GenGrain; 384 385 int threads_count = 0; 386 size_t thread_increase_size = 0; 387 388 size_t new_size_candidate = old_size / NewRatio; 389 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease 390 // and reverts to previous value if any overflow happens 391 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment); 392 393 // Adjust new generation size 394 desired_new_size = clamp(desired_new_size, min_new_size, max_new_size); 395 assert(desired_new_size <= max_new_size, "just checking"); 396 397 bool changed = false; 398 if (desired_new_size > new_size_before) { 399 size_t change = desired_new_size - new_size_before; 400 assert(change % alignment == 0, "just checking"); 401 if (expand(change)) { 402 changed = true; 403 } 404 // If the heap failed to expand to the desired size, 405 // "changed" will be false. If the expansion failed 406 // (and at this point it was expected to succeed), 407 // ignore the failure (leaving "changed" as false). 408 } 409 if (desired_new_size < new_size_before && eden()->is_empty()) { 410 // bail out of shrinking if objects in eden 411 size_t change = new_size_before - desired_new_size; 412 assert(change % alignment == 0, "just checking"); 413 _virtual_space.shrink_by(change); 414 changed = true; 415 } 416 if (changed) { 417 // The spaces have already been mangled at this point but 418 // may not have been cleared (set top = bottom) and should be. 419 // Mangling was done when the heap was being expanded. 420 compute_space_boundaries(eden()->used(), 421 SpaceDecorator::Clear, 422 SpaceDecorator::DontMangle); 423 MemRegion cmr((HeapWord*)_virtual_space.low(), 424 (HeapWord*)_virtual_space.high()); 425 gch->rem_set()->resize_covered_region(cmr); 426 427 log_debug(gc, ergo, heap)( 428 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 429 new_size_before/K, _virtual_space.committed_size()/K, 430 eden()->capacity()/K, from()->capacity()/K); 431 log_trace(gc, ergo, heap)( 432 " [allowed " SIZE_FORMAT "K extra for %d threads]", 433 thread_increase_size/K, threads_count); 434 } 435 } 436 437 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) { 438 assert(false, "NYI -- are you sure you want to call this?"); 439 } 440 441 442 size_t DefNewGeneration::capacity() const { 443 return eden()->capacity() 444 + from()->capacity(); // to() is only used during scavenge 445 } 446 447 448 size_t DefNewGeneration::used() const { 449 return eden()->used() 450 + from()->used(); // to() is only used during scavenge 451 } 452 453 454 size_t DefNewGeneration::free() const { 455 return eden()->free() 456 + from()->free(); // to() is only used during scavenge 457 } 458 459 size_t DefNewGeneration::max_capacity() const { 460 const size_t reserved_bytes = reserved().byte_size(); 461 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment); 462 } 463 464 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 465 return eden()->free(); 466 } 467 468 size_t DefNewGeneration::capacity_before_gc() const { 469 return eden()->capacity(); 470 } 471 472 size_t DefNewGeneration::contiguous_available() const { 473 return eden()->free(); 474 } 475 476 477 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); } 478 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 479 480 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 481 eden()->object_iterate(blk); 482 from()->object_iterate(blk); 483 } 484 485 486 void DefNewGeneration::space_iterate(SpaceClosure* blk, 487 bool usedOnly) { 488 blk->do_space(eden()); 489 blk->do_space(from()); 490 blk->do_space(to()); 491 } 492 493 // The last collection bailed out, we are running out of heap space, 494 // so we try to allocate the from-space, too. 495 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 496 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc(); 497 498 // If the Heap_lock is not locked by this thread, this will be called 499 // again later with the Heap_lock held. 500 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread())); 501 502 HeapWord* result = NULL; 503 if (do_alloc) { 504 result = from()->allocate(size); 505 } 506 507 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s", 508 size, 509 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 510 "true" : "false", 511 Heap_lock->is_locked() ? "locked" : "unlocked", 512 from()->free(), 513 should_try_alloc ? "" : " should_allocate_from_space: NOT", 514 do_alloc ? " Heap_lock is not owned by self" : "", 515 result == NULL ? "NULL" : "object"); 516 517 return result; 518 } 519 520 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 521 bool is_tlab, 522 bool parallel) { 523 // We don't attempt to expand the young generation (but perhaps we should.) 524 return allocate(size, is_tlab); 525 } 526 527 void DefNewGeneration::adjust_desired_tenuring_threshold() { 528 // Set the desired survivor size to half the real survivor space 529 size_t const survivor_capacity = to()->capacity() / HeapWordSize; 530 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 531 532 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size); 533 534 if (UsePerfData) { 535 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters(); 536 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold); 537 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize); 538 } 539 540 age_table()->print_age_table(_tenuring_threshold); 541 } 542 543 void DefNewGeneration::collect(bool full, 544 bool clear_all_soft_refs, 545 size_t size, 546 bool is_tlab) { 547 assert(full || size > 0, "otherwise we don't want to collect"); 548 549 SerialHeap* heap = SerialHeap::heap(); 550 551 _gc_timer->register_gc_start(); 552 DefNewTracer gc_tracer; 553 gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start()); 554 555 _old_gen = heap->old_gen(); 556 557 // If the next generation is too full to accommodate promotion 558 // from this generation, pass on collection; let the next generation 559 // do it. 560 if (!collection_attempt_is_safe()) { 561 log_trace(gc)(":: Collection attempt not safe ::"); 562 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 563 return; 564 } 565 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 566 567 init_assuming_no_promotion_failure(); 568 569 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause()); 570 571 heap->trace_heap_before_gc(&gc_tracer); 572 573 // These can be shared for all code paths 574 IsAliveClosure is_alive(this); 575 ScanWeakRefClosure scan_weak_ref(this); 576 577 age_table()->clear(); 578 to()->clear(SpaceDecorator::Mangle); 579 // The preserved marks should be empty at the start of the GC. 580 _preserved_marks_set.init(1); 581 582 heap->rem_set()->prepare_for_younger_refs_iterate(false); 583 584 assert(heap->no_allocs_since_save_marks(), 585 "save marks have not been newly set."); 586 587 FastScanClosure fsc_with_no_gc_barrier(this, false); 588 FastScanClosure fsc_with_gc_barrier(this, true); 589 590 CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier, 591 heap->rem_set()->cld_rem_set()->accumulate_modified_oops()); 592 593 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 594 FastEvacuateFollowersClosure evacuate_followers(heap, 595 &fsc_with_no_gc_barrier, 596 &fsc_with_gc_barrier); 597 598 assert(heap->no_allocs_since_save_marks(), 599 "save marks have not been newly set."); 600 601 { 602 // DefNew needs to run with n_threads == 0, to make sure the serial 603 // version of the card table scanning code is used. 604 // See: CardTableRS::non_clean_card_iterate_possibly_parallel. 605 StrongRootsScope srs(0); 606 607 heap->young_process_roots(&srs, 608 &fsc_with_no_gc_barrier, 609 &fsc_with_gc_barrier, 610 &cld_scan_closure); 611 } 612 613 // "evacuate followers". 614 evacuate_followers.do_void(); 615 616 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 617 ReferenceProcessor* rp = ref_processor(); 618 rp->setup_policy(clear_all_soft_refs); 619 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues()); 620 const ReferenceProcessorStats& stats = 621 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 622 NULL, &pt); 623 gc_tracer.report_gc_reference_stats(stats); 624 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 625 pt.print_all_references(); 626 627 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set."); 628 629 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 630 631 // Verify that the usage of keep_alive didn't copy any objects. 632 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set."); 633 634 if (!_promotion_failed) { 635 // Swap the survivor spaces. 636 eden()->clear(SpaceDecorator::Mangle); 637 from()->clear(SpaceDecorator::Mangle); 638 if (ZapUnusedHeapArea) { 639 // This is now done here because of the piece-meal mangling which 640 // can check for valid mangling at intermediate points in the 641 // collection(s). When a young collection fails to collect 642 // sufficient space resizing of the young generation can occur 643 // an redistribute the spaces in the young generation. Mangle 644 // here so that unzapped regions don't get distributed to 645 // other spaces. 646 to()->mangle_unused_area(); 647 } 648 swap_spaces(); 649 650 assert(to()->is_empty(), "to space should be empty now"); 651 652 adjust_desired_tenuring_threshold(); 653 654 // A successful scavenge should restart the GC time limit count which is 655 // for full GC's. 656 AdaptiveSizePolicy* size_policy = heap->size_policy(); 657 size_policy->reset_gc_overhead_limit_count(); 658 assert(!heap->incremental_collection_failed(), "Should be clear"); 659 } else { 660 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 661 _promo_failure_scan_stack.clear(true); // Clear cached segments. 662 663 remove_forwarding_pointers(); 664 log_info(gc, promotion)("Promotion failed"); 665 // Add to-space to the list of space to compact 666 // when a promotion failure has occurred. In that 667 // case there can be live objects in to-space 668 // as a result of a partial evacuation of eden 669 // and from-space. 670 swap_spaces(); // For uniformity wrt ParNewGeneration. 671 from()->set_next_compaction_space(to()); 672 heap->set_incremental_collection_failed(); 673 674 // Inform the next generation that a promotion failure occurred. 675 _old_gen->promotion_failure_occurred(); 676 gc_tracer.report_promotion_failed(_promotion_failed_info); 677 678 // Reset the PromotionFailureALot counters. 679 NOT_PRODUCT(heap->reset_promotion_should_fail();) 680 } 681 // We should have processed and cleared all the preserved marks. 682 _preserved_marks_set.reclaim(); 683 // set new iteration safe limit for the survivor spaces 684 from()->set_concurrent_iteration_safe_limit(from()->top()); 685 to()->set_concurrent_iteration_safe_limit(to()->top()); 686 687 // We need to use a monotonically non-decreasing time in ms 688 // or we will see time-warp warnings and os::javaTimeMillis() 689 // does not guarantee monotonicity. 690 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 691 update_time_of_last_gc(now); 692 693 heap->trace_heap_after_gc(&gc_tracer); 694 695 _gc_timer->register_gc_end(); 696 697 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 698 } 699 700 void DefNewGeneration::init_assuming_no_promotion_failure() { 701 _promotion_failed = false; 702 _promotion_failed_info.reset(); 703 from()->set_next_compaction_space(NULL); 704 } 705 706 void DefNewGeneration::remove_forwarding_pointers() { 707 RemoveForwardedPointerClosure rspc; 708 eden()->object_iterate(&rspc); 709 from()->object_iterate(&rspc); 710 restore_preserved_marks(); 711 } 712 713 void DefNewGeneration::restore_preserved_marks() { 714 _preserved_marks_set.restore(NULL); 715 } 716 717 void DefNewGeneration::handle_promotion_failure(oop old) { 718 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size()); 719 720 _promotion_failed = true; 721 _promotion_failed_info.register_copy_failure(old->size()); 722 _preserved_marks_set.get()->push_if_necessary(old, old->mark_raw()); 723 // forward to self 724 old->forward_to(old); 725 726 _promo_failure_scan_stack.push(old); 727 728 if (!_promo_failure_drain_in_progress) { 729 // prevent recursion in copy_to_survivor_space() 730 _promo_failure_drain_in_progress = true; 731 drain_promo_failure_scan_stack(); 732 _promo_failure_drain_in_progress = false; 733 } 734 } 735 736 oop DefNewGeneration::copy_to_survivor_space(oop old) { 737 assert(is_in_reserved(old) && !old->is_forwarded(), 738 "shouldn't be scavenging this oop"); 739 size_t s = old->size(); 740 oop obj = NULL; 741 742 // Try allocating obj in to-space (unless too old) 743 if (old->age() < tenuring_threshold()) { 744 obj = (oop) to()->allocate_aligned(s); 745 } 746 747 // Otherwise try allocating obj tenured 748 if (obj == NULL) { 749 obj = _old_gen->promote(old, s); 750 if (obj == NULL) { 751 handle_promotion_failure(old); 752 return old; 753 } 754 } else { 755 // Prefetch beyond obj 756 const intx interval = PrefetchCopyIntervalInBytes; 757 Prefetch::write(obj, interval); 758 759 // Copy obj 760 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s); 761 762 // Increment age if obj still in new generation 763 obj->incr_age(); 764 age_table()->add(obj, s); 765 } 766 767 // Done, insert forward pointer to obj in this header 768 old->forward_to(obj); 769 770 return obj; 771 } 772 773 void DefNewGeneration::drain_promo_failure_scan_stack() { 774 while (!_promo_failure_scan_stack.is_empty()) { 775 oop obj = _promo_failure_scan_stack.pop(); 776 obj->oop_iterate(_promo_failure_scan_stack_closure); 777 } 778 } 779 780 void DefNewGeneration::save_marks() { 781 eden()->set_saved_mark(); 782 to()->set_saved_mark(); 783 from()->set_saved_mark(); 784 } 785 786 787 void DefNewGeneration::reset_saved_marks() { 788 eden()->reset_saved_mark(); 789 to()->reset_saved_mark(); 790 from()->reset_saved_mark(); 791 } 792 793 794 bool DefNewGeneration::no_allocs_since_save_marks() { 795 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 796 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 797 return to()->saved_mark_at_top(); 798 } 799 800 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 801 size_t max_alloc_words) { 802 if (requestor == this || _promotion_failed) { 803 return; 804 } 805 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation"); 806 807 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 808 if (to_space->top() > to_space->bottom()) { 809 trace("to_space not empty when contribute_scratch called"); 810 } 811 */ 812 813 ContiguousSpace* to_space = to(); 814 assert(to_space->end() >= to_space->top(), "pointers out of order"); 815 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 816 if (free_words >= MinFreeScratchWords) { 817 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 818 sb->num_words = free_words; 819 sb->next = list; 820 list = sb; 821 } 822 } 823 824 void DefNewGeneration::reset_scratch() { 825 // If contributing scratch in to_space, mangle all of 826 // to_space if ZapUnusedHeapArea. This is needed because 827 // top is not maintained while using to-space as scratch. 828 if (ZapUnusedHeapArea) { 829 to()->mangle_unused_area_complete(); 830 } 831 } 832 833 bool DefNewGeneration::collection_attempt_is_safe() { 834 if (!to()->is_empty()) { 835 log_trace(gc)(":: to is not empty ::"); 836 return false; 837 } 838 if (_old_gen == NULL) { 839 GenCollectedHeap* gch = GenCollectedHeap::heap(); 840 _old_gen = gch->old_gen(); 841 } 842 return _old_gen->promotion_attempt_is_safe(used()); 843 } 844 845 void DefNewGeneration::gc_epilogue(bool full) { 846 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 847 848 assert(!GCLocker::is_active(), "We should not be executing here"); 849 // Check if the heap is approaching full after a collection has 850 // been done. Generally the young generation is empty at 851 // a minimum at the end of a collection. If it is not, then 852 // the heap is approaching full. 853 GenCollectedHeap* gch = GenCollectedHeap::heap(); 854 if (full) { 855 DEBUG_ONLY(seen_incremental_collection_failed = false;) 856 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 857 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 858 GCCause::to_string(gch->gc_cause())); 859 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 860 set_should_allocate_from_space(); // we seem to be running out of space 861 } else { 862 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 863 GCCause::to_string(gch->gc_cause())); 864 gch->clear_incremental_collection_failed(); // We just did a full collection 865 clear_should_allocate_from_space(); // if set 866 } 867 } else { 868 #ifdef ASSERT 869 // It is possible that incremental_collection_failed() == true 870 // here, because an attempted scavenge did not succeed. The policy 871 // is normally expected to cause a full collection which should 872 // clear that condition, so we should not be here twice in a row 873 // with incremental_collection_failed() == true without having done 874 // a full collection in between. 875 if (!seen_incremental_collection_failed && 876 gch->incremental_collection_failed()) { 877 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 878 GCCause::to_string(gch->gc_cause())); 879 seen_incremental_collection_failed = true; 880 } else if (seen_incremental_collection_failed) { 881 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 882 GCCause::to_string(gch->gc_cause())); 883 assert(gch->gc_cause() == GCCause::_scavenge_alot || 884 !gch->incremental_collection_failed(), 885 "Twice in a row"); 886 seen_incremental_collection_failed = false; 887 } 888 #endif // ASSERT 889 } 890 891 if (ZapUnusedHeapArea) { 892 eden()->check_mangled_unused_area_complete(); 893 from()->check_mangled_unused_area_complete(); 894 to()->check_mangled_unused_area_complete(); 895 } 896 897 if (!CleanChunkPoolAsync) { 898 Chunk::clean_chunk_pool(); 899 } 900 901 // update the generation and space performance counters 902 update_counters(); 903 gch->counters()->update_counters(); 904 } 905 906 void DefNewGeneration::record_spaces_top() { 907 assert(ZapUnusedHeapArea, "Not mangling unused space"); 908 eden()->set_top_for_allocations(); 909 to()->set_top_for_allocations(); 910 from()->set_top_for_allocations(); 911 } 912 913 void DefNewGeneration::ref_processor_init() { 914 Generation::ref_processor_init(); 915 } 916 917 918 void DefNewGeneration::update_counters() { 919 if (UsePerfData) { 920 _eden_counters->update_all(); 921 _from_counters->update_all(); 922 _to_counters->update_all(); 923 _gen_counters->update_all(); 924 } 925 } 926 927 void DefNewGeneration::verify() { 928 eden()->verify(); 929 from()->verify(); 930 to()->verify(); 931 } 932 933 void DefNewGeneration::print_on(outputStream* st) const { 934 Generation::print_on(st); 935 st->print(" eden"); 936 eden()->print_on(st); 937 st->print(" from"); 938 from()->print_on(st); 939 st->print(" to "); 940 to()->print_on(st); 941 } 942 943 944 const char* DefNewGeneration::name() const { 945 return "def new generation"; 946 } 947 948 // Moved from inline file as they are not called inline 949 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 950 return eden(); 951 } 952 953 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 954 // This is the slow-path allocation for the DefNewGeneration. 955 // Most allocations are fast-path in compiled code. 956 // We try to allocate from the eden. If that works, we are happy. 957 // Note that since DefNewGeneration supports lock-free allocation, we 958 // have to use it here, as well. 959 HeapWord* result = eden()->par_allocate(word_size); 960 if (result != NULL) { 961 if (_old_gen != NULL) { 962 _old_gen->sample_eden_chunk(); 963 } 964 } else { 965 // If the eden is full and the last collection bailed out, we are running 966 // out of heap space, and we try to allocate the from-space, too. 967 // allocate_from_space can't be inlined because that would introduce a 968 // circular dependency at compile time. 969 result = allocate_from_space(word_size); 970 } 971 return result; 972 } 973 974 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 975 bool is_tlab) { 976 HeapWord* res = eden()->par_allocate(word_size); 977 if (_old_gen != NULL) { 978 _old_gen->sample_eden_chunk(); 979 } 980 return res; 981 } 982 983 size_t DefNewGeneration::tlab_capacity() const { 984 return eden()->capacity(); 985 } 986 987 size_t DefNewGeneration::tlab_used() const { 988 return eden()->used(); 989 } 990 991 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 992 return unsafe_max_alloc_nogc(); 993 }