1 /* 2 * Copyright (c) 2001, 2018, 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.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::ParNew || 70 _young_gen->kind() == Generation::DefNew, "Expected the young generation here"); 71 } 72 73 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 74 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded(); 75 } 76 77 DefNewGeneration::KeepAliveClosure:: 78 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 79 _rs = GenCollectedHeap::heap()->rem_set(); 80 } 81 82 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 83 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 84 85 86 DefNewGeneration::FastKeepAliveClosure:: 87 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 88 DefNewGeneration::KeepAliveClosure(cl) { 89 _boundary = g->reserved().end(); 90 } 91 92 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 93 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 94 95 DefNewGeneration::FastEvacuateFollowersClosure:: 96 FastEvacuateFollowersClosure(SerialHeap* heap, 97 FastScanClosure* cur, 98 FastScanClosure* older) : 99 _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older) 100 { 101 } 102 103 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 104 do { 105 _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older); 106 } while (!_heap->no_allocs_since_save_marks()); 107 guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan"); 108 } 109 110 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) : 111 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 112 { 113 _boundary = _g->reserved().end(); 114 } 115 116 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 117 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 118 { 119 _boundary = _g->reserved().end(); 120 } 121 122 void CLDScanClosure::do_cld(ClassLoaderData* cld) { 123 NOT_PRODUCT(ResourceMark rm); 124 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s", 125 p2i(cld), 126 cld->loader_name_and_id(), 127 cld->has_modified_oops() ? "true" : "false"); 128 129 // If the cld has not been dirtied we know that there's 130 // no references into the young gen and we can skip it. 131 if (cld->has_modified_oops()) { 132 if (_accumulate_modified_oops) { 133 cld->accumulate_modified_oops(); 134 } 135 136 // Tell the closure which CLD is being scanned so that it can be dirtied 137 // if oops are left pointing into the young gen. 138 _scavenge_closure->set_scanned_cld(cld); 139 140 // Clean the cld since we're going to scavenge all the metadata. 141 cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true); 142 143 _scavenge_closure->set_scanned_cld(NULL); 144 } 145 } 146 147 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 148 _g(g) 149 { 150 _boundary = _g->reserved().end(); 151 } 152 153 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 154 size_t initial_size, 155 size_t min_size, 156 size_t max_size, 157 const char* policy) 158 : Generation(rs, initial_size), 159 _preserved_marks_set(false /* in_c_heap */), 160 _promo_failure_drain_in_progress(false), 161 _should_allocate_from_space(false) 162 { 163 MemRegion cmr((HeapWord*)_virtual_space.low(), 164 (HeapWord*)_virtual_space.high()); 165 GenCollectedHeap* gch = GenCollectedHeap::heap(); 166 167 gch->rem_set()->resize_covered_region(cmr); 168 169 _eden_space = new ContiguousSpace(); 170 _from_space = new ContiguousSpace(); 171 _to_space = new ContiguousSpace(); 172 173 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) { 174 vm_exit_during_initialization("Could not allocate a new gen space"); 175 } 176 177 // Compute the maximum eden and survivor space sizes. These sizes 178 // are computed assuming the entire reserved space is committed. 179 // These values are exported as performance counters. 180 uintx size = _virtual_space.reserved_size(); 181 _max_survivor_size = compute_survivor_size(size, SpaceAlignment); 182 _max_eden_size = size - (2*_max_survivor_size); 183 184 // allocate the performance counters 185 186 // Generation counters -- generation 0, 3 subspaces 187 _gen_counters = new GenerationCounters("new", 0, 3, 188 min_size, max_size, &_virtual_space); 189 _gc_counters = new CollectorCounters(policy, 0); 190 191 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 192 _gen_counters); 193 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 194 _gen_counters); 195 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 196 _gen_counters); 197 198 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 199 update_counters(); 200 _old_gen = NULL; 201 _tenuring_threshold = MaxTenuringThreshold; 202 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 203 204 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer(); 205 } 206 207 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 208 bool clear_space, 209 bool mangle_space) { 210 // If the spaces are being cleared (only done at heap initialization 211 // currently), the survivor spaces need not be empty. 212 // Otherwise, no care is taken for used areas in the survivor spaces 213 // so check. 214 assert(clear_space || (to()->is_empty() && from()->is_empty()), 215 "Initialization of the survivor spaces assumes these are empty"); 216 217 // Compute sizes 218 uintx size = _virtual_space.committed_size(); 219 uintx survivor_size = compute_survivor_size(size, SpaceAlignment); 220 uintx eden_size = size - (2*survivor_size); 221 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 222 223 if (eden_size < minimum_eden_size) { 224 // May happen due to 64Kb rounding, if so adjust eden size back up 225 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment); 226 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 227 uintx unaligned_survivor_size = 228 align_down(maximum_survivor_size, SpaceAlignment); 229 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment); 230 eden_size = size - (2*survivor_size); 231 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 232 assert(eden_size >= minimum_eden_size, "just checking"); 233 } 234 235 char *eden_start = _virtual_space.low(); 236 char *from_start = eden_start + eden_size; 237 char *to_start = from_start + survivor_size; 238 char *to_end = to_start + survivor_size; 239 240 assert(to_end == _virtual_space.high(), "just checking"); 241 assert(Space::is_aligned(eden_start), "checking alignment"); 242 assert(Space::is_aligned(from_start), "checking alignment"); 243 assert(Space::is_aligned(to_start), "checking alignment"); 244 245 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 246 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 247 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 248 249 // A minimum eden size implies that there is a part of eden that 250 // is being used and that affects the initialization of any 251 // newly formed eden. 252 bool live_in_eden = minimum_eden_size > 0; 253 254 // If not clearing the spaces, do some checking to verify that 255 // the space are already mangled. 256 if (!clear_space) { 257 // Must check mangling before the spaces are reshaped. Otherwise, 258 // the bottom or end of one space may have moved into another 259 // a failure of the check may not correctly indicate which space 260 // is not properly mangled. 261 if (ZapUnusedHeapArea) { 262 HeapWord* limit = (HeapWord*) _virtual_space.high(); 263 eden()->check_mangled_unused_area(limit); 264 from()->check_mangled_unused_area(limit); 265 to()->check_mangled_unused_area(limit); 266 } 267 } 268 269 // Reset the spaces for their new regions. 270 eden()->initialize(edenMR, 271 clear_space && !live_in_eden, 272 SpaceDecorator::Mangle); 273 // If clear_space and live_in_eden, we will not have cleared any 274 // portion of eden above its top. This can cause newly 275 // expanded space not to be mangled if using ZapUnusedHeapArea. 276 // We explicitly do such mangling here. 277 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 278 eden()->mangle_unused_area(); 279 } 280 from()->initialize(fromMR, clear_space, mangle_space); 281 to()->initialize(toMR, clear_space, mangle_space); 282 283 // Set next compaction spaces. 284 eden()->set_next_compaction_space(from()); 285 // The to-space is normally empty before a compaction so need 286 // not be considered. The exception is during promotion 287 // failure handling when to-space can contain live objects. 288 from()->set_next_compaction_space(NULL); 289 } 290 291 void DefNewGeneration::swap_spaces() { 292 ContiguousSpace* s = from(); 293 _from_space = to(); 294 _to_space = s; 295 eden()->set_next_compaction_space(from()); 296 // The to-space is normally empty before a compaction so need 297 // not be considered. The exception is during promotion 298 // failure handling when to-space can contain live objects. 299 from()->set_next_compaction_space(NULL); 300 301 if (UsePerfData) { 302 CSpaceCounters* c = _from_counters; 303 _from_counters = _to_counters; 304 _to_counters = c; 305 } 306 } 307 308 bool DefNewGeneration::expand(size_t bytes) { 309 MutexLocker x(ExpandHeap_lock); 310 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 311 bool success = _virtual_space.expand_by(bytes); 312 if (success && ZapUnusedHeapArea) { 313 // Mangle newly committed space immediately because it 314 // can be done here more simply that after the new 315 // spaces have been computed. 316 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 317 MemRegion mangle_region(prev_high, new_high); 318 SpaceMangler::mangle_region(mangle_region); 319 } 320 321 // Do not attempt an expand-to-the reserve size. The 322 // request should properly observe the maximum size of 323 // the generation so an expand-to-reserve should be 324 // unnecessary. Also a second call to expand-to-reserve 325 // value potentially can cause an undue expansion. 326 // For example if the first expand fail for unknown reasons, 327 // but the second succeeds and expands the heap to its maximum 328 // value. 329 if (GCLocker::is_active()) { 330 log_debug(gc)("Garbage collection disabled, expanded heap instead"); 331 } 332 333 return success; 334 } 335 336 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate, 337 size_t new_size_before, 338 size_t alignment) const { 339 size_t desired_new_size = new_size_before; 340 341 if (NewSizeThreadIncrease > 0) { 342 int threads_count; 343 size_t thread_increase_size = 0; 344 345 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'. 346 threads_count = Threads::number_of_non_daemon_threads(); 347 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) { 348 thread_increase_size = threads_count * NewSizeThreadIncrease; 349 350 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'. 351 if (new_size_candidate <= max_uintx - thread_increase_size) { 352 new_size_candidate += thread_increase_size; 353 354 // 3. Check an overflow at 'align_up'. 355 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1)); 356 if (new_size_candidate <= aligned_max) { 357 desired_new_size = align_up(new_size_candidate, alignment); 358 } 359 } 360 } 361 } 362 363 return desired_new_size; 364 } 365 366 void DefNewGeneration::compute_new_size() { 367 // This is called after a GC that includes the old generation, so from-space 368 // will normally be empty. 369 // Note that we check both spaces, since if scavenge failed they revert roles. 370 // If not we bail out (otherwise we would have to relocate the objects). 371 if (!from()->is_empty() || !to()->is_empty()) { 372 return; 373 } 374 375 GenCollectedHeap* gch = GenCollectedHeap::heap(); 376 377 size_t old_size = gch->old_gen()->capacity(); 378 size_t new_size_before = _virtual_space.committed_size(); 379 size_t min_new_size = initial_size(); 380 size_t max_new_size = reserved().byte_size(); 381 assert(min_new_size <= new_size_before && 382 new_size_before <= max_new_size, 383 "just checking"); 384 // All space sizes must be multiples of Generation::GenGrain. 385 size_t alignment = Generation::GenGrain; 386 387 int threads_count = 0; 388 size_t thread_increase_size = 0; 389 390 size_t new_size_candidate = old_size / NewRatio; 391 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease 392 // and reverts to previous value if any overflow happens 393 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment); 394 395 // Adjust new generation size 396 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size); 397 assert(desired_new_size <= max_new_size, "just checking"); 398 399 bool changed = false; 400 if (desired_new_size > new_size_before) { 401 size_t change = desired_new_size - new_size_before; 402 assert(change % alignment == 0, "just checking"); 403 if (expand(change)) { 404 changed = true; 405 } 406 // If the heap failed to expand to the desired size, 407 // "changed" will be false. If the expansion failed 408 // (and at this point it was expected to succeed), 409 // ignore the failure (leaving "changed" as false). 410 } 411 if (desired_new_size < new_size_before && eden()->is_empty()) { 412 // bail out of shrinking if objects in eden 413 size_t change = new_size_before - desired_new_size; 414 assert(change % alignment == 0, "just checking"); 415 _virtual_space.shrink_by(change); 416 changed = true; 417 } 418 if (changed) { 419 // The spaces have already been mangled at this point but 420 // may not have been cleared (set top = bottom) and should be. 421 // Mangling was done when the heap was being expanded. 422 compute_space_boundaries(eden()->used(), 423 SpaceDecorator::Clear, 424 SpaceDecorator::DontMangle); 425 MemRegion cmr((HeapWord*)_virtual_space.low(), 426 (HeapWord*)_virtual_space.high()); 427 gch->rem_set()->resize_covered_region(cmr); 428 429 log_debug(gc, ergo, heap)( 430 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 431 new_size_before/K, _virtual_space.committed_size()/K, 432 eden()->capacity()/K, from()->capacity()/K); 433 log_trace(gc, ergo, heap)( 434 " [allowed " SIZE_FORMAT "K extra for %d threads]", 435 thread_increase_size/K, threads_count); 436 } 437 } 438 439 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) { 440 assert(false, "NYI -- are you sure you want to call this?"); 441 } 442 443 444 size_t DefNewGeneration::capacity() const { 445 return eden()->capacity() 446 + from()->capacity(); // to() is only used during scavenge 447 } 448 449 450 size_t DefNewGeneration::used() const { 451 return eden()->used() 452 + from()->used(); // to() is only used during scavenge 453 } 454 455 456 size_t DefNewGeneration::free() const { 457 return eden()->free() 458 + from()->free(); // to() is only used during scavenge 459 } 460 461 size_t DefNewGeneration::max_capacity() const { 462 const size_t reserved_bytes = reserved().byte_size(); 463 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment); 464 } 465 466 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 467 return eden()->free(); 468 } 469 470 size_t DefNewGeneration::capacity_before_gc() const { 471 return eden()->capacity(); 472 } 473 474 size_t DefNewGeneration::contiguous_available() const { 475 return eden()->free(); 476 } 477 478 479 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); } 480 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 481 482 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 483 eden()->object_iterate(blk); 484 from()->object_iterate(blk); 485 } 486 487 488 void DefNewGeneration::space_iterate(SpaceClosure* blk, 489 bool usedOnly) { 490 blk->do_space(eden()); 491 blk->do_space(from()); 492 blk->do_space(to()); 493 } 494 495 // The last collection bailed out, we are running out of heap space, 496 // so we try to allocate the from-space, too. 497 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 498 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc(); 499 500 // If the Heap_lock is not locked by this thread, this will be called 501 // again later with the Heap_lock held. 502 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread())); 503 504 HeapWord* result = NULL; 505 if (do_alloc) { 506 result = from()->allocate(size); 507 } 508 509 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s", 510 size, 511 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 512 "true" : "false", 513 Heap_lock->is_locked() ? "locked" : "unlocked", 514 from()->free(), 515 should_try_alloc ? "" : " should_allocate_from_space: NOT", 516 do_alloc ? " Heap_lock is not owned by self" : "", 517 result == NULL ? "NULL" : "object"); 518 519 return result; 520 } 521 522 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 523 bool is_tlab, 524 bool parallel) { 525 // We don't attempt to expand the young generation (but perhaps we should.) 526 return allocate(size, is_tlab); 527 } 528 529 void DefNewGeneration::adjust_desired_tenuring_threshold() { 530 // Set the desired survivor size to half the real survivor space 531 size_t const survivor_capacity = to()->capacity() / HeapWordSize; 532 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 533 534 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size); 535 536 if (UsePerfData) { 537 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters(); 538 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold); 539 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize); 540 } 541 542 age_table()->print_age_table(_tenuring_threshold); 543 } 544 545 void DefNewGeneration::collect(bool full, 546 bool clear_all_soft_refs, 547 size_t size, 548 bool is_tlab) { 549 assert(full || size > 0, "otherwise we don't want to collect"); 550 551 SerialHeap* heap = SerialHeap::heap(); 552 553 _gc_timer->register_gc_start(); 554 DefNewTracer gc_tracer; 555 gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start()); 556 557 _old_gen = heap->old_gen(); 558 559 // If the next generation is too full to accommodate promotion 560 // from this generation, pass on collection; let the next generation 561 // do it. 562 if (!collection_attempt_is_safe()) { 563 log_trace(gc)(":: Collection attempt not safe ::"); 564 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 565 return; 566 } 567 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 568 569 init_assuming_no_promotion_failure(); 570 571 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause()); 572 573 heap->trace_heap_before_gc(&gc_tracer); 574 575 // These can be shared for all code paths 576 IsAliveClosure is_alive(this); 577 ScanWeakRefClosure scan_weak_ref(this); 578 579 age_table()->clear(); 580 to()->clear(SpaceDecorator::Mangle); 581 // The preserved marks should be empty at the start of the GC. 582 _preserved_marks_set.init(1); 583 584 heap->rem_set()->prepare_for_younger_refs_iterate(false); 585 586 assert(heap->no_allocs_since_save_marks(), 587 "save marks have not been newly set."); 588 589 FastScanClosure fsc_with_no_gc_barrier(this, false); 590 FastScanClosure fsc_with_gc_barrier(this, true); 591 592 CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier, 593 heap->rem_set()->cld_rem_set()->accumulate_modified_oops()); 594 595 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 596 FastEvacuateFollowersClosure evacuate_followers(heap, 597 &fsc_with_no_gc_barrier, 598 &fsc_with_gc_barrier); 599 600 assert(heap->no_allocs_since_save_marks(), 601 "save marks have not been newly set."); 602 603 { 604 // DefNew needs to run with n_threads == 0, to make sure the serial 605 // version of the card table scanning code is used. 606 // See: CardTableRS::non_clean_card_iterate_possibly_parallel. 607 StrongRootsScope srs(0); 608 609 heap->young_process_roots(&srs, 610 &fsc_with_no_gc_barrier, 611 &fsc_with_gc_barrier, 612 &cld_scan_closure); 613 } 614 615 // "evacuate followers". 616 evacuate_followers.do_void(); 617 618 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 619 ReferenceProcessor* rp = ref_processor(); 620 rp->setup_policy(clear_all_soft_refs); 621 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues()); 622 const ReferenceProcessorStats& stats = 623 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 624 NULL, &pt); 625 gc_tracer.report_gc_reference_stats(stats); 626 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 627 pt.print_all_references(); 628 629 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set."); 630 631 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 632 633 // Verify that the usage of keep_alive didn't copy any objects. 634 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set."); 635 636 if (!_promotion_failed) { 637 // Swap the survivor spaces. 638 eden()->clear(SpaceDecorator::Mangle); 639 from()->clear(SpaceDecorator::Mangle); 640 if (ZapUnusedHeapArea) { 641 // This is now done here because of the piece-meal mangling which 642 // can check for valid mangling at intermediate points in the 643 // collection(s). When a young collection fails to collect 644 // sufficient space resizing of the young generation can occur 645 // an redistribute the spaces in the young generation. Mangle 646 // here so that unzapped regions don't get distributed to 647 // other spaces. 648 to()->mangle_unused_area(); 649 } 650 swap_spaces(); 651 652 assert(to()->is_empty(), "to space should be empty now"); 653 654 adjust_desired_tenuring_threshold(); 655 656 // A successful scavenge should restart the GC time limit count which is 657 // for full GC's. 658 AdaptiveSizePolicy* size_policy = heap->size_policy(); 659 size_policy->reset_gc_overhead_limit_count(); 660 assert(!heap->incremental_collection_failed(), "Should be clear"); 661 } else { 662 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 663 _promo_failure_scan_stack.clear(true); // Clear cached segments. 664 665 remove_forwarding_pointers(); 666 log_info(gc, promotion)("Promotion failed"); 667 // Add to-space to the list of space to compact 668 // when a promotion failure has occurred. In that 669 // case there can be live objects in to-space 670 // as a result of a partial evacuation of eden 671 // and from-space. 672 swap_spaces(); // For uniformity wrt ParNewGeneration. 673 from()->set_next_compaction_space(to()); 674 heap->set_incremental_collection_failed(); 675 676 // Inform the next generation that a promotion failure occurred. 677 _old_gen->promotion_failure_occurred(); 678 gc_tracer.report_promotion_failed(_promotion_failed_info); 679 680 // Reset the PromotionFailureALot counters. 681 NOT_PRODUCT(heap->reset_promotion_should_fail();) 682 } 683 // We should have processed and cleared all the preserved marks. 684 _preserved_marks_set.reclaim(); 685 // set new iteration safe limit for the survivor spaces 686 from()->set_concurrent_iteration_safe_limit(from()->top()); 687 to()->set_concurrent_iteration_safe_limit(to()->top()); 688 689 // We need to use a monotonically non-decreasing time in ms 690 // or we will see time-warp warnings and os::javaTimeMillis() 691 // does not guarantee monotonicity. 692 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 693 update_time_of_last_gc(now); 694 695 heap->trace_heap_after_gc(&gc_tracer); 696 697 _gc_timer->register_gc_end(); 698 699 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 700 } 701 702 void DefNewGeneration::init_assuming_no_promotion_failure() { 703 _promotion_failed = false; 704 _promotion_failed_info.reset(); 705 from()->set_next_compaction_space(NULL); 706 } 707 708 void DefNewGeneration::remove_forwarding_pointers() { 709 RemoveForwardedPointerClosure rspc; 710 eden()->object_iterate(&rspc); 711 from()->object_iterate(&rspc); 712 restore_preserved_marks(); 713 } 714 715 void DefNewGeneration::restore_preserved_marks() { 716 SharedRestorePreservedMarksTaskExecutor task_executor(NULL); 717 _preserved_marks_set.restore(&task_executor); 718 } 719 720 void DefNewGeneration::handle_promotion_failure(oop old) { 721 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size()); 722 723 _promotion_failed = true; 724 _promotion_failed_info.register_copy_failure(old->size()); 725 _preserved_marks_set.get()->push_if_necessary(old, old->mark_raw()); 726 // forward to self 727 old->forward_to(old); 728 729 _promo_failure_scan_stack.push(old); 730 731 if (!_promo_failure_drain_in_progress) { 732 // prevent recursion in copy_to_survivor_space() 733 _promo_failure_drain_in_progress = true; 734 drain_promo_failure_scan_stack(); 735 _promo_failure_drain_in_progress = false; 736 } 737 } 738 739 oop DefNewGeneration::copy_to_survivor_space(oop old) { 740 assert(is_in_reserved(old) && !old->is_forwarded(), 741 "shouldn't be scavenging this oop"); 742 size_t s = old->size(); 743 oop obj = NULL; 744 745 // Try allocating obj in to-space (unless too old) 746 if (old->age() < tenuring_threshold()) { 747 obj = (oop) to()->allocate_aligned(s); 748 } 749 750 // Otherwise try allocating obj tenured 751 if (obj == NULL) { 752 obj = _old_gen->promote(old, s); 753 if (obj == NULL) { 754 handle_promotion_failure(old); 755 return old; 756 } 757 } else { 758 // Prefetch beyond obj 759 const intx interval = PrefetchCopyIntervalInBytes; 760 Prefetch::write(obj, interval); 761 762 // Copy obj 763 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 764 765 // Increment age if obj still in new generation 766 obj->incr_age(); 767 age_table()->add(obj, s); 768 } 769 770 // Done, insert forward pointer to obj in this header 771 old->forward_to(obj); 772 773 return obj; 774 } 775 776 void DefNewGeneration::drain_promo_failure_scan_stack() { 777 while (!_promo_failure_scan_stack.is_empty()) { 778 oop obj = _promo_failure_scan_stack.pop(); 779 obj->oop_iterate(_promo_failure_scan_stack_closure); 780 } 781 } 782 783 void DefNewGeneration::save_marks() { 784 eden()->set_saved_mark(); 785 to()->set_saved_mark(); 786 from()->set_saved_mark(); 787 } 788 789 790 void DefNewGeneration::reset_saved_marks() { 791 eden()->reset_saved_mark(); 792 to()->reset_saved_mark(); 793 from()->reset_saved_mark(); 794 } 795 796 797 bool DefNewGeneration::no_allocs_since_save_marks() { 798 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 799 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 800 return to()->saved_mark_at_top(); 801 } 802 803 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 804 size_t max_alloc_words) { 805 if (requestor == this || _promotion_failed) { 806 return; 807 } 808 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation"); 809 810 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 811 if (to_space->top() > to_space->bottom()) { 812 trace("to_space not empty when contribute_scratch called"); 813 } 814 */ 815 816 ContiguousSpace* to_space = to(); 817 assert(to_space->end() >= to_space->top(), "pointers out of order"); 818 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 819 if (free_words >= MinFreeScratchWords) { 820 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 821 sb->num_words = free_words; 822 sb->next = list; 823 list = sb; 824 } 825 } 826 827 void DefNewGeneration::reset_scratch() { 828 // If contributing scratch in to_space, mangle all of 829 // to_space if ZapUnusedHeapArea. This is needed because 830 // top is not maintained while using to-space as scratch. 831 if (ZapUnusedHeapArea) { 832 to()->mangle_unused_area_complete(); 833 } 834 } 835 836 bool DefNewGeneration::collection_attempt_is_safe() { 837 if (!to()->is_empty()) { 838 log_trace(gc)(":: to is not empty ::"); 839 return false; 840 } 841 if (_old_gen == NULL) { 842 GenCollectedHeap* gch = GenCollectedHeap::heap(); 843 _old_gen = gch->old_gen(); 844 } 845 return _old_gen->promotion_attempt_is_safe(used()); 846 } 847 848 void DefNewGeneration::gc_epilogue(bool full) { 849 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 850 851 assert(!GCLocker::is_active(), "We should not be executing here"); 852 // Check if the heap is approaching full after a collection has 853 // been done. Generally the young generation is empty at 854 // a minimum at the end of a collection. If it is not, then 855 // the heap is approaching full. 856 GenCollectedHeap* gch = GenCollectedHeap::heap(); 857 if (full) { 858 DEBUG_ONLY(seen_incremental_collection_failed = false;) 859 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 860 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 861 GCCause::to_string(gch->gc_cause())); 862 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 863 set_should_allocate_from_space(); // we seem to be running out of space 864 } else { 865 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 866 GCCause::to_string(gch->gc_cause())); 867 gch->clear_incremental_collection_failed(); // We just did a full collection 868 clear_should_allocate_from_space(); // if set 869 } 870 } else { 871 #ifdef ASSERT 872 // It is possible that incremental_collection_failed() == true 873 // here, because an attempted scavenge did not succeed. The policy 874 // is normally expected to cause a full collection which should 875 // clear that condition, so we should not be here twice in a row 876 // with incremental_collection_failed() == true without having done 877 // a full collection in between. 878 if (!seen_incremental_collection_failed && 879 gch->incremental_collection_failed()) { 880 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 881 GCCause::to_string(gch->gc_cause())); 882 seen_incremental_collection_failed = true; 883 } else if (seen_incremental_collection_failed) { 884 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 885 GCCause::to_string(gch->gc_cause())); 886 assert(gch->gc_cause() == GCCause::_scavenge_alot || 887 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 888 !gch->incremental_collection_failed(), 889 "Twice in a row"); 890 seen_incremental_collection_failed = false; 891 } 892 #endif // ASSERT 893 } 894 895 if (ZapUnusedHeapArea) { 896 eden()->check_mangled_unused_area_complete(); 897 from()->check_mangled_unused_area_complete(); 898 to()->check_mangled_unused_area_complete(); 899 } 900 901 if (!CleanChunkPoolAsync) { 902 Chunk::clean_chunk_pool(); 903 } 904 905 // update the generation and space performance counters 906 update_counters(); 907 gch->counters()->update_counters(); 908 } 909 910 void DefNewGeneration::record_spaces_top() { 911 assert(ZapUnusedHeapArea, "Not mangling unused space"); 912 eden()->set_top_for_allocations(); 913 to()->set_top_for_allocations(); 914 from()->set_top_for_allocations(); 915 } 916 917 void DefNewGeneration::ref_processor_init() { 918 Generation::ref_processor_init(); 919 } 920 921 922 void DefNewGeneration::update_counters() { 923 if (UsePerfData) { 924 _eden_counters->update_all(); 925 _from_counters->update_all(); 926 _to_counters->update_all(); 927 _gen_counters->update_all(); 928 } 929 } 930 931 void DefNewGeneration::verify() { 932 eden()->verify(); 933 from()->verify(); 934 to()->verify(); 935 } 936 937 void DefNewGeneration::print_on(outputStream* st) const { 938 Generation::print_on(st); 939 st->print(" eden"); 940 eden()->print_on(st); 941 st->print(" from"); 942 from()->print_on(st); 943 st->print(" to "); 944 to()->print_on(st); 945 } 946 947 948 const char* DefNewGeneration::name() const { 949 return "def new generation"; 950 } 951 952 // Moved from inline file as they are not called inline 953 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 954 return eden(); 955 } 956 957 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 958 // This is the slow-path allocation for the DefNewGeneration. 959 // Most allocations are fast-path in compiled code. 960 // We try to allocate from the eden. If that works, we are happy. 961 // Note that since DefNewGeneration supports lock-free allocation, we 962 // have to use it here, as well. 963 HeapWord* result = eden()->par_allocate(word_size); 964 if (result != NULL) { 965 if (_old_gen != NULL) { 966 _old_gen->sample_eden_chunk(); 967 } 968 } else { 969 // If the eden is full and the last collection bailed out, we are running 970 // out of heap space, and we try to allocate the from-space, too. 971 // allocate_from_space can't be inlined because that would introduce a 972 // circular dependency at compile time. 973 result = allocate_from_space(word_size); 974 } 975 return result; 976 } 977 978 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 979 bool is_tlab) { 980 HeapWord* res = eden()->par_allocate(word_size); 981 if (_old_gen != NULL) { 982 _old_gen->sample_eden_chunk(); 983 } 984 return res; 985 } 986 987 size_t DefNewGeneration::tlab_capacity() const { 988 return eden()->capacity(); 989 } 990 991 size_t DefNewGeneration::tlab_used() const { 992 return eden()->used(); 993 } 994 995 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 996 return unsafe_max_alloc_nogc(); 997 }