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/g1ConcurrentHeapResize.hpp" 42 #include "gc/g1/g1ConcurrentHeapResizeThread.hpp" 43 #include "gc/g1/g1DirtyCardQueue.hpp" 44 #include "gc/g1/g1EvacStats.inline.hpp" 45 #include "gc/g1/g1FullCollector.hpp" 46 #include "gc/g1/g1GCPhaseTimes.hpp" 47 #include "gc/g1/g1HeapSizingPolicy.hpp" 48 #include "gc/g1/g1HeapTransition.hpp" 49 #include "gc/g1/g1HeapVerifier.hpp" 50 #include "gc/g1/g1HotCardCache.hpp" 51 #include "gc/g1/g1MemoryPool.hpp" 52 #include "gc/g1/g1OopClosures.inline.hpp" 53 #include "gc/g1/g1ParallelCleaning.hpp" 54 #include "gc/g1/g1ParScanThreadState.inline.hpp" 55 #include "gc/g1/g1Policy.hpp" 56 #include "gc/g1/g1RedirtyCardsQueue.hpp" 57 #include "gc/g1/g1RegionToSpaceMapper.hpp" 58 #include "gc/g1/g1RemSet.hpp" 59 #include "gc/g1/g1RootClosures.hpp" 60 #include "gc/g1/g1RootProcessor.hpp" 61 #include "gc/g1/g1SATBMarkQueueSet.hpp" 62 #include "gc/g1/g1StringDedup.hpp" 63 #include "gc/g1/g1ThreadLocalData.hpp" 64 #include "gc/g1/g1Trace.hpp" 65 #include "gc/g1/g1YCTypes.hpp" 66 #include "gc/g1/g1YoungRemSetSamplingThread.hpp" 67 #include "gc/g1/g1VMOperations.hpp" 68 #include "gc/g1/heapRegion.inline.hpp" 69 #include "gc/g1/heapRegionRemSet.hpp" 70 #include "gc/g1/heapRegionSet.inline.hpp" 71 #include "gc/shared/gcBehaviours.hpp" 72 #include "gc/shared/gcHeapSummary.hpp" 73 #include "gc/shared/gcId.hpp" 74 #include "gc/shared/gcLocker.hpp" 75 #include "gc/shared/gcTimer.hpp" 76 #include "gc/shared/gcTraceTime.inline.hpp" 77 #include "gc/shared/generationSpec.hpp" 78 #include "gc/shared/isGCActiveMark.hpp" 79 #include "gc/shared/locationPrinter.inline.hpp" 80 #include "gc/shared/oopStorageParState.hpp" 81 #include "gc/shared/preservedMarks.inline.hpp" 82 #include "gc/shared/suspendibleThreadSet.hpp" 83 #include "gc/shared/referenceProcessor.inline.hpp" 84 #include "gc/shared/taskqueue.inline.hpp" 85 #include "gc/shared/weakProcessor.inline.hpp" 86 #include "gc/shared/workerPolicy.hpp" 87 #include "logging/log.hpp" 88 #include "memory/allocation.hpp" 89 #include "memory/iterator.hpp" 90 #include "memory/resourceArea.hpp" 91 #include "memory/universe.hpp" 92 #include "oops/access.inline.hpp" 93 #include "oops/compressedOops.inline.hpp" 94 #include "oops/oop.inline.hpp" 95 #include "runtime/atomic.hpp" 96 #include "runtime/flags/flagSetting.hpp" 97 #include "runtime/handles.inline.hpp" 98 #include "runtime/init.hpp" 99 #include "runtime/orderAccess.hpp" 100 #include "runtime/threadSMR.hpp" 101 #include "runtime/vmThread.hpp" 102 #include "utilities/align.hpp" 103 #include "utilities/bitMap.inline.hpp" 104 #include "utilities/globalDefinitions.hpp" 105 #include "utilities/stack.inline.hpp" 106 107 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 108 109 // INVARIANTS/NOTES 110 // 111 // All allocation activity covered by the G1CollectedHeap interface is 112 // serialized by acquiring the HeapLock. This happens in mem_allocate 113 // and allocate_new_tlab, which are the "entry" points to the 114 // allocation code from the rest of the JVM. (Note that this does not 115 // apply to TLAB allocation, which is not part of this interface: it 116 // is done by clients of this interface.) 117 118 class RedirtyLoggedCardTableEntryClosure : public G1CardTableEntryClosure { 119 private: 120 size_t _num_dirtied; 121 G1CollectedHeap* _g1h; 122 G1CardTable* _g1_ct; 123 124 HeapRegion* region_for_card(CardValue* card_ptr) const { 125 return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr)); 126 } 127 128 bool will_become_free(HeapRegion* hr) const { 129 // A region will be freed by free_collection_set if the region is in the 130 // collection set and has not had an evacuation failure. 131 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 132 } 133 134 public: 135 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : G1CardTableEntryClosure(), 136 _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { } 137 138 void do_card_ptr(CardValue* card_ptr, uint worker_id) { 139 HeapRegion* hr = region_for_card(card_ptr); 140 141 // Should only dirty cards in regions that won't be freed. 142 if (!will_become_free(hr)) { 143 *card_ptr = G1CardTable::dirty_card_val(); 144 _num_dirtied++; 145 } 146 } 147 148 size_t num_dirtied() const { return _num_dirtied; } 149 }; 150 151 152 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 153 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 154 } 155 156 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 157 // The from card cache is not the memory that is actually committed. So we cannot 158 // take advantage of the zero_filled parameter. 159 reset_from_card_cache(start_idx, num_regions); 160 } 161 162 Tickspan G1CollectedHeap::run_task(AbstractGangTask* task) { 163 Ticks start = Ticks::now(); 164 workers()->run_task(task, workers()->active_workers()); 165 return Ticks::now() - start; 166 } 167 168 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 169 MemRegion mr) { 170 return new HeapRegion(hrs_index, bot(), mr); 171 } 172 173 // Private methods. 174 175 HeapRegion* G1CollectedHeap::new_region(size_t word_size, 176 HeapRegionType type, 177 bool do_expand, 178 uint node_index) { 179 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 180 "the only time we use this to allocate a humongous region is " 181 "when we are allocating a single humongous region"); 182 183 HeapRegion* res = _hrm->allocate_free_region(type, node_index); 184 185 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 186 // Currently, only attempts to allocate GC alloc regions set 187 // do_expand to true. So, we should only reach here during a 188 // safepoint. If this assumption changes we might have to 189 // reconsider the use of _expand_heap_after_alloc_failure. 190 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 191 192 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 193 word_size * HeapWordSize); 194 195 assert(word_size * HeapWordSize < HeapRegion::GrainBytes, 196 "This kind of expansion should never be more than one region. Size: " SIZE_FORMAT, 197 word_size * HeapWordSize); 198 if (expand_single_region(node_index)) { 199 // Given that expand_single_region() succeeded in expanding the heap, and we 200 // always expand the heap by an amount aligned to the heap 201 // region size, the free list should in theory not be empty. 202 // In either case allocate_free_region() will check for NULL. 203 res = _hrm->allocate_free_region(type, node_index); 204 } else { 205 _expand_heap_after_alloc_failure = false; 206 } 207 } 208 return res; 209 } 210 211 HeapWord* 212 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 213 uint num_regions, 214 size_t word_size) { 215 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 216 assert(is_humongous(word_size), "word_size should be humongous"); 217 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 218 219 // Index of last region in the series. 220 uint last = first + num_regions - 1; 221 222 // We need to initialize the region(s) we just discovered. This is 223 // a bit tricky given that it can happen concurrently with 224 // refinement threads refining cards on these regions and 225 // potentially wanting to refine the BOT as they are scanning 226 // those cards (this can happen shortly after a cleanup; see CR 227 // 6991377). So we have to set up the region(s) carefully and in 228 // a specific order. 229 230 // The word size sum of all the regions we will allocate. 231 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 232 assert(word_size <= word_size_sum, "sanity"); 233 234 // This will be the "starts humongous" region. 235 HeapRegion* first_hr = region_at(first); 236 // The header of the new object will be placed at the bottom of 237 // the first region. 238 HeapWord* new_obj = first_hr->bottom(); 239 // This will be the new top of the new object. 240 HeapWord* obj_top = new_obj + word_size; 241 242 // First, we need to zero the header of the space that we will be 243 // allocating. When we update top further down, some refinement 244 // threads might try to scan the region. By zeroing the header we 245 // ensure that any thread that will try to scan the region will 246 // come across the zero klass word and bail out. 247 // 248 // NOTE: It would not have been correct to have used 249 // CollectedHeap::fill_with_object() and make the space look like 250 // an int array. The thread that is doing the allocation will 251 // later update the object header to a potentially different array 252 // type and, for a very short period of time, the klass and length 253 // fields will be inconsistent. This could cause a refinement 254 // thread to calculate the object size incorrectly. 255 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 256 257 // Next, pad out the unused tail of the last region with filler 258 // objects, for improved usage accounting. 259 // How many words we use for filler objects. 260 size_t word_fill_size = word_size_sum - word_size; 261 262 // How many words memory we "waste" which cannot hold a filler object. 263 size_t words_not_fillable = 0; 264 265 if (word_fill_size >= min_fill_size()) { 266 fill_with_objects(obj_top, word_fill_size); 267 } else if (word_fill_size > 0) { 268 // We have space to fill, but we cannot fit an object there. 269 words_not_fillable = word_fill_size; 270 word_fill_size = 0; 271 } 272 273 // We will set up the first region as "starts humongous". This 274 // will also update the BOT covering all the regions to reflect 275 // that there is a single object that starts at the bottom of the 276 // first region. 277 first_hr->set_starts_humongous(obj_top, word_fill_size); 278 _policy->remset_tracker()->update_at_allocate(first_hr); 279 // Then, if there are any, we will set up the "continues 280 // humongous" regions. 281 HeapRegion* hr = NULL; 282 for (uint i = first + 1; i <= last; ++i) { 283 hr = region_at(i); 284 hr->set_continues_humongous(first_hr); 285 _policy->remset_tracker()->update_at_allocate(hr); 286 } 287 288 // Up to this point no concurrent thread would have been able to 289 // do any scanning on any region in this series. All the top 290 // fields still point to bottom, so the intersection between 291 // [bottom,top] and [card_start,card_end] will be empty. Before we 292 // update the top fields, we'll do a storestore to make sure that 293 // no thread sees the update to top before the zeroing of the 294 // object header and the BOT initialization. 295 OrderAccess::storestore(); 296 297 // Now, we will update the top fields of the "continues humongous" 298 // regions except the last one. 299 for (uint i = first; i < last; ++i) { 300 hr = region_at(i); 301 hr->set_top(hr->end()); 302 } 303 304 hr = region_at(last); 305 // If we cannot fit a filler object, we must set top to the end 306 // of the humongous object, otherwise we cannot iterate the heap 307 // and the BOT will not be complete. 308 hr->set_top(hr->end() - words_not_fillable); 309 310 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 311 "obj_top should be in last region"); 312 313 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 314 315 assert(words_not_fillable == 0 || 316 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 317 "Miscalculation in humongous allocation"); 318 319 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 320 321 for (uint i = first; i <= last; ++i) { 322 hr = region_at(i); 323 _humongous_set.add(hr); 324 _hr_printer.alloc(hr); 325 } 326 327 return new_obj; 328 } 329 330 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 331 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 332 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 333 } 334 335 // If could fit into free regions w/o expansion, try. 336 // Otherwise, if can expand, do so. 337 // Otherwise, if using ex regions might help, try with ex given back. 338 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) { 339 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 340 341 _verifier->verify_region_sets_optional(); 342 343 uint first = G1_NO_HRM_INDEX; 344 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 345 346 if (obj_regions == 1) { 347 // Only one region to allocate, try to use a fast path by directly allocating 348 // from the free lists. Do not try to expand here, we will potentially do that 349 // later. 350 HeapRegion* hr = new_region(word_size, HeapRegionType::Humongous, false /* do_expand */); 351 if (hr != NULL) { 352 first = hr->hrm_index(); 353 } 354 } else { 355 // Policy: Try only empty regions (i.e. already committed first). Maybe we 356 // are lucky enough to find some. 357 first = _hrm->find_contiguous_only_empty(obj_regions); 358 if (first != G1_NO_HRM_INDEX) { 359 _hrm->allocate_free_regions_starting_at(first, obj_regions); 360 } 361 } 362 363 if (first == G1_NO_HRM_INDEX) { 364 // Policy: We could not find enough regions for the humongous object in the 365 // free list. Look through the heap to find a mix of free and uncommitted regions. 366 // If so, try expansion. 367 first = _hrm->find_contiguous_empty_or_unavailable(obj_regions); 368 if (first != G1_NO_HRM_INDEX) { 369 // We found something. Make sure these regions are committed, i.e. expand 370 // the heap. Alternatively we could do a defragmentation GC. 371 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 372 word_size * HeapWordSize); 373 374 _hrm->expand_at(first, obj_regions, workers()); 375 policy()->record_new_heap_size(num_regions()); 376 377 #ifdef ASSERT 378 for (uint i = first; i < first + obj_regions; ++i) { 379 HeapRegion* hr = region_at(i); 380 assert(hr->is_free(), "sanity"); 381 assert(hr->is_empty(), "sanity"); 382 assert(is_on_master_free_list(hr), "sanity"); 383 } 384 #endif 385 _hrm->allocate_free_regions_starting_at(first, obj_regions); 386 } else { 387 // Policy: Potentially trigger a defragmentation GC. 388 } 389 } 390 391 HeapWord* result = NULL; 392 if (first != G1_NO_HRM_INDEX) { 393 result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size); 394 assert(result != NULL, "it should always return a valid result"); 395 396 // A successful humongous object allocation changes the used space 397 // information of the old generation so we need to recalculate the 398 // sizes and update the jstat counters here. 399 g1mm()->update_sizes(); 400 } 401 402 _verifier->verify_region_sets_optional(); 403 404 return result; 405 } 406 407 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size, 408 size_t requested_size, 409 size_t* actual_size) { 410 assert_heap_not_locked_and_not_at_safepoint(); 411 assert(!is_humongous(requested_size), "we do not allow humongous TLABs"); 412 413 return attempt_allocation(min_size, requested_size, actual_size); 414 } 415 416 HeapWord* 417 G1CollectedHeap::mem_allocate(size_t word_size, 418 bool* gc_overhead_limit_was_exceeded) { 419 assert_heap_not_locked_and_not_at_safepoint(); 420 421 if (is_humongous(word_size)) { 422 return attempt_allocation_humongous(word_size); 423 } 424 size_t dummy = 0; 425 return attempt_allocation(word_size, word_size, &dummy); 426 } 427 428 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) { 429 ResourceMark rm; // For retrieving the thread names in log messages. 430 431 // Make sure you read the note in attempt_allocation_humongous(). 432 433 assert_heap_not_locked_and_not_at_safepoint(); 434 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 435 "be called for humongous allocation requests"); 436 437 // We should only get here after the first-level allocation attempt 438 // (attempt_allocation()) failed to allocate. 439 440 // We will loop until a) we manage to successfully perform the 441 // allocation or b) we successfully schedule a collection which 442 // fails to perform the allocation. b) is the only case when we'll 443 // return NULL. 444 HeapWord* result = NULL; 445 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 446 bool should_try_gc; 447 uint gc_count_before; 448 449 { 450 MutexLocker x(Heap_lock); 451 result = _allocator->attempt_allocation_locked(word_size); 452 if (result != NULL) { 453 return result; 454 } 455 456 // If the GCLocker is active and we are bound for a GC, try expanding young gen. 457 // This is different to when only GCLocker::needs_gc() is set: try to avoid 458 // waiting because the GCLocker is active to not wait too long. 459 if (GCLocker::is_active_and_needs_gc() && policy()->can_expand_young_list()) { 460 // No need for an ergo message here, can_expand_young_list() does this when 461 // it returns true. 462 result = _allocator->attempt_allocation_force(word_size); 463 if (result != NULL) { 464 return result; 465 } 466 } 467 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 468 // the GCLocker initiated GC has been performed and then retry. This includes 469 // the case when the GC Locker is not active but has not been performed. 470 should_try_gc = !GCLocker::needs_gc(); 471 // Read the GC count while still holding the Heap_lock. 472 gc_count_before = total_collections(); 473 } 474 475 if (should_try_gc) { 476 bool succeeded; 477 result = do_collection_pause(word_size, gc_count_before, &succeeded, 478 GCCause::_g1_inc_collection_pause); 479 if (result != NULL) { 480 assert(succeeded, "only way to get back a non-NULL result"); 481 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 482 Thread::current()->name(), p2i(result)); 483 return result; 484 } 485 486 if (succeeded) { 487 // We successfully scheduled a collection which failed to allocate. No 488 // point in trying to allocate further. We'll just return NULL. 489 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 490 SIZE_FORMAT " words", Thread::current()->name(), word_size); 491 return NULL; 492 } 493 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words", 494 Thread::current()->name(), word_size); 495 } else { 496 // Failed to schedule a collection. 497 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 498 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 499 SIZE_FORMAT " words", Thread::current()->name(), word_size); 500 return NULL; 501 } 502 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 503 // The GCLocker is either active or the GCLocker initiated 504 // GC has not yet been performed. Stall until it is and 505 // then retry the allocation. 506 GCLocker::stall_until_clear(); 507 gclocker_retry_count += 1; 508 } 509 510 // We can reach here if we were unsuccessful in scheduling a 511 // collection (because another thread beat us to it) or if we were 512 // stalled due to the GC locker. In either can we should retry the 513 // allocation attempt in case another thread successfully 514 // performed a collection and reclaimed enough space. We do the 515 // first attempt (without holding the Heap_lock) here and the 516 // follow-on attempt will be at the start of the next loop 517 // iteration (after taking the Heap_lock). 518 size_t dummy = 0; 519 result = _allocator->attempt_allocation(word_size, word_size, &dummy); 520 if (result != NULL) { 521 return result; 522 } 523 524 // Give a warning if we seem to be looping forever. 525 if ((QueuedAllocationWarningCount > 0) && 526 (try_count % QueuedAllocationWarningCount == 0)) { 527 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 528 Thread::current()->name(), try_count, word_size); 529 } 530 } 531 532 ShouldNotReachHere(); 533 return NULL; 534 } 535 536 void G1CollectedHeap::begin_archive_alloc_range(bool open) { 537 assert_at_safepoint_on_vm_thread(); 538 if (_archive_allocator == NULL) { 539 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open); 540 } 541 } 542 543 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 544 // Allocations in archive regions cannot be of a size that would be considered 545 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 546 // may be different at archive-restore time. 547 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 548 } 549 550 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 551 assert_at_safepoint_on_vm_thread(); 552 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 553 if (is_archive_alloc_too_large(word_size)) { 554 return NULL; 555 } 556 return _archive_allocator->archive_mem_allocate(word_size); 557 } 558 559 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 560 size_t end_alignment_in_bytes) { 561 assert_at_safepoint_on_vm_thread(); 562 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 563 564 // Call complete_archive to do the real work, filling in the MemRegion 565 // array with the archive regions. 566 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 567 delete _archive_allocator; 568 _archive_allocator = NULL; 569 } 570 571 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 572 assert(ranges != NULL, "MemRegion array NULL"); 573 assert(count != 0, "No MemRegions provided"); 574 MemRegion reserved = _hrm->reserved(); 575 for (size_t i = 0; i < count; i++) { 576 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 577 return false; 578 } 579 } 580 return true; 581 } 582 583 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, 584 size_t count, 585 bool open) { 586 assert(!is_init_completed(), "Expect to be called at JVM init time"); 587 assert(ranges != NULL, "MemRegion array NULL"); 588 assert(count != 0, "No MemRegions provided"); 589 MutexLocker x(Heap_lock); 590 591 MemRegion reserved = _hrm->reserved(); 592 HeapWord* prev_last_addr = NULL; 593 HeapRegion* prev_last_region = NULL; 594 595 // Temporarily disable pretouching of heap pages. This interface is used 596 // when mmap'ing archived heap data in, so pre-touching is wasted. 597 FlagSetting fs(AlwaysPreTouch, false); 598 599 // Enable archive object checking used by G1MarkSweep. We have to let it know 600 // about each archive range, so that objects in those ranges aren't marked. 601 G1ArchiveAllocator::enable_archive_object_check(); 602 603 // For each specified MemRegion range, allocate the corresponding G1 604 // regions and mark them as archive regions. We expect the ranges 605 // in ascending starting address order, without overlap. 606 for (size_t i = 0; i < count; i++) { 607 MemRegion curr_range = ranges[i]; 608 HeapWord* start_address = curr_range.start(); 609 size_t word_size = curr_range.word_size(); 610 HeapWord* last_address = curr_range.last(); 611 size_t commits = 0; 612 613 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 614 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 615 p2i(start_address), p2i(last_address)); 616 guarantee(start_address > prev_last_addr, 617 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 618 p2i(start_address), p2i(prev_last_addr)); 619 prev_last_addr = last_address; 620 621 // Check for ranges that start in the same G1 region in which the previous 622 // range ended, and adjust the start address so we don't try to allocate 623 // the same region again. If the current range is entirely within that 624 // region, skip it, just adjusting the recorded top. 625 HeapRegion* start_region = _hrm->addr_to_region(start_address); 626 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 627 start_address = start_region->end(); 628 if (start_address > last_address) { 629 increase_used(word_size * HeapWordSize); 630 start_region->set_top(last_address + 1); 631 continue; 632 } 633 start_region->set_top(start_address); 634 curr_range = MemRegion(start_address, last_address + 1); 635 start_region = _hrm->addr_to_region(start_address); 636 } 637 638 // Perform the actual region allocation, exiting if it fails. 639 // Then note how much new space we have allocated. 640 if (!_hrm->allocate_containing_regions(curr_range, &commits, workers())) { 641 return false; 642 } 643 increase_used(word_size * HeapWordSize); 644 if (commits != 0) { 645 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 646 HeapRegion::GrainWords * HeapWordSize * commits); 647 648 } 649 650 // Mark each G1 region touched by the range as archive, add it to 651 // the old set, and set top. 652 HeapRegion* curr_region = _hrm->addr_to_region(start_address); 653 HeapRegion* last_region = _hrm->addr_to_region(last_address); 654 prev_last_region = last_region; 655 656 while (curr_region != NULL) { 657 assert(curr_region->is_empty() && !curr_region->is_pinned(), 658 "Region already in use (index %u)", curr_region->hrm_index()); 659 if (open) { 660 curr_region->set_open_archive(); 661 } else { 662 curr_region->set_closed_archive(); 663 } 664 _hr_printer.alloc(curr_region); 665 _archive_set.add(curr_region); 666 HeapWord* top; 667 HeapRegion* next_region; 668 if (curr_region != last_region) { 669 top = curr_region->end(); 670 next_region = _hrm->next_region_in_heap(curr_region); 671 } else { 672 top = last_address + 1; 673 next_region = NULL; 674 } 675 curr_region->set_top(top); 676 curr_region = next_region; 677 } 678 679 // Notify mark-sweep of the archive 680 G1ArchiveAllocator::set_range_archive(curr_range, open); 681 } 682 return true; 683 } 684 685 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 686 assert(!is_init_completed(), "Expect to be called at JVM init time"); 687 assert(ranges != NULL, "MemRegion array NULL"); 688 assert(count != 0, "No MemRegions provided"); 689 MemRegion reserved = _hrm->reserved(); 690 HeapWord *prev_last_addr = NULL; 691 HeapRegion* prev_last_region = NULL; 692 693 // For each MemRegion, create filler objects, if needed, in the G1 regions 694 // that contain the address range. The address range actually within the 695 // MemRegion will not be modified. That is assumed to have been initialized 696 // elsewhere, probably via an mmap of archived heap data. 697 MutexLocker x(Heap_lock); 698 for (size_t i = 0; i < count; i++) { 699 HeapWord* start_address = ranges[i].start(); 700 HeapWord* last_address = ranges[i].last(); 701 702 assert(reserved.contains(start_address) && reserved.contains(last_address), 703 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 704 p2i(start_address), p2i(last_address)); 705 assert(start_address > prev_last_addr, 706 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 707 p2i(start_address), p2i(prev_last_addr)); 708 709 HeapRegion* start_region = _hrm->addr_to_region(start_address); 710 HeapRegion* last_region = _hrm->addr_to_region(last_address); 711 HeapWord* bottom_address = start_region->bottom(); 712 713 // Check for a range beginning in the same region in which the 714 // previous one ended. 715 if (start_region == prev_last_region) { 716 bottom_address = prev_last_addr + 1; 717 } 718 719 // Verify that the regions were all marked as archive regions by 720 // alloc_archive_regions. 721 HeapRegion* curr_region = start_region; 722 while (curr_region != NULL) { 723 guarantee(curr_region->is_archive(), 724 "Expected archive region at index %u", curr_region->hrm_index()); 725 if (curr_region != last_region) { 726 curr_region = _hrm->next_region_in_heap(curr_region); 727 } else { 728 curr_region = NULL; 729 } 730 } 731 732 prev_last_addr = last_address; 733 prev_last_region = last_region; 734 735 // Fill the memory below the allocated range with dummy object(s), 736 // if the region bottom does not match the range start, or if the previous 737 // range ended within the same G1 region, and there is a gap. 738 if (start_address != bottom_address) { 739 size_t fill_size = pointer_delta(start_address, bottom_address); 740 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 741 increase_used(fill_size * HeapWordSize); 742 } 743 } 744 } 745 746 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size, 747 size_t desired_word_size, 748 size_t* actual_word_size) { 749 assert_heap_not_locked_and_not_at_safepoint(); 750 assert(!is_humongous(desired_word_size), "attempt_allocation() should not " 751 "be called for humongous allocation requests"); 752 753 HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size); 754 755 if (result == NULL) { 756 *actual_word_size = desired_word_size; 757 result = attempt_allocation_slow(desired_word_size); 758 } 759 760 assert_heap_not_locked(); 761 if (result != NULL) { 762 assert(*actual_word_size != 0, "Actual size must have been set here"); 763 dirty_young_block(result, *actual_word_size); 764 } else { 765 *actual_word_size = 0; 766 } 767 768 return result; 769 } 770 771 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count, bool is_open) { 772 assert(!is_init_completed(), "Expect to be called at JVM init time"); 773 assert(ranges != NULL, "MemRegion array NULL"); 774 assert(count != 0, "No MemRegions provided"); 775 MemRegion reserved = _hrm->reserved(); 776 HeapWord* prev_last_addr = NULL; 777 HeapRegion* prev_last_region = NULL; 778 size_t size_used = 0; 779 size_t uncommitted_regions = 0; 780 781 // For each Memregion, free the G1 regions that constitute it, and 782 // notify mark-sweep that the range is no longer to be considered 'archive.' 783 MutexLocker x(Heap_lock); 784 for (size_t i = 0; i < count; i++) { 785 HeapWord* start_address = ranges[i].start(); 786 HeapWord* last_address = ranges[i].last(); 787 788 assert(reserved.contains(start_address) && reserved.contains(last_address), 789 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 790 p2i(start_address), p2i(last_address)); 791 assert(start_address > prev_last_addr, 792 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 793 p2i(start_address), p2i(prev_last_addr)); 794 size_used += ranges[i].byte_size(); 795 prev_last_addr = last_address; 796 797 HeapRegion* start_region = _hrm->addr_to_region(start_address); 798 HeapRegion* last_region = _hrm->addr_to_region(last_address); 799 800 // Check for ranges that start in the same G1 region in which the previous 801 // range ended, and adjust the start address so we don't try to free 802 // the same region again. If the current range is entirely within that 803 // region, skip it. 804 if (start_region == prev_last_region) { 805 start_address = start_region->end(); 806 if (start_address > last_address) { 807 continue; 808 } 809 start_region = _hrm->addr_to_region(start_address); 810 } 811 prev_last_region = last_region; 812 813 // After verifying that each region was marked as an archive region by 814 // alloc_archive_regions, set it free and empty and uncommit it. 815 HeapRegion* curr_region = start_region; 816 while (curr_region != NULL) { 817 guarantee(curr_region->is_archive(), 818 "Expected archive region at index %u", curr_region->hrm_index()); 819 uint curr_index = curr_region->hrm_index(); 820 _archive_set.remove(curr_region); 821 curr_region->set_free(); 822 curr_region->set_top(curr_region->bottom()); 823 if (curr_region != last_region) { 824 curr_region = _hrm->next_region_in_heap(curr_region); 825 } else { 826 curr_region = NULL; 827 } 828 _hrm->shrink_at(curr_index, 1); 829 uncommitted_regions++; 830 } 831 832 // Notify mark-sweep that this is no longer an archive range. 833 G1ArchiveAllocator::clear_range_archive(ranges[i], is_open); 834 } 835 836 if (uncommitted_regions != 0) { 837 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 838 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 839 } 840 decrease_used(size_used); 841 } 842 843 oop G1CollectedHeap::materialize_archived_object(oop obj) { 844 assert(obj != NULL, "archived obj is NULL"); 845 assert(G1ArchiveAllocator::is_archived_object(obj), "must be archived object"); 846 847 // Loading an archived object makes it strongly reachable. If it is 848 // loaded during concurrent marking, it must be enqueued to the SATB 849 // queue, shading the previously white object gray. 850 G1BarrierSet::enqueue(obj); 851 852 return obj; 853 } 854 855 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) { 856 ResourceMark rm; // For retrieving the thread names in log messages. 857 858 // The structure of this method has a lot of similarities to 859 // attempt_allocation_slow(). The reason these two were not merged 860 // into a single one is that such a method would require several "if 861 // allocation is not humongous do this, otherwise do that" 862 // conditional paths which would obscure its flow. In fact, an early 863 // version of this code did use a unified method which was harder to 864 // follow and, as a result, it had subtle bugs that were hard to 865 // track down. So keeping these two methods separate allows each to 866 // be more readable. It will be good to keep these two in sync as 867 // much as possible. 868 869 assert_heap_not_locked_and_not_at_safepoint(); 870 assert(is_humongous(word_size), "attempt_allocation_humongous() " 871 "should only be called for humongous allocations"); 872 873 // Humongous objects can exhaust the heap quickly, so we should check if we 874 // need to start a marking cycle at each humongous object allocation. We do 875 // the check before we do the actual allocation. The reason for doing it 876 // before the allocation is that we avoid having to keep track of the newly 877 // allocated memory while we do a GC. 878 if (policy()->need_to_start_conc_mark("concurrent humongous allocation", 879 word_size)) { 880 collect(GCCause::_g1_humongous_allocation); 881 } 882 883 // We will loop until a) we manage to successfully perform the 884 // allocation or b) we successfully schedule a collection which 885 // fails to perform the allocation. b) is the only case when we'll 886 // return NULL. 887 HeapWord* result = NULL; 888 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 889 bool should_try_gc; 890 uint gc_count_before; 891 892 893 { 894 MutexLocker x(Heap_lock); 895 896 // Given that humongous objects are not allocated in young 897 // regions, we'll first try to do the allocation without doing a 898 // collection hoping that there's enough space in the heap. 899 result = humongous_obj_allocate(word_size); 900 if (result != NULL) { 901 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 902 policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 903 return result; 904 } 905 906 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 907 // the GCLocker initiated GC has been performed and then retry. This includes 908 // the case when the GC Locker is not active but has not been performed. 909 should_try_gc = !GCLocker::needs_gc(); 910 // Read the GC count while still holding the Heap_lock. 911 gc_count_before = total_collections(); 912 } 913 914 if (should_try_gc) { 915 bool succeeded; 916 result = do_collection_pause(word_size, gc_count_before, &succeeded, 917 GCCause::_g1_humongous_allocation); 918 if (result != NULL) { 919 assert(succeeded, "only way to get back a non-NULL result"); 920 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 921 Thread::current()->name(), p2i(result)); 922 return result; 923 } 924 925 if (succeeded) { 926 // We successfully scheduled a collection which failed to allocate. No 927 // point in trying to allocate further. We'll just return NULL. 928 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 929 SIZE_FORMAT " words", Thread::current()->name(), word_size); 930 return NULL; 931 } 932 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "", 933 Thread::current()->name(), word_size); 934 } else { 935 // Failed to schedule a collection. 936 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 937 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 938 SIZE_FORMAT " words", Thread::current()->name(), word_size); 939 return NULL; 940 } 941 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 942 // The GCLocker is either active or the GCLocker initiated 943 // GC has not yet been performed. Stall until it is and 944 // then retry the allocation. 945 GCLocker::stall_until_clear(); 946 gclocker_retry_count += 1; 947 } 948 949 950 // We can reach here if we were unsuccessful in scheduling a 951 // collection (because another thread beat us to it) or if we were 952 // stalled due to the GC locker. In either can we should retry the 953 // allocation attempt in case another thread successfully 954 // performed a collection and reclaimed enough space. 955 // Humongous object allocation always needs a lock, so we wait for the retry 956 // in the next iteration of the loop, unlike for the regular iteration case. 957 // Give a warning if we seem to be looping forever. 958 959 if ((QueuedAllocationWarningCount > 0) && 960 (try_count % QueuedAllocationWarningCount == 0)) { 961 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 962 Thread::current()->name(), try_count, word_size); 963 } 964 } 965 966 ShouldNotReachHere(); 967 return NULL; 968 } 969 970 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 971 bool expect_null_mutator_alloc_region) { 972 assert_at_safepoint_on_vm_thread(); 973 assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region, 974 "the current alloc region was unexpectedly found to be non-NULL"); 975 976 if (!is_humongous(word_size)) { 977 return _allocator->attempt_allocation_locked(word_size); 978 } else { 979 HeapWord* result = humongous_obj_allocate(word_size); 980 if (result != NULL && policy()->need_to_start_conc_mark("STW humongous allocation")) { 981 collector_state()->set_initiate_conc_mark_if_possible(true); 982 } 983 return result; 984 } 985 986 ShouldNotReachHere(); 987 } 988 989 class PostCompactionPrinterClosure: public HeapRegionClosure { 990 private: 991 G1HRPrinter* _hr_printer; 992 public: 993 bool do_heap_region(HeapRegion* hr) { 994 assert(!hr->is_young(), "not expecting to find young regions"); 995 _hr_printer->post_compaction(hr); 996 return false; 997 } 998 999 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1000 : _hr_printer(hr_printer) { } 1001 }; 1002 1003 void G1CollectedHeap::print_hrm_post_compaction() { 1004 if (_hr_printer.is_active()) { 1005 PostCompactionPrinterClosure cl(hr_printer()); 1006 heap_region_iterate(&cl); 1007 } 1008 } 1009 1010 void G1CollectedHeap::abort_concurrent_cycle() { 1011 // If we start the compaction before the CM threads finish 1012 // scanning the root regions we might trip them over as we'll 1013 // be moving objects / updating references. So let's wait until 1014 // they are done. By telling them to abort, they should complete 1015 // early. 1016 _cm->root_regions()->abort(); 1017 _cm->root_regions()->wait_until_scan_finished(); 1018 1019 // Disable discovery and empty the discovered lists 1020 // for the CM ref processor. 1021 _ref_processor_cm->disable_discovery(); 1022 _ref_processor_cm->abandon_partial_discovery(); 1023 _ref_processor_cm->verify_no_references_recorded(); 1024 1025 // Abandon current iterations of concurrent marking and concurrent 1026 // refinement, if any are in progress. 1027 concurrent_mark()->concurrent_cycle_abort(); 1028 1029 // Wait for the finish of concurrent heap resize 1030 concurrent_heap_resize()->wait_for_concurrent_work_finish(); 1031 } 1032 1033 void G1CollectedHeap::prepare_heap_for_full_collection() { 1034 // Make sure we'll choose a new allocation region afterwards. 1035 _allocator->release_mutator_alloc_regions(); 1036 _allocator->abandon_gc_alloc_regions(); 1037 1038 // We may have added regions to the current incremental collection 1039 // set between the last GC or pause and now. We need to clear the 1040 // incremental collection set and then start rebuilding it afresh 1041 // after this full GC. 1042 abandon_collection_set(collection_set()); 1043 1044 tear_down_region_sets(false /* free_list_only */); 1045 1046 hrm()->prepare_for_full_collection_start(); 1047 } 1048 1049 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1050 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1051 assert_used_and_recalculate_used_equal(this); 1052 _verifier->verify_region_sets_optional(); 1053 _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull); 1054 _verifier->check_bitmaps("Full GC Start"); 1055 } 1056 1057 void G1CollectedHeap::prepare_heap_for_mutators(bool explicit_gc) { 1058 hrm()->prepare_for_full_collection_end(); 1059 1060 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1061 ClassLoaderDataGraph::purge(); 1062 MetaspaceUtils::verify_metrics(); 1063 1064 // Prepare heap for normal collections. 1065 assert(num_free_regions() == 0, "we should not have added any free regions"); 1066 rebuild_region_sets(false /* free_list_only */); 1067 abort_refinement(); 1068 1069 // If explicit full GC, we will limit within SoftMaxHeapSize 1070 resize_heap_if_necessary(explicit_gc); 1071 1072 // Rebuild the strong code root lists for each region 1073 rebuild_strong_code_roots(); 1074 1075 // Purge code root memory 1076 purge_code_root_memory(); 1077 1078 // Start a new incremental collection set for the next pause 1079 start_new_collection_set(); 1080 1081 _allocator->init_mutator_alloc_regions(); 1082 1083 // Post collection state updates. 1084 MetaspaceGC::compute_new_size(); 1085 } 1086 1087 void G1CollectedHeap::abort_refinement() { 1088 if (_hot_card_cache->use_cache()) { 1089 _hot_card_cache->reset_hot_cache(); 1090 } 1091 1092 // Discard all remembered set updates. 1093 G1BarrierSet::dirty_card_queue_set().abandon_logs(); 1094 assert(G1BarrierSet::dirty_card_queue_set().num_cards() == 0, 1095 "DCQS should be empty"); 1096 } 1097 1098 void G1CollectedHeap::verify_after_full_collection() { 1099 _hrm->verify_optional(); 1100 _verifier->verify_region_sets_optional(); 1101 _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull); 1102 // Clear the previous marking bitmap, if needed for bitmap verification. 1103 // Note we cannot do this when we clear the next marking bitmap in 1104 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1105 // objects marked during a full GC against the previous bitmap. 1106 // But we need to clear it before calling check_bitmaps below since 1107 // the full GC has compacted objects and updated TAMS but not updated 1108 // the prev bitmap. 1109 if (G1VerifyBitmaps) { 1110 GCTraceTime(Debug, gc) tm("Clear Prev Bitmap for Verification"); 1111 _cm->clear_prev_bitmap(workers()); 1112 } 1113 // This call implicitly verifies that the next bitmap is clear after Full GC. 1114 _verifier->check_bitmaps("Full GC End"); 1115 1116 // At this point there should be no regions in the 1117 // entire heap tagged as young. 1118 assert(check_young_list_empty(), "young list should be empty at this point"); 1119 1120 // Note: since we've just done a full GC, concurrent 1121 // marking is no longer active. Therefore we need not 1122 // re-enable reference discovery for the CM ref processor. 1123 // That will be done at the start of the next marking cycle. 1124 // We also know that the STW processor should no longer 1125 // discover any new references. 1126 assert(!_ref_processor_stw->discovery_enabled(), "Postcondition"); 1127 assert(!_ref_processor_cm->discovery_enabled(), "Postcondition"); 1128 _ref_processor_stw->verify_no_references_recorded(); 1129 _ref_processor_cm->verify_no_references_recorded(); 1130 } 1131 1132 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1133 // Post collection logging. 1134 // We should do this after we potentially resize the heap so 1135 // that all the COMMIT / UNCOMMIT events are generated before 1136 // the compaction events. 1137 print_hrm_post_compaction(); 1138 heap_transition->print(); 1139 print_heap_after_gc(); 1140 print_heap_regions(); 1141 #ifdef TRACESPINNING 1142 ParallelTaskTerminator::print_termination_counts(); 1143 #endif 1144 } 1145 1146 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1147 bool clear_all_soft_refs) { 1148 assert_at_safepoint_on_vm_thread(); 1149 1150 if (GCLocker::check_active_before_gc()) { 1151 // Full GC was not completed. 1152 return false; 1153 } 1154 1155 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1156 soft_ref_policy()->should_clear_all_soft_refs(); 1157 1158 G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs); 1159 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1160 1161 collector.prepare_collection(); 1162 collector.collect(); 1163 collector.complete_collection(); 1164 1165 // Full collection was successfully completed. 1166 return true; 1167 } 1168 1169 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1170 // Currently, there is no facility in the do_full_collection(bool) API to notify 1171 // the caller that the collection did not succeed (e.g., because it was locked 1172 // out by the GC locker). So, right now, we'll ignore the return value. 1173 bool dummy = do_full_collection(true, /* explicit_gc */ 1174 clear_all_soft_refs); 1175 } 1176 1177 void G1CollectedHeap::resize_heap_if_necessary(bool limit_within_soft_max_heap_size) { 1178 assert_at_safepoint_on_vm_thread(); 1179 1180 // Capacity, free and used after the GC counted as full regions to 1181 // include the waste in the following calculations. 1182 const size_t capacity_after_gc = capacity(); 1183 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes(); 1184 1185 // This is enforced in arguments.cpp. 1186 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1187 "otherwise the code below doesn't make sense"); 1188 1189 // We don't have floating point command-line arguments 1190 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1191 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1192 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1193 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1194 1195 // Try to limit within SoftMaxHeapSize if possible 1196 size_t max_heap_size_limit = 0; 1197 size_t min_heap_size_limit = 0; 1198 if (limit_within_soft_max_heap_size && (capacity() <= SoftMaxHeapSize)) { 1199 max_heap_size_limit = SoftMaxHeapSize; 1200 min_heap_size_limit = MIN2(SoftMaxHeapSize, MinHeapSize); 1201 } else { 1202 max_heap_size_limit = MaxHeapSize; 1203 min_heap_size_limit = MinHeapSize; 1204 } 1205 1206 1207 // We have to be careful here as these two calculations can overflow 1208 // 32-bit size_t's. 1209 double used_after_gc_d = (double) used_after_gc; 1210 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1211 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1212 1213 // Let's make sure that they are both under the max heap size, which 1214 // by default will make them fit into a size_t. 1215 double desired_capacity_upper_bound = (double) max_heap_size_limit; 1216 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1217 desired_capacity_upper_bound); 1218 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1219 desired_capacity_upper_bound); 1220 1221 // We can now safely turn them into size_t's. 1222 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1223 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1224 1225 // This assert only makes sense here, before we adjust them 1226 // with respect to the min and max heap size. 1227 assert(minimum_desired_capacity <= maximum_desired_capacity, 1228 "minimum_desired_capacity = " SIZE_FORMAT ", " 1229 "maximum_desired_capacity = " SIZE_FORMAT, 1230 minimum_desired_capacity, maximum_desired_capacity); 1231 1232 // Should not be greater than the heap max size. No need to adjust 1233 // it with respect to the heap min size as it's a lower bound (i.e., 1234 // we'll try to make the capacity larger than it, not smaller). 1235 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size_limit); 1236 // Should not be less than the heap min size. No need to adjust it 1237 // with respect to the heap max size as it's an upper bound (i.e., 1238 // we'll try to make the capacity smaller than it, not greater). 1239 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size_limit); 1240 1241 if (capacity_after_gc < minimum_desired_capacity) { 1242 // Don't expand unless it's significant 1243 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1244 1245 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity). " 1246 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1247 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1248 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio); 1249 1250 expand(expand_bytes, _workers); 1251 1252 // No expansion, now see if we want to shrink 1253 } else if (capacity_after_gc > maximum_desired_capacity) { 1254 // Capacity too large, compute shrinking size 1255 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1256 1257 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity). " 1258 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1259 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1260 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio); 1261 1262 shrink(shrink_bytes); 1263 } 1264 } 1265 1266 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1267 bool do_gc, 1268 bool clear_all_soft_refs, 1269 bool expect_null_mutator_alloc_region, 1270 bool* gc_succeeded) { 1271 *gc_succeeded = true; 1272 // Let's attempt the allocation first. 1273 HeapWord* result = 1274 attempt_allocation_at_safepoint(word_size, 1275 expect_null_mutator_alloc_region); 1276 if (result != NULL) { 1277 return result; 1278 } 1279 1280 // In a G1 heap, we're supposed to keep allocation from failing by 1281 // incremental pauses. Therefore, at least for now, we'll favor 1282 // expansion over collection. (This might change in the future if we can 1283 // do something smarter than full collection to satisfy a failed alloc.) 1284 result = expand_and_allocate(word_size); 1285 if (result != NULL) { 1286 return result; 1287 } 1288 1289 if (do_gc) { 1290 // Expansion didn't work, we'll try to do a Full GC. 1291 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1292 clear_all_soft_refs); 1293 } 1294 1295 return NULL; 1296 } 1297 1298 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1299 bool* succeeded) { 1300 assert_at_safepoint_on_vm_thread(); 1301 1302 // Attempts to allocate followed by Full GC. 1303 HeapWord* result = 1304 satisfy_failed_allocation_helper(word_size, 1305 true, /* do_gc */ 1306 false, /* clear_all_soft_refs */ 1307 false, /* expect_null_mutator_alloc_region */ 1308 succeeded); 1309 1310 if (result != NULL || !*succeeded) { 1311 return result; 1312 } 1313 1314 // Attempts to allocate followed by Full GC that will collect all soft references. 1315 result = satisfy_failed_allocation_helper(word_size, 1316 true, /* do_gc */ 1317 true, /* clear_all_soft_refs */ 1318 true, /* expect_null_mutator_alloc_region */ 1319 succeeded); 1320 1321 if (result != NULL || !*succeeded) { 1322 return result; 1323 } 1324 1325 // Attempts to allocate, no GC 1326 result = satisfy_failed_allocation_helper(word_size, 1327 false, /* do_gc */ 1328 false, /* clear_all_soft_refs */ 1329 true, /* expect_null_mutator_alloc_region */ 1330 succeeded); 1331 1332 if (result != NULL) { 1333 return result; 1334 } 1335 1336 assert(!soft_ref_policy()->should_clear_all_soft_refs(), 1337 "Flag should have been handled and cleared prior to this point"); 1338 1339 // What else? We might try synchronous finalization later. If the total 1340 // space available is large enough for the allocation, then a more 1341 // complete compaction phase than we've tried so far might be 1342 // appropriate. 1343 return NULL; 1344 } 1345 1346 // Attempting to expand the heap sufficiently 1347 // to support an allocation of the given "word_size". If 1348 // successful, perform the allocation and return the address of the 1349 // allocated block, or else "NULL". 1350 1351 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1352 assert_at_safepoint_on_vm_thread(); 1353 1354 _verifier->verify_region_sets_optional(); 1355 1356 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1357 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1358 word_size * HeapWordSize); 1359 1360 1361 if (expand(expand_bytes, _workers)) { 1362 _hrm->verify_optional(); 1363 _verifier->verify_region_sets_optional(); 1364 return attempt_allocation_at_safepoint(word_size, 1365 false /* expect_null_mutator_alloc_region */); 1366 } 1367 return NULL; 1368 } 1369 1370 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1371 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1372 aligned_expand_bytes = align_up(aligned_expand_bytes, 1373 HeapRegion::GrainBytes); 1374 1375 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1376 expand_bytes, aligned_expand_bytes); 1377 1378 if (is_maximal_no_gc()) { 1379 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1380 return false; 1381 } 1382 1383 double expand_heap_start_time_sec = os::elapsedTime(); 1384 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1385 assert(regions_to_expand > 0, "Must expand by at least one region"); 1386 1387 uint expanded_by = _hrm->expand_by(regions_to_expand, pretouch_workers); 1388 if (expand_time_ms != NULL) { 1389 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1390 } 1391 1392 if (expanded_by > 0) { 1393 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1394 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1395 policy()->record_new_heap_size(num_regions()); 1396 } else { 1397 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1398 1399 // The expansion of the virtual storage space was unsuccessful. 1400 // Let's see if it was because we ran out of swap. 1401 if (G1ExitOnExpansionFailure && 1402 _hrm->available() >= regions_to_expand) { 1403 // We had head room... 1404 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1405 } 1406 } 1407 return regions_to_expand > 0; 1408 } 1409 1410 bool G1CollectedHeap::expand_single_region(uint node_index) { 1411 uint expanded_by = _hrm->expand_on_preferred_node(node_index); 1412 1413 if (expanded_by == 0) { 1414 assert(is_maximal_no_gc(), "Should be no regions left, available: %u", _hrm->available()); 1415 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1416 return false; 1417 } 1418 1419 policy()->record_new_heap_size(num_regions()); 1420 return true; 1421 } 1422 1423 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1424 size_t aligned_shrink_bytes = 1425 ReservedSpace::page_align_size_down(shrink_bytes); 1426 aligned_shrink_bytes = align_down(aligned_shrink_bytes, 1427 HeapRegion::GrainBytes); 1428 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1429 1430 uint num_regions_removed = _hrm->shrink_by(num_regions_to_remove); 1431 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1432 1433 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", 1434 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1435 if (num_regions_removed > 0) { 1436 policy()->record_new_heap_size(num_regions()); 1437 } else { 1438 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1439 } 1440 } 1441 1442 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1443 _verifier->verify_region_sets_optional(); 1444 1445 // We should only reach here at the end of a Full GC or during Remark which 1446 // means we should not not be holding to any GC alloc regions. The method 1447 // below will make sure of that and do any remaining clean up. 1448 _allocator->abandon_gc_alloc_regions(); 1449 1450 // Instead of tearing down / rebuilding the free lists here, we 1451 // could instead use the remove_all_pending() method on free_list to 1452 // remove only the ones that we need to remove. 1453 tear_down_region_sets(true /* free_list_only */); 1454 shrink_helper(shrink_bytes); 1455 rebuild_region_sets(true /* free_list_only */); 1456 1457 _hrm->verify_optional(); 1458 _verifier->verify_region_sets_optional(); 1459 } 1460 1461 class OldRegionSetChecker : public HeapRegionSetChecker { 1462 public: 1463 void check_mt_safety() { 1464 // Master Old Set MT safety protocol: 1465 // (a) If we're at a safepoint, operations on the master old set 1466 // should be invoked: 1467 // - by the VM thread (which will serialize them), or 1468 // - by the GC workers while holding the FreeList_lock, if we're 1469 // at a safepoint for an evacuation pause (this lock is taken 1470 // anyway when an GC alloc region is retired so that a new one 1471 // is allocated from the free list), or 1472 // - by the GC workers while holding the OldSets_lock, if we're at a 1473 // safepoint for a cleanup pause. 1474 // (b) If we're not at a safepoint, operations on the master old set 1475 // should be invoked while holding the Heap_lock. 1476 1477 if (SafepointSynchronize::is_at_safepoint()) { 1478 guarantee(Thread::current()->is_VM_thread() || 1479 FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(), 1480 "master old set MT safety protocol at a safepoint"); 1481 } else { 1482 guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint"); 1483 } 1484 } 1485 bool is_correct_type(HeapRegion* hr) { return hr->is_old(); } 1486 const char* get_description() { return "Old Regions"; } 1487 }; 1488 1489 class ArchiveRegionSetChecker : public HeapRegionSetChecker { 1490 public: 1491 void check_mt_safety() { 1492 guarantee(!Universe::is_fully_initialized() || SafepointSynchronize::is_at_safepoint(), 1493 "May only change archive regions during initialization or safepoint."); 1494 } 1495 bool is_correct_type(HeapRegion* hr) { return hr->is_archive(); } 1496 const char* get_description() { return "Archive Regions"; } 1497 }; 1498 1499 class HumongousRegionSetChecker : public HeapRegionSetChecker { 1500 public: 1501 void check_mt_safety() { 1502 // Humongous Set MT safety protocol: 1503 // (a) If we're at a safepoint, operations on the master humongous 1504 // set should be invoked by either the VM thread (which will 1505 // serialize them) or by the GC workers while holding the 1506 // OldSets_lock. 1507 // (b) If we're not at a safepoint, operations on the master 1508 // humongous set should be invoked while holding the Heap_lock. 1509 1510 if (SafepointSynchronize::is_at_safepoint()) { 1511 guarantee(Thread::current()->is_VM_thread() || 1512 OldSets_lock->owned_by_self(), 1513 "master humongous set MT safety protocol at a safepoint"); 1514 } else { 1515 guarantee(Heap_lock->owned_by_self(), 1516 "master humongous set MT safety protocol outside a safepoint"); 1517 } 1518 } 1519 bool is_correct_type(HeapRegion* hr) { return hr->is_humongous(); } 1520 const char* get_description() { return "Humongous Regions"; } 1521 }; 1522 1523 G1CollectedHeap::G1CollectedHeap() : 1524 CollectedHeap(), 1525 _young_gen_sampling_thread(NULL), 1526 _workers(NULL), 1527 _card_table(NULL), 1528 _soft_ref_policy(), 1529 _old_set("Old Region Set", new OldRegionSetChecker()), 1530 _archive_set("Archive Region Set", new ArchiveRegionSetChecker()), 1531 _humongous_set("Humongous Region Set", new HumongousRegionSetChecker()), 1532 _bot(NULL), 1533 _listener(), 1534 _numa(G1NUMA::create()), 1535 _hrm(NULL), 1536 _allocator(NULL), 1537 _verifier(NULL), 1538 _summary_bytes_used(0), 1539 _bytes_used_during_gc(0), 1540 _archive_allocator(NULL), 1541 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1542 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1543 _expand_heap_after_alloc_failure(true), 1544 _prev_soft_max_heap_size(MaxHeapSize), 1545 _g1mm(NULL), 1546 _humongous_reclaim_candidates(), 1547 _has_humongous_reclaim_candidates(false), 1548 _hr_printer(), 1549 _collector_state(), 1550 _old_marking_cycles_started(0), 1551 _old_marking_cycles_completed(0), 1552 _eden(), 1553 _survivor(), 1554 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1555 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1556 _policy(G1Policy::create_policy(_gc_timer_stw)), 1557 _heap_sizing_policy(NULL), 1558 _collection_set(this, _policy), 1559 _hot_card_cache(NULL), 1560 _rem_set(NULL), 1561 _cm(NULL), 1562 _cm_thread(NULL), 1563 _cr(NULL), 1564 _concurrent_heap_resize(NULL), 1565 _concurrent_heap_resize_thread(NULL), 1566 _task_queues(NULL), 1567 _evacuation_failed(false), 1568 _evacuation_failed_info_array(NULL), 1569 _preserved_marks_set(true /* in_c_heap */), 1570 #ifndef PRODUCT 1571 _evacuation_failure_alot_for_current_gc(false), 1572 _evacuation_failure_alot_gc_number(0), 1573 _evacuation_failure_alot_count(0), 1574 #endif 1575 _ref_processor_stw(NULL), 1576 _is_alive_closure_stw(this), 1577 _is_subject_to_discovery_stw(this), 1578 _ref_processor_cm(NULL), 1579 _is_alive_closure_cm(this), 1580 _is_subject_to_discovery_cm(this), 1581 _region_attr() { 1582 1583 _verifier = new G1HeapVerifier(this); 1584 1585 _allocator = new G1Allocator(this); 1586 1587 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _policy->analytics()); 1588 1589 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1590 1591 // Override the default _filler_array_max_size so that no humongous filler 1592 // objects are created. 1593 _filler_array_max_size = _humongous_object_threshold_in_words; 1594 1595 uint n_queues = ParallelGCThreads; 1596 _task_queues = new RefToScanQueueSet(n_queues); 1597 1598 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1599 1600 for (uint i = 0; i < n_queues; i++) { 1601 RefToScanQueue* q = new RefToScanQueue(); 1602 q->initialize(); 1603 _task_queues->register_queue(i, q); 1604 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1605 } 1606 1607 // Initialize the G1EvacuationFailureALot counters and flags. 1608 NOT_PRODUCT(reset_evacuation_should_fail();) 1609 _gc_tracer_stw->initialize(); 1610 1611 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1612 } 1613 1614 static size_t actual_reserved_page_size(ReservedSpace rs) { 1615 size_t page_size = os::vm_page_size(); 1616 if (UseLargePages) { 1617 // There are two ways to manage large page memory. 1618 // 1. OS supports committing large page memory. 1619 // 2. OS doesn't support committing large page memory so ReservedSpace manages it. 1620 // And ReservedSpace calls it 'special'. If we failed to set 'special', 1621 // we reserved memory without large page. 1622 if (os::can_commit_large_page_memory() || rs.special()) { 1623 // An alignment at ReservedSpace comes from preferred page size or 1624 // heap alignment, and if the alignment came from heap alignment, it could be 1625 // larger than large pages size. So need to cap with the large page size. 1626 page_size = MIN2(rs.alignment(), os::large_page_size()); 1627 } 1628 } 1629 1630 return page_size; 1631 } 1632 1633 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1634 size_t size, 1635 size_t translation_factor) { 1636 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1637 // Allocate a new reserved space, preferring to use large pages. 1638 ReservedSpace rs(size, preferred_page_size); 1639 size_t page_size = actual_reserved_page_size(rs); 1640 G1RegionToSpaceMapper* result = 1641 G1RegionToSpaceMapper::create_mapper(rs, 1642 size, 1643 page_size, 1644 HeapRegion::GrainBytes, 1645 translation_factor, 1646 mtGC); 1647 1648 os::trace_page_sizes_for_requested_size(description, 1649 size, 1650 preferred_page_size, 1651 page_size, 1652 rs.base(), 1653 rs.size()); 1654 1655 return result; 1656 } 1657 1658 jint G1CollectedHeap::initialize_concurrent_refinement() { 1659 jint ecode = JNI_OK; 1660 _cr = G1ConcurrentRefine::create(&ecode); 1661 return ecode; 1662 } 1663 1664 jint G1CollectedHeap::initialize_young_gen_sampling_thread() { 1665 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread(); 1666 if (_young_gen_sampling_thread->osthread() == NULL) { 1667 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread"); 1668 return JNI_ENOMEM; 1669 } 1670 return JNI_OK; 1671 } 1672 1673 jint G1CollectedHeap::initialize() { 1674 1675 // Necessary to satisfy locking discipline assertions. 1676 1677 MutexLocker x(Heap_lock); 1678 1679 // While there are no constraints in the GC code that HeapWordSize 1680 // be any particular value, there are multiple other areas in the 1681 // system which believe this to be true (e.g. oop->object_size in some 1682 // cases incorrectly returns the size in wordSize units rather than 1683 // HeapWordSize). 1684 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1685 1686 size_t init_byte_size = InitialHeapSize; 1687 size_t reserved_byte_size = G1Arguments::heap_reserved_size_bytes(); 1688 1689 // Ensure that the sizes are properly aligned. 1690 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1691 Universe::check_alignment(reserved_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1692 Universe::check_alignment(reserved_byte_size, HeapAlignment, "g1 heap"); 1693 1694 // Reserve the maximum. 1695 1696 // When compressed oops are enabled, the preferred heap base 1697 // is calculated by subtracting the requested size from the 1698 // 32Gb boundary and using the result as the base address for 1699 // heap reservation. If the requested size is not aligned to 1700 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1701 // into the ReservedHeapSpace constructor) then the actual 1702 // base of the reserved heap may end up differing from the 1703 // address that was requested (i.e. the preferred heap base). 1704 // If this happens then we could end up using a non-optimal 1705 // compressed oops mode. 1706 1707 ReservedHeapSpace heap_rs = Universe::reserve_heap(reserved_byte_size, 1708 HeapAlignment); 1709 1710 initialize_reserved_region(heap_rs); 1711 1712 // Create the barrier set for the entire reserved region. 1713 G1CardTable* ct = new G1CardTable(heap_rs.region()); 1714 ct->initialize(); 1715 G1BarrierSet* bs = new G1BarrierSet(ct); 1716 bs->initialize(); 1717 assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity"); 1718 BarrierSet::set_barrier_set(bs); 1719 _card_table = ct; 1720 1721 { 1722 G1SATBMarkQueueSet& satbqs = bs->satb_mark_queue_set(); 1723 satbqs.set_process_completed_buffers_threshold(G1SATBProcessCompletedThreshold); 1724 satbqs.set_buffer_enqueue_threshold_percentage(G1SATBBufferEnqueueingThresholdPercent); 1725 } 1726 1727 // Create the hot card cache. 1728 _hot_card_cache = new G1HotCardCache(this); 1729 1730 // Carve out the G1 part of the heap. 1731 ReservedSpace g1_rs = heap_rs.first_part(reserved_byte_size); 1732 size_t page_size = actual_reserved_page_size(heap_rs); 1733 G1RegionToSpaceMapper* heap_storage = 1734 G1RegionToSpaceMapper::create_heap_mapper(g1_rs, 1735 g1_rs.size(), 1736 page_size, 1737 HeapRegion::GrainBytes, 1738 1, 1739 mtJavaHeap); 1740 if(heap_storage == NULL) { 1741 vm_shutdown_during_initialization("Could not initialize G1 heap"); 1742 return JNI_ERR; 1743 } 1744 1745 os::trace_page_sizes("Heap", 1746 MinHeapSize, 1747 reserved_byte_size, 1748 page_size, 1749 heap_rs.base(), 1750 heap_rs.size()); 1751 heap_storage->set_mapping_changed_listener(&_listener); 1752 1753 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1754 G1RegionToSpaceMapper* bot_storage = 1755 create_aux_memory_mapper("Block Offset Table", 1756 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1757 G1BlockOffsetTable::heap_map_factor()); 1758 1759 G1RegionToSpaceMapper* cardtable_storage = 1760 create_aux_memory_mapper("Card Table", 1761 G1CardTable::compute_size(g1_rs.size() / HeapWordSize), 1762 G1CardTable::heap_map_factor()); 1763 1764 G1RegionToSpaceMapper* card_counts_storage = 1765 create_aux_memory_mapper("Card Counts Table", 1766 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1767 G1CardCounts::heap_map_factor()); 1768 1769 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1770 G1RegionToSpaceMapper* prev_bitmap_storage = 1771 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1772 G1RegionToSpaceMapper* next_bitmap_storage = 1773 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1774 1775 _hrm = HeapRegionManager::create_manager(this); 1776 1777 _hrm->initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1778 _card_table->initialize(cardtable_storage); 1779 1780 // Do later initialization work for concurrent refinement. 1781 _hot_card_cache->initialize(card_counts_storage); 1782 1783 // 6843694 - ensure that the maximum region index can fit 1784 // in the remembered set structures. 1785 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1786 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1787 1788 // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not 1789 // start within the first card. 1790 guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card."); 1791 // Also create a G1 rem set. 1792 _rem_set = new G1RemSet(this, _card_table, _hot_card_cache); 1793 _rem_set->initialize(max_reserved_capacity(), max_regions()); 1794 1795 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1796 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1797 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1798 "too many cards per region"); 1799 1800 FreeRegionList::set_unrealistically_long_length(max_expandable_regions() + 1); 1801 1802 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1803 1804 { 1805 HeapWord* start = _hrm->reserved().start(); 1806 HeapWord* end = _hrm->reserved().end(); 1807 size_t granularity = HeapRegion::GrainBytes; 1808 1809 _region_attr.initialize(start, end, granularity); 1810 _humongous_reclaim_candidates.initialize(start, end, granularity); 1811 } 1812 1813 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1814 true /* are_GC_task_threads */, 1815 false /* are_ConcurrentGC_threads */); 1816 if (_workers == NULL) { 1817 return JNI_ENOMEM; 1818 } 1819 _workers->initialize_workers(); 1820 1821 _numa->set_region_info(HeapRegion::GrainBytes, page_size); 1822 1823 // Create the G1ConcurrentMark data structure and thread. 1824 // (Must do this late, so that "max_regions" is defined.) 1825 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1826 if (_cm == NULL || !_cm->completed_initialization()) { 1827 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1828 return JNI_ENOMEM; 1829 } 1830 _cm_thread = _cm->cm_thread(); 1831 1832 _concurrent_heap_resize = new G1ConcurrentHeapResize(this, _hrm); 1833 if (_concurrent_heap_resize == NULL || !_concurrent_heap_resize->completed_initialization()) { 1834 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentHeapResize"); 1835 return JNI_ENOMEM; 1836 } 1837 _concurrent_heap_resize_thread = _concurrent_heap_resize->resize_thread(); 1838 1839 // Now expand into the initial heap size. 1840 if (!expand(init_byte_size, _workers)) { 1841 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1842 return JNI_ENOMEM; 1843 } 1844 1845 // Perform any initialization actions delegated to the policy. 1846 policy()->init(this, &_collection_set); 1847 1848 jint ecode = initialize_concurrent_refinement(); 1849 if (ecode != JNI_OK) { 1850 return ecode; 1851 } 1852 1853 ecode = initialize_young_gen_sampling_thread(); 1854 if (ecode != JNI_OK) { 1855 return ecode; 1856 } 1857 1858 { 1859 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 1860 dcqs.set_process_cards_threshold(concurrent_refine()->yellow_zone()); 1861 dcqs.set_max_cards(concurrent_refine()->red_zone()); 1862 } 1863 1864 // Here we allocate the dummy HeapRegion that is required by the 1865 // G1AllocRegion class. 1866 HeapRegion* dummy_region = _hrm->get_dummy_region(); 1867 1868 // We'll re-use the same region whether the alloc region will 1869 // require BOT updates or not and, if it doesn't, then a non-young 1870 // region will complain that it cannot support allocations without 1871 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1872 dummy_region->set_eden(); 1873 // Make sure it's full. 1874 dummy_region->set_top(dummy_region->end()); 1875 G1AllocRegion::setup(this, dummy_region); 1876 1877 _allocator->init_mutator_alloc_regions(); 1878 1879 // Do create of the monitoring and management support so that 1880 // values in the heap have been properly initialized. 1881 _g1mm = new G1MonitoringSupport(this); 1882 1883 G1StringDedup::initialize(); 1884 1885 _preserved_marks_set.init(ParallelGCThreads); 1886 1887 _collection_set.initialize(max_regions()); 1888 1889 return JNI_OK; 1890 } 1891 1892 void G1CollectedHeap::stop() { 1893 // Stop all concurrent threads. We do this to make sure these threads 1894 // do not continue to execute and access resources (e.g. logging) 1895 // that are destroyed during shutdown. 1896 _cr->stop(); 1897 _young_gen_sampling_thread->stop(); 1898 _cm_thread->stop(); 1899 _concurrent_heap_resize_thread->stop(); 1900 if (G1StringDedup::is_enabled()) { 1901 G1StringDedup::stop(); 1902 } 1903 } 1904 1905 void G1CollectedHeap::safepoint_synchronize_begin() { 1906 SuspendibleThreadSet::synchronize(); 1907 } 1908 1909 void G1CollectedHeap::safepoint_synchronize_end() { 1910 SuspendibleThreadSet::desynchronize(); 1911 } 1912 1913 void G1CollectedHeap::post_initialize() { 1914 CollectedHeap::post_initialize(); 1915 ref_processing_init(); 1916 } 1917 1918 void G1CollectedHeap::ref_processing_init() { 1919 // Reference processing in G1 currently works as follows: 1920 // 1921 // * There are two reference processor instances. One is 1922 // used to record and process discovered references 1923 // during concurrent marking; the other is used to 1924 // record and process references during STW pauses 1925 // (both full and incremental). 1926 // * Both ref processors need to 'span' the entire heap as 1927 // the regions in the collection set may be dotted around. 1928 // 1929 // * For the concurrent marking ref processor: 1930 // * Reference discovery is enabled at initial marking. 1931 // * Reference discovery is disabled and the discovered 1932 // references processed etc during remarking. 1933 // * Reference discovery is MT (see below). 1934 // * Reference discovery requires a barrier (see below). 1935 // * Reference processing may or may not be MT 1936 // (depending on the value of ParallelRefProcEnabled 1937 // and ParallelGCThreads). 1938 // * A full GC disables reference discovery by the CM 1939 // ref processor and abandons any entries on it's 1940 // discovered lists. 1941 // 1942 // * For the STW processor: 1943 // * Non MT discovery is enabled at the start of a full GC. 1944 // * Processing and enqueueing during a full GC is non-MT. 1945 // * During a full GC, references are processed after marking. 1946 // 1947 // * Discovery (may or may not be MT) is enabled at the start 1948 // of an incremental evacuation pause. 1949 // * References are processed near the end of a STW evacuation pause. 1950 // * For both types of GC: 1951 // * Discovery is atomic - i.e. not concurrent. 1952 // * Reference discovery will not need a barrier. 1953 1954 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1); 1955 1956 // Concurrent Mark ref processor 1957 _ref_processor_cm = 1958 new ReferenceProcessor(&_is_subject_to_discovery_cm, 1959 mt_processing, // mt processing 1960 ParallelGCThreads, // degree of mt processing 1961 (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery 1962 MAX2(ParallelGCThreads, ConcGCThreads), // degree of mt discovery 1963 false, // Reference discovery is not atomic 1964 &_is_alive_closure_cm, // is alive closure 1965 true); // allow changes to number of processing threads 1966 1967 // STW ref processor 1968 _ref_processor_stw = 1969 new ReferenceProcessor(&_is_subject_to_discovery_stw, 1970 mt_processing, // mt processing 1971 ParallelGCThreads, // degree of mt processing 1972 (ParallelGCThreads > 1), // mt discovery 1973 ParallelGCThreads, // degree of mt discovery 1974 true, // Reference discovery is atomic 1975 &_is_alive_closure_stw, // is alive closure 1976 true); // allow changes to number of processing threads 1977 } 1978 1979 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() { 1980 return &_soft_ref_policy; 1981 } 1982 1983 size_t G1CollectedHeap::capacity() const { 1984 return _hrm->length() * HeapRegion::GrainBytes; 1985 } 1986 1987 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const { 1988 return _hrm->total_free_bytes(); 1989 } 1990 1991 void G1CollectedHeap::iterate_hcc_closure(G1CardTableEntryClosure* cl, uint worker_id) { 1992 _hot_card_cache->drain(cl, worker_id); 1993 } 1994 1995 // Computes the sum of the storage used by the various regions. 1996 size_t G1CollectedHeap::used() const { 1997 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 1998 if (_archive_allocator != NULL) { 1999 result += _archive_allocator->used(); 2000 } 2001 return result; 2002 } 2003 2004 size_t G1CollectedHeap::used_unlocked() const { 2005 return _summary_bytes_used; 2006 } 2007 2008 class SumUsedClosure: public HeapRegionClosure { 2009 size_t _used; 2010 public: 2011 SumUsedClosure() : _used(0) {} 2012 bool do_heap_region(HeapRegion* r) { 2013 _used += r->used(); 2014 return false; 2015 } 2016 size_t result() { return _used; } 2017 }; 2018 2019 size_t G1CollectedHeap::recalculate_used() const { 2020 SumUsedClosure blk; 2021 heap_region_iterate(&blk); 2022 return blk.result(); 2023 } 2024 2025 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2026 switch (cause) { 2027 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2028 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2029 case GCCause::_wb_conc_mark: return true; 2030 default : return false; 2031 } 2032 } 2033 2034 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2035 switch (cause) { 2036 case GCCause::_g1_humongous_allocation: return true; 2037 case GCCause::_g1_periodic_collection: return G1PeriodicGCInvokesConcurrent; 2038 default: return is_user_requested_concurrent_full_gc(cause); 2039 } 2040 } 2041 2042 bool G1CollectedHeap::should_upgrade_to_full_gc(GCCause::Cause cause) { 2043 if (policy()->force_upgrade_to_full()) { 2044 return true; 2045 } else if (should_do_concurrent_full_gc(_gc_cause)) { 2046 return false; 2047 } else if (has_regions_left_for_allocation()) { 2048 return false; 2049 } else { 2050 return true; 2051 } 2052 } 2053 2054 #ifndef PRODUCT 2055 void G1CollectedHeap::allocate_dummy_regions() { 2056 // Let's fill up most of the region 2057 size_t word_size = HeapRegion::GrainWords - 1024; 2058 // And as a result the region we'll allocate will be humongous. 2059 guarantee(is_humongous(word_size), "sanity"); 2060 2061 // _filler_array_max_size is set to humongous object threshold 2062 // but temporarily change it to use CollectedHeap::fill_with_object(). 2063 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2064 2065 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2066 // Let's use the existing mechanism for the allocation 2067 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 2068 if (dummy_obj != NULL) { 2069 MemRegion mr(dummy_obj, word_size); 2070 CollectedHeap::fill_with_object(mr); 2071 } else { 2072 // If we can't allocate once, we probably cannot allocate 2073 // again. Let's get out of the loop. 2074 break; 2075 } 2076 } 2077 } 2078 #endif // !PRODUCT 2079 2080 void G1CollectedHeap::increment_old_marking_cycles_started() { 2081 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2082 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2083 "Wrong marking cycle count (started: %d, completed: %d)", 2084 _old_marking_cycles_started, _old_marking_cycles_completed); 2085 2086 _old_marking_cycles_started++; 2087 } 2088 2089 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2090 MonitorLocker ml(G1OldGCCount_lock, Mutex::_no_safepoint_check_flag); 2091 2092 // We assume that if concurrent == true, then the caller is a 2093 // concurrent thread that was joined the Suspendible Thread 2094 // Set. If there's ever a cheap way to check this, we should add an 2095 // assert here. 2096 2097 // Given that this method is called at the end of a Full GC or of a 2098 // concurrent cycle, and those can be nested (i.e., a Full GC can 2099 // interrupt a concurrent cycle), the number of full collections 2100 // completed should be either one (in the case where there was no 2101 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2102 // behind the number of full collections started. 2103 2104 // This is the case for the inner caller, i.e. a Full GC. 2105 assert(concurrent || 2106 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2107 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2108 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2109 "is inconsistent with _old_marking_cycles_completed = %u", 2110 _old_marking_cycles_started, _old_marking_cycles_completed); 2111 2112 // This is the case for the outer caller, i.e. the concurrent cycle. 2113 assert(!concurrent || 2114 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2115 "for outer caller (concurrent cycle): " 2116 "_old_marking_cycles_started = %u " 2117 "is inconsistent with _old_marking_cycles_completed = %u", 2118 _old_marking_cycles_started, _old_marking_cycles_completed); 2119 2120 _old_marking_cycles_completed += 1; 2121 2122 // We need to clear the "in_progress" flag in the CM thread before 2123 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2124 // is set) so that if a waiter requests another System.gc() it doesn't 2125 // incorrectly see that a marking cycle is still in progress. 2126 if (concurrent) { 2127 _cm_thread->set_idle(); 2128 } 2129 2130 // Notify threads waiting in System.gc() (with ExplicitGCInvokesConcurrent) 2131 // for a full GC to finish that their wait is over. 2132 ml.notify_all(); 2133 } 2134 2135 void G1CollectedHeap::collect(GCCause::Cause cause) { 2136 try_collect(cause); 2137 } 2138 2139 // Return true if (x < y) with allowance for wraparound. 2140 static bool gc_counter_less_than(uint x, uint y) { 2141 return (x - y) > (UINT_MAX/2); 2142 } 2143 2144 // LOG_COLLECT_CONCURRENTLY(cause, msg, args...) 2145 // Macro so msg printing is format-checked. 2146 #define LOG_COLLECT_CONCURRENTLY(cause, ...) \ 2147 do { \ 2148 LogTarget(Trace, gc) LOG_COLLECT_CONCURRENTLY_lt; \ 2149 if (LOG_COLLECT_CONCURRENTLY_lt.is_enabled()) { \ 2150 ResourceMark rm; /* For thread name. */ \ 2151 LogStream LOG_COLLECT_CONCURRENTLY_s(&LOG_COLLECT_CONCURRENTLY_lt); \ 2152 LOG_COLLECT_CONCURRENTLY_s.print("%s: Try Collect Concurrently (%s): ", \ 2153 Thread::current()->name(), \ 2154 GCCause::to_string(cause)); \ 2155 LOG_COLLECT_CONCURRENTLY_s.print(__VA_ARGS__); \ 2156 } \ 2157 } while (0) 2158 2159 #define LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, result) \ 2160 LOG_COLLECT_CONCURRENTLY(cause, "complete %s", BOOL_TO_STR(result)) 2161 2162 bool G1CollectedHeap::try_collect_concurrently(GCCause::Cause cause, 2163 uint gc_counter, 2164 uint old_marking_started_before) { 2165 assert_heap_not_locked(); 2166 assert(should_do_concurrent_full_gc(cause), 2167 "Non-concurrent cause %s", GCCause::to_string(cause)); 2168 2169 for (uint i = 1; true; ++i) { 2170 // Try to schedule an initial-mark evacuation pause that will 2171 // start a concurrent cycle. 2172 LOG_COLLECT_CONCURRENTLY(cause, "attempt %u", i); 2173 VM_G1TryInitiateConcMark op(gc_counter, 2174 cause, 2175 policy()->max_pause_time_ms()); 2176 VMThread::execute(&op); 2177 2178 // Request is trivially finished. 2179 if (cause == GCCause::_g1_periodic_collection) { 2180 LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, op.gc_succeeded()); 2181 return op.gc_succeeded(); 2182 } 2183 2184 // Lock to get consistent set of values. 2185 uint old_marking_started_after; 2186 uint old_marking_completed_after; 2187 { 2188 MutexLocker ml(Heap_lock); 2189 // Update gc_counter for retrying VMOp if needed. Captured here to be 2190 // consistent with the values we use below for termination tests. If 2191 // a retry is needed after a possible wait, and another collection 2192 // occurs in the meantime, it will cause our retry to be skipped and 2193 // we'll recheck for termination with updated conditions from that 2194 // more recent collection. That's what we want, rather than having 2195 // our retry possibly perform an unnecessary collection. 2196 gc_counter = total_collections(); 2197 old_marking_started_after = _old_marking_cycles_started; 2198 old_marking_completed_after = _old_marking_cycles_completed; 2199 } 2200 2201 if (!GCCause::is_user_requested_gc(cause)) { 2202 // For an "automatic" (not user-requested) collection, we just need to 2203 // ensure that progress is made. 2204 // 2205 // Request is finished if any of 2206 // (1) the VMOp successfully performed a GC, 2207 // (2) a concurrent cycle was already in progress, 2208 // (3) a new cycle was started (by this thread or some other), or 2209 // (4) a Full GC was performed. 2210 // Cases (3) and (4) are detected together by a change to 2211 // _old_marking_cycles_started. 2212 // 2213 // Note that (1) does not imply (3). If we're still in the mixed 2214 // phase of an earlier concurrent collection, the request to make the 2215 // collection an initial-mark won't be honored. If we don't check for 2216 // both conditions we'll spin doing back-to-back collections. 2217 if (op.gc_succeeded() || 2218 op.cycle_already_in_progress() || 2219 (old_marking_started_before != old_marking_started_after)) { 2220 LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true); 2221 return true; 2222 } 2223 } else { // User-requested GC. 2224 // For a user-requested collection, we want to ensure that a complete 2225 // full collection has been performed before returning, but without 2226 // waiting for more than needed. 2227 2228 // For user-requested GCs (unlike non-UR), a successful VMOp implies a 2229 // new cycle was started. That's good, because it's not clear what we 2230 // should do otherwise. Trying again just does back to back GCs. 2231 // Can't wait for someone else to start a cycle. And returning fails 2232 // to meet the goal of ensuring a full collection was performed. 2233 assert(!op.gc_succeeded() || 2234 (old_marking_started_before != old_marking_started_after), 2235 "invariant: succeeded %s, started before %u, started after %u", 2236 BOOL_TO_STR(op.gc_succeeded()), 2237 old_marking_started_before, old_marking_started_after); 2238 2239 // Request is finished if a full collection (concurrent or stw) 2240 // was started after this request and has completed, e.g. 2241 // started_before < completed_after. 2242 if (gc_counter_less_than(old_marking_started_before, 2243 old_marking_completed_after)) { 2244 LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true); 2245 return true; 2246 } 2247 2248 if (old_marking_started_after != old_marking_completed_after) { 2249 // If there is an in-progress cycle (possibly started by us), then 2250 // wait for that cycle to complete, e.g. 2251 // while completed_now < started_after. 2252 LOG_COLLECT_CONCURRENTLY(cause, "wait"); 2253 MonitorLocker ml(G1OldGCCount_lock); 2254 while (gc_counter_less_than(_old_marking_cycles_completed, 2255 old_marking_started_after)) { 2256 ml.wait(); 2257 } 2258 // Request is finished if the collection we just waited for was 2259 // started after this request. 2260 if (old_marking_started_before != old_marking_started_after) { 2261 LOG_COLLECT_CONCURRENTLY(cause, "complete after wait"); 2262 return true; 2263 } 2264 } 2265 2266 // If VMOp was successful then it started a new cycle that the above 2267 // wait &etc should have recognized as finishing this request. This 2268 // differs from a non-user-request, where gc_succeeded does not imply 2269 // a new cycle was started. 2270 assert(!op.gc_succeeded(), "invariant"); 2271 2272 // If VMOp failed because a cycle was already in progress, it is now 2273 // complete. But it didn't finish this user-requested GC, so try 2274 // again. 2275 if (op.cycle_already_in_progress()) { 2276 LOG_COLLECT_CONCURRENTLY(cause, "retry after in-progress"); 2277 continue; 2278 } 2279 } 2280 2281 // Collection failed and should be retried. 2282 assert(op.transient_failure(), "invariant"); 2283 2284 // If GCLocker is active, wait until clear before retrying. 2285 if (GCLocker::is_active_and_needs_gc()) { 2286 LOG_COLLECT_CONCURRENTLY(cause, "gc-locker stall"); 2287 GCLocker::stall_until_clear(); 2288 } 2289 2290 LOG_COLLECT_CONCURRENTLY(cause, "retry"); 2291 } 2292 } 2293 2294 bool G1CollectedHeap::try_collect(GCCause::Cause cause) { 2295 assert_heap_not_locked(); 2296 2297 // Lock to get consistent set of values. 2298 uint gc_count_before; 2299 uint full_gc_count_before; 2300 uint old_marking_started_before; 2301 { 2302 MutexLocker ml(Heap_lock); 2303 gc_count_before = total_collections(); 2304 full_gc_count_before = total_full_collections(); 2305 old_marking_started_before = _old_marking_cycles_started; 2306 } 2307 2308 if (should_do_concurrent_full_gc(cause)) { 2309 return try_collect_concurrently(cause, 2310 gc_count_before, 2311 old_marking_started_before); 2312 } else if (GCLocker::should_discard(cause, gc_count_before)) { 2313 // Indicate failure to be consistent with VMOp failure due to 2314 // another collection slipping in after our gc_count but before 2315 // our request is processed. 2316 return false; 2317 } else if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2318 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2319 2320 // Schedule a standard evacuation pause. We're setting word_size 2321 // to 0 which means that we are not requesting a post-GC allocation. 2322 VM_G1CollectForAllocation op(0, /* word_size */ 2323 gc_count_before, 2324 cause, 2325 policy()->max_pause_time_ms()); 2326 VMThread::execute(&op); 2327 return op.gc_succeeded(); 2328 } else { 2329 // Schedule a Full GC. 2330 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2331 VMThread::execute(&op); 2332 return op.gc_succeeded(); 2333 } 2334 } 2335 2336 bool G1CollectedHeap::is_in(const void* p) const { 2337 if (_hrm->reserved().contains(p)) { 2338 // Given that we know that p is in the reserved space, 2339 // heap_region_containing() should successfully 2340 // return the containing region. 2341 HeapRegion* hr = heap_region_containing(p); 2342 return hr->is_in(p); 2343 } else { 2344 return false; 2345 } 2346 } 2347 2348 #ifdef ASSERT 2349 bool G1CollectedHeap::is_in_exact(const void* p) const { 2350 bool contains = reserved_region().contains(p); 2351 bool available = _hrm->is_available(addr_to_region((HeapWord*)p)); 2352 if (contains && available) { 2353 return true; 2354 } else { 2355 return false; 2356 } 2357 } 2358 #endif 2359 2360 // Iteration functions. 2361 2362 // Iterates an ObjectClosure over all objects within a HeapRegion. 2363 2364 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2365 ObjectClosure* _cl; 2366 public: 2367 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2368 bool do_heap_region(HeapRegion* r) { 2369 if (!r->is_continues_humongous()) { 2370 r->object_iterate(_cl); 2371 } 2372 return false; 2373 } 2374 }; 2375 2376 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2377 IterateObjectClosureRegionClosure blk(cl); 2378 heap_region_iterate(&blk); 2379 } 2380 2381 void G1CollectedHeap::keep_alive(oop obj) { 2382 G1BarrierSet::enqueue(obj); 2383 } 2384 2385 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2386 _hrm->iterate(cl); 2387 } 2388 2389 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl, 2390 HeapRegionClaimer *hrclaimer, 2391 uint worker_id) const { 2392 _hrm->par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id)); 2393 } 2394 2395 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl, 2396 HeapRegionClaimer *hrclaimer) const { 2397 _hrm->par_iterate(cl, hrclaimer, 0); 2398 } 2399 2400 void G1CollectedHeap::collection_set_iterate_all(HeapRegionClosure* cl) { 2401 _collection_set.iterate(cl); 2402 } 2403 2404 void G1CollectedHeap::collection_set_par_iterate_all(HeapRegionClosure* cl, HeapRegionClaimer* hr_claimer, uint worker_id) { 2405 _collection_set.par_iterate(cl, hr_claimer, worker_id, workers()->active_workers()); 2406 } 2407 2408 void G1CollectedHeap::collection_set_iterate_increment_from(HeapRegionClosure *cl, HeapRegionClaimer* hr_claimer, uint worker_id) { 2409 _collection_set.iterate_incremental_part_from(cl, hr_claimer, worker_id, workers()->active_workers()); 2410 } 2411 2412 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2413 HeapRegion* hr = heap_region_containing(addr); 2414 return hr->block_start(addr); 2415 } 2416 2417 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2418 HeapRegion* hr = heap_region_containing(addr); 2419 return hr->block_is_obj(addr); 2420 } 2421 2422 bool G1CollectedHeap::supports_tlab_allocation() const { 2423 return true; 2424 } 2425 2426 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2427 return (_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2428 } 2429 2430 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2431 return _eden.length() * HeapRegion::GrainBytes; 2432 } 2433 2434 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2435 // must be equal to the humongous object limit. 2436 size_t G1CollectedHeap::max_tlab_size() const { 2437 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2438 } 2439 2440 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2441 return _allocator->unsafe_max_tlab_alloc(); 2442 } 2443 2444 size_t G1CollectedHeap::max_capacity() const { 2445 return _hrm->max_expandable_length() * HeapRegion::GrainBytes; 2446 } 2447 2448 size_t G1CollectedHeap::max_reserved_capacity() const { 2449 return _hrm->max_length() * HeapRegion::GrainBytes; 2450 } 2451 2452 jlong G1CollectedHeap::millis_since_last_gc() { 2453 // See the notes in GenCollectedHeap::millis_since_last_gc() 2454 // for more information about the implementation. 2455 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2456 _policy->collection_pause_end_millis(); 2457 if (ret_val < 0) { 2458 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2459 ". returning zero instead.", ret_val); 2460 return 0; 2461 } 2462 return ret_val; 2463 } 2464 2465 void G1CollectedHeap::deduplicate_string(oop str) { 2466 assert(java_lang_String::is_instance(str), "invariant"); 2467 2468 if (G1StringDedup::is_enabled()) { 2469 G1StringDedup::deduplicate(str); 2470 } 2471 } 2472 2473 void G1CollectedHeap::prepare_for_verify() { 2474 _verifier->prepare_for_verify(); 2475 } 2476 2477 void G1CollectedHeap::verify(VerifyOption vo) { 2478 _verifier->verify(vo); 2479 } 2480 2481 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2482 return true; 2483 } 2484 2485 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2486 return _cm_thread->request_concurrent_phase(phase); 2487 } 2488 2489 bool G1CollectedHeap::is_heterogeneous_heap() const { 2490 return G1Arguments::is_heterogeneous_heap(); 2491 } 2492 2493 class PrintRegionClosure: public HeapRegionClosure { 2494 outputStream* _st; 2495 public: 2496 PrintRegionClosure(outputStream* st) : _st(st) {} 2497 bool do_heap_region(HeapRegion* r) { 2498 r->print_on(_st); 2499 return false; 2500 } 2501 }; 2502 2503 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2504 const HeapRegion* hr, 2505 const VerifyOption vo) const { 2506 switch (vo) { 2507 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2508 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2509 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr); 2510 default: ShouldNotReachHere(); 2511 } 2512 return false; // keep some compilers happy 2513 } 2514 2515 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2516 const VerifyOption vo) const { 2517 switch (vo) { 2518 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2519 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2520 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj); 2521 default: ShouldNotReachHere(); 2522 } 2523 return false; // keep some compilers happy 2524 } 2525 2526 void G1CollectedHeap::print_heap_regions() const { 2527 LogTarget(Trace, gc, heap, region) lt; 2528 if (lt.is_enabled()) { 2529 LogStream ls(lt); 2530 print_regions_on(&ls); 2531 } 2532 } 2533 2534 void G1CollectedHeap::print_on(outputStream* st) const { 2535 st->print(" %-20s", "garbage-first heap"); 2536 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2537 capacity()/K, used_unlocked()/K); 2538 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")", 2539 p2i(_hrm->reserved().start()), 2540 p2i(_hrm->reserved().end())); 2541 st->cr(); 2542 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2543 uint young_regions = young_regions_count(); 2544 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2545 (size_t) young_regions * HeapRegion::GrainBytes / K); 2546 uint survivor_regions = survivor_regions_count(); 2547 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2548 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2549 st->cr(); 2550 if (_numa->is_enabled()) { 2551 uint num_nodes = _numa->num_active_nodes(); 2552 st->print(" remaining free region(s) on each NUMA node: "); 2553 const int* node_ids = _numa->node_ids(); 2554 for (uint node_index = 0; node_index < num_nodes; node_index++) { 2555 st->print("%d=%u ", node_ids[node_index], _hrm->num_free_regions(node_index)); 2556 } 2557 st->cr(); 2558 } 2559 MetaspaceUtils::print_on(st); 2560 } 2561 2562 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2563 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2564 "HS=humongous(starts), HC=humongous(continues), " 2565 "CS=collection set, F=free, " 2566 "OA=open archive, CA=closed archive, " 2567 "TAMS=top-at-mark-start (previous, next)"); 2568 PrintRegionClosure blk(st); 2569 heap_region_iterate(&blk); 2570 } 2571 2572 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2573 print_on(st); 2574 2575 // Print the per-region information. 2576 print_regions_on(st); 2577 } 2578 2579 void G1CollectedHeap::print_on_error(outputStream* st) const { 2580 this->CollectedHeap::print_on_error(st); 2581 2582 if (_cm != NULL) { 2583 st->cr(); 2584 _cm->print_on_error(st); 2585 } 2586 } 2587 2588 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2589 workers()->print_worker_threads_on(st); 2590 _cm_thread->print_on(st); 2591 st->cr(); 2592 _cm->print_worker_threads_on(st); 2593 _cr->print_threads_on(st); 2594 _young_gen_sampling_thread->print_on(st); 2595 if (G1StringDedup::is_enabled()) { 2596 G1StringDedup::print_worker_threads_on(st); 2597 } 2598 } 2599 2600 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2601 workers()->threads_do(tc); 2602 tc->do_thread(_cm_thread); 2603 _cm->threads_do(tc); 2604 _cr->threads_do(tc); 2605 tc->do_thread(_young_gen_sampling_thread); 2606 if (G1StringDedup::is_enabled()) { 2607 G1StringDedup::threads_do(tc); 2608 } 2609 } 2610 2611 void G1CollectedHeap::print_tracing_info() const { 2612 rem_set()->print_summary_info(); 2613 concurrent_mark()->print_summary_info(); 2614 } 2615 2616 #ifndef PRODUCT 2617 // Helpful for debugging RSet issues. 2618 2619 class PrintRSetsClosure : public HeapRegionClosure { 2620 private: 2621 const char* _msg; 2622 size_t _occupied_sum; 2623 2624 public: 2625 bool do_heap_region(HeapRegion* r) { 2626 HeapRegionRemSet* hrrs = r->rem_set(); 2627 size_t occupied = hrrs->occupied(); 2628 _occupied_sum += occupied; 2629 2630 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2631 if (occupied == 0) { 2632 tty->print_cr(" RSet is empty"); 2633 } else { 2634 hrrs->print(); 2635 } 2636 tty->print_cr("----------"); 2637 return false; 2638 } 2639 2640 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2641 tty->cr(); 2642 tty->print_cr("========================================"); 2643 tty->print_cr("%s", msg); 2644 tty->cr(); 2645 } 2646 2647 ~PrintRSetsClosure() { 2648 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2649 tty->print_cr("========================================"); 2650 tty->cr(); 2651 } 2652 }; 2653 2654 void G1CollectedHeap::print_cset_rsets() { 2655 PrintRSetsClosure cl("Printing CSet RSets"); 2656 collection_set_iterate_all(&cl); 2657 } 2658 2659 void G1CollectedHeap::print_all_rsets() { 2660 PrintRSetsClosure cl("Printing All RSets");; 2661 heap_region_iterate(&cl); 2662 } 2663 #endif // PRODUCT 2664 2665 bool G1CollectedHeap::print_location(outputStream* st, void* addr) const { 2666 return BlockLocationPrinter<G1CollectedHeap>::print_location(st, addr); 2667 } 2668 2669 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2670 2671 size_t eden_used_bytes = _eden.used_bytes(); 2672 size_t survivor_used_bytes = _survivor.used_bytes(); 2673 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2674 2675 size_t eden_capacity_bytes = 2676 (policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2677 2678 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2679 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2680 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2681 } 2682 2683 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2684 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2685 stats->unused(), stats->used(), stats->region_end_waste(), 2686 stats->regions_filled(), stats->direct_allocated(), 2687 stats->failure_used(), stats->failure_waste()); 2688 } 2689 2690 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2691 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2692 gc_tracer->report_gc_heap_summary(when, heap_summary); 2693 2694 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2695 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2696 } 2697 2698 G1CollectedHeap* G1CollectedHeap::heap() { 2699 CollectedHeap* heap = Universe::heap(); 2700 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2701 assert(heap->kind() == CollectedHeap::G1, "Invalid name"); 2702 return (G1CollectedHeap*)heap; 2703 } 2704 2705 void G1CollectedHeap::gc_prologue(bool full) { 2706 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2707 2708 // This summary needs to be printed before incrementing total collections. 2709 rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2710 2711 // Update common counters. 2712 increment_total_collections(full /* full gc */); 2713 if (full || collector_state()->in_initial_mark_gc()) { 2714 increment_old_marking_cycles_started(); 2715 } 2716 2717 // Fill TLAB's and such 2718 double start = os::elapsedTime(); 2719 ensure_parsability(true); 2720 phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2721 } 2722 2723 void G1CollectedHeap::gc_epilogue(bool full) { 2724 // Update common counters. 2725 if (full) { 2726 // Update the number of full collections that have been completed. 2727 increment_old_marking_cycles_completed(false /* concurrent */); 2728 } 2729 2730 // We are at the end of the GC. Total collections has already been increased. 2731 rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2732 2733 // FIXME: what is this about? 2734 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2735 // is set. 2736 #if COMPILER2_OR_JVMCI 2737 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2738 #endif 2739 2740 double start = os::elapsedTime(); 2741 resize_all_tlabs(); 2742 phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2743 2744 MemoryService::track_memory_usage(); 2745 // We have just completed a GC. Update the soft reference 2746 // policy with the new heap occupancy 2747 Universe::update_heap_info_at_gc(); 2748 2749 // Print NUMA statistics. 2750 _numa->print_statistics(); 2751 } 2752 2753 void G1CollectedHeap::verify_numa_regions(const char* desc) { 2754 LogTarget(Trace, gc, heap, verify) lt; 2755 2756 if (lt.is_enabled()) { 2757 LogStream ls(lt); 2758 // Iterate all heap regions to print matching between preferred numa id and actual numa id. 2759 G1NodeIndexCheckClosure cl(desc, _numa, &ls); 2760 heap_region_iterate(&cl); 2761 } 2762 } 2763 2764 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2765 uint gc_count_before, 2766 bool* succeeded, 2767 GCCause::Cause gc_cause) { 2768 assert_heap_not_locked_and_not_at_safepoint(); 2769 VM_G1CollectForAllocation op(word_size, 2770 gc_count_before, 2771 gc_cause, 2772 policy()->max_pause_time_ms()); 2773 VMThread::execute(&op); 2774 2775 HeapWord* result = op.result(); 2776 bool ret_succeeded = op.prologue_succeeded() && op.gc_succeeded(); 2777 assert(result == NULL || ret_succeeded, 2778 "the result should be NULL if the VM did not succeed"); 2779 *succeeded = ret_succeeded; 2780 2781 assert_heap_not_locked(); 2782 return result; 2783 } 2784 2785 void G1CollectedHeap::do_concurrent_mark() { 2786 MutexLocker x(CGC_lock, Mutex::_no_safepoint_check_flag); 2787 if (!_cm_thread->in_progress()) { 2788 _cm_thread->set_started(); 2789 CGC_lock->notify(); 2790 } 2791 } 2792 2793 size_t G1CollectedHeap::pending_card_num() { 2794 struct CountCardsClosure : public ThreadClosure { 2795 size_t _cards; 2796 CountCardsClosure() : _cards(0) {} 2797 virtual void do_thread(Thread* t) { 2798 _cards += G1ThreadLocalData::dirty_card_queue(t).size(); 2799 } 2800 } count_from_threads; 2801 Threads::threads_do(&count_from_threads); 2802 2803 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 2804 dcqs.verify_num_cards(); 2805 2806 return dcqs.num_cards() + count_from_threads._cards; 2807 } 2808 2809 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const { 2810 // We don't nominate objects with many remembered set entries, on 2811 // the assumption that such objects are likely still live. 2812 HeapRegionRemSet* rem_set = r->rem_set(); 2813 2814 return G1EagerReclaimHumongousObjectsWithStaleRefs ? 2815 rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) : 2816 G1EagerReclaimHumongousObjects && rem_set->is_empty(); 2817 } 2818 2819 #ifndef PRODUCT 2820 void G1CollectedHeap::verify_region_attr_remset_update() { 2821 class VerifyRegionAttrRemSet : public HeapRegionClosure { 2822 public: 2823 virtual bool do_heap_region(HeapRegion* r) { 2824 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2825 bool const needs_remset_update = g1h->region_attr(r->bottom()).needs_remset_update(); 2826 assert(r->rem_set()->is_tracked() == needs_remset_update, 2827 "Region %u remset tracking status (%s) different to region attribute (%s)", 2828 r->hrm_index(), BOOL_TO_STR(r->rem_set()->is_tracked()), BOOL_TO_STR(needs_remset_update)); 2829 return false; 2830 } 2831 } cl; 2832 heap_region_iterate(&cl); 2833 } 2834 #endif 2835 2836 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2837 public: 2838 bool do_heap_region(HeapRegion* hr) { 2839 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2840 hr->verify_rem_set(); 2841 } 2842 return false; 2843 } 2844 }; 2845 2846 uint G1CollectedHeap::num_task_queues() const { 2847 return _task_queues->size(); 2848 } 2849 2850 #if TASKQUEUE_STATS 2851 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2852 st->print_raw_cr("GC Task Stats"); 2853 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2854 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2855 } 2856 2857 void G1CollectedHeap::print_taskqueue_stats() const { 2858 if (!log_is_enabled(Trace, gc, task, stats)) { 2859 return; 2860 } 2861 Log(gc, task, stats) log; 2862 ResourceMark rm; 2863 LogStream ls(log.trace()); 2864 outputStream* st = &ls; 2865 2866 print_taskqueue_stats_hdr(st); 2867 2868 TaskQueueStats totals; 2869 const uint n = num_task_queues(); 2870 for (uint i = 0; i < n; ++i) { 2871 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2872 totals += task_queue(i)->stats; 2873 } 2874 st->print_raw("tot "); totals.print(st); st->cr(); 2875 2876 DEBUG_ONLY(totals.verify()); 2877 } 2878 2879 void G1CollectedHeap::reset_taskqueue_stats() { 2880 const uint n = num_task_queues(); 2881 for (uint i = 0; i < n; ++i) { 2882 task_queue(i)->stats.reset(); 2883 } 2884 } 2885 #endif // TASKQUEUE_STATS 2886 2887 void G1CollectedHeap::wait_for_root_region_scanning() { 2888 double scan_wait_start = os::elapsedTime(); 2889 // We have to wait until the CM threads finish scanning the 2890 // root regions as it's the only way to ensure that all the 2891 // objects on them have been correctly scanned before we start 2892 // moving them during the GC. 2893 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2894 double wait_time_ms = 0.0; 2895 if (waited) { 2896 double scan_wait_end = os::elapsedTime(); 2897 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2898 } 2899 phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2900 } 2901 2902 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2903 private: 2904 G1HRPrinter* _hr_printer; 2905 public: 2906 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2907 2908 virtual bool do_heap_region(HeapRegion* r) { 2909 _hr_printer->cset(r); 2910 return false; 2911 } 2912 }; 2913 2914 void G1CollectedHeap::start_new_collection_set() { 2915 double start = os::elapsedTime(); 2916 2917 collection_set()->start_incremental_building(); 2918 2919 clear_region_attr(); 2920 2921 guarantee(_eden.length() == 0, "eden should have been cleared"); 2922 policy()->transfer_survivors_to_cset(survivor()); 2923 2924 // We redo the verification but now wrt to the new CSet which 2925 // has just got initialized after the previous CSet was freed. 2926 _cm->verify_no_collection_set_oops(); 2927 2928 phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 2929 } 2930 2931 void G1CollectedHeap::calculate_collection_set(G1EvacuationInfo& evacuation_info, double target_pause_time_ms) { 2932 2933 _collection_set.finalize_initial_collection_set(target_pause_time_ms, &_survivor); 2934 evacuation_info.set_collectionset_regions(collection_set()->region_length() + 2935 collection_set()->optional_region_length()); 2936 2937 _cm->verify_no_collection_set_oops(); 2938 2939 if (_hr_printer.is_active()) { 2940 G1PrintCollectionSetClosure cl(&_hr_printer); 2941 _collection_set.iterate(&cl); 2942 _collection_set.iterate_optional(&cl); 2943 } 2944 } 2945 2946 G1HeapVerifier::G1VerifyType G1CollectedHeap::young_collection_verify_type() const { 2947 if (collector_state()->in_initial_mark_gc()) { 2948 return G1HeapVerifier::G1VerifyConcurrentStart; 2949 } else if (collector_state()->in_young_only_phase()) { 2950 return G1HeapVerifier::G1VerifyYoungNormal; 2951 } else { 2952 return G1HeapVerifier::G1VerifyMixed; 2953 } 2954 } 2955 2956 void G1CollectedHeap::verify_before_young_collection(G1HeapVerifier::G1VerifyType type) { 2957 if (VerifyRememberedSets) { 2958 log_info(gc, verify)("[Verifying RemSets before GC]"); 2959 VerifyRegionRemSetClosure v_cl; 2960 heap_region_iterate(&v_cl); 2961 } 2962 _verifier->verify_before_gc(type); 2963 _verifier->check_bitmaps("GC Start"); 2964 verify_numa_regions("GC Start"); 2965 } 2966 2967 void G1CollectedHeap::verify_after_young_collection(G1HeapVerifier::G1VerifyType type) { 2968 if (VerifyRememberedSets) { 2969 log_info(gc, verify)("[Verifying RemSets after GC]"); 2970 VerifyRegionRemSetClosure v_cl; 2971 heap_region_iterate(&v_cl); 2972 } 2973 _verifier->verify_after_gc(type); 2974 _verifier->check_bitmaps("GC End"); 2975 verify_numa_regions("GC End"); 2976 } 2977 2978 bool G1CollectedHeap::check_soft_max_heap_size_changed() { 2979 if (AllocateOldGenAt != NULL) { 2980 // Do not support yet 2981 FLAG_SET_ERGO(SoftMaxHeapSize, MaxHeapSize); 2982 return false; 2983 } 2984 if (SoftMaxHeapSize != _prev_soft_max_heap_size) { 2985 if (!is_aligned(SoftMaxHeapSize, HeapAlignment)) { 2986 FLAG_SET_ERGO(SoftMaxHeapSize, align_up(SoftMaxHeapSize, HeapAlignment)); 2987 } 2988 if (SoftMaxHeapSize != _prev_soft_max_heap_size) { 2989 _prev_soft_max_heap_size = SoftMaxHeapSize; 2990 return true; 2991 } 2992 } 2993 return false; 2994 } 2995 2996 void G1CollectedHeap::adjust_heap_after_young_collection() { 2997 if (concurrent_heap_resize()->resize_thread()->during_cycle()) { 2998 // Do not adjust if concurrent resizing is in progress 2999 return; 3000 } 3001 3002 double start_time_ms = os::elapsedTime(); 3003 shrink_heap_after_young_collection(); 3004 phase_times()->record_or_add_adjust_heap_time((os::elapsedTime() - start_time_ms) * MILLIUNITS); 3005 3006 if (!concurrent_heap_resize()->resize_thread()->during_cycle()) { 3007 expand_heap_after_young_collection(); 3008 } 3009 } 3010 3011 void G1CollectedHeap::expand_heap_after_young_collection(){ 3012 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3013 if (expand_bytes > 0) { 3014 // No need for an ergo logging here, 3015 // expansion_amount() does this when it returns a value > 0. 3016 double expand_ms; 3017 if (!expand(expand_bytes, _workers, &expand_ms)) { 3018 // We failed to expand the heap. Cannot do anything about it. 3019 } 3020 phase_times()->record_expand_heap_time(expand_ms); 3021 } 3022 } 3023 3024 void G1CollectedHeap::shrink_heap_after_young_collection() { 3025 // If SoftMaxHeapSize changed, we can trigger an concurrent mark cycle 3026 bool can_trigger_initial_mark = check_soft_max_heap_size_changed(); 3027 3028 if (capacity() <= SoftMaxHeapSize) { 3029 return; 3030 } 3031 3032 if (!collector_state()->in_young_only_phase() || 3033 collector_state()->in_initial_mark_gc() || 3034 collector_state()->in_young_gc_before_mixed() || 3035 concurrent_mark()->cm_thread()->during_cycle()) { 3036 // Only do the shrink in normal young GC 3037 // If in concurrent cycle, we will wait for the finish of mixed GCs 3038 return; 3039 } 3040 3041 if (_heap_sizing_policy->can_shrink_heap_size_to(SoftMaxHeapSize)) { 3042 size_t shrink_bytes = capacity() - SoftMaxHeapSize; 3043 concurrent_heap_resize()->shrink(shrink_bytes); 3044 policy()->record_new_heap_size(SoftMaxHeapSize); 3045 } else if (can_trigger_initial_mark) { 3046 // Trigger a concurrent mark cycle 3047 collector_state()->set_initiate_conc_mark_if_possible(true); 3048 } 3049 } 3050 3051 const char* G1CollectedHeap::young_gc_name() const { 3052 if (collector_state()->in_initial_mark_gc()) { 3053 return "Pause Young (Concurrent Start)"; 3054 } else if (collector_state()->in_young_only_phase()) { 3055 if (collector_state()->in_young_gc_before_mixed()) { 3056 return "Pause Young (Prepare Mixed)"; 3057 } else { 3058 return "Pause Young (Normal)"; 3059 } 3060 } else { 3061 return "Pause Young (Mixed)"; 3062 } 3063 } 3064 3065 bool G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3066 assert_at_safepoint_on_vm_thread(); 3067 guarantee(!is_gc_active(), "collection is not reentrant"); 3068 3069 if (GCLocker::check_active_before_gc()) { 3070 return false; 3071 } 3072 3073 GCIdMark gc_id_mark; 3074 3075 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3076 ResourceMark rm; 3077 3078 policy()->note_gc_start(); 3079 3080 _gc_timer_stw->register_gc_start(); 3081 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3082 3083 wait_for_root_region_scanning(); 3084 3085 print_heap_before_gc(); 3086 print_heap_regions(); 3087 trace_heap_before_gc(_gc_tracer_stw); 3088 3089 _verifier->verify_region_sets_optional(); 3090 _verifier->verify_dirty_young_regions(); 3091 3092 // We should not be doing initial mark unless the conc mark thread is running 3093 if (!_cm_thread->should_terminate()) { 3094 // This call will decide whether this pause is an initial-mark 3095 // pause. If it is, in_initial_mark_gc() will return true 3096 // for the duration of this pause. 3097 policy()->decide_on_conc_mark_initiation(); 3098 } 3099 3100 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3101 assert(!collector_state()->in_initial_mark_gc() || 3102 collector_state()->in_young_only_phase(), "sanity"); 3103 // We also do not allow mixed GCs during marking. 3104 assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity"); 3105 3106 // Record whether this pause is an initial mark. When the current 3107 // thread has completed its logging output and it's safe to signal 3108 // the CM thread, the flag's value in the policy has been reset. 3109 bool should_start_conc_mark = collector_state()->in_initial_mark_gc(); 3110 if (should_start_conc_mark) { 3111 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 3112 } 3113 3114 // Inner scope for scope based logging, timers, and stats collection 3115 { 3116 G1EvacuationInfo evacuation_info; 3117 3118 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3119 3120 GCTraceCPUTime tcpu; 3121 3122 GCTraceTime(Info, gc) tm(young_gc_name(), NULL, gc_cause(), true); 3123 3124 uint active_workers = WorkerPolicy::calc_active_workers(workers()->total_workers(), 3125 workers()->active_workers(), 3126 Threads::number_of_non_daemon_threads()); 3127 active_workers = workers()->update_active_workers(active_workers); 3128 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 3129 3130 G1MonitoringScope ms(g1mm(), 3131 false /* full_gc */, 3132 collector_state()->yc_type() == Mixed /* all_memory_pools_affected */); 3133 3134 G1HeapTransition heap_transition(this); 3135 3136 { 3137 IsGCActiveMark x; 3138 3139 gc_prologue(false); 3140 3141 G1HeapVerifier::G1VerifyType verify_type = young_collection_verify_type(); 3142 verify_before_young_collection(verify_type); 3143 3144 { 3145 // The elapsed time induced by the start time below deliberately elides 3146 // the possible verification above. 3147 double sample_start_time_sec = os::elapsedTime(); 3148 3149 // Please see comment in g1CollectedHeap.hpp and 3150 // G1CollectedHeap::ref_processing_init() to see how 3151 // reference processing currently works in G1. 3152 _ref_processor_stw->enable_discovery(); 3153 3154 // We want to temporarily turn off discovery by the 3155 // CM ref processor, if necessary, and turn it back on 3156 // on again later if we do. Using a scoped 3157 // NoRefDiscovery object will do this. 3158 NoRefDiscovery no_cm_discovery(_ref_processor_cm); 3159 3160 policy()->record_collection_pause_start(sample_start_time_sec); 3161 3162 double check_concurrent_resize_start_time_ms = os::elapsedTime(); 3163 concurrent_heap_resize()->check_concurrent_work_finish(); 3164 phase_times()->record_or_add_adjust_heap_time((os::elapsedTime() - check_concurrent_resize_start_time_ms) * MILLIUNITS); 3165 3166 // Forget the current allocation region (we might even choose it to be part 3167 // of the collection set!). 3168 _allocator->release_mutator_alloc_regions(); 3169 3170 calculate_collection_set(evacuation_info, target_pause_time_ms); 3171 3172 G1RedirtyCardsQueueSet rdcqs(G1BarrierSet::dirty_card_queue_set().allocator()); 3173 G1ParScanThreadStateSet per_thread_states(this, 3174 &rdcqs, 3175 workers()->active_workers(), 3176 collection_set()->young_region_length(), 3177 collection_set()->optional_region_length()); 3178 pre_evacuate_collection_set(evacuation_info, &per_thread_states); 3179 3180 // Actually do the work... 3181 evacuate_initial_collection_set(&per_thread_states); 3182 3183 if (_collection_set.optional_region_length() != 0) { 3184 evacuate_optional_collection_set(&per_thread_states); 3185 } 3186 post_evacuate_collection_set(evacuation_info, &rdcqs, &per_thread_states); 3187 3188 start_new_collection_set(); 3189 3190 _survivor_evac_stats.adjust_desired_plab_sz(); 3191 _old_evac_stats.adjust_desired_plab_sz(); 3192 3193 if (should_start_conc_mark) { 3194 // We have to do this before we notify the CM threads that 3195 // they can start working to make sure that all the 3196 // appropriate initialization is done on the CM object. 3197 concurrent_mark()->post_initial_mark(); 3198 // Note that we don't actually trigger the CM thread at 3199 // this point. We do that later when we're sure that 3200 // the current thread has completed its logging output. 3201 } 3202 3203 allocate_dummy_regions(); 3204 3205 _allocator->init_mutator_alloc_regions(); 3206 3207 adjust_heap_after_young_collection(); 3208 3209 double sample_end_time_sec = os::elapsedTime(); 3210 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3211 policy()->record_collection_pause_end(pause_time_ms); 3212 } 3213 3214 verify_after_young_collection(verify_type); 3215 3216 #ifdef TRACESPINNING 3217 ParallelTaskTerminator::print_termination_counts(); 3218 #endif 3219 3220 gc_epilogue(false); 3221 } 3222 3223 // Print the remainder of the GC log output. 3224 if (evacuation_failed()) { 3225 log_info(gc)("To-space exhausted"); 3226 } 3227 3228 policy()->print_phases(); 3229 heap_transition.print(); 3230 3231 _hrm->verify_optional(); 3232 _verifier->verify_region_sets_optional(); 3233 3234 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3235 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3236 3237 print_heap_after_gc(); 3238 print_heap_regions(); 3239 trace_heap_after_gc(_gc_tracer_stw); 3240 3241 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3242 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3243 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3244 // before any GC notifications are raised. 3245 g1mm()->update_sizes(); 3246 3247 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3248 _gc_tracer_stw->report_tenuring_threshold(_policy->tenuring_threshold()); 3249 _gc_timer_stw->register_gc_end(); 3250 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3251 } 3252 // It should now be safe to tell the concurrent mark thread to start 3253 // without its logging output interfering with the logging output 3254 // that came from the pause. 3255 3256 if (should_start_conc_mark) { 3257 // CAUTION: after the doConcurrentMark() call below, the concurrent marking 3258 // thread(s) could be running concurrently with us. Make sure that anything 3259 // after this point does not assume that we are the only GC thread running. 3260 // Note: of course, the actual marking work will not start until the safepoint 3261 // itself is released in SuspendibleThreadSet::desynchronize(). 3262 do_concurrent_mark(); 3263 } 3264 3265 return true; 3266 } 3267 3268 void G1CollectedHeap::remove_self_forwarding_pointers(G1RedirtyCardsQueueSet* rdcqs) { 3269 G1ParRemoveSelfForwardPtrsTask rsfp_task(rdcqs); 3270 workers()->run_task(&rsfp_task); 3271 } 3272 3273 void G1CollectedHeap::restore_after_evac_failure(G1RedirtyCardsQueueSet* rdcqs) { 3274 double remove_self_forwards_start = os::elapsedTime(); 3275 3276 remove_self_forwarding_pointers(rdcqs); 3277 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3278 _preserved_marks_set.restore(&task_executor); 3279 3280 phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3281 } 3282 3283 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markWord m) { 3284 if (!_evacuation_failed) { 3285 _evacuation_failed = true; 3286 } 3287 3288 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3289 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3290 } 3291 3292 bool G1ParEvacuateFollowersClosure::offer_termination() { 3293 EventGCPhaseParallel event; 3294 G1ParScanThreadState* const pss = par_scan_state(); 3295 start_term_time(); 3296 const bool res = terminator()->offer_termination(); 3297 end_term_time(); 3298 event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(G1GCPhaseTimes::Termination)); 3299 return res; 3300 } 3301 3302 void G1ParEvacuateFollowersClosure::do_void() { 3303 EventGCPhaseParallel event; 3304 G1ParScanThreadState* const pss = par_scan_state(); 3305 pss->trim_queue(); 3306 event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase)); 3307 do { 3308 EventGCPhaseParallel event; 3309 pss->steal_and_trim_queue(queues()); 3310 event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase)); 3311 } while (!offer_termination()); 3312 } 3313 3314 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3315 bool class_unloading_occurred) { 3316 uint num_workers = workers()->active_workers(); 3317 G1ParallelCleaningTask unlink_task(is_alive, num_workers, class_unloading_occurred, false); 3318 workers()->run_task(&unlink_task); 3319 } 3320 3321 // Clean string dedup data structures. 3322 // Ideally we would prefer to use a StringDedupCleaningTask here, but we want to 3323 // record the durations of the phases. Hence the almost-copy. 3324 class G1StringDedupCleaningTask : public AbstractGangTask { 3325 BoolObjectClosure* _is_alive; 3326 OopClosure* _keep_alive; 3327 G1GCPhaseTimes* _phase_times; 3328 3329 public: 3330 G1StringDedupCleaningTask(BoolObjectClosure* is_alive, 3331 OopClosure* keep_alive, 3332 G1GCPhaseTimes* phase_times) : 3333 AbstractGangTask("Partial Cleaning Task"), 3334 _is_alive(is_alive), 3335 _keep_alive(keep_alive), 3336 _phase_times(phase_times) 3337 { 3338 assert(G1StringDedup::is_enabled(), "String deduplication disabled."); 3339 StringDedup::gc_prologue(true); 3340 } 3341 3342 ~G1StringDedupCleaningTask() { 3343 StringDedup::gc_epilogue(); 3344 } 3345 3346 void work(uint worker_id) { 3347 StringDedupUnlinkOrOopsDoClosure cl(_is_alive, _keep_alive); 3348 { 3349 G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id); 3350 StringDedupQueue::unlink_or_oops_do(&cl); 3351 } 3352 { 3353 G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id); 3354 StringDedupTable::unlink_or_oops_do(&cl, worker_id); 3355 } 3356 } 3357 }; 3358 3359 void G1CollectedHeap::string_dedup_cleaning(BoolObjectClosure* is_alive, 3360 OopClosure* keep_alive, 3361 G1GCPhaseTimes* phase_times) { 3362 G1StringDedupCleaningTask cl(is_alive, keep_alive, phase_times); 3363 workers()->run_task(&cl); 3364 } 3365 3366 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3367 private: 3368 G1RedirtyCardsQueueSet* _qset; 3369 G1CollectedHeap* _g1h; 3370 BufferNode* volatile _nodes; 3371 3372 void par_apply(RedirtyLoggedCardTableEntryClosure* cl, uint worker_id) { 3373 size_t buffer_size = _qset->buffer_size(); 3374 BufferNode* next = Atomic::load(&_nodes); 3375 while (next != NULL) { 3376 BufferNode* node = next; 3377 next = Atomic::cmpxchg(&_nodes, node, node->next()); 3378 if (next == node) { 3379 cl->apply_to_buffer(node, buffer_size, worker_id); 3380 next = node->next(); 3381 } 3382 } 3383 } 3384 3385 public: 3386 G1RedirtyLoggedCardsTask(G1RedirtyCardsQueueSet* qset, G1CollectedHeap* g1h) : 3387 AbstractGangTask("Redirty Cards"), 3388 _qset(qset), _g1h(g1h), _nodes(qset->all_completed_buffers()) { } 3389 3390 virtual void work(uint worker_id) { 3391 G1GCPhaseTimes* p = _g1h->phase_times(); 3392 G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::RedirtyCards, worker_id); 3393 3394 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3395 par_apply(&cl, worker_id); 3396 3397 p->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3398 } 3399 }; 3400 3401 void G1CollectedHeap::redirty_logged_cards(G1RedirtyCardsQueueSet* rdcqs) { 3402 double redirty_logged_cards_start = os::elapsedTime(); 3403 3404 G1RedirtyLoggedCardsTask redirty_task(rdcqs, this); 3405 workers()->run_task(&redirty_task); 3406 3407 G1DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set(); 3408 dcq.merge_bufferlists(rdcqs); 3409 3410 phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3411 } 3412 3413 // Weak Reference Processing support 3414 3415 bool G1STWIsAliveClosure::do_object_b(oop p) { 3416 // An object is reachable if it is outside the collection set, 3417 // or is inside and copied. 3418 return !_g1h->is_in_cset(p) || p->is_forwarded(); 3419 } 3420 3421 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) { 3422 assert(obj != NULL, "must not be NULL"); 3423 assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj)); 3424 // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below 3425 // may falsely indicate that this is not the case here: however the collection set only 3426 // contains old regions when concurrent mark is not running. 3427 return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor(); 3428 } 3429 3430 // Non Copying Keep Alive closure 3431 class G1KeepAliveClosure: public OopClosure { 3432 G1CollectedHeap*_g1h; 3433 public: 3434 G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {} 3435 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3436 void do_oop(oop* p) { 3437 oop obj = *p; 3438 assert(obj != NULL, "the caller should have filtered out NULL values"); 3439 3440 const G1HeapRegionAttr region_attr =_g1h->region_attr(obj); 3441 if (!region_attr.is_in_cset_or_humongous()) { 3442 return; 3443 } 3444 if (region_attr.is_in_cset()) { 3445 assert( obj->is_forwarded(), "invariant" ); 3446 *p = obj->forwardee(); 3447 } else { 3448 assert(!obj->is_forwarded(), "invariant" ); 3449 assert(region_attr.is_humongous(), 3450 "Only allowed G1HeapRegionAttr state is IsHumongous, but is %d", region_attr.type()); 3451 _g1h->set_humongous_is_live(obj); 3452 } 3453 } 3454 }; 3455 3456 // Copying Keep Alive closure - can be called from both 3457 // serial and parallel code as long as different worker 3458 // threads utilize different G1ParScanThreadState instances 3459 // and different queues. 3460 3461 class G1CopyingKeepAliveClosure: public OopClosure { 3462 G1CollectedHeap* _g1h; 3463 G1ParScanThreadState* _par_scan_state; 3464 3465 public: 3466 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3467 G1ParScanThreadState* pss): 3468 _g1h(g1h), 3469 _par_scan_state(pss) 3470 {} 3471 3472 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3473 virtual void do_oop( oop* p) { do_oop_work(p); } 3474 3475 template <class T> void do_oop_work(T* p) { 3476 oop obj = RawAccess<>::oop_load(p); 3477 3478 if (_g1h->is_in_cset_or_humongous(obj)) { 3479 // If the referent object has been forwarded (either copied 3480 // to a new location or to itself in the event of an 3481 // evacuation failure) then we need to update the reference 3482 // field and, if both reference and referent are in the G1 3483 // heap, update the RSet for the referent. 3484 // 3485 // If the referent has not been forwarded then we have to keep 3486 // it alive by policy. Therefore we have copy the referent. 3487 // 3488 // When the queue is drained (after each phase of reference processing) 3489 // the object and it's followers will be copied, the reference field set 3490 // to point to the new location, and the RSet updated. 3491 _par_scan_state->push_on_queue(p); 3492 } 3493 } 3494 }; 3495 3496 // Serial drain queue closure. Called as the 'complete_gc' 3497 // closure for each discovered list in some of the 3498 // reference processing phases. 3499 3500 class G1STWDrainQueueClosure: public VoidClosure { 3501 protected: 3502 G1CollectedHeap* _g1h; 3503 G1ParScanThreadState* _par_scan_state; 3504 3505 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3506 3507 public: 3508 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3509 _g1h(g1h), 3510 _par_scan_state(pss) 3511 { } 3512 3513 void do_void() { 3514 G1ParScanThreadState* const pss = par_scan_state(); 3515 pss->trim_queue(); 3516 } 3517 }; 3518 3519 // Parallel Reference Processing closures 3520 3521 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3522 // processing during G1 evacuation pauses. 3523 3524 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3525 private: 3526 G1CollectedHeap* _g1h; 3527 G1ParScanThreadStateSet* _pss; 3528 RefToScanQueueSet* _queues; 3529 WorkGang* _workers; 3530 3531 public: 3532 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3533 G1ParScanThreadStateSet* per_thread_states, 3534 WorkGang* workers, 3535 RefToScanQueueSet *task_queues) : 3536 _g1h(g1h), 3537 _pss(per_thread_states), 3538 _queues(task_queues), 3539 _workers(workers) 3540 { 3541 g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers()); 3542 } 3543 3544 // Executes the given task using concurrent marking worker threads. 3545 virtual void execute(ProcessTask& task, uint ergo_workers); 3546 }; 3547 3548 // Gang task for possibly parallel reference processing 3549 3550 class G1STWRefProcTaskProxy: public AbstractGangTask { 3551 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 3552 ProcessTask& _proc_task; 3553 G1CollectedHeap* _g1h; 3554 G1ParScanThreadStateSet* _pss; 3555 RefToScanQueueSet* _task_queues; 3556 ParallelTaskTerminator* _terminator; 3557 3558 public: 3559 G1STWRefProcTaskProxy(ProcessTask& proc_task, 3560 G1CollectedHeap* g1h, 3561 G1ParScanThreadStateSet* per_thread_states, 3562 RefToScanQueueSet *task_queues, 3563 ParallelTaskTerminator* terminator) : 3564 AbstractGangTask("Process reference objects in parallel"), 3565 _proc_task(proc_task), 3566 _g1h(g1h), 3567 _pss(per_thread_states), 3568 _task_queues(task_queues), 3569 _terminator(terminator) 3570 {} 3571 3572 virtual void work(uint worker_id) { 3573 // The reference processing task executed by a single worker. 3574 ResourceMark rm; 3575 HandleMark hm; 3576 3577 G1STWIsAliveClosure is_alive(_g1h); 3578 3579 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3580 pss->set_ref_discoverer(NULL); 3581 3582 // Keep alive closure. 3583 G1CopyingKeepAliveClosure keep_alive(_g1h, pss); 3584 3585 // Complete GC closure 3586 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator, G1GCPhaseTimes::ObjCopy); 3587 3588 // Call the reference processing task's work routine. 3589 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 3590 3591 // Note we cannot assert that the refs array is empty here as not all 3592 // of the processing tasks (specifically phase2 - pp2_work) execute 3593 // the complete_gc closure (which ordinarily would drain the queue) so 3594 // the queue may not be empty. 3595 } 3596 }; 3597 3598 // Driver routine for parallel reference processing. 3599 // Creates an instance of the ref processing gang 3600 // task and has the worker threads execute it. 3601 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) { 3602 assert(_workers != NULL, "Need parallel worker threads."); 3603 3604 assert(_workers->active_workers() >= ergo_workers, 3605 "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)", 3606 ergo_workers, _workers->active_workers()); 3607 TaskTerminator terminator(ergo_workers, _queues); 3608 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, terminator.terminator()); 3609 3610 _workers->run_task(&proc_task_proxy, ergo_workers); 3611 } 3612 3613 // End of weak reference support closures 3614 3615 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 3616 double ref_proc_start = os::elapsedTime(); 3617 3618 ReferenceProcessor* rp = _ref_processor_stw; 3619 assert(rp->discovery_enabled(), "should have been enabled"); 3620 3621 // Closure to test whether a referent is alive. 3622 G1STWIsAliveClosure is_alive(this); 3623 3624 // Even when parallel reference processing is enabled, the processing 3625 // of JNI refs is serial and performed serially by the current thread 3626 // rather than by a worker. The following PSS will be used for processing 3627 // JNI refs. 3628 3629 // Use only a single queue for this PSS. 3630 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 3631 pss->set_ref_discoverer(NULL); 3632 assert(pss->queue_is_empty(), "pre-condition"); 3633 3634 // Keep alive closure. 3635 G1CopyingKeepAliveClosure keep_alive(this, pss); 3636 3637 // Serial Complete GC closure 3638 G1STWDrainQueueClosure drain_queue(this, pss); 3639 3640 // Setup the soft refs policy... 3641 rp->setup_policy(false); 3642 3643 ReferenceProcessorPhaseTimes* pt = phase_times()->ref_phase_times(); 3644 3645 ReferenceProcessorStats stats; 3646 if (!rp->processing_is_mt()) { 3647 // Serial reference processing... 3648 stats = rp->process_discovered_references(&is_alive, 3649 &keep_alive, 3650 &drain_queue, 3651 NULL, 3652 pt); 3653 } else { 3654 uint no_of_gc_workers = workers()->active_workers(); 3655 3656 // Parallel reference processing 3657 assert(no_of_gc_workers <= rp->max_num_queues(), 3658 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 3659 no_of_gc_workers, rp->max_num_queues()); 3660 3661 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues); 3662 stats = rp->process_discovered_references(&is_alive, 3663 &keep_alive, 3664 &drain_queue, 3665 &par_task_executor, 3666 pt); 3667 } 3668 3669 _gc_tracer_stw->report_gc_reference_stats(stats); 3670 3671 // We have completed copying any necessary live referent objects. 3672 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 3673 3674 make_pending_list_reachable(); 3675 3676 assert(!rp->discovery_enabled(), "Postcondition"); 3677 rp->verify_no_references_recorded(); 3678 3679 double ref_proc_time = os::elapsedTime() - ref_proc_start; 3680 phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 3681 } 3682 3683 void G1CollectedHeap::make_pending_list_reachable() { 3684 if (collector_state()->in_initial_mark_gc()) { 3685 oop pll_head = Universe::reference_pending_list(); 3686 if (pll_head != NULL) { 3687 // Any valid worker id is fine here as we are in the VM thread and single-threaded. 3688 _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head); 3689 } 3690 } 3691 } 3692 3693 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 3694 Ticks start = Ticks::now(); 3695 per_thread_states->flush(); 3696 phase_times()->record_or_add_time_secs(G1GCPhaseTimes::MergePSS, 0 /* worker_id */, (Ticks::now() - start).seconds()); 3697 } 3698 3699 class G1PrepareEvacuationTask : public AbstractGangTask { 3700 class G1PrepareRegionsClosure : public HeapRegionClosure { 3701 G1CollectedHeap* _g1h; 3702 G1PrepareEvacuationTask* _parent_task; 3703 size_t _worker_humongous_total; 3704 size_t _worker_humongous_candidates; 3705 3706 bool humongous_region_is_candidate(HeapRegion* region) const { 3707 assert(region->is_starts_humongous(), "Must start a humongous object"); 3708 3709 oop obj = oop(region->bottom()); 3710 3711 // Dead objects cannot be eager reclaim candidates. Due to class 3712 // unloading it is unsafe to query their classes so we return early. 3713 if (_g1h->is_obj_dead(obj, region)) { 3714 return false; 3715 } 3716 3717 // If we do not have a complete remembered set for the region, then we can 3718 // not be sure that we have all references to it. 3719 if (!region->rem_set()->is_complete()) { 3720 return false; 3721 } 3722 // Candidate selection must satisfy the following constraints 3723 // while concurrent marking is in progress: 3724 // 3725 // * In order to maintain SATB invariants, an object must not be 3726 // reclaimed if it was allocated before the start of marking and 3727 // has not had its references scanned. Such an object must have 3728 // its references (including type metadata) scanned to ensure no 3729 // live objects are missed by the marking process. Objects 3730 // allocated after the start of concurrent marking don't need to 3731 // be scanned. 3732 // 3733 // * An object must not be reclaimed if it is on the concurrent 3734 // mark stack. Objects allocated after the start of concurrent 3735 // marking are never pushed on the mark stack. 3736 // 3737 // Nominating only objects allocated after the start of concurrent 3738 // marking is sufficient to meet both constraints. This may miss 3739 // some objects that satisfy the constraints, but the marking data 3740 // structures don't support efficiently performing the needed 3741 // additional tests or scrubbing of the mark stack. 3742 // 3743 // However, we presently only nominate is_typeArray() objects. 3744 // A humongous object containing references induces remembered 3745 // set entries on other regions. In order to reclaim such an 3746 // object, those remembered sets would need to be cleaned up. 3747 // 3748 // We also treat is_typeArray() objects specially, allowing them 3749 // to be reclaimed even if allocated before the start of 3750 // concurrent mark. For this we rely on mark stack insertion to 3751 // exclude is_typeArray() objects, preventing reclaiming an object 3752 // that is in the mark stack. We also rely on the metadata for 3753 // such objects to be built-in and so ensured to be kept live. 3754 // Frequent allocation and drop of large binary blobs is an 3755 // important use case for eager reclaim, and this special handling 3756 // may reduce needed headroom. 3757 3758 return obj->is_typeArray() && 3759 _g1h->is_potential_eager_reclaim_candidate(region); 3760 } 3761 3762 public: 3763 G1PrepareRegionsClosure(G1CollectedHeap* g1h, G1PrepareEvacuationTask* parent_task) : 3764 _g1h(g1h), 3765 _parent_task(parent_task), 3766 _worker_humongous_total(0), 3767 _worker_humongous_candidates(0) { } 3768 3769 ~G1PrepareRegionsClosure() { 3770 _parent_task->add_humongous_candidates(_worker_humongous_candidates); 3771 _parent_task->add_humongous_total(_worker_humongous_total); 3772 } 3773 3774 virtual bool do_heap_region(HeapRegion* hr) { 3775 // First prepare the region for scanning 3776 _g1h->rem_set()->prepare_region_for_scan(hr); 3777 3778 // Now check if region is a humongous candidate 3779 if (!hr->is_starts_humongous()) { 3780 _g1h->register_region_with_region_attr(hr); 3781 return false; 3782 } 3783 3784 uint index = hr->hrm_index(); 3785 if (humongous_region_is_candidate(hr)) { 3786 _g1h->set_humongous_reclaim_candidate(index, true); 3787 _g1h->register_humongous_region_with_region_attr(index); 3788 _worker_humongous_candidates++; 3789 // We will later handle the remembered sets of these regions. 3790 } else { 3791 _g1h->set_humongous_reclaim_candidate(index, false); 3792 _g1h->register_region_with_region_attr(hr); 3793 } 3794 _worker_humongous_total++; 3795 3796 return false; 3797 } 3798 }; 3799 3800 G1CollectedHeap* _g1h; 3801 HeapRegionClaimer _claimer; 3802 volatile size_t _humongous_total; 3803 volatile size_t _humongous_candidates; 3804 public: 3805 G1PrepareEvacuationTask(G1CollectedHeap* g1h) : 3806 AbstractGangTask("Prepare Evacuation"), 3807 _g1h(g1h), 3808 _claimer(_g1h->workers()->active_workers()), 3809 _humongous_total(0), 3810 _humongous_candidates(0) { } 3811 3812 ~G1PrepareEvacuationTask() { 3813 _g1h->set_has_humongous_reclaim_candidate(_humongous_candidates > 0); 3814 } 3815 3816 void work(uint worker_id) { 3817 G1PrepareRegionsClosure cl(_g1h, this); 3818 _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_claimer, worker_id); 3819 } 3820 3821 void add_humongous_candidates(size_t candidates) { 3822 Atomic::add(&_humongous_candidates, candidates); 3823 } 3824 3825 void add_humongous_total(size_t total) { 3826 Atomic::add(&_humongous_total, total); 3827 } 3828 3829 size_t humongous_candidates() { 3830 return _humongous_candidates; 3831 } 3832 3833 size_t humongous_total() { 3834 return _humongous_total; 3835 } 3836 }; 3837 3838 void G1CollectedHeap::pre_evacuate_collection_set(G1EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 3839 _bytes_used_during_gc = 0; 3840 3841 _expand_heap_after_alloc_failure = true; 3842 _evacuation_failed = false; 3843 3844 // Disable the hot card cache. 3845 _hot_card_cache->reset_hot_cache_claimed_index(); 3846 _hot_card_cache->set_use_cache(false); 3847 3848 // Initialize the GC alloc regions. 3849 _allocator->init_gc_alloc_regions(evacuation_info); 3850 3851 { 3852 Ticks start = Ticks::now(); 3853 rem_set()->prepare_for_scan_heap_roots(); 3854 phase_times()->record_prepare_heap_roots_time_ms((Ticks::now() - start).seconds() * 1000.0); 3855 } 3856 3857 { 3858 G1PrepareEvacuationTask g1_prep_task(this); 3859 Tickspan task_time = run_task(&g1_prep_task); 3860 3861 phase_times()->record_register_regions(task_time.seconds() * 1000.0, 3862 g1_prep_task.humongous_total(), 3863 g1_prep_task.humongous_candidates()); 3864 } 3865 3866 assert(_verifier->check_region_attr_table(), "Inconsistency in the region attributes table."); 3867 _preserved_marks_set.assert_empty(); 3868 3869 #if COMPILER2_OR_JVMCI 3870 DerivedPointerTable::clear(); 3871 #endif 3872 3873 // InitialMark needs claim bits to keep track of the marked-through CLDs. 3874 if (collector_state()->in_initial_mark_gc()) { 3875 concurrent_mark()->pre_initial_mark(); 3876 3877 double start_clear_claimed_marks = os::elapsedTime(); 3878 3879 ClassLoaderDataGraph::clear_claimed_marks(); 3880 3881 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 3882 phase_times()->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 3883 } 3884 3885 // Should G1EvacuationFailureALot be in effect for this GC? 3886 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 3887 } 3888 3889 class G1EvacuateRegionsBaseTask : public AbstractGangTask { 3890 protected: 3891 G1CollectedHeap* _g1h; 3892 G1ParScanThreadStateSet* _per_thread_states; 3893 RefToScanQueueSet* _task_queues; 3894 TaskTerminator _terminator; 3895 uint _num_workers; 3896 3897 void evacuate_live_objects(G1ParScanThreadState* pss, 3898 uint worker_id, 3899 G1GCPhaseTimes::GCParPhases objcopy_phase, 3900 G1GCPhaseTimes::GCParPhases termination_phase) { 3901 G1GCPhaseTimes* p = _g1h->phase_times(); 3902 3903 Ticks start = Ticks::now(); 3904 G1ParEvacuateFollowersClosure cl(_g1h, pss, _task_queues, _terminator.terminator(), objcopy_phase); 3905 cl.do_void(); 3906 3907 assert(pss->queue_is_empty(), "should be empty"); 3908 3909 Tickspan evac_time = (Ticks::now() - start); 3910 p->record_or_add_time_secs(objcopy_phase, worker_id, evac_time.seconds() - cl.term_time()); 3911 3912 if (termination_phase == G1GCPhaseTimes::Termination) { 3913 p->record_time_secs(termination_phase, worker_id, cl.term_time()); 3914 p->record_thread_work_item(termination_phase, worker_id, cl.term_attempts()); 3915 } else { 3916 p->record_or_add_time_secs(termination_phase, worker_id, cl.term_time()); 3917 p->record_or_add_thread_work_item(termination_phase, worker_id, cl.term_attempts()); 3918 } 3919 assert(pss->trim_ticks().seconds() == 0.0, "Unexpected partial trimming during evacuation"); 3920 } 3921 3922 virtual void start_work(uint worker_id) { } 3923 3924 virtual void end_work(uint worker_id) { } 3925 3926 virtual void scan_roots(G1ParScanThreadState* pss, uint worker_id) = 0; 3927 3928 virtual void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) = 0; 3929 3930 public: 3931 G1EvacuateRegionsBaseTask(const char* name, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet* task_queues, uint num_workers) : 3932 AbstractGangTask(name), 3933 _g1h(G1CollectedHeap::heap()), 3934 _per_thread_states(per_thread_states), 3935 _task_queues(task_queues), 3936 _terminator(num_workers, _task_queues), 3937 _num_workers(num_workers) 3938 { } 3939 3940 void work(uint worker_id) { 3941 start_work(worker_id); 3942 3943 { 3944 ResourceMark rm; 3945 HandleMark hm; 3946 3947 G1ParScanThreadState* pss = _per_thread_states->state_for_worker(worker_id); 3948 pss->set_ref_discoverer(_g1h->ref_processor_stw()); 3949 3950 scan_roots(pss, worker_id); 3951 evacuate_live_objects(pss, worker_id); 3952 } 3953 3954 end_work(worker_id); 3955 } 3956 }; 3957 3958 class G1EvacuateRegionsTask : public G1EvacuateRegionsBaseTask { 3959 G1RootProcessor* _root_processor; 3960 3961 void scan_roots(G1ParScanThreadState* pss, uint worker_id) { 3962 _root_processor->evacuate_roots(pss, worker_id); 3963 _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ObjCopy); 3964 _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::CodeRoots, G1GCPhaseTimes::ObjCopy); 3965 } 3966 3967 void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) { 3968 G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::ObjCopy, G1GCPhaseTimes::Termination); 3969 } 3970 3971 void start_work(uint worker_id) { 3972 _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, Ticks::now().seconds()); 3973 } 3974 3975 void end_work(uint worker_id) { 3976 _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, Ticks::now().seconds()); 3977 } 3978 3979 public: 3980 G1EvacuateRegionsTask(G1CollectedHeap* g1h, 3981 G1ParScanThreadStateSet* per_thread_states, 3982 RefToScanQueueSet* task_queues, 3983 G1RootProcessor* root_processor, 3984 uint num_workers) : 3985 G1EvacuateRegionsBaseTask("G1 Evacuate Regions", per_thread_states, task_queues, num_workers), 3986 _root_processor(root_processor) 3987 { } 3988 }; 3989 3990 void G1CollectedHeap::evacuate_initial_collection_set(G1ParScanThreadStateSet* per_thread_states) { 3991 G1GCPhaseTimes* p = phase_times(); 3992 3993 { 3994 Ticks start = Ticks::now(); 3995 rem_set()->merge_heap_roots(true /* initial_evacuation */); 3996 p->record_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0); 3997 } 3998 3999 Tickspan task_time; 4000 const uint num_workers = workers()->active_workers(); 4001 4002 Ticks start_processing = Ticks::now(); 4003 { 4004 G1RootProcessor root_processor(this, num_workers); 4005 G1EvacuateRegionsTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, num_workers); 4006 task_time = run_task(&g1_par_task); 4007 // Closing the inner scope will execute the destructor for the G1RootProcessor object. 4008 // To extract its code root fixup time we measure total time of this scope and 4009 // subtract from the time the WorkGang task took. 4010 } 4011 Tickspan total_processing = Ticks::now() - start_processing; 4012 4013 p->record_initial_evac_time(task_time.seconds() * 1000.0); 4014 p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0); 4015 } 4016 4017 class G1EvacuateOptionalRegionsTask : public G1EvacuateRegionsBaseTask { 4018 4019 void scan_roots(G1ParScanThreadState* pss, uint worker_id) { 4020 _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptObjCopy); 4021 _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptCodeRoots, G1GCPhaseTimes::OptObjCopy); 4022 } 4023 4024 void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) { 4025 G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::OptObjCopy, G1GCPhaseTimes::OptTermination); 4026 } 4027 4028 public: 4029 G1EvacuateOptionalRegionsTask(G1ParScanThreadStateSet* per_thread_states, 4030 RefToScanQueueSet* queues, 4031 uint num_workers) : 4032 G1EvacuateRegionsBaseTask("G1 Evacuate Optional Regions", per_thread_states, queues, num_workers) { 4033 } 4034 }; 4035 4036 void G1CollectedHeap::evacuate_next_optional_regions(G1ParScanThreadStateSet* per_thread_states) { 4037 class G1MarkScope : public MarkScope { }; 4038 4039 Tickspan task_time; 4040 4041 Ticks start_processing = Ticks::now(); 4042 { 4043 G1MarkScope code_mark_scope; 4044 G1EvacuateOptionalRegionsTask task(per_thread_states, _task_queues, workers()->active_workers()); 4045 task_time = run_task(&task); 4046 // See comment in evacuate_collection_set() for the reason of the scope. 4047 } 4048 Tickspan total_processing = Ticks::now() - start_processing; 4049 4050 G1GCPhaseTimes* p = phase_times(); 4051 p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0); 4052 } 4053 4054 void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) { 4055 const double gc_start_time_ms = phase_times()->cur_collection_start_sec() * 1000.0; 4056 4057 while (!evacuation_failed() && _collection_set.optional_region_length() > 0) { 4058 4059 double time_used_ms = os::elapsedTime() * 1000.0 - gc_start_time_ms; 4060 double time_left_ms = MaxGCPauseMillis - time_used_ms; 4061 4062 if (time_left_ms < 0 || 4063 !_collection_set.finalize_optional_for_evacuation(time_left_ms * policy()->optional_evacuation_fraction())) { 4064 log_trace(gc, ergo, cset)("Skipping evacuation of %u optional regions, no more regions can be evacuated in %.3fms", 4065 _collection_set.optional_region_length(), time_left_ms); 4066 break; 4067 } 4068 4069 { 4070 Ticks start = Ticks::now(); 4071 rem_set()->merge_heap_roots(false /* initial_evacuation */); 4072 phase_times()->record_or_add_optional_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0); 4073 } 4074 4075 { 4076 Ticks start = Ticks::now(); 4077 evacuate_next_optional_regions(per_thread_states); 4078 phase_times()->record_or_add_optional_evac_time((Ticks::now() - start).seconds() * 1000.0); 4079 } 4080 } 4081 4082 _collection_set.abandon_optional_collection_set(per_thread_states); 4083 } 4084 4085 void G1CollectedHeap::post_evacuate_collection_set(G1EvacuationInfo& evacuation_info, 4086 G1RedirtyCardsQueueSet* rdcqs, 4087 G1ParScanThreadStateSet* per_thread_states) { 4088 G1GCPhaseTimes* p = phase_times(); 4089 4090 rem_set()->cleanup_after_scan_heap_roots(); 4091 4092 // Process any discovered reference objects - we have 4093 // to do this _before_ we retire the GC alloc regions 4094 // as we may have to copy some 'reachable' referent 4095 // objects (and their reachable sub-graphs) that were 4096 // not copied during the pause. 4097 process_discovered_references(per_thread_states); 4098 4099 G1STWIsAliveClosure is_alive(this); 4100 G1KeepAliveClosure keep_alive(this); 4101 4102 WeakProcessor::weak_oops_do(workers(), &is_alive, &keep_alive, p->weak_phase_times()); 4103 4104 if (G1StringDedup::is_enabled()) { 4105 double string_dedup_time_ms = os::elapsedTime(); 4106 4107 string_dedup_cleaning(&is_alive, &keep_alive, p); 4108 4109 double string_cleanup_time_ms = (os::elapsedTime() - string_dedup_time_ms) * 1000.0; 4110 p->record_string_deduplication_time(string_cleanup_time_ms); 4111 } 4112 4113 _allocator->release_gc_alloc_regions(evacuation_info); 4114 4115 if (evacuation_failed()) { 4116 restore_after_evac_failure(rdcqs); 4117 4118 // Reset the G1EvacuationFailureALot counters and flags 4119 NOT_PRODUCT(reset_evacuation_should_fail();) 4120 4121 double recalculate_used_start = os::elapsedTime(); 4122 set_used(recalculate_used()); 4123 p->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 4124 4125 if (_archive_allocator != NULL) { 4126 _archive_allocator->clear_used(); 4127 } 4128 for (uint i = 0; i < ParallelGCThreads; i++) { 4129 if (_evacuation_failed_info_array[i].has_failed()) { 4130 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 4131 } 4132 } 4133 } else { 4134 // The "used" of the the collection set have already been subtracted 4135 // when they were freed. Add in the bytes used. 4136 increase_used(_bytes_used_during_gc); 4137 } 4138 4139 _preserved_marks_set.assert_empty(); 4140 4141 merge_per_thread_state_info(per_thread_states); 4142 4143 // Reset and re-enable the hot card cache. 4144 // Note the counts for the cards in the regions in the 4145 // collection set are reset when the collection set is freed. 4146 _hot_card_cache->reset_hot_cache(); 4147 _hot_card_cache->set_use_cache(true); 4148 4149 purge_code_root_memory(); 4150 4151 redirty_logged_cards(rdcqs); 4152 4153 free_collection_set(&_collection_set, evacuation_info, per_thread_states->surviving_young_words()); 4154 4155 eagerly_reclaim_humongous_regions(); 4156 4157 record_obj_copy_mem_stats(); 4158 4159 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 4160 evacuation_info.set_bytes_used(_bytes_used_during_gc); 4161 4162 #if COMPILER2_OR_JVMCI 4163 double start = os::elapsedTime(); 4164 DerivedPointerTable::update_pointers(); 4165 phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4166 #endif 4167 policy()->print_age_table(); 4168 } 4169 4170 void G1CollectedHeap::record_obj_copy_mem_stats() { 4171 policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4172 4173 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4174 create_g1_evac_summary(&_old_evac_stats)); 4175 } 4176 4177 void G1CollectedHeap::free_region(HeapRegion* hr, FreeRegionList* free_list) { 4178 assert(!hr->is_free(), "the region should not be free"); 4179 assert(!hr->is_empty(), "the region should not be empty"); 4180 assert(_hrm->is_available(hr->hrm_index()), "region should be committed"); 4181 4182 if (G1VerifyBitmaps) { 4183 MemRegion mr(hr->bottom(), hr->end()); 4184 concurrent_mark()->clear_range_in_prev_bitmap(mr); 4185 } 4186 4187 // Clear the card counts for this region. 4188 // Note: we only need to do this if the region is not young 4189 // (since we don't refine cards in young regions). 4190 if (!hr->is_young()) { 4191 _hot_card_cache->reset_card_counts(hr); 4192 } 4193 4194 // Reset region metadata to allow reuse. 4195 hr->hr_clear(true /* clear_space */); 4196 _policy->remset_tracker()->update_at_free(hr); 4197 4198 if (free_list != NULL) { 4199 free_list->add_ordered(hr); 4200 } 4201 } 4202 4203 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4204 FreeRegionList* free_list) { 4205 assert(hr->is_humongous(), "this is only for humongous regions"); 4206 assert(free_list != NULL, "pre-condition"); 4207 hr->clear_humongous(); 4208 free_region(hr, free_list); 4209 } 4210 4211 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4212 const uint humongous_regions_removed) { 4213 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4214 MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4215 _old_set.bulk_remove(old_regions_removed); 4216 _humongous_set.bulk_remove(humongous_regions_removed); 4217 } 4218 4219 } 4220 4221 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4222 assert(list != NULL, "list can't be null"); 4223 if (!list->is_empty()) { 4224 MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4225 _hrm->insert_list_into_free_list(list); 4226 } 4227 } 4228 4229 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4230 decrease_used(bytes); 4231 } 4232 4233 class G1FreeCollectionSetTask : public AbstractGangTask { 4234 // Helper class to keep statistics for the collection set freeing 4235 class FreeCSetStats { 4236 size_t _before_used_bytes; // Usage in regions successfully evacutate 4237 size_t _after_used_bytes; // Usage in regions failing evacuation 4238 size_t _bytes_allocated_in_old_since_last_gc; // Size of young regions turned into old 4239 size_t _failure_used_words; // Live size in failed regions 4240 size_t _failure_waste_words; // Wasted size in failed regions 4241 size_t _rs_length; // Remembered set size 4242 uint _regions_freed; // Number of regions freed 4243 public: 4244 FreeCSetStats() : 4245 _before_used_bytes(0), 4246 _after_used_bytes(0), 4247 _bytes_allocated_in_old_since_last_gc(0), 4248 _failure_used_words(0), 4249 _failure_waste_words(0), 4250 _rs_length(0), 4251 _regions_freed(0) { } 4252 4253 void merge_stats(FreeCSetStats* other) { 4254 assert(other != NULL, "invariant"); 4255 _before_used_bytes += other->_before_used_bytes; 4256 _after_used_bytes += other->_after_used_bytes; 4257 _bytes_allocated_in_old_since_last_gc += other->_bytes_allocated_in_old_since_last_gc; 4258 _failure_used_words += other->_failure_used_words; 4259 _failure_waste_words += other->_failure_waste_words; 4260 _rs_length += other->_rs_length; 4261 _regions_freed += other->_regions_freed; 4262 } 4263 4264 void report(G1CollectedHeap* g1h, G1EvacuationInfo* evacuation_info) { 4265 evacuation_info->set_regions_freed(_regions_freed); 4266 evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4267 4268 g1h->decrement_summary_bytes(_before_used_bytes); 4269 g1h->alloc_buffer_stats(G1HeapRegionAttr::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4270 4271 G1Policy *policy = g1h->policy(); 4272 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4273 policy->record_rs_length(_rs_length); 4274 policy->cset_regions_freed(); 4275 } 4276 4277 void account_failed_region(HeapRegion* r) { 4278 size_t used_words = r->marked_bytes() / HeapWordSize; 4279 _failure_used_words += used_words; 4280 _failure_waste_words += HeapRegion::GrainWords - used_words; 4281 _after_used_bytes += r->used(); 4282 4283 // When moving a young gen region to old gen, we "allocate" that whole 4284 // region there. This is in addition to any already evacuated objects. 4285 // Notify the policy about that. Old gen regions do not cause an 4286 // additional allocation: both the objects still in the region and the 4287 // ones already moved are accounted for elsewhere. 4288 if (r->is_young()) { 4289 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4290 } 4291 } 4292 4293 void account_evacuated_region(HeapRegion* r) { 4294 _before_used_bytes += r->used(); 4295 _regions_freed += 1; 4296 } 4297 4298 void account_rs_length(HeapRegion* r) { 4299 _rs_length += r->rem_set()->occupied(); 4300 } 4301 }; 4302 4303 // Closure applied to all regions in the collection set. 4304 class FreeCSetClosure : public HeapRegionClosure { 4305 // Helper to send JFR events for regions. 4306 class JFREventForRegion { 4307 EventGCPhaseParallel _event; 4308 public: 4309 JFREventForRegion(HeapRegion* region, uint worker_id) : _event() { 4310 _event.set_gcId(GCId::current()); 4311 _event.set_gcWorkerId(worker_id); 4312 if (region->is_young()) { 4313 _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::YoungFreeCSet)); 4314 } else { 4315 _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::NonYoungFreeCSet)); 4316 } 4317 } 4318 4319 ~JFREventForRegion() { 4320 _event.commit(); 4321 } 4322 }; 4323 4324 // Helper to do timing for region work. 4325 class TimerForRegion { 4326 Tickspan& _time; 4327 Ticks _start_time; 4328 public: 4329 TimerForRegion(Tickspan& time) : _time(time), _start_time(Ticks::now()) { } 4330 ~TimerForRegion() { 4331 _time += Ticks::now() - _start_time; 4332 } 4333 }; 4334 4335 // FreeCSetClosure members 4336 G1CollectedHeap* _g1h; 4337 const size_t* _surviving_young_words; 4338 uint _worker_id; 4339 Tickspan _young_time; 4340 Tickspan _non_young_time; 4341 FreeCSetStats* _stats; 4342 4343 void assert_in_cset(HeapRegion* r) { 4344 assert(r->young_index_in_cset() != 0 && 4345 (uint)r->young_index_in_cset() <= _g1h->collection_set()->young_region_length(), 4346 "Young index %u is wrong for region %u of type %s with %u young regions", 4347 r->young_index_in_cset(), r->hrm_index(), r->get_type_str(), _g1h->collection_set()->young_region_length()); 4348 } 4349 4350 void handle_evacuated_region(HeapRegion* r) { 4351 assert(!r->is_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4352 stats()->account_evacuated_region(r); 4353 4354 // Free the region and and its remembered set. 4355 _g1h->free_region(r, NULL); 4356 } 4357 4358 void handle_failed_region(HeapRegion* r) { 4359 // Do some allocation statistics accounting. Regions that failed evacuation 4360 // are always made old, so there is no need to update anything in the young 4361 // gen statistics, but we need to update old gen statistics. 4362 stats()->account_failed_region(r); 4363 4364 // Update the region state due to the failed evacuation. 4365 r->handle_evacuation_failure(); 4366 4367 // Add region to old set, need to hold lock. 4368 MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4369 _g1h->old_set_add(r); 4370 } 4371 4372 Tickspan& timer_for_region(HeapRegion* r) { 4373 return r->is_young() ? _young_time : _non_young_time; 4374 } 4375 4376 FreeCSetStats* stats() { 4377 return _stats; 4378 } 4379 public: 4380 FreeCSetClosure(const size_t* surviving_young_words, 4381 uint worker_id, 4382 FreeCSetStats* stats) : 4383 HeapRegionClosure(), 4384 _g1h(G1CollectedHeap::heap()), 4385 _surviving_young_words(surviving_young_words), 4386 _worker_id(worker_id), 4387 _young_time(), 4388 _non_young_time(), 4389 _stats(stats) { } 4390 4391 virtual bool do_heap_region(HeapRegion* r) { 4392 assert(r->in_collection_set(), "Invariant: %u missing from CSet", r->hrm_index()); 4393 JFREventForRegion event(r, _worker_id); 4394 TimerForRegion timer(timer_for_region(r)); 4395 4396 _g1h->clear_region_attr(r); 4397 stats()->account_rs_length(r); 4398 4399 if (r->is_young()) { 4400 assert_in_cset(r); 4401 r->record_surv_words_in_group(_surviving_young_words[r->young_index_in_cset()]); 4402 } 4403 4404 if (r->evacuation_failed()) { 4405 handle_failed_region(r); 4406 } else { 4407 handle_evacuated_region(r); 4408 } 4409 assert(!_g1h->is_on_master_free_list(r), "sanity"); 4410 4411 return false; 4412 } 4413 4414 void report_timing(Tickspan parallel_time) { 4415 G1GCPhaseTimes* pt = _g1h->phase_times(); 4416 pt->record_time_secs(G1GCPhaseTimes::ParFreeCSet, _worker_id, parallel_time.seconds()); 4417 if (_young_time.value() > 0) { 4418 pt->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, _worker_id, _young_time.seconds()); 4419 } 4420 if (_non_young_time.value() > 0) { 4421 pt->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, _worker_id, _non_young_time.seconds()); 4422 } 4423 } 4424 }; 4425 4426 // G1FreeCollectionSetTask members 4427 G1CollectedHeap* _g1h; 4428 G1EvacuationInfo* _evacuation_info; 4429 FreeCSetStats* _worker_stats; 4430 HeapRegionClaimer _claimer; 4431 const size_t* _surviving_young_words; 4432 uint _active_workers; 4433 4434 FreeCSetStats* worker_stats(uint worker) { 4435 return &_worker_stats[worker]; 4436 } 4437 4438 void report_statistics() { 4439 // Merge the accounting 4440 FreeCSetStats total_stats; 4441 for (uint worker = 0; worker < _active_workers; worker++) { 4442 total_stats.merge_stats(worker_stats(worker)); 4443 } 4444 total_stats.report(_g1h, _evacuation_info); 4445 } 4446 4447 public: 4448 G1FreeCollectionSetTask(G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words, uint active_workers) : 4449 AbstractGangTask("G1 Free Collection Set"), 4450 _g1h(G1CollectedHeap::heap()), 4451 _evacuation_info(evacuation_info), 4452 _worker_stats(NEW_C_HEAP_ARRAY(FreeCSetStats, active_workers, mtGC)), 4453 _claimer(active_workers), 4454 _surviving_young_words(surviving_young_words), 4455 _active_workers(active_workers) { 4456 for (uint worker = 0; worker < active_workers; worker++) { 4457 ::new (&_worker_stats[worker]) FreeCSetStats(); 4458 } 4459 } 4460 4461 ~G1FreeCollectionSetTask() { 4462 Ticks serial_time = Ticks::now(); 4463 report_statistics(); 4464 for (uint worker = 0; worker < _active_workers; worker++) { 4465 _worker_stats[worker].~FreeCSetStats(); 4466 } 4467 FREE_C_HEAP_ARRAY(FreeCSetStats, _worker_stats); 4468 _g1h->phase_times()->record_serial_free_cset_time_ms((Ticks::now() - serial_time).seconds() * 1000.0); 4469 } 4470 4471 virtual void work(uint worker_id) { 4472 EventGCPhaseParallel event; 4473 Ticks start = Ticks::now(); 4474 FreeCSetClosure cl(_surviving_young_words, worker_id, worker_stats(worker_id)); 4475 _g1h->collection_set_par_iterate_all(&cl, &_claimer, worker_id); 4476 4477 // Report the total parallel time along with some more detailed metrics. 4478 cl.report_timing(Ticks::now() - start); 4479 event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::ParFreeCSet)); 4480 } 4481 }; 4482 4483 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, G1EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4484 _eden.clear(); 4485 4486 // The free collections set is split up in two tasks, the first 4487 // frees the collection set and records what regions are free, 4488 // and the second one rebuilds the free list. This proved to be 4489 // more efficient than adding a sorted list to another. 4490 4491 Ticks free_cset_start_time = Ticks::now(); 4492 { 4493 uint const num_cs_regions = _collection_set.region_length(); 4494 uint const num_workers = clamp(num_cs_regions, 1u, workers()->active_workers()); 4495 G1FreeCollectionSetTask cl(&evacuation_info, surviving_young_words, num_workers); 4496 4497 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u (%u)", 4498 cl.name(), num_workers, num_cs_regions, num_regions()); 4499 workers()->run_task(&cl, num_workers); 4500 } 4501 4502 Ticks free_cset_end_time = Ticks::now(); 4503 phase_times()->record_total_free_cset_time_ms((free_cset_end_time - free_cset_start_time).seconds() * 1000.0); 4504 4505 // Now rebuild the free region list. 4506 hrm()->rebuild_free_list(workers()); 4507 phase_times()->record_total_rebuild_freelist_time_ms((Ticks::now() - free_cset_end_time).seconds() * 1000.0); 4508 4509 collection_set->clear(); 4510 } 4511 4512 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4513 private: 4514 FreeRegionList* _free_region_list; 4515 HeapRegionSet* _proxy_set; 4516 uint _humongous_objects_reclaimed; 4517 uint _humongous_regions_reclaimed; 4518 size_t _freed_bytes; 4519 public: 4520 4521 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4522 _free_region_list(free_region_list), _proxy_set(NULL), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4523 } 4524 4525 virtual bool do_heap_region(HeapRegion* r) { 4526 if (!r->is_starts_humongous()) { 4527 return false; 4528 } 4529 4530 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4531 4532 oop obj = (oop)r->bottom(); 4533 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap(); 4534 4535 // The following checks whether the humongous object is live are sufficient. 4536 // The main additional check (in addition to having a reference from the roots 4537 // or the young gen) is whether the humongous object has a remembered set entry. 4538 // 4539 // A humongous object cannot be live if there is no remembered set for it 4540 // because: 4541 // - there can be no references from within humongous starts regions referencing 4542 // the object because we never allocate other objects into them. 4543 // (I.e. there are no intra-region references that may be missed by the 4544 // remembered set) 4545 // - as soon there is a remembered set entry to the humongous starts region 4546 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4547 // until the end of a concurrent mark. 4548 // 4549 // It is not required to check whether the object has been found dead by marking 4550 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4551 // all objects allocated during that time are considered live. 4552 // SATB marking is even more conservative than the remembered set. 4553 // So if at this point in the collection there is no remembered set entry, 4554 // nobody has a reference to it. 4555 // At the start of collection we flush all refinement logs, and remembered sets 4556 // are completely up-to-date wrt to references to the humongous object. 4557 // 4558 // Other implementation considerations: 4559 // - never consider object arrays at this time because they would pose 4560 // considerable effort for cleaning up the the remembered sets. This is 4561 // required because stale remembered sets might reference locations that 4562 // are currently allocated into. 4563 uint region_idx = r->hrm_index(); 4564 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4565 !r->rem_set()->is_empty()) { 4566 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", 4567 region_idx, 4568 (size_t)obj->size() * HeapWordSize, 4569 p2i(r->bottom()), 4570 r->rem_set()->occupied(), 4571 r->rem_set()->strong_code_roots_list_length(), 4572 next_bitmap->is_marked(r->bottom()), 4573 g1h->is_humongous_reclaim_candidate(region_idx), 4574 obj->is_typeArray() 4575 ); 4576 return false; 4577 } 4578 4579 guarantee(obj->is_typeArray(), 4580 "Only eagerly reclaiming type arrays is supported, but the object " 4581 PTR_FORMAT " is not.", p2i(r->bottom())); 4582 4583 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", 4584 region_idx, 4585 (size_t)obj->size() * HeapWordSize, 4586 p2i(r->bottom()), 4587 r->rem_set()->occupied(), 4588 r->rem_set()->strong_code_roots_list_length(), 4589 next_bitmap->is_marked(r->bottom()), 4590 g1h->is_humongous_reclaim_candidate(region_idx), 4591 obj->is_typeArray() 4592 ); 4593 4594 G1ConcurrentMark* const cm = g1h->concurrent_mark(); 4595 cm->humongous_object_eagerly_reclaimed(r); 4596 assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj), 4597 "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s", 4598 region_idx, 4599 BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)), 4600 BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj))); 4601 _humongous_objects_reclaimed++; 4602 do { 4603 HeapRegion* next = g1h->next_region_in_humongous(r); 4604 _freed_bytes += r->used(); 4605 r->set_containing_set(NULL); 4606 _humongous_regions_reclaimed++; 4607 g1h->free_humongous_region(r, _free_region_list); 4608 r = next; 4609 } while (r != NULL); 4610 4611 return false; 4612 } 4613 4614 uint humongous_objects_reclaimed() { 4615 return _humongous_objects_reclaimed; 4616 } 4617 4618 uint humongous_regions_reclaimed() { 4619 return _humongous_regions_reclaimed; 4620 } 4621 4622 size_t bytes_freed() const { 4623 return _freed_bytes; 4624 } 4625 }; 4626 4627 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4628 assert_at_safepoint_on_vm_thread(); 4629 4630 if (!G1EagerReclaimHumongousObjects || 4631 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4632 phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4633 return; 4634 } 4635 4636 double start_time = os::elapsedTime(); 4637 4638 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4639 4640 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4641 heap_region_iterate(&cl); 4642 4643 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4644 4645 G1HRPrinter* hrp = hr_printer(); 4646 if (hrp->is_active()) { 4647 FreeRegionListIterator iter(&local_cleanup_list); 4648 while (iter.more_available()) { 4649 HeapRegion* hr = iter.get_next(); 4650 hrp->cleanup(hr); 4651 } 4652 } 4653 4654 prepend_to_freelist(&local_cleanup_list); 4655 decrement_summary_bytes(cl.bytes_freed()); 4656 4657 phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4658 cl.humongous_objects_reclaimed()); 4659 } 4660 4661 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4662 public: 4663 virtual bool do_heap_region(HeapRegion* r) { 4664 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4665 G1CollectedHeap::heap()->clear_region_attr(r); 4666 r->clear_young_index_in_cset(); 4667 return false; 4668 } 4669 }; 4670 4671 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4672 G1AbandonCollectionSetClosure cl; 4673 collection_set_iterate_all(&cl); 4674 4675 collection_set->clear(); 4676 collection_set->stop_incremental_building(); 4677 } 4678 4679 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 4680 return _allocator->is_retained_old_region(hr); 4681 } 4682 4683 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 4684 _eden.add(hr); 4685 _policy->set_region_eden(hr); 4686 } 4687 4688 #ifdef ASSERT 4689 4690 class NoYoungRegionsClosure: public HeapRegionClosure { 4691 private: 4692 bool _success; 4693 public: 4694 NoYoungRegionsClosure() : _success(true) { } 4695 bool do_heap_region(HeapRegion* r) { 4696 if (r->is_young()) { 4697 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 4698 p2i(r->bottom()), p2i(r->end())); 4699 _success = false; 4700 } 4701 return false; 4702 } 4703 bool success() { return _success; } 4704 }; 4705 4706 bool G1CollectedHeap::check_young_list_empty() { 4707 bool ret = (young_regions_count() == 0); 4708 4709 NoYoungRegionsClosure closure; 4710 heap_region_iterate(&closure); 4711 ret = ret && closure.success(); 4712 4713 return ret; 4714 } 4715 4716 #endif // ASSERT 4717 4718 class TearDownRegionSetsClosure : public HeapRegionClosure { 4719 HeapRegionSet *_old_set; 4720 4721 public: 4722 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 4723 4724 bool do_heap_region(HeapRegion* r) { 4725 if (r->is_old()) { 4726 _old_set->remove(r); 4727 } else if(r->is_young()) { 4728 r->uninstall_surv_rate_group(); 4729 } else { 4730 // We ignore free regions, we'll empty the free list afterwards. 4731 // We ignore humongous and archive regions, we're not tearing down these 4732 // sets. 4733 assert(r->is_archive() || r->is_free() || r->is_humongous(), 4734 "it cannot be another type"); 4735 } 4736 return false; 4737 } 4738 4739 ~TearDownRegionSetsClosure() { 4740 assert(_old_set->is_empty(), "post-condition"); 4741 } 4742 }; 4743 4744 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 4745 assert_at_safepoint_on_vm_thread(); 4746 assert(_hrm->num_of_concurrent_resizing_regions() == 0, "should not have concurrent resizing regions"); 4747 4748 if (!free_list_only) { 4749 TearDownRegionSetsClosure cl(&_old_set); 4750 heap_region_iterate(&cl); 4751 4752 // Note that emptying the _young_list is postponed and instead done as 4753 // the first step when rebuilding the regions sets again. The reason for 4754 // this is that during a full GC string deduplication needs to know if 4755 // a collected region was young or old when the full GC was initiated. 4756 } 4757 _hrm->remove_all_free_regions(); 4758 } 4759 4760 void G1CollectedHeap::increase_used(size_t bytes) { 4761 _summary_bytes_used += bytes; 4762 } 4763 4764 void G1CollectedHeap::decrease_used(size_t bytes) { 4765 assert(_summary_bytes_used >= bytes, 4766 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 4767 _summary_bytes_used, bytes); 4768 _summary_bytes_used -= bytes; 4769 } 4770 4771 void G1CollectedHeap::set_used(size_t bytes) { 4772 _summary_bytes_used = bytes; 4773 } 4774 4775 class RebuildRegionSetsClosure : public HeapRegionClosure { 4776 private: 4777 bool _free_list_only; 4778 4779 HeapRegionSet* _old_set; 4780 HeapRegionManager* _hrm; 4781 4782 size_t _total_used; 4783 4784 public: 4785 RebuildRegionSetsClosure(bool free_list_only, 4786 HeapRegionSet* old_set, 4787 HeapRegionManager* hrm) : 4788 _free_list_only(free_list_only), 4789 _old_set(old_set), _hrm(hrm), _total_used(0) { 4790 assert(_hrm->num_free_regions() == 0, "pre-condition"); 4791 if (!free_list_only) { 4792 assert(_old_set->is_empty(), "pre-condition"); 4793 } 4794 } 4795 4796 bool do_heap_region(HeapRegion* r) { 4797 if (r->is_empty()) { 4798 assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets."); 4799 // Add free regions to the free list 4800 r->set_free(); 4801 _hrm->insert_into_free_list(r); 4802 } else if (!_free_list_only) { 4803 assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared."); 4804 4805 if (r->is_archive() || r->is_humongous()) { 4806 // We ignore archive and humongous regions. We left these sets unchanged. 4807 } else { 4808 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 4809 // We now move all (non-humongous, non-old, non-archive) regions to old gen, and register them as such. 4810 r->move_to_old(); 4811 _old_set->add(r); 4812 } 4813 _total_used += r->used(); 4814 } 4815 4816 return false; 4817 } 4818 4819 size_t total_used() { 4820 return _total_used; 4821 } 4822 }; 4823 4824 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 4825 assert_at_safepoint_on_vm_thread(); 4826 4827 if (!free_list_only) { 4828 _eden.clear(); 4829 _survivor.clear(); 4830 } 4831 4832 RebuildRegionSetsClosure cl(free_list_only, &_old_set, _hrm); 4833 heap_region_iterate(&cl); 4834 4835 if (!free_list_only) { 4836 set_used(cl.total_used()); 4837 if (_archive_allocator != NULL) { 4838 _archive_allocator->clear_used(); 4839 } 4840 } 4841 assert_used_and_recalculate_used_equal(this); 4842 } 4843 4844 // Methods for the mutator alloc region 4845 4846 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 4847 bool force, 4848 uint node_index) { 4849 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4850 bool should_allocate = policy()->should_allocate_mutator_region(); 4851 if (force || should_allocate) { 4852 HeapRegion* new_alloc_region = new_region(word_size, 4853 HeapRegionType::Eden, 4854 false /* do_expand */, 4855 node_index); 4856 if (new_alloc_region != NULL) { 4857 set_region_short_lived_locked(new_alloc_region); 4858 _hr_printer.alloc(new_alloc_region, !should_allocate); 4859 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 4860 _policy->remset_tracker()->update_at_allocate(new_alloc_region); 4861 return new_alloc_region; 4862 } 4863 } 4864 return NULL; 4865 } 4866 4867 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 4868 size_t allocated_bytes) { 4869 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4870 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 4871 4872 collection_set()->add_eden_region(alloc_region); 4873 increase_used(allocated_bytes); 4874 _eden.add_used_bytes(allocated_bytes); 4875 _hr_printer.retire(alloc_region); 4876 4877 // We update the eden sizes here, when the region is retired, 4878 // instead of when it's allocated, since this is the point that its 4879 // used space has been recorded in _summary_bytes_used. 4880 g1mm()->update_eden_size(); 4881 } 4882 4883 // Methods for the GC alloc regions 4884 4885 bool G1CollectedHeap::has_more_regions(G1HeapRegionAttr dest) { 4886 if (dest.is_old()) { 4887 return true; 4888 } else { 4889 return survivor_regions_count() < policy()->max_survivor_regions(); 4890 } 4891 } 4892 4893 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, G1HeapRegionAttr dest, uint node_index) { 4894 assert(FreeList_lock->owned_by_self(), "pre-condition"); 4895 4896 if (!has_more_regions(dest)) { 4897 return NULL; 4898 } 4899 4900 HeapRegionType type; 4901 if (dest.is_young()) { 4902 type = HeapRegionType::Survivor; 4903 } else { 4904 type = HeapRegionType::Old; 4905 } 4906 4907 HeapRegion* new_alloc_region = new_region(word_size, 4908 type, 4909 true /* do_expand */, 4910 node_index); 4911 4912 if (new_alloc_region != NULL) { 4913 if (type.is_survivor()) { 4914 new_alloc_region->set_survivor(); 4915 _survivor.add(new_alloc_region); 4916 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 4917 } else { 4918 new_alloc_region->set_old(); 4919 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 4920 } 4921 _policy->remset_tracker()->update_at_allocate(new_alloc_region); 4922 register_region_with_region_attr(new_alloc_region); 4923 _hr_printer.alloc(new_alloc_region); 4924 return new_alloc_region; 4925 } 4926 return NULL; 4927 } 4928 4929 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 4930 size_t allocated_bytes, 4931 G1HeapRegionAttr dest) { 4932 _bytes_used_during_gc += allocated_bytes; 4933 if (dest.is_old()) { 4934 old_set_add(alloc_region); 4935 } else { 4936 assert(dest.is_young(), "Retiring alloc region should be young (%d)", dest.type()); 4937 _survivor.add_used_bytes(allocated_bytes); 4938 } 4939 4940 bool const during_im = collector_state()->in_initial_mark_gc(); 4941 if (during_im && allocated_bytes > 0) { 4942 _cm->root_regions()->add(alloc_region->next_top_at_mark_start(), alloc_region->top()); 4943 } 4944 _hr_printer.retire(alloc_region); 4945 } 4946 4947 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 4948 bool expanded = false; 4949 uint index = _hrm->find_highest_free(&expanded); 4950 4951 if (index != G1_NO_HRM_INDEX) { 4952 if (expanded) { 4953 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 4954 HeapRegion::GrainWords * HeapWordSize); 4955 } 4956 _hrm->allocate_free_regions_starting_at(index, 1); 4957 return region_at(index); 4958 } 4959 return NULL; 4960 } 4961 4962 // Optimized nmethod scanning 4963 4964 class RegisterNMethodOopClosure: public OopClosure { 4965 G1CollectedHeap* _g1h; 4966 nmethod* _nm; 4967 4968 template <class T> void do_oop_work(T* p) { 4969 T heap_oop = RawAccess<>::oop_load(p); 4970 if (!CompressedOops::is_null(heap_oop)) { 4971 oop obj = CompressedOops::decode_not_null(heap_oop); 4972 HeapRegion* hr = _g1h->heap_region_containing(obj); 4973 assert(!hr->is_continues_humongous(), 4974 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 4975 " starting at " HR_FORMAT, 4976 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 4977 4978 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 4979 hr->add_strong_code_root_locked(_nm); 4980 } 4981 } 4982 4983 public: 4984 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 4985 _g1h(g1h), _nm(nm) {} 4986 4987 void do_oop(oop* p) { do_oop_work(p); } 4988 void do_oop(narrowOop* p) { do_oop_work(p); } 4989 }; 4990 4991 class UnregisterNMethodOopClosure: public OopClosure { 4992 G1CollectedHeap* _g1h; 4993 nmethod* _nm; 4994 4995 template <class T> void do_oop_work(T* p) { 4996 T heap_oop = RawAccess<>::oop_load(p); 4997 if (!CompressedOops::is_null(heap_oop)) { 4998 oop obj = CompressedOops::decode_not_null(heap_oop); 4999 HeapRegion* hr = _g1h->heap_region_containing(obj); 5000 assert(!hr->is_continues_humongous(), 5001 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5002 " starting at " HR_FORMAT, 5003 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5004 5005 hr->remove_strong_code_root(_nm); 5006 } 5007 } 5008 5009 public: 5010 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5011 _g1h(g1h), _nm(nm) {} 5012 5013 void do_oop(oop* p) { do_oop_work(p); } 5014 void do_oop(narrowOop* p) { do_oop_work(p); } 5015 }; 5016 5017 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5018 guarantee(nm != NULL, "sanity"); 5019 RegisterNMethodOopClosure reg_cl(this, nm); 5020 nm->oops_do(®_cl); 5021 } 5022 5023 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5024 guarantee(nm != NULL, "sanity"); 5025 UnregisterNMethodOopClosure reg_cl(this, nm); 5026 nm->oops_do(®_cl, true); 5027 } 5028 5029 void G1CollectedHeap::purge_code_root_memory() { 5030 double purge_start = os::elapsedTime(); 5031 G1CodeRootSet::purge(); 5032 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5033 phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5034 } 5035 5036 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5037 G1CollectedHeap* _g1h; 5038 5039 public: 5040 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5041 _g1h(g1h) {} 5042 5043 void do_code_blob(CodeBlob* cb) { 5044 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5045 if (nm == NULL) { 5046 return; 5047 } 5048 5049 _g1h->register_nmethod(nm); 5050 } 5051 }; 5052 5053 void G1CollectedHeap::rebuild_strong_code_roots() { 5054 RebuildStrongCodeRootClosure blob_cl(this); 5055 CodeCache::blobs_do(&blob_cl); 5056 } 5057 5058 void G1CollectedHeap::initialize_serviceability() { 5059 _g1mm->initialize_serviceability(); 5060 } 5061 5062 MemoryUsage G1CollectedHeap::memory_usage() { 5063 return _g1mm->memory_usage(); 5064 } 5065 5066 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() { 5067 return _g1mm->memory_managers(); 5068 } 5069 5070 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() { 5071 return _g1mm->memory_pools(); 5072 }