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_implementation/shared/collectorCounters.hpp" 27 #include "gc_implementation/shared/gcPolicyCounters.hpp" 28 #include "gc_implementation/shared/gcHeapSummary.hpp" 29 #include "gc_implementation/shared/gcTimer.hpp" 30 #include "gc_implementation/shared/gcTraceTime.hpp" 31 #include "gc_implementation/shared/gcTrace.hpp" 32 #include "gc_implementation/shared/spaceDecorator.hpp" 33 #include "memory/defNewGeneration.inline.hpp" 34 #include "memory/gcLocker.inline.hpp" 35 #include "memory/genCollectedHeap.hpp" 36 #include "memory/genOopClosures.inline.hpp" 37 #include "memory/genRemSet.hpp" 38 #include "memory/generationSpec.hpp" 39 #include "memory/iterator.hpp" 40 #include "memory/referencePolicy.hpp" 41 #include "memory/space.inline.hpp" 42 #include "oops/instanceRefKlass.hpp" 43 #include "oops/oop.inline.hpp" 44 #include "runtime/atomic.inline.hpp" 45 #include "runtime/java.hpp" 46 #include "runtime/prefetch.inline.hpp" 47 #include "runtime/thread.inline.hpp" 48 #include "utilities/copy.hpp" 49 #include "utilities/globalDefinitions.hpp" 50 #include "utilities/stack.inline.hpp" 51 #if INCLUDE_ALL_GCS 52 #include "gc_implementation/parNew/parOopClosures.hpp" 53 #endif 54 55 // 56 // DefNewGeneration functions. 57 58 // Methods of protected closure types. 59 60 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* gen) : _gen(gen) { 61 assert(_gen == GenCollectedHeap::heap()->young_gen(), "Expected the young generation here"); 62 } 63 64 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 65 return (HeapWord*)p >= _gen->reserved().end() || p->is_forwarded(); 66 } 67 68 DefNewGeneration::KeepAliveClosure:: 69 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 70 GenRemSet* rs = GenCollectedHeap::heap()->rem_set(); 71 _rs = (CardTableRS*)rs; 72 } 73 74 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 75 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 76 77 78 DefNewGeneration::FastKeepAliveClosure:: 79 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 80 DefNewGeneration::KeepAliveClosure(cl) { 81 _boundary = g->reserved().end(); 82 } 83 84 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 85 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 86 87 DefNewGeneration::EvacuateFollowersClosure:: 88 EvacuateFollowersClosure(GenCollectedHeap* gch, 89 ScanClosure* cur, 90 ScanClosure* older) : 91 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older) 92 {} 93 94 void DefNewGeneration::EvacuateFollowersClosure::do_void() { 95 do { 96 _gch->oop_since_save_marks_iterate(Generation::Young, _scan_cur_or_nonheap, 97 _scan_older); 98 } while (!_gch->no_allocs_since_save_marks(Generation::Young)); 99 } 100 101 DefNewGeneration::FastEvacuateFollowersClosure:: 102 FastEvacuateFollowersClosure(GenCollectedHeap* gch, 103 FastScanClosure* cur, 104 FastScanClosure* older) : 105 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older) 106 { 107 assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew"); 108 _gen = (DefNewGeneration*)_gch->young_gen(); 109 } 110 111 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 112 do { 113 _gch->oop_since_save_marks_iterate(Generation::Young, _scan_cur_or_nonheap, _scan_older); 114 } while (!_gch->no_allocs_since_save_marks(Generation::Young)); 115 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan"); 116 } 117 118 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) : 119 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 120 { 121 _boundary = _g->reserved().end(); 122 } 123 124 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); } 125 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); } 126 127 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 128 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 129 { 130 _boundary = _g->reserved().end(); 131 } 132 133 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); } 134 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); } 135 136 void KlassScanClosure::do_klass(Klass* klass) { 137 #ifndef PRODUCT 138 if (TraceScavenge) { 139 ResourceMark rm; 140 gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s", 141 p2i(klass), 142 klass->external_name(), 143 klass->has_modified_oops() ? "true" : "false"); 144 } 145 #endif 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 _promo_failure_drain_in_progress(false), 190 _should_allocate_from_space(false) 191 { 192 MemRegion cmr((HeapWord*)_virtual_space.low(), 193 (HeapWord*)_virtual_space.high()); 194 GenCollectedHeap* gch = GenCollectedHeap::heap(); 195 196 gch->barrier_set()->resize_covered_region(cmr); 197 198 _eden_space = new ContiguousSpace(); 199 _from_space = new ContiguousSpace(); 200 _to_space = new ContiguousSpace(); 201 202 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) 203 vm_exit_during_initialization("Could not allocate a new gen space"); 204 205 // Compute the maximum eden and survivor space sizes. These sizes 206 // are computed assuming the entire reserved space is committed. 207 // These values are exported as performance counters. 208 uintx alignment = gch->collector_policy()->space_alignment(); 209 uintx size = _virtual_space.reserved_size(); 210 _max_survivor_size = compute_survivor_size(size, alignment); 211 _max_eden_size = size - (2*_max_survivor_size); 212 213 // allocate the performance counters 214 GenCollectorPolicy* gcp = (GenCollectorPolicy*)gch->collector_policy(); 215 216 // Generation counters -- generation 0, 3 subspaces 217 _gen_counters = new GenerationCounters("new", 0, 3, 218 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space); 219 _gc_counters = new CollectorCounters(policy, 0); 220 221 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 222 _gen_counters); 223 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 224 _gen_counters); 225 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 226 _gen_counters); 227 228 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 229 update_counters(); 230 _old_gen = NULL; 231 _tenuring_threshold = MaxTenuringThreshold; 232 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 233 234 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer(); 235 } 236 237 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 238 bool clear_space, 239 bool mangle_space) { 240 uintx alignment = 241 GenCollectedHeap::heap()->collector_policy()->space_alignment(); 242 243 // If the spaces are being cleared (only done at heap initialization 244 // currently), the survivor spaces need not be empty. 245 // Otherwise, no care is taken for used areas in the survivor spaces 246 // so check. 247 assert(clear_space || (to()->is_empty() && from()->is_empty()), 248 "Initialization of the survivor spaces assumes these are empty"); 249 250 // Compute sizes 251 uintx size = _virtual_space.committed_size(); 252 uintx survivor_size = compute_survivor_size(size, alignment); 253 uintx eden_size = size - (2*survivor_size); 254 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 255 256 if (eden_size < minimum_eden_size) { 257 // May happen due to 64Kb rounding, if so adjust eden size back up 258 minimum_eden_size = align_size_up(minimum_eden_size, alignment); 259 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 260 uintx unaligned_survivor_size = 261 align_size_down(maximum_survivor_size, alignment); 262 survivor_size = MAX2(unaligned_survivor_size, alignment); 263 eden_size = size - (2*survivor_size); 264 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 265 assert(eden_size >= minimum_eden_size, "just checking"); 266 } 267 268 char *eden_start = _virtual_space.low(); 269 char *from_start = eden_start + eden_size; 270 char *to_start = from_start + survivor_size; 271 char *to_end = to_start + survivor_size; 272 273 assert(to_end == _virtual_space.high(), "just checking"); 274 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment"); 275 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment"); 276 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment"); 277 278 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 279 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 280 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 281 282 // A minimum eden size implies that there is a part of eden that 283 // is being used and that affects the initialization of any 284 // newly formed eden. 285 bool live_in_eden = minimum_eden_size > 0; 286 287 // If not clearing the spaces, do some checking to verify that 288 // the space are already mangled. 289 if (!clear_space) { 290 // Must check mangling before the spaces are reshaped. Otherwise, 291 // the bottom or end of one space may have moved into another 292 // a failure of the check may not correctly indicate which space 293 // is not properly mangled. 294 if (ZapUnusedHeapArea) { 295 HeapWord* limit = (HeapWord*) _virtual_space.high(); 296 eden()->check_mangled_unused_area(limit); 297 from()->check_mangled_unused_area(limit); 298 to()->check_mangled_unused_area(limit); 299 } 300 } 301 302 // Reset the spaces for their new regions. 303 eden()->initialize(edenMR, 304 clear_space && !live_in_eden, 305 SpaceDecorator::Mangle); 306 // If clear_space and live_in_eden, we will not have cleared any 307 // portion of eden above its top. This can cause newly 308 // expanded space not to be mangled if using ZapUnusedHeapArea. 309 // We explicitly do such mangling here. 310 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 311 eden()->mangle_unused_area(); 312 } 313 from()->initialize(fromMR, clear_space, mangle_space); 314 to()->initialize(toMR, clear_space, mangle_space); 315 316 // Set next compaction spaces. 317 eden()->set_next_compaction_space(from()); 318 // The to-space is normally empty before a compaction so need 319 // not be considered. The exception is during promotion 320 // failure handling when to-space can contain live objects. 321 from()->set_next_compaction_space(NULL); 322 } 323 324 void DefNewGeneration::swap_spaces() { 325 ContiguousSpace* s = from(); 326 _from_space = to(); 327 _to_space = s; 328 eden()->set_next_compaction_space(from()); 329 // The to-space is normally empty before a compaction so need 330 // not be considered. The exception is during promotion 331 // failure handling when to-space can contain live objects. 332 from()->set_next_compaction_space(NULL); 333 334 if (UsePerfData) { 335 CSpaceCounters* c = _from_counters; 336 _from_counters = _to_counters; 337 _to_counters = c; 338 } 339 } 340 341 bool DefNewGeneration::expand(size_t bytes) { 342 MutexLocker x(ExpandHeap_lock); 343 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 344 bool success = _virtual_space.expand_by(bytes); 345 if (success && ZapUnusedHeapArea) { 346 // Mangle newly committed space immediately because it 347 // can be done here more simply that after the new 348 // spaces have been computed. 349 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 350 MemRegion mangle_region(prev_high, new_high); 351 SpaceMangler::mangle_region(mangle_region); 352 } 353 354 // Do not attempt an expand-to-the reserve size. The 355 // request should properly observe the maximum size of 356 // the generation so an expand-to-reserve should be 357 // unnecessary. Also a second call to expand-to-reserve 358 // value potentially can cause an undue expansion. 359 // For example if the first expand fail for unknown reasons, 360 // but the second succeeds and expands the heap to its maximum 361 // value. 362 if (GC_locker::is_active()) { 363 if (PrintGC && Verbose) { 364 gclog_or_tty->print_cr("Garbage collection disabled, " 365 "expanded heap instead"); 366 } 367 } 368 369 return success; 370 } 371 372 void DefNewGeneration::compute_new_size() { 373 // This is called after a GC that includes the old generation, so from-space 374 // will normally be empty. 375 // Note that we check both spaces, since if scavenge failed they revert roles. 376 // If not we bail out (otherwise we would have to relocate the objects). 377 if (!from()->is_empty() || !to()->is_empty()) { 378 return; 379 } 380 381 GenCollectedHeap* gch = GenCollectedHeap::heap(); 382 383 size_t old_size = gch->old_gen()->capacity(); 384 size_t new_size_before = _virtual_space.committed_size(); 385 size_t min_new_size = spec()->init_size(); 386 size_t max_new_size = reserved().byte_size(); 387 assert(min_new_size <= new_size_before && 388 new_size_before <= max_new_size, 389 "just checking"); 390 // All space sizes must be multiples of Generation::GenGrain. 391 size_t alignment = Generation::GenGrain; 392 393 // Compute desired new generation size based on NewRatio and 394 // NewSizeThreadIncrease 395 size_t desired_new_size = old_size/NewRatio; 396 int threads_count = Threads::number_of_non_daemon_threads(); 397 size_t thread_increase_size = threads_count * NewSizeThreadIncrease; 398 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment); 399 400 // Adjust new generation size 401 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size); 402 assert(desired_new_size <= max_new_size, "just checking"); 403 404 bool changed = false; 405 if (desired_new_size > new_size_before) { 406 size_t change = desired_new_size - new_size_before; 407 assert(change % alignment == 0, "just checking"); 408 if (expand(change)) { 409 changed = true; 410 } 411 // If the heap failed to expand to the desired size, 412 // "changed" will be false. If the expansion failed 413 // (and at this point it was expected to succeed), 414 // ignore the failure (leaving "changed" as false). 415 } 416 if (desired_new_size < new_size_before && eden()->is_empty()) { 417 // bail out of shrinking if objects in eden 418 size_t change = new_size_before - desired_new_size; 419 assert(change % alignment == 0, "just checking"); 420 _virtual_space.shrink_by(change); 421 changed = true; 422 } 423 if (changed) { 424 // The spaces have already been mangled at this point but 425 // may not have been cleared (set top = bottom) and should be. 426 // Mangling was done when the heap was being expanded. 427 compute_space_boundaries(eden()->used(), 428 SpaceDecorator::Clear, 429 SpaceDecorator::DontMangle); 430 MemRegion cmr((HeapWord*)_virtual_space.low(), 431 (HeapWord*)_virtual_space.high()); 432 gch->barrier_set()->resize_covered_region(cmr); 433 if (Verbose && PrintGC) { 434 size_t new_size_after = _virtual_space.committed_size(); 435 size_t eden_size_after = eden()->capacity(); 436 size_t survivor_size_after = from()->capacity(); 437 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->" 438 SIZE_FORMAT "K [eden=" 439 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 440 new_size_before/K, new_size_after/K, 441 eden_size_after/K, survivor_size_after/K); 442 if (WizardMode) { 443 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]", 444 thread_increase_size/K, threads_count); 445 } 446 gclog_or_tty->cr(); 447 } 448 } 449 } 450 451 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) { 452 assert(false, "NYI -- are you sure you want to call this?"); 453 } 454 455 456 size_t DefNewGeneration::capacity() const { 457 return eden()->capacity() 458 + from()->capacity(); // to() is only used during scavenge 459 } 460 461 462 size_t DefNewGeneration::used() const { 463 return eden()->used() 464 + from()->used(); // to() is only used during scavenge 465 } 466 467 468 size_t DefNewGeneration::free() const { 469 return eden()->free() 470 + from()->free(); // to() is only used during scavenge 471 } 472 473 size_t DefNewGeneration::max_capacity() const { 474 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment(); 475 const size_t reserved_bytes = reserved().byte_size(); 476 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment); 477 } 478 479 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 480 return eden()->free(); 481 } 482 483 size_t DefNewGeneration::capacity_before_gc() const { 484 return eden()->capacity(); 485 } 486 487 size_t DefNewGeneration::contiguous_available() const { 488 return eden()->free(); 489 } 490 491 492 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); } 493 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 494 495 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 496 eden()->object_iterate(blk); 497 from()->object_iterate(blk); 498 } 499 500 501 void DefNewGeneration::space_iterate(SpaceClosure* blk, 502 bool usedOnly) { 503 blk->do_space(eden()); 504 blk->do_space(from()); 505 blk->do_space(to()); 506 } 507 508 // The last collection bailed out, we are running out of heap space, 509 // so we try to allocate the from-space, too. 510 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 511 HeapWord* result = NULL; 512 if (Verbose && PrintGCDetails) { 513 gclog_or_tty->print("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):" 514 " will_fail: %s" 515 " heap_lock: %s" 516 " free: " SIZE_FORMAT, 517 size, 518 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 519 "true" : "false", 520 Heap_lock->is_locked() ? "locked" : "unlocked", 521 from()->free()); 522 } 523 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) { 524 if (Heap_lock->owned_by_self() || 525 (SafepointSynchronize::is_at_safepoint() && 526 Thread::current()->is_VM_thread())) { 527 // If the Heap_lock is not locked by this thread, this will be called 528 // again later with the Heap_lock held. 529 result = from()->allocate(size); 530 } else if (PrintGC && Verbose) { 531 gclog_or_tty->print_cr(" Heap_lock is not owned by self"); 532 } 533 } else if (PrintGC && Verbose) { 534 gclog_or_tty->print_cr(" should_allocate_from_space: NOT"); 535 } 536 if (PrintGC && Verbose) { 537 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object"); 538 } 539 return result; 540 } 541 542 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 543 bool is_tlab, 544 bool parallel) { 545 // We don't attempt to expand the young generation (but perhaps we should.) 546 return allocate(size, is_tlab); 547 } 548 549 void DefNewGeneration::adjust_desired_tenuring_threshold() { 550 // Set the desired survivor size to half the real survivor space 551 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->collector_policy()->counters(); 552 _tenuring_threshold = 553 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, gc_counters); 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 GenCollectedHeap* gch = GenCollectedHeap::heap(); 563 564 _gc_timer->register_gc_start(); 565 DefNewTracer gc_tracer; 566 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start()); 567 568 _old_gen = gch->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 if (Verbose && PrintGCDetails) { 575 gclog_or_tty->print(" :: Collection attempt not safe :: "); 576 } 577 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 578 return; 579 } 580 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 581 582 init_assuming_no_promotion_failure(); 583 584 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id()); 585 // Capture heap used before collection (for printing). 586 size_t gch_prev_used = gch->used(); 587 588 gch->trace_heap_before_gc(&gc_tracer); 589 590 // These can be shared for all code paths 591 IsAliveClosure is_alive(this); 592 ScanWeakRefClosure scan_weak_ref(this); 593 594 age_table()->clear(); 595 to()->clear(SpaceDecorator::Mangle); 596 597 gch->rem_set()->prepare_for_younger_refs_iterate(false); 598 599 assert(gch->no_allocs_since_save_marks(Generation::Young), 600 "save marks have not been newly set."); 601 602 // Not very pretty. 603 CollectorPolicy* cp = gch->collector_policy(); 604 605 FastScanClosure fsc_with_no_gc_barrier(this, false); 606 FastScanClosure fsc_with_gc_barrier(this, true); 607 608 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier, 609 gch->rem_set()->klass_rem_set()); 610 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure, 611 &fsc_with_no_gc_barrier, 612 false); 613 614 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 615 FastEvacuateFollowersClosure evacuate_followers(gch, 616 &fsc_with_no_gc_barrier, 617 &fsc_with_gc_barrier); 618 619 assert(gch->no_allocs_since_save_marks(Generation::Young), 620 "save marks have not been newly set."); 621 622 gch->gen_process_roots(Generation::Young, 623 true, // Process younger gens, if any, 624 // as strong roots. 625 true, // activate StrongRootsScope 626 GenCollectedHeap::SO_ScavengeCodeCache, 627 GenCollectedHeap::StrongAndWeakRoots, 628 &fsc_with_no_gc_barrier, 629 &fsc_with_gc_barrier, 630 &cld_scan_closure); 631 632 // "evacuate followers". 633 evacuate_followers.do_void(); 634 635 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 636 ReferenceProcessor* rp = ref_processor(); 637 rp->setup_policy(clear_all_soft_refs); 638 const ReferenceProcessorStats& stats = 639 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 640 NULL, _gc_timer, gc_tracer.gc_id()); 641 gc_tracer.report_gc_reference_stats(stats); 642 643 if (!_promotion_failed) { 644 // Swap the survivor spaces. 645 eden()->clear(SpaceDecorator::Mangle); 646 from()->clear(SpaceDecorator::Mangle); 647 if (ZapUnusedHeapArea) { 648 // This is now done here because of the piece-meal mangling which 649 // can check for valid mangling at intermediate points in the 650 // collection(s). When a minor collection fails to collect 651 // sufficient space resizing of the young generation can occur 652 // an redistribute the spaces in the young generation. Mangle 653 // here so that unzapped regions don't get distributed to 654 // other spaces. 655 to()->mangle_unused_area(); 656 } 657 swap_spaces(); 658 659 assert(to()->is_empty(), "to space should be empty now"); 660 661 adjust_desired_tenuring_threshold(); 662 663 // A successful scavenge should restart the GC time limit count which is 664 // for full GC's. 665 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); 666 size_policy->reset_gc_overhead_limit_count(); 667 assert(!gch->incremental_collection_failed(), "Should be clear"); 668 } else { 669 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 670 _promo_failure_scan_stack.clear(true); // Clear cached segments. 671 672 remove_forwarding_pointers(); 673 if (PrintGCDetails) { 674 gclog_or_tty->print(" (promotion failed) "); 675 } 676 // Add to-space to the list of space to compact 677 // when a promotion failure has occurred. In that 678 // case there can be live objects in to-space 679 // as a result of a partial evacuation of eden 680 // and from-space. 681 swap_spaces(); // For uniformity wrt ParNewGeneration. 682 from()->set_next_compaction_space(to()); 683 gch->set_incremental_collection_failed(); 684 685 // Inform the next generation that a promotion failure occurred. 686 _old_gen->promotion_failure_occurred(); 687 gc_tracer.report_promotion_failed(_promotion_failed_info); 688 689 // Reset the PromotionFailureALot counters. 690 NOT_PRODUCT(gch->reset_promotion_should_fail();) 691 } 692 if (PrintGC && !PrintGCDetails) { 693 gch->print_heap_change(gch_prev_used); 694 } 695 // set new iteration safe limit for the survivor spaces 696 from()->set_concurrent_iteration_safe_limit(from()->top()); 697 to()->set_concurrent_iteration_safe_limit(to()->top()); 698 699 // We need to use a monotonically non-decreasing time in ms 700 // or we will see time-warp warnings and os::javaTimeMillis() 701 // does not guarantee monotonicity. 702 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 703 update_time_of_last_gc(now); 704 705 gch->trace_heap_after_gc(&gc_tracer); 706 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 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 class RemoveForwardPointerClosure: public ObjectClosure { 714 public: 715 void do_object(oop obj) { 716 obj->init_mark(); 717 } 718 }; 719 720 void DefNewGeneration::init_assuming_no_promotion_failure() { 721 _promotion_failed = false; 722 _promotion_failed_info.reset(); 723 from()->set_next_compaction_space(NULL); 724 } 725 726 void DefNewGeneration::remove_forwarding_pointers() { 727 RemoveForwardPointerClosure rspc; 728 eden()->object_iterate(&rspc); 729 from()->object_iterate(&rspc); 730 731 // Now restore saved marks, if any. 732 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(), 733 "should be the same"); 734 while (!_objs_with_preserved_marks.is_empty()) { 735 oop obj = _objs_with_preserved_marks.pop(); 736 markOop m = _preserved_marks_of_objs.pop(); 737 obj->set_mark(m); 738 } 739 _objs_with_preserved_marks.clear(true); 740 _preserved_marks_of_objs.clear(true); 741 } 742 743 void DefNewGeneration::preserve_mark(oop obj, markOop m) { 744 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj), 745 "Oversaving!"); 746 _objs_with_preserved_marks.push(obj); 747 _preserved_marks_of_objs.push(m); 748 } 749 750 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) { 751 if (m->must_be_preserved_for_promotion_failure(obj)) { 752 preserve_mark(obj, m); 753 } 754 } 755 756 void DefNewGeneration::handle_promotion_failure(oop old) { 757 if (PrintPromotionFailure && !_promotion_failed) { 758 gclog_or_tty->print(" (promotion failure size = %d) ", 759 old->size()); 760 } 761 _promotion_failed = true; 762 _promotion_failed_info.register_copy_failure(old->size()); 763 preserve_mark_if_necessary(old, old->mark()); 764 // forward to self 765 old->forward_to(old); 766 767 _promo_failure_scan_stack.push(old); 768 769 if (!_promo_failure_drain_in_progress) { 770 // prevent recursion in copy_to_survivor_space() 771 _promo_failure_drain_in_progress = true; 772 drain_promo_failure_scan_stack(); 773 _promo_failure_drain_in_progress = false; 774 } 775 } 776 777 oop DefNewGeneration::copy_to_survivor_space(oop old) { 778 assert(is_in_reserved(old) && !old->is_forwarded(), 779 "shouldn't be scavenging this oop"); 780 size_t s = old->size(); 781 oop obj = NULL; 782 783 // Try allocating obj in to-space (unless too old) 784 if (old->age() < tenuring_threshold()) { 785 obj = (oop) to()->allocate_aligned(s); 786 } 787 788 // Otherwise try allocating obj tenured 789 if (obj == NULL) { 790 obj = _old_gen->promote(old, s); 791 if (obj == NULL) { 792 handle_promotion_failure(old); 793 return old; 794 } 795 } else { 796 // Prefetch beyond obj 797 const intx interval = PrefetchCopyIntervalInBytes; 798 Prefetch::write(obj, interval); 799 800 // Copy obj 801 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 802 803 // Increment age if obj still in new generation 804 obj->incr_age(); 805 age_table()->add(obj, s); 806 } 807 808 // Done, insert forward pointer to obj in this header 809 old->forward_to(obj); 810 811 return obj; 812 } 813 814 void DefNewGeneration::drain_promo_failure_scan_stack() { 815 while (!_promo_failure_scan_stack.is_empty()) { 816 oop obj = _promo_failure_scan_stack.pop(); 817 obj->oop_iterate(_promo_failure_scan_stack_closure); 818 } 819 } 820 821 void DefNewGeneration::save_marks() { 822 eden()->set_saved_mark(); 823 to()->set_saved_mark(); 824 from()->set_saved_mark(); 825 } 826 827 828 void DefNewGeneration::reset_saved_marks() { 829 eden()->reset_saved_mark(); 830 to()->reset_saved_mark(); 831 from()->reset_saved_mark(); 832 } 833 834 835 bool DefNewGeneration::no_allocs_since_save_marks() { 836 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 837 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 838 return to()->saved_mark_at_top(); 839 } 840 841 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ 842 \ 843 void DefNewGeneration:: \ 844 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ 845 cl->set_generation(this); \ 846 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \ 847 to()->oop_since_save_marks_iterate##nv_suffix(cl); \ 848 from()->oop_since_save_marks_iterate##nv_suffix(cl); \ 849 cl->reset_generation(); \ 850 save_marks(); \ 851 } 852 853 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN) 854 855 #undef DefNew_SINCE_SAVE_MARKS_DEFN 856 857 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 858 size_t max_alloc_words) { 859 if (requestor == this || _promotion_failed) { 860 return; 861 } 862 assert(requestor == GenCollectedHeap::heap()->old_gen(), "We should not call our own generation"); 863 864 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 865 if (to_space->top() > to_space->bottom()) { 866 trace("to_space not empty when contribute_scratch called"); 867 } 868 */ 869 870 ContiguousSpace* to_space = to(); 871 assert(to_space->end() >= to_space->top(), "pointers out of order"); 872 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 873 if (free_words >= MinFreeScratchWords) { 874 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 875 sb->num_words = free_words; 876 sb->next = list; 877 list = sb; 878 } 879 } 880 881 void DefNewGeneration::reset_scratch() { 882 // If contributing scratch in to_space, mangle all of 883 // to_space if ZapUnusedHeapArea. This is needed because 884 // top is not maintained while using to-space as scratch. 885 if (ZapUnusedHeapArea) { 886 to()->mangle_unused_area_complete(); 887 } 888 } 889 890 bool DefNewGeneration::collection_attempt_is_safe() { 891 if (!to()->is_empty()) { 892 if (Verbose && PrintGCDetails) { 893 gclog_or_tty->print(" :: to is not empty :: "); 894 } 895 return false; 896 } 897 if (_old_gen == NULL) { 898 GenCollectedHeap* gch = GenCollectedHeap::heap(); 899 _old_gen = gch->old_gen(); 900 } 901 return _old_gen->promotion_attempt_is_safe(used()); 902 } 903 904 void DefNewGeneration::gc_epilogue(bool full) { 905 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 906 907 assert(!GC_locker::is_active(), "We should not be executing here"); 908 // Check if the heap is approaching full after a collection has 909 // been done. Generally the young generation is empty at 910 // a minimum at the end of a collection. If it is not, then 911 // the heap is approaching full. 912 GenCollectedHeap* gch = GenCollectedHeap::heap(); 913 if (full) { 914 DEBUG_ONLY(seen_incremental_collection_failed = false;) 915 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 916 if (Verbose && PrintGCDetails) { 917 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 918 GCCause::to_string(gch->gc_cause())); 919 } 920 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 921 set_should_allocate_from_space(); // we seem to be running out of space 922 } else { 923 if (Verbose && PrintGCDetails) { 924 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 925 GCCause::to_string(gch->gc_cause())); 926 } 927 gch->clear_incremental_collection_failed(); // We just did a full collection 928 clear_should_allocate_from_space(); // if set 929 } 930 } else { 931 #ifdef ASSERT 932 // It is possible that incremental_collection_failed() == true 933 // here, because an attempted scavenge did not succeed. The policy 934 // is normally expected to cause a full collection which should 935 // clear that condition, so we should not be here twice in a row 936 // with incremental_collection_failed() == true without having done 937 // a full collection in between. 938 if (!seen_incremental_collection_failed && 939 gch->incremental_collection_failed()) { 940 if (Verbose && PrintGCDetails) { 941 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 942 GCCause::to_string(gch->gc_cause())); 943 } 944 seen_incremental_collection_failed = true; 945 } else if (seen_incremental_collection_failed) { 946 if (Verbose && PrintGCDetails) { 947 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 948 GCCause::to_string(gch->gc_cause())); 949 } 950 assert(gch->gc_cause() == GCCause::_scavenge_alot || 951 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 952 !gch->incremental_collection_failed(), 953 "Twice in a row"); 954 seen_incremental_collection_failed = false; 955 } 956 #endif // ASSERT 957 } 958 959 if (ZapUnusedHeapArea) { 960 eden()->check_mangled_unused_area_complete(); 961 from()->check_mangled_unused_area_complete(); 962 to()->check_mangled_unused_area_complete(); 963 } 964 965 if (!CleanChunkPoolAsync) { 966 Chunk::clean_chunk_pool(); 967 } 968 969 // update the generation and space performance counters 970 update_counters(); 971 gch->collector_policy()->counters()->update_counters(); 972 } 973 974 void DefNewGeneration::record_spaces_top() { 975 assert(ZapUnusedHeapArea, "Not mangling unused space"); 976 eden()->set_top_for_allocations(); 977 to()->set_top_for_allocations(); 978 from()->set_top_for_allocations(); 979 } 980 981 void DefNewGeneration::ref_processor_init() { 982 Generation::ref_processor_init(); 983 } 984 985 986 void DefNewGeneration::update_counters() { 987 if (UsePerfData) { 988 _eden_counters->update_all(); 989 _from_counters->update_all(); 990 _to_counters->update_all(); 991 _gen_counters->update_all(); 992 } 993 } 994 995 void DefNewGeneration::verify() { 996 eden()->verify(); 997 from()->verify(); 998 to()->verify(); 999 } 1000 1001 void DefNewGeneration::print_on(outputStream* st) const { 1002 Generation::print_on(st); 1003 st->print(" eden"); 1004 eden()->print_on(st); 1005 st->print(" from"); 1006 from()->print_on(st); 1007 st->print(" to "); 1008 to()->print_on(st); 1009 } 1010 1011 1012 const char* DefNewGeneration::name() const { 1013 return "def new generation"; 1014 } 1015 1016 // Moved from inline file as they are not called inline 1017 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 1018 return eden(); 1019 } 1020 1021 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 1022 // This is the slow-path allocation for the DefNewGeneration. 1023 // Most allocations are fast-path in compiled code. 1024 // We try to allocate from the eden. If that works, we are happy. 1025 // Note that since DefNewGeneration supports lock-free allocation, we 1026 // have to use it here, as well. 1027 HeapWord* result = eden()->par_allocate(word_size); 1028 if (result != NULL) { 1029 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1030 _old_gen->sample_eden_chunk(); 1031 } 1032 } else { 1033 // If the eden is full and the last collection bailed out, we are running 1034 // out of heap space, and we try to allocate the from-space, too. 1035 // allocate_from_space can't be inlined because that would introduce a 1036 // circular dependency at compile time. 1037 result = allocate_from_space(word_size); 1038 } 1039 return result; 1040 } 1041 1042 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 1043 bool is_tlab) { 1044 HeapWord* res = eden()->par_allocate(word_size); 1045 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1046 _old_gen->sample_eden_chunk(); 1047 } 1048 return res; 1049 } 1050 1051 size_t DefNewGeneration::tlab_capacity() const { 1052 return eden()->capacity(); 1053 } 1054 1055 size_t DefNewGeneration::tlab_used() const { 1056 return eden()->used(); 1057 } 1058 1059 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1060 return unsafe_max_alloc_nogc(); 1061 }