1 /* 2 * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/metadataOnStackMark.hpp" 27 #include "classfile/stringTable.hpp" 28 #include "classfile/symbolTable.hpp" 29 #include "code/codeCache.hpp" 30 #include "code/icBuffer.hpp" 31 #include "gc/g1/bufferingOopClosure.hpp" 32 #include "gc/g1/concurrentG1Refine.hpp" 33 #include "gc/g1/concurrentG1RefineThread.hpp" 34 #include "gc/g1/concurrentMarkThread.inline.hpp" 35 #include "gc/g1/g1Allocator.inline.hpp" 36 #include "gc/g1/g1CollectedHeap.inline.hpp" 37 #include "gc/g1/g1CollectionSet.hpp" 38 #include "gc/g1/g1CollectorPolicy.hpp" 39 #include "gc/g1/g1CollectorState.hpp" 40 #include "gc/g1/g1EvacStats.inline.hpp" 41 #include "gc/g1/g1GCPhaseTimes.hpp" 42 #include "gc/g1/g1HeapSizingPolicy.hpp" 43 #include "gc/g1/g1HeapTransition.hpp" 44 #include "gc/g1/g1HeapVerifier.hpp" 45 #include "gc/g1/g1MarkSweep.hpp" 46 #include "gc/g1/g1OopClosures.inline.hpp" 47 #include "gc/g1/g1ParScanThreadState.inline.hpp" 48 #include "gc/g1/g1RegionToSpaceMapper.hpp" 49 #include "gc/g1/g1RemSet.inline.hpp" 50 #include "gc/g1/g1RootClosures.hpp" 51 #include "gc/g1/g1RootProcessor.hpp" 52 #include "gc/g1/g1StringDedup.hpp" 53 #include "gc/g1/g1YCTypes.hpp" 54 #include "gc/g1/heapRegion.inline.hpp" 55 #include "gc/g1/heapRegionRemSet.hpp" 56 #include "gc/g1/heapRegionSet.inline.hpp" 57 #include "gc/g1/suspendibleThreadSet.hpp" 58 #include "gc/g1/vm_operations_g1.hpp" 59 #include "gc/shared/gcHeapSummary.hpp" 60 #include "gc/shared/gcId.hpp" 61 #include "gc/shared/gcLocker.inline.hpp" 62 #include "gc/shared/gcTimer.hpp" 63 #include "gc/shared/gcTrace.hpp" 64 #include "gc/shared/gcTraceTime.inline.hpp" 65 #include "gc/shared/generationSpec.hpp" 66 #include "gc/shared/isGCActiveMark.hpp" 67 #include "gc/shared/referenceProcessor.inline.hpp" 68 #include "gc/shared/taskqueue.inline.hpp" 69 #include "logging/log.hpp" 70 #include "memory/allocation.hpp" 71 #include "memory/iterator.hpp" 72 #include "oops/oop.inline.hpp" 73 #include "runtime/atomic.inline.hpp" 74 #include "runtime/init.hpp" 75 #include "runtime/orderAccess.inline.hpp" 76 #include "runtime/vmThread.hpp" 77 #include "utilities/globalDefinitions.hpp" 78 #include "utilities/stack.inline.hpp" 79 80 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 81 82 // INVARIANTS/NOTES 83 // 84 // All allocation activity covered by the G1CollectedHeap interface is 85 // serialized by acquiring the HeapLock. This happens in mem_allocate 86 // and allocate_new_tlab, which are the "entry" points to the 87 // allocation code from the rest of the JVM. (Note that this does not 88 // apply to TLAB allocation, which is not part of this interface: it 89 // is done by clients of this interface.) 90 91 // Local to this file. 92 93 class RefineCardTableEntryClosure: public CardTableEntryClosure { 94 bool _concurrent; 95 public: 96 RefineCardTableEntryClosure() : _concurrent(true) { } 97 98 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 99 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false); 100 // This path is executed by the concurrent refine or mutator threads, 101 // concurrently, and so we do not care if card_ptr contains references 102 // that point into the collection set. 103 assert(!oops_into_cset, "should be"); 104 105 if (_concurrent && SuspendibleThreadSet::should_yield()) { 106 // Caller will actually yield. 107 return false; 108 } 109 // Otherwise, we finished successfully; return true. 110 return true; 111 } 112 113 void set_concurrent(bool b) { _concurrent = b; } 114 }; 115 116 117 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 118 private: 119 size_t _num_dirtied; 120 G1CollectedHeap* _g1h; 121 G1SATBCardTableLoggingModRefBS* _g1_bs; 122 123 HeapRegion* region_for_card(jbyte* card_ptr) const { 124 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 125 } 126 127 bool will_become_free(HeapRegion* hr) const { 128 // A region will be freed by free_collection_set if the region is in the 129 // collection set and has not had an evacuation failure. 130 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 131 } 132 133 public: 134 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 135 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 136 137 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 138 HeapRegion* hr = region_for_card(card_ptr); 139 140 // Should only dirty cards in regions that won't be freed. 141 if (!will_become_free(hr)) { 142 *card_ptr = CardTableModRefBS::dirty_card_val(); 143 _num_dirtied++; 144 } 145 146 return true; 147 } 148 149 size_t num_dirtied() const { return _num_dirtied; } 150 }; 151 152 153 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 154 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 155 } 156 157 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 158 // The from card cache is not the memory that is actually committed. So we cannot 159 // take advantage of the zero_filled parameter. 160 reset_from_card_cache(start_idx, num_regions); 161 } 162 163 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 164 { 165 // Claim the right to put the region on the dirty cards region list 166 // by installing a self pointer. 167 HeapRegion* next = hr->get_next_dirty_cards_region(); 168 if (next == NULL) { 169 HeapRegion* res = (HeapRegion*) 170 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 171 NULL); 172 if (res == NULL) { 173 HeapRegion* head; 174 do { 175 // Put the region to the dirty cards region list. 176 head = _dirty_cards_region_list; 177 next = (HeapRegion*) 178 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 179 if (next == head) { 180 assert(hr->get_next_dirty_cards_region() == hr, 181 "hr->get_next_dirty_cards_region() != hr"); 182 if (next == NULL) { 183 // The last region in the list points to itself. 184 hr->set_next_dirty_cards_region(hr); 185 } else { 186 hr->set_next_dirty_cards_region(next); 187 } 188 } 189 } while (next != head); 190 } 191 } 192 } 193 194 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 195 { 196 HeapRegion* head; 197 HeapRegion* hr; 198 do { 199 head = _dirty_cards_region_list; 200 if (head == NULL) { 201 return NULL; 202 } 203 HeapRegion* new_head = head->get_next_dirty_cards_region(); 204 if (head == new_head) { 205 // The last region. 206 new_head = NULL; 207 } 208 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 209 head); 210 } while (hr != head); 211 assert(hr != NULL, "invariant"); 212 hr->set_next_dirty_cards_region(NULL); 213 return hr; 214 } 215 216 // Returns true if the reference points to an object that 217 // can move in an incremental collection. 218 bool G1CollectedHeap::is_scavengable(const void* p) { 219 HeapRegion* hr = heap_region_containing(p); 220 return !hr->is_pinned(); 221 } 222 223 // Private methods. 224 225 HeapRegion* 226 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 227 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 228 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 229 if (!_secondary_free_list.is_empty()) { 230 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 231 "secondary_free_list has %u entries", 232 _secondary_free_list.length()); 233 // It looks as if there are free regions available on the 234 // secondary_free_list. Let's move them to the free_list and try 235 // again to allocate from it. 236 append_secondary_free_list(); 237 238 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 239 "empty we should have moved at least one entry to the free_list"); 240 HeapRegion* res = _hrm.allocate_free_region(is_old); 241 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 242 "allocated " HR_FORMAT " from secondary_free_list", 243 HR_FORMAT_PARAMS(res)); 244 return res; 245 } 246 247 // Wait here until we get notified either when (a) there are no 248 // more free regions coming or (b) some regions have been moved on 249 // the secondary_free_list. 250 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 251 } 252 253 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 254 "could not allocate from secondary_free_list"); 255 return NULL; 256 } 257 258 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 259 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 260 "the only time we use this to allocate a humongous region is " 261 "when we are allocating a single humongous region"); 262 263 HeapRegion* res; 264 if (G1StressConcRegionFreeing) { 265 if (!_secondary_free_list.is_empty()) { 266 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 267 "forced to look at the secondary_free_list"); 268 res = new_region_try_secondary_free_list(is_old); 269 if (res != NULL) { 270 return res; 271 } 272 } 273 } 274 275 res = _hrm.allocate_free_region(is_old); 276 277 if (res == NULL) { 278 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 279 "res == NULL, trying the secondary_free_list"); 280 res = new_region_try_secondary_free_list(is_old); 281 } 282 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 283 // Currently, only attempts to allocate GC alloc regions set 284 // do_expand to true. So, we should only reach here during a 285 // safepoint. If this assumption changes we might have to 286 // reconsider the use of _expand_heap_after_alloc_failure. 287 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 288 289 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 290 word_size * HeapWordSize); 291 292 if (expand(word_size * HeapWordSize)) { 293 // Given that expand() succeeded in expanding the heap, and we 294 // always expand the heap by an amount aligned to the heap 295 // region size, the free list should in theory not be empty. 296 // In either case allocate_free_region() will check for NULL. 297 res = _hrm.allocate_free_region(is_old); 298 } else { 299 _expand_heap_after_alloc_failure = false; 300 } 301 } 302 return res; 303 } 304 305 HeapWord* 306 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 307 uint num_regions, 308 size_t word_size, 309 AllocationContext_t context) { 310 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 311 assert(is_humongous(word_size), "word_size should be humongous"); 312 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 313 314 // Index of last region in the series. 315 uint last = first + num_regions - 1; 316 317 // We need to initialize the region(s) we just discovered. This is 318 // a bit tricky given that it can happen concurrently with 319 // refinement threads refining cards on these regions and 320 // potentially wanting to refine the BOT as they are scanning 321 // those cards (this can happen shortly after a cleanup; see CR 322 // 6991377). So we have to set up the region(s) carefully and in 323 // a specific order. 324 325 // The word size sum of all the regions we will allocate. 326 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 327 assert(word_size <= word_size_sum, "sanity"); 328 329 // This will be the "starts humongous" region. 330 HeapRegion* first_hr = region_at(first); 331 // The header of the new object will be placed at the bottom of 332 // the first region. 333 HeapWord* new_obj = first_hr->bottom(); 334 // This will be the new top of the new object. 335 HeapWord* obj_top = new_obj + word_size; 336 337 // First, we need to zero the header of the space that we will be 338 // allocating. When we update top further down, some refinement 339 // threads might try to scan the region. By zeroing the header we 340 // ensure that any thread that will try to scan the region will 341 // come across the zero klass word and bail out. 342 // 343 // NOTE: It would not have been correct to have used 344 // CollectedHeap::fill_with_object() and make the space look like 345 // an int array. The thread that is doing the allocation will 346 // later update the object header to a potentially different array 347 // type and, for a very short period of time, the klass and length 348 // fields will be inconsistent. This could cause a refinement 349 // thread to calculate the object size incorrectly. 350 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 351 352 // How many words we use for filler objects. 353 size_t word_fill_size = word_size_sum - word_size; 354 355 // How many words memory we "waste" which cannot hold a filler object. 356 size_t words_not_fillable = 0; 357 358 if (word_fill_size >= min_fill_size()) { 359 fill_with_objects(obj_top, word_fill_size); 360 } else if (word_fill_size > 0) { 361 // We have space to fill, but we cannot fit an object there. 362 words_not_fillable = word_fill_size; 363 word_fill_size = 0; 364 } 365 366 // We will set up the first region as "starts humongous". This 367 // will also update the BOT covering all the regions to reflect 368 // that there is a single object that starts at the bottom of the 369 // first region. 370 first_hr->set_starts_humongous(obj_top, word_fill_size); 371 first_hr->set_allocation_context(context); 372 // Then, if there are any, we will set up the "continues 373 // humongous" regions. 374 HeapRegion* hr = NULL; 375 for (uint i = first + 1; i <= last; ++i) { 376 hr = region_at(i); 377 hr->set_continues_humongous(first_hr); 378 hr->set_allocation_context(context); 379 } 380 381 // Up to this point no concurrent thread would have been able to 382 // do any scanning on any region in this series. All the top 383 // fields still point to bottom, so the intersection between 384 // [bottom,top] and [card_start,card_end] will be empty. Before we 385 // update the top fields, we'll do a storestore to make sure that 386 // no thread sees the update to top before the zeroing of the 387 // object header and the BOT initialization. 388 OrderAccess::storestore(); 389 390 // Now, we will update the top fields of the "continues humongous" 391 // regions except the last one. 392 for (uint i = first; i < last; ++i) { 393 hr = region_at(i); 394 hr->set_top(hr->end()); 395 } 396 397 hr = region_at(last); 398 // If we cannot fit a filler object, we must set top to the end 399 // of the humongous object, otherwise we cannot iterate the heap 400 // and the BOT will not be complete. 401 hr->set_top(hr->end() - words_not_fillable); 402 403 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 404 "obj_top should be in last region"); 405 406 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 407 408 assert(words_not_fillable == 0 || 409 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 410 "Miscalculation in humongous allocation"); 411 412 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 413 414 for (uint i = first; i <= last; ++i) { 415 hr = region_at(i); 416 _humongous_set.add(hr); 417 _hr_printer.alloc(hr); 418 } 419 420 return new_obj; 421 } 422 423 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 424 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 425 return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 426 } 427 428 // If could fit into free regions w/o expansion, try. 429 // Otherwise, if can expand, do so. 430 // Otherwise, if using ex regions might help, try with ex given back. 431 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 432 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 433 434 _verifier->verify_region_sets_optional(); 435 436 uint first = G1_NO_HRM_INDEX; 437 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 438 439 if (obj_regions == 1) { 440 // Only one region to allocate, try to use a fast path by directly allocating 441 // from the free lists. Do not try to expand here, we will potentially do that 442 // later. 443 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 444 if (hr != NULL) { 445 first = hr->hrm_index(); 446 } 447 } else { 448 // We can't allocate humongous regions spanning more than one region while 449 // cleanupComplete() is running, since some of the regions we find to be 450 // empty might not yet be added to the free list. It is not straightforward 451 // to know in which list they are on so that we can remove them. We only 452 // need to do this if we need to allocate more than one region to satisfy the 453 // current humongous allocation request. If we are only allocating one region 454 // we use the one-region region allocation code (see above), that already 455 // potentially waits for regions from the secondary free list. 456 wait_while_free_regions_coming(); 457 append_secondary_free_list_if_not_empty_with_lock(); 458 459 // Policy: Try only empty regions (i.e. already committed first). Maybe we 460 // are lucky enough to find some. 461 first = _hrm.find_contiguous_only_empty(obj_regions); 462 if (first != G1_NO_HRM_INDEX) { 463 _hrm.allocate_free_regions_starting_at(first, obj_regions); 464 } 465 } 466 467 if (first == G1_NO_HRM_INDEX) { 468 // Policy: We could not find enough regions for the humongous object in the 469 // free list. Look through the heap to find a mix of free and uncommitted regions. 470 // If so, try expansion. 471 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 472 if (first != G1_NO_HRM_INDEX) { 473 // We found something. Make sure these regions are committed, i.e. expand 474 // the heap. Alternatively we could do a defragmentation GC. 475 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 476 word_size * HeapWordSize); 477 478 479 _hrm.expand_at(first, obj_regions); 480 g1_policy()->record_new_heap_size(num_regions()); 481 482 #ifdef ASSERT 483 for (uint i = first; i < first + obj_regions; ++i) { 484 HeapRegion* hr = region_at(i); 485 assert(hr->is_free(), "sanity"); 486 assert(hr->is_empty(), "sanity"); 487 assert(is_on_master_free_list(hr), "sanity"); 488 } 489 #endif 490 _hrm.allocate_free_regions_starting_at(first, obj_regions); 491 } else { 492 // Policy: Potentially trigger a defragmentation GC. 493 } 494 } 495 496 HeapWord* result = NULL; 497 if (first != G1_NO_HRM_INDEX) { 498 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 499 word_size, context); 500 assert(result != NULL, "it should always return a valid result"); 501 502 // A successful humongous object allocation changes the used space 503 // information of the old generation so we need to recalculate the 504 // sizes and update the jstat counters here. 505 g1mm()->update_sizes(); 506 } 507 508 _verifier->verify_region_sets_optional(); 509 510 return result; 511 } 512 513 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 514 assert_heap_not_locked_and_not_at_safepoint(); 515 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 516 517 uint dummy_gc_count_before; 518 uint dummy_gclocker_retry_count = 0; 519 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 520 } 521 522 HeapWord* 523 G1CollectedHeap::mem_allocate(size_t word_size, 524 bool* gc_overhead_limit_was_exceeded) { 525 assert_heap_not_locked_and_not_at_safepoint(); 526 527 // Loop until the allocation is satisfied, or unsatisfied after GC. 528 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 529 uint gc_count_before; 530 531 HeapWord* result = NULL; 532 if (!is_humongous(word_size)) { 533 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 534 } else { 535 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 536 } 537 if (result != NULL) { 538 return result; 539 } 540 541 // Create the garbage collection operation... 542 VM_G1CollectForAllocation op(gc_count_before, word_size); 543 op.set_allocation_context(AllocationContext::current()); 544 545 // ...and get the VM thread to execute it. 546 VMThread::execute(&op); 547 548 if (op.prologue_succeeded() && op.pause_succeeded()) { 549 // If the operation was successful we'll return the result even 550 // if it is NULL. If the allocation attempt failed immediately 551 // after a Full GC, it's unlikely we'll be able to allocate now. 552 HeapWord* result = op.result(); 553 if (result != NULL && !is_humongous(word_size)) { 554 // Allocations that take place on VM operations do not do any 555 // card dirtying and we have to do it here. We only have to do 556 // this for non-humongous allocations, though. 557 dirty_young_block(result, word_size); 558 } 559 return result; 560 } else { 561 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 562 return NULL; 563 } 564 assert(op.result() == NULL, 565 "the result should be NULL if the VM op did not succeed"); 566 } 567 568 // Give a warning if we seem to be looping forever. 569 if ((QueuedAllocationWarningCount > 0) && 570 (try_count % QueuedAllocationWarningCount == 0)) { 571 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 572 } 573 } 574 575 ShouldNotReachHere(); 576 return NULL; 577 } 578 579 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 580 AllocationContext_t context, 581 uint* gc_count_before_ret, 582 uint* gclocker_retry_count_ret) { 583 // Make sure you read the note in attempt_allocation_humongous(). 584 585 assert_heap_not_locked_and_not_at_safepoint(); 586 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 587 "be called for humongous allocation requests"); 588 589 // We should only get here after the first-level allocation attempt 590 // (attempt_allocation()) failed to allocate. 591 592 // We will loop until a) we manage to successfully perform the 593 // allocation or b) we successfully schedule a collection which 594 // fails to perform the allocation. b) is the only case when we'll 595 // return NULL. 596 HeapWord* result = NULL; 597 for (int try_count = 1; /* we'll return */; try_count += 1) { 598 bool should_try_gc; 599 uint gc_count_before; 600 601 { 602 MutexLockerEx x(Heap_lock); 603 result = _allocator->attempt_allocation_locked(word_size, context); 604 if (result != NULL) { 605 return result; 606 } 607 608 if (GCLocker::is_active_and_needs_gc()) { 609 if (g1_policy()->can_expand_young_list()) { 610 // No need for an ergo verbose message here, 611 // can_expand_young_list() does this when it returns true. 612 result = _allocator->attempt_allocation_force(word_size, context); 613 if (result != NULL) { 614 return result; 615 } 616 } 617 should_try_gc = false; 618 } else { 619 // The GCLocker may not be active but the GCLocker initiated 620 // GC may not yet have been performed (GCLocker::needs_gc() 621 // returns true). In this case we do not try this GC and 622 // wait until the GCLocker initiated GC is performed, and 623 // then retry the allocation. 624 if (GCLocker::needs_gc()) { 625 should_try_gc = false; 626 } else { 627 // Read the GC count while still holding the Heap_lock. 628 gc_count_before = total_collections(); 629 should_try_gc = true; 630 } 631 } 632 } 633 634 if (should_try_gc) { 635 bool succeeded; 636 result = do_collection_pause(word_size, gc_count_before, &succeeded, 637 GCCause::_g1_inc_collection_pause); 638 if (result != NULL) { 639 assert(succeeded, "only way to get back a non-NULL result"); 640 return result; 641 } 642 643 if (succeeded) { 644 // If we get here we successfully scheduled a collection which 645 // failed to allocate. No point in trying to allocate 646 // further. We'll just return NULL. 647 MutexLockerEx x(Heap_lock); 648 *gc_count_before_ret = total_collections(); 649 return NULL; 650 } 651 } else { 652 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 653 MutexLockerEx x(Heap_lock); 654 *gc_count_before_ret = total_collections(); 655 return NULL; 656 } 657 // The GCLocker is either active or the GCLocker initiated 658 // GC has not yet been performed. Stall until it is and 659 // then retry the allocation. 660 GCLocker::stall_until_clear(); 661 (*gclocker_retry_count_ret) += 1; 662 } 663 664 // We can reach here if we were unsuccessful in scheduling a 665 // collection (because another thread beat us to it) or if we were 666 // stalled due to the GC locker. In either can we should retry the 667 // allocation attempt in case another thread successfully 668 // performed a collection and reclaimed enough space. We do the 669 // first attempt (without holding the Heap_lock) here and the 670 // follow-on attempt will be at the start of the next loop 671 // iteration (after taking the Heap_lock). 672 result = _allocator->attempt_allocation(word_size, context); 673 if (result != NULL) { 674 return result; 675 } 676 677 // Give a warning if we seem to be looping forever. 678 if ((QueuedAllocationWarningCount > 0) && 679 (try_count % QueuedAllocationWarningCount == 0)) { 680 warning("G1CollectedHeap::attempt_allocation_slow() " 681 "retries %d times", try_count); 682 } 683 } 684 685 ShouldNotReachHere(); 686 return NULL; 687 } 688 689 void G1CollectedHeap::begin_archive_alloc_range() { 690 assert_at_safepoint(true /* should_be_vm_thread */); 691 if (_archive_allocator == NULL) { 692 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 693 } 694 } 695 696 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 697 // Allocations in archive regions cannot be of a size that would be considered 698 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 699 // may be different at archive-restore time. 700 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 701 } 702 703 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 704 assert_at_safepoint(true /* should_be_vm_thread */); 705 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 706 if (is_archive_alloc_too_large(word_size)) { 707 return NULL; 708 } 709 return _archive_allocator->archive_mem_allocate(word_size); 710 } 711 712 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 713 size_t end_alignment_in_bytes) { 714 assert_at_safepoint(true /* should_be_vm_thread */); 715 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 716 717 // Call complete_archive to do the real work, filling in the MemRegion 718 // array with the archive regions. 719 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 720 delete _archive_allocator; 721 _archive_allocator = NULL; 722 } 723 724 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 725 assert(ranges != NULL, "MemRegion array NULL"); 726 assert(count != 0, "No MemRegions provided"); 727 MemRegion reserved = _hrm.reserved(); 728 for (size_t i = 0; i < count; i++) { 729 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 730 return false; 731 } 732 } 733 return true; 734 } 735 736 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 737 assert(!is_init_completed(), "Expect to be called at JVM init time"); 738 assert(ranges != NULL, "MemRegion array NULL"); 739 assert(count != 0, "No MemRegions provided"); 740 MutexLockerEx x(Heap_lock); 741 742 MemRegion reserved = _hrm.reserved(); 743 HeapWord* prev_last_addr = NULL; 744 HeapRegion* prev_last_region = NULL; 745 746 // Temporarily disable pretouching of heap pages. This interface is used 747 // when mmap'ing archived heap data in, so pre-touching is wasted. 748 FlagSetting fs(AlwaysPreTouch, false); 749 750 // Enable archive object checking in G1MarkSweep. We have to let it know 751 // about each archive range, so that objects in those ranges aren't marked. 752 G1MarkSweep::enable_archive_object_check(); 753 754 // For each specified MemRegion range, allocate the corresponding G1 755 // regions and mark them as archive regions. We expect the ranges in 756 // ascending starting address order, without overlap. 757 for (size_t i = 0; i < count; i++) { 758 MemRegion curr_range = ranges[i]; 759 HeapWord* start_address = curr_range.start(); 760 size_t word_size = curr_range.word_size(); 761 HeapWord* last_address = curr_range.last(); 762 size_t commits = 0; 763 764 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 765 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 766 p2i(start_address), p2i(last_address)); 767 guarantee(start_address > prev_last_addr, 768 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 769 p2i(start_address), p2i(prev_last_addr)); 770 prev_last_addr = last_address; 771 772 // Check for ranges that start in the same G1 region in which the previous 773 // range ended, and adjust the start address so we don't try to allocate 774 // the same region again. If the current range is entirely within that 775 // region, skip it, just adjusting the recorded top. 776 HeapRegion* start_region = _hrm.addr_to_region(start_address); 777 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 778 start_address = start_region->end(); 779 if (start_address > last_address) { 780 increase_used(word_size * HeapWordSize); 781 start_region->set_top(last_address + 1); 782 continue; 783 } 784 start_region->set_top(start_address); 785 curr_range = MemRegion(start_address, last_address + 1); 786 start_region = _hrm.addr_to_region(start_address); 787 } 788 789 // Perform the actual region allocation, exiting if it fails. 790 // Then note how much new space we have allocated. 791 if (!_hrm.allocate_containing_regions(curr_range, &commits)) { 792 return false; 793 } 794 increase_used(word_size * HeapWordSize); 795 if (commits != 0) { 796 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 797 HeapRegion::GrainWords * HeapWordSize * commits); 798 799 } 800 801 // Mark each G1 region touched by the range as archive, add it to the old set, 802 // and set the allocation context and top. 803 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 804 HeapRegion* last_region = _hrm.addr_to_region(last_address); 805 prev_last_region = last_region; 806 807 while (curr_region != NULL) { 808 assert(curr_region->is_empty() && !curr_region->is_pinned(), 809 "Region already in use (index %u)", curr_region->hrm_index()); 810 curr_region->set_allocation_context(AllocationContext::system()); 811 curr_region->set_archive(); 812 _hr_printer.alloc(curr_region); 813 _old_set.add(curr_region); 814 if (curr_region != last_region) { 815 curr_region->set_top(curr_region->end()); 816 curr_region = _hrm.next_region_in_heap(curr_region); 817 } else { 818 curr_region->set_top(last_address + 1); 819 curr_region = NULL; 820 } 821 } 822 823 // Notify mark-sweep of the archive range. 824 G1MarkSweep::set_range_archive(curr_range, true); 825 } 826 return true; 827 } 828 829 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 830 assert(!is_init_completed(), "Expect to be called at JVM init time"); 831 assert(ranges != NULL, "MemRegion array NULL"); 832 assert(count != 0, "No MemRegions provided"); 833 MemRegion reserved = _hrm.reserved(); 834 HeapWord *prev_last_addr = NULL; 835 HeapRegion* prev_last_region = NULL; 836 837 // For each MemRegion, create filler objects, if needed, in the G1 regions 838 // that contain the address range. The address range actually within the 839 // MemRegion will not be modified. That is assumed to have been initialized 840 // elsewhere, probably via an mmap of archived heap data. 841 MutexLockerEx x(Heap_lock); 842 for (size_t i = 0; i < count; i++) { 843 HeapWord* start_address = ranges[i].start(); 844 HeapWord* last_address = ranges[i].last(); 845 846 assert(reserved.contains(start_address) && reserved.contains(last_address), 847 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 848 p2i(start_address), p2i(last_address)); 849 assert(start_address > prev_last_addr, 850 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 851 p2i(start_address), p2i(prev_last_addr)); 852 853 HeapRegion* start_region = _hrm.addr_to_region(start_address); 854 HeapRegion* last_region = _hrm.addr_to_region(last_address); 855 HeapWord* bottom_address = start_region->bottom(); 856 857 // Check for a range beginning in the same region in which the 858 // previous one ended. 859 if (start_region == prev_last_region) { 860 bottom_address = prev_last_addr + 1; 861 } 862 863 // Verify that the regions were all marked as archive regions by 864 // alloc_archive_regions. 865 HeapRegion* curr_region = start_region; 866 while (curr_region != NULL) { 867 guarantee(curr_region->is_archive(), 868 "Expected archive region at index %u", curr_region->hrm_index()); 869 if (curr_region != last_region) { 870 curr_region = _hrm.next_region_in_heap(curr_region); 871 } else { 872 curr_region = NULL; 873 } 874 } 875 876 prev_last_addr = last_address; 877 prev_last_region = last_region; 878 879 // Fill the memory below the allocated range with dummy object(s), 880 // if the region bottom does not match the range start, or if the previous 881 // range ended within the same G1 region, and there is a gap. 882 if (start_address != bottom_address) { 883 size_t fill_size = pointer_delta(start_address, bottom_address); 884 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 885 increase_used(fill_size * HeapWordSize); 886 } 887 } 888 } 889 890 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 891 uint* gc_count_before_ret, 892 uint* gclocker_retry_count_ret) { 893 assert_heap_not_locked_and_not_at_safepoint(); 894 assert(!is_humongous(word_size), "attempt_allocation() should not " 895 "be called for humongous allocation requests"); 896 897 AllocationContext_t context = AllocationContext::current(); 898 HeapWord* result = _allocator->attempt_allocation(word_size, context); 899 900 if (result == NULL) { 901 result = attempt_allocation_slow(word_size, 902 context, 903 gc_count_before_ret, 904 gclocker_retry_count_ret); 905 } 906 assert_heap_not_locked(); 907 if (result != NULL) { 908 dirty_young_block(result, word_size); 909 } 910 return result; 911 } 912 913 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 914 assert(!is_init_completed(), "Expect to be called at JVM init time"); 915 assert(ranges != NULL, "MemRegion array NULL"); 916 assert(count != 0, "No MemRegions provided"); 917 MemRegion reserved = _hrm.reserved(); 918 HeapWord* prev_last_addr = NULL; 919 HeapRegion* prev_last_region = NULL; 920 size_t size_used = 0; 921 size_t uncommitted_regions = 0; 922 923 // For each Memregion, free the G1 regions that constitute it, and 924 // notify mark-sweep that the range is no longer to be considered 'archive.' 925 MutexLockerEx x(Heap_lock); 926 for (size_t i = 0; i < count; i++) { 927 HeapWord* start_address = ranges[i].start(); 928 HeapWord* last_address = ranges[i].last(); 929 930 assert(reserved.contains(start_address) && reserved.contains(last_address), 931 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 932 p2i(start_address), p2i(last_address)); 933 assert(start_address > prev_last_addr, 934 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 935 p2i(start_address), p2i(prev_last_addr)); 936 size_used += ranges[i].byte_size(); 937 prev_last_addr = last_address; 938 939 HeapRegion* start_region = _hrm.addr_to_region(start_address); 940 HeapRegion* last_region = _hrm.addr_to_region(last_address); 941 942 // Check for ranges that start in the same G1 region in which the previous 943 // range ended, and adjust the start address so we don't try to free 944 // the same region again. If the current range is entirely within that 945 // region, skip it. 946 if (start_region == prev_last_region) { 947 start_address = start_region->end(); 948 if (start_address > last_address) { 949 continue; 950 } 951 start_region = _hrm.addr_to_region(start_address); 952 } 953 prev_last_region = last_region; 954 955 // After verifying that each region was marked as an archive region by 956 // alloc_archive_regions, set it free and empty and uncommit it. 957 HeapRegion* curr_region = start_region; 958 while (curr_region != NULL) { 959 guarantee(curr_region->is_archive(), 960 "Expected archive region at index %u", curr_region->hrm_index()); 961 uint curr_index = curr_region->hrm_index(); 962 _old_set.remove(curr_region); 963 curr_region->set_free(); 964 curr_region->set_top(curr_region->bottom()); 965 if (curr_region != last_region) { 966 curr_region = _hrm.next_region_in_heap(curr_region); 967 } else { 968 curr_region = NULL; 969 } 970 _hrm.shrink_at(curr_index, 1); 971 uncommitted_regions++; 972 } 973 974 // Notify mark-sweep that this is no longer an archive range. 975 G1MarkSweep::set_range_archive(ranges[i], false); 976 } 977 978 if (uncommitted_regions != 0) { 979 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 980 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 981 } 982 decrease_used(size_used); 983 } 984 985 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 986 uint* gc_count_before_ret, 987 uint* gclocker_retry_count_ret) { 988 // The structure of this method has a lot of similarities to 989 // attempt_allocation_slow(). The reason these two were not merged 990 // into a single one is that such a method would require several "if 991 // allocation is not humongous do this, otherwise do that" 992 // conditional paths which would obscure its flow. In fact, an early 993 // version of this code did use a unified method which was harder to 994 // follow and, as a result, it had subtle bugs that were hard to 995 // track down. So keeping these two methods separate allows each to 996 // be more readable. It will be good to keep these two in sync as 997 // much as possible. 998 999 assert_heap_not_locked_and_not_at_safepoint(); 1000 assert(is_humongous(word_size), "attempt_allocation_humongous() " 1001 "should only be called for humongous allocations"); 1002 1003 // Humongous objects can exhaust the heap quickly, so we should check if we 1004 // need to start a marking cycle at each humongous object allocation. We do 1005 // the check before we do the actual allocation. The reason for doing it 1006 // before the allocation is that we avoid having to keep track of the newly 1007 // allocated memory while we do a GC. 1008 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 1009 word_size)) { 1010 collect(GCCause::_g1_humongous_allocation); 1011 } 1012 1013 // We will loop until a) we manage to successfully perform the 1014 // allocation or b) we successfully schedule a collection which 1015 // fails to perform the allocation. b) is the only case when we'll 1016 // return NULL. 1017 HeapWord* result = NULL; 1018 for (int try_count = 1; /* we'll return */; try_count += 1) { 1019 bool should_try_gc; 1020 uint gc_count_before; 1021 1022 { 1023 MutexLockerEx x(Heap_lock); 1024 1025 // Given that humongous objects are not allocated in young 1026 // regions, we'll first try to do the allocation without doing a 1027 // collection hoping that there's enough space in the heap. 1028 result = humongous_obj_allocate(word_size, AllocationContext::current()); 1029 if (result != NULL) { 1030 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 1031 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 1032 return result; 1033 } 1034 1035 if (GCLocker::is_active_and_needs_gc()) { 1036 should_try_gc = false; 1037 } else { 1038 // The GCLocker may not be active but the GCLocker initiated 1039 // GC may not yet have been performed (GCLocker::needs_gc() 1040 // returns true). In this case we do not try this GC and 1041 // wait until the GCLocker initiated GC is performed, and 1042 // then retry the allocation. 1043 if (GCLocker::needs_gc()) { 1044 should_try_gc = false; 1045 } else { 1046 // Read the GC count while still holding the Heap_lock. 1047 gc_count_before = total_collections(); 1048 should_try_gc = true; 1049 } 1050 } 1051 } 1052 1053 if (should_try_gc) { 1054 // If we failed to allocate the humongous object, we should try to 1055 // do a collection pause (if we're allowed) in case it reclaims 1056 // enough space for the allocation to succeed after the pause. 1057 1058 bool succeeded; 1059 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1060 GCCause::_g1_humongous_allocation); 1061 if (result != NULL) { 1062 assert(succeeded, "only way to get back a non-NULL result"); 1063 return result; 1064 } 1065 1066 if (succeeded) { 1067 // If we get here we successfully scheduled a collection which 1068 // failed to allocate. No point in trying to allocate 1069 // further. We'll just return NULL. 1070 MutexLockerEx x(Heap_lock); 1071 *gc_count_before_ret = total_collections(); 1072 return NULL; 1073 } 1074 } else { 1075 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1076 MutexLockerEx x(Heap_lock); 1077 *gc_count_before_ret = total_collections(); 1078 return NULL; 1079 } 1080 // The GCLocker is either active or the GCLocker initiated 1081 // GC has not yet been performed. Stall until it is and 1082 // then retry the allocation. 1083 GCLocker::stall_until_clear(); 1084 (*gclocker_retry_count_ret) += 1; 1085 } 1086 1087 // We can reach here if we were unsuccessful in scheduling a 1088 // collection (because another thread beat us to it) or if we were 1089 // stalled due to the GC locker. In either can we should retry the 1090 // allocation attempt in case another thread successfully 1091 // performed a collection and reclaimed enough space. Give a 1092 // warning if we seem to be looping forever. 1093 1094 if ((QueuedAllocationWarningCount > 0) && 1095 (try_count % QueuedAllocationWarningCount == 0)) { 1096 warning("G1CollectedHeap::attempt_allocation_humongous() " 1097 "retries %d times", try_count); 1098 } 1099 } 1100 1101 ShouldNotReachHere(); 1102 return NULL; 1103 } 1104 1105 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1106 AllocationContext_t context, 1107 bool expect_null_mutator_alloc_region) { 1108 assert_at_safepoint(true /* should_be_vm_thread */); 1109 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1110 "the current alloc region was unexpectedly found to be non-NULL"); 1111 1112 if (!is_humongous(word_size)) { 1113 return _allocator->attempt_allocation_locked(word_size, context); 1114 } else { 1115 HeapWord* result = humongous_obj_allocate(word_size, context); 1116 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1117 collector_state()->set_initiate_conc_mark_if_possible(true); 1118 } 1119 return result; 1120 } 1121 1122 ShouldNotReachHere(); 1123 } 1124 1125 class PostMCRemSetClearClosure: public HeapRegionClosure { 1126 G1CollectedHeap* _g1h; 1127 ModRefBarrierSet* _mr_bs; 1128 public: 1129 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1130 _g1h(g1h), _mr_bs(mr_bs) {} 1131 1132 bool doHeapRegion(HeapRegion* r) { 1133 HeapRegionRemSet* hrrs = r->rem_set(); 1134 1135 _g1h->reset_gc_time_stamps(r); 1136 1137 if (r->is_continues_humongous()) { 1138 // We'll assert that the strong code root list and RSet is empty 1139 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1140 assert(hrrs->occupied() == 0, "RSet should be empty"); 1141 } else { 1142 hrrs->clear(); 1143 } 1144 // You might think here that we could clear just the cards 1145 // corresponding to the used region. But no: if we leave a dirty card 1146 // in a region we might allocate into, then it would prevent that card 1147 // from being enqueued, and cause it to be missed. 1148 // Re: the performance cost: we shouldn't be doing full GC anyway! 1149 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1150 1151 return false; 1152 } 1153 }; 1154 1155 void G1CollectedHeap::clear_rsets_post_compaction() { 1156 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1157 heap_region_iterate(&rs_clear); 1158 } 1159 1160 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1161 G1CollectedHeap* _g1h; 1162 UpdateRSOopClosure _cl; 1163 public: 1164 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1165 _cl(g1->g1_rem_set(), worker_i), 1166 _g1h(g1) 1167 { } 1168 1169 bool doHeapRegion(HeapRegion* r) { 1170 if (!r->is_continues_humongous()) { 1171 _cl.set_from(r); 1172 r->oop_iterate(&_cl); 1173 } 1174 return false; 1175 } 1176 }; 1177 1178 class ParRebuildRSTask: public AbstractGangTask { 1179 G1CollectedHeap* _g1; 1180 HeapRegionClaimer _hrclaimer; 1181 1182 public: 1183 ParRebuildRSTask(G1CollectedHeap* g1) : 1184 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1185 1186 void work(uint worker_id) { 1187 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1188 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1189 } 1190 }; 1191 1192 class PostCompactionPrinterClosure: public HeapRegionClosure { 1193 private: 1194 G1HRPrinter* _hr_printer; 1195 public: 1196 bool doHeapRegion(HeapRegion* hr) { 1197 assert(!hr->is_young(), "not expecting to find young regions"); 1198 _hr_printer->post_compaction(hr); 1199 return false; 1200 } 1201 1202 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1203 : _hr_printer(hr_printer) { } 1204 }; 1205 1206 void G1CollectedHeap::print_hrm_post_compaction() { 1207 if (_hr_printer.is_active()) { 1208 PostCompactionPrinterClosure cl(hr_printer()); 1209 heap_region_iterate(&cl); 1210 } 1211 1212 } 1213 1214 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1215 bool clear_all_soft_refs) { 1216 assert_at_safepoint(true /* should_be_vm_thread */); 1217 1218 if (GCLocker::check_active_before_gc()) { 1219 return false; 1220 } 1221 1222 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1223 gc_timer->register_gc_start(); 1224 1225 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1226 GCIdMark gc_id_mark; 1227 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1228 1229 SvcGCMarker sgcm(SvcGCMarker::FULL); 1230 ResourceMark rm; 1231 1232 print_heap_before_gc(); 1233 trace_heap_before_gc(gc_tracer); 1234 1235 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1236 1237 _verifier->verify_region_sets_optional(); 1238 1239 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1240 collector_policy()->should_clear_all_soft_refs(); 1241 1242 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1243 1244 { 1245 IsGCActiveMark x; 1246 1247 // Timing 1248 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1249 GCTraceCPUTime tcpu; 1250 1251 { 1252 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1253 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1254 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1255 1256 G1HeapTransition heap_transition(this); 1257 g1_policy()->record_full_collection_start(); 1258 1259 // Note: When we have a more flexible GC logging framework that 1260 // allows us to add optional attributes to a GC log record we 1261 // could consider timing and reporting how long we wait in the 1262 // following two methods. 1263 wait_while_free_regions_coming(); 1264 // If we start the compaction before the CM threads finish 1265 // scanning the root regions we might trip them over as we'll 1266 // be moving objects / updating references. So let's wait until 1267 // they are done. By telling them to abort, they should complete 1268 // early. 1269 _cm->root_regions()->abort(); 1270 _cm->root_regions()->wait_until_scan_finished(); 1271 append_secondary_free_list_if_not_empty_with_lock(); 1272 1273 gc_prologue(true); 1274 increment_total_collections(true /* full gc */); 1275 increment_old_marking_cycles_started(); 1276 1277 assert(used() == recalculate_used(), "Should be equal"); 1278 1279 _verifier->verify_before_gc(); 1280 1281 _verifier->check_bitmaps("Full GC Start"); 1282 pre_full_gc_dump(gc_timer); 1283 1284 #if defined(COMPILER2) || INCLUDE_JVMCI 1285 DerivedPointerTable::clear(); 1286 #endif 1287 1288 // Disable discovery and empty the discovered lists 1289 // for the CM ref processor. 1290 ref_processor_cm()->disable_discovery(); 1291 ref_processor_cm()->abandon_partial_discovery(); 1292 ref_processor_cm()->verify_no_references_recorded(); 1293 1294 // Abandon current iterations of concurrent marking and concurrent 1295 // refinement, if any are in progress. 1296 concurrent_mark()->abort(); 1297 1298 // Make sure we'll choose a new allocation region afterwards. 1299 _allocator->release_mutator_alloc_region(); 1300 _allocator->abandon_gc_alloc_regions(); 1301 g1_rem_set()->cleanupHRRS(); 1302 1303 // We may have added regions to the current incremental collection 1304 // set between the last GC or pause and now. We need to clear the 1305 // incremental collection set and then start rebuilding it afresh 1306 // after this full GC. 1307 abandon_collection_set(collection_set()->inc_head()); 1308 collection_set()->clear_incremental(); 1309 collection_set()->stop_incremental_building(); 1310 1311 tear_down_region_sets(false /* free_list_only */); 1312 collector_state()->set_gcs_are_young(true); 1313 1314 // See the comments in g1CollectedHeap.hpp and 1315 // G1CollectedHeap::ref_processing_init() about 1316 // how reference processing currently works in G1. 1317 1318 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1319 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1320 1321 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1322 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1323 1324 ref_processor_stw()->enable_discovery(); 1325 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1326 1327 // Do collection work 1328 { 1329 HandleMark hm; // Discard invalid handles created during gc 1330 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1331 } 1332 1333 assert(num_free_regions() == 0, "we should not have added any free regions"); 1334 rebuild_region_sets(false /* free_list_only */); 1335 1336 // Enqueue any discovered reference objects that have 1337 // not been removed from the discovered lists. 1338 ref_processor_stw()->enqueue_discovered_references(); 1339 1340 #if defined(COMPILER2) || INCLUDE_JVMCI 1341 DerivedPointerTable::update_pointers(); 1342 #endif 1343 1344 MemoryService::track_memory_usage(); 1345 1346 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1347 ref_processor_stw()->verify_no_references_recorded(); 1348 1349 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1350 ClassLoaderDataGraph::purge(); 1351 MetaspaceAux::verify_metrics(); 1352 1353 // Note: since we've just done a full GC, concurrent 1354 // marking is no longer active. Therefore we need not 1355 // re-enable reference discovery for the CM ref processor. 1356 // That will be done at the start of the next marking cycle. 1357 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1358 ref_processor_cm()->verify_no_references_recorded(); 1359 1360 reset_gc_time_stamp(); 1361 // Since everything potentially moved, we will clear all remembered 1362 // sets, and clear all cards. Later we will rebuild remembered 1363 // sets. We will also reset the GC time stamps of the regions. 1364 clear_rsets_post_compaction(); 1365 check_gc_time_stamps(); 1366 1367 resize_if_necessary_after_full_collection(); 1368 1369 // We should do this after we potentially resize the heap so 1370 // that all the COMMIT / UNCOMMIT events are generated before 1371 // the compaction events. 1372 print_hrm_post_compaction(); 1373 1374 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1375 if (hot_card_cache->use_cache()) { 1376 hot_card_cache->reset_card_counts(); 1377 hot_card_cache->reset_hot_cache(); 1378 } 1379 1380 // Rebuild remembered sets of all regions. 1381 uint n_workers = 1382 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1383 workers()->active_workers(), 1384 Threads::number_of_non_daemon_threads()); 1385 workers()->set_active_workers(n_workers); 1386 1387 ParRebuildRSTask rebuild_rs_task(this); 1388 workers()->run_task(&rebuild_rs_task); 1389 1390 // Rebuild the strong code root lists for each region 1391 rebuild_strong_code_roots(); 1392 1393 if (true) { // FIXME 1394 MetaspaceGC::compute_new_size(); 1395 } 1396 1397 #ifdef TRACESPINNING 1398 ParallelTaskTerminator::print_termination_counts(); 1399 #endif 1400 1401 // Discard all rset updates 1402 JavaThread::dirty_card_queue_set().abandon_logs(); 1403 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1404 1405 // At this point there should be no regions in the 1406 // entire heap tagged as young. 1407 assert(check_young_list_empty(true /* check_heap */), 1408 "young list should be empty at this point"); 1409 1410 // Update the number of full collections that have been completed. 1411 increment_old_marking_cycles_completed(false /* concurrent */); 1412 1413 _hrm.verify_optional(); 1414 _verifier->verify_region_sets_optional(); 1415 1416 _verifier->verify_after_gc(); 1417 1418 // Clear the previous marking bitmap, if needed for bitmap verification. 1419 // Note we cannot do this when we clear the next marking bitmap in 1420 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1421 // objects marked during a full GC against the previous bitmap. 1422 // But we need to clear it before calling check_bitmaps below since 1423 // the full GC has compacted objects and updated TAMS but not updated 1424 // the prev bitmap. 1425 if (G1VerifyBitmaps) { 1426 ((G1CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll(); 1427 } 1428 _verifier->check_bitmaps("Full GC End"); 1429 1430 // Start a new incremental collection set for the next pause 1431 assert(collection_set()->head() == NULL, "must be"); 1432 collection_set()->start_incremental_building(); 1433 1434 clear_cset_fast_test(); 1435 1436 _allocator->init_mutator_alloc_region(); 1437 1438 g1_policy()->record_full_collection_end(); 1439 1440 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1441 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1442 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1443 // before any GC notifications are raised. 1444 g1mm()->update_sizes(); 1445 1446 gc_epilogue(true); 1447 1448 heap_transition.print(); 1449 1450 print_heap_after_gc(); 1451 trace_heap_after_gc(gc_tracer); 1452 1453 post_full_gc_dump(gc_timer); 1454 } 1455 1456 gc_timer->register_gc_end(); 1457 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1458 } 1459 1460 return true; 1461 } 1462 1463 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1464 // Currently, there is no facility in the do_full_collection(bool) API to notify 1465 // the caller that the collection did not succeed (e.g., because it was locked 1466 // out by the GC locker). So, right now, we'll ignore the return value. 1467 bool dummy = do_full_collection(true, /* explicit_gc */ 1468 clear_all_soft_refs); 1469 } 1470 1471 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1472 // Include bytes that will be pre-allocated to support collections, as "used". 1473 const size_t used_after_gc = used(); 1474 const size_t capacity_after_gc = capacity(); 1475 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1476 1477 // This is enforced in arguments.cpp. 1478 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1479 "otherwise the code below doesn't make sense"); 1480 1481 // We don't have floating point command-line arguments 1482 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1483 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1484 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1485 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1486 1487 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1488 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1489 1490 // We have to be careful here as these two calculations can overflow 1491 // 32-bit size_t's. 1492 double used_after_gc_d = (double) used_after_gc; 1493 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1494 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1495 1496 // Let's make sure that they are both under the max heap size, which 1497 // by default will make them fit into a size_t. 1498 double desired_capacity_upper_bound = (double) max_heap_size; 1499 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1500 desired_capacity_upper_bound); 1501 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1502 desired_capacity_upper_bound); 1503 1504 // We can now safely turn them into size_t's. 1505 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1506 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1507 1508 // This assert only makes sense here, before we adjust them 1509 // with respect to the min and max heap size. 1510 assert(minimum_desired_capacity <= maximum_desired_capacity, 1511 "minimum_desired_capacity = " SIZE_FORMAT ", " 1512 "maximum_desired_capacity = " SIZE_FORMAT, 1513 minimum_desired_capacity, maximum_desired_capacity); 1514 1515 // Should not be greater than the heap max size. No need to adjust 1516 // it with respect to the heap min size as it's a lower bound (i.e., 1517 // we'll try to make the capacity larger than it, not smaller). 1518 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1519 // Should not be less than the heap min size. No need to adjust it 1520 // with respect to the heap max size as it's an upper bound (i.e., 1521 // we'll try to make the capacity smaller than it, not greater). 1522 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1523 1524 if (capacity_after_gc < minimum_desired_capacity) { 1525 // Don't expand unless it's significant 1526 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1527 1528 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1529 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1530 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1531 1532 expand(expand_bytes); 1533 1534 // No expansion, now see if we want to shrink 1535 } else if (capacity_after_gc > maximum_desired_capacity) { 1536 // Capacity too large, compute shrinking size 1537 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1538 1539 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1540 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1541 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1542 1543 shrink(shrink_bytes); 1544 } 1545 } 1546 1547 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1548 AllocationContext_t context, 1549 bool do_gc, 1550 bool clear_all_soft_refs, 1551 bool expect_null_mutator_alloc_region, 1552 bool* gc_succeeded) { 1553 *gc_succeeded = true; 1554 // Let's attempt the allocation first. 1555 HeapWord* result = 1556 attempt_allocation_at_safepoint(word_size, 1557 context, 1558 expect_null_mutator_alloc_region); 1559 if (result != NULL) { 1560 assert(*gc_succeeded, "sanity"); 1561 return result; 1562 } 1563 1564 // In a G1 heap, we're supposed to keep allocation from failing by 1565 // incremental pauses. Therefore, at least for now, we'll favor 1566 // expansion over collection. (This might change in the future if we can 1567 // do something smarter than full collection to satisfy a failed alloc.) 1568 result = expand_and_allocate(word_size, context); 1569 if (result != NULL) { 1570 assert(*gc_succeeded, "sanity"); 1571 return result; 1572 } 1573 1574 if (do_gc) { 1575 // Expansion didn't work, we'll try to do a Full GC. 1576 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1577 clear_all_soft_refs); 1578 } 1579 1580 return NULL; 1581 } 1582 1583 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1584 AllocationContext_t context, 1585 bool* succeeded) { 1586 assert_at_safepoint(true /* should_be_vm_thread */); 1587 1588 // Attempts to allocate followed by Full GC. 1589 HeapWord* result = 1590 satisfy_failed_allocation_helper(word_size, 1591 context, 1592 true, /* do_gc */ 1593 false, /* clear_all_soft_refs */ 1594 false, /* expect_null_mutator_alloc_region */ 1595 succeeded); 1596 1597 if (result != NULL || !*succeeded) { 1598 return result; 1599 } 1600 1601 // Attempts to allocate followed by Full GC that will collect all soft references. 1602 result = satisfy_failed_allocation_helper(word_size, 1603 context, 1604 true, /* do_gc */ 1605 true, /* clear_all_soft_refs */ 1606 true, /* expect_null_mutator_alloc_region */ 1607 succeeded); 1608 1609 if (result != NULL || !*succeeded) { 1610 return result; 1611 } 1612 1613 // Attempts to allocate, no GC 1614 result = satisfy_failed_allocation_helper(word_size, 1615 context, 1616 false, /* do_gc */ 1617 false, /* clear_all_soft_refs */ 1618 true, /* expect_null_mutator_alloc_region */ 1619 succeeded); 1620 1621 if (result != NULL) { 1622 assert(*succeeded, "sanity"); 1623 return result; 1624 } 1625 1626 assert(!collector_policy()->should_clear_all_soft_refs(), 1627 "Flag should have been handled and cleared prior to this point"); 1628 1629 // What else? We might try synchronous finalization later. If the total 1630 // space available is large enough for the allocation, then a more 1631 // complete compaction phase than we've tried so far might be 1632 // appropriate. 1633 assert(*succeeded, "sanity"); 1634 return NULL; 1635 } 1636 1637 // Attempting to expand the heap sufficiently 1638 // to support an allocation of the given "word_size". If 1639 // successful, perform the allocation and return the address of the 1640 // allocated block, or else "NULL". 1641 1642 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1643 assert_at_safepoint(true /* should_be_vm_thread */); 1644 1645 _verifier->verify_region_sets_optional(); 1646 1647 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1648 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1649 word_size * HeapWordSize); 1650 1651 1652 if (expand(expand_bytes)) { 1653 _hrm.verify_optional(); 1654 _verifier->verify_region_sets_optional(); 1655 return attempt_allocation_at_safepoint(word_size, 1656 context, 1657 false /* expect_null_mutator_alloc_region */); 1658 } 1659 return NULL; 1660 } 1661 1662 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) { 1663 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1664 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1665 HeapRegion::GrainBytes); 1666 1667 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B", 1668 expand_bytes, aligned_expand_bytes); 1669 1670 if (is_maximal_no_gc()) { 1671 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1672 return false; 1673 } 1674 1675 double expand_heap_start_time_sec = os::elapsedTime(); 1676 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1677 assert(regions_to_expand > 0, "Must expand by at least one region"); 1678 1679 uint expanded_by = _hrm.expand_by(regions_to_expand); 1680 if (expand_time_ms != NULL) { 1681 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1682 } 1683 1684 if (expanded_by > 0) { 1685 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1686 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1687 g1_policy()->record_new_heap_size(num_regions()); 1688 } else { 1689 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1690 1691 // The expansion of the virtual storage space was unsuccessful. 1692 // Let's see if it was because we ran out of swap. 1693 if (G1ExitOnExpansionFailure && 1694 _hrm.available() >= regions_to_expand) { 1695 // We had head room... 1696 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1697 } 1698 } 1699 return regions_to_expand > 0; 1700 } 1701 1702 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1703 size_t aligned_shrink_bytes = 1704 ReservedSpace::page_align_size_down(shrink_bytes); 1705 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1706 HeapRegion::GrainBytes); 1707 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1708 1709 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1710 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1711 1712 1713 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", 1714 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1715 if (num_regions_removed > 0) { 1716 g1_policy()->record_new_heap_size(num_regions()); 1717 } else { 1718 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1719 } 1720 } 1721 1722 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1723 _verifier->verify_region_sets_optional(); 1724 1725 // We should only reach here at the end of a Full GC which means we 1726 // should not not be holding to any GC alloc regions. The method 1727 // below will make sure of that and do any remaining clean up. 1728 _allocator->abandon_gc_alloc_regions(); 1729 1730 // Instead of tearing down / rebuilding the free lists here, we 1731 // could instead use the remove_all_pending() method on free_list to 1732 // remove only the ones that we need to remove. 1733 tear_down_region_sets(true /* free_list_only */); 1734 shrink_helper(shrink_bytes); 1735 rebuild_region_sets(true /* free_list_only */); 1736 1737 _hrm.verify_optional(); 1738 _verifier->verify_region_sets_optional(); 1739 } 1740 1741 // Public methods. 1742 1743 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1744 CollectedHeap(), 1745 _g1_policy(policy_), 1746 _collection_set(this), 1747 _dirty_card_queue_set(false), 1748 _is_alive_closure_cm(this), 1749 _is_alive_closure_stw(this), 1750 _ref_processor_cm(NULL), 1751 _ref_processor_stw(NULL), 1752 _bot(NULL), 1753 _cg1r(NULL), 1754 _g1mm(NULL), 1755 _refine_cte_cl(NULL), 1756 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1757 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1758 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1759 _humongous_reclaim_candidates(), 1760 _has_humongous_reclaim_candidates(false), 1761 _archive_allocator(NULL), 1762 _free_regions_coming(false), 1763 _young_list(new YoungList(this)), 1764 _gc_time_stamp(0), 1765 _summary_bytes_used(0), 1766 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1767 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1768 _expand_heap_after_alloc_failure(true), 1769 _old_marking_cycles_started(0), 1770 _old_marking_cycles_completed(0), 1771 _heap_summary_sent(false), 1772 _in_cset_fast_test(), 1773 _dirty_cards_region_list(NULL), 1774 _worker_cset_start_region(NULL), 1775 _worker_cset_start_region_time_stamp(NULL), 1776 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1777 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1778 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1779 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1780 1781 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1782 /* are_GC_task_threads */true, 1783 /* are_ConcurrentGC_threads */false); 1784 _workers->initialize_workers(); 1785 _verifier = new G1HeapVerifier(this); 1786 1787 _allocator = G1Allocator::create_allocator(this); 1788 1789 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1790 1791 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1792 1793 // Override the default _filler_array_max_size so that no humongous filler 1794 // objects are created. 1795 _filler_array_max_size = _humongous_object_threshold_in_words; 1796 1797 uint n_queues = ParallelGCThreads; 1798 _task_queues = new RefToScanQueueSet(n_queues); 1799 1800 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1801 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC); 1802 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1803 1804 for (uint i = 0; i < n_queues; i++) { 1805 RefToScanQueue* q = new RefToScanQueue(); 1806 q->initialize(); 1807 _task_queues->register_queue(i, q); 1808 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1809 } 1810 clear_cset_start_regions(); 1811 1812 // Initialize the G1EvacuationFailureALot counters and flags. 1813 NOT_PRODUCT(reset_evacuation_should_fail();) 1814 1815 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1816 } 1817 1818 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1819 size_t size, 1820 size_t translation_factor) { 1821 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1822 // Allocate a new reserved space, preferring to use large pages. 1823 ReservedSpace rs(size, preferred_page_size); 1824 G1RegionToSpaceMapper* result = 1825 G1RegionToSpaceMapper::create_mapper(rs, 1826 size, 1827 rs.alignment(), 1828 HeapRegion::GrainBytes, 1829 translation_factor, 1830 mtGC); 1831 if (TracePageSizes) { 1832 tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT, 1833 description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size); 1834 } 1835 return result; 1836 } 1837 1838 jint G1CollectedHeap::initialize() { 1839 CollectedHeap::pre_initialize(); 1840 os::enable_vtime(); 1841 1842 // Necessary to satisfy locking discipline assertions. 1843 1844 MutexLocker x(Heap_lock); 1845 1846 // While there are no constraints in the GC code that HeapWordSize 1847 // be any particular value, there are multiple other areas in the 1848 // system which believe this to be true (e.g. oop->object_size in some 1849 // cases incorrectly returns the size in wordSize units rather than 1850 // HeapWordSize). 1851 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1852 1853 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1854 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1855 size_t heap_alignment = collector_policy()->heap_alignment(); 1856 1857 // Ensure that the sizes are properly aligned. 1858 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1859 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1860 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1861 1862 _refine_cte_cl = new RefineCardTableEntryClosure(); 1863 1864 jint ecode = JNI_OK; 1865 _cg1r = ConcurrentG1Refine::create(this, _refine_cte_cl, &ecode); 1866 if (_cg1r == NULL) { 1867 return ecode; 1868 } 1869 1870 // Reserve the maximum. 1871 1872 // When compressed oops are enabled, the preferred heap base 1873 // is calculated by subtracting the requested size from the 1874 // 32Gb boundary and using the result as the base address for 1875 // heap reservation. If the requested size is not aligned to 1876 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1877 // into the ReservedHeapSpace constructor) then the actual 1878 // base of the reserved heap may end up differing from the 1879 // address that was requested (i.e. the preferred heap base). 1880 // If this happens then we could end up using a non-optimal 1881 // compressed oops mode. 1882 1883 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1884 heap_alignment); 1885 1886 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1887 1888 // Create the barrier set for the entire reserved region. 1889 G1SATBCardTableLoggingModRefBS* bs 1890 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1891 bs->initialize(); 1892 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1893 set_barrier_set(bs); 1894 1895 // Also create a G1 rem set. 1896 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 1897 1898 // Carve out the G1 part of the heap. 1899 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1900 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1901 G1RegionToSpaceMapper* heap_storage = 1902 G1RegionToSpaceMapper::create_mapper(g1_rs, 1903 g1_rs.size(), 1904 page_size, 1905 HeapRegion::GrainBytes, 1906 1, 1907 mtJavaHeap); 1908 os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(), 1909 max_byte_size, page_size, 1910 heap_rs.base(), 1911 heap_rs.size()); 1912 heap_storage->set_mapping_changed_listener(&_listener); 1913 1914 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1915 G1RegionToSpaceMapper* bot_storage = 1916 create_aux_memory_mapper("Block offset table", 1917 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1918 G1BlockOffsetTable::heap_map_factor()); 1919 1920 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1921 G1RegionToSpaceMapper* cardtable_storage = 1922 create_aux_memory_mapper("Card table", 1923 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1924 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1925 1926 G1RegionToSpaceMapper* card_counts_storage = 1927 create_aux_memory_mapper("Card counts table", 1928 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1929 G1CardCounts::heap_map_factor()); 1930 1931 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1932 G1RegionToSpaceMapper* prev_bitmap_storage = 1933 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1934 G1RegionToSpaceMapper* next_bitmap_storage = 1935 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1936 1937 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1938 g1_barrier_set()->initialize(cardtable_storage); 1939 // Do later initialization work for concurrent refinement. 1940 _cg1r->init(card_counts_storage); 1941 1942 // 6843694 - ensure that the maximum region index can fit 1943 // in the remembered set structures. 1944 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1945 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1946 1947 G1RemSet::initialize(max_regions()); 1948 1949 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1950 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1951 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1952 "too many cards per region"); 1953 1954 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1955 1956 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1957 1958 { 1959 HeapWord* start = _hrm.reserved().start(); 1960 HeapWord* end = _hrm.reserved().end(); 1961 size_t granularity = HeapRegion::GrainBytes; 1962 1963 _in_cset_fast_test.initialize(start, end, granularity); 1964 _humongous_reclaim_candidates.initialize(start, end, granularity); 1965 } 1966 1967 // Create the G1ConcurrentMark data structure and thread. 1968 // (Must do this late, so that "max_regions" is defined.) 1969 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1970 if (_cm == NULL || !_cm->completed_initialization()) { 1971 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1972 return JNI_ENOMEM; 1973 } 1974 _cmThread = _cm->cmThread(); 1975 1976 // Now expand into the initial heap size. 1977 if (!expand(init_byte_size)) { 1978 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1979 return JNI_ENOMEM; 1980 } 1981 1982 // Perform any initialization actions delegated to the policy. 1983 g1_policy()->init(); 1984 1985 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1986 SATB_Q_FL_lock, 1987 G1SATBProcessCompletedThreshold, 1988 Shared_SATB_Q_lock); 1989 1990 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 1991 DirtyCardQ_CBL_mon, 1992 DirtyCardQ_FL_lock, 1993 (int)concurrent_g1_refine()->yellow_zone(), 1994 (int)concurrent_g1_refine()->red_zone(), 1995 Shared_DirtyCardQ_lock, 1996 NULL, // fl_owner 1997 true); // init_free_ids 1998 1999 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 2000 DirtyCardQ_CBL_mon, 2001 DirtyCardQ_FL_lock, 2002 -1, // never trigger processing 2003 -1, // no limit on length 2004 Shared_DirtyCardQ_lock, 2005 &JavaThread::dirty_card_queue_set()); 2006 2007 // Here we allocate the dummy HeapRegion that is required by the 2008 // G1AllocRegion class. 2009 HeapRegion* dummy_region = _hrm.get_dummy_region(); 2010 2011 // We'll re-use the same region whether the alloc region will 2012 // require BOT updates or not and, if it doesn't, then a non-young 2013 // region will complain that it cannot support allocations without 2014 // BOT updates. So we'll tag the dummy region as eden to avoid that. 2015 dummy_region->set_eden(); 2016 // Make sure it's full. 2017 dummy_region->set_top(dummy_region->end()); 2018 G1AllocRegion::setup(this, dummy_region); 2019 2020 _allocator->init_mutator_alloc_region(); 2021 2022 // Do create of the monitoring and management support so that 2023 // values in the heap have been properly initialized. 2024 _g1mm = new G1MonitoringSupport(this); 2025 2026 G1StringDedup::initialize(); 2027 2028 _preserved_objs = NEW_C_HEAP_ARRAY(OopAndMarkOopStack, ParallelGCThreads, mtGC); 2029 for (uint i = 0; i < ParallelGCThreads; i++) { 2030 new (&_preserved_objs[i]) OopAndMarkOopStack(); 2031 } 2032 2033 return JNI_OK; 2034 } 2035 2036 void G1CollectedHeap::stop() { 2037 // Stop all concurrent threads. We do this to make sure these threads 2038 // do not continue to execute and access resources (e.g. logging) 2039 // that are destroyed during shutdown. 2040 _cg1r->stop(); 2041 _cmThread->stop(); 2042 if (G1StringDedup::is_enabled()) { 2043 G1StringDedup::stop(); 2044 } 2045 } 2046 2047 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2048 return HeapRegion::max_region_size(); 2049 } 2050 2051 void G1CollectedHeap::post_initialize() { 2052 CollectedHeap::post_initialize(); 2053 ref_processing_init(); 2054 } 2055 2056 void G1CollectedHeap::ref_processing_init() { 2057 // Reference processing in G1 currently works as follows: 2058 // 2059 // * There are two reference processor instances. One is 2060 // used to record and process discovered references 2061 // during concurrent marking; the other is used to 2062 // record and process references during STW pauses 2063 // (both full and incremental). 2064 // * Both ref processors need to 'span' the entire heap as 2065 // the regions in the collection set may be dotted around. 2066 // 2067 // * For the concurrent marking ref processor: 2068 // * Reference discovery is enabled at initial marking. 2069 // * Reference discovery is disabled and the discovered 2070 // references processed etc during remarking. 2071 // * Reference discovery is MT (see below). 2072 // * Reference discovery requires a barrier (see below). 2073 // * Reference processing may or may not be MT 2074 // (depending on the value of ParallelRefProcEnabled 2075 // and ParallelGCThreads). 2076 // * A full GC disables reference discovery by the CM 2077 // ref processor and abandons any entries on it's 2078 // discovered lists. 2079 // 2080 // * For the STW processor: 2081 // * Non MT discovery is enabled at the start of a full GC. 2082 // * Processing and enqueueing during a full GC is non-MT. 2083 // * During a full GC, references are processed after marking. 2084 // 2085 // * Discovery (may or may not be MT) is enabled at the start 2086 // of an incremental evacuation pause. 2087 // * References are processed near the end of a STW evacuation pause. 2088 // * For both types of GC: 2089 // * Discovery is atomic - i.e. not concurrent. 2090 // * Reference discovery will not need a barrier. 2091 2092 MemRegion mr = reserved_region(); 2093 2094 // Concurrent Mark ref processor 2095 _ref_processor_cm = 2096 new ReferenceProcessor(mr, // span 2097 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2098 // mt processing 2099 ParallelGCThreads, 2100 // degree of mt processing 2101 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2102 // mt discovery 2103 MAX2(ParallelGCThreads, ConcGCThreads), 2104 // degree of mt discovery 2105 false, 2106 // Reference discovery is not atomic 2107 &_is_alive_closure_cm); 2108 // is alive closure 2109 // (for efficiency/performance) 2110 2111 // STW ref processor 2112 _ref_processor_stw = 2113 new ReferenceProcessor(mr, // span 2114 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2115 // mt processing 2116 ParallelGCThreads, 2117 // degree of mt processing 2118 (ParallelGCThreads > 1), 2119 // mt discovery 2120 ParallelGCThreads, 2121 // degree of mt discovery 2122 true, 2123 // Reference discovery is atomic 2124 &_is_alive_closure_stw); 2125 // is alive closure 2126 // (for efficiency/performance) 2127 } 2128 2129 CollectorPolicy* G1CollectedHeap::collector_policy() const { 2130 return g1_policy(); 2131 } 2132 2133 size_t G1CollectedHeap::capacity() const { 2134 return _hrm.length() * HeapRegion::GrainBytes; 2135 } 2136 2137 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2138 hr->reset_gc_time_stamp(); 2139 } 2140 2141 #ifndef PRODUCT 2142 2143 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2144 private: 2145 unsigned _gc_time_stamp; 2146 bool _failures; 2147 2148 public: 2149 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2150 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2151 2152 virtual bool doHeapRegion(HeapRegion* hr) { 2153 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2154 if (_gc_time_stamp != region_gc_time_stamp) { 2155 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 2156 region_gc_time_stamp, _gc_time_stamp); 2157 _failures = true; 2158 } 2159 return false; 2160 } 2161 2162 bool failures() { return _failures; } 2163 }; 2164 2165 void G1CollectedHeap::check_gc_time_stamps() { 2166 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2167 heap_region_iterate(&cl); 2168 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2169 } 2170 #endif // PRODUCT 2171 2172 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2173 _cg1r->hot_card_cache()->drain(cl, worker_i); 2174 } 2175 2176 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2177 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2178 size_t n_completed_buffers = 0; 2179 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2180 n_completed_buffers++; 2181 } 2182 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2183 dcqs.clear_n_completed_buffers(); 2184 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2185 } 2186 2187 // Computes the sum of the storage used by the various regions. 2188 size_t G1CollectedHeap::used() const { 2189 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2190 if (_archive_allocator != NULL) { 2191 result += _archive_allocator->used(); 2192 } 2193 return result; 2194 } 2195 2196 size_t G1CollectedHeap::used_unlocked() const { 2197 return _summary_bytes_used; 2198 } 2199 2200 class SumUsedClosure: public HeapRegionClosure { 2201 size_t _used; 2202 public: 2203 SumUsedClosure() : _used(0) {} 2204 bool doHeapRegion(HeapRegion* r) { 2205 _used += r->used(); 2206 return false; 2207 } 2208 size_t result() { return _used; } 2209 }; 2210 2211 size_t G1CollectedHeap::recalculate_used() const { 2212 double recalculate_used_start = os::elapsedTime(); 2213 2214 SumUsedClosure blk; 2215 heap_region_iterate(&blk); 2216 2217 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2218 return blk.result(); 2219 } 2220 2221 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2222 switch (cause) { 2223 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2224 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2225 case GCCause::_update_allocation_context_stats_inc: return true; 2226 case GCCause::_wb_conc_mark: return true; 2227 default : return false; 2228 } 2229 } 2230 2231 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2232 switch (cause) { 2233 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2234 case GCCause::_g1_humongous_allocation: return true; 2235 default: return is_user_requested_concurrent_full_gc(cause); 2236 } 2237 } 2238 2239 #ifndef PRODUCT 2240 void G1CollectedHeap::allocate_dummy_regions() { 2241 // Let's fill up most of the region 2242 size_t word_size = HeapRegion::GrainWords - 1024; 2243 // And as a result the region we'll allocate will be humongous. 2244 guarantee(is_humongous(word_size), "sanity"); 2245 2246 // _filler_array_max_size is set to humongous object threshold 2247 // but temporarily change it to use CollectedHeap::fill_with_object(). 2248 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2249 2250 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2251 // Let's use the existing mechanism for the allocation 2252 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2253 AllocationContext::system()); 2254 if (dummy_obj != NULL) { 2255 MemRegion mr(dummy_obj, word_size); 2256 CollectedHeap::fill_with_object(mr); 2257 } else { 2258 // If we can't allocate once, we probably cannot allocate 2259 // again. Let's get out of the loop. 2260 break; 2261 } 2262 } 2263 } 2264 #endif // !PRODUCT 2265 2266 void G1CollectedHeap::increment_old_marking_cycles_started() { 2267 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2268 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2269 "Wrong marking cycle count (started: %d, completed: %d)", 2270 _old_marking_cycles_started, _old_marking_cycles_completed); 2271 2272 _old_marking_cycles_started++; 2273 } 2274 2275 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2276 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2277 2278 // We assume that if concurrent == true, then the caller is a 2279 // concurrent thread that was joined the Suspendible Thread 2280 // Set. If there's ever a cheap way to check this, we should add an 2281 // assert here. 2282 2283 // Given that this method is called at the end of a Full GC or of a 2284 // concurrent cycle, and those can be nested (i.e., a Full GC can 2285 // interrupt a concurrent cycle), the number of full collections 2286 // completed should be either one (in the case where there was no 2287 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2288 // behind the number of full collections started. 2289 2290 // This is the case for the inner caller, i.e. a Full GC. 2291 assert(concurrent || 2292 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2293 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2294 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2295 "is inconsistent with _old_marking_cycles_completed = %u", 2296 _old_marking_cycles_started, _old_marking_cycles_completed); 2297 2298 // This is the case for the outer caller, i.e. the concurrent cycle. 2299 assert(!concurrent || 2300 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2301 "for outer caller (concurrent cycle): " 2302 "_old_marking_cycles_started = %u " 2303 "is inconsistent with _old_marking_cycles_completed = %u", 2304 _old_marking_cycles_started, _old_marking_cycles_completed); 2305 2306 _old_marking_cycles_completed += 1; 2307 2308 // We need to clear the "in_progress" flag in the CM thread before 2309 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2310 // is set) so that if a waiter requests another System.gc() it doesn't 2311 // incorrectly see that a marking cycle is still in progress. 2312 if (concurrent) { 2313 _cmThread->set_idle(); 2314 } 2315 2316 // This notify_all() will ensure that a thread that called 2317 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2318 // and it's waiting for a full GC to finish will be woken up. It is 2319 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2320 FullGCCount_lock->notify_all(); 2321 } 2322 2323 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2324 GCIdMarkAndRestore conc_gc_id_mark; 2325 collector_state()->set_concurrent_cycle_started(true); 2326 _gc_timer_cm->register_gc_start(start_time); 2327 2328 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2329 trace_heap_before_gc(_gc_tracer_cm); 2330 _cmThread->set_gc_id(GCId::current()); 2331 } 2332 2333 void G1CollectedHeap::register_concurrent_cycle_end() { 2334 if (collector_state()->concurrent_cycle_started()) { 2335 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2336 if (_cm->has_aborted()) { 2337 _gc_tracer_cm->report_concurrent_mode_failure(); 2338 2339 // ConcurrentGCTimer will be ended as well. 2340 _cm->register_concurrent_gc_end_and_stop_timer(); 2341 } else { 2342 _gc_timer_cm->register_gc_end(); 2343 } 2344 2345 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2346 2347 // Clear state variables to prepare for the next concurrent cycle. 2348 collector_state()->set_concurrent_cycle_started(false); 2349 _heap_summary_sent = false; 2350 } 2351 } 2352 2353 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2354 if (collector_state()->concurrent_cycle_started()) { 2355 // This function can be called when: 2356 // the cleanup pause is run 2357 // the concurrent cycle is aborted before the cleanup pause. 2358 // the concurrent cycle is aborted after the cleanup pause, 2359 // but before the concurrent cycle end has been registered. 2360 // Make sure that we only send the heap information once. 2361 if (!_heap_summary_sent) { 2362 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2363 trace_heap_after_gc(_gc_tracer_cm); 2364 _heap_summary_sent = true; 2365 } 2366 } 2367 } 2368 2369 void G1CollectedHeap::collect(GCCause::Cause cause) { 2370 assert_heap_not_locked(); 2371 2372 uint gc_count_before; 2373 uint old_marking_count_before; 2374 uint full_gc_count_before; 2375 bool retry_gc; 2376 2377 do { 2378 retry_gc = false; 2379 2380 { 2381 MutexLocker ml(Heap_lock); 2382 2383 // Read the GC count while holding the Heap_lock 2384 gc_count_before = total_collections(); 2385 full_gc_count_before = total_full_collections(); 2386 old_marking_count_before = _old_marking_cycles_started; 2387 } 2388 2389 if (should_do_concurrent_full_gc(cause)) { 2390 // Schedule an initial-mark evacuation pause that will start a 2391 // concurrent cycle. We're setting word_size to 0 which means that 2392 // we are not requesting a post-GC allocation. 2393 VM_G1IncCollectionPause op(gc_count_before, 2394 0, /* word_size */ 2395 true, /* should_initiate_conc_mark */ 2396 g1_policy()->max_pause_time_ms(), 2397 cause); 2398 op.set_allocation_context(AllocationContext::current()); 2399 2400 VMThread::execute(&op); 2401 if (!op.pause_succeeded()) { 2402 if (old_marking_count_before == _old_marking_cycles_started) { 2403 retry_gc = op.should_retry_gc(); 2404 } else { 2405 // A Full GC happened while we were trying to schedule the 2406 // initial-mark GC. No point in starting a new cycle given 2407 // that the whole heap was collected anyway. 2408 } 2409 2410 if (retry_gc) { 2411 if (GCLocker::is_active_and_needs_gc()) { 2412 GCLocker::stall_until_clear(); 2413 } 2414 } 2415 } 2416 } else { 2417 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2418 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2419 2420 // Schedule a standard evacuation pause. We're setting word_size 2421 // to 0 which means that we are not requesting a post-GC allocation. 2422 VM_G1IncCollectionPause op(gc_count_before, 2423 0, /* word_size */ 2424 false, /* should_initiate_conc_mark */ 2425 g1_policy()->max_pause_time_ms(), 2426 cause); 2427 VMThread::execute(&op); 2428 } else { 2429 // Schedule a Full GC. 2430 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2431 VMThread::execute(&op); 2432 } 2433 } 2434 } while (retry_gc); 2435 } 2436 2437 bool G1CollectedHeap::is_in(const void* p) const { 2438 if (_hrm.reserved().contains(p)) { 2439 // Given that we know that p is in the reserved space, 2440 // heap_region_containing() should successfully 2441 // return the containing region. 2442 HeapRegion* hr = heap_region_containing(p); 2443 return hr->is_in(p); 2444 } else { 2445 return false; 2446 } 2447 } 2448 2449 #ifdef ASSERT 2450 bool G1CollectedHeap::is_in_exact(const void* p) const { 2451 bool contains = reserved_region().contains(p); 2452 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2453 if (contains && available) { 2454 return true; 2455 } else { 2456 return false; 2457 } 2458 } 2459 #endif 2460 2461 bool G1CollectedHeap::obj_in_cs(oop obj) { 2462 HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj); 2463 return r != NULL && r->in_collection_set(); 2464 } 2465 2466 // Iteration functions. 2467 2468 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2469 2470 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2471 ExtendedOopClosure* _cl; 2472 public: 2473 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2474 bool doHeapRegion(HeapRegion* r) { 2475 if (!r->is_continues_humongous()) { 2476 r->oop_iterate(_cl); 2477 } 2478 return false; 2479 } 2480 }; 2481 2482 // Iterates an ObjectClosure over all objects within a HeapRegion. 2483 2484 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2485 ObjectClosure* _cl; 2486 public: 2487 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2488 bool doHeapRegion(HeapRegion* r) { 2489 if (!r->is_continues_humongous()) { 2490 r->object_iterate(_cl); 2491 } 2492 return false; 2493 } 2494 }; 2495 2496 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2497 IterateObjectClosureRegionClosure blk(cl); 2498 heap_region_iterate(&blk); 2499 } 2500 2501 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2502 _hrm.iterate(cl); 2503 } 2504 2505 void 2506 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2507 uint worker_id, 2508 HeapRegionClaimer *hrclaimer, 2509 bool concurrent) const { 2510 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2511 } 2512 2513 // Clear the cached CSet starting regions and (more importantly) 2514 // the time stamps. Called when we reset the GC time stamp. 2515 void G1CollectedHeap::clear_cset_start_regions() { 2516 assert(_worker_cset_start_region != NULL, "sanity"); 2517 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2518 2519 for (uint i = 0; i < ParallelGCThreads; i++) { 2520 _worker_cset_start_region[i] = NULL; 2521 _worker_cset_start_region_time_stamp[i] = 0; 2522 } 2523 } 2524 2525 // Given the id of a worker, obtain or calculate a suitable 2526 // starting region for iterating over the current collection set. 2527 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2528 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2529 2530 HeapRegion* result = NULL; 2531 unsigned gc_time_stamp = get_gc_time_stamp(); 2532 2533 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2534 // Cached starting region for current worker was set 2535 // during the current pause - so it's valid. 2536 // Note: the cached starting heap region may be NULL 2537 // (when the collection set is empty). 2538 result = _worker_cset_start_region[worker_i]; 2539 assert(result == NULL || result->in_collection_set(), "sanity"); 2540 return result; 2541 } 2542 2543 // The cached entry was not valid so let's calculate 2544 // a suitable starting heap region for this worker. 2545 2546 // We want the parallel threads to start their collection 2547 // set iteration at different collection set regions to 2548 // avoid contention. 2549 // If we have: 2550 // n collection set regions 2551 // p threads 2552 // Then thread t will start at region floor ((t * n) / p) 2553 2554 result = collection_set()->head(); 2555 uint cs_size = collection_set()->region_length(); 2556 uint active_workers = workers()->active_workers(); 2557 2558 uint end_ind = (cs_size * worker_i) / active_workers; 2559 uint start_ind = 0; 2560 2561 if (worker_i > 0 && 2562 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2563 // Previous workers starting region is valid 2564 // so let's iterate from there 2565 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2566 OrderAccess::loadload(); 2567 result = _worker_cset_start_region[worker_i - 1]; 2568 } 2569 2570 for (uint i = start_ind; i < end_ind; i++) { 2571 result = result->next_in_collection_set(); 2572 } 2573 2574 // Note: the calculated starting heap region may be NULL 2575 // (when the collection set is empty). 2576 assert(result == NULL || result->in_collection_set(), "sanity"); 2577 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2578 "should be updated only once per pause"); 2579 _worker_cset_start_region[worker_i] = result; 2580 OrderAccess::storestore(); 2581 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2582 return result; 2583 } 2584 2585 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2586 HeapRegion* r = collection_set()->head(); 2587 while (r != NULL) { 2588 HeapRegion* next = r->next_in_collection_set(); 2589 if (cl->doHeapRegion(r)) { 2590 cl->incomplete(); 2591 return; 2592 } 2593 r = next; 2594 } 2595 } 2596 2597 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2598 HeapRegionClosure *cl) { 2599 if (r == NULL) { 2600 // The CSet is empty so there's nothing to do. 2601 return; 2602 } 2603 2604 assert(r->in_collection_set(), 2605 "Start region must be a member of the collection set."); 2606 HeapRegion* cur = r; 2607 while (cur != NULL) { 2608 HeapRegion* next = cur->next_in_collection_set(); 2609 if (cl->doHeapRegion(cur) && false) { 2610 cl->incomplete(); 2611 return; 2612 } 2613 cur = next; 2614 } 2615 cur = collection_set()->head(); 2616 while (cur != r) { 2617 HeapRegion* next = cur->next_in_collection_set(); 2618 if (cl->doHeapRegion(cur) && false) { 2619 cl->incomplete(); 2620 return; 2621 } 2622 cur = next; 2623 } 2624 } 2625 2626 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2627 HeapRegion* result = _hrm.next_region_in_heap(from); 2628 while (result != NULL && result->is_pinned()) { 2629 result = _hrm.next_region_in_heap(result); 2630 } 2631 return result; 2632 } 2633 2634 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2635 HeapRegion* hr = heap_region_containing(addr); 2636 return hr->block_start(addr); 2637 } 2638 2639 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2640 HeapRegion* hr = heap_region_containing(addr); 2641 return hr->block_size(addr); 2642 } 2643 2644 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2645 HeapRegion* hr = heap_region_containing(addr); 2646 return hr->block_is_obj(addr); 2647 } 2648 2649 bool G1CollectedHeap::supports_tlab_allocation() const { 2650 return true; 2651 } 2652 2653 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2654 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2655 } 2656 2657 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2658 return young_list()->eden_used_bytes(); 2659 } 2660 2661 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2662 // must be equal to the humongous object limit. 2663 size_t G1CollectedHeap::max_tlab_size() const { 2664 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2665 } 2666 2667 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2668 AllocationContext_t context = AllocationContext::current(); 2669 return _allocator->unsafe_max_tlab_alloc(context); 2670 } 2671 2672 size_t G1CollectedHeap::max_capacity() const { 2673 return _hrm.reserved().byte_size(); 2674 } 2675 2676 jlong G1CollectedHeap::millis_since_last_gc() { 2677 // assert(false, "NYI"); 2678 return 0; 2679 } 2680 2681 void G1CollectedHeap::prepare_for_verify() { 2682 _verifier->prepare_for_verify(); 2683 } 2684 2685 void G1CollectedHeap::verify(VerifyOption vo) { 2686 _verifier->verify(vo); 2687 } 2688 2689 class PrintRegionClosure: public HeapRegionClosure { 2690 outputStream* _st; 2691 public: 2692 PrintRegionClosure(outputStream* st) : _st(st) {} 2693 bool doHeapRegion(HeapRegion* r) { 2694 r->print_on(_st); 2695 return false; 2696 } 2697 }; 2698 2699 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2700 const HeapRegion* hr, 2701 const VerifyOption vo) const { 2702 switch (vo) { 2703 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2704 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2705 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 2706 default: ShouldNotReachHere(); 2707 } 2708 return false; // keep some compilers happy 2709 } 2710 2711 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2712 const VerifyOption vo) const { 2713 switch (vo) { 2714 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2715 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2716 case VerifyOption_G1UseMarkWord: { 2717 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 2718 return !obj->is_gc_marked() && !hr->is_archive(); 2719 } 2720 default: ShouldNotReachHere(); 2721 } 2722 return false; // keep some compilers happy 2723 } 2724 2725 void G1CollectedHeap::print_on(outputStream* st) const { 2726 st->print(" %-20s", "garbage-first heap"); 2727 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2728 capacity()/K, used_unlocked()/K); 2729 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 2730 p2i(_hrm.reserved().start()), 2731 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 2732 p2i(_hrm.reserved().end())); 2733 st->cr(); 2734 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2735 uint young_regions = _young_list->length(); 2736 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2737 (size_t) young_regions * HeapRegion::GrainBytes / K); 2738 uint survivor_regions = _young_list->survivor_length(); 2739 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2740 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2741 st->cr(); 2742 MetaspaceAux::print_on(st); 2743 } 2744 2745 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2746 print_on(st); 2747 2748 // Print the per-region information. 2749 st->cr(); 2750 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2751 "HS=humongous(starts), HC=humongous(continues), " 2752 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2753 "AC=allocation context, " 2754 "TAMS=top-at-mark-start (previous, next)"); 2755 PrintRegionClosure blk(st); 2756 heap_region_iterate(&blk); 2757 } 2758 2759 void G1CollectedHeap::print_on_error(outputStream* st) const { 2760 this->CollectedHeap::print_on_error(st); 2761 2762 if (_cm != NULL) { 2763 st->cr(); 2764 _cm->print_on_error(st); 2765 } 2766 } 2767 2768 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2769 workers()->print_worker_threads_on(st); 2770 _cmThread->print_on(st); 2771 st->cr(); 2772 _cm->print_worker_threads_on(st); 2773 _cg1r->print_worker_threads_on(st); 2774 if (G1StringDedup::is_enabled()) { 2775 G1StringDedup::print_worker_threads_on(st); 2776 } 2777 } 2778 2779 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2780 workers()->threads_do(tc); 2781 tc->do_thread(_cmThread); 2782 _cg1r->threads_do(tc); 2783 if (G1StringDedup::is_enabled()) { 2784 G1StringDedup::threads_do(tc); 2785 } 2786 } 2787 2788 void G1CollectedHeap::print_tracing_info() const { 2789 g1_rem_set()->print_summary_info(); 2790 concurrent_mark()->print_summary_info(); 2791 g1_policy()->print_yg_surv_rate_info(); 2792 } 2793 2794 #ifndef PRODUCT 2795 // Helpful for debugging RSet issues. 2796 2797 class PrintRSetsClosure : public HeapRegionClosure { 2798 private: 2799 const char* _msg; 2800 size_t _occupied_sum; 2801 2802 public: 2803 bool doHeapRegion(HeapRegion* r) { 2804 HeapRegionRemSet* hrrs = r->rem_set(); 2805 size_t occupied = hrrs->occupied(); 2806 _occupied_sum += occupied; 2807 2808 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2809 if (occupied == 0) { 2810 tty->print_cr(" RSet is empty"); 2811 } else { 2812 hrrs->print(); 2813 } 2814 tty->print_cr("----------"); 2815 return false; 2816 } 2817 2818 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2819 tty->cr(); 2820 tty->print_cr("========================================"); 2821 tty->print_cr("%s", msg); 2822 tty->cr(); 2823 } 2824 2825 ~PrintRSetsClosure() { 2826 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2827 tty->print_cr("========================================"); 2828 tty->cr(); 2829 } 2830 }; 2831 2832 void G1CollectedHeap::print_cset_rsets() { 2833 PrintRSetsClosure cl("Printing CSet RSets"); 2834 collection_set_iterate(&cl); 2835 } 2836 2837 void G1CollectedHeap::print_all_rsets() { 2838 PrintRSetsClosure cl("Printing All RSets");; 2839 heap_region_iterate(&cl); 2840 } 2841 #endif // PRODUCT 2842 2843 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2844 YoungList* young_list = heap()->young_list(); 2845 2846 size_t eden_used_bytes = young_list->eden_used_bytes(); 2847 size_t survivor_used_bytes = young_list->survivor_used_bytes(); 2848 2849 size_t eden_capacity_bytes = 2850 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2851 2852 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2853 return G1HeapSummary(heap_summary, used(), eden_used_bytes, eden_capacity_bytes, survivor_used_bytes, num_regions()); 2854 } 2855 2856 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2857 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2858 stats->unused(), stats->used(), stats->region_end_waste(), 2859 stats->regions_filled(), stats->direct_allocated(), 2860 stats->failure_used(), stats->failure_waste()); 2861 } 2862 2863 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2864 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2865 gc_tracer->report_gc_heap_summary(when, heap_summary); 2866 2867 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2868 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2869 } 2870 2871 2872 G1CollectedHeap* G1CollectedHeap::heap() { 2873 CollectedHeap* heap = Universe::heap(); 2874 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2875 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2876 return (G1CollectedHeap*)heap; 2877 } 2878 2879 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 2880 // always_do_update_barrier = false; 2881 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2882 // Fill TLAB's and such 2883 accumulate_statistics_all_tlabs(); 2884 ensure_parsability(true); 2885 2886 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2887 } 2888 2889 void G1CollectedHeap::gc_epilogue(bool full) { 2890 // we are at the end of the GC. Total collections has already been increased. 2891 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2892 2893 // FIXME: what is this about? 2894 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2895 // is set. 2896 #if defined(COMPILER2) || INCLUDE_JVMCI 2897 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2898 #endif 2899 // always_do_update_barrier = true; 2900 2901 resize_all_tlabs(); 2902 allocation_context_stats().update(full); 2903 2904 // We have just completed a GC. Update the soft reference 2905 // policy with the new heap occupancy 2906 Universe::update_heap_info_at_gc(); 2907 } 2908 2909 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2910 uint gc_count_before, 2911 bool* succeeded, 2912 GCCause::Cause gc_cause) { 2913 assert_heap_not_locked_and_not_at_safepoint(); 2914 VM_G1IncCollectionPause op(gc_count_before, 2915 word_size, 2916 false, /* should_initiate_conc_mark */ 2917 g1_policy()->max_pause_time_ms(), 2918 gc_cause); 2919 2920 op.set_allocation_context(AllocationContext::current()); 2921 VMThread::execute(&op); 2922 2923 HeapWord* result = op.result(); 2924 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2925 assert(result == NULL || ret_succeeded, 2926 "the result should be NULL if the VM did not succeed"); 2927 *succeeded = ret_succeeded; 2928 2929 assert_heap_not_locked(); 2930 return result; 2931 } 2932 2933 void 2934 G1CollectedHeap::doConcurrentMark() { 2935 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2936 if (!_cmThread->in_progress()) { 2937 _cmThread->set_started(); 2938 CGC_lock->notify(); 2939 } 2940 } 2941 2942 size_t G1CollectedHeap::pending_card_num() { 2943 size_t extra_cards = 0; 2944 JavaThread *curr = Threads::first(); 2945 while (curr != NULL) { 2946 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2947 extra_cards += dcq.size(); 2948 curr = curr->next(); 2949 } 2950 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2951 size_t buffer_size = dcqs.buffer_size(); 2952 size_t buffer_num = dcqs.completed_buffers_num(); 2953 2954 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 2955 // in bytes - not the number of 'entries'. We need to convert 2956 // into a number of cards. 2957 return (buffer_size * buffer_num + extra_cards) / oopSize; 2958 } 2959 2960 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2961 private: 2962 size_t _total_humongous; 2963 size_t _candidate_humongous; 2964 2965 DirtyCardQueue _dcq; 2966 2967 // We don't nominate objects with many remembered set entries, on 2968 // the assumption that such objects are likely still live. 2969 bool is_remset_small(HeapRegion* region) const { 2970 HeapRegionRemSet* const rset = region->rem_set(); 2971 return G1EagerReclaimHumongousObjectsWithStaleRefs 2972 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2973 : rset->is_empty(); 2974 } 2975 2976 bool is_typeArray_region(HeapRegion* region) const { 2977 return oop(region->bottom())->is_typeArray(); 2978 } 2979 2980 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2981 assert(region->is_starts_humongous(), "Must start a humongous object"); 2982 2983 // Candidate selection must satisfy the following constraints 2984 // while concurrent marking is in progress: 2985 // 2986 // * In order to maintain SATB invariants, an object must not be 2987 // reclaimed if it was allocated before the start of marking and 2988 // has not had its references scanned. Such an object must have 2989 // its references (including type metadata) scanned to ensure no 2990 // live objects are missed by the marking process. Objects 2991 // allocated after the start of concurrent marking don't need to 2992 // be scanned. 2993 // 2994 // * An object must not be reclaimed if it is on the concurrent 2995 // mark stack. Objects allocated after the start of concurrent 2996 // marking are never pushed on the mark stack. 2997 // 2998 // Nominating only objects allocated after the start of concurrent 2999 // marking is sufficient to meet both constraints. This may miss 3000 // some objects that satisfy the constraints, but the marking data 3001 // structures don't support efficiently performing the needed 3002 // additional tests or scrubbing of the mark stack. 3003 // 3004 // However, we presently only nominate is_typeArray() objects. 3005 // A humongous object containing references induces remembered 3006 // set entries on other regions. In order to reclaim such an 3007 // object, those remembered sets would need to be cleaned up. 3008 // 3009 // We also treat is_typeArray() objects specially, allowing them 3010 // to be reclaimed even if allocated before the start of 3011 // concurrent mark. For this we rely on mark stack insertion to 3012 // exclude is_typeArray() objects, preventing reclaiming an object 3013 // that is in the mark stack. We also rely on the metadata for 3014 // such objects to be built-in and so ensured to be kept live. 3015 // Frequent allocation and drop of large binary blobs is an 3016 // important use case for eager reclaim, and this special handling 3017 // may reduce needed headroom. 3018 3019 return is_typeArray_region(region) && is_remset_small(region); 3020 } 3021 3022 public: 3023 RegisterHumongousWithInCSetFastTestClosure() 3024 : _total_humongous(0), 3025 _candidate_humongous(0), 3026 _dcq(&JavaThread::dirty_card_queue_set()) { 3027 } 3028 3029 virtual bool doHeapRegion(HeapRegion* r) { 3030 if (!r->is_starts_humongous()) { 3031 return false; 3032 } 3033 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3034 3035 bool is_candidate = humongous_region_is_candidate(g1h, r); 3036 uint rindex = r->hrm_index(); 3037 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 3038 if (is_candidate) { 3039 _candidate_humongous++; 3040 g1h->register_humongous_region_with_cset(rindex); 3041 // Is_candidate already filters out humongous object with large remembered sets. 3042 // If we have a humongous object with a few remembered sets, we simply flush these 3043 // remembered set entries into the DCQS. That will result in automatic 3044 // re-evaluation of their remembered set entries during the following evacuation 3045 // phase. 3046 if (!r->rem_set()->is_empty()) { 3047 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 3048 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 3049 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 3050 HeapRegionRemSetIterator hrrs(r->rem_set()); 3051 size_t card_index; 3052 while (hrrs.has_next(card_index)) { 3053 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 3054 // The remembered set might contain references to already freed 3055 // regions. Filter out such entries to avoid failing card table 3056 // verification. 3057 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 3058 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 3059 *card_ptr = CardTableModRefBS::dirty_card_val(); 3060 _dcq.enqueue(card_ptr); 3061 } 3062 } 3063 } 3064 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 3065 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 3066 hrrs.n_yielded(), r->rem_set()->occupied()); 3067 r->rem_set()->clear_locked(); 3068 } 3069 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 3070 } 3071 _total_humongous++; 3072 3073 return false; 3074 } 3075 3076 size_t total_humongous() const { return _total_humongous; } 3077 size_t candidate_humongous() const { return _candidate_humongous; } 3078 3079 void flush_rem_set_entries() { _dcq.flush(); } 3080 }; 3081 3082 void G1CollectedHeap::register_humongous_regions_with_cset() { 3083 if (!G1EagerReclaimHumongousObjects) { 3084 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 3085 return; 3086 } 3087 double time = os::elapsed_counter(); 3088 3089 // Collect reclaim candidate information and register candidates with cset. 3090 RegisterHumongousWithInCSetFastTestClosure cl; 3091 heap_region_iterate(&cl); 3092 3093 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 3094 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 3095 cl.total_humongous(), 3096 cl.candidate_humongous()); 3097 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3098 3099 // Finally flush all remembered set entries to re-check into the global DCQS. 3100 cl.flush_rem_set_entries(); 3101 } 3102 3103 class VerifyRegionRemSetClosure : public HeapRegionClosure { 3104 public: 3105 bool doHeapRegion(HeapRegion* hr) { 3106 if (!hr->is_archive() && !hr->is_continues_humongous()) { 3107 hr->verify_rem_set(); 3108 } 3109 return false; 3110 } 3111 }; 3112 3113 #ifdef ASSERT 3114 class VerifyCSetClosure: public HeapRegionClosure { 3115 public: 3116 bool doHeapRegion(HeapRegion* hr) { 3117 // Here we check that the CSet region's RSet is ready for parallel 3118 // iteration. The fields that we'll verify are only manipulated 3119 // when the region is part of a CSet and is collected. Afterwards, 3120 // we reset these fields when we clear the region's RSet (when the 3121 // region is freed) so they are ready when the region is 3122 // re-allocated. The only exception to this is if there's an 3123 // evacuation failure and instead of freeing the region we leave 3124 // it in the heap. In that case, we reset these fields during 3125 // evacuation failure handling. 3126 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3127 3128 // Here's a good place to add any other checks we'd like to 3129 // perform on CSet regions. 3130 return false; 3131 } 3132 }; 3133 #endif // ASSERT 3134 3135 uint G1CollectedHeap::num_task_queues() const { 3136 return _task_queues->size(); 3137 } 3138 3139 #if TASKQUEUE_STATS 3140 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3141 st->print_raw_cr("GC Task Stats"); 3142 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3143 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3144 } 3145 3146 void G1CollectedHeap::print_taskqueue_stats() const { 3147 if (!log_develop_is_enabled(Trace, gc, task, stats)) { 3148 return; 3149 } 3150 LogHandle(gc, task, stats) log; 3151 ResourceMark rm; 3152 outputStream* st = log.trace_stream(); 3153 3154 print_taskqueue_stats_hdr(st); 3155 3156 TaskQueueStats totals; 3157 const uint n = num_task_queues(); 3158 for (uint i = 0; i < n; ++i) { 3159 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 3160 totals += task_queue(i)->stats; 3161 } 3162 st->print_raw("tot "); totals.print(st); st->cr(); 3163 3164 DEBUG_ONLY(totals.verify()); 3165 } 3166 3167 void G1CollectedHeap::reset_taskqueue_stats() { 3168 const uint n = num_task_queues(); 3169 for (uint i = 0; i < n; ++i) { 3170 task_queue(i)->stats.reset(); 3171 } 3172 } 3173 #endif // TASKQUEUE_STATS 3174 3175 void G1CollectedHeap::wait_for_root_region_scanning() { 3176 double scan_wait_start = os::elapsedTime(); 3177 // We have to wait until the CM threads finish scanning the 3178 // root regions as it's the only way to ensure that all the 3179 // objects on them have been correctly scanned before we start 3180 // moving them during the GC. 3181 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3182 double wait_time_ms = 0.0; 3183 if (waited) { 3184 double scan_wait_end = os::elapsedTime(); 3185 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3186 } 3187 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3188 } 3189 3190 bool 3191 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3192 assert_at_safepoint(true /* should_be_vm_thread */); 3193 guarantee(!is_gc_active(), "collection is not reentrant"); 3194 3195 if (GCLocker::check_active_before_gc()) { 3196 return false; 3197 } 3198 3199 _gc_timer_stw->register_gc_start(); 3200 3201 GCIdMark gc_id_mark; 3202 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3203 3204 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3205 ResourceMark rm; 3206 3207 wait_for_root_region_scanning(); 3208 3209 print_heap_before_gc(); 3210 trace_heap_before_gc(_gc_tracer_stw); 3211 3212 _verifier->verify_region_sets_optional(); 3213 _verifier->verify_dirty_young_regions(); 3214 3215 // This call will decide whether this pause is an initial-mark 3216 // pause. If it is, during_initial_mark_pause() will return true 3217 // for the duration of this pause. 3218 g1_policy()->decide_on_conc_mark_initiation(); 3219 3220 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3221 assert(!collector_state()->during_initial_mark_pause() || 3222 collector_state()->gcs_are_young(), "sanity"); 3223 3224 // We also do not allow mixed GCs during marking. 3225 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3226 3227 // Record whether this pause is an initial mark. When the current 3228 // thread has completed its logging output and it's safe to signal 3229 // the CM thread, the flag's value in the policy has been reset. 3230 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3231 3232 // Inner scope for scope based logging, timers, and stats collection 3233 { 3234 EvacuationInfo evacuation_info; 3235 3236 if (collector_state()->during_initial_mark_pause()) { 3237 // We are about to start a marking cycle, so we increment the 3238 // full collection counter. 3239 increment_old_marking_cycles_started(); 3240 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3241 } 3242 3243 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3244 3245 GCTraceCPUTime tcpu; 3246 3247 FormatBuffer<> gc_string("Pause "); 3248 if (collector_state()->during_initial_mark_pause()) { 3249 gc_string.append("Initial Mark"); 3250 } else if (collector_state()->gcs_are_young()) { 3251 gc_string.append("Young"); 3252 } else { 3253 gc_string.append("Mixed"); 3254 } 3255 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 3256 3257 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3258 workers()->active_workers(), 3259 Threads::number_of_non_daemon_threads()); 3260 workers()->set_active_workers(active_workers); 3261 3262 g1_policy()->note_gc_start(active_workers); 3263 3264 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3265 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3266 3267 // If the secondary_free_list is not empty, append it to the 3268 // free_list. No need to wait for the cleanup operation to finish; 3269 // the region allocation code will check the secondary_free_list 3270 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3271 // set, skip this step so that the region allocation code has to 3272 // get entries from the secondary_free_list. 3273 if (!G1StressConcRegionFreeing) { 3274 append_secondary_free_list_if_not_empty_with_lock(); 3275 } 3276 3277 G1HeapTransition heap_transition(this); 3278 size_t heap_used_bytes_before_gc = used(); 3279 3280 assert(check_young_list_well_formed(), "young list should be well formed"); 3281 3282 // Don't dynamically change the number of GC threads this early. A value of 3283 // 0 is used to indicate serial work. When parallel work is done, 3284 // it will be set. 3285 3286 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3287 IsGCActiveMark x; 3288 3289 gc_prologue(false); 3290 increment_total_collections(false /* full gc */); 3291 increment_gc_time_stamp(); 3292 3293 if (VerifyRememberedSets) { 3294 log_info(gc, verify)("[Verifying RemSets before GC]"); 3295 VerifyRegionRemSetClosure v_cl; 3296 heap_region_iterate(&v_cl); 3297 } 3298 3299 _verifier->verify_before_gc(); 3300 3301 _verifier->check_bitmaps("GC Start"); 3302 3303 #if defined(COMPILER2) || INCLUDE_JVMCI 3304 DerivedPointerTable::clear(); 3305 #endif 3306 3307 // Please see comment in g1CollectedHeap.hpp and 3308 // G1CollectedHeap::ref_processing_init() to see how 3309 // reference processing currently works in G1. 3310 3311 // Enable discovery in the STW reference processor 3312 if (g1_policy()->should_process_references()) { 3313 ref_processor_stw()->enable_discovery(); 3314 } else { 3315 ref_processor_stw()->disable_discovery(); 3316 } 3317 3318 { 3319 // We want to temporarily turn off discovery by the 3320 // CM ref processor, if necessary, and turn it back on 3321 // on again later if we do. Using a scoped 3322 // NoRefDiscovery object will do this. 3323 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3324 3325 // Forget the current alloc region (we might even choose it to be part 3326 // of the collection set!). 3327 _allocator->release_mutator_alloc_region(); 3328 3329 // This timing is only used by the ergonomics to handle our pause target. 3330 // It is unclear why this should not include the full pause. We will 3331 // investigate this in CR 7178365. 3332 // 3333 // Preserving the old comment here if that helps the investigation: 3334 // 3335 // The elapsed time induced by the start time below deliberately elides 3336 // the possible verification above. 3337 double sample_start_time_sec = os::elapsedTime(); 3338 3339 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3340 3341 if (collector_state()->during_initial_mark_pause()) { 3342 concurrent_mark()->checkpointRootsInitialPre(); 3343 } 3344 3345 g1_policy()->finalize_collection_set(target_pause_time_ms); 3346 3347 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3348 3349 // Make sure the remembered sets are up to date. This needs to be 3350 // done before register_humongous_regions_with_cset(), because the 3351 // remembered sets are used there to choose eager reclaim candidates. 3352 // If the remembered sets are not up to date we might miss some 3353 // entries that need to be handled. 3354 g1_rem_set()->cleanupHRRS(); 3355 3356 register_humongous_regions_with_cset(); 3357 3358 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3359 3360 _cm->note_start_of_gc(); 3361 // We call this after finalize_cset() to 3362 // ensure that the CSet has been finalized. 3363 _cm->verify_no_cset_oops(); 3364 3365 if (_hr_printer.is_active()) { 3366 HeapRegion* hr = collection_set()->head(); 3367 while (hr != NULL) { 3368 _hr_printer.cset(hr); 3369 hr = hr->next_in_collection_set(); 3370 } 3371 } 3372 3373 #ifdef ASSERT 3374 VerifyCSetClosure cl; 3375 collection_set_iterate(&cl); 3376 #endif // ASSERT 3377 3378 // Initialize the GC alloc regions. 3379 _allocator->init_gc_alloc_regions(evacuation_info); 3380 3381 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3382 pre_evacuate_collection_set(); 3383 3384 // Actually do the work... 3385 evacuate_collection_set(evacuation_info, &per_thread_states); 3386 3387 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3388 3389 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3390 free_collection_set(collection_set()->head(), evacuation_info, surviving_young_words); 3391 3392 eagerly_reclaim_humongous_regions(); 3393 3394 collection_set()->clear_head(); 3395 3396 record_obj_copy_mem_stats(); 3397 _survivor_evac_stats.adjust_desired_plab_sz(); 3398 _old_evac_stats.adjust_desired_plab_sz(); 3399 3400 // Start a new incremental collection set for the next pause. 3401 collection_set()->start_incremental_building(); 3402 3403 clear_cset_fast_test(); 3404 3405 // Don't check the whole heap at this point as the 3406 // GC alloc regions from this pause have been tagged 3407 // as survivors and moved on to the survivor list. 3408 // Survivor regions will fail the !is_young() check. 3409 assert(check_young_list_empty(false /* check_heap */), 3410 "young list should be empty"); 3411 3412 _young_list->reset_auxilary_lists(); 3413 3414 if (evacuation_failed()) { 3415 set_used(recalculate_used()); 3416 if (_archive_allocator != NULL) { 3417 _archive_allocator->clear_used(); 3418 } 3419 for (uint i = 0; i < ParallelGCThreads; i++) { 3420 if (_evacuation_failed_info_array[i].has_failed()) { 3421 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3422 } 3423 } 3424 } else { 3425 // The "used" of the the collection set have already been subtracted 3426 // when they were freed. Add in the bytes evacuated. 3427 increase_used(g1_policy()->bytes_copied_during_gc()); 3428 } 3429 3430 if (collector_state()->during_initial_mark_pause()) { 3431 // We have to do this before we notify the CM threads that 3432 // they can start working to make sure that all the 3433 // appropriate initialization is done on the CM object. 3434 concurrent_mark()->checkpointRootsInitialPost(); 3435 collector_state()->set_mark_in_progress(true); 3436 // Note that we don't actually trigger the CM thread at 3437 // this point. We do that later when we're sure that 3438 // the current thread has completed its logging output. 3439 } 3440 3441 allocate_dummy_regions(); 3442 3443 _allocator->init_mutator_alloc_region(); 3444 3445 { 3446 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3447 if (expand_bytes > 0) { 3448 size_t bytes_before = capacity(); 3449 // No need for an ergo logging here, 3450 // expansion_amount() does this when it returns a value > 0. 3451 double expand_ms; 3452 if (!expand(expand_bytes, &expand_ms)) { 3453 // We failed to expand the heap. Cannot do anything about it. 3454 } 3455 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3456 } 3457 } 3458 3459 // We redo the verification but now wrt to the new CSet which 3460 // has just got initialized after the previous CSet was freed. 3461 _cm->verify_no_cset_oops(); 3462 _cm->note_end_of_gc(); 3463 3464 // This timing is only used by the ergonomics to handle our pause target. 3465 // It is unclear why this should not include the full pause. We will 3466 // investigate this in CR 7178365. 3467 double sample_end_time_sec = os::elapsedTime(); 3468 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3469 size_t total_cards_scanned = per_thread_states.total_cards_scanned(); 3470 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3471 3472 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3473 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3474 3475 MemoryService::track_memory_usage(); 3476 3477 // In prepare_for_verify() below we'll need to scan the deferred 3478 // update buffers to bring the RSets up-to-date if 3479 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3480 // the update buffers we'll probably need to scan cards on the 3481 // regions we just allocated to (i.e., the GC alloc 3482 // regions). However, during the last GC we called 3483 // set_saved_mark() on all the GC alloc regions, so card 3484 // scanning might skip the [saved_mark_word()...top()] area of 3485 // those regions (i.e., the area we allocated objects into 3486 // during the last GC). But it shouldn't. Given that 3487 // saved_mark_word() is conditional on whether the GC time stamp 3488 // on the region is current or not, by incrementing the GC time 3489 // stamp here we invalidate all the GC time stamps on all the 3490 // regions and saved_mark_word() will simply return top() for 3491 // all the regions. This is a nicer way of ensuring this rather 3492 // than iterating over the regions and fixing them. In fact, the 3493 // GC time stamp increment here also ensures that 3494 // saved_mark_word() will return top() between pauses, i.e., 3495 // during concurrent refinement. So we don't need the 3496 // is_gc_active() check to decided which top to use when 3497 // scanning cards (see CR 7039627). 3498 increment_gc_time_stamp(); 3499 3500 if (VerifyRememberedSets) { 3501 log_info(gc, verify)("[Verifying RemSets after GC]"); 3502 VerifyRegionRemSetClosure v_cl; 3503 heap_region_iterate(&v_cl); 3504 } 3505 3506 _verifier->verify_after_gc(); 3507 _verifier->check_bitmaps("GC End"); 3508 3509 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3510 ref_processor_stw()->verify_no_references_recorded(); 3511 3512 // CM reference discovery will be re-enabled if necessary. 3513 } 3514 3515 #ifdef TRACESPINNING 3516 ParallelTaskTerminator::print_termination_counts(); 3517 #endif 3518 3519 gc_epilogue(false); 3520 } 3521 3522 // Print the remainder of the GC log output. 3523 if (evacuation_failed()) { 3524 log_info(gc)("To-space exhausted"); 3525 } 3526 3527 g1_policy()->print_phases(); 3528 heap_transition.print(); 3529 3530 // It is not yet to safe to tell the concurrent mark to 3531 // start as we have some optional output below. We don't want the 3532 // output from the concurrent mark thread interfering with this 3533 // logging output either. 3534 3535 _hrm.verify_optional(); 3536 _verifier->verify_region_sets_optional(); 3537 3538 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3539 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3540 3541 print_heap_after_gc(); 3542 trace_heap_after_gc(_gc_tracer_stw); 3543 3544 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3545 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3546 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3547 // before any GC notifications are raised. 3548 g1mm()->update_sizes(); 3549 3550 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3551 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3552 _gc_timer_stw->register_gc_end(); 3553 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3554 } 3555 // It should now be safe to tell the concurrent mark thread to start 3556 // without its logging output interfering with the logging output 3557 // that came from the pause. 3558 3559 if (should_start_conc_mark) { 3560 // CAUTION: after the doConcurrentMark() call below, 3561 // the concurrent marking thread(s) could be running 3562 // concurrently with us. Make sure that anything after 3563 // this point does not assume that we are the only GC thread 3564 // running. Note: of course, the actual marking work will 3565 // not start until the safepoint itself is released in 3566 // SuspendibleThreadSet::desynchronize(). 3567 doConcurrentMark(); 3568 } 3569 3570 return true; 3571 } 3572 3573 void G1CollectedHeap::restore_preserved_marks() { 3574 G1RestorePreservedMarksTask rpm_task(_preserved_objs); 3575 workers()->run_task(&rpm_task); 3576 } 3577 3578 void G1CollectedHeap::remove_self_forwarding_pointers() { 3579 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3580 workers()->run_task(&rsfp_task); 3581 } 3582 3583 void G1CollectedHeap::restore_after_evac_failure() { 3584 double remove_self_forwards_start = os::elapsedTime(); 3585 3586 remove_self_forwarding_pointers(); 3587 restore_preserved_marks(); 3588 3589 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3590 } 3591 3592 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3593 if (!_evacuation_failed) { 3594 _evacuation_failed = true; 3595 } 3596 3597 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3598 3599 // We want to call the "for_promotion_failure" version only in the 3600 // case of a promotion failure. 3601 if (m->must_be_preserved_for_promotion_failure(obj)) { 3602 OopAndMarkOop elem(obj, m); 3603 _preserved_objs[worker_id].push(elem); 3604 } 3605 } 3606 3607 bool G1ParEvacuateFollowersClosure::offer_termination() { 3608 G1ParScanThreadState* const pss = par_scan_state(); 3609 start_term_time(); 3610 const bool res = terminator()->offer_termination(); 3611 end_term_time(); 3612 return res; 3613 } 3614 3615 void G1ParEvacuateFollowersClosure::do_void() { 3616 G1ParScanThreadState* const pss = par_scan_state(); 3617 pss->trim_queue(); 3618 do { 3619 pss->steal_and_trim_queue(queues()); 3620 } while (!offer_termination()); 3621 } 3622 3623 class G1ParTask : public AbstractGangTask { 3624 protected: 3625 G1CollectedHeap* _g1h; 3626 G1ParScanThreadStateSet* _pss; 3627 RefToScanQueueSet* _queues; 3628 G1RootProcessor* _root_processor; 3629 ParallelTaskTerminator _terminator; 3630 uint _n_workers; 3631 3632 public: 3633 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3634 : AbstractGangTask("G1 collection"), 3635 _g1h(g1h), 3636 _pss(per_thread_states), 3637 _queues(task_queues), 3638 _root_processor(root_processor), 3639 _terminator(n_workers, _queues), 3640 _n_workers(n_workers) 3641 {} 3642 3643 void work(uint worker_id) { 3644 if (worker_id >= _n_workers) return; // no work needed this round 3645 3646 double start_sec = os::elapsedTime(); 3647 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3648 3649 { 3650 ResourceMark rm; 3651 HandleMark hm; 3652 3653 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3654 3655 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3656 pss->set_ref_processor(rp); 3657 3658 double start_strong_roots_sec = os::elapsedTime(); 3659 3660 _root_processor->evacuate_roots(pss->closures(), worker_id); 3661 3662 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss); 3663 3664 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3665 // treating the nmethods visited to act as roots for concurrent marking. 3666 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3667 // objects copied by the current evacuation. 3668 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl, 3669 pss->closures()->weak_codeblobs(), 3670 worker_id); 3671 3672 _pss->add_cards_scanned(worker_id, cards_scanned); 3673 3674 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3675 3676 double term_sec = 0.0; 3677 size_t evac_term_attempts = 0; 3678 { 3679 double start = os::elapsedTime(); 3680 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3681 evac.do_void(); 3682 3683 evac_term_attempts = evac.term_attempts(); 3684 term_sec = evac.term_time(); 3685 double elapsed_sec = os::elapsedTime() - start; 3686 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3687 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3688 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3689 } 3690 3691 assert(pss->queue_is_empty(), "should be empty"); 3692 3693 if (log_is_enabled(Debug, gc, task, stats)) { 3694 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3695 size_t lab_waste; 3696 size_t lab_undo_waste; 3697 pss->waste(lab_waste, lab_undo_waste); 3698 _g1h->print_termination_stats(worker_id, 3699 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3700 strong_roots_sec * 1000.0, /* strong roots time */ 3701 term_sec * 1000.0, /* evac term time */ 3702 evac_term_attempts, /* evac term attempts */ 3703 lab_waste, /* alloc buffer waste */ 3704 lab_undo_waste /* undo waste */ 3705 ); 3706 } 3707 3708 // Close the inner scope so that the ResourceMark and HandleMark 3709 // destructors are executed here and are included as part of the 3710 // "GC Worker Time". 3711 } 3712 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3713 } 3714 }; 3715 3716 void G1CollectedHeap::print_termination_stats_hdr() { 3717 log_debug(gc, task, stats)("GC Termination Stats"); 3718 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3719 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3720 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3721 } 3722 3723 void G1CollectedHeap::print_termination_stats(uint worker_id, 3724 double elapsed_ms, 3725 double strong_roots_ms, 3726 double term_ms, 3727 size_t term_attempts, 3728 size_t alloc_buffer_waste, 3729 size_t undo_waste) const { 3730 log_debug(gc, task, stats) 3731 ("%3d %9.2f %9.2f %6.2f " 3732 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3733 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3734 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3735 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3736 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3737 alloc_buffer_waste * HeapWordSize / K, 3738 undo_waste * HeapWordSize / K); 3739 } 3740 3741 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 3742 private: 3743 BoolObjectClosure* _is_alive; 3744 int _initial_string_table_size; 3745 int _initial_symbol_table_size; 3746 3747 bool _process_strings; 3748 int _strings_processed; 3749 int _strings_removed; 3750 3751 bool _process_symbols; 3752 int _symbols_processed; 3753 int _symbols_removed; 3754 3755 public: 3756 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 3757 AbstractGangTask("String/Symbol Unlinking"), 3758 _is_alive(is_alive), 3759 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3760 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 3761 3762 _initial_string_table_size = StringTable::the_table()->table_size(); 3763 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3764 if (process_strings) { 3765 StringTable::clear_parallel_claimed_index(); 3766 } 3767 if (process_symbols) { 3768 SymbolTable::clear_parallel_claimed_index(); 3769 } 3770 } 3771 3772 ~G1StringSymbolTableUnlinkTask() { 3773 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3774 "claim value %d after unlink less than initial string table size %d", 3775 StringTable::parallel_claimed_index(), _initial_string_table_size); 3776 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3777 "claim value %d after unlink less than initial symbol table size %d", 3778 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3779 3780 log_debug(gc, stringdedup)("Cleaned string and symbol table, " 3781 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3782 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3783 strings_processed(), strings_removed(), 3784 symbols_processed(), symbols_removed()); 3785 } 3786 3787 void work(uint worker_id) { 3788 int strings_processed = 0; 3789 int strings_removed = 0; 3790 int symbols_processed = 0; 3791 int symbols_removed = 0; 3792 if (_process_strings) { 3793 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3794 Atomic::add(strings_processed, &_strings_processed); 3795 Atomic::add(strings_removed, &_strings_removed); 3796 } 3797 if (_process_symbols) { 3798 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3799 Atomic::add(symbols_processed, &_symbols_processed); 3800 Atomic::add(symbols_removed, &_symbols_removed); 3801 } 3802 } 3803 3804 size_t strings_processed() const { return (size_t)_strings_processed; } 3805 size_t strings_removed() const { return (size_t)_strings_removed; } 3806 3807 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3808 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3809 }; 3810 3811 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3812 private: 3813 static Monitor* _lock; 3814 3815 BoolObjectClosure* const _is_alive; 3816 const bool _unloading_occurred; 3817 const uint _num_workers; 3818 3819 // Variables used to claim nmethods. 3820 nmethod* _first_nmethod; 3821 volatile nmethod* _claimed_nmethod; 3822 3823 // The list of nmethods that need to be processed by the second pass. 3824 volatile nmethod* _postponed_list; 3825 volatile uint _num_entered_barrier; 3826 3827 public: 3828 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3829 _is_alive(is_alive), 3830 _unloading_occurred(unloading_occurred), 3831 _num_workers(num_workers), 3832 _first_nmethod(NULL), 3833 _claimed_nmethod(NULL), 3834 _postponed_list(NULL), 3835 _num_entered_barrier(0) 3836 { 3837 nmethod::increase_unloading_clock(); 3838 // Get first alive nmethod 3839 NMethodIterator iter = NMethodIterator(); 3840 if(iter.next_alive()) { 3841 _first_nmethod = iter.method(); 3842 } 3843 _claimed_nmethod = (volatile nmethod*)_first_nmethod; 3844 } 3845 3846 ~G1CodeCacheUnloadingTask() { 3847 CodeCache::verify_clean_inline_caches(); 3848 3849 CodeCache::set_needs_cache_clean(false); 3850 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3851 3852 CodeCache::verify_icholder_relocations(); 3853 } 3854 3855 private: 3856 void add_to_postponed_list(nmethod* nm) { 3857 nmethod* old; 3858 do { 3859 old = (nmethod*)_postponed_list; 3860 nm->set_unloading_next(old); 3861 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 3862 } 3863 3864 void clean_nmethod(nmethod* nm) { 3865 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3866 3867 if (postponed) { 3868 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3869 add_to_postponed_list(nm); 3870 } 3871 3872 // Mark that this thread has been cleaned/unloaded. 3873 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3874 nm->set_unloading_clock(nmethod::global_unloading_clock()); 3875 } 3876 3877 void clean_nmethod_postponed(nmethod* nm) { 3878 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3879 } 3880 3881 static const int MaxClaimNmethods = 16; 3882 3883 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) { 3884 nmethod* first; 3885 NMethodIterator last; 3886 3887 do { 3888 *num_claimed_nmethods = 0; 3889 3890 first = (nmethod*)_claimed_nmethod; 3891 last = NMethodIterator(first); 3892 3893 if (first != NULL) { 3894 3895 for (int i = 0; i < MaxClaimNmethods; i++) { 3896 if (!last.next_alive()) { 3897 break; 3898 } 3899 claimed_nmethods[i] = last.method(); 3900 (*num_claimed_nmethods)++; 3901 } 3902 } 3903 3904 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 3905 } 3906 3907 nmethod* claim_postponed_nmethod() { 3908 nmethod* claim; 3909 nmethod* next; 3910 3911 do { 3912 claim = (nmethod*)_postponed_list; 3913 if (claim == NULL) { 3914 return NULL; 3915 } 3916 3917 next = claim->unloading_next(); 3918 3919 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 3920 3921 return claim; 3922 } 3923 3924 public: 3925 // Mark that we're done with the first pass of nmethod cleaning. 3926 void barrier_mark(uint worker_id) { 3927 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3928 _num_entered_barrier++; 3929 if (_num_entered_barrier == _num_workers) { 3930 ml.notify_all(); 3931 } 3932 } 3933 3934 // See if we have to wait for the other workers to 3935 // finish their first-pass nmethod cleaning work. 3936 void barrier_wait(uint worker_id) { 3937 if (_num_entered_barrier < _num_workers) { 3938 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3939 while (_num_entered_barrier < _num_workers) { 3940 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3941 } 3942 } 3943 } 3944 3945 // Cleaning and unloading of nmethods. Some work has to be postponed 3946 // to the second pass, when we know which nmethods survive. 3947 void work_first_pass(uint worker_id) { 3948 // The first nmethods is claimed by the first worker. 3949 if (worker_id == 0 && _first_nmethod != NULL) { 3950 clean_nmethod(_first_nmethod); 3951 _first_nmethod = NULL; 3952 } 3953 3954 int num_claimed_nmethods; 3955 nmethod* claimed_nmethods[MaxClaimNmethods]; 3956 3957 while (true) { 3958 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3959 3960 if (num_claimed_nmethods == 0) { 3961 break; 3962 } 3963 3964 for (int i = 0; i < num_claimed_nmethods; i++) { 3965 clean_nmethod(claimed_nmethods[i]); 3966 } 3967 } 3968 } 3969 3970 void work_second_pass(uint worker_id) { 3971 nmethod* nm; 3972 // Take care of postponed nmethods. 3973 while ((nm = claim_postponed_nmethod()) != NULL) { 3974 clean_nmethod_postponed(nm); 3975 } 3976 } 3977 }; 3978 3979 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3980 3981 class G1KlassCleaningTask : public StackObj { 3982 BoolObjectClosure* _is_alive; 3983 volatile jint _clean_klass_tree_claimed; 3984 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3985 3986 public: 3987 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3988 _is_alive(is_alive), 3989 _clean_klass_tree_claimed(0), 3990 _klass_iterator() { 3991 } 3992 3993 private: 3994 bool claim_clean_klass_tree_task() { 3995 if (_clean_klass_tree_claimed) { 3996 return false; 3997 } 3998 3999 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 4000 } 4001 4002 InstanceKlass* claim_next_klass() { 4003 Klass* klass; 4004 do { 4005 klass =_klass_iterator.next_klass(); 4006 } while (klass != NULL && !klass->is_instance_klass()); 4007 4008 // this can be null so don't call InstanceKlass::cast 4009 return static_cast<InstanceKlass*>(klass); 4010 } 4011 4012 public: 4013 4014 void clean_klass(InstanceKlass* ik) { 4015 ik->clean_weak_instanceklass_links(_is_alive); 4016 } 4017 4018 void work() { 4019 ResourceMark rm; 4020 4021 // One worker will clean the subklass/sibling klass tree. 4022 if (claim_clean_klass_tree_task()) { 4023 Klass::clean_subklass_tree(_is_alive); 4024 } 4025 4026 // All workers will help cleaning the classes, 4027 InstanceKlass* klass; 4028 while ((klass = claim_next_klass()) != NULL) { 4029 clean_klass(klass); 4030 } 4031 } 4032 }; 4033 4034 // To minimize the remark pause times, the tasks below are done in parallel. 4035 class G1ParallelCleaningTask : public AbstractGangTask { 4036 private: 4037 G1StringSymbolTableUnlinkTask _string_symbol_task; 4038 G1CodeCacheUnloadingTask _code_cache_task; 4039 G1KlassCleaningTask _klass_cleaning_task; 4040 4041 public: 4042 // The constructor is run in the VMThread. 4043 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 4044 AbstractGangTask("Parallel Cleaning"), 4045 _string_symbol_task(is_alive, process_strings, process_symbols), 4046 _code_cache_task(num_workers, is_alive, unloading_occurred), 4047 _klass_cleaning_task(is_alive) { 4048 } 4049 4050 // The parallel work done by all worker threads. 4051 void work(uint worker_id) { 4052 // Do first pass of code cache cleaning. 4053 _code_cache_task.work_first_pass(worker_id); 4054 4055 // Let the threads mark that the first pass is done. 4056 _code_cache_task.barrier_mark(worker_id); 4057 4058 // Clean the Strings and Symbols. 4059 _string_symbol_task.work(worker_id); 4060 4061 // Wait for all workers to finish the first code cache cleaning pass. 4062 _code_cache_task.barrier_wait(worker_id); 4063 4064 // Do the second code cache cleaning work, which realize on 4065 // the liveness information gathered during the first pass. 4066 _code_cache_task.work_second_pass(worker_id); 4067 4068 // Clean all klasses that were not unloaded. 4069 _klass_cleaning_task.work(); 4070 } 4071 }; 4072 4073 4074 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 4075 bool process_strings, 4076 bool process_symbols, 4077 bool class_unloading_occurred) { 4078 uint n_workers = workers()->active_workers(); 4079 4080 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 4081 n_workers, class_unloading_occurred); 4082 workers()->run_task(&g1_unlink_task); 4083 } 4084 4085 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 4086 bool process_strings, bool process_symbols) { 4087 { 4088 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 4089 workers()->run_task(&g1_unlink_task); 4090 } 4091 4092 if (G1StringDedup::is_enabled()) { 4093 G1StringDedup::unlink(is_alive); 4094 } 4095 } 4096 4097 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 4098 private: 4099 DirtyCardQueueSet* _queue; 4100 G1CollectedHeap* _g1h; 4101 public: 4102 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 4103 _queue(queue), _g1h(g1h) { } 4104 4105 virtual void work(uint worker_id) { 4106 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 4107 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 4108 4109 RedirtyLoggedCardTableEntryClosure cl(_g1h); 4110 _queue->par_apply_closure_to_all_completed_buffers(&cl); 4111 4112 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 4113 } 4114 }; 4115 4116 void G1CollectedHeap::redirty_logged_cards() { 4117 double redirty_logged_cards_start = os::elapsedTime(); 4118 4119 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 4120 dirty_card_queue_set().reset_for_par_iteration(); 4121 workers()->run_task(&redirty_task); 4122 4123 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 4124 dcq.merge_bufferlists(&dirty_card_queue_set()); 4125 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 4126 4127 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 4128 } 4129 4130 // Weak Reference Processing support 4131 4132 // An always "is_alive" closure that is used to preserve referents. 4133 // If the object is non-null then it's alive. Used in the preservation 4134 // of referent objects that are pointed to by reference objects 4135 // discovered by the CM ref processor. 4136 class G1AlwaysAliveClosure: public BoolObjectClosure { 4137 G1CollectedHeap* _g1; 4138 public: 4139 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4140 bool do_object_b(oop p) { 4141 if (p != NULL) { 4142 return true; 4143 } 4144 return false; 4145 } 4146 }; 4147 4148 bool G1STWIsAliveClosure::do_object_b(oop p) { 4149 // An object is reachable if it is outside the collection set, 4150 // or is inside and copied. 4151 return !_g1->is_in_cset(p) || p->is_forwarded(); 4152 } 4153 4154 // Non Copying Keep Alive closure 4155 class G1KeepAliveClosure: public OopClosure { 4156 G1CollectedHeap* _g1; 4157 public: 4158 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4159 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 4160 void do_oop(oop* p) { 4161 oop obj = *p; 4162 assert(obj != NULL, "the caller should have filtered out NULL values"); 4163 4164 const InCSetState cset_state = _g1->in_cset_state(obj); 4165 if (!cset_state.is_in_cset_or_humongous()) { 4166 return; 4167 } 4168 if (cset_state.is_in_cset()) { 4169 assert( obj->is_forwarded(), "invariant" ); 4170 *p = obj->forwardee(); 4171 } else { 4172 assert(!obj->is_forwarded(), "invariant" ); 4173 assert(cset_state.is_humongous(), 4174 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 4175 _g1->set_humongous_is_live(obj); 4176 } 4177 } 4178 }; 4179 4180 // Copying Keep Alive closure - can be called from both 4181 // serial and parallel code as long as different worker 4182 // threads utilize different G1ParScanThreadState instances 4183 // and different queues. 4184 4185 class G1CopyingKeepAliveClosure: public OopClosure { 4186 G1CollectedHeap* _g1h; 4187 OopClosure* _copy_non_heap_obj_cl; 4188 G1ParScanThreadState* _par_scan_state; 4189 4190 public: 4191 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4192 OopClosure* non_heap_obj_cl, 4193 G1ParScanThreadState* pss): 4194 _g1h(g1h), 4195 _copy_non_heap_obj_cl(non_heap_obj_cl), 4196 _par_scan_state(pss) 4197 {} 4198 4199 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4200 virtual void do_oop( oop* p) { do_oop_work(p); } 4201 4202 template <class T> void do_oop_work(T* p) { 4203 oop obj = oopDesc::load_decode_heap_oop(p); 4204 4205 if (_g1h->is_in_cset_or_humongous(obj)) { 4206 // If the referent object has been forwarded (either copied 4207 // to a new location or to itself in the event of an 4208 // evacuation failure) then we need to update the reference 4209 // field and, if both reference and referent are in the G1 4210 // heap, update the RSet for the referent. 4211 // 4212 // If the referent has not been forwarded then we have to keep 4213 // it alive by policy. Therefore we have copy the referent. 4214 // 4215 // If the reference field is in the G1 heap then we can push 4216 // on the PSS queue. When the queue is drained (after each 4217 // phase of reference processing) the object and it's followers 4218 // will be copied, the reference field set to point to the 4219 // new location, and the RSet updated. Otherwise we need to 4220 // use the the non-heap or metadata closures directly to copy 4221 // the referent object and update the pointer, while avoiding 4222 // updating the RSet. 4223 4224 if (_g1h->is_in_g1_reserved(p)) { 4225 _par_scan_state->push_on_queue(p); 4226 } else { 4227 assert(!Metaspace::contains((const void*)p), 4228 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4229 _copy_non_heap_obj_cl->do_oop(p); 4230 } 4231 } 4232 } 4233 }; 4234 4235 // Serial drain queue closure. Called as the 'complete_gc' 4236 // closure for each discovered list in some of the 4237 // reference processing phases. 4238 4239 class G1STWDrainQueueClosure: public VoidClosure { 4240 protected: 4241 G1CollectedHeap* _g1h; 4242 G1ParScanThreadState* _par_scan_state; 4243 4244 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4245 4246 public: 4247 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4248 _g1h(g1h), 4249 _par_scan_state(pss) 4250 { } 4251 4252 void do_void() { 4253 G1ParScanThreadState* const pss = par_scan_state(); 4254 pss->trim_queue(); 4255 } 4256 }; 4257 4258 // Parallel Reference Processing closures 4259 4260 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4261 // processing during G1 evacuation pauses. 4262 4263 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4264 private: 4265 G1CollectedHeap* _g1h; 4266 G1ParScanThreadStateSet* _pss; 4267 RefToScanQueueSet* _queues; 4268 WorkGang* _workers; 4269 uint _active_workers; 4270 4271 public: 4272 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4273 G1ParScanThreadStateSet* per_thread_states, 4274 WorkGang* workers, 4275 RefToScanQueueSet *task_queues, 4276 uint n_workers) : 4277 _g1h(g1h), 4278 _pss(per_thread_states), 4279 _queues(task_queues), 4280 _workers(workers), 4281 _active_workers(n_workers) 4282 { 4283 assert(n_workers > 0, "shouldn't call this otherwise"); 4284 } 4285 4286 // Executes the given task using concurrent marking worker threads. 4287 virtual void execute(ProcessTask& task); 4288 virtual void execute(EnqueueTask& task); 4289 }; 4290 4291 // Gang task for possibly parallel reference processing 4292 4293 class G1STWRefProcTaskProxy: public AbstractGangTask { 4294 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4295 ProcessTask& _proc_task; 4296 G1CollectedHeap* _g1h; 4297 G1ParScanThreadStateSet* _pss; 4298 RefToScanQueueSet* _task_queues; 4299 ParallelTaskTerminator* _terminator; 4300 4301 public: 4302 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4303 G1CollectedHeap* g1h, 4304 G1ParScanThreadStateSet* per_thread_states, 4305 RefToScanQueueSet *task_queues, 4306 ParallelTaskTerminator* terminator) : 4307 AbstractGangTask("Process reference objects in parallel"), 4308 _proc_task(proc_task), 4309 _g1h(g1h), 4310 _pss(per_thread_states), 4311 _task_queues(task_queues), 4312 _terminator(terminator) 4313 {} 4314 4315 virtual void work(uint worker_id) { 4316 // The reference processing task executed by a single worker. 4317 ResourceMark rm; 4318 HandleMark hm; 4319 4320 G1STWIsAliveClosure is_alive(_g1h); 4321 4322 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4323 pss->set_ref_processor(NULL); 4324 4325 // Keep alive closure. 4326 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4327 4328 // Complete GC closure 4329 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4330 4331 // Call the reference processing task's work routine. 4332 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4333 4334 // Note we cannot assert that the refs array is empty here as not all 4335 // of the processing tasks (specifically phase2 - pp2_work) execute 4336 // the complete_gc closure (which ordinarily would drain the queue) so 4337 // the queue may not be empty. 4338 } 4339 }; 4340 4341 // Driver routine for parallel reference processing. 4342 // Creates an instance of the ref processing gang 4343 // task and has the worker threads execute it. 4344 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4345 assert(_workers != NULL, "Need parallel worker threads."); 4346 4347 ParallelTaskTerminator terminator(_active_workers, _queues); 4348 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4349 4350 _workers->run_task(&proc_task_proxy); 4351 } 4352 4353 // Gang task for parallel reference enqueueing. 4354 4355 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4356 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4357 EnqueueTask& _enq_task; 4358 4359 public: 4360 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4361 AbstractGangTask("Enqueue reference objects in parallel"), 4362 _enq_task(enq_task) 4363 { } 4364 4365 virtual void work(uint worker_id) { 4366 _enq_task.work(worker_id); 4367 } 4368 }; 4369 4370 // Driver routine for parallel reference enqueueing. 4371 // Creates an instance of the ref enqueueing gang 4372 // task and has the worker threads execute it. 4373 4374 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4375 assert(_workers != NULL, "Need parallel worker threads."); 4376 4377 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4378 4379 _workers->run_task(&enq_task_proxy); 4380 } 4381 4382 // End of weak reference support closures 4383 4384 // Abstract task used to preserve (i.e. copy) any referent objects 4385 // that are in the collection set and are pointed to by reference 4386 // objects discovered by the CM ref processor. 4387 4388 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4389 protected: 4390 G1CollectedHeap* _g1h; 4391 G1ParScanThreadStateSet* _pss; 4392 RefToScanQueueSet* _queues; 4393 ParallelTaskTerminator _terminator; 4394 uint _n_workers; 4395 4396 public: 4397 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4398 AbstractGangTask("ParPreserveCMReferents"), 4399 _g1h(g1h), 4400 _pss(per_thread_states), 4401 _queues(task_queues), 4402 _terminator(workers, _queues), 4403 _n_workers(workers) 4404 { } 4405 4406 void work(uint worker_id) { 4407 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4408 4409 ResourceMark rm; 4410 HandleMark hm; 4411 4412 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4413 pss->set_ref_processor(NULL); 4414 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4415 4416 // Is alive closure 4417 G1AlwaysAliveClosure always_alive(_g1h); 4418 4419 // Copying keep alive closure. Applied to referent objects that need 4420 // to be copied. 4421 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4422 4423 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4424 4425 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4426 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4427 4428 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4429 // So this must be true - but assert just in case someone decides to 4430 // change the worker ids. 4431 assert(worker_id < limit, "sanity"); 4432 assert(!rp->discovery_is_atomic(), "check this code"); 4433 4434 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4435 for (uint idx = worker_id; idx < limit; idx += stride) { 4436 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4437 4438 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4439 while (iter.has_next()) { 4440 // Since discovery is not atomic for the CM ref processor, we 4441 // can see some null referent objects. 4442 iter.load_ptrs(DEBUG_ONLY(true)); 4443 oop ref = iter.obj(); 4444 4445 // This will filter nulls. 4446 if (iter.is_referent_alive()) { 4447 iter.make_referent_alive(); 4448 } 4449 iter.move_to_next(); 4450 } 4451 } 4452 4453 // Drain the queue - which may cause stealing 4454 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4455 drain_queue.do_void(); 4456 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4457 assert(pss->queue_is_empty(), "should be"); 4458 } 4459 }; 4460 4461 void G1CollectedHeap::process_weak_jni_handles() { 4462 double ref_proc_start = os::elapsedTime(); 4463 4464 G1STWIsAliveClosure is_alive(this); 4465 G1KeepAliveClosure keep_alive(this); 4466 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 4467 4468 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4469 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4470 } 4471 4472 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4473 double preserve_cm_referents_start = os::elapsedTime(); 4474 // Any reference objects, in the collection set, that were 'discovered' 4475 // by the CM ref processor should have already been copied (either by 4476 // applying the external root copy closure to the discovered lists, or 4477 // by following an RSet entry). 4478 // 4479 // But some of the referents, that are in the collection set, that these 4480 // reference objects point to may not have been copied: the STW ref 4481 // processor would have seen that the reference object had already 4482 // been 'discovered' and would have skipped discovering the reference, 4483 // but would not have treated the reference object as a regular oop. 4484 // As a result the copy closure would not have been applied to the 4485 // referent object. 4486 // 4487 // We need to explicitly copy these referent objects - the references 4488 // will be processed at the end of remarking. 4489 // 4490 // We also need to do this copying before we process the reference 4491 // objects discovered by the STW ref processor in case one of these 4492 // referents points to another object which is also referenced by an 4493 // object discovered by the STW ref processor. 4494 4495 uint no_of_gc_workers = workers()->active_workers(); 4496 4497 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4498 per_thread_states, 4499 no_of_gc_workers, 4500 _task_queues); 4501 workers()->run_task(&keep_cm_referents); 4502 4503 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms((os::elapsedTime() - preserve_cm_referents_start) * 1000.0); 4504 } 4505 4506 // Weak Reference processing during an evacuation pause (part 1). 4507 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4508 double ref_proc_start = os::elapsedTime(); 4509 4510 ReferenceProcessor* rp = _ref_processor_stw; 4511 assert(rp->discovery_enabled(), "should have been enabled"); 4512 4513 // Closure to test whether a referent is alive. 4514 G1STWIsAliveClosure is_alive(this); 4515 4516 // Even when parallel reference processing is enabled, the processing 4517 // of JNI refs is serial and performed serially by the current thread 4518 // rather than by a worker. The following PSS will be used for processing 4519 // JNI refs. 4520 4521 // Use only a single queue for this PSS. 4522 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4523 pss->set_ref_processor(NULL); 4524 assert(pss->queue_is_empty(), "pre-condition"); 4525 4526 // Keep alive closure. 4527 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4528 4529 // Serial Complete GC closure 4530 G1STWDrainQueueClosure drain_queue(this, pss); 4531 4532 // Setup the soft refs policy... 4533 rp->setup_policy(false); 4534 4535 ReferenceProcessorStats stats; 4536 if (!rp->processing_is_mt()) { 4537 // Serial reference processing... 4538 stats = rp->process_discovered_references(&is_alive, 4539 &keep_alive, 4540 &drain_queue, 4541 NULL, 4542 _gc_timer_stw); 4543 } else { 4544 uint no_of_gc_workers = workers()->active_workers(); 4545 4546 // Parallel reference processing 4547 assert(rp->num_q() == no_of_gc_workers, "sanity"); 4548 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 4549 4550 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4551 stats = rp->process_discovered_references(&is_alive, 4552 &keep_alive, 4553 &drain_queue, 4554 &par_task_executor, 4555 _gc_timer_stw); 4556 } 4557 4558 _gc_tracer_stw->report_gc_reference_stats(stats); 4559 4560 // We have completed copying any necessary live referent objects. 4561 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4562 4563 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4564 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4565 } 4566 4567 // Weak Reference processing during an evacuation pause (part 2). 4568 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4569 double ref_enq_start = os::elapsedTime(); 4570 4571 ReferenceProcessor* rp = _ref_processor_stw; 4572 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4573 4574 // Now enqueue any remaining on the discovered lists on to 4575 // the pending list. 4576 if (!rp->processing_is_mt()) { 4577 // Serial reference processing... 4578 rp->enqueue_discovered_references(); 4579 } else { 4580 // Parallel reference enqueueing 4581 4582 uint n_workers = workers()->active_workers(); 4583 4584 assert(rp->num_q() == n_workers, "sanity"); 4585 assert(n_workers <= rp->max_num_q(), "sanity"); 4586 4587 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4588 rp->enqueue_discovered_references(&par_task_executor); 4589 } 4590 4591 rp->verify_no_references_recorded(); 4592 assert(!rp->discovery_enabled(), "should have been disabled"); 4593 4594 // FIXME 4595 // CM's reference processing also cleans up the string and symbol tables. 4596 // Should we do that here also? We could, but it is a serial operation 4597 // and could significantly increase the pause time. 4598 4599 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4600 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4601 } 4602 4603 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4604 double merge_pss_time_start = os::elapsedTime(); 4605 per_thread_states->flush(); 4606 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4607 } 4608 4609 void G1CollectedHeap::pre_evacuate_collection_set() { 4610 _expand_heap_after_alloc_failure = true; 4611 _evacuation_failed = false; 4612 4613 // Disable the hot card cache. 4614 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 4615 hot_card_cache->reset_hot_cache_claimed_index(); 4616 hot_card_cache->set_use_cache(false); 4617 4618 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4619 } 4620 4621 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4622 // Should G1EvacuationFailureALot be in effect for this GC? 4623 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4624 4625 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4626 double start_par_time_sec = os::elapsedTime(); 4627 double end_par_time_sec; 4628 4629 { 4630 const uint n_workers = workers()->active_workers(); 4631 G1RootProcessor root_processor(this, n_workers); 4632 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4633 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4634 if (collector_state()->during_initial_mark_pause()) { 4635 ClassLoaderDataGraph::clear_claimed_marks(); 4636 } 4637 4638 print_termination_stats_hdr(); 4639 4640 workers()->run_task(&g1_par_task); 4641 end_par_time_sec = os::elapsedTime(); 4642 4643 // Closing the inner scope will execute the destructor 4644 // for the G1RootProcessor object. We record the current 4645 // elapsed time before closing the scope so that time 4646 // taken for the destructor is NOT included in the 4647 // reported parallel time. 4648 } 4649 4650 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4651 4652 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4653 phase_times->record_par_time(par_time_ms); 4654 4655 double code_root_fixup_time_ms = 4656 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4657 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4658 } 4659 4660 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4661 // Process any discovered reference objects - we have 4662 // to do this _before_ we retire the GC alloc regions 4663 // as we may have to copy some 'reachable' referent 4664 // objects (and their reachable sub-graphs) that were 4665 // not copied during the pause. 4666 if (g1_policy()->should_process_references()) { 4667 preserve_cm_referents(per_thread_states); 4668 process_discovered_references(per_thread_states); 4669 } else { 4670 ref_processor_stw()->verify_no_references_recorded(); 4671 process_weak_jni_handles(); 4672 } 4673 4674 if (G1StringDedup::is_enabled()) { 4675 double fixup_start = os::elapsedTime(); 4676 4677 G1STWIsAliveClosure is_alive(this); 4678 G1KeepAliveClosure keep_alive(this); 4679 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4680 4681 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4682 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4683 } 4684 4685 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4686 4687 if (evacuation_failed()) { 4688 restore_after_evac_failure(); 4689 4690 // Reset the G1EvacuationFailureALot counters and flags 4691 // Note: the values are reset only when an actual 4692 // evacuation failure occurs. 4693 NOT_PRODUCT(reset_evacuation_should_fail();) 4694 } 4695 4696 // Enqueue any remaining references remaining on the STW 4697 // reference processor's discovered lists. We need to do 4698 // this after the card table is cleaned (and verified) as 4699 // the act of enqueueing entries on to the pending list 4700 // will log these updates (and dirty their associated 4701 // cards). We need these updates logged to update any 4702 // RSets. 4703 if (g1_policy()->should_process_references()) { 4704 enqueue_discovered_references(per_thread_states); 4705 } else { 4706 g1_policy()->phase_times()->record_ref_enq_time(0); 4707 } 4708 4709 _allocator->release_gc_alloc_regions(evacuation_info); 4710 4711 merge_per_thread_state_info(per_thread_states); 4712 4713 // Reset and re-enable the hot card cache. 4714 // Note the counts for the cards in the regions in the 4715 // collection set are reset when the collection set is freed. 4716 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 4717 hot_card_cache->reset_hot_cache(); 4718 hot_card_cache->set_use_cache(true); 4719 4720 purge_code_root_memory(); 4721 4722 redirty_logged_cards(); 4723 #if defined(COMPILER2) || INCLUDE_JVMCI 4724 DerivedPointerTable::update_pointers(); 4725 #endif 4726 } 4727 4728 void G1CollectedHeap::record_obj_copy_mem_stats() { 4729 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4730 4731 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4732 create_g1_evac_summary(&_old_evac_stats)); 4733 } 4734 4735 void G1CollectedHeap::free_region(HeapRegion* hr, 4736 FreeRegionList* free_list, 4737 bool par, 4738 bool locked) { 4739 assert(!hr->is_free(), "the region should not be free"); 4740 assert(!hr->is_empty(), "the region should not be empty"); 4741 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4742 assert(free_list != NULL, "pre-condition"); 4743 4744 if (G1VerifyBitmaps) { 4745 MemRegion mr(hr->bottom(), hr->end()); 4746 concurrent_mark()->clearRangePrevBitmap(mr); 4747 } 4748 4749 // Clear the card counts for this region. 4750 // Note: we only need to do this if the region is not young 4751 // (since we don't refine cards in young regions). 4752 if (!hr->is_young()) { 4753 _cg1r->hot_card_cache()->reset_card_counts(hr); 4754 } 4755 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 4756 free_list->add_ordered(hr); 4757 } 4758 4759 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4760 FreeRegionList* free_list, 4761 bool par) { 4762 assert(hr->is_humongous(), "this is only for humongous regions"); 4763 assert(free_list != NULL, "pre-condition"); 4764 hr->clear_humongous(); 4765 free_region(hr, free_list, par); 4766 } 4767 4768 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4769 const uint humongous_regions_removed) { 4770 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4771 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4772 _old_set.bulk_remove(old_regions_removed); 4773 _humongous_set.bulk_remove(humongous_regions_removed); 4774 } 4775 4776 } 4777 4778 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4779 assert(list != NULL, "list can't be null"); 4780 if (!list->is_empty()) { 4781 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4782 _hrm.insert_list_into_free_list(list); 4783 } 4784 } 4785 4786 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4787 decrease_used(bytes); 4788 } 4789 4790 class G1ParCleanupCTTask : public AbstractGangTask { 4791 G1SATBCardTableModRefBS* _ct_bs; 4792 G1CollectedHeap* _g1h; 4793 HeapRegion* volatile _su_head; 4794 public: 4795 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 4796 G1CollectedHeap* g1h) : 4797 AbstractGangTask("G1 Par Cleanup CT Task"), 4798 _ct_bs(ct_bs), _g1h(g1h) { } 4799 4800 void work(uint worker_id) { 4801 HeapRegion* r; 4802 while (r = _g1h->pop_dirty_cards_region()) { 4803 clear_cards(r); 4804 } 4805 } 4806 4807 void clear_cards(HeapRegion* r) { 4808 // Cards of the survivors should have already been dirtied. 4809 if (!r->is_survivor()) { 4810 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 4811 } 4812 } 4813 }; 4814 4815 class G1ParScrubRemSetTask: public AbstractGangTask { 4816 protected: 4817 G1RemSet* _g1rs; 4818 BitMap* _region_bm; 4819 BitMap* _card_bm; 4820 HeapRegionClaimer _hrclaimer; 4821 4822 public: 4823 G1ParScrubRemSetTask(G1RemSet* g1_rs, BitMap* region_bm, BitMap* card_bm, uint num_workers) : 4824 AbstractGangTask("G1 ScrubRS"), 4825 _g1rs(g1_rs), 4826 _region_bm(region_bm), 4827 _card_bm(card_bm), 4828 _hrclaimer(num_workers) { 4829 } 4830 4831 void work(uint worker_id) { 4832 _g1rs->scrub(_region_bm, _card_bm, worker_id, &_hrclaimer); 4833 } 4834 }; 4835 4836 void G1CollectedHeap::scrub_rem_set(BitMap* region_bm, BitMap* card_bm) { 4837 uint num_workers = workers()->active_workers(); 4838 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), region_bm, card_bm, num_workers); 4839 workers()->run_task(&g1_par_scrub_rs_task); 4840 } 4841 4842 void G1CollectedHeap::cleanUpCardTable() { 4843 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 4844 double start = os::elapsedTime(); 4845 4846 { 4847 // Iterate over the dirty cards region list. 4848 G1ParCleanupCTTask cleanup_task(ct_bs, this); 4849 4850 workers()->run_task(&cleanup_task); 4851 #ifndef PRODUCT 4852 _verifier->verify_card_table_cleanup(); 4853 #endif 4854 } 4855 4856 double elapsed = os::elapsedTime() - start; 4857 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 4858 } 4859 4860 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4861 size_t pre_used = 0; 4862 FreeRegionList local_free_list("Local List for CSet Freeing"); 4863 4864 double young_time_ms = 0.0; 4865 double non_young_time_ms = 0.0; 4866 4867 // Since the collection set is a superset of the the young list, 4868 // all we need to do to clear the young list is clear its 4869 // head and length, and unlink any young regions in the code below 4870 _young_list->clear(); 4871 4872 G1CollectorPolicy* policy = g1_policy(); 4873 4874 double start_sec = os::elapsedTime(); 4875 bool non_young = true; 4876 4877 HeapRegion* cur = cs_head; 4878 int age_bound = -1; 4879 size_t rs_lengths = 0; 4880 4881 while (cur != NULL) { 4882 assert(!is_on_master_free_list(cur), "sanity"); 4883 if (non_young) { 4884 if (cur->is_young()) { 4885 double end_sec = os::elapsedTime(); 4886 double elapsed_ms = (end_sec - start_sec) * 1000.0; 4887 non_young_time_ms += elapsed_ms; 4888 4889 start_sec = os::elapsedTime(); 4890 non_young = false; 4891 } 4892 } else { 4893 if (!cur->is_young()) { 4894 double end_sec = os::elapsedTime(); 4895 double elapsed_ms = (end_sec - start_sec) * 1000.0; 4896 young_time_ms += elapsed_ms; 4897 4898 start_sec = os::elapsedTime(); 4899 non_young = true; 4900 } 4901 } 4902 4903 rs_lengths += cur->rem_set()->occupied_locked(); 4904 4905 HeapRegion* next = cur->next_in_collection_set(); 4906 assert(cur->in_collection_set(), "bad CS"); 4907 cur->set_next_in_collection_set(NULL); 4908 clear_in_cset(cur); 4909 4910 if (cur->is_young()) { 4911 int index = cur->young_index_in_cset(); 4912 assert(index != -1, "invariant"); 4913 assert((uint) index < collection_set()->young_region_length(), "invariant"); 4914 size_t words_survived = surviving_young_words[index]; 4915 cur->record_surv_words_in_group(words_survived); 4916 4917 // At this point the we have 'popped' cur from the collection set 4918 // (linked via next_in_collection_set()) but it is still in the 4919 // young list (linked via next_young_region()). Clear the 4920 // _next_young_region field. 4921 cur->set_next_young_region(NULL); 4922 } else { 4923 int index = cur->young_index_in_cset(); 4924 assert(index == -1, "invariant"); 4925 } 4926 4927 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 4928 (!cur->is_young() && cur->young_index_in_cset() == -1), 4929 "invariant" ); 4930 4931 if (!cur->evacuation_failed()) { 4932 MemRegion used_mr = cur->used_region(); 4933 4934 // And the region is empty. 4935 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 4936 pre_used += cur->used(); 4937 free_region(cur, &local_free_list, false /* par */, true /* locked */); 4938 } else { 4939 cur->uninstall_surv_rate_group(); 4940 if (cur->is_young()) { 4941 cur->set_young_index_in_cset(-1); 4942 } 4943 cur->set_evacuation_failed(false); 4944 // When moving a young gen region to old gen, we "allocate" that whole region 4945 // there. This is in addition to any already evacuated objects. Notify the 4946 // policy about that. 4947 // Old gen regions do not cause an additional allocation: both the objects 4948 // still in the region and the ones already moved are accounted for elsewhere. 4949 if (cur->is_young()) { 4950 policy->add_bytes_allocated_in_old_since_last_gc(HeapRegion::GrainBytes); 4951 } 4952 // The region is now considered to be old. 4953 cur->set_old(); 4954 // Do some allocation statistics accounting. Regions that failed evacuation 4955 // are always made old, so there is no need to update anything in the young 4956 // gen statistics, but we need to update old gen statistics. 4957 size_t used_words = cur->marked_bytes() / HeapWordSize; 4958 _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words); 4959 _old_set.add(cur); 4960 evacuation_info.increment_collectionset_used_after(cur->used()); 4961 } 4962 cur = next; 4963 } 4964 4965 evacuation_info.set_regions_freed(local_free_list.length()); 4966 policy->record_max_rs_lengths(rs_lengths); 4967 policy->cset_regions_freed(); 4968 4969 double end_sec = os::elapsedTime(); 4970 double elapsed_ms = (end_sec - start_sec) * 1000.0; 4971 4972 if (non_young) { 4973 non_young_time_ms += elapsed_ms; 4974 } else { 4975 young_time_ms += elapsed_ms; 4976 } 4977 4978 prepend_to_freelist(&local_free_list); 4979 decrement_summary_bytes(pre_used); 4980 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 4981 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 4982 } 4983 4984 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4985 private: 4986 FreeRegionList* _free_region_list; 4987 HeapRegionSet* _proxy_set; 4988 uint _humongous_regions_removed; 4989 size_t _freed_bytes; 4990 public: 4991 4992 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4993 _free_region_list(free_region_list), _humongous_regions_removed(0), _freed_bytes(0) { 4994 } 4995 4996 virtual bool doHeapRegion(HeapRegion* r) { 4997 if (!r->is_starts_humongous()) { 4998 return false; 4999 } 5000 5001 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 5002 5003 oop obj = (oop)r->bottom(); 5004 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 5005 5006 // The following checks whether the humongous object is live are sufficient. 5007 // The main additional check (in addition to having a reference from the roots 5008 // or the young gen) is whether the humongous object has a remembered set entry. 5009 // 5010 // A humongous object cannot be live if there is no remembered set for it 5011 // because: 5012 // - there can be no references from within humongous starts regions referencing 5013 // the object because we never allocate other objects into them. 5014 // (I.e. there are no intra-region references that may be missed by the 5015 // remembered set) 5016 // - as soon there is a remembered set entry to the humongous starts region 5017 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 5018 // until the end of a concurrent mark. 5019 // 5020 // It is not required to check whether the object has been found dead by marking 5021 // or not, in fact it would prevent reclamation within a concurrent cycle, as 5022 // all objects allocated during that time are considered live. 5023 // SATB marking is even more conservative than the remembered set. 5024 // So if at this point in the collection there is no remembered set entry, 5025 // nobody has a reference to it. 5026 // At the start of collection we flush all refinement logs, and remembered sets 5027 // are completely up-to-date wrt to references to the humongous object. 5028 // 5029 // Other implementation considerations: 5030 // - never consider object arrays at this time because they would pose 5031 // considerable effort for cleaning up the the remembered sets. This is 5032 // required because stale remembered sets might reference locations that 5033 // are currently allocated into. 5034 uint region_idx = r->hrm_index(); 5035 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 5036 !r->rem_set()->is_empty()) { 5037 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", 5038 region_idx, 5039 (size_t)obj->size() * HeapWordSize, 5040 p2i(r->bottom()), 5041 r->rem_set()->occupied(), 5042 r->rem_set()->strong_code_roots_list_length(), 5043 next_bitmap->isMarked(r->bottom()), 5044 g1h->is_humongous_reclaim_candidate(region_idx), 5045 obj->is_typeArray() 5046 ); 5047 return false; 5048 } 5049 5050 guarantee(obj->is_typeArray(), 5051 "Only eagerly reclaiming type arrays is supported, but the object " 5052 PTR_FORMAT " is not.", p2i(r->bottom())); 5053 5054 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", 5055 region_idx, 5056 (size_t)obj->size() * HeapWordSize, 5057 p2i(r->bottom()), 5058 r->rem_set()->occupied(), 5059 r->rem_set()->strong_code_roots_list_length(), 5060 next_bitmap->isMarked(r->bottom()), 5061 g1h->is_humongous_reclaim_candidate(region_idx), 5062 obj->is_typeArray() 5063 ); 5064 5065 // Need to clear mark bit of the humongous object if already set. 5066 if (next_bitmap->isMarked(r->bottom())) { 5067 next_bitmap->clear(r->bottom()); 5068 } 5069 do { 5070 HeapRegion* next = g1h->next_region_in_humongous(r); 5071 _freed_bytes += r->used(); 5072 r->set_containing_set(NULL); 5073 _humongous_regions_removed++; 5074 g1h->free_humongous_region(r, _free_region_list, false); 5075 r = next; 5076 } while (r != NULL); 5077 5078 return false; 5079 } 5080 5081 uint humongous_free_count() { 5082 return _humongous_regions_removed; 5083 } 5084 5085 size_t bytes_freed() const { 5086 return _freed_bytes; 5087 } 5088 }; 5089 5090 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 5091 assert_at_safepoint(true); 5092 5093 if (!G1EagerReclaimHumongousObjects || 5094 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 5095 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5096 return; 5097 } 5098 5099 double start_time = os::elapsedTime(); 5100 5101 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5102 5103 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5104 heap_region_iterate(&cl); 5105 5106 remove_from_old_sets(0, cl.humongous_free_count()); 5107 5108 G1HRPrinter* hrp = hr_printer(); 5109 if (hrp->is_active()) { 5110 FreeRegionListIterator iter(&local_cleanup_list); 5111 while (iter.more_available()) { 5112 HeapRegion* hr = iter.get_next(); 5113 hrp->cleanup(hr); 5114 } 5115 } 5116 5117 prepend_to_freelist(&local_cleanup_list); 5118 decrement_summary_bytes(cl.bytes_freed()); 5119 5120 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5121 cl.humongous_free_count()); 5122 } 5123 5124 // This routine is similar to the above but does not record 5125 // any policy statistics or update free lists; we are abandoning 5126 // the current incremental collection set in preparation of a 5127 // full collection. After the full GC we will start to build up 5128 // the incremental collection set again. 5129 // This is only called when we're doing a full collection 5130 // and is immediately followed by the tearing down of the young list. 5131 5132 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 5133 HeapRegion* cur = cs_head; 5134 5135 while (cur != NULL) { 5136 HeapRegion* next = cur->next_in_collection_set(); 5137 assert(cur->in_collection_set(), "bad CS"); 5138 cur->set_next_in_collection_set(NULL); 5139 clear_in_cset(cur); 5140 cur->set_young_index_in_cset(-1); 5141 cur = next; 5142 } 5143 } 5144 5145 void G1CollectedHeap::set_free_regions_coming() { 5146 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 5147 5148 assert(!free_regions_coming(), "pre-condition"); 5149 _free_regions_coming = true; 5150 } 5151 5152 void G1CollectedHeap::reset_free_regions_coming() { 5153 assert(free_regions_coming(), "pre-condition"); 5154 5155 { 5156 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5157 _free_regions_coming = false; 5158 SecondaryFreeList_lock->notify_all(); 5159 } 5160 5161 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 5162 } 5163 5164 void G1CollectedHeap::wait_while_free_regions_coming() { 5165 // Most of the time we won't have to wait, so let's do a quick test 5166 // first before we take the lock. 5167 if (!free_regions_coming()) { 5168 return; 5169 } 5170 5171 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 5172 5173 { 5174 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5175 while (free_regions_coming()) { 5176 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5177 } 5178 } 5179 5180 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 5181 } 5182 5183 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5184 return _allocator->is_retained_old_region(hr); 5185 } 5186 5187 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5188 _young_list->push_region(hr); 5189 } 5190 5191 class NoYoungRegionsClosure: public HeapRegionClosure { 5192 private: 5193 bool _success; 5194 public: 5195 NoYoungRegionsClosure() : _success(true) { } 5196 bool doHeapRegion(HeapRegion* r) { 5197 if (r->is_young()) { 5198 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5199 p2i(r->bottom()), p2i(r->end())); 5200 _success = false; 5201 } 5202 return false; 5203 } 5204 bool success() { return _success; } 5205 }; 5206 5207 bool G1CollectedHeap::check_young_list_empty(bool check_heap) { 5208 bool ret = _young_list->check_list_empty(); 5209 5210 if (check_heap) { 5211 NoYoungRegionsClosure closure; 5212 heap_region_iterate(&closure); 5213 ret = ret && closure.success(); 5214 } 5215 5216 return ret; 5217 } 5218 5219 class TearDownRegionSetsClosure : public HeapRegionClosure { 5220 private: 5221 HeapRegionSet *_old_set; 5222 5223 public: 5224 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5225 5226 bool doHeapRegion(HeapRegion* r) { 5227 if (r->is_old()) { 5228 _old_set->remove(r); 5229 } else { 5230 // We ignore free regions, we'll empty the free list afterwards. 5231 // We ignore young regions, we'll empty the young list afterwards. 5232 // We ignore humongous regions, we're not tearing down the 5233 // humongous regions set. 5234 assert(r->is_free() || r->is_young() || r->is_humongous(), 5235 "it cannot be another type"); 5236 } 5237 return false; 5238 } 5239 5240 ~TearDownRegionSetsClosure() { 5241 assert(_old_set->is_empty(), "post-condition"); 5242 } 5243 }; 5244 5245 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5246 assert_at_safepoint(true /* should_be_vm_thread */); 5247 5248 if (!free_list_only) { 5249 TearDownRegionSetsClosure cl(&_old_set); 5250 heap_region_iterate(&cl); 5251 5252 // Note that emptying the _young_list is postponed and instead done as 5253 // the first step when rebuilding the regions sets again. The reason for 5254 // this is that during a full GC string deduplication needs to know if 5255 // a collected region was young or old when the full GC was initiated. 5256 } 5257 _hrm.remove_all_free_regions(); 5258 } 5259 5260 void G1CollectedHeap::increase_used(size_t bytes) { 5261 _summary_bytes_used += bytes; 5262 } 5263 5264 void G1CollectedHeap::decrease_used(size_t bytes) { 5265 assert(_summary_bytes_used >= bytes, 5266 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5267 _summary_bytes_used, bytes); 5268 _summary_bytes_used -= bytes; 5269 } 5270 5271 void G1CollectedHeap::set_used(size_t bytes) { 5272 _summary_bytes_used = bytes; 5273 } 5274 5275 class RebuildRegionSetsClosure : public HeapRegionClosure { 5276 private: 5277 bool _free_list_only; 5278 HeapRegionSet* _old_set; 5279 HeapRegionManager* _hrm; 5280 size_t _total_used; 5281 5282 public: 5283 RebuildRegionSetsClosure(bool free_list_only, 5284 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5285 _free_list_only(free_list_only), 5286 _old_set(old_set), _hrm(hrm), _total_used(0) { 5287 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5288 if (!free_list_only) { 5289 assert(_old_set->is_empty(), "pre-condition"); 5290 } 5291 } 5292 5293 bool doHeapRegion(HeapRegion* r) { 5294 if (r->is_empty()) { 5295 // Add free regions to the free list 5296 r->set_free(); 5297 r->set_allocation_context(AllocationContext::system()); 5298 _hrm->insert_into_free_list(r); 5299 } else if (!_free_list_only) { 5300 assert(!r->is_young(), "we should not come across young regions"); 5301 5302 if (r->is_humongous()) { 5303 // We ignore humongous regions. We left the humongous set unchanged. 5304 } else { 5305 // Objects that were compacted would have ended up on regions 5306 // that were previously old or free. Archive regions (which are 5307 // old) will not have been touched. 5308 assert(r->is_free() || r->is_old(), "invariant"); 5309 // We now consider them old, so register as such. Leave 5310 // archive regions set that way, however, while still adding 5311 // them to the old set. 5312 if (!r->is_archive()) { 5313 r->set_old(); 5314 } 5315 _old_set->add(r); 5316 } 5317 _total_used += r->used(); 5318 } 5319 5320 return false; 5321 } 5322 5323 size_t total_used() { 5324 return _total_used; 5325 } 5326 }; 5327 5328 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5329 assert_at_safepoint(true /* should_be_vm_thread */); 5330 5331 if (!free_list_only) { 5332 _young_list->empty_list(); 5333 } 5334 5335 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5336 heap_region_iterate(&cl); 5337 5338 if (!free_list_only) { 5339 set_used(cl.total_used()); 5340 if (_archive_allocator != NULL) { 5341 _archive_allocator->clear_used(); 5342 } 5343 } 5344 assert(used_unlocked() == recalculate_used(), 5345 "inconsistent used_unlocked(), " 5346 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5347 used_unlocked(), recalculate_used()); 5348 } 5349 5350 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 5351 _refine_cte_cl->set_concurrent(concurrent); 5352 } 5353 5354 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5355 HeapRegion* hr = heap_region_containing(p); 5356 return hr->is_in(p); 5357 } 5358 5359 // Methods for the mutator alloc region 5360 5361 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5362 bool force) { 5363 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5364 assert(!force || g1_policy()->can_expand_young_list(), 5365 "if force is true we should be able to expand the young list"); 5366 bool young_list_full = g1_policy()->is_young_list_full(); 5367 if (force || !young_list_full) { 5368 HeapRegion* new_alloc_region = new_region(word_size, 5369 false /* is_old */, 5370 false /* do_expand */); 5371 if (new_alloc_region != NULL) { 5372 set_region_short_lived_locked(new_alloc_region); 5373 _hr_printer.alloc(new_alloc_region, young_list_full); 5374 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5375 return new_alloc_region; 5376 } 5377 } 5378 return NULL; 5379 } 5380 5381 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5382 size_t allocated_bytes) { 5383 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5384 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5385 5386 collection_set()->add_eden_region(alloc_region); 5387 increase_used(allocated_bytes); 5388 _hr_printer.retire(alloc_region); 5389 // We update the eden sizes here, when the region is retired, 5390 // instead of when it's allocated, since this is the point that its 5391 // used space has been recored in _summary_bytes_used. 5392 g1mm()->update_eden_size(); 5393 } 5394 5395 // Methods for the GC alloc regions 5396 5397 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 5398 uint count, 5399 InCSetState dest) { 5400 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5401 5402 if (count < g1_policy()->max_regions(dest)) { 5403 const bool is_survivor = (dest.is_young()); 5404 HeapRegion* new_alloc_region = new_region(word_size, 5405 !is_survivor, 5406 true /* do_expand */); 5407 if (new_alloc_region != NULL) { 5408 // We really only need to do this for old regions given that we 5409 // should never scan survivors. But it doesn't hurt to do it 5410 // for survivors too. 5411 new_alloc_region->record_timestamp(); 5412 if (is_survivor) { 5413 new_alloc_region->set_survivor(); 5414 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5415 } else { 5416 new_alloc_region->set_old(); 5417 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5418 } 5419 _hr_printer.alloc(new_alloc_region); 5420 bool during_im = collector_state()->during_initial_mark_pause(); 5421 new_alloc_region->note_start_of_copying(during_im); 5422 return new_alloc_region; 5423 } 5424 } 5425 return NULL; 5426 } 5427 5428 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5429 size_t allocated_bytes, 5430 InCSetState dest) { 5431 bool during_im = collector_state()->during_initial_mark_pause(); 5432 alloc_region->note_end_of_copying(during_im); 5433 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5434 if (dest.is_young()) { 5435 young_list()->add_survivor_region(alloc_region); 5436 } else { 5437 _old_set.add(alloc_region); 5438 } 5439 _hr_printer.retire(alloc_region); 5440 } 5441 5442 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5443 bool expanded = false; 5444 uint index = _hrm.find_highest_free(&expanded); 5445 5446 if (index != G1_NO_HRM_INDEX) { 5447 if (expanded) { 5448 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5449 HeapRegion::GrainWords * HeapWordSize); 5450 } 5451 _hrm.allocate_free_regions_starting_at(index, 1); 5452 return region_at(index); 5453 } 5454 return NULL; 5455 } 5456 5457 // Optimized nmethod scanning 5458 5459 class RegisterNMethodOopClosure: public OopClosure { 5460 G1CollectedHeap* _g1h; 5461 nmethod* _nm; 5462 5463 template <class T> void do_oop_work(T* p) { 5464 T heap_oop = oopDesc::load_heap_oop(p); 5465 if (!oopDesc::is_null(heap_oop)) { 5466 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5467 HeapRegion* hr = _g1h->heap_region_containing(obj); 5468 assert(!hr->is_continues_humongous(), 5469 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5470 " starting at " HR_FORMAT, 5471 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5472 5473 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5474 hr->add_strong_code_root_locked(_nm); 5475 } 5476 } 5477 5478 public: 5479 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5480 _g1h(g1h), _nm(nm) {} 5481 5482 void do_oop(oop* p) { do_oop_work(p); } 5483 void do_oop(narrowOop* p) { do_oop_work(p); } 5484 }; 5485 5486 class UnregisterNMethodOopClosure: public OopClosure { 5487 G1CollectedHeap* _g1h; 5488 nmethod* _nm; 5489 5490 template <class T> void do_oop_work(T* p) { 5491 T heap_oop = oopDesc::load_heap_oop(p); 5492 if (!oopDesc::is_null(heap_oop)) { 5493 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5494 HeapRegion* hr = _g1h->heap_region_containing(obj); 5495 assert(!hr->is_continues_humongous(), 5496 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5497 " starting at " HR_FORMAT, 5498 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5499 5500 hr->remove_strong_code_root(_nm); 5501 } 5502 } 5503 5504 public: 5505 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5506 _g1h(g1h), _nm(nm) {} 5507 5508 void do_oop(oop* p) { do_oop_work(p); } 5509 void do_oop(narrowOop* p) { do_oop_work(p); } 5510 }; 5511 5512 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5513 CollectedHeap::register_nmethod(nm); 5514 5515 guarantee(nm != NULL, "sanity"); 5516 RegisterNMethodOopClosure reg_cl(this, nm); 5517 nm->oops_do(®_cl); 5518 } 5519 5520 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5521 CollectedHeap::unregister_nmethod(nm); 5522 5523 guarantee(nm != NULL, "sanity"); 5524 UnregisterNMethodOopClosure reg_cl(this, nm); 5525 nm->oops_do(®_cl, true); 5526 } 5527 5528 void G1CollectedHeap::purge_code_root_memory() { 5529 double purge_start = os::elapsedTime(); 5530 G1CodeRootSet::purge(); 5531 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5532 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5533 } 5534 5535 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5536 G1CollectedHeap* _g1h; 5537 5538 public: 5539 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5540 _g1h(g1h) {} 5541 5542 void do_code_blob(CodeBlob* cb) { 5543 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5544 if (nm == NULL) { 5545 return; 5546 } 5547 5548 if (ScavengeRootsInCode) { 5549 _g1h->register_nmethod(nm); 5550 } 5551 } 5552 }; 5553 5554 void G1CollectedHeap::rebuild_strong_code_roots() { 5555 RebuildStrongCodeRootClosure blob_cl(this); 5556 CodeCache::blobs_do(&blob_cl); 5557 }