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