1 /* 2 * Copyright (c) 2000, 2013, 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/gcTraceTime.hpp" 32 #include "gc_implementation/shared/vmGCOperations.hpp" 33 #include "gc_interface/collectedHeap.inline.hpp" 34 #include "memory/filemap.hpp" 35 #include "memory/gcLocker.inline.hpp" 36 #include "memory/genCollectedHeap.hpp" 37 #include "memory/genOopClosures.inline.hpp" 38 #include "memory/generation.inline.hpp" 39 #include "memory/generationSpec.hpp" 40 #include "memory/resourceArea.hpp" 41 #include "memory/sharedHeap.hpp" 42 #include "memory/space.hpp" 43 #include "oops/oop.inline.hpp" 44 #include "oops/oop.inline2.hpp" 45 #include "runtime/biasedLocking.hpp" 46 #include "runtime/fprofiler.hpp" 47 #include "runtime/handles.hpp" 48 #include "runtime/handles.inline.hpp" 49 #include "runtime/java.hpp" 50 #include "runtime/vmThread.hpp" 51 #include "services/memoryService.hpp" 52 #include "utilities/vmError.hpp" 53 #include "utilities/workgroup.hpp" 54 #include "utilities/macros.hpp" 55 #if INCLUDE_ALL_GCS 56 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp" 57 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp" 58 #endif // INCLUDE_ALL_GCS 59 60 GenCollectedHeap* GenCollectedHeap::_gch; 61 NOT_PRODUCT(size_t GenCollectedHeap::_skip_header_HeapWords = 0;) 62 63 // The set of potentially parallel tasks in strong root scanning. 64 enum GCH_process_strong_roots_tasks { 65 // We probably want to parallelize both of these internally, but for now... 66 GCH_PS_younger_gens, 67 // Leave this one last. 68 GCH_PS_NumElements 69 }; 70 71 GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy) : 72 SharedHeap(policy), 73 _gen_policy(policy), 74 _gen_process_strong_tasks(new SubTasksDone(GCH_PS_NumElements)), 75 _full_collections_completed(0) 76 { 77 if (_gen_process_strong_tasks == NULL || 78 !_gen_process_strong_tasks->valid()) { 79 vm_exit_during_initialization("Failed necessary allocation."); 80 } 81 assert(policy != NULL, "Sanity check"); 82 } 83 84 jint GenCollectedHeap::initialize() { 85 CollectedHeap::pre_initialize(); 86 87 int i; 88 _n_gens = gen_policy()->number_of_generations(); 89 90 // While there are no constraints in the GC code that HeapWordSize 91 // be any particular value, there are multiple other areas in the 92 // system which believe this to be true (e.g. oop->object_size in some 93 // cases incorrectly returns the size in wordSize units rather than 94 // HeapWordSize). 95 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 96 97 // The heap must be at least as aligned as generations. 98 size_t gen_alignment = Generation::GenGrain; 99 100 _gen_specs = gen_policy()->generations(); 101 102 // Make sure the sizes are all aligned. 103 for (i = 0; i < _n_gens; i++) { 104 _gen_specs[i]->align(gen_alignment); 105 } 106 107 // Allocate space for the heap. 108 109 char* heap_address; 110 size_t total_reserved = 0; 111 int n_covered_regions = 0; 112 ReservedSpace heap_rs; 113 114 size_t heap_alignment = collector_policy()->max_alignment(); 115 116 heap_address = allocate(heap_alignment, &total_reserved, 117 &n_covered_regions, &heap_rs); 118 119 if (!heap_rs.is_reserved()) { 120 vm_shutdown_during_initialization( 121 "Could not reserve enough space for object heap"); 122 return JNI_ENOMEM; 123 } 124 125 _reserved = MemRegion((HeapWord*)heap_rs.base(), 126 (HeapWord*)(heap_rs.base() + heap_rs.size())); 127 128 // It is important to do this in a way such that concurrent readers can't 129 // temporarily think something is in the heap. (Seen this happen in asserts.) 130 _reserved.set_word_size(0); 131 _reserved.set_start((HeapWord*)heap_rs.base()); 132 size_t actual_heap_size = heap_rs.size(); 133 _reserved.set_end((HeapWord*)(heap_rs.base() + actual_heap_size)); 134 135 _rem_set = collector_policy()->create_rem_set(_reserved, n_covered_regions); 136 set_barrier_set(rem_set()->bs()); 137 138 _gch = this; 139 140 for (i = 0; i < _n_gens; i++) { 141 ReservedSpace this_rs = heap_rs.first_part(_gen_specs[i]->max_size(), false, false); 142 _gens[i] = _gen_specs[i]->init(this_rs, i, rem_set()); 143 heap_rs = heap_rs.last_part(_gen_specs[i]->max_size()); 144 } 145 clear_incremental_collection_failed(); 146 147 #if INCLUDE_ALL_GCS 148 // If we are running CMS, create the collector responsible 149 // for collecting the CMS generations. 150 if (collector_policy()->is_concurrent_mark_sweep_policy()) { 151 bool success = create_cms_collector(); 152 if (!success) return JNI_ENOMEM; 153 } 154 #endif // INCLUDE_ALL_GCS 155 156 return JNI_OK; 157 } 158 159 160 char* GenCollectedHeap::allocate(size_t alignment, 161 size_t* _total_reserved, 162 int* _n_covered_regions, 163 ReservedSpace* heap_rs){ 164 const char overflow_msg[] = "The size of the object heap + VM data exceeds " 165 "the maximum representable size"; 166 167 // Now figure out the total size. 168 size_t total_reserved = 0; 169 int n_covered_regions = 0; 170 const size_t pageSize = UseLargePages ? 171 os::large_page_size() : os::vm_page_size(); 172 173 assert(alignment % pageSize == 0, "Must be"); 174 175 for (int i = 0; i < _n_gens; i++) { 176 total_reserved += _gen_specs[i]->max_size(); 177 if (total_reserved < _gen_specs[i]->max_size()) { 178 vm_exit_during_initialization(overflow_msg); 179 } 180 n_covered_regions += _gen_specs[i]->n_covered_regions(); 181 } 182 assert(total_reserved % alignment == 0, 183 err_msg("Gen size; total_reserved=" SIZE_FORMAT ", alignment=" 184 SIZE_FORMAT, total_reserved, alignment)); 185 186 // Needed until the cardtable is fixed to have the right number 187 // of covered regions. 188 n_covered_regions += 2; 189 190 *_total_reserved = total_reserved; 191 *_n_covered_regions = n_covered_regions; 192 193 *heap_rs = Universe::reserve_heap(total_reserved, alignment); 194 return heap_rs->base(); 195 } 196 197 198 void GenCollectedHeap::post_initialize() { 199 SharedHeap::post_initialize(); 200 TwoGenerationCollectorPolicy *policy = 201 (TwoGenerationCollectorPolicy *)collector_policy(); 202 guarantee(policy->is_two_generation_policy(), "Illegal policy type"); 203 DefNewGeneration* def_new_gen = (DefNewGeneration*) get_gen(0); 204 assert(def_new_gen->kind() == Generation::DefNew || 205 def_new_gen->kind() == Generation::ParNew || 206 def_new_gen->kind() == Generation::ASParNew, 207 "Wrong generation kind"); 208 209 Generation* old_gen = get_gen(1); 210 assert(old_gen->kind() == Generation::ConcurrentMarkSweep || 211 old_gen->kind() == Generation::ASConcurrentMarkSweep || 212 old_gen->kind() == Generation::MarkSweepCompact, 213 "Wrong generation kind"); 214 215 policy->initialize_size_policy(def_new_gen->eden()->capacity(), 216 old_gen->capacity(), 217 def_new_gen->from()->capacity()); 218 policy->initialize_gc_policy_counters(); 219 } 220 221 void GenCollectedHeap::ref_processing_init() { 222 SharedHeap::ref_processing_init(); 223 for (int i = 0; i < _n_gens; i++) { 224 _gens[i]->ref_processor_init(); 225 } 226 } 227 228 size_t GenCollectedHeap::capacity() const { 229 size_t res = 0; 230 for (int i = 0; i < _n_gens; i++) { 231 res += _gens[i]->capacity(); 232 } 233 return res; 234 } 235 236 size_t GenCollectedHeap::used() const { 237 size_t res = 0; 238 for (int i = 0; i < _n_gens; i++) { 239 res += _gens[i]->used(); 240 } 241 return res; 242 } 243 244 // Save the "used_region" for generations level and lower. 245 void GenCollectedHeap::save_used_regions(int level) { 246 assert(level < _n_gens, "Illegal level parameter"); 247 for (int i = level; i >= 0; i--) { 248 _gens[i]->save_used_region(); 249 } 250 } 251 252 size_t GenCollectedHeap::max_capacity() const { 253 size_t res = 0; 254 for (int i = 0; i < _n_gens; i++) { 255 res += _gens[i]->max_capacity(); 256 } 257 return res; 258 } 259 260 // Update the _full_collections_completed counter 261 // at the end of a stop-world full GC. 262 unsigned int GenCollectedHeap::update_full_collections_completed() { 263 MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 264 assert(_full_collections_completed <= _total_full_collections, 265 "Can't complete more collections than were started"); 266 _full_collections_completed = _total_full_collections; 267 ml.notify_all(); 268 return _full_collections_completed; 269 } 270 271 // Update the _full_collections_completed counter, as appropriate, 272 // at the end of a concurrent GC cycle. Note the conditional update 273 // below to allow this method to be called by a concurrent collector 274 // without synchronizing in any manner with the VM thread (which 275 // may already have initiated a STW full collection "concurrently"). 276 unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) { 277 MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 278 assert((_full_collections_completed <= _total_full_collections) && 279 (count <= _total_full_collections), 280 "Can't complete more collections than were started"); 281 if (count > _full_collections_completed) { 282 _full_collections_completed = count; 283 ml.notify_all(); 284 } 285 return _full_collections_completed; 286 } 287 288 289 #ifndef PRODUCT 290 // Override of memory state checking method in CollectedHeap: 291 // Some collectors (CMS for example) can't have badHeapWordVal written 292 // in the first two words of an object. (For instance , in the case of 293 // CMS these words hold state used to synchronize between certain 294 // (concurrent) GC steps and direct allocating mutators.) 295 // The skip_header_HeapWords() method below, allows us to skip 296 // over the requisite number of HeapWord's. Note that (for 297 // generational collectors) this means that those many words are 298 // skipped in each object, irrespective of the generation in which 299 // that object lives. The resultant loss of precision seems to be 300 // harmless and the pain of avoiding that imprecision appears somewhat 301 // higher than we are prepared to pay for such rudimentary debugging 302 // support. 303 void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr, 304 size_t size) { 305 if (CheckMemoryInitialization && ZapUnusedHeapArea) { 306 // We are asked to check a size in HeapWords, 307 // but the memory is mangled in juint words. 308 juint* start = (juint*) (addr + skip_header_HeapWords()); 309 juint* end = (juint*) (addr + size); 310 for (juint* slot = start; slot < end; slot += 1) { 311 assert(*slot == badHeapWordVal, 312 "Found non badHeapWordValue in pre-allocation check"); 313 } 314 } 315 } 316 #endif 317 318 HeapWord* GenCollectedHeap::attempt_allocation(size_t size, 319 bool is_tlab, 320 bool first_only) { 321 HeapWord* res; 322 for (int i = 0; i < _n_gens; i++) { 323 if (_gens[i]->should_allocate(size, is_tlab)) { 324 res = _gens[i]->allocate(size, is_tlab); 325 if (res != NULL) return res; 326 else if (first_only) break; 327 } 328 } 329 // Otherwise... 330 return NULL; 331 } 332 333 HeapWord* GenCollectedHeap::mem_allocate(size_t size, 334 bool* gc_overhead_limit_was_exceeded) { 335 return collector_policy()->mem_allocate_work(size, 336 false /* is_tlab */, 337 gc_overhead_limit_was_exceeded); 338 } 339 340 bool GenCollectedHeap::must_clear_all_soft_refs() { 341 return _gc_cause == GCCause::_last_ditch_collection; 342 } 343 344 bool GenCollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 345 return UseConcMarkSweepGC && 346 ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) || 347 (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent)); 348 } 349 350 void GenCollectedHeap::do_collection(bool full, 351 bool clear_all_soft_refs, 352 size_t size, 353 bool is_tlab, 354 int max_level) { 355 bool prepared_for_verification = false; 356 ResourceMark rm; 357 DEBUG_ONLY(Thread* my_thread = Thread::current();) 358 359 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); 360 assert(my_thread->is_VM_thread() || 361 my_thread->is_ConcurrentGC_thread(), 362 "incorrect thread type capability"); 363 assert(Heap_lock->is_locked(), 364 "the requesting thread should have the Heap_lock"); 365 guarantee(!is_gc_active(), "collection is not reentrant"); 366 assert(max_level < n_gens(), "sanity check"); 367 368 if (GC_locker::check_active_before_gc()) { 369 return; // GC is disabled (e.g. JNI GetXXXCritical operation) 370 } 371 372 const bool do_clear_all_soft_refs = clear_all_soft_refs || 373 collector_policy()->should_clear_all_soft_refs(); 374 375 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 376 377 const size_t metadata_prev_used = MetaspaceAux::allocated_used_bytes(); 378 379 print_heap_before_gc(); 380 381 { 382 FlagSetting fl(_is_gc_active, true); 383 384 bool complete = full && (max_level == (n_gens()-1)); 385 const char* gc_cause_prefix = complete ? "Full GC" : "GC"; 386 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); 387 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); 388 GCTraceTime t(GCCauseString(gc_cause_prefix, gc_cause()), PrintGCDetails, false, NULL); 389 390 gc_prologue(complete); 391 increment_total_collections(complete); 392 393 size_t gch_prev_used = used(); 394 395 int starting_level = 0; 396 if (full) { 397 // Search for the oldest generation which will collect all younger 398 // generations, and start collection loop there. 399 for (int i = max_level; i >= 0; i--) { 400 if (_gens[i]->full_collects_younger_generations()) { 401 starting_level = i; 402 break; 403 } 404 } 405 } 406 407 bool must_restore_marks_for_biased_locking = false; 408 409 int max_level_collected = starting_level; 410 for (int i = starting_level; i <= max_level; i++) { 411 if (_gens[i]->should_collect(full, size, is_tlab)) { 412 if (i == n_gens() - 1) { // a major collection is to happen 413 if (!complete) { 414 // The full_collections increment was missed above. 415 increment_total_full_collections(); 416 } 417 pre_full_gc_dump(NULL); // do any pre full gc dumps 418 } 419 // Timer for individual generations. Last argument is false: no CR 420 // FIXME: We should try to start the timing earlier to cover more of the GC pause 421 GCTraceTime t1(_gens[i]->short_name(), PrintGCDetails, false, NULL); 422 TraceCollectorStats tcs(_gens[i]->counters()); 423 TraceMemoryManagerStats tmms(_gens[i]->kind(),gc_cause()); 424 425 size_t prev_used = _gens[i]->used(); 426 _gens[i]->stat_record()->invocations++; 427 _gens[i]->stat_record()->accumulated_time.start(); 428 429 // Must be done anew before each collection because 430 // a previous collection will do mangling and will 431 // change top of some spaces. 432 record_gen_tops_before_GC(); 433 434 if (PrintGC && Verbose) { 435 gclog_or_tty->print("level=%d invoke=%d size=" SIZE_FORMAT, 436 i, 437 _gens[i]->stat_record()->invocations, 438 size*HeapWordSize); 439 } 440 441 if (VerifyBeforeGC && i >= VerifyGCLevel && 442 total_collections() >= VerifyGCStartAt) { 443 HandleMark hm; // Discard invalid handles created during verification 444 if (!prepared_for_verification) { 445 prepare_for_verify(); 446 prepared_for_verification = true; 447 } 448 Universe::verify(" VerifyBeforeGC:"); 449 } 450 COMPILER2_PRESENT(DerivedPointerTable::clear()); 451 452 if (!must_restore_marks_for_biased_locking && 453 _gens[i]->performs_in_place_marking()) { 454 // We perform this mark word preservation work lazily 455 // because it's only at this point that we know whether we 456 // absolutely have to do it; we want to avoid doing it for 457 // scavenge-only collections where it's unnecessary 458 must_restore_marks_for_biased_locking = true; 459 BiasedLocking::preserve_marks(); 460 } 461 462 // Do collection work 463 { 464 // Note on ref discovery: For what appear to be historical reasons, 465 // GCH enables and disabled (by enqueing) refs discovery. 466 // In the future this should be moved into the generation's 467 // collect method so that ref discovery and enqueueing concerns 468 // are local to a generation. The collect method could return 469 // an appropriate indication in the case that notification on 470 // the ref lock was needed. This will make the treatment of 471 // weak refs more uniform (and indeed remove such concerns 472 // from GCH). XXX 473 474 HandleMark hm; // Discard invalid handles created during gc 475 save_marks(); // save marks for all gens 476 // We want to discover references, but not process them yet. 477 // This mode is disabled in process_discovered_references if the 478 // generation does some collection work, or in 479 // enqueue_discovered_references if the generation returns 480 // without doing any work. 481 ReferenceProcessor* rp = _gens[i]->ref_processor(); 482 // If the discovery of ("weak") refs in this generation is 483 // atomic wrt other collectors in this configuration, we 484 // are guaranteed to have empty discovered ref lists. 485 if (rp->discovery_is_atomic()) { 486 rp->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); 487 rp->setup_policy(do_clear_all_soft_refs); 488 } else { 489 // collect() below will enable discovery as appropriate 490 } 491 _gens[i]->collect(full, do_clear_all_soft_refs, size, is_tlab); 492 if (!rp->enqueuing_is_done()) { 493 rp->enqueue_discovered_references(); 494 } else { 495 rp->set_enqueuing_is_done(false); 496 } 497 rp->verify_no_references_recorded(); 498 } 499 max_level_collected = i; 500 501 // Determine if allocation request was met. 502 if (size > 0) { 503 if (!is_tlab || _gens[i]->supports_tlab_allocation()) { 504 if (size*HeapWordSize <= _gens[i]->unsafe_max_alloc_nogc()) { 505 size = 0; 506 } 507 } 508 } 509 510 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 511 512 _gens[i]->stat_record()->accumulated_time.stop(); 513 514 update_gc_stats(i, full); 515 516 if (VerifyAfterGC && i >= VerifyGCLevel && 517 total_collections() >= VerifyGCStartAt) { 518 HandleMark hm; // Discard invalid handles created during verification 519 Universe::verify(" VerifyAfterGC:"); 520 } 521 522 if (PrintGCDetails) { 523 gclog_or_tty->print(":"); 524 _gens[i]->print_heap_change(prev_used); 525 } 526 } 527 } 528 529 // Update "complete" boolean wrt what actually transpired -- 530 // for instance, a promotion failure could have led to 531 // a whole heap collection. 532 complete = complete || (max_level_collected == n_gens() - 1); 533 534 if (complete) { // We did a "major" collection 535 // FIXME: See comment at pre_full_gc_dump call 536 post_full_gc_dump(NULL); // do any post full gc dumps 537 } 538 539 if (PrintGCDetails) { 540 print_heap_change(gch_prev_used); 541 542 // Print metaspace info for full GC with PrintGCDetails flag. 543 if (complete) { 544 MetaspaceAux::print_metaspace_change(metadata_prev_used); 545 } 546 } 547 548 for (int j = max_level_collected; j >= 0; j -= 1) { 549 // Adjust generation sizes. 550 _gens[j]->compute_new_size(); 551 } 552 553 if (complete) { 554 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 555 ClassLoaderDataGraph::purge(); 556 MetaspaceAux::verify_metrics(); 557 // Resize the metaspace capacity after full collections 558 MetaspaceGC::compute_new_size(); 559 update_full_collections_completed(); 560 } 561 562 // Track memory usage and detect low memory after GC finishes 563 MemoryService::track_memory_usage(); 564 565 gc_epilogue(complete); 566 567 if (must_restore_marks_for_biased_locking) { 568 BiasedLocking::restore_marks(); 569 } 570 } 571 572 AdaptiveSizePolicy* sp = gen_policy()->size_policy(); 573 AdaptiveSizePolicyOutput(sp, total_collections()); 574 575 print_heap_after_gc(); 576 577 #ifdef TRACESPINNING 578 ParallelTaskTerminator::print_termination_counts(); 579 #endif 580 } 581 582 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) { 583 return collector_policy()->satisfy_failed_allocation(size, is_tlab); 584 } 585 586 void GenCollectedHeap::set_par_threads(uint t) { 587 SharedHeap::set_par_threads(t); 588 _gen_process_strong_tasks->set_n_threads(t); 589 } 590 591 void GenCollectedHeap:: 592 gen_process_strong_roots(int level, 593 bool younger_gens_as_roots, 594 bool activate_scope, 595 bool is_scavenging, 596 SharedHeap::ScanningOption so, 597 OopsInGenClosure* not_older_gens, 598 bool do_code_roots, 599 OopsInGenClosure* older_gens, 600 KlassClosure* klass_closure) { 601 // General strong roots. 602 603 if (!do_code_roots) { 604 SharedHeap::process_strong_roots(activate_scope, is_scavenging, so, 605 not_older_gens, NULL, klass_closure); 606 } else { 607 bool do_code_marking = (activate_scope || nmethod::oops_do_marking_is_active()); 608 CodeBlobToOopClosure code_roots(not_older_gens, /*do_marking=*/ do_code_marking); 609 SharedHeap::process_strong_roots(activate_scope, is_scavenging, so, 610 not_older_gens, &code_roots, klass_closure); 611 } 612 613 if (younger_gens_as_roots) { 614 if (!_gen_process_strong_tasks->is_task_claimed(GCH_PS_younger_gens)) { 615 for (int i = 0; i < level; i++) { 616 not_older_gens->set_generation(_gens[i]); 617 _gens[i]->oop_iterate(not_older_gens); 618 } 619 not_older_gens->reset_generation(); 620 } 621 } 622 // When collection is parallel, all threads get to cooperate to do 623 // older-gen scanning. 624 for (int i = level+1; i < _n_gens; i++) { 625 older_gens->set_generation(_gens[i]); 626 rem_set()->younger_refs_iterate(_gens[i], older_gens); 627 older_gens->reset_generation(); 628 } 629 630 _gen_process_strong_tasks->all_tasks_completed(); 631 } 632 633 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure, 634 CodeBlobClosure* code_roots) { 635 SharedHeap::process_weak_roots(root_closure, code_roots); 636 // "Local" "weak" refs 637 for (int i = 0; i < _n_gens; i++) { 638 _gens[i]->ref_processor()->weak_oops_do(root_closure); 639 } 640 } 641 642 #define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix) \ 643 void GenCollectedHeap:: \ 644 oop_since_save_marks_iterate(int level, \ 645 OopClosureType* cur, \ 646 OopClosureType* older) { \ 647 _gens[level]->oop_since_save_marks_iterate##nv_suffix(cur); \ 648 for (int i = level+1; i < n_gens(); i++) { \ 649 _gens[i]->oop_since_save_marks_iterate##nv_suffix(older); \ 650 } \ 651 } 652 653 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN) 654 655 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN 656 657 bool GenCollectedHeap::no_allocs_since_save_marks(int level) { 658 for (int i = level; i < _n_gens; i++) { 659 if (!_gens[i]->no_allocs_since_save_marks()) return false; 660 } 661 return true; 662 } 663 664 bool GenCollectedHeap::supports_inline_contig_alloc() const { 665 return _gens[0]->supports_inline_contig_alloc(); 666 } 667 668 HeapWord** GenCollectedHeap::top_addr() const { 669 return _gens[0]->top_addr(); 670 } 671 672 HeapWord** GenCollectedHeap::end_addr() const { 673 return _gens[0]->end_addr(); 674 } 675 676 size_t GenCollectedHeap::unsafe_max_alloc() { 677 return _gens[0]->unsafe_max_alloc_nogc(); 678 } 679 680 // public collection interfaces 681 682 void GenCollectedHeap::collect(GCCause::Cause cause) { 683 if (should_do_concurrent_full_gc(cause)) { 684 #if INCLUDE_ALL_GCS 685 // mostly concurrent full collection 686 collect_mostly_concurrent(cause); 687 #else // INCLUDE_ALL_GCS 688 ShouldNotReachHere(); 689 #endif // INCLUDE_ALL_GCS 690 } else { 691 #ifdef ASSERT 692 if (cause == GCCause::_scavenge_alot) { 693 // minor collection only 694 collect(cause, 0); 695 } else { 696 // Stop-the-world full collection 697 collect(cause, n_gens() - 1); 698 } 699 #else 700 // Stop-the-world full collection 701 collect(cause, n_gens() - 1); 702 #endif 703 } 704 } 705 706 void GenCollectedHeap::collect(GCCause::Cause cause, int max_level) { 707 // The caller doesn't have the Heap_lock 708 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock"); 709 MutexLocker ml(Heap_lock); 710 collect_locked(cause, max_level); 711 } 712 713 void GenCollectedHeap::collect_locked(GCCause::Cause cause) { 714 // The caller has the Heap_lock 715 assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock"); 716 collect_locked(cause, n_gens() - 1); 717 } 718 719 // this is the private collection interface 720 // The Heap_lock is expected to be held on entry. 721 722 void GenCollectedHeap::collect_locked(GCCause::Cause cause, int max_level) { 723 // Read the GC count while holding the Heap_lock 724 unsigned int gc_count_before = total_collections(); 725 unsigned int full_gc_count_before = total_full_collections(); 726 { 727 MutexUnlocker mu(Heap_lock); // give up heap lock, execute gets it back 728 VM_GenCollectFull op(gc_count_before, full_gc_count_before, 729 cause, max_level); 730 VMThread::execute(&op); 731 } 732 } 733 734 #if INCLUDE_ALL_GCS 735 bool GenCollectedHeap::create_cms_collector() { 736 737 assert(((_gens[1]->kind() == Generation::ConcurrentMarkSweep) || 738 (_gens[1]->kind() == Generation::ASConcurrentMarkSweep)), 739 "Unexpected generation kinds"); 740 // Skip two header words in the block content verification 741 NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();) 742 CMSCollector* collector = new CMSCollector( 743 (ConcurrentMarkSweepGeneration*)_gens[1], 744 _rem_set->as_CardTableRS(), 745 (ConcurrentMarkSweepPolicy*) collector_policy()); 746 747 if (collector == NULL || !collector->completed_initialization()) { 748 if (collector) { 749 delete collector; // Be nice in embedded situation 750 } 751 vm_shutdown_during_initialization("Could not create CMS collector"); 752 return false; 753 } 754 return true; // success 755 } 756 757 void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) { 758 assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock"); 759 760 MutexLocker ml(Heap_lock); 761 // Read the GC counts while holding the Heap_lock 762 unsigned int full_gc_count_before = total_full_collections(); 763 unsigned int gc_count_before = total_collections(); 764 { 765 MutexUnlocker mu(Heap_lock); 766 VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause); 767 VMThread::execute(&op); 768 } 769 } 770 #endif // INCLUDE_ALL_GCS 771 772 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs) { 773 do_full_collection(clear_all_soft_refs, _n_gens - 1); 774 } 775 776 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs, 777 int max_level) { 778 int local_max_level; 779 if (!incremental_collection_will_fail(false /* don't consult_young */) && 780 gc_cause() == GCCause::_gc_locker) { 781 local_max_level = 0; 782 } else { 783 local_max_level = max_level; 784 } 785 786 do_collection(true /* full */, 787 clear_all_soft_refs /* clear_all_soft_refs */, 788 0 /* size */, 789 false /* is_tlab */, 790 local_max_level /* max_level */); 791 // Hack XXX FIX ME !!! 792 // A scavenge may not have been attempted, or may have 793 // been attempted and failed, because the old gen was too full 794 if (local_max_level == 0 && gc_cause() == GCCause::_gc_locker && 795 incremental_collection_will_fail(false /* don't consult_young */)) { 796 if (PrintGCDetails) { 797 gclog_or_tty->print_cr("GC locker: Trying a full collection " 798 "because scavenge failed"); 799 } 800 // This time allow the old gen to be collected as well 801 do_collection(true /* full */, 802 clear_all_soft_refs /* clear_all_soft_refs */, 803 0 /* size */, 804 false /* is_tlab */, 805 n_gens() - 1 /* max_level */); 806 } 807 } 808 809 bool GenCollectedHeap::is_in_young(oop p) { 810 bool result = ((HeapWord*)p) < _gens[_n_gens - 1]->reserved().start(); 811 assert(result == _gens[0]->is_in_reserved(p), 812 err_msg("incorrect test - result=%d, p=" PTR_FORMAT, result, (void*)p)); 813 return result; 814 } 815 816 // Returns "TRUE" iff "p" points into the committed areas of the heap. 817 bool GenCollectedHeap::is_in(const void* p) const { 818 #ifndef ASSERT 819 guarantee(VerifyBeforeGC || 820 VerifyDuringGC || 821 VerifyBeforeExit || 822 VerifyDuringStartup || 823 PrintAssembly || 824 tty->count() != 0 || // already printing 825 VerifyAfterGC || 826 VMError::fatal_error_in_progress(), "too expensive"); 827 828 #endif 829 // This might be sped up with a cache of the last generation that 830 // answered yes. 831 for (int i = 0; i < _n_gens; i++) { 832 if (_gens[i]->is_in(p)) return true; 833 } 834 // Otherwise... 835 return false; 836 } 837 838 #ifdef ASSERT 839 // Don't implement this by using is_in_young(). This method is used 840 // in some cases to check that is_in_young() is correct. 841 bool GenCollectedHeap::is_in_partial_collection(const void* p) { 842 assert(is_in_reserved(p) || p == NULL, 843 "Does not work if address is non-null and outside of the heap"); 844 return p < _gens[_n_gens - 2]->reserved().end() && p != NULL; 845 } 846 #endif 847 848 void GenCollectedHeap::oop_iterate(ExtendedOopClosure* cl) { 849 for (int i = 0; i < _n_gens; i++) { 850 _gens[i]->oop_iterate(cl); 851 } 852 } 853 854 void GenCollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) { 855 for (int i = 0; i < _n_gens; i++) { 856 _gens[i]->oop_iterate(mr, cl); 857 } 858 } 859 860 void GenCollectedHeap::object_iterate(ObjectClosure* cl) { 861 for (int i = 0; i < _n_gens; i++) { 862 _gens[i]->object_iterate(cl); 863 } 864 } 865 866 void GenCollectedHeap::safe_object_iterate(ObjectClosure* cl) { 867 for (int i = 0; i < _n_gens; i++) { 868 _gens[i]->safe_object_iterate(cl); 869 } 870 } 871 872 Space* GenCollectedHeap::space_containing(const void* addr) const { 873 for (int i = 0; i < _n_gens; i++) { 874 Space* res = _gens[i]->space_containing(addr); 875 if (res != NULL) return res; 876 } 877 // Otherwise... 878 assert(false, "Could not find containing space"); 879 return NULL; 880 } 881 882 883 HeapWord* GenCollectedHeap::block_start(const void* addr) const { 884 assert(is_in_reserved(addr), "block_start of address outside of heap"); 885 for (int i = 0; i < _n_gens; i++) { 886 if (_gens[i]->is_in_reserved(addr)) { 887 assert(_gens[i]->is_in(addr), 888 "addr should be in allocated part of generation"); 889 return _gens[i]->block_start(addr); 890 } 891 } 892 assert(false, "Some generation should contain the address"); 893 return NULL; 894 } 895 896 size_t GenCollectedHeap::block_size(const HeapWord* addr) const { 897 assert(is_in_reserved(addr), "block_size of address outside of heap"); 898 for (int i = 0; i < _n_gens; i++) { 899 if (_gens[i]->is_in_reserved(addr)) { 900 assert(_gens[i]->is_in(addr), 901 "addr should be in allocated part of generation"); 902 return _gens[i]->block_size(addr); 903 } 904 } 905 assert(false, "Some generation should contain the address"); 906 return 0; 907 } 908 909 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const { 910 assert(is_in_reserved(addr), "block_is_obj of address outside of heap"); 911 assert(block_start(addr) == addr, "addr must be a block start"); 912 for (int i = 0; i < _n_gens; i++) { 913 if (_gens[i]->is_in_reserved(addr)) { 914 return _gens[i]->block_is_obj(addr); 915 } 916 } 917 assert(false, "Some generation should contain the address"); 918 return false; 919 } 920 921 bool GenCollectedHeap::supports_tlab_allocation() const { 922 for (int i = 0; i < _n_gens; i += 1) { 923 if (_gens[i]->supports_tlab_allocation()) { 924 return true; 925 } 926 } 927 return false; 928 } 929 930 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const { 931 size_t result = 0; 932 for (int i = 0; i < _n_gens; i += 1) { 933 if (_gens[i]->supports_tlab_allocation()) { 934 result += _gens[i]->tlab_capacity(); 935 } 936 } 937 return result; 938 } 939 940 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const { 941 size_t result = 0; 942 for (int i = 0; i < _n_gens; i += 1) { 943 if (_gens[i]->supports_tlab_allocation()) { 944 result += _gens[i]->unsafe_max_tlab_alloc(); 945 } 946 } 947 return result; 948 } 949 950 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) { 951 bool gc_overhead_limit_was_exceeded; 952 return collector_policy()->mem_allocate_work(size /* size */, 953 true /* is_tlab */, 954 &gc_overhead_limit_was_exceeded); 955 } 956 957 // Requires "*prev_ptr" to be non-NULL. Deletes and a block of minimal size 958 // from the list headed by "*prev_ptr". 959 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) { 960 bool first = true; 961 size_t min_size = 0; // "first" makes this conceptually infinite. 962 ScratchBlock **smallest_ptr, *smallest; 963 ScratchBlock *cur = *prev_ptr; 964 while (cur) { 965 assert(*prev_ptr == cur, "just checking"); 966 if (first || cur->num_words < min_size) { 967 smallest_ptr = prev_ptr; 968 smallest = cur; 969 min_size = smallest->num_words; 970 first = false; 971 } 972 prev_ptr = &cur->next; 973 cur = cur->next; 974 } 975 smallest = *smallest_ptr; 976 *smallest_ptr = smallest->next; 977 return smallest; 978 } 979 980 // Sort the scratch block list headed by res into decreasing size order, 981 // and set "res" to the result. 982 static void sort_scratch_list(ScratchBlock*& list) { 983 ScratchBlock* sorted = NULL; 984 ScratchBlock* unsorted = list; 985 while (unsorted) { 986 ScratchBlock *smallest = removeSmallestScratch(&unsorted); 987 smallest->next = sorted; 988 sorted = smallest; 989 } 990 list = sorted; 991 } 992 993 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor, 994 size_t max_alloc_words) { 995 ScratchBlock* res = NULL; 996 for (int i = 0; i < _n_gens; i++) { 997 _gens[i]->contribute_scratch(res, requestor, max_alloc_words); 998 } 999 sort_scratch_list(res); 1000 return res; 1001 } 1002 1003 void GenCollectedHeap::release_scratch() { 1004 for (int i = 0; i < _n_gens; i++) { 1005 _gens[i]->reset_scratch(); 1006 } 1007 } 1008 1009 class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure { 1010 void do_generation(Generation* gen) { 1011 gen->prepare_for_verify(); 1012 } 1013 }; 1014 1015 void GenCollectedHeap::prepare_for_verify() { 1016 ensure_parsability(false); // no need to retire TLABs 1017 GenPrepareForVerifyClosure blk; 1018 generation_iterate(&blk, false); 1019 } 1020 1021 1022 void GenCollectedHeap::generation_iterate(GenClosure* cl, 1023 bool old_to_young) { 1024 if (old_to_young) { 1025 for (int i = _n_gens-1; i >= 0; i--) { 1026 cl->do_generation(_gens[i]); 1027 } 1028 } else { 1029 for (int i = 0; i < _n_gens; i++) { 1030 cl->do_generation(_gens[i]); 1031 } 1032 } 1033 } 1034 1035 void GenCollectedHeap::space_iterate(SpaceClosure* cl) { 1036 for (int i = 0; i < _n_gens; i++) { 1037 _gens[i]->space_iterate(cl, true); 1038 } 1039 } 1040 1041 bool GenCollectedHeap::is_maximal_no_gc() const { 1042 for (int i = 0; i < _n_gens; i++) { 1043 if (!_gens[i]->is_maximal_no_gc()) { 1044 return false; 1045 } 1046 } 1047 return true; 1048 } 1049 1050 void GenCollectedHeap::save_marks() { 1051 for (int i = 0; i < _n_gens; i++) { 1052 _gens[i]->save_marks(); 1053 } 1054 } 1055 1056 GenCollectedHeap* GenCollectedHeap::heap() { 1057 assert(_gch != NULL, "Uninitialized access to GenCollectedHeap::heap()"); 1058 assert(_gch->kind() == CollectedHeap::GenCollectedHeap, "not a generational heap"); 1059 return _gch; 1060 } 1061 1062 1063 void GenCollectedHeap::prepare_for_compaction() { 1064 guarantee(_n_gens = 2, "Wrong number of generations"); 1065 Generation* old_gen = _gens[1]; 1066 // Start by compacting into same gen. 1067 CompactPoint cp(old_gen, NULL, NULL); 1068 old_gen->prepare_for_compaction(&cp); 1069 Generation* young_gen = _gens[0]; 1070 young_gen->prepare_for_compaction(&cp); 1071 } 1072 1073 GCStats* GenCollectedHeap::gc_stats(int level) const { 1074 return _gens[level]->gc_stats(); 1075 } 1076 1077 void GenCollectedHeap::verify(bool silent, VerifyOption option /* ignored */) { 1078 for (int i = _n_gens-1; i >= 0; i--) { 1079 Generation* g = _gens[i]; 1080 if (!silent) { 1081 gclog_or_tty->print(g->name()); 1082 gclog_or_tty->print(" "); 1083 } 1084 g->verify(); 1085 } 1086 if (!silent) { 1087 gclog_or_tty->print("remset "); 1088 } 1089 rem_set()->verify(); 1090 } 1091 1092 void GenCollectedHeap::print_on(outputStream* st) const { 1093 for (int i = 0; i < _n_gens; i++) { 1094 _gens[i]->print_on(st); 1095 } 1096 MetaspaceAux::print_on(st); 1097 } 1098 1099 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const { 1100 if (workers() != NULL) { 1101 workers()->threads_do(tc); 1102 } 1103 #if INCLUDE_ALL_GCS 1104 if (UseConcMarkSweepGC) { 1105 ConcurrentMarkSweepThread::threads_do(tc); 1106 } 1107 #endif // INCLUDE_ALL_GCS 1108 } 1109 1110 void GenCollectedHeap::print_gc_threads_on(outputStream* st) const { 1111 #if INCLUDE_ALL_GCS 1112 if (UseParNewGC) { 1113 workers()->print_worker_threads_on(st); 1114 } 1115 if (UseConcMarkSweepGC) { 1116 ConcurrentMarkSweepThread::print_all_on(st); 1117 } 1118 #endif // INCLUDE_ALL_GCS 1119 } 1120 1121 void GenCollectedHeap::print_on_error(outputStream* st) const { 1122 this->CollectedHeap::print_on_error(st); 1123 1124 #if INCLUDE_ALL_GCS 1125 if (UseConcMarkSweepGC) { 1126 st->cr(); 1127 CMSCollector::print_on_error(st); 1128 } 1129 #endif // INCLUDE_ALL_GCS 1130 } 1131 1132 void GenCollectedHeap::print_tracing_info() const { 1133 if (TraceGen0Time) { 1134 get_gen(0)->print_summary_info(); 1135 } 1136 if (TraceGen1Time) { 1137 get_gen(1)->print_summary_info(); 1138 } 1139 } 1140 1141 void GenCollectedHeap::print_heap_change(size_t prev_used) const { 1142 if (PrintGCDetails && Verbose) { 1143 gclog_or_tty->print(" " SIZE_FORMAT 1144 "->" SIZE_FORMAT 1145 "(" SIZE_FORMAT ")", 1146 prev_used, used(), capacity()); 1147 } else { 1148 gclog_or_tty->print(" " SIZE_FORMAT "K" 1149 "->" SIZE_FORMAT "K" 1150 "(" SIZE_FORMAT "K)", 1151 prev_used / K, used() / K, capacity() / K); 1152 } 1153 } 1154 1155 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure { 1156 private: 1157 bool _full; 1158 public: 1159 void do_generation(Generation* gen) { 1160 gen->gc_prologue(_full); 1161 } 1162 GenGCPrologueClosure(bool full) : _full(full) {}; 1163 }; 1164 1165 void GenCollectedHeap::gc_prologue(bool full) { 1166 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 1167 1168 always_do_update_barrier = false; 1169 // Fill TLAB's and such 1170 CollectedHeap::accumulate_statistics_all_tlabs(); 1171 ensure_parsability(true); // retire TLABs 1172 1173 // Walk generations 1174 GenGCPrologueClosure blk(full); 1175 generation_iterate(&blk, false); // not old-to-young. 1176 }; 1177 1178 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure { 1179 private: 1180 bool _full; 1181 public: 1182 void do_generation(Generation* gen) { 1183 gen->gc_epilogue(_full); 1184 } 1185 GenGCEpilogueClosure(bool full) : _full(full) {}; 1186 }; 1187 1188 void GenCollectedHeap::gc_epilogue(bool full) { 1189 #ifdef COMPILER2 1190 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 1191 size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr())); 1192 guarantee(actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps"); 1193 #endif /* COMPILER2 */ 1194 1195 resize_all_tlabs(); 1196 1197 GenGCEpilogueClosure blk(full); 1198 generation_iterate(&blk, false); // not old-to-young. 1199 1200 if (!CleanChunkPoolAsync) { 1201 Chunk::clean_chunk_pool(); 1202 } 1203 1204 MetaspaceCounters::update_performance_counters(); 1205 CompressedClassSpaceCounters::update_performance_counters(); 1206 1207 always_do_update_barrier = UseConcMarkSweepGC; 1208 }; 1209 1210 #ifndef PRODUCT 1211 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure { 1212 private: 1213 public: 1214 void do_generation(Generation* gen) { 1215 gen->record_spaces_top(); 1216 } 1217 }; 1218 1219 void GenCollectedHeap::record_gen_tops_before_GC() { 1220 if (ZapUnusedHeapArea) { 1221 GenGCSaveTopsBeforeGCClosure blk; 1222 generation_iterate(&blk, false); // not old-to-young. 1223 } 1224 } 1225 #endif // not PRODUCT 1226 1227 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure { 1228 public: 1229 void do_generation(Generation* gen) { 1230 gen->ensure_parsability(); 1231 } 1232 }; 1233 1234 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) { 1235 CollectedHeap::ensure_parsability(retire_tlabs); 1236 GenEnsureParsabilityClosure ep_cl; 1237 generation_iterate(&ep_cl, false); 1238 } 1239 1240 oop GenCollectedHeap::handle_failed_promotion(Generation* old_gen, 1241 oop obj, 1242 size_t obj_size) { 1243 guarantee(old_gen->level() == 1, "We only get here with an old generation"); 1244 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in"); 1245 HeapWord* result = NULL; 1246 1247 result = old_gen->expand_and_allocate(obj_size, false); 1248 1249 if (result != NULL) { 1250 Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size); 1251 } 1252 return oop(result); 1253 } 1254 1255 class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure { 1256 jlong _time; // in ms 1257 jlong _now; // in ms 1258 1259 public: 1260 GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { } 1261 1262 jlong time() { return _time; } 1263 1264 void do_generation(Generation* gen) { 1265 _time = MIN2(_time, gen->time_of_last_gc(_now)); 1266 } 1267 }; 1268 1269 jlong GenCollectedHeap::millis_since_last_gc() { 1270 // We need a monotonically non-decreasing time in ms but 1271 // os::javaTimeMillis() does not guarantee monotonicity. 1272 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 1273 GenTimeOfLastGCClosure tolgc_cl(now); 1274 // iterate over generations getting the oldest 1275 // time that a generation was collected 1276 generation_iterate(&tolgc_cl, false); 1277 1278 // javaTimeNanos() is guaranteed to be monotonically non-decreasing 1279 // provided the underlying platform provides such a time source 1280 // (and it is bug free). So we still have to guard against getting 1281 // back a time later than 'now'. 1282 jlong retVal = now - tolgc_cl.time(); 1283 if (retVal < 0) { 1284 NOT_PRODUCT(warning("time warp: "INT64_FORMAT, retVal);) 1285 return 0; 1286 } 1287 return retVal; 1288 }