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/metadataOnStackMark.hpp" 27 #include "classfile/stringTable.hpp" 28 #include "classfile/symbolTable.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/g1StringDedup.hpp" 56 #include "gc/g1/g1ThreadLocalData.hpp" 57 #include "gc/g1/g1YCTypes.hpp" 58 #include "gc/g1/g1YoungRemSetSamplingThread.hpp" 59 #include "gc/g1/heapRegion.inline.hpp" 60 #include "gc/g1/heapRegionRemSet.hpp" 61 #include "gc/g1/heapRegionSet.inline.hpp" 62 #include "gc/g1/vm_operations_g1.hpp" 63 #include "gc/shared/adaptiveSizePolicy.hpp" 64 #include "gc/shared/gcHeapSummary.hpp" 65 #include "gc/shared/gcId.hpp" 66 #include "gc/shared/gcLocker.hpp" 67 #include "gc/shared/gcTimer.hpp" 68 #include "gc/shared/gcTrace.hpp" 69 #include "gc/shared/gcTraceTime.inline.hpp" 70 #include "gc/shared/generationSpec.hpp" 71 #include "gc/shared/isGCActiveMark.hpp" 72 #include "gc/shared/preservedMarks.inline.hpp" 73 #include "gc/shared/suspendibleThreadSet.hpp" 74 #include "gc/shared/referenceProcessor.inline.hpp" 75 #include "gc/shared/taskqueue.inline.hpp" 76 #include "gc/shared/weakProcessor.hpp" 77 #include "logging/log.hpp" 78 #include "memory/allocation.hpp" 79 #include "memory/iterator.hpp" 80 #include "memory/resourceArea.hpp" 81 #include "oops/access.inline.hpp" 82 #include "oops/compressedOops.inline.hpp" 83 #include "oops/oop.inline.hpp" 84 #include "prims/resolvedMethodTable.hpp" 85 #include "runtime/atomic.hpp" 86 #include "runtime/handles.inline.hpp" 87 #include "runtime/init.hpp" 88 #include "runtime/orderAccess.inline.hpp" 89 #include "runtime/threadSMR.hpp" 90 #include "runtime/vmThread.hpp" 91 #include "utilities/align.hpp" 92 #include "utilities/globalDefinitions.hpp" 93 #include "utilities/stack.inline.hpp" 94 95 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 96 97 // INVARIANTS/NOTES 98 // 99 // All allocation activity covered by the G1CollectedHeap interface is 100 // serialized by acquiring the HeapLock. This happens in mem_allocate 101 // and allocate_new_tlab, which are the "entry" points to the 102 // allocation code from the rest of the JVM. (Note that this does not 103 // apply to TLAB allocation, which is not part of this interface: it 104 // is done by clients of this interface.) 105 106 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 107 private: 108 size_t _num_dirtied; 109 G1CollectedHeap* _g1h; 110 G1CardTable* _g1_ct; 111 112 HeapRegion* region_for_card(jbyte* card_ptr) const { 113 return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr)); 114 } 115 116 bool will_become_free(HeapRegion* hr) const { 117 // A region will be freed by free_collection_set if the region is in the 118 // collection set and has not had an evacuation failure. 119 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 120 } 121 122 public: 123 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 124 _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { } 125 126 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 127 HeapRegion* hr = region_for_card(card_ptr); 128 129 // Should only dirty cards in regions that won't be freed. 130 if (!will_become_free(hr)) { 131 *card_ptr = G1CardTable::dirty_card_val(); 132 _num_dirtied++; 133 } 134 135 return true; 136 } 137 138 size_t num_dirtied() const { return _num_dirtied; } 139 }; 140 141 142 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 143 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 144 } 145 146 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 147 // The from card cache is not the memory that is actually committed. So we cannot 148 // take advantage of the zero_filled parameter. 149 reset_from_card_cache(start_idx, num_regions); 150 } 151 152 153 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 154 MemRegion mr) { 155 return new HeapRegion(hrs_index, bot(), mr); 156 } 157 158 // Private methods. 159 160 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 161 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 162 "the only time we use this to allocate a humongous region is " 163 "when we are allocating a single humongous region"); 164 165 HeapRegion* res = _hrm.allocate_free_region(is_old); 166 167 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 168 // Currently, only attempts to allocate GC alloc regions set 169 // do_expand to true. So, we should only reach here during a 170 // safepoint. If this assumption changes we might have to 171 // reconsider the use of _expand_heap_after_alloc_failure. 172 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 173 174 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 175 word_size * HeapWordSize); 176 177 if (expand(word_size * HeapWordSize)) { 178 // Given that expand() succeeded in expanding the heap, and we 179 // always expand the heap by an amount aligned to the heap 180 // region size, the free list should in theory not be empty. 181 // In either case allocate_free_region() will check for NULL. 182 res = _hrm.allocate_free_region(is_old); 183 } else { 184 _expand_heap_after_alloc_failure = false; 185 } 186 } 187 return res; 188 } 189 190 HeapWord* 191 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 192 uint num_regions, 193 size_t word_size) { 194 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 195 assert(is_humongous(word_size), "word_size should be humongous"); 196 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 197 198 // Index of last region in the series. 199 uint last = first + num_regions - 1; 200 201 // We need to initialize the region(s) we just discovered. This is 202 // a bit tricky given that it can happen concurrently with 203 // refinement threads refining cards on these regions and 204 // potentially wanting to refine the BOT as they are scanning 205 // those cards (this can happen shortly after a cleanup; see CR 206 // 6991377). So we have to set up the region(s) carefully and in 207 // a specific order. 208 209 // The word size sum of all the regions we will allocate. 210 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 211 assert(word_size <= word_size_sum, "sanity"); 212 213 // This will be the "starts humongous" region. 214 HeapRegion* first_hr = region_at(first); 215 // The header of the new object will be placed at the bottom of 216 // the first region. 217 HeapWord* new_obj = first_hr->bottom(); 218 // This will be the new top of the new object. 219 HeapWord* obj_top = new_obj + word_size; 220 221 // First, we need to zero the header of the space that we will be 222 // allocating. When we update top further down, some refinement 223 // threads might try to scan the region. By zeroing the header we 224 // ensure that any thread that will try to scan the region will 225 // come across the zero klass word and bail out. 226 // 227 // NOTE: It would not have been correct to have used 228 // CollectedHeap::fill_with_object() and make the space look like 229 // an int array. The thread that is doing the allocation will 230 // later update the object header to a potentially different array 231 // type and, for a very short period of time, the klass and length 232 // fields will be inconsistent. This could cause a refinement 233 // thread to calculate the object size incorrectly. 234 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 235 236 // Next, pad out the unused tail of the last region with filler 237 // objects, for improved usage accounting. 238 // How many words we use for filler objects. 239 size_t word_fill_size = word_size_sum - word_size; 240 241 // How many words memory we "waste" which cannot hold a filler object. 242 size_t words_not_fillable = 0; 243 244 if (word_fill_size >= min_fill_size()) { 245 fill_with_objects(obj_top, word_fill_size); 246 } else if (word_fill_size > 0) { 247 // We have space to fill, but we cannot fit an object there. 248 words_not_fillable = word_fill_size; 249 word_fill_size = 0; 250 } 251 252 // We will set up the first region as "starts humongous". This 253 // will also update the BOT covering all the regions to reflect 254 // that there is a single object that starts at the bottom of the 255 // first region. 256 first_hr->set_starts_humongous(obj_top, word_fill_size); 257 _g1_policy->remset_tracker()->update_at_allocate(first_hr); 258 // Then, if there are any, we will set up the "continues 259 // humongous" regions. 260 HeapRegion* hr = NULL; 261 for (uint i = first + 1; i <= last; ++i) { 262 hr = region_at(i); 263 hr->set_continues_humongous(first_hr); 264 _g1_policy->remset_tracker()->update_at_allocate(hr); 265 } 266 267 // Up to this point no concurrent thread would have been able to 268 // do any scanning on any region in this series. All the top 269 // fields still point to bottom, so the intersection between 270 // [bottom,top] and [card_start,card_end] will be empty. Before we 271 // update the top fields, we'll do a storestore to make sure that 272 // no thread sees the update to top before the zeroing of the 273 // object header and the BOT initialization. 274 OrderAccess::storestore(); 275 276 // Now, we will update the top fields of the "continues humongous" 277 // regions except the last one. 278 for (uint i = first; i < last; ++i) { 279 hr = region_at(i); 280 hr->set_top(hr->end()); 281 } 282 283 hr = region_at(last); 284 // If we cannot fit a filler object, we must set top to the end 285 // of the humongous object, otherwise we cannot iterate the heap 286 // and the BOT will not be complete. 287 hr->set_top(hr->end() - words_not_fillable); 288 289 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 290 "obj_top should be in last region"); 291 292 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 293 294 assert(words_not_fillable == 0 || 295 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 296 "Miscalculation in humongous allocation"); 297 298 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 299 300 for (uint i = first; i <= last; ++i) { 301 hr = region_at(i); 302 _humongous_set.add(hr); 303 _hr_printer.alloc(hr); 304 } 305 306 return new_obj; 307 } 308 309 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 310 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 311 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 312 } 313 314 // If could fit into free regions w/o expansion, try. 315 // Otherwise, if can expand, do so. 316 // Otherwise, if using ex regions might help, try with ex given back. 317 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) { 318 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 319 320 _verifier->verify_region_sets_optional(); 321 322 uint first = G1_NO_HRM_INDEX; 323 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 324 325 if (obj_regions == 1) { 326 // Only one region to allocate, try to use a fast path by directly allocating 327 // from the free lists. Do not try to expand here, we will potentially do that 328 // later. 329 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 330 if (hr != NULL) { 331 first = hr->hrm_index(); 332 } 333 } else { 334 // Policy: Try only empty regions (i.e. already committed first). Maybe we 335 // are lucky enough to find some. 336 first = _hrm.find_contiguous_only_empty(obj_regions); 337 if (first != G1_NO_HRM_INDEX) { 338 _hrm.allocate_free_regions_starting_at(first, obj_regions); 339 } 340 } 341 342 if (first == G1_NO_HRM_INDEX) { 343 // Policy: We could not find enough regions for the humongous object in the 344 // free list. Look through the heap to find a mix of free and uncommitted regions. 345 // If so, try expansion. 346 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 347 if (first != G1_NO_HRM_INDEX) { 348 // We found something. Make sure these regions are committed, i.e. expand 349 // the heap. Alternatively we could do a defragmentation GC. 350 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 351 word_size * HeapWordSize); 352 353 _hrm.expand_at(first, obj_regions, workers()); 354 g1_policy()->record_new_heap_size(num_regions()); 355 356 #ifdef ASSERT 357 for (uint i = first; i < first + obj_regions; ++i) { 358 HeapRegion* hr = region_at(i); 359 assert(hr->is_free(), "sanity"); 360 assert(hr->is_empty(), "sanity"); 361 assert(is_on_master_free_list(hr), "sanity"); 362 } 363 #endif 364 _hrm.allocate_free_regions_starting_at(first, obj_regions); 365 } else { 366 // Policy: Potentially trigger a defragmentation GC. 367 } 368 } 369 370 HeapWord* result = NULL; 371 if (first != G1_NO_HRM_INDEX) { 372 result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size); 373 assert(result != NULL, "it should always return a valid result"); 374 375 // A successful humongous object allocation changes the used space 376 // information of the old generation so we need to recalculate the 377 // sizes and update the jstat counters here. 378 g1mm()->update_sizes(); 379 } 380 381 _verifier->verify_region_sets_optional(); 382 383 return result; 384 } 385 386 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 387 assert_heap_not_locked_and_not_at_safepoint(); 388 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 389 390 return attempt_allocation(word_size); 391 } 392 393 HeapWord* 394 G1CollectedHeap::mem_allocate(size_t word_size, 395 bool* gc_overhead_limit_was_exceeded) { 396 assert_heap_not_locked_and_not_at_safepoint(); 397 398 if (is_humongous(word_size)) { 399 return attempt_allocation_humongous(word_size); 400 } 401 return attempt_allocation(word_size); 402 } 403 404 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) { 405 ResourceMark rm; // For retrieving the thread names in log messages. 406 407 // Make sure you read the note in attempt_allocation_humongous(). 408 409 assert_heap_not_locked_and_not_at_safepoint(); 410 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 411 "be called for humongous allocation requests"); 412 413 // We should only get here after the first-level allocation attempt 414 // (attempt_allocation()) failed to allocate. 415 416 // We will loop until a) we manage to successfully perform the 417 // allocation or b) we successfully schedule a collection which 418 // fails to perform the allocation. b) is the only case when we'll 419 // return NULL. 420 HeapWord* result = NULL; 421 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 422 bool should_try_gc; 423 uint gc_count_before; 424 425 { 426 MutexLockerEx x(Heap_lock); 427 result = _allocator->attempt_allocation_locked(word_size); 428 if (result != NULL) { 429 return result; 430 } 431 432 // If the GCLocker is active and we are bound for a GC, try expanding young gen. 433 // This is different to when only GCLocker::needs_gc() is set: try to avoid 434 // waiting because the GCLocker is active to not wait too long. 435 if (GCLocker::is_active_and_needs_gc() && g1_policy()->can_expand_young_list()) { 436 // No need for an ergo message here, can_expand_young_list() does this when 437 // it returns true. 438 result = _allocator->attempt_allocation_force(word_size); 439 if (result != NULL) { 440 return result; 441 } 442 } 443 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 444 // the GCLocker initiated GC has been performed and then retry. This includes 445 // the case when the GC Locker is not active but has not been performed. 446 should_try_gc = !GCLocker::needs_gc(); 447 // Read the GC count while still holding the Heap_lock. 448 gc_count_before = total_collections(); 449 } 450 451 if (should_try_gc) { 452 bool succeeded; 453 result = do_collection_pause(word_size, gc_count_before, &succeeded, 454 GCCause::_g1_inc_collection_pause); 455 if (result != NULL) { 456 assert(succeeded, "only way to get back a non-NULL result"); 457 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 458 Thread::current()->name(), p2i(result)); 459 return result; 460 } 461 462 if (succeeded) { 463 // We successfully scheduled a collection which failed to allocate. No 464 // point in trying to allocate further. We'll just return NULL. 465 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 466 SIZE_FORMAT " words", Thread::current()->name(), word_size); 467 return NULL; 468 } 469 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words", 470 Thread::current()->name(), word_size); 471 } else { 472 // Failed to schedule a collection. 473 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 474 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 475 SIZE_FORMAT " words", Thread::current()->name(), word_size); 476 return NULL; 477 } 478 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 479 // The GCLocker is either active or the GCLocker initiated 480 // GC has not yet been performed. Stall until it is and 481 // then retry the allocation. 482 GCLocker::stall_until_clear(); 483 gclocker_retry_count += 1; 484 } 485 486 // We can reach here if we were unsuccessful in scheduling a 487 // collection (because another thread beat us to it) or if we were 488 // stalled due to the GC locker. In either can we should retry the 489 // allocation attempt in case another thread successfully 490 // performed a collection and reclaimed enough space. We do the 491 // first attempt (without holding the Heap_lock) here and the 492 // follow-on attempt will be at the start of the next loop 493 // iteration (after taking the Heap_lock). 494 495 result = _allocator->attempt_allocation(word_size); 496 if (result != NULL) { 497 return result; 498 } 499 500 // Give a warning if we seem to be looping forever. 501 if ((QueuedAllocationWarningCount > 0) && 502 (try_count % QueuedAllocationWarningCount == 0)) { 503 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 504 Thread::current()->name(), try_count, word_size); 505 } 506 } 507 508 ShouldNotReachHere(); 509 return NULL; 510 } 511 512 void G1CollectedHeap::begin_archive_alloc_range(bool open) { 513 assert_at_safepoint_on_vm_thread(); 514 if (_archive_allocator == NULL) { 515 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open); 516 } 517 } 518 519 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 520 // Allocations in archive regions cannot be of a size that would be considered 521 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 522 // may be different at archive-restore time. 523 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 524 } 525 526 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 527 assert_at_safepoint_on_vm_thread(); 528 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 529 if (is_archive_alloc_too_large(word_size)) { 530 return NULL; 531 } 532 return _archive_allocator->archive_mem_allocate(word_size); 533 } 534 535 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 536 size_t end_alignment_in_bytes) { 537 assert_at_safepoint_on_vm_thread(); 538 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 539 540 // Call complete_archive to do the real work, filling in the MemRegion 541 // array with the archive regions. 542 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 543 delete _archive_allocator; 544 _archive_allocator = NULL; 545 } 546 547 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 548 assert(ranges != NULL, "MemRegion array NULL"); 549 assert(count != 0, "No MemRegions provided"); 550 MemRegion reserved = _hrm.reserved(); 551 for (size_t i = 0; i < count; i++) { 552 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 553 return false; 554 } 555 } 556 return true; 557 } 558 559 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, 560 size_t count, 561 bool open) { 562 assert(!is_init_completed(), "Expect to be called at JVM init time"); 563 assert(ranges != NULL, "MemRegion array NULL"); 564 assert(count != 0, "No MemRegions provided"); 565 MutexLockerEx x(Heap_lock); 566 567 MemRegion reserved = _hrm.reserved(); 568 HeapWord* prev_last_addr = NULL; 569 HeapRegion* prev_last_region = NULL; 570 571 // Temporarily disable pretouching of heap pages. This interface is used 572 // when mmap'ing archived heap data in, so pre-touching is wasted. 573 FlagSetting fs(AlwaysPreTouch, false); 574 575 // Enable archive object checking used by G1MarkSweep. We have to let it know 576 // about each archive range, so that objects in those ranges aren't marked. 577 G1ArchiveAllocator::enable_archive_object_check(); 578 579 // For each specified MemRegion range, allocate the corresponding G1 580 // regions and mark them as archive regions. We expect the ranges 581 // in ascending starting address order, without overlap. 582 for (size_t i = 0; i < count; i++) { 583 MemRegion curr_range = ranges[i]; 584 HeapWord* start_address = curr_range.start(); 585 size_t word_size = curr_range.word_size(); 586 HeapWord* last_address = curr_range.last(); 587 size_t commits = 0; 588 589 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 590 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 591 p2i(start_address), p2i(last_address)); 592 guarantee(start_address > prev_last_addr, 593 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 594 p2i(start_address), p2i(prev_last_addr)); 595 prev_last_addr = last_address; 596 597 // Check for ranges that start in the same G1 region in which the previous 598 // range ended, and adjust the start address so we don't try to allocate 599 // the same region again. If the current range is entirely within that 600 // region, skip it, just adjusting the recorded top. 601 HeapRegion* start_region = _hrm.addr_to_region(start_address); 602 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 603 start_address = start_region->end(); 604 if (start_address > last_address) { 605 increase_used(word_size * HeapWordSize); 606 start_region->set_top(last_address + 1); 607 continue; 608 } 609 start_region->set_top(start_address); 610 curr_range = MemRegion(start_address, last_address + 1); 611 start_region = _hrm.addr_to_region(start_address); 612 } 613 614 // Perform the actual region allocation, exiting if it fails. 615 // Then note how much new space we have allocated. 616 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 617 return false; 618 } 619 increase_used(word_size * HeapWordSize); 620 if (commits != 0) { 621 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 622 HeapRegion::GrainWords * HeapWordSize * commits); 623 624 } 625 626 // Mark each G1 region touched by the range as archive, add it to 627 // the old set, and set top. 628 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 629 HeapRegion* last_region = _hrm.addr_to_region(last_address); 630 prev_last_region = last_region; 631 632 while (curr_region != NULL) { 633 assert(curr_region->is_empty() && !curr_region->is_pinned(), 634 "Region already in use (index %u)", curr_region->hrm_index()); 635 if (open) { 636 curr_region->set_open_archive(); 637 } else { 638 curr_region->set_closed_archive(); 639 } 640 _hr_printer.alloc(curr_region); 641 _old_set.add(curr_region); 642 HeapWord* top; 643 HeapRegion* next_region; 644 if (curr_region != last_region) { 645 top = curr_region->end(); 646 next_region = _hrm.next_region_in_heap(curr_region); 647 } else { 648 top = last_address + 1; 649 next_region = NULL; 650 } 651 curr_region->set_top(top); 652 curr_region->set_first_dead(top); 653 curr_region->set_end_of_live(top); 654 curr_region = next_region; 655 } 656 657 // Notify mark-sweep of the archive 658 G1ArchiveAllocator::set_range_archive(curr_range, open); 659 } 660 return true; 661 } 662 663 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 664 assert(!is_init_completed(), "Expect to be called at JVM init time"); 665 assert(ranges != NULL, "MemRegion array NULL"); 666 assert(count != 0, "No MemRegions provided"); 667 MemRegion reserved = _hrm.reserved(); 668 HeapWord *prev_last_addr = NULL; 669 HeapRegion* prev_last_region = NULL; 670 671 // For each MemRegion, create filler objects, if needed, in the G1 regions 672 // that contain the address range. The address range actually within the 673 // MemRegion will not be modified. That is assumed to have been initialized 674 // elsewhere, probably via an mmap of archived heap data. 675 MutexLockerEx x(Heap_lock); 676 for (size_t i = 0; i < count; i++) { 677 HeapWord* start_address = ranges[i].start(); 678 HeapWord* last_address = ranges[i].last(); 679 680 assert(reserved.contains(start_address) && reserved.contains(last_address), 681 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 682 p2i(start_address), p2i(last_address)); 683 assert(start_address > prev_last_addr, 684 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 685 p2i(start_address), p2i(prev_last_addr)); 686 687 HeapRegion* start_region = _hrm.addr_to_region(start_address); 688 HeapRegion* last_region = _hrm.addr_to_region(last_address); 689 HeapWord* bottom_address = start_region->bottom(); 690 691 // Check for a range beginning in the same region in which the 692 // previous one ended. 693 if (start_region == prev_last_region) { 694 bottom_address = prev_last_addr + 1; 695 } 696 697 // Verify that the regions were all marked as archive regions by 698 // alloc_archive_regions. 699 HeapRegion* curr_region = start_region; 700 while (curr_region != NULL) { 701 guarantee(curr_region->is_archive(), 702 "Expected archive region at index %u", curr_region->hrm_index()); 703 if (curr_region != last_region) { 704 curr_region = _hrm.next_region_in_heap(curr_region); 705 } else { 706 curr_region = NULL; 707 } 708 } 709 710 prev_last_addr = last_address; 711 prev_last_region = last_region; 712 713 // Fill the memory below the allocated range with dummy object(s), 714 // if the region bottom does not match the range start, or if the previous 715 // range ended within the same G1 region, and there is a gap. 716 if (start_address != bottom_address) { 717 size_t fill_size = pointer_delta(start_address, bottom_address); 718 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 719 increase_used(fill_size * HeapWordSize); 720 } 721 } 722 } 723 724 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size) { 725 assert_heap_not_locked_and_not_at_safepoint(); 726 assert(!is_humongous(word_size), "attempt_allocation() should not " 727 "be called for humongous allocation requests"); 728 729 HeapWord* result = _allocator->attempt_allocation(word_size); 730 731 if (result == NULL) { 732 result = attempt_allocation_slow(word_size); 733 } 734 assert_heap_not_locked(); 735 if (result != NULL) { 736 dirty_young_block(result, word_size); 737 } 738 return result; 739 } 740 741 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 742 assert(!is_init_completed(), "Expect to be called at JVM init time"); 743 assert(ranges != NULL, "MemRegion array NULL"); 744 assert(count != 0, "No MemRegions provided"); 745 MemRegion reserved = _hrm.reserved(); 746 HeapWord* prev_last_addr = NULL; 747 HeapRegion* prev_last_region = NULL; 748 size_t size_used = 0; 749 size_t uncommitted_regions = 0; 750 751 // For each Memregion, free the G1 regions that constitute it, and 752 // notify mark-sweep that the range is no longer to be considered 'archive.' 753 MutexLockerEx x(Heap_lock); 754 for (size_t i = 0; i < count; i++) { 755 HeapWord* start_address = ranges[i].start(); 756 HeapWord* last_address = ranges[i].last(); 757 758 assert(reserved.contains(start_address) && reserved.contains(last_address), 759 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 760 p2i(start_address), p2i(last_address)); 761 assert(start_address > prev_last_addr, 762 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 763 p2i(start_address), p2i(prev_last_addr)); 764 size_used += ranges[i].byte_size(); 765 prev_last_addr = last_address; 766 767 HeapRegion* start_region = _hrm.addr_to_region(start_address); 768 HeapRegion* last_region = _hrm.addr_to_region(last_address); 769 770 // Check for ranges that start in the same G1 region in which the previous 771 // range ended, and adjust the start address so we don't try to free 772 // the same region again. If the current range is entirely within that 773 // region, skip it. 774 if (start_region == prev_last_region) { 775 start_address = start_region->end(); 776 if (start_address > last_address) { 777 continue; 778 } 779 start_region = _hrm.addr_to_region(start_address); 780 } 781 prev_last_region = last_region; 782 783 // After verifying that each region was marked as an archive region by 784 // alloc_archive_regions, set it free and empty and uncommit it. 785 HeapRegion* curr_region = start_region; 786 while (curr_region != NULL) { 787 guarantee(curr_region->is_archive(), 788 "Expected archive region at index %u", curr_region->hrm_index()); 789 uint curr_index = curr_region->hrm_index(); 790 _old_set.remove(curr_region); 791 curr_region->set_free(); 792 curr_region->set_top(curr_region->bottom()); 793 if (curr_region != last_region) { 794 curr_region = _hrm.next_region_in_heap(curr_region); 795 } else { 796 curr_region = NULL; 797 } 798 _hrm.shrink_at(curr_index, 1); 799 uncommitted_regions++; 800 } 801 802 // Notify mark-sweep that this is no longer an archive range. 803 G1ArchiveAllocator::set_range_archive(ranges[i], false); 804 } 805 806 if (uncommitted_regions != 0) { 807 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 808 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 809 } 810 decrease_used(size_used); 811 } 812 813 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) { 814 ResourceMark rm; // For retrieving the thread names in log messages. 815 816 // The structure of this method has a lot of similarities to 817 // attempt_allocation_slow(). The reason these two were not merged 818 // into a single one is that such a method would require several "if 819 // allocation is not humongous do this, otherwise do that" 820 // conditional paths which would obscure its flow. In fact, an early 821 // version of this code did use a unified method which was harder to 822 // follow and, as a result, it had subtle bugs that were hard to 823 // track down. So keeping these two methods separate allows each to 824 // be more readable. It will be good to keep these two in sync as 825 // much as possible. 826 827 assert_heap_not_locked_and_not_at_safepoint(); 828 assert(is_humongous(word_size), "attempt_allocation_humongous() " 829 "should only be called for humongous allocations"); 830 831 // Humongous objects can exhaust the heap quickly, so we should check if we 832 // need to start a marking cycle at each humongous object allocation. We do 833 // the check before we do the actual allocation. The reason for doing it 834 // before the allocation is that we avoid having to keep track of the newly 835 // allocated memory while we do a GC. 836 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 837 word_size)) { 838 collect(GCCause::_g1_humongous_allocation); 839 } 840 841 // We will loop until a) we manage to successfully perform the 842 // allocation or b) we successfully schedule a collection which 843 // fails to perform the allocation. b) is the only case when we'll 844 // return NULL. 845 HeapWord* result = NULL; 846 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 847 bool should_try_gc; 848 uint gc_count_before; 849 850 851 { 852 MutexLockerEx x(Heap_lock); 853 854 // Given that humongous objects are not allocated in young 855 // regions, we'll first try to do the allocation without doing a 856 // collection hoping that there's enough space in the heap. 857 result = humongous_obj_allocate(word_size); 858 if (result != NULL) { 859 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 860 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 861 return result; 862 } 863 864 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 865 // the GCLocker initiated GC has been performed and then retry. This includes 866 // the case when the GC Locker is not active but has not been performed. 867 should_try_gc = !GCLocker::needs_gc(); 868 // Read the GC count while still holding the Heap_lock. 869 gc_count_before = total_collections(); 870 } 871 872 if (should_try_gc) { 873 bool succeeded; 874 result = do_collection_pause(word_size, gc_count_before, &succeeded, 875 GCCause::_g1_humongous_allocation); 876 if (result != NULL) { 877 assert(succeeded, "only way to get back a non-NULL result"); 878 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 879 Thread::current()->name(), p2i(result)); 880 return result; 881 } 882 883 if (succeeded) { 884 // We successfully scheduled a collection which failed to allocate. No 885 // point in trying to allocate further. We'll just return NULL. 886 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 887 SIZE_FORMAT " words", Thread::current()->name(), word_size); 888 return NULL; 889 } 890 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "", 891 Thread::current()->name(), word_size); 892 } else { 893 // Failed to schedule a collection. 894 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 895 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 896 SIZE_FORMAT " words", Thread::current()->name(), word_size); 897 return NULL; 898 } 899 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 900 // The GCLocker is either active or the GCLocker initiated 901 // GC has not yet been performed. Stall until it is and 902 // then retry the allocation. 903 GCLocker::stall_until_clear(); 904 gclocker_retry_count += 1; 905 } 906 907 908 // We can reach here if we were unsuccessful in scheduling a 909 // collection (because another thread beat us to it) or if we were 910 // stalled due to the GC locker. In either can we should retry the 911 // allocation attempt in case another thread successfully 912 // performed a collection and reclaimed enough space. 913 // Humongous object allocation always needs a lock, so we wait for the retry 914 // in the next iteration of the loop, unlike for the regular iteration case. 915 // Give a warning if we seem to be looping forever. 916 917 if ((QueuedAllocationWarningCount > 0) && 918 (try_count % QueuedAllocationWarningCount == 0)) { 919 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 920 Thread::current()->name(), try_count, word_size); 921 } 922 } 923 924 ShouldNotReachHere(); 925 return NULL; 926 } 927 928 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 929 bool expect_null_mutator_alloc_region) { 930 assert_at_safepoint_on_vm_thread(); 931 assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region, 932 "the current alloc region was unexpectedly found to be non-NULL"); 933 934 if (!is_humongous(word_size)) { 935 return _allocator->attempt_allocation_locked(word_size); 936 } else { 937 HeapWord* result = humongous_obj_allocate(word_size); 938 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 939 collector_state()->set_initiate_conc_mark_if_possible(true); 940 } 941 return result; 942 } 943 944 ShouldNotReachHere(); 945 } 946 947 class PostCompactionPrinterClosure: public HeapRegionClosure { 948 private: 949 G1HRPrinter* _hr_printer; 950 public: 951 bool do_heap_region(HeapRegion* hr) { 952 assert(!hr->is_young(), "not expecting to find young regions"); 953 _hr_printer->post_compaction(hr); 954 return false; 955 } 956 957 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 958 : _hr_printer(hr_printer) { } 959 }; 960 961 void G1CollectedHeap::print_hrm_post_compaction() { 962 if (_hr_printer.is_active()) { 963 PostCompactionPrinterClosure cl(hr_printer()); 964 heap_region_iterate(&cl); 965 } 966 } 967 968 void G1CollectedHeap::abort_concurrent_cycle() { 969 // If we start the compaction before the CM threads finish 970 // scanning the root regions we might trip them over as we'll 971 // be moving objects / updating references. So let's wait until 972 // they are done. By telling them to abort, they should complete 973 // early. 974 _cm->root_regions()->abort(); 975 _cm->root_regions()->wait_until_scan_finished(); 976 977 // Disable discovery and empty the discovered lists 978 // for the CM ref processor. 979 ref_processor_cm()->disable_discovery(); 980 ref_processor_cm()->abandon_partial_discovery(); 981 ref_processor_cm()->verify_no_references_recorded(); 982 983 // Abandon current iterations of concurrent marking and concurrent 984 // refinement, if any are in progress. 985 concurrent_mark()->concurrent_cycle_abort(); 986 } 987 988 void G1CollectedHeap::prepare_heap_for_full_collection() { 989 // Make sure we'll choose a new allocation region afterwards. 990 _allocator->release_mutator_alloc_region(); 991 _allocator->abandon_gc_alloc_regions(); 992 g1_rem_set()->cleanupHRRS(); 993 994 // We may have added regions to the current incremental collection 995 // set between the last GC or pause and now. We need to clear the 996 // incremental collection set and then start rebuilding it afresh 997 // after this full GC. 998 abandon_collection_set(collection_set()); 999 1000 tear_down_region_sets(false /* free_list_only */); 1001 } 1002 1003 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1004 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1005 assert(used() == recalculate_used(), "Should be equal"); 1006 _verifier->verify_region_sets_optional(); 1007 _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull); 1008 _verifier->check_bitmaps("Full GC Start"); 1009 } 1010 1011 void G1CollectedHeap::prepare_heap_for_mutators() { 1012 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1013 ClassLoaderDataGraph::purge(); 1014 MetaspaceUtils::verify_metrics(); 1015 1016 // Prepare heap for normal collections. 1017 assert(num_free_regions() == 0, "we should not have added any free regions"); 1018 rebuild_region_sets(false /* free_list_only */); 1019 abort_refinement(); 1020 resize_if_necessary_after_full_collection(); 1021 1022 // Rebuild the strong code root lists for each region 1023 rebuild_strong_code_roots(); 1024 1025 // Start a new incremental collection set for the next pause 1026 start_new_collection_set(); 1027 1028 _allocator->init_mutator_alloc_region(); 1029 1030 // Post collection state updates. 1031 MetaspaceGC::compute_new_size(); 1032 } 1033 1034 void G1CollectedHeap::abort_refinement() { 1035 if (_hot_card_cache->use_cache()) { 1036 _hot_card_cache->reset_hot_cache(); 1037 } 1038 1039 // Discard all remembered set updates. 1040 G1BarrierSet::dirty_card_queue_set().abandon_logs(); 1041 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1042 } 1043 1044 void G1CollectedHeap::verify_after_full_collection() { 1045 _hrm.verify_optional(); 1046 _verifier->verify_region_sets_optional(); 1047 _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull); 1048 // Clear the previous marking bitmap, if needed for bitmap verification. 1049 // Note we cannot do this when we clear the next marking bitmap in 1050 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1051 // objects marked during a full GC against the previous bitmap. 1052 // But we need to clear it before calling check_bitmaps below since 1053 // the full GC has compacted objects and updated TAMS but not updated 1054 // the prev bitmap. 1055 if (G1VerifyBitmaps) { 1056 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1057 _cm->clear_prev_bitmap(workers()); 1058 } 1059 _verifier->check_bitmaps("Full GC End"); 1060 1061 // At this point there should be no regions in the 1062 // entire heap tagged as young. 1063 assert(check_young_list_empty(), "young list should be empty at this point"); 1064 1065 // Note: since we've just done a full GC, concurrent 1066 // marking is no longer active. Therefore we need not 1067 // re-enable reference discovery for the CM ref processor. 1068 // That will be done at the start of the next marking cycle. 1069 // We also know that the STW processor should no longer 1070 // discover any new references. 1071 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1072 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1073 ref_processor_stw()->verify_no_references_recorded(); 1074 ref_processor_cm()->verify_no_references_recorded(); 1075 } 1076 1077 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1078 // Post collection logging. 1079 // We should do this after we potentially resize the heap so 1080 // that all the COMMIT / UNCOMMIT events are generated before 1081 // the compaction events. 1082 print_hrm_post_compaction(); 1083 heap_transition->print(); 1084 print_heap_after_gc(); 1085 print_heap_regions(); 1086 #ifdef TRACESPINNING 1087 ParallelTaskTerminator::print_termination_counts(); 1088 #endif 1089 } 1090 1091 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1092 bool clear_all_soft_refs) { 1093 assert_at_safepoint_on_vm_thread(); 1094 1095 if (GCLocker::check_active_before_gc()) { 1096 // Full GC was not completed. 1097 return false; 1098 } 1099 1100 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1101 soft_ref_policy()->should_clear_all_soft_refs(); 1102 1103 G1FullCollector collector(this, &_full_gc_memory_manager, explicit_gc, do_clear_all_soft_refs); 1104 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1105 1106 collector.prepare_collection(); 1107 collector.collect(); 1108 collector.complete_collection(); 1109 1110 // Full collection was successfully completed. 1111 return true; 1112 } 1113 1114 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1115 // Currently, there is no facility in the do_full_collection(bool) API to notify 1116 // the caller that the collection did not succeed (e.g., because it was locked 1117 // out by the GC locker). So, right now, we'll ignore the return value. 1118 bool dummy = do_full_collection(true, /* explicit_gc */ 1119 clear_all_soft_refs); 1120 } 1121 1122 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1123 // Capacity, free and used after the GC counted as full regions to 1124 // include the waste in the following calculations. 1125 const size_t capacity_after_gc = capacity(); 1126 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes(); 1127 1128 // This is enforced in arguments.cpp. 1129 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1130 "otherwise the code below doesn't make sense"); 1131 1132 // We don't have floating point command-line arguments 1133 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1134 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1135 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1136 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1137 1138 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1139 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1140 1141 // We have to be careful here as these two calculations can overflow 1142 // 32-bit size_t's. 1143 double used_after_gc_d = (double) used_after_gc; 1144 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1145 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1146 1147 // Let's make sure that they are both under the max heap size, which 1148 // by default will make them fit into a size_t. 1149 double desired_capacity_upper_bound = (double) max_heap_size; 1150 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1151 desired_capacity_upper_bound); 1152 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1153 desired_capacity_upper_bound); 1154 1155 // We can now safely turn them into size_t's. 1156 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1157 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1158 1159 // This assert only makes sense here, before we adjust them 1160 // with respect to the min and max heap size. 1161 assert(minimum_desired_capacity <= maximum_desired_capacity, 1162 "minimum_desired_capacity = " SIZE_FORMAT ", " 1163 "maximum_desired_capacity = " SIZE_FORMAT, 1164 minimum_desired_capacity, maximum_desired_capacity); 1165 1166 // Should not be greater than the heap max size. No need to adjust 1167 // it with respect to the heap min size as it's a lower bound (i.e., 1168 // we'll try to make the capacity larger than it, not smaller). 1169 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1170 // Should not be less than the heap min size. No need to adjust it 1171 // with respect to the heap max size as it's an upper bound (i.e., 1172 // we'll try to make the capacity smaller than it, not greater). 1173 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1174 1175 if (capacity_after_gc < minimum_desired_capacity) { 1176 // Don't expand unless it's significant 1177 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1178 1179 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1180 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1181 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1182 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio); 1183 1184 expand(expand_bytes, _workers); 1185 1186 // No expansion, now see if we want to shrink 1187 } else if (capacity_after_gc > maximum_desired_capacity) { 1188 // Capacity too large, compute shrinking size 1189 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1190 1191 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1192 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1193 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1194 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio); 1195 1196 shrink(shrink_bytes); 1197 } 1198 } 1199 1200 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1201 bool do_gc, 1202 bool clear_all_soft_refs, 1203 bool expect_null_mutator_alloc_region, 1204 bool* gc_succeeded) { 1205 *gc_succeeded = true; 1206 // Let's attempt the allocation first. 1207 HeapWord* result = 1208 attempt_allocation_at_safepoint(word_size, 1209 expect_null_mutator_alloc_region); 1210 if (result != NULL) { 1211 return result; 1212 } 1213 1214 // In a G1 heap, we're supposed to keep allocation from failing by 1215 // incremental pauses. Therefore, at least for now, we'll favor 1216 // expansion over collection. (This might change in the future if we can 1217 // do something smarter than full collection to satisfy a failed alloc.) 1218 result = expand_and_allocate(word_size); 1219 if (result != NULL) { 1220 return result; 1221 } 1222 1223 if (do_gc) { 1224 // Expansion didn't work, we'll try to do a Full GC. 1225 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1226 clear_all_soft_refs); 1227 } 1228 1229 return NULL; 1230 } 1231 1232 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1233 bool* succeeded) { 1234 assert_at_safepoint_on_vm_thread(); 1235 1236 // Attempts to allocate followed by Full GC. 1237 HeapWord* result = 1238 satisfy_failed_allocation_helper(word_size, 1239 true, /* do_gc */ 1240 false, /* clear_all_soft_refs */ 1241 false, /* expect_null_mutator_alloc_region */ 1242 succeeded); 1243 1244 if (result != NULL || !*succeeded) { 1245 return result; 1246 } 1247 1248 // Attempts to allocate followed by Full GC that will collect all soft references. 1249 result = satisfy_failed_allocation_helper(word_size, 1250 true, /* do_gc */ 1251 true, /* clear_all_soft_refs */ 1252 true, /* expect_null_mutator_alloc_region */ 1253 succeeded); 1254 1255 if (result != NULL || !*succeeded) { 1256 return result; 1257 } 1258 1259 // Attempts to allocate, no GC 1260 result = satisfy_failed_allocation_helper(word_size, 1261 false, /* do_gc */ 1262 false, /* clear_all_soft_refs */ 1263 true, /* expect_null_mutator_alloc_region */ 1264 succeeded); 1265 1266 if (result != NULL) { 1267 return result; 1268 } 1269 1270 assert(!soft_ref_policy()->should_clear_all_soft_refs(), 1271 "Flag should have been handled and cleared prior to this point"); 1272 1273 // What else? We might try synchronous finalization later. If the total 1274 // space available is large enough for the allocation, then a more 1275 // complete compaction phase than we've tried so far might be 1276 // appropriate. 1277 return NULL; 1278 } 1279 1280 // Attempting to expand the heap sufficiently 1281 // to support an allocation of the given "word_size". If 1282 // successful, perform the allocation and return the address of the 1283 // allocated block, or else "NULL". 1284 1285 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1286 assert_at_safepoint_on_vm_thread(); 1287 1288 _verifier->verify_region_sets_optional(); 1289 1290 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1291 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1292 word_size * HeapWordSize); 1293 1294 1295 if (expand(expand_bytes, _workers)) { 1296 _hrm.verify_optional(); 1297 _verifier->verify_region_sets_optional(); 1298 return attempt_allocation_at_safepoint(word_size, 1299 false /* expect_null_mutator_alloc_region */); 1300 } 1301 return NULL; 1302 } 1303 1304 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1305 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1306 aligned_expand_bytes = align_up(aligned_expand_bytes, 1307 HeapRegion::GrainBytes); 1308 1309 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1310 expand_bytes, aligned_expand_bytes); 1311 1312 if (is_maximal_no_gc()) { 1313 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1314 return false; 1315 } 1316 1317 double expand_heap_start_time_sec = os::elapsedTime(); 1318 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1319 assert(regions_to_expand > 0, "Must expand by at least one region"); 1320 1321 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers); 1322 if (expand_time_ms != NULL) { 1323 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1324 } 1325 1326 if (expanded_by > 0) { 1327 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1328 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1329 g1_policy()->record_new_heap_size(num_regions()); 1330 } else { 1331 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1332 1333 // The expansion of the virtual storage space was unsuccessful. 1334 // Let's see if it was because we ran out of swap. 1335 if (G1ExitOnExpansionFailure && 1336 _hrm.available() >= regions_to_expand) { 1337 // We had head room... 1338 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1339 } 1340 } 1341 return regions_to_expand > 0; 1342 } 1343 1344 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1345 size_t aligned_shrink_bytes = 1346 ReservedSpace::page_align_size_down(shrink_bytes); 1347 aligned_shrink_bytes = align_down(aligned_shrink_bytes, 1348 HeapRegion::GrainBytes); 1349 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1350 1351 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1352 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1353 1354 1355 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", 1356 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1357 if (num_regions_removed > 0) { 1358 g1_policy()->record_new_heap_size(num_regions()); 1359 } else { 1360 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1361 } 1362 } 1363 1364 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1365 _verifier->verify_region_sets_optional(); 1366 1367 // We should only reach here at the end of a Full GC which means we 1368 // should not not be holding to any GC alloc regions. The method 1369 // below will make sure of that and do any remaining clean up. 1370 _allocator->abandon_gc_alloc_regions(); 1371 1372 // Instead of tearing down / rebuilding the free lists here, we 1373 // could instead use the remove_all_pending() method on free_list to 1374 // remove only the ones that we need to remove. 1375 tear_down_region_sets(true /* free_list_only */); 1376 shrink_helper(shrink_bytes); 1377 rebuild_region_sets(true /* free_list_only */); 1378 1379 _hrm.verify_optional(); 1380 _verifier->verify_region_sets_optional(); 1381 } 1382 1383 // Public methods. 1384 1385 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1386 CollectedHeap(), 1387 _young_gen_sampling_thread(NULL), 1388 _collector_policy(collector_policy), 1389 _soft_ref_policy(), 1390 _card_table(NULL), 1391 _memory_manager("G1 Young Generation", "end of minor GC"), 1392 _full_gc_memory_manager("G1 Old Generation", "end of major GC"), 1393 _eden_pool(NULL), 1394 _survivor_pool(NULL), 1395 _old_pool(NULL), 1396 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1397 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1398 _g1_policy(new G1Policy(_gc_timer_stw)), 1399 _collection_set(this, _g1_policy), 1400 _dirty_card_queue_set(false), 1401 _is_alive_closure_cm(this), 1402 _is_alive_closure_stw(this), 1403 _ref_processor_cm(NULL), 1404 _ref_processor_stw(NULL), 1405 _bot(NULL), 1406 _hot_card_cache(NULL), 1407 _g1_rem_set(NULL), 1408 _cr(NULL), 1409 _g1mm(NULL), 1410 _preserved_marks_set(true /* in_c_heap */), 1411 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1412 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1413 _humongous_reclaim_candidates(), 1414 _has_humongous_reclaim_candidates(false), 1415 _archive_allocator(NULL), 1416 _summary_bytes_used(0), 1417 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1418 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1419 _expand_heap_after_alloc_failure(true), 1420 _old_marking_cycles_started(0), 1421 _old_marking_cycles_completed(0), 1422 _in_cset_fast_test() { 1423 1424 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1425 /* are_GC_task_threads */true, 1426 /* are_ConcurrentGC_threads */false); 1427 _workers->initialize_workers(); 1428 _verifier = new G1HeapVerifier(this); 1429 1430 _allocator = new G1Allocator(this); 1431 1432 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1433 1434 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1435 1436 // Override the default _filler_array_max_size so that no humongous filler 1437 // objects are created. 1438 _filler_array_max_size = _humongous_object_threshold_in_words; 1439 1440 uint n_queues = ParallelGCThreads; 1441 _task_queues = new RefToScanQueueSet(n_queues); 1442 1443 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1444 1445 for (uint i = 0; i < n_queues; i++) { 1446 RefToScanQueue* q = new RefToScanQueue(); 1447 q->initialize(); 1448 _task_queues->register_queue(i, q); 1449 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1450 } 1451 1452 // Initialize the G1EvacuationFailureALot counters and flags. 1453 NOT_PRODUCT(reset_evacuation_should_fail();) 1454 1455 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1456 } 1457 1458 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1459 size_t size, 1460 size_t translation_factor) { 1461 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1462 // Allocate a new reserved space, preferring to use large pages. 1463 ReservedSpace rs(size, preferred_page_size); 1464 G1RegionToSpaceMapper* result = 1465 G1RegionToSpaceMapper::create_mapper(rs, 1466 size, 1467 rs.alignment(), 1468 HeapRegion::GrainBytes, 1469 translation_factor, 1470 mtGC); 1471 1472 os::trace_page_sizes_for_requested_size(description, 1473 size, 1474 preferred_page_size, 1475 rs.alignment(), 1476 rs.base(), 1477 rs.size()); 1478 1479 return result; 1480 } 1481 1482 jint G1CollectedHeap::initialize_concurrent_refinement() { 1483 jint ecode = JNI_OK; 1484 _cr = G1ConcurrentRefine::create(&ecode); 1485 return ecode; 1486 } 1487 1488 jint G1CollectedHeap::initialize_young_gen_sampling_thread() { 1489 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread(); 1490 if (_young_gen_sampling_thread->osthread() == NULL) { 1491 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread"); 1492 return JNI_ENOMEM; 1493 } 1494 return JNI_OK; 1495 } 1496 1497 jint G1CollectedHeap::initialize() { 1498 os::enable_vtime(); 1499 1500 // Necessary to satisfy locking discipline assertions. 1501 1502 MutexLocker x(Heap_lock); 1503 1504 // While there are no constraints in the GC code that HeapWordSize 1505 // be any particular value, there are multiple other areas in the 1506 // system which believe this to be true (e.g. oop->object_size in some 1507 // cases incorrectly returns the size in wordSize units rather than 1508 // HeapWordSize). 1509 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1510 1511 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1512 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1513 size_t heap_alignment = collector_policy()->heap_alignment(); 1514 1515 // Ensure that the sizes are properly aligned. 1516 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1517 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1518 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1519 1520 // Reserve the maximum. 1521 1522 // When compressed oops are enabled, the preferred heap base 1523 // is calculated by subtracting the requested size from the 1524 // 32Gb boundary and using the result as the base address for 1525 // heap reservation. If the requested size is not aligned to 1526 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1527 // into the ReservedHeapSpace constructor) then the actual 1528 // base of the reserved heap may end up differing from the 1529 // address that was requested (i.e. the preferred heap base). 1530 // If this happens then we could end up using a non-optimal 1531 // compressed oops mode. 1532 1533 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1534 heap_alignment); 1535 1536 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1537 1538 // Create the barrier set for the entire reserved region. 1539 G1CardTable* ct = new G1CardTable(reserved_region()); 1540 ct->initialize(); 1541 G1BarrierSet* bs = new G1BarrierSet(ct); 1542 bs->initialize(); 1543 assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity"); 1544 BarrierSet::set_barrier_set(bs); 1545 _card_table = ct; 1546 1547 // Create the hot card cache. 1548 _hot_card_cache = new G1HotCardCache(this); 1549 1550 // Carve out the G1 part of the heap. 1551 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1552 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1553 G1RegionToSpaceMapper* heap_storage = 1554 G1RegionToSpaceMapper::create_mapper(g1_rs, 1555 g1_rs.size(), 1556 page_size, 1557 HeapRegion::GrainBytes, 1558 1, 1559 mtJavaHeap); 1560 os::trace_page_sizes("Heap", 1561 collector_policy()->min_heap_byte_size(), 1562 max_byte_size, 1563 page_size, 1564 heap_rs.base(), 1565 heap_rs.size()); 1566 heap_storage->set_mapping_changed_listener(&_listener); 1567 1568 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1569 G1RegionToSpaceMapper* bot_storage = 1570 create_aux_memory_mapper("Block Offset Table", 1571 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1572 G1BlockOffsetTable::heap_map_factor()); 1573 1574 G1RegionToSpaceMapper* cardtable_storage = 1575 create_aux_memory_mapper("Card Table", 1576 G1CardTable::compute_size(g1_rs.size() / HeapWordSize), 1577 G1CardTable::heap_map_factor()); 1578 1579 G1RegionToSpaceMapper* card_counts_storage = 1580 create_aux_memory_mapper("Card Counts Table", 1581 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1582 G1CardCounts::heap_map_factor()); 1583 1584 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1585 G1RegionToSpaceMapper* prev_bitmap_storage = 1586 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1587 G1RegionToSpaceMapper* next_bitmap_storage = 1588 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1589 1590 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1591 _card_table->initialize(cardtable_storage); 1592 // Do later initialization work for concurrent refinement. 1593 _hot_card_cache->initialize(card_counts_storage); 1594 1595 // 6843694 - ensure that the maximum region index can fit 1596 // in the remembered set structures. 1597 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1598 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1599 1600 // Also create a G1 rem set. 1601 _g1_rem_set = new G1RemSet(this, _card_table, _hot_card_cache); 1602 _g1_rem_set->initialize(max_capacity(), max_regions()); 1603 1604 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1605 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1606 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1607 "too many cards per region"); 1608 1609 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1610 1611 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1612 1613 { 1614 HeapWord* start = _hrm.reserved().start(); 1615 HeapWord* end = _hrm.reserved().end(); 1616 size_t granularity = HeapRegion::GrainBytes; 1617 1618 _in_cset_fast_test.initialize(start, end, granularity); 1619 _humongous_reclaim_candidates.initialize(start, end, granularity); 1620 } 1621 1622 // Create the G1ConcurrentMark data structure and thread. 1623 // (Must do this late, so that "max_regions" is defined.) 1624 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1625 if (_cm == NULL || !_cm->completed_initialization()) { 1626 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1627 return JNI_ENOMEM; 1628 } 1629 _cm_thread = _cm->cm_thread(); 1630 1631 // Now expand into the initial heap size. 1632 if (!expand(init_byte_size, _workers)) { 1633 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1634 return JNI_ENOMEM; 1635 } 1636 1637 // Perform any initialization actions delegated to the policy. 1638 g1_policy()->init(this, &_collection_set); 1639 1640 G1BarrierSet::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1641 SATB_Q_FL_lock, 1642 G1SATBProcessCompletedThreshold, 1643 Shared_SATB_Q_lock); 1644 1645 jint ecode = initialize_concurrent_refinement(); 1646 if (ecode != JNI_OK) { 1647 return ecode; 1648 } 1649 1650 ecode = initialize_young_gen_sampling_thread(); 1651 if (ecode != JNI_OK) { 1652 return ecode; 1653 } 1654 1655 G1BarrierSet::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1656 DirtyCardQ_FL_lock, 1657 (int)concurrent_refine()->yellow_zone(), 1658 (int)concurrent_refine()->red_zone(), 1659 Shared_DirtyCardQ_lock, 1660 NULL, // fl_owner 1661 true); // init_free_ids 1662 1663 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1664 DirtyCardQ_FL_lock, 1665 -1, // never trigger processing 1666 -1, // no limit on length 1667 Shared_DirtyCardQ_lock, 1668 &G1BarrierSet::dirty_card_queue_set()); 1669 1670 // Here we allocate the dummy HeapRegion that is required by the 1671 // G1AllocRegion class. 1672 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1673 1674 // We'll re-use the same region whether the alloc region will 1675 // require BOT updates or not and, if it doesn't, then a non-young 1676 // region will complain that it cannot support allocations without 1677 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1678 dummy_region->set_eden(); 1679 // Make sure it's full. 1680 dummy_region->set_top(dummy_region->end()); 1681 G1AllocRegion::setup(this, dummy_region); 1682 1683 _allocator->init_mutator_alloc_region(); 1684 1685 // Do create of the monitoring and management support so that 1686 // values in the heap have been properly initialized. 1687 _g1mm = new G1MonitoringSupport(this); 1688 1689 G1StringDedup::initialize(); 1690 1691 _preserved_marks_set.init(ParallelGCThreads); 1692 1693 _collection_set.initialize(max_regions()); 1694 1695 return JNI_OK; 1696 } 1697 1698 void G1CollectedHeap::initialize_serviceability() { 1699 _eden_pool = new G1EdenPool(this); 1700 _survivor_pool = new G1SurvivorPool(this); 1701 _old_pool = new G1OldGenPool(this); 1702 1703 _full_gc_memory_manager.add_pool(_eden_pool); 1704 _full_gc_memory_manager.add_pool(_survivor_pool); 1705 _full_gc_memory_manager.add_pool(_old_pool); 1706 1707 _memory_manager.add_pool(_eden_pool); 1708 _memory_manager.add_pool(_survivor_pool); 1709 1710 } 1711 1712 void G1CollectedHeap::stop() { 1713 // Stop all concurrent threads. We do this to make sure these threads 1714 // do not continue to execute and access resources (e.g. logging) 1715 // that are destroyed during shutdown. 1716 _cr->stop(); 1717 _young_gen_sampling_thread->stop(); 1718 _cm_thread->stop(); 1719 if (G1StringDedup::is_enabled()) { 1720 G1StringDedup::stop(); 1721 } 1722 } 1723 1724 void G1CollectedHeap::safepoint_synchronize_begin() { 1725 SuspendibleThreadSet::synchronize(); 1726 } 1727 1728 void G1CollectedHeap::safepoint_synchronize_end() { 1729 SuspendibleThreadSet::desynchronize(); 1730 } 1731 1732 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1733 return HeapRegion::max_region_size(); 1734 } 1735 1736 void G1CollectedHeap::post_initialize() { 1737 CollectedHeap::post_initialize(); 1738 ref_processing_init(); 1739 } 1740 1741 void G1CollectedHeap::ref_processing_init() { 1742 // Reference processing in G1 currently works as follows: 1743 // 1744 // * There are two reference processor instances. One is 1745 // used to record and process discovered references 1746 // during concurrent marking; the other is used to 1747 // record and process references during STW pauses 1748 // (both full and incremental). 1749 // * Both ref processors need to 'span' the entire heap as 1750 // the regions in the collection set may be dotted around. 1751 // 1752 // * For the concurrent marking ref processor: 1753 // * Reference discovery is enabled at initial marking. 1754 // * Reference discovery is disabled and the discovered 1755 // references processed etc during remarking. 1756 // * Reference discovery is MT (see below). 1757 // * Reference discovery requires a barrier (see below). 1758 // * Reference processing may or may not be MT 1759 // (depending on the value of ParallelRefProcEnabled 1760 // and ParallelGCThreads). 1761 // * A full GC disables reference discovery by the CM 1762 // ref processor and abandons any entries on it's 1763 // discovered lists. 1764 // 1765 // * For the STW processor: 1766 // * Non MT discovery is enabled at the start of a full GC. 1767 // * Processing and enqueueing during a full GC is non-MT. 1768 // * During a full GC, references are processed after marking. 1769 // 1770 // * Discovery (may or may not be MT) is enabled at the start 1771 // of an incremental evacuation pause. 1772 // * References are processed near the end of a STW evacuation pause. 1773 // * For both types of GC: 1774 // * Discovery is atomic - i.e. not concurrent. 1775 // * Reference discovery will not need a barrier. 1776 1777 MemRegion mr = reserved_region(); 1778 1779 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1); 1780 1781 // Concurrent Mark ref processor 1782 _ref_processor_cm = 1783 new ReferenceProcessor(mr, // span 1784 mt_processing, 1785 // mt processing 1786 ParallelGCThreads, 1787 // degree of mt processing 1788 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 1789 // mt discovery 1790 MAX2(ParallelGCThreads, ConcGCThreads), 1791 // degree of mt discovery 1792 false, 1793 // Reference discovery is not atomic 1794 &_is_alive_closure_cm); 1795 // is alive closure 1796 // (for efficiency/performance) 1797 1798 // STW ref processor 1799 _ref_processor_stw = 1800 new ReferenceProcessor(mr, // span 1801 mt_processing, 1802 // mt processing 1803 ParallelGCThreads, 1804 // degree of mt processing 1805 (ParallelGCThreads > 1), 1806 // mt discovery 1807 ParallelGCThreads, 1808 // degree of mt discovery 1809 true, 1810 // Reference discovery is atomic 1811 &_is_alive_closure_stw); 1812 // is alive closure 1813 // (for efficiency/performance) 1814 } 1815 1816 CollectorPolicy* G1CollectedHeap::collector_policy() const { 1817 return _collector_policy; 1818 } 1819 1820 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() { 1821 return &_soft_ref_policy; 1822 } 1823 1824 size_t G1CollectedHeap::capacity() const { 1825 return _hrm.length() * HeapRegion::GrainBytes; 1826 } 1827 1828 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const { 1829 return _hrm.total_free_bytes(); 1830 } 1831 1832 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 1833 _hot_card_cache->drain(cl, worker_i); 1834 } 1835 1836 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 1837 DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 1838 size_t n_completed_buffers = 0; 1839 while (dcqs.apply_closure_during_gc(cl, worker_i)) { 1840 n_completed_buffers++; 1841 } 1842 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers, G1GCPhaseTimes::UpdateRSProcessedBuffers); 1843 dcqs.clear_n_completed_buffers(); 1844 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 1845 } 1846 1847 // Computes the sum of the storage used by the various regions. 1848 size_t G1CollectedHeap::used() const { 1849 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 1850 if (_archive_allocator != NULL) { 1851 result += _archive_allocator->used(); 1852 } 1853 return result; 1854 } 1855 1856 size_t G1CollectedHeap::used_unlocked() const { 1857 return _summary_bytes_used; 1858 } 1859 1860 class SumUsedClosure: public HeapRegionClosure { 1861 size_t _used; 1862 public: 1863 SumUsedClosure() : _used(0) {} 1864 bool do_heap_region(HeapRegion* r) { 1865 _used += r->used(); 1866 return false; 1867 } 1868 size_t result() { return _used; } 1869 }; 1870 1871 size_t G1CollectedHeap::recalculate_used() const { 1872 double recalculate_used_start = os::elapsedTime(); 1873 1874 SumUsedClosure blk; 1875 heap_region_iterate(&blk); 1876 1877 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 1878 return blk.result(); 1879 } 1880 1881 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 1882 switch (cause) { 1883 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 1884 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 1885 case GCCause::_wb_conc_mark: return true; 1886 default : return false; 1887 } 1888 } 1889 1890 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 1891 switch (cause) { 1892 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 1893 case GCCause::_g1_humongous_allocation: return true; 1894 default: return is_user_requested_concurrent_full_gc(cause); 1895 } 1896 } 1897 1898 #ifndef PRODUCT 1899 void G1CollectedHeap::allocate_dummy_regions() { 1900 // Let's fill up most of the region 1901 size_t word_size = HeapRegion::GrainWords - 1024; 1902 // And as a result the region we'll allocate will be humongous. 1903 guarantee(is_humongous(word_size), "sanity"); 1904 1905 // _filler_array_max_size is set to humongous object threshold 1906 // but temporarily change it to use CollectedHeap::fill_with_object(). 1907 SizeTFlagSetting fs(_filler_array_max_size, word_size); 1908 1909 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 1910 // Let's use the existing mechanism for the allocation 1911 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 1912 if (dummy_obj != NULL) { 1913 MemRegion mr(dummy_obj, word_size); 1914 CollectedHeap::fill_with_object(mr); 1915 } else { 1916 // If we can't allocate once, we probably cannot allocate 1917 // again. Let's get out of the loop. 1918 break; 1919 } 1920 } 1921 } 1922 #endif // !PRODUCT 1923 1924 void G1CollectedHeap::increment_old_marking_cycles_started() { 1925 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 1926 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 1927 "Wrong marking cycle count (started: %d, completed: %d)", 1928 _old_marking_cycles_started, _old_marking_cycles_completed); 1929 1930 _old_marking_cycles_started++; 1931 } 1932 1933 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 1934 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 1935 1936 // We assume that if concurrent == true, then the caller is a 1937 // concurrent thread that was joined the Suspendible Thread 1938 // Set. If there's ever a cheap way to check this, we should add an 1939 // assert here. 1940 1941 // Given that this method is called at the end of a Full GC or of a 1942 // concurrent cycle, and those can be nested (i.e., a Full GC can 1943 // interrupt a concurrent cycle), the number of full collections 1944 // completed should be either one (in the case where there was no 1945 // nesting) or two (when a Full GC interrupted a concurrent cycle) 1946 // behind the number of full collections started. 1947 1948 // This is the case for the inner caller, i.e. a Full GC. 1949 assert(concurrent || 1950 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 1951 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 1952 "for inner caller (Full GC): _old_marking_cycles_started = %u " 1953 "is inconsistent with _old_marking_cycles_completed = %u", 1954 _old_marking_cycles_started, _old_marking_cycles_completed); 1955 1956 // This is the case for the outer caller, i.e. the concurrent cycle. 1957 assert(!concurrent || 1958 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 1959 "for outer caller (concurrent cycle): " 1960 "_old_marking_cycles_started = %u " 1961 "is inconsistent with _old_marking_cycles_completed = %u", 1962 _old_marking_cycles_started, _old_marking_cycles_completed); 1963 1964 _old_marking_cycles_completed += 1; 1965 1966 // We need to clear the "in_progress" flag in the CM thread before 1967 // we wake up any waiters (especially when ExplicitInvokesConcurrent 1968 // is set) so that if a waiter requests another System.gc() it doesn't 1969 // incorrectly see that a marking cycle is still in progress. 1970 if (concurrent) { 1971 _cm_thread->set_idle(); 1972 } 1973 1974 // This notify_all() will ensure that a thread that called 1975 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 1976 // and it's waiting for a full GC to finish will be woken up. It is 1977 // waiting in VM_G1CollectForAllocation::doit_epilogue(). 1978 FullGCCount_lock->notify_all(); 1979 } 1980 1981 void G1CollectedHeap::collect(GCCause::Cause cause) { 1982 assert_heap_not_locked(); 1983 1984 uint gc_count_before; 1985 uint old_marking_count_before; 1986 uint full_gc_count_before; 1987 bool retry_gc; 1988 1989 do { 1990 retry_gc = false; 1991 1992 { 1993 MutexLocker ml(Heap_lock); 1994 1995 // Read the GC count while holding the Heap_lock 1996 gc_count_before = total_collections(); 1997 full_gc_count_before = total_full_collections(); 1998 old_marking_count_before = _old_marking_cycles_started; 1999 } 2000 2001 if (should_do_concurrent_full_gc(cause)) { 2002 // Schedule an initial-mark evacuation pause that will start a 2003 // concurrent cycle. We're setting word_size to 0 which means that 2004 // we are not requesting a post-GC allocation. 2005 VM_G1CollectForAllocation op(0, /* word_size */ 2006 gc_count_before, 2007 cause, 2008 true, /* should_initiate_conc_mark */ 2009 g1_policy()->max_pause_time_ms()); 2010 VMThread::execute(&op); 2011 if (!op.pause_succeeded()) { 2012 if (old_marking_count_before == _old_marking_cycles_started) { 2013 retry_gc = op.should_retry_gc(); 2014 } else { 2015 // A Full GC happened while we were trying to schedule the 2016 // initial-mark GC. No point in starting a new cycle given 2017 // that the whole heap was collected anyway. 2018 } 2019 2020 if (retry_gc) { 2021 if (GCLocker::is_active_and_needs_gc()) { 2022 GCLocker::stall_until_clear(); 2023 } 2024 } 2025 } 2026 } else { 2027 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2028 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2029 2030 // Schedule a standard evacuation pause. We're setting word_size 2031 // to 0 which means that we are not requesting a post-GC allocation. 2032 VM_G1CollectForAllocation op(0, /* word_size */ 2033 gc_count_before, 2034 cause, 2035 false, /* should_initiate_conc_mark */ 2036 g1_policy()->max_pause_time_ms()); 2037 VMThread::execute(&op); 2038 } else { 2039 // Schedule a Full GC. 2040 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2041 VMThread::execute(&op); 2042 } 2043 } 2044 } while (retry_gc); 2045 } 2046 2047 bool G1CollectedHeap::is_in(const void* p) const { 2048 if (_hrm.reserved().contains(p)) { 2049 // Given that we know that p is in the reserved space, 2050 // heap_region_containing() should successfully 2051 // return the containing region. 2052 HeapRegion* hr = heap_region_containing(p); 2053 return hr->is_in(p); 2054 } else { 2055 return false; 2056 } 2057 } 2058 2059 #ifdef ASSERT 2060 bool G1CollectedHeap::is_in_exact(const void* p) const { 2061 bool contains = reserved_region().contains(p); 2062 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2063 if (contains && available) { 2064 return true; 2065 } else { 2066 return false; 2067 } 2068 } 2069 #endif 2070 2071 // Iteration functions. 2072 2073 // Iterates an ObjectClosure over all objects within a HeapRegion. 2074 2075 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2076 ObjectClosure* _cl; 2077 public: 2078 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2079 bool do_heap_region(HeapRegion* r) { 2080 if (!r->is_continues_humongous()) { 2081 r->object_iterate(_cl); 2082 } 2083 return false; 2084 } 2085 }; 2086 2087 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2088 IterateObjectClosureRegionClosure blk(cl); 2089 heap_region_iterate(&blk); 2090 } 2091 2092 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2093 _hrm.iterate(cl); 2094 } 2095 2096 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl, 2097 HeapRegionClaimer *hrclaimer, 2098 uint worker_id) const { 2099 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id)); 2100 } 2101 2102 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl, 2103 HeapRegionClaimer *hrclaimer) const { 2104 _hrm.par_iterate(cl, hrclaimer, 0); 2105 } 2106 2107 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2108 _collection_set.iterate(cl); 2109 } 2110 2111 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2112 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2113 } 2114 2115 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2116 HeapRegion* hr = heap_region_containing(addr); 2117 return hr->block_start(addr); 2118 } 2119 2120 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2121 HeapRegion* hr = heap_region_containing(addr); 2122 return hr->block_size(addr); 2123 } 2124 2125 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2126 HeapRegion* hr = heap_region_containing(addr); 2127 return hr->block_is_obj(addr); 2128 } 2129 2130 bool G1CollectedHeap::supports_tlab_allocation() const { 2131 return true; 2132 } 2133 2134 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2135 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2136 } 2137 2138 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2139 return _eden.length() * HeapRegion::GrainBytes; 2140 } 2141 2142 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2143 // must be equal to the humongous object limit. 2144 size_t G1CollectedHeap::max_tlab_size() const { 2145 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2146 } 2147 2148 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2149 return _allocator->unsafe_max_tlab_alloc(); 2150 } 2151 2152 size_t G1CollectedHeap::max_capacity() const { 2153 return _hrm.reserved().byte_size(); 2154 } 2155 2156 jlong G1CollectedHeap::millis_since_last_gc() { 2157 // See the notes in GenCollectedHeap::millis_since_last_gc() 2158 // for more information about the implementation. 2159 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2160 _g1_policy->collection_pause_end_millis(); 2161 if (ret_val < 0) { 2162 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2163 ". returning zero instead.", ret_val); 2164 return 0; 2165 } 2166 return ret_val; 2167 } 2168 2169 void G1CollectedHeap::prepare_for_verify() { 2170 _verifier->prepare_for_verify(); 2171 } 2172 2173 void G1CollectedHeap::verify(VerifyOption vo) { 2174 _verifier->verify(vo); 2175 } 2176 2177 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2178 return true; 2179 } 2180 2181 const char* const* G1CollectedHeap::concurrent_phases() const { 2182 return _cm_thread->concurrent_phases(); 2183 } 2184 2185 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2186 return _cm_thread->request_concurrent_phase(phase); 2187 } 2188 2189 class PrintRegionClosure: public HeapRegionClosure { 2190 outputStream* _st; 2191 public: 2192 PrintRegionClosure(outputStream* st) : _st(st) {} 2193 bool do_heap_region(HeapRegion* r) { 2194 r->print_on(_st); 2195 return false; 2196 } 2197 }; 2198 2199 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2200 const HeapRegion* hr, 2201 const VerifyOption vo) const { 2202 switch (vo) { 2203 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2204 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2205 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr); 2206 default: ShouldNotReachHere(); 2207 } 2208 return false; // keep some compilers happy 2209 } 2210 2211 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2212 const VerifyOption vo) const { 2213 switch (vo) { 2214 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2215 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2216 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj); 2217 default: ShouldNotReachHere(); 2218 } 2219 return false; // keep some compilers happy 2220 } 2221 2222 void G1CollectedHeap::print_heap_regions() const { 2223 LogTarget(Trace, gc, heap, region) lt; 2224 if (lt.is_enabled()) { 2225 LogStream ls(lt); 2226 print_regions_on(&ls); 2227 } 2228 } 2229 2230 void G1CollectedHeap::print_on(outputStream* st) const { 2231 st->print(" %-20s", "garbage-first heap"); 2232 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2233 capacity()/K, used_unlocked()/K); 2234 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")", 2235 p2i(_hrm.reserved().start()), 2236 p2i(_hrm.reserved().end())); 2237 st->cr(); 2238 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2239 uint young_regions = young_regions_count(); 2240 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2241 (size_t) young_regions * HeapRegion::GrainBytes / K); 2242 uint survivor_regions = survivor_regions_count(); 2243 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2244 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2245 st->cr(); 2246 MetaspaceUtils::print_on(st); 2247 } 2248 2249 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2250 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2251 "HS=humongous(starts), HC=humongous(continues), " 2252 "CS=collection set, F=free, A=archive, " 2253 "TAMS=top-at-mark-start (previous, next)"); 2254 PrintRegionClosure blk(st); 2255 heap_region_iterate(&blk); 2256 } 2257 2258 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2259 print_on(st); 2260 2261 // Print the per-region information. 2262 print_regions_on(st); 2263 } 2264 2265 void G1CollectedHeap::print_on_error(outputStream* st) const { 2266 this->CollectedHeap::print_on_error(st); 2267 2268 if (_cm != NULL) { 2269 st->cr(); 2270 _cm->print_on_error(st); 2271 } 2272 } 2273 2274 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2275 workers()->print_worker_threads_on(st); 2276 _cm_thread->print_on(st); 2277 st->cr(); 2278 _cm->print_worker_threads_on(st); 2279 _cr->print_threads_on(st); 2280 _young_gen_sampling_thread->print_on(st); 2281 if (G1StringDedup::is_enabled()) { 2282 G1StringDedup::print_worker_threads_on(st); 2283 } 2284 } 2285 2286 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2287 workers()->threads_do(tc); 2288 tc->do_thread(_cm_thread); 2289 _cm->threads_do(tc); 2290 _cr->threads_do(tc); 2291 tc->do_thread(_young_gen_sampling_thread); 2292 if (G1StringDedup::is_enabled()) { 2293 G1StringDedup::threads_do(tc); 2294 } 2295 } 2296 2297 void G1CollectedHeap::print_tracing_info() const { 2298 g1_rem_set()->print_summary_info(); 2299 concurrent_mark()->print_summary_info(); 2300 } 2301 2302 #ifndef PRODUCT 2303 // Helpful for debugging RSet issues. 2304 2305 class PrintRSetsClosure : public HeapRegionClosure { 2306 private: 2307 const char* _msg; 2308 size_t _occupied_sum; 2309 2310 public: 2311 bool do_heap_region(HeapRegion* r) { 2312 HeapRegionRemSet* hrrs = r->rem_set(); 2313 size_t occupied = hrrs->occupied(); 2314 _occupied_sum += occupied; 2315 2316 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2317 if (occupied == 0) { 2318 tty->print_cr(" RSet is empty"); 2319 } else { 2320 hrrs->print(); 2321 } 2322 tty->print_cr("----------"); 2323 return false; 2324 } 2325 2326 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2327 tty->cr(); 2328 tty->print_cr("========================================"); 2329 tty->print_cr("%s", msg); 2330 tty->cr(); 2331 } 2332 2333 ~PrintRSetsClosure() { 2334 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2335 tty->print_cr("========================================"); 2336 tty->cr(); 2337 } 2338 }; 2339 2340 void G1CollectedHeap::print_cset_rsets() { 2341 PrintRSetsClosure cl("Printing CSet RSets"); 2342 collection_set_iterate(&cl); 2343 } 2344 2345 void G1CollectedHeap::print_all_rsets() { 2346 PrintRSetsClosure cl("Printing All RSets");; 2347 heap_region_iterate(&cl); 2348 } 2349 #endif // PRODUCT 2350 2351 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2352 2353 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2354 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2355 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2356 2357 size_t eden_capacity_bytes = 2358 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2359 2360 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2361 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2362 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2363 } 2364 2365 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2366 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2367 stats->unused(), stats->used(), stats->region_end_waste(), 2368 stats->regions_filled(), stats->direct_allocated(), 2369 stats->failure_used(), stats->failure_waste()); 2370 } 2371 2372 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2373 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2374 gc_tracer->report_gc_heap_summary(when, heap_summary); 2375 2376 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2377 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2378 } 2379 2380 G1CollectedHeap* G1CollectedHeap::heap() { 2381 CollectedHeap* heap = Universe::heap(); 2382 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2383 assert(heap->kind() == CollectedHeap::G1, "Invalid name"); 2384 return (G1CollectedHeap*)heap; 2385 } 2386 2387 void G1CollectedHeap::gc_prologue(bool full) { 2388 // always_do_update_barrier = false; 2389 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2390 2391 // This summary needs to be printed before incrementing total collections. 2392 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2393 2394 // Update common counters. 2395 increment_total_collections(full /* full gc */); 2396 if (full) { 2397 increment_old_marking_cycles_started(); 2398 } 2399 2400 // Fill TLAB's and such 2401 double start = os::elapsedTime(); 2402 accumulate_statistics_all_tlabs(); 2403 ensure_parsability(true); 2404 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2405 } 2406 2407 void G1CollectedHeap::gc_epilogue(bool full) { 2408 // Update common counters. 2409 if (full) { 2410 // Update the number of full collections that have been completed. 2411 increment_old_marking_cycles_completed(false /* concurrent */); 2412 } 2413 2414 // We are at the end of the GC. Total collections has already been increased. 2415 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2416 2417 // FIXME: what is this about? 2418 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2419 // is set. 2420 #if COMPILER2_OR_JVMCI 2421 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2422 #endif 2423 // always_do_update_barrier = true; 2424 2425 double start = os::elapsedTime(); 2426 resize_all_tlabs(); 2427 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2428 2429 MemoryService::track_memory_usage(); 2430 // We have just completed a GC. Update the soft reference 2431 // policy with the new heap occupancy 2432 Universe::update_heap_info_at_gc(); 2433 } 2434 2435 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2436 uint gc_count_before, 2437 bool* succeeded, 2438 GCCause::Cause gc_cause) { 2439 assert_heap_not_locked_and_not_at_safepoint(); 2440 VM_G1CollectForAllocation op(word_size, 2441 gc_count_before, 2442 gc_cause, 2443 false, /* should_initiate_conc_mark */ 2444 g1_policy()->max_pause_time_ms()); 2445 VMThread::execute(&op); 2446 2447 HeapWord* result = op.result(); 2448 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2449 assert(result == NULL || ret_succeeded, 2450 "the result should be NULL if the VM did not succeed"); 2451 *succeeded = ret_succeeded; 2452 2453 assert_heap_not_locked(); 2454 return result; 2455 } 2456 2457 void G1CollectedHeap::do_concurrent_mark() { 2458 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2459 if (!_cm_thread->in_progress()) { 2460 _cm_thread->set_started(); 2461 CGC_lock->notify(); 2462 } 2463 } 2464 2465 size_t G1CollectedHeap::pending_card_num() { 2466 size_t extra_cards = 0; 2467 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) { 2468 DirtyCardQueue& dcq = G1ThreadLocalData::dirty_card_queue(curr); 2469 extra_cards += dcq.size(); 2470 } 2471 DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 2472 size_t buffer_size = dcqs.buffer_size(); 2473 size_t buffer_num = dcqs.completed_buffers_num(); 2474 2475 return buffer_size * buffer_num + extra_cards; 2476 } 2477 2478 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const { 2479 // We don't nominate objects with many remembered set entries, on 2480 // the assumption that such objects are likely still live. 2481 HeapRegionRemSet* rem_set = r->rem_set(); 2482 2483 return G1EagerReclaimHumongousObjectsWithStaleRefs ? 2484 rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) : 2485 G1EagerReclaimHumongousObjects && rem_set->is_empty(); 2486 } 2487 2488 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2489 private: 2490 size_t _total_humongous; 2491 size_t _candidate_humongous; 2492 2493 DirtyCardQueue _dcq; 2494 2495 bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const { 2496 assert(region->is_starts_humongous(), "Must start a humongous object"); 2497 2498 oop obj = oop(region->bottom()); 2499 2500 // Dead objects cannot be eager reclaim candidates. Due to class 2501 // unloading it is unsafe to query their classes so we return early. 2502 if (g1h->is_obj_dead(obj, region)) { 2503 return false; 2504 } 2505 2506 // If we do not have a complete remembered set for the region, then we can 2507 // not be sure that we have all references to it. 2508 if (!region->rem_set()->is_complete()) { 2509 return false; 2510 } 2511 // Candidate selection must satisfy the following constraints 2512 // while concurrent marking is in progress: 2513 // 2514 // * In order to maintain SATB invariants, an object must not be 2515 // reclaimed if it was allocated before the start of marking and 2516 // has not had its references scanned. Such an object must have 2517 // its references (including type metadata) scanned to ensure no 2518 // live objects are missed by the marking process. Objects 2519 // allocated after the start of concurrent marking don't need to 2520 // be scanned. 2521 // 2522 // * An object must not be reclaimed if it is on the concurrent 2523 // mark stack. Objects allocated after the start of concurrent 2524 // marking are never pushed on the mark stack. 2525 // 2526 // Nominating only objects allocated after the start of concurrent 2527 // marking is sufficient to meet both constraints. This may miss 2528 // some objects that satisfy the constraints, but the marking data 2529 // structures don't support efficiently performing the needed 2530 // additional tests or scrubbing of the mark stack. 2531 // 2532 // However, we presently only nominate is_typeArray() objects. 2533 // A humongous object containing references induces remembered 2534 // set entries on other regions. In order to reclaim such an 2535 // object, those remembered sets would need to be cleaned up. 2536 // 2537 // We also treat is_typeArray() objects specially, allowing them 2538 // to be reclaimed even if allocated before the start of 2539 // concurrent mark. For this we rely on mark stack insertion to 2540 // exclude is_typeArray() objects, preventing reclaiming an object 2541 // that is in the mark stack. We also rely on the metadata for 2542 // such objects to be built-in and so ensured to be kept live. 2543 // Frequent allocation and drop of large binary blobs is an 2544 // important use case for eager reclaim, and this special handling 2545 // may reduce needed headroom. 2546 2547 return obj->is_typeArray() && 2548 g1h->is_potential_eager_reclaim_candidate(region); 2549 } 2550 2551 public: 2552 RegisterHumongousWithInCSetFastTestClosure() 2553 : _total_humongous(0), 2554 _candidate_humongous(0), 2555 _dcq(&G1BarrierSet::dirty_card_queue_set()) { 2556 } 2557 2558 virtual bool do_heap_region(HeapRegion* r) { 2559 if (!r->is_starts_humongous()) { 2560 return false; 2561 } 2562 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2563 2564 bool is_candidate = humongous_region_is_candidate(g1h, r); 2565 uint rindex = r->hrm_index(); 2566 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2567 if (is_candidate) { 2568 _candidate_humongous++; 2569 g1h->register_humongous_region_with_cset(rindex); 2570 // Is_candidate already filters out humongous object with large remembered sets. 2571 // If we have a humongous object with a few remembered sets, we simply flush these 2572 // remembered set entries into the DCQS. That will result in automatic 2573 // re-evaluation of their remembered set entries during the following evacuation 2574 // phase. 2575 if (!r->rem_set()->is_empty()) { 2576 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2577 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2578 G1CardTable* ct = g1h->card_table(); 2579 HeapRegionRemSetIterator hrrs(r->rem_set()); 2580 size_t card_index; 2581 while (hrrs.has_next(card_index)) { 2582 jbyte* card_ptr = (jbyte*)ct->byte_for_index(card_index); 2583 // The remembered set might contain references to already freed 2584 // regions. Filter out such entries to avoid failing card table 2585 // verification. 2586 if (g1h->is_in_closed_subset(ct->addr_for(card_ptr))) { 2587 if (*card_ptr != G1CardTable::dirty_card_val()) { 2588 *card_ptr = G1CardTable::dirty_card_val(); 2589 _dcq.enqueue(card_ptr); 2590 } 2591 } 2592 } 2593 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2594 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2595 hrrs.n_yielded(), r->rem_set()->occupied()); 2596 // We should only clear the card based remembered set here as we will not 2597 // implicitly rebuild anything else during eager reclaim. Note that at the moment 2598 // (and probably never) we do not enter this path if there are other kind of 2599 // remembered sets for this region. 2600 r->rem_set()->clear_locked(true /* only_cardset */); 2601 // Clear_locked() above sets the state to Empty. However we want to continue 2602 // collecting remembered set entries for humongous regions that were not 2603 // reclaimed. 2604 r->rem_set()->set_state_complete(); 2605 } 2606 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2607 } 2608 _total_humongous++; 2609 2610 return false; 2611 } 2612 2613 size_t total_humongous() const { return _total_humongous; } 2614 size_t candidate_humongous() const { return _candidate_humongous; } 2615 2616 void flush_rem_set_entries() { _dcq.flush(); } 2617 }; 2618 2619 void G1CollectedHeap::register_humongous_regions_with_cset() { 2620 if (!G1EagerReclaimHumongousObjects) { 2621 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2622 return; 2623 } 2624 double time = os::elapsed_counter(); 2625 2626 // Collect reclaim candidate information and register candidates with cset. 2627 RegisterHumongousWithInCSetFastTestClosure cl; 2628 heap_region_iterate(&cl); 2629 2630 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2631 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2632 cl.total_humongous(), 2633 cl.candidate_humongous()); 2634 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2635 2636 // Finally flush all remembered set entries to re-check into the global DCQS. 2637 cl.flush_rem_set_entries(); 2638 } 2639 2640 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2641 public: 2642 bool do_heap_region(HeapRegion* hr) { 2643 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2644 hr->verify_rem_set(); 2645 } 2646 return false; 2647 } 2648 }; 2649 2650 uint G1CollectedHeap::num_task_queues() const { 2651 return _task_queues->size(); 2652 } 2653 2654 #if TASKQUEUE_STATS 2655 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2656 st->print_raw_cr("GC Task Stats"); 2657 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2658 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2659 } 2660 2661 void G1CollectedHeap::print_taskqueue_stats() const { 2662 if (!log_is_enabled(Trace, gc, task, stats)) { 2663 return; 2664 } 2665 Log(gc, task, stats) log; 2666 ResourceMark rm; 2667 LogStream ls(log.trace()); 2668 outputStream* st = &ls; 2669 2670 print_taskqueue_stats_hdr(st); 2671 2672 TaskQueueStats totals; 2673 const uint n = num_task_queues(); 2674 for (uint i = 0; i < n; ++i) { 2675 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2676 totals += task_queue(i)->stats; 2677 } 2678 st->print_raw("tot "); totals.print(st); st->cr(); 2679 2680 DEBUG_ONLY(totals.verify()); 2681 } 2682 2683 void G1CollectedHeap::reset_taskqueue_stats() { 2684 const uint n = num_task_queues(); 2685 for (uint i = 0; i < n; ++i) { 2686 task_queue(i)->stats.reset(); 2687 } 2688 } 2689 #endif // TASKQUEUE_STATS 2690 2691 void G1CollectedHeap::wait_for_root_region_scanning() { 2692 double scan_wait_start = os::elapsedTime(); 2693 // We have to wait until the CM threads finish scanning the 2694 // root regions as it's the only way to ensure that all the 2695 // objects on them have been correctly scanned before we start 2696 // moving them during the GC. 2697 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2698 double wait_time_ms = 0.0; 2699 if (waited) { 2700 double scan_wait_end = os::elapsedTime(); 2701 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2702 } 2703 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2704 } 2705 2706 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2707 private: 2708 G1HRPrinter* _hr_printer; 2709 public: 2710 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2711 2712 virtual bool do_heap_region(HeapRegion* r) { 2713 _hr_printer->cset(r); 2714 return false; 2715 } 2716 }; 2717 2718 void G1CollectedHeap::start_new_collection_set() { 2719 collection_set()->start_incremental_building(); 2720 2721 clear_cset_fast_test(); 2722 2723 guarantee(_eden.length() == 0, "eden should have been cleared"); 2724 g1_policy()->transfer_survivors_to_cset(survivor()); 2725 } 2726 2727 bool 2728 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2729 assert_at_safepoint_on_vm_thread(); 2730 guarantee(!is_gc_active(), "collection is not reentrant"); 2731 2732 if (GCLocker::check_active_before_gc()) { 2733 return false; 2734 } 2735 2736 _gc_timer_stw->register_gc_start(); 2737 2738 GCIdMark gc_id_mark; 2739 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2740 2741 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2742 ResourceMark rm; 2743 2744 g1_policy()->note_gc_start(); 2745 2746 wait_for_root_region_scanning(); 2747 2748 print_heap_before_gc(); 2749 print_heap_regions(); 2750 trace_heap_before_gc(_gc_tracer_stw); 2751 2752 _verifier->verify_region_sets_optional(); 2753 _verifier->verify_dirty_young_regions(); 2754 2755 // We should not be doing initial mark unless the conc mark thread is running 2756 if (!_cm_thread->should_terminate()) { 2757 // This call will decide whether this pause is an initial-mark 2758 // pause. If it is, in_initial_mark_gc() will return true 2759 // for the duration of this pause. 2760 g1_policy()->decide_on_conc_mark_initiation(); 2761 } 2762 2763 // We do not allow initial-mark to be piggy-backed on a mixed GC. 2764 assert(!collector_state()->in_initial_mark_gc() || 2765 collector_state()->in_young_only_phase(), "sanity"); 2766 2767 // We also do not allow mixed GCs during marking. 2768 assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity"); 2769 2770 // Record whether this pause is an initial mark. When the current 2771 // thread has completed its logging output and it's safe to signal 2772 // the CM thread, the flag's value in the policy has been reset. 2773 bool should_start_conc_mark = collector_state()->in_initial_mark_gc(); 2774 2775 // Inner scope for scope based logging, timers, and stats collection 2776 { 2777 EvacuationInfo evacuation_info; 2778 2779 if (collector_state()->in_initial_mark_gc()) { 2780 // We are about to start a marking cycle, so we increment the 2781 // full collection counter. 2782 increment_old_marking_cycles_started(); 2783 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 2784 } 2785 2786 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 2787 2788 GCTraceCPUTime tcpu; 2789 2790 G1HeapVerifier::G1VerifyType verify_type; 2791 FormatBuffer<> gc_string("Pause "); 2792 if (collector_state()->in_initial_mark_gc()) { 2793 gc_string.append("Initial Mark"); 2794 verify_type = G1HeapVerifier::G1VerifyInitialMark; 2795 } else if (collector_state()->in_young_only_phase()) { 2796 gc_string.append("Young"); 2797 verify_type = G1HeapVerifier::G1VerifyYoungOnly; 2798 } else { 2799 gc_string.append("Mixed"); 2800 verify_type = G1HeapVerifier::G1VerifyMixed; 2801 } 2802 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 2803 2804 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 2805 workers()->active_workers(), 2806 Threads::number_of_non_daemon_threads()); 2807 active_workers = workers()->update_active_workers(active_workers); 2808 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 2809 2810 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 2811 TraceMemoryManagerStats tms(&_memory_manager, gc_cause()); 2812 2813 G1HeapTransition heap_transition(this); 2814 size_t heap_used_bytes_before_gc = used(); 2815 2816 // Don't dynamically change the number of GC threads this early. A value of 2817 // 0 is used to indicate serial work. When parallel work is done, 2818 // it will be set. 2819 2820 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 2821 IsGCActiveMark x; 2822 2823 gc_prologue(false); 2824 2825 if (VerifyRememberedSets) { 2826 log_info(gc, verify)("[Verifying RemSets before GC]"); 2827 VerifyRegionRemSetClosure v_cl; 2828 heap_region_iterate(&v_cl); 2829 } 2830 2831 _verifier->verify_before_gc(verify_type); 2832 2833 _verifier->check_bitmaps("GC Start"); 2834 2835 #if COMPILER2_OR_JVMCI 2836 DerivedPointerTable::clear(); 2837 #endif 2838 2839 // Please see comment in g1CollectedHeap.hpp and 2840 // G1CollectedHeap::ref_processing_init() to see how 2841 // reference processing currently works in G1. 2842 2843 // Enable discovery in the STW reference processor 2844 ref_processor_stw()->enable_discovery(); 2845 2846 { 2847 // We want to temporarily turn off discovery by the 2848 // CM ref processor, if necessary, and turn it back on 2849 // on again later if we do. Using a scoped 2850 // NoRefDiscovery object will do this. 2851 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 2852 2853 // Forget the current alloc region (we might even choose it to be part 2854 // of the collection set!). 2855 _allocator->release_mutator_alloc_region(); 2856 2857 // This timing is only used by the ergonomics to handle our pause target. 2858 // It is unclear why this should not include the full pause. We will 2859 // investigate this in CR 7178365. 2860 // 2861 // Preserving the old comment here if that helps the investigation: 2862 // 2863 // The elapsed time induced by the start time below deliberately elides 2864 // the possible verification above. 2865 double sample_start_time_sec = os::elapsedTime(); 2866 2867 g1_policy()->record_collection_pause_start(sample_start_time_sec); 2868 2869 if (collector_state()->in_initial_mark_gc()) { 2870 concurrent_mark()->pre_initial_mark(); 2871 } 2872 2873 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 2874 2875 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 2876 2877 // Make sure the remembered sets are up to date. This needs to be 2878 // done before register_humongous_regions_with_cset(), because the 2879 // remembered sets are used there to choose eager reclaim candidates. 2880 // If the remembered sets are not up to date we might miss some 2881 // entries that need to be handled. 2882 g1_rem_set()->cleanupHRRS(); 2883 2884 register_humongous_regions_with_cset(); 2885 2886 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 2887 2888 // We call this after finalize_cset() to 2889 // ensure that the CSet has been finalized. 2890 _cm->verify_no_cset_oops(); 2891 2892 if (_hr_printer.is_active()) { 2893 G1PrintCollectionSetClosure cl(&_hr_printer); 2894 _collection_set.iterate(&cl); 2895 } 2896 2897 // Initialize the GC alloc regions. 2898 _allocator->init_gc_alloc_regions(evacuation_info); 2899 2900 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 2901 pre_evacuate_collection_set(); 2902 2903 // Actually do the work... 2904 evacuate_collection_set(&per_thread_states); 2905 2906 post_evacuate_collection_set(evacuation_info, &per_thread_states); 2907 2908 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 2909 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 2910 2911 eagerly_reclaim_humongous_regions(); 2912 2913 record_obj_copy_mem_stats(); 2914 _survivor_evac_stats.adjust_desired_plab_sz(); 2915 _old_evac_stats.adjust_desired_plab_sz(); 2916 2917 double start = os::elapsedTime(); 2918 start_new_collection_set(); 2919 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 2920 2921 if (evacuation_failed()) { 2922 set_used(recalculate_used()); 2923 if (_archive_allocator != NULL) { 2924 _archive_allocator->clear_used(); 2925 } 2926 for (uint i = 0; i < ParallelGCThreads; i++) { 2927 if (_evacuation_failed_info_array[i].has_failed()) { 2928 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 2929 } 2930 } 2931 } else { 2932 // The "used" of the the collection set have already been subtracted 2933 // when they were freed. Add in the bytes evacuated. 2934 increase_used(g1_policy()->bytes_copied_during_gc()); 2935 } 2936 2937 if (collector_state()->in_initial_mark_gc()) { 2938 // We have to do this before we notify the CM threads that 2939 // they can start working to make sure that all the 2940 // appropriate initialization is done on the CM object. 2941 concurrent_mark()->post_initial_mark(); 2942 // Note that we don't actually trigger the CM thread at 2943 // this point. We do that later when we're sure that 2944 // the current thread has completed its logging output. 2945 } 2946 2947 allocate_dummy_regions(); 2948 2949 _allocator->init_mutator_alloc_region(); 2950 2951 { 2952 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 2953 if (expand_bytes > 0) { 2954 size_t bytes_before = capacity(); 2955 // No need for an ergo logging here, 2956 // expansion_amount() does this when it returns a value > 0. 2957 double expand_ms; 2958 if (!expand(expand_bytes, _workers, &expand_ms)) { 2959 // We failed to expand the heap. Cannot do anything about it. 2960 } 2961 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 2962 } 2963 } 2964 2965 // We redo the verification but now wrt to the new CSet which 2966 // has just got initialized after the previous CSet was freed. 2967 _cm->verify_no_cset_oops(); 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 double sample_end_time_sec = os::elapsedTime(); 2973 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 2974 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards); 2975 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 2976 2977 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 2978 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 2979 2980 if (VerifyRememberedSets) { 2981 log_info(gc, verify)("[Verifying RemSets after GC]"); 2982 VerifyRegionRemSetClosure v_cl; 2983 heap_region_iterate(&v_cl); 2984 } 2985 2986 _verifier->verify_after_gc(verify_type); 2987 _verifier->check_bitmaps("GC End"); 2988 2989 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 2990 ref_processor_stw()->verify_no_references_recorded(); 2991 2992 // CM reference discovery will be re-enabled if necessary. 2993 } 2994 2995 #ifdef TRACESPINNING 2996 ParallelTaskTerminator::print_termination_counts(); 2997 #endif 2998 2999 gc_epilogue(false); 3000 } 3001 3002 // Print the remainder of the GC log output. 3003 if (evacuation_failed()) { 3004 log_info(gc)("To-space exhausted"); 3005 } 3006 3007 g1_policy()->print_phases(); 3008 heap_transition.print(); 3009 3010 // It is not yet to safe to tell the concurrent mark to 3011 // start as we have some optional output below. We don't want the 3012 // output from the concurrent mark thread interfering with this 3013 // logging output either. 3014 3015 _hrm.verify_optional(); 3016 _verifier->verify_region_sets_optional(); 3017 3018 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3019 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3020 3021 print_heap_after_gc(); 3022 print_heap_regions(); 3023 trace_heap_after_gc(_gc_tracer_stw); 3024 3025 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3026 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3027 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3028 // before any GC notifications are raised. 3029 g1mm()->update_sizes(); 3030 3031 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3032 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3033 _gc_timer_stw->register_gc_end(); 3034 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3035 } 3036 // It should now be safe to tell the concurrent mark thread to start 3037 // without its logging output interfering with the logging output 3038 // that came from the pause. 3039 3040 if (should_start_conc_mark) { 3041 // CAUTION: after the doConcurrentMark() call below, 3042 // the concurrent marking thread(s) could be running 3043 // concurrently with us. Make sure that anything after 3044 // this point does not assume that we are the only GC thread 3045 // running. Note: of course, the actual marking work will 3046 // not start until the safepoint itself is released in 3047 // SuspendibleThreadSet::desynchronize(). 3048 do_concurrent_mark(); 3049 } 3050 3051 return true; 3052 } 3053 3054 void G1CollectedHeap::remove_self_forwarding_pointers() { 3055 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3056 workers()->run_task(&rsfp_task); 3057 } 3058 3059 void G1CollectedHeap::restore_after_evac_failure() { 3060 double remove_self_forwards_start = os::elapsedTime(); 3061 3062 remove_self_forwarding_pointers(); 3063 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3064 _preserved_marks_set.restore(&task_executor); 3065 3066 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3067 } 3068 3069 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3070 if (!_evacuation_failed) { 3071 _evacuation_failed = true; 3072 } 3073 3074 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3075 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3076 } 3077 3078 bool G1ParEvacuateFollowersClosure::offer_termination() { 3079 G1ParScanThreadState* const pss = par_scan_state(); 3080 start_term_time(); 3081 const bool res = terminator()->offer_termination(); 3082 end_term_time(); 3083 return res; 3084 } 3085 3086 void G1ParEvacuateFollowersClosure::do_void() { 3087 G1ParScanThreadState* const pss = par_scan_state(); 3088 pss->trim_queue(); 3089 do { 3090 pss->steal_and_trim_queue(queues()); 3091 } while (!offer_termination()); 3092 } 3093 3094 class G1ParTask : public AbstractGangTask { 3095 protected: 3096 G1CollectedHeap* _g1h; 3097 G1ParScanThreadStateSet* _pss; 3098 RefToScanQueueSet* _queues; 3099 G1RootProcessor* _root_processor; 3100 ParallelTaskTerminator _terminator; 3101 uint _n_workers; 3102 3103 public: 3104 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3105 : AbstractGangTask("G1 collection"), 3106 _g1h(g1h), 3107 _pss(per_thread_states), 3108 _queues(task_queues), 3109 _root_processor(root_processor), 3110 _terminator(n_workers, _queues), 3111 _n_workers(n_workers) 3112 {} 3113 3114 void work(uint worker_id) { 3115 if (worker_id >= _n_workers) return; // no work needed this round 3116 3117 double start_sec = os::elapsedTime(); 3118 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3119 3120 { 3121 ResourceMark rm; 3122 HandleMark hm; 3123 3124 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3125 3126 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3127 pss->set_ref_processor(rp); 3128 3129 double start_strong_roots_sec = os::elapsedTime(); 3130 3131 _root_processor->evacuate_roots(pss, worker_id); 3132 3133 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3134 // treating the nmethods visited to act as roots for concurrent marking. 3135 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3136 // objects copied by the current evacuation. 3137 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, worker_id); 3138 3139 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3140 3141 double term_sec = 0.0; 3142 size_t evac_term_attempts = 0; 3143 { 3144 double start = os::elapsedTime(); 3145 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3146 evac.do_void(); 3147 3148 evac_term_attempts = evac.term_attempts(); 3149 term_sec = evac.term_time(); 3150 double elapsed_sec = os::elapsedTime() - start; 3151 3152 G1GCPhaseTimes* p = _g1h->g1_policy()->phase_times(); 3153 p->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3154 p->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3155 p->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3156 } 3157 3158 assert(pss->queue_is_empty(), "should be empty"); 3159 3160 if (log_is_enabled(Debug, gc, task, stats)) { 3161 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3162 size_t lab_waste; 3163 size_t lab_undo_waste; 3164 pss->waste(lab_waste, lab_undo_waste); 3165 _g1h->print_termination_stats(worker_id, 3166 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3167 strong_roots_sec * 1000.0, /* strong roots time */ 3168 term_sec * 1000.0, /* evac term time */ 3169 evac_term_attempts, /* evac term attempts */ 3170 lab_waste, /* alloc buffer waste */ 3171 lab_undo_waste /* undo waste */ 3172 ); 3173 } 3174 3175 // Close the inner scope so that the ResourceMark and HandleMark 3176 // destructors are executed here and are included as part of the 3177 // "GC Worker Time". 3178 } 3179 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3180 } 3181 }; 3182 3183 void G1CollectedHeap::print_termination_stats_hdr() { 3184 log_debug(gc, task, stats)("GC Termination Stats"); 3185 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3186 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3187 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3188 } 3189 3190 void G1CollectedHeap::print_termination_stats(uint worker_id, 3191 double elapsed_ms, 3192 double strong_roots_ms, 3193 double term_ms, 3194 size_t term_attempts, 3195 size_t alloc_buffer_waste, 3196 size_t undo_waste) const { 3197 log_debug(gc, task, stats) 3198 ("%3d %9.2f %9.2f %6.2f " 3199 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3200 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3201 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3202 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3203 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3204 alloc_buffer_waste * HeapWordSize / K, 3205 undo_waste * HeapWordSize / K); 3206 } 3207 3208 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3209 private: 3210 BoolObjectClosure* _is_alive; 3211 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3212 3213 int _initial_string_table_size; 3214 int _initial_symbol_table_size; 3215 3216 bool _process_strings; 3217 int _strings_processed; 3218 int _strings_removed; 3219 3220 bool _process_symbols; 3221 int _symbols_processed; 3222 int _symbols_removed; 3223 3224 bool _process_string_dedup; 3225 3226 public: 3227 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3228 AbstractGangTask("String/Symbol Unlinking"), 3229 _is_alive(is_alive), 3230 _dedup_closure(is_alive, NULL, false), 3231 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3232 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3233 _process_string_dedup(process_string_dedup) { 3234 3235 _initial_string_table_size = StringTable::the_table()->table_size(); 3236 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3237 if (process_strings) { 3238 StringTable::clear_parallel_claimed_index(); 3239 } 3240 if (process_symbols) { 3241 SymbolTable::clear_parallel_claimed_index(); 3242 } 3243 } 3244 3245 ~G1StringAndSymbolCleaningTask() { 3246 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3247 "claim value %d after unlink less than initial string table size %d", 3248 StringTable::parallel_claimed_index(), _initial_string_table_size); 3249 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3250 "claim value %d after unlink less than initial symbol table size %d", 3251 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3252 3253 log_info(gc, stringtable)( 3254 "Cleaned string and symbol table, " 3255 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3256 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3257 strings_processed(), strings_removed(), 3258 symbols_processed(), symbols_removed()); 3259 } 3260 3261 void work(uint worker_id) { 3262 int strings_processed = 0; 3263 int strings_removed = 0; 3264 int symbols_processed = 0; 3265 int symbols_removed = 0; 3266 if (_process_strings) { 3267 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3268 Atomic::add(strings_processed, &_strings_processed); 3269 Atomic::add(strings_removed, &_strings_removed); 3270 } 3271 if (_process_symbols) { 3272 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3273 Atomic::add(symbols_processed, &_symbols_processed); 3274 Atomic::add(symbols_removed, &_symbols_removed); 3275 } 3276 if (_process_string_dedup) { 3277 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3278 } 3279 } 3280 3281 size_t strings_processed() const { return (size_t)_strings_processed; } 3282 size_t strings_removed() const { return (size_t)_strings_removed; } 3283 3284 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3285 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3286 }; 3287 3288 class G1CodeCacheUnloadingTask { 3289 private: 3290 static Monitor* _lock; 3291 3292 BoolObjectClosure* const _is_alive; 3293 const bool _unloading_occurred; 3294 const uint _num_workers; 3295 3296 // Variables used to claim nmethods. 3297 CompiledMethod* _first_nmethod; 3298 CompiledMethod* volatile _claimed_nmethod; 3299 3300 // The list of nmethods that need to be processed by the second pass. 3301 CompiledMethod* volatile _postponed_list; 3302 volatile uint _num_entered_barrier; 3303 3304 public: 3305 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3306 _is_alive(is_alive), 3307 _unloading_occurred(unloading_occurred), 3308 _num_workers(num_workers), 3309 _first_nmethod(NULL), 3310 _claimed_nmethod(NULL), 3311 _postponed_list(NULL), 3312 _num_entered_barrier(0) 3313 { 3314 CompiledMethod::increase_unloading_clock(); 3315 // Get first alive nmethod 3316 CompiledMethodIterator iter = CompiledMethodIterator(); 3317 if(iter.next_alive()) { 3318 _first_nmethod = iter.method(); 3319 } 3320 _claimed_nmethod = _first_nmethod; 3321 } 3322 3323 ~G1CodeCacheUnloadingTask() { 3324 CodeCache::verify_clean_inline_caches(); 3325 3326 CodeCache::set_needs_cache_clean(false); 3327 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3328 3329 CodeCache::verify_icholder_relocations(); 3330 } 3331 3332 private: 3333 void add_to_postponed_list(CompiledMethod* nm) { 3334 CompiledMethod* old; 3335 do { 3336 old = _postponed_list; 3337 nm->set_unloading_next(old); 3338 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old); 3339 } 3340 3341 void clean_nmethod(CompiledMethod* nm) { 3342 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3343 3344 if (postponed) { 3345 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3346 add_to_postponed_list(nm); 3347 } 3348 3349 // Mark that this thread has been cleaned/unloaded. 3350 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3351 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3352 } 3353 3354 void clean_nmethod_postponed(CompiledMethod* nm) { 3355 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3356 } 3357 3358 static const int MaxClaimNmethods = 16; 3359 3360 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3361 CompiledMethod* first; 3362 CompiledMethodIterator last; 3363 3364 do { 3365 *num_claimed_nmethods = 0; 3366 3367 first = _claimed_nmethod; 3368 last = CompiledMethodIterator(first); 3369 3370 if (first != NULL) { 3371 3372 for (int i = 0; i < MaxClaimNmethods; i++) { 3373 if (!last.next_alive()) { 3374 break; 3375 } 3376 claimed_nmethods[i] = last.method(); 3377 (*num_claimed_nmethods)++; 3378 } 3379 } 3380 3381 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first); 3382 } 3383 3384 CompiledMethod* claim_postponed_nmethod() { 3385 CompiledMethod* claim; 3386 CompiledMethod* next; 3387 3388 do { 3389 claim = _postponed_list; 3390 if (claim == NULL) { 3391 return NULL; 3392 } 3393 3394 next = claim->unloading_next(); 3395 3396 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim); 3397 3398 return claim; 3399 } 3400 3401 public: 3402 // Mark that we're done with the first pass of nmethod cleaning. 3403 void barrier_mark(uint worker_id) { 3404 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3405 _num_entered_barrier++; 3406 if (_num_entered_barrier == _num_workers) { 3407 ml.notify_all(); 3408 } 3409 } 3410 3411 // See if we have to wait for the other workers to 3412 // finish their first-pass nmethod cleaning work. 3413 void barrier_wait(uint worker_id) { 3414 if (_num_entered_barrier < _num_workers) { 3415 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3416 while (_num_entered_barrier < _num_workers) { 3417 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3418 } 3419 } 3420 } 3421 3422 // Cleaning and unloading of nmethods. Some work has to be postponed 3423 // to the second pass, when we know which nmethods survive. 3424 void work_first_pass(uint worker_id) { 3425 // The first nmethods is claimed by the first worker. 3426 if (worker_id == 0 && _first_nmethod != NULL) { 3427 clean_nmethod(_first_nmethod); 3428 _first_nmethod = NULL; 3429 } 3430 3431 int num_claimed_nmethods; 3432 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3433 3434 while (true) { 3435 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3436 3437 if (num_claimed_nmethods == 0) { 3438 break; 3439 } 3440 3441 for (int i = 0; i < num_claimed_nmethods; i++) { 3442 clean_nmethod(claimed_nmethods[i]); 3443 } 3444 } 3445 } 3446 3447 void work_second_pass(uint worker_id) { 3448 CompiledMethod* nm; 3449 // Take care of postponed nmethods. 3450 while ((nm = claim_postponed_nmethod()) != NULL) { 3451 clean_nmethod_postponed(nm); 3452 } 3453 } 3454 }; 3455 3456 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3457 3458 class G1KlassCleaningTask : public StackObj { 3459 BoolObjectClosure* _is_alive; 3460 volatile int _clean_klass_tree_claimed; 3461 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3462 3463 public: 3464 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3465 _is_alive(is_alive), 3466 _clean_klass_tree_claimed(0), 3467 _klass_iterator() { 3468 } 3469 3470 private: 3471 bool claim_clean_klass_tree_task() { 3472 if (_clean_klass_tree_claimed) { 3473 return false; 3474 } 3475 3476 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0; 3477 } 3478 3479 InstanceKlass* claim_next_klass() { 3480 Klass* klass; 3481 do { 3482 klass =_klass_iterator.next_klass(); 3483 } while (klass != NULL && !klass->is_instance_klass()); 3484 3485 // this can be null so don't call InstanceKlass::cast 3486 return static_cast<InstanceKlass*>(klass); 3487 } 3488 3489 public: 3490 3491 void clean_klass(InstanceKlass* ik) { 3492 ik->clean_weak_instanceklass_links(_is_alive); 3493 } 3494 3495 void work() { 3496 ResourceMark rm; 3497 3498 // One worker will clean the subklass/sibling klass tree. 3499 if (claim_clean_klass_tree_task()) { 3500 Klass::clean_subklass_tree(_is_alive); 3501 } 3502 3503 // All workers will help cleaning the classes, 3504 InstanceKlass* klass; 3505 while ((klass = claim_next_klass()) != NULL) { 3506 clean_klass(klass); 3507 } 3508 } 3509 }; 3510 3511 class G1ResolvedMethodCleaningTask : public StackObj { 3512 BoolObjectClosure* _is_alive; 3513 volatile int _resolved_method_task_claimed; 3514 public: 3515 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) : 3516 _is_alive(is_alive), _resolved_method_task_claimed(0) {} 3517 3518 bool claim_resolved_method_task() { 3519 if (_resolved_method_task_claimed) { 3520 return false; 3521 } 3522 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0; 3523 } 3524 3525 // These aren't big, one thread can do it all. 3526 void work() { 3527 if (claim_resolved_method_task()) { 3528 ResolvedMethodTable::unlink(_is_alive); 3529 } 3530 } 3531 }; 3532 3533 3534 // To minimize the remark pause times, the tasks below are done in parallel. 3535 class G1ParallelCleaningTask : public AbstractGangTask { 3536 private: 3537 G1StringAndSymbolCleaningTask _string_symbol_task; 3538 G1CodeCacheUnloadingTask _code_cache_task; 3539 G1KlassCleaningTask _klass_cleaning_task; 3540 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task; 3541 3542 public: 3543 // The constructor is run in the VMThread. 3544 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3545 AbstractGangTask("Parallel Cleaning"), 3546 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3547 _code_cache_task(num_workers, is_alive, unloading_occurred), 3548 _klass_cleaning_task(is_alive), 3549 _resolved_method_cleaning_task(is_alive) { 3550 } 3551 3552 // The parallel work done by all worker threads. 3553 void work(uint worker_id) { 3554 // Do first pass of code cache cleaning. 3555 _code_cache_task.work_first_pass(worker_id); 3556 3557 // Let the threads mark that the first pass is done. 3558 _code_cache_task.barrier_mark(worker_id); 3559 3560 // Clean the Strings and Symbols. 3561 _string_symbol_task.work(worker_id); 3562 3563 // Clean unreferenced things in the ResolvedMethodTable 3564 _resolved_method_cleaning_task.work(); 3565 3566 // Wait for all workers to finish the first code cache cleaning pass. 3567 _code_cache_task.barrier_wait(worker_id); 3568 3569 // Do the second code cache cleaning work, which realize on 3570 // the liveness information gathered during the first pass. 3571 _code_cache_task.work_second_pass(worker_id); 3572 3573 // Clean all klasses that were not unloaded. 3574 _klass_cleaning_task.work(); 3575 } 3576 }; 3577 3578 3579 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3580 bool class_unloading_occurred) { 3581 uint n_workers = workers()->active_workers(); 3582 3583 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3584 workers()->run_task(&g1_unlink_task); 3585 } 3586 3587 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3588 bool process_strings, 3589 bool process_symbols, 3590 bool process_string_dedup) { 3591 if (!process_strings && !process_symbols && !process_string_dedup) { 3592 // Nothing to clean. 3593 return; 3594 } 3595 3596 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3597 workers()->run_task(&g1_unlink_task); 3598 3599 } 3600 3601 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3602 private: 3603 DirtyCardQueueSet* _queue; 3604 G1CollectedHeap* _g1h; 3605 public: 3606 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3607 _queue(queue), _g1h(g1h) { } 3608 3609 virtual void work(uint worker_id) { 3610 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3611 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3612 3613 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3614 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3615 3616 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3617 } 3618 }; 3619 3620 void G1CollectedHeap::redirty_logged_cards() { 3621 double redirty_logged_cards_start = os::elapsedTime(); 3622 3623 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3624 dirty_card_queue_set().reset_for_par_iteration(); 3625 workers()->run_task(&redirty_task); 3626 3627 DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set(); 3628 dcq.merge_bufferlists(&dirty_card_queue_set()); 3629 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3630 3631 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3632 } 3633 3634 // Weak Reference Processing support 3635 3636 // An always "is_alive" closure that is used to preserve referents. 3637 // If the object is non-null then it's alive. Used in the preservation 3638 // of referent objects that are pointed to by reference objects 3639 // discovered by the CM ref processor. 3640 class G1AlwaysAliveClosure: public BoolObjectClosure { 3641 public: 3642 bool do_object_b(oop p) { 3643 if (p != NULL) { 3644 return true; 3645 } 3646 return false; 3647 } 3648 }; 3649 3650 bool G1STWIsAliveClosure::do_object_b(oop p) { 3651 // An object is reachable if it is outside the collection set, 3652 // or is inside and copied. 3653 return !_g1h->is_in_cset(p) || p->is_forwarded(); 3654 } 3655 3656 // Non Copying Keep Alive closure 3657 class G1KeepAliveClosure: public OopClosure { 3658 G1CollectedHeap*_g1h; 3659 public: 3660 G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {} 3661 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3662 void do_oop(oop* p) { 3663 oop obj = *p; 3664 assert(obj != NULL, "the caller should have filtered out NULL values"); 3665 3666 const InCSetState cset_state =_g1h->in_cset_state(obj); 3667 if (!cset_state.is_in_cset_or_humongous()) { 3668 return; 3669 } 3670 if (cset_state.is_in_cset()) { 3671 assert( obj->is_forwarded(), "invariant" ); 3672 *p = obj->forwardee(); 3673 } else { 3674 assert(!obj->is_forwarded(), "invariant" ); 3675 assert(cset_state.is_humongous(), 3676 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3677 _g1h->set_humongous_is_live(obj); 3678 } 3679 } 3680 }; 3681 3682 // Copying Keep Alive closure - can be called from both 3683 // serial and parallel code as long as different worker 3684 // threads utilize different G1ParScanThreadState instances 3685 // and different queues. 3686 3687 class G1CopyingKeepAliveClosure: public OopClosure { 3688 G1CollectedHeap* _g1h; 3689 OopClosure* _copy_non_heap_obj_cl; 3690 G1ParScanThreadState* _par_scan_state; 3691 3692 public: 3693 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3694 OopClosure* non_heap_obj_cl, 3695 G1ParScanThreadState* pss): 3696 _g1h(g1h), 3697 _copy_non_heap_obj_cl(non_heap_obj_cl), 3698 _par_scan_state(pss) 3699 {} 3700 3701 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3702 virtual void do_oop( oop* p) { do_oop_work(p); } 3703 3704 template <class T> void do_oop_work(T* p) { 3705 oop obj = RawAccess<>::oop_load(p); 3706 3707 if (_g1h->is_in_cset_or_humongous(obj)) { 3708 // If the referent object has been forwarded (either copied 3709 // to a new location or to itself in the event of an 3710 // evacuation failure) then we need to update the reference 3711 // field and, if both reference and referent are in the G1 3712 // heap, update the RSet for the referent. 3713 // 3714 // If the referent has not been forwarded then we have to keep 3715 // it alive by policy. Therefore we have copy the referent. 3716 // 3717 // If the reference field is in the G1 heap then we can push 3718 // on the PSS queue. When the queue is drained (after each 3719 // phase of reference processing) the object and it's followers 3720 // will be copied, the reference field set to point to the 3721 // new location, and the RSet updated. Otherwise we need to 3722 // use the the non-heap or metadata closures directly to copy 3723 // the referent object and update the pointer, while avoiding 3724 // updating the RSet. 3725 3726 if (_g1h->is_in_g1_reserved(p)) { 3727 _par_scan_state->push_on_queue(p); 3728 } else { 3729 assert(!Metaspace::contains((const void*)p), 3730 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 3731 _copy_non_heap_obj_cl->do_oop(p); 3732 } 3733 } 3734 } 3735 }; 3736 3737 // Serial drain queue closure. Called as the 'complete_gc' 3738 // closure for each discovered list in some of the 3739 // reference processing phases. 3740 3741 class G1STWDrainQueueClosure: public VoidClosure { 3742 protected: 3743 G1CollectedHeap* _g1h; 3744 G1ParScanThreadState* _par_scan_state; 3745 3746 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3747 3748 public: 3749 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3750 _g1h(g1h), 3751 _par_scan_state(pss) 3752 { } 3753 3754 void do_void() { 3755 G1ParScanThreadState* const pss = par_scan_state(); 3756 pss->trim_queue(); 3757 } 3758 }; 3759 3760 // Parallel Reference Processing closures 3761 3762 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3763 // processing during G1 evacuation pauses. 3764 3765 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3766 private: 3767 G1CollectedHeap* _g1h; 3768 G1ParScanThreadStateSet* _pss; 3769 RefToScanQueueSet* _queues; 3770 WorkGang* _workers; 3771 uint _active_workers; 3772 3773 public: 3774 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3775 G1ParScanThreadStateSet* per_thread_states, 3776 WorkGang* workers, 3777 RefToScanQueueSet *task_queues, 3778 uint n_workers) : 3779 _g1h(g1h), 3780 _pss(per_thread_states), 3781 _queues(task_queues), 3782 _workers(workers), 3783 _active_workers(n_workers) 3784 { 3785 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 3786 } 3787 3788 // Executes the given task using concurrent marking worker threads. 3789 virtual void execute(ProcessTask& task); 3790 virtual void execute(EnqueueTask& task); 3791 }; 3792 3793 // Gang task for possibly parallel reference processing 3794 3795 class G1STWRefProcTaskProxy: public AbstractGangTask { 3796 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 3797 ProcessTask& _proc_task; 3798 G1CollectedHeap* _g1h; 3799 G1ParScanThreadStateSet* _pss; 3800 RefToScanQueueSet* _task_queues; 3801 ParallelTaskTerminator* _terminator; 3802 3803 public: 3804 G1STWRefProcTaskProxy(ProcessTask& proc_task, 3805 G1CollectedHeap* g1h, 3806 G1ParScanThreadStateSet* per_thread_states, 3807 RefToScanQueueSet *task_queues, 3808 ParallelTaskTerminator* terminator) : 3809 AbstractGangTask("Process reference objects in parallel"), 3810 _proc_task(proc_task), 3811 _g1h(g1h), 3812 _pss(per_thread_states), 3813 _task_queues(task_queues), 3814 _terminator(terminator) 3815 {} 3816 3817 virtual void work(uint worker_id) { 3818 // The reference processing task executed by a single worker. 3819 ResourceMark rm; 3820 HandleMark hm; 3821 3822 G1STWIsAliveClosure is_alive(_g1h); 3823 3824 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3825 pss->set_ref_processor(NULL); 3826 3827 // Keep alive closure. 3828 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 3829 3830 // Complete GC closure 3831 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 3832 3833 // Call the reference processing task's work routine. 3834 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 3835 3836 // Note we cannot assert that the refs array is empty here as not all 3837 // of the processing tasks (specifically phase2 - pp2_work) execute 3838 // the complete_gc closure (which ordinarily would drain the queue) so 3839 // the queue may not be empty. 3840 } 3841 }; 3842 3843 // Driver routine for parallel reference processing. 3844 // Creates an instance of the ref processing gang 3845 // task and has the worker threads execute it. 3846 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 3847 assert(_workers != NULL, "Need parallel worker threads."); 3848 3849 ParallelTaskTerminator terminator(_active_workers, _queues); 3850 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 3851 3852 _workers->run_task(&proc_task_proxy); 3853 } 3854 3855 // Gang task for parallel reference enqueueing. 3856 3857 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 3858 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 3859 EnqueueTask& _enq_task; 3860 3861 public: 3862 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 3863 AbstractGangTask("Enqueue reference objects in parallel"), 3864 _enq_task(enq_task) 3865 { } 3866 3867 virtual void work(uint worker_id) { 3868 _enq_task.work(worker_id); 3869 } 3870 }; 3871 3872 // Driver routine for parallel reference enqueueing. 3873 // Creates an instance of the ref enqueueing gang 3874 // task and has the worker threads execute it. 3875 3876 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 3877 assert(_workers != NULL, "Need parallel worker threads."); 3878 3879 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 3880 3881 _workers->run_task(&enq_task_proxy); 3882 } 3883 3884 // End of weak reference support closures 3885 3886 // Abstract task used to preserve (i.e. copy) any referent objects 3887 // that are in the collection set and are pointed to by reference 3888 // objects discovered by the CM ref processor. 3889 3890 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 3891 protected: 3892 G1CollectedHeap* _g1h; 3893 G1ParScanThreadStateSet* _pss; 3894 RefToScanQueueSet* _queues; 3895 ParallelTaskTerminator _terminator; 3896 uint _n_workers; 3897 3898 public: 3899 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 3900 AbstractGangTask("ParPreserveCMReferents"), 3901 _g1h(g1h), 3902 _pss(per_thread_states), 3903 _queues(task_queues), 3904 _terminator(workers, _queues), 3905 _n_workers(workers) 3906 { 3907 g1h->ref_processor_cm()->set_active_mt_degree(workers); 3908 } 3909 3910 void work(uint worker_id) { 3911 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 3912 3913 ResourceMark rm; 3914 HandleMark hm; 3915 3916 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3917 pss->set_ref_processor(NULL); 3918 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 3919 3920 // Is alive closure 3921 G1AlwaysAliveClosure always_alive; 3922 3923 // Copying keep alive closure. Applied to referent objects that need 3924 // to be copied. 3925 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 3926 3927 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 3928 3929 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 3930 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 3931 3932 // limit is set using max_num_q() - which was set using ParallelGCThreads. 3933 // So this must be true - but assert just in case someone decides to 3934 // change the worker ids. 3935 assert(worker_id < limit, "sanity"); 3936 assert(!rp->discovery_is_atomic(), "check this code"); 3937 3938 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 3939 for (uint idx = worker_id; idx < limit; idx += stride) { 3940 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 3941 3942 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 3943 while (iter.has_next()) { 3944 // Since discovery is not atomic for the CM ref processor, we 3945 // can see some null referent objects. 3946 iter.load_ptrs(DEBUG_ONLY(true)); 3947 oop ref = iter.obj(); 3948 3949 // This will filter nulls. 3950 if (iter.is_referent_alive()) { 3951 iter.make_referent_alive(); 3952 } 3953 iter.move_to_next(); 3954 } 3955 } 3956 3957 // Drain the queue - which may cause stealing 3958 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 3959 drain_queue.do_void(); 3960 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 3961 assert(pss->queue_is_empty(), "should be"); 3962 } 3963 }; 3964 3965 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 3966 // Any reference objects, in the collection set, that were 'discovered' 3967 // by the CM ref processor should have already been copied (either by 3968 // applying the external root copy closure to the discovered lists, or 3969 // by following an RSet entry). 3970 // 3971 // But some of the referents, that are in the collection set, that these 3972 // reference objects point to may not have been copied: the STW ref 3973 // processor would have seen that the reference object had already 3974 // been 'discovered' and would have skipped discovering the reference, 3975 // but would not have treated the reference object as a regular oop. 3976 // As a result the copy closure would not have been applied to the 3977 // referent object. 3978 // 3979 // We need to explicitly copy these referent objects - the references 3980 // will be processed at the end of remarking. 3981 // 3982 // We also need to do this copying before we process the reference 3983 // objects discovered by the STW ref processor in case one of these 3984 // referents points to another object which is also referenced by an 3985 // object discovered by the STW ref processor. 3986 double preserve_cm_referents_time = 0.0; 3987 3988 // To avoid spawning task when there is no work to do, check that 3989 // a concurrent cycle is active and that some references have been 3990 // discovered. 3991 if (concurrent_mark()->cm_thread()->during_cycle() && 3992 ref_processor_cm()->has_discovered_references()) { 3993 double preserve_cm_referents_start = os::elapsedTime(); 3994 uint no_of_gc_workers = workers()->active_workers(); 3995 G1ParPreserveCMReferentsTask keep_cm_referents(this, 3996 per_thread_states, 3997 no_of_gc_workers, 3998 _task_queues); 3999 workers()->run_task(&keep_cm_referents); 4000 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4001 } 4002 4003 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4004 } 4005 4006 // Weak Reference processing during an evacuation pause (part 1). 4007 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4008 double ref_proc_start = os::elapsedTime(); 4009 4010 ReferenceProcessor* rp = _ref_processor_stw; 4011 assert(rp->discovery_enabled(), "should have been enabled"); 4012 4013 // Closure to test whether a referent is alive. 4014 G1STWIsAliveClosure is_alive(this); 4015 4016 // Even when parallel reference processing is enabled, the processing 4017 // of JNI refs is serial and performed serially by the current thread 4018 // rather than by a worker. The following PSS will be used for processing 4019 // JNI refs. 4020 4021 // Use only a single queue for this PSS. 4022 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4023 pss->set_ref_processor(NULL); 4024 assert(pss->queue_is_empty(), "pre-condition"); 4025 4026 // Keep alive closure. 4027 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4028 4029 // Serial Complete GC closure 4030 G1STWDrainQueueClosure drain_queue(this, pss); 4031 4032 // Setup the soft refs policy... 4033 rp->setup_policy(false); 4034 4035 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4036 4037 ReferenceProcessorStats stats; 4038 if (!rp->processing_is_mt()) { 4039 // Serial reference processing... 4040 stats = rp->process_discovered_references(&is_alive, 4041 &keep_alive, 4042 &drain_queue, 4043 NULL, 4044 pt); 4045 } else { 4046 uint no_of_gc_workers = workers()->active_workers(); 4047 4048 // Parallel reference processing 4049 assert(no_of_gc_workers <= rp->max_num_q(), 4050 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4051 no_of_gc_workers, rp->max_num_q()); 4052 4053 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4054 stats = rp->process_discovered_references(&is_alive, 4055 &keep_alive, 4056 &drain_queue, 4057 &par_task_executor, 4058 pt); 4059 } 4060 4061 _gc_tracer_stw->report_gc_reference_stats(stats); 4062 4063 // We have completed copying any necessary live referent objects. 4064 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4065 4066 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4067 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4068 } 4069 4070 // Weak Reference processing during an evacuation pause (part 2). 4071 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4072 double ref_enq_start = os::elapsedTime(); 4073 4074 ReferenceProcessor* rp = _ref_processor_stw; 4075 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4076 4077 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4078 4079 // Now enqueue any remaining on the discovered lists on to 4080 // the pending list. 4081 if (!rp->processing_is_mt()) { 4082 // Serial reference processing... 4083 rp->enqueue_discovered_references(NULL, pt); 4084 } else { 4085 // Parallel reference enqueueing 4086 4087 uint n_workers = workers()->active_workers(); 4088 4089 assert(n_workers <= rp->max_num_q(), 4090 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4091 n_workers, rp->max_num_q()); 4092 4093 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4094 rp->enqueue_discovered_references(&par_task_executor, pt); 4095 } 4096 4097 rp->verify_no_references_recorded(); 4098 assert(!rp->discovery_enabled(), "should have been disabled"); 4099 4100 // If during an initial mark pause we install a pending list head which is not otherwise reachable 4101 // ensure that it is marked in the bitmap for concurrent marking to discover. 4102 if (collector_state()->in_initial_mark_gc()) { 4103 oop pll_head = Universe::reference_pending_list(); 4104 if (pll_head != NULL) { 4105 // Any valid worker id is fine here as we are in the VM thread and single-threaded. 4106 _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head); 4107 } 4108 } 4109 4110 // FIXME 4111 // CM's reference processing also cleans up the string and symbol tables. 4112 // Should we do that here also? We could, but it is a serial operation 4113 // and could significantly increase the pause time. 4114 4115 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4116 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4117 } 4118 4119 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4120 double merge_pss_time_start = os::elapsedTime(); 4121 per_thread_states->flush(); 4122 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4123 } 4124 4125 void G1CollectedHeap::pre_evacuate_collection_set() { 4126 _expand_heap_after_alloc_failure = true; 4127 _evacuation_failed = false; 4128 4129 // Disable the hot card cache. 4130 _hot_card_cache->reset_hot_cache_claimed_index(); 4131 _hot_card_cache->set_use_cache(false); 4132 4133 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4134 _preserved_marks_set.assert_empty(); 4135 4136 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4137 4138 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4139 if (collector_state()->in_initial_mark_gc()) { 4140 double start_clear_claimed_marks = os::elapsedTime(); 4141 4142 ClassLoaderDataGraph::clear_claimed_marks(); 4143 4144 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4145 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4146 } 4147 } 4148 4149 void G1CollectedHeap::evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states) { 4150 // Should G1EvacuationFailureALot be in effect for this GC? 4151 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4152 4153 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4154 4155 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4156 4157 double start_par_time_sec = os::elapsedTime(); 4158 double end_par_time_sec; 4159 4160 { 4161 const uint n_workers = workers()->active_workers(); 4162 G1RootProcessor root_processor(this, n_workers); 4163 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4164 4165 print_termination_stats_hdr(); 4166 4167 workers()->run_task(&g1_par_task); 4168 end_par_time_sec = os::elapsedTime(); 4169 4170 // Closing the inner scope will execute the destructor 4171 // for the G1RootProcessor object. We record the current 4172 // elapsed time before closing the scope so that time 4173 // taken for the destructor is NOT included in the 4174 // reported parallel time. 4175 } 4176 4177 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4178 phase_times->record_par_time(par_time_ms); 4179 4180 double code_root_fixup_time_ms = 4181 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4182 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4183 } 4184 4185 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4186 // Process any discovered reference objects - we have 4187 // to do this _before_ we retire the GC alloc regions 4188 // as we may have to copy some 'reachable' referent 4189 // objects (and their reachable sub-graphs) that were 4190 // not copied during the pause. 4191 preserve_cm_referents(per_thread_states); 4192 process_discovered_references(per_thread_states); 4193 4194 G1STWIsAliveClosure is_alive(this); 4195 G1KeepAliveClosure keep_alive(this); 4196 4197 { 4198 double start = os::elapsedTime(); 4199 4200 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 4201 4202 double time_ms = (os::elapsedTime() - start) * 1000.0; 4203 g1_policy()->phase_times()->record_weak_ref_proc_time(time_ms); 4204 } 4205 4206 if (G1StringDedup::is_enabled()) { 4207 double fixup_start = os::elapsedTime(); 4208 4209 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4210 4211 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4212 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4213 } 4214 4215 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4216 4217 if (evacuation_failed()) { 4218 restore_after_evac_failure(); 4219 4220 // Reset the G1EvacuationFailureALot counters and flags 4221 // Note: the values are reset only when an actual 4222 // evacuation failure occurs. 4223 NOT_PRODUCT(reset_evacuation_should_fail();) 4224 } 4225 4226 _preserved_marks_set.assert_empty(); 4227 4228 // Enqueue any remaining references remaining on the STW 4229 // reference processor's discovered lists. We need to do 4230 // this after the card table is cleaned (and verified) as 4231 // the act of enqueueing entries on to the pending list 4232 // will log these updates (and dirty their associated 4233 // cards). We need these updates logged to update any 4234 // RSets. 4235 enqueue_discovered_references(per_thread_states); 4236 4237 _allocator->release_gc_alloc_regions(evacuation_info); 4238 4239 merge_per_thread_state_info(per_thread_states); 4240 4241 // Reset and re-enable the hot card cache. 4242 // Note the counts for the cards in the regions in the 4243 // collection set are reset when the collection set is freed. 4244 _hot_card_cache->reset_hot_cache(); 4245 _hot_card_cache->set_use_cache(true); 4246 4247 purge_code_root_memory(); 4248 4249 redirty_logged_cards(); 4250 #if COMPILER2_OR_JVMCI 4251 double start = os::elapsedTime(); 4252 DerivedPointerTable::update_pointers(); 4253 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4254 #endif 4255 g1_policy()->print_age_table(); 4256 } 4257 4258 void G1CollectedHeap::record_obj_copy_mem_stats() { 4259 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4260 4261 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4262 create_g1_evac_summary(&_old_evac_stats)); 4263 } 4264 4265 void G1CollectedHeap::free_region(HeapRegion* hr, 4266 FreeRegionList* free_list, 4267 bool skip_remset, 4268 bool skip_hot_card_cache, 4269 bool locked) { 4270 assert(!hr->is_free(), "the region should not be free"); 4271 assert(!hr->is_empty(), "the region should not be empty"); 4272 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4273 assert(free_list != NULL, "pre-condition"); 4274 4275 if (G1VerifyBitmaps) { 4276 MemRegion mr(hr->bottom(), hr->end()); 4277 concurrent_mark()->clear_range_in_prev_bitmap(mr); 4278 } 4279 4280 // Clear the card counts for this region. 4281 // Note: we only need to do this if the region is not young 4282 // (since we don't refine cards in young regions). 4283 if (!skip_hot_card_cache && !hr->is_young()) { 4284 _hot_card_cache->reset_card_counts(hr); 4285 } 4286 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4287 _g1_policy->remset_tracker()->update_at_free(hr); 4288 free_list->add_ordered(hr); 4289 } 4290 4291 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4292 FreeRegionList* free_list) { 4293 assert(hr->is_humongous(), "this is only for humongous regions"); 4294 assert(free_list != NULL, "pre-condition"); 4295 hr->clear_humongous(); 4296 free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */); 4297 } 4298 4299 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4300 const uint humongous_regions_removed) { 4301 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4302 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4303 _old_set.bulk_remove(old_regions_removed); 4304 _humongous_set.bulk_remove(humongous_regions_removed); 4305 } 4306 4307 } 4308 4309 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4310 assert(list != NULL, "list can't be null"); 4311 if (!list->is_empty()) { 4312 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4313 _hrm.insert_list_into_free_list(list); 4314 } 4315 } 4316 4317 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4318 decrease_used(bytes); 4319 } 4320 4321 class G1FreeCollectionSetTask : public AbstractGangTask { 4322 private: 4323 4324 // Closure applied to all regions in the collection set to do work that needs to 4325 // be done serially in a single thread. 4326 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4327 private: 4328 EvacuationInfo* _evacuation_info; 4329 const size_t* _surviving_young_words; 4330 4331 // Bytes used in successfully evacuated regions before the evacuation. 4332 size_t _before_used_bytes; 4333 // Bytes used in unsucessfully evacuated regions before the evacuation 4334 size_t _after_used_bytes; 4335 4336 size_t _bytes_allocated_in_old_since_last_gc; 4337 4338 size_t _failure_used_words; 4339 size_t _failure_waste_words; 4340 4341 FreeRegionList _local_free_list; 4342 public: 4343 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4344 HeapRegionClosure(), 4345 _evacuation_info(evacuation_info), 4346 _surviving_young_words(surviving_young_words), 4347 _before_used_bytes(0), 4348 _after_used_bytes(0), 4349 _bytes_allocated_in_old_since_last_gc(0), 4350 _failure_used_words(0), 4351 _failure_waste_words(0), 4352 _local_free_list("Local Region List for CSet Freeing") { 4353 } 4354 4355 virtual bool do_heap_region(HeapRegion* r) { 4356 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4357 4358 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4359 g1h->clear_in_cset(r); 4360 4361 if (r->is_young()) { 4362 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4363 "Young index %d is wrong for region %u of type %s with %u young regions", 4364 r->young_index_in_cset(), 4365 r->hrm_index(), 4366 r->get_type_str(), 4367 g1h->collection_set()->young_region_length()); 4368 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4369 r->record_surv_words_in_group(words_survived); 4370 } 4371 4372 if (!r->evacuation_failed()) { 4373 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4374 _before_used_bytes += r->used(); 4375 g1h->free_region(r, 4376 &_local_free_list, 4377 true, /* skip_remset */ 4378 true, /* skip_hot_card_cache */ 4379 true /* locked */); 4380 } else { 4381 r->uninstall_surv_rate_group(); 4382 r->set_young_index_in_cset(-1); 4383 r->set_evacuation_failed(false); 4384 // When moving a young gen region to old gen, we "allocate" that whole region 4385 // there. This is in addition to any already evacuated objects. Notify the 4386 // policy about that. 4387 // Old gen regions do not cause an additional allocation: both the objects 4388 // still in the region and the ones already moved are accounted for elsewhere. 4389 if (r->is_young()) { 4390 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4391 } 4392 // The region is now considered to be old. 4393 r->set_old(); 4394 // Do some allocation statistics accounting. Regions that failed evacuation 4395 // are always made old, so there is no need to update anything in the young 4396 // gen statistics, but we need to update old gen statistics. 4397 size_t used_words = r->marked_bytes() / HeapWordSize; 4398 4399 _failure_used_words += used_words; 4400 _failure_waste_words += HeapRegion::GrainWords - used_words; 4401 4402 g1h->old_set_add(r); 4403 _after_used_bytes += r->used(); 4404 } 4405 return false; 4406 } 4407 4408 void complete_work() { 4409 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4410 4411 _evacuation_info->set_regions_freed(_local_free_list.length()); 4412 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4413 4414 g1h->prepend_to_freelist(&_local_free_list); 4415 g1h->decrement_summary_bytes(_before_used_bytes); 4416 4417 G1Policy* policy = g1h->g1_policy(); 4418 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4419 4420 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4421 } 4422 }; 4423 4424 G1CollectionSet* _collection_set; 4425 G1SerialFreeCollectionSetClosure _cl; 4426 const size_t* _surviving_young_words; 4427 4428 size_t _rs_lengths; 4429 4430 volatile jint _serial_work_claim; 4431 4432 struct WorkItem { 4433 uint region_idx; 4434 bool is_young; 4435 bool evacuation_failed; 4436 4437 WorkItem(HeapRegion* r) { 4438 region_idx = r->hrm_index(); 4439 is_young = r->is_young(); 4440 evacuation_failed = r->evacuation_failed(); 4441 } 4442 }; 4443 4444 volatile size_t _parallel_work_claim; 4445 size_t _num_work_items; 4446 WorkItem* _work_items; 4447 4448 void do_serial_work() { 4449 // Need to grab the lock to be allowed to modify the old region list. 4450 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4451 _collection_set->iterate(&_cl); 4452 } 4453 4454 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4455 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4456 4457 HeapRegion* r = g1h->region_at(region_idx); 4458 assert(!g1h->is_on_master_free_list(r), "sanity"); 4459 4460 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4461 4462 if (!is_young) { 4463 g1h->_hot_card_cache->reset_card_counts(r); 4464 } 4465 4466 if (!evacuation_failed) { 4467 r->rem_set()->clear_locked(); 4468 } 4469 } 4470 4471 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4472 private: 4473 size_t _cur_idx; 4474 WorkItem* _work_items; 4475 public: 4476 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4477 4478 virtual bool do_heap_region(HeapRegion* r) { 4479 _work_items[_cur_idx++] = WorkItem(r); 4480 return false; 4481 } 4482 }; 4483 4484 void prepare_work() { 4485 G1PrepareFreeCollectionSetClosure cl(_work_items); 4486 _collection_set->iterate(&cl); 4487 } 4488 4489 void complete_work() { 4490 _cl.complete_work(); 4491 4492 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4493 policy->record_max_rs_lengths(_rs_lengths); 4494 policy->cset_regions_freed(); 4495 } 4496 public: 4497 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4498 AbstractGangTask("G1 Free Collection Set"), 4499 _cl(evacuation_info, surviving_young_words), 4500 _collection_set(collection_set), 4501 _surviving_young_words(surviving_young_words), 4502 _serial_work_claim(0), 4503 _rs_lengths(0), 4504 _parallel_work_claim(0), 4505 _num_work_items(collection_set->region_length()), 4506 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4507 prepare_work(); 4508 } 4509 4510 ~G1FreeCollectionSetTask() { 4511 complete_work(); 4512 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4513 } 4514 4515 // Chunk size for work distribution. The chosen value has been determined experimentally 4516 // to be a good tradeoff between overhead and achievable parallelism. 4517 static uint chunk_size() { return 32; } 4518 4519 virtual void work(uint worker_id) { 4520 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4521 4522 // Claim serial work. 4523 if (_serial_work_claim == 0) { 4524 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4525 if (value == 0) { 4526 double serial_time = os::elapsedTime(); 4527 do_serial_work(); 4528 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4529 } 4530 } 4531 4532 // Start parallel work. 4533 double young_time = 0.0; 4534 bool has_young_time = false; 4535 double non_young_time = 0.0; 4536 bool has_non_young_time = false; 4537 4538 while (true) { 4539 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4540 size_t cur = end - chunk_size(); 4541 4542 if (cur >= _num_work_items) { 4543 break; 4544 } 4545 4546 double start_time = os::elapsedTime(); 4547 4548 end = MIN2(end, _num_work_items); 4549 4550 for (; cur < end; cur++) { 4551 bool is_young = _work_items[cur].is_young; 4552 4553 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4554 4555 double end_time = os::elapsedTime(); 4556 double time_taken = end_time - start_time; 4557 if (is_young) { 4558 young_time += time_taken; 4559 has_young_time = true; 4560 } else { 4561 non_young_time += time_taken; 4562 has_non_young_time = true; 4563 } 4564 start_time = end_time; 4565 } 4566 } 4567 4568 if (has_young_time) { 4569 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4570 } 4571 if (has_non_young_time) { 4572 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time); 4573 } 4574 } 4575 }; 4576 4577 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4578 _eden.clear(); 4579 4580 double free_cset_start_time = os::elapsedTime(); 4581 4582 { 4583 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4584 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4585 4586 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4587 4588 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4589 cl.name(), 4590 num_workers, 4591 _collection_set.region_length()); 4592 workers()->run_task(&cl, num_workers); 4593 } 4594 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4595 4596 collection_set->clear(); 4597 } 4598 4599 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4600 private: 4601 FreeRegionList* _free_region_list; 4602 HeapRegionSet* _proxy_set; 4603 uint _humongous_objects_reclaimed; 4604 uint _humongous_regions_reclaimed; 4605 size_t _freed_bytes; 4606 public: 4607 4608 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4609 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4610 } 4611 4612 virtual bool do_heap_region(HeapRegion* r) { 4613 if (!r->is_starts_humongous()) { 4614 return false; 4615 } 4616 4617 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4618 4619 oop obj = (oop)r->bottom(); 4620 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap(); 4621 4622 // The following checks whether the humongous object is live are sufficient. 4623 // The main additional check (in addition to having a reference from the roots 4624 // or the young gen) is whether the humongous object has a remembered set entry. 4625 // 4626 // A humongous object cannot be live if there is no remembered set for it 4627 // because: 4628 // - there can be no references from within humongous starts regions referencing 4629 // the object because we never allocate other objects into them. 4630 // (I.e. there are no intra-region references that may be missed by the 4631 // remembered set) 4632 // - as soon there is a remembered set entry to the humongous starts region 4633 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4634 // until the end of a concurrent mark. 4635 // 4636 // It is not required to check whether the object has been found dead by marking 4637 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4638 // all objects allocated during that time are considered live. 4639 // SATB marking is even more conservative than the remembered set. 4640 // So if at this point in the collection there is no remembered set entry, 4641 // nobody has a reference to it. 4642 // At the start of collection we flush all refinement logs, and remembered sets 4643 // are completely up-to-date wrt to references to the humongous object. 4644 // 4645 // Other implementation considerations: 4646 // - never consider object arrays at this time because they would pose 4647 // considerable effort for cleaning up the the remembered sets. This is 4648 // required because stale remembered sets might reference locations that 4649 // are currently allocated into. 4650 uint region_idx = r->hrm_index(); 4651 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4652 !r->rem_set()->is_empty()) { 4653 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", 4654 region_idx, 4655 (size_t)obj->size() * HeapWordSize, 4656 p2i(r->bottom()), 4657 r->rem_set()->occupied(), 4658 r->rem_set()->strong_code_roots_list_length(), 4659 next_bitmap->is_marked(r->bottom()), 4660 g1h->is_humongous_reclaim_candidate(region_idx), 4661 obj->is_typeArray() 4662 ); 4663 return false; 4664 } 4665 4666 guarantee(obj->is_typeArray(), 4667 "Only eagerly reclaiming type arrays is supported, but the object " 4668 PTR_FORMAT " is not.", p2i(r->bottom())); 4669 4670 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", 4671 region_idx, 4672 (size_t)obj->size() * HeapWordSize, 4673 p2i(r->bottom()), 4674 r->rem_set()->occupied(), 4675 r->rem_set()->strong_code_roots_list_length(), 4676 next_bitmap->is_marked(r->bottom()), 4677 g1h->is_humongous_reclaim_candidate(region_idx), 4678 obj->is_typeArray() 4679 ); 4680 4681 G1ConcurrentMark* const cm = g1h->concurrent_mark(); 4682 cm->humongous_object_eagerly_reclaimed(r); 4683 assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj), 4684 "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s", 4685 region_idx, 4686 BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)), 4687 BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj))); 4688 _humongous_objects_reclaimed++; 4689 do { 4690 HeapRegion* next = g1h->next_region_in_humongous(r); 4691 _freed_bytes += r->used(); 4692 r->set_containing_set(NULL); 4693 _humongous_regions_reclaimed++; 4694 g1h->free_humongous_region(r, _free_region_list); 4695 r = next; 4696 } while (r != NULL); 4697 4698 return false; 4699 } 4700 4701 uint humongous_objects_reclaimed() { 4702 return _humongous_objects_reclaimed; 4703 } 4704 4705 uint humongous_regions_reclaimed() { 4706 return _humongous_regions_reclaimed; 4707 } 4708 4709 size_t bytes_freed() const { 4710 return _freed_bytes; 4711 } 4712 }; 4713 4714 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4715 assert_at_safepoint_on_vm_thread(); 4716 4717 if (!G1EagerReclaimHumongousObjects || 4718 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4719 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4720 return; 4721 } 4722 4723 double start_time = os::elapsedTime(); 4724 4725 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4726 4727 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4728 heap_region_iterate(&cl); 4729 4730 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4731 4732 G1HRPrinter* hrp = hr_printer(); 4733 if (hrp->is_active()) { 4734 FreeRegionListIterator iter(&local_cleanup_list); 4735 while (iter.more_available()) { 4736 HeapRegion* hr = iter.get_next(); 4737 hrp->cleanup(hr); 4738 } 4739 } 4740 4741 prepend_to_freelist(&local_cleanup_list); 4742 decrement_summary_bytes(cl.bytes_freed()); 4743 4744 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4745 cl.humongous_objects_reclaimed()); 4746 } 4747 4748 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4749 public: 4750 virtual bool do_heap_region(HeapRegion* r) { 4751 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4752 G1CollectedHeap::heap()->clear_in_cset(r); 4753 r->set_young_index_in_cset(-1); 4754 return false; 4755 } 4756 }; 4757 4758 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4759 G1AbandonCollectionSetClosure cl; 4760 collection_set->iterate(&cl); 4761 4762 collection_set->clear(); 4763 collection_set->stop_incremental_building(); 4764 } 4765 4766 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 4767 return _allocator->is_retained_old_region(hr); 4768 } 4769 4770 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 4771 _eden.add(hr); 4772 _g1_policy->set_region_eden(hr); 4773 } 4774 4775 #ifdef ASSERT 4776 4777 class NoYoungRegionsClosure: public HeapRegionClosure { 4778 private: 4779 bool _success; 4780 public: 4781 NoYoungRegionsClosure() : _success(true) { } 4782 bool do_heap_region(HeapRegion* r) { 4783 if (r->is_young()) { 4784 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 4785 p2i(r->bottom()), p2i(r->end())); 4786 _success = false; 4787 } 4788 return false; 4789 } 4790 bool success() { return _success; } 4791 }; 4792 4793 bool G1CollectedHeap::check_young_list_empty() { 4794 bool ret = (young_regions_count() == 0); 4795 4796 NoYoungRegionsClosure closure; 4797 heap_region_iterate(&closure); 4798 ret = ret && closure.success(); 4799 4800 return ret; 4801 } 4802 4803 #endif // ASSERT 4804 4805 class TearDownRegionSetsClosure : public HeapRegionClosure { 4806 private: 4807 HeapRegionSet *_old_set; 4808 4809 public: 4810 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 4811 4812 bool do_heap_region(HeapRegion* r) { 4813 if (r->is_old()) { 4814 _old_set->remove(r); 4815 } else if(r->is_young()) { 4816 r->uninstall_surv_rate_group(); 4817 } else { 4818 // We ignore free regions, we'll empty the free list afterwards. 4819 // We ignore humongous regions, we're not tearing down the 4820 // humongous regions set. 4821 assert(r->is_free() || r->is_humongous(), 4822 "it cannot be another type"); 4823 } 4824 return false; 4825 } 4826 4827 ~TearDownRegionSetsClosure() { 4828 assert(_old_set->is_empty(), "post-condition"); 4829 } 4830 }; 4831 4832 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 4833 assert_at_safepoint_on_vm_thread(); 4834 4835 if (!free_list_only) { 4836 TearDownRegionSetsClosure cl(&_old_set); 4837 heap_region_iterate(&cl); 4838 4839 // Note that emptying the _young_list is postponed and instead done as 4840 // the first step when rebuilding the regions sets again. The reason for 4841 // this is that during a full GC string deduplication needs to know if 4842 // a collected region was young or old when the full GC was initiated. 4843 } 4844 _hrm.remove_all_free_regions(); 4845 } 4846 4847 void G1CollectedHeap::increase_used(size_t bytes) { 4848 _summary_bytes_used += bytes; 4849 } 4850 4851 void G1CollectedHeap::decrease_used(size_t bytes) { 4852 assert(_summary_bytes_used >= bytes, 4853 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 4854 _summary_bytes_used, bytes); 4855 _summary_bytes_used -= bytes; 4856 } 4857 4858 void G1CollectedHeap::set_used(size_t bytes) { 4859 _summary_bytes_used = bytes; 4860 } 4861 4862 class RebuildRegionSetsClosure : public HeapRegionClosure { 4863 private: 4864 bool _free_list_only; 4865 HeapRegionSet* _old_set; 4866 HeapRegionManager* _hrm; 4867 size_t _total_used; 4868 4869 public: 4870 RebuildRegionSetsClosure(bool free_list_only, 4871 HeapRegionSet* old_set, HeapRegionManager* hrm) : 4872 _free_list_only(free_list_only), 4873 _old_set(old_set), _hrm(hrm), _total_used(0) { 4874 assert(_hrm->num_free_regions() == 0, "pre-condition"); 4875 if (!free_list_only) { 4876 assert(_old_set->is_empty(), "pre-condition"); 4877 } 4878 } 4879 4880 bool do_heap_region(HeapRegion* r) { 4881 // After full GC, no region should have a remembered set. 4882 r->rem_set()->clear(true); 4883 if (r->is_empty()) { 4884 // Add free regions to the free list 4885 r->set_free(); 4886 _hrm->insert_into_free_list(r); 4887 } else if (!_free_list_only) { 4888 4889 if (r->is_humongous()) { 4890 // We ignore humongous regions. We left the humongous set unchanged. 4891 } else { 4892 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 4893 // We now move all (non-humongous, non-old) regions to old gen, and register them as such. 4894 r->move_to_old(); 4895 _old_set->add(r); 4896 } 4897 _total_used += r->used(); 4898 } 4899 4900 return false; 4901 } 4902 4903 size_t total_used() { 4904 return _total_used; 4905 } 4906 }; 4907 4908 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 4909 assert_at_safepoint_on_vm_thread(); 4910 4911 if (!free_list_only) { 4912 _eden.clear(); 4913 _survivor.clear(); 4914 } 4915 4916 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 4917 heap_region_iterate(&cl); 4918 4919 if (!free_list_only) { 4920 set_used(cl.total_used()); 4921 if (_archive_allocator != NULL) { 4922 _archive_allocator->clear_used(); 4923 } 4924 } 4925 assert(used_unlocked() == recalculate_used(), 4926 "inconsistent used_unlocked(), " 4927 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 4928 used_unlocked(), recalculate_used()); 4929 } 4930 4931 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 4932 HeapRegion* hr = heap_region_containing(p); 4933 return hr->is_in(p); 4934 } 4935 4936 // Methods for the mutator alloc region 4937 4938 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 4939 bool force) { 4940 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4941 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 4942 if (force || should_allocate) { 4943 HeapRegion* new_alloc_region = new_region(word_size, 4944 false /* is_old */, 4945 false /* do_expand */); 4946 if (new_alloc_region != NULL) { 4947 set_region_short_lived_locked(new_alloc_region); 4948 _hr_printer.alloc(new_alloc_region, !should_allocate); 4949 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 4950 _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region); 4951 return new_alloc_region; 4952 } 4953 } 4954 return NULL; 4955 } 4956 4957 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 4958 size_t allocated_bytes) { 4959 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4960 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 4961 4962 collection_set()->add_eden_region(alloc_region); 4963 increase_used(allocated_bytes); 4964 _hr_printer.retire(alloc_region); 4965 // We update the eden sizes here, when the region is retired, 4966 // instead of when it's allocated, since this is the point that its 4967 // used space has been recored in _summary_bytes_used. 4968 g1mm()->update_eden_size(); 4969 } 4970 4971 // Methods for the GC alloc regions 4972 4973 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 4974 if (dest.is_old()) { 4975 return true; 4976 } else { 4977 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 4978 } 4979 } 4980 4981 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 4982 assert(FreeList_lock->owned_by_self(), "pre-condition"); 4983 4984 if (!has_more_regions(dest)) { 4985 return NULL; 4986 } 4987 4988 const bool is_survivor = dest.is_young(); 4989 4990 HeapRegion* new_alloc_region = new_region(word_size, 4991 !is_survivor, 4992 true /* do_expand */); 4993 if (new_alloc_region != NULL) { 4994 if (is_survivor) { 4995 new_alloc_region->set_survivor(); 4996 _survivor.add(new_alloc_region); 4997 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 4998 } else { 4999 new_alloc_region->set_old(); 5000 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5001 } 5002 _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region); 5003 _hr_printer.alloc(new_alloc_region); 5004 bool during_im = collector_state()->in_initial_mark_gc(); 5005 new_alloc_region->note_start_of_copying(during_im); 5006 return new_alloc_region; 5007 } 5008 return NULL; 5009 } 5010 5011 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5012 size_t allocated_bytes, 5013 InCSetState dest) { 5014 bool during_im = collector_state()->in_initial_mark_gc(); 5015 alloc_region->note_end_of_copying(during_im); 5016 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5017 if (dest.is_old()) { 5018 _old_set.add(alloc_region); 5019 } 5020 _hr_printer.retire(alloc_region); 5021 } 5022 5023 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5024 bool expanded = false; 5025 uint index = _hrm.find_highest_free(&expanded); 5026 5027 if (index != G1_NO_HRM_INDEX) { 5028 if (expanded) { 5029 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5030 HeapRegion::GrainWords * HeapWordSize); 5031 } 5032 _hrm.allocate_free_regions_starting_at(index, 1); 5033 return region_at(index); 5034 } 5035 return NULL; 5036 } 5037 5038 // Optimized nmethod scanning 5039 5040 class RegisterNMethodOopClosure: public OopClosure { 5041 G1CollectedHeap* _g1h; 5042 nmethod* _nm; 5043 5044 template <class T> void do_oop_work(T* p) { 5045 T heap_oop = RawAccess<>::oop_load(p); 5046 if (!CompressedOops::is_null(heap_oop)) { 5047 oop obj = CompressedOops::decode_not_null(heap_oop); 5048 HeapRegion* hr = _g1h->heap_region_containing(obj); 5049 assert(!hr->is_continues_humongous(), 5050 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5051 " starting at " HR_FORMAT, 5052 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5053 5054 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5055 hr->add_strong_code_root_locked(_nm); 5056 } 5057 } 5058 5059 public: 5060 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5061 _g1h(g1h), _nm(nm) {} 5062 5063 void do_oop(oop* p) { do_oop_work(p); } 5064 void do_oop(narrowOop* p) { do_oop_work(p); } 5065 }; 5066 5067 class UnregisterNMethodOopClosure: public OopClosure { 5068 G1CollectedHeap* _g1h; 5069 nmethod* _nm; 5070 5071 template <class T> void do_oop_work(T* p) { 5072 T heap_oop = RawAccess<>::oop_load(p); 5073 if (!CompressedOops::is_null(heap_oop)) { 5074 oop obj = CompressedOops::decode_not_null(heap_oop); 5075 HeapRegion* hr = _g1h->heap_region_containing(obj); 5076 assert(!hr->is_continues_humongous(), 5077 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5078 " starting at " HR_FORMAT, 5079 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5080 5081 hr->remove_strong_code_root(_nm); 5082 } 5083 } 5084 5085 public: 5086 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5087 _g1h(g1h), _nm(nm) {} 5088 5089 void do_oop(oop* p) { do_oop_work(p); } 5090 void do_oop(narrowOop* p) { do_oop_work(p); } 5091 }; 5092 5093 // Returns true if the reference points to an object that 5094 // can move in an incremental collection. 5095 bool G1CollectedHeap::is_scavengable(oop obj) { 5096 HeapRegion* hr = heap_region_containing(obj); 5097 return !hr->is_pinned(); 5098 } 5099 5100 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5101 guarantee(nm != NULL, "sanity"); 5102 RegisterNMethodOopClosure reg_cl(this, nm); 5103 nm->oops_do(®_cl); 5104 } 5105 5106 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5107 guarantee(nm != NULL, "sanity"); 5108 UnregisterNMethodOopClosure reg_cl(this, nm); 5109 nm->oops_do(®_cl, true); 5110 } 5111 5112 void G1CollectedHeap::purge_code_root_memory() { 5113 double purge_start = os::elapsedTime(); 5114 G1CodeRootSet::purge(); 5115 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5116 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5117 } 5118 5119 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5120 G1CollectedHeap* _g1h; 5121 5122 public: 5123 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5124 _g1h(g1h) {} 5125 5126 void do_code_blob(CodeBlob* cb) { 5127 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5128 if (nm == NULL) { 5129 return; 5130 } 5131 5132 if (ScavengeRootsInCode) { 5133 _g1h->register_nmethod(nm); 5134 } 5135 } 5136 }; 5137 5138 void G1CollectedHeap::rebuild_strong_code_roots() { 5139 RebuildStrongCodeRootClosure blob_cl(this); 5140 CodeCache::blobs_do(&blob_cl); 5141 } 5142 5143 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() { 5144 GrowableArray<GCMemoryManager*> memory_managers(2); 5145 memory_managers.append(&_memory_manager); 5146 memory_managers.append(&_full_gc_memory_manager); 5147 return memory_managers; 5148 } 5149 5150 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() { 5151 GrowableArray<MemoryPool*> memory_pools(3); 5152 memory_pools.append(_eden_pool); 5153 memory_pools.append(_survivor_pool); 5154 memory_pools.append(_old_pool); 5155 return memory_pools; 5156 }