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/space.inline.hpp" 44 #include "gc/shared/spaceDecorator.hpp" 45 #include "gc/shared/strongRootsScope.hpp" 46 #include "gc/shared/weakProcessor.hpp" 47 #include "logging/log.hpp" 48 #include "memory/iterator.hpp" 49 #include "memory/resourceArea.hpp" 50 #include "oops/instanceRefKlass.hpp" 51 #include "oops/oop.inline.hpp" 52 #include "runtime/atomic.hpp" 53 #include "runtime/java.hpp" 54 #include "runtime/prefetch.inline.hpp" 55 #include "runtime/thread.inline.hpp" 56 #include "utilities/align.hpp" 57 #include "utilities/copy.hpp" 58 #include "utilities/globalDefinitions.hpp" 59 #include "utilities/stack.inline.hpp" 60 61 // 62 // DefNewGeneration functions. 63 64 // Methods of protected closure types. 65 66 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) { 67 assert(_young_gen->kind() == Generation::ParNew || 68 _young_gen->kind() == Generation::DefNew, "Expected the young generation here"); 69 } 70 71 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 72 return (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 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); } 115 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); } 116 117 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 118 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 119 { 120 _boundary = _g->reserved().end(); 121 } 122 123 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); } 124 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); } 125 126 void CLDScanClosure::do_cld(ClassLoaderData* cld) { 127 NOT_PRODUCT(ResourceMark rm); 128 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s", 129 p2i(cld), 130 cld->loader_name_and_id(), 131 cld->has_modified_oops() ? "true" : "false"); 132 133 // If the cld has not been dirtied we know that there's 134 // no references into the young gen and we can skip it. 135 if (cld->has_modified_oops()) { 136 if (_accumulate_modified_oops) { 137 cld->accumulate_modified_oops(); 138 } 139 140 // Tell the closure which CLD is being scanned so that it can be dirtied 141 // if oops are left pointing into the young gen. 142 _scavenge_closure->set_scanned_cld(cld); 143 144 // Clean the cld since we're going to scavenge all the metadata. 145 cld->oops_do(_scavenge_closure, false, /*clear_modified_oops*/true); 146 147 _scavenge_closure->set_scanned_cld(NULL); 148 } 149 } 150 151 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 152 _g(g) 153 { 154 _boundary = _g->reserved().end(); 155 } 156 157 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); } 158 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); } 159 160 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 161 size_t initial_size, 162 const char* policy) 163 : Generation(rs, initial_size), 164 _preserved_marks_set(false /* in_c_heap */), 165 _promo_failure_drain_in_progress(false), 166 _should_allocate_from_space(false) 167 { 168 MemRegion cmr((HeapWord*)_virtual_space.low(), 169 (HeapWord*)_virtual_space.high()); 170 GenCollectedHeap* gch = GenCollectedHeap::heap(); 171 172 gch->rem_set()->resize_covered_region(cmr); 173 174 _eden_space = new ContiguousSpace(); 175 _from_space = new ContiguousSpace(); 176 _to_space = new ContiguousSpace(); 177 178 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) { 179 vm_exit_during_initialization("Could not allocate a new gen space"); 180 } 181 182 // Compute the maximum eden and survivor space sizes. These sizes 183 // are computed assuming the entire reserved space is committed. 184 // These values are exported as performance counters. 185 uintx alignment = gch->collector_policy()->space_alignment(); 186 uintx size = _virtual_space.reserved_size(); 187 _max_survivor_size = compute_survivor_size(size, alignment); 188 _max_eden_size = size - (2*_max_survivor_size); 189 190 // allocate the performance counters 191 GenCollectorPolicy* gcp = gch->gen_policy(); 192 193 // Generation counters -- generation 0, 3 subspaces 194 _gen_counters = new GenerationCounters("new", 0, 3, 195 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space); 196 _gc_counters = new CollectorCounters(policy, 0); 197 198 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 199 _gen_counters); 200 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 201 _gen_counters); 202 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 203 _gen_counters); 204 205 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 206 update_counters(); 207 _old_gen = NULL; 208 _tenuring_threshold = MaxTenuringThreshold; 209 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 210 211 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer(); 212 } 213 214 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 215 bool clear_space, 216 bool mangle_space) { 217 uintx alignment = 218 GenCollectedHeap::heap()->collector_policy()->space_alignment(); 219 220 // If the spaces are being cleared (only done at heap initialization 221 // currently), the survivor spaces need not be empty. 222 // Otherwise, no care is taken for used areas in the survivor spaces 223 // so check. 224 assert(clear_space || (to()->is_empty() && from()->is_empty()), 225 "Initialization of the survivor spaces assumes these are empty"); 226 227 // Compute sizes 228 uintx size = _virtual_space.committed_size(); 229 uintx survivor_size = compute_survivor_size(size, alignment); 230 uintx eden_size = size - (2*survivor_size); 231 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 232 233 if (eden_size < minimum_eden_size) { 234 // May happen due to 64Kb rounding, if so adjust eden size back up 235 minimum_eden_size = align_up(minimum_eden_size, alignment); 236 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 237 uintx unaligned_survivor_size = 238 align_down(maximum_survivor_size, alignment); 239 survivor_size = MAX2(unaligned_survivor_size, alignment); 240 eden_size = size - (2*survivor_size); 241 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 242 assert(eden_size >= minimum_eden_size, "just checking"); 243 } 244 245 char *eden_start = _virtual_space.low(); 246 char *from_start = eden_start + eden_size; 247 char *to_start = from_start + survivor_size; 248 char *to_end = to_start + survivor_size; 249 250 assert(to_end == _virtual_space.high(), "just checking"); 251 assert(Space::is_aligned(eden_start), "checking alignment"); 252 assert(Space::is_aligned(from_start), "checking alignment"); 253 assert(Space::is_aligned(to_start), "checking alignment"); 254 255 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 256 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 257 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 258 259 // A minimum eden size implies that there is a part of eden that 260 // is being used and that affects the initialization of any 261 // newly formed eden. 262 bool live_in_eden = minimum_eden_size > 0; 263 264 // If not clearing the spaces, do some checking to verify that 265 // the space are already mangled. 266 if (!clear_space) { 267 // Must check mangling before the spaces are reshaped. Otherwise, 268 // the bottom or end of one space may have moved into another 269 // a failure of the check may not correctly indicate which space 270 // is not properly mangled. 271 if (ZapUnusedHeapArea) { 272 HeapWord* limit = (HeapWord*) _virtual_space.high(); 273 eden()->check_mangled_unused_area(limit); 274 from()->check_mangled_unused_area(limit); 275 to()->check_mangled_unused_area(limit); 276 } 277 } 278 279 // Reset the spaces for their new regions. 280 eden()->initialize(edenMR, 281 clear_space && !live_in_eden, 282 SpaceDecorator::Mangle); 283 // If clear_space and live_in_eden, we will not have cleared any 284 // portion of eden above its top. This can cause newly 285 // expanded space not to be mangled if using ZapUnusedHeapArea. 286 // We explicitly do such mangling here. 287 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 288 eden()->mangle_unused_area(); 289 } 290 from()->initialize(fromMR, clear_space, mangle_space); 291 to()->initialize(toMR, clear_space, mangle_space); 292 293 // Set next compaction spaces. 294 eden()->set_next_compaction_space(from()); 295 // The to-space is normally empty before a compaction so need 296 // not be considered. The exception is during promotion 297 // failure handling when to-space can contain live objects. 298 from()->set_next_compaction_space(NULL); 299 } 300 301 void DefNewGeneration::swap_spaces() { 302 ContiguousSpace* s = from(); 303 _from_space = to(); 304 _to_space = s; 305 eden()->set_next_compaction_space(from()); 306 // The to-space is normally empty before a compaction so need 307 // not be considered. The exception is during promotion 308 // failure handling when to-space can contain live objects. 309 from()->set_next_compaction_space(NULL); 310 311 if (UsePerfData) { 312 CSpaceCounters* c = _from_counters; 313 _from_counters = _to_counters; 314 _to_counters = c; 315 } 316 } 317 318 bool DefNewGeneration::expand(size_t bytes) { 319 MutexLocker x(ExpandHeap_lock); 320 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 321 bool success = _virtual_space.expand_by(bytes); 322 if (success && ZapUnusedHeapArea) { 323 // Mangle newly committed space immediately because it 324 // can be done here more simply that after the new 325 // spaces have been computed. 326 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 327 MemRegion mangle_region(prev_high, new_high); 328 SpaceMangler::mangle_region(mangle_region); 329 } 330 331 // Do not attempt an expand-to-the reserve size. The 332 // request should properly observe the maximum size of 333 // the generation so an expand-to-reserve should be 334 // unnecessary. Also a second call to expand-to-reserve 335 // value potentially can cause an undue expansion. 336 // For example if the first expand fail for unknown reasons, 337 // but the second succeeds and expands the heap to its maximum 338 // value. 339 if (GCLocker::is_active()) { 340 log_debug(gc)("Garbage collection disabled, expanded heap instead"); 341 } 342 343 return success; 344 } 345 346 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate, 347 size_t new_size_before, 348 size_t alignment) const { 349 size_t desired_new_size = new_size_before; 350 351 if (NewSizeThreadIncrease > 0) { 352 int threads_count; 353 size_t thread_increase_size = 0; 354 355 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'. 356 threads_count = Threads::number_of_non_daemon_threads(); 357 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) { 358 thread_increase_size = threads_count * NewSizeThreadIncrease; 359 360 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'. 361 if (new_size_candidate <= max_uintx - thread_increase_size) { 362 new_size_candidate += thread_increase_size; 363 364 // 3. Check an overflow at 'align_up'. 365 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1)); 366 if (new_size_candidate <= aligned_max) { 367 desired_new_size = align_up(new_size_candidate, alignment); 368 } 369 } 370 } 371 } 372 373 return desired_new_size; 374 } 375 376 void DefNewGeneration::compute_new_size() { 377 // This is called after a GC that includes the old generation, so from-space 378 // will normally be empty. 379 // Note that we check both spaces, since if scavenge failed they revert roles. 380 // If not we bail out (otherwise we would have to relocate the objects). 381 if (!from()->is_empty() || !to()->is_empty()) { 382 return; 383 } 384 385 GenCollectedHeap* gch = GenCollectedHeap::heap(); 386 387 size_t old_size = gch->old_gen()->capacity(); 388 size_t new_size_before = _virtual_space.committed_size(); 389 size_t min_new_size = initial_size(); 390 size_t max_new_size = reserved().byte_size(); 391 assert(min_new_size <= new_size_before && 392 new_size_before <= max_new_size, 393 "just checking"); 394 // All space sizes must be multiples of Generation::GenGrain. 395 size_t alignment = Generation::GenGrain; 396 397 int threads_count = 0; 398 size_t thread_increase_size = 0; 399 400 size_t new_size_candidate = old_size / NewRatio; 401 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease 402 // and reverts to previous value if any overflow happens 403 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment); 404 405 // Adjust new generation size 406 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size); 407 assert(desired_new_size <= max_new_size, "just checking"); 408 409 bool changed = false; 410 if (desired_new_size > new_size_before) { 411 size_t change = desired_new_size - new_size_before; 412 assert(change % alignment == 0, "just checking"); 413 if (expand(change)) { 414 changed = true; 415 } 416 // If the heap failed to expand to the desired size, 417 // "changed" will be false. If the expansion failed 418 // (and at this point it was expected to succeed), 419 // ignore the failure (leaving "changed" as false). 420 } 421 if (desired_new_size < new_size_before && eden()->is_empty()) { 422 // bail out of shrinking if objects in eden 423 size_t change = new_size_before - desired_new_size; 424 assert(change % alignment == 0, "just checking"); 425 _virtual_space.shrink_by(change); 426 changed = true; 427 } 428 if (changed) { 429 // The spaces have already been mangled at this point but 430 // may not have been cleared (set top = bottom) and should be. 431 // Mangling was done when the heap was being expanded. 432 compute_space_boundaries(eden()->used(), 433 SpaceDecorator::Clear, 434 SpaceDecorator::DontMangle); 435 MemRegion cmr((HeapWord*)_virtual_space.low(), 436 (HeapWord*)_virtual_space.high()); 437 gch->rem_set()->resize_covered_region(cmr); 438 439 log_debug(gc, ergo, heap)( 440 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 441 new_size_before/K, _virtual_space.committed_size()/K, 442 eden()->capacity()/K, from()->capacity()/K); 443 log_trace(gc, ergo, heap)( 444 " [allowed " SIZE_FORMAT "K extra for %d threads]", 445 thread_increase_size/K, threads_count); 446 } 447 } 448 449 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) { 450 assert(false, "NYI -- are you sure you want to call this?"); 451 } 452 453 454 size_t DefNewGeneration::capacity() const { 455 return eden()->capacity() 456 + from()->capacity(); // to() is only used during scavenge 457 } 458 459 460 size_t DefNewGeneration::used() const { 461 return eden()->used() 462 + from()->used(); // to() is only used during scavenge 463 } 464 465 466 size_t DefNewGeneration::free() const { 467 return eden()->free() 468 + from()->free(); // to() is only used during scavenge 469 } 470 471 size_t DefNewGeneration::max_capacity() const { 472 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment(); 473 const size_t reserved_bytes = reserved().byte_size(); 474 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment); 475 } 476 477 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 478 return eden()->free(); 479 } 480 481 size_t DefNewGeneration::capacity_before_gc() const { 482 return eden()->capacity(); 483 } 484 485 size_t DefNewGeneration::contiguous_available() const { 486 return eden()->free(); 487 } 488 489 490 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); } 491 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 492 493 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 494 eden()->object_iterate(blk); 495 from()->object_iterate(blk); 496 } 497 498 499 void DefNewGeneration::space_iterate(SpaceClosure* blk, 500 bool usedOnly) { 501 blk->do_space(eden()); 502 blk->do_space(from()); 503 blk->do_space(to()); 504 } 505 506 // The last collection bailed out, we are running out of heap space, 507 // so we try to allocate the from-space, too. 508 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 509 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc(); 510 511 // If the Heap_lock is not locked by this thread, this will be called 512 // again later with the Heap_lock held. 513 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread())); 514 515 HeapWord* result = NULL; 516 if (do_alloc) { 517 result = from()->allocate(size); 518 } 519 520 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s", 521 size, 522 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 523 "true" : "false", 524 Heap_lock->is_locked() ? "locked" : "unlocked", 525 from()->free(), 526 should_try_alloc ? "" : " should_allocate_from_space: NOT", 527 do_alloc ? " Heap_lock is not owned by self" : "", 528 result == NULL ? "NULL" : "object"); 529 530 return result; 531 } 532 533 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 534 bool is_tlab, 535 bool parallel) { 536 // We don't attempt to expand the young generation (but perhaps we should.) 537 return allocate(size, is_tlab); 538 } 539 540 void DefNewGeneration::adjust_desired_tenuring_threshold() { 541 // Set the desired survivor size to half the real survivor space 542 size_t const survivor_capacity = to()->capacity() / HeapWordSize; 543 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 544 545 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size); 546 547 if (UsePerfData) { 548 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters(); 549 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold); 550 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize); 551 } 552 553 age_table()->print_age_table(_tenuring_threshold); 554 } 555 556 void DefNewGeneration::collect(bool full, 557 bool clear_all_soft_refs, 558 size_t size, 559 bool is_tlab) { 560 assert(full || size > 0, "otherwise we don't want to collect"); 561 562 SerialHeap* heap = SerialHeap::heap(); 563 564 _gc_timer->register_gc_start(); 565 DefNewTracer gc_tracer; 566 gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start()); 567 568 _old_gen = heap->old_gen(); 569 570 // If the next generation is too full to accommodate promotion 571 // from this generation, pass on collection; let the next generation 572 // do it. 573 if (!collection_attempt_is_safe()) { 574 log_trace(gc)(":: Collection attempt not safe ::"); 575 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 576 return; 577 } 578 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 579 580 init_assuming_no_promotion_failure(); 581 582 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause()); 583 584 heap->trace_heap_before_gc(&gc_tracer); 585 586 // These can be shared for all code paths 587 IsAliveClosure is_alive(this); 588 ScanWeakRefClosure scan_weak_ref(this); 589 590 age_table()->clear(); 591 to()->clear(SpaceDecorator::Mangle); 592 // The preserved marks should be empty at the start of the GC. 593 _preserved_marks_set.init(1); 594 595 heap->rem_set()->prepare_for_younger_refs_iterate(false); 596 597 assert(heap->no_allocs_since_save_marks(), 598 "save marks have not been newly set."); 599 600 FastScanClosure fsc_with_no_gc_barrier(this, false); 601 FastScanClosure fsc_with_gc_barrier(this, true); 602 603 CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier, 604 heap->rem_set()->cld_rem_set()->accumulate_modified_oops()); 605 606 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 607 FastEvacuateFollowersClosure evacuate_followers(heap, 608 &fsc_with_no_gc_barrier, 609 &fsc_with_gc_barrier); 610 611 assert(heap->no_allocs_since_save_marks(), 612 "save marks have not been newly set."); 613 614 { 615 // DefNew needs to run with n_threads == 0, to make sure the serial 616 // version of the card table scanning code is used. 617 // See: CardTableRS::non_clean_card_iterate_possibly_parallel. 618 StrongRootsScope srs(0); 619 620 heap->young_process_roots(&srs, 621 &fsc_with_no_gc_barrier, 622 &fsc_with_gc_barrier, 623 &cld_scan_closure); 624 } 625 626 // "evacuate followers". 627 evacuate_followers.do_void(); 628 629 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 630 ReferenceProcessor* rp = ref_processor(); 631 rp->setup_policy(clear_all_soft_refs); 632 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues()); 633 const ReferenceProcessorStats& stats = 634 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 635 NULL, &pt); 636 gc_tracer.report_gc_reference_stats(stats); 637 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 638 pt.print_all_references(); 639 640 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set."); 641 642 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 643 644 // Verify that the usage of keep_alive didn't copy any objects. 645 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set."); 646 647 if (!_promotion_failed) { 648 // Swap the survivor spaces. 649 eden()->clear(SpaceDecorator::Mangle); 650 from()->clear(SpaceDecorator::Mangle); 651 if (ZapUnusedHeapArea) { 652 // This is now done here because of the piece-meal mangling which 653 // can check for valid mangling at intermediate points in the 654 // collection(s). When a young collection fails to collect 655 // sufficient space resizing of the young generation can occur 656 // an redistribute the spaces in the young generation. Mangle 657 // here so that unzapped regions don't get distributed to 658 // other spaces. 659 to()->mangle_unused_area(); 660 } 661 swap_spaces(); 662 663 assert(to()->is_empty(), "to space should be empty now"); 664 665 adjust_desired_tenuring_threshold(); 666 667 // A successful scavenge should restart the GC time limit count which is 668 // for full GC's. 669 AdaptiveSizePolicy* size_policy = heap->size_policy(); 670 size_policy->reset_gc_overhead_limit_count(); 671 assert(!heap->incremental_collection_failed(), "Should be clear"); 672 } else { 673 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 674 _promo_failure_scan_stack.clear(true); // Clear cached segments. 675 676 remove_forwarding_pointers(); 677 log_info(gc, promotion)("Promotion failed"); 678 // Add to-space to the list of space to compact 679 // when a promotion failure has occurred. In that 680 // case there can be live objects in to-space 681 // as a result of a partial evacuation of eden 682 // and from-space. 683 swap_spaces(); // For uniformity wrt ParNewGeneration. 684 from()->set_next_compaction_space(to()); 685 heap->set_incremental_collection_failed(); 686 687 // Inform the next generation that a promotion failure occurred. 688 _old_gen->promotion_failure_occurred(); 689 gc_tracer.report_promotion_failed(_promotion_failed_info); 690 691 // Reset the PromotionFailureALot counters. 692 NOT_PRODUCT(heap->reset_promotion_should_fail();) 693 } 694 // We should have processed and cleared all the preserved marks. 695 _preserved_marks_set.reclaim(); 696 // set new iteration safe limit for the survivor spaces 697 from()->set_concurrent_iteration_safe_limit(from()->top()); 698 to()->set_concurrent_iteration_safe_limit(to()->top()); 699 700 // We need to use a monotonically non-decreasing time in ms 701 // or we will see time-warp warnings and os::javaTimeMillis() 702 // does not guarantee monotonicity. 703 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 704 update_time_of_last_gc(now); 705 706 heap->trace_heap_after_gc(&gc_tracer); 707 708 _gc_timer->register_gc_end(); 709 710 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 711 } 712 713 void DefNewGeneration::init_assuming_no_promotion_failure() { 714 _promotion_failed = false; 715 _promotion_failed_info.reset(); 716 from()->set_next_compaction_space(NULL); 717 } 718 719 void DefNewGeneration::remove_forwarding_pointers() { 720 RemoveForwardedPointerClosure rspc; 721 eden()->object_iterate(&rspc); 722 from()->object_iterate(&rspc); 723 restore_preserved_marks(); 724 } 725 726 void DefNewGeneration::restore_preserved_marks() { 727 SharedRestorePreservedMarksTaskExecutor task_executor(NULL); 728 _preserved_marks_set.restore(&task_executor); 729 } 730 731 void DefNewGeneration::handle_promotion_failure(oop old) { 732 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size()); 733 734 _promotion_failed = true; 735 _promotion_failed_info.register_copy_failure(old->size()); 736 _preserved_marks_set.get()->push_if_necessary(old, old->mark_raw()); 737 // forward to self 738 old->forward_to(old); 739 740 _promo_failure_scan_stack.push(old); 741 742 if (!_promo_failure_drain_in_progress) { 743 // prevent recursion in copy_to_survivor_space() 744 _promo_failure_drain_in_progress = true; 745 drain_promo_failure_scan_stack(); 746 _promo_failure_drain_in_progress = false; 747 } 748 } 749 750 oop DefNewGeneration::copy_to_survivor_space(oop old) { 751 assert(is_in_reserved(old) && !old->is_forwarded(), 752 "shouldn't be scavenging this oop"); 753 size_t s = old->size(); 754 oop obj = NULL; 755 756 // Try allocating obj in to-space (unless too old) 757 if (old->age() < tenuring_threshold()) { 758 obj = (oop) to()->allocate_aligned(s); 759 } 760 761 // Otherwise try allocating obj tenured 762 if (obj == NULL) { 763 obj = _old_gen->promote(old, s); 764 if (obj == NULL) { 765 handle_promotion_failure(old); 766 return old; 767 } 768 } else { 769 // Prefetch beyond obj 770 const intx interval = PrefetchCopyIntervalInBytes; 771 Prefetch::write(obj, interval); 772 773 // Copy obj 774 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 775 776 // Increment age if obj still in new generation 777 obj->incr_age(); 778 age_table()->add(obj, s); 779 } 780 781 // Done, insert forward pointer to obj in this header 782 old->forward_to(obj); 783 784 return obj; 785 } 786 787 void DefNewGeneration::drain_promo_failure_scan_stack() { 788 while (!_promo_failure_scan_stack.is_empty()) { 789 oop obj = _promo_failure_scan_stack.pop(); 790 obj->oop_iterate(_promo_failure_scan_stack_closure); 791 } 792 } 793 794 void DefNewGeneration::save_marks() { 795 eden()->set_saved_mark(); 796 to()->set_saved_mark(); 797 from()->set_saved_mark(); 798 } 799 800 801 void DefNewGeneration::reset_saved_marks() { 802 eden()->reset_saved_mark(); 803 to()->reset_saved_mark(); 804 from()->reset_saved_mark(); 805 } 806 807 808 bool DefNewGeneration::no_allocs_since_save_marks() { 809 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 810 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 811 return to()->saved_mark_at_top(); 812 } 813 814 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 815 size_t max_alloc_words) { 816 if (requestor == this || _promotion_failed) { 817 return; 818 } 819 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation"); 820 821 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 822 if (to_space->top() > to_space->bottom()) { 823 trace("to_space not empty when contribute_scratch called"); 824 } 825 */ 826 827 ContiguousSpace* to_space = to(); 828 assert(to_space->end() >= to_space->top(), "pointers out of order"); 829 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 830 if (free_words >= MinFreeScratchWords) { 831 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 832 sb->num_words = free_words; 833 sb->next = list; 834 list = sb; 835 } 836 } 837 838 void DefNewGeneration::reset_scratch() { 839 // If contributing scratch in to_space, mangle all of 840 // to_space if ZapUnusedHeapArea. This is needed because 841 // top is not maintained while using to-space as scratch. 842 if (ZapUnusedHeapArea) { 843 to()->mangle_unused_area_complete(); 844 } 845 } 846 847 bool DefNewGeneration::collection_attempt_is_safe() { 848 if (!to()->is_empty()) { 849 log_trace(gc)(":: to is not empty ::"); 850 return false; 851 } 852 if (_old_gen == NULL) { 853 GenCollectedHeap* gch = GenCollectedHeap::heap(); 854 _old_gen = gch->old_gen(); 855 } 856 return _old_gen->promotion_attempt_is_safe(used()); 857 } 858 859 void DefNewGeneration::gc_epilogue(bool full) { 860 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 861 862 assert(!GCLocker::is_active(), "We should not be executing here"); 863 // Check if the heap is approaching full after a collection has 864 // been done. Generally the young generation is empty at 865 // a minimum at the end of a collection. If it is not, then 866 // the heap is approaching full. 867 GenCollectedHeap* gch = GenCollectedHeap::heap(); 868 if (full) { 869 DEBUG_ONLY(seen_incremental_collection_failed = false;) 870 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 871 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 872 GCCause::to_string(gch->gc_cause())); 873 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 874 set_should_allocate_from_space(); // we seem to be running out of space 875 } else { 876 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 877 GCCause::to_string(gch->gc_cause())); 878 gch->clear_incremental_collection_failed(); // We just did a full collection 879 clear_should_allocate_from_space(); // if set 880 } 881 } else { 882 #ifdef ASSERT 883 // It is possible that incremental_collection_failed() == true 884 // here, because an attempted scavenge did not succeed. The policy 885 // is normally expected to cause a full collection which should 886 // clear that condition, so we should not be here twice in a row 887 // with incremental_collection_failed() == true without having done 888 // a full collection in between. 889 if (!seen_incremental_collection_failed && 890 gch->incremental_collection_failed()) { 891 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 892 GCCause::to_string(gch->gc_cause())); 893 seen_incremental_collection_failed = true; 894 } else if (seen_incremental_collection_failed) { 895 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 896 GCCause::to_string(gch->gc_cause())); 897 assert(gch->gc_cause() == GCCause::_scavenge_alot || 898 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 899 !gch->incremental_collection_failed(), 900 "Twice in a row"); 901 seen_incremental_collection_failed = false; 902 } 903 #endif // ASSERT 904 } 905 906 if (ZapUnusedHeapArea) { 907 eden()->check_mangled_unused_area_complete(); 908 from()->check_mangled_unused_area_complete(); 909 to()->check_mangled_unused_area_complete(); 910 } 911 912 if (!CleanChunkPoolAsync) { 913 Chunk::clean_chunk_pool(); 914 } 915 916 // update the generation and space performance counters 917 update_counters(); 918 gch->counters()->update_counters(); 919 } 920 921 void DefNewGeneration::record_spaces_top() { 922 assert(ZapUnusedHeapArea, "Not mangling unused space"); 923 eden()->set_top_for_allocations(); 924 to()->set_top_for_allocations(); 925 from()->set_top_for_allocations(); 926 } 927 928 void DefNewGeneration::ref_processor_init() { 929 Generation::ref_processor_init(); 930 } 931 932 933 void DefNewGeneration::update_counters() { 934 if (UsePerfData) { 935 _eden_counters->update_all(); 936 _from_counters->update_all(); 937 _to_counters->update_all(); 938 _gen_counters->update_all(); 939 } 940 } 941 942 void DefNewGeneration::verify() { 943 eden()->verify(); 944 from()->verify(); 945 to()->verify(); 946 } 947 948 void DefNewGeneration::print_on(outputStream* st) const { 949 Generation::print_on(st); 950 st->print(" eden"); 951 eden()->print_on(st); 952 st->print(" from"); 953 from()->print_on(st); 954 st->print(" to "); 955 to()->print_on(st); 956 } 957 958 959 const char* DefNewGeneration::name() const { 960 return "def new generation"; 961 } 962 963 // Moved from inline file as they are not called inline 964 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 965 return eden(); 966 } 967 968 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 969 // This is the slow-path allocation for the DefNewGeneration. 970 // Most allocations are fast-path in compiled code. 971 // We try to allocate from the eden. If that works, we are happy. 972 // Note that since DefNewGeneration supports lock-free allocation, we 973 // have to use it here, as well. 974 HeapWord* result = eden()->par_allocate(word_size); 975 if (result != NULL) { 976 if (_old_gen != NULL) { 977 _old_gen->sample_eden_chunk(); 978 } 979 } else { 980 // If the eden is full and the last collection bailed out, we are running 981 // out of heap space, and we try to allocate the from-space, too. 982 // allocate_from_space can't be inlined because that would introduce a 983 // circular dependency at compile time. 984 result = allocate_from_space(word_size); 985 } 986 return result; 987 } 988 989 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 990 bool is_tlab) { 991 HeapWord* res = eden()->par_allocate(word_size); 992 if (_old_gen != NULL) { 993 _old_gen->sample_eden_chunk(); 994 } 995 return res; 996 } 997 998 size_t DefNewGeneration::tlab_capacity() const { 999 return eden()->capacity(); 1000 } 1001 1002 size_t DefNewGeneration::tlab_used() const { 1003 return eden()->used(); 1004 } 1005 1006 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1007 return unsafe_max_alloc_nogc(); 1008 }