1 /* 2 * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/metadataOnStackMark.hpp" 27 #include "classfile/stringTable.hpp" 28 #include "classfile/symbolTable.hpp" 29 #include "code/codeCache.hpp" 30 #include "code/icBuffer.hpp" 31 #include "gc/g1/bufferingOopClosure.hpp" 32 #include "gc/g1/concurrentG1Refine.hpp" 33 #include "gc/g1/concurrentG1RefineThread.hpp" 34 #include "gc/g1/concurrentMarkThread.inline.hpp" 35 #include "gc/g1/g1Allocator.inline.hpp" 36 #include "gc/g1/g1CollectedHeap.inline.hpp" 37 #include "gc/g1/g1CollectionSet.hpp" 38 #include "gc/g1/g1CollectorPolicy.hpp" 39 #include "gc/g1/g1CollectorState.hpp" 40 #include "gc/g1/g1EvacStats.inline.hpp" 41 #include "gc/g1/g1GCPhaseTimes.hpp" 42 #include "gc/g1/g1HeapSizingPolicy.hpp" 43 #include "gc/g1/g1HeapTransition.hpp" 44 #include "gc/g1/g1HeapVerifier.hpp" 45 #include "gc/g1/g1MarkSweep.hpp" 46 #include "gc/g1/g1OopClosures.inline.hpp" 47 #include "gc/g1/g1ParScanThreadState.inline.hpp" 48 #include "gc/g1/g1Policy.hpp" 49 #include "gc/g1/g1RegionToSpaceMapper.hpp" 50 #include "gc/g1/g1RemSet.inline.hpp" 51 #include "gc/g1/g1RootClosures.hpp" 52 #include "gc/g1/g1RootProcessor.hpp" 53 #include "gc/g1/g1StringDedup.hpp" 54 #include "gc/g1/g1YCTypes.hpp" 55 #include "gc/g1/heapRegion.inline.hpp" 56 #include "gc/g1/heapRegionRemSet.hpp" 57 #include "gc/g1/heapRegionSet.inline.hpp" 58 #include "gc/g1/suspendibleThreadSet.hpp" 59 #include "gc/g1/vm_operations_g1.hpp" 60 #include "gc/shared/gcHeapSummary.hpp" 61 #include "gc/shared/gcId.hpp" 62 #include "gc/shared/gcLocker.inline.hpp" 63 #include "gc/shared/gcTimer.hpp" 64 #include "gc/shared/gcTrace.hpp" 65 #include "gc/shared/gcTraceTime.inline.hpp" 66 #include "gc/shared/generationSpec.hpp" 67 #include "gc/shared/isGCActiveMark.hpp" 68 #include "gc/shared/referenceProcessor.inline.hpp" 69 #include "gc/shared/taskqueue.inline.hpp" 70 #include "logging/log.hpp" 71 #include "memory/allocation.hpp" 72 #include "memory/iterator.hpp" 73 #include "memory/resourceArea.hpp" 74 #include "oops/oop.inline.hpp" 75 #include "runtime/atomic.inline.hpp" 76 #include "runtime/init.hpp" 77 #include "runtime/orderAccess.inline.hpp" 78 #include "runtime/vmThread.hpp" 79 #include "utilities/globalDefinitions.hpp" 80 #include "utilities/stack.inline.hpp" 81 82 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 83 84 // INVARIANTS/NOTES 85 // 86 // All allocation activity covered by the G1CollectedHeap interface is 87 // serialized by acquiring the HeapLock. This happens in mem_allocate 88 // and allocate_new_tlab, which are the "entry" points to the 89 // allocation code from the rest of the JVM. (Note that this does not 90 // apply to TLAB allocation, which is not part of this interface: it 91 // is done by clients of this interface.) 92 93 // Local to this file. 94 95 class RefineCardTableEntryClosure: public CardTableEntryClosure { 96 bool _concurrent; 97 public: 98 RefineCardTableEntryClosure() : _concurrent(true) { } 99 100 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 101 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, NULL); 102 // This path is executed by the concurrent refine or mutator threads, 103 // concurrently, and so we do not care if card_ptr contains references 104 // that point into the collection set. 105 assert(!oops_into_cset, "should be"); 106 107 if (_concurrent && SuspendibleThreadSet::should_yield()) { 108 // Caller will actually yield. 109 return false; 110 } 111 // Otherwise, we finished successfully; return true. 112 return true; 113 } 114 115 void set_concurrent(bool b) { _concurrent = b; } 116 }; 117 118 119 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 120 private: 121 size_t _num_dirtied; 122 G1CollectedHeap* _g1h; 123 G1SATBCardTableLoggingModRefBS* _g1_bs; 124 125 HeapRegion* region_for_card(jbyte* card_ptr) const { 126 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 127 } 128 129 bool will_become_free(HeapRegion* hr) const { 130 // A region will be freed by free_collection_set if the region is in the 131 // collection set and has not had an evacuation failure. 132 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 133 } 134 135 public: 136 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 137 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 138 139 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 140 HeapRegion* hr = region_for_card(card_ptr); 141 142 // Should only dirty cards in regions that won't be freed. 143 if (!will_become_free(hr)) { 144 *card_ptr = CardTableModRefBS::dirty_card_val(); 145 _num_dirtied++; 146 } 147 148 return true; 149 } 150 151 size_t num_dirtied() const { return _num_dirtied; } 152 }; 153 154 155 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 156 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 157 } 158 159 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 160 // The from card cache is not the memory that is actually committed. So we cannot 161 // take advantage of the zero_filled parameter. 162 reset_from_card_cache(start_idx, num_regions); 163 } 164 165 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 166 { 167 // Claim the right to put the region on the dirty cards region list 168 // by installing a self pointer. 169 HeapRegion* next = hr->get_next_dirty_cards_region(); 170 if (next == NULL) { 171 HeapRegion* res = (HeapRegion*) 172 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 173 NULL); 174 if (res == NULL) { 175 HeapRegion* head; 176 do { 177 // Put the region to the dirty cards region list. 178 head = _dirty_cards_region_list; 179 next = (HeapRegion*) 180 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 181 if (next == head) { 182 assert(hr->get_next_dirty_cards_region() == hr, 183 "hr->get_next_dirty_cards_region() != hr"); 184 if (next == NULL) { 185 // The last region in the list points to itself. 186 hr->set_next_dirty_cards_region(hr); 187 } else { 188 hr->set_next_dirty_cards_region(next); 189 } 190 } 191 } while (next != head); 192 } 193 } 194 } 195 196 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 197 { 198 HeapRegion* head; 199 HeapRegion* hr; 200 do { 201 head = _dirty_cards_region_list; 202 if (head == NULL) { 203 return NULL; 204 } 205 HeapRegion* new_head = head->get_next_dirty_cards_region(); 206 if (head == new_head) { 207 // The last region. 208 new_head = NULL; 209 } 210 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 211 head); 212 } while (hr != head); 213 assert(hr != NULL, "invariant"); 214 hr->set_next_dirty_cards_region(NULL); 215 return hr; 216 } 217 218 // Returns true if the reference points to an object that 219 // can move in an incremental collection. 220 bool G1CollectedHeap::is_scavengable(const void* p) { 221 HeapRegion* hr = heap_region_containing(p); 222 return !hr->is_pinned(); 223 } 224 225 // Private methods. 226 227 HeapRegion* 228 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 229 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 230 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 231 if (!_secondary_free_list.is_empty()) { 232 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 233 "secondary_free_list has %u entries", 234 _secondary_free_list.length()); 235 // It looks as if there are free regions available on the 236 // secondary_free_list. Let's move them to the free_list and try 237 // again to allocate from it. 238 append_secondary_free_list(); 239 240 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 241 "empty we should have moved at least one entry to the free_list"); 242 HeapRegion* res = _hrm.allocate_free_region(is_old); 243 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 244 "allocated " HR_FORMAT " from secondary_free_list", 245 HR_FORMAT_PARAMS(res)); 246 return res; 247 } 248 249 // Wait here until we get notified either when (a) there are no 250 // more free regions coming or (b) some regions have been moved on 251 // the secondary_free_list. 252 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 253 } 254 255 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 256 "could not allocate from secondary_free_list"); 257 return NULL; 258 } 259 260 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 261 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 262 "the only time we use this to allocate a humongous region is " 263 "when we are allocating a single humongous region"); 264 265 HeapRegion* res; 266 if (G1StressConcRegionFreeing) { 267 if (!_secondary_free_list.is_empty()) { 268 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 269 "forced to look at the secondary_free_list"); 270 res = new_region_try_secondary_free_list(is_old); 271 if (res != NULL) { 272 return res; 273 } 274 } 275 } 276 277 res = _hrm.allocate_free_region(is_old); 278 279 if (res == NULL) { 280 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 281 "res == NULL, trying the secondary_free_list"); 282 res = new_region_try_secondary_free_list(is_old); 283 } 284 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 285 // Currently, only attempts to allocate GC alloc regions set 286 // do_expand to true. So, we should only reach here during a 287 // safepoint. If this assumption changes we might have to 288 // reconsider the use of _expand_heap_after_alloc_failure. 289 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 290 291 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 292 word_size * HeapWordSize); 293 294 if (expand(word_size * HeapWordSize)) { 295 // Given that expand() succeeded in expanding the heap, and we 296 // always expand the heap by an amount aligned to the heap 297 // region size, the free list should in theory not be empty. 298 // In either case allocate_free_region() will check for NULL. 299 res = _hrm.allocate_free_region(is_old); 300 } else { 301 _expand_heap_after_alloc_failure = false; 302 } 303 } 304 return res; 305 } 306 307 HeapWord* 308 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 309 uint num_regions, 310 size_t word_size, 311 AllocationContext_t context) { 312 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 313 assert(is_humongous(word_size), "word_size should be humongous"); 314 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 315 316 // Index of last region in the series. 317 uint last = first + num_regions - 1; 318 319 // We need to initialize the region(s) we just discovered. This is 320 // a bit tricky given that it can happen concurrently with 321 // refinement threads refining cards on these regions and 322 // potentially wanting to refine the BOT as they are scanning 323 // those cards (this can happen shortly after a cleanup; see CR 324 // 6991377). So we have to set up the region(s) carefully and in 325 // a specific order. 326 327 // The word size sum of all the regions we will allocate. 328 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 329 assert(word_size <= word_size_sum, "sanity"); 330 331 // This will be the "starts humongous" region. 332 HeapRegion* first_hr = region_at(first); 333 // The header of the new object will be placed at the bottom of 334 // the first region. 335 HeapWord* new_obj = first_hr->bottom(); 336 // This will be the new top of the new object. 337 HeapWord* obj_top = new_obj + word_size; 338 339 // First, we need to zero the header of the space that we will be 340 // allocating. When we update top further down, some refinement 341 // threads might try to scan the region. By zeroing the header we 342 // ensure that any thread that will try to scan the region will 343 // come across the zero klass word and bail out. 344 // 345 // NOTE: It would not have been correct to have used 346 // CollectedHeap::fill_with_object() and make the space look like 347 // an int array. The thread that is doing the allocation will 348 // later update the object header to a potentially different array 349 // type and, for a very short period of time, the klass and length 350 // fields will be inconsistent. This could cause a refinement 351 // thread to calculate the object size incorrectly. 352 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 353 354 // How many words we use for filler objects. 355 size_t word_fill_size = word_size_sum - word_size; 356 357 // How many words memory we "waste" which cannot hold a filler object. 358 size_t words_not_fillable = 0; 359 360 if (word_fill_size >= min_fill_size()) { 361 fill_with_objects(obj_top, word_fill_size); 362 } else if (word_fill_size > 0) { 363 // We have space to fill, but we cannot fit an object there. 364 words_not_fillable = word_fill_size; 365 word_fill_size = 0; 366 } 367 368 // We will set up the first region as "starts humongous". This 369 // will also update the BOT covering all the regions to reflect 370 // that there is a single object that starts at the bottom of the 371 // first region. 372 first_hr->set_starts_humongous(obj_top, word_fill_size); 373 first_hr->set_allocation_context(context); 374 // Then, if there are any, we will set up the "continues 375 // humongous" regions. 376 HeapRegion* hr = NULL; 377 for (uint i = first + 1; i <= last; ++i) { 378 hr = region_at(i); 379 hr->set_continues_humongous(first_hr); 380 hr->set_allocation_context(context); 381 } 382 383 // Up to this point no concurrent thread would have been able to 384 // do any scanning on any region in this series. All the top 385 // fields still point to bottom, so the intersection between 386 // [bottom,top] and [card_start,card_end] will be empty. Before we 387 // update the top fields, we'll do a storestore to make sure that 388 // no thread sees the update to top before the zeroing of the 389 // object header and the BOT initialization. 390 OrderAccess::storestore(); 391 392 // Now, we will update the top fields of the "continues humongous" 393 // regions except the last one. 394 for (uint i = first; i < last; ++i) { 395 hr = region_at(i); 396 hr->set_top(hr->end()); 397 } 398 399 hr = region_at(last); 400 // If we cannot fit a filler object, we must set top to the end 401 // of the humongous object, otherwise we cannot iterate the heap 402 // and the BOT will not be complete. 403 hr->set_top(hr->end() - words_not_fillable); 404 405 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 406 "obj_top should be in last region"); 407 408 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 409 410 assert(words_not_fillable == 0 || 411 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 412 "Miscalculation in humongous allocation"); 413 414 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 415 416 for (uint i = first; i <= last; ++i) { 417 hr = region_at(i); 418 _humongous_set.add(hr); 419 _hr_printer.alloc(hr); 420 } 421 422 return new_obj; 423 } 424 425 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 426 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 427 return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 428 } 429 430 // If could fit into free regions w/o expansion, try. 431 // Otherwise, if can expand, do so. 432 // Otherwise, if using ex regions might help, try with ex given back. 433 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 434 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 435 436 _verifier->verify_region_sets_optional(); 437 438 uint first = G1_NO_HRM_INDEX; 439 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 440 441 if (obj_regions == 1) { 442 // Only one region to allocate, try to use a fast path by directly allocating 443 // from the free lists. Do not try to expand here, we will potentially do that 444 // later. 445 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 446 if (hr != NULL) { 447 first = hr->hrm_index(); 448 } 449 } else { 450 // We can't allocate humongous regions spanning more than one region while 451 // cleanupComplete() is running, since some of the regions we find to be 452 // empty might not yet be added to the free list. It is not straightforward 453 // to know in which list they are on so that we can remove them. We only 454 // need to do this if we need to allocate more than one region to satisfy the 455 // current humongous allocation request. If we are only allocating one region 456 // we use the one-region region allocation code (see above), that already 457 // potentially waits for regions from the secondary free list. 458 wait_while_free_regions_coming(); 459 append_secondary_free_list_if_not_empty_with_lock(); 460 461 // Policy: Try only empty regions (i.e. already committed first). Maybe we 462 // are lucky enough to find some. 463 first = _hrm.find_contiguous_only_empty(obj_regions); 464 if (first != G1_NO_HRM_INDEX) { 465 _hrm.allocate_free_regions_starting_at(first, obj_regions); 466 } 467 } 468 469 if (first == G1_NO_HRM_INDEX) { 470 // Policy: We could not find enough regions for the humongous object in the 471 // free list. Look through the heap to find a mix of free and uncommitted regions. 472 // If so, try expansion. 473 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 474 if (first != G1_NO_HRM_INDEX) { 475 // We found something. Make sure these regions are committed, i.e. expand 476 // the heap. Alternatively we could do a defragmentation GC. 477 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 478 word_size * HeapWordSize); 479 480 481 _hrm.expand_at(first, obj_regions); 482 g1_policy()->record_new_heap_size(num_regions()); 483 484 #ifdef ASSERT 485 for (uint i = first; i < first + obj_regions; ++i) { 486 HeapRegion* hr = region_at(i); 487 assert(hr->is_free(), "sanity"); 488 assert(hr->is_empty(), "sanity"); 489 assert(is_on_master_free_list(hr), "sanity"); 490 } 491 #endif 492 _hrm.allocate_free_regions_starting_at(first, obj_regions); 493 } else { 494 // Policy: Potentially trigger a defragmentation GC. 495 } 496 } 497 498 HeapWord* result = NULL; 499 if (first != G1_NO_HRM_INDEX) { 500 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 501 word_size, context); 502 assert(result != NULL, "it should always return a valid result"); 503 504 // A successful humongous object allocation changes the used space 505 // information of the old generation so we need to recalculate the 506 // sizes and update the jstat counters here. 507 g1mm()->update_sizes(); 508 } 509 510 _verifier->verify_region_sets_optional(); 511 512 return result; 513 } 514 515 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 516 assert_heap_not_locked_and_not_at_safepoint(); 517 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 518 519 uint dummy_gc_count_before; 520 uint dummy_gclocker_retry_count = 0; 521 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 522 } 523 524 HeapWord* 525 G1CollectedHeap::mem_allocate(size_t word_size, 526 bool* gc_overhead_limit_was_exceeded) { 527 assert_heap_not_locked_and_not_at_safepoint(); 528 529 // Loop until the allocation is satisfied, or unsatisfied after GC. 530 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 531 uint gc_count_before; 532 533 HeapWord* result = NULL; 534 if (!is_humongous(word_size)) { 535 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 536 } else { 537 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 538 } 539 if (result != NULL) { 540 return result; 541 } 542 543 // Create the garbage collection operation... 544 VM_G1CollectForAllocation op(gc_count_before, word_size); 545 op.set_allocation_context(AllocationContext::current()); 546 547 // ...and get the VM thread to execute it. 548 VMThread::execute(&op); 549 550 if (op.prologue_succeeded() && op.pause_succeeded()) { 551 // If the operation was successful we'll return the result even 552 // if it is NULL. If the allocation attempt failed immediately 553 // after a Full GC, it's unlikely we'll be able to allocate now. 554 HeapWord* result = op.result(); 555 if (result != NULL && !is_humongous(word_size)) { 556 // Allocations that take place on VM operations do not do any 557 // card dirtying and we have to do it here. We only have to do 558 // this for non-humongous allocations, though. 559 dirty_young_block(result, word_size); 560 } 561 return result; 562 } else { 563 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 564 return NULL; 565 } 566 assert(op.result() == NULL, 567 "the result should be NULL if the VM op did not succeed"); 568 } 569 570 // Give a warning if we seem to be looping forever. 571 if ((QueuedAllocationWarningCount > 0) && 572 (try_count % QueuedAllocationWarningCount == 0)) { 573 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count); 574 } 575 } 576 577 ShouldNotReachHere(); 578 return NULL; 579 } 580 581 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 582 AllocationContext_t context, 583 uint* gc_count_before_ret, 584 uint* gclocker_retry_count_ret) { 585 // Make sure you read the note in attempt_allocation_humongous(). 586 587 assert_heap_not_locked_and_not_at_safepoint(); 588 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 589 "be called for humongous allocation requests"); 590 591 // We should only get here after the first-level allocation attempt 592 // (attempt_allocation()) failed to allocate. 593 594 // We will loop until a) we manage to successfully perform the 595 // allocation or b) we successfully schedule a collection which 596 // fails to perform the allocation. b) is the only case when we'll 597 // return NULL. 598 HeapWord* result = NULL; 599 for (int try_count = 1; /* we'll return */; try_count += 1) { 600 bool should_try_gc; 601 uint gc_count_before; 602 603 { 604 MutexLockerEx x(Heap_lock); 605 result = _allocator->attempt_allocation_locked(word_size, context); 606 if (result != NULL) { 607 return result; 608 } 609 610 if (GCLocker::is_active_and_needs_gc()) { 611 if (g1_policy()->can_expand_young_list()) { 612 // No need for an ergo verbose message here, 613 // can_expand_young_list() does this when it returns true. 614 result = _allocator->attempt_allocation_force(word_size, context); 615 if (result != NULL) { 616 return result; 617 } 618 } 619 should_try_gc = false; 620 } else { 621 // The GCLocker may not be active but the GCLocker initiated 622 // GC may not yet have been performed (GCLocker::needs_gc() 623 // returns true). In this case we do not try this GC and 624 // wait until the GCLocker initiated GC is performed, and 625 // then retry the allocation. 626 if (GCLocker::needs_gc()) { 627 should_try_gc = false; 628 } else { 629 // Read the GC count while still holding the Heap_lock. 630 gc_count_before = total_collections(); 631 should_try_gc = true; 632 } 633 } 634 } 635 636 if (should_try_gc) { 637 bool succeeded; 638 result = do_collection_pause(word_size, gc_count_before, &succeeded, 639 GCCause::_g1_inc_collection_pause); 640 if (result != NULL) { 641 assert(succeeded, "only way to get back a non-NULL result"); 642 return result; 643 } 644 645 if (succeeded) { 646 // If we get here we successfully scheduled a collection which 647 // failed to allocate. No point in trying to allocate 648 // further. We'll just return NULL. 649 MutexLockerEx x(Heap_lock); 650 *gc_count_before_ret = total_collections(); 651 return NULL; 652 } 653 } else { 654 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 655 MutexLockerEx x(Heap_lock); 656 *gc_count_before_ret = total_collections(); 657 return NULL; 658 } 659 // The GCLocker is either active or the GCLocker initiated 660 // GC has not yet been performed. Stall until it is and 661 // then retry the allocation. 662 GCLocker::stall_until_clear(); 663 (*gclocker_retry_count_ret) += 1; 664 } 665 666 // We can reach here if we were unsuccessful in scheduling a 667 // collection (because another thread beat us to it) or if we were 668 // stalled due to the GC locker. In either can we should retry the 669 // allocation attempt in case another thread successfully 670 // performed a collection and reclaimed enough space. We do the 671 // first attempt (without holding the Heap_lock) here and the 672 // follow-on attempt will be at the start of the next loop 673 // iteration (after taking the Heap_lock). 674 result = _allocator->attempt_allocation(word_size, context); 675 if (result != NULL) { 676 return result; 677 } 678 679 // Give a warning if we seem to be looping forever. 680 if ((QueuedAllocationWarningCount > 0) && 681 (try_count % QueuedAllocationWarningCount == 0)) { 682 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() " 683 "retries %d times", try_count); 684 } 685 } 686 687 ShouldNotReachHere(); 688 return NULL; 689 } 690 691 void G1CollectedHeap::begin_archive_alloc_range() { 692 assert_at_safepoint(true /* should_be_vm_thread */); 693 if (_archive_allocator == NULL) { 694 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 695 } 696 } 697 698 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 699 // Allocations in archive regions cannot be of a size that would be considered 700 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 701 // may be different at archive-restore time. 702 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 703 } 704 705 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 706 assert_at_safepoint(true /* should_be_vm_thread */); 707 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 708 if (is_archive_alloc_too_large(word_size)) { 709 return NULL; 710 } 711 return _archive_allocator->archive_mem_allocate(word_size); 712 } 713 714 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 715 size_t end_alignment_in_bytes) { 716 assert_at_safepoint(true /* should_be_vm_thread */); 717 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 718 719 // Call complete_archive to do the real work, filling in the MemRegion 720 // array with the archive regions. 721 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 722 delete _archive_allocator; 723 _archive_allocator = NULL; 724 } 725 726 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 727 assert(ranges != NULL, "MemRegion array NULL"); 728 assert(count != 0, "No MemRegions provided"); 729 MemRegion reserved = _hrm.reserved(); 730 for (size_t i = 0; i < count; i++) { 731 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 732 return false; 733 } 734 } 735 return true; 736 } 737 738 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 739 assert(!is_init_completed(), "Expect to be called at JVM init time"); 740 assert(ranges != NULL, "MemRegion array NULL"); 741 assert(count != 0, "No MemRegions provided"); 742 MutexLockerEx x(Heap_lock); 743 744 MemRegion reserved = _hrm.reserved(); 745 HeapWord* prev_last_addr = NULL; 746 HeapRegion* prev_last_region = NULL; 747 748 // Temporarily disable pretouching of heap pages. This interface is used 749 // when mmap'ing archived heap data in, so pre-touching is wasted. 750 FlagSetting fs(AlwaysPreTouch, false); 751 752 // Enable archive object checking in G1MarkSweep. We have to let it know 753 // about each archive range, so that objects in those ranges aren't marked. 754 G1MarkSweep::enable_archive_object_check(); 755 756 // For each specified MemRegion range, allocate the corresponding G1 757 // regions and mark them as archive regions. We expect the ranges in 758 // ascending starting address order, without overlap. 759 for (size_t i = 0; i < count; i++) { 760 MemRegion curr_range = ranges[i]; 761 HeapWord* start_address = curr_range.start(); 762 size_t word_size = curr_range.word_size(); 763 HeapWord* last_address = curr_range.last(); 764 size_t commits = 0; 765 766 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 767 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 768 p2i(start_address), p2i(last_address)); 769 guarantee(start_address > prev_last_addr, 770 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 771 p2i(start_address), p2i(prev_last_addr)); 772 prev_last_addr = last_address; 773 774 // Check for ranges that start in the same G1 region in which the previous 775 // range ended, and adjust the start address so we don't try to allocate 776 // the same region again. If the current range is entirely within that 777 // region, skip it, just adjusting the recorded top. 778 HeapRegion* start_region = _hrm.addr_to_region(start_address); 779 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 780 start_address = start_region->end(); 781 if (start_address > last_address) { 782 increase_used(word_size * HeapWordSize); 783 start_region->set_top(last_address + 1); 784 continue; 785 } 786 start_region->set_top(start_address); 787 curr_range = MemRegion(start_address, last_address + 1); 788 start_region = _hrm.addr_to_region(start_address); 789 } 790 791 // Perform the actual region allocation, exiting if it fails. 792 // Then note how much new space we have allocated. 793 if (!_hrm.allocate_containing_regions(curr_range, &commits)) { 794 return false; 795 } 796 increase_used(word_size * HeapWordSize); 797 if (commits != 0) { 798 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 799 HeapRegion::GrainWords * HeapWordSize * commits); 800 801 } 802 803 // Mark each G1 region touched by the range as archive, add it to the old set, 804 // and set the allocation context and top. 805 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 806 HeapRegion* last_region = _hrm.addr_to_region(last_address); 807 prev_last_region = last_region; 808 809 while (curr_region != NULL) { 810 assert(curr_region->is_empty() && !curr_region->is_pinned(), 811 "Region already in use (index %u)", curr_region->hrm_index()); 812 curr_region->set_allocation_context(AllocationContext::system()); 813 curr_region->set_archive(); 814 _hr_printer.alloc(curr_region); 815 _old_set.add(curr_region); 816 if (curr_region != last_region) { 817 curr_region->set_top(curr_region->end()); 818 curr_region = _hrm.next_region_in_heap(curr_region); 819 } else { 820 curr_region->set_top(last_address + 1); 821 curr_region = NULL; 822 } 823 } 824 825 // Notify mark-sweep of the archive range. 826 G1MarkSweep::set_range_archive(curr_range, true); 827 } 828 return true; 829 } 830 831 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 832 assert(!is_init_completed(), "Expect to be called at JVM init time"); 833 assert(ranges != NULL, "MemRegion array NULL"); 834 assert(count != 0, "No MemRegions provided"); 835 MemRegion reserved = _hrm.reserved(); 836 HeapWord *prev_last_addr = NULL; 837 HeapRegion* prev_last_region = NULL; 838 839 // For each MemRegion, create filler objects, if needed, in the G1 regions 840 // that contain the address range. The address range actually within the 841 // MemRegion will not be modified. That is assumed to have been initialized 842 // elsewhere, probably via an mmap of archived heap data. 843 MutexLockerEx x(Heap_lock); 844 for (size_t i = 0; i < count; i++) { 845 HeapWord* start_address = ranges[i].start(); 846 HeapWord* last_address = ranges[i].last(); 847 848 assert(reserved.contains(start_address) && reserved.contains(last_address), 849 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 850 p2i(start_address), p2i(last_address)); 851 assert(start_address > prev_last_addr, 852 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 853 p2i(start_address), p2i(prev_last_addr)); 854 855 HeapRegion* start_region = _hrm.addr_to_region(start_address); 856 HeapRegion* last_region = _hrm.addr_to_region(last_address); 857 HeapWord* bottom_address = start_region->bottom(); 858 859 // Check for a range beginning in the same region in which the 860 // previous one ended. 861 if (start_region == prev_last_region) { 862 bottom_address = prev_last_addr + 1; 863 } 864 865 // Verify that the regions were all marked as archive regions by 866 // alloc_archive_regions. 867 HeapRegion* curr_region = start_region; 868 while (curr_region != NULL) { 869 guarantee(curr_region->is_archive(), 870 "Expected archive region at index %u", curr_region->hrm_index()); 871 if (curr_region != last_region) { 872 curr_region = _hrm.next_region_in_heap(curr_region); 873 } else { 874 curr_region = NULL; 875 } 876 } 877 878 prev_last_addr = last_address; 879 prev_last_region = last_region; 880 881 // Fill the memory below the allocated range with dummy object(s), 882 // if the region bottom does not match the range start, or if the previous 883 // range ended within the same G1 region, and there is a gap. 884 if (start_address != bottom_address) { 885 size_t fill_size = pointer_delta(start_address, bottom_address); 886 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 887 increase_used(fill_size * HeapWordSize); 888 } 889 } 890 } 891 892 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 893 uint* gc_count_before_ret, 894 uint* gclocker_retry_count_ret) { 895 assert_heap_not_locked_and_not_at_safepoint(); 896 assert(!is_humongous(word_size), "attempt_allocation() should not " 897 "be called for humongous allocation requests"); 898 899 AllocationContext_t context = AllocationContext::current(); 900 HeapWord* result = _allocator->attempt_allocation(word_size, context); 901 902 if (result == NULL) { 903 result = attempt_allocation_slow(word_size, 904 context, 905 gc_count_before_ret, 906 gclocker_retry_count_ret); 907 } 908 assert_heap_not_locked(); 909 if (result != NULL) { 910 dirty_young_block(result, word_size); 911 } 912 return result; 913 } 914 915 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 916 assert(!is_init_completed(), "Expect to be called at JVM init time"); 917 assert(ranges != NULL, "MemRegion array NULL"); 918 assert(count != 0, "No MemRegions provided"); 919 MemRegion reserved = _hrm.reserved(); 920 HeapWord* prev_last_addr = NULL; 921 HeapRegion* prev_last_region = NULL; 922 size_t size_used = 0; 923 size_t uncommitted_regions = 0; 924 925 // For each Memregion, free the G1 regions that constitute it, and 926 // notify mark-sweep that the range is no longer to be considered 'archive.' 927 MutexLockerEx x(Heap_lock); 928 for (size_t i = 0; i < count; i++) { 929 HeapWord* start_address = ranges[i].start(); 930 HeapWord* last_address = ranges[i].last(); 931 932 assert(reserved.contains(start_address) && reserved.contains(last_address), 933 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 934 p2i(start_address), p2i(last_address)); 935 assert(start_address > prev_last_addr, 936 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 937 p2i(start_address), p2i(prev_last_addr)); 938 size_used += ranges[i].byte_size(); 939 prev_last_addr = last_address; 940 941 HeapRegion* start_region = _hrm.addr_to_region(start_address); 942 HeapRegion* last_region = _hrm.addr_to_region(last_address); 943 944 // Check for ranges that start in the same G1 region in which the previous 945 // range ended, and adjust the start address so we don't try to free 946 // the same region again. If the current range is entirely within that 947 // region, skip it. 948 if (start_region == prev_last_region) { 949 start_address = start_region->end(); 950 if (start_address > last_address) { 951 continue; 952 } 953 start_region = _hrm.addr_to_region(start_address); 954 } 955 prev_last_region = last_region; 956 957 // After verifying that each region was marked as an archive region by 958 // alloc_archive_regions, set it free and empty and uncommit it. 959 HeapRegion* curr_region = start_region; 960 while (curr_region != NULL) { 961 guarantee(curr_region->is_archive(), 962 "Expected archive region at index %u", curr_region->hrm_index()); 963 uint curr_index = curr_region->hrm_index(); 964 _old_set.remove(curr_region); 965 curr_region->set_free(); 966 curr_region->set_top(curr_region->bottom()); 967 if (curr_region != last_region) { 968 curr_region = _hrm.next_region_in_heap(curr_region); 969 } else { 970 curr_region = NULL; 971 } 972 _hrm.shrink_at(curr_index, 1); 973 uncommitted_regions++; 974 } 975 976 // Notify mark-sweep that this is no longer an archive range. 977 G1MarkSweep::set_range_archive(ranges[i], false); 978 } 979 980 if (uncommitted_regions != 0) { 981 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 982 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 983 } 984 decrease_used(size_used); 985 } 986 987 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 988 uint* gc_count_before_ret, 989 uint* gclocker_retry_count_ret) { 990 // The structure of this method has a lot of similarities to 991 // attempt_allocation_slow(). The reason these two were not merged 992 // into a single one is that such a method would require several "if 993 // allocation is not humongous do this, otherwise do that" 994 // conditional paths which would obscure its flow. In fact, an early 995 // version of this code did use a unified method which was harder to 996 // follow and, as a result, it had subtle bugs that were hard to 997 // track down. So keeping these two methods separate allows each to 998 // be more readable. It will be good to keep these two in sync as 999 // much as possible. 1000 1001 assert_heap_not_locked_and_not_at_safepoint(); 1002 assert(is_humongous(word_size), "attempt_allocation_humongous() " 1003 "should only be called for humongous allocations"); 1004 1005 // Humongous objects can exhaust the heap quickly, so we should check if we 1006 // need to start a marking cycle at each humongous object allocation. We do 1007 // the check before we do the actual allocation. The reason for doing it 1008 // before the allocation is that we avoid having to keep track of the newly 1009 // allocated memory while we do a GC. 1010 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 1011 word_size)) { 1012 collect(GCCause::_g1_humongous_allocation); 1013 } 1014 1015 // We will loop until a) we manage to successfully perform the 1016 // allocation or b) we successfully schedule a collection which 1017 // fails to perform the allocation. b) is the only case when we'll 1018 // return NULL. 1019 HeapWord* result = NULL; 1020 for (int try_count = 1; /* we'll return */; try_count += 1) { 1021 bool should_try_gc; 1022 uint gc_count_before; 1023 1024 { 1025 MutexLockerEx x(Heap_lock); 1026 1027 // Given that humongous objects are not allocated in young 1028 // regions, we'll first try to do the allocation without doing a 1029 // collection hoping that there's enough space in the heap. 1030 result = humongous_obj_allocate(word_size, AllocationContext::current()); 1031 if (result != NULL) { 1032 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 1033 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 1034 return result; 1035 } 1036 1037 if (GCLocker::is_active_and_needs_gc()) { 1038 should_try_gc = false; 1039 } else { 1040 // The GCLocker may not be active but the GCLocker initiated 1041 // GC may not yet have been performed (GCLocker::needs_gc() 1042 // returns true). In this case we do not try this GC and 1043 // wait until the GCLocker initiated GC is performed, and 1044 // then retry the allocation. 1045 if (GCLocker::needs_gc()) { 1046 should_try_gc = false; 1047 } else { 1048 // Read the GC count while still holding the Heap_lock. 1049 gc_count_before = total_collections(); 1050 should_try_gc = true; 1051 } 1052 } 1053 } 1054 1055 if (should_try_gc) { 1056 // If we failed to allocate the humongous object, we should try to 1057 // do a collection pause (if we're allowed) in case it reclaims 1058 // enough space for the allocation to succeed after the pause. 1059 1060 bool succeeded; 1061 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1062 GCCause::_g1_humongous_allocation); 1063 if (result != NULL) { 1064 assert(succeeded, "only way to get back a non-NULL result"); 1065 return result; 1066 } 1067 1068 if (succeeded) { 1069 // If we get here we successfully scheduled a collection which 1070 // failed to allocate. No point in trying to allocate 1071 // further. We'll just return NULL. 1072 MutexLockerEx x(Heap_lock); 1073 *gc_count_before_ret = total_collections(); 1074 return NULL; 1075 } 1076 } else { 1077 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1078 MutexLockerEx x(Heap_lock); 1079 *gc_count_before_ret = total_collections(); 1080 return NULL; 1081 } 1082 // The GCLocker is either active or the GCLocker initiated 1083 // GC has not yet been performed. Stall until it is and 1084 // then retry the allocation. 1085 GCLocker::stall_until_clear(); 1086 (*gclocker_retry_count_ret) += 1; 1087 } 1088 1089 // We can reach here if we were unsuccessful in scheduling a 1090 // collection (because another thread beat us to it) or if we were 1091 // stalled due to the GC locker. In either can we should retry the 1092 // allocation attempt in case another thread successfully 1093 // performed a collection and reclaimed enough space. Give a 1094 // warning if we seem to be looping forever. 1095 1096 if ((QueuedAllocationWarningCount > 0) && 1097 (try_count % QueuedAllocationWarningCount == 0)) { 1098 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() " 1099 "retries %d times", try_count); 1100 } 1101 } 1102 1103 ShouldNotReachHere(); 1104 return NULL; 1105 } 1106 1107 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1108 AllocationContext_t context, 1109 bool expect_null_mutator_alloc_region) { 1110 assert_at_safepoint(true /* should_be_vm_thread */); 1111 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1112 "the current alloc region was unexpectedly found to be non-NULL"); 1113 1114 if (!is_humongous(word_size)) { 1115 return _allocator->attempt_allocation_locked(word_size, context); 1116 } else { 1117 HeapWord* result = humongous_obj_allocate(word_size, context); 1118 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1119 collector_state()->set_initiate_conc_mark_if_possible(true); 1120 } 1121 return result; 1122 } 1123 1124 ShouldNotReachHere(); 1125 } 1126 1127 class PostMCRemSetClearClosure: public HeapRegionClosure { 1128 G1CollectedHeap* _g1h; 1129 ModRefBarrierSet* _mr_bs; 1130 public: 1131 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1132 _g1h(g1h), _mr_bs(mr_bs) {} 1133 1134 bool doHeapRegion(HeapRegion* r) { 1135 HeapRegionRemSet* hrrs = r->rem_set(); 1136 1137 _g1h->reset_gc_time_stamps(r); 1138 1139 if (r->is_continues_humongous()) { 1140 // We'll assert that the strong code root list and RSet is empty 1141 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1142 assert(hrrs->occupied() == 0, "RSet should be empty"); 1143 } else { 1144 hrrs->clear(); 1145 } 1146 // You might think here that we could clear just the cards 1147 // corresponding to the used region. But no: if we leave a dirty card 1148 // in a region we might allocate into, then it would prevent that card 1149 // from being enqueued, and cause it to be missed. 1150 // Re: the performance cost: we shouldn't be doing full GC anyway! 1151 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1152 1153 return false; 1154 } 1155 }; 1156 1157 void G1CollectedHeap::clear_rsets_post_compaction() { 1158 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1159 heap_region_iterate(&rs_clear); 1160 } 1161 1162 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1163 G1CollectedHeap* _g1h; 1164 UpdateRSOopClosure _cl; 1165 public: 1166 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1167 _cl(g1->g1_rem_set(), worker_i), 1168 _g1h(g1) 1169 { } 1170 1171 bool doHeapRegion(HeapRegion* r) { 1172 if (!r->is_continues_humongous()) { 1173 _cl.set_from(r); 1174 r->oop_iterate(&_cl); 1175 } 1176 return false; 1177 } 1178 }; 1179 1180 class ParRebuildRSTask: public AbstractGangTask { 1181 G1CollectedHeap* _g1; 1182 HeapRegionClaimer _hrclaimer; 1183 1184 public: 1185 ParRebuildRSTask(G1CollectedHeap* g1) : 1186 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1187 1188 void work(uint worker_id) { 1189 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1190 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1191 } 1192 }; 1193 1194 class PostCompactionPrinterClosure: public HeapRegionClosure { 1195 private: 1196 G1HRPrinter* _hr_printer; 1197 public: 1198 bool doHeapRegion(HeapRegion* hr) { 1199 assert(!hr->is_young(), "not expecting to find young regions"); 1200 _hr_printer->post_compaction(hr); 1201 return false; 1202 } 1203 1204 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1205 : _hr_printer(hr_printer) { } 1206 }; 1207 1208 void G1CollectedHeap::print_hrm_post_compaction() { 1209 if (_hr_printer.is_active()) { 1210 PostCompactionPrinterClosure cl(hr_printer()); 1211 heap_region_iterate(&cl); 1212 } 1213 1214 } 1215 1216 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1217 bool clear_all_soft_refs) { 1218 assert_at_safepoint(true /* should_be_vm_thread */); 1219 1220 if (GCLocker::check_active_before_gc()) { 1221 return false; 1222 } 1223 1224 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1225 gc_timer->register_gc_start(); 1226 1227 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1228 GCIdMark gc_id_mark; 1229 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1230 1231 SvcGCMarker sgcm(SvcGCMarker::FULL); 1232 ResourceMark rm; 1233 1234 print_heap_before_gc(); 1235 print_heap_regions(); 1236 trace_heap_before_gc(gc_tracer); 1237 1238 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1239 1240 _verifier->verify_region_sets_optional(); 1241 1242 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1243 collector_policy()->should_clear_all_soft_refs(); 1244 1245 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1246 1247 { 1248 IsGCActiveMark x; 1249 1250 // Timing 1251 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1252 GCTraceCPUTime tcpu; 1253 1254 { 1255 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1256 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1257 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1258 1259 G1HeapTransition heap_transition(this); 1260 g1_policy()->record_full_collection_start(); 1261 1262 // Note: When we have a more flexible GC logging framework that 1263 // allows us to add optional attributes to a GC log record we 1264 // could consider timing and reporting how long we wait in the 1265 // following two methods. 1266 wait_while_free_regions_coming(); 1267 // If we start the compaction before the CM threads finish 1268 // scanning the root regions we might trip them over as we'll 1269 // be moving objects / updating references. So let's wait until 1270 // they are done. By telling them to abort, they should complete 1271 // early. 1272 _cm->root_regions()->abort(); 1273 _cm->root_regions()->wait_until_scan_finished(); 1274 append_secondary_free_list_if_not_empty_with_lock(); 1275 1276 gc_prologue(true); 1277 increment_total_collections(true /* full gc */); 1278 increment_old_marking_cycles_started(); 1279 1280 assert(used() == recalculate_used(), "Should be equal"); 1281 1282 _verifier->verify_before_gc(); 1283 1284 _verifier->check_bitmaps("Full GC Start"); 1285 pre_full_gc_dump(gc_timer); 1286 1287 #if defined(COMPILER2) || INCLUDE_JVMCI 1288 DerivedPointerTable::clear(); 1289 #endif 1290 1291 // Disable discovery and empty the discovered lists 1292 // for the CM ref processor. 1293 ref_processor_cm()->disable_discovery(); 1294 ref_processor_cm()->abandon_partial_discovery(); 1295 ref_processor_cm()->verify_no_references_recorded(); 1296 1297 // Abandon current iterations of concurrent marking and concurrent 1298 // refinement, if any are in progress. 1299 concurrent_mark()->abort(); 1300 1301 // Make sure we'll choose a new allocation region afterwards. 1302 _allocator->release_mutator_alloc_region(); 1303 _allocator->abandon_gc_alloc_regions(); 1304 g1_rem_set()->cleanupHRRS(); 1305 1306 // We may have added regions to the current incremental collection 1307 // set between the last GC or pause and now. We need to clear the 1308 // incremental collection set and then start rebuilding it afresh 1309 // after this full GC. 1310 abandon_collection_set(collection_set()->inc_head()); 1311 collection_set()->clear_incremental(); 1312 collection_set()->stop_incremental_building(); 1313 1314 tear_down_region_sets(false /* free_list_only */); 1315 collector_state()->set_gcs_are_young(true); 1316 1317 // See the comments in g1CollectedHeap.hpp and 1318 // G1CollectedHeap::ref_processing_init() about 1319 // how reference processing currently works in G1. 1320 1321 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1322 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1323 1324 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1325 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1326 1327 ref_processor_stw()->enable_discovery(); 1328 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1329 1330 // Do collection work 1331 { 1332 HandleMark hm; // Discard invalid handles created during gc 1333 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1334 } 1335 1336 assert(num_free_regions() == 0, "we should not have added any free regions"); 1337 rebuild_region_sets(false /* free_list_only */); 1338 1339 // Enqueue any discovered reference objects that have 1340 // not been removed from the discovered lists. 1341 ref_processor_stw()->enqueue_discovered_references(); 1342 1343 #if defined(COMPILER2) || INCLUDE_JVMCI 1344 DerivedPointerTable::update_pointers(); 1345 #endif 1346 1347 MemoryService::track_memory_usage(); 1348 1349 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1350 ref_processor_stw()->verify_no_references_recorded(); 1351 1352 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1353 ClassLoaderDataGraph::purge(); 1354 MetaspaceAux::verify_metrics(); 1355 1356 // Note: since we've just done a full GC, concurrent 1357 // marking is no longer active. Therefore we need not 1358 // re-enable reference discovery for the CM ref processor. 1359 // That will be done at the start of the next marking cycle. 1360 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1361 ref_processor_cm()->verify_no_references_recorded(); 1362 1363 reset_gc_time_stamp(); 1364 // Since everything potentially moved, we will clear all remembered 1365 // sets, and clear all cards. Later we will rebuild remembered 1366 // sets. We will also reset the GC time stamps of the regions. 1367 clear_rsets_post_compaction(); 1368 check_gc_time_stamps(); 1369 1370 resize_if_necessary_after_full_collection(); 1371 1372 // We should do this after we potentially resize the heap so 1373 // that all the COMMIT / UNCOMMIT events are generated before 1374 // the compaction events. 1375 print_hrm_post_compaction(); 1376 1377 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1378 if (hot_card_cache->use_cache()) { 1379 hot_card_cache->reset_card_counts(); 1380 hot_card_cache->reset_hot_cache(); 1381 } 1382 1383 // Rebuild remembered sets of all regions. 1384 uint n_workers = 1385 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1386 workers()->active_workers(), 1387 Threads::number_of_non_daemon_threads()); 1388 workers()->set_active_workers(n_workers); 1389 1390 ParRebuildRSTask rebuild_rs_task(this); 1391 workers()->run_task(&rebuild_rs_task); 1392 1393 // Rebuild the strong code root lists for each region 1394 rebuild_strong_code_roots(); 1395 1396 if (true) { // FIXME 1397 MetaspaceGC::compute_new_size(); 1398 } 1399 1400 #ifdef TRACESPINNING 1401 ParallelTaskTerminator::print_termination_counts(); 1402 #endif 1403 1404 // Discard all rset updates 1405 JavaThread::dirty_card_queue_set().abandon_logs(); 1406 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1407 1408 // At this point there should be no regions in the 1409 // entire heap tagged as young. 1410 assert(check_young_list_empty(true /* check_heap */), 1411 "young list should be empty at this point"); 1412 1413 // Update the number of full collections that have been completed. 1414 increment_old_marking_cycles_completed(false /* concurrent */); 1415 1416 _hrm.verify_optional(); 1417 _verifier->verify_region_sets_optional(); 1418 1419 _verifier->verify_after_gc(); 1420 1421 // Clear the previous marking bitmap, if needed for bitmap verification. 1422 // Note we cannot do this when we clear the next marking bitmap in 1423 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1424 // objects marked during a full GC against the previous bitmap. 1425 // But we need to clear it before calling check_bitmaps below since 1426 // the full GC has compacted objects and updated TAMS but not updated 1427 // the prev bitmap. 1428 if (G1VerifyBitmaps) { 1429 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1430 _cm->clear_prev_bitmap(workers()); 1431 } 1432 _verifier->check_bitmaps("Full GC End"); 1433 1434 // Start a new incremental collection set for the next pause 1435 assert(collection_set()->head() == NULL, "must be"); 1436 collection_set()->start_incremental_building(); 1437 1438 clear_cset_fast_test(); 1439 1440 _allocator->init_mutator_alloc_region(); 1441 1442 g1_policy()->record_full_collection_end(); 1443 1444 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1445 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1446 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1447 // before any GC notifications are raised. 1448 g1mm()->update_sizes(); 1449 1450 gc_epilogue(true); 1451 1452 heap_transition.print(); 1453 1454 print_heap_after_gc(); 1455 print_heap_regions(); 1456 trace_heap_after_gc(gc_tracer); 1457 1458 post_full_gc_dump(gc_timer); 1459 } 1460 1461 gc_timer->register_gc_end(); 1462 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1463 } 1464 1465 return true; 1466 } 1467 1468 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1469 // Currently, there is no facility in the do_full_collection(bool) API to notify 1470 // the caller that the collection did not succeed (e.g., because it was locked 1471 // out by the GC locker). So, right now, we'll ignore the return value. 1472 bool dummy = do_full_collection(true, /* explicit_gc */ 1473 clear_all_soft_refs); 1474 } 1475 1476 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1477 // Include bytes that will be pre-allocated to support collections, as "used". 1478 const size_t used_after_gc = used(); 1479 const size_t capacity_after_gc = capacity(); 1480 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1481 1482 // This is enforced in arguments.cpp. 1483 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1484 "otherwise the code below doesn't make sense"); 1485 1486 // We don't have floating point command-line arguments 1487 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1488 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1489 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1490 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1491 1492 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1493 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1494 1495 // We have to be careful here as these two calculations can overflow 1496 // 32-bit size_t's. 1497 double used_after_gc_d = (double) used_after_gc; 1498 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1499 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1500 1501 // Let's make sure that they are both under the max heap size, which 1502 // by default will make them fit into a size_t. 1503 double desired_capacity_upper_bound = (double) max_heap_size; 1504 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1505 desired_capacity_upper_bound); 1506 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1507 desired_capacity_upper_bound); 1508 1509 // We can now safely turn them into size_t's. 1510 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1511 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1512 1513 // This assert only makes sense here, before we adjust them 1514 // with respect to the min and max heap size. 1515 assert(minimum_desired_capacity <= maximum_desired_capacity, 1516 "minimum_desired_capacity = " SIZE_FORMAT ", " 1517 "maximum_desired_capacity = " SIZE_FORMAT, 1518 minimum_desired_capacity, maximum_desired_capacity); 1519 1520 // Should not be greater than the heap max size. No need to adjust 1521 // it with respect to the heap min size as it's a lower bound (i.e., 1522 // we'll try to make the capacity larger than it, not smaller). 1523 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1524 // Should not be less than the heap min size. No need to adjust it 1525 // with respect to the heap max size as it's an upper bound (i.e., 1526 // we'll try to make the capacity smaller than it, not greater). 1527 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1528 1529 if (capacity_after_gc < minimum_desired_capacity) { 1530 // Don't expand unless it's significant 1531 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1532 1533 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1534 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1535 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1536 1537 expand(expand_bytes); 1538 1539 // No expansion, now see if we want to shrink 1540 } else if (capacity_after_gc > maximum_desired_capacity) { 1541 // Capacity too large, compute shrinking size 1542 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1543 1544 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1545 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1546 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1547 1548 shrink(shrink_bytes); 1549 } 1550 } 1551 1552 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1553 AllocationContext_t context, 1554 bool do_gc, 1555 bool clear_all_soft_refs, 1556 bool expect_null_mutator_alloc_region, 1557 bool* gc_succeeded) { 1558 *gc_succeeded = true; 1559 // Let's attempt the allocation first. 1560 HeapWord* result = 1561 attempt_allocation_at_safepoint(word_size, 1562 context, 1563 expect_null_mutator_alloc_region); 1564 if (result != NULL) { 1565 assert(*gc_succeeded, "sanity"); 1566 return result; 1567 } 1568 1569 // In a G1 heap, we're supposed to keep allocation from failing by 1570 // incremental pauses. Therefore, at least for now, we'll favor 1571 // expansion over collection. (This might change in the future if we can 1572 // do something smarter than full collection to satisfy a failed alloc.) 1573 result = expand_and_allocate(word_size, context); 1574 if (result != NULL) { 1575 assert(*gc_succeeded, "sanity"); 1576 return result; 1577 } 1578 1579 if (do_gc) { 1580 // Expansion didn't work, we'll try to do a Full GC. 1581 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1582 clear_all_soft_refs); 1583 } 1584 1585 return NULL; 1586 } 1587 1588 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1589 AllocationContext_t context, 1590 bool* succeeded) { 1591 assert_at_safepoint(true /* should_be_vm_thread */); 1592 1593 // Attempts to allocate followed by Full GC. 1594 HeapWord* result = 1595 satisfy_failed_allocation_helper(word_size, 1596 context, 1597 true, /* do_gc */ 1598 false, /* clear_all_soft_refs */ 1599 false, /* expect_null_mutator_alloc_region */ 1600 succeeded); 1601 1602 if (result != NULL || !*succeeded) { 1603 return result; 1604 } 1605 1606 // Attempts to allocate followed by Full GC that will collect all soft references. 1607 result = satisfy_failed_allocation_helper(word_size, 1608 context, 1609 true, /* do_gc */ 1610 true, /* clear_all_soft_refs */ 1611 true, /* expect_null_mutator_alloc_region */ 1612 succeeded); 1613 1614 if (result != NULL || !*succeeded) { 1615 return result; 1616 } 1617 1618 // Attempts to allocate, no GC 1619 result = satisfy_failed_allocation_helper(word_size, 1620 context, 1621 false, /* do_gc */ 1622 false, /* clear_all_soft_refs */ 1623 true, /* expect_null_mutator_alloc_region */ 1624 succeeded); 1625 1626 if (result != NULL) { 1627 assert(*succeeded, "sanity"); 1628 return result; 1629 } 1630 1631 assert(!collector_policy()->should_clear_all_soft_refs(), 1632 "Flag should have been handled and cleared prior to this point"); 1633 1634 // What else? We might try synchronous finalization later. If the total 1635 // space available is large enough for the allocation, then a more 1636 // complete compaction phase than we've tried so far might be 1637 // appropriate. 1638 assert(*succeeded, "sanity"); 1639 return NULL; 1640 } 1641 1642 // Attempting to expand the heap sufficiently 1643 // to support an allocation of the given "word_size". If 1644 // successful, perform the allocation and return the address of the 1645 // allocated block, or else "NULL". 1646 1647 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1648 assert_at_safepoint(true /* should_be_vm_thread */); 1649 1650 _verifier->verify_region_sets_optional(); 1651 1652 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1653 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1654 word_size * HeapWordSize); 1655 1656 1657 if (expand(expand_bytes)) { 1658 _hrm.verify_optional(); 1659 _verifier->verify_region_sets_optional(); 1660 return attempt_allocation_at_safepoint(word_size, 1661 context, 1662 false /* expect_null_mutator_alloc_region */); 1663 } 1664 return NULL; 1665 } 1666 1667 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) { 1668 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1669 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1670 HeapRegion::GrainBytes); 1671 1672 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B", 1673 expand_bytes, aligned_expand_bytes); 1674 1675 if (is_maximal_no_gc()) { 1676 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1677 return false; 1678 } 1679 1680 double expand_heap_start_time_sec = os::elapsedTime(); 1681 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1682 assert(regions_to_expand > 0, "Must expand by at least one region"); 1683 1684 uint expanded_by = _hrm.expand_by(regions_to_expand); 1685 if (expand_time_ms != NULL) { 1686 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1687 } 1688 1689 if (expanded_by > 0) { 1690 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1691 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1692 g1_policy()->record_new_heap_size(num_regions()); 1693 } else { 1694 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1695 1696 // The expansion of the virtual storage space was unsuccessful. 1697 // Let's see if it was because we ran out of swap. 1698 if (G1ExitOnExpansionFailure && 1699 _hrm.available() >= regions_to_expand) { 1700 // We had head room... 1701 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1702 } 1703 } 1704 return regions_to_expand > 0; 1705 } 1706 1707 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1708 size_t aligned_shrink_bytes = 1709 ReservedSpace::page_align_size_down(shrink_bytes); 1710 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1711 HeapRegion::GrainBytes); 1712 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1713 1714 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1715 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1716 1717 1718 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", 1719 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1720 if (num_regions_removed > 0) { 1721 g1_policy()->record_new_heap_size(num_regions()); 1722 } else { 1723 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1724 } 1725 } 1726 1727 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1728 _verifier->verify_region_sets_optional(); 1729 1730 // We should only reach here at the end of a Full GC which means we 1731 // should not not be holding to any GC alloc regions. The method 1732 // below will make sure of that and do any remaining clean up. 1733 _allocator->abandon_gc_alloc_regions(); 1734 1735 // Instead of tearing down / rebuilding the free lists here, we 1736 // could instead use the remove_all_pending() method on free_list to 1737 // remove only the ones that we need to remove. 1738 tear_down_region_sets(true /* free_list_only */); 1739 shrink_helper(shrink_bytes); 1740 rebuild_region_sets(true /* free_list_only */); 1741 1742 _hrm.verify_optional(); 1743 _verifier->verify_region_sets_optional(); 1744 } 1745 1746 // Public methods. 1747 1748 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1749 CollectedHeap(), 1750 _collector_policy(collector_policy), 1751 _g1_policy(create_g1_policy()), 1752 _collection_set(this, _g1_policy), 1753 _dirty_card_queue_set(false), 1754 _is_alive_closure_cm(this), 1755 _is_alive_closure_stw(this), 1756 _ref_processor_cm(NULL), 1757 _ref_processor_stw(NULL), 1758 _bot(NULL), 1759 _cg1r(NULL), 1760 _g1mm(NULL), 1761 _refine_cte_cl(NULL), 1762 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1763 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1764 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1765 _humongous_reclaim_candidates(), 1766 _has_humongous_reclaim_candidates(false), 1767 _archive_allocator(NULL), 1768 _free_regions_coming(false), 1769 _young_list(new YoungList(this)), 1770 _gc_time_stamp(0), 1771 _summary_bytes_used(0), 1772 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1773 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1774 _expand_heap_after_alloc_failure(true), 1775 _old_marking_cycles_started(0), 1776 _old_marking_cycles_completed(0), 1777 _in_cset_fast_test(), 1778 _dirty_cards_region_list(NULL), 1779 _worker_cset_start_region(NULL), 1780 _worker_cset_start_region_time_stamp(NULL), 1781 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1782 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) { 1783 1784 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1785 /* are_GC_task_threads */true, 1786 /* are_ConcurrentGC_threads */false); 1787 _workers->initialize_workers(); 1788 _verifier = new G1HeapVerifier(this); 1789 1790 _allocator = G1Allocator::create_allocator(this); 1791 1792 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1793 1794 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1795 1796 // Override the default _filler_array_max_size so that no humongous filler 1797 // objects are created. 1798 _filler_array_max_size = _humongous_object_threshold_in_words; 1799 1800 uint n_queues = ParallelGCThreads; 1801 _task_queues = new RefToScanQueueSet(n_queues); 1802 1803 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1804 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC); 1805 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1806 1807 for (uint i = 0; i < n_queues; i++) { 1808 RefToScanQueue* q = new RefToScanQueue(); 1809 q->initialize(); 1810 _task_queues->register_queue(i, q); 1811 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1812 } 1813 clear_cset_start_regions(); 1814 1815 // Initialize the G1EvacuationFailureALot counters and flags. 1816 NOT_PRODUCT(reset_evacuation_should_fail();) 1817 1818 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1819 } 1820 1821 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1822 size_t size, 1823 size_t translation_factor) { 1824 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1825 // Allocate a new reserved space, preferring to use large pages. 1826 ReservedSpace rs(size, preferred_page_size); 1827 G1RegionToSpaceMapper* result = 1828 G1RegionToSpaceMapper::create_mapper(rs, 1829 size, 1830 rs.alignment(), 1831 HeapRegion::GrainBytes, 1832 translation_factor, 1833 mtGC); 1834 1835 os::trace_page_sizes_for_requested_size(description, 1836 size, 1837 preferred_page_size, 1838 rs.alignment(), 1839 rs.base(), 1840 rs.size()); 1841 1842 return result; 1843 } 1844 1845 jint G1CollectedHeap::initialize() { 1846 CollectedHeap::pre_initialize(); 1847 os::enable_vtime(); 1848 1849 // Necessary to satisfy locking discipline assertions. 1850 1851 MutexLocker x(Heap_lock); 1852 1853 // While there are no constraints in the GC code that HeapWordSize 1854 // be any particular value, there are multiple other areas in the 1855 // system which believe this to be true (e.g. oop->object_size in some 1856 // cases incorrectly returns the size in wordSize units rather than 1857 // HeapWordSize). 1858 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1859 1860 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1861 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1862 size_t heap_alignment = collector_policy()->heap_alignment(); 1863 1864 // Ensure that the sizes are properly aligned. 1865 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1866 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1867 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1868 1869 _refine_cte_cl = new RefineCardTableEntryClosure(); 1870 1871 jint ecode = JNI_OK; 1872 _cg1r = ConcurrentG1Refine::create(this, _refine_cte_cl, &ecode); 1873 if (_cg1r == NULL) { 1874 return ecode; 1875 } 1876 1877 // Reserve the maximum. 1878 1879 // When compressed oops are enabled, the preferred heap base 1880 // is calculated by subtracting the requested size from the 1881 // 32Gb boundary and using the result as the base address for 1882 // heap reservation. If the requested size is not aligned to 1883 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1884 // into the ReservedHeapSpace constructor) then the actual 1885 // base of the reserved heap may end up differing from the 1886 // address that was requested (i.e. the preferred heap base). 1887 // If this happens then we could end up using a non-optimal 1888 // compressed oops mode. 1889 1890 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1891 heap_alignment); 1892 1893 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1894 1895 // Create the barrier set for the entire reserved region. 1896 G1SATBCardTableLoggingModRefBS* bs 1897 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1898 bs->initialize(); 1899 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1900 set_barrier_set(bs); 1901 1902 // Also create a G1 rem set. 1903 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 1904 1905 // Carve out the G1 part of the heap. 1906 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1907 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1908 G1RegionToSpaceMapper* heap_storage = 1909 G1RegionToSpaceMapper::create_mapper(g1_rs, 1910 g1_rs.size(), 1911 page_size, 1912 HeapRegion::GrainBytes, 1913 1, 1914 mtJavaHeap); 1915 os::trace_page_sizes("Heap", 1916 collector_policy()->min_heap_byte_size(), 1917 max_byte_size, 1918 page_size, 1919 heap_rs.base(), 1920 heap_rs.size()); 1921 heap_storage->set_mapping_changed_listener(&_listener); 1922 1923 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1924 G1RegionToSpaceMapper* bot_storage = 1925 create_aux_memory_mapper("Block Offset Table", 1926 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1927 G1BlockOffsetTable::heap_map_factor()); 1928 1929 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1930 G1RegionToSpaceMapper* cardtable_storage = 1931 create_aux_memory_mapper("Card Table", 1932 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1933 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1934 1935 G1RegionToSpaceMapper* card_counts_storage = 1936 create_aux_memory_mapper("Card Counts Table", 1937 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1938 G1CardCounts::heap_map_factor()); 1939 1940 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1941 G1RegionToSpaceMapper* prev_bitmap_storage = 1942 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1943 G1RegionToSpaceMapper* next_bitmap_storage = 1944 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1945 1946 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1947 g1_barrier_set()->initialize(cardtable_storage); 1948 // Do later initialization work for concurrent refinement. 1949 _cg1r->init(card_counts_storage); 1950 1951 // 6843694 - ensure that the maximum region index can fit 1952 // in the remembered set structures. 1953 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1954 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1955 1956 g1_rem_set()->initialize(max_capacity(), max_regions()); 1957 1958 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1959 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1960 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1961 "too many cards per region"); 1962 1963 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1964 1965 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1966 1967 { 1968 HeapWord* start = _hrm.reserved().start(); 1969 HeapWord* end = _hrm.reserved().end(); 1970 size_t granularity = HeapRegion::GrainBytes; 1971 1972 _in_cset_fast_test.initialize(start, end, granularity); 1973 _humongous_reclaim_candidates.initialize(start, end, granularity); 1974 } 1975 1976 // Create the G1ConcurrentMark data structure and thread. 1977 // (Must do this late, so that "max_regions" is defined.) 1978 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1979 if (_cm == NULL || !_cm->completed_initialization()) { 1980 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1981 return JNI_ENOMEM; 1982 } 1983 _cmThread = _cm->cmThread(); 1984 1985 // Now expand into the initial heap size. 1986 if (!expand(init_byte_size)) { 1987 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1988 return JNI_ENOMEM; 1989 } 1990 1991 // Perform any initialization actions delegated to the policy. 1992 g1_policy()->init(this, &_collection_set); 1993 1994 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1995 SATB_Q_FL_lock, 1996 G1SATBProcessCompletedThreshold, 1997 Shared_SATB_Q_lock); 1998 1999 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 2000 DirtyCardQ_CBL_mon, 2001 DirtyCardQ_FL_lock, 2002 (int)concurrent_g1_refine()->yellow_zone(), 2003 (int)concurrent_g1_refine()->red_zone(), 2004 Shared_DirtyCardQ_lock, 2005 NULL, // fl_owner 2006 true); // init_free_ids 2007 2008 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 2009 DirtyCardQ_CBL_mon, 2010 DirtyCardQ_FL_lock, 2011 -1, // never trigger processing 2012 -1, // no limit on length 2013 Shared_DirtyCardQ_lock, 2014 &JavaThread::dirty_card_queue_set()); 2015 2016 // Here we allocate the dummy HeapRegion that is required by the 2017 // G1AllocRegion class. 2018 HeapRegion* dummy_region = _hrm.get_dummy_region(); 2019 2020 // We'll re-use the same region whether the alloc region will 2021 // require BOT updates or not and, if it doesn't, then a non-young 2022 // region will complain that it cannot support allocations without 2023 // BOT updates. So we'll tag the dummy region as eden to avoid that. 2024 dummy_region->set_eden(); 2025 // Make sure it's full. 2026 dummy_region->set_top(dummy_region->end()); 2027 G1AllocRegion::setup(this, dummy_region); 2028 2029 _allocator->init_mutator_alloc_region(); 2030 2031 // Do create of the monitoring and management support so that 2032 // values in the heap have been properly initialized. 2033 _g1mm = new G1MonitoringSupport(this); 2034 2035 G1StringDedup::initialize(); 2036 2037 _preserved_objs = NEW_C_HEAP_ARRAY(OopAndMarkOopStack, ParallelGCThreads, mtGC); 2038 for (uint i = 0; i < ParallelGCThreads; i++) { 2039 new (&_preserved_objs[i]) OopAndMarkOopStack(); 2040 } 2041 2042 return JNI_OK; 2043 } 2044 2045 void G1CollectedHeap::stop() { 2046 // Stop all concurrent threads. We do this to make sure these threads 2047 // do not continue to execute and access resources (e.g. logging) 2048 // that are destroyed during shutdown. 2049 _cg1r->stop(); 2050 _cmThread->stop(); 2051 if (G1StringDedup::is_enabled()) { 2052 G1StringDedup::stop(); 2053 } 2054 } 2055 2056 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2057 return HeapRegion::max_region_size(); 2058 } 2059 2060 void G1CollectedHeap::post_initialize() { 2061 ref_processing_init(); 2062 } 2063 2064 void G1CollectedHeap::ref_processing_init() { 2065 // Reference processing in G1 currently works as follows: 2066 // 2067 // * There are two reference processor instances. One is 2068 // used to record and process discovered references 2069 // during concurrent marking; the other is used to 2070 // record and process references during STW pauses 2071 // (both full and incremental). 2072 // * Both ref processors need to 'span' the entire heap as 2073 // the regions in the collection set may be dotted around. 2074 // 2075 // * For the concurrent marking ref processor: 2076 // * Reference discovery is enabled at initial marking. 2077 // * Reference discovery is disabled and the discovered 2078 // references processed etc during remarking. 2079 // * Reference discovery is MT (see below). 2080 // * Reference discovery requires a barrier (see below). 2081 // * Reference processing may or may not be MT 2082 // (depending on the value of ParallelRefProcEnabled 2083 // and ParallelGCThreads). 2084 // * A full GC disables reference discovery by the CM 2085 // ref processor and abandons any entries on it's 2086 // discovered lists. 2087 // 2088 // * For the STW processor: 2089 // * Non MT discovery is enabled at the start of a full GC. 2090 // * Processing and enqueueing during a full GC is non-MT. 2091 // * During a full GC, references are processed after marking. 2092 // 2093 // * Discovery (may or may not be MT) is enabled at the start 2094 // of an incremental evacuation pause. 2095 // * References are processed near the end of a STW evacuation pause. 2096 // * For both types of GC: 2097 // * Discovery is atomic - i.e. not concurrent. 2098 // * Reference discovery will not need a barrier. 2099 2100 MemRegion mr = reserved_region(); 2101 2102 // Concurrent Mark ref processor 2103 _ref_processor_cm = 2104 new ReferenceProcessor(mr, // span 2105 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2106 // mt processing 2107 ParallelGCThreads, 2108 // degree of mt processing 2109 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2110 // mt discovery 2111 MAX2(ParallelGCThreads, ConcGCThreads), 2112 // degree of mt discovery 2113 false, 2114 // Reference discovery is not atomic 2115 &_is_alive_closure_cm); 2116 // is alive closure 2117 // (for efficiency/performance) 2118 2119 // STW ref processor 2120 _ref_processor_stw = 2121 new ReferenceProcessor(mr, // span 2122 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2123 // mt processing 2124 ParallelGCThreads, 2125 // degree of mt processing 2126 (ParallelGCThreads > 1), 2127 // mt discovery 2128 ParallelGCThreads, 2129 // degree of mt discovery 2130 true, 2131 // Reference discovery is atomic 2132 &_is_alive_closure_stw); 2133 // is alive closure 2134 // (for efficiency/performance) 2135 } 2136 2137 CollectorPolicy* G1CollectedHeap::collector_policy() const { 2138 return _collector_policy; 2139 } 2140 2141 size_t G1CollectedHeap::capacity() const { 2142 return _hrm.length() * HeapRegion::GrainBytes; 2143 } 2144 2145 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2146 hr->reset_gc_time_stamp(); 2147 } 2148 2149 #ifndef PRODUCT 2150 2151 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2152 private: 2153 unsigned _gc_time_stamp; 2154 bool _failures; 2155 2156 public: 2157 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2158 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2159 2160 virtual bool doHeapRegion(HeapRegion* hr) { 2161 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2162 if (_gc_time_stamp != region_gc_time_stamp) { 2163 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 2164 region_gc_time_stamp, _gc_time_stamp); 2165 _failures = true; 2166 } 2167 return false; 2168 } 2169 2170 bool failures() { return _failures; } 2171 }; 2172 2173 void G1CollectedHeap::check_gc_time_stamps() { 2174 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2175 heap_region_iterate(&cl); 2176 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2177 } 2178 #endif // PRODUCT 2179 2180 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2181 _cg1r->hot_card_cache()->drain(cl, worker_i); 2182 } 2183 2184 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2185 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2186 size_t n_completed_buffers = 0; 2187 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2188 n_completed_buffers++; 2189 } 2190 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2191 dcqs.clear_n_completed_buffers(); 2192 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2193 } 2194 2195 // Computes the sum of the storage used by the various regions. 2196 size_t G1CollectedHeap::used() const { 2197 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2198 if (_archive_allocator != NULL) { 2199 result += _archive_allocator->used(); 2200 } 2201 return result; 2202 } 2203 2204 size_t G1CollectedHeap::used_unlocked() const { 2205 return _summary_bytes_used; 2206 } 2207 2208 class SumUsedClosure: public HeapRegionClosure { 2209 size_t _used; 2210 public: 2211 SumUsedClosure() : _used(0) {} 2212 bool doHeapRegion(HeapRegion* r) { 2213 _used += r->used(); 2214 return false; 2215 } 2216 size_t result() { return _used; } 2217 }; 2218 2219 size_t G1CollectedHeap::recalculate_used() const { 2220 double recalculate_used_start = os::elapsedTime(); 2221 2222 SumUsedClosure blk; 2223 heap_region_iterate(&blk); 2224 2225 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2226 return blk.result(); 2227 } 2228 2229 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2230 switch (cause) { 2231 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2232 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2233 case GCCause::_update_allocation_context_stats_inc: return true; 2234 case GCCause::_wb_conc_mark: return true; 2235 default : return false; 2236 } 2237 } 2238 2239 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2240 switch (cause) { 2241 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2242 case GCCause::_g1_humongous_allocation: return true; 2243 default: return is_user_requested_concurrent_full_gc(cause); 2244 } 2245 } 2246 2247 #ifndef PRODUCT 2248 void G1CollectedHeap::allocate_dummy_regions() { 2249 // Let's fill up most of the region 2250 size_t word_size = HeapRegion::GrainWords - 1024; 2251 // And as a result the region we'll allocate will be humongous. 2252 guarantee(is_humongous(word_size), "sanity"); 2253 2254 // _filler_array_max_size is set to humongous object threshold 2255 // but temporarily change it to use CollectedHeap::fill_with_object(). 2256 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2257 2258 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2259 // Let's use the existing mechanism for the allocation 2260 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2261 AllocationContext::system()); 2262 if (dummy_obj != NULL) { 2263 MemRegion mr(dummy_obj, word_size); 2264 CollectedHeap::fill_with_object(mr); 2265 } else { 2266 // If we can't allocate once, we probably cannot allocate 2267 // again. Let's get out of the loop. 2268 break; 2269 } 2270 } 2271 } 2272 #endif // !PRODUCT 2273 2274 void G1CollectedHeap::increment_old_marking_cycles_started() { 2275 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2276 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2277 "Wrong marking cycle count (started: %d, completed: %d)", 2278 _old_marking_cycles_started, _old_marking_cycles_completed); 2279 2280 _old_marking_cycles_started++; 2281 } 2282 2283 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2284 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2285 2286 // We assume that if concurrent == true, then the caller is a 2287 // concurrent thread that was joined the Suspendible Thread 2288 // Set. If there's ever a cheap way to check this, we should add an 2289 // assert here. 2290 2291 // Given that this method is called at the end of a Full GC or of a 2292 // concurrent cycle, and those can be nested (i.e., a Full GC can 2293 // interrupt a concurrent cycle), the number of full collections 2294 // completed should be either one (in the case where there was no 2295 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2296 // behind the number of full collections started. 2297 2298 // This is the case for the inner caller, i.e. a Full GC. 2299 assert(concurrent || 2300 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2301 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2302 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2303 "is inconsistent with _old_marking_cycles_completed = %u", 2304 _old_marking_cycles_started, _old_marking_cycles_completed); 2305 2306 // This is the case for the outer caller, i.e. the concurrent cycle. 2307 assert(!concurrent || 2308 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2309 "for outer caller (concurrent cycle): " 2310 "_old_marking_cycles_started = %u " 2311 "is inconsistent with _old_marking_cycles_completed = %u", 2312 _old_marking_cycles_started, _old_marking_cycles_completed); 2313 2314 _old_marking_cycles_completed += 1; 2315 2316 // We need to clear the "in_progress" flag in the CM thread before 2317 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2318 // is set) so that if a waiter requests another System.gc() it doesn't 2319 // incorrectly see that a marking cycle is still in progress. 2320 if (concurrent) { 2321 _cmThread->set_idle(); 2322 } 2323 2324 // This notify_all() will ensure that a thread that called 2325 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2326 // and it's waiting for a full GC to finish will be woken up. It is 2327 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2328 FullGCCount_lock->notify_all(); 2329 } 2330 2331 void G1CollectedHeap::collect(GCCause::Cause cause) { 2332 assert_heap_not_locked(); 2333 2334 uint gc_count_before; 2335 uint old_marking_count_before; 2336 uint full_gc_count_before; 2337 bool retry_gc; 2338 2339 do { 2340 retry_gc = false; 2341 2342 { 2343 MutexLocker ml(Heap_lock); 2344 2345 // Read the GC count while holding the Heap_lock 2346 gc_count_before = total_collections(); 2347 full_gc_count_before = total_full_collections(); 2348 old_marking_count_before = _old_marking_cycles_started; 2349 } 2350 2351 if (should_do_concurrent_full_gc(cause)) { 2352 // Schedule an initial-mark evacuation pause that will start a 2353 // concurrent cycle. We're setting word_size to 0 which means that 2354 // we are not requesting a post-GC allocation. 2355 VM_G1IncCollectionPause op(gc_count_before, 2356 0, /* word_size */ 2357 true, /* should_initiate_conc_mark */ 2358 g1_policy()->max_pause_time_ms(), 2359 cause); 2360 op.set_allocation_context(AllocationContext::current()); 2361 2362 VMThread::execute(&op); 2363 if (!op.pause_succeeded()) { 2364 if (old_marking_count_before == _old_marking_cycles_started) { 2365 retry_gc = op.should_retry_gc(); 2366 } else { 2367 // A Full GC happened while we were trying to schedule the 2368 // initial-mark GC. No point in starting a new cycle given 2369 // that the whole heap was collected anyway. 2370 } 2371 2372 if (retry_gc) { 2373 if (GCLocker::is_active_and_needs_gc()) { 2374 GCLocker::stall_until_clear(); 2375 } 2376 } 2377 } 2378 } else { 2379 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2380 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2381 2382 // Schedule a standard evacuation pause. We're setting word_size 2383 // to 0 which means that we are not requesting a post-GC allocation. 2384 VM_G1IncCollectionPause op(gc_count_before, 2385 0, /* word_size */ 2386 false, /* should_initiate_conc_mark */ 2387 g1_policy()->max_pause_time_ms(), 2388 cause); 2389 VMThread::execute(&op); 2390 } else { 2391 // Schedule a Full GC. 2392 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2393 VMThread::execute(&op); 2394 } 2395 } 2396 } while (retry_gc); 2397 } 2398 2399 bool G1CollectedHeap::is_in(const void* p) const { 2400 if (_hrm.reserved().contains(p)) { 2401 // Given that we know that p is in the reserved space, 2402 // heap_region_containing() should successfully 2403 // return the containing region. 2404 HeapRegion* hr = heap_region_containing(p); 2405 return hr->is_in(p); 2406 } else { 2407 return false; 2408 } 2409 } 2410 2411 #ifdef ASSERT 2412 bool G1CollectedHeap::is_in_exact(const void* p) const { 2413 bool contains = reserved_region().contains(p); 2414 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2415 if (contains && available) { 2416 return true; 2417 } else { 2418 return false; 2419 } 2420 } 2421 #endif 2422 2423 bool G1CollectedHeap::obj_in_cs(oop obj) { 2424 HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj); 2425 return r != NULL && r->in_collection_set(); 2426 } 2427 2428 // Iteration functions. 2429 2430 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2431 2432 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2433 ExtendedOopClosure* _cl; 2434 public: 2435 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2436 bool doHeapRegion(HeapRegion* r) { 2437 if (!r->is_continues_humongous()) { 2438 r->oop_iterate(_cl); 2439 } 2440 return false; 2441 } 2442 }; 2443 2444 // Iterates an ObjectClosure over all objects within a HeapRegion. 2445 2446 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2447 ObjectClosure* _cl; 2448 public: 2449 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2450 bool doHeapRegion(HeapRegion* r) { 2451 if (!r->is_continues_humongous()) { 2452 r->object_iterate(_cl); 2453 } 2454 return false; 2455 } 2456 }; 2457 2458 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2459 IterateObjectClosureRegionClosure blk(cl); 2460 heap_region_iterate(&blk); 2461 } 2462 2463 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2464 _hrm.iterate(cl); 2465 } 2466 2467 void 2468 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2469 uint worker_id, 2470 HeapRegionClaimer *hrclaimer, 2471 bool concurrent) const { 2472 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2473 } 2474 2475 // Clear the cached CSet starting regions and (more importantly) 2476 // the time stamps. Called when we reset the GC time stamp. 2477 void G1CollectedHeap::clear_cset_start_regions() { 2478 assert(_worker_cset_start_region != NULL, "sanity"); 2479 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2480 2481 for (uint i = 0; i < ParallelGCThreads; i++) { 2482 _worker_cset_start_region[i] = NULL; 2483 _worker_cset_start_region_time_stamp[i] = 0; 2484 } 2485 } 2486 2487 // Given the id of a worker, obtain or calculate a suitable 2488 // starting region for iterating over the current collection set. 2489 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2490 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2491 2492 HeapRegion* result = NULL; 2493 unsigned gc_time_stamp = get_gc_time_stamp(); 2494 2495 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2496 // Cached starting region for current worker was set 2497 // during the current pause - so it's valid. 2498 // Note: the cached starting heap region may be NULL 2499 // (when the collection set is empty). 2500 result = _worker_cset_start_region[worker_i]; 2501 assert(result == NULL || result->in_collection_set(), "sanity"); 2502 return result; 2503 } 2504 2505 // The cached entry was not valid so let's calculate 2506 // a suitable starting heap region for this worker. 2507 2508 // We want the parallel threads to start their collection 2509 // set iteration at different collection set regions to 2510 // avoid contention. 2511 // If we have: 2512 // n collection set regions 2513 // p threads 2514 // Then thread t will start at region floor ((t * n) / p) 2515 2516 result = collection_set()->head(); 2517 uint cs_size = collection_set()->region_length(); 2518 uint active_workers = workers()->active_workers(); 2519 2520 uint end_ind = (cs_size * worker_i) / active_workers; 2521 uint start_ind = 0; 2522 2523 if (worker_i > 0 && 2524 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2525 // Previous workers starting region is valid 2526 // so let's iterate from there 2527 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2528 OrderAccess::loadload(); 2529 result = _worker_cset_start_region[worker_i - 1]; 2530 } 2531 2532 for (uint i = start_ind; i < end_ind; i++) { 2533 result = result->next_in_collection_set(); 2534 } 2535 2536 // Note: the calculated starting heap region may be NULL 2537 // (when the collection set is empty). 2538 assert(result == NULL || result->in_collection_set(), "sanity"); 2539 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2540 "should be updated only once per pause"); 2541 _worker_cset_start_region[worker_i] = result; 2542 OrderAccess::storestore(); 2543 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2544 return result; 2545 } 2546 2547 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2548 HeapRegion* r = collection_set()->head(); 2549 while (r != NULL) { 2550 HeapRegion* next = r->next_in_collection_set(); 2551 if (cl->doHeapRegion(r)) { 2552 cl->incomplete(); 2553 return; 2554 } 2555 r = next; 2556 } 2557 } 2558 2559 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2560 HeapRegionClosure *cl) { 2561 if (r == NULL) { 2562 // The CSet is empty so there's nothing to do. 2563 return; 2564 } 2565 2566 assert(r->in_collection_set(), 2567 "Start region must be a member of the collection set."); 2568 HeapRegion* cur = r; 2569 while (cur != NULL) { 2570 HeapRegion* next = cur->next_in_collection_set(); 2571 if (cl->doHeapRegion(cur) && false) { 2572 cl->incomplete(); 2573 return; 2574 } 2575 cur = next; 2576 } 2577 cur = collection_set()->head(); 2578 while (cur != r) { 2579 HeapRegion* next = cur->next_in_collection_set(); 2580 if (cl->doHeapRegion(cur) && false) { 2581 cl->incomplete(); 2582 return; 2583 } 2584 cur = next; 2585 } 2586 } 2587 2588 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2589 HeapRegion* result = _hrm.next_region_in_heap(from); 2590 while (result != NULL && result->is_pinned()) { 2591 result = _hrm.next_region_in_heap(result); 2592 } 2593 return result; 2594 } 2595 2596 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2597 HeapRegion* hr = heap_region_containing(addr); 2598 return hr->block_start(addr); 2599 } 2600 2601 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2602 HeapRegion* hr = heap_region_containing(addr); 2603 return hr->block_size(addr); 2604 } 2605 2606 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2607 HeapRegion* hr = heap_region_containing(addr); 2608 return hr->block_is_obj(addr); 2609 } 2610 2611 bool G1CollectedHeap::supports_tlab_allocation() const { 2612 return true; 2613 } 2614 2615 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2616 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2617 } 2618 2619 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2620 return young_list()->eden_used_bytes(); 2621 } 2622 2623 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2624 // must be equal to the humongous object limit. 2625 size_t G1CollectedHeap::max_tlab_size() const { 2626 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2627 } 2628 2629 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2630 AllocationContext_t context = AllocationContext::current(); 2631 return _allocator->unsafe_max_tlab_alloc(context); 2632 } 2633 2634 size_t G1CollectedHeap::max_capacity() const { 2635 return _hrm.reserved().byte_size(); 2636 } 2637 2638 jlong G1CollectedHeap::millis_since_last_gc() { 2639 // assert(false, "NYI"); 2640 return 0; 2641 } 2642 2643 void G1CollectedHeap::prepare_for_verify() { 2644 _verifier->prepare_for_verify(); 2645 } 2646 2647 void G1CollectedHeap::verify(VerifyOption vo) { 2648 _verifier->verify(vo); 2649 } 2650 2651 class PrintRegionClosure: public HeapRegionClosure { 2652 outputStream* _st; 2653 public: 2654 PrintRegionClosure(outputStream* st) : _st(st) {} 2655 bool doHeapRegion(HeapRegion* r) { 2656 r->print_on(_st); 2657 return false; 2658 } 2659 }; 2660 2661 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2662 const HeapRegion* hr, 2663 const VerifyOption vo) const { 2664 switch (vo) { 2665 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2666 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2667 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 2668 default: ShouldNotReachHere(); 2669 } 2670 return false; // keep some compilers happy 2671 } 2672 2673 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2674 const VerifyOption vo) const { 2675 switch (vo) { 2676 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2677 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2678 case VerifyOption_G1UseMarkWord: { 2679 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 2680 return !obj->is_gc_marked() && !hr->is_archive(); 2681 } 2682 default: ShouldNotReachHere(); 2683 } 2684 return false; // keep some compilers happy 2685 } 2686 2687 void G1CollectedHeap::print_heap_regions() const { 2688 Log(gc, heap, region) log; 2689 if (log.is_trace()) { 2690 ResourceMark rm; 2691 print_regions_on(log.trace_stream()); 2692 } 2693 } 2694 2695 void G1CollectedHeap::print_on(outputStream* st) const { 2696 st->print(" %-20s", "garbage-first heap"); 2697 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2698 capacity()/K, used_unlocked()/K); 2699 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 2700 p2i(_hrm.reserved().start()), 2701 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 2702 p2i(_hrm.reserved().end())); 2703 st->cr(); 2704 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2705 uint young_regions = _young_list->length(); 2706 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2707 (size_t) young_regions * HeapRegion::GrainBytes / K); 2708 uint survivor_regions = _young_list->survivor_length(); 2709 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2710 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2711 st->cr(); 2712 MetaspaceAux::print_on(st); 2713 } 2714 2715 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2716 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2717 "HS=humongous(starts), HC=humongous(continues), " 2718 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2719 "AC=allocation context, " 2720 "TAMS=top-at-mark-start (previous, next)"); 2721 PrintRegionClosure blk(st); 2722 heap_region_iterate(&blk); 2723 } 2724 2725 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2726 print_on(st); 2727 2728 // Print the per-region information. 2729 print_regions_on(st); 2730 } 2731 2732 void G1CollectedHeap::print_on_error(outputStream* st) const { 2733 this->CollectedHeap::print_on_error(st); 2734 2735 if (_cm != NULL) { 2736 st->cr(); 2737 _cm->print_on_error(st); 2738 } 2739 } 2740 2741 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2742 workers()->print_worker_threads_on(st); 2743 _cmThread->print_on(st); 2744 st->cr(); 2745 _cm->print_worker_threads_on(st); 2746 _cg1r->print_worker_threads_on(st); // also prints the sample thread 2747 if (G1StringDedup::is_enabled()) { 2748 G1StringDedup::print_worker_threads_on(st); 2749 } 2750 } 2751 2752 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2753 workers()->threads_do(tc); 2754 tc->do_thread(_cmThread); 2755 _cm->threads_do(tc); 2756 _cg1r->threads_do(tc); // also iterates over the sample thread 2757 if (G1StringDedup::is_enabled()) { 2758 G1StringDedup::threads_do(tc); 2759 } 2760 } 2761 2762 void G1CollectedHeap::print_tracing_info() const { 2763 g1_rem_set()->print_summary_info(); 2764 concurrent_mark()->print_summary_info(); 2765 g1_policy()->print_yg_surv_rate_info(); 2766 } 2767 2768 #ifndef PRODUCT 2769 // Helpful for debugging RSet issues. 2770 2771 class PrintRSetsClosure : public HeapRegionClosure { 2772 private: 2773 const char* _msg; 2774 size_t _occupied_sum; 2775 2776 public: 2777 bool doHeapRegion(HeapRegion* r) { 2778 HeapRegionRemSet* hrrs = r->rem_set(); 2779 size_t occupied = hrrs->occupied(); 2780 _occupied_sum += occupied; 2781 2782 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2783 if (occupied == 0) { 2784 tty->print_cr(" RSet is empty"); 2785 } else { 2786 hrrs->print(); 2787 } 2788 tty->print_cr("----------"); 2789 return false; 2790 } 2791 2792 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2793 tty->cr(); 2794 tty->print_cr("========================================"); 2795 tty->print_cr("%s", msg); 2796 tty->cr(); 2797 } 2798 2799 ~PrintRSetsClosure() { 2800 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2801 tty->print_cr("========================================"); 2802 tty->cr(); 2803 } 2804 }; 2805 2806 void G1CollectedHeap::print_cset_rsets() { 2807 PrintRSetsClosure cl("Printing CSet RSets"); 2808 collection_set_iterate(&cl); 2809 } 2810 2811 void G1CollectedHeap::print_all_rsets() { 2812 PrintRSetsClosure cl("Printing All RSets");; 2813 heap_region_iterate(&cl); 2814 } 2815 #endif // PRODUCT 2816 2817 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2818 YoungList* young_list = heap()->young_list(); 2819 2820 size_t eden_used_bytes = young_list->eden_used_bytes(); 2821 size_t survivor_used_bytes = young_list->survivor_used_bytes(); 2822 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2823 2824 size_t eden_capacity_bytes = 2825 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2826 2827 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2828 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2829 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2830 } 2831 2832 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2833 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2834 stats->unused(), stats->used(), stats->region_end_waste(), 2835 stats->regions_filled(), stats->direct_allocated(), 2836 stats->failure_used(), stats->failure_waste()); 2837 } 2838 2839 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2840 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2841 gc_tracer->report_gc_heap_summary(when, heap_summary); 2842 2843 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2844 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2845 } 2846 2847 G1CollectedHeap* G1CollectedHeap::heap() { 2848 CollectedHeap* heap = Universe::heap(); 2849 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2850 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2851 return (G1CollectedHeap*)heap; 2852 } 2853 2854 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 2855 // always_do_update_barrier = false; 2856 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2857 // Fill TLAB's and such 2858 accumulate_statistics_all_tlabs(); 2859 ensure_parsability(true); 2860 2861 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2862 } 2863 2864 void G1CollectedHeap::gc_epilogue(bool full) { 2865 // we are at the end of the GC. Total collections has already been increased. 2866 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2867 2868 // FIXME: what is this about? 2869 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2870 // is set. 2871 #if defined(COMPILER2) || INCLUDE_JVMCI 2872 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2873 #endif 2874 // always_do_update_barrier = true; 2875 2876 resize_all_tlabs(); 2877 allocation_context_stats().update(full); 2878 2879 // We have just completed a GC. Update the soft reference 2880 // policy with the new heap occupancy 2881 Universe::update_heap_info_at_gc(); 2882 } 2883 2884 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2885 uint gc_count_before, 2886 bool* succeeded, 2887 GCCause::Cause gc_cause) { 2888 assert_heap_not_locked_and_not_at_safepoint(); 2889 VM_G1IncCollectionPause op(gc_count_before, 2890 word_size, 2891 false, /* should_initiate_conc_mark */ 2892 g1_policy()->max_pause_time_ms(), 2893 gc_cause); 2894 2895 op.set_allocation_context(AllocationContext::current()); 2896 VMThread::execute(&op); 2897 2898 HeapWord* result = op.result(); 2899 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2900 assert(result == NULL || ret_succeeded, 2901 "the result should be NULL if the VM did not succeed"); 2902 *succeeded = ret_succeeded; 2903 2904 assert_heap_not_locked(); 2905 return result; 2906 } 2907 2908 void 2909 G1CollectedHeap::doConcurrentMark() { 2910 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2911 if (!_cmThread->in_progress()) { 2912 _cmThread->set_started(); 2913 CGC_lock->notify(); 2914 } 2915 } 2916 2917 size_t G1CollectedHeap::pending_card_num() { 2918 size_t extra_cards = 0; 2919 JavaThread *curr = Threads::first(); 2920 while (curr != NULL) { 2921 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2922 extra_cards += dcq.size(); 2923 curr = curr->next(); 2924 } 2925 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2926 size_t buffer_size = dcqs.buffer_size(); 2927 size_t buffer_num = dcqs.completed_buffers_num(); 2928 2929 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 2930 // in bytes - not the number of 'entries'. We need to convert 2931 // into a number of cards. 2932 return (buffer_size * buffer_num + extra_cards) / oopSize; 2933 } 2934 2935 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2936 private: 2937 size_t _total_humongous; 2938 size_t _candidate_humongous; 2939 2940 DirtyCardQueue _dcq; 2941 2942 // We don't nominate objects with many remembered set entries, on 2943 // the assumption that such objects are likely still live. 2944 bool is_remset_small(HeapRegion* region) const { 2945 HeapRegionRemSet* const rset = region->rem_set(); 2946 return G1EagerReclaimHumongousObjectsWithStaleRefs 2947 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2948 : rset->is_empty(); 2949 } 2950 2951 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2952 assert(region->is_starts_humongous(), "Must start a humongous object"); 2953 2954 oop obj = oop(region->bottom()); 2955 2956 // Dead objects cannot be eager reclaim candidates. Due to class 2957 // unloading it is unsafe to query their classes so we return early. 2958 if (heap->is_obj_dead(obj, region)) { 2959 return false; 2960 } 2961 2962 // Candidate selection must satisfy the following constraints 2963 // while concurrent marking is in progress: 2964 // 2965 // * In order to maintain SATB invariants, an object must not be 2966 // reclaimed if it was allocated before the start of marking and 2967 // has not had its references scanned. Such an object must have 2968 // its references (including type metadata) scanned to ensure no 2969 // live objects are missed by the marking process. Objects 2970 // allocated after the start of concurrent marking don't need to 2971 // be scanned. 2972 // 2973 // * An object must not be reclaimed if it is on the concurrent 2974 // mark stack. Objects allocated after the start of concurrent 2975 // marking are never pushed on the mark stack. 2976 // 2977 // Nominating only objects allocated after the start of concurrent 2978 // marking is sufficient to meet both constraints. This may miss 2979 // some objects that satisfy the constraints, but the marking data 2980 // structures don't support efficiently performing the needed 2981 // additional tests or scrubbing of the mark stack. 2982 // 2983 // However, we presently only nominate is_typeArray() objects. 2984 // A humongous object containing references induces remembered 2985 // set entries on other regions. In order to reclaim such an 2986 // object, those remembered sets would need to be cleaned up. 2987 // 2988 // We also treat is_typeArray() objects specially, allowing them 2989 // to be reclaimed even if allocated before the start of 2990 // concurrent mark. For this we rely on mark stack insertion to 2991 // exclude is_typeArray() objects, preventing reclaiming an object 2992 // that is in the mark stack. We also rely on the metadata for 2993 // such objects to be built-in and so ensured to be kept live. 2994 // Frequent allocation and drop of large binary blobs is an 2995 // important use case for eager reclaim, and this special handling 2996 // may reduce needed headroom. 2997 2998 return obj->is_typeArray() && is_remset_small(region); 2999 } 3000 3001 public: 3002 RegisterHumongousWithInCSetFastTestClosure() 3003 : _total_humongous(0), 3004 _candidate_humongous(0), 3005 _dcq(&JavaThread::dirty_card_queue_set()) { 3006 } 3007 3008 virtual bool doHeapRegion(HeapRegion* r) { 3009 if (!r->is_starts_humongous()) { 3010 return false; 3011 } 3012 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3013 3014 bool is_candidate = humongous_region_is_candidate(g1h, r); 3015 uint rindex = r->hrm_index(); 3016 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 3017 if (is_candidate) { 3018 _candidate_humongous++; 3019 g1h->register_humongous_region_with_cset(rindex); 3020 // Is_candidate already filters out humongous object with large remembered sets. 3021 // If we have a humongous object with a few remembered sets, we simply flush these 3022 // remembered set entries into the DCQS. That will result in automatic 3023 // re-evaluation of their remembered set entries during the following evacuation 3024 // phase. 3025 if (!r->rem_set()->is_empty()) { 3026 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 3027 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 3028 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 3029 HeapRegionRemSetIterator hrrs(r->rem_set()); 3030 size_t card_index; 3031 while (hrrs.has_next(card_index)) { 3032 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 3033 // The remembered set might contain references to already freed 3034 // regions. Filter out such entries to avoid failing card table 3035 // verification. 3036 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 3037 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 3038 *card_ptr = CardTableModRefBS::dirty_card_val(); 3039 _dcq.enqueue(card_ptr); 3040 } 3041 } 3042 } 3043 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 3044 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 3045 hrrs.n_yielded(), r->rem_set()->occupied()); 3046 r->rem_set()->clear_locked(); 3047 } 3048 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 3049 } 3050 _total_humongous++; 3051 3052 return false; 3053 } 3054 3055 size_t total_humongous() const { return _total_humongous; } 3056 size_t candidate_humongous() const { return _candidate_humongous; } 3057 3058 void flush_rem_set_entries() { _dcq.flush(); } 3059 }; 3060 3061 void G1CollectedHeap::register_humongous_regions_with_cset() { 3062 if (!G1EagerReclaimHumongousObjects) { 3063 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 3064 return; 3065 } 3066 double time = os::elapsed_counter(); 3067 3068 // Collect reclaim candidate information and register candidates with cset. 3069 RegisterHumongousWithInCSetFastTestClosure cl; 3070 heap_region_iterate(&cl); 3071 3072 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 3073 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 3074 cl.total_humongous(), 3075 cl.candidate_humongous()); 3076 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3077 3078 // Finally flush all remembered set entries to re-check into the global DCQS. 3079 cl.flush_rem_set_entries(); 3080 } 3081 3082 class VerifyRegionRemSetClosure : public HeapRegionClosure { 3083 public: 3084 bool doHeapRegion(HeapRegion* hr) { 3085 if (!hr->is_archive() && !hr->is_continues_humongous()) { 3086 hr->verify_rem_set(); 3087 } 3088 return false; 3089 } 3090 }; 3091 3092 uint G1CollectedHeap::num_task_queues() const { 3093 return _task_queues->size(); 3094 } 3095 3096 #if TASKQUEUE_STATS 3097 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3098 st->print_raw_cr("GC Task Stats"); 3099 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3100 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3101 } 3102 3103 void G1CollectedHeap::print_taskqueue_stats() const { 3104 if (!log_is_enabled(Trace, gc, task, stats)) { 3105 return; 3106 } 3107 Log(gc, task, stats) log; 3108 ResourceMark rm; 3109 outputStream* st = log.trace_stream(); 3110 3111 print_taskqueue_stats_hdr(st); 3112 3113 TaskQueueStats totals; 3114 const uint n = num_task_queues(); 3115 for (uint i = 0; i < n; ++i) { 3116 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 3117 totals += task_queue(i)->stats; 3118 } 3119 st->print_raw("tot "); totals.print(st); st->cr(); 3120 3121 DEBUG_ONLY(totals.verify()); 3122 } 3123 3124 void G1CollectedHeap::reset_taskqueue_stats() { 3125 const uint n = num_task_queues(); 3126 for (uint i = 0; i < n; ++i) { 3127 task_queue(i)->stats.reset(); 3128 } 3129 } 3130 #endif // TASKQUEUE_STATS 3131 3132 void G1CollectedHeap::wait_for_root_region_scanning() { 3133 double scan_wait_start = os::elapsedTime(); 3134 // We have to wait until the CM threads finish scanning the 3135 // root regions as it's the only way to ensure that all the 3136 // objects on them have been correctly scanned before we start 3137 // moving them during the GC. 3138 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3139 double wait_time_ms = 0.0; 3140 if (waited) { 3141 double scan_wait_end = os::elapsedTime(); 3142 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3143 } 3144 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3145 } 3146 3147 bool 3148 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3149 assert_at_safepoint(true /* should_be_vm_thread */); 3150 guarantee(!is_gc_active(), "collection is not reentrant"); 3151 3152 if (GCLocker::check_active_before_gc()) { 3153 return false; 3154 } 3155 3156 _gc_timer_stw->register_gc_start(); 3157 3158 GCIdMark gc_id_mark; 3159 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3160 3161 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3162 ResourceMark rm; 3163 3164 wait_for_root_region_scanning(); 3165 3166 print_heap_before_gc(); 3167 print_heap_regions(); 3168 trace_heap_before_gc(_gc_tracer_stw); 3169 3170 _verifier->verify_region_sets_optional(); 3171 _verifier->verify_dirty_young_regions(); 3172 3173 // We should not be doing initial mark unless the conc mark thread is running 3174 if (!_cmThread->should_terminate()) { 3175 // This call will decide whether this pause is an initial-mark 3176 // pause. If it is, during_initial_mark_pause() will return true 3177 // for the duration of this pause. 3178 g1_policy()->decide_on_conc_mark_initiation(); 3179 } 3180 3181 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3182 assert(!collector_state()->during_initial_mark_pause() || 3183 collector_state()->gcs_are_young(), "sanity"); 3184 3185 // We also do not allow mixed GCs during marking. 3186 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3187 3188 // Record whether this pause is an initial mark. When the current 3189 // thread has completed its logging output and it's safe to signal 3190 // the CM thread, the flag's value in the policy has been reset. 3191 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3192 3193 // Inner scope for scope based logging, timers, and stats collection 3194 { 3195 EvacuationInfo evacuation_info; 3196 3197 if (collector_state()->during_initial_mark_pause()) { 3198 // We are about to start a marking cycle, so we increment the 3199 // full collection counter. 3200 increment_old_marking_cycles_started(); 3201 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 3202 } 3203 3204 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3205 3206 GCTraceCPUTime tcpu; 3207 3208 FormatBuffer<> gc_string("Pause "); 3209 if (collector_state()->during_initial_mark_pause()) { 3210 gc_string.append("Initial Mark"); 3211 } else if (collector_state()->gcs_are_young()) { 3212 gc_string.append("Young"); 3213 } else { 3214 gc_string.append("Mixed"); 3215 } 3216 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 3217 3218 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3219 workers()->active_workers(), 3220 Threads::number_of_non_daemon_threads()); 3221 workers()->set_active_workers(active_workers); 3222 3223 g1_policy()->note_gc_start(); 3224 3225 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3226 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3227 3228 // If the secondary_free_list is not empty, append it to the 3229 // free_list. No need to wait for the cleanup operation to finish; 3230 // the region allocation code will check the secondary_free_list 3231 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3232 // set, skip this step so that the region allocation code has to 3233 // get entries from the secondary_free_list. 3234 if (!G1StressConcRegionFreeing) { 3235 append_secondary_free_list_if_not_empty_with_lock(); 3236 } 3237 3238 G1HeapTransition heap_transition(this); 3239 size_t heap_used_bytes_before_gc = used(); 3240 3241 assert(check_young_list_well_formed(), "young list should be well formed"); 3242 3243 // Don't dynamically change the number of GC threads this early. A value of 3244 // 0 is used to indicate serial work. When parallel work is done, 3245 // it will be set. 3246 3247 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3248 IsGCActiveMark x; 3249 3250 gc_prologue(false); 3251 increment_total_collections(false /* full gc */); 3252 increment_gc_time_stamp(); 3253 3254 if (VerifyRememberedSets) { 3255 log_info(gc, verify)("[Verifying RemSets before GC]"); 3256 VerifyRegionRemSetClosure v_cl; 3257 heap_region_iterate(&v_cl); 3258 } 3259 3260 _verifier->verify_before_gc(); 3261 3262 _verifier->check_bitmaps("GC Start"); 3263 3264 #if defined(COMPILER2) || INCLUDE_JVMCI 3265 DerivedPointerTable::clear(); 3266 #endif 3267 3268 // Please see comment in g1CollectedHeap.hpp and 3269 // G1CollectedHeap::ref_processing_init() to see how 3270 // reference processing currently works in G1. 3271 3272 // Enable discovery in the STW reference processor 3273 if (g1_policy()->should_process_references()) { 3274 ref_processor_stw()->enable_discovery(); 3275 } else { 3276 ref_processor_stw()->disable_discovery(); 3277 } 3278 3279 { 3280 // We want to temporarily turn off discovery by the 3281 // CM ref processor, if necessary, and turn it back on 3282 // on again later if we do. Using a scoped 3283 // NoRefDiscovery object will do this. 3284 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3285 3286 // Forget the current alloc region (we might even choose it to be part 3287 // of the collection set!). 3288 _allocator->release_mutator_alloc_region(); 3289 3290 // This timing is only used by the ergonomics to handle our pause target. 3291 // It is unclear why this should not include the full pause. We will 3292 // investigate this in CR 7178365. 3293 // 3294 // Preserving the old comment here if that helps the investigation: 3295 // 3296 // The elapsed time induced by the start time below deliberately elides 3297 // the possible verification above. 3298 double sample_start_time_sec = os::elapsedTime(); 3299 3300 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3301 3302 if (collector_state()->during_initial_mark_pause()) { 3303 concurrent_mark()->checkpointRootsInitialPre(); 3304 } 3305 3306 g1_policy()->finalize_collection_set(target_pause_time_ms); 3307 3308 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3309 3310 // Make sure the remembered sets are up to date. This needs to be 3311 // done before register_humongous_regions_with_cset(), because the 3312 // remembered sets are used there to choose eager reclaim candidates. 3313 // If the remembered sets are not up to date we might miss some 3314 // entries that need to be handled. 3315 g1_rem_set()->cleanupHRRS(); 3316 3317 register_humongous_regions_with_cset(); 3318 3319 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3320 3321 _cm->note_start_of_gc(); 3322 // We call this after finalize_cset() to 3323 // ensure that the CSet has been finalized. 3324 _cm->verify_no_cset_oops(); 3325 3326 if (_hr_printer.is_active()) { 3327 HeapRegion* hr = collection_set()->head(); 3328 while (hr != NULL) { 3329 _hr_printer.cset(hr); 3330 hr = hr->next_in_collection_set(); 3331 } 3332 } 3333 3334 // Initialize the GC alloc regions. 3335 _allocator->init_gc_alloc_regions(evacuation_info); 3336 3337 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3338 pre_evacuate_collection_set(); 3339 3340 // Actually do the work... 3341 evacuate_collection_set(evacuation_info, &per_thread_states); 3342 3343 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3344 3345 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3346 free_collection_set(collection_set()->head(), evacuation_info, surviving_young_words); 3347 3348 eagerly_reclaim_humongous_regions(); 3349 3350 collection_set()->clear_head(); 3351 3352 record_obj_copy_mem_stats(); 3353 _survivor_evac_stats.adjust_desired_plab_sz(); 3354 _old_evac_stats.adjust_desired_plab_sz(); 3355 3356 // Start a new incremental collection set for the next pause. 3357 collection_set()->start_incremental_building(); 3358 3359 clear_cset_fast_test(); 3360 3361 // Don't check the whole heap at this point as the 3362 // GC alloc regions from this pause have been tagged 3363 // as survivors and moved on to the survivor list. 3364 // Survivor regions will fail the !is_young() check. 3365 assert(check_young_list_empty(false /* check_heap */), 3366 "young list should be empty"); 3367 3368 _young_list->reset_auxilary_lists(); 3369 3370 if (evacuation_failed()) { 3371 set_used(recalculate_used()); 3372 if (_archive_allocator != NULL) { 3373 _archive_allocator->clear_used(); 3374 } 3375 for (uint i = 0; i < ParallelGCThreads; i++) { 3376 if (_evacuation_failed_info_array[i].has_failed()) { 3377 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3378 } 3379 } 3380 } else { 3381 // The "used" of the the collection set have already been subtracted 3382 // when they were freed. Add in the bytes evacuated. 3383 increase_used(g1_policy()->bytes_copied_during_gc()); 3384 } 3385 3386 if (collector_state()->during_initial_mark_pause()) { 3387 // We have to do this before we notify the CM threads that 3388 // they can start working to make sure that all the 3389 // appropriate initialization is done on the CM object. 3390 concurrent_mark()->checkpointRootsInitialPost(); 3391 collector_state()->set_mark_in_progress(true); 3392 // Note that we don't actually trigger the CM thread at 3393 // this point. We do that later when we're sure that 3394 // the current thread has completed its logging output. 3395 } 3396 3397 allocate_dummy_regions(); 3398 3399 _allocator->init_mutator_alloc_region(); 3400 3401 { 3402 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3403 if (expand_bytes > 0) { 3404 size_t bytes_before = capacity(); 3405 // No need for an ergo logging here, 3406 // expansion_amount() does this when it returns a value > 0. 3407 double expand_ms; 3408 if (!expand(expand_bytes, &expand_ms)) { 3409 // We failed to expand the heap. Cannot do anything about it. 3410 } 3411 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3412 } 3413 } 3414 3415 // We redo the verification but now wrt to the new CSet which 3416 // has just got initialized after the previous CSet was freed. 3417 _cm->verify_no_cset_oops(); 3418 _cm->note_end_of_gc(); 3419 3420 // This timing is only used by the ergonomics to handle our pause target. 3421 // It is unclear why this should not include the full pause. We will 3422 // investigate this in CR 7178365. 3423 double sample_end_time_sec = os::elapsedTime(); 3424 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3425 size_t total_cards_scanned = per_thread_states.total_cards_scanned(); 3426 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3427 3428 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3429 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3430 3431 MemoryService::track_memory_usage(); 3432 3433 // In prepare_for_verify() below we'll need to scan the deferred 3434 // update buffers to bring the RSets up-to-date if 3435 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3436 // the update buffers we'll probably need to scan cards on the 3437 // regions we just allocated to (i.e., the GC alloc 3438 // regions). However, during the last GC we called 3439 // set_saved_mark() on all the GC alloc regions, so card 3440 // scanning might skip the [saved_mark_word()...top()] area of 3441 // those regions (i.e., the area we allocated objects into 3442 // during the last GC). But it shouldn't. Given that 3443 // saved_mark_word() is conditional on whether the GC time stamp 3444 // on the region is current or not, by incrementing the GC time 3445 // stamp here we invalidate all the GC time stamps on all the 3446 // regions and saved_mark_word() will simply return top() for 3447 // all the regions. This is a nicer way of ensuring this rather 3448 // than iterating over the regions and fixing them. In fact, the 3449 // GC time stamp increment here also ensures that 3450 // saved_mark_word() will return top() between pauses, i.e., 3451 // during concurrent refinement. So we don't need the 3452 // is_gc_active() check to decided which top to use when 3453 // scanning cards (see CR 7039627). 3454 increment_gc_time_stamp(); 3455 3456 if (VerifyRememberedSets) { 3457 log_info(gc, verify)("[Verifying RemSets after GC]"); 3458 VerifyRegionRemSetClosure v_cl; 3459 heap_region_iterate(&v_cl); 3460 } 3461 3462 _verifier->verify_after_gc(); 3463 _verifier->check_bitmaps("GC End"); 3464 3465 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3466 ref_processor_stw()->verify_no_references_recorded(); 3467 3468 // CM reference discovery will be re-enabled if necessary. 3469 } 3470 3471 #ifdef TRACESPINNING 3472 ParallelTaskTerminator::print_termination_counts(); 3473 #endif 3474 3475 gc_epilogue(false); 3476 } 3477 3478 // Print the remainder of the GC log output. 3479 if (evacuation_failed()) { 3480 log_info(gc)("To-space exhausted"); 3481 } 3482 3483 g1_policy()->print_phases(); 3484 heap_transition.print(); 3485 3486 // It is not yet to safe to tell the concurrent mark to 3487 // start as we have some optional output below. We don't want the 3488 // output from the concurrent mark thread interfering with this 3489 // logging output either. 3490 3491 _hrm.verify_optional(); 3492 _verifier->verify_region_sets_optional(); 3493 3494 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3495 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3496 3497 print_heap_after_gc(); 3498 print_heap_regions(); 3499 trace_heap_after_gc(_gc_tracer_stw); 3500 3501 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3502 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3503 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3504 // before any GC notifications are raised. 3505 g1mm()->update_sizes(); 3506 3507 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3508 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3509 _gc_timer_stw->register_gc_end(); 3510 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3511 } 3512 // It should now be safe to tell the concurrent mark thread to start 3513 // without its logging output interfering with the logging output 3514 // that came from the pause. 3515 3516 if (should_start_conc_mark) { 3517 // CAUTION: after the doConcurrentMark() call below, 3518 // the concurrent marking thread(s) could be running 3519 // concurrently with us. Make sure that anything after 3520 // this point does not assume that we are the only GC thread 3521 // running. Note: of course, the actual marking work will 3522 // not start until the safepoint itself is released in 3523 // SuspendibleThreadSet::desynchronize(). 3524 doConcurrentMark(); 3525 } 3526 3527 return true; 3528 } 3529 3530 void G1CollectedHeap::restore_preserved_marks() { 3531 G1RestorePreservedMarksTask rpm_task(_preserved_objs); 3532 workers()->run_task(&rpm_task); 3533 } 3534 3535 void G1CollectedHeap::remove_self_forwarding_pointers() { 3536 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3537 workers()->run_task(&rsfp_task); 3538 } 3539 3540 void G1CollectedHeap::restore_after_evac_failure() { 3541 double remove_self_forwards_start = os::elapsedTime(); 3542 3543 remove_self_forwarding_pointers(); 3544 restore_preserved_marks(); 3545 3546 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3547 } 3548 3549 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3550 if (!_evacuation_failed) { 3551 _evacuation_failed = true; 3552 } 3553 3554 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3555 3556 // We want to call the "for_promotion_failure" version only in the 3557 // case of a promotion failure. 3558 if (m->must_be_preserved_for_promotion_failure(obj)) { 3559 OopAndMarkOop elem(obj, m); 3560 _preserved_objs[worker_id].push(elem); 3561 } 3562 } 3563 3564 bool G1ParEvacuateFollowersClosure::offer_termination() { 3565 G1ParScanThreadState* const pss = par_scan_state(); 3566 start_term_time(); 3567 const bool res = terminator()->offer_termination(); 3568 end_term_time(); 3569 return res; 3570 } 3571 3572 void G1ParEvacuateFollowersClosure::do_void() { 3573 G1ParScanThreadState* const pss = par_scan_state(); 3574 pss->trim_queue(); 3575 do { 3576 pss->steal_and_trim_queue(queues()); 3577 } while (!offer_termination()); 3578 } 3579 3580 class G1ParTask : public AbstractGangTask { 3581 protected: 3582 G1CollectedHeap* _g1h; 3583 G1ParScanThreadStateSet* _pss; 3584 RefToScanQueueSet* _queues; 3585 G1RootProcessor* _root_processor; 3586 ParallelTaskTerminator _terminator; 3587 uint _n_workers; 3588 3589 public: 3590 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3591 : AbstractGangTask("G1 collection"), 3592 _g1h(g1h), 3593 _pss(per_thread_states), 3594 _queues(task_queues), 3595 _root_processor(root_processor), 3596 _terminator(n_workers, _queues), 3597 _n_workers(n_workers) 3598 {} 3599 3600 void work(uint worker_id) { 3601 if (worker_id >= _n_workers) return; // no work needed this round 3602 3603 double start_sec = os::elapsedTime(); 3604 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3605 3606 { 3607 ResourceMark rm; 3608 HandleMark hm; 3609 3610 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3611 3612 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3613 pss->set_ref_processor(rp); 3614 3615 double start_strong_roots_sec = os::elapsedTime(); 3616 3617 _root_processor->evacuate_roots(pss->closures(), worker_id); 3618 3619 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss); 3620 3621 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3622 // treating the nmethods visited to act as roots for concurrent marking. 3623 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3624 // objects copied by the current evacuation. 3625 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl, 3626 pss->closures()->weak_codeblobs(), 3627 worker_id); 3628 3629 _pss->add_cards_scanned(worker_id, cards_scanned); 3630 3631 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3632 3633 double term_sec = 0.0; 3634 size_t evac_term_attempts = 0; 3635 { 3636 double start = os::elapsedTime(); 3637 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3638 evac.do_void(); 3639 3640 evac_term_attempts = evac.term_attempts(); 3641 term_sec = evac.term_time(); 3642 double elapsed_sec = os::elapsedTime() - start; 3643 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3644 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3645 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3646 } 3647 3648 assert(pss->queue_is_empty(), "should be empty"); 3649 3650 if (log_is_enabled(Debug, gc, task, stats)) { 3651 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3652 size_t lab_waste; 3653 size_t lab_undo_waste; 3654 pss->waste(lab_waste, lab_undo_waste); 3655 _g1h->print_termination_stats(worker_id, 3656 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3657 strong_roots_sec * 1000.0, /* strong roots time */ 3658 term_sec * 1000.0, /* evac term time */ 3659 evac_term_attempts, /* evac term attempts */ 3660 lab_waste, /* alloc buffer waste */ 3661 lab_undo_waste /* undo waste */ 3662 ); 3663 } 3664 3665 // Close the inner scope so that the ResourceMark and HandleMark 3666 // destructors are executed here and are included as part of the 3667 // "GC Worker Time". 3668 } 3669 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3670 } 3671 }; 3672 3673 void G1CollectedHeap::print_termination_stats_hdr() { 3674 log_debug(gc, task, stats)("GC Termination Stats"); 3675 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3676 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3677 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3678 } 3679 3680 void G1CollectedHeap::print_termination_stats(uint worker_id, 3681 double elapsed_ms, 3682 double strong_roots_ms, 3683 double term_ms, 3684 size_t term_attempts, 3685 size_t alloc_buffer_waste, 3686 size_t undo_waste) const { 3687 log_debug(gc, task, stats) 3688 ("%3d %9.2f %9.2f %6.2f " 3689 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3690 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3691 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3692 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3693 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3694 alloc_buffer_waste * HeapWordSize / K, 3695 undo_waste * HeapWordSize / K); 3696 } 3697 3698 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 3699 private: 3700 BoolObjectClosure* _is_alive; 3701 int _initial_string_table_size; 3702 int _initial_symbol_table_size; 3703 3704 bool _process_strings; 3705 int _strings_processed; 3706 int _strings_removed; 3707 3708 bool _process_symbols; 3709 int _symbols_processed; 3710 int _symbols_removed; 3711 3712 public: 3713 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 3714 AbstractGangTask("String/Symbol Unlinking"), 3715 _is_alive(is_alive), 3716 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3717 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 3718 3719 _initial_string_table_size = StringTable::the_table()->table_size(); 3720 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3721 if (process_strings) { 3722 StringTable::clear_parallel_claimed_index(); 3723 } 3724 if (process_symbols) { 3725 SymbolTable::clear_parallel_claimed_index(); 3726 } 3727 } 3728 3729 ~G1StringSymbolTableUnlinkTask() { 3730 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3731 "claim value %d after unlink less than initial string table size %d", 3732 StringTable::parallel_claimed_index(), _initial_string_table_size); 3733 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3734 "claim value %d after unlink less than initial symbol table size %d", 3735 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3736 3737 log_info(gc, stringtable)( 3738 "Cleaned string and symbol table, " 3739 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3740 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3741 strings_processed(), strings_removed(), 3742 symbols_processed(), symbols_removed()); 3743 } 3744 3745 void work(uint worker_id) { 3746 int strings_processed = 0; 3747 int strings_removed = 0; 3748 int symbols_processed = 0; 3749 int symbols_removed = 0; 3750 if (_process_strings) { 3751 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3752 Atomic::add(strings_processed, &_strings_processed); 3753 Atomic::add(strings_removed, &_strings_removed); 3754 } 3755 if (_process_symbols) { 3756 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3757 Atomic::add(symbols_processed, &_symbols_processed); 3758 Atomic::add(symbols_removed, &_symbols_removed); 3759 } 3760 } 3761 3762 size_t strings_processed() const { return (size_t)_strings_processed; } 3763 size_t strings_removed() const { return (size_t)_strings_removed; } 3764 3765 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3766 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3767 }; 3768 3769 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3770 private: 3771 static Monitor* _lock; 3772 3773 BoolObjectClosure* const _is_alive; 3774 const bool _unloading_occurred; 3775 const uint _num_workers; 3776 3777 // Variables used to claim nmethods. 3778 nmethod* _first_nmethod; 3779 volatile nmethod* _claimed_nmethod; 3780 3781 // The list of nmethods that need to be processed by the second pass. 3782 volatile nmethod* _postponed_list; 3783 volatile uint _num_entered_barrier; 3784 3785 public: 3786 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3787 _is_alive(is_alive), 3788 _unloading_occurred(unloading_occurred), 3789 _num_workers(num_workers), 3790 _first_nmethod(NULL), 3791 _claimed_nmethod(NULL), 3792 _postponed_list(NULL), 3793 _num_entered_barrier(0) 3794 { 3795 nmethod::increase_unloading_clock(); 3796 // Get first alive nmethod 3797 NMethodIterator iter = NMethodIterator(); 3798 if(iter.next_alive()) { 3799 _first_nmethod = iter.method(); 3800 } 3801 _claimed_nmethod = (volatile nmethod*)_first_nmethod; 3802 } 3803 3804 ~G1CodeCacheUnloadingTask() { 3805 CodeCache::verify_clean_inline_caches(); 3806 3807 CodeCache::set_needs_cache_clean(false); 3808 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3809 3810 CodeCache::verify_icholder_relocations(); 3811 } 3812 3813 private: 3814 void add_to_postponed_list(nmethod* nm) { 3815 nmethod* old; 3816 do { 3817 old = (nmethod*)_postponed_list; 3818 nm->set_unloading_next(old); 3819 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 3820 } 3821 3822 void clean_nmethod(nmethod* nm) { 3823 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3824 3825 if (postponed) { 3826 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3827 add_to_postponed_list(nm); 3828 } 3829 3830 // Mark that this thread has been cleaned/unloaded. 3831 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3832 nm->set_unloading_clock(nmethod::global_unloading_clock()); 3833 } 3834 3835 void clean_nmethod_postponed(nmethod* nm) { 3836 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3837 } 3838 3839 static const int MaxClaimNmethods = 16; 3840 3841 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) { 3842 nmethod* first; 3843 NMethodIterator last; 3844 3845 do { 3846 *num_claimed_nmethods = 0; 3847 3848 first = (nmethod*)_claimed_nmethod; 3849 last = NMethodIterator(first); 3850 3851 if (first != NULL) { 3852 3853 for (int i = 0; i < MaxClaimNmethods; i++) { 3854 if (!last.next_alive()) { 3855 break; 3856 } 3857 claimed_nmethods[i] = last.method(); 3858 (*num_claimed_nmethods)++; 3859 } 3860 } 3861 3862 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 3863 } 3864 3865 nmethod* claim_postponed_nmethod() { 3866 nmethod* claim; 3867 nmethod* next; 3868 3869 do { 3870 claim = (nmethod*)_postponed_list; 3871 if (claim == NULL) { 3872 return NULL; 3873 } 3874 3875 next = claim->unloading_next(); 3876 3877 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 3878 3879 return claim; 3880 } 3881 3882 public: 3883 // Mark that we're done with the first pass of nmethod cleaning. 3884 void barrier_mark(uint worker_id) { 3885 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3886 _num_entered_barrier++; 3887 if (_num_entered_barrier == _num_workers) { 3888 ml.notify_all(); 3889 } 3890 } 3891 3892 // See if we have to wait for the other workers to 3893 // finish their first-pass nmethod cleaning work. 3894 void barrier_wait(uint worker_id) { 3895 if (_num_entered_barrier < _num_workers) { 3896 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3897 while (_num_entered_barrier < _num_workers) { 3898 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3899 } 3900 } 3901 } 3902 3903 // Cleaning and unloading of nmethods. Some work has to be postponed 3904 // to the second pass, when we know which nmethods survive. 3905 void work_first_pass(uint worker_id) { 3906 // The first nmethods is claimed by the first worker. 3907 if (worker_id == 0 && _first_nmethod != NULL) { 3908 clean_nmethod(_first_nmethod); 3909 _first_nmethod = NULL; 3910 } 3911 3912 int num_claimed_nmethods; 3913 nmethod* claimed_nmethods[MaxClaimNmethods]; 3914 3915 while (true) { 3916 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3917 3918 if (num_claimed_nmethods == 0) { 3919 break; 3920 } 3921 3922 for (int i = 0; i < num_claimed_nmethods; i++) { 3923 clean_nmethod(claimed_nmethods[i]); 3924 } 3925 } 3926 } 3927 3928 void work_second_pass(uint worker_id) { 3929 nmethod* nm; 3930 // Take care of postponed nmethods. 3931 while ((nm = claim_postponed_nmethod()) != NULL) { 3932 clean_nmethod_postponed(nm); 3933 } 3934 } 3935 }; 3936 3937 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3938 3939 class G1KlassCleaningTask : public StackObj { 3940 BoolObjectClosure* _is_alive; 3941 volatile jint _clean_klass_tree_claimed; 3942 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3943 3944 public: 3945 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3946 _is_alive(is_alive), 3947 _clean_klass_tree_claimed(0), 3948 _klass_iterator() { 3949 } 3950 3951 private: 3952 bool claim_clean_klass_tree_task() { 3953 if (_clean_klass_tree_claimed) { 3954 return false; 3955 } 3956 3957 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 3958 } 3959 3960 InstanceKlass* claim_next_klass() { 3961 Klass* klass; 3962 do { 3963 klass =_klass_iterator.next_klass(); 3964 } while (klass != NULL && !klass->is_instance_klass()); 3965 3966 // this can be null so don't call InstanceKlass::cast 3967 return static_cast<InstanceKlass*>(klass); 3968 } 3969 3970 public: 3971 3972 void clean_klass(InstanceKlass* ik) { 3973 ik->clean_weak_instanceklass_links(_is_alive); 3974 } 3975 3976 void work() { 3977 ResourceMark rm; 3978 3979 // One worker will clean the subklass/sibling klass tree. 3980 if (claim_clean_klass_tree_task()) { 3981 Klass::clean_subklass_tree(_is_alive); 3982 } 3983 3984 // All workers will help cleaning the classes, 3985 InstanceKlass* klass; 3986 while ((klass = claim_next_klass()) != NULL) { 3987 clean_klass(klass); 3988 } 3989 } 3990 }; 3991 3992 // To minimize the remark pause times, the tasks below are done in parallel. 3993 class G1ParallelCleaningTask : public AbstractGangTask { 3994 private: 3995 G1StringSymbolTableUnlinkTask _string_symbol_task; 3996 G1CodeCacheUnloadingTask _code_cache_task; 3997 G1KlassCleaningTask _klass_cleaning_task; 3998 3999 public: 4000 // The constructor is run in the VMThread. 4001 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 4002 AbstractGangTask("Parallel Cleaning"), 4003 _string_symbol_task(is_alive, process_strings, process_symbols), 4004 _code_cache_task(num_workers, is_alive, unloading_occurred), 4005 _klass_cleaning_task(is_alive) { 4006 } 4007 4008 // The parallel work done by all worker threads. 4009 void work(uint worker_id) { 4010 // Do first pass of code cache cleaning. 4011 _code_cache_task.work_first_pass(worker_id); 4012 4013 // Let the threads mark that the first pass is done. 4014 _code_cache_task.barrier_mark(worker_id); 4015 4016 // Clean the Strings and Symbols. 4017 _string_symbol_task.work(worker_id); 4018 4019 // Wait for all workers to finish the first code cache cleaning pass. 4020 _code_cache_task.barrier_wait(worker_id); 4021 4022 // Do the second code cache cleaning work, which realize on 4023 // the liveness information gathered during the first pass. 4024 _code_cache_task.work_second_pass(worker_id); 4025 4026 // Clean all klasses that were not unloaded. 4027 _klass_cleaning_task.work(); 4028 } 4029 }; 4030 4031 4032 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 4033 bool process_strings, 4034 bool process_symbols, 4035 bool class_unloading_occurred) { 4036 uint n_workers = workers()->active_workers(); 4037 4038 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 4039 n_workers, class_unloading_occurred); 4040 workers()->run_task(&g1_unlink_task); 4041 } 4042 4043 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 4044 bool process_strings, bool process_symbols) { 4045 { // Timing scope 4046 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 4047 workers()->run_task(&g1_unlink_task); 4048 } 4049 } 4050 4051 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 4052 private: 4053 DirtyCardQueueSet* _queue; 4054 G1CollectedHeap* _g1h; 4055 public: 4056 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 4057 _queue(queue), _g1h(g1h) { } 4058 4059 virtual void work(uint worker_id) { 4060 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 4061 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 4062 4063 RedirtyLoggedCardTableEntryClosure cl(_g1h); 4064 _queue->par_apply_closure_to_all_completed_buffers(&cl); 4065 4066 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 4067 } 4068 }; 4069 4070 void G1CollectedHeap::redirty_logged_cards() { 4071 double redirty_logged_cards_start = os::elapsedTime(); 4072 4073 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 4074 dirty_card_queue_set().reset_for_par_iteration(); 4075 workers()->run_task(&redirty_task); 4076 4077 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 4078 dcq.merge_bufferlists(&dirty_card_queue_set()); 4079 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 4080 4081 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 4082 } 4083 4084 // Weak Reference Processing support 4085 4086 // An always "is_alive" closure that is used to preserve referents. 4087 // If the object is non-null then it's alive. Used in the preservation 4088 // of referent objects that are pointed to by reference objects 4089 // discovered by the CM ref processor. 4090 class G1AlwaysAliveClosure: public BoolObjectClosure { 4091 G1CollectedHeap* _g1; 4092 public: 4093 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4094 bool do_object_b(oop p) { 4095 if (p != NULL) { 4096 return true; 4097 } 4098 return false; 4099 } 4100 }; 4101 4102 bool G1STWIsAliveClosure::do_object_b(oop p) { 4103 // An object is reachable if it is outside the collection set, 4104 // or is inside and copied. 4105 return !_g1->is_in_cset(p) || p->is_forwarded(); 4106 } 4107 4108 // Non Copying Keep Alive closure 4109 class G1KeepAliveClosure: public OopClosure { 4110 G1CollectedHeap* _g1; 4111 public: 4112 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4113 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 4114 void do_oop(oop* p) { 4115 oop obj = *p; 4116 assert(obj != NULL, "the caller should have filtered out NULL values"); 4117 4118 const InCSetState cset_state = _g1->in_cset_state(obj); 4119 if (!cset_state.is_in_cset_or_humongous()) { 4120 return; 4121 } 4122 if (cset_state.is_in_cset()) { 4123 assert( obj->is_forwarded(), "invariant" ); 4124 *p = obj->forwardee(); 4125 } else { 4126 assert(!obj->is_forwarded(), "invariant" ); 4127 assert(cset_state.is_humongous(), 4128 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 4129 _g1->set_humongous_is_live(obj); 4130 } 4131 } 4132 }; 4133 4134 // Copying Keep Alive closure - can be called from both 4135 // serial and parallel code as long as different worker 4136 // threads utilize different G1ParScanThreadState instances 4137 // and different queues. 4138 4139 class G1CopyingKeepAliveClosure: public OopClosure { 4140 G1CollectedHeap* _g1h; 4141 OopClosure* _copy_non_heap_obj_cl; 4142 G1ParScanThreadState* _par_scan_state; 4143 4144 public: 4145 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4146 OopClosure* non_heap_obj_cl, 4147 G1ParScanThreadState* pss): 4148 _g1h(g1h), 4149 _copy_non_heap_obj_cl(non_heap_obj_cl), 4150 _par_scan_state(pss) 4151 {} 4152 4153 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4154 virtual void do_oop( oop* p) { do_oop_work(p); } 4155 4156 template <class T> void do_oop_work(T* p) { 4157 oop obj = oopDesc::load_decode_heap_oop(p); 4158 4159 if (_g1h->is_in_cset_or_humongous(obj)) { 4160 // If the referent object has been forwarded (either copied 4161 // to a new location or to itself in the event of an 4162 // evacuation failure) then we need to update the reference 4163 // field and, if both reference and referent are in the G1 4164 // heap, update the RSet for the referent. 4165 // 4166 // If the referent has not been forwarded then we have to keep 4167 // it alive by policy. Therefore we have copy the referent. 4168 // 4169 // If the reference field is in the G1 heap then we can push 4170 // on the PSS queue. When the queue is drained (after each 4171 // phase of reference processing) the object and it's followers 4172 // will be copied, the reference field set to point to the 4173 // new location, and the RSet updated. Otherwise we need to 4174 // use the the non-heap or metadata closures directly to copy 4175 // the referent object and update the pointer, while avoiding 4176 // updating the RSet. 4177 4178 if (_g1h->is_in_g1_reserved(p)) { 4179 _par_scan_state->push_on_queue(p); 4180 } else { 4181 assert(!Metaspace::contains((const void*)p), 4182 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4183 _copy_non_heap_obj_cl->do_oop(p); 4184 } 4185 } 4186 } 4187 }; 4188 4189 // Serial drain queue closure. Called as the 'complete_gc' 4190 // closure for each discovered list in some of the 4191 // reference processing phases. 4192 4193 class G1STWDrainQueueClosure: public VoidClosure { 4194 protected: 4195 G1CollectedHeap* _g1h; 4196 G1ParScanThreadState* _par_scan_state; 4197 4198 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4199 4200 public: 4201 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4202 _g1h(g1h), 4203 _par_scan_state(pss) 4204 { } 4205 4206 void do_void() { 4207 G1ParScanThreadState* const pss = par_scan_state(); 4208 pss->trim_queue(); 4209 } 4210 }; 4211 4212 // Parallel Reference Processing closures 4213 4214 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4215 // processing during G1 evacuation pauses. 4216 4217 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4218 private: 4219 G1CollectedHeap* _g1h; 4220 G1ParScanThreadStateSet* _pss; 4221 RefToScanQueueSet* _queues; 4222 WorkGang* _workers; 4223 uint _active_workers; 4224 4225 public: 4226 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4227 G1ParScanThreadStateSet* per_thread_states, 4228 WorkGang* workers, 4229 RefToScanQueueSet *task_queues, 4230 uint n_workers) : 4231 _g1h(g1h), 4232 _pss(per_thread_states), 4233 _queues(task_queues), 4234 _workers(workers), 4235 _active_workers(n_workers) 4236 { 4237 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 4238 } 4239 4240 // Executes the given task using concurrent marking worker threads. 4241 virtual void execute(ProcessTask& task); 4242 virtual void execute(EnqueueTask& task); 4243 }; 4244 4245 // Gang task for possibly parallel reference processing 4246 4247 class G1STWRefProcTaskProxy: public AbstractGangTask { 4248 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4249 ProcessTask& _proc_task; 4250 G1CollectedHeap* _g1h; 4251 G1ParScanThreadStateSet* _pss; 4252 RefToScanQueueSet* _task_queues; 4253 ParallelTaskTerminator* _terminator; 4254 4255 public: 4256 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4257 G1CollectedHeap* g1h, 4258 G1ParScanThreadStateSet* per_thread_states, 4259 RefToScanQueueSet *task_queues, 4260 ParallelTaskTerminator* terminator) : 4261 AbstractGangTask("Process reference objects in parallel"), 4262 _proc_task(proc_task), 4263 _g1h(g1h), 4264 _pss(per_thread_states), 4265 _task_queues(task_queues), 4266 _terminator(terminator) 4267 {} 4268 4269 virtual void work(uint worker_id) { 4270 // The reference processing task executed by a single worker. 4271 ResourceMark rm; 4272 HandleMark hm; 4273 4274 G1STWIsAliveClosure is_alive(_g1h); 4275 4276 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4277 pss->set_ref_processor(NULL); 4278 4279 // Keep alive closure. 4280 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4281 4282 // Complete GC closure 4283 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4284 4285 // Call the reference processing task's work routine. 4286 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4287 4288 // Note we cannot assert that the refs array is empty here as not all 4289 // of the processing tasks (specifically phase2 - pp2_work) execute 4290 // the complete_gc closure (which ordinarily would drain the queue) so 4291 // the queue may not be empty. 4292 } 4293 }; 4294 4295 // Driver routine for parallel reference processing. 4296 // Creates an instance of the ref processing gang 4297 // task and has the worker threads execute it. 4298 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4299 assert(_workers != NULL, "Need parallel worker threads."); 4300 4301 ParallelTaskTerminator terminator(_active_workers, _queues); 4302 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4303 4304 _workers->run_task(&proc_task_proxy); 4305 } 4306 4307 // Gang task for parallel reference enqueueing. 4308 4309 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4310 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4311 EnqueueTask& _enq_task; 4312 4313 public: 4314 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4315 AbstractGangTask("Enqueue reference objects in parallel"), 4316 _enq_task(enq_task) 4317 { } 4318 4319 virtual void work(uint worker_id) { 4320 _enq_task.work(worker_id); 4321 } 4322 }; 4323 4324 // Driver routine for parallel reference enqueueing. 4325 // Creates an instance of the ref enqueueing gang 4326 // task and has the worker threads execute it. 4327 4328 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4329 assert(_workers != NULL, "Need parallel worker threads."); 4330 4331 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4332 4333 _workers->run_task(&enq_task_proxy); 4334 } 4335 4336 // End of weak reference support closures 4337 4338 // Abstract task used to preserve (i.e. copy) any referent objects 4339 // that are in the collection set and are pointed to by reference 4340 // objects discovered by the CM ref processor. 4341 4342 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4343 protected: 4344 G1CollectedHeap* _g1h; 4345 G1ParScanThreadStateSet* _pss; 4346 RefToScanQueueSet* _queues; 4347 ParallelTaskTerminator _terminator; 4348 uint _n_workers; 4349 4350 public: 4351 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4352 AbstractGangTask("ParPreserveCMReferents"), 4353 _g1h(g1h), 4354 _pss(per_thread_states), 4355 _queues(task_queues), 4356 _terminator(workers, _queues), 4357 _n_workers(workers) 4358 { 4359 g1h->ref_processor_cm()->set_active_mt_degree(workers); 4360 } 4361 4362 void work(uint worker_id) { 4363 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4364 4365 ResourceMark rm; 4366 HandleMark hm; 4367 4368 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4369 pss->set_ref_processor(NULL); 4370 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4371 4372 // Is alive closure 4373 G1AlwaysAliveClosure always_alive(_g1h); 4374 4375 // Copying keep alive closure. Applied to referent objects that need 4376 // to be copied. 4377 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4378 4379 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4380 4381 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4382 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4383 4384 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4385 // So this must be true - but assert just in case someone decides to 4386 // change the worker ids. 4387 assert(worker_id < limit, "sanity"); 4388 assert(!rp->discovery_is_atomic(), "check this code"); 4389 4390 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4391 for (uint idx = worker_id; idx < limit; idx += stride) { 4392 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4393 4394 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4395 while (iter.has_next()) { 4396 // Since discovery is not atomic for the CM ref processor, we 4397 // can see some null referent objects. 4398 iter.load_ptrs(DEBUG_ONLY(true)); 4399 oop ref = iter.obj(); 4400 4401 // This will filter nulls. 4402 if (iter.is_referent_alive()) { 4403 iter.make_referent_alive(); 4404 } 4405 iter.move_to_next(); 4406 } 4407 } 4408 4409 // Drain the queue - which may cause stealing 4410 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4411 drain_queue.do_void(); 4412 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4413 assert(pss->queue_is_empty(), "should be"); 4414 } 4415 }; 4416 4417 void G1CollectedHeap::process_weak_jni_handles() { 4418 double ref_proc_start = os::elapsedTime(); 4419 4420 G1STWIsAliveClosure is_alive(this); 4421 G1KeepAliveClosure keep_alive(this); 4422 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 4423 4424 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4425 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4426 } 4427 4428 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4429 // Any reference objects, in the collection set, that were 'discovered' 4430 // by the CM ref processor should have already been copied (either by 4431 // applying the external root copy closure to the discovered lists, or 4432 // by following an RSet entry). 4433 // 4434 // But some of the referents, that are in the collection set, that these 4435 // reference objects point to may not have been copied: the STW ref 4436 // processor would have seen that the reference object had already 4437 // been 'discovered' and would have skipped discovering the reference, 4438 // but would not have treated the reference object as a regular oop. 4439 // As a result the copy closure would not have been applied to the 4440 // referent object. 4441 // 4442 // We need to explicitly copy these referent objects - the references 4443 // will be processed at the end of remarking. 4444 // 4445 // We also need to do this copying before we process the reference 4446 // objects discovered by the STW ref processor in case one of these 4447 // referents points to another object which is also referenced by an 4448 // object discovered by the STW ref processor. 4449 double preserve_cm_referents_time = 0.0; 4450 4451 // To avoid spawning task when there is no work to do, check that 4452 // a concurrent cycle is active and that some references have been 4453 // discovered. 4454 if (concurrent_mark()->cmThread()->during_cycle() && 4455 ref_processor_cm()->has_discovered_references()) { 4456 double preserve_cm_referents_start = os::elapsedTime(); 4457 uint no_of_gc_workers = workers()->active_workers(); 4458 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4459 per_thread_states, 4460 no_of_gc_workers, 4461 _task_queues); 4462 workers()->run_task(&keep_cm_referents); 4463 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4464 } 4465 4466 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4467 } 4468 4469 // Weak Reference processing during an evacuation pause (part 1). 4470 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4471 double ref_proc_start = os::elapsedTime(); 4472 4473 ReferenceProcessor* rp = _ref_processor_stw; 4474 assert(rp->discovery_enabled(), "should have been enabled"); 4475 4476 // Closure to test whether a referent is alive. 4477 G1STWIsAliveClosure is_alive(this); 4478 4479 // Even when parallel reference processing is enabled, the processing 4480 // of JNI refs is serial and performed serially by the current thread 4481 // rather than by a worker. The following PSS will be used for processing 4482 // JNI refs. 4483 4484 // Use only a single queue for this PSS. 4485 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4486 pss->set_ref_processor(NULL); 4487 assert(pss->queue_is_empty(), "pre-condition"); 4488 4489 // Keep alive closure. 4490 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4491 4492 // Serial Complete GC closure 4493 G1STWDrainQueueClosure drain_queue(this, pss); 4494 4495 // Setup the soft refs policy... 4496 rp->setup_policy(false); 4497 4498 ReferenceProcessorStats stats; 4499 if (!rp->processing_is_mt()) { 4500 // Serial reference processing... 4501 stats = rp->process_discovered_references(&is_alive, 4502 &keep_alive, 4503 &drain_queue, 4504 NULL, 4505 _gc_timer_stw); 4506 } else { 4507 uint no_of_gc_workers = workers()->active_workers(); 4508 4509 // Parallel reference processing 4510 assert(no_of_gc_workers <= rp->max_num_q(), 4511 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4512 no_of_gc_workers, rp->max_num_q()); 4513 4514 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4515 stats = rp->process_discovered_references(&is_alive, 4516 &keep_alive, 4517 &drain_queue, 4518 &par_task_executor, 4519 _gc_timer_stw); 4520 } 4521 4522 _gc_tracer_stw->report_gc_reference_stats(stats); 4523 4524 // We have completed copying any necessary live referent objects. 4525 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4526 4527 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4528 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4529 } 4530 4531 // Weak Reference processing during an evacuation pause (part 2). 4532 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4533 double ref_enq_start = os::elapsedTime(); 4534 4535 ReferenceProcessor* rp = _ref_processor_stw; 4536 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4537 4538 // Now enqueue any remaining on the discovered lists on to 4539 // the pending list. 4540 if (!rp->processing_is_mt()) { 4541 // Serial reference processing... 4542 rp->enqueue_discovered_references(); 4543 } else { 4544 // Parallel reference enqueueing 4545 4546 uint n_workers = workers()->active_workers(); 4547 4548 assert(n_workers <= rp->max_num_q(), 4549 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4550 n_workers, rp->max_num_q()); 4551 4552 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4553 rp->enqueue_discovered_references(&par_task_executor); 4554 } 4555 4556 rp->verify_no_references_recorded(); 4557 assert(!rp->discovery_enabled(), "should have been disabled"); 4558 4559 // FIXME 4560 // CM's reference processing also cleans up the string and symbol tables. 4561 // Should we do that here also? We could, but it is a serial operation 4562 // and could significantly increase the pause time. 4563 4564 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4565 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4566 } 4567 4568 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4569 double merge_pss_time_start = os::elapsedTime(); 4570 per_thread_states->flush(); 4571 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4572 } 4573 4574 void G1CollectedHeap::pre_evacuate_collection_set() { 4575 _expand_heap_after_alloc_failure = true; 4576 _evacuation_failed = false; 4577 4578 // Disable the hot card cache. 4579 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 4580 hot_card_cache->reset_hot_cache_claimed_index(); 4581 hot_card_cache->set_use_cache(false); 4582 4583 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4584 } 4585 4586 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4587 // Should G1EvacuationFailureALot be in effect for this GC? 4588 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4589 4590 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4591 double start_par_time_sec = os::elapsedTime(); 4592 double end_par_time_sec; 4593 4594 { 4595 const uint n_workers = workers()->active_workers(); 4596 G1RootProcessor root_processor(this, n_workers); 4597 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4598 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4599 if (collector_state()->during_initial_mark_pause()) { 4600 ClassLoaderDataGraph::clear_claimed_marks(); 4601 } 4602 4603 print_termination_stats_hdr(); 4604 4605 workers()->run_task(&g1_par_task); 4606 end_par_time_sec = os::elapsedTime(); 4607 4608 // Closing the inner scope will execute the destructor 4609 // for the G1RootProcessor object. We record the current 4610 // elapsed time before closing the scope so that time 4611 // taken for the destructor is NOT included in the 4612 // reported parallel time. 4613 } 4614 4615 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4616 4617 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4618 phase_times->record_par_time(par_time_ms); 4619 4620 double code_root_fixup_time_ms = 4621 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4622 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4623 } 4624 4625 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4626 // Process any discovered reference objects - we have 4627 // to do this _before_ we retire the GC alloc regions 4628 // as we may have to copy some 'reachable' referent 4629 // objects (and their reachable sub-graphs) that were 4630 // not copied during the pause. 4631 if (g1_policy()->should_process_references()) { 4632 preserve_cm_referents(per_thread_states); 4633 process_discovered_references(per_thread_states); 4634 } else { 4635 ref_processor_stw()->verify_no_references_recorded(); 4636 process_weak_jni_handles(); 4637 } 4638 4639 if (G1StringDedup::is_enabled()) { 4640 double fixup_start = os::elapsedTime(); 4641 4642 G1STWIsAliveClosure is_alive(this); 4643 G1KeepAliveClosure keep_alive(this); 4644 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4645 4646 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4647 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4648 } 4649 4650 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4651 4652 if (evacuation_failed()) { 4653 restore_after_evac_failure(); 4654 4655 // Reset the G1EvacuationFailureALot counters and flags 4656 // Note: the values are reset only when an actual 4657 // evacuation failure occurs. 4658 NOT_PRODUCT(reset_evacuation_should_fail();) 4659 } 4660 4661 // Enqueue any remaining references remaining on the STW 4662 // reference processor's discovered lists. We need to do 4663 // this after the card table is cleaned (and verified) as 4664 // the act of enqueueing entries on to the pending list 4665 // will log these updates (and dirty their associated 4666 // cards). We need these updates logged to update any 4667 // RSets. 4668 if (g1_policy()->should_process_references()) { 4669 enqueue_discovered_references(per_thread_states); 4670 } else { 4671 g1_policy()->phase_times()->record_ref_enq_time(0); 4672 } 4673 4674 _allocator->release_gc_alloc_regions(evacuation_info); 4675 4676 merge_per_thread_state_info(per_thread_states); 4677 4678 // Reset and re-enable the hot card cache. 4679 // Note the counts for the cards in the regions in the 4680 // collection set are reset when the collection set is freed. 4681 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 4682 hot_card_cache->reset_hot_cache(); 4683 hot_card_cache->set_use_cache(true); 4684 4685 purge_code_root_memory(); 4686 4687 redirty_logged_cards(); 4688 #if defined(COMPILER2) || INCLUDE_JVMCI 4689 DerivedPointerTable::update_pointers(); 4690 #endif 4691 } 4692 4693 void G1CollectedHeap::record_obj_copy_mem_stats() { 4694 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4695 4696 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4697 create_g1_evac_summary(&_old_evac_stats)); 4698 } 4699 4700 void G1CollectedHeap::free_region(HeapRegion* hr, 4701 FreeRegionList* free_list, 4702 bool par, 4703 bool locked) { 4704 assert(!hr->is_free(), "the region should not be free"); 4705 assert(!hr->is_empty(), "the region should not be empty"); 4706 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4707 assert(free_list != NULL, "pre-condition"); 4708 4709 if (G1VerifyBitmaps) { 4710 MemRegion mr(hr->bottom(), hr->end()); 4711 concurrent_mark()->clearRangePrevBitmap(mr); 4712 } 4713 4714 // Clear the card counts for this region. 4715 // Note: we only need to do this if the region is not young 4716 // (since we don't refine cards in young regions). 4717 if (!hr->is_young()) { 4718 _cg1r->hot_card_cache()->reset_card_counts(hr); 4719 } 4720 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 4721 free_list->add_ordered(hr); 4722 } 4723 4724 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4725 FreeRegionList* free_list, 4726 bool par) { 4727 assert(hr->is_humongous(), "this is only for humongous regions"); 4728 assert(free_list != NULL, "pre-condition"); 4729 hr->clear_humongous(); 4730 free_region(hr, free_list, par); 4731 } 4732 4733 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4734 const uint humongous_regions_removed) { 4735 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4736 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4737 _old_set.bulk_remove(old_regions_removed); 4738 _humongous_set.bulk_remove(humongous_regions_removed); 4739 } 4740 4741 } 4742 4743 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4744 assert(list != NULL, "list can't be null"); 4745 if (!list->is_empty()) { 4746 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4747 _hrm.insert_list_into_free_list(list); 4748 } 4749 } 4750 4751 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4752 decrease_used(bytes); 4753 } 4754 4755 class G1ParCleanupCTTask : public AbstractGangTask { 4756 G1SATBCardTableModRefBS* _ct_bs; 4757 G1CollectedHeap* _g1h; 4758 HeapRegion* volatile _su_head; 4759 public: 4760 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 4761 G1CollectedHeap* g1h) : 4762 AbstractGangTask("G1 Par Cleanup CT Task"), 4763 _ct_bs(ct_bs), _g1h(g1h) { } 4764 4765 void work(uint worker_id) { 4766 HeapRegion* r; 4767 while (r = _g1h->pop_dirty_cards_region()) { 4768 clear_cards(r); 4769 } 4770 } 4771 4772 void clear_cards(HeapRegion* r) { 4773 // Cards of the survivors should have already been dirtied. 4774 if (!r->is_survivor()) { 4775 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 4776 } 4777 } 4778 }; 4779 4780 class G1ParScrubRemSetTask: public AbstractGangTask { 4781 protected: 4782 G1RemSet* _g1rs; 4783 HeapRegionClaimer _hrclaimer; 4784 4785 public: 4786 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) : 4787 AbstractGangTask("G1 ScrubRS"), 4788 _g1rs(g1_rs), 4789 _hrclaimer(num_workers) { 4790 } 4791 4792 void work(uint worker_id) { 4793 _g1rs->scrub(worker_id, &_hrclaimer); 4794 } 4795 }; 4796 4797 void G1CollectedHeap::scrub_rem_set() { 4798 uint num_workers = workers()->active_workers(); 4799 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers); 4800 workers()->run_task(&g1_par_scrub_rs_task); 4801 } 4802 4803 void G1CollectedHeap::cleanUpCardTable() { 4804 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 4805 double start = os::elapsedTime(); 4806 4807 { 4808 // Iterate over the dirty cards region list. 4809 G1ParCleanupCTTask cleanup_task(ct_bs, this); 4810 4811 workers()->run_task(&cleanup_task); 4812 #ifndef PRODUCT 4813 // Need to synchronize with concurrent cleanup since it needs to 4814 // finish its card table clearing before we can verify. 4815 wait_while_free_regions_coming(); 4816 _verifier->verify_card_table_cleanup(); 4817 #endif 4818 } 4819 4820 double elapsed = os::elapsedTime() - start; 4821 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 4822 } 4823 4824 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4825 size_t pre_used = 0; 4826 FreeRegionList local_free_list("Local List for CSet Freeing"); 4827 4828 double young_time_ms = 0.0; 4829 double non_young_time_ms = 0.0; 4830 4831 // Since the collection set is a superset of the the young list, 4832 // all we need to do to clear the young list is clear its 4833 // head and length, and unlink any young regions in the code below 4834 _young_list->clear(); 4835 4836 G1Policy* policy = g1_policy(); 4837 4838 double start_sec = os::elapsedTime(); 4839 bool non_young = true; 4840 4841 HeapRegion* cur = cs_head; 4842 int age_bound = -1; 4843 size_t rs_lengths = 0; 4844 4845 while (cur != NULL) { 4846 assert(!is_on_master_free_list(cur), "sanity"); 4847 if (non_young) { 4848 if (cur->is_young()) { 4849 double end_sec = os::elapsedTime(); 4850 double elapsed_ms = (end_sec - start_sec) * 1000.0; 4851 non_young_time_ms += elapsed_ms; 4852 4853 start_sec = os::elapsedTime(); 4854 non_young = false; 4855 } 4856 } else { 4857 if (!cur->is_young()) { 4858 double end_sec = os::elapsedTime(); 4859 double elapsed_ms = (end_sec - start_sec) * 1000.0; 4860 young_time_ms += elapsed_ms; 4861 4862 start_sec = os::elapsedTime(); 4863 non_young = true; 4864 } 4865 } 4866 4867 rs_lengths += cur->rem_set()->occupied_locked(); 4868 4869 HeapRegion* next = cur->next_in_collection_set(); 4870 assert(cur->in_collection_set(), "bad CS"); 4871 cur->set_next_in_collection_set(NULL); 4872 clear_in_cset(cur); 4873 4874 if (cur->is_young()) { 4875 int index = cur->young_index_in_cset(); 4876 assert(index != -1, "invariant"); 4877 assert((uint) index < collection_set()->young_region_length(), "invariant"); 4878 size_t words_survived = surviving_young_words[index]; 4879 cur->record_surv_words_in_group(words_survived); 4880 4881 // At this point the we have 'popped' cur from the collection set 4882 // (linked via next_in_collection_set()) but it is still in the 4883 // young list (linked via next_young_region()). Clear the 4884 // _next_young_region field. 4885 cur->set_next_young_region(NULL); 4886 } else { 4887 int index = cur->young_index_in_cset(); 4888 assert(index == -1, "invariant"); 4889 } 4890 4891 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 4892 (!cur->is_young() && cur->young_index_in_cset() == -1), 4893 "invariant" ); 4894 4895 if (!cur->evacuation_failed()) { 4896 MemRegion used_mr = cur->used_region(); 4897 4898 // And the region is empty. 4899 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 4900 pre_used += cur->used(); 4901 free_region(cur, &local_free_list, false /* par */, true /* locked */); 4902 } else { 4903 cur->uninstall_surv_rate_group(); 4904 if (cur->is_young()) { 4905 cur->set_young_index_in_cset(-1); 4906 } 4907 cur->set_evacuation_failed(false); 4908 // When moving a young gen region to old gen, we "allocate" that whole region 4909 // there. This is in addition to any already evacuated objects. Notify the 4910 // policy about that. 4911 // Old gen regions do not cause an additional allocation: both the objects 4912 // still in the region and the ones already moved are accounted for elsewhere. 4913 if (cur->is_young()) { 4914 policy->add_bytes_allocated_in_old_since_last_gc(HeapRegion::GrainBytes); 4915 } 4916 // The region is now considered to be old. 4917 cur->set_old(); 4918 // Do some allocation statistics accounting. Regions that failed evacuation 4919 // are always made old, so there is no need to update anything in the young 4920 // gen statistics, but we need to update old gen statistics. 4921 size_t used_words = cur->marked_bytes() / HeapWordSize; 4922 _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words); 4923 _old_set.add(cur); 4924 evacuation_info.increment_collectionset_used_after(cur->used()); 4925 } 4926 cur = next; 4927 } 4928 4929 evacuation_info.set_regions_freed(local_free_list.length()); 4930 policy->record_max_rs_lengths(rs_lengths); 4931 policy->cset_regions_freed(); 4932 4933 double end_sec = os::elapsedTime(); 4934 double elapsed_ms = (end_sec - start_sec) * 1000.0; 4935 4936 if (non_young) { 4937 non_young_time_ms += elapsed_ms; 4938 } else { 4939 young_time_ms += elapsed_ms; 4940 } 4941 4942 prepend_to_freelist(&local_free_list); 4943 decrement_summary_bytes(pre_used); 4944 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 4945 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 4946 } 4947 4948 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4949 private: 4950 FreeRegionList* _free_region_list; 4951 HeapRegionSet* _proxy_set; 4952 uint _humongous_regions_removed; 4953 size_t _freed_bytes; 4954 public: 4955 4956 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4957 _free_region_list(free_region_list), _humongous_regions_removed(0), _freed_bytes(0) { 4958 } 4959 4960 virtual bool doHeapRegion(HeapRegion* r) { 4961 if (!r->is_starts_humongous()) { 4962 return false; 4963 } 4964 4965 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4966 4967 oop obj = (oop)r->bottom(); 4968 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 4969 4970 // The following checks whether the humongous object is live are sufficient. 4971 // The main additional check (in addition to having a reference from the roots 4972 // or the young gen) is whether the humongous object has a remembered set entry. 4973 // 4974 // A humongous object cannot be live if there is no remembered set for it 4975 // because: 4976 // - there can be no references from within humongous starts regions referencing 4977 // the object because we never allocate other objects into them. 4978 // (I.e. there are no intra-region references that may be missed by the 4979 // remembered set) 4980 // - as soon there is a remembered set entry to the humongous starts region 4981 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4982 // until the end of a concurrent mark. 4983 // 4984 // It is not required to check whether the object has been found dead by marking 4985 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4986 // all objects allocated during that time are considered live. 4987 // SATB marking is even more conservative than the remembered set. 4988 // So if at this point in the collection there is no remembered set entry, 4989 // nobody has a reference to it. 4990 // At the start of collection we flush all refinement logs, and remembered sets 4991 // are completely up-to-date wrt to references to the humongous object. 4992 // 4993 // Other implementation considerations: 4994 // - never consider object arrays at this time because they would pose 4995 // considerable effort for cleaning up the the remembered sets. This is 4996 // required because stale remembered sets might reference locations that 4997 // are currently allocated into. 4998 uint region_idx = r->hrm_index(); 4999 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 5000 !r->rem_set()->is_empty()) { 5001 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", 5002 region_idx, 5003 (size_t)obj->size() * HeapWordSize, 5004 p2i(r->bottom()), 5005 r->rem_set()->occupied(), 5006 r->rem_set()->strong_code_roots_list_length(), 5007 next_bitmap->isMarked(r->bottom()), 5008 g1h->is_humongous_reclaim_candidate(region_idx), 5009 obj->is_typeArray() 5010 ); 5011 return false; 5012 } 5013 5014 guarantee(obj->is_typeArray(), 5015 "Only eagerly reclaiming type arrays is supported, but the object " 5016 PTR_FORMAT " is not.", p2i(r->bottom())); 5017 5018 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", 5019 region_idx, 5020 (size_t)obj->size() * HeapWordSize, 5021 p2i(r->bottom()), 5022 r->rem_set()->occupied(), 5023 r->rem_set()->strong_code_roots_list_length(), 5024 next_bitmap->isMarked(r->bottom()), 5025 g1h->is_humongous_reclaim_candidate(region_idx), 5026 obj->is_typeArray() 5027 ); 5028 5029 // Need to clear mark bit of the humongous object if already set. 5030 if (next_bitmap->isMarked(r->bottom())) { 5031 next_bitmap->clear(r->bottom()); 5032 } 5033 do { 5034 HeapRegion* next = g1h->next_region_in_humongous(r); 5035 _freed_bytes += r->used(); 5036 r->set_containing_set(NULL); 5037 _humongous_regions_removed++; 5038 g1h->free_humongous_region(r, _free_region_list, false); 5039 r = next; 5040 } while (r != NULL); 5041 5042 return false; 5043 } 5044 5045 uint humongous_free_count() { 5046 return _humongous_regions_removed; 5047 } 5048 5049 size_t bytes_freed() const { 5050 return _freed_bytes; 5051 } 5052 }; 5053 5054 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 5055 assert_at_safepoint(true); 5056 5057 if (!G1EagerReclaimHumongousObjects || 5058 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 5059 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5060 return; 5061 } 5062 5063 double start_time = os::elapsedTime(); 5064 5065 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5066 5067 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5068 heap_region_iterate(&cl); 5069 5070 remove_from_old_sets(0, cl.humongous_free_count()); 5071 5072 G1HRPrinter* hrp = hr_printer(); 5073 if (hrp->is_active()) { 5074 FreeRegionListIterator iter(&local_cleanup_list); 5075 while (iter.more_available()) { 5076 HeapRegion* hr = iter.get_next(); 5077 hrp->cleanup(hr); 5078 } 5079 } 5080 5081 prepend_to_freelist(&local_cleanup_list); 5082 decrement_summary_bytes(cl.bytes_freed()); 5083 5084 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5085 cl.humongous_free_count()); 5086 } 5087 5088 // This routine is similar to the above but does not record 5089 // any policy statistics or update free lists; we are abandoning 5090 // the current incremental collection set in preparation of a 5091 // full collection. After the full GC we will start to build up 5092 // the incremental collection set again. 5093 // This is only called when we're doing a full collection 5094 // and is immediately followed by the tearing down of the young list. 5095 5096 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 5097 HeapRegion* cur = cs_head; 5098 5099 while (cur != NULL) { 5100 HeapRegion* next = cur->next_in_collection_set(); 5101 assert(cur->in_collection_set(), "bad CS"); 5102 cur->set_next_in_collection_set(NULL); 5103 clear_in_cset(cur); 5104 cur->set_young_index_in_cset(-1); 5105 cur = next; 5106 } 5107 } 5108 5109 void G1CollectedHeap::set_free_regions_coming() { 5110 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 5111 5112 assert(!free_regions_coming(), "pre-condition"); 5113 _free_regions_coming = true; 5114 } 5115 5116 void G1CollectedHeap::reset_free_regions_coming() { 5117 assert(free_regions_coming(), "pre-condition"); 5118 5119 { 5120 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5121 _free_regions_coming = false; 5122 SecondaryFreeList_lock->notify_all(); 5123 } 5124 5125 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 5126 } 5127 5128 void G1CollectedHeap::wait_while_free_regions_coming() { 5129 // Most of the time we won't have to wait, so let's do a quick test 5130 // first before we take the lock. 5131 if (!free_regions_coming()) { 5132 return; 5133 } 5134 5135 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 5136 5137 { 5138 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5139 while (free_regions_coming()) { 5140 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5141 } 5142 } 5143 5144 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 5145 } 5146 5147 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5148 return _allocator->is_retained_old_region(hr); 5149 } 5150 5151 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5152 _young_list->push_region(hr); 5153 } 5154 5155 class NoYoungRegionsClosure: public HeapRegionClosure { 5156 private: 5157 bool _success; 5158 public: 5159 NoYoungRegionsClosure() : _success(true) { } 5160 bool doHeapRegion(HeapRegion* r) { 5161 if (r->is_young()) { 5162 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5163 p2i(r->bottom()), p2i(r->end())); 5164 _success = false; 5165 } 5166 return false; 5167 } 5168 bool success() { return _success; } 5169 }; 5170 5171 bool G1CollectedHeap::check_young_list_empty(bool check_heap) { 5172 bool ret = _young_list->check_list_empty(); 5173 5174 if (check_heap) { 5175 NoYoungRegionsClosure closure; 5176 heap_region_iterate(&closure); 5177 ret = ret && closure.success(); 5178 } 5179 5180 return ret; 5181 } 5182 5183 class TearDownRegionSetsClosure : public HeapRegionClosure { 5184 private: 5185 HeapRegionSet *_old_set; 5186 5187 public: 5188 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5189 5190 bool doHeapRegion(HeapRegion* r) { 5191 if (r->is_old()) { 5192 _old_set->remove(r); 5193 } else { 5194 // We ignore free regions, we'll empty the free list afterwards. 5195 // We ignore young regions, we'll empty the young list afterwards. 5196 // We ignore humongous regions, we're not tearing down the 5197 // humongous regions set. 5198 assert(r->is_free() || r->is_young() || r->is_humongous(), 5199 "it cannot be another type"); 5200 } 5201 return false; 5202 } 5203 5204 ~TearDownRegionSetsClosure() { 5205 assert(_old_set->is_empty(), "post-condition"); 5206 } 5207 }; 5208 5209 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5210 assert_at_safepoint(true /* should_be_vm_thread */); 5211 5212 if (!free_list_only) { 5213 TearDownRegionSetsClosure cl(&_old_set); 5214 heap_region_iterate(&cl); 5215 5216 // Note that emptying the _young_list is postponed and instead done as 5217 // the first step when rebuilding the regions sets again. The reason for 5218 // this is that during a full GC string deduplication needs to know if 5219 // a collected region was young or old when the full GC was initiated. 5220 } 5221 _hrm.remove_all_free_regions(); 5222 } 5223 5224 void G1CollectedHeap::increase_used(size_t bytes) { 5225 _summary_bytes_used += bytes; 5226 } 5227 5228 void G1CollectedHeap::decrease_used(size_t bytes) { 5229 assert(_summary_bytes_used >= bytes, 5230 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5231 _summary_bytes_used, bytes); 5232 _summary_bytes_used -= bytes; 5233 } 5234 5235 void G1CollectedHeap::set_used(size_t bytes) { 5236 _summary_bytes_used = bytes; 5237 } 5238 5239 class RebuildRegionSetsClosure : public HeapRegionClosure { 5240 private: 5241 bool _free_list_only; 5242 HeapRegionSet* _old_set; 5243 HeapRegionManager* _hrm; 5244 size_t _total_used; 5245 5246 public: 5247 RebuildRegionSetsClosure(bool free_list_only, 5248 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5249 _free_list_only(free_list_only), 5250 _old_set(old_set), _hrm(hrm), _total_used(0) { 5251 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5252 if (!free_list_only) { 5253 assert(_old_set->is_empty(), "pre-condition"); 5254 } 5255 } 5256 5257 bool doHeapRegion(HeapRegion* r) { 5258 if (r->is_empty()) { 5259 // Add free regions to the free list 5260 r->set_free(); 5261 r->set_allocation_context(AllocationContext::system()); 5262 _hrm->insert_into_free_list(r); 5263 } else if (!_free_list_only) { 5264 assert(!r->is_young(), "we should not come across young regions"); 5265 5266 if (r->is_humongous()) { 5267 // We ignore humongous regions. We left the humongous set unchanged. 5268 } else { 5269 // Objects that were compacted would have ended up on regions 5270 // that were previously old or free. Archive regions (which are 5271 // old) will not have been touched. 5272 assert(r->is_free() || r->is_old(), "invariant"); 5273 // We now consider them old, so register as such. Leave 5274 // archive regions set that way, however, while still adding 5275 // them to the old set. 5276 if (!r->is_archive()) { 5277 r->set_old(); 5278 } 5279 _old_set->add(r); 5280 } 5281 _total_used += r->used(); 5282 } 5283 5284 return false; 5285 } 5286 5287 size_t total_used() { 5288 return _total_used; 5289 } 5290 }; 5291 5292 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5293 assert_at_safepoint(true /* should_be_vm_thread */); 5294 5295 if (!free_list_only) { 5296 _young_list->empty_list(); 5297 } 5298 5299 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5300 heap_region_iterate(&cl); 5301 5302 if (!free_list_only) { 5303 set_used(cl.total_used()); 5304 if (_archive_allocator != NULL) { 5305 _archive_allocator->clear_used(); 5306 } 5307 } 5308 assert(used_unlocked() == recalculate_used(), 5309 "inconsistent used_unlocked(), " 5310 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5311 used_unlocked(), recalculate_used()); 5312 } 5313 5314 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 5315 _refine_cte_cl->set_concurrent(concurrent); 5316 } 5317 5318 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5319 HeapRegion* hr = heap_region_containing(p); 5320 return hr->is_in(p); 5321 } 5322 5323 // Methods for the mutator alloc region 5324 5325 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5326 bool force) { 5327 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5328 assert(!force || g1_policy()->can_expand_young_list(), 5329 "if force is true we should be able to expand the young list"); 5330 bool young_list_full = g1_policy()->is_young_list_full(); 5331 if (force || !young_list_full) { 5332 HeapRegion* new_alloc_region = new_region(word_size, 5333 false /* is_old */, 5334 false /* do_expand */); 5335 if (new_alloc_region != NULL) { 5336 set_region_short_lived_locked(new_alloc_region); 5337 _hr_printer.alloc(new_alloc_region, young_list_full); 5338 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5339 return new_alloc_region; 5340 } 5341 } 5342 return NULL; 5343 } 5344 5345 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5346 size_t allocated_bytes) { 5347 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5348 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5349 5350 collection_set()->add_eden_region(alloc_region); 5351 increase_used(allocated_bytes); 5352 _hr_printer.retire(alloc_region); 5353 // We update the eden sizes here, when the region is retired, 5354 // instead of when it's allocated, since this is the point that its 5355 // used space has been recored in _summary_bytes_used. 5356 g1mm()->update_eden_size(); 5357 } 5358 5359 // Methods for the GC alloc regions 5360 5361 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 5362 if (dest.is_old()) { 5363 return true; 5364 } else { 5365 return young_list()->survivor_length() < g1_policy()->max_survivor_regions(); 5366 } 5367 } 5368 5369 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 5370 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5371 5372 if (!has_more_regions(dest)) { 5373 return NULL; 5374 } 5375 5376 const bool is_survivor = dest.is_young(); 5377 5378 HeapRegion* new_alloc_region = new_region(word_size, 5379 !is_survivor, 5380 true /* do_expand */); 5381 if (new_alloc_region != NULL) { 5382 // We really only need to do this for old regions given that we 5383 // should never scan survivors. But it doesn't hurt to do it 5384 // for survivors too. 5385 new_alloc_region->record_timestamp(); 5386 if (is_survivor) { 5387 new_alloc_region->set_survivor(); 5388 young_list()->add_survivor_region(new_alloc_region); 5389 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5390 } else { 5391 new_alloc_region->set_old(); 5392 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5393 } 5394 _hr_printer.alloc(new_alloc_region); 5395 bool during_im = collector_state()->during_initial_mark_pause(); 5396 new_alloc_region->note_start_of_copying(during_im); 5397 return new_alloc_region; 5398 } 5399 return NULL; 5400 } 5401 5402 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5403 size_t allocated_bytes, 5404 InCSetState dest) { 5405 bool during_im = collector_state()->during_initial_mark_pause(); 5406 alloc_region->note_end_of_copying(during_im); 5407 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5408 if (dest.is_old()) { 5409 _old_set.add(alloc_region); 5410 } 5411 _hr_printer.retire(alloc_region); 5412 } 5413 5414 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5415 bool expanded = false; 5416 uint index = _hrm.find_highest_free(&expanded); 5417 5418 if (index != G1_NO_HRM_INDEX) { 5419 if (expanded) { 5420 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5421 HeapRegion::GrainWords * HeapWordSize); 5422 } 5423 _hrm.allocate_free_regions_starting_at(index, 1); 5424 return region_at(index); 5425 } 5426 return NULL; 5427 } 5428 5429 // Optimized nmethod scanning 5430 5431 class RegisterNMethodOopClosure: public OopClosure { 5432 G1CollectedHeap* _g1h; 5433 nmethod* _nm; 5434 5435 template <class T> void do_oop_work(T* p) { 5436 T heap_oop = oopDesc::load_heap_oop(p); 5437 if (!oopDesc::is_null(heap_oop)) { 5438 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5439 HeapRegion* hr = _g1h->heap_region_containing(obj); 5440 assert(!hr->is_continues_humongous(), 5441 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5442 " starting at " HR_FORMAT, 5443 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5444 5445 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5446 hr->add_strong_code_root_locked(_nm); 5447 } 5448 } 5449 5450 public: 5451 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5452 _g1h(g1h), _nm(nm) {} 5453 5454 void do_oop(oop* p) { do_oop_work(p); } 5455 void do_oop(narrowOop* p) { do_oop_work(p); } 5456 }; 5457 5458 class UnregisterNMethodOopClosure: public OopClosure { 5459 G1CollectedHeap* _g1h; 5460 nmethod* _nm; 5461 5462 template <class T> void do_oop_work(T* p) { 5463 T heap_oop = oopDesc::load_heap_oop(p); 5464 if (!oopDesc::is_null(heap_oop)) { 5465 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5466 HeapRegion* hr = _g1h->heap_region_containing(obj); 5467 assert(!hr->is_continues_humongous(), 5468 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5469 " starting at " HR_FORMAT, 5470 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5471 5472 hr->remove_strong_code_root(_nm); 5473 } 5474 } 5475 5476 public: 5477 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5478 _g1h(g1h), _nm(nm) {} 5479 5480 void do_oop(oop* p) { do_oop_work(p); } 5481 void do_oop(narrowOop* p) { do_oop_work(p); } 5482 }; 5483 5484 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5485 CollectedHeap::register_nmethod(nm); 5486 5487 guarantee(nm != NULL, "sanity"); 5488 RegisterNMethodOopClosure reg_cl(this, nm); 5489 nm->oops_do(®_cl); 5490 } 5491 5492 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5493 CollectedHeap::unregister_nmethod(nm); 5494 5495 guarantee(nm != NULL, "sanity"); 5496 UnregisterNMethodOopClosure reg_cl(this, nm); 5497 nm->oops_do(®_cl, true); 5498 } 5499 5500 void G1CollectedHeap::purge_code_root_memory() { 5501 double purge_start = os::elapsedTime(); 5502 G1CodeRootSet::purge(); 5503 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5504 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5505 } 5506 5507 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5508 G1CollectedHeap* _g1h; 5509 5510 public: 5511 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5512 _g1h(g1h) {} 5513 5514 void do_code_blob(CodeBlob* cb) { 5515 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5516 if (nm == NULL) { 5517 return; 5518 } 5519 5520 if (ScavengeRootsInCode) { 5521 _g1h->register_nmethod(nm); 5522 } 5523 } 5524 }; 5525 5526 void G1CollectedHeap::rebuild_strong_code_roots() { 5527 RebuildStrongCodeRootClosure blob_cl(this); 5528 CodeCache::blobs_do(&blob_cl); 5529 }