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 _reserved = MemRegion((HeapWord*)heap_rs.base(), 127 (HeapWord*)(heap_rs.base() + heap_rs.size())); 128 129 // It is important to do this in a way such that concurrent readers can't 130 // temporarily think somethings in the heap. (Seen this happen in asserts.) 131 _reserved.set_word_size(0); 132 _reserved.set_start((HeapWord*)heap_rs.base()); 133 size_t actual_heap_size = heap_rs.size(); 134 _reserved.set_end((HeapWord*)(heap_rs.base() + actual_heap_size)); 135 136 _rem_set = collector_policy()->create_rem_set(_reserved, n_covered_regions); 137 set_barrier_set(rem_set()->bs()); 138 139 _gch = this; 140 141 for (i = 0; i < _n_gens; i++) { 142 ReservedSpace this_rs = heap_rs.first_part(_gen_specs[i]->max_size(), false, false); 143 _gens[i] = _gen_specs[i]->init(this_rs, i, rem_set()); 144 heap_rs = heap_rs.last_part(_gen_specs[i]->max_size()); 145 } 146 clear_incremental_collection_failed(); 147 148 #if INCLUDE_ALL_GCS 149 // If we are running CMS, create the collector responsible 150 // for collecting the CMS generations. 151 if (collector_policy()->is_concurrent_mark_sweep_policy()) { 152 bool success = create_cms_collector(); 153 if (!success) return JNI_ENOMEM; 154 } 155 #endif // INCLUDE_ALL_GCS 156 157 return JNI_OK; 158 } 159 160 161 char* GenCollectedHeap::allocate(size_t alignment, 162 size_t* _total_reserved, 163 int* _n_covered_regions, 164 ReservedSpace* heap_rs){ 165 const char overflow_msg[] = "The size of the object heap + VM data exceeds " 166 "the maximum representable size"; 167 168 // Now figure out the total size. 169 size_t total_reserved = 0; 170 int n_covered_regions = 0; 171 const size_t pageSize = UseLargePages ? 172 os::large_page_size() : os::vm_page_size(); 173 174 assert(alignment % pageSize == 0, "Must be"); 175 176 for (int i = 0; i < _n_gens; i++) { 177 total_reserved += _gen_specs[i]->max_size(); 178 if (total_reserved < _gen_specs[i]->max_size()) { 179 vm_exit_during_initialization(overflow_msg); 180 } 181 n_covered_regions += _gen_specs[i]->n_covered_regions(); 182 } 183 assert(total_reserved % alignment == 0, 184 err_msg("Gen size; total_reserved=" SIZE_FORMAT ", alignment=" 185 SIZE_FORMAT, total_reserved, alignment)); 186 187 // Needed until the cardtable is fixed to have the right number 188 // of covered regions. 189 n_covered_regions += 2; 190 191 *_total_reserved = total_reserved; 192 *_n_covered_regions = n_covered_regions; 193 194 *heap_rs = Universe::reserve_heap(total_reserved, alignment); 195 return heap_rs->base(); 196 } 197 198 199 void GenCollectedHeap::post_initialize() { 200 SharedHeap::post_initialize(); 201 TwoGenerationCollectorPolicy *policy = 202 (TwoGenerationCollectorPolicy *)collector_policy(); 203 guarantee(policy->is_two_generation_policy(), "Illegal policy type"); 204 DefNewGeneration* def_new_gen = (DefNewGeneration*) get_gen(0); 205 assert(def_new_gen->kind() == Generation::DefNew || 206 def_new_gen->kind() == Generation::ParNew || 207 def_new_gen->kind() == Generation::ASParNew, 208 "Wrong generation kind"); 209 210 Generation* old_gen = get_gen(1); 211 assert(old_gen->kind() == Generation::ConcurrentMarkSweep || 212 old_gen->kind() == Generation::ASConcurrentMarkSweep || 213 old_gen->kind() == Generation::MarkSweepCompact, 214 "Wrong generation kind"); 215 216 policy->initialize_size_policy(def_new_gen->eden()->capacity(), 217 old_gen->capacity(), 218 def_new_gen->from()->capacity()); 219 policy->initialize_gc_policy_counters(); 220 } 221 222 void GenCollectedHeap::ref_processing_init() { 223 SharedHeap::ref_processing_init(); 224 for (int i = 0; i < _n_gens; i++) { 225 _gens[i]->ref_processor_init(); 226 } 227 } 228 229 size_t GenCollectedHeap::capacity() const { 230 size_t res = 0; 231 for (int i = 0; i < _n_gens; i++) { 232 res += _gens[i]->capacity(); 233 } 234 return res; 235 } 236 237 size_t GenCollectedHeap::used() const { 238 size_t res = 0; 239 for (int i = 0; i < _n_gens; i++) { 240 res += _gens[i]->used(); 241 } 242 return res; 243 } 244 245 // Save the "used_region" for generations level and lower. 246 void GenCollectedHeap::save_used_regions(int level) { 247 assert(level < _n_gens, "Illegal level parameter"); 248 for (int i = level; i >= 0; i--) { 249 _gens[i]->save_used_region(); 250 } 251 } 252 253 size_t GenCollectedHeap::max_capacity() const { 254 size_t res = 0; 255 for (int i = 0; i < _n_gens; i++) { 256 res += _gens[i]->max_capacity(); 257 } 258 return res; 259 } 260 261 // Update the _full_collections_completed counter 262 // at the end of a stop-world full GC. 263 unsigned int GenCollectedHeap::update_full_collections_completed() { 264 MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 265 assert(_full_collections_completed <= _total_full_collections, 266 "Can't complete more collections than were started"); 267 _full_collections_completed = _total_full_collections; 268 ml.notify_all(); 269 return _full_collections_completed; 270 } 271 272 // Update the _full_collections_completed counter, as appropriate, 273 // at the end of a concurrent GC cycle. Note the conditional update 274 // below to allow this method to be called by a concurrent collector 275 // without synchronizing in any manner with the VM thread (which 276 // may already have initiated a STW full collection "concurrently"). 277 unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) { 278 MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 279 assert((_full_collections_completed <= _total_full_collections) && 280 (count <= _total_full_collections), 281 "Can't complete more collections than were started"); 282 if (count > _full_collections_completed) { 283 _full_collections_completed = count; 284 ml.notify_all(); 285 } 286 return _full_collections_completed; 287 } 288 289 290 #ifndef PRODUCT 291 // Override of memory state checking method in CollectedHeap: 292 // Some collectors (CMS for example) can't have badHeapWordVal written 293 // in the first two words of an object. (For instance , in the case of 294 // CMS these words hold state used to synchronize between certain 295 // (concurrent) GC steps and direct allocating mutators.) 296 // The skip_header_HeapWords() method below, allows us to skip 297 // over the requisite number of HeapWord's. Note that (for 298 // generational collectors) this means that those many words are 299 // skipped in each object, irrespective of the generation in which 300 // that object lives. The resultant loss of precision seems to be 301 // harmless and the pain of avoiding that imprecision appears somewhat 302 // higher than we are prepared to pay for such rudimentary debugging 303 // support. 304 void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr, 305 size_t size) { 306 if (CheckMemoryInitialization && ZapUnusedHeapArea) { 307 // We are asked to check a size in HeapWords, 308 // but the memory is mangled in juint words. 309 juint* start = (juint*) (addr + skip_header_HeapWords()); 310 juint* end = (juint*) (addr + size); 311 for (juint* slot = start; slot < end; slot += 1) { 312 assert(*slot == badHeapWordVal, 313 "Found non badHeapWordValue in pre-allocation check"); 314 } 315 } 316 } 317 #endif 318 319 HeapWord* GenCollectedHeap::attempt_allocation(size_t size, 320 bool is_tlab, 321 bool first_only) { 322 HeapWord* res; 323 for (int i = 0; i < _n_gens; i++) { 324 if (_gens[i]->should_allocate(size, is_tlab)) { 325 res = _gens[i]->allocate(size, is_tlab); 326 if (res != NULL) return res; 327 else if (first_only) break; 328 } 329 } 330 // Otherwise... 331 return NULL; 332 } 333 334 HeapWord* GenCollectedHeap::mem_allocate(size_t size, 335 bool* gc_overhead_limit_was_exceeded) { 336 return collector_policy()->mem_allocate_work(size, 337 false /* is_tlab */, 338 gc_overhead_limit_was_exceeded); 339 } 340 341 bool GenCollectedHeap::must_clear_all_soft_refs() { 342 return _gc_cause == GCCause::_last_ditch_collection; 343 } 344 345 bool GenCollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 346 return UseConcMarkSweepGC && 347 ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) || 348 (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent)); 349 } 350 351 void GenCollectedHeap::do_collection(bool full, 352 bool clear_all_soft_refs, 353 size_t size, 354 bool is_tlab, 355 int max_level) { 356 bool prepared_for_verification = false; 357 ResourceMark rm; 358 DEBUG_ONLY(Thread* my_thread = Thread::current();) 359 360 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); 361 assert(my_thread->is_VM_thread() || 362 my_thread->is_ConcurrentGC_thread(), 363 "incorrect thread type capability"); 364 assert(Heap_lock->is_locked(), 365 "the requesting thread should have the Heap_lock"); 366 guarantee(!is_gc_active(), "collection is not reentrant"); 367 assert(max_level < n_gens(), "sanity check"); 368 369 if (GC_locker::check_active_before_gc()) { 370 return; // GC is disabled (e.g. JNI GetXXXCritical operation) 371 } 372 373 const bool do_clear_all_soft_refs = clear_all_soft_refs || 374 collector_policy()->should_clear_all_soft_refs(); 375 376 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 377 378 const size_t metadata_prev_used = MetaspaceAux::used_bytes(); 379 380 print_heap_before_gc(); 381 382 { 383 FlagSetting fl(_is_gc_active, true); 384 385 bool complete = full && (max_level == (n_gens()-1)); 386 const char* gc_cause_prefix = complete ? "Full GC" : "GC"; 387 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); 388 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); 389 // The PrintGCDetails logging starts before we have incremented the GC id. We will do that later 390 // so we can assume here that the next GC id is what we want. 391 GCTraceTime t(GCCauseString(gc_cause_prefix, gc_cause()), PrintGCDetails, false, NULL, GCId::peek()); 392 393 gc_prologue(complete); 394 increment_total_collections(complete); 395 396 size_t gch_prev_used = used(); 397 398 int starting_level = 0; 399 if (full) { 400 // Search for the oldest generation which will collect all younger 401 // generations, and start collection loop there. 402 for (int i = max_level; i >= 0; i--) { 403 if (_gens[i]->full_collects_younger_generations()) { 404 starting_level = i; 405 break; 406 } 407 } 408 } 409 410 bool must_restore_marks_for_biased_locking = false; 411 412 int max_level_collected = starting_level; 413 for (int i = starting_level; i <= max_level; i++) { 414 if (_gens[i]->should_collect(full, size, is_tlab)) { 415 if (i == n_gens() - 1) { // a major collection is to happen 416 if (!complete) { 417 // The full_collections increment was missed above. 418 increment_total_full_collections(); 419 } 420 pre_full_gc_dump(NULL); // do any pre full gc dumps 421 } 422 // Timer for individual generations. Last argument is false: no CR 423 // FIXME: We should try to start the timing earlier to cover more of the GC pause 424 // The PrintGCDetails logging starts before we have incremented the GC id. We will do that later 425 // so we can assume here that the next GC id is what we want. 426 GCTraceTime t1(_gens[i]->short_name(), PrintGCDetails, false, NULL, GCId::peek()); 427 TraceCollectorStats tcs(_gens[i]->counters()); 428 TraceMemoryManagerStats tmms(_gens[i]->kind(),gc_cause()); 429 430 size_t prev_used = _gens[i]->used(); 431 _gens[i]->stat_record()->invocations++; 432 _gens[i]->stat_record()->accumulated_time.start(); 433 434 // Must be done anew before each collection because 435 // a previous collection will do mangling and will 436 // change top of some spaces. 437 record_gen_tops_before_GC(); 438 439 if (PrintGC && Verbose) { 440 gclog_or_tty->print("level=%d invoke=%d size=" SIZE_FORMAT, 441 i, 442 _gens[i]->stat_record()->invocations, 443 size*HeapWordSize); 444 } 445 446 if (VerifyBeforeGC && i >= VerifyGCLevel && 447 total_collections() >= VerifyGCStartAt) { 448 HandleMark hm; // Discard invalid handles created during verification 449 if (!prepared_for_verification) { 450 prepare_for_verify(); 451 prepared_for_verification = true; 452 } 453 Universe::verify(" VerifyBeforeGC:"); 454 } 455 COMPILER2_PRESENT(DerivedPointerTable::clear()); 456 457 if (!must_restore_marks_for_biased_locking && 458 _gens[i]->performs_in_place_marking()) { 459 // We perform this mark word preservation work lazily 460 // because it's only at this point that we know whether we 461 // absolutely have to do it; we want to avoid doing it for 462 // scavenge-only collections where it's unnecessary 463 must_restore_marks_for_biased_locking = true; 464 BiasedLocking::preserve_marks(); 465 } 466 467 // Do collection work 468 { 469 // Note on ref discovery: For what appear to be historical reasons, 470 // GCH enables and disabled (by enqueing) refs discovery. 471 // In the future this should be moved into the generation's 472 // collect method so that ref discovery and enqueueing concerns 473 // are local to a generation. The collect method could return 474 // an appropriate indication in the case that notification on 475 // the ref lock was needed. This will make the treatment of 476 // weak refs more uniform (and indeed remove such concerns 477 // from GCH). XXX 478 479 HandleMark hm; // Discard invalid handles created during gc 480 save_marks(); // save marks for all gens 481 // We want to discover references, but not process them yet. 482 // This mode is disabled in process_discovered_references if the 483 // generation does some collection work, or in 484 // enqueue_discovered_references if the generation returns 485 // without doing any work. 486 ReferenceProcessor* rp = _gens[i]->ref_processor(); 487 // If the discovery of ("weak") refs in this generation is 488 // atomic wrt other collectors in this configuration, we 489 // are guaranteed to have empty discovered ref lists. 490 if (rp->discovery_is_atomic()) { 491 rp->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); 492 rp->setup_policy(do_clear_all_soft_refs); 493 } else { 494 // collect() below will enable discovery as appropriate 495 } 496 _gens[i]->collect(full, do_clear_all_soft_refs, size, is_tlab); 497 if (!rp->enqueuing_is_done()) { 498 rp->enqueue_discovered_references(); 499 } else { 500 rp->set_enqueuing_is_done(false); 501 } 502 rp->verify_no_references_recorded(); 503 } 504 max_level_collected = i; 505 506 // Determine if allocation request was met. 507 if (size > 0) { 508 if (!is_tlab || _gens[i]->supports_tlab_allocation()) { 509 if (size*HeapWordSize <= _gens[i]->unsafe_max_alloc_nogc()) { 510 size = 0; 511 } 512 } 513 } 514 515 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 516 517 _gens[i]->stat_record()->accumulated_time.stop(); 518 519 update_gc_stats(i, full); 520 521 if (VerifyAfterGC && i >= VerifyGCLevel && 522 total_collections() >= VerifyGCStartAt) { 523 HandleMark hm; // Discard invalid handles created during verification 524 Universe::verify(" VerifyAfterGC:"); 525 } 526 527 if (PrintGCDetails) { 528 gclog_or_tty->print(":"); 529 _gens[i]->print_heap_change(prev_used); 530 } 531 } 532 } 533 534 // Update "complete" boolean wrt what actually transpired -- 535 // for instance, a promotion failure could have led to 536 // a whole heap collection. 537 complete = complete || (max_level_collected == n_gens() - 1); 538 539 if (complete) { // We did a "major" collection 540 // FIXME: See comment at pre_full_gc_dump call 541 post_full_gc_dump(NULL); // do any post full gc dumps 542 } 543 544 if (PrintGCDetails) { 545 print_heap_change(gch_prev_used); 546 547 // Print metaspace info for full GC with PrintGCDetails flag. 548 if (complete) { 549 MetaspaceAux::print_metaspace_change(metadata_prev_used); 550 } 551 } 552 553 for (int j = max_level_collected; j >= 0; j -= 1) { 554 // Adjust generation sizes. 555 _gens[j]->compute_new_size(); 556 } 557 558 if (complete) { 559 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 560 ClassLoaderDataGraph::purge(); 561 MetaspaceAux::verify_metrics(); 562 // Resize the metaspace capacity after full collections 563 MetaspaceGC::compute_new_size(); 564 update_full_collections_completed(); 565 } 566 567 // Track memory usage and detect low memory after GC finishes 568 MemoryService::track_memory_usage(); 569 570 gc_epilogue(complete); 571 572 if (must_restore_marks_for_biased_locking) { 573 BiasedLocking::restore_marks(); 574 } 575 } 576 577 AdaptiveSizePolicy* sp = gen_policy()->size_policy(); 578 AdaptiveSizePolicyOutput(sp, total_collections()); 579 580 print_heap_after_gc(); 581 582 #ifdef TRACESPINNING 583 ParallelTaskTerminator::print_termination_counts(); 584 #endif 585 } 586 587 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) { 588 return collector_policy()->satisfy_failed_allocation(size, is_tlab); 589 } 590 591 void GenCollectedHeap::set_par_threads(uint t) { 592 SharedHeap::set_par_threads(t); 593 _gen_process_roots_tasks->set_n_threads(t); 594 } 595 596 void GenCollectedHeap:: 597 gen_process_roots(int level, 598 bool younger_gens_as_roots, 599 bool activate_scope, 600 SharedHeap::ScanningOption so, 601 OopsInGenClosure* not_older_gens, 602 OopsInGenClosure* weak_roots, 603 OopsInGenClosure* older_gens, 604 CLDClosure* cld_closure, 605 CLDClosure* weak_cld_closure, 606 CodeBlobClosure* code_closure) { 607 608 // General roots. 609 SharedHeap::process_roots(activate_scope, so, 610 not_older_gens, weak_roots, 611 cld_closure, weak_cld_closure, 612 code_closure); 613 614 if (younger_gens_as_roots) { 615 if (!_gen_process_roots_tasks->is_task_claimed(GCH_PS_younger_gens)) { 616 for (int i = 0; i < level; i++) { 617 not_older_gens->set_generation(_gens[i]); 618 _gens[i]->oop_iterate(not_older_gens); 619 } 620 not_older_gens->reset_generation(); 621 } 622 } 623 // When collection is parallel, all threads get to cooperate to do 624 // older-gen scanning. 625 for (int i = level+1; i < _n_gens; i++) { 626 older_gens->set_generation(_gens[i]); 627 rem_set()->younger_refs_iterate(_gens[i], older_gens); 628 older_gens->reset_generation(); 629 } 630 631 _gen_process_roots_tasks->all_tasks_completed(); 632 } 633 634 void GenCollectedHeap:: 635 gen_process_roots(int level, 636 bool younger_gens_as_roots, 637 bool activate_scope, 638 SharedHeap::ScanningOption so, 639 bool only_strong_roots, 640 OopsInGenClosure* not_older_gens, 641 OopsInGenClosure* older_gens, 642 CLDClosure* cld_closure) { 643 644 const bool is_adjust_phase = !only_strong_roots && !younger_gens_as_roots; 645 646 bool is_moving_collection = false; 647 if (level == 0 || is_adjust_phase) { 648 // young collections are always moving 649 is_moving_collection = true; 650 } 651 652 MarkingCodeBlobClosure mark_code_closure(not_older_gens, is_moving_collection); 653 CodeBlobClosure* code_closure = &mark_code_closure; 654 655 gen_process_roots(level, 656 younger_gens_as_roots, 657 activate_scope, so, 658 not_older_gens, only_strong_roots ? NULL : not_older_gens, 659 older_gens, 660 cld_closure, only_strong_roots ? NULL : cld_closure, 661 code_closure); 662 663 } 664 665 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure) { 666 SharedHeap::process_weak_roots(root_closure); 667 // "Local" "weak" refs 668 for (int i = 0; i < _n_gens; i++) { 669 _gens[i]->ref_processor()->weak_oops_do(root_closure); 670 } 671 } 672 673 #define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix) \ 674 void GenCollectedHeap:: \ 675 oop_since_save_marks_iterate(int level, \ 676 OopClosureType* cur, \ 677 OopClosureType* older) { \ 678 _gens[level]->oop_since_save_marks_iterate##nv_suffix(cur); \ 679 for (int i = level+1; i < n_gens(); i++) { \ 680 _gens[i]->oop_since_save_marks_iterate##nv_suffix(older); \ 681 } \ 682 } 683 684 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN) 685 686 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN 687 688 bool GenCollectedHeap::no_allocs_since_save_marks(int level) { 689 for (int i = level; i < _n_gens; i++) { 690 if (!_gens[i]->no_allocs_since_save_marks()) return false; 691 } 692 return true; 693 } 694 695 bool GenCollectedHeap::supports_inline_contig_alloc() const { 696 return _gens[0]->supports_inline_contig_alloc(); 697 } 698 699 HeapWord** GenCollectedHeap::top_addr() const { 700 return _gens[0]->top_addr(); 701 } 702 703 HeapWord** GenCollectedHeap::end_addr() const { 704 return _gens[0]->end_addr(); 705 } 706 707 // public collection interfaces 708 709 void GenCollectedHeap::collect(GCCause::Cause cause) { 710 if (should_do_concurrent_full_gc(cause)) { 711 #if INCLUDE_ALL_GCS 712 // mostly concurrent full collection 713 collect_mostly_concurrent(cause); 714 #else // INCLUDE_ALL_GCS 715 ShouldNotReachHere(); 716 #endif // INCLUDE_ALL_GCS 717 } else if (cause == GCCause::_wb_young_gc) { 718 // minor collection for WhiteBox API 719 collect(cause, 0); 720 } else { 721 #ifdef ASSERT 722 if (cause == GCCause::_scavenge_alot) { 723 // minor collection only 724 collect(cause, 0); 725 } else { 726 // Stop-the-world full collection 727 collect(cause, n_gens() - 1); 728 } 729 #else 730 // Stop-the-world full collection 731 collect(cause, n_gens() - 1); 732 #endif 733 } 734 } 735 736 void GenCollectedHeap::collect(GCCause::Cause cause, int max_level) { 737 // The caller doesn't have the Heap_lock 738 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock"); 739 MutexLocker ml(Heap_lock); 740 collect_locked(cause, max_level); 741 } 742 743 void GenCollectedHeap::collect_locked(GCCause::Cause cause) { 744 // The caller has the Heap_lock 745 assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock"); 746 collect_locked(cause, n_gens() - 1); 747 } 748 749 // this is the private collection interface 750 // The Heap_lock is expected to be held on entry. 751 752 void GenCollectedHeap::collect_locked(GCCause::Cause cause, int max_level) { 753 // Read the GC count while holding the Heap_lock 754 unsigned int gc_count_before = total_collections(); 755 unsigned int full_gc_count_before = total_full_collections(); 756 { 757 MutexUnlocker mu(Heap_lock); // give up heap lock, execute gets it back 758 VM_GenCollectFull op(gc_count_before, full_gc_count_before, 759 cause, max_level); 760 VMThread::execute(&op); 761 } 762 } 763 764 #if INCLUDE_ALL_GCS 765 bool GenCollectedHeap::create_cms_collector() { 766 767 assert(((_gens[1]->kind() == Generation::ConcurrentMarkSweep) || 768 (_gens[1]->kind() == Generation::ASConcurrentMarkSweep)), 769 "Unexpected generation kinds"); 770 // Skip two header words in the block content verification 771 NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();) 772 CMSCollector* collector = new CMSCollector( 773 (ConcurrentMarkSweepGeneration*)_gens[1], 774 _rem_set->as_CardTableRS(), 775 (ConcurrentMarkSweepPolicy*) collector_policy()); 776 777 if (collector == NULL || !collector->completed_initialization()) { 778 if (collector) { 779 delete collector; // Be nice in embedded situation 780 } 781 vm_shutdown_during_initialization("Could not create CMS collector"); 782 return false; 783 } 784 return true; // success 785 } 786 787 void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) { 788 assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock"); 789 790 MutexLocker ml(Heap_lock); 791 // Read the GC counts while holding the Heap_lock 792 unsigned int full_gc_count_before = total_full_collections(); 793 unsigned int gc_count_before = total_collections(); 794 { 795 MutexUnlocker mu(Heap_lock); 796 VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause); 797 VMThread::execute(&op); 798 } 799 } 800 #endif // INCLUDE_ALL_GCS 801 802 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs) { 803 do_full_collection(clear_all_soft_refs, _n_gens - 1); 804 } 805 806 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs, 807 int max_level) { 808 int local_max_level; 809 if (!incremental_collection_will_fail(false /* don't consult_young */) && 810 gc_cause() == GCCause::_gc_locker) { 811 local_max_level = 0; 812 } else { 813 local_max_level = max_level; 814 } 815 816 do_collection(true /* full */, 817 clear_all_soft_refs /* clear_all_soft_refs */, 818 0 /* size */, 819 false /* is_tlab */, 820 local_max_level /* max_level */); 821 // Hack XXX FIX ME !!! 822 // A scavenge may not have been attempted, or may have 823 // been attempted and failed, because the old gen was too full 824 if (local_max_level == 0 && gc_cause() == GCCause::_gc_locker && 825 incremental_collection_will_fail(false /* don't consult_young */)) { 826 if (PrintGCDetails) { 827 gclog_or_tty->print_cr("GC locker: Trying a full collection " 828 "because scavenge failed"); 829 } 830 // This time allow the old gen to be collected as well 831 do_collection(true /* full */, 832 clear_all_soft_refs /* clear_all_soft_refs */, 833 0 /* size */, 834 false /* is_tlab */, 835 n_gens() - 1 /* max_level */); 836 } 837 } 838 839 bool GenCollectedHeap::is_in_young(oop p) { 840 bool result = ((HeapWord*)p) < _gens[_n_gens - 1]->reserved().start(); 841 assert(result == _gens[0]->is_in_reserved(p), 842 err_msg("incorrect test - result=%d, p=" PTR_FORMAT, result, p2i((void*)p))); 843 return result; 844 } 845 846 // Returns "TRUE" iff "p" points into the committed areas of the heap. 847 bool GenCollectedHeap::is_in(const void* p) const { 848 #ifndef ASSERT 849 guarantee(VerifyBeforeGC || 850 VerifyDuringGC || 851 VerifyBeforeExit || 852 VerifyDuringStartup || 853 PrintAssembly || 854 tty->count() != 0 || // already printing 855 VerifyAfterGC || 856 VMError::fatal_error_in_progress(), "too expensive"); 857 858 #endif 859 // This might be sped up with a cache of the last generation that 860 // answered yes. 861 for (int i = 0; i < _n_gens; i++) { 862 if (_gens[i]->is_in(p)) return true; 863 } 864 // Otherwise... 865 return false; 866 } 867 868 #ifdef ASSERT 869 // Don't implement this by using is_in_young(). This method is used 870 // in some cases to check that is_in_young() is correct. 871 bool GenCollectedHeap::is_in_partial_collection(const void* p) { 872 assert(is_in_reserved(p) || p == NULL, 873 "Does not work if address is non-null and outside of the heap"); 874 return p < _gens[_n_gens - 2]->reserved().end() && p != NULL; 875 } 876 #endif 877 878 void GenCollectedHeap::oop_iterate(ExtendedOopClosure* cl) { 879 for (int i = 0; i < _n_gens; i++) { 880 _gens[i]->oop_iterate(cl); 881 } 882 } 883 884 void GenCollectedHeap::object_iterate(ObjectClosure* cl) { 885 for (int i = 0; i < _n_gens; i++) { 886 _gens[i]->object_iterate(cl); 887 } 888 } 889 890 void GenCollectedHeap::safe_object_iterate(ObjectClosure* cl) { 891 for (int i = 0; i < _n_gens; i++) { 892 _gens[i]->safe_object_iterate(cl); 893 } 894 } 895 896 Space* GenCollectedHeap::space_containing(const void* addr) const { 897 for (int i = 0; i < _n_gens; i++) { 898 Space* res = _gens[i]->space_containing(addr); 899 if (res != NULL) return res; 900 } 901 // Otherwise... 902 assert(false, "Could not find containing space"); 903 return NULL; 904 } 905 906 907 HeapWord* GenCollectedHeap::block_start(const void* addr) const { 908 assert(is_in_reserved(addr), "block_start of address outside of heap"); 909 for (int i = 0; i < _n_gens; i++) { 910 if (_gens[i]->is_in_reserved(addr)) { 911 assert(_gens[i]->is_in(addr), 912 "addr should be in allocated part of generation"); 913 return _gens[i]->block_start(addr); 914 } 915 } 916 assert(false, "Some generation should contain the address"); 917 return NULL; 918 } 919 920 size_t GenCollectedHeap::block_size(const HeapWord* addr) const { 921 assert(is_in_reserved(addr), "block_size of address outside of heap"); 922 for (int i = 0; i < _n_gens; i++) { 923 if (_gens[i]->is_in_reserved(addr)) { 924 assert(_gens[i]->is_in(addr), 925 "addr should be in allocated part of generation"); 926 return _gens[i]->block_size(addr); 927 } 928 } 929 assert(false, "Some generation should contain the address"); 930 return 0; 931 } 932 933 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const { 934 assert(is_in_reserved(addr), "block_is_obj of address outside of heap"); 935 assert(block_start(addr) == addr, "addr must be a block start"); 936 for (int i = 0; i < _n_gens; i++) { 937 if (_gens[i]->is_in_reserved(addr)) { 938 return _gens[i]->block_is_obj(addr); 939 } 940 } 941 assert(false, "Some generation should contain the address"); 942 return false; 943 } 944 945 bool GenCollectedHeap::supports_tlab_allocation() const { 946 for (int i = 0; i < _n_gens; i += 1) { 947 if (_gens[i]->supports_tlab_allocation()) { 948 return true; 949 } 950 } 951 return false; 952 } 953 954 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const { 955 size_t result = 0; 956 for (int i = 0; i < _n_gens; i += 1) { 957 if (_gens[i]->supports_tlab_allocation()) { 958 result += _gens[i]->tlab_capacity(); 959 } 960 } 961 return result; 962 } 963 964 size_t GenCollectedHeap::tlab_used(Thread* thr) const { 965 size_t result = 0; 966 for (int i = 0; i < _n_gens; i += 1) { 967 if (_gens[i]->supports_tlab_allocation()) { 968 result += _gens[i]->tlab_used(); 969 } 970 } 971 return result; 972 } 973 974 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const { 975 size_t result = 0; 976 for (int i = 0; i < _n_gens; i += 1) { 977 if (_gens[i]->supports_tlab_allocation()) { 978 result += _gens[i]->unsafe_max_tlab_alloc(); 979 } 980 } 981 return result; 982 } 983 984 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) { 985 bool gc_overhead_limit_was_exceeded; 986 return collector_policy()->mem_allocate_work(size /* size */, 987 true /* is_tlab */, 988 &gc_overhead_limit_was_exceeded); 989 } 990 991 // Requires "*prev_ptr" to be non-NULL. Deletes and a block of minimal size 992 // from the list headed by "*prev_ptr". 993 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) { 994 bool first = true; 995 size_t min_size = 0; // "first" makes this conceptually infinite. 996 ScratchBlock **smallest_ptr, *smallest; 997 ScratchBlock *cur = *prev_ptr; 998 while (cur) { 999 assert(*prev_ptr == cur, "just checking"); 1000 if (first || cur->num_words < min_size) { 1001 smallest_ptr = prev_ptr; 1002 smallest = cur; 1003 min_size = smallest->num_words; 1004 first = false; 1005 } 1006 prev_ptr = &cur->next; 1007 cur = cur->next; 1008 } 1009 smallest = *smallest_ptr; 1010 *smallest_ptr = smallest->next; 1011 return smallest; 1012 } 1013 1014 // Sort the scratch block list headed by res into decreasing size order, 1015 // and set "res" to the result. 1016 static void sort_scratch_list(ScratchBlock*& list) { 1017 ScratchBlock* sorted = NULL; 1018 ScratchBlock* unsorted = list; 1019 while (unsorted) { 1020 ScratchBlock *smallest = removeSmallestScratch(&unsorted); 1021 smallest->next = sorted; 1022 sorted = smallest; 1023 } 1024 list = sorted; 1025 } 1026 1027 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor, 1028 size_t max_alloc_words) { 1029 ScratchBlock* res = NULL; 1030 for (int i = 0; i < _n_gens; i++) { 1031 _gens[i]->contribute_scratch(res, requestor, max_alloc_words); 1032 } 1033 sort_scratch_list(res); 1034 return res; 1035 } 1036 1037 void GenCollectedHeap::release_scratch() { 1038 for (int i = 0; i < _n_gens; i++) { 1039 _gens[i]->reset_scratch(); 1040 } 1041 } 1042 1043 class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure { 1044 void do_generation(Generation* gen) { 1045 gen->prepare_for_verify(); 1046 } 1047 }; 1048 1049 void GenCollectedHeap::prepare_for_verify() { 1050 ensure_parsability(false); // no need to retire TLABs 1051 GenPrepareForVerifyClosure blk; 1052 generation_iterate(&blk, false); 1053 } 1054 1055 1056 void GenCollectedHeap::generation_iterate(GenClosure* cl, 1057 bool old_to_young) { 1058 if (old_to_young) { 1059 for (int i = _n_gens-1; i >= 0; i--) { 1060 cl->do_generation(_gens[i]); 1061 } 1062 } else { 1063 for (int i = 0; i < _n_gens; i++) { 1064 cl->do_generation(_gens[i]); 1065 } 1066 } 1067 } 1068 1069 void GenCollectedHeap::space_iterate(SpaceClosure* cl) { 1070 for (int i = 0; i < _n_gens; i++) { 1071 _gens[i]->space_iterate(cl, true); 1072 } 1073 } 1074 1075 bool GenCollectedHeap::is_maximal_no_gc() const { 1076 for (int i = 0; i < _n_gens; i++) { 1077 if (!_gens[i]->is_maximal_no_gc()) { 1078 return false; 1079 } 1080 } 1081 return true; 1082 } 1083 1084 void GenCollectedHeap::save_marks() { 1085 for (int i = 0; i < _n_gens; i++) { 1086 _gens[i]->save_marks(); 1087 } 1088 } 1089 1090 GenCollectedHeap* GenCollectedHeap::heap() { 1091 assert(_gch != NULL, "Uninitialized access to GenCollectedHeap::heap()"); 1092 assert(_gch->kind() == CollectedHeap::GenCollectedHeap, "not a generational heap"); 1093 return _gch; 1094 } 1095 1096 1097 void GenCollectedHeap::prepare_for_compaction() { 1098 guarantee(_n_gens = 2, "Wrong number of generations"); 1099 Generation* old_gen = _gens[1]; 1100 // Start by compacting into same gen. 1101 CompactPoint cp(old_gen); 1102 old_gen->prepare_for_compaction(&cp); 1103 Generation* young_gen = _gens[0]; 1104 young_gen->prepare_for_compaction(&cp); 1105 } 1106 1107 GCStats* GenCollectedHeap::gc_stats(int level) const { 1108 return _gens[level]->gc_stats(); 1109 } 1110 1111 void GenCollectedHeap::verify(bool silent, VerifyOption option /* ignored */) { 1112 for (int i = _n_gens-1; i >= 0; i--) { 1113 Generation* g = _gens[i]; 1114 if (!silent) { 1115 gclog_or_tty->print("%s", g->name()); 1116 gclog_or_tty->print(" "); 1117 } 1118 g->verify(); 1119 } 1120 if (!silent) { 1121 gclog_or_tty->print("remset "); 1122 } 1123 rem_set()->verify(); 1124 } 1125 1126 void GenCollectedHeap::print_on(outputStream* st) const { 1127 for (int i = 0; i < _n_gens; i++) { 1128 _gens[i]->print_on(st); 1129 } 1130 MetaspaceAux::print_on(st); 1131 } 1132 1133 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const { 1134 if (workers() != NULL) { 1135 workers()->threads_do(tc); 1136 } 1137 #if INCLUDE_ALL_GCS 1138 if (UseConcMarkSweepGC) { 1139 ConcurrentMarkSweepThread::threads_do(tc); 1140 } 1141 #endif // INCLUDE_ALL_GCS 1142 } 1143 1144 void GenCollectedHeap::print_gc_threads_on(outputStream* st) const { 1145 #if INCLUDE_ALL_GCS 1146 if (UseParNewGC) { 1147 workers()->print_worker_threads_on(st); 1148 } 1149 if (UseConcMarkSweepGC) { 1150 ConcurrentMarkSweepThread::print_all_on(st); 1151 } 1152 #endif // INCLUDE_ALL_GCS 1153 } 1154 1155 void GenCollectedHeap::print_on_error(outputStream* st) const { 1156 this->CollectedHeap::print_on_error(st); 1157 1158 #if INCLUDE_ALL_GCS 1159 if (UseConcMarkSweepGC) { 1160 st->cr(); 1161 CMSCollector::print_on_error(st); 1162 } 1163 #endif // INCLUDE_ALL_GCS 1164 } 1165 1166 void GenCollectedHeap::print_tracing_info() const { 1167 if (TraceGen0Time) { 1168 get_gen(0)->print_summary_info(); 1169 } 1170 if (TraceGen1Time) { 1171 get_gen(1)->print_summary_info(); 1172 } 1173 } 1174 1175 void GenCollectedHeap::print_heap_change(size_t prev_used) const { 1176 if (PrintGCDetails && Verbose) { 1177 gclog_or_tty->print(" " SIZE_FORMAT 1178 "->" SIZE_FORMAT 1179 "(" SIZE_FORMAT ")", 1180 prev_used, used(), capacity()); 1181 } else { 1182 gclog_or_tty->print(" " SIZE_FORMAT "K" 1183 "->" SIZE_FORMAT "K" 1184 "(" SIZE_FORMAT "K)", 1185 prev_used / K, used() / K, capacity() / K); 1186 } 1187 } 1188 1189 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure { 1190 private: 1191 bool _full; 1192 public: 1193 void do_generation(Generation* gen) { 1194 gen->gc_prologue(_full); 1195 } 1196 GenGCPrologueClosure(bool full) : _full(full) {}; 1197 }; 1198 1199 void GenCollectedHeap::gc_prologue(bool full) { 1200 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 1201 1202 always_do_update_barrier = false; 1203 // Fill TLAB's and such 1204 CollectedHeap::accumulate_statistics_all_tlabs(); 1205 ensure_parsability(true); // retire TLABs 1206 1207 // Walk generations 1208 GenGCPrologueClosure blk(full); 1209 generation_iterate(&blk, false); // not old-to-young. 1210 }; 1211 1212 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure { 1213 private: 1214 bool _full; 1215 public: 1216 void do_generation(Generation* gen) { 1217 gen->gc_epilogue(_full); 1218 } 1219 GenGCEpilogueClosure(bool full) : _full(full) {}; 1220 }; 1221 1222 void GenCollectedHeap::gc_epilogue(bool full) { 1223 #ifdef COMPILER2 1224 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 1225 size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr())); 1226 guarantee(actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps"); 1227 #endif /* COMPILER2 */ 1228 1229 resize_all_tlabs(); 1230 1231 GenGCEpilogueClosure blk(full); 1232 generation_iterate(&blk, false); // not old-to-young. 1233 1234 if (!CleanChunkPoolAsync) { 1235 Chunk::clean_chunk_pool(); 1236 } 1237 1238 MetaspaceCounters::update_performance_counters(); 1239 CompressedClassSpaceCounters::update_performance_counters(); 1240 1241 always_do_update_barrier = UseConcMarkSweepGC; 1242 }; 1243 1244 #ifndef PRODUCT 1245 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure { 1246 private: 1247 public: 1248 void do_generation(Generation* gen) { 1249 gen->record_spaces_top(); 1250 } 1251 }; 1252 1253 void GenCollectedHeap::record_gen_tops_before_GC() { 1254 if (ZapUnusedHeapArea) { 1255 GenGCSaveTopsBeforeGCClosure blk; 1256 generation_iterate(&blk, false); // not old-to-young. 1257 } 1258 } 1259 #endif // not PRODUCT 1260 1261 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure { 1262 public: 1263 void do_generation(Generation* gen) { 1264 gen->ensure_parsability(); 1265 } 1266 }; 1267 1268 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) { 1269 CollectedHeap::ensure_parsability(retire_tlabs); 1270 GenEnsureParsabilityClosure ep_cl; 1271 generation_iterate(&ep_cl, false); 1272 } 1273 1274 oop GenCollectedHeap::handle_failed_promotion(Generation* old_gen, 1275 oop obj, 1276 size_t obj_size) { 1277 guarantee(old_gen->level() == 1, "We only get here with an old generation"); 1278 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in"); 1279 HeapWord* result = NULL; 1280 1281 result = old_gen->expand_and_allocate(obj_size, false); 1282 1283 if (result != NULL) { 1284 Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size); 1285 } 1286 return oop(result); 1287 } 1288 1289 class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure { 1290 jlong _time; // in ms 1291 jlong _now; // in ms 1292 1293 public: 1294 GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { } 1295 1296 jlong time() { return _time; } 1297 1298 void do_generation(Generation* gen) { 1299 _time = MIN2(_time, gen->time_of_last_gc(_now)); 1300 } 1301 }; 1302 1303 jlong GenCollectedHeap::millis_since_last_gc() { 1304 // We need a monotonically non-deccreasing time in ms but 1305 // os::javaTimeMillis() does not guarantee monotonicity. 1306 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 1307 GenTimeOfLastGCClosure tolgc_cl(now); 1308 // iterate over generations getting the oldest 1309 // time that a generation was collected 1310 generation_iterate(&tolgc_cl, false); 1311 1312 // javaTimeNanos() is guaranteed to be monotonically non-decreasing 1313 // provided the underlying platform provides such a time source 1314 // (and it is bug free). So we still have to guard against getting 1315 // back a time later than 'now'. 1316 jlong retVal = now - tolgc_cl.time(); 1317 if (retVal < 0) { 1318 NOT_PRODUCT(warning("time warp: "INT64_FORMAT, (int64_t) retVal);) 1319 return 0; 1320 } 1321 return retVal; 1322 }