1 /* 2 * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/metadataOnStackMark.hpp" 27 #include "classfile/stringTable.hpp" 28 #include "classfile/symbolTable.hpp" 29 #include "code/codeCache.hpp" 30 #include "code/icBuffer.hpp" 31 #include "gc/g1/bufferingOopClosure.hpp" 32 #include "gc/g1/concurrentMarkThread.inline.hpp" 33 #include "gc/g1/g1Allocator.inline.hpp" 34 #include "gc/g1/g1CollectedHeap.inline.hpp" 35 #include "gc/g1/g1CollectionSet.hpp" 36 #include "gc/g1/g1CollectorPolicy.hpp" 37 #include "gc/g1/g1CollectorState.hpp" 38 #include "gc/g1/g1ConcurrentRefine.hpp" 39 #include "gc/g1/g1ConcurrentRefineThread.hpp" 40 #include "gc/g1/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/g1YCTypes.hpp" 57 #include "gc/g1/g1YoungRemSetSamplingThread.hpp" 58 #include "gc/g1/heapRegion.inline.hpp" 59 #include "gc/g1/heapRegionRemSet.hpp" 60 #include "gc/g1/heapRegionSet.inline.hpp" 61 #include "gc/g1/vm_operations_g1.hpp" 62 #include "gc/shared/adaptiveSizePolicy.hpp" 63 #include "gc/shared/gcHeapSummary.hpp" 64 #include "gc/shared/gcId.hpp" 65 #include "gc/shared/gcLocker.hpp" 66 #include "gc/shared/gcTimer.hpp" 67 #include "gc/shared/gcTrace.hpp" 68 #include "gc/shared/gcTraceTime.inline.hpp" 69 #include "gc/shared/generationSpec.hpp" 70 #include "gc/shared/isGCActiveMark.hpp" 71 #include "gc/shared/preservedMarks.inline.hpp" 72 #include "gc/shared/suspendibleThreadSet.hpp" 73 #include "gc/shared/referenceProcessor.inline.hpp" 74 #include "gc/shared/taskqueue.inline.hpp" 75 #include "gc/shared/weakProcessor.hpp" 76 #include "logging/log.hpp" 77 #include "memory/allocation.hpp" 78 #include "memory/iterator.hpp" 79 #include "memory/resourceArea.hpp" 80 #include "oops/access.inline.hpp" 81 #include "oops/compressedOops.inline.hpp" 82 #include "oops/oop.inline.hpp" 83 #include "prims/resolvedMethodTable.hpp" 84 #include "runtime/atomic.hpp" 85 #include "runtime/handles.inline.hpp" 86 #include "runtime/init.hpp" 87 #include "runtime/orderAccess.inline.hpp" 88 #include "runtime/threadSMR.hpp" 89 #include "runtime/vmThread.hpp" 90 #include "utilities/align.hpp" 91 #include "utilities/globalDefinitions.hpp" 92 #include "utilities/stack.inline.hpp" 93 94 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 95 96 // INVARIANTS/NOTES 97 // 98 // All allocation activity covered by the G1CollectedHeap interface is 99 // serialized by acquiring the HeapLock. This happens in mem_allocate 100 // and allocate_new_tlab, which are the "entry" points to the 101 // allocation code from the rest of the JVM. (Note that this does not 102 // apply to TLAB allocation, which is not part of this interface: it 103 // is done by clients of this interface.) 104 105 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 106 private: 107 size_t _num_dirtied; 108 G1CollectedHeap* _g1h; 109 G1CardTable* _g1_ct; 110 111 HeapRegion* region_for_card(jbyte* card_ptr) const { 112 return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr)); 113 } 114 115 bool will_become_free(HeapRegion* hr) const { 116 // A region will be freed by free_collection_set if the region is in the 117 // collection set and has not had an evacuation failure. 118 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 119 } 120 121 public: 122 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 123 _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { } 124 125 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 126 HeapRegion* hr = region_for_card(card_ptr); 127 128 // Should only dirty cards in regions that won't be freed. 129 if (!will_become_free(hr)) { 130 *card_ptr = G1CardTable::dirty_card_val(); 131 _num_dirtied++; 132 } 133 134 return true; 135 } 136 137 size_t num_dirtied() const { return _num_dirtied; } 138 }; 139 140 141 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 142 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 143 } 144 145 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 146 // The from card cache is not the memory that is actually committed. So we cannot 147 // take advantage of the zero_filled parameter. 148 reset_from_card_cache(start_idx, num_regions); 149 } 150 151 152 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 153 MemRegion mr) { 154 return new HeapRegion(hrs_index, bot(), mr); 155 } 156 157 // Private methods. 158 159 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 160 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 161 "the only time we use this to allocate a humongous region is " 162 "when we are allocating a single humongous region"); 163 164 HeapRegion* res = _hrm.allocate_free_region(is_old); 165 166 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 167 // Currently, only attempts to allocate GC alloc regions set 168 // do_expand to true. So, we should only reach here during a 169 // safepoint. If this assumption changes we might have to 170 // reconsider the use of _expand_heap_after_alloc_failure. 171 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 172 173 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 174 word_size * HeapWordSize); 175 176 if (expand(word_size * HeapWordSize)) { 177 // Given that expand() succeeded in expanding the heap, and we 178 // always expand the heap by an amount aligned to the heap 179 // region size, the free list should in theory not be empty. 180 // In either case allocate_free_region() will check for NULL. 181 res = _hrm.allocate_free_region(is_old); 182 } else { 183 _expand_heap_after_alloc_failure = false; 184 } 185 } 186 return res; 187 } 188 189 HeapWord* 190 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 191 uint num_regions, 192 size_t word_size) { 193 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 194 assert(is_humongous(word_size), "word_size should be humongous"); 195 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 196 197 // Index of last region in the series. 198 uint last = first + num_regions - 1; 199 200 // We need to initialize the region(s) we just discovered. This is 201 // a bit tricky given that it can happen concurrently with 202 // refinement threads refining cards on these regions and 203 // potentially wanting to refine the BOT as they are scanning 204 // those cards (this can happen shortly after a cleanup; see CR 205 // 6991377). So we have to set up the region(s) carefully and in 206 // a specific order. 207 208 // The word size sum of all the regions we will allocate. 209 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 210 assert(word_size <= word_size_sum, "sanity"); 211 212 // This will be the "starts humongous" region. 213 HeapRegion* first_hr = region_at(first); 214 // The header of the new object will be placed at the bottom of 215 // the first region. 216 HeapWord* new_obj = first_hr->bottom(); 217 // This will be the new top of the new object. 218 HeapWord* obj_top = new_obj + word_size; 219 220 // First, we need to zero the header of the space that we will be 221 // allocating. When we update top further down, some refinement 222 // threads might try to scan the region. By zeroing the header we 223 // ensure that any thread that will try to scan the region will 224 // come across the zero klass word and bail out. 225 // 226 // NOTE: It would not have been correct to have used 227 // CollectedHeap::fill_with_object() and make the space look like 228 // an int array. The thread that is doing the allocation will 229 // later update the object header to a potentially different array 230 // type and, for a very short period of time, the klass and length 231 // fields will be inconsistent. This could cause a refinement 232 // thread to calculate the object size incorrectly. 233 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 234 235 // Next, pad out the unused tail of the last region with filler 236 // objects, for improved usage accounting. 237 // How many words we use for filler objects. 238 size_t word_fill_size = word_size_sum - word_size; 239 240 // How many words memory we "waste" which cannot hold a filler object. 241 size_t words_not_fillable = 0; 242 243 if (word_fill_size >= min_fill_size()) { 244 fill_with_objects(obj_top, word_fill_size); 245 } else if (word_fill_size > 0) { 246 // We have space to fill, but we cannot fit an object there. 247 words_not_fillable = word_fill_size; 248 word_fill_size = 0; 249 } 250 251 // We will set up the first region as "starts humongous". This 252 // will also update the BOT covering all the regions to reflect 253 // that there is a single object that starts at the bottom of the 254 // first region. 255 first_hr->set_starts_humongous(obj_top, word_fill_size); 256 _g1_policy->remset_tracker()->update_at_allocate(first_hr); 257 // Then, if there are any, we will set up the "continues 258 // humongous" regions. 259 HeapRegion* hr = NULL; 260 for (uint i = first + 1; i <= last; ++i) { 261 hr = region_at(i); 262 hr->set_continues_humongous(first_hr); 263 _g1_policy->remset_tracker()->update_at_allocate(hr); 264 } 265 266 // Up to this point no concurrent thread would have been able to 267 // do any scanning on any region in this series. All the top 268 // fields still point to bottom, so the intersection between 269 // [bottom,top] and [card_start,card_end] will be empty. Before we 270 // update the top fields, we'll do a storestore to make sure that 271 // no thread sees the update to top before the zeroing of the 272 // object header and the BOT initialization. 273 OrderAccess::storestore(); 274 275 // Now, we will update the top fields of the "continues humongous" 276 // regions except the last one. 277 for (uint i = first; i < last; ++i) { 278 hr = region_at(i); 279 hr->set_top(hr->end()); 280 } 281 282 hr = region_at(last); 283 // If we cannot fit a filler object, we must set top to the end 284 // of the humongous object, otherwise we cannot iterate the heap 285 // and the BOT will not be complete. 286 hr->set_top(hr->end() - words_not_fillable); 287 288 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 289 "obj_top should be in last region"); 290 291 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 292 293 assert(words_not_fillable == 0 || 294 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 295 "Miscalculation in humongous allocation"); 296 297 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 298 299 for (uint i = first; i <= last; ++i) { 300 hr = region_at(i); 301 _humongous_set.add(hr); 302 _hr_printer.alloc(hr); 303 } 304 305 return new_obj; 306 } 307 308 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 309 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 310 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 311 } 312 313 // If could fit into free regions w/o expansion, try. 314 // Otherwise, if can expand, do so. 315 // Otherwise, if using ex regions might help, try with ex given back. 316 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) { 317 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 318 319 _verifier->verify_region_sets_optional(); 320 321 uint first = G1_NO_HRM_INDEX; 322 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 323 324 if (obj_regions == 1) { 325 // Only one region to allocate, try to use a fast path by directly allocating 326 // from the free lists. Do not try to expand here, we will potentially do that 327 // later. 328 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 329 if (hr != NULL) { 330 first = hr->hrm_index(); 331 } 332 } else { 333 // Policy: Try only empty regions (i.e. already committed first). Maybe we 334 // are lucky enough to find some. 335 first = _hrm.find_contiguous_only_empty(obj_regions); 336 if (first != G1_NO_HRM_INDEX) { 337 _hrm.allocate_free_regions_starting_at(first, obj_regions); 338 } 339 } 340 341 if (first == G1_NO_HRM_INDEX) { 342 // Policy: We could not find enough regions for the humongous object in the 343 // free list. Look through the heap to find a mix of free and uncommitted regions. 344 // If so, try expansion. 345 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 346 if (first != G1_NO_HRM_INDEX) { 347 // We found something. Make sure these regions are committed, i.e. expand 348 // the heap. Alternatively we could do a defragmentation GC. 349 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 350 word_size * HeapWordSize); 351 352 _hrm.expand_at(first, obj_regions, workers()); 353 g1_policy()->record_new_heap_size(num_regions()); 354 355 #ifdef ASSERT 356 for (uint i = first; i < first + obj_regions; ++i) { 357 HeapRegion* hr = region_at(i); 358 assert(hr->is_free(), "sanity"); 359 assert(hr->is_empty(), "sanity"); 360 assert(is_on_master_free_list(hr), "sanity"); 361 } 362 #endif 363 _hrm.allocate_free_regions_starting_at(first, obj_regions); 364 } else { 365 // Policy: Potentially trigger a defragmentation GC. 366 } 367 } 368 369 HeapWord* result = NULL; 370 if (first != G1_NO_HRM_INDEX) { 371 result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size); 372 assert(result != NULL, "it should always return a valid result"); 373 374 // A successful humongous object allocation changes the used space 375 // information of the old generation so we need to recalculate the 376 // sizes and update the jstat counters here. 377 g1mm()->update_sizes(); 378 } 379 380 _verifier->verify_region_sets_optional(); 381 382 return result; 383 } 384 385 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 386 assert_heap_not_locked_and_not_at_safepoint(); 387 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 388 389 return attempt_allocation(word_size); 390 } 391 392 HeapWord* 393 G1CollectedHeap::mem_allocate(size_t word_size, 394 bool* gc_overhead_limit_was_exceeded) { 395 assert_heap_not_locked_and_not_at_safepoint(); 396 397 if (is_humongous(word_size)) { 398 return attempt_allocation_humongous(word_size); 399 } 400 return attempt_allocation(word_size); 401 } 402 403 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) { 404 ResourceMark rm; // For retrieving the thread names in log messages. 405 406 // Make sure you read the note in attempt_allocation_humongous(). 407 408 assert_heap_not_locked_and_not_at_safepoint(); 409 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 410 "be called for humongous allocation requests"); 411 412 // We should only get here after the first-level allocation attempt 413 // (attempt_allocation()) failed to allocate. 414 415 // We will loop until a) we manage to successfully perform the 416 // allocation or b) we successfully schedule a collection which 417 // fails to perform the allocation. b) is the only case when we'll 418 // return NULL. 419 HeapWord* result = NULL; 420 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 421 bool should_try_gc; 422 uint gc_count_before; 423 424 { 425 MutexLockerEx x(Heap_lock); 426 result = _allocator->attempt_allocation_locked(word_size); 427 if (result != NULL) { 428 return result; 429 } 430 431 // If the GCLocker is active and we are bound for a GC, try expanding young gen. 432 // This is different to when only GCLocker::needs_gc() is set: try to avoid 433 // waiting because the GCLocker is active to not wait too long. 434 if (GCLocker::is_active_and_needs_gc() && g1_policy()->can_expand_young_list()) { 435 // No need for an ergo message here, can_expand_young_list() does this when 436 // it returns true. 437 result = _allocator->attempt_allocation_force(word_size); 438 if (result != NULL) { 439 return result; 440 } 441 } 442 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 443 // the GCLocker initiated GC has been performed and then retry. This includes 444 // the case when the GC Locker is not active but has not been performed. 445 should_try_gc = !GCLocker::needs_gc(); 446 // Read the GC count while still holding the Heap_lock. 447 gc_count_before = total_collections(); 448 } 449 450 if (should_try_gc) { 451 bool succeeded; 452 result = do_collection_pause(word_size, gc_count_before, &succeeded, 453 GCCause::_g1_inc_collection_pause); 454 if (result != NULL) { 455 assert(succeeded, "only way to get back a non-NULL result"); 456 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 457 Thread::current()->name(), p2i(result)); 458 return result; 459 } 460 461 if (succeeded) { 462 // We successfully scheduled a collection which failed to allocate. No 463 // point in trying to allocate further. We'll just return NULL. 464 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 465 SIZE_FORMAT " words", Thread::current()->name(), word_size); 466 return NULL; 467 } 468 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words", 469 Thread::current()->name(), word_size); 470 } else { 471 // Failed to schedule a collection. 472 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 473 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 474 SIZE_FORMAT " words", Thread::current()->name(), word_size); 475 return NULL; 476 } 477 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 478 // The GCLocker is either active or the GCLocker initiated 479 // GC has not yet been performed. Stall until it is and 480 // then retry the allocation. 481 GCLocker::stall_until_clear(); 482 gclocker_retry_count += 1; 483 } 484 485 // We can reach here if we were unsuccessful in scheduling a 486 // collection (because another thread beat us to it) or if we were 487 // stalled due to the GC locker. In either can we should retry the 488 // allocation attempt in case another thread successfully 489 // performed a collection and reclaimed enough space. We do the 490 // first attempt (without holding the Heap_lock) here and the 491 // follow-on attempt will be at the start of the next loop 492 // iteration (after taking the Heap_lock). 493 494 result = _allocator->attempt_allocation(word_size); 495 if (result != NULL) { 496 return result; 497 } 498 499 // Give a warning if we seem to be looping forever. 500 if ((QueuedAllocationWarningCount > 0) && 501 (try_count % QueuedAllocationWarningCount == 0)) { 502 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 503 Thread::current()->name(), try_count, word_size); 504 } 505 } 506 507 ShouldNotReachHere(); 508 return NULL; 509 } 510 511 void G1CollectedHeap::begin_archive_alloc_range(bool open) { 512 assert_at_safepoint_on_vm_thread(); 513 if (_archive_allocator == NULL) { 514 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open); 515 } 516 } 517 518 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 519 // Allocations in archive regions cannot be of a size that would be considered 520 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 521 // may be different at archive-restore time. 522 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 523 } 524 525 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 526 assert_at_safepoint_on_vm_thread(); 527 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 528 if (is_archive_alloc_too_large(word_size)) { 529 return NULL; 530 } 531 return _archive_allocator->archive_mem_allocate(word_size); 532 } 533 534 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 535 size_t end_alignment_in_bytes) { 536 assert_at_safepoint_on_vm_thread(); 537 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 538 539 // Call complete_archive to do the real work, filling in the MemRegion 540 // array with the archive regions. 541 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 542 delete _archive_allocator; 543 _archive_allocator = NULL; 544 } 545 546 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 547 assert(ranges != NULL, "MemRegion array NULL"); 548 assert(count != 0, "No MemRegions provided"); 549 MemRegion reserved = _hrm.reserved(); 550 for (size_t i = 0; i < count; i++) { 551 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 552 return false; 553 } 554 } 555 return true; 556 } 557 558 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, 559 size_t count, 560 bool open) { 561 assert(!is_init_completed(), "Expect to be called at JVM init time"); 562 assert(ranges != NULL, "MemRegion array NULL"); 563 assert(count != 0, "No MemRegions provided"); 564 MutexLockerEx x(Heap_lock); 565 566 MemRegion reserved = _hrm.reserved(); 567 HeapWord* prev_last_addr = NULL; 568 HeapRegion* prev_last_region = NULL; 569 570 // Temporarily disable pretouching of heap pages. This interface is used 571 // when mmap'ing archived heap data in, so pre-touching is wasted. 572 FlagSetting fs(AlwaysPreTouch, false); 573 574 // Enable archive object checking used by G1MarkSweep. We have to let it know 575 // about each archive range, so that objects in those ranges aren't marked. 576 G1ArchiveAllocator::enable_archive_object_check(); 577 578 // For each specified MemRegion range, allocate the corresponding G1 579 // regions and mark them as archive regions. We expect the ranges 580 // in ascending starting address order, without overlap. 581 for (size_t i = 0; i < count; i++) { 582 MemRegion curr_range = ranges[i]; 583 HeapWord* start_address = curr_range.start(); 584 size_t word_size = curr_range.word_size(); 585 HeapWord* last_address = curr_range.last(); 586 size_t commits = 0; 587 588 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 589 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 590 p2i(start_address), p2i(last_address)); 591 guarantee(start_address > prev_last_addr, 592 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 593 p2i(start_address), p2i(prev_last_addr)); 594 prev_last_addr = last_address; 595 596 // Check for ranges that start in the same G1 region in which the previous 597 // range ended, and adjust the start address so we don't try to allocate 598 // the same region again. If the current range is entirely within that 599 // region, skip it, just adjusting the recorded top. 600 HeapRegion* start_region = _hrm.addr_to_region(start_address); 601 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 602 start_address = start_region->end(); 603 if (start_address > last_address) { 604 increase_used(word_size * HeapWordSize); 605 start_region->set_top(last_address + 1); 606 continue; 607 } 608 start_region->set_top(start_address); 609 curr_range = MemRegion(start_address, last_address + 1); 610 start_region = _hrm.addr_to_region(start_address); 611 } 612 613 // Perform the actual region allocation, exiting if it fails. 614 // Then note how much new space we have allocated. 615 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 616 return false; 617 } 618 increase_used(word_size * HeapWordSize); 619 if (commits != 0) { 620 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 621 HeapRegion::GrainWords * HeapWordSize * commits); 622 623 } 624 625 // Mark each G1 region touched by the range as archive, add it to 626 // the old set, and set top. 627 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 628 HeapRegion* last_region = _hrm.addr_to_region(last_address); 629 prev_last_region = last_region; 630 631 while (curr_region != NULL) { 632 assert(curr_region->is_empty() && !curr_region->is_pinned(), 633 "Region already in use (index %u)", curr_region->hrm_index()); 634 if (open) { 635 curr_region->set_open_archive(); 636 } else { 637 curr_region->set_closed_archive(); 638 } 639 _hr_printer.alloc(curr_region); 640 _old_set.add(curr_region); 641 HeapWord* top; 642 HeapRegion* next_region; 643 if (curr_region != last_region) { 644 top = curr_region->end(); 645 next_region = _hrm.next_region_in_heap(curr_region); 646 } else { 647 top = last_address + 1; 648 next_region = NULL; 649 } 650 curr_region->set_top(top); 651 curr_region->set_first_dead(top); 652 curr_region->set_end_of_live(top); 653 curr_region = next_region; 654 } 655 656 // Notify mark-sweep of the archive 657 G1ArchiveAllocator::set_range_archive(curr_range, open); 658 } 659 return true; 660 } 661 662 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 663 assert(!is_init_completed(), "Expect to be called at JVM init time"); 664 assert(ranges != NULL, "MemRegion array NULL"); 665 assert(count != 0, "No MemRegions provided"); 666 MemRegion reserved = _hrm.reserved(); 667 HeapWord *prev_last_addr = NULL; 668 HeapRegion* prev_last_region = NULL; 669 670 // For each MemRegion, create filler objects, if needed, in the G1 regions 671 // that contain the address range. The address range actually within the 672 // MemRegion will not be modified. That is assumed to have been initialized 673 // elsewhere, probably via an mmap of archived heap data. 674 MutexLockerEx x(Heap_lock); 675 for (size_t i = 0; i < count; i++) { 676 HeapWord* start_address = ranges[i].start(); 677 HeapWord* last_address = ranges[i].last(); 678 679 assert(reserved.contains(start_address) && reserved.contains(last_address), 680 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 681 p2i(start_address), p2i(last_address)); 682 assert(start_address > prev_last_addr, 683 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 684 p2i(start_address), p2i(prev_last_addr)); 685 686 HeapRegion* start_region = _hrm.addr_to_region(start_address); 687 HeapRegion* last_region = _hrm.addr_to_region(last_address); 688 HeapWord* bottom_address = start_region->bottom(); 689 690 // Check for a range beginning in the same region in which the 691 // previous one ended. 692 if (start_region == prev_last_region) { 693 bottom_address = prev_last_addr + 1; 694 } 695 696 // Verify that the regions were all marked as archive regions by 697 // alloc_archive_regions. 698 HeapRegion* curr_region = start_region; 699 while (curr_region != NULL) { 700 guarantee(curr_region->is_archive(), 701 "Expected archive region at index %u", curr_region->hrm_index()); 702 if (curr_region != last_region) { 703 curr_region = _hrm.next_region_in_heap(curr_region); 704 } else { 705 curr_region = NULL; 706 } 707 } 708 709 prev_last_addr = last_address; 710 prev_last_region = last_region; 711 712 // Fill the memory below the allocated range with dummy object(s), 713 // if the region bottom does not match the range start, or if the previous 714 // range ended within the same G1 region, and there is a gap. 715 if (start_address != bottom_address) { 716 size_t fill_size = pointer_delta(start_address, bottom_address); 717 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 718 increase_used(fill_size * HeapWordSize); 719 } 720 } 721 } 722 723 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size) { 724 assert_heap_not_locked_and_not_at_safepoint(); 725 assert(!is_humongous(word_size), "attempt_allocation() should not " 726 "be called for humongous allocation requests"); 727 728 HeapWord* result = _allocator->attempt_allocation(word_size); 729 730 if (result == NULL) { 731 result = attempt_allocation_slow(word_size); 732 } 733 assert_heap_not_locked(); 734 if (result != NULL) { 735 dirty_young_block(result, word_size); 736 } 737 return result; 738 } 739 740 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 741 assert(!is_init_completed(), "Expect to be called at JVM init time"); 742 assert(ranges != NULL, "MemRegion array NULL"); 743 assert(count != 0, "No MemRegions provided"); 744 MemRegion reserved = _hrm.reserved(); 745 HeapWord* prev_last_addr = NULL; 746 HeapRegion* prev_last_region = NULL; 747 size_t size_used = 0; 748 size_t uncommitted_regions = 0; 749 750 // For each Memregion, free the G1 regions that constitute it, and 751 // notify mark-sweep that the range is no longer to be considered 'archive.' 752 MutexLockerEx x(Heap_lock); 753 for (size_t i = 0; i < count; i++) { 754 HeapWord* start_address = ranges[i].start(); 755 HeapWord* last_address = ranges[i].last(); 756 757 assert(reserved.contains(start_address) && reserved.contains(last_address), 758 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 759 p2i(start_address), p2i(last_address)); 760 assert(start_address > prev_last_addr, 761 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 762 p2i(start_address), p2i(prev_last_addr)); 763 size_used += ranges[i].byte_size(); 764 prev_last_addr = last_address; 765 766 HeapRegion* start_region = _hrm.addr_to_region(start_address); 767 HeapRegion* last_region = _hrm.addr_to_region(last_address); 768 769 // Check for ranges that start in the same G1 region in which the previous 770 // range ended, and adjust the start address so we don't try to free 771 // the same region again. If the current range is entirely within that 772 // region, skip it. 773 if (start_region == prev_last_region) { 774 start_address = start_region->end(); 775 if (start_address > last_address) { 776 continue; 777 } 778 start_region = _hrm.addr_to_region(start_address); 779 } 780 prev_last_region = last_region; 781 782 // After verifying that each region was marked as an archive region by 783 // alloc_archive_regions, set it free and empty and uncommit it. 784 HeapRegion* curr_region = start_region; 785 while (curr_region != NULL) { 786 guarantee(curr_region->is_archive(), 787 "Expected archive region at index %u", curr_region->hrm_index()); 788 uint curr_index = curr_region->hrm_index(); 789 _old_set.remove(curr_region); 790 curr_region->set_free(); 791 curr_region->set_top(curr_region->bottom()); 792 if (curr_region != last_region) { 793 curr_region = _hrm.next_region_in_heap(curr_region); 794 } else { 795 curr_region = NULL; 796 } 797 _hrm.shrink_at(curr_index, 1); 798 uncommitted_regions++; 799 } 800 801 // Notify mark-sweep that this is no longer an archive range. 802 G1ArchiveAllocator::set_range_archive(ranges[i], false); 803 } 804 805 if (uncommitted_regions != 0) { 806 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 807 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 808 } 809 decrease_used(size_used); 810 } 811 812 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) { 813 ResourceMark rm; // For retrieving the thread names in log messages. 814 815 // The structure of this method has a lot of similarities to 816 // attempt_allocation_slow(). The reason these two were not merged 817 // into a single one is that such a method would require several "if 818 // allocation is not humongous do this, otherwise do that" 819 // conditional paths which would obscure its flow. In fact, an early 820 // version of this code did use a unified method which was harder to 821 // follow and, as a result, it had subtle bugs that were hard to 822 // track down. So keeping these two methods separate allows each to 823 // be more readable. It will be good to keep these two in sync as 824 // much as possible. 825 826 assert_heap_not_locked_and_not_at_safepoint(); 827 assert(is_humongous(word_size), "attempt_allocation_humongous() " 828 "should only be called for humongous allocations"); 829 830 // Humongous objects can exhaust the heap quickly, so we should check if we 831 // need to start a marking cycle at each humongous object allocation. We do 832 // the check before we do the actual allocation. The reason for doing it 833 // before the allocation is that we avoid having to keep track of the newly 834 // allocated memory while we do a GC. 835 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 836 word_size)) { 837 collect(GCCause::_g1_humongous_allocation); 838 } 839 840 // We will loop until a) we manage to successfully perform the 841 // allocation or b) we successfully schedule a collection which 842 // fails to perform the allocation. b) is the only case when we'll 843 // return NULL. 844 HeapWord* result = NULL; 845 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 846 bool should_try_gc; 847 uint gc_count_before; 848 849 850 { 851 MutexLockerEx x(Heap_lock); 852 853 // Given that humongous objects are not allocated in young 854 // regions, we'll first try to do the allocation without doing a 855 // collection hoping that there's enough space in the heap. 856 result = humongous_obj_allocate(word_size); 857 if (result != NULL) { 858 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 859 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 860 return result; 861 } 862 863 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 864 // the GCLocker initiated GC has been performed and then retry. This includes 865 // the case when the GC Locker is not active but has not been performed. 866 should_try_gc = !GCLocker::needs_gc(); 867 // Read the GC count while still holding the Heap_lock. 868 gc_count_before = total_collections(); 869 } 870 871 if (should_try_gc) { 872 bool succeeded; 873 result = do_collection_pause(word_size, gc_count_before, &succeeded, 874 GCCause::_g1_humongous_allocation); 875 if (result != NULL) { 876 assert(succeeded, "only way to get back a non-NULL result"); 877 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 878 Thread::current()->name(), p2i(result)); 879 return result; 880 } 881 882 if (succeeded) { 883 // We successfully scheduled a collection which failed to allocate. No 884 // point in trying to allocate further. We'll just return NULL. 885 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 886 SIZE_FORMAT " words", Thread::current()->name(), word_size); 887 return NULL; 888 } 889 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "", 890 Thread::current()->name(), word_size); 891 } else { 892 // Failed to schedule a collection. 893 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 894 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 895 SIZE_FORMAT " words", Thread::current()->name(), word_size); 896 return NULL; 897 } 898 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 899 // The GCLocker is either active or the GCLocker initiated 900 // GC has not yet been performed. Stall until it is and 901 // then retry the allocation. 902 GCLocker::stall_until_clear(); 903 gclocker_retry_count += 1; 904 } 905 906 907 // We can reach here if we were unsuccessful in scheduling a 908 // collection (because another thread beat us to it) or if we were 909 // stalled due to the GC locker. In either can we should retry the 910 // allocation attempt in case another thread successfully 911 // performed a collection and reclaimed enough space. 912 // Humongous object allocation always needs a lock, so we wait for the retry 913 // in the next iteration of the loop, unlike for the regular iteration case. 914 // Give a warning if we seem to be looping forever. 915 916 if ((QueuedAllocationWarningCount > 0) && 917 (try_count % QueuedAllocationWarningCount == 0)) { 918 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 919 Thread::current()->name(), try_count, word_size); 920 } 921 } 922 923 ShouldNotReachHere(); 924 return NULL; 925 } 926 927 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 928 bool expect_null_mutator_alloc_region) { 929 assert_at_safepoint_on_vm_thread(); 930 assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region, 931 "the current alloc region was unexpectedly found to be non-NULL"); 932 933 if (!is_humongous(word_size)) { 934 return _allocator->attempt_allocation_locked(word_size); 935 } else { 936 HeapWord* result = humongous_obj_allocate(word_size); 937 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 938 collector_state()->set_initiate_conc_mark_if_possible(true); 939 } 940 return result; 941 } 942 943 ShouldNotReachHere(); 944 } 945 946 class PostCompactionPrinterClosure: public HeapRegionClosure { 947 private: 948 G1HRPrinter* _hr_printer; 949 public: 950 bool do_heap_region(HeapRegion* hr) { 951 assert(!hr->is_young(), "not expecting to find young regions"); 952 _hr_printer->post_compaction(hr); 953 return false; 954 } 955 956 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 957 : _hr_printer(hr_printer) { } 958 }; 959 960 void G1CollectedHeap::print_hrm_post_compaction() { 961 if (_hr_printer.is_active()) { 962 PostCompactionPrinterClosure cl(hr_printer()); 963 heap_region_iterate(&cl); 964 } 965 } 966 967 void G1CollectedHeap::abort_concurrent_cycle() { 968 // If we start the compaction before the CM threads finish 969 // scanning the root regions we might trip them over as we'll 970 // be moving objects / updating references. So let's wait until 971 // they are done. By telling them to abort, they should complete 972 // early. 973 _cm->root_regions()->abort(); 974 _cm->root_regions()->wait_until_scan_finished(); 975 976 // Disable discovery and empty the discovered lists 977 // for the CM ref processor. 978 ref_processor_cm()->disable_discovery(); 979 ref_processor_cm()->abandon_partial_discovery(); 980 ref_processor_cm()->verify_no_references_recorded(); 981 982 // Abandon current iterations of concurrent marking and concurrent 983 // refinement, if any are in progress. 984 concurrent_mark()->concurrent_cycle_abort(); 985 } 986 987 void G1CollectedHeap::prepare_heap_for_full_collection() { 988 // Make sure we'll choose a new allocation region afterwards. 989 _allocator->release_mutator_alloc_region(); 990 _allocator->abandon_gc_alloc_regions(); 991 g1_rem_set()->cleanupHRRS(); 992 993 // We may have added regions to the current incremental collection 994 // set between the last GC or pause and now. We need to clear the 995 // incremental collection set and then start rebuilding it afresh 996 // after this full GC. 997 abandon_collection_set(collection_set()); 998 999 tear_down_region_sets(false /* free_list_only */); 1000 } 1001 1002 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1003 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1004 assert(used() == recalculate_used(), "Should be equal"); 1005 _verifier->verify_region_sets_optional(); 1006 _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull); 1007 _verifier->check_bitmaps("Full GC Start"); 1008 } 1009 1010 void G1CollectedHeap::prepare_heap_for_mutators() { 1011 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1012 ClassLoaderDataGraph::purge(); 1013 MetaspaceUtils::verify_metrics(); 1014 1015 // Prepare heap for normal collections. 1016 assert(num_free_regions() == 0, "we should not have added any free regions"); 1017 rebuild_region_sets(false /* free_list_only */); 1018 abort_refinement(); 1019 resize_if_necessary_after_full_collection(); 1020 1021 // Rebuild the strong code root lists for each region 1022 rebuild_strong_code_roots(); 1023 1024 // Start a new incremental collection set for the next pause 1025 start_new_collection_set(); 1026 1027 _allocator->init_mutator_alloc_region(); 1028 1029 // Post collection state updates. 1030 MetaspaceGC::compute_new_size(); 1031 } 1032 1033 void G1CollectedHeap::abort_refinement() { 1034 if (_hot_card_cache->use_cache()) { 1035 _hot_card_cache->reset_hot_cache(); 1036 } 1037 1038 // Discard all remembered set updates. 1039 JavaThread::dirty_card_queue_set().abandon_logs(); 1040 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1041 } 1042 1043 void G1CollectedHeap::verify_after_full_collection() { 1044 _hrm.verify_optional(); 1045 _verifier->verify_region_sets_optional(); 1046 _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull); 1047 // Clear the previous marking bitmap, if needed for bitmap verification. 1048 // Note we cannot do this when we clear the next marking bitmap in 1049 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1050 // objects marked during a full GC against the previous bitmap. 1051 // But we need to clear it before calling check_bitmaps below since 1052 // the full GC has compacted objects and updated TAMS but not updated 1053 // the prev bitmap. 1054 if (G1VerifyBitmaps) { 1055 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1056 _cm->clear_prev_bitmap(workers()); 1057 } 1058 _verifier->check_bitmaps("Full GC End"); 1059 1060 // At this point there should be no regions in the 1061 // entire heap tagged as young. 1062 assert(check_young_list_empty(), "young list should be empty at this point"); 1063 1064 // Note: since we've just done a full GC, concurrent 1065 // marking is no longer active. Therefore we need not 1066 // re-enable reference discovery for the CM ref processor. 1067 // That will be done at the start of the next marking cycle. 1068 // We also know that the STW processor should no longer 1069 // discover any new references. 1070 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1071 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1072 ref_processor_stw()->verify_no_references_recorded(); 1073 ref_processor_cm()->verify_no_references_recorded(); 1074 } 1075 1076 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1077 // Post collection logging. 1078 // We should do this after we potentially resize the heap so 1079 // that all the COMMIT / UNCOMMIT events are generated before 1080 // the compaction events. 1081 print_hrm_post_compaction(); 1082 heap_transition->print(); 1083 print_heap_after_gc(); 1084 print_heap_regions(); 1085 #ifdef TRACESPINNING 1086 ParallelTaskTerminator::print_termination_counts(); 1087 #endif 1088 } 1089 1090 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1091 bool clear_all_soft_refs) { 1092 assert_at_safepoint_on_vm_thread(); 1093 1094 if (GCLocker::check_active_before_gc()) { 1095 // Full GC was not completed. 1096 return false; 1097 } 1098 1099 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1100 soft_ref_policy()->should_clear_all_soft_refs(); 1101 1102 G1FullCollector collector(this, &_full_gc_memory_manager, explicit_gc, do_clear_all_soft_refs); 1103 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1104 1105 collector.prepare_collection(); 1106 collector.collect(); 1107 collector.complete_collection(); 1108 1109 // Full collection was successfully completed. 1110 return true; 1111 } 1112 1113 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1114 // Currently, there is no facility in the do_full_collection(bool) API to notify 1115 // the caller that the collection did not succeed (e.g., because it was locked 1116 // out by the GC locker). So, right now, we'll ignore the return value. 1117 bool dummy = do_full_collection(true, /* explicit_gc */ 1118 clear_all_soft_refs); 1119 } 1120 1121 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1122 // Capacity, free and used after the GC counted as full regions to 1123 // include the waste in the following calculations. 1124 const size_t capacity_after_gc = capacity(); 1125 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes(); 1126 1127 // This is enforced in arguments.cpp. 1128 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1129 "otherwise the code below doesn't make sense"); 1130 1131 // We don't have floating point command-line arguments 1132 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1133 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1134 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1135 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1136 1137 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1138 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1139 1140 // We have to be careful here as these two calculations can overflow 1141 // 32-bit size_t's. 1142 double used_after_gc_d = (double) used_after_gc; 1143 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1144 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1145 1146 // Let's make sure that they are both under the max heap size, which 1147 // by default will make them fit into a size_t. 1148 double desired_capacity_upper_bound = (double) max_heap_size; 1149 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1150 desired_capacity_upper_bound); 1151 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1152 desired_capacity_upper_bound); 1153 1154 // We can now safely turn them into size_t's. 1155 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1156 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1157 1158 // This assert only makes sense here, before we adjust them 1159 // with respect to the min and max heap size. 1160 assert(minimum_desired_capacity <= maximum_desired_capacity, 1161 "minimum_desired_capacity = " SIZE_FORMAT ", " 1162 "maximum_desired_capacity = " SIZE_FORMAT, 1163 minimum_desired_capacity, maximum_desired_capacity); 1164 1165 // Should not be greater than the heap max size. No need to adjust 1166 // it with respect to the heap min size as it's a lower bound (i.e., 1167 // we'll try to make the capacity larger than it, not smaller). 1168 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1169 // Should not be less than the heap min size. No need to adjust it 1170 // with respect to the heap max size as it's an upper bound (i.e., 1171 // we'll try to make the capacity smaller than it, not greater). 1172 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1173 1174 if (capacity_after_gc < minimum_desired_capacity) { 1175 // Don't expand unless it's significant 1176 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1177 1178 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1179 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1180 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1181 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio); 1182 1183 expand(expand_bytes, _workers); 1184 1185 // No expansion, now see if we want to shrink 1186 } else if (capacity_after_gc > maximum_desired_capacity) { 1187 // Capacity too large, compute shrinking size 1188 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1189 1190 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1191 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1192 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1193 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio); 1194 1195 shrink(shrink_bytes); 1196 } 1197 } 1198 1199 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1200 bool do_gc, 1201 bool clear_all_soft_refs, 1202 bool expect_null_mutator_alloc_region, 1203 bool* gc_succeeded) { 1204 *gc_succeeded = true; 1205 // Let's attempt the allocation first. 1206 HeapWord* result = 1207 attempt_allocation_at_safepoint(word_size, 1208 expect_null_mutator_alloc_region); 1209 if (result != NULL) { 1210 return result; 1211 } 1212 1213 // In a G1 heap, we're supposed to keep allocation from failing by 1214 // incremental pauses. Therefore, at least for now, we'll favor 1215 // expansion over collection. (This might change in the future if we can 1216 // do something smarter than full collection to satisfy a failed alloc.) 1217 result = expand_and_allocate(word_size); 1218 if (result != NULL) { 1219 return result; 1220 } 1221 1222 if (do_gc) { 1223 // Expansion didn't work, we'll try to do a Full GC. 1224 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1225 clear_all_soft_refs); 1226 } 1227 1228 return NULL; 1229 } 1230 1231 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1232 bool* succeeded) { 1233 assert_at_safepoint_on_vm_thread(); 1234 1235 // Attempts to allocate followed by Full GC. 1236 HeapWord* result = 1237 satisfy_failed_allocation_helper(word_size, 1238 true, /* do_gc */ 1239 false, /* clear_all_soft_refs */ 1240 false, /* expect_null_mutator_alloc_region */ 1241 succeeded); 1242 1243 if (result != NULL || !*succeeded) { 1244 return result; 1245 } 1246 1247 // Attempts to allocate followed by Full GC that will collect all soft references. 1248 result = satisfy_failed_allocation_helper(word_size, 1249 true, /* do_gc */ 1250 true, /* clear_all_soft_refs */ 1251 true, /* expect_null_mutator_alloc_region */ 1252 succeeded); 1253 1254 if (result != NULL || !*succeeded) { 1255 return result; 1256 } 1257 1258 // Attempts to allocate, no GC 1259 result = satisfy_failed_allocation_helper(word_size, 1260 false, /* do_gc */ 1261 false, /* clear_all_soft_refs */ 1262 true, /* expect_null_mutator_alloc_region */ 1263 succeeded); 1264 1265 if (result != NULL) { 1266 return result; 1267 } 1268 1269 assert(!soft_ref_policy()->should_clear_all_soft_refs(), 1270 "Flag should have been handled and cleared prior to this point"); 1271 1272 // What else? We might try synchronous finalization later. If the total 1273 // space available is large enough for the allocation, then a more 1274 // complete compaction phase than we've tried so far might be 1275 // appropriate. 1276 return NULL; 1277 } 1278 1279 // Attempting to expand the heap sufficiently 1280 // to support an allocation of the given "word_size". If 1281 // successful, perform the allocation and return the address of the 1282 // allocated block, or else "NULL". 1283 1284 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1285 assert_at_safepoint_on_vm_thread(); 1286 1287 _verifier->verify_region_sets_optional(); 1288 1289 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1290 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1291 word_size * HeapWordSize); 1292 1293 1294 if (expand(expand_bytes, _workers)) { 1295 _hrm.verify_optional(); 1296 _verifier->verify_region_sets_optional(); 1297 return attempt_allocation_at_safepoint(word_size, 1298 false /* expect_null_mutator_alloc_region */); 1299 } 1300 return NULL; 1301 } 1302 1303 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1304 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1305 aligned_expand_bytes = align_up(aligned_expand_bytes, 1306 HeapRegion::GrainBytes); 1307 1308 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1309 expand_bytes, aligned_expand_bytes); 1310 1311 if (is_maximal_no_gc()) { 1312 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1313 return false; 1314 } 1315 1316 double expand_heap_start_time_sec = os::elapsedTime(); 1317 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1318 assert(regions_to_expand > 0, "Must expand by at least one region"); 1319 1320 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers); 1321 if (expand_time_ms != NULL) { 1322 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1323 } 1324 1325 if (expanded_by > 0) { 1326 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1327 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1328 g1_policy()->record_new_heap_size(num_regions()); 1329 } else { 1330 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1331 1332 // The expansion of the virtual storage space was unsuccessful. 1333 // Let's see if it was because we ran out of swap. 1334 if (G1ExitOnExpansionFailure && 1335 _hrm.available() >= regions_to_expand) { 1336 // We had head room... 1337 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1338 } 1339 } 1340 return regions_to_expand > 0; 1341 } 1342 1343 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1344 size_t aligned_shrink_bytes = 1345 ReservedSpace::page_align_size_down(shrink_bytes); 1346 aligned_shrink_bytes = align_down(aligned_shrink_bytes, 1347 HeapRegion::GrainBytes); 1348 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1349 1350 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1351 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1352 1353 1354 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", 1355 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1356 if (num_regions_removed > 0) { 1357 g1_policy()->record_new_heap_size(num_regions()); 1358 } else { 1359 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1360 } 1361 } 1362 1363 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1364 _verifier->verify_region_sets_optional(); 1365 1366 // We should only reach here at the end of a Full GC which means we 1367 // should not not be holding to any GC alloc regions. The method 1368 // below will make sure of that and do any remaining clean up. 1369 _allocator->abandon_gc_alloc_regions(); 1370 1371 // Instead of tearing down / rebuilding the free lists here, we 1372 // could instead use the remove_all_pending() method on free_list to 1373 // remove only the ones that we need to remove. 1374 tear_down_region_sets(true /* free_list_only */); 1375 shrink_helper(shrink_bytes); 1376 rebuild_region_sets(true /* free_list_only */); 1377 1378 _hrm.verify_optional(); 1379 _verifier->verify_region_sets_optional(); 1380 } 1381 1382 // Public methods. 1383 1384 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1385 CollectedHeap(), 1386 _young_gen_sampling_thread(NULL), 1387 _collector_policy(collector_policy), 1388 _soft_ref_policy(), 1389 _card_table(NULL), 1390 _memory_manager("G1 Young Generation", "end of minor GC"), 1391 _full_gc_memory_manager("G1 Old Generation", "end of major GC"), 1392 _eden_pool(NULL), 1393 _survivor_pool(NULL), 1394 _old_pool(NULL), 1395 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1396 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1397 _g1_policy(new G1Policy(_gc_timer_stw)), 1398 _collection_set(this, _g1_policy), 1399 _dirty_card_queue_set(false), 1400 _is_alive_closure_cm(this), 1401 _is_alive_closure_stw(this), 1402 _ref_processor_cm(NULL), 1403 _ref_processor_stw(NULL), 1404 _bot(NULL), 1405 _hot_card_cache(NULL), 1406 _g1_rem_set(NULL), 1407 _cr(NULL), 1408 _g1mm(NULL), 1409 _preserved_marks_set(true /* in_c_heap */), 1410 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1411 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1412 _humongous_reclaim_candidates(), 1413 _has_humongous_reclaim_candidates(false), 1414 _archive_allocator(NULL), 1415 _summary_bytes_used(0), 1416 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1417 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1418 _expand_heap_after_alloc_failure(true), 1419 _old_marking_cycles_started(0), 1420 _old_marking_cycles_completed(0), 1421 _in_cset_fast_test() { 1422 1423 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1424 /* are_GC_task_threads */true, 1425 /* are_ConcurrentGC_threads */false); 1426 _workers->initialize_workers(); 1427 _verifier = new G1HeapVerifier(this); 1428 1429 _allocator = new G1DefaultAllocator(this); 1430 1431 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1432 1433 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1434 1435 // Override the default _filler_array_max_size so that no humongous filler 1436 // objects are created. 1437 _filler_array_max_size = _humongous_object_threshold_in_words; 1438 1439 uint n_queues = ParallelGCThreads; 1440 _task_queues = new RefToScanQueueSet(n_queues); 1441 1442 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1443 1444 for (uint i = 0; i < n_queues; i++) { 1445 RefToScanQueue* q = new RefToScanQueue(); 1446 q->initialize(); 1447 _task_queues->register_queue(i, q); 1448 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1449 } 1450 1451 // Initialize the G1EvacuationFailureALot counters and flags. 1452 NOT_PRODUCT(reset_evacuation_should_fail();) 1453 1454 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1455 } 1456 1457 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1458 size_t size, 1459 size_t translation_factor) { 1460 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1461 // Allocate a new reserved space, preferring to use large pages. 1462 ReservedSpace rs(size, preferred_page_size); 1463 G1RegionToSpaceMapper* result = 1464 G1RegionToSpaceMapper::create_mapper(rs, 1465 size, 1466 rs.alignment(), 1467 HeapRegion::GrainBytes, 1468 translation_factor, 1469 mtGC); 1470 1471 os::trace_page_sizes_for_requested_size(description, 1472 size, 1473 preferred_page_size, 1474 rs.alignment(), 1475 rs.base(), 1476 rs.size()); 1477 1478 return result; 1479 } 1480 1481 jint G1CollectedHeap::initialize_concurrent_refinement() { 1482 jint ecode = JNI_OK; 1483 _cr = G1ConcurrentRefine::create(&ecode); 1484 return ecode; 1485 } 1486 1487 jint G1CollectedHeap::initialize_young_gen_sampling_thread() { 1488 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread(); 1489 if (_young_gen_sampling_thread->osthread() == NULL) { 1490 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread"); 1491 return JNI_ENOMEM; 1492 } 1493 return JNI_OK; 1494 } 1495 1496 jint G1CollectedHeap::initialize() { 1497 os::enable_vtime(); 1498 1499 // Necessary to satisfy locking discipline assertions. 1500 1501 MutexLocker x(Heap_lock); 1502 1503 // While there are no constraints in the GC code that HeapWordSize 1504 // be any particular value, there are multiple other areas in the 1505 // system which believe this to be true (e.g. oop->object_size in some 1506 // cases incorrectly returns the size in wordSize units rather than 1507 // HeapWordSize). 1508 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1509 1510 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1511 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1512 size_t heap_alignment = collector_policy()->heap_alignment(); 1513 1514 // Ensure that the sizes are properly aligned. 1515 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1516 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1517 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1518 1519 // Reserve the maximum. 1520 1521 // When compressed oops are enabled, the preferred heap base 1522 // is calculated by subtracting the requested size from the 1523 // 32Gb boundary and using the result as the base address for 1524 // heap reservation. If the requested size is not aligned to 1525 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1526 // into the ReservedHeapSpace constructor) then the actual 1527 // base of the reserved heap may end up differing from the 1528 // address that was requested (i.e. the preferred heap base). 1529 // If this happens then we could end up using a non-optimal 1530 // compressed oops mode. 1531 1532 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1533 heap_alignment); 1534 1535 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1536 1537 // Create the barrier set for the entire reserved region. 1538 G1CardTable* ct = new G1CardTable(reserved_region()); 1539 ct->initialize(); 1540 G1BarrierSet* bs = new G1BarrierSet(ct); 1541 bs->initialize(); 1542 assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity"); 1543 set_barrier_set(bs); 1544 _card_table = ct; 1545 1546 // Create the hot card cache. 1547 _hot_card_cache = new G1HotCardCache(this); 1548 1549 // Carve out the G1 part of the heap. 1550 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1551 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1552 G1RegionToSpaceMapper* heap_storage = 1553 G1RegionToSpaceMapper::create_mapper(g1_rs, 1554 g1_rs.size(), 1555 page_size, 1556 HeapRegion::GrainBytes, 1557 1, 1558 mtJavaHeap); 1559 os::trace_page_sizes("Heap", 1560 collector_policy()->min_heap_byte_size(), 1561 max_byte_size, 1562 page_size, 1563 heap_rs.base(), 1564 heap_rs.size()); 1565 heap_storage->set_mapping_changed_listener(&_listener); 1566 1567 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1568 G1RegionToSpaceMapper* bot_storage = 1569 create_aux_memory_mapper("Block Offset Table", 1570 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1571 G1BlockOffsetTable::heap_map_factor()); 1572 1573 G1RegionToSpaceMapper* cardtable_storage = 1574 create_aux_memory_mapper("Card Table", 1575 G1CardTable::compute_size(g1_rs.size() / HeapWordSize), 1576 G1CardTable::heap_map_factor()); 1577 1578 G1RegionToSpaceMapper* card_counts_storage = 1579 create_aux_memory_mapper("Card Counts Table", 1580 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1581 G1CardCounts::heap_map_factor()); 1582 1583 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1584 G1RegionToSpaceMapper* prev_bitmap_storage = 1585 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1586 G1RegionToSpaceMapper* next_bitmap_storage = 1587 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1588 1589 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1590 _card_table->initialize(cardtable_storage); 1591 // Do later initialization work for concurrent refinement. 1592 _hot_card_cache->initialize(card_counts_storage); 1593 1594 // 6843694 - ensure that the maximum region index can fit 1595 // in the remembered set structures. 1596 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1597 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1598 1599 // Also create a G1 rem set. 1600 _g1_rem_set = new G1RemSet(this, _card_table, _hot_card_cache); 1601 _g1_rem_set->initialize(max_capacity(), max_regions()); 1602 1603 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1604 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1605 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1606 "too many cards per region"); 1607 1608 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1609 1610 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1611 1612 { 1613 HeapWord* start = _hrm.reserved().start(); 1614 HeapWord* end = _hrm.reserved().end(); 1615 size_t granularity = HeapRegion::GrainBytes; 1616 1617 _in_cset_fast_test.initialize(start, end, granularity); 1618 _humongous_reclaim_candidates.initialize(start, end, granularity); 1619 } 1620 1621 // Create the G1ConcurrentMark data structure and thread. 1622 // (Must do this late, so that "max_regions" is defined.) 1623 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1624 if (_cm == NULL || !_cm->completed_initialization()) { 1625 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1626 return JNI_ENOMEM; 1627 } 1628 _cmThread = _cm->cm_thread(); 1629 1630 // Now expand into the initial heap size. 1631 if (!expand(init_byte_size, _workers)) { 1632 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1633 return JNI_ENOMEM; 1634 } 1635 1636 // Perform any initialization actions delegated to the policy. 1637 g1_policy()->init(this, &_collection_set); 1638 1639 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1640 SATB_Q_FL_lock, 1641 G1SATBProcessCompletedThreshold, 1642 Shared_SATB_Q_lock); 1643 1644 jint ecode = initialize_concurrent_refinement(); 1645 if (ecode != JNI_OK) { 1646 return ecode; 1647 } 1648 1649 ecode = initialize_young_gen_sampling_thread(); 1650 if (ecode != JNI_OK) { 1651 return ecode; 1652 } 1653 1654 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1655 DirtyCardQ_FL_lock, 1656 (int)concurrent_refine()->yellow_zone(), 1657 (int)concurrent_refine()->red_zone(), 1658 Shared_DirtyCardQ_lock, 1659 NULL, // fl_owner 1660 true); // init_free_ids 1661 1662 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1663 DirtyCardQ_FL_lock, 1664 -1, // never trigger processing 1665 -1, // no limit on length 1666 Shared_DirtyCardQ_lock, 1667 &JavaThread::dirty_card_queue_set()); 1668 1669 // Here we allocate the dummy HeapRegion that is required by the 1670 // G1AllocRegion class. 1671 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1672 1673 // We'll re-use the same region whether the alloc region will 1674 // require BOT updates or not and, if it doesn't, then a non-young 1675 // region will complain that it cannot support allocations without 1676 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1677 dummy_region->set_eden(); 1678 // Make sure it's full. 1679 dummy_region->set_top(dummy_region->end()); 1680 G1AllocRegion::setup(this, dummy_region); 1681 1682 _allocator->init_mutator_alloc_region(); 1683 1684 // Do create of the monitoring and management support so that 1685 // values in the heap have been properly initialized. 1686 _g1mm = new G1MonitoringSupport(this); 1687 1688 G1StringDedup::initialize(); 1689 1690 _preserved_marks_set.init(ParallelGCThreads); 1691 1692 _collection_set.initialize(max_regions()); 1693 1694 return JNI_OK; 1695 } 1696 1697 void G1CollectedHeap::initialize_serviceability() { 1698 _eden_pool = new G1EdenPool(this); 1699 _survivor_pool = new G1SurvivorPool(this); 1700 _old_pool = new G1OldGenPool(this); 1701 1702 _full_gc_memory_manager.add_pool(_eden_pool); 1703 _full_gc_memory_manager.add_pool(_survivor_pool); 1704 _full_gc_memory_manager.add_pool(_old_pool); 1705 1706 _memory_manager.add_pool(_eden_pool); 1707 _memory_manager.add_pool(_survivor_pool); 1708 1709 } 1710 1711 void G1CollectedHeap::stop() { 1712 // Stop all concurrent threads. We do this to make sure these threads 1713 // do not continue to execute and access resources (e.g. logging) 1714 // that are destroyed during shutdown. 1715 _cr->stop(); 1716 _young_gen_sampling_thread->stop(); 1717 _cmThread->stop(); 1718 if (G1StringDedup::is_enabled()) { 1719 G1StringDedup::stop(); 1720 } 1721 } 1722 1723 void G1CollectedHeap::safepoint_synchronize_begin() { 1724 SuspendibleThreadSet::synchronize(); 1725 } 1726 1727 void G1CollectedHeap::safepoint_synchronize_end() { 1728 SuspendibleThreadSet::desynchronize(); 1729 } 1730 1731 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1732 return HeapRegion::max_region_size(); 1733 } 1734 1735 void G1CollectedHeap::post_initialize() { 1736 CollectedHeap::post_initialize(); 1737 ref_processing_init(); 1738 } 1739 1740 void G1CollectedHeap::ref_processing_init() { 1741 // Reference processing in G1 currently works as follows: 1742 // 1743 // * There are two reference processor instances. One is 1744 // used to record and process discovered references 1745 // during concurrent marking; the other is used to 1746 // record and process references during STW pauses 1747 // (both full and incremental). 1748 // * Both ref processors need to 'span' the entire heap as 1749 // the regions in the collection set may be dotted around. 1750 // 1751 // * For the concurrent marking ref processor: 1752 // * Reference discovery is enabled at initial marking. 1753 // * Reference discovery is disabled and the discovered 1754 // references processed etc during remarking. 1755 // * Reference discovery is MT (see below). 1756 // * Reference discovery requires a barrier (see below). 1757 // * Reference processing may or may not be MT 1758 // (depending on the value of ParallelRefProcEnabled 1759 // and ParallelGCThreads). 1760 // * A full GC disables reference discovery by the CM 1761 // ref processor and abandons any entries on it's 1762 // discovered lists. 1763 // 1764 // * For the STW processor: 1765 // * Non MT discovery is enabled at the start of a full GC. 1766 // * Processing and enqueueing during a full GC is non-MT. 1767 // * During a full GC, references are processed after marking. 1768 // 1769 // * Discovery (may or may not be MT) is enabled at the start 1770 // of an incremental evacuation pause. 1771 // * References are processed near the end of a STW evacuation pause. 1772 // * For both types of GC: 1773 // * Discovery is atomic - i.e. not concurrent. 1774 // * Reference discovery will not need a barrier. 1775 1776 MemRegion mr = reserved_region(); 1777 1778 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1); 1779 1780 // Concurrent Mark ref processor 1781 _ref_processor_cm = 1782 new ReferenceProcessor(mr, // span 1783 mt_processing, 1784 // mt processing 1785 ParallelGCThreads, 1786 // degree of mt processing 1787 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 1788 // mt discovery 1789 MAX2(ParallelGCThreads, ConcGCThreads), 1790 // degree of mt discovery 1791 false, 1792 // Reference discovery is not atomic 1793 &_is_alive_closure_cm); 1794 // is alive closure 1795 // (for efficiency/performance) 1796 1797 // STW ref processor 1798 _ref_processor_stw = 1799 new ReferenceProcessor(mr, // span 1800 mt_processing, 1801 // mt processing 1802 ParallelGCThreads, 1803 // degree of mt processing 1804 (ParallelGCThreads > 1), 1805 // mt discovery 1806 ParallelGCThreads, 1807 // degree of mt discovery 1808 true, 1809 // Reference discovery is atomic 1810 &_is_alive_closure_stw); 1811 // is alive closure 1812 // (for efficiency/performance) 1813 } 1814 1815 CollectorPolicy* G1CollectedHeap::collector_policy() const { 1816 return _collector_policy; 1817 } 1818 1819 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() { 1820 return &_soft_ref_policy; 1821 } 1822 1823 size_t G1CollectedHeap::capacity() const { 1824 return _hrm.length() * HeapRegion::GrainBytes; 1825 } 1826 1827 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const { 1828 return _hrm.total_free_bytes(); 1829 } 1830 1831 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 1832 _hot_card_cache->drain(cl, worker_i); 1833 } 1834 1835 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 1836 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 1837 size_t n_completed_buffers = 0; 1838 while (dcqs.apply_closure_during_gc(cl, worker_i)) { 1839 n_completed_buffers++; 1840 } 1841 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 1842 dcqs.clear_n_completed_buffers(); 1843 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 1844 } 1845 1846 // Computes the sum of the storage used by the various regions. 1847 size_t G1CollectedHeap::used() const { 1848 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 1849 if (_archive_allocator != NULL) { 1850 result += _archive_allocator->used(); 1851 } 1852 return result; 1853 } 1854 1855 size_t G1CollectedHeap::used_unlocked() const { 1856 return _summary_bytes_used; 1857 } 1858 1859 class SumUsedClosure: public HeapRegionClosure { 1860 size_t _used; 1861 public: 1862 SumUsedClosure() : _used(0) {} 1863 bool do_heap_region(HeapRegion* r) { 1864 _used += r->used(); 1865 return false; 1866 } 1867 size_t result() { return _used; } 1868 }; 1869 1870 size_t G1CollectedHeap::recalculate_used() const { 1871 double recalculate_used_start = os::elapsedTime(); 1872 1873 SumUsedClosure blk; 1874 heap_region_iterate(&blk); 1875 1876 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 1877 return blk.result(); 1878 } 1879 1880 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 1881 switch (cause) { 1882 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 1883 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 1884 case GCCause::_wb_conc_mark: return true; 1885 default : return false; 1886 } 1887 } 1888 1889 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 1890 switch (cause) { 1891 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 1892 case GCCause::_g1_humongous_allocation: return true; 1893 default: return is_user_requested_concurrent_full_gc(cause); 1894 } 1895 } 1896 1897 #ifndef PRODUCT 1898 void G1CollectedHeap::allocate_dummy_regions() { 1899 // Let's fill up most of the region 1900 size_t word_size = HeapRegion::GrainWords - 1024; 1901 // And as a result the region we'll allocate will be humongous. 1902 guarantee(is_humongous(word_size), "sanity"); 1903 1904 // _filler_array_max_size is set to humongous object threshold 1905 // but temporarily change it to use CollectedHeap::fill_with_object(). 1906 SizeTFlagSetting fs(_filler_array_max_size, word_size); 1907 1908 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 1909 // Let's use the existing mechanism for the allocation 1910 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 1911 if (dummy_obj != NULL) { 1912 MemRegion mr(dummy_obj, word_size); 1913 CollectedHeap::fill_with_object(mr); 1914 } else { 1915 // If we can't allocate once, we probably cannot allocate 1916 // again. Let's get out of the loop. 1917 break; 1918 } 1919 } 1920 } 1921 #endif // !PRODUCT 1922 1923 void G1CollectedHeap::increment_old_marking_cycles_started() { 1924 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 1925 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 1926 "Wrong marking cycle count (started: %d, completed: %d)", 1927 _old_marking_cycles_started, _old_marking_cycles_completed); 1928 1929 _old_marking_cycles_started++; 1930 } 1931 1932 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 1933 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 1934 1935 // We assume that if concurrent == true, then the caller is a 1936 // concurrent thread that was joined the Suspendible Thread 1937 // Set. If there's ever a cheap way to check this, we should add an 1938 // assert here. 1939 1940 // Given that this method is called at the end of a Full GC or of a 1941 // concurrent cycle, and those can be nested (i.e., a Full GC can 1942 // interrupt a concurrent cycle), the number of full collections 1943 // completed should be either one (in the case where there was no 1944 // nesting) or two (when a Full GC interrupted a concurrent cycle) 1945 // behind the number of full collections started. 1946 1947 // This is the case for the inner caller, i.e. a Full GC. 1948 assert(concurrent || 1949 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 1950 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 1951 "for inner caller (Full GC): _old_marking_cycles_started = %u " 1952 "is inconsistent with _old_marking_cycles_completed = %u", 1953 _old_marking_cycles_started, _old_marking_cycles_completed); 1954 1955 // This is the case for the outer caller, i.e. the concurrent cycle. 1956 assert(!concurrent || 1957 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 1958 "for outer caller (concurrent cycle): " 1959 "_old_marking_cycles_started = %u " 1960 "is inconsistent with _old_marking_cycles_completed = %u", 1961 _old_marking_cycles_started, _old_marking_cycles_completed); 1962 1963 _old_marking_cycles_completed += 1; 1964 1965 // We need to clear the "in_progress" flag in the CM thread before 1966 // we wake up any waiters (especially when ExplicitInvokesConcurrent 1967 // is set) so that if a waiter requests another System.gc() it doesn't 1968 // incorrectly see that a marking cycle is still in progress. 1969 if (concurrent) { 1970 _cmThread->set_idle(); 1971 } 1972 1973 // This notify_all() will ensure that a thread that called 1974 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 1975 // and it's waiting for a full GC to finish will be woken up. It is 1976 // waiting in VM_G1CollectForAllocation::doit_epilogue(). 1977 FullGCCount_lock->notify_all(); 1978 } 1979 1980 void G1CollectedHeap::collect(GCCause::Cause cause) { 1981 assert_heap_not_locked(); 1982 1983 uint gc_count_before; 1984 uint old_marking_count_before; 1985 uint full_gc_count_before; 1986 bool retry_gc; 1987 1988 do { 1989 retry_gc = false; 1990 1991 { 1992 MutexLocker ml(Heap_lock); 1993 1994 // Read the GC count while holding the Heap_lock 1995 gc_count_before = total_collections(); 1996 full_gc_count_before = total_full_collections(); 1997 old_marking_count_before = _old_marking_cycles_started; 1998 } 1999 2000 if (should_do_concurrent_full_gc(cause)) { 2001 // Schedule an initial-mark evacuation pause that will start a 2002 // concurrent cycle. We're setting word_size to 0 which means that 2003 // we are not requesting a post-GC allocation. 2004 VM_G1CollectForAllocation op(0, /* word_size */ 2005 gc_count_before, 2006 cause, 2007 true, /* should_initiate_conc_mark */ 2008 g1_policy()->max_pause_time_ms()); 2009 VMThread::execute(&op); 2010 if (!op.pause_succeeded()) { 2011 if (old_marking_count_before == _old_marking_cycles_started) { 2012 retry_gc = op.should_retry_gc(); 2013 } else { 2014 // A Full GC happened while we were trying to schedule the 2015 // initial-mark GC. No point in starting a new cycle given 2016 // that the whole heap was collected anyway. 2017 } 2018 2019 if (retry_gc) { 2020 if (GCLocker::is_active_and_needs_gc()) { 2021 GCLocker::stall_until_clear(); 2022 } 2023 } 2024 } 2025 } else { 2026 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2027 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2028 2029 // Schedule a standard evacuation pause. We're setting word_size 2030 // to 0 which means that we are not requesting a post-GC allocation. 2031 VM_G1CollectForAllocation op(0, /* word_size */ 2032 gc_count_before, 2033 cause, 2034 false, /* should_initiate_conc_mark */ 2035 g1_policy()->max_pause_time_ms()); 2036 VMThread::execute(&op); 2037 } else { 2038 // Schedule a Full GC. 2039 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2040 VMThread::execute(&op); 2041 } 2042 } 2043 } while (retry_gc); 2044 } 2045 2046 bool G1CollectedHeap::is_in(const void* p) const { 2047 if (_hrm.reserved().contains(p)) { 2048 // Given that we know that p is in the reserved space, 2049 // heap_region_containing() should successfully 2050 // return the containing region. 2051 HeapRegion* hr = heap_region_containing(p); 2052 return hr->is_in(p); 2053 } else { 2054 return false; 2055 } 2056 } 2057 2058 #ifdef ASSERT 2059 bool G1CollectedHeap::is_in_exact(const void* p) const { 2060 bool contains = reserved_region().contains(p); 2061 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2062 if (contains && available) { 2063 return true; 2064 } else { 2065 return false; 2066 } 2067 } 2068 #endif 2069 2070 // Iteration functions. 2071 2072 // Iterates an ObjectClosure over all objects within a HeapRegion. 2073 2074 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2075 ObjectClosure* _cl; 2076 public: 2077 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2078 bool do_heap_region(HeapRegion* r) { 2079 if (!r->is_continues_humongous()) { 2080 r->object_iterate(_cl); 2081 } 2082 return false; 2083 } 2084 }; 2085 2086 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2087 IterateObjectClosureRegionClosure blk(cl); 2088 heap_region_iterate(&blk); 2089 } 2090 2091 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2092 _hrm.iterate(cl); 2093 } 2094 2095 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl, 2096 HeapRegionClaimer *hrclaimer, 2097 uint worker_id) const { 2098 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id)); 2099 } 2100 2101 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl, 2102 HeapRegionClaimer *hrclaimer) const { 2103 _hrm.par_iterate(cl, hrclaimer, 0); 2104 } 2105 2106 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2107 _collection_set.iterate(cl); 2108 } 2109 2110 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2111 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2112 } 2113 2114 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2115 HeapRegion* hr = heap_region_containing(addr); 2116 return hr->block_start(addr); 2117 } 2118 2119 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2120 HeapRegion* hr = heap_region_containing(addr); 2121 return hr->block_size(addr); 2122 } 2123 2124 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2125 HeapRegion* hr = heap_region_containing(addr); 2126 return hr->block_is_obj(addr); 2127 } 2128 2129 bool G1CollectedHeap::supports_tlab_allocation() const { 2130 return true; 2131 } 2132 2133 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2134 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2135 } 2136 2137 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2138 return _eden.length() * HeapRegion::GrainBytes; 2139 } 2140 2141 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2142 // must be equal to the humongous object limit. 2143 size_t G1CollectedHeap::max_tlab_size() const { 2144 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2145 } 2146 2147 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2148 return _allocator->unsafe_max_tlab_alloc(); 2149 } 2150 2151 size_t G1CollectedHeap::max_capacity() const { 2152 return _hrm.reserved().byte_size(); 2153 } 2154 2155 jlong G1CollectedHeap::millis_since_last_gc() { 2156 // See the notes in GenCollectedHeap::millis_since_last_gc() 2157 // for more information about the implementation. 2158 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2159 _g1_policy->collection_pause_end_millis(); 2160 if (ret_val < 0) { 2161 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2162 ". returning zero instead.", ret_val); 2163 return 0; 2164 } 2165 return ret_val; 2166 } 2167 2168 void G1CollectedHeap::prepare_for_verify() { 2169 _verifier->prepare_for_verify(); 2170 } 2171 2172 void G1CollectedHeap::verify(VerifyOption vo) { 2173 _verifier->verify(vo); 2174 } 2175 2176 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2177 return true; 2178 } 2179 2180 const char* const* G1CollectedHeap::concurrent_phases() const { 2181 return _cmThread->concurrent_phases(); 2182 } 2183 2184 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2185 return _cmThread->request_concurrent_phase(phase); 2186 } 2187 2188 class PrintRegionClosure: public HeapRegionClosure { 2189 outputStream* _st; 2190 public: 2191 PrintRegionClosure(outputStream* st) : _st(st) {} 2192 bool do_heap_region(HeapRegion* r) { 2193 r->print_on(_st); 2194 return false; 2195 } 2196 }; 2197 2198 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2199 const HeapRegion* hr, 2200 const VerifyOption vo) const { 2201 switch (vo) { 2202 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2203 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2204 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr); 2205 default: ShouldNotReachHere(); 2206 } 2207 return false; // keep some compilers happy 2208 } 2209 2210 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2211 const VerifyOption vo) const { 2212 switch (vo) { 2213 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2214 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2215 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj); 2216 default: ShouldNotReachHere(); 2217 } 2218 return false; // keep some compilers happy 2219 } 2220 2221 void G1CollectedHeap::print_heap_regions() const { 2222 LogTarget(Trace, gc, heap, region) lt; 2223 if (lt.is_enabled()) { 2224 LogStream ls(lt); 2225 print_regions_on(&ls); 2226 } 2227 } 2228 2229 void G1CollectedHeap::print_on(outputStream* st) const { 2230 st->print(" %-20s", "garbage-first heap"); 2231 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2232 capacity()/K, used_unlocked()/K); 2233 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")", 2234 p2i(_hrm.reserved().start()), 2235 p2i(_hrm.reserved().end())); 2236 st->cr(); 2237 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2238 uint young_regions = young_regions_count(); 2239 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2240 (size_t) young_regions * HeapRegion::GrainBytes / K); 2241 uint survivor_regions = survivor_regions_count(); 2242 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2243 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2244 st->cr(); 2245 MetaspaceUtils::print_on(st); 2246 } 2247 2248 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2249 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2250 "HS=humongous(starts), HC=humongous(continues), " 2251 "CS=collection set, F=free, A=archive, " 2252 "TAMS=top-at-mark-start (previous, next)"); 2253 PrintRegionClosure blk(st); 2254 heap_region_iterate(&blk); 2255 } 2256 2257 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2258 print_on(st); 2259 2260 // Print the per-region information. 2261 print_regions_on(st); 2262 } 2263 2264 void G1CollectedHeap::print_on_error(outputStream* st) const { 2265 this->CollectedHeap::print_on_error(st); 2266 2267 if (_cm != NULL) { 2268 st->cr(); 2269 _cm->print_on_error(st); 2270 } 2271 } 2272 2273 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2274 workers()->print_worker_threads_on(st); 2275 _cmThread->print_on(st); 2276 st->cr(); 2277 _cm->print_worker_threads_on(st); 2278 _cr->print_threads_on(st); 2279 _young_gen_sampling_thread->print_on(st); 2280 if (G1StringDedup::is_enabled()) { 2281 G1StringDedup::print_worker_threads_on(st); 2282 } 2283 } 2284 2285 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2286 workers()->threads_do(tc); 2287 tc->do_thread(_cmThread); 2288 _cm->threads_do(tc); 2289 _cr->threads_do(tc); 2290 tc->do_thread(_young_gen_sampling_thread); 2291 if (G1StringDedup::is_enabled()) { 2292 G1StringDedup::threads_do(tc); 2293 } 2294 } 2295 2296 void G1CollectedHeap::print_tracing_info() const { 2297 g1_rem_set()->print_summary_info(); 2298 concurrent_mark()->print_summary_info(); 2299 } 2300 2301 #ifndef PRODUCT 2302 // Helpful for debugging RSet issues. 2303 2304 class PrintRSetsClosure : public HeapRegionClosure { 2305 private: 2306 const char* _msg; 2307 size_t _occupied_sum; 2308 2309 public: 2310 bool do_heap_region(HeapRegion* r) { 2311 HeapRegionRemSet* hrrs = r->rem_set(); 2312 size_t occupied = hrrs->occupied(); 2313 _occupied_sum += occupied; 2314 2315 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2316 if (occupied == 0) { 2317 tty->print_cr(" RSet is empty"); 2318 } else { 2319 hrrs->print(); 2320 } 2321 tty->print_cr("----------"); 2322 return false; 2323 } 2324 2325 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2326 tty->cr(); 2327 tty->print_cr("========================================"); 2328 tty->print_cr("%s", msg); 2329 tty->cr(); 2330 } 2331 2332 ~PrintRSetsClosure() { 2333 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2334 tty->print_cr("========================================"); 2335 tty->cr(); 2336 } 2337 }; 2338 2339 void G1CollectedHeap::print_cset_rsets() { 2340 PrintRSetsClosure cl("Printing CSet RSets"); 2341 collection_set_iterate(&cl); 2342 } 2343 2344 void G1CollectedHeap::print_all_rsets() { 2345 PrintRSetsClosure cl("Printing All RSets");; 2346 heap_region_iterate(&cl); 2347 } 2348 #endif // PRODUCT 2349 2350 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2351 2352 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2353 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2354 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2355 2356 size_t eden_capacity_bytes = 2357 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2358 2359 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2360 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2361 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2362 } 2363 2364 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2365 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2366 stats->unused(), stats->used(), stats->region_end_waste(), 2367 stats->regions_filled(), stats->direct_allocated(), 2368 stats->failure_used(), stats->failure_waste()); 2369 } 2370 2371 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2372 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2373 gc_tracer->report_gc_heap_summary(when, heap_summary); 2374 2375 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2376 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2377 } 2378 2379 G1CollectedHeap* G1CollectedHeap::heap() { 2380 CollectedHeap* heap = Universe::heap(); 2381 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2382 assert(heap->kind() == CollectedHeap::G1, "Invalid name"); 2383 return (G1CollectedHeap*)heap; 2384 } 2385 2386 void G1CollectedHeap::gc_prologue(bool full) { 2387 // always_do_update_barrier = false; 2388 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2389 2390 // This summary needs to be printed before incrementing total collections. 2391 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2392 2393 // Update common counters. 2394 increment_total_collections(full /* full gc */); 2395 if (full) { 2396 increment_old_marking_cycles_started(); 2397 } 2398 2399 // Fill TLAB's and such 2400 double start = os::elapsedTime(); 2401 accumulate_statistics_all_tlabs(); 2402 ensure_parsability(true); 2403 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2404 } 2405 2406 void G1CollectedHeap::gc_epilogue(bool full) { 2407 // Update common counters. 2408 if (full) { 2409 // Update the number of full collections that have been completed. 2410 increment_old_marking_cycles_completed(false /* concurrent */); 2411 } 2412 2413 // We are at the end of the GC. Total collections has already been increased. 2414 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2415 2416 // FIXME: what is this about? 2417 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2418 // is set. 2419 #if COMPILER2_OR_JVMCI 2420 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2421 #endif 2422 // always_do_update_barrier = true; 2423 2424 double start = os::elapsedTime(); 2425 resize_all_tlabs(); 2426 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2427 2428 MemoryService::track_memory_usage(); 2429 // We have just completed a GC. Update the soft reference 2430 // policy with the new heap occupancy 2431 Universe::update_heap_info_at_gc(); 2432 } 2433 2434 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2435 uint gc_count_before, 2436 bool* succeeded, 2437 GCCause::Cause gc_cause) { 2438 assert_heap_not_locked_and_not_at_safepoint(); 2439 VM_G1CollectForAllocation op(word_size, 2440 gc_count_before, 2441 gc_cause, 2442 false, /* should_initiate_conc_mark */ 2443 g1_policy()->max_pause_time_ms()); 2444 VMThread::execute(&op); 2445 2446 HeapWord* result = op.result(); 2447 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2448 assert(result == NULL || ret_succeeded, 2449 "the result should be NULL if the VM did not succeed"); 2450 *succeeded = ret_succeeded; 2451 2452 assert_heap_not_locked(); 2453 return result; 2454 } 2455 2456 void G1CollectedHeap::do_concurrent_mark() { 2457 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2458 if (!_cmThread->in_progress()) { 2459 _cmThread->set_started(); 2460 CGC_lock->notify(); 2461 } 2462 } 2463 2464 size_t G1CollectedHeap::pending_card_num() { 2465 size_t extra_cards = 0; 2466 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) { 2467 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2468 extra_cards += dcq.size(); 2469 } 2470 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2471 size_t buffer_size = dcqs.buffer_size(); 2472 size_t buffer_num = dcqs.completed_buffers_num(); 2473 2474 return buffer_size * buffer_num + extra_cards; 2475 } 2476 2477 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const { 2478 // We don't nominate objects with many remembered set entries, on 2479 // the assumption that such objects are likely still live. 2480 HeapRegionRemSet* rem_set = r->rem_set(); 2481 2482 return G1EagerReclaimHumongousObjectsWithStaleRefs ? 2483 rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) : 2484 G1EagerReclaimHumongousObjects && rem_set->is_empty(); 2485 } 2486 2487 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2488 private: 2489 size_t _total_humongous; 2490 size_t _candidate_humongous; 2491 2492 DirtyCardQueue _dcq; 2493 2494 bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const { 2495 assert(region->is_starts_humongous(), "Must start a humongous object"); 2496 2497 oop obj = oop(region->bottom()); 2498 2499 // Dead objects cannot be eager reclaim candidates. Due to class 2500 // unloading it is unsafe to query their classes so we return early. 2501 if (g1h->is_obj_dead(obj, region)) { 2502 return false; 2503 } 2504 2505 // If we do not have a complete remembered set for the region, then we can 2506 // not be sure that we have all references to it. 2507 if (!region->rem_set()->is_complete()) { 2508 return false; 2509 } 2510 // Candidate selection must satisfy the following constraints 2511 // while concurrent marking is in progress: 2512 // 2513 // * In order to maintain SATB invariants, an object must not be 2514 // reclaimed if it was allocated before the start of marking and 2515 // has not had its references scanned. Such an object must have 2516 // its references (including type metadata) scanned to ensure no 2517 // live objects are missed by the marking process. Objects 2518 // allocated after the start of concurrent marking don't need to 2519 // be scanned. 2520 // 2521 // * An object must not be reclaimed if it is on the concurrent 2522 // mark stack. Objects allocated after the start of concurrent 2523 // marking are never pushed on the mark stack. 2524 // 2525 // Nominating only objects allocated after the start of concurrent 2526 // marking is sufficient to meet both constraints. This may miss 2527 // some objects that satisfy the constraints, but the marking data 2528 // structures don't support efficiently performing the needed 2529 // additional tests or scrubbing of the mark stack. 2530 // 2531 // However, we presently only nominate is_typeArray() objects. 2532 // A humongous object containing references induces remembered 2533 // set entries on other regions. In order to reclaim such an 2534 // object, those remembered sets would need to be cleaned up. 2535 // 2536 // We also treat is_typeArray() objects specially, allowing them 2537 // to be reclaimed even if allocated before the start of 2538 // concurrent mark. For this we rely on mark stack insertion to 2539 // exclude is_typeArray() objects, preventing reclaiming an object 2540 // that is in the mark stack. We also rely on the metadata for 2541 // such objects to be built-in and so ensured to be kept live. 2542 // Frequent allocation and drop of large binary blobs is an 2543 // important use case for eager reclaim, and this special handling 2544 // may reduce needed headroom. 2545 2546 return obj->is_typeArray() && 2547 g1h->is_potential_eager_reclaim_candidate(region); 2548 } 2549 2550 public: 2551 RegisterHumongousWithInCSetFastTestClosure() 2552 : _total_humongous(0), 2553 _candidate_humongous(0), 2554 _dcq(&JavaThread::dirty_card_queue_set()) { 2555 } 2556 2557 virtual bool do_heap_region(HeapRegion* r) { 2558 if (!r->is_starts_humongous()) { 2559 return false; 2560 } 2561 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2562 2563 bool is_candidate = humongous_region_is_candidate(g1h, r); 2564 uint rindex = r->hrm_index(); 2565 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2566 if (is_candidate) { 2567 _candidate_humongous++; 2568 g1h->register_humongous_region_with_cset(rindex); 2569 // Is_candidate already filters out humongous object with large remembered sets. 2570 // If we have a humongous object with a few remembered sets, we simply flush these 2571 // remembered set entries into the DCQS. That will result in automatic 2572 // re-evaluation of their remembered set entries during the following evacuation 2573 // phase. 2574 if (!r->rem_set()->is_empty()) { 2575 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2576 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2577 G1CardTable* ct = g1h->card_table(); 2578 HeapRegionRemSetIterator hrrs(r->rem_set()); 2579 size_t card_index; 2580 while (hrrs.has_next(card_index)) { 2581 jbyte* card_ptr = (jbyte*)ct->byte_for_index(card_index); 2582 // The remembered set might contain references to already freed 2583 // regions. Filter out such entries to avoid failing card table 2584 // verification. 2585 if (g1h->is_in_closed_subset(ct->addr_for(card_ptr))) { 2586 if (*card_ptr != G1CardTable::dirty_card_val()) { 2587 *card_ptr = G1CardTable::dirty_card_val(); 2588 _dcq.enqueue(card_ptr); 2589 } 2590 } 2591 } 2592 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2593 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2594 hrrs.n_yielded(), r->rem_set()->occupied()); 2595 // We should only clear the card based remembered set here as we will not 2596 // implicitly rebuild anything else during eager reclaim. Note that at the moment 2597 // (and probably never) we do not enter this path if there are other kind of 2598 // remembered sets for this region. 2599 r->rem_set()->clear_locked(true /* only_cardset */); 2600 // Clear_locked() above sets the state to Empty. However we want to continue 2601 // collecting remembered set entries for humongous regions that were not 2602 // reclaimed. 2603 r->rem_set()->set_state_complete(); 2604 } 2605 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2606 } 2607 _total_humongous++; 2608 2609 return false; 2610 } 2611 2612 size_t total_humongous() const { return _total_humongous; } 2613 size_t candidate_humongous() const { return _candidate_humongous; } 2614 2615 void flush_rem_set_entries() { _dcq.flush(); } 2616 }; 2617 2618 void G1CollectedHeap::register_humongous_regions_with_cset() { 2619 if (!G1EagerReclaimHumongousObjects) { 2620 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2621 return; 2622 } 2623 double time = os::elapsed_counter(); 2624 2625 // Collect reclaim candidate information and register candidates with cset. 2626 RegisterHumongousWithInCSetFastTestClosure cl; 2627 heap_region_iterate(&cl); 2628 2629 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2630 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2631 cl.total_humongous(), 2632 cl.candidate_humongous()); 2633 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2634 2635 // Finally flush all remembered set entries to re-check into the global DCQS. 2636 cl.flush_rem_set_entries(); 2637 } 2638 2639 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2640 public: 2641 bool do_heap_region(HeapRegion* hr) { 2642 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2643 hr->verify_rem_set(); 2644 } 2645 return false; 2646 } 2647 }; 2648 2649 uint G1CollectedHeap::num_task_queues() const { 2650 return _task_queues->size(); 2651 } 2652 2653 #if TASKQUEUE_STATS 2654 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2655 st->print_raw_cr("GC Task Stats"); 2656 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2657 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2658 } 2659 2660 void G1CollectedHeap::print_taskqueue_stats() const { 2661 if (!log_is_enabled(Trace, gc, task, stats)) { 2662 return; 2663 } 2664 Log(gc, task, stats) log; 2665 ResourceMark rm; 2666 LogStream ls(log.trace()); 2667 outputStream* st = &ls; 2668 2669 print_taskqueue_stats_hdr(st); 2670 2671 TaskQueueStats totals; 2672 const uint n = num_task_queues(); 2673 for (uint i = 0; i < n; ++i) { 2674 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2675 totals += task_queue(i)->stats; 2676 } 2677 st->print_raw("tot "); totals.print(st); st->cr(); 2678 2679 DEBUG_ONLY(totals.verify()); 2680 } 2681 2682 void G1CollectedHeap::reset_taskqueue_stats() { 2683 const uint n = num_task_queues(); 2684 for (uint i = 0; i < n; ++i) { 2685 task_queue(i)->stats.reset(); 2686 } 2687 } 2688 #endif // TASKQUEUE_STATS 2689 2690 void G1CollectedHeap::wait_for_root_region_scanning() { 2691 double scan_wait_start = os::elapsedTime(); 2692 // We have to wait until the CM threads finish scanning the 2693 // root regions as it's the only way to ensure that all the 2694 // objects on them have been correctly scanned before we start 2695 // moving them during the GC. 2696 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2697 double wait_time_ms = 0.0; 2698 if (waited) { 2699 double scan_wait_end = os::elapsedTime(); 2700 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2701 } 2702 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2703 } 2704 2705 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2706 private: 2707 G1HRPrinter* _hr_printer; 2708 public: 2709 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2710 2711 virtual bool do_heap_region(HeapRegion* r) { 2712 _hr_printer->cset(r); 2713 return false; 2714 } 2715 }; 2716 2717 void G1CollectedHeap::start_new_collection_set() { 2718 collection_set()->start_incremental_building(); 2719 2720 clear_cset_fast_test(); 2721 2722 guarantee(_eden.length() == 0, "eden should have been cleared"); 2723 g1_policy()->transfer_survivors_to_cset(survivor()); 2724 } 2725 2726 bool 2727 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2728 assert_at_safepoint_on_vm_thread(); 2729 guarantee(!is_gc_active(), "collection is not reentrant"); 2730 2731 if (GCLocker::check_active_before_gc()) { 2732 return false; 2733 } 2734 2735 _gc_timer_stw->register_gc_start(); 2736 2737 GCIdMark gc_id_mark; 2738 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2739 2740 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2741 ResourceMark rm; 2742 2743 g1_policy()->note_gc_start(); 2744 2745 wait_for_root_region_scanning(); 2746 2747 print_heap_before_gc(); 2748 print_heap_regions(); 2749 trace_heap_before_gc(_gc_tracer_stw); 2750 2751 _verifier->verify_region_sets_optional(); 2752 _verifier->verify_dirty_young_regions(); 2753 2754 // We should not be doing initial mark unless the conc mark thread is running 2755 if (!_cmThread->should_terminate()) { 2756 // This call will decide whether this pause is an initial-mark 2757 // pause. If it is, in_initial_mark_gc() will return true 2758 // for the duration of this pause. 2759 g1_policy()->decide_on_conc_mark_initiation(); 2760 } 2761 2762 // We do not allow initial-mark to be piggy-backed on a mixed GC. 2763 assert(!collector_state()->in_initial_mark_gc() || 2764 collector_state()->in_young_only_phase(), "sanity"); 2765 2766 // We also do not allow mixed GCs during marking. 2767 assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity"); 2768 2769 // Record whether this pause is an initial mark. When the current 2770 // thread has completed its logging output and it's safe to signal 2771 // the CM thread, the flag's value in the policy has been reset. 2772 bool should_start_conc_mark = collector_state()->in_initial_mark_gc(); 2773 2774 // Inner scope for scope based logging, timers, and stats collection 2775 { 2776 EvacuationInfo evacuation_info; 2777 2778 if (collector_state()->in_initial_mark_gc()) { 2779 // We are about to start a marking cycle, so we increment the 2780 // full collection counter. 2781 increment_old_marking_cycles_started(); 2782 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 2783 } 2784 2785 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 2786 2787 GCTraceCPUTime tcpu; 2788 2789 G1HeapVerifier::G1VerifyType verify_type; 2790 FormatBuffer<> gc_string("Pause "); 2791 if (collector_state()->in_initial_mark_gc()) { 2792 gc_string.append("Initial Mark"); 2793 verify_type = G1HeapVerifier::G1VerifyInitialMark; 2794 } else if (collector_state()->in_young_only_phase()) { 2795 gc_string.append("Young"); 2796 verify_type = G1HeapVerifier::G1VerifyYoungOnly; 2797 } else { 2798 gc_string.append("Mixed"); 2799 verify_type = G1HeapVerifier::G1VerifyMixed; 2800 } 2801 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 2802 2803 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 2804 workers()->active_workers(), 2805 Threads::number_of_non_daemon_threads()); 2806 active_workers = workers()->update_active_workers(active_workers); 2807 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 2808 2809 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 2810 TraceMemoryManagerStats tms(&_memory_manager, gc_cause()); 2811 2812 G1HeapTransition heap_transition(this); 2813 size_t heap_used_bytes_before_gc = used(); 2814 2815 // Don't dynamically change the number of GC threads this early. A value of 2816 // 0 is used to indicate serial work. When parallel work is done, 2817 // it will be set. 2818 2819 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 2820 IsGCActiveMark x; 2821 2822 gc_prologue(false); 2823 2824 if (VerifyRememberedSets) { 2825 log_info(gc, verify)("[Verifying RemSets before GC]"); 2826 VerifyRegionRemSetClosure v_cl; 2827 heap_region_iterate(&v_cl); 2828 } 2829 2830 _verifier->verify_before_gc(verify_type); 2831 2832 _verifier->check_bitmaps("GC Start"); 2833 2834 #if COMPILER2_OR_JVMCI 2835 DerivedPointerTable::clear(); 2836 #endif 2837 2838 // Please see comment in g1CollectedHeap.hpp and 2839 // G1CollectedHeap::ref_processing_init() to see how 2840 // reference processing currently works in G1. 2841 2842 // Enable discovery in the STW reference processor 2843 if (g1_policy()->should_process_references()) { 2844 ref_processor_stw()->enable_discovery(); 2845 } else { 2846 ref_processor_stw()->disable_discovery(); 2847 } 2848 2849 { 2850 // We want to temporarily turn off discovery by the 2851 // CM ref processor, if necessary, and turn it back on 2852 // on again later if we do. Using a scoped 2853 // NoRefDiscovery object will do this. 2854 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 2855 2856 // Forget the current alloc region (we might even choose it to be part 2857 // of the collection set!). 2858 _allocator->release_mutator_alloc_region(); 2859 2860 // This timing is only used by the ergonomics to handle our pause target. 2861 // It is unclear why this should not include the full pause. We will 2862 // investigate this in CR 7178365. 2863 // 2864 // Preserving the old comment here if that helps the investigation: 2865 // 2866 // The elapsed time induced by the start time below deliberately elides 2867 // the possible verification above. 2868 double sample_start_time_sec = os::elapsedTime(); 2869 2870 g1_policy()->record_collection_pause_start(sample_start_time_sec); 2871 2872 if (collector_state()->in_initial_mark_gc()) { 2873 concurrent_mark()->pre_initial_mark(); 2874 } 2875 2876 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 2877 2878 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 2879 2880 // Make sure the remembered sets are up to date. This needs to be 2881 // done before register_humongous_regions_with_cset(), because the 2882 // remembered sets are used there to choose eager reclaim candidates. 2883 // If the remembered sets are not up to date we might miss some 2884 // entries that need to be handled. 2885 g1_rem_set()->cleanupHRRS(); 2886 2887 register_humongous_regions_with_cset(); 2888 2889 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 2890 2891 // We call this after finalize_cset() to 2892 // ensure that the CSet has been finalized. 2893 _cm->verify_no_cset_oops(); 2894 2895 if (_hr_printer.is_active()) { 2896 G1PrintCollectionSetClosure cl(&_hr_printer); 2897 _collection_set.iterate(&cl); 2898 } 2899 2900 // Initialize the GC alloc regions. 2901 _allocator->init_gc_alloc_regions(evacuation_info); 2902 2903 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 2904 pre_evacuate_collection_set(); 2905 2906 // Actually do the work... 2907 evacuate_collection_set(&per_thread_states); 2908 2909 post_evacuate_collection_set(evacuation_info, &per_thread_states); 2910 2911 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 2912 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 2913 2914 eagerly_reclaim_humongous_regions(); 2915 2916 record_obj_copy_mem_stats(); 2917 _survivor_evac_stats.adjust_desired_plab_sz(); 2918 _old_evac_stats.adjust_desired_plab_sz(); 2919 2920 double start = os::elapsedTime(); 2921 start_new_collection_set(); 2922 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 2923 2924 if (evacuation_failed()) { 2925 set_used(recalculate_used()); 2926 if (_archive_allocator != NULL) { 2927 _archive_allocator->clear_used(); 2928 } 2929 for (uint i = 0; i < ParallelGCThreads; i++) { 2930 if (_evacuation_failed_info_array[i].has_failed()) { 2931 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 2932 } 2933 } 2934 } else { 2935 // The "used" of the the collection set have already been subtracted 2936 // when they were freed. Add in the bytes evacuated. 2937 increase_used(g1_policy()->bytes_copied_during_gc()); 2938 } 2939 2940 if (collector_state()->in_initial_mark_gc()) { 2941 // We have to do this before we notify the CM threads that 2942 // they can start working to make sure that all the 2943 // appropriate initialization is done on the CM object. 2944 concurrent_mark()->post_initial_mark(); 2945 // Note that we don't actually trigger the CM thread at 2946 // this point. We do that later when we're sure that 2947 // the current thread has completed its logging output. 2948 } 2949 2950 allocate_dummy_regions(); 2951 2952 _allocator->init_mutator_alloc_region(); 2953 2954 { 2955 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 2956 if (expand_bytes > 0) { 2957 size_t bytes_before = capacity(); 2958 // No need for an ergo logging here, 2959 // expansion_amount() does this when it returns a value > 0. 2960 double expand_ms; 2961 if (!expand(expand_bytes, _workers, &expand_ms)) { 2962 // We failed to expand the heap. Cannot do anything about it. 2963 } 2964 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 2965 } 2966 } 2967 2968 // We redo the verification but now wrt to the new CSet which 2969 // has just got initialized after the previous CSet was freed. 2970 _cm->verify_no_cset_oops(); 2971 2972 // This timing is only used by the ergonomics to handle our pause target. 2973 // It is unclear why this should not include the full pause. We will 2974 // investigate this in CR 7178365. 2975 double sample_end_time_sec = os::elapsedTime(); 2976 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 2977 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards); 2978 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 2979 2980 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 2981 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 2982 2983 if (VerifyRememberedSets) { 2984 log_info(gc, verify)("[Verifying RemSets after GC]"); 2985 VerifyRegionRemSetClosure v_cl; 2986 heap_region_iterate(&v_cl); 2987 } 2988 2989 _verifier->verify_after_gc(verify_type); 2990 _verifier->check_bitmaps("GC End"); 2991 2992 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 2993 ref_processor_stw()->verify_no_references_recorded(); 2994 2995 // CM reference discovery will be re-enabled if necessary. 2996 } 2997 2998 #ifdef TRACESPINNING 2999 ParallelTaskTerminator::print_termination_counts(); 3000 #endif 3001 3002 gc_epilogue(false); 3003 } 3004 3005 // Print the remainder of the GC log output. 3006 if (evacuation_failed()) { 3007 log_info(gc)("To-space exhausted"); 3008 } 3009 3010 g1_policy()->print_phases(); 3011 heap_transition.print(); 3012 3013 // It is not yet to safe to tell the concurrent mark to 3014 // start as we have some optional output below. We don't want the 3015 // output from the concurrent mark thread interfering with this 3016 // logging output either. 3017 3018 _hrm.verify_optional(); 3019 _verifier->verify_region_sets_optional(); 3020 3021 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3022 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3023 3024 print_heap_after_gc(); 3025 print_heap_regions(); 3026 trace_heap_after_gc(_gc_tracer_stw); 3027 3028 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3029 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3030 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3031 // before any GC notifications are raised. 3032 g1mm()->update_sizes(); 3033 3034 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3035 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3036 _gc_timer_stw->register_gc_end(); 3037 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3038 } 3039 // It should now be safe to tell the concurrent mark thread to start 3040 // without its logging output interfering with the logging output 3041 // that came from the pause. 3042 3043 if (should_start_conc_mark) { 3044 // CAUTION: after the doConcurrentMark() call below, 3045 // the concurrent marking thread(s) could be running 3046 // concurrently with us. Make sure that anything after 3047 // this point does not assume that we are the only GC thread 3048 // running. Note: of course, the actual marking work will 3049 // not start until the safepoint itself is released in 3050 // SuspendibleThreadSet::desynchronize(). 3051 do_concurrent_mark(); 3052 } 3053 3054 return true; 3055 } 3056 3057 void G1CollectedHeap::remove_self_forwarding_pointers() { 3058 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3059 workers()->run_task(&rsfp_task); 3060 } 3061 3062 void G1CollectedHeap::restore_after_evac_failure() { 3063 double remove_self_forwards_start = os::elapsedTime(); 3064 3065 remove_self_forwarding_pointers(); 3066 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3067 _preserved_marks_set.restore(&task_executor); 3068 3069 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3070 } 3071 3072 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3073 if (!_evacuation_failed) { 3074 _evacuation_failed = true; 3075 } 3076 3077 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3078 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3079 } 3080 3081 bool G1ParEvacuateFollowersClosure::offer_termination() { 3082 G1ParScanThreadState* const pss = par_scan_state(); 3083 start_term_time(); 3084 const bool res = terminator()->offer_termination(); 3085 end_term_time(); 3086 return res; 3087 } 3088 3089 void G1ParEvacuateFollowersClosure::do_void() { 3090 G1ParScanThreadState* const pss = par_scan_state(); 3091 pss->trim_queue(); 3092 do { 3093 pss->steal_and_trim_queue(queues()); 3094 } while (!offer_termination()); 3095 } 3096 3097 class G1ParTask : public AbstractGangTask { 3098 protected: 3099 G1CollectedHeap* _g1h; 3100 G1ParScanThreadStateSet* _pss; 3101 RefToScanQueueSet* _queues; 3102 G1RootProcessor* _root_processor; 3103 ParallelTaskTerminator _terminator; 3104 uint _n_workers; 3105 3106 public: 3107 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3108 : AbstractGangTask("G1 collection"), 3109 _g1h(g1h), 3110 _pss(per_thread_states), 3111 _queues(task_queues), 3112 _root_processor(root_processor), 3113 _terminator(n_workers, _queues), 3114 _n_workers(n_workers) 3115 {} 3116 3117 void work(uint worker_id) { 3118 if (worker_id >= _n_workers) return; // no work needed this round 3119 3120 double start_sec = os::elapsedTime(); 3121 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3122 3123 { 3124 ResourceMark rm; 3125 HandleMark hm; 3126 3127 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3128 3129 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3130 pss->set_ref_processor(rp); 3131 3132 double start_strong_roots_sec = os::elapsedTime(); 3133 3134 _root_processor->evacuate_roots(pss->closures(), worker_id); 3135 3136 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3137 // treating the nmethods visited to act as roots for concurrent marking. 3138 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3139 // objects copied by the current evacuation. 3140 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, 3141 pss->closures()->weak_codeblobs(), 3142 worker_id); 3143 3144 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3145 3146 double term_sec = 0.0; 3147 size_t evac_term_attempts = 0; 3148 { 3149 double start = os::elapsedTime(); 3150 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3151 evac.do_void(); 3152 3153 evac_term_attempts = evac.term_attempts(); 3154 term_sec = evac.term_time(); 3155 double elapsed_sec = os::elapsedTime() - start; 3156 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3157 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3158 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3159 } 3160 3161 assert(pss->queue_is_empty(), "should be empty"); 3162 3163 if (log_is_enabled(Debug, gc, task, stats)) { 3164 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3165 size_t lab_waste; 3166 size_t lab_undo_waste; 3167 pss->waste(lab_waste, lab_undo_waste); 3168 _g1h->print_termination_stats(worker_id, 3169 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3170 strong_roots_sec * 1000.0, /* strong roots time */ 3171 term_sec * 1000.0, /* evac term time */ 3172 evac_term_attempts, /* evac term attempts */ 3173 lab_waste, /* alloc buffer waste */ 3174 lab_undo_waste /* undo waste */ 3175 ); 3176 } 3177 3178 // Close the inner scope so that the ResourceMark and HandleMark 3179 // destructors are executed here and are included as part of the 3180 // "GC Worker Time". 3181 } 3182 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3183 } 3184 }; 3185 3186 void G1CollectedHeap::print_termination_stats_hdr() { 3187 log_debug(gc, task, stats)("GC Termination Stats"); 3188 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3189 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3190 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3191 } 3192 3193 void G1CollectedHeap::print_termination_stats(uint worker_id, 3194 double elapsed_ms, 3195 double strong_roots_ms, 3196 double term_ms, 3197 size_t term_attempts, 3198 size_t alloc_buffer_waste, 3199 size_t undo_waste) const { 3200 log_debug(gc, task, stats) 3201 ("%3d %9.2f %9.2f %6.2f " 3202 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3203 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3204 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3205 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3206 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3207 alloc_buffer_waste * HeapWordSize / K, 3208 undo_waste * HeapWordSize / K); 3209 } 3210 3211 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3212 private: 3213 BoolObjectClosure* _is_alive; 3214 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3215 3216 int _initial_string_table_size; 3217 int _initial_symbol_table_size; 3218 3219 bool _process_strings; 3220 int _strings_processed; 3221 int _strings_removed; 3222 3223 bool _process_symbols; 3224 int _symbols_processed; 3225 int _symbols_removed; 3226 3227 bool _process_string_dedup; 3228 3229 public: 3230 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3231 AbstractGangTask("String/Symbol Unlinking"), 3232 _is_alive(is_alive), 3233 _dedup_closure(is_alive, NULL, false), 3234 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3235 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3236 _process_string_dedup(process_string_dedup) { 3237 3238 _initial_string_table_size = StringTable::the_table()->table_size(); 3239 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3240 if (process_strings) { 3241 StringTable::clear_parallel_claimed_index(); 3242 } 3243 if (process_symbols) { 3244 SymbolTable::clear_parallel_claimed_index(); 3245 } 3246 } 3247 3248 ~G1StringAndSymbolCleaningTask() { 3249 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3250 "claim value %d after unlink less than initial string table size %d", 3251 StringTable::parallel_claimed_index(), _initial_string_table_size); 3252 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3253 "claim value %d after unlink less than initial symbol table size %d", 3254 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3255 3256 log_info(gc, stringtable)( 3257 "Cleaned string and symbol table, " 3258 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3259 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3260 strings_processed(), strings_removed(), 3261 symbols_processed(), symbols_removed()); 3262 } 3263 3264 void work(uint worker_id) { 3265 int strings_processed = 0; 3266 int strings_removed = 0; 3267 int symbols_processed = 0; 3268 int symbols_removed = 0; 3269 if (_process_strings) { 3270 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3271 Atomic::add(strings_processed, &_strings_processed); 3272 Atomic::add(strings_removed, &_strings_removed); 3273 } 3274 if (_process_symbols) { 3275 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3276 Atomic::add(symbols_processed, &_symbols_processed); 3277 Atomic::add(symbols_removed, &_symbols_removed); 3278 } 3279 if (_process_string_dedup) { 3280 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3281 } 3282 } 3283 3284 size_t strings_processed() const { return (size_t)_strings_processed; } 3285 size_t strings_removed() const { return (size_t)_strings_removed; } 3286 3287 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3288 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3289 }; 3290 3291 class G1CodeCacheUnloadingTask { 3292 private: 3293 static Monitor* _lock; 3294 3295 BoolObjectClosure* const _is_alive; 3296 const bool _unloading_occurred; 3297 const uint _num_workers; 3298 3299 // Variables used to claim nmethods. 3300 CompiledMethod* _first_nmethod; 3301 CompiledMethod* volatile _claimed_nmethod; 3302 3303 // The list of nmethods that need to be processed by the second pass. 3304 CompiledMethod* volatile _postponed_list; 3305 volatile uint _num_entered_barrier; 3306 3307 public: 3308 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3309 _is_alive(is_alive), 3310 _unloading_occurred(unloading_occurred), 3311 _num_workers(num_workers), 3312 _first_nmethod(NULL), 3313 _claimed_nmethod(NULL), 3314 _postponed_list(NULL), 3315 _num_entered_barrier(0) 3316 { 3317 CompiledMethod::increase_unloading_clock(); 3318 // Get first alive nmethod 3319 CompiledMethodIterator iter = CompiledMethodIterator(); 3320 if(iter.next_alive()) { 3321 _first_nmethod = iter.method(); 3322 } 3323 _claimed_nmethod = _first_nmethod; 3324 } 3325 3326 ~G1CodeCacheUnloadingTask() { 3327 CodeCache::verify_clean_inline_caches(); 3328 3329 CodeCache::set_needs_cache_clean(false); 3330 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3331 3332 CodeCache::verify_icholder_relocations(); 3333 } 3334 3335 private: 3336 void add_to_postponed_list(CompiledMethod* nm) { 3337 CompiledMethod* old; 3338 do { 3339 old = _postponed_list; 3340 nm->set_unloading_next(old); 3341 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old); 3342 } 3343 3344 void clean_nmethod(CompiledMethod* nm) { 3345 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3346 3347 if (postponed) { 3348 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3349 add_to_postponed_list(nm); 3350 } 3351 3352 // Mark that this thread has been cleaned/unloaded. 3353 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3354 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3355 } 3356 3357 void clean_nmethod_postponed(CompiledMethod* nm) { 3358 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3359 } 3360 3361 static const int MaxClaimNmethods = 16; 3362 3363 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3364 CompiledMethod* first; 3365 CompiledMethodIterator last; 3366 3367 do { 3368 *num_claimed_nmethods = 0; 3369 3370 first = _claimed_nmethod; 3371 last = CompiledMethodIterator(first); 3372 3373 if (first != NULL) { 3374 3375 for (int i = 0; i < MaxClaimNmethods; i++) { 3376 if (!last.next_alive()) { 3377 break; 3378 } 3379 claimed_nmethods[i] = last.method(); 3380 (*num_claimed_nmethods)++; 3381 } 3382 } 3383 3384 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first); 3385 } 3386 3387 CompiledMethod* claim_postponed_nmethod() { 3388 CompiledMethod* claim; 3389 CompiledMethod* next; 3390 3391 do { 3392 claim = _postponed_list; 3393 if (claim == NULL) { 3394 return NULL; 3395 } 3396 3397 next = claim->unloading_next(); 3398 3399 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim); 3400 3401 return claim; 3402 } 3403 3404 public: 3405 // Mark that we're done with the first pass of nmethod cleaning. 3406 void barrier_mark(uint worker_id) { 3407 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3408 _num_entered_barrier++; 3409 if (_num_entered_barrier == _num_workers) { 3410 ml.notify_all(); 3411 } 3412 } 3413 3414 // See if we have to wait for the other workers to 3415 // finish their first-pass nmethod cleaning work. 3416 void barrier_wait(uint worker_id) { 3417 if (_num_entered_barrier < _num_workers) { 3418 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3419 while (_num_entered_barrier < _num_workers) { 3420 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3421 } 3422 } 3423 } 3424 3425 // Cleaning and unloading of nmethods. Some work has to be postponed 3426 // to the second pass, when we know which nmethods survive. 3427 void work_first_pass(uint worker_id) { 3428 // The first nmethods is claimed by the first worker. 3429 if (worker_id == 0 && _first_nmethod != NULL) { 3430 clean_nmethod(_first_nmethod); 3431 _first_nmethod = NULL; 3432 } 3433 3434 int num_claimed_nmethods; 3435 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3436 3437 while (true) { 3438 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3439 3440 if (num_claimed_nmethods == 0) { 3441 break; 3442 } 3443 3444 for (int i = 0; i < num_claimed_nmethods; i++) { 3445 clean_nmethod(claimed_nmethods[i]); 3446 } 3447 } 3448 } 3449 3450 void work_second_pass(uint worker_id) { 3451 CompiledMethod* nm; 3452 // Take care of postponed nmethods. 3453 while ((nm = claim_postponed_nmethod()) != NULL) { 3454 clean_nmethod_postponed(nm); 3455 } 3456 } 3457 }; 3458 3459 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3460 3461 class G1KlassCleaningTask : public StackObj { 3462 BoolObjectClosure* _is_alive; 3463 volatile int _clean_klass_tree_claimed; 3464 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3465 3466 public: 3467 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3468 _is_alive(is_alive), 3469 _clean_klass_tree_claimed(0), 3470 _klass_iterator() { 3471 } 3472 3473 private: 3474 bool claim_clean_klass_tree_task() { 3475 if (_clean_klass_tree_claimed) { 3476 return false; 3477 } 3478 3479 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0; 3480 } 3481 3482 InstanceKlass* claim_next_klass() { 3483 Klass* klass; 3484 do { 3485 klass =_klass_iterator.next_klass(); 3486 } while (klass != NULL && !klass->is_instance_klass()); 3487 3488 // this can be null so don't call InstanceKlass::cast 3489 return static_cast<InstanceKlass*>(klass); 3490 } 3491 3492 public: 3493 3494 void clean_klass(InstanceKlass* ik) { 3495 ik->clean_weak_instanceklass_links(_is_alive); 3496 } 3497 3498 void work() { 3499 ResourceMark rm; 3500 3501 // One worker will clean the subklass/sibling klass tree. 3502 if (claim_clean_klass_tree_task()) { 3503 Klass::clean_subklass_tree(_is_alive); 3504 } 3505 3506 // All workers will help cleaning the classes, 3507 InstanceKlass* klass; 3508 while ((klass = claim_next_klass()) != NULL) { 3509 clean_klass(klass); 3510 } 3511 } 3512 }; 3513 3514 class G1ResolvedMethodCleaningTask : public StackObj { 3515 BoolObjectClosure* _is_alive; 3516 volatile int _resolved_method_task_claimed; 3517 public: 3518 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) : 3519 _is_alive(is_alive), _resolved_method_task_claimed(0) {} 3520 3521 bool claim_resolved_method_task() { 3522 if (_resolved_method_task_claimed) { 3523 return false; 3524 } 3525 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0; 3526 } 3527 3528 // These aren't big, one thread can do it all. 3529 void work() { 3530 if (claim_resolved_method_task()) { 3531 ResolvedMethodTable::unlink(_is_alive); 3532 } 3533 } 3534 }; 3535 3536 3537 // To minimize the remark pause times, the tasks below are done in parallel. 3538 class G1ParallelCleaningTask : public AbstractGangTask { 3539 private: 3540 G1StringAndSymbolCleaningTask _string_symbol_task; 3541 G1CodeCacheUnloadingTask _code_cache_task; 3542 G1KlassCleaningTask _klass_cleaning_task; 3543 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task; 3544 3545 public: 3546 // The constructor is run in the VMThread. 3547 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3548 AbstractGangTask("Parallel Cleaning"), 3549 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3550 _code_cache_task(num_workers, is_alive, unloading_occurred), 3551 _klass_cleaning_task(is_alive), 3552 _resolved_method_cleaning_task(is_alive) { 3553 } 3554 3555 // The parallel work done by all worker threads. 3556 void work(uint worker_id) { 3557 // Do first pass of code cache cleaning. 3558 _code_cache_task.work_first_pass(worker_id); 3559 3560 // Let the threads mark that the first pass is done. 3561 _code_cache_task.barrier_mark(worker_id); 3562 3563 // Clean the Strings and Symbols. 3564 _string_symbol_task.work(worker_id); 3565 3566 // Clean unreferenced things in the ResolvedMethodTable 3567 _resolved_method_cleaning_task.work(); 3568 3569 // Wait for all workers to finish the first code cache cleaning pass. 3570 _code_cache_task.barrier_wait(worker_id); 3571 3572 // Do the second code cache cleaning work, which realize on 3573 // the liveness information gathered during the first pass. 3574 _code_cache_task.work_second_pass(worker_id); 3575 3576 // Clean all klasses that were not unloaded. 3577 _klass_cleaning_task.work(); 3578 } 3579 }; 3580 3581 3582 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3583 bool class_unloading_occurred) { 3584 uint n_workers = workers()->active_workers(); 3585 3586 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3587 workers()->run_task(&g1_unlink_task); 3588 } 3589 3590 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3591 bool process_strings, 3592 bool process_symbols, 3593 bool process_string_dedup) { 3594 if (!process_strings && !process_symbols && !process_string_dedup) { 3595 // Nothing to clean. 3596 return; 3597 } 3598 3599 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3600 workers()->run_task(&g1_unlink_task); 3601 3602 } 3603 3604 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3605 private: 3606 DirtyCardQueueSet* _queue; 3607 G1CollectedHeap* _g1h; 3608 public: 3609 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3610 _queue(queue), _g1h(g1h) { } 3611 3612 virtual void work(uint worker_id) { 3613 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3614 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3615 3616 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3617 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3618 3619 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3620 } 3621 }; 3622 3623 void G1CollectedHeap::redirty_logged_cards() { 3624 double redirty_logged_cards_start = os::elapsedTime(); 3625 3626 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3627 dirty_card_queue_set().reset_for_par_iteration(); 3628 workers()->run_task(&redirty_task); 3629 3630 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 3631 dcq.merge_bufferlists(&dirty_card_queue_set()); 3632 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3633 3634 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3635 } 3636 3637 // Weak Reference Processing support 3638 3639 // An always "is_alive" closure that is used to preserve referents. 3640 // If the object is non-null then it's alive. Used in the preservation 3641 // of referent objects that are pointed to by reference objects 3642 // discovered by the CM ref processor. 3643 class G1AlwaysAliveClosure: public BoolObjectClosure { 3644 public: 3645 bool do_object_b(oop p) { 3646 if (p != NULL) { 3647 return true; 3648 } 3649 return false; 3650 } 3651 }; 3652 3653 bool G1STWIsAliveClosure::do_object_b(oop p) { 3654 // An object is reachable if it is outside the collection set, 3655 // or is inside and copied. 3656 return !_g1h->is_in_cset(p) || p->is_forwarded(); 3657 } 3658 3659 // Non Copying Keep Alive closure 3660 class G1KeepAliveClosure: public OopClosure { 3661 G1CollectedHeap*_g1h; 3662 public: 3663 G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {} 3664 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3665 void do_oop(oop* p) { 3666 oop obj = *p; 3667 assert(obj != NULL, "the caller should have filtered out NULL values"); 3668 3669 const InCSetState cset_state =_g1h->in_cset_state(obj); 3670 if (!cset_state.is_in_cset_or_humongous()) { 3671 return; 3672 } 3673 if (cset_state.is_in_cset()) { 3674 assert( obj->is_forwarded(), "invariant" ); 3675 *p = obj->forwardee(); 3676 } else { 3677 assert(!obj->is_forwarded(), "invariant" ); 3678 assert(cset_state.is_humongous(), 3679 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3680 _g1h->set_humongous_is_live(obj); 3681 } 3682 } 3683 }; 3684 3685 // Copying Keep Alive closure - can be called from both 3686 // serial and parallel code as long as different worker 3687 // threads utilize different G1ParScanThreadState instances 3688 // and different queues. 3689 3690 class G1CopyingKeepAliveClosure: public OopClosure { 3691 G1CollectedHeap* _g1h; 3692 OopClosure* _copy_non_heap_obj_cl; 3693 G1ParScanThreadState* _par_scan_state; 3694 3695 public: 3696 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3697 OopClosure* non_heap_obj_cl, 3698 G1ParScanThreadState* pss): 3699 _g1h(g1h), 3700 _copy_non_heap_obj_cl(non_heap_obj_cl), 3701 _par_scan_state(pss) 3702 {} 3703 3704 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3705 virtual void do_oop( oop* p) { do_oop_work(p); } 3706 3707 template <class T> void do_oop_work(T* p) { 3708 oop obj = RawAccess<>::oop_load(p); 3709 3710 if (_g1h->is_in_cset_or_humongous(obj)) { 3711 // If the referent object has been forwarded (either copied 3712 // to a new location or to itself in the event of an 3713 // evacuation failure) then we need to update the reference 3714 // field and, if both reference and referent are in the G1 3715 // heap, update the RSet for the referent. 3716 // 3717 // If the referent has not been forwarded then we have to keep 3718 // it alive by policy. Therefore we have copy the referent. 3719 // 3720 // If the reference field is in the G1 heap then we can push 3721 // on the PSS queue. When the queue is drained (after each 3722 // phase of reference processing) the object and it's followers 3723 // will be copied, the reference field set to point to the 3724 // new location, and the RSet updated. Otherwise we need to 3725 // use the the non-heap or metadata closures directly to copy 3726 // the referent object and update the pointer, while avoiding 3727 // updating the RSet. 3728 3729 if (_g1h->is_in_g1_reserved(p)) { 3730 _par_scan_state->push_on_queue(p); 3731 } else { 3732 assert(!Metaspace::contains((const void*)p), 3733 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 3734 _copy_non_heap_obj_cl->do_oop(p); 3735 } 3736 } 3737 } 3738 }; 3739 3740 // Serial drain queue closure. Called as the 'complete_gc' 3741 // closure for each discovered list in some of the 3742 // reference processing phases. 3743 3744 class G1STWDrainQueueClosure: public VoidClosure { 3745 protected: 3746 G1CollectedHeap* _g1h; 3747 G1ParScanThreadState* _par_scan_state; 3748 3749 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3750 3751 public: 3752 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3753 _g1h(g1h), 3754 _par_scan_state(pss) 3755 { } 3756 3757 void do_void() { 3758 G1ParScanThreadState* const pss = par_scan_state(); 3759 pss->trim_queue(); 3760 } 3761 }; 3762 3763 // Parallel Reference Processing closures 3764 3765 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3766 // processing during G1 evacuation pauses. 3767 3768 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3769 private: 3770 G1CollectedHeap* _g1h; 3771 G1ParScanThreadStateSet* _pss; 3772 RefToScanQueueSet* _queues; 3773 WorkGang* _workers; 3774 uint _active_workers; 3775 3776 public: 3777 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3778 G1ParScanThreadStateSet* per_thread_states, 3779 WorkGang* workers, 3780 RefToScanQueueSet *task_queues, 3781 uint n_workers) : 3782 _g1h(g1h), 3783 _pss(per_thread_states), 3784 _queues(task_queues), 3785 _workers(workers), 3786 _active_workers(n_workers) 3787 { 3788 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 3789 } 3790 3791 // Executes the given task using concurrent marking worker threads. 3792 virtual void execute(ProcessTask& task); 3793 virtual void execute(EnqueueTask& task); 3794 }; 3795 3796 // Gang task for possibly parallel reference processing 3797 3798 class G1STWRefProcTaskProxy: public AbstractGangTask { 3799 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 3800 ProcessTask& _proc_task; 3801 G1CollectedHeap* _g1h; 3802 G1ParScanThreadStateSet* _pss; 3803 RefToScanQueueSet* _task_queues; 3804 ParallelTaskTerminator* _terminator; 3805 3806 public: 3807 G1STWRefProcTaskProxy(ProcessTask& proc_task, 3808 G1CollectedHeap* g1h, 3809 G1ParScanThreadStateSet* per_thread_states, 3810 RefToScanQueueSet *task_queues, 3811 ParallelTaskTerminator* terminator) : 3812 AbstractGangTask("Process reference objects in parallel"), 3813 _proc_task(proc_task), 3814 _g1h(g1h), 3815 _pss(per_thread_states), 3816 _task_queues(task_queues), 3817 _terminator(terminator) 3818 {} 3819 3820 virtual void work(uint worker_id) { 3821 // The reference processing task executed by a single worker. 3822 ResourceMark rm; 3823 HandleMark hm; 3824 3825 G1STWIsAliveClosure is_alive(_g1h); 3826 3827 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3828 pss->set_ref_processor(NULL); 3829 3830 // Keep alive closure. 3831 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 3832 3833 // Complete GC closure 3834 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 3835 3836 // Call the reference processing task's work routine. 3837 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 3838 3839 // Note we cannot assert that the refs array is empty here as not all 3840 // of the processing tasks (specifically phase2 - pp2_work) execute 3841 // the complete_gc closure (which ordinarily would drain the queue) so 3842 // the queue may not be empty. 3843 } 3844 }; 3845 3846 // Driver routine for parallel reference processing. 3847 // Creates an instance of the ref processing gang 3848 // task and has the worker threads execute it. 3849 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 3850 assert(_workers != NULL, "Need parallel worker threads."); 3851 3852 ParallelTaskTerminator terminator(_active_workers, _queues); 3853 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 3854 3855 _workers->run_task(&proc_task_proxy); 3856 } 3857 3858 // Gang task for parallel reference enqueueing. 3859 3860 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 3861 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 3862 EnqueueTask& _enq_task; 3863 3864 public: 3865 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 3866 AbstractGangTask("Enqueue reference objects in parallel"), 3867 _enq_task(enq_task) 3868 { } 3869 3870 virtual void work(uint worker_id) { 3871 _enq_task.work(worker_id); 3872 } 3873 }; 3874 3875 // Driver routine for parallel reference enqueueing. 3876 // Creates an instance of the ref enqueueing gang 3877 // task and has the worker threads execute it. 3878 3879 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 3880 assert(_workers != NULL, "Need parallel worker threads."); 3881 3882 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 3883 3884 _workers->run_task(&enq_task_proxy); 3885 } 3886 3887 // End of weak reference support closures 3888 3889 // Abstract task used to preserve (i.e. copy) any referent objects 3890 // that are in the collection set and are pointed to by reference 3891 // objects discovered by the CM ref processor. 3892 3893 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 3894 protected: 3895 G1CollectedHeap* _g1h; 3896 G1ParScanThreadStateSet* _pss; 3897 RefToScanQueueSet* _queues; 3898 ParallelTaskTerminator _terminator; 3899 uint _n_workers; 3900 3901 public: 3902 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 3903 AbstractGangTask("ParPreserveCMReferents"), 3904 _g1h(g1h), 3905 _pss(per_thread_states), 3906 _queues(task_queues), 3907 _terminator(workers, _queues), 3908 _n_workers(workers) 3909 { 3910 g1h->ref_processor_cm()->set_active_mt_degree(workers); 3911 } 3912 3913 void work(uint worker_id) { 3914 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 3915 3916 ResourceMark rm; 3917 HandleMark hm; 3918 3919 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3920 pss->set_ref_processor(NULL); 3921 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 3922 3923 // Is alive closure 3924 G1AlwaysAliveClosure always_alive; 3925 3926 // Copying keep alive closure. Applied to referent objects that need 3927 // to be copied. 3928 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 3929 3930 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 3931 3932 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 3933 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 3934 3935 // limit is set using max_num_q() - which was set using ParallelGCThreads. 3936 // So this must be true - but assert just in case someone decides to 3937 // change the worker ids. 3938 assert(worker_id < limit, "sanity"); 3939 assert(!rp->discovery_is_atomic(), "check this code"); 3940 3941 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 3942 for (uint idx = worker_id; idx < limit; idx += stride) { 3943 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 3944 3945 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 3946 while (iter.has_next()) { 3947 // Since discovery is not atomic for the CM ref processor, we 3948 // can see some null referent objects. 3949 iter.load_ptrs(DEBUG_ONLY(true)); 3950 oop ref = iter.obj(); 3951 3952 // This will filter nulls. 3953 if (iter.is_referent_alive()) { 3954 iter.make_referent_alive(); 3955 } 3956 iter.move_to_next(); 3957 } 3958 } 3959 3960 // Drain the queue - which may cause stealing 3961 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 3962 drain_queue.do_void(); 3963 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 3964 assert(pss->queue_is_empty(), "should be"); 3965 } 3966 }; 3967 3968 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 3969 // Any reference objects, in the collection set, that were 'discovered' 3970 // by the CM ref processor should have already been copied (either by 3971 // applying the external root copy closure to the discovered lists, or 3972 // by following an RSet entry). 3973 // 3974 // But some of the referents, that are in the collection set, that these 3975 // reference objects point to may not have been copied: the STW ref 3976 // processor would have seen that the reference object had already 3977 // been 'discovered' and would have skipped discovering the reference, 3978 // but would not have treated the reference object as a regular oop. 3979 // As a result the copy closure would not have been applied to the 3980 // referent object. 3981 // 3982 // We need to explicitly copy these referent objects - the references 3983 // will be processed at the end of remarking. 3984 // 3985 // We also need to do this copying before we process the reference 3986 // objects discovered by the STW ref processor in case one of these 3987 // referents points to another object which is also referenced by an 3988 // object discovered by the STW ref processor. 3989 double preserve_cm_referents_time = 0.0; 3990 3991 // To avoid spawning task when there is no work to do, check that 3992 // a concurrent cycle is active and that some references have been 3993 // discovered. 3994 if (concurrent_mark()->cm_thread()->during_cycle() && 3995 ref_processor_cm()->has_discovered_references()) { 3996 double preserve_cm_referents_start = os::elapsedTime(); 3997 uint no_of_gc_workers = workers()->active_workers(); 3998 G1ParPreserveCMReferentsTask keep_cm_referents(this, 3999 per_thread_states, 4000 no_of_gc_workers, 4001 _task_queues); 4002 workers()->run_task(&keep_cm_referents); 4003 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4004 } 4005 4006 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4007 } 4008 4009 // Weak Reference processing during an evacuation pause (part 1). 4010 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4011 double ref_proc_start = os::elapsedTime(); 4012 4013 ReferenceProcessor* rp = _ref_processor_stw; 4014 assert(rp->discovery_enabled(), "should have been enabled"); 4015 4016 // Closure to test whether a referent is alive. 4017 G1STWIsAliveClosure is_alive(this); 4018 4019 // Even when parallel reference processing is enabled, the processing 4020 // of JNI refs is serial and performed serially by the current thread 4021 // rather than by a worker. The following PSS will be used for processing 4022 // JNI refs. 4023 4024 // Use only a single queue for this PSS. 4025 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4026 pss->set_ref_processor(NULL); 4027 assert(pss->queue_is_empty(), "pre-condition"); 4028 4029 // Keep alive closure. 4030 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4031 4032 // Serial Complete GC closure 4033 G1STWDrainQueueClosure drain_queue(this, pss); 4034 4035 // Setup the soft refs policy... 4036 rp->setup_policy(false); 4037 4038 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4039 4040 ReferenceProcessorStats stats; 4041 if (!rp->processing_is_mt()) { 4042 // Serial reference processing... 4043 stats = rp->process_discovered_references(&is_alive, 4044 &keep_alive, 4045 &drain_queue, 4046 NULL, 4047 pt); 4048 } else { 4049 uint no_of_gc_workers = workers()->active_workers(); 4050 4051 // Parallel reference processing 4052 assert(no_of_gc_workers <= rp->max_num_q(), 4053 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4054 no_of_gc_workers, rp->max_num_q()); 4055 4056 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4057 stats = rp->process_discovered_references(&is_alive, 4058 &keep_alive, 4059 &drain_queue, 4060 &par_task_executor, 4061 pt); 4062 } 4063 4064 _gc_tracer_stw->report_gc_reference_stats(stats); 4065 4066 // We have completed copying any necessary live referent objects. 4067 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4068 4069 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4070 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4071 } 4072 4073 // Weak Reference processing during an evacuation pause (part 2). 4074 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4075 double ref_enq_start = os::elapsedTime(); 4076 4077 ReferenceProcessor* rp = _ref_processor_stw; 4078 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4079 4080 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4081 4082 // Now enqueue any remaining on the discovered lists on to 4083 // the pending list. 4084 if (!rp->processing_is_mt()) { 4085 // Serial reference processing... 4086 rp->enqueue_discovered_references(NULL, pt); 4087 } else { 4088 // Parallel reference enqueueing 4089 4090 uint n_workers = workers()->active_workers(); 4091 4092 assert(n_workers <= rp->max_num_q(), 4093 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4094 n_workers, rp->max_num_q()); 4095 4096 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4097 rp->enqueue_discovered_references(&par_task_executor, pt); 4098 } 4099 4100 rp->verify_no_references_recorded(); 4101 assert(!rp->discovery_enabled(), "should have been disabled"); 4102 4103 // If during an initial mark pause we install a pending list head which is not otherwise reachable 4104 // ensure that it is marked in the bitmap for concurrent marking to discover. 4105 if (collector_state()->in_initial_mark_gc()) { 4106 oop pll_head = Universe::reference_pending_list(); 4107 if (pll_head != NULL) { 4108 // Any valid worker id is fine here as we are in the VM thread and single-threaded. 4109 _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head); 4110 } 4111 } 4112 4113 // FIXME 4114 // CM's reference processing also cleans up the string and symbol tables. 4115 // Should we do that here also? We could, but it is a serial operation 4116 // and could significantly increase the pause time. 4117 4118 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4119 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4120 } 4121 4122 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4123 double merge_pss_time_start = os::elapsedTime(); 4124 per_thread_states->flush(); 4125 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4126 } 4127 4128 void G1CollectedHeap::pre_evacuate_collection_set() { 4129 _expand_heap_after_alloc_failure = true; 4130 _evacuation_failed = false; 4131 4132 // Disable the hot card cache. 4133 _hot_card_cache->reset_hot_cache_claimed_index(); 4134 _hot_card_cache->set_use_cache(false); 4135 4136 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4137 _preserved_marks_set.assert_empty(); 4138 4139 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4140 4141 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4142 if (collector_state()->in_initial_mark_gc()) { 4143 double start_clear_claimed_marks = os::elapsedTime(); 4144 4145 ClassLoaderDataGraph::clear_claimed_marks(); 4146 4147 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4148 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4149 } 4150 } 4151 4152 void G1CollectedHeap::evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states) { 4153 // Should G1EvacuationFailureALot be in effect for this GC? 4154 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4155 4156 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4157 4158 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4159 4160 double start_par_time_sec = os::elapsedTime(); 4161 double end_par_time_sec; 4162 4163 { 4164 const uint n_workers = workers()->active_workers(); 4165 G1RootProcessor root_processor(this, n_workers); 4166 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4167 4168 print_termination_stats_hdr(); 4169 4170 workers()->run_task(&g1_par_task); 4171 end_par_time_sec = os::elapsedTime(); 4172 4173 // Closing the inner scope will execute the destructor 4174 // for the G1RootProcessor object. We record the current 4175 // elapsed time before closing the scope so that time 4176 // taken for the destructor is NOT included in the 4177 // reported parallel time. 4178 } 4179 4180 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4181 phase_times->record_par_time(par_time_ms); 4182 4183 double code_root_fixup_time_ms = 4184 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4185 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4186 } 4187 4188 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4189 // Process any discovered reference objects - we have 4190 // to do this _before_ we retire the GC alloc regions 4191 // as we may have to copy some 'reachable' referent 4192 // objects (and their reachable sub-graphs) that were 4193 // not copied during the pause. 4194 if (g1_policy()->should_process_references()) { 4195 preserve_cm_referents(per_thread_states); 4196 process_discovered_references(per_thread_states); 4197 } else { 4198 ref_processor_stw()->verify_no_references_recorded(); 4199 } 4200 4201 G1STWIsAliveClosure is_alive(this); 4202 G1KeepAliveClosure keep_alive(this); 4203 4204 { 4205 double start = os::elapsedTime(); 4206 4207 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 4208 4209 double time_ms = (os::elapsedTime() - start) * 1000.0; 4210 g1_policy()->phase_times()->record_ref_proc_time(time_ms); 4211 } 4212 4213 if (G1StringDedup::is_enabled()) { 4214 double fixup_start = os::elapsedTime(); 4215 4216 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4217 4218 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4219 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4220 } 4221 4222 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4223 4224 if (evacuation_failed()) { 4225 restore_after_evac_failure(); 4226 4227 // Reset the G1EvacuationFailureALot counters and flags 4228 // Note: the values are reset only when an actual 4229 // evacuation failure occurs. 4230 NOT_PRODUCT(reset_evacuation_should_fail();) 4231 } 4232 4233 _preserved_marks_set.assert_empty(); 4234 4235 // Enqueue any remaining references remaining on the STW 4236 // reference processor's discovered lists. We need to do 4237 // this after the card table is cleaned (and verified) as 4238 // the act of enqueueing entries on to the pending list 4239 // will log these updates (and dirty their associated 4240 // cards). We need these updates logged to update any 4241 // RSets. 4242 if (g1_policy()->should_process_references()) { 4243 enqueue_discovered_references(per_thread_states); 4244 } else { 4245 g1_policy()->phase_times()->record_ref_enq_time(0); 4246 } 4247 4248 _allocator->release_gc_alloc_regions(evacuation_info); 4249 4250 merge_per_thread_state_info(per_thread_states); 4251 4252 // Reset and re-enable the hot card cache. 4253 // Note the counts for the cards in the regions in the 4254 // collection set are reset when the collection set is freed. 4255 _hot_card_cache->reset_hot_cache(); 4256 _hot_card_cache->set_use_cache(true); 4257 4258 purge_code_root_memory(); 4259 4260 redirty_logged_cards(); 4261 #if COMPILER2_OR_JVMCI 4262 double start = os::elapsedTime(); 4263 DerivedPointerTable::update_pointers(); 4264 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4265 #endif 4266 g1_policy()->print_age_table(); 4267 } 4268 4269 void G1CollectedHeap::record_obj_copy_mem_stats() { 4270 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4271 4272 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4273 create_g1_evac_summary(&_old_evac_stats)); 4274 } 4275 4276 void G1CollectedHeap::free_region(HeapRegion* hr, 4277 FreeRegionList* free_list, 4278 bool skip_remset, 4279 bool skip_hot_card_cache, 4280 bool locked) { 4281 assert(!hr->is_free(), "the region should not be free"); 4282 assert(!hr->is_empty(), "the region should not be empty"); 4283 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4284 assert(free_list != NULL, "pre-condition"); 4285 4286 if (G1VerifyBitmaps) { 4287 MemRegion mr(hr->bottom(), hr->end()); 4288 concurrent_mark()->clear_range_in_prev_bitmap(mr); 4289 } 4290 4291 // Clear the card counts for this region. 4292 // Note: we only need to do this if the region is not young 4293 // (since we don't refine cards in young regions). 4294 if (!skip_hot_card_cache && !hr->is_young()) { 4295 _hot_card_cache->reset_card_counts(hr); 4296 } 4297 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4298 _g1_policy->remset_tracker()->update_at_free(hr); 4299 free_list->add_ordered(hr); 4300 } 4301 4302 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4303 FreeRegionList* free_list) { 4304 assert(hr->is_humongous(), "this is only for humongous regions"); 4305 assert(free_list != NULL, "pre-condition"); 4306 hr->clear_humongous(); 4307 free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */); 4308 } 4309 4310 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4311 const uint humongous_regions_removed) { 4312 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4313 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4314 _old_set.bulk_remove(old_regions_removed); 4315 _humongous_set.bulk_remove(humongous_regions_removed); 4316 } 4317 4318 } 4319 4320 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4321 assert(list != NULL, "list can't be null"); 4322 if (!list->is_empty()) { 4323 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4324 _hrm.insert_list_into_free_list(list); 4325 } 4326 } 4327 4328 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4329 decrease_used(bytes); 4330 } 4331 4332 class G1FreeCollectionSetTask : public AbstractGangTask { 4333 private: 4334 4335 // Closure applied to all regions in the collection set to do work that needs to 4336 // be done serially in a single thread. 4337 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4338 private: 4339 EvacuationInfo* _evacuation_info; 4340 const size_t* _surviving_young_words; 4341 4342 // Bytes used in successfully evacuated regions before the evacuation. 4343 size_t _before_used_bytes; 4344 // Bytes used in unsucessfully evacuated regions before the evacuation 4345 size_t _after_used_bytes; 4346 4347 size_t _bytes_allocated_in_old_since_last_gc; 4348 4349 size_t _failure_used_words; 4350 size_t _failure_waste_words; 4351 4352 FreeRegionList _local_free_list; 4353 public: 4354 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4355 HeapRegionClosure(), 4356 _evacuation_info(evacuation_info), 4357 _surviving_young_words(surviving_young_words), 4358 _before_used_bytes(0), 4359 _after_used_bytes(0), 4360 _bytes_allocated_in_old_since_last_gc(0), 4361 _failure_used_words(0), 4362 _failure_waste_words(0), 4363 _local_free_list("Local Region List for CSet Freeing") { 4364 } 4365 4366 virtual bool do_heap_region(HeapRegion* r) { 4367 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4368 4369 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4370 g1h->clear_in_cset(r); 4371 4372 if (r->is_young()) { 4373 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4374 "Young index %d is wrong for region %u of type %s with %u young regions", 4375 r->young_index_in_cset(), 4376 r->hrm_index(), 4377 r->get_type_str(), 4378 g1h->collection_set()->young_region_length()); 4379 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4380 r->record_surv_words_in_group(words_survived); 4381 } 4382 4383 if (!r->evacuation_failed()) { 4384 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4385 _before_used_bytes += r->used(); 4386 g1h->free_region(r, 4387 &_local_free_list, 4388 true, /* skip_remset */ 4389 true, /* skip_hot_card_cache */ 4390 true /* locked */); 4391 } else { 4392 r->uninstall_surv_rate_group(); 4393 r->set_young_index_in_cset(-1); 4394 r->set_evacuation_failed(false); 4395 // When moving a young gen region to old gen, we "allocate" that whole region 4396 // there. This is in addition to any already evacuated objects. Notify the 4397 // policy about that. 4398 // Old gen regions do not cause an additional allocation: both the objects 4399 // still in the region and the ones already moved are accounted for elsewhere. 4400 if (r->is_young()) { 4401 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4402 } 4403 // The region is now considered to be old. 4404 r->set_old(); 4405 // Do some allocation statistics accounting. Regions that failed evacuation 4406 // are always made old, so there is no need to update anything in the young 4407 // gen statistics, but we need to update old gen statistics. 4408 size_t used_words = r->marked_bytes() / HeapWordSize; 4409 4410 _failure_used_words += used_words; 4411 _failure_waste_words += HeapRegion::GrainWords - used_words; 4412 4413 g1h->old_set_add(r); 4414 _after_used_bytes += r->used(); 4415 } 4416 return false; 4417 } 4418 4419 void complete_work() { 4420 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4421 4422 _evacuation_info->set_regions_freed(_local_free_list.length()); 4423 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4424 4425 g1h->prepend_to_freelist(&_local_free_list); 4426 g1h->decrement_summary_bytes(_before_used_bytes); 4427 4428 G1Policy* policy = g1h->g1_policy(); 4429 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4430 4431 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4432 } 4433 }; 4434 4435 G1CollectionSet* _collection_set; 4436 G1SerialFreeCollectionSetClosure _cl; 4437 const size_t* _surviving_young_words; 4438 4439 size_t _rs_lengths; 4440 4441 volatile jint _serial_work_claim; 4442 4443 struct WorkItem { 4444 uint region_idx; 4445 bool is_young; 4446 bool evacuation_failed; 4447 4448 WorkItem(HeapRegion* r) { 4449 region_idx = r->hrm_index(); 4450 is_young = r->is_young(); 4451 evacuation_failed = r->evacuation_failed(); 4452 } 4453 }; 4454 4455 volatile size_t _parallel_work_claim; 4456 size_t _num_work_items; 4457 WorkItem* _work_items; 4458 4459 void do_serial_work() { 4460 // Need to grab the lock to be allowed to modify the old region list. 4461 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4462 _collection_set->iterate(&_cl); 4463 } 4464 4465 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4466 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4467 4468 HeapRegion* r = g1h->region_at(region_idx); 4469 assert(!g1h->is_on_master_free_list(r), "sanity"); 4470 4471 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4472 4473 if (!is_young) { 4474 g1h->_hot_card_cache->reset_card_counts(r); 4475 } 4476 4477 if (!evacuation_failed) { 4478 r->rem_set()->clear_locked(); 4479 } 4480 } 4481 4482 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4483 private: 4484 size_t _cur_idx; 4485 WorkItem* _work_items; 4486 public: 4487 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4488 4489 virtual bool do_heap_region(HeapRegion* r) { 4490 _work_items[_cur_idx++] = WorkItem(r); 4491 return false; 4492 } 4493 }; 4494 4495 void prepare_work() { 4496 G1PrepareFreeCollectionSetClosure cl(_work_items); 4497 _collection_set->iterate(&cl); 4498 } 4499 4500 void complete_work() { 4501 _cl.complete_work(); 4502 4503 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4504 policy->record_max_rs_lengths(_rs_lengths); 4505 policy->cset_regions_freed(); 4506 } 4507 public: 4508 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4509 AbstractGangTask("G1 Free Collection Set"), 4510 _cl(evacuation_info, surviving_young_words), 4511 _collection_set(collection_set), 4512 _surviving_young_words(surviving_young_words), 4513 _serial_work_claim(0), 4514 _rs_lengths(0), 4515 _parallel_work_claim(0), 4516 _num_work_items(collection_set->region_length()), 4517 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4518 prepare_work(); 4519 } 4520 4521 ~G1FreeCollectionSetTask() { 4522 complete_work(); 4523 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4524 } 4525 4526 // Chunk size for work distribution. The chosen value has been determined experimentally 4527 // to be a good tradeoff between overhead and achievable parallelism. 4528 static uint chunk_size() { return 32; } 4529 4530 virtual void work(uint worker_id) { 4531 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4532 4533 // Claim serial work. 4534 if (_serial_work_claim == 0) { 4535 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4536 if (value == 0) { 4537 double serial_time = os::elapsedTime(); 4538 do_serial_work(); 4539 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4540 } 4541 } 4542 4543 // Start parallel work. 4544 double young_time = 0.0; 4545 bool has_young_time = false; 4546 double non_young_time = 0.0; 4547 bool has_non_young_time = false; 4548 4549 while (true) { 4550 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4551 size_t cur = end - chunk_size(); 4552 4553 if (cur >= _num_work_items) { 4554 break; 4555 } 4556 4557 double start_time = os::elapsedTime(); 4558 4559 end = MIN2(end, _num_work_items); 4560 4561 for (; cur < end; cur++) { 4562 bool is_young = _work_items[cur].is_young; 4563 4564 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4565 4566 double end_time = os::elapsedTime(); 4567 double time_taken = end_time - start_time; 4568 if (is_young) { 4569 young_time += time_taken; 4570 has_young_time = true; 4571 } else { 4572 non_young_time += time_taken; 4573 has_non_young_time = true; 4574 } 4575 start_time = end_time; 4576 } 4577 } 4578 4579 if (has_young_time) { 4580 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4581 } 4582 if (has_non_young_time) { 4583 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time); 4584 } 4585 } 4586 }; 4587 4588 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4589 _eden.clear(); 4590 4591 double free_cset_start_time = os::elapsedTime(); 4592 4593 { 4594 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4595 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4596 4597 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4598 4599 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4600 cl.name(), 4601 num_workers, 4602 _collection_set.region_length()); 4603 workers()->run_task(&cl, num_workers); 4604 } 4605 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4606 4607 collection_set->clear(); 4608 } 4609 4610 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4611 private: 4612 FreeRegionList* _free_region_list; 4613 HeapRegionSet* _proxy_set; 4614 uint _humongous_objects_reclaimed; 4615 uint _humongous_regions_reclaimed; 4616 size_t _freed_bytes; 4617 public: 4618 4619 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4620 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4621 } 4622 4623 virtual bool do_heap_region(HeapRegion* r) { 4624 if (!r->is_starts_humongous()) { 4625 return false; 4626 } 4627 4628 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4629 4630 oop obj = (oop)r->bottom(); 4631 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap(); 4632 4633 // The following checks whether the humongous object is live are sufficient. 4634 // The main additional check (in addition to having a reference from the roots 4635 // or the young gen) is whether the humongous object has a remembered set entry. 4636 // 4637 // A humongous object cannot be live if there is no remembered set for it 4638 // because: 4639 // - there can be no references from within humongous starts regions referencing 4640 // the object because we never allocate other objects into them. 4641 // (I.e. there are no intra-region references that may be missed by the 4642 // remembered set) 4643 // - as soon there is a remembered set entry to the humongous starts region 4644 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4645 // until the end of a concurrent mark. 4646 // 4647 // It is not required to check whether the object has been found dead by marking 4648 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4649 // all objects allocated during that time are considered live. 4650 // SATB marking is even more conservative than the remembered set. 4651 // So if at this point in the collection there is no remembered set entry, 4652 // nobody has a reference to it. 4653 // At the start of collection we flush all refinement logs, and remembered sets 4654 // are completely up-to-date wrt to references to the humongous object. 4655 // 4656 // Other implementation considerations: 4657 // - never consider object arrays at this time because they would pose 4658 // considerable effort for cleaning up the the remembered sets. This is 4659 // required because stale remembered sets might reference locations that 4660 // are currently allocated into. 4661 uint region_idx = r->hrm_index(); 4662 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4663 !r->rem_set()->is_empty()) { 4664 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", 4665 region_idx, 4666 (size_t)obj->size() * HeapWordSize, 4667 p2i(r->bottom()), 4668 r->rem_set()->occupied(), 4669 r->rem_set()->strong_code_roots_list_length(), 4670 next_bitmap->is_marked(r->bottom()), 4671 g1h->is_humongous_reclaim_candidate(region_idx), 4672 obj->is_typeArray() 4673 ); 4674 return false; 4675 } 4676 4677 guarantee(obj->is_typeArray(), 4678 "Only eagerly reclaiming type arrays is supported, but the object " 4679 PTR_FORMAT " is not.", p2i(r->bottom())); 4680 4681 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", 4682 region_idx, 4683 (size_t)obj->size() * HeapWordSize, 4684 p2i(r->bottom()), 4685 r->rem_set()->occupied(), 4686 r->rem_set()->strong_code_roots_list_length(), 4687 next_bitmap->is_marked(r->bottom()), 4688 g1h->is_humongous_reclaim_candidate(region_idx), 4689 obj->is_typeArray() 4690 ); 4691 4692 G1ConcurrentMark* const cm = g1h->concurrent_mark(); 4693 cm->humongous_object_eagerly_reclaimed(r); 4694 assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj), 4695 "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s", 4696 region_idx, 4697 BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)), 4698 BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj))); 4699 _humongous_objects_reclaimed++; 4700 do { 4701 HeapRegion* next = g1h->next_region_in_humongous(r); 4702 _freed_bytes += r->used(); 4703 r->set_containing_set(NULL); 4704 _humongous_regions_reclaimed++; 4705 g1h->free_humongous_region(r, _free_region_list); 4706 r = next; 4707 } while (r != NULL); 4708 4709 return false; 4710 } 4711 4712 uint humongous_objects_reclaimed() { 4713 return _humongous_objects_reclaimed; 4714 } 4715 4716 uint humongous_regions_reclaimed() { 4717 return _humongous_regions_reclaimed; 4718 } 4719 4720 size_t bytes_freed() const { 4721 return _freed_bytes; 4722 } 4723 }; 4724 4725 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4726 assert_at_safepoint_on_vm_thread(); 4727 4728 if (!G1EagerReclaimHumongousObjects || 4729 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4730 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4731 return; 4732 } 4733 4734 double start_time = os::elapsedTime(); 4735 4736 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4737 4738 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4739 heap_region_iterate(&cl); 4740 4741 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4742 4743 G1HRPrinter* hrp = hr_printer(); 4744 if (hrp->is_active()) { 4745 FreeRegionListIterator iter(&local_cleanup_list); 4746 while (iter.more_available()) { 4747 HeapRegion* hr = iter.get_next(); 4748 hrp->cleanup(hr); 4749 } 4750 } 4751 4752 prepend_to_freelist(&local_cleanup_list); 4753 decrement_summary_bytes(cl.bytes_freed()); 4754 4755 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4756 cl.humongous_objects_reclaimed()); 4757 } 4758 4759 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4760 public: 4761 virtual bool do_heap_region(HeapRegion* r) { 4762 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4763 G1CollectedHeap::heap()->clear_in_cset(r); 4764 r->set_young_index_in_cset(-1); 4765 return false; 4766 } 4767 }; 4768 4769 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4770 G1AbandonCollectionSetClosure cl; 4771 collection_set->iterate(&cl); 4772 4773 collection_set->clear(); 4774 collection_set->stop_incremental_building(); 4775 } 4776 4777 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 4778 return _allocator->is_retained_old_region(hr); 4779 } 4780 4781 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 4782 _eden.add(hr); 4783 _g1_policy->set_region_eden(hr); 4784 } 4785 4786 #ifdef ASSERT 4787 4788 class NoYoungRegionsClosure: public HeapRegionClosure { 4789 private: 4790 bool _success; 4791 public: 4792 NoYoungRegionsClosure() : _success(true) { } 4793 bool do_heap_region(HeapRegion* r) { 4794 if (r->is_young()) { 4795 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 4796 p2i(r->bottom()), p2i(r->end())); 4797 _success = false; 4798 } 4799 return false; 4800 } 4801 bool success() { return _success; } 4802 }; 4803 4804 bool G1CollectedHeap::check_young_list_empty() { 4805 bool ret = (young_regions_count() == 0); 4806 4807 NoYoungRegionsClosure closure; 4808 heap_region_iterate(&closure); 4809 ret = ret && closure.success(); 4810 4811 return ret; 4812 } 4813 4814 #endif // ASSERT 4815 4816 class TearDownRegionSetsClosure : public HeapRegionClosure { 4817 private: 4818 HeapRegionSet *_old_set; 4819 4820 public: 4821 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 4822 4823 bool do_heap_region(HeapRegion* r) { 4824 if (r->is_old()) { 4825 _old_set->remove(r); 4826 } else if(r->is_young()) { 4827 r->uninstall_surv_rate_group(); 4828 } else { 4829 // We ignore free regions, we'll empty the free list afterwards. 4830 // We ignore humongous regions, we're not tearing down the 4831 // humongous regions set. 4832 assert(r->is_free() || r->is_humongous(), 4833 "it cannot be another type"); 4834 } 4835 return false; 4836 } 4837 4838 ~TearDownRegionSetsClosure() { 4839 assert(_old_set->is_empty(), "post-condition"); 4840 } 4841 }; 4842 4843 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 4844 assert_at_safepoint_on_vm_thread(); 4845 4846 if (!free_list_only) { 4847 TearDownRegionSetsClosure cl(&_old_set); 4848 heap_region_iterate(&cl); 4849 4850 // Note that emptying the _young_list is postponed and instead done as 4851 // the first step when rebuilding the regions sets again. The reason for 4852 // this is that during a full GC string deduplication needs to know if 4853 // a collected region was young or old when the full GC was initiated. 4854 } 4855 _hrm.remove_all_free_regions(); 4856 } 4857 4858 void G1CollectedHeap::increase_used(size_t bytes) { 4859 _summary_bytes_used += bytes; 4860 } 4861 4862 void G1CollectedHeap::decrease_used(size_t bytes) { 4863 assert(_summary_bytes_used >= bytes, 4864 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 4865 _summary_bytes_used, bytes); 4866 _summary_bytes_used -= bytes; 4867 } 4868 4869 void G1CollectedHeap::set_used(size_t bytes) { 4870 _summary_bytes_used = bytes; 4871 } 4872 4873 class RebuildRegionSetsClosure : public HeapRegionClosure { 4874 private: 4875 bool _free_list_only; 4876 HeapRegionSet* _old_set; 4877 HeapRegionManager* _hrm; 4878 size_t _total_used; 4879 4880 public: 4881 RebuildRegionSetsClosure(bool free_list_only, 4882 HeapRegionSet* old_set, HeapRegionManager* hrm) : 4883 _free_list_only(free_list_only), 4884 _old_set(old_set), _hrm(hrm), _total_used(0) { 4885 assert(_hrm->num_free_regions() == 0, "pre-condition"); 4886 if (!free_list_only) { 4887 assert(_old_set->is_empty(), "pre-condition"); 4888 } 4889 } 4890 4891 bool do_heap_region(HeapRegion* r) { 4892 // After full GC, no region should have a remembered set. 4893 r->rem_set()->clear(true); 4894 if (r->is_empty()) { 4895 // Add free regions to the free list 4896 r->set_free(); 4897 _hrm->insert_into_free_list(r); 4898 } else if (!_free_list_only) { 4899 4900 if (r->is_humongous()) { 4901 // We ignore humongous regions. We left the humongous set unchanged. 4902 } else { 4903 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 4904 // We now move all (non-humongous, non-old) regions to old gen, and register them as such. 4905 r->move_to_old(); 4906 _old_set->add(r); 4907 } 4908 _total_used += r->used(); 4909 } 4910 4911 return false; 4912 } 4913 4914 size_t total_used() { 4915 return _total_used; 4916 } 4917 }; 4918 4919 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 4920 assert_at_safepoint_on_vm_thread(); 4921 4922 if (!free_list_only) { 4923 _eden.clear(); 4924 _survivor.clear(); 4925 } 4926 4927 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 4928 heap_region_iterate(&cl); 4929 4930 if (!free_list_only) { 4931 set_used(cl.total_used()); 4932 if (_archive_allocator != NULL) { 4933 _archive_allocator->clear_used(); 4934 } 4935 } 4936 assert(used_unlocked() == recalculate_used(), 4937 "inconsistent used_unlocked(), " 4938 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 4939 used_unlocked(), recalculate_used()); 4940 } 4941 4942 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 4943 HeapRegion* hr = heap_region_containing(p); 4944 return hr->is_in(p); 4945 } 4946 4947 // Methods for the mutator alloc region 4948 4949 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 4950 bool force) { 4951 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4952 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 4953 if (force || should_allocate) { 4954 HeapRegion* new_alloc_region = new_region(word_size, 4955 false /* is_old */, 4956 false /* do_expand */); 4957 if (new_alloc_region != NULL) { 4958 set_region_short_lived_locked(new_alloc_region); 4959 _hr_printer.alloc(new_alloc_region, !should_allocate); 4960 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 4961 _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region); 4962 return new_alloc_region; 4963 } 4964 } 4965 return NULL; 4966 } 4967 4968 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 4969 size_t allocated_bytes) { 4970 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4971 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 4972 4973 collection_set()->add_eden_region(alloc_region); 4974 increase_used(allocated_bytes); 4975 _hr_printer.retire(alloc_region); 4976 // We update the eden sizes here, when the region is retired, 4977 // instead of when it's allocated, since this is the point that its 4978 // used space has been recored in _summary_bytes_used. 4979 g1mm()->update_eden_size(); 4980 } 4981 4982 // Methods for the GC alloc regions 4983 4984 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 4985 if (dest.is_old()) { 4986 return true; 4987 } else { 4988 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 4989 } 4990 } 4991 4992 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 4993 assert(FreeList_lock->owned_by_self(), "pre-condition"); 4994 4995 if (!has_more_regions(dest)) { 4996 return NULL; 4997 } 4998 4999 const bool is_survivor = dest.is_young(); 5000 5001 HeapRegion* new_alloc_region = new_region(word_size, 5002 !is_survivor, 5003 true /* do_expand */); 5004 if (new_alloc_region != NULL) { 5005 if (is_survivor) { 5006 new_alloc_region->set_survivor(); 5007 _survivor.add(new_alloc_region); 5008 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5009 } else { 5010 new_alloc_region->set_old(); 5011 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5012 } 5013 _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region); 5014 _hr_printer.alloc(new_alloc_region); 5015 bool during_im = collector_state()->in_initial_mark_gc(); 5016 new_alloc_region->note_start_of_copying(during_im); 5017 return new_alloc_region; 5018 } 5019 return NULL; 5020 } 5021 5022 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5023 size_t allocated_bytes, 5024 InCSetState dest) { 5025 bool during_im = collector_state()->in_initial_mark_gc(); 5026 alloc_region->note_end_of_copying(during_im); 5027 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5028 if (dest.is_old()) { 5029 _old_set.add(alloc_region); 5030 } 5031 _hr_printer.retire(alloc_region); 5032 } 5033 5034 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5035 bool expanded = false; 5036 uint index = _hrm.find_highest_free(&expanded); 5037 5038 if (index != G1_NO_HRM_INDEX) { 5039 if (expanded) { 5040 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5041 HeapRegion::GrainWords * HeapWordSize); 5042 } 5043 _hrm.allocate_free_regions_starting_at(index, 1); 5044 return region_at(index); 5045 } 5046 return NULL; 5047 } 5048 5049 // Optimized nmethod scanning 5050 5051 class RegisterNMethodOopClosure: public OopClosure { 5052 G1CollectedHeap* _g1h; 5053 nmethod* _nm; 5054 5055 template <class T> void do_oop_work(T* p) { 5056 T heap_oop = RawAccess<>::oop_load(p); 5057 if (!CompressedOops::is_null(heap_oop)) { 5058 oop obj = CompressedOops::decode_not_null(heap_oop); 5059 HeapRegion* hr = _g1h->heap_region_containing(obj); 5060 assert(!hr->is_continues_humongous(), 5061 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5062 " starting at " HR_FORMAT, 5063 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5064 5065 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5066 hr->add_strong_code_root_locked(_nm); 5067 } 5068 } 5069 5070 public: 5071 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5072 _g1h(g1h), _nm(nm) {} 5073 5074 void do_oop(oop* p) { do_oop_work(p); } 5075 void do_oop(narrowOop* p) { do_oop_work(p); } 5076 }; 5077 5078 class UnregisterNMethodOopClosure: public OopClosure { 5079 G1CollectedHeap* _g1h; 5080 nmethod* _nm; 5081 5082 template <class T> void do_oop_work(T* p) { 5083 T heap_oop = RawAccess<>::oop_load(p); 5084 if (!CompressedOops::is_null(heap_oop)) { 5085 oop obj = CompressedOops::decode_not_null(heap_oop); 5086 HeapRegion* hr = _g1h->heap_region_containing(obj); 5087 assert(!hr->is_continues_humongous(), 5088 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5089 " starting at " HR_FORMAT, 5090 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5091 5092 hr->remove_strong_code_root(_nm); 5093 } 5094 } 5095 5096 public: 5097 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5098 _g1h(g1h), _nm(nm) {} 5099 5100 void do_oop(oop* p) { do_oop_work(p); } 5101 void do_oop(narrowOop* p) { do_oop_work(p); } 5102 }; 5103 5104 // Returns true if the reference points to an object that 5105 // can move in an incremental collection. 5106 bool G1CollectedHeap::is_scavengable(oop obj) { 5107 HeapRegion* hr = heap_region_containing(obj); 5108 return !hr->is_pinned(); 5109 } 5110 5111 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5112 guarantee(nm != NULL, "sanity"); 5113 RegisterNMethodOopClosure reg_cl(this, nm); 5114 nm->oops_do(®_cl); 5115 } 5116 5117 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5118 guarantee(nm != NULL, "sanity"); 5119 UnregisterNMethodOopClosure reg_cl(this, nm); 5120 nm->oops_do(®_cl, true); 5121 } 5122 5123 void G1CollectedHeap::purge_code_root_memory() { 5124 double purge_start = os::elapsedTime(); 5125 G1CodeRootSet::purge(); 5126 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5127 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5128 } 5129 5130 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5131 G1CollectedHeap* _g1h; 5132 5133 public: 5134 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5135 _g1h(g1h) {} 5136 5137 void do_code_blob(CodeBlob* cb) { 5138 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5139 if (nm == NULL) { 5140 return; 5141 } 5142 5143 if (ScavengeRootsInCode) { 5144 _g1h->register_nmethod(nm); 5145 } 5146 } 5147 }; 5148 5149 void G1CollectedHeap::rebuild_strong_code_roots() { 5150 RebuildStrongCodeRootClosure blob_cl(this); 5151 CodeCache::blobs_do(&blob_cl); 5152 } 5153 5154 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() { 5155 GrowableArray<GCMemoryManager*> memory_managers(2); 5156 memory_managers.append(&_memory_manager); 5157 memory_managers.append(&_full_gc_memory_manager); 5158 return memory_managers; 5159 } 5160 5161 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() { 5162 GrowableArray<MemoryPool*> memory_pools(3); 5163 memory_pools.append(_eden_pool); 5164 memory_pools.append(_survivor_pool); 5165 memory_pools.append(_old_pool); 5166 return memory_pools; 5167 }