1 /* 2 * Copyright (c) 2001, 2018, 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/g1BarrierSet.hpp" 33 #include "gc/g1/g1CollectedHeap.inline.hpp" 34 #include "gc/g1/g1CollectionSet.hpp" 35 #include "gc/g1/g1CollectorPolicy.hpp" 36 #include "gc/g1/g1CollectorState.hpp" 37 #include "gc/g1/g1ConcurrentRefine.hpp" 38 #include "gc/g1/g1ConcurrentRefineThread.hpp" 39 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp" 40 #include "gc/g1/g1EvacStats.inline.hpp" 41 #include "gc/g1/g1FullCollector.hpp" 42 #include "gc/g1/g1GCPhaseTimes.hpp" 43 #include "gc/g1/g1HeapSizingPolicy.hpp" 44 #include "gc/g1/g1HeapTransition.hpp" 45 #include "gc/g1/g1HeapVerifier.hpp" 46 #include "gc/g1/g1HotCardCache.hpp" 47 #include "gc/g1/g1MemoryPool.hpp" 48 #include "gc/g1/g1OopClosures.inline.hpp" 49 #include "gc/g1/g1ParScanThreadState.inline.hpp" 50 #include "gc/g1/g1Policy.hpp" 51 #include "gc/g1/g1RegionToSpaceMapper.hpp" 52 #include "gc/g1/g1RemSet.hpp" 53 #include "gc/g1/g1RootClosures.hpp" 54 #include "gc/g1/g1RootProcessor.hpp" 55 #include "gc/g1/g1SATBMarkQueueSet.hpp" 56 #include "gc/g1/g1StringDedup.hpp" 57 #include "gc/g1/g1ThreadLocalData.hpp" 58 #include "gc/g1/g1YCTypes.hpp" 59 #include "gc/g1/g1YoungRemSetSamplingThread.hpp" 60 #include "gc/g1/g1VMOperations.hpp" 61 #include "gc/g1/heapRegion.inline.hpp" 62 #include "gc/g1/heapRegionRemSet.hpp" 63 #include "gc/g1/heapRegionSet.inline.hpp" 64 #include "gc/shared/gcBehaviours.hpp" 65 #include "gc/shared/gcHeapSummary.hpp" 66 #include "gc/shared/gcId.hpp" 67 #include "gc/shared/gcLocker.hpp" 68 #include "gc/shared/gcTimer.hpp" 69 #include "gc/shared/gcTrace.hpp" 70 #include "gc/shared/gcTraceTime.inline.hpp" 71 #include "gc/shared/generationSpec.hpp" 72 #include "gc/shared/isGCActiveMark.hpp" 73 #include "gc/shared/oopStorageParState.hpp" 74 #include "gc/shared/parallelCleaning.hpp" 75 #include "gc/shared/preservedMarks.inline.hpp" 76 #include "gc/shared/suspendibleThreadSet.hpp" 77 #include "gc/shared/referenceProcessor.inline.hpp" 78 #include "gc/shared/taskqueue.inline.hpp" 79 #include "gc/shared/weakProcessor.inline.hpp" 80 #include "gc/shared/workerPolicy.hpp" 81 #include "logging/log.hpp" 82 #include "memory/allocation.hpp" 83 #include "memory/iterator.hpp" 84 #include "memory/resourceArea.hpp" 85 #include "oops/access.inline.hpp" 86 #include "oops/compressedOops.inline.hpp" 87 #include "oops/oop.inline.hpp" 88 #include "runtime/atomic.hpp" 89 #include "runtime/flags/flagSetting.hpp" 90 #include "runtime/handles.inline.hpp" 91 #include "runtime/init.hpp" 92 #include "runtime/orderAccess.hpp" 93 #include "runtime/threadSMR.hpp" 94 #include "runtime/vmThread.hpp" 95 #include "utilities/align.hpp" 96 #include "utilities/globalDefinitions.hpp" 97 #include "utilities/stack.inline.hpp" 98 99 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 100 101 // INVARIANTS/NOTES 102 // 103 // All allocation activity covered by the G1CollectedHeap interface is 104 // serialized by acquiring the HeapLock. This happens in mem_allocate 105 // and allocate_new_tlab, which are the "entry" points to the 106 // allocation code from the rest of the JVM. (Note that this does not 107 // apply to TLAB allocation, which is not part of this interface: it 108 // is done by clients of this interface.) 109 110 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 111 private: 112 size_t _num_dirtied; 113 G1CollectedHeap* _g1h; 114 G1CardTable* _g1_ct; 115 116 HeapRegion* region_for_card(jbyte* card_ptr) const { 117 return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr)); 118 } 119 120 bool will_become_free(HeapRegion* hr) const { 121 // A region will be freed by free_collection_set if the region is in the 122 // collection set and has not had an evacuation failure. 123 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 124 } 125 126 public: 127 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 128 _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { } 129 130 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 131 HeapRegion* hr = region_for_card(card_ptr); 132 133 // Should only dirty cards in regions that won't be freed. 134 if (!will_become_free(hr)) { 135 *card_ptr = G1CardTable::dirty_card_val(); 136 _num_dirtied++; 137 } 138 139 return true; 140 } 141 142 size_t num_dirtied() const { return _num_dirtied; } 143 }; 144 145 146 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 147 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 148 } 149 150 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 151 // The from card cache is not the memory that is actually committed. So we cannot 152 // take advantage of the zero_filled parameter. 153 reset_from_card_cache(start_idx, num_regions); 154 } 155 156 157 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 158 MemRegion mr) { 159 return new HeapRegion(hrs_index, bot(), mr); 160 } 161 162 // Private methods. 163 164 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 165 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 166 "the only time we use this to allocate a humongous region is " 167 "when we are allocating a single humongous region"); 168 169 HeapRegion* res = _hrm.allocate_free_region(is_old); 170 171 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 172 // Currently, only attempts to allocate GC alloc regions set 173 // do_expand to true. So, we should only reach here during a 174 // safepoint. If this assumption changes we might have to 175 // reconsider the use of _expand_heap_after_alloc_failure. 176 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 177 178 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 179 word_size * HeapWordSize); 180 181 if (expand(word_size * HeapWordSize)) { 182 // Given that expand() succeeded in expanding the heap, and we 183 // always expand the heap by an amount aligned to the heap 184 // region size, the free list should in theory not be empty. 185 // In either case allocate_free_region() will check for NULL. 186 res = _hrm.allocate_free_region(is_old); 187 } else { 188 _expand_heap_after_alloc_failure = false; 189 } 190 } 191 return res; 192 } 193 194 HeapWord* 195 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 196 uint num_regions, 197 size_t word_size) { 198 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 199 assert(is_humongous(word_size), "word_size should be humongous"); 200 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 201 202 // Index of last region in the series. 203 uint last = first + num_regions - 1; 204 205 // We need to initialize the region(s) we just discovered. This is 206 // a bit tricky given that it can happen concurrently with 207 // refinement threads refining cards on these regions and 208 // potentially wanting to refine the BOT as they are scanning 209 // those cards (this can happen shortly after a cleanup; see CR 210 // 6991377). So we have to set up the region(s) carefully and in 211 // a specific order. 212 213 // The word size sum of all the regions we will allocate. 214 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 215 assert(word_size <= word_size_sum, "sanity"); 216 217 // This will be the "starts humongous" region. 218 HeapRegion* first_hr = region_at(first); 219 // The header of the new object will be placed at the bottom of 220 // the first region. 221 HeapWord* new_obj = first_hr->bottom(); 222 // This will be the new top of the new object. 223 HeapWord* obj_top = new_obj + word_size; 224 225 // First, we need to zero the header of the space that we will be 226 // allocating. When we update top further down, some refinement 227 // threads might try to scan the region. By zeroing the header we 228 // ensure that any thread that will try to scan the region will 229 // come across the zero klass word and bail out. 230 // 231 // NOTE: It would not have been correct to have used 232 // CollectedHeap::fill_with_object() and make the space look like 233 // an int array. The thread that is doing the allocation will 234 // later update the object header to a potentially different array 235 // type and, for a very short period of time, the klass and length 236 // fields will be inconsistent. This could cause a refinement 237 // thread to calculate the object size incorrectly. 238 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 239 240 // Next, pad out the unused tail of the last region with filler 241 // objects, for improved usage accounting. 242 // How many words we use for filler objects. 243 size_t word_fill_size = word_size_sum - word_size; 244 245 // How many words memory we "waste" which cannot hold a filler object. 246 size_t words_not_fillable = 0; 247 248 if (word_fill_size >= min_fill_size()) { 249 fill_with_objects(obj_top, word_fill_size); 250 } else if (word_fill_size > 0) { 251 // We have space to fill, but we cannot fit an object there. 252 words_not_fillable = word_fill_size; 253 word_fill_size = 0; 254 } 255 256 // We will set up the first region as "starts humongous". This 257 // will also update the BOT covering all the regions to reflect 258 // that there is a single object that starts at the bottom of the 259 // first region. 260 first_hr->set_starts_humongous(obj_top, word_fill_size); 261 _g1_policy->remset_tracker()->update_at_allocate(first_hr); 262 // Then, if there are any, we will set up the "continues 263 // humongous" regions. 264 HeapRegion* hr = NULL; 265 for (uint i = first + 1; i <= last; ++i) { 266 hr = region_at(i); 267 hr->set_continues_humongous(first_hr); 268 _g1_policy->remset_tracker()->update_at_allocate(hr); 269 } 270 271 // Up to this point no concurrent thread would have been able to 272 // do any scanning on any region in this series. All the top 273 // fields still point to bottom, so the intersection between 274 // [bottom,top] and [card_start,card_end] will be empty. Before we 275 // update the top fields, we'll do a storestore to make sure that 276 // no thread sees the update to top before the zeroing of the 277 // object header and the BOT initialization. 278 OrderAccess::storestore(); 279 280 // Now, we will update the top fields of the "continues humongous" 281 // regions except the last one. 282 for (uint i = first; i < last; ++i) { 283 hr = region_at(i); 284 hr->set_top(hr->end()); 285 } 286 287 hr = region_at(last); 288 // If we cannot fit a filler object, we must set top to the end 289 // of the humongous object, otherwise we cannot iterate the heap 290 // and the BOT will not be complete. 291 hr->set_top(hr->end() - words_not_fillable); 292 293 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 294 "obj_top should be in last region"); 295 296 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 297 298 assert(words_not_fillable == 0 || 299 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 300 "Miscalculation in humongous allocation"); 301 302 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 303 304 for (uint i = first; i <= last; ++i) { 305 hr = region_at(i); 306 _humongous_set.add(hr); 307 _hr_printer.alloc(hr); 308 } 309 310 return new_obj; 311 } 312 313 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 314 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 315 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 316 } 317 318 // If could fit into free regions w/o expansion, try. 319 // Otherwise, if can expand, do so. 320 // Otherwise, if using ex regions might help, try with ex given back. 321 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) { 322 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 323 324 _verifier->verify_region_sets_optional(); 325 326 uint first = G1_NO_HRM_INDEX; 327 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 328 329 if (obj_regions == 1) { 330 // Only one region to allocate, try to use a fast path by directly allocating 331 // from the free lists. Do not try to expand here, we will potentially do that 332 // later. 333 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 334 if (hr != NULL) { 335 first = hr->hrm_index(); 336 } 337 } else { 338 // Policy: Try only empty regions (i.e. already committed first). Maybe we 339 // are lucky enough to find some. 340 first = _hrm.find_contiguous_only_empty(obj_regions); 341 if (first != G1_NO_HRM_INDEX) { 342 _hrm.allocate_free_regions_starting_at(first, obj_regions); 343 } 344 } 345 346 if (first == G1_NO_HRM_INDEX) { 347 // Policy: We could not find enough regions for the humongous object in the 348 // free list. Look through the heap to find a mix of free and uncommitted regions. 349 // If so, try expansion. 350 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 351 if (first != G1_NO_HRM_INDEX) { 352 // We found something. Make sure these regions are committed, i.e. expand 353 // the heap. Alternatively we could do a defragmentation GC. 354 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 355 word_size * HeapWordSize); 356 357 _hrm.expand_at(first, obj_regions, workers()); 358 g1_policy()->record_new_heap_size(num_regions()); 359 360 #ifdef ASSERT 361 for (uint i = first; i < first + obj_regions; ++i) { 362 HeapRegion* hr = region_at(i); 363 assert(hr->is_free(), "sanity"); 364 assert(hr->is_empty(), "sanity"); 365 assert(is_on_master_free_list(hr), "sanity"); 366 } 367 #endif 368 _hrm.allocate_free_regions_starting_at(first, obj_regions); 369 } else { 370 // Policy: Potentially trigger a defragmentation GC. 371 } 372 } 373 374 HeapWord* result = NULL; 375 if (first != G1_NO_HRM_INDEX) { 376 result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size); 377 assert(result != NULL, "it should always return a valid result"); 378 379 // A successful humongous object allocation changes the used space 380 // information of the old generation so we need to recalculate the 381 // sizes and update the jstat counters here. 382 g1mm()->update_sizes(); 383 } 384 385 _verifier->verify_region_sets_optional(); 386 387 return result; 388 } 389 390 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size, 391 size_t requested_size, 392 size_t* actual_size) { 393 assert_heap_not_locked_and_not_at_safepoint(); 394 assert(!is_humongous(requested_size), "we do not allow humongous TLABs"); 395 396 return attempt_allocation(min_size, requested_size, actual_size); 397 } 398 399 HeapWord* 400 G1CollectedHeap::mem_allocate(size_t word_size, 401 bool* gc_overhead_limit_was_exceeded) { 402 assert_heap_not_locked_and_not_at_safepoint(); 403 404 if (is_humongous(word_size)) { 405 return attempt_allocation_humongous(word_size); 406 } 407 size_t dummy = 0; 408 return attempt_allocation(word_size, word_size, &dummy); 409 } 410 411 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) { 412 ResourceMark rm; // For retrieving the thread names in log messages. 413 414 // Make sure you read the note in attempt_allocation_humongous(). 415 416 assert_heap_not_locked_and_not_at_safepoint(); 417 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 418 "be called for humongous allocation requests"); 419 420 // We should only get here after the first-level allocation attempt 421 // (attempt_allocation()) failed to allocate. 422 423 // We will loop until a) we manage to successfully perform the 424 // allocation or b) we successfully schedule a collection which 425 // fails to perform the allocation. b) is the only case when we'll 426 // return NULL. 427 HeapWord* result = NULL; 428 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 429 bool should_try_gc; 430 uint gc_count_before; 431 432 { 433 MutexLockerEx x(Heap_lock); 434 result = _allocator->attempt_allocation_locked(word_size); 435 if (result != NULL) { 436 return result; 437 } 438 439 // If the GCLocker is active and we are bound for a GC, try expanding young gen. 440 // This is different to when only GCLocker::needs_gc() is set: try to avoid 441 // waiting because the GCLocker is active to not wait too long. 442 if (GCLocker::is_active_and_needs_gc() && g1_policy()->can_expand_young_list()) { 443 // No need for an ergo message here, can_expand_young_list() does this when 444 // it returns true. 445 result = _allocator->attempt_allocation_force(word_size); 446 if (result != NULL) { 447 return result; 448 } 449 } 450 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 451 // the GCLocker initiated GC has been performed and then retry. This includes 452 // the case when the GC Locker is not active but has not been performed. 453 should_try_gc = !GCLocker::needs_gc(); 454 // Read the GC count while still holding the Heap_lock. 455 gc_count_before = total_collections(); 456 } 457 458 if (should_try_gc) { 459 bool succeeded; 460 result = do_collection_pause(word_size, gc_count_before, &succeeded, 461 GCCause::_g1_inc_collection_pause); 462 if (result != NULL) { 463 assert(succeeded, "only way to get back a non-NULL result"); 464 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 465 Thread::current()->name(), p2i(result)); 466 return result; 467 } 468 469 if (succeeded) { 470 // We successfully scheduled a collection which failed to allocate. No 471 // point in trying to allocate further. We'll just return NULL. 472 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 473 SIZE_FORMAT " words", Thread::current()->name(), word_size); 474 return NULL; 475 } 476 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words", 477 Thread::current()->name(), word_size); 478 } else { 479 // Failed to schedule a collection. 480 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 481 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 482 SIZE_FORMAT " words", Thread::current()->name(), word_size); 483 return NULL; 484 } 485 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 486 // The GCLocker is either active or the GCLocker initiated 487 // GC has not yet been performed. Stall until it is and 488 // then retry the allocation. 489 GCLocker::stall_until_clear(); 490 gclocker_retry_count += 1; 491 } 492 493 // We can reach here if we were unsuccessful in scheduling a 494 // collection (because another thread beat us to it) or if we were 495 // stalled due to the GC locker. In either can we should retry the 496 // allocation attempt in case another thread successfully 497 // performed a collection and reclaimed enough space. We do the 498 // first attempt (without holding the Heap_lock) here and the 499 // follow-on attempt will be at the start of the next loop 500 // iteration (after taking the Heap_lock). 501 size_t dummy = 0; 502 result = _allocator->attempt_allocation(word_size, word_size, &dummy); 503 if (result != NULL) { 504 return result; 505 } 506 507 // Give a warning if we seem to be looping forever. 508 if ((QueuedAllocationWarningCount > 0) && 509 (try_count % QueuedAllocationWarningCount == 0)) { 510 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 511 Thread::current()->name(), try_count, word_size); 512 } 513 } 514 515 ShouldNotReachHere(); 516 return NULL; 517 } 518 519 void G1CollectedHeap::begin_archive_alloc_range(bool open) { 520 assert_at_safepoint_on_vm_thread(); 521 if (_archive_allocator == NULL) { 522 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open); 523 } 524 } 525 526 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 527 // Allocations in archive regions cannot be of a size that would be considered 528 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 529 // may be different at archive-restore time. 530 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 531 } 532 533 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 534 assert_at_safepoint_on_vm_thread(); 535 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 536 if (is_archive_alloc_too_large(word_size)) { 537 return NULL; 538 } 539 return _archive_allocator->archive_mem_allocate(word_size); 540 } 541 542 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 543 size_t end_alignment_in_bytes) { 544 assert_at_safepoint_on_vm_thread(); 545 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 546 547 // Call complete_archive to do the real work, filling in the MemRegion 548 // array with the archive regions. 549 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 550 delete _archive_allocator; 551 _archive_allocator = NULL; 552 } 553 554 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 555 assert(ranges != NULL, "MemRegion array NULL"); 556 assert(count != 0, "No MemRegions provided"); 557 MemRegion reserved = _hrm.reserved(); 558 for (size_t i = 0; i < count; i++) { 559 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 560 return false; 561 } 562 } 563 return true; 564 } 565 566 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, 567 size_t count, 568 bool open) { 569 assert(!is_init_completed(), "Expect to be called at JVM init time"); 570 assert(ranges != NULL, "MemRegion array NULL"); 571 assert(count != 0, "No MemRegions provided"); 572 MutexLockerEx x(Heap_lock); 573 574 MemRegion reserved = _hrm.reserved(); 575 HeapWord* prev_last_addr = NULL; 576 HeapRegion* prev_last_region = NULL; 577 578 // Temporarily disable pretouching of heap pages. This interface is used 579 // when mmap'ing archived heap data in, so pre-touching is wasted. 580 FlagSetting fs(AlwaysPreTouch, false); 581 582 // Enable archive object checking used by G1MarkSweep. We have to let it know 583 // about each archive range, so that objects in those ranges aren't marked. 584 G1ArchiveAllocator::enable_archive_object_check(); 585 586 // For each specified MemRegion range, allocate the corresponding G1 587 // regions and mark them as archive regions. We expect the ranges 588 // in ascending starting address order, without overlap. 589 for (size_t i = 0; i < count; i++) { 590 MemRegion curr_range = ranges[i]; 591 HeapWord* start_address = curr_range.start(); 592 size_t word_size = curr_range.word_size(); 593 HeapWord* last_address = curr_range.last(); 594 size_t commits = 0; 595 596 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 597 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 598 p2i(start_address), p2i(last_address)); 599 guarantee(start_address > prev_last_addr, 600 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 601 p2i(start_address), p2i(prev_last_addr)); 602 prev_last_addr = last_address; 603 604 // Check for ranges that start in the same G1 region in which the previous 605 // range ended, and adjust the start address so we don't try to allocate 606 // the same region again. If the current range is entirely within that 607 // region, skip it, just adjusting the recorded top. 608 HeapRegion* start_region = _hrm.addr_to_region(start_address); 609 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 610 start_address = start_region->end(); 611 if (start_address > last_address) { 612 increase_used(word_size * HeapWordSize); 613 start_region->set_top(last_address + 1); 614 continue; 615 } 616 start_region->set_top(start_address); 617 curr_range = MemRegion(start_address, last_address + 1); 618 start_region = _hrm.addr_to_region(start_address); 619 } 620 621 // Perform the actual region allocation, exiting if it fails. 622 // Then note how much new space we have allocated. 623 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 624 return false; 625 } 626 increase_used(word_size * HeapWordSize); 627 if (commits != 0) { 628 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 629 HeapRegion::GrainWords * HeapWordSize * commits); 630 631 } 632 633 // Mark each G1 region touched by the range as archive, add it to 634 // the old set, and set top. 635 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 636 HeapRegion* last_region = _hrm.addr_to_region(last_address); 637 prev_last_region = last_region; 638 639 while (curr_region != NULL) { 640 assert(curr_region->is_empty() && !curr_region->is_pinned(), 641 "Region already in use (index %u)", curr_region->hrm_index()); 642 if (open) { 643 curr_region->set_open_archive(); 644 } else { 645 curr_region->set_closed_archive(); 646 } 647 _hr_printer.alloc(curr_region); 648 _archive_set.add(curr_region); 649 HeapWord* top; 650 HeapRegion* next_region; 651 if (curr_region != last_region) { 652 top = curr_region->end(); 653 next_region = _hrm.next_region_in_heap(curr_region); 654 } else { 655 top = last_address + 1; 656 next_region = NULL; 657 } 658 curr_region->set_top(top); 659 curr_region->set_first_dead(top); 660 curr_region->set_end_of_live(top); 661 curr_region = next_region; 662 } 663 664 // Notify mark-sweep of the archive 665 G1ArchiveAllocator::set_range_archive(curr_range, open); 666 } 667 return true; 668 } 669 670 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 671 assert(!is_init_completed(), "Expect to be called at JVM init time"); 672 assert(ranges != NULL, "MemRegion array NULL"); 673 assert(count != 0, "No MemRegions provided"); 674 MemRegion reserved = _hrm.reserved(); 675 HeapWord *prev_last_addr = NULL; 676 HeapRegion* prev_last_region = NULL; 677 678 // For each MemRegion, create filler objects, if needed, in the G1 regions 679 // that contain the address range. The address range actually within the 680 // MemRegion will not be modified. That is assumed to have been initialized 681 // elsewhere, probably via an mmap of archived heap data. 682 MutexLockerEx x(Heap_lock); 683 for (size_t i = 0; i < count; i++) { 684 HeapWord* start_address = ranges[i].start(); 685 HeapWord* last_address = ranges[i].last(); 686 687 assert(reserved.contains(start_address) && reserved.contains(last_address), 688 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 689 p2i(start_address), p2i(last_address)); 690 assert(start_address > prev_last_addr, 691 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 692 p2i(start_address), p2i(prev_last_addr)); 693 694 HeapRegion* start_region = _hrm.addr_to_region(start_address); 695 HeapRegion* last_region = _hrm.addr_to_region(last_address); 696 HeapWord* bottom_address = start_region->bottom(); 697 698 // Check for a range beginning in the same region in which the 699 // previous one ended. 700 if (start_region == prev_last_region) { 701 bottom_address = prev_last_addr + 1; 702 } 703 704 // Verify that the regions were all marked as archive regions by 705 // alloc_archive_regions. 706 HeapRegion* curr_region = start_region; 707 while (curr_region != NULL) { 708 guarantee(curr_region->is_archive(), 709 "Expected archive region at index %u", curr_region->hrm_index()); 710 if (curr_region != last_region) { 711 curr_region = _hrm.next_region_in_heap(curr_region); 712 } else { 713 curr_region = NULL; 714 } 715 } 716 717 prev_last_addr = last_address; 718 prev_last_region = last_region; 719 720 // Fill the memory below the allocated range with dummy object(s), 721 // if the region bottom does not match the range start, or if the previous 722 // range ended within the same G1 region, and there is a gap. 723 if (start_address != bottom_address) { 724 size_t fill_size = pointer_delta(start_address, bottom_address); 725 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 726 increase_used(fill_size * HeapWordSize); 727 } 728 } 729 } 730 731 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size, 732 size_t desired_word_size, 733 size_t* actual_word_size) { 734 assert_heap_not_locked_and_not_at_safepoint(); 735 assert(!is_humongous(desired_word_size), "attempt_allocation() should not " 736 "be called for humongous allocation requests"); 737 738 HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size); 739 740 if (result == NULL) { 741 *actual_word_size = desired_word_size; 742 result = attempt_allocation_slow(desired_word_size); 743 } 744 745 assert_heap_not_locked(); 746 if (result != NULL) { 747 assert(*actual_word_size != 0, "Actual size must have been set here"); 748 dirty_young_block(result, *actual_word_size); 749 } else { 750 *actual_word_size = 0; 751 } 752 753 return result; 754 } 755 756 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count, bool is_open) { 757 assert(!is_init_completed(), "Expect to be called at JVM init time"); 758 assert(ranges != NULL, "MemRegion array NULL"); 759 assert(count != 0, "No MemRegions provided"); 760 MemRegion reserved = _hrm.reserved(); 761 HeapWord* prev_last_addr = NULL; 762 HeapRegion* prev_last_region = NULL; 763 size_t size_used = 0; 764 size_t uncommitted_regions = 0; 765 766 // For each Memregion, free the G1 regions that constitute it, and 767 // notify mark-sweep that the range is no longer to be considered 'archive.' 768 MutexLockerEx x(Heap_lock); 769 for (size_t i = 0; i < count; i++) { 770 HeapWord* start_address = ranges[i].start(); 771 HeapWord* last_address = ranges[i].last(); 772 773 assert(reserved.contains(start_address) && reserved.contains(last_address), 774 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 775 p2i(start_address), p2i(last_address)); 776 assert(start_address > prev_last_addr, 777 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 778 p2i(start_address), p2i(prev_last_addr)); 779 size_used += ranges[i].byte_size(); 780 prev_last_addr = last_address; 781 782 HeapRegion* start_region = _hrm.addr_to_region(start_address); 783 HeapRegion* last_region = _hrm.addr_to_region(last_address); 784 785 // Check for ranges that start in the same G1 region in which the previous 786 // range ended, and adjust the start address so we don't try to free 787 // the same region again. If the current range is entirely within that 788 // region, skip it. 789 if (start_region == prev_last_region) { 790 start_address = start_region->end(); 791 if (start_address > last_address) { 792 continue; 793 } 794 start_region = _hrm.addr_to_region(start_address); 795 } 796 prev_last_region = last_region; 797 798 // After verifying that each region was marked as an archive region by 799 // alloc_archive_regions, set it free and empty and uncommit it. 800 HeapRegion* curr_region = start_region; 801 while (curr_region != NULL) { 802 guarantee(curr_region->is_archive(), 803 "Expected archive region at index %u", curr_region->hrm_index()); 804 uint curr_index = curr_region->hrm_index(); 805 _archive_set.remove(curr_region); 806 curr_region->set_free(); 807 curr_region->set_top(curr_region->bottom()); 808 if (curr_region != last_region) { 809 curr_region = _hrm.next_region_in_heap(curr_region); 810 } else { 811 curr_region = NULL; 812 } 813 _hrm.shrink_at(curr_index, 1); 814 uncommitted_regions++; 815 } 816 817 // Notify mark-sweep that this is no longer an archive range. 818 G1ArchiveAllocator::clear_range_archive(ranges[i], is_open); 819 } 820 821 if (uncommitted_regions != 0) { 822 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 823 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 824 } 825 decrease_used(size_used); 826 } 827 828 oop G1CollectedHeap::materialize_archived_object(oop obj) { 829 assert(obj != NULL, "archived obj is NULL"); 830 assert(G1ArchiveAllocator::is_archived_object(obj), "must be archived object"); 831 832 // Loading an archived object makes it strongly reachable. If it is 833 // loaded during concurrent marking, it must be enqueued to the SATB 834 // queue, shading the previously white object gray. 835 G1BarrierSet::enqueue(obj); 836 837 return obj; 838 } 839 840 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) { 841 ResourceMark rm; // For retrieving the thread names in log messages. 842 843 // The structure of this method has a lot of similarities to 844 // attempt_allocation_slow(). The reason these two were not merged 845 // into a single one is that such a method would require several "if 846 // allocation is not humongous do this, otherwise do that" 847 // conditional paths which would obscure its flow. In fact, an early 848 // version of this code did use a unified method which was harder to 849 // follow and, as a result, it had subtle bugs that were hard to 850 // track down. So keeping these two methods separate allows each to 851 // be more readable. It will be good to keep these two in sync as 852 // much as possible. 853 854 assert_heap_not_locked_and_not_at_safepoint(); 855 assert(is_humongous(word_size), "attempt_allocation_humongous() " 856 "should only be called for humongous allocations"); 857 858 // Humongous objects can exhaust the heap quickly, so we should check if we 859 // need to start a marking cycle at each humongous object allocation. We do 860 // the check before we do the actual allocation. The reason for doing it 861 // before the allocation is that we avoid having to keep track of the newly 862 // allocated memory while we do a GC. 863 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 864 word_size)) { 865 collect(GCCause::_g1_humongous_allocation); 866 } 867 868 // We will loop until a) we manage to successfully perform the 869 // allocation or b) we successfully schedule a collection which 870 // fails to perform the allocation. b) is the only case when we'll 871 // return NULL. 872 HeapWord* result = NULL; 873 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 874 bool should_try_gc; 875 uint gc_count_before; 876 877 878 { 879 MutexLockerEx x(Heap_lock); 880 881 // Given that humongous objects are not allocated in young 882 // regions, we'll first try to do the allocation without doing a 883 // collection hoping that there's enough space in the heap. 884 result = humongous_obj_allocate(word_size); 885 if (result != NULL) { 886 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 887 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 888 return result; 889 } 890 891 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 892 // the GCLocker initiated GC has been performed and then retry. This includes 893 // the case when the GC Locker is not active but has not been performed. 894 should_try_gc = !GCLocker::needs_gc(); 895 // Read the GC count while still holding the Heap_lock. 896 gc_count_before = total_collections(); 897 } 898 899 if (should_try_gc) { 900 bool succeeded; 901 result = do_collection_pause(word_size, gc_count_before, &succeeded, 902 GCCause::_g1_humongous_allocation); 903 if (result != NULL) { 904 assert(succeeded, "only way to get back a non-NULL result"); 905 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 906 Thread::current()->name(), p2i(result)); 907 return result; 908 } 909 910 if (succeeded) { 911 // We successfully scheduled a collection which failed to allocate. No 912 // point in trying to allocate further. We'll just return NULL. 913 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 914 SIZE_FORMAT " words", Thread::current()->name(), word_size); 915 return NULL; 916 } 917 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "", 918 Thread::current()->name(), word_size); 919 } else { 920 // Failed to schedule a collection. 921 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 922 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 923 SIZE_FORMAT " words", Thread::current()->name(), word_size); 924 return NULL; 925 } 926 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 927 // The GCLocker is either active or the GCLocker initiated 928 // GC has not yet been performed. Stall until it is and 929 // then retry the allocation. 930 GCLocker::stall_until_clear(); 931 gclocker_retry_count += 1; 932 } 933 934 935 // We can reach here if we were unsuccessful in scheduling a 936 // collection (because another thread beat us to it) or if we were 937 // stalled due to the GC locker. In either can we should retry the 938 // allocation attempt in case another thread successfully 939 // performed a collection and reclaimed enough space. 940 // Humongous object allocation always needs a lock, so we wait for the retry 941 // in the next iteration of the loop, unlike for the regular iteration case. 942 // Give a warning if we seem to be looping forever. 943 944 if ((QueuedAllocationWarningCount > 0) && 945 (try_count % QueuedAllocationWarningCount == 0)) { 946 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 947 Thread::current()->name(), try_count, word_size); 948 } 949 } 950 951 ShouldNotReachHere(); 952 return NULL; 953 } 954 955 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 956 bool expect_null_mutator_alloc_region) { 957 assert_at_safepoint_on_vm_thread(); 958 assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region, 959 "the current alloc region was unexpectedly found to be non-NULL"); 960 961 if (!is_humongous(word_size)) { 962 return _allocator->attempt_allocation_locked(word_size); 963 } else { 964 HeapWord* result = humongous_obj_allocate(word_size); 965 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 966 collector_state()->set_initiate_conc_mark_if_possible(true); 967 } 968 return result; 969 } 970 971 ShouldNotReachHere(); 972 } 973 974 class PostCompactionPrinterClosure: public HeapRegionClosure { 975 private: 976 G1HRPrinter* _hr_printer; 977 public: 978 bool do_heap_region(HeapRegion* hr) { 979 assert(!hr->is_young(), "not expecting to find young regions"); 980 _hr_printer->post_compaction(hr); 981 return false; 982 } 983 984 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 985 : _hr_printer(hr_printer) { } 986 }; 987 988 void G1CollectedHeap::print_hrm_post_compaction() { 989 if (_hr_printer.is_active()) { 990 PostCompactionPrinterClosure cl(hr_printer()); 991 heap_region_iterate(&cl); 992 } 993 } 994 995 void G1CollectedHeap::abort_concurrent_cycle() { 996 // If we start the compaction before the CM threads finish 997 // scanning the root regions we might trip them over as we'll 998 // be moving objects / updating references. So let's wait until 999 // they are done. By telling them to abort, they should complete 1000 // early. 1001 _cm->root_regions()->abort(); 1002 _cm->root_regions()->wait_until_scan_finished(); 1003 1004 // Disable discovery and empty the discovered lists 1005 // for the CM ref processor. 1006 _ref_processor_cm->disable_discovery(); 1007 _ref_processor_cm->abandon_partial_discovery(); 1008 _ref_processor_cm->verify_no_references_recorded(); 1009 1010 // Abandon current iterations of concurrent marking and concurrent 1011 // refinement, if any are in progress. 1012 concurrent_mark()->concurrent_cycle_abort(); 1013 } 1014 1015 void G1CollectedHeap::prepare_heap_for_full_collection() { 1016 // Make sure we'll choose a new allocation region afterwards. 1017 _allocator->release_mutator_alloc_region(); 1018 _allocator->abandon_gc_alloc_regions(); 1019 1020 // We may have added regions to the current incremental collection 1021 // set between the last GC or pause and now. We need to clear the 1022 // incremental collection set and then start rebuilding it afresh 1023 // after this full GC. 1024 abandon_collection_set(collection_set()); 1025 1026 tear_down_region_sets(false /* free_list_only */); 1027 } 1028 1029 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1030 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1031 assert(used() == recalculate_used(), "Should be equal"); 1032 _verifier->verify_region_sets_optional(); 1033 _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull); 1034 _verifier->check_bitmaps("Full GC Start"); 1035 } 1036 1037 void G1CollectedHeap::prepare_heap_for_mutators() { 1038 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1039 ClassLoaderDataGraph::purge(); 1040 MetaspaceUtils::verify_metrics(); 1041 1042 // Prepare heap for normal collections. 1043 assert(num_free_regions() == 0, "we should not have added any free regions"); 1044 rebuild_region_sets(false /* free_list_only */); 1045 abort_refinement(); 1046 resize_heap_if_necessary(); 1047 1048 // Rebuild the strong code root lists for each region 1049 rebuild_strong_code_roots(); 1050 1051 // Purge code root memory 1052 purge_code_root_memory(); 1053 1054 // Start a new incremental collection set for the next pause 1055 start_new_collection_set(); 1056 1057 _allocator->init_mutator_alloc_region(); 1058 1059 // Post collection state updates. 1060 MetaspaceGC::compute_new_size(); 1061 } 1062 1063 void G1CollectedHeap::abort_refinement() { 1064 if (_hot_card_cache->use_cache()) { 1065 _hot_card_cache->reset_hot_cache(); 1066 } 1067 1068 // Discard all remembered set updates. 1069 G1BarrierSet::dirty_card_queue_set().abandon_logs(); 1070 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1071 } 1072 1073 void G1CollectedHeap::verify_after_full_collection() { 1074 _hrm.verify_optional(); 1075 _verifier->verify_region_sets_optional(); 1076 _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull); 1077 // Clear the previous marking bitmap, if needed for bitmap verification. 1078 // Note we cannot do this when we clear the next marking bitmap in 1079 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1080 // objects marked during a full GC against the previous bitmap. 1081 // But we need to clear it before calling check_bitmaps below since 1082 // the full GC has compacted objects and updated TAMS but not updated 1083 // the prev bitmap. 1084 if (G1VerifyBitmaps) { 1085 GCTraceTime(Debug, gc)("Clear Prev Bitmap for Verification"); 1086 _cm->clear_prev_bitmap(workers()); 1087 } 1088 // This call implicitly verifies that the next bitmap is clear after Full GC. 1089 _verifier->check_bitmaps("Full GC End"); 1090 1091 // At this point there should be no regions in the 1092 // entire heap tagged as young. 1093 assert(check_young_list_empty(), "young list should be empty at this point"); 1094 1095 // Note: since we've just done a full GC, concurrent 1096 // marking is no longer active. Therefore we need not 1097 // re-enable reference discovery for the CM ref processor. 1098 // That will be done at the start of the next marking cycle. 1099 // We also know that the STW processor should no longer 1100 // discover any new references. 1101 assert(!_ref_processor_stw->discovery_enabled(), "Postcondition"); 1102 assert(!_ref_processor_cm->discovery_enabled(), "Postcondition"); 1103 _ref_processor_stw->verify_no_references_recorded(); 1104 _ref_processor_cm->verify_no_references_recorded(); 1105 } 1106 1107 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1108 // Post collection logging. 1109 // We should do this after we potentially resize the heap so 1110 // that all the COMMIT / UNCOMMIT events are generated before 1111 // the compaction events. 1112 print_hrm_post_compaction(); 1113 heap_transition->print(); 1114 print_heap_after_gc(); 1115 print_heap_regions(); 1116 #ifdef TRACESPINNING 1117 ParallelTaskTerminator::print_termination_counts(); 1118 #endif 1119 } 1120 1121 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1122 bool clear_all_soft_refs) { 1123 assert_at_safepoint_on_vm_thread(); 1124 1125 if (GCLocker::check_active_before_gc()) { 1126 // Full GC was not completed. 1127 return false; 1128 } 1129 1130 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1131 soft_ref_policy()->should_clear_all_soft_refs(); 1132 1133 G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs); 1134 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1135 1136 collector.prepare_collection(); 1137 collector.collect(); 1138 collector.complete_collection(); 1139 1140 // Full collection was successfully completed. 1141 return true; 1142 } 1143 1144 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1145 // Currently, there is no facility in the do_full_collection(bool) API to notify 1146 // the caller that the collection did not succeed (e.g., because it was locked 1147 // out by the GC locker). So, right now, we'll ignore the return value. 1148 bool dummy = do_full_collection(true, /* explicit_gc */ 1149 clear_all_soft_refs); 1150 } 1151 1152 void G1CollectedHeap::resize_heap_if_necessary() { 1153 // Capacity, free and used after the GC counted as full regions to 1154 // include the waste in the following calculations. 1155 const size_t capacity_after_gc = capacity(); 1156 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes(); 1157 1158 // This is enforced in arguments.cpp. 1159 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1160 "otherwise the code below doesn't make sense"); 1161 1162 // We don't have floating point command-line arguments 1163 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1164 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1165 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1166 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1167 1168 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1169 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1170 1171 // We have to be careful here as these two calculations can overflow 1172 // 32-bit size_t's. 1173 double used_after_gc_d = (double) used_after_gc; 1174 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1175 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1176 1177 // Let's make sure that they are both under the max heap size, which 1178 // by default will make them fit into a size_t. 1179 double desired_capacity_upper_bound = (double) max_heap_size; 1180 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1181 desired_capacity_upper_bound); 1182 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1183 desired_capacity_upper_bound); 1184 1185 // We can now safely turn them into size_t's. 1186 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1187 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1188 1189 // This assert only makes sense here, before we adjust them 1190 // with respect to the min and max heap size. 1191 assert(minimum_desired_capacity <= maximum_desired_capacity, 1192 "minimum_desired_capacity = " SIZE_FORMAT ", " 1193 "maximum_desired_capacity = " SIZE_FORMAT, 1194 minimum_desired_capacity, maximum_desired_capacity); 1195 1196 // Should not be greater than the heap max size. No need to adjust 1197 // it with respect to the heap min size as it's a lower bound (i.e., 1198 // we'll try to make the capacity larger than it, not smaller). 1199 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1200 // Should not be less than the heap min size. No need to adjust it 1201 // with respect to the heap max size as it's an upper bound (i.e., 1202 // we'll try to make the capacity smaller than it, not greater). 1203 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1204 1205 if (capacity_after_gc < minimum_desired_capacity) { 1206 // Don't expand unless it's significant 1207 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1208 1209 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity). " 1210 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1211 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1212 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio); 1213 1214 expand(expand_bytes, _workers); 1215 1216 // No expansion, now see if we want to shrink 1217 } else if (capacity_after_gc > maximum_desired_capacity) { 1218 // Capacity too large, compute shrinking size 1219 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1220 1221 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity). " 1222 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1223 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1224 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio); 1225 1226 shrink(shrink_bytes); 1227 } 1228 } 1229 1230 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1231 bool do_gc, 1232 bool clear_all_soft_refs, 1233 bool expect_null_mutator_alloc_region, 1234 bool* gc_succeeded) { 1235 *gc_succeeded = true; 1236 // Let's attempt the allocation first. 1237 HeapWord* result = 1238 attempt_allocation_at_safepoint(word_size, 1239 expect_null_mutator_alloc_region); 1240 if (result != NULL) { 1241 return result; 1242 } 1243 1244 // In a G1 heap, we're supposed to keep allocation from failing by 1245 // incremental pauses. Therefore, at least for now, we'll favor 1246 // expansion over collection. (This might change in the future if we can 1247 // do something smarter than full collection to satisfy a failed alloc.) 1248 result = expand_and_allocate(word_size); 1249 if (result != NULL) { 1250 return result; 1251 } 1252 1253 if (do_gc) { 1254 // Expansion didn't work, we'll try to do a Full GC. 1255 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1256 clear_all_soft_refs); 1257 } 1258 1259 return NULL; 1260 } 1261 1262 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1263 bool* succeeded) { 1264 assert_at_safepoint_on_vm_thread(); 1265 1266 // Attempts to allocate followed by Full GC. 1267 HeapWord* result = 1268 satisfy_failed_allocation_helper(word_size, 1269 true, /* do_gc */ 1270 false, /* clear_all_soft_refs */ 1271 false, /* expect_null_mutator_alloc_region */ 1272 succeeded); 1273 1274 if (result != NULL || !*succeeded) { 1275 return result; 1276 } 1277 1278 // Attempts to allocate followed by Full GC that will collect all soft references. 1279 result = satisfy_failed_allocation_helper(word_size, 1280 true, /* do_gc */ 1281 true, /* clear_all_soft_refs */ 1282 true, /* expect_null_mutator_alloc_region */ 1283 succeeded); 1284 1285 if (result != NULL || !*succeeded) { 1286 return result; 1287 } 1288 1289 // Attempts to allocate, no GC 1290 result = satisfy_failed_allocation_helper(word_size, 1291 false, /* do_gc */ 1292 false, /* clear_all_soft_refs */ 1293 true, /* expect_null_mutator_alloc_region */ 1294 succeeded); 1295 1296 if (result != NULL) { 1297 return result; 1298 } 1299 1300 assert(!soft_ref_policy()->should_clear_all_soft_refs(), 1301 "Flag should have been handled and cleared prior to this point"); 1302 1303 // What else? We might try synchronous finalization later. If the total 1304 // space available is large enough for the allocation, then a more 1305 // complete compaction phase than we've tried so far might be 1306 // appropriate. 1307 return NULL; 1308 } 1309 1310 // Attempting to expand the heap sufficiently 1311 // to support an allocation of the given "word_size". If 1312 // successful, perform the allocation and return the address of the 1313 // allocated block, or else "NULL". 1314 1315 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1316 assert_at_safepoint_on_vm_thread(); 1317 1318 _verifier->verify_region_sets_optional(); 1319 1320 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1321 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1322 word_size * HeapWordSize); 1323 1324 1325 if (expand(expand_bytes, _workers)) { 1326 _hrm.verify_optional(); 1327 _verifier->verify_region_sets_optional(); 1328 return attempt_allocation_at_safepoint(word_size, 1329 false /* expect_null_mutator_alloc_region */); 1330 } 1331 return NULL; 1332 } 1333 1334 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1335 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1336 aligned_expand_bytes = align_up(aligned_expand_bytes, 1337 HeapRegion::GrainBytes); 1338 1339 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1340 expand_bytes, aligned_expand_bytes); 1341 1342 if (is_maximal_no_gc()) { 1343 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1344 return false; 1345 } 1346 1347 double expand_heap_start_time_sec = os::elapsedTime(); 1348 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1349 assert(regions_to_expand > 0, "Must expand by at least one region"); 1350 1351 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers); 1352 if (expand_time_ms != NULL) { 1353 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1354 } 1355 1356 if (expanded_by > 0) { 1357 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1358 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1359 g1_policy()->record_new_heap_size(num_regions()); 1360 } else { 1361 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1362 1363 // The expansion of the virtual storage space was unsuccessful. 1364 // Let's see if it was because we ran out of swap. 1365 if (G1ExitOnExpansionFailure && 1366 _hrm.available() >= regions_to_expand) { 1367 // We had head room... 1368 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1369 } 1370 } 1371 return regions_to_expand > 0; 1372 } 1373 1374 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1375 size_t aligned_shrink_bytes = 1376 ReservedSpace::page_align_size_down(shrink_bytes); 1377 aligned_shrink_bytes = align_down(aligned_shrink_bytes, 1378 HeapRegion::GrainBytes); 1379 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1380 1381 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1382 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1383 1384 1385 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", 1386 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1387 if (num_regions_removed > 0) { 1388 g1_policy()->record_new_heap_size(num_regions()); 1389 } else { 1390 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1391 } 1392 } 1393 1394 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1395 _verifier->verify_region_sets_optional(); 1396 1397 // We should only reach here at the end of a Full GC or during Remark which 1398 // means we should not not be holding to any GC alloc regions. The method 1399 // below will make sure of that and do any remaining clean up. 1400 _allocator->abandon_gc_alloc_regions(); 1401 1402 // Instead of tearing down / rebuilding the free lists here, we 1403 // could instead use the remove_all_pending() method on free_list to 1404 // remove only the ones that we need to remove. 1405 tear_down_region_sets(true /* free_list_only */); 1406 shrink_helper(shrink_bytes); 1407 rebuild_region_sets(true /* free_list_only */); 1408 1409 _hrm.verify_optional(); 1410 _verifier->verify_region_sets_optional(); 1411 } 1412 1413 class OldRegionSetChecker : public HeapRegionSetChecker { 1414 public: 1415 void check_mt_safety() { 1416 // Master Old Set MT safety protocol: 1417 // (a) If we're at a safepoint, operations on the master old set 1418 // should be invoked: 1419 // - by the VM thread (which will serialize them), or 1420 // - by the GC workers while holding the FreeList_lock, if we're 1421 // at a safepoint for an evacuation pause (this lock is taken 1422 // anyway when an GC alloc region is retired so that a new one 1423 // is allocated from the free list), or 1424 // - by the GC workers while holding the OldSets_lock, if we're at a 1425 // safepoint for a cleanup pause. 1426 // (b) If we're not at a safepoint, operations on the master old set 1427 // should be invoked while holding the Heap_lock. 1428 1429 if (SafepointSynchronize::is_at_safepoint()) { 1430 guarantee(Thread::current()->is_VM_thread() || 1431 FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(), 1432 "master old set MT safety protocol at a safepoint"); 1433 } else { 1434 guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint"); 1435 } 1436 } 1437 bool is_correct_type(HeapRegion* hr) { return hr->is_old(); } 1438 const char* get_description() { return "Old Regions"; } 1439 }; 1440 1441 class ArchiveRegionSetChecker : public HeapRegionSetChecker { 1442 public: 1443 void check_mt_safety() { 1444 guarantee(!Universe::is_fully_initialized() || SafepointSynchronize::is_at_safepoint(), 1445 "May only change archive regions during initialization or safepoint."); 1446 } 1447 bool is_correct_type(HeapRegion* hr) { return hr->is_archive(); } 1448 const char* get_description() { return "Archive Regions"; } 1449 }; 1450 1451 class HumongousRegionSetChecker : public HeapRegionSetChecker { 1452 public: 1453 void check_mt_safety() { 1454 // Humongous Set MT safety protocol: 1455 // (a) If we're at a safepoint, operations on the master humongous 1456 // set should be invoked by either the VM thread (which will 1457 // serialize them) or by the GC workers while holding the 1458 // OldSets_lock. 1459 // (b) If we're not at a safepoint, operations on the master 1460 // humongous set should be invoked while holding the Heap_lock. 1461 1462 if (SafepointSynchronize::is_at_safepoint()) { 1463 guarantee(Thread::current()->is_VM_thread() || 1464 OldSets_lock->owned_by_self(), 1465 "master humongous set MT safety protocol at a safepoint"); 1466 } else { 1467 guarantee(Heap_lock->owned_by_self(), 1468 "master humongous set MT safety protocol outside a safepoint"); 1469 } 1470 } 1471 bool is_correct_type(HeapRegion* hr) { return hr->is_humongous(); } 1472 const char* get_description() { return "Humongous Regions"; } 1473 }; 1474 1475 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1476 CollectedHeap(), 1477 _young_gen_sampling_thread(NULL), 1478 _workers(NULL), 1479 _collector_policy(collector_policy), 1480 _card_table(NULL), 1481 _soft_ref_policy(), 1482 _old_set("Old Region Set", new OldRegionSetChecker()), 1483 _archive_set("Archive Region Set", new ArchiveRegionSetChecker()), 1484 _humongous_set("Humongous Region Set", new HumongousRegionSetChecker()), 1485 _bot(NULL), 1486 _listener(), 1487 _hrm(), 1488 _allocator(NULL), 1489 _verifier(NULL), 1490 _summary_bytes_used(0), 1491 _archive_allocator(NULL), 1492 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1493 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1494 _expand_heap_after_alloc_failure(true), 1495 _g1mm(NULL), 1496 _humongous_reclaim_candidates(), 1497 _has_humongous_reclaim_candidates(false), 1498 _hr_printer(), 1499 _collector_state(), 1500 _old_marking_cycles_started(0), 1501 _old_marking_cycles_completed(0), 1502 _eden(), 1503 _survivor(), 1504 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1505 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1506 _g1_policy(new G1Policy(_gc_timer_stw)), 1507 _heap_sizing_policy(NULL), 1508 _collection_set(this, _g1_policy), 1509 _hot_card_cache(NULL), 1510 _g1_rem_set(NULL), 1511 _dirty_card_queue_set(false), 1512 _cm(NULL), 1513 _cm_thread(NULL), 1514 _cr(NULL), 1515 _task_queues(NULL), 1516 _evacuation_failed(false), 1517 _evacuation_failed_info_array(NULL), 1518 _preserved_marks_set(true /* in_c_heap */), 1519 #ifndef PRODUCT 1520 _evacuation_failure_alot_for_current_gc(false), 1521 _evacuation_failure_alot_gc_number(0), 1522 _evacuation_failure_alot_count(0), 1523 #endif 1524 _ref_processor_stw(NULL), 1525 _is_alive_closure_stw(this), 1526 _is_subject_to_discovery_stw(this), 1527 _ref_processor_cm(NULL), 1528 _is_alive_closure_cm(this), 1529 _is_subject_to_discovery_cm(this), 1530 _in_cset_fast_test() { 1531 1532 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1533 true /* are_GC_task_threads */, 1534 false /* are_ConcurrentGC_threads */); 1535 _workers->initialize_workers(); 1536 _verifier = new G1HeapVerifier(this); 1537 1538 _allocator = new G1Allocator(this); 1539 1540 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1541 1542 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1543 1544 // Override the default _filler_array_max_size so that no humongous filler 1545 // objects are created. 1546 _filler_array_max_size = _humongous_object_threshold_in_words; 1547 1548 uint n_queues = ParallelGCThreads; 1549 _task_queues = new RefToScanQueueSet(n_queues); 1550 1551 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1552 1553 for (uint i = 0; i < n_queues; i++) { 1554 RefToScanQueue* q = new RefToScanQueue(); 1555 q->initialize(); 1556 _task_queues->register_queue(i, q); 1557 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1558 } 1559 1560 // Initialize the G1EvacuationFailureALot counters and flags. 1561 NOT_PRODUCT(reset_evacuation_should_fail();) 1562 1563 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1564 } 1565 1566 static size_t actual_reserved_page_size(ReservedSpace rs) { 1567 size_t page_size = os::vm_page_size(); 1568 if (UseLargePages) { 1569 // There are two ways to manage large page memory. 1570 // 1. OS supports committing large page memory. 1571 // 2. OS doesn't support committing large page memory so ReservedSpace manages it. 1572 // And ReservedSpace calls it 'special'. If we failed to set 'special', 1573 // we reserved memory without large page. 1574 if (os::can_commit_large_page_memory() || rs.special()) { 1575 page_size = rs.alignment(); 1576 } 1577 } 1578 1579 return page_size; 1580 } 1581 1582 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1583 size_t size, 1584 size_t translation_factor) { 1585 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1586 // Allocate a new reserved space, preferring to use large pages. 1587 ReservedSpace rs(size, preferred_page_size); 1588 size_t page_size = actual_reserved_page_size(rs); 1589 G1RegionToSpaceMapper* result = 1590 G1RegionToSpaceMapper::create_mapper(rs, 1591 size, 1592 page_size, 1593 HeapRegion::GrainBytes, 1594 translation_factor, 1595 mtGC); 1596 1597 os::trace_page_sizes_for_requested_size(description, 1598 size, 1599 preferred_page_size, 1600 page_size, 1601 rs.base(), 1602 rs.size()); 1603 1604 return result; 1605 } 1606 1607 jint G1CollectedHeap::initialize_concurrent_refinement() { 1608 jint ecode = JNI_OK; 1609 _cr = G1ConcurrentRefine::create(&ecode); 1610 return ecode; 1611 } 1612 1613 jint G1CollectedHeap::initialize_young_gen_sampling_thread() { 1614 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread(); 1615 if (_young_gen_sampling_thread->osthread() == NULL) { 1616 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread"); 1617 return JNI_ENOMEM; 1618 } 1619 return JNI_OK; 1620 } 1621 1622 jint G1CollectedHeap::initialize() { 1623 os::enable_vtime(); 1624 1625 // Necessary to satisfy locking discipline assertions. 1626 1627 MutexLocker x(Heap_lock); 1628 1629 // While there are no constraints in the GC code that HeapWordSize 1630 // be any particular value, there are multiple other areas in the 1631 // system which believe this to be true (e.g. oop->object_size in some 1632 // cases incorrectly returns the size in wordSize units rather than 1633 // HeapWordSize). 1634 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1635 1636 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1637 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1638 size_t heap_alignment = collector_policy()->heap_alignment(); 1639 1640 // Ensure that the sizes are properly aligned. 1641 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1642 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1643 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1644 1645 // Reserve the maximum. 1646 1647 // When compressed oops are enabled, the preferred heap base 1648 // is calculated by subtracting the requested size from the 1649 // 32Gb boundary and using the result as the base address for 1650 // heap reservation. If the requested size is not aligned to 1651 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1652 // into the ReservedHeapSpace constructor) then the actual 1653 // base of the reserved heap may end up differing from the 1654 // address that was requested (i.e. the preferred heap base). 1655 // If this happens then we could end up using a non-optimal 1656 // compressed oops mode. 1657 1658 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1659 heap_alignment); 1660 1661 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1662 1663 // Create the barrier set for the entire reserved region. 1664 G1CardTable* ct = new G1CardTable(reserved_region()); 1665 ct->initialize(); 1666 G1BarrierSet* bs = new G1BarrierSet(ct); 1667 bs->initialize(); 1668 assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity"); 1669 BarrierSet::set_barrier_set(bs); 1670 _card_table = ct; 1671 1672 G1BarrierSet::satb_mark_queue_set().initialize(this, 1673 SATB_Q_CBL_mon, 1674 &bs->satb_mark_queue_buffer_allocator(), 1675 G1SATBProcessCompletedThreshold, 1676 G1SATBBufferEnqueueingThresholdPercent, 1677 Shared_SATB_Q_lock); 1678 1679 // process_completed_buffers_threshold and max_completed_buffers are updated 1680 // later, based on the concurrent refinement object. 1681 G1BarrierSet::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1682 &bs->dirty_card_queue_buffer_allocator(), 1683 Shared_DirtyCardQ_lock, 1684 true); // init_free_ids 1685 1686 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1687 &bs->dirty_card_queue_buffer_allocator(), 1688 Shared_DirtyCardQ_lock); 1689 1690 // Create the hot card cache. 1691 _hot_card_cache = new G1HotCardCache(this); 1692 1693 // Carve out the G1 part of the heap. 1694 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1695 size_t page_size = actual_reserved_page_size(heap_rs); 1696 G1RegionToSpaceMapper* heap_storage = 1697 G1RegionToSpaceMapper::create_mapper(g1_rs, 1698 g1_rs.size(), 1699 page_size, 1700 HeapRegion::GrainBytes, 1701 1, 1702 mtJavaHeap); 1703 os::trace_page_sizes("Heap", 1704 collector_policy()->min_heap_byte_size(), 1705 max_byte_size, 1706 page_size, 1707 heap_rs.base(), 1708 heap_rs.size()); 1709 heap_storage->set_mapping_changed_listener(&_listener); 1710 1711 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1712 G1RegionToSpaceMapper* bot_storage = 1713 create_aux_memory_mapper("Block Offset Table", 1714 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1715 G1BlockOffsetTable::heap_map_factor()); 1716 1717 G1RegionToSpaceMapper* cardtable_storage = 1718 create_aux_memory_mapper("Card Table", 1719 G1CardTable::compute_size(g1_rs.size() / HeapWordSize), 1720 G1CardTable::heap_map_factor()); 1721 1722 G1RegionToSpaceMapper* card_counts_storage = 1723 create_aux_memory_mapper("Card Counts Table", 1724 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1725 G1CardCounts::heap_map_factor()); 1726 1727 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1728 G1RegionToSpaceMapper* prev_bitmap_storage = 1729 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1730 G1RegionToSpaceMapper* next_bitmap_storage = 1731 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1732 1733 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1734 _card_table->initialize(cardtable_storage); 1735 // Do later initialization work for concurrent refinement. 1736 _hot_card_cache->initialize(card_counts_storage); 1737 1738 // 6843694 - ensure that the maximum region index can fit 1739 // in the remembered set structures. 1740 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1741 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1742 1743 // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not 1744 // start within the first card. 1745 guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card."); 1746 // Also create a G1 rem set. 1747 _g1_rem_set = new G1RemSet(this, _card_table, _hot_card_cache); 1748 _g1_rem_set->initialize(max_capacity(), max_regions()); 1749 1750 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1751 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1752 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1753 "too many cards per region"); 1754 1755 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1756 1757 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1758 1759 { 1760 HeapWord* start = _hrm.reserved().start(); 1761 HeapWord* end = _hrm.reserved().end(); 1762 size_t granularity = HeapRegion::GrainBytes; 1763 1764 _in_cset_fast_test.initialize(start, end, granularity); 1765 _humongous_reclaim_candidates.initialize(start, end, granularity); 1766 } 1767 1768 // Create the G1ConcurrentMark data structure and thread. 1769 // (Must do this late, so that "max_regions" is defined.) 1770 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1771 if (_cm == NULL || !_cm->completed_initialization()) { 1772 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1773 return JNI_ENOMEM; 1774 } 1775 _cm_thread = _cm->cm_thread(); 1776 1777 // Now expand into the initial heap size. 1778 if (!expand(init_byte_size, _workers)) { 1779 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1780 return JNI_ENOMEM; 1781 } 1782 1783 // Perform any initialization actions delegated to the policy. 1784 g1_policy()->init(this, &_collection_set); 1785 1786 jint ecode = initialize_concurrent_refinement(); 1787 if (ecode != JNI_OK) { 1788 return ecode; 1789 } 1790 1791 ecode = initialize_young_gen_sampling_thread(); 1792 if (ecode != JNI_OK) { 1793 return ecode; 1794 } 1795 1796 { 1797 DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 1798 dcqs.set_process_completed_buffers_threshold(concurrent_refine()->yellow_zone()); 1799 dcqs.set_max_completed_buffers(concurrent_refine()->red_zone()); 1800 } 1801 1802 // Here we allocate the dummy HeapRegion that is required by the 1803 // G1AllocRegion class. 1804 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1805 1806 // We'll re-use the same region whether the alloc region will 1807 // require BOT updates or not and, if it doesn't, then a non-young 1808 // region will complain that it cannot support allocations without 1809 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1810 dummy_region->set_eden(); 1811 // Make sure it's full. 1812 dummy_region->set_top(dummy_region->end()); 1813 G1AllocRegion::setup(this, dummy_region); 1814 1815 _allocator->init_mutator_alloc_region(); 1816 1817 // Do create of the monitoring and management support so that 1818 // values in the heap have been properly initialized. 1819 _g1mm = new G1MonitoringSupport(this); 1820 1821 G1StringDedup::initialize(); 1822 1823 _preserved_marks_set.init(ParallelGCThreads); 1824 1825 _collection_set.initialize(max_regions()); 1826 1827 return JNI_OK; 1828 } 1829 1830 void G1CollectedHeap::stop() { 1831 // Stop all concurrent threads. We do this to make sure these threads 1832 // do not continue to execute and access resources (e.g. logging) 1833 // that are destroyed during shutdown. 1834 _cr->stop(); 1835 _young_gen_sampling_thread->stop(); 1836 _cm_thread->stop(); 1837 if (G1StringDedup::is_enabled()) { 1838 G1StringDedup::stop(); 1839 } 1840 } 1841 1842 void G1CollectedHeap::safepoint_synchronize_begin() { 1843 SuspendibleThreadSet::synchronize(); 1844 } 1845 1846 void G1CollectedHeap::safepoint_synchronize_end() { 1847 SuspendibleThreadSet::desynchronize(); 1848 } 1849 1850 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1851 return HeapRegion::max_region_size(); 1852 } 1853 1854 void G1CollectedHeap::post_initialize() { 1855 CollectedHeap::post_initialize(); 1856 ref_processing_init(); 1857 } 1858 1859 void G1CollectedHeap::ref_processing_init() { 1860 // Reference processing in G1 currently works as follows: 1861 // 1862 // * There are two reference processor instances. One is 1863 // used to record and process discovered references 1864 // during concurrent marking; the other is used to 1865 // record and process references during STW pauses 1866 // (both full and incremental). 1867 // * Both ref processors need to 'span' the entire heap as 1868 // the regions in the collection set may be dotted around. 1869 // 1870 // * For the concurrent marking ref processor: 1871 // * Reference discovery is enabled at initial marking. 1872 // * Reference discovery is disabled and the discovered 1873 // references processed etc during remarking. 1874 // * Reference discovery is MT (see below). 1875 // * Reference discovery requires a barrier (see below). 1876 // * Reference processing may or may not be MT 1877 // (depending on the value of ParallelRefProcEnabled 1878 // and ParallelGCThreads). 1879 // * A full GC disables reference discovery by the CM 1880 // ref processor and abandons any entries on it's 1881 // discovered lists. 1882 // 1883 // * For the STW processor: 1884 // * Non MT discovery is enabled at the start of a full GC. 1885 // * Processing and enqueueing during a full GC is non-MT. 1886 // * During a full GC, references are processed after marking. 1887 // 1888 // * Discovery (may or may not be MT) is enabled at the start 1889 // of an incremental evacuation pause. 1890 // * References are processed near the end of a STW evacuation pause. 1891 // * For both types of GC: 1892 // * Discovery is atomic - i.e. not concurrent. 1893 // * Reference discovery will not need a barrier. 1894 1895 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1); 1896 1897 // Concurrent Mark ref processor 1898 _ref_processor_cm = 1899 new ReferenceProcessor(&_is_subject_to_discovery_cm, 1900 mt_processing, // mt processing 1901 ParallelGCThreads, // degree of mt processing 1902 (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery 1903 MAX2(ParallelGCThreads, ConcGCThreads), // degree of mt discovery 1904 false, // Reference discovery is not atomic 1905 &_is_alive_closure_cm, // is alive closure 1906 true); // allow changes to number of processing threads 1907 1908 // STW ref processor 1909 _ref_processor_stw = 1910 new ReferenceProcessor(&_is_subject_to_discovery_stw, 1911 mt_processing, // mt processing 1912 ParallelGCThreads, // degree of mt processing 1913 (ParallelGCThreads > 1), // mt discovery 1914 ParallelGCThreads, // degree of mt discovery 1915 true, // Reference discovery is atomic 1916 &_is_alive_closure_stw, // is alive closure 1917 true); // allow changes to number of processing threads 1918 } 1919 1920 CollectorPolicy* G1CollectedHeap::collector_policy() const { 1921 return _collector_policy; 1922 } 1923 1924 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() { 1925 return &_soft_ref_policy; 1926 } 1927 1928 size_t G1CollectedHeap::capacity() const { 1929 return _hrm.length() * HeapRegion::GrainBytes; 1930 } 1931 1932 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const { 1933 return _hrm.total_free_bytes(); 1934 } 1935 1936 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 1937 _hot_card_cache->drain(cl, worker_i); 1938 } 1939 1940 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 1941 DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 1942 size_t n_completed_buffers = 0; 1943 while (dcqs.apply_closure_during_gc(cl, worker_i)) { 1944 n_completed_buffers++; 1945 } 1946 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers, G1GCPhaseTimes::UpdateRSProcessedBuffers); 1947 dcqs.clear_n_completed_buffers(); 1948 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 1949 } 1950 1951 // Computes the sum of the storage used by the various regions. 1952 size_t G1CollectedHeap::used() const { 1953 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 1954 if (_archive_allocator != NULL) { 1955 result += _archive_allocator->used(); 1956 } 1957 return result; 1958 } 1959 1960 size_t G1CollectedHeap::used_unlocked() const { 1961 return _summary_bytes_used; 1962 } 1963 1964 class SumUsedClosure: public HeapRegionClosure { 1965 size_t _used; 1966 public: 1967 SumUsedClosure() : _used(0) {} 1968 bool do_heap_region(HeapRegion* r) { 1969 _used += r->used(); 1970 return false; 1971 } 1972 size_t result() { return _used; } 1973 }; 1974 1975 size_t G1CollectedHeap::recalculate_used() const { 1976 SumUsedClosure blk; 1977 heap_region_iterate(&blk); 1978 return blk.result(); 1979 } 1980 1981 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 1982 switch (cause) { 1983 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 1984 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 1985 case GCCause::_wb_conc_mark: return true; 1986 default : return false; 1987 } 1988 } 1989 1990 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 1991 switch (cause) { 1992 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 1993 case GCCause::_g1_humongous_allocation: return true; 1994 default: return is_user_requested_concurrent_full_gc(cause); 1995 } 1996 } 1997 1998 #ifndef PRODUCT 1999 void G1CollectedHeap::allocate_dummy_regions() { 2000 // Let's fill up most of the region 2001 size_t word_size = HeapRegion::GrainWords - 1024; 2002 // And as a result the region we'll allocate will be humongous. 2003 guarantee(is_humongous(word_size), "sanity"); 2004 2005 // _filler_array_max_size is set to humongous object threshold 2006 // but temporarily change it to use CollectedHeap::fill_with_object(). 2007 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2008 2009 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2010 // Let's use the existing mechanism for the allocation 2011 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 2012 if (dummy_obj != NULL) { 2013 MemRegion mr(dummy_obj, word_size); 2014 CollectedHeap::fill_with_object(mr); 2015 } else { 2016 // If we can't allocate once, we probably cannot allocate 2017 // again. Let's get out of the loop. 2018 break; 2019 } 2020 } 2021 } 2022 #endif // !PRODUCT 2023 2024 void G1CollectedHeap::increment_old_marking_cycles_started() { 2025 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2026 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2027 "Wrong marking cycle count (started: %d, completed: %d)", 2028 _old_marking_cycles_started, _old_marking_cycles_completed); 2029 2030 _old_marking_cycles_started++; 2031 } 2032 2033 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2034 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2035 2036 // We assume that if concurrent == true, then the caller is a 2037 // concurrent thread that was joined the Suspendible Thread 2038 // Set. If there's ever a cheap way to check this, we should add an 2039 // assert here. 2040 2041 // Given that this method is called at the end of a Full GC or of a 2042 // concurrent cycle, and those can be nested (i.e., a Full GC can 2043 // interrupt a concurrent cycle), the number of full collections 2044 // completed should be either one (in the case where there was no 2045 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2046 // behind the number of full collections started. 2047 2048 // This is the case for the inner caller, i.e. a Full GC. 2049 assert(concurrent || 2050 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2051 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2052 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2053 "is inconsistent with _old_marking_cycles_completed = %u", 2054 _old_marking_cycles_started, _old_marking_cycles_completed); 2055 2056 // This is the case for the outer caller, i.e. the concurrent cycle. 2057 assert(!concurrent || 2058 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2059 "for outer caller (concurrent cycle): " 2060 "_old_marking_cycles_started = %u " 2061 "is inconsistent with _old_marking_cycles_completed = %u", 2062 _old_marking_cycles_started, _old_marking_cycles_completed); 2063 2064 _old_marking_cycles_completed += 1; 2065 2066 // We need to clear the "in_progress" flag in the CM thread before 2067 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2068 // is set) so that if a waiter requests another System.gc() it doesn't 2069 // incorrectly see that a marking cycle is still in progress. 2070 if (concurrent) { 2071 _cm_thread->set_idle(); 2072 } 2073 2074 // This notify_all() will ensure that a thread that called 2075 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2076 // and it's waiting for a full GC to finish will be woken up. It is 2077 // waiting in VM_G1CollectForAllocation::doit_epilogue(). 2078 FullGCCount_lock->notify_all(); 2079 } 2080 2081 void G1CollectedHeap::collect(GCCause::Cause cause) { 2082 assert_heap_not_locked(); 2083 2084 uint gc_count_before; 2085 uint old_marking_count_before; 2086 uint full_gc_count_before; 2087 bool retry_gc; 2088 2089 do { 2090 retry_gc = false; 2091 2092 { 2093 MutexLocker ml(Heap_lock); 2094 2095 // Read the GC count while holding the Heap_lock 2096 gc_count_before = total_collections(); 2097 full_gc_count_before = total_full_collections(); 2098 old_marking_count_before = _old_marking_cycles_started; 2099 } 2100 2101 if (should_do_concurrent_full_gc(cause)) { 2102 // Schedule an initial-mark evacuation pause that will start a 2103 // concurrent cycle. We're setting word_size to 0 which means that 2104 // we are not requesting a post-GC allocation. 2105 VM_G1CollectForAllocation op(0, /* word_size */ 2106 gc_count_before, 2107 cause, 2108 true, /* should_initiate_conc_mark */ 2109 g1_policy()->max_pause_time_ms()); 2110 VMThread::execute(&op); 2111 if (!op.pause_succeeded()) { 2112 if (old_marking_count_before == _old_marking_cycles_started) { 2113 retry_gc = op.should_retry_gc(); 2114 } else { 2115 // A Full GC happened while we were trying to schedule the 2116 // initial-mark GC. No point in starting a new cycle given 2117 // that the whole heap was collected anyway. 2118 } 2119 2120 if (retry_gc) { 2121 if (GCLocker::is_active_and_needs_gc()) { 2122 GCLocker::stall_until_clear(); 2123 } 2124 } 2125 } 2126 } else { 2127 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2128 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2129 2130 // Schedule a standard evacuation pause. We're setting word_size 2131 // to 0 which means that we are not requesting a post-GC allocation. 2132 VM_G1CollectForAllocation op(0, /* word_size */ 2133 gc_count_before, 2134 cause, 2135 false, /* should_initiate_conc_mark */ 2136 g1_policy()->max_pause_time_ms()); 2137 VMThread::execute(&op); 2138 } else { 2139 // Schedule a Full GC. 2140 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2141 VMThread::execute(&op); 2142 } 2143 } 2144 } while (retry_gc); 2145 } 2146 2147 bool G1CollectedHeap::is_in(const void* p) const { 2148 if (_hrm.reserved().contains(p)) { 2149 // Given that we know that p is in the reserved space, 2150 // heap_region_containing() should successfully 2151 // return the containing region. 2152 HeapRegion* hr = heap_region_containing(p); 2153 return hr->is_in(p); 2154 } else { 2155 return false; 2156 } 2157 } 2158 2159 #ifdef ASSERT 2160 bool G1CollectedHeap::is_in_exact(const void* p) const { 2161 bool contains = reserved_region().contains(p); 2162 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2163 if (contains && available) { 2164 return true; 2165 } else { 2166 return false; 2167 } 2168 } 2169 #endif 2170 2171 // Iteration functions. 2172 2173 // Iterates an ObjectClosure over all objects within a HeapRegion. 2174 2175 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2176 ObjectClosure* _cl; 2177 public: 2178 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2179 bool do_heap_region(HeapRegion* r) { 2180 if (!r->is_continues_humongous()) { 2181 r->object_iterate(_cl); 2182 } 2183 return false; 2184 } 2185 }; 2186 2187 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2188 IterateObjectClosureRegionClosure blk(cl); 2189 heap_region_iterate(&blk); 2190 } 2191 2192 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2193 _hrm.iterate(cl); 2194 } 2195 2196 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl, 2197 HeapRegionClaimer *hrclaimer, 2198 uint worker_id) const { 2199 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id)); 2200 } 2201 2202 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl, 2203 HeapRegionClaimer *hrclaimer) const { 2204 _hrm.par_iterate(cl, hrclaimer, 0); 2205 } 2206 2207 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2208 _collection_set.iterate(cl); 2209 } 2210 2211 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2212 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2213 } 2214 2215 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2216 HeapRegion* hr = heap_region_containing(addr); 2217 return hr->block_start(addr); 2218 } 2219 2220 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2221 HeapRegion* hr = heap_region_containing(addr); 2222 return hr->block_size(addr); 2223 } 2224 2225 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2226 HeapRegion* hr = heap_region_containing(addr); 2227 return hr->block_is_obj(addr); 2228 } 2229 2230 bool G1CollectedHeap::supports_tlab_allocation() const { 2231 return true; 2232 } 2233 2234 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2235 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2236 } 2237 2238 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2239 return _eden.length() * HeapRegion::GrainBytes; 2240 } 2241 2242 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2243 // must be equal to the humongous object limit. 2244 size_t G1CollectedHeap::max_tlab_size() const { 2245 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2246 } 2247 2248 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2249 return _allocator->unsafe_max_tlab_alloc(); 2250 } 2251 2252 size_t G1CollectedHeap::max_capacity() const { 2253 return _hrm.reserved().byte_size(); 2254 } 2255 2256 jlong G1CollectedHeap::millis_since_last_gc() { 2257 // See the notes in GenCollectedHeap::millis_since_last_gc() 2258 // for more information about the implementation. 2259 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2260 _g1_policy->collection_pause_end_millis(); 2261 if (ret_val < 0) { 2262 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2263 ". returning zero instead.", ret_val); 2264 return 0; 2265 } 2266 return ret_val; 2267 } 2268 2269 void G1CollectedHeap::deduplicate_string(oop str) { 2270 assert(java_lang_String::is_instance(str), "invariant"); 2271 2272 if (G1StringDedup::is_enabled()) { 2273 G1StringDedup::deduplicate(str); 2274 } 2275 } 2276 2277 void G1CollectedHeap::prepare_for_verify() { 2278 _verifier->prepare_for_verify(); 2279 } 2280 2281 void G1CollectedHeap::verify(VerifyOption vo) { 2282 _verifier->verify(vo); 2283 } 2284 2285 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2286 return true; 2287 } 2288 2289 const char* const* G1CollectedHeap::concurrent_phases() const { 2290 return _cm_thread->concurrent_phases(); 2291 } 2292 2293 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2294 return _cm_thread->request_concurrent_phase(phase); 2295 } 2296 2297 class PrintRegionClosure: public HeapRegionClosure { 2298 outputStream* _st; 2299 public: 2300 PrintRegionClosure(outputStream* st) : _st(st) {} 2301 bool do_heap_region(HeapRegion* r) { 2302 r->print_on(_st); 2303 return false; 2304 } 2305 }; 2306 2307 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2308 const HeapRegion* hr, 2309 const VerifyOption vo) const { 2310 switch (vo) { 2311 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2312 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2313 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr); 2314 default: ShouldNotReachHere(); 2315 } 2316 return false; // keep some compilers happy 2317 } 2318 2319 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2320 const VerifyOption vo) const { 2321 switch (vo) { 2322 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2323 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2324 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj); 2325 default: ShouldNotReachHere(); 2326 } 2327 return false; // keep some compilers happy 2328 } 2329 2330 void G1CollectedHeap::print_heap_regions() const { 2331 LogTarget(Trace, gc, heap, region) lt; 2332 if (lt.is_enabled()) { 2333 LogStream ls(lt); 2334 print_regions_on(&ls); 2335 } 2336 } 2337 2338 void G1CollectedHeap::print_on(outputStream* st) const { 2339 st->print(" %-20s", "garbage-first heap"); 2340 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2341 capacity()/K, used_unlocked()/K); 2342 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")", 2343 p2i(_hrm.reserved().start()), 2344 p2i(_hrm.reserved().end())); 2345 st->cr(); 2346 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2347 uint young_regions = young_regions_count(); 2348 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2349 (size_t) young_regions * HeapRegion::GrainBytes / K); 2350 uint survivor_regions = survivor_regions_count(); 2351 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2352 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2353 st->cr(); 2354 MetaspaceUtils::print_on(st); 2355 } 2356 2357 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2358 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2359 "HS=humongous(starts), HC=humongous(continues), " 2360 "CS=collection set, F=free, A=archive, " 2361 "TAMS=top-at-mark-start (previous, next)"); 2362 PrintRegionClosure blk(st); 2363 heap_region_iterate(&blk); 2364 } 2365 2366 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2367 print_on(st); 2368 2369 // Print the per-region information. 2370 print_regions_on(st); 2371 } 2372 2373 void G1CollectedHeap::print_on_error(outputStream* st) const { 2374 this->CollectedHeap::print_on_error(st); 2375 2376 if (_cm != NULL) { 2377 st->cr(); 2378 _cm->print_on_error(st); 2379 } 2380 } 2381 2382 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2383 workers()->print_worker_threads_on(st); 2384 _cm_thread->print_on(st); 2385 st->cr(); 2386 _cm->print_worker_threads_on(st); 2387 _cr->print_threads_on(st); 2388 _young_gen_sampling_thread->print_on(st); 2389 if (G1StringDedup::is_enabled()) { 2390 G1StringDedup::print_worker_threads_on(st); 2391 } 2392 } 2393 2394 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2395 workers()->threads_do(tc); 2396 tc->do_thread(_cm_thread); 2397 _cm->threads_do(tc); 2398 _cr->threads_do(tc); 2399 tc->do_thread(_young_gen_sampling_thread); 2400 if (G1StringDedup::is_enabled()) { 2401 G1StringDedup::threads_do(tc); 2402 } 2403 } 2404 2405 void G1CollectedHeap::print_tracing_info() const { 2406 g1_rem_set()->print_summary_info(); 2407 concurrent_mark()->print_summary_info(); 2408 } 2409 2410 #ifndef PRODUCT 2411 // Helpful for debugging RSet issues. 2412 2413 class PrintRSetsClosure : public HeapRegionClosure { 2414 private: 2415 const char* _msg; 2416 size_t _occupied_sum; 2417 2418 public: 2419 bool do_heap_region(HeapRegion* r) { 2420 HeapRegionRemSet* hrrs = r->rem_set(); 2421 size_t occupied = hrrs->occupied(); 2422 _occupied_sum += occupied; 2423 2424 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2425 if (occupied == 0) { 2426 tty->print_cr(" RSet is empty"); 2427 } else { 2428 hrrs->print(); 2429 } 2430 tty->print_cr("----------"); 2431 return false; 2432 } 2433 2434 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2435 tty->cr(); 2436 tty->print_cr("========================================"); 2437 tty->print_cr("%s", msg); 2438 tty->cr(); 2439 } 2440 2441 ~PrintRSetsClosure() { 2442 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2443 tty->print_cr("========================================"); 2444 tty->cr(); 2445 } 2446 }; 2447 2448 void G1CollectedHeap::print_cset_rsets() { 2449 PrintRSetsClosure cl("Printing CSet RSets"); 2450 collection_set_iterate(&cl); 2451 } 2452 2453 void G1CollectedHeap::print_all_rsets() { 2454 PrintRSetsClosure cl("Printing All RSets");; 2455 heap_region_iterate(&cl); 2456 } 2457 #endif // PRODUCT 2458 2459 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2460 2461 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2462 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2463 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2464 2465 size_t eden_capacity_bytes = 2466 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2467 2468 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2469 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2470 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2471 } 2472 2473 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2474 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2475 stats->unused(), stats->used(), stats->region_end_waste(), 2476 stats->regions_filled(), stats->direct_allocated(), 2477 stats->failure_used(), stats->failure_waste()); 2478 } 2479 2480 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2481 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2482 gc_tracer->report_gc_heap_summary(when, heap_summary); 2483 2484 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2485 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2486 } 2487 2488 G1CollectedHeap* G1CollectedHeap::heap() { 2489 CollectedHeap* heap = Universe::heap(); 2490 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2491 assert(heap->kind() == CollectedHeap::G1, "Invalid name"); 2492 return (G1CollectedHeap*)heap; 2493 } 2494 2495 void G1CollectedHeap::gc_prologue(bool full) { 2496 // always_do_update_barrier = false; 2497 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2498 2499 // This summary needs to be printed before incrementing total collections. 2500 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2501 2502 // Update common counters. 2503 increment_total_collections(full /* full gc */); 2504 if (full) { 2505 increment_old_marking_cycles_started(); 2506 } 2507 2508 // Fill TLAB's and such 2509 double start = os::elapsedTime(); 2510 ensure_parsability(true); 2511 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2512 } 2513 2514 void G1CollectedHeap::gc_epilogue(bool full) { 2515 // Update common counters. 2516 if (full) { 2517 // Update the number of full collections that have been completed. 2518 increment_old_marking_cycles_completed(false /* concurrent */); 2519 } 2520 2521 // We are at the end of the GC. Total collections has already been increased. 2522 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2523 2524 // FIXME: what is this about? 2525 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2526 // is set. 2527 #if COMPILER2_OR_JVMCI 2528 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2529 #endif 2530 // always_do_update_barrier = true; 2531 2532 double start = os::elapsedTime(); 2533 resize_all_tlabs(); 2534 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2535 2536 MemoryService::track_memory_usage(); 2537 // We have just completed a GC. Update the soft reference 2538 // policy with the new heap occupancy 2539 Universe::update_heap_info_at_gc(); 2540 } 2541 2542 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2543 uint gc_count_before, 2544 bool* succeeded, 2545 GCCause::Cause gc_cause) { 2546 assert_heap_not_locked_and_not_at_safepoint(); 2547 VM_G1CollectForAllocation op(word_size, 2548 gc_count_before, 2549 gc_cause, 2550 false, /* should_initiate_conc_mark */ 2551 g1_policy()->max_pause_time_ms()); 2552 VMThread::execute(&op); 2553 2554 HeapWord* result = op.result(); 2555 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2556 assert(result == NULL || ret_succeeded, 2557 "the result should be NULL if the VM did not succeed"); 2558 *succeeded = ret_succeeded; 2559 2560 assert_heap_not_locked(); 2561 return result; 2562 } 2563 2564 void G1CollectedHeap::do_concurrent_mark() { 2565 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2566 if (!_cm_thread->in_progress()) { 2567 _cm_thread->set_started(); 2568 CGC_lock->notify(); 2569 } 2570 } 2571 2572 size_t G1CollectedHeap::pending_card_num() { 2573 size_t extra_cards = 0; 2574 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) { 2575 DirtyCardQueue& dcq = G1ThreadLocalData::dirty_card_queue(curr); 2576 extra_cards += dcq.size(); 2577 } 2578 DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 2579 size_t buffer_size = dcqs.buffer_size(); 2580 size_t buffer_num = dcqs.completed_buffers_num(); 2581 2582 return buffer_size * buffer_num + extra_cards; 2583 } 2584 2585 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const { 2586 // We don't nominate objects with many remembered set entries, on 2587 // the assumption that such objects are likely still live. 2588 HeapRegionRemSet* rem_set = r->rem_set(); 2589 2590 return G1EagerReclaimHumongousObjectsWithStaleRefs ? 2591 rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) : 2592 G1EagerReclaimHumongousObjects && rem_set->is_empty(); 2593 } 2594 2595 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2596 private: 2597 size_t _total_humongous; 2598 size_t _candidate_humongous; 2599 2600 DirtyCardQueue _dcq; 2601 2602 bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const { 2603 assert(region->is_starts_humongous(), "Must start a humongous object"); 2604 2605 oop obj = oop(region->bottom()); 2606 2607 // Dead objects cannot be eager reclaim candidates. Due to class 2608 // unloading it is unsafe to query their classes so we return early. 2609 if (g1h->is_obj_dead(obj, region)) { 2610 return false; 2611 } 2612 2613 // If we do not have a complete remembered set for the region, then we can 2614 // not be sure that we have all references to it. 2615 if (!region->rem_set()->is_complete()) { 2616 return false; 2617 } 2618 // Candidate selection must satisfy the following constraints 2619 // while concurrent marking is in progress: 2620 // 2621 // * In order to maintain SATB invariants, an object must not be 2622 // reclaimed if it was allocated before the start of marking and 2623 // has not had its references scanned. Such an object must have 2624 // its references (including type metadata) scanned to ensure no 2625 // live objects are missed by the marking process. Objects 2626 // allocated after the start of concurrent marking don't need to 2627 // be scanned. 2628 // 2629 // * An object must not be reclaimed if it is on the concurrent 2630 // mark stack. Objects allocated after the start of concurrent 2631 // marking are never pushed on the mark stack. 2632 // 2633 // Nominating only objects allocated after the start of concurrent 2634 // marking is sufficient to meet both constraints. This may miss 2635 // some objects that satisfy the constraints, but the marking data 2636 // structures don't support efficiently performing the needed 2637 // additional tests or scrubbing of the mark stack. 2638 // 2639 // However, we presently only nominate is_typeArray() objects. 2640 // A humongous object containing references induces remembered 2641 // set entries on other regions. In order to reclaim such an 2642 // object, those remembered sets would need to be cleaned up. 2643 // 2644 // We also treat is_typeArray() objects specially, allowing them 2645 // to be reclaimed even if allocated before the start of 2646 // concurrent mark. For this we rely on mark stack insertion to 2647 // exclude is_typeArray() objects, preventing reclaiming an object 2648 // that is in the mark stack. We also rely on the metadata for 2649 // such objects to be built-in and so ensured to be kept live. 2650 // Frequent allocation and drop of large binary blobs is an 2651 // important use case for eager reclaim, and this special handling 2652 // may reduce needed headroom. 2653 2654 return obj->is_typeArray() && 2655 g1h->is_potential_eager_reclaim_candidate(region); 2656 } 2657 2658 public: 2659 RegisterHumongousWithInCSetFastTestClosure() 2660 : _total_humongous(0), 2661 _candidate_humongous(0), 2662 _dcq(&G1BarrierSet::dirty_card_queue_set()) { 2663 } 2664 2665 virtual bool do_heap_region(HeapRegion* r) { 2666 if (!r->is_starts_humongous()) { 2667 return false; 2668 } 2669 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2670 2671 bool is_candidate = humongous_region_is_candidate(g1h, r); 2672 uint rindex = r->hrm_index(); 2673 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2674 if (is_candidate) { 2675 _candidate_humongous++; 2676 g1h->register_humongous_region_with_cset(rindex); 2677 // Is_candidate already filters out humongous object with large remembered sets. 2678 // If we have a humongous object with a few remembered sets, we simply flush these 2679 // remembered set entries into the DCQS. That will result in automatic 2680 // re-evaluation of their remembered set entries during the following evacuation 2681 // phase. 2682 if (!r->rem_set()->is_empty()) { 2683 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2684 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2685 G1CardTable* ct = g1h->card_table(); 2686 HeapRegionRemSetIterator hrrs(r->rem_set()); 2687 size_t card_index; 2688 while (hrrs.has_next(card_index)) { 2689 jbyte* card_ptr = (jbyte*)ct->byte_for_index(card_index); 2690 // The remembered set might contain references to already freed 2691 // regions. Filter out such entries to avoid failing card table 2692 // verification. 2693 if (g1h->is_in_closed_subset(ct->addr_for(card_ptr))) { 2694 if (*card_ptr != G1CardTable::dirty_card_val()) { 2695 *card_ptr = G1CardTable::dirty_card_val(); 2696 _dcq.enqueue(card_ptr); 2697 } 2698 } 2699 } 2700 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2701 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2702 hrrs.n_yielded(), r->rem_set()->occupied()); 2703 // We should only clear the card based remembered set here as we will not 2704 // implicitly rebuild anything else during eager reclaim. Note that at the moment 2705 // (and probably never) we do not enter this path if there are other kind of 2706 // remembered sets for this region. 2707 r->rem_set()->clear_locked(true /* only_cardset */); 2708 // Clear_locked() above sets the state to Empty. However we want to continue 2709 // collecting remembered set entries for humongous regions that were not 2710 // reclaimed. 2711 r->rem_set()->set_state_complete(); 2712 } 2713 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2714 } 2715 _total_humongous++; 2716 2717 return false; 2718 } 2719 2720 size_t total_humongous() const { return _total_humongous; } 2721 size_t candidate_humongous() const { return _candidate_humongous; } 2722 2723 void flush_rem_set_entries() { _dcq.flush(); } 2724 }; 2725 2726 void G1CollectedHeap::register_humongous_regions_with_cset() { 2727 if (!G1EagerReclaimHumongousObjects) { 2728 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2729 return; 2730 } 2731 double time = os::elapsed_counter(); 2732 2733 // Collect reclaim candidate information and register candidates with cset. 2734 RegisterHumongousWithInCSetFastTestClosure cl; 2735 heap_region_iterate(&cl); 2736 2737 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2738 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2739 cl.total_humongous(), 2740 cl.candidate_humongous()); 2741 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2742 2743 // Finally flush all remembered set entries to re-check into the global DCQS. 2744 cl.flush_rem_set_entries(); 2745 } 2746 2747 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2748 public: 2749 bool do_heap_region(HeapRegion* hr) { 2750 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2751 hr->verify_rem_set(); 2752 } 2753 return false; 2754 } 2755 }; 2756 2757 uint G1CollectedHeap::num_task_queues() const { 2758 return _task_queues->size(); 2759 } 2760 2761 #if TASKQUEUE_STATS 2762 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2763 st->print_raw_cr("GC Task Stats"); 2764 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2765 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2766 } 2767 2768 void G1CollectedHeap::print_taskqueue_stats() const { 2769 if (!log_is_enabled(Trace, gc, task, stats)) { 2770 return; 2771 } 2772 Log(gc, task, stats) log; 2773 ResourceMark rm; 2774 LogStream ls(log.trace()); 2775 outputStream* st = &ls; 2776 2777 print_taskqueue_stats_hdr(st); 2778 2779 TaskQueueStats totals; 2780 const uint n = num_task_queues(); 2781 for (uint i = 0; i < n; ++i) { 2782 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2783 totals += task_queue(i)->stats; 2784 } 2785 st->print_raw("tot "); totals.print(st); st->cr(); 2786 2787 DEBUG_ONLY(totals.verify()); 2788 } 2789 2790 void G1CollectedHeap::reset_taskqueue_stats() { 2791 const uint n = num_task_queues(); 2792 for (uint i = 0; i < n; ++i) { 2793 task_queue(i)->stats.reset(); 2794 } 2795 } 2796 #endif // TASKQUEUE_STATS 2797 2798 void G1CollectedHeap::wait_for_root_region_scanning() { 2799 double scan_wait_start = os::elapsedTime(); 2800 // We have to wait until the CM threads finish scanning the 2801 // root regions as it's the only way to ensure that all the 2802 // objects on them have been correctly scanned before we start 2803 // moving them during the GC. 2804 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2805 double wait_time_ms = 0.0; 2806 if (waited) { 2807 double scan_wait_end = os::elapsedTime(); 2808 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2809 } 2810 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2811 } 2812 2813 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2814 private: 2815 G1HRPrinter* _hr_printer; 2816 public: 2817 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2818 2819 virtual bool do_heap_region(HeapRegion* r) { 2820 _hr_printer->cset(r); 2821 return false; 2822 } 2823 }; 2824 2825 void G1CollectedHeap::start_new_collection_set() { 2826 collection_set()->start_incremental_building(); 2827 2828 clear_cset_fast_test(); 2829 2830 guarantee(_eden.length() == 0, "eden should have been cleared"); 2831 g1_policy()->transfer_survivors_to_cset(survivor()); 2832 } 2833 2834 bool 2835 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2836 assert_at_safepoint_on_vm_thread(); 2837 guarantee(!is_gc_active(), "collection is not reentrant"); 2838 2839 if (GCLocker::check_active_before_gc()) { 2840 return false; 2841 } 2842 2843 _gc_timer_stw->register_gc_start(); 2844 2845 GCIdMark gc_id_mark; 2846 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2847 2848 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2849 ResourceMark rm; 2850 2851 g1_policy()->note_gc_start(); 2852 2853 wait_for_root_region_scanning(); 2854 2855 print_heap_before_gc(); 2856 print_heap_regions(); 2857 trace_heap_before_gc(_gc_tracer_stw); 2858 2859 _verifier->verify_region_sets_optional(); 2860 _verifier->verify_dirty_young_regions(); 2861 2862 // We should not be doing initial mark unless the conc mark thread is running 2863 if (!_cm_thread->should_terminate()) { 2864 // This call will decide whether this pause is an initial-mark 2865 // pause. If it is, in_initial_mark_gc() will return true 2866 // for the duration of this pause. 2867 g1_policy()->decide_on_conc_mark_initiation(); 2868 } 2869 2870 // We do not allow initial-mark to be piggy-backed on a mixed GC. 2871 assert(!collector_state()->in_initial_mark_gc() || 2872 collector_state()->in_young_only_phase(), "sanity"); 2873 2874 // We also do not allow mixed GCs during marking. 2875 assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity"); 2876 2877 // Record whether this pause is an initial mark. When the current 2878 // thread has completed its logging output and it's safe to signal 2879 // the CM thread, the flag's value in the policy has been reset. 2880 bool should_start_conc_mark = collector_state()->in_initial_mark_gc(); 2881 2882 // Inner scope for scope based logging, timers, and stats collection 2883 { 2884 EvacuationInfo evacuation_info; 2885 2886 if (collector_state()->in_initial_mark_gc()) { 2887 // We are about to start a marking cycle, so we increment the 2888 // full collection counter. 2889 increment_old_marking_cycles_started(); 2890 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 2891 } 2892 2893 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 2894 2895 GCTraceCPUTime tcpu; 2896 2897 G1HeapVerifier::G1VerifyType verify_type; 2898 FormatBuffer<> gc_string("Pause Young "); 2899 if (collector_state()->in_initial_mark_gc()) { 2900 gc_string.append("(Concurrent Start)"); 2901 verify_type = G1HeapVerifier::G1VerifyConcurrentStart; 2902 } else if (collector_state()->in_young_only_phase()) { 2903 if (collector_state()->in_young_gc_before_mixed()) { 2904 gc_string.append("(Prepare Mixed)"); 2905 } else { 2906 gc_string.append("(Normal)"); 2907 } 2908 verify_type = G1HeapVerifier::G1VerifyYoungNormal; 2909 } else { 2910 gc_string.append("(Mixed)"); 2911 verify_type = G1HeapVerifier::G1VerifyMixed; 2912 } 2913 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 2914 2915 uint active_workers = WorkerPolicy::calc_active_workers(workers()->total_workers(), 2916 workers()->active_workers(), 2917 Threads::number_of_non_daemon_threads()); 2918 active_workers = workers()->update_active_workers(active_workers); 2919 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 2920 2921 G1MonitoringScope ms(g1mm(), 2922 false /* full_gc */, 2923 collector_state()->yc_type() == Mixed /* all_memory_pools_affected */); 2924 2925 G1HeapTransition heap_transition(this); 2926 size_t heap_used_bytes_before_gc = used(); 2927 2928 // Don't dynamically change the number of GC threads this early. A value of 2929 // 0 is used to indicate serial work. When parallel work is done, 2930 // it will be set. 2931 2932 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 2933 IsGCActiveMark x; 2934 2935 gc_prologue(false); 2936 2937 if (VerifyRememberedSets) { 2938 log_info(gc, verify)("[Verifying RemSets before GC]"); 2939 VerifyRegionRemSetClosure v_cl; 2940 heap_region_iterate(&v_cl); 2941 } 2942 2943 _verifier->verify_before_gc(verify_type); 2944 2945 _verifier->check_bitmaps("GC Start"); 2946 2947 #if COMPILER2_OR_JVMCI 2948 DerivedPointerTable::clear(); 2949 #endif 2950 2951 // Please see comment in g1CollectedHeap.hpp and 2952 // G1CollectedHeap::ref_processing_init() to see how 2953 // reference processing currently works in G1. 2954 2955 // Enable discovery in the STW reference processor 2956 _ref_processor_stw->enable_discovery(); 2957 2958 { 2959 // We want to temporarily turn off discovery by the 2960 // CM ref processor, if necessary, and turn it back on 2961 // on again later if we do. Using a scoped 2962 // NoRefDiscovery object will do this. 2963 NoRefDiscovery no_cm_discovery(_ref_processor_cm); 2964 2965 // Forget the current alloc region (we might even choose it to be part 2966 // of the collection set!). 2967 _allocator->release_mutator_alloc_region(); 2968 2969 // This timing is only used by the ergonomics to handle our pause target. 2970 // It is unclear why this should not include the full pause. We will 2971 // investigate this in CR 7178365. 2972 // 2973 // Preserving the old comment here if that helps the investigation: 2974 // 2975 // The elapsed time induced by the start time below deliberately elides 2976 // the possible verification above. 2977 double sample_start_time_sec = os::elapsedTime(); 2978 2979 g1_policy()->record_collection_pause_start(sample_start_time_sec); 2980 2981 if (collector_state()->in_initial_mark_gc()) { 2982 concurrent_mark()->pre_initial_mark(); 2983 } 2984 2985 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 2986 2987 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 2988 2989 register_humongous_regions_with_cset(); 2990 2991 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 2992 2993 // We call this after finalize_cset() to 2994 // ensure that the CSet has been finalized. 2995 _cm->verify_no_cset_oops(); 2996 2997 if (_hr_printer.is_active()) { 2998 G1PrintCollectionSetClosure cl(&_hr_printer); 2999 _collection_set.iterate(&cl); 3000 } 3001 3002 // Initialize the GC alloc regions. 3003 _allocator->init_gc_alloc_regions(evacuation_info); 3004 3005 G1ParScanThreadStateSet per_thread_states(this, 3006 workers()->active_workers(), 3007 collection_set()->young_region_length(), 3008 collection_set()->optional_region_length()); 3009 pre_evacuate_collection_set(); 3010 3011 // Actually do the work... 3012 evacuate_collection_set(&per_thread_states); 3013 evacuate_optional_collection_set(&per_thread_states); 3014 3015 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3016 3017 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3018 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 3019 3020 eagerly_reclaim_humongous_regions(); 3021 3022 record_obj_copy_mem_stats(); 3023 _survivor_evac_stats.adjust_desired_plab_sz(); 3024 _old_evac_stats.adjust_desired_plab_sz(); 3025 3026 double start = os::elapsedTime(); 3027 start_new_collection_set(); 3028 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 3029 3030 if (evacuation_failed()) { 3031 double recalculate_used_start = os::elapsedTime(); 3032 set_used(recalculate_used()); 3033 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 3034 3035 if (_archive_allocator != NULL) { 3036 _archive_allocator->clear_used(); 3037 } 3038 for (uint i = 0; i < ParallelGCThreads; i++) { 3039 if (_evacuation_failed_info_array[i].has_failed()) { 3040 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3041 } 3042 } 3043 } else { 3044 // The "used" of the the collection set have already been subtracted 3045 // when they were freed. Add in the bytes evacuated. 3046 increase_used(g1_policy()->bytes_copied_during_gc()); 3047 } 3048 3049 if (collector_state()->in_initial_mark_gc()) { 3050 // We have to do this before we notify the CM threads that 3051 // they can start working to make sure that all the 3052 // appropriate initialization is done on the CM object. 3053 concurrent_mark()->post_initial_mark(); 3054 // Note that we don't actually trigger the CM thread at 3055 // this point. We do that later when we're sure that 3056 // the current thread has completed its logging output. 3057 } 3058 3059 allocate_dummy_regions(); 3060 3061 _allocator->init_mutator_alloc_region(); 3062 3063 { 3064 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3065 if (expand_bytes > 0) { 3066 size_t bytes_before = capacity(); 3067 // No need for an ergo logging here, 3068 // expansion_amount() does this when it returns a value > 0. 3069 double expand_ms; 3070 if (!expand(expand_bytes, _workers, &expand_ms)) { 3071 // We failed to expand the heap. Cannot do anything about it. 3072 } 3073 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3074 } 3075 } 3076 3077 // We redo the verification but now wrt to the new CSet which 3078 // has just got initialized after the previous CSet was freed. 3079 _cm->verify_no_cset_oops(); 3080 3081 // This timing is only used by the ergonomics to handle our pause target. 3082 // It is unclear why this should not include the full pause. We will 3083 // investigate this in CR 7178365. 3084 double sample_end_time_sec = os::elapsedTime(); 3085 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3086 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards); 3087 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3088 3089 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3090 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3091 3092 if (VerifyRememberedSets) { 3093 log_info(gc, verify)("[Verifying RemSets after GC]"); 3094 VerifyRegionRemSetClosure v_cl; 3095 heap_region_iterate(&v_cl); 3096 } 3097 3098 _verifier->verify_after_gc(verify_type); 3099 _verifier->check_bitmaps("GC End"); 3100 3101 assert(!_ref_processor_stw->discovery_enabled(), "Postcondition"); 3102 _ref_processor_stw->verify_no_references_recorded(); 3103 3104 // CM reference discovery will be re-enabled if necessary. 3105 } 3106 3107 #ifdef TRACESPINNING 3108 ParallelTaskTerminator::print_termination_counts(); 3109 #endif 3110 3111 gc_epilogue(false); 3112 } 3113 3114 // Print the remainder of the GC log output. 3115 if (evacuation_failed()) { 3116 log_info(gc)("To-space exhausted"); 3117 } 3118 3119 g1_policy()->print_phases(); 3120 heap_transition.print(); 3121 3122 // It is not yet to safe to tell the concurrent mark to 3123 // start as we have some optional output below. We don't want the 3124 // output from the concurrent mark thread interfering with this 3125 // logging output either. 3126 3127 _hrm.verify_optional(); 3128 _verifier->verify_region_sets_optional(); 3129 3130 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3131 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3132 3133 print_heap_after_gc(); 3134 print_heap_regions(); 3135 trace_heap_after_gc(_gc_tracer_stw); 3136 3137 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3138 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3139 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3140 // before any GC notifications are raised. 3141 g1mm()->update_sizes(); 3142 3143 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3144 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3145 _gc_timer_stw->register_gc_end(); 3146 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3147 } 3148 // It should now be safe to tell the concurrent mark thread to start 3149 // without its logging output interfering with the logging output 3150 // that came from the pause. 3151 3152 if (should_start_conc_mark) { 3153 // CAUTION: after the doConcurrentMark() call below, 3154 // the concurrent marking thread(s) could be running 3155 // concurrently with us. Make sure that anything after 3156 // this point does not assume that we are the only GC thread 3157 // running. Note: of course, the actual marking work will 3158 // not start until the safepoint itself is released in 3159 // SuspendibleThreadSet::desynchronize(). 3160 do_concurrent_mark(); 3161 } 3162 3163 return true; 3164 } 3165 3166 void G1CollectedHeap::remove_self_forwarding_pointers() { 3167 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3168 workers()->run_task(&rsfp_task); 3169 } 3170 3171 void G1CollectedHeap::restore_after_evac_failure() { 3172 double remove_self_forwards_start = os::elapsedTime(); 3173 3174 remove_self_forwarding_pointers(); 3175 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3176 _preserved_marks_set.restore(&task_executor); 3177 3178 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3179 } 3180 3181 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3182 if (!_evacuation_failed) { 3183 _evacuation_failed = true; 3184 } 3185 3186 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3187 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3188 } 3189 3190 bool G1ParEvacuateFollowersClosure::offer_termination() { 3191 EventGCPhaseParallel event; 3192 G1ParScanThreadState* const pss = par_scan_state(); 3193 start_term_time(); 3194 const bool res = terminator()->offer_termination(); 3195 end_term_time(); 3196 event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(G1GCPhaseTimes::Termination)); 3197 return res; 3198 } 3199 3200 void G1ParEvacuateFollowersClosure::do_void() { 3201 EventGCPhaseParallel event; 3202 G1ParScanThreadState* const pss = par_scan_state(); 3203 pss->trim_queue(); 3204 event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase)); 3205 do { 3206 EventGCPhaseParallel event; 3207 pss->steal_and_trim_queue(queues()); 3208 event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase)); 3209 } while (!offer_termination()); 3210 } 3211 3212 class G1ParTask : public AbstractGangTask { 3213 protected: 3214 G1CollectedHeap* _g1h; 3215 G1ParScanThreadStateSet* _pss; 3216 RefToScanQueueSet* _queues; 3217 G1RootProcessor* _root_processor; 3218 TaskTerminator _terminator; 3219 uint _n_workers; 3220 3221 public: 3222 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3223 : AbstractGangTask("G1 collection"), 3224 _g1h(g1h), 3225 _pss(per_thread_states), 3226 _queues(task_queues), 3227 _root_processor(root_processor), 3228 _terminator(n_workers, _queues), 3229 _n_workers(n_workers) 3230 {} 3231 3232 void work(uint worker_id) { 3233 if (worker_id >= _n_workers) return; // no work needed this round 3234 3235 double start_sec = os::elapsedTime(); 3236 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3237 3238 { 3239 ResourceMark rm; 3240 HandleMark hm; 3241 3242 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3243 3244 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3245 pss->set_ref_discoverer(rp); 3246 3247 double start_strong_roots_sec = os::elapsedTime(); 3248 3249 _root_processor->evacuate_roots(pss, worker_id); 3250 3251 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3252 // treating the nmethods visited to act as roots for concurrent marking. 3253 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3254 // objects copied by the current evacuation. 3255 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, worker_id); 3256 3257 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3258 3259 double term_sec = 0.0; 3260 size_t evac_term_attempts = 0; 3261 { 3262 double start = os::elapsedTime(); 3263 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, _terminator.terminator(), G1GCPhaseTimes::ObjCopy); 3264 evac.do_void(); 3265 3266 evac_term_attempts = evac.term_attempts(); 3267 term_sec = evac.term_time(); 3268 double elapsed_sec = os::elapsedTime() - start; 3269 3270 G1GCPhaseTimes* p = _g1h->g1_policy()->phase_times(); 3271 p->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3272 p->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3273 p->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3274 } 3275 3276 assert(pss->queue_is_empty(), "should be empty"); 3277 3278 if (log_is_enabled(Debug, gc, task, stats)) { 3279 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3280 size_t lab_waste; 3281 size_t lab_undo_waste; 3282 pss->waste(lab_waste, lab_undo_waste); 3283 _g1h->print_termination_stats(worker_id, 3284 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3285 strong_roots_sec * 1000.0, /* strong roots time */ 3286 term_sec * 1000.0, /* evac term time */ 3287 evac_term_attempts, /* evac term attempts */ 3288 lab_waste, /* alloc buffer waste */ 3289 lab_undo_waste /* undo waste */ 3290 ); 3291 } 3292 3293 // Close the inner scope so that the ResourceMark and HandleMark 3294 // destructors are executed here and are included as part of the 3295 // "GC Worker Time". 3296 } 3297 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3298 } 3299 }; 3300 3301 void G1CollectedHeap::print_termination_stats_hdr() { 3302 log_debug(gc, task, stats)("GC Termination Stats"); 3303 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3304 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3305 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3306 } 3307 3308 void G1CollectedHeap::print_termination_stats(uint worker_id, 3309 double elapsed_ms, 3310 double strong_roots_ms, 3311 double term_ms, 3312 size_t term_attempts, 3313 size_t alloc_buffer_waste, 3314 size_t undo_waste) const { 3315 log_debug(gc, task, stats) 3316 ("%3d %9.2f %9.2f %6.2f " 3317 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3318 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3319 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3320 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3321 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3322 alloc_buffer_waste * HeapWordSize / K, 3323 undo_waste * HeapWordSize / K); 3324 } 3325 3326 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3327 bool class_unloading_occurred) { 3328 uint n_workers = workers()->active_workers(); 3329 3330 G1StringDedupUnlinkOrOopsDoClosure dedup_closure(is_alive, NULL, false); 3331 ParallelCleaningTask g1_unlink_task(is_alive, &dedup_closure, n_workers, class_unloading_occurred); 3332 workers()->run_task(&g1_unlink_task); 3333 } 3334 3335 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3336 bool process_strings, 3337 bool process_string_dedup) { 3338 if (!process_strings && !process_string_dedup) { 3339 // Nothing to clean. 3340 return; 3341 } 3342 3343 G1StringDedupUnlinkOrOopsDoClosure dedup_closure(is_alive, NULL, false); 3344 StringCleaningTask g1_unlink_task(is_alive, process_string_dedup ? &dedup_closure : NULL, process_strings); 3345 workers()->run_task(&g1_unlink_task); 3346 } 3347 3348 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3349 private: 3350 DirtyCardQueueSet* _queue; 3351 G1CollectedHeap* _g1h; 3352 public: 3353 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3354 _queue(queue), _g1h(g1h) { } 3355 3356 virtual void work(uint worker_id) { 3357 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3358 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3359 3360 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3361 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3362 3363 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3364 } 3365 }; 3366 3367 void G1CollectedHeap::redirty_logged_cards() { 3368 double redirty_logged_cards_start = os::elapsedTime(); 3369 3370 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3371 dirty_card_queue_set().reset_for_par_iteration(); 3372 workers()->run_task(&redirty_task); 3373 3374 DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set(); 3375 dcq.merge_bufferlists(&dirty_card_queue_set()); 3376 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3377 3378 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3379 } 3380 3381 // Weak Reference Processing support 3382 3383 bool G1STWIsAliveClosure::do_object_b(oop p) { 3384 // An object is reachable if it is outside the collection set, 3385 // or is inside and copied. 3386 return !_g1h->is_in_cset(p) || p->is_forwarded(); 3387 } 3388 3389 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) { 3390 assert(obj != NULL, "must not be NULL"); 3391 assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj)); 3392 // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below 3393 // may falsely indicate that this is not the case here: however the collection set only 3394 // contains old regions when concurrent mark is not running. 3395 return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor(); 3396 } 3397 3398 // Non Copying Keep Alive closure 3399 class G1KeepAliveClosure: public OopClosure { 3400 G1CollectedHeap*_g1h; 3401 public: 3402 G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {} 3403 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3404 void do_oop(oop* p) { 3405 oop obj = *p; 3406 assert(obj != NULL, "the caller should have filtered out NULL values"); 3407 3408 const InCSetState cset_state =_g1h->in_cset_state(obj); 3409 if (!cset_state.is_in_cset_or_humongous()) { 3410 return; 3411 } 3412 if (cset_state.is_in_cset()) { 3413 assert( obj->is_forwarded(), "invariant" ); 3414 *p = obj->forwardee(); 3415 } else { 3416 assert(!obj->is_forwarded(), "invariant" ); 3417 assert(cset_state.is_humongous(), 3418 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3419 _g1h->set_humongous_is_live(obj); 3420 } 3421 } 3422 }; 3423 3424 // Copying Keep Alive closure - can be called from both 3425 // serial and parallel code as long as different worker 3426 // threads utilize different G1ParScanThreadState instances 3427 // and different queues. 3428 3429 class G1CopyingKeepAliveClosure: public OopClosure { 3430 G1CollectedHeap* _g1h; 3431 G1ParScanThreadState* _par_scan_state; 3432 3433 public: 3434 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3435 G1ParScanThreadState* pss): 3436 _g1h(g1h), 3437 _par_scan_state(pss) 3438 {} 3439 3440 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3441 virtual void do_oop( oop* p) { do_oop_work(p); } 3442 3443 template <class T> void do_oop_work(T* p) { 3444 oop obj = RawAccess<>::oop_load(p); 3445 3446 if (_g1h->is_in_cset_or_humongous(obj)) { 3447 // If the referent object has been forwarded (either copied 3448 // to a new location or to itself in the event of an 3449 // evacuation failure) then we need to update the reference 3450 // field and, if both reference and referent are in the G1 3451 // heap, update the RSet for the referent. 3452 // 3453 // If the referent has not been forwarded then we have to keep 3454 // it alive by policy. Therefore we have copy the referent. 3455 // 3456 // When the queue is drained (after each phase of reference processing) 3457 // the object and it's followers will be copied, the reference field set 3458 // to point to the new location, and the RSet updated. 3459 _par_scan_state->push_on_queue(p); 3460 } 3461 } 3462 }; 3463 3464 // Serial drain queue closure. Called as the 'complete_gc' 3465 // closure for each discovered list in some of the 3466 // reference processing phases. 3467 3468 class G1STWDrainQueueClosure: public VoidClosure { 3469 protected: 3470 G1CollectedHeap* _g1h; 3471 G1ParScanThreadState* _par_scan_state; 3472 3473 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3474 3475 public: 3476 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3477 _g1h(g1h), 3478 _par_scan_state(pss) 3479 { } 3480 3481 void do_void() { 3482 G1ParScanThreadState* const pss = par_scan_state(); 3483 pss->trim_queue(); 3484 } 3485 }; 3486 3487 // Parallel Reference Processing closures 3488 3489 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3490 // processing during G1 evacuation pauses. 3491 3492 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3493 private: 3494 G1CollectedHeap* _g1h; 3495 G1ParScanThreadStateSet* _pss; 3496 RefToScanQueueSet* _queues; 3497 WorkGang* _workers; 3498 3499 public: 3500 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3501 G1ParScanThreadStateSet* per_thread_states, 3502 WorkGang* workers, 3503 RefToScanQueueSet *task_queues) : 3504 _g1h(g1h), 3505 _pss(per_thread_states), 3506 _queues(task_queues), 3507 _workers(workers) 3508 { 3509 g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers()); 3510 } 3511 3512 // Executes the given task using concurrent marking worker threads. 3513 virtual void execute(ProcessTask& task, uint ergo_workers); 3514 }; 3515 3516 // Gang task for possibly parallel reference processing 3517 3518 class G1STWRefProcTaskProxy: public AbstractGangTask { 3519 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 3520 ProcessTask& _proc_task; 3521 G1CollectedHeap* _g1h; 3522 G1ParScanThreadStateSet* _pss; 3523 RefToScanQueueSet* _task_queues; 3524 ParallelTaskTerminator* _terminator; 3525 3526 public: 3527 G1STWRefProcTaskProxy(ProcessTask& proc_task, 3528 G1CollectedHeap* g1h, 3529 G1ParScanThreadStateSet* per_thread_states, 3530 RefToScanQueueSet *task_queues, 3531 ParallelTaskTerminator* terminator) : 3532 AbstractGangTask("Process reference objects in parallel"), 3533 _proc_task(proc_task), 3534 _g1h(g1h), 3535 _pss(per_thread_states), 3536 _task_queues(task_queues), 3537 _terminator(terminator) 3538 {} 3539 3540 virtual void work(uint worker_id) { 3541 // The reference processing task executed by a single worker. 3542 ResourceMark rm; 3543 HandleMark hm; 3544 3545 G1STWIsAliveClosure is_alive(_g1h); 3546 3547 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3548 pss->set_ref_discoverer(NULL); 3549 3550 // Keep alive closure. 3551 G1CopyingKeepAliveClosure keep_alive(_g1h, pss); 3552 3553 // Complete GC closure 3554 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator, G1GCPhaseTimes::ObjCopy); 3555 3556 // Call the reference processing task's work routine. 3557 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 3558 3559 // Note we cannot assert that the refs array is empty here as not all 3560 // of the processing tasks (specifically phase2 - pp2_work) execute 3561 // the complete_gc closure (which ordinarily would drain the queue) so 3562 // the queue may not be empty. 3563 } 3564 }; 3565 3566 // Driver routine for parallel reference processing. 3567 // Creates an instance of the ref processing gang 3568 // task and has the worker threads execute it. 3569 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) { 3570 assert(_workers != NULL, "Need parallel worker threads."); 3571 3572 assert(_workers->active_workers() >= ergo_workers, 3573 "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)", 3574 ergo_workers, _workers->active_workers()); 3575 TaskTerminator terminator(ergo_workers, _queues); 3576 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, terminator.terminator()); 3577 3578 _workers->run_task(&proc_task_proxy, ergo_workers); 3579 } 3580 3581 // End of weak reference support closures 3582 3583 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 3584 double ref_proc_start = os::elapsedTime(); 3585 3586 ReferenceProcessor* rp = _ref_processor_stw; 3587 assert(rp->discovery_enabled(), "should have been enabled"); 3588 3589 // Closure to test whether a referent is alive. 3590 G1STWIsAliveClosure is_alive(this); 3591 3592 // Even when parallel reference processing is enabled, the processing 3593 // of JNI refs is serial and performed serially by the current thread 3594 // rather than by a worker. The following PSS will be used for processing 3595 // JNI refs. 3596 3597 // Use only a single queue for this PSS. 3598 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 3599 pss->set_ref_discoverer(NULL); 3600 assert(pss->queue_is_empty(), "pre-condition"); 3601 3602 // Keep alive closure. 3603 G1CopyingKeepAliveClosure keep_alive(this, pss); 3604 3605 // Serial Complete GC closure 3606 G1STWDrainQueueClosure drain_queue(this, pss); 3607 3608 // Setup the soft refs policy... 3609 rp->setup_policy(false); 3610 3611 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 3612 3613 ReferenceProcessorStats stats; 3614 if (!rp->processing_is_mt()) { 3615 // Serial reference processing... 3616 stats = rp->process_discovered_references(&is_alive, 3617 &keep_alive, 3618 &drain_queue, 3619 NULL, 3620 pt); 3621 } else { 3622 uint no_of_gc_workers = workers()->active_workers(); 3623 3624 // Parallel reference processing 3625 assert(no_of_gc_workers <= rp->max_num_queues(), 3626 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 3627 no_of_gc_workers, rp->max_num_queues()); 3628 3629 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues); 3630 stats = rp->process_discovered_references(&is_alive, 3631 &keep_alive, 3632 &drain_queue, 3633 &par_task_executor, 3634 pt); 3635 } 3636 3637 _gc_tracer_stw->report_gc_reference_stats(stats); 3638 3639 // We have completed copying any necessary live referent objects. 3640 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 3641 3642 make_pending_list_reachable(); 3643 3644 rp->verify_no_references_recorded(); 3645 3646 double ref_proc_time = os::elapsedTime() - ref_proc_start; 3647 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 3648 } 3649 3650 void G1CollectedHeap::make_pending_list_reachable() { 3651 if (collector_state()->in_initial_mark_gc()) { 3652 oop pll_head = Universe::reference_pending_list(); 3653 if (pll_head != NULL) { 3654 // Any valid worker id is fine here as we are in the VM thread and single-threaded. 3655 _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head); 3656 } 3657 } 3658 } 3659 3660 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 3661 double merge_pss_time_start = os::elapsedTime(); 3662 per_thread_states->flush(); 3663 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 3664 } 3665 3666 void G1CollectedHeap::pre_evacuate_collection_set() { 3667 _expand_heap_after_alloc_failure = true; 3668 _evacuation_failed = false; 3669 3670 // Disable the hot card cache. 3671 _hot_card_cache->reset_hot_cache_claimed_index(); 3672 _hot_card_cache->set_use_cache(false); 3673 3674 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 3675 _preserved_marks_set.assert_empty(); 3676 3677 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 3678 3679 // InitialMark needs claim bits to keep track of the marked-through CLDs. 3680 if (collector_state()->in_initial_mark_gc()) { 3681 double start_clear_claimed_marks = os::elapsedTime(); 3682 3683 ClassLoaderDataGraph::clear_claimed_marks(); 3684 3685 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 3686 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 3687 } 3688 } 3689 3690 void G1CollectedHeap::evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states) { 3691 // Should G1EvacuationFailureALot be in effect for this GC? 3692 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 3693 3694 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 3695 3696 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 3697 3698 double start_par_time_sec = os::elapsedTime(); 3699 double end_par_time_sec; 3700 3701 { 3702 const uint n_workers = workers()->active_workers(); 3703 G1RootProcessor root_processor(this, n_workers); 3704 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 3705 3706 print_termination_stats_hdr(); 3707 3708 workers()->run_task(&g1_par_task); 3709 end_par_time_sec = os::elapsedTime(); 3710 3711 // Closing the inner scope will execute the destructor 3712 // for the G1RootProcessor object. We record the current 3713 // elapsed time before closing the scope so that time 3714 // taken for the destructor is NOT included in the 3715 // reported parallel time. 3716 } 3717 3718 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 3719 phase_times->record_par_time(par_time_ms); 3720 3721 double code_root_fixup_time_ms = 3722 (os::elapsedTime() - end_par_time_sec) * 1000.0; 3723 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 3724 } 3725 3726 class G1EvacuateOptionalRegionTask : public AbstractGangTask { 3727 G1CollectedHeap* _g1h; 3728 G1ParScanThreadStateSet* _per_thread_states; 3729 G1OptionalCSet* _optional; 3730 RefToScanQueueSet* _queues; 3731 ParallelTaskTerminator _terminator; 3732 3733 Tickspan trim_ticks(G1ParScanThreadState* pss) { 3734 Tickspan copy_time = pss->trim_ticks(); 3735 pss->reset_trim_ticks(); 3736 return copy_time; 3737 } 3738 3739 void scan_roots(G1ParScanThreadState* pss, uint worker_id) { 3740 G1EvacuationRootClosures* root_cls = pss->closures(); 3741 G1ScanObjsDuringScanRSClosure obj_cl(_g1h, pss); 3742 3743 size_t scanned = 0; 3744 size_t claimed = 0; 3745 size_t skipped = 0; 3746 size_t used_memory = 0; 3747 3748 Ticks start = Ticks::now(); 3749 Tickspan copy_time; 3750 3751 for (uint i = _optional->current_index(); i < _optional->current_limit(); i++) { 3752 HeapRegion* hr = _optional->region_at(i); 3753 G1ScanRSForOptionalClosure scan_opt_cl(&obj_cl); 3754 pss->oops_into_optional_region(hr)->oops_do(&scan_opt_cl, root_cls->raw_strong_oops()); 3755 copy_time += trim_ticks(pss); 3756 3757 G1ScanRSForRegionClosure scan_rs_cl(_g1h->g1_rem_set()->scan_state(), &obj_cl, pss, G1GCPhaseTimes::OptScanRS, worker_id); 3758 scan_rs_cl.do_heap_region(hr); 3759 copy_time += trim_ticks(pss); 3760 scanned += scan_rs_cl.cards_scanned(); 3761 claimed += scan_rs_cl.cards_claimed(); 3762 skipped += scan_rs_cl.cards_skipped(); 3763 3764 // Chunk lists for this region is no longer needed. 3765 used_memory += pss->oops_into_optional_region(hr)->used_memory(); 3766 } 3767 3768 Tickspan scan_time = (Ticks::now() - start) - copy_time; 3769 G1GCPhaseTimes* p = _g1h->g1_policy()->phase_times(); 3770 p->record_or_add_time_secs(G1GCPhaseTimes::OptScanRS, worker_id, scan_time.seconds()); 3771 p->record_or_add_time_secs(G1GCPhaseTimes::OptObjCopy, worker_id, copy_time.seconds()); 3772 3773 p->record_or_add_thread_work_item(G1GCPhaseTimes::OptScanRS, worker_id, scanned, G1GCPhaseTimes::OptCSetScannedCards); 3774 p->record_or_add_thread_work_item(G1GCPhaseTimes::OptScanRS, worker_id, claimed, G1GCPhaseTimes::OptCSetClaimedCards); 3775 p->record_or_add_thread_work_item(G1GCPhaseTimes::OptScanRS, worker_id, skipped, G1GCPhaseTimes::OptCSetSkippedCards); 3776 p->record_or_add_thread_work_item(G1GCPhaseTimes::OptScanRS, worker_id, used_memory, G1GCPhaseTimes::OptCSetUsedMemory); 3777 } 3778 3779 void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) { 3780 Ticks start = Ticks::now(); 3781 G1ParEvacuateFollowersClosure cl(_g1h, pss, _queues, &_terminator, G1GCPhaseTimes::OptObjCopy); 3782 cl.do_void(); 3783 3784 Tickspan evac_time = (Ticks::now() - start); 3785 G1GCPhaseTimes* p = _g1h->g1_policy()->phase_times(); 3786 p->record_or_add_time_secs(G1GCPhaseTimes::OptObjCopy, worker_id, evac_time.seconds()); 3787 assert(pss->trim_ticks().seconds() == 0.0, "Unexpected partial trimming done during optional evacuation"); 3788 } 3789 3790 public: 3791 G1EvacuateOptionalRegionTask(G1CollectedHeap* g1h, 3792 G1ParScanThreadStateSet* per_thread_states, 3793 G1OptionalCSet* cset, 3794 RefToScanQueueSet* queues, 3795 uint n_workers) : 3796 AbstractGangTask("G1 Evacuation Optional Region Task"), 3797 _g1h(g1h), 3798 _per_thread_states(per_thread_states), 3799 _optional(cset), 3800 _queues(queues), 3801 _terminator(n_workers, _queues) { 3802 } 3803 3804 void work(uint worker_id) { 3805 ResourceMark rm; 3806 HandleMark hm; 3807 3808 G1ParScanThreadState* pss = _per_thread_states->state_for_worker(worker_id); 3809 pss->set_ref_discoverer(_g1h->ref_processor_stw()); 3810 3811 scan_roots(pss, worker_id); 3812 evacuate_live_objects(pss, worker_id); 3813 } 3814 }; 3815 3816 void G1CollectedHeap::evacuate_optional_regions(G1ParScanThreadStateSet* per_thread_states, G1OptionalCSet* ocset) { 3817 class G1MarkScope : public MarkScope {}; 3818 G1MarkScope code_mark_scope; 3819 3820 G1EvacuateOptionalRegionTask task(this, per_thread_states, ocset, _task_queues, workers()->active_workers()); 3821 workers()->run_task(&task); 3822 } 3823 3824 void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) { 3825 G1OptionalCSet optional_cset(&_collection_set, per_thread_states); 3826 if (optional_cset.is_empty()) { 3827 return; 3828 } 3829 3830 if (evacuation_failed()) { 3831 return; 3832 } 3833 3834 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 3835 const double gc_start_time_ms = phase_times->cur_collection_start_sec() * 1000.0; 3836 3837 double start_time_sec = os::elapsedTime(); 3838 3839 do { 3840 double time_used_ms = os::elapsedTime() * 1000.0 - gc_start_time_ms; 3841 double time_left_ms = MaxGCPauseMillis - time_used_ms; 3842 3843 if (time_left_ms < 0) { 3844 log_trace(gc, ergo, cset)("Skipping %u optional regions, pause time exceeded %.3fms", optional_cset.size(), time_used_ms); 3845 break; 3846 } 3847 3848 optional_cset.prepare_evacuation(time_left_ms * _g1_policy->optional_evacuation_fraction()); 3849 if (optional_cset.prepare_failed()) { 3850 log_trace(gc, ergo, cset)("Skipping %u optional regions, no regions can be evacuated in %.3fms", optional_cset.size(), time_left_ms); 3851 break; 3852 } 3853 3854 evacuate_optional_regions(per_thread_states, &optional_cset); 3855 3856 optional_cset.complete_evacuation(); 3857 if (optional_cset.evacuation_failed()) { 3858 break; 3859 } 3860 } while (!optional_cset.is_empty()); 3861 3862 phase_times->record_optional_evacuation((os::elapsedTime() - start_time_sec) * 1000.0); 3863 } 3864 3865 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 3866 // Also cleans the card table from temporary duplicate detection information used 3867 // during UpdateRS/ScanRS. 3868 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 3869 3870 // Process any discovered reference objects - we have 3871 // to do this _before_ we retire the GC alloc regions 3872 // as we may have to copy some 'reachable' referent 3873 // objects (and their reachable sub-graphs) that were 3874 // not copied during the pause. 3875 process_discovered_references(per_thread_states); 3876 3877 // FIXME 3878 // CM's reference processing also cleans up the string table. 3879 // Should we do that here also? We could, but it is a serial operation 3880 // and could significantly increase the pause time. 3881 3882 G1STWIsAliveClosure is_alive(this); 3883 G1KeepAliveClosure keep_alive(this); 3884 3885 WeakProcessor::weak_oops_do(workers(), &is_alive, &keep_alive, 3886 g1_policy()->phase_times()->weak_phase_times()); 3887 3888 if (G1StringDedup::is_enabled()) { 3889 double fixup_start = os::elapsedTime(); 3890 3891 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 3892 3893 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 3894 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 3895 } 3896 3897 if (evacuation_failed()) { 3898 restore_after_evac_failure(); 3899 3900 // Reset the G1EvacuationFailureALot counters and flags 3901 // Note: the values are reset only when an actual 3902 // evacuation failure occurs. 3903 NOT_PRODUCT(reset_evacuation_should_fail();) 3904 } 3905 3906 _preserved_marks_set.assert_empty(); 3907 3908 _allocator->release_gc_alloc_regions(evacuation_info); 3909 3910 merge_per_thread_state_info(per_thread_states); 3911 3912 // Reset and re-enable the hot card cache. 3913 // Note the counts for the cards in the regions in the 3914 // collection set are reset when the collection set is freed. 3915 _hot_card_cache->reset_hot_cache(); 3916 _hot_card_cache->set_use_cache(true); 3917 3918 purge_code_root_memory(); 3919 3920 redirty_logged_cards(); 3921 #if COMPILER2_OR_JVMCI 3922 double start = os::elapsedTime(); 3923 DerivedPointerTable::update_pointers(); 3924 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 3925 #endif 3926 g1_policy()->print_age_table(); 3927 } 3928 3929 void G1CollectedHeap::record_obj_copy_mem_stats() { 3930 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 3931 3932 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 3933 create_g1_evac_summary(&_old_evac_stats)); 3934 } 3935 3936 void G1CollectedHeap::free_region(HeapRegion* hr, 3937 FreeRegionList* free_list, 3938 bool skip_remset, 3939 bool skip_hot_card_cache, 3940 bool locked) { 3941 assert(!hr->is_free(), "the region should not be free"); 3942 assert(!hr->is_empty(), "the region should not be empty"); 3943 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 3944 assert(free_list != NULL, "pre-condition"); 3945 3946 if (G1VerifyBitmaps) { 3947 MemRegion mr(hr->bottom(), hr->end()); 3948 concurrent_mark()->clear_range_in_prev_bitmap(mr); 3949 } 3950 3951 // Clear the card counts for this region. 3952 // Note: we only need to do this if the region is not young 3953 // (since we don't refine cards in young regions). 3954 if (!skip_hot_card_cache && !hr->is_young()) { 3955 _hot_card_cache->reset_card_counts(hr); 3956 } 3957 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 3958 _g1_policy->remset_tracker()->update_at_free(hr); 3959 free_list->add_ordered(hr); 3960 } 3961 3962 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 3963 FreeRegionList* free_list) { 3964 assert(hr->is_humongous(), "this is only for humongous regions"); 3965 assert(free_list != NULL, "pre-condition"); 3966 hr->clear_humongous(); 3967 free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */); 3968 } 3969 3970 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 3971 const uint humongous_regions_removed) { 3972 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 3973 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 3974 _old_set.bulk_remove(old_regions_removed); 3975 _humongous_set.bulk_remove(humongous_regions_removed); 3976 } 3977 3978 } 3979 3980 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 3981 assert(list != NULL, "list can't be null"); 3982 if (!list->is_empty()) { 3983 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 3984 _hrm.insert_list_into_free_list(list); 3985 } 3986 } 3987 3988 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 3989 decrease_used(bytes); 3990 } 3991 3992 class G1FreeCollectionSetTask : public AbstractGangTask { 3993 private: 3994 3995 // Closure applied to all regions in the collection set to do work that needs to 3996 // be done serially in a single thread. 3997 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 3998 private: 3999 EvacuationInfo* _evacuation_info; 4000 const size_t* _surviving_young_words; 4001 4002 // Bytes used in successfully evacuated regions before the evacuation. 4003 size_t _before_used_bytes; 4004 // Bytes used in unsucessfully evacuated regions before the evacuation 4005 size_t _after_used_bytes; 4006 4007 size_t _bytes_allocated_in_old_since_last_gc; 4008 4009 size_t _failure_used_words; 4010 size_t _failure_waste_words; 4011 4012 FreeRegionList _local_free_list; 4013 public: 4014 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4015 HeapRegionClosure(), 4016 _evacuation_info(evacuation_info), 4017 _surviving_young_words(surviving_young_words), 4018 _before_used_bytes(0), 4019 _after_used_bytes(0), 4020 _bytes_allocated_in_old_since_last_gc(0), 4021 _failure_used_words(0), 4022 _failure_waste_words(0), 4023 _local_free_list("Local Region List for CSet Freeing") { 4024 } 4025 4026 virtual bool do_heap_region(HeapRegion* r) { 4027 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4028 4029 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4030 g1h->clear_in_cset(r); 4031 4032 if (r->is_young()) { 4033 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4034 "Young index %d is wrong for region %u of type %s with %u young regions", 4035 r->young_index_in_cset(), 4036 r->hrm_index(), 4037 r->get_type_str(), 4038 g1h->collection_set()->young_region_length()); 4039 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4040 r->record_surv_words_in_group(words_survived); 4041 } 4042 4043 if (!r->evacuation_failed()) { 4044 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4045 _before_used_bytes += r->used(); 4046 g1h->free_region(r, 4047 &_local_free_list, 4048 true, /* skip_remset */ 4049 true, /* skip_hot_card_cache */ 4050 true /* locked */); 4051 } else { 4052 r->uninstall_surv_rate_group(); 4053 r->set_young_index_in_cset(-1); 4054 r->set_evacuation_failed(false); 4055 // When moving a young gen region to old gen, we "allocate" that whole region 4056 // there. This is in addition to any already evacuated objects. Notify the 4057 // policy about that. 4058 // Old gen regions do not cause an additional allocation: both the objects 4059 // still in the region and the ones already moved are accounted for elsewhere. 4060 if (r->is_young()) { 4061 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4062 } 4063 // The region is now considered to be old. 4064 r->set_old(); 4065 // Do some allocation statistics accounting. Regions that failed evacuation 4066 // are always made old, so there is no need to update anything in the young 4067 // gen statistics, but we need to update old gen statistics. 4068 size_t used_words = r->marked_bytes() / HeapWordSize; 4069 4070 _failure_used_words += used_words; 4071 _failure_waste_words += HeapRegion::GrainWords - used_words; 4072 4073 g1h->old_set_add(r); 4074 _after_used_bytes += r->used(); 4075 } 4076 return false; 4077 } 4078 4079 void complete_work() { 4080 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4081 4082 _evacuation_info->set_regions_freed(_local_free_list.length()); 4083 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4084 4085 g1h->prepend_to_freelist(&_local_free_list); 4086 g1h->decrement_summary_bytes(_before_used_bytes); 4087 4088 G1Policy* policy = g1h->g1_policy(); 4089 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4090 4091 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4092 } 4093 }; 4094 4095 G1CollectionSet* _collection_set; 4096 G1SerialFreeCollectionSetClosure _cl; 4097 const size_t* _surviving_young_words; 4098 4099 size_t _rs_lengths; 4100 4101 volatile jint _serial_work_claim; 4102 4103 struct WorkItem { 4104 uint region_idx; 4105 bool is_young; 4106 bool evacuation_failed; 4107 4108 WorkItem(HeapRegion* r) { 4109 region_idx = r->hrm_index(); 4110 is_young = r->is_young(); 4111 evacuation_failed = r->evacuation_failed(); 4112 } 4113 }; 4114 4115 volatile size_t _parallel_work_claim; 4116 size_t _num_work_items; 4117 WorkItem* _work_items; 4118 4119 void do_serial_work() { 4120 // Need to grab the lock to be allowed to modify the old region list. 4121 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4122 _collection_set->iterate(&_cl); 4123 } 4124 4125 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4126 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4127 4128 HeapRegion* r = g1h->region_at(region_idx); 4129 assert(!g1h->is_on_master_free_list(r), "sanity"); 4130 4131 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4132 4133 if (!is_young) { 4134 g1h->_hot_card_cache->reset_card_counts(r); 4135 } 4136 4137 if (!evacuation_failed) { 4138 r->rem_set()->clear_locked(); 4139 } 4140 } 4141 4142 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4143 private: 4144 size_t _cur_idx; 4145 WorkItem* _work_items; 4146 public: 4147 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4148 4149 virtual bool do_heap_region(HeapRegion* r) { 4150 _work_items[_cur_idx++] = WorkItem(r); 4151 return false; 4152 } 4153 }; 4154 4155 void prepare_work() { 4156 G1PrepareFreeCollectionSetClosure cl(_work_items); 4157 _collection_set->iterate(&cl); 4158 } 4159 4160 void complete_work() { 4161 _cl.complete_work(); 4162 4163 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4164 policy->record_max_rs_lengths(_rs_lengths); 4165 policy->cset_regions_freed(); 4166 } 4167 public: 4168 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4169 AbstractGangTask("G1 Free Collection Set"), 4170 _collection_set(collection_set), 4171 _cl(evacuation_info, surviving_young_words), 4172 _surviving_young_words(surviving_young_words), 4173 _rs_lengths(0), 4174 _serial_work_claim(0), 4175 _parallel_work_claim(0), 4176 _num_work_items(collection_set->region_length()), 4177 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4178 prepare_work(); 4179 } 4180 4181 ~G1FreeCollectionSetTask() { 4182 complete_work(); 4183 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4184 } 4185 4186 // Chunk size for work distribution. The chosen value has been determined experimentally 4187 // to be a good tradeoff between overhead and achievable parallelism. 4188 static uint chunk_size() { return 32; } 4189 4190 virtual void work(uint worker_id) { 4191 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4192 4193 // Claim serial work. 4194 if (_serial_work_claim == 0) { 4195 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4196 if (value == 0) { 4197 double serial_time = os::elapsedTime(); 4198 do_serial_work(); 4199 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4200 } 4201 } 4202 4203 // Start parallel work. 4204 double young_time = 0.0; 4205 bool has_young_time = false; 4206 double non_young_time = 0.0; 4207 bool has_non_young_time = false; 4208 4209 while (true) { 4210 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4211 size_t cur = end - chunk_size(); 4212 4213 if (cur >= _num_work_items) { 4214 break; 4215 } 4216 4217 EventGCPhaseParallel event; 4218 double start_time = os::elapsedTime(); 4219 4220 end = MIN2(end, _num_work_items); 4221 4222 for (; cur < end; cur++) { 4223 bool is_young = _work_items[cur].is_young; 4224 4225 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4226 4227 double end_time = os::elapsedTime(); 4228 double time_taken = end_time - start_time; 4229 if (is_young) { 4230 young_time += time_taken; 4231 has_young_time = true; 4232 event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::YoungFreeCSet)); 4233 } else { 4234 non_young_time += time_taken; 4235 has_non_young_time = true; 4236 event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::NonYoungFreeCSet)); 4237 } 4238 start_time = end_time; 4239 } 4240 } 4241 4242 if (has_young_time) { 4243 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4244 } 4245 if (has_non_young_time) { 4246 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time); 4247 } 4248 } 4249 }; 4250 4251 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4252 _eden.clear(); 4253 4254 double free_cset_start_time = os::elapsedTime(); 4255 4256 { 4257 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4258 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4259 4260 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4261 4262 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4263 cl.name(), 4264 num_workers, 4265 _collection_set.region_length()); 4266 workers()->run_task(&cl, num_workers); 4267 } 4268 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4269 4270 collection_set->clear(); 4271 } 4272 4273 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4274 private: 4275 FreeRegionList* _free_region_list; 4276 HeapRegionSet* _proxy_set; 4277 uint _humongous_objects_reclaimed; 4278 uint _humongous_regions_reclaimed; 4279 size_t _freed_bytes; 4280 public: 4281 4282 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4283 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4284 } 4285 4286 virtual bool do_heap_region(HeapRegion* r) { 4287 if (!r->is_starts_humongous()) { 4288 return false; 4289 } 4290 4291 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4292 4293 oop obj = (oop)r->bottom(); 4294 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap(); 4295 4296 // The following checks whether the humongous object is live are sufficient. 4297 // The main additional check (in addition to having a reference from the roots 4298 // or the young gen) is whether the humongous object has a remembered set entry. 4299 // 4300 // A humongous object cannot be live if there is no remembered set for it 4301 // because: 4302 // - there can be no references from within humongous starts regions referencing 4303 // the object because we never allocate other objects into them. 4304 // (I.e. there are no intra-region references that may be missed by the 4305 // remembered set) 4306 // - as soon there is a remembered set entry to the humongous starts region 4307 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4308 // until the end of a concurrent mark. 4309 // 4310 // It is not required to check whether the object has been found dead by marking 4311 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4312 // all objects allocated during that time are considered live. 4313 // SATB marking is even more conservative than the remembered set. 4314 // So if at this point in the collection there is no remembered set entry, 4315 // nobody has a reference to it. 4316 // At the start of collection we flush all refinement logs, and remembered sets 4317 // are completely up-to-date wrt to references to the humongous object. 4318 // 4319 // Other implementation considerations: 4320 // - never consider object arrays at this time because they would pose 4321 // considerable effort for cleaning up the the remembered sets. This is 4322 // required because stale remembered sets might reference locations that 4323 // are currently allocated into. 4324 uint region_idx = r->hrm_index(); 4325 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4326 !r->rem_set()->is_empty()) { 4327 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", 4328 region_idx, 4329 (size_t)obj->size() * HeapWordSize, 4330 p2i(r->bottom()), 4331 r->rem_set()->occupied(), 4332 r->rem_set()->strong_code_roots_list_length(), 4333 next_bitmap->is_marked(r->bottom()), 4334 g1h->is_humongous_reclaim_candidate(region_idx), 4335 obj->is_typeArray() 4336 ); 4337 return false; 4338 } 4339 4340 guarantee(obj->is_typeArray(), 4341 "Only eagerly reclaiming type arrays is supported, but the object " 4342 PTR_FORMAT " is not.", p2i(r->bottom())); 4343 4344 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", 4345 region_idx, 4346 (size_t)obj->size() * HeapWordSize, 4347 p2i(r->bottom()), 4348 r->rem_set()->occupied(), 4349 r->rem_set()->strong_code_roots_list_length(), 4350 next_bitmap->is_marked(r->bottom()), 4351 g1h->is_humongous_reclaim_candidate(region_idx), 4352 obj->is_typeArray() 4353 ); 4354 4355 G1ConcurrentMark* const cm = g1h->concurrent_mark(); 4356 cm->humongous_object_eagerly_reclaimed(r); 4357 assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj), 4358 "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s", 4359 region_idx, 4360 BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)), 4361 BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj))); 4362 _humongous_objects_reclaimed++; 4363 do { 4364 HeapRegion* next = g1h->next_region_in_humongous(r); 4365 _freed_bytes += r->used(); 4366 r->set_containing_set(NULL); 4367 _humongous_regions_reclaimed++; 4368 g1h->free_humongous_region(r, _free_region_list); 4369 r = next; 4370 } while (r != NULL); 4371 4372 return false; 4373 } 4374 4375 uint humongous_objects_reclaimed() { 4376 return _humongous_objects_reclaimed; 4377 } 4378 4379 uint humongous_regions_reclaimed() { 4380 return _humongous_regions_reclaimed; 4381 } 4382 4383 size_t bytes_freed() const { 4384 return _freed_bytes; 4385 } 4386 }; 4387 4388 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4389 assert_at_safepoint_on_vm_thread(); 4390 4391 if (!G1EagerReclaimHumongousObjects || 4392 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4393 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4394 return; 4395 } 4396 4397 double start_time = os::elapsedTime(); 4398 4399 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4400 4401 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4402 heap_region_iterate(&cl); 4403 4404 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4405 4406 G1HRPrinter* hrp = hr_printer(); 4407 if (hrp->is_active()) { 4408 FreeRegionListIterator iter(&local_cleanup_list); 4409 while (iter.more_available()) { 4410 HeapRegion* hr = iter.get_next(); 4411 hrp->cleanup(hr); 4412 } 4413 } 4414 4415 prepend_to_freelist(&local_cleanup_list); 4416 decrement_summary_bytes(cl.bytes_freed()); 4417 4418 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4419 cl.humongous_objects_reclaimed()); 4420 } 4421 4422 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4423 public: 4424 virtual bool do_heap_region(HeapRegion* r) { 4425 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4426 G1CollectedHeap::heap()->clear_in_cset(r); 4427 r->set_young_index_in_cset(-1); 4428 return false; 4429 } 4430 }; 4431 4432 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4433 G1AbandonCollectionSetClosure cl; 4434 collection_set->iterate(&cl); 4435 4436 collection_set->clear(); 4437 collection_set->stop_incremental_building(); 4438 } 4439 4440 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 4441 return _allocator->is_retained_old_region(hr); 4442 } 4443 4444 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 4445 _eden.add(hr); 4446 _g1_policy->set_region_eden(hr); 4447 } 4448 4449 #ifdef ASSERT 4450 4451 class NoYoungRegionsClosure: public HeapRegionClosure { 4452 private: 4453 bool _success; 4454 public: 4455 NoYoungRegionsClosure() : _success(true) { } 4456 bool do_heap_region(HeapRegion* r) { 4457 if (r->is_young()) { 4458 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 4459 p2i(r->bottom()), p2i(r->end())); 4460 _success = false; 4461 } 4462 return false; 4463 } 4464 bool success() { return _success; } 4465 }; 4466 4467 bool G1CollectedHeap::check_young_list_empty() { 4468 bool ret = (young_regions_count() == 0); 4469 4470 NoYoungRegionsClosure closure; 4471 heap_region_iterate(&closure); 4472 ret = ret && closure.success(); 4473 4474 return ret; 4475 } 4476 4477 #endif // ASSERT 4478 4479 class TearDownRegionSetsClosure : public HeapRegionClosure { 4480 HeapRegionSet *_old_set; 4481 4482 public: 4483 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 4484 4485 bool do_heap_region(HeapRegion* r) { 4486 if (r->is_old()) { 4487 _old_set->remove(r); 4488 } else if(r->is_young()) { 4489 r->uninstall_surv_rate_group(); 4490 } else { 4491 // We ignore free regions, we'll empty the free list afterwards. 4492 // We ignore humongous and archive regions, we're not tearing down these 4493 // sets. 4494 assert(r->is_archive() || r->is_free() || r->is_humongous(), 4495 "it cannot be another type"); 4496 } 4497 return false; 4498 } 4499 4500 ~TearDownRegionSetsClosure() { 4501 assert(_old_set->is_empty(), "post-condition"); 4502 } 4503 }; 4504 4505 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 4506 assert_at_safepoint_on_vm_thread(); 4507 4508 if (!free_list_only) { 4509 TearDownRegionSetsClosure cl(&_old_set); 4510 heap_region_iterate(&cl); 4511 4512 // Note that emptying the _young_list is postponed and instead done as 4513 // the first step when rebuilding the regions sets again. The reason for 4514 // this is that during a full GC string deduplication needs to know if 4515 // a collected region was young or old when the full GC was initiated. 4516 } 4517 _hrm.remove_all_free_regions(); 4518 } 4519 4520 void G1CollectedHeap::increase_used(size_t bytes) { 4521 _summary_bytes_used += bytes; 4522 } 4523 4524 void G1CollectedHeap::decrease_used(size_t bytes) { 4525 assert(_summary_bytes_used >= bytes, 4526 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 4527 _summary_bytes_used, bytes); 4528 _summary_bytes_used -= bytes; 4529 } 4530 4531 void G1CollectedHeap::set_used(size_t bytes) { 4532 _summary_bytes_used = bytes; 4533 } 4534 4535 class RebuildRegionSetsClosure : public HeapRegionClosure { 4536 private: 4537 bool _free_list_only; 4538 4539 HeapRegionSet* _old_set; 4540 HeapRegionManager* _hrm; 4541 4542 size_t _total_used; 4543 4544 public: 4545 RebuildRegionSetsClosure(bool free_list_only, 4546 HeapRegionSet* old_set, 4547 HeapRegionManager* hrm) : 4548 _free_list_only(free_list_only), 4549 _old_set(old_set), _hrm(hrm), _total_used(0) { 4550 assert(_hrm->num_free_regions() == 0, "pre-condition"); 4551 if (!free_list_only) { 4552 assert(_old_set->is_empty(), "pre-condition"); 4553 } 4554 } 4555 4556 bool do_heap_region(HeapRegion* r) { 4557 if (r->is_empty()) { 4558 assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets."); 4559 // Add free regions to the free list 4560 r->set_free(); 4561 _hrm->insert_into_free_list(r); 4562 } else if (!_free_list_only) { 4563 assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared."); 4564 4565 if (r->is_archive() || r->is_humongous()) { 4566 // We ignore archive and humongous regions. We left these sets unchanged. 4567 } else { 4568 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 4569 // We now move all (non-humongous, non-old, non-archive) regions to old gen, and register them as such. 4570 r->move_to_old(); 4571 _old_set->add(r); 4572 } 4573 _total_used += r->used(); 4574 } 4575 4576 return false; 4577 } 4578 4579 size_t total_used() { 4580 return _total_used; 4581 } 4582 }; 4583 4584 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 4585 assert_at_safepoint_on_vm_thread(); 4586 4587 if (!free_list_only) { 4588 _eden.clear(); 4589 _survivor.clear(); 4590 } 4591 4592 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 4593 heap_region_iterate(&cl); 4594 4595 if (!free_list_only) { 4596 set_used(cl.total_used()); 4597 if (_archive_allocator != NULL) { 4598 _archive_allocator->clear_used(); 4599 } 4600 } 4601 assert(used() == recalculate_used(), 4602 "inconsistent used(), value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 4603 used(), recalculate_used()); 4604 } 4605 4606 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 4607 HeapRegion* hr = heap_region_containing(p); 4608 return hr->is_in(p); 4609 } 4610 4611 // Methods for the mutator alloc region 4612 4613 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 4614 bool force) { 4615 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4616 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 4617 if (force || should_allocate) { 4618 HeapRegion* new_alloc_region = new_region(word_size, 4619 false /* is_old */, 4620 false /* do_expand */); 4621 if (new_alloc_region != NULL) { 4622 set_region_short_lived_locked(new_alloc_region); 4623 _hr_printer.alloc(new_alloc_region, !should_allocate); 4624 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 4625 _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region); 4626 return new_alloc_region; 4627 } 4628 } 4629 return NULL; 4630 } 4631 4632 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 4633 size_t allocated_bytes) { 4634 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4635 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 4636 4637 collection_set()->add_eden_region(alloc_region); 4638 increase_used(allocated_bytes); 4639 _hr_printer.retire(alloc_region); 4640 // We update the eden sizes here, when the region is retired, 4641 // instead of when it's allocated, since this is the point that its 4642 // used space has been recorded in _summary_bytes_used. 4643 g1mm()->update_eden_size(); 4644 } 4645 4646 // Methods for the GC alloc regions 4647 4648 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 4649 if (dest.is_old()) { 4650 return true; 4651 } else { 4652 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 4653 } 4654 } 4655 4656 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 4657 assert(FreeList_lock->owned_by_self(), "pre-condition"); 4658 4659 if (!has_more_regions(dest)) { 4660 return NULL; 4661 } 4662 4663 const bool is_survivor = dest.is_young(); 4664 4665 HeapRegion* new_alloc_region = new_region(word_size, 4666 !is_survivor, 4667 true /* do_expand */); 4668 if (new_alloc_region != NULL) { 4669 if (is_survivor) { 4670 new_alloc_region->set_survivor(); 4671 _survivor.add(new_alloc_region); 4672 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 4673 } else { 4674 new_alloc_region->set_old(); 4675 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 4676 } 4677 _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region); 4678 _hr_printer.alloc(new_alloc_region); 4679 return new_alloc_region; 4680 } 4681 return NULL; 4682 } 4683 4684 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 4685 size_t allocated_bytes, 4686 InCSetState dest) { 4687 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 4688 if (dest.is_old()) { 4689 old_set_add(alloc_region); 4690 } 4691 4692 bool const during_im = collector_state()->in_initial_mark_gc(); 4693 if (during_im && allocated_bytes > 0) { 4694 _cm->root_regions()->add(alloc_region); 4695 } 4696 _hr_printer.retire(alloc_region); 4697 } 4698 4699 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 4700 bool expanded = false; 4701 uint index = _hrm.find_highest_free(&expanded); 4702 4703 if (index != G1_NO_HRM_INDEX) { 4704 if (expanded) { 4705 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 4706 HeapRegion::GrainWords * HeapWordSize); 4707 } 4708 _hrm.allocate_free_regions_starting_at(index, 1); 4709 return region_at(index); 4710 } 4711 return NULL; 4712 } 4713 4714 // Optimized nmethod scanning 4715 4716 class RegisterNMethodOopClosure: public OopClosure { 4717 G1CollectedHeap* _g1h; 4718 nmethod* _nm; 4719 4720 template <class T> void do_oop_work(T* p) { 4721 T heap_oop = RawAccess<>::oop_load(p); 4722 if (!CompressedOops::is_null(heap_oop)) { 4723 oop obj = CompressedOops::decode_not_null(heap_oop); 4724 HeapRegion* hr = _g1h->heap_region_containing(obj); 4725 assert(!hr->is_continues_humongous(), 4726 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 4727 " starting at " HR_FORMAT, 4728 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 4729 4730 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 4731 hr->add_strong_code_root_locked(_nm); 4732 } 4733 } 4734 4735 public: 4736 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 4737 _g1h(g1h), _nm(nm) {} 4738 4739 void do_oop(oop* p) { do_oop_work(p); } 4740 void do_oop(narrowOop* p) { do_oop_work(p); } 4741 }; 4742 4743 class UnregisterNMethodOopClosure: public OopClosure { 4744 G1CollectedHeap* _g1h; 4745 nmethod* _nm; 4746 4747 template <class T> void do_oop_work(T* p) { 4748 T heap_oop = RawAccess<>::oop_load(p); 4749 if (!CompressedOops::is_null(heap_oop)) { 4750 oop obj = CompressedOops::decode_not_null(heap_oop); 4751 HeapRegion* hr = _g1h->heap_region_containing(obj); 4752 assert(!hr->is_continues_humongous(), 4753 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 4754 " starting at " HR_FORMAT, 4755 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 4756 4757 hr->remove_strong_code_root(_nm); 4758 } 4759 } 4760 4761 public: 4762 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 4763 _g1h(g1h), _nm(nm) {} 4764 4765 void do_oop(oop* p) { do_oop_work(p); } 4766 void do_oop(narrowOop* p) { do_oop_work(p); } 4767 }; 4768 4769 // Returns true if the reference points to an object that 4770 // can move in an incremental collection. 4771 bool G1CollectedHeap::is_scavengable(oop obj) { 4772 HeapRegion* hr = heap_region_containing(obj); 4773 return !hr->is_pinned(); 4774 } 4775 4776 void G1CollectedHeap::register_nmethod(nmethod* nm) { 4777 guarantee(nm != NULL, "sanity"); 4778 RegisterNMethodOopClosure reg_cl(this, nm); 4779 nm->oops_do(®_cl); 4780 } 4781 4782 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 4783 guarantee(nm != NULL, "sanity"); 4784 UnregisterNMethodOopClosure reg_cl(this, nm); 4785 nm->oops_do(®_cl, true); 4786 } 4787 4788 void G1CollectedHeap::purge_code_root_memory() { 4789 double purge_start = os::elapsedTime(); 4790 G1CodeRootSet::purge(); 4791 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 4792 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 4793 } 4794 4795 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 4796 G1CollectedHeap* _g1h; 4797 4798 public: 4799 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 4800 _g1h(g1h) {} 4801 4802 void do_code_blob(CodeBlob* cb) { 4803 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 4804 if (nm == NULL) { 4805 return; 4806 } 4807 4808 if (ScavengeRootsInCode) { 4809 _g1h->register_nmethod(nm); 4810 } 4811 } 4812 }; 4813 4814 void G1CollectedHeap::rebuild_strong_code_roots() { 4815 RebuildStrongCodeRootClosure blob_cl(this); 4816 CodeCache::blobs_do(&blob_cl); 4817 } 4818 4819 void G1CollectedHeap::initialize_serviceability() { 4820 _g1mm->initialize_serviceability(); 4821 } 4822 4823 MemoryUsage G1CollectedHeap::memory_usage() { 4824 return _g1mm->memory_usage(); 4825 } 4826 4827 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() { 4828 return _g1mm->memory_managers(); 4829 } 4830 4831 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() { 4832 return _g1mm->memory_pools(); 4833 }