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 = initial_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->young_process_roots(&srs, 631 &fsc_with_no_gc_barrier, 632 &fsc_with_gc_barrier, 633 &cld_scan_closure); 634 } 635 636 // "evacuate followers". 637 evacuate_followers.do_void(); 638 639 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 640 ReferenceProcessor* rp = ref_processor(); 641 rp->setup_policy(clear_all_soft_refs); 642 const ReferenceProcessorStats& stats = 643 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 644 NULL, _gc_timer); 645 gc_tracer.report_gc_reference_stats(stats); 646 647 if (!_promotion_failed) { 648 // Swap the survivor spaces. 649 eden()->clear(SpaceDecorator::Mangle); 650 from()->clear(SpaceDecorator::Mangle); 651 if (ZapUnusedHeapArea) { 652 // This is now done here because of the piece-meal mangling which 653 // can check for valid mangling at intermediate points in the 654 // collection(s). When a young collection fails to collect 655 // sufficient space resizing of the young generation can occur 656 // an redistribute the spaces in the young generation. Mangle 657 // here so that unzapped regions don't get distributed to 658 // other spaces. 659 to()->mangle_unused_area(); 660 } 661 swap_spaces(); 662 663 assert(to()->is_empty(), "to space should be empty now"); 664 665 adjust_desired_tenuring_threshold(); 666 667 // A successful scavenge should restart the GC time limit count which is 668 // for full GC's. 669 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); 670 size_policy->reset_gc_overhead_limit_count(); 671 assert(!gch->incremental_collection_failed(), "Should be clear"); 672 } else { 673 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 674 _promo_failure_scan_stack.clear(true); // Clear cached segments. 675 676 remove_forwarding_pointers(); 677 if (PrintGCDetails) { 678 gclog_or_tty->print(" (promotion failed) "); 679 } 680 // Add to-space to the list of space to compact 681 // when a promotion failure has occurred. In that 682 // case there can be live objects in to-space 683 // as a result of a partial evacuation of eden 684 // and from-space. 685 swap_spaces(); // For uniformity wrt ParNewGeneration. 686 from()->set_next_compaction_space(to()); 687 gch->set_incremental_collection_failed(); 688 689 // Inform the next generation that a promotion failure occurred. 690 _old_gen->promotion_failure_occurred(); 691 gc_tracer.report_promotion_failed(_promotion_failed_info); 692 693 // Reset the PromotionFailureALot counters. 694 NOT_PRODUCT(gch->reset_promotion_should_fail();) 695 } 696 if (PrintGC && !PrintGCDetails) { 697 gch->print_heap_change(gch_prev_used); 698 } 699 // set new iteration safe limit for the survivor spaces 700 from()->set_concurrent_iteration_safe_limit(from()->top()); 701 to()->set_concurrent_iteration_safe_limit(to()->top()); 702 703 // We need to use a monotonically non-decreasing time in ms 704 // or we will see time-warp warnings and os::javaTimeMillis() 705 // does not guarantee monotonicity. 706 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 707 update_time_of_last_gc(now); 708 709 gch->trace_heap_after_gc(&gc_tracer); 710 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 711 712 _gc_timer->register_gc_end(); 713 714 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 715 } 716 717 class RemoveForwardPointerClosure: public ObjectClosure { 718 public: 719 void do_object(oop obj) { 720 obj->init_mark(); 721 } 722 }; 723 724 void DefNewGeneration::init_assuming_no_promotion_failure() { 725 _promotion_failed = false; 726 _promotion_failed_info.reset(); 727 from()->set_next_compaction_space(NULL); 728 } 729 730 void DefNewGeneration::remove_forwarding_pointers() { 731 RemoveForwardPointerClosure rspc; 732 eden()->object_iterate(&rspc); 733 from()->object_iterate(&rspc); 734 735 // Now restore saved marks, if any. 736 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(), 737 "should be the same"); 738 while (!_objs_with_preserved_marks.is_empty()) { 739 oop obj = _objs_with_preserved_marks.pop(); 740 markOop m = _preserved_marks_of_objs.pop(); 741 obj->set_mark(m); 742 } 743 _objs_with_preserved_marks.clear(true); 744 _preserved_marks_of_objs.clear(true); 745 } 746 747 void DefNewGeneration::preserve_mark(oop obj, markOop m) { 748 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj), 749 "Oversaving!"); 750 _objs_with_preserved_marks.push(obj); 751 _preserved_marks_of_objs.push(m); 752 } 753 754 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) { 755 if (m->must_be_preserved_for_promotion_failure(obj)) { 756 preserve_mark(obj, m); 757 } 758 } 759 760 void DefNewGeneration::handle_promotion_failure(oop old) { 761 if (PrintPromotionFailure && !_promotion_failed) { 762 gclog_or_tty->print(" (promotion failure size = %d) ", 763 old->size()); 764 } 765 _promotion_failed = true; 766 _promotion_failed_info.register_copy_failure(old->size()); 767 preserve_mark_if_necessary(old, old->mark()); 768 // forward to self 769 old->forward_to(old); 770 771 _promo_failure_scan_stack.push(old); 772 773 if (!_promo_failure_drain_in_progress) { 774 // prevent recursion in copy_to_survivor_space() 775 _promo_failure_drain_in_progress = true; 776 drain_promo_failure_scan_stack(); 777 _promo_failure_drain_in_progress = false; 778 } 779 } 780 781 oop DefNewGeneration::copy_to_survivor_space(oop old) { 782 assert(is_in_reserved(old) && !old->is_forwarded(), 783 "shouldn't be scavenging this oop"); 784 size_t s = old->size(); 785 oop obj = NULL; 786 787 // Try allocating obj in to-space (unless too old) 788 if (old->age() < tenuring_threshold()) { 789 obj = (oop) to()->allocate_aligned(s); 790 } 791 792 // Otherwise try allocating obj tenured 793 if (obj == NULL) { 794 obj = _old_gen->promote(old, s); 795 if (obj == NULL) { 796 handle_promotion_failure(old); 797 return old; 798 } 799 } else { 800 // Prefetch beyond obj 801 const intx interval = PrefetchCopyIntervalInBytes; 802 Prefetch::write(obj, interval); 803 804 // Copy obj 805 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 806 807 // Increment age if obj still in new generation 808 obj->incr_age(); 809 age_table()->add(obj, s); 810 } 811 812 // Done, insert forward pointer to obj in this header 813 old->forward_to(obj); 814 815 return obj; 816 } 817 818 void DefNewGeneration::drain_promo_failure_scan_stack() { 819 while (!_promo_failure_scan_stack.is_empty()) { 820 oop obj = _promo_failure_scan_stack.pop(); 821 obj->oop_iterate(_promo_failure_scan_stack_closure); 822 } 823 } 824 825 void DefNewGeneration::save_marks() { 826 eden()->set_saved_mark(); 827 to()->set_saved_mark(); 828 from()->set_saved_mark(); 829 } 830 831 832 void DefNewGeneration::reset_saved_marks() { 833 eden()->reset_saved_mark(); 834 to()->reset_saved_mark(); 835 from()->reset_saved_mark(); 836 } 837 838 839 bool DefNewGeneration::no_allocs_since_save_marks() { 840 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 841 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 842 return to()->saved_mark_at_top(); 843 } 844 845 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ 846 \ 847 void DefNewGeneration:: \ 848 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ 849 cl->assert_generation(this); \ 850 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \ 851 to()->oop_since_save_marks_iterate##nv_suffix(cl); \ 852 from()->oop_since_save_marks_iterate##nv_suffix(cl); \ 853 save_marks(); \ 854 } 855 856 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN) 857 858 #undef DefNew_SINCE_SAVE_MARKS_DEFN 859 860 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 861 size_t max_alloc_words) { 862 if (requestor == this || _promotion_failed) { 863 return; 864 } 865 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation"); 866 867 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 868 if (to_space->top() > to_space->bottom()) { 869 trace("to_space not empty when contribute_scratch called"); 870 } 871 */ 872 873 ContiguousSpace* to_space = to(); 874 assert(to_space->end() >= to_space->top(), "pointers out of order"); 875 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 876 if (free_words >= MinFreeScratchWords) { 877 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 878 sb->num_words = free_words; 879 sb->next = list; 880 list = sb; 881 } 882 } 883 884 void DefNewGeneration::reset_scratch() { 885 // If contributing scratch in to_space, mangle all of 886 // to_space if ZapUnusedHeapArea. This is needed because 887 // top is not maintained while using to-space as scratch. 888 if (ZapUnusedHeapArea) { 889 to()->mangle_unused_area_complete(); 890 } 891 } 892 893 bool DefNewGeneration::collection_attempt_is_safe() { 894 if (!to()->is_empty()) { 895 if (Verbose && PrintGCDetails) { 896 gclog_or_tty->print(" :: to is not empty :: "); 897 } 898 return false; 899 } 900 if (_old_gen == NULL) { 901 GenCollectedHeap* gch = GenCollectedHeap::heap(); 902 _old_gen = gch->old_gen(); 903 } 904 return _old_gen->promotion_attempt_is_safe(used()); 905 } 906 907 void DefNewGeneration::gc_epilogue(bool full) { 908 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 909 910 assert(!GC_locker::is_active(), "We should not be executing here"); 911 // Check if the heap is approaching full after a collection has 912 // been done. Generally the young generation is empty at 913 // a minimum at the end of a collection. If it is not, then 914 // the heap is approaching full. 915 GenCollectedHeap* gch = GenCollectedHeap::heap(); 916 if (full) { 917 DEBUG_ONLY(seen_incremental_collection_failed = false;) 918 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 919 if (Verbose && PrintGCDetails) { 920 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 921 GCCause::to_string(gch->gc_cause())); 922 } 923 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 924 set_should_allocate_from_space(); // we seem to be running out of space 925 } else { 926 if (Verbose && PrintGCDetails) { 927 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 928 GCCause::to_string(gch->gc_cause())); 929 } 930 gch->clear_incremental_collection_failed(); // We just did a full collection 931 clear_should_allocate_from_space(); // if set 932 } 933 } else { 934 #ifdef ASSERT 935 // It is possible that incremental_collection_failed() == true 936 // here, because an attempted scavenge did not succeed. The policy 937 // is normally expected to cause a full collection which should 938 // clear that condition, so we should not be here twice in a row 939 // with incremental_collection_failed() == true without having done 940 // a full collection in between. 941 if (!seen_incremental_collection_failed && 942 gch->incremental_collection_failed()) { 943 if (Verbose && PrintGCDetails) { 944 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 945 GCCause::to_string(gch->gc_cause())); 946 } 947 seen_incremental_collection_failed = true; 948 } else if (seen_incremental_collection_failed) { 949 if (Verbose && PrintGCDetails) { 950 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 951 GCCause::to_string(gch->gc_cause())); 952 } 953 assert(gch->gc_cause() == GCCause::_scavenge_alot || 954 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 955 !gch->incremental_collection_failed(), 956 "Twice in a row"); 957 seen_incremental_collection_failed = false; 958 } 959 #endif // ASSERT 960 } 961 962 if (ZapUnusedHeapArea) { 963 eden()->check_mangled_unused_area_complete(); 964 from()->check_mangled_unused_area_complete(); 965 to()->check_mangled_unused_area_complete(); 966 } 967 968 if (!CleanChunkPoolAsync) { 969 Chunk::clean_chunk_pool(); 970 } 971 972 // update the generation and space performance counters 973 update_counters(); 974 gch->collector_policy()->counters()->update_counters(); 975 } 976 977 void DefNewGeneration::record_spaces_top() { 978 assert(ZapUnusedHeapArea, "Not mangling unused space"); 979 eden()->set_top_for_allocations(); 980 to()->set_top_for_allocations(); 981 from()->set_top_for_allocations(); 982 } 983 984 void DefNewGeneration::ref_processor_init() { 985 Generation::ref_processor_init(); 986 } 987 988 989 void DefNewGeneration::update_counters() { 990 if (UsePerfData) { 991 _eden_counters->update_all(); 992 _from_counters->update_all(); 993 _to_counters->update_all(); 994 _gen_counters->update_all(); 995 } 996 } 997 998 void DefNewGeneration::verify() { 999 eden()->verify(); 1000 from()->verify(); 1001 to()->verify(); 1002 } 1003 1004 void DefNewGeneration::print_on(outputStream* st) const { 1005 Generation::print_on(st); 1006 st->print(" eden"); 1007 eden()->print_on(st); 1008 st->print(" from"); 1009 from()->print_on(st); 1010 st->print(" to "); 1011 to()->print_on(st); 1012 } 1013 1014 1015 const char* DefNewGeneration::name() const { 1016 return "def new generation"; 1017 } 1018 1019 // Moved from inline file as they are not called inline 1020 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 1021 return eden(); 1022 } 1023 1024 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 1025 // This is the slow-path allocation for the DefNewGeneration. 1026 // Most allocations are fast-path in compiled code. 1027 // We try to allocate from the eden. If that works, we are happy. 1028 // Note that since DefNewGeneration supports lock-free allocation, we 1029 // have to use it here, as well. 1030 HeapWord* result = eden()->par_allocate(word_size); 1031 if (result != NULL) { 1032 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1033 _old_gen->sample_eden_chunk(); 1034 } 1035 } else { 1036 // If the eden is full and the last collection bailed out, we are running 1037 // out of heap space, and we try to allocate the from-space, too. 1038 // allocate_from_space can't be inlined because that would introduce a 1039 // circular dependency at compile time. 1040 result = allocate_from_space(word_size); 1041 } 1042 return result; 1043 } 1044 1045 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 1046 bool is_tlab) { 1047 HeapWord* res = eden()->par_allocate(word_size); 1048 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1049 _old_gen->sample_eden_chunk(); 1050 } 1051 return res; 1052 } 1053 1054 size_t DefNewGeneration::tlab_capacity() const { 1055 return eden()->capacity(); 1056 } 1057 1058 size_t DefNewGeneration::tlab_used() const { 1059 return eden()->used(); 1060 } 1061 1062 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1063 return unsafe_max_alloc_nogc(); 1064 }