1 /* 2 * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/metadataOnStackMark.hpp" 27 #include "classfile/stringTable.hpp" 28 #include "classfile/symbolTable.hpp" 29 #include "code/codeCache.hpp" 30 #include "code/icBuffer.hpp" 31 #include "gc/g1/g1Allocator.inline.hpp" 32 #include "gc/g1/g1BarrierSet.hpp" 33 #include "gc/g1/g1CollectedHeap.inline.hpp" 34 #include "gc/g1/g1CollectionSet.hpp" 35 #include "gc/g1/g1CollectorPolicy.hpp" 36 #include "gc/g1/g1CollectorState.hpp" 37 #include "gc/g1/g1ConcurrentRefine.hpp" 38 #include "gc/g1/g1ConcurrentRefineThread.hpp" 39 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp" 40 #include "gc/g1/g1EvacStats.inline.hpp" 41 #include "gc/g1/g1FullCollector.hpp" 42 #include "gc/g1/g1GCPhaseTimes.hpp" 43 #include "gc/g1/g1HeapSizingPolicy.hpp" 44 #include "gc/g1/g1HeapTransition.hpp" 45 #include "gc/g1/g1HeapVerifier.hpp" 46 #include "gc/g1/g1HotCardCache.hpp" 47 #include "gc/g1/g1MemoryPool.hpp" 48 #include "gc/g1/g1OopClosures.inline.hpp" 49 #include "gc/g1/g1ParScanThreadState.inline.hpp" 50 #include "gc/g1/g1Policy.hpp" 51 #include "gc/g1/g1RegionToSpaceMapper.hpp" 52 #include "gc/g1/g1RemSet.hpp" 53 #include "gc/g1/g1RootClosures.hpp" 54 #include "gc/g1/g1RootProcessor.hpp" 55 #include "gc/g1/g1StringDedup.hpp" 56 #include "gc/g1/g1ThreadLocalData.hpp" 57 #include "gc/g1/g1YCTypes.hpp" 58 #include "gc/g1/g1YoungRemSetSamplingThread.hpp" 59 #include "gc/g1/heapRegion.inline.hpp" 60 #include "gc/g1/heapRegionRemSet.hpp" 61 #include "gc/g1/heapRegionSet.inline.hpp" 62 #include "gc/g1/vm_operations_g1.hpp" 63 #include "gc/shared/adaptiveSizePolicy.hpp" 64 #include "gc/shared/gcHeapSummary.hpp" 65 #include "gc/shared/gcId.hpp" 66 #include "gc/shared/gcLocker.hpp" 67 #include "gc/shared/gcTimer.hpp" 68 #include "gc/shared/gcTrace.hpp" 69 #include "gc/shared/gcTraceTime.inline.hpp" 70 #include "gc/shared/generationSpec.hpp" 71 #include "gc/shared/isGCActiveMark.hpp" 72 #include "gc/shared/oopStorageParState.hpp" 73 #include "gc/shared/preservedMarks.inline.hpp" 74 #include "gc/shared/suspendibleThreadSet.hpp" 75 #include "gc/shared/referenceProcessor.inline.hpp" 76 #include "gc/shared/taskqueue.inline.hpp" 77 #include "gc/shared/weakProcessor.hpp" 78 #include "logging/log.hpp" 79 #include "memory/allocation.hpp" 80 #include "memory/iterator.hpp" 81 #include "memory/metaspaceShared.hpp" 82 #include "memory/resourceArea.hpp" 83 #include "oops/access.inline.hpp" 84 #include "oops/compressedOops.inline.hpp" 85 #include "oops/oop.inline.hpp" 86 #include "prims/resolvedMethodTable.hpp" 87 #include "runtime/atomic.hpp" 88 #include "runtime/flags/flagSetting.hpp" 89 #include "runtime/handles.inline.hpp" 90 #include "runtime/init.hpp" 91 #include "runtime/orderAccess.hpp" 92 #include "runtime/threadSMR.hpp" 93 #include "runtime/vmThread.hpp" 94 #include "utilities/align.hpp" 95 #include "utilities/globalDefinitions.hpp" 96 #include "utilities/stack.inline.hpp" 97 98 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 99 100 // INVARIANTS/NOTES 101 // 102 // All allocation activity covered by the G1CollectedHeap interface is 103 // serialized by acquiring the HeapLock. This happens in mem_allocate 104 // and allocate_new_tlab, which are the "entry" points to the 105 // allocation code from the rest of the JVM. (Note that this does not 106 // apply to TLAB allocation, which is not part of this interface: it 107 // is done by clients of this interface.) 108 109 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 110 private: 111 size_t _num_dirtied; 112 G1CollectedHeap* _g1h; 113 G1CardTable* _g1_ct; 114 115 HeapRegion* region_for_card(jbyte* card_ptr) const { 116 return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr)); 117 } 118 119 bool will_become_free(HeapRegion* hr) const { 120 // A region will be freed by free_collection_set if the region is in the 121 // collection set and has not had an evacuation failure. 122 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 123 } 124 125 public: 126 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 127 _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { } 128 129 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 130 HeapRegion* hr = region_for_card(card_ptr); 131 132 // Should only dirty cards in regions that won't be freed. 133 if (!will_become_free(hr)) { 134 *card_ptr = G1CardTable::dirty_card_val(); 135 _num_dirtied++; 136 } 137 138 return true; 139 } 140 141 size_t num_dirtied() const { return _num_dirtied; } 142 }; 143 144 145 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 146 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 147 } 148 149 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 150 // The from card cache is not the memory that is actually committed. So we cannot 151 // take advantage of the zero_filled parameter. 152 reset_from_card_cache(start_idx, num_regions); 153 } 154 155 156 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 157 MemRegion mr) { 158 return new HeapRegion(hrs_index, bot(), mr); 159 } 160 161 // Private methods. 162 163 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 164 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 165 "the only time we use this to allocate a humongous region is " 166 "when we are allocating a single humongous region"); 167 168 HeapRegion* res = _hrm.allocate_free_region(is_old); 169 170 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 171 // Currently, only attempts to allocate GC alloc regions set 172 // do_expand to true. So, we should only reach here during a 173 // safepoint. If this assumption changes we might have to 174 // reconsider the use of _expand_heap_after_alloc_failure. 175 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 176 177 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 178 word_size * HeapWordSize); 179 180 if (expand(word_size * HeapWordSize)) { 181 // Given that expand() succeeded in expanding the heap, and we 182 // always expand the heap by an amount aligned to the heap 183 // region size, the free list should in theory not be empty. 184 // In either case allocate_free_region() will check for NULL. 185 res = _hrm.allocate_free_region(is_old); 186 } else { 187 _expand_heap_after_alloc_failure = false; 188 } 189 } 190 return res; 191 } 192 193 HeapWord* 194 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 195 uint num_regions, 196 size_t word_size) { 197 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 198 assert(is_humongous(word_size), "word_size should be humongous"); 199 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 200 201 // Index of last region in the series. 202 uint last = first + num_regions - 1; 203 204 // We need to initialize the region(s) we just discovered. This is 205 // a bit tricky given that it can happen concurrently with 206 // refinement threads refining cards on these regions and 207 // potentially wanting to refine the BOT as they are scanning 208 // those cards (this can happen shortly after a cleanup; see CR 209 // 6991377). So we have to set up the region(s) carefully and in 210 // a specific order. 211 212 // The word size sum of all the regions we will allocate. 213 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 214 assert(word_size <= word_size_sum, "sanity"); 215 216 // This will be the "starts humongous" region. 217 HeapRegion* first_hr = region_at(first); 218 // The header of the new object will be placed at the bottom of 219 // the first region. 220 HeapWord* new_obj = first_hr->bottom(); 221 // This will be the new top of the new object. 222 HeapWord* obj_top = new_obj + word_size; 223 224 // First, we need to zero the header of the space that we will be 225 // allocating. When we update top further down, some refinement 226 // threads might try to scan the region. By zeroing the header we 227 // ensure that any thread that will try to scan the region will 228 // come across the zero klass word and bail out. 229 // 230 // NOTE: It would not have been correct to have used 231 // CollectedHeap::fill_with_object() and make the space look like 232 // an int array. The thread that is doing the allocation will 233 // later update the object header to a potentially different array 234 // type and, for a very short period of time, the klass and length 235 // fields will be inconsistent. This could cause a refinement 236 // thread to calculate the object size incorrectly. 237 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 238 239 // Next, pad out the unused tail of the last region with filler 240 // objects, for improved usage accounting. 241 // How many words we use for filler objects. 242 size_t word_fill_size = word_size_sum - word_size; 243 244 // How many words memory we "waste" which cannot hold a filler object. 245 size_t words_not_fillable = 0; 246 247 if (word_fill_size >= min_fill_size()) { 248 fill_with_objects(obj_top, word_fill_size); 249 } else if (word_fill_size > 0) { 250 // We have space to fill, but we cannot fit an object there. 251 words_not_fillable = word_fill_size; 252 word_fill_size = 0; 253 } 254 255 // We will set up the first region as "starts humongous". This 256 // will also update the BOT covering all the regions to reflect 257 // that there is a single object that starts at the bottom of the 258 // first region. 259 first_hr->set_starts_humongous(obj_top, word_fill_size); 260 _g1_policy->remset_tracker()->update_at_allocate(first_hr); 261 // Then, if there are any, we will set up the "continues 262 // humongous" regions. 263 HeapRegion* hr = NULL; 264 for (uint i = first + 1; i <= last; ++i) { 265 hr = region_at(i); 266 hr->set_continues_humongous(first_hr); 267 _g1_policy->remset_tracker()->update_at_allocate(hr); 268 } 269 270 // Up to this point no concurrent thread would have been able to 271 // do any scanning on any region in this series. All the top 272 // fields still point to bottom, so the intersection between 273 // [bottom,top] and [card_start,card_end] will be empty. Before we 274 // update the top fields, we'll do a storestore to make sure that 275 // no thread sees the update to top before the zeroing of the 276 // object header and the BOT initialization. 277 OrderAccess::storestore(); 278 279 // Now, we will update the top fields of the "continues humongous" 280 // regions except the last one. 281 for (uint i = first; i < last; ++i) { 282 hr = region_at(i); 283 hr->set_top(hr->end()); 284 } 285 286 hr = region_at(last); 287 // If we cannot fit a filler object, we must set top to the end 288 // of the humongous object, otherwise we cannot iterate the heap 289 // and the BOT will not be complete. 290 hr->set_top(hr->end() - words_not_fillable); 291 292 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 293 "obj_top should be in last region"); 294 295 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 296 297 assert(words_not_fillable == 0 || 298 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 299 "Miscalculation in humongous allocation"); 300 301 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 302 303 for (uint i = first; i <= last; ++i) { 304 hr = region_at(i); 305 _humongous_set.add(hr); 306 _hr_printer.alloc(hr); 307 } 308 309 return new_obj; 310 } 311 312 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 313 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 314 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 315 } 316 317 // If could fit into free regions w/o expansion, try. 318 // Otherwise, if can expand, do so. 319 // Otherwise, if using ex regions might help, try with ex given back. 320 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) { 321 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 322 323 _verifier->verify_region_sets_optional(); 324 325 uint first = G1_NO_HRM_INDEX; 326 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 327 328 if (obj_regions == 1) { 329 // Only one region to allocate, try to use a fast path by directly allocating 330 // from the free lists. Do not try to expand here, we will potentially do that 331 // later. 332 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 333 if (hr != NULL) { 334 first = hr->hrm_index(); 335 } 336 } else { 337 // Policy: Try only empty regions (i.e. already committed first). Maybe we 338 // are lucky enough to find some. 339 first = _hrm.find_contiguous_only_empty(obj_regions); 340 if (first != G1_NO_HRM_INDEX) { 341 _hrm.allocate_free_regions_starting_at(first, obj_regions); 342 } 343 } 344 345 if (first == G1_NO_HRM_INDEX) { 346 // Policy: We could not find enough regions for the humongous object in the 347 // free list. Look through the heap to find a mix of free and uncommitted regions. 348 // If so, try expansion. 349 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 350 if (first != G1_NO_HRM_INDEX) { 351 // We found something. Make sure these regions are committed, i.e. expand 352 // the heap. Alternatively we could do a defragmentation GC. 353 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 354 word_size * HeapWordSize); 355 356 _hrm.expand_at(first, obj_regions, workers()); 357 g1_policy()->record_new_heap_size(num_regions()); 358 359 #ifdef ASSERT 360 for (uint i = first; i < first + obj_regions; ++i) { 361 HeapRegion* hr = region_at(i); 362 assert(hr->is_free(), "sanity"); 363 assert(hr->is_empty(), "sanity"); 364 assert(is_on_master_free_list(hr), "sanity"); 365 } 366 #endif 367 _hrm.allocate_free_regions_starting_at(first, obj_regions); 368 } else { 369 // Policy: Potentially trigger a defragmentation GC. 370 } 371 } 372 373 HeapWord* result = NULL; 374 if (first != G1_NO_HRM_INDEX) { 375 result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size); 376 assert(result != NULL, "it should always return a valid result"); 377 378 // A successful humongous object allocation changes the used space 379 // information of the old generation so we need to recalculate the 380 // sizes and update the jstat counters here. 381 g1mm()->update_sizes(); 382 } 383 384 _verifier->verify_region_sets_optional(); 385 386 return result; 387 } 388 389 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size, 390 size_t requested_size, 391 size_t* actual_size) { 392 assert_heap_not_locked_and_not_at_safepoint(); 393 assert(!is_humongous(requested_size), "we do not allow humongous TLABs"); 394 395 return attempt_allocation(min_size, requested_size, actual_size); 396 } 397 398 HeapWord* 399 G1CollectedHeap::mem_allocate(size_t word_size, 400 bool* gc_overhead_limit_was_exceeded) { 401 assert_heap_not_locked_and_not_at_safepoint(); 402 403 if (is_humongous(word_size)) { 404 return attempt_allocation_humongous(word_size); 405 } 406 size_t dummy = 0; 407 return attempt_allocation(word_size, word_size, &dummy); 408 } 409 410 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) { 411 ResourceMark rm; // For retrieving the thread names in log messages. 412 413 // Make sure you read the note in attempt_allocation_humongous(). 414 415 assert_heap_not_locked_and_not_at_safepoint(); 416 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 417 "be called for humongous allocation requests"); 418 419 // We should only get here after the first-level allocation attempt 420 // (attempt_allocation()) failed to allocate. 421 422 // We will loop until a) we manage to successfully perform the 423 // allocation or b) we successfully schedule a collection which 424 // fails to perform the allocation. b) is the only case when we'll 425 // return NULL. 426 HeapWord* result = NULL; 427 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 428 bool should_try_gc; 429 uint gc_count_before; 430 431 { 432 MutexLockerEx x(Heap_lock); 433 result = _allocator->attempt_allocation_locked(word_size); 434 if (result != NULL) { 435 return result; 436 } 437 438 // If the GCLocker is active and we are bound for a GC, try expanding young gen. 439 // This is different to when only GCLocker::needs_gc() is set: try to avoid 440 // waiting because the GCLocker is active to not wait too long. 441 if (GCLocker::is_active_and_needs_gc() && g1_policy()->can_expand_young_list()) { 442 // No need for an ergo message here, can_expand_young_list() does this when 443 // it returns true. 444 result = _allocator->attempt_allocation_force(word_size); 445 if (result != NULL) { 446 return result; 447 } 448 } 449 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 450 // the GCLocker initiated GC has been performed and then retry. This includes 451 // the case when the GC Locker is not active but has not been performed. 452 should_try_gc = !GCLocker::needs_gc(); 453 // Read the GC count while still holding the Heap_lock. 454 gc_count_before = total_collections(); 455 } 456 457 if (should_try_gc) { 458 bool succeeded; 459 result = do_collection_pause(word_size, gc_count_before, &succeeded, 460 GCCause::_g1_inc_collection_pause); 461 if (result != NULL) { 462 assert(succeeded, "only way to get back a non-NULL result"); 463 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 464 Thread::current()->name(), p2i(result)); 465 return result; 466 } 467 468 if (succeeded) { 469 // We successfully scheduled a collection which failed to allocate. No 470 // point in trying to allocate further. We'll just return NULL. 471 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 472 SIZE_FORMAT " words", Thread::current()->name(), word_size); 473 return NULL; 474 } 475 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words", 476 Thread::current()->name(), word_size); 477 } else { 478 // Failed to schedule a collection. 479 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 480 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 481 SIZE_FORMAT " words", Thread::current()->name(), word_size); 482 return NULL; 483 } 484 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 485 // The GCLocker is either active or the GCLocker initiated 486 // GC has not yet been performed. Stall until it is and 487 // then retry the allocation. 488 GCLocker::stall_until_clear(); 489 gclocker_retry_count += 1; 490 } 491 492 // We can reach here if we were unsuccessful in scheduling a 493 // collection (because another thread beat us to it) or if we were 494 // stalled due to the GC locker. In either can we should retry the 495 // allocation attempt in case another thread successfully 496 // performed a collection and reclaimed enough space. We do the 497 // first attempt (without holding the Heap_lock) here and the 498 // follow-on attempt will be at the start of the next loop 499 // iteration (after taking the Heap_lock). 500 size_t dummy = 0; 501 result = _allocator->attempt_allocation(word_size, word_size, &dummy); 502 if (result != NULL) { 503 return result; 504 } 505 506 // Give a warning if we seem to be looping forever. 507 if ((QueuedAllocationWarningCount > 0) && 508 (try_count % QueuedAllocationWarningCount == 0)) { 509 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 510 Thread::current()->name(), try_count, word_size); 511 } 512 } 513 514 ShouldNotReachHere(); 515 return NULL; 516 } 517 518 void G1CollectedHeap::begin_archive_alloc_range(bool open) { 519 assert_at_safepoint_on_vm_thread(); 520 if (_archive_allocator == NULL) { 521 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open); 522 } 523 } 524 525 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 526 // Allocations in archive regions cannot be of a size that would be considered 527 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 528 // may be different at archive-restore time. 529 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 530 } 531 532 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 533 assert_at_safepoint_on_vm_thread(); 534 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 535 if (is_archive_alloc_too_large(word_size)) { 536 return NULL; 537 } 538 return _archive_allocator->archive_mem_allocate(word_size); 539 } 540 541 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 542 size_t end_alignment_in_bytes) { 543 assert_at_safepoint_on_vm_thread(); 544 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 545 546 // Call complete_archive to do the real work, filling in the MemRegion 547 // array with the archive regions. 548 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 549 delete _archive_allocator; 550 _archive_allocator = NULL; 551 } 552 553 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 554 assert(ranges != NULL, "MemRegion array NULL"); 555 assert(count != 0, "No MemRegions provided"); 556 MemRegion reserved = _hrm.reserved(); 557 for (size_t i = 0; i < count; i++) { 558 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 559 return false; 560 } 561 } 562 return true; 563 } 564 565 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, 566 size_t count, 567 bool open) { 568 assert(!is_init_completed(), "Expect to be called at JVM init time"); 569 assert(ranges != NULL, "MemRegion array NULL"); 570 assert(count != 0, "No MemRegions provided"); 571 MutexLockerEx x(Heap_lock); 572 573 MemRegion reserved = _hrm.reserved(); 574 HeapWord* prev_last_addr = NULL; 575 HeapRegion* prev_last_region = NULL; 576 577 // Temporarily disable pretouching of heap pages. This interface is used 578 // when mmap'ing archived heap data in, so pre-touching is wasted. 579 FlagSetting fs(AlwaysPreTouch, false); 580 581 // Enable archive object checking used by G1MarkSweep. We have to let it know 582 // about each archive range, so that objects in those ranges aren't marked. 583 G1ArchiveAllocator::enable_archive_object_check(); 584 585 // For each specified MemRegion range, allocate the corresponding G1 586 // regions and mark them as archive regions. We expect the ranges 587 // in ascending starting address order, without overlap. 588 for (size_t i = 0; i < count; i++) { 589 MemRegion curr_range = ranges[i]; 590 HeapWord* start_address = curr_range.start(); 591 size_t word_size = curr_range.word_size(); 592 HeapWord* last_address = curr_range.last(); 593 size_t commits = 0; 594 595 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 596 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 597 p2i(start_address), p2i(last_address)); 598 guarantee(start_address > prev_last_addr, 599 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 600 p2i(start_address), p2i(prev_last_addr)); 601 prev_last_addr = last_address; 602 603 // Check for ranges that start in the same G1 region in which the previous 604 // range ended, and adjust the start address so we don't try to allocate 605 // the same region again. If the current range is entirely within that 606 // region, skip it, just adjusting the recorded top. 607 HeapRegion* start_region = _hrm.addr_to_region(start_address); 608 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 609 start_address = start_region->end(); 610 if (start_address > last_address) { 611 increase_used(word_size * HeapWordSize); 612 start_region->set_top(last_address + 1); 613 continue; 614 } 615 start_region->set_top(start_address); 616 curr_range = MemRegion(start_address, last_address + 1); 617 start_region = _hrm.addr_to_region(start_address); 618 } 619 620 // Perform the actual region allocation, exiting if it fails. 621 // Then note how much new space we have allocated. 622 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 623 return false; 624 } 625 increase_used(word_size * HeapWordSize); 626 if (commits != 0) { 627 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 628 HeapRegion::GrainWords * HeapWordSize * commits); 629 630 } 631 632 // Mark each G1 region touched by the range as archive, add it to 633 // the old set, and set top. 634 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 635 HeapRegion* last_region = _hrm.addr_to_region(last_address); 636 prev_last_region = last_region; 637 638 while (curr_region != NULL) { 639 assert(curr_region->is_empty() && !curr_region->is_pinned(), 640 "Region already in use (index %u)", curr_region->hrm_index()); 641 if (open) { 642 curr_region->set_open_archive(); 643 } else { 644 curr_region->set_closed_archive(); 645 } 646 _hr_printer.alloc(curr_region); 647 _old_set.add(curr_region); 648 HeapWord* top; 649 HeapRegion* next_region; 650 if (curr_region != last_region) { 651 top = curr_region->end(); 652 next_region = _hrm.next_region_in_heap(curr_region); 653 } else { 654 top = last_address + 1; 655 next_region = NULL; 656 } 657 curr_region->set_top(top); 658 curr_region->set_first_dead(top); 659 curr_region->set_end_of_live(top); 660 curr_region = next_region; 661 } 662 663 // Notify mark-sweep of the archive 664 G1ArchiveAllocator::set_range_archive(curr_range, open); 665 } 666 return true; 667 } 668 669 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 670 assert(!is_init_completed(), "Expect to be called at JVM init time"); 671 assert(ranges != NULL, "MemRegion array NULL"); 672 assert(count != 0, "No MemRegions provided"); 673 MemRegion reserved = _hrm.reserved(); 674 HeapWord *prev_last_addr = NULL; 675 HeapRegion* prev_last_region = NULL; 676 677 // For each MemRegion, create filler objects, if needed, in the G1 regions 678 // that contain the address range. The address range actually within the 679 // MemRegion will not be modified. That is assumed to have been initialized 680 // elsewhere, probably via an mmap of archived heap data. 681 MutexLockerEx x(Heap_lock); 682 for (size_t i = 0; i < count; i++) { 683 HeapWord* start_address = ranges[i].start(); 684 HeapWord* last_address = ranges[i].last(); 685 686 assert(reserved.contains(start_address) && reserved.contains(last_address), 687 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 688 p2i(start_address), p2i(last_address)); 689 assert(start_address > prev_last_addr, 690 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 691 p2i(start_address), p2i(prev_last_addr)); 692 693 HeapRegion* start_region = _hrm.addr_to_region(start_address); 694 HeapRegion* last_region = _hrm.addr_to_region(last_address); 695 HeapWord* bottom_address = start_region->bottom(); 696 697 // Check for a range beginning in the same region in which the 698 // previous one ended. 699 if (start_region == prev_last_region) { 700 bottom_address = prev_last_addr + 1; 701 } 702 703 // Verify that the regions were all marked as archive regions by 704 // alloc_archive_regions. 705 HeapRegion* curr_region = start_region; 706 while (curr_region != NULL) { 707 guarantee(curr_region->is_archive(), 708 "Expected archive region at index %u", curr_region->hrm_index()); 709 if (curr_region != last_region) { 710 curr_region = _hrm.next_region_in_heap(curr_region); 711 } else { 712 curr_region = NULL; 713 } 714 } 715 716 prev_last_addr = last_address; 717 prev_last_region = last_region; 718 719 // Fill the memory below the allocated range with dummy object(s), 720 // if the region bottom does not match the range start, or if the previous 721 // range ended within the same G1 region, and there is a gap. 722 if (start_address != bottom_address) { 723 size_t fill_size = pointer_delta(start_address, bottom_address); 724 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 725 increase_used(fill_size * HeapWordSize); 726 } 727 } 728 } 729 730 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size, 731 size_t desired_word_size, 732 size_t* actual_word_size) { 733 assert_heap_not_locked_and_not_at_safepoint(); 734 assert(!is_humongous(desired_word_size), "attempt_allocation() should not " 735 "be called for humongous allocation requests"); 736 737 HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size); 738 739 if (result == NULL) { 740 *actual_word_size = desired_word_size; 741 result = attempt_allocation_slow(desired_word_size); 742 } 743 744 assert_heap_not_locked(); 745 if (result != NULL) { 746 assert(*actual_word_size != 0, "Actual size must have been set here"); 747 dirty_young_block(result, *actual_word_size); 748 } else { 749 *actual_word_size = 0; 750 } 751 752 return result; 753 } 754 755 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 756 assert(!is_init_completed(), "Expect to be called at JVM init time"); 757 assert(ranges != NULL, "MemRegion array NULL"); 758 assert(count != 0, "No MemRegions provided"); 759 MemRegion reserved = _hrm.reserved(); 760 HeapWord* prev_last_addr = NULL; 761 HeapRegion* prev_last_region = NULL; 762 size_t size_used = 0; 763 size_t uncommitted_regions = 0; 764 765 // For each Memregion, free the G1 regions that constitute it, and 766 // notify mark-sweep that the range is no longer to be considered 'archive.' 767 MutexLockerEx x(Heap_lock); 768 for (size_t i = 0; i < count; i++) { 769 HeapWord* start_address = ranges[i].start(); 770 HeapWord* last_address = ranges[i].last(); 771 772 assert(reserved.contains(start_address) && reserved.contains(last_address), 773 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 774 p2i(start_address), p2i(last_address)); 775 assert(start_address > prev_last_addr, 776 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 777 p2i(start_address), p2i(prev_last_addr)); 778 size_used += ranges[i].byte_size(); 779 prev_last_addr = last_address; 780 781 HeapRegion* start_region = _hrm.addr_to_region(start_address); 782 HeapRegion* last_region = _hrm.addr_to_region(last_address); 783 784 // Check for ranges that start in the same G1 region in which the previous 785 // range ended, and adjust the start address so we don't try to free 786 // the same region again. If the current range is entirely within that 787 // region, skip it. 788 if (start_region == prev_last_region) { 789 start_address = start_region->end(); 790 if (start_address > last_address) { 791 continue; 792 } 793 start_region = _hrm.addr_to_region(start_address); 794 } 795 prev_last_region = last_region; 796 797 // After verifying that each region was marked as an archive region by 798 // alloc_archive_regions, set it free and empty and uncommit it. 799 HeapRegion* curr_region = start_region; 800 while (curr_region != NULL) { 801 guarantee(curr_region->is_archive(), 802 "Expected archive region at index %u", curr_region->hrm_index()); 803 uint curr_index = curr_region->hrm_index(); 804 _old_set.remove(curr_region); 805 curr_region->set_free(); 806 curr_region->set_top(curr_region->bottom()); 807 if (curr_region != last_region) { 808 curr_region = _hrm.next_region_in_heap(curr_region); 809 } else { 810 curr_region = NULL; 811 } 812 _hrm.shrink_at(curr_index, 1); 813 uncommitted_regions++; 814 } 815 816 // Notify mark-sweep that this is no longer an archive range. 817 G1ArchiveAllocator::set_range_archive(ranges[i], false); 818 } 819 820 if (uncommitted_regions != 0) { 821 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 822 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 823 } 824 decrease_used(size_used); 825 } 826 827 oop G1CollectedHeap::materialize_archived_object(oop obj) { 828 assert(obj != NULL, "archived obj is NULL"); 829 assert(MetaspaceShared::is_archive_object(obj), "must be archived object"); 830 831 // Loading an archived object makes it strongly reachable. If it is 832 // loaded during concurrent marking, it must be enqueued to the SATB 833 // queue, shading the previously white object gray. 834 G1BarrierSet::enqueue(obj); 835 836 return obj; 837 } 838 839 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) { 840 ResourceMark rm; // For retrieving the thread names in log messages. 841 842 // The structure of this method has a lot of similarities to 843 // attempt_allocation_slow(). The reason these two were not merged 844 // into a single one is that such a method would require several "if 845 // allocation is not humongous do this, otherwise do that" 846 // conditional paths which would obscure its flow. In fact, an early 847 // version of this code did use a unified method which was harder to 848 // follow and, as a result, it had subtle bugs that were hard to 849 // track down. So keeping these two methods separate allows each to 850 // be more readable. It will be good to keep these two in sync as 851 // much as possible. 852 853 assert_heap_not_locked_and_not_at_safepoint(); 854 assert(is_humongous(word_size), "attempt_allocation_humongous() " 855 "should only be called for humongous allocations"); 856 857 // Humongous objects can exhaust the heap quickly, so we should check if we 858 // need to start a marking cycle at each humongous object allocation. We do 859 // the check before we do the actual allocation. The reason for doing it 860 // before the allocation is that we avoid having to keep track of the newly 861 // allocated memory while we do a GC. 862 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 863 word_size)) { 864 collect(GCCause::_g1_humongous_allocation); 865 } 866 867 // We will loop until a) we manage to successfully perform the 868 // allocation or b) we successfully schedule a collection which 869 // fails to perform the allocation. b) is the only case when we'll 870 // return NULL. 871 HeapWord* result = NULL; 872 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 873 bool should_try_gc; 874 uint gc_count_before; 875 876 877 { 878 MutexLockerEx x(Heap_lock); 879 880 // Given that humongous objects are not allocated in young 881 // regions, we'll first try to do the allocation without doing a 882 // collection hoping that there's enough space in the heap. 883 result = humongous_obj_allocate(word_size); 884 if (result != NULL) { 885 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 886 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 887 return result; 888 } 889 890 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until 891 // the GCLocker initiated GC has been performed and then retry. This includes 892 // the case when the GC Locker is not active but has not been performed. 893 should_try_gc = !GCLocker::needs_gc(); 894 // Read the GC count while still holding the Heap_lock. 895 gc_count_before = total_collections(); 896 } 897 898 if (should_try_gc) { 899 bool succeeded; 900 result = do_collection_pause(word_size, gc_count_before, &succeeded, 901 GCCause::_g1_humongous_allocation); 902 if (result != NULL) { 903 assert(succeeded, "only way to get back a non-NULL result"); 904 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT, 905 Thread::current()->name(), p2i(result)); 906 return result; 907 } 908 909 if (succeeded) { 910 // We successfully scheduled a collection which failed to allocate. No 911 // point in trying to allocate further. We'll just return NULL. 912 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate " 913 SIZE_FORMAT " words", Thread::current()->name(), word_size); 914 return NULL; 915 } 916 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "", 917 Thread::current()->name(), word_size); 918 } else { 919 // Failed to schedule a collection. 920 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 921 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating " 922 SIZE_FORMAT " words", Thread::current()->name(), word_size); 923 return NULL; 924 } 925 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name()); 926 // The GCLocker is either active or the GCLocker initiated 927 // GC has not yet been performed. Stall until it is and 928 // then retry the allocation. 929 GCLocker::stall_until_clear(); 930 gclocker_retry_count += 1; 931 } 932 933 934 // We can reach here if we were unsuccessful in scheduling a 935 // collection (because another thread beat us to it) or if we were 936 // stalled due to the GC locker. In either can we should retry the 937 // allocation attempt in case another thread successfully 938 // performed a collection and reclaimed enough space. 939 // Humongous object allocation always needs a lock, so we wait for the retry 940 // in the next iteration of the loop, unlike for the regular iteration case. 941 // Give a warning if we seem to be looping forever. 942 943 if ((QueuedAllocationWarningCount > 0) && 944 (try_count % QueuedAllocationWarningCount == 0)) { 945 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words", 946 Thread::current()->name(), try_count, word_size); 947 } 948 } 949 950 ShouldNotReachHere(); 951 return NULL; 952 } 953 954 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 955 bool expect_null_mutator_alloc_region) { 956 assert_at_safepoint_on_vm_thread(); 957 assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region, 958 "the current alloc region was unexpectedly found to be non-NULL"); 959 960 if (!is_humongous(word_size)) { 961 return _allocator->attempt_allocation_locked(word_size); 962 } else { 963 HeapWord* result = humongous_obj_allocate(word_size); 964 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 965 collector_state()->set_initiate_conc_mark_if_possible(true); 966 } 967 return result; 968 } 969 970 ShouldNotReachHere(); 971 } 972 973 class PostCompactionPrinterClosure: public HeapRegionClosure { 974 private: 975 G1HRPrinter* _hr_printer; 976 public: 977 bool do_heap_region(HeapRegion* hr) { 978 assert(!hr->is_young(), "not expecting to find young regions"); 979 _hr_printer->post_compaction(hr); 980 return false; 981 } 982 983 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 984 : _hr_printer(hr_printer) { } 985 }; 986 987 void G1CollectedHeap::print_hrm_post_compaction() { 988 if (_hr_printer.is_active()) { 989 PostCompactionPrinterClosure cl(hr_printer()); 990 heap_region_iterate(&cl); 991 } 992 } 993 994 void G1CollectedHeap::abort_concurrent_cycle() { 995 // If we start the compaction before the CM threads finish 996 // scanning the root regions we might trip them over as we'll 997 // be moving objects / updating references. So let's wait until 998 // they are done. By telling them to abort, they should complete 999 // early. 1000 _cm->root_regions()->abort(); 1001 _cm->root_regions()->wait_until_scan_finished(); 1002 1003 // Disable discovery and empty the discovered lists 1004 // for the CM ref processor. 1005 _ref_processor_cm->disable_discovery(); 1006 _ref_processor_cm->abandon_partial_discovery(); 1007 _ref_processor_cm->verify_no_references_recorded(); 1008 1009 // Abandon current iterations of concurrent marking and concurrent 1010 // refinement, if any are in progress. 1011 concurrent_mark()->concurrent_cycle_abort(); 1012 } 1013 1014 void G1CollectedHeap::prepare_heap_for_full_collection() { 1015 // Make sure we'll choose a new allocation region afterwards. 1016 _allocator->release_mutator_alloc_region(); 1017 _allocator->abandon_gc_alloc_regions(); 1018 g1_rem_set()->cleanupHRRS(); 1019 1020 // We may have added regions to the current incremental collection 1021 // set between the last GC or pause and now. We need to clear the 1022 // incremental collection set and then start rebuilding it afresh 1023 // after this full GC. 1024 abandon_collection_set(collection_set()); 1025 1026 tear_down_region_sets(false /* free_list_only */); 1027 } 1028 1029 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1030 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1031 assert(used() == recalculate_used(), "Should be equal"); 1032 _verifier->verify_region_sets_optional(); 1033 _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull); 1034 _verifier->check_bitmaps("Full GC Start"); 1035 } 1036 1037 void G1CollectedHeap::prepare_heap_for_mutators() { 1038 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1039 ClassLoaderDataGraph::purge(); 1040 MetaspaceUtils::verify_metrics(); 1041 1042 // Prepare heap for normal collections. 1043 assert(num_free_regions() == 0, "we should not have added any free regions"); 1044 rebuild_region_sets(false /* free_list_only */); 1045 abort_refinement(); 1046 resize_if_necessary_after_full_collection(); 1047 1048 // Rebuild the strong code root lists for each region 1049 rebuild_strong_code_roots(); 1050 1051 // Start a new incremental collection set for the next pause 1052 start_new_collection_set(); 1053 1054 _allocator->init_mutator_alloc_region(); 1055 1056 // Post collection state updates. 1057 MetaspaceGC::compute_new_size(); 1058 } 1059 1060 void G1CollectedHeap::abort_refinement() { 1061 if (_hot_card_cache->use_cache()) { 1062 _hot_card_cache->reset_hot_cache(); 1063 } 1064 1065 // Discard all remembered set updates. 1066 G1BarrierSet::dirty_card_queue_set().abandon_logs(); 1067 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1068 } 1069 1070 void G1CollectedHeap::verify_after_full_collection() { 1071 _hrm.verify_optional(); 1072 _verifier->verify_region_sets_optional(); 1073 _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull); 1074 // Clear the previous marking bitmap, if needed for bitmap verification. 1075 // Note we cannot do this when we clear the next marking bitmap in 1076 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1077 // objects marked during a full GC against the previous bitmap. 1078 // But we need to clear it before calling check_bitmaps below since 1079 // the full GC has compacted objects and updated TAMS but not updated 1080 // the prev bitmap. 1081 if (G1VerifyBitmaps) { 1082 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1083 _cm->clear_prev_bitmap(workers()); 1084 } 1085 _verifier->check_bitmaps("Full GC End"); 1086 1087 // At this point there should be no regions in the 1088 // entire heap tagged as young. 1089 assert(check_young_list_empty(), "young list should be empty at this point"); 1090 1091 // Note: since we've just done a full GC, concurrent 1092 // marking is no longer active. Therefore we need not 1093 // re-enable reference discovery for the CM ref processor. 1094 // That will be done at the start of the next marking cycle. 1095 // We also know that the STW processor should no longer 1096 // discover any new references. 1097 assert(!_ref_processor_stw->discovery_enabled(), "Postcondition"); 1098 assert(!_ref_processor_cm->discovery_enabled(), "Postcondition"); 1099 _ref_processor_stw->verify_no_references_recorded(); 1100 _ref_processor_cm->verify_no_references_recorded(); 1101 } 1102 1103 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1104 // Post collection logging. 1105 // We should do this after we potentially resize the heap so 1106 // that all the COMMIT / UNCOMMIT events are generated before 1107 // the compaction events. 1108 print_hrm_post_compaction(); 1109 heap_transition->print(); 1110 print_heap_after_gc(); 1111 print_heap_regions(); 1112 #ifdef TRACESPINNING 1113 ParallelTaskTerminator::print_termination_counts(); 1114 #endif 1115 } 1116 1117 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1118 bool clear_all_soft_refs) { 1119 assert_at_safepoint_on_vm_thread(); 1120 1121 if (GCLocker::check_active_before_gc()) { 1122 // Full GC was not completed. 1123 return false; 1124 } 1125 1126 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1127 soft_ref_policy()->should_clear_all_soft_refs(); 1128 1129 G1FullCollector collector(this, &_full_gc_memory_manager, explicit_gc, do_clear_all_soft_refs); 1130 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1131 1132 collector.prepare_collection(); 1133 collector.collect(); 1134 collector.complete_collection(); 1135 1136 // Full collection was successfully completed. 1137 return true; 1138 } 1139 1140 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1141 // Currently, there is no facility in the do_full_collection(bool) API to notify 1142 // the caller that the collection did not succeed (e.g., because it was locked 1143 // out by the GC locker). So, right now, we'll ignore the return value. 1144 bool dummy = do_full_collection(true, /* explicit_gc */ 1145 clear_all_soft_refs); 1146 } 1147 1148 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1149 // Capacity, free and used after the GC counted as full regions to 1150 // include the waste in the following calculations. 1151 const size_t capacity_after_gc = capacity(); 1152 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes(); 1153 1154 // This is enforced in arguments.cpp. 1155 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1156 "otherwise the code below doesn't make sense"); 1157 1158 // We don't have floating point command-line arguments 1159 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1160 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1161 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1162 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1163 1164 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1165 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1166 1167 // We have to be careful here as these two calculations can overflow 1168 // 32-bit size_t's. 1169 double used_after_gc_d = (double) used_after_gc; 1170 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1171 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1172 1173 // Let's make sure that they are both under the max heap size, which 1174 // by default will make them fit into a size_t. 1175 double desired_capacity_upper_bound = (double) max_heap_size; 1176 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1177 desired_capacity_upper_bound); 1178 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1179 desired_capacity_upper_bound); 1180 1181 // We can now safely turn them into size_t's. 1182 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1183 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1184 1185 // This assert only makes sense here, before we adjust them 1186 // with respect to the min and max heap size. 1187 assert(minimum_desired_capacity <= maximum_desired_capacity, 1188 "minimum_desired_capacity = " SIZE_FORMAT ", " 1189 "maximum_desired_capacity = " SIZE_FORMAT, 1190 minimum_desired_capacity, maximum_desired_capacity); 1191 1192 // Should not be greater than the heap max size. No need to adjust 1193 // it with respect to the heap min size as it's a lower bound (i.e., 1194 // we'll try to make the capacity larger than it, not smaller). 1195 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1196 // Should not be less than the heap min size. No need to adjust it 1197 // with respect to the heap max size as it's an upper bound (i.e., 1198 // we'll try to make the capacity smaller than it, not greater). 1199 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1200 1201 if (capacity_after_gc < minimum_desired_capacity) { 1202 // Don't expand unless it's significant 1203 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1204 1205 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1206 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1207 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1208 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio); 1209 1210 expand(expand_bytes, _workers); 1211 1212 // No expansion, now see if we want to shrink 1213 } else if (capacity_after_gc > maximum_desired_capacity) { 1214 // Capacity too large, compute shrinking size 1215 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1216 1217 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1218 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1219 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1220 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio); 1221 1222 shrink(shrink_bytes); 1223 } 1224 } 1225 1226 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1227 bool do_gc, 1228 bool clear_all_soft_refs, 1229 bool expect_null_mutator_alloc_region, 1230 bool* gc_succeeded) { 1231 *gc_succeeded = true; 1232 // Let's attempt the allocation first. 1233 HeapWord* result = 1234 attempt_allocation_at_safepoint(word_size, 1235 expect_null_mutator_alloc_region); 1236 if (result != NULL) { 1237 return result; 1238 } 1239 1240 // In a G1 heap, we're supposed to keep allocation from failing by 1241 // incremental pauses. Therefore, at least for now, we'll favor 1242 // expansion over collection. (This might change in the future if we can 1243 // do something smarter than full collection to satisfy a failed alloc.) 1244 result = expand_and_allocate(word_size); 1245 if (result != NULL) { 1246 return result; 1247 } 1248 1249 if (do_gc) { 1250 // Expansion didn't work, we'll try to do a Full GC. 1251 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1252 clear_all_soft_refs); 1253 } 1254 1255 return NULL; 1256 } 1257 1258 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1259 bool* succeeded) { 1260 assert_at_safepoint_on_vm_thread(); 1261 1262 // Attempts to allocate followed by Full GC. 1263 HeapWord* result = 1264 satisfy_failed_allocation_helper(word_size, 1265 true, /* do_gc */ 1266 false, /* clear_all_soft_refs */ 1267 false, /* expect_null_mutator_alloc_region */ 1268 succeeded); 1269 1270 if (result != NULL || !*succeeded) { 1271 return result; 1272 } 1273 1274 // Attempts to allocate followed by Full GC that will collect all soft references. 1275 result = satisfy_failed_allocation_helper(word_size, 1276 true, /* do_gc */ 1277 true, /* clear_all_soft_refs */ 1278 true, /* expect_null_mutator_alloc_region */ 1279 succeeded); 1280 1281 if (result != NULL || !*succeeded) { 1282 return result; 1283 } 1284 1285 // Attempts to allocate, no GC 1286 result = satisfy_failed_allocation_helper(word_size, 1287 false, /* do_gc */ 1288 false, /* clear_all_soft_refs */ 1289 true, /* expect_null_mutator_alloc_region */ 1290 succeeded); 1291 1292 if (result != NULL) { 1293 return result; 1294 } 1295 1296 assert(!soft_ref_policy()->should_clear_all_soft_refs(), 1297 "Flag should have been handled and cleared prior to this point"); 1298 1299 // What else? We might try synchronous finalization later. If the total 1300 // space available is large enough for the allocation, then a more 1301 // complete compaction phase than we've tried so far might be 1302 // appropriate. 1303 return NULL; 1304 } 1305 1306 // Attempting to expand the heap sufficiently 1307 // to support an allocation of the given "word_size". If 1308 // successful, perform the allocation and return the address of the 1309 // allocated block, or else "NULL". 1310 1311 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1312 assert_at_safepoint_on_vm_thread(); 1313 1314 _verifier->verify_region_sets_optional(); 1315 1316 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1317 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1318 word_size * HeapWordSize); 1319 1320 1321 if (expand(expand_bytes, _workers)) { 1322 _hrm.verify_optional(); 1323 _verifier->verify_region_sets_optional(); 1324 return attempt_allocation_at_safepoint(word_size, 1325 false /* expect_null_mutator_alloc_region */); 1326 } 1327 return NULL; 1328 } 1329 1330 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1331 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1332 aligned_expand_bytes = align_up(aligned_expand_bytes, 1333 HeapRegion::GrainBytes); 1334 1335 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1336 expand_bytes, aligned_expand_bytes); 1337 1338 if (is_maximal_no_gc()) { 1339 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1340 return false; 1341 } 1342 1343 double expand_heap_start_time_sec = os::elapsedTime(); 1344 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1345 assert(regions_to_expand > 0, "Must expand by at least one region"); 1346 1347 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers); 1348 if (expand_time_ms != NULL) { 1349 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1350 } 1351 1352 if (expanded_by > 0) { 1353 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1354 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1355 g1_policy()->record_new_heap_size(num_regions()); 1356 } else { 1357 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1358 1359 // The expansion of the virtual storage space was unsuccessful. 1360 // Let's see if it was because we ran out of swap. 1361 if (G1ExitOnExpansionFailure && 1362 _hrm.available() >= regions_to_expand) { 1363 // We had head room... 1364 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1365 } 1366 } 1367 return regions_to_expand > 0; 1368 } 1369 1370 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1371 size_t aligned_shrink_bytes = 1372 ReservedSpace::page_align_size_down(shrink_bytes); 1373 aligned_shrink_bytes = align_down(aligned_shrink_bytes, 1374 HeapRegion::GrainBytes); 1375 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1376 1377 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1378 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1379 1380 1381 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", 1382 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1383 if (num_regions_removed > 0) { 1384 g1_policy()->record_new_heap_size(num_regions()); 1385 } else { 1386 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1387 } 1388 } 1389 1390 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1391 _verifier->verify_region_sets_optional(); 1392 1393 // We should only reach here at the end of a Full GC which means we 1394 // should not not be holding to any GC alloc regions. The method 1395 // below will make sure of that and do any remaining clean up. 1396 _allocator->abandon_gc_alloc_regions(); 1397 1398 // Instead of tearing down / rebuilding the free lists here, we 1399 // could instead use the remove_all_pending() method on free_list to 1400 // remove only the ones that we need to remove. 1401 tear_down_region_sets(true /* free_list_only */); 1402 shrink_helper(shrink_bytes); 1403 rebuild_region_sets(true /* free_list_only */); 1404 1405 _hrm.verify_optional(); 1406 _verifier->verify_region_sets_optional(); 1407 } 1408 1409 // Public methods. 1410 1411 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1412 CollectedHeap(), 1413 _young_gen_sampling_thread(NULL), 1414 _collector_policy(collector_policy), 1415 _soft_ref_policy(), 1416 _card_table(NULL), 1417 _memory_manager("G1 Young Generation", "end of minor GC"), 1418 _full_gc_memory_manager("G1 Old Generation", "end of major GC"), 1419 _eden_pool(NULL), 1420 _survivor_pool(NULL), 1421 _old_pool(NULL), 1422 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1423 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1424 _g1_policy(new G1Policy(_gc_timer_stw)), 1425 _collection_set(this, _g1_policy), 1426 _dirty_card_queue_set(false), 1427 _ref_processor_stw(NULL), 1428 _is_alive_closure_stw(this), 1429 _is_subject_to_discovery_stw(this), 1430 _ref_processor_cm(NULL), 1431 _is_alive_closure_cm(this), 1432 _is_subject_to_discovery_cm(this), 1433 _bot(NULL), 1434 _hot_card_cache(NULL), 1435 _g1_rem_set(NULL), 1436 _cr(NULL), 1437 _g1mm(NULL), 1438 _preserved_marks_set(true /* in_c_heap */), 1439 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1440 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1441 _humongous_reclaim_candidates(), 1442 _has_humongous_reclaim_candidates(false), 1443 _archive_allocator(NULL), 1444 _summary_bytes_used(0), 1445 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1446 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1447 _expand_heap_after_alloc_failure(true), 1448 _old_marking_cycles_started(0), 1449 _old_marking_cycles_completed(0), 1450 _in_cset_fast_test() { 1451 1452 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1453 /* are_GC_task_threads */true, 1454 /* are_ConcurrentGC_threads */false); 1455 _workers->initialize_workers(); 1456 _verifier = new G1HeapVerifier(this); 1457 1458 _allocator = new G1Allocator(this); 1459 1460 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1461 1462 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1463 1464 // Override the default _filler_array_max_size so that no humongous filler 1465 // objects are created. 1466 _filler_array_max_size = _humongous_object_threshold_in_words; 1467 1468 uint n_queues = ParallelGCThreads; 1469 _task_queues = new RefToScanQueueSet(n_queues); 1470 1471 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1472 1473 for (uint i = 0; i < n_queues; i++) { 1474 RefToScanQueue* q = new RefToScanQueue(); 1475 q->initialize(); 1476 _task_queues->register_queue(i, q); 1477 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1478 } 1479 1480 // Initialize the G1EvacuationFailureALot counters and flags. 1481 NOT_PRODUCT(reset_evacuation_should_fail();) 1482 1483 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1484 } 1485 1486 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1487 size_t size, 1488 size_t translation_factor) { 1489 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1490 // Allocate a new reserved space, preferring to use large pages. 1491 ReservedSpace rs(size, preferred_page_size); 1492 G1RegionToSpaceMapper* result = 1493 G1RegionToSpaceMapper::create_mapper(rs, 1494 size, 1495 rs.alignment(), 1496 HeapRegion::GrainBytes, 1497 translation_factor, 1498 mtGC); 1499 1500 os::trace_page_sizes_for_requested_size(description, 1501 size, 1502 preferred_page_size, 1503 rs.alignment(), 1504 rs.base(), 1505 rs.size()); 1506 1507 return result; 1508 } 1509 1510 jint G1CollectedHeap::initialize_concurrent_refinement() { 1511 jint ecode = JNI_OK; 1512 _cr = G1ConcurrentRefine::create(&ecode); 1513 return ecode; 1514 } 1515 1516 jint G1CollectedHeap::initialize_young_gen_sampling_thread() { 1517 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread(); 1518 if (_young_gen_sampling_thread->osthread() == NULL) { 1519 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread"); 1520 return JNI_ENOMEM; 1521 } 1522 return JNI_OK; 1523 } 1524 1525 jint G1CollectedHeap::initialize() { 1526 os::enable_vtime(); 1527 1528 // Necessary to satisfy locking discipline assertions. 1529 1530 MutexLocker x(Heap_lock); 1531 1532 // While there are no constraints in the GC code that HeapWordSize 1533 // be any particular value, there are multiple other areas in the 1534 // system which believe this to be true (e.g. oop->object_size in some 1535 // cases incorrectly returns the size in wordSize units rather than 1536 // HeapWordSize). 1537 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1538 1539 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1540 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1541 size_t heap_alignment = collector_policy()->heap_alignment(); 1542 1543 // Ensure that the sizes are properly aligned. 1544 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1545 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1546 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1547 1548 // Reserve the maximum. 1549 1550 // When compressed oops are enabled, the preferred heap base 1551 // is calculated by subtracting the requested size from the 1552 // 32Gb boundary and using the result as the base address for 1553 // heap reservation. If the requested size is not aligned to 1554 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1555 // into the ReservedHeapSpace constructor) then the actual 1556 // base of the reserved heap may end up differing from the 1557 // address that was requested (i.e. the preferred heap base). 1558 // If this happens then we could end up using a non-optimal 1559 // compressed oops mode. 1560 1561 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1562 heap_alignment); 1563 1564 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1565 1566 // Create the barrier set for the entire reserved region. 1567 G1CardTable* ct = new G1CardTable(reserved_region()); 1568 ct->initialize(); 1569 G1BarrierSet* bs = new G1BarrierSet(ct); 1570 bs->initialize(); 1571 assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity"); 1572 BarrierSet::set_barrier_set(bs); 1573 _card_table = ct; 1574 1575 // Create the hot card cache. 1576 _hot_card_cache = new G1HotCardCache(this); 1577 1578 // Carve out the G1 part of the heap. 1579 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1580 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1581 G1RegionToSpaceMapper* heap_storage = 1582 G1RegionToSpaceMapper::create_mapper(g1_rs, 1583 g1_rs.size(), 1584 page_size, 1585 HeapRegion::GrainBytes, 1586 1, 1587 mtJavaHeap); 1588 os::trace_page_sizes("Heap", 1589 collector_policy()->min_heap_byte_size(), 1590 max_byte_size, 1591 page_size, 1592 heap_rs.base(), 1593 heap_rs.size()); 1594 heap_storage->set_mapping_changed_listener(&_listener); 1595 1596 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1597 G1RegionToSpaceMapper* bot_storage = 1598 create_aux_memory_mapper("Block Offset Table", 1599 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1600 G1BlockOffsetTable::heap_map_factor()); 1601 1602 G1RegionToSpaceMapper* cardtable_storage = 1603 create_aux_memory_mapper("Card Table", 1604 G1CardTable::compute_size(g1_rs.size() / HeapWordSize), 1605 G1CardTable::heap_map_factor()); 1606 1607 G1RegionToSpaceMapper* card_counts_storage = 1608 create_aux_memory_mapper("Card Counts Table", 1609 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1610 G1CardCounts::heap_map_factor()); 1611 1612 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1613 G1RegionToSpaceMapper* prev_bitmap_storage = 1614 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1615 G1RegionToSpaceMapper* next_bitmap_storage = 1616 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1617 1618 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1619 _card_table->initialize(cardtable_storage); 1620 // Do later initialization work for concurrent refinement. 1621 _hot_card_cache->initialize(card_counts_storage); 1622 1623 // 6843694 - ensure that the maximum region index can fit 1624 // in the remembered set structures. 1625 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1626 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1627 1628 // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not 1629 // start within the first card. 1630 guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card."); 1631 // Also create a G1 rem set. 1632 _g1_rem_set = new G1RemSet(this, _card_table, _hot_card_cache); 1633 _g1_rem_set->initialize(max_capacity(), max_regions()); 1634 1635 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1636 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1637 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1638 "too many cards per region"); 1639 1640 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1641 1642 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1643 1644 { 1645 HeapWord* start = _hrm.reserved().start(); 1646 HeapWord* end = _hrm.reserved().end(); 1647 size_t granularity = HeapRegion::GrainBytes; 1648 1649 _in_cset_fast_test.initialize(start, end, granularity); 1650 _humongous_reclaim_candidates.initialize(start, end, granularity); 1651 } 1652 1653 // Create the G1ConcurrentMark data structure and thread. 1654 // (Must do this late, so that "max_regions" is defined.) 1655 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1656 if (_cm == NULL || !_cm->completed_initialization()) { 1657 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1658 return JNI_ENOMEM; 1659 } 1660 _cm_thread = _cm->cm_thread(); 1661 1662 // Now expand into the initial heap size. 1663 if (!expand(init_byte_size, _workers)) { 1664 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1665 return JNI_ENOMEM; 1666 } 1667 1668 // Perform any initialization actions delegated to the policy. 1669 g1_policy()->init(this, &_collection_set); 1670 1671 G1BarrierSet::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1672 SATB_Q_FL_lock, 1673 G1SATBProcessCompletedThreshold, 1674 Shared_SATB_Q_lock); 1675 1676 jint ecode = initialize_concurrent_refinement(); 1677 if (ecode != JNI_OK) { 1678 return ecode; 1679 } 1680 1681 ecode = initialize_young_gen_sampling_thread(); 1682 if (ecode != JNI_OK) { 1683 return ecode; 1684 } 1685 1686 G1BarrierSet::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1687 DirtyCardQ_FL_lock, 1688 (int)concurrent_refine()->yellow_zone(), 1689 (int)concurrent_refine()->red_zone(), 1690 Shared_DirtyCardQ_lock, 1691 NULL, // fl_owner 1692 true); // init_free_ids 1693 1694 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1695 DirtyCardQ_FL_lock, 1696 -1, // never trigger processing 1697 -1, // no limit on length 1698 Shared_DirtyCardQ_lock, 1699 &G1BarrierSet::dirty_card_queue_set()); 1700 1701 // Here we allocate the dummy HeapRegion that is required by the 1702 // G1AllocRegion class. 1703 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1704 1705 // We'll re-use the same region whether the alloc region will 1706 // require BOT updates or not and, if it doesn't, then a non-young 1707 // region will complain that it cannot support allocations without 1708 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1709 dummy_region->set_eden(); 1710 // Make sure it's full. 1711 dummy_region->set_top(dummy_region->end()); 1712 G1AllocRegion::setup(this, dummy_region); 1713 1714 _allocator->init_mutator_alloc_region(); 1715 1716 // Do create of the monitoring and management support so that 1717 // values in the heap have been properly initialized. 1718 _g1mm = new G1MonitoringSupport(this); 1719 1720 G1StringDedup::initialize(); 1721 1722 _preserved_marks_set.init(ParallelGCThreads); 1723 1724 _collection_set.initialize(max_regions()); 1725 1726 return JNI_OK; 1727 } 1728 1729 void G1CollectedHeap::initialize_serviceability() { 1730 _eden_pool = new G1EdenPool(this); 1731 _survivor_pool = new G1SurvivorPool(this); 1732 _old_pool = new G1OldGenPool(this); 1733 1734 _full_gc_memory_manager.add_pool(_eden_pool); 1735 _full_gc_memory_manager.add_pool(_survivor_pool); 1736 _full_gc_memory_manager.add_pool(_old_pool); 1737 1738 _memory_manager.add_pool(_eden_pool); 1739 _memory_manager.add_pool(_survivor_pool); 1740 1741 } 1742 1743 void G1CollectedHeap::stop() { 1744 // Stop all concurrent threads. We do this to make sure these threads 1745 // do not continue to execute and access resources (e.g. logging) 1746 // that are destroyed during shutdown. 1747 _cr->stop(); 1748 _young_gen_sampling_thread->stop(); 1749 _cm_thread->stop(); 1750 if (G1StringDedup::is_enabled()) { 1751 G1StringDedup::stop(); 1752 } 1753 } 1754 1755 void G1CollectedHeap::safepoint_synchronize_begin() { 1756 SuspendibleThreadSet::synchronize(); 1757 } 1758 1759 void G1CollectedHeap::safepoint_synchronize_end() { 1760 SuspendibleThreadSet::desynchronize(); 1761 } 1762 1763 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1764 return HeapRegion::max_region_size(); 1765 } 1766 1767 void G1CollectedHeap::post_initialize() { 1768 CollectedHeap::post_initialize(); 1769 ref_processing_init(); 1770 } 1771 1772 void G1CollectedHeap::ref_processing_init() { 1773 // Reference processing in G1 currently works as follows: 1774 // 1775 // * There are two reference processor instances. One is 1776 // used to record and process discovered references 1777 // during concurrent marking; the other is used to 1778 // record and process references during STW pauses 1779 // (both full and incremental). 1780 // * Both ref processors need to 'span' the entire heap as 1781 // the regions in the collection set may be dotted around. 1782 // 1783 // * For the concurrent marking ref processor: 1784 // * Reference discovery is enabled at initial marking. 1785 // * Reference discovery is disabled and the discovered 1786 // references processed etc during remarking. 1787 // * Reference discovery is MT (see below). 1788 // * Reference discovery requires a barrier (see below). 1789 // * Reference processing may or may not be MT 1790 // (depending on the value of ParallelRefProcEnabled 1791 // and ParallelGCThreads). 1792 // * A full GC disables reference discovery by the CM 1793 // ref processor and abandons any entries on it's 1794 // discovered lists. 1795 // 1796 // * For the STW processor: 1797 // * Non MT discovery is enabled at the start of a full GC. 1798 // * Processing and enqueueing during a full GC is non-MT. 1799 // * During a full GC, references are processed after marking. 1800 // 1801 // * Discovery (may or may not be MT) is enabled at the start 1802 // of an incremental evacuation pause. 1803 // * References are processed near the end of a STW evacuation pause. 1804 // * For both types of GC: 1805 // * Discovery is atomic - i.e. not concurrent. 1806 // * Reference discovery will not need a barrier. 1807 1808 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1); 1809 1810 // Concurrent Mark ref processor 1811 _ref_processor_cm = 1812 new ReferenceProcessor(&_is_subject_to_discovery_cm, 1813 mt_processing, // mt processing 1814 ParallelGCThreads, // degree of mt processing 1815 (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery 1816 MAX2(ParallelGCThreads, ConcGCThreads), // degree of mt discovery 1817 false, // Reference discovery is not atomic 1818 &_is_alive_closure_cm); // is alive closure 1819 1820 // STW ref processor 1821 _ref_processor_stw = 1822 new ReferenceProcessor(&_is_subject_to_discovery_stw, 1823 mt_processing, // mt processing 1824 ParallelGCThreads, // degree of mt processing 1825 (ParallelGCThreads > 1), // mt discovery 1826 ParallelGCThreads, // degree of mt discovery 1827 true, // Reference discovery is atomic 1828 &_is_alive_closure_stw); // is alive closure 1829 } 1830 1831 CollectorPolicy* G1CollectedHeap::collector_policy() const { 1832 return _collector_policy; 1833 } 1834 1835 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() { 1836 return &_soft_ref_policy; 1837 } 1838 1839 size_t G1CollectedHeap::capacity() const { 1840 return _hrm.length() * HeapRegion::GrainBytes; 1841 } 1842 1843 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const { 1844 return _hrm.total_free_bytes(); 1845 } 1846 1847 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 1848 _hot_card_cache->drain(cl, worker_i); 1849 } 1850 1851 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 1852 DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 1853 size_t n_completed_buffers = 0; 1854 while (dcqs.apply_closure_during_gc(cl, worker_i)) { 1855 n_completed_buffers++; 1856 } 1857 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers, G1GCPhaseTimes::UpdateRSProcessedBuffers); 1858 dcqs.clear_n_completed_buffers(); 1859 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 1860 } 1861 1862 // Computes the sum of the storage used by the various regions. 1863 size_t G1CollectedHeap::used() const { 1864 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 1865 if (_archive_allocator != NULL) { 1866 result += _archive_allocator->used(); 1867 } 1868 return result; 1869 } 1870 1871 size_t G1CollectedHeap::used_unlocked() const { 1872 return _summary_bytes_used; 1873 } 1874 1875 class SumUsedClosure: public HeapRegionClosure { 1876 size_t _used; 1877 public: 1878 SumUsedClosure() : _used(0) {} 1879 bool do_heap_region(HeapRegion* r) { 1880 _used += r->used(); 1881 return false; 1882 } 1883 size_t result() { return _used; } 1884 }; 1885 1886 size_t G1CollectedHeap::recalculate_used() const { 1887 double recalculate_used_start = os::elapsedTime(); 1888 1889 SumUsedClosure blk; 1890 heap_region_iterate(&blk); 1891 1892 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 1893 return blk.result(); 1894 } 1895 1896 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 1897 switch (cause) { 1898 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 1899 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 1900 case GCCause::_wb_conc_mark: return true; 1901 default : return false; 1902 } 1903 } 1904 1905 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 1906 switch (cause) { 1907 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 1908 case GCCause::_g1_humongous_allocation: return true; 1909 default: return is_user_requested_concurrent_full_gc(cause); 1910 } 1911 } 1912 1913 #ifndef PRODUCT 1914 void G1CollectedHeap::allocate_dummy_regions() { 1915 // Let's fill up most of the region 1916 size_t word_size = HeapRegion::GrainWords - 1024; 1917 // And as a result the region we'll allocate will be humongous. 1918 guarantee(is_humongous(word_size), "sanity"); 1919 1920 // _filler_array_max_size is set to humongous object threshold 1921 // but temporarily change it to use CollectedHeap::fill_with_object(). 1922 SizeTFlagSetting fs(_filler_array_max_size, word_size); 1923 1924 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 1925 // Let's use the existing mechanism for the allocation 1926 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 1927 if (dummy_obj != NULL) { 1928 MemRegion mr(dummy_obj, word_size); 1929 CollectedHeap::fill_with_object(mr); 1930 } else { 1931 // If we can't allocate once, we probably cannot allocate 1932 // again. Let's get out of the loop. 1933 break; 1934 } 1935 } 1936 } 1937 #endif // !PRODUCT 1938 1939 void G1CollectedHeap::increment_old_marking_cycles_started() { 1940 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 1941 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 1942 "Wrong marking cycle count (started: %d, completed: %d)", 1943 _old_marking_cycles_started, _old_marking_cycles_completed); 1944 1945 _old_marking_cycles_started++; 1946 } 1947 1948 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 1949 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 1950 1951 // We assume that if concurrent == true, then the caller is a 1952 // concurrent thread that was joined the Suspendible Thread 1953 // Set. If there's ever a cheap way to check this, we should add an 1954 // assert here. 1955 1956 // Given that this method is called at the end of a Full GC or of a 1957 // concurrent cycle, and those can be nested (i.e., a Full GC can 1958 // interrupt a concurrent cycle), the number of full collections 1959 // completed should be either one (in the case where there was no 1960 // nesting) or two (when a Full GC interrupted a concurrent cycle) 1961 // behind the number of full collections started. 1962 1963 // This is the case for the inner caller, i.e. a Full GC. 1964 assert(concurrent || 1965 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 1966 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 1967 "for inner caller (Full GC): _old_marking_cycles_started = %u " 1968 "is inconsistent with _old_marking_cycles_completed = %u", 1969 _old_marking_cycles_started, _old_marking_cycles_completed); 1970 1971 // This is the case for the outer caller, i.e. the concurrent cycle. 1972 assert(!concurrent || 1973 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 1974 "for outer caller (concurrent cycle): " 1975 "_old_marking_cycles_started = %u " 1976 "is inconsistent with _old_marking_cycles_completed = %u", 1977 _old_marking_cycles_started, _old_marking_cycles_completed); 1978 1979 _old_marking_cycles_completed += 1; 1980 1981 // We need to clear the "in_progress" flag in the CM thread before 1982 // we wake up any waiters (especially when ExplicitInvokesConcurrent 1983 // is set) so that if a waiter requests another System.gc() it doesn't 1984 // incorrectly see that a marking cycle is still in progress. 1985 if (concurrent) { 1986 _cm_thread->set_idle(); 1987 } 1988 1989 // This notify_all() will ensure that a thread that called 1990 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 1991 // and it's waiting for a full GC to finish will be woken up. It is 1992 // waiting in VM_G1CollectForAllocation::doit_epilogue(). 1993 FullGCCount_lock->notify_all(); 1994 } 1995 1996 void G1CollectedHeap::collect(GCCause::Cause cause) { 1997 assert_heap_not_locked(); 1998 1999 uint gc_count_before; 2000 uint old_marking_count_before; 2001 uint full_gc_count_before; 2002 bool retry_gc; 2003 2004 do { 2005 retry_gc = false; 2006 2007 { 2008 MutexLocker ml(Heap_lock); 2009 2010 // Read the GC count while holding the Heap_lock 2011 gc_count_before = total_collections(); 2012 full_gc_count_before = total_full_collections(); 2013 old_marking_count_before = _old_marking_cycles_started; 2014 } 2015 2016 if (should_do_concurrent_full_gc(cause)) { 2017 // Schedule an initial-mark evacuation pause that will start a 2018 // concurrent cycle. We're setting word_size to 0 which means that 2019 // we are not requesting a post-GC allocation. 2020 VM_G1CollectForAllocation op(0, /* word_size */ 2021 gc_count_before, 2022 cause, 2023 true, /* should_initiate_conc_mark */ 2024 g1_policy()->max_pause_time_ms()); 2025 VMThread::execute(&op); 2026 if (!op.pause_succeeded()) { 2027 if (old_marking_count_before == _old_marking_cycles_started) { 2028 retry_gc = op.should_retry_gc(); 2029 } else { 2030 // A Full GC happened while we were trying to schedule the 2031 // initial-mark GC. No point in starting a new cycle given 2032 // that the whole heap was collected anyway. 2033 } 2034 2035 if (retry_gc) { 2036 if (GCLocker::is_active_and_needs_gc()) { 2037 GCLocker::stall_until_clear(); 2038 } 2039 } 2040 } 2041 } else { 2042 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2043 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2044 2045 // Schedule a standard evacuation pause. We're setting word_size 2046 // to 0 which means that we are not requesting a post-GC allocation. 2047 VM_G1CollectForAllocation op(0, /* word_size */ 2048 gc_count_before, 2049 cause, 2050 false, /* should_initiate_conc_mark */ 2051 g1_policy()->max_pause_time_ms()); 2052 VMThread::execute(&op); 2053 } else { 2054 // Schedule a Full GC. 2055 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2056 VMThread::execute(&op); 2057 } 2058 } 2059 } while (retry_gc); 2060 } 2061 2062 bool G1CollectedHeap::is_in(const void* p) const { 2063 if (_hrm.reserved().contains(p)) { 2064 // Given that we know that p is in the reserved space, 2065 // heap_region_containing() should successfully 2066 // return the containing region. 2067 HeapRegion* hr = heap_region_containing(p); 2068 return hr->is_in(p); 2069 } else { 2070 return false; 2071 } 2072 } 2073 2074 #ifdef ASSERT 2075 bool G1CollectedHeap::is_in_exact(const void* p) const { 2076 bool contains = reserved_region().contains(p); 2077 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2078 if (contains && available) { 2079 return true; 2080 } else { 2081 return false; 2082 } 2083 } 2084 #endif 2085 2086 // Iteration functions. 2087 2088 // Iterates an ObjectClosure over all objects within a HeapRegion. 2089 2090 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2091 ObjectClosure* _cl; 2092 public: 2093 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2094 bool do_heap_region(HeapRegion* r) { 2095 if (!r->is_continues_humongous()) { 2096 r->object_iterate(_cl); 2097 } 2098 return false; 2099 } 2100 }; 2101 2102 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2103 IterateObjectClosureRegionClosure blk(cl); 2104 heap_region_iterate(&blk); 2105 } 2106 2107 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2108 _hrm.iterate(cl); 2109 } 2110 2111 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl, 2112 HeapRegionClaimer *hrclaimer, 2113 uint worker_id) const { 2114 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id)); 2115 } 2116 2117 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl, 2118 HeapRegionClaimer *hrclaimer) const { 2119 _hrm.par_iterate(cl, hrclaimer, 0); 2120 } 2121 2122 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2123 _collection_set.iterate(cl); 2124 } 2125 2126 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2127 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2128 } 2129 2130 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2131 HeapRegion* hr = heap_region_containing(addr); 2132 return hr->block_start(addr); 2133 } 2134 2135 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2136 HeapRegion* hr = heap_region_containing(addr); 2137 return hr->block_size(addr); 2138 } 2139 2140 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2141 HeapRegion* hr = heap_region_containing(addr); 2142 return hr->block_is_obj(addr); 2143 } 2144 2145 bool G1CollectedHeap::supports_tlab_allocation() const { 2146 return true; 2147 } 2148 2149 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2150 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2151 } 2152 2153 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2154 return _eden.length() * HeapRegion::GrainBytes; 2155 } 2156 2157 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2158 // must be equal to the humongous object limit. 2159 size_t G1CollectedHeap::max_tlab_size() const { 2160 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2161 } 2162 2163 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2164 return _allocator->unsafe_max_tlab_alloc(); 2165 } 2166 2167 size_t G1CollectedHeap::max_capacity() const { 2168 return _hrm.reserved().byte_size(); 2169 } 2170 2171 jlong G1CollectedHeap::millis_since_last_gc() { 2172 // See the notes in GenCollectedHeap::millis_since_last_gc() 2173 // for more information about the implementation. 2174 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2175 _g1_policy->collection_pause_end_millis(); 2176 if (ret_val < 0) { 2177 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2178 ". returning zero instead.", ret_val); 2179 return 0; 2180 } 2181 return ret_val; 2182 } 2183 2184 void G1CollectedHeap::deduplicate_string(oop str) { 2185 assert(java_lang_String::is_instance(str), "invariant"); 2186 2187 if (G1StringDedup::is_enabled()) { 2188 G1StringDedup::deduplicate(str); 2189 } 2190 } 2191 2192 void G1CollectedHeap::prepare_for_verify() { 2193 _verifier->prepare_for_verify(); 2194 } 2195 2196 void G1CollectedHeap::verify(VerifyOption vo) { 2197 _verifier->verify(vo); 2198 } 2199 2200 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2201 return true; 2202 } 2203 2204 const char* const* G1CollectedHeap::concurrent_phases() const { 2205 return _cm_thread->concurrent_phases(); 2206 } 2207 2208 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2209 return _cm_thread->request_concurrent_phase(phase); 2210 } 2211 2212 class PrintRegionClosure: public HeapRegionClosure { 2213 outputStream* _st; 2214 public: 2215 PrintRegionClosure(outputStream* st) : _st(st) {} 2216 bool do_heap_region(HeapRegion* r) { 2217 r->print_on(_st); 2218 return false; 2219 } 2220 }; 2221 2222 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2223 const HeapRegion* hr, 2224 const VerifyOption vo) const { 2225 switch (vo) { 2226 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2227 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2228 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr); 2229 default: ShouldNotReachHere(); 2230 } 2231 return false; // keep some compilers happy 2232 } 2233 2234 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2235 const VerifyOption vo) const { 2236 switch (vo) { 2237 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2238 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2239 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj); 2240 default: ShouldNotReachHere(); 2241 } 2242 return false; // keep some compilers happy 2243 } 2244 2245 void G1CollectedHeap::print_heap_regions() const { 2246 LogTarget(Trace, gc, heap, region) lt; 2247 if (lt.is_enabled()) { 2248 LogStream ls(lt); 2249 print_regions_on(&ls); 2250 } 2251 } 2252 2253 void G1CollectedHeap::print_on(outputStream* st) const { 2254 st->print(" %-20s", "garbage-first heap"); 2255 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2256 capacity()/K, used_unlocked()/K); 2257 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")", 2258 p2i(_hrm.reserved().start()), 2259 p2i(_hrm.reserved().end())); 2260 st->cr(); 2261 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2262 uint young_regions = young_regions_count(); 2263 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2264 (size_t) young_regions * HeapRegion::GrainBytes / K); 2265 uint survivor_regions = survivor_regions_count(); 2266 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2267 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2268 st->cr(); 2269 MetaspaceUtils::print_on(st); 2270 } 2271 2272 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2273 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2274 "HS=humongous(starts), HC=humongous(continues), " 2275 "CS=collection set, F=free, A=archive, " 2276 "TAMS=top-at-mark-start (previous, next)"); 2277 PrintRegionClosure blk(st); 2278 heap_region_iterate(&blk); 2279 } 2280 2281 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2282 print_on(st); 2283 2284 // Print the per-region information. 2285 print_regions_on(st); 2286 } 2287 2288 void G1CollectedHeap::print_on_error(outputStream* st) const { 2289 this->CollectedHeap::print_on_error(st); 2290 2291 if (_cm != NULL) { 2292 st->cr(); 2293 _cm->print_on_error(st); 2294 } 2295 } 2296 2297 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2298 workers()->print_worker_threads_on(st); 2299 _cm_thread->print_on(st); 2300 st->cr(); 2301 _cm->print_worker_threads_on(st); 2302 _cr->print_threads_on(st); 2303 _young_gen_sampling_thread->print_on(st); 2304 if (G1StringDedup::is_enabled()) { 2305 G1StringDedup::print_worker_threads_on(st); 2306 } 2307 } 2308 2309 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2310 workers()->threads_do(tc); 2311 tc->do_thread(_cm_thread); 2312 _cm->threads_do(tc); 2313 _cr->threads_do(tc); 2314 tc->do_thread(_young_gen_sampling_thread); 2315 if (G1StringDedup::is_enabled()) { 2316 G1StringDedup::threads_do(tc); 2317 } 2318 } 2319 2320 void G1CollectedHeap::print_tracing_info() const { 2321 g1_rem_set()->print_summary_info(); 2322 concurrent_mark()->print_summary_info(); 2323 } 2324 2325 #ifndef PRODUCT 2326 // Helpful for debugging RSet issues. 2327 2328 class PrintRSetsClosure : public HeapRegionClosure { 2329 private: 2330 const char* _msg; 2331 size_t _occupied_sum; 2332 2333 public: 2334 bool do_heap_region(HeapRegion* r) { 2335 HeapRegionRemSet* hrrs = r->rem_set(); 2336 size_t occupied = hrrs->occupied(); 2337 _occupied_sum += occupied; 2338 2339 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2340 if (occupied == 0) { 2341 tty->print_cr(" RSet is empty"); 2342 } else { 2343 hrrs->print(); 2344 } 2345 tty->print_cr("----------"); 2346 return false; 2347 } 2348 2349 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2350 tty->cr(); 2351 tty->print_cr("========================================"); 2352 tty->print_cr("%s", msg); 2353 tty->cr(); 2354 } 2355 2356 ~PrintRSetsClosure() { 2357 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2358 tty->print_cr("========================================"); 2359 tty->cr(); 2360 } 2361 }; 2362 2363 void G1CollectedHeap::print_cset_rsets() { 2364 PrintRSetsClosure cl("Printing CSet RSets"); 2365 collection_set_iterate(&cl); 2366 } 2367 2368 void G1CollectedHeap::print_all_rsets() { 2369 PrintRSetsClosure cl("Printing All RSets");; 2370 heap_region_iterate(&cl); 2371 } 2372 #endif // PRODUCT 2373 2374 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2375 2376 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2377 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2378 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2379 2380 size_t eden_capacity_bytes = 2381 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2382 2383 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2384 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2385 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2386 } 2387 2388 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2389 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2390 stats->unused(), stats->used(), stats->region_end_waste(), 2391 stats->regions_filled(), stats->direct_allocated(), 2392 stats->failure_used(), stats->failure_waste()); 2393 } 2394 2395 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2396 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2397 gc_tracer->report_gc_heap_summary(when, heap_summary); 2398 2399 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2400 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2401 } 2402 2403 G1CollectedHeap* G1CollectedHeap::heap() { 2404 CollectedHeap* heap = Universe::heap(); 2405 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2406 assert(heap->kind() == CollectedHeap::G1, "Invalid name"); 2407 return (G1CollectedHeap*)heap; 2408 } 2409 2410 void G1CollectedHeap::gc_prologue(bool full) { 2411 // always_do_update_barrier = false; 2412 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2413 2414 // This summary needs to be printed before incrementing total collections. 2415 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2416 2417 // Update common counters. 2418 increment_total_collections(full /* full gc */); 2419 if (full) { 2420 increment_old_marking_cycles_started(); 2421 } 2422 2423 // Fill TLAB's and such 2424 double start = os::elapsedTime(); 2425 accumulate_statistics_all_tlabs(); 2426 ensure_parsability(true); 2427 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2428 } 2429 2430 void G1CollectedHeap::gc_epilogue(bool full) { 2431 // Update common counters. 2432 if (full) { 2433 // Update the number of full collections that have been completed. 2434 increment_old_marking_cycles_completed(false /* concurrent */); 2435 } 2436 2437 // We are at the end of the GC. Total collections has already been increased. 2438 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2439 2440 // FIXME: what is this about? 2441 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2442 // is set. 2443 #if COMPILER2_OR_JVMCI 2444 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2445 #endif 2446 // always_do_update_barrier = true; 2447 2448 double start = os::elapsedTime(); 2449 resize_all_tlabs(); 2450 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2451 2452 MemoryService::track_memory_usage(); 2453 // We have just completed a GC. Update the soft reference 2454 // policy with the new heap occupancy 2455 Universe::update_heap_info_at_gc(); 2456 } 2457 2458 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2459 uint gc_count_before, 2460 bool* succeeded, 2461 GCCause::Cause gc_cause) { 2462 assert_heap_not_locked_and_not_at_safepoint(); 2463 VM_G1CollectForAllocation op(word_size, 2464 gc_count_before, 2465 gc_cause, 2466 false, /* should_initiate_conc_mark */ 2467 g1_policy()->max_pause_time_ms()); 2468 VMThread::execute(&op); 2469 2470 HeapWord* result = op.result(); 2471 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2472 assert(result == NULL || ret_succeeded, 2473 "the result should be NULL if the VM did not succeed"); 2474 *succeeded = ret_succeeded; 2475 2476 assert_heap_not_locked(); 2477 return result; 2478 } 2479 2480 void G1CollectedHeap::do_concurrent_mark() { 2481 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2482 if (!_cm_thread->in_progress()) { 2483 _cm_thread->set_started(); 2484 CGC_lock->notify(); 2485 } 2486 } 2487 2488 size_t G1CollectedHeap::pending_card_num() { 2489 size_t extra_cards = 0; 2490 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) { 2491 DirtyCardQueue& dcq = G1ThreadLocalData::dirty_card_queue(curr); 2492 extra_cards += dcq.size(); 2493 } 2494 DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 2495 size_t buffer_size = dcqs.buffer_size(); 2496 size_t buffer_num = dcqs.completed_buffers_num(); 2497 2498 return buffer_size * buffer_num + extra_cards; 2499 } 2500 2501 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const { 2502 // We don't nominate objects with many remembered set entries, on 2503 // the assumption that such objects are likely still live. 2504 HeapRegionRemSet* rem_set = r->rem_set(); 2505 2506 return G1EagerReclaimHumongousObjectsWithStaleRefs ? 2507 rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) : 2508 G1EagerReclaimHumongousObjects && rem_set->is_empty(); 2509 } 2510 2511 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2512 private: 2513 size_t _total_humongous; 2514 size_t _candidate_humongous; 2515 2516 DirtyCardQueue _dcq; 2517 2518 bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const { 2519 assert(region->is_starts_humongous(), "Must start a humongous object"); 2520 2521 oop obj = oop(region->bottom()); 2522 2523 // Dead objects cannot be eager reclaim candidates. Due to class 2524 // unloading it is unsafe to query their classes so we return early. 2525 if (g1h->is_obj_dead(obj, region)) { 2526 return false; 2527 } 2528 2529 // If we do not have a complete remembered set for the region, then we can 2530 // not be sure that we have all references to it. 2531 if (!region->rem_set()->is_complete()) { 2532 return false; 2533 } 2534 // Candidate selection must satisfy the following constraints 2535 // while concurrent marking is in progress: 2536 // 2537 // * In order to maintain SATB invariants, an object must not be 2538 // reclaimed if it was allocated before the start of marking and 2539 // has not had its references scanned. Such an object must have 2540 // its references (including type metadata) scanned to ensure no 2541 // live objects are missed by the marking process. Objects 2542 // allocated after the start of concurrent marking don't need to 2543 // be scanned. 2544 // 2545 // * An object must not be reclaimed if it is on the concurrent 2546 // mark stack. Objects allocated after the start of concurrent 2547 // marking are never pushed on the mark stack. 2548 // 2549 // Nominating only objects allocated after the start of concurrent 2550 // marking is sufficient to meet both constraints. This may miss 2551 // some objects that satisfy the constraints, but the marking data 2552 // structures don't support efficiently performing the needed 2553 // additional tests or scrubbing of the mark stack. 2554 // 2555 // However, we presently only nominate is_typeArray() objects. 2556 // A humongous object containing references induces remembered 2557 // set entries on other regions. In order to reclaim such an 2558 // object, those remembered sets would need to be cleaned up. 2559 // 2560 // We also treat is_typeArray() objects specially, allowing them 2561 // to be reclaimed even if allocated before the start of 2562 // concurrent mark. For this we rely on mark stack insertion to 2563 // exclude is_typeArray() objects, preventing reclaiming an object 2564 // that is in the mark stack. We also rely on the metadata for 2565 // such objects to be built-in and so ensured to be kept live. 2566 // Frequent allocation and drop of large binary blobs is an 2567 // important use case for eager reclaim, and this special handling 2568 // may reduce needed headroom. 2569 2570 return obj->is_typeArray() && 2571 g1h->is_potential_eager_reclaim_candidate(region); 2572 } 2573 2574 public: 2575 RegisterHumongousWithInCSetFastTestClosure() 2576 : _total_humongous(0), 2577 _candidate_humongous(0), 2578 _dcq(&G1BarrierSet::dirty_card_queue_set()) { 2579 } 2580 2581 virtual bool do_heap_region(HeapRegion* r) { 2582 if (!r->is_starts_humongous()) { 2583 return false; 2584 } 2585 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2586 2587 bool is_candidate = humongous_region_is_candidate(g1h, r); 2588 uint rindex = r->hrm_index(); 2589 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2590 if (is_candidate) { 2591 _candidate_humongous++; 2592 g1h->register_humongous_region_with_cset(rindex); 2593 // Is_candidate already filters out humongous object with large remembered sets. 2594 // If we have a humongous object with a few remembered sets, we simply flush these 2595 // remembered set entries into the DCQS. That will result in automatic 2596 // re-evaluation of their remembered set entries during the following evacuation 2597 // phase. 2598 if (!r->rem_set()->is_empty()) { 2599 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2600 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2601 G1CardTable* ct = g1h->card_table(); 2602 HeapRegionRemSetIterator hrrs(r->rem_set()); 2603 size_t card_index; 2604 while (hrrs.has_next(card_index)) { 2605 jbyte* card_ptr = (jbyte*)ct->byte_for_index(card_index); 2606 // The remembered set might contain references to already freed 2607 // regions. Filter out such entries to avoid failing card table 2608 // verification. 2609 if (g1h->is_in_closed_subset(ct->addr_for(card_ptr))) { 2610 if (*card_ptr != G1CardTable::dirty_card_val()) { 2611 *card_ptr = G1CardTable::dirty_card_val(); 2612 _dcq.enqueue(card_ptr); 2613 } 2614 } 2615 } 2616 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2617 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2618 hrrs.n_yielded(), r->rem_set()->occupied()); 2619 // We should only clear the card based remembered set here as we will not 2620 // implicitly rebuild anything else during eager reclaim. Note that at the moment 2621 // (and probably never) we do not enter this path if there are other kind of 2622 // remembered sets for this region. 2623 r->rem_set()->clear_locked(true /* only_cardset */); 2624 // Clear_locked() above sets the state to Empty. However we want to continue 2625 // collecting remembered set entries for humongous regions that were not 2626 // reclaimed. 2627 r->rem_set()->set_state_complete(); 2628 } 2629 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2630 } 2631 _total_humongous++; 2632 2633 return false; 2634 } 2635 2636 size_t total_humongous() const { return _total_humongous; } 2637 size_t candidate_humongous() const { return _candidate_humongous; } 2638 2639 void flush_rem_set_entries() { _dcq.flush(); } 2640 }; 2641 2642 void G1CollectedHeap::register_humongous_regions_with_cset() { 2643 if (!G1EagerReclaimHumongousObjects) { 2644 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2645 return; 2646 } 2647 double time = os::elapsed_counter(); 2648 2649 // Collect reclaim candidate information and register candidates with cset. 2650 RegisterHumongousWithInCSetFastTestClosure cl; 2651 heap_region_iterate(&cl); 2652 2653 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2654 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2655 cl.total_humongous(), 2656 cl.candidate_humongous()); 2657 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2658 2659 // Finally flush all remembered set entries to re-check into the global DCQS. 2660 cl.flush_rem_set_entries(); 2661 } 2662 2663 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2664 public: 2665 bool do_heap_region(HeapRegion* hr) { 2666 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2667 hr->verify_rem_set(); 2668 } 2669 return false; 2670 } 2671 }; 2672 2673 uint G1CollectedHeap::num_task_queues() const { 2674 return _task_queues->size(); 2675 } 2676 2677 #if TASKQUEUE_STATS 2678 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2679 st->print_raw_cr("GC Task Stats"); 2680 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2681 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2682 } 2683 2684 void G1CollectedHeap::print_taskqueue_stats() const { 2685 if (!log_is_enabled(Trace, gc, task, stats)) { 2686 return; 2687 } 2688 Log(gc, task, stats) log; 2689 ResourceMark rm; 2690 LogStream ls(log.trace()); 2691 outputStream* st = &ls; 2692 2693 print_taskqueue_stats_hdr(st); 2694 2695 TaskQueueStats totals; 2696 const uint n = num_task_queues(); 2697 for (uint i = 0; i < n; ++i) { 2698 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2699 totals += task_queue(i)->stats; 2700 } 2701 st->print_raw("tot "); totals.print(st); st->cr(); 2702 2703 DEBUG_ONLY(totals.verify()); 2704 } 2705 2706 void G1CollectedHeap::reset_taskqueue_stats() { 2707 const uint n = num_task_queues(); 2708 for (uint i = 0; i < n; ++i) { 2709 task_queue(i)->stats.reset(); 2710 } 2711 } 2712 #endif // TASKQUEUE_STATS 2713 2714 void G1CollectedHeap::wait_for_root_region_scanning() { 2715 double scan_wait_start = os::elapsedTime(); 2716 // We have to wait until the CM threads finish scanning the 2717 // root regions as it's the only way to ensure that all the 2718 // objects on them have been correctly scanned before we start 2719 // moving them during the GC. 2720 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2721 double wait_time_ms = 0.0; 2722 if (waited) { 2723 double scan_wait_end = os::elapsedTime(); 2724 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2725 } 2726 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2727 } 2728 2729 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2730 private: 2731 G1HRPrinter* _hr_printer; 2732 public: 2733 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2734 2735 virtual bool do_heap_region(HeapRegion* r) { 2736 _hr_printer->cset(r); 2737 return false; 2738 } 2739 }; 2740 2741 void G1CollectedHeap::start_new_collection_set() { 2742 collection_set()->start_incremental_building(); 2743 2744 clear_cset_fast_test(); 2745 2746 guarantee(_eden.length() == 0, "eden should have been cleared"); 2747 g1_policy()->transfer_survivors_to_cset(survivor()); 2748 } 2749 2750 bool 2751 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2752 assert_at_safepoint_on_vm_thread(); 2753 guarantee(!is_gc_active(), "collection is not reentrant"); 2754 2755 if (GCLocker::check_active_before_gc()) { 2756 return false; 2757 } 2758 2759 _gc_timer_stw->register_gc_start(); 2760 2761 GCIdMark gc_id_mark; 2762 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2763 2764 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2765 ResourceMark rm; 2766 2767 g1_policy()->note_gc_start(); 2768 2769 wait_for_root_region_scanning(); 2770 2771 print_heap_before_gc(); 2772 print_heap_regions(); 2773 trace_heap_before_gc(_gc_tracer_stw); 2774 2775 _verifier->verify_region_sets_optional(); 2776 _verifier->verify_dirty_young_regions(); 2777 2778 // We should not be doing initial mark unless the conc mark thread is running 2779 if (!_cm_thread->should_terminate()) { 2780 // This call will decide whether this pause is an initial-mark 2781 // pause. If it is, in_initial_mark_gc() will return true 2782 // for the duration of this pause. 2783 g1_policy()->decide_on_conc_mark_initiation(); 2784 } 2785 2786 // We do not allow initial-mark to be piggy-backed on a mixed GC. 2787 assert(!collector_state()->in_initial_mark_gc() || 2788 collector_state()->in_young_only_phase(), "sanity"); 2789 2790 // We also do not allow mixed GCs during marking. 2791 assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity"); 2792 2793 // Record whether this pause is an initial mark. When the current 2794 // thread has completed its logging output and it's safe to signal 2795 // the CM thread, the flag's value in the policy has been reset. 2796 bool should_start_conc_mark = collector_state()->in_initial_mark_gc(); 2797 2798 // Inner scope for scope based logging, timers, and stats collection 2799 { 2800 EvacuationInfo evacuation_info; 2801 2802 if (collector_state()->in_initial_mark_gc()) { 2803 // We are about to start a marking cycle, so we increment the 2804 // full collection counter. 2805 increment_old_marking_cycles_started(); 2806 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 2807 } 2808 2809 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 2810 2811 GCTraceCPUTime tcpu; 2812 2813 G1HeapVerifier::G1VerifyType verify_type; 2814 FormatBuffer<> gc_string("Pause "); 2815 if (collector_state()->in_initial_mark_gc()) { 2816 gc_string.append("Initial Mark"); 2817 verify_type = G1HeapVerifier::G1VerifyInitialMark; 2818 } else if (collector_state()->in_young_only_phase()) { 2819 gc_string.append("Young"); 2820 verify_type = G1HeapVerifier::G1VerifyYoungOnly; 2821 } else { 2822 gc_string.append("Mixed"); 2823 verify_type = G1HeapVerifier::G1VerifyMixed; 2824 } 2825 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 2826 2827 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 2828 workers()->active_workers(), 2829 Threads::number_of_non_daemon_threads()); 2830 active_workers = workers()->update_active_workers(active_workers); 2831 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 2832 2833 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 2834 TraceMemoryManagerStats tms(&_memory_manager, gc_cause()); 2835 2836 G1HeapTransition heap_transition(this); 2837 size_t heap_used_bytes_before_gc = used(); 2838 2839 // Don't dynamically change the number of GC threads this early. A value of 2840 // 0 is used to indicate serial work. When parallel work is done, 2841 // it will be set. 2842 2843 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 2844 IsGCActiveMark x; 2845 2846 gc_prologue(false); 2847 2848 if (VerifyRememberedSets) { 2849 log_info(gc, verify)("[Verifying RemSets before GC]"); 2850 VerifyRegionRemSetClosure v_cl; 2851 heap_region_iterate(&v_cl); 2852 } 2853 2854 _verifier->verify_before_gc(verify_type); 2855 2856 _verifier->check_bitmaps("GC Start"); 2857 2858 #if COMPILER2_OR_JVMCI 2859 DerivedPointerTable::clear(); 2860 #endif 2861 2862 // Please see comment in g1CollectedHeap.hpp and 2863 // G1CollectedHeap::ref_processing_init() to see how 2864 // reference processing currently works in G1. 2865 2866 // Enable discovery in the STW reference processor 2867 _ref_processor_stw->enable_discovery(); 2868 2869 { 2870 // We want to temporarily turn off discovery by the 2871 // CM ref processor, if necessary, and turn it back on 2872 // on again later if we do. Using a scoped 2873 // NoRefDiscovery object will do this. 2874 NoRefDiscovery no_cm_discovery(_ref_processor_cm); 2875 2876 // Forget the current alloc region (we might even choose it to be part 2877 // of the collection set!). 2878 _allocator->release_mutator_alloc_region(); 2879 2880 // This timing is only used by the ergonomics to handle our pause target. 2881 // It is unclear why this should not include the full pause. We will 2882 // investigate this in CR 7178365. 2883 // 2884 // Preserving the old comment here if that helps the investigation: 2885 // 2886 // The elapsed time induced by the start time below deliberately elides 2887 // the possible verification above. 2888 double sample_start_time_sec = os::elapsedTime(); 2889 2890 g1_policy()->record_collection_pause_start(sample_start_time_sec); 2891 2892 if (collector_state()->in_initial_mark_gc()) { 2893 concurrent_mark()->pre_initial_mark(); 2894 } 2895 2896 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 2897 2898 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 2899 2900 // Make sure the remembered sets are up to date. This needs to be 2901 // done before register_humongous_regions_with_cset(), because the 2902 // remembered sets are used there to choose eager reclaim candidates. 2903 // If the remembered sets are not up to date we might miss some 2904 // entries that need to be handled. 2905 g1_rem_set()->cleanupHRRS(); 2906 2907 register_humongous_regions_with_cset(); 2908 2909 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 2910 2911 // We call this after finalize_cset() to 2912 // ensure that the CSet has been finalized. 2913 _cm->verify_no_cset_oops(); 2914 2915 if (_hr_printer.is_active()) { 2916 G1PrintCollectionSetClosure cl(&_hr_printer); 2917 _collection_set.iterate(&cl); 2918 } 2919 2920 // Initialize the GC alloc regions. 2921 _allocator->init_gc_alloc_regions(evacuation_info); 2922 2923 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 2924 pre_evacuate_collection_set(); 2925 2926 // Actually do the work... 2927 evacuate_collection_set(&per_thread_states); 2928 2929 post_evacuate_collection_set(evacuation_info, &per_thread_states); 2930 2931 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 2932 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 2933 2934 eagerly_reclaim_humongous_regions(); 2935 2936 record_obj_copy_mem_stats(); 2937 _survivor_evac_stats.adjust_desired_plab_sz(); 2938 _old_evac_stats.adjust_desired_plab_sz(); 2939 2940 double start = os::elapsedTime(); 2941 start_new_collection_set(); 2942 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 2943 2944 if (evacuation_failed()) { 2945 set_used(recalculate_used()); 2946 if (_archive_allocator != NULL) { 2947 _archive_allocator->clear_used(); 2948 } 2949 for (uint i = 0; i < ParallelGCThreads; i++) { 2950 if (_evacuation_failed_info_array[i].has_failed()) { 2951 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 2952 } 2953 } 2954 } else { 2955 // The "used" of the the collection set have already been subtracted 2956 // when they were freed. Add in the bytes evacuated. 2957 increase_used(g1_policy()->bytes_copied_during_gc()); 2958 } 2959 2960 if (collector_state()->in_initial_mark_gc()) { 2961 // We have to do this before we notify the CM threads that 2962 // they can start working to make sure that all the 2963 // appropriate initialization is done on the CM object. 2964 concurrent_mark()->post_initial_mark(); 2965 // Note that we don't actually trigger the CM thread at 2966 // this point. We do that later when we're sure that 2967 // the current thread has completed its logging output. 2968 } 2969 2970 allocate_dummy_regions(); 2971 2972 _allocator->init_mutator_alloc_region(); 2973 2974 { 2975 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 2976 if (expand_bytes > 0) { 2977 size_t bytes_before = capacity(); 2978 // No need for an ergo logging here, 2979 // expansion_amount() does this when it returns a value > 0. 2980 double expand_ms; 2981 if (!expand(expand_bytes, _workers, &expand_ms)) { 2982 // We failed to expand the heap. Cannot do anything about it. 2983 } 2984 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 2985 } 2986 } 2987 2988 // We redo the verification but now wrt to the new CSet which 2989 // has just got initialized after the previous CSet was freed. 2990 _cm->verify_no_cset_oops(); 2991 2992 // This timing is only used by the ergonomics to handle our pause target. 2993 // It is unclear why this should not include the full pause. We will 2994 // investigate this in CR 7178365. 2995 double sample_end_time_sec = os::elapsedTime(); 2996 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 2997 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards); 2998 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 2999 3000 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3001 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3002 3003 if (VerifyRememberedSets) { 3004 log_info(gc, verify)("[Verifying RemSets after GC]"); 3005 VerifyRegionRemSetClosure v_cl; 3006 heap_region_iterate(&v_cl); 3007 } 3008 3009 _verifier->verify_after_gc(verify_type); 3010 _verifier->check_bitmaps("GC End"); 3011 3012 assert(!_ref_processor_stw->discovery_enabled(), "Postcondition"); 3013 _ref_processor_stw->verify_no_references_recorded(); 3014 3015 // CM reference discovery will be re-enabled if necessary. 3016 } 3017 3018 #ifdef TRACESPINNING 3019 ParallelTaskTerminator::print_termination_counts(); 3020 #endif 3021 3022 gc_epilogue(false); 3023 } 3024 3025 // Print the remainder of the GC log output. 3026 if (evacuation_failed()) { 3027 log_info(gc)("To-space exhausted"); 3028 } 3029 3030 g1_policy()->print_phases(); 3031 heap_transition.print(); 3032 3033 // It is not yet to safe to tell the concurrent mark to 3034 // start as we have some optional output below. We don't want the 3035 // output from the concurrent mark thread interfering with this 3036 // logging output either. 3037 3038 _hrm.verify_optional(); 3039 _verifier->verify_region_sets_optional(); 3040 3041 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3042 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3043 3044 print_heap_after_gc(); 3045 print_heap_regions(); 3046 trace_heap_after_gc(_gc_tracer_stw); 3047 3048 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3049 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3050 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3051 // before any GC notifications are raised. 3052 g1mm()->update_sizes(); 3053 3054 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3055 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3056 _gc_timer_stw->register_gc_end(); 3057 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3058 } 3059 // It should now be safe to tell the concurrent mark thread to start 3060 // without its logging output interfering with the logging output 3061 // that came from the pause. 3062 3063 if (should_start_conc_mark) { 3064 // CAUTION: after the doConcurrentMark() call below, 3065 // the concurrent marking thread(s) could be running 3066 // concurrently with us. Make sure that anything after 3067 // this point does not assume that we are the only GC thread 3068 // running. Note: of course, the actual marking work will 3069 // not start until the safepoint itself is released in 3070 // SuspendibleThreadSet::desynchronize(). 3071 do_concurrent_mark(); 3072 } 3073 3074 return true; 3075 } 3076 3077 void G1CollectedHeap::remove_self_forwarding_pointers() { 3078 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3079 workers()->run_task(&rsfp_task); 3080 } 3081 3082 void G1CollectedHeap::restore_after_evac_failure() { 3083 double remove_self_forwards_start = os::elapsedTime(); 3084 3085 remove_self_forwarding_pointers(); 3086 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3087 _preserved_marks_set.restore(&task_executor); 3088 3089 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3090 } 3091 3092 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3093 if (!_evacuation_failed) { 3094 _evacuation_failed = true; 3095 } 3096 3097 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3098 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3099 } 3100 3101 bool G1ParEvacuateFollowersClosure::offer_termination() { 3102 G1ParScanThreadState* const pss = par_scan_state(); 3103 start_term_time(); 3104 const bool res = terminator()->offer_termination(); 3105 end_term_time(); 3106 return res; 3107 } 3108 3109 void G1ParEvacuateFollowersClosure::do_void() { 3110 G1ParScanThreadState* const pss = par_scan_state(); 3111 pss->trim_queue(); 3112 do { 3113 pss->steal_and_trim_queue(queues()); 3114 } while (!offer_termination()); 3115 } 3116 3117 class G1ParTask : public AbstractGangTask { 3118 protected: 3119 G1CollectedHeap* _g1h; 3120 G1ParScanThreadStateSet* _pss; 3121 RefToScanQueueSet* _queues; 3122 G1RootProcessor* _root_processor; 3123 ParallelTaskTerminator _terminator; 3124 uint _n_workers; 3125 3126 public: 3127 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3128 : AbstractGangTask("G1 collection"), 3129 _g1h(g1h), 3130 _pss(per_thread_states), 3131 _queues(task_queues), 3132 _root_processor(root_processor), 3133 _terminator(n_workers, _queues), 3134 _n_workers(n_workers) 3135 {} 3136 3137 void work(uint worker_id) { 3138 if (worker_id >= _n_workers) return; // no work needed this round 3139 3140 double start_sec = os::elapsedTime(); 3141 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3142 3143 { 3144 ResourceMark rm; 3145 HandleMark hm; 3146 3147 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3148 3149 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3150 pss->set_ref_discoverer(rp); 3151 3152 double start_strong_roots_sec = os::elapsedTime(); 3153 3154 _root_processor->evacuate_roots(pss, worker_id); 3155 3156 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3157 // treating the nmethods visited to act as roots for concurrent marking. 3158 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3159 // objects copied by the current evacuation. 3160 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, worker_id); 3161 3162 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3163 3164 double term_sec = 0.0; 3165 size_t evac_term_attempts = 0; 3166 { 3167 double start = os::elapsedTime(); 3168 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3169 evac.do_void(); 3170 3171 evac_term_attempts = evac.term_attempts(); 3172 term_sec = evac.term_time(); 3173 double elapsed_sec = os::elapsedTime() - start; 3174 3175 G1GCPhaseTimes* p = _g1h->g1_policy()->phase_times(); 3176 p->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3177 p->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3178 p->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3179 } 3180 3181 assert(pss->queue_is_empty(), "should be empty"); 3182 3183 if (log_is_enabled(Debug, gc, task, stats)) { 3184 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3185 size_t lab_waste; 3186 size_t lab_undo_waste; 3187 pss->waste(lab_waste, lab_undo_waste); 3188 _g1h->print_termination_stats(worker_id, 3189 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3190 strong_roots_sec * 1000.0, /* strong roots time */ 3191 term_sec * 1000.0, /* evac term time */ 3192 evac_term_attempts, /* evac term attempts */ 3193 lab_waste, /* alloc buffer waste */ 3194 lab_undo_waste /* undo waste */ 3195 ); 3196 } 3197 3198 // Close the inner scope so that the ResourceMark and HandleMark 3199 // destructors are executed here and are included as part of the 3200 // "GC Worker Time". 3201 } 3202 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3203 } 3204 }; 3205 3206 void G1CollectedHeap::print_termination_stats_hdr() { 3207 log_debug(gc, task, stats)("GC Termination Stats"); 3208 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3209 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3210 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3211 } 3212 3213 void G1CollectedHeap::print_termination_stats(uint worker_id, 3214 double elapsed_ms, 3215 double strong_roots_ms, 3216 double term_ms, 3217 size_t term_attempts, 3218 size_t alloc_buffer_waste, 3219 size_t undo_waste) const { 3220 log_debug(gc, task, stats) 3221 ("%3d %9.2f %9.2f %6.2f " 3222 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3223 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3224 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3225 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3226 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3227 alloc_buffer_waste * HeapWordSize / K, 3228 undo_waste * HeapWordSize / K); 3229 } 3230 3231 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3232 private: 3233 BoolObjectClosure* _is_alive; 3234 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3235 OopStorage::ParState<false /* concurrent */, false /* const */> _par_state_string; 3236 3237 int _initial_string_table_size; 3238 int _initial_symbol_table_size; 3239 3240 bool _process_strings; 3241 int _strings_processed; 3242 int _strings_removed; 3243 3244 bool _process_symbols; 3245 int _symbols_processed; 3246 int _symbols_removed; 3247 3248 bool _process_string_dedup; 3249 3250 public: 3251 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3252 AbstractGangTask("String/Symbol Unlinking"), 3253 _is_alive(is_alive), 3254 _dedup_closure(is_alive, NULL, false), 3255 _par_state_string(StringTable::weak_storage()), 3256 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3257 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3258 _process_string_dedup(process_string_dedup) { 3259 3260 _initial_string_table_size = (int) StringTable::the_table()->table_size(); 3261 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3262 if (process_symbols) { 3263 SymbolTable::clear_parallel_claimed_index(); 3264 } 3265 } 3266 3267 ~G1StringAndSymbolCleaningTask() { 3268 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3269 "claim value %d after unlink less than initial symbol table size %d", 3270 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3271 3272 log_info(gc, stringtable)( 3273 "Cleaned string and symbol table, " 3274 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3275 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3276 strings_processed(), strings_removed(), 3277 symbols_processed(), symbols_removed()); 3278 } 3279 3280 void work(uint worker_id) { 3281 int strings_processed = 0; 3282 int strings_removed = 0; 3283 int symbols_processed = 0; 3284 int symbols_removed = 0; 3285 if (_process_strings) { 3286 StringTable::possibly_parallel_unlink(&_par_state_string, _is_alive, &strings_processed, &strings_removed); 3287 Atomic::add(strings_processed, &_strings_processed); 3288 Atomic::add(strings_removed, &_strings_removed); 3289 } 3290 if (_process_symbols) { 3291 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3292 Atomic::add(symbols_processed, &_symbols_processed); 3293 Atomic::add(symbols_removed, &_symbols_removed); 3294 } 3295 if (_process_string_dedup) { 3296 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3297 } 3298 } 3299 3300 size_t strings_processed() const { return (size_t)_strings_processed; } 3301 size_t strings_removed() const { return (size_t)_strings_removed; } 3302 3303 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3304 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3305 }; 3306 3307 class G1CodeCacheUnloadingTask { 3308 private: 3309 static Monitor* _lock; 3310 3311 BoolObjectClosure* const _is_alive; 3312 const bool _unloading_occurred; 3313 const uint _num_workers; 3314 3315 // Variables used to claim nmethods. 3316 CompiledMethod* _first_nmethod; 3317 CompiledMethod* volatile _claimed_nmethod; 3318 3319 // The list of nmethods that need to be processed by the second pass. 3320 CompiledMethod* volatile _postponed_list; 3321 volatile uint _num_entered_barrier; 3322 3323 public: 3324 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3325 _is_alive(is_alive), 3326 _unloading_occurred(unloading_occurred), 3327 _num_workers(num_workers), 3328 _first_nmethod(NULL), 3329 _claimed_nmethod(NULL), 3330 _postponed_list(NULL), 3331 _num_entered_barrier(0) 3332 { 3333 CompiledMethod::increase_unloading_clock(); 3334 // Get first alive nmethod 3335 CompiledMethodIterator iter = CompiledMethodIterator(); 3336 if(iter.next_alive()) { 3337 _first_nmethod = iter.method(); 3338 } 3339 _claimed_nmethod = _first_nmethod; 3340 } 3341 3342 ~G1CodeCacheUnloadingTask() { 3343 CodeCache::verify_clean_inline_caches(); 3344 3345 CodeCache::set_needs_cache_clean(false); 3346 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3347 3348 CodeCache::verify_icholder_relocations(); 3349 } 3350 3351 private: 3352 void add_to_postponed_list(CompiledMethod* nm) { 3353 CompiledMethod* old; 3354 do { 3355 old = _postponed_list; 3356 nm->set_unloading_next(old); 3357 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old); 3358 } 3359 3360 void clean_nmethod(CompiledMethod* nm) { 3361 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3362 3363 if (postponed) { 3364 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3365 add_to_postponed_list(nm); 3366 } 3367 3368 // Mark that this nmethod has been cleaned/unloaded. 3369 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3370 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3371 } 3372 3373 void clean_nmethod_postponed(CompiledMethod* nm) { 3374 nm->do_unloading_parallel_postponed(); 3375 } 3376 3377 static const int MaxClaimNmethods = 16; 3378 3379 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3380 CompiledMethod* first; 3381 CompiledMethodIterator last; 3382 3383 do { 3384 *num_claimed_nmethods = 0; 3385 3386 first = _claimed_nmethod; 3387 last = CompiledMethodIterator(first); 3388 3389 if (first != NULL) { 3390 3391 for (int i = 0; i < MaxClaimNmethods; i++) { 3392 if (!last.next_alive()) { 3393 break; 3394 } 3395 claimed_nmethods[i] = last.method(); 3396 (*num_claimed_nmethods)++; 3397 } 3398 } 3399 3400 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first); 3401 } 3402 3403 CompiledMethod* claim_postponed_nmethod() { 3404 CompiledMethod* claim; 3405 CompiledMethod* next; 3406 3407 do { 3408 claim = _postponed_list; 3409 if (claim == NULL) { 3410 return NULL; 3411 } 3412 3413 next = claim->unloading_next(); 3414 3415 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim); 3416 3417 return claim; 3418 } 3419 3420 public: 3421 // Mark that we're done with the first pass of nmethod cleaning. 3422 void barrier_mark(uint worker_id) { 3423 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3424 _num_entered_barrier++; 3425 if (_num_entered_barrier == _num_workers) { 3426 ml.notify_all(); 3427 } 3428 } 3429 3430 // See if we have to wait for the other workers to 3431 // finish their first-pass nmethod cleaning work. 3432 void barrier_wait(uint worker_id) { 3433 if (_num_entered_barrier < _num_workers) { 3434 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3435 while (_num_entered_barrier < _num_workers) { 3436 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3437 } 3438 } 3439 } 3440 3441 // Cleaning and unloading of nmethods. Some work has to be postponed 3442 // to the second pass, when we know which nmethods survive. 3443 void work_first_pass(uint worker_id) { 3444 // The first nmethods is claimed by the first worker. 3445 if (worker_id == 0 && _first_nmethod != NULL) { 3446 clean_nmethod(_first_nmethod); 3447 _first_nmethod = NULL; 3448 } 3449 3450 int num_claimed_nmethods; 3451 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3452 3453 while (true) { 3454 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3455 3456 if (num_claimed_nmethods == 0) { 3457 break; 3458 } 3459 3460 for (int i = 0; i < num_claimed_nmethods; i++) { 3461 clean_nmethod(claimed_nmethods[i]); 3462 } 3463 } 3464 } 3465 3466 void work_second_pass(uint worker_id) { 3467 CompiledMethod* nm; 3468 // Take care of postponed nmethods. 3469 while ((nm = claim_postponed_nmethod()) != NULL) { 3470 clean_nmethod_postponed(nm); 3471 } 3472 } 3473 }; 3474 3475 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3476 3477 class G1KlassCleaningTask : public StackObj { 3478 volatile int _clean_klass_tree_claimed; 3479 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3480 3481 public: 3482 G1KlassCleaningTask() : 3483 _clean_klass_tree_claimed(0), 3484 _klass_iterator() { 3485 } 3486 3487 private: 3488 bool claim_clean_klass_tree_task() { 3489 if (_clean_klass_tree_claimed) { 3490 return false; 3491 } 3492 3493 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0; 3494 } 3495 3496 InstanceKlass* claim_next_klass() { 3497 Klass* klass; 3498 do { 3499 klass =_klass_iterator.next_klass(); 3500 } while (klass != NULL && !klass->is_instance_klass()); 3501 3502 // this can be null so don't call InstanceKlass::cast 3503 return static_cast<InstanceKlass*>(klass); 3504 } 3505 3506 public: 3507 3508 void clean_klass(InstanceKlass* ik) { 3509 ik->clean_weak_instanceklass_links(); 3510 } 3511 3512 void work() { 3513 ResourceMark rm; 3514 3515 // One worker will clean the subklass/sibling klass tree. 3516 if (claim_clean_klass_tree_task()) { 3517 Klass::clean_subklass_tree(); 3518 } 3519 3520 // All workers will help cleaning the classes, 3521 InstanceKlass* klass; 3522 while ((klass = claim_next_klass()) != NULL) { 3523 clean_klass(klass); 3524 } 3525 } 3526 }; 3527 3528 class G1ResolvedMethodCleaningTask : public StackObj { 3529 volatile int _resolved_method_task_claimed; 3530 public: 3531 G1ResolvedMethodCleaningTask() : 3532 _resolved_method_task_claimed(0) {} 3533 3534 bool claim_resolved_method_task() { 3535 if (_resolved_method_task_claimed) { 3536 return false; 3537 } 3538 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0; 3539 } 3540 3541 // These aren't big, one thread can do it all. 3542 void work() { 3543 if (claim_resolved_method_task()) { 3544 ResolvedMethodTable::unlink(); 3545 } 3546 } 3547 }; 3548 3549 3550 // To minimize the remark pause times, the tasks below are done in parallel. 3551 class G1ParallelCleaningTask : public AbstractGangTask { 3552 private: 3553 bool _unloading_occurred; 3554 G1StringAndSymbolCleaningTask _string_symbol_task; 3555 G1CodeCacheUnloadingTask _code_cache_task; 3556 G1KlassCleaningTask _klass_cleaning_task; 3557 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task; 3558 3559 public: 3560 // The constructor is run in the VMThread. 3561 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3562 AbstractGangTask("Parallel Cleaning"), 3563 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3564 _code_cache_task(num_workers, is_alive, unloading_occurred), 3565 _klass_cleaning_task(), 3566 _unloading_occurred(unloading_occurred), 3567 _resolved_method_cleaning_task() { 3568 } 3569 3570 // The parallel work done by all worker threads. 3571 void work(uint worker_id) { 3572 // Do first pass of code cache cleaning. 3573 _code_cache_task.work_first_pass(worker_id); 3574 3575 // Let the threads mark that the first pass is done. 3576 _code_cache_task.barrier_mark(worker_id); 3577 3578 // Clean the Strings and Symbols. 3579 _string_symbol_task.work(worker_id); 3580 3581 // Clean unreferenced things in the ResolvedMethodTable 3582 _resolved_method_cleaning_task.work(); 3583 3584 // Wait for all workers to finish the first code cache cleaning pass. 3585 _code_cache_task.barrier_wait(worker_id); 3586 3587 // Do the second code cache cleaning work, which realize on 3588 // the liveness information gathered during the first pass. 3589 _code_cache_task.work_second_pass(worker_id); 3590 3591 // Clean all klasses that were not unloaded. 3592 // The weak metadata in klass doesn't need to be 3593 // processed if there was no unloading. 3594 if (_unloading_occurred) { 3595 _klass_cleaning_task.work(); 3596 } 3597 } 3598 }; 3599 3600 3601 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3602 bool class_unloading_occurred) { 3603 uint n_workers = workers()->active_workers(); 3604 3605 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3606 workers()->run_task(&g1_unlink_task); 3607 } 3608 3609 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3610 bool process_strings, 3611 bool process_symbols, 3612 bool process_string_dedup) { 3613 if (!process_strings && !process_symbols && !process_string_dedup) { 3614 // Nothing to clean. 3615 return; 3616 } 3617 3618 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3619 workers()->run_task(&g1_unlink_task); 3620 3621 } 3622 3623 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3624 private: 3625 DirtyCardQueueSet* _queue; 3626 G1CollectedHeap* _g1h; 3627 public: 3628 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3629 _queue(queue), _g1h(g1h) { } 3630 3631 virtual void work(uint worker_id) { 3632 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3633 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3634 3635 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3636 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3637 3638 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3639 } 3640 }; 3641 3642 void G1CollectedHeap::redirty_logged_cards() { 3643 double redirty_logged_cards_start = os::elapsedTime(); 3644 3645 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3646 dirty_card_queue_set().reset_for_par_iteration(); 3647 workers()->run_task(&redirty_task); 3648 3649 DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set(); 3650 dcq.merge_bufferlists(&dirty_card_queue_set()); 3651 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3652 3653 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3654 } 3655 3656 // Weak Reference Processing support 3657 3658 bool G1STWIsAliveClosure::do_object_b(oop p) { 3659 // An object is reachable if it is outside the collection set, 3660 // or is inside and copied. 3661 return !_g1h->is_in_cset(p) || p->is_forwarded(); 3662 } 3663 3664 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) { 3665 assert(obj != NULL, "must not be NULL"); 3666 assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj)); 3667 // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below 3668 // may falsely indicate that this is not the case here: however the collection set only 3669 // contains old regions when concurrent mark is not running. 3670 return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor(); 3671 } 3672 3673 // Non Copying Keep Alive closure 3674 class G1KeepAliveClosure: public OopClosure { 3675 G1CollectedHeap*_g1h; 3676 public: 3677 G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {} 3678 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3679 void do_oop(oop* p) { 3680 oop obj = *p; 3681 assert(obj != NULL, "the caller should have filtered out NULL values"); 3682 3683 const InCSetState cset_state =_g1h->in_cset_state(obj); 3684 if (!cset_state.is_in_cset_or_humongous()) { 3685 return; 3686 } 3687 if (cset_state.is_in_cset()) { 3688 assert( obj->is_forwarded(), "invariant" ); 3689 *p = obj->forwardee(); 3690 } else { 3691 assert(!obj->is_forwarded(), "invariant" ); 3692 assert(cset_state.is_humongous(), 3693 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3694 _g1h->set_humongous_is_live(obj); 3695 } 3696 } 3697 }; 3698 3699 // Copying Keep Alive closure - can be called from both 3700 // serial and parallel code as long as different worker 3701 // threads utilize different G1ParScanThreadState instances 3702 // and different queues. 3703 3704 class G1CopyingKeepAliveClosure: public OopClosure { 3705 G1CollectedHeap* _g1h; 3706 OopClosure* _copy_non_heap_obj_cl; 3707 G1ParScanThreadState* _par_scan_state; 3708 3709 public: 3710 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3711 OopClosure* non_heap_obj_cl, 3712 G1ParScanThreadState* pss): 3713 _g1h(g1h), 3714 _copy_non_heap_obj_cl(non_heap_obj_cl), 3715 _par_scan_state(pss) 3716 {} 3717 3718 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3719 virtual void do_oop( oop* p) { do_oop_work(p); } 3720 3721 template <class T> void do_oop_work(T* p) { 3722 oop obj = RawAccess<>::oop_load(p); 3723 3724 if (_g1h->is_in_cset_or_humongous(obj)) { 3725 // If the referent object has been forwarded (either copied 3726 // to a new location or to itself in the event of an 3727 // evacuation failure) then we need to update the reference 3728 // field and, if both reference and referent are in the G1 3729 // heap, update the RSet for the referent. 3730 // 3731 // If the referent has not been forwarded then we have to keep 3732 // it alive by policy. Therefore we have copy the referent. 3733 // 3734 // If the reference field is in the G1 heap then we can push 3735 // on the PSS queue. When the queue is drained (after each 3736 // phase of reference processing) the object and it's followers 3737 // will be copied, the reference field set to point to the 3738 // new location, and the RSet updated. Otherwise we need to 3739 // use the the non-heap or metadata closures directly to copy 3740 // the referent object and update the pointer, while avoiding 3741 // updating the RSet. 3742 3743 if (_g1h->is_in_g1_reserved(p)) { 3744 _par_scan_state->push_on_queue(p); 3745 } else { 3746 assert(!Metaspace::contains((const void*)p), 3747 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 3748 _copy_non_heap_obj_cl->do_oop(p); 3749 } 3750 } 3751 } 3752 }; 3753 3754 // Serial drain queue closure. Called as the 'complete_gc' 3755 // closure for each discovered list in some of the 3756 // reference processing phases. 3757 3758 class G1STWDrainQueueClosure: public VoidClosure { 3759 protected: 3760 G1CollectedHeap* _g1h; 3761 G1ParScanThreadState* _par_scan_state; 3762 3763 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3764 3765 public: 3766 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3767 _g1h(g1h), 3768 _par_scan_state(pss) 3769 { } 3770 3771 void do_void() { 3772 G1ParScanThreadState* const pss = par_scan_state(); 3773 pss->trim_queue(); 3774 } 3775 }; 3776 3777 // Parallel Reference Processing closures 3778 3779 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3780 // processing during G1 evacuation pauses. 3781 3782 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3783 private: 3784 G1CollectedHeap* _g1h; 3785 G1ParScanThreadStateSet* _pss; 3786 RefToScanQueueSet* _queues; 3787 WorkGang* _workers; 3788 uint _active_workers; 3789 3790 public: 3791 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3792 G1ParScanThreadStateSet* per_thread_states, 3793 WorkGang* workers, 3794 RefToScanQueueSet *task_queues, 3795 uint n_workers) : 3796 _g1h(g1h), 3797 _pss(per_thread_states), 3798 _queues(task_queues), 3799 _workers(workers), 3800 _active_workers(n_workers) 3801 { 3802 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 3803 } 3804 3805 // Executes the given task using concurrent marking worker threads. 3806 virtual void execute(ProcessTask& task); 3807 }; 3808 3809 // Gang task for possibly parallel reference processing 3810 3811 class G1STWRefProcTaskProxy: public AbstractGangTask { 3812 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 3813 ProcessTask& _proc_task; 3814 G1CollectedHeap* _g1h; 3815 G1ParScanThreadStateSet* _pss; 3816 RefToScanQueueSet* _task_queues; 3817 ParallelTaskTerminator* _terminator; 3818 3819 public: 3820 G1STWRefProcTaskProxy(ProcessTask& proc_task, 3821 G1CollectedHeap* g1h, 3822 G1ParScanThreadStateSet* per_thread_states, 3823 RefToScanQueueSet *task_queues, 3824 ParallelTaskTerminator* terminator) : 3825 AbstractGangTask("Process reference objects in parallel"), 3826 _proc_task(proc_task), 3827 _g1h(g1h), 3828 _pss(per_thread_states), 3829 _task_queues(task_queues), 3830 _terminator(terminator) 3831 {} 3832 3833 virtual void work(uint worker_id) { 3834 // The reference processing task executed by a single worker. 3835 ResourceMark rm; 3836 HandleMark hm; 3837 3838 G1STWIsAliveClosure is_alive(_g1h); 3839 3840 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3841 pss->set_ref_discoverer(NULL); 3842 3843 // Keep alive closure. 3844 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 3845 3846 // Complete GC closure 3847 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 3848 3849 // Call the reference processing task's work routine. 3850 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 3851 3852 // Note we cannot assert that the refs array is empty here as not all 3853 // of the processing tasks (specifically phase2 - pp2_work) execute 3854 // the complete_gc closure (which ordinarily would drain the queue) so 3855 // the queue may not be empty. 3856 } 3857 }; 3858 3859 // Driver routine for parallel reference processing. 3860 // Creates an instance of the ref processing gang 3861 // task and has the worker threads execute it. 3862 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 3863 assert(_workers != NULL, "Need parallel worker threads."); 3864 3865 ParallelTaskTerminator terminator(_active_workers, _queues); 3866 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 3867 3868 _workers->run_task(&proc_task_proxy); 3869 } 3870 3871 // End of weak reference support closures 3872 3873 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 3874 double ref_proc_start = os::elapsedTime(); 3875 3876 ReferenceProcessor* rp = _ref_processor_stw; 3877 assert(rp->discovery_enabled(), "should have been enabled"); 3878 3879 // Closure to test whether a referent is alive. 3880 G1STWIsAliveClosure is_alive(this); 3881 3882 // Even when parallel reference processing is enabled, the processing 3883 // of JNI refs is serial and performed serially by the current thread 3884 // rather than by a worker. The following PSS will be used for processing 3885 // JNI refs. 3886 3887 // Use only a single queue for this PSS. 3888 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 3889 pss->set_ref_discoverer(NULL); 3890 assert(pss->queue_is_empty(), "pre-condition"); 3891 3892 // Keep alive closure. 3893 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 3894 3895 // Serial Complete GC closure 3896 G1STWDrainQueueClosure drain_queue(this, pss); 3897 3898 // Setup the soft refs policy... 3899 rp->setup_policy(false); 3900 3901 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 3902 3903 ReferenceProcessorStats stats; 3904 if (!rp->processing_is_mt()) { 3905 // Serial reference processing... 3906 stats = rp->process_discovered_references(&is_alive, 3907 &keep_alive, 3908 &drain_queue, 3909 NULL, 3910 pt); 3911 } else { 3912 uint no_of_gc_workers = workers()->active_workers(); 3913 3914 // Parallel reference processing 3915 assert(no_of_gc_workers <= rp->max_num_queues(), 3916 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 3917 no_of_gc_workers, rp->max_num_queues()); 3918 3919 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 3920 stats = rp->process_discovered_references(&is_alive, 3921 &keep_alive, 3922 &drain_queue, 3923 &par_task_executor, 3924 pt); 3925 } 3926 3927 _gc_tracer_stw->report_gc_reference_stats(stats); 3928 3929 // We have completed copying any necessary live referent objects. 3930 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 3931 3932 make_pending_list_reachable(); 3933 3934 rp->verify_no_references_recorded(); 3935 3936 double ref_proc_time = os::elapsedTime() - ref_proc_start; 3937 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 3938 } 3939 3940 void G1CollectedHeap::make_pending_list_reachable() { 3941 if (collector_state()->in_initial_mark_gc()) { 3942 oop pll_head = Universe::reference_pending_list(); 3943 if (pll_head != NULL) { 3944 // Any valid worker id is fine here as we are in the VM thread and single-threaded. 3945 _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head); 3946 } 3947 } 3948 } 3949 3950 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 3951 double merge_pss_time_start = os::elapsedTime(); 3952 per_thread_states->flush(); 3953 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 3954 } 3955 3956 void G1CollectedHeap::pre_evacuate_collection_set() { 3957 _expand_heap_after_alloc_failure = true; 3958 _evacuation_failed = false; 3959 3960 // Disable the hot card cache. 3961 _hot_card_cache->reset_hot_cache_claimed_index(); 3962 _hot_card_cache->set_use_cache(false); 3963 3964 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 3965 _preserved_marks_set.assert_empty(); 3966 3967 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 3968 3969 // InitialMark needs claim bits to keep track of the marked-through CLDs. 3970 if (collector_state()->in_initial_mark_gc()) { 3971 double start_clear_claimed_marks = os::elapsedTime(); 3972 3973 ClassLoaderDataGraph::clear_claimed_marks(); 3974 3975 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 3976 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 3977 } 3978 } 3979 3980 void G1CollectedHeap::evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states) { 3981 // Should G1EvacuationFailureALot be in effect for this GC? 3982 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 3983 3984 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 3985 3986 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 3987 3988 double start_par_time_sec = os::elapsedTime(); 3989 double end_par_time_sec; 3990 3991 { 3992 const uint n_workers = workers()->active_workers(); 3993 G1RootProcessor root_processor(this, n_workers); 3994 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 3995 3996 print_termination_stats_hdr(); 3997 3998 workers()->run_task(&g1_par_task); 3999 end_par_time_sec = os::elapsedTime(); 4000 4001 // Closing the inner scope will execute the destructor 4002 // for the G1RootProcessor object. We record the current 4003 // elapsed time before closing the scope so that time 4004 // taken for the destructor is NOT included in the 4005 // reported parallel time. 4006 } 4007 4008 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4009 phase_times->record_par_time(par_time_ms); 4010 4011 double code_root_fixup_time_ms = 4012 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4013 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4014 } 4015 4016 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4017 // Also cleans the card table from temporary duplicate detection information used 4018 // during UpdateRS/ScanRS. 4019 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4020 4021 // Process any discovered reference objects - we have 4022 // to do this _before_ we retire the GC alloc regions 4023 // as we may have to copy some 'reachable' referent 4024 // objects (and their reachable sub-graphs) that were 4025 // not copied during the pause. 4026 process_discovered_references(per_thread_states); 4027 4028 // FIXME 4029 // CM's reference processing also cleans up the string and symbol tables. 4030 // Should we do that here also? We could, but it is a serial operation 4031 // and could significantly increase the pause time. 4032 4033 G1STWIsAliveClosure is_alive(this); 4034 G1KeepAliveClosure keep_alive(this); 4035 4036 { 4037 double start = os::elapsedTime(); 4038 4039 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 4040 4041 double time_ms = (os::elapsedTime() - start) * 1000.0; 4042 g1_policy()->phase_times()->record_weak_ref_proc_time(time_ms); 4043 } 4044 4045 if (G1StringDedup::is_enabled()) { 4046 double fixup_start = os::elapsedTime(); 4047 4048 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4049 4050 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4051 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4052 } 4053 4054 if (evacuation_failed()) { 4055 restore_after_evac_failure(); 4056 4057 // Reset the G1EvacuationFailureALot counters and flags 4058 // Note: the values are reset only when an actual 4059 // evacuation failure occurs. 4060 NOT_PRODUCT(reset_evacuation_should_fail();) 4061 } 4062 4063 _preserved_marks_set.assert_empty(); 4064 4065 _allocator->release_gc_alloc_regions(evacuation_info); 4066 4067 merge_per_thread_state_info(per_thread_states); 4068 4069 // Reset and re-enable the hot card cache. 4070 // Note the counts for the cards in the regions in the 4071 // collection set are reset when the collection set is freed. 4072 _hot_card_cache->reset_hot_cache(); 4073 _hot_card_cache->set_use_cache(true); 4074 4075 purge_code_root_memory(); 4076 4077 redirty_logged_cards(); 4078 #if COMPILER2_OR_JVMCI 4079 double start = os::elapsedTime(); 4080 DerivedPointerTable::update_pointers(); 4081 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4082 #endif 4083 g1_policy()->print_age_table(); 4084 } 4085 4086 void G1CollectedHeap::record_obj_copy_mem_stats() { 4087 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4088 4089 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4090 create_g1_evac_summary(&_old_evac_stats)); 4091 } 4092 4093 void G1CollectedHeap::free_region(HeapRegion* hr, 4094 FreeRegionList* free_list, 4095 bool skip_remset, 4096 bool skip_hot_card_cache, 4097 bool locked) { 4098 assert(!hr->is_free(), "the region should not be free"); 4099 assert(!hr->is_empty(), "the region should not be empty"); 4100 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4101 assert(free_list != NULL, "pre-condition"); 4102 4103 if (G1VerifyBitmaps) { 4104 MemRegion mr(hr->bottom(), hr->end()); 4105 concurrent_mark()->clear_range_in_prev_bitmap(mr); 4106 } 4107 4108 // Clear the card counts for this region. 4109 // Note: we only need to do this if the region is not young 4110 // (since we don't refine cards in young regions). 4111 if (!skip_hot_card_cache && !hr->is_young()) { 4112 _hot_card_cache->reset_card_counts(hr); 4113 } 4114 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4115 _g1_policy->remset_tracker()->update_at_free(hr); 4116 free_list->add_ordered(hr); 4117 } 4118 4119 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4120 FreeRegionList* free_list) { 4121 assert(hr->is_humongous(), "this is only for humongous regions"); 4122 assert(free_list != NULL, "pre-condition"); 4123 hr->clear_humongous(); 4124 free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */); 4125 } 4126 4127 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4128 const uint humongous_regions_removed) { 4129 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4130 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4131 _old_set.bulk_remove(old_regions_removed); 4132 _humongous_set.bulk_remove(humongous_regions_removed); 4133 } 4134 4135 } 4136 4137 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4138 assert(list != NULL, "list can't be null"); 4139 if (!list->is_empty()) { 4140 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4141 _hrm.insert_list_into_free_list(list); 4142 } 4143 } 4144 4145 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4146 decrease_used(bytes); 4147 } 4148 4149 class G1FreeCollectionSetTask : public AbstractGangTask { 4150 private: 4151 4152 // Closure applied to all regions in the collection set to do work that needs to 4153 // be done serially in a single thread. 4154 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4155 private: 4156 EvacuationInfo* _evacuation_info; 4157 const size_t* _surviving_young_words; 4158 4159 // Bytes used in successfully evacuated regions before the evacuation. 4160 size_t _before_used_bytes; 4161 // Bytes used in unsucessfully evacuated regions before the evacuation 4162 size_t _after_used_bytes; 4163 4164 size_t _bytes_allocated_in_old_since_last_gc; 4165 4166 size_t _failure_used_words; 4167 size_t _failure_waste_words; 4168 4169 FreeRegionList _local_free_list; 4170 public: 4171 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4172 HeapRegionClosure(), 4173 _evacuation_info(evacuation_info), 4174 _surviving_young_words(surviving_young_words), 4175 _before_used_bytes(0), 4176 _after_used_bytes(0), 4177 _bytes_allocated_in_old_since_last_gc(0), 4178 _failure_used_words(0), 4179 _failure_waste_words(0), 4180 _local_free_list("Local Region List for CSet Freeing") { 4181 } 4182 4183 virtual bool do_heap_region(HeapRegion* r) { 4184 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4185 4186 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4187 g1h->clear_in_cset(r); 4188 4189 if (r->is_young()) { 4190 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4191 "Young index %d is wrong for region %u of type %s with %u young regions", 4192 r->young_index_in_cset(), 4193 r->hrm_index(), 4194 r->get_type_str(), 4195 g1h->collection_set()->young_region_length()); 4196 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4197 r->record_surv_words_in_group(words_survived); 4198 } 4199 4200 if (!r->evacuation_failed()) { 4201 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4202 _before_used_bytes += r->used(); 4203 g1h->free_region(r, 4204 &_local_free_list, 4205 true, /* skip_remset */ 4206 true, /* skip_hot_card_cache */ 4207 true /* locked */); 4208 } else { 4209 r->uninstall_surv_rate_group(); 4210 r->set_young_index_in_cset(-1); 4211 r->set_evacuation_failed(false); 4212 // When moving a young gen region to old gen, we "allocate" that whole region 4213 // there. This is in addition to any already evacuated objects. Notify the 4214 // policy about that. 4215 // Old gen regions do not cause an additional allocation: both the objects 4216 // still in the region and the ones already moved are accounted for elsewhere. 4217 if (r->is_young()) { 4218 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4219 } 4220 // The region is now considered to be old. 4221 r->set_old(); 4222 // Do some allocation statistics accounting. Regions that failed evacuation 4223 // are always made old, so there is no need to update anything in the young 4224 // gen statistics, but we need to update old gen statistics. 4225 size_t used_words = r->marked_bytes() / HeapWordSize; 4226 4227 _failure_used_words += used_words; 4228 _failure_waste_words += HeapRegion::GrainWords - used_words; 4229 4230 g1h->old_set_add(r); 4231 _after_used_bytes += r->used(); 4232 } 4233 return false; 4234 } 4235 4236 void complete_work() { 4237 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4238 4239 _evacuation_info->set_regions_freed(_local_free_list.length()); 4240 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4241 4242 g1h->prepend_to_freelist(&_local_free_list); 4243 g1h->decrement_summary_bytes(_before_used_bytes); 4244 4245 G1Policy* policy = g1h->g1_policy(); 4246 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4247 4248 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4249 } 4250 }; 4251 4252 G1CollectionSet* _collection_set; 4253 G1SerialFreeCollectionSetClosure _cl; 4254 const size_t* _surviving_young_words; 4255 4256 size_t _rs_lengths; 4257 4258 volatile jint _serial_work_claim; 4259 4260 struct WorkItem { 4261 uint region_idx; 4262 bool is_young; 4263 bool evacuation_failed; 4264 4265 WorkItem(HeapRegion* r) { 4266 region_idx = r->hrm_index(); 4267 is_young = r->is_young(); 4268 evacuation_failed = r->evacuation_failed(); 4269 } 4270 }; 4271 4272 volatile size_t _parallel_work_claim; 4273 size_t _num_work_items; 4274 WorkItem* _work_items; 4275 4276 void do_serial_work() { 4277 // Need to grab the lock to be allowed to modify the old region list. 4278 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4279 _collection_set->iterate(&_cl); 4280 } 4281 4282 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4283 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4284 4285 HeapRegion* r = g1h->region_at(region_idx); 4286 assert(!g1h->is_on_master_free_list(r), "sanity"); 4287 4288 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4289 4290 if (!is_young) { 4291 g1h->_hot_card_cache->reset_card_counts(r); 4292 } 4293 4294 if (!evacuation_failed) { 4295 r->rem_set()->clear_locked(); 4296 } 4297 } 4298 4299 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4300 private: 4301 size_t _cur_idx; 4302 WorkItem* _work_items; 4303 public: 4304 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4305 4306 virtual bool do_heap_region(HeapRegion* r) { 4307 _work_items[_cur_idx++] = WorkItem(r); 4308 return false; 4309 } 4310 }; 4311 4312 void prepare_work() { 4313 G1PrepareFreeCollectionSetClosure cl(_work_items); 4314 _collection_set->iterate(&cl); 4315 } 4316 4317 void complete_work() { 4318 _cl.complete_work(); 4319 4320 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4321 policy->record_max_rs_lengths(_rs_lengths); 4322 policy->cset_regions_freed(); 4323 } 4324 public: 4325 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4326 AbstractGangTask("G1 Free Collection Set"), 4327 _cl(evacuation_info, surviving_young_words), 4328 _collection_set(collection_set), 4329 _surviving_young_words(surviving_young_words), 4330 _serial_work_claim(0), 4331 _rs_lengths(0), 4332 _parallel_work_claim(0), 4333 _num_work_items(collection_set->region_length()), 4334 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4335 prepare_work(); 4336 } 4337 4338 ~G1FreeCollectionSetTask() { 4339 complete_work(); 4340 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4341 } 4342 4343 // Chunk size for work distribution. The chosen value has been determined experimentally 4344 // to be a good tradeoff between overhead and achievable parallelism. 4345 static uint chunk_size() { return 32; } 4346 4347 virtual void work(uint worker_id) { 4348 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4349 4350 // Claim serial work. 4351 if (_serial_work_claim == 0) { 4352 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4353 if (value == 0) { 4354 double serial_time = os::elapsedTime(); 4355 do_serial_work(); 4356 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4357 } 4358 } 4359 4360 // Start parallel work. 4361 double young_time = 0.0; 4362 bool has_young_time = false; 4363 double non_young_time = 0.0; 4364 bool has_non_young_time = false; 4365 4366 while (true) { 4367 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4368 size_t cur = end - chunk_size(); 4369 4370 if (cur >= _num_work_items) { 4371 break; 4372 } 4373 4374 double start_time = os::elapsedTime(); 4375 4376 end = MIN2(end, _num_work_items); 4377 4378 for (; cur < end; cur++) { 4379 bool is_young = _work_items[cur].is_young; 4380 4381 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4382 4383 double end_time = os::elapsedTime(); 4384 double time_taken = end_time - start_time; 4385 if (is_young) { 4386 young_time += time_taken; 4387 has_young_time = true; 4388 } else { 4389 non_young_time += time_taken; 4390 has_non_young_time = true; 4391 } 4392 start_time = end_time; 4393 } 4394 } 4395 4396 if (has_young_time) { 4397 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4398 } 4399 if (has_non_young_time) { 4400 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time); 4401 } 4402 } 4403 }; 4404 4405 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4406 _eden.clear(); 4407 4408 double free_cset_start_time = os::elapsedTime(); 4409 4410 { 4411 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4412 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4413 4414 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4415 4416 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4417 cl.name(), 4418 num_workers, 4419 _collection_set.region_length()); 4420 workers()->run_task(&cl, num_workers); 4421 } 4422 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4423 4424 collection_set->clear(); 4425 } 4426 4427 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4428 private: 4429 FreeRegionList* _free_region_list; 4430 HeapRegionSet* _proxy_set; 4431 uint _humongous_objects_reclaimed; 4432 uint _humongous_regions_reclaimed; 4433 size_t _freed_bytes; 4434 public: 4435 4436 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4437 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4438 } 4439 4440 virtual bool do_heap_region(HeapRegion* r) { 4441 if (!r->is_starts_humongous()) { 4442 return false; 4443 } 4444 4445 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4446 4447 oop obj = (oop)r->bottom(); 4448 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap(); 4449 4450 // The following checks whether the humongous object is live are sufficient. 4451 // The main additional check (in addition to having a reference from the roots 4452 // or the young gen) is whether the humongous object has a remembered set entry. 4453 // 4454 // A humongous object cannot be live if there is no remembered set for it 4455 // because: 4456 // - there can be no references from within humongous starts regions referencing 4457 // the object because we never allocate other objects into them. 4458 // (I.e. there are no intra-region references that may be missed by the 4459 // remembered set) 4460 // - as soon there is a remembered set entry to the humongous starts region 4461 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4462 // until the end of a concurrent mark. 4463 // 4464 // It is not required to check whether the object has been found dead by marking 4465 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4466 // all objects allocated during that time are considered live. 4467 // SATB marking is even more conservative than the remembered set. 4468 // So if at this point in the collection there is no remembered set entry, 4469 // nobody has a reference to it. 4470 // At the start of collection we flush all refinement logs, and remembered sets 4471 // are completely up-to-date wrt to references to the humongous object. 4472 // 4473 // Other implementation considerations: 4474 // - never consider object arrays at this time because they would pose 4475 // considerable effort for cleaning up the the remembered sets. This is 4476 // required because stale remembered sets might reference locations that 4477 // are currently allocated into. 4478 uint region_idx = r->hrm_index(); 4479 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4480 !r->rem_set()->is_empty()) { 4481 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", 4482 region_idx, 4483 (size_t)obj->size() * HeapWordSize, 4484 p2i(r->bottom()), 4485 r->rem_set()->occupied(), 4486 r->rem_set()->strong_code_roots_list_length(), 4487 next_bitmap->is_marked(r->bottom()), 4488 g1h->is_humongous_reclaim_candidate(region_idx), 4489 obj->is_typeArray() 4490 ); 4491 return false; 4492 } 4493 4494 guarantee(obj->is_typeArray(), 4495 "Only eagerly reclaiming type arrays is supported, but the object " 4496 PTR_FORMAT " is not.", p2i(r->bottom())); 4497 4498 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", 4499 region_idx, 4500 (size_t)obj->size() * HeapWordSize, 4501 p2i(r->bottom()), 4502 r->rem_set()->occupied(), 4503 r->rem_set()->strong_code_roots_list_length(), 4504 next_bitmap->is_marked(r->bottom()), 4505 g1h->is_humongous_reclaim_candidate(region_idx), 4506 obj->is_typeArray() 4507 ); 4508 4509 G1ConcurrentMark* const cm = g1h->concurrent_mark(); 4510 cm->humongous_object_eagerly_reclaimed(r); 4511 assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj), 4512 "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s", 4513 region_idx, 4514 BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)), 4515 BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj))); 4516 _humongous_objects_reclaimed++; 4517 do { 4518 HeapRegion* next = g1h->next_region_in_humongous(r); 4519 _freed_bytes += r->used(); 4520 r->set_containing_set(NULL); 4521 _humongous_regions_reclaimed++; 4522 g1h->free_humongous_region(r, _free_region_list); 4523 r = next; 4524 } while (r != NULL); 4525 4526 return false; 4527 } 4528 4529 uint humongous_objects_reclaimed() { 4530 return _humongous_objects_reclaimed; 4531 } 4532 4533 uint humongous_regions_reclaimed() { 4534 return _humongous_regions_reclaimed; 4535 } 4536 4537 size_t bytes_freed() const { 4538 return _freed_bytes; 4539 } 4540 }; 4541 4542 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4543 assert_at_safepoint_on_vm_thread(); 4544 4545 if (!G1EagerReclaimHumongousObjects || 4546 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4547 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4548 return; 4549 } 4550 4551 double start_time = os::elapsedTime(); 4552 4553 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4554 4555 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4556 heap_region_iterate(&cl); 4557 4558 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4559 4560 G1HRPrinter* hrp = hr_printer(); 4561 if (hrp->is_active()) { 4562 FreeRegionListIterator iter(&local_cleanup_list); 4563 while (iter.more_available()) { 4564 HeapRegion* hr = iter.get_next(); 4565 hrp->cleanup(hr); 4566 } 4567 } 4568 4569 prepend_to_freelist(&local_cleanup_list); 4570 decrement_summary_bytes(cl.bytes_freed()); 4571 4572 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4573 cl.humongous_objects_reclaimed()); 4574 } 4575 4576 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4577 public: 4578 virtual bool do_heap_region(HeapRegion* r) { 4579 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4580 G1CollectedHeap::heap()->clear_in_cset(r); 4581 r->set_young_index_in_cset(-1); 4582 return false; 4583 } 4584 }; 4585 4586 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4587 G1AbandonCollectionSetClosure cl; 4588 collection_set->iterate(&cl); 4589 4590 collection_set->clear(); 4591 collection_set->stop_incremental_building(); 4592 } 4593 4594 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 4595 return _allocator->is_retained_old_region(hr); 4596 } 4597 4598 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 4599 _eden.add(hr); 4600 _g1_policy->set_region_eden(hr); 4601 } 4602 4603 #ifdef ASSERT 4604 4605 class NoYoungRegionsClosure: public HeapRegionClosure { 4606 private: 4607 bool _success; 4608 public: 4609 NoYoungRegionsClosure() : _success(true) { } 4610 bool do_heap_region(HeapRegion* r) { 4611 if (r->is_young()) { 4612 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 4613 p2i(r->bottom()), p2i(r->end())); 4614 _success = false; 4615 } 4616 return false; 4617 } 4618 bool success() { return _success; } 4619 }; 4620 4621 bool G1CollectedHeap::check_young_list_empty() { 4622 bool ret = (young_regions_count() == 0); 4623 4624 NoYoungRegionsClosure closure; 4625 heap_region_iterate(&closure); 4626 ret = ret && closure.success(); 4627 4628 return ret; 4629 } 4630 4631 #endif // ASSERT 4632 4633 class TearDownRegionSetsClosure : public HeapRegionClosure { 4634 private: 4635 HeapRegionSet *_old_set; 4636 4637 public: 4638 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 4639 4640 bool do_heap_region(HeapRegion* r) { 4641 if (r->is_old()) { 4642 _old_set->remove(r); 4643 } else if(r->is_young()) { 4644 r->uninstall_surv_rate_group(); 4645 } else { 4646 // We ignore free regions, we'll empty the free list afterwards. 4647 // We ignore humongous regions, we're not tearing down the 4648 // humongous regions set. 4649 assert(r->is_free() || r->is_humongous(), 4650 "it cannot be another type"); 4651 } 4652 return false; 4653 } 4654 4655 ~TearDownRegionSetsClosure() { 4656 assert(_old_set->is_empty(), "post-condition"); 4657 } 4658 }; 4659 4660 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 4661 assert_at_safepoint_on_vm_thread(); 4662 4663 if (!free_list_only) { 4664 TearDownRegionSetsClosure cl(&_old_set); 4665 heap_region_iterate(&cl); 4666 4667 // Note that emptying the _young_list is postponed and instead done as 4668 // the first step when rebuilding the regions sets again. The reason for 4669 // this is that during a full GC string deduplication needs to know if 4670 // a collected region was young or old when the full GC was initiated. 4671 } 4672 _hrm.remove_all_free_regions(); 4673 } 4674 4675 void G1CollectedHeap::increase_used(size_t bytes) { 4676 _summary_bytes_used += bytes; 4677 } 4678 4679 void G1CollectedHeap::decrease_used(size_t bytes) { 4680 assert(_summary_bytes_used >= bytes, 4681 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 4682 _summary_bytes_used, bytes); 4683 _summary_bytes_used -= bytes; 4684 } 4685 4686 void G1CollectedHeap::set_used(size_t bytes) { 4687 _summary_bytes_used = bytes; 4688 } 4689 4690 class RebuildRegionSetsClosure : public HeapRegionClosure { 4691 private: 4692 bool _free_list_only; 4693 HeapRegionSet* _old_set; 4694 HeapRegionManager* _hrm; 4695 size_t _total_used; 4696 4697 public: 4698 RebuildRegionSetsClosure(bool free_list_only, 4699 HeapRegionSet* old_set, HeapRegionManager* hrm) : 4700 _free_list_only(free_list_only), 4701 _old_set(old_set), _hrm(hrm), _total_used(0) { 4702 assert(_hrm->num_free_regions() == 0, "pre-condition"); 4703 if (!free_list_only) { 4704 assert(_old_set->is_empty(), "pre-condition"); 4705 } 4706 } 4707 4708 bool do_heap_region(HeapRegion* r) { 4709 // After full GC, no region should have a remembered set. 4710 r->rem_set()->clear(true); 4711 if (r->is_empty()) { 4712 // Add free regions to the free list 4713 r->set_free(); 4714 _hrm->insert_into_free_list(r); 4715 } else if (!_free_list_only) { 4716 4717 if (r->is_humongous()) { 4718 // We ignore humongous regions. We left the humongous set unchanged. 4719 } else { 4720 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 4721 // We now move all (non-humongous, non-old) regions to old gen, and register them as such. 4722 r->move_to_old(); 4723 _old_set->add(r); 4724 } 4725 _total_used += r->used(); 4726 } 4727 4728 return false; 4729 } 4730 4731 size_t total_used() { 4732 return _total_used; 4733 } 4734 }; 4735 4736 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 4737 assert_at_safepoint_on_vm_thread(); 4738 4739 if (!free_list_only) { 4740 _eden.clear(); 4741 _survivor.clear(); 4742 } 4743 4744 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 4745 heap_region_iterate(&cl); 4746 4747 if (!free_list_only) { 4748 set_used(cl.total_used()); 4749 if (_archive_allocator != NULL) { 4750 _archive_allocator->clear_used(); 4751 } 4752 } 4753 assert(used_unlocked() == recalculate_used(), 4754 "inconsistent used_unlocked(), " 4755 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 4756 used_unlocked(), recalculate_used()); 4757 } 4758 4759 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 4760 HeapRegion* hr = heap_region_containing(p); 4761 return hr->is_in(p); 4762 } 4763 4764 // Methods for the mutator alloc region 4765 4766 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 4767 bool force) { 4768 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4769 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 4770 if (force || should_allocate) { 4771 HeapRegion* new_alloc_region = new_region(word_size, 4772 false /* is_old */, 4773 false /* do_expand */); 4774 if (new_alloc_region != NULL) { 4775 set_region_short_lived_locked(new_alloc_region); 4776 _hr_printer.alloc(new_alloc_region, !should_allocate); 4777 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 4778 _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region); 4779 return new_alloc_region; 4780 } 4781 } 4782 return NULL; 4783 } 4784 4785 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 4786 size_t allocated_bytes) { 4787 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 4788 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 4789 4790 collection_set()->add_eden_region(alloc_region); 4791 increase_used(allocated_bytes); 4792 _hr_printer.retire(alloc_region); 4793 // We update the eden sizes here, when the region is retired, 4794 // instead of when it's allocated, since this is the point that its 4795 // used space has been recored in _summary_bytes_used. 4796 g1mm()->update_eden_size(); 4797 } 4798 4799 // Methods for the GC alloc regions 4800 4801 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 4802 if (dest.is_old()) { 4803 return true; 4804 } else { 4805 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 4806 } 4807 } 4808 4809 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 4810 assert(FreeList_lock->owned_by_self(), "pre-condition"); 4811 4812 if (!has_more_regions(dest)) { 4813 return NULL; 4814 } 4815 4816 const bool is_survivor = dest.is_young(); 4817 4818 HeapRegion* new_alloc_region = new_region(word_size, 4819 !is_survivor, 4820 true /* do_expand */); 4821 if (new_alloc_region != NULL) { 4822 if (is_survivor) { 4823 new_alloc_region->set_survivor(); 4824 _survivor.add(new_alloc_region); 4825 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 4826 } else { 4827 new_alloc_region->set_old(); 4828 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 4829 } 4830 _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region); 4831 _hr_printer.alloc(new_alloc_region); 4832 bool during_im = collector_state()->in_initial_mark_gc(); 4833 new_alloc_region->note_start_of_copying(during_im); 4834 return new_alloc_region; 4835 } 4836 return NULL; 4837 } 4838 4839 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 4840 size_t allocated_bytes, 4841 InCSetState dest) { 4842 bool during_im = collector_state()->in_initial_mark_gc(); 4843 alloc_region->note_end_of_copying(during_im); 4844 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 4845 if (dest.is_old()) { 4846 _old_set.add(alloc_region); 4847 } 4848 _hr_printer.retire(alloc_region); 4849 } 4850 4851 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 4852 bool expanded = false; 4853 uint index = _hrm.find_highest_free(&expanded); 4854 4855 if (index != G1_NO_HRM_INDEX) { 4856 if (expanded) { 4857 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 4858 HeapRegion::GrainWords * HeapWordSize); 4859 } 4860 _hrm.allocate_free_regions_starting_at(index, 1); 4861 return region_at(index); 4862 } 4863 return NULL; 4864 } 4865 4866 // Optimized nmethod scanning 4867 4868 class RegisterNMethodOopClosure: public OopClosure { 4869 G1CollectedHeap* _g1h; 4870 nmethod* _nm; 4871 4872 template <class T> void do_oop_work(T* p) { 4873 T heap_oop = RawAccess<>::oop_load(p); 4874 if (!CompressedOops::is_null(heap_oop)) { 4875 oop obj = CompressedOops::decode_not_null(heap_oop); 4876 HeapRegion* hr = _g1h->heap_region_containing(obj); 4877 assert(!hr->is_continues_humongous(), 4878 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 4879 " starting at " HR_FORMAT, 4880 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 4881 4882 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 4883 hr->add_strong_code_root_locked(_nm); 4884 } 4885 } 4886 4887 public: 4888 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 4889 _g1h(g1h), _nm(nm) {} 4890 4891 void do_oop(oop* p) { do_oop_work(p); } 4892 void do_oop(narrowOop* p) { do_oop_work(p); } 4893 }; 4894 4895 class UnregisterNMethodOopClosure: public OopClosure { 4896 G1CollectedHeap* _g1h; 4897 nmethod* _nm; 4898 4899 template <class T> void do_oop_work(T* p) { 4900 T heap_oop = RawAccess<>::oop_load(p); 4901 if (!CompressedOops::is_null(heap_oop)) { 4902 oop obj = CompressedOops::decode_not_null(heap_oop); 4903 HeapRegion* hr = _g1h->heap_region_containing(obj); 4904 assert(!hr->is_continues_humongous(), 4905 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 4906 " starting at " HR_FORMAT, 4907 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 4908 4909 hr->remove_strong_code_root(_nm); 4910 } 4911 } 4912 4913 public: 4914 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 4915 _g1h(g1h), _nm(nm) {} 4916 4917 void do_oop(oop* p) { do_oop_work(p); } 4918 void do_oop(narrowOop* p) { do_oop_work(p); } 4919 }; 4920 4921 // Returns true if the reference points to an object that 4922 // can move in an incremental collection. 4923 bool G1CollectedHeap::is_scavengable(oop obj) { 4924 HeapRegion* hr = heap_region_containing(obj); 4925 return !hr->is_pinned(); 4926 } 4927 4928 void G1CollectedHeap::register_nmethod(nmethod* nm) { 4929 guarantee(nm != NULL, "sanity"); 4930 RegisterNMethodOopClosure reg_cl(this, nm); 4931 nm->oops_do(®_cl); 4932 } 4933 4934 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 4935 guarantee(nm != NULL, "sanity"); 4936 UnregisterNMethodOopClosure reg_cl(this, nm); 4937 nm->oops_do(®_cl, true); 4938 } 4939 4940 void G1CollectedHeap::purge_code_root_memory() { 4941 double purge_start = os::elapsedTime(); 4942 G1CodeRootSet::purge(); 4943 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 4944 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 4945 } 4946 4947 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 4948 G1CollectedHeap* _g1h; 4949 4950 public: 4951 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 4952 _g1h(g1h) {} 4953 4954 void do_code_blob(CodeBlob* cb) { 4955 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 4956 if (nm == NULL) { 4957 return; 4958 } 4959 4960 if (ScavengeRootsInCode) { 4961 _g1h->register_nmethod(nm); 4962 } 4963 } 4964 }; 4965 4966 void G1CollectedHeap::rebuild_strong_code_roots() { 4967 RebuildStrongCodeRootClosure blob_cl(this); 4968 CodeCache::blobs_do(&blob_cl); 4969 } 4970 4971 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() { 4972 GrowableArray<GCMemoryManager*> memory_managers(2); 4973 memory_managers.append(&_memory_manager); 4974 memory_managers.append(&_full_gc_memory_manager); 4975 return memory_managers; 4976 } 4977 4978 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() { 4979 GrowableArray<MemoryPool*> memory_pools(3); 4980 memory_pools.append(_eden_pool); 4981 memory_pools.append(_survivor_pool); 4982 memory_pools.append(_old_pool); 4983 return memory_pools; 4984 }