1 /* 2 * Copyright (c) 2001, 2015, 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/collectorCounters.hpp" 28 #include "gc/shared/gcHeapSummary.hpp" 29 #include "gc/shared/gcLocker.inline.hpp" 30 #include "gc/shared/gcPolicyCounters.hpp" 31 #include "gc/shared/gcTimer.hpp" 32 #include "gc/shared/gcTrace.hpp" 33 #include "gc/shared/gcTraceTime.hpp" 34 #include "gc/shared/genCollectedHeap.hpp" 35 #include "gc/shared/genOopClosures.inline.hpp" 36 #include "gc/shared/genRemSet.hpp" 37 #include "gc/shared/generationSpec.hpp" 38 #include "gc/shared/referencePolicy.hpp" 39 #include "gc/shared/space.inline.hpp" 40 #include "gc/shared/spaceDecorator.hpp" 41 #include "gc/shared/strongRootsScope.hpp" 42 #include "memory/iterator.hpp" 43 #include "oops/instanceRefKlass.hpp" 44 #include "oops/oop.inline.hpp" 45 #include "runtime/atomic.inline.hpp" 46 #include "runtime/java.hpp" 47 #include "runtime/prefetch.inline.hpp" 48 #include "runtime/thread.inline.hpp" 49 #include "utilities/copy.hpp" 50 #include "utilities/globalDefinitions.hpp" 51 #include "utilities/stack.inline.hpp" 52 #if INCLUDE_ALL_GCS 53 #include "gc/cms/parOopClosures.hpp" 54 #endif 55 56 // 57 // DefNewGeneration functions. 58 59 // Methods of protected closure types. 60 61 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) { 62 assert(_young_gen->kind() == Generation::ParNew || 63 _young_gen->kind() == Generation::DefNew, "Expected the young generation here"); 64 } 65 66 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 67 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded(); 68 } 69 70 DefNewGeneration::KeepAliveClosure:: 71 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 72 GenRemSet* rs = GenCollectedHeap::heap()->rem_set(); 73 _rs = (CardTableRS*)rs; 74 } 75 76 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 77 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 78 79 80 DefNewGeneration::FastKeepAliveClosure:: 81 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 82 DefNewGeneration::KeepAliveClosure(cl) { 83 _boundary = g->reserved().end(); 84 } 85 86 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 87 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 88 89 DefNewGeneration::EvacuateFollowersClosure:: 90 EvacuateFollowersClosure(GenCollectedHeap* gch, 91 ScanClosure* cur, 92 ScanClosure* older) : 93 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older) 94 {} 95 96 void DefNewGeneration::EvacuateFollowersClosure::do_void() { 97 do { 98 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older); 99 } while (!_gch->no_allocs_since_save_marks()); 100 } 101 102 DefNewGeneration::FastEvacuateFollowersClosure:: 103 FastEvacuateFollowersClosure(GenCollectedHeap* gch, 104 FastScanClosure* cur, 105 FastScanClosure* older) : 106 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older) 107 { 108 assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew"); 109 _young_gen = (DefNewGeneration*)_gch->young_gen(); 110 } 111 112 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 113 do { 114 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older); 115 } while (!_gch->no_allocs_since_save_marks()); 116 guarantee(_young_gen->promo_failure_scan_is_complete(), "Failed to finish scan"); 117 } 118 119 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) : 120 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 121 { 122 _boundary = _g->reserved().end(); 123 } 124 125 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); } 126 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); } 127 128 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 129 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 130 { 131 _boundary = _g->reserved().end(); 132 } 133 134 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); } 135 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); } 136 137 void KlassScanClosure::do_klass(Klass* klass) { 138 #ifndef PRODUCT 139 if (TraceScavenge) { 140 ResourceMark rm; 141 gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s", 142 p2i(klass), 143 klass->external_name(), 144 klass->has_modified_oops() ? "true" : "false"); 145 } 146 #endif 147 148 // If the klass has not been dirtied we know that there's 149 // no references into the young gen and we can skip it. 150 if (klass->has_modified_oops()) { 151 if (_accumulate_modified_oops) { 152 klass->accumulate_modified_oops(); 153 } 154 155 // Clear this state since we're going to scavenge all the metadata. 156 klass->clear_modified_oops(); 157 158 // Tell the closure which Klass is being scanned so that it can be dirtied 159 // if oops are left pointing into the young gen. 160 _scavenge_closure->set_scanned_klass(klass); 161 162 klass->oops_do(_scavenge_closure); 163 164 _scavenge_closure->set_scanned_klass(NULL); 165 } 166 } 167 168 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 169 _g(g) 170 { 171 _boundary = _g->reserved().end(); 172 } 173 174 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); } 175 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); } 176 177 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); } 178 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); } 179 180 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure, 181 KlassRemSet* klass_rem_set) 182 : _scavenge_closure(scavenge_closure), 183 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {} 184 185 186 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 187 size_t initial_size, 188 const char* policy) 189 : Generation(rs, initial_size), 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->barrier_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 (GC_locker::is_active()) { 365 if (PrintGC && Verbose) { 366 gclog_or_tty->print_cr("Garbage collection disabled, " 367 "expanded heap instead"); 368 } 369 } 370 371 return success; 372 } 373 374 void DefNewGeneration::compute_new_size() { 375 // This is called after a GC that includes the old generation, so from-space 376 // will normally be empty. 377 // Note that we check both spaces, since if scavenge failed they revert roles. 378 // If not we bail out (otherwise we would have to relocate the objects). 379 if (!from()->is_empty() || !to()->is_empty()) { 380 return; 381 } 382 383 GenCollectedHeap* gch = GenCollectedHeap::heap(); 384 385 size_t old_size = gch->old_gen()->capacity(); 386 size_t new_size_before = _virtual_space.committed_size(); 387 size_t min_new_size = spec()->init_size(); 388 size_t max_new_size = reserved().byte_size(); 389 assert(min_new_size <= new_size_before && 390 new_size_before <= max_new_size, 391 "just checking"); 392 // All space sizes must be multiples of Generation::GenGrain. 393 size_t alignment = Generation::GenGrain; 394 395 // Compute desired new generation size based on NewRatio and 396 // NewSizeThreadIncrease 397 size_t desired_new_size = old_size/NewRatio; 398 int threads_count = Threads::number_of_non_daemon_threads(); 399 size_t thread_increase_size = threads_count * NewSizeThreadIncrease; 400 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment); 401 402 // Adjust new generation size 403 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size); 404 assert(desired_new_size <= max_new_size, "just checking"); 405 406 bool changed = false; 407 if (desired_new_size > new_size_before) { 408 size_t change = desired_new_size - new_size_before; 409 assert(change % alignment == 0, "just checking"); 410 if (expand(change)) { 411 changed = true; 412 } 413 // If the heap failed to expand to the desired size, 414 // "changed" will be false. If the expansion failed 415 // (and at this point it was expected to succeed), 416 // ignore the failure (leaving "changed" as false). 417 } 418 if (desired_new_size < new_size_before && eden()->is_empty()) { 419 // bail out of shrinking if objects in eden 420 size_t change = new_size_before - desired_new_size; 421 assert(change % alignment == 0, "just checking"); 422 _virtual_space.shrink_by(change); 423 changed = true; 424 } 425 if (changed) { 426 // The spaces have already been mangled at this point but 427 // may not have been cleared (set top = bottom) and should be. 428 // Mangling was done when the heap was being expanded. 429 compute_space_boundaries(eden()->used(), 430 SpaceDecorator::Clear, 431 SpaceDecorator::DontMangle); 432 MemRegion cmr((HeapWord*)_virtual_space.low(), 433 (HeapWord*)_virtual_space.high()); 434 gch->barrier_set()->resize_covered_region(cmr); 435 if (Verbose && PrintGC) { 436 size_t new_size_after = _virtual_space.committed_size(); 437 size_t eden_size_after = eden()->capacity(); 438 size_t survivor_size_after = from()->capacity(); 439 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->" 440 SIZE_FORMAT "K [eden=" 441 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 442 new_size_before/K, new_size_after/K, 443 eden_size_after/K, survivor_size_after/K); 444 if (WizardMode) { 445 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]", 446 thread_increase_size/K, threads_count); 447 } 448 gclog_or_tty->cr(); 449 } 450 } 451 } 452 453 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) { 454 assert(false, "NYI -- are you sure you want to call this?"); 455 } 456 457 458 size_t DefNewGeneration::capacity() const { 459 return eden()->capacity() 460 + from()->capacity(); // to() is only used during scavenge 461 } 462 463 464 size_t DefNewGeneration::used() const { 465 return eden()->used() 466 + from()->used(); // to() is only used during scavenge 467 } 468 469 470 size_t DefNewGeneration::free() const { 471 return eden()->free() 472 + from()->free(); // to() is only used during scavenge 473 } 474 475 size_t DefNewGeneration::max_capacity() const { 476 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment(); 477 const size_t reserved_bytes = reserved().byte_size(); 478 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment); 479 } 480 481 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 482 return eden()->free(); 483 } 484 485 size_t DefNewGeneration::capacity_before_gc() const { 486 return eden()->capacity(); 487 } 488 489 size_t DefNewGeneration::contiguous_available() const { 490 return eden()->free(); 491 } 492 493 494 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); } 495 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 496 497 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 498 eden()->object_iterate(blk); 499 from()->object_iterate(blk); 500 } 501 502 503 void DefNewGeneration::space_iterate(SpaceClosure* blk, 504 bool usedOnly) { 505 blk->do_space(eden()); 506 blk->do_space(from()); 507 blk->do_space(to()); 508 } 509 510 // The last collection bailed out, we are running out of heap space, 511 // so we try to allocate the from-space, too. 512 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 513 HeapWord* result = NULL; 514 if (Verbose && PrintGCDetails) { 515 gclog_or_tty->print("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):" 516 " will_fail: %s" 517 " heap_lock: %s" 518 " free: " SIZE_FORMAT, 519 size, 520 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 521 "true" : "false", 522 Heap_lock->is_locked() ? "locked" : "unlocked", 523 from()->free()); 524 } 525 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) { 526 if (Heap_lock->owned_by_self() || 527 (SafepointSynchronize::is_at_safepoint() && 528 Thread::current()->is_VM_thread())) { 529 // If the Heap_lock is not locked by this thread, this will be called 530 // again later with the Heap_lock held. 531 result = from()->allocate(size); 532 } else if (PrintGC && Verbose) { 533 gclog_or_tty->print_cr(" Heap_lock is not owned by self"); 534 } 535 } else if (PrintGC && Verbose) { 536 gclog_or_tty->print_cr(" should_allocate_from_space: NOT"); 537 } 538 if (PrintGC && Verbose) { 539 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object"); 540 } 541 return result; 542 } 543 544 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 545 bool is_tlab, 546 bool parallel) { 547 // We don't attempt to expand the young generation (but perhaps we should.) 548 return allocate(size, is_tlab); 549 } 550 551 void DefNewGeneration::adjust_desired_tenuring_threshold() { 552 // Set the desired survivor size to half the real survivor space 553 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->collector_policy()->counters(); 554 _tenuring_threshold = 555 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, gc_counters); 556 } 557 558 void DefNewGeneration::collect(bool full, 559 bool clear_all_soft_refs, 560 size_t size, 561 bool is_tlab) { 562 assert(full || size > 0, "otherwise we don't want to collect"); 563 564 GenCollectedHeap* gch = GenCollectedHeap::heap(); 565 566 _gc_timer->register_gc_start(); 567 DefNewTracer gc_tracer; 568 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start()); 569 570 _old_gen = gch->old_gen(); 571 572 // If the next generation is too full to accommodate promotion 573 // from this generation, pass on collection; let the next generation 574 // do it. 575 if (!collection_attempt_is_safe()) { 576 if (Verbose && PrintGCDetails) { 577 gclog_or_tty->print(" :: Collection attempt not safe :: "); 578 } 579 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 580 return; 581 } 582 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 583 584 init_assuming_no_promotion_failure(); 585 586 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL); 587 // Capture heap used before collection (for printing). 588 size_t gch_prev_used = gch->used(); 589 590 gch->trace_heap_before_gc(&gc_tracer); 591 592 // These can be shared for all code paths 593 IsAliveClosure is_alive(this); 594 ScanWeakRefClosure scan_weak_ref(this); 595 596 age_table()->clear(); 597 to()->clear(SpaceDecorator::Mangle); 598 599 gch->rem_set()->prepare_for_younger_refs_iterate(false); 600 601 assert(gch->no_allocs_since_save_marks(), 602 "save marks have not been newly set."); 603 604 // Not very pretty. 605 CollectorPolicy* cp = gch->collector_policy(); 606 607 FastScanClosure fsc_with_no_gc_barrier(this, false); 608 FastScanClosure fsc_with_gc_barrier(this, true); 609 610 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier, 611 gch->rem_set()->klass_rem_set()); 612 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure, 613 &fsc_with_no_gc_barrier, 614 false); 615 616 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 617 FastEvacuateFollowersClosure evacuate_followers(gch, 618 &fsc_with_no_gc_barrier, 619 &fsc_with_gc_barrier); 620 621 assert(gch->no_allocs_since_save_marks(), 622 "save marks have not been newly set."); 623 624 { 625 // DefNew needs to run with n_threads == 0, to make sure the serial 626 // version of the card table scanning code is used. 627 // See: CardTableModRefBSForCTRS::non_clean_card_iterate_possibly_parallel. 628 StrongRootsScope srs(0); 629 630 gch->gen_process_roots(&srs, 631 GenCollectedHeap::YoungGen, 632 true, // Process younger gens, if any, 633 // as strong roots. 634 GenCollectedHeap::SO_ScavengeCodeCache, 635 GenCollectedHeap::StrongAndWeakRoots, 636 &fsc_with_no_gc_barrier, 637 &fsc_with_gc_barrier, 638 &cld_scan_closure); 639 } 640 641 // "evacuate followers". 642 evacuate_followers.do_void(); 643 644 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 645 ReferenceProcessor* rp = ref_processor(); 646 rp->setup_policy(clear_all_soft_refs); 647 const ReferenceProcessorStats& stats = 648 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 649 NULL, _gc_timer); 650 gc_tracer.report_gc_reference_stats(stats); 651 652 if (!_promotion_failed) { 653 // Swap the survivor spaces. 654 eden()->clear(SpaceDecorator::Mangle); 655 from()->clear(SpaceDecorator::Mangle); 656 if (ZapUnusedHeapArea) { 657 // This is now done here because of the piece-meal mangling which 658 // can check for valid mangling at intermediate points in the 659 // collection(s). When a young collection fails to collect 660 // sufficient space resizing of the young generation can occur 661 // an redistribute the spaces in the young generation. Mangle 662 // here so that unzapped regions don't get distributed to 663 // other spaces. 664 to()->mangle_unused_area(); 665 } 666 swap_spaces(); 667 668 assert(to()->is_empty(), "to space should be empty now"); 669 670 adjust_desired_tenuring_threshold(); 671 672 // A successful scavenge should restart the GC time limit count which is 673 // for full GC's. 674 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); 675 size_policy->reset_gc_overhead_limit_count(); 676 assert(!gch->incremental_collection_failed(), "Should be clear"); 677 } else { 678 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 679 _promo_failure_scan_stack.clear(true); // Clear cached segments. 680 681 remove_forwarding_pointers(); 682 if (PrintGCDetails) { 683 gclog_or_tty->print(" (promotion failed) "); 684 } 685 // Add to-space to the list of space to compact 686 // when a promotion failure has occurred. In that 687 // case there can be live objects in to-space 688 // as a result of a partial evacuation of eden 689 // and from-space. 690 swap_spaces(); // For uniformity wrt ParNewGeneration. 691 from()->set_next_compaction_space(to()); 692 gch->set_incremental_collection_failed(); 693 694 // Inform the next generation that a promotion failure occurred. 695 _old_gen->promotion_failure_occurred(); 696 gc_tracer.report_promotion_failed(_promotion_failed_info); 697 698 // Reset the PromotionFailureALot counters. 699 NOT_PRODUCT(gch->reset_promotion_should_fail();) 700 } 701 if (PrintGC && !PrintGCDetails) { 702 gch->print_heap_change(gch_prev_used); 703 } 704 // set new iteration safe limit for the survivor spaces 705 from()->set_concurrent_iteration_safe_limit(from()->top()); 706 to()->set_concurrent_iteration_safe_limit(to()->top()); 707 708 // We need to use a monotonically non-decreasing time in ms 709 // or we will see time-warp warnings and os::javaTimeMillis() 710 // does not guarantee monotonicity. 711 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 712 update_time_of_last_gc(now); 713 714 gch->trace_heap_after_gc(&gc_tracer); 715 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 716 717 _gc_timer->register_gc_end(); 718 719 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 720 } 721 722 class RemoveForwardPointerClosure: public ObjectClosure { 723 public: 724 void do_object(oop obj) { 725 obj->init_mark(); 726 } 727 }; 728 729 void DefNewGeneration::init_assuming_no_promotion_failure() { 730 _promotion_failed = false; 731 _promotion_failed_info.reset(); 732 from()->set_next_compaction_space(NULL); 733 } 734 735 void DefNewGeneration::remove_forwarding_pointers() { 736 RemoveForwardPointerClosure rspc; 737 eden()->object_iterate(&rspc); 738 from()->object_iterate(&rspc); 739 740 // Now restore saved marks, if any. 741 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(), 742 "should be the same"); 743 while (!_objs_with_preserved_marks.is_empty()) { 744 oop obj = _objs_with_preserved_marks.pop(); 745 markOop m = _preserved_marks_of_objs.pop(); 746 obj->set_mark(m); 747 } 748 _objs_with_preserved_marks.clear(true); 749 _preserved_marks_of_objs.clear(true); 750 } 751 752 void DefNewGeneration::preserve_mark(oop obj, markOop m) { 753 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj), 754 "Oversaving!"); 755 _objs_with_preserved_marks.push(obj); 756 _preserved_marks_of_objs.push(m); 757 } 758 759 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) { 760 if (m->must_be_preserved_for_promotion_failure(obj)) { 761 preserve_mark(obj, m); 762 } 763 } 764 765 void DefNewGeneration::handle_promotion_failure(oop old) { 766 if (PrintPromotionFailure && !_promotion_failed) { 767 gclog_or_tty->print(" (promotion failure size = %d) ", 768 old->size()); 769 } 770 _promotion_failed = true; 771 _promotion_failed_info.register_copy_failure(old->size()); 772 preserve_mark_if_necessary(old, old->mark()); 773 // forward to self 774 old->forward_to(old); 775 776 _promo_failure_scan_stack.push(old); 777 778 if (!_promo_failure_drain_in_progress) { 779 // prevent recursion in copy_to_survivor_space() 780 _promo_failure_drain_in_progress = true; 781 drain_promo_failure_scan_stack(); 782 _promo_failure_drain_in_progress = false; 783 } 784 } 785 786 oop DefNewGeneration::copy_to_survivor_space(oop old) { 787 assert(is_in_reserved(old) && !old->is_forwarded(), 788 "shouldn't be scavenging this oop"); 789 size_t s = old->size(); 790 oop obj = NULL; 791 792 // Try allocating obj in to-space (unless too old) 793 if (old->age() < tenuring_threshold()) { 794 obj = (oop) to()->allocate_aligned(s); 795 } 796 797 // Otherwise try allocating obj tenured 798 if (obj == NULL) { 799 obj = _old_gen->promote(old, s); 800 if (obj == NULL) { 801 handle_promotion_failure(old); 802 return old; 803 } 804 } else { 805 // Prefetch beyond obj 806 const intx interval = PrefetchCopyIntervalInBytes; 807 Prefetch::write(obj, interval); 808 809 // Copy obj 810 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 811 812 // Increment age if obj still in new generation 813 obj->incr_age(); 814 age_table()->add(obj, s); 815 } 816 817 // Done, insert forward pointer to obj in this header 818 old->forward_to(obj); 819 820 return obj; 821 } 822 823 void DefNewGeneration::drain_promo_failure_scan_stack() { 824 while (!_promo_failure_scan_stack.is_empty()) { 825 oop obj = _promo_failure_scan_stack.pop(); 826 obj->oop_iterate(_promo_failure_scan_stack_closure); 827 } 828 } 829 830 void DefNewGeneration::save_marks() { 831 eden()->set_saved_mark(); 832 to()->set_saved_mark(); 833 from()->set_saved_mark(); 834 } 835 836 837 void DefNewGeneration::reset_saved_marks() { 838 eden()->reset_saved_mark(); 839 to()->reset_saved_mark(); 840 from()->reset_saved_mark(); 841 } 842 843 844 bool DefNewGeneration::no_allocs_since_save_marks() { 845 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 846 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 847 return to()->saved_mark_at_top(); 848 } 849 850 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ 851 \ 852 void DefNewGeneration:: \ 853 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ 854 cl->set_generation(this); \ 855 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \ 856 to()->oop_since_save_marks_iterate##nv_suffix(cl); \ 857 from()->oop_since_save_marks_iterate##nv_suffix(cl); \ 858 cl->reset_generation(); \ 859 save_marks(); \ 860 } 861 862 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN) 863 864 #undef DefNew_SINCE_SAVE_MARKS_DEFN 865 866 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 867 size_t max_alloc_words) { 868 if (requestor == this || _promotion_failed) { 869 return; 870 } 871 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation"); 872 873 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 874 if (to_space->top() > to_space->bottom()) { 875 trace("to_space not empty when contribute_scratch called"); 876 } 877 */ 878 879 ContiguousSpace* to_space = to(); 880 assert(to_space->end() >= to_space->top(), "pointers out of order"); 881 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 882 if (free_words >= MinFreeScratchWords) { 883 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 884 sb->num_words = free_words; 885 sb->next = list; 886 list = sb; 887 } 888 } 889 890 void DefNewGeneration::reset_scratch() { 891 // If contributing scratch in to_space, mangle all of 892 // to_space if ZapUnusedHeapArea. This is needed because 893 // top is not maintained while using to-space as scratch. 894 if (ZapUnusedHeapArea) { 895 to()->mangle_unused_area_complete(); 896 } 897 } 898 899 bool DefNewGeneration::collection_attempt_is_safe() { 900 if (!to()->is_empty()) { 901 if (Verbose && PrintGCDetails) { 902 gclog_or_tty->print(" :: to is not empty :: "); 903 } 904 return false; 905 } 906 if (_old_gen == NULL) { 907 GenCollectedHeap* gch = GenCollectedHeap::heap(); 908 _old_gen = gch->old_gen(); 909 } 910 return _old_gen->promotion_attempt_is_safe(used()); 911 } 912 913 void DefNewGeneration::gc_epilogue(bool full) { 914 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 915 916 assert(!GC_locker::is_active(), "We should not be executing here"); 917 // Check if the heap is approaching full after a collection has 918 // been done. Generally the young generation is empty at 919 // a minimum at the end of a collection. If it is not, then 920 // the heap is approaching full. 921 GenCollectedHeap* gch = GenCollectedHeap::heap(); 922 if (full) { 923 DEBUG_ONLY(seen_incremental_collection_failed = false;) 924 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 925 if (Verbose && PrintGCDetails) { 926 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 927 GCCause::to_string(gch->gc_cause())); 928 } 929 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 930 set_should_allocate_from_space(); // we seem to be running out of space 931 } else { 932 if (Verbose && PrintGCDetails) { 933 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 934 GCCause::to_string(gch->gc_cause())); 935 } 936 gch->clear_incremental_collection_failed(); // We just did a full collection 937 clear_should_allocate_from_space(); // if set 938 } 939 } else { 940 #ifdef ASSERT 941 // It is possible that incremental_collection_failed() == true 942 // here, because an attempted scavenge did not succeed. The policy 943 // is normally expected to cause a full collection which should 944 // clear that condition, so we should not be here twice in a row 945 // with incremental_collection_failed() == true without having done 946 // a full collection in between. 947 if (!seen_incremental_collection_failed && 948 gch->incremental_collection_failed()) { 949 if (Verbose && PrintGCDetails) { 950 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 951 GCCause::to_string(gch->gc_cause())); 952 } 953 seen_incremental_collection_failed = true; 954 } else if (seen_incremental_collection_failed) { 955 if (Verbose && PrintGCDetails) { 956 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 957 GCCause::to_string(gch->gc_cause())); 958 } 959 assert(gch->gc_cause() == GCCause::_scavenge_alot || 960 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 961 !gch->incremental_collection_failed(), 962 "Twice in a row"); 963 seen_incremental_collection_failed = false; 964 } 965 #endif // ASSERT 966 } 967 968 if (ZapUnusedHeapArea) { 969 eden()->check_mangled_unused_area_complete(); 970 from()->check_mangled_unused_area_complete(); 971 to()->check_mangled_unused_area_complete(); 972 } 973 974 if (!CleanChunkPoolAsync) { 975 Chunk::clean_chunk_pool(); 976 } 977 978 // update the generation and space performance counters 979 update_counters(); 980 gch->collector_policy()->counters()->update_counters(); 981 } 982 983 void DefNewGeneration::record_spaces_top() { 984 assert(ZapUnusedHeapArea, "Not mangling unused space"); 985 eden()->set_top_for_allocations(); 986 to()->set_top_for_allocations(); 987 from()->set_top_for_allocations(); 988 } 989 990 void DefNewGeneration::ref_processor_init() { 991 Generation::ref_processor_init(); 992 } 993 994 995 void DefNewGeneration::update_counters() { 996 if (UsePerfData) { 997 _eden_counters->update_all(); 998 _from_counters->update_all(); 999 _to_counters->update_all(); 1000 _gen_counters->update_all(); 1001 } 1002 } 1003 1004 void DefNewGeneration::verify() { 1005 eden()->verify(); 1006 from()->verify(); 1007 to()->verify(); 1008 } 1009 1010 void DefNewGeneration::print_on(outputStream* st) const { 1011 Generation::print_on(st); 1012 st->print(" eden"); 1013 eden()->print_on(st); 1014 st->print(" from"); 1015 from()->print_on(st); 1016 st->print(" to "); 1017 to()->print_on(st); 1018 } 1019 1020 1021 const char* DefNewGeneration::name() const { 1022 return "def new generation"; 1023 } 1024 1025 // Moved from inline file as they are not called inline 1026 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 1027 return eden(); 1028 } 1029 1030 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 1031 // This is the slow-path allocation for the DefNewGeneration. 1032 // Most allocations are fast-path in compiled code. 1033 // We try to allocate from the eden. If that works, we are happy. 1034 // Note that since DefNewGeneration supports lock-free allocation, we 1035 // have to use it here, as well. 1036 HeapWord* result = eden()->par_allocate(word_size); 1037 if (result != NULL) { 1038 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1039 _old_gen->sample_eden_chunk(); 1040 } 1041 } else { 1042 // If the eden is full and the last collection bailed out, we are running 1043 // out of heap space, and we try to allocate the from-space, too. 1044 // allocate_from_space can't be inlined because that would introduce a 1045 // circular dependency at compile time. 1046 result = allocate_from_space(word_size); 1047 } 1048 return result; 1049 } 1050 1051 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 1052 bool is_tlab) { 1053 HeapWord* res = eden()->par_allocate(word_size); 1054 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1055 _old_gen->sample_eden_chunk(); 1056 } 1057 return res; 1058 } 1059 1060 size_t DefNewGeneration::tlab_capacity() const { 1061 return eden()->capacity(); 1062 } 1063 1064 size_t DefNewGeneration::tlab_used() const { 1065 return eden()->used(); 1066 } 1067 1068 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1069 return unsafe_max_alloc_nogc(); 1070 }