1 /* 2 * Copyright (c) 2001, 2019, 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/classLoaderDataGraph.hpp" 27 #include "classfile/metadataOnStackMark.hpp" 28 #include "classfile/stringTable.hpp" 29 #include "code/codeCache.hpp" 30 #include "code/icBuffer.hpp" 31 #include "gc/g1/g1Allocator.inline.hpp" 32 #include "gc/g1/g1Arguments.hpp" 33 #include "gc/g1/g1BarrierSet.hpp" 34 #include "gc/g1/g1CardTableEntryClosure.hpp" 35 #include "gc/g1/g1CollectedHeap.inline.hpp" 36 #include "gc/g1/g1CollectionSet.hpp" 37 #include "gc/g1/g1CollectorState.hpp" 38 #include "gc/g1/g1ConcurrentRefine.hpp" 39 #include "gc/g1/g1ConcurrentRefineThread.hpp" 40 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp" 41 #include "gc/g1/g1DirtyCardQueue.hpp" 42 #include "gc/g1/g1EvacStats.inline.hpp" 43 #include "gc/g1/g1FullCollector.hpp" 44 #include "gc/g1/g1GCPhaseTimes.hpp" 45 #include "gc/g1/g1HeapSizingPolicy.hpp" 46 #include "gc/g1/g1HeapTransition.hpp" 47 #include "gc/g1/g1HeapVerifier.hpp" 48 #include "gc/g1/g1HotCardCache.hpp" 49 #include "gc/g1/g1MemoryPool.hpp" 50 #include "gc/g1/g1OopClosures.inline.hpp" 51 #include "gc/g1/g1ParallelCleaning.hpp" 52 #include "gc/g1/g1ParScanThreadState.inline.hpp" 53 #include "gc/g1/g1Policy.hpp" 54 #include "gc/g1/g1RedirtyCardsQueue.hpp" 55 #include "gc/g1/g1RegionToSpaceMapper.hpp" 56 #include "gc/g1/g1RemSet.hpp" 57 #include "gc/g1/g1RootClosures.hpp" 58 #include "gc/g1/g1RootProcessor.hpp" 59 #include "gc/g1/g1SATBMarkQueueSet.hpp" 60 #include "gc/g1/g1StringDedup.hpp" 61 #include "gc/g1/g1ThreadLocalData.hpp" 62 #include "gc/g1/g1Trace.hpp" 63 #include "gc/g1/g1YCTypes.hpp" 64 #include "gc/g1/g1YoungRemSetSamplingThread.hpp" 65 #include "gc/g1/g1VMOperations.hpp" 66 #include "gc/g1/heapRegion.inline.hpp" 67 #include "gc/g1/heapRegionRemSet.hpp" 68 #include "gc/g1/heapRegionSet.inline.hpp" 69 #include "gc/shared/gcBehaviours.hpp" 70 #include "gc/shared/gcHeapSummary.hpp" 71 #include "gc/shared/gcId.hpp" 72 #include "gc/shared/gcLocker.hpp" 73 #include "gc/shared/gcTimer.hpp" 74 #include "gc/shared/gcTraceTime.inline.hpp" 75 #include "gc/shared/generationSpec.hpp" 76 #include "gc/shared/isGCActiveMark.hpp" 77 #include "gc/shared/locationPrinter.inline.hpp" 78 #include "gc/shared/oopStorageParState.hpp" 79 #include "gc/shared/preservedMarks.inline.hpp" 80 #include "gc/shared/suspendibleThreadSet.hpp" 81 #include "gc/shared/referenceProcessor.inline.hpp" 82 #include "gc/shared/taskqueue.inline.hpp" 83 #include "gc/shared/weakProcessor.inline.hpp" 84 #include "gc/shared/workerPolicy.hpp" 85 #include "logging/log.hpp" 86 #include "memory/allocation.hpp" 87 #include "memory/iterator.hpp" 88 #include "memory/resourceArea.hpp" 89 #include "memory/universe.hpp" 90 #include "oops/access.inline.hpp" 91 #include "oops/compressedOops.inline.hpp" 92 #include "oops/oop.inline.hpp" 93 #include "runtime/atomic.hpp" 94 #include "runtime/flags/flagSetting.hpp" 95 #include "runtime/handles.inline.hpp" 96 #include "runtime/init.hpp" 97 #include "runtime/orderAccess.hpp" 98 #include "runtime/threadSMR.hpp" 99 #include "runtime/vmThread.hpp" 100 #include "utilities/align.hpp" 101 #include "utilities/bitMap.inline.hpp" 102 #include "utilities/globalDefinitions.hpp" 103 #include "utilities/stack.inline.hpp" 104 105 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 106 107 // INVARIANTS/NOTES 108 // 109 // All allocation activity covered by the G1CollectedHeap interface is 110 // serialized by acquiring the HeapLock. This happens in mem_allocate 111 // and allocate_new_tlab, which are the "entry" points to the 112 // allocation code from the rest of the JVM. (Note that this does not 113 // apply to TLAB allocation, which is not part of this interface: it 114 // is done by clients of this interface.) 115 116 class RedirtyLoggedCardTableEntryClosure : public G1CardTableEntryClosure { 117 private: 118 size_t _num_dirtied; 119 G1CollectedHeap* _g1h; 120 G1CardTable* _g1_ct; 121 122 HeapRegion* region_for_card(CardValue* card_ptr) const { 123 return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr)); 124 } 125 126 bool will_become_free(HeapRegion* hr) const { 127 // A region will be freed by free_collection_set if the region is in the 128 // collection set and has not had an evacuation failure. 129 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 130 } 131 132 public: 133 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : G1CardTableEntryClosure(), 134 _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { } 135 136 void do_card_ptr(CardValue* card_ptr, uint worker_id) { 137 HeapRegion* hr = region_for_card(card_ptr); 138 139 // Should only dirty cards in regions that won't be freed. 140 if (!will_become_free(hr)) { 141 *card_ptr = G1CardTable::dirty_card_val(); 142 _num_dirtied++; 143 } 144 } 145 146 size_t num_dirtied() const { return _num_dirtied; } 147 }; 148 149 150 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 151 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 152 } 153 154 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 155 // The from card cache is not the memory that is actually committed. So we cannot 156 // take advantage of the zero_filled parameter. 157 reset_from_card_cache(start_idx, num_regions); 158 } 159 160 Tickspan G1CollectedHeap::run_task(AbstractGangTask* task) { 161 Ticks start = Ticks::now(); 162 workers()->run_task(task, workers()->active_workers()); 163 return Ticks::now() - start; 164 } 165 166 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 167 MemRegion mr) { 168 return new HeapRegion(hrs_index, bot(), mr); 169 } 170 171 // Private methods. 172 173 HeapRegion* G1CollectedHeap::new_region(size_t word_size, 174 HeapRegionType type, 175 bool do_expand, 176 uint node_index) { 177 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 178 "the only time we use this to allocate a humongous region is " 179 "when we are allocating a single humongous region"); 180 181 HeapRegion* res = _hrm->allocate_free_region(type, node_index); 182 183 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 184 // Currently, only attempts to allocate GC alloc regions set 185 // do_expand to true. So, we should only reach here during a 186 // safepoint. If this assumption changes we might have to 187 // reconsider the use of _expand_heap_after_alloc_failure. 188 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 189 190 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 191 word_size * HeapWordSize); 192 193 assert(word_size * HeapWordSize < HeapRegion::GrainBytes, 194 "This kind of expansion should never be more than one region. Size: " SIZE_FORMAT, 195 word_size * HeapWordSize); 196 if (expand_single_region(node_index)) { 197 // Given that expand_single_region() succeeded in expanding the heap, and we 198 // always expand the heap by an amount aligned to the heap 199 // region size, the free list should in theory not be empty. 200 // In either case allocate_free_region() will check for NULL. 201 res = _hrm->allocate_free_region(type, node_index); 202 } else { 203 _expand_heap_after_alloc_failure = false; 204 } 205 } 206 return res; 207 } 208 209 HeapWord* 210 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 211 uint num_regions, 212 size_t word_size) { 213 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 214 assert(is_humongous(word_size), "word_size should be humongous"); 215 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 216 217 // Index of last region in the series. 218 uint last = first + num_regions - 1; 219 220 // We need to initialize the region(s) we just discovered. This is 221 // a bit tricky given that it can happen concurrently with 222 // refinement threads refining cards on these regions and 223 // potentially wanting to refine the BOT as they are scanning 224 // those cards (this can happen shortly after a cleanup; see CR 225 // 6991377). So we have to set up the region(s) carefully and in 226 // a specific order. 227 228 // The word size sum of all the regions we will allocate. 229 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 230 assert(word_size <= word_size_sum, "sanity"); 231 232 // This will be the "starts humongous" region. 233 HeapRegion* first_hr = region_at(first); 234 // The header of the new object will be placed at the bottom of 235 // the first region. 236 HeapWord* new_obj = first_hr->bottom(); 237 // This will be the new top of the new object. 238 HeapWord* obj_top = new_obj + word_size; 239 240 // First, we need to zero the header of the space that we will be 241 // allocating. When we update top further down, some refinement 242 // threads might try to scan the region. By zeroing the header we 243 // ensure that any thread that will try to scan the region will 244 // come across the zero klass word and bail out. 245 // 246 // NOTE: It would not have been correct to have used 247 // CollectedHeap::fill_with_object() and make the space look like 248 // an int array. The thread that is doing the allocation will 249 // later update the object header to a potentially different array 250 // type and, for a very short period of time, the klass and length 251 // fields will be inconsistent. This could cause a refinement 252 // thread to calculate the object size incorrectly. 253 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 254 255 // Next, pad out the unused tail of the last region with filler 256 // objects, for improved usage accounting. 257 // How many words we use for filler objects. 258 size_t word_fill_size = word_size_sum - word_size; 259 260 // How many words memory we "waste" which cannot hold a filler object. 261 size_t words_not_fillable = 0; 262 263 if (word_fill_size >= min_fill_size()) { 264 fill_with_objects(obj_top, word_fill_size); 265 } else if (word_fill_size > 0) { 266 // We have space to fill, but we cannot fit an object there. 267 words_not_fillable = word_fill_size; 268 word_fill_size = 0; 269 } 270 271 // We will set up the first region as "starts humongous". This 272 // will also update the BOT covering all the regions to reflect 273 // that there is a single object that starts at the bottom of the 274 // first region. 275 first_hr->set_starts_humongous(obj_top, word_fill_size); 276 _policy->remset_tracker()->update_at_allocate(first_hr); 277 // Then, if there are any, we will set up the "continues 278 // humongous" regions. 279 HeapRegion* hr = NULL; 280 for (uint i = first + 1; i <= last; ++i) { 281 hr = region_at(i); 282 hr->set_continues_humongous(first_hr); 283 _policy->remset_tracker()->update_at_allocate(hr); 284 } 285 286 // Up to this point no concurrent thread would have been able to 287 // do any scanning on any region in this series. All the top 288 // fields still point to bottom, so the intersection between 289 // [bottom,top] and [card_start,card_end] will be empty. Before we 290 // update the top fields, we'll do a storestore to make sure that 291 // no thread sees the update to top before the zeroing of the 292 // object header and the BOT initialization. 293 OrderAccess::storestore(); 294 295 // Now, we will update the top fields of the "continues humongous" 296 // regions except the last one. 297 for (uint i = first; i < last; ++i) { 298 hr = region_at(i); 299 hr->set_top(hr->end()); 300 } 301 302 hr = region_at(last); 303 // If we cannot fit a filler object, we must set top to the end 304 // of the humongous object, otherwise we cannot iterate the heap 305 // and the BOT will not be complete. 306 hr->set_top(hr->end() - words_not_fillable); 307 308 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 309 "obj_top should be in last region"); 310 311 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 312 313 assert(words_not_fillable == 0 || 314 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 315 "Miscalculation in humongous allocation"); 316 317 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 318 319 for (uint i = first; i <= last; ++i) { 320 hr = region_at(i); 321 _humongous_set.add(hr); 322 _hr_printer.alloc(hr); 323 } 324 325 return new_obj; 326 } 327 328 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 329 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 330 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 331 } 332 333 // If could fit into free regions w/o expansion, try. 334 // Otherwise, if can expand, do so. 335 // Otherwise, if using ex regions might help, try with ex given back. 336 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) { 337 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 338 339 _verifier->verify_region_sets_optional(); 340 341 uint first = G1_NO_HRM_INDEX; 342 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 343 344 if (obj_regions == 1) { 345 // Only one region to allocate, try to use a fast path by directly allocating 346 // from the free lists. Do not try to expand here, we will potentially do that 347 // later. 348 HeapRegion* hr = new_region(word_size, HeapRegionType::Humongous, false /* do_expand */); 349 if (hr != NULL) { 350 first = hr->hrm_index(); 351 } 352 } else { 353 // Policy: Try only empty regions (i.e. already committed first). Maybe we 354 // are lucky enough to find some. 355 first = _hrm->find_contiguous_only_empty(obj_regions); 356 if (first != G1_NO_HRM_INDEX) { 357 _hrm->allocate_free_regions_starting_at(first, obj_regions); 358 } 359 } 360 361 if (first == G1_NO_HRM_INDEX) { 362 // Policy: We could not find enough regions for the humongous object in the 363 // free list. Look through the heap to find a mix of free and uncommitted regions. 364 // If so, try expansion. 365 first = _hrm->find_contiguous_empty_or_unavailable(obj_regions); 366 if (first != G1_NO_HRM_INDEX) { 367 // We found something. Make sure these regions are committed, i.e. expand 368 // the heap. Alternatively we could do a defragmentation GC. 369 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 370 word_size * HeapWordSize); 371 372 _hrm->expand_at(first, obj_regions, workers()); 373 policy()->record_new_heap_size(num_regions()); 374 375 #ifdef ASSERT 376 for (uint i = first; i < first + obj_regions; ++i) { 377 HeapRegion* hr = region_at(i); 378 assert(hr->is_free(), "sanity"); 379 assert(hr->is_empty(), "sanity"); 380 assert(is_on_master_free_list(hr), "sanity"); 381 } 382 #endif 383 _hrm->allocate_free_regions_starting_at(first, obj_regions); 384 } else { 385 // Policy: Potentially trigger a defragmentation GC. 386 } 387 } 388 389 HeapWord* result = NULL; 390 if (first != G1_NO_HRM_INDEX) { 391 result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size); 392 assert(result != NULL, "it should always return a valid result"); 393 394 // A successful humongous object allocation changes the used space 395 // information of the old generation so we need to recalculate the 396 // sizes and update the jstat counters here. 397 g1mm()->update_sizes(); 398 } 399 400 _verifier->verify_region_sets_optional(); 401 402 return result; 403 } 404 405 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size, 406 size_t requested_size, 407 size_t* actual_size) { 408 assert_heap_not_locked_and_not_at_safepoint(); 409 assert(!is_humongous(requested_size), "we do not allow humongous TLABs"); 410 411 return attempt_allocation(min_size, requested_size, actual_size); 412 } 413 414 HeapWord* 415 G1CollectedHeap::mem_allocate(size_t word_size, 416 bool* gc_overhead_limit_was_exceeded) { 417 assert_heap_not_locked_and_not_at_safepoint(); 418 419 if (is_humongous(word_size)) { 420 return attempt_allocation_humongous(word_size); 421 } 422 size_t dummy = 0; 423 return attempt_allocation(word_size, word_size, &dummy); 424 } 425 426 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) { 427 ResourceMark rm; // For retrieving the thread names in log messages. 428 429 // Make sure you read the note in attempt_allocation_humongous(). 430 431 assert_heap_not_locked_and_not_at_safepoint(); 432 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 433 "be called for humongous allocation requests"); 434 435 // We should only get here after the first-level allocation attempt 436 // (attempt_allocation()) failed to allocate. 437 438 // We will loop until a) we manage to successfully perform the 439 // allocation or b) we successfully schedule a collection which 440 // fails to perform the allocation. b) is the only case when we'll 441 // return NULL. 442 HeapWord* result = NULL; 443 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 444 bool should_try_gc; 445 uint gc_count_before; 446 447 { 448 MutexLocker x(Heap_lock); 449 result = _allocator->attempt_allocation_locked(word_size); 450 if (result != NULL) { 451 return result; 452 } 453 454 // If the GCLocker is active and we are bound for a GC, try expanding young gen. 455 // This is different to when only GCLocker::needs_gc() is set: try to avoid 456 // waiting because the GCLocker is active to not wait too long. 457 if (GCLocker::is_active_and_needs_gc() && policy()->can_expand_young_list()) { 458 // No need for an ergo message here, can_expand_young_list() does this when 459 // it returns true. 460 result = _allocator->attempt_allocation_force(word_size); 461 if (result != NULL) { 462 return result; 463 } 464 } 465 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 466 // the GCLocker initiated GC has been performed and then retry. This includes 467 // the case when the GC Locker is not active but has not been performed. 468 should_try_gc = !GCLocker::needs_gc(); 469 // Read the GC count while still holding the Heap_lock. 470 gc_count_before = total_collections(); 471 } 472 473 if (should_try_gc) { 474 bool succeeded; 475 result = do_collection_pause(word_size, gc_count_before, &succeeded, 476 GCCause::_g1_inc_collection_pause); 477 if (result != NULL) { 478 assert(succeeded, "only way to get back a non-NULL result"); 479 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 480 Thread::current()->name(), p2i(result)); 481 return result; 482 } 483 484 if (succeeded) { 485 // We successfully scheduled a collection which failed to allocate. No 486 // point in trying to allocate further. We'll just return NULL. 487 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 488 SIZE_FORMAT " words", Thread::current()->name(), word_size); 489 return NULL; 490 } 491 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words", 492 Thread::current()->name(), word_size); 493 } else { 494 // Failed to schedule a collection. 495 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 496 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 497 SIZE_FORMAT " words", Thread::current()->name(), word_size); 498 return NULL; 499 } 500 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 501 // The GCLocker is either active or the GCLocker initiated 502 // GC has not yet been performed. Stall until it is and 503 // then retry the allocation. 504 GCLocker::stall_until_clear(); 505 gclocker_retry_count += 1; 506 } 507 508 // We can reach here if we were unsuccessful in scheduling a 509 // collection (because another thread beat us to it) or if we were 510 // stalled due to the GC locker. In either can we should retry the 511 // allocation attempt in case another thread successfully 512 // performed a collection and reclaimed enough space. We do the 513 // first attempt (without holding the Heap_lock) here and the 514 // follow-on attempt will be at the start of the next loop 515 // iteration (after taking the Heap_lock). 516 size_t dummy = 0; 517 result = _allocator->attempt_allocation(word_size, word_size, &dummy); 518 if (result != NULL) { 519 return result; 520 } 521 522 // Give a warning if we seem to be looping forever. 523 if ((QueuedAllocationWarningCount > 0) && 524 (try_count % QueuedAllocationWarningCount == 0)) { 525 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 526 Thread::current()->name(), try_count, word_size); 527 } 528 } 529 530 ShouldNotReachHere(); 531 return NULL; 532 } 533 534 void G1CollectedHeap::begin_archive_alloc_range(bool open) { 535 assert_at_safepoint_on_vm_thread(); 536 if (_archive_allocator == NULL) { 537 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open); 538 } 539 } 540 541 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 542 // Allocations in archive regions cannot be of a size that would be considered 543 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 544 // may be different at archive-restore time. 545 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 546 } 547 548 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 549 assert_at_safepoint_on_vm_thread(); 550 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 551 if (is_archive_alloc_too_large(word_size)) { 552 return NULL; 553 } 554 return _archive_allocator->archive_mem_allocate(word_size); 555 } 556 557 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 558 size_t end_alignment_in_bytes) { 559 assert_at_safepoint_on_vm_thread(); 560 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 561 562 // Call complete_archive to do the real work, filling in the MemRegion 563 // array with the archive regions. 564 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 565 delete _archive_allocator; 566 _archive_allocator = NULL; 567 } 568 569 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 570 assert(ranges != NULL, "MemRegion array NULL"); 571 assert(count != 0, "No MemRegions provided"); 572 MemRegion reserved = _hrm->reserved(); 573 for (size_t i = 0; i < count; i++) { 574 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 575 return false; 576 } 577 } 578 return true; 579 } 580 581 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, 582 size_t count, 583 bool open) { 584 assert(!is_init_completed(), "Expect to be called at JVM init time"); 585 assert(ranges != NULL, "MemRegion array NULL"); 586 assert(count != 0, "No MemRegions provided"); 587 MutexLocker x(Heap_lock); 588 589 MemRegion reserved = _hrm->reserved(); 590 HeapWord* prev_last_addr = NULL; 591 HeapRegion* prev_last_region = NULL; 592 593 // Temporarily disable pretouching of heap pages. This interface is used 594 // when mmap'ing archived heap data in, so pre-touching is wasted. 595 FlagSetting fs(AlwaysPreTouch, false); 596 597 // Enable archive object checking used by G1MarkSweep. We have to let it know 598 // about each archive range, so that objects in those ranges aren't marked. 599 G1ArchiveAllocator::enable_archive_object_check(); 600 601 // For each specified MemRegion range, allocate the corresponding G1 602 // regions and mark them as archive regions. We expect the ranges 603 // in ascending starting address order, without overlap. 604 for (size_t i = 0; i < count; i++) { 605 MemRegion curr_range = ranges[i]; 606 HeapWord* start_address = curr_range.start(); 607 size_t word_size = curr_range.word_size(); 608 HeapWord* last_address = curr_range.last(); 609 size_t commits = 0; 610 611 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 612 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 613 p2i(start_address), p2i(last_address)); 614 guarantee(start_address > prev_last_addr, 615 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 616 p2i(start_address), p2i(prev_last_addr)); 617 prev_last_addr = last_address; 618 619 // Check for ranges that start in the same G1 region in which the previous 620 // range ended, and adjust the start address so we don't try to allocate 621 // the same region again. If the current range is entirely within that 622 // region, skip it, just adjusting the recorded top. 623 HeapRegion* start_region = _hrm->addr_to_region(start_address); 624 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 625 start_address = start_region->end(); 626 if (start_address > last_address) { 627 increase_used(word_size * HeapWordSize); 628 start_region->set_top(last_address + 1); 629 continue; 630 } 631 start_region->set_top(start_address); 632 curr_range = MemRegion(start_address, last_address + 1); 633 start_region = _hrm->addr_to_region(start_address); 634 } 635 636 // Perform the actual region allocation, exiting if it fails. 637 // Then note how much new space we have allocated. 638 if (!_hrm->allocate_containing_regions(curr_range, &commits, workers())) { 639 return false; 640 } 641 increase_used(word_size * HeapWordSize); 642 if (commits != 0) { 643 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 644 HeapRegion::GrainWords * HeapWordSize * commits); 645 646 } 647 648 // Mark each G1 region touched by the range as archive, add it to 649 // the old set, and set top. 650 HeapRegion* curr_region = _hrm->addr_to_region(start_address); 651 HeapRegion* last_region = _hrm->addr_to_region(last_address); 652 prev_last_region = last_region; 653 654 while (curr_region != NULL) { 655 assert(curr_region->is_empty() && !curr_region->is_pinned(), 656 "Region already in use (index %u)", curr_region->hrm_index()); 657 if (open) { 658 curr_region->set_open_archive(); 659 } else { 660 curr_region->set_closed_archive(); 661 } 662 _hr_printer.alloc(curr_region); 663 _archive_set.add(curr_region); 664 HeapWord* top; 665 HeapRegion* next_region; 666 if (curr_region != last_region) { 667 top = curr_region->end(); 668 next_region = _hrm->next_region_in_heap(curr_region); 669 } else { 670 top = last_address + 1; 671 next_region = NULL; 672 } 673 curr_region->set_top(top); 674 curr_region = next_region; 675 } 676 677 // Notify mark-sweep of the archive 678 G1ArchiveAllocator::set_range_archive(curr_range, open); 679 } 680 return true; 681 } 682 683 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 684 assert(!is_init_completed(), "Expect to be called at JVM init time"); 685 assert(ranges != NULL, "MemRegion array NULL"); 686 assert(count != 0, "No MemRegions provided"); 687 MemRegion reserved = _hrm->reserved(); 688 HeapWord *prev_last_addr = NULL; 689 HeapRegion* prev_last_region = NULL; 690 691 // For each MemRegion, create filler objects, if needed, in the G1 regions 692 // that contain the address range. The address range actually within the 693 // MemRegion will not be modified. That is assumed to have been initialized 694 // elsewhere, probably via an mmap of archived heap data. 695 MutexLocker x(Heap_lock); 696 for (size_t i = 0; i < count; i++) { 697 HeapWord* start_address = ranges[i].start(); 698 HeapWord* last_address = ranges[i].last(); 699 700 assert(reserved.contains(start_address) && reserved.contains(last_address), 701 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 702 p2i(start_address), p2i(last_address)); 703 assert(start_address > prev_last_addr, 704 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 705 p2i(start_address), p2i(prev_last_addr)); 706 707 HeapRegion* start_region = _hrm->addr_to_region(start_address); 708 HeapRegion* last_region = _hrm->addr_to_region(last_address); 709 HeapWord* bottom_address = start_region->bottom(); 710 711 // Check for a range beginning in the same region in which the 712 // previous one ended. 713 if (start_region == prev_last_region) { 714 bottom_address = prev_last_addr + 1; 715 } 716 717 // Verify that the regions were all marked as archive regions by 718 // alloc_archive_regions. 719 HeapRegion* curr_region = start_region; 720 while (curr_region != NULL) { 721 guarantee(curr_region->is_archive(), 722 "Expected archive region at index %u", curr_region->hrm_index()); 723 if (curr_region != last_region) { 724 curr_region = _hrm->next_region_in_heap(curr_region); 725 } else { 726 curr_region = NULL; 727 } 728 } 729 730 prev_last_addr = last_address; 731 prev_last_region = last_region; 732 733 // Fill the memory below the allocated range with dummy object(s), 734 // if the region bottom does not match the range start, or if the previous 735 // range ended within the same G1 region, and there is a gap. 736 if (start_address != bottom_address) { 737 size_t fill_size = pointer_delta(start_address, bottom_address); 738 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 739 increase_used(fill_size * HeapWordSize); 740 } 741 } 742 } 743 744 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size, 745 size_t desired_word_size, 746 size_t* actual_word_size) { 747 assert_heap_not_locked_and_not_at_safepoint(); 748 assert(!is_humongous(desired_word_size), "attempt_allocation() should not " 749 "be called for humongous allocation requests"); 750 751 HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size); 752 753 if (result == NULL) { 754 *actual_word_size = desired_word_size; 755 result = attempt_allocation_slow(desired_word_size); 756 } 757 758 assert_heap_not_locked(); 759 if (result != NULL) { 760 assert(*actual_word_size != 0, "Actual size must have been set here"); 761 dirty_young_block(result, *actual_word_size); 762 } else { 763 *actual_word_size = 0; 764 } 765 766 return result; 767 } 768 769 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count, bool is_open) { 770 assert(!is_init_completed(), "Expect to be called at JVM init time"); 771 assert(ranges != NULL, "MemRegion array NULL"); 772 assert(count != 0, "No MemRegions provided"); 773 MemRegion reserved = _hrm->reserved(); 774 HeapWord* prev_last_addr = NULL; 775 HeapRegion* prev_last_region = NULL; 776 size_t size_used = 0; 777 size_t uncommitted_regions = 0; 778 779 // For each Memregion, free the G1 regions that constitute it, and 780 // notify mark-sweep that the range is no longer to be considered 'archive.' 781 MutexLocker x(Heap_lock); 782 for (size_t i = 0; i < count; i++) { 783 HeapWord* start_address = ranges[i].start(); 784 HeapWord* last_address = ranges[i].last(); 785 786 assert(reserved.contains(start_address) && reserved.contains(last_address), 787 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 788 p2i(start_address), p2i(last_address)); 789 assert(start_address > prev_last_addr, 790 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 791 p2i(start_address), p2i(prev_last_addr)); 792 size_used += ranges[i].byte_size(); 793 prev_last_addr = last_address; 794 795 HeapRegion* start_region = _hrm->addr_to_region(start_address); 796 HeapRegion* last_region = _hrm->addr_to_region(last_address); 797 798 // Check for ranges that start in the same G1 region in which the previous 799 // range ended, and adjust the start address so we don't try to free 800 // the same region again. If the current range is entirely within that 801 // region, skip it. 802 if (start_region == prev_last_region) { 803 start_address = start_region->end(); 804 if (start_address > last_address) { 805 continue; 806 } 807 start_region = _hrm->addr_to_region(start_address); 808 } 809 prev_last_region = last_region; 810 811 // After verifying that each region was marked as an archive region by 812 // alloc_archive_regions, set it free and empty and uncommit it. 813 HeapRegion* curr_region = start_region; 814 while (curr_region != NULL) { 815 guarantee(curr_region->is_archive(), 816 "Expected archive region at index %u", curr_region->hrm_index()); 817 uint curr_index = curr_region->hrm_index(); 818 _archive_set.remove(curr_region); 819 curr_region->set_free(); 820 curr_region->set_top(curr_region->bottom()); 821 if (curr_region != last_region) { 822 curr_region = _hrm->next_region_in_heap(curr_region); 823 } else { 824 curr_region = NULL; 825 } 826 _hrm->shrink_at(curr_index, 1); 827 uncommitted_regions++; 828 } 829 830 // Notify mark-sweep that this is no longer an archive range. 831 G1ArchiveAllocator::clear_range_archive(ranges[i], is_open); 832 } 833 834 if (uncommitted_regions != 0) { 835 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 836 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 837 } 838 decrease_used(size_used); 839 } 840 841 oop G1CollectedHeap::materialize_archived_object(oop obj) { 842 assert(obj != NULL, "archived obj is NULL"); 843 assert(G1ArchiveAllocator::is_archived_object(obj), "must be archived object"); 844 845 // Loading an archived object makes it strongly reachable. If it is 846 // loaded during concurrent marking, it must be enqueued to the SATB 847 // queue, shading the previously white object gray. 848 G1BarrierSet::enqueue(obj); 849 850 return obj; 851 } 852 853 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) { 854 ResourceMark rm; // For retrieving the thread names in log messages. 855 856 // The structure of this method has a lot of similarities to 857 // attempt_allocation_slow(). The reason these two were not merged 858 // into a single one is that such a method would require several "if 859 // allocation is not humongous do this, otherwise do that" 860 // conditional paths which would obscure its flow. In fact, an early 861 // version of this code did use a unified method which was harder to 862 // follow and, as a result, it had subtle bugs that were hard to 863 // track down. So keeping these two methods separate allows each to 864 // be more readable. It will be good to keep these two in sync as 865 // much as possible. 866 867 assert_heap_not_locked_and_not_at_safepoint(); 868 assert(is_humongous(word_size), "attempt_allocation_humongous() " 869 "should only be called for humongous allocations"); 870 871 // Humongous objects can exhaust the heap quickly, so we should check if we 872 // need to start a marking cycle at each humongous object allocation. We do 873 // the check before we do the actual allocation. The reason for doing it 874 // before the allocation is that we avoid having to keep track of the newly 875 // allocated memory while we do a GC. 876 if (policy()->need_to_start_conc_mark("concurrent humongous allocation", 877 word_size)) { 878 collect(GCCause::_g1_humongous_allocation); 879 } 880 881 // We will loop until a) we manage to successfully perform the 882 // allocation or b) we successfully schedule a collection which 883 // fails to perform the allocation. b) is the only case when we'll 884 // return NULL. 885 HeapWord* result = NULL; 886 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 887 bool should_try_gc; 888 uint gc_count_before; 889 890 891 { 892 MutexLocker x(Heap_lock); 893 894 // Given that humongous objects are not allocated in young 895 // regions, we'll first try to do the allocation without doing a 896 // collection hoping that there's enough space in the heap. 897 result = humongous_obj_allocate(word_size); 898 if (result != NULL) { 899 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 900 policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 901 return result; 902 } 903 904 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 905 // the GCLocker initiated GC has been performed and then retry. This includes 906 // the case when the GC Locker is not active but has not been performed. 907 should_try_gc = !GCLocker::needs_gc(); 908 // Read the GC count while still holding the Heap_lock. 909 gc_count_before = total_collections(); 910 } 911 912 if (should_try_gc) { 913 bool succeeded; 914 result = do_collection_pause(word_size, gc_count_before, &succeeded, 915 GCCause::_g1_humongous_allocation); 916 if (result != NULL) { 917 assert(succeeded, "only way to get back a non-NULL result"); 918 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 919 Thread::current()->name(), p2i(result)); 920 return result; 921 } 922 923 if (succeeded) { 924 // We successfully scheduled a collection which failed to allocate. No 925 // point in trying to allocate further. We'll just return NULL. 926 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 927 SIZE_FORMAT " words", Thread::current()->name(), word_size); 928 return NULL; 929 } 930 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "", 931 Thread::current()->name(), word_size); 932 } else { 933 // Failed to schedule a collection. 934 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 935 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 936 SIZE_FORMAT " words", Thread::current()->name(), word_size); 937 return NULL; 938 } 939 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 940 // The GCLocker is either active or the GCLocker initiated 941 // GC has not yet been performed. Stall until it is and 942 // then retry the allocation. 943 GCLocker::stall_until_clear(); 944 gclocker_retry_count += 1; 945 } 946 947 948 // We can reach here if we were unsuccessful in scheduling a 949 // collection (because another thread beat us to it) or if we were 950 // stalled due to the GC locker. In either can we should retry the 951 // allocation attempt in case another thread successfully 952 // performed a collection and reclaimed enough space. 953 // Humongous object allocation always needs a lock, so we wait for the retry 954 // in the next iteration of the loop, unlike for the regular iteration case. 955 // Give a warning if we seem to be looping forever. 956 957 if ((QueuedAllocationWarningCount > 0) && 958 (try_count % QueuedAllocationWarningCount == 0)) { 959 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 960 Thread::current()->name(), try_count, word_size); 961 } 962 } 963 964 ShouldNotReachHere(); 965 return NULL; 966 } 967 968 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 969 bool expect_null_mutator_alloc_region) { 970 assert_at_safepoint_on_vm_thread(); 971 assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region, 972 "the current alloc region was unexpectedly found to be non-NULL"); 973 974 if (!is_humongous(word_size)) { 975 return _allocator->attempt_allocation_locked(word_size); 976 } else { 977 HeapWord* result = humongous_obj_allocate(word_size); 978 if (result != NULL && policy()->need_to_start_conc_mark("STW humongous allocation")) { 979 collector_state()->set_initiate_conc_mark_if_possible(true); 980 } 981 return result; 982 } 983 984 ShouldNotReachHere(); 985 } 986 987 class PostCompactionPrinterClosure: public HeapRegionClosure { 988 private: 989 G1HRPrinter* _hr_printer; 990 public: 991 bool do_heap_region(HeapRegion* hr) { 992 assert(!hr->is_young(), "not expecting to find young regions"); 993 _hr_printer->post_compaction(hr); 994 return false; 995 } 996 997 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 998 : _hr_printer(hr_printer) { } 999 }; 1000 1001 void G1CollectedHeap::print_hrm_post_compaction() { 1002 if (_hr_printer.is_active()) { 1003 PostCompactionPrinterClosure cl(hr_printer()); 1004 heap_region_iterate(&cl); 1005 } 1006 } 1007 1008 void G1CollectedHeap::abort_concurrent_cycle() { 1009 // If we start the compaction before the CM threads finish 1010 // scanning the root regions we might trip them over as we'll 1011 // be moving objects / updating references. So let's wait until 1012 // they are done. By telling them to abort, they should complete 1013 // early. 1014 _cm->root_regions()->abort(); 1015 _cm->root_regions()->wait_until_scan_finished(); 1016 1017 // Disable discovery and empty the discovered lists 1018 // for the CM ref processor. 1019 _ref_processor_cm->disable_discovery(); 1020 _ref_processor_cm->abandon_partial_discovery(); 1021 _ref_processor_cm->verify_no_references_recorded(); 1022 1023 // Abandon current iterations of concurrent marking and concurrent 1024 // refinement, if any are in progress. 1025 concurrent_mark()->concurrent_cycle_abort(); 1026 } 1027 1028 void G1CollectedHeap::prepare_heap_for_full_collection() { 1029 // Make sure we'll choose a new allocation region afterwards. 1030 _allocator->release_mutator_alloc_regions(); 1031 _allocator->abandon_gc_alloc_regions(); 1032 1033 // We may have added regions to the current incremental collection 1034 // set between the last GC or pause and now. We need to clear the 1035 // incremental collection set and then start rebuilding it afresh 1036 // after this full GC. 1037 abandon_collection_set(collection_set()); 1038 1039 tear_down_region_sets(false /* free_list_only */); 1040 1041 hrm()->prepare_for_full_collection_start(); 1042 } 1043 1044 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1045 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1046 assert_used_and_recalculate_used_equal(this); 1047 _verifier->verify_region_sets_optional(); 1048 _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull); 1049 _verifier->check_bitmaps("Full GC Start"); 1050 } 1051 1052 void G1CollectedHeap::prepare_heap_for_mutators() { 1053 hrm()->prepare_for_full_collection_end(); 1054 1055 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1056 ClassLoaderDataGraph::purge(); 1057 MetaspaceUtils::verify_metrics(); 1058 1059 // Prepare heap for normal collections. 1060 assert(num_free_regions() == 0, "we should not have added any free regions"); 1061 rebuild_region_sets(false /* free_list_only */); 1062 abort_refinement(); 1063 resize_heap_if_necessary(); 1064 1065 // Rebuild the strong code root lists for each region 1066 rebuild_strong_code_roots(); 1067 1068 // Purge code root memory 1069 purge_code_root_memory(); 1070 1071 // Start a new incremental collection set for the next pause 1072 start_new_collection_set(); 1073 1074 _allocator->init_mutator_alloc_regions(); 1075 1076 // Post collection state updates. 1077 MetaspaceGC::compute_new_size(); 1078 } 1079 1080 void G1CollectedHeap::abort_refinement() { 1081 if (_hot_card_cache->use_cache()) { 1082 _hot_card_cache->reset_hot_cache(); 1083 } 1084 1085 // Discard all remembered set updates. 1086 G1BarrierSet::dirty_card_queue_set().abandon_logs(); 1087 assert(G1BarrierSet::dirty_card_queue_set().num_cards() == 0, 1088 "DCQS should be empty"); 1089 } 1090 1091 void G1CollectedHeap::verify_after_full_collection() { 1092 _hrm->verify_optional(); 1093 _verifier->verify_region_sets_optional(); 1094 _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull); 1095 // Clear the previous marking bitmap, if needed for bitmap verification. 1096 // Note we cannot do this when we clear the next marking bitmap in 1097 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1098 // objects marked during a full GC against the previous bitmap. 1099 // But we need to clear it before calling check_bitmaps below since 1100 // the full GC has compacted objects and updated TAMS but not updated 1101 // the prev bitmap. 1102 if (G1VerifyBitmaps) { 1103 GCTraceTime(Debug, gc) tm("Clear Prev Bitmap for Verification"); 1104 _cm->clear_prev_bitmap(workers()); 1105 } 1106 // This call implicitly verifies that the next bitmap is clear after Full GC. 1107 _verifier->check_bitmaps("Full GC End"); 1108 1109 // At this point there should be no regions in the 1110 // entire heap tagged as young. 1111 assert(check_young_list_empty(), "young list should be empty at this point"); 1112 1113 // Note: since we've just done a full GC, concurrent 1114 // marking is no longer active. Therefore we need not 1115 // re-enable reference discovery for the CM ref processor. 1116 // That will be done at the start of the next marking cycle. 1117 // We also know that the STW processor should no longer 1118 // discover any new references. 1119 assert(!_ref_processor_stw->discovery_enabled(), "Postcondition"); 1120 assert(!_ref_processor_cm->discovery_enabled(), "Postcondition"); 1121 _ref_processor_stw->verify_no_references_recorded(); 1122 _ref_processor_cm->verify_no_references_recorded(); 1123 } 1124 1125 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1126 // Post collection logging. 1127 // We should do this after we potentially resize the heap so 1128 // that all the COMMIT / UNCOMMIT events are generated before 1129 // the compaction events. 1130 print_hrm_post_compaction(); 1131 heap_transition->print(); 1132 print_heap_after_gc(); 1133 print_heap_regions(); 1134 #ifdef TRACESPINNING 1135 ParallelTaskTerminator::print_termination_counts(); 1136 #endif 1137 } 1138 1139 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1140 bool clear_all_soft_refs) { 1141 assert_at_safepoint_on_vm_thread(); 1142 1143 if (GCLocker::check_active_before_gc()) { 1144 // Full GC was not completed. 1145 return false; 1146 } 1147 1148 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1149 soft_ref_policy()->should_clear_all_soft_refs(); 1150 1151 G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs); 1152 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1153 1154 collector.prepare_collection(); 1155 collector.collect(); 1156 collector.complete_collection(); 1157 1158 // Full collection was successfully completed. 1159 return true; 1160 } 1161 1162 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1163 // Currently, there is no facility in the do_full_collection(bool) API to notify 1164 // the caller that the collection did not succeed (e.g., because it was locked 1165 // out by the GC locker). So, right now, we'll ignore the return value. 1166 bool dummy = do_full_collection(true, /* explicit_gc */ 1167 clear_all_soft_refs); 1168 } 1169 1170 void G1CollectedHeap::resize_heap_if_necessary() { 1171 assert_at_safepoint_on_vm_thread(); 1172 1173 // Capacity, free and used after the GC counted as full regions to 1174 // include the waste in the following calculations. 1175 const size_t capacity_after_gc = capacity(); 1176 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes(); 1177 1178 // This is enforced in arguments.cpp. 1179 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1180 "otherwise the code below doesn't make sense"); 1181 1182 // We don't have floating point command-line arguments 1183 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1184 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1185 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1186 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1187 1188 // We have to be careful here as these two calculations can overflow 1189 // 32-bit size_t's. 1190 double used_after_gc_d = (double) used_after_gc; 1191 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1192 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1193 1194 // Let's make sure that they are both under the max heap size, which 1195 // by default will make them fit into a size_t. 1196 double desired_capacity_upper_bound = (double) MaxHeapSize; 1197 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1198 desired_capacity_upper_bound); 1199 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1200 desired_capacity_upper_bound); 1201 1202 // We can now safely turn them into size_t's. 1203 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1204 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1205 1206 // This assert only makes sense here, before we adjust them 1207 // with respect to the min and max heap size. 1208 assert(minimum_desired_capacity <= maximum_desired_capacity, 1209 "minimum_desired_capacity = " SIZE_FORMAT ", " 1210 "maximum_desired_capacity = " SIZE_FORMAT, 1211 minimum_desired_capacity, maximum_desired_capacity); 1212 1213 // Should not be greater than the heap max size. No need to adjust 1214 // it with respect to the heap min size as it's a lower bound (i.e., 1215 // we'll try to make the capacity larger than it, not smaller). 1216 minimum_desired_capacity = MIN2(minimum_desired_capacity, MaxHeapSize); 1217 // Should not be less than the heap min size. No need to adjust it 1218 // with respect to the heap max size as it's an upper bound (i.e., 1219 // we'll try to make the capacity smaller than it, not greater). 1220 maximum_desired_capacity = MAX2(maximum_desired_capacity, MinHeapSize); 1221 1222 if (capacity_after_gc < minimum_desired_capacity) { 1223 // Don't expand unless it's significant 1224 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1225 1226 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity). " 1227 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1228 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1229 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio); 1230 1231 expand(expand_bytes, _workers); 1232 1233 // No expansion, now see if we want to shrink 1234 } else if (capacity_after_gc > maximum_desired_capacity) { 1235 // Capacity too large, compute shrinking size 1236 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1237 1238 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity). " 1239 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1240 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1241 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio); 1242 1243 shrink(shrink_bytes); 1244 } 1245 } 1246 1247 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1248 bool do_gc, 1249 bool clear_all_soft_refs, 1250 bool expect_null_mutator_alloc_region, 1251 bool* gc_succeeded) { 1252 *gc_succeeded = true; 1253 // Let's attempt the allocation first. 1254 HeapWord* result = 1255 attempt_allocation_at_safepoint(word_size, 1256 expect_null_mutator_alloc_region); 1257 if (result != NULL) { 1258 return result; 1259 } 1260 1261 // In a G1 heap, we're supposed to keep allocation from failing by 1262 // incremental pauses. Therefore, at least for now, we'll favor 1263 // expansion over collection. (This might change in the future if we can 1264 // do something smarter than full collection to satisfy a failed alloc.) 1265 result = expand_and_allocate(word_size); 1266 if (result != NULL) { 1267 return result; 1268 } 1269 1270 if (do_gc) { 1271 // Expansion didn't work, we'll try to do a Full GC. 1272 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1273 clear_all_soft_refs); 1274 } 1275 1276 return NULL; 1277 } 1278 1279 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1280 bool* succeeded) { 1281 assert_at_safepoint_on_vm_thread(); 1282 1283 // Attempts to allocate followed by Full GC. 1284 HeapWord* result = 1285 satisfy_failed_allocation_helper(word_size, 1286 true, /* do_gc */ 1287 false, /* clear_all_soft_refs */ 1288 false, /* expect_null_mutator_alloc_region */ 1289 succeeded); 1290 1291 if (result != NULL || !*succeeded) { 1292 return result; 1293 } 1294 1295 // Attempts to allocate followed by Full GC that will collect all soft references. 1296 result = satisfy_failed_allocation_helper(word_size, 1297 true, /* do_gc */ 1298 true, /* clear_all_soft_refs */ 1299 true, /* expect_null_mutator_alloc_region */ 1300 succeeded); 1301 1302 if (result != NULL || !*succeeded) { 1303 return result; 1304 } 1305 1306 // Attempts to allocate, no GC 1307 result = satisfy_failed_allocation_helper(word_size, 1308 false, /* do_gc */ 1309 false, /* clear_all_soft_refs */ 1310 true, /* expect_null_mutator_alloc_region */ 1311 succeeded); 1312 1313 if (result != NULL) { 1314 return result; 1315 } 1316 1317 assert(!soft_ref_policy()->should_clear_all_soft_refs(), 1318 "Flag should have been handled and cleared prior to this point"); 1319 1320 // What else? We might try synchronous finalization later. If the total 1321 // space available is large enough for the allocation, then a more 1322 // complete compaction phase than we've tried so far might be 1323 // appropriate. 1324 return NULL; 1325 } 1326 1327 // Attempting to expand the heap sufficiently 1328 // to support an allocation of the given "word_size". If 1329 // successful, perform the allocation and return the address of the 1330 // allocated block, or else "NULL". 1331 1332 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1333 assert_at_safepoint_on_vm_thread(); 1334 1335 _verifier->verify_region_sets_optional(); 1336 1337 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1338 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1339 word_size * HeapWordSize); 1340 1341 1342 if (expand(expand_bytes, _workers)) { 1343 _hrm->verify_optional(); 1344 _verifier->verify_region_sets_optional(); 1345 return attempt_allocation_at_safepoint(word_size, 1346 false /* expect_null_mutator_alloc_region */); 1347 } 1348 return NULL; 1349 } 1350 1351 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1352 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1353 aligned_expand_bytes = align_up(aligned_expand_bytes, 1354 HeapRegion::GrainBytes); 1355 1356 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1357 expand_bytes, aligned_expand_bytes); 1358 1359 if (is_maximal_no_gc()) { 1360 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1361 return false; 1362 } 1363 1364 double expand_heap_start_time_sec = os::elapsedTime(); 1365 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1366 assert(regions_to_expand > 0, "Must expand by at least one region"); 1367 1368 uint expanded_by = _hrm->expand_by(regions_to_expand, pretouch_workers); 1369 if (expand_time_ms != NULL) { 1370 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1371 } 1372 1373 if (expanded_by > 0) { 1374 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1375 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1376 policy()->record_new_heap_size(num_regions()); 1377 } else { 1378 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1379 1380 // The expansion of the virtual storage space was unsuccessful. 1381 // Let's see if it was because we ran out of swap. 1382 if (G1ExitOnExpansionFailure && 1383 _hrm->available() >= regions_to_expand) { 1384 // We had head room... 1385 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1386 } 1387 } 1388 return regions_to_expand > 0; 1389 } 1390 1391 bool G1CollectedHeap::expand_single_region(uint node_index) { 1392 uint expanded_by = _hrm->expand_on_preferred_node(node_index); 1393 1394 if (expanded_by == 0) { 1395 assert(is_maximal_no_gc(), "Should be no regions left, available: %u", _hrm->available()); 1396 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1397 return false; 1398 } 1399 1400 policy()->record_new_heap_size(num_regions()); 1401 return true; 1402 } 1403 1404 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1405 size_t aligned_shrink_bytes = 1406 ReservedSpace::page_align_size_down(shrink_bytes); 1407 aligned_shrink_bytes = align_down(aligned_shrink_bytes, 1408 HeapRegion::GrainBytes); 1409 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1410 1411 uint num_regions_removed = _hrm->shrink_by(num_regions_to_remove); 1412 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1413 1414 log_debug(gc, ergo, heap)("Shrink the heap. requested shrinking amount: " SIZE_FORMAT "B aligned shrinking amount: " SIZE_FORMAT "B attempted shrinking amount: " SIZE_FORMAT "B", 1415 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1416 if (num_regions_removed > 0) { 1417 policy()->record_new_heap_size(num_regions()); 1418 } else { 1419 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1420 } 1421 } 1422 1423 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1424 _verifier->verify_region_sets_optional(); 1425 1426 // We should only reach here at the end of a Full GC or during Remark which 1427 // means we should not not be holding to any GC alloc regions. The method 1428 // below will make sure of that and do any remaining clean up. 1429 _allocator->abandon_gc_alloc_regions(); 1430 1431 // Instead of tearing down / rebuilding the free lists here, we 1432 // could instead use the remove_all_pending() method on free_list to 1433 // remove only the ones that we need to remove. 1434 tear_down_region_sets(true /* free_list_only */); 1435 shrink_helper(shrink_bytes); 1436 rebuild_region_sets(true /* free_list_only */); 1437 1438 _hrm->verify_optional(); 1439 _verifier->verify_region_sets_optional(); 1440 } 1441 1442 class OldRegionSetChecker : public HeapRegionSetChecker { 1443 public: 1444 void check_mt_safety() { 1445 // Master Old Set MT safety protocol: 1446 // (a) If we're at a safepoint, operations on the master old set 1447 // should be invoked: 1448 // - by the VM thread (which will serialize them), or 1449 // - by the GC workers while holding the FreeList_lock, if we're 1450 // at a safepoint for an evacuation pause (this lock is taken 1451 // anyway when an GC alloc region is retired so that a new one 1452 // is allocated from the free list), or 1453 // - by the GC workers while holding the OldSets_lock, if we're at a 1454 // safepoint for a cleanup pause. 1455 // (b) If we're not at a safepoint, operations on the master old set 1456 // should be invoked while holding the Heap_lock. 1457 1458 if (SafepointSynchronize::is_at_safepoint()) { 1459 guarantee(Thread::current()->is_VM_thread() || 1460 FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(), 1461 "master old set MT safety protocol at a safepoint"); 1462 } else { 1463 guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint"); 1464 } 1465 } 1466 bool is_correct_type(HeapRegion* hr) { return hr->is_old(); } 1467 const char* get_description() { return "Old Regions"; } 1468 }; 1469 1470 class ArchiveRegionSetChecker : public HeapRegionSetChecker { 1471 public: 1472 void check_mt_safety() { 1473 guarantee(!Universe::is_fully_initialized() || SafepointSynchronize::is_at_safepoint(), 1474 "May only change archive regions during initialization or safepoint."); 1475 } 1476 bool is_correct_type(HeapRegion* hr) { return hr->is_archive(); } 1477 const char* get_description() { return "Archive Regions"; } 1478 }; 1479 1480 class HumongousRegionSetChecker : public HeapRegionSetChecker { 1481 public: 1482 void check_mt_safety() { 1483 // Humongous Set MT safety protocol: 1484 // (a) If we're at a safepoint, operations on the master humongous 1485 // set should be invoked by either the VM thread (which will 1486 // serialize them) or by the GC workers while holding the 1487 // OldSets_lock. 1488 // (b) If we're not at a safepoint, operations on the master 1489 // humongous set should be invoked while holding the Heap_lock. 1490 1491 if (SafepointSynchronize::is_at_safepoint()) { 1492 guarantee(Thread::current()->is_VM_thread() || 1493 OldSets_lock->owned_by_self(), 1494 "master humongous set MT safety protocol at a safepoint"); 1495 } else { 1496 guarantee(Heap_lock->owned_by_self(), 1497 "master humongous set MT safety protocol outside a safepoint"); 1498 } 1499 } 1500 bool is_correct_type(HeapRegion* hr) { return hr->is_humongous(); } 1501 const char* get_description() { return "Humongous Regions"; } 1502 }; 1503 1504 G1CollectedHeap::G1CollectedHeap() : 1505 CollectedHeap(), 1506 _young_gen_sampling_thread(NULL), 1507 _workers(NULL), 1508 _card_table(NULL), 1509 _soft_ref_policy(), 1510 _old_set("Old Region Set", new OldRegionSetChecker()), 1511 _archive_set("Archive Region Set", new ArchiveRegionSetChecker()), 1512 _humongous_set("Humongous Region Set", new HumongousRegionSetChecker()), 1513 _bot(NULL), 1514 _listener(), 1515 _numa(G1NUMA::create()), 1516 _hrm(NULL), 1517 _allocator(NULL), 1518 _verifier(NULL), 1519 _summary_bytes_used(0), 1520 _bytes_used_during_gc(0), 1521 _archive_allocator(NULL), 1522 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1523 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1524 _expand_heap_after_alloc_failure(true), 1525 _g1mm(NULL), 1526 _humongous_reclaim_candidates(), 1527 _has_humongous_reclaim_candidates(false), 1528 _hr_printer(), 1529 _collector_state(), 1530 _old_marking_cycles_started(0), 1531 _old_marking_cycles_completed(0), 1532 _eden(), 1533 _survivor(), 1534 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1535 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1536 _policy(G1Policy::create_policy(_gc_timer_stw)), 1537 _heap_sizing_policy(NULL), 1538 _collection_set(this, _policy), 1539 _hot_card_cache(NULL), 1540 _rem_set(NULL), 1541 _cm(NULL), 1542 _cm_thread(NULL), 1543 _cr(NULL), 1544 _task_queues(NULL), 1545 _evacuation_failed(false), 1546 _evacuation_failed_info_array(NULL), 1547 _preserved_marks_set(true /* in_c_heap */), 1548 #ifndef PRODUCT 1549 _evacuation_failure_alot_for_current_gc(false), 1550 _evacuation_failure_alot_gc_number(0), 1551 _evacuation_failure_alot_count(0), 1552 #endif 1553 _ref_processor_stw(NULL), 1554 _is_alive_closure_stw(this), 1555 _is_subject_to_discovery_stw(this), 1556 _ref_processor_cm(NULL), 1557 _is_alive_closure_cm(this), 1558 _is_subject_to_discovery_cm(this), 1559 _region_attr() { 1560 1561 _verifier = new G1HeapVerifier(this); 1562 1563 _allocator = new G1Allocator(this); 1564 1565 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _policy->analytics()); 1566 1567 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1568 1569 // Override the default _filler_array_max_size so that no humongous filler 1570 // objects are created. 1571 _filler_array_max_size = _humongous_object_threshold_in_words; 1572 1573 uint n_queues = ParallelGCThreads; 1574 _task_queues = new RefToScanQueueSet(n_queues); 1575 1576 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1577 1578 for (uint i = 0; i < n_queues; i++) { 1579 RefToScanQueue* q = new RefToScanQueue(); 1580 q->initialize(); 1581 _task_queues->register_queue(i, q); 1582 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1583 } 1584 1585 // Initialize the G1EvacuationFailureALot counters and flags. 1586 NOT_PRODUCT(reset_evacuation_should_fail();) 1587 _gc_tracer_stw->initialize(); 1588 1589 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1590 } 1591 1592 static size_t actual_reserved_page_size(ReservedSpace rs) { 1593 size_t page_size = os::vm_page_size(); 1594 if (UseLargePages) { 1595 // There are two ways to manage large page memory. 1596 // 1. OS supports committing large page memory. 1597 // 2. OS doesn't support committing large page memory so ReservedSpace manages it. 1598 // And ReservedSpace calls it 'special'. If we failed to set 'special', 1599 // we reserved memory without large page. 1600 if (os::can_commit_large_page_memory() || rs.special()) { 1601 // An alignment at ReservedSpace comes from preferred page size or 1602 // heap alignment, and if the alignment came from heap alignment, it could be 1603 // larger than large pages size. So need to cap with the large page size. 1604 page_size = MIN2(rs.alignment(), os::large_page_size()); 1605 } 1606 } 1607 1608 return page_size; 1609 } 1610 1611 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1612 size_t size, 1613 size_t translation_factor) { 1614 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1615 // Allocate a new reserved space, preferring to use large pages. 1616 ReservedSpace rs(size, preferred_page_size); 1617 size_t page_size = actual_reserved_page_size(rs); 1618 G1RegionToSpaceMapper* result = 1619 G1RegionToSpaceMapper::create_mapper(rs, 1620 size, 1621 page_size, 1622 HeapRegion::GrainBytes, 1623 translation_factor, 1624 mtGC); 1625 1626 os::trace_page_sizes_for_requested_size(description, 1627 size, 1628 preferred_page_size, 1629 page_size, 1630 rs.base(), 1631 rs.size()); 1632 1633 return result; 1634 } 1635 1636 jint G1CollectedHeap::initialize_concurrent_refinement() { 1637 jint ecode = JNI_OK; 1638 _cr = G1ConcurrentRefine::create(&ecode); 1639 return ecode; 1640 } 1641 1642 jint G1CollectedHeap::initialize_young_gen_sampling_thread() { 1643 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread(); 1644 if (_young_gen_sampling_thread->osthread() == NULL) { 1645 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread"); 1646 return JNI_ENOMEM; 1647 } 1648 return JNI_OK; 1649 } 1650 1651 jint G1CollectedHeap::initialize() { 1652 1653 // Necessary to satisfy locking discipline assertions. 1654 1655 MutexLocker x(Heap_lock); 1656 1657 // While there are no constraints in the GC code that HeapWordSize 1658 // be any particular value, there are multiple other areas in the 1659 // system which believe this to be true (e.g. oop->object_size in some 1660 // cases incorrectly returns the size in wordSize units rather than 1661 // HeapWordSize). 1662 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1663 1664 size_t init_byte_size = InitialHeapSize; 1665 size_t reserved_byte_size = G1Arguments::heap_reserved_size_bytes(); 1666 1667 // Ensure that the sizes are properly aligned. 1668 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1669 Universe::check_alignment(reserved_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1670 Universe::check_alignment(reserved_byte_size, HeapAlignment, "g1 heap"); 1671 1672 // Reserve the maximum. 1673 1674 // When compressed oops are enabled, the preferred heap base 1675 // is calculated by subtracting the requested size from the 1676 // 32Gb boundary and using the result as the base address for 1677 // heap reservation. If the requested size is not aligned to 1678 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1679 // into the ReservedHeapSpace constructor) then the actual 1680 // base of the reserved heap may end up differing from the 1681 // address that was requested (i.e. the preferred heap base). 1682 // If this happens then we could end up using a non-optimal 1683 // compressed oops mode. 1684 1685 ReservedHeapSpace heap_rs = Universe::reserve_heap(reserved_byte_size, 1686 HeapAlignment); 1687 1688 initialize_reserved_region(heap_rs); 1689 1690 // Create the barrier set for the entire reserved region. 1691 G1CardTable* ct = new G1CardTable(heap_rs.region()); 1692 ct->initialize(); 1693 G1BarrierSet* bs = new G1BarrierSet(ct); 1694 bs->initialize(); 1695 assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity"); 1696 BarrierSet::set_barrier_set(bs); 1697 _card_table = ct; 1698 1699 { 1700 G1SATBMarkQueueSet& satbqs = bs->satb_mark_queue_set(); 1701 satbqs.set_process_completed_buffers_threshold(G1SATBProcessCompletedThreshold); 1702 satbqs.set_buffer_enqueue_threshold_percentage(G1SATBBufferEnqueueingThresholdPercent); 1703 } 1704 1705 // Create the hot card cache. 1706 _hot_card_cache = new G1HotCardCache(this); 1707 1708 // Carve out the G1 part of the heap. 1709 ReservedSpace g1_rs = heap_rs.first_part(reserved_byte_size); 1710 size_t page_size = actual_reserved_page_size(heap_rs); 1711 G1RegionToSpaceMapper* heap_storage = 1712 G1RegionToSpaceMapper::create_heap_mapper(g1_rs, 1713 g1_rs.size(), 1714 page_size, 1715 HeapRegion::GrainBytes, 1716 1, 1717 mtJavaHeap); 1718 if(heap_storage == NULL) { 1719 vm_shutdown_during_initialization("Could not initialize G1 heap"); 1720 return JNI_ERR; 1721 } 1722 1723 os::trace_page_sizes("Heap", 1724 MinHeapSize, 1725 reserved_byte_size, 1726 page_size, 1727 heap_rs.base(), 1728 heap_rs.size()); 1729 heap_storage->set_mapping_changed_listener(&_listener); 1730 1731 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1732 G1RegionToSpaceMapper* bot_storage = 1733 create_aux_memory_mapper("Block Offset Table", 1734 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1735 G1BlockOffsetTable::heap_map_factor()); 1736 1737 G1RegionToSpaceMapper* cardtable_storage = 1738 create_aux_memory_mapper("Card Table", 1739 G1CardTable::compute_size(g1_rs.size() / HeapWordSize), 1740 G1CardTable::heap_map_factor()); 1741 1742 G1RegionToSpaceMapper* card_counts_storage = 1743 create_aux_memory_mapper("Card Counts Table", 1744 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1745 G1CardCounts::heap_map_factor()); 1746 1747 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1748 G1RegionToSpaceMapper* prev_bitmap_storage = 1749 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1750 G1RegionToSpaceMapper* next_bitmap_storage = 1751 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1752 1753 _hrm = HeapRegionManager::create_manager(this); 1754 1755 _hrm->initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1756 _card_table->initialize(cardtable_storage); 1757 1758 // Do later initialization work for concurrent refinement. 1759 _hot_card_cache->initialize(card_counts_storage); 1760 1761 // 6843694 - ensure that the maximum region index can fit 1762 // in the remembered set structures. 1763 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1764 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1765 1766 // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not 1767 // start within the first card. 1768 guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card."); 1769 // Also create a G1 rem set. 1770 _rem_set = new G1RemSet(this, _card_table, _hot_card_cache); 1771 _rem_set->initialize(max_reserved_capacity(), max_regions()); 1772 1773 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1774 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1775 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1776 "too many cards per region"); 1777 1778 FreeRegionList::set_unrealistically_long_length(max_expandable_regions() + 1); 1779 1780 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1781 1782 { 1783 HeapWord* start = _hrm->reserved().start(); 1784 HeapWord* end = _hrm->reserved().end(); 1785 size_t granularity = HeapRegion::GrainBytes; 1786 1787 _region_attr.initialize(start, end, granularity); 1788 _humongous_reclaim_candidates.initialize(start, end, granularity); 1789 } 1790 1791 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1792 true /* are_GC_task_threads */, 1793 false /* are_ConcurrentGC_threads */); 1794 if (_workers == NULL) { 1795 return JNI_ENOMEM; 1796 } 1797 _workers->initialize_workers(); 1798 1799 _numa->set_region_info(HeapRegion::GrainBytes, page_size); 1800 1801 // Create the G1ConcurrentMark data structure and thread. 1802 // (Must do this late, so that "max_regions" is defined.) 1803 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1804 if (_cm == NULL || !_cm->completed_initialization()) { 1805 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1806 return JNI_ENOMEM; 1807 } 1808 _cm_thread = _cm->cm_thread(); 1809 1810 // Now expand into the initial heap size. 1811 if (!expand(init_byte_size, _workers)) { 1812 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1813 return JNI_ENOMEM; 1814 } 1815 1816 // Perform any initialization actions delegated to the policy. 1817 policy()->init(this, &_collection_set); 1818 1819 jint ecode = initialize_concurrent_refinement(); 1820 if (ecode != JNI_OK) { 1821 return ecode; 1822 } 1823 1824 ecode = initialize_young_gen_sampling_thread(); 1825 if (ecode != JNI_OK) { 1826 return ecode; 1827 } 1828 1829 { 1830 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 1831 dcqs.set_process_cards_threshold(concurrent_refine()->yellow_zone()); 1832 dcqs.set_max_cards(concurrent_refine()->red_zone()); 1833 } 1834 1835 // Here we allocate the dummy HeapRegion that is required by the 1836 // G1AllocRegion class. 1837 HeapRegion* dummy_region = _hrm->get_dummy_region(); 1838 1839 // We'll re-use the same region whether the alloc region will 1840 // require BOT updates or not and, if it doesn't, then a non-young 1841 // region will complain that it cannot support allocations without 1842 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1843 dummy_region->set_eden(); 1844 // Make sure it's full. 1845 dummy_region->set_top(dummy_region->end()); 1846 G1AllocRegion::setup(this, dummy_region); 1847 1848 _allocator->init_mutator_alloc_regions(); 1849 1850 // Do create of the monitoring and management support so that 1851 // values in the heap have been properly initialized. 1852 _g1mm = new G1MonitoringSupport(this); 1853 1854 G1StringDedup::initialize(); 1855 1856 _preserved_marks_set.init(ParallelGCThreads); 1857 1858 _collection_set.initialize(max_regions()); 1859 1860 return JNI_OK; 1861 } 1862 1863 void G1CollectedHeap::stop() { 1864 // Stop all concurrent threads. We do this to make sure these threads 1865 // do not continue to execute and access resources (e.g. logging) 1866 // that are destroyed during shutdown. 1867 _cr->stop(); 1868 _young_gen_sampling_thread->stop(); 1869 _cm_thread->stop(); 1870 if (G1StringDedup::is_enabled()) { 1871 G1StringDedup::stop(); 1872 } 1873 } 1874 1875 void G1CollectedHeap::safepoint_synchronize_begin() { 1876 SuspendibleThreadSet::synchronize(); 1877 } 1878 1879 void G1CollectedHeap::safepoint_synchronize_end() { 1880 SuspendibleThreadSet::desynchronize(); 1881 } 1882 1883 void G1CollectedHeap::post_initialize() { 1884 CollectedHeap::post_initialize(); 1885 ref_processing_init(); 1886 } 1887 1888 void G1CollectedHeap::ref_processing_init() { 1889 // Reference processing in G1 currently works as follows: 1890 // 1891 // * There are two reference processor instances. One is 1892 // used to record and process discovered references 1893 // during concurrent marking; the other is used to 1894 // record and process references during STW pauses 1895 // (both full and incremental). 1896 // * Both ref processors need to 'span' the entire heap as 1897 // the regions in the collection set may be dotted around. 1898 // 1899 // * For the concurrent marking ref processor: 1900 // * Reference discovery is enabled at initial marking. 1901 // * Reference discovery is disabled and the discovered 1902 // references processed etc during remarking. 1903 // * Reference discovery is MT (see below). 1904 // * Reference discovery requires a barrier (see below). 1905 // * Reference processing may or may not be MT 1906 // (depending on the value of ParallelRefProcEnabled 1907 // and ParallelGCThreads). 1908 // * A full GC disables reference discovery by the CM 1909 // ref processor and abandons any entries on it's 1910 // discovered lists. 1911 // 1912 // * For the STW processor: 1913 // * Non MT discovery is enabled at the start of a full GC. 1914 // * Processing and enqueueing during a full GC is non-MT. 1915 // * During a full GC, references are processed after marking. 1916 // 1917 // * Discovery (may or may not be MT) is enabled at the start 1918 // of an incremental evacuation pause. 1919 // * References are processed near the end of a STW evacuation pause. 1920 // * For both types of GC: 1921 // * Discovery is atomic - i.e. not concurrent. 1922 // * Reference discovery will not need a barrier. 1923 1924 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1); 1925 1926 // Concurrent Mark ref processor 1927 _ref_processor_cm = 1928 new ReferenceProcessor(&_is_subject_to_discovery_cm, 1929 mt_processing, // mt processing 1930 ParallelGCThreads, // degree of mt processing 1931 (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery 1932 MAX2(ParallelGCThreads, ConcGCThreads), // degree of mt discovery 1933 false, // Reference discovery is not atomic 1934 &_is_alive_closure_cm, // is alive closure 1935 true); // allow changes to number of processing threads 1936 1937 // STW ref processor 1938 _ref_processor_stw = 1939 new ReferenceProcessor(&_is_subject_to_discovery_stw, 1940 mt_processing, // mt processing 1941 ParallelGCThreads, // degree of mt processing 1942 (ParallelGCThreads > 1), // mt discovery 1943 ParallelGCThreads, // degree of mt discovery 1944 true, // Reference discovery is atomic 1945 &_is_alive_closure_stw, // is alive closure 1946 true); // allow changes to number of processing threads 1947 } 1948 1949 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() { 1950 return &_soft_ref_policy; 1951 } 1952 1953 size_t G1CollectedHeap::capacity() const { 1954 return _hrm->length() * HeapRegion::GrainBytes; 1955 } 1956 1957 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const { 1958 return _hrm->total_free_bytes(); 1959 } 1960 1961 void G1CollectedHeap::iterate_hcc_closure(G1CardTableEntryClosure* cl, uint worker_id) { 1962 _hot_card_cache->drain(cl, worker_id); 1963 } 1964 1965 // Computes the sum of the storage used by the various regions. 1966 size_t G1CollectedHeap::used() const { 1967 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 1968 if (_archive_allocator != NULL) { 1969 result += _archive_allocator->used(); 1970 } 1971 return result; 1972 } 1973 1974 size_t G1CollectedHeap::used_unlocked() const { 1975 return _summary_bytes_used; 1976 } 1977 1978 class SumUsedClosure: public HeapRegionClosure { 1979 size_t _used; 1980 public: 1981 SumUsedClosure() : _used(0) {} 1982 bool do_heap_region(HeapRegion* r) { 1983 _used += r->used(); 1984 return false; 1985 } 1986 size_t result() { return _used; } 1987 }; 1988 1989 size_t G1CollectedHeap::recalculate_used() const { 1990 SumUsedClosure blk; 1991 heap_region_iterate(&blk); 1992 return blk.result(); 1993 } 1994 1995 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 1996 switch (cause) { 1997 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 1998 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 1999 case GCCause::_wb_conc_mark: return true; 2000 default : return false; 2001 } 2002 } 2003 2004 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2005 switch (cause) { 2006 case GCCause::_g1_humongous_allocation: return true; 2007 case GCCause::_g1_periodic_collection: return G1PeriodicGCInvokesConcurrent; 2008 default: return is_user_requested_concurrent_full_gc(cause); 2009 } 2010 } 2011 2012 bool G1CollectedHeap::should_upgrade_to_full_gc(GCCause::Cause cause) { 2013 if (policy()->force_upgrade_to_full()) { 2014 return true; 2015 } else if (should_do_concurrent_full_gc(_gc_cause)) { 2016 return false; 2017 } else if (has_regions_left_for_allocation()) { 2018 return false; 2019 } else { 2020 return true; 2021 } 2022 } 2023 2024 #ifndef PRODUCT 2025 void G1CollectedHeap::allocate_dummy_regions() { 2026 // Let's fill up most of the region 2027 size_t word_size = HeapRegion::GrainWords - 1024; 2028 // And as a result the region we'll allocate will be humongous. 2029 guarantee(is_humongous(word_size), "sanity"); 2030 2031 // _filler_array_max_size is set to humongous object threshold 2032 // but temporarily change it to use CollectedHeap::fill_with_object(). 2033 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2034 2035 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2036 // Let's use the existing mechanism for the allocation 2037 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 2038 if (dummy_obj != NULL) { 2039 MemRegion mr(dummy_obj, word_size); 2040 CollectedHeap::fill_with_object(mr); 2041 } else { 2042 // If we can't allocate once, we probably cannot allocate 2043 // again. Let's get out of the loop. 2044 break; 2045 } 2046 } 2047 } 2048 #endif // !PRODUCT 2049 2050 void G1CollectedHeap::increment_old_marking_cycles_started() { 2051 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2052 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2053 "Wrong marking cycle count (started: %d, completed: %d)", 2054 _old_marking_cycles_started, _old_marking_cycles_completed); 2055 2056 _old_marking_cycles_started++; 2057 } 2058 2059 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2060 MonitorLocker ml(G1OldGCCount_lock, Mutex::_no_safepoint_check_flag); 2061 2062 // We assume that if concurrent == true, then the caller is a 2063 // concurrent thread that was joined the Suspendible Thread 2064 // Set. If there's ever a cheap way to check this, we should add an 2065 // assert here. 2066 2067 // Given that this method is called at the end of a Full GC or of a 2068 // concurrent cycle, and those can be nested (i.e., a Full GC can 2069 // interrupt a concurrent cycle), the number of full collections 2070 // completed should be either one (in the case where there was no 2071 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2072 // behind the number of full collections started. 2073 2074 // This is the case for the inner caller, i.e. a Full GC. 2075 assert(concurrent || 2076 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2077 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2078 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2079 "is inconsistent with _old_marking_cycles_completed = %u", 2080 _old_marking_cycles_started, _old_marking_cycles_completed); 2081 2082 // This is the case for the outer caller, i.e. the concurrent cycle. 2083 assert(!concurrent || 2084 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2085 "for outer caller (concurrent cycle): " 2086 "_old_marking_cycles_started = %u " 2087 "is inconsistent with _old_marking_cycles_completed = %u", 2088 _old_marking_cycles_started, _old_marking_cycles_completed); 2089 2090 _old_marking_cycles_completed += 1; 2091 2092 // We need to clear the "in_progress" flag in the CM thread before 2093 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2094 // is set) so that if a waiter requests another System.gc() it doesn't 2095 // incorrectly see that a marking cycle is still in progress. 2096 if (concurrent) { 2097 _cm_thread->set_idle(); 2098 } 2099 2100 // Notify threads waiting in System.gc() (with ExplicitGCInvokesConcurrent) 2101 // for a full GC to finish that their wait is over. 2102 ml.notify_all(); 2103 } 2104 2105 void G1CollectedHeap::collect(GCCause::Cause cause) { 2106 try_collect(cause); 2107 } 2108 2109 // Return true if (x < y) with allowance for wraparound. 2110 static bool gc_counter_less_than(uint x, uint y) { 2111 return (x - y) > (UINT_MAX/2); 2112 } 2113 2114 // LOG_COLLECT_CONCURRENTLY(cause, msg, args...) 2115 // Macro so msg printing is format-checked. 2116 #define LOG_COLLECT_CONCURRENTLY(cause, ...) \ 2117 do { \ 2118 LogTarget(Trace, gc) LOG_COLLECT_CONCURRENTLY_lt; \ 2119 if (LOG_COLLECT_CONCURRENTLY_lt.is_enabled()) { \ 2120 ResourceMark rm; /* For thread name. */ \ 2121 LogStream LOG_COLLECT_CONCURRENTLY_s(&LOG_COLLECT_CONCURRENTLY_lt); \ 2122 LOG_COLLECT_CONCURRENTLY_s.print("%s: Try Collect Concurrently (%s): ", \ 2123 Thread::current()->name(), \ 2124 GCCause::to_string(cause)); \ 2125 LOG_COLLECT_CONCURRENTLY_s.print(__VA_ARGS__); \ 2126 } \ 2127 } while (0) 2128 2129 #define LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, result) \ 2130 LOG_COLLECT_CONCURRENTLY(cause, "complete %s", BOOL_TO_STR(result)) 2131 2132 bool G1CollectedHeap::try_collect_concurrently(GCCause::Cause cause, 2133 uint gc_counter, 2134 uint old_marking_started_before) { 2135 assert_heap_not_locked(); 2136 assert(should_do_concurrent_full_gc(cause), 2137 "Non-concurrent cause %s", GCCause::to_string(cause)); 2138 2139 for (uint i = 1; true; ++i) { 2140 // Try to schedule an initial-mark evacuation pause that will 2141 // start a concurrent cycle. 2142 LOG_COLLECT_CONCURRENTLY(cause, "attempt %u", i); 2143 VM_G1TryInitiateConcMark op(gc_counter, 2144 cause, 2145 policy()->max_pause_time_ms()); 2146 VMThread::execute(&op); 2147 2148 // Request is trivially finished. 2149 if (cause == GCCause::_g1_periodic_collection) { 2150 LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, op.gc_succeeded()); 2151 return op.gc_succeeded(); 2152 } 2153 2154 // Lock to get consistent set of values. 2155 uint old_marking_started_after; 2156 uint old_marking_completed_after; 2157 { 2158 MutexLocker ml(Heap_lock); 2159 // Update gc_counter for retrying VMOp if needed. Captured here to be 2160 // consistent with the values we use below for termination tests. If 2161 // a retry is needed after a possible wait, and another collection 2162 // occurs in the meantime, it will cause our retry to be skipped and 2163 // we'll recheck for termination with updated conditions from that 2164 // more recent collection. That's what we want, rather than having 2165 // our retry possibly perform an unnecessary collection. 2166 gc_counter = total_collections(); 2167 old_marking_started_after = _old_marking_cycles_started; 2168 old_marking_completed_after = _old_marking_cycles_completed; 2169 } 2170 2171 if (!GCCause::is_user_requested_gc(cause)) { 2172 // For an "automatic" (not user-requested) collection, we just need to 2173 // ensure that progress is made. 2174 // 2175 // Request is finished if any of 2176 // (1) the VMOp successfully performed a GC, 2177 // (2) a concurrent cycle was already in progress, 2178 // (3) a new cycle was started (by this thread or some other), or 2179 // (4) a Full GC was performed. 2180 // Cases (3) and (4) are detected together by a change to 2181 // _old_marking_cycles_started. 2182 // 2183 // Note that (1) does not imply (3). If we're still in the mixed 2184 // phase of an earlier concurrent collection, the request to make the 2185 // collection an initial-mark won't be honored. If we don't check for 2186 // both conditions we'll spin doing back-to-back collections. 2187 if (op.gc_succeeded() || 2188 op.cycle_already_in_progress() || 2189 (old_marking_started_before != old_marking_started_after)) { 2190 LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true); 2191 return true; 2192 } 2193 } else { // User-requested GC. 2194 // For a user-requested collection, we want to ensure that a complete 2195 // full collection has been performed before returning, but without 2196 // waiting for more than needed. 2197 2198 // For user-requested GCs (unlike non-UR), a successful VMOp implies a 2199 // new cycle was started. That's good, because it's not clear what we 2200 // should do otherwise. Trying again just does back to back GCs. 2201 // Can't wait for someone else to start a cycle. And returning fails 2202 // to meet the goal of ensuring a full collection was performed. 2203 assert(!op.gc_succeeded() || 2204 (old_marking_started_before != old_marking_started_after), 2205 "invariant: succeeded %s, started before %u, started after %u", 2206 BOOL_TO_STR(op.gc_succeeded()), 2207 old_marking_started_before, old_marking_started_after); 2208 2209 // Request is finished if a full collection (concurrent or stw) 2210 // was started after this request and has completed, e.g. 2211 // started_before < completed_after. 2212 if (gc_counter_less_than(old_marking_started_before, 2213 old_marking_completed_after)) { 2214 LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true); 2215 return true; 2216 } 2217 2218 if (old_marking_started_after != old_marking_completed_after) { 2219 // If there is an in-progress cycle (possibly started by us), then 2220 // wait for that cycle to complete, e.g. 2221 // while completed_now < started_after. 2222 LOG_COLLECT_CONCURRENTLY(cause, "wait"); 2223 MonitorLocker ml(G1OldGCCount_lock); 2224 while (gc_counter_less_than(_old_marking_cycles_completed, 2225 old_marking_started_after)) { 2226 ml.wait(); 2227 } 2228 // Request is finished if the collection we just waited for was 2229 // started after this request. 2230 if (old_marking_started_before != old_marking_started_after) { 2231 LOG_COLLECT_CONCURRENTLY(cause, "complete after wait"); 2232 return true; 2233 } 2234 } 2235 2236 // If VMOp was successful then it started a new cycle that the above 2237 // wait &etc should have recognized as finishing this request. This 2238 // differs from a non-user-request, where gc_succeeded does not imply 2239 // a new cycle was started. 2240 assert(!op.gc_succeeded(), "invariant"); 2241 2242 // If VMOp failed because a cycle was already in progress, it is now 2243 // complete. But it didn't finish this user-requested GC, so try 2244 // again. 2245 if (op.cycle_already_in_progress()) { 2246 LOG_COLLECT_CONCURRENTLY(cause, "retry after in-progress"); 2247 continue; 2248 } 2249 } 2250 2251 // Collection failed and should be retried. 2252 assert(op.transient_failure(), "invariant"); 2253 2254 // If GCLocker is active, wait until clear before retrying. 2255 if (GCLocker::is_active_and_needs_gc()) { 2256 LOG_COLLECT_CONCURRENTLY(cause, "gc-locker stall"); 2257 GCLocker::stall_until_clear(); 2258 } 2259 2260 LOG_COLLECT_CONCURRENTLY(cause, "retry"); 2261 } 2262 } 2263 2264 bool G1CollectedHeap::try_collect(GCCause::Cause cause) { 2265 assert_heap_not_locked(); 2266 2267 // Lock to get consistent set of values. 2268 uint gc_count_before; 2269 uint full_gc_count_before; 2270 uint old_marking_started_before; 2271 { 2272 MutexLocker ml(Heap_lock); 2273 gc_count_before = total_collections(); 2274 full_gc_count_before = total_full_collections(); 2275 old_marking_started_before = _old_marking_cycles_started; 2276 } 2277 2278 if (should_do_concurrent_full_gc(cause)) { 2279 return try_collect_concurrently(cause, 2280 gc_count_before, 2281 old_marking_started_before); 2282 } else if (GCLocker::should_discard(cause, gc_count_before)) { 2283 // Indicate failure to be consistent with VMOp failure due to 2284 // another collection slipping in after our gc_count but before 2285 // our request is processed. 2286 return false; 2287 } else if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2288 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2289 2290 // Schedule a standard evacuation pause. We're setting word_size 2291 // to 0 which means that we are not requesting a post-GC allocation. 2292 VM_G1CollectForAllocation op(0, /* word_size */ 2293 gc_count_before, 2294 cause, 2295 policy()->max_pause_time_ms()); 2296 VMThread::execute(&op); 2297 return op.gc_succeeded(); 2298 } else { 2299 // Schedule a Full GC. 2300 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2301 VMThread::execute(&op); 2302 return op.gc_succeeded(); 2303 } 2304 } 2305 2306 bool G1CollectedHeap::is_in(const void* p) const { 2307 if (_hrm->reserved().contains(p)) { 2308 // Given that we know that p is in the reserved space, 2309 // heap_region_containing() should successfully 2310 // return the containing region. 2311 HeapRegion* hr = heap_region_containing(p); 2312 return hr->is_in(p); 2313 } else { 2314 return false; 2315 } 2316 } 2317 2318 #ifdef ASSERT 2319 bool G1CollectedHeap::is_in_exact(const void* p) const { 2320 bool contains = reserved_region().contains(p); 2321 bool available = _hrm->is_available(addr_to_region((HeapWord*)p)); 2322 if (contains && available) { 2323 return true; 2324 } else { 2325 return false; 2326 } 2327 } 2328 #endif 2329 2330 // Iteration functions. 2331 2332 // Iterates an ObjectClosure over all objects within a HeapRegion. 2333 2334 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2335 ObjectClosure* _cl; 2336 public: 2337 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2338 bool do_heap_region(HeapRegion* r) { 2339 if (!r->is_continues_humongous()) { 2340 r->object_iterate(_cl); 2341 } 2342 return false; 2343 } 2344 }; 2345 2346 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2347 IterateObjectClosureRegionClosure blk(cl); 2348 heap_region_iterate(&blk); 2349 } 2350 2351 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2352 _hrm->iterate(cl); 2353 } 2354 2355 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl, 2356 HeapRegionClaimer *hrclaimer, 2357 uint worker_id) const { 2358 _hrm->par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id)); 2359 } 2360 2361 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl, 2362 HeapRegionClaimer *hrclaimer) const { 2363 _hrm->par_iterate(cl, hrclaimer, 0); 2364 } 2365 2366 void G1CollectedHeap::collection_set_iterate_all(HeapRegionClosure* cl) { 2367 _collection_set.iterate(cl); 2368 } 2369 2370 void G1CollectedHeap::collection_set_par_iterate_all(HeapRegionClosure* cl, HeapRegionClaimer* hr_claimer, uint worker_id) { 2371 _collection_set.par_iterate(cl, hr_claimer, worker_id, workers()->active_workers()); 2372 } 2373 2374 void G1CollectedHeap::collection_set_iterate_increment_from(HeapRegionClosure *cl, HeapRegionClaimer* hr_claimer, uint worker_id) { 2375 _collection_set.iterate_incremental_part_from(cl, hr_claimer, worker_id, workers()->active_workers()); 2376 } 2377 2378 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2379 HeapRegion* hr = heap_region_containing(addr); 2380 return hr->block_start(addr); 2381 } 2382 2383 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2384 HeapRegion* hr = heap_region_containing(addr); 2385 return hr->block_is_obj(addr); 2386 } 2387 2388 bool G1CollectedHeap::supports_tlab_allocation() const { 2389 return true; 2390 } 2391 2392 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2393 return (_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2394 } 2395 2396 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2397 return _eden.length() * HeapRegion::GrainBytes; 2398 } 2399 2400 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2401 // must be equal to the humongous object limit. 2402 size_t G1CollectedHeap::max_tlab_size() const { 2403 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2404 } 2405 2406 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2407 return _allocator->unsafe_max_tlab_alloc(); 2408 } 2409 2410 size_t G1CollectedHeap::max_capacity() const { 2411 return _hrm->max_expandable_length() * HeapRegion::GrainBytes; 2412 } 2413 2414 size_t G1CollectedHeap::max_reserved_capacity() const { 2415 return _hrm->max_length() * HeapRegion::GrainBytes; 2416 } 2417 2418 jlong G1CollectedHeap::millis_since_last_gc() { 2419 // See the notes in GenCollectedHeap::millis_since_last_gc() 2420 // for more information about the implementation. 2421 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2422 _policy->collection_pause_end_millis(); 2423 if (ret_val < 0) { 2424 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2425 ". returning zero instead.", ret_val); 2426 return 0; 2427 } 2428 return ret_val; 2429 } 2430 2431 void G1CollectedHeap::deduplicate_string(oop str) { 2432 assert(java_lang_String::is_instance(str), "invariant"); 2433 2434 if (G1StringDedup::is_enabled()) { 2435 G1StringDedup::deduplicate(str); 2436 } 2437 } 2438 2439 void G1CollectedHeap::prepare_for_verify() { 2440 _verifier->prepare_for_verify(); 2441 } 2442 2443 void G1CollectedHeap::verify(VerifyOption vo) { 2444 _verifier->verify(vo); 2445 } 2446 2447 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2448 return true; 2449 } 2450 2451 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2452 return _cm_thread->request_concurrent_phase(phase); 2453 } 2454 2455 bool G1CollectedHeap::is_heterogeneous_heap() const { 2456 return G1Arguments::is_heterogeneous_heap(); 2457 } 2458 2459 class PrintRegionClosure: public HeapRegionClosure { 2460 outputStream* _st; 2461 public: 2462 PrintRegionClosure(outputStream* st) : _st(st) {} 2463 bool do_heap_region(HeapRegion* r) { 2464 r->print_on(_st); 2465 return false; 2466 } 2467 }; 2468 2469 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2470 const HeapRegion* hr, 2471 const VerifyOption vo) const { 2472 switch (vo) { 2473 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2474 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2475 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr); 2476 default: ShouldNotReachHere(); 2477 } 2478 return false; // keep some compilers happy 2479 } 2480 2481 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2482 const VerifyOption vo) const { 2483 switch (vo) { 2484 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2485 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2486 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj); 2487 default: ShouldNotReachHere(); 2488 } 2489 return false; // keep some compilers happy 2490 } 2491 2492 void G1CollectedHeap::print_heap_regions() const { 2493 LogTarget(Trace, gc, heap, region) lt; 2494 if (lt.is_enabled()) { 2495 LogStream ls(lt); 2496 print_regions_on(&ls); 2497 } 2498 } 2499 2500 void G1CollectedHeap::print_on(outputStream* st) const { 2501 st->print(" %-20s", "garbage-first heap"); 2502 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2503 capacity()/K, used_unlocked()/K); 2504 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")", 2505 p2i(_hrm->reserved().start()), 2506 p2i(_hrm->reserved().end())); 2507 st->cr(); 2508 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2509 uint young_regions = young_regions_count(); 2510 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2511 (size_t) young_regions * HeapRegion::GrainBytes / K); 2512 uint survivor_regions = survivor_regions_count(); 2513 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2514 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2515 st->cr(); 2516 if (_numa->is_enabled()) { 2517 uint num_nodes = _numa->num_active_nodes(); 2518 st->print(" remaining free region(s) on each NUMA node: "); 2519 const int* node_ids = _numa->node_ids(); 2520 for (uint node_index = 0; node_index < num_nodes; node_index++) { 2521 st->print("%d=%u ", node_ids[node_index], _hrm->num_free_regions(node_index)); 2522 } 2523 st->cr(); 2524 } 2525 MetaspaceUtils::print_on(st); 2526 } 2527 2528 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2529 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2530 "HS=humongous(starts), HC=humongous(continues), " 2531 "CS=collection set, F=free, " 2532 "OA=open archive, CA=closed archive, " 2533 "TAMS=top-at-mark-start (previous, next)"); 2534 PrintRegionClosure blk(st); 2535 heap_region_iterate(&blk); 2536 } 2537 2538 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2539 print_on(st); 2540 2541 // Print the per-region information. 2542 print_regions_on(st); 2543 } 2544 2545 void G1CollectedHeap::print_on_error(outputStream* st) const { 2546 this->CollectedHeap::print_on_error(st); 2547 2548 if (_cm != NULL) { 2549 st->cr(); 2550 _cm->print_on_error(st); 2551 } 2552 } 2553 2554 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2555 workers()->print_worker_threads_on(st); 2556 _cm_thread->print_on(st); 2557 st->cr(); 2558 _cm->print_worker_threads_on(st); 2559 _cr->print_threads_on(st); 2560 _young_gen_sampling_thread->print_on(st); 2561 if (G1StringDedup::is_enabled()) { 2562 G1StringDedup::print_worker_threads_on(st); 2563 } 2564 } 2565 2566 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2567 workers()->threads_do(tc); 2568 tc->do_thread(_cm_thread); 2569 _cm->threads_do(tc); 2570 _cr->threads_do(tc); 2571 tc->do_thread(_young_gen_sampling_thread); 2572 if (G1StringDedup::is_enabled()) { 2573 G1StringDedup::threads_do(tc); 2574 } 2575 } 2576 2577 void G1CollectedHeap::print_tracing_info() const { 2578 rem_set()->print_summary_info(); 2579 concurrent_mark()->print_summary_info(); 2580 } 2581 2582 #ifndef PRODUCT 2583 // Helpful for debugging RSet issues. 2584 2585 class PrintRSetsClosure : public HeapRegionClosure { 2586 private: 2587 const char* _msg; 2588 size_t _occupied_sum; 2589 2590 public: 2591 bool do_heap_region(HeapRegion* r) { 2592 HeapRegionRemSet* hrrs = r->rem_set(); 2593 size_t occupied = hrrs->occupied(); 2594 _occupied_sum += occupied; 2595 2596 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2597 if (occupied == 0) { 2598 tty->print_cr(" RSet is empty"); 2599 } else { 2600 hrrs->print(); 2601 } 2602 tty->print_cr("----------"); 2603 return false; 2604 } 2605 2606 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2607 tty->cr(); 2608 tty->print_cr("========================================"); 2609 tty->print_cr("%s", msg); 2610 tty->cr(); 2611 } 2612 2613 ~PrintRSetsClosure() { 2614 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2615 tty->print_cr("========================================"); 2616 tty->cr(); 2617 } 2618 }; 2619 2620 void G1CollectedHeap::print_cset_rsets() { 2621 PrintRSetsClosure cl("Printing CSet RSets"); 2622 collection_set_iterate_all(&cl); 2623 } 2624 2625 void G1CollectedHeap::print_all_rsets() { 2626 PrintRSetsClosure cl("Printing All RSets");; 2627 heap_region_iterate(&cl); 2628 } 2629 #endif // PRODUCT 2630 2631 bool G1CollectedHeap::print_location(outputStream* st, void* addr) const { 2632 return BlockLocationPrinter<G1CollectedHeap>::print_location(st, addr); 2633 } 2634 2635 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2636 2637 size_t eden_used_bytes = _eden.used_bytes(); 2638 size_t survivor_used_bytes = _survivor.used_bytes(); 2639 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2640 2641 size_t eden_capacity_bytes = 2642 (policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2643 2644 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2645 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2646 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2647 } 2648 2649 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2650 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2651 stats->unused(), stats->used(), stats->region_end_waste(), 2652 stats->regions_filled(), stats->direct_allocated(), 2653 stats->failure_used(), stats->failure_waste()); 2654 } 2655 2656 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2657 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2658 gc_tracer->report_gc_heap_summary(when, heap_summary); 2659 2660 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2661 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2662 } 2663 2664 G1CollectedHeap* G1CollectedHeap::heap() { 2665 CollectedHeap* heap = Universe::heap(); 2666 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2667 assert(heap->kind() == CollectedHeap::G1, "Invalid name"); 2668 return (G1CollectedHeap*)heap; 2669 } 2670 2671 void G1CollectedHeap::gc_prologue(bool full) { 2672 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2673 2674 // This summary needs to be printed before incrementing total collections. 2675 rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2676 2677 // Update common counters. 2678 increment_total_collections(full /* full gc */); 2679 if (full || collector_state()->in_initial_mark_gc()) { 2680 increment_old_marking_cycles_started(); 2681 } 2682 2683 // Fill TLAB's and such 2684 double start = os::elapsedTime(); 2685 ensure_parsability(true); 2686 phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2687 } 2688 2689 void G1CollectedHeap::gc_epilogue(bool full) { 2690 // Update common counters. 2691 if (full) { 2692 // Update the number of full collections that have been completed. 2693 increment_old_marking_cycles_completed(false /* concurrent */); 2694 } 2695 2696 // We are at the end of the GC. Total collections has already been increased. 2697 rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2698 2699 // FIXME: what is this about? 2700 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2701 // is set. 2702 #if COMPILER2_OR_JVMCI 2703 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2704 #endif 2705 2706 double start = os::elapsedTime(); 2707 resize_all_tlabs(); 2708 phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2709 2710 MemoryService::track_memory_usage(); 2711 // We have just completed a GC. Update the soft reference 2712 // policy with the new heap occupancy 2713 Universe::update_heap_info_at_gc(); 2714 2715 // Print NUMA statistics. 2716 _numa->print_statistics(); 2717 } 2718 2719 void G1CollectedHeap::verify_numa_regions(const char* desc) { 2720 LogTarget(Trace, gc, heap, verify) lt; 2721 2722 if (lt.is_enabled()) { 2723 LogStream ls(lt); 2724 // Iterate all heap regions to print matching between preferred numa id and actual numa id. 2725 G1NodeIndexCheckClosure cl(desc, _numa, &ls); 2726 heap_region_iterate(&cl); 2727 } 2728 } 2729 2730 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2731 uint gc_count_before, 2732 bool* succeeded, 2733 GCCause::Cause gc_cause) { 2734 assert_heap_not_locked_and_not_at_safepoint(); 2735 VM_G1CollectForAllocation op(word_size, 2736 gc_count_before, 2737 gc_cause, 2738 policy()->max_pause_time_ms()); 2739 VMThread::execute(&op); 2740 2741 HeapWord* result = op.result(); 2742 bool ret_succeeded = op.prologue_succeeded() && op.gc_succeeded(); 2743 assert(result == NULL || ret_succeeded, 2744 "the result should be NULL if the VM did not succeed"); 2745 *succeeded = ret_succeeded; 2746 2747 assert_heap_not_locked(); 2748 return result; 2749 } 2750 2751 void G1CollectedHeap::do_concurrent_mark() { 2752 MutexLocker x(CGC_lock, Mutex::_no_safepoint_check_flag); 2753 if (!_cm_thread->in_progress()) { 2754 _cm_thread->set_started(); 2755 CGC_lock->notify(); 2756 } 2757 } 2758 2759 size_t G1CollectedHeap::pending_card_num() { 2760 struct CountCardsClosure : public ThreadClosure { 2761 size_t _cards; 2762 CountCardsClosure() : _cards(0) {} 2763 virtual void do_thread(Thread* t) { 2764 _cards += G1ThreadLocalData::dirty_card_queue(t).size(); 2765 } 2766 } count_from_threads; 2767 Threads::threads_do(&count_from_threads); 2768 2769 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 2770 dcqs.verify_num_cards(); 2771 2772 return dcqs.num_cards() + count_from_threads._cards; 2773 } 2774 2775 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const { 2776 // We don't nominate objects with many remembered set entries, on 2777 // the assumption that such objects are likely still live. 2778 HeapRegionRemSet* rem_set = r->rem_set(); 2779 2780 return G1EagerReclaimHumongousObjectsWithStaleRefs ? 2781 rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) : 2782 G1EagerReclaimHumongousObjects && rem_set->is_empty(); 2783 } 2784 2785 #ifndef PRODUCT 2786 void G1CollectedHeap::verify_region_attr_remset_update() { 2787 class VerifyRegionAttrRemSet : public HeapRegionClosure { 2788 public: 2789 virtual bool do_heap_region(HeapRegion* r) { 2790 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2791 bool const needs_remset_update = g1h->region_attr(r->bottom()).needs_remset_update(); 2792 assert(r->rem_set()->is_tracked() == needs_remset_update, 2793 "Region %u remset tracking status (%s) different to region attribute (%s)", 2794 r->hrm_index(), BOOL_TO_STR(r->rem_set()->is_tracked()), BOOL_TO_STR(needs_remset_update)); 2795 return false; 2796 } 2797 } cl; 2798 heap_region_iterate(&cl); 2799 } 2800 #endif 2801 2802 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2803 public: 2804 bool do_heap_region(HeapRegion* hr) { 2805 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2806 hr->verify_rem_set(); 2807 } 2808 return false; 2809 } 2810 }; 2811 2812 uint G1CollectedHeap::num_task_queues() const { 2813 return _task_queues->size(); 2814 } 2815 2816 #if TASKQUEUE_STATS 2817 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2818 st->print_raw_cr("GC Task Stats"); 2819 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2820 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2821 } 2822 2823 void G1CollectedHeap::print_taskqueue_stats() const { 2824 if (!log_is_enabled(Trace, gc, task, stats)) { 2825 return; 2826 } 2827 Log(gc, task, stats) log; 2828 ResourceMark rm; 2829 LogStream ls(log.trace()); 2830 outputStream* st = &ls; 2831 2832 print_taskqueue_stats_hdr(st); 2833 2834 TaskQueueStats totals; 2835 const uint n = num_task_queues(); 2836 for (uint i = 0; i < n; ++i) { 2837 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2838 totals += task_queue(i)->stats; 2839 } 2840 st->print_raw("tot "); totals.print(st); st->cr(); 2841 2842 DEBUG_ONLY(totals.verify()); 2843 } 2844 2845 void G1CollectedHeap::reset_taskqueue_stats() { 2846 const uint n = num_task_queues(); 2847 for (uint i = 0; i < n; ++i) { 2848 task_queue(i)->stats.reset(); 2849 } 2850 } 2851 #endif // TASKQUEUE_STATS 2852 2853 void G1CollectedHeap::wait_for_root_region_scanning() { 2854 double scan_wait_start = os::elapsedTime(); 2855 // We have to wait until the CM threads finish scanning the 2856 // root regions as it's the only way to ensure that all the 2857 // objects on them have been correctly scanned before we start 2858 // moving them during the GC. 2859 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2860 double wait_time_ms = 0.0; 2861 if (waited) { 2862 double scan_wait_end = os::elapsedTime(); 2863 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2864 } 2865 phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2866 } 2867 2868 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2869 private: 2870 G1HRPrinter* _hr_printer; 2871 public: 2872 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2873 2874 virtual bool do_heap_region(HeapRegion* r) { 2875 _hr_printer->cset(r); 2876 return false; 2877 } 2878 }; 2879 2880 void G1CollectedHeap::start_new_collection_set() { 2881 double start = os::elapsedTime(); 2882 2883 collection_set()->start_incremental_building(); 2884 2885 clear_region_attr(); 2886 2887 guarantee(_eden.length() == 0, "eden should have been cleared"); 2888 policy()->transfer_survivors_to_cset(survivor()); 2889 2890 // We redo the verification but now wrt to the new CSet which 2891 // has just got initialized after the previous CSet was freed. 2892 _cm->verify_no_collection_set_oops(); 2893 2894 phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 2895 } 2896 2897 void G1CollectedHeap::calculate_collection_set(G1EvacuationInfo& evacuation_info, double target_pause_time_ms) { 2898 2899 _collection_set.finalize_initial_collection_set(target_pause_time_ms, &_survivor); 2900 evacuation_info.set_collectionset_regions(collection_set()->region_length() + 2901 collection_set()->optional_region_length()); 2902 2903 _cm->verify_no_collection_set_oops(); 2904 2905 if (_hr_printer.is_active()) { 2906 G1PrintCollectionSetClosure cl(&_hr_printer); 2907 _collection_set.iterate(&cl); 2908 _collection_set.iterate_optional(&cl); 2909 } 2910 } 2911 2912 G1HeapVerifier::G1VerifyType G1CollectedHeap::young_collection_verify_type() const { 2913 if (collector_state()->in_initial_mark_gc()) { 2914 return G1HeapVerifier::G1VerifyConcurrentStart; 2915 } else if (collector_state()->in_young_only_phase()) { 2916 return G1HeapVerifier::G1VerifyYoungNormal; 2917 } else { 2918 return G1HeapVerifier::G1VerifyMixed; 2919 } 2920 } 2921 2922 void G1CollectedHeap::verify_before_young_collection(G1HeapVerifier::G1VerifyType type) { 2923 if (VerifyRememberedSets) { 2924 log_info(gc, verify)("[Verifying RemSets before GC]"); 2925 VerifyRegionRemSetClosure v_cl; 2926 heap_region_iterate(&v_cl); 2927 } 2928 _verifier->verify_before_gc(type); 2929 _verifier->check_bitmaps("GC Start"); 2930 verify_numa_regions("GC Start"); 2931 } 2932 2933 void G1CollectedHeap::verify_after_young_collection(G1HeapVerifier::G1VerifyType type) { 2934 if (VerifyRememberedSets) { 2935 log_info(gc, verify)("[Verifying RemSets after GC]"); 2936 VerifyRegionRemSetClosure v_cl; 2937 heap_region_iterate(&v_cl); 2938 } 2939 _verifier->verify_after_gc(type); 2940 _verifier->check_bitmaps("GC End"); 2941 verify_numa_regions("GC End"); 2942 } 2943 2944 void G1CollectedHeap::expand_heap_after_young_collection(){ 2945 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 2946 if (expand_bytes > 0) { 2947 // No need for an ergo logging here, 2948 // expansion_amount() does this when it returns a value > 0. 2949 double expand_ms; 2950 if (!expand(expand_bytes, _workers, &expand_ms)) { 2951 // We failed to expand the heap. Cannot do anything about it. 2952 } 2953 phase_times()->record_expand_heap_time(expand_ms); 2954 } 2955 } 2956 2957 const char* G1CollectedHeap::young_gc_name() const { 2958 if (collector_state()->in_initial_mark_gc()) { 2959 return "Pause Young (Concurrent Start)"; 2960 } else if (collector_state()->in_young_only_phase()) { 2961 if (collector_state()->in_young_gc_before_mixed()) { 2962 return "Pause Young (Prepare Mixed)"; 2963 } else { 2964 return "Pause Young (Normal)"; 2965 } 2966 } else { 2967 return "Pause Young (Mixed)"; 2968 } 2969 } 2970 2971 bool G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2972 assert_at_safepoint_on_vm_thread(); 2973 guarantee(!is_gc_active(), "collection is not reentrant"); 2974 2975 if (GCLocker::check_active_before_gc()) { 2976 return false; 2977 } 2978 2979 GCIdMark gc_id_mark; 2980 2981 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2982 ResourceMark rm; 2983 2984 policy()->note_gc_start(); 2985 2986 _gc_timer_stw->register_gc_start(); 2987 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2988 2989 wait_for_root_region_scanning(); 2990 2991 print_heap_before_gc(); 2992 print_heap_regions(); 2993 trace_heap_before_gc(_gc_tracer_stw); 2994 2995 _verifier->verify_region_sets_optional(); 2996 _verifier->verify_dirty_young_regions(); 2997 2998 // We should not be doing initial mark unless the conc mark thread is running 2999 if (!_cm_thread->should_terminate()) { 3000 // This call will decide whether this pause is an initial-mark 3001 // pause. If it is, in_initial_mark_gc() will return true 3002 // for the duration of this pause. 3003 policy()->decide_on_conc_mark_initiation(); 3004 } 3005 3006 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3007 assert(!collector_state()->in_initial_mark_gc() || 3008 collector_state()->in_young_only_phase(), "sanity"); 3009 // We also do not allow mixed GCs during marking. 3010 assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity"); 3011 3012 // Record whether this pause is an initial mark. When the current 3013 // thread has completed its logging output and it's safe to signal 3014 // the CM thread, the flag's value in the policy has been reset. 3015 bool should_start_conc_mark = collector_state()->in_initial_mark_gc(); 3016 if (should_start_conc_mark) { 3017 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 3018 } 3019 3020 // Inner scope for scope based logging, timers, and stats collection 3021 { 3022 G1EvacuationInfo evacuation_info; 3023 3024 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3025 3026 GCTraceCPUTime tcpu; 3027 3028 GCTraceTime(Info, gc) tm(young_gc_name(), NULL, gc_cause(), true); 3029 3030 uint active_workers = WorkerPolicy::calc_active_workers(workers()->total_workers(), 3031 workers()->active_workers(), 3032 Threads::number_of_non_daemon_threads()); 3033 active_workers = workers()->update_active_workers(active_workers); 3034 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 3035 3036 G1MonitoringScope ms(g1mm(), 3037 false /* full_gc */, 3038 collector_state()->yc_type() == Mixed /* all_memory_pools_affected */); 3039 3040 G1HeapTransition heap_transition(this); 3041 3042 { 3043 IsGCActiveMark x; 3044 3045 gc_prologue(false); 3046 3047 G1HeapVerifier::G1VerifyType verify_type = young_collection_verify_type(); 3048 verify_before_young_collection(verify_type); 3049 3050 { 3051 // The elapsed time induced by the start time below deliberately elides 3052 // the possible verification above. 3053 double sample_start_time_sec = os::elapsedTime(); 3054 3055 // Please see comment in g1CollectedHeap.hpp and 3056 // G1CollectedHeap::ref_processing_init() to see how 3057 // reference processing currently works in G1. 3058 _ref_processor_stw->enable_discovery(); 3059 3060 // We want to temporarily turn off discovery by the 3061 // CM ref processor, if necessary, and turn it back on 3062 // on again later if we do. Using a scoped 3063 // NoRefDiscovery object will do this. 3064 NoRefDiscovery no_cm_discovery(_ref_processor_cm); 3065 3066 policy()->record_collection_pause_start(sample_start_time_sec); 3067 3068 // Forget the current allocation region (we might even choose it to be part 3069 // of the collection set!). 3070 _allocator->release_mutator_alloc_regions(); 3071 3072 calculate_collection_set(evacuation_info, target_pause_time_ms); 3073 3074 G1RedirtyCardsQueueSet rdcqs(G1BarrierSet::dirty_card_queue_set().allocator()); 3075 G1ParScanThreadStateSet per_thread_states(this, 3076 &rdcqs, 3077 workers()->active_workers(), 3078 collection_set()->young_region_length(), 3079 collection_set()->optional_region_length()); 3080 pre_evacuate_collection_set(evacuation_info, &per_thread_states); 3081 3082 // Actually do the work... 3083 evacuate_initial_collection_set(&per_thread_states); 3084 3085 if (_collection_set.optional_region_length() != 0) { 3086 evacuate_optional_collection_set(&per_thread_states); 3087 } 3088 post_evacuate_collection_set(evacuation_info, &rdcqs, &per_thread_states); 3089 3090 start_new_collection_set(); 3091 3092 _survivor_evac_stats.adjust_desired_plab_sz(); 3093 _old_evac_stats.adjust_desired_plab_sz(); 3094 3095 if (should_start_conc_mark) { 3096 // We have to do this before we notify the CM threads that 3097 // they can start working to make sure that all the 3098 // appropriate initialization is done on the CM object. 3099 concurrent_mark()->post_initial_mark(); 3100 // Note that we don't actually trigger the CM thread at 3101 // this point. We do that later when we're sure that 3102 // the current thread has completed its logging output. 3103 } 3104 3105 allocate_dummy_regions(); 3106 3107 _allocator->init_mutator_alloc_regions(); 3108 3109 expand_heap_after_young_collection(); 3110 3111 double sample_end_time_sec = os::elapsedTime(); 3112 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3113 policy()->record_collection_pause_end(pause_time_ms); 3114 } 3115 3116 verify_after_young_collection(verify_type); 3117 3118 #ifdef TRACESPINNING 3119 ParallelTaskTerminator::print_termination_counts(); 3120 #endif 3121 3122 gc_epilogue(false); 3123 } 3124 3125 // Print the remainder of the GC log output. 3126 if (evacuation_failed()) { 3127 log_info(gc)("To-space exhausted"); 3128 } 3129 3130 policy()->print_phases(); 3131 heap_transition.print(); 3132 3133 _hrm->verify_optional(); 3134 _verifier->verify_region_sets_optional(); 3135 3136 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3137 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3138 3139 print_heap_after_gc(); 3140 print_heap_regions(); 3141 trace_heap_after_gc(_gc_tracer_stw); 3142 3143 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3144 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3145 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3146 // before any GC notifications are raised. 3147 g1mm()->update_sizes(); 3148 3149 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3150 _gc_tracer_stw->report_tenuring_threshold(_policy->tenuring_threshold()); 3151 _gc_timer_stw->register_gc_end(); 3152 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3153 } 3154 // It should now be safe to tell the concurrent mark thread to start 3155 // without its logging output interfering with the logging output 3156 // that came from the pause. 3157 3158 if (should_start_conc_mark) { 3159 // CAUTION: after the doConcurrentMark() call below, the concurrent marking 3160 // thread(s) could be running concurrently with us. Make sure that anything 3161 // after this point does not assume that we are the only GC thread running. 3162 // Note: of course, the actual marking work will not start until the safepoint 3163 // itself is released in SuspendibleThreadSet::desynchronize(). 3164 do_concurrent_mark(); 3165 } 3166 3167 return true; 3168 } 3169 3170 void G1CollectedHeap::remove_self_forwarding_pointers(G1RedirtyCardsQueueSet* rdcqs) { 3171 G1ParRemoveSelfForwardPtrsTask rsfp_task(rdcqs); 3172 workers()->run_task(&rsfp_task); 3173 } 3174 3175 void G1CollectedHeap::restore_after_evac_failure(G1RedirtyCardsQueueSet* rdcqs) { 3176 double remove_self_forwards_start = os::elapsedTime(); 3177 3178 remove_self_forwarding_pointers(rdcqs); 3179 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3180 _preserved_marks_set.restore(&task_executor); 3181 3182 phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3183 } 3184 3185 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markWord m) { 3186 if (!_evacuation_failed) { 3187 _evacuation_failed = true; 3188 } 3189 3190 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3191 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3192 } 3193 3194 bool G1ParEvacuateFollowersClosure::offer_termination() { 3195 EventGCPhaseParallel event; 3196 G1ParScanThreadState* const pss = par_scan_state(); 3197 start_term_time(); 3198 const bool res = terminator()->offer_termination(); 3199 end_term_time(); 3200 event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(G1GCPhaseTimes::Termination)); 3201 return res; 3202 } 3203 3204 void G1ParEvacuateFollowersClosure::do_void() { 3205 EventGCPhaseParallel event; 3206 G1ParScanThreadState* const pss = par_scan_state(); 3207 pss->trim_queue(); 3208 event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase)); 3209 do { 3210 EventGCPhaseParallel event; 3211 pss->steal_and_trim_queue(queues()); 3212 event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase)); 3213 } while (!offer_termination()); 3214 } 3215 3216 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3217 bool class_unloading_occurred) { 3218 uint num_workers = workers()->active_workers(); 3219 G1ParallelCleaningTask unlink_task(is_alive, num_workers, class_unloading_occurred, false); 3220 workers()->run_task(&unlink_task); 3221 } 3222 3223 // Clean string dedup data structures. 3224 // Ideally we would prefer to use a StringDedupCleaningTask here, but we want to 3225 // record the durations of the phases. Hence the almost-copy. 3226 class G1StringDedupCleaningTask : public AbstractGangTask { 3227 BoolObjectClosure* _is_alive; 3228 OopClosure* _keep_alive; 3229 G1GCPhaseTimes* _phase_times; 3230 3231 public: 3232 G1StringDedupCleaningTask(BoolObjectClosure* is_alive, 3233 OopClosure* keep_alive, 3234 G1GCPhaseTimes* phase_times) : 3235 AbstractGangTask("Partial Cleaning Task"), 3236 _is_alive(is_alive), 3237 _keep_alive(keep_alive), 3238 _phase_times(phase_times) 3239 { 3240 assert(G1StringDedup::is_enabled(), "String deduplication disabled."); 3241 StringDedup::gc_prologue(true); 3242 } 3243 3244 ~G1StringDedupCleaningTask() { 3245 StringDedup::gc_epilogue(); 3246 } 3247 3248 void work(uint worker_id) { 3249 StringDedupUnlinkOrOopsDoClosure cl(_is_alive, _keep_alive); 3250 { 3251 G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id); 3252 StringDedupQueue::unlink_or_oops_do(&cl); 3253 } 3254 { 3255 G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id); 3256 StringDedupTable::unlink_or_oops_do(&cl, worker_id); 3257 } 3258 } 3259 }; 3260 3261 void G1CollectedHeap::string_dedup_cleaning(BoolObjectClosure* is_alive, 3262 OopClosure* keep_alive, 3263 G1GCPhaseTimes* phase_times) { 3264 G1StringDedupCleaningTask cl(is_alive, keep_alive, phase_times); 3265 workers()->run_task(&cl); 3266 } 3267 3268 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3269 private: 3270 G1RedirtyCardsQueueSet* _qset; 3271 G1CollectedHeap* _g1h; 3272 BufferNode* volatile _nodes; 3273 3274 void par_apply(RedirtyLoggedCardTableEntryClosure* cl, uint worker_id) { 3275 size_t buffer_size = _qset->buffer_size(); 3276 BufferNode* next = Atomic::load(&_nodes); 3277 while (next != NULL) { 3278 BufferNode* node = next; 3279 next = Atomic::cmpxchg(&_nodes, node, node->next()); 3280 if (next == node) { 3281 cl->apply_to_buffer(node, buffer_size, worker_id); 3282 next = node->next(); 3283 } 3284 } 3285 } 3286 3287 public: 3288 G1RedirtyLoggedCardsTask(G1RedirtyCardsQueueSet* qset, G1CollectedHeap* g1h) : 3289 AbstractGangTask("Redirty Cards"), 3290 _qset(qset), _g1h(g1h), _nodes(qset->all_completed_buffers()) { } 3291 3292 virtual void work(uint worker_id) { 3293 G1GCPhaseTimes* p = _g1h->phase_times(); 3294 G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::RedirtyCards, worker_id); 3295 3296 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3297 par_apply(&cl, worker_id); 3298 3299 p->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3300 } 3301 }; 3302 3303 void G1CollectedHeap::redirty_logged_cards(G1RedirtyCardsQueueSet* rdcqs) { 3304 double redirty_logged_cards_start = os::elapsedTime(); 3305 3306 G1RedirtyLoggedCardsTask redirty_task(rdcqs, this); 3307 workers()->run_task(&redirty_task); 3308 3309 G1DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set(); 3310 dcq.merge_bufferlists(rdcqs); 3311 3312 phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3313 } 3314 3315 // Weak Reference Processing support 3316 3317 bool G1STWIsAliveClosure::do_object_b(oop p) { 3318 // An object is reachable if it is outside the collection set, 3319 // or is inside and copied. 3320 return !_g1h->is_in_cset(p) || p->is_forwarded(); 3321 } 3322 3323 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) { 3324 assert(obj != NULL, "must not be NULL"); 3325 assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj)); 3326 // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below 3327 // may falsely indicate that this is not the case here: however the collection set only 3328 // contains old regions when concurrent mark is not running. 3329 return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor(); 3330 } 3331 3332 // Non Copying Keep Alive closure 3333 class G1KeepAliveClosure: public OopClosure { 3334 G1CollectedHeap*_g1h; 3335 public: 3336 G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {} 3337 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3338 void do_oop(oop* p) { 3339 oop obj = *p; 3340 assert(obj != NULL, "the caller should have filtered out NULL values"); 3341 3342 const G1HeapRegionAttr region_attr =_g1h->region_attr(obj); 3343 if (!region_attr.is_in_cset_or_humongous()) { 3344 return; 3345 } 3346 if (region_attr.is_in_cset()) { 3347 assert( obj->is_forwarded(), "invariant" ); 3348 *p = obj->forwardee(); 3349 } else { 3350 assert(!obj->is_forwarded(), "invariant" ); 3351 assert(region_attr.is_humongous(), 3352 "Only allowed G1HeapRegionAttr state is IsHumongous, but is %d", region_attr.type()); 3353 _g1h->set_humongous_is_live(obj); 3354 } 3355 } 3356 }; 3357 3358 // Copying Keep Alive closure - can be called from both 3359 // serial and parallel code as long as different worker 3360 // threads utilize different G1ParScanThreadState instances 3361 // and different queues. 3362 3363 class G1CopyingKeepAliveClosure: public OopClosure { 3364 G1CollectedHeap* _g1h; 3365 G1ParScanThreadState* _par_scan_state; 3366 3367 public: 3368 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3369 G1ParScanThreadState* pss): 3370 _g1h(g1h), 3371 _par_scan_state(pss) 3372 {} 3373 3374 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3375 virtual void do_oop( oop* p) { do_oop_work(p); } 3376 3377 template <class T> void do_oop_work(T* p) { 3378 oop obj = RawAccess<>::oop_load(p); 3379 3380 if (_g1h->is_in_cset_or_humongous(obj)) { 3381 // If the referent object has been forwarded (either copied 3382 // to a new location or to itself in the event of an 3383 // evacuation failure) then we need to update the reference 3384 // field and, if both reference and referent are in the G1 3385 // heap, update the RSet for the referent. 3386 // 3387 // If the referent has not been forwarded then we have to keep 3388 // it alive by policy. Therefore we have copy the referent. 3389 // 3390 // When the queue is drained (after each phase of reference processing) 3391 // the object and it's followers will be copied, the reference field set 3392 // to point to the new location, and the RSet updated. 3393 _par_scan_state->push_on_queue(p); 3394 } 3395 } 3396 }; 3397 3398 // Serial drain queue closure. Called as the 'complete_gc' 3399 // closure for each discovered list in some of the 3400 // reference processing phases. 3401 3402 class G1STWDrainQueueClosure: public VoidClosure { 3403 protected: 3404 G1CollectedHeap* _g1h; 3405 G1ParScanThreadState* _par_scan_state; 3406 3407 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3408 3409 public: 3410 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3411 _g1h(g1h), 3412 _par_scan_state(pss) 3413 { } 3414 3415 void do_void() { 3416 G1ParScanThreadState* const pss = par_scan_state(); 3417 pss->trim_queue(); 3418 } 3419 }; 3420 3421 // Parallel Reference Processing closures 3422 3423 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3424 // processing during G1 evacuation pauses. 3425 3426 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3427 private: 3428 G1CollectedHeap* _g1h; 3429 G1ParScanThreadStateSet* _pss; 3430 RefToScanQueueSet* _queues; 3431 WorkGang* _workers; 3432 3433 public: 3434 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3435 G1ParScanThreadStateSet* per_thread_states, 3436 WorkGang* workers, 3437 RefToScanQueueSet *task_queues) : 3438 _g1h(g1h), 3439 _pss(per_thread_states), 3440 _queues(task_queues), 3441 _workers(workers) 3442 { 3443 g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers()); 3444 } 3445 3446 // Executes the given task using concurrent marking worker threads. 3447 virtual void execute(ProcessTask& task, uint ergo_workers); 3448 }; 3449 3450 // Gang task for possibly parallel reference processing 3451 3452 class G1STWRefProcTaskProxy: public AbstractGangTask { 3453 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 3454 ProcessTask& _proc_task; 3455 G1CollectedHeap* _g1h; 3456 G1ParScanThreadStateSet* _pss; 3457 RefToScanQueueSet* _task_queues; 3458 ParallelTaskTerminator* _terminator; 3459 3460 public: 3461 G1STWRefProcTaskProxy(ProcessTask& proc_task, 3462 G1CollectedHeap* g1h, 3463 G1ParScanThreadStateSet* per_thread_states, 3464 RefToScanQueueSet *task_queues, 3465 ParallelTaskTerminator* terminator) : 3466 AbstractGangTask("Process reference objects in parallel"), 3467 _proc_task(proc_task), 3468 _g1h(g1h), 3469 _pss(per_thread_states), 3470 _task_queues(task_queues), 3471 _terminator(terminator) 3472 {} 3473 3474 virtual void work(uint worker_id) { 3475 // The reference processing task executed by a single worker. 3476 ResourceMark rm; 3477 HandleMark hm; 3478 3479 G1STWIsAliveClosure is_alive(_g1h); 3480 3481 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3482 pss->set_ref_discoverer(NULL); 3483 3484 // Keep alive closure. 3485 G1CopyingKeepAliveClosure keep_alive(_g1h, pss); 3486 3487 // Complete GC closure 3488 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator, G1GCPhaseTimes::ObjCopy); 3489 3490 // Call the reference processing task's work routine. 3491 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 3492 3493 // Note we cannot assert that the refs array is empty here as not all 3494 // of the processing tasks (specifically phase2 - pp2_work) execute 3495 // the complete_gc closure (which ordinarily would drain the queue) so 3496 // the queue may not be empty. 3497 } 3498 }; 3499 3500 // Driver routine for parallel reference processing. 3501 // Creates an instance of the ref processing gang 3502 // task and has the worker threads execute it. 3503 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) { 3504 assert(_workers != NULL, "Need parallel worker threads."); 3505 3506 assert(_workers->active_workers() >= ergo_workers, 3507 "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)", 3508 ergo_workers, _workers->active_workers()); 3509 TaskTerminator terminator(ergo_workers, _queues); 3510 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, terminator.terminator()); 3511 3512 _workers->run_task(&proc_task_proxy, ergo_workers); 3513 } 3514 3515 // End of weak reference support closures 3516 3517 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 3518 double ref_proc_start = os::elapsedTime(); 3519 3520 ReferenceProcessor* rp = _ref_processor_stw; 3521 assert(rp->discovery_enabled(), "should have been enabled"); 3522 3523 // Closure to test whether a referent is alive. 3524 G1STWIsAliveClosure is_alive(this); 3525 3526 // Even when parallel reference processing is enabled, the processing 3527 // of JNI refs is serial and performed serially by the current thread 3528 // rather than by a worker. The following PSS will be used for processing 3529 // JNI refs. 3530 3531 // Use only a single queue for this PSS. 3532 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 3533 pss->set_ref_discoverer(NULL); 3534 assert(pss->queue_is_empty(), "pre-condition"); 3535 3536 // Keep alive closure. 3537 G1CopyingKeepAliveClosure keep_alive(this, pss); 3538 3539 // Serial Complete GC closure 3540 G1STWDrainQueueClosure drain_queue(this, pss); 3541 3542 // Setup the soft refs policy... 3543 rp->setup_policy(false); 3544 3545 ReferenceProcessorPhaseTimes* pt = phase_times()->ref_phase_times(); 3546 3547 ReferenceProcessorStats stats; 3548 if (!rp->processing_is_mt()) { 3549 // Serial reference processing... 3550 stats = rp->process_discovered_references(&is_alive, 3551 &keep_alive, 3552 &drain_queue, 3553 NULL, 3554 pt); 3555 } else { 3556 uint no_of_gc_workers = workers()->active_workers(); 3557 3558 // Parallel reference processing 3559 assert(no_of_gc_workers <= rp->max_num_queues(), 3560 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 3561 no_of_gc_workers, rp->max_num_queues()); 3562 3563 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues); 3564 stats = rp->process_discovered_references(&is_alive, 3565 &keep_alive, 3566 &drain_queue, 3567 &par_task_executor, 3568 pt); 3569 } 3570 3571 _gc_tracer_stw->report_gc_reference_stats(stats); 3572 3573 // We have completed copying any necessary live referent objects. 3574 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 3575 3576 make_pending_list_reachable(); 3577 3578 assert(!rp->discovery_enabled(), "Postcondition"); 3579 rp->verify_no_references_recorded(); 3580 3581 double ref_proc_time = os::elapsedTime() - ref_proc_start; 3582 phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 3583 } 3584 3585 void G1CollectedHeap::make_pending_list_reachable() { 3586 if (collector_state()->in_initial_mark_gc()) { 3587 oop pll_head = Universe::reference_pending_list(); 3588 if (pll_head != NULL) { 3589 // Any valid worker id is fine here as we are in the VM thread and single-threaded. 3590 _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head); 3591 } 3592 } 3593 } 3594 3595 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 3596 Ticks start = Ticks::now(); 3597 per_thread_states->flush(); 3598 phase_times()->record_or_add_time_secs(G1GCPhaseTimes::MergePSS, 0 /* worker_id */, (Ticks::now() - start).seconds()); 3599 } 3600 3601 class G1PrepareEvacuationTask : public AbstractGangTask { 3602 class G1PrepareRegionsClosure : public HeapRegionClosure { 3603 G1CollectedHeap* _g1h; 3604 G1PrepareEvacuationTask* _parent_task; 3605 size_t _worker_humongous_total; 3606 size_t _worker_humongous_candidates; 3607 3608 bool humongous_region_is_candidate(HeapRegion* region) const { 3609 assert(region->is_starts_humongous(), "Must start a humongous object"); 3610 3611 oop obj = oop(region->bottom()); 3612 3613 // Dead objects cannot be eager reclaim candidates. Due to class 3614 // unloading it is unsafe to query their classes so we return early. 3615 if (_g1h->is_obj_dead(obj, region)) { 3616 return false; 3617 } 3618 3619 // If we do not have a complete remembered set for the region, then we can 3620 // not be sure that we have all references to it. 3621 if (!region->rem_set()->is_complete()) { 3622 return false; 3623 } 3624 // Candidate selection must satisfy the following constraints 3625 // while concurrent marking is in progress: 3626 // 3627 // * In order to maintain SATB invariants, an object must not be 3628 // reclaimed if it was allocated before the start of marking and 3629 // has not had its references scanned. Such an object must have 3630 // its references (including type metadata) scanned to ensure no 3631 // live objects are missed by the marking process. Objects 3632 // allocated after the start of concurrent marking don't need to 3633 // be scanned. 3634 // 3635 // * An object must not be reclaimed if it is on the concurrent 3636 // mark stack. Objects allocated after the start of concurrent 3637 // marking are never pushed on the mark stack. 3638 // 3639 // Nominating only objects allocated after the start of concurrent 3640 // marking is sufficient to meet both constraints. This may miss 3641 // some objects that satisfy the constraints, but the marking data 3642 // structures don't support efficiently performing the needed 3643 // additional tests or scrubbing of the mark stack. 3644 // 3645 // However, we presently only nominate is_typeArray() objects. 3646 // A humongous object containing references induces remembered 3647 // set entries on other regions. In order to reclaim such an 3648 // object, those remembered sets would need to be cleaned up. 3649 // 3650 // We also treat is_typeArray() objects specially, allowing them 3651 // to be reclaimed even if allocated before the start of 3652 // concurrent mark. For this we rely on mark stack insertion to 3653 // exclude is_typeArray() objects, preventing reclaiming an object 3654 // that is in the mark stack. We also rely on the metadata for 3655 // such objects to be built-in and so ensured to be kept live. 3656 // Frequent allocation and drop of large binary blobs is an 3657 // important use case for eager reclaim, and this special handling 3658 // may reduce needed headroom. 3659 3660 return obj->is_typeArray() && 3661 _g1h->is_potential_eager_reclaim_candidate(region); 3662 } 3663 3664 public: 3665 G1PrepareRegionsClosure(G1CollectedHeap* g1h, G1PrepareEvacuationTask* parent_task) : 3666 _g1h(g1h), 3667 _parent_task(parent_task), 3668 _worker_humongous_total(0), 3669 _worker_humongous_candidates(0) { } 3670 3671 ~G1PrepareRegionsClosure() { 3672 _parent_task->add_humongous_candidates(_worker_humongous_candidates); 3673 _parent_task->add_humongous_total(_worker_humongous_total); 3674 } 3675 3676 virtual bool do_heap_region(HeapRegion* hr) { 3677 // First prepare the region for scanning 3678 _g1h->rem_set()->prepare_region_for_scan(hr); 3679 3680 // Now check if region is a humongous candidate 3681 if (!hr->is_starts_humongous()) { 3682 _g1h->register_region_with_region_attr(hr); 3683 return false; 3684 } 3685 3686 uint index = hr->hrm_index(); 3687 if (humongous_region_is_candidate(hr)) { 3688 _g1h->set_humongous_reclaim_candidate(index, true); 3689 _g1h->register_humongous_region_with_region_attr(index); 3690 _worker_humongous_candidates++; 3691 // We will later handle the remembered sets of these regions. 3692 } else { 3693 _g1h->set_humongous_reclaim_candidate(index, false); 3694 _g1h->register_region_with_region_attr(hr); 3695 } 3696 _worker_humongous_total++; 3697 3698 return false; 3699 } 3700 }; 3701 3702 G1CollectedHeap* _g1h; 3703 HeapRegionClaimer _claimer; 3704 volatile size_t _humongous_total; 3705 volatile size_t _humongous_candidates; 3706 public: 3707 G1PrepareEvacuationTask(G1CollectedHeap* g1h) : 3708 AbstractGangTask("Prepare Evacuation"), 3709 _g1h(g1h), 3710 _claimer(_g1h->workers()->active_workers()), 3711 _humongous_total(0), 3712 _humongous_candidates(0) { } 3713 3714 ~G1PrepareEvacuationTask() { 3715 _g1h->set_has_humongous_reclaim_candidate(_humongous_candidates > 0); 3716 } 3717 3718 void work(uint worker_id) { 3719 G1PrepareRegionsClosure cl(_g1h, this); 3720 _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_claimer, worker_id); 3721 } 3722 3723 void add_humongous_candidates(size_t candidates) { 3724 Atomic::add(&_humongous_candidates, candidates); 3725 } 3726 3727 void add_humongous_total(size_t total) { 3728 Atomic::add(&_humongous_total, total); 3729 } 3730 3731 size_t humongous_candidates() { 3732 return _humongous_candidates; 3733 } 3734 3735 size_t humongous_total() { 3736 return _humongous_total; 3737 } 3738 }; 3739 3740 void G1CollectedHeap::pre_evacuate_collection_set(G1EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 3741 _bytes_used_during_gc = 0; 3742 3743 _expand_heap_after_alloc_failure = true; 3744 _evacuation_failed = false; 3745 3746 // Disable the hot card cache. 3747 _hot_card_cache->reset_hot_cache_claimed_index(); 3748 _hot_card_cache->set_use_cache(false); 3749 3750 // Initialize the GC alloc regions. 3751 _allocator->init_gc_alloc_regions(evacuation_info); 3752 3753 { 3754 Ticks start = Ticks::now(); 3755 rem_set()->prepare_for_scan_heap_roots(); 3756 phase_times()->record_prepare_heap_roots_time_ms((Ticks::now() - start).seconds() * 1000.0); 3757 } 3758 3759 { 3760 G1PrepareEvacuationTask g1_prep_task(this); 3761 Tickspan task_time = run_task(&g1_prep_task); 3762 3763 phase_times()->record_register_regions(task_time.seconds() * 1000.0, 3764 g1_prep_task.humongous_total(), 3765 g1_prep_task.humongous_candidates()); 3766 } 3767 3768 assert(_verifier->check_region_attr_table(), "Inconsistency in the region attributes table."); 3769 _preserved_marks_set.assert_empty(); 3770 3771 #if COMPILER2_OR_JVMCI 3772 DerivedPointerTable::clear(); 3773 #endif 3774 3775 // InitialMark needs claim bits to keep track of the marked-through CLDs. 3776 if (collector_state()->in_initial_mark_gc()) { 3777 concurrent_mark()->pre_initial_mark(); 3778 3779 double start_clear_claimed_marks = os::elapsedTime(); 3780 3781 ClassLoaderDataGraph::clear_claimed_marks(); 3782 3783 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 3784 phase_times()->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 3785 } 3786 3787 // Should G1EvacuationFailureALot be in effect for this GC? 3788 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 3789 } 3790 3791 class G1EvacuateRegionsBaseTask : public AbstractGangTask { 3792 protected: 3793 G1CollectedHeap* _g1h; 3794 G1ParScanThreadStateSet* _per_thread_states; 3795 RefToScanQueueSet* _task_queues; 3796 TaskTerminator _terminator; 3797 uint _num_workers; 3798 3799 void evacuate_live_objects(G1ParScanThreadState* pss, 3800 uint worker_id, 3801 G1GCPhaseTimes::GCParPhases objcopy_phase, 3802 G1GCPhaseTimes::GCParPhases termination_phase) { 3803 G1GCPhaseTimes* p = _g1h->phase_times(); 3804 3805 Ticks start = Ticks::now(); 3806 G1ParEvacuateFollowersClosure cl(_g1h, pss, _task_queues, _terminator.terminator(), objcopy_phase); 3807 cl.do_void(); 3808 3809 assert(pss->queue_is_empty(), "should be empty"); 3810 3811 Tickspan evac_time = (Ticks::now() - start); 3812 p->record_or_add_time_secs(objcopy_phase, worker_id, evac_time.seconds() - cl.term_time()); 3813 3814 if (termination_phase == G1GCPhaseTimes::Termination) { 3815 p->record_time_secs(termination_phase, worker_id, cl.term_time()); 3816 p->record_thread_work_item(termination_phase, worker_id, cl.term_attempts()); 3817 } else { 3818 p->record_or_add_time_secs(termination_phase, worker_id, cl.term_time()); 3819 p->record_or_add_thread_work_item(termination_phase, worker_id, cl.term_attempts()); 3820 } 3821 assert(pss->trim_ticks().seconds() == 0.0, "Unexpected partial trimming during evacuation"); 3822 } 3823 3824 virtual void start_work(uint worker_id) { } 3825 3826 virtual void end_work(uint worker_id) { } 3827 3828 virtual void scan_roots(G1ParScanThreadState* pss, uint worker_id) = 0; 3829 3830 virtual void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) = 0; 3831 3832 public: 3833 G1EvacuateRegionsBaseTask(const char* name, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet* task_queues, uint num_workers) : 3834 AbstractGangTask(name), 3835 _g1h(G1CollectedHeap::heap()), 3836 _per_thread_states(per_thread_states), 3837 _task_queues(task_queues), 3838 _terminator(num_workers, _task_queues), 3839 _num_workers(num_workers) 3840 { } 3841 3842 void work(uint worker_id) { 3843 start_work(worker_id); 3844 3845 { 3846 ResourceMark rm; 3847 HandleMark hm; 3848 3849 G1ParScanThreadState* pss = _per_thread_states->state_for_worker(worker_id); 3850 pss->set_ref_discoverer(_g1h->ref_processor_stw()); 3851 3852 scan_roots(pss, worker_id); 3853 evacuate_live_objects(pss, worker_id); 3854 } 3855 3856 end_work(worker_id); 3857 } 3858 }; 3859 3860 class G1EvacuateRegionsTask : public G1EvacuateRegionsBaseTask { 3861 G1RootProcessor* _root_processor; 3862 3863 void scan_roots(G1ParScanThreadState* pss, uint worker_id) { 3864 _root_processor->evacuate_roots(pss, worker_id); 3865 _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ObjCopy); 3866 _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::CodeRoots, G1GCPhaseTimes::ObjCopy); 3867 } 3868 3869 void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) { 3870 G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::ObjCopy, G1GCPhaseTimes::Termination); 3871 } 3872 3873 void start_work(uint worker_id) { 3874 _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, Ticks::now().seconds()); 3875 } 3876 3877 void end_work(uint worker_id) { 3878 _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, Ticks::now().seconds()); 3879 } 3880 3881 public: 3882 G1EvacuateRegionsTask(G1CollectedHeap* g1h, 3883 G1ParScanThreadStateSet* per_thread_states, 3884 RefToScanQueueSet* task_queues, 3885 G1RootProcessor* root_processor, 3886 uint num_workers) : 3887 G1EvacuateRegionsBaseTask("G1 Evacuate Regions", per_thread_states, task_queues, num_workers), 3888 _root_processor(root_processor) 3889 { } 3890 }; 3891 3892 void G1CollectedHeap::evacuate_initial_collection_set(G1ParScanThreadStateSet* per_thread_states) { 3893 G1GCPhaseTimes* p = phase_times(); 3894 3895 { 3896 Ticks start = Ticks::now(); 3897 rem_set()->merge_heap_roots(true /* initial_evacuation */); 3898 p->record_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0); 3899 } 3900 3901 Tickspan task_time; 3902 const uint num_workers = workers()->active_workers(); 3903 3904 Ticks start_processing = Ticks::now(); 3905 { 3906 G1RootProcessor root_processor(this, num_workers); 3907 G1EvacuateRegionsTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, num_workers); 3908 task_time = run_task(&g1_par_task); 3909 // Closing the inner scope will execute the destructor for the G1RootProcessor object. 3910 // To extract its code root fixup time we measure total time of this scope and 3911 // subtract from the time the WorkGang task took. 3912 } 3913 Tickspan total_processing = Ticks::now() - start_processing; 3914 3915 p->record_initial_evac_time(task_time.seconds() * 1000.0); 3916 p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0); 3917 } 3918 3919 class G1EvacuateOptionalRegionsTask : public G1EvacuateRegionsBaseTask { 3920 3921 void scan_roots(G1ParScanThreadState* pss, uint worker_id) { 3922 _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptObjCopy); 3923 _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptCodeRoots, G1GCPhaseTimes::OptObjCopy); 3924 } 3925 3926 void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) { 3927 G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::OptObjCopy, G1GCPhaseTimes::OptTermination); 3928 } 3929 3930 public: 3931 G1EvacuateOptionalRegionsTask(G1ParScanThreadStateSet* per_thread_states, 3932 RefToScanQueueSet* queues, 3933 uint num_workers) : 3934 G1EvacuateRegionsBaseTask("G1 Evacuate Optional Regions", per_thread_states, queues, num_workers) { 3935 } 3936 }; 3937 3938 void G1CollectedHeap::evacuate_next_optional_regions(G1ParScanThreadStateSet* per_thread_states) { 3939 class G1MarkScope : public MarkScope { }; 3940 3941 Tickspan task_time; 3942 3943 Ticks start_processing = Ticks::now(); 3944 { 3945 G1MarkScope code_mark_scope; 3946 G1EvacuateOptionalRegionsTask task(per_thread_states, _task_queues, workers()->active_workers()); 3947 task_time = run_task(&task); 3948 // See comment in evacuate_collection_set() for the reason of the scope. 3949 } 3950 Tickspan total_processing = Ticks::now() - start_processing; 3951 3952 G1GCPhaseTimes* p = phase_times(); 3953 p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0); 3954 } 3955 3956 void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) { 3957 const double gc_start_time_ms = phase_times()->cur_collection_start_sec() * 1000.0; 3958 3959 while (!evacuation_failed() && _collection_set.optional_region_length() > 0) { 3960 3961 double time_used_ms = os::elapsedTime() * 1000.0 - gc_start_time_ms; 3962 double time_left_ms = MaxGCPauseMillis - time_used_ms; 3963 3964 if (time_left_ms < 0 || 3965 !_collection_set.finalize_optional_for_evacuation(time_left_ms * policy()->optional_evacuation_fraction())) { 3966 log_trace(gc, ergo, cset)("Skipping evacuation of %u optional regions, no more regions can be evacuated in %.3fms", 3967 _collection_set.optional_region_length(), time_left_ms); 3968 break; 3969 } 3970 3971 { 3972 Ticks start = Ticks::now(); 3973 rem_set()->merge_heap_roots(false /* initial_evacuation */); 3974 phase_times()->record_or_add_optional_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0); 3975 } 3976 3977 { 3978 Ticks start = Ticks::now(); 3979 evacuate_next_optional_regions(per_thread_states); 3980 phase_times()->record_or_add_optional_evac_time((Ticks::now() - start).seconds() * 1000.0); 3981 } 3982 } 3983 3984 _collection_set.abandon_optional_collection_set(per_thread_states); 3985 } 3986 3987 void G1CollectedHeap::post_evacuate_collection_set(G1EvacuationInfo& evacuation_info, 3988 G1RedirtyCardsQueueSet* rdcqs, 3989 G1ParScanThreadStateSet* per_thread_states) { 3990 G1GCPhaseTimes* p = phase_times(); 3991 3992 rem_set()->cleanup_after_scan_heap_roots(); 3993 3994 // Process any discovered reference objects - we have 3995 // to do this _before_ we retire the GC alloc regions 3996 // as we may have to copy some 'reachable' referent 3997 // objects (and their reachable sub-graphs) that were 3998 // not copied during the pause. 3999 process_discovered_references(per_thread_states); 4000 4001 G1STWIsAliveClosure is_alive(this); 4002 G1KeepAliveClosure keep_alive(this); 4003 4004 WeakProcessor::weak_oops_do(workers(), &is_alive, &keep_alive, p->weak_phase_times()); 4005 4006 if (G1StringDedup::is_enabled()) { 4007 double string_dedup_time_ms = os::elapsedTime(); 4008 4009 string_dedup_cleaning(&is_alive, &keep_alive, p); 4010 4011 double string_cleanup_time_ms = (os::elapsedTime() - string_dedup_time_ms) * 1000.0; 4012 p->record_string_deduplication_time(string_cleanup_time_ms); 4013 } 4014 4015 _allocator->release_gc_alloc_regions(evacuation_info); 4016 4017 if (evacuation_failed()) { 4018 restore_after_evac_failure(rdcqs); 4019 4020 // Reset the G1EvacuationFailureALot counters and flags 4021 NOT_PRODUCT(reset_evacuation_should_fail();) 4022 4023 double recalculate_used_start = os::elapsedTime(); 4024 set_used(recalculate_used()); 4025 p->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 4026 4027 if (_archive_allocator != NULL) { 4028 _archive_allocator->clear_used(); 4029 } 4030 for (uint i = 0; i < ParallelGCThreads; i++) { 4031 if (_evacuation_failed_info_array[i].has_failed()) { 4032 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 4033 } 4034 } 4035 } else { 4036 // The "used" of the the collection set have already been subtracted 4037 // when they were freed. Add in the bytes used. 4038 increase_used(_bytes_used_during_gc); 4039 } 4040 4041 _preserved_marks_set.assert_empty(); 4042 4043 merge_per_thread_state_info(per_thread_states); 4044 4045 // Reset and re-enable the hot card cache. 4046 // Note the counts for the cards in the regions in the 4047 // collection set are reset when the collection set is freed. 4048 _hot_card_cache->reset_hot_cache(); 4049 _hot_card_cache->set_use_cache(true); 4050 4051 purge_code_root_memory(); 4052 4053 redirty_logged_cards(rdcqs); 4054 4055 free_collection_set(&_collection_set, evacuation_info, per_thread_states->surviving_young_words()); 4056 4057 eagerly_reclaim_humongous_regions(); 4058 4059 record_obj_copy_mem_stats(); 4060 4061 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 4062 evacuation_info.set_bytes_used(_bytes_used_during_gc); 4063 4064 #if COMPILER2_OR_JVMCI 4065 double start = os::elapsedTime(); 4066 DerivedPointerTable::update_pointers(); 4067 phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4068 #endif 4069 policy()->print_age_table(); 4070 } 4071 4072 void G1CollectedHeap::record_obj_copy_mem_stats() { 4073 policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4074 4075 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4076 create_g1_evac_summary(&_old_evac_stats)); 4077 } 4078 4079 void G1CollectedHeap::free_region(HeapRegion* hr, 4080 FreeRegionList* free_list, 4081 bool skip_remset, 4082 bool skip_hot_card_cache, 4083 bool locked) { 4084 assert(!hr->is_free(), "the region should not be free"); 4085 assert(!hr->is_empty(), "the region should not be empty"); 4086 assert(_hrm->is_available(hr->hrm_index()), "region should be committed"); 4087 4088 if (G1VerifyBitmaps) { 4089 MemRegion mr(hr->bottom(), hr->end()); 4090 concurrent_mark()->clear_range_in_prev_bitmap(mr); 4091 } 4092 4093 // Clear the card counts for this region. 4094 // Note: we only need to do this if the region is not young 4095 // (since we don't refine cards in young regions). 4096 if (!skip_hot_card_cache && !hr->is_young()) { 4097 _hot_card_cache->reset_card_counts(hr); 4098 } 4099 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4100 _policy->remset_tracker()->update_at_free(hr); 4101 if (free_list != NULL) { 4102 free_list->add_ordered(hr); 4103 } 4104 } 4105 4106 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4107 FreeRegionList* free_list) { 4108 assert(hr->is_humongous(), "this is only for humongous regions"); 4109 assert(free_list != NULL, "pre-condition"); 4110 hr->clear_humongous(); 4111 free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */); 4112 } 4113 4114 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4115 const uint humongous_regions_removed) { 4116 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4117 MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4118 _old_set.bulk_remove(old_regions_removed); 4119 _humongous_set.bulk_remove(humongous_regions_removed); 4120 } 4121 4122 } 4123 4124 void G1CollectedHeap::abandon_freelist() { 4125 MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4126 _hrm->abandon_free_list(); 4127 } 4128 4129 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4130 assert(list != NULL, "list can't be null"); 4131 if (!list->is_empty()) { 4132 MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4133 _hrm->insert_list_into_free_list(list); 4134 } 4135 } 4136 4137 void G1CollectedHeap::append_to_freelist(FreeRegionList* list) { 4138 assert(list != NULL, "list can't be null"); 4139 if (!list->is_empty()) { 4140 MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4141 _hrm->append_to_free_list(list); 4142 } 4143 } 4144 4145 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4146 decrease_used(bytes); 4147 } 4148 4149 class G1FreeCollectionSetTask : public AbstractGangTask { 4150 // Helper class to keep statistics for the collection set freeing 4151 class FreeCSetStats { 4152 size_t _before_used_bytes; // Usage in regions successfully evacutate 4153 size_t _after_used_bytes; // Usage in regions failing evacuation 4154 size_t _bytes_allocated_in_old_since_last_gc; // Size of young regions turned into old 4155 size_t _failure_used_words; // Live size in failed regions 4156 size_t _failure_waste_words; // Wasted size in failed regions 4157 size_t _rs_length; // Remembered set size 4158 uint _regions_freed; // Number of regions freed 4159 public: 4160 FreeCSetStats() : 4161 _before_used_bytes(0), 4162 _after_used_bytes(0), 4163 _bytes_allocated_in_old_since_last_gc(0), 4164 _failure_used_words(0), 4165 _failure_waste_words(0), 4166 _rs_length(0), 4167 _regions_freed(0) { } 4168 4169 void merge_stats(FreeCSetStats* other) { 4170 assert(other != NULL, "invariant"); 4171 _before_used_bytes += other->_before_used_bytes; 4172 _after_used_bytes += other->_after_used_bytes; 4173 _bytes_allocated_in_old_since_last_gc += other->_bytes_allocated_in_old_since_last_gc; 4174 _failure_used_words += other->_failure_used_words; 4175 _failure_waste_words += other->_failure_waste_words; 4176 _rs_length += other->_rs_length; 4177 _regions_freed += other->_regions_freed; 4178 } 4179 4180 void report(G1CollectedHeap* g1h, G1EvacuationInfo* evacuation_info) { 4181 evacuation_info->set_regions_freed(_regions_freed); 4182 evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4183 4184 g1h->decrement_summary_bytes(_before_used_bytes); 4185 g1h->alloc_buffer_stats(G1HeapRegionAttr::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4186 4187 G1Policy *policy = g1h->policy(); 4188 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4189 policy->record_rs_length(_rs_length); 4190 policy->cset_regions_freed(); 4191 } 4192 4193 void update_used_before(size_t value) { _before_used_bytes += value; } 4194 void update_used_after(size_t value) { _after_used_bytes += value; } 4195 void update_bytes_alloc_in_old(size_t value) { _bytes_allocated_in_old_since_last_gc += value; } 4196 void update_failure_used(size_t value) { _failure_used_words += value; } 4197 void update_failure_waste(size_t value) { _failure_waste_words += value; } 4198 void update_rs_length(size_t value) { _rs_length += value; } 4199 void increment_regions_freed() { _regions_freed += 1; } 4200 }; 4201 4202 // Closure applied to all regions in the collection set. 4203 class G1FreeCollectionSetClosure : public HeapRegionClosure { 4204 // Helper to send JFR events for regions. 4205 class EventForRegion { 4206 EventGCPhaseParallel _event; 4207 public: 4208 EventForRegion(HeapRegion* region, uint worker_id) : _event() { 4209 _event.set_gcId(GCId::current()); 4210 _event.set_gcWorkerId(worker_id); 4211 if (region->is_young()) { 4212 _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::YoungFreeCSet)); 4213 } else { 4214 _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::NonYoungFreeCSet)); 4215 } 4216 } 4217 4218 ~EventForRegion() { 4219 _event.commit(); 4220 } 4221 }; 4222 4223 // Helper to do timing for region work. 4224 class TimerForRegion { 4225 double& _time; 4226 double _start_time; 4227 public: 4228 TimerForRegion(double& time) : _time(time), _start_time(os::elapsedTime()) { } 4229 ~TimerForRegion() { 4230 _time += os::elapsedTime() - _start_time; 4231 } 4232 }; 4233 4234 // G1FreeCollectionSetClosure members 4235 G1CollectedHeap* _g1h; 4236 const size_t* _surviving_young_words; 4237 uint _worker_id; 4238 double _young_time; 4239 double _non_young_time; 4240 FreeCSetStats* _stats; 4241 4242 void assert_in_cset(HeapRegion* r) { 4243 assert(r->young_index_in_cset() != 0 && 4244 (uint)r->young_index_in_cset() <= _g1h->collection_set()->young_region_length(), 4245 "Young index %u is wrong for region %u of type %s with %u young regions", 4246 r->young_index_in_cset(), r->hrm_index(), r->get_type_str(), _g1h->collection_set()->young_region_length()); 4247 } 4248 4249 void handle_evacuated_region(HeapRegion* r) { 4250 assert(!r->is_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4251 // Update stats. 4252 stats()->update_used_before(r->used()); 4253 stats()->increment_regions_freed(); 4254 4255 // Free the region and mark it in the bit map so it gets added to the new free list. 4256 r->rem_set()->clear_locked(); 4257 _g1h->free_region(r, NULL, true /* skip_remset */, true /* skip_hot_card_cache */, true /* locked */); 4258 } 4259 4260 void handle_failed_region(HeapRegion* r) { 4261 // Do some allocation statistics accounting. Regions that failed evacuation 4262 // are always made old, so there is no need to update anything in the young 4263 // gen statistics, but we need to update old gen statistics. 4264 size_t used_words = r->marked_bytes() / HeapWordSize; 4265 stats()->update_failure_used(used_words); 4266 stats()->update_failure_waste(HeapRegion::GrainWords - used_words); 4267 stats()->update_used_after(r->used()); 4268 // When moving a young gen region to old gen, we "allocate" that whole 4269 // region there. This is in addition to any already evacuated objects. 4270 // Notify the policy about that. Old gen regions do not cause an 4271 // additional allocation: both the objects still in the region and the 4272 // ones already moved are accounted for elsewhere. 4273 if (r->is_young()) { 4274 stats()->update_bytes_alloc_in_old(HeapRegion::GrainBytes); 4275 } 4276 4277 // Update the region state due to the failed evacuation. 4278 r->handle_evacuation_failed(); 4279 4280 // Add region to old set, need to hold lock. 4281 MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4282 _g1h->old_set_add(r); 4283 } 4284 4285 double& timer_for_region(HeapRegion* r) { 4286 return r->is_young() ? _young_time : _non_young_time; 4287 } 4288 public: 4289 G1FreeCollectionSetClosure(const size_t* surviving_young_words, 4290 uint worker_id, 4291 FreeCSetStats* stats) : 4292 HeapRegionClosure(), 4293 _g1h(G1CollectedHeap::heap()), 4294 _surviving_young_words(surviving_young_words), 4295 _worker_id(worker_id), 4296 _young_time(0.0), 4297 _non_young_time(0.0), 4298 _stats(stats) { } 4299 4300 virtual bool do_heap_region(HeapRegion* r) { 4301 assert(r->in_collection_set(), "Invariant: %u missing from CSet", r->hrm_index()); 4302 EventForRegion event(r, _worker_id); 4303 TimerForRegion timer(timer_for_region(r)); 4304 4305 _g1h->clear_region_attr(r); 4306 stats()->update_rs_length(r->rem_set()->occupied_locked()); 4307 4308 if (r->is_young()) { 4309 assert_in_cset(r); 4310 r->record_surv_words_in_group(_surviving_young_words[r->young_index_in_cset()]); 4311 } else { 4312 _g1h->hot_card_cache()->reset_card_counts(r); 4313 } 4314 4315 if (r->evacuation_failed()) { 4316 handle_failed_region(r); 4317 } else { 4318 handle_evacuated_region(r); 4319 } 4320 assert(!_g1h->is_on_master_free_list(r), "sanity"); 4321 4322 return false; 4323 } 4324 4325 FreeCSetStats* stats() { 4326 return _stats; 4327 } 4328 4329 void report_timing(double parallel_time) { 4330 G1GCPhaseTimes* pt = _g1h->phase_times(); 4331 pt->record_time_secs(G1GCPhaseTimes::ParFreeCSet, _worker_id, parallel_time); 4332 if (_young_time > 0.0) { 4333 pt->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, _worker_id, _young_time); 4334 } 4335 if (_non_young_time > 0.0) { 4336 pt->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, _worker_id, _non_young_time); 4337 } 4338 } 4339 }; 4340 4341 // G1FreeCollectionSetTask members 4342 G1CollectedHeap* _g1h; 4343 G1EvacuationInfo* _evacuation_info; 4344 FreeCSetStats* _worker_stats; 4345 HeapRegionClaimer _claimer; 4346 const size_t* _surviving_young_words; 4347 uint _active_workers; 4348 4349 FreeCSetStats* worker_stats(uint worker) { 4350 return &_worker_stats[worker]; 4351 } 4352 4353 void report_statistics() { 4354 // Merge the accounting 4355 FreeCSetStats total_stats; 4356 for (uint worker = 0; worker < _active_workers; worker++) { 4357 total_stats.merge_stats(worker_stats(worker)); 4358 } 4359 total_stats.report(_g1h, _evacuation_info); 4360 } 4361 4362 public: 4363 G1FreeCollectionSetTask(G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words, uint active_workers) : 4364 AbstractGangTask("G1 Free Collection Set"), 4365 _g1h(G1CollectedHeap::heap()), 4366 _evacuation_info(evacuation_info), 4367 _worker_stats(NEW_C_HEAP_ARRAY(FreeCSetStats, active_workers, mtGC)), 4368 _claimer(active_workers), 4369 _surviving_young_words(surviving_young_words), 4370 _active_workers(active_workers) { 4371 for (uint worker = 0; worker < active_workers; worker++) { 4372 ::new (&_worker_stats[worker]) FreeCSetStats(); 4373 } 4374 } 4375 4376 ~G1FreeCollectionSetTask() { 4377 double serial_time = os::elapsedTime(); 4378 report_statistics(); 4379 FREE_C_HEAP_ARRAY(FreeCSetStats, _worker_stats); 4380 _g1h->phase_times()->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4381 } 4382 4383 virtual void work(uint worker_id) { 4384 EventGCPhaseParallel event; 4385 double start = os::elapsedTime(); 4386 G1FreeCollectionSetClosure cl(_surviving_young_words, worker_id, worker_stats(worker_id)); 4387 _g1h->collection_set_par_iterate_all(&cl, &_claimer, worker_id); 4388 4389 // Report the total parallel time along with some more detailed metrics. 4390 cl.report_timing(os::elapsedTime() - start); 4391 event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::ParFreeCSet)); 4392 } 4393 }; 4394 4395 class G1RebuildFreeListTask : public AbstractGangTask { 4396 G1CollectedHeap* _g1h; 4397 FreeRegionList* _worker_freelists; 4398 uint _worker_chunk_size; 4399 uint _num_workers; 4400 4401 FreeRegionList* worker_freelist(uint worker) { return &_worker_freelists[worker]; } 4402 4403 // Take the partial free lists and link them together. 4404 void rebuild_freelist() { 4405 // Abandon current free list to allow a rebuild using the 4406 // workers chunked free lists. 4407 _g1h->abandon_freelist(); 4408 for (uint worker = 0; worker < _num_workers; worker++) { 4409 _g1h->append_to_freelist(worker_freelist(worker)); 4410 } 4411 } 4412 public: 4413 G1RebuildFreeListTask(G1CollectedHeap* g1, uint num_workers) : 4414 AbstractGangTask("G1 Rebuild Free List Task"), 4415 _g1h(g1), 4416 _worker_freelists(NEW_C_HEAP_ARRAY(FreeRegionList, num_workers, mtGC)), 4417 _worker_chunk_size((_g1h->max_regions() + num_workers - 1) / num_workers), 4418 _num_workers(num_workers) { 4419 for (uint worker = 0; worker < _num_workers; worker++) { 4420 ::new (&_worker_freelists[worker]) FreeRegionList("Appendable Worker Free List"); 4421 } 4422 } 4423 4424 ~G1RebuildFreeListTask() { 4425 double serial_time = os::elapsedTime(); 4426 rebuild_freelist(); 4427 FREE_C_HEAP_ARRAY(FreeRegionList, _worker_freelists); 4428 _g1h->phase_times()->record_serial_rebuild_freelist_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4429 } 4430 4431 // Each worker creates a free list for a chunk of the heap. The chunks won't 4432 // be overlapping so we don't need to do any claiming. 4433 virtual void work(uint worker_id) { 4434 double start_time = os::elapsedTime(); 4435 EventGCPhaseParallel event; 4436 4437 uint start = worker_id * _worker_chunk_size; 4438 uint end = MIN2(start + _worker_chunk_size, _g1h->max_regions()); 4439 4440 // If start is outside the heap, this worker has nothing to do. 4441 if (start > end) { 4442 return; 4443 } 4444 4445 FreeRegionList* free_list = worker_freelist(worker_id); 4446 for (uint i = start; i < end; i++) { 4447 if (!_g1h->hrm()->is_available(i)) { 4448 continue; 4449 } 4450 HeapRegion* region = _g1h->region_at(i); 4451 if (region->is_free()) { 4452 region->unlink_from_list(); 4453 free_list->add_to_tail(region); 4454 } 4455 } 4456 4457 event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::RebuildFreeList)); 4458 _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::RebuildFreeList, worker_id, os::elapsedTime() - start_time); 4459 } 4460 }; 4461 4462 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, G1EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4463 _eden.clear(); 4464 4465 // The free collections set is split up in two tasks, the first 4466 // frees the collection set and records what regions are free, 4467 // and the second one rebuilds the free list. This proved to be 4468 // more efficient than adding a sorted list to another. 4469 4470 double free_cset_start_time = os::elapsedTime(); 4471 { 4472 uint const num_cs_regions = _collection_set.region_length(); 4473 uint const num_workers = clamp(num_cs_regions, 1u, workers()->active_workers()); 4474 G1FreeCollectionSetTask cl(&evacuation_info, surviving_young_words, num_workers); 4475 4476 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u (%u)", 4477 cl.name(), num_workers, num_cs_regions, num_regions()); 4478 workers()->run_task(&cl, num_workers); 4479 } 4480 4481 double free_cset_end_time = os::elapsedTime(); 4482 phase_times()->record_total_free_cset_time_ms((free_cset_end_time - free_cset_start_time) * 1000.0); 4483 { 4484 uint const num_workers = workers()->active_workers(); 4485 G1RebuildFreeListTask cl(this, num_workers); 4486 4487 log_debug(gc, ergo)("Running %s using %u workers for rebuilding free list of %u (%u) regions", 4488 cl.name(), num_workers, num_free_regions(), num_regions()); 4489 workers()->run_task(&cl, num_workers); 4490 } 4491 phase_times()->record_total_rebuild_freelist_time_ms((os::elapsedTime() - free_cset_end_time) * 1000.0); 4492 4493 collection_set->clear(); 4494 } 4495 4496 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4497 private: 4498 FreeRegionList* _free_region_list; 4499 HeapRegionSet* _proxy_set; 4500 uint _humongous_objects_reclaimed; 4501 uint _humongous_regions_reclaimed; 4502 size_t _freed_bytes; 4503 public: 4504 4505 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4506 _free_region_list(free_region_list), _proxy_set(NULL), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4507 } 4508 4509 virtual bool do_heap_region(HeapRegion* r) { 4510 if (!r->is_starts_humongous()) { 4511 return false; 4512 } 4513 4514 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4515 4516 oop obj = (oop)r->bottom(); 4517 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap(); 4518 4519 // The following checks whether the humongous object is live are sufficient. 4520 // The main additional check (in addition to having a reference from the roots 4521 // or the young gen) is whether the humongous object has a remembered set entry. 4522 // 4523 // A humongous object cannot be live if there is no remembered set for it 4524 // because: 4525 // - there can be no references from within humongous starts regions referencing 4526 // the object because we never allocate other objects into them. 4527 // (I.e. there are no intra-region references that may be missed by the 4528 // remembered set) 4529 // - as soon there is a remembered set entry to the humongous starts region 4530 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4531 // until the end of a concurrent mark. 4532 // 4533 // It is not required to check whether the object has been found dead by marking 4534 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4535 // all objects allocated during that time are considered live. 4536 // SATB marking is even more conservative than the remembered set. 4537 // So if at this point in the collection there is no remembered set entry, 4538 // nobody has a reference to it. 4539 // At the start of collection we flush all refinement logs, and remembered sets 4540 // are completely up-to-date wrt to references to the humongous object. 4541 // 4542 // Other implementation considerations: 4543 // - never consider object arrays at this time because they would pose 4544 // considerable effort for cleaning up the the remembered sets. This is 4545 // required because stale remembered sets might reference locations that 4546 // are currently allocated into. 4547 uint region_idx = r->hrm_index(); 4548 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4549 !r->rem_set()->is_empty()) { 4550 log_debug(gc, humongous)("Live humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d", 4551 region_idx, 4552 (size_t)obj->size() * HeapWordSize, 4553 p2i(r->bottom()), 4554 r->rem_set()->occupied(), 4555 r->rem_set()->strong_code_roots_list_length(), 4556 next_bitmap->is_marked(r->bottom()), 4557 g1h->is_humongous_reclaim_candidate(region_idx), 4558 obj->is_typeArray() 4559 ); 4560 return false; 4561 } 4562 4563 guarantee(obj->is_typeArray(), 4564 "Only eagerly reclaiming type arrays is supported, but the object " 4565 PTR_FORMAT " is not.", p2i(r->bottom())); 4566 4567 log_debug(gc, humongous)("Dead humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d", 4568 region_idx, 4569 (size_t)obj->size() * HeapWordSize, 4570 p2i(r->bottom()), 4571 r->rem_set()->occupied(), 4572 r->rem_set()->strong_code_roots_list_length(), 4573 next_bitmap->is_marked(r->bottom()), 4574 g1h->is_humongous_reclaim_candidate(region_idx), 4575 obj->is_typeArray() 4576 ); 4577 4578 G1ConcurrentMark* const cm = g1h->concurrent_mark(); 4579 cm->humongous_object_eagerly_reclaimed(r); 4580 assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj), 4581 "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s", 4582 region_idx, 4583 BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)), 4584 BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj))); 4585 _humongous_objects_reclaimed++; 4586 do { 4587 HeapRegion* next = g1h->next_region_in_humongous(r); 4588 _freed_bytes += r->used(); 4589 r->set_containing_set(NULL); 4590 _humongous_regions_reclaimed++; 4591 g1h->free_humongous_region(r, _free_region_list); 4592 r = next; 4593 } while (r != NULL); 4594 4595 return false; 4596 } 4597 4598 uint humongous_objects_reclaimed() { 4599 return _humongous_objects_reclaimed; 4600 } 4601 4602 uint humongous_regions_reclaimed() { 4603 return _humongous_regions_reclaimed; 4604 } 4605 4606 size_t bytes_freed() const { 4607 return _freed_bytes; 4608 } 4609 }; 4610 4611 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4612 assert_at_safepoint_on_vm_thread(); 4613 4614 if (!G1EagerReclaimHumongousObjects || 4615 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4616 phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4617 return; 4618 } 4619 4620 double start_time = os::elapsedTime(); 4621 4622 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4623 4624 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4625 heap_region_iterate(&cl); 4626 4627 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4628 4629 G1HRPrinter* hrp = hr_printer(); 4630 if (hrp->is_active()) { 4631 FreeRegionListIterator iter(&local_cleanup_list); 4632 while (iter.more_available()) { 4633 HeapRegion* hr = iter.get_next(); 4634 hrp->cleanup(hr); 4635 } 4636 } 4637 4638 prepend_to_freelist(&local_cleanup_list); 4639 decrement_summary_bytes(cl.bytes_freed()); 4640 4641 phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4642 cl.humongous_objects_reclaimed()); 4643 } 4644 4645 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4646 public: 4647 virtual bool do_heap_region(HeapRegion* r) { 4648 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4649 G1CollectedHeap::heap()->clear_region_attr(r); 4650 r->clear_young_index_in_cset(); 4651 return false; 4652 } 4653 }; 4654 4655 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4656 G1AbandonCollectionSetClosure cl; 4657 collection_set_iterate_all(&cl); 4658 4659 collection_set->clear(); 4660 collection_set->stop_incremental_building(); 4661 } 4662 4663 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 4664 return _allocator->is_retained_old_region(hr); 4665 } 4666 4667 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 4668 _eden.add(hr); 4669 _policy->set_region_eden(hr); 4670 } 4671 4672 #ifdef ASSERT 4673 4674 class NoYoungRegionsClosure: public HeapRegionClosure { 4675 private: 4676 bool _success; 4677 public: 4678 NoYoungRegionsClosure() : _success(true) { } 4679 bool do_heap_region(HeapRegion* r) { 4680 if (r->is_young()) { 4681 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 4682 p2i(r->bottom()), p2i(r->end())); 4683 _success = false; 4684 } 4685 return false; 4686 } 4687 bool success() { return _success; } 4688 }; 4689 4690 bool G1CollectedHeap::check_young_list_empty() { 4691 bool ret = (young_regions_count() == 0); 4692 4693 NoYoungRegionsClosure closure; 4694 heap_region_iterate(&closure); 4695 ret = ret && closure.success(); 4696 4697 return ret; 4698 } 4699 4700 #endif // ASSERT 4701 4702 class TearDownRegionSetsClosure : public HeapRegionClosure { 4703 HeapRegionSet *_old_set; 4704 4705 public: 4706 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 4707 4708 bool do_heap_region(HeapRegion* r) { 4709 if (r->is_old()) { 4710 _old_set->remove(r); 4711 } else if(r->is_young()) { 4712 r->uninstall_surv_rate_group(); 4713 } else { 4714 // We ignore free regions, we'll empty the free list afterwards. 4715 // We ignore humongous and archive regions, we're not tearing down these 4716 // sets. 4717 assert(r->is_archive() || r->is_free() || r->is_humongous(), 4718 "it cannot be another type"); 4719 } 4720 return false; 4721 } 4722 4723 ~TearDownRegionSetsClosure() { 4724 assert(_old_set->is_empty(), "post-condition"); 4725 } 4726 }; 4727 4728 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 4729 assert_at_safepoint_on_vm_thread(); 4730 4731 if (!free_list_only) { 4732 TearDownRegionSetsClosure cl(&_old_set); 4733 heap_region_iterate(&cl); 4734 4735 // Note that emptying the _young_list is postponed and instead done as 4736 // the first step when rebuilding the regions sets again. The reason for 4737 // this is that during a full GC string deduplication needs to know if 4738 // a collected region was young or old when the full GC was initiated. 4739 } 4740 _hrm->remove_all_free_regions(); 4741 } 4742 4743 void G1CollectedHeap::increase_used(size_t bytes) { 4744 _summary_bytes_used += bytes; 4745 } 4746 4747 void G1CollectedHeap::decrease_used(size_t bytes) { 4748 assert(_summary_bytes_used >= bytes, 4749 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 4750 _summary_bytes_used, bytes); 4751 _summary_bytes_used -= bytes; 4752 } 4753 4754 void G1CollectedHeap::set_used(size_t bytes) { 4755 _summary_bytes_used = bytes; 4756 } 4757 4758 class RebuildRegionSetsClosure : public HeapRegionClosure { 4759 private: 4760 bool _free_list_only; 4761 4762 HeapRegionSet* _old_set; 4763 HeapRegionManager* _hrm; 4764 4765 size_t _total_used; 4766 4767 public: 4768 RebuildRegionSetsClosure(bool free_list_only, 4769 HeapRegionSet* old_set, 4770 HeapRegionManager* hrm) : 4771 _free_list_only(free_list_only), 4772 _old_set(old_set), _hrm(hrm), _total_used(0) { 4773 assert(_hrm->num_free_regions() == 0, "pre-condition"); 4774 if (!free_list_only) { 4775 assert(_old_set->is_empty(), "pre-condition"); 4776 } 4777 } 4778 4779 bool do_heap_region(HeapRegion* r) { 4780 if (r->is_empty()) { 4781 assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets."); 4782 // Add free regions to the free list 4783 r->set_free(); 4784 _hrm->insert_into_free_list(r); 4785 } else if (!_free_list_only) { 4786 assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared."); 4787 4788 if (r->is_archive() || r->is_humongous()) { 4789 // We ignore archive and humongous regions. We left these sets unchanged. 4790 } else { 4791 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 4792 // We now move all (non-humongous, non-old, non-archive) regions to old gen, and register them as such. 4793 r->move_to_old(); 4794 _old_set->add(r); 4795 } 4796 _total_used += r->used(); 4797 } 4798 4799 return false; 4800 } 4801 4802 size_t total_used() { 4803 return _total_used; 4804 } 4805 }; 4806 4807 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 4808 assert_at_safepoint_on_vm_thread(); 4809 4810 if (!free_list_only) { 4811 _eden.clear(); 4812 _survivor.clear(); 4813 } 4814 4815 RebuildRegionSetsClosure cl(free_list_only, &_old_set, _hrm); 4816 heap_region_iterate(&cl); 4817 4818 if (!free_list_only) { 4819 set_used(cl.total_used()); 4820 if (_archive_allocator != NULL) { 4821 _archive_allocator->clear_used(); 4822 } 4823 } 4824 assert_used_and_recalculate_used_equal(this); 4825 } 4826 4827 // Methods for the mutator alloc region 4828 4829 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 4830 bool force, 4831 uint node_index) { 4832 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4833 bool should_allocate = policy()->should_allocate_mutator_region(); 4834 if (force || should_allocate) { 4835 HeapRegion* new_alloc_region = new_region(word_size, 4836 HeapRegionType::Eden, 4837 false /* do_expand */, 4838 node_index); 4839 if (new_alloc_region != NULL) { 4840 set_region_short_lived_locked(new_alloc_region); 4841 _hr_printer.alloc(new_alloc_region, !should_allocate); 4842 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 4843 _policy->remset_tracker()->update_at_allocate(new_alloc_region); 4844 return new_alloc_region; 4845 } 4846 } 4847 return NULL; 4848 } 4849 4850 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 4851 size_t allocated_bytes) { 4852 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4853 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 4854 4855 collection_set()->add_eden_region(alloc_region); 4856 increase_used(allocated_bytes); 4857 _eden.add_used_bytes(allocated_bytes); 4858 _hr_printer.retire(alloc_region); 4859 4860 // We update the eden sizes here, when the region is retired, 4861 // instead of when it's allocated, since this is the point that its 4862 // used space has been recorded in _summary_bytes_used. 4863 g1mm()->update_eden_size(); 4864 } 4865 4866 // Methods for the GC alloc regions 4867 4868 bool G1CollectedHeap::has_more_regions(G1HeapRegionAttr dest) { 4869 if (dest.is_old()) { 4870 return true; 4871 } else { 4872 return survivor_regions_count() < policy()->max_survivor_regions(); 4873 } 4874 } 4875 4876 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, G1HeapRegionAttr dest, uint node_index) { 4877 assert(FreeList_lock->owned_by_self(), "pre-condition"); 4878 4879 if (!has_more_regions(dest)) { 4880 return NULL; 4881 } 4882 4883 HeapRegionType type; 4884 if (dest.is_young()) { 4885 type = HeapRegionType::Survivor; 4886 } else { 4887 type = HeapRegionType::Old; 4888 } 4889 4890 HeapRegion* new_alloc_region = new_region(word_size, 4891 type, 4892 true /* do_expand */, 4893 node_index); 4894 4895 if (new_alloc_region != NULL) { 4896 if (type.is_survivor()) { 4897 new_alloc_region->set_survivor(); 4898 _survivor.add(new_alloc_region); 4899 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 4900 } else { 4901 new_alloc_region->set_old(); 4902 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 4903 } 4904 _policy->remset_tracker()->update_at_allocate(new_alloc_region); 4905 register_region_with_region_attr(new_alloc_region); 4906 _hr_printer.alloc(new_alloc_region); 4907 return new_alloc_region; 4908 } 4909 return NULL; 4910 } 4911 4912 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 4913 size_t allocated_bytes, 4914 G1HeapRegionAttr dest) { 4915 _bytes_used_during_gc += allocated_bytes; 4916 if (dest.is_old()) { 4917 old_set_add(alloc_region); 4918 } else { 4919 assert(dest.is_young(), "Retiring alloc region should be young (%d)", dest.type()); 4920 _survivor.add_used_bytes(allocated_bytes); 4921 } 4922 4923 bool const during_im = collector_state()->in_initial_mark_gc(); 4924 if (during_im && allocated_bytes > 0) { 4925 _cm->root_regions()->add(alloc_region->next_top_at_mark_start(), alloc_region->top()); 4926 } 4927 _hr_printer.retire(alloc_region); 4928 } 4929 4930 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 4931 bool expanded = false; 4932 uint index = _hrm->find_highest_free(&expanded); 4933 4934 if (index != G1_NO_HRM_INDEX) { 4935 if (expanded) { 4936 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 4937 HeapRegion::GrainWords * HeapWordSize); 4938 } 4939 _hrm->allocate_free_regions_starting_at(index, 1); 4940 return region_at(index); 4941 } 4942 return NULL; 4943 } 4944 4945 // Optimized nmethod scanning 4946 4947 class RegisterNMethodOopClosure: public OopClosure { 4948 G1CollectedHeap* _g1h; 4949 nmethod* _nm; 4950 4951 template <class T> void do_oop_work(T* p) { 4952 T heap_oop = RawAccess<>::oop_load(p); 4953 if (!CompressedOops::is_null(heap_oop)) { 4954 oop obj = CompressedOops::decode_not_null(heap_oop); 4955 HeapRegion* hr = _g1h->heap_region_containing(obj); 4956 assert(!hr->is_continues_humongous(), 4957 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 4958 " starting at " HR_FORMAT, 4959 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 4960 4961 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 4962 hr->add_strong_code_root_locked(_nm); 4963 } 4964 } 4965 4966 public: 4967 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 4968 _g1h(g1h), _nm(nm) {} 4969 4970 void do_oop(oop* p) { do_oop_work(p); } 4971 void do_oop(narrowOop* p) { do_oop_work(p); } 4972 }; 4973 4974 class UnregisterNMethodOopClosure: public OopClosure { 4975 G1CollectedHeap* _g1h; 4976 nmethod* _nm; 4977 4978 template <class T> void do_oop_work(T* p) { 4979 T heap_oop = RawAccess<>::oop_load(p); 4980 if (!CompressedOops::is_null(heap_oop)) { 4981 oop obj = CompressedOops::decode_not_null(heap_oop); 4982 HeapRegion* hr = _g1h->heap_region_containing(obj); 4983 assert(!hr->is_continues_humongous(), 4984 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 4985 " starting at " HR_FORMAT, 4986 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 4987 4988 hr->remove_strong_code_root(_nm); 4989 } 4990 } 4991 4992 public: 4993 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 4994 _g1h(g1h), _nm(nm) {} 4995 4996 void do_oop(oop* p) { do_oop_work(p); } 4997 void do_oop(narrowOop* p) { do_oop_work(p); } 4998 }; 4999 5000 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5001 guarantee(nm != NULL, "sanity"); 5002 RegisterNMethodOopClosure reg_cl(this, nm); 5003 nm->oops_do(®_cl); 5004 } 5005 5006 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5007 guarantee(nm != NULL, "sanity"); 5008 UnregisterNMethodOopClosure reg_cl(this, nm); 5009 nm->oops_do(®_cl, true); 5010 } 5011 5012 void G1CollectedHeap::purge_code_root_memory() { 5013 double purge_start = os::elapsedTime(); 5014 G1CodeRootSet::purge(); 5015 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5016 phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5017 } 5018 5019 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5020 G1CollectedHeap* _g1h; 5021 5022 public: 5023 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5024 _g1h(g1h) {} 5025 5026 void do_code_blob(CodeBlob* cb) { 5027 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5028 if (nm == NULL) { 5029 return; 5030 } 5031 5032 _g1h->register_nmethod(nm); 5033 } 5034 }; 5035 5036 void G1CollectedHeap::rebuild_strong_code_roots() { 5037 RebuildStrongCodeRootClosure blob_cl(this); 5038 CodeCache::blobs_do(&blob_cl); 5039 } 5040 5041 void G1CollectedHeap::initialize_serviceability() { 5042 _g1mm->initialize_serviceability(); 5043 } 5044 5045 MemoryUsage G1CollectedHeap::memory_usage() { 5046 return _g1mm->memory_usage(); 5047 } 5048 5049 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() { 5050 return _g1mm->memory_managers(); 5051 } 5052 5053 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() { 5054 return _g1mm->memory_pools(); 5055 }