1 /* 2 * Copyright (c) 2001, 2015, 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/g1MarkSweep.hpp" 42 #include "gc/g1/g1OopClosures.inline.hpp" 43 #include "gc/g1/g1ParScanThreadState.inline.hpp" 44 #include "gc/g1/g1RegionToSpaceMapper.hpp" 45 #include "gc/g1/g1RemSet.inline.hpp" 46 #include "gc/g1/g1RootClosures.hpp" 47 #include "gc/g1/g1RootProcessor.hpp" 48 #include "gc/g1/g1StringDedup.hpp" 49 #include "gc/g1/g1YCTypes.hpp" 50 #include "gc/g1/heapRegion.inline.hpp" 51 #include "gc/g1/heapRegionRemSet.hpp" 52 #include "gc/g1/heapRegionSet.inline.hpp" 53 #include "gc/g1/suspendibleThreadSet.hpp" 54 #include "gc/g1/vm_operations_g1.hpp" 55 #include "gc/shared/gcHeapSummary.hpp" 56 #include "gc/shared/gcId.hpp" 57 #include "gc/shared/gcLocker.inline.hpp" 58 #include "gc/shared/gcTimer.hpp" 59 #include "gc/shared/gcTrace.hpp" 60 #include "gc/shared/gcTraceTime.inline.hpp" 61 #include "gc/shared/generationSpec.hpp" 62 #include "gc/shared/isGCActiveMark.hpp" 63 #include "gc/shared/referenceProcessor.hpp" 64 #include "gc/shared/taskqueue.inline.hpp" 65 #include "logging/log.hpp" 66 #include "memory/allocation.hpp" 67 #include "memory/iterator.hpp" 68 #include "oops/oop.inline.hpp" 69 #include "runtime/atomic.inline.hpp" 70 #include "runtime/init.hpp" 71 #include "runtime/orderAccess.inline.hpp" 72 #include "runtime/vmThread.hpp" 73 #include "utilities/globalDefinitions.hpp" 74 #include "utilities/stack.inline.hpp" 75 76 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 77 78 // INVARIANTS/NOTES 79 // 80 // All allocation activity covered by the G1CollectedHeap interface is 81 // serialized by acquiring the HeapLock. This happens in mem_allocate 82 // and allocate_new_tlab, which are the "entry" points to the 83 // allocation code from the rest of the JVM. (Note that this does not 84 // apply to TLAB allocation, which is not part of this interface: it 85 // is done by clients of this interface.) 86 87 // Local to this file. 88 89 class RefineCardTableEntryClosure: public CardTableEntryClosure { 90 bool _concurrent; 91 public: 92 RefineCardTableEntryClosure() : _concurrent(true) { } 93 94 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 95 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false); 96 // This path is executed by the concurrent refine or mutator threads, 97 // concurrently, and so we do not care if card_ptr contains references 98 // that point into the collection set. 99 assert(!oops_into_cset, "should be"); 100 101 if (_concurrent && SuspendibleThreadSet::should_yield()) { 102 // Caller will actually yield. 103 return false; 104 } 105 // Otherwise, we finished successfully; return true. 106 return true; 107 } 108 109 void set_concurrent(bool b) { _concurrent = b; } 110 }; 111 112 113 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 114 private: 115 size_t _num_dirtied; 116 G1CollectedHeap* _g1h; 117 G1SATBCardTableLoggingModRefBS* _g1_bs; 118 119 HeapRegion* region_for_card(jbyte* card_ptr) const { 120 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 121 } 122 123 bool will_become_free(HeapRegion* hr) const { 124 // A region will be freed by free_collection_set if the region is in the 125 // collection set and has not had an evacuation failure. 126 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 127 } 128 129 public: 130 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 131 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 132 133 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 134 HeapRegion* hr = region_for_card(card_ptr); 135 136 // Should only dirty cards in regions that won't be freed. 137 if (!will_become_free(hr)) { 138 *card_ptr = CardTableModRefBS::dirty_card_val(); 139 _num_dirtied++; 140 } 141 142 return true; 143 } 144 145 size_t num_dirtied() const { return _num_dirtied; } 146 }; 147 148 149 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 150 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 151 } 152 153 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 154 // The from card cache is not the memory that is actually committed. So we cannot 155 // take advantage of the zero_filled parameter. 156 reset_from_card_cache(start_idx, num_regions); 157 } 158 159 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 160 { 161 // Claim the right to put the region on the dirty cards region list 162 // by installing a self pointer. 163 HeapRegion* next = hr->get_next_dirty_cards_region(); 164 if (next == NULL) { 165 HeapRegion* res = (HeapRegion*) 166 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 167 NULL); 168 if (res == NULL) { 169 HeapRegion* head; 170 do { 171 // Put the region to the dirty cards region list. 172 head = _dirty_cards_region_list; 173 next = (HeapRegion*) 174 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 175 if (next == head) { 176 assert(hr->get_next_dirty_cards_region() == hr, 177 "hr->get_next_dirty_cards_region() != hr"); 178 if (next == NULL) { 179 // The last region in the list points to itself. 180 hr->set_next_dirty_cards_region(hr); 181 } else { 182 hr->set_next_dirty_cards_region(next); 183 } 184 } 185 } while (next != head); 186 } 187 } 188 } 189 190 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 191 { 192 HeapRegion* head; 193 HeapRegion* hr; 194 do { 195 head = _dirty_cards_region_list; 196 if (head == NULL) { 197 return NULL; 198 } 199 HeapRegion* new_head = head->get_next_dirty_cards_region(); 200 if (head == new_head) { 201 // The last region. 202 new_head = NULL; 203 } 204 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 205 head); 206 } while (hr != head); 207 assert(hr != NULL, "invariant"); 208 hr->set_next_dirty_cards_region(NULL); 209 return hr; 210 } 211 212 // Returns true if the reference points to an object that 213 // can move in an incremental collection. 214 bool G1CollectedHeap::is_scavengable(const void* p) { 215 HeapRegion* hr = heap_region_containing(p); 216 return !hr->is_pinned(); 217 } 218 219 // Private methods. 220 221 HeapRegion* 222 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 223 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 224 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 225 if (!_secondary_free_list.is_empty()) { 226 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 227 "secondary_free_list has %u entries", 228 _secondary_free_list.length()); 229 // It looks as if there are free regions available on the 230 // secondary_free_list. Let's move them to the free_list and try 231 // again to allocate from it. 232 append_secondary_free_list(); 233 234 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 235 "empty we should have moved at least one entry to the free_list"); 236 HeapRegion* res = _hrm.allocate_free_region(is_old); 237 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 238 "allocated " HR_FORMAT " from secondary_free_list", 239 HR_FORMAT_PARAMS(res)); 240 return res; 241 } 242 243 // Wait here until we get notified either when (a) there are no 244 // more free regions coming or (b) some regions have been moved on 245 // the secondary_free_list. 246 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 247 } 248 249 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 250 "could not allocate from secondary_free_list"); 251 return NULL; 252 } 253 254 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 255 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 256 "the only time we use this to allocate a humongous region is " 257 "when we are allocating a single humongous region"); 258 259 HeapRegion* res; 260 if (G1StressConcRegionFreeing) { 261 if (!_secondary_free_list.is_empty()) { 262 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 263 "forced to look at the secondary_free_list"); 264 res = new_region_try_secondary_free_list(is_old); 265 if (res != NULL) { 266 return res; 267 } 268 } 269 } 270 271 res = _hrm.allocate_free_region(is_old); 272 273 if (res == NULL) { 274 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 275 "res == NULL, trying the secondary_free_list"); 276 res = new_region_try_secondary_free_list(is_old); 277 } 278 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 279 // Currently, only attempts to allocate GC alloc regions set 280 // do_expand to true. So, we should only reach here during a 281 // safepoint. If this assumption changes we might have to 282 // reconsider the use of _expand_heap_after_alloc_failure. 283 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 284 285 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 286 word_size * HeapWordSize); 287 288 if (expand(word_size * HeapWordSize)) { 289 // Given that expand() succeeded in expanding the heap, and we 290 // always expand the heap by an amount aligned to the heap 291 // region size, the free list should in theory not be empty. 292 // In either case allocate_free_region() will check for NULL. 293 res = _hrm.allocate_free_region(is_old); 294 } else { 295 _expand_heap_after_alloc_failure = false; 296 } 297 } 298 return res; 299 } 300 301 HeapWord* 302 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 303 uint num_regions, 304 size_t word_size, 305 AllocationContext_t context) { 306 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 307 assert(is_humongous(word_size), "word_size should be humongous"); 308 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 309 310 // Index of last region in the series. 311 uint last = first + num_regions - 1; 312 313 // We need to initialize the region(s) we just discovered. This is 314 // a bit tricky given that it can happen concurrently with 315 // refinement threads refining cards on these regions and 316 // potentially wanting to refine the BOT as they are scanning 317 // those cards (this can happen shortly after a cleanup; see CR 318 // 6991377). So we have to set up the region(s) carefully and in 319 // a specific order. 320 321 // The word size sum of all the regions we will allocate. 322 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 323 assert(word_size <= word_size_sum, "sanity"); 324 325 // This will be the "starts humongous" region. 326 HeapRegion* first_hr = region_at(first); 327 // The header of the new object will be placed at the bottom of 328 // the first region. 329 HeapWord* new_obj = first_hr->bottom(); 330 // This will be the new top of the new object. 331 HeapWord* obj_top = new_obj + word_size; 332 333 // First, we need to zero the header of the space that we will be 334 // allocating. When we update top further down, some refinement 335 // threads might try to scan the region. By zeroing the header we 336 // ensure that any thread that will try to scan the region will 337 // come across the zero klass word and bail out. 338 // 339 // NOTE: It would not have been correct to have used 340 // CollectedHeap::fill_with_object() and make the space look like 341 // an int array. The thread that is doing the allocation will 342 // later update the object header to a potentially different array 343 // type and, for a very short period of time, the klass and length 344 // fields will be inconsistent. This could cause a refinement 345 // thread to calculate the object size incorrectly. 346 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 347 348 // How many words we use for filler objects. 349 size_t word_fill_size = word_size_sum - word_size; 350 351 // How many words memory we "waste" which cannot hold a filler object. 352 size_t words_not_fillable = 0; 353 354 if (word_fill_size >= min_fill_size()) { 355 fill_with_objects(obj_top, word_fill_size); 356 } else if (word_fill_size > 0) { 357 // We have space to fill, but we cannot fit an object there. 358 words_not_fillable = word_fill_size; 359 word_fill_size = 0; 360 } 361 362 // We will set up the first region as "starts humongous". This 363 // will also update the BOT covering all the regions to reflect 364 // that there is a single object that starts at the bottom of the 365 // first region. 366 first_hr->set_starts_humongous(obj_top, word_fill_size); 367 first_hr->set_allocation_context(context); 368 // Then, if there are any, we will set up the "continues 369 // humongous" regions. 370 HeapRegion* hr = NULL; 371 for (uint i = first + 1; i <= last; ++i) { 372 hr = region_at(i); 373 hr->set_continues_humongous(first_hr); 374 hr->set_allocation_context(context); 375 } 376 377 // Up to this point no concurrent thread would have been able to 378 // do any scanning on any region in this series. All the top 379 // fields still point to bottom, so the intersection between 380 // [bottom,top] and [card_start,card_end] will be empty. Before we 381 // update the top fields, we'll do a storestore to make sure that 382 // no thread sees the update to top before the zeroing of the 383 // object header and the BOT initialization. 384 OrderAccess::storestore(); 385 386 // Now, we will update the top fields of the "continues humongous" 387 // regions except the last one. 388 for (uint i = first; i < last; ++i) { 389 hr = region_at(i); 390 hr->set_top(hr->end()); 391 } 392 393 hr = region_at(last); 394 // If we cannot fit a filler object, we must set top to the end 395 // of the humongous object, otherwise we cannot iterate the heap 396 // and the BOT will not be complete. 397 hr->set_top(hr->end() - words_not_fillable); 398 399 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 400 "obj_top should be in last region"); 401 402 check_bitmaps("Humongous Region Allocation", first_hr); 403 404 assert(words_not_fillable == 0 || 405 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 406 "Miscalculation in humongous allocation"); 407 408 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 409 410 for (uint i = first; i <= last; ++i) { 411 hr = region_at(i); 412 _humongous_set.add(hr); 413 _hr_printer.alloc(hr); 414 } 415 416 return new_obj; 417 } 418 419 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 420 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 421 return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 422 } 423 424 // If could fit into free regions w/o expansion, try. 425 // Otherwise, if can expand, do so. 426 // Otherwise, if using ex regions might help, try with ex given back. 427 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 428 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 429 430 verify_region_sets_optional(); 431 432 uint first = G1_NO_HRM_INDEX; 433 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 434 435 if (obj_regions == 1) { 436 // Only one region to allocate, try to use a fast path by directly allocating 437 // from the free lists. Do not try to expand here, we will potentially do that 438 // later. 439 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 440 if (hr != NULL) { 441 first = hr->hrm_index(); 442 } 443 } else { 444 // We can't allocate humongous regions spanning more than one region while 445 // cleanupComplete() is running, since some of the regions we find to be 446 // empty might not yet be added to the free list. It is not straightforward 447 // to know in which list they are on so that we can remove them. We only 448 // need to do this if we need to allocate more than one region to satisfy the 449 // current humongous allocation request. If we are only allocating one region 450 // we use the one-region region allocation code (see above), that already 451 // potentially waits for regions from the secondary free list. 452 wait_while_free_regions_coming(); 453 append_secondary_free_list_if_not_empty_with_lock(); 454 455 // Policy: Try only empty regions (i.e. already committed first). Maybe we 456 // are lucky enough to find some. 457 first = _hrm.find_contiguous_only_empty(obj_regions); 458 if (first != G1_NO_HRM_INDEX) { 459 _hrm.allocate_free_regions_starting_at(first, obj_regions); 460 } 461 } 462 463 if (first == G1_NO_HRM_INDEX) { 464 // Policy: We could not find enough regions for the humongous object in the 465 // free list. Look through the heap to find a mix of free and uncommitted regions. 466 // If so, try expansion. 467 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 468 if (first != G1_NO_HRM_INDEX) { 469 // We found something. Make sure these regions are committed, i.e. expand 470 // the heap. Alternatively we could do a defragmentation GC. 471 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 472 word_size * HeapWordSize); 473 474 475 _hrm.expand_at(first, obj_regions); 476 g1_policy()->record_new_heap_size(num_regions()); 477 478 #ifdef ASSERT 479 for (uint i = first; i < first + obj_regions; ++i) { 480 HeapRegion* hr = region_at(i); 481 assert(hr->is_free(), "sanity"); 482 assert(hr->is_empty(), "sanity"); 483 assert(is_on_master_free_list(hr), "sanity"); 484 } 485 #endif 486 _hrm.allocate_free_regions_starting_at(first, obj_regions); 487 } else { 488 // Policy: Potentially trigger a defragmentation GC. 489 } 490 } 491 492 HeapWord* result = NULL; 493 if (first != G1_NO_HRM_INDEX) { 494 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 495 word_size, context); 496 assert(result != NULL, "it should always return a valid result"); 497 498 // A successful humongous object allocation changes the used space 499 // information of the old generation so we need to recalculate the 500 // sizes and update the jstat counters here. 501 g1mm()->update_sizes(); 502 } 503 504 verify_region_sets_optional(); 505 506 return result; 507 } 508 509 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 510 assert_heap_not_locked_and_not_at_safepoint(); 511 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 512 513 uint dummy_gc_count_before; 514 uint dummy_gclocker_retry_count = 0; 515 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 516 } 517 518 HeapWord* 519 G1CollectedHeap::mem_allocate(size_t word_size, 520 bool* gc_overhead_limit_was_exceeded) { 521 assert_heap_not_locked_and_not_at_safepoint(); 522 523 // Loop until the allocation is satisfied, or unsatisfied after GC. 524 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 525 uint gc_count_before; 526 527 HeapWord* result = NULL; 528 if (!is_humongous(word_size)) { 529 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 530 } else { 531 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 532 } 533 if (result != NULL) { 534 return result; 535 } 536 537 // Create the garbage collection operation... 538 VM_G1CollectForAllocation op(gc_count_before, word_size); 539 op.set_allocation_context(AllocationContext::current()); 540 541 // ...and get the VM thread to execute it. 542 VMThread::execute(&op); 543 544 if (op.prologue_succeeded() && op.pause_succeeded()) { 545 // If the operation was successful we'll return the result even 546 // if it is NULL. If the allocation attempt failed immediately 547 // after a Full GC, it's unlikely we'll be able to allocate now. 548 HeapWord* result = op.result(); 549 if (result != NULL && !is_humongous(word_size)) { 550 // Allocations that take place on VM operations do not do any 551 // card dirtying and we have to do it here. We only have to do 552 // this for non-humongous allocations, though. 553 dirty_young_block(result, word_size); 554 } 555 return result; 556 } else { 557 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 558 return NULL; 559 } 560 assert(op.result() == NULL, 561 "the result should be NULL if the VM op did not succeed"); 562 } 563 564 // Give a warning if we seem to be looping forever. 565 if ((QueuedAllocationWarningCount > 0) && 566 (try_count % QueuedAllocationWarningCount == 0)) { 567 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 568 } 569 } 570 571 ShouldNotReachHere(); 572 return NULL; 573 } 574 575 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 576 AllocationContext_t context, 577 uint* gc_count_before_ret, 578 uint* gclocker_retry_count_ret) { 579 // Make sure you read the note in attempt_allocation_humongous(). 580 581 assert_heap_not_locked_and_not_at_safepoint(); 582 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 583 "be called for humongous allocation requests"); 584 585 // We should only get here after the first-level allocation attempt 586 // (attempt_allocation()) failed to allocate. 587 588 // We will loop until a) we manage to successfully perform the 589 // allocation or b) we successfully schedule a collection which 590 // fails to perform the allocation. b) is the only case when we'll 591 // return NULL. 592 HeapWord* result = NULL; 593 for (int try_count = 1; /* we'll return */; try_count += 1) { 594 bool should_try_gc; 595 uint gc_count_before; 596 597 { 598 MutexLockerEx x(Heap_lock); 599 result = _allocator->attempt_allocation_locked(word_size, context); 600 if (result != NULL) { 601 return result; 602 } 603 604 if (GCLocker::is_active_and_needs_gc()) { 605 if (g1_policy()->can_expand_young_list()) { 606 // No need for an ergo verbose message here, 607 // can_expand_young_list() does this when it returns true. 608 result = _allocator->attempt_allocation_force(word_size, context); 609 if (result != NULL) { 610 return result; 611 } 612 } 613 should_try_gc = false; 614 } else { 615 // The GCLocker may not be active but the GCLocker initiated 616 // GC may not yet have been performed (GCLocker::needs_gc() 617 // returns true). In this case we do not try this GC and 618 // wait until the GCLocker initiated GC is performed, and 619 // then retry the allocation. 620 if (GCLocker::needs_gc()) { 621 should_try_gc = false; 622 } else { 623 // Read the GC count while still holding the Heap_lock. 624 gc_count_before = total_collections(); 625 should_try_gc = true; 626 } 627 } 628 } 629 630 if (should_try_gc) { 631 bool succeeded; 632 result = do_collection_pause(word_size, gc_count_before, &succeeded, 633 GCCause::_g1_inc_collection_pause); 634 if (result != NULL) { 635 assert(succeeded, "only way to get back a non-NULL result"); 636 return result; 637 } 638 639 if (succeeded) { 640 // If we get here we successfully scheduled a collection which 641 // failed to allocate. No point in trying to allocate 642 // further. We'll just return NULL. 643 MutexLockerEx x(Heap_lock); 644 *gc_count_before_ret = total_collections(); 645 return NULL; 646 } 647 } else { 648 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 649 MutexLockerEx x(Heap_lock); 650 *gc_count_before_ret = total_collections(); 651 return NULL; 652 } 653 // The GCLocker is either active or the GCLocker initiated 654 // GC has not yet been performed. Stall until it is and 655 // then retry the allocation. 656 GCLocker::stall_until_clear(); 657 (*gclocker_retry_count_ret) += 1; 658 } 659 660 // We can reach here if we were unsuccessful in scheduling a 661 // collection (because another thread beat us to it) or if we were 662 // stalled due to the GC locker. In either can we should retry the 663 // allocation attempt in case another thread successfully 664 // performed a collection and reclaimed enough space. We do the 665 // first attempt (without holding the Heap_lock) here and the 666 // follow-on attempt will be at the start of the next loop 667 // iteration (after taking the Heap_lock). 668 result = _allocator->attempt_allocation(word_size, context); 669 if (result != NULL) { 670 return result; 671 } 672 673 // Give a warning if we seem to be looping forever. 674 if ((QueuedAllocationWarningCount > 0) && 675 (try_count % QueuedAllocationWarningCount == 0)) { 676 warning("G1CollectedHeap::attempt_allocation_slow() " 677 "retries %d times", try_count); 678 } 679 } 680 681 ShouldNotReachHere(); 682 return NULL; 683 } 684 685 void G1CollectedHeap::begin_archive_alloc_range() { 686 assert_at_safepoint(true /* should_be_vm_thread */); 687 if (_archive_allocator == NULL) { 688 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 689 } 690 } 691 692 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 693 // Allocations in archive regions cannot be of a size that would be considered 694 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 695 // may be different at archive-restore time. 696 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 697 } 698 699 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 700 assert_at_safepoint(true /* should_be_vm_thread */); 701 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 702 if (is_archive_alloc_too_large(word_size)) { 703 return NULL; 704 } 705 return _archive_allocator->archive_mem_allocate(word_size); 706 } 707 708 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 709 size_t end_alignment_in_bytes) { 710 assert_at_safepoint(true /* should_be_vm_thread */); 711 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 712 713 // Call complete_archive to do the real work, filling in the MemRegion 714 // array with the archive regions. 715 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 716 delete _archive_allocator; 717 _archive_allocator = NULL; 718 } 719 720 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 721 assert(ranges != NULL, "MemRegion array NULL"); 722 assert(count != 0, "No MemRegions provided"); 723 MemRegion reserved = _hrm.reserved(); 724 for (size_t i = 0; i < count; i++) { 725 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 726 return false; 727 } 728 } 729 return true; 730 } 731 732 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 733 assert(!is_init_completed(), "Expect to be called at JVM init time"); 734 assert(ranges != NULL, "MemRegion array NULL"); 735 assert(count != 0, "No MemRegions provided"); 736 MutexLockerEx x(Heap_lock); 737 738 MemRegion reserved = _hrm.reserved(); 739 HeapWord* prev_last_addr = NULL; 740 HeapRegion* prev_last_region = NULL; 741 742 // Temporarily disable pretouching of heap pages. This interface is used 743 // when mmap'ing archived heap data in, so pre-touching is wasted. 744 FlagSetting fs(AlwaysPreTouch, false); 745 746 // Enable archive object checking in G1MarkSweep. We have to let it know 747 // about each archive range, so that objects in those ranges aren't marked. 748 G1MarkSweep::enable_archive_object_check(); 749 750 // For each specified MemRegion range, allocate the corresponding G1 751 // regions and mark them as archive regions. We expect the ranges in 752 // ascending starting address order, without overlap. 753 for (size_t i = 0; i < count; i++) { 754 MemRegion curr_range = ranges[i]; 755 HeapWord* start_address = curr_range.start(); 756 size_t word_size = curr_range.word_size(); 757 HeapWord* last_address = curr_range.last(); 758 size_t commits = 0; 759 760 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 761 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 762 p2i(start_address), p2i(last_address)); 763 guarantee(start_address > prev_last_addr, 764 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 765 p2i(start_address), p2i(prev_last_addr)); 766 prev_last_addr = last_address; 767 768 // Check for ranges that start in the same G1 region in which the previous 769 // range ended, and adjust the start address so we don't try to allocate 770 // the same region again. If the current range is entirely within that 771 // region, skip it, just adjusting the recorded top. 772 HeapRegion* start_region = _hrm.addr_to_region(start_address); 773 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 774 start_address = start_region->end(); 775 if (start_address > last_address) { 776 increase_used(word_size * HeapWordSize); 777 start_region->set_top(last_address + 1); 778 continue; 779 } 780 start_region->set_top(start_address); 781 curr_range = MemRegion(start_address, last_address + 1); 782 start_region = _hrm.addr_to_region(start_address); 783 } 784 785 // Perform the actual region allocation, exiting if it fails. 786 // Then note how much new space we have allocated. 787 if (!_hrm.allocate_containing_regions(curr_range, &commits)) { 788 return false; 789 } 790 increase_used(word_size * HeapWordSize); 791 if (commits != 0) { 792 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 793 HeapRegion::GrainWords * HeapWordSize * commits); 794 795 } 796 797 // Mark each G1 region touched by the range as archive, add it to the old set, 798 // and set the allocation context and top. 799 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 800 HeapRegion* last_region = _hrm.addr_to_region(last_address); 801 prev_last_region = last_region; 802 803 while (curr_region != NULL) { 804 assert(curr_region->is_empty() && !curr_region->is_pinned(), 805 "Region already in use (index %u)", curr_region->hrm_index()); 806 curr_region->set_allocation_context(AllocationContext::system()); 807 curr_region->set_archive(); 808 _hr_printer.alloc(curr_region); 809 _old_set.add(curr_region); 810 if (curr_region != last_region) { 811 curr_region->set_top(curr_region->end()); 812 curr_region = _hrm.next_region_in_heap(curr_region); 813 } else { 814 curr_region->set_top(last_address + 1); 815 curr_region = NULL; 816 } 817 } 818 819 // Notify mark-sweep of the archive range. 820 G1MarkSweep::set_range_archive(curr_range, true); 821 } 822 return true; 823 } 824 825 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 826 assert(!is_init_completed(), "Expect to be called at JVM init time"); 827 assert(ranges != NULL, "MemRegion array NULL"); 828 assert(count != 0, "No MemRegions provided"); 829 MemRegion reserved = _hrm.reserved(); 830 HeapWord *prev_last_addr = NULL; 831 HeapRegion* prev_last_region = NULL; 832 833 // For each MemRegion, create filler objects, if needed, in the G1 regions 834 // that contain the address range. The address range actually within the 835 // MemRegion will not be modified. That is assumed to have been initialized 836 // elsewhere, probably via an mmap of archived heap data. 837 MutexLockerEx x(Heap_lock); 838 for (size_t i = 0; i < count; i++) { 839 HeapWord* start_address = ranges[i].start(); 840 HeapWord* last_address = ranges[i].last(); 841 842 assert(reserved.contains(start_address) && reserved.contains(last_address), 843 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 844 p2i(start_address), p2i(last_address)); 845 assert(start_address > prev_last_addr, 846 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 847 p2i(start_address), p2i(prev_last_addr)); 848 849 HeapRegion* start_region = _hrm.addr_to_region(start_address); 850 HeapRegion* last_region = _hrm.addr_to_region(last_address); 851 HeapWord* bottom_address = start_region->bottom(); 852 853 // Check for a range beginning in the same region in which the 854 // previous one ended. 855 if (start_region == prev_last_region) { 856 bottom_address = prev_last_addr + 1; 857 } 858 859 // Verify that the regions were all marked as archive regions by 860 // alloc_archive_regions. 861 HeapRegion* curr_region = start_region; 862 while (curr_region != NULL) { 863 guarantee(curr_region->is_archive(), 864 "Expected archive region at index %u", curr_region->hrm_index()); 865 if (curr_region != last_region) { 866 curr_region = _hrm.next_region_in_heap(curr_region); 867 } else { 868 curr_region = NULL; 869 } 870 } 871 872 prev_last_addr = last_address; 873 prev_last_region = last_region; 874 875 // Fill the memory below the allocated range with dummy object(s), 876 // if the region bottom does not match the range start, or if the previous 877 // range ended within the same G1 region, and there is a gap. 878 if (start_address != bottom_address) { 879 size_t fill_size = pointer_delta(start_address, bottom_address); 880 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 881 increase_used(fill_size * HeapWordSize); 882 } 883 } 884 } 885 886 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 887 uint* gc_count_before_ret, 888 uint* gclocker_retry_count_ret) { 889 assert_heap_not_locked_and_not_at_safepoint(); 890 assert(!is_humongous(word_size), "attempt_allocation() should not " 891 "be called for humongous allocation requests"); 892 893 AllocationContext_t context = AllocationContext::current(); 894 HeapWord* result = _allocator->attempt_allocation(word_size, context); 895 896 if (result == NULL) { 897 result = attempt_allocation_slow(word_size, 898 context, 899 gc_count_before_ret, 900 gclocker_retry_count_ret); 901 } 902 assert_heap_not_locked(); 903 if (result != NULL) { 904 dirty_young_block(result, word_size); 905 } 906 return result; 907 } 908 909 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 910 assert(!is_init_completed(), "Expect to be called at JVM init time"); 911 assert(ranges != NULL, "MemRegion array NULL"); 912 assert(count != 0, "No MemRegions provided"); 913 MemRegion reserved = _hrm.reserved(); 914 HeapWord* prev_last_addr = NULL; 915 HeapRegion* prev_last_region = NULL; 916 size_t size_used = 0; 917 size_t uncommitted_regions = 0; 918 919 // For each Memregion, free the G1 regions that constitute it, and 920 // notify mark-sweep that the range is no longer to be considered 'archive.' 921 MutexLockerEx x(Heap_lock); 922 for (size_t i = 0; i < count; i++) { 923 HeapWord* start_address = ranges[i].start(); 924 HeapWord* last_address = ranges[i].last(); 925 926 assert(reserved.contains(start_address) && reserved.contains(last_address), 927 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 928 p2i(start_address), p2i(last_address)); 929 assert(start_address > prev_last_addr, 930 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 931 p2i(start_address), p2i(prev_last_addr)); 932 size_used += ranges[i].byte_size(); 933 prev_last_addr = last_address; 934 935 HeapRegion* start_region = _hrm.addr_to_region(start_address); 936 HeapRegion* last_region = _hrm.addr_to_region(last_address); 937 938 // Check for ranges that start in the same G1 region in which the previous 939 // range ended, and adjust the start address so we don't try to free 940 // the same region again. If the current range is entirely within that 941 // region, skip it. 942 if (start_region == prev_last_region) { 943 start_address = start_region->end(); 944 if (start_address > last_address) { 945 continue; 946 } 947 start_region = _hrm.addr_to_region(start_address); 948 } 949 prev_last_region = last_region; 950 951 // After verifying that each region was marked as an archive region by 952 // alloc_archive_regions, set it free and empty and uncommit it. 953 HeapRegion* curr_region = start_region; 954 while (curr_region != NULL) { 955 guarantee(curr_region->is_archive(), 956 "Expected archive region at index %u", curr_region->hrm_index()); 957 uint curr_index = curr_region->hrm_index(); 958 _old_set.remove(curr_region); 959 curr_region->set_free(); 960 curr_region->set_top(curr_region->bottom()); 961 if (curr_region != last_region) { 962 curr_region = _hrm.next_region_in_heap(curr_region); 963 } else { 964 curr_region = NULL; 965 } 966 _hrm.shrink_at(curr_index, 1); 967 uncommitted_regions++; 968 } 969 970 // Notify mark-sweep that this is no longer an archive range. 971 G1MarkSweep::set_range_archive(ranges[i], false); 972 } 973 974 if (uncommitted_regions != 0) { 975 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 976 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 977 } 978 decrease_used(size_used); 979 } 980 981 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 982 uint* gc_count_before_ret, 983 uint* gclocker_retry_count_ret) { 984 // The structure of this method has a lot of similarities to 985 // attempt_allocation_slow(). The reason these two were not merged 986 // into a single one is that such a method would require several "if 987 // allocation is not humongous do this, otherwise do that" 988 // conditional paths which would obscure its flow. In fact, an early 989 // version of this code did use a unified method which was harder to 990 // follow and, as a result, it had subtle bugs that were hard to 991 // track down. So keeping these two methods separate allows each to 992 // be more readable. It will be good to keep these two in sync as 993 // much as possible. 994 995 assert_heap_not_locked_and_not_at_safepoint(); 996 assert(is_humongous(word_size), "attempt_allocation_humongous() " 997 "should only be called for humongous allocations"); 998 999 // Humongous objects can exhaust the heap quickly, so we should check if we 1000 // need to start a marking cycle at each humongous object allocation. We do 1001 // the check before we do the actual allocation. The reason for doing it 1002 // before the allocation is that we avoid having to keep track of the newly 1003 // allocated memory while we do a GC. 1004 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 1005 word_size)) { 1006 collect(GCCause::_g1_humongous_allocation); 1007 } 1008 1009 // We will loop until a) we manage to successfully perform the 1010 // allocation or b) we successfully schedule a collection which 1011 // fails to perform the allocation. b) is the only case when we'll 1012 // return NULL. 1013 HeapWord* result = NULL; 1014 for (int try_count = 1; /* we'll return */; try_count += 1) { 1015 bool should_try_gc; 1016 uint gc_count_before; 1017 1018 { 1019 MutexLockerEx x(Heap_lock); 1020 1021 // Given that humongous objects are not allocated in young 1022 // regions, we'll first try to do the allocation without doing a 1023 // collection hoping that there's enough space in the heap. 1024 result = humongous_obj_allocate(word_size, AllocationContext::current()); 1025 if (result != NULL) { 1026 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 1027 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 1028 return result; 1029 } 1030 1031 if (GCLocker::is_active_and_needs_gc()) { 1032 should_try_gc = false; 1033 } else { 1034 // The GCLocker may not be active but the GCLocker initiated 1035 // GC may not yet have been performed (GCLocker::needs_gc() 1036 // returns true). In this case we do not try this GC and 1037 // wait until the GCLocker initiated GC is performed, and 1038 // then retry the allocation. 1039 if (GCLocker::needs_gc()) { 1040 should_try_gc = false; 1041 } else { 1042 // Read the GC count while still holding the Heap_lock. 1043 gc_count_before = total_collections(); 1044 should_try_gc = true; 1045 } 1046 } 1047 } 1048 1049 if (should_try_gc) { 1050 // If we failed to allocate the humongous object, we should try to 1051 // do a collection pause (if we're allowed) in case it reclaims 1052 // enough space for the allocation to succeed after the pause. 1053 1054 bool succeeded; 1055 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1056 GCCause::_g1_humongous_allocation); 1057 if (result != NULL) { 1058 assert(succeeded, "only way to get back a non-NULL result"); 1059 return result; 1060 } 1061 1062 if (succeeded) { 1063 // If we get here we successfully scheduled a collection which 1064 // failed to allocate. No point in trying to allocate 1065 // further. We'll just return NULL. 1066 MutexLockerEx x(Heap_lock); 1067 *gc_count_before_ret = total_collections(); 1068 return NULL; 1069 } 1070 } else { 1071 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1072 MutexLockerEx x(Heap_lock); 1073 *gc_count_before_ret = total_collections(); 1074 return NULL; 1075 } 1076 // The GCLocker is either active or the GCLocker initiated 1077 // GC has not yet been performed. Stall until it is and 1078 // then retry the allocation. 1079 GCLocker::stall_until_clear(); 1080 (*gclocker_retry_count_ret) += 1; 1081 } 1082 1083 // We can reach here if we were unsuccessful in scheduling a 1084 // collection (because another thread beat us to it) or if we were 1085 // stalled due to the GC locker. In either can we should retry the 1086 // allocation attempt in case another thread successfully 1087 // performed a collection and reclaimed enough space. Give a 1088 // warning if we seem to be looping forever. 1089 1090 if ((QueuedAllocationWarningCount > 0) && 1091 (try_count % QueuedAllocationWarningCount == 0)) { 1092 warning("G1CollectedHeap::attempt_allocation_humongous() " 1093 "retries %d times", try_count); 1094 } 1095 } 1096 1097 ShouldNotReachHere(); 1098 return NULL; 1099 } 1100 1101 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1102 AllocationContext_t context, 1103 bool expect_null_mutator_alloc_region) { 1104 assert_at_safepoint(true /* should_be_vm_thread */); 1105 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1106 "the current alloc region was unexpectedly found to be non-NULL"); 1107 1108 if (!is_humongous(word_size)) { 1109 return _allocator->attempt_allocation_locked(word_size, context); 1110 } else { 1111 HeapWord* result = humongous_obj_allocate(word_size, context); 1112 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1113 collector_state()->set_initiate_conc_mark_if_possible(true); 1114 } 1115 return result; 1116 } 1117 1118 ShouldNotReachHere(); 1119 } 1120 1121 class PostMCRemSetClearClosure: public HeapRegionClosure { 1122 G1CollectedHeap* _g1h; 1123 ModRefBarrierSet* _mr_bs; 1124 public: 1125 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1126 _g1h(g1h), _mr_bs(mr_bs) {} 1127 1128 bool doHeapRegion(HeapRegion* r) { 1129 HeapRegionRemSet* hrrs = r->rem_set(); 1130 1131 _g1h->reset_gc_time_stamps(r); 1132 1133 if (r->is_continues_humongous()) { 1134 // We'll assert that the strong code root list and RSet is empty 1135 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1136 assert(hrrs->occupied() == 0, "RSet should be empty"); 1137 } else { 1138 hrrs->clear(); 1139 } 1140 // You might think here that we could clear just the cards 1141 // corresponding to the used region. But no: if we leave a dirty card 1142 // in a region we might allocate into, then it would prevent that card 1143 // from being enqueued, and cause it to be missed. 1144 // Re: the performance cost: we shouldn't be doing full GC anyway! 1145 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1146 1147 return false; 1148 } 1149 }; 1150 1151 void G1CollectedHeap::clear_rsets_post_compaction() { 1152 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1153 heap_region_iterate(&rs_clear); 1154 } 1155 1156 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1157 G1CollectedHeap* _g1h; 1158 UpdateRSOopClosure _cl; 1159 public: 1160 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1161 _cl(g1->g1_rem_set(), worker_i), 1162 _g1h(g1) 1163 { } 1164 1165 bool doHeapRegion(HeapRegion* r) { 1166 if (!r->is_continues_humongous()) { 1167 _cl.set_from(r); 1168 r->oop_iterate(&_cl); 1169 } 1170 return false; 1171 } 1172 }; 1173 1174 class ParRebuildRSTask: public AbstractGangTask { 1175 G1CollectedHeap* _g1; 1176 HeapRegionClaimer _hrclaimer; 1177 1178 public: 1179 ParRebuildRSTask(G1CollectedHeap* g1) : 1180 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1181 1182 void work(uint worker_id) { 1183 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1184 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1185 } 1186 }; 1187 1188 class PostCompactionPrinterClosure: public HeapRegionClosure { 1189 private: 1190 G1HRPrinter* _hr_printer; 1191 public: 1192 bool doHeapRegion(HeapRegion* hr) { 1193 assert(!hr->is_young(), "not expecting to find young regions"); 1194 _hr_printer->post_compaction(hr); 1195 return false; 1196 } 1197 1198 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1199 : _hr_printer(hr_printer) { } 1200 }; 1201 1202 void G1CollectedHeap::print_hrm_post_compaction() { 1203 if (_hr_printer.is_active()) { 1204 PostCompactionPrinterClosure cl(hr_printer()); 1205 heap_region_iterate(&cl); 1206 } 1207 1208 } 1209 1210 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1211 bool clear_all_soft_refs) { 1212 assert_at_safepoint(true /* should_be_vm_thread */); 1213 1214 if (GCLocker::check_active_before_gc()) { 1215 return false; 1216 } 1217 1218 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1219 gc_timer->register_gc_start(); 1220 1221 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1222 GCIdMark gc_id_mark; 1223 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1224 1225 SvcGCMarker sgcm(SvcGCMarker::FULL); 1226 ResourceMark rm; 1227 1228 print_heap_before_gc(); 1229 trace_heap_before_gc(gc_tracer); 1230 1231 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1232 1233 verify_region_sets_optional(); 1234 1235 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1236 collector_policy()->should_clear_all_soft_refs(); 1237 1238 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1239 1240 { 1241 IsGCActiveMark x; 1242 1243 // Timing 1244 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1245 GCTraceCPUTime tcpu; 1246 1247 { 1248 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1249 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1250 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1251 1252 g1_policy()->record_full_collection_start(); 1253 1254 // Note: When we have a more flexible GC logging framework that 1255 // allows us to add optional attributes to a GC log record we 1256 // could consider timing and reporting how long we wait in the 1257 // following two methods. 1258 wait_while_free_regions_coming(); 1259 // If we start the compaction before the CM threads finish 1260 // scanning the root regions we might trip them over as we'll 1261 // be moving objects / updating references. So let's wait until 1262 // they are done. By telling them to abort, they should complete 1263 // early. 1264 _cm->root_regions()->abort(); 1265 _cm->root_regions()->wait_until_scan_finished(); 1266 append_secondary_free_list_if_not_empty_with_lock(); 1267 1268 gc_prologue(true); 1269 increment_total_collections(true /* full gc */); 1270 increment_old_marking_cycles_started(); 1271 1272 assert(used() == recalculate_used(), "Should be equal"); 1273 1274 verify_before_gc(); 1275 1276 check_bitmaps("Full GC Start"); 1277 pre_full_gc_dump(gc_timer); 1278 1279 #if defined(COMPILER2) || INCLUDE_JVMCI 1280 DerivedPointerTable::clear(); 1281 #endif 1282 1283 // Disable discovery and empty the discovered lists 1284 // for the CM ref processor. 1285 ref_processor_cm()->disable_discovery(); 1286 ref_processor_cm()->abandon_partial_discovery(); 1287 ref_processor_cm()->verify_no_references_recorded(); 1288 1289 // Abandon current iterations of concurrent marking and concurrent 1290 // refinement, if any are in progress. We have to do this before 1291 // wait_until_scan_finished() below. 1292 concurrent_mark()->abort(); 1293 1294 // Make sure we'll choose a new allocation region afterwards. 1295 _allocator->release_mutator_alloc_region(); 1296 _allocator->abandon_gc_alloc_regions(); 1297 g1_rem_set()->cleanupHRRS(); 1298 1299 // We may have added regions to the current incremental collection 1300 // set between the last GC or pause and now. We need to clear the 1301 // incremental collection set and then start rebuilding it afresh 1302 // after this full GC. 1303 abandon_collection_set(g1_policy()->inc_cset_head()); 1304 g1_policy()->clear_incremental_cset(); 1305 g1_policy()->stop_incremental_cset_building(); 1306 1307 tear_down_region_sets(false /* free_list_only */); 1308 collector_state()->set_gcs_are_young(true); 1309 1310 // See the comments in g1CollectedHeap.hpp and 1311 // G1CollectedHeap::ref_processing_init() about 1312 // how reference processing currently works in G1. 1313 1314 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1315 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1316 1317 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1318 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1319 1320 ref_processor_stw()->enable_discovery(); 1321 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1322 1323 // Do collection work 1324 { 1325 HandleMark hm; // Discard invalid handles created during gc 1326 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1327 } 1328 1329 assert(num_free_regions() == 0, "we should not have added any free regions"); 1330 rebuild_region_sets(false /* free_list_only */); 1331 1332 // Enqueue any discovered reference objects that have 1333 // not been removed from the discovered lists. 1334 ref_processor_stw()->enqueue_discovered_references(); 1335 1336 #if defined(COMPILER2) || INCLUDE_JVMCI 1337 DerivedPointerTable::update_pointers(); 1338 #endif 1339 1340 MemoryService::track_memory_usage(); 1341 1342 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1343 ref_processor_stw()->verify_no_references_recorded(); 1344 1345 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1346 ClassLoaderDataGraph::purge(); 1347 MetaspaceAux::verify_metrics(); 1348 1349 // Note: since we've just done a full GC, concurrent 1350 // marking is no longer active. Therefore we need not 1351 // re-enable reference discovery for the CM ref processor. 1352 // That will be done at the start of the next marking cycle. 1353 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1354 ref_processor_cm()->verify_no_references_recorded(); 1355 1356 reset_gc_time_stamp(); 1357 // Since everything potentially moved, we will clear all remembered 1358 // sets, and clear all cards. Later we will rebuild remembered 1359 // sets. We will also reset the GC time stamps of the regions. 1360 clear_rsets_post_compaction(); 1361 check_gc_time_stamps(); 1362 1363 resize_if_necessary_after_full_collection(); 1364 1365 // We should do this after we potentially resize the heap so 1366 // that all the COMMIT / UNCOMMIT events are generated before 1367 // the compaction events. 1368 print_hrm_post_compaction(); 1369 1370 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1371 if (hot_card_cache->use_cache()) { 1372 hot_card_cache->reset_card_counts(); 1373 hot_card_cache->reset_hot_cache(); 1374 } 1375 1376 // Rebuild remembered sets of all regions. 1377 uint n_workers = 1378 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1379 workers()->active_workers(), 1380 Threads::number_of_non_daemon_threads()); 1381 workers()->set_active_workers(n_workers); 1382 1383 ParRebuildRSTask rebuild_rs_task(this); 1384 workers()->run_task(&rebuild_rs_task); 1385 1386 // Rebuild the strong code root lists for each region 1387 rebuild_strong_code_roots(); 1388 1389 if (true) { // FIXME 1390 MetaspaceGC::compute_new_size(); 1391 } 1392 1393 #ifdef TRACESPINNING 1394 ParallelTaskTerminator::print_termination_counts(); 1395 #endif 1396 1397 // Discard all rset updates 1398 JavaThread::dirty_card_queue_set().abandon_logs(); 1399 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1400 1401 _young_list->reset_sampled_info(); 1402 // At this point there should be no regions in the 1403 // entire heap tagged as young. 1404 assert(check_young_list_empty(true /* check_heap */), 1405 "young list should be empty at this point"); 1406 1407 // Update the number of full collections that have been completed. 1408 increment_old_marking_cycles_completed(false /* concurrent */); 1409 1410 _hrm.verify_optional(); 1411 verify_region_sets_optional(); 1412 1413 verify_after_gc(); 1414 1415 // Clear the previous marking bitmap, if needed for bitmap verification. 1416 // Note we cannot do this when we clear the next marking bitmap in 1417 // ConcurrentMark::abort() above since VerifyDuringGC verifies the 1418 // objects marked during a full GC against the previous bitmap. 1419 // But we need to clear it before calling check_bitmaps below since 1420 // the full GC has compacted objects and updated TAMS but not updated 1421 // the prev bitmap. 1422 if (G1VerifyBitmaps) { 1423 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll(); 1424 } 1425 check_bitmaps("Full GC End"); 1426 1427 // Start a new incremental collection set for the next pause 1428 assert(g1_policy()->collection_set() == NULL, "must be"); 1429 g1_policy()->start_incremental_cset_building(); 1430 1431 clear_cset_fast_test(); 1432 1433 _allocator->init_mutator_alloc_region(); 1434 1435 g1_policy()->record_full_collection_end(); 1436 1437 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1438 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1439 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1440 // before any GC notifications are raised. 1441 g1mm()->update_sizes(); 1442 1443 gc_epilogue(true); 1444 } 1445 1446 g1_policy()->print_detailed_heap_transition(); 1447 1448 print_heap_after_gc(); 1449 trace_heap_after_gc(gc_tracer); 1450 1451 post_full_gc_dump(gc_timer); 1452 1453 gc_timer->register_gc_end(); 1454 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1455 } 1456 1457 return true; 1458 } 1459 1460 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1461 // Currently, there is no facility in the do_full_collection(bool) API to notify 1462 // the caller that the collection did not succeed (e.g., because it was locked 1463 // out by the GC locker). So, right now, we'll ignore the return value. 1464 bool dummy = do_full_collection(true, /* explicit_gc */ 1465 clear_all_soft_refs); 1466 } 1467 1468 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1469 // Include bytes that will be pre-allocated to support collections, as "used". 1470 const size_t used_after_gc = used(); 1471 const size_t capacity_after_gc = capacity(); 1472 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1473 1474 // This is enforced in arguments.cpp. 1475 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1476 "otherwise the code below doesn't make sense"); 1477 1478 // We don't have floating point command-line arguments 1479 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1480 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1481 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1482 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1483 1484 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1485 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1486 1487 // We have to be careful here as these two calculations can overflow 1488 // 32-bit size_t's. 1489 double used_after_gc_d = (double) used_after_gc; 1490 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1491 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1492 1493 // Let's make sure that they are both under the max heap size, which 1494 // by default will make them fit into a size_t. 1495 double desired_capacity_upper_bound = (double) max_heap_size; 1496 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1497 desired_capacity_upper_bound); 1498 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1499 desired_capacity_upper_bound); 1500 1501 // We can now safely turn them into size_t's. 1502 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1503 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1504 1505 // This assert only makes sense here, before we adjust them 1506 // with respect to the min and max heap size. 1507 assert(minimum_desired_capacity <= maximum_desired_capacity, 1508 "minimum_desired_capacity = " SIZE_FORMAT ", " 1509 "maximum_desired_capacity = " SIZE_FORMAT, 1510 minimum_desired_capacity, maximum_desired_capacity); 1511 1512 // Should not be greater than the heap max size. No need to adjust 1513 // it with respect to the heap min size as it's a lower bound (i.e., 1514 // we'll try to make the capacity larger than it, not smaller). 1515 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1516 // Should not be less than the heap min size. No need to adjust it 1517 // with respect to the heap max size as it's an upper bound (i.e., 1518 // we'll try to make the capacity smaller than it, not greater). 1519 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1520 1521 if (capacity_after_gc < minimum_desired_capacity) { 1522 // Don't expand unless it's significant 1523 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1524 1525 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1526 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1527 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1528 1529 expand(expand_bytes); 1530 1531 // No expansion, now see if we want to shrink 1532 } else if (capacity_after_gc > maximum_desired_capacity) { 1533 // Capacity too large, compute shrinking size 1534 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1535 1536 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1537 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1538 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1539 1540 shrink(shrink_bytes); 1541 } 1542 } 1543 1544 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1545 AllocationContext_t context, 1546 bool do_gc, 1547 bool clear_all_soft_refs, 1548 bool expect_null_mutator_alloc_region, 1549 bool* gc_succeeded) { 1550 *gc_succeeded = true; 1551 // Let's attempt the allocation first. 1552 HeapWord* result = 1553 attempt_allocation_at_safepoint(word_size, 1554 context, 1555 expect_null_mutator_alloc_region); 1556 if (result != NULL) { 1557 assert(*gc_succeeded, "sanity"); 1558 return result; 1559 } 1560 1561 // In a G1 heap, we're supposed to keep allocation from failing by 1562 // incremental pauses. Therefore, at least for now, we'll favor 1563 // expansion over collection. (This might change in the future if we can 1564 // do something smarter than full collection to satisfy a failed alloc.) 1565 result = expand_and_allocate(word_size, context); 1566 if (result != NULL) { 1567 assert(*gc_succeeded, "sanity"); 1568 return result; 1569 } 1570 1571 if (do_gc) { 1572 // Expansion didn't work, we'll try to do a Full GC. 1573 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1574 clear_all_soft_refs); 1575 } 1576 1577 return NULL; 1578 } 1579 1580 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1581 AllocationContext_t context, 1582 bool* succeeded) { 1583 assert_at_safepoint(true /* should_be_vm_thread */); 1584 1585 // Attempts to allocate followed by Full GC. 1586 HeapWord* result = 1587 satisfy_failed_allocation_helper(word_size, 1588 context, 1589 true, /* do_gc */ 1590 false, /* clear_all_soft_refs */ 1591 false, /* expect_null_mutator_alloc_region */ 1592 succeeded); 1593 1594 if (result != NULL || !*succeeded) { 1595 return result; 1596 } 1597 1598 // Attempts to allocate followed by Full GC that will collect all soft references. 1599 result = satisfy_failed_allocation_helper(word_size, 1600 context, 1601 true, /* do_gc */ 1602 true, /* clear_all_soft_refs */ 1603 true, /* expect_null_mutator_alloc_region */ 1604 succeeded); 1605 1606 if (result != NULL || !*succeeded) { 1607 return result; 1608 } 1609 1610 // Attempts to allocate, no GC 1611 result = satisfy_failed_allocation_helper(word_size, 1612 context, 1613 false, /* do_gc */ 1614 false, /* clear_all_soft_refs */ 1615 true, /* expect_null_mutator_alloc_region */ 1616 succeeded); 1617 1618 if (result != NULL) { 1619 assert(*succeeded, "sanity"); 1620 return result; 1621 } 1622 1623 assert(!collector_policy()->should_clear_all_soft_refs(), 1624 "Flag should have been handled and cleared prior to this point"); 1625 1626 // What else? We might try synchronous finalization later. If the total 1627 // space available is large enough for the allocation, then a more 1628 // complete compaction phase than we've tried so far might be 1629 // appropriate. 1630 assert(*succeeded, "sanity"); 1631 return NULL; 1632 } 1633 1634 // Attempting to expand the heap sufficiently 1635 // to support an allocation of the given "word_size". If 1636 // successful, perform the allocation and return the address of the 1637 // allocated block, or else "NULL". 1638 1639 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1640 assert_at_safepoint(true /* should_be_vm_thread */); 1641 1642 verify_region_sets_optional(); 1643 1644 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1645 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1646 word_size * HeapWordSize); 1647 1648 1649 if (expand(expand_bytes)) { 1650 _hrm.verify_optional(); 1651 verify_region_sets_optional(); 1652 return attempt_allocation_at_safepoint(word_size, 1653 context, 1654 false /* expect_null_mutator_alloc_region */); 1655 } 1656 return NULL; 1657 } 1658 1659 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) { 1660 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1661 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1662 HeapRegion::GrainBytes); 1663 1664 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B", 1665 expand_bytes, aligned_expand_bytes); 1666 1667 if (is_maximal_no_gc()) { 1668 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1669 return false; 1670 } 1671 1672 double expand_heap_start_time_sec = os::elapsedTime(); 1673 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1674 assert(regions_to_expand > 0, "Must expand by at least one region"); 1675 1676 uint expanded_by = _hrm.expand_by(regions_to_expand); 1677 if (expand_time_ms != NULL) { 1678 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1679 } 1680 1681 if (expanded_by > 0) { 1682 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1683 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1684 g1_policy()->record_new_heap_size(num_regions()); 1685 } else { 1686 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1687 1688 // The expansion of the virtual storage space was unsuccessful. 1689 // Let's see if it was because we ran out of swap. 1690 if (G1ExitOnExpansionFailure && 1691 _hrm.available() >= regions_to_expand) { 1692 // We had head room... 1693 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1694 } 1695 } 1696 return regions_to_expand > 0; 1697 } 1698 1699 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1700 size_t aligned_shrink_bytes = 1701 ReservedSpace::page_align_size_down(shrink_bytes); 1702 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1703 HeapRegion::GrainBytes); 1704 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1705 1706 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1707 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1708 1709 1710 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", 1711 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1712 if (num_regions_removed > 0) { 1713 g1_policy()->record_new_heap_size(num_regions()); 1714 } else { 1715 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1716 } 1717 } 1718 1719 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1720 verify_region_sets_optional(); 1721 1722 // We should only reach here at the end of a Full GC which means we 1723 // should not not be holding to any GC alloc regions. The method 1724 // below will make sure of that and do any remaining clean up. 1725 _allocator->abandon_gc_alloc_regions(); 1726 1727 // Instead of tearing down / rebuilding the free lists here, we 1728 // could instead use the remove_all_pending() method on free_list to 1729 // remove only the ones that we need to remove. 1730 tear_down_region_sets(true /* free_list_only */); 1731 shrink_helper(shrink_bytes); 1732 rebuild_region_sets(true /* free_list_only */); 1733 1734 _hrm.verify_optional(); 1735 verify_region_sets_optional(); 1736 } 1737 1738 // Public methods. 1739 1740 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1741 CollectedHeap(), 1742 _g1_policy(policy_), 1743 _dirty_card_queue_set(false), 1744 _is_alive_closure_cm(this), 1745 _is_alive_closure_stw(this), 1746 _ref_processor_cm(NULL), 1747 _ref_processor_stw(NULL), 1748 _bot(NULL), 1749 _cg1r(NULL), 1750 _g1mm(NULL), 1751 _refine_cte_cl(NULL), 1752 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1753 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1754 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1755 _humongous_reclaim_candidates(), 1756 _has_humongous_reclaim_candidates(false), 1757 _archive_allocator(NULL), 1758 _free_regions_coming(false), 1759 _young_list(new YoungList(this)), 1760 _gc_time_stamp(0), 1761 _summary_bytes_used(0), 1762 _survivor_evac_stats(YoungPLABSize, PLABWeight), 1763 _old_evac_stats(OldPLABSize, PLABWeight), 1764 _expand_heap_after_alloc_failure(true), 1765 _old_marking_cycles_started(0), 1766 _old_marking_cycles_completed(0), 1767 _heap_summary_sent(false), 1768 _in_cset_fast_test(), 1769 _dirty_cards_region_list(NULL), 1770 _worker_cset_start_region(NULL), 1771 _worker_cset_start_region_time_stamp(NULL), 1772 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1773 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1774 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1775 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1776 1777 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1778 /* are_GC_task_threads */true, 1779 /* are_ConcurrentGC_threads */false); 1780 _workers->initialize_workers(); 1781 1782 _allocator = G1Allocator::create_allocator(this); 1783 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1784 1785 // Override the default _filler_array_max_size so that no humongous filler 1786 // objects are created. 1787 _filler_array_max_size = _humongous_object_threshold_in_words; 1788 1789 uint n_queues = ParallelGCThreads; 1790 _task_queues = new RefToScanQueueSet(n_queues); 1791 1792 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1793 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC); 1794 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1795 1796 for (uint i = 0; i < n_queues; i++) { 1797 RefToScanQueue* q = new RefToScanQueue(); 1798 q->initialize(); 1799 _task_queues->register_queue(i, q); 1800 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1801 } 1802 clear_cset_start_regions(); 1803 1804 // Initialize the G1EvacuationFailureALot counters and flags. 1805 NOT_PRODUCT(reset_evacuation_should_fail();) 1806 1807 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1808 } 1809 1810 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1811 size_t size, 1812 size_t translation_factor) { 1813 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1814 // Allocate a new reserved space, preferring to use large pages. 1815 ReservedSpace rs(size, preferred_page_size); 1816 G1RegionToSpaceMapper* result = 1817 G1RegionToSpaceMapper::create_mapper(rs, 1818 size, 1819 rs.alignment(), 1820 HeapRegion::GrainBytes, 1821 translation_factor, 1822 mtGC); 1823 if (TracePageSizes) { 1824 tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT, 1825 description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size); 1826 } 1827 return result; 1828 } 1829 1830 jint G1CollectedHeap::initialize() { 1831 CollectedHeap::pre_initialize(); 1832 os::enable_vtime(); 1833 1834 // Necessary to satisfy locking discipline assertions. 1835 1836 MutexLocker x(Heap_lock); 1837 1838 // While there are no constraints in the GC code that HeapWordSize 1839 // be any particular value, there are multiple other areas in the 1840 // system which believe this to be true (e.g. oop->object_size in some 1841 // cases incorrectly returns the size in wordSize units rather than 1842 // HeapWordSize). 1843 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1844 1845 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1846 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1847 size_t heap_alignment = collector_policy()->heap_alignment(); 1848 1849 // Ensure that the sizes are properly aligned. 1850 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1851 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1852 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1853 1854 _refine_cte_cl = new RefineCardTableEntryClosure(); 1855 1856 jint ecode = JNI_OK; 1857 _cg1r = ConcurrentG1Refine::create(this, _refine_cte_cl, &ecode); 1858 if (_cg1r == NULL) { 1859 return ecode; 1860 } 1861 1862 // Reserve the maximum. 1863 1864 // When compressed oops are enabled, the preferred heap base 1865 // is calculated by subtracting the requested size from the 1866 // 32Gb boundary and using the result as the base address for 1867 // heap reservation. If the requested size is not aligned to 1868 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1869 // into the ReservedHeapSpace constructor) then the actual 1870 // base of the reserved heap may end up differing from the 1871 // address that was requested (i.e. the preferred heap base). 1872 // If this happens then we could end up using a non-optimal 1873 // compressed oops mode. 1874 1875 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1876 heap_alignment); 1877 1878 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1879 1880 // Create the barrier set for the entire reserved region. 1881 G1SATBCardTableLoggingModRefBS* bs 1882 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1883 bs->initialize(); 1884 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1885 set_barrier_set(bs); 1886 1887 // Also create a G1 rem set. 1888 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 1889 1890 // Carve out the G1 part of the heap. 1891 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1892 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1893 G1RegionToSpaceMapper* heap_storage = 1894 G1RegionToSpaceMapper::create_mapper(g1_rs, 1895 g1_rs.size(), 1896 page_size, 1897 HeapRegion::GrainBytes, 1898 1, 1899 mtJavaHeap); 1900 os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(), 1901 max_byte_size, page_size, 1902 heap_rs.base(), 1903 heap_rs.size()); 1904 heap_storage->set_mapping_changed_listener(&_listener); 1905 1906 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1907 G1RegionToSpaceMapper* bot_storage = 1908 create_aux_memory_mapper("Block offset table", 1909 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1910 G1BlockOffsetTable::heap_map_factor()); 1911 1912 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1913 G1RegionToSpaceMapper* cardtable_storage = 1914 create_aux_memory_mapper("Card table", 1915 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1916 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1917 1918 G1RegionToSpaceMapper* card_counts_storage = 1919 create_aux_memory_mapper("Card counts table", 1920 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1921 G1CardCounts::heap_map_factor()); 1922 1923 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size()); 1924 G1RegionToSpaceMapper* prev_bitmap_storage = 1925 create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1926 G1RegionToSpaceMapper* next_bitmap_storage = 1927 create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1928 1929 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1930 g1_barrier_set()->initialize(cardtable_storage); 1931 // Do later initialization work for concurrent refinement. 1932 _cg1r->init(card_counts_storage); 1933 1934 // 6843694 - ensure that the maximum region index can fit 1935 // in the remembered set structures. 1936 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1937 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1938 1939 G1RemSet::initialize(max_regions()); 1940 1941 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1942 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1943 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1944 "too many cards per region"); 1945 1946 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1947 1948 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1949 1950 { 1951 HeapWord* start = _hrm.reserved().start(); 1952 HeapWord* end = _hrm.reserved().end(); 1953 size_t granularity = HeapRegion::GrainBytes; 1954 1955 _in_cset_fast_test.initialize(start, end, granularity); 1956 _humongous_reclaim_candidates.initialize(start, end, granularity); 1957 } 1958 1959 // Create the ConcurrentMark data structure and thread. 1960 // (Must do this late, so that "max_regions" is defined.) 1961 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1962 if (_cm == NULL || !_cm->completed_initialization()) { 1963 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 1964 return JNI_ENOMEM; 1965 } 1966 _cmThread = _cm->cmThread(); 1967 1968 // Now expand into the initial heap size. 1969 if (!expand(init_byte_size)) { 1970 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1971 return JNI_ENOMEM; 1972 } 1973 1974 // Perform any initialization actions delegated to the policy. 1975 g1_policy()->init(); 1976 1977 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1978 SATB_Q_FL_lock, 1979 G1SATBProcessCompletedThreshold, 1980 Shared_SATB_Q_lock); 1981 1982 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 1983 DirtyCardQ_CBL_mon, 1984 DirtyCardQ_FL_lock, 1985 concurrent_g1_refine()->yellow_zone(), 1986 concurrent_g1_refine()->red_zone(), 1987 Shared_DirtyCardQ_lock, 1988 NULL, // fl_owner 1989 true); // init_free_ids 1990 1991 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 1992 DirtyCardQ_CBL_mon, 1993 DirtyCardQ_FL_lock, 1994 -1, // never trigger processing 1995 -1, // no limit on length 1996 Shared_DirtyCardQ_lock, 1997 &JavaThread::dirty_card_queue_set()); 1998 1999 // Here we allocate the dummy HeapRegion that is required by the 2000 // G1AllocRegion class. 2001 HeapRegion* dummy_region = _hrm.get_dummy_region(); 2002 2003 // We'll re-use the same region whether the alloc region will 2004 // require BOT updates or not and, if it doesn't, then a non-young 2005 // region will complain that it cannot support allocations without 2006 // BOT updates. So we'll tag the dummy region as eden to avoid that. 2007 dummy_region->set_eden(); 2008 // Make sure it's full. 2009 dummy_region->set_top(dummy_region->end()); 2010 G1AllocRegion::setup(this, dummy_region); 2011 2012 _allocator->init_mutator_alloc_region(); 2013 2014 // Do create of the monitoring and management support so that 2015 // values in the heap have been properly initialized. 2016 _g1mm = new G1MonitoringSupport(this); 2017 2018 G1StringDedup::initialize(); 2019 2020 _preserved_objs = NEW_C_HEAP_ARRAY(OopAndMarkOopStack, ParallelGCThreads, mtGC); 2021 for (uint i = 0; i < ParallelGCThreads; i++) { 2022 new (&_preserved_objs[i]) OopAndMarkOopStack(); 2023 } 2024 2025 return JNI_OK; 2026 } 2027 2028 void G1CollectedHeap::stop() { 2029 // Stop all concurrent threads. We do this to make sure these threads 2030 // do not continue to execute and access resources (e.g. logging) 2031 // that are destroyed during shutdown. 2032 _cg1r->stop(); 2033 _cmThread->stop(); 2034 if (G1StringDedup::is_enabled()) { 2035 G1StringDedup::stop(); 2036 } 2037 } 2038 2039 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2040 return HeapRegion::max_region_size(); 2041 } 2042 2043 void G1CollectedHeap::post_initialize() { 2044 CollectedHeap::post_initialize(); 2045 ref_processing_init(); 2046 } 2047 2048 void G1CollectedHeap::ref_processing_init() { 2049 // Reference processing in G1 currently works as follows: 2050 // 2051 // * There are two reference processor instances. One is 2052 // used to record and process discovered references 2053 // during concurrent marking; the other is used to 2054 // record and process references during STW pauses 2055 // (both full and incremental). 2056 // * Both ref processors need to 'span' the entire heap as 2057 // the regions in the collection set may be dotted around. 2058 // 2059 // * For the concurrent marking ref processor: 2060 // * Reference discovery is enabled at initial marking. 2061 // * Reference discovery is disabled and the discovered 2062 // references processed etc during remarking. 2063 // * Reference discovery is MT (see below). 2064 // * Reference discovery requires a barrier (see below). 2065 // * Reference processing may or may not be MT 2066 // (depending on the value of ParallelRefProcEnabled 2067 // and ParallelGCThreads). 2068 // * A full GC disables reference discovery by the CM 2069 // ref processor and abandons any entries on it's 2070 // discovered lists. 2071 // 2072 // * For the STW processor: 2073 // * Non MT discovery is enabled at the start of a full GC. 2074 // * Processing and enqueueing during a full GC is non-MT. 2075 // * During a full GC, references are processed after marking. 2076 // 2077 // * Discovery (may or may not be MT) is enabled at the start 2078 // of an incremental evacuation pause. 2079 // * References are processed near the end of a STW evacuation pause. 2080 // * For both types of GC: 2081 // * Discovery is atomic - i.e. not concurrent. 2082 // * Reference discovery will not need a barrier. 2083 2084 MemRegion mr = reserved_region(); 2085 2086 // Concurrent Mark ref processor 2087 _ref_processor_cm = 2088 new ReferenceProcessor(mr, // span 2089 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2090 // mt processing 2091 ParallelGCThreads, 2092 // degree of mt processing 2093 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2094 // mt discovery 2095 MAX2(ParallelGCThreads, ConcGCThreads), 2096 // degree of mt discovery 2097 false, 2098 // Reference discovery is not atomic 2099 &_is_alive_closure_cm); 2100 // is alive closure 2101 // (for efficiency/performance) 2102 2103 // STW ref processor 2104 _ref_processor_stw = 2105 new ReferenceProcessor(mr, // span 2106 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2107 // mt processing 2108 ParallelGCThreads, 2109 // degree of mt processing 2110 (ParallelGCThreads > 1), 2111 // mt discovery 2112 ParallelGCThreads, 2113 // degree of mt discovery 2114 true, 2115 // Reference discovery is atomic 2116 &_is_alive_closure_stw); 2117 // is alive closure 2118 // (for efficiency/performance) 2119 } 2120 2121 CollectorPolicy* G1CollectedHeap::collector_policy() const { 2122 return g1_policy(); 2123 } 2124 2125 size_t G1CollectedHeap::capacity() const { 2126 return _hrm.length() * HeapRegion::GrainBytes; 2127 } 2128 2129 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2130 hr->reset_gc_time_stamp(); 2131 } 2132 2133 #ifndef PRODUCT 2134 2135 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2136 private: 2137 unsigned _gc_time_stamp; 2138 bool _failures; 2139 2140 public: 2141 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2142 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2143 2144 virtual bool doHeapRegion(HeapRegion* hr) { 2145 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2146 if (_gc_time_stamp != region_gc_time_stamp) { 2147 log_info(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 2148 region_gc_time_stamp, _gc_time_stamp); 2149 _failures = true; 2150 } 2151 return false; 2152 } 2153 2154 bool failures() { return _failures; } 2155 }; 2156 2157 void G1CollectedHeap::check_gc_time_stamps() { 2158 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2159 heap_region_iterate(&cl); 2160 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2161 } 2162 #endif // PRODUCT 2163 2164 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2165 _cg1r->hot_card_cache()->drain(cl, worker_i); 2166 } 2167 2168 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2169 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2170 size_t n_completed_buffers = 0; 2171 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2172 n_completed_buffers++; 2173 } 2174 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2175 dcqs.clear_n_completed_buffers(); 2176 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2177 } 2178 2179 // Computes the sum of the storage used by the various regions. 2180 size_t G1CollectedHeap::used() const { 2181 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2182 if (_archive_allocator != NULL) { 2183 result += _archive_allocator->used(); 2184 } 2185 return result; 2186 } 2187 2188 size_t G1CollectedHeap::used_unlocked() const { 2189 return _summary_bytes_used; 2190 } 2191 2192 class SumUsedClosure: public HeapRegionClosure { 2193 size_t _used; 2194 public: 2195 SumUsedClosure() : _used(0) {} 2196 bool doHeapRegion(HeapRegion* r) { 2197 _used += r->used(); 2198 return false; 2199 } 2200 size_t result() { return _used; } 2201 }; 2202 2203 size_t G1CollectedHeap::recalculate_used() const { 2204 double recalculate_used_start = os::elapsedTime(); 2205 2206 SumUsedClosure blk; 2207 heap_region_iterate(&blk); 2208 2209 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2210 return blk.result(); 2211 } 2212 2213 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2214 switch (cause) { 2215 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2216 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2217 case GCCause::_update_allocation_context_stats_inc: return true; 2218 case GCCause::_wb_conc_mark: return true; 2219 default : return false; 2220 } 2221 } 2222 2223 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2224 switch (cause) { 2225 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2226 case GCCause::_g1_humongous_allocation: return true; 2227 default: return is_user_requested_concurrent_full_gc(cause); 2228 } 2229 } 2230 2231 #ifndef PRODUCT 2232 void G1CollectedHeap::allocate_dummy_regions() { 2233 // Let's fill up most of the region 2234 size_t word_size = HeapRegion::GrainWords - 1024; 2235 // And as a result the region we'll allocate will be humongous. 2236 guarantee(is_humongous(word_size), "sanity"); 2237 2238 // _filler_array_max_size is set to humongous object threshold 2239 // but temporarily change it to use CollectedHeap::fill_with_object(). 2240 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2241 2242 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2243 // Let's use the existing mechanism for the allocation 2244 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2245 AllocationContext::system()); 2246 if (dummy_obj != NULL) { 2247 MemRegion mr(dummy_obj, word_size); 2248 CollectedHeap::fill_with_object(mr); 2249 } else { 2250 // If we can't allocate once, we probably cannot allocate 2251 // again. Let's get out of the loop. 2252 break; 2253 } 2254 } 2255 } 2256 #endif // !PRODUCT 2257 2258 void G1CollectedHeap::increment_old_marking_cycles_started() { 2259 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2260 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2261 "Wrong marking cycle count (started: %d, completed: %d)", 2262 _old_marking_cycles_started, _old_marking_cycles_completed); 2263 2264 _old_marking_cycles_started++; 2265 } 2266 2267 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2268 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2269 2270 // We assume that if concurrent == true, then the caller is a 2271 // concurrent thread that was joined the Suspendible Thread 2272 // Set. If there's ever a cheap way to check this, we should add an 2273 // assert here. 2274 2275 // Given that this method is called at the end of a Full GC or of a 2276 // concurrent cycle, and those can be nested (i.e., a Full GC can 2277 // interrupt a concurrent cycle), the number of full collections 2278 // completed should be either one (in the case where there was no 2279 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2280 // behind the number of full collections started. 2281 2282 // This is the case for the inner caller, i.e. a Full GC. 2283 assert(concurrent || 2284 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2285 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2286 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2287 "is inconsistent with _old_marking_cycles_completed = %u", 2288 _old_marking_cycles_started, _old_marking_cycles_completed); 2289 2290 // This is the case for the outer caller, i.e. the concurrent cycle. 2291 assert(!concurrent || 2292 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2293 "for outer caller (concurrent cycle): " 2294 "_old_marking_cycles_started = %u " 2295 "is inconsistent with _old_marking_cycles_completed = %u", 2296 _old_marking_cycles_started, _old_marking_cycles_completed); 2297 2298 _old_marking_cycles_completed += 1; 2299 2300 // We need to clear the "in_progress" flag in the CM thread before 2301 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2302 // is set) so that if a waiter requests another System.gc() it doesn't 2303 // incorrectly see that a marking cycle is still in progress. 2304 if (concurrent) { 2305 _cmThread->set_idle(); 2306 } 2307 2308 // This notify_all() will ensure that a thread that called 2309 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2310 // and it's waiting for a full GC to finish will be woken up. It is 2311 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2312 FullGCCount_lock->notify_all(); 2313 } 2314 2315 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2316 GCIdMarkAndRestore conc_gc_id_mark; 2317 collector_state()->set_concurrent_cycle_started(true); 2318 _gc_timer_cm->register_gc_start(start_time); 2319 2320 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2321 trace_heap_before_gc(_gc_tracer_cm); 2322 _cmThread->set_gc_id(GCId::current()); 2323 } 2324 2325 void G1CollectedHeap::register_concurrent_cycle_end() { 2326 if (collector_state()->concurrent_cycle_started()) { 2327 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2328 if (_cm->has_aborted()) { 2329 _gc_tracer_cm->report_concurrent_mode_failure(); 2330 } 2331 2332 _gc_timer_cm->register_gc_end(); 2333 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2334 2335 // Clear state variables to prepare for the next concurrent cycle. 2336 collector_state()->set_concurrent_cycle_started(false); 2337 _heap_summary_sent = false; 2338 } 2339 } 2340 2341 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2342 if (collector_state()->concurrent_cycle_started()) { 2343 // This function can be called when: 2344 // the cleanup pause is run 2345 // the concurrent cycle is aborted before the cleanup pause. 2346 // the concurrent cycle is aborted after the cleanup pause, 2347 // but before the concurrent cycle end has been registered. 2348 // Make sure that we only send the heap information once. 2349 if (!_heap_summary_sent) { 2350 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2351 trace_heap_after_gc(_gc_tracer_cm); 2352 _heap_summary_sent = true; 2353 } 2354 } 2355 } 2356 2357 void G1CollectedHeap::collect(GCCause::Cause cause) { 2358 assert_heap_not_locked(); 2359 2360 uint gc_count_before; 2361 uint old_marking_count_before; 2362 uint full_gc_count_before; 2363 bool retry_gc; 2364 2365 do { 2366 retry_gc = false; 2367 2368 { 2369 MutexLocker ml(Heap_lock); 2370 2371 // Read the GC count while holding the Heap_lock 2372 gc_count_before = total_collections(); 2373 full_gc_count_before = total_full_collections(); 2374 old_marking_count_before = _old_marking_cycles_started; 2375 } 2376 2377 if (should_do_concurrent_full_gc(cause)) { 2378 // Schedule an initial-mark evacuation pause that will start a 2379 // concurrent cycle. We're setting word_size to 0 which means that 2380 // we are not requesting a post-GC allocation. 2381 VM_G1IncCollectionPause op(gc_count_before, 2382 0, /* word_size */ 2383 true, /* should_initiate_conc_mark */ 2384 g1_policy()->max_pause_time_ms(), 2385 cause); 2386 op.set_allocation_context(AllocationContext::current()); 2387 2388 VMThread::execute(&op); 2389 if (!op.pause_succeeded()) { 2390 if (old_marking_count_before == _old_marking_cycles_started) { 2391 retry_gc = op.should_retry_gc(); 2392 } else { 2393 // A Full GC happened while we were trying to schedule the 2394 // initial-mark GC. No point in starting a new cycle given 2395 // that the whole heap was collected anyway. 2396 } 2397 2398 if (retry_gc) { 2399 if (GCLocker::is_active_and_needs_gc()) { 2400 GCLocker::stall_until_clear(); 2401 } 2402 } 2403 } 2404 } else { 2405 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2406 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2407 2408 // Schedule a standard evacuation pause. We're setting word_size 2409 // to 0 which means that we are not requesting a post-GC allocation. 2410 VM_G1IncCollectionPause op(gc_count_before, 2411 0, /* word_size */ 2412 false, /* should_initiate_conc_mark */ 2413 g1_policy()->max_pause_time_ms(), 2414 cause); 2415 VMThread::execute(&op); 2416 } else { 2417 // Schedule a Full GC. 2418 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2419 VMThread::execute(&op); 2420 } 2421 } 2422 } while (retry_gc); 2423 } 2424 2425 bool G1CollectedHeap::is_in(const void* p) const { 2426 if (_hrm.reserved().contains(p)) { 2427 // Given that we know that p is in the reserved space, 2428 // heap_region_containing() should successfully 2429 // return the containing region. 2430 HeapRegion* hr = heap_region_containing(p); 2431 return hr->is_in(p); 2432 } else { 2433 return false; 2434 } 2435 } 2436 2437 #ifdef ASSERT 2438 bool G1CollectedHeap::is_in_exact(const void* p) const { 2439 bool contains = reserved_region().contains(p); 2440 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2441 if (contains && available) { 2442 return true; 2443 } else { 2444 return false; 2445 } 2446 } 2447 #endif 2448 2449 bool G1CollectedHeap::obj_in_cs(oop obj) { 2450 HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj); 2451 return r != NULL && r->in_collection_set(); 2452 } 2453 2454 // Iteration functions. 2455 2456 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2457 2458 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2459 ExtendedOopClosure* _cl; 2460 public: 2461 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2462 bool doHeapRegion(HeapRegion* r) { 2463 if (!r->is_continues_humongous()) { 2464 r->oop_iterate(_cl); 2465 } 2466 return false; 2467 } 2468 }; 2469 2470 // Iterates an ObjectClosure over all objects within a HeapRegion. 2471 2472 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2473 ObjectClosure* _cl; 2474 public: 2475 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2476 bool doHeapRegion(HeapRegion* r) { 2477 if (!r->is_continues_humongous()) { 2478 r->object_iterate(_cl); 2479 } 2480 return false; 2481 } 2482 }; 2483 2484 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2485 IterateObjectClosureRegionClosure blk(cl); 2486 heap_region_iterate(&blk); 2487 } 2488 2489 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2490 _hrm.iterate(cl); 2491 } 2492 2493 void 2494 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2495 uint worker_id, 2496 HeapRegionClaimer *hrclaimer, 2497 bool concurrent) const { 2498 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2499 } 2500 2501 // Clear the cached CSet starting regions and (more importantly) 2502 // the time stamps. Called when we reset the GC time stamp. 2503 void G1CollectedHeap::clear_cset_start_regions() { 2504 assert(_worker_cset_start_region != NULL, "sanity"); 2505 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2506 2507 for (uint i = 0; i < ParallelGCThreads; i++) { 2508 _worker_cset_start_region[i] = NULL; 2509 _worker_cset_start_region_time_stamp[i] = 0; 2510 } 2511 } 2512 2513 // Given the id of a worker, obtain or calculate a suitable 2514 // starting region for iterating over the current collection set. 2515 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2516 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2517 2518 HeapRegion* result = NULL; 2519 unsigned gc_time_stamp = get_gc_time_stamp(); 2520 2521 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2522 // Cached starting region for current worker was set 2523 // during the current pause - so it's valid. 2524 // Note: the cached starting heap region may be NULL 2525 // (when the collection set is empty). 2526 result = _worker_cset_start_region[worker_i]; 2527 assert(result == NULL || result->in_collection_set(), "sanity"); 2528 return result; 2529 } 2530 2531 // The cached entry was not valid so let's calculate 2532 // a suitable starting heap region for this worker. 2533 2534 // We want the parallel threads to start their collection 2535 // set iteration at different collection set regions to 2536 // avoid contention. 2537 // If we have: 2538 // n collection set regions 2539 // p threads 2540 // Then thread t will start at region floor ((t * n) / p) 2541 2542 result = g1_policy()->collection_set(); 2543 uint cs_size = g1_policy()->cset_region_length(); 2544 uint active_workers = workers()->active_workers(); 2545 2546 uint end_ind = (cs_size * worker_i) / active_workers; 2547 uint start_ind = 0; 2548 2549 if (worker_i > 0 && 2550 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2551 // Previous workers starting region is valid 2552 // so let's iterate from there 2553 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2554 result = _worker_cset_start_region[worker_i - 1]; 2555 } 2556 2557 for (uint i = start_ind; i < end_ind; i++) { 2558 result = result->next_in_collection_set(); 2559 } 2560 2561 // Note: the calculated starting heap region may be NULL 2562 // (when the collection set is empty). 2563 assert(result == NULL || result->in_collection_set(), "sanity"); 2564 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2565 "should be updated only once per pause"); 2566 _worker_cset_start_region[worker_i] = result; 2567 OrderAccess::storestore(); 2568 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2569 return result; 2570 } 2571 2572 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2573 HeapRegion* r = g1_policy()->collection_set(); 2574 while (r != NULL) { 2575 HeapRegion* next = r->next_in_collection_set(); 2576 if (cl->doHeapRegion(r)) { 2577 cl->incomplete(); 2578 return; 2579 } 2580 r = next; 2581 } 2582 } 2583 2584 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2585 HeapRegionClosure *cl) { 2586 if (r == NULL) { 2587 // The CSet is empty so there's nothing to do. 2588 return; 2589 } 2590 2591 assert(r->in_collection_set(), 2592 "Start region must be a member of the collection set."); 2593 HeapRegion* cur = r; 2594 while (cur != NULL) { 2595 HeapRegion* next = cur->next_in_collection_set(); 2596 if (cl->doHeapRegion(cur) && false) { 2597 cl->incomplete(); 2598 return; 2599 } 2600 cur = next; 2601 } 2602 cur = g1_policy()->collection_set(); 2603 while (cur != r) { 2604 HeapRegion* next = cur->next_in_collection_set(); 2605 if (cl->doHeapRegion(cur) && false) { 2606 cl->incomplete(); 2607 return; 2608 } 2609 cur = next; 2610 } 2611 } 2612 2613 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2614 HeapRegion* result = _hrm.next_region_in_heap(from); 2615 while (result != NULL && result->is_pinned()) { 2616 result = _hrm.next_region_in_heap(result); 2617 } 2618 return result; 2619 } 2620 2621 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2622 HeapRegion* hr = heap_region_containing(addr); 2623 return hr->block_start(addr); 2624 } 2625 2626 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2627 HeapRegion* hr = heap_region_containing(addr); 2628 return hr->block_size(addr); 2629 } 2630 2631 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2632 HeapRegion* hr = heap_region_containing(addr); 2633 return hr->block_is_obj(addr); 2634 } 2635 2636 bool G1CollectedHeap::supports_tlab_allocation() const { 2637 return true; 2638 } 2639 2640 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2641 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2642 } 2643 2644 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2645 return young_list()->eden_used_bytes(); 2646 } 2647 2648 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2649 // must be equal to the humongous object limit. 2650 size_t G1CollectedHeap::max_tlab_size() const { 2651 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2652 } 2653 2654 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2655 AllocationContext_t context = AllocationContext::current(); 2656 return _allocator->unsafe_max_tlab_alloc(context); 2657 } 2658 2659 size_t G1CollectedHeap::max_capacity() const { 2660 return _hrm.reserved().byte_size(); 2661 } 2662 2663 jlong G1CollectedHeap::millis_since_last_gc() { 2664 // assert(false, "NYI"); 2665 return 0; 2666 } 2667 2668 void G1CollectedHeap::prepare_for_verify() { 2669 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2670 ensure_parsability(false); 2671 } 2672 g1_rem_set()->prepare_for_verify(); 2673 } 2674 2675 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 2676 VerifyOption vo) { 2677 switch (vo) { 2678 case VerifyOption_G1UsePrevMarking: 2679 return hr->obj_allocated_since_prev_marking(obj); 2680 case VerifyOption_G1UseNextMarking: 2681 return hr->obj_allocated_since_next_marking(obj); 2682 case VerifyOption_G1UseMarkWord: 2683 return false; 2684 default: 2685 ShouldNotReachHere(); 2686 } 2687 return false; // keep some compilers happy 2688 } 2689 2690 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 2691 switch (vo) { 2692 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 2693 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 2694 case VerifyOption_G1UseMarkWord: return NULL; 2695 default: ShouldNotReachHere(); 2696 } 2697 return NULL; // keep some compilers happy 2698 } 2699 2700 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 2701 switch (vo) { 2702 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 2703 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 2704 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 2705 default: ShouldNotReachHere(); 2706 } 2707 return false; // keep some compilers happy 2708 } 2709 2710 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 2711 switch (vo) { 2712 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 2713 case VerifyOption_G1UseNextMarking: return "NTAMS"; 2714 case VerifyOption_G1UseMarkWord: return "NONE"; 2715 default: ShouldNotReachHere(); 2716 } 2717 return NULL; // keep some compilers happy 2718 } 2719 2720 class VerifyRootsClosure: public OopClosure { 2721 private: 2722 G1CollectedHeap* _g1h; 2723 VerifyOption _vo; 2724 bool _failures; 2725 public: 2726 // _vo == UsePrevMarking -> use "prev" marking information, 2727 // _vo == UseNextMarking -> use "next" marking information, 2728 // _vo == UseMarkWord -> use mark word from object header. 2729 VerifyRootsClosure(VerifyOption vo) : 2730 _g1h(G1CollectedHeap::heap()), 2731 _vo(vo), 2732 _failures(false) { } 2733 2734 bool failures() { return _failures; } 2735 2736 template <class T> void do_oop_nv(T* p) { 2737 T heap_oop = oopDesc::load_heap_oop(p); 2738 if (!oopDesc::is_null(heap_oop)) { 2739 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2740 if (_g1h->is_obj_dead_cond(obj, _vo)) { 2741 LogHandle(gc, verify) log; 2742 log.info("Root location " PTR_FORMAT " points to dead obj " PTR_FORMAT, p2i(p), p2i(obj)); 2743 if (_vo == VerifyOption_G1UseMarkWord) { 2744 log.info(" Mark word: " PTR_FORMAT, p2i(obj->mark())); 2745 } 2746 ResourceMark rm; 2747 obj->print_on(log.info_stream()); 2748 _failures = true; 2749 } 2750 } 2751 } 2752 2753 void do_oop(oop* p) { do_oop_nv(p); } 2754 void do_oop(narrowOop* p) { do_oop_nv(p); } 2755 }; 2756 2757 class G1VerifyCodeRootOopClosure: public OopClosure { 2758 G1CollectedHeap* _g1h; 2759 OopClosure* _root_cl; 2760 nmethod* _nm; 2761 VerifyOption _vo; 2762 bool _failures; 2763 2764 template <class T> void do_oop_work(T* p) { 2765 // First verify that this root is live 2766 _root_cl->do_oop(p); 2767 2768 if (!G1VerifyHeapRegionCodeRoots) { 2769 // We're not verifying the code roots attached to heap region. 2770 return; 2771 } 2772 2773 // Don't check the code roots during marking verification in a full GC 2774 if (_vo == VerifyOption_G1UseMarkWord) { 2775 return; 2776 } 2777 2778 // Now verify that the current nmethod (which contains p) is 2779 // in the code root list of the heap region containing the 2780 // object referenced by p. 2781 2782 T heap_oop = oopDesc::load_heap_oop(p); 2783 if (!oopDesc::is_null(heap_oop)) { 2784 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2785 2786 // Now fetch the region containing the object 2787 HeapRegion* hr = _g1h->heap_region_containing(obj); 2788 HeapRegionRemSet* hrrs = hr->rem_set(); 2789 // Verify that the strong code root list for this region 2790 // contains the nmethod 2791 if (!hrrs->strong_code_roots_list_contains(_nm)) { 2792 log_info(gc, verify)("Code root location " PTR_FORMAT " " 2793 "from nmethod " PTR_FORMAT " not in strong " 2794 "code roots for region [" PTR_FORMAT "," PTR_FORMAT ")", 2795 p2i(p), p2i(_nm), p2i(hr->bottom()), p2i(hr->end())); 2796 _failures = true; 2797 } 2798 } 2799 } 2800 2801 public: 2802 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo): 2803 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {} 2804 2805 void do_oop(oop* p) { do_oop_work(p); } 2806 void do_oop(narrowOop* p) { do_oop_work(p); } 2807 2808 void set_nmethod(nmethod* nm) { _nm = nm; } 2809 bool failures() { return _failures; } 2810 }; 2811 2812 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure { 2813 G1VerifyCodeRootOopClosure* _oop_cl; 2814 2815 public: 2816 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl): 2817 _oop_cl(oop_cl) {} 2818 2819 void do_code_blob(CodeBlob* cb) { 2820 nmethod* nm = cb->as_nmethod_or_null(); 2821 if (nm != NULL) { 2822 _oop_cl->set_nmethod(nm); 2823 nm->oops_do(_oop_cl); 2824 } 2825 } 2826 }; 2827 2828 class YoungRefCounterClosure : public OopClosure { 2829 G1CollectedHeap* _g1h; 2830 int _count; 2831 public: 2832 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 2833 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 2834 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 2835 2836 int count() { return _count; } 2837 void reset_count() { _count = 0; }; 2838 }; 2839 2840 class VerifyKlassClosure: public KlassClosure { 2841 YoungRefCounterClosure _young_ref_counter_closure; 2842 OopClosure *_oop_closure; 2843 public: 2844 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 2845 void do_klass(Klass* k) { 2846 k->oops_do(_oop_closure); 2847 2848 _young_ref_counter_closure.reset_count(); 2849 k->oops_do(&_young_ref_counter_closure); 2850 if (_young_ref_counter_closure.count() > 0) { 2851 guarantee(k->has_modified_oops(), "Klass " PTR_FORMAT ", has young refs but is not dirty.", p2i(k)); 2852 } 2853 } 2854 }; 2855 2856 class VerifyLivenessOopClosure: public OopClosure { 2857 G1CollectedHeap* _g1h; 2858 VerifyOption _vo; 2859 public: 2860 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 2861 _g1h(g1h), _vo(vo) 2862 { } 2863 void do_oop(narrowOop *p) { do_oop_work(p); } 2864 void do_oop( oop *p) { do_oop_work(p); } 2865 2866 template <class T> void do_oop_work(T *p) { 2867 oop obj = oopDesc::load_decode_heap_oop(p); 2868 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 2869 "Dead object referenced by a not dead object"); 2870 } 2871 }; 2872 2873 class VerifyObjsInRegionClosure: public ObjectClosure { 2874 private: 2875 G1CollectedHeap* _g1h; 2876 size_t _live_bytes; 2877 HeapRegion *_hr; 2878 VerifyOption _vo; 2879 public: 2880 // _vo == UsePrevMarking -> use "prev" marking information, 2881 // _vo == UseNextMarking -> use "next" marking information, 2882 // _vo == UseMarkWord -> use mark word from object header. 2883 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 2884 : _live_bytes(0), _hr(hr), _vo(vo) { 2885 _g1h = G1CollectedHeap::heap(); 2886 } 2887 void do_object(oop o) { 2888 VerifyLivenessOopClosure isLive(_g1h, _vo); 2889 assert(o != NULL, "Huh?"); 2890 if (!_g1h->is_obj_dead_cond(o, _vo)) { 2891 // If the object is alive according to the mark word, 2892 // then verify that the marking information agrees. 2893 // Note we can't verify the contra-positive of the 2894 // above: if the object is dead (according to the mark 2895 // word), it may not be marked, or may have been marked 2896 // but has since became dead, or may have been allocated 2897 // since the last marking. 2898 if (_vo == VerifyOption_G1UseMarkWord) { 2899 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 2900 } 2901 2902 o->oop_iterate_no_header(&isLive); 2903 if (!_hr->obj_allocated_since_prev_marking(o)) { 2904 size_t obj_size = o->size(); // Make sure we don't overflow 2905 _live_bytes += (obj_size * HeapWordSize); 2906 } 2907 } 2908 } 2909 size_t live_bytes() { return _live_bytes; } 2910 }; 2911 2912 class VerifyArchiveOopClosure: public OopClosure { 2913 public: 2914 VerifyArchiveOopClosure(HeapRegion *hr) { } 2915 void do_oop(narrowOop *p) { do_oop_work(p); } 2916 void do_oop( oop *p) { do_oop_work(p); } 2917 2918 template <class T> void do_oop_work(T *p) { 2919 oop obj = oopDesc::load_decode_heap_oop(p); 2920 guarantee(obj == NULL || G1MarkSweep::in_archive_range(obj), 2921 "Archive object at " PTR_FORMAT " references a non-archive object at " PTR_FORMAT, 2922 p2i(p), p2i(obj)); 2923 } 2924 }; 2925 2926 class VerifyArchiveRegionClosure: public ObjectClosure { 2927 public: 2928 VerifyArchiveRegionClosure(HeapRegion *hr) { } 2929 // Verify that all object pointers are to archive regions. 2930 void do_object(oop o) { 2931 VerifyArchiveOopClosure checkOop(NULL); 2932 assert(o != NULL, "Should not be here for NULL oops"); 2933 o->oop_iterate_no_header(&checkOop); 2934 } 2935 }; 2936 2937 class VerifyRegionClosure: public HeapRegionClosure { 2938 private: 2939 bool _par; 2940 VerifyOption _vo; 2941 bool _failures; 2942 public: 2943 // _vo == UsePrevMarking -> use "prev" marking information, 2944 // _vo == UseNextMarking -> use "next" marking information, 2945 // _vo == UseMarkWord -> use mark word from object header. 2946 VerifyRegionClosure(bool par, VerifyOption vo) 2947 : _par(par), 2948 _vo(vo), 2949 _failures(false) {} 2950 2951 bool failures() { 2952 return _failures; 2953 } 2954 2955 bool doHeapRegion(HeapRegion* r) { 2956 // For archive regions, verify there are no heap pointers to 2957 // non-pinned regions. For all others, verify liveness info. 2958 if (r->is_archive()) { 2959 VerifyArchiveRegionClosure verify_oop_pointers(r); 2960 r->object_iterate(&verify_oop_pointers); 2961 return true; 2962 } 2963 if (!r->is_continues_humongous()) { 2964 bool failures = false; 2965 r->verify(_vo, &failures); 2966 if (failures) { 2967 _failures = true; 2968 } else if (!r->is_starts_humongous()) { 2969 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 2970 r->object_iterate(¬_dead_yet_cl); 2971 if (_vo != VerifyOption_G1UseNextMarking) { 2972 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 2973 log_info(gc, verify)("[" PTR_FORMAT "," PTR_FORMAT "] max_live_bytes " SIZE_FORMAT " < calculated " SIZE_FORMAT, 2974 p2i(r->bottom()), p2i(r->end()), r->max_live_bytes(), not_dead_yet_cl.live_bytes()); 2975 _failures = true; 2976 } 2977 } else { 2978 // When vo == UseNextMarking we cannot currently do a sanity 2979 // check on the live bytes as the calculation has not been 2980 // finalized yet. 2981 } 2982 } 2983 } 2984 return false; // stop the region iteration if we hit a failure 2985 } 2986 }; 2987 2988 // This is the task used for parallel verification of the heap regions 2989 2990 class G1ParVerifyTask: public AbstractGangTask { 2991 private: 2992 G1CollectedHeap* _g1h; 2993 VerifyOption _vo; 2994 bool _failures; 2995 HeapRegionClaimer _hrclaimer; 2996 2997 public: 2998 // _vo == UsePrevMarking -> use "prev" marking information, 2999 // _vo == UseNextMarking -> use "next" marking information, 3000 // _vo == UseMarkWord -> use mark word from object header. 3001 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3002 AbstractGangTask("Parallel verify task"), 3003 _g1h(g1h), 3004 _vo(vo), 3005 _failures(false), 3006 _hrclaimer(g1h->workers()->active_workers()) {} 3007 3008 bool failures() { 3009 return _failures; 3010 } 3011 3012 void work(uint worker_id) { 3013 HandleMark hm; 3014 VerifyRegionClosure blk(true, _vo); 3015 _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer); 3016 if (blk.failures()) { 3017 _failures = true; 3018 } 3019 } 3020 }; 3021 3022 void G1CollectedHeap::verify(VerifyOption vo) { 3023 if (!SafepointSynchronize::is_at_safepoint()) { 3024 log_info(gc, verify)("Skipping verification. Not at safepoint."); 3025 } 3026 3027 assert(Thread::current()->is_VM_thread(), 3028 "Expected to be executed serially by the VM thread at this point"); 3029 3030 log_debug(gc, verify)("Roots"); 3031 VerifyRootsClosure rootsCl(vo); 3032 VerifyKlassClosure klassCl(this, &rootsCl); 3033 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false); 3034 3035 // We apply the relevant closures to all the oops in the 3036 // system dictionary, class loader data graph, the string table 3037 // and the nmethods in the code cache. 3038 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo); 3039 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl); 3040 3041 { 3042 G1RootProcessor root_processor(this, 1); 3043 root_processor.process_all_roots(&rootsCl, 3044 &cldCl, 3045 &blobsCl); 3046 } 3047 3048 bool failures = rootsCl.failures() || codeRootsCl.failures(); 3049 3050 if (vo != VerifyOption_G1UseMarkWord) { 3051 // If we're verifying during a full GC then the region sets 3052 // will have been torn down at the start of the GC. Therefore 3053 // verifying the region sets will fail. So we only verify 3054 // the region sets when not in a full GC. 3055 log_debug(gc, verify)("HeapRegionSets"); 3056 verify_region_sets(); 3057 } 3058 3059 log_debug(gc, verify)("HeapRegions"); 3060 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3061 3062 G1ParVerifyTask task(this, vo); 3063 workers()->run_task(&task); 3064 if (task.failures()) { 3065 failures = true; 3066 } 3067 3068 } else { 3069 VerifyRegionClosure blk(false, vo); 3070 heap_region_iterate(&blk); 3071 if (blk.failures()) { 3072 failures = true; 3073 } 3074 } 3075 3076 if (G1StringDedup::is_enabled()) { 3077 log_debug(gc, verify)("StrDedup"); 3078 G1StringDedup::verify(); 3079 } 3080 3081 if (failures) { 3082 log_info(gc, verify)("Heap after failed verification:"); 3083 // It helps to have the per-region information in the output to 3084 // help us track down what went wrong. This is why we call 3085 // print_extended_on() instead of print_on(). 3086 LogHandle(gc, verify) log; 3087 ResourceMark rm; 3088 print_extended_on(log.info_stream()); 3089 } 3090 guarantee(!failures, "there should not have been any failures"); 3091 } 3092 3093 double G1CollectedHeap::verify(bool guard, const char* msg) { 3094 double verify_time_ms = 0.0; 3095 3096 if (guard && total_collections() >= VerifyGCStartAt) { 3097 double verify_start = os::elapsedTime(); 3098 HandleMark hm; // Discard invalid handles created during verification 3099 prepare_for_verify(); 3100 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 3101 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 3102 } 3103 3104 return verify_time_ms; 3105 } 3106 3107 void G1CollectedHeap::verify_before_gc() { 3108 double verify_time_ms = verify(VerifyBeforeGC, "Before GC"); 3109 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 3110 } 3111 3112 void G1CollectedHeap::verify_after_gc() { 3113 double verify_time_ms = verify(VerifyAfterGC, "After GC"); 3114 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 3115 } 3116 3117 class PrintRegionClosure: public HeapRegionClosure { 3118 outputStream* _st; 3119 public: 3120 PrintRegionClosure(outputStream* st) : _st(st) {} 3121 bool doHeapRegion(HeapRegion* r) { 3122 r->print_on(_st); 3123 return false; 3124 } 3125 }; 3126 3127 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3128 const HeapRegion* hr, 3129 const VerifyOption vo) const { 3130 switch (vo) { 3131 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 3132 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 3133 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 3134 default: ShouldNotReachHere(); 3135 } 3136 return false; // keep some compilers happy 3137 } 3138 3139 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3140 const VerifyOption vo) const { 3141 switch (vo) { 3142 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 3143 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 3144 case VerifyOption_G1UseMarkWord: { 3145 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 3146 return !obj->is_gc_marked() && !hr->is_archive(); 3147 } 3148 default: ShouldNotReachHere(); 3149 } 3150 return false; // keep some compilers happy 3151 } 3152 3153 void G1CollectedHeap::print_on(outputStream* st) const { 3154 st->print(" %-20s", "garbage-first heap"); 3155 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3156 capacity()/K, used_unlocked()/K); 3157 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 3158 p2i(_hrm.reserved().start()), 3159 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 3160 p2i(_hrm.reserved().end())); 3161 st->cr(); 3162 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3163 uint young_regions = _young_list->length(); 3164 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3165 (size_t) young_regions * HeapRegion::GrainBytes / K); 3166 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3167 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3168 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3169 st->cr(); 3170 MetaspaceAux::print_on(st); 3171 } 3172 3173 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3174 print_on(st); 3175 3176 // Print the per-region information. 3177 st->cr(); 3178 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 3179 "HS=humongous(starts), HC=humongous(continues), " 3180 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 3181 "AC=allocation context, " 3182 "TAMS=top-at-mark-start (previous, next)"); 3183 PrintRegionClosure blk(st); 3184 heap_region_iterate(&blk); 3185 } 3186 3187 void G1CollectedHeap::print_on_error(outputStream* st) const { 3188 this->CollectedHeap::print_on_error(st); 3189 3190 if (_cm != NULL) { 3191 st->cr(); 3192 _cm->print_on_error(st); 3193 } 3194 } 3195 3196 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3197 workers()->print_worker_threads_on(st); 3198 _cmThread->print_on(st); 3199 st->cr(); 3200 _cm->print_worker_threads_on(st); 3201 _cg1r->print_worker_threads_on(st); 3202 if (G1StringDedup::is_enabled()) { 3203 G1StringDedup::print_worker_threads_on(st); 3204 } 3205 } 3206 3207 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3208 workers()->threads_do(tc); 3209 tc->do_thread(_cmThread); 3210 _cg1r->threads_do(tc); 3211 if (G1StringDedup::is_enabled()) { 3212 G1StringDedup::threads_do(tc); 3213 } 3214 } 3215 3216 void G1CollectedHeap::print_tracing_info() const { 3217 // We'll overload this to mean "trace GC pause statistics." 3218 if (TraceYoungGenTime || TraceOldGenTime) { 3219 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3220 // to that. 3221 g1_policy()->print_tracing_info(); 3222 } 3223 g1_rem_set()->print_summary_info(); 3224 concurrent_mark()->print_summary_info(); 3225 g1_policy()->print_yg_surv_rate_info(); 3226 } 3227 3228 #ifndef PRODUCT 3229 // Helpful for debugging RSet issues. 3230 3231 class PrintRSetsClosure : public HeapRegionClosure { 3232 private: 3233 const char* _msg; 3234 size_t _occupied_sum; 3235 3236 public: 3237 bool doHeapRegion(HeapRegion* r) { 3238 HeapRegionRemSet* hrrs = r->rem_set(); 3239 size_t occupied = hrrs->occupied(); 3240 _occupied_sum += occupied; 3241 3242 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 3243 if (occupied == 0) { 3244 tty->print_cr(" RSet is empty"); 3245 } else { 3246 hrrs->print(); 3247 } 3248 tty->print_cr("----------"); 3249 return false; 3250 } 3251 3252 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3253 tty->cr(); 3254 tty->print_cr("========================================"); 3255 tty->print_cr("%s", msg); 3256 tty->cr(); 3257 } 3258 3259 ~PrintRSetsClosure() { 3260 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 3261 tty->print_cr("========================================"); 3262 tty->cr(); 3263 } 3264 }; 3265 3266 void G1CollectedHeap::print_cset_rsets() { 3267 PrintRSetsClosure cl("Printing CSet RSets"); 3268 collection_set_iterate(&cl); 3269 } 3270 3271 void G1CollectedHeap::print_all_rsets() { 3272 PrintRSetsClosure cl("Printing All RSets");; 3273 heap_region_iterate(&cl); 3274 } 3275 #endif // PRODUCT 3276 3277 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 3278 YoungList* young_list = heap()->young_list(); 3279 3280 size_t eden_used_bytes = young_list->eden_used_bytes(); 3281 size_t survivor_used_bytes = young_list->survivor_used_bytes(); 3282 3283 size_t eden_capacity_bytes = 3284 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 3285 3286 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 3287 return G1HeapSummary(heap_summary, used(), eden_used_bytes, eden_capacity_bytes, survivor_used_bytes); 3288 } 3289 3290 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 3291 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 3292 stats->unused(), stats->used(), stats->region_end_waste(), 3293 stats->regions_filled(), stats->direct_allocated(), 3294 stats->failure_used(), stats->failure_waste()); 3295 } 3296 3297 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 3298 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 3299 gc_tracer->report_gc_heap_summary(when, heap_summary); 3300 3301 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 3302 gc_tracer->report_metaspace_summary(when, metaspace_summary); 3303 } 3304 3305 3306 G1CollectedHeap* G1CollectedHeap::heap() { 3307 CollectedHeap* heap = Universe::heap(); 3308 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 3309 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 3310 return (G1CollectedHeap*)heap; 3311 } 3312 3313 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3314 // always_do_update_barrier = false; 3315 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3316 // Fill TLAB's and such 3317 accumulate_statistics_all_tlabs(); 3318 ensure_parsability(true); 3319 3320 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 3321 } 3322 3323 void G1CollectedHeap::gc_epilogue(bool full) { 3324 // we are at the end of the GC. Total collections has already been increased. 3325 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 3326 3327 // FIXME: what is this about? 3328 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3329 // is set. 3330 #if defined(COMPILER2) || INCLUDE_JVMCI 3331 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 3332 #endif 3333 // always_do_update_barrier = true; 3334 3335 resize_all_tlabs(); 3336 allocation_context_stats().update(full); 3337 3338 // We have just completed a GC. Update the soft reference 3339 // policy with the new heap occupancy 3340 Universe::update_heap_info_at_gc(); 3341 } 3342 3343 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3344 uint gc_count_before, 3345 bool* succeeded, 3346 GCCause::Cause gc_cause) { 3347 assert_heap_not_locked_and_not_at_safepoint(); 3348 g1_policy()->record_stop_world_start(); 3349 VM_G1IncCollectionPause op(gc_count_before, 3350 word_size, 3351 false, /* should_initiate_conc_mark */ 3352 g1_policy()->max_pause_time_ms(), 3353 gc_cause); 3354 3355 op.set_allocation_context(AllocationContext::current()); 3356 VMThread::execute(&op); 3357 3358 HeapWord* result = op.result(); 3359 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3360 assert(result == NULL || ret_succeeded, 3361 "the result should be NULL if the VM did not succeed"); 3362 *succeeded = ret_succeeded; 3363 3364 assert_heap_not_locked(); 3365 return result; 3366 } 3367 3368 void 3369 G1CollectedHeap::doConcurrentMark() { 3370 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3371 if (!_cmThread->in_progress()) { 3372 _cmThread->set_started(); 3373 CGC_lock->notify(); 3374 } 3375 } 3376 3377 size_t G1CollectedHeap::pending_card_num() { 3378 size_t extra_cards = 0; 3379 JavaThread *curr = Threads::first(); 3380 while (curr != NULL) { 3381 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3382 extra_cards += dcq.size(); 3383 curr = curr->next(); 3384 } 3385 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3386 size_t buffer_size = dcqs.buffer_size(); 3387 size_t buffer_num = dcqs.completed_buffers_num(); 3388 3389 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3390 // in bytes - not the number of 'entries'. We need to convert 3391 // into a number of cards. 3392 return (buffer_size * buffer_num + extra_cards) / oopSize; 3393 } 3394 3395 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 3396 private: 3397 size_t _total_humongous; 3398 size_t _candidate_humongous; 3399 3400 DirtyCardQueue _dcq; 3401 3402 // We don't nominate objects with many remembered set entries, on 3403 // the assumption that such objects are likely still live. 3404 bool is_remset_small(HeapRegion* region) const { 3405 HeapRegionRemSet* const rset = region->rem_set(); 3406 return G1EagerReclaimHumongousObjectsWithStaleRefs 3407 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 3408 : rset->is_empty(); 3409 } 3410 3411 bool is_typeArray_region(HeapRegion* region) const { 3412 return oop(region->bottom())->is_typeArray(); 3413 } 3414 3415 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 3416 assert(region->is_starts_humongous(), "Must start a humongous object"); 3417 3418 // Candidate selection must satisfy the following constraints 3419 // while concurrent marking is in progress: 3420 // 3421 // * In order to maintain SATB invariants, an object must not be 3422 // reclaimed if it was allocated before the start of marking and 3423 // has not had its references scanned. Such an object must have 3424 // its references (including type metadata) scanned to ensure no 3425 // live objects are missed by the marking process. Objects 3426 // allocated after the start of concurrent marking don't need to 3427 // be scanned. 3428 // 3429 // * An object must not be reclaimed if it is on the concurrent 3430 // mark stack. Objects allocated after the start of concurrent 3431 // marking are never pushed on the mark stack. 3432 // 3433 // Nominating only objects allocated after the start of concurrent 3434 // marking is sufficient to meet both constraints. This may miss 3435 // some objects that satisfy the constraints, but the marking data 3436 // structures don't support efficiently performing the needed 3437 // additional tests or scrubbing of the mark stack. 3438 // 3439 // However, we presently only nominate is_typeArray() objects. 3440 // A humongous object containing references induces remembered 3441 // set entries on other regions. In order to reclaim such an 3442 // object, those remembered sets would need to be cleaned up. 3443 // 3444 // We also treat is_typeArray() objects specially, allowing them 3445 // to be reclaimed even if allocated before the start of 3446 // concurrent mark. For this we rely on mark stack insertion to 3447 // exclude is_typeArray() objects, preventing reclaiming an object 3448 // that is in the mark stack. We also rely on the metadata for 3449 // such objects to be built-in and so ensured to be kept live. 3450 // Frequent allocation and drop of large binary blobs is an 3451 // important use case for eager reclaim, and this special handling 3452 // may reduce needed headroom. 3453 3454 return is_typeArray_region(region) && is_remset_small(region); 3455 } 3456 3457 public: 3458 RegisterHumongousWithInCSetFastTestClosure() 3459 : _total_humongous(0), 3460 _candidate_humongous(0), 3461 _dcq(&JavaThread::dirty_card_queue_set()) { 3462 } 3463 3464 virtual bool doHeapRegion(HeapRegion* r) { 3465 if (!r->is_starts_humongous()) { 3466 return false; 3467 } 3468 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3469 3470 bool is_candidate = humongous_region_is_candidate(g1h, r); 3471 uint rindex = r->hrm_index(); 3472 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 3473 if (is_candidate) { 3474 _candidate_humongous++; 3475 g1h->register_humongous_region_with_cset(rindex); 3476 // Is_candidate already filters out humongous object with large remembered sets. 3477 // If we have a humongous object with a few remembered sets, we simply flush these 3478 // remembered set entries into the DCQS. That will result in automatic 3479 // re-evaluation of their remembered set entries during the following evacuation 3480 // phase. 3481 if (!r->rem_set()->is_empty()) { 3482 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 3483 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 3484 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 3485 HeapRegionRemSetIterator hrrs(r->rem_set()); 3486 size_t card_index; 3487 while (hrrs.has_next(card_index)) { 3488 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 3489 // The remembered set might contain references to already freed 3490 // regions. Filter out such entries to avoid failing card table 3491 // verification. 3492 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 3493 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 3494 *card_ptr = CardTableModRefBS::dirty_card_val(); 3495 _dcq.enqueue(card_ptr); 3496 } 3497 } 3498 } 3499 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 3500 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 3501 hrrs.n_yielded(), r->rem_set()->occupied()); 3502 r->rem_set()->clear_locked(); 3503 } 3504 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 3505 } 3506 _total_humongous++; 3507 3508 return false; 3509 } 3510 3511 size_t total_humongous() const { return _total_humongous; } 3512 size_t candidate_humongous() const { return _candidate_humongous; } 3513 3514 void flush_rem_set_entries() { _dcq.flush(); } 3515 }; 3516 3517 void G1CollectedHeap::register_humongous_regions_with_cset() { 3518 if (!G1EagerReclaimHumongousObjects) { 3519 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 3520 return; 3521 } 3522 double time = os::elapsed_counter(); 3523 3524 // Collect reclaim candidate information and register candidates with cset. 3525 RegisterHumongousWithInCSetFastTestClosure cl; 3526 heap_region_iterate(&cl); 3527 3528 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 3529 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 3530 cl.total_humongous(), 3531 cl.candidate_humongous()); 3532 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3533 3534 // Finally flush all remembered set entries to re-check into the global DCQS. 3535 cl.flush_rem_set_entries(); 3536 } 3537 3538 #ifdef ASSERT 3539 class VerifyCSetClosure: public HeapRegionClosure { 3540 public: 3541 bool doHeapRegion(HeapRegion* hr) { 3542 // Here we check that the CSet region's RSet is ready for parallel 3543 // iteration. The fields that we'll verify are only manipulated 3544 // when the region is part of a CSet and is collected. Afterwards, 3545 // we reset these fields when we clear the region's RSet (when the 3546 // region is freed) so they are ready when the region is 3547 // re-allocated. The only exception to this is if there's an 3548 // evacuation failure and instead of freeing the region we leave 3549 // it in the heap. In that case, we reset these fields during 3550 // evacuation failure handling. 3551 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3552 3553 // Here's a good place to add any other checks we'd like to 3554 // perform on CSet regions. 3555 return false; 3556 } 3557 }; 3558 #endif // ASSERT 3559 3560 uint G1CollectedHeap::num_task_queues() const { 3561 return _task_queues->size(); 3562 } 3563 3564 #if TASKQUEUE_STATS 3565 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3566 st->print_raw_cr("GC Task Stats"); 3567 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3568 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3569 } 3570 3571 void G1CollectedHeap::print_taskqueue_stats() const { 3572 if (!develop_log_is_enabled(Trace, gc, task, stats)) { 3573 return; 3574 } 3575 LogHandle(gc, task, stats) log; 3576 ResourceMark rm; 3577 outputStream* st = log.trace_stream(); 3578 3579 print_taskqueue_stats_hdr(st); 3580 3581 TaskQueueStats totals; 3582 const uint n = num_task_queues(); 3583 for (uint i = 0; i < n; ++i) { 3584 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 3585 totals += task_queue(i)->stats; 3586 } 3587 st->print_raw("tot "); totals.print(st); st->cr(); 3588 3589 DEBUG_ONLY(totals.verify()); 3590 } 3591 3592 void G1CollectedHeap::reset_taskqueue_stats() { 3593 const uint n = num_task_queues(); 3594 for (uint i = 0; i < n; ++i) { 3595 task_queue(i)->stats.reset(); 3596 } 3597 } 3598 #endif // TASKQUEUE_STATS 3599 3600 void G1CollectedHeap::log_gc_footer(jlong pause_time_counter) { 3601 if (evacuation_failed()) { 3602 log_info(gc)("To-space exhausted"); 3603 } 3604 3605 double pause_time_ms = TimeHelper::counter_to_millis(pause_time_counter); 3606 g1_policy()->print_phases(pause_time_ms); 3607 3608 g1_policy()->print_detailed_heap_transition(); 3609 } 3610 3611 3612 void G1CollectedHeap::wait_for_root_region_scanning() { 3613 double scan_wait_start = os::elapsedTime(); 3614 // We have to wait until the CM threads finish scanning the 3615 // root regions as it's the only way to ensure that all the 3616 // objects on them have been correctly scanned before we start 3617 // moving them during the GC. 3618 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3619 double wait_time_ms = 0.0; 3620 if (waited) { 3621 double scan_wait_end = os::elapsedTime(); 3622 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3623 } 3624 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3625 } 3626 3627 bool 3628 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3629 assert_at_safepoint(true /* should_be_vm_thread */); 3630 guarantee(!is_gc_active(), "collection is not reentrant"); 3631 3632 if (GCLocker::check_active_before_gc()) { 3633 return false; 3634 } 3635 3636 _gc_timer_stw->register_gc_start(); 3637 3638 GCIdMark gc_id_mark; 3639 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3640 3641 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3642 ResourceMark rm; 3643 3644 wait_for_root_region_scanning(); 3645 3646 print_heap_before_gc(); 3647 trace_heap_before_gc(_gc_tracer_stw); 3648 3649 verify_region_sets_optional(); 3650 verify_dirty_young_regions(); 3651 3652 // This call will decide whether this pause is an initial-mark 3653 // pause. If it is, during_initial_mark_pause() will return true 3654 // for the duration of this pause. 3655 g1_policy()->decide_on_conc_mark_initiation(); 3656 3657 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3658 assert(!collector_state()->during_initial_mark_pause() || 3659 collector_state()->gcs_are_young(), "sanity"); 3660 3661 // We also do not allow mixed GCs during marking. 3662 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3663 3664 // Record whether this pause is an initial mark. When the current 3665 // thread has completed its logging output and it's safe to signal 3666 // the CM thread, the flag's value in the policy has been reset. 3667 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3668 3669 // Inner scope for scope based logging, timers, and stats collection 3670 { 3671 EvacuationInfo evacuation_info; 3672 3673 if (collector_state()->during_initial_mark_pause()) { 3674 // We are about to start a marking cycle, so we increment the 3675 // full collection counter. 3676 increment_old_marking_cycles_started(); 3677 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3678 } 3679 3680 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3681 3682 GCTraceCPUTime tcpu; 3683 3684 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3685 workers()->active_workers(), 3686 Threads::number_of_non_daemon_threads()); 3687 workers()->set_active_workers(active_workers); 3688 FormatBuffer<> gc_string("Pause "); 3689 if (collector_state()->during_initial_mark_pause()) { 3690 gc_string.append("Initial Mark"); 3691 } else if (collector_state()->gcs_are_young()) { 3692 gc_string.append("Young"); 3693 } else { 3694 gc_string.append("Mixed"); 3695 } 3696 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 3697 3698 jlong pause_start_counter = os::elapsed_counter(); 3699 g1_policy()->note_gc_start(active_workers); 3700 3701 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3702 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3703 3704 // If the secondary_free_list is not empty, append it to the 3705 // free_list. No need to wait for the cleanup operation to finish; 3706 // the region allocation code will check the secondary_free_list 3707 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3708 // set, skip this step so that the region allocation code has to 3709 // get entries from the secondary_free_list. 3710 if (!G1StressConcRegionFreeing) { 3711 append_secondary_free_list_if_not_empty_with_lock(); 3712 } 3713 3714 assert(check_young_list_well_formed(), "young list should be well formed"); 3715 3716 // Don't dynamically change the number of GC threads this early. A value of 3717 // 0 is used to indicate serial work. When parallel work is done, 3718 // it will be set. 3719 3720 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3721 IsGCActiveMark x; 3722 3723 gc_prologue(false); 3724 increment_total_collections(false /* full gc */); 3725 increment_gc_time_stamp(); 3726 3727 verify_before_gc(); 3728 3729 check_bitmaps("GC Start"); 3730 3731 #if defined(COMPILER2) || INCLUDE_JVMCI 3732 DerivedPointerTable::clear(); 3733 #endif 3734 3735 // Please see comment in g1CollectedHeap.hpp and 3736 // G1CollectedHeap::ref_processing_init() to see how 3737 // reference processing currently works in G1. 3738 3739 // Enable discovery in the STW reference processor 3740 if (g1_policy()->should_process_references()) { 3741 ref_processor_stw()->enable_discovery(); 3742 } else { 3743 ref_processor_stw()->disable_discovery(); 3744 } 3745 3746 { 3747 // We want to temporarily turn off discovery by the 3748 // CM ref processor, if necessary, and turn it back on 3749 // on again later if we do. Using a scoped 3750 // NoRefDiscovery object will do this. 3751 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3752 3753 // Forget the current alloc region (we might even choose it to be part 3754 // of the collection set!). 3755 _allocator->release_mutator_alloc_region(); 3756 3757 // This timing is only used by the ergonomics to handle our pause target. 3758 // It is unclear why this should not include the full pause. We will 3759 // investigate this in CR 7178365. 3760 // 3761 // Preserving the old comment here if that helps the investigation: 3762 // 3763 // The elapsed time induced by the start time below deliberately elides 3764 // the possible verification above. 3765 double sample_start_time_sec = os::elapsedTime(); 3766 3767 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3768 3769 if (collector_state()->during_initial_mark_pause()) { 3770 concurrent_mark()->checkpointRootsInitialPre(); 3771 } 3772 3773 double time_remaining_ms = g1_policy()->finalize_young_cset_part(target_pause_time_ms); 3774 g1_policy()->finalize_old_cset_part(time_remaining_ms); 3775 3776 evacuation_info.set_collectionset_regions(g1_policy()->cset_region_length()); 3777 3778 // Make sure the remembered sets are up to date. This needs to be 3779 // done before register_humongous_regions_with_cset(), because the 3780 // remembered sets are used there to choose eager reclaim candidates. 3781 // If the remembered sets are not up to date we might miss some 3782 // entries that need to be handled. 3783 g1_rem_set()->cleanupHRRS(); 3784 3785 register_humongous_regions_with_cset(); 3786 3787 assert(check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3788 3789 _cm->note_start_of_gc(); 3790 // We call this after finalize_cset() to 3791 // ensure that the CSet has been finalized. 3792 _cm->verify_no_cset_oops(); 3793 3794 if (_hr_printer.is_active()) { 3795 HeapRegion* hr = g1_policy()->collection_set(); 3796 while (hr != NULL) { 3797 _hr_printer.cset(hr); 3798 hr = hr->next_in_collection_set(); 3799 } 3800 } 3801 3802 #ifdef ASSERT 3803 VerifyCSetClosure cl; 3804 collection_set_iterate(&cl); 3805 #endif // ASSERT 3806 3807 // Initialize the GC alloc regions. 3808 _allocator->init_gc_alloc_regions(evacuation_info); 3809 3810 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), g1_policy()->young_cset_region_length()); 3811 pre_evacuate_collection_set(); 3812 3813 // Actually do the work... 3814 evacuate_collection_set(evacuation_info, &per_thread_states); 3815 3816 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3817 3818 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3819 free_collection_set(g1_policy()->collection_set(), evacuation_info, surviving_young_words); 3820 3821 eagerly_reclaim_humongous_regions(); 3822 3823 g1_policy()->clear_collection_set(); 3824 3825 // Start a new incremental collection set for the next pause. 3826 g1_policy()->start_incremental_cset_building(); 3827 3828 clear_cset_fast_test(); 3829 3830 _young_list->reset_sampled_info(); 3831 3832 // Don't check the whole heap at this point as the 3833 // GC alloc regions from this pause have been tagged 3834 // as survivors and moved on to the survivor list. 3835 // Survivor regions will fail the !is_young() check. 3836 assert(check_young_list_empty(false /* check_heap */), 3837 "young list should be empty"); 3838 3839 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3840 _young_list->first_survivor_region(), 3841 _young_list->last_survivor_region()); 3842 3843 _young_list->reset_auxilary_lists(); 3844 3845 if (evacuation_failed()) { 3846 set_used(recalculate_used()); 3847 if (_archive_allocator != NULL) { 3848 _archive_allocator->clear_used(); 3849 } 3850 for (uint i = 0; i < ParallelGCThreads; i++) { 3851 if (_evacuation_failed_info_array[i].has_failed()) { 3852 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3853 } 3854 } 3855 } else { 3856 // The "used" of the the collection set have already been subtracted 3857 // when they were freed. Add in the bytes evacuated. 3858 increase_used(g1_policy()->bytes_copied_during_gc()); 3859 } 3860 3861 if (collector_state()->during_initial_mark_pause()) { 3862 // We have to do this before we notify the CM threads that 3863 // they can start working to make sure that all the 3864 // appropriate initialization is done on the CM object. 3865 concurrent_mark()->checkpointRootsInitialPost(); 3866 collector_state()->set_mark_in_progress(true); 3867 // Note that we don't actually trigger the CM thread at 3868 // this point. We do that later when we're sure that 3869 // the current thread has completed its logging output. 3870 } 3871 3872 allocate_dummy_regions(); 3873 3874 _allocator->init_mutator_alloc_region(); 3875 3876 { 3877 size_t expand_bytes = g1_policy()->expansion_amount(); 3878 if (expand_bytes > 0) { 3879 size_t bytes_before = capacity(); 3880 // No need for an ergo logging here, 3881 // expansion_amount() does this when it returns a value > 0. 3882 double expand_ms; 3883 if (!expand(expand_bytes, &expand_ms)) { 3884 // We failed to expand the heap. Cannot do anything about it. 3885 } 3886 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3887 } 3888 } 3889 3890 // We redo the verification but now wrt to the new CSet which 3891 // has just got initialized after the previous CSet was freed. 3892 _cm->verify_no_cset_oops(); 3893 _cm->note_end_of_gc(); 3894 3895 // This timing is only used by the ergonomics to handle our pause target. 3896 // It is unclear why this should not include the full pause. We will 3897 // investigate this in CR 7178365. 3898 double sample_end_time_sec = os::elapsedTime(); 3899 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3900 size_t total_cards_scanned = per_thread_states.total_cards_scanned(); 3901 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned); 3902 3903 evacuation_info.set_collectionset_used_before(g1_policy()->collection_set_bytes_used_before()); 3904 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3905 3906 MemoryService::track_memory_usage(); 3907 3908 // In prepare_for_verify() below we'll need to scan the deferred 3909 // update buffers to bring the RSets up-to-date if 3910 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3911 // the update buffers we'll probably need to scan cards on the 3912 // regions we just allocated to (i.e., the GC alloc 3913 // regions). However, during the last GC we called 3914 // set_saved_mark() on all the GC alloc regions, so card 3915 // scanning might skip the [saved_mark_word()...top()] area of 3916 // those regions (i.e., the area we allocated objects into 3917 // during the last GC). But it shouldn't. Given that 3918 // saved_mark_word() is conditional on whether the GC time stamp 3919 // on the region is current or not, by incrementing the GC time 3920 // stamp here we invalidate all the GC time stamps on all the 3921 // regions and saved_mark_word() will simply return top() for 3922 // all the regions. This is a nicer way of ensuring this rather 3923 // than iterating over the regions and fixing them. In fact, the 3924 // GC time stamp increment here also ensures that 3925 // saved_mark_word() will return top() between pauses, i.e., 3926 // during concurrent refinement. So we don't need the 3927 // is_gc_active() check to decided which top to use when 3928 // scanning cards (see CR 7039627). 3929 increment_gc_time_stamp(); 3930 3931 verify_after_gc(); 3932 check_bitmaps("GC End"); 3933 3934 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3935 ref_processor_stw()->verify_no_references_recorded(); 3936 3937 // CM reference discovery will be re-enabled if necessary. 3938 } 3939 3940 #ifdef TRACESPINNING 3941 ParallelTaskTerminator::print_termination_counts(); 3942 #endif 3943 3944 gc_epilogue(false); 3945 } 3946 3947 // Print the remainder of the GC log output. 3948 log_gc_footer(os::elapsed_counter() - pause_start_counter); 3949 3950 // It is not yet to safe to tell the concurrent mark to 3951 // start as we have some optional output below. We don't want the 3952 // output from the concurrent mark thread interfering with this 3953 // logging output either. 3954 3955 _hrm.verify_optional(); 3956 verify_region_sets_optional(); 3957 3958 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3959 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3960 3961 print_heap_after_gc(); 3962 trace_heap_after_gc(_gc_tracer_stw); 3963 3964 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3965 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3966 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3967 // before any GC notifications are raised. 3968 g1mm()->update_sizes(); 3969 3970 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3971 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3972 _gc_timer_stw->register_gc_end(); 3973 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3974 } 3975 // It should now be safe to tell the concurrent mark thread to start 3976 // without its logging output interfering with the logging output 3977 // that came from the pause. 3978 3979 if (should_start_conc_mark) { 3980 // CAUTION: after the doConcurrentMark() call below, 3981 // the concurrent marking thread(s) could be running 3982 // concurrently with us. Make sure that anything after 3983 // this point does not assume that we are the only GC thread 3984 // running. Note: of course, the actual marking work will 3985 // not start until the safepoint itself is released in 3986 // SuspendibleThreadSet::desynchronize(). 3987 doConcurrentMark(); 3988 } 3989 3990 return true; 3991 } 3992 3993 void G1CollectedHeap::restore_preserved_marks() { 3994 G1RestorePreservedMarksTask rpm_task(_preserved_objs); 3995 workers()->run_task(&rpm_task); 3996 } 3997 3998 void G1CollectedHeap::remove_self_forwarding_pointers() { 3999 G1ParRemoveSelfForwardPtrsTask rsfp_task; 4000 workers()->run_task(&rsfp_task); 4001 } 4002 4003 void G1CollectedHeap::restore_after_evac_failure() { 4004 double remove_self_forwards_start = os::elapsedTime(); 4005 4006 remove_self_forwarding_pointers(); 4007 restore_preserved_marks(); 4008 4009 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 4010 } 4011 4012 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 4013 if (!_evacuation_failed) { 4014 _evacuation_failed = true; 4015 } 4016 4017 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 4018 4019 // We want to call the "for_promotion_failure" version only in the 4020 // case of a promotion failure. 4021 if (m->must_be_preserved_for_promotion_failure(obj)) { 4022 OopAndMarkOop elem(obj, m); 4023 _preserved_objs[worker_id].push(elem); 4024 } 4025 } 4026 4027 bool G1ParEvacuateFollowersClosure::offer_termination() { 4028 G1ParScanThreadState* const pss = par_scan_state(); 4029 start_term_time(); 4030 const bool res = terminator()->offer_termination(); 4031 end_term_time(); 4032 return res; 4033 } 4034 4035 void G1ParEvacuateFollowersClosure::do_void() { 4036 G1ParScanThreadState* const pss = par_scan_state(); 4037 pss->trim_queue(); 4038 do { 4039 pss->steal_and_trim_queue(queues()); 4040 } while (!offer_termination()); 4041 } 4042 4043 class G1ParTask : public AbstractGangTask { 4044 protected: 4045 G1CollectedHeap* _g1h; 4046 G1ParScanThreadStateSet* _pss; 4047 RefToScanQueueSet* _queues; 4048 G1RootProcessor* _root_processor; 4049 ParallelTaskTerminator _terminator; 4050 uint _n_workers; 4051 4052 public: 4053 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 4054 : AbstractGangTask("G1 collection"), 4055 _g1h(g1h), 4056 _pss(per_thread_states), 4057 _queues(task_queues), 4058 _root_processor(root_processor), 4059 _terminator(n_workers, _queues), 4060 _n_workers(n_workers) 4061 {} 4062 4063 void work(uint worker_id) { 4064 if (worker_id >= _n_workers) return; // no work needed this round 4065 4066 double start_sec = os::elapsedTime(); 4067 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 4068 4069 { 4070 ResourceMark rm; 4071 HandleMark hm; 4072 4073 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4074 4075 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4076 pss->set_ref_processor(rp); 4077 4078 double start_strong_roots_sec = os::elapsedTime(); 4079 4080 _root_processor->evacuate_roots(pss->closures(), worker_id); 4081 4082 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss); 4083 4084 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 4085 // treating the nmethods visited to act as roots for concurrent marking. 4086 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 4087 // objects copied by the current evacuation. 4088 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl, 4089 pss->closures()->weak_codeblobs(), 4090 worker_id); 4091 4092 _pss->add_cards_scanned(worker_id, cards_scanned); 4093 4094 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 4095 4096 double term_sec = 0.0; 4097 size_t evac_term_attempts = 0; 4098 { 4099 double start = os::elapsedTime(); 4100 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 4101 evac.do_void(); 4102 4103 evac_term_attempts = evac.term_attempts(); 4104 term_sec = evac.term_time(); 4105 double elapsed_sec = os::elapsedTime() - start; 4106 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 4107 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 4108 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 4109 } 4110 4111 assert(pss->queue_is_empty(), "should be empty"); 4112 4113 if (log_is_enabled(Debug, gc, task, stats)) { 4114 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 4115 size_t lab_waste; 4116 size_t lab_undo_waste; 4117 pss->waste(lab_waste, lab_undo_waste); 4118 _g1h->print_termination_stats(worker_id, 4119 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 4120 strong_roots_sec * 1000.0, /* strong roots time */ 4121 term_sec * 1000.0, /* evac term time */ 4122 evac_term_attempts, /* evac term attempts */ 4123 lab_waste, /* alloc buffer waste */ 4124 lab_undo_waste /* undo waste */ 4125 ); 4126 } 4127 4128 // Close the inner scope so that the ResourceMark and HandleMark 4129 // destructors are executed here and are included as part of the 4130 // "GC Worker Time". 4131 } 4132 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 4133 } 4134 }; 4135 4136 void G1CollectedHeap::print_termination_stats_hdr() { 4137 log_debug(gc, task, stats)("GC Termination Stats"); 4138 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 4139 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 4140 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 4141 } 4142 4143 void G1CollectedHeap::print_termination_stats(uint worker_id, 4144 double elapsed_ms, 4145 double strong_roots_ms, 4146 double term_ms, 4147 size_t term_attempts, 4148 size_t alloc_buffer_waste, 4149 size_t undo_waste) const { 4150 log_debug(gc, task, stats) 4151 ("%3d %9.2f %9.2f %6.2f " 4152 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 4153 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 4154 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 4155 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 4156 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 4157 alloc_buffer_waste * HeapWordSize / K, 4158 undo_waste * HeapWordSize / K); 4159 } 4160 4161 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 4162 private: 4163 BoolObjectClosure* _is_alive; 4164 int _initial_string_table_size; 4165 int _initial_symbol_table_size; 4166 4167 bool _process_strings; 4168 int _strings_processed; 4169 int _strings_removed; 4170 4171 bool _process_symbols; 4172 int _symbols_processed; 4173 int _symbols_removed; 4174 4175 public: 4176 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 4177 AbstractGangTask("String/Symbol Unlinking"), 4178 _is_alive(is_alive), 4179 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 4180 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 4181 4182 _initial_string_table_size = StringTable::the_table()->table_size(); 4183 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 4184 if (process_strings) { 4185 StringTable::clear_parallel_claimed_index(); 4186 } 4187 if (process_symbols) { 4188 SymbolTable::clear_parallel_claimed_index(); 4189 } 4190 } 4191 4192 ~G1StringSymbolTableUnlinkTask() { 4193 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 4194 "claim value %d after unlink less than initial string table size %d", 4195 StringTable::parallel_claimed_index(), _initial_string_table_size); 4196 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 4197 "claim value %d after unlink less than initial symbol table size %d", 4198 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 4199 4200 log_debug(gc, stringdedup)("Cleaned string and symbol table, " 4201 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 4202 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 4203 strings_processed(), strings_removed(), 4204 symbols_processed(), symbols_removed()); 4205 } 4206 4207 void work(uint worker_id) { 4208 int strings_processed = 0; 4209 int strings_removed = 0; 4210 int symbols_processed = 0; 4211 int symbols_removed = 0; 4212 if (_process_strings) { 4213 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 4214 Atomic::add(strings_processed, &_strings_processed); 4215 Atomic::add(strings_removed, &_strings_removed); 4216 } 4217 if (_process_symbols) { 4218 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 4219 Atomic::add(symbols_processed, &_symbols_processed); 4220 Atomic::add(symbols_removed, &_symbols_removed); 4221 } 4222 } 4223 4224 size_t strings_processed() const { return (size_t)_strings_processed; } 4225 size_t strings_removed() const { return (size_t)_strings_removed; } 4226 4227 size_t symbols_processed() const { return (size_t)_symbols_processed; } 4228 size_t symbols_removed() const { return (size_t)_symbols_removed; } 4229 }; 4230 4231 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 4232 private: 4233 static Monitor* _lock; 4234 4235 BoolObjectClosure* const _is_alive; 4236 const bool _unloading_occurred; 4237 const uint _num_workers; 4238 4239 // Variables used to claim nmethods. 4240 nmethod* _first_nmethod; 4241 volatile nmethod* _claimed_nmethod; 4242 4243 // The list of nmethods that need to be processed by the second pass. 4244 volatile nmethod* _postponed_list; 4245 volatile uint _num_entered_barrier; 4246 4247 public: 4248 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 4249 _is_alive(is_alive), 4250 _unloading_occurred(unloading_occurred), 4251 _num_workers(num_workers), 4252 _first_nmethod(NULL), 4253 _claimed_nmethod(NULL), 4254 _postponed_list(NULL), 4255 _num_entered_barrier(0) 4256 { 4257 nmethod::increase_unloading_clock(); 4258 // Get first alive nmethod 4259 NMethodIterator iter = NMethodIterator(); 4260 if(iter.next_alive()) { 4261 _first_nmethod = iter.method(); 4262 } 4263 _claimed_nmethod = (volatile nmethod*)_first_nmethod; 4264 } 4265 4266 ~G1CodeCacheUnloadingTask() { 4267 CodeCache::verify_clean_inline_caches(); 4268 4269 CodeCache::set_needs_cache_clean(false); 4270 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 4271 4272 CodeCache::verify_icholder_relocations(); 4273 } 4274 4275 private: 4276 void add_to_postponed_list(nmethod* nm) { 4277 nmethod* old; 4278 do { 4279 old = (nmethod*)_postponed_list; 4280 nm->set_unloading_next(old); 4281 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 4282 } 4283 4284 void clean_nmethod(nmethod* nm) { 4285 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 4286 4287 if (postponed) { 4288 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 4289 add_to_postponed_list(nm); 4290 } 4291 4292 // Mark that this thread has been cleaned/unloaded. 4293 // After this call, it will be safe to ask if this nmethod was unloaded or not. 4294 nm->set_unloading_clock(nmethod::global_unloading_clock()); 4295 } 4296 4297 void clean_nmethod_postponed(nmethod* nm) { 4298 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 4299 } 4300 4301 static const int MaxClaimNmethods = 16; 4302 4303 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) { 4304 nmethod* first; 4305 NMethodIterator last; 4306 4307 do { 4308 *num_claimed_nmethods = 0; 4309 4310 first = (nmethod*)_claimed_nmethod; 4311 last = NMethodIterator(first); 4312 4313 if (first != NULL) { 4314 4315 for (int i = 0; i < MaxClaimNmethods; i++) { 4316 if (!last.next_alive()) { 4317 break; 4318 } 4319 claimed_nmethods[i] = last.method(); 4320 (*num_claimed_nmethods)++; 4321 } 4322 } 4323 4324 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 4325 } 4326 4327 nmethod* claim_postponed_nmethod() { 4328 nmethod* claim; 4329 nmethod* next; 4330 4331 do { 4332 claim = (nmethod*)_postponed_list; 4333 if (claim == NULL) { 4334 return NULL; 4335 } 4336 4337 next = claim->unloading_next(); 4338 4339 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 4340 4341 return claim; 4342 } 4343 4344 public: 4345 // Mark that we're done with the first pass of nmethod cleaning. 4346 void barrier_mark(uint worker_id) { 4347 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4348 _num_entered_barrier++; 4349 if (_num_entered_barrier == _num_workers) { 4350 ml.notify_all(); 4351 } 4352 } 4353 4354 // See if we have to wait for the other workers to 4355 // finish their first-pass nmethod cleaning work. 4356 void barrier_wait(uint worker_id) { 4357 if (_num_entered_barrier < _num_workers) { 4358 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4359 while (_num_entered_barrier < _num_workers) { 4360 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 4361 } 4362 } 4363 } 4364 4365 // Cleaning and unloading of nmethods. Some work has to be postponed 4366 // to the second pass, when we know which nmethods survive. 4367 void work_first_pass(uint worker_id) { 4368 // The first nmethods is claimed by the first worker. 4369 if (worker_id == 0 && _first_nmethod != NULL) { 4370 clean_nmethod(_first_nmethod); 4371 _first_nmethod = NULL; 4372 } 4373 4374 int num_claimed_nmethods; 4375 nmethod* claimed_nmethods[MaxClaimNmethods]; 4376 4377 while (true) { 4378 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 4379 4380 if (num_claimed_nmethods == 0) { 4381 break; 4382 } 4383 4384 for (int i = 0; i < num_claimed_nmethods; i++) { 4385 clean_nmethod(claimed_nmethods[i]); 4386 } 4387 } 4388 } 4389 4390 void work_second_pass(uint worker_id) { 4391 nmethod* nm; 4392 // Take care of postponed nmethods. 4393 while ((nm = claim_postponed_nmethod()) != NULL) { 4394 clean_nmethod_postponed(nm); 4395 } 4396 } 4397 }; 4398 4399 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 4400 4401 class G1KlassCleaningTask : public StackObj { 4402 BoolObjectClosure* _is_alive; 4403 volatile jint _clean_klass_tree_claimed; 4404 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 4405 4406 public: 4407 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 4408 _is_alive(is_alive), 4409 _clean_klass_tree_claimed(0), 4410 _klass_iterator() { 4411 } 4412 4413 private: 4414 bool claim_clean_klass_tree_task() { 4415 if (_clean_klass_tree_claimed) { 4416 return false; 4417 } 4418 4419 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 4420 } 4421 4422 InstanceKlass* claim_next_klass() { 4423 Klass* klass; 4424 do { 4425 klass =_klass_iterator.next_klass(); 4426 } while (klass != NULL && !klass->is_instance_klass()); 4427 4428 // this can be null so don't call InstanceKlass::cast 4429 return static_cast<InstanceKlass*>(klass); 4430 } 4431 4432 public: 4433 4434 void clean_klass(InstanceKlass* ik) { 4435 ik->clean_weak_instanceklass_links(_is_alive); 4436 } 4437 4438 void work() { 4439 ResourceMark rm; 4440 4441 // One worker will clean the subklass/sibling klass tree. 4442 if (claim_clean_klass_tree_task()) { 4443 Klass::clean_subklass_tree(_is_alive); 4444 } 4445 4446 // All workers will help cleaning the classes, 4447 InstanceKlass* klass; 4448 while ((klass = claim_next_klass()) != NULL) { 4449 clean_klass(klass); 4450 } 4451 } 4452 }; 4453 4454 // To minimize the remark pause times, the tasks below are done in parallel. 4455 class G1ParallelCleaningTask : public AbstractGangTask { 4456 private: 4457 G1StringSymbolTableUnlinkTask _string_symbol_task; 4458 G1CodeCacheUnloadingTask _code_cache_task; 4459 G1KlassCleaningTask _klass_cleaning_task; 4460 4461 public: 4462 // The constructor is run in the VMThread. 4463 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 4464 AbstractGangTask("Parallel Cleaning"), 4465 _string_symbol_task(is_alive, process_strings, process_symbols), 4466 _code_cache_task(num_workers, is_alive, unloading_occurred), 4467 _klass_cleaning_task(is_alive) { 4468 } 4469 4470 // The parallel work done by all worker threads. 4471 void work(uint worker_id) { 4472 // Do first pass of code cache cleaning. 4473 _code_cache_task.work_first_pass(worker_id); 4474 4475 // Let the threads mark that the first pass is done. 4476 _code_cache_task.barrier_mark(worker_id); 4477 4478 // Clean the Strings and Symbols. 4479 _string_symbol_task.work(worker_id); 4480 4481 // Wait for all workers to finish the first code cache cleaning pass. 4482 _code_cache_task.barrier_wait(worker_id); 4483 4484 // Do the second code cache cleaning work, which realize on 4485 // the liveness information gathered during the first pass. 4486 _code_cache_task.work_second_pass(worker_id); 4487 4488 // Clean all klasses that were not unloaded. 4489 _klass_cleaning_task.work(); 4490 } 4491 }; 4492 4493 4494 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 4495 bool process_strings, 4496 bool process_symbols, 4497 bool class_unloading_occurred) { 4498 uint n_workers = workers()->active_workers(); 4499 4500 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 4501 n_workers, class_unloading_occurred); 4502 workers()->run_task(&g1_unlink_task); 4503 } 4504 4505 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 4506 bool process_strings, bool process_symbols) { 4507 { 4508 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 4509 workers()->run_task(&g1_unlink_task); 4510 } 4511 4512 if (G1StringDedup::is_enabled()) { 4513 G1StringDedup::unlink(is_alive); 4514 } 4515 } 4516 4517 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 4518 private: 4519 DirtyCardQueueSet* _queue; 4520 G1CollectedHeap* _g1h; 4521 public: 4522 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 4523 _queue(queue), _g1h(g1h) { } 4524 4525 virtual void work(uint worker_id) { 4526 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 4527 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 4528 4529 RedirtyLoggedCardTableEntryClosure cl(_g1h); 4530 _queue->par_apply_closure_to_all_completed_buffers(&cl); 4531 4532 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 4533 } 4534 }; 4535 4536 void G1CollectedHeap::redirty_logged_cards() { 4537 double redirty_logged_cards_start = os::elapsedTime(); 4538 4539 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 4540 dirty_card_queue_set().reset_for_par_iteration(); 4541 workers()->run_task(&redirty_task); 4542 4543 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 4544 dcq.merge_bufferlists(&dirty_card_queue_set()); 4545 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 4546 4547 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 4548 } 4549 4550 // Weak Reference Processing support 4551 4552 // An always "is_alive" closure that is used to preserve referents. 4553 // If the object is non-null then it's alive. Used in the preservation 4554 // of referent objects that are pointed to by reference objects 4555 // discovered by the CM ref processor. 4556 class G1AlwaysAliveClosure: public BoolObjectClosure { 4557 G1CollectedHeap* _g1; 4558 public: 4559 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4560 bool do_object_b(oop p) { 4561 if (p != NULL) { 4562 return true; 4563 } 4564 return false; 4565 } 4566 }; 4567 4568 bool G1STWIsAliveClosure::do_object_b(oop p) { 4569 // An object is reachable if it is outside the collection set, 4570 // or is inside and copied. 4571 return !_g1->is_in_cset(p) || p->is_forwarded(); 4572 } 4573 4574 // Non Copying Keep Alive closure 4575 class G1KeepAliveClosure: public OopClosure { 4576 G1CollectedHeap* _g1; 4577 public: 4578 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4579 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 4580 void do_oop(oop* p) { 4581 oop obj = *p; 4582 assert(obj != NULL, "the caller should have filtered out NULL values"); 4583 4584 const InCSetState cset_state = _g1->in_cset_state(obj); 4585 if (!cset_state.is_in_cset_or_humongous()) { 4586 return; 4587 } 4588 if (cset_state.is_in_cset()) { 4589 assert( obj->is_forwarded(), "invariant" ); 4590 *p = obj->forwardee(); 4591 } else { 4592 assert(!obj->is_forwarded(), "invariant" ); 4593 assert(cset_state.is_humongous(), 4594 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 4595 _g1->set_humongous_is_live(obj); 4596 } 4597 } 4598 }; 4599 4600 // Copying Keep Alive closure - can be called from both 4601 // serial and parallel code as long as different worker 4602 // threads utilize different G1ParScanThreadState instances 4603 // and different queues. 4604 4605 class G1CopyingKeepAliveClosure: public OopClosure { 4606 G1CollectedHeap* _g1h; 4607 OopClosure* _copy_non_heap_obj_cl; 4608 G1ParScanThreadState* _par_scan_state; 4609 4610 public: 4611 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4612 OopClosure* non_heap_obj_cl, 4613 G1ParScanThreadState* pss): 4614 _g1h(g1h), 4615 _copy_non_heap_obj_cl(non_heap_obj_cl), 4616 _par_scan_state(pss) 4617 {} 4618 4619 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4620 virtual void do_oop( oop* p) { do_oop_work(p); } 4621 4622 template <class T> void do_oop_work(T* p) { 4623 oop obj = oopDesc::load_decode_heap_oop(p); 4624 4625 if (_g1h->is_in_cset_or_humongous(obj)) { 4626 // If the referent object has been forwarded (either copied 4627 // to a new location or to itself in the event of an 4628 // evacuation failure) then we need to update the reference 4629 // field and, if both reference and referent are in the G1 4630 // heap, update the RSet for the referent. 4631 // 4632 // If the referent has not been forwarded then we have to keep 4633 // it alive by policy. Therefore we have copy the referent. 4634 // 4635 // If the reference field is in the G1 heap then we can push 4636 // on the PSS queue. When the queue is drained (after each 4637 // phase of reference processing) the object and it's followers 4638 // will be copied, the reference field set to point to the 4639 // new location, and the RSet updated. Otherwise we need to 4640 // use the the non-heap or metadata closures directly to copy 4641 // the referent object and update the pointer, while avoiding 4642 // updating the RSet. 4643 4644 if (_g1h->is_in_g1_reserved(p)) { 4645 _par_scan_state->push_on_queue(p); 4646 } else { 4647 assert(!Metaspace::contains((const void*)p), 4648 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4649 _copy_non_heap_obj_cl->do_oop(p); 4650 } 4651 } 4652 } 4653 }; 4654 4655 // Serial drain queue closure. Called as the 'complete_gc' 4656 // closure for each discovered list in some of the 4657 // reference processing phases. 4658 4659 class G1STWDrainQueueClosure: public VoidClosure { 4660 protected: 4661 G1CollectedHeap* _g1h; 4662 G1ParScanThreadState* _par_scan_state; 4663 4664 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4665 4666 public: 4667 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4668 _g1h(g1h), 4669 _par_scan_state(pss) 4670 { } 4671 4672 void do_void() { 4673 G1ParScanThreadState* const pss = par_scan_state(); 4674 pss->trim_queue(); 4675 } 4676 }; 4677 4678 // Parallel Reference Processing closures 4679 4680 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4681 // processing during G1 evacuation pauses. 4682 4683 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4684 private: 4685 G1CollectedHeap* _g1h; 4686 G1ParScanThreadStateSet* _pss; 4687 RefToScanQueueSet* _queues; 4688 WorkGang* _workers; 4689 uint _active_workers; 4690 4691 public: 4692 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4693 G1ParScanThreadStateSet* per_thread_states, 4694 WorkGang* workers, 4695 RefToScanQueueSet *task_queues, 4696 uint n_workers) : 4697 _g1h(g1h), 4698 _pss(per_thread_states), 4699 _queues(task_queues), 4700 _workers(workers), 4701 _active_workers(n_workers) 4702 { 4703 assert(n_workers > 0, "shouldn't call this otherwise"); 4704 } 4705 4706 // Executes the given task using concurrent marking worker threads. 4707 virtual void execute(ProcessTask& task); 4708 virtual void execute(EnqueueTask& task); 4709 }; 4710 4711 // Gang task for possibly parallel reference processing 4712 4713 class G1STWRefProcTaskProxy: public AbstractGangTask { 4714 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4715 ProcessTask& _proc_task; 4716 G1CollectedHeap* _g1h; 4717 G1ParScanThreadStateSet* _pss; 4718 RefToScanQueueSet* _task_queues; 4719 ParallelTaskTerminator* _terminator; 4720 4721 public: 4722 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4723 G1CollectedHeap* g1h, 4724 G1ParScanThreadStateSet* per_thread_states, 4725 RefToScanQueueSet *task_queues, 4726 ParallelTaskTerminator* terminator) : 4727 AbstractGangTask("Process reference objects in parallel"), 4728 _proc_task(proc_task), 4729 _g1h(g1h), 4730 _pss(per_thread_states), 4731 _task_queues(task_queues), 4732 _terminator(terminator) 4733 {} 4734 4735 virtual void work(uint worker_id) { 4736 // The reference processing task executed by a single worker. 4737 ResourceMark rm; 4738 HandleMark hm; 4739 4740 G1STWIsAliveClosure is_alive(_g1h); 4741 4742 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4743 pss->set_ref_processor(NULL); 4744 4745 // Keep alive closure. 4746 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4747 4748 // Complete GC closure 4749 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4750 4751 // Call the reference processing task's work routine. 4752 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4753 4754 // Note we cannot assert that the refs array is empty here as not all 4755 // of the processing tasks (specifically phase2 - pp2_work) execute 4756 // the complete_gc closure (which ordinarily would drain the queue) so 4757 // the queue may not be empty. 4758 } 4759 }; 4760 4761 // Driver routine for parallel reference processing. 4762 // Creates an instance of the ref processing gang 4763 // task and has the worker threads execute it. 4764 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4765 assert(_workers != NULL, "Need parallel worker threads."); 4766 4767 ParallelTaskTerminator terminator(_active_workers, _queues); 4768 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4769 4770 _workers->run_task(&proc_task_proxy); 4771 } 4772 4773 // Gang task for parallel reference enqueueing. 4774 4775 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4776 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4777 EnqueueTask& _enq_task; 4778 4779 public: 4780 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4781 AbstractGangTask("Enqueue reference objects in parallel"), 4782 _enq_task(enq_task) 4783 { } 4784 4785 virtual void work(uint worker_id) { 4786 _enq_task.work(worker_id); 4787 } 4788 }; 4789 4790 // Driver routine for parallel reference enqueueing. 4791 // Creates an instance of the ref enqueueing gang 4792 // task and has the worker threads execute it. 4793 4794 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4795 assert(_workers != NULL, "Need parallel worker threads."); 4796 4797 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4798 4799 _workers->run_task(&enq_task_proxy); 4800 } 4801 4802 // End of weak reference support closures 4803 4804 // Abstract task used to preserve (i.e. copy) any referent objects 4805 // that are in the collection set and are pointed to by reference 4806 // objects discovered by the CM ref processor. 4807 4808 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4809 protected: 4810 G1CollectedHeap* _g1h; 4811 G1ParScanThreadStateSet* _pss; 4812 RefToScanQueueSet* _queues; 4813 ParallelTaskTerminator _terminator; 4814 uint _n_workers; 4815 4816 public: 4817 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4818 AbstractGangTask("ParPreserveCMReferents"), 4819 _g1h(g1h), 4820 _pss(per_thread_states), 4821 _queues(task_queues), 4822 _terminator(workers, _queues), 4823 _n_workers(workers) 4824 { } 4825 4826 void work(uint worker_id) { 4827 ResourceMark rm; 4828 HandleMark hm; 4829 4830 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4831 pss->set_ref_processor(NULL); 4832 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4833 4834 // Is alive closure 4835 G1AlwaysAliveClosure always_alive(_g1h); 4836 4837 // Copying keep alive closure. Applied to referent objects that need 4838 // to be copied. 4839 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4840 4841 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4842 4843 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4844 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4845 4846 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4847 // So this must be true - but assert just in case someone decides to 4848 // change the worker ids. 4849 assert(worker_id < limit, "sanity"); 4850 assert(!rp->discovery_is_atomic(), "check this code"); 4851 4852 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4853 for (uint idx = worker_id; idx < limit; idx += stride) { 4854 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4855 4856 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4857 while (iter.has_next()) { 4858 // Since discovery is not atomic for the CM ref processor, we 4859 // can see some null referent objects. 4860 iter.load_ptrs(DEBUG_ONLY(true)); 4861 oop ref = iter.obj(); 4862 4863 // This will filter nulls. 4864 if (iter.is_referent_alive()) { 4865 iter.make_referent_alive(); 4866 } 4867 iter.move_to_next(); 4868 } 4869 } 4870 4871 // Drain the queue - which may cause stealing 4872 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4873 drain_queue.do_void(); 4874 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4875 assert(pss->queue_is_empty(), "should be"); 4876 } 4877 }; 4878 4879 void G1CollectedHeap::process_weak_jni_handles() { 4880 double ref_proc_start = os::elapsedTime(); 4881 4882 G1STWIsAliveClosure is_alive(this); 4883 G1KeepAliveClosure keep_alive(this); 4884 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 4885 4886 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4887 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4888 } 4889 4890 // Weak Reference processing during an evacuation pause (part 1). 4891 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4892 double ref_proc_start = os::elapsedTime(); 4893 4894 ReferenceProcessor* rp = _ref_processor_stw; 4895 assert(rp->discovery_enabled(), "should have been enabled"); 4896 4897 // Any reference objects, in the collection set, that were 'discovered' 4898 // by the CM ref processor should have already been copied (either by 4899 // applying the external root copy closure to the discovered lists, or 4900 // by following an RSet entry). 4901 // 4902 // But some of the referents, that are in the collection set, that these 4903 // reference objects point to may not have been copied: the STW ref 4904 // processor would have seen that the reference object had already 4905 // been 'discovered' and would have skipped discovering the reference, 4906 // but would not have treated the reference object as a regular oop. 4907 // As a result the copy closure would not have been applied to the 4908 // referent object. 4909 // 4910 // We need to explicitly copy these referent objects - the references 4911 // will be processed at the end of remarking. 4912 // 4913 // We also need to do this copying before we process the reference 4914 // objects discovered by the STW ref processor in case one of these 4915 // referents points to another object which is also referenced by an 4916 // object discovered by the STW ref processor. 4917 4918 uint no_of_gc_workers = workers()->active_workers(); 4919 4920 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4921 per_thread_states, 4922 no_of_gc_workers, 4923 _task_queues); 4924 4925 workers()->run_task(&keep_cm_referents); 4926 4927 // Closure to test whether a referent is alive. 4928 G1STWIsAliveClosure is_alive(this); 4929 4930 // Even when parallel reference processing is enabled, the processing 4931 // of JNI refs is serial and performed serially by the current thread 4932 // rather than by a worker. The following PSS will be used for processing 4933 // JNI refs. 4934 4935 // Use only a single queue for this PSS. 4936 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4937 pss->set_ref_processor(NULL); 4938 assert(pss->queue_is_empty(), "pre-condition"); 4939 4940 // Keep alive closure. 4941 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4942 4943 // Serial Complete GC closure 4944 G1STWDrainQueueClosure drain_queue(this, pss); 4945 4946 // Setup the soft refs policy... 4947 rp->setup_policy(false); 4948 4949 ReferenceProcessorStats stats; 4950 if (!rp->processing_is_mt()) { 4951 // Serial reference processing... 4952 stats = rp->process_discovered_references(&is_alive, 4953 &keep_alive, 4954 &drain_queue, 4955 NULL, 4956 _gc_timer_stw); 4957 } else { 4958 // Parallel reference processing 4959 assert(rp->num_q() == no_of_gc_workers, "sanity"); 4960 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 4961 4962 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4963 stats = rp->process_discovered_references(&is_alive, 4964 &keep_alive, 4965 &drain_queue, 4966 &par_task_executor, 4967 _gc_timer_stw); 4968 } 4969 4970 _gc_tracer_stw->report_gc_reference_stats(stats); 4971 4972 // We have completed copying any necessary live referent objects. 4973 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4974 4975 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4976 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4977 } 4978 4979 // Weak Reference processing during an evacuation pause (part 2). 4980 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4981 double ref_enq_start = os::elapsedTime(); 4982 4983 ReferenceProcessor* rp = _ref_processor_stw; 4984 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4985 4986 // Now enqueue any remaining on the discovered lists on to 4987 // the pending list. 4988 if (!rp->processing_is_mt()) { 4989 // Serial reference processing... 4990 rp->enqueue_discovered_references(); 4991 } else { 4992 // Parallel reference enqueueing 4993 4994 uint n_workers = workers()->active_workers(); 4995 4996 assert(rp->num_q() == n_workers, "sanity"); 4997 assert(n_workers <= rp->max_num_q(), "sanity"); 4998 4999 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 5000 rp->enqueue_discovered_references(&par_task_executor); 5001 } 5002 5003 rp->verify_no_references_recorded(); 5004 assert(!rp->discovery_enabled(), "should have been disabled"); 5005 5006 // FIXME 5007 // CM's reference processing also cleans up the string and symbol tables. 5008 // Should we do that here also? We could, but it is a serial operation 5009 // and could significantly increase the pause time. 5010 5011 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5012 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5013 } 5014 5015 void G1CollectedHeap::pre_evacuate_collection_set() { 5016 _expand_heap_after_alloc_failure = true; 5017 _evacuation_failed = false; 5018 5019 // Disable the hot card cache. 5020 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5021 hot_card_cache->reset_hot_cache_claimed_index(); 5022 hot_card_cache->set_use_cache(false); 5023 5024 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5025 } 5026 5027 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 5028 // Should G1EvacuationFailureALot be in effect for this GC? 5029 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5030 5031 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5032 double start_par_time_sec = os::elapsedTime(); 5033 double end_par_time_sec; 5034 5035 { 5036 const uint n_workers = workers()->active_workers(); 5037 G1RootProcessor root_processor(this, n_workers); 5038 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 5039 // InitialMark needs claim bits to keep track of the marked-through CLDs. 5040 if (collector_state()->during_initial_mark_pause()) { 5041 ClassLoaderDataGraph::clear_claimed_marks(); 5042 } 5043 5044 print_termination_stats_hdr(); 5045 5046 workers()->run_task(&g1_par_task); 5047 end_par_time_sec = os::elapsedTime(); 5048 5049 // Closing the inner scope will execute the destructor 5050 // for the G1RootProcessor object. We record the current 5051 // elapsed time before closing the scope so that time 5052 // taken for the destructor is NOT included in the 5053 // reported parallel time. 5054 } 5055 5056 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 5057 5058 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5059 phase_times->record_par_time(par_time_ms); 5060 5061 double code_root_fixup_time_ms = 5062 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5063 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 5064 } 5065 5066 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 5067 // Process any discovered reference objects - we have 5068 // to do this _before_ we retire the GC alloc regions 5069 // as we may have to copy some 'reachable' referent 5070 // objects (and their reachable sub-graphs) that were 5071 // not copied during the pause. 5072 if (g1_policy()->should_process_references()) { 5073 process_discovered_references(per_thread_states); 5074 } else { 5075 ref_processor_stw()->verify_no_references_recorded(); 5076 process_weak_jni_handles(); 5077 } 5078 5079 if (G1StringDedup::is_enabled()) { 5080 double fixup_start = os::elapsedTime(); 5081 5082 G1STWIsAliveClosure is_alive(this); 5083 G1KeepAliveClosure keep_alive(this); 5084 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 5085 5086 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 5087 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 5088 } 5089 5090 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5091 5092 if (evacuation_failed()) { 5093 restore_after_evac_failure(); 5094 5095 // Reset the G1EvacuationFailureALot counters and flags 5096 // Note: the values are reset only when an actual 5097 // evacuation failure occurs. 5098 NOT_PRODUCT(reset_evacuation_should_fail();) 5099 } 5100 5101 // Enqueue any remaining references remaining on the STW 5102 // reference processor's discovered lists. We need to do 5103 // this after the card table is cleaned (and verified) as 5104 // the act of enqueueing entries on to the pending list 5105 // will log these updates (and dirty their associated 5106 // cards). We need these updates logged to update any 5107 // RSets. 5108 if (g1_policy()->should_process_references()) { 5109 enqueue_discovered_references(per_thread_states); 5110 } else { 5111 g1_policy()->phase_times()->record_ref_enq_time(0); 5112 } 5113 5114 _allocator->release_gc_alloc_regions(evacuation_info); 5115 5116 per_thread_states->flush(); 5117 5118 record_obj_copy_mem_stats(); 5119 5120 _survivor_evac_stats.adjust_desired_plab_sz(); 5121 _old_evac_stats.adjust_desired_plab_sz(); 5122 5123 // Reset and re-enable the hot card cache. 5124 // Note the counts for the cards in the regions in the 5125 // collection set are reset when the collection set is freed. 5126 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5127 hot_card_cache->reset_hot_cache(); 5128 hot_card_cache->set_use_cache(true); 5129 5130 purge_code_root_memory(); 5131 5132 redirty_logged_cards(); 5133 #if defined(COMPILER2) || INCLUDE_JVMCI 5134 DerivedPointerTable::update_pointers(); 5135 #endif 5136 } 5137 5138 void G1CollectedHeap::record_obj_copy_mem_stats() { 5139 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 5140 5141 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 5142 create_g1_evac_summary(&_old_evac_stats)); 5143 } 5144 5145 void G1CollectedHeap::free_region(HeapRegion* hr, 5146 FreeRegionList* free_list, 5147 bool par, 5148 bool locked) { 5149 assert(!hr->is_free(), "the region should not be free"); 5150 assert(!hr->is_empty(), "the region should not be empty"); 5151 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 5152 assert(free_list != NULL, "pre-condition"); 5153 5154 if (G1VerifyBitmaps) { 5155 MemRegion mr(hr->bottom(), hr->end()); 5156 concurrent_mark()->clearRangePrevBitmap(mr); 5157 } 5158 5159 // Clear the card counts for this region. 5160 // Note: we only need to do this if the region is not young 5161 // (since we don't refine cards in young regions). 5162 if (!hr->is_young()) { 5163 _cg1r->hot_card_cache()->reset_card_counts(hr); 5164 } 5165 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 5166 free_list->add_ordered(hr); 5167 } 5168 5169 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5170 FreeRegionList* free_list, 5171 bool par) { 5172 assert(hr->is_humongous(), "this is only for humongous regions"); 5173 assert(free_list != NULL, "pre-condition"); 5174 hr->clear_humongous(); 5175 free_region(hr, free_list, par); 5176 } 5177 5178 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 5179 const uint humongous_regions_removed) { 5180 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 5181 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5182 _old_set.bulk_remove(old_regions_removed); 5183 _humongous_set.bulk_remove(humongous_regions_removed); 5184 } 5185 5186 } 5187 5188 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 5189 assert(list != NULL, "list can't be null"); 5190 if (!list->is_empty()) { 5191 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 5192 _hrm.insert_list_into_free_list(list); 5193 } 5194 } 5195 5196 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 5197 decrease_used(bytes); 5198 } 5199 5200 class G1ParCleanupCTTask : public AbstractGangTask { 5201 G1SATBCardTableModRefBS* _ct_bs; 5202 G1CollectedHeap* _g1h; 5203 HeapRegion* volatile _su_head; 5204 public: 5205 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 5206 G1CollectedHeap* g1h) : 5207 AbstractGangTask("G1 Par Cleanup CT Task"), 5208 _ct_bs(ct_bs), _g1h(g1h) { } 5209 5210 void work(uint worker_id) { 5211 HeapRegion* r; 5212 while (r = _g1h->pop_dirty_cards_region()) { 5213 clear_cards(r); 5214 } 5215 } 5216 5217 void clear_cards(HeapRegion* r) { 5218 // Cards of the survivors should have already been dirtied. 5219 if (!r->is_survivor()) { 5220 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 5221 } 5222 } 5223 }; 5224 5225 #ifndef PRODUCT 5226 class G1VerifyCardTableCleanup: public HeapRegionClosure { 5227 G1CollectedHeap* _g1h; 5228 G1SATBCardTableModRefBS* _ct_bs; 5229 public: 5230 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs) 5231 : _g1h(g1h), _ct_bs(ct_bs) { } 5232 virtual bool doHeapRegion(HeapRegion* r) { 5233 if (r->is_survivor()) { 5234 _g1h->verify_dirty_region(r); 5235 } else { 5236 _g1h->verify_not_dirty_region(r); 5237 } 5238 return false; 5239 } 5240 }; 5241 5242 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 5243 // All of the region should be clean. 5244 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5245 MemRegion mr(hr->bottom(), hr->end()); 5246 ct_bs->verify_not_dirty_region(mr); 5247 } 5248 5249 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 5250 // We cannot guarantee that [bottom(),end()] is dirty. Threads 5251 // dirty allocated blocks as they allocate them. The thread that 5252 // retires each region and replaces it with a new one will do a 5253 // maximal allocation to fill in [pre_dummy_top(),end()] but will 5254 // not dirty that area (one less thing to have to do while holding 5255 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 5256 // is dirty. 5257 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5258 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 5259 if (hr->is_young()) { 5260 ct_bs->verify_g1_young_region(mr); 5261 } else { 5262 ct_bs->verify_dirty_region(mr); 5263 } 5264 } 5265 5266 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 5267 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5268 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 5269 verify_dirty_region(hr); 5270 } 5271 } 5272 5273 void G1CollectedHeap::verify_dirty_young_regions() { 5274 verify_dirty_young_list(_young_list->first_region()); 5275 } 5276 5277 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 5278 HeapWord* tams, HeapWord* end) { 5279 guarantee(tams <= end, 5280 "tams: " PTR_FORMAT " end: " PTR_FORMAT, p2i(tams), p2i(end)); 5281 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end); 5282 if (result < end) { 5283 log_info(gc, verify)("## wrong marked address on %s bitmap: " PTR_FORMAT, bitmap_name, p2i(result)); 5284 log_info(gc, verify)("## %s tams: " PTR_FORMAT " end: " PTR_FORMAT, bitmap_name, p2i(tams), p2i(end)); 5285 return false; 5286 } 5287 return true; 5288 } 5289 5290 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) { 5291 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap(); 5292 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap(); 5293 5294 HeapWord* bottom = hr->bottom(); 5295 HeapWord* ptams = hr->prev_top_at_mark_start(); 5296 HeapWord* ntams = hr->next_top_at_mark_start(); 5297 HeapWord* end = hr->end(); 5298 5299 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end); 5300 5301 bool res_n = true; 5302 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window 5303 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap 5304 // if we happen to be in that state. 5305 if (collector_state()->mark_in_progress() || !_cmThread->in_progress()) { 5306 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end); 5307 } 5308 if (!res_p || !res_n) { 5309 log_info(gc, verify)("#### Bitmap verification failed for " HR_FORMAT, HR_FORMAT_PARAMS(hr)); 5310 log_info(gc, verify)("#### Caller: %s", caller); 5311 return false; 5312 } 5313 return true; 5314 } 5315 5316 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) { 5317 if (!G1VerifyBitmaps) return; 5318 5319 guarantee(verify_bitmaps(caller, hr), "bitmap verification"); 5320 } 5321 5322 class G1VerifyBitmapClosure : public HeapRegionClosure { 5323 private: 5324 const char* _caller; 5325 G1CollectedHeap* _g1h; 5326 bool _failures; 5327 5328 public: 5329 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) : 5330 _caller(caller), _g1h(g1h), _failures(false) { } 5331 5332 bool failures() { return _failures; } 5333 5334 virtual bool doHeapRegion(HeapRegion* hr) { 5335 bool result = _g1h->verify_bitmaps(_caller, hr); 5336 if (!result) { 5337 _failures = true; 5338 } 5339 return false; 5340 } 5341 }; 5342 5343 void G1CollectedHeap::check_bitmaps(const char* caller) { 5344 if (!G1VerifyBitmaps) return; 5345 5346 G1VerifyBitmapClosure cl(caller, this); 5347 heap_region_iterate(&cl); 5348 guarantee(!cl.failures(), "bitmap verification"); 5349 } 5350 5351 class G1CheckCSetFastTableClosure : public HeapRegionClosure { 5352 private: 5353 bool _failures; 5354 public: 5355 G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { } 5356 5357 virtual bool doHeapRegion(HeapRegion* hr) { 5358 uint i = hr->hrm_index(); 5359 InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i); 5360 if (hr->is_humongous()) { 5361 if (hr->in_collection_set()) { 5362 log_info(gc, verify)("## humongous region %u in CSet", i); 5363 _failures = true; 5364 return true; 5365 } 5366 if (cset_state.is_in_cset()) { 5367 log_info(gc, verify)("## inconsistent cset state " CSETSTATE_FORMAT " for humongous region %u", cset_state.value(), i); 5368 _failures = true; 5369 return true; 5370 } 5371 if (hr->is_continues_humongous() && cset_state.is_humongous()) { 5372 log_info(gc, verify)("## inconsistent cset state " CSETSTATE_FORMAT " for continues humongous region %u", cset_state.value(), i); 5373 _failures = true; 5374 return true; 5375 } 5376 } else { 5377 if (cset_state.is_humongous()) { 5378 log_info(gc, verify)("## inconsistent cset state " CSETSTATE_FORMAT " for non-humongous region %u", cset_state.value(), i); 5379 _failures = true; 5380 return true; 5381 } 5382 if (hr->in_collection_set() != cset_state.is_in_cset()) { 5383 log_info(gc, verify)("## in CSet %d / cset state " CSETSTATE_FORMAT " inconsistency for region %u", 5384 hr->in_collection_set(), cset_state.value(), i); 5385 _failures = true; 5386 return true; 5387 } 5388 if (cset_state.is_in_cset()) { 5389 if (hr->is_young() != (cset_state.is_young())) { 5390 log_info(gc, verify)("## is_young %d / cset state " CSETSTATE_FORMAT " inconsistency for region %u", 5391 hr->is_young(), cset_state.value(), i); 5392 _failures = true; 5393 return true; 5394 } 5395 if (hr->is_old() != (cset_state.is_old())) { 5396 log_info(gc, verify)("## is_old %d / cset state " CSETSTATE_FORMAT " inconsistency for region %u", 5397 hr->is_old(), cset_state.value(), i); 5398 _failures = true; 5399 return true; 5400 } 5401 } 5402 } 5403 return false; 5404 } 5405 5406 bool failures() const { return _failures; } 5407 }; 5408 5409 bool G1CollectedHeap::check_cset_fast_test() { 5410 G1CheckCSetFastTableClosure cl; 5411 _hrm.iterate(&cl); 5412 return !cl.failures(); 5413 } 5414 #endif // PRODUCT 5415 5416 class G1ParScrubRemSetTask: public AbstractGangTask { 5417 protected: 5418 G1RemSet* _g1rs; 5419 BitMap* _region_bm; 5420 BitMap* _card_bm; 5421 HeapRegionClaimer _hrclaimer; 5422 5423 public: 5424 G1ParScrubRemSetTask(G1RemSet* g1_rs, BitMap* region_bm, BitMap* card_bm, uint num_workers) : 5425 AbstractGangTask("G1 ScrubRS"), 5426 _g1rs(g1_rs), 5427 _region_bm(region_bm), 5428 _card_bm(card_bm), 5429 _hrclaimer(num_workers) { 5430 } 5431 5432 void work(uint worker_id) { 5433 _g1rs->scrub(_region_bm, _card_bm, worker_id, &_hrclaimer); 5434 } 5435 }; 5436 5437 void G1CollectedHeap::scrub_rem_set(BitMap* region_bm, BitMap* card_bm) { 5438 uint num_workers = workers()->active_workers(); 5439 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), region_bm, card_bm, num_workers); 5440 workers()->run_task(&g1_par_scrub_rs_task); 5441 } 5442 5443 void G1CollectedHeap::cleanUpCardTable() { 5444 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5445 double start = os::elapsedTime(); 5446 5447 { 5448 // Iterate over the dirty cards region list. 5449 G1ParCleanupCTTask cleanup_task(ct_bs, this); 5450 5451 workers()->run_task(&cleanup_task); 5452 #ifndef PRODUCT 5453 if (G1VerifyCTCleanup || VerifyAfterGC) { 5454 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 5455 heap_region_iterate(&cleanup_verifier); 5456 } 5457 #endif 5458 } 5459 5460 double elapsed = os::elapsedTime() - start; 5461 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 5462 } 5463 5464 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 5465 size_t pre_used = 0; 5466 FreeRegionList local_free_list("Local List for CSet Freeing"); 5467 5468 double young_time_ms = 0.0; 5469 double non_young_time_ms = 0.0; 5470 5471 // Since the collection set is a superset of the the young list, 5472 // all we need to do to clear the young list is clear its 5473 // head and length, and unlink any young regions in the code below 5474 _young_list->clear(); 5475 5476 G1CollectorPolicy* policy = g1_policy(); 5477 5478 double start_sec = os::elapsedTime(); 5479 bool non_young = true; 5480 5481 HeapRegion* cur = cs_head; 5482 int age_bound = -1; 5483 size_t rs_lengths = 0; 5484 5485 while (cur != NULL) { 5486 assert(!is_on_master_free_list(cur), "sanity"); 5487 if (non_young) { 5488 if (cur->is_young()) { 5489 double end_sec = os::elapsedTime(); 5490 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5491 non_young_time_ms += elapsed_ms; 5492 5493 start_sec = os::elapsedTime(); 5494 non_young = false; 5495 } 5496 } else { 5497 if (!cur->is_young()) { 5498 double end_sec = os::elapsedTime(); 5499 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5500 young_time_ms += elapsed_ms; 5501 5502 start_sec = os::elapsedTime(); 5503 non_young = true; 5504 } 5505 } 5506 5507 rs_lengths += cur->rem_set()->occupied_locked(); 5508 5509 HeapRegion* next = cur->next_in_collection_set(); 5510 assert(cur->in_collection_set(), "bad CS"); 5511 cur->set_next_in_collection_set(NULL); 5512 clear_in_cset(cur); 5513 5514 if (cur->is_young()) { 5515 int index = cur->young_index_in_cset(); 5516 assert(index != -1, "invariant"); 5517 assert((uint) index < policy->young_cset_region_length(), "invariant"); 5518 size_t words_survived = surviving_young_words[index]; 5519 cur->record_surv_words_in_group(words_survived); 5520 5521 // At this point the we have 'popped' cur from the collection set 5522 // (linked via next_in_collection_set()) but it is still in the 5523 // young list (linked via next_young_region()). Clear the 5524 // _next_young_region field. 5525 cur->set_next_young_region(NULL); 5526 } else { 5527 int index = cur->young_index_in_cset(); 5528 assert(index == -1, "invariant"); 5529 } 5530 5531 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 5532 (!cur->is_young() && cur->young_index_in_cset() == -1), 5533 "invariant" ); 5534 5535 if (!cur->evacuation_failed()) { 5536 MemRegion used_mr = cur->used_region(); 5537 5538 // And the region is empty. 5539 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 5540 pre_used += cur->used(); 5541 free_region(cur, &local_free_list, false /* par */, true /* locked */); 5542 } else { 5543 cur->uninstall_surv_rate_group(); 5544 if (cur->is_young()) { 5545 cur->set_young_index_in_cset(-1); 5546 } 5547 cur->set_evacuation_failed(false); 5548 // When moving a young gen region to old gen, we "allocate" that whole region 5549 // there. This is in addition to any already evacuated objects. Notify the 5550 // policy about that. 5551 // Old gen regions do not cause an additional allocation: both the objects 5552 // still in the region and the ones already moved are accounted for elsewhere. 5553 if (cur->is_young()) { 5554 policy->add_bytes_allocated_in_old_since_last_gc(HeapRegion::GrainBytes); 5555 } 5556 // The region is now considered to be old. 5557 cur->set_old(); 5558 // Do some allocation statistics accounting. Regions that failed evacuation 5559 // are always made old, so there is no need to update anything in the young 5560 // gen statistics, but we need to update old gen statistics. 5561 size_t used_words = cur->marked_bytes() / HeapWordSize; 5562 _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words); 5563 _old_set.add(cur); 5564 evacuation_info.increment_collectionset_used_after(cur->used()); 5565 } 5566 cur = next; 5567 } 5568 5569 evacuation_info.set_regions_freed(local_free_list.length()); 5570 policy->record_max_rs_lengths(rs_lengths); 5571 policy->cset_regions_freed(); 5572 5573 double end_sec = os::elapsedTime(); 5574 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5575 5576 if (non_young) { 5577 non_young_time_ms += elapsed_ms; 5578 } else { 5579 young_time_ms += elapsed_ms; 5580 } 5581 5582 prepend_to_freelist(&local_free_list); 5583 decrement_summary_bytes(pre_used); 5584 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 5585 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 5586 } 5587 5588 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 5589 private: 5590 FreeRegionList* _free_region_list; 5591 HeapRegionSet* _proxy_set; 5592 uint _humongous_regions_removed; 5593 size_t _freed_bytes; 5594 public: 5595 5596 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 5597 _free_region_list(free_region_list), _humongous_regions_removed(0), _freed_bytes(0) { 5598 } 5599 5600 virtual bool doHeapRegion(HeapRegion* r) { 5601 if (!r->is_starts_humongous()) { 5602 return false; 5603 } 5604 5605 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 5606 5607 oop obj = (oop)r->bottom(); 5608 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 5609 5610 // The following checks whether the humongous object is live are sufficient. 5611 // The main additional check (in addition to having a reference from the roots 5612 // or the young gen) is whether the humongous object has a remembered set entry. 5613 // 5614 // A humongous object cannot be live if there is no remembered set for it 5615 // because: 5616 // - there can be no references from within humongous starts regions referencing 5617 // the object because we never allocate other objects into them. 5618 // (I.e. there are no intra-region references that may be missed by the 5619 // remembered set) 5620 // - as soon there is a remembered set entry to the humongous starts region 5621 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 5622 // until the end of a concurrent mark. 5623 // 5624 // It is not required to check whether the object has been found dead by marking 5625 // or not, in fact it would prevent reclamation within a concurrent cycle, as 5626 // all objects allocated during that time are considered live. 5627 // SATB marking is even more conservative than the remembered set. 5628 // So if at this point in the collection there is no remembered set entry, 5629 // nobody has a reference to it. 5630 // At the start of collection we flush all refinement logs, and remembered sets 5631 // are completely up-to-date wrt to references to the humongous object. 5632 // 5633 // Other implementation considerations: 5634 // - never consider object arrays at this time because they would pose 5635 // considerable effort for cleaning up the the remembered sets. This is 5636 // required because stale remembered sets might reference locations that 5637 // are currently allocated into. 5638 uint region_idx = r->hrm_index(); 5639 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 5640 !r->rem_set()->is_empty()) { 5641 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", 5642 region_idx, 5643 (size_t)obj->size() * HeapWordSize, 5644 p2i(r->bottom()), 5645 r->rem_set()->occupied(), 5646 r->rem_set()->strong_code_roots_list_length(), 5647 next_bitmap->isMarked(r->bottom()), 5648 g1h->is_humongous_reclaim_candidate(region_idx), 5649 obj->is_typeArray() 5650 ); 5651 return false; 5652 } 5653 5654 guarantee(obj->is_typeArray(), 5655 "Only eagerly reclaiming type arrays is supported, but the object " 5656 PTR_FORMAT " is not.", p2i(r->bottom())); 5657 5658 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", 5659 region_idx, 5660 (size_t)obj->size() * HeapWordSize, 5661 p2i(r->bottom()), 5662 r->rem_set()->occupied(), 5663 r->rem_set()->strong_code_roots_list_length(), 5664 next_bitmap->isMarked(r->bottom()), 5665 g1h->is_humongous_reclaim_candidate(region_idx), 5666 obj->is_typeArray() 5667 ); 5668 5669 // Need to clear mark bit of the humongous object if already set. 5670 if (next_bitmap->isMarked(r->bottom())) { 5671 next_bitmap->clear(r->bottom()); 5672 } 5673 do { 5674 HeapRegion* next = g1h->next_region_in_humongous(r); 5675 _freed_bytes += r->used(); 5676 r->set_containing_set(NULL); 5677 _humongous_regions_removed++; 5678 g1h->free_humongous_region(r, _free_region_list, false); 5679 r = next; 5680 } while (r != NULL); 5681 5682 return false; 5683 } 5684 5685 uint humongous_free_count() { 5686 return _humongous_regions_removed; 5687 } 5688 5689 size_t bytes_freed() const { 5690 return _freed_bytes; 5691 } 5692 }; 5693 5694 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 5695 assert_at_safepoint(true); 5696 5697 if (!G1EagerReclaimHumongousObjects || 5698 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 5699 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5700 return; 5701 } 5702 5703 double start_time = os::elapsedTime(); 5704 5705 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5706 5707 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5708 heap_region_iterate(&cl); 5709 5710 remove_from_old_sets(0, cl.humongous_free_count()); 5711 5712 G1HRPrinter* hrp = hr_printer(); 5713 if (hrp->is_active()) { 5714 FreeRegionListIterator iter(&local_cleanup_list); 5715 while (iter.more_available()) { 5716 HeapRegion* hr = iter.get_next(); 5717 hrp->cleanup(hr); 5718 } 5719 } 5720 5721 prepend_to_freelist(&local_cleanup_list); 5722 decrement_summary_bytes(cl.bytes_freed()); 5723 5724 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5725 cl.humongous_free_count()); 5726 } 5727 5728 // This routine is similar to the above but does not record 5729 // any policy statistics or update free lists; we are abandoning 5730 // the current incremental collection set in preparation of a 5731 // full collection. After the full GC we will start to build up 5732 // the incremental collection set again. 5733 // This is only called when we're doing a full collection 5734 // and is immediately followed by the tearing down of the young list. 5735 5736 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 5737 HeapRegion* cur = cs_head; 5738 5739 while (cur != NULL) { 5740 HeapRegion* next = cur->next_in_collection_set(); 5741 assert(cur->in_collection_set(), "bad CS"); 5742 cur->set_next_in_collection_set(NULL); 5743 clear_in_cset(cur); 5744 cur->set_young_index_in_cset(-1); 5745 cur = next; 5746 } 5747 } 5748 5749 void G1CollectedHeap::set_free_regions_coming() { 5750 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 5751 5752 assert(!free_regions_coming(), "pre-condition"); 5753 _free_regions_coming = true; 5754 } 5755 5756 void G1CollectedHeap::reset_free_regions_coming() { 5757 assert(free_regions_coming(), "pre-condition"); 5758 5759 { 5760 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5761 _free_regions_coming = false; 5762 SecondaryFreeList_lock->notify_all(); 5763 } 5764 5765 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 5766 } 5767 5768 void G1CollectedHeap::wait_while_free_regions_coming() { 5769 // Most of the time we won't have to wait, so let's do a quick test 5770 // first before we take the lock. 5771 if (!free_regions_coming()) { 5772 return; 5773 } 5774 5775 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 5776 5777 { 5778 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5779 while (free_regions_coming()) { 5780 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5781 } 5782 } 5783 5784 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 5785 } 5786 5787 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5788 return _allocator->is_retained_old_region(hr); 5789 } 5790 5791 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5792 _young_list->push_region(hr); 5793 } 5794 5795 class NoYoungRegionsClosure: public HeapRegionClosure { 5796 private: 5797 bool _success; 5798 public: 5799 NoYoungRegionsClosure() : _success(true) { } 5800 bool doHeapRegion(HeapRegion* r) { 5801 if (r->is_young()) { 5802 log_info(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5803 p2i(r->bottom()), p2i(r->end())); 5804 _success = false; 5805 } 5806 return false; 5807 } 5808 bool success() { return _success; } 5809 }; 5810 5811 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 5812 bool ret = _young_list->check_list_empty(check_sample); 5813 5814 if (check_heap) { 5815 NoYoungRegionsClosure closure; 5816 heap_region_iterate(&closure); 5817 ret = ret && closure.success(); 5818 } 5819 5820 return ret; 5821 } 5822 5823 class TearDownRegionSetsClosure : public HeapRegionClosure { 5824 private: 5825 HeapRegionSet *_old_set; 5826 5827 public: 5828 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5829 5830 bool doHeapRegion(HeapRegion* r) { 5831 if (r->is_old()) { 5832 _old_set->remove(r); 5833 } else { 5834 // We ignore free regions, we'll empty the free list afterwards. 5835 // We ignore young regions, we'll empty the young list afterwards. 5836 // We ignore humongous regions, we're not tearing down the 5837 // humongous regions set. 5838 assert(r->is_free() || r->is_young() || r->is_humongous(), 5839 "it cannot be another type"); 5840 } 5841 return false; 5842 } 5843 5844 ~TearDownRegionSetsClosure() { 5845 assert(_old_set->is_empty(), "post-condition"); 5846 } 5847 }; 5848 5849 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5850 assert_at_safepoint(true /* should_be_vm_thread */); 5851 5852 if (!free_list_only) { 5853 TearDownRegionSetsClosure cl(&_old_set); 5854 heap_region_iterate(&cl); 5855 5856 // Note that emptying the _young_list is postponed and instead done as 5857 // the first step when rebuilding the regions sets again. The reason for 5858 // this is that during a full GC string deduplication needs to know if 5859 // a collected region was young or old when the full GC was initiated. 5860 } 5861 _hrm.remove_all_free_regions(); 5862 } 5863 5864 void G1CollectedHeap::increase_used(size_t bytes) { 5865 _summary_bytes_used += bytes; 5866 } 5867 5868 void G1CollectedHeap::decrease_used(size_t bytes) { 5869 assert(_summary_bytes_used >= bytes, 5870 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5871 _summary_bytes_used, bytes); 5872 _summary_bytes_used -= bytes; 5873 } 5874 5875 void G1CollectedHeap::set_used(size_t bytes) { 5876 _summary_bytes_used = bytes; 5877 } 5878 5879 class RebuildRegionSetsClosure : public HeapRegionClosure { 5880 private: 5881 bool _free_list_only; 5882 HeapRegionSet* _old_set; 5883 HeapRegionManager* _hrm; 5884 size_t _total_used; 5885 5886 public: 5887 RebuildRegionSetsClosure(bool free_list_only, 5888 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5889 _free_list_only(free_list_only), 5890 _old_set(old_set), _hrm(hrm), _total_used(0) { 5891 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5892 if (!free_list_only) { 5893 assert(_old_set->is_empty(), "pre-condition"); 5894 } 5895 } 5896 5897 bool doHeapRegion(HeapRegion* r) { 5898 if (r->is_empty()) { 5899 // Add free regions to the free list 5900 r->set_free(); 5901 r->set_allocation_context(AllocationContext::system()); 5902 _hrm->insert_into_free_list(r); 5903 } else if (!_free_list_only) { 5904 assert(!r->is_young(), "we should not come across young regions"); 5905 5906 if (r->is_humongous()) { 5907 // We ignore humongous regions. We left the humongous set unchanged. 5908 } else { 5909 // Objects that were compacted would have ended up on regions 5910 // that were previously old or free. Archive regions (which are 5911 // old) will not have been touched. 5912 assert(r->is_free() || r->is_old(), "invariant"); 5913 // We now consider them old, so register as such. Leave 5914 // archive regions set that way, however, while still adding 5915 // them to the old set. 5916 if (!r->is_archive()) { 5917 r->set_old(); 5918 } 5919 _old_set->add(r); 5920 } 5921 _total_used += r->used(); 5922 } 5923 5924 return false; 5925 } 5926 5927 size_t total_used() { 5928 return _total_used; 5929 } 5930 }; 5931 5932 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5933 assert_at_safepoint(true /* should_be_vm_thread */); 5934 5935 if (!free_list_only) { 5936 _young_list->empty_list(); 5937 } 5938 5939 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5940 heap_region_iterate(&cl); 5941 5942 if (!free_list_only) { 5943 set_used(cl.total_used()); 5944 if (_archive_allocator != NULL) { 5945 _archive_allocator->clear_used(); 5946 } 5947 } 5948 assert(used_unlocked() == recalculate_used(), 5949 "inconsistent used_unlocked(), " 5950 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5951 used_unlocked(), recalculate_used()); 5952 } 5953 5954 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 5955 _refine_cte_cl->set_concurrent(concurrent); 5956 } 5957 5958 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5959 HeapRegion* hr = heap_region_containing(p); 5960 return hr->is_in(p); 5961 } 5962 5963 // Methods for the mutator alloc region 5964 5965 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5966 bool force) { 5967 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5968 assert(!force || g1_policy()->can_expand_young_list(), 5969 "if force is true we should be able to expand the young list"); 5970 bool young_list_full = g1_policy()->is_young_list_full(); 5971 if (force || !young_list_full) { 5972 HeapRegion* new_alloc_region = new_region(word_size, 5973 false /* is_old */, 5974 false /* do_expand */); 5975 if (new_alloc_region != NULL) { 5976 set_region_short_lived_locked(new_alloc_region); 5977 _hr_printer.alloc(new_alloc_region, young_list_full); 5978 check_bitmaps("Mutator Region Allocation", new_alloc_region); 5979 return new_alloc_region; 5980 } 5981 } 5982 return NULL; 5983 } 5984 5985 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5986 size_t allocated_bytes) { 5987 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5988 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5989 5990 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 5991 increase_used(allocated_bytes); 5992 _hr_printer.retire(alloc_region); 5993 // We update the eden sizes here, when the region is retired, 5994 // instead of when it's allocated, since this is the point that its 5995 // used space has been recored in _summary_bytes_used. 5996 g1mm()->update_eden_size(); 5997 } 5998 5999 // Methods for the GC alloc regions 6000 6001 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6002 uint count, 6003 InCSetState dest) { 6004 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6005 6006 if (count < g1_policy()->max_regions(dest)) { 6007 const bool is_survivor = (dest.is_young()); 6008 HeapRegion* new_alloc_region = new_region(word_size, 6009 !is_survivor, 6010 true /* do_expand */); 6011 if (new_alloc_region != NULL) { 6012 // We really only need to do this for old regions given that we 6013 // should never scan survivors. But it doesn't hurt to do it 6014 // for survivors too. 6015 new_alloc_region->record_timestamp(); 6016 if (is_survivor) { 6017 new_alloc_region->set_survivor(); 6018 check_bitmaps("Survivor Region Allocation", new_alloc_region); 6019 } else { 6020 new_alloc_region->set_old(); 6021 check_bitmaps("Old Region Allocation", new_alloc_region); 6022 } 6023 _hr_printer.alloc(new_alloc_region); 6024 bool during_im = collector_state()->during_initial_mark_pause(); 6025 new_alloc_region->note_start_of_copying(during_im); 6026 return new_alloc_region; 6027 } 6028 } 6029 return NULL; 6030 } 6031 6032 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6033 size_t allocated_bytes, 6034 InCSetState dest) { 6035 bool during_im = collector_state()->during_initial_mark_pause(); 6036 alloc_region->note_end_of_copying(during_im); 6037 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6038 if (dest.is_young()) { 6039 young_list()->add_survivor_region(alloc_region); 6040 } else { 6041 _old_set.add(alloc_region); 6042 } 6043 _hr_printer.retire(alloc_region); 6044 } 6045 6046 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 6047 bool expanded = false; 6048 uint index = _hrm.find_highest_free(&expanded); 6049 6050 if (index != G1_NO_HRM_INDEX) { 6051 if (expanded) { 6052 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 6053 HeapRegion::GrainWords * HeapWordSize); 6054 } 6055 _hrm.allocate_free_regions_starting_at(index, 1); 6056 return region_at(index); 6057 } 6058 return NULL; 6059 } 6060 6061 // Heap region set verification 6062 6063 class VerifyRegionListsClosure : public HeapRegionClosure { 6064 private: 6065 HeapRegionSet* _old_set; 6066 HeapRegionSet* _humongous_set; 6067 HeapRegionManager* _hrm; 6068 6069 public: 6070 uint _old_count; 6071 uint _humongous_count; 6072 uint _free_count; 6073 6074 VerifyRegionListsClosure(HeapRegionSet* old_set, 6075 HeapRegionSet* humongous_set, 6076 HeapRegionManager* hrm) : 6077 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm), 6078 _old_count(), _humongous_count(), _free_count(){ } 6079 6080 bool doHeapRegion(HeapRegion* hr) { 6081 if (hr->is_young()) { 6082 // TODO 6083 } else if (hr->is_humongous()) { 6084 assert(hr->containing_set() == _humongous_set, "Heap region %u is humongous but not in humongous set.", hr->hrm_index()); 6085 _humongous_count++; 6086 } else if (hr->is_empty()) { 6087 assert(_hrm->is_free(hr), "Heap region %u is empty but not on the free list.", hr->hrm_index()); 6088 _free_count++; 6089 } else if (hr->is_old()) { 6090 assert(hr->containing_set() == _old_set, "Heap region %u is old but not in the old set.", hr->hrm_index()); 6091 _old_count++; 6092 } else { 6093 // There are no other valid region types. Check for one invalid 6094 // one we can identify: pinned without old or humongous set. 6095 assert(!hr->is_pinned(), "Heap region %u is pinned but not old (archive) or humongous.", hr->hrm_index()); 6096 ShouldNotReachHere(); 6097 } 6098 return false; 6099 } 6100 6101 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) { 6102 guarantee(old_set->length() == _old_count, "Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count); 6103 guarantee(humongous_set->length() == _humongous_count, "Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count); 6104 guarantee(free_list->num_free_regions() == _free_count, "Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count); 6105 } 6106 }; 6107 6108 void G1CollectedHeap::verify_region_sets() { 6109 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6110 6111 // First, check the explicit lists. 6112 _hrm.verify(); 6113 { 6114 // Given that a concurrent operation might be adding regions to 6115 // the secondary free list we have to take the lock before 6116 // verifying it. 6117 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6118 _secondary_free_list.verify_list(); 6119 } 6120 6121 // If a concurrent region freeing operation is in progress it will 6122 // be difficult to correctly attributed any free regions we come 6123 // across to the correct free list given that they might belong to 6124 // one of several (free_list, secondary_free_list, any local lists, 6125 // etc.). So, if that's the case we will skip the rest of the 6126 // verification operation. Alternatively, waiting for the concurrent 6127 // operation to complete will have a non-trivial effect on the GC's 6128 // operation (no concurrent operation will last longer than the 6129 // interval between two calls to verification) and it might hide 6130 // any issues that we would like to catch during testing. 6131 if (free_regions_coming()) { 6132 return; 6133 } 6134 6135 // Make sure we append the secondary_free_list on the free_list so 6136 // that all free regions we will come across can be safely 6137 // attributed to the free_list. 6138 append_secondary_free_list_if_not_empty_with_lock(); 6139 6140 // Finally, make sure that the region accounting in the lists is 6141 // consistent with what we see in the heap. 6142 6143 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm); 6144 heap_region_iterate(&cl); 6145 cl.verify_counts(&_old_set, &_humongous_set, &_hrm); 6146 } 6147 6148 // Optimized nmethod scanning 6149 6150 class RegisterNMethodOopClosure: public OopClosure { 6151 G1CollectedHeap* _g1h; 6152 nmethod* _nm; 6153 6154 template <class T> void do_oop_work(T* p) { 6155 T heap_oop = oopDesc::load_heap_oop(p); 6156 if (!oopDesc::is_null(heap_oop)) { 6157 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6158 HeapRegion* hr = _g1h->heap_region_containing(obj); 6159 assert(!hr->is_continues_humongous(), 6160 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6161 " starting at " HR_FORMAT, 6162 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 6163 6164 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 6165 hr->add_strong_code_root_locked(_nm); 6166 } 6167 } 6168 6169 public: 6170 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6171 _g1h(g1h), _nm(nm) {} 6172 6173 void do_oop(oop* p) { do_oop_work(p); } 6174 void do_oop(narrowOop* p) { do_oop_work(p); } 6175 }; 6176 6177 class UnregisterNMethodOopClosure: public OopClosure { 6178 G1CollectedHeap* _g1h; 6179 nmethod* _nm; 6180 6181 template <class T> void do_oop_work(T* p) { 6182 T heap_oop = oopDesc::load_heap_oop(p); 6183 if (!oopDesc::is_null(heap_oop)) { 6184 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6185 HeapRegion* hr = _g1h->heap_region_containing(obj); 6186 assert(!hr->is_continues_humongous(), 6187 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6188 " starting at " HR_FORMAT, 6189 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 6190 6191 hr->remove_strong_code_root(_nm); 6192 } 6193 } 6194 6195 public: 6196 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6197 _g1h(g1h), _nm(nm) {} 6198 6199 void do_oop(oop* p) { do_oop_work(p); } 6200 void do_oop(narrowOop* p) { do_oop_work(p); } 6201 }; 6202 6203 void G1CollectedHeap::register_nmethod(nmethod* nm) { 6204 CollectedHeap::register_nmethod(nm); 6205 6206 guarantee(nm != NULL, "sanity"); 6207 RegisterNMethodOopClosure reg_cl(this, nm); 6208 nm->oops_do(®_cl); 6209 } 6210 6211 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 6212 CollectedHeap::unregister_nmethod(nm); 6213 6214 guarantee(nm != NULL, "sanity"); 6215 UnregisterNMethodOopClosure reg_cl(this, nm); 6216 nm->oops_do(®_cl, true); 6217 } 6218 6219 void G1CollectedHeap::purge_code_root_memory() { 6220 double purge_start = os::elapsedTime(); 6221 G1CodeRootSet::purge(); 6222 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 6223 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 6224 } 6225 6226 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 6227 G1CollectedHeap* _g1h; 6228 6229 public: 6230 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 6231 _g1h(g1h) {} 6232 6233 void do_code_blob(CodeBlob* cb) { 6234 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 6235 if (nm == NULL) { 6236 return; 6237 } 6238 6239 if (ScavengeRootsInCode) { 6240 _g1h->register_nmethod(nm); 6241 } 6242 } 6243 }; 6244 6245 void G1CollectedHeap::rebuild_strong_code_roots() { 6246 RebuildStrongCodeRootClosure blob_cl(this); 6247 CodeCache::blobs_do(&blob_cl); 6248 }