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/g1HeapTransition.hpp" 43 #include "gc/g1/g1HeapVerifier.hpp" 44 #include "gc/g1/g1MarkSweep.hpp" 45 #include "gc/g1/g1OopClosures.inline.hpp" 46 #include "gc/g1/g1ParScanThreadState.inline.hpp" 47 #include "gc/g1/g1RegionToSpaceMapper.hpp" 48 #include "gc/g1/g1RemSet.inline.hpp" 49 #include "gc/g1/g1RootClosures.hpp" 50 #include "gc/g1/g1RootProcessor.hpp" 51 #include "gc/g1/g1StringDedup.hpp" 52 #include "gc/g1/g1YCTypes.hpp" 53 #include "gc/g1/heapRegion.inline.hpp" 54 #include "gc/g1/heapRegionRemSet.hpp" 55 #include "gc/g1/heapRegionSet.inline.hpp" 56 #include "gc/g1/suspendibleThreadSet.hpp" 57 #include "gc/g1/vm_operations_g1.hpp" 58 #include "gc/shared/gcHeapSummary.hpp" 59 #include "gc/shared/gcId.hpp" 60 #include "gc/shared/gcLocker.inline.hpp" 61 #include "gc/shared/gcTimer.hpp" 62 #include "gc/shared/gcTrace.hpp" 63 #include "gc/shared/gcTraceTime.inline.hpp" 64 #include "gc/shared/generationSpec.hpp" 65 #include "gc/shared/isGCActiveMark.hpp" 66 #include "gc/shared/referenceProcessor.inline.hpp" 67 #include "gc/shared/taskqueue.inline.hpp" 68 #include "logging/log.hpp" 69 #include "memory/allocation.hpp" 70 #include "memory/iterator.hpp" 71 #include "oops/oop.inline.hpp" 72 #include "runtime/atomic.inline.hpp" 73 #include "runtime/init.hpp" 74 #include "runtime/orderAccess.inline.hpp" 75 #include "runtime/vmThread.hpp" 76 #include "utilities/globalDefinitions.hpp" 77 #include "utilities/stack.inline.hpp" 78 79 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 80 81 // INVARIANTS/NOTES 82 // 83 // All allocation activity covered by the G1CollectedHeap interface is 84 // serialized by acquiring the HeapLock. This happens in mem_allocate 85 // and allocate_new_tlab, which are the "entry" points to the 86 // allocation code from the rest of the JVM. (Note that this does not 87 // apply to TLAB allocation, which is not part of this interface: it 88 // is done by clients of this interface.) 89 90 // Local to this file. 91 92 class RefineCardTableEntryClosure: public CardTableEntryClosure { 93 bool _concurrent; 94 public: 95 RefineCardTableEntryClosure() : _concurrent(true) { } 96 97 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 98 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false); 99 // This path is executed by the concurrent refine or mutator threads, 100 // concurrently, and so we do not care if card_ptr contains references 101 // that point into the collection set. 102 assert(!oops_into_cset, "should be"); 103 104 if (_concurrent && SuspendibleThreadSet::should_yield()) { 105 // Caller will actually yield. 106 return false; 107 } 108 // Otherwise, we finished successfully; return true. 109 return true; 110 } 111 112 void set_concurrent(bool b) { _concurrent = b; } 113 }; 114 115 116 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 117 private: 118 size_t _num_dirtied; 119 G1CollectedHeap* _g1h; 120 G1SATBCardTableLoggingModRefBS* _g1_bs; 121 122 HeapRegion* region_for_card(jbyte* card_ptr) const { 123 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 124 } 125 126 bool will_become_free(HeapRegion* hr) const { 127 // A region will be freed by free_collection_set if the region is in the 128 // collection set and has not had an evacuation failure. 129 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 130 } 131 132 public: 133 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 134 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 135 136 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 137 HeapRegion* hr = region_for_card(card_ptr); 138 139 // Should only dirty cards in regions that won't be freed. 140 if (!will_become_free(hr)) { 141 *card_ptr = CardTableModRefBS::dirty_card_val(); 142 _num_dirtied++; 143 } 144 145 return true; 146 } 147 148 size_t num_dirtied() const { return _num_dirtied; } 149 }; 150 151 152 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 153 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 154 } 155 156 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 157 // The from card cache is not the memory that is actually committed. So we cannot 158 // take advantage of the zero_filled parameter. 159 reset_from_card_cache(start_idx, num_regions); 160 } 161 162 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 163 { 164 // Claim the right to put the region on the dirty cards region list 165 // by installing a self pointer. 166 HeapRegion* next = hr->get_next_dirty_cards_region(); 167 if (next == NULL) { 168 HeapRegion* res = (HeapRegion*) 169 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 170 NULL); 171 if (res == NULL) { 172 HeapRegion* head; 173 do { 174 // Put the region to the dirty cards region list. 175 head = _dirty_cards_region_list; 176 next = (HeapRegion*) 177 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 178 if (next == head) { 179 assert(hr->get_next_dirty_cards_region() == hr, 180 "hr->get_next_dirty_cards_region() != hr"); 181 if (next == NULL) { 182 // The last region in the list points to itself. 183 hr->set_next_dirty_cards_region(hr); 184 } else { 185 hr->set_next_dirty_cards_region(next); 186 } 187 } 188 } while (next != head); 189 } 190 } 191 } 192 193 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 194 { 195 HeapRegion* head; 196 HeapRegion* hr; 197 do { 198 head = _dirty_cards_region_list; 199 if (head == NULL) { 200 return NULL; 201 } 202 HeapRegion* new_head = head->get_next_dirty_cards_region(); 203 if (head == new_head) { 204 // The last region. 205 new_head = NULL; 206 } 207 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 208 head); 209 } while (hr != head); 210 assert(hr != NULL, "invariant"); 211 hr->set_next_dirty_cards_region(NULL); 212 return hr; 213 } 214 215 // Returns true if the reference points to an object that 216 // can move in an incremental collection. 217 bool G1CollectedHeap::is_scavengable(const void* p) { 218 HeapRegion* hr = heap_region_containing(p); 219 return !hr->is_pinned(); 220 } 221 222 // Private methods. 223 224 HeapRegion* 225 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 226 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 227 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 228 if (!_secondary_free_list.is_empty()) { 229 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 230 "secondary_free_list has %u entries", 231 _secondary_free_list.length()); 232 // It looks as if there are free regions available on the 233 // secondary_free_list. Let's move them to the free_list and try 234 // again to allocate from it. 235 append_secondary_free_list(); 236 237 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 238 "empty we should have moved at least one entry to the free_list"); 239 HeapRegion* res = _hrm.allocate_free_region(is_old); 240 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 241 "allocated " HR_FORMAT " from secondary_free_list", 242 HR_FORMAT_PARAMS(res)); 243 return res; 244 } 245 246 // Wait here until we get notified either when (a) there are no 247 // more free regions coming or (b) some regions have been moved on 248 // the secondary_free_list. 249 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 250 } 251 252 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 253 "could not allocate from secondary_free_list"); 254 return NULL; 255 } 256 257 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 258 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 259 "the only time we use this to allocate a humongous region is " 260 "when we are allocating a single humongous region"); 261 262 HeapRegion* res; 263 if (G1StressConcRegionFreeing) { 264 if (!_secondary_free_list.is_empty()) { 265 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 266 "forced to look at the secondary_free_list"); 267 res = new_region_try_secondary_free_list(is_old); 268 if (res != NULL) { 269 return res; 270 } 271 } 272 } 273 274 res = _hrm.allocate_free_region(is_old); 275 276 if (res == NULL) { 277 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 278 "res == NULL, trying the secondary_free_list"); 279 res = new_region_try_secondary_free_list(is_old); 280 } 281 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 282 // Currently, only attempts to allocate GC alloc regions set 283 // do_expand to true. So, we should only reach here during a 284 // safepoint. If this assumption changes we might have to 285 // reconsider the use of _expand_heap_after_alloc_failure. 286 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 287 288 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 289 word_size * HeapWordSize); 290 291 if (expand(word_size * HeapWordSize)) { 292 // Given that expand() succeeded in expanding the heap, and we 293 // always expand the heap by an amount aligned to the heap 294 // region size, the free list should in theory not be empty. 295 // In either case allocate_free_region() will check for NULL. 296 res = _hrm.allocate_free_region(is_old); 297 } else { 298 _expand_heap_after_alloc_failure = false; 299 } 300 } 301 return res; 302 } 303 304 HeapWord* 305 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 306 uint num_regions, 307 size_t word_size, 308 AllocationContext_t context) { 309 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 310 assert(is_humongous(word_size), "word_size should be humongous"); 311 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 312 313 // Index of last region in the series. 314 uint last = first + num_regions - 1; 315 316 // We need to initialize the region(s) we just discovered. This is 317 // a bit tricky given that it can happen concurrently with 318 // refinement threads refining cards on these regions and 319 // potentially wanting to refine the BOT as they are scanning 320 // those cards (this can happen shortly after a cleanup; see CR 321 // 6991377). So we have to set up the region(s) carefully and in 322 // a specific order. 323 324 // The word size sum of all the regions we will allocate. 325 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 326 assert(word_size <= word_size_sum, "sanity"); 327 328 // This will be the "starts humongous" region. 329 HeapRegion* first_hr = region_at(first); 330 // The header of the new object will be placed at the bottom of 331 // the first region. 332 HeapWord* new_obj = first_hr->bottom(); 333 // This will be the new top of the new object. 334 HeapWord* obj_top = new_obj + word_size; 335 336 // First, we need to zero the header of the space that we will be 337 // allocating. When we update top further down, some refinement 338 // threads might try to scan the region. By zeroing the header we 339 // ensure that any thread that will try to scan the region will 340 // come across the zero klass word and bail out. 341 // 342 // NOTE: It would not have been correct to have used 343 // CollectedHeap::fill_with_object() and make the space look like 344 // an int array. The thread that is doing the allocation will 345 // later update the object header to a potentially different array 346 // type and, for a very short period of time, the klass and length 347 // fields will be inconsistent. This could cause a refinement 348 // thread to calculate the object size incorrectly. 349 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 350 351 // How many words we use for filler objects. 352 size_t word_fill_size = word_size_sum - word_size; 353 354 // How many words memory we "waste" which cannot hold a filler object. 355 size_t words_not_fillable = 0; 356 357 if (word_fill_size >= min_fill_size()) { 358 fill_with_objects(obj_top, word_fill_size); 359 } else if (word_fill_size > 0) { 360 // We have space to fill, but we cannot fit an object there. 361 words_not_fillable = word_fill_size; 362 word_fill_size = 0; 363 } 364 365 // We will set up the first region as "starts humongous". This 366 // will also update the BOT covering all the regions to reflect 367 // that there is a single object that starts at the bottom of the 368 // first region. 369 first_hr->set_starts_humongous(obj_top, word_fill_size); 370 first_hr->set_allocation_context(context); 371 // Then, if there are any, we will set up the "continues 372 // humongous" regions. 373 HeapRegion* hr = NULL; 374 for (uint i = first + 1; i <= last; ++i) { 375 hr = region_at(i); 376 hr->set_continues_humongous(first_hr); 377 hr->set_allocation_context(context); 378 } 379 380 // Up to this point no concurrent thread would have been able to 381 // do any scanning on any region in this series. All the top 382 // fields still point to bottom, so the intersection between 383 // [bottom,top] and [card_start,card_end] will be empty. Before we 384 // update the top fields, we'll do a storestore to make sure that 385 // no thread sees the update to top before the zeroing of the 386 // object header and the BOT initialization. 387 OrderAccess::storestore(); 388 389 // Now, we will update the top fields of the "continues humongous" 390 // regions except the last one. 391 for (uint i = first; i < last; ++i) { 392 hr = region_at(i); 393 hr->set_top(hr->end()); 394 } 395 396 hr = region_at(last); 397 // If we cannot fit a filler object, we must set top to the end 398 // of the humongous object, otherwise we cannot iterate the heap 399 // and the BOT will not be complete. 400 hr->set_top(hr->end() - words_not_fillable); 401 402 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 403 "obj_top should be in last region"); 404 405 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 406 407 assert(words_not_fillable == 0 || 408 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 409 "Miscalculation in humongous allocation"); 410 411 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 412 413 for (uint i = first; i <= last; ++i) { 414 hr = region_at(i); 415 _humongous_set.add(hr); 416 _hr_printer.alloc(hr); 417 } 418 419 return new_obj; 420 } 421 422 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 423 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 424 return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 425 } 426 427 // If could fit into free regions w/o expansion, try. 428 // Otherwise, if can expand, do so. 429 // Otherwise, if using ex regions might help, try with ex given back. 430 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 431 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 432 433 _verifier->verify_region_sets_optional(); 434 435 uint first = G1_NO_HRM_INDEX; 436 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 437 438 if (obj_regions == 1) { 439 // Only one region to allocate, try to use a fast path by directly allocating 440 // from the free lists. Do not try to expand here, we will potentially do that 441 // later. 442 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 443 if (hr != NULL) { 444 first = hr->hrm_index(); 445 } 446 } else { 447 // We can't allocate humongous regions spanning more than one region while 448 // cleanupComplete() is running, since some of the regions we find to be 449 // empty might not yet be added to the free list. It is not straightforward 450 // to know in which list they are on so that we can remove them. We only 451 // need to do this if we need to allocate more than one region to satisfy the 452 // current humongous allocation request. If we are only allocating one region 453 // we use the one-region region allocation code (see above), that already 454 // potentially waits for regions from the secondary free list. 455 wait_while_free_regions_coming(); 456 append_secondary_free_list_if_not_empty_with_lock(); 457 458 // Policy: Try only empty regions (i.e. already committed first). Maybe we 459 // are lucky enough to find some. 460 first = _hrm.find_contiguous_only_empty(obj_regions); 461 if (first != G1_NO_HRM_INDEX) { 462 _hrm.allocate_free_regions_starting_at(first, obj_regions); 463 } 464 } 465 466 if (first == G1_NO_HRM_INDEX) { 467 // Policy: We could not find enough regions for the humongous object in the 468 // free list. Look through the heap to find a mix of free and uncommitted regions. 469 // If so, try expansion. 470 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 471 if (first != G1_NO_HRM_INDEX) { 472 // We found something. Make sure these regions are committed, i.e. expand 473 // the heap. Alternatively we could do a defragmentation GC. 474 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 475 word_size * HeapWordSize); 476 477 478 _hrm.expand_at(first, obj_regions); 479 g1_policy()->record_new_heap_size(num_regions()); 480 481 #ifdef ASSERT 482 for (uint i = first; i < first + obj_regions; ++i) { 483 HeapRegion* hr = region_at(i); 484 assert(hr->is_free(), "sanity"); 485 assert(hr->is_empty(), "sanity"); 486 assert(is_on_master_free_list(hr), "sanity"); 487 } 488 #endif 489 _hrm.allocate_free_regions_starting_at(first, obj_regions); 490 } else { 491 // Policy: Potentially trigger a defragmentation GC. 492 } 493 } 494 495 HeapWord* result = NULL; 496 if (first != G1_NO_HRM_INDEX) { 497 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 498 word_size, context); 499 assert(result != NULL, "it should always return a valid result"); 500 501 // A successful humongous object allocation changes the used space 502 // information of the old generation so we need to recalculate the 503 // sizes and update the jstat counters here. 504 g1mm()->update_sizes(); 505 } 506 507 _verifier->verify_region_sets_optional(); 508 509 return result; 510 } 511 512 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 513 assert_heap_not_locked_and_not_at_safepoint(); 514 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 515 516 uint dummy_gc_count_before; 517 uint dummy_gclocker_retry_count = 0; 518 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 519 } 520 521 HeapWord* 522 G1CollectedHeap::mem_allocate(size_t word_size, 523 bool* gc_overhead_limit_was_exceeded) { 524 assert_heap_not_locked_and_not_at_safepoint(); 525 526 // Loop until the allocation is satisfied, or unsatisfied after GC. 527 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 528 uint gc_count_before; 529 530 HeapWord* result = NULL; 531 if (!is_humongous(word_size)) { 532 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 533 } else { 534 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 535 } 536 if (result != NULL) { 537 return result; 538 } 539 540 // Create the garbage collection operation... 541 VM_G1CollectForAllocation op(gc_count_before, word_size); 542 op.set_allocation_context(AllocationContext::current()); 543 544 // ...and get the VM thread to execute it. 545 VMThread::execute(&op); 546 547 if (op.prologue_succeeded() && op.pause_succeeded()) { 548 // If the operation was successful we'll return the result even 549 // if it is NULL. If the allocation attempt failed immediately 550 // after a Full GC, it's unlikely we'll be able to allocate now. 551 HeapWord* result = op.result(); 552 if (result != NULL && !is_humongous(word_size)) { 553 // Allocations that take place on VM operations do not do any 554 // card dirtying and we have to do it here. We only have to do 555 // this for non-humongous allocations, though. 556 dirty_young_block(result, word_size); 557 } 558 return result; 559 } else { 560 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 561 return NULL; 562 } 563 assert(op.result() == NULL, 564 "the result should be NULL if the VM op did not succeed"); 565 } 566 567 // Give a warning if we seem to be looping forever. 568 if ((QueuedAllocationWarningCount > 0) && 569 (try_count % QueuedAllocationWarningCount == 0)) { 570 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 571 } 572 } 573 574 ShouldNotReachHere(); 575 return NULL; 576 } 577 578 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 579 AllocationContext_t context, 580 uint* gc_count_before_ret, 581 uint* gclocker_retry_count_ret) { 582 // Make sure you read the note in attempt_allocation_humongous(). 583 584 assert_heap_not_locked_and_not_at_safepoint(); 585 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 586 "be called for humongous allocation requests"); 587 588 // We should only get here after the first-level allocation attempt 589 // (attempt_allocation()) failed to allocate. 590 591 // We will loop until a) we manage to successfully perform the 592 // allocation or b) we successfully schedule a collection which 593 // fails to perform the allocation. b) is the only case when we'll 594 // return NULL. 595 HeapWord* result = NULL; 596 for (int try_count = 1; /* we'll return */; try_count += 1) { 597 bool should_try_gc; 598 uint gc_count_before; 599 600 { 601 MutexLockerEx x(Heap_lock); 602 result = _allocator->attempt_allocation_locked(word_size, context); 603 if (result != NULL) { 604 return result; 605 } 606 607 if (GCLocker::is_active_and_needs_gc()) { 608 if (g1_policy()->can_expand_young_list()) { 609 // No need for an ergo verbose message here, 610 // can_expand_young_list() does this when it returns true. 611 result = _allocator->attempt_allocation_force(word_size, context); 612 if (result != NULL) { 613 return result; 614 } 615 } 616 should_try_gc = false; 617 } else { 618 // The GCLocker may not be active but the GCLocker initiated 619 // GC may not yet have been performed (GCLocker::needs_gc() 620 // returns true). In this case we do not try this GC and 621 // wait until the GCLocker initiated GC is performed, and 622 // then retry the allocation. 623 if (GCLocker::needs_gc()) { 624 should_try_gc = false; 625 } else { 626 // Read the GC count while still holding the Heap_lock. 627 gc_count_before = total_collections(); 628 should_try_gc = true; 629 } 630 } 631 } 632 633 if (should_try_gc) { 634 bool succeeded; 635 result = do_collection_pause(word_size, gc_count_before, &succeeded, 636 GCCause::_g1_inc_collection_pause); 637 if (result != NULL) { 638 assert(succeeded, "only way to get back a non-NULL result"); 639 return result; 640 } 641 642 if (succeeded) { 643 // If we get here we successfully scheduled a collection which 644 // failed to allocate. No point in trying to allocate 645 // further. We'll just return NULL. 646 MutexLockerEx x(Heap_lock); 647 *gc_count_before_ret = total_collections(); 648 return NULL; 649 } 650 } else { 651 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 652 MutexLockerEx x(Heap_lock); 653 *gc_count_before_ret = total_collections(); 654 return NULL; 655 } 656 // The GCLocker is either active or the GCLocker initiated 657 // GC has not yet been performed. Stall until it is and 658 // then retry the allocation. 659 GCLocker::stall_until_clear(); 660 (*gclocker_retry_count_ret) += 1; 661 } 662 663 // We can reach here if we were unsuccessful in scheduling a 664 // collection (because another thread beat us to it) or if we were 665 // stalled due to the GC locker. In either can we should retry the 666 // allocation attempt in case another thread successfully 667 // performed a collection and reclaimed enough space. We do the 668 // first attempt (without holding the Heap_lock) here and the 669 // follow-on attempt will be at the start of the next loop 670 // iteration (after taking the Heap_lock). 671 result = _allocator->attempt_allocation(word_size, context); 672 if (result != NULL) { 673 return result; 674 } 675 676 // Give a warning if we seem to be looping forever. 677 if ((QueuedAllocationWarningCount > 0) && 678 (try_count % QueuedAllocationWarningCount == 0)) { 679 warning("G1CollectedHeap::attempt_allocation_slow() " 680 "retries %d times", try_count); 681 } 682 } 683 684 ShouldNotReachHere(); 685 return NULL; 686 } 687 688 void G1CollectedHeap::begin_archive_alloc_range() { 689 assert_at_safepoint(true /* should_be_vm_thread */); 690 if (_archive_allocator == NULL) { 691 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 692 } 693 } 694 695 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 696 // Allocations in archive regions cannot be of a size that would be considered 697 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 698 // may be different at archive-restore time. 699 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 700 } 701 702 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 703 assert_at_safepoint(true /* should_be_vm_thread */); 704 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 705 if (is_archive_alloc_too_large(word_size)) { 706 return NULL; 707 } 708 return _archive_allocator->archive_mem_allocate(word_size); 709 } 710 711 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 712 size_t end_alignment_in_bytes) { 713 assert_at_safepoint(true /* should_be_vm_thread */); 714 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 715 716 // Call complete_archive to do the real work, filling in the MemRegion 717 // array with the archive regions. 718 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 719 delete _archive_allocator; 720 _archive_allocator = NULL; 721 } 722 723 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 724 assert(ranges != NULL, "MemRegion array NULL"); 725 assert(count != 0, "No MemRegions provided"); 726 MemRegion reserved = _hrm.reserved(); 727 for (size_t i = 0; i < count; i++) { 728 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 729 return false; 730 } 731 } 732 return true; 733 } 734 735 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 736 assert(!is_init_completed(), "Expect to be called at JVM init time"); 737 assert(ranges != NULL, "MemRegion array NULL"); 738 assert(count != 0, "No MemRegions provided"); 739 MutexLockerEx x(Heap_lock); 740 741 MemRegion reserved = _hrm.reserved(); 742 HeapWord* prev_last_addr = NULL; 743 HeapRegion* prev_last_region = NULL; 744 745 // Temporarily disable pretouching of heap pages. This interface is used 746 // when mmap'ing archived heap data in, so pre-touching is wasted. 747 FlagSetting fs(AlwaysPreTouch, false); 748 749 // Enable archive object checking in G1MarkSweep. We have to let it know 750 // about each archive range, so that objects in those ranges aren't marked. 751 G1MarkSweep::enable_archive_object_check(); 752 753 // For each specified MemRegion range, allocate the corresponding G1 754 // regions and mark them as archive regions. We expect the ranges in 755 // ascending starting address order, without overlap. 756 for (size_t i = 0; i < count; i++) { 757 MemRegion curr_range = ranges[i]; 758 HeapWord* start_address = curr_range.start(); 759 size_t word_size = curr_range.word_size(); 760 HeapWord* last_address = curr_range.last(); 761 size_t commits = 0; 762 763 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 764 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 765 p2i(start_address), p2i(last_address)); 766 guarantee(start_address > prev_last_addr, 767 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 768 p2i(start_address), p2i(prev_last_addr)); 769 prev_last_addr = last_address; 770 771 // Check for ranges that start in the same G1 region in which the previous 772 // range ended, and adjust the start address so we don't try to allocate 773 // the same region again. If the current range is entirely within that 774 // region, skip it, just adjusting the recorded top. 775 HeapRegion* start_region = _hrm.addr_to_region(start_address); 776 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 777 start_address = start_region->end(); 778 if (start_address > last_address) { 779 increase_used(word_size * HeapWordSize); 780 start_region->set_top(last_address + 1); 781 continue; 782 } 783 start_region->set_top(start_address); 784 curr_range = MemRegion(start_address, last_address + 1); 785 start_region = _hrm.addr_to_region(start_address); 786 } 787 788 // Perform the actual region allocation, exiting if it fails. 789 // Then note how much new space we have allocated. 790 if (!_hrm.allocate_containing_regions(curr_range, &commits)) { 791 return false; 792 } 793 increase_used(word_size * HeapWordSize); 794 if (commits != 0) { 795 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 796 HeapRegion::GrainWords * HeapWordSize * commits); 797 798 } 799 800 // Mark each G1 region touched by the range as archive, add it to the old set, 801 // and set the allocation context and top. 802 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 803 HeapRegion* last_region = _hrm.addr_to_region(last_address); 804 prev_last_region = last_region; 805 806 while (curr_region != NULL) { 807 assert(curr_region->is_empty() && !curr_region->is_pinned(), 808 "Region already in use (index %u)", curr_region->hrm_index()); 809 curr_region->set_allocation_context(AllocationContext::system()); 810 curr_region->set_archive(); 811 _hr_printer.alloc(curr_region); 812 _old_set.add(curr_region); 813 if (curr_region != last_region) { 814 curr_region->set_top(curr_region->end()); 815 curr_region = _hrm.next_region_in_heap(curr_region); 816 } else { 817 curr_region->set_top(last_address + 1); 818 curr_region = NULL; 819 } 820 } 821 822 // Notify mark-sweep of the archive range. 823 G1MarkSweep::set_range_archive(curr_range, true); 824 } 825 return true; 826 } 827 828 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 829 assert(!is_init_completed(), "Expect to be called at JVM init time"); 830 assert(ranges != NULL, "MemRegion array NULL"); 831 assert(count != 0, "No MemRegions provided"); 832 MemRegion reserved = _hrm.reserved(); 833 HeapWord *prev_last_addr = NULL; 834 HeapRegion* prev_last_region = NULL; 835 836 // For each MemRegion, create filler objects, if needed, in the G1 regions 837 // that contain the address range. The address range actually within the 838 // MemRegion will not be modified. That is assumed to have been initialized 839 // elsewhere, probably via an mmap of archived heap data. 840 MutexLockerEx x(Heap_lock); 841 for (size_t i = 0; i < count; i++) { 842 HeapWord* start_address = ranges[i].start(); 843 HeapWord* last_address = ranges[i].last(); 844 845 assert(reserved.contains(start_address) && reserved.contains(last_address), 846 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 847 p2i(start_address), p2i(last_address)); 848 assert(start_address > prev_last_addr, 849 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 850 p2i(start_address), p2i(prev_last_addr)); 851 852 HeapRegion* start_region = _hrm.addr_to_region(start_address); 853 HeapRegion* last_region = _hrm.addr_to_region(last_address); 854 HeapWord* bottom_address = start_region->bottom(); 855 856 // Check for a range beginning in the same region in which the 857 // previous one ended. 858 if (start_region == prev_last_region) { 859 bottom_address = prev_last_addr + 1; 860 } 861 862 // Verify that the regions were all marked as archive regions by 863 // alloc_archive_regions. 864 HeapRegion* curr_region = start_region; 865 while (curr_region != NULL) { 866 guarantee(curr_region->is_archive(), 867 "Expected archive region at index %u", curr_region->hrm_index()); 868 if (curr_region != last_region) { 869 curr_region = _hrm.next_region_in_heap(curr_region); 870 } else { 871 curr_region = NULL; 872 } 873 } 874 875 prev_last_addr = last_address; 876 prev_last_region = last_region; 877 878 // Fill the memory below the allocated range with dummy object(s), 879 // if the region bottom does not match the range start, or if the previous 880 // range ended within the same G1 region, and there is a gap. 881 if (start_address != bottom_address) { 882 size_t fill_size = pointer_delta(start_address, bottom_address); 883 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 884 increase_used(fill_size * HeapWordSize); 885 } 886 } 887 } 888 889 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 890 uint* gc_count_before_ret, 891 uint* gclocker_retry_count_ret) { 892 assert_heap_not_locked_and_not_at_safepoint(); 893 assert(!is_humongous(word_size), "attempt_allocation() should not " 894 "be called for humongous allocation requests"); 895 896 AllocationContext_t context = AllocationContext::current(); 897 HeapWord* result = _allocator->attempt_allocation(word_size, context); 898 899 if (result == NULL) { 900 result = attempt_allocation_slow(word_size, 901 context, 902 gc_count_before_ret, 903 gclocker_retry_count_ret); 904 } 905 assert_heap_not_locked(); 906 if (result != NULL) { 907 dirty_young_block(result, word_size); 908 } 909 return result; 910 } 911 912 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 913 assert(!is_init_completed(), "Expect to be called at JVM init time"); 914 assert(ranges != NULL, "MemRegion array NULL"); 915 assert(count != 0, "No MemRegions provided"); 916 MemRegion reserved = _hrm.reserved(); 917 HeapWord* prev_last_addr = NULL; 918 HeapRegion* prev_last_region = NULL; 919 size_t size_used = 0; 920 size_t uncommitted_regions = 0; 921 922 // For each Memregion, free the G1 regions that constitute it, and 923 // notify mark-sweep that the range is no longer to be considered 'archive.' 924 MutexLockerEx x(Heap_lock); 925 for (size_t i = 0; i < count; i++) { 926 HeapWord* start_address = ranges[i].start(); 927 HeapWord* last_address = ranges[i].last(); 928 929 assert(reserved.contains(start_address) && reserved.contains(last_address), 930 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 931 p2i(start_address), p2i(last_address)); 932 assert(start_address > prev_last_addr, 933 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 934 p2i(start_address), p2i(prev_last_addr)); 935 size_used += ranges[i].byte_size(); 936 prev_last_addr = last_address; 937 938 HeapRegion* start_region = _hrm.addr_to_region(start_address); 939 HeapRegion* last_region = _hrm.addr_to_region(last_address); 940 941 // Check for ranges that start in the same G1 region in which the previous 942 // range ended, and adjust the start address so we don't try to free 943 // the same region again. If the current range is entirely within that 944 // region, skip it. 945 if (start_region == prev_last_region) { 946 start_address = start_region->end(); 947 if (start_address > last_address) { 948 continue; 949 } 950 start_region = _hrm.addr_to_region(start_address); 951 } 952 prev_last_region = last_region; 953 954 // After verifying that each region was marked as an archive region by 955 // alloc_archive_regions, set it free and empty and uncommit it. 956 HeapRegion* curr_region = start_region; 957 while (curr_region != NULL) { 958 guarantee(curr_region->is_archive(), 959 "Expected archive region at index %u", curr_region->hrm_index()); 960 uint curr_index = curr_region->hrm_index(); 961 _old_set.remove(curr_region); 962 curr_region->set_free(); 963 curr_region->set_top(curr_region->bottom()); 964 if (curr_region != last_region) { 965 curr_region = _hrm.next_region_in_heap(curr_region); 966 } else { 967 curr_region = NULL; 968 } 969 _hrm.shrink_at(curr_index, 1); 970 uncommitted_regions++; 971 } 972 973 // Notify mark-sweep that this is no longer an archive range. 974 G1MarkSweep::set_range_archive(ranges[i], false); 975 } 976 977 if (uncommitted_regions != 0) { 978 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 979 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 980 } 981 decrease_used(size_used); 982 } 983 984 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 985 uint* gc_count_before_ret, 986 uint* gclocker_retry_count_ret) { 987 // The structure of this method has a lot of similarities to 988 // attempt_allocation_slow(). The reason these two were not merged 989 // into a single one is that such a method would require several "if 990 // allocation is not humongous do this, otherwise do that" 991 // conditional paths which would obscure its flow. In fact, an early 992 // version of this code did use a unified method which was harder to 993 // follow and, as a result, it had subtle bugs that were hard to 994 // track down. So keeping these two methods separate allows each to 995 // be more readable. It will be good to keep these two in sync as 996 // much as possible. 997 998 assert_heap_not_locked_and_not_at_safepoint(); 999 assert(is_humongous(word_size), "attempt_allocation_humongous() " 1000 "should only be called for humongous allocations"); 1001 1002 // Humongous objects can exhaust the heap quickly, so we should check if we 1003 // need to start a marking cycle at each humongous object allocation. We do 1004 // the check before we do the actual allocation. The reason for doing it 1005 // before the allocation is that we avoid having to keep track of the newly 1006 // allocated memory while we do a GC. 1007 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 1008 word_size)) { 1009 collect(GCCause::_g1_humongous_allocation); 1010 } 1011 1012 // We will loop until a) we manage to successfully perform the 1013 // allocation or b) we successfully schedule a collection which 1014 // fails to perform the allocation. b) is the only case when we'll 1015 // return NULL. 1016 HeapWord* result = NULL; 1017 for (int try_count = 1; /* we'll return */; try_count += 1) { 1018 bool should_try_gc; 1019 uint gc_count_before; 1020 1021 { 1022 MutexLockerEx x(Heap_lock); 1023 1024 // Given that humongous objects are not allocated in young 1025 // regions, we'll first try to do the allocation without doing a 1026 // collection hoping that there's enough space in the heap. 1027 result = humongous_obj_allocate(word_size, AllocationContext::current()); 1028 if (result != NULL) { 1029 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 1030 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 1031 return result; 1032 } 1033 1034 if (GCLocker::is_active_and_needs_gc()) { 1035 should_try_gc = false; 1036 } else { 1037 // The GCLocker may not be active but the GCLocker initiated 1038 // GC may not yet have been performed (GCLocker::needs_gc() 1039 // returns true). In this case we do not try this GC and 1040 // wait until the GCLocker initiated GC is performed, and 1041 // then retry the allocation. 1042 if (GCLocker::needs_gc()) { 1043 should_try_gc = false; 1044 } else { 1045 // Read the GC count while still holding the Heap_lock. 1046 gc_count_before = total_collections(); 1047 should_try_gc = true; 1048 } 1049 } 1050 } 1051 1052 if (should_try_gc) { 1053 // If we failed to allocate the humongous object, we should try to 1054 // do a collection pause (if we're allowed) in case it reclaims 1055 // enough space for the allocation to succeed after the pause. 1056 1057 bool succeeded; 1058 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1059 GCCause::_g1_humongous_allocation); 1060 if (result != NULL) { 1061 assert(succeeded, "only way to get back a non-NULL result"); 1062 return result; 1063 } 1064 1065 if (succeeded) { 1066 // If we get here we successfully scheduled a collection which 1067 // failed to allocate. No point in trying to allocate 1068 // further. We'll just return NULL. 1069 MutexLockerEx x(Heap_lock); 1070 *gc_count_before_ret = total_collections(); 1071 return NULL; 1072 } 1073 } else { 1074 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1075 MutexLockerEx x(Heap_lock); 1076 *gc_count_before_ret = total_collections(); 1077 return NULL; 1078 } 1079 // The GCLocker is either active or the GCLocker initiated 1080 // GC has not yet been performed. Stall until it is and 1081 // then retry the allocation. 1082 GCLocker::stall_until_clear(); 1083 (*gclocker_retry_count_ret) += 1; 1084 } 1085 1086 // We can reach here if we were unsuccessful in scheduling a 1087 // collection (because another thread beat us to it) or if we were 1088 // stalled due to the GC locker. In either can we should retry the 1089 // allocation attempt in case another thread successfully 1090 // performed a collection and reclaimed enough space. Give a 1091 // warning if we seem to be looping forever. 1092 1093 if ((QueuedAllocationWarningCount > 0) && 1094 (try_count % QueuedAllocationWarningCount == 0)) { 1095 warning("G1CollectedHeap::attempt_allocation_humongous() " 1096 "retries %d times", try_count); 1097 } 1098 } 1099 1100 ShouldNotReachHere(); 1101 return NULL; 1102 } 1103 1104 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1105 AllocationContext_t context, 1106 bool expect_null_mutator_alloc_region) { 1107 assert_at_safepoint(true /* should_be_vm_thread */); 1108 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1109 "the current alloc region was unexpectedly found to be non-NULL"); 1110 1111 if (!is_humongous(word_size)) { 1112 return _allocator->attempt_allocation_locked(word_size, context); 1113 } else { 1114 HeapWord* result = humongous_obj_allocate(word_size, context); 1115 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1116 collector_state()->set_initiate_conc_mark_if_possible(true); 1117 } 1118 return result; 1119 } 1120 1121 ShouldNotReachHere(); 1122 } 1123 1124 class PostMCRemSetClearClosure: public HeapRegionClosure { 1125 G1CollectedHeap* _g1h; 1126 ModRefBarrierSet* _mr_bs; 1127 public: 1128 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1129 _g1h(g1h), _mr_bs(mr_bs) {} 1130 1131 bool doHeapRegion(HeapRegion* r) { 1132 HeapRegionRemSet* hrrs = r->rem_set(); 1133 1134 _g1h->reset_gc_time_stamps(r); 1135 1136 if (r->is_continues_humongous()) { 1137 // We'll assert that the strong code root list and RSet is empty 1138 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1139 assert(hrrs->occupied() == 0, "RSet should be empty"); 1140 } else { 1141 hrrs->clear(); 1142 } 1143 // You might think here that we could clear just the cards 1144 // corresponding to the used region. But no: if we leave a dirty card 1145 // in a region we might allocate into, then it would prevent that card 1146 // from being enqueued, and cause it to be missed. 1147 // Re: the performance cost: we shouldn't be doing full GC anyway! 1148 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1149 1150 return false; 1151 } 1152 }; 1153 1154 void G1CollectedHeap::clear_rsets_post_compaction() { 1155 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1156 heap_region_iterate(&rs_clear); 1157 } 1158 1159 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1160 G1CollectedHeap* _g1h; 1161 UpdateRSOopClosure _cl; 1162 public: 1163 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1164 _cl(g1->g1_rem_set(), worker_i), 1165 _g1h(g1) 1166 { } 1167 1168 bool doHeapRegion(HeapRegion* r) { 1169 if (!r->is_continues_humongous()) { 1170 _cl.set_from(r); 1171 r->oop_iterate(&_cl); 1172 } 1173 return false; 1174 } 1175 }; 1176 1177 class ParRebuildRSTask: public AbstractGangTask { 1178 G1CollectedHeap* _g1; 1179 HeapRegionClaimer _hrclaimer; 1180 1181 public: 1182 ParRebuildRSTask(G1CollectedHeap* g1) : 1183 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1184 1185 void work(uint worker_id) { 1186 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1187 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1188 } 1189 }; 1190 1191 class PostCompactionPrinterClosure: public HeapRegionClosure { 1192 private: 1193 G1HRPrinter* _hr_printer; 1194 public: 1195 bool doHeapRegion(HeapRegion* hr) { 1196 assert(!hr->is_young(), "not expecting to find young regions"); 1197 _hr_printer->post_compaction(hr); 1198 return false; 1199 } 1200 1201 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1202 : _hr_printer(hr_printer) { } 1203 }; 1204 1205 void G1CollectedHeap::print_hrm_post_compaction() { 1206 if (_hr_printer.is_active()) { 1207 PostCompactionPrinterClosure cl(hr_printer()); 1208 heap_region_iterate(&cl); 1209 } 1210 1211 } 1212 1213 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1214 bool clear_all_soft_refs) { 1215 assert_at_safepoint(true /* should_be_vm_thread */); 1216 1217 if (GCLocker::check_active_before_gc()) { 1218 return false; 1219 } 1220 1221 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1222 gc_timer->register_gc_start(); 1223 1224 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1225 GCIdMark gc_id_mark; 1226 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1227 1228 SvcGCMarker sgcm(SvcGCMarker::FULL); 1229 ResourceMark rm; 1230 1231 print_heap_before_gc(); 1232 trace_heap_before_gc(gc_tracer); 1233 1234 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1235 1236 _verifier->verify_region_sets_optional(); 1237 1238 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1239 collector_policy()->should_clear_all_soft_refs(); 1240 1241 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1242 1243 { 1244 IsGCActiveMark x; 1245 1246 // Timing 1247 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1248 GCTraceCPUTime tcpu; 1249 1250 { 1251 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1252 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1253 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1254 1255 G1HeapTransition heap_transition(this); 1256 g1_policy()->record_full_collection_start(); 1257 1258 // Note: When we have a more flexible GC logging framework that 1259 // allows us to add optional attributes to a GC log record we 1260 // could consider timing and reporting how long we wait in the 1261 // following two methods. 1262 wait_while_free_regions_coming(); 1263 // If we start the compaction before the CM threads finish 1264 // scanning the root regions we might trip them over as we'll 1265 // be moving objects / updating references. So let's wait until 1266 // they are done. By telling them to abort, they should complete 1267 // early. 1268 _cm->root_regions()->abort(); 1269 _cm->root_regions()->wait_until_scan_finished(); 1270 append_secondary_free_list_if_not_empty_with_lock(); 1271 1272 gc_prologue(true); 1273 increment_total_collections(true /* full gc */); 1274 increment_old_marking_cycles_started(); 1275 1276 assert(used() == recalculate_used(), "Should be equal"); 1277 1278 _verifier->verify_before_gc(); 1279 1280 _verifier->check_bitmaps("Full GC Start"); 1281 pre_full_gc_dump(gc_timer); 1282 1283 #if defined(COMPILER2) || INCLUDE_JVMCI 1284 DerivedPointerTable::clear(); 1285 #endif 1286 1287 // Disable discovery and empty the discovered lists 1288 // for the CM ref processor. 1289 ref_processor_cm()->disable_discovery(); 1290 ref_processor_cm()->abandon_partial_discovery(); 1291 ref_processor_cm()->verify_no_references_recorded(); 1292 1293 // Abandon current iterations of concurrent marking and concurrent 1294 // refinement, if any are in progress. 1295 concurrent_mark()->abort(); 1296 1297 // Make sure we'll choose a new allocation region afterwards. 1298 _allocator->release_mutator_alloc_region(); 1299 _allocator->abandon_gc_alloc_regions(); 1300 g1_rem_set()->cleanupHRRS(); 1301 1302 // We may have added regions to the current incremental collection 1303 // set between the last GC or pause and now. We need to clear the 1304 // incremental collection set and then start rebuilding it afresh 1305 // after this full GC. 1306 abandon_collection_set(collection_set()->inc_head()); 1307 collection_set()->clear_incremental(); 1308 collection_set()->stop_incremental_building(); 1309 1310 tear_down_region_sets(false /* free_list_only */); 1311 collector_state()->set_gcs_are_young(true); 1312 1313 // See the comments in g1CollectedHeap.hpp and 1314 // G1CollectedHeap::ref_processing_init() about 1315 // how reference processing currently works in G1. 1316 1317 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1318 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1319 1320 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1321 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1322 1323 ref_processor_stw()->enable_discovery(); 1324 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1325 1326 // Do collection work 1327 { 1328 HandleMark hm; // Discard invalid handles created during gc 1329 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1330 } 1331 1332 assert(num_free_regions() == 0, "we should not have added any free regions"); 1333 rebuild_region_sets(false /* free_list_only */); 1334 1335 // Enqueue any discovered reference objects that have 1336 // not been removed from the discovered lists. 1337 ref_processor_stw()->enqueue_discovered_references(); 1338 1339 #if defined(COMPILER2) || INCLUDE_JVMCI 1340 DerivedPointerTable::update_pointers(); 1341 #endif 1342 1343 MemoryService::track_memory_usage(); 1344 1345 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1346 ref_processor_stw()->verify_no_references_recorded(); 1347 1348 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1349 ClassLoaderDataGraph::purge(); 1350 MetaspaceAux::verify_metrics(); 1351 1352 // Note: since we've just done a full GC, concurrent 1353 // marking is no longer active. Therefore we need not 1354 // re-enable reference discovery for the CM ref processor. 1355 // That will be done at the start of the next marking cycle. 1356 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1357 ref_processor_cm()->verify_no_references_recorded(); 1358 1359 reset_gc_time_stamp(); 1360 // Since everything potentially moved, we will clear all remembered 1361 // sets, and clear all cards. Later we will rebuild remembered 1362 // sets. We will also reset the GC time stamps of the regions. 1363 clear_rsets_post_compaction(); 1364 check_gc_time_stamps(); 1365 1366 resize_if_necessary_after_full_collection(); 1367 1368 // We should do this after we potentially resize the heap so 1369 // that all the COMMIT / UNCOMMIT events are generated before 1370 // the compaction events. 1371 print_hrm_post_compaction(); 1372 1373 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1374 if (hot_card_cache->use_cache()) { 1375 hot_card_cache->reset_card_counts(); 1376 hot_card_cache->reset_hot_cache(); 1377 } 1378 1379 // Rebuild remembered sets of all regions. 1380 uint n_workers = 1381 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1382 workers()->active_workers(), 1383 Threads::number_of_non_daemon_threads()); 1384 workers()->set_active_workers(n_workers); 1385 1386 ParRebuildRSTask rebuild_rs_task(this); 1387 workers()->run_task(&rebuild_rs_task); 1388 1389 // Rebuild the strong code root lists for each region 1390 rebuild_strong_code_roots(); 1391 1392 if (true) { // FIXME 1393 MetaspaceGC::compute_new_size(); 1394 } 1395 1396 #ifdef TRACESPINNING 1397 ParallelTaskTerminator::print_termination_counts(); 1398 #endif 1399 1400 // Discard all rset updates 1401 JavaThread::dirty_card_queue_set().abandon_logs(); 1402 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1403 1404 // At this point there should be no regions in the 1405 // entire heap tagged as young. 1406 assert(check_young_list_empty(true /* check_heap */), 1407 "young list should be empty at this point"); 1408 1409 // Update the number of full collections that have been completed. 1410 increment_old_marking_cycles_completed(false /* concurrent */); 1411 1412 _hrm.verify_optional(); 1413 _verifier->verify_region_sets_optional(); 1414 1415 _verifier->verify_after_gc(); 1416 1417 // Clear the previous marking bitmap, if needed for bitmap verification. 1418 // Note we cannot do this when we clear the next marking bitmap in 1419 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1420 // objects marked during a full GC against the previous bitmap. 1421 // But we need to clear it before calling check_bitmaps below since 1422 // the full GC has compacted objects and updated TAMS but not updated 1423 // the prev bitmap. 1424 if (G1VerifyBitmaps) { 1425 ((G1CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll(); 1426 } 1427 _verifier->check_bitmaps("Full GC End"); 1428 1429 // Start a new incremental collection set for the next pause 1430 assert(collection_set()->head() == NULL, "must be"); 1431 collection_set()->start_incremental_building(); 1432 1433 clear_cset_fast_test(); 1434 1435 _allocator->init_mutator_alloc_region(); 1436 1437 g1_policy()->record_full_collection_end(); 1438 1439 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1440 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1441 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1442 // before any GC notifications are raised. 1443 g1mm()->update_sizes(); 1444 1445 gc_epilogue(true); 1446 1447 heap_transition.print(); 1448 1449 print_heap_after_gc(); 1450 trace_heap_after_gc(gc_tracer); 1451 1452 post_full_gc_dump(gc_timer); 1453 } 1454 1455 gc_timer->register_gc_end(); 1456 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1457 } 1458 1459 return true; 1460 } 1461 1462 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1463 // Currently, there is no facility in the do_full_collection(bool) API to notify 1464 // the caller that the collection did not succeed (e.g., because it was locked 1465 // out by the GC locker). So, right now, we'll ignore the return value. 1466 bool dummy = do_full_collection(true, /* explicit_gc */ 1467 clear_all_soft_refs); 1468 } 1469 1470 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1471 // Include bytes that will be pre-allocated to support collections, as "used". 1472 const size_t used_after_gc = used(); 1473 const size_t capacity_after_gc = capacity(); 1474 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1475 1476 // This is enforced in arguments.cpp. 1477 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1478 "otherwise the code below doesn't make sense"); 1479 1480 // We don't have floating point command-line arguments 1481 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1482 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1483 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1484 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1485 1486 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1487 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1488 1489 // We have to be careful here as these two calculations can overflow 1490 // 32-bit size_t's. 1491 double used_after_gc_d = (double) used_after_gc; 1492 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1493 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1494 1495 // Let's make sure that they are both under the max heap size, which 1496 // by default will make them fit into a size_t. 1497 double desired_capacity_upper_bound = (double) max_heap_size; 1498 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1499 desired_capacity_upper_bound); 1500 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1501 desired_capacity_upper_bound); 1502 1503 // We can now safely turn them into size_t's. 1504 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1505 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1506 1507 // This assert only makes sense here, before we adjust them 1508 // with respect to the min and max heap size. 1509 assert(minimum_desired_capacity <= maximum_desired_capacity, 1510 "minimum_desired_capacity = " SIZE_FORMAT ", " 1511 "maximum_desired_capacity = " SIZE_FORMAT, 1512 minimum_desired_capacity, maximum_desired_capacity); 1513 1514 // Should not be greater than the heap max size. No need to adjust 1515 // it with respect to the heap min size as it's a lower bound (i.e., 1516 // we'll try to make the capacity larger than it, not smaller). 1517 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1518 // Should not be less than the heap min size. No need to adjust it 1519 // with respect to the heap max size as it's an upper bound (i.e., 1520 // we'll try to make the capacity smaller than it, not greater). 1521 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1522 1523 if (capacity_after_gc < minimum_desired_capacity) { 1524 // Don't expand unless it's significant 1525 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1526 1527 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1528 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1529 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1530 1531 expand(expand_bytes); 1532 1533 // No expansion, now see if we want to shrink 1534 } else if (capacity_after_gc > maximum_desired_capacity) { 1535 // Capacity too large, compute shrinking size 1536 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1537 1538 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1539 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1540 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1541 1542 shrink(shrink_bytes); 1543 } 1544 } 1545 1546 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1547 AllocationContext_t context, 1548 bool do_gc, 1549 bool clear_all_soft_refs, 1550 bool expect_null_mutator_alloc_region, 1551 bool* gc_succeeded) { 1552 *gc_succeeded = true; 1553 // Let's attempt the allocation first. 1554 HeapWord* result = 1555 attempt_allocation_at_safepoint(word_size, 1556 context, 1557 expect_null_mutator_alloc_region); 1558 if (result != NULL) { 1559 assert(*gc_succeeded, "sanity"); 1560 return result; 1561 } 1562 1563 // In a G1 heap, we're supposed to keep allocation from failing by 1564 // incremental pauses. Therefore, at least for now, we'll favor 1565 // expansion over collection. (This might change in the future if we can 1566 // do something smarter than full collection to satisfy a failed alloc.) 1567 result = expand_and_allocate(word_size, context); 1568 if (result != NULL) { 1569 assert(*gc_succeeded, "sanity"); 1570 return result; 1571 } 1572 1573 if (do_gc) { 1574 // Expansion didn't work, we'll try to do a Full GC. 1575 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1576 clear_all_soft_refs); 1577 } 1578 1579 return NULL; 1580 } 1581 1582 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1583 AllocationContext_t context, 1584 bool* succeeded) { 1585 assert_at_safepoint(true /* should_be_vm_thread */); 1586 1587 // Attempts to allocate followed by Full GC. 1588 HeapWord* result = 1589 satisfy_failed_allocation_helper(word_size, 1590 context, 1591 true, /* do_gc */ 1592 false, /* clear_all_soft_refs */ 1593 false, /* expect_null_mutator_alloc_region */ 1594 succeeded); 1595 1596 if (result != NULL || !*succeeded) { 1597 return result; 1598 } 1599 1600 // Attempts to allocate followed by Full GC that will collect all soft references. 1601 result = satisfy_failed_allocation_helper(word_size, 1602 context, 1603 true, /* do_gc */ 1604 true, /* clear_all_soft_refs */ 1605 true, /* expect_null_mutator_alloc_region */ 1606 succeeded); 1607 1608 if (result != NULL || !*succeeded) { 1609 return result; 1610 } 1611 1612 // Attempts to allocate, no GC 1613 result = satisfy_failed_allocation_helper(word_size, 1614 context, 1615 false, /* do_gc */ 1616 false, /* clear_all_soft_refs */ 1617 true, /* expect_null_mutator_alloc_region */ 1618 succeeded); 1619 1620 if (result != NULL) { 1621 assert(*succeeded, "sanity"); 1622 return result; 1623 } 1624 1625 assert(!collector_policy()->should_clear_all_soft_refs(), 1626 "Flag should have been handled and cleared prior to this point"); 1627 1628 // What else? We might try synchronous finalization later. If the total 1629 // space available is large enough for the allocation, then a more 1630 // complete compaction phase than we've tried so far might be 1631 // appropriate. 1632 assert(*succeeded, "sanity"); 1633 return NULL; 1634 } 1635 1636 // Attempting to expand the heap sufficiently 1637 // to support an allocation of the given "word_size". If 1638 // successful, perform the allocation and return the address of the 1639 // allocated block, or else "NULL". 1640 1641 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1642 assert_at_safepoint(true /* should_be_vm_thread */); 1643 1644 _verifier->verify_region_sets_optional(); 1645 1646 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1647 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1648 word_size * HeapWordSize); 1649 1650 1651 if (expand(expand_bytes)) { 1652 _hrm.verify_optional(); 1653 _verifier->verify_region_sets_optional(); 1654 return attempt_allocation_at_safepoint(word_size, 1655 context, 1656 false /* expect_null_mutator_alloc_region */); 1657 } 1658 return NULL; 1659 } 1660 1661 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) { 1662 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1663 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1664 HeapRegion::GrainBytes); 1665 1666 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B", 1667 expand_bytes, aligned_expand_bytes); 1668 1669 if (is_maximal_no_gc()) { 1670 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1671 return false; 1672 } 1673 1674 double expand_heap_start_time_sec = os::elapsedTime(); 1675 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1676 assert(regions_to_expand > 0, "Must expand by at least one region"); 1677 1678 uint expanded_by = _hrm.expand_by(regions_to_expand); 1679 if (expand_time_ms != NULL) { 1680 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1681 } 1682 1683 if (expanded_by > 0) { 1684 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1685 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1686 g1_policy()->record_new_heap_size(num_regions()); 1687 } else { 1688 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1689 1690 // The expansion of the virtual storage space was unsuccessful. 1691 // Let's see if it was because we ran out of swap. 1692 if (G1ExitOnExpansionFailure && 1693 _hrm.available() >= regions_to_expand) { 1694 // We had head room... 1695 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1696 } 1697 } 1698 return regions_to_expand > 0; 1699 } 1700 1701 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1702 size_t aligned_shrink_bytes = 1703 ReservedSpace::page_align_size_down(shrink_bytes); 1704 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1705 HeapRegion::GrainBytes); 1706 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1707 1708 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1709 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1710 1711 1712 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", 1713 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1714 if (num_regions_removed > 0) { 1715 g1_policy()->record_new_heap_size(num_regions()); 1716 } else { 1717 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1718 } 1719 } 1720 1721 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1722 _verifier->verify_region_sets_optional(); 1723 1724 // We should only reach here at the end of a Full GC which means we 1725 // should not not be holding to any GC alloc regions. The method 1726 // below will make sure of that and do any remaining clean up. 1727 _allocator->abandon_gc_alloc_regions(); 1728 1729 // Instead of tearing down / rebuilding the free lists here, we 1730 // could instead use the remove_all_pending() method on free_list to 1731 // remove only the ones that we need to remove. 1732 tear_down_region_sets(true /* free_list_only */); 1733 shrink_helper(shrink_bytes); 1734 rebuild_region_sets(true /* free_list_only */); 1735 1736 _hrm.verify_optional(); 1737 _verifier->verify_region_sets_optional(); 1738 } 1739 1740 // Public methods. 1741 1742 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1743 CollectedHeap(), 1744 _g1_policy(policy_), 1745 _collection_set(new G1CollectionSet(this, policy_)), 1746 _dirty_card_queue_set(false), 1747 _is_alive_closure_cm(this), 1748 _is_alive_closure_stw(this), 1749 _ref_processor_cm(NULL), 1750 _ref_processor_stw(NULL), 1751 _bot(NULL), 1752 _cg1r(NULL), 1753 _g1mm(NULL), 1754 _refine_cte_cl(NULL), 1755 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1756 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1757 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1758 _humongous_reclaim_candidates(), 1759 _has_humongous_reclaim_candidates(false), 1760 _archive_allocator(NULL), 1761 _free_regions_coming(false), 1762 _young_list(new YoungList(this)), 1763 _gc_time_stamp(0), 1764 _summary_bytes_used(0), 1765 _survivor_evac_stats(YoungPLABSize, PLABWeight), 1766 _old_evac_stats(OldPLABSize, PLABWeight), 1767 _expand_heap_after_alloc_failure(true), 1768 _old_marking_cycles_started(0), 1769 _old_marking_cycles_completed(0), 1770 _heap_summary_sent(false), 1771 _in_cset_fast_test(), 1772 _dirty_cards_region_list(NULL), 1773 _worker_cset_start_region(NULL), 1774 _worker_cset_start_region_time_stamp(NULL), 1775 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1776 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1777 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1778 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1779 1780 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1781 /* are_GC_task_threads */true, 1782 /* are_ConcurrentGC_threads */false); 1783 _workers->initialize_workers(); 1784 _verifier = new G1HeapVerifier(this); 1785 1786 _allocator = G1Allocator::create_allocator(this); 1787 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1788 1789 // Override the default _filler_array_max_size so that no humongous filler 1790 // objects are created. 1791 _filler_array_max_size = _humongous_object_threshold_in_words; 1792 1793 uint n_queues = ParallelGCThreads; 1794 _task_queues = new RefToScanQueueSet(n_queues); 1795 1796 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1797 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC); 1798 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1799 1800 for (uint i = 0; i < n_queues; i++) { 1801 RefToScanQueue* q = new RefToScanQueue(); 1802 q->initialize(); 1803 _task_queues->register_queue(i, q); 1804 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1805 } 1806 clear_cset_start_regions(); 1807 1808 // Initialize the G1EvacuationFailureALot counters and flags. 1809 NOT_PRODUCT(reset_evacuation_should_fail();) 1810 1811 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1812 } 1813 1814 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1815 size_t size, 1816 size_t translation_factor) { 1817 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1818 // Allocate a new reserved space, preferring to use large pages. 1819 ReservedSpace rs(size, preferred_page_size); 1820 G1RegionToSpaceMapper* result = 1821 G1RegionToSpaceMapper::create_mapper(rs, 1822 size, 1823 rs.alignment(), 1824 HeapRegion::GrainBytes, 1825 translation_factor, 1826 mtGC); 1827 if (TracePageSizes) { 1828 tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT, 1829 description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size); 1830 } 1831 return result; 1832 } 1833 1834 jint G1CollectedHeap::initialize() { 1835 CollectedHeap::pre_initialize(); 1836 os::enable_vtime(); 1837 1838 // Necessary to satisfy locking discipline assertions. 1839 1840 MutexLocker x(Heap_lock); 1841 1842 // While there are no constraints in the GC code that HeapWordSize 1843 // be any particular value, there are multiple other areas in the 1844 // system which believe this to be true (e.g. oop->object_size in some 1845 // cases incorrectly returns the size in wordSize units rather than 1846 // HeapWordSize). 1847 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1848 1849 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1850 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1851 size_t heap_alignment = collector_policy()->heap_alignment(); 1852 1853 // Ensure that the sizes are properly aligned. 1854 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1855 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1856 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1857 1858 _refine_cte_cl = new RefineCardTableEntryClosure(); 1859 1860 jint ecode = JNI_OK; 1861 _cg1r = ConcurrentG1Refine::create(this, _refine_cte_cl, &ecode); 1862 if (_cg1r == NULL) { 1863 return ecode; 1864 } 1865 1866 // Reserve the maximum. 1867 1868 // When compressed oops are enabled, the preferred heap base 1869 // is calculated by subtracting the requested size from the 1870 // 32Gb boundary and using the result as the base address for 1871 // heap reservation. If the requested size is not aligned to 1872 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1873 // into the ReservedHeapSpace constructor) then the actual 1874 // base of the reserved heap may end up differing from the 1875 // address that was requested (i.e. the preferred heap base). 1876 // If this happens then we could end up using a non-optimal 1877 // compressed oops mode. 1878 1879 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1880 heap_alignment); 1881 1882 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1883 1884 // Create the barrier set for the entire reserved region. 1885 G1SATBCardTableLoggingModRefBS* bs 1886 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1887 bs->initialize(); 1888 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1889 set_barrier_set(bs); 1890 1891 // Also create a G1 rem set. 1892 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 1893 1894 // Carve out the G1 part of the heap. 1895 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1896 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1897 G1RegionToSpaceMapper* heap_storage = 1898 G1RegionToSpaceMapper::create_mapper(g1_rs, 1899 g1_rs.size(), 1900 page_size, 1901 HeapRegion::GrainBytes, 1902 1, 1903 mtJavaHeap); 1904 os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(), 1905 max_byte_size, page_size, 1906 heap_rs.base(), 1907 heap_rs.size()); 1908 heap_storage->set_mapping_changed_listener(&_listener); 1909 1910 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1911 G1RegionToSpaceMapper* bot_storage = 1912 create_aux_memory_mapper("Block offset table", 1913 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1914 G1BlockOffsetTable::heap_map_factor()); 1915 1916 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1917 G1RegionToSpaceMapper* cardtable_storage = 1918 create_aux_memory_mapper("Card table", 1919 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1920 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1921 1922 G1RegionToSpaceMapper* card_counts_storage = 1923 create_aux_memory_mapper("Card counts table", 1924 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1925 G1CardCounts::heap_map_factor()); 1926 1927 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1928 G1RegionToSpaceMapper* prev_bitmap_storage = 1929 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1930 G1RegionToSpaceMapper* next_bitmap_storage = 1931 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1932 1933 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1934 g1_barrier_set()->initialize(cardtable_storage); 1935 // Do later initialization work for concurrent refinement. 1936 _cg1r->init(card_counts_storage); 1937 1938 // 6843694 - ensure that the maximum region index can fit 1939 // in the remembered set structures. 1940 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1941 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1942 1943 G1RemSet::initialize(max_regions()); 1944 1945 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1946 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1947 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1948 "too many cards per region"); 1949 1950 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1951 1952 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1953 1954 { 1955 HeapWord* start = _hrm.reserved().start(); 1956 HeapWord* end = _hrm.reserved().end(); 1957 size_t granularity = HeapRegion::GrainBytes; 1958 1959 _in_cset_fast_test.initialize(start, end, granularity); 1960 _humongous_reclaim_candidates.initialize(start, end, granularity); 1961 } 1962 1963 // Create the G1ConcurrentMark data structure and thread. 1964 // (Must do this late, so that "max_regions" is defined.) 1965 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1966 if (_cm == NULL || !_cm->completed_initialization()) { 1967 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1968 return JNI_ENOMEM; 1969 } 1970 _cmThread = _cm->cmThread(); 1971 1972 // Now expand into the initial heap size. 1973 if (!expand(init_byte_size)) { 1974 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1975 return JNI_ENOMEM; 1976 } 1977 1978 // Perform any initialization actions delegated to the policy. 1979 g1_policy()->init(); 1980 1981 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1982 SATB_Q_FL_lock, 1983 G1SATBProcessCompletedThreshold, 1984 Shared_SATB_Q_lock); 1985 1986 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 1987 DirtyCardQ_CBL_mon, 1988 DirtyCardQ_FL_lock, 1989 concurrent_g1_refine()->yellow_zone(), 1990 concurrent_g1_refine()->red_zone(), 1991 Shared_DirtyCardQ_lock, 1992 NULL, // fl_owner 1993 true); // init_free_ids 1994 1995 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 1996 DirtyCardQ_CBL_mon, 1997 DirtyCardQ_FL_lock, 1998 -1, // never trigger processing 1999 -1, // no limit on length 2000 Shared_DirtyCardQ_lock, 2001 &JavaThread::dirty_card_queue_set()); 2002 2003 // Here we allocate the dummy HeapRegion that is required by the 2004 // G1AllocRegion class. 2005 HeapRegion* dummy_region = _hrm.get_dummy_region(); 2006 2007 // We'll re-use the same region whether the alloc region will 2008 // require BOT updates or not and, if it doesn't, then a non-young 2009 // region will complain that it cannot support allocations without 2010 // BOT updates. So we'll tag the dummy region as eden to avoid that. 2011 dummy_region->set_eden(); 2012 // Make sure it's full. 2013 dummy_region->set_top(dummy_region->end()); 2014 G1AllocRegion::setup(this, dummy_region); 2015 2016 _allocator->init_mutator_alloc_region(); 2017 2018 // Do create of the monitoring and management support so that 2019 // values in the heap have been properly initialized. 2020 _g1mm = new G1MonitoringSupport(this); 2021 2022 G1StringDedup::initialize(); 2023 2024 _preserved_objs = NEW_C_HEAP_ARRAY(OopAndMarkOopStack, ParallelGCThreads, mtGC); 2025 for (uint i = 0; i < ParallelGCThreads; i++) { 2026 new (&_preserved_objs[i]) OopAndMarkOopStack(); 2027 } 2028 2029 return JNI_OK; 2030 } 2031 2032 void G1CollectedHeap::stop() { 2033 // Stop all concurrent threads. We do this to make sure these threads 2034 // do not continue to execute and access resources (e.g. logging) 2035 // that are destroyed during shutdown. 2036 _cg1r->stop(); 2037 _cmThread->stop(); 2038 if (G1StringDedup::is_enabled()) { 2039 G1StringDedup::stop(); 2040 } 2041 } 2042 2043 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2044 return HeapRegion::max_region_size(); 2045 } 2046 2047 void G1CollectedHeap::post_initialize() { 2048 CollectedHeap::post_initialize(); 2049 ref_processing_init(); 2050 } 2051 2052 void G1CollectedHeap::ref_processing_init() { 2053 // Reference processing in G1 currently works as follows: 2054 // 2055 // * There are two reference processor instances. One is 2056 // used to record and process discovered references 2057 // during concurrent marking; the other is used to 2058 // record and process references during STW pauses 2059 // (both full and incremental). 2060 // * Both ref processors need to 'span' the entire heap as 2061 // the regions in the collection set may be dotted around. 2062 // 2063 // * For the concurrent marking ref processor: 2064 // * Reference discovery is enabled at initial marking. 2065 // * Reference discovery is disabled and the discovered 2066 // references processed etc during remarking. 2067 // * Reference discovery is MT (see below). 2068 // * Reference discovery requires a barrier (see below). 2069 // * Reference processing may or may not be MT 2070 // (depending on the value of ParallelRefProcEnabled 2071 // and ParallelGCThreads). 2072 // * A full GC disables reference discovery by the CM 2073 // ref processor and abandons any entries on it's 2074 // discovered lists. 2075 // 2076 // * For the STW processor: 2077 // * Non MT discovery is enabled at the start of a full GC. 2078 // * Processing and enqueueing during a full GC is non-MT. 2079 // * During a full GC, references are processed after marking. 2080 // 2081 // * Discovery (may or may not be MT) is enabled at the start 2082 // of an incremental evacuation pause. 2083 // * References are processed near the end of a STW evacuation pause. 2084 // * For both types of GC: 2085 // * Discovery is atomic - i.e. not concurrent. 2086 // * Reference discovery will not need a barrier. 2087 2088 MemRegion mr = reserved_region(); 2089 2090 // Concurrent Mark ref processor 2091 _ref_processor_cm = 2092 new ReferenceProcessor(mr, // span 2093 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2094 // mt processing 2095 ParallelGCThreads, 2096 // degree of mt processing 2097 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2098 // mt discovery 2099 MAX2(ParallelGCThreads, ConcGCThreads), 2100 // degree of mt discovery 2101 false, 2102 // Reference discovery is not atomic 2103 &_is_alive_closure_cm); 2104 // is alive closure 2105 // (for efficiency/performance) 2106 2107 // STW ref processor 2108 _ref_processor_stw = 2109 new ReferenceProcessor(mr, // span 2110 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2111 // mt processing 2112 ParallelGCThreads, 2113 // degree of mt processing 2114 (ParallelGCThreads > 1), 2115 // mt discovery 2116 ParallelGCThreads, 2117 // degree of mt discovery 2118 true, 2119 // Reference discovery is atomic 2120 &_is_alive_closure_stw); 2121 // is alive closure 2122 // (for efficiency/performance) 2123 } 2124 2125 CollectorPolicy* G1CollectedHeap::collector_policy() const { 2126 return g1_policy(); 2127 } 2128 2129 size_t G1CollectedHeap::capacity() const { 2130 return _hrm.length() * HeapRegion::GrainBytes; 2131 } 2132 2133 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2134 hr->reset_gc_time_stamp(); 2135 } 2136 2137 #ifndef PRODUCT 2138 2139 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2140 private: 2141 unsigned _gc_time_stamp; 2142 bool _failures; 2143 2144 public: 2145 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2146 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2147 2148 virtual bool doHeapRegion(HeapRegion* hr) { 2149 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2150 if (_gc_time_stamp != region_gc_time_stamp) { 2151 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 2152 region_gc_time_stamp, _gc_time_stamp); 2153 _failures = true; 2154 } 2155 return false; 2156 } 2157 2158 bool failures() { return _failures; } 2159 }; 2160 2161 void G1CollectedHeap::check_gc_time_stamps() { 2162 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2163 heap_region_iterate(&cl); 2164 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2165 } 2166 #endif // PRODUCT 2167 2168 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2169 _cg1r->hot_card_cache()->drain(cl, worker_i); 2170 } 2171 2172 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2173 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2174 size_t n_completed_buffers = 0; 2175 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2176 n_completed_buffers++; 2177 } 2178 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2179 dcqs.clear_n_completed_buffers(); 2180 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2181 } 2182 2183 // Computes the sum of the storage used by the various regions. 2184 size_t G1CollectedHeap::used() const { 2185 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2186 if (_archive_allocator != NULL) { 2187 result += _archive_allocator->used(); 2188 } 2189 return result; 2190 } 2191 2192 size_t G1CollectedHeap::used_unlocked() const { 2193 return _summary_bytes_used; 2194 } 2195 2196 class SumUsedClosure: public HeapRegionClosure { 2197 size_t _used; 2198 public: 2199 SumUsedClosure() : _used(0) {} 2200 bool doHeapRegion(HeapRegion* r) { 2201 _used += r->used(); 2202 return false; 2203 } 2204 size_t result() { return _used; } 2205 }; 2206 2207 size_t G1CollectedHeap::recalculate_used() const { 2208 double recalculate_used_start = os::elapsedTime(); 2209 2210 SumUsedClosure blk; 2211 heap_region_iterate(&blk); 2212 2213 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2214 return blk.result(); 2215 } 2216 2217 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2218 switch (cause) { 2219 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2220 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2221 case GCCause::_update_allocation_context_stats_inc: return true; 2222 case GCCause::_wb_conc_mark: return true; 2223 default : return false; 2224 } 2225 } 2226 2227 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2228 switch (cause) { 2229 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2230 case GCCause::_g1_humongous_allocation: return true; 2231 default: return is_user_requested_concurrent_full_gc(cause); 2232 } 2233 } 2234 2235 #ifndef PRODUCT 2236 void G1CollectedHeap::allocate_dummy_regions() { 2237 // Let's fill up most of the region 2238 size_t word_size = HeapRegion::GrainWords - 1024; 2239 // And as a result the region we'll allocate will be humongous. 2240 guarantee(is_humongous(word_size), "sanity"); 2241 2242 // _filler_array_max_size is set to humongous object threshold 2243 // but temporarily change it to use CollectedHeap::fill_with_object(). 2244 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2245 2246 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2247 // Let's use the existing mechanism for the allocation 2248 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2249 AllocationContext::system()); 2250 if (dummy_obj != NULL) { 2251 MemRegion mr(dummy_obj, word_size); 2252 CollectedHeap::fill_with_object(mr); 2253 } else { 2254 // If we can't allocate once, we probably cannot allocate 2255 // again. Let's get out of the loop. 2256 break; 2257 } 2258 } 2259 } 2260 #endif // !PRODUCT 2261 2262 void G1CollectedHeap::increment_old_marking_cycles_started() { 2263 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2264 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2265 "Wrong marking cycle count (started: %d, completed: %d)", 2266 _old_marking_cycles_started, _old_marking_cycles_completed); 2267 2268 _old_marking_cycles_started++; 2269 } 2270 2271 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2272 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2273 2274 // We assume that if concurrent == true, then the caller is a 2275 // concurrent thread that was joined the Suspendible Thread 2276 // Set. If there's ever a cheap way to check this, we should add an 2277 // assert here. 2278 2279 // Given that this method is called at the end of a Full GC or of a 2280 // concurrent cycle, and those can be nested (i.e., a Full GC can 2281 // interrupt a concurrent cycle), the number of full collections 2282 // completed should be either one (in the case where there was no 2283 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2284 // behind the number of full collections started. 2285 2286 // This is the case for the inner caller, i.e. a Full GC. 2287 assert(concurrent || 2288 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2289 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2290 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2291 "is inconsistent with _old_marking_cycles_completed = %u", 2292 _old_marking_cycles_started, _old_marking_cycles_completed); 2293 2294 // This is the case for the outer caller, i.e. the concurrent cycle. 2295 assert(!concurrent || 2296 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2297 "for outer caller (concurrent cycle): " 2298 "_old_marking_cycles_started = %u " 2299 "is inconsistent with _old_marking_cycles_completed = %u", 2300 _old_marking_cycles_started, _old_marking_cycles_completed); 2301 2302 _old_marking_cycles_completed += 1; 2303 2304 // We need to clear the "in_progress" flag in the CM thread before 2305 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2306 // is set) so that if a waiter requests another System.gc() it doesn't 2307 // incorrectly see that a marking cycle is still in progress. 2308 if (concurrent) { 2309 _cmThread->set_idle(); 2310 } 2311 2312 // This notify_all() will ensure that a thread that called 2313 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2314 // and it's waiting for a full GC to finish will be woken up. It is 2315 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2316 FullGCCount_lock->notify_all(); 2317 } 2318 2319 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2320 GCIdMarkAndRestore conc_gc_id_mark; 2321 collector_state()->set_concurrent_cycle_started(true); 2322 _gc_timer_cm->register_gc_start(start_time); 2323 2324 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2325 trace_heap_before_gc(_gc_tracer_cm); 2326 _cmThread->set_gc_id(GCId::current()); 2327 } 2328 2329 void G1CollectedHeap::register_concurrent_cycle_end() { 2330 if (collector_state()->concurrent_cycle_started()) { 2331 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2332 if (_cm->has_aborted()) { 2333 _gc_tracer_cm->report_concurrent_mode_failure(); 2334 } 2335 2336 _gc_timer_cm->register_gc_end(); 2337 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2338 2339 // Clear state variables to prepare for the next concurrent cycle. 2340 collector_state()->set_concurrent_cycle_started(false); 2341 _heap_summary_sent = false; 2342 } 2343 } 2344 2345 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2346 if (collector_state()->concurrent_cycle_started()) { 2347 // This function can be called when: 2348 // the cleanup pause is run 2349 // the concurrent cycle is aborted before the cleanup pause. 2350 // the concurrent cycle is aborted after the cleanup pause, 2351 // but before the concurrent cycle end has been registered. 2352 // Make sure that we only send the heap information once. 2353 if (!_heap_summary_sent) { 2354 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2355 trace_heap_after_gc(_gc_tracer_cm); 2356 _heap_summary_sent = true; 2357 } 2358 } 2359 } 2360 2361 void G1CollectedHeap::collect(GCCause::Cause cause) { 2362 assert_heap_not_locked(); 2363 2364 uint gc_count_before; 2365 uint old_marking_count_before; 2366 uint full_gc_count_before; 2367 bool retry_gc; 2368 2369 do { 2370 retry_gc = false; 2371 2372 { 2373 MutexLocker ml(Heap_lock); 2374 2375 // Read the GC count while holding the Heap_lock 2376 gc_count_before = total_collections(); 2377 full_gc_count_before = total_full_collections(); 2378 old_marking_count_before = _old_marking_cycles_started; 2379 } 2380 2381 if (should_do_concurrent_full_gc(cause)) { 2382 // Schedule an initial-mark evacuation pause that will start a 2383 // concurrent cycle. We're setting word_size to 0 which means that 2384 // we are not requesting a post-GC allocation. 2385 VM_G1IncCollectionPause op(gc_count_before, 2386 0, /* word_size */ 2387 true, /* should_initiate_conc_mark */ 2388 g1_policy()->max_pause_time_ms(), 2389 cause); 2390 op.set_allocation_context(AllocationContext::current()); 2391 2392 VMThread::execute(&op); 2393 if (!op.pause_succeeded()) { 2394 if (old_marking_count_before == _old_marking_cycles_started) { 2395 retry_gc = op.should_retry_gc(); 2396 } else { 2397 // A Full GC happened while we were trying to schedule the 2398 // initial-mark GC. No point in starting a new cycle given 2399 // that the whole heap was collected anyway. 2400 } 2401 2402 if (retry_gc) { 2403 if (GCLocker::is_active_and_needs_gc()) { 2404 GCLocker::stall_until_clear(); 2405 } 2406 } 2407 } 2408 } else { 2409 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2410 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2411 2412 // Schedule a standard evacuation pause. We're setting word_size 2413 // to 0 which means that we are not requesting a post-GC allocation. 2414 VM_G1IncCollectionPause op(gc_count_before, 2415 0, /* word_size */ 2416 false, /* should_initiate_conc_mark */ 2417 g1_policy()->max_pause_time_ms(), 2418 cause); 2419 VMThread::execute(&op); 2420 } else { 2421 // Schedule a Full GC. 2422 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2423 VMThread::execute(&op); 2424 } 2425 } 2426 } while (retry_gc); 2427 } 2428 2429 bool G1CollectedHeap::is_in(const void* p) const { 2430 if (_hrm.reserved().contains(p)) { 2431 // Given that we know that p is in the reserved space, 2432 // heap_region_containing() should successfully 2433 // return the containing region. 2434 HeapRegion* hr = heap_region_containing(p); 2435 return hr->is_in(p); 2436 } else { 2437 return false; 2438 } 2439 } 2440 2441 #ifdef ASSERT 2442 bool G1CollectedHeap::is_in_exact(const void* p) const { 2443 bool contains = reserved_region().contains(p); 2444 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2445 if (contains && available) { 2446 return true; 2447 } else { 2448 return false; 2449 } 2450 } 2451 #endif 2452 2453 bool G1CollectedHeap::obj_in_cs(oop obj) { 2454 HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj); 2455 return r != NULL && r->in_collection_set(); 2456 } 2457 2458 // Iteration functions. 2459 2460 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2461 2462 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2463 ExtendedOopClosure* _cl; 2464 public: 2465 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2466 bool doHeapRegion(HeapRegion* r) { 2467 if (!r->is_continues_humongous()) { 2468 r->oop_iterate(_cl); 2469 } 2470 return false; 2471 } 2472 }; 2473 2474 // Iterates an ObjectClosure over all objects within a HeapRegion. 2475 2476 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2477 ObjectClosure* _cl; 2478 public: 2479 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2480 bool doHeapRegion(HeapRegion* r) { 2481 if (!r->is_continues_humongous()) { 2482 r->object_iterate(_cl); 2483 } 2484 return false; 2485 } 2486 }; 2487 2488 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2489 IterateObjectClosureRegionClosure blk(cl); 2490 heap_region_iterate(&blk); 2491 } 2492 2493 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2494 _hrm.iterate(cl); 2495 } 2496 2497 void 2498 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2499 uint worker_id, 2500 HeapRegionClaimer *hrclaimer, 2501 bool concurrent) const { 2502 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2503 } 2504 2505 // Clear the cached CSet starting regions and (more importantly) 2506 // the time stamps. Called when we reset the GC time stamp. 2507 void G1CollectedHeap::clear_cset_start_regions() { 2508 assert(_worker_cset_start_region != NULL, "sanity"); 2509 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2510 2511 for (uint i = 0; i < ParallelGCThreads; i++) { 2512 _worker_cset_start_region[i] = NULL; 2513 _worker_cset_start_region_time_stamp[i] = 0; 2514 } 2515 } 2516 2517 // Given the id of a worker, obtain or calculate a suitable 2518 // starting region for iterating over the current collection set. 2519 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2520 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2521 2522 HeapRegion* result = NULL; 2523 unsigned gc_time_stamp = get_gc_time_stamp(); 2524 2525 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2526 // Cached starting region for current worker was set 2527 // during the current pause - so it's valid. 2528 // Note: the cached starting heap region may be NULL 2529 // (when the collection set is empty). 2530 result = _worker_cset_start_region[worker_i]; 2531 assert(result == NULL || result->in_collection_set(), "sanity"); 2532 return result; 2533 } 2534 2535 // The cached entry was not valid so let's calculate 2536 // a suitable starting heap region for this worker. 2537 2538 // We want the parallel threads to start their collection 2539 // set iteration at different collection set regions to 2540 // avoid contention. 2541 // If we have: 2542 // n collection set regions 2543 // p threads 2544 // Then thread t will start at region floor ((t * n) / p) 2545 2546 result = collection_set()->head(); 2547 uint cs_size = collection_set()->region_length(); 2548 uint active_workers = workers()->active_workers(); 2549 2550 uint end_ind = (cs_size * worker_i) / active_workers; 2551 uint start_ind = 0; 2552 2553 if (worker_i > 0 && 2554 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2555 // Previous workers starting region is valid 2556 // so let's iterate from there 2557 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2558 OrderAccess::loadload(); 2559 result = _worker_cset_start_region[worker_i - 1]; 2560 } 2561 2562 for (uint i = start_ind; i < end_ind; i++) { 2563 result = result->next_in_collection_set(); 2564 } 2565 2566 // Note: the calculated starting heap region may be NULL 2567 // (when the collection set is empty). 2568 assert(result == NULL || result->in_collection_set(), "sanity"); 2569 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2570 "should be updated only once per pause"); 2571 _worker_cset_start_region[worker_i] = result; 2572 OrderAccess::storestore(); 2573 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2574 return result; 2575 } 2576 2577 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2578 HeapRegion* r = collection_set()->head(); 2579 while (r != NULL) { 2580 HeapRegion* next = r->next_in_collection_set(); 2581 if (cl->doHeapRegion(r)) { 2582 cl->incomplete(); 2583 return; 2584 } 2585 r = next; 2586 } 2587 } 2588 2589 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2590 HeapRegionClosure *cl) { 2591 if (r == NULL) { 2592 // The CSet is empty so there's nothing to do. 2593 return; 2594 } 2595 2596 assert(r->in_collection_set(), 2597 "Start region must be a member of the collection set."); 2598 HeapRegion* cur = r; 2599 while (cur != NULL) { 2600 HeapRegion* next = cur->next_in_collection_set(); 2601 if (cl->doHeapRegion(cur) && false) { 2602 cl->incomplete(); 2603 return; 2604 } 2605 cur = next; 2606 } 2607 cur = collection_set()->head(); 2608 while (cur != r) { 2609 HeapRegion* next = cur->next_in_collection_set(); 2610 if (cl->doHeapRegion(cur) && false) { 2611 cl->incomplete(); 2612 return; 2613 } 2614 cur = next; 2615 } 2616 } 2617 2618 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2619 HeapRegion* result = _hrm.next_region_in_heap(from); 2620 while (result != NULL && result->is_pinned()) { 2621 result = _hrm.next_region_in_heap(result); 2622 } 2623 return result; 2624 } 2625 2626 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2627 HeapRegion* hr = heap_region_containing(addr); 2628 return hr->block_start(addr); 2629 } 2630 2631 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2632 HeapRegion* hr = heap_region_containing(addr); 2633 return hr->block_size(addr); 2634 } 2635 2636 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2637 HeapRegion* hr = heap_region_containing(addr); 2638 return hr->block_is_obj(addr); 2639 } 2640 2641 bool G1CollectedHeap::supports_tlab_allocation() const { 2642 return true; 2643 } 2644 2645 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2646 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2647 } 2648 2649 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2650 return young_list()->eden_used_bytes(); 2651 } 2652 2653 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2654 // must be equal to the humongous object limit. 2655 size_t G1CollectedHeap::max_tlab_size() const { 2656 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2657 } 2658 2659 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2660 AllocationContext_t context = AllocationContext::current(); 2661 return _allocator->unsafe_max_tlab_alloc(context); 2662 } 2663 2664 size_t G1CollectedHeap::max_capacity() const { 2665 return _hrm.reserved().byte_size(); 2666 } 2667 2668 jlong G1CollectedHeap::millis_since_last_gc() { 2669 // assert(false, "NYI"); 2670 return 0; 2671 } 2672 2673 void G1CollectedHeap::prepare_for_verify() { 2674 _verifier->prepare_for_verify(); 2675 } 2676 2677 void G1CollectedHeap::verify(VerifyOption vo) { 2678 _verifier->verify(vo); 2679 } 2680 2681 class PrintRegionClosure: public HeapRegionClosure { 2682 outputStream* _st; 2683 public: 2684 PrintRegionClosure(outputStream* st) : _st(st) {} 2685 bool doHeapRegion(HeapRegion* r) { 2686 r->print_on(_st); 2687 return false; 2688 } 2689 }; 2690 2691 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2692 const HeapRegion* hr, 2693 const VerifyOption vo) const { 2694 switch (vo) { 2695 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2696 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2697 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 2698 default: ShouldNotReachHere(); 2699 } 2700 return false; // keep some compilers happy 2701 } 2702 2703 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2704 const VerifyOption vo) const { 2705 switch (vo) { 2706 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2707 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2708 case VerifyOption_G1UseMarkWord: { 2709 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 2710 return !obj->is_gc_marked() && !hr->is_archive(); 2711 } 2712 default: ShouldNotReachHere(); 2713 } 2714 return false; // keep some compilers happy 2715 } 2716 2717 void G1CollectedHeap::print_on(outputStream* st) const { 2718 st->print(" %-20s", "garbage-first heap"); 2719 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2720 capacity()/K, used_unlocked()/K); 2721 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 2722 p2i(_hrm.reserved().start()), 2723 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 2724 p2i(_hrm.reserved().end())); 2725 st->cr(); 2726 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2727 uint young_regions = _young_list->length(); 2728 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2729 (size_t) young_regions * HeapRegion::GrainBytes / K); 2730 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 2731 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2732 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2733 st->cr(); 2734 MetaspaceAux::print_on(st); 2735 } 2736 2737 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2738 print_on(st); 2739 2740 // Print the per-region information. 2741 st->cr(); 2742 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2743 "HS=humongous(starts), HC=humongous(continues), " 2744 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2745 "AC=allocation context, " 2746 "TAMS=top-at-mark-start (previous, next)"); 2747 PrintRegionClosure blk(st); 2748 heap_region_iterate(&blk); 2749 } 2750 2751 void G1CollectedHeap::print_on_error(outputStream* st) const { 2752 this->CollectedHeap::print_on_error(st); 2753 2754 if (_cm != NULL) { 2755 st->cr(); 2756 _cm->print_on_error(st); 2757 } 2758 } 2759 2760 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2761 workers()->print_worker_threads_on(st); 2762 _cmThread->print_on(st); 2763 st->cr(); 2764 _cm->print_worker_threads_on(st); 2765 _cg1r->print_worker_threads_on(st); 2766 if (G1StringDedup::is_enabled()) { 2767 G1StringDedup::print_worker_threads_on(st); 2768 } 2769 } 2770 2771 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2772 workers()->threads_do(tc); 2773 tc->do_thread(_cmThread); 2774 _cg1r->threads_do(tc); 2775 if (G1StringDedup::is_enabled()) { 2776 G1StringDedup::threads_do(tc); 2777 } 2778 } 2779 2780 void G1CollectedHeap::print_tracing_info() const { 2781 g1_rem_set()->print_summary_info(); 2782 concurrent_mark()->print_summary_info(); 2783 g1_policy()->print_yg_surv_rate_info(); 2784 } 2785 2786 #ifndef PRODUCT 2787 // Helpful for debugging RSet issues. 2788 2789 class PrintRSetsClosure : public HeapRegionClosure { 2790 private: 2791 const char* _msg; 2792 size_t _occupied_sum; 2793 2794 public: 2795 bool doHeapRegion(HeapRegion* r) { 2796 HeapRegionRemSet* hrrs = r->rem_set(); 2797 size_t occupied = hrrs->occupied(); 2798 _occupied_sum += occupied; 2799 2800 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2801 if (occupied == 0) { 2802 tty->print_cr(" RSet is empty"); 2803 } else { 2804 hrrs->print(); 2805 } 2806 tty->print_cr("----------"); 2807 return false; 2808 } 2809 2810 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2811 tty->cr(); 2812 tty->print_cr("========================================"); 2813 tty->print_cr("%s", msg); 2814 tty->cr(); 2815 } 2816 2817 ~PrintRSetsClosure() { 2818 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2819 tty->print_cr("========================================"); 2820 tty->cr(); 2821 } 2822 }; 2823 2824 void G1CollectedHeap::print_cset_rsets() { 2825 PrintRSetsClosure cl("Printing CSet RSets"); 2826 collection_set_iterate(&cl); 2827 } 2828 2829 void G1CollectedHeap::print_all_rsets() { 2830 PrintRSetsClosure cl("Printing All RSets");; 2831 heap_region_iterate(&cl); 2832 } 2833 #endif // PRODUCT 2834 2835 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2836 YoungList* young_list = heap()->young_list(); 2837 2838 size_t eden_used_bytes = young_list->eden_used_bytes(); 2839 size_t survivor_used_bytes = young_list->survivor_used_bytes(); 2840 2841 size_t eden_capacity_bytes = 2842 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2843 2844 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2845 return G1HeapSummary(heap_summary, used(), eden_used_bytes, eden_capacity_bytes, survivor_used_bytes, num_regions()); 2846 } 2847 2848 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2849 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2850 stats->unused(), stats->used(), stats->region_end_waste(), 2851 stats->regions_filled(), stats->direct_allocated(), 2852 stats->failure_used(), stats->failure_waste()); 2853 } 2854 2855 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2856 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2857 gc_tracer->report_gc_heap_summary(when, heap_summary); 2858 2859 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2860 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2861 } 2862 2863 2864 G1CollectedHeap* G1CollectedHeap::heap() { 2865 CollectedHeap* heap = Universe::heap(); 2866 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2867 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2868 return (G1CollectedHeap*)heap; 2869 } 2870 2871 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 2872 // always_do_update_barrier = false; 2873 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2874 // Fill TLAB's and such 2875 accumulate_statistics_all_tlabs(); 2876 ensure_parsability(true); 2877 2878 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2879 } 2880 2881 void G1CollectedHeap::gc_epilogue(bool full) { 2882 // we are at the end of the GC. Total collections has already been increased. 2883 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2884 2885 // FIXME: what is this about? 2886 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2887 // is set. 2888 #if defined(COMPILER2) || INCLUDE_JVMCI 2889 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2890 #endif 2891 // always_do_update_barrier = true; 2892 2893 resize_all_tlabs(); 2894 allocation_context_stats().update(full); 2895 2896 // We have just completed a GC. Update the soft reference 2897 // policy with the new heap occupancy 2898 Universe::update_heap_info_at_gc(); 2899 } 2900 2901 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2902 uint gc_count_before, 2903 bool* succeeded, 2904 GCCause::Cause gc_cause) { 2905 assert_heap_not_locked_and_not_at_safepoint(); 2906 VM_G1IncCollectionPause op(gc_count_before, 2907 word_size, 2908 false, /* should_initiate_conc_mark */ 2909 g1_policy()->max_pause_time_ms(), 2910 gc_cause); 2911 2912 op.set_allocation_context(AllocationContext::current()); 2913 VMThread::execute(&op); 2914 2915 HeapWord* result = op.result(); 2916 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2917 assert(result == NULL || ret_succeeded, 2918 "the result should be NULL if the VM did not succeed"); 2919 *succeeded = ret_succeeded; 2920 2921 assert_heap_not_locked(); 2922 return result; 2923 } 2924 2925 void 2926 G1CollectedHeap::doConcurrentMark() { 2927 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2928 if (!_cmThread->in_progress()) { 2929 _cmThread->set_started(); 2930 CGC_lock->notify(); 2931 } 2932 } 2933 2934 size_t G1CollectedHeap::pending_card_num() { 2935 size_t extra_cards = 0; 2936 JavaThread *curr = Threads::first(); 2937 while (curr != NULL) { 2938 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2939 extra_cards += dcq.size(); 2940 curr = curr->next(); 2941 } 2942 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2943 size_t buffer_size = dcqs.buffer_size(); 2944 size_t buffer_num = dcqs.completed_buffers_num(); 2945 2946 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 2947 // in bytes - not the number of 'entries'. We need to convert 2948 // into a number of cards. 2949 return (buffer_size * buffer_num + extra_cards) / oopSize; 2950 } 2951 2952 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2953 private: 2954 size_t _total_humongous; 2955 size_t _candidate_humongous; 2956 2957 DirtyCardQueue _dcq; 2958 2959 // We don't nominate objects with many remembered set entries, on 2960 // the assumption that such objects are likely still live. 2961 bool is_remset_small(HeapRegion* region) const { 2962 HeapRegionRemSet* const rset = region->rem_set(); 2963 return G1EagerReclaimHumongousObjectsWithStaleRefs 2964 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2965 : rset->is_empty(); 2966 } 2967 2968 bool is_typeArray_region(HeapRegion* region) const { 2969 return oop(region->bottom())->is_typeArray(); 2970 } 2971 2972 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2973 assert(region->is_starts_humongous(), "Must start a humongous object"); 2974 2975 // Candidate selection must satisfy the following constraints 2976 // while concurrent marking is in progress: 2977 // 2978 // * In order to maintain SATB invariants, an object must not be 2979 // reclaimed if it was allocated before the start of marking and 2980 // has not had its references scanned. Such an object must have 2981 // its references (including type metadata) scanned to ensure no 2982 // live objects are missed by the marking process. Objects 2983 // allocated after the start of concurrent marking don't need to 2984 // be scanned. 2985 // 2986 // * An object must not be reclaimed if it is on the concurrent 2987 // mark stack. Objects allocated after the start of concurrent 2988 // marking are never pushed on the mark stack. 2989 // 2990 // Nominating only objects allocated after the start of concurrent 2991 // marking is sufficient to meet both constraints. This may miss 2992 // some objects that satisfy the constraints, but the marking data 2993 // structures don't support efficiently performing the needed 2994 // additional tests or scrubbing of the mark stack. 2995 // 2996 // However, we presently only nominate is_typeArray() objects. 2997 // A humongous object containing references induces remembered 2998 // set entries on other regions. In order to reclaim such an 2999 // object, those remembered sets would need to be cleaned up. 3000 // 3001 // We also treat is_typeArray() objects specially, allowing them 3002 // to be reclaimed even if allocated before the start of 3003 // concurrent mark. For this we rely on mark stack insertion to 3004 // exclude is_typeArray() objects, preventing reclaiming an object 3005 // that is in the mark stack. We also rely on the metadata for 3006 // such objects to be built-in and so ensured to be kept live. 3007 // Frequent allocation and drop of large binary blobs is an 3008 // important use case for eager reclaim, and this special handling 3009 // may reduce needed headroom. 3010 3011 return is_typeArray_region(region) && is_remset_small(region); 3012 } 3013 3014 public: 3015 RegisterHumongousWithInCSetFastTestClosure() 3016 : _total_humongous(0), 3017 _candidate_humongous(0), 3018 _dcq(&JavaThread::dirty_card_queue_set()) { 3019 } 3020 3021 virtual bool doHeapRegion(HeapRegion* r) { 3022 if (!r->is_starts_humongous()) { 3023 return false; 3024 } 3025 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3026 3027 bool is_candidate = humongous_region_is_candidate(g1h, r); 3028 uint rindex = r->hrm_index(); 3029 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 3030 if (is_candidate) { 3031 _candidate_humongous++; 3032 g1h->register_humongous_region_with_cset(rindex); 3033 // Is_candidate already filters out humongous object with large remembered sets. 3034 // If we have a humongous object with a few remembered sets, we simply flush these 3035 // remembered set entries into the DCQS. That will result in automatic 3036 // re-evaluation of their remembered set entries during the following evacuation 3037 // phase. 3038 if (!r->rem_set()->is_empty()) { 3039 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 3040 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 3041 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 3042 HeapRegionRemSetIterator hrrs(r->rem_set()); 3043 size_t card_index; 3044 while (hrrs.has_next(card_index)) { 3045 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 3046 // The remembered set might contain references to already freed 3047 // regions. Filter out such entries to avoid failing card table 3048 // verification. 3049 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 3050 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 3051 *card_ptr = CardTableModRefBS::dirty_card_val(); 3052 _dcq.enqueue(card_ptr); 3053 } 3054 } 3055 } 3056 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 3057 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 3058 hrrs.n_yielded(), r->rem_set()->occupied()); 3059 r->rem_set()->clear_locked(); 3060 } 3061 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 3062 } 3063 _total_humongous++; 3064 3065 return false; 3066 } 3067 3068 size_t total_humongous() const { return _total_humongous; } 3069 size_t candidate_humongous() const { return _candidate_humongous; } 3070 3071 void flush_rem_set_entries() { _dcq.flush(); } 3072 }; 3073 3074 void G1CollectedHeap::register_humongous_regions_with_cset() { 3075 if (!G1EagerReclaimHumongousObjects) { 3076 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 3077 return; 3078 } 3079 double time = os::elapsed_counter(); 3080 3081 // Collect reclaim candidate information and register candidates with cset. 3082 RegisterHumongousWithInCSetFastTestClosure cl; 3083 heap_region_iterate(&cl); 3084 3085 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 3086 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 3087 cl.total_humongous(), 3088 cl.candidate_humongous()); 3089 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3090 3091 // Finally flush all remembered set entries to re-check into the global DCQS. 3092 cl.flush_rem_set_entries(); 3093 } 3094 3095 class VerifyRegionRemSetClosure : public HeapRegionClosure { 3096 public: 3097 bool doHeapRegion(HeapRegion* hr) { 3098 if (!hr->is_archive() && !hr->is_continues_humongous()) { 3099 hr->verify_rem_set(); 3100 } 3101 return false; 3102 } 3103 }; 3104 3105 #ifdef ASSERT 3106 class VerifyCSetClosure: public HeapRegionClosure { 3107 public: 3108 bool doHeapRegion(HeapRegion* hr) { 3109 // Here we check that the CSet region's RSet is ready for parallel 3110 // iteration. The fields that we'll verify are only manipulated 3111 // when the region is part of a CSet and is collected. Afterwards, 3112 // we reset these fields when we clear the region's RSet (when the 3113 // region is freed) so they are ready when the region is 3114 // re-allocated. The only exception to this is if there's an 3115 // evacuation failure and instead of freeing the region we leave 3116 // it in the heap. In that case, we reset these fields during 3117 // evacuation failure handling. 3118 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3119 3120 // Here's a good place to add any other checks we'd like to 3121 // perform on CSet regions. 3122 return false; 3123 } 3124 }; 3125 #endif // ASSERT 3126 3127 uint G1CollectedHeap::num_task_queues() const { 3128 return _task_queues->size(); 3129 } 3130 3131 #if TASKQUEUE_STATS 3132 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3133 st->print_raw_cr("GC Task Stats"); 3134 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3135 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3136 } 3137 3138 void G1CollectedHeap::print_taskqueue_stats() const { 3139 if (!log_develop_is_enabled(Trace, gc, task, stats)) { 3140 return; 3141 } 3142 LogHandle(gc, task, stats) log; 3143 ResourceMark rm; 3144 outputStream* st = log.trace_stream(); 3145 3146 print_taskqueue_stats_hdr(st); 3147 3148 TaskQueueStats totals; 3149 const uint n = num_task_queues(); 3150 for (uint i = 0; i < n; ++i) { 3151 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 3152 totals += task_queue(i)->stats; 3153 } 3154 st->print_raw("tot "); totals.print(st); st->cr(); 3155 3156 DEBUG_ONLY(totals.verify()); 3157 } 3158 3159 void G1CollectedHeap::reset_taskqueue_stats() { 3160 const uint n = num_task_queues(); 3161 for (uint i = 0; i < n; ++i) { 3162 task_queue(i)->stats.reset(); 3163 } 3164 } 3165 #endif // TASKQUEUE_STATS 3166 3167 void G1CollectedHeap::wait_for_root_region_scanning() { 3168 double scan_wait_start = os::elapsedTime(); 3169 // We have to wait until the CM threads finish scanning the 3170 // root regions as it's the only way to ensure that all the 3171 // objects on them have been correctly scanned before we start 3172 // moving them during the GC. 3173 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3174 double wait_time_ms = 0.0; 3175 if (waited) { 3176 double scan_wait_end = os::elapsedTime(); 3177 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3178 } 3179 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3180 } 3181 3182 bool 3183 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3184 assert_at_safepoint(true /* should_be_vm_thread */); 3185 guarantee(!is_gc_active(), "collection is not reentrant"); 3186 3187 if (GCLocker::check_active_before_gc()) { 3188 return false; 3189 } 3190 3191 _gc_timer_stw->register_gc_start(); 3192 3193 GCIdMark gc_id_mark; 3194 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3195 3196 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3197 ResourceMark rm; 3198 3199 wait_for_root_region_scanning(); 3200 3201 print_heap_before_gc(); 3202 trace_heap_before_gc(_gc_tracer_stw); 3203 3204 _verifier->verify_region_sets_optional(); 3205 _verifier->verify_dirty_young_regions(); 3206 3207 // This call will decide whether this pause is an initial-mark 3208 // pause. If it is, during_initial_mark_pause() will return true 3209 // for the duration of this pause. 3210 g1_policy()->decide_on_conc_mark_initiation(); 3211 3212 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3213 assert(!collector_state()->during_initial_mark_pause() || 3214 collector_state()->gcs_are_young(), "sanity"); 3215 3216 // We also do not allow mixed GCs during marking. 3217 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3218 3219 // Record whether this pause is an initial mark. When the current 3220 // thread has completed its logging output and it's safe to signal 3221 // the CM thread, the flag's value in the policy has been reset. 3222 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3223 3224 // Inner scope for scope based logging, timers, and stats collection 3225 { 3226 EvacuationInfo evacuation_info; 3227 3228 if (collector_state()->during_initial_mark_pause()) { 3229 // We are about to start a marking cycle, so we increment the 3230 // full collection counter. 3231 increment_old_marking_cycles_started(); 3232 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3233 } 3234 3235 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3236 3237 GCTraceCPUTime tcpu; 3238 3239 FormatBuffer<> gc_string("Pause "); 3240 if (collector_state()->during_initial_mark_pause()) { 3241 gc_string.append("Initial Mark"); 3242 } else if (collector_state()->gcs_are_young()) { 3243 gc_string.append("Young"); 3244 } else { 3245 gc_string.append("Mixed"); 3246 } 3247 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 3248 3249 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3250 workers()->active_workers(), 3251 Threads::number_of_non_daemon_threads()); 3252 workers()->set_active_workers(active_workers); 3253 3254 g1_policy()->note_gc_start(active_workers); 3255 3256 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3257 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3258 3259 // If the secondary_free_list is not empty, append it to the 3260 // free_list. No need to wait for the cleanup operation to finish; 3261 // the region allocation code will check the secondary_free_list 3262 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3263 // set, skip this step so that the region allocation code has to 3264 // get entries from the secondary_free_list. 3265 if (!G1StressConcRegionFreeing) { 3266 append_secondary_free_list_if_not_empty_with_lock(); 3267 } 3268 3269 G1HeapTransition heap_transition(this); 3270 size_t heap_used_bytes_before_gc = used(); 3271 3272 assert(check_young_list_well_formed(), "young list should be well formed"); 3273 3274 // Don't dynamically change the number of GC threads this early. A value of 3275 // 0 is used to indicate serial work. When parallel work is done, 3276 // it will be set. 3277 3278 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3279 IsGCActiveMark x; 3280 3281 gc_prologue(false); 3282 increment_total_collections(false /* full gc */); 3283 increment_gc_time_stamp(); 3284 3285 if (VerifyRememberedSets) { 3286 log_info(gc, verify)("[Verifying RemSets before GC]"); 3287 VerifyRegionRemSetClosure v_cl; 3288 heap_region_iterate(&v_cl); 3289 } 3290 3291 _verifier->verify_before_gc(); 3292 3293 _verifier->check_bitmaps("GC Start"); 3294 3295 #if defined(COMPILER2) || INCLUDE_JVMCI 3296 DerivedPointerTable::clear(); 3297 #endif 3298 3299 // Please see comment in g1CollectedHeap.hpp and 3300 // G1CollectedHeap::ref_processing_init() to see how 3301 // reference processing currently works in G1. 3302 3303 // Enable discovery in the STW reference processor 3304 if (g1_policy()->should_process_references()) { 3305 ref_processor_stw()->enable_discovery(); 3306 } else { 3307 ref_processor_stw()->disable_discovery(); 3308 } 3309 3310 { 3311 // We want to temporarily turn off discovery by the 3312 // CM ref processor, if necessary, and turn it back on 3313 // on again later if we do. Using a scoped 3314 // NoRefDiscovery object will do this. 3315 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3316 3317 // Forget the current alloc region (we might even choose it to be part 3318 // of the collection set!). 3319 _allocator->release_mutator_alloc_region(); 3320 3321 // This timing is only used by the ergonomics to handle our pause target. 3322 // It is unclear why this should not include the full pause. We will 3323 // investigate this in CR 7178365. 3324 // 3325 // Preserving the old comment here if that helps the investigation: 3326 // 3327 // The elapsed time induced by the start time below deliberately elides 3328 // the possible verification above. 3329 double sample_start_time_sec = os::elapsedTime(); 3330 3331 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3332 3333 if (collector_state()->during_initial_mark_pause()) { 3334 concurrent_mark()->checkpointRootsInitialPre(); 3335 } 3336 3337 g1_policy()->finalize_collection_set(target_pause_time_ms); 3338 3339 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3340 3341 // Make sure the remembered sets are up to date. This needs to be 3342 // done before register_humongous_regions_with_cset(), because the 3343 // remembered sets are used there to choose eager reclaim candidates. 3344 // If the remembered sets are not up to date we might miss some 3345 // entries that need to be handled. 3346 g1_rem_set()->cleanupHRRS(); 3347 3348 register_humongous_regions_with_cset(); 3349 3350 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3351 3352 _cm->note_start_of_gc(); 3353 // We call this after finalize_cset() to 3354 // ensure that the CSet has been finalized. 3355 _cm->verify_no_cset_oops(); 3356 3357 if (_hr_printer.is_active()) { 3358 HeapRegion* hr = collection_set()->head(); 3359 while (hr != NULL) { 3360 _hr_printer.cset(hr); 3361 hr = hr->next_in_collection_set(); 3362 } 3363 } 3364 3365 #ifdef ASSERT 3366 VerifyCSetClosure cl; 3367 collection_set_iterate(&cl); 3368 #endif // ASSERT 3369 3370 // Initialize the GC alloc regions. 3371 _allocator->init_gc_alloc_regions(evacuation_info); 3372 3373 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3374 pre_evacuate_collection_set(); 3375 3376 // Actually do the work... 3377 evacuate_collection_set(evacuation_info, &per_thread_states); 3378 3379 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3380 3381 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3382 free_collection_set(collection_set()->head(), evacuation_info, surviving_young_words); 3383 3384 eagerly_reclaim_humongous_regions(); 3385 3386 collection_set()->clear_head(); 3387 3388 // Start a new incremental collection set for the next pause. 3389 collection_set()->start_incremental_building(); 3390 3391 clear_cset_fast_test(); 3392 3393 // Don't check the whole heap at this point as the 3394 // GC alloc regions from this pause have been tagged 3395 // as survivors and moved on to the survivor list. 3396 // Survivor regions will fail the !is_young() check. 3397 assert(check_young_list_empty(false /* check_heap */), 3398 "young list should be empty"); 3399 3400 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3401 _young_list->first_survivor_region(), 3402 _young_list->last_survivor_region()); 3403 3404 _young_list->reset_auxilary_lists(); 3405 3406 if (evacuation_failed()) { 3407 set_used(recalculate_used()); 3408 if (_archive_allocator != NULL) { 3409 _archive_allocator->clear_used(); 3410 } 3411 for (uint i = 0; i < ParallelGCThreads; i++) { 3412 if (_evacuation_failed_info_array[i].has_failed()) { 3413 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3414 } 3415 } 3416 } else { 3417 // The "used" of the the collection set have already been subtracted 3418 // when they were freed. Add in the bytes evacuated. 3419 increase_used(g1_policy()->bytes_copied_during_gc()); 3420 } 3421 3422 if (collector_state()->during_initial_mark_pause()) { 3423 // We have to do this before we notify the CM threads that 3424 // they can start working to make sure that all the 3425 // appropriate initialization is done on the CM object. 3426 concurrent_mark()->checkpointRootsInitialPost(); 3427 collector_state()->set_mark_in_progress(true); 3428 // Note that we don't actually trigger the CM thread at 3429 // this point. We do that later when we're sure that 3430 // the current thread has completed its logging output. 3431 } 3432 3433 allocate_dummy_regions(); 3434 3435 _allocator->init_mutator_alloc_region(); 3436 3437 { 3438 size_t expand_bytes = g1_policy()->expansion_amount(); 3439 if (expand_bytes > 0) { 3440 size_t bytes_before = capacity(); 3441 // No need for an ergo logging here, 3442 // expansion_amount() does this when it returns a value > 0. 3443 double expand_ms; 3444 if (!expand(expand_bytes, &expand_ms)) { 3445 // We failed to expand the heap. Cannot do anything about it. 3446 } 3447 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3448 } 3449 } 3450 3451 // We redo the verification but now wrt to the new CSet which 3452 // has just got initialized after the previous CSet was freed. 3453 _cm->verify_no_cset_oops(); 3454 _cm->note_end_of_gc(); 3455 3456 // This timing is only used by the ergonomics to handle our pause target. 3457 // It is unclear why this should not include the full pause. We will 3458 // investigate this in CR 7178365. 3459 double sample_end_time_sec = os::elapsedTime(); 3460 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3461 size_t total_cards_scanned = per_thread_states.total_cards_scanned(); 3462 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3463 3464 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3465 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3466 3467 MemoryService::track_memory_usage(); 3468 3469 // In prepare_for_verify() below we'll need to scan the deferred 3470 // update buffers to bring the RSets up-to-date if 3471 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3472 // the update buffers we'll probably need to scan cards on the 3473 // regions we just allocated to (i.e., the GC alloc 3474 // regions). However, during the last GC we called 3475 // set_saved_mark() on all the GC alloc regions, so card 3476 // scanning might skip the [saved_mark_word()...top()] area of 3477 // those regions (i.e., the area we allocated objects into 3478 // during the last GC). But it shouldn't. Given that 3479 // saved_mark_word() is conditional on whether the GC time stamp 3480 // on the region is current or not, by incrementing the GC time 3481 // stamp here we invalidate all the GC time stamps on all the 3482 // regions and saved_mark_word() will simply return top() for 3483 // all the regions. This is a nicer way of ensuring this rather 3484 // than iterating over the regions and fixing them. In fact, the 3485 // GC time stamp increment here also ensures that 3486 // saved_mark_word() will return top() between pauses, i.e., 3487 // during concurrent refinement. So we don't need the 3488 // is_gc_active() check to decided which top to use when 3489 // scanning cards (see CR 7039627). 3490 increment_gc_time_stamp(); 3491 3492 if (VerifyRememberedSets) { 3493 log_info(gc, verify)("[Verifying RemSets after GC]"); 3494 VerifyRegionRemSetClosure v_cl; 3495 heap_region_iterate(&v_cl); 3496 } 3497 3498 _verifier->verify_after_gc(); 3499 _verifier->check_bitmaps("GC End"); 3500 3501 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3502 ref_processor_stw()->verify_no_references_recorded(); 3503 3504 // CM reference discovery will be re-enabled if necessary. 3505 } 3506 3507 #ifdef TRACESPINNING 3508 ParallelTaskTerminator::print_termination_counts(); 3509 #endif 3510 3511 gc_epilogue(false); 3512 } 3513 3514 // Print the remainder of the GC log output. 3515 if (evacuation_failed()) { 3516 log_info(gc)("To-space exhausted"); 3517 } 3518 3519 g1_policy()->print_phases(); 3520 heap_transition.print(); 3521 3522 // It is not yet to safe to tell the concurrent mark to 3523 // start as we have some optional output below. We don't want the 3524 // output from the concurrent mark thread interfering with this 3525 // logging output either. 3526 3527 _hrm.verify_optional(); 3528 _verifier->verify_region_sets_optional(); 3529 3530 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3531 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3532 3533 print_heap_after_gc(); 3534 trace_heap_after_gc(_gc_tracer_stw); 3535 3536 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3537 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3538 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3539 // before any GC notifications are raised. 3540 g1mm()->update_sizes(); 3541 3542 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3543 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3544 _gc_timer_stw->register_gc_end(); 3545 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3546 } 3547 // It should now be safe to tell the concurrent mark thread to start 3548 // without its logging output interfering with the logging output 3549 // that came from the pause. 3550 3551 if (should_start_conc_mark) { 3552 // CAUTION: after the doConcurrentMark() call below, 3553 // the concurrent marking thread(s) could be running 3554 // concurrently with us. Make sure that anything after 3555 // this point does not assume that we are the only GC thread 3556 // running. Note: of course, the actual marking work will 3557 // not start until the safepoint itself is released in 3558 // SuspendibleThreadSet::desynchronize(). 3559 doConcurrentMark(); 3560 } 3561 3562 return true; 3563 } 3564 3565 void G1CollectedHeap::restore_preserved_marks() { 3566 G1RestorePreservedMarksTask rpm_task(_preserved_objs); 3567 workers()->run_task(&rpm_task); 3568 } 3569 3570 void G1CollectedHeap::remove_self_forwarding_pointers() { 3571 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3572 workers()->run_task(&rsfp_task); 3573 } 3574 3575 void G1CollectedHeap::restore_after_evac_failure() { 3576 double remove_self_forwards_start = os::elapsedTime(); 3577 3578 remove_self_forwarding_pointers(); 3579 restore_preserved_marks(); 3580 3581 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3582 } 3583 3584 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3585 if (!_evacuation_failed) { 3586 _evacuation_failed = true; 3587 } 3588 3589 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3590 3591 // We want to call the "for_promotion_failure" version only in the 3592 // case of a promotion failure. 3593 if (m->must_be_preserved_for_promotion_failure(obj)) { 3594 OopAndMarkOop elem(obj, m); 3595 _preserved_objs[worker_id].push(elem); 3596 } 3597 } 3598 3599 bool G1ParEvacuateFollowersClosure::offer_termination() { 3600 G1ParScanThreadState* const pss = par_scan_state(); 3601 start_term_time(); 3602 const bool res = terminator()->offer_termination(); 3603 end_term_time(); 3604 return res; 3605 } 3606 3607 void G1ParEvacuateFollowersClosure::do_void() { 3608 G1ParScanThreadState* const pss = par_scan_state(); 3609 pss->trim_queue(); 3610 do { 3611 pss->steal_and_trim_queue(queues()); 3612 } while (!offer_termination()); 3613 } 3614 3615 class G1ParTask : public AbstractGangTask { 3616 protected: 3617 G1CollectedHeap* _g1h; 3618 G1ParScanThreadStateSet* _pss; 3619 RefToScanQueueSet* _queues; 3620 G1RootProcessor* _root_processor; 3621 ParallelTaskTerminator _terminator; 3622 uint _n_workers; 3623 3624 public: 3625 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3626 : AbstractGangTask("G1 collection"), 3627 _g1h(g1h), 3628 _pss(per_thread_states), 3629 _queues(task_queues), 3630 _root_processor(root_processor), 3631 _terminator(n_workers, _queues), 3632 _n_workers(n_workers) 3633 {} 3634 3635 void work(uint worker_id) { 3636 if (worker_id >= _n_workers) return; // no work needed this round 3637 3638 double start_sec = os::elapsedTime(); 3639 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3640 3641 { 3642 ResourceMark rm; 3643 HandleMark hm; 3644 3645 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3646 3647 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3648 pss->set_ref_processor(rp); 3649 3650 double start_strong_roots_sec = os::elapsedTime(); 3651 3652 _root_processor->evacuate_roots(pss->closures(), worker_id); 3653 3654 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss); 3655 3656 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3657 // treating the nmethods visited to act as roots for concurrent marking. 3658 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3659 // objects copied by the current evacuation. 3660 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl, 3661 pss->closures()->weak_codeblobs(), 3662 worker_id); 3663 3664 _pss->add_cards_scanned(worker_id, cards_scanned); 3665 3666 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3667 3668 double term_sec = 0.0; 3669 size_t evac_term_attempts = 0; 3670 { 3671 double start = os::elapsedTime(); 3672 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3673 evac.do_void(); 3674 3675 evac_term_attempts = evac.term_attempts(); 3676 term_sec = evac.term_time(); 3677 double elapsed_sec = os::elapsedTime() - start; 3678 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3679 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3680 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3681 } 3682 3683 assert(pss->queue_is_empty(), "should be empty"); 3684 3685 if (log_is_enabled(Debug, gc, task, stats)) { 3686 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3687 size_t lab_waste; 3688 size_t lab_undo_waste; 3689 pss->waste(lab_waste, lab_undo_waste); 3690 _g1h->print_termination_stats(worker_id, 3691 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3692 strong_roots_sec * 1000.0, /* strong roots time */ 3693 term_sec * 1000.0, /* evac term time */ 3694 evac_term_attempts, /* evac term attempts */ 3695 lab_waste, /* alloc buffer waste */ 3696 lab_undo_waste /* undo waste */ 3697 ); 3698 } 3699 3700 // Close the inner scope so that the ResourceMark and HandleMark 3701 // destructors are executed here and are included as part of the 3702 // "GC Worker Time". 3703 } 3704 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3705 } 3706 }; 3707 3708 void G1CollectedHeap::print_termination_stats_hdr() { 3709 log_debug(gc, task, stats)("GC Termination Stats"); 3710 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3711 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3712 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3713 } 3714 3715 void G1CollectedHeap::print_termination_stats(uint worker_id, 3716 double elapsed_ms, 3717 double strong_roots_ms, 3718 double term_ms, 3719 size_t term_attempts, 3720 size_t alloc_buffer_waste, 3721 size_t undo_waste) const { 3722 log_debug(gc, task, stats) 3723 ("%3d %9.2f %9.2f %6.2f " 3724 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3725 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3726 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3727 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3728 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3729 alloc_buffer_waste * HeapWordSize / K, 3730 undo_waste * HeapWordSize / K); 3731 } 3732 3733 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 3734 private: 3735 BoolObjectClosure* _is_alive; 3736 int _initial_string_table_size; 3737 int _initial_symbol_table_size; 3738 3739 bool _process_strings; 3740 int _strings_processed; 3741 int _strings_removed; 3742 3743 bool _process_symbols; 3744 int _symbols_processed; 3745 int _symbols_removed; 3746 3747 public: 3748 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 3749 AbstractGangTask("String/Symbol Unlinking"), 3750 _is_alive(is_alive), 3751 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3752 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 3753 3754 _initial_string_table_size = StringTable::the_table()->table_size(); 3755 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3756 if (process_strings) { 3757 StringTable::clear_parallel_claimed_index(); 3758 } 3759 if (process_symbols) { 3760 SymbolTable::clear_parallel_claimed_index(); 3761 } 3762 } 3763 3764 ~G1StringSymbolTableUnlinkTask() { 3765 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3766 "claim value %d after unlink less than initial string table size %d", 3767 StringTable::parallel_claimed_index(), _initial_string_table_size); 3768 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3769 "claim value %d after unlink less than initial symbol table size %d", 3770 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3771 3772 log_debug(gc, stringdedup)("Cleaned string and symbol table, " 3773 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3774 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3775 strings_processed(), strings_removed(), 3776 symbols_processed(), symbols_removed()); 3777 } 3778 3779 void work(uint worker_id) { 3780 int strings_processed = 0; 3781 int strings_removed = 0; 3782 int symbols_processed = 0; 3783 int symbols_removed = 0; 3784 if (_process_strings) { 3785 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3786 Atomic::add(strings_processed, &_strings_processed); 3787 Atomic::add(strings_removed, &_strings_removed); 3788 } 3789 if (_process_symbols) { 3790 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3791 Atomic::add(symbols_processed, &_symbols_processed); 3792 Atomic::add(symbols_removed, &_symbols_removed); 3793 } 3794 } 3795 3796 size_t strings_processed() const { return (size_t)_strings_processed; } 3797 size_t strings_removed() const { return (size_t)_strings_removed; } 3798 3799 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3800 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3801 }; 3802 3803 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3804 private: 3805 static Monitor* _lock; 3806 3807 BoolObjectClosure* const _is_alive; 3808 const bool _unloading_occurred; 3809 const uint _num_workers; 3810 3811 // Variables used to claim nmethods. 3812 nmethod* _first_nmethod; 3813 volatile nmethod* _claimed_nmethod; 3814 3815 // The list of nmethods that need to be processed by the second pass. 3816 volatile nmethod* _postponed_list; 3817 volatile uint _num_entered_barrier; 3818 3819 public: 3820 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3821 _is_alive(is_alive), 3822 _unloading_occurred(unloading_occurred), 3823 _num_workers(num_workers), 3824 _first_nmethod(NULL), 3825 _claimed_nmethod(NULL), 3826 _postponed_list(NULL), 3827 _num_entered_barrier(0) 3828 { 3829 nmethod::increase_unloading_clock(); 3830 // Get first alive nmethod 3831 NMethodIterator iter = NMethodIterator(); 3832 if(iter.next_alive()) { 3833 _first_nmethod = iter.method(); 3834 } 3835 _claimed_nmethod = (volatile nmethod*)_first_nmethod; 3836 } 3837 3838 ~G1CodeCacheUnloadingTask() { 3839 CodeCache::verify_clean_inline_caches(); 3840 3841 CodeCache::set_needs_cache_clean(false); 3842 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3843 3844 CodeCache::verify_icholder_relocations(); 3845 } 3846 3847 private: 3848 void add_to_postponed_list(nmethod* nm) { 3849 nmethod* old; 3850 do { 3851 old = (nmethod*)_postponed_list; 3852 nm->set_unloading_next(old); 3853 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 3854 } 3855 3856 void clean_nmethod(nmethod* nm) { 3857 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3858 3859 if (postponed) { 3860 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3861 add_to_postponed_list(nm); 3862 } 3863 3864 // Mark that this thread has been cleaned/unloaded. 3865 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3866 nm->set_unloading_clock(nmethod::global_unloading_clock()); 3867 } 3868 3869 void clean_nmethod_postponed(nmethod* nm) { 3870 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3871 } 3872 3873 static const int MaxClaimNmethods = 16; 3874 3875 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) { 3876 nmethod* first; 3877 NMethodIterator last; 3878 3879 do { 3880 *num_claimed_nmethods = 0; 3881 3882 first = (nmethod*)_claimed_nmethod; 3883 last = NMethodIterator(first); 3884 3885 if (first != NULL) { 3886 3887 for (int i = 0; i < MaxClaimNmethods; i++) { 3888 if (!last.next_alive()) { 3889 break; 3890 } 3891 claimed_nmethods[i] = last.method(); 3892 (*num_claimed_nmethods)++; 3893 } 3894 } 3895 3896 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 3897 } 3898 3899 nmethod* claim_postponed_nmethod() { 3900 nmethod* claim; 3901 nmethod* next; 3902 3903 do { 3904 claim = (nmethod*)_postponed_list; 3905 if (claim == NULL) { 3906 return NULL; 3907 } 3908 3909 next = claim->unloading_next(); 3910 3911 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 3912 3913 return claim; 3914 } 3915 3916 public: 3917 // Mark that we're done with the first pass of nmethod cleaning. 3918 void barrier_mark(uint worker_id) { 3919 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3920 _num_entered_barrier++; 3921 if (_num_entered_barrier == _num_workers) { 3922 ml.notify_all(); 3923 } 3924 } 3925 3926 // See if we have to wait for the other workers to 3927 // finish their first-pass nmethod cleaning work. 3928 void barrier_wait(uint worker_id) { 3929 if (_num_entered_barrier < _num_workers) { 3930 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3931 while (_num_entered_barrier < _num_workers) { 3932 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3933 } 3934 } 3935 } 3936 3937 // Cleaning and unloading of nmethods. Some work has to be postponed 3938 // to the second pass, when we know which nmethods survive. 3939 void work_first_pass(uint worker_id) { 3940 // The first nmethods is claimed by the first worker. 3941 if (worker_id == 0 && _first_nmethod != NULL) { 3942 clean_nmethod(_first_nmethod); 3943 _first_nmethod = NULL; 3944 } 3945 3946 int num_claimed_nmethods; 3947 nmethod* claimed_nmethods[MaxClaimNmethods]; 3948 3949 while (true) { 3950 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3951 3952 if (num_claimed_nmethods == 0) { 3953 break; 3954 } 3955 3956 for (int i = 0; i < num_claimed_nmethods; i++) { 3957 clean_nmethod(claimed_nmethods[i]); 3958 } 3959 } 3960 } 3961 3962 void work_second_pass(uint worker_id) { 3963 nmethod* nm; 3964 // Take care of postponed nmethods. 3965 while ((nm = claim_postponed_nmethod()) != NULL) { 3966 clean_nmethod_postponed(nm); 3967 } 3968 } 3969 }; 3970 3971 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3972 3973 class G1KlassCleaningTask : public StackObj { 3974 BoolObjectClosure* _is_alive; 3975 volatile jint _clean_klass_tree_claimed; 3976 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3977 3978 public: 3979 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3980 _is_alive(is_alive), 3981 _clean_klass_tree_claimed(0), 3982 _klass_iterator() { 3983 } 3984 3985 private: 3986 bool claim_clean_klass_tree_task() { 3987 if (_clean_klass_tree_claimed) { 3988 return false; 3989 } 3990 3991 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 3992 } 3993 3994 InstanceKlass* claim_next_klass() { 3995 Klass* klass; 3996 do { 3997 klass =_klass_iterator.next_klass(); 3998 } while (klass != NULL && !klass->is_instance_klass()); 3999 4000 // this can be null so don't call InstanceKlass::cast 4001 return static_cast<InstanceKlass*>(klass); 4002 } 4003 4004 public: 4005 4006 void clean_klass(InstanceKlass* ik) { 4007 ik->clean_weak_instanceklass_links(_is_alive); 4008 } 4009 4010 void work() { 4011 ResourceMark rm; 4012 4013 // One worker will clean the subklass/sibling klass tree. 4014 if (claim_clean_klass_tree_task()) { 4015 Klass::clean_subklass_tree(_is_alive); 4016 } 4017 4018 // All workers will help cleaning the classes, 4019 InstanceKlass* klass; 4020 while ((klass = claim_next_klass()) != NULL) { 4021 clean_klass(klass); 4022 } 4023 } 4024 }; 4025 4026 // To minimize the remark pause times, the tasks below are done in parallel. 4027 class G1ParallelCleaningTask : public AbstractGangTask { 4028 private: 4029 G1StringSymbolTableUnlinkTask _string_symbol_task; 4030 G1CodeCacheUnloadingTask _code_cache_task; 4031 G1KlassCleaningTask _klass_cleaning_task; 4032 4033 public: 4034 // The constructor is run in the VMThread. 4035 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 4036 AbstractGangTask("Parallel Cleaning"), 4037 _string_symbol_task(is_alive, process_strings, process_symbols), 4038 _code_cache_task(num_workers, is_alive, unloading_occurred), 4039 _klass_cleaning_task(is_alive) { 4040 } 4041 4042 // The parallel work done by all worker threads. 4043 void work(uint worker_id) { 4044 // Do first pass of code cache cleaning. 4045 _code_cache_task.work_first_pass(worker_id); 4046 4047 // Let the threads mark that the first pass is done. 4048 _code_cache_task.barrier_mark(worker_id); 4049 4050 // Clean the Strings and Symbols. 4051 _string_symbol_task.work(worker_id); 4052 4053 // Wait for all workers to finish the first code cache cleaning pass. 4054 _code_cache_task.barrier_wait(worker_id); 4055 4056 // Do the second code cache cleaning work, which realize on 4057 // the liveness information gathered during the first pass. 4058 _code_cache_task.work_second_pass(worker_id); 4059 4060 // Clean all klasses that were not unloaded. 4061 _klass_cleaning_task.work(); 4062 } 4063 }; 4064 4065 4066 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 4067 bool process_strings, 4068 bool process_symbols, 4069 bool class_unloading_occurred) { 4070 uint n_workers = workers()->active_workers(); 4071 4072 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 4073 n_workers, class_unloading_occurred); 4074 workers()->run_task(&g1_unlink_task); 4075 } 4076 4077 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 4078 bool process_strings, bool process_symbols) { 4079 { 4080 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 4081 workers()->run_task(&g1_unlink_task); 4082 } 4083 4084 if (G1StringDedup::is_enabled()) { 4085 G1StringDedup::unlink(is_alive); 4086 } 4087 } 4088 4089 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 4090 private: 4091 DirtyCardQueueSet* _queue; 4092 G1CollectedHeap* _g1h; 4093 public: 4094 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 4095 _queue(queue), _g1h(g1h) { } 4096 4097 virtual void work(uint worker_id) { 4098 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 4099 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 4100 4101 RedirtyLoggedCardTableEntryClosure cl(_g1h); 4102 _queue->par_apply_closure_to_all_completed_buffers(&cl); 4103 4104 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 4105 } 4106 }; 4107 4108 void G1CollectedHeap::redirty_logged_cards() { 4109 double redirty_logged_cards_start = os::elapsedTime(); 4110 4111 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 4112 dirty_card_queue_set().reset_for_par_iteration(); 4113 workers()->run_task(&redirty_task); 4114 4115 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 4116 dcq.merge_bufferlists(&dirty_card_queue_set()); 4117 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 4118 4119 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 4120 } 4121 4122 // Weak Reference Processing support 4123 4124 // An always "is_alive" closure that is used to preserve referents. 4125 // If the object is non-null then it's alive. Used in the preservation 4126 // of referent objects that are pointed to by reference objects 4127 // discovered by the CM ref processor. 4128 class G1AlwaysAliveClosure: public BoolObjectClosure { 4129 G1CollectedHeap* _g1; 4130 public: 4131 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4132 bool do_object_b(oop p) { 4133 if (p != NULL) { 4134 return true; 4135 } 4136 return false; 4137 } 4138 }; 4139 4140 bool G1STWIsAliveClosure::do_object_b(oop p) { 4141 // An object is reachable if it is outside the collection set, 4142 // or is inside and copied. 4143 return !_g1->is_in_cset(p) || p->is_forwarded(); 4144 } 4145 4146 // Non Copying Keep Alive closure 4147 class G1KeepAliveClosure: public OopClosure { 4148 G1CollectedHeap* _g1; 4149 public: 4150 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4151 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 4152 void do_oop(oop* p) { 4153 oop obj = *p; 4154 assert(obj != NULL, "the caller should have filtered out NULL values"); 4155 4156 const InCSetState cset_state = _g1->in_cset_state(obj); 4157 if (!cset_state.is_in_cset_or_humongous()) { 4158 return; 4159 } 4160 if (cset_state.is_in_cset()) { 4161 assert( obj->is_forwarded(), "invariant" ); 4162 *p = obj->forwardee(); 4163 } else { 4164 assert(!obj->is_forwarded(), "invariant" ); 4165 assert(cset_state.is_humongous(), 4166 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 4167 _g1->set_humongous_is_live(obj); 4168 } 4169 } 4170 }; 4171 4172 // Copying Keep Alive closure - can be called from both 4173 // serial and parallel code as long as different worker 4174 // threads utilize different G1ParScanThreadState instances 4175 // and different queues. 4176 4177 class G1CopyingKeepAliveClosure: public OopClosure { 4178 G1CollectedHeap* _g1h; 4179 OopClosure* _copy_non_heap_obj_cl; 4180 G1ParScanThreadState* _par_scan_state; 4181 4182 public: 4183 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4184 OopClosure* non_heap_obj_cl, 4185 G1ParScanThreadState* pss): 4186 _g1h(g1h), 4187 _copy_non_heap_obj_cl(non_heap_obj_cl), 4188 _par_scan_state(pss) 4189 {} 4190 4191 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4192 virtual void do_oop( oop* p) { do_oop_work(p); } 4193 4194 template <class T> void do_oop_work(T* p) { 4195 oop obj = oopDesc::load_decode_heap_oop(p); 4196 4197 if (_g1h->is_in_cset_or_humongous(obj)) { 4198 // If the referent object has been forwarded (either copied 4199 // to a new location or to itself in the event of an 4200 // evacuation failure) then we need to update the reference 4201 // field and, if both reference and referent are in the G1 4202 // heap, update the RSet for the referent. 4203 // 4204 // If the referent has not been forwarded then we have to keep 4205 // it alive by policy. Therefore we have copy the referent. 4206 // 4207 // If the reference field is in the G1 heap then we can push 4208 // on the PSS queue. When the queue is drained (after each 4209 // phase of reference processing) the object and it's followers 4210 // will be copied, the reference field set to point to the 4211 // new location, and the RSet updated. Otherwise we need to 4212 // use the the non-heap or metadata closures directly to copy 4213 // the referent object and update the pointer, while avoiding 4214 // updating the RSet. 4215 4216 if (_g1h->is_in_g1_reserved(p)) { 4217 _par_scan_state->push_on_queue(p); 4218 } else { 4219 assert(!Metaspace::contains((const void*)p), 4220 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4221 _copy_non_heap_obj_cl->do_oop(p); 4222 } 4223 } 4224 } 4225 }; 4226 4227 // Serial drain queue closure. Called as the 'complete_gc' 4228 // closure for each discovered list in some of the 4229 // reference processing phases. 4230 4231 class G1STWDrainQueueClosure: public VoidClosure { 4232 protected: 4233 G1CollectedHeap* _g1h; 4234 G1ParScanThreadState* _par_scan_state; 4235 4236 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4237 4238 public: 4239 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4240 _g1h(g1h), 4241 _par_scan_state(pss) 4242 { } 4243 4244 void do_void() { 4245 G1ParScanThreadState* const pss = par_scan_state(); 4246 pss->trim_queue(); 4247 } 4248 }; 4249 4250 // Parallel Reference Processing closures 4251 4252 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4253 // processing during G1 evacuation pauses. 4254 4255 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4256 private: 4257 G1CollectedHeap* _g1h; 4258 G1ParScanThreadStateSet* _pss; 4259 RefToScanQueueSet* _queues; 4260 WorkGang* _workers; 4261 uint _active_workers; 4262 4263 public: 4264 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4265 G1ParScanThreadStateSet* per_thread_states, 4266 WorkGang* workers, 4267 RefToScanQueueSet *task_queues, 4268 uint n_workers) : 4269 _g1h(g1h), 4270 _pss(per_thread_states), 4271 _queues(task_queues), 4272 _workers(workers), 4273 _active_workers(n_workers) 4274 { 4275 assert(n_workers > 0, "shouldn't call this otherwise"); 4276 } 4277 4278 // Executes the given task using concurrent marking worker threads. 4279 virtual void execute(ProcessTask& task); 4280 virtual void execute(EnqueueTask& task); 4281 }; 4282 4283 // Gang task for possibly parallel reference processing 4284 4285 class G1STWRefProcTaskProxy: public AbstractGangTask { 4286 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4287 ProcessTask& _proc_task; 4288 G1CollectedHeap* _g1h; 4289 G1ParScanThreadStateSet* _pss; 4290 RefToScanQueueSet* _task_queues; 4291 ParallelTaskTerminator* _terminator; 4292 4293 public: 4294 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4295 G1CollectedHeap* g1h, 4296 G1ParScanThreadStateSet* per_thread_states, 4297 RefToScanQueueSet *task_queues, 4298 ParallelTaskTerminator* terminator) : 4299 AbstractGangTask("Process reference objects in parallel"), 4300 _proc_task(proc_task), 4301 _g1h(g1h), 4302 _pss(per_thread_states), 4303 _task_queues(task_queues), 4304 _terminator(terminator) 4305 {} 4306 4307 virtual void work(uint worker_id) { 4308 // The reference processing task executed by a single worker. 4309 ResourceMark rm; 4310 HandleMark hm; 4311 4312 G1STWIsAliveClosure is_alive(_g1h); 4313 4314 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4315 pss->set_ref_processor(NULL); 4316 4317 // Keep alive closure. 4318 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4319 4320 // Complete GC closure 4321 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4322 4323 // Call the reference processing task's work routine. 4324 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4325 4326 // Note we cannot assert that the refs array is empty here as not all 4327 // of the processing tasks (specifically phase2 - pp2_work) execute 4328 // the complete_gc closure (which ordinarily would drain the queue) so 4329 // the queue may not be empty. 4330 } 4331 }; 4332 4333 // Driver routine for parallel reference processing. 4334 // Creates an instance of the ref processing gang 4335 // task and has the worker threads execute it. 4336 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4337 assert(_workers != NULL, "Need parallel worker threads."); 4338 4339 ParallelTaskTerminator terminator(_active_workers, _queues); 4340 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4341 4342 _workers->run_task(&proc_task_proxy); 4343 } 4344 4345 // Gang task for parallel reference enqueueing. 4346 4347 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4348 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4349 EnqueueTask& _enq_task; 4350 4351 public: 4352 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4353 AbstractGangTask("Enqueue reference objects in parallel"), 4354 _enq_task(enq_task) 4355 { } 4356 4357 virtual void work(uint worker_id) { 4358 _enq_task.work(worker_id); 4359 } 4360 }; 4361 4362 // Driver routine for parallel reference enqueueing. 4363 // Creates an instance of the ref enqueueing gang 4364 // task and has the worker threads execute it. 4365 4366 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4367 assert(_workers != NULL, "Need parallel worker threads."); 4368 4369 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4370 4371 _workers->run_task(&enq_task_proxy); 4372 } 4373 4374 // End of weak reference support closures 4375 4376 // Abstract task used to preserve (i.e. copy) any referent objects 4377 // that are in the collection set and are pointed to by reference 4378 // objects discovered by the CM ref processor. 4379 4380 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4381 protected: 4382 G1CollectedHeap* _g1h; 4383 G1ParScanThreadStateSet* _pss; 4384 RefToScanQueueSet* _queues; 4385 ParallelTaskTerminator _terminator; 4386 uint _n_workers; 4387 4388 public: 4389 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4390 AbstractGangTask("ParPreserveCMReferents"), 4391 _g1h(g1h), 4392 _pss(per_thread_states), 4393 _queues(task_queues), 4394 _terminator(workers, _queues), 4395 _n_workers(workers) 4396 { } 4397 4398 void work(uint worker_id) { 4399 ResourceMark rm; 4400 HandleMark hm; 4401 4402 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4403 pss->set_ref_processor(NULL); 4404 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4405 4406 // Is alive closure 4407 G1AlwaysAliveClosure always_alive(_g1h); 4408 4409 // Copying keep alive closure. Applied to referent objects that need 4410 // to be copied. 4411 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4412 4413 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4414 4415 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4416 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4417 4418 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4419 // So this must be true - but assert just in case someone decides to 4420 // change the worker ids. 4421 assert(worker_id < limit, "sanity"); 4422 assert(!rp->discovery_is_atomic(), "check this code"); 4423 4424 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4425 for (uint idx = worker_id; idx < limit; idx += stride) { 4426 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4427 4428 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4429 while (iter.has_next()) { 4430 // Since discovery is not atomic for the CM ref processor, we 4431 // can see some null referent objects. 4432 iter.load_ptrs(DEBUG_ONLY(true)); 4433 oop ref = iter.obj(); 4434 4435 // This will filter nulls. 4436 if (iter.is_referent_alive()) { 4437 iter.make_referent_alive(); 4438 } 4439 iter.move_to_next(); 4440 } 4441 } 4442 4443 // Drain the queue - which may cause stealing 4444 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4445 drain_queue.do_void(); 4446 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4447 assert(pss->queue_is_empty(), "should be"); 4448 } 4449 }; 4450 4451 void G1CollectedHeap::process_weak_jni_handles() { 4452 double ref_proc_start = os::elapsedTime(); 4453 4454 G1STWIsAliveClosure is_alive(this); 4455 G1KeepAliveClosure keep_alive(this); 4456 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 4457 4458 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4459 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4460 } 4461 4462 // Weak Reference processing during an evacuation pause (part 1). 4463 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4464 double ref_proc_start = os::elapsedTime(); 4465 4466 ReferenceProcessor* rp = _ref_processor_stw; 4467 assert(rp->discovery_enabled(), "should have been enabled"); 4468 4469 // Any reference objects, in the collection set, that were 'discovered' 4470 // by the CM ref processor should have already been copied (either by 4471 // applying the external root copy closure to the discovered lists, or 4472 // by following an RSet entry). 4473 // 4474 // But some of the referents, that are in the collection set, that these 4475 // reference objects point to may not have been copied: the STW ref 4476 // processor would have seen that the reference object had already 4477 // been 'discovered' and would have skipped discovering the reference, 4478 // but would not have treated the reference object as a regular oop. 4479 // As a result the copy closure would not have been applied to the 4480 // referent object. 4481 // 4482 // We need to explicitly copy these referent objects - the references 4483 // will be processed at the end of remarking. 4484 // 4485 // We also need to do this copying before we process the reference 4486 // objects discovered by the STW ref processor in case one of these 4487 // referents points to another object which is also referenced by an 4488 // object discovered by the STW ref processor. 4489 4490 uint no_of_gc_workers = workers()->active_workers(); 4491 4492 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4493 per_thread_states, 4494 no_of_gc_workers, 4495 _task_queues); 4496 4497 workers()->run_task(&keep_cm_referents); 4498 4499 // Closure to test whether a referent is alive. 4500 G1STWIsAliveClosure is_alive(this); 4501 4502 // Even when parallel reference processing is enabled, the processing 4503 // of JNI refs is serial and performed serially by the current thread 4504 // rather than by a worker. The following PSS will be used for processing 4505 // JNI refs. 4506 4507 // Use only a single queue for this PSS. 4508 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4509 pss->set_ref_processor(NULL); 4510 assert(pss->queue_is_empty(), "pre-condition"); 4511 4512 // Keep alive closure. 4513 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4514 4515 // Serial Complete GC closure 4516 G1STWDrainQueueClosure drain_queue(this, pss); 4517 4518 // Setup the soft refs policy... 4519 rp->setup_policy(false); 4520 4521 ReferenceProcessorStats stats; 4522 if (!rp->processing_is_mt()) { 4523 // Serial reference processing... 4524 stats = rp->process_discovered_references(&is_alive, 4525 &keep_alive, 4526 &drain_queue, 4527 NULL, 4528 _gc_timer_stw); 4529 } else { 4530 // Parallel reference processing 4531 assert(rp->num_q() == no_of_gc_workers, "sanity"); 4532 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 4533 4534 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4535 stats = rp->process_discovered_references(&is_alive, 4536 &keep_alive, 4537 &drain_queue, 4538 &par_task_executor, 4539 _gc_timer_stw); 4540 } 4541 4542 _gc_tracer_stw->report_gc_reference_stats(stats); 4543 4544 // We have completed copying any necessary live referent objects. 4545 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4546 4547 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4548 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4549 } 4550 4551 // Weak Reference processing during an evacuation pause (part 2). 4552 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4553 double ref_enq_start = os::elapsedTime(); 4554 4555 ReferenceProcessor* rp = _ref_processor_stw; 4556 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4557 4558 // Now enqueue any remaining on the discovered lists on to 4559 // the pending list. 4560 if (!rp->processing_is_mt()) { 4561 // Serial reference processing... 4562 rp->enqueue_discovered_references(); 4563 } else { 4564 // Parallel reference enqueueing 4565 4566 uint n_workers = workers()->active_workers(); 4567 4568 assert(rp->num_q() == n_workers, "sanity"); 4569 assert(n_workers <= rp->max_num_q(), "sanity"); 4570 4571 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4572 rp->enqueue_discovered_references(&par_task_executor); 4573 } 4574 4575 rp->verify_no_references_recorded(); 4576 assert(!rp->discovery_enabled(), "should have been disabled"); 4577 4578 // FIXME 4579 // CM's reference processing also cleans up the string and symbol tables. 4580 // Should we do that here also? We could, but it is a serial operation 4581 // and could significantly increase the pause time. 4582 4583 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4584 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4585 } 4586 4587 void G1CollectedHeap::pre_evacuate_collection_set() { 4588 _expand_heap_after_alloc_failure = true; 4589 _evacuation_failed = false; 4590 4591 // Disable the hot card cache. 4592 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 4593 hot_card_cache->reset_hot_cache_claimed_index(); 4594 hot_card_cache->set_use_cache(false); 4595 4596 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4597 } 4598 4599 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4600 // Should G1EvacuationFailureALot be in effect for this GC? 4601 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4602 4603 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4604 double start_par_time_sec = os::elapsedTime(); 4605 double end_par_time_sec; 4606 4607 { 4608 const uint n_workers = workers()->active_workers(); 4609 G1RootProcessor root_processor(this, n_workers); 4610 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4611 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4612 if (collector_state()->during_initial_mark_pause()) { 4613 ClassLoaderDataGraph::clear_claimed_marks(); 4614 } 4615 4616 print_termination_stats_hdr(); 4617 4618 workers()->run_task(&g1_par_task); 4619 end_par_time_sec = os::elapsedTime(); 4620 4621 // Closing the inner scope will execute the destructor 4622 // for the G1RootProcessor object. We record the current 4623 // elapsed time before closing the scope so that time 4624 // taken for the destructor is NOT included in the 4625 // reported parallel time. 4626 } 4627 4628 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4629 4630 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4631 phase_times->record_par_time(par_time_ms); 4632 4633 double code_root_fixup_time_ms = 4634 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4635 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4636 } 4637 4638 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4639 // Process any discovered reference objects - we have 4640 // to do this _before_ we retire the GC alloc regions 4641 // as we may have to copy some 'reachable' referent 4642 // objects (and their reachable sub-graphs) that were 4643 // not copied during the pause. 4644 if (g1_policy()->should_process_references()) { 4645 process_discovered_references(per_thread_states); 4646 } else { 4647 ref_processor_stw()->verify_no_references_recorded(); 4648 process_weak_jni_handles(); 4649 } 4650 4651 if (G1StringDedup::is_enabled()) { 4652 double fixup_start = os::elapsedTime(); 4653 4654 G1STWIsAliveClosure is_alive(this); 4655 G1KeepAliveClosure keep_alive(this); 4656 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4657 4658 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4659 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4660 } 4661 4662 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4663 4664 if (evacuation_failed()) { 4665 restore_after_evac_failure(); 4666 4667 // Reset the G1EvacuationFailureALot counters and flags 4668 // Note: the values are reset only when an actual 4669 // evacuation failure occurs. 4670 NOT_PRODUCT(reset_evacuation_should_fail();) 4671 } 4672 4673 // Enqueue any remaining references remaining on the STW 4674 // reference processor's discovered lists. We need to do 4675 // this after the card table is cleaned (and verified) as 4676 // the act of enqueueing entries on to the pending list 4677 // will log these updates (and dirty their associated 4678 // cards). We need these updates logged to update any 4679 // RSets. 4680 if (g1_policy()->should_process_references()) { 4681 enqueue_discovered_references(per_thread_states); 4682 } else { 4683 g1_policy()->phase_times()->record_ref_enq_time(0); 4684 } 4685 4686 _allocator->release_gc_alloc_regions(evacuation_info); 4687 4688 per_thread_states->flush(); 4689 4690 record_obj_copy_mem_stats(); 4691 4692 _survivor_evac_stats.adjust_desired_plab_sz(); 4693 _old_evac_stats.adjust_desired_plab_sz(); 4694 4695 // Reset and re-enable the hot card cache. 4696 // Note the counts for the cards in the regions in the 4697 // collection set are reset when the collection set is freed. 4698 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 4699 hot_card_cache->reset_hot_cache(); 4700 hot_card_cache->set_use_cache(true); 4701 4702 purge_code_root_memory(); 4703 4704 redirty_logged_cards(); 4705 #if defined(COMPILER2) || INCLUDE_JVMCI 4706 DerivedPointerTable::update_pointers(); 4707 #endif 4708 } 4709 4710 void G1CollectedHeap::record_obj_copy_mem_stats() { 4711 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4712 4713 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4714 create_g1_evac_summary(&_old_evac_stats)); 4715 } 4716 4717 void G1CollectedHeap::free_region(HeapRegion* hr, 4718 FreeRegionList* free_list, 4719 bool par, 4720 bool locked) { 4721 assert(!hr->is_free(), "the region should not be free"); 4722 assert(!hr->is_empty(), "the region should not be empty"); 4723 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4724 assert(free_list != NULL, "pre-condition"); 4725 4726 if (G1VerifyBitmaps) { 4727 MemRegion mr(hr->bottom(), hr->end()); 4728 concurrent_mark()->clearRangePrevBitmap(mr); 4729 } 4730 4731 // Clear the card counts for this region. 4732 // Note: we only need to do this if the region is not young 4733 // (since we don't refine cards in young regions). 4734 if (!hr->is_young()) { 4735 _cg1r->hot_card_cache()->reset_card_counts(hr); 4736 } 4737 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 4738 free_list->add_ordered(hr); 4739 } 4740 4741 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4742 FreeRegionList* free_list, 4743 bool par) { 4744 assert(hr->is_humongous(), "this is only for humongous regions"); 4745 assert(free_list != NULL, "pre-condition"); 4746 hr->clear_humongous(); 4747 free_region(hr, free_list, par); 4748 } 4749 4750 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4751 const uint humongous_regions_removed) { 4752 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4753 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4754 _old_set.bulk_remove(old_regions_removed); 4755 _humongous_set.bulk_remove(humongous_regions_removed); 4756 } 4757 4758 } 4759 4760 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4761 assert(list != NULL, "list can't be null"); 4762 if (!list->is_empty()) { 4763 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4764 _hrm.insert_list_into_free_list(list); 4765 } 4766 } 4767 4768 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4769 decrease_used(bytes); 4770 } 4771 4772 class G1ParCleanupCTTask : public AbstractGangTask { 4773 G1SATBCardTableModRefBS* _ct_bs; 4774 G1CollectedHeap* _g1h; 4775 HeapRegion* volatile _su_head; 4776 public: 4777 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 4778 G1CollectedHeap* g1h) : 4779 AbstractGangTask("G1 Par Cleanup CT Task"), 4780 _ct_bs(ct_bs), _g1h(g1h) { } 4781 4782 void work(uint worker_id) { 4783 HeapRegion* r; 4784 while (r = _g1h->pop_dirty_cards_region()) { 4785 clear_cards(r); 4786 } 4787 } 4788 4789 void clear_cards(HeapRegion* r) { 4790 // Cards of the survivors should have already been dirtied. 4791 if (!r->is_survivor()) { 4792 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 4793 } 4794 } 4795 }; 4796 4797 class G1ParScrubRemSetTask: public AbstractGangTask { 4798 protected: 4799 G1RemSet* _g1rs; 4800 BitMap* _region_bm; 4801 BitMap* _card_bm; 4802 HeapRegionClaimer _hrclaimer; 4803 4804 public: 4805 G1ParScrubRemSetTask(G1RemSet* g1_rs, BitMap* region_bm, BitMap* card_bm, uint num_workers) : 4806 AbstractGangTask("G1 ScrubRS"), 4807 _g1rs(g1_rs), 4808 _region_bm(region_bm), 4809 _card_bm(card_bm), 4810 _hrclaimer(num_workers) { 4811 } 4812 4813 void work(uint worker_id) { 4814 _g1rs->scrub(_region_bm, _card_bm, worker_id, &_hrclaimer); 4815 } 4816 }; 4817 4818 void G1CollectedHeap::scrub_rem_set(BitMap* region_bm, BitMap* card_bm) { 4819 uint num_workers = workers()->active_workers(); 4820 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), region_bm, card_bm, num_workers); 4821 workers()->run_task(&g1_par_scrub_rs_task); 4822 } 4823 4824 void G1CollectedHeap::cleanUpCardTable() { 4825 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 4826 double start = os::elapsedTime(); 4827 4828 { 4829 // Iterate over the dirty cards region list. 4830 G1ParCleanupCTTask cleanup_task(ct_bs, this); 4831 4832 workers()->run_task(&cleanup_task); 4833 #ifndef PRODUCT 4834 _verifier->verify_card_table_cleanup(); 4835 #endif 4836 } 4837 4838 double elapsed = os::elapsedTime() - start; 4839 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 4840 } 4841 4842 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4843 size_t pre_used = 0; 4844 FreeRegionList local_free_list("Local List for CSet Freeing"); 4845 4846 double young_time_ms = 0.0; 4847 double non_young_time_ms = 0.0; 4848 4849 // Since the collection set is a superset of the the young list, 4850 // all we need to do to clear the young list is clear its 4851 // head and length, and unlink any young regions in the code below 4852 _young_list->clear(); 4853 4854 G1CollectorPolicy* policy = g1_policy(); 4855 4856 double start_sec = os::elapsedTime(); 4857 bool non_young = true; 4858 4859 HeapRegion* cur = cs_head; 4860 int age_bound = -1; 4861 size_t rs_lengths = 0; 4862 4863 while (cur != NULL) { 4864 assert(!is_on_master_free_list(cur), "sanity"); 4865 if (non_young) { 4866 if (cur->is_young()) { 4867 double end_sec = os::elapsedTime(); 4868 double elapsed_ms = (end_sec - start_sec) * 1000.0; 4869 non_young_time_ms += elapsed_ms; 4870 4871 start_sec = os::elapsedTime(); 4872 non_young = false; 4873 } 4874 } else { 4875 if (!cur->is_young()) { 4876 double end_sec = os::elapsedTime(); 4877 double elapsed_ms = (end_sec - start_sec) * 1000.0; 4878 young_time_ms += elapsed_ms; 4879 4880 start_sec = os::elapsedTime(); 4881 non_young = true; 4882 } 4883 } 4884 4885 rs_lengths += cur->rem_set()->occupied_locked(); 4886 4887 HeapRegion* next = cur->next_in_collection_set(); 4888 assert(cur->in_collection_set(), "bad CS"); 4889 cur->set_next_in_collection_set(NULL); 4890 clear_in_cset(cur); 4891 4892 if (cur->is_young()) { 4893 int index = cur->young_index_in_cset(); 4894 assert(index != -1, "invariant"); 4895 assert((uint) index < collection_set()->young_region_length(), "invariant"); 4896 size_t words_survived = surviving_young_words[index]; 4897 cur->record_surv_words_in_group(words_survived); 4898 4899 // At this point the we have 'popped' cur from the collection set 4900 // (linked via next_in_collection_set()) but it is still in the 4901 // young list (linked via next_young_region()). Clear the 4902 // _next_young_region field. 4903 cur->set_next_young_region(NULL); 4904 } else { 4905 int index = cur->young_index_in_cset(); 4906 assert(index == -1, "invariant"); 4907 } 4908 4909 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 4910 (!cur->is_young() && cur->young_index_in_cset() == -1), 4911 "invariant" ); 4912 4913 if (!cur->evacuation_failed()) { 4914 MemRegion used_mr = cur->used_region(); 4915 4916 // And the region is empty. 4917 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 4918 pre_used += cur->used(); 4919 free_region(cur, &local_free_list, false /* par */, true /* locked */); 4920 } else { 4921 cur->uninstall_surv_rate_group(); 4922 if (cur->is_young()) { 4923 cur->set_young_index_in_cset(-1); 4924 } 4925 cur->set_evacuation_failed(false); 4926 // When moving a young gen region to old gen, we "allocate" that whole region 4927 // there. This is in addition to any already evacuated objects. Notify the 4928 // policy about that. 4929 // Old gen regions do not cause an additional allocation: both the objects 4930 // still in the region and the ones already moved are accounted for elsewhere. 4931 if (cur->is_young()) { 4932 policy->add_bytes_allocated_in_old_since_last_gc(HeapRegion::GrainBytes); 4933 } 4934 // The region is now considered to be old. 4935 cur->set_old(); 4936 // Do some allocation statistics accounting. Regions that failed evacuation 4937 // are always made old, so there is no need to update anything in the young 4938 // gen statistics, but we need to update old gen statistics. 4939 size_t used_words = cur->marked_bytes() / HeapWordSize; 4940 _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words); 4941 _old_set.add(cur); 4942 evacuation_info.increment_collectionset_used_after(cur->used()); 4943 } 4944 cur = next; 4945 } 4946 4947 evacuation_info.set_regions_freed(local_free_list.length()); 4948 policy->record_max_rs_lengths(rs_lengths); 4949 policy->cset_regions_freed(); 4950 4951 double end_sec = os::elapsedTime(); 4952 double elapsed_ms = (end_sec - start_sec) * 1000.0; 4953 4954 if (non_young) { 4955 non_young_time_ms += elapsed_ms; 4956 } else { 4957 young_time_ms += elapsed_ms; 4958 } 4959 4960 prepend_to_freelist(&local_free_list); 4961 decrement_summary_bytes(pre_used); 4962 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 4963 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 4964 } 4965 4966 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4967 private: 4968 FreeRegionList* _free_region_list; 4969 HeapRegionSet* _proxy_set; 4970 uint _humongous_regions_removed; 4971 size_t _freed_bytes; 4972 public: 4973 4974 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4975 _free_region_list(free_region_list), _humongous_regions_removed(0), _freed_bytes(0) { 4976 } 4977 4978 virtual bool doHeapRegion(HeapRegion* r) { 4979 if (!r->is_starts_humongous()) { 4980 return false; 4981 } 4982 4983 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4984 4985 oop obj = (oop)r->bottom(); 4986 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 4987 4988 // The following checks whether the humongous object is live are sufficient. 4989 // The main additional check (in addition to having a reference from the roots 4990 // or the young gen) is whether the humongous object has a remembered set entry. 4991 // 4992 // A humongous object cannot be live if there is no remembered set for it 4993 // because: 4994 // - there can be no references from within humongous starts regions referencing 4995 // the object because we never allocate other objects into them. 4996 // (I.e. there are no intra-region references that may be missed by the 4997 // remembered set) 4998 // - as soon there is a remembered set entry to the humongous starts region 4999 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 5000 // until the end of a concurrent mark. 5001 // 5002 // It is not required to check whether the object has been found dead by marking 5003 // or not, in fact it would prevent reclamation within a concurrent cycle, as 5004 // all objects allocated during that time are considered live. 5005 // SATB marking is even more conservative than the remembered set. 5006 // So if at this point in the collection there is no remembered set entry, 5007 // nobody has a reference to it. 5008 // At the start of collection we flush all refinement logs, and remembered sets 5009 // are completely up-to-date wrt to references to the humongous object. 5010 // 5011 // Other implementation considerations: 5012 // - never consider object arrays at this time because they would pose 5013 // considerable effort for cleaning up the the remembered sets. This is 5014 // required because stale remembered sets might reference locations that 5015 // are currently allocated into. 5016 uint region_idx = r->hrm_index(); 5017 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 5018 !r->rem_set()->is_empty()) { 5019 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", 5020 region_idx, 5021 (size_t)obj->size() * HeapWordSize, 5022 p2i(r->bottom()), 5023 r->rem_set()->occupied(), 5024 r->rem_set()->strong_code_roots_list_length(), 5025 next_bitmap->isMarked(r->bottom()), 5026 g1h->is_humongous_reclaim_candidate(region_idx), 5027 obj->is_typeArray() 5028 ); 5029 return false; 5030 } 5031 5032 guarantee(obj->is_typeArray(), 5033 "Only eagerly reclaiming type arrays is supported, but the object " 5034 PTR_FORMAT " is not.", p2i(r->bottom())); 5035 5036 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", 5037 region_idx, 5038 (size_t)obj->size() * HeapWordSize, 5039 p2i(r->bottom()), 5040 r->rem_set()->occupied(), 5041 r->rem_set()->strong_code_roots_list_length(), 5042 next_bitmap->isMarked(r->bottom()), 5043 g1h->is_humongous_reclaim_candidate(region_idx), 5044 obj->is_typeArray() 5045 ); 5046 5047 // Need to clear mark bit of the humongous object if already set. 5048 if (next_bitmap->isMarked(r->bottom())) { 5049 next_bitmap->clear(r->bottom()); 5050 } 5051 do { 5052 HeapRegion* next = g1h->next_region_in_humongous(r); 5053 _freed_bytes += r->used(); 5054 r->set_containing_set(NULL); 5055 _humongous_regions_removed++; 5056 g1h->free_humongous_region(r, _free_region_list, false); 5057 r = next; 5058 } while (r != NULL); 5059 5060 return false; 5061 } 5062 5063 uint humongous_free_count() { 5064 return _humongous_regions_removed; 5065 } 5066 5067 size_t bytes_freed() const { 5068 return _freed_bytes; 5069 } 5070 }; 5071 5072 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 5073 assert_at_safepoint(true); 5074 5075 if (!G1EagerReclaimHumongousObjects || 5076 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 5077 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5078 return; 5079 } 5080 5081 double start_time = os::elapsedTime(); 5082 5083 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5084 5085 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5086 heap_region_iterate(&cl); 5087 5088 remove_from_old_sets(0, cl.humongous_free_count()); 5089 5090 G1HRPrinter* hrp = hr_printer(); 5091 if (hrp->is_active()) { 5092 FreeRegionListIterator iter(&local_cleanup_list); 5093 while (iter.more_available()) { 5094 HeapRegion* hr = iter.get_next(); 5095 hrp->cleanup(hr); 5096 } 5097 } 5098 5099 prepend_to_freelist(&local_cleanup_list); 5100 decrement_summary_bytes(cl.bytes_freed()); 5101 5102 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5103 cl.humongous_free_count()); 5104 } 5105 5106 // This routine is similar to the above but does not record 5107 // any policy statistics or update free lists; we are abandoning 5108 // the current incremental collection set in preparation of a 5109 // full collection. After the full GC we will start to build up 5110 // the incremental collection set again. 5111 // This is only called when we're doing a full collection 5112 // and is immediately followed by the tearing down of the young list. 5113 5114 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 5115 HeapRegion* cur = cs_head; 5116 5117 while (cur != NULL) { 5118 HeapRegion* next = cur->next_in_collection_set(); 5119 assert(cur->in_collection_set(), "bad CS"); 5120 cur->set_next_in_collection_set(NULL); 5121 clear_in_cset(cur); 5122 cur->set_young_index_in_cset(-1); 5123 cur = next; 5124 } 5125 } 5126 5127 void G1CollectedHeap::set_free_regions_coming() { 5128 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 5129 5130 assert(!free_regions_coming(), "pre-condition"); 5131 _free_regions_coming = true; 5132 } 5133 5134 void G1CollectedHeap::reset_free_regions_coming() { 5135 assert(free_regions_coming(), "pre-condition"); 5136 5137 { 5138 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5139 _free_regions_coming = false; 5140 SecondaryFreeList_lock->notify_all(); 5141 } 5142 5143 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 5144 } 5145 5146 void G1CollectedHeap::wait_while_free_regions_coming() { 5147 // Most of the time we won't have to wait, so let's do a quick test 5148 // first before we take the lock. 5149 if (!free_regions_coming()) { 5150 return; 5151 } 5152 5153 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 5154 5155 { 5156 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5157 while (free_regions_coming()) { 5158 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5159 } 5160 } 5161 5162 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 5163 } 5164 5165 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5166 return _allocator->is_retained_old_region(hr); 5167 } 5168 5169 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5170 _young_list->push_region(hr); 5171 } 5172 5173 class NoYoungRegionsClosure: public HeapRegionClosure { 5174 private: 5175 bool _success; 5176 public: 5177 NoYoungRegionsClosure() : _success(true) { } 5178 bool doHeapRegion(HeapRegion* r) { 5179 if (r->is_young()) { 5180 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5181 p2i(r->bottom()), p2i(r->end())); 5182 _success = false; 5183 } 5184 return false; 5185 } 5186 bool success() { return _success; } 5187 }; 5188 5189 bool G1CollectedHeap::check_young_list_empty(bool check_heap) { 5190 bool ret = _young_list->check_list_empty(); 5191 5192 if (check_heap) { 5193 NoYoungRegionsClosure closure; 5194 heap_region_iterate(&closure); 5195 ret = ret && closure.success(); 5196 } 5197 5198 return ret; 5199 } 5200 5201 class TearDownRegionSetsClosure : public HeapRegionClosure { 5202 private: 5203 HeapRegionSet *_old_set; 5204 5205 public: 5206 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5207 5208 bool doHeapRegion(HeapRegion* r) { 5209 if (r->is_old()) { 5210 _old_set->remove(r); 5211 } else { 5212 // We ignore free regions, we'll empty the free list afterwards. 5213 // We ignore young regions, we'll empty the young list afterwards. 5214 // We ignore humongous regions, we're not tearing down the 5215 // humongous regions set. 5216 assert(r->is_free() || r->is_young() || r->is_humongous(), 5217 "it cannot be another type"); 5218 } 5219 return false; 5220 } 5221 5222 ~TearDownRegionSetsClosure() { 5223 assert(_old_set->is_empty(), "post-condition"); 5224 } 5225 }; 5226 5227 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5228 assert_at_safepoint(true /* should_be_vm_thread */); 5229 5230 if (!free_list_only) { 5231 TearDownRegionSetsClosure cl(&_old_set); 5232 heap_region_iterate(&cl); 5233 5234 // Note that emptying the _young_list is postponed and instead done as 5235 // the first step when rebuilding the regions sets again. The reason for 5236 // this is that during a full GC string deduplication needs to know if 5237 // a collected region was young or old when the full GC was initiated. 5238 } 5239 _hrm.remove_all_free_regions(); 5240 } 5241 5242 void G1CollectedHeap::increase_used(size_t bytes) { 5243 _summary_bytes_used += bytes; 5244 } 5245 5246 void G1CollectedHeap::decrease_used(size_t bytes) { 5247 assert(_summary_bytes_used >= bytes, 5248 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5249 _summary_bytes_used, bytes); 5250 _summary_bytes_used -= bytes; 5251 } 5252 5253 void G1CollectedHeap::set_used(size_t bytes) { 5254 _summary_bytes_used = bytes; 5255 } 5256 5257 class RebuildRegionSetsClosure : public HeapRegionClosure { 5258 private: 5259 bool _free_list_only; 5260 HeapRegionSet* _old_set; 5261 HeapRegionManager* _hrm; 5262 size_t _total_used; 5263 5264 public: 5265 RebuildRegionSetsClosure(bool free_list_only, 5266 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5267 _free_list_only(free_list_only), 5268 _old_set(old_set), _hrm(hrm), _total_used(0) { 5269 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5270 if (!free_list_only) { 5271 assert(_old_set->is_empty(), "pre-condition"); 5272 } 5273 } 5274 5275 bool doHeapRegion(HeapRegion* r) { 5276 if (r->is_empty()) { 5277 // Add free regions to the free list 5278 r->set_free(); 5279 r->set_allocation_context(AllocationContext::system()); 5280 _hrm->insert_into_free_list(r); 5281 } else if (!_free_list_only) { 5282 assert(!r->is_young(), "we should not come across young regions"); 5283 5284 if (r->is_humongous()) { 5285 // We ignore humongous regions. We left the humongous set unchanged. 5286 } else { 5287 // Objects that were compacted would have ended up on regions 5288 // that were previously old or free. Archive regions (which are 5289 // old) will not have been touched. 5290 assert(r->is_free() || r->is_old(), "invariant"); 5291 // We now consider them old, so register as such. Leave 5292 // archive regions set that way, however, while still adding 5293 // them to the old set. 5294 if (!r->is_archive()) { 5295 r->set_old(); 5296 } 5297 _old_set->add(r); 5298 } 5299 _total_used += r->used(); 5300 } 5301 5302 return false; 5303 } 5304 5305 size_t total_used() { 5306 return _total_used; 5307 } 5308 }; 5309 5310 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5311 assert_at_safepoint(true /* should_be_vm_thread */); 5312 5313 if (!free_list_only) { 5314 _young_list->empty_list(); 5315 } 5316 5317 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5318 heap_region_iterate(&cl); 5319 5320 if (!free_list_only) { 5321 set_used(cl.total_used()); 5322 if (_archive_allocator != NULL) { 5323 _archive_allocator->clear_used(); 5324 } 5325 } 5326 assert(used_unlocked() == recalculate_used(), 5327 "inconsistent used_unlocked(), " 5328 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5329 used_unlocked(), recalculate_used()); 5330 } 5331 5332 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 5333 _refine_cte_cl->set_concurrent(concurrent); 5334 } 5335 5336 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5337 HeapRegion* hr = heap_region_containing(p); 5338 return hr->is_in(p); 5339 } 5340 5341 // Methods for the mutator alloc region 5342 5343 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5344 bool force) { 5345 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5346 assert(!force || g1_policy()->can_expand_young_list(), 5347 "if force is true we should be able to expand the young list"); 5348 bool young_list_full = g1_policy()->is_young_list_full(); 5349 if (force || !young_list_full) { 5350 HeapRegion* new_alloc_region = new_region(word_size, 5351 false /* is_old */, 5352 false /* do_expand */); 5353 if (new_alloc_region != NULL) { 5354 set_region_short_lived_locked(new_alloc_region); 5355 _hr_printer.alloc(new_alloc_region, young_list_full); 5356 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5357 return new_alloc_region; 5358 } 5359 } 5360 return NULL; 5361 } 5362 5363 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5364 size_t allocated_bytes) { 5365 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5366 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5367 5368 collection_set()->add_eden_region(alloc_region); 5369 increase_used(allocated_bytes); 5370 _hr_printer.retire(alloc_region); 5371 // We update the eden sizes here, when the region is retired, 5372 // instead of when it's allocated, since this is the point that its 5373 // used space has been recored in _summary_bytes_used. 5374 g1mm()->update_eden_size(); 5375 } 5376 5377 // Methods for the GC alloc regions 5378 5379 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 5380 uint count, 5381 InCSetState dest) { 5382 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5383 5384 if (count < g1_policy()->max_regions(dest)) { 5385 const bool is_survivor = (dest.is_young()); 5386 HeapRegion* new_alloc_region = new_region(word_size, 5387 !is_survivor, 5388 true /* do_expand */); 5389 if (new_alloc_region != NULL) { 5390 // We really only need to do this for old regions given that we 5391 // should never scan survivors. But it doesn't hurt to do it 5392 // for survivors too. 5393 new_alloc_region->record_timestamp(); 5394 if (is_survivor) { 5395 new_alloc_region->set_survivor(); 5396 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5397 } else { 5398 new_alloc_region->set_old(); 5399 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5400 } 5401 _hr_printer.alloc(new_alloc_region); 5402 bool during_im = collector_state()->during_initial_mark_pause(); 5403 new_alloc_region->note_start_of_copying(during_im); 5404 return new_alloc_region; 5405 } 5406 } 5407 return NULL; 5408 } 5409 5410 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5411 size_t allocated_bytes, 5412 InCSetState dest) { 5413 bool during_im = collector_state()->during_initial_mark_pause(); 5414 alloc_region->note_end_of_copying(during_im); 5415 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5416 if (dest.is_young()) { 5417 young_list()->add_survivor_region(alloc_region); 5418 } else { 5419 _old_set.add(alloc_region); 5420 } 5421 _hr_printer.retire(alloc_region); 5422 } 5423 5424 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5425 bool expanded = false; 5426 uint index = _hrm.find_highest_free(&expanded); 5427 5428 if (index != G1_NO_HRM_INDEX) { 5429 if (expanded) { 5430 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5431 HeapRegion::GrainWords * HeapWordSize); 5432 } 5433 _hrm.allocate_free_regions_starting_at(index, 1); 5434 return region_at(index); 5435 } 5436 return NULL; 5437 } 5438 5439 // Optimized nmethod scanning 5440 5441 class RegisterNMethodOopClosure: public OopClosure { 5442 G1CollectedHeap* _g1h; 5443 nmethod* _nm; 5444 5445 template <class T> void do_oop_work(T* p) { 5446 T heap_oop = oopDesc::load_heap_oop(p); 5447 if (!oopDesc::is_null(heap_oop)) { 5448 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5449 HeapRegion* hr = _g1h->heap_region_containing(obj); 5450 assert(!hr->is_continues_humongous(), 5451 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5452 " starting at " HR_FORMAT, 5453 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5454 5455 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5456 hr->add_strong_code_root_locked(_nm); 5457 } 5458 } 5459 5460 public: 5461 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5462 _g1h(g1h), _nm(nm) {} 5463 5464 void do_oop(oop* p) { do_oop_work(p); } 5465 void do_oop(narrowOop* p) { do_oop_work(p); } 5466 }; 5467 5468 class UnregisterNMethodOopClosure: public OopClosure { 5469 G1CollectedHeap* _g1h; 5470 nmethod* _nm; 5471 5472 template <class T> void do_oop_work(T* p) { 5473 T heap_oop = oopDesc::load_heap_oop(p); 5474 if (!oopDesc::is_null(heap_oop)) { 5475 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5476 HeapRegion* hr = _g1h->heap_region_containing(obj); 5477 assert(!hr->is_continues_humongous(), 5478 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5479 " starting at " HR_FORMAT, 5480 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5481 5482 hr->remove_strong_code_root(_nm); 5483 } 5484 } 5485 5486 public: 5487 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5488 _g1h(g1h), _nm(nm) {} 5489 5490 void do_oop(oop* p) { do_oop_work(p); } 5491 void do_oop(narrowOop* p) { do_oop_work(p); } 5492 }; 5493 5494 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5495 CollectedHeap::register_nmethod(nm); 5496 5497 guarantee(nm != NULL, "sanity"); 5498 RegisterNMethodOopClosure reg_cl(this, nm); 5499 nm->oops_do(®_cl); 5500 } 5501 5502 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5503 CollectedHeap::unregister_nmethod(nm); 5504 5505 guarantee(nm != NULL, "sanity"); 5506 UnregisterNMethodOopClosure reg_cl(this, nm); 5507 nm->oops_do(®_cl, true); 5508 } 5509 5510 void G1CollectedHeap::purge_code_root_memory() { 5511 double purge_start = os::elapsedTime(); 5512 G1CodeRootSet::purge(); 5513 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5514 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5515 } 5516 5517 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5518 G1CollectedHeap* _g1h; 5519 5520 public: 5521 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5522 _g1h(g1h) {} 5523 5524 void do_code_blob(CodeBlob* cb) { 5525 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5526 if (nm == NULL) { 5527 return; 5528 } 5529 5530 if (ScavengeRootsInCode) { 5531 _g1h->register_nmethod(nm); 5532 } 5533 } 5534 }; 5535 5536 void G1CollectedHeap::rebuild_strong_code_roots() { 5537 RebuildStrongCodeRootClosure blob_cl(this); 5538 CodeCache::blobs_do(&blob_cl); 5539 }