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/bufferingOopClosure.hpp" 32 #include "gc/g1/g1Allocator.inline.hpp" 33 #include "gc/g1/g1BarrierSet.hpp" 34 #include "gc/g1/g1CollectedHeap.inline.hpp" 35 #include "gc/g1/g1CollectionSet.hpp" 36 #include "gc/g1/g1CollectorPolicy.hpp" 37 #include "gc/g1/g1CollectorState.hpp" 38 #include "gc/g1/g1ConcurrentRefine.hpp" 39 #include "gc/g1/g1ConcurrentRefineThread.hpp" 40 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp" 41 #include "gc/g1/g1EvacStats.inline.hpp" 42 #include "gc/g1/g1FullCollector.hpp" 43 #include "gc/g1/g1GCPhaseTimes.hpp" 44 #include "gc/g1/g1HeapSizingPolicy.hpp" 45 #include "gc/g1/g1HeapTransition.hpp" 46 #include "gc/g1/g1HeapVerifier.hpp" 47 #include "gc/g1/g1HotCardCache.hpp" 48 #include "gc/g1/g1MemoryPool.hpp" 49 #include "gc/g1/g1OopClosures.inline.hpp" 50 #include "gc/g1/g1ParScanThreadState.inline.hpp" 51 #include "gc/g1/g1Policy.hpp" 52 #include "gc/g1/g1RegionToSpaceMapper.hpp" 53 #include "gc/g1/g1RemSet.hpp" 54 #include "gc/g1/g1RootClosures.hpp" 55 #include "gc/g1/g1RootProcessor.hpp" 56 #include "gc/g1/g1StringDedup.hpp" 57 #include "gc/g1/g1ThreadLocalData.hpp" 58 #include "gc/g1/g1YCTypes.hpp" 59 #include "gc/g1/g1YoungRemSetSamplingThread.hpp" 60 #include "gc/g1/heapRegion.inline.hpp" 61 #include "gc/g1/heapRegionRemSet.hpp" 62 #include "gc/g1/heapRegionSet.inline.hpp" 63 #include "gc/g1/vm_operations_g1.hpp" 64 #include "gc/shared/adaptiveSizePolicy.hpp" 65 #include "gc/shared/gcHeapSummary.hpp" 66 #include "gc/shared/gcId.hpp" 67 #include "gc/shared/gcLocker.hpp" 68 #include "gc/shared/gcTimer.hpp" 69 #include "gc/shared/gcTrace.hpp" 70 #include "gc/shared/gcTraceTime.inline.hpp" 71 #include "gc/shared/generationSpec.hpp" 72 #include "gc/shared/isGCActiveMark.hpp" 73 #include "gc/shared/preservedMarks.inline.hpp" 74 #include "gc/shared/suspendibleThreadSet.hpp" 75 #include "gc/shared/referenceProcessor.inline.hpp" 76 #include "gc/shared/taskqueue.inline.hpp" 77 #include "gc/shared/weakProcessor.hpp" 78 #include "logging/log.hpp" 79 #include "memory/allocation.hpp" 80 #include "memory/iterator.hpp" 81 #include "memory/resourceArea.hpp" 82 #include "oops/access.inline.hpp" 83 #include "oops/compressedOops.inline.hpp" 84 #include "oops/oop.inline.hpp" 85 #include "prims/resolvedMethodTable.hpp" 86 #include "runtime/atomic.hpp" 87 #include "runtime/handles.inline.hpp" 88 #include "runtime/init.hpp" 89 #include "runtime/orderAccess.inline.hpp" 90 #include "runtime/threadSMR.hpp" 91 #include "runtime/vmThread.hpp" 92 #include "utilities/align.hpp" 93 #include "utilities/globalDefinitions.hpp" 94 #include "utilities/stack.inline.hpp" 95 96 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 97 98 // INVARIANTS/NOTES 99 // 100 // All allocation activity covered by the G1CollectedHeap interface is 101 // serialized by acquiring the HeapLock. This happens in mem_allocate 102 // and allocate_new_tlab, which are the "entry" points to the 103 // allocation code from the rest of the JVM. (Note that this does not 104 // apply to TLAB allocation, which is not part of this interface: it 105 // is done by clients of this interface.) 106 107 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 108 private: 109 size_t _num_dirtied; 110 G1CollectedHeap* _g1h; 111 G1CardTable* _g1_ct; 112 113 HeapRegion* region_for_card(jbyte* card_ptr) const { 114 return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr)); 115 } 116 117 bool will_become_free(HeapRegion* hr) const { 118 // A region will be freed by free_collection_set if the region is in the 119 // collection set and has not had an evacuation failure. 120 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 121 } 122 123 public: 124 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 125 _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { } 126 127 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 128 HeapRegion* hr = region_for_card(card_ptr); 129 130 // Should only dirty cards in regions that won't be freed. 131 if (!will_become_free(hr)) { 132 *card_ptr = G1CardTable::dirty_card_val(); 133 _num_dirtied++; 134 } 135 136 return true; 137 } 138 139 size_t num_dirtied() const { return _num_dirtied; } 140 }; 141 142 143 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 144 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 145 } 146 147 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 148 // The from card cache is not the memory that is actually committed. So we cannot 149 // take advantage of the zero_filled parameter. 150 reset_from_card_cache(start_idx, num_regions); 151 } 152 153 154 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 155 MemRegion mr) { 156 return new HeapRegion(hrs_index, bot(), mr); 157 } 158 159 // Private methods. 160 161 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 162 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 163 "the only time we use this to allocate a humongous region is " 164 "when we are allocating a single humongous region"); 165 166 HeapRegion* res = _hrm.allocate_free_region(is_old); 167 168 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 169 // Currently, only attempts to allocate GC alloc regions set 170 // do_expand to true. So, we should only reach here during a 171 // safepoint. If this assumption changes we might have to 172 // reconsider the use of _expand_heap_after_alloc_failure. 173 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 174 175 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 176 word_size * HeapWordSize); 177 178 if (expand(word_size * HeapWordSize)) { 179 // Given that expand() succeeded in expanding the heap, and we 180 // always expand the heap by an amount aligned to the heap 181 // region size, the free list should in theory not be empty. 182 // In either case allocate_free_region() will check for NULL. 183 res = _hrm.allocate_free_region(is_old); 184 } else { 185 _expand_heap_after_alloc_failure = false; 186 } 187 } 188 return res; 189 } 190 191 HeapWord* 192 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 193 uint num_regions, 194 size_t word_size) { 195 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 196 assert(is_humongous(word_size), "word_size should be humongous"); 197 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 198 199 // Index of last region in the series. 200 uint last = first + num_regions - 1; 201 202 // We need to initialize the region(s) we just discovered. This is 203 // a bit tricky given that it can happen concurrently with 204 // refinement threads refining cards on these regions and 205 // potentially wanting to refine the BOT as they are scanning 206 // those cards (this can happen shortly after a cleanup; see CR 207 // 6991377). So we have to set up the region(s) carefully and in 208 // a specific order. 209 210 // The word size sum of all the regions we will allocate. 211 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 212 assert(word_size <= word_size_sum, "sanity"); 213 214 // This will be the "starts humongous" region. 215 HeapRegion* first_hr = region_at(first); 216 // The header of the new object will be placed at the bottom of 217 // the first region. 218 HeapWord* new_obj = first_hr->bottom(); 219 // This will be the new top of the new object. 220 HeapWord* obj_top = new_obj + word_size; 221 222 // First, we need to zero the header of the space that we will be 223 // allocating. When we update top further down, some refinement 224 // threads might try to scan the region. By zeroing the header we 225 // ensure that any thread that will try to scan the region will 226 // come across the zero klass word and bail out. 227 // 228 // NOTE: It would not have been correct to have used 229 // CollectedHeap::fill_with_object() and make the space look like 230 // an int array. The thread that is doing the allocation will 231 // later update the object header to a potentially different array 232 // type and, for a very short period of time, the klass and length 233 // fields will be inconsistent. This could cause a refinement 234 // thread to calculate the object size incorrectly. 235 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 236 237 // Next, pad out the unused tail of the last region with filler 238 // objects, for improved usage accounting. 239 // How many words we use for filler objects. 240 size_t word_fill_size = word_size_sum - word_size; 241 242 // How many words memory we "waste" which cannot hold a filler object. 243 size_t words_not_fillable = 0; 244 245 if (word_fill_size >= min_fill_size()) { 246 fill_with_objects(obj_top, word_fill_size); 247 } else if (word_fill_size > 0) { 248 // We have space to fill, but we cannot fit an object there. 249 words_not_fillable = word_fill_size; 250 word_fill_size = 0; 251 } 252 253 // We will set up the first region as "starts humongous". This 254 // will also update the BOT covering all the regions to reflect 255 // that there is a single object that starts at the bottom of the 256 // first region. 257 first_hr->set_starts_humongous(obj_top, word_fill_size); 258 _g1_policy->remset_tracker()->update_at_allocate(first_hr); 259 // Then, if there are any, we will set up the "continues 260 // humongous" regions. 261 HeapRegion* hr = NULL; 262 for (uint i = first + 1; i <= last; ++i) { 263 hr = region_at(i); 264 hr->set_continues_humongous(first_hr); 265 _g1_policy->remset_tracker()->update_at_allocate(hr); 266 } 267 268 // Up to this point no concurrent thread would have been able to 269 // do any scanning on any region in this series. All the top 270 // fields still point to bottom, so the intersection between 271 // [bottom,top] and [card_start,card_end] will be empty. Before we 272 // update the top fields, we'll do a storestore to make sure that 273 // no thread sees the update to top before the zeroing of the 274 // object header and the BOT initialization. 275 OrderAccess::storestore(); 276 277 // Now, we will update the top fields of the "continues humongous" 278 // regions except the last one. 279 for (uint i = first; i < last; ++i) { 280 hr = region_at(i); 281 hr->set_top(hr->end()); 282 } 283 284 hr = region_at(last); 285 // If we cannot fit a filler object, we must set top to the end 286 // of the humongous object, otherwise we cannot iterate the heap 287 // and the BOT will not be complete. 288 hr->set_top(hr->end() - words_not_fillable); 289 290 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 291 "obj_top should be in last region"); 292 293 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 294 295 assert(words_not_fillable == 0 || 296 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 297 "Miscalculation in humongous allocation"); 298 299 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 300 301 for (uint i = first; i <= last; ++i) { 302 hr = region_at(i); 303 _humongous_set.add(hr); 304 _hr_printer.alloc(hr); 305 } 306 307 return new_obj; 308 } 309 310 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 311 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 312 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 313 } 314 315 // If could fit into free regions w/o expansion, try. 316 // Otherwise, if can expand, do so. 317 // Otherwise, if using ex regions might help, try with ex given back. 318 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) { 319 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 320 321 _verifier->verify_region_sets_optional(); 322 323 uint first = G1_NO_HRM_INDEX; 324 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 325 326 if (obj_regions == 1) { 327 // Only one region to allocate, try to use a fast path by directly allocating 328 // from the free lists. Do not try to expand here, we will potentially do that 329 // later. 330 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 331 if (hr != NULL) { 332 first = hr->hrm_index(); 333 } 334 } else { 335 // Policy: Try only empty regions (i.e. already committed first). Maybe we 336 // are lucky enough to find some. 337 first = _hrm.find_contiguous_only_empty(obj_regions); 338 if (first != G1_NO_HRM_INDEX) { 339 _hrm.allocate_free_regions_starting_at(first, obj_regions); 340 } 341 } 342 343 if (first == G1_NO_HRM_INDEX) { 344 // Policy: We could not find enough regions for the humongous object in the 345 // free list. Look through the heap to find a mix of free and uncommitted regions. 346 // If so, try expansion. 347 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 348 if (first != G1_NO_HRM_INDEX) { 349 // We found something. Make sure these regions are committed, i.e. expand 350 // the heap. Alternatively we could do a defragmentation GC. 351 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 352 word_size * HeapWordSize); 353 354 _hrm.expand_at(first, obj_regions, workers()); 355 g1_policy()->record_new_heap_size(num_regions()); 356 357 #ifdef ASSERT 358 for (uint i = first; i < first + obj_regions; ++i) { 359 HeapRegion* hr = region_at(i); 360 assert(hr->is_free(), "sanity"); 361 assert(hr->is_empty(), "sanity"); 362 assert(is_on_master_free_list(hr), "sanity"); 363 } 364 #endif 365 _hrm.allocate_free_regions_starting_at(first, obj_regions); 366 } else { 367 // Policy: Potentially trigger a defragmentation GC. 368 } 369 } 370 371 HeapWord* result = NULL; 372 if (first != G1_NO_HRM_INDEX) { 373 result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size); 374 assert(result != NULL, "it should always return a valid result"); 375 376 // A successful humongous object allocation changes the used space 377 // information of the old generation so we need to recalculate the 378 // sizes and update the jstat counters here. 379 g1mm()->update_sizes(); 380 } 381 382 _verifier->verify_region_sets_optional(); 383 384 return result; 385 } 386 387 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 388 assert_heap_not_locked_and_not_at_safepoint(); 389 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 390 391 return attempt_allocation(word_size); 392 } 393 394 HeapWord* 395 G1CollectedHeap::mem_allocate(size_t word_size, 396 bool* gc_overhead_limit_was_exceeded) { 397 assert_heap_not_locked_and_not_at_safepoint(); 398 399 if (is_humongous(word_size)) { 400 return attempt_allocation_humongous(word_size); 401 } 402 return attempt_allocation(word_size); 403 } 404 405 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) { 406 ResourceMark rm; // For retrieving the thread names in log messages. 407 408 // Make sure you read the note in attempt_allocation_humongous(). 409 410 assert_heap_not_locked_and_not_at_safepoint(); 411 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 412 "be called for humongous allocation requests"); 413 414 // We should only get here after the first-level allocation attempt 415 // (attempt_allocation()) failed to allocate. 416 417 // We will loop until a) we manage to successfully perform the 418 // allocation or b) we successfully schedule a collection which 419 // fails to perform the allocation. b) is the only case when we'll 420 // return NULL. 421 HeapWord* result = NULL; 422 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 423 bool should_try_gc; 424 uint gc_count_before; 425 426 { 427 MutexLockerEx x(Heap_lock); 428 result = _allocator->attempt_allocation_locked(word_size); 429 if (result != NULL) { 430 return result; 431 } 432 433 // If the GCLocker is active and we are bound for a GC, try expanding young gen. 434 // This is different to when only GCLocker::needs_gc() is set: try to avoid 435 // waiting because the GCLocker is active to not wait too long. 436 if (GCLocker::is_active_and_needs_gc() && g1_policy()->can_expand_young_list()) { 437 // No need for an ergo message here, can_expand_young_list() does this when 438 // it returns true. 439 result = _allocator->attempt_allocation_force(word_size); 440 if (result != NULL) { 441 return result; 442 } 443 } 444 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 445 // the GCLocker initiated GC has been performed and then retry. This includes 446 // the case when the GC Locker is not active but has not been performed. 447 should_try_gc = !GCLocker::needs_gc(); 448 // Read the GC count while still holding the Heap_lock. 449 gc_count_before = total_collections(); 450 } 451 452 if (should_try_gc) { 453 bool succeeded; 454 result = do_collection_pause(word_size, gc_count_before, &succeeded, 455 GCCause::_g1_inc_collection_pause); 456 if (result != NULL) { 457 assert(succeeded, "only way to get back a non-NULL result"); 458 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 459 Thread::current()->name(), p2i(result)); 460 return result; 461 } 462 463 if (succeeded) { 464 // We successfully scheduled a collection which failed to allocate. No 465 // point in trying to allocate further. We'll just return NULL. 466 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 467 SIZE_FORMAT " words", Thread::current()->name(), word_size); 468 return NULL; 469 } 470 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words", 471 Thread::current()->name(), word_size); 472 } else { 473 // Failed to schedule a collection. 474 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 475 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 476 SIZE_FORMAT " words", Thread::current()->name(), word_size); 477 return NULL; 478 } 479 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 480 // The GCLocker is either active or the GCLocker initiated 481 // GC has not yet been performed. Stall until it is and 482 // then retry the allocation. 483 GCLocker::stall_until_clear(); 484 gclocker_retry_count += 1; 485 } 486 487 // We can reach here if we were unsuccessful in scheduling a 488 // collection (because another thread beat us to it) or if we were 489 // stalled due to the GC locker. In either can we should retry the 490 // allocation attempt in case another thread successfully 491 // performed a collection and reclaimed enough space. We do the 492 // first attempt (without holding the Heap_lock) here and the 493 // follow-on attempt will be at the start of the next loop 494 // iteration (after taking the Heap_lock). 495 496 result = _allocator->attempt_allocation(word_size); 497 if (result != NULL) { 498 return result; 499 } 500 501 // Give a warning if we seem to be looping forever. 502 if ((QueuedAllocationWarningCount > 0) && 503 (try_count % QueuedAllocationWarningCount == 0)) { 504 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 505 Thread::current()->name(), try_count, word_size); 506 } 507 } 508 509 ShouldNotReachHere(); 510 return NULL; 511 } 512 513 void G1CollectedHeap::begin_archive_alloc_range(bool open) { 514 assert_at_safepoint_on_vm_thread(); 515 if (_archive_allocator == NULL) { 516 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open); 517 } 518 } 519 520 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 521 // Allocations in archive regions cannot be of a size that would be considered 522 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 523 // may be different at archive-restore time. 524 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 525 } 526 527 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 528 assert_at_safepoint_on_vm_thread(); 529 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 530 if (is_archive_alloc_too_large(word_size)) { 531 return NULL; 532 } 533 return _archive_allocator->archive_mem_allocate(word_size); 534 } 535 536 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 537 size_t end_alignment_in_bytes) { 538 assert_at_safepoint_on_vm_thread(); 539 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 540 541 // Call complete_archive to do the real work, filling in the MemRegion 542 // array with the archive regions. 543 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 544 delete _archive_allocator; 545 _archive_allocator = NULL; 546 } 547 548 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 549 assert(ranges != NULL, "MemRegion array NULL"); 550 assert(count != 0, "No MemRegions provided"); 551 MemRegion reserved = _hrm.reserved(); 552 for (size_t i = 0; i < count; i++) { 553 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 554 return false; 555 } 556 } 557 return true; 558 } 559 560 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, 561 size_t count, 562 bool open) { 563 assert(!is_init_completed(), "Expect to be called at JVM init time"); 564 assert(ranges != NULL, "MemRegion array NULL"); 565 assert(count != 0, "No MemRegions provided"); 566 MutexLockerEx x(Heap_lock); 567 568 MemRegion reserved = _hrm.reserved(); 569 HeapWord* prev_last_addr = NULL; 570 HeapRegion* prev_last_region = NULL; 571 572 // Temporarily disable pretouching of heap pages. This interface is used 573 // when mmap'ing archived heap data in, so pre-touching is wasted. 574 FlagSetting fs(AlwaysPreTouch, false); 575 576 // Enable archive object checking used by G1MarkSweep. We have to let it know 577 // about each archive range, so that objects in those ranges aren't marked. 578 G1ArchiveAllocator::enable_archive_object_check(); 579 580 // For each specified MemRegion range, allocate the corresponding G1 581 // regions and mark them as archive regions. We expect the ranges 582 // in ascending starting address order, without overlap. 583 for (size_t i = 0; i < count; i++) { 584 MemRegion curr_range = ranges[i]; 585 HeapWord* start_address = curr_range.start(); 586 size_t word_size = curr_range.word_size(); 587 HeapWord* last_address = curr_range.last(); 588 size_t commits = 0; 589 590 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 591 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 592 p2i(start_address), p2i(last_address)); 593 guarantee(start_address > prev_last_addr, 594 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 595 p2i(start_address), p2i(prev_last_addr)); 596 prev_last_addr = last_address; 597 598 // Check for ranges that start in the same G1 region in which the previous 599 // range ended, and adjust the start address so we don't try to allocate 600 // the same region again. If the current range is entirely within that 601 // region, skip it, just adjusting the recorded top. 602 HeapRegion* start_region = _hrm.addr_to_region(start_address); 603 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 604 start_address = start_region->end(); 605 if (start_address > last_address) { 606 increase_used(word_size * HeapWordSize); 607 start_region->set_top(last_address + 1); 608 continue; 609 } 610 start_region->set_top(start_address); 611 curr_range = MemRegion(start_address, last_address + 1); 612 start_region = _hrm.addr_to_region(start_address); 613 } 614 615 // Perform the actual region allocation, exiting if it fails. 616 // Then note how much new space we have allocated. 617 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 618 return false; 619 } 620 increase_used(word_size * HeapWordSize); 621 if (commits != 0) { 622 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 623 HeapRegion::GrainWords * HeapWordSize * commits); 624 625 } 626 627 // Mark each G1 region touched by the range as archive, add it to 628 // the old set, and set top. 629 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 630 HeapRegion* last_region = _hrm.addr_to_region(last_address); 631 prev_last_region = last_region; 632 633 while (curr_region != NULL) { 634 assert(curr_region->is_empty() && !curr_region->is_pinned(), 635 "Region already in use (index %u)", curr_region->hrm_index()); 636 if (open) { 637 curr_region->set_open_archive(); 638 } else { 639 curr_region->set_closed_archive(); 640 } 641 _hr_printer.alloc(curr_region); 642 _old_set.add(curr_region); 643 HeapWord* top; 644 HeapRegion* next_region; 645 if (curr_region != last_region) { 646 top = curr_region->end(); 647 next_region = _hrm.next_region_in_heap(curr_region); 648 } else { 649 top = last_address + 1; 650 next_region = NULL; 651 } 652 curr_region->set_top(top); 653 curr_region->set_first_dead(top); 654 curr_region->set_end_of_live(top); 655 curr_region = next_region; 656 } 657 658 // Notify mark-sweep of the archive 659 G1ArchiveAllocator::set_range_archive(curr_range, open); 660 } 661 return true; 662 } 663 664 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 665 assert(!is_init_completed(), "Expect to be called at JVM init time"); 666 assert(ranges != NULL, "MemRegion array NULL"); 667 assert(count != 0, "No MemRegions provided"); 668 MemRegion reserved = _hrm.reserved(); 669 HeapWord *prev_last_addr = NULL; 670 HeapRegion* prev_last_region = NULL; 671 672 // For each MemRegion, create filler objects, if needed, in the G1 regions 673 // that contain the address range. The address range actually within the 674 // MemRegion will not be modified. That is assumed to have been initialized 675 // elsewhere, probably via an mmap of archived heap data. 676 MutexLockerEx x(Heap_lock); 677 for (size_t i = 0; i < count; i++) { 678 HeapWord* start_address = ranges[i].start(); 679 HeapWord* last_address = ranges[i].last(); 680 681 assert(reserved.contains(start_address) && reserved.contains(last_address), 682 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 683 p2i(start_address), p2i(last_address)); 684 assert(start_address > prev_last_addr, 685 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 686 p2i(start_address), p2i(prev_last_addr)); 687 688 HeapRegion* start_region = _hrm.addr_to_region(start_address); 689 HeapRegion* last_region = _hrm.addr_to_region(last_address); 690 HeapWord* bottom_address = start_region->bottom(); 691 692 // Check for a range beginning in the same region in which the 693 // previous one ended. 694 if (start_region == prev_last_region) { 695 bottom_address = prev_last_addr + 1; 696 } 697 698 // Verify that the regions were all marked as archive regions by 699 // alloc_archive_regions. 700 HeapRegion* curr_region = start_region; 701 while (curr_region != NULL) { 702 guarantee(curr_region->is_archive(), 703 "Expected archive region at index %u", curr_region->hrm_index()); 704 if (curr_region != last_region) { 705 curr_region = _hrm.next_region_in_heap(curr_region); 706 } else { 707 curr_region = NULL; 708 } 709 } 710 711 prev_last_addr = last_address; 712 prev_last_region = last_region; 713 714 // Fill the memory below the allocated range with dummy object(s), 715 // if the region bottom does not match the range start, or if the previous 716 // range ended within the same G1 region, and there is a gap. 717 if (start_address != bottom_address) { 718 size_t fill_size = pointer_delta(start_address, bottom_address); 719 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 720 increase_used(fill_size * HeapWordSize); 721 } 722 } 723 } 724 725 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size) { 726 assert_heap_not_locked_and_not_at_safepoint(); 727 assert(!is_humongous(word_size), "attempt_allocation() should not " 728 "be called for humongous allocation requests"); 729 730 HeapWord* result = _allocator->attempt_allocation(word_size); 731 732 if (result == NULL) { 733 result = attempt_allocation_slow(word_size); 734 } 735 assert_heap_not_locked(); 736 if (result != NULL) { 737 dirty_young_block(result, word_size); 738 } 739 return result; 740 } 741 742 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 743 assert(!is_init_completed(), "Expect to be called at JVM init time"); 744 assert(ranges != NULL, "MemRegion array NULL"); 745 assert(count != 0, "No MemRegions provided"); 746 MemRegion reserved = _hrm.reserved(); 747 HeapWord* prev_last_addr = NULL; 748 HeapRegion* prev_last_region = NULL; 749 size_t size_used = 0; 750 size_t uncommitted_regions = 0; 751 752 // For each Memregion, free the G1 regions that constitute it, and 753 // notify mark-sweep that the range is no longer to be considered 'archive.' 754 MutexLockerEx x(Heap_lock); 755 for (size_t i = 0; i < count; i++) { 756 HeapWord* start_address = ranges[i].start(); 757 HeapWord* last_address = ranges[i].last(); 758 759 assert(reserved.contains(start_address) && reserved.contains(last_address), 760 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 761 p2i(start_address), p2i(last_address)); 762 assert(start_address > prev_last_addr, 763 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 764 p2i(start_address), p2i(prev_last_addr)); 765 size_used += ranges[i].byte_size(); 766 prev_last_addr = last_address; 767 768 HeapRegion* start_region = _hrm.addr_to_region(start_address); 769 HeapRegion* last_region = _hrm.addr_to_region(last_address); 770 771 // Check for ranges that start in the same G1 region in which the previous 772 // range ended, and adjust the start address so we don't try to free 773 // the same region again. If the current range is entirely within that 774 // region, skip it. 775 if (start_region == prev_last_region) { 776 start_address = start_region->end(); 777 if (start_address > last_address) { 778 continue; 779 } 780 start_region = _hrm.addr_to_region(start_address); 781 } 782 prev_last_region = last_region; 783 784 // After verifying that each region was marked as an archive region by 785 // alloc_archive_regions, set it free and empty and uncommit it. 786 HeapRegion* curr_region = start_region; 787 while (curr_region != NULL) { 788 guarantee(curr_region->is_archive(), 789 "Expected archive region at index %u", curr_region->hrm_index()); 790 uint curr_index = curr_region->hrm_index(); 791 _old_set.remove(curr_region); 792 curr_region->set_free(); 793 curr_region->set_top(curr_region->bottom()); 794 if (curr_region != last_region) { 795 curr_region = _hrm.next_region_in_heap(curr_region); 796 } else { 797 curr_region = NULL; 798 } 799 _hrm.shrink_at(curr_index, 1); 800 uncommitted_regions++; 801 } 802 803 // Notify mark-sweep that this is no longer an archive range. 804 G1ArchiveAllocator::set_range_archive(ranges[i], false); 805 } 806 807 if (uncommitted_regions != 0) { 808 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 809 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 810 } 811 decrease_used(size_used); 812 } 813 814 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) { 815 ResourceMark rm; // For retrieving the thread names in log messages. 816 817 // The structure of this method has a lot of similarities to 818 // attempt_allocation_slow(). The reason these two were not merged 819 // into a single one is that such a method would require several "if 820 // allocation is not humongous do this, otherwise do that" 821 // conditional paths which would obscure its flow. In fact, an early 822 // version of this code did use a unified method which was harder to 823 // follow and, as a result, it had subtle bugs that were hard to 824 // track down. So keeping these two methods separate allows each to 825 // be more readable. It will be good to keep these two in sync as 826 // much as possible. 827 828 assert_heap_not_locked_and_not_at_safepoint(); 829 assert(is_humongous(word_size), "attempt_allocation_humongous() " 830 "should only be called for humongous allocations"); 831 832 // Humongous objects can exhaust the heap quickly, so we should check if we 833 // need to start a marking cycle at each humongous object allocation. We do 834 // the check before we do the actual allocation. The reason for doing it 835 // before the allocation is that we avoid having to keep track of the newly 836 // allocated memory while we do a GC. 837 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 838 word_size)) { 839 collect(GCCause::_g1_humongous_allocation); 840 } 841 842 // We will loop until a) we manage to successfully perform the 843 // allocation or b) we successfully schedule a collection which 844 // fails to perform the allocation. b) is the only case when we'll 845 // return NULL. 846 HeapWord* result = NULL; 847 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 848 bool should_try_gc; 849 uint gc_count_before; 850 851 852 { 853 MutexLockerEx x(Heap_lock); 854 855 // Given that humongous objects are not allocated in young 856 // regions, we'll first try to do the allocation without doing a 857 // collection hoping that there's enough space in the heap. 858 result = humongous_obj_allocate(word_size); 859 if (result != NULL) { 860 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 861 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 862 return result; 863 } 864 865 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 866 // the GCLocker initiated GC has been performed and then retry. This includes 867 // the case when the GC Locker is not active but has not been performed. 868 should_try_gc = !GCLocker::needs_gc(); 869 // Read the GC count while still holding the Heap_lock. 870 gc_count_before = total_collections(); 871 } 872 873 if (should_try_gc) { 874 bool succeeded; 875 result = do_collection_pause(word_size, gc_count_before, &succeeded, 876 GCCause::_g1_humongous_allocation); 877 if (result != NULL) { 878 assert(succeeded, "only way to get back a non-NULL result"); 879 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 880 Thread::current()->name(), p2i(result)); 881 return result; 882 } 883 884 if (succeeded) { 885 // We successfully scheduled a collection which failed to allocate. No 886 // point in trying to allocate further. We'll just return NULL. 887 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 888 SIZE_FORMAT " words", Thread::current()->name(), word_size); 889 return NULL; 890 } 891 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "", 892 Thread::current()->name(), word_size); 893 } else { 894 // Failed to schedule a collection. 895 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 896 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 897 SIZE_FORMAT " words", Thread::current()->name(), word_size); 898 return NULL; 899 } 900 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 901 // The GCLocker is either active or the GCLocker initiated 902 // GC has not yet been performed. Stall until it is and 903 // then retry the allocation. 904 GCLocker::stall_until_clear(); 905 gclocker_retry_count += 1; 906 } 907 908 909 // We can reach here if we were unsuccessful in scheduling a 910 // collection (because another thread beat us to it) or if we were 911 // stalled due to the GC locker. In either can we should retry the 912 // allocation attempt in case another thread successfully 913 // performed a collection and reclaimed enough space. 914 // Humongous object allocation always needs a lock, so we wait for the retry 915 // in the next iteration of the loop, unlike for the regular iteration case. 916 // Give a warning if we seem to be looping forever. 917 918 if ((QueuedAllocationWarningCount > 0) && 919 (try_count % QueuedAllocationWarningCount == 0)) { 920 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 921 Thread::current()->name(), try_count, word_size); 922 } 923 } 924 925 ShouldNotReachHere(); 926 return NULL; 927 } 928 929 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 930 bool expect_null_mutator_alloc_region) { 931 assert_at_safepoint_on_vm_thread(); 932 assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region, 933 "the current alloc region was unexpectedly found to be non-NULL"); 934 935 if (!is_humongous(word_size)) { 936 return _allocator->attempt_allocation_locked(word_size); 937 } else { 938 HeapWord* result = humongous_obj_allocate(word_size); 939 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 940 collector_state()->set_initiate_conc_mark_if_possible(true); 941 } 942 return result; 943 } 944 945 ShouldNotReachHere(); 946 } 947 948 class PostCompactionPrinterClosure: public HeapRegionClosure { 949 private: 950 G1HRPrinter* _hr_printer; 951 public: 952 bool do_heap_region(HeapRegion* hr) { 953 assert(!hr->is_young(), "not expecting to find young regions"); 954 _hr_printer->post_compaction(hr); 955 return false; 956 } 957 958 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 959 : _hr_printer(hr_printer) { } 960 }; 961 962 void G1CollectedHeap::print_hrm_post_compaction() { 963 if (_hr_printer.is_active()) { 964 PostCompactionPrinterClosure cl(hr_printer()); 965 heap_region_iterate(&cl); 966 } 967 } 968 969 void G1CollectedHeap::abort_concurrent_cycle() { 970 // If we start the compaction before the CM threads finish 971 // scanning the root regions we might trip them over as we'll 972 // be moving objects / updating references. So let's wait until 973 // they are done. By telling them to abort, they should complete 974 // early. 975 _cm->root_regions()->abort(); 976 _cm->root_regions()->wait_until_scan_finished(); 977 978 // Disable discovery and empty the discovered lists 979 // for the CM ref processor. 980 ref_processor_cm()->disable_discovery(); 981 ref_processor_cm()->abandon_partial_discovery(); 982 ref_processor_cm()->verify_no_references_recorded(); 983 984 // Abandon current iterations of concurrent marking and concurrent 985 // refinement, if any are in progress. 986 concurrent_mark()->concurrent_cycle_abort(); 987 } 988 989 void G1CollectedHeap::prepare_heap_for_full_collection() { 990 // Make sure we'll choose a new allocation region afterwards. 991 _allocator->release_mutator_alloc_region(); 992 _allocator->abandon_gc_alloc_regions(); 993 g1_rem_set()->cleanupHRRS(); 994 995 // We may have added regions to the current incremental collection 996 // set between the last GC or pause and now. We need to clear the 997 // incremental collection set and then start rebuilding it afresh 998 // after this full GC. 999 abandon_collection_set(collection_set()); 1000 1001 tear_down_region_sets(false /* free_list_only */); 1002 } 1003 1004 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1005 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1006 assert(used() == recalculate_used(), "Should be equal"); 1007 _verifier->verify_region_sets_optional(); 1008 _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull); 1009 _verifier->check_bitmaps("Full GC Start"); 1010 } 1011 1012 void G1CollectedHeap::prepare_heap_for_mutators() { 1013 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1014 ClassLoaderDataGraph::purge(); 1015 MetaspaceUtils::verify_metrics(); 1016 1017 // Prepare heap for normal collections. 1018 assert(num_free_regions() == 0, "we should not have added any free regions"); 1019 rebuild_region_sets(false /* free_list_only */); 1020 abort_refinement(); 1021 resize_if_necessary_after_full_collection(); 1022 1023 // Rebuild the strong code root lists for each region 1024 rebuild_strong_code_roots(); 1025 1026 // Start a new incremental collection set for the next pause 1027 start_new_collection_set(); 1028 1029 _allocator->init_mutator_alloc_region(); 1030 1031 // Post collection state updates. 1032 MetaspaceGC::compute_new_size(); 1033 } 1034 1035 void G1CollectedHeap::abort_refinement() { 1036 if (_hot_card_cache->use_cache()) { 1037 _hot_card_cache->reset_hot_cache(); 1038 } 1039 1040 // Discard all remembered set updates. 1041 G1BarrierSet::dirty_card_queue_set().abandon_logs(); 1042 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1043 } 1044 1045 void G1CollectedHeap::verify_after_full_collection() { 1046 _hrm.verify_optional(); 1047 _verifier->verify_region_sets_optional(); 1048 _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull); 1049 // Clear the previous marking bitmap, if needed for bitmap verification. 1050 // Note we cannot do this when we clear the next marking bitmap in 1051 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1052 // objects marked during a full GC against the previous bitmap. 1053 // But we need to clear it before calling check_bitmaps below since 1054 // the full GC has compacted objects and updated TAMS but not updated 1055 // the prev bitmap. 1056 if (G1VerifyBitmaps) { 1057 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1058 _cm->clear_prev_bitmap(workers()); 1059 } 1060 _verifier->check_bitmaps("Full GC End"); 1061 1062 // At this point there should be no regions in the 1063 // entire heap tagged as young. 1064 assert(check_young_list_empty(), "young list should be empty at this point"); 1065 1066 // Note: since we've just done a full GC, concurrent 1067 // marking is no longer active. Therefore we need not 1068 // re-enable reference discovery for the CM ref processor. 1069 // That will be done at the start of the next marking cycle. 1070 // We also know that the STW processor should no longer 1071 // discover any new references. 1072 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1073 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1074 ref_processor_stw()->verify_no_references_recorded(); 1075 ref_processor_cm()->verify_no_references_recorded(); 1076 } 1077 1078 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1079 // Post collection logging. 1080 // We should do this after we potentially resize the heap so 1081 // that all the COMMIT / UNCOMMIT events are generated before 1082 // the compaction events. 1083 print_hrm_post_compaction(); 1084 heap_transition->print(); 1085 print_heap_after_gc(); 1086 print_heap_regions(); 1087 #ifdef TRACESPINNING 1088 ParallelTaskTerminator::print_termination_counts(); 1089 #endif 1090 } 1091 1092 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1093 bool clear_all_soft_refs) { 1094 assert_at_safepoint_on_vm_thread(); 1095 1096 if (GCLocker::check_active_before_gc()) { 1097 // Full GC was not completed. 1098 return false; 1099 } 1100 1101 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1102 soft_ref_policy()->should_clear_all_soft_refs(); 1103 1104 G1FullCollector collector(this, &_full_gc_memory_manager, explicit_gc, do_clear_all_soft_refs); 1105 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1106 1107 collector.prepare_collection(); 1108 collector.collect(); 1109 collector.complete_collection(); 1110 1111 // Full collection was successfully completed. 1112 return true; 1113 } 1114 1115 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1116 // Currently, there is no facility in the do_full_collection(bool) API to notify 1117 // the caller that the collection did not succeed (e.g., because it was locked 1118 // out by the GC locker). So, right now, we'll ignore the return value. 1119 bool dummy = do_full_collection(true, /* explicit_gc */ 1120 clear_all_soft_refs); 1121 } 1122 1123 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1124 // Capacity, free and used after the GC counted as full regions to 1125 // include the waste in the following calculations. 1126 const size_t capacity_after_gc = capacity(); 1127 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes(); 1128 1129 // This is enforced in arguments.cpp. 1130 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1131 "otherwise the code below doesn't make sense"); 1132 1133 // We don't have floating point command-line arguments 1134 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1135 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1136 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1137 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1138 1139 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1140 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1141 1142 // We have to be careful here as these two calculations can overflow 1143 // 32-bit size_t's. 1144 double used_after_gc_d = (double) used_after_gc; 1145 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1146 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1147 1148 // Let's make sure that they are both under the max heap size, which 1149 // by default will make them fit into a size_t. 1150 double desired_capacity_upper_bound = (double) max_heap_size; 1151 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1152 desired_capacity_upper_bound); 1153 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1154 desired_capacity_upper_bound); 1155 1156 // We can now safely turn them into size_t's. 1157 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1158 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1159 1160 // This assert only makes sense here, before we adjust them 1161 // with respect to the min and max heap size. 1162 assert(minimum_desired_capacity <= maximum_desired_capacity, 1163 "minimum_desired_capacity = " SIZE_FORMAT ", " 1164 "maximum_desired_capacity = " SIZE_FORMAT, 1165 minimum_desired_capacity, maximum_desired_capacity); 1166 1167 // Should not be greater than the heap max size. No need to adjust 1168 // it with respect to the heap min size as it's a lower bound (i.e., 1169 // we'll try to make the capacity larger than it, not smaller). 1170 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1171 // Should not be less than the heap min size. No need to adjust it 1172 // with respect to the heap max size as it's an upper bound (i.e., 1173 // we'll try to make the capacity smaller than it, not greater). 1174 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1175 1176 if (capacity_after_gc < minimum_desired_capacity) { 1177 // Don't expand unless it's significant 1178 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1179 1180 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1181 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1182 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1183 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio); 1184 1185 expand(expand_bytes, _workers); 1186 1187 // No expansion, now see if we want to shrink 1188 } else if (capacity_after_gc > maximum_desired_capacity) { 1189 // Capacity too large, compute shrinking size 1190 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1191 1192 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1193 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1194 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1195 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio); 1196 1197 shrink(shrink_bytes); 1198 } 1199 } 1200 1201 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1202 bool do_gc, 1203 bool clear_all_soft_refs, 1204 bool expect_null_mutator_alloc_region, 1205 bool* gc_succeeded) { 1206 *gc_succeeded = true; 1207 // Let's attempt the allocation first. 1208 HeapWord* result = 1209 attempt_allocation_at_safepoint(word_size, 1210 expect_null_mutator_alloc_region); 1211 if (result != NULL) { 1212 return result; 1213 } 1214 1215 // In a G1 heap, we're supposed to keep allocation from failing by 1216 // incremental pauses. Therefore, at least for now, we'll favor 1217 // expansion over collection. (This might change in the future if we can 1218 // do something smarter than full collection to satisfy a failed alloc.) 1219 result = expand_and_allocate(word_size); 1220 if (result != NULL) { 1221 return result; 1222 } 1223 1224 if (do_gc) { 1225 // Expansion didn't work, we'll try to do a Full GC. 1226 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1227 clear_all_soft_refs); 1228 } 1229 1230 return NULL; 1231 } 1232 1233 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1234 bool* succeeded) { 1235 assert_at_safepoint_on_vm_thread(); 1236 1237 // Attempts to allocate followed by Full GC. 1238 HeapWord* result = 1239 satisfy_failed_allocation_helper(word_size, 1240 true, /* do_gc */ 1241 false, /* clear_all_soft_refs */ 1242 false, /* expect_null_mutator_alloc_region */ 1243 succeeded); 1244 1245 if (result != NULL || !*succeeded) { 1246 return result; 1247 } 1248 1249 // Attempts to allocate followed by Full GC that will collect all soft references. 1250 result = satisfy_failed_allocation_helper(word_size, 1251 true, /* do_gc */ 1252 true, /* clear_all_soft_refs */ 1253 true, /* expect_null_mutator_alloc_region */ 1254 succeeded); 1255 1256 if (result != NULL || !*succeeded) { 1257 return result; 1258 } 1259 1260 // Attempts to allocate, no GC 1261 result = satisfy_failed_allocation_helper(word_size, 1262 false, /* do_gc */ 1263 false, /* clear_all_soft_refs */ 1264 true, /* expect_null_mutator_alloc_region */ 1265 succeeded); 1266 1267 if (result != NULL) { 1268 return result; 1269 } 1270 1271 assert(!soft_ref_policy()->should_clear_all_soft_refs(), 1272 "Flag should have been handled and cleared prior to this point"); 1273 1274 // What else? We might try synchronous finalization later. If the total 1275 // space available is large enough for the allocation, then a more 1276 // complete compaction phase than we've tried so far might be 1277 // appropriate. 1278 return NULL; 1279 } 1280 1281 // Attempting to expand the heap sufficiently 1282 // to support an allocation of the given "word_size". If 1283 // successful, perform the allocation and return the address of the 1284 // allocated block, or else "NULL". 1285 1286 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1287 assert_at_safepoint_on_vm_thread(); 1288 1289 _verifier->verify_region_sets_optional(); 1290 1291 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1292 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1293 word_size * HeapWordSize); 1294 1295 1296 if (expand(expand_bytes, _workers)) { 1297 _hrm.verify_optional(); 1298 _verifier->verify_region_sets_optional(); 1299 return attempt_allocation_at_safepoint(word_size, 1300 false /* expect_null_mutator_alloc_region */); 1301 } 1302 return NULL; 1303 } 1304 1305 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1306 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1307 aligned_expand_bytes = align_up(aligned_expand_bytes, 1308 HeapRegion::GrainBytes); 1309 1310 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1311 expand_bytes, aligned_expand_bytes); 1312 1313 if (is_maximal_no_gc()) { 1314 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1315 return false; 1316 } 1317 1318 double expand_heap_start_time_sec = os::elapsedTime(); 1319 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1320 assert(regions_to_expand > 0, "Must expand by at least one region"); 1321 1322 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers); 1323 if (expand_time_ms != NULL) { 1324 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1325 } 1326 1327 if (expanded_by > 0) { 1328 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1329 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1330 g1_policy()->record_new_heap_size(num_regions()); 1331 } else { 1332 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1333 1334 // The expansion of the virtual storage space was unsuccessful. 1335 // Let's see if it was because we ran out of swap. 1336 if (G1ExitOnExpansionFailure && 1337 _hrm.available() >= regions_to_expand) { 1338 // We had head room... 1339 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1340 } 1341 } 1342 return regions_to_expand > 0; 1343 } 1344 1345 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1346 size_t aligned_shrink_bytes = 1347 ReservedSpace::page_align_size_down(shrink_bytes); 1348 aligned_shrink_bytes = align_down(aligned_shrink_bytes, 1349 HeapRegion::GrainBytes); 1350 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1351 1352 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1353 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1354 1355 1356 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", 1357 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1358 if (num_regions_removed > 0) { 1359 g1_policy()->record_new_heap_size(num_regions()); 1360 } else { 1361 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1362 } 1363 } 1364 1365 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1366 _verifier->verify_region_sets_optional(); 1367 1368 // We should only reach here at the end of a Full GC which means we 1369 // should not not be holding to any GC alloc regions. The method 1370 // below will make sure of that and do any remaining clean up. 1371 _allocator->abandon_gc_alloc_regions(); 1372 1373 // Instead of tearing down / rebuilding the free lists here, we 1374 // could instead use the remove_all_pending() method on free_list to 1375 // remove only the ones that we need to remove. 1376 tear_down_region_sets(true /* free_list_only */); 1377 shrink_helper(shrink_bytes); 1378 rebuild_region_sets(true /* free_list_only */); 1379 1380 _hrm.verify_optional(); 1381 _verifier->verify_region_sets_optional(); 1382 } 1383 1384 // Public methods. 1385 1386 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1387 CollectedHeap(), 1388 _young_gen_sampling_thread(NULL), 1389 _collector_policy(collector_policy), 1390 _soft_ref_policy(), 1391 _card_table(NULL), 1392 _memory_manager("G1 Young Generation", "end of minor GC"), 1393 _full_gc_memory_manager("G1 Old Generation", "end of major GC"), 1394 _eden_pool(NULL), 1395 _survivor_pool(NULL), 1396 _old_pool(NULL), 1397 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1398 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1399 _g1_policy(new G1Policy(_gc_timer_stw)), 1400 _collection_set(this, _g1_policy), 1401 _dirty_card_queue_set(false), 1402 _is_alive_closure_cm(this), 1403 _is_alive_closure_stw(this), 1404 _ref_processor_cm(NULL), 1405 _ref_processor_stw(NULL), 1406 _bot(NULL), 1407 _hot_card_cache(NULL), 1408 _g1_rem_set(NULL), 1409 _cr(NULL), 1410 _g1mm(NULL), 1411 _preserved_marks_set(true /* in_c_heap */), 1412 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1413 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1414 _humongous_reclaim_candidates(), 1415 _has_humongous_reclaim_candidates(false), 1416 _archive_allocator(NULL), 1417 _summary_bytes_used(0), 1418 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1419 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1420 _expand_heap_after_alloc_failure(true), 1421 _old_marking_cycles_started(0), 1422 _old_marking_cycles_completed(0), 1423 _in_cset_fast_test() { 1424 1425 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1426 /* are_GC_task_threads */true, 1427 /* are_ConcurrentGC_threads */false); 1428 _workers->initialize_workers(); 1429 _verifier = new G1HeapVerifier(this); 1430 1431 _allocator = new G1Allocator(this); 1432 1433 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1434 1435 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1436 1437 // Override the default _filler_array_max_size so that no humongous filler 1438 // objects are created. 1439 _filler_array_max_size = _humongous_object_threshold_in_words; 1440 1441 uint n_queues = ParallelGCThreads; 1442 _task_queues = new RefToScanQueueSet(n_queues); 1443 1444 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1445 1446 for (uint i = 0; i < n_queues; i++) { 1447 RefToScanQueue* q = new RefToScanQueue(); 1448 q->initialize(); 1449 _task_queues->register_queue(i, q); 1450 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1451 } 1452 1453 // Initialize the G1EvacuationFailureALot counters and flags. 1454 NOT_PRODUCT(reset_evacuation_should_fail();) 1455 1456 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1457 } 1458 1459 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1460 size_t size, 1461 size_t translation_factor) { 1462 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1463 // Allocate a new reserved space, preferring to use large pages. 1464 ReservedSpace rs(size, preferred_page_size); 1465 G1RegionToSpaceMapper* result = 1466 G1RegionToSpaceMapper::create_mapper(rs, 1467 size, 1468 rs.alignment(), 1469 HeapRegion::GrainBytes, 1470 translation_factor, 1471 mtGC); 1472 1473 os::trace_page_sizes_for_requested_size(description, 1474 size, 1475 preferred_page_size, 1476 rs.alignment(), 1477 rs.base(), 1478 rs.size()); 1479 1480 return result; 1481 } 1482 1483 jint G1CollectedHeap::initialize_concurrent_refinement() { 1484 jint ecode = JNI_OK; 1485 _cr = G1ConcurrentRefine::create(&ecode); 1486 return ecode; 1487 } 1488 1489 jint G1CollectedHeap::initialize_young_gen_sampling_thread() { 1490 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread(); 1491 if (_young_gen_sampling_thread->osthread() == NULL) { 1492 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread"); 1493 return JNI_ENOMEM; 1494 } 1495 return JNI_OK; 1496 } 1497 1498 jint G1CollectedHeap::initialize() { 1499 os::enable_vtime(); 1500 1501 // Necessary to satisfy locking discipline assertions. 1502 1503 MutexLocker x(Heap_lock); 1504 1505 // While there are no constraints in the GC code that HeapWordSize 1506 // be any particular value, there are multiple other areas in the 1507 // system which believe this to be true (e.g. oop->object_size in some 1508 // cases incorrectly returns the size in wordSize units rather than 1509 // HeapWordSize). 1510 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1511 1512 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1513 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1514 size_t heap_alignment = collector_policy()->heap_alignment(); 1515 1516 // Ensure that the sizes are properly aligned. 1517 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1518 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1519 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1520 1521 // Reserve the maximum. 1522 1523 // When compressed oops are enabled, the preferred heap base 1524 // is calculated by subtracting the requested size from the 1525 // 32Gb boundary and using the result as the base address for 1526 // heap reservation. If the requested size is not aligned to 1527 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1528 // into the ReservedHeapSpace constructor) then the actual 1529 // base of the reserved heap may end up differing from the 1530 // address that was requested (i.e. the preferred heap base). 1531 // If this happens then we could end up using a non-optimal 1532 // compressed oops mode. 1533 1534 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1535 heap_alignment); 1536 1537 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1538 1539 // Create the barrier set for the entire reserved region. 1540 G1CardTable* ct = new G1CardTable(reserved_region()); 1541 ct->initialize(); 1542 G1BarrierSet* bs = new G1BarrierSet(ct); 1543 bs->initialize(); 1544 assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity"); 1545 BarrierSet::set_barrier_set(bs); 1546 _card_table = ct; 1547 1548 // Create the hot card cache. 1549 _hot_card_cache = new G1HotCardCache(this); 1550 1551 // Carve out the G1 part of the heap. 1552 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1553 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1554 G1RegionToSpaceMapper* heap_storage = 1555 G1RegionToSpaceMapper::create_mapper(g1_rs, 1556 g1_rs.size(), 1557 page_size, 1558 HeapRegion::GrainBytes, 1559 1, 1560 mtJavaHeap); 1561 os::trace_page_sizes("Heap", 1562 collector_policy()->min_heap_byte_size(), 1563 max_byte_size, 1564 page_size, 1565 heap_rs.base(), 1566 heap_rs.size()); 1567 heap_storage->set_mapping_changed_listener(&_listener); 1568 1569 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1570 G1RegionToSpaceMapper* bot_storage = 1571 create_aux_memory_mapper("Block Offset Table", 1572 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1573 G1BlockOffsetTable::heap_map_factor()); 1574 1575 G1RegionToSpaceMapper* cardtable_storage = 1576 create_aux_memory_mapper("Card Table", 1577 G1CardTable::compute_size(g1_rs.size() / HeapWordSize), 1578 G1CardTable::heap_map_factor()); 1579 1580 G1RegionToSpaceMapper* card_counts_storage = 1581 create_aux_memory_mapper("Card Counts Table", 1582 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1583 G1CardCounts::heap_map_factor()); 1584 1585 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1586 G1RegionToSpaceMapper* prev_bitmap_storage = 1587 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1588 G1RegionToSpaceMapper* next_bitmap_storage = 1589 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1590 1591 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1592 _card_table->initialize(cardtable_storage); 1593 // Do later initialization work for concurrent refinement. 1594 _hot_card_cache->initialize(card_counts_storage); 1595 1596 // 6843694 - ensure that the maximum region index can fit 1597 // in the remembered set structures. 1598 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1599 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1600 1601 // Also create a G1 rem set. 1602 _g1_rem_set = new G1RemSet(this, _card_table, _hot_card_cache); 1603 _g1_rem_set->initialize(max_capacity(), max_regions()); 1604 1605 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1606 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1607 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1608 "too many cards per region"); 1609 1610 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1611 1612 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1613 1614 { 1615 HeapWord* start = _hrm.reserved().start(); 1616 HeapWord* end = _hrm.reserved().end(); 1617 size_t granularity = HeapRegion::GrainBytes; 1618 1619 _in_cset_fast_test.initialize(start, end, granularity); 1620 _humongous_reclaim_candidates.initialize(start, end, granularity); 1621 } 1622 1623 // Create the G1ConcurrentMark data structure and thread. 1624 // (Must do this late, so that "max_regions" is defined.) 1625 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1626 if (_cm == NULL || !_cm->completed_initialization()) { 1627 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1628 return JNI_ENOMEM; 1629 } 1630 _cm_thread = _cm->cm_thread(); 1631 1632 // Now expand into the initial heap size. 1633 if (!expand(init_byte_size, _workers)) { 1634 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1635 return JNI_ENOMEM; 1636 } 1637 1638 // Perform any initialization actions delegated to the policy. 1639 g1_policy()->init(this, &_collection_set); 1640 1641 G1BarrierSet::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1642 SATB_Q_FL_lock, 1643 G1SATBProcessCompletedThreshold, 1644 Shared_SATB_Q_lock); 1645 1646 jint ecode = initialize_concurrent_refinement(); 1647 if (ecode != JNI_OK) { 1648 return ecode; 1649 } 1650 1651 ecode = initialize_young_gen_sampling_thread(); 1652 if (ecode != JNI_OK) { 1653 return ecode; 1654 } 1655 1656 G1BarrierSet::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1657 DirtyCardQ_FL_lock, 1658 (int)concurrent_refine()->yellow_zone(), 1659 (int)concurrent_refine()->red_zone(), 1660 Shared_DirtyCardQ_lock, 1661 NULL, // fl_owner 1662 true); // init_free_ids 1663 1664 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1665 DirtyCardQ_FL_lock, 1666 -1, // never trigger processing 1667 -1, // no limit on length 1668 Shared_DirtyCardQ_lock, 1669 &G1BarrierSet::dirty_card_queue_set()); 1670 1671 // Here we allocate the dummy HeapRegion that is required by the 1672 // G1AllocRegion class. 1673 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1674 1675 // We'll re-use the same region whether the alloc region will 1676 // require BOT updates or not and, if it doesn't, then a non-young 1677 // region will complain that it cannot support allocations without 1678 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1679 dummy_region->set_eden(); 1680 // Make sure it's full. 1681 dummy_region->set_top(dummy_region->end()); 1682 G1AllocRegion::setup(this, dummy_region); 1683 1684 _allocator->init_mutator_alloc_region(); 1685 1686 // Do create of the monitoring and management support so that 1687 // values in the heap have been properly initialized. 1688 _g1mm = new G1MonitoringSupport(this); 1689 1690 G1StringDedup::initialize(); 1691 1692 _preserved_marks_set.init(ParallelGCThreads); 1693 1694 _collection_set.initialize(max_regions()); 1695 1696 return JNI_OK; 1697 } 1698 1699 void G1CollectedHeap::initialize_serviceability() { 1700 _eden_pool = new G1EdenPool(this); 1701 _survivor_pool = new G1SurvivorPool(this); 1702 _old_pool = new G1OldGenPool(this); 1703 1704 _full_gc_memory_manager.add_pool(_eden_pool); 1705 _full_gc_memory_manager.add_pool(_survivor_pool); 1706 _full_gc_memory_manager.add_pool(_old_pool); 1707 1708 _memory_manager.add_pool(_eden_pool); 1709 _memory_manager.add_pool(_survivor_pool); 1710 1711 } 1712 1713 void G1CollectedHeap::stop() { 1714 // Stop all concurrent threads. We do this to make sure these threads 1715 // do not continue to execute and access resources (e.g. logging) 1716 // that are destroyed during shutdown. 1717 _cr->stop(); 1718 _young_gen_sampling_thread->stop(); 1719 _cm_thread->stop(); 1720 if (G1StringDedup::is_enabled()) { 1721 G1StringDedup::stop(); 1722 } 1723 } 1724 1725 void G1CollectedHeap::safepoint_synchronize_begin() { 1726 SuspendibleThreadSet::synchronize(); 1727 } 1728 1729 void G1CollectedHeap::safepoint_synchronize_end() { 1730 SuspendibleThreadSet::desynchronize(); 1731 } 1732 1733 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1734 return HeapRegion::max_region_size(); 1735 } 1736 1737 void G1CollectedHeap::post_initialize() { 1738 CollectedHeap::post_initialize(); 1739 ref_processing_init(); 1740 } 1741 1742 void G1CollectedHeap::ref_processing_init() { 1743 // Reference processing in G1 currently works as follows: 1744 // 1745 // * There are two reference processor instances. One is 1746 // used to record and process discovered references 1747 // during concurrent marking; the other is used to 1748 // record and process references during STW pauses 1749 // (both full and incremental). 1750 // * Both ref processors need to 'span' the entire heap as 1751 // the regions in the collection set may be dotted around. 1752 // 1753 // * For the concurrent marking ref processor: 1754 // * Reference discovery is enabled at initial marking. 1755 // * Reference discovery is disabled and the discovered 1756 // references processed etc during remarking. 1757 // * Reference discovery is MT (see below). 1758 // * Reference discovery requires a barrier (see below). 1759 // * Reference processing may or may not be MT 1760 // (depending on the value of ParallelRefProcEnabled 1761 // and ParallelGCThreads). 1762 // * A full GC disables reference discovery by the CM 1763 // ref processor and abandons any entries on it's 1764 // discovered lists. 1765 // 1766 // * For the STW processor: 1767 // * Non MT discovery is enabled at the start of a full GC. 1768 // * Processing and enqueueing during a full GC is non-MT. 1769 // * During a full GC, references are processed after marking. 1770 // 1771 // * Discovery (may or may not be MT) is enabled at the start 1772 // of an incremental evacuation pause. 1773 // * References are processed near the end of a STW evacuation pause. 1774 // * For both types of GC: 1775 // * Discovery is atomic - i.e. not concurrent. 1776 // * Reference discovery will not need a barrier. 1777 1778 MemRegion mr = reserved_region(); 1779 1780 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1); 1781 1782 // Concurrent Mark ref processor 1783 _ref_processor_cm = 1784 new ReferenceProcessor(mr, // span 1785 mt_processing, 1786 // mt processing 1787 ParallelGCThreads, 1788 // degree of mt processing 1789 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 1790 // mt discovery 1791 MAX2(ParallelGCThreads, ConcGCThreads), 1792 // degree of mt discovery 1793 false, 1794 // Reference discovery is not atomic 1795 &_is_alive_closure_cm); 1796 // is alive closure 1797 // (for efficiency/performance) 1798 1799 // STW ref processor 1800 _ref_processor_stw = 1801 new ReferenceProcessor(mr, // span 1802 mt_processing, 1803 // mt processing 1804 ParallelGCThreads, 1805 // degree of mt processing 1806 (ParallelGCThreads > 1), 1807 // mt discovery 1808 ParallelGCThreads, 1809 // degree of mt discovery 1810 true, 1811 // Reference discovery is atomic 1812 &_is_alive_closure_stw); 1813 // is alive closure 1814 // (for efficiency/performance) 1815 } 1816 1817 CollectorPolicy* G1CollectedHeap::collector_policy() const { 1818 return _collector_policy; 1819 } 1820 1821 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() { 1822 return &_soft_ref_policy; 1823 } 1824 1825 size_t G1CollectedHeap::capacity() const { 1826 return _hrm.length() * HeapRegion::GrainBytes; 1827 } 1828 1829 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const { 1830 return _hrm.total_free_bytes(); 1831 } 1832 1833 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 1834 _hot_card_cache->drain(cl, worker_i); 1835 } 1836 1837 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 1838 DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 1839 size_t n_completed_buffers = 0; 1840 while (dcqs.apply_closure_during_gc(cl, worker_i)) { 1841 n_completed_buffers++; 1842 } 1843 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 1844 dcqs.clear_n_completed_buffers(); 1845 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 1846 } 1847 1848 // Computes the sum of the storage used by the various regions. 1849 size_t G1CollectedHeap::used() const { 1850 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 1851 if (_archive_allocator != NULL) { 1852 result += _archive_allocator->used(); 1853 } 1854 return result; 1855 } 1856 1857 size_t G1CollectedHeap::used_unlocked() const { 1858 return _summary_bytes_used; 1859 } 1860 1861 class SumUsedClosure: public HeapRegionClosure { 1862 size_t _used; 1863 public: 1864 SumUsedClosure() : _used(0) {} 1865 bool do_heap_region(HeapRegion* r) { 1866 _used += r->used(); 1867 return false; 1868 } 1869 size_t result() { return _used; } 1870 }; 1871 1872 size_t G1CollectedHeap::recalculate_used() const { 1873 double recalculate_used_start = os::elapsedTime(); 1874 1875 SumUsedClosure blk; 1876 heap_region_iterate(&blk); 1877 1878 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 1879 return blk.result(); 1880 } 1881 1882 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 1883 switch (cause) { 1884 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 1885 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 1886 case GCCause::_wb_conc_mark: return true; 1887 default : return false; 1888 } 1889 } 1890 1891 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 1892 switch (cause) { 1893 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 1894 case GCCause::_g1_humongous_allocation: return true; 1895 default: return is_user_requested_concurrent_full_gc(cause); 1896 } 1897 } 1898 1899 #ifndef PRODUCT 1900 void G1CollectedHeap::allocate_dummy_regions() { 1901 // Let's fill up most of the region 1902 size_t word_size = HeapRegion::GrainWords - 1024; 1903 // And as a result the region we'll allocate will be humongous. 1904 guarantee(is_humongous(word_size), "sanity"); 1905 1906 // _filler_array_max_size is set to humongous object threshold 1907 // but temporarily change it to use CollectedHeap::fill_with_object(). 1908 SizeTFlagSetting fs(_filler_array_max_size, word_size); 1909 1910 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 1911 // Let's use the existing mechanism for the allocation 1912 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 1913 if (dummy_obj != NULL) { 1914 MemRegion mr(dummy_obj, word_size); 1915 CollectedHeap::fill_with_object(mr); 1916 } else { 1917 // If we can't allocate once, we probably cannot allocate 1918 // again. Let's get out of the loop. 1919 break; 1920 } 1921 } 1922 } 1923 #endif // !PRODUCT 1924 1925 void G1CollectedHeap::increment_old_marking_cycles_started() { 1926 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 1927 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 1928 "Wrong marking cycle count (started: %d, completed: %d)", 1929 _old_marking_cycles_started, _old_marking_cycles_completed); 1930 1931 _old_marking_cycles_started++; 1932 } 1933 1934 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 1935 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 1936 1937 // We assume that if concurrent == true, then the caller is a 1938 // concurrent thread that was joined the Suspendible Thread 1939 // Set. If there's ever a cheap way to check this, we should add an 1940 // assert here. 1941 1942 // Given that this method is called at the end of a Full GC or of a 1943 // concurrent cycle, and those can be nested (i.e., a Full GC can 1944 // interrupt a concurrent cycle), the number of full collections 1945 // completed should be either one (in the case where there was no 1946 // nesting) or two (when a Full GC interrupted a concurrent cycle) 1947 // behind the number of full collections started. 1948 1949 // This is the case for the inner caller, i.e. a Full GC. 1950 assert(concurrent || 1951 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 1952 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 1953 "for inner caller (Full GC): _old_marking_cycles_started = %u " 1954 "is inconsistent with _old_marking_cycles_completed = %u", 1955 _old_marking_cycles_started, _old_marking_cycles_completed); 1956 1957 // This is the case for the outer caller, i.e. the concurrent cycle. 1958 assert(!concurrent || 1959 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 1960 "for outer caller (concurrent cycle): " 1961 "_old_marking_cycles_started = %u " 1962 "is inconsistent with _old_marking_cycles_completed = %u", 1963 _old_marking_cycles_started, _old_marking_cycles_completed); 1964 1965 _old_marking_cycles_completed += 1; 1966 1967 // We need to clear the "in_progress" flag in the CM thread before 1968 // we wake up any waiters (especially when ExplicitInvokesConcurrent 1969 // is set) so that if a waiter requests another System.gc() it doesn't 1970 // incorrectly see that a marking cycle is still in progress. 1971 if (concurrent) { 1972 _cm_thread->set_idle(); 1973 } 1974 1975 // This notify_all() will ensure that a thread that called 1976 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 1977 // and it's waiting for a full GC to finish will be woken up. It is 1978 // waiting in VM_G1CollectForAllocation::doit_epilogue(). 1979 FullGCCount_lock->notify_all(); 1980 } 1981 1982 void G1CollectedHeap::collect(GCCause::Cause cause) { 1983 assert_heap_not_locked(); 1984 1985 uint gc_count_before; 1986 uint old_marking_count_before; 1987 uint full_gc_count_before; 1988 bool retry_gc; 1989 1990 do { 1991 retry_gc = false; 1992 1993 { 1994 MutexLocker ml(Heap_lock); 1995 1996 // Read the GC count while holding the Heap_lock 1997 gc_count_before = total_collections(); 1998 full_gc_count_before = total_full_collections(); 1999 old_marking_count_before = _old_marking_cycles_started; 2000 } 2001 2002 if (should_do_concurrent_full_gc(cause)) { 2003 // Schedule an initial-mark evacuation pause that will start a 2004 // concurrent cycle. We're setting word_size to 0 which means that 2005 // we are not requesting a post-GC allocation. 2006 VM_G1CollectForAllocation op(0, /* word_size */ 2007 gc_count_before, 2008 cause, 2009 true, /* should_initiate_conc_mark */ 2010 g1_policy()->max_pause_time_ms()); 2011 VMThread::execute(&op); 2012 if (!op.pause_succeeded()) { 2013 if (old_marking_count_before == _old_marking_cycles_started) { 2014 retry_gc = op.should_retry_gc(); 2015 } else { 2016 // A Full GC happened while we were trying to schedule the 2017 // initial-mark GC. No point in starting a new cycle given 2018 // that the whole heap was collected anyway. 2019 } 2020 2021 if (retry_gc) { 2022 if (GCLocker::is_active_and_needs_gc()) { 2023 GCLocker::stall_until_clear(); 2024 } 2025 } 2026 } 2027 } else { 2028 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2029 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2030 2031 // Schedule a standard evacuation pause. We're setting word_size 2032 // to 0 which means that we are not requesting a post-GC allocation. 2033 VM_G1CollectForAllocation op(0, /* word_size */ 2034 gc_count_before, 2035 cause, 2036 false, /* should_initiate_conc_mark */ 2037 g1_policy()->max_pause_time_ms()); 2038 VMThread::execute(&op); 2039 } else { 2040 // Schedule a Full GC. 2041 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2042 VMThread::execute(&op); 2043 } 2044 } 2045 } while (retry_gc); 2046 } 2047 2048 bool G1CollectedHeap::is_in(const void* p) const { 2049 if (_hrm.reserved().contains(p)) { 2050 // Given that we know that p is in the reserved space, 2051 // heap_region_containing() should successfully 2052 // return the containing region. 2053 HeapRegion* hr = heap_region_containing(p); 2054 return hr->is_in(p); 2055 } else { 2056 return false; 2057 } 2058 } 2059 2060 #ifdef ASSERT 2061 bool G1CollectedHeap::is_in_exact(const void* p) const { 2062 bool contains = reserved_region().contains(p); 2063 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2064 if (contains && available) { 2065 return true; 2066 } else { 2067 return false; 2068 } 2069 } 2070 #endif 2071 2072 // Iteration functions. 2073 2074 // Iterates an ObjectClosure over all objects within a HeapRegion. 2075 2076 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2077 ObjectClosure* _cl; 2078 public: 2079 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2080 bool do_heap_region(HeapRegion* r) { 2081 if (!r->is_continues_humongous()) { 2082 r->object_iterate(_cl); 2083 } 2084 return false; 2085 } 2086 }; 2087 2088 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2089 IterateObjectClosureRegionClosure blk(cl); 2090 heap_region_iterate(&blk); 2091 } 2092 2093 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2094 _hrm.iterate(cl); 2095 } 2096 2097 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl, 2098 HeapRegionClaimer *hrclaimer, 2099 uint worker_id) const { 2100 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id)); 2101 } 2102 2103 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl, 2104 HeapRegionClaimer *hrclaimer) const { 2105 _hrm.par_iterate(cl, hrclaimer, 0); 2106 } 2107 2108 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2109 _collection_set.iterate(cl); 2110 } 2111 2112 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2113 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2114 } 2115 2116 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2117 HeapRegion* hr = heap_region_containing(addr); 2118 return hr->block_start(addr); 2119 } 2120 2121 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2122 HeapRegion* hr = heap_region_containing(addr); 2123 return hr->block_size(addr); 2124 } 2125 2126 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2127 HeapRegion* hr = heap_region_containing(addr); 2128 return hr->block_is_obj(addr); 2129 } 2130 2131 bool G1CollectedHeap::supports_tlab_allocation() const { 2132 return true; 2133 } 2134 2135 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2136 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2137 } 2138 2139 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2140 return _eden.length() * HeapRegion::GrainBytes; 2141 } 2142 2143 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2144 // must be equal to the humongous object limit. 2145 size_t G1CollectedHeap::max_tlab_size() const { 2146 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2147 } 2148 2149 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2150 return _allocator->unsafe_max_tlab_alloc(); 2151 } 2152 2153 size_t G1CollectedHeap::max_capacity() const { 2154 return _hrm.reserved().byte_size(); 2155 } 2156 2157 jlong G1CollectedHeap::millis_since_last_gc() { 2158 // See the notes in GenCollectedHeap::millis_since_last_gc() 2159 // for more information about the implementation. 2160 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2161 _g1_policy->collection_pause_end_millis(); 2162 if (ret_val < 0) { 2163 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2164 ". returning zero instead.", ret_val); 2165 return 0; 2166 } 2167 return ret_val; 2168 } 2169 2170 void G1CollectedHeap::prepare_for_verify() { 2171 _verifier->prepare_for_verify(); 2172 } 2173 2174 void G1CollectedHeap::verify(VerifyOption vo) { 2175 _verifier->verify(vo); 2176 } 2177 2178 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2179 return true; 2180 } 2181 2182 const char* const* G1CollectedHeap::concurrent_phases() const { 2183 return _cm_thread->concurrent_phases(); 2184 } 2185 2186 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2187 return _cm_thread->request_concurrent_phase(phase); 2188 } 2189 2190 class PrintRegionClosure: public HeapRegionClosure { 2191 outputStream* _st; 2192 public: 2193 PrintRegionClosure(outputStream* st) : _st(st) {} 2194 bool do_heap_region(HeapRegion* r) { 2195 r->print_on(_st); 2196 return false; 2197 } 2198 }; 2199 2200 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2201 const HeapRegion* hr, 2202 const VerifyOption vo) const { 2203 switch (vo) { 2204 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2205 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2206 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr); 2207 default: ShouldNotReachHere(); 2208 } 2209 return false; // keep some compilers happy 2210 } 2211 2212 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2213 const VerifyOption vo) const { 2214 switch (vo) { 2215 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2216 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2217 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj); 2218 default: ShouldNotReachHere(); 2219 } 2220 return false; // keep some compilers happy 2221 } 2222 2223 void G1CollectedHeap::print_heap_regions() const { 2224 LogTarget(Trace, gc, heap, region) lt; 2225 if (lt.is_enabled()) { 2226 LogStream ls(lt); 2227 print_regions_on(&ls); 2228 } 2229 } 2230 2231 void G1CollectedHeap::print_on(outputStream* st) const { 2232 st->print(" %-20s", "garbage-first heap"); 2233 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2234 capacity()/K, used_unlocked()/K); 2235 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")", 2236 p2i(_hrm.reserved().start()), 2237 p2i(_hrm.reserved().end())); 2238 st->cr(); 2239 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2240 uint young_regions = young_regions_count(); 2241 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2242 (size_t) young_regions * HeapRegion::GrainBytes / K); 2243 uint survivor_regions = survivor_regions_count(); 2244 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2245 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2246 st->cr(); 2247 MetaspaceUtils::print_on(st); 2248 } 2249 2250 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2251 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2252 "HS=humongous(starts), HC=humongous(continues), " 2253 "CS=collection set, F=free, A=archive, " 2254 "TAMS=top-at-mark-start (previous, next)"); 2255 PrintRegionClosure blk(st); 2256 heap_region_iterate(&blk); 2257 } 2258 2259 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2260 print_on(st); 2261 2262 // Print the per-region information. 2263 print_regions_on(st); 2264 } 2265 2266 void G1CollectedHeap::print_on_error(outputStream* st) const { 2267 this->CollectedHeap::print_on_error(st); 2268 2269 if (_cm != NULL) { 2270 st->cr(); 2271 _cm->print_on_error(st); 2272 } 2273 } 2274 2275 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2276 workers()->print_worker_threads_on(st); 2277 _cm_thread->print_on(st); 2278 st->cr(); 2279 _cm->print_worker_threads_on(st); 2280 _cr->print_threads_on(st); 2281 _young_gen_sampling_thread->print_on(st); 2282 if (G1StringDedup::is_enabled()) { 2283 G1StringDedup::print_worker_threads_on(st); 2284 } 2285 } 2286 2287 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2288 workers()->threads_do(tc); 2289 tc->do_thread(_cm_thread); 2290 _cm->threads_do(tc); 2291 _cr->threads_do(tc); 2292 tc->do_thread(_young_gen_sampling_thread); 2293 if (G1StringDedup::is_enabled()) { 2294 G1StringDedup::threads_do(tc); 2295 } 2296 } 2297 2298 void G1CollectedHeap::print_tracing_info() const { 2299 g1_rem_set()->print_summary_info(); 2300 concurrent_mark()->print_summary_info(); 2301 } 2302 2303 #ifndef PRODUCT 2304 // Helpful for debugging RSet issues. 2305 2306 class PrintRSetsClosure : public HeapRegionClosure { 2307 private: 2308 const char* _msg; 2309 size_t _occupied_sum; 2310 2311 public: 2312 bool do_heap_region(HeapRegion* r) { 2313 HeapRegionRemSet* hrrs = r->rem_set(); 2314 size_t occupied = hrrs->occupied(); 2315 _occupied_sum += occupied; 2316 2317 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2318 if (occupied == 0) { 2319 tty->print_cr(" RSet is empty"); 2320 } else { 2321 hrrs->print(); 2322 } 2323 tty->print_cr("----------"); 2324 return false; 2325 } 2326 2327 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2328 tty->cr(); 2329 tty->print_cr("========================================"); 2330 tty->print_cr("%s", msg); 2331 tty->cr(); 2332 } 2333 2334 ~PrintRSetsClosure() { 2335 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2336 tty->print_cr("========================================"); 2337 tty->cr(); 2338 } 2339 }; 2340 2341 void G1CollectedHeap::print_cset_rsets() { 2342 PrintRSetsClosure cl("Printing CSet RSets"); 2343 collection_set_iterate(&cl); 2344 } 2345 2346 void G1CollectedHeap::print_all_rsets() { 2347 PrintRSetsClosure cl("Printing All RSets");; 2348 heap_region_iterate(&cl); 2349 } 2350 #endif // PRODUCT 2351 2352 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2353 2354 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2355 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2356 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2357 2358 size_t eden_capacity_bytes = 2359 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2360 2361 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2362 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2363 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2364 } 2365 2366 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2367 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2368 stats->unused(), stats->used(), stats->region_end_waste(), 2369 stats->regions_filled(), stats->direct_allocated(), 2370 stats->failure_used(), stats->failure_waste()); 2371 } 2372 2373 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2374 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2375 gc_tracer->report_gc_heap_summary(when, heap_summary); 2376 2377 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2378 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2379 } 2380 2381 G1CollectedHeap* G1CollectedHeap::heap() { 2382 CollectedHeap* heap = Universe::heap(); 2383 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2384 assert(heap->kind() == CollectedHeap::G1, "Invalid name"); 2385 return (G1CollectedHeap*)heap; 2386 } 2387 2388 void G1CollectedHeap::gc_prologue(bool full) { 2389 // always_do_update_barrier = false; 2390 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2391 2392 // This summary needs to be printed before incrementing total collections. 2393 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2394 2395 // Update common counters. 2396 increment_total_collections(full /* full gc */); 2397 if (full) { 2398 increment_old_marking_cycles_started(); 2399 } 2400 2401 // Fill TLAB's and such 2402 double start = os::elapsedTime(); 2403 accumulate_statistics_all_tlabs(); 2404 ensure_parsability(true); 2405 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2406 } 2407 2408 void G1CollectedHeap::gc_epilogue(bool full) { 2409 // Update common counters. 2410 if (full) { 2411 // Update the number of full collections that have been completed. 2412 increment_old_marking_cycles_completed(false /* concurrent */); 2413 } 2414 2415 // We are at the end of the GC. Total collections has already been increased. 2416 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2417 2418 // FIXME: what is this about? 2419 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2420 // is set. 2421 #if COMPILER2_OR_JVMCI 2422 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2423 #endif 2424 // always_do_update_barrier = true; 2425 2426 double start = os::elapsedTime(); 2427 resize_all_tlabs(); 2428 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2429 2430 MemoryService::track_memory_usage(); 2431 // We have just completed a GC. Update the soft reference 2432 // policy with the new heap occupancy 2433 Universe::update_heap_info_at_gc(); 2434 } 2435 2436 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2437 uint gc_count_before, 2438 bool* succeeded, 2439 GCCause::Cause gc_cause) { 2440 assert_heap_not_locked_and_not_at_safepoint(); 2441 VM_G1CollectForAllocation op(word_size, 2442 gc_count_before, 2443 gc_cause, 2444 false, /* should_initiate_conc_mark */ 2445 g1_policy()->max_pause_time_ms()); 2446 VMThread::execute(&op); 2447 2448 HeapWord* result = op.result(); 2449 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2450 assert(result == NULL || ret_succeeded, 2451 "the result should be NULL if the VM did not succeed"); 2452 *succeeded = ret_succeeded; 2453 2454 assert_heap_not_locked(); 2455 return result; 2456 } 2457 2458 void G1CollectedHeap::do_concurrent_mark() { 2459 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2460 if (!_cm_thread->in_progress()) { 2461 _cm_thread->set_started(); 2462 CGC_lock->notify(); 2463 } 2464 } 2465 2466 size_t G1CollectedHeap::pending_card_num() { 2467 size_t extra_cards = 0; 2468 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) { 2469 DirtyCardQueue& dcq = G1ThreadLocalData::dirty_card_queue(curr); 2470 extra_cards += dcq.size(); 2471 } 2472 DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 2473 size_t buffer_size = dcqs.buffer_size(); 2474 size_t buffer_num = dcqs.completed_buffers_num(); 2475 2476 return buffer_size * buffer_num + extra_cards; 2477 } 2478 2479 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const { 2480 // We don't nominate objects with many remembered set entries, on 2481 // the assumption that such objects are likely still live. 2482 HeapRegionRemSet* rem_set = r->rem_set(); 2483 2484 return G1EagerReclaimHumongousObjectsWithStaleRefs ? 2485 rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) : 2486 G1EagerReclaimHumongousObjects && rem_set->is_empty(); 2487 } 2488 2489 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2490 private: 2491 size_t _total_humongous; 2492 size_t _candidate_humongous; 2493 2494 DirtyCardQueue _dcq; 2495 2496 bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const { 2497 assert(region->is_starts_humongous(), "Must start a humongous object"); 2498 2499 oop obj = oop(region->bottom()); 2500 2501 // Dead objects cannot be eager reclaim candidates. Due to class 2502 // unloading it is unsafe to query their classes so we return early. 2503 if (g1h->is_obj_dead(obj, region)) { 2504 return false; 2505 } 2506 2507 // If we do not have a complete remembered set for the region, then we can 2508 // not be sure that we have all references to it. 2509 if (!region->rem_set()->is_complete()) { 2510 return false; 2511 } 2512 // Candidate selection must satisfy the following constraints 2513 // while concurrent marking is in progress: 2514 // 2515 // * In order to maintain SATB invariants, an object must not be 2516 // reclaimed if it was allocated before the start of marking and 2517 // has not had its references scanned. Such an object must have 2518 // its references (including type metadata) scanned to ensure no 2519 // live objects are missed by the marking process. Objects 2520 // allocated after the start of concurrent marking don't need to 2521 // be scanned. 2522 // 2523 // * An object must not be reclaimed if it is on the concurrent 2524 // mark stack. Objects allocated after the start of concurrent 2525 // marking are never pushed on the mark stack. 2526 // 2527 // Nominating only objects allocated after the start of concurrent 2528 // marking is sufficient to meet both constraints. This may miss 2529 // some objects that satisfy the constraints, but the marking data 2530 // structures don't support efficiently performing the needed 2531 // additional tests or scrubbing of the mark stack. 2532 // 2533 // However, we presently only nominate is_typeArray() objects. 2534 // A humongous object containing references induces remembered 2535 // set entries on other regions. In order to reclaim such an 2536 // object, those remembered sets would need to be cleaned up. 2537 // 2538 // We also treat is_typeArray() objects specially, allowing them 2539 // to be reclaimed even if allocated before the start of 2540 // concurrent mark. For this we rely on mark stack insertion to 2541 // exclude is_typeArray() objects, preventing reclaiming an object 2542 // that is in the mark stack. We also rely on the metadata for 2543 // such objects to be built-in and so ensured to be kept live. 2544 // Frequent allocation and drop of large binary blobs is an 2545 // important use case for eager reclaim, and this special handling 2546 // may reduce needed headroom. 2547 2548 return obj->is_typeArray() && 2549 g1h->is_potential_eager_reclaim_candidate(region); 2550 } 2551 2552 public: 2553 RegisterHumongousWithInCSetFastTestClosure() 2554 : _total_humongous(0), 2555 _candidate_humongous(0), 2556 _dcq(&G1BarrierSet::dirty_card_queue_set()) { 2557 } 2558 2559 virtual bool do_heap_region(HeapRegion* r) { 2560 if (!r->is_starts_humongous()) { 2561 return false; 2562 } 2563 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2564 2565 bool is_candidate = humongous_region_is_candidate(g1h, r); 2566 uint rindex = r->hrm_index(); 2567 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2568 if (is_candidate) { 2569 _candidate_humongous++; 2570 g1h->register_humongous_region_with_cset(rindex); 2571 // Is_candidate already filters out humongous object with large remembered sets. 2572 // If we have a humongous object with a few remembered sets, we simply flush these 2573 // remembered set entries into the DCQS. That will result in automatic 2574 // re-evaluation of their remembered set entries during the following evacuation 2575 // phase. 2576 if (!r->rem_set()->is_empty()) { 2577 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2578 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2579 G1CardTable* ct = g1h->card_table(); 2580 HeapRegionRemSetIterator hrrs(r->rem_set()); 2581 size_t card_index; 2582 while (hrrs.has_next(card_index)) { 2583 jbyte* card_ptr = (jbyte*)ct->byte_for_index(card_index); 2584 // The remembered set might contain references to already freed 2585 // regions. Filter out such entries to avoid failing card table 2586 // verification. 2587 if (g1h->is_in_closed_subset(ct->addr_for(card_ptr))) { 2588 if (*card_ptr != G1CardTable::dirty_card_val()) { 2589 *card_ptr = G1CardTable::dirty_card_val(); 2590 _dcq.enqueue(card_ptr); 2591 } 2592 } 2593 } 2594 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2595 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2596 hrrs.n_yielded(), r->rem_set()->occupied()); 2597 // We should only clear the card based remembered set here as we will not 2598 // implicitly rebuild anything else during eager reclaim. Note that at the moment 2599 // (and probably never) we do not enter this path if there are other kind of 2600 // remembered sets for this region. 2601 r->rem_set()->clear_locked(true /* only_cardset */); 2602 // Clear_locked() above sets the state to Empty. However we want to continue 2603 // collecting remembered set entries for humongous regions that were not 2604 // reclaimed. 2605 r->rem_set()->set_state_complete(); 2606 } 2607 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2608 } 2609 _total_humongous++; 2610 2611 return false; 2612 } 2613 2614 size_t total_humongous() const { return _total_humongous; } 2615 size_t candidate_humongous() const { return _candidate_humongous; } 2616 2617 void flush_rem_set_entries() { _dcq.flush(); } 2618 }; 2619 2620 void G1CollectedHeap::register_humongous_regions_with_cset() { 2621 if (!G1EagerReclaimHumongousObjects) { 2622 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2623 return; 2624 } 2625 double time = os::elapsed_counter(); 2626 2627 // Collect reclaim candidate information and register candidates with cset. 2628 RegisterHumongousWithInCSetFastTestClosure cl; 2629 heap_region_iterate(&cl); 2630 2631 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2632 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2633 cl.total_humongous(), 2634 cl.candidate_humongous()); 2635 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2636 2637 // Finally flush all remembered set entries to re-check into the global DCQS. 2638 cl.flush_rem_set_entries(); 2639 } 2640 2641 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2642 public: 2643 bool do_heap_region(HeapRegion* hr) { 2644 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2645 hr->verify_rem_set(); 2646 } 2647 return false; 2648 } 2649 }; 2650 2651 uint G1CollectedHeap::num_task_queues() const { 2652 return _task_queues->size(); 2653 } 2654 2655 #if TASKQUEUE_STATS 2656 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2657 st->print_raw_cr("GC Task Stats"); 2658 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2659 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2660 } 2661 2662 void G1CollectedHeap::print_taskqueue_stats() const { 2663 if (!log_is_enabled(Trace, gc, task, stats)) { 2664 return; 2665 } 2666 Log(gc, task, stats) log; 2667 ResourceMark rm; 2668 LogStream ls(log.trace()); 2669 outputStream* st = &ls; 2670 2671 print_taskqueue_stats_hdr(st); 2672 2673 TaskQueueStats totals; 2674 const uint n = num_task_queues(); 2675 for (uint i = 0; i < n; ++i) { 2676 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2677 totals += task_queue(i)->stats; 2678 } 2679 st->print_raw("tot "); totals.print(st); st->cr(); 2680 2681 DEBUG_ONLY(totals.verify()); 2682 } 2683 2684 void G1CollectedHeap::reset_taskqueue_stats() { 2685 const uint n = num_task_queues(); 2686 for (uint i = 0; i < n; ++i) { 2687 task_queue(i)->stats.reset(); 2688 } 2689 } 2690 #endif // TASKQUEUE_STATS 2691 2692 void G1CollectedHeap::wait_for_root_region_scanning() { 2693 double scan_wait_start = os::elapsedTime(); 2694 // We have to wait until the CM threads finish scanning the 2695 // root regions as it's the only way to ensure that all the 2696 // objects on them have been correctly scanned before we start 2697 // moving them during the GC. 2698 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2699 double wait_time_ms = 0.0; 2700 if (waited) { 2701 double scan_wait_end = os::elapsedTime(); 2702 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2703 } 2704 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2705 } 2706 2707 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2708 private: 2709 G1HRPrinter* _hr_printer; 2710 public: 2711 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2712 2713 virtual bool do_heap_region(HeapRegion* r) { 2714 _hr_printer->cset(r); 2715 return false; 2716 } 2717 }; 2718 2719 void G1CollectedHeap::start_new_collection_set() { 2720 collection_set()->start_incremental_building(); 2721 2722 clear_cset_fast_test(); 2723 2724 guarantee(_eden.length() == 0, "eden should have been cleared"); 2725 g1_policy()->transfer_survivors_to_cset(survivor()); 2726 } 2727 2728 bool 2729 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2730 assert_at_safepoint_on_vm_thread(); 2731 guarantee(!is_gc_active(), "collection is not reentrant"); 2732 2733 if (GCLocker::check_active_before_gc()) { 2734 return false; 2735 } 2736 2737 _gc_timer_stw->register_gc_start(); 2738 2739 GCIdMark gc_id_mark; 2740 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2741 2742 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2743 ResourceMark rm; 2744 2745 g1_policy()->note_gc_start(); 2746 2747 wait_for_root_region_scanning(); 2748 2749 print_heap_before_gc(); 2750 print_heap_regions(); 2751 trace_heap_before_gc(_gc_tracer_stw); 2752 2753 _verifier->verify_region_sets_optional(); 2754 _verifier->verify_dirty_young_regions(); 2755 2756 // We should not be doing initial mark unless the conc mark thread is running 2757 if (!_cm_thread->should_terminate()) { 2758 // This call will decide whether this pause is an initial-mark 2759 // pause. If it is, in_initial_mark_gc() will return true 2760 // for the duration of this pause. 2761 g1_policy()->decide_on_conc_mark_initiation(); 2762 } 2763 2764 // We do not allow initial-mark to be piggy-backed on a mixed GC. 2765 assert(!collector_state()->in_initial_mark_gc() || 2766 collector_state()->in_young_only_phase(), "sanity"); 2767 2768 // We also do not allow mixed GCs during marking. 2769 assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity"); 2770 2771 // Record whether this pause is an initial mark. When the current 2772 // thread has completed its logging output and it's safe to signal 2773 // the CM thread, the flag's value in the policy has been reset. 2774 bool should_start_conc_mark = collector_state()->in_initial_mark_gc(); 2775 2776 // Inner scope for scope based logging, timers, and stats collection 2777 { 2778 EvacuationInfo evacuation_info; 2779 2780 if (collector_state()->in_initial_mark_gc()) { 2781 // We are about to start a marking cycle, so we increment the 2782 // full collection counter. 2783 increment_old_marking_cycles_started(); 2784 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 2785 } 2786 2787 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 2788 2789 GCTraceCPUTime tcpu; 2790 2791 G1HeapVerifier::G1VerifyType verify_type; 2792 FormatBuffer<> gc_string("Pause "); 2793 if (collector_state()->in_initial_mark_gc()) { 2794 gc_string.append("Initial Mark"); 2795 verify_type = G1HeapVerifier::G1VerifyInitialMark; 2796 } else if (collector_state()->in_young_only_phase()) { 2797 gc_string.append("Young"); 2798 verify_type = G1HeapVerifier::G1VerifyYoungOnly; 2799 } else { 2800 gc_string.append("Mixed"); 2801 verify_type = G1HeapVerifier::G1VerifyMixed; 2802 } 2803 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 2804 2805 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 2806 workers()->active_workers(), 2807 Threads::number_of_non_daemon_threads()); 2808 active_workers = workers()->update_active_workers(active_workers); 2809 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 2810 2811 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 2812 TraceMemoryManagerStats tms(&_memory_manager, gc_cause()); 2813 2814 G1HeapTransition heap_transition(this); 2815 size_t heap_used_bytes_before_gc = used(); 2816 2817 // Don't dynamically change the number of GC threads this early. A value of 2818 // 0 is used to indicate serial work. When parallel work is done, 2819 // it will be set. 2820 2821 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 2822 IsGCActiveMark x; 2823 2824 gc_prologue(false); 2825 2826 if (VerifyRememberedSets) { 2827 log_info(gc, verify)("[Verifying RemSets before GC]"); 2828 VerifyRegionRemSetClosure v_cl; 2829 heap_region_iterate(&v_cl); 2830 } 2831 2832 _verifier->verify_before_gc(verify_type); 2833 2834 _verifier->check_bitmaps("GC Start"); 2835 2836 #if COMPILER2_OR_JVMCI 2837 DerivedPointerTable::clear(); 2838 #endif 2839 2840 // Please see comment in g1CollectedHeap.hpp and 2841 // G1CollectedHeap::ref_processing_init() to see how 2842 // reference processing currently works in G1. 2843 2844 // Enable discovery in the STW reference processor 2845 ref_processor_stw()->enable_discovery(); 2846 2847 { 2848 // We want to temporarily turn off discovery by the 2849 // CM ref processor, if necessary, and turn it back on 2850 // on again later if we do. Using a scoped 2851 // NoRefDiscovery object will do this. 2852 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 2853 2854 // Forget the current alloc region (we might even choose it to be part 2855 // of the collection set!). 2856 _allocator->release_mutator_alloc_region(); 2857 2858 // This timing is only used by the ergonomics to handle our pause target. 2859 // It is unclear why this should not include the full pause. We will 2860 // investigate this in CR 7178365. 2861 // 2862 // Preserving the old comment here if that helps the investigation: 2863 // 2864 // The elapsed time induced by the start time below deliberately elides 2865 // the possible verification above. 2866 double sample_start_time_sec = os::elapsedTime(); 2867 2868 g1_policy()->record_collection_pause_start(sample_start_time_sec); 2869 2870 if (collector_state()->in_initial_mark_gc()) { 2871 concurrent_mark()->pre_initial_mark(); 2872 } 2873 2874 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 2875 2876 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 2877 2878 // Make sure the remembered sets are up to date. This needs to be 2879 // done before register_humongous_regions_with_cset(), because the 2880 // remembered sets are used there to choose eager reclaim candidates. 2881 // If the remembered sets are not up to date we might miss some 2882 // entries that need to be handled. 2883 g1_rem_set()->cleanupHRRS(); 2884 2885 register_humongous_regions_with_cset(); 2886 2887 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 2888 2889 // We call this after finalize_cset() to 2890 // ensure that the CSet has been finalized. 2891 _cm->verify_no_cset_oops(); 2892 2893 if (_hr_printer.is_active()) { 2894 G1PrintCollectionSetClosure cl(&_hr_printer); 2895 _collection_set.iterate(&cl); 2896 } 2897 2898 // Initialize the GC alloc regions. 2899 _allocator->init_gc_alloc_regions(evacuation_info); 2900 2901 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 2902 pre_evacuate_collection_set(); 2903 2904 // Actually do the work... 2905 evacuate_collection_set(&per_thread_states); 2906 2907 post_evacuate_collection_set(evacuation_info, &per_thread_states); 2908 2909 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 2910 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 2911 2912 eagerly_reclaim_humongous_regions(); 2913 2914 record_obj_copy_mem_stats(); 2915 _survivor_evac_stats.adjust_desired_plab_sz(); 2916 _old_evac_stats.adjust_desired_plab_sz(); 2917 2918 double start = os::elapsedTime(); 2919 start_new_collection_set(); 2920 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 2921 2922 if (evacuation_failed()) { 2923 set_used(recalculate_used()); 2924 if (_archive_allocator != NULL) { 2925 _archive_allocator->clear_used(); 2926 } 2927 for (uint i = 0; i < ParallelGCThreads; i++) { 2928 if (_evacuation_failed_info_array[i].has_failed()) { 2929 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 2930 } 2931 } 2932 } else { 2933 // The "used" of the the collection set have already been subtracted 2934 // when they were freed. Add in the bytes evacuated. 2935 increase_used(g1_policy()->bytes_copied_during_gc()); 2936 } 2937 2938 if (collector_state()->in_initial_mark_gc()) { 2939 // We have to do this before we notify the CM threads that 2940 // they can start working to make sure that all the 2941 // appropriate initialization is done on the CM object. 2942 concurrent_mark()->post_initial_mark(); 2943 // Note that we don't actually trigger the CM thread at 2944 // this point. We do that later when we're sure that 2945 // the current thread has completed its logging output. 2946 } 2947 2948 allocate_dummy_regions(); 2949 2950 _allocator->init_mutator_alloc_region(); 2951 2952 { 2953 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 2954 if (expand_bytes > 0) { 2955 size_t bytes_before = capacity(); 2956 // No need for an ergo logging here, 2957 // expansion_amount() does this when it returns a value > 0. 2958 double expand_ms; 2959 if (!expand(expand_bytes, _workers, &expand_ms)) { 2960 // We failed to expand the heap. Cannot do anything about it. 2961 } 2962 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 2963 } 2964 } 2965 2966 // We redo the verification but now wrt to the new CSet which 2967 // has just got initialized after the previous CSet was freed. 2968 _cm->verify_no_cset_oops(); 2969 2970 // This timing is only used by the ergonomics to handle our pause target. 2971 // It is unclear why this should not include the full pause. We will 2972 // investigate this in CR 7178365. 2973 double sample_end_time_sec = os::elapsedTime(); 2974 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 2975 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards); 2976 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 2977 2978 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 2979 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 2980 2981 if (VerifyRememberedSets) { 2982 log_info(gc, verify)("[Verifying RemSets after GC]"); 2983 VerifyRegionRemSetClosure v_cl; 2984 heap_region_iterate(&v_cl); 2985 } 2986 2987 _verifier->verify_after_gc(verify_type); 2988 _verifier->check_bitmaps("GC End"); 2989 2990 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 2991 ref_processor_stw()->verify_no_references_recorded(); 2992 2993 // CM reference discovery will be re-enabled if necessary. 2994 } 2995 2996 #ifdef TRACESPINNING 2997 ParallelTaskTerminator::print_termination_counts(); 2998 #endif 2999 3000 gc_epilogue(false); 3001 } 3002 3003 // Print the remainder of the GC log output. 3004 if (evacuation_failed()) { 3005 log_info(gc)("To-space exhausted"); 3006 } 3007 3008 g1_policy()->print_phases(); 3009 heap_transition.print(); 3010 3011 // It is not yet to safe to tell the concurrent mark to 3012 // start as we have some optional output below. We don't want the 3013 // output from the concurrent mark thread interfering with this 3014 // logging output either. 3015 3016 _hrm.verify_optional(); 3017 _verifier->verify_region_sets_optional(); 3018 3019 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3020 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3021 3022 print_heap_after_gc(); 3023 print_heap_regions(); 3024 trace_heap_after_gc(_gc_tracer_stw); 3025 3026 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3027 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3028 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3029 // before any GC notifications are raised. 3030 g1mm()->update_sizes(); 3031 3032 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3033 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3034 _gc_timer_stw->register_gc_end(); 3035 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3036 } 3037 // It should now be safe to tell the concurrent mark thread to start 3038 // without its logging output interfering with the logging output 3039 // that came from the pause. 3040 3041 if (should_start_conc_mark) { 3042 // CAUTION: after the doConcurrentMark() call below, 3043 // the concurrent marking thread(s) could be running 3044 // concurrently with us. Make sure that anything after 3045 // this point does not assume that we are the only GC thread 3046 // running. Note: of course, the actual marking work will 3047 // not start until the safepoint itself is released in 3048 // SuspendibleThreadSet::desynchronize(). 3049 do_concurrent_mark(); 3050 } 3051 3052 return true; 3053 } 3054 3055 void G1CollectedHeap::remove_self_forwarding_pointers() { 3056 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3057 workers()->run_task(&rsfp_task); 3058 } 3059 3060 void G1CollectedHeap::restore_after_evac_failure() { 3061 double remove_self_forwards_start = os::elapsedTime(); 3062 3063 remove_self_forwarding_pointers(); 3064 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3065 _preserved_marks_set.restore(&task_executor); 3066 3067 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3068 } 3069 3070 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3071 if (!_evacuation_failed) { 3072 _evacuation_failed = true; 3073 } 3074 3075 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3076 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3077 } 3078 3079 bool G1ParEvacuateFollowersClosure::offer_termination() { 3080 G1ParScanThreadState* const pss = par_scan_state(); 3081 start_term_time(); 3082 const bool res = terminator()->offer_termination(); 3083 end_term_time(); 3084 return res; 3085 } 3086 3087 void G1ParEvacuateFollowersClosure::do_void() { 3088 G1ParScanThreadState* const pss = par_scan_state(); 3089 pss->trim_queue(); 3090 do { 3091 pss->steal_and_trim_queue(queues()); 3092 } while (!offer_termination()); 3093 } 3094 3095 class G1ParTask : public AbstractGangTask { 3096 protected: 3097 G1CollectedHeap* _g1h; 3098 G1ParScanThreadStateSet* _pss; 3099 RefToScanQueueSet* _queues; 3100 G1RootProcessor* _root_processor; 3101 ParallelTaskTerminator _terminator; 3102 uint _n_workers; 3103 3104 public: 3105 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3106 : AbstractGangTask("G1 collection"), 3107 _g1h(g1h), 3108 _pss(per_thread_states), 3109 _queues(task_queues), 3110 _root_processor(root_processor), 3111 _terminator(n_workers, _queues), 3112 _n_workers(n_workers) 3113 {} 3114 3115 void work(uint worker_id) { 3116 if (worker_id >= _n_workers) return; // no work needed this round 3117 3118 double start_sec = os::elapsedTime(); 3119 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3120 3121 { 3122 ResourceMark rm; 3123 HandleMark hm; 3124 3125 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3126 3127 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3128 pss->set_ref_processor(rp); 3129 3130 double start_strong_roots_sec = os::elapsedTime(); 3131 3132 _root_processor->evacuate_roots(pss->closures(), worker_id); 3133 3134 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3135 // treating the nmethods visited to act as roots for concurrent marking. 3136 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3137 // objects copied by the current evacuation. 3138 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, 3139 pss->closures()->weak_codeblobs(), 3140 worker_id); 3141 3142 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3143 3144 double term_sec = 0.0; 3145 size_t evac_term_attempts = 0; 3146 { 3147 double start = os::elapsedTime(); 3148 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3149 evac.do_void(); 3150 3151 evac_term_attempts = evac.term_attempts(); 3152 term_sec = evac.term_time(); 3153 double elapsed_sec = os::elapsedTime() - start; 3154 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3155 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3156 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3157 } 3158 3159 assert(pss->queue_is_empty(), "should be empty"); 3160 3161 if (log_is_enabled(Debug, gc, task, stats)) { 3162 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3163 size_t lab_waste; 3164 size_t lab_undo_waste; 3165 pss->waste(lab_waste, lab_undo_waste); 3166 _g1h->print_termination_stats(worker_id, 3167 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3168 strong_roots_sec * 1000.0, /* strong roots time */ 3169 term_sec * 1000.0, /* evac term time */ 3170 evac_term_attempts, /* evac term attempts */ 3171 lab_waste, /* alloc buffer waste */ 3172 lab_undo_waste /* undo waste */ 3173 ); 3174 } 3175 3176 // Close the inner scope so that the ResourceMark and HandleMark 3177 // destructors are executed here and are included as part of the 3178 // "GC Worker Time". 3179 } 3180 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3181 } 3182 }; 3183 3184 void G1CollectedHeap::print_termination_stats_hdr() { 3185 log_debug(gc, task, stats)("GC Termination Stats"); 3186 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3187 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3188 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3189 } 3190 3191 void G1CollectedHeap::print_termination_stats(uint worker_id, 3192 double elapsed_ms, 3193 double strong_roots_ms, 3194 double term_ms, 3195 size_t term_attempts, 3196 size_t alloc_buffer_waste, 3197 size_t undo_waste) const { 3198 log_debug(gc, task, stats) 3199 ("%3d %9.2f %9.2f %6.2f " 3200 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3201 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3202 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3203 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3204 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3205 alloc_buffer_waste * HeapWordSize / K, 3206 undo_waste * HeapWordSize / K); 3207 } 3208 3209 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3210 private: 3211 BoolObjectClosure* _is_alive; 3212 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3213 3214 int _initial_string_table_size; 3215 int _initial_symbol_table_size; 3216 3217 bool _process_strings; 3218 int _strings_processed; 3219 int _strings_removed; 3220 3221 bool _process_symbols; 3222 int _symbols_processed; 3223 int _symbols_removed; 3224 3225 bool _process_string_dedup; 3226 3227 public: 3228 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3229 AbstractGangTask("String/Symbol Unlinking"), 3230 _is_alive(is_alive), 3231 _dedup_closure(is_alive, NULL, false), 3232 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3233 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3234 _process_string_dedup(process_string_dedup) { 3235 3236 _initial_string_table_size = StringTable::the_table()->table_size(); 3237 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3238 if (process_strings) { 3239 StringTable::clear_parallel_claimed_index(); 3240 } 3241 if (process_symbols) { 3242 SymbolTable::clear_parallel_claimed_index(); 3243 } 3244 } 3245 3246 ~G1StringAndSymbolCleaningTask() { 3247 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3248 "claim value %d after unlink less than initial string table size %d", 3249 StringTable::parallel_claimed_index(), _initial_string_table_size); 3250 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3251 "claim value %d after unlink less than initial symbol table size %d", 3252 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3253 3254 log_info(gc, stringtable)( 3255 "Cleaned string and symbol table, " 3256 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3257 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3258 strings_processed(), strings_removed(), 3259 symbols_processed(), symbols_removed()); 3260 } 3261 3262 void work(uint worker_id) { 3263 int strings_processed = 0; 3264 int strings_removed = 0; 3265 int symbols_processed = 0; 3266 int symbols_removed = 0; 3267 if (_process_strings) { 3268 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3269 Atomic::add(strings_processed, &_strings_processed); 3270 Atomic::add(strings_removed, &_strings_removed); 3271 } 3272 if (_process_symbols) { 3273 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3274 Atomic::add(symbols_processed, &_symbols_processed); 3275 Atomic::add(symbols_removed, &_symbols_removed); 3276 } 3277 if (_process_string_dedup) { 3278 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3279 } 3280 } 3281 3282 size_t strings_processed() const { return (size_t)_strings_processed; } 3283 size_t strings_removed() const { return (size_t)_strings_removed; } 3284 3285 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3286 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3287 }; 3288 3289 class G1CodeCacheUnloadingTask { 3290 private: 3291 static Monitor* _lock; 3292 3293 BoolObjectClosure* const _is_alive; 3294 const bool _unloading_occurred; 3295 const uint _num_workers; 3296 3297 // Variables used to claim nmethods. 3298 CompiledMethod* _first_nmethod; 3299 CompiledMethod* volatile _claimed_nmethod; 3300 3301 // The list of nmethods that need to be processed by the second pass. 3302 CompiledMethod* volatile _postponed_list; 3303 volatile uint _num_entered_barrier; 3304 3305 public: 3306 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3307 _is_alive(is_alive), 3308 _unloading_occurred(unloading_occurred), 3309 _num_workers(num_workers), 3310 _first_nmethod(NULL), 3311 _claimed_nmethod(NULL), 3312 _postponed_list(NULL), 3313 _num_entered_barrier(0) 3314 { 3315 CompiledMethod::increase_unloading_clock(); 3316 // Get first alive nmethod 3317 CompiledMethodIterator iter = CompiledMethodIterator(); 3318 if(iter.next_alive()) { 3319 _first_nmethod = iter.method(); 3320 } 3321 _claimed_nmethod = _first_nmethod; 3322 } 3323 3324 ~G1CodeCacheUnloadingTask() { 3325 CodeCache::verify_clean_inline_caches(); 3326 3327 CodeCache::set_needs_cache_clean(false); 3328 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3329 3330 CodeCache::verify_icholder_relocations(); 3331 } 3332 3333 private: 3334 void add_to_postponed_list(CompiledMethod* nm) { 3335 CompiledMethod* old; 3336 do { 3337 old = _postponed_list; 3338 nm->set_unloading_next(old); 3339 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old); 3340 } 3341 3342 void clean_nmethod(CompiledMethod* nm) { 3343 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3344 3345 if (postponed) { 3346 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3347 add_to_postponed_list(nm); 3348 } 3349 3350 // Mark that this thread has been cleaned/unloaded. 3351 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3352 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3353 } 3354 3355 void clean_nmethod_postponed(CompiledMethod* nm) { 3356 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3357 } 3358 3359 static const int MaxClaimNmethods = 16; 3360 3361 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3362 CompiledMethod* first; 3363 CompiledMethodIterator last; 3364 3365 do { 3366 *num_claimed_nmethods = 0; 3367 3368 first = _claimed_nmethod; 3369 last = CompiledMethodIterator(first); 3370 3371 if (first != NULL) { 3372 3373 for (int i = 0; i < MaxClaimNmethods; i++) { 3374 if (!last.next_alive()) { 3375 break; 3376 } 3377 claimed_nmethods[i] = last.method(); 3378 (*num_claimed_nmethods)++; 3379 } 3380 } 3381 3382 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first); 3383 } 3384 3385 CompiledMethod* claim_postponed_nmethod() { 3386 CompiledMethod* claim; 3387 CompiledMethod* next; 3388 3389 do { 3390 claim = _postponed_list; 3391 if (claim == NULL) { 3392 return NULL; 3393 } 3394 3395 next = claim->unloading_next(); 3396 3397 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim); 3398 3399 return claim; 3400 } 3401 3402 public: 3403 // Mark that we're done with the first pass of nmethod cleaning. 3404 void barrier_mark(uint worker_id) { 3405 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3406 _num_entered_barrier++; 3407 if (_num_entered_barrier == _num_workers) { 3408 ml.notify_all(); 3409 } 3410 } 3411 3412 // See if we have to wait for the other workers to 3413 // finish their first-pass nmethod cleaning work. 3414 void barrier_wait(uint worker_id) { 3415 if (_num_entered_barrier < _num_workers) { 3416 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3417 while (_num_entered_barrier < _num_workers) { 3418 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3419 } 3420 } 3421 } 3422 3423 // Cleaning and unloading of nmethods. Some work has to be postponed 3424 // to the second pass, when we know which nmethods survive. 3425 void work_first_pass(uint worker_id) { 3426 // The first nmethods is claimed by the first worker. 3427 if (worker_id == 0 && _first_nmethod != NULL) { 3428 clean_nmethod(_first_nmethod); 3429 _first_nmethod = NULL; 3430 } 3431 3432 int num_claimed_nmethods; 3433 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3434 3435 while (true) { 3436 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3437 3438 if (num_claimed_nmethods == 0) { 3439 break; 3440 } 3441 3442 for (int i = 0; i < num_claimed_nmethods; i++) { 3443 clean_nmethod(claimed_nmethods[i]); 3444 } 3445 } 3446 } 3447 3448 void work_second_pass(uint worker_id) { 3449 CompiledMethod* nm; 3450 // Take care of postponed nmethods. 3451 while ((nm = claim_postponed_nmethod()) != NULL) { 3452 clean_nmethod_postponed(nm); 3453 } 3454 } 3455 }; 3456 3457 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3458 3459 class G1KlassCleaningTask : public StackObj { 3460 BoolObjectClosure* _is_alive; 3461 volatile int _clean_klass_tree_claimed; 3462 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3463 3464 public: 3465 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3466 _is_alive(is_alive), 3467 _clean_klass_tree_claimed(0), 3468 _klass_iterator() { 3469 } 3470 3471 private: 3472 bool claim_clean_klass_tree_task() { 3473 if (_clean_klass_tree_claimed) { 3474 return false; 3475 } 3476 3477 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0; 3478 } 3479 3480 InstanceKlass* claim_next_klass() { 3481 Klass* klass; 3482 do { 3483 klass =_klass_iterator.next_klass(); 3484 } while (klass != NULL && !klass->is_instance_klass()); 3485 3486 // this can be null so don't call InstanceKlass::cast 3487 return static_cast<InstanceKlass*>(klass); 3488 } 3489 3490 public: 3491 3492 void clean_klass(InstanceKlass* ik) { 3493 ik->clean_weak_instanceklass_links(_is_alive); 3494 } 3495 3496 void work() { 3497 ResourceMark rm; 3498 3499 // One worker will clean the subklass/sibling klass tree. 3500 if (claim_clean_klass_tree_task()) { 3501 Klass::clean_subklass_tree(_is_alive); 3502 } 3503 3504 // All workers will help cleaning the classes, 3505 InstanceKlass* klass; 3506 while ((klass = claim_next_klass()) != NULL) { 3507 clean_klass(klass); 3508 } 3509 } 3510 }; 3511 3512 class G1ResolvedMethodCleaningTask : public StackObj { 3513 BoolObjectClosure* _is_alive; 3514 volatile int _resolved_method_task_claimed; 3515 public: 3516 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) : 3517 _is_alive(is_alive), _resolved_method_task_claimed(0) {} 3518 3519 bool claim_resolved_method_task() { 3520 if (_resolved_method_task_claimed) { 3521 return false; 3522 } 3523 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0; 3524 } 3525 3526 // These aren't big, one thread can do it all. 3527 void work() { 3528 if (claim_resolved_method_task()) { 3529 ResolvedMethodTable::unlink(_is_alive); 3530 } 3531 } 3532 }; 3533 3534 3535 // To minimize the remark pause times, the tasks below are done in parallel. 3536 class G1ParallelCleaningTask : public AbstractGangTask { 3537 private: 3538 G1StringAndSymbolCleaningTask _string_symbol_task; 3539 G1CodeCacheUnloadingTask _code_cache_task; 3540 G1KlassCleaningTask _klass_cleaning_task; 3541 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task; 3542 3543 public: 3544 // The constructor is run in the VMThread. 3545 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3546 AbstractGangTask("Parallel Cleaning"), 3547 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3548 _code_cache_task(num_workers, is_alive, unloading_occurred), 3549 _klass_cleaning_task(is_alive), 3550 _resolved_method_cleaning_task(is_alive) { 3551 } 3552 3553 // The parallel work done by all worker threads. 3554 void work(uint worker_id) { 3555 // Do first pass of code cache cleaning. 3556 _code_cache_task.work_first_pass(worker_id); 3557 3558 // Let the threads mark that the first pass is done. 3559 _code_cache_task.barrier_mark(worker_id); 3560 3561 // Clean the Strings and Symbols. 3562 _string_symbol_task.work(worker_id); 3563 3564 // Clean unreferenced things in the ResolvedMethodTable 3565 _resolved_method_cleaning_task.work(); 3566 3567 // Wait for all workers to finish the first code cache cleaning pass. 3568 _code_cache_task.barrier_wait(worker_id); 3569 3570 // Do the second code cache cleaning work, which realize on 3571 // the liveness information gathered during the first pass. 3572 _code_cache_task.work_second_pass(worker_id); 3573 3574 // Clean all klasses that were not unloaded. 3575 _klass_cleaning_task.work(); 3576 } 3577 }; 3578 3579 3580 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3581 bool class_unloading_occurred) { 3582 uint n_workers = workers()->active_workers(); 3583 3584 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3585 workers()->run_task(&g1_unlink_task); 3586 } 3587 3588 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3589 bool process_strings, 3590 bool process_symbols, 3591 bool process_string_dedup) { 3592 if (!process_strings && !process_symbols && !process_string_dedup) { 3593 // Nothing to clean. 3594 return; 3595 } 3596 3597 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3598 workers()->run_task(&g1_unlink_task); 3599 3600 } 3601 3602 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3603 private: 3604 DirtyCardQueueSet* _queue; 3605 G1CollectedHeap* _g1h; 3606 public: 3607 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3608 _queue(queue), _g1h(g1h) { } 3609 3610 virtual void work(uint worker_id) { 3611 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3612 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3613 3614 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3615 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3616 3617 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3618 } 3619 }; 3620 3621 void G1CollectedHeap::redirty_logged_cards() { 3622 double redirty_logged_cards_start = os::elapsedTime(); 3623 3624 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3625 dirty_card_queue_set().reset_for_par_iteration(); 3626 workers()->run_task(&redirty_task); 3627 3628 DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set(); 3629 dcq.merge_bufferlists(&dirty_card_queue_set()); 3630 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3631 3632 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3633 } 3634 3635 // Weak Reference Processing support 3636 3637 // An always "is_alive" closure that is used to preserve referents. 3638 // If the object is non-null then it's alive. Used in the preservation 3639 // of referent objects that are pointed to by reference objects 3640 // discovered by the CM ref processor. 3641 class G1AlwaysAliveClosure: public BoolObjectClosure { 3642 G1CollectedHeap* _g1; 3643 public: 3644 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3645 bool do_object_b(oop p) { 3646 if (p != NULL) { 3647 return true; 3648 } 3649 return false; 3650 } 3651 }; 3652 3653 bool G1STWIsAliveClosure::do_object_b(oop p) { 3654 // An object is reachable if it is outside the collection set, 3655 // or is inside and copied. 3656 return !_g1->is_in_cset(p) || p->is_forwarded(); 3657 } 3658 3659 // Non Copying Keep Alive closure 3660 class G1KeepAliveClosure: public OopClosure { 3661 G1CollectedHeap* _g1; 3662 public: 3663 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3664 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3665 void do_oop(oop* p) { 3666 oop obj = *p; 3667 assert(obj != NULL, "the caller should have filtered out NULL values"); 3668 3669 const InCSetState cset_state = _g1->in_cset_state(obj); 3670 if (!cset_state.is_in_cset_or_humongous()) { 3671 return; 3672 } 3673 if (cset_state.is_in_cset()) { 3674 assert( obj->is_forwarded(), "invariant" ); 3675 *p = obj->forwardee(); 3676 } else { 3677 assert(!obj->is_forwarded(), "invariant" ); 3678 assert(cset_state.is_humongous(), 3679 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3680 _g1->set_humongous_is_live(obj); 3681 } 3682 } 3683 }; 3684 3685 // Copying Keep Alive closure - can be called from both 3686 // serial and parallel code as long as different worker 3687 // threads utilize different G1ParScanThreadState instances 3688 // and different queues. 3689 3690 class G1CopyingKeepAliveClosure: public OopClosure { 3691 G1CollectedHeap* _g1h; 3692 OopClosure* _copy_non_heap_obj_cl; 3693 G1ParScanThreadState* _par_scan_state; 3694 3695 public: 3696 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3697 OopClosure* non_heap_obj_cl, 3698 G1ParScanThreadState* pss): 3699 _g1h(g1h), 3700 _copy_non_heap_obj_cl(non_heap_obj_cl), 3701 _par_scan_state(pss) 3702 {} 3703 3704 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3705 virtual void do_oop( oop* p) { do_oop_work(p); } 3706 3707 template <class T> void do_oop_work(T* p) { 3708 oop obj = RawAccess<>::oop_load(p); 3709 3710 if (_g1h->is_in_cset_or_humongous(obj)) { 3711 // If the referent object has been forwarded (either copied 3712 // to a new location or to itself in the event of an 3713 // evacuation failure) then we need to update the reference 3714 // field and, if both reference and referent are in the G1 3715 // heap, update the RSet for the referent. 3716 // 3717 // If the referent has not been forwarded then we have to keep 3718 // it alive by policy. Therefore we have copy the referent. 3719 // 3720 // If the reference field is in the G1 heap then we can push 3721 // on the PSS queue. When the queue is drained (after each 3722 // phase of reference processing) the object and it's followers 3723 // will be copied, the reference field set to point to the 3724 // new location, and the RSet updated. Otherwise we need to 3725 // use the the non-heap or metadata closures directly to copy 3726 // the referent object and update the pointer, while avoiding 3727 // updating the RSet. 3728 3729 if (_g1h->is_in_g1_reserved(p)) { 3730 _par_scan_state->push_on_queue(p); 3731 } else { 3732 assert(!Metaspace::contains((const void*)p), 3733 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 3734 _copy_non_heap_obj_cl->do_oop(p); 3735 } 3736 } 3737 } 3738 }; 3739 3740 // Serial drain queue closure. Called as the 'complete_gc' 3741 // closure for each discovered list in some of the 3742 // reference processing phases. 3743 3744 class G1STWDrainQueueClosure: public VoidClosure { 3745 protected: 3746 G1CollectedHeap* _g1h; 3747 G1ParScanThreadState* _par_scan_state; 3748 3749 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3750 3751 public: 3752 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3753 _g1h(g1h), 3754 _par_scan_state(pss) 3755 { } 3756 3757 void do_void() { 3758 G1ParScanThreadState* const pss = par_scan_state(); 3759 pss->trim_queue(); 3760 } 3761 }; 3762 3763 // Parallel Reference Processing closures 3764 3765 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3766 // processing during G1 evacuation pauses. 3767 3768 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3769 private: 3770 G1CollectedHeap* _g1h; 3771 G1ParScanThreadStateSet* _pss; 3772 RefToScanQueueSet* _queues; 3773 WorkGang* _workers; 3774 uint _active_workers; 3775 3776 public: 3777 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3778 G1ParScanThreadStateSet* per_thread_states, 3779 WorkGang* workers, 3780 RefToScanQueueSet *task_queues, 3781 uint n_workers) : 3782 _g1h(g1h), 3783 _pss(per_thread_states), 3784 _queues(task_queues), 3785 _workers(workers), 3786 _active_workers(n_workers) 3787 { 3788 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 3789 } 3790 3791 // Executes the given task using concurrent marking worker threads. 3792 virtual void execute(ProcessTask& task); 3793 virtual void execute(EnqueueTask& task); 3794 }; 3795 3796 // Gang task for possibly parallel reference processing 3797 3798 class G1STWRefProcTaskProxy: public AbstractGangTask { 3799 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 3800 ProcessTask& _proc_task; 3801 G1CollectedHeap* _g1h; 3802 G1ParScanThreadStateSet* _pss; 3803 RefToScanQueueSet* _task_queues; 3804 ParallelTaskTerminator* _terminator; 3805 3806 public: 3807 G1STWRefProcTaskProxy(ProcessTask& proc_task, 3808 G1CollectedHeap* g1h, 3809 G1ParScanThreadStateSet* per_thread_states, 3810 RefToScanQueueSet *task_queues, 3811 ParallelTaskTerminator* terminator) : 3812 AbstractGangTask("Process reference objects in parallel"), 3813 _proc_task(proc_task), 3814 _g1h(g1h), 3815 _pss(per_thread_states), 3816 _task_queues(task_queues), 3817 _terminator(terminator) 3818 {} 3819 3820 virtual void work(uint worker_id) { 3821 // The reference processing task executed by a single worker. 3822 ResourceMark rm; 3823 HandleMark hm; 3824 3825 G1STWIsAliveClosure is_alive(_g1h); 3826 3827 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3828 pss->set_ref_processor(NULL); 3829 3830 // Keep alive closure. 3831 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 3832 3833 // Complete GC closure 3834 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 3835 3836 // Call the reference processing task's work routine. 3837 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 3838 3839 // Note we cannot assert that the refs array is empty here as not all 3840 // of the processing tasks (specifically phase2 - pp2_work) execute 3841 // the complete_gc closure (which ordinarily would drain the queue) so 3842 // the queue may not be empty. 3843 } 3844 }; 3845 3846 // Driver routine for parallel reference processing. 3847 // Creates an instance of the ref processing gang 3848 // task and has the worker threads execute it. 3849 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 3850 assert(_workers != NULL, "Need parallel worker threads."); 3851 3852 ParallelTaskTerminator terminator(_active_workers, _queues); 3853 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 3854 3855 _workers->run_task(&proc_task_proxy); 3856 } 3857 3858 // Gang task for parallel reference enqueueing. 3859 3860 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 3861 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 3862 EnqueueTask& _enq_task; 3863 3864 public: 3865 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 3866 AbstractGangTask("Enqueue reference objects in parallel"), 3867 _enq_task(enq_task) 3868 { } 3869 3870 virtual void work(uint worker_id) { 3871 _enq_task.work(worker_id); 3872 } 3873 }; 3874 3875 // Driver routine for parallel reference enqueueing. 3876 // Creates an instance of the ref enqueueing gang 3877 // task and has the worker threads execute it. 3878 3879 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 3880 assert(_workers != NULL, "Need parallel worker threads."); 3881 3882 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 3883 3884 _workers->run_task(&enq_task_proxy); 3885 } 3886 3887 // End of weak reference support closures 3888 3889 // Abstract task used to preserve (i.e. copy) any referent objects 3890 // that are in the collection set and are pointed to by reference 3891 // objects discovered by the CM ref processor. 3892 3893 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 3894 protected: 3895 G1CollectedHeap* _g1h; 3896 G1ParScanThreadStateSet* _pss; 3897 RefToScanQueueSet* _queues; 3898 ParallelTaskTerminator _terminator; 3899 uint _n_workers; 3900 3901 public: 3902 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 3903 AbstractGangTask("ParPreserveCMReferents"), 3904 _g1h(g1h), 3905 _pss(per_thread_states), 3906 _queues(task_queues), 3907 _terminator(workers, _queues), 3908 _n_workers(workers) 3909 { 3910 g1h->ref_processor_cm()->set_active_mt_degree(workers); 3911 } 3912 3913 void work(uint worker_id) { 3914 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 3915 3916 ResourceMark rm; 3917 HandleMark hm; 3918 3919 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3920 pss->set_ref_processor(NULL); 3921 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 3922 3923 // Is alive closure 3924 G1AlwaysAliveClosure always_alive(_g1h); 3925 3926 // Copying keep alive closure. Applied to referent objects that need 3927 // to be copied. 3928 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 3929 3930 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 3931 3932 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 3933 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 3934 3935 // limit is set using max_num_q() - which was set using ParallelGCThreads. 3936 // So this must be true - but assert just in case someone decides to 3937 // change the worker ids. 3938 assert(worker_id < limit, "sanity"); 3939 assert(!rp->discovery_is_atomic(), "check this code"); 3940 3941 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 3942 for (uint idx = worker_id; idx < limit; idx += stride) { 3943 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 3944 3945 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 3946 while (iter.has_next()) { 3947 // Since discovery is not atomic for the CM ref processor, we 3948 // can see some null referent objects. 3949 iter.load_ptrs(DEBUG_ONLY(true)); 3950 oop ref = iter.obj(); 3951 3952 // This will filter nulls. 3953 if (iter.is_referent_alive()) { 3954 iter.make_referent_alive(); 3955 } 3956 iter.move_to_next(); 3957 } 3958 } 3959 3960 // Drain the queue - which may cause stealing 3961 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 3962 drain_queue.do_void(); 3963 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 3964 assert(pss->queue_is_empty(), "should be"); 3965 } 3966 }; 3967 3968 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 3969 // Any reference objects, in the collection set, that were 'discovered' 3970 // by the CM ref processor should have already been copied (either by 3971 // applying the external root copy closure to the discovered lists, or 3972 // by following an RSet entry). 3973 // 3974 // But some of the referents, that are in the collection set, that these 3975 // reference objects point to may not have been copied: the STW ref 3976 // processor would have seen that the reference object had already 3977 // been 'discovered' and would have skipped discovering the reference, 3978 // but would not have treated the reference object as a regular oop. 3979 // As a result the copy closure would not have been applied to the 3980 // referent object. 3981 // 3982 // We need to explicitly copy these referent objects - the references 3983 // will be processed at the end of remarking. 3984 // 3985 // We also need to do this copying before we process the reference 3986 // objects discovered by the STW ref processor in case one of these 3987 // referents points to another object which is also referenced by an 3988 // object discovered by the STW ref processor. 3989 double preserve_cm_referents_time = 0.0; 3990 3991 // To avoid spawning task when there is no work to do, check that 3992 // a concurrent cycle is active and that some references have been 3993 // discovered. 3994 if (concurrent_mark()->cm_thread()->during_cycle() && 3995 ref_processor_cm()->has_discovered_references()) { 3996 double preserve_cm_referents_start = os::elapsedTime(); 3997 uint no_of_gc_workers = workers()->active_workers(); 3998 G1ParPreserveCMReferentsTask keep_cm_referents(this, 3999 per_thread_states, 4000 no_of_gc_workers, 4001 _task_queues); 4002 workers()->run_task(&keep_cm_referents); 4003 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4004 } 4005 4006 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4007 } 4008 4009 // Weak Reference processing during an evacuation pause (part 1). 4010 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4011 double ref_proc_start = os::elapsedTime(); 4012 4013 ReferenceProcessor* rp = _ref_processor_stw; 4014 assert(rp->discovery_enabled(), "should have been enabled"); 4015 4016 // Closure to test whether a referent is alive. 4017 G1STWIsAliveClosure is_alive(this); 4018 4019 // Even when parallel reference processing is enabled, the processing 4020 // of JNI refs is serial and performed serially by the current thread 4021 // rather than by a worker. The following PSS will be used for processing 4022 // JNI refs. 4023 4024 // Use only a single queue for this PSS. 4025 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4026 pss->set_ref_processor(NULL); 4027 assert(pss->queue_is_empty(), "pre-condition"); 4028 4029 // Keep alive closure. 4030 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4031 4032 // Serial Complete GC closure 4033 G1STWDrainQueueClosure drain_queue(this, pss); 4034 4035 // Setup the soft refs policy... 4036 rp->setup_policy(false); 4037 4038 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4039 4040 ReferenceProcessorStats stats; 4041 if (!rp->processing_is_mt()) { 4042 // Serial reference processing... 4043 stats = rp->process_discovered_references(&is_alive, 4044 &keep_alive, 4045 &drain_queue, 4046 NULL, 4047 pt); 4048 } else { 4049 uint no_of_gc_workers = workers()->active_workers(); 4050 4051 // Parallel reference processing 4052 assert(no_of_gc_workers <= rp->max_num_q(), 4053 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4054 no_of_gc_workers, rp->max_num_q()); 4055 4056 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4057 stats = rp->process_discovered_references(&is_alive, 4058 &keep_alive, 4059 &drain_queue, 4060 &par_task_executor, 4061 pt); 4062 } 4063 4064 _gc_tracer_stw->report_gc_reference_stats(stats); 4065 4066 // We have completed copying any necessary live referent objects. 4067 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4068 4069 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4070 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4071 } 4072 4073 // Weak Reference processing during an evacuation pause (part 2). 4074 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4075 double ref_enq_start = os::elapsedTime(); 4076 4077 ReferenceProcessor* rp = _ref_processor_stw; 4078 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4079 4080 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4081 4082 // Now enqueue any remaining on the discovered lists on to 4083 // the pending list. 4084 if (!rp->processing_is_mt()) { 4085 // Serial reference processing... 4086 rp->enqueue_discovered_references(NULL, pt); 4087 } else { 4088 // Parallel reference enqueueing 4089 4090 uint n_workers = workers()->active_workers(); 4091 4092 assert(n_workers <= rp->max_num_q(), 4093 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4094 n_workers, rp->max_num_q()); 4095 4096 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4097 rp->enqueue_discovered_references(&par_task_executor, pt); 4098 } 4099 4100 rp->verify_no_references_recorded(); 4101 assert(!rp->discovery_enabled(), "should have been disabled"); 4102 4103 // If during an initial mark pause we install a pending list head which is not otherwise reachable 4104 // ensure that it is marked in the bitmap for concurrent marking to discover. 4105 if (collector_state()->in_initial_mark_gc()) { 4106 oop pll_head = Universe::reference_pending_list(); 4107 if (pll_head != NULL) { 4108 // Any valid worker id is fine here as we are in the VM thread and single-threaded. 4109 _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head); 4110 } 4111 } 4112 4113 // FIXME 4114 // CM's reference processing also cleans up the string and symbol tables. 4115 // Should we do that here also? We could, but it is a serial operation 4116 // and could significantly increase the pause time. 4117 4118 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4119 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4120 } 4121 4122 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4123 double merge_pss_time_start = os::elapsedTime(); 4124 per_thread_states->flush(); 4125 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4126 } 4127 4128 void G1CollectedHeap::pre_evacuate_collection_set() { 4129 _expand_heap_after_alloc_failure = true; 4130 _evacuation_failed = false; 4131 4132 // Disable the hot card cache. 4133 _hot_card_cache->reset_hot_cache_claimed_index(); 4134 _hot_card_cache->set_use_cache(false); 4135 4136 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4137 _preserved_marks_set.assert_empty(); 4138 4139 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4140 4141 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4142 if (collector_state()->in_initial_mark_gc()) { 4143 double start_clear_claimed_marks = os::elapsedTime(); 4144 4145 ClassLoaderDataGraph::clear_claimed_marks(); 4146 4147 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4148 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4149 } 4150 } 4151 4152 void G1CollectedHeap::evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states) { 4153 // Should G1EvacuationFailureALot be in effect for this GC? 4154 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4155 4156 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4157 4158 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4159 4160 double start_par_time_sec = os::elapsedTime(); 4161 double end_par_time_sec; 4162 4163 { 4164 const uint n_workers = workers()->active_workers(); 4165 G1RootProcessor root_processor(this, n_workers); 4166 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4167 4168 print_termination_stats_hdr(); 4169 4170 workers()->run_task(&g1_par_task); 4171 end_par_time_sec = os::elapsedTime(); 4172 4173 // Closing the inner scope will execute the destructor 4174 // for the G1RootProcessor object. We record the current 4175 // elapsed time before closing the scope so that time 4176 // taken for the destructor is NOT included in the 4177 // reported parallel time. 4178 } 4179 4180 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4181 phase_times->record_par_time(par_time_ms); 4182 4183 double code_root_fixup_time_ms = 4184 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4185 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4186 } 4187 4188 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4189 // Process any discovered reference objects - we have 4190 // to do this _before_ we retire the GC alloc regions 4191 // as we may have to copy some 'reachable' referent 4192 // objects (and their reachable sub-graphs) that were 4193 // not copied during the pause. 4194 preserve_cm_referents(per_thread_states); 4195 process_discovered_references(per_thread_states); 4196 4197 G1STWIsAliveClosure is_alive(this); 4198 G1KeepAliveClosure keep_alive(this); 4199 4200 { 4201 double start = os::elapsedTime(); 4202 4203 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 4204 4205 double time_ms = (os::elapsedTime() - start) * 1000.0; 4206 g1_policy()->phase_times()->record_ref_proc_time(time_ms); 4207 } 4208 4209 if (G1StringDedup::is_enabled()) { 4210 double fixup_start = os::elapsedTime(); 4211 4212 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4213 4214 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4215 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4216 } 4217 4218 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4219 4220 if (evacuation_failed()) { 4221 restore_after_evac_failure(); 4222 4223 // Reset the G1EvacuationFailureALot counters and flags 4224 // Note: the values are reset only when an actual 4225 // evacuation failure occurs. 4226 NOT_PRODUCT(reset_evacuation_should_fail();) 4227 } 4228 4229 _preserved_marks_set.assert_empty(); 4230 4231 // Enqueue any remaining references remaining on the STW 4232 // reference processor's discovered lists. We need to do 4233 // this after the card table is cleaned (and verified) as 4234 // the act of enqueueing entries on to the pending list 4235 // will log these updates (and dirty their associated 4236 // cards). We need these updates logged to update any 4237 // RSets. 4238 enqueue_discovered_references(per_thread_states); 4239 4240 _allocator->release_gc_alloc_regions(evacuation_info); 4241 4242 merge_per_thread_state_info(per_thread_states); 4243 4244 // Reset and re-enable the hot card cache. 4245 // Note the counts for the cards in the regions in the 4246 // collection set are reset when the collection set is freed. 4247 _hot_card_cache->reset_hot_cache(); 4248 _hot_card_cache->set_use_cache(true); 4249 4250 purge_code_root_memory(); 4251 4252 redirty_logged_cards(); 4253 #if COMPILER2_OR_JVMCI 4254 double start = os::elapsedTime(); 4255 DerivedPointerTable::update_pointers(); 4256 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4257 #endif 4258 g1_policy()->print_age_table(); 4259 } 4260 4261 void G1CollectedHeap::record_obj_copy_mem_stats() { 4262 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4263 4264 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4265 create_g1_evac_summary(&_old_evac_stats)); 4266 } 4267 4268 void G1CollectedHeap::free_region(HeapRegion* hr, 4269 FreeRegionList* free_list, 4270 bool skip_remset, 4271 bool skip_hot_card_cache, 4272 bool locked) { 4273 assert(!hr->is_free(), "the region should not be free"); 4274 assert(!hr->is_empty(), "the region should not be empty"); 4275 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4276 assert(free_list != NULL, "pre-condition"); 4277 4278 if (G1VerifyBitmaps) { 4279 MemRegion mr(hr->bottom(), hr->end()); 4280 concurrent_mark()->clear_range_in_prev_bitmap(mr); 4281 } 4282 4283 // Clear the card counts for this region. 4284 // Note: we only need to do this if the region is not young 4285 // (since we don't refine cards in young regions). 4286 if (!skip_hot_card_cache && !hr->is_young()) { 4287 _hot_card_cache->reset_card_counts(hr); 4288 } 4289 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4290 _g1_policy->remset_tracker()->update_at_free(hr); 4291 free_list->add_ordered(hr); 4292 } 4293 4294 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4295 FreeRegionList* free_list) { 4296 assert(hr->is_humongous(), "this is only for humongous regions"); 4297 assert(free_list != NULL, "pre-condition"); 4298 hr->clear_humongous(); 4299 free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */); 4300 } 4301 4302 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4303 const uint humongous_regions_removed) { 4304 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4305 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4306 _old_set.bulk_remove(old_regions_removed); 4307 _humongous_set.bulk_remove(humongous_regions_removed); 4308 } 4309 4310 } 4311 4312 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4313 assert(list != NULL, "list can't be null"); 4314 if (!list->is_empty()) { 4315 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4316 _hrm.insert_list_into_free_list(list); 4317 } 4318 } 4319 4320 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4321 decrease_used(bytes); 4322 } 4323 4324 class G1FreeCollectionSetTask : public AbstractGangTask { 4325 private: 4326 4327 // Closure applied to all regions in the collection set to do work that needs to 4328 // be done serially in a single thread. 4329 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4330 private: 4331 EvacuationInfo* _evacuation_info; 4332 const size_t* _surviving_young_words; 4333 4334 // Bytes used in successfully evacuated regions before the evacuation. 4335 size_t _before_used_bytes; 4336 // Bytes used in unsucessfully evacuated regions before the evacuation 4337 size_t _after_used_bytes; 4338 4339 size_t _bytes_allocated_in_old_since_last_gc; 4340 4341 size_t _failure_used_words; 4342 size_t _failure_waste_words; 4343 4344 FreeRegionList _local_free_list; 4345 public: 4346 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4347 HeapRegionClosure(), 4348 _evacuation_info(evacuation_info), 4349 _surviving_young_words(surviving_young_words), 4350 _before_used_bytes(0), 4351 _after_used_bytes(0), 4352 _bytes_allocated_in_old_since_last_gc(0), 4353 _failure_used_words(0), 4354 _failure_waste_words(0), 4355 _local_free_list("Local Region List for CSet Freeing") { 4356 } 4357 4358 virtual bool do_heap_region(HeapRegion* r) { 4359 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4360 4361 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4362 g1h->clear_in_cset(r); 4363 4364 if (r->is_young()) { 4365 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4366 "Young index %d is wrong for region %u of type %s with %u young regions", 4367 r->young_index_in_cset(), 4368 r->hrm_index(), 4369 r->get_type_str(), 4370 g1h->collection_set()->young_region_length()); 4371 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4372 r->record_surv_words_in_group(words_survived); 4373 } 4374 4375 if (!r->evacuation_failed()) { 4376 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4377 _before_used_bytes += r->used(); 4378 g1h->free_region(r, 4379 &_local_free_list, 4380 true, /* skip_remset */ 4381 true, /* skip_hot_card_cache */ 4382 true /* locked */); 4383 } else { 4384 r->uninstall_surv_rate_group(); 4385 r->set_young_index_in_cset(-1); 4386 r->set_evacuation_failed(false); 4387 // When moving a young gen region to old gen, we "allocate" that whole region 4388 // there. This is in addition to any already evacuated objects. Notify the 4389 // policy about that. 4390 // Old gen regions do not cause an additional allocation: both the objects 4391 // still in the region and the ones already moved are accounted for elsewhere. 4392 if (r->is_young()) { 4393 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4394 } 4395 // The region is now considered to be old. 4396 r->set_old(); 4397 // Do some allocation statistics accounting. Regions that failed evacuation 4398 // are always made old, so there is no need to update anything in the young 4399 // gen statistics, but we need to update old gen statistics. 4400 size_t used_words = r->marked_bytes() / HeapWordSize; 4401 4402 _failure_used_words += used_words; 4403 _failure_waste_words += HeapRegion::GrainWords - used_words; 4404 4405 g1h->old_set_add(r); 4406 _after_used_bytes += r->used(); 4407 } 4408 return false; 4409 } 4410 4411 void complete_work() { 4412 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4413 4414 _evacuation_info->set_regions_freed(_local_free_list.length()); 4415 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4416 4417 g1h->prepend_to_freelist(&_local_free_list); 4418 g1h->decrement_summary_bytes(_before_used_bytes); 4419 4420 G1Policy* policy = g1h->g1_policy(); 4421 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4422 4423 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4424 } 4425 }; 4426 4427 G1CollectionSet* _collection_set; 4428 G1SerialFreeCollectionSetClosure _cl; 4429 const size_t* _surviving_young_words; 4430 4431 size_t _rs_lengths; 4432 4433 volatile jint _serial_work_claim; 4434 4435 struct WorkItem { 4436 uint region_idx; 4437 bool is_young; 4438 bool evacuation_failed; 4439 4440 WorkItem(HeapRegion* r) { 4441 region_idx = r->hrm_index(); 4442 is_young = r->is_young(); 4443 evacuation_failed = r->evacuation_failed(); 4444 } 4445 }; 4446 4447 volatile size_t _parallel_work_claim; 4448 size_t _num_work_items; 4449 WorkItem* _work_items; 4450 4451 void do_serial_work() { 4452 // Need to grab the lock to be allowed to modify the old region list. 4453 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4454 _collection_set->iterate(&_cl); 4455 } 4456 4457 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4458 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4459 4460 HeapRegion* r = g1h->region_at(region_idx); 4461 assert(!g1h->is_on_master_free_list(r), "sanity"); 4462 4463 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4464 4465 if (!is_young) { 4466 g1h->_hot_card_cache->reset_card_counts(r); 4467 } 4468 4469 if (!evacuation_failed) { 4470 r->rem_set()->clear_locked(); 4471 } 4472 } 4473 4474 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4475 private: 4476 size_t _cur_idx; 4477 WorkItem* _work_items; 4478 public: 4479 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4480 4481 virtual bool do_heap_region(HeapRegion* r) { 4482 _work_items[_cur_idx++] = WorkItem(r); 4483 return false; 4484 } 4485 }; 4486 4487 void prepare_work() { 4488 G1PrepareFreeCollectionSetClosure cl(_work_items); 4489 _collection_set->iterate(&cl); 4490 } 4491 4492 void complete_work() { 4493 _cl.complete_work(); 4494 4495 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4496 policy->record_max_rs_lengths(_rs_lengths); 4497 policy->cset_regions_freed(); 4498 } 4499 public: 4500 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4501 AbstractGangTask("G1 Free Collection Set"), 4502 _cl(evacuation_info, surviving_young_words), 4503 _collection_set(collection_set), 4504 _surviving_young_words(surviving_young_words), 4505 _serial_work_claim(0), 4506 _rs_lengths(0), 4507 _parallel_work_claim(0), 4508 _num_work_items(collection_set->region_length()), 4509 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4510 prepare_work(); 4511 } 4512 4513 ~G1FreeCollectionSetTask() { 4514 complete_work(); 4515 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4516 } 4517 4518 // Chunk size for work distribution. The chosen value has been determined experimentally 4519 // to be a good tradeoff between overhead and achievable parallelism. 4520 static uint chunk_size() { return 32; } 4521 4522 virtual void work(uint worker_id) { 4523 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4524 4525 // Claim serial work. 4526 if (_serial_work_claim == 0) { 4527 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4528 if (value == 0) { 4529 double serial_time = os::elapsedTime(); 4530 do_serial_work(); 4531 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4532 } 4533 } 4534 4535 // Start parallel work. 4536 double young_time = 0.0; 4537 bool has_young_time = false; 4538 double non_young_time = 0.0; 4539 bool has_non_young_time = false; 4540 4541 while (true) { 4542 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4543 size_t cur = end - chunk_size(); 4544 4545 if (cur >= _num_work_items) { 4546 break; 4547 } 4548 4549 double start_time = os::elapsedTime(); 4550 4551 end = MIN2(end, _num_work_items); 4552 4553 for (; cur < end; cur++) { 4554 bool is_young = _work_items[cur].is_young; 4555 4556 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4557 4558 double end_time = os::elapsedTime(); 4559 double time_taken = end_time - start_time; 4560 if (is_young) { 4561 young_time += time_taken; 4562 has_young_time = true; 4563 } else { 4564 non_young_time += time_taken; 4565 has_non_young_time = true; 4566 } 4567 start_time = end_time; 4568 } 4569 } 4570 4571 if (has_young_time) { 4572 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4573 } 4574 if (has_non_young_time) { 4575 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time); 4576 } 4577 } 4578 }; 4579 4580 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4581 _eden.clear(); 4582 4583 double free_cset_start_time = os::elapsedTime(); 4584 4585 { 4586 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4587 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4588 4589 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4590 4591 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4592 cl.name(), 4593 num_workers, 4594 _collection_set.region_length()); 4595 workers()->run_task(&cl, num_workers); 4596 } 4597 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4598 4599 collection_set->clear(); 4600 } 4601 4602 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4603 private: 4604 FreeRegionList* _free_region_list; 4605 HeapRegionSet* _proxy_set; 4606 uint _humongous_objects_reclaimed; 4607 uint _humongous_regions_reclaimed; 4608 size_t _freed_bytes; 4609 public: 4610 4611 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4612 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4613 } 4614 4615 virtual bool do_heap_region(HeapRegion* r) { 4616 if (!r->is_starts_humongous()) { 4617 return false; 4618 } 4619 4620 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4621 4622 oop obj = (oop)r->bottom(); 4623 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap(); 4624 4625 // The following checks whether the humongous object is live are sufficient. 4626 // The main additional check (in addition to having a reference from the roots 4627 // or the young gen) is whether the humongous object has a remembered set entry. 4628 // 4629 // A humongous object cannot be live if there is no remembered set for it 4630 // because: 4631 // - there can be no references from within humongous starts regions referencing 4632 // the object because we never allocate other objects into them. 4633 // (I.e. there are no intra-region references that may be missed by the 4634 // remembered set) 4635 // - as soon there is a remembered set entry to the humongous starts region 4636 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4637 // until the end of a concurrent mark. 4638 // 4639 // It is not required to check whether the object has been found dead by marking 4640 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4641 // all objects allocated during that time are considered live. 4642 // SATB marking is even more conservative than the remembered set. 4643 // So if at this point in the collection there is no remembered set entry, 4644 // nobody has a reference to it. 4645 // At the start of collection we flush all refinement logs, and remembered sets 4646 // are completely up-to-date wrt to references to the humongous object. 4647 // 4648 // Other implementation considerations: 4649 // - never consider object arrays at this time because they would pose 4650 // considerable effort for cleaning up the the remembered sets. This is 4651 // required because stale remembered sets might reference locations that 4652 // are currently allocated into. 4653 uint region_idx = r->hrm_index(); 4654 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4655 !r->rem_set()->is_empty()) { 4656 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", 4657 region_idx, 4658 (size_t)obj->size() * HeapWordSize, 4659 p2i(r->bottom()), 4660 r->rem_set()->occupied(), 4661 r->rem_set()->strong_code_roots_list_length(), 4662 next_bitmap->is_marked(r->bottom()), 4663 g1h->is_humongous_reclaim_candidate(region_idx), 4664 obj->is_typeArray() 4665 ); 4666 return false; 4667 } 4668 4669 guarantee(obj->is_typeArray(), 4670 "Only eagerly reclaiming type arrays is supported, but the object " 4671 PTR_FORMAT " is not.", p2i(r->bottom())); 4672 4673 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", 4674 region_idx, 4675 (size_t)obj->size() * HeapWordSize, 4676 p2i(r->bottom()), 4677 r->rem_set()->occupied(), 4678 r->rem_set()->strong_code_roots_list_length(), 4679 next_bitmap->is_marked(r->bottom()), 4680 g1h->is_humongous_reclaim_candidate(region_idx), 4681 obj->is_typeArray() 4682 ); 4683 4684 G1ConcurrentMark* const cm = g1h->concurrent_mark(); 4685 cm->humongous_object_eagerly_reclaimed(r); 4686 assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj), 4687 "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s", 4688 region_idx, 4689 BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)), 4690 BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj))); 4691 _humongous_objects_reclaimed++; 4692 do { 4693 HeapRegion* next = g1h->next_region_in_humongous(r); 4694 _freed_bytes += r->used(); 4695 r->set_containing_set(NULL); 4696 _humongous_regions_reclaimed++; 4697 g1h->free_humongous_region(r, _free_region_list); 4698 r = next; 4699 } while (r != NULL); 4700 4701 return false; 4702 } 4703 4704 uint humongous_objects_reclaimed() { 4705 return _humongous_objects_reclaimed; 4706 } 4707 4708 uint humongous_regions_reclaimed() { 4709 return _humongous_regions_reclaimed; 4710 } 4711 4712 size_t bytes_freed() const { 4713 return _freed_bytes; 4714 } 4715 }; 4716 4717 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4718 assert_at_safepoint_on_vm_thread(); 4719 4720 if (!G1EagerReclaimHumongousObjects || 4721 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4722 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4723 return; 4724 } 4725 4726 double start_time = os::elapsedTime(); 4727 4728 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4729 4730 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4731 heap_region_iterate(&cl); 4732 4733 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4734 4735 G1HRPrinter* hrp = hr_printer(); 4736 if (hrp->is_active()) { 4737 FreeRegionListIterator iter(&local_cleanup_list); 4738 while (iter.more_available()) { 4739 HeapRegion* hr = iter.get_next(); 4740 hrp->cleanup(hr); 4741 } 4742 } 4743 4744 prepend_to_freelist(&local_cleanup_list); 4745 decrement_summary_bytes(cl.bytes_freed()); 4746 4747 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4748 cl.humongous_objects_reclaimed()); 4749 } 4750 4751 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4752 public: 4753 virtual bool do_heap_region(HeapRegion* r) { 4754 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4755 G1CollectedHeap::heap()->clear_in_cset(r); 4756 r->set_young_index_in_cset(-1); 4757 return false; 4758 } 4759 }; 4760 4761 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4762 G1AbandonCollectionSetClosure cl; 4763 collection_set->iterate(&cl); 4764 4765 collection_set->clear(); 4766 collection_set->stop_incremental_building(); 4767 } 4768 4769 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 4770 return _allocator->is_retained_old_region(hr); 4771 } 4772 4773 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 4774 _eden.add(hr); 4775 _g1_policy->set_region_eden(hr); 4776 } 4777 4778 #ifdef ASSERT 4779 4780 class NoYoungRegionsClosure: public HeapRegionClosure { 4781 private: 4782 bool _success; 4783 public: 4784 NoYoungRegionsClosure() : _success(true) { } 4785 bool do_heap_region(HeapRegion* r) { 4786 if (r->is_young()) { 4787 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 4788 p2i(r->bottom()), p2i(r->end())); 4789 _success = false; 4790 } 4791 return false; 4792 } 4793 bool success() { return _success; } 4794 }; 4795 4796 bool G1CollectedHeap::check_young_list_empty() { 4797 bool ret = (young_regions_count() == 0); 4798 4799 NoYoungRegionsClosure closure; 4800 heap_region_iterate(&closure); 4801 ret = ret && closure.success(); 4802 4803 return ret; 4804 } 4805 4806 #endif // ASSERT 4807 4808 class TearDownRegionSetsClosure : public HeapRegionClosure { 4809 private: 4810 HeapRegionSet *_old_set; 4811 4812 public: 4813 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 4814 4815 bool do_heap_region(HeapRegion* r) { 4816 if (r->is_old()) { 4817 _old_set->remove(r); 4818 } else if(r->is_young()) { 4819 r->uninstall_surv_rate_group(); 4820 } else { 4821 // We ignore free regions, we'll empty the free list afterwards. 4822 // We ignore humongous regions, we're not tearing down the 4823 // humongous regions set. 4824 assert(r->is_free() || r->is_humongous(), 4825 "it cannot be another type"); 4826 } 4827 return false; 4828 } 4829 4830 ~TearDownRegionSetsClosure() { 4831 assert(_old_set->is_empty(), "post-condition"); 4832 } 4833 }; 4834 4835 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 4836 assert_at_safepoint_on_vm_thread(); 4837 4838 if (!free_list_only) { 4839 TearDownRegionSetsClosure cl(&_old_set); 4840 heap_region_iterate(&cl); 4841 4842 // Note that emptying the _young_list is postponed and instead done as 4843 // the first step when rebuilding the regions sets again. The reason for 4844 // this is that during a full GC string deduplication needs to know if 4845 // a collected region was young or old when the full GC was initiated. 4846 } 4847 _hrm.remove_all_free_regions(); 4848 } 4849 4850 void G1CollectedHeap::increase_used(size_t bytes) { 4851 _summary_bytes_used += bytes; 4852 } 4853 4854 void G1CollectedHeap::decrease_used(size_t bytes) { 4855 assert(_summary_bytes_used >= bytes, 4856 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 4857 _summary_bytes_used, bytes); 4858 _summary_bytes_used -= bytes; 4859 } 4860 4861 void G1CollectedHeap::set_used(size_t bytes) { 4862 _summary_bytes_used = bytes; 4863 } 4864 4865 class RebuildRegionSetsClosure : public HeapRegionClosure { 4866 private: 4867 bool _free_list_only; 4868 HeapRegionSet* _old_set; 4869 HeapRegionManager* _hrm; 4870 size_t _total_used; 4871 4872 public: 4873 RebuildRegionSetsClosure(bool free_list_only, 4874 HeapRegionSet* old_set, HeapRegionManager* hrm) : 4875 _free_list_only(free_list_only), 4876 _old_set(old_set), _hrm(hrm), _total_used(0) { 4877 assert(_hrm->num_free_regions() == 0, "pre-condition"); 4878 if (!free_list_only) { 4879 assert(_old_set->is_empty(), "pre-condition"); 4880 } 4881 } 4882 4883 bool do_heap_region(HeapRegion* r) { 4884 // After full GC, no region should have a remembered set. 4885 r->rem_set()->clear(true); 4886 if (r->is_empty()) { 4887 // Add free regions to the free list 4888 r->set_free(); 4889 _hrm->insert_into_free_list(r); 4890 } else if (!_free_list_only) { 4891 4892 if (r->is_humongous()) { 4893 // We ignore humongous regions. We left the humongous set unchanged. 4894 } else { 4895 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 4896 // We now move all (non-humongous, non-old) regions to old gen, and register them as such. 4897 r->move_to_old(); 4898 _old_set->add(r); 4899 } 4900 _total_used += r->used(); 4901 } 4902 4903 return false; 4904 } 4905 4906 size_t total_used() { 4907 return _total_used; 4908 } 4909 }; 4910 4911 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 4912 assert_at_safepoint_on_vm_thread(); 4913 4914 if (!free_list_only) { 4915 _eden.clear(); 4916 _survivor.clear(); 4917 } 4918 4919 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 4920 heap_region_iterate(&cl); 4921 4922 if (!free_list_only) { 4923 set_used(cl.total_used()); 4924 if (_archive_allocator != NULL) { 4925 _archive_allocator->clear_used(); 4926 } 4927 } 4928 assert(used_unlocked() == recalculate_used(), 4929 "inconsistent used_unlocked(), " 4930 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 4931 used_unlocked(), recalculate_used()); 4932 } 4933 4934 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 4935 HeapRegion* hr = heap_region_containing(p); 4936 return hr->is_in(p); 4937 } 4938 4939 // Methods for the mutator alloc region 4940 4941 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 4942 bool force) { 4943 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4944 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 4945 if (force || should_allocate) { 4946 HeapRegion* new_alloc_region = new_region(word_size, 4947 false /* is_old */, 4948 false /* do_expand */); 4949 if (new_alloc_region != NULL) { 4950 set_region_short_lived_locked(new_alloc_region); 4951 _hr_printer.alloc(new_alloc_region, !should_allocate); 4952 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 4953 _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region); 4954 return new_alloc_region; 4955 } 4956 } 4957 return NULL; 4958 } 4959 4960 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 4961 size_t allocated_bytes) { 4962 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4963 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 4964 4965 collection_set()->add_eden_region(alloc_region); 4966 increase_used(allocated_bytes); 4967 _hr_printer.retire(alloc_region); 4968 // We update the eden sizes here, when the region is retired, 4969 // instead of when it's allocated, since this is the point that its 4970 // used space has been recored in _summary_bytes_used. 4971 g1mm()->update_eden_size(); 4972 } 4973 4974 // Methods for the GC alloc regions 4975 4976 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 4977 if (dest.is_old()) { 4978 return true; 4979 } else { 4980 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 4981 } 4982 } 4983 4984 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 4985 assert(FreeList_lock->owned_by_self(), "pre-condition"); 4986 4987 if (!has_more_regions(dest)) { 4988 return NULL; 4989 } 4990 4991 const bool is_survivor = dest.is_young(); 4992 4993 HeapRegion* new_alloc_region = new_region(word_size, 4994 !is_survivor, 4995 true /* do_expand */); 4996 if (new_alloc_region != NULL) { 4997 if (is_survivor) { 4998 new_alloc_region->set_survivor(); 4999 _survivor.add(new_alloc_region); 5000 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5001 } else { 5002 new_alloc_region->set_old(); 5003 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5004 } 5005 _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region); 5006 _hr_printer.alloc(new_alloc_region); 5007 bool during_im = collector_state()->in_initial_mark_gc(); 5008 new_alloc_region->note_start_of_copying(during_im); 5009 return new_alloc_region; 5010 } 5011 return NULL; 5012 } 5013 5014 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5015 size_t allocated_bytes, 5016 InCSetState dest) { 5017 bool during_im = collector_state()->in_initial_mark_gc(); 5018 alloc_region->note_end_of_copying(during_im); 5019 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5020 if (dest.is_old()) { 5021 _old_set.add(alloc_region); 5022 } 5023 _hr_printer.retire(alloc_region); 5024 } 5025 5026 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5027 bool expanded = false; 5028 uint index = _hrm.find_highest_free(&expanded); 5029 5030 if (index != G1_NO_HRM_INDEX) { 5031 if (expanded) { 5032 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5033 HeapRegion::GrainWords * HeapWordSize); 5034 } 5035 _hrm.allocate_free_regions_starting_at(index, 1); 5036 return region_at(index); 5037 } 5038 return NULL; 5039 } 5040 5041 // Optimized nmethod scanning 5042 5043 class RegisterNMethodOopClosure: public OopClosure { 5044 G1CollectedHeap* _g1h; 5045 nmethod* _nm; 5046 5047 template <class T> void do_oop_work(T* p) { 5048 T heap_oop = RawAccess<>::oop_load(p); 5049 if (!CompressedOops::is_null(heap_oop)) { 5050 oop obj = CompressedOops::decode_not_null(heap_oop); 5051 HeapRegion* hr = _g1h->heap_region_containing(obj); 5052 assert(!hr->is_continues_humongous(), 5053 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5054 " starting at " HR_FORMAT, 5055 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5056 5057 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5058 hr->add_strong_code_root_locked(_nm); 5059 } 5060 } 5061 5062 public: 5063 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5064 _g1h(g1h), _nm(nm) {} 5065 5066 void do_oop(oop* p) { do_oop_work(p); } 5067 void do_oop(narrowOop* p) { do_oop_work(p); } 5068 }; 5069 5070 class UnregisterNMethodOopClosure: public OopClosure { 5071 G1CollectedHeap* _g1h; 5072 nmethod* _nm; 5073 5074 template <class T> void do_oop_work(T* p) { 5075 T heap_oop = RawAccess<>::oop_load(p); 5076 if (!CompressedOops::is_null(heap_oop)) { 5077 oop obj = CompressedOops::decode_not_null(heap_oop); 5078 HeapRegion* hr = _g1h->heap_region_containing(obj); 5079 assert(!hr->is_continues_humongous(), 5080 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5081 " starting at " HR_FORMAT, 5082 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5083 5084 hr->remove_strong_code_root(_nm); 5085 } 5086 } 5087 5088 public: 5089 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5090 _g1h(g1h), _nm(nm) {} 5091 5092 void do_oop(oop* p) { do_oop_work(p); } 5093 void do_oop(narrowOop* p) { do_oop_work(p); } 5094 }; 5095 5096 // Returns true if the reference points to an object that 5097 // can move in an incremental collection. 5098 bool G1CollectedHeap::is_scavengable(oop obj) { 5099 HeapRegion* hr = heap_region_containing(obj); 5100 return !hr->is_pinned(); 5101 } 5102 5103 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5104 guarantee(nm != NULL, "sanity"); 5105 RegisterNMethodOopClosure reg_cl(this, nm); 5106 nm->oops_do(®_cl); 5107 } 5108 5109 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5110 guarantee(nm != NULL, "sanity"); 5111 UnregisterNMethodOopClosure reg_cl(this, nm); 5112 nm->oops_do(®_cl, true); 5113 } 5114 5115 void G1CollectedHeap::purge_code_root_memory() { 5116 double purge_start = os::elapsedTime(); 5117 G1CodeRootSet::purge(); 5118 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5119 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5120 } 5121 5122 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5123 G1CollectedHeap* _g1h; 5124 5125 public: 5126 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5127 _g1h(g1h) {} 5128 5129 void do_code_blob(CodeBlob* cb) { 5130 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5131 if (nm == NULL) { 5132 return; 5133 } 5134 5135 if (ScavengeRootsInCode) { 5136 _g1h->register_nmethod(nm); 5137 } 5138 } 5139 }; 5140 5141 void G1CollectedHeap::rebuild_strong_code_roots() { 5142 RebuildStrongCodeRootClosure blob_cl(this); 5143 CodeCache::blobs_do(&blob_cl); 5144 } 5145 5146 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() { 5147 GrowableArray<GCMemoryManager*> memory_managers(2); 5148 memory_managers.append(&_memory_manager); 5149 memory_managers.append(&_full_gc_memory_manager); 5150 return memory_managers; 5151 } 5152 5153 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() { 5154 GrowableArray<MemoryPool*> memory_pools(3); 5155 memory_pools.append(_eden_pool); 5156 memory_pools.append(_survivor_pool); 5157 memory_pools.append(_old_pool); 5158 return memory_pools; 5159 }