1 /* 2 * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/metadataOnStackMark.hpp" 27 #include "classfile/stringTable.hpp" 28 #include "classfile/symbolTable.hpp" 29 #include "code/codeCache.hpp" 30 #include "code/icBuffer.hpp" 31 #include "gc/g1/g1Allocator.inline.hpp" 32 #include "gc/g1/g1BarrierSet.hpp" 33 #include "gc/g1/g1CollectedHeap.inline.hpp" 34 #include "gc/g1/g1CollectionSet.hpp" 35 #include "gc/g1/g1CollectorPolicy.hpp" 36 #include "gc/g1/g1CollectorState.hpp" 37 #include "gc/g1/g1ConcurrentRefine.hpp" 38 #include "gc/g1/g1ConcurrentRefineThread.hpp" 39 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp" 40 #include "gc/g1/g1EvacStats.inline.hpp" 41 #include "gc/g1/g1FullCollector.hpp" 42 #include "gc/g1/g1GCPhaseTimes.hpp" 43 #include "gc/g1/g1HeapSizingPolicy.hpp" 44 #include "gc/g1/g1HeapTransition.hpp" 45 #include "gc/g1/g1HeapVerifier.hpp" 46 #include "gc/g1/g1HotCardCache.hpp" 47 #include "gc/g1/g1MemoryPool.hpp" 48 #include "gc/g1/g1OopClosures.inline.hpp" 49 #include "gc/g1/g1ParScanThreadState.inline.hpp" 50 #include "gc/g1/g1Policy.hpp" 51 #include "gc/g1/g1RegionToSpaceMapper.hpp" 52 #include "gc/g1/g1RemSet.hpp" 53 #include "gc/g1/g1RootClosures.hpp" 54 #include "gc/g1/g1RootProcessor.hpp" 55 #include "gc/g1/g1StringDedup.hpp" 56 #include "gc/g1/g1ThreadLocalData.hpp" 57 #include "gc/g1/g1YCTypes.hpp" 58 #include "gc/g1/g1YoungRemSetSamplingThread.hpp" 59 #include "gc/g1/heapRegion.inline.hpp" 60 #include "gc/g1/heapRegionRemSet.hpp" 61 #include "gc/g1/heapRegionSet.inline.hpp" 62 #include "gc/g1/vm_operations_g1.hpp" 63 #include "gc/shared/adaptiveSizePolicy.hpp" 64 #include "gc/shared/gcHeapSummary.hpp" 65 #include "gc/shared/gcId.hpp" 66 #include "gc/shared/gcLocker.hpp" 67 #include "gc/shared/gcTimer.hpp" 68 #include "gc/shared/gcTrace.hpp" 69 #include "gc/shared/gcTraceTime.inline.hpp" 70 #include "gc/shared/generationSpec.hpp" 71 #include "gc/shared/isGCActiveMark.hpp" 72 #include "gc/shared/preservedMarks.inline.hpp" 73 #include "gc/shared/suspendibleThreadSet.hpp" 74 #include "gc/shared/referenceProcessor.inline.hpp" 75 #include "gc/shared/taskqueue.inline.hpp" 76 #include "gc/shared/weakProcessor.hpp" 77 #include "logging/log.hpp" 78 #include "memory/allocation.hpp" 79 #include "memory/iterator.hpp" 80 #include "memory/resourceArea.hpp" 81 #include "oops/access.inline.hpp" 82 #include "oops/compressedOops.inline.hpp" 83 #include "oops/oop.inline.hpp" 84 #include "prims/resolvedMethodTable.hpp" 85 #include "runtime/atomic.hpp" 86 #include "runtime/flags/flagSetting.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 min_size, 388 size_t requested_size, 389 size_t* actual_size) { 390 assert_heap_not_locked_and_not_at_safepoint(); 391 assert(!is_humongous(requested_size), "we do not allow humongous TLABs"); 392 393 return attempt_allocation(min_size, requested_size, actual_size); 394 } 395 396 HeapWord* 397 G1CollectedHeap::mem_allocate(size_t word_size, 398 bool* gc_overhead_limit_was_exceeded) { 399 assert_heap_not_locked_and_not_at_safepoint(); 400 401 if (is_humongous(word_size)) { 402 return attempt_allocation_humongous(word_size); 403 } 404 size_t dummy = 0; 405 return attempt_allocation(word_size, word_size, &dummy); 406 } 407 408 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) { 409 ResourceMark rm; // For retrieving the thread names in log messages. 410 411 // Make sure you read the note in attempt_allocation_humongous(). 412 413 assert_heap_not_locked_and_not_at_safepoint(); 414 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 415 "be called for humongous allocation requests"); 416 417 // We should only get here after the first-level allocation attempt 418 // (attempt_allocation()) failed to allocate. 419 420 // We will loop until a) we manage to successfully perform the 421 // allocation or b) we successfully schedule a collection which 422 // fails to perform the allocation. b) is the only case when we'll 423 // return NULL. 424 HeapWord* result = NULL; 425 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 426 bool should_try_gc; 427 uint gc_count_before; 428 429 { 430 MutexLockerEx x(Heap_lock); 431 result = _allocator->attempt_allocation_locked(word_size); 432 if (result != NULL) { 433 return result; 434 } 435 436 // If the GCLocker is active and we are bound for a GC, try expanding young gen. 437 // This is different to when only GCLocker::needs_gc() is set: try to avoid 438 // waiting because the GCLocker is active to not wait too long. 439 if (GCLocker::is_active_and_needs_gc() && g1_policy()->can_expand_young_list()) { 440 // No need for an ergo message here, can_expand_young_list() does this when 441 // it returns true. 442 result = _allocator->attempt_allocation_force(word_size); 443 if (result != NULL) { 444 return result; 445 } 446 } 447 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 448 // the GCLocker initiated GC has been performed and then retry. This includes 449 // the case when the GC Locker is not active but has not been performed. 450 should_try_gc = !GCLocker::needs_gc(); 451 // Read the GC count while still holding the Heap_lock. 452 gc_count_before = total_collections(); 453 } 454 455 if (should_try_gc) { 456 bool succeeded; 457 result = do_collection_pause(word_size, gc_count_before, &succeeded, 458 GCCause::_g1_inc_collection_pause); 459 if (result != NULL) { 460 assert(succeeded, "only way to get back a non-NULL result"); 461 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 462 Thread::current()->name(), p2i(result)); 463 return result; 464 } 465 466 if (succeeded) { 467 // We successfully scheduled a collection which failed to allocate. No 468 // point in trying to allocate further. We'll just return NULL. 469 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 470 SIZE_FORMAT " words", Thread::current()->name(), word_size); 471 return NULL; 472 } 473 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words", 474 Thread::current()->name(), word_size); 475 } else { 476 // Failed to schedule a collection. 477 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 478 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 479 SIZE_FORMAT " words", Thread::current()->name(), word_size); 480 return NULL; 481 } 482 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 483 // The GCLocker is either active or the GCLocker initiated 484 // GC has not yet been performed. Stall until it is and 485 // then retry the allocation. 486 GCLocker::stall_until_clear(); 487 gclocker_retry_count += 1; 488 } 489 490 // We can reach here if we were unsuccessful in scheduling a 491 // collection (because another thread beat us to it) or if we were 492 // stalled due to the GC locker. In either can we should retry the 493 // allocation attempt in case another thread successfully 494 // performed a collection and reclaimed enough space. We do the 495 // first attempt (without holding the Heap_lock) here and the 496 // follow-on attempt will be at the start of the next loop 497 // iteration (after taking the Heap_lock). 498 size_t dummy = 0; 499 result = _allocator->attempt_allocation(word_size, word_size, &dummy); 500 if (result != NULL) { 501 return result; 502 } 503 504 // Give a warning if we seem to be looping forever. 505 if ((QueuedAllocationWarningCount > 0) && 506 (try_count % QueuedAllocationWarningCount == 0)) { 507 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 508 Thread::current()->name(), try_count, word_size); 509 } 510 } 511 512 ShouldNotReachHere(); 513 return NULL; 514 } 515 516 void G1CollectedHeap::begin_archive_alloc_range(bool open) { 517 assert_at_safepoint_on_vm_thread(); 518 if (_archive_allocator == NULL) { 519 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open); 520 } 521 } 522 523 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 524 // Allocations in archive regions cannot be of a size that would be considered 525 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 526 // may be different at archive-restore time. 527 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 528 } 529 530 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 531 assert_at_safepoint_on_vm_thread(); 532 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 533 if (is_archive_alloc_too_large(word_size)) { 534 return NULL; 535 } 536 return _archive_allocator->archive_mem_allocate(word_size); 537 } 538 539 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 540 size_t end_alignment_in_bytes) { 541 assert_at_safepoint_on_vm_thread(); 542 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 543 544 // Call complete_archive to do the real work, filling in the MemRegion 545 // array with the archive regions. 546 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 547 delete _archive_allocator; 548 _archive_allocator = NULL; 549 } 550 551 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 552 assert(ranges != NULL, "MemRegion array NULL"); 553 assert(count != 0, "No MemRegions provided"); 554 MemRegion reserved = _hrm.reserved(); 555 for (size_t i = 0; i < count; i++) { 556 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 557 return false; 558 } 559 } 560 return true; 561 } 562 563 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, 564 size_t count, 565 bool open) { 566 assert(!is_init_completed(), "Expect to be called at JVM init time"); 567 assert(ranges != NULL, "MemRegion array NULL"); 568 assert(count != 0, "No MemRegions provided"); 569 MutexLockerEx x(Heap_lock); 570 571 MemRegion reserved = _hrm.reserved(); 572 HeapWord* prev_last_addr = NULL; 573 HeapRegion* prev_last_region = NULL; 574 575 // Temporarily disable pretouching of heap pages. This interface is used 576 // when mmap'ing archived heap data in, so pre-touching is wasted. 577 FlagSetting fs(AlwaysPreTouch, false); 578 579 // Enable archive object checking used by G1MarkSweep. We have to let it know 580 // about each archive range, so that objects in those ranges aren't marked. 581 G1ArchiveAllocator::enable_archive_object_check(); 582 583 // For each specified MemRegion range, allocate the corresponding G1 584 // regions and mark them as archive regions. We expect the ranges 585 // in ascending starting address order, without overlap. 586 for (size_t i = 0; i < count; i++) { 587 MemRegion curr_range = ranges[i]; 588 HeapWord* start_address = curr_range.start(); 589 size_t word_size = curr_range.word_size(); 590 HeapWord* last_address = curr_range.last(); 591 size_t commits = 0; 592 593 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 594 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 595 p2i(start_address), p2i(last_address)); 596 guarantee(start_address > prev_last_addr, 597 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 598 p2i(start_address), p2i(prev_last_addr)); 599 prev_last_addr = last_address; 600 601 // Check for ranges that start in the same G1 region in which the previous 602 // range ended, and adjust the start address so we don't try to allocate 603 // the same region again. If the current range is entirely within that 604 // region, skip it, just adjusting the recorded top. 605 HeapRegion* start_region = _hrm.addr_to_region(start_address); 606 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 607 start_address = start_region->end(); 608 if (start_address > last_address) { 609 increase_used(word_size * HeapWordSize); 610 start_region->set_top(last_address + 1); 611 continue; 612 } 613 start_region->set_top(start_address); 614 curr_range = MemRegion(start_address, last_address + 1); 615 start_region = _hrm.addr_to_region(start_address); 616 } 617 618 // Perform the actual region allocation, exiting if it fails. 619 // Then note how much new space we have allocated. 620 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 621 return false; 622 } 623 increase_used(word_size * HeapWordSize); 624 if (commits != 0) { 625 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 626 HeapRegion::GrainWords * HeapWordSize * commits); 627 628 } 629 630 // Mark each G1 region touched by the range as archive, add it to 631 // the old set, and set top. 632 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 633 HeapRegion* last_region = _hrm.addr_to_region(last_address); 634 prev_last_region = last_region; 635 636 while (curr_region != NULL) { 637 assert(curr_region->is_empty() && !curr_region->is_pinned(), 638 "Region already in use (index %u)", curr_region->hrm_index()); 639 if (open) { 640 curr_region->set_open_archive(); 641 } else { 642 curr_region->set_closed_archive(); 643 } 644 _hr_printer.alloc(curr_region); 645 _old_set.add(curr_region); 646 HeapWord* top; 647 HeapRegion* next_region; 648 if (curr_region != last_region) { 649 top = curr_region->end(); 650 next_region = _hrm.next_region_in_heap(curr_region); 651 } else { 652 top = last_address + 1; 653 next_region = NULL; 654 } 655 curr_region->set_top(top); 656 curr_region->set_first_dead(top); 657 curr_region->set_end_of_live(top); 658 curr_region = next_region; 659 } 660 661 // Notify mark-sweep of the archive 662 G1ArchiveAllocator::set_range_archive(curr_range, open); 663 } 664 return true; 665 } 666 667 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 668 assert(!is_init_completed(), "Expect to be called at JVM init time"); 669 assert(ranges != NULL, "MemRegion array NULL"); 670 assert(count != 0, "No MemRegions provided"); 671 MemRegion reserved = _hrm.reserved(); 672 HeapWord *prev_last_addr = NULL; 673 HeapRegion* prev_last_region = NULL; 674 675 // For each MemRegion, create filler objects, if needed, in the G1 regions 676 // that contain the address range. The address range actually within the 677 // MemRegion will not be modified. That is assumed to have been initialized 678 // elsewhere, probably via an mmap of archived heap data. 679 MutexLockerEx x(Heap_lock); 680 for (size_t i = 0; i < count; i++) { 681 HeapWord* start_address = ranges[i].start(); 682 HeapWord* last_address = ranges[i].last(); 683 684 assert(reserved.contains(start_address) && reserved.contains(last_address), 685 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 686 p2i(start_address), p2i(last_address)); 687 assert(start_address > prev_last_addr, 688 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 689 p2i(start_address), p2i(prev_last_addr)); 690 691 HeapRegion* start_region = _hrm.addr_to_region(start_address); 692 HeapRegion* last_region = _hrm.addr_to_region(last_address); 693 HeapWord* bottom_address = start_region->bottom(); 694 695 // Check for a range beginning in the same region in which the 696 // previous one ended. 697 if (start_region == prev_last_region) { 698 bottom_address = prev_last_addr + 1; 699 } 700 701 // Verify that the regions were all marked as archive regions by 702 // alloc_archive_regions. 703 HeapRegion* curr_region = start_region; 704 while (curr_region != NULL) { 705 guarantee(curr_region->is_archive(), 706 "Expected archive region at index %u", curr_region->hrm_index()); 707 if (curr_region != last_region) { 708 curr_region = _hrm.next_region_in_heap(curr_region); 709 } else { 710 curr_region = NULL; 711 } 712 } 713 714 prev_last_addr = last_address; 715 prev_last_region = last_region; 716 717 // Fill the memory below the allocated range with dummy object(s), 718 // if the region bottom does not match the range start, or if the previous 719 // range ended within the same G1 region, and there is a gap. 720 if (start_address != bottom_address) { 721 size_t fill_size = pointer_delta(start_address, bottom_address); 722 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 723 increase_used(fill_size * HeapWordSize); 724 } 725 } 726 } 727 728 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size, 729 size_t desired_word_size, 730 size_t* actual_word_size) { 731 assert_heap_not_locked_and_not_at_safepoint(); 732 assert(!is_humongous(desired_word_size), "attempt_allocation() should not " 733 "be called for humongous allocation requests"); 734 735 HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size); 736 737 if (result == NULL) { 738 *actual_word_size = desired_word_size; 739 result = attempt_allocation_slow(desired_word_size); 740 } 741 742 assert_heap_not_locked(); 743 if (result != NULL) { 744 assert(*actual_word_size != 0, "Actual size must have been set here"); 745 dirty_young_block(result, *actual_word_size); 746 } else { 747 *actual_word_size = 0; 748 } 749 750 return result; 751 } 752 753 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 754 assert(!is_init_completed(), "Expect to be called at JVM init time"); 755 assert(ranges != NULL, "MemRegion array NULL"); 756 assert(count != 0, "No MemRegions provided"); 757 MemRegion reserved = _hrm.reserved(); 758 HeapWord* prev_last_addr = NULL; 759 HeapRegion* prev_last_region = NULL; 760 size_t size_used = 0; 761 size_t uncommitted_regions = 0; 762 763 // For each Memregion, free the G1 regions that constitute it, and 764 // notify mark-sweep that the range is no longer to be considered 'archive.' 765 MutexLockerEx x(Heap_lock); 766 for (size_t i = 0; i < count; i++) { 767 HeapWord* start_address = ranges[i].start(); 768 HeapWord* last_address = ranges[i].last(); 769 770 assert(reserved.contains(start_address) && reserved.contains(last_address), 771 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 772 p2i(start_address), p2i(last_address)); 773 assert(start_address > prev_last_addr, 774 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 775 p2i(start_address), p2i(prev_last_addr)); 776 size_used += ranges[i].byte_size(); 777 prev_last_addr = last_address; 778 779 HeapRegion* start_region = _hrm.addr_to_region(start_address); 780 HeapRegion* last_region = _hrm.addr_to_region(last_address); 781 782 // Check for ranges that start in the same G1 region in which the previous 783 // range ended, and adjust the start address so we don't try to free 784 // the same region again. If the current range is entirely within that 785 // region, skip it. 786 if (start_region == prev_last_region) { 787 start_address = start_region->end(); 788 if (start_address > last_address) { 789 continue; 790 } 791 start_region = _hrm.addr_to_region(start_address); 792 } 793 prev_last_region = last_region; 794 795 // After verifying that each region was marked as an archive region by 796 // alloc_archive_regions, set it free and empty and uncommit it. 797 HeapRegion* curr_region = start_region; 798 while (curr_region != NULL) { 799 guarantee(curr_region->is_archive(), 800 "Expected archive region at index %u", curr_region->hrm_index()); 801 uint curr_index = curr_region->hrm_index(); 802 _old_set.remove(curr_region); 803 curr_region->set_free(); 804 curr_region->set_top(curr_region->bottom()); 805 if (curr_region != last_region) { 806 curr_region = _hrm.next_region_in_heap(curr_region); 807 } else { 808 curr_region = NULL; 809 } 810 _hrm.shrink_at(curr_index, 1); 811 uncommitted_regions++; 812 } 813 814 // Notify mark-sweep that this is no longer an archive range. 815 G1ArchiveAllocator::set_range_archive(ranges[i], false); 816 } 817 818 if (uncommitted_regions != 0) { 819 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 820 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 821 } 822 decrease_used(size_used); 823 } 824 825 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) { 826 ResourceMark rm; // For retrieving the thread names in log messages. 827 828 // The structure of this method has a lot of similarities to 829 // attempt_allocation_slow(). The reason these two were not merged 830 // into a single one is that such a method would require several "if 831 // allocation is not humongous do this, otherwise do that" 832 // conditional paths which would obscure its flow. In fact, an early 833 // version of this code did use a unified method which was harder to 834 // follow and, as a result, it had subtle bugs that were hard to 835 // track down. So keeping these two methods separate allows each to 836 // be more readable. It will be good to keep these two in sync as 837 // much as possible. 838 839 assert_heap_not_locked_and_not_at_safepoint(); 840 assert(is_humongous(word_size), "attempt_allocation_humongous() " 841 "should only be called for humongous allocations"); 842 843 // Humongous objects can exhaust the heap quickly, so we should check if we 844 // need to start a marking cycle at each humongous object allocation. We do 845 // the check before we do the actual allocation. The reason for doing it 846 // before the allocation is that we avoid having to keep track of the newly 847 // allocated memory while we do a GC. 848 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 849 word_size)) { 850 collect(GCCause::_g1_humongous_allocation); 851 } 852 853 // We will loop until a) we manage to successfully perform the 854 // allocation or b) we successfully schedule a collection which 855 // fails to perform the allocation. b) is the only case when we'll 856 // return NULL. 857 HeapWord* result = NULL; 858 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 859 bool should_try_gc; 860 uint gc_count_before; 861 862 863 { 864 MutexLockerEx x(Heap_lock); 865 866 // Given that humongous objects are not allocated in young 867 // regions, we'll first try to do the allocation without doing a 868 // collection hoping that there's enough space in the heap. 869 result = humongous_obj_allocate(word_size); 870 if (result != NULL) { 871 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 872 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 873 return result; 874 } 875 876 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 877 // the GCLocker initiated GC has been performed and then retry. This includes 878 // the case when the GC Locker is not active but has not been performed. 879 should_try_gc = !GCLocker::needs_gc(); 880 // Read the GC count while still holding the Heap_lock. 881 gc_count_before = total_collections(); 882 } 883 884 if (should_try_gc) { 885 bool succeeded; 886 result = do_collection_pause(word_size, gc_count_before, &succeeded, 887 GCCause::_g1_humongous_allocation); 888 if (result != NULL) { 889 assert(succeeded, "only way to get back a non-NULL result"); 890 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 891 Thread::current()->name(), p2i(result)); 892 return result; 893 } 894 895 if (succeeded) { 896 // We successfully scheduled a collection which failed to allocate. No 897 // point in trying to allocate further. We'll just return NULL. 898 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 899 SIZE_FORMAT " words", Thread::current()->name(), word_size); 900 return NULL; 901 } 902 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "", 903 Thread::current()->name(), word_size); 904 } else { 905 // Failed to schedule a collection. 906 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 907 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 908 SIZE_FORMAT " words", Thread::current()->name(), word_size); 909 return NULL; 910 } 911 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 912 // The GCLocker is either active or the GCLocker initiated 913 // GC has not yet been performed. Stall until it is and 914 // then retry the allocation. 915 GCLocker::stall_until_clear(); 916 gclocker_retry_count += 1; 917 } 918 919 920 // We can reach here if we were unsuccessful in scheduling a 921 // collection (because another thread beat us to it) or if we were 922 // stalled due to the GC locker. In either can we should retry the 923 // allocation attempt in case another thread successfully 924 // performed a collection and reclaimed enough space. 925 // Humongous object allocation always needs a lock, so we wait for the retry 926 // in the next iteration of the loop, unlike for the regular iteration case. 927 // Give a warning if we seem to be looping forever. 928 929 if ((QueuedAllocationWarningCount > 0) && 930 (try_count % QueuedAllocationWarningCount == 0)) { 931 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 932 Thread::current()->name(), try_count, word_size); 933 } 934 } 935 936 ShouldNotReachHere(); 937 return NULL; 938 } 939 940 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 941 bool expect_null_mutator_alloc_region) { 942 assert_at_safepoint_on_vm_thread(); 943 assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region, 944 "the current alloc region was unexpectedly found to be non-NULL"); 945 946 if (!is_humongous(word_size)) { 947 return _allocator->attempt_allocation_locked(word_size); 948 } else { 949 HeapWord* result = humongous_obj_allocate(word_size); 950 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 951 collector_state()->set_initiate_conc_mark_if_possible(true); 952 } 953 return result; 954 } 955 956 ShouldNotReachHere(); 957 } 958 959 class PostCompactionPrinterClosure: public HeapRegionClosure { 960 private: 961 G1HRPrinter* _hr_printer; 962 public: 963 bool do_heap_region(HeapRegion* hr) { 964 assert(!hr->is_young(), "not expecting to find young regions"); 965 _hr_printer->post_compaction(hr); 966 return false; 967 } 968 969 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 970 : _hr_printer(hr_printer) { } 971 }; 972 973 void G1CollectedHeap::print_hrm_post_compaction() { 974 if (_hr_printer.is_active()) { 975 PostCompactionPrinterClosure cl(hr_printer()); 976 heap_region_iterate(&cl); 977 } 978 } 979 980 void G1CollectedHeap::abort_concurrent_cycle() { 981 // If we start the compaction before the CM threads finish 982 // scanning the root regions we might trip them over as we'll 983 // be moving objects / updating references. So let's wait until 984 // they are done. By telling them to abort, they should complete 985 // early. 986 _cm->root_regions()->abort(); 987 _cm->root_regions()->wait_until_scan_finished(); 988 989 // Disable discovery and empty the discovered lists 990 // for the CM ref processor. 991 ref_processor_cm()->disable_discovery(); 992 ref_processor_cm()->abandon_partial_discovery(); 993 ref_processor_cm()->verify_no_references_recorded(); 994 995 // Abandon current iterations of concurrent marking and concurrent 996 // refinement, if any are in progress. 997 concurrent_mark()->concurrent_cycle_abort(); 998 } 999 1000 void G1CollectedHeap::prepare_heap_for_full_collection() { 1001 // Make sure we'll choose a new allocation region afterwards. 1002 _allocator->release_mutator_alloc_region(); 1003 _allocator->abandon_gc_alloc_regions(); 1004 g1_rem_set()->cleanupHRRS(); 1005 1006 // We may have added regions to the current incremental collection 1007 // set between the last GC or pause and now. We need to clear the 1008 // incremental collection set and then start rebuilding it afresh 1009 // after this full GC. 1010 abandon_collection_set(collection_set()); 1011 1012 tear_down_region_sets(false /* free_list_only */); 1013 } 1014 1015 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1016 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1017 assert(used() == recalculate_used(), "Should be equal"); 1018 _verifier->verify_region_sets_optional(); 1019 _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull); 1020 _verifier->check_bitmaps("Full GC Start"); 1021 } 1022 1023 void G1CollectedHeap::prepare_heap_for_mutators() { 1024 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1025 ClassLoaderDataGraph::purge(); 1026 MetaspaceUtils::verify_metrics(); 1027 1028 // Prepare heap for normal collections. 1029 assert(num_free_regions() == 0, "we should not have added any free regions"); 1030 rebuild_region_sets(false /* free_list_only */); 1031 abort_refinement(); 1032 resize_if_necessary_after_full_collection(); 1033 1034 // Rebuild the strong code root lists for each region 1035 rebuild_strong_code_roots(); 1036 1037 // Start a new incremental collection set for the next pause 1038 start_new_collection_set(); 1039 1040 _allocator->init_mutator_alloc_region(); 1041 1042 // Post collection state updates. 1043 MetaspaceGC::compute_new_size(); 1044 } 1045 1046 void G1CollectedHeap::abort_refinement() { 1047 if (_hot_card_cache->use_cache()) { 1048 _hot_card_cache->reset_hot_cache(); 1049 } 1050 1051 // Discard all remembered set updates. 1052 G1BarrierSet::dirty_card_queue_set().abandon_logs(); 1053 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1054 } 1055 1056 void G1CollectedHeap::verify_after_full_collection() { 1057 _hrm.verify_optional(); 1058 _verifier->verify_region_sets_optional(); 1059 _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull); 1060 // Clear the previous marking bitmap, if needed for bitmap verification. 1061 // Note we cannot do this when we clear the next marking bitmap in 1062 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1063 // objects marked during a full GC against the previous bitmap. 1064 // But we need to clear it before calling check_bitmaps below since 1065 // the full GC has compacted objects and updated TAMS but not updated 1066 // the prev bitmap. 1067 if (G1VerifyBitmaps) { 1068 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1069 _cm->clear_prev_bitmap(workers()); 1070 } 1071 _verifier->check_bitmaps("Full GC End"); 1072 1073 // At this point there should be no regions in the 1074 // entire heap tagged as young. 1075 assert(check_young_list_empty(), "young list should be empty at this point"); 1076 1077 // Note: since we've just done a full GC, concurrent 1078 // marking is no longer active. Therefore we need not 1079 // re-enable reference discovery for the CM ref processor. 1080 // That will be done at the start of the next marking cycle. 1081 // We also know that the STW processor should no longer 1082 // discover any new references. 1083 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1084 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1085 ref_processor_stw()->verify_no_references_recorded(); 1086 ref_processor_cm()->verify_no_references_recorded(); 1087 } 1088 1089 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1090 // Post collection logging. 1091 // We should do this after we potentially resize the heap so 1092 // that all the COMMIT / UNCOMMIT events are generated before 1093 // the compaction events. 1094 print_hrm_post_compaction(); 1095 heap_transition->print(); 1096 print_heap_after_gc(); 1097 print_heap_regions(); 1098 #ifdef TRACESPINNING 1099 ParallelTaskTerminator::print_termination_counts(); 1100 #endif 1101 } 1102 1103 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1104 bool clear_all_soft_refs) { 1105 assert_at_safepoint_on_vm_thread(); 1106 1107 if (GCLocker::check_active_before_gc()) { 1108 // Full GC was not completed. 1109 return false; 1110 } 1111 1112 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1113 soft_ref_policy()->should_clear_all_soft_refs(); 1114 1115 G1FullCollector collector(this, &_full_gc_memory_manager, explicit_gc, do_clear_all_soft_refs); 1116 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1117 1118 collector.prepare_collection(); 1119 collector.collect(); 1120 collector.complete_collection(); 1121 1122 // Full collection was successfully completed. 1123 return true; 1124 } 1125 1126 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1127 // Currently, there is no facility in the do_full_collection(bool) API to notify 1128 // the caller that the collection did not succeed (e.g., because it was locked 1129 // out by the GC locker). So, right now, we'll ignore the return value. 1130 bool dummy = do_full_collection(true, /* explicit_gc */ 1131 clear_all_soft_refs); 1132 } 1133 1134 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1135 // Capacity, free and used after the GC counted as full regions to 1136 // include the waste in the following calculations. 1137 const size_t capacity_after_gc = capacity(); 1138 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes(); 1139 1140 // This is enforced in arguments.cpp. 1141 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1142 "otherwise the code below doesn't make sense"); 1143 1144 // We don't have floating point command-line arguments 1145 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1146 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1147 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1148 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1149 1150 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1151 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1152 1153 // We have to be careful here as these two calculations can overflow 1154 // 32-bit size_t's. 1155 double used_after_gc_d = (double) used_after_gc; 1156 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1157 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1158 1159 // Let's make sure that they are both under the max heap size, which 1160 // by default will make them fit into a size_t. 1161 double desired_capacity_upper_bound = (double) max_heap_size; 1162 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1163 desired_capacity_upper_bound); 1164 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1165 desired_capacity_upper_bound); 1166 1167 // We can now safely turn them into size_t's. 1168 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1169 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1170 1171 // This assert only makes sense here, before we adjust them 1172 // with respect to the min and max heap size. 1173 assert(minimum_desired_capacity <= maximum_desired_capacity, 1174 "minimum_desired_capacity = " SIZE_FORMAT ", " 1175 "maximum_desired_capacity = " SIZE_FORMAT, 1176 minimum_desired_capacity, maximum_desired_capacity); 1177 1178 // Should not be greater than the heap max size. No need to adjust 1179 // it with respect to the heap min size as it's a lower bound (i.e., 1180 // we'll try to make the capacity larger than it, not smaller). 1181 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1182 // Should not be less than the heap min size. No need to adjust it 1183 // with respect to the heap max size as it's an upper bound (i.e., 1184 // we'll try to make the capacity smaller than it, not greater). 1185 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1186 1187 if (capacity_after_gc < minimum_desired_capacity) { 1188 // Don't expand unless it's significant 1189 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1190 1191 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1192 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1193 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1194 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio); 1195 1196 expand(expand_bytes, _workers); 1197 1198 // No expansion, now see if we want to shrink 1199 } else if (capacity_after_gc > maximum_desired_capacity) { 1200 // Capacity too large, compute shrinking size 1201 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1202 1203 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1204 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1205 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1206 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio); 1207 1208 shrink(shrink_bytes); 1209 } 1210 } 1211 1212 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1213 bool do_gc, 1214 bool clear_all_soft_refs, 1215 bool expect_null_mutator_alloc_region, 1216 bool* gc_succeeded) { 1217 *gc_succeeded = true; 1218 // Let's attempt the allocation first. 1219 HeapWord* result = 1220 attempt_allocation_at_safepoint(word_size, 1221 expect_null_mutator_alloc_region); 1222 if (result != NULL) { 1223 return result; 1224 } 1225 1226 // In a G1 heap, we're supposed to keep allocation from failing by 1227 // incremental pauses. Therefore, at least for now, we'll favor 1228 // expansion over collection. (This might change in the future if we can 1229 // do something smarter than full collection to satisfy a failed alloc.) 1230 result = expand_and_allocate(word_size); 1231 if (result != NULL) { 1232 return result; 1233 } 1234 1235 if (do_gc) { 1236 // Expansion didn't work, we'll try to do a Full GC. 1237 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1238 clear_all_soft_refs); 1239 } 1240 1241 return NULL; 1242 } 1243 1244 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1245 bool* succeeded) { 1246 assert_at_safepoint_on_vm_thread(); 1247 1248 // Attempts to allocate followed by Full GC. 1249 HeapWord* result = 1250 satisfy_failed_allocation_helper(word_size, 1251 true, /* do_gc */ 1252 false, /* clear_all_soft_refs */ 1253 false, /* expect_null_mutator_alloc_region */ 1254 succeeded); 1255 1256 if (result != NULL || !*succeeded) { 1257 return result; 1258 } 1259 1260 // Attempts to allocate followed by Full GC that will collect all soft references. 1261 result = satisfy_failed_allocation_helper(word_size, 1262 true, /* do_gc */ 1263 true, /* clear_all_soft_refs */ 1264 true, /* expect_null_mutator_alloc_region */ 1265 succeeded); 1266 1267 if (result != NULL || !*succeeded) { 1268 return result; 1269 } 1270 1271 // Attempts to allocate, no GC 1272 result = satisfy_failed_allocation_helper(word_size, 1273 false, /* do_gc */ 1274 false, /* clear_all_soft_refs */ 1275 true, /* expect_null_mutator_alloc_region */ 1276 succeeded); 1277 1278 if (result != NULL) { 1279 return result; 1280 } 1281 1282 assert(!soft_ref_policy()->should_clear_all_soft_refs(), 1283 "Flag should have been handled and cleared prior to this point"); 1284 1285 // What else? We might try synchronous finalization later. If the total 1286 // space available is large enough for the allocation, then a more 1287 // complete compaction phase than we've tried so far might be 1288 // appropriate. 1289 return NULL; 1290 } 1291 1292 // Attempting to expand the heap sufficiently 1293 // to support an allocation of the given "word_size". If 1294 // successful, perform the allocation and return the address of the 1295 // allocated block, or else "NULL". 1296 1297 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1298 assert_at_safepoint_on_vm_thread(); 1299 1300 _verifier->verify_region_sets_optional(); 1301 1302 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1303 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1304 word_size * HeapWordSize); 1305 1306 1307 if (expand(expand_bytes, _workers)) { 1308 _hrm.verify_optional(); 1309 _verifier->verify_region_sets_optional(); 1310 return attempt_allocation_at_safepoint(word_size, 1311 false /* expect_null_mutator_alloc_region */); 1312 } 1313 return NULL; 1314 } 1315 1316 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1317 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1318 aligned_expand_bytes = align_up(aligned_expand_bytes, 1319 HeapRegion::GrainBytes); 1320 1321 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1322 expand_bytes, aligned_expand_bytes); 1323 1324 if (is_maximal_no_gc()) { 1325 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1326 return false; 1327 } 1328 1329 double expand_heap_start_time_sec = os::elapsedTime(); 1330 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1331 assert(regions_to_expand > 0, "Must expand by at least one region"); 1332 1333 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers); 1334 if (expand_time_ms != NULL) { 1335 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1336 } 1337 1338 if (expanded_by > 0) { 1339 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1340 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1341 g1_policy()->record_new_heap_size(num_regions()); 1342 } else { 1343 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1344 1345 // The expansion of the virtual storage space was unsuccessful. 1346 // Let's see if it was because we ran out of swap. 1347 if (G1ExitOnExpansionFailure && 1348 _hrm.available() >= regions_to_expand) { 1349 // We had head room... 1350 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1351 } 1352 } 1353 return regions_to_expand > 0; 1354 } 1355 1356 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1357 size_t aligned_shrink_bytes = 1358 ReservedSpace::page_align_size_down(shrink_bytes); 1359 aligned_shrink_bytes = align_down(aligned_shrink_bytes, 1360 HeapRegion::GrainBytes); 1361 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1362 1363 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1364 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1365 1366 1367 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", 1368 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1369 if (num_regions_removed > 0) { 1370 g1_policy()->record_new_heap_size(num_regions()); 1371 } else { 1372 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1373 } 1374 } 1375 1376 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1377 _verifier->verify_region_sets_optional(); 1378 1379 // We should only reach here at the end of a Full GC which means we 1380 // should not not be holding to any GC alloc regions. The method 1381 // below will make sure of that and do any remaining clean up. 1382 _allocator->abandon_gc_alloc_regions(); 1383 1384 // Instead of tearing down / rebuilding the free lists here, we 1385 // could instead use the remove_all_pending() method on free_list to 1386 // remove only the ones that we need to remove. 1387 tear_down_region_sets(true /* free_list_only */); 1388 shrink_helper(shrink_bytes); 1389 rebuild_region_sets(true /* free_list_only */); 1390 1391 _hrm.verify_optional(); 1392 _verifier->verify_region_sets_optional(); 1393 } 1394 1395 // Public methods. 1396 1397 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1398 CollectedHeap(), 1399 _young_gen_sampling_thread(NULL), 1400 _collector_policy(collector_policy), 1401 _soft_ref_policy(), 1402 _card_table(NULL), 1403 _memory_manager("G1 Young Generation", "end of minor GC"), 1404 _full_gc_memory_manager("G1 Old Generation", "end of major GC"), 1405 _eden_pool(NULL), 1406 _survivor_pool(NULL), 1407 _old_pool(NULL), 1408 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1409 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1410 _g1_policy(new G1Policy(_gc_timer_stw)), 1411 _collection_set(this, _g1_policy), 1412 _dirty_card_queue_set(false), 1413 _is_alive_closure_cm(this), 1414 _is_alive_closure_stw(this), 1415 _ref_processor_cm(NULL), 1416 _ref_processor_stw(NULL), 1417 _bot(NULL), 1418 _hot_card_cache(NULL), 1419 _g1_rem_set(NULL), 1420 _cr(NULL), 1421 _g1mm(NULL), 1422 _preserved_marks_set(true /* in_c_heap */), 1423 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1424 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1425 _humongous_reclaim_candidates(), 1426 _has_humongous_reclaim_candidates(false), 1427 _archive_allocator(NULL), 1428 _summary_bytes_used(0), 1429 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1430 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1431 _expand_heap_after_alloc_failure(true), 1432 _old_marking_cycles_started(0), 1433 _old_marking_cycles_completed(0), 1434 _in_cset_fast_test() { 1435 1436 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1437 /* are_GC_task_threads */true, 1438 /* are_ConcurrentGC_threads */false); 1439 _workers->initialize_workers(); 1440 _verifier = new G1HeapVerifier(this); 1441 1442 _allocator = new G1Allocator(this); 1443 1444 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1445 1446 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1447 1448 // Override the default _filler_array_max_size so that no humongous filler 1449 // objects are created. 1450 _filler_array_max_size = _humongous_object_threshold_in_words; 1451 1452 uint n_queues = ParallelGCThreads; 1453 _task_queues = new RefToScanQueueSet(n_queues); 1454 1455 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1456 1457 for (uint i = 0; i < n_queues; i++) { 1458 RefToScanQueue* q = new RefToScanQueue(); 1459 q->initialize(); 1460 _task_queues->register_queue(i, q); 1461 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1462 } 1463 1464 // Initialize the G1EvacuationFailureALot counters and flags. 1465 NOT_PRODUCT(reset_evacuation_should_fail();) 1466 1467 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1468 } 1469 1470 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1471 size_t size, 1472 size_t translation_factor) { 1473 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1474 // Allocate a new reserved space, preferring to use large pages. 1475 ReservedSpace rs(size, preferred_page_size); 1476 G1RegionToSpaceMapper* result = 1477 G1RegionToSpaceMapper::create_mapper(rs, 1478 size, 1479 rs.alignment(), 1480 HeapRegion::GrainBytes, 1481 translation_factor, 1482 mtGC); 1483 1484 os::trace_page_sizes_for_requested_size(description, 1485 size, 1486 preferred_page_size, 1487 rs.alignment(), 1488 rs.base(), 1489 rs.size()); 1490 1491 return result; 1492 } 1493 1494 jint G1CollectedHeap::initialize_concurrent_refinement() { 1495 jint ecode = JNI_OK; 1496 _cr = G1ConcurrentRefine::create(&ecode); 1497 return ecode; 1498 } 1499 1500 jint G1CollectedHeap::initialize_young_gen_sampling_thread() { 1501 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread(); 1502 if (_young_gen_sampling_thread->osthread() == NULL) { 1503 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread"); 1504 return JNI_ENOMEM; 1505 } 1506 return JNI_OK; 1507 } 1508 1509 jint G1CollectedHeap::initialize() { 1510 os::enable_vtime(); 1511 1512 // Necessary to satisfy locking discipline assertions. 1513 1514 MutexLocker x(Heap_lock); 1515 1516 // While there are no constraints in the GC code that HeapWordSize 1517 // be any particular value, there are multiple other areas in the 1518 // system which believe this to be true (e.g. oop->object_size in some 1519 // cases incorrectly returns the size in wordSize units rather than 1520 // HeapWordSize). 1521 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1522 1523 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1524 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1525 size_t heap_alignment = collector_policy()->heap_alignment(); 1526 1527 // Ensure that the sizes are properly aligned. 1528 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1529 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1530 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1531 1532 // Reserve the maximum. 1533 1534 // When compressed oops are enabled, the preferred heap base 1535 // is calculated by subtracting the requested size from the 1536 // 32Gb boundary and using the result as the base address for 1537 // heap reservation. If the requested size is not aligned to 1538 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1539 // into the ReservedHeapSpace constructor) then the actual 1540 // base of the reserved heap may end up differing from the 1541 // address that was requested (i.e. the preferred heap base). 1542 // If this happens then we could end up using a non-optimal 1543 // compressed oops mode. 1544 1545 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1546 heap_alignment); 1547 1548 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1549 1550 // Create the barrier set for the entire reserved region. 1551 G1CardTable* ct = new G1CardTable(reserved_region()); 1552 ct->initialize(); 1553 G1BarrierSet* bs = new G1BarrierSet(ct); 1554 bs->initialize(); 1555 assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity"); 1556 BarrierSet::set_barrier_set(bs); 1557 _card_table = ct; 1558 1559 // Create the hot card cache. 1560 _hot_card_cache = new G1HotCardCache(this); 1561 1562 // Carve out the G1 part of the heap. 1563 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1564 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1565 G1RegionToSpaceMapper* heap_storage = 1566 G1RegionToSpaceMapper::create_mapper(g1_rs, 1567 g1_rs.size(), 1568 page_size, 1569 HeapRegion::GrainBytes, 1570 1, 1571 mtJavaHeap); 1572 os::trace_page_sizes("Heap", 1573 collector_policy()->min_heap_byte_size(), 1574 max_byte_size, 1575 page_size, 1576 heap_rs.base(), 1577 heap_rs.size()); 1578 heap_storage->set_mapping_changed_listener(&_listener); 1579 1580 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1581 G1RegionToSpaceMapper* bot_storage = 1582 create_aux_memory_mapper("Block Offset Table", 1583 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1584 G1BlockOffsetTable::heap_map_factor()); 1585 1586 G1RegionToSpaceMapper* cardtable_storage = 1587 create_aux_memory_mapper("Card Table", 1588 G1CardTable::compute_size(g1_rs.size() / HeapWordSize), 1589 G1CardTable::heap_map_factor()); 1590 1591 G1RegionToSpaceMapper* card_counts_storage = 1592 create_aux_memory_mapper("Card Counts Table", 1593 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1594 G1CardCounts::heap_map_factor()); 1595 1596 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1597 G1RegionToSpaceMapper* prev_bitmap_storage = 1598 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1599 G1RegionToSpaceMapper* next_bitmap_storage = 1600 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1601 1602 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1603 _card_table->initialize(cardtable_storage); 1604 // Do later initialization work for concurrent refinement. 1605 _hot_card_cache->initialize(card_counts_storage); 1606 1607 // 6843694 - ensure that the maximum region index can fit 1608 // in the remembered set structures. 1609 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1610 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1611 1612 // Also create a G1 rem set. 1613 _g1_rem_set = new G1RemSet(this, _card_table, _hot_card_cache); 1614 _g1_rem_set->initialize(max_capacity(), max_regions()); 1615 1616 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1617 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1618 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1619 "too many cards per region"); 1620 1621 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1622 1623 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1624 1625 { 1626 HeapWord* start = _hrm.reserved().start(); 1627 HeapWord* end = _hrm.reserved().end(); 1628 size_t granularity = HeapRegion::GrainBytes; 1629 1630 _in_cset_fast_test.initialize(start, end, granularity); 1631 _humongous_reclaim_candidates.initialize(start, end, granularity); 1632 } 1633 1634 // Create the G1ConcurrentMark data structure and thread. 1635 // (Must do this late, so that "max_regions" is defined.) 1636 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1637 if (_cm == NULL || !_cm->completed_initialization()) { 1638 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1639 return JNI_ENOMEM; 1640 } 1641 _cm_thread = _cm->cm_thread(); 1642 1643 // Now expand into the initial heap size. 1644 if (!expand(init_byte_size, _workers)) { 1645 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1646 return JNI_ENOMEM; 1647 } 1648 1649 // Perform any initialization actions delegated to the policy. 1650 g1_policy()->init(this, &_collection_set); 1651 1652 G1BarrierSet::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1653 SATB_Q_FL_lock, 1654 G1SATBProcessCompletedThreshold, 1655 Shared_SATB_Q_lock); 1656 1657 jint ecode = initialize_concurrent_refinement(); 1658 if (ecode != JNI_OK) { 1659 return ecode; 1660 } 1661 1662 ecode = initialize_young_gen_sampling_thread(); 1663 if (ecode != JNI_OK) { 1664 return ecode; 1665 } 1666 1667 G1BarrierSet::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1668 DirtyCardQ_FL_lock, 1669 (int)concurrent_refine()->yellow_zone(), 1670 (int)concurrent_refine()->red_zone(), 1671 Shared_DirtyCardQ_lock, 1672 NULL, // fl_owner 1673 true); // init_free_ids 1674 1675 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1676 DirtyCardQ_FL_lock, 1677 -1, // never trigger processing 1678 -1, // no limit on length 1679 Shared_DirtyCardQ_lock, 1680 &G1BarrierSet::dirty_card_queue_set()); 1681 1682 // Here we allocate the dummy HeapRegion that is required by the 1683 // G1AllocRegion class. 1684 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1685 1686 // We'll re-use the same region whether the alloc region will 1687 // require BOT updates or not and, if it doesn't, then a non-young 1688 // region will complain that it cannot support allocations without 1689 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1690 dummy_region->set_eden(); 1691 // Make sure it's full. 1692 dummy_region->set_top(dummy_region->end()); 1693 G1AllocRegion::setup(this, dummy_region); 1694 1695 _allocator->init_mutator_alloc_region(); 1696 1697 // Do create of the monitoring and management support so that 1698 // values in the heap have been properly initialized. 1699 _g1mm = new G1MonitoringSupport(this); 1700 1701 G1StringDedup::initialize(); 1702 1703 _preserved_marks_set.init(ParallelGCThreads); 1704 1705 _collection_set.initialize(max_regions()); 1706 1707 return JNI_OK; 1708 } 1709 1710 void G1CollectedHeap::initialize_serviceability() { 1711 _eden_pool = new G1EdenPool(this); 1712 _survivor_pool = new G1SurvivorPool(this); 1713 _old_pool = new G1OldGenPool(this); 1714 1715 _full_gc_memory_manager.add_pool(_eden_pool); 1716 _full_gc_memory_manager.add_pool(_survivor_pool); 1717 _full_gc_memory_manager.add_pool(_old_pool); 1718 1719 _memory_manager.add_pool(_eden_pool); 1720 _memory_manager.add_pool(_survivor_pool); 1721 1722 } 1723 1724 void G1CollectedHeap::stop() { 1725 // Stop all concurrent threads. We do this to make sure these threads 1726 // do not continue to execute and access resources (e.g. logging) 1727 // that are destroyed during shutdown. 1728 _cr->stop(); 1729 _young_gen_sampling_thread->stop(); 1730 _cm_thread->stop(); 1731 if (G1StringDedup::is_enabled()) { 1732 G1StringDedup::stop(); 1733 } 1734 } 1735 1736 void G1CollectedHeap::safepoint_synchronize_begin() { 1737 SuspendibleThreadSet::synchronize(); 1738 } 1739 1740 void G1CollectedHeap::safepoint_synchronize_end() { 1741 SuspendibleThreadSet::desynchronize(); 1742 } 1743 1744 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1745 return HeapRegion::max_region_size(); 1746 } 1747 1748 void G1CollectedHeap::post_initialize() { 1749 CollectedHeap::post_initialize(); 1750 ref_processing_init(); 1751 } 1752 1753 void G1CollectedHeap::ref_processing_init() { 1754 // Reference processing in G1 currently works as follows: 1755 // 1756 // * There are two reference processor instances. One is 1757 // used to record and process discovered references 1758 // during concurrent marking; the other is used to 1759 // record and process references during STW pauses 1760 // (both full and incremental). 1761 // * Both ref processors need to 'span' the entire heap as 1762 // the regions in the collection set may be dotted around. 1763 // 1764 // * For the concurrent marking ref processor: 1765 // * Reference discovery is enabled at initial marking. 1766 // * Reference discovery is disabled and the discovered 1767 // references processed etc during remarking. 1768 // * Reference discovery is MT (see below). 1769 // * Reference discovery requires a barrier (see below). 1770 // * Reference processing may or may not be MT 1771 // (depending on the value of ParallelRefProcEnabled 1772 // and ParallelGCThreads). 1773 // * A full GC disables reference discovery by the CM 1774 // ref processor and abandons any entries on it's 1775 // discovered lists. 1776 // 1777 // * For the STW processor: 1778 // * Non MT discovery is enabled at the start of a full GC. 1779 // * Processing and enqueueing during a full GC is non-MT. 1780 // * During a full GC, references are processed after marking. 1781 // 1782 // * Discovery (may or may not be MT) is enabled at the start 1783 // of an incremental evacuation pause. 1784 // * References are processed near the end of a STW evacuation pause. 1785 // * For both types of GC: 1786 // * Discovery is atomic - i.e. not concurrent. 1787 // * Reference discovery will not need a barrier. 1788 1789 MemRegion mr = reserved_region(); 1790 1791 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1); 1792 1793 // Concurrent Mark ref processor 1794 _ref_processor_cm = 1795 new ReferenceProcessor(mr, // span 1796 mt_processing, 1797 // mt processing 1798 ParallelGCThreads, 1799 // degree of mt processing 1800 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 1801 // mt discovery 1802 MAX2(ParallelGCThreads, ConcGCThreads), 1803 // degree of mt discovery 1804 false, 1805 // Reference discovery is not atomic 1806 &_is_alive_closure_cm); 1807 // is alive closure 1808 // (for efficiency/performance) 1809 1810 // STW ref processor 1811 _ref_processor_stw = 1812 new ReferenceProcessor(mr, // span 1813 mt_processing, 1814 // mt processing 1815 ParallelGCThreads, 1816 // degree of mt processing 1817 (ParallelGCThreads > 1), 1818 // mt discovery 1819 ParallelGCThreads, 1820 // degree of mt discovery 1821 true, 1822 // Reference discovery is atomic 1823 &_is_alive_closure_stw); 1824 // is alive closure 1825 // (for efficiency/performance) 1826 } 1827 1828 CollectorPolicy* G1CollectedHeap::collector_policy() const { 1829 return _collector_policy; 1830 } 1831 1832 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() { 1833 return &_soft_ref_policy; 1834 } 1835 1836 size_t G1CollectedHeap::capacity() const { 1837 return _hrm.length() * HeapRegion::GrainBytes; 1838 } 1839 1840 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const { 1841 return _hrm.total_free_bytes(); 1842 } 1843 1844 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 1845 _hot_card_cache->drain(cl, worker_i); 1846 } 1847 1848 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 1849 DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 1850 size_t n_completed_buffers = 0; 1851 while (dcqs.apply_closure_during_gc(cl, worker_i)) { 1852 n_completed_buffers++; 1853 } 1854 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers, G1GCPhaseTimes::UpdateRSProcessedBuffers); 1855 dcqs.clear_n_completed_buffers(); 1856 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 1857 } 1858 1859 // Computes the sum of the storage used by the various regions. 1860 size_t G1CollectedHeap::used() const { 1861 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 1862 if (_archive_allocator != NULL) { 1863 result += _archive_allocator->used(); 1864 } 1865 return result; 1866 } 1867 1868 size_t G1CollectedHeap::used_unlocked() const { 1869 return _summary_bytes_used; 1870 } 1871 1872 class SumUsedClosure: public HeapRegionClosure { 1873 size_t _used; 1874 public: 1875 SumUsedClosure() : _used(0) {} 1876 bool do_heap_region(HeapRegion* r) { 1877 _used += r->used(); 1878 return false; 1879 } 1880 size_t result() { return _used; } 1881 }; 1882 1883 size_t G1CollectedHeap::recalculate_used() const { 1884 double recalculate_used_start = os::elapsedTime(); 1885 1886 SumUsedClosure blk; 1887 heap_region_iterate(&blk); 1888 1889 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 1890 return blk.result(); 1891 } 1892 1893 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 1894 switch (cause) { 1895 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 1896 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 1897 case GCCause::_wb_conc_mark: return true; 1898 default : return false; 1899 } 1900 } 1901 1902 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 1903 switch (cause) { 1904 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 1905 case GCCause::_g1_humongous_allocation: return true; 1906 default: return is_user_requested_concurrent_full_gc(cause); 1907 } 1908 } 1909 1910 #ifndef PRODUCT 1911 void G1CollectedHeap::allocate_dummy_regions() { 1912 // Let's fill up most of the region 1913 size_t word_size = HeapRegion::GrainWords - 1024; 1914 // And as a result the region we'll allocate will be humongous. 1915 guarantee(is_humongous(word_size), "sanity"); 1916 1917 // _filler_array_max_size is set to humongous object threshold 1918 // but temporarily change it to use CollectedHeap::fill_with_object(). 1919 SizeTFlagSetting fs(_filler_array_max_size, word_size); 1920 1921 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 1922 // Let's use the existing mechanism for the allocation 1923 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 1924 if (dummy_obj != NULL) { 1925 MemRegion mr(dummy_obj, word_size); 1926 CollectedHeap::fill_with_object(mr); 1927 } else { 1928 // If we can't allocate once, we probably cannot allocate 1929 // again. Let's get out of the loop. 1930 break; 1931 } 1932 } 1933 } 1934 #endif // !PRODUCT 1935 1936 void G1CollectedHeap::increment_old_marking_cycles_started() { 1937 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 1938 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 1939 "Wrong marking cycle count (started: %d, completed: %d)", 1940 _old_marking_cycles_started, _old_marking_cycles_completed); 1941 1942 _old_marking_cycles_started++; 1943 } 1944 1945 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 1946 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 1947 1948 // We assume that if concurrent == true, then the caller is a 1949 // concurrent thread that was joined the Suspendible Thread 1950 // Set. If there's ever a cheap way to check this, we should add an 1951 // assert here. 1952 1953 // Given that this method is called at the end of a Full GC or of a 1954 // concurrent cycle, and those can be nested (i.e., a Full GC can 1955 // interrupt a concurrent cycle), the number of full collections 1956 // completed should be either one (in the case where there was no 1957 // nesting) or two (when a Full GC interrupted a concurrent cycle) 1958 // behind the number of full collections started. 1959 1960 // This is the case for the inner caller, i.e. a Full GC. 1961 assert(concurrent || 1962 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 1963 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 1964 "for inner caller (Full GC): _old_marking_cycles_started = %u " 1965 "is inconsistent with _old_marking_cycles_completed = %u", 1966 _old_marking_cycles_started, _old_marking_cycles_completed); 1967 1968 // This is the case for the outer caller, i.e. the concurrent cycle. 1969 assert(!concurrent || 1970 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 1971 "for outer caller (concurrent cycle): " 1972 "_old_marking_cycles_started = %u " 1973 "is inconsistent with _old_marking_cycles_completed = %u", 1974 _old_marking_cycles_started, _old_marking_cycles_completed); 1975 1976 _old_marking_cycles_completed += 1; 1977 1978 // We need to clear the "in_progress" flag in the CM thread before 1979 // we wake up any waiters (especially when ExplicitInvokesConcurrent 1980 // is set) so that if a waiter requests another System.gc() it doesn't 1981 // incorrectly see that a marking cycle is still in progress. 1982 if (concurrent) { 1983 _cm_thread->set_idle(); 1984 } 1985 1986 // This notify_all() will ensure that a thread that called 1987 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 1988 // and it's waiting for a full GC to finish will be woken up. It is 1989 // waiting in VM_G1CollectForAllocation::doit_epilogue(). 1990 FullGCCount_lock->notify_all(); 1991 } 1992 1993 void G1CollectedHeap::collect(GCCause::Cause cause) { 1994 assert_heap_not_locked(); 1995 1996 uint gc_count_before; 1997 uint old_marking_count_before; 1998 uint full_gc_count_before; 1999 bool retry_gc; 2000 2001 do { 2002 retry_gc = false; 2003 2004 { 2005 MutexLocker ml(Heap_lock); 2006 2007 // Read the GC count while holding the Heap_lock 2008 gc_count_before = total_collections(); 2009 full_gc_count_before = total_full_collections(); 2010 old_marking_count_before = _old_marking_cycles_started; 2011 } 2012 2013 if (should_do_concurrent_full_gc(cause)) { 2014 // Schedule an initial-mark evacuation pause that will start a 2015 // concurrent cycle. We're setting word_size to 0 which means that 2016 // we are not requesting a post-GC allocation. 2017 VM_G1CollectForAllocation op(0, /* word_size */ 2018 gc_count_before, 2019 cause, 2020 true, /* should_initiate_conc_mark */ 2021 g1_policy()->max_pause_time_ms()); 2022 VMThread::execute(&op); 2023 if (!op.pause_succeeded()) { 2024 if (old_marking_count_before == _old_marking_cycles_started) { 2025 retry_gc = op.should_retry_gc(); 2026 } else { 2027 // A Full GC happened while we were trying to schedule the 2028 // initial-mark GC. No point in starting a new cycle given 2029 // that the whole heap was collected anyway. 2030 } 2031 2032 if (retry_gc) { 2033 if (GCLocker::is_active_and_needs_gc()) { 2034 GCLocker::stall_until_clear(); 2035 } 2036 } 2037 } 2038 } else { 2039 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2040 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2041 2042 // Schedule a standard evacuation pause. We're setting word_size 2043 // to 0 which means that we are not requesting a post-GC allocation. 2044 VM_G1CollectForAllocation op(0, /* word_size */ 2045 gc_count_before, 2046 cause, 2047 false, /* should_initiate_conc_mark */ 2048 g1_policy()->max_pause_time_ms()); 2049 VMThread::execute(&op); 2050 } else { 2051 // Schedule a Full GC. 2052 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2053 VMThread::execute(&op); 2054 } 2055 } 2056 } while (retry_gc); 2057 } 2058 2059 bool G1CollectedHeap::is_in(const void* p) const { 2060 if (_hrm.reserved().contains(p)) { 2061 // Given that we know that p is in the reserved space, 2062 // heap_region_containing() should successfully 2063 // return the containing region. 2064 HeapRegion* hr = heap_region_containing(p); 2065 return hr->is_in(p); 2066 } else { 2067 return false; 2068 } 2069 } 2070 2071 #ifdef ASSERT 2072 bool G1CollectedHeap::is_in_exact(const void* p) const { 2073 bool contains = reserved_region().contains(p); 2074 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2075 if (contains && available) { 2076 return true; 2077 } else { 2078 return false; 2079 } 2080 } 2081 #endif 2082 2083 // Iteration functions. 2084 2085 // Iterates an ObjectClosure over all objects within a HeapRegion. 2086 2087 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2088 ObjectClosure* _cl; 2089 public: 2090 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2091 bool do_heap_region(HeapRegion* r) { 2092 if (!r->is_continues_humongous()) { 2093 r->object_iterate(_cl); 2094 } 2095 return false; 2096 } 2097 }; 2098 2099 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2100 IterateObjectClosureRegionClosure blk(cl); 2101 heap_region_iterate(&blk); 2102 } 2103 2104 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2105 _hrm.iterate(cl); 2106 } 2107 2108 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl, 2109 HeapRegionClaimer *hrclaimer, 2110 uint worker_id) const { 2111 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id)); 2112 } 2113 2114 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl, 2115 HeapRegionClaimer *hrclaimer) const { 2116 _hrm.par_iterate(cl, hrclaimer, 0); 2117 } 2118 2119 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2120 _collection_set.iterate(cl); 2121 } 2122 2123 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2124 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2125 } 2126 2127 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2128 HeapRegion* hr = heap_region_containing(addr); 2129 return hr->block_start(addr); 2130 } 2131 2132 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2133 HeapRegion* hr = heap_region_containing(addr); 2134 return hr->block_size(addr); 2135 } 2136 2137 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2138 HeapRegion* hr = heap_region_containing(addr); 2139 return hr->block_is_obj(addr); 2140 } 2141 2142 bool G1CollectedHeap::supports_tlab_allocation() const { 2143 return true; 2144 } 2145 2146 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2147 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2148 } 2149 2150 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2151 return _eden.length() * HeapRegion::GrainBytes; 2152 } 2153 2154 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2155 // must be equal to the humongous object limit. 2156 size_t G1CollectedHeap::max_tlab_size() const { 2157 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2158 } 2159 2160 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2161 return _allocator->unsafe_max_tlab_alloc(); 2162 } 2163 2164 size_t G1CollectedHeap::max_capacity() const { 2165 return _hrm.reserved().byte_size(); 2166 } 2167 2168 jlong G1CollectedHeap::millis_since_last_gc() { 2169 // See the notes in GenCollectedHeap::millis_since_last_gc() 2170 // for more information about the implementation. 2171 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2172 _g1_policy->collection_pause_end_millis(); 2173 if (ret_val < 0) { 2174 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2175 ". returning zero instead.", ret_val); 2176 return 0; 2177 } 2178 return ret_val; 2179 } 2180 2181 void G1CollectedHeap::prepare_for_verify() { 2182 _verifier->prepare_for_verify(); 2183 } 2184 2185 void G1CollectedHeap::verify(VerifyOption vo) { 2186 _verifier->verify(vo); 2187 } 2188 2189 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2190 return true; 2191 } 2192 2193 const char* const* G1CollectedHeap::concurrent_phases() const { 2194 return _cm_thread->concurrent_phases(); 2195 } 2196 2197 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2198 return _cm_thread->request_concurrent_phase(phase); 2199 } 2200 2201 class PrintRegionClosure: public HeapRegionClosure { 2202 outputStream* _st; 2203 public: 2204 PrintRegionClosure(outputStream* st) : _st(st) {} 2205 bool do_heap_region(HeapRegion* r) { 2206 r->print_on(_st); 2207 return false; 2208 } 2209 }; 2210 2211 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2212 const HeapRegion* hr, 2213 const VerifyOption vo) const { 2214 switch (vo) { 2215 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2216 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2217 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr); 2218 default: ShouldNotReachHere(); 2219 } 2220 return false; // keep some compilers happy 2221 } 2222 2223 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2224 const VerifyOption vo) const { 2225 switch (vo) { 2226 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2227 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2228 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj); 2229 default: ShouldNotReachHere(); 2230 } 2231 return false; // keep some compilers happy 2232 } 2233 2234 void G1CollectedHeap::print_heap_regions() const { 2235 LogTarget(Trace, gc, heap, region) lt; 2236 if (lt.is_enabled()) { 2237 LogStream ls(lt); 2238 print_regions_on(&ls); 2239 } 2240 } 2241 2242 void G1CollectedHeap::print_on(outputStream* st) const { 2243 st->print(" %-20s", "garbage-first heap"); 2244 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2245 capacity()/K, used_unlocked()/K); 2246 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")", 2247 p2i(_hrm.reserved().start()), 2248 p2i(_hrm.reserved().end())); 2249 st->cr(); 2250 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2251 uint young_regions = young_regions_count(); 2252 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2253 (size_t) young_regions * HeapRegion::GrainBytes / K); 2254 uint survivor_regions = survivor_regions_count(); 2255 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2256 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2257 st->cr(); 2258 MetaspaceUtils::print_on(st); 2259 } 2260 2261 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2262 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2263 "HS=humongous(starts), HC=humongous(continues), " 2264 "CS=collection set, F=free, A=archive, " 2265 "TAMS=top-at-mark-start (previous, next)"); 2266 PrintRegionClosure blk(st); 2267 heap_region_iterate(&blk); 2268 } 2269 2270 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2271 print_on(st); 2272 2273 // Print the per-region information. 2274 print_regions_on(st); 2275 } 2276 2277 void G1CollectedHeap::print_on_error(outputStream* st) const { 2278 this->CollectedHeap::print_on_error(st); 2279 2280 if (_cm != NULL) { 2281 st->cr(); 2282 _cm->print_on_error(st); 2283 } 2284 } 2285 2286 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2287 workers()->print_worker_threads_on(st); 2288 _cm_thread->print_on(st); 2289 st->cr(); 2290 _cm->print_worker_threads_on(st); 2291 _cr->print_threads_on(st); 2292 _young_gen_sampling_thread->print_on(st); 2293 if (G1StringDedup::is_enabled()) { 2294 G1StringDedup::print_worker_threads_on(st); 2295 } 2296 } 2297 2298 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2299 workers()->threads_do(tc); 2300 tc->do_thread(_cm_thread); 2301 _cm->threads_do(tc); 2302 _cr->threads_do(tc); 2303 tc->do_thread(_young_gen_sampling_thread); 2304 if (G1StringDedup::is_enabled()) { 2305 G1StringDedup::threads_do(tc); 2306 } 2307 } 2308 2309 void G1CollectedHeap::print_tracing_info() const { 2310 g1_rem_set()->print_summary_info(); 2311 concurrent_mark()->print_summary_info(); 2312 } 2313 2314 #ifndef PRODUCT 2315 // Helpful for debugging RSet issues. 2316 2317 class PrintRSetsClosure : public HeapRegionClosure { 2318 private: 2319 const char* _msg; 2320 size_t _occupied_sum; 2321 2322 public: 2323 bool do_heap_region(HeapRegion* r) { 2324 HeapRegionRemSet* hrrs = r->rem_set(); 2325 size_t occupied = hrrs->occupied(); 2326 _occupied_sum += occupied; 2327 2328 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2329 if (occupied == 0) { 2330 tty->print_cr(" RSet is empty"); 2331 } else { 2332 hrrs->print(); 2333 } 2334 tty->print_cr("----------"); 2335 return false; 2336 } 2337 2338 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2339 tty->cr(); 2340 tty->print_cr("========================================"); 2341 tty->print_cr("%s", msg); 2342 tty->cr(); 2343 } 2344 2345 ~PrintRSetsClosure() { 2346 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2347 tty->print_cr("========================================"); 2348 tty->cr(); 2349 } 2350 }; 2351 2352 void G1CollectedHeap::print_cset_rsets() { 2353 PrintRSetsClosure cl("Printing CSet RSets"); 2354 collection_set_iterate(&cl); 2355 } 2356 2357 void G1CollectedHeap::print_all_rsets() { 2358 PrintRSetsClosure cl("Printing All RSets");; 2359 heap_region_iterate(&cl); 2360 } 2361 #endif // PRODUCT 2362 2363 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2364 2365 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2366 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2367 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2368 2369 size_t eden_capacity_bytes = 2370 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2371 2372 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2373 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2374 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2375 } 2376 2377 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2378 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2379 stats->unused(), stats->used(), stats->region_end_waste(), 2380 stats->regions_filled(), stats->direct_allocated(), 2381 stats->failure_used(), stats->failure_waste()); 2382 } 2383 2384 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2385 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2386 gc_tracer->report_gc_heap_summary(when, heap_summary); 2387 2388 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2389 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2390 } 2391 2392 G1CollectedHeap* G1CollectedHeap::heap() { 2393 CollectedHeap* heap = Universe::heap(); 2394 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2395 assert(heap->kind() == CollectedHeap::G1, "Invalid name"); 2396 return (G1CollectedHeap*)heap; 2397 } 2398 2399 void G1CollectedHeap::gc_prologue(bool full) { 2400 // always_do_update_barrier = false; 2401 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2402 2403 // This summary needs to be printed before incrementing total collections. 2404 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2405 2406 // Update common counters. 2407 increment_total_collections(full /* full gc */); 2408 if (full) { 2409 increment_old_marking_cycles_started(); 2410 } 2411 2412 // Fill TLAB's and such 2413 double start = os::elapsedTime(); 2414 accumulate_statistics_all_tlabs(); 2415 ensure_parsability(true); 2416 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2417 } 2418 2419 void G1CollectedHeap::gc_epilogue(bool full) { 2420 // Update common counters. 2421 if (full) { 2422 // Update the number of full collections that have been completed. 2423 increment_old_marking_cycles_completed(false /* concurrent */); 2424 } 2425 2426 // We are at the end of the GC. Total collections has already been increased. 2427 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2428 2429 // FIXME: what is this about? 2430 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2431 // is set. 2432 #if COMPILER2_OR_JVMCI 2433 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2434 #endif 2435 // always_do_update_barrier = true; 2436 2437 double start = os::elapsedTime(); 2438 resize_all_tlabs(); 2439 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2440 2441 MemoryService::track_memory_usage(); 2442 // We have just completed a GC. Update the soft reference 2443 // policy with the new heap occupancy 2444 Universe::update_heap_info_at_gc(); 2445 } 2446 2447 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2448 uint gc_count_before, 2449 bool* succeeded, 2450 GCCause::Cause gc_cause) { 2451 assert_heap_not_locked_and_not_at_safepoint(); 2452 VM_G1CollectForAllocation op(word_size, 2453 gc_count_before, 2454 gc_cause, 2455 false, /* should_initiate_conc_mark */ 2456 g1_policy()->max_pause_time_ms()); 2457 VMThread::execute(&op); 2458 2459 HeapWord* result = op.result(); 2460 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2461 assert(result == NULL || ret_succeeded, 2462 "the result should be NULL if the VM did not succeed"); 2463 *succeeded = ret_succeeded; 2464 2465 assert_heap_not_locked(); 2466 return result; 2467 } 2468 2469 void G1CollectedHeap::do_concurrent_mark() { 2470 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2471 if (!_cm_thread->in_progress()) { 2472 _cm_thread->set_started(); 2473 CGC_lock->notify(); 2474 } 2475 } 2476 2477 size_t G1CollectedHeap::pending_card_num() { 2478 size_t extra_cards = 0; 2479 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) { 2480 DirtyCardQueue& dcq = G1ThreadLocalData::dirty_card_queue(curr); 2481 extra_cards += dcq.size(); 2482 } 2483 DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 2484 size_t buffer_size = dcqs.buffer_size(); 2485 size_t buffer_num = dcqs.completed_buffers_num(); 2486 2487 return buffer_size * buffer_num + extra_cards; 2488 } 2489 2490 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const { 2491 // We don't nominate objects with many remembered set entries, on 2492 // the assumption that such objects are likely still live. 2493 HeapRegionRemSet* rem_set = r->rem_set(); 2494 2495 return G1EagerReclaimHumongousObjectsWithStaleRefs ? 2496 rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) : 2497 G1EagerReclaimHumongousObjects && rem_set->is_empty(); 2498 } 2499 2500 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2501 private: 2502 size_t _total_humongous; 2503 size_t _candidate_humongous; 2504 2505 DirtyCardQueue _dcq; 2506 2507 bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const { 2508 assert(region->is_starts_humongous(), "Must start a humongous object"); 2509 2510 oop obj = oop(region->bottom()); 2511 2512 // Dead objects cannot be eager reclaim candidates. Due to class 2513 // unloading it is unsafe to query their classes so we return early. 2514 if (g1h->is_obj_dead(obj, region)) { 2515 return false; 2516 } 2517 2518 // If we do not have a complete remembered set for the region, then we can 2519 // not be sure that we have all references to it. 2520 if (!region->rem_set()->is_complete()) { 2521 return false; 2522 } 2523 // Candidate selection must satisfy the following constraints 2524 // while concurrent marking is in progress: 2525 // 2526 // * In order to maintain SATB invariants, an object must not be 2527 // reclaimed if it was allocated before the start of marking and 2528 // has not had its references scanned. Such an object must have 2529 // its references (including type metadata) scanned to ensure no 2530 // live objects are missed by the marking process. Objects 2531 // allocated after the start of concurrent marking don't need to 2532 // be scanned. 2533 // 2534 // * An object must not be reclaimed if it is on the concurrent 2535 // mark stack. Objects allocated after the start of concurrent 2536 // marking are never pushed on the mark stack. 2537 // 2538 // Nominating only objects allocated after the start of concurrent 2539 // marking is sufficient to meet both constraints. This may miss 2540 // some objects that satisfy the constraints, but the marking data 2541 // structures don't support efficiently performing the needed 2542 // additional tests or scrubbing of the mark stack. 2543 // 2544 // However, we presently only nominate is_typeArray() objects. 2545 // A humongous object containing references induces remembered 2546 // set entries on other regions. In order to reclaim such an 2547 // object, those remembered sets would need to be cleaned up. 2548 // 2549 // We also treat is_typeArray() objects specially, allowing them 2550 // to be reclaimed even if allocated before the start of 2551 // concurrent mark. For this we rely on mark stack insertion to 2552 // exclude is_typeArray() objects, preventing reclaiming an object 2553 // that is in the mark stack. We also rely on the metadata for 2554 // such objects to be built-in and so ensured to be kept live. 2555 // Frequent allocation and drop of large binary blobs is an 2556 // important use case for eager reclaim, and this special handling 2557 // may reduce needed headroom. 2558 2559 return obj->is_typeArray() && 2560 g1h->is_potential_eager_reclaim_candidate(region); 2561 } 2562 2563 public: 2564 RegisterHumongousWithInCSetFastTestClosure() 2565 : _total_humongous(0), 2566 _candidate_humongous(0), 2567 _dcq(&G1BarrierSet::dirty_card_queue_set()) { 2568 } 2569 2570 virtual bool do_heap_region(HeapRegion* r) { 2571 if (!r->is_starts_humongous()) { 2572 return false; 2573 } 2574 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2575 2576 bool is_candidate = humongous_region_is_candidate(g1h, r); 2577 uint rindex = r->hrm_index(); 2578 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2579 if (is_candidate) { 2580 _candidate_humongous++; 2581 g1h->register_humongous_region_with_cset(rindex); 2582 // Is_candidate already filters out humongous object with large remembered sets. 2583 // If we have a humongous object with a few remembered sets, we simply flush these 2584 // remembered set entries into the DCQS. That will result in automatic 2585 // re-evaluation of their remembered set entries during the following evacuation 2586 // phase. 2587 if (!r->rem_set()->is_empty()) { 2588 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2589 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2590 G1CardTable* ct = g1h->card_table(); 2591 HeapRegionRemSetIterator hrrs(r->rem_set()); 2592 size_t card_index; 2593 while (hrrs.has_next(card_index)) { 2594 jbyte* card_ptr = (jbyte*)ct->byte_for_index(card_index); 2595 // The remembered set might contain references to already freed 2596 // regions. Filter out such entries to avoid failing card table 2597 // verification. 2598 if (g1h->is_in_closed_subset(ct->addr_for(card_ptr))) { 2599 if (*card_ptr != G1CardTable::dirty_card_val()) { 2600 *card_ptr = G1CardTable::dirty_card_val(); 2601 _dcq.enqueue(card_ptr); 2602 } 2603 } 2604 } 2605 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2606 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2607 hrrs.n_yielded(), r->rem_set()->occupied()); 2608 // We should only clear the card based remembered set here as we will not 2609 // implicitly rebuild anything else during eager reclaim. Note that at the moment 2610 // (and probably never) we do not enter this path if there are other kind of 2611 // remembered sets for this region. 2612 r->rem_set()->clear_locked(true /* only_cardset */); 2613 // Clear_locked() above sets the state to Empty. However we want to continue 2614 // collecting remembered set entries for humongous regions that were not 2615 // reclaimed. 2616 r->rem_set()->set_state_complete(); 2617 } 2618 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2619 } 2620 _total_humongous++; 2621 2622 return false; 2623 } 2624 2625 size_t total_humongous() const { return _total_humongous; } 2626 size_t candidate_humongous() const { return _candidate_humongous; } 2627 2628 void flush_rem_set_entries() { _dcq.flush(); } 2629 }; 2630 2631 void G1CollectedHeap::register_humongous_regions_with_cset() { 2632 if (!G1EagerReclaimHumongousObjects) { 2633 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2634 return; 2635 } 2636 double time = os::elapsed_counter(); 2637 2638 // Collect reclaim candidate information and register candidates with cset. 2639 RegisterHumongousWithInCSetFastTestClosure cl; 2640 heap_region_iterate(&cl); 2641 2642 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2643 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2644 cl.total_humongous(), 2645 cl.candidate_humongous()); 2646 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2647 2648 // Finally flush all remembered set entries to re-check into the global DCQS. 2649 cl.flush_rem_set_entries(); 2650 } 2651 2652 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2653 public: 2654 bool do_heap_region(HeapRegion* hr) { 2655 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2656 hr->verify_rem_set(); 2657 } 2658 return false; 2659 } 2660 }; 2661 2662 uint G1CollectedHeap::num_task_queues() const { 2663 return _task_queues->size(); 2664 } 2665 2666 #if TASKQUEUE_STATS 2667 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2668 st->print_raw_cr("GC Task Stats"); 2669 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2670 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2671 } 2672 2673 void G1CollectedHeap::print_taskqueue_stats() const { 2674 if (!log_is_enabled(Trace, gc, task, stats)) { 2675 return; 2676 } 2677 Log(gc, task, stats) log; 2678 ResourceMark rm; 2679 LogStream ls(log.trace()); 2680 outputStream* st = &ls; 2681 2682 print_taskqueue_stats_hdr(st); 2683 2684 TaskQueueStats totals; 2685 const uint n = num_task_queues(); 2686 for (uint i = 0; i < n; ++i) { 2687 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2688 totals += task_queue(i)->stats; 2689 } 2690 st->print_raw("tot "); totals.print(st); st->cr(); 2691 2692 DEBUG_ONLY(totals.verify()); 2693 } 2694 2695 void G1CollectedHeap::reset_taskqueue_stats() { 2696 const uint n = num_task_queues(); 2697 for (uint i = 0; i < n; ++i) { 2698 task_queue(i)->stats.reset(); 2699 } 2700 } 2701 #endif // TASKQUEUE_STATS 2702 2703 void G1CollectedHeap::wait_for_root_region_scanning() { 2704 double scan_wait_start = os::elapsedTime(); 2705 // We have to wait until the CM threads finish scanning the 2706 // root regions as it's the only way to ensure that all the 2707 // objects on them have been correctly scanned before we start 2708 // moving them during the GC. 2709 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2710 double wait_time_ms = 0.0; 2711 if (waited) { 2712 double scan_wait_end = os::elapsedTime(); 2713 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2714 } 2715 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2716 } 2717 2718 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2719 private: 2720 G1HRPrinter* _hr_printer; 2721 public: 2722 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2723 2724 virtual bool do_heap_region(HeapRegion* r) { 2725 _hr_printer->cset(r); 2726 return false; 2727 } 2728 }; 2729 2730 void G1CollectedHeap::start_new_collection_set() { 2731 collection_set()->start_incremental_building(); 2732 2733 clear_cset_fast_test(); 2734 2735 guarantee(_eden.length() == 0, "eden should have been cleared"); 2736 g1_policy()->transfer_survivors_to_cset(survivor()); 2737 } 2738 2739 bool 2740 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2741 assert_at_safepoint_on_vm_thread(); 2742 guarantee(!is_gc_active(), "collection is not reentrant"); 2743 2744 if (GCLocker::check_active_before_gc()) { 2745 return false; 2746 } 2747 2748 _gc_timer_stw->register_gc_start(); 2749 2750 GCIdMark gc_id_mark; 2751 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2752 2753 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2754 ResourceMark rm; 2755 2756 g1_policy()->note_gc_start(); 2757 2758 wait_for_root_region_scanning(); 2759 2760 print_heap_before_gc(); 2761 print_heap_regions(); 2762 trace_heap_before_gc(_gc_tracer_stw); 2763 2764 _verifier->verify_region_sets_optional(); 2765 _verifier->verify_dirty_young_regions(); 2766 2767 // We should not be doing initial mark unless the conc mark thread is running 2768 if (!_cm_thread->should_terminate()) { 2769 // This call will decide whether this pause is an initial-mark 2770 // pause. If it is, in_initial_mark_gc() will return true 2771 // for the duration of this pause. 2772 g1_policy()->decide_on_conc_mark_initiation(); 2773 } 2774 2775 // We do not allow initial-mark to be piggy-backed on a mixed GC. 2776 assert(!collector_state()->in_initial_mark_gc() || 2777 collector_state()->in_young_only_phase(), "sanity"); 2778 2779 // We also do not allow mixed GCs during marking. 2780 assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity"); 2781 2782 // Record whether this pause is an initial mark. When the current 2783 // thread has completed its logging output and it's safe to signal 2784 // the CM thread, the flag's value in the policy has been reset. 2785 bool should_start_conc_mark = collector_state()->in_initial_mark_gc(); 2786 2787 // Inner scope for scope based logging, timers, and stats collection 2788 { 2789 EvacuationInfo evacuation_info; 2790 2791 if (collector_state()->in_initial_mark_gc()) { 2792 // We are about to start a marking cycle, so we increment the 2793 // full collection counter. 2794 increment_old_marking_cycles_started(); 2795 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 2796 } 2797 2798 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 2799 2800 GCTraceCPUTime tcpu; 2801 2802 G1HeapVerifier::G1VerifyType verify_type; 2803 FormatBuffer<> gc_string("Pause "); 2804 if (collector_state()->in_initial_mark_gc()) { 2805 gc_string.append("Initial Mark"); 2806 verify_type = G1HeapVerifier::G1VerifyInitialMark; 2807 } else if (collector_state()->in_young_only_phase()) { 2808 gc_string.append("Young"); 2809 verify_type = G1HeapVerifier::G1VerifyYoungOnly; 2810 } else { 2811 gc_string.append("Mixed"); 2812 verify_type = G1HeapVerifier::G1VerifyMixed; 2813 } 2814 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 2815 2816 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 2817 workers()->active_workers(), 2818 Threads::number_of_non_daemon_threads()); 2819 active_workers = workers()->update_active_workers(active_workers); 2820 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 2821 2822 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 2823 TraceMemoryManagerStats tms(&_memory_manager, gc_cause()); 2824 2825 G1HeapTransition heap_transition(this); 2826 size_t heap_used_bytes_before_gc = used(); 2827 2828 // Don't dynamically change the number of GC threads this early. A value of 2829 // 0 is used to indicate serial work. When parallel work is done, 2830 // it will be set. 2831 2832 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 2833 IsGCActiveMark x; 2834 2835 gc_prologue(false); 2836 2837 if (VerifyRememberedSets) { 2838 log_info(gc, verify)("[Verifying RemSets before GC]"); 2839 VerifyRegionRemSetClosure v_cl; 2840 heap_region_iterate(&v_cl); 2841 } 2842 2843 _verifier->verify_before_gc(verify_type); 2844 2845 _verifier->check_bitmaps("GC Start"); 2846 2847 #if COMPILER2_OR_JVMCI 2848 DerivedPointerTable::clear(); 2849 #endif 2850 2851 // Please see comment in g1CollectedHeap.hpp and 2852 // G1CollectedHeap::ref_processing_init() to see how 2853 // reference processing currently works in G1. 2854 2855 // Enable discovery in the STW reference processor 2856 ref_processor_stw()->enable_discovery(); 2857 2858 { 2859 // We want to temporarily turn off discovery by the 2860 // CM ref processor, if necessary, and turn it back on 2861 // on again later if we do. Using a scoped 2862 // NoRefDiscovery object will do this. 2863 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 2864 2865 // Forget the current alloc region (we might even choose it to be part 2866 // of the collection set!). 2867 _allocator->release_mutator_alloc_region(); 2868 2869 // This timing is only used by the ergonomics to handle our pause target. 2870 // It is unclear why this should not include the full pause. We will 2871 // investigate this in CR 7178365. 2872 // 2873 // Preserving the old comment here if that helps the investigation: 2874 // 2875 // The elapsed time induced by the start time below deliberately elides 2876 // the possible verification above. 2877 double sample_start_time_sec = os::elapsedTime(); 2878 2879 g1_policy()->record_collection_pause_start(sample_start_time_sec); 2880 2881 if (collector_state()->in_initial_mark_gc()) { 2882 concurrent_mark()->pre_initial_mark(); 2883 } 2884 2885 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 2886 2887 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 2888 2889 // Make sure the remembered sets are up to date. This needs to be 2890 // done before register_humongous_regions_with_cset(), because the 2891 // remembered sets are used there to choose eager reclaim candidates. 2892 // If the remembered sets are not up to date we might miss some 2893 // entries that need to be handled. 2894 g1_rem_set()->cleanupHRRS(); 2895 2896 register_humongous_regions_with_cset(); 2897 2898 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 2899 2900 // We call this after finalize_cset() to 2901 // ensure that the CSet has been finalized. 2902 _cm->verify_no_cset_oops(); 2903 2904 if (_hr_printer.is_active()) { 2905 G1PrintCollectionSetClosure cl(&_hr_printer); 2906 _collection_set.iterate(&cl); 2907 } 2908 2909 // Initialize the GC alloc regions. 2910 _allocator->init_gc_alloc_regions(evacuation_info); 2911 2912 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 2913 pre_evacuate_collection_set(); 2914 2915 // Actually do the work... 2916 evacuate_collection_set(&per_thread_states); 2917 2918 post_evacuate_collection_set(evacuation_info, &per_thread_states); 2919 2920 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 2921 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 2922 2923 eagerly_reclaim_humongous_regions(); 2924 2925 record_obj_copy_mem_stats(); 2926 _survivor_evac_stats.adjust_desired_plab_sz(); 2927 _old_evac_stats.adjust_desired_plab_sz(); 2928 2929 double start = os::elapsedTime(); 2930 start_new_collection_set(); 2931 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 2932 2933 if (evacuation_failed()) { 2934 set_used(recalculate_used()); 2935 if (_archive_allocator != NULL) { 2936 _archive_allocator->clear_used(); 2937 } 2938 for (uint i = 0; i < ParallelGCThreads; i++) { 2939 if (_evacuation_failed_info_array[i].has_failed()) { 2940 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 2941 } 2942 } 2943 } else { 2944 // The "used" of the the collection set have already been subtracted 2945 // when they were freed. Add in the bytes evacuated. 2946 increase_used(g1_policy()->bytes_copied_during_gc()); 2947 } 2948 2949 if (collector_state()->in_initial_mark_gc()) { 2950 // We have to do this before we notify the CM threads that 2951 // they can start working to make sure that all the 2952 // appropriate initialization is done on the CM object. 2953 concurrent_mark()->post_initial_mark(); 2954 // Note that we don't actually trigger the CM thread at 2955 // this point. We do that later when we're sure that 2956 // the current thread has completed its logging output. 2957 } 2958 2959 allocate_dummy_regions(); 2960 2961 _allocator->init_mutator_alloc_region(); 2962 2963 { 2964 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 2965 if (expand_bytes > 0) { 2966 size_t bytes_before = capacity(); 2967 // No need for an ergo logging here, 2968 // expansion_amount() does this when it returns a value > 0. 2969 double expand_ms; 2970 if (!expand(expand_bytes, _workers, &expand_ms)) { 2971 // We failed to expand the heap. Cannot do anything about it. 2972 } 2973 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 2974 } 2975 } 2976 2977 // We redo the verification but now wrt to the new CSet which 2978 // has just got initialized after the previous CSet was freed. 2979 _cm->verify_no_cset_oops(); 2980 2981 // This timing is only used by the ergonomics to handle our pause target. 2982 // It is unclear why this should not include the full pause. We will 2983 // investigate this in CR 7178365. 2984 double sample_end_time_sec = os::elapsedTime(); 2985 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 2986 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards); 2987 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 2988 2989 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 2990 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 2991 2992 if (VerifyRememberedSets) { 2993 log_info(gc, verify)("[Verifying RemSets after GC]"); 2994 VerifyRegionRemSetClosure v_cl; 2995 heap_region_iterate(&v_cl); 2996 } 2997 2998 _verifier->verify_after_gc(verify_type); 2999 _verifier->check_bitmaps("GC End"); 3000 3001 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3002 ref_processor_stw()->verify_no_references_recorded(); 3003 3004 // CM reference discovery will be re-enabled if necessary. 3005 } 3006 3007 #ifdef TRACESPINNING 3008 ParallelTaskTerminator::print_termination_counts(); 3009 #endif 3010 3011 gc_epilogue(false); 3012 } 3013 3014 // Print the remainder of the GC log output. 3015 if (evacuation_failed()) { 3016 log_info(gc)("To-space exhausted"); 3017 } 3018 3019 g1_policy()->print_phases(); 3020 heap_transition.print(); 3021 3022 // It is not yet to safe to tell the concurrent mark to 3023 // start as we have some optional output below. We don't want the 3024 // output from the concurrent mark thread interfering with this 3025 // logging output either. 3026 3027 _hrm.verify_optional(); 3028 _verifier->verify_region_sets_optional(); 3029 3030 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3031 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3032 3033 print_heap_after_gc(); 3034 print_heap_regions(); 3035 trace_heap_after_gc(_gc_tracer_stw); 3036 3037 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3038 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3039 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3040 // before any GC notifications are raised. 3041 g1mm()->update_sizes(); 3042 3043 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3044 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3045 _gc_timer_stw->register_gc_end(); 3046 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3047 } 3048 // It should now be safe to tell the concurrent mark thread to start 3049 // without its logging output interfering with the logging output 3050 // that came from the pause. 3051 3052 if (should_start_conc_mark) { 3053 // CAUTION: after the doConcurrentMark() call below, 3054 // the concurrent marking thread(s) could be running 3055 // concurrently with us. Make sure that anything after 3056 // this point does not assume that we are the only GC thread 3057 // running. Note: of course, the actual marking work will 3058 // not start until the safepoint itself is released in 3059 // SuspendibleThreadSet::desynchronize(). 3060 do_concurrent_mark(); 3061 } 3062 3063 return true; 3064 } 3065 3066 void G1CollectedHeap::remove_self_forwarding_pointers() { 3067 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3068 workers()->run_task(&rsfp_task); 3069 } 3070 3071 void G1CollectedHeap::restore_after_evac_failure() { 3072 double remove_self_forwards_start = os::elapsedTime(); 3073 3074 remove_self_forwarding_pointers(); 3075 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3076 _preserved_marks_set.restore(&task_executor); 3077 3078 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3079 } 3080 3081 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3082 if (!_evacuation_failed) { 3083 _evacuation_failed = true; 3084 } 3085 3086 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3087 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3088 } 3089 3090 bool G1ParEvacuateFollowersClosure::offer_termination() { 3091 G1ParScanThreadState* const pss = par_scan_state(); 3092 start_term_time(); 3093 const bool res = terminator()->offer_termination(); 3094 end_term_time(); 3095 return res; 3096 } 3097 3098 void G1ParEvacuateFollowersClosure::do_void() { 3099 G1ParScanThreadState* const pss = par_scan_state(); 3100 pss->trim_queue(); 3101 do { 3102 pss->steal_and_trim_queue(queues()); 3103 } while (!offer_termination()); 3104 } 3105 3106 class G1ParTask : public AbstractGangTask { 3107 protected: 3108 G1CollectedHeap* _g1h; 3109 G1ParScanThreadStateSet* _pss; 3110 RefToScanQueueSet* _queues; 3111 G1RootProcessor* _root_processor; 3112 ParallelTaskTerminator _terminator; 3113 uint _n_workers; 3114 3115 public: 3116 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3117 : AbstractGangTask("G1 collection"), 3118 _g1h(g1h), 3119 _pss(per_thread_states), 3120 _queues(task_queues), 3121 _root_processor(root_processor), 3122 _terminator(n_workers, _queues), 3123 _n_workers(n_workers) 3124 {} 3125 3126 void work(uint worker_id) { 3127 if (worker_id >= _n_workers) return; // no work needed this round 3128 3129 double start_sec = os::elapsedTime(); 3130 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3131 3132 { 3133 ResourceMark rm; 3134 HandleMark hm; 3135 3136 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3137 3138 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3139 pss->set_ref_discoverer(rp); 3140 3141 double start_strong_roots_sec = os::elapsedTime(); 3142 3143 _root_processor->evacuate_roots(pss, worker_id); 3144 3145 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3146 // treating the nmethods visited to act as roots for concurrent marking. 3147 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3148 // objects copied by the current evacuation. 3149 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, worker_id); 3150 3151 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3152 3153 double term_sec = 0.0; 3154 size_t evac_term_attempts = 0; 3155 { 3156 double start = os::elapsedTime(); 3157 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3158 evac.do_void(); 3159 3160 evac_term_attempts = evac.term_attempts(); 3161 term_sec = evac.term_time(); 3162 double elapsed_sec = os::elapsedTime() - start; 3163 3164 G1GCPhaseTimes* p = _g1h->g1_policy()->phase_times(); 3165 p->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3166 p->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3167 p->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3168 } 3169 3170 assert(pss->queue_is_empty(), "should be empty"); 3171 3172 if (log_is_enabled(Debug, gc, task, stats)) { 3173 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3174 size_t lab_waste; 3175 size_t lab_undo_waste; 3176 pss->waste(lab_waste, lab_undo_waste); 3177 _g1h->print_termination_stats(worker_id, 3178 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3179 strong_roots_sec * 1000.0, /* strong roots time */ 3180 term_sec * 1000.0, /* evac term time */ 3181 evac_term_attempts, /* evac term attempts */ 3182 lab_waste, /* alloc buffer waste */ 3183 lab_undo_waste /* undo waste */ 3184 ); 3185 } 3186 3187 // Close the inner scope so that the ResourceMark and HandleMark 3188 // destructors are executed here and are included as part of the 3189 // "GC Worker Time". 3190 } 3191 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3192 } 3193 }; 3194 3195 void G1CollectedHeap::print_termination_stats_hdr() { 3196 log_debug(gc, task, stats)("GC Termination Stats"); 3197 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3198 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3199 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3200 } 3201 3202 void G1CollectedHeap::print_termination_stats(uint worker_id, 3203 double elapsed_ms, 3204 double strong_roots_ms, 3205 double term_ms, 3206 size_t term_attempts, 3207 size_t alloc_buffer_waste, 3208 size_t undo_waste) const { 3209 log_debug(gc, task, stats) 3210 ("%3d %9.2f %9.2f %6.2f " 3211 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3212 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3213 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3214 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3215 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3216 alloc_buffer_waste * HeapWordSize / K, 3217 undo_waste * HeapWordSize / K); 3218 } 3219 3220 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3221 private: 3222 BoolObjectClosure* _is_alive; 3223 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3224 3225 int _initial_string_table_size; 3226 int _initial_symbol_table_size; 3227 3228 bool _process_strings; 3229 int _strings_processed; 3230 int _strings_removed; 3231 3232 bool _process_symbols; 3233 int _symbols_processed; 3234 int _symbols_removed; 3235 3236 bool _process_string_dedup; 3237 3238 public: 3239 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3240 AbstractGangTask("String/Symbol Unlinking"), 3241 _is_alive(is_alive), 3242 _dedup_closure(is_alive, NULL, false), 3243 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3244 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3245 _process_string_dedup(process_string_dedup) { 3246 3247 _initial_string_table_size = StringTable::the_table()->table_size(); 3248 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3249 if (process_strings) { 3250 StringTable::clear_parallel_claimed_index(); 3251 } 3252 if (process_symbols) { 3253 SymbolTable::clear_parallel_claimed_index(); 3254 } 3255 } 3256 3257 ~G1StringAndSymbolCleaningTask() { 3258 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3259 "claim value %d after unlink less than initial string table size %d", 3260 StringTable::parallel_claimed_index(), _initial_string_table_size); 3261 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3262 "claim value %d after unlink less than initial symbol table size %d", 3263 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3264 3265 log_info(gc, stringtable)( 3266 "Cleaned string and symbol table, " 3267 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3268 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3269 strings_processed(), strings_removed(), 3270 symbols_processed(), symbols_removed()); 3271 } 3272 3273 void work(uint worker_id) { 3274 int strings_processed = 0; 3275 int strings_removed = 0; 3276 int symbols_processed = 0; 3277 int symbols_removed = 0; 3278 if (_process_strings) { 3279 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3280 Atomic::add(strings_processed, &_strings_processed); 3281 Atomic::add(strings_removed, &_strings_removed); 3282 } 3283 if (_process_symbols) { 3284 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3285 Atomic::add(symbols_processed, &_symbols_processed); 3286 Atomic::add(symbols_removed, &_symbols_removed); 3287 } 3288 if (_process_string_dedup) { 3289 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3290 } 3291 } 3292 3293 size_t strings_processed() const { return (size_t)_strings_processed; } 3294 size_t strings_removed() const { return (size_t)_strings_removed; } 3295 3296 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3297 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3298 }; 3299 3300 class G1CodeCacheUnloadingTask { 3301 private: 3302 static Monitor* _lock; 3303 3304 BoolObjectClosure* const _is_alive; 3305 const bool _unloading_occurred; 3306 const uint _num_workers; 3307 3308 // Variables used to claim nmethods. 3309 CompiledMethod* _first_nmethod; 3310 CompiledMethod* volatile _claimed_nmethod; 3311 3312 // The list of nmethods that need to be processed by the second pass. 3313 CompiledMethod* volatile _postponed_list; 3314 volatile uint _num_entered_barrier; 3315 3316 public: 3317 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3318 _is_alive(is_alive), 3319 _unloading_occurred(unloading_occurred), 3320 _num_workers(num_workers), 3321 _first_nmethod(NULL), 3322 _claimed_nmethod(NULL), 3323 _postponed_list(NULL), 3324 _num_entered_barrier(0) 3325 { 3326 CompiledMethod::increase_unloading_clock(); 3327 // Get first alive nmethod 3328 CompiledMethodIterator iter = CompiledMethodIterator(); 3329 if(iter.next_alive()) { 3330 _first_nmethod = iter.method(); 3331 } 3332 _claimed_nmethod = _first_nmethod; 3333 } 3334 3335 ~G1CodeCacheUnloadingTask() { 3336 CodeCache::verify_clean_inline_caches(); 3337 3338 CodeCache::set_needs_cache_clean(false); 3339 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3340 3341 CodeCache::verify_icholder_relocations(); 3342 } 3343 3344 private: 3345 void add_to_postponed_list(CompiledMethod* nm) { 3346 CompiledMethod* old; 3347 do { 3348 old = _postponed_list; 3349 nm->set_unloading_next(old); 3350 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old); 3351 } 3352 3353 void clean_nmethod(CompiledMethod* nm) { 3354 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3355 3356 if (postponed) { 3357 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3358 add_to_postponed_list(nm); 3359 } 3360 3361 // Mark that this thread has been cleaned/unloaded. 3362 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3363 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3364 } 3365 3366 void clean_nmethod_postponed(CompiledMethod* nm) { 3367 nm->do_unloading_parallel_postponed(); 3368 } 3369 3370 static const int MaxClaimNmethods = 16; 3371 3372 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3373 CompiledMethod* first; 3374 CompiledMethodIterator last; 3375 3376 do { 3377 *num_claimed_nmethods = 0; 3378 3379 first = _claimed_nmethod; 3380 last = CompiledMethodIterator(first); 3381 3382 if (first != NULL) { 3383 3384 for (int i = 0; i < MaxClaimNmethods; i++) { 3385 if (!last.next_alive()) { 3386 break; 3387 } 3388 claimed_nmethods[i] = last.method(); 3389 (*num_claimed_nmethods)++; 3390 } 3391 } 3392 3393 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first); 3394 } 3395 3396 CompiledMethod* claim_postponed_nmethod() { 3397 CompiledMethod* claim; 3398 CompiledMethod* next; 3399 3400 do { 3401 claim = _postponed_list; 3402 if (claim == NULL) { 3403 return NULL; 3404 } 3405 3406 next = claim->unloading_next(); 3407 3408 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim); 3409 3410 return claim; 3411 } 3412 3413 public: 3414 // Mark that we're done with the first pass of nmethod cleaning. 3415 void barrier_mark(uint worker_id) { 3416 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3417 _num_entered_barrier++; 3418 if (_num_entered_barrier == _num_workers) { 3419 ml.notify_all(); 3420 } 3421 } 3422 3423 // See if we have to wait for the other workers to 3424 // finish their first-pass nmethod cleaning work. 3425 void barrier_wait(uint worker_id) { 3426 if (_num_entered_barrier < _num_workers) { 3427 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3428 while (_num_entered_barrier < _num_workers) { 3429 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3430 } 3431 } 3432 } 3433 3434 // Cleaning and unloading of nmethods. Some work has to be postponed 3435 // to the second pass, when we know which nmethods survive. 3436 void work_first_pass(uint worker_id) { 3437 // The first nmethods is claimed by the first worker. 3438 if (worker_id == 0 && _first_nmethod != NULL) { 3439 clean_nmethod(_first_nmethod); 3440 _first_nmethod = NULL; 3441 } 3442 3443 int num_claimed_nmethods; 3444 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3445 3446 while (true) { 3447 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3448 3449 if (num_claimed_nmethods == 0) { 3450 break; 3451 } 3452 3453 for (int i = 0; i < num_claimed_nmethods; i++) { 3454 clean_nmethod(claimed_nmethods[i]); 3455 } 3456 } 3457 } 3458 3459 void work_second_pass(uint worker_id) { 3460 CompiledMethod* nm; 3461 // Take care of postponed nmethods. 3462 while ((nm = claim_postponed_nmethod()) != NULL) { 3463 clean_nmethod_postponed(nm); 3464 } 3465 } 3466 }; 3467 3468 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3469 3470 class G1KlassCleaningTask : public StackObj { 3471 volatile int _clean_klass_tree_claimed; 3472 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3473 3474 public: 3475 G1KlassCleaningTask() : 3476 _clean_klass_tree_claimed(0), 3477 _klass_iterator() { 3478 } 3479 3480 private: 3481 bool claim_clean_klass_tree_task() { 3482 if (_clean_klass_tree_claimed) { 3483 return false; 3484 } 3485 3486 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0; 3487 } 3488 3489 InstanceKlass* claim_next_klass() { 3490 Klass* klass; 3491 do { 3492 klass =_klass_iterator.next_klass(); 3493 } while (klass != NULL && !klass->is_instance_klass()); 3494 3495 // this can be null so don't call InstanceKlass::cast 3496 return static_cast<InstanceKlass*>(klass); 3497 } 3498 3499 public: 3500 3501 void clean_klass(InstanceKlass* ik) { 3502 ik->clean_weak_instanceklass_links(); 3503 } 3504 3505 void work() { 3506 ResourceMark rm; 3507 3508 // One worker will clean the subklass/sibling klass tree. 3509 if (claim_clean_klass_tree_task()) { 3510 Klass::clean_subklass_tree(); 3511 } 3512 3513 // All workers will help cleaning the classes, 3514 InstanceKlass* klass; 3515 while ((klass = claim_next_klass()) != NULL) { 3516 clean_klass(klass); 3517 } 3518 } 3519 }; 3520 3521 class G1ResolvedMethodCleaningTask : public StackObj { 3522 volatile int _resolved_method_task_claimed; 3523 public: 3524 G1ResolvedMethodCleaningTask() : 3525 _resolved_method_task_claimed(0) {} 3526 3527 bool claim_resolved_method_task() { 3528 if (_resolved_method_task_claimed) { 3529 return false; 3530 } 3531 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0; 3532 } 3533 3534 // These aren't big, one thread can do it all. 3535 void work() { 3536 if (claim_resolved_method_task()) { 3537 ResolvedMethodTable::unlink(); 3538 } 3539 } 3540 }; 3541 3542 3543 // To minimize the remark pause times, the tasks below are done in parallel. 3544 class G1ParallelCleaningTask : public AbstractGangTask { 3545 private: 3546 G1StringAndSymbolCleaningTask _string_symbol_task; 3547 G1CodeCacheUnloadingTask _code_cache_task; 3548 G1KlassCleaningTask _klass_cleaning_task; 3549 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task; 3550 3551 public: 3552 // The constructor is run in the VMThread. 3553 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3554 AbstractGangTask("Parallel Cleaning"), 3555 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3556 _code_cache_task(num_workers, is_alive, unloading_occurred), 3557 _klass_cleaning_task(), 3558 _resolved_method_cleaning_task() { 3559 } 3560 3561 // The parallel work done by all worker threads. 3562 void work(uint worker_id) { 3563 // Do first pass of code cache cleaning. 3564 _code_cache_task.work_first_pass(worker_id); 3565 3566 // Let the threads mark that the first pass is done. 3567 _code_cache_task.barrier_mark(worker_id); 3568 3569 // Clean the Strings and Symbols. 3570 _string_symbol_task.work(worker_id); 3571 3572 // Clean unreferenced things in the ResolvedMethodTable 3573 _resolved_method_cleaning_task.work(); 3574 3575 // Wait for all workers to finish the first code cache cleaning pass. 3576 _code_cache_task.barrier_wait(worker_id); 3577 3578 // Do the second code cache cleaning work, which realize on 3579 // the liveness information gathered during the first pass. 3580 _code_cache_task.work_second_pass(worker_id); 3581 3582 // Clean all klasses that were not unloaded. 3583 _klass_cleaning_task.work(); 3584 } 3585 }; 3586 3587 3588 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3589 bool class_unloading_occurred) { 3590 uint n_workers = workers()->active_workers(); 3591 3592 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3593 workers()->run_task(&g1_unlink_task); 3594 } 3595 3596 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3597 bool process_strings, 3598 bool process_symbols, 3599 bool process_string_dedup) { 3600 if (!process_strings && !process_symbols && !process_string_dedup) { 3601 // Nothing to clean. 3602 return; 3603 } 3604 3605 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3606 workers()->run_task(&g1_unlink_task); 3607 3608 } 3609 3610 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3611 private: 3612 DirtyCardQueueSet* _queue; 3613 G1CollectedHeap* _g1h; 3614 public: 3615 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3616 _queue(queue), _g1h(g1h) { } 3617 3618 virtual void work(uint worker_id) { 3619 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3620 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3621 3622 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3623 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3624 3625 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3626 } 3627 }; 3628 3629 void G1CollectedHeap::redirty_logged_cards() { 3630 double redirty_logged_cards_start = os::elapsedTime(); 3631 3632 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3633 dirty_card_queue_set().reset_for_par_iteration(); 3634 workers()->run_task(&redirty_task); 3635 3636 DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set(); 3637 dcq.merge_bufferlists(&dirty_card_queue_set()); 3638 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3639 3640 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3641 } 3642 3643 // Weak Reference Processing support 3644 3645 // An always "is_alive" closure that is used to preserve referents. 3646 // If the object is non-null then it's alive. Used in the preservation 3647 // of referent objects that are pointed to by reference objects 3648 // discovered by the CM ref processor. 3649 class G1AlwaysAliveClosure: public BoolObjectClosure { 3650 public: 3651 bool do_object_b(oop p) { 3652 if (p != NULL) { 3653 return true; 3654 } 3655 return false; 3656 } 3657 }; 3658 3659 bool G1STWIsAliveClosure::do_object_b(oop p) { 3660 // An object is reachable if it is outside the collection set, 3661 // or is inside and copied. 3662 return !_g1h->is_in_cset(p) || p->is_forwarded(); 3663 } 3664 3665 // Non Copying Keep Alive closure 3666 class G1KeepAliveClosure: public OopClosure { 3667 G1CollectedHeap*_g1h; 3668 public: 3669 G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {} 3670 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3671 void do_oop(oop* p) { 3672 oop obj = *p; 3673 assert(obj != NULL, "the caller should have filtered out NULL values"); 3674 3675 const InCSetState cset_state =_g1h->in_cset_state(obj); 3676 if (!cset_state.is_in_cset_or_humongous()) { 3677 return; 3678 } 3679 if (cset_state.is_in_cset()) { 3680 assert( obj->is_forwarded(), "invariant" ); 3681 *p = obj->forwardee(); 3682 } else { 3683 assert(!obj->is_forwarded(), "invariant" ); 3684 assert(cset_state.is_humongous(), 3685 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3686 _g1h->set_humongous_is_live(obj); 3687 } 3688 } 3689 }; 3690 3691 // Copying Keep Alive closure - can be called from both 3692 // serial and parallel code as long as different worker 3693 // threads utilize different G1ParScanThreadState instances 3694 // and different queues. 3695 3696 class G1CopyingKeepAliveClosure: public OopClosure { 3697 G1CollectedHeap* _g1h; 3698 OopClosure* _copy_non_heap_obj_cl; 3699 G1ParScanThreadState* _par_scan_state; 3700 3701 public: 3702 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3703 OopClosure* non_heap_obj_cl, 3704 G1ParScanThreadState* pss): 3705 _g1h(g1h), 3706 _copy_non_heap_obj_cl(non_heap_obj_cl), 3707 _par_scan_state(pss) 3708 {} 3709 3710 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3711 virtual void do_oop( oop* p) { do_oop_work(p); } 3712 3713 template <class T> void do_oop_work(T* p) { 3714 oop obj = RawAccess<>::oop_load(p); 3715 3716 if (_g1h->is_in_cset_or_humongous(obj)) { 3717 // If the referent object has been forwarded (either copied 3718 // to a new location or to itself in the event of an 3719 // evacuation failure) then we need to update the reference 3720 // field and, if both reference and referent are in the G1 3721 // heap, update the RSet for the referent. 3722 // 3723 // If the referent has not been forwarded then we have to keep 3724 // it alive by policy. Therefore we have copy the referent. 3725 // 3726 // If the reference field is in the G1 heap then we can push 3727 // on the PSS queue. When the queue is drained (after each 3728 // phase of reference processing) the object and it's followers 3729 // will be copied, the reference field set to point to the 3730 // new location, and the RSet updated. Otherwise we need to 3731 // use the the non-heap or metadata closures directly to copy 3732 // the referent object and update the pointer, while avoiding 3733 // updating the RSet. 3734 3735 if (_g1h->is_in_g1_reserved(p)) { 3736 _par_scan_state->push_on_queue(p); 3737 } else { 3738 assert(!Metaspace::contains((const void*)p), 3739 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 3740 _copy_non_heap_obj_cl->do_oop(p); 3741 } 3742 } 3743 } 3744 }; 3745 3746 // Serial drain queue closure. Called as the 'complete_gc' 3747 // closure for each discovered list in some of the 3748 // reference processing phases. 3749 3750 class G1STWDrainQueueClosure: public VoidClosure { 3751 protected: 3752 G1CollectedHeap* _g1h; 3753 G1ParScanThreadState* _par_scan_state; 3754 3755 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3756 3757 public: 3758 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3759 _g1h(g1h), 3760 _par_scan_state(pss) 3761 { } 3762 3763 void do_void() { 3764 G1ParScanThreadState* const pss = par_scan_state(); 3765 pss->trim_queue(); 3766 } 3767 }; 3768 3769 // Parallel Reference Processing closures 3770 3771 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3772 // processing during G1 evacuation pauses. 3773 3774 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3775 private: 3776 G1CollectedHeap* _g1h; 3777 G1ParScanThreadStateSet* _pss; 3778 RefToScanQueueSet* _queues; 3779 WorkGang* _workers; 3780 uint _active_workers; 3781 3782 public: 3783 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3784 G1ParScanThreadStateSet* per_thread_states, 3785 WorkGang* workers, 3786 RefToScanQueueSet *task_queues, 3787 uint n_workers) : 3788 _g1h(g1h), 3789 _pss(per_thread_states), 3790 _queues(task_queues), 3791 _workers(workers), 3792 _active_workers(n_workers) 3793 { 3794 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 3795 } 3796 3797 // Executes the given task using concurrent marking worker threads. 3798 virtual void execute(ProcessTask& task); 3799 virtual void execute(EnqueueTask& task); 3800 }; 3801 3802 // Gang task for possibly parallel reference processing 3803 3804 class G1STWRefProcTaskProxy: public AbstractGangTask { 3805 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 3806 ProcessTask& _proc_task; 3807 G1CollectedHeap* _g1h; 3808 G1ParScanThreadStateSet* _pss; 3809 RefToScanQueueSet* _task_queues; 3810 ParallelTaskTerminator* _terminator; 3811 3812 public: 3813 G1STWRefProcTaskProxy(ProcessTask& proc_task, 3814 G1CollectedHeap* g1h, 3815 G1ParScanThreadStateSet* per_thread_states, 3816 RefToScanQueueSet *task_queues, 3817 ParallelTaskTerminator* terminator) : 3818 AbstractGangTask("Process reference objects in parallel"), 3819 _proc_task(proc_task), 3820 _g1h(g1h), 3821 _pss(per_thread_states), 3822 _task_queues(task_queues), 3823 _terminator(terminator) 3824 {} 3825 3826 virtual void work(uint worker_id) { 3827 // The reference processing task executed by a single worker. 3828 ResourceMark rm; 3829 HandleMark hm; 3830 3831 G1STWIsAliveClosure is_alive(_g1h); 3832 3833 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3834 pss->set_ref_discoverer(NULL); 3835 3836 // Keep alive closure. 3837 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 3838 3839 // Complete GC closure 3840 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 3841 3842 // Call the reference processing task's work routine. 3843 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 3844 3845 // Note we cannot assert that the refs array is empty here as not all 3846 // of the processing tasks (specifically phase2 - pp2_work) execute 3847 // the complete_gc closure (which ordinarily would drain the queue) so 3848 // the queue may not be empty. 3849 } 3850 }; 3851 3852 // Driver routine for parallel reference processing. 3853 // Creates an instance of the ref processing gang 3854 // task and has the worker threads execute it. 3855 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 3856 assert(_workers != NULL, "Need parallel worker threads."); 3857 3858 ParallelTaskTerminator terminator(_active_workers, _queues); 3859 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 3860 3861 _workers->run_task(&proc_task_proxy); 3862 } 3863 3864 // Gang task for parallel reference enqueueing. 3865 3866 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 3867 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 3868 EnqueueTask& _enq_task; 3869 3870 public: 3871 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 3872 AbstractGangTask("Enqueue reference objects in parallel"), 3873 _enq_task(enq_task) 3874 { } 3875 3876 virtual void work(uint worker_id) { 3877 _enq_task.work(worker_id); 3878 } 3879 }; 3880 3881 // Driver routine for parallel reference enqueueing. 3882 // Creates an instance of the ref enqueueing gang 3883 // task and has the worker threads execute it. 3884 3885 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 3886 assert(_workers != NULL, "Need parallel worker threads."); 3887 3888 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 3889 3890 _workers->run_task(&enq_task_proxy); 3891 } 3892 3893 // End of weak reference support closures 3894 3895 // Abstract task used to preserve (i.e. copy) any referent objects 3896 // that are in the collection set and are pointed to by reference 3897 // objects discovered by the CM ref processor. 3898 3899 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 3900 protected: 3901 G1CollectedHeap* _g1h; 3902 G1ParScanThreadStateSet* _pss; 3903 RefToScanQueueSet* _queues; 3904 ParallelTaskTerminator _terminator; 3905 uint _n_workers; 3906 3907 public: 3908 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 3909 AbstractGangTask("ParPreserveCMReferents"), 3910 _g1h(g1h), 3911 _pss(per_thread_states), 3912 _queues(task_queues), 3913 _terminator(workers, _queues), 3914 _n_workers(workers) 3915 { 3916 g1h->ref_processor_cm()->set_active_mt_degree(workers); 3917 } 3918 3919 void work(uint worker_id) { 3920 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 3921 3922 ResourceMark rm; 3923 HandleMark hm; 3924 3925 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3926 pss->set_ref_discoverer(NULL); 3927 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 3928 3929 // Is alive closure 3930 G1AlwaysAliveClosure always_alive; 3931 3932 // Copying keep alive closure. Applied to referent objects that need 3933 // to be copied. 3934 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 3935 3936 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 3937 3938 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 3939 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 3940 3941 // limit is set using max_num_q() - which was set using ParallelGCThreads. 3942 // So this must be true - but assert just in case someone decides to 3943 // change the worker ids. 3944 assert(worker_id < limit, "sanity"); 3945 assert(!rp->discovery_is_atomic(), "check this code"); 3946 3947 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 3948 for (uint idx = worker_id; idx < limit; idx += stride) { 3949 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 3950 3951 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 3952 while (iter.has_next()) { 3953 // Since discovery is not atomic for the CM ref processor, we 3954 // can see some null referent objects. 3955 iter.load_ptrs(DEBUG_ONLY(true)); 3956 oop ref = iter.obj(); 3957 3958 // This will filter nulls. 3959 if (iter.is_referent_alive()) { 3960 iter.make_referent_alive(); 3961 } 3962 iter.move_to_next(); 3963 } 3964 } 3965 3966 // Drain the queue - which may cause stealing 3967 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 3968 drain_queue.do_void(); 3969 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 3970 assert(pss->queue_is_empty(), "should be"); 3971 } 3972 }; 3973 3974 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 3975 // Any reference objects, in the collection set, that were 'discovered' 3976 // by the CM ref processor should have already been copied (either by 3977 // applying the external root copy closure to the discovered lists, or 3978 // by following an RSet entry). 3979 // 3980 // But some of the referents, that are in the collection set, that these 3981 // reference objects point to may not have been copied: the STW ref 3982 // processor would have seen that the reference object had already 3983 // been 'discovered' and would have skipped discovering the reference, 3984 // but would not have treated the reference object as a regular oop. 3985 // As a result the copy closure would not have been applied to the 3986 // referent object. 3987 // 3988 // We need to explicitly copy these referent objects - the references 3989 // will be processed at the end of remarking. 3990 // 3991 // We also need to do this copying before we process the reference 3992 // objects discovered by the STW ref processor in case one of these 3993 // referents points to another object which is also referenced by an 3994 // object discovered by the STW ref processor. 3995 double preserve_cm_referents_time = 0.0; 3996 3997 // To avoid spawning task when there is no work to do, check that 3998 // a concurrent cycle is active and that some references have been 3999 // discovered. 4000 if (concurrent_mark()->cm_thread()->during_cycle() && 4001 ref_processor_cm()->has_discovered_references()) { 4002 double preserve_cm_referents_start = os::elapsedTime(); 4003 uint no_of_gc_workers = workers()->active_workers(); 4004 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4005 per_thread_states, 4006 no_of_gc_workers, 4007 _task_queues); 4008 workers()->run_task(&keep_cm_referents); 4009 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4010 } 4011 4012 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4013 } 4014 4015 // Weak Reference processing during an evacuation pause (part 1). 4016 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4017 double ref_proc_start = os::elapsedTime(); 4018 4019 ReferenceProcessor* rp = _ref_processor_stw; 4020 assert(rp->discovery_enabled(), "should have been enabled"); 4021 4022 // Closure to test whether a referent is alive. 4023 G1STWIsAliveClosure is_alive(this); 4024 4025 // Even when parallel reference processing is enabled, the processing 4026 // of JNI refs is serial and performed serially by the current thread 4027 // rather than by a worker. The following PSS will be used for processing 4028 // JNI refs. 4029 4030 // Use only a single queue for this PSS. 4031 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4032 pss->set_ref_discoverer(NULL); 4033 assert(pss->queue_is_empty(), "pre-condition"); 4034 4035 // Keep alive closure. 4036 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4037 4038 // Serial Complete GC closure 4039 G1STWDrainQueueClosure drain_queue(this, pss); 4040 4041 // Setup the soft refs policy... 4042 rp->setup_policy(false); 4043 4044 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4045 4046 ReferenceProcessorStats stats; 4047 if (!rp->processing_is_mt()) { 4048 // Serial reference processing... 4049 stats = rp->process_discovered_references(&is_alive, 4050 &keep_alive, 4051 &drain_queue, 4052 NULL, 4053 pt); 4054 } else { 4055 uint no_of_gc_workers = workers()->active_workers(); 4056 4057 // Parallel reference processing 4058 assert(no_of_gc_workers <= rp->max_num_q(), 4059 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4060 no_of_gc_workers, rp->max_num_q()); 4061 4062 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4063 stats = rp->process_discovered_references(&is_alive, 4064 &keep_alive, 4065 &drain_queue, 4066 &par_task_executor, 4067 pt); 4068 } 4069 4070 _gc_tracer_stw->report_gc_reference_stats(stats); 4071 4072 // We have completed copying any necessary live referent objects. 4073 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4074 4075 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4076 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4077 } 4078 4079 // Weak Reference processing during an evacuation pause (part 2). 4080 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4081 double ref_enq_start = os::elapsedTime(); 4082 4083 ReferenceProcessor* rp = _ref_processor_stw; 4084 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4085 4086 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4087 4088 // Now enqueue any remaining on the discovered lists on to 4089 // the pending list. 4090 if (!rp->processing_is_mt()) { 4091 // Serial reference processing... 4092 rp->enqueue_discovered_references(NULL, pt); 4093 } else { 4094 // Parallel reference enqueueing 4095 4096 uint n_workers = workers()->active_workers(); 4097 4098 assert(n_workers <= rp->max_num_q(), 4099 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4100 n_workers, rp->max_num_q()); 4101 4102 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4103 rp->enqueue_discovered_references(&par_task_executor, pt); 4104 } 4105 4106 rp->verify_no_references_recorded(); 4107 assert(!rp->discovery_enabled(), "should have been disabled"); 4108 4109 // If during an initial mark pause we install a pending list head which is not otherwise reachable 4110 // ensure that it is marked in the bitmap for concurrent marking to discover. 4111 if (collector_state()->in_initial_mark_gc()) { 4112 oop pll_head = Universe::reference_pending_list(); 4113 if (pll_head != NULL) { 4114 // Any valid worker id is fine here as we are in the VM thread and single-threaded. 4115 _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head); 4116 } 4117 } 4118 4119 // FIXME 4120 // CM's reference processing also cleans up the string and symbol tables. 4121 // Should we do that here also? We could, but it is a serial operation 4122 // and could significantly increase the pause time. 4123 4124 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4125 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4126 } 4127 4128 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4129 double merge_pss_time_start = os::elapsedTime(); 4130 per_thread_states->flush(); 4131 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4132 } 4133 4134 void G1CollectedHeap::pre_evacuate_collection_set() { 4135 _expand_heap_after_alloc_failure = true; 4136 _evacuation_failed = false; 4137 4138 // Disable the hot card cache. 4139 _hot_card_cache->reset_hot_cache_claimed_index(); 4140 _hot_card_cache->set_use_cache(false); 4141 4142 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4143 _preserved_marks_set.assert_empty(); 4144 4145 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4146 4147 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4148 if (collector_state()->in_initial_mark_gc()) { 4149 double start_clear_claimed_marks = os::elapsedTime(); 4150 4151 ClassLoaderDataGraph::clear_claimed_marks(); 4152 4153 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4154 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4155 } 4156 } 4157 4158 void G1CollectedHeap::evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states) { 4159 // Should G1EvacuationFailureALot be in effect for this GC? 4160 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4161 4162 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4163 4164 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4165 4166 double start_par_time_sec = os::elapsedTime(); 4167 double end_par_time_sec; 4168 4169 { 4170 const uint n_workers = workers()->active_workers(); 4171 G1RootProcessor root_processor(this, n_workers); 4172 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4173 4174 print_termination_stats_hdr(); 4175 4176 workers()->run_task(&g1_par_task); 4177 end_par_time_sec = os::elapsedTime(); 4178 4179 // Closing the inner scope will execute the destructor 4180 // for the G1RootProcessor object. We record the current 4181 // elapsed time before closing the scope so that time 4182 // taken for the destructor is NOT included in the 4183 // reported parallel time. 4184 } 4185 4186 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4187 phase_times->record_par_time(par_time_ms); 4188 4189 double code_root_fixup_time_ms = 4190 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4191 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4192 } 4193 4194 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4195 // Process any discovered reference objects - we have 4196 // to do this _before_ we retire the GC alloc regions 4197 // as we may have to copy some 'reachable' referent 4198 // objects (and their reachable sub-graphs) that were 4199 // not copied during the pause. 4200 preserve_cm_referents(per_thread_states); 4201 process_discovered_references(per_thread_states); 4202 4203 G1STWIsAliveClosure is_alive(this); 4204 G1KeepAliveClosure keep_alive(this); 4205 4206 { 4207 double start = os::elapsedTime(); 4208 4209 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 4210 4211 double time_ms = (os::elapsedTime() - start) * 1000.0; 4212 g1_policy()->phase_times()->record_weak_ref_proc_time(time_ms); 4213 } 4214 4215 if (G1StringDedup::is_enabled()) { 4216 double fixup_start = os::elapsedTime(); 4217 4218 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4219 4220 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4221 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4222 } 4223 4224 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4225 4226 if (evacuation_failed()) { 4227 restore_after_evac_failure(); 4228 4229 // Reset the G1EvacuationFailureALot counters and flags 4230 // Note: the values are reset only when an actual 4231 // evacuation failure occurs. 4232 NOT_PRODUCT(reset_evacuation_should_fail();) 4233 } 4234 4235 _preserved_marks_set.assert_empty(); 4236 4237 // Enqueue any remaining references remaining on the STW 4238 // reference processor's discovered lists. We need to do 4239 // this after the card table is cleaned (and verified) as 4240 // the act of enqueueing entries on to the pending list 4241 // will log these updates (and dirty their associated 4242 // cards). We need these updates logged to update any 4243 // RSets. 4244 enqueue_discovered_references(per_thread_states); 4245 4246 _allocator->release_gc_alloc_regions(evacuation_info); 4247 4248 merge_per_thread_state_info(per_thread_states); 4249 4250 // Reset and re-enable the hot card cache. 4251 // Note the counts for the cards in the regions in the 4252 // collection set are reset when the collection set is freed. 4253 _hot_card_cache->reset_hot_cache(); 4254 _hot_card_cache->set_use_cache(true); 4255 4256 purge_code_root_memory(); 4257 4258 redirty_logged_cards(); 4259 #if COMPILER2_OR_JVMCI 4260 double start = os::elapsedTime(); 4261 DerivedPointerTable::update_pointers(); 4262 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4263 #endif 4264 g1_policy()->print_age_table(); 4265 } 4266 4267 void G1CollectedHeap::record_obj_copy_mem_stats() { 4268 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4269 4270 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4271 create_g1_evac_summary(&_old_evac_stats)); 4272 } 4273 4274 void G1CollectedHeap::free_region(HeapRegion* hr, 4275 FreeRegionList* free_list, 4276 bool skip_remset, 4277 bool skip_hot_card_cache, 4278 bool locked) { 4279 assert(!hr->is_free(), "the region should not be free"); 4280 assert(!hr->is_empty(), "the region should not be empty"); 4281 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4282 assert(free_list != NULL, "pre-condition"); 4283 4284 if (G1VerifyBitmaps) { 4285 MemRegion mr(hr->bottom(), hr->end()); 4286 concurrent_mark()->clear_range_in_prev_bitmap(mr); 4287 } 4288 4289 // Clear the card counts for this region. 4290 // Note: we only need to do this if the region is not young 4291 // (since we don't refine cards in young regions). 4292 if (!skip_hot_card_cache && !hr->is_young()) { 4293 _hot_card_cache->reset_card_counts(hr); 4294 } 4295 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4296 _g1_policy->remset_tracker()->update_at_free(hr); 4297 free_list->add_ordered(hr); 4298 } 4299 4300 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4301 FreeRegionList* free_list) { 4302 assert(hr->is_humongous(), "this is only for humongous regions"); 4303 assert(free_list != NULL, "pre-condition"); 4304 hr->clear_humongous(); 4305 free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */); 4306 } 4307 4308 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4309 const uint humongous_regions_removed) { 4310 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4311 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4312 _old_set.bulk_remove(old_regions_removed); 4313 _humongous_set.bulk_remove(humongous_regions_removed); 4314 } 4315 4316 } 4317 4318 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4319 assert(list != NULL, "list can't be null"); 4320 if (!list->is_empty()) { 4321 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4322 _hrm.insert_list_into_free_list(list); 4323 } 4324 } 4325 4326 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4327 decrease_used(bytes); 4328 } 4329 4330 class G1FreeCollectionSetTask : public AbstractGangTask { 4331 private: 4332 4333 // Closure applied to all regions in the collection set to do work that needs to 4334 // be done serially in a single thread. 4335 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4336 private: 4337 EvacuationInfo* _evacuation_info; 4338 const size_t* _surviving_young_words; 4339 4340 // Bytes used in successfully evacuated regions before the evacuation. 4341 size_t _before_used_bytes; 4342 // Bytes used in unsucessfully evacuated regions before the evacuation 4343 size_t _after_used_bytes; 4344 4345 size_t _bytes_allocated_in_old_since_last_gc; 4346 4347 size_t _failure_used_words; 4348 size_t _failure_waste_words; 4349 4350 FreeRegionList _local_free_list; 4351 public: 4352 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4353 HeapRegionClosure(), 4354 _evacuation_info(evacuation_info), 4355 _surviving_young_words(surviving_young_words), 4356 _before_used_bytes(0), 4357 _after_used_bytes(0), 4358 _bytes_allocated_in_old_since_last_gc(0), 4359 _failure_used_words(0), 4360 _failure_waste_words(0), 4361 _local_free_list("Local Region List for CSet Freeing") { 4362 } 4363 4364 virtual bool do_heap_region(HeapRegion* r) { 4365 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4366 4367 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4368 g1h->clear_in_cset(r); 4369 4370 if (r->is_young()) { 4371 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4372 "Young index %d is wrong for region %u of type %s with %u young regions", 4373 r->young_index_in_cset(), 4374 r->hrm_index(), 4375 r->get_type_str(), 4376 g1h->collection_set()->young_region_length()); 4377 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4378 r->record_surv_words_in_group(words_survived); 4379 } 4380 4381 if (!r->evacuation_failed()) { 4382 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4383 _before_used_bytes += r->used(); 4384 g1h->free_region(r, 4385 &_local_free_list, 4386 true, /* skip_remset */ 4387 true, /* skip_hot_card_cache */ 4388 true /* locked */); 4389 } else { 4390 r->uninstall_surv_rate_group(); 4391 r->set_young_index_in_cset(-1); 4392 r->set_evacuation_failed(false); 4393 // When moving a young gen region to old gen, we "allocate" that whole region 4394 // there. This is in addition to any already evacuated objects. Notify the 4395 // policy about that. 4396 // Old gen regions do not cause an additional allocation: both the objects 4397 // still in the region and the ones already moved are accounted for elsewhere. 4398 if (r->is_young()) { 4399 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4400 } 4401 // The region is now considered to be old. 4402 r->set_old(); 4403 // Do some allocation statistics accounting. Regions that failed evacuation 4404 // are always made old, so there is no need to update anything in the young 4405 // gen statistics, but we need to update old gen statistics. 4406 size_t used_words = r->marked_bytes() / HeapWordSize; 4407 4408 _failure_used_words += used_words; 4409 _failure_waste_words += HeapRegion::GrainWords - used_words; 4410 4411 g1h->old_set_add(r); 4412 _after_used_bytes += r->used(); 4413 } 4414 return false; 4415 } 4416 4417 void complete_work() { 4418 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4419 4420 _evacuation_info->set_regions_freed(_local_free_list.length()); 4421 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4422 4423 g1h->prepend_to_freelist(&_local_free_list); 4424 g1h->decrement_summary_bytes(_before_used_bytes); 4425 4426 G1Policy* policy = g1h->g1_policy(); 4427 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4428 4429 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4430 } 4431 }; 4432 4433 G1CollectionSet* _collection_set; 4434 G1SerialFreeCollectionSetClosure _cl; 4435 const size_t* _surviving_young_words; 4436 4437 size_t _rs_lengths; 4438 4439 volatile jint _serial_work_claim; 4440 4441 struct WorkItem { 4442 uint region_idx; 4443 bool is_young; 4444 bool evacuation_failed; 4445 4446 WorkItem(HeapRegion* r) { 4447 region_idx = r->hrm_index(); 4448 is_young = r->is_young(); 4449 evacuation_failed = r->evacuation_failed(); 4450 } 4451 }; 4452 4453 volatile size_t _parallel_work_claim; 4454 size_t _num_work_items; 4455 WorkItem* _work_items; 4456 4457 void do_serial_work() { 4458 // Need to grab the lock to be allowed to modify the old region list. 4459 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4460 _collection_set->iterate(&_cl); 4461 } 4462 4463 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4464 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4465 4466 HeapRegion* r = g1h->region_at(region_idx); 4467 assert(!g1h->is_on_master_free_list(r), "sanity"); 4468 4469 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4470 4471 if (!is_young) { 4472 g1h->_hot_card_cache->reset_card_counts(r); 4473 } 4474 4475 if (!evacuation_failed) { 4476 r->rem_set()->clear_locked(); 4477 } 4478 } 4479 4480 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4481 private: 4482 size_t _cur_idx; 4483 WorkItem* _work_items; 4484 public: 4485 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4486 4487 virtual bool do_heap_region(HeapRegion* r) { 4488 _work_items[_cur_idx++] = WorkItem(r); 4489 return false; 4490 } 4491 }; 4492 4493 void prepare_work() { 4494 G1PrepareFreeCollectionSetClosure cl(_work_items); 4495 _collection_set->iterate(&cl); 4496 } 4497 4498 void complete_work() { 4499 _cl.complete_work(); 4500 4501 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4502 policy->record_max_rs_lengths(_rs_lengths); 4503 policy->cset_regions_freed(); 4504 } 4505 public: 4506 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4507 AbstractGangTask("G1 Free Collection Set"), 4508 _cl(evacuation_info, surviving_young_words), 4509 _collection_set(collection_set), 4510 _surviving_young_words(surviving_young_words), 4511 _serial_work_claim(0), 4512 _rs_lengths(0), 4513 _parallel_work_claim(0), 4514 _num_work_items(collection_set->region_length()), 4515 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4516 prepare_work(); 4517 } 4518 4519 ~G1FreeCollectionSetTask() { 4520 complete_work(); 4521 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4522 } 4523 4524 // Chunk size for work distribution. The chosen value has been determined experimentally 4525 // to be a good tradeoff between overhead and achievable parallelism. 4526 static uint chunk_size() { return 32; } 4527 4528 virtual void work(uint worker_id) { 4529 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4530 4531 // Claim serial work. 4532 if (_serial_work_claim == 0) { 4533 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4534 if (value == 0) { 4535 double serial_time = os::elapsedTime(); 4536 do_serial_work(); 4537 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4538 } 4539 } 4540 4541 // Start parallel work. 4542 double young_time = 0.0; 4543 bool has_young_time = false; 4544 double non_young_time = 0.0; 4545 bool has_non_young_time = false; 4546 4547 while (true) { 4548 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4549 size_t cur = end - chunk_size(); 4550 4551 if (cur >= _num_work_items) { 4552 break; 4553 } 4554 4555 double start_time = os::elapsedTime(); 4556 4557 end = MIN2(end, _num_work_items); 4558 4559 for (; cur < end; cur++) { 4560 bool is_young = _work_items[cur].is_young; 4561 4562 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4563 4564 double end_time = os::elapsedTime(); 4565 double time_taken = end_time - start_time; 4566 if (is_young) { 4567 young_time += time_taken; 4568 has_young_time = true; 4569 } else { 4570 non_young_time += time_taken; 4571 has_non_young_time = true; 4572 } 4573 start_time = end_time; 4574 } 4575 } 4576 4577 if (has_young_time) { 4578 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4579 } 4580 if (has_non_young_time) { 4581 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time); 4582 } 4583 } 4584 }; 4585 4586 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4587 _eden.clear(); 4588 4589 double free_cset_start_time = os::elapsedTime(); 4590 4591 { 4592 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4593 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4594 4595 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4596 4597 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4598 cl.name(), 4599 num_workers, 4600 _collection_set.region_length()); 4601 workers()->run_task(&cl, num_workers); 4602 } 4603 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4604 4605 collection_set->clear(); 4606 } 4607 4608 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4609 private: 4610 FreeRegionList* _free_region_list; 4611 HeapRegionSet* _proxy_set; 4612 uint _humongous_objects_reclaimed; 4613 uint _humongous_regions_reclaimed; 4614 size_t _freed_bytes; 4615 public: 4616 4617 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4618 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4619 } 4620 4621 virtual bool do_heap_region(HeapRegion* r) { 4622 if (!r->is_starts_humongous()) { 4623 return false; 4624 } 4625 4626 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4627 4628 oop obj = (oop)r->bottom(); 4629 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap(); 4630 4631 // The following checks whether the humongous object is live are sufficient. 4632 // The main additional check (in addition to having a reference from the roots 4633 // or the young gen) is whether the humongous object has a remembered set entry. 4634 // 4635 // A humongous object cannot be live if there is no remembered set for it 4636 // because: 4637 // - there can be no references from within humongous starts regions referencing 4638 // the object because we never allocate other objects into them. 4639 // (I.e. there are no intra-region references that may be missed by the 4640 // remembered set) 4641 // - as soon there is a remembered set entry to the humongous starts region 4642 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4643 // until the end of a concurrent mark. 4644 // 4645 // It is not required to check whether the object has been found dead by marking 4646 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4647 // all objects allocated during that time are considered live. 4648 // SATB marking is even more conservative than the remembered set. 4649 // So if at this point in the collection there is no remembered set entry, 4650 // nobody has a reference to it. 4651 // At the start of collection we flush all refinement logs, and remembered sets 4652 // are completely up-to-date wrt to references to the humongous object. 4653 // 4654 // Other implementation considerations: 4655 // - never consider object arrays at this time because they would pose 4656 // considerable effort for cleaning up the the remembered sets. This is 4657 // required because stale remembered sets might reference locations that 4658 // are currently allocated into. 4659 uint region_idx = r->hrm_index(); 4660 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4661 !r->rem_set()->is_empty()) { 4662 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", 4663 region_idx, 4664 (size_t)obj->size() * HeapWordSize, 4665 p2i(r->bottom()), 4666 r->rem_set()->occupied(), 4667 r->rem_set()->strong_code_roots_list_length(), 4668 next_bitmap->is_marked(r->bottom()), 4669 g1h->is_humongous_reclaim_candidate(region_idx), 4670 obj->is_typeArray() 4671 ); 4672 return false; 4673 } 4674 4675 guarantee(obj->is_typeArray(), 4676 "Only eagerly reclaiming type arrays is supported, but the object " 4677 PTR_FORMAT " is not.", p2i(r->bottom())); 4678 4679 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", 4680 region_idx, 4681 (size_t)obj->size() * HeapWordSize, 4682 p2i(r->bottom()), 4683 r->rem_set()->occupied(), 4684 r->rem_set()->strong_code_roots_list_length(), 4685 next_bitmap->is_marked(r->bottom()), 4686 g1h->is_humongous_reclaim_candidate(region_idx), 4687 obj->is_typeArray() 4688 ); 4689 4690 G1ConcurrentMark* const cm = g1h->concurrent_mark(); 4691 cm->humongous_object_eagerly_reclaimed(r); 4692 assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj), 4693 "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s", 4694 region_idx, 4695 BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)), 4696 BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj))); 4697 _humongous_objects_reclaimed++; 4698 do { 4699 HeapRegion* next = g1h->next_region_in_humongous(r); 4700 _freed_bytes += r->used(); 4701 r->set_containing_set(NULL); 4702 _humongous_regions_reclaimed++; 4703 g1h->free_humongous_region(r, _free_region_list); 4704 r = next; 4705 } while (r != NULL); 4706 4707 return false; 4708 } 4709 4710 uint humongous_objects_reclaimed() { 4711 return _humongous_objects_reclaimed; 4712 } 4713 4714 uint humongous_regions_reclaimed() { 4715 return _humongous_regions_reclaimed; 4716 } 4717 4718 size_t bytes_freed() const { 4719 return _freed_bytes; 4720 } 4721 }; 4722 4723 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4724 assert_at_safepoint_on_vm_thread(); 4725 4726 if (!G1EagerReclaimHumongousObjects || 4727 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4728 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4729 return; 4730 } 4731 4732 double start_time = os::elapsedTime(); 4733 4734 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4735 4736 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4737 heap_region_iterate(&cl); 4738 4739 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4740 4741 G1HRPrinter* hrp = hr_printer(); 4742 if (hrp->is_active()) { 4743 FreeRegionListIterator iter(&local_cleanup_list); 4744 while (iter.more_available()) { 4745 HeapRegion* hr = iter.get_next(); 4746 hrp->cleanup(hr); 4747 } 4748 } 4749 4750 prepend_to_freelist(&local_cleanup_list); 4751 decrement_summary_bytes(cl.bytes_freed()); 4752 4753 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4754 cl.humongous_objects_reclaimed()); 4755 } 4756 4757 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4758 public: 4759 virtual bool do_heap_region(HeapRegion* r) { 4760 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4761 G1CollectedHeap::heap()->clear_in_cset(r); 4762 r->set_young_index_in_cset(-1); 4763 return false; 4764 } 4765 }; 4766 4767 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4768 G1AbandonCollectionSetClosure cl; 4769 collection_set->iterate(&cl); 4770 4771 collection_set->clear(); 4772 collection_set->stop_incremental_building(); 4773 } 4774 4775 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 4776 return _allocator->is_retained_old_region(hr); 4777 } 4778 4779 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 4780 _eden.add(hr); 4781 _g1_policy->set_region_eden(hr); 4782 } 4783 4784 #ifdef ASSERT 4785 4786 class NoYoungRegionsClosure: public HeapRegionClosure { 4787 private: 4788 bool _success; 4789 public: 4790 NoYoungRegionsClosure() : _success(true) { } 4791 bool do_heap_region(HeapRegion* r) { 4792 if (r->is_young()) { 4793 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 4794 p2i(r->bottom()), p2i(r->end())); 4795 _success = false; 4796 } 4797 return false; 4798 } 4799 bool success() { return _success; } 4800 }; 4801 4802 bool G1CollectedHeap::check_young_list_empty() { 4803 bool ret = (young_regions_count() == 0); 4804 4805 NoYoungRegionsClosure closure; 4806 heap_region_iterate(&closure); 4807 ret = ret && closure.success(); 4808 4809 return ret; 4810 } 4811 4812 #endif // ASSERT 4813 4814 class TearDownRegionSetsClosure : public HeapRegionClosure { 4815 private: 4816 HeapRegionSet *_old_set; 4817 4818 public: 4819 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 4820 4821 bool do_heap_region(HeapRegion* r) { 4822 if (r->is_old()) { 4823 _old_set->remove(r); 4824 } else if(r->is_young()) { 4825 r->uninstall_surv_rate_group(); 4826 } else { 4827 // We ignore free regions, we'll empty the free list afterwards. 4828 // We ignore humongous regions, we're not tearing down the 4829 // humongous regions set. 4830 assert(r->is_free() || r->is_humongous(), 4831 "it cannot be another type"); 4832 } 4833 return false; 4834 } 4835 4836 ~TearDownRegionSetsClosure() { 4837 assert(_old_set->is_empty(), "post-condition"); 4838 } 4839 }; 4840 4841 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 4842 assert_at_safepoint_on_vm_thread(); 4843 4844 if (!free_list_only) { 4845 TearDownRegionSetsClosure cl(&_old_set); 4846 heap_region_iterate(&cl); 4847 4848 // Note that emptying the _young_list is postponed and instead done as 4849 // the first step when rebuilding the regions sets again. The reason for 4850 // this is that during a full GC string deduplication needs to know if 4851 // a collected region was young or old when the full GC was initiated. 4852 } 4853 _hrm.remove_all_free_regions(); 4854 } 4855 4856 void G1CollectedHeap::increase_used(size_t bytes) { 4857 _summary_bytes_used += bytes; 4858 } 4859 4860 void G1CollectedHeap::decrease_used(size_t bytes) { 4861 assert(_summary_bytes_used >= bytes, 4862 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 4863 _summary_bytes_used, bytes); 4864 _summary_bytes_used -= bytes; 4865 } 4866 4867 void G1CollectedHeap::set_used(size_t bytes) { 4868 _summary_bytes_used = bytes; 4869 } 4870 4871 class RebuildRegionSetsClosure : public HeapRegionClosure { 4872 private: 4873 bool _free_list_only; 4874 HeapRegionSet* _old_set; 4875 HeapRegionManager* _hrm; 4876 size_t _total_used; 4877 4878 public: 4879 RebuildRegionSetsClosure(bool free_list_only, 4880 HeapRegionSet* old_set, HeapRegionManager* hrm) : 4881 _free_list_only(free_list_only), 4882 _old_set(old_set), _hrm(hrm), _total_used(0) { 4883 assert(_hrm->num_free_regions() == 0, "pre-condition"); 4884 if (!free_list_only) { 4885 assert(_old_set->is_empty(), "pre-condition"); 4886 } 4887 } 4888 4889 bool do_heap_region(HeapRegion* r) { 4890 // After full GC, no region should have a remembered set. 4891 r->rem_set()->clear(true); 4892 if (r->is_empty()) { 4893 // Add free regions to the free list 4894 r->set_free(); 4895 _hrm->insert_into_free_list(r); 4896 } else if (!_free_list_only) { 4897 4898 if (r->is_humongous()) { 4899 // We ignore humongous regions. We left the humongous set unchanged. 4900 } else { 4901 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 4902 // We now move all (non-humongous, non-old) regions to old gen, and register them as such. 4903 r->move_to_old(); 4904 _old_set->add(r); 4905 } 4906 _total_used += r->used(); 4907 } 4908 4909 return false; 4910 } 4911 4912 size_t total_used() { 4913 return _total_used; 4914 } 4915 }; 4916 4917 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 4918 assert_at_safepoint_on_vm_thread(); 4919 4920 if (!free_list_only) { 4921 _eden.clear(); 4922 _survivor.clear(); 4923 } 4924 4925 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 4926 heap_region_iterate(&cl); 4927 4928 if (!free_list_only) { 4929 set_used(cl.total_used()); 4930 if (_archive_allocator != NULL) { 4931 _archive_allocator->clear_used(); 4932 } 4933 } 4934 assert(used_unlocked() == recalculate_used(), 4935 "inconsistent used_unlocked(), " 4936 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 4937 used_unlocked(), recalculate_used()); 4938 } 4939 4940 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 4941 HeapRegion* hr = heap_region_containing(p); 4942 return hr->is_in(p); 4943 } 4944 4945 // Methods for the mutator alloc region 4946 4947 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 4948 bool force) { 4949 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4950 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 4951 if (force || should_allocate) { 4952 HeapRegion* new_alloc_region = new_region(word_size, 4953 false /* is_old */, 4954 false /* do_expand */); 4955 if (new_alloc_region != NULL) { 4956 set_region_short_lived_locked(new_alloc_region); 4957 _hr_printer.alloc(new_alloc_region, !should_allocate); 4958 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 4959 _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region); 4960 return new_alloc_region; 4961 } 4962 } 4963 return NULL; 4964 } 4965 4966 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 4967 size_t allocated_bytes) { 4968 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4969 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 4970 4971 collection_set()->add_eden_region(alloc_region); 4972 increase_used(allocated_bytes); 4973 _hr_printer.retire(alloc_region); 4974 // We update the eden sizes here, when the region is retired, 4975 // instead of when it's allocated, since this is the point that its 4976 // used space has been recored in _summary_bytes_used. 4977 g1mm()->update_eden_size(); 4978 } 4979 4980 // Methods for the GC alloc regions 4981 4982 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 4983 if (dest.is_old()) { 4984 return true; 4985 } else { 4986 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 4987 } 4988 } 4989 4990 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 4991 assert(FreeList_lock->owned_by_self(), "pre-condition"); 4992 4993 if (!has_more_regions(dest)) { 4994 return NULL; 4995 } 4996 4997 const bool is_survivor = dest.is_young(); 4998 4999 HeapRegion* new_alloc_region = new_region(word_size, 5000 !is_survivor, 5001 true /* do_expand */); 5002 if (new_alloc_region != NULL) { 5003 if (is_survivor) { 5004 new_alloc_region->set_survivor(); 5005 _survivor.add(new_alloc_region); 5006 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5007 } else { 5008 new_alloc_region->set_old(); 5009 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5010 } 5011 _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region); 5012 _hr_printer.alloc(new_alloc_region); 5013 bool during_im = collector_state()->in_initial_mark_gc(); 5014 new_alloc_region->note_start_of_copying(during_im); 5015 return new_alloc_region; 5016 } 5017 return NULL; 5018 } 5019 5020 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5021 size_t allocated_bytes, 5022 InCSetState dest) { 5023 bool during_im = collector_state()->in_initial_mark_gc(); 5024 alloc_region->note_end_of_copying(during_im); 5025 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5026 if (dest.is_old()) { 5027 _old_set.add(alloc_region); 5028 } 5029 _hr_printer.retire(alloc_region); 5030 } 5031 5032 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5033 bool expanded = false; 5034 uint index = _hrm.find_highest_free(&expanded); 5035 5036 if (index != G1_NO_HRM_INDEX) { 5037 if (expanded) { 5038 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5039 HeapRegion::GrainWords * HeapWordSize); 5040 } 5041 _hrm.allocate_free_regions_starting_at(index, 1); 5042 return region_at(index); 5043 } 5044 return NULL; 5045 } 5046 5047 // Optimized nmethod scanning 5048 5049 class RegisterNMethodOopClosure: public OopClosure { 5050 G1CollectedHeap* _g1h; 5051 nmethod* _nm; 5052 5053 template <class T> void do_oop_work(T* p) { 5054 T heap_oop = RawAccess<>::oop_load(p); 5055 if (!CompressedOops::is_null(heap_oop)) { 5056 oop obj = CompressedOops::decode_not_null(heap_oop); 5057 HeapRegion* hr = _g1h->heap_region_containing(obj); 5058 assert(!hr->is_continues_humongous(), 5059 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5060 " starting at " HR_FORMAT, 5061 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5062 5063 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5064 hr->add_strong_code_root_locked(_nm); 5065 } 5066 } 5067 5068 public: 5069 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5070 _g1h(g1h), _nm(nm) {} 5071 5072 void do_oop(oop* p) { do_oop_work(p); } 5073 void do_oop(narrowOop* p) { do_oop_work(p); } 5074 }; 5075 5076 class UnregisterNMethodOopClosure: public OopClosure { 5077 G1CollectedHeap* _g1h; 5078 nmethod* _nm; 5079 5080 template <class T> void do_oop_work(T* p) { 5081 T heap_oop = RawAccess<>::oop_load(p); 5082 if (!CompressedOops::is_null(heap_oop)) { 5083 oop obj = CompressedOops::decode_not_null(heap_oop); 5084 HeapRegion* hr = _g1h->heap_region_containing(obj); 5085 assert(!hr->is_continues_humongous(), 5086 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5087 " starting at " HR_FORMAT, 5088 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5089 5090 hr->remove_strong_code_root(_nm); 5091 } 5092 } 5093 5094 public: 5095 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5096 _g1h(g1h), _nm(nm) {} 5097 5098 void do_oop(oop* p) { do_oop_work(p); } 5099 void do_oop(narrowOop* p) { do_oop_work(p); } 5100 }; 5101 5102 // Returns true if the reference points to an object that 5103 // can move in an incremental collection. 5104 bool G1CollectedHeap::is_scavengable(oop obj) { 5105 HeapRegion* hr = heap_region_containing(obj); 5106 return !hr->is_pinned(); 5107 } 5108 5109 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5110 guarantee(nm != NULL, "sanity"); 5111 RegisterNMethodOopClosure reg_cl(this, nm); 5112 nm->oops_do(®_cl); 5113 } 5114 5115 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5116 guarantee(nm != NULL, "sanity"); 5117 UnregisterNMethodOopClosure reg_cl(this, nm); 5118 nm->oops_do(®_cl, true); 5119 } 5120 5121 void G1CollectedHeap::purge_code_root_memory() { 5122 double purge_start = os::elapsedTime(); 5123 G1CodeRootSet::purge(); 5124 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5125 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5126 } 5127 5128 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5129 G1CollectedHeap* _g1h; 5130 5131 public: 5132 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5133 _g1h(g1h) {} 5134 5135 void do_code_blob(CodeBlob* cb) { 5136 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5137 if (nm == NULL) { 5138 return; 5139 } 5140 5141 if (ScavengeRootsInCode) { 5142 _g1h->register_nmethod(nm); 5143 } 5144 } 5145 }; 5146 5147 void G1CollectedHeap::rebuild_strong_code_roots() { 5148 RebuildStrongCodeRootClosure blob_cl(this); 5149 CodeCache::blobs_do(&blob_cl); 5150 } 5151 5152 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() { 5153 GrowableArray<GCMemoryManager*> memory_managers(2); 5154 memory_managers.append(&_memory_manager); 5155 memory_managers.append(&_full_gc_memory_manager); 5156 return memory_managers; 5157 } 5158 5159 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() { 5160 GrowableArray<MemoryPool*> memory_pools(3); 5161 memory_pools.append(_eden_pool); 5162 memory_pools.append(_survivor_pool); 5163 memory_pools.append(_old_pool); 5164 return memory_pools; 5165 }