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