1 /* 2 * Copyright (c) 2001, 2016, 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/shared/ageTable.inline.hpp" 28 #include "gc/shared/cardTableRS.hpp" 29 #include "gc/shared/collectorCounters.hpp" 30 #include "gc/shared/gcHeapSummary.hpp" 31 #include "gc/shared/gcLocker.inline.hpp" 32 #include "gc/shared/gcPolicyCounters.hpp" 33 #include "gc/shared/gcTimer.hpp" 34 #include "gc/shared/gcTrace.hpp" 35 #include "gc/shared/gcTraceTime.inline.hpp" 36 #include "gc/shared/genCollectedHeap.hpp" 37 #include "gc/shared/genOopClosures.inline.hpp" 38 #include "gc/shared/generationSpec.hpp" 39 #include "gc/shared/preservedMarks.inline.hpp" 40 #include "gc/shared/referencePolicy.hpp" 41 #include "gc/shared/space.inline.hpp" 42 #include "gc/shared/spaceDecorator.hpp" 43 #include "gc/shared/strongRootsScope.hpp" 44 #include "logging/log.hpp" 45 #include "memory/iterator.hpp" 46 #include "memory/resourceArea.hpp" 47 #include "oops/instanceRefKlass.hpp" 48 #include "oops/oop.inline.hpp" 49 #include "runtime/atomic.hpp" 50 #include "runtime/java.hpp" 51 #include "runtime/prefetch.inline.hpp" 52 #include "runtime/thread.inline.hpp" 53 #include "utilities/copy.hpp" 54 #include "utilities/globalDefinitions.hpp" 55 #include "utilities/stack.inline.hpp" 56 #if INCLUDE_ALL_GCS 57 #include "gc/cms/parOopClosures.hpp" 58 #endif 59 60 // 61 // DefNewGeneration functions. 62 63 // Methods of protected closure types. 64 65 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) { 66 assert(_young_gen->kind() == Generation::ParNew || 67 _young_gen->kind() == Generation::DefNew, "Expected the young generation here"); 68 } 69 70 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 71 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded(); 72 } 73 74 DefNewGeneration::KeepAliveClosure:: 75 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 76 _rs = GenCollectedHeap::heap()->rem_set(); 77 } 78 79 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 80 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 81 82 83 DefNewGeneration::FastKeepAliveClosure:: 84 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 85 DefNewGeneration::KeepAliveClosure(cl) { 86 _boundary = g->reserved().end(); 87 } 88 89 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 90 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 91 92 DefNewGeneration::EvacuateFollowersClosure:: 93 EvacuateFollowersClosure(GenCollectedHeap* gch, 94 ScanClosure* cur, 95 ScanClosure* older) : 96 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older) 97 {} 98 99 void DefNewGeneration::EvacuateFollowersClosure::do_void() { 100 do { 101 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older); 102 } while (!_gch->no_allocs_since_save_marks()); 103 } 104 105 DefNewGeneration::FastEvacuateFollowersClosure:: 106 FastEvacuateFollowersClosure(GenCollectedHeap* gch, 107 FastScanClosure* cur, 108 FastScanClosure* older) : 109 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older) 110 { 111 assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew"); 112 _young_gen = (DefNewGeneration*)_gch->young_gen(); 113 } 114 115 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 116 do { 117 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older); 118 } while (!_gch->no_allocs_since_save_marks()); 119 guarantee(_young_gen->promo_failure_scan_is_complete(), "Failed to finish scan"); 120 } 121 122 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) : 123 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 124 { 125 _boundary = _g->reserved().end(); 126 } 127 128 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); } 129 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); } 130 131 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 132 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 133 { 134 _boundary = _g->reserved().end(); 135 } 136 137 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); } 138 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); } 139 140 void KlassScanClosure::do_klass(Klass* klass) { 141 NOT_PRODUCT(ResourceMark rm); 142 log_develop_trace(gc, scavenge)("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s", 143 p2i(klass), 144 klass->external_name(), 145 klass->has_modified_oops() ? "true" : "false"); 146 147 // If the klass has not been dirtied we know that there's 148 // no references into the young gen and we can skip it. 149 if (klass->has_modified_oops()) { 150 if (_accumulate_modified_oops) { 151 klass->accumulate_modified_oops(); 152 } 153 154 // Clear this state since we're going to scavenge all the metadata. 155 klass->clear_modified_oops(); 156 157 // Tell the closure which Klass is being scanned so that it can be dirtied 158 // if oops are left pointing into the young gen. 159 _scavenge_closure->set_scanned_klass(klass); 160 161 klass->oops_do(_scavenge_closure); 162 163 _scavenge_closure->set_scanned_klass(NULL); 164 } 165 } 166 167 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 168 _g(g) 169 { 170 _boundary = _g->reserved().end(); 171 } 172 173 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); } 174 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); } 175 176 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); } 177 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); } 178 179 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure, 180 KlassRemSet* klass_rem_set) 181 : _scavenge_closure(scavenge_closure), 182 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {} 183 184 185 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 186 size_t initial_size, 187 const char* policy) 188 : Generation(rs, initial_size), 189 _preserved_marks_set(false /* in_c_heap */), 190 _promo_failure_drain_in_progress(false), 191 _should_allocate_from_space(false) 192 { 193 MemRegion cmr((HeapWord*)_virtual_space.low(), 194 (HeapWord*)_virtual_space.high()); 195 GenCollectedHeap* gch = GenCollectedHeap::heap(); 196 197 gch->rem_set()->resize_covered_region(cmr); 198 199 _eden_space = new ContiguousSpace(); 200 _from_space = new ContiguousSpace(); 201 _to_space = new ContiguousSpace(); 202 203 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) { 204 vm_exit_during_initialization("Could not allocate a new gen space"); 205 } 206 207 // Compute the maximum eden and survivor space sizes. These sizes 208 // are computed assuming the entire reserved space is committed. 209 // These values are exported as performance counters. 210 uintx alignment = gch->collector_policy()->space_alignment(); 211 uintx size = _virtual_space.reserved_size(); 212 _max_survivor_size = compute_survivor_size(size, alignment); 213 _max_eden_size = size - (2*_max_survivor_size); 214 215 // allocate the performance counters 216 GenCollectorPolicy* gcp = gch->gen_policy(); 217 218 // Generation counters -- generation 0, 3 subspaces 219 _gen_counters = new GenerationCounters("new", 0, 3, 220 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space); 221 _gc_counters = new CollectorCounters(policy, 0); 222 223 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 224 _gen_counters); 225 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 226 _gen_counters); 227 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 228 _gen_counters); 229 230 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 231 update_counters(); 232 _old_gen = NULL; 233 _tenuring_threshold = MaxTenuringThreshold; 234 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 235 236 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer(); 237 } 238 239 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 240 bool clear_space, 241 bool mangle_space) { 242 uintx alignment = 243 GenCollectedHeap::heap()->collector_policy()->space_alignment(); 244 245 // If the spaces are being cleared (only done at heap initialization 246 // currently), the survivor spaces need not be empty. 247 // Otherwise, no care is taken for used areas in the survivor spaces 248 // so check. 249 assert(clear_space || (to()->is_empty() && from()->is_empty()), 250 "Initialization of the survivor spaces assumes these are empty"); 251 252 // Compute sizes 253 uintx size = _virtual_space.committed_size(); 254 uintx survivor_size = compute_survivor_size(size, alignment); 255 uintx eden_size = size - (2*survivor_size); 256 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 257 258 if (eden_size < minimum_eden_size) { 259 // May happen due to 64Kb rounding, if so adjust eden size back up 260 minimum_eden_size = align_size_up(minimum_eden_size, alignment); 261 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 262 uintx unaligned_survivor_size = 263 align_size_down(maximum_survivor_size, alignment); 264 survivor_size = MAX2(unaligned_survivor_size, alignment); 265 eden_size = size - (2*survivor_size); 266 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 267 assert(eden_size >= minimum_eden_size, "just checking"); 268 } 269 270 char *eden_start = _virtual_space.low(); 271 char *from_start = eden_start + eden_size; 272 char *to_start = from_start + survivor_size; 273 char *to_end = to_start + survivor_size; 274 275 assert(to_end == _virtual_space.high(), "just checking"); 276 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment"); 277 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment"); 278 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment"); 279 280 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 281 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 282 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 283 284 // A minimum eden size implies that there is a part of eden that 285 // is being used and that affects the initialization of any 286 // newly formed eden. 287 bool live_in_eden = minimum_eden_size > 0; 288 289 // If not clearing the spaces, do some checking to verify that 290 // the space are already mangled. 291 if (!clear_space) { 292 // Must check mangling before the spaces are reshaped. Otherwise, 293 // the bottom or end of one space may have moved into another 294 // a failure of the check may not correctly indicate which space 295 // is not properly mangled. 296 if (ZapUnusedHeapArea) { 297 HeapWord* limit = (HeapWord*) _virtual_space.high(); 298 eden()->check_mangled_unused_area(limit); 299 from()->check_mangled_unused_area(limit); 300 to()->check_mangled_unused_area(limit); 301 } 302 } 303 304 // Reset the spaces for their new regions. 305 eden()->initialize(edenMR, 306 clear_space && !live_in_eden, 307 SpaceDecorator::Mangle); 308 // If clear_space and live_in_eden, we will not have cleared any 309 // portion of eden above its top. This can cause newly 310 // expanded space not to be mangled if using ZapUnusedHeapArea. 311 // We explicitly do such mangling here. 312 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 313 eden()->mangle_unused_area(); 314 } 315 from()->initialize(fromMR, clear_space, mangle_space); 316 to()->initialize(toMR, clear_space, mangle_space); 317 318 // Set next compaction spaces. 319 eden()->set_next_compaction_space(from()); 320 // The to-space is normally empty before a compaction so need 321 // not be considered. The exception is during promotion 322 // failure handling when to-space can contain live objects. 323 from()->set_next_compaction_space(NULL); 324 } 325 326 void DefNewGeneration::swap_spaces() { 327 ContiguousSpace* s = from(); 328 _from_space = to(); 329 _to_space = s; 330 eden()->set_next_compaction_space(from()); 331 // The to-space is normally empty before a compaction so need 332 // not be considered. The exception is during promotion 333 // failure handling when to-space can contain live objects. 334 from()->set_next_compaction_space(NULL); 335 336 if (UsePerfData) { 337 CSpaceCounters* c = _from_counters; 338 _from_counters = _to_counters; 339 _to_counters = c; 340 } 341 } 342 343 bool DefNewGeneration::expand(size_t bytes) { 344 MutexLocker x(ExpandHeap_lock); 345 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 346 bool success = _virtual_space.expand_by(bytes); 347 if (success && ZapUnusedHeapArea) { 348 // Mangle newly committed space immediately because it 349 // can be done here more simply that after the new 350 // spaces have been computed. 351 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 352 MemRegion mangle_region(prev_high, new_high); 353 SpaceMangler::mangle_region(mangle_region); 354 } 355 356 // Do not attempt an expand-to-the reserve size. The 357 // request should properly observe the maximum size of 358 // the generation so an expand-to-reserve should be 359 // unnecessary. Also a second call to expand-to-reserve 360 // value potentially can cause an undue expansion. 361 // For example if the first expand fail for unknown reasons, 362 // but the second succeeds and expands the heap to its maximum 363 // value. 364 if (GCLocker::is_active()) { 365 log_debug(gc)("Garbage collection disabled, expanded heap instead"); 366 } 367 368 return success; 369 } 370 371 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate, 372 size_t new_size_before, 373 size_t alignment) const { 374 size_t desired_new_size = new_size_before; 375 376 if (NewSizeThreadIncrease > 0) { 377 int threads_count; 378 size_t thread_increase_size = 0; 379 380 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'. 381 threads_count = Threads::number_of_non_daemon_threads(); 382 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) { 383 thread_increase_size = threads_count * NewSizeThreadIncrease; 384 385 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'. 386 if (new_size_candidate <= max_uintx - thread_increase_size) { 387 new_size_candidate += thread_increase_size; 388 389 // 3. Check an overflow at 'align_size_up'. 390 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1)); 391 if (new_size_candidate <= aligned_max) { 392 desired_new_size = align_size_up(new_size_candidate, alignment); 393 } 394 } 395 } 396 } 397 398 return desired_new_size; 399 } 400 401 void DefNewGeneration::compute_new_size() { 402 // This is called after a GC that includes the old generation, so from-space 403 // will normally be empty. 404 // Note that we check both spaces, since if scavenge failed they revert roles. 405 // If not we bail out (otherwise we would have to relocate the objects). 406 if (!from()->is_empty() || !to()->is_empty()) { 407 return; 408 } 409 410 GenCollectedHeap* gch = GenCollectedHeap::heap(); 411 412 size_t old_size = gch->old_gen()->capacity(); 413 size_t new_size_before = _virtual_space.committed_size(); 414 size_t min_new_size = initial_size(); 415 size_t max_new_size = reserved().byte_size(); 416 assert(min_new_size <= new_size_before && 417 new_size_before <= max_new_size, 418 "just checking"); 419 // All space sizes must be multiples of Generation::GenGrain. 420 size_t alignment = Generation::GenGrain; 421 422 int threads_count = 0; 423 size_t thread_increase_size = 0; 424 425 size_t new_size_candidate = old_size / NewRatio; 426 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease 427 // and reverts to previous value if any overflow happens 428 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment); 429 430 // Adjust new generation size 431 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size); 432 assert(desired_new_size <= max_new_size, "just checking"); 433 434 bool changed = false; 435 if (desired_new_size > new_size_before) { 436 size_t change = desired_new_size - new_size_before; 437 assert(change % alignment == 0, "just checking"); 438 if (expand(change)) { 439 changed = true; 440 } 441 // If the heap failed to expand to the desired size, 442 // "changed" will be false. If the expansion failed 443 // (and at this point it was expected to succeed), 444 // ignore the failure (leaving "changed" as false). 445 } 446 if (desired_new_size < new_size_before && eden()->is_empty()) { 447 // bail out of shrinking if objects in eden 448 size_t change = new_size_before - desired_new_size; 449 assert(change % alignment == 0, "just checking"); 450 _virtual_space.shrink_by(change); 451 changed = true; 452 } 453 if (changed) { 454 // The spaces have already been mangled at this point but 455 // may not have been cleared (set top = bottom) and should be. 456 // Mangling was done when the heap was being expanded. 457 compute_space_boundaries(eden()->used(), 458 SpaceDecorator::Clear, 459 SpaceDecorator::DontMangle); 460 MemRegion cmr((HeapWord*)_virtual_space.low(), 461 (HeapWord*)_virtual_space.high()); 462 gch->rem_set()->resize_covered_region(cmr); 463 464 log_debug(gc, ergo, heap)( 465 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 466 new_size_before/K, _virtual_space.committed_size()/K, 467 eden()->capacity()/K, from()->capacity()/K); 468 log_trace(gc, ergo, heap)( 469 " [allowed " SIZE_FORMAT "K extra for %d threads]", 470 thread_increase_size/K, threads_count); 471 } 472 } 473 474 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) { 475 assert(false, "NYI -- are you sure you want to call this?"); 476 } 477 478 479 size_t DefNewGeneration::capacity() const { 480 return eden()->capacity() 481 + from()->capacity(); // to() is only used during scavenge 482 } 483 484 485 size_t DefNewGeneration::used() const { 486 return eden()->used() 487 + from()->used(); // to() is only used during scavenge 488 } 489 490 491 size_t DefNewGeneration::free() const { 492 return eden()->free() 493 + from()->free(); // to() is only used during scavenge 494 } 495 496 size_t DefNewGeneration::max_capacity() const { 497 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment(); 498 const size_t reserved_bytes = reserved().byte_size(); 499 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment); 500 } 501 502 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 503 return eden()->free(); 504 } 505 506 size_t DefNewGeneration::capacity_before_gc() const { 507 return eden()->capacity(); 508 } 509 510 size_t DefNewGeneration::contiguous_available() const { 511 return eden()->free(); 512 } 513 514 515 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); } 516 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 517 518 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 519 eden()->object_iterate(blk); 520 from()->object_iterate(blk); 521 } 522 523 524 void DefNewGeneration::space_iterate(SpaceClosure* blk, 525 bool usedOnly) { 526 blk->do_space(eden()); 527 blk->do_space(from()); 528 blk->do_space(to()); 529 } 530 531 // The last collection bailed out, we are running out of heap space, 532 // so we try to allocate the from-space, too. 533 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 534 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc(); 535 536 // If the Heap_lock is not locked by this thread, this will be called 537 // again later with the Heap_lock held. 538 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread())); 539 540 HeapWord* result = NULL; 541 if (do_alloc) { 542 result = from()->allocate(size); 543 } 544 545 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s", 546 size, 547 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 548 "true" : "false", 549 Heap_lock->is_locked() ? "locked" : "unlocked", 550 from()->free(), 551 should_try_alloc ? "" : " should_allocate_from_space: NOT", 552 do_alloc ? " Heap_lock is not owned by self" : "", 553 result == NULL ? "NULL" : "object"); 554 555 return result; 556 } 557 558 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 559 bool is_tlab, 560 bool parallel) { 561 // We don't attempt to expand the young generation (but perhaps we should.) 562 return allocate(size, is_tlab); 563 } 564 565 void DefNewGeneration::adjust_desired_tenuring_threshold() { 566 // Set the desired survivor size to half the real survivor space 567 size_t const survivor_capacity = to()->capacity() / HeapWordSize; 568 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 569 570 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size); 571 572 if (UsePerfData) { 573 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->gen_policy()->counters(); 574 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold); 575 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize); 576 } 577 578 age_table()->print_age_table(_tenuring_threshold); 579 } 580 581 void DefNewGeneration::collect(bool full, 582 bool clear_all_soft_refs, 583 size_t size, 584 bool is_tlab) { 585 assert(full || size > 0, "otherwise we don't want to collect"); 586 587 GenCollectedHeap* gch = GenCollectedHeap::heap(); 588 589 _gc_timer->register_gc_start(); 590 DefNewTracer gc_tracer; 591 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start()); 592 593 _old_gen = gch->old_gen(); 594 595 // If the next generation is too full to accommodate promotion 596 // from this generation, pass on collection; let the next generation 597 // do it. 598 if (!collection_attempt_is_safe()) { 599 log_trace(gc)(":: Collection attempt not safe ::"); 600 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 601 return; 602 } 603 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 604 605 init_assuming_no_promotion_failure(); 606 607 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, gch->gc_cause()); 608 609 gch->trace_heap_before_gc(&gc_tracer); 610 611 // These can be shared for all code paths 612 IsAliveClosure is_alive(this); 613 ScanWeakRefClosure scan_weak_ref(this); 614 615 age_table()->clear(); 616 to()->clear(SpaceDecorator::Mangle); 617 // The preserved marks should be empty at the start of the GC. 618 _preserved_marks_set.init(1); 619 620 gch->rem_set()->prepare_for_younger_refs_iterate(false); 621 622 assert(gch->no_allocs_since_save_marks(), 623 "save marks have not been newly set."); 624 625 // Not very pretty. 626 CollectorPolicy* cp = gch->collector_policy(); 627 628 FastScanClosure fsc_with_no_gc_barrier(this, false); 629 FastScanClosure fsc_with_gc_barrier(this, true); 630 631 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier, 632 gch->rem_set()->klass_rem_set()); 633 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure, 634 &fsc_with_no_gc_barrier, 635 false); 636 637 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 638 FastEvacuateFollowersClosure evacuate_followers(gch, 639 &fsc_with_no_gc_barrier, 640 &fsc_with_gc_barrier); 641 642 assert(gch->no_allocs_since_save_marks(), 643 "save marks have not been newly set."); 644 645 { 646 // DefNew needs to run with n_threads == 0, to make sure the serial 647 // version of the card table scanning code is used. 648 // See: CardTableRS::non_clean_card_iterate_possibly_parallel. 649 StrongRootsScope srs(0); 650 651 gch->young_process_roots(&srs, 652 &fsc_with_no_gc_barrier, 653 &fsc_with_gc_barrier, 654 &cld_scan_closure); 655 } 656 657 // "evacuate followers". 658 evacuate_followers.do_void(); 659 660 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 661 ReferenceProcessor* rp = ref_processor(); 662 rp->setup_policy(clear_all_soft_refs); 663 const ReferenceProcessorStats& stats = 664 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 665 NULL, _gc_timer); 666 gc_tracer.report_gc_reference_stats(stats); 667 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 668 669 if (!_promotion_failed) { 670 // Swap the survivor spaces. 671 eden()->clear(SpaceDecorator::Mangle); 672 from()->clear(SpaceDecorator::Mangle); 673 if (ZapUnusedHeapArea) { 674 // This is now done here because of the piece-meal mangling which 675 // can check for valid mangling at intermediate points in the 676 // collection(s). When a young collection fails to collect 677 // sufficient space resizing of the young generation can occur 678 // an redistribute the spaces in the young generation. Mangle 679 // here so that unzapped regions don't get distributed to 680 // other spaces. 681 to()->mangle_unused_area(); 682 } 683 swap_spaces(); 684 685 assert(to()->is_empty(), "to space should be empty now"); 686 687 adjust_desired_tenuring_threshold(); 688 689 // A successful scavenge should restart the GC time limit count which is 690 // for full GC's. 691 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); 692 size_policy->reset_gc_overhead_limit_count(); 693 assert(!gch->incremental_collection_failed(), "Should be clear"); 694 } else { 695 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 696 _promo_failure_scan_stack.clear(true); // Clear cached segments. 697 698 remove_forwarding_pointers(); 699 log_info(gc, promotion)("Promotion failed"); 700 // Add to-space to the list of space to compact 701 // when a promotion failure has occurred. In that 702 // case there can be live objects in to-space 703 // as a result of a partial evacuation of eden 704 // and from-space. 705 swap_spaces(); // For uniformity wrt ParNewGeneration. 706 from()->set_next_compaction_space(to()); 707 gch->set_incremental_collection_failed(); 708 709 // Inform the next generation that a promotion failure occurred. 710 _old_gen->promotion_failure_occurred(); 711 gc_tracer.report_promotion_failed(_promotion_failed_info); 712 713 // Reset the PromotionFailureALot counters. 714 NOT_PRODUCT(gch->reset_promotion_should_fail();) 715 } 716 // We should have processed and cleared all the preserved marks. 717 _preserved_marks_set.reclaim(); 718 // set new iteration safe limit for the survivor spaces 719 from()->set_concurrent_iteration_safe_limit(from()->top()); 720 to()->set_concurrent_iteration_safe_limit(to()->top()); 721 722 // We need to use a monotonically non-decreasing time in ms 723 // or we will see time-warp warnings and os::javaTimeMillis() 724 // does not guarantee monotonicity. 725 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 726 update_time_of_last_gc(now); 727 728 gch->trace_heap_after_gc(&gc_tracer); 729 730 _gc_timer->register_gc_end(); 731 732 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 733 } 734 735 void DefNewGeneration::init_assuming_no_promotion_failure() { 736 _promotion_failed = false; 737 _promotion_failed_info.reset(); 738 from()->set_next_compaction_space(NULL); 739 } 740 741 void DefNewGeneration::remove_forwarding_pointers() { 742 RemoveForwardedPointerClosure rspc; 743 eden()->object_iterate(&rspc); 744 from()->object_iterate(&rspc); 745 746 SharedRestorePreservedMarksTaskExecutor task_executor(GenCollectedHeap::heap()->workers()); 747 _preserved_marks_set.restore(&task_executor); 748 } 749 750 void DefNewGeneration::handle_promotion_failure(oop old) { 751 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size()); 752 753 _promotion_failed = true; 754 _promotion_failed_info.register_copy_failure(old->size()); 755 _preserved_marks_set.get()->push_if_necessary(old, old->mark()); 756 // forward to self 757 old->forward_to(old); 758 759 _promo_failure_scan_stack.push(old); 760 761 if (!_promo_failure_drain_in_progress) { 762 // prevent recursion in copy_to_survivor_space() 763 _promo_failure_drain_in_progress = true; 764 drain_promo_failure_scan_stack(); 765 _promo_failure_drain_in_progress = false; 766 } 767 } 768 769 oop DefNewGeneration::copy_to_survivor_space(oop old) { 770 assert(is_in_reserved(old) && !old->is_forwarded(), 771 "shouldn't be scavenging this oop"); 772 size_t s = old->size(); 773 oop obj = NULL; 774 775 // Try allocating obj in to-space (unless too old) 776 if (old->age() < tenuring_threshold()) { 777 obj = (oop) to()->allocate_aligned(s); 778 } 779 780 // Otherwise try allocating obj tenured 781 if (obj == NULL) { 782 obj = _old_gen->promote(old, s); 783 if (obj == NULL) { 784 handle_promotion_failure(old); 785 return old; 786 } 787 } else { 788 // Prefetch beyond obj 789 const intx interval = PrefetchCopyIntervalInBytes; 790 Prefetch::write(obj, interval); 791 792 // Copy obj 793 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 794 795 // Increment age if obj still in new generation 796 obj->incr_age(); 797 age_table()->add(obj, s); 798 } 799 800 // Done, insert forward pointer to obj in this header 801 old->forward_to(obj); 802 803 return obj; 804 } 805 806 void DefNewGeneration::drain_promo_failure_scan_stack() { 807 while (!_promo_failure_scan_stack.is_empty()) { 808 oop obj = _promo_failure_scan_stack.pop(); 809 obj->oop_iterate(_promo_failure_scan_stack_closure); 810 } 811 } 812 813 void DefNewGeneration::save_marks() { 814 eden()->set_saved_mark(); 815 to()->set_saved_mark(); 816 from()->set_saved_mark(); 817 } 818 819 820 void DefNewGeneration::reset_saved_marks() { 821 eden()->reset_saved_mark(); 822 to()->reset_saved_mark(); 823 from()->reset_saved_mark(); 824 } 825 826 827 bool DefNewGeneration::no_allocs_since_save_marks() { 828 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 829 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 830 return to()->saved_mark_at_top(); 831 } 832 833 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ 834 \ 835 void DefNewGeneration:: \ 836 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ 837 cl->set_generation(this); \ 838 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \ 839 to()->oop_since_save_marks_iterate##nv_suffix(cl); \ 840 from()->oop_since_save_marks_iterate##nv_suffix(cl); \ 841 cl->reset_generation(); \ 842 save_marks(); \ 843 } 844 845 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN) 846 847 #undef DefNew_SINCE_SAVE_MARKS_DEFN 848 849 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 850 size_t max_alloc_words) { 851 if (requestor == this || _promotion_failed) { 852 return; 853 } 854 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation"); 855 856 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 857 if (to_space->top() > to_space->bottom()) { 858 trace("to_space not empty when contribute_scratch called"); 859 } 860 */ 861 862 ContiguousSpace* to_space = to(); 863 assert(to_space->end() >= to_space->top(), "pointers out of order"); 864 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 865 if (free_words >= MinFreeScratchWords) { 866 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 867 sb->num_words = free_words; 868 sb->next = list; 869 list = sb; 870 } 871 } 872 873 void DefNewGeneration::reset_scratch() { 874 // If contributing scratch in to_space, mangle all of 875 // to_space if ZapUnusedHeapArea. This is needed because 876 // top is not maintained while using to-space as scratch. 877 if (ZapUnusedHeapArea) { 878 to()->mangle_unused_area_complete(); 879 } 880 } 881 882 bool DefNewGeneration::collection_attempt_is_safe() { 883 if (!to()->is_empty()) { 884 log_trace(gc)(":: to is not empty ::"); 885 return false; 886 } 887 if (_old_gen == NULL) { 888 GenCollectedHeap* gch = GenCollectedHeap::heap(); 889 _old_gen = gch->old_gen(); 890 } 891 return _old_gen->promotion_attempt_is_safe(used()); 892 } 893 894 void DefNewGeneration::gc_epilogue(bool full) { 895 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 896 897 assert(!GCLocker::is_active(), "We should not be executing here"); 898 // Check if the heap is approaching full after a collection has 899 // been done. Generally the young generation is empty at 900 // a minimum at the end of a collection. If it is not, then 901 // the heap is approaching full. 902 GenCollectedHeap* gch = GenCollectedHeap::heap(); 903 if (full) { 904 DEBUG_ONLY(seen_incremental_collection_failed = false;) 905 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 906 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 907 GCCause::to_string(gch->gc_cause())); 908 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 909 set_should_allocate_from_space(); // we seem to be running out of space 910 } else { 911 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 912 GCCause::to_string(gch->gc_cause())); 913 gch->clear_incremental_collection_failed(); // We just did a full collection 914 clear_should_allocate_from_space(); // if set 915 } 916 } else { 917 #ifdef ASSERT 918 // It is possible that incremental_collection_failed() == true 919 // here, because an attempted scavenge did not succeed. The policy 920 // is normally expected to cause a full collection which should 921 // clear that condition, so we should not be here twice in a row 922 // with incremental_collection_failed() == true without having done 923 // a full collection in between. 924 if (!seen_incremental_collection_failed && 925 gch->incremental_collection_failed()) { 926 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 927 GCCause::to_string(gch->gc_cause())); 928 seen_incremental_collection_failed = true; 929 } else if (seen_incremental_collection_failed) { 930 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 931 GCCause::to_string(gch->gc_cause())); 932 assert(gch->gc_cause() == GCCause::_scavenge_alot || 933 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 934 !gch->incremental_collection_failed(), 935 "Twice in a row"); 936 seen_incremental_collection_failed = false; 937 } 938 #endif // ASSERT 939 } 940 941 if (ZapUnusedHeapArea) { 942 eden()->check_mangled_unused_area_complete(); 943 from()->check_mangled_unused_area_complete(); 944 to()->check_mangled_unused_area_complete(); 945 } 946 947 if (!CleanChunkPoolAsync) { 948 Chunk::clean_chunk_pool(); 949 } 950 951 // update the generation and space performance counters 952 update_counters(); 953 gch->gen_policy()->counters()->update_counters(); 954 } 955 956 void DefNewGeneration::record_spaces_top() { 957 assert(ZapUnusedHeapArea, "Not mangling unused space"); 958 eden()->set_top_for_allocations(); 959 to()->set_top_for_allocations(); 960 from()->set_top_for_allocations(); 961 } 962 963 void DefNewGeneration::ref_processor_init() { 964 Generation::ref_processor_init(); 965 } 966 967 968 void DefNewGeneration::update_counters() { 969 if (UsePerfData) { 970 _eden_counters->update_all(); 971 _from_counters->update_all(); 972 _to_counters->update_all(); 973 _gen_counters->update_all(); 974 } 975 } 976 977 void DefNewGeneration::verify() { 978 eden()->verify(); 979 from()->verify(); 980 to()->verify(); 981 } 982 983 void DefNewGeneration::print_on(outputStream* st) const { 984 Generation::print_on(st); 985 st->print(" eden"); 986 eden()->print_on(st); 987 st->print(" from"); 988 from()->print_on(st); 989 st->print(" to "); 990 to()->print_on(st); 991 } 992 993 994 const char* DefNewGeneration::name() const { 995 return "def new generation"; 996 } 997 998 // Moved from inline file as they are not called inline 999 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 1000 return eden(); 1001 } 1002 1003 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 1004 // This is the slow-path allocation for the DefNewGeneration. 1005 // Most allocations are fast-path in compiled code. 1006 // We try to allocate from the eden. If that works, we are happy. 1007 // Note that since DefNewGeneration supports lock-free allocation, we 1008 // have to use it here, as well. 1009 HeapWord* result = eden()->par_allocate(word_size); 1010 if (result != NULL) { 1011 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1012 _old_gen->sample_eden_chunk(); 1013 } 1014 } else { 1015 // If the eden is full and the last collection bailed out, we are running 1016 // out of heap space, and we try to allocate the from-space, too. 1017 // allocate_from_space can't be inlined because that would introduce a 1018 // circular dependency at compile time. 1019 result = allocate_from_space(word_size); 1020 } 1021 return result; 1022 } 1023 1024 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 1025 bool is_tlab) { 1026 HeapWord* res = eden()->par_allocate(word_size); 1027 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1028 _old_gen->sample_eden_chunk(); 1029 } 1030 return res; 1031 } 1032 1033 size_t DefNewGeneration::tlab_capacity() const { 1034 return eden()->capacity(); 1035 } 1036 1037 size_t DefNewGeneration::tlab_used() const { 1038 return eden()->used(); 1039 } 1040 1041 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1042 return unsafe_max_alloc_nogc(); 1043 }