1 /* 2 * Copyright (c) 2000, 2014, 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 "classfile/symbolTable.hpp" 27 #include "classfile/systemDictionary.hpp" 28 #include "classfile/vmSymbols.hpp" 29 #include "code/icBuffer.hpp" 30 #include "gc_implementation/shared/collectorCounters.hpp" 31 #include "gc_implementation/shared/gcTrace.hpp" 32 #include "gc_implementation/shared/gcTraceTime.hpp" 33 #include "gc_implementation/shared/vmGCOperations.hpp" 34 #include "gc_interface/collectedHeap.inline.hpp" 35 #include "memory/filemap.hpp" 36 #include "memory/gcLocker.inline.hpp" 37 #include "memory/genCollectedHeap.hpp" 38 #include "memory/genOopClosures.inline.hpp" 39 #include "memory/generation.inline.hpp" 40 #include "memory/generationSpec.hpp" 41 #include "memory/resourceArea.hpp" 42 #include "memory/sharedHeap.hpp" 43 #include "memory/space.hpp" 44 #include "oops/oop.inline.hpp" 45 #include "oops/oop.inline2.hpp" 46 #include "runtime/biasedLocking.hpp" 47 #include "runtime/fprofiler.hpp" 48 #include "runtime/handles.hpp" 49 #include "runtime/handles.inline.hpp" 50 #include "runtime/java.hpp" 51 #include "runtime/vmThread.hpp" 52 #include "services/memoryService.hpp" 53 #include "utilities/vmError.hpp" 54 #include "utilities/workgroup.hpp" 55 #include "utilities/macros.hpp" 56 #if INCLUDE_ALL_GCS 57 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp" 58 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp" 59 #endif // INCLUDE_ALL_GCS 60 61 GenCollectedHeap* GenCollectedHeap::_gch; 62 NOT_PRODUCT(size_t GenCollectedHeap::_skip_header_HeapWords = 0;) 63 64 // The set of potentially parallel tasks in root scanning. 65 enum GCH_strong_roots_tasks { 66 // We probably want to parallelize both of these internally, but for now... 67 GCH_PS_younger_gens, 68 // Leave this one last. 69 GCH_PS_NumElements 70 }; 71 72 GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy) : 73 SharedHeap(policy), 74 _gen_policy(policy), 75 _gen_process_roots_tasks(new SubTasksDone(GCH_PS_NumElements)), 76 _full_collections_completed(0) 77 { 78 if (_gen_process_roots_tasks == NULL || 79 !_gen_process_roots_tasks->valid()) { 80 vm_exit_during_initialization("Failed necessary allocation."); 81 } 82 assert(policy != NULL, "Sanity check"); 83 } 84 85 jint GenCollectedHeap::initialize() { 86 CollectedHeap::pre_initialize(); 87 88 int i; 89 _n_gens = gen_policy()->number_of_generations(); 90 91 // While there are no constraints in the GC code that HeapWordSize 92 // be any particular value, there are multiple other areas in the 93 // system which believe this to be true (e.g. oop->object_size in some 94 // cases incorrectly returns the size in wordSize units rather than 95 // HeapWordSize). 96 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 97 98 // The heap must be at least as aligned as generations. 99 size_t gen_alignment = Generation::GenGrain; 100 101 _gen_specs = gen_policy()->generations(); 102 103 // Make sure the sizes are all aligned. 104 for (i = 0; i < _n_gens; i++) { 105 _gen_specs[i]->align(gen_alignment); 106 } 107 108 // Allocate space for the heap. 109 110 char* heap_address; 111 size_t total_reserved = 0; 112 int n_covered_regions = 0; 113 ReservedSpace heap_rs; 114 115 size_t heap_alignment = collector_policy()->heap_alignment(); 116 117 heap_address = allocate(heap_alignment, &total_reserved, 118 &n_covered_regions, &heap_rs); 119 120 if (!heap_rs.is_reserved()) { 121 vm_shutdown_during_initialization( 122 "Could not reserve enough space for object heap"); 123 return JNI_ENOMEM; 124 } 125 126 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 127 128 _rem_set = collector_policy()->create_rem_set(reserved_region(), n_covered_regions); 129 set_barrier_set(rem_set()->bs()); 130 131 _gch = this; 132 133 for (i = 0; i < _n_gens; i++) { 134 ReservedSpace this_rs = heap_rs.first_part(_gen_specs[i]->max_size(), false, false); 135 _gens[i] = _gen_specs[i]->init(this_rs, i, rem_set()); 136 heap_rs = heap_rs.last_part(_gen_specs[i]->max_size()); 137 } 138 clear_incremental_collection_failed(); 139 140 #if INCLUDE_ALL_GCS 141 // If we are running CMS, create the collector responsible 142 // for collecting the CMS generations. 143 if (collector_policy()->is_concurrent_mark_sweep_policy()) { 144 bool success = create_cms_collector(); 145 if (!success) return JNI_ENOMEM; 146 } 147 #endif // INCLUDE_ALL_GCS 148 149 return JNI_OK; 150 } 151 152 153 char* GenCollectedHeap::allocate(size_t alignment, 154 size_t* _total_reserved, 155 int* _n_covered_regions, 156 ReservedSpace* heap_rs){ 157 const char overflow_msg[] = "The size of the object heap + VM data exceeds " 158 "the maximum representable size"; 159 160 // Now figure out the total size. 161 size_t total_reserved = 0; 162 int n_covered_regions = 0; 163 const size_t pageSize = UseLargePages ? 164 os::large_page_size() : os::vm_page_size(); 165 166 assert(alignment % pageSize == 0, "Must be"); 167 168 for (int i = 0; i < _n_gens; i++) { 169 total_reserved += _gen_specs[i]->max_size(); 170 if (total_reserved < _gen_specs[i]->max_size()) { 171 vm_exit_during_initialization(overflow_msg); 172 } 173 n_covered_regions += _gen_specs[i]->n_covered_regions(); 174 } 175 assert(total_reserved % alignment == 0, 176 err_msg("Gen size; total_reserved=" SIZE_FORMAT ", alignment=" 177 SIZE_FORMAT, total_reserved, alignment)); 178 179 // Needed until the cardtable is fixed to have the right number 180 // of covered regions. 181 n_covered_regions += 2; 182 183 *_total_reserved = total_reserved; 184 *_n_covered_regions = n_covered_regions; 185 186 *heap_rs = Universe::reserve_heap(total_reserved, alignment); 187 return heap_rs->base(); 188 } 189 190 191 void GenCollectedHeap::post_initialize() { 192 SharedHeap::post_initialize(); 193 GenCollectorPolicy *policy = (GenCollectorPolicy *)collector_policy(); 194 guarantee(policy->is_generation_policy(), "Illegal policy type"); 195 DefNewGeneration* def_new_gen = (DefNewGeneration*) get_gen(0); 196 assert(def_new_gen->kind() == Generation::DefNew || 197 def_new_gen->kind() == Generation::ParNew, 198 "Wrong generation kind"); 199 200 Generation* old_gen = get_gen(1); 201 assert(old_gen->kind() == Generation::ConcurrentMarkSweep || 202 old_gen->kind() == Generation::MarkSweepCompact, 203 "Wrong generation kind"); 204 205 policy->initialize_size_policy(def_new_gen->eden()->capacity(), 206 old_gen->capacity(), 207 def_new_gen->from()->capacity()); 208 policy->initialize_gc_policy_counters(); 209 } 210 211 void GenCollectedHeap::ref_processing_init() { 212 SharedHeap::ref_processing_init(); 213 for (int i = 0; i < _n_gens; i++) { 214 _gens[i]->ref_processor_init(); 215 } 216 } 217 218 size_t GenCollectedHeap::capacity() const { 219 size_t res = 0; 220 for (int i = 0; i < _n_gens; i++) { 221 res += _gens[i]->capacity(); 222 } 223 return res; 224 } 225 226 size_t GenCollectedHeap::used() const { 227 size_t res = 0; 228 for (int i = 0; i < _n_gens; i++) { 229 res += _gens[i]->used(); 230 } 231 return res; 232 } 233 234 // Save the "used_region" for generations level and lower. 235 void GenCollectedHeap::save_used_regions(int level) { 236 assert(level < _n_gens, "Illegal level parameter"); 237 for (int i = level; i >= 0; i--) { 238 _gens[i]->save_used_region(); 239 } 240 } 241 242 size_t GenCollectedHeap::max_capacity() const { 243 size_t res = 0; 244 for (int i = 0; i < _n_gens; i++) { 245 res += _gens[i]->max_capacity(); 246 } 247 return res; 248 } 249 250 // Update the _full_collections_completed counter 251 // at the end of a stop-world full GC. 252 unsigned int GenCollectedHeap::update_full_collections_completed() { 253 MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 254 assert(_full_collections_completed <= _total_full_collections, 255 "Can't complete more collections than were started"); 256 _full_collections_completed = _total_full_collections; 257 ml.notify_all(); 258 return _full_collections_completed; 259 } 260 261 // Update the _full_collections_completed counter, as appropriate, 262 // at the end of a concurrent GC cycle. Note the conditional update 263 // below to allow this method to be called by a concurrent collector 264 // without synchronizing in any manner with the VM thread (which 265 // may already have initiated a STW full collection "concurrently"). 266 unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) { 267 MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 268 assert((_full_collections_completed <= _total_full_collections) && 269 (count <= _total_full_collections), 270 "Can't complete more collections than were started"); 271 if (count > _full_collections_completed) { 272 _full_collections_completed = count; 273 ml.notify_all(); 274 } 275 return _full_collections_completed; 276 } 277 278 279 #ifndef PRODUCT 280 // Override of memory state checking method in CollectedHeap: 281 // Some collectors (CMS for example) can't have badHeapWordVal written 282 // in the first two words of an object. (For instance , in the case of 283 // CMS these words hold state used to synchronize between certain 284 // (concurrent) GC steps and direct allocating mutators.) 285 // The skip_header_HeapWords() method below, allows us to skip 286 // over the requisite number of HeapWord's. Note that (for 287 // generational collectors) this means that those many words are 288 // skipped in each object, irrespective of the generation in which 289 // that object lives. The resultant loss of precision seems to be 290 // harmless and the pain of avoiding that imprecision appears somewhat 291 // higher than we are prepared to pay for such rudimentary debugging 292 // support. 293 void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr, 294 size_t size) { 295 if (CheckMemoryInitialization && ZapUnusedHeapArea) { 296 // We are asked to check a size in HeapWords, 297 // but the memory is mangled in juint words. 298 juint* start = (juint*) (addr + skip_header_HeapWords()); 299 juint* end = (juint*) (addr + size); 300 for (juint* slot = start; slot < end; slot += 1) { 301 assert(*slot == badHeapWordVal, 302 "Found non badHeapWordValue in pre-allocation check"); 303 } 304 } 305 } 306 #endif 307 308 HeapWord* GenCollectedHeap::attempt_allocation(size_t size, 309 bool is_tlab, 310 bool first_only) { 311 HeapWord* res; 312 for (int i = 0; i < _n_gens; i++) { 313 if (_gens[i]->should_allocate(size, is_tlab)) { 314 res = _gens[i]->allocate(size, is_tlab); 315 if (res != NULL) return res; 316 else if (first_only) break; 317 } 318 } 319 // Otherwise... 320 return NULL; 321 } 322 323 HeapWord* GenCollectedHeap::mem_allocate(size_t size, 324 bool* gc_overhead_limit_was_exceeded) { 325 return collector_policy()->mem_allocate_work(size, 326 false /* is_tlab */, 327 gc_overhead_limit_was_exceeded); 328 } 329 330 bool GenCollectedHeap::must_clear_all_soft_refs() { 331 return _gc_cause == GCCause::_last_ditch_collection; 332 } 333 334 bool GenCollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 335 return UseConcMarkSweepGC && 336 ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) || 337 (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent)); 338 } 339 340 void GenCollectedHeap::do_collection(bool full, 341 bool clear_all_soft_refs, 342 size_t size, 343 bool is_tlab, 344 int max_level) { 345 bool prepared_for_verification = false; 346 ResourceMark rm; 347 DEBUG_ONLY(Thread* my_thread = Thread::current();) 348 349 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); 350 assert(my_thread->is_VM_thread() || 351 my_thread->is_ConcurrentGC_thread(), 352 "incorrect thread type capability"); 353 assert(Heap_lock->is_locked(), 354 "the requesting thread should have the Heap_lock"); 355 guarantee(!is_gc_active(), "collection is not reentrant"); 356 assert(max_level < n_gens(), "sanity check"); 357 358 if (GC_locker::check_active_before_gc()) { 359 return; // GC is disabled (e.g. JNI GetXXXCritical operation) 360 } 361 362 const bool do_clear_all_soft_refs = clear_all_soft_refs || 363 collector_policy()->should_clear_all_soft_refs(); 364 365 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 366 367 const size_t metadata_prev_used = MetaspaceAux::used_bytes(); 368 369 print_heap_before_gc(); 370 371 { 372 FlagSetting fl(_is_gc_active, true); 373 374 bool complete = full && (max_level == (n_gens()-1)); 375 const char* gc_cause_prefix = complete ? "Full GC" : "GC"; 376 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); 377 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); 378 // The PrintGCDetails logging starts before we have incremented the GC id. We will do that later 379 // so we can assume here that the next GC id is what we want. 380 GCTraceTime t(GCCauseString(gc_cause_prefix, gc_cause()), PrintGCDetails, false, NULL, GCId::peek()); 381 382 gc_prologue(complete); 383 increment_total_collections(complete); 384 385 size_t gch_prev_used = used(); 386 387 int starting_level = 0; 388 if (full) { 389 // Search for the oldest generation which will collect all younger 390 // generations, and start collection loop there. 391 for (int i = max_level; i >= 0; i--) { 392 if (_gens[i]->full_collects_younger_generations()) { 393 starting_level = i; 394 break; 395 } 396 } 397 } 398 399 bool must_restore_marks_for_biased_locking = false; 400 401 int max_level_collected = starting_level; 402 for (int i = starting_level; i <= max_level; i++) { 403 if (_gens[i]->should_collect(full, size, is_tlab)) { 404 if (i == n_gens() - 1) { // a major collection is to happen 405 if (!complete) { 406 // The full_collections increment was missed above. 407 increment_total_full_collections(); 408 } 409 pre_full_gc_dump(NULL); // do any pre full gc dumps 410 } 411 // Timer for individual generations. Last argument is false: no CR 412 // FIXME: We should try to start the timing earlier to cover more of the GC pause 413 // The PrintGCDetails logging starts before we have incremented the GC id. We will do that later 414 // so we can assume here that the next GC id is what we want. 415 GCTraceTime t1(_gens[i]->short_name(), PrintGCDetails, false, NULL, GCId::peek()); 416 TraceCollectorStats tcs(_gens[i]->counters()); 417 TraceMemoryManagerStats tmms(_gens[i]->kind(),gc_cause()); 418 419 size_t prev_used = _gens[i]->used(); 420 _gens[i]->stat_record()->invocations++; 421 _gens[i]->stat_record()->accumulated_time.start(); 422 423 // Must be done anew before each collection because 424 // a previous collection will do mangling and will 425 // change top of some spaces. 426 record_gen_tops_before_GC(); 427 428 if (PrintGC && Verbose) { 429 gclog_or_tty->print("level=%d invoke=%d size=" SIZE_FORMAT, 430 i, 431 _gens[i]->stat_record()->invocations, 432 size*HeapWordSize); 433 } 434 435 if (VerifyBeforeGC && i >= VerifyGCLevel && 436 total_collections() >= VerifyGCStartAt) { 437 HandleMark hm; // Discard invalid handles created during verification 438 if (!prepared_for_verification) { 439 prepare_for_verify(); 440 prepared_for_verification = true; 441 } 442 Universe::verify(" VerifyBeforeGC:"); 443 } 444 COMPILER2_PRESENT(DerivedPointerTable::clear()); 445 446 if (!must_restore_marks_for_biased_locking && 447 _gens[i]->performs_in_place_marking()) { 448 // We perform this mark word preservation work lazily 449 // because it's only at this point that we know whether we 450 // absolutely have to do it; we want to avoid doing it for 451 // scavenge-only collections where it's unnecessary 452 must_restore_marks_for_biased_locking = true; 453 BiasedLocking::preserve_marks(); 454 } 455 456 // Do collection work 457 { 458 // Note on ref discovery: For what appear to be historical reasons, 459 // GCH enables and disabled (by enqueing) refs discovery. 460 // In the future this should be moved into the generation's 461 // collect method so that ref discovery and enqueueing concerns 462 // are local to a generation. The collect method could return 463 // an appropriate indication in the case that notification on 464 // the ref lock was needed. This will make the treatment of 465 // weak refs more uniform (and indeed remove such concerns 466 // from GCH). XXX 467 468 HandleMark hm; // Discard invalid handles created during gc 469 save_marks(); // save marks for all gens 470 // We want to discover references, but not process them yet. 471 // This mode is disabled in process_discovered_references if the 472 // generation does some collection work, or in 473 // enqueue_discovered_references if the generation returns 474 // without doing any work. 475 ReferenceProcessor* rp = _gens[i]->ref_processor(); 476 // If the discovery of ("weak") refs in this generation is 477 // atomic wrt other collectors in this configuration, we 478 // are guaranteed to have empty discovered ref lists. 479 if (rp->discovery_is_atomic()) { 480 rp->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); 481 rp->setup_policy(do_clear_all_soft_refs); 482 } else { 483 // collect() below will enable discovery as appropriate 484 } 485 _gens[i]->collect(full, do_clear_all_soft_refs, size, is_tlab); 486 if (!rp->enqueuing_is_done()) { 487 rp->enqueue_discovered_references(); 488 } else { 489 rp->set_enqueuing_is_done(false); 490 } 491 rp->verify_no_references_recorded(); 492 } 493 max_level_collected = i; 494 495 // Determine if allocation request was met. 496 if (size > 0) { 497 if (!is_tlab || _gens[i]->supports_tlab_allocation()) { 498 if (size*HeapWordSize <= _gens[i]->unsafe_max_alloc_nogc()) { 499 size = 0; 500 } 501 } 502 } 503 504 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 505 506 _gens[i]->stat_record()->accumulated_time.stop(); 507 508 update_gc_stats(i, full); 509 510 if (VerifyAfterGC && i >= VerifyGCLevel && 511 total_collections() >= VerifyGCStartAt) { 512 HandleMark hm; // Discard invalid handles created during verification 513 Universe::verify(" VerifyAfterGC:"); 514 } 515 516 if (PrintGCDetails) { 517 gclog_or_tty->print(":"); 518 _gens[i]->print_heap_change(prev_used); 519 } 520 } 521 } 522 523 // Update "complete" boolean wrt what actually transpired -- 524 // for instance, a promotion failure could have led to 525 // a whole heap collection. 526 complete = complete || (max_level_collected == n_gens() - 1); 527 528 if (complete) { // We did a "major" collection 529 // FIXME: See comment at pre_full_gc_dump call 530 post_full_gc_dump(NULL); // do any post full gc dumps 531 } 532 533 if (PrintGCDetails) { 534 print_heap_change(gch_prev_used); 535 536 // Print metaspace info for full GC with PrintGCDetails flag. 537 if (complete) { 538 MetaspaceAux::print_metaspace_change(metadata_prev_used); 539 } 540 } 541 542 for (int j = max_level_collected; j >= 0; j -= 1) { 543 // Adjust generation sizes. 544 _gens[j]->compute_new_size(); 545 } 546 547 if (complete) { 548 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 549 ClassLoaderDataGraph::purge(); 550 MetaspaceAux::verify_metrics(); 551 // Resize the metaspace capacity after full collections 552 MetaspaceGC::compute_new_size(); 553 update_full_collections_completed(); 554 } 555 556 // Track memory usage and detect low memory after GC finishes 557 MemoryService::track_memory_usage(); 558 559 gc_epilogue(complete); 560 561 if (must_restore_marks_for_biased_locking) { 562 BiasedLocking::restore_marks(); 563 } 564 } 565 566 print_heap_after_gc(); 567 568 #ifdef TRACESPINNING 569 ParallelTaskTerminator::print_termination_counts(); 570 #endif 571 } 572 573 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) { 574 return collector_policy()->satisfy_failed_allocation(size, is_tlab); 575 } 576 577 void GenCollectedHeap::set_par_threads(uint t) { 578 SharedHeap::set_par_threads(t); 579 _gen_process_roots_tasks->set_n_threads(t); 580 } 581 582 void GenCollectedHeap:: 583 gen_process_roots(int level, 584 bool younger_gens_as_roots, 585 bool activate_scope, 586 SharedHeap::ScanningOption so, 587 OopsInGenClosure* not_older_gens, 588 OopsInGenClosure* weak_roots, 589 OopsInGenClosure* older_gens, 590 CLDClosure* cld_closure, 591 CLDClosure* weak_cld_closure, 592 CodeBlobClosure* code_closure) { 593 594 // General roots. 595 SharedHeap::process_roots(activate_scope, so, 596 not_older_gens, weak_roots, 597 cld_closure, weak_cld_closure, 598 code_closure); 599 600 if (younger_gens_as_roots) { 601 if (!_gen_process_roots_tasks->is_task_claimed(GCH_PS_younger_gens)) { 602 for (int i = 0; i < level; i++) { 603 not_older_gens->set_generation(_gens[i]); 604 _gens[i]->oop_iterate(not_older_gens); 605 } 606 not_older_gens->reset_generation(); 607 } 608 } 609 // When collection is parallel, all threads get to cooperate to do 610 // older-gen scanning. 611 for (int i = level+1; i < _n_gens; i++) { 612 older_gens->set_generation(_gens[i]); 613 rem_set()->younger_refs_iterate(_gens[i], older_gens); 614 older_gens->reset_generation(); 615 } 616 617 _gen_process_roots_tasks->all_tasks_completed(); 618 } 619 620 void GenCollectedHeap:: 621 gen_process_roots(int level, 622 bool younger_gens_as_roots, 623 bool activate_scope, 624 SharedHeap::ScanningOption so, 625 bool only_strong_roots, 626 OopsInGenClosure* not_older_gens, 627 OopsInGenClosure* older_gens, 628 CLDClosure* cld_closure) { 629 630 const bool is_adjust_phase = !only_strong_roots && !younger_gens_as_roots; 631 632 bool is_moving_collection = false; 633 if (level == 0 || is_adjust_phase) { 634 // young collections are always moving 635 is_moving_collection = true; 636 } 637 638 MarkingCodeBlobClosure mark_code_closure(not_older_gens, is_moving_collection); 639 CodeBlobClosure* code_closure = &mark_code_closure; 640 641 gen_process_roots(level, 642 younger_gens_as_roots, 643 activate_scope, so, 644 not_older_gens, only_strong_roots ? NULL : not_older_gens, 645 older_gens, 646 cld_closure, only_strong_roots ? NULL : cld_closure, 647 code_closure); 648 649 } 650 651 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure) { 652 SharedHeap::process_weak_roots(root_closure); 653 // "Local" "weak" refs 654 for (int i = 0; i < _n_gens; i++) { 655 _gens[i]->ref_processor()->weak_oops_do(root_closure); 656 } 657 } 658 659 #define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix) \ 660 void GenCollectedHeap:: \ 661 oop_since_save_marks_iterate(int level, \ 662 OopClosureType* cur, \ 663 OopClosureType* older) { \ 664 _gens[level]->oop_since_save_marks_iterate##nv_suffix(cur); \ 665 for (int i = level+1; i < n_gens(); i++) { \ 666 _gens[i]->oop_since_save_marks_iterate##nv_suffix(older); \ 667 } \ 668 } 669 670 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN) 671 672 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN 673 674 bool GenCollectedHeap::no_allocs_since_save_marks(int level) { 675 for (int i = level; i < _n_gens; i++) { 676 if (!_gens[i]->no_allocs_since_save_marks()) return false; 677 } 678 return true; 679 } 680 681 bool GenCollectedHeap::supports_inline_contig_alloc() const { 682 return _gens[0]->supports_inline_contig_alloc(); 683 } 684 685 HeapWord** GenCollectedHeap::top_addr() const { 686 return _gens[0]->top_addr(); 687 } 688 689 HeapWord** GenCollectedHeap::end_addr() const { 690 return _gens[0]->end_addr(); 691 } 692 693 // public collection interfaces 694 695 void GenCollectedHeap::collect(GCCause::Cause cause) { 696 if (should_do_concurrent_full_gc(cause)) { 697 #if INCLUDE_ALL_GCS 698 // mostly concurrent full collection 699 collect_mostly_concurrent(cause); 700 #else // INCLUDE_ALL_GCS 701 ShouldNotReachHere(); 702 #endif // INCLUDE_ALL_GCS 703 } else if (cause == GCCause::_wb_young_gc) { 704 // minor collection for WhiteBox API 705 collect(cause, 0); 706 } else { 707 #ifdef ASSERT 708 if (cause == GCCause::_scavenge_alot) { 709 // minor collection only 710 collect(cause, 0); 711 } else { 712 // Stop-the-world full collection 713 collect(cause, n_gens() - 1); 714 } 715 #else 716 // Stop-the-world full collection 717 collect(cause, n_gens() - 1); 718 #endif 719 } 720 } 721 722 void GenCollectedHeap::collect(GCCause::Cause cause, int max_level) { 723 // The caller doesn't have the Heap_lock 724 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock"); 725 MutexLocker ml(Heap_lock); 726 collect_locked(cause, max_level); 727 } 728 729 void GenCollectedHeap::collect_locked(GCCause::Cause cause) { 730 // The caller has the Heap_lock 731 assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock"); 732 collect_locked(cause, n_gens() - 1); 733 } 734 735 // this is the private collection interface 736 // The Heap_lock is expected to be held on entry. 737 738 void GenCollectedHeap::collect_locked(GCCause::Cause cause, int max_level) { 739 // Read the GC count while holding the Heap_lock 740 unsigned int gc_count_before = total_collections(); 741 unsigned int full_gc_count_before = total_full_collections(); 742 { 743 MutexUnlocker mu(Heap_lock); // give up heap lock, execute gets it back 744 VM_GenCollectFull op(gc_count_before, full_gc_count_before, 745 cause, max_level); 746 VMThread::execute(&op); 747 } 748 } 749 750 #if INCLUDE_ALL_GCS 751 bool GenCollectedHeap::create_cms_collector() { 752 753 assert(_gens[1]->kind() == Generation::ConcurrentMarkSweep, 754 "Unexpected generation kinds"); 755 // Skip two header words in the block content verification 756 NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();) 757 CMSCollector* collector = new CMSCollector( 758 (ConcurrentMarkSweepGeneration*)_gens[1], 759 _rem_set->as_CardTableRS(), 760 (ConcurrentMarkSweepPolicy*) collector_policy()); 761 762 if (collector == NULL || !collector->completed_initialization()) { 763 if (collector) { 764 delete collector; // Be nice in embedded situation 765 } 766 vm_shutdown_during_initialization("Could not create CMS collector"); 767 return false; 768 } 769 return true; // success 770 } 771 772 void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) { 773 assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock"); 774 775 MutexLocker ml(Heap_lock); 776 // Read the GC counts while holding the Heap_lock 777 unsigned int full_gc_count_before = total_full_collections(); 778 unsigned int gc_count_before = total_collections(); 779 { 780 MutexUnlocker mu(Heap_lock); 781 VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause); 782 VMThread::execute(&op); 783 } 784 } 785 #endif // INCLUDE_ALL_GCS 786 787 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs) { 788 do_full_collection(clear_all_soft_refs, _n_gens - 1); 789 } 790 791 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs, 792 int max_level) { 793 int local_max_level; 794 if (!incremental_collection_will_fail(false /* don't consult_young */) && 795 gc_cause() == GCCause::_gc_locker) { 796 local_max_level = 0; 797 } else { 798 local_max_level = max_level; 799 } 800 801 do_collection(true /* full */, 802 clear_all_soft_refs /* clear_all_soft_refs */, 803 0 /* size */, 804 false /* is_tlab */, 805 local_max_level /* max_level */); 806 // Hack XXX FIX ME !!! 807 // A scavenge may not have been attempted, or may have 808 // been attempted and failed, because the old gen was too full 809 if (local_max_level == 0 && gc_cause() == GCCause::_gc_locker && 810 incremental_collection_will_fail(false /* don't consult_young */)) { 811 if (PrintGCDetails) { 812 gclog_or_tty->print_cr("GC locker: Trying a full collection " 813 "because scavenge failed"); 814 } 815 // This time allow the old gen to be collected as well 816 do_collection(true /* full */, 817 clear_all_soft_refs /* clear_all_soft_refs */, 818 0 /* size */, 819 false /* is_tlab */, 820 n_gens() - 1 /* max_level */); 821 } 822 } 823 824 bool GenCollectedHeap::is_in_young(oop p) { 825 bool result = ((HeapWord*)p) < _gens[_n_gens - 1]->reserved().start(); 826 assert(result == _gens[0]->is_in_reserved(p), 827 err_msg("incorrect test - result=%d, p=" INTPTR_FORMAT, result, p2i((void*)p))); 828 return result; 829 } 830 831 // Returns "TRUE" iff "p" points into the committed areas of the heap. 832 bool GenCollectedHeap::is_in(const void* p) const { 833 #ifndef ASSERT 834 guarantee(VerifyBeforeGC || 835 VerifyDuringGC || 836 VerifyBeforeExit || 837 VerifyDuringStartup || 838 PrintAssembly || 839 tty->count() != 0 || // already printing 840 VerifyAfterGC || 841 VMError::fatal_error_in_progress(), "too expensive"); 842 843 #endif 844 // This might be sped up with a cache of the last generation that 845 // answered yes. 846 for (int i = 0; i < _n_gens; i++) { 847 if (_gens[i]->is_in(p)) return true; 848 } 849 // Otherwise... 850 return false; 851 } 852 853 #ifdef ASSERT 854 // Don't implement this by using is_in_young(). This method is used 855 // in some cases to check that is_in_young() is correct. 856 bool GenCollectedHeap::is_in_partial_collection(const void* p) { 857 assert(is_in_reserved(p) || p == NULL, 858 "Does not work if address is non-null and outside of the heap"); 859 return p < _gens[_n_gens - 2]->reserved().end() && p != NULL; 860 } 861 #endif 862 863 void GenCollectedHeap::oop_iterate(ExtendedOopClosure* cl) { 864 for (int i = 0; i < _n_gens; i++) { 865 _gens[i]->oop_iterate(cl); 866 } 867 } 868 869 void GenCollectedHeap::object_iterate(ObjectClosure* cl) { 870 for (int i = 0; i < _n_gens; i++) { 871 _gens[i]->object_iterate(cl); 872 } 873 } 874 875 void GenCollectedHeap::safe_object_iterate(ObjectClosure* cl) { 876 for (int i = 0; i < _n_gens; i++) { 877 _gens[i]->safe_object_iterate(cl); 878 } 879 } 880 881 Space* GenCollectedHeap::space_containing(const void* addr) const { 882 for (int i = 0; i < _n_gens; i++) { 883 Space* res = _gens[i]->space_containing(addr); 884 if (res != NULL) return res; 885 } 886 // Otherwise... 887 assert(false, "Could not find containing space"); 888 return NULL; 889 } 890 891 892 HeapWord* GenCollectedHeap::block_start(const void* addr) const { 893 assert(is_in_reserved(addr), "block_start of address outside of heap"); 894 for (int i = 0; i < _n_gens; i++) { 895 if (_gens[i]->is_in_reserved(addr)) { 896 assert(_gens[i]->is_in(addr), 897 "addr should be in allocated part of generation"); 898 return _gens[i]->block_start(addr); 899 } 900 } 901 assert(false, "Some generation should contain the address"); 902 return NULL; 903 } 904 905 size_t GenCollectedHeap::block_size(const HeapWord* addr) const { 906 assert(is_in_reserved(addr), "block_size of address outside of heap"); 907 for (int i = 0; i < _n_gens; i++) { 908 if (_gens[i]->is_in_reserved(addr)) { 909 assert(_gens[i]->is_in(addr), 910 "addr should be in allocated part of generation"); 911 return _gens[i]->block_size(addr); 912 } 913 } 914 assert(false, "Some generation should contain the address"); 915 return 0; 916 } 917 918 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const { 919 assert(is_in_reserved(addr), "block_is_obj of address outside of heap"); 920 assert(block_start(addr) == addr, "addr must be a block start"); 921 for (int i = 0; i < _n_gens; i++) { 922 if (_gens[i]->is_in_reserved(addr)) { 923 return _gens[i]->block_is_obj(addr); 924 } 925 } 926 assert(false, "Some generation should contain the address"); 927 return false; 928 } 929 930 bool GenCollectedHeap::supports_tlab_allocation() const { 931 for (int i = 0; i < _n_gens; i += 1) { 932 if (_gens[i]->supports_tlab_allocation()) { 933 return true; 934 } 935 } 936 return false; 937 } 938 939 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const { 940 size_t result = 0; 941 for (int i = 0; i < _n_gens; i += 1) { 942 if (_gens[i]->supports_tlab_allocation()) { 943 result += _gens[i]->tlab_capacity(); 944 } 945 } 946 return result; 947 } 948 949 size_t GenCollectedHeap::tlab_used(Thread* thr) const { 950 size_t result = 0; 951 for (int i = 0; i < _n_gens; i += 1) { 952 if (_gens[i]->supports_tlab_allocation()) { 953 result += _gens[i]->tlab_used(); 954 } 955 } 956 return result; 957 } 958 959 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const { 960 size_t result = 0; 961 for (int i = 0; i < _n_gens; i += 1) { 962 if (_gens[i]->supports_tlab_allocation()) { 963 result += _gens[i]->unsafe_max_tlab_alloc(); 964 } 965 } 966 return result; 967 } 968 969 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) { 970 bool gc_overhead_limit_was_exceeded; 971 return collector_policy()->mem_allocate_work(size /* size */, 972 true /* is_tlab */, 973 &gc_overhead_limit_was_exceeded); 974 } 975 976 // Requires "*prev_ptr" to be non-NULL. Deletes and a block of minimal size 977 // from the list headed by "*prev_ptr". 978 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) { 979 bool first = true; 980 size_t min_size = 0; // "first" makes this conceptually infinite. 981 ScratchBlock **smallest_ptr, *smallest; 982 ScratchBlock *cur = *prev_ptr; 983 while (cur) { 984 assert(*prev_ptr == cur, "just checking"); 985 if (first || cur->num_words < min_size) { 986 smallest_ptr = prev_ptr; 987 smallest = cur; 988 min_size = smallest->num_words; 989 first = false; 990 } 991 prev_ptr = &cur->next; 992 cur = cur->next; 993 } 994 smallest = *smallest_ptr; 995 *smallest_ptr = smallest->next; 996 return smallest; 997 } 998 999 // Sort the scratch block list headed by res into decreasing size order, 1000 // and set "res" to the result. 1001 static void sort_scratch_list(ScratchBlock*& list) { 1002 ScratchBlock* sorted = NULL; 1003 ScratchBlock* unsorted = list; 1004 while (unsorted) { 1005 ScratchBlock *smallest = removeSmallestScratch(&unsorted); 1006 smallest->next = sorted; 1007 sorted = smallest; 1008 } 1009 list = sorted; 1010 } 1011 1012 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor, 1013 size_t max_alloc_words) { 1014 ScratchBlock* res = NULL; 1015 for (int i = 0; i < _n_gens; i++) { 1016 _gens[i]->contribute_scratch(res, requestor, max_alloc_words); 1017 } 1018 sort_scratch_list(res); 1019 return res; 1020 } 1021 1022 void GenCollectedHeap::release_scratch() { 1023 for (int i = 0; i < _n_gens; i++) { 1024 _gens[i]->reset_scratch(); 1025 } 1026 } 1027 1028 class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure { 1029 void do_generation(Generation* gen) { 1030 gen->prepare_for_verify(); 1031 } 1032 }; 1033 1034 void GenCollectedHeap::prepare_for_verify() { 1035 ensure_parsability(false); // no need to retire TLABs 1036 GenPrepareForVerifyClosure blk; 1037 generation_iterate(&blk, false); 1038 } 1039 1040 1041 void GenCollectedHeap::generation_iterate(GenClosure* cl, 1042 bool old_to_young) { 1043 if (old_to_young) { 1044 for (int i = _n_gens-1; i >= 0; i--) { 1045 cl->do_generation(_gens[i]); 1046 } 1047 } else { 1048 for (int i = 0; i < _n_gens; i++) { 1049 cl->do_generation(_gens[i]); 1050 } 1051 } 1052 } 1053 1054 void GenCollectedHeap::space_iterate(SpaceClosure* cl) { 1055 for (int i = 0; i < _n_gens; i++) { 1056 _gens[i]->space_iterate(cl, true); 1057 } 1058 } 1059 1060 bool GenCollectedHeap::is_maximal_no_gc() const { 1061 for (int i = 0; i < _n_gens; i++) { 1062 if (!_gens[i]->is_maximal_no_gc()) { 1063 return false; 1064 } 1065 } 1066 return true; 1067 } 1068 1069 void GenCollectedHeap::save_marks() { 1070 for (int i = 0; i < _n_gens; i++) { 1071 _gens[i]->save_marks(); 1072 } 1073 } 1074 1075 GenCollectedHeap* GenCollectedHeap::heap() { 1076 assert(_gch != NULL, "Uninitialized access to GenCollectedHeap::heap()"); 1077 assert(_gch->kind() == CollectedHeap::GenCollectedHeap, "not a generational heap"); 1078 return _gch; 1079 } 1080 1081 1082 void GenCollectedHeap::prepare_for_compaction() { 1083 guarantee(_n_gens = 2, "Wrong number of generations"); 1084 Generation* old_gen = _gens[1]; 1085 // Start by compacting into same gen. 1086 CompactPoint cp(old_gen); 1087 old_gen->prepare_for_compaction(&cp); 1088 Generation* young_gen = _gens[0]; 1089 young_gen->prepare_for_compaction(&cp); 1090 } 1091 1092 GCStats* GenCollectedHeap::gc_stats(int level) const { 1093 return _gens[level]->gc_stats(); 1094 } 1095 1096 void GenCollectedHeap::verify(bool silent, VerifyOption option /* ignored */) { 1097 for (int i = _n_gens-1; i >= 0; i--) { 1098 Generation* g = _gens[i]; 1099 if (!silent) { 1100 gclog_or_tty->print("%s", g->name()); 1101 gclog_or_tty->print(" "); 1102 } 1103 g->verify(); 1104 } 1105 if (!silent) { 1106 gclog_or_tty->print("remset "); 1107 } 1108 rem_set()->verify(); 1109 } 1110 1111 void GenCollectedHeap::print_on(outputStream* st) const { 1112 for (int i = 0; i < _n_gens; i++) { 1113 _gens[i]->print_on(st); 1114 } 1115 MetaspaceAux::print_on(st); 1116 } 1117 1118 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const { 1119 if (workers() != NULL) { 1120 workers()->threads_do(tc); 1121 } 1122 #if INCLUDE_ALL_GCS 1123 if (UseConcMarkSweepGC) { 1124 ConcurrentMarkSweepThread::threads_do(tc); 1125 } 1126 #endif // INCLUDE_ALL_GCS 1127 } 1128 1129 void GenCollectedHeap::print_gc_threads_on(outputStream* st) const { 1130 #if INCLUDE_ALL_GCS 1131 if (UseParNewGC) { 1132 workers()->print_worker_threads_on(st); 1133 } 1134 if (UseConcMarkSweepGC) { 1135 ConcurrentMarkSweepThread::print_all_on(st); 1136 } 1137 #endif // INCLUDE_ALL_GCS 1138 } 1139 1140 void GenCollectedHeap::print_on_error(outputStream* st) const { 1141 this->CollectedHeap::print_on_error(st); 1142 1143 #if INCLUDE_ALL_GCS 1144 if (UseConcMarkSweepGC) { 1145 st->cr(); 1146 CMSCollector::print_on_error(st); 1147 } 1148 #endif // INCLUDE_ALL_GCS 1149 } 1150 1151 void GenCollectedHeap::print_tracing_info() const { 1152 if (TraceYoungGenTime) { 1153 get_gen(0)->print_summary_info(); 1154 } 1155 if (TraceOldGenTime) { 1156 get_gen(1)->print_summary_info(); 1157 } 1158 } 1159 1160 void GenCollectedHeap::print_heap_change(size_t prev_used) const { 1161 if (PrintGCDetails && Verbose) { 1162 gclog_or_tty->print(" " SIZE_FORMAT 1163 "->" SIZE_FORMAT 1164 "(" SIZE_FORMAT ")", 1165 prev_used, used(), capacity()); 1166 } else { 1167 gclog_or_tty->print(" " SIZE_FORMAT "K" 1168 "->" SIZE_FORMAT "K" 1169 "(" SIZE_FORMAT "K)", 1170 prev_used / K, used() / K, capacity() / K); 1171 } 1172 } 1173 1174 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure { 1175 private: 1176 bool _full; 1177 public: 1178 void do_generation(Generation* gen) { 1179 gen->gc_prologue(_full); 1180 } 1181 GenGCPrologueClosure(bool full) : _full(full) {}; 1182 }; 1183 1184 void GenCollectedHeap::gc_prologue(bool full) { 1185 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 1186 1187 always_do_update_barrier = false; 1188 // Fill TLAB's and such 1189 CollectedHeap::accumulate_statistics_all_tlabs(); 1190 ensure_parsability(true); // retire TLABs 1191 1192 // Walk generations 1193 GenGCPrologueClosure blk(full); 1194 generation_iterate(&blk, false); // not old-to-young. 1195 }; 1196 1197 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure { 1198 private: 1199 bool _full; 1200 public: 1201 void do_generation(Generation* gen) { 1202 gen->gc_epilogue(_full); 1203 } 1204 GenGCEpilogueClosure(bool full) : _full(full) {}; 1205 }; 1206 1207 void GenCollectedHeap::gc_epilogue(bool full) { 1208 #ifdef COMPILER2 1209 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 1210 size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr())); 1211 guarantee(actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps"); 1212 #endif /* COMPILER2 */ 1213 1214 resize_all_tlabs(); 1215 1216 GenGCEpilogueClosure blk(full); 1217 generation_iterate(&blk, false); // not old-to-young. 1218 1219 if (!CleanChunkPoolAsync) { 1220 Chunk::clean_chunk_pool(); 1221 } 1222 1223 MetaspaceCounters::update_performance_counters(); 1224 CompressedClassSpaceCounters::update_performance_counters(); 1225 1226 always_do_update_barrier = UseConcMarkSweepGC; 1227 }; 1228 1229 #ifndef PRODUCT 1230 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure { 1231 private: 1232 public: 1233 void do_generation(Generation* gen) { 1234 gen->record_spaces_top(); 1235 } 1236 }; 1237 1238 void GenCollectedHeap::record_gen_tops_before_GC() { 1239 if (ZapUnusedHeapArea) { 1240 GenGCSaveTopsBeforeGCClosure blk; 1241 generation_iterate(&blk, false); // not old-to-young. 1242 } 1243 } 1244 #endif // not PRODUCT 1245 1246 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure { 1247 public: 1248 void do_generation(Generation* gen) { 1249 gen->ensure_parsability(); 1250 } 1251 }; 1252 1253 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) { 1254 CollectedHeap::ensure_parsability(retire_tlabs); 1255 GenEnsureParsabilityClosure ep_cl; 1256 generation_iterate(&ep_cl, false); 1257 } 1258 1259 oop GenCollectedHeap::handle_failed_promotion(Generation* old_gen, 1260 oop obj, 1261 size_t obj_size) { 1262 guarantee(old_gen->level() == 1, "We only get here with an old generation"); 1263 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in"); 1264 HeapWord* result = NULL; 1265 1266 result = old_gen->expand_and_allocate(obj_size, false); 1267 1268 if (result != NULL) { 1269 Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size); 1270 } 1271 return oop(result); 1272 } 1273 1274 class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure { 1275 jlong _time; // in ms 1276 jlong _now; // in ms 1277 1278 public: 1279 GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { } 1280 1281 jlong time() { return _time; } 1282 1283 void do_generation(Generation* gen) { 1284 _time = MIN2(_time, gen->time_of_last_gc(_now)); 1285 } 1286 }; 1287 1288 jlong GenCollectedHeap::millis_since_last_gc() { 1289 // We need a monotonically non-decreasing time in ms but 1290 // os::javaTimeMillis() does not guarantee monotonicity. 1291 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 1292 GenTimeOfLastGCClosure tolgc_cl(now); 1293 // iterate over generations getting the oldest 1294 // time that a generation was collected 1295 generation_iterate(&tolgc_cl, false); 1296 1297 // javaTimeNanos() is guaranteed to be monotonically non-decreasing 1298 // provided the underlying platform provides such a time source 1299 // (and it is bug free). So we still have to guard against getting 1300 // back a time later than 'now'. 1301 jlong retVal = now - tolgc_cl.time(); 1302 if (retVal < 0) { 1303 NOT_PRODUCT(warning("time warp: "INT64_FORMAT, (int64_t) retVal);) 1304 return 0; 1305 } 1306 return retVal; 1307 }