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 "code/codeCache.hpp" 29 #include "code/icBuffer.hpp" 30 #include "gc/g1/bufferingOopClosure.hpp" 31 #include "gc/g1/concurrentG1Refine.hpp" 32 #include "gc/g1/concurrentG1RefineThread.hpp" 33 #include "gc/g1/concurrentMarkThread.inline.hpp" 34 #include "gc/g1/g1Allocator.inline.hpp" 35 #include "gc/g1/g1CollectedHeap.inline.hpp" 36 #include "gc/g1/g1CollectorPolicy.hpp" 37 #include "gc/g1/g1CollectorState.hpp" 38 #include "gc/g1/g1EvacFailure.hpp" 39 #include "gc/g1/g1GCPhaseTimes.hpp" 40 #include "gc/g1/g1MarkSweep.hpp" 41 #include "gc/g1/g1OopClosures.inline.hpp" 42 #include "gc/g1/g1ParScanThreadState.inline.hpp" 43 #include "gc/g1/g1RegionToSpaceMapper.hpp" 44 #include "gc/g1/g1RemSet.inline.hpp" 45 #include "gc/g1/g1RootClosures.hpp" 46 #include "gc/g1/g1RootProcessor.hpp" 47 #include "gc/g1/g1StringDedup.hpp" 48 #include "gc/g1/g1YCTypes.hpp" 49 #include "gc/g1/heapRegion.inline.hpp" 50 #include "gc/g1/heapRegionRemSet.hpp" 51 #include "gc/g1/heapRegionSet.inline.hpp" 52 #include "gc/g1/suspendibleThreadSet.hpp" 53 #include "gc/g1/vm_operations_g1.hpp" 54 #include "gc/shared/gcHeapSummary.hpp" 55 #include "gc/shared/gcId.hpp" 56 #include "gc/shared/gcLocker.inline.hpp" 57 #include "gc/shared/gcTimer.hpp" 58 #include "gc/shared/gcTrace.hpp" 59 #include "gc/shared/gcTraceTime.hpp" 60 #include "gc/shared/generationSpec.hpp" 61 #include "gc/shared/isGCActiveMark.hpp" 62 #include "gc/shared/referenceProcessor.hpp" 63 #include "gc/shared/taskqueue.inline.hpp" 64 #include "logging/log.hpp" 65 #include "memory/allocation.hpp" 66 #include "memory/iterator.hpp" 67 #include "oops/oop.inline.hpp" 68 #include "runtime/atomic.inline.hpp" 69 #include "runtime/init.hpp" 70 #include "runtime/orderAccess.inline.hpp" 71 #include "runtime/vmThread.hpp" 72 #include "utilities/globalDefinitions.hpp" 73 #include "utilities/stack.inline.hpp" 74 75 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 76 77 // INVARIANTS/NOTES 78 // 79 // All allocation activity covered by the G1CollectedHeap interface is 80 // serialized by acquiring the HeapLock. This happens in mem_allocate 81 // and allocate_new_tlab, which are the "entry" points to the 82 // allocation code from the rest of the JVM. (Note that this does not 83 // apply to TLAB allocation, which is not part of this interface: it 84 // is done by clients of this interface.) 85 86 // Local to this file. 87 88 class RefineCardTableEntryClosure: public CardTableEntryClosure { 89 bool _concurrent; 90 public: 91 RefineCardTableEntryClosure() : _concurrent(true) { } 92 93 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 94 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false); 95 // This path is executed by the concurrent refine or mutator threads, 96 // concurrently, and so we do not care if card_ptr contains references 97 // that point into the collection set. 98 assert(!oops_into_cset, "should be"); 99 100 if (_concurrent && SuspendibleThreadSet::should_yield()) { 101 // Caller will actually yield. 102 return false; 103 } 104 // Otherwise, we finished successfully; return true. 105 return true; 106 } 107 108 void set_concurrent(bool b) { _concurrent = b; } 109 }; 110 111 112 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 113 private: 114 size_t _num_processed; 115 116 public: 117 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { } 118 119 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 120 *card_ptr = CardTableModRefBS::dirty_card_val(); 121 _num_processed++; 122 return true; 123 } 124 125 size_t num_processed() const { return _num_processed; } 126 }; 127 128 129 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 130 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 131 } 132 133 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 134 // The from card cache is not the memory that is actually committed. So we cannot 135 // take advantage of the zero_filled parameter. 136 reset_from_card_cache(start_idx, num_regions); 137 } 138 139 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 140 { 141 // Claim the right to put the region on the dirty cards region list 142 // by installing a self pointer. 143 HeapRegion* next = hr->get_next_dirty_cards_region(); 144 if (next == NULL) { 145 HeapRegion* res = (HeapRegion*) 146 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 147 NULL); 148 if (res == NULL) { 149 HeapRegion* head; 150 do { 151 // Put the region to the dirty cards region list. 152 head = _dirty_cards_region_list; 153 next = (HeapRegion*) 154 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 155 if (next == head) { 156 assert(hr->get_next_dirty_cards_region() == hr, 157 "hr->get_next_dirty_cards_region() != hr"); 158 if (next == NULL) { 159 // The last region in the list points to itself. 160 hr->set_next_dirty_cards_region(hr); 161 } else { 162 hr->set_next_dirty_cards_region(next); 163 } 164 } 165 } while (next != head); 166 } 167 } 168 } 169 170 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 171 { 172 HeapRegion* head; 173 HeapRegion* hr; 174 do { 175 head = _dirty_cards_region_list; 176 if (head == NULL) { 177 return NULL; 178 } 179 HeapRegion* new_head = head->get_next_dirty_cards_region(); 180 if (head == new_head) { 181 // The last region. 182 new_head = NULL; 183 } 184 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 185 head); 186 } while (hr != head); 187 assert(hr != NULL, "invariant"); 188 hr->set_next_dirty_cards_region(NULL); 189 return hr; 190 } 191 192 // Returns true if the reference points to an object that 193 // can move in an incremental collection. 194 bool G1CollectedHeap::is_scavengable(const void* p) { 195 HeapRegion* hr = heap_region_containing(p); 196 return !hr->is_pinned(); 197 } 198 199 // Private methods. 200 201 HeapRegion* 202 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 203 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 204 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 205 if (!_secondary_free_list.is_empty()) { 206 log_develop(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 207 "secondary_free_list has %u entries", 208 _secondary_free_list.length()); 209 // It looks as if there are free regions available on the 210 // secondary_free_list. Let's move them to the free_list and try 211 // again to allocate from it. 212 append_secondary_free_list(); 213 214 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 215 "empty we should have moved at least one entry to the free_list"); 216 HeapRegion* res = _hrm.allocate_free_region(is_old); 217 log_develop(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 218 "allocated " HR_FORMAT " from secondary_free_list", 219 HR_FORMAT_PARAMS(res)); 220 return res; 221 } 222 223 // Wait here until we get notified either when (a) there are no 224 // more free regions coming or (b) some regions have been moved on 225 // the secondary_free_list. 226 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 227 } 228 229 log_develop(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 230 "could not allocate from secondary_free_list"); 231 return NULL; 232 } 233 234 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 235 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 236 "the only time we use this to allocate a humongous region is " 237 "when we are allocating a single humongous region"); 238 239 HeapRegion* res; 240 if (G1StressConcRegionFreeing) { 241 if (!_secondary_free_list.is_empty()) { 242 log_develop(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 243 "forced to look at the secondary_free_list"); 244 res = new_region_try_secondary_free_list(is_old); 245 if (res != NULL) { 246 return res; 247 } 248 } 249 } 250 251 res = _hrm.allocate_free_region(is_old); 252 253 if (res == NULL) { 254 log_develop(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 255 "res == NULL, trying the secondary_free_list"); 256 res = new_region_try_secondary_free_list(is_old); 257 } 258 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 259 // Currently, only attempts to allocate GC alloc regions set 260 // do_expand to true. So, we should only reach here during a 261 // safepoint. If this assumption changes we might have to 262 // reconsider the use of _expand_heap_after_alloc_failure. 263 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 264 265 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 266 word_size * HeapWordSize); 267 268 if (expand(word_size * HeapWordSize)) { 269 // Given that expand() succeeded in expanding the heap, and we 270 // always expand the heap by an amount aligned to the heap 271 // region size, the free list should in theory not be empty. 272 // In either case allocate_free_region() will check for NULL. 273 res = _hrm.allocate_free_region(is_old); 274 } else { 275 _expand_heap_after_alloc_failure = false; 276 } 277 } 278 return res; 279 } 280 281 HeapWord* 282 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 283 uint num_regions, 284 size_t word_size, 285 AllocationContext_t context) { 286 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 287 assert(is_humongous(word_size), "word_size should be humongous"); 288 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 289 290 // Index of last region in the series + 1. 291 uint last = first + num_regions; 292 293 // We need to initialize the region(s) we just discovered. This is 294 // a bit tricky given that it can happen concurrently with 295 // refinement threads refining cards on these regions and 296 // potentially wanting to refine the BOT as they are scanning 297 // those cards (this can happen shortly after a cleanup; see CR 298 // 6991377). So we have to set up the region(s) carefully and in 299 // a specific order. 300 301 // The word size sum of all the regions we will allocate. 302 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 303 assert(word_size <= word_size_sum, "sanity"); 304 305 // This will be the "starts humongous" region. 306 HeapRegion* first_hr = region_at(first); 307 // The header of the new object will be placed at the bottom of 308 // the first region. 309 HeapWord* new_obj = first_hr->bottom(); 310 // This will be the new top of the new object. 311 HeapWord* obj_top = new_obj + word_size; 312 313 // First, we need to zero the header of the space that we will be 314 // allocating. When we update top further down, some refinement 315 // threads might try to scan the region. By zeroing the header we 316 // ensure that any thread that will try to scan the region will 317 // come across the zero klass word and bail out. 318 // 319 // NOTE: It would not have been correct to have used 320 // CollectedHeap::fill_with_object() and make the space look like 321 // an int array. The thread that is doing the allocation will 322 // later update the object header to a potentially different array 323 // type and, for a very short period of time, the klass and length 324 // fields will be inconsistent. This could cause a refinement 325 // thread to calculate the object size incorrectly. 326 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 327 328 // We will set up the first region as "starts humongous". This 329 // will also update the BOT covering all the regions to reflect 330 // that there is a single object that starts at the bottom of the 331 // first region. 332 first_hr->set_starts_humongous(obj_top); 333 first_hr->set_allocation_context(context); 334 // Then, if there are any, we will set up the "continues 335 // humongous" regions. 336 HeapRegion* hr = NULL; 337 for (uint i = first + 1; i < last; ++i) { 338 hr = region_at(i); 339 hr->set_continues_humongous(first_hr); 340 hr->set_allocation_context(context); 341 } 342 343 // Up to this point no concurrent thread would have been able to 344 // do any scanning on any region in this series. All the top 345 // fields still point to bottom, so the intersection between 346 // [bottom,top] and [card_start,card_end] will be empty. Before we 347 // update the top fields, we'll do a storestore to make sure that 348 // no thread sees the update to top before the zeroing of the 349 // object header and the BOT initialization. 350 OrderAccess::storestore(); 351 352 // Now that the BOT and the object header have been initialized, 353 // we can update top of the "starts humongous" region. 354 first_hr->set_top(MIN2(first_hr->end(), obj_top)); 355 if (_hr_printer.is_active()) { 356 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, first_hr->top()); 357 } 358 359 // Now, we will update the top fields of the "continues humongous" 360 // regions. 361 hr = NULL; 362 for (uint i = first + 1; i < last; ++i) { 363 hr = region_at(i); 364 if ((i + 1) == last) { 365 // last continues humongous region 366 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 367 "new_top should fall on this region"); 368 hr->set_top(obj_top); 369 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, obj_top); 370 } else { 371 // not last one 372 assert(obj_top > hr->end(), "obj_top should be above this region"); 373 hr->set_top(hr->end()); 374 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 375 } 376 } 377 // If we have continues humongous regions (hr != NULL), its top should 378 // match obj_top. 379 assert(hr == NULL || (hr->top() == obj_top), "sanity"); 380 check_bitmaps("Humongous Region Allocation", first_hr); 381 382 increase_used(word_size * HeapWordSize); 383 384 for (uint i = first; i < last; ++i) { 385 _humongous_set.add(region_at(i)); 386 } 387 388 return new_obj; 389 } 390 391 // If could fit into free regions w/o expansion, try. 392 // Otherwise, if can expand, do so. 393 // Otherwise, if using ex regions might help, try with ex given back. 394 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 395 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 396 397 verify_region_sets_optional(); 398 399 uint first = G1_NO_HRM_INDEX; 400 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords); 401 402 if (obj_regions == 1) { 403 // Only one region to allocate, try to use a fast path by directly allocating 404 // from the free lists. Do not try to expand here, we will potentially do that 405 // later. 406 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 407 if (hr != NULL) { 408 first = hr->hrm_index(); 409 } 410 } else { 411 // We can't allocate humongous regions spanning more than one region while 412 // cleanupComplete() is running, since some of the regions we find to be 413 // empty might not yet be added to the free list. It is not straightforward 414 // to know in which list they are on so that we can remove them. We only 415 // need to do this if we need to allocate more than one region to satisfy the 416 // current humongous allocation request. If we are only allocating one region 417 // we use the one-region region allocation code (see above), that already 418 // potentially waits for regions from the secondary free list. 419 wait_while_free_regions_coming(); 420 append_secondary_free_list_if_not_empty_with_lock(); 421 422 // Policy: Try only empty regions (i.e. already committed first). Maybe we 423 // are lucky enough to find some. 424 first = _hrm.find_contiguous_only_empty(obj_regions); 425 if (first != G1_NO_HRM_INDEX) { 426 _hrm.allocate_free_regions_starting_at(first, obj_regions); 427 } 428 } 429 430 if (first == G1_NO_HRM_INDEX) { 431 // Policy: We could not find enough regions for the humongous object in the 432 // free list. Look through the heap to find a mix of free and uncommitted regions. 433 // If so, try expansion. 434 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 435 if (first != G1_NO_HRM_INDEX) { 436 // We found something. Make sure these regions are committed, i.e. expand 437 // the heap. Alternatively we could do a defragmentation GC. 438 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 439 word_size * HeapWordSize); 440 441 442 _hrm.expand_at(first, obj_regions); 443 g1_policy()->record_new_heap_size(num_regions()); 444 445 #ifdef ASSERT 446 for (uint i = first; i < first + obj_regions; ++i) { 447 HeapRegion* hr = region_at(i); 448 assert(hr->is_free(), "sanity"); 449 assert(hr->is_empty(), "sanity"); 450 assert(is_on_master_free_list(hr), "sanity"); 451 } 452 #endif 453 _hrm.allocate_free_regions_starting_at(first, obj_regions); 454 } else { 455 // Policy: Potentially trigger a defragmentation GC. 456 } 457 } 458 459 HeapWord* result = NULL; 460 if (first != G1_NO_HRM_INDEX) { 461 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 462 word_size, context); 463 assert(result != NULL, "it should always return a valid result"); 464 465 // A successful humongous object allocation changes the used space 466 // information of the old generation so we need to recalculate the 467 // sizes and update the jstat counters here. 468 g1mm()->update_sizes(); 469 } 470 471 verify_region_sets_optional(); 472 473 return result; 474 } 475 476 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 477 assert_heap_not_locked_and_not_at_safepoint(); 478 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 479 480 uint dummy_gc_count_before; 481 uint dummy_gclocker_retry_count = 0; 482 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 483 } 484 485 HeapWord* 486 G1CollectedHeap::mem_allocate(size_t word_size, 487 bool* gc_overhead_limit_was_exceeded) { 488 assert_heap_not_locked_and_not_at_safepoint(); 489 490 // Loop until the allocation is satisfied, or unsatisfied after GC. 491 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 492 uint gc_count_before; 493 494 HeapWord* result = NULL; 495 if (!is_humongous(word_size)) { 496 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 497 } else { 498 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 499 } 500 if (result != NULL) { 501 return result; 502 } 503 504 // Create the garbage collection operation... 505 VM_G1CollectForAllocation op(gc_count_before, word_size); 506 op.set_allocation_context(AllocationContext::current()); 507 508 // ...and get the VM thread to execute it. 509 VMThread::execute(&op); 510 511 if (op.prologue_succeeded() && op.pause_succeeded()) { 512 // If the operation was successful we'll return the result even 513 // if it is NULL. If the allocation attempt failed immediately 514 // after a Full GC, it's unlikely we'll be able to allocate now. 515 HeapWord* result = op.result(); 516 if (result != NULL && !is_humongous(word_size)) { 517 // Allocations that take place on VM operations do not do any 518 // card dirtying and we have to do it here. We only have to do 519 // this for non-humongous allocations, though. 520 dirty_young_block(result, word_size); 521 } 522 return result; 523 } else { 524 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 525 return NULL; 526 } 527 assert(op.result() == NULL, 528 "the result should be NULL if the VM op did not succeed"); 529 } 530 531 // Give a warning if we seem to be looping forever. 532 if ((QueuedAllocationWarningCount > 0) && 533 (try_count % QueuedAllocationWarningCount == 0)) { 534 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 535 } 536 } 537 538 ShouldNotReachHere(); 539 return NULL; 540 } 541 542 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 543 AllocationContext_t context, 544 uint* gc_count_before_ret, 545 uint* gclocker_retry_count_ret) { 546 // Make sure you read the note in attempt_allocation_humongous(). 547 548 assert_heap_not_locked_and_not_at_safepoint(); 549 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 550 "be called for humongous allocation requests"); 551 552 // We should only get here after the first-level allocation attempt 553 // (attempt_allocation()) failed to allocate. 554 555 // We will loop until a) we manage to successfully perform the 556 // allocation or b) we successfully schedule a collection which 557 // fails to perform the allocation. b) is the only case when we'll 558 // return NULL. 559 HeapWord* result = NULL; 560 for (int try_count = 1; /* we'll return */; try_count += 1) { 561 bool should_try_gc; 562 uint gc_count_before; 563 564 { 565 MutexLockerEx x(Heap_lock); 566 result = _allocator->attempt_allocation_locked(word_size, context); 567 if (result != NULL) { 568 return result; 569 } 570 571 if (GC_locker::is_active_and_needs_gc()) { 572 if (g1_policy()->can_expand_young_list()) { 573 // No need for an ergo verbose message here, 574 // can_expand_young_list() does this when it returns true. 575 result = _allocator->attempt_allocation_force(word_size, context); 576 if (result != NULL) { 577 return result; 578 } 579 } 580 should_try_gc = false; 581 } else { 582 // The GCLocker may not be active but the GCLocker initiated 583 // GC may not yet have been performed (GCLocker::needs_gc() 584 // returns true). In this case we do not try this GC and 585 // wait until the GCLocker initiated GC is performed, and 586 // then retry the allocation. 587 if (GC_locker::needs_gc()) { 588 should_try_gc = false; 589 } else { 590 // Read the GC count while still holding the Heap_lock. 591 gc_count_before = total_collections(); 592 should_try_gc = true; 593 } 594 } 595 } 596 597 if (should_try_gc) { 598 bool succeeded; 599 result = do_collection_pause(word_size, gc_count_before, &succeeded, 600 GCCause::_g1_inc_collection_pause); 601 if (result != NULL) { 602 assert(succeeded, "only way to get back a non-NULL result"); 603 return result; 604 } 605 606 if (succeeded) { 607 // If we get here we successfully scheduled a collection which 608 // failed to allocate. No point in trying to allocate 609 // further. We'll just return NULL. 610 MutexLockerEx x(Heap_lock); 611 *gc_count_before_ret = total_collections(); 612 return NULL; 613 } 614 } else { 615 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 616 MutexLockerEx x(Heap_lock); 617 *gc_count_before_ret = total_collections(); 618 return NULL; 619 } 620 // The GCLocker is either active or the GCLocker initiated 621 // GC has not yet been performed. Stall until it is and 622 // then retry the allocation. 623 GC_locker::stall_until_clear(); 624 (*gclocker_retry_count_ret) += 1; 625 } 626 627 // We can reach here if we were unsuccessful in scheduling a 628 // collection (because another thread beat us to it) or if we were 629 // stalled due to the GC locker. In either can we should retry the 630 // allocation attempt in case another thread successfully 631 // performed a collection and reclaimed enough space. We do the 632 // first attempt (without holding the Heap_lock) here and the 633 // follow-on attempt will be at the start of the next loop 634 // iteration (after taking the Heap_lock). 635 result = _allocator->attempt_allocation(word_size, context); 636 if (result != NULL) { 637 return result; 638 } 639 640 // Give a warning if we seem to be looping forever. 641 if ((QueuedAllocationWarningCount > 0) && 642 (try_count % QueuedAllocationWarningCount == 0)) { 643 warning("G1CollectedHeap::attempt_allocation_slow() " 644 "retries %d times", try_count); 645 } 646 } 647 648 ShouldNotReachHere(); 649 return NULL; 650 } 651 652 void G1CollectedHeap::begin_archive_alloc_range() { 653 assert_at_safepoint(true /* should_be_vm_thread */); 654 if (_archive_allocator == NULL) { 655 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 656 } 657 } 658 659 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 660 // Allocations in archive regions cannot be of a size that would be considered 661 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 662 // may be different at archive-restore time. 663 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 664 } 665 666 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 667 assert_at_safepoint(true /* should_be_vm_thread */); 668 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 669 if (is_archive_alloc_too_large(word_size)) { 670 return NULL; 671 } 672 return _archive_allocator->archive_mem_allocate(word_size); 673 } 674 675 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 676 size_t end_alignment_in_bytes) { 677 assert_at_safepoint(true /* should_be_vm_thread */); 678 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 679 680 // Call complete_archive to do the real work, filling in the MemRegion 681 // array with the archive regions. 682 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 683 delete _archive_allocator; 684 _archive_allocator = NULL; 685 } 686 687 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 688 assert(ranges != NULL, "MemRegion array NULL"); 689 assert(count != 0, "No MemRegions provided"); 690 MemRegion reserved = _hrm.reserved(); 691 for (size_t i = 0; i < count; i++) { 692 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 693 return false; 694 } 695 } 696 return true; 697 } 698 699 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 700 assert(!is_init_completed(), "Expect to be called at JVM init time"); 701 assert(ranges != NULL, "MemRegion array NULL"); 702 assert(count != 0, "No MemRegions provided"); 703 MutexLockerEx x(Heap_lock); 704 705 MemRegion reserved = _hrm.reserved(); 706 HeapWord* prev_last_addr = NULL; 707 HeapRegion* prev_last_region = NULL; 708 709 // Temporarily disable pretouching of heap pages. This interface is used 710 // when mmap'ing archived heap data in, so pre-touching is wasted. 711 FlagSetting fs(AlwaysPreTouch, false); 712 713 // Enable archive object checking in G1MarkSweep. We have to let it know 714 // about each archive range, so that objects in those ranges aren't marked. 715 G1MarkSweep::enable_archive_object_check(); 716 717 // For each specified MemRegion range, allocate the corresponding G1 718 // regions and mark them as archive regions. We expect the ranges in 719 // ascending starting address order, without overlap. 720 for (size_t i = 0; i < count; i++) { 721 MemRegion curr_range = ranges[i]; 722 HeapWord* start_address = curr_range.start(); 723 size_t word_size = curr_range.word_size(); 724 HeapWord* last_address = curr_range.last(); 725 size_t commits = 0; 726 727 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 728 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 729 p2i(start_address), p2i(last_address)); 730 guarantee(start_address > prev_last_addr, 731 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 732 p2i(start_address), p2i(prev_last_addr)); 733 prev_last_addr = last_address; 734 735 // Check for ranges that start in the same G1 region in which the previous 736 // range ended, and adjust the start address so we don't try to allocate 737 // the same region again. If the current range is entirely within that 738 // region, skip it, just adjusting the recorded top. 739 HeapRegion* start_region = _hrm.addr_to_region(start_address); 740 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 741 start_address = start_region->end(); 742 if (start_address > last_address) { 743 increase_used(word_size * HeapWordSize); 744 start_region->set_top(last_address + 1); 745 continue; 746 } 747 start_region->set_top(start_address); 748 curr_range = MemRegion(start_address, last_address + 1); 749 start_region = _hrm.addr_to_region(start_address); 750 } 751 752 // Perform the actual region allocation, exiting if it fails. 753 // Then note how much new space we have allocated. 754 if (!_hrm.allocate_containing_regions(curr_range, &commits)) { 755 return false; 756 } 757 increase_used(word_size * HeapWordSize); 758 if (commits != 0) { 759 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 760 HeapRegion::GrainWords * HeapWordSize * commits); 761 762 } 763 764 // Mark each G1 region touched by the range as archive, add it to the old set, 765 // and set the allocation context and top. 766 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 767 HeapRegion* last_region = _hrm.addr_to_region(last_address); 768 prev_last_region = last_region; 769 770 while (curr_region != NULL) { 771 assert(curr_region->is_empty() && !curr_region->is_pinned(), 772 "Region already in use (index %u)", curr_region->hrm_index()); 773 _hr_printer.alloc(curr_region, G1HRPrinter::Archive); 774 curr_region->set_allocation_context(AllocationContext::system()); 775 curr_region->set_archive(); 776 _old_set.add(curr_region); 777 if (curr_region != last_region) { 778 curr_region->set_top(curr_region->end()); 779 curr_region = _hrm.next_region_in_heap(curr_region); 780 } else { 781 curr_region->set_top(last_address + 1); 782 curr_region = NULL; 783 } 784 } 785 786 // Notify mark-sweep of the archive range. 787 G1MarkSweep::set_range_archive(curr_range, true); 788 } 789 return true; 790 } 791 792 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 793 assert(!is_init_completed(), "Expect to be called at JVM init time"); 794 assert(ranges != NULL, "MemRegion array NULL"); 795 assert(count != 0, "No MemRegions provided"); 796 MemRegion reserved = _hrm.reserved(); 797 HeapWord *prev_last_addr = NULL; 798 HeapRegion* prev_last_region = NULL; 799 800 // For each MemRegion, create filler objects, if needed, in the G1 regions 801 // that contain the address range. The address range actually within the 802 // MemRegion will not be modified. That is assumed to have been initialized 803 // elsewhere, probably via an mmap of archived heap data. 804 MutexLockerEx x(Heap_lock); 805 for (size_t i = 0; i < count; i++) { 806 HeapWord* start_address = ranges[i].start(); 807 HeapWord* last_address = ranges[i].last(); 808 809 assert(reserved.contains(start_address) && reserved.contains(last_address), 810 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 811 p2i(start_address), p2i(last_address)); 812 assert(start_address > prev_last_addr, 813 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 814 p2i(start_address), p2i(prev_last_addr)); 815 816 HeapRegion* start_region = _hrm.addr_to_region(start_address); 817 HeapRegion* last_region = _hrm.addr_to_region(last_address); 818 HeapWord* bottom_address = start_region->bottom(); 819 820 // Check for a range beginning in the same region in which the 821 // previous one ended. 822 if (start_region == prev_last_region) { 823 bottom_address = prev_last_addr + 1; 824 } 825 826 // Verify that the regions were all marked as archive regions by 827 // alloc_archive_regions. 828 HeapRegion* curr_region = start_region; 829 while (curr_region != NULL) { 830 guarantee(curr_region->is_archive(), 831 "Expected archive region at index %u", curr_region->hrm_index()); 832 if (curr_region != last_region) { 833 curr_region = _hrm.next_region_in_heap(curr_region); 834 } else { 835 curr_region = NULL; 836 } 837 } 838 839 prev_last_addr = last_address; 840 prev_last_region = last_region; 841 842 // Fill the memory below the allocated range with dummy object(s), 843 // if the region bottom does not match the range start, or if the previous 844 // range ended within the same G1 region, and there is a gap. 845 if (start_address != bottom_address) { 846 size_t fill_size = pointer_delta(start_address, bottom_address); 847 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 848 increase_used(fill_size * HeapWordSize); 849 } 850 } 851 } 852 853 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 854 uint* gc_count_before_ret, 855 uint* gclocker_retry_count_ret) { 856 assert_heap_not_locked_and_not_at_safepoint(); 857 assert(!is_humongous(word_size), "attempt_allocation() should not " 858 "be called for humongous allocation requests"); 859 860 AllocationContext_t context = AllocationContext::current(); 861 HeapWord* result = _allocator->attempt_allocation(word_size, context); 862 863 if (result == NULL) { 864 result = attempt_allocation_slow(word_size, 865 context, 866 gc_count_before_ret, 867 gclocker_retry_count_ret); 868 } 869 assert_heap_not_locked(); 870 if (result != NULL) { 871 dirty_young_block(result, word_size); 872 } 873 return result; 874 } 875 876 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 877 assert(!is_init_completed(), "Expect to be called at JVM init time"); 878 assert(ranges != NULL, "MemRegion array NULL"); 879 assert(count != 0, "No MemRegions provided"); 880 MemRegion reserved = _hrm.reserved(); 881 HeapWord* prev_last_addr = NULL; 882 HeapRegion* prev_last_region = NULL; 883 size_t size_used = 0; 884 size_t uncommitted_regions = 0; 885 886 // For each Memregion, free the G1 regions that constitute it, and 887 // notify mark-sweep that the range is no longer to be considered 'archive.' 888 MutexLockerEx x(Heap_lock); 889 for (size_t i = 0; i < count; i++) { 890 HeapWord* start_address = ranges[i].start(); 891 HeapWord* last_address = ranges[i].last(); 892 893 assert(reserved.contains(start_address) && reserved.contains(last_address), 894 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 895 p2i(start_address), p2i(last_address)); 896 assert(start_address > prev_last_addr, 897 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 898 p2i(start_address), p2i(prev_last_addr)); 899 size_used += ranges[i].byte_size(); 900 prev_last_addr = last_address; 901 902 HeapRegion* start_region = _hrm.addr_to_region(start_address); 903 HeapRegion* last_region = _hrm.addr_to_region(last_address); 904 905 // Check for ranges that start in the same G1 region in which the previous 906 // range ended, and adjust the start address so we don't try to free 907 // the same region again. If the current range is entirely within that 908 // region, skip it. 909 if (start_region == prev_last_region) { 910 start_address = start_region->end(); 911 if (start_address > last_address) { 912 continue; 913 } 914 start_region = _hrm.addr_to_region(start_address); 915 } 916 prev_last_region = last_region; 917 918 // After verifying that each region was marked as an archive region by 919 // alloc_archive_regions, set it free and empty and uncommit it. 920 HeapRegion* curr_region = start_region; 921 while (curr_region != NULL) { 922 guarantee(curr_region->is_archive(), 923 "Expected archive region at index %u", curr_region->hrm_index()); 924 uint curr_index = curr_region->hrm_index(); 925 _old_set.remove(curr_region); 926 curr_region->set_free(); 927 curr_region->set_top(curr_region->bottom()); 928 if (curr_region != last_region) { 929 curr_region = _hrm.next_region_in_heap(curr_region); 930 } else { 931 curr_region = NULL; 932 } 933 _hrm.shrink_at(curr_index, 1); 934 uncommitted_regions++; 935 } 936 937 // Notify mark-sweep that this is no longer an archive range. 938 G1MarkSweep::set_range_archive(ranges[i], false); 939 } 940 941 if (uncommitted_regions != 0) { 942 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 943 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 944 } 945 decrease_used(size_used); 946 } 947 948 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 949 uint* gc_count_before_ret, 950 uint* gclocker_retry_count_ret) { 951 // The structure of this method has a lot of similarities to 952 // attempt_allocation_slow(). The reason these two were not merged 953 // into a single one is that such a method would require several "if 954 // allocation is not humongous do this, otherwise do that" 955 // conditional paths which would obscure its flow. In fact, an early 956 // version of this code did use a unified method which was harder to 957 // follow and, as a result, it had subtle bugs that were hard to 958 // track down. So keeping these two methods separate allows each to 959 // be more readable. It will be good to keep these two in sync as 960 // much as possible. 961 962 assert_heap_not_locked_and_not_at_safepoint(); 963 assert(is_humongous(word_size), "attempt_allocation_humongous() " 964 "should only be called for humongous allocations"); 965 966 // Humongous objects can exhaust the heap quickly, so we should check if we 967 // need to start a marking cycle at each humongous object allocation. We do 968 // the check before we do the actual allocation. The reason for doing it 969 // before the allocation is that we avoid having to keep track of the newly 970 // allocated memory while we do a GC. 971 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 972 word_size)) { 973 collect(GCCause::_g1_humongous_allocation); 974 } 975 976 // We will loop until a) we manage to successfully perform the 977 // allocation or b) we successfully schedule a collection which 978 // fails to perform the allocation. b) is the only case when we'll 979 // return NULL. 980 HeapWord* result = NULL; 981 for (int try_count = 1; /* we'll return */; try_count += 1) { 982 bool should_try_gc; 983 uint gc_count_before; 984 985 { 986 MutexLockerEx x(Heap_lock); 987 988 // Given that humongous objects are not allocated in young 989 // regions, we'll first try to do the allocation without doing a 990 // collection hoping that there's enough space in the heap. 991 result = humongous_obj_allocate(word_size, AllocationContext::current()); 992 if (result != NULL) { 993 return result; 994 } 995 996 if (GC_locker::is_active_and_needs_gc()) { 997 should_try_gc = false; 998 } else { 999 // The GCLocker may not be active but the GCLocker initiated 1000 // GC may not yet have been performed (GCLocker::needs_gc() 1001 // returns true). In this case we do not try this GC and 1002 // wait until the GCLocker initiated GC is performed, and 1003 // then retry the allocation. 1004 if (GC_locker::needs_gc()) { 1005 should_try_gc = false; 1006 } else { 1007 // Read the GC count while still holding the Heap_lock. 1008 gc_count_before = total_collections(); 1009 should_try_gc = true; 1010 } 1011 } 1012 } 1013 1014 if (should_try_gc) { 1015 // If we failed to allocate the humongous object, we should try to 1016 // do a collection pause (if we're allowed) in case it reclaims 1017 // enough space for the allocation to succeed after the pause. 1018 1019 bool succeeded; 1020 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1021 GCCause::_g1_humongous_allocation); 1022 if (result != NULL) { 1023 assert(succeeded, "only way to get back a non-NULL result"); 1024 return result; 1025 } 1026 1027 if (succeeded) { 1028 // If we get here we successfully scheduled a collection which 1029 // failed to allocate. No point in trying to allocate 1030 // further. We'll just return NULL. 1031 MutexLockerEx x(Heap_lock); 1032 *gc_count_before_ret = total_collections(); 1033 return NULL; 1034 } 1035 } else { 1036 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1037 MutexLockerEx x(Heap_lock); 1038 *gc_count_before_ret = total_collections(); 1039 return NULL; 1040 } 1041 // The GCLocker is either active or the GCLocker initiated 1042 // GC has not yet been performed. Stall until it is and 1043 // then retry the allocation. 1044 GC_locker::stall_until_clear(); 1045 (*gclocker_retry_count_ret) += 1; 1046 } 1047 1048 // We can reach here if we were unsuccessful in scheduling a 1049 // collection (because another thread beat us to it) or if we were 1050 // stalled due to the GC locker. In either can we should retry the 1051 // allocation attempt in case another thread successfully 1052 // performed a collection and reclaimed enough space. Give a 1053 // warning if we seem to be looping forever. 1054 1055 if ((QueuedAllocationWarningCount > 0) && 1056 (try_count % QueuedAllocationWarningCount == 0)) { 1057 warning("G1CollectedHeap::attempt_allocation_humongous() " 1058 "retries %d times", try_count); 1059 } 1060 } 1061 1062 ShouldNotReachHere(); 1063 return NULL; 1064 } 1065 1066 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1067 AllocationContext_t context, 1068 bool expect_null_mutator_alloc_region) { 1069 assert_at_safepoint(true /* should_be_vm_thread */); 1070 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1071 "the current alloc region was unexpectedly found to be non-NULL"); 1072 1073 if (!is_humongous(word_size)) { 1074 return _allocator->attempt_allocation_locked(word_size, context); 1075 } else { 1076 HeapWord* result = humongous_obj_allocate(word_size, context); 1077 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1078 collector_state()->set_initiate_conc_mark_if_possible(true); 1079 } 1080 return result; 1081 } 1082 1083 ShouldNotReachHere(); 1084 } 1085 1086 class PostMCRemSetClearClosure: public HeapRegionClosure { 1087 G1CollectedHeap* _g1h; 1088 ModRefBarrierSet* _mr_bs; 1089 public: 1090 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1091 _g1h(g1h), _mr_bs(mr_bs) {} 1092 1093 bool doHeapRegion(HeapRegion* r) { 1094 HeapRegionRemSet* hrrs = r->rem_set(); 1095 1096 _g1h->reset_gc_time_stamps(r); 1097 1098 if (r->is_continues_humongous()) { 1099 // We'll assert that the strong code root list and RSet is empty 1100 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1101 assert(hrrs->occupied() == 0, "RSet should be empty"); 1102 } else { 1103 hrrs->clear(); 1104 } 1105 // You might think here that we could clear just the cards 1106 // corresponding to the used region. But no: if we leave a dirty card 1107 // in a region we might allocate into, then it would prevent that card 1108 // from being enqueued, and cause it to be missed. 1109 // Re: the performance cost: we shouldn't be doing full GC anyway! 1110 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1111 1112 return false; 1113 } 1114 }; 1115 1116 void G1CollectedHeap::clear_rsets_post_compaction() { 1117 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1118 heap_region_iterate(&rs_clear); 1119 } 1120 1121 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1122 G1CollectedHeap* _g1h; 1123 UpdateRSOopClosure _cl; 1124 public: 1125 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1126 _cl(g1->g1_rem_set(), worker_i), 1127 _g1h(g1) 1128 { } 1129 1130 bool doHeapRegion(HeapRegion* r) { 1131 if (!r->is_continues_humongous()) { 1132 _cl.set_from(r); 1133 r->oop_iterate(&_cl); 1134 } 1135 return false; 1136 } 1137 }; 1138 1139 class ParRebuildRSTask: public AbstractGangTask { 1140 G1CollectedHeap* _g1; 1141 HeapRegionClaimer _hrclaimer; 1142 1143 public: 1144 ParRebuildRSTask(G1CollectedHeap* g1) : 1145 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1146 1147 void work(uint worker_id) { 1148 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1149 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1150 } 1151 }; 1152 1153 class PostCompactionPrinterClosure: public HeapRegionClosure { 1154 private: 1155 G1HRPrinter* _hr_printer; 1156 public: 1157 bool doHeapRegion(HeapRegion* hr) { 1158 assert(!hr->is_young(), "not expecting to find young regions"); 1159 if (hr->is_free()) { 1160 // We only generate output for non-empty regions. 1161 } else if (hr->is_starts_humongous()) { 1162 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1163 } else if (hr->is_continues_humongous()) { 1164 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1165 } else if (hr->is_archive()) { 1166 _hr_printer->post_compaction(hr, G1HRPrinter::Archive); 1167 } else if (hr->is_old()) { 1168 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1169 } else { 1170 ShouldNotReachHere(); 1171 } 1172 return false; 1173 } 1174 1175 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1176 : _hr_printer(hr_printer) { } 1177 }; 1178 1179 void G1CollectedHeap::print_hrm_post_compaction() { 1180 if (_hr_printer.is_active()) { 1181 PostCompactionPrinterClosure cl(hr_printer()); 1182 heap_region_iterate(&cl); 1183 } 1184 1185 } 1186 1187 bool G1CollectedHeap::do_collection(bool explicit_gc, 1188 bool clear_all_soft_refs, 1189 size_t word_size) { 1190 assert_at_safepoint(true /* should_be_vm_thread */); 1191 1192 if (GC_locker::check_active_before_gc()) { 1193 return false; 1194 } 1195 1196 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1197 gc_timer->register_gc_start(); 1198 1199 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1200 GCIdMark gc_id_mark; 1201 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1202 1203 SvcGCMarker sgcm(SvcGCMarker::FULL); 1204 ResourceMark rm; 1205 1206 print_heap_before_gc(); 1207 trace_heap_before_gc(gc_tracer); 1208 1209 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1210 1211 verify_region_sets_optional(); 1212 1213 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1214 collector_policy()->should_clear_all_soft_refs(); 1215 1216 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1217 1218 { 1219 IsGCActiveMark x; 1220 1221 // Timing 1222 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1223 GCTraceCPUTime tcpu; 1224 1225 { 1226 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1227 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1228 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1229 1230 g1_policy()->record_full_collection_start(); 1231 1232 // Note: When we have a more flexible GC logging framework that 1233 // allows us to add optional attributes to a GC log record we 1234 // could consider timing and reporting how long we wait in the 1235 // following two methods. 1236 wait_while_free_regions_coming(); 1237 // If we start the compaction before the CM threads finish 1238 // scanning the root regions we might trip them over as we'll 1239 // be moving objects / updating references. So let's wait until 1240 // they are done. By telling them to abort, they should complete 1241 // early. 1242 _cm->root_regions()->abort(); 1243 _cm->root_regions()->wait_until_scan_finished(); 1244 append_secondary_free_list_if_not_empty_with_lock(); 1245 1246 gc_prologue(true); 1247 increment_total_collections(true /* full gc */); 1248 increment_old_marking_cycles_started(); 1249 1250 assert(used() == recalculate_used(), "Should be equal"); 1251 1252 verify_before_gc(); 1253 1254 check_bitmaps("Full GC Start"); 1255 pre_full_gc_dump(gc_timer); 1256 1257 #if defined(COMPILER2) || INCLUDE_JVMCI 1258 DerivedPointerTable::clear(); 1259 #endif 1260 1261 // Disable discovery and empty the discovered lists 1262 // for the CM ref processor. 1263 ref_processor_cm()->disable_discovery(); 1264 ref_processor_cm()->abandon_partial_discovery(); 1265 ref_processor_cm()->verify_no_references_recorded(); 1266 1267 // Abandon current iterations of concurrent marking and concurrent 1268 // refinement, if any are in progress. We have to do this before 1269 // wait_until_scan_finished() below. 1270 concurrent_mark()->abort(); 1271 1272 // Make sure we'll choose a new allocation region afterwards. 1273 _allocator->release_mutator_alloc_region(); 1274 _allocator->abandon_gc_alloc_regions(); 1275 g1_rem_set()->cleanupHRRS(); 1276 1277 // We may have added regions to the current incremental collection 1278 // set between the last GC or pause and now. We need to clear the 1279 // incremental collection set and then start rebuilding it afresh 1280 // after this full GC. 1281 abandon_collection_set(g1_policy()->inc_cset_head()); 1282 g1_policy()->clear_incremental_cset(); 1283 g1_policy()->stop_incremental_cset_building(); 1284 1285 tear_down_region_sets(false /* free_list_only */); 1286 collector_state()->set_gcs_are_young(true); 1287 1288 // See the comments in g1CollectedHeap.hpp and 1289 // G1CollectedHeap::ref_processing_init() about 1290 // how reference processing currently works in G1. 1291 1292 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1293 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1294 1295 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1296 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1297 1298 ref_processor_stw()->enable_discovery(); 1299 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1300 1301 // Do collection work 1302 { 1303 HandleMark hm; // Discard invalid handles created during gc 1304 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1305 } 1306 1307 assert(num_free_regions() == 0, "we should not have added any free regions"); 1308 rebuild_region_sets(false /* free_list_only */); 1309 1310 // Enqueue any discovered reference objects that have 1311 // not been removed from the discovered lists. 1312 ref_processor_stw()->enqueue_discovered_references(); 1313 1314 #if defined(COMPILER2) || INCLUDE_JVMCI 1315 DerivedPointerTable::update_pointers(); 1316 #endif 1317 1318 MemoryService::track_memory_usage(); 1319 1320 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1321 ref_processor_stw()->verify_no_references_recorded(); 1322 1323 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1324 ClassLoaderDataGraph::purge(); 1325 MetaspaceAux::verify_metrics(); 1326 1327 // Note: since we've just done a full GC, concurrent 1328 // marking is no longer active. Therefore we need not 1329 // re-enable reference discovery for the CM ref processor. 1330 // That will be done at the start of the next marking cycle. 1331 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1332 ref_processor_cm()->verify_no_references_recorded(); 1333 1334 reset_gc_time_stamp(); 1335 // Since everything potentially moved, we will clear all remembered 1336 // sets, and clear all cards. Later we will rebuild remembered 1337 // sets. We will also reset the GC time stamps of the regions. 1338 clear_rsets_post_compaction(); 1339 check_gc_time_stamps(); 1340 1341 // Resize the heap if necessary. 1342 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); 1343 1344 // We should do this after we potentially resize the heap so 1345 // that all the COMMIT / UNCOMMIT events are generated before 1346 // the compaction events. 1347 print_hrm_post_compaction(); 1348 1349 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1350 if (hot_card_cache->use_cache()) { 1351 hot_card_cache->reset_card_counts(); 1352 hot_card_cache->reset_hot_cache(); 1353 } 1354 1355 // Rebuild remembered sets of all regions. 1356 uint n_workers = 1357 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1358 workers()->active_workers(), 1359 Threads::number_of_non_daemon_threads()); 1360 workers()->set_active_workers(n_workers); 1361 1362 ParRebuildRSTask rebuild_rs_task(this); 1363 workers()->run_task(&rebuild_rs_task); 1364 1365 // Rebuild the strong code root lists for each region 1366 rebuild_strong_code_roots(); 1367 1368 if (true) { // FIXME 1369 MetaspaceGC::compute_new_size(); 1370 } 1371 1372 #ifdef TRACESPINNING 1373 ParallelTaskTerminator::print_termination_counts(); 1374 #endif 1375 1376 // Discard all rset updates 1377 JavaThread::dirty_card_queue_set().abandon_logs(); 1378 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1379 1380 _young_list->reset_sampled_info(); 1381 // At this point there should be no regions in the 1382 // entire heap tagged as young. 1383 assert(check_young_list_empty(true /* check_heap */), 1384 "young list should be empty at this point"); 1385 1386 // Update the number of full collections that have been completed. 1387 increment_old_marking_cycles_completed(false /* concurrent */); 1388 1389 _hrm.verify_optional(); 1390 verify_region_sets_optional(); 1391 1392 verify_after_gc(); 1393 1394 // Clear the previous marking bitmap, if needed for bitmap verification. 1395 // Note we cannot do this when we clear the next marking bitmap in 1396 // ConcurrentMark::abort() above since VerifyDuringGC verifies the 1397 // objects marked during a full GC against the previous bitmap. 1398 // But we need to clear it before calling check_bitmaps below since 1399 // the full GC has compacted objects and updated TAMS but not updated 1400 // the prev bitmap. 1401 if (G1VerifyBitmaps) { 1402 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll(); 1403 } 1404 check_bitmaps("Full GC End"); 1405 1406 // Start a new incremental collection set for the next pause 1407 assert(g1_policy()->collection_set() == NULL, "must be"); 1408 g1_policy()->start_incremental_cset_building(); 1409 1410 clear_cset_fast_test(); 1411 1412 _allocator->init_mutator_alloc_region(); 1413 1414 g1_policy()->record_full_collection_end(); 1415 1416 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1417 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1418 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1419 // before any GC notifications are raised. 1420 g1mm()->update_sizes(); 1421 1422 gc_epilogue(true); 1423 } 1424 1425 g1_policy()->print_detailed_heap_transition(); 1426 1427 print_heap_after_gc(); 1428 trace_heap_after_gc(gc_tracer); 1429 1430 post_full_gc_dump(gc_timer); 1431 1432 gc_timer->register_gc_end(); 1433 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1434 } 1435 1436 return true; 1437 } 1438 1439 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1440 // do_collection() will return whether it succeeded in performing 1441 // the GC. Currently, there is no facility on the 1442 // do_full_collection() API to notify the caller than the collection 1443 // did not succeed (e.g., because it was locked out by the GC 1444 // locker). So, right now, we'll ignore the return value. 1445 bool dummy = do_collection(true, /* explicit_gc */ 1446 clear_all_soft_refs, 1447 0 /* word_size */); 1448 } 1449 1450 // This code is mostly copied from TenuredGeneration. 1451 void 1452 G1CollectedHeap:: 1453 resize_if_necessary_after_full_collection(size_t word_size) { 1454 // Include the current allocation, if any, and bytes that will be 1455 // pre-allocated to support collections, as "used". 1456 const size_t used_after_gc = used(); 1457 const size_t capacity_after_gc = capacity(); 1458 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1459 1460 // This is enforced in arguments.cpp. 1461 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1462 "otherwise the code below doesn't make sense"); 1463 1464 // We don't have floating point command-line arguments 1465 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1466 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1467 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1468 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1469 1470 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1471 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1472 1473 // We have to be careful here as these two calculations can overflow 1474 // 32-bit size_t's. 1475 double used_after_gc_d = (double) used_after_gc; 1476 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1477 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1478 1479 // Let's make sure that they are both under the max heap size, which 1480 // by default will make them fit into a size_t. 1481 double desired_capacity_upper_bound = (double) max_heap_size; 1482 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1483 desired_capacity_upper_bound); 1484 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1485 desired_capacity_upper_bound); 1486 1487 // We can now safely turn them into size_t's. 1488 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1489 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1490 1491 // This assert only makes sense here, before we adjust them 1492 // with respect to the min and max heap size. 1493 assert(minimum_desired_capacity <= maximum_desired_capacity, 1494 "minimum_desired_capacity = " SIZE_FORMAT ", " 1495 "maximum_desired_capacity = " SIZE_FORMAT, 1496 minimum_desired_capacity, maximum_desired_capacity); 1497 1498 // Should not be greater than the heap max size. No need to adjust 1499 // it with respect to the heap min size as it's a lower bound (i.e., 1500 // we'll try to make the capacity larger than it, not smaller). 1501 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1502 // Should not be less than the heap min size. No need to adjust it 1503 // with respect to the heap max size as it's an upper bound (i.e., 1504 // we'll try to make the capacity smaller than it, not greater). 1505 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1506 1507 if (capacity_after_gc < minimum_desired_capacity) { 1508 // Don't expand unless it's significant 1509 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1510 1511 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1512 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1513 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1514 1515 expand(expand_bytes); 1516 1517 // No expansion, now see if we want to shrink 1518 } else if (capacity_after_gc > maximum_desired_capacity) { 1519 // Capacity too large, compute shrinking size 1520 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1521 1522 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1523 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1524 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1525 1526 shrink(shrink_bytes); 1527 } 1528 } 1529 1530 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1531 AllocationContext_t context, 1532 bool do_gc, 1533 bool clear_all_soft_refs, 1534 bool expect_null_mutator_alloc_region, 1535 bool* gc_succeeded) { 1536 *gc_succeeded = true; 1537 // Let's attempt the allocation first. 1538 HeapWord* result = 1539 attempt_allocation_at_safepoint(word_size, 1540 context, 1541 expect_null_mutator_alloc_region); 1542 if (result != NULL) { 1543 assert(*gc_succeeded, "sanity"); 1544 return result; 1545 } 1546 1547 // In a G1 heap, we're supposed to keep allocation from failing by 1548 // incremental pauses. Therefore, at least for now, we'll favor 1549 // expansion over collection. (This might change in the future if we can 1550 // do something smarter than full collection to satisfy a failed alloc.) 1551 result = expand_and_allocate(word_size, context); 1552 if (result != NULL) { 1553 assert(*gc_succeeded, "sanity"); 1554 return result; 1555 } 1556 1557 if (do_gc) { 1558 // Expansion didn't work, we'll try to do a Full GC. 1559 *gc_succeeded = do_collection(false, /* explicit_gc */ 1560 clear_all_soft_refs, 1561 word_size); 1562 } 1563 1564 return NULL; 1565 } 1566 1567 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1568 AllocationContext_t context, 1569 bool* succeeded) { 1570 assert_at_safepoint(true /* should_be_vm_thread */); 1571 1572 // Attempts to allocate followed by Full GC. 1573 HeapWord* result = 1574 satisfy_failed_allocation_helper(word_size, 1575 context, 1576 true, /* do_gc */ 1577 false, /* clear_all_soft_refs */ 1578 false, /* expect_null_mutator_alloc_region */ 1579 succeeded); 1580 1581 if (result != NULL || !*succeeded) { 1582 return result; 1583 } 1584 1585 // Attempts to allocate followed by Full GC that will collect all soft references. 1586 result = satisfy_failed_allocation_helper(word_size, 1587 context, 1588 true, /* do_gc */ 1589 true, /* clear_all_soft_refs */ 1590 true, /* expect_null_mutator_alloc_region */ 1591 succeeded); 1592 1593 if (result != NULL || !*succeeded) { 1594 return result; 1595 } 1596 1597 // Attempts to allocate, no GC 1598 result = satisfy_failed_allocation_helper(word_size, 1599 context, 1600 false, /* do_gc */ 1601 false, /* clear_all_soft_refs */ 1602 true, /* expect_null_mutator_alloc_region */ 1603 succeeded); 1604 1605 if (result != NULL) { 1606 assert(*succeeded, "sanity"); 1607 return result; 1608 } 1609 1610 assert(!collector_policy()->should_clear_all_soft_refs(), 1611 "Flag should have been handled and cleared prior to this point"); 1612 1613 // What else? We might try synchronous finalization later. If the total 1614 // space available is large enough for the allocation, then a more 1615 // complete compaction phase than we've tried so far might be 1616 // appropriate. 1617 assert(*succeeded, "sanity"); 1618 return NULL; 1619 } 1620 1621 // Attempting to expand the heap sufficiently 1622 // to support an allocation of the given "word_size". If 1623 // successful, perform the allocation and return the address of the 1624 // allocated block, or else "NULL". 1625 1626 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1627 assert_at_safepoint(true /* should_be_vm_thread */); 1628 1629 verify_region_sets_optional(); 1630 1631 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1632 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1633 word_size * HeapWordSize); 1634 1635 1636 if (expand(expand_bytes)) { 1637 _hrm.verify_optional(); 1638 verify_region_sets_optional(); 1639 return attempt_allocation_at_safepoint(word_size, 1640 context, 1641 false /* expect_null_mutator_alloc_region */); 1642 } 1643 return NULL; 1644 } 1645 1646 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) { 1647 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1648 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1649 HeapRegion::GrainBytes); 1650 1651 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B", 1652 expand_bytes, aligned_expand_bytes); 1653 1654 if (is_maximal_no_gc()) { 1655 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1656 return false; 1657 } 1658 1659 double expand_heap_start_time_sec = os::elapsedTime(); 1660 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1661 assert(regions_to_expand > 0, "Must expand by at least one region"); 1662 1663 uint expanded_by = _hrm.expand_by(regions_to_expand); 1664 if (expand_time_ms != NULL) { 1665 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1666 } 1667 1668 if (expanded_by > 0) { 1669 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1670 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1671 g1_policy()->record_new_heap_size(num_regions()); 1672 } else { 1673 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1674 1675 // The expansion of the virtual storage space was unsuccessful. 1676 // Let's see if it was because we ran out of swap. 1677 if (G1ExitOnExpansionFailure && 1678 _hrm.available() >= regions_to_expand) { 1679 // We had head room... 1680 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1681 } 1682 } 1683 return regions_to_expand > 0; 1684 } 1685 1686 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1687 size_t aligned_shrink_bytes = 1688 ReservedSpace::page_align_size_down(shrink_bytes); 1689 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1690 HeapRegion::GrainBytes); 1691 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1692 1693 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1694 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1695 1696 1697 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", 1698 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1699 if (num_regions_removed > 0) { 1700 g1_policy()->record_new_heap_size(num_regions()); 1701 } else { 1702 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1703 } 1704 } 1705 1706 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1707 verify_region_sets_optional(); 1708 1709 // We should only reach here at the end of a Full GC which means we 1710 // should not not be holding to any GC alloc regions. The method 1711 // below will make sure of that and do any remaining clean up. 1712 _allocator->abandon_gc_alloc_regions(); 1713 1714 // Instead of tearing down / rebuilding the free lists here, we 1715 // could instead use the remove_all_pending() method on free_list to 1716 // remove only the ones that we need to remove. 1717 tear_down_region_sets(true /* free_list_only */); 1718 shrink_helper(shrink_bytes); 1719 rebuild_region_sets(true /* free_list_only */); 1720 1721 _hrm.verify_optional(); 1722 verify_region_sets_optional(); 1723 } 1724 1725 // Public methods. 1726 1727 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1728 CollectedHeap(), 1729 _g1_policy(policy_), 1730 _dirty_card_queue_set(false), 1731 _is_alive_closure_cm(this), 1732 _is_alive_closure_stw(this), 1733 _ref_processor_cm(NULL), 1734 _ref_processor_stw(NULL), 1735 _bot_shared(NULL), 1736 _cg1r(NULL), 1737 _g1mm(NULL), 1738 _refine_cte_cl(NULL), 1739 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1740 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1741 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1742 _humongous_reclaim_candidates(), 1743 _has_humongous_reclaim_candidates(false), 1744 _archive_allocator(NULL), 1745 _free_regions_coming(false), 1746 _young_list(new YoungList(this)), 1747 _gc_time_stamp(0), 1748 _summary_bytes_used(0), 1749 _survivor_evac_stats(YoungPLABSize, PLABWeight), 1750 _old_evac_stats(OldPLABSize, PLABWeight), 1751 _expand_heap_after_alloc_failure(true), 1752 _old_marking_cycles_started(0), 1753 _old_marking_cycles_completed(0), 1754 _heap_summary_sent(false), 1755 _in_cset_fast_test(), 1756 _dirty_cards_region_list(NULL), 1757 _worker_cset_start_region(NULL), 1758 _worker_cset_start_region_time_stamp(NULL), 1759 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1760 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1761 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1762 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1763 1764 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1765 /* are_GC_task_threads */true, 1766 /* are_ConcurrentGC_threads */false); 1767 _workers->initialize_workers(); 1768 1769 _allocator = G1Allocator::create_allocator(this); 1770 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1771 1772 // Override the default _filler_array_max_size so that no humongous filler 1773 // objects are created. 1774 _filler_array_max_size = _humongous_object_threshold_in_words; 1775 1776 uint n_queues = ParallelGCThreads; 1777 _task_queues = new RefToScanQueueSet(n_queues); 1778 1779 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1780 assert(n_rem_sets > 0, "Invariant."); 1781 1782 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1783 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC); 1784 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1785 1786 for (uint i = 0; i < n_queues; i++) { 1787 RefToScanQueue* q = new RefToScanQueue(); 1788 q->initialize(); 1789 _task_queues->register_queue(i, q); 1790 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1791 } 1792 clear_cset_start_regions(); 1793 1794 // Initialize the G1EvacuationFailureALot counters and flags. 1795 NOT_PRODUCT(reset_evacuation_should_fail();) 1796 1797 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1798 } 1799 1800 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1801 size_t size, 1802 size_t translation_factor) { 1803 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1804 // Allocate a new reserved space, preferring to use large pages. 1805 ReservedSpace rs(size, preferred_page_size); 1806 G1RegionToSpaceMapper* result = 1807 G1RegionToSpaceMapper::create_mapper(rs, 1808 size, 1809 rs.alignment(), 1810 HeapRegion::GrainBytes, 1811 translation_factor, 1812 mtGC); 1813 if (TracePageSizes) { 1814 tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT, 1815 description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size); 1816 } 1817 return result; 1818 } 1819 1820 jint G1CollectedHeap::initialize() { 1821 CollectedHeap::pre_initialize(); 1822 os::enable_vtime(); 1823 1824 // Necessary to satisfy locking discipline assertions. 1825 1826 MutexLocker x(Heap_lock); 1827 1828 // While there are no constraints in the GC code that HeapWordSize 1829 // be any particular value, there are multiple other areas in the 1830 // system which believe this to be true (e.g. oop->object_size in some 1831 // cases incorrectly returns the size in wordSize units rather than 1832 // HeapWordSize). 1833 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1834 1835 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1836 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1837 size_t heap_alignment = collector_policy()->heap_alignment(); 1838 1839 // Ensure that the sizes are properly aligned. 1840 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1841 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1842 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1843 1844 _refine_cte_cl = new RefineCardTableEntryClosure(); 1845 1846 jint ecode = JNI_OK; 1847 _cg1r = ConcurrentG1Refine::create(this, _refine_cte_cl, &ecode); 1848 if (_cg1r == NULL) { 1849 return ecode; 1850 } 1851 1852 // Reserve the maximum. 1853 1854 // When compressed oops are enabled, the preferred heap base 1855 // is calculated by subtracting the requested size from the 1856 // 32Gb boundary and using the result as the base address for 1857 // heap reservation. If the requested size is not aligned to 1858 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1859 // into the ReservedHeapSpace constructor) then the actual 1860 // base of the reserved heap may end up differing from the 1861 // address that was requested (i.e. the preferred heap base). 1862 // If this happens then we could end up using a non-optimal 1863 // compressed oops mode. 1864 1865 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1866 heap_alignment); 1867 1868 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1869 1870 // Create the barrier set for the entire reserved region. 1871 G1SATBCardTableLoggingModRefBS* bs 1872 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1873 bs->initialize(); 1874 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1875 set_barrier_set(bs); 1876 1877 // Also create a G1 rem set. 1878 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 1879 1880 // Carve out the G1 part of the heap. 1881 1882 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1883 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1884 G1RegionToSpaceMapper* heap_storage = 1885 G1RegionToSpaceMapper::create_mapper(g1_rs, 1886 g1_rs.size(), 1887 page_size, 1888 HeapRegion::GrainBytes, 1889 1, 1890 mtJavaHeap); 1891 os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(), 1892 max_byte_size, page_size, 1893 heap_rs.base(), 1894 heap_rs.size()); 1895 heap_storage->set_mapping_changed_listener(&_listener); 1896 1897 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1898 G1RegionToSpaceMapper* bot_storage = 1899 create_aux_memory_mapper("Block offset table", 1900 G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize), 1901 G1BlockOffsetSharedArray::heap_map_factor()); 1902 1903 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1904 G1RegionToSpaceMapper* cardtable_storage = 1905 create_aux_memory_mapper("Card table", 1906 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1907 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1908 1909 G1RegionToSpaceMapper* card_counts_storage = 1910 create_aux_memory_mapper("Card counts table", 1911 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1912 G1CardCounts::heap_map_factor()); 1913 1914 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size()); 1915 G1RegionToSpaceMapper* prev_bitmap_storage = 1916 create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1917 G1RegionToSpaceMapper* next_bitmap_storage = 1918 create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1919 1920 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1921 g1_barrier_set()->initialize(cardtable_storage); 1922 // Do later initialization work for concurrent refinement. 1923 _cg1r->init(card_counts_storage); 1924 1925 // 6843694 - ensure that the maximum region index can fit 1926 // in the remembered set structures. 1927 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1928 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1929 1930 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1931 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1932 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1933 "too many cards per region"); 1934 1935 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1936 1937 _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage); 1938 1939 { 1940 HeapWord* start = _hrm.reserved().start(); 1941 HeapWord* end = _hrm.reserved().end(); 1942 size_t granularity = HeapRegion::GrainBytes; 1943 1944 _in_cset_fast_test.initialize(start, end, granularity); 1945 _humongous_reclaim_candidates.initialize(start, end, granularity); 1946 } 1947 1948 // Create the ConcurrentMark data structure and thread. 1949 // (Must do this late, so that "max_regions" is defined.) 1950 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1951 if (_cm == NULL || !_cm->completed_initialization()) { 1952 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 1953 return JNI_ENOMEM; 1954 } 1955 _cmThread = _cm->cmThread(); 1956 1957 // Initialize the from_card cache structure of HeapRegionRemSet. 1958 HeapRegionRemSet::init_heap(max_regions()); 1959 1960 // Now expand into the initial heap size. 1961 if (!expand(init_byte_size)) { 1962 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1963 return JNI_ENOMEM; 1964 } 1965 1966 // Perform any initialization actions delegated to the policy. 1967 g1_policy()->init(); 1968 1969 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1970 SATB_Q_FL_lock, 1971 G1SATBProcessCompletedThreshold, 1972 Shared_SATB_Q_lock); 1973 1974 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 1975 DirtyCardQ_CBL_mon, 1976 DirtyCardQ_FL_lock, 1977 concurrent_g1_refine()->yellow_zone(), 1978 concurrent_g1_refine()->red_zone(), 1979 Shared_DirtyCardQ_lock); 1980 1981 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 1982 DirtyCardQ_CBL_mon, 1983 DirtyCardQ_FL_lock, 1984 -1, // never trigger processing 1985 -1, // no limit on length 1986 Shared_DirtyCardQ_lock, 1987 &JavaThread::dirty_card_queue_set()); 1988 1989 // Here we allocate the dummy HeapRegion that is required by the 1990 // G1AllocRegion class. 1991 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1992 1993 // We'll re-use the same region whether the alloc region will 1994 // require BOT updates or not and, if it doesn't, then a non-young 1995 // region will complain that it cannot support allocations without 1996 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1997 dummy_region->set_eden(); 1998 // Make sure it's full. 1999 dummy_region->set_top(dummy_region->end()); 2000 G1AllocRegion::setup(this, dummy_region); 2001 2002 _allocator->init_mutator_alloc_region(); 2003 2004 // Do create of the monitoring and management support so that 2005 // values in the heap have been properly initialized. 2006 _g1mm = new G1MonitoringSupport(this); 2007 2008 G1StringDedup::initialize(); 2009 2010 _preserved_objs = NEW_C_HEAP_ARRAY(OopAndMarkOopStack, ParallelGCThreads, mtGC); 2011 for (uint i = 0; i < ParallelGCThreads; i++) { 2012 new (&_preserved_objs[i]) OopAndMarkOopStack(); 2013 } 2014 2015 return JNI_OK; 2016 } 2017 2018 void G1CollectedHeap::stop() { 2019 // Stop all concurrent threads. We do this to make sure these threads 2020 // do not continue to execute and access resources (e.g. logging) 2021 // that are destroyed during shutdown. 2022 _cg1r->stop(); 2023 _cmThread->stop(); 2024 if (G1StringDedup::is_enabled()) { 2025 G1StringDedup::stop(); 2026 } 2027 } 2028 2029 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2030 return HeapRegion::max_region_size(); 2031 } 2032 2033 void G1CollectedHeap::post_initialize() { 2034 CollectedHeap::post_initialize(); 2035 ref_processing_init(); 2036 } 2037 2038 void G1CollectedHeap::ref_processing_init() { 2039 // Reference processing in G1 currently works as follows: 2040 // 2041 // * There are two reference processor instances. One is 2042 // used to record and process discovered references 2043 // during concurrent marking; the other is used to 2044 // record and process references during STW pauses 2045 // (both full and incremental). 2046 // * Both ref processors need to 'span' the entire heap as 2047 // the regions in the collection set may be dotted around. 2048 // 2049 // * For the concurrent marking ref processor: 2050 // * Reference discovery is enabled at initial marking. 2051 // * Reference discovery is disabled and the discovered 2052 // references processed etc during remarking. 2053 // * Reference discovery is MT (see below). 2054 // * Reference discovery requires a barrier (see below). 2055 // * Reference processing may or may not be MT 2056 // (depending on the value of ParallelRefProcEnabled 2057 // and ParallelGCThreads). 2058 // * A full GC disables reference discovery by the CM 2059 // ref processor and abandons any entries on it's 2060 // discovered lists. 2061 // 2062 // * For the STW processor: 2063 // * Non MT discovery is enabled at the start of a full GC. 2064 // * Processing and enqueueing during a full GC is non-MT. 2065 // * During a full GC, references are processed after marking. 2066 // 2067 // * Discovery (may or may not be MT) is enabled at the start 2068 // of an incremental evacuation pause. 2069 // * References are processed near the end of a STW evacuation pause. 2070 // * For both types of GC: 2071 // * Discovery is atomic - i.e. not concurrent. 2072 // * Reference discovery will not need a barrier. 2073 2074 MemRegion mr = reserved_region(); 2075 2076 // Concurrent Mark ref processor 2077 _ref_processor_cm = 2078 new ReferenceProcessor(mr, // span 2079 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2080 // mt processing 2081 ParallelGCThreads, 2082 // degree of mt processing 2083 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2084 // mt discovery 2085 MAX2(ParallelGCThreads, ConcGCThreads), 2086 // degree of mt discovery 2087 false, 2088 // Reference discovery is not atomic 2089 &_is_alive_closure_cm); 2090 // is alive closure 2091 // (for efficiency/performance) 2092 2093 // STW ref processor 2094 _ref_processor_stw = 2095 new ReferenceProcessor(mr, // span 2096 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2097 // mt processing 2098 ParallelGCThreads, 2099 // degree of mt processing 2100 (ParallelGCThreads > 1), 2101 // mt discovery 2102 ParallelGCThreads, 2103 // degree of mt discovery 2104 true, 2105 // Reference discovery is atomic 2106 &_is_alive_closure_stw); 2107 // is alive closure 2108 // (for efficiency/performance) 2109 } 2110 2111 CollectorPolicy* G1CollectedHeap::collector_policy() const { 2112 return g1_policy(); 2113 } 2114 2115 size_t G1CollectedHeap::capacity() const { 2116 return _hrm.length() * HeapRegion::GrainBytes; 2117 } 2118 2119 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2120 hr->reset_gc_time_stamp(); 2121 } 2122 2123 #ifndef PRODUCT 2124 2125 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2126 private: 2127 unsigned _gc_time_stamp; 2128 bool _failures; 2129 2130 public: 2131 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2132 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2133 2134 virtual bool doHeapRegion(HeapRegion* hr) { 2135 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2136 if (_gc_time_stamp != region_gc_time_stamp) { 2137 log_info(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 2138 region_gc_time_stamp, _gc_time_stamp); 2139 _failures = true; 2140 } 2141 return false; 2142 } 2143 2144 bool failures() { return _failures; } 2145 }; 2146 2147 void G1CollectedHeap::check_gc_time_stamps() { 2148 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2149 heap_region_iterate(&cl); 2150 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2151 } 2152 #endif // PRODUCT 2153 2154 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2155 _cg1r->hot_card_cache()->drain(cl, worker_i); 2156 } 2157 2158 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2159 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2160 size_t n_completed_buffers = 0; 2161 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2162 n_completed_buffers++; 2163 } 2164 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2165 dcqs.clear_n_completed_buffers(); 2166 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2167 } 2168 2169 // Computes the sum of the storage used by the various regions. 2170 size_t G1CollectedHeap::used() const { 2171 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2172 if (_archive_allocator != NULL) { 2173 result += _archive_allocator->used(); 2174 } 2175 return result; 2176 } 2177 2178 size_t G1CollectedHeap::used_unlocked() const { 2179 return _summary_bytes_used; 2180 } 2181 2182 class SumUsedClosure: public HeapRegionClosure { 2183 size_t _used; 2184 public: 2185 SumUsedClosure() : _used(0) {} 2186 bool doHeapRegion(HeapRegion* r) { 2187 _used += r->used(); 2188 return false; 2189 } 2190 size_t result() { return _used; } 2191 }; 2192 2193 size_t G1CollectedHeap::recalculate_used() const { 2194 double recalculate_used_start = os::elapsedTime(); 2195 2196 SumUsedClosure blk; 2197 heap_region_iterate(&blk); 2198 2199 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2200 return blk.result(); 2201 } 2202 2203 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2204 switch (cause) { 2205 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2206 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2207 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2208 case GCCause::_g1_humongous_allocation: return true; 2209 case GCCause::_update_allocation_context_stats_inc: return true; 2210 case GCCause::_wb_conc_mark: return true; 2211 default: return false; 2212 } 2213 } 2214 2215 #ifndef PRODUCT 2216 void G1CollectedHeap::allocate_dummy_regions() { 2217 // Let's fill up most of the region 2218 size_t word_size = HeapRegion::GrainWords - 1024; 2219 // And as a result the region we'll allocate will be humongous. 2220 guarantee(is_humongous(word_size), "sanity"); 2221 2222 // _filler_array_max_size is set to humongous object threshold 2223 // but temporarily change it to use CollectedHeap::fill_with_object(). 2224 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2225 2226 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2227 // Let's use the existing mechanism for the allocation 2228 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2229 AllocationContext::system()); 2230 if (dummy_obj != NULL) { 2231 MemRegion mr(dummy_obj, word_size); 2232 CollectedHeap::fill_with_object(mr); 2233 } else { 2234 // If we can't allocate once, we probably cannot allocate 2235 // again. Let's get out of the loop. 2236 break; 2237 } 2238 } 2239 } 2240 #endif // !PRODUCT 2241 2242 void G1CollectedHeap::increment_old_marking_cycles_started() { 2243 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2244 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2245 "Wrong marking cycle count (started: %d, completed: %d)", 2246 _old_marking_cycles_started, _old_marking_cycles_completed); 2247 2248 _old_marking_cycles_started++; 2249 } 2250 2251 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2252 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2253 2254 // We assume that if concurrent == true, then the caller is a 2255 // concurrent thread that was joined the Suspendible Thread 2256 // Set. If there's ever a cheap way to check this, we should add an 2257 // assert here. 2258 2259 // Given that this method is called at the end of a Full GC or of a 2260 // concurrent cycle, and those can be nested (i.e., a Full GC can 2261 // interrupt a concurrent cycle), the number of full collections 2262 // completed should be either one (in the case where there was no 2263 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2264 // behind the number of full collections started. 2265 2266 // This is the case for the inner caller, i.e. a Full GC. 2267 assert(concurrent || 2268 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2269 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2270 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2271 "is inconsistent with _old_marking_cycles_completed = %u", 2272 _old_marking_cycles_started, _old_marking_cycles_completed); 2273 2274 // This is the case for the outer caller, i.e. the concurrent cycle. 2275 assert(!concurrent || 2276 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2277 "for outer caller (concurrent cycle): " 2278 "_old_marking_cycles_started = %u " 2279 "is inconsistent with _old_marking_cycles_completed = %u", 2280 _old_marking_cycles_started, _old_marking_cycles_completed); 2281 2282 _old_marking_cycles_completed += 1; 2283 2284 // We need to clear the "in_progress" flag in the CM thread before 2285 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2286 // is set) so that if a waiter requests another System.gc() it doesn't 2287 // incorrectly see that a marking cycle is still in progress. 2288 if (concurrent) { 2289 _cmThread->set_idle(); 2290 } 2291 2292 // This notify_all() will ensure that a thread that called 2293 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2294 // and it's waiting for a full GC to finish will be woken up. It is 2295 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2296 FullGCCount_lock->notify_all(); 2297 } 2298 2299 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2300 GCIdMarkAndRestore conc_gc_id_mark; 2301 collector_state()->set_concurrent_cycle_started(true); 2302 _gc_timer_cm->register_gc_start(start_time); 2303 2304 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2305 trace_heap_before_gc(_gc_tracer_cm); 2306 _cmThread->set_gc_id(GCId::current()); 2307 } 2308 2309 void G1CollectedHeap::register_concurrent_cycle_end() { 2310 if (collector_state()->concurrent_cycle_started()) { 2311 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2312 if (_cm->has_aborted()) { 2313 _gc_tracer_cm->report_concurrent_mode_failure(); 2314 } 2315 2316 _gc_timer_cm->register_gc_end(); 2317 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2318 2319 // Clear state variables to prepare for the next concurrent cycle. 2320 collector_state()->set_concurrent_cycle_started(false); 2321 _heap_summary_sent = false; 2322 } 2323 } 2324 2325 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2326 if (collector_state()->concurrent_cycle_started()) { 2327 // This function can be called when: 2328 // the cleanup pause is run 2329 // the concurrent cycle is aborted before the cleanup pause. 2330 // the concurrent cycle is aborted after the cleanup pause, 2331 // but before the concurrent cycle end has been registered. 2332 // Make sure that we only send the heap information once. 2333 if (!_heap_summary_sent) { 2334 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2335 trace_heap_after_gc(_gc_tracer_cm); 2336 _heap_summary_sent = true; 2337 } 2338 } 2339 } 2340 2341 void G1CollectedHeap::collect(GCCause::Cause cause) { 2342 assert_heap_not_locked(); 2343 2344 uint gc_count_before; 2345 uint old_marking_count_before; 2346 uint full_gc_count_before; 2347 bool retry_gc; 2348 2349 do { 2350 retry_gc = false; 2351 2352 { 2353 MutexLocker ml(Heap_lock); 2354 2355 // Read the GC count while holding the Heap_lock 2356 gc_count_before = total_collections(); 2357 full_gc_count_before = total_full_collections(); 2358 old_marking_count_before = _old_marking_cycles_started; 2359 } 2360 2361 if (should_do_concurrent_full_gc(cause)) { 2362 // Schedule an initial-mark evacuation pause that will start a 2363 // concurrent cycle. We're setting word_size to 0 which means that 2364 // we are not requesting a post-GC allocation. 2365 VM_G1IncCollectionPause op(gc_count_before, 2366 0, /* word_size */ 2367 true, /* should_initiate_conc_mark */ 2368 g1_policy()->max_pause_time_ms(), 2369 cause); 2370 op.set_allocation_context(AllocationContext::current()); 2371 2372 VMThread::execute(&op); 2373 if (!op.pause_succeeded()) { 2374 if (old_marking_count_before == _old_marking_cycles_started) { 2375 retry_gc = op.should_retry_gc(); 2376 } else { 2377 // A Full GC happened while we were trying to schedule the 2378 // initial-mark GC. No point in starting a new cycle given 2379 // that the whole heap was collected anyway. 2380 } 2381 2382 if (retry_gc) { 2383 if (GC_locker::is_active_and_needs_gc()) { 2384 GC_locker::stall_until_clear(); 2385 } 2386 } 2387 } 2388 } else { 2389 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2390 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2391 2392 // Schedule a standard evacuation pause. We're setting word_size 2393 // to 0 which means that we are not requesting a post-GC allocation. 2394 VM_G1IncCollectionPause op(gc_count_before, 2395 0, /* word_size */ 2396 false, /* should_initiate_conc_mark */ 2397 g1_policy()->max_pause_time_ms(), 2398 cause); 2399 VMThread::execute(&op); 2400 } else { 2401 // Schedule a Full GC. 2402 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2403 VMThread::execute(&op); 2404 } 2405 } 2406 } while (retry_gc); 2407 } 2408 2409 bool G1CollectedHeap::is_in(const void* p) const { 2410 if (_hrm.reserved().contains(p)) { 2411 // Given that we know that p is in the reserved space, 2412 // heap_region_containing() should successfully 2413 // return the containing region. 2414 HeapRegion* hr = heap_region_containing(p); 2415 return hr->is_in(p); 2416 } else { 2417 return false; 2418 } 2419 } 2420 2421 #ifdef ASSERT 2422 bool G1CollectedHeap::is_in_exact(const void* p) const { 2423 bool contains = reserved_region().contains(p); 2424 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2425 if (contains && available) { 2426 return true; 2427 } else { 2428 return false; 2429 } 2430 } 2431 #endif 2432 2433 bool G1CollectedHeap::obj_in_cs(oop obj) { 2434 HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj); 2435 return r != NULL && r->in_collection_set(); 2436 } 2437 2438 // Iteration functions. 2439 2440 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2441 2442 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2443 ExtendedOopClosure* _cl; 2444 public: 2445 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2446 bool doHeapRegion(HeapRegion* r) { 2447 if (!r->is_continues_humongous()) { 2448 r->oop_iterate(_cl); 2449 } 2450 return false; 2451 } 2452 }; 2453 2454 // Iterates an ObjectClosure over all objects within a HeapRegion. 2455 2456 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2457 ObjectClosure* _cl; 2458 public: 2459 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2460 bool doHeapRegion(HeapRegion* r) { 2461 if (!r->is_continues_humongous()) { 2462 r->object_iterate(_cl); 2463 } 2464 return false; 2465 } 2466 }; 2467 2468 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2469 IterateObjectClosureRegionClosure blk(cl); 2470 heap_region_iterate(&blk); 2471 } 2472 2473 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2474 _hrm.iterate(cl); 2475 } 2476 2477 void 2478 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2479 uint worker_id, 2480 HeapRegionClaimer *hrclaimer, 2481 bool concurrent) const { 2482 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2483 } 2484 2485 // Clear the cached CSet starting regions and (more importantly) 2486 // the time stamps. Called when we reset the GC time stamp. 2487 void G1CollectedHeap::clear_cset_start_regions() { 2488 assert(_worker_cset_start_region != NULL, "sanity"); 2489 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2490 2491 for (uint i = 0; i < ParallelGCThreads; i++) { 2492 _worker_cset_start_region[i] = NULL; 2493 _worker_cset_start_region_time_stamp[i] = 0; 2494 } 2495 } 2496 2497 // Given the id of a worker, obtain or calculate a suitable 2498 // starting region for iterating over the current collection set. 2499 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2500 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2501 2502 HeapRegion* result = NULL; 2503 unsigned gc_time_stamp = get_gc_time_stamp(); 2504 2505 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2506 // Cached starting region for current worker was set 2507 // during the current pause - so it's valid. 2508 // Note: the cached starting heap region may be NULL 2509 // (when the collection set is empty). 2510 result = _worker_cset_start_region[worker_i]; 2511 assert(result == NULL || result->in_collection_set(), "sanity"); 2512 return result; 2513 } 2514 2515 // The cached entry was not valid so let's calculate 2516 // a suitable starting heap region for this worker. 2517 2518 // We want the parallel threads to start their collection 2519 // set iteration at different collection set regions to 2520 // avoid contention. 2521 // If we have: 2522 // n collection set regions 2523 // p threads 2524 // Then thread t will start at region floor ((t * n) / p) 2525 2526 result = g1_policy()->collection_set(); 2527 uint cs_size = g1_policy()->cset_region_length(); 2528 uint active_workers = workers()->active_workers(); 2529 2530 uint end_ind = (cs_size * worker_i) / active_workers; 2531 uint start_ind = 0; 2532 2533 if (worker_i > 0 && 2534 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2535 // Previous workers starting region is valid 2536 // so let's iterate from there 2537 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2538 result = _worker_cset_start_region[worker_i - 1]; 2539 } 2540 2541 for (uint i = start_ind; i < end_ind; i++) { 2542 result = result->next_in_collection_set(); 2543 } 2544 2545 // Note: the calculated starting heap region may be NULL 2546 // (when the collection set is empty). 2547 assert(result == NULL || result->in_collection_set(), "sanity"); 2548 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2549 "should be updated only once per pause"); 2550 _worker_cset_start_region[worker_i] = result; 2551 OrderAccess::storestore(); 2552 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2553 return result; 2554 } 2555 2556 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2557 HeapRegion* r = g1_policy()->collection_set(); 2558 while (r != NULL) { 2559 HeapRegion* next = r->next_in_collection_set(); 2560 if (cl->doHeapRegion(r)) { 2561 cl->incomplete(); 2562 return; 2563 } 2564 r = next; 2565 } 2566 } 2567 2568 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2569 HeapRegionClosure *cl) { 2570 if (r == NULL) { 2571 // The CSet is empty so there's nothing to do. 2572 return; 2573 } 2574 2575 assert(r->in_collection_set(), 2576 "Start region must be a member of the collection set."); 2577 HeapRegion* cur = r; 2578 while (cur != NULL) { 2579 HeapRegion* next = cur->next_in_collection_set(); 2580 if (cl->doHeapRegion(cur) && false) { 2581 cl->incomplete(); 2582 return; 2583 } 2584 cur = next; 2585 } 2586 cur = g1_policy()->collection_set(); 2587 while (cur != r) { 2588 HeapRegion* next = cur->next_in_collection_set(); 2589 if (cl->doHeapRegion(cur) && false) { 2590 cl->incomplete(); 2591 return; 2592 } 2593 cur = next; 2594 } 2595 } 2596 2597 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2598 HeapRegion* result = _hrm.next_region_in_heap(from); 2599 while (result != NULL && result->is_pinned()) { 2600 result = _hrm.next_region_in_heap(result); 2601 } 2602 return result; 2603 } 2604 2605 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2606 HeapRegion* hr = heap_region_containing(addr); 2607 return hr->block_start(addr); 2608 } 2609 2610 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2611 HeapRegion* hr = heap_region_containing(addr); 2612 return hr->block_size(addr); 2613 } 2614 2615 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2616 HeapRegion* hr = heap_region_containing(addr); 2617 return hr->block_is_obj(addr); 2618 } 2619 2620 bool G1CollectedHeap::supports_tlab_allocation() const { 2621 return true; 2622 } 2623 2624 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2625 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2626 } 2627 2628 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2629 return young_list()->eden_used_bytes(); 2630 } 2631 2632 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2633 // must be equal to the humongous object limit. 2634 size_t G1CollectedHeap::max_tlab_size() const { 2635 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2636 } 2637 2638 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2639 AllocationContext_t context = AllocationContext::current(); 2640 return _allocator->unsafe_max_tlab_alloc(context); 2641 } 2642 2643 size_t G1CollectedHeap::max_capacity() const { 2644 return _hrm.reserved().byte_size(); 2645 } 2646 2647 jlong G1CollectedHeap::millis_since_last_gc() { 2648 // assert(false, "NYI"); 2649 return 0; 2650 } 2651 2652 void G1CollectedHeap::prepare_for_verify() { 2653 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2654 ensure_parsability(false); 2655 } 2656 g1_rem_set()->prepare_for_verify(); 2657 } 2658 2659 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 2660 VerifyOption vo) { 2661 switch (vo) { 2662 case VerifyOption_G1UsePrevMarking: 2663 return hr->obj_allocated_since_prev_marking(obj); 2664 case VerifyOption_G1UseNextMarking: 2665 return hr->obj_allocated_since_next_marking(obj); 2666 case VerifyOption_G1UseMarkWord: 2667 return false; 2668 default: 2669 ShouldNotReachHere(); 2670 } 2671 return false; // keep some compilers happy 2672 } 2673 2674 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 2675 switch (vo) { 2676 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 2677 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 2678 case VerifyOption_G1UseMarkWord: return NULL; 2679 default: ShouldNotReachHere(); 2680 } 2681 return NULL; // keep some compilers happy 2682 } 2683 2684 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 2685 switch (vo) { 2686 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 2687 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 2688 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 2689 default: ShouldNotReachHere(); 2690 } 2691 return false; // keep some compilers happy 2692 } 2693 2694 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 2695 switch (vo) { 2696 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 2697 case VerifyOption_G1UseNextMarking: return "NTAMS"; 2698 case VerifyOption_G1UseMarkWord: return "NONE"; 2699 default: ShouldNotReachHere(); 2700 } 2701 return NULL; // keep some compilers happy 2702 } 2703 2704 class VerifyRootsClosure: public OopClosure { 2705 private: 2706 G1CollectedHeap* _g1h; 2707 VerifyOption _vo; 2708 bool _failures; 2709 public: 2710 // _vo == UsePrevMarking -> use "prev" marking information, 2711 // _vo == UseNextMarking -> use "next" marking information, 2712 // _vo == UseMarkWord -> use mark word from object header. 2713 VerifyRootsClosure(VerifyOption vo) : 2714 _g1h(G1CollectedHeap::heap()), 2715 _vo(vo), 2716 _failures(false) { } 2717 2718 bool failures() { return _failures; } 2719 2720 template <class T> void do_oop_nv(T* p) { 2721 T heap_oop = oopDesc::load_heap_oop(p); 2722 if (!oopDesc::is_null(heap_oop)) { 2723 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2724 if (_g1h->is_obj_dead_cond(obj, _vo)) { 2725 LogHandle(gc, verify) log; 2726 log.info("Root location " PTR_FORMAT " points to dead obj " PTR_FORMAT, p2i(p), p2i(obj)); 2727 if (_vo == VerifyOption_G1UseMarkWord) { 2728 log.info(" Mark word: " INTPTR_FORMAT, (intptr_t)obj->mark()); 2729 } 2730 ResourceMark rm; 2731 obj->print_on(log.info_stream()); 2732 _failures = true; 2733 } 2734 } 2735 } 2736 2737 void do_oop(oop* p) { do_oop_nv(p); } 2738 void do_oop(narrowOop* p) { do_oop_nv(p); } 2739 }; 2740 2741 class G1VerifyCodeRootOopClosure: public OopClosure { 2742 G1CollectedHeap* _g1h; 2743 OopClosure* _root_cl; 2744 nmethod* _nm; 2745 VerifyOption _vo; 2746 bool _failures; 2747 2748 template <class T> void do_oop_work(T* p) { 2749 // First verify that this root is live 2750 _root_cl->do_oop(p); 2751 2752 if (!G1VerifyHeapRegionCodeRoots) { 2753 // We're not verifying the code roots attached to heap region. 2754 return; 2755 } 2756 2757 // Don't check the code roots during marking verification in a full GC 2758 if (_vo == VerifyOption_G1UseMarkWord) { 2759 return; 2760 } 2761 2762 // Now verify that the current nmethod (which contains p) is 2763 // in the code root list of the heap region containing the 2764 // object referenced by p. 2765 2766 T heap_oop = oopDesc::load_heap_oop(p); 2767 if (!oopDesc::is_null(heap_oop)) { 2768 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2769 2770 // Now fetch the region containing the object 2771 HeapRegion* hr = _g1h->heap_region_containing(obj); 2772 HeapRegionRemSet* hrrs = hr->rem_set(); 2773 // Verify that the strong code root list for this region 2774 // contains the nmethod 2775 if (!hrrs->strong_code_roots_list_contains(_nm)) { 2776 log_info(gc, verify)("Code root location " PTR_FORMAT " " 2777 "from nmethod " PTR_FORMAT " not in strong " 2778 "code roots for region [" PTR_FORMAT "," PTR_FORMAT ")", 2779 p2i(p), p2i(_nm), p2i(hr->bottom()), p2i(hr->end())); 2780 _failures = true; 2781 } 2782 } 2783 } 2784 2785 public: 2786 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo): 2787 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {} 2788 2789 void do_oop(oop* p) { do_oop_work(p); } 2790 void do_oop(narrowOop* p) { do_oop_work(p); } 2791 2792 void set_nmethod(nmethod* nm) { _nm = nm; } 2793 bool failures() { return _failures; } 2794 }; 2795 2796 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure { 2797 G1VerifyCodeRootOopClosure* _oop_cl; 2798 2799 public: 2800 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl): 2801 _oop_cl(oop_cl) {} 2802 2803 void do_code_blob(CodeBlob* cb) { 2804 nmethod* nm = cb->as_nmethod_or_null(); 2805 if (nm != NULL) { 2806 _oop_cl->set_nmethod(nm); 2807 nm->oops_do(_oop_cl); 2808 } 2809 } 2810 }; 2811 2812 class YoungRefCounterClosure : public OopClosure { 2813 G1CollectedHeap* _g1h; 2814 int _count; 2815 public: 2816 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 2817 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 2818 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 2819 2820 int count() { return _count; } 2821 void reset_count() { _count = 0; }; 2822 }; 2823 2824 class VerifyKlassClosure: public KlassClosure { 2825 YoungRefCounterClosure _young_ref_counter_closure; 2826 OopClosure *_oop_closure; 2827 public: 2828 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 2829 void do_klass(Klass* k) { 2830 k->oops_do(_oop_closure); 2831 2832 _young_ref_counter_closure.reset_count(); 2833 k->oops_do(&_young_ref_counter_closure); 2834 if (_young_ref_counter_closure.count() > 0) { 2835 guarantee(k->has_modified_oops(), "Klass " PTR_FORMAT ", has young refs but is not dirty.", p2i(k)); 2836 } 2837 } 2838 }; 2839 2840 class VerifyLivenessOopClosure: public OopClosure { 2841 G1CollectedHeap* _g1h; 2842 VerifyOption _vo; 2843 public: 2844 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 2845 _g1h(g1h), _vo(vo) 2846 { } 2847 void do_oop(narrowOop *p) { do_oop_work(p); } 2848 void do_oop( oop *p) { do_oop_work(p); } 2849 2850 template <class T> void do_oop_work(T *p) { 2851 oop obj = oopDesc::load_decode_heap_oop(p); 2852 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 2853 "Dead object referenced by a not dead object"); 2854 } 2855 }; 2856 2857 class VerifyObjsInRegionClosure: public ObjectClosure { 2858 private: 2859 G1CollectedHeap* _g1h; 2860 size_t _live_bytes; 2861 HeapRegion *_hr; 2862 VerifyOption _vo; 2863 public: 2864 // _vo == UsePrevMarking -> use "prev" marking information, 2865 // _vo == UseNextMarking -> use "next" marking information, 2866 // _vo == UseMarkWord -> use mark word from object header. 2867 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 2868 : _live_bytes(0), _hr(hr), _vo(vo) { 2869 _g1h = G1CollectedHeap::heap(); 2870 } 2871 void do_object(oop o) { 2872 VerifyLivenessOopClosure isLive(_g1h, _vo); 2873 assert(o != NULL, "Huh?"); 2874 if (!_g1h->is_obj_dead_cond(o, _vo)) { 2875 // If the object is alive according to the mark word, 2876 // then verify that the marking information agrees. 2877 // Note we can't verify the contra-positive of the 2878 // above: if the object is dead (according to the mark 2879 // word), it may not be marked, or may have been marked 2880 // but has since became dead, or may have been allocated 2881 // since the last marking. 2882 if (_vo == VerifyOption_G1UseMarkWord) { 2883 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 2884 } 2885 2886 o->oop_iterate_no_header(&isLive); 2887 if (!_hr->obj_allocated_since_prev_marking(o)) { 2888 size_t obj_size = o->size(); // Make sure we don't overflow 2889 _live_bytes += (obj_size * HeapWordSize); 2890 } 2891 } 2892 } 2893 size_t live_bytes() { return _live_bytes; } 2894 }; 2895 2896 class VerifyArchiveOopClosure: public OopClosure { 2897 public: 2898 VerifyArchiveOopClosure(HeapRegion *hr) { } 2899 void do_oop(narrowOop *p) { do_oop_work(p); } 2900 void do_oop( oop *p) { do_oop_work(p); } 2901 2902 template <class T> void do_oop_work(T *p) { 2903 oop obj = oopDesc::load_decode_heap_oop(p); 2904 guarantee(obj == NULL || G1MarkSweep::in_archive_range(obj), 2905 "Archive object at " PTR_FORMAT " references a non-archive object at " PTR_FORMAT, 2906 p2i(p), p2i(obj)); 2907 } 2908 }; 2909 2910 class VerifyArchiveRegionClosure: public ObjectClosure { 2911 public: 2912 VerifyArchiveRegionClosure(HeapRegion *hr) { } 2913 // Verify that all object pointers are to archive regions. 2914 void do_object(oop o) { 2915 VerifyArchiveOopClosure checkOop(NULL); 2916 assert(o != NULL, "Should not be here for NULL oops"); 2917 o->oop_iterate_no_header(&checkOop); 2918 } 2919 }; 2920 2921 class VerifyRegionClosure: public HeapRegionClosure { 2922 private: 2923 bool _par; 2924 VerifyOption _vo; 2925 bool _failures; 2926 public: 2927 // _vo == UsePrevMarking -> use "prev" marking information, 2928 // _vo == UseNextMarking -> use "next" marking information, 2929 // _vo == UseMarkWord -> use mark word from object header. 2930 VerifyRegionClosure(bool par, VerifyOption vo) 2931 : _par(par), 2932 _vo(vo), 2933 _failures(false) {} 2934 2935 bool failures() { 2936 return _failures; 2937 } 2938 2939 bool doHeapRegion(HeapRegion* r) { 2940 // For archive regions, verify there are no heap pointers to 2941 // non-pinned regions. For all others, verify liveness info. 2942 if (r->is_archive()) { 2943 VerifyArchiveRegionClosure verify_oop_pointers(r); 2944 r->object_iterate(&verify_oop_pointers); 2945 return true; 2946 } 2947 if (!r->is_continues_humongous()) { 2948 bool failures = false; 2949 r->verify(_vo, &failures); 2950 if (failures) { 2951 _failures = true; 2952 } else if (!r->is_starts_humongous()) { 2953 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 2954 r->object_iterate(¬_dead_yet_cl); 2955 if (_vo != VerifyOption_G1UseNextMarking) { 2956 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 2957 log_info(gc, verify)("[" PTR_FORMAT "," PTR_FORMAT "] max_live_bytes " SIZE_FORMAT " < calculated " SIZE_FORMAT, 2958 p2i(r->bottom()), p2i(r->end()), r->max_live_bytes(), not_dead_yet_cl.live_bytes()); 2959 _failures = true; 2960 } 2961 } else { 2962 // When vo == UseNextMarking we cannot currently do a sanity 2963 // check on the live bytes as the calculation has not been 2964 // finalized yet. 2965 } 2966 } 2967 } 2968 return false; // stop the region iteration if we hit a failure 2969 } 2970 }; 2971 2972 // This is the task used for parallel verification of the heap regions 2973 2974 class G1ParVerifyTask: public AbstractGangTask { 2975 private: 2976 G1CollectedHeap* _g1h; 2977 VerifyOption _vo; 2978 bool _failures; 2979 HeapRegionClaimer _hrclaimer; 2980 2981 public: 2982 // _vo == UsePrevMarking -> use "prev" marking information, 2983 // _vo == UseNextMarking -> use "next" marking information, 2984 // _vo == UseMarkWord -> use mark word from object header. 2985 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 2986 AbstractGangTask("Parallel verify task"), 2987 _g1h(g1h), 2988 _vo(vo), 2989 _failures(false), 2990 _hrclaimer(g1h->workers()->active_workers()) {} 2991 2992 bool failures() { 2993 return _failures; 2994 } 2995 2996 void work(uint worker_id) { 2997 HandleMark hm; 2998 VerifyRegionClosure blk(true, _vo); 2999 _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer); 3000 if (blk.failures()) { 3001 _failures = true; 3002 } 3003 } 3004 }; 3005 3006 void G1CollectedHeap::verify(VerifyOption vo) { 3007 if (!SafepointSynchronize::is_at_safepoint()) { 3008 log_info(gc, verify)("Skipping verification. Not at safepoint."); 3009 } 3010 3011 assert(Thread::current()->is_VM_thread(), 3012 "Expected to be executed serially by the VM thread at this point"); 3013 3014 log_debug(gc, verify)("Roots"); 3015 VerifyRootsClosure rootsCl(vo); 3016 VerifyKlassClosure klassCl(this, &rootsCl); 3017 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false); 3018 3019 // We apply the relevant closures to all the oops in the 3020 // system dictionary, class loader data graph, the string table 3021 // and the nmethods in the code cache. 3022 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo); 3023 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl); 3024 3025 { 3026 G1RootProcessor root_processor(this, 1); 3027 root_processor.process_all_roots(&rootsCl, 3028 &cldCl, 3029 &blobsCl); 3030 } 3031 3032 bool failures = rootsCl.failures() || codeRootsCl.failures(); 3033 3034 if (vo != VerifyOption_G1UseMarkWord) { 3035 // If we're verifying during a full GC then the region sets 3036 // will have been torn down at the start of the GC. Therefore 3037 // verifying the region sets will fail. So we only verify 3038 // the region sets when not in a full GC. 3039 log_debug(gc, verify)("HeapRegionSets"); 3040 verify_region_sets(); 3041 } 3042 3043 log_debug(gc, verify)("HeapRegions"); 3044 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3045 3046 G1ParVerifyTask task(this, vo); 3047 workers()->run_task(&task); 3048 if (task.failures()) { 3049 failures = true; 3050 } 3051 3052 } else { 3053 VerifyRegionClosure blk(false, vo); 3054 heap_region_iterate(&blk); 3055 if (blk.failures()) { 3056 failures = true; 3057 } 3058 } 3059 3060 if (G1StringDedup::is_enabled()) { 3061 log_debug(gc, verify)("StrDedup"); 3062 G1StringDedup::verify(); 3063 } 3064 3065 if (failures) { 3066 log_info(gc, verify)("Heap after failed verification:"); 3067 // It helps to have the per-region information in the output to 3068 // help us track down what went wrong. This is why we call 3069 // print_extended_on() instead of print_on(). 3070 LogHandle(gc, verify) log; 3071 ResourceMark rm; 3072 print_extended_on(log.info_stream()); 3073 } 3074 guarantee(!failures, "there should not have been any failures"); 3075 } 3076 3077 double G1CollectedHeap::verify(bool guard, const char* msg) { 3078 double verify_time_ms = 0.0; 3079 3080 if (guard && total_collections() >= VerifyGCStartAt) { 3081 double verify_start = os::elapsedTime(); 3082 HandleMark hm; // Discard invalid handles created during verification 3083 prepare_for_verify(); 3084 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 3085 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 3086 } 3087 3088 return verify_time_ms; 3089 } 3090 3091 void G1CollectedHeap::verify_before_gc() { 3092 double verify_time_ms = verify(VerifyBeforeGC, "Before GC"); 3093 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 3094 } 3095 3096 void G1CollectedHeap::verify_after_gc() { 3097 double verify_time_ms = verify(VerifyAfterGC, "After GC"); 3098 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 3099 } 3100 3101 class PrintRegionClosure: public HeapRegionClosure { 3102 outputStream* _st; 3103 public: 3104 PrintRegionClosure(outputStream* st) : _st(st) {} 3105 bool doHeapRegion(HeapRegion* r) { 3106 r->print_on(_st); 3107 return false; 3108 } 3109 }; 3110 3111 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3112 const HeapRegion* hr, 3113 const VerifyOption vo) const { 3114 switch (vo) { 3115 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 3116 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 3117 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 3118 default: ShouldNotReachHere(); 3119 } 3120 return false; // keep some compilers happy 3121 } 3122 3123 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3124 const VerifyOption vo) const { 3125 switch (vo) { 3126 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 3127 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 3128 case VerifyOption_G1UseMarkWord: { 3129 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 3130 return !obj->is_gc_marked() && !hr->is_archive(); 3131 } 3132 default: ShouldNotReachHere(); 3133 } 3134 return false; // keep some compilers happy 3135 } 3136 3137 void G1CollectedHeap::print_on(outputStream* st) const { 3138 st->print(" %-20s", "garbage-first heap"); 3139 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3140 capacity()/K, used_unlocked()/K); 3141 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 3142 p2i(_hrm.reserved().start()), 3143 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 3144 p2i(_hrm.reserved().end())); 3145 st->cr(); 3146 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3147 uint young_regions = _young_list->length(); 3148 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3149 (size_t) young_regions * HeapRegion::GrainBytes / K); 3150 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3151 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3152 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3153 st->cr(); 3154 MetaspaceAux::print_on(st); 3155 } 3156 3157 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3158 print_on(st); 3159 3160 // Print the per-region information. 3161 st->cr(); 3162 st->print_cr("Heap Regions: (E=young(eden), S=young(survivor), O=old, " 3163 "HS=humongous(starts), HC=humongous(continues), " 3164 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 3165 "PTAMS=previous top-at-mark-start, " 3166 "NTAMS=next top-at-mark-start)"); 3167 PrintRegionClosure blk(st); 3168 heap_region_iterate(&blk); 3169 } 3170 3171 void G1CollectedHeap::print_on_error(outputStream* st) const { 3172 this->CollectedHeap::print_on_error(st); 3173 3174 if (_cm != NULL) { 3175 st->cr(); 3176 _cm->print_on_error(st); 3177 } 3178 } 3179 3180 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3181 workers()->print_worker_threads_on(st); 3182 _cmThread->print_on(st); 3183 st->cr(); 3184 _cm->print_worker_threads_on(st); 3185 _cg1r->print_worker_threads_on(st); 3186 if (G1StringDedup::is_enabled()) { 3187 G1StringDedup::print_worker_threads_on(st); 3188 } 3189 } 3190 3191 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3192 workers()->threads_do(tc); 3193 tc->do_thread(_cmThread); 3194 _cg1r->threads_do(tc); 3195 if (G1StringDedup::is_enabled()) { 3196 G1StringDedup::threads_do(tc); 3197 } 3198 } 3199 3200 void G1CollectedHeap::print_tracing_info() const { 3201 // We'll overload this to mean "trace GC pause statistics." 3202 if (TraceYoungGenTime || TraceOldGenTime) { 3203 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3204 // to that. 3205 g1_policy()->print_tracing_info(); 3206 } 3207 g1_rem_set()->print_summary_info(); 3208 concurrent_mark()->print_summary_info(); 3209 g1_policy()->print_yg_surv_rate_info(); 3210 } 3211 3212 #ifndef PRODUCT 3213 // Helpful for debugging RSet issues. 3214 3215 class PrintRSetsClosure : public HeapRegionClosure { 3216 private: 3217 const char* _msg; 3218 size_t _occupied_sum; 3219 3220 public: 3221 bool doHeapRegion(HeapRegion* r) { 3222 HeapRegionRemSet* hrrs = r->rem_set(); 3223 size_t occupied = hrrs->occupied(); 3224 _occupied_sum += occupied; 3225 3226 tty->print_cr("Printing RSet for region " HR_FORMAT, 3227 HR_FORMAT_PARAMS(r)); 3228 if (occupied == 0) { 3229 tty->print_cr(" RSet is empty"); 3230 } else { 3231 hrrs->print(); 3232 } 3233 tty->print_cr("----------"); 3234 return false; 3235 } 3236 3237 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3238 tty->cr(); 3239 tty->print_cr("========================================"); 3240 tty->print_cr("%s", msg); 3241 tty->cr(); 3242 } 3243 3244 ~PrintRSetsClosure() { 3245 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 3246 tty->print_cr("========================================"); 3247 tty->cr(); 3248 } 3249 }; 3250 3251 void G1CollectedHeap::print_cset_rsets() { 3252 PrintRSetsClosure cl("Printing CSet RSets"); 3253 collection_set_iterate(&cl); 3254 } 3255 3256 void G1CollectedHeap::print_all_rsets() { 3257 PrintRSetsClosure cl("Printing All RSets");; 3258 heap_region_iterate(&cl); 3259 } 3260 #endif // PRODUCT 3261 3262 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 3263 YoungList* young_list = heap()->young_list(); 3264 3265 size_t eden_used_bytes = young_list->eden_used_bytes(); 3266 size_t survivor_used_bytes = young_list->survivor_used_bytes(); 3267 3268 size_t eden_capacity_bytes = 3269 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 3270 3271 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 3272 return G1HeapSummary(heap_summary, used(), eden_used_bytes, eden_capacity_bytes, survivor_used_bytes); 3273 } 3274 3275 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 3276 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 3277 stats->unused(), stats->used(), stats->region_end_waste(), 3278 stats->regions_filled(), stats->direct_allocated(), 3279 stats->failure_used(), stats->failure_waste()); 3280 } 3281 3282 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 3283 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 3284 gc_tracer->report_gc_heap_summary(when, heap_summary); 3285 3286 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 3287 gc_tracer->report_metaspace_summary(when, metaspace_summary); 3288 } 3289 3290 3291 G1CollectedHeap* G1CollectedHeap::heap() { 3292 CollectedHeap* heap = Universe::heap(); 3293 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 3294 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 3295 return (G1CollectedHeap*)heap; 3296 } 3297 3298 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3299 // always_do_update_barrier = false; 3300 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3301 // Fill TLAB's and such 3302 accumulate_statistics_all_tlabs(); 3303 ensure_parsability(true); 3304 3305 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 3306 } 3307 3308 void G1CollectedHeap::gc_epilogue(bool full) { 3309 // we are at the end of the GC. Total collections has already been increased. 3310 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 3311 3312 // FIXME: what is this about? 3313 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3314 // is set. 3315 #if defined(COMPILER2) || INCLUDE_JVMCI 3316 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 3317 #endif 3318 // always_do_update_barrier = true; 3319 3320 resize_all_tlabs(); 3321 allocation_context_stats().update(full); 3322 3323 // We have just completed a GC. Update the soft reference 3324 // policy with the new heap occupancy 3325 Universe::update_heap_info_at_gc(); 3326 } 3327 3328 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3329 uint gc_count_before, 3330 bool* succeeded, 3331 GCCause::Cause gc_cause) { 3332 assert_heap_not_locked_and_not_at_safepoint(); 3333 g1_policy()->record_stop_world_start(); 3334 VM_G1IncCollectionPause op(gc_count_before, 3335 word_size, 3336 false, /* should_initiate_conc_mark */ 3337 g1_policy()->max_pause_time_ms(), 3338 gc_cause); 3339 3340 op.set_allocation_context(AllocationContext::current()); 3341 VMThread::execute(&op); 3342 3343 HeapWord* result = op.result(); 3344 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3345 assert(result == NULL || ret_succeeded, 3346 "the result should be NULL if the VM did not succeed"); 3347 *succeeded = ret_succeeded; 3348 3349 assert_heap_not_locked(); 3350 return result; 3351 } 3352 3353 void 3354 G1CollectedHeap::doConcurrentMark() { 3355 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3356 if (!_cmThread->in_progress()) { 3357 _cmThread->set_started(); 3358 CGC_lock->notify(); 3359 } 3360 } 3361 3362 size_t G1CollectedHeap::pending_card_num() { 3363 size_t extra_cards = 0; 3364 JavaThread *curr = Threads::first(); 3365 while (curr != NULL) { 3366 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3367 extra_cards += dcq.size(); 3368 curr = curr->next(); 3369 } 3370 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3371 size_t buffer_size = dcqs.buffer_size(); 3372 size_t buffer_num = dcqs.completed_buffers_num(); 3373 3374 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3375 // in bytes - not the number of 'entries'. We need to convert 3376 // into a number of cards. 3377 return (buffer_size * buffer_num + extra_cards) / oopSize; 3378 } 3379 3380 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 3381 private: 3382 size_t _total_humongous; 3383 size_t _candidate_humongous; 3384 3385 DirtyCardQueue _dcq; 3386 3387 // We don't nominate objects with many remembered set entries, on 3388 // the assumption that such objects are likely still live. 3389 bool is_remset_small(HeapRegion* region) const { 3390 HeapRegionRemSet* const rset = region->rem_set(); 3391 return G1EagerReclaimHumongousObjectsWithStaleRefs 3392 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 3393 : rset->is_empty(); 3394 } 3395 3396 bool is_typeArray_region(HeapRegion* region) const { 3397 return oop(region->bottom())->is_typeArray(); 3398 } 3399 3400 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 3401 assert(region->is_starts_humongous(), "Must start a humongous object"); 3402 3403 // Candidate selection must satisfy the following constraints 3404 // while concurrent marking is in progress: 3405 // 3406 // * In order to maintain SATB invariants, an object must not be 3407 // reclaimed if it was allocated before the start of marking and 3408 // has not had its references scanned. Such an object must have 3409 // its references (including type metadata) scanned to ensure no 3410 // live objects are missed by the marking process. Objects 3411 // allocated after the start of concurrent marking don't need to 3412 // be scanned. 3413 // 3414 // * An object must not be reclaimed if it is on the concurrent 3415 // mark stack. Objects allocated after the start of concurrent 3416 // marking are never pushed on the mark stack. 3417 // 3418 // Nominating only objects allocated after the start of concurrent 3419 // marking is sufficient to meet both constraints. This may miss 3420 // some objects that satisfy the constraints, but the marking data 3421 // structures don't support efficiently performing the needed 3422 // additional tests or scrubbing of the mark stack. 3423 // 3424 // However, we presently only nominate is_typeArray() objects. 3425 // A humongous object containing references induces remembered 3426 // set entries on other regions. In order to reclaim such an 3427 // object, those remembered sets would need to be cleaned up. 3428 // 3429 // We also treat is_typeArray() objects specially, allowing them 3430 // to be reclaimed even if allocated before the start of 3431 // concurrent mark. For this we rely on mark stack insertion to 3432 // exclude is_typeArray() objects, preventing reclaiming an object 3433 // that is in the mark stack. We also rely on the metadata for 3434 // such objects to be built-in and so ensured to be kept live. 3435 // Frequent allocation and drop of large binary blobs is an 3436 // important use case for eager reclaim, and this special handling 3437 // may reduce needed headroom. 3438 3439 return is_typeArray_region(region) && is_remset_small(region); 3440 } 3441 3442 public: 3443 RegisterHumongousWithInCSetFastTestClosure() 3444 : _total_humongous(0), 3445 _candidate_humongous(0), 3446 _dcq(&JavaThread::dirty_card_queue_set()) { 3447 } 3448 3449 virtual bool doHeapRegion(HeapRegion* r) { 3450 if (!r->is_starts_humongous()) { 3451 return false; 3452 } 3453 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3454 3455 bool is_candidate = humongous_region_is_candidate(g1h, r); 3456 uint rindex = r->hrm_index(); 3457 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 3458 if (is_candidate) { 3459 _candidate_humongous++; 3460 g1h->register_humongous_region_with_cset(rindex); 3461 // Is_candidate already filters out humongous object with large remembered sets. 3462 // If we have a humongous object with a few remembered sets, we simply flush these 3463 // remembered set entries into the DCQS. That will result in automatic 3464 // re-evaluation of their remembered set entries during the following evacuation 3465 // phase. 3466 if (!r->rem_set()->is_empty()) { 3467 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 3468 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 3469 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 3470 HeapRegionRemSetIterator hrrs(r->rem_set()); 3471 size_t card_index; 3472 while (hrrs.has_next(card_index)) { 3473 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 3474 // The remembered set might contain references to already freed 3475 // regions. Filter out such entries to avoid failing card table 3476 // verification. 3477 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 3478 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 3479 *card_ptr = CardTableModRefBS::dirty_card_val(); 3480 _dcq.enqueue(card_ptr); 3481 } 3482 } 3483 } 3484 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 3485 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 3486 hrrs.n_yielded(), r->rem_set()->occupied()); 3487 r->rem_set()->clear_locked(); 3488 } 3489 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 3490 } 3491 _total_humongous++; 3492 3493 return false; 3494 } 3495 3496 size_t total_humongous() const { return _total_humongous; } 3497 size_t candidate_humongous() const { return _candidate_humongous; } 3498 3499 void flush_rem_set_entries() { _dcq.flush(); } 3500 }; 3501 3502 void G1CollectedHeap::register_humongous_regions_with_cset() { 3503 if (!G1EagerReclaimHumongousObjects) { 3504 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 3505 return; 3506 } 3507 double time = os::elapsed_counter(); 3508 3509 // Collect reclaim candidate information and register candidates with cset. 3510 RegisterHumongousWithInCSetFastTestClosure cl; 3511 heap_region_iterate(&cl); 3512 3513 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 3514 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 3515 cl.total_humongous(), 3516 cl.candidate_humongous()); 3517 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3518 3519 // Finally flush all remembered set entries to re-check into the global DCQS. 3520 cl.flush_rem_set_entries(); 3521 } 3522 3523 #ifdef ASSERT 3524 class VerifyCSetClosure: public HeapRegionClosure { 3525 public: 3526 bool doHeapRegion(HeapRegion* hr) { 3527 // Here we check that the CSet region's RSet is ready for parallel 3528 // iteration. The fields that we'll verify are only manipulated 3529 // when the region is part of a CSet and is collected. Afterwards, 3530 // we reset these fields when we clear the region's RSet (when the 3531 // region is freed) so they are ready when the region is 3532 // re-allocated. The only exception to this is if there's an 3533 // evacuation failure and instead of freeing the region we leave 3534 // it in the heap. In that case, we reset these fields during 3535 // evacuation failure handling. 3536 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3537 3538 // Here's a good place to add any other checks we'd like to 3539 // perform on CSet regions. 3540 return false; 3541 } 3542 }; 3543 #endif // ASSERT 3544 3545 uint G1CollectedHeap::num_task_queues() const { 3546 return _task_queues->size(); 3547 } 3548 3549 #if TASKQUEUE_STATS 3550 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3551 st->print_raw_cr("GC Task Stats"); 3552 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3553 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3554 } 3555 3556 void G1CollectedHeap::print_taskqueue_stats() const { 3557 LogHandle(gc, task, stats) log; 3558 if (!log.is_develop()) { 3559 return; 3560 } 3561 ResourceMark rm; 3562 outputStream* st = log.develop_stream(); 3563 3564 print_taskqueue_stats_hdr(st); 3565 3566 TaskQueueStats totals; 3567 const uint n = num_task_queues(); 3568 for (uint i = 0; i < n; ++i) { 3569 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 3570 totals += task_queue(i)->stats; 3571 } 3572 st->print_raw("tot "); totals.print(st); st->cr(); 3573 3574 DEBUG_ONLY(totals.verify()); 3575 } 3576 3577 void G1CollectedHeap::reset_taskqueue_stats() { 3578 const uint n = num_task_queues(); 3579 for (uint i = 0; i < n; ++i) { 3580 task_queue(i)->stats.reset(); 3581 } 3582 } 3583 #endif // TASKQUEUE_STATS 3584 3585 void G1CollectedHeap::log_gc_footer(double pause_time_counter) { 3586 if (evacuation_failed()) { 3587 log_info(gc)("To-space exhausted"); 3588 } 3589 3590 double pause_time_sec = TimeHelper::counter_to_seconds(pause_time_counter); 3591 g1_policy()->print_phases(pause_time_sec); 3592 3593 g1_policy()->print_detailed_heap_transition(); 3594 } 3595 3596 3597 void G1CollectedHeap::wait_for_root_region_scanning() { 3598 double scan_wait_start = os::elapsedTime(); 3599 // We have to wait until the CM threads finish scanning the 3600 // root regions as it's the only way to ensure that all the 3601 // objects on them have been correctly scanned before we start 3602 // moving them during the GC. 3603 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3604 double wait_time_ms = 0.0; 3605 if (waited) { 3606 double scan_wait_end = os::elapsedTime(); 3607 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3608 } 3609 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3610 } 3611 3612 bool 3613 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3614 assert_at_safepoint(true /* should_be_vm_thread */); 3615 guarantee(!is_gc_active(), "collection is not reentrant"); 3616 3617 if (GC_locker::check_active_before_gc()) { 3618 return false; 3619 } 3620 3621 _gc_timer_stw->register_gc_start(); 3622 3623 GCIdMark gc_id_mark; 3624 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3625 3626 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3627 ResourceMark rm; 3628 3629 wait_for_root_region_scanning(); 3630 3631 print_heap_before_gc(); 3632 trace_heap_before_gc(_gc_tracer_stw); 3633 3634 verify_region_sets_optional(); 3635 verify_dirty_young_regions(); 3636 3637 // This call will decide whether this pause is an initial-mark 3638 // pause. If it is, during_initial_mark_pause() will return true 3639 // for the duration of this pause. 3640 g1_policy()->decide_on_conc_mark_initiation(); 3641 3642 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3643 assert(!collector_state()->during_initial_mark_pause() || 3644 collector_state()->gcs_are_young(), "sanity"); 3645 3646 // We also do not allow mixed GCs during marking. 3647 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3648 3649 // Record whether this pause is an initial mark. When the current 3650 // thread has completed its logging output and it's safe to signal 3651 // the CM thread, the flag's value in the policy has been reset. 3652 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3653 3654 // Inner scope for scope based logging, timers, and stats collection 3655 { 3656 EvacuationInfo evacuation_info; 3657 3658 if (collector_state()->during_initial_mark_pause()) { 3659 // We are about to start a marking cycle, so we increment the 3660 // full collection counter. 3661 increment_old_marking_cycles_started(); 3662 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3663 } 3664 3665 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3666 3667 GCTraceCPUTime tcpu; 3668 3669 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3670 workers()->active_workers(), 3671 Threads::number_of_non_daemon_threads()); 3672 workers()->set_active_workers(active_workers); 3673 FormatBuffer<> gc_string("Pause "); 3674 if (collector_state()->during_initial_mark_pause()) { 3675 gc_string.append("Initial Mark"); 3676 } else if (collector_state()->gcs_are_young()) { 3677 gc_string.append("Young"); 3678 } else { 3679 gc_string.append("Mixed"); 3680 } 3681 GCTraceTime(Info, gc) tm5(gc_string, NULL, gc_cause(), true); 3682 3683 3684 double pause_start_sec = os::elapsedTime(); 3685 double pause_start_counter = os::elapsed_counter(); 3686 g1_policy()->note_gc_start(active_workers); 3687 3688 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3689 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3690 3691 // If the secondary_free_list is not empty, append it to the 3692 // free_list. No need to wait for the cleanup operation to finish; 3693 // the region allocation code will check the secondary_free_list 3694 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3695 // set, skip this step so that the region allocation code has to 3696 // get entries from the secondary_free_list. 3697 if (!G1StressConcRegionFreeing) { 3698 append_secondary_free_list_if_not_empty_with_lock(); 3699 } 3700 3701 assert(check_young_list_well_formed(), "young list should be well formed"); 3702 3703 // Don't dynamically change the number of GC threads this early. A value of 3704 // 0 is used to indicate serial work. When parallel work is done, 3705 // it will be set. 3706 3707 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3708 IsGCActiveMark x; 3709 3710 gc_prologue(false); 3711 increment_total_collections(false /* full gc */); 3712 increment_gc_time_stamp(); 3713 3714 verify_before_gc(); 3715 3716 check_bitmaps("GC Start"); 3717 3718 #if defined(COMPILER2) || INCLUDE_JVMCI 3719 DerivedPointerTable::clear(); 3720 #endif 3721 3722 // Please see comment in g1CollectedHeap.hpp and 3723 // G1CollectedHeap::ref_processing_init() to see how 3724 // reference processing currently works in G1. 3725 3726 // Enable discovery in the STW reference processor 3727 ref_processor_stw()->enable_discovery(); 3728 3729 { 3730 // We want to temporarily turn off discovery by the 3731 // CM ref processor, if necessary, and turn it back on 3732 // on again later if we do. Using a scoped 3733 // NoRefDiscovery object will do this. 3734 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3735 3736 // Forget the current alloc region (we might even choose it to be part 3737 // of the collection set!). 3738 _allocator->release_mutator_alloc_region(); 3739 3740 // This timing is only used by the ergonomics to handle our pause target. 3741 // It is unclear why this should not include the full pause. We will 3742 // investigate this in CR 7178365. 3743 // 3744 // Preserving the old comment here if that helps the investigation: 3745 // 3746 // The elapsed time induced by the start time below deliberately elides 3747 // the possible verification above. 3748 double sample_start_time_sec = os::elapsedTime(); 3749 3750 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3751 3752 if (collector_state()->during_initial_mark_pause()) { 3753 concurrent_mark()->checkpointRootsInitialPre(); 3754 } 3755 3756 double time_remaining_ms = g1_policy()->finalize_young_cset_part(target_pause_time_ms); 3757 g1_policy()->finalize_old_cset_part(time_remaining_ms); 3758 3759 evacuation_info.set_collectionset_regions(g1_policy()->cset_region_length()); 3760 3761 // Make sure the remembered sets are up to date. This needs to be 3762 // done before register_humongous_regions_with_cset(), because the 3763 // remembered sets are used there to choose eager reclaim candidates. 3764 // If the remembered sets are not up to date we might miss some 3765 // entries that need to be handled. 3766 g1_rem_set()->cleanupHRRS(); 3767 3768 register_humongous_regions_with_cset(); 3769 3770 assert(check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3771 3772 _cm->note_start_of_gc(); 3773 // We call this after finalize_cset() to 3774 // ensure that the CSet has been finalized. 3775 _cm->verify_no_cset_oops(); 3776 3777 if (_hr_printer.is_active()) { 3778 HeapRegion* hr = g1_policy()->collection_set(); 3779 while (hr != NULL) { 3780 _hr_printer.cset(hr); 3781 hr = hr->next_in_collection_set(); 3782 } 3783 } 3784 3785 #ifdef ASSERT 3786 VerifyCSetClosure cl; 3787 collection_set_iterate(&cl); 3788 #endif // ASSERT 3789 3790 // Initialize the GC alloc regions. 3791 _allocator->init_gc_alloc_regions(evacuation_info); 3792 3793 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), g1_policy()->young_cset_region_length()); 3794 pre_evacuate_collection_set(); 3795 3796 // Actually do the work... 3797 evacuate_collection_set(evacuation_info, &per_thread_states); 3798 3799 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3800 3801 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3802 free_collection_set(g1_policy()->collection_set(), evacuation_info, surviving_young_words); 3803 3804 eagerly_reclaim_humongous_regions(); 3805 3806 g1_policy()->clear_collection_set(); 3807 3808 // Start a new incremental collection set for the next pause. 3809 g1_policy()->start_incremental_cset_building(); 3810 3811 clear_cset_fast_test(); 3812 3813 _young_list->reset_sampled_info(); 3814 3815 // Don't check the whole heap at this point as the 3816 // GC alloc regions from this pause have been tagged 3817 // as survivors and moved on to the survivor list. 3818 // Survivor regions will fail the !is_young() check. 3819 assert(check_young_list_empty(false /* check_heap */), 3820 "young list should be empty"); 3821 3822 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3823 _young_list->first_survivor_region(), 3824 _young_list->last_survivor_region()); 3825 3826 _young_list->reset_auxilary_lists(); 3827 3828 if (evacuation_failed()) { 3829 set_used(recalculate_used()); 3830 if (_archive_allocator != NULL) { 3831 _archive_allocator->clear_used(); 3832 } 3833 for (uint i = 0; i < ParallelGCThreads; i++) { 3834 if (_evacuation_failed_info_array[i].has_failed()) { 3835 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3836 } 3837 } 3838 } else { 3839 // The "used" of the the collection set have already been subtracted 3840 // when they were freed. Add in the bytes evacuated. 3841 increase_used(g1_policy()->bytes_copied_during_gc()); 3842 } 3843 3844 if (collector_state()->during_initial_mark_pause()) { 3845 // We have to do this before we notify the CM threads that 3846 // they can start working to make sure that all the 3847 // appropriate initialization is done on the CM object. 3848 concurrent_mark()->checkpointRootsInitialPost(); 3849 collector_state()->set_mark_in_progress(true); 3850 // Note that we don't actually trigger the CM thread at 3851 // this point. We do that later when we're sure that 3852 // the current thread has completed its logging output. 3853 } 3854 3855 allocate_dummy_regions(); 3856 3857 _allocator->init_mutator_alloc_region(); 3858 3859 { 3860 size_t expand_bytes = g1_policy()->expansion_amount(); 3861 if (expand_bytes > 0) { 3862 size_t bytes_before = capacity(); 3863 // No need for an ergo logging here, 3864 // expansion_amount() does this when it returns a value > 0. 3865 double expand_ms; 3866 if (!expand(expand_bytes, &expand_ms)) { 3867 // We failed to expand the heap. Cannot do anything about it. 3868 } 3869 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3870 } 3871 } 3872 3873 // We redo the verification but now wrt to the new CSet which 3874 // has just got initialized after the previous CSet was freed. 3875 _cm->verify_no_cset_oops(); 3876 _cm->note_end_of_gc(); 3877 3878 // This timing is only used by the ergonomics to handle our pause target. 3879 // It is unclear why this should not include the full pause. We will 3880 // investigate this in CR 7178365. 3881 double sample_end_time_sec = os::elapsedTime(); 3882 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3883 size_t total_cards_scanned = per_thread_states.total_cards_scanned(); 3884 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned); 3885 3886 evacuation_info.set_collectionset_used_before(g1_policy()->collection_set_bytes_used_before()); 3887 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3888 3889 MemoryService::track_memory_usage(); 3890 3891 // In prepare_for_verify() below we'll need to scan the deferred 3892 // update buffers to bring the RSets up-to-date if 3893 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3894 // the update buffers we'll probably need to scan cards on the 3895 // regions we just allocated to (i.e., the GC alloc 3896 // regions). However, during the last GC we called 3897 // set_saved_mark() on all the GC alloc regions, so card 3898 // scanning might skip the [saved_mark_word()...top()] area of 3899 // those regions (i.e., the area we allocated objects into 3900 // during the last GC). But it shouldn't. Given that 3901 // saved_mark_word() is conditional on whether the GC time stamp 3902 // on the region is current or not, by incrementing the GC time 3903 // stamp here we invalidate all the GC time stamps on all the 3904 // regions and saved_mark_word() will simply return top() for 3905 // all the regions. This is a nicer way of ensuring this rather 3906 // than iterating over the regions and fixing them. In fact, the 3907 // GC time stamp increment here also ensures that 3908 // saved_mark_word() will return top() between pauses, i.e., 3909 // during concurrent refinement. So we don't need the 3910 // is_gc_active() check to decided which top to use when 3911 // scanning cards (see CR 7039627). 3912 increment_gc_time_stamp(); 3913 3914 verify_after_gc(); 3915 check_bitmaps("GC End"); 3916 3917 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3918 ref_processor_stw()->verify_no_references_recorded(); 3919 3920 // CM reference discovery will be re-enabled if necessary. 3921 } 3922 3923 #ifdef TRACESPINNING 3924 ParallelTaskTerminator::print_termination_counts(); 3925 #endif 3926 3927 gc_epilogue(false); 3928 } 3929 3930 // Print the remainder of the GC log output. 3931 log_gc_footer(os::elapsed_counter() - pause_start_counter); 3932 3933 // It is not yet to safe to tell the concurrent mark to 3934 // start as we have some optional output below. We don't want the 3935 // output from the concurrent mark thread interfering with this 3936 // logging output either. 3937 3938 _hrm.verify_optional(); 3939 verify_region_sets_optional(); 3940 3941 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3942 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3943 3944 print_heap_after_gc(); 3945 trace_heap_after_gc(_gc_tracer_stw); 3946 3947 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3948 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3949 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3950 // before any GC notifications are raised. 3951 g1mm()->update_sizes(); 3952 3953 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3954 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3955 _gc_timer_stw->register_gc_end(); 3956 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3957 } 3958 // It should now be safe to tell the concurrent mark thread to start 3959 // without its logging output interfering with the logging output 3960 // that came from the pause. 3961 3962 if (should_start_conc_mark) { 3963 // CAUTION: after the doConcurrentMark() call below, 3964 // the concurrent marking thread(s) could be running 3965 // concurrently with us. Make sure that anything after 3966 // this point does not assume that we are the only GC thread 3967 // running. Note: of course, the actual marking work will 3968 // not start until the safepoint itself is released in 3969 // SuspendibleThreadSet::desynchronize(). 3970 doConcurrentMark(); 3971 } 3972 3973 return true; 3974 } 3975 3976 void G1CollectedHeap::remove_self_forwarding_pointers() { 3977 double remove_self_forwards_start = os::elapsedTime(); 3978 3979 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3980 workers()->run_task(&rsfp_task); 3981 3982 // Now restore saved marks, if any. 3983 for (uint i = 0; i < ParallelGCThreads; i++) { 3984 OopAndMarkOopStack& cur = _preserved_objs[i]; 3985 while (!cur.is_empty()) { 3986 OopAndMarkOop elem = cur.pop(); 3987 elem.set_mark(); 3988 } 3989 cur.clear(true); 3990 } 3991 3992 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3993 } 3994 3995 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3996 if (!_evacuation_failed) { 3997 _evacuation_failed = true; 3998 } 3999 4000 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 4001 4002 // We want to call the "for_promotion_failure" version only in the 4003 // case of a promotion failure. 4004 if (m->must_be_preserved_for_promotion_failure(obj)) { 4005 OopAndMarkOop elem(obj, m); 4006 _preserved_objs[worker_id].push(elem); 4007 } 4008 } 4009 4010 class G1ParEvacuateFollowersClosure : public VoidClosure { 4011 private: 4012 double _start_term; 4013 double _term_time; 4014 size_t _term_attempts; 4015 4016 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); } 4017 void end_term_time() { _term_time += os::elapsedTime() - _start_term; } 4018 protected: 4019 G1CollectedHeap* _g1h; 4020 G1ParScanThreadState* _par_scan_state; 4021 RefToScanQueueSet* _queues; 4022 ParallelTaskTerminator* _terminator; 4023 4024 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4025 RefToScanQueueSet* queues() { return _queues; } 4026 ParallelTaskTerminator* terminator() { return _terminator; } 4027 4028 public: 4029 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4030 G1ParScanThreadState* par_scan_state, 4031 RefToScanQueueSet* queues, 4032 ParallelTaskTerminator* terminator) 4033 : _g1h(g1h), _par_scan_state(par_scan_state), 4034 _queues(queues), _terminator(terminator), 4035 _start_term(0.0), _term_time(0.0), _term_attempts(0) {} 4036 4037 void do_void(); 4038 4039 double term_time() const { return _term_time; } 4040 size_t term_attempts() const { return _term_attempts; } 4041 4042 private: 4043 inline bool offer_termination(); 4044 }; 4045 4046 bool G1ParEvacuateFollowersClosure::offer_termination() { 4047 G1ParScanThreadState* const pss = par_scan_state(); 4048 start_term_time(); 4049 const bool res = terminator()->offer_termination(); 4050 end_term_time(); 4051 return res; 4052 } 4053 4054 void G1ParEvacuateFollowersClosure::do_void() { 4055 G1ParScanThreadState* const pss = par_scan_state(); 4056 pss->trim_queue(); 4057 do { 4058 pss->steal_and_trim_queue(queues()); 4059 } while (!offer_termination()); 4060 } 4061 4062 class G1ParTask : public AbstractGangTask { 4063 protected: 4064 G1CollectedHeap* _g1h; 4065 G1ParScanThreadStateSet* _pss; 4066 RefToScanQueueSet* _queues; 4067 G1RootProcessor* _root_processor; 4068 ParallelTaskTerminator _terminator; 4069 uint _n_workers; 4070 4071 public: 4072 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 4073 : AbstractGangTask("G1 collection"), 4074 _g1h(g1h), 4075 _pss(per_thread_states), 4076 _queues(task_queues), 4077 _root_processor(root_processor), 4078 _terminator(n_workers, _queues), 4079 _n_workers(n_workers) 4080 {} 4081 4082 void work(uint worker_id) { 4083 if (worker_id >= _n_workers) return; // no work needed this round 4084 4085 double start_sec = os::elapsedTime(); 4086 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 4087 4088 { 4089 ResourceMark rm; 4090 HandleMark hm; 4091 4092 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4093 4094 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4095 pss->set_ref_processor(rp); 4096 4097 double start_strong_roots_sec = os::elapsedTime(); 4098 4099 _root_processor->evacuate_roots(pss->closures(), worker_id); 4100 4101 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss); 4102 4103 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 4104 // treating the nmethods visited to act as roots for concurrent marking. 4105 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 4106 // objects copied by the current evacuation. 4107 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl, 4108 pss->closures()->weak_codeblobs(), 4109 worker_id); 4110 4111 _pss->add_cards_scanned(worker_id, cards_scanned); 4112 4113 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 4114 4115 double term_sec = 0.0; 4116 size_t evac_term_attempts = 0; 4117 { 4118 double start = os::elapsedTime(); 4119 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 4120 evac.do_void(); 4121 4122 evac_term_attempts = evac.term_attempts(); 4123 term_sec = evac.term_time(); 4124 double elapsed_sec = os::elapsedTime() - start; 4125 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 4126 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 4127 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 4128 } 4129 4130 assert(pss->queue_is_empty(), "should be empty"); 4131 4132 if (log_is_enabled(Debug, gc, task, stats)) { 4133 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 4134 size_t lab_waste; 4135 size_t lab_undo_waste; 4136 pss->waste(lab_waste, lab_undo_waste); 4137 _g1h->print_termination_stats(worker_id, 4138 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 4139 strong_roots_sec * 1000.0, /* strong roots time */ 4140 term_sec * 1000.0, /* evac term time */ 4141 evac_term_attempts, /* evac term attempts */ 4142 lab_waste, /* alloc buffer waste */ 4143 lab_undo_waste /* undo waste */ 4144 ); 4145 } 4146 4147 // Close the inner scope so that the ResourceMark and HandleMark 4148 // destructors are executed here and are included as part of the 4149 // "GC Worker Time". 4150 } 4151 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 4152 } 4153 }; 4154 4155 void G1CollectedHeap::print_termination_stats_hdr() { 4156 LogHandle(gc, task, stats) log; 4157 if (!log.is_debug()) { 4158 return; 4159 } 4160 log.debug("GC Termination Stats"); 4161 log.debug(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 4162 log.debug("thr ms ms %% ms %% attempts total alloc undo"); 4163 log.debug("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 4164 } 4165 4166 void G1CollectedHeap::print_termination_stats(uint worker_id, 4167 double elapsed_ms, 4168 double strong_roots_ms, 4169 double term_ms, 4170 size_t term_attempts, 4171 size_t alloc_buffer_waste, 4172 size_t undo_waste) const { 4173 log_debug(gc, task, stats) 4174 ("%3d %9.2f %9.2f %6.2f " 4175 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 4176 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 4177 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 4178 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 4179 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 4180 alloc_buffer_waste * HeapWordSize / K, 4181 undo_waste * HeapWordSize / K); 4182 } 4183 4184 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 4185 private: 4186 BoolObjectClosure* _is_alive; 4187 int _initial_string_table_size; 4188 int _initial_symbol_table_size; 4189 4190 bool _process_strings; 4191 int _strings_processed; 4192 int _strings_removed; 4193 4194 bool _process_symbols; 4195 int _symbols_processed; 4196 int _symbols_removed; 4197 4198 public: 4199 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 4200 AbstractGangTask("String/Symbol Unlinking"), 4201 _is_alive(is_alive), 4202 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 4203 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 4204 4205 _initial_string_table_size = StringTable::the_table()->table_size(); 4206 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 4207 if (process_strings) { 4208 StringTable::clear_parallel_claimed_index(); 4209 } 4210 if (process_symbols) { 4211 SymbolTable::clear_parallel_claimed_index(); 4212 } 4213 } 4214 4215 ~G1StringSymbolTableUnlinkTask() { 4216 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 4217 "claim value %d after unlink less than initial string table size %d", 4218 StringTable::parallel_claimed_index(), _initial_string_table_size); 4219 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 4220 "claim value %d after unlink less than initial symbol table size %d", 4221 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 4222 4223 log_trace(gc, stringdedup)("Cleaned string and symbol table, " 4224 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 4225 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 4226 strings_processed(), strings_removed(), 4227 symbols_processed(), symbols_removed()); 4228 } 4229 4230 void work(uint worker_id) { 4231 int strings_processed = 0; 4232 int strings_removed = 0; 4233 int symbols_processed = 0; 4234 int symbols_removed = 0; 4235 if (_process_strings) { 4236 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 4237 Atomic::add(strings_processed, &_strings_processed); 4238 Atomic::add(strings_removed, &_strings_removed); 4239 } 4240 if (_process_symbols) { 4241 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 4242 Atomic::add(symbols_processed, &_symbols_processed); 4243 Atomic::add(symbols_removed, &_symbols_removed); 4244 } 4245 } 4246 4247 size_t strings_processed() const { return (size_t)_strings_processed; } 4248 size_t strings_removed() const { return (size_t)_strings_removed; } 4249 4250 size_t symbols_processed() const { return (size_t)_symbols_processed; } 4251 size_t symbols_removed() const { return (size_t)_symbols_removed; } 4252 }; 4253 4254 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 4255 private: 4256 static Monitor* _lock; 4257 4258 BoolObjectClosure* const _is_alive; 4259 const bool _unloading_occurred; 4260 const uint _num_workers; 4261 4262 // Variables used to claim nmethods. 4263 nmethod* _first_nmethod; 4264 volatile nmethod* _claimed_nmethod; 4265 4266 // The list of nmethods that need to be processed by the second pass. 4267 volatile nmethod* _postponed_list; 4268 volatile uint _num_entered_barrier; 4269 4270 public: 4271 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 4272 _is_alive(is_alive), 4273 _unloading_occurred(unloading_occurred), 4274 _num_workers(num_workers), 4275 _first_nmethod(NULL), 4276 _claimed_nmethod(NULL), 4277 _postponed_list(NULL), 4278 _num_entered_barrier(0) 4279 { 4280 nmethod::increase_unloading_clock(); 4281 // Get first alive nmethod 4282 NMethodIterator iter = NMethodIterator(); 4283 if(iter.next_alive()) { 4284 _first_nmethod = iter.method(); 4285 } 4286 _claimed_nmethod = (volatile nmethod*)_first_nmethod; 4287 } 4288 4289 ~G1CodeCacheUnloadingTask() { 4290 CodeCache::verify_clean_inline_caches(); 4291 4292 CodeCache::set_needs_cache_clean(false); 4293 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 4294 4295 CodeCache::verify_icholder_relocations(); 4296 } 4297 4298 private: 4299 void add_to_postponed_list(nmethod* nm) { 4300 nmethod* old; 4301 do { 4302 old = (nmethod*)_postponed_list; 4303 nm->set_unloading_next(old); 4304 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 4305 } 4306 4307 void clean_nmethod(nmethod* nm) { 4308 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 4309 4310 if (postponed) { 4311 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 4312 add_to_postponed_list(nm); 4313 } 4314 4315 // Mark that this thread has been cleaned/unloaded. 4316 // After this call, it will be safe to ask if this nmethod was unloaded or not. 4317 nm->set_unloading_clock(nmethod::global_unloading_clock()); 4318 } 4319 4320 void clean_nmethod_postponed(nmethod* nm) { 4321 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 4322 } 4323 4324 static const int MaxClaimNmethods = 16; 4325 4326 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) { 4327 nmethod* first; 4328 NMethodIterator last; 4329 4330 do { 4331 *num_claimed_nmethods = 0; 4332 4333 first = (nmethod*)_claimed_nmethod; 4334 last = NMethodIterator(first); 4335 4336 if (first != NULL) { 4337 4338 for (int i = 0; i < MaxClaimNmethods; i++) { 4339 if (!last.next_alive()) { 4340 break; 4341 } 4342 claimed_nmethods[i] = last.method(); 4343 (*num_claimed_nmethods)++; 4344 } 4345 } 4346 4347 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 4348 } 4349 4350 nmethod* claim_postponed_nmethod() { 4351 nmethod* claim; 4352 nmethod* next; 4353 4354 do { 4355 claim = (nmethod*)_postponed_list; 4356 if (claim == NULL) { 4357 return NULL; 4358 } 4359 4360 next = claim->unloading_next(); 4361 4362 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 4363 4364 return claim; 4365 } 4366 4367 public: 4368 // Mark that we're done with the first pass of nmethod cleaning. 4369 void barrier_mark(uint worker_id) { 4370 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4371 _num_entered_barrier++; 4372 if (_num_entered_barrier == _num_workers) { 4373 ml.notify_all(); 4374 } 4375 } 4376 4377 // See if we have to wait for the other workers to 4378 // finish their first-pass nmethod cleaning work. 4379 void barrier_wait(uint worker_id) { 4380 if (_num_entered_barrier < _num_workers) { 4381 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4382 while (_num_entered_barrier < _num_workers) { 4383 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 4384 } 4385 } 4386 } 4387 4388 // Cleaning and unloading of nmethods. Some work has to be postponed 4389 // to the second pass, when we know which nmethods survive. 4390 void work_first_pass(uint worker_id) { 4391 // The first nmethods is claimed by the first worker. 4392 if (worker_id == 0 && _first_nmethod != NULL) { 4393 clean_nmethod(_first_nmethod); 4394 _first_nmethod = NULL; 4395 } 4396 4397 int num_claimed_nmethods; 4398 nmethod* claimed_nmethods[MaxClaimNmethods]; 4399 4400 while (true) { 4401 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 4402 4403 if (num_claimed_nmethods == 0) { 4404 break; 4405 } 4406 4407 for (int i = 0; i < num_claimed_nmethods; i++) { 4408 clean_nmethod(claimed_nmethods[i]); 4409 } 4410 } 4411 } 4412 4413 void work_second_pass(uint worker_id) { 4414 nmethod* nm; 4415 // Take care of postponed nmethods. 4416 while ((nm = claim_postponed_nmethod()) != NULL) { 4417 clean_nmethod_postponed(nm); 4418 } 4419 } 4420 }; 4421 4422 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 4423 4424 class G1KlassCleaningTask : public StackObj { 4425 BoolObjectClosure* _is_alive; 4426 volatile jint _clean_klass_tree_claimed; 4427 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 4428 4429 public: 4430 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 4431 _is_alive(is_alive), 4432 _clean_klass_tree_claimed(0), 4433 _klass_iterator() { 4434 } 4435 4436 private: 4437 bool claim_clean_klass_tree_task() { 4438 if (_clean_klass_tree_claimed) { 4439 return false; 4440 } 4441 4442 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 4443 } 4444 4445 InstanceKlass* claim_next_klass() { 4446 Klass* klass; 4447 do { 4448 klass =_klass_iterator.next_klass(); 4449 } while (klass != NULL && !klass->is_instance_klass()); 4450 4451 // this can be null so don't call InstanceKlass::cast 4452 return static_cast<InstanceKlass*>(klass); 4453 } 4454 4455 public: 4456 4457 void clean_klass(InstanceKlass* ik) { 4458 ik->clean_weak_instanceklass_links(_is_alive); 4459 } 4460 4461 void work() { 4462 ResourceMark rm; 4463 4464 // One worker will clean the subklass/sibling klass tree. 4465 if (claim_clean_klass_tree_task()) { 4466 Klass::clean_subklass_tree(_is_alive); 4467 } 4468 4469 // All workers will help cleaning the classes, 4470 InstanceKlass* klass; 4471 while ((klass = claim_next_klass()) != NULL) { 4472 clean_klass(klass); 4473 } 4474 } 4475 }; 4476 4477 // To minimize the remark pause times, the tasks below are done in parallel. 4478 class G1ParallelCleaningTask : public AbstractGangTask { 4479 private: 4480 G1StringSymbolTableUnlinkTask _string_symbol_task; 4481 G1CodeCacheUnloadingTask _code_cache_task; 4482 G1KlassCleaningTask _klass_cleaning_task; 4483 4484 public: 4485 // The constructor is run in the VMThread. 4486 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 4487 AbstractGangTask("Parallel Cleaning"), 4488 _string_symbol_task(is_alive, process_strings, process_symbols), 4489 _code_cache_task(num_workers, is_alive, unloading_occurred), 4490 _klass_cleaning_task(is_alive) { 4491 } 4492 4493 // The parallel work done by all worker threads. 4494 void work(uint worker_id) { 4495 // Do first pass of code cache cleaning. 4496 _code_cache_task.work_first_pass(worker_id); 4497 4498 // Let the threads mark that the first pass is done. 4499 _code_cache_task.barrier_mark(worker_id); 4500 4501 // Clean the Strings and Symbols. 4502 _string_symbol_task.work(worker_id); 4503 4504 // Wait for all workers to finish the first code cache cleaning pass. 4505 _code_cache_task.barrier_wait(worker_id); 4506 4507 // Do the second code cache cleaning work, which realize on 4508 // the liveness information gathered during the first pass. 4509 _code_cache_task.work_second_pass(worker_id); 4510 4511 // Clean all klasses that were not unloaded. 4512 _klass_cleaning_task.work(); 4513 } 4514 }; 4515 4516 4517 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 4518 bool process_strings, 4519 bool process_symbols, 4520 bool class_unloading_occurred) { 4521 uint n_workers = workers()->active_workers(); 4522 4523 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 4524 n_workers, class_unloading_occurred); 4525 workers()->run_task(&g1_unlink_task); 4526 } 4527 4528 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 4529 bool process_strings, bool process_symbols) { 4530 { 4531 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 4532 workers()->run_task(&g1_unlink_task); 4533 } 4534 4535 if (G1StringDedup::is_enabled()) { 4536 G1StringDedup::unlink(is_alive); 4537 } 4538 } 4539 4540 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 4541 private: 4542 DirtyCardQueueSet* _queue; 4543 public: 4544 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { } 4545 4546 virtual void work(uint worker_id) { 4547 G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4548 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 4549 4550 RedirtyLoggedCardTableEntryClosure cl; 4551 _queue->par_apply_closure_to_all_completed_buffers(&cl); 4552 4553 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed()); 4554 } 4555 }; 4556 4557 void G1CollectedHeap::redirty_logged_cards() { 4558 double redirty_logged_cards_start = os::elapsedTime(); 4559 4560 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set()); 4561 dirty_card_queue_set().reset_for_par_iteration(); 4562 workers()->run_task(&redirty_task); 4563 4564 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 4565 dcq.merge_bufferlists(&dirty_card_queue_set()); 4566 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 4567 4568 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 4569 } 4570 4571 // Weak Reference Processing support 4572 4573 // An always "is_alive" closure that is used to preserve referents. 4574 // If the object is non-null then it's alive. Used in the preservation 4575 // of referent objects that are pointed to by reference objects 4576 // discovered by the CM ref processor. 4577 class G1AlwaysAliveClosure: public BoolObjectClosure { 4578 G1CollectedHeap* _g1; 4579 public: 4580 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4581 bool do_object_b(oop p) { 4582 if (p != NULL) { 4583 return true; 4584 } 4585 return false; 4586 } 4587 }; 4588 4589 bool G1STWIsAliveClosure::do_object_b(oop p) { 4590 // An object is reachable if it is outside the collection set, 4591 // or is inside and copied. 4592 return !_g1->is_in_cset(p) || p->is_forwarded(); 4593 } 4594 4595 // Non Copying Keep Alive closure 4596 class G1KeepAliveClosure: public OopClosure { 4597 G1CollectedHeap* _g1; 4598 public: 4599 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4600 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 4601 void do_oop(oop* p) { 4602 oop obj = *p; 4603 assert(obj != NULL, "the caller should have filtered out NULL values"); 4604 4605 const InCSetState cset_state = _g1->in_cset_state(obj); 4606 if (!cset_state.is_in_cset_or_humongous()) { 4607 return; 4608 } 4609 if (cset_state.is_in_cset()) { 4610 assert( obj->is_forwarded(), "invariant" ); 4611 *p = obj->forwardee(); 4612 } else { 4613 assert(!obj->is_forwarded(), "invariant" ); 4614 assert(cset_state.is_humongous(), 4615 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 4616 _g1->set_humongous_is_live(obj); 4617 } 4618 } 4619 }; 4620 4621 // Copying Keep Alive closure - can be called from both 4622 // serial and parallel code as long as different worker 4623 // threads utilize different G1ParScanThreadState instances 4624 // and different queues. 4625 4626 class G1CopyingKeepAliveClosure: public OopClosure { 4627 G1CollectedHeap* _g1h; 4628 OopClosure* _copy_non_heap_obj_cl; 4629 G1ParScanThreadState* _par_scan_state; 4630 4631 public: 4632 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4633 OopClosure* non_heap_obj_cl, 4634 G1ParScanThreadState* pss): 4635 _g1h(g1h), 4636 _copy_non_heap_obj_cl(non_heap_obj_cl), 4637 _par_scan_state(pss) 4638 {} 4639 4640 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4641 virtual void do_oop( oop* p) { do_oop_work(p); } 4642 4643 template <class T> void do_oop_work(T* p) { 4644 oop obj = oopDesc::load_decode_heap_oop(p); 4645 4646 if (_g1h->is_in_cset_or_humongous(obj)) { 4647 // If the referent object has been forwarded (either copied 4648 // to a new location or to itself in the event of an 4649 // evacuation failure) then we need to update the reference 4650 // field and, if both reference and referent are in the G1 4651 // heap, update the RSet for the referent. 4652 // 4653 // If the referent has not been forwarded then we have to keep 4654 // it alive by policy. Therefore we have copy the referent. 4655 // 4656 // If the reference field is in the G1 heap then we can push 4657 // on the PSS queue. When the queue is drained (after each 4658 // phase of reference processing) the object and it's followers 4659 // will be copied, the reference field set to point to the 4660 // new location, and the RSet updated. Otherwise we need to 4661 // use the the non-heap or metadata closures directly to copy 4662 // the referent object and update the pointer, while avoiding 4663 // updating the RSet. 4664 4665 if (_g1h->is_in_g1_reserved(p)) { 4666 _par_scan_state->push_on_queue(p); 4667 } else { 4668 assert(!Metaspace::contains((const void*)p), 4669 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4670 _copy_non_heap_obj_cl->do_oop(p); 4671 } 4672 } 4673 } 4674 }; 4675 4676 // Serial drain queue closure. Called as the 'complete_gc' 4677 // closure for each discovered list in some of the 4678 // reference processing phases. 4679 4680 class G1STWDrainQueueClosure: public VoidClosure { 4681 protected: 4682 G1CollectedHeap* _g1h; 4683 G1ParScanThreadState* _par_scan_state; 4684 4685 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4686 4687 public: 4688 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4689 _g1h(g1h), 4690 _par_scan_state(pss) 4691 { } 4692 4693 void do_void() { 4694 G1ParScanThreadState* const pss = par_scan_state(); 4695 pss->trim_queue(); 4696 } 4697 }; 4698 4699 // Parallel Reference Processing closures 4700 4701 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4702 // processing during G1 evacuation pauses. 4703 4704 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4705 private: 4706 G1CollectedHeap* _g1h; 4707 G1ParScanThreadStateSet* _pss; 4708 RefToScanQueueSet* _queues; 4709 WorkGang* _workers; 4710 uint _active_workers; 4711 4712 public: 4713 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4714 G1ParScanThreadStateSet* per_thread_states, 4715 WorkGang* workers, 4716 RefToScanQueueSet *task_queues, 4717 uint n_workers) : 4718 _g1h(g1h), 4719 _pss(per_thread_states), 4720 _queues(task_queues), 4721 _workers(workers), 4722 _active_workers(n_workers) 4723 { 4724 assert(n_workers > 0, "shouldn't call this otherwise"); 4725 } 4726 4727 // Executes the given task using concurrent marking worker threads. 4728 virtual void execute(ProcessTask& task); 4729 virtual void execute(EnqueueTask& task); 4730 }; 4731 4732 // Gang task for possibly parallel reference processing 4733 4734 class G1STWRefProcTaskProxy: public AbstractGangTask { 4735 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4736 ProcessTask& _proc_task; 4737 G1CollectedHeap* _g1h; 4738 G1ParScanThreadStateSet* _pss; 4739 RefToScanQueueSet* _task_queues; 4740 ParallelTaskTerminator* _terminator; 4741 4742 public: 4743 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4744 G1CollectedHeap* g1h, 4745 G1ParScanThreadStateSet* per_thread_states, 4746 RefToScanQueueSet *task_queues, 4747 ParallelTaskTerminator* terminator) : 4748 AbstractGangTask("Process reference objects in parallel"), 4749 _proc_task(proc_task), 4750 _g1h(g1h), 4751 _pss(per_thread_states), 4752 _task_queues(task_queues), 4753 _terminator(terminator) 4754 {} 4755 4756 virtual void work(uint worker_id) { 4757 // The reference processing task executed by a single worker. 4758 ResourceMark rm; 4759 HandleMark hm; 4760 4761 G1STWIsAliveClosure is_alive(_g1h); 4762 4763 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4764 pss->set_ref_processor(NULL); 4765 4766 // Keep alive closure. 4767 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4768 4769 // Complete GC closure 4770 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4771 4772 // Call the reference processing task's work routine. 4773 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4774 4775 // Note we cannot assert that the refs array is empty here as not all 4776 // of the processing tasks (specifically phase2 - pp2_work) execute 4777 // the complete_gc closure (which ordinarily would drain the queue) so 4778 // the queue may not be empty. 4779 } 4780 }; 4781 4782 // Driver routine for parallel reference processing. 4783 // Creates an instance of the ref processing gang 4784 // task and has the worker threads execute it. 4785 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4786 assert(_workers != NULL, "Need parallel worker threads."); 4787 4788 ParallelTaskTerminator terminator(_active_workers, _queues); 4789 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4790 4791 _workers->run_task(&proc_task_proxy); 4792 } 4793 4794 // Gang task for parallel reference enqueueing. 4795 4796 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4797 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4798 EnqueueTask& _enq_task; 4799 4800 public: 4801 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4802 AbstractGangTask("Enqueue reference objects in parallel"), 4803 _enq_task(enq_task) 4804 { } 4805 4806 virtual void work(uint worker_id) { 4807 _enq_task.work(worker_id); 4808 } 4809 }; 4810 4811 // Driver routine for parallel reference enqueueing. 4812 // Creates an instance of the ref enqueueing gang 4813 // task and has the worker threads execute it. 4814 4815 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4816 assert(_workers != NULL, "Need parallel worker threads."); 4817 4818 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4819 4820 _workers->run_task(&enq_task_proxy); 4821 } 4822 4823 // End of weak reference support closures 4824 4825 // Abstract task used to preserve (i.e. copy) any referent objects 4826 // that are in the collection set and are pointed to by reference 4827 // objects discovered by the CM ref processor. 4828 4829 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4830 protected: 4831 G1CollectedHeap* _g1h; 4832 G1ParScanThreadStateSet* _pss; 4833 RefToScanQueueSet* _queues; 4834 ParallelTaskTerminator _terminator; 4835 uint _n_workers; 4836 4837 public: 4838 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4839 AbstractGangTask("ParPreserveCMReferents"), 4840 _g1h(g1h), 4841 _pss(per_thread_states), 4842 _queues(task_queues), 4843 _terminator(workers, _queues), 4844 _n_workers(workers) 4845 { } 4846 4847 void work(uint worker_id) { 4848 ResourceMark rm; 4849 HandleMark hm; 4850 4851 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4852 pss->set_ref_processor(NULL); 4853 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4854 4855 // Is alive closure 4856 G1AlwaysAliveClosure always_alive(_g1h); 4857 4858 // Copying keep alive closure. Applied to referent objects that need 4859 // to be copied. 4860 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4861 4862 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4863 4864 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4865 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4866 4867 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4868 // So this must be true - but assert just in case someone decides to 4869 // change the worker ids. 4870 assert(worker_id < limit, "sanity"); 4871 assert(!rp->discovery_is_atomic(), "check this code"); 4872 4873 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4874 for (uint idx = worker_id; idx < limit; idx += stride) { 4875 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4876 4877 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4878 while (iter.has_next()) { 4879 // Since discovery is not atomic for the CM ref processor, we 4880 // can see some null referent objects. 4881 iter.load_ptrs(DEBUG_ONLY(true)); 4882 oop ref = iter.obj(); 4883 4884 // This will filter nulls. 4885 if (iter.is_referent_alive()) { 4886 iter.make_referent_alive(); 4887 } 4888 iter.move_to_next(); 4889 } 4890 } 4891 4892 // Drain the queue - which may cause stealing 4893 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4894 drain_queue.do_void(); 4895 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4896 assert(pss->queue_is_empty(), "should be"); 4897 } 4898 }; 4899 4900 // Weak Reference processing during an evacuation pause (part 1). 4901 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4902 double ref_proc_start = os::elapsedTime(); 4903 4904 ReferenceProcessor* rp = _ref_processor_stw; 4905 assert(rp->discovery_enabled(), "should have been enabled"); 4906 4907 // Any reference objects, in the collection set, that were 'discovered' 4908 // by the CM ref processor should have already been copied (either by 4909 // applying the external root copy closure to the discovered lists, or 4910 // by following an RSet entry). 4911 // 4912 // But some of the referents, that are in the collection set, that these 4913 // reference objects point to may not have been copied: the STW ref 4914 // processor would have seen that the reference object had already 4915 // been 'discovered' and would have skipped discovering the reference, 4916 // but would not have treated the reference object as a regular oop. 4917 // As a result the copy closure would not have been applied to the 4918 // referent object. 4919 // 4920 // We need to explicitly copy these referent objects - the references 4921 // will be processed at the end of remarking. 4922 // 4923 // We also need to do this copying before we process the reference 4924 // objects discovered by the STW ref processor in case one of these 4925 // referents points to another object which is also referenced by an 4926 // object discovered by the STW ref processor. 4927 4928 uint no_of_gc_workers = workers()->active_workers(); 4929 4930 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4931 per_thread_states, 4932 no_of_gc_workers, 4933 _task_queues); 4934 4935 workers()->run_task(&keep_cm_referents); 4936 4937 // Closure to test whether a referent is alive. 4938 G1STWIsAliveClosure is_alive(this); 4939 4940 // Even when parallel reference processing is enabled, the processing 4941 // of JNI refs is serial and performed serially by the current thread 4942 // rather than by a worker. The following PSS will be used for processing 4943 // JNI refs. 4944 4945 // Use only a single queue for this PSS. 4946 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4947 pss->set_ref_processor(NULL); 4948 assert(pss->queue_is_empty(), "pre-condition"); 4949 4950 // Keep alive closure. 4951 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4952 4953 // Serial Complete GC closure 4954 G1STWDrainQueueClosure drain_queue(this, pss); 4955 4956 // Setup the soft refs policy... 4957 rp->setup_policy(false); 4958 4959 ReferenceProcessorStats stats; 4960 if (!rp->processing_is_mt()) { 4961 // Serial reference processing... 4962 stats = rp->process_discovered_references(&is_alive, 4963 &keep_alive, 4964 &drain_queue, 4965 NULL, 4966 _gc_timer_stw); 4967 } else { 4968 // Parallel reference processing 4969 assert(rp->num_q() == no_of_gc_workers, "sanity"); 4970 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 4971 4972 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4973 stats = rp->process_discovered_references(&is_alive, 4974 &keep_alive, 4975 &drain_queue, 4976 &par_task_executor, 4977 _gc_timer_stw); 4978 } 4979 4980 _gc_tracer_stw->report_gc_reference_stats(stats); 4981 4982 // We have completed copying any necessary live referent objects. 4983 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4984 4985 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4986 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4987 } 4988 4989 // Weak Reference processing during an evacuation pause (part 2). 4990 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4991 double ref_enq_start = os::elapsedTime(); 4992 4993 ReferenceProcessor* rp = _ref_processor_stw; 4994 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4995 4996 // Now enqueue any remaining on the discovered lists on to 4997 // the pending list. 4998 if (!rp->processing_is_mt()) { 4999 // Serial reference processing... 5000 rp->enqueue_discovered_references(); 5001 } else { 5002 // Parallel reference enqueueing 5003 5004 uint n_workers = workers()->active_workers(); 5005 5006 assert(rp->num_q() == n_workers, "sanity"); 5007 assert(n_workers <= rp->max_num_q(), "sanity"); 5008 5009 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 5010 rp->enqueue_discovered_references(&par_task_executor); 5011 } 5012 5013 rp->verify_no_references_recorded(); 5014 assert(!rp->discovery_enabled(), "should have been disabled"); 5015 5016 // FIXME 5017 // CM's reference processing also cleans up the string and symbol tables. 5018 // Should we do that here also? We could, but it is a serial operation 5019 // and could significantly increase the pause time. 5020 5021 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5022 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5023 } 5024 5025 void G1CollectedHeap::pre_evacuate_collection_set() { 5026 _expand_heap_after_alloc_failure = true; 5027 _evacuation_failed = false; 5028 5029 // Disable the hot card cache. 5030 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5031 hot_card_cache->reset_hot_cache_claimed_index(); 5032 hot_card_cache->set_use_cache(false); 5033 5034 } 5035 5036 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 5037 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5038 5039 // Should G1EvacuationFailureALot be in effect for this GC? 5040 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5041 5042 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5043 double start_par_time_sec = os::elapsedTime(); 5044 double end_par_time_sec; 5045 5046 { 5047 const uint n_workers = workers()->active_workers(); 5048 G1RootProcessor root_processor(this, n_workers); 5049 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 5050 // InitialMark needs claim bits to keep track of the marked-through CLDs. 5051 if (collector_state()->during_initial_mark_pause()) { 5052 ClassLoaderDataGraph::clear_claimed_marks(); 5053 } 5054 5055 print_termination_stats_hdr(); 5056 5057 workers()->run_task(&g1_par_task); 5058 end_par_time_sec = os::elapsedTime(); 5059 5060 // Closing the inner scope will execute the destructor 5061 // for the G1RootProcessor object. We record the current 5062 // elapsed time before closing the scope so that time 5063 // taken for the destructor is NOT included in the 5064 // reported parallel time. 5065 } 5066 5067 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 5068 5069 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5070 phase_times->record_par_time(par_time_ms); 5071 5072 double code_root_fixup_time_ms = 5073 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5074 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 5075 5076 // Process any discovered reference objects - we have 5077 // to do this _before_ we retire the GC alloc regions 5078 // as we may have to copy some 'reachable' referent 5079 // objects (and their reachable sub-graphs) that were 5080 // not copied during the pause. 5081 process_discovered_references(per_thread_states); 5082 5083 if (G1StringDedup::is_enabled()) { 5084 double fixup_start = os::elapsedTime(); 5085 5086 G1STWIsAliveClosure is_alive(this); 5087 G1KeepAliveClosure keep_alive(this); 5088 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times); 5089 5090 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 5091 phase_times->record_string_dedup_fixup_time(fixup_time_ms); 5092 } 5093 5094 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5095 5096 if (evacuation_failed()) { 5097 remove_self_forwarding_pointers(); 5098 5099 // Reset the G1EvacuationFailureALot counters and flags 5100 // Note: the values are reset only when an actual 5101 // evacuation failure occurs. 5102 NOT_PRODUCT(reset_evacuation_should_fail();) 5103 } 5104 5105 // Enqueue any remaining references remaining on the STW 5106 // reference processor's discovered lists. We need to do 5107 // this after the card table is cleaned (and verified) as 5108 // the act of enqueueing entries on to the pending list 5109 // will log these updates (and dirty their associated 5110 // cards). We need these updates logged to update any 5111 // RSets. 5112 enqueue_discovered_references(per_thread_states); 5113 } 5114 5115 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 5116 _allocator->release_gc_alloc_regions(evacuation_info); 5117 5118 per_thread_states->flush(); 5119 5120 record_obj_copy_mem_stats(); 5121 5122 _survivor_evac_stats.adjust_desired_plab_sz(); 5123 _old_evac_stats.adjust_desired_plab_sz(); 5124 5125 // Reset and re-enable the hot card cache. 5126 // Note the counts for the cards in the regions in the 5127 // collection set are reset when the collection set is freed. 5128 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5129 hot_card_cache->reset_hot_cache(); 5130 hot_card_cache->set_use_cache(true); 5131 5132 purge_code_root_memory(); 5133 5134 redirty_logged_cards(); 5135 #if defined(COMPILER2) || INCLUDE_JVMCI 5136 DerivedPointerTable::update_pointers(); 5137 #endif 5138 } 5139 5140 void G1CollectedHeap::record_obj_copy_mem_stats() { 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 HeapRegionSetCount& old_regions_removed, 5179 const HeapRegionSetCount& humongous_regions_removed) { 5180 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 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)("\n## 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)("\n## inconsistent cset state %d 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)("\n## inconsistent cset state %d 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)("\n## inconsistent cset state %d 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)("\n## in CSet %d / cset state %d 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)("\n## is_young %d / cset state %d 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)("\n## is_old %d / cset state %d 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 void G1CollectedHeap::cleanUpCardTable() { 5417 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5418 double start = os::elapsedTime(); 5419 5420 { 5421 // Iterate over the dirty cards region list. 5422 G1ParCleanupCTTask cleanup_task(ct_bs, this); 5423 5424 workers()->run_task(&cleanup_task); 5425 #ifndef PRODUCT 5426 if (G1VerifyCTCleanup || VerifyAfterGC) { 5427 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 5428 heap_region_iterate(&cleanup_verifier); 5429 } 5430 #endif 5431 } 5432 5433 double elapsed = os::elapsedTime() - start; 5434 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 5435 } 5436 5437 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 5438 size_t pre_used = 0; 5439 FreeRegionList local_free_list("Local List for CSet Freeing"); 5440 5441 double young_time_ms = 0.0; 5442 double non_young_time_ms = 0.0; 5443 5444 // Since the collection set is a superset of the the young list, 5445 // all we need to do to clear the young list is clear its 5446 // head and length, and unlink any young regions in the code below 5447 _young_list->clear(); 5448 5449 G1CollectorPolicy* policy = g1_policy(); 5450 5451 double start_sec = os::elapsedTime(); 5452 bool non_young = true; 5453 5454 HeapRegion* cur = cs_head; 5455 int age_bound = -1; 5456 size_t rs_lengths = 0; 5457 5458 while (cur != NULL) { 5459 assert(!is_on_master_free_list(cur), "sanity"); 5460 if (non_young) { 5461 if (cur->is_young()) { 5462 double end_sec = os::elapsedTime(); 5463 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5464 non_young_time_ms += elapsed_ms; 5465 5466 start_sec = os::elapsedTime(); 5467 non_young = false; 5468 } 5469 } else { 5470 if (!cur->is_young()) { 5471 double end_sec = os::elapsedTime(); 5472 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5473 young_time_ms += elapsed_ms; 5474 5475 start_sec = os::elapsedTime(); 5476 non_young = true; 5477 } 5478 } 5479 5480 rs_lengths += cur->rem_set()->occupied_locked(); 5481 5482 HeapRegion* next = cur->next_in_collection_set(); 5483 assert(cur->in_collection_set(), "bad CS"); 5484 cur->set_next_in_collection_set(NULL); 5485 clear_in_cset(cur); 5486 5487 if (cur->is_young()) { 5488 int index = cur->young_index_in_cset(); 5489 assert(index != -1, "invariant"); 5490 assert((uint) index < policy->young_cset_region_length(), "invariant"); 5491 size_t words_survived = surviving_young_words[index]; 5492 cur->record_surv_words_in_group(words_survived); 5493 5494 // At this point the we have 'popped' cur from the collection set 5495 // (linked via next_in_collection_set()) but it is still in the 5496 // young list (linked via next_young_region()). Clear the 5497 // _next_young_region field. 5498 cur->set_next_young_region(NULL); 5499 } else { 5500 int index = cur->young_index_in_cset(); 5501 assert(index == -1, "invariant"); 5502 } 5503 5504 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 5505 (!cur->is_young() && cur->young_index_in_cset() == -1), 5506 "invariant" ); 5507 5508 if (!cur->evacuation_failed()) { 5509 MemRegion used_mr = cur->used_region(); 5510 5511 // And the region is empty. 5512 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 5513 pre_used += cur->used(); 5514 free_region(cur, &local_free_list, false /* par */, true /* locked */); 5515 } else { 5516 cur->uninstall_surv_rate_group(); 5517 if (cur->is_young()) { 5518 cur->set_young_index_in_cset(-1); 5519 } 5520 cur->set_evacuation_failed(false); 5521 // The region is now considered to be old. 5522 cur->set_old(); 5523 // Do some allocation statistics accounting. Regions that failed evacuation 5524 // are always made old, so there is no need to update anything in the young 5525 // gen statistics, but we need to update old gen statistics. 5526 size_t used_words = cur->marked_bytes() / HeapWordSize; 5527 _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words); 5528 _old_set.add(cur); 5529 evacuation_info.increment_collectionset_used_after(cur->used()); 5530 } 5531 cur = next; 5532 } 5533 5534 evacuation_info.set_regions_freed(local_free_list.length()); 5535 policy->record_max_rs_lengths(rs_lengths); 5536 policy->cset_regions_freed(); 5537 5538 double end_sec = os::elapsedTime(); 5539 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5540 5541 if (non_young) { 5542 non_young_time_ms += elapsed_ms; 5543 } else { 5544 young_time_ms += elapsed_ms; 5545 } 5546 5547 prepend_to_freelist(&local_free_list); 5548 decrement_summary_bytes(pre_used); 5549 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 5550 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 5551 } 5552 5553 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 5554 private: 5555 FreeRegionList* _free_region_list; 5556 HeapRegionSet* _proxy_set; 5557 HeapRegionSetCount _humongous_regions_removed; 5558 size_t _freed_bytes; 5559 public: 5560 5561 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 5562 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) { 5563 } 5564 5565 virtual bool doHeapRegion(HeapRegion* r) { 5566 if (!r->is_starts_humongous()) { 5567 return false; 5568 } 5569 5570 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 5571 5572 oop obj = (oop)r->bottom(); 5573 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 5574 5575 // The following checks whether the humongous object is live are sufficient. 5576 // The main additional check (in addition to having a reference from the roots 5577 // or the young gen) is whether the humongous object has a remembered set entry. 5578 // 5579 // A humongous object cannot be live if there is no remembered set for it 5580 // because: 5581 // - there can be no references from within humongous starts regions referencing 5582 // the object because we never allocate other objects into them. 5583 // (I.e. there are no intra-region references that may be missed by the 5584 // remembered set) 5585 // - as soon there is a remembered set entry to the humongous starts region 5586 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 5587 // until the end of a concurrent mark. 5588 // 5589 // It is not required to check whether the object has been found dead by marking 5590 // or not, in fact it would prevent reclamation within a concurrent cycle, as 5591 // all objects allocated during that time are considered live. 5592 // SATB marking is even more conservative than the remembered set. 5593 // So if at this point in the collection there is no remembered set entry, 5594 // nobody has a reference to it. 5595 // At the start of collection we flush all refinement logs, and remembered sets 5596 // are completely up-to-date wrt to references to the humongous object. 5597 // 5598 // Other implementation considerations: 5599 // - never consider object arrays at this time because they would pose 5600 // considerable effort for cleaning up the the remembered sets. This is 5601 // required because stale remembered sets might reference locations that 5602 // are currently allocated into. 5603 uint region_idx = r->hrm_index(); 5604 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 5605 !r->rem_set()->is_empty()) { 5606 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", 5607 region_idx, 5608 (size_t)obj->size() * HeapWordSize, 5609 p2i(r->bottom()), 5610 r->rem_set()->occupied(), 5611 r->rem_set()->strong_code_roots_list_length(), 5612 next_bitmap->isMarked(r->bottom()), 5613 g1h->is_humongous_reclaim_candidate(region_idx), 5614 obj->is_typeArray() 5615 ); 5616 return false; 5617 } 5618 5619 guarantee(obj->is_typeArray(), 5620 "Only eagerly reclaiming type arrays is supported, but the object " 5621 PTR_FORMAT " is not.", p2i(r->bottom())); 5622 5623 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", 5624 region_idx, 5625 (size_t)obj->size() * HeapWordSize, 5626 p2i(r->bottom()), 5627 r->rem_set()->occupied(), 5628 r->rem_set()->strong_code_roots_list_length(), 5629 next_bitmap->isMarked(r->bottom()), 5630 g1h->is_humongous_reclaim_candidate(region_idx), 5631 obj->is_typeArray() 5632 ); 5633 5634 // Need to clear mark bit of the humongous object if already set. 5635 if (next_bitmap->isMarked(r->bottom())) { 5636 next_bitmap->clear(r->bottom()); 5637 } 5638 do { 5639 HeapRegion* next = g1h->next_region_in_humongous(r); 5640 _freed_bytes += r->used(); 5641 r->set_containing_set(NULL); 5642 _humongous_regions_removed.increment(1u, r->capacity()); 5643 g1h->free_humongous_region(r, _free_region_list, false); 5644 r = next; 5645 } while (r != NULL); 5646 5647 return false; 5648 } 5649 5650 HeapRegionSetCount& humongous_free_count() { 5651 return _humongous_regions_removed; 5652 } 5653 5654 size_t bytes_freed() const { 5655 return _freed_bytes; 5656 } 5657 5658 size_t humongous_reclaimed() const { 5659 return _humongous_regions_removed.length(); 5660 } 5661 }; 5662 5663 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 5664 assert_at_safepoint(true); 5665 5666 if (!G1EagerReclaimHumongousObjects || 5667 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 5668 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5669 return; 5670 } 5671 5672 double start_time = os::elapsedTime(); 5673 5674 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5675 5676 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5677 heap_region_iterate(&cl); 5678 5679 HeapRegionSetCount empty_set; 5680 remove_from_old_sets(empty_set, cl.humongous_free_count()); 5681 5682 G1HRPrinter* hrp = hr_printer(); 5683 if (hrp->is_active()) { 5684 FreeRegionListIterator iter(&local_cleanup_list); 5685 while (iter.more_available()) { 5686 HeapRegion* hr = iter.get_next(); 5687 hrp->cleanup(hr); 5688 } 5689 } 5690 5691 prepend_to_freelist(&local_cleanup_list); 5692 decrement_summary_bytes(cl.bytes_freed()); 5693 5694 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5695 cl.humongous_reclaimed()); 5696 } 5697 5698 // This routine is similar to the above but does not record 5699 // any policy statistics or update free lists; we are abandoning 5700 // the current incremental collection set in preparation of a 5701 // full collection. After the full GC we will start to build up 5702 // the incremental collection set again. 5703 // This is only called when we're doing a full collection 5704 // and is immediately followed by the tearing down of the young list. 5705 5706 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 5707 HeapRegion* cur = cs_head; 5708 5709 while (cur != NULL) { 5710 HeapRegion* next = cur->next_in_collection_set(); 5711 assert(cur->in_collection_set(), "bad CS"); 5712 cur->set_next_in_collection_set(NULL); 5713 clear_in_cset(cur); 5714 cur->set_young_index_in_cset(-1); 5715 cur = next; 5716 } 5717 } 5718 5719 void G1CollectedHeap::set_free_regions_coming() { 5720 log_develop(gc, freelist)("G1ConcRegionFreeing [cm thread] : " 5721 "setting free regions coming"); 5722 5723 assert(!free_regions_coming(), "pre-condition"); 5724 _free_regions_coming = true; 5725 } 5726 5727 void G1CollectedHeap::reset_free_regions_coming() { 5728 assert(free_regions_coming(), "pre-condition"); 5729 5730 { 5731 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5732 _free_regions_coming = false; 5733 SecondaryFreeList_lock->notify_all(); 5734 } 5735 5736 log_develop(gc, freelist)("G1ConcRegionFreeing [cm thread] : " 5737 "reset free regions coming"); 5738 } 5739 5740 void G1CollectedHeap::wait_while_free_regions_coming() { 5741 // Most of the time we won't have to wait, so let's do a quick test 5742 // first before we take the lock. 5743 if (!free_regions_coming()) { 5744 return; 5745 } 5746 5747 log_develop(gc, freelist)("G1ConcRegionFreeing [other] : " 5748 "waiting for free regions"); 5749 5750 { 5751 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5752 while (free_regions_coming()) { 5753 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5754 } 5755 } 5756 5757 log_develop(gc, freelist)("G1ConcRegionFreeing [other] : " 5758 "done waiting for free regions"); 5759 } 5760 5761 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5762 return _allocator->is_retained_old_region(hr); 5763 } 5764 5765 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5766 _young_list->push_region(hr); 5767 } 5768 5769 class NoYoungRegionsClosure: public HeapRegionClosure { 5770 private: 5771 bool _success; 5772 public: 5773 NoYoungRegionsClosure() : _success(true) { } 5774 bool doHeapRegion(HeapRegion* r) { 5775 if (r->is_young()) { 5776 log_info(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5777 p2i(r->bottom()), p2i(r->end())); 5778 _success = false; 5779 } 5780 return false; 5781 } 5782 bool success() { return _success; } 5783 }; 5784 5785 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 5786 bool ret = _young_list->check_list_empty(check_sample); 5787 5788 if (check_heap) { 5789 NoYoungRegionsClosure closure; 5790 heap_region_iterate(&closure); 5791 ret = ret && closure.success(); 5792 } 5793 5794 return ret; 5795 } 5796 5797 class TearDownRegionSetsClosure : public HeapRegionClosure { 5798 private: 5799 HeapRegionSet *_old_set; 5800 5801 public: 5802 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5803 5804 bool doHeapRegion(HeapRegion* r) { 5805 if (r->is_old()) { 5806 _old_set->remove(r); 5807 } else { 5808 // We ignore free regions, we'll empty the free list afterwards. 5809 // We ignore young regions, we'll empty the young list afterwards. 5810 // We ignore humongous regions, we're not tearing down the 5811 // humongous regions set. 5812 assert(r->is_free() || r->is_young() || r->is_humongous(), 5813 "it cannot be another type"); 5814 } 5815 return false; 5816 } 5817 5818 ~TearDownRegionSetsClosure() { 5819 assert(_old_set->is_empty(), "post-condition"); 5820 } 5821 }; 5822 5823 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5824 assert_at_safepoint(true /* should_be_vm_thread */); 5825 5826 if (!free_list_only) { 5827 TearDownRegionSetsClosure cl(&_old_set); 5828 heap_region_iterate(&cl); 5829 5830 // Note that emptying the _young_list is postponed and instead done as 5831 // the first step when rebuilding the regions sets again. The reason for 5832 // this is that during a full GC string deduplication needs to know if 5833 // a collected region was young or old when the full GC was initiated. 5834 } 5835 _hrm.remove_all_free_regions(); 5836 } 5837 5838 void G1CollectedHeap::increase_used(size_t bytes) { 5839 _summary_bytes_used += bytes; 5840 } 5841 5842 void G1CollectedHeap::decrease_used(size_t bytes) { 5843 assert(_summary_bytes_used >= bytes, 5844 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5845 _summary_bytes_used, bytes); 5846 _summary_bytes_used -= bytes; 5847 } 5848 5849 void G1CollectedHeap::set_used(size_t bytes) { 5850 _summary_bytes_used = bytes; 5851 } 5852 5853 class RebuildRegionSetsClosure : public HeapRegionClosure { 5854 private: 5855 bool _free_list_only; 5856 HeapRegionSet* _old_set; 5857 HeapRegionManager* _hrm; 5858 size_t _total_used; 5859 5860 public: 5861 RebuildRegionSetsClosure(bool free_list_only, 5862 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5863 _free_list_only(free_list_only), 5864 _old_set(old_set), _hrm(hrm), _total_used(0) { 5865 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5866 if (!free_list_only) { 5867 assert(_old_set->is_empty(), "pre-condition"); 5868 } 5869 } 5870 5871 bool doHeapRegion(HeapRegion* r) { 5872 if (r->is_empty()) { 5873 // Add free regions to the free list 5874 r->set_free(); 5875 r->set_allocation_context(AllocationContext::system()); 5876 _hrm->insert_into_free_list(r); 5877 } else if (!_free_list_only) { 5878 assert(!r->is_young(), "we should not come across young regions"); 5879 5880 if (r->is_humongous()) { 5881 // We ignore humongous regions. We left the humongous set unchanged. 5882 } else { 5883 // Objects that were compacted would have ended up on regions 5884 // that were previously old or free. Archive regions (which are 5885 // old) will not have been touched. 5886 assert(r->is_free() || r->is_old(), "invariant"); 5887 // We now consider them old, so register as such. Leave 5888 // archive regions set that way, however, while still adding 5889 // them to the old set. 5890 if (!r->is_archive()) { 5891 r->set_old(); 5892 } 5893 _old_set->add(r); 5894 } 5895 _total_used += r->used(); 5896 } 5897 5898 return false; 5899 } 5900 5901 size_t total_used() { 5902 return _total_used; 5903 } 5904 }; 5905 5906 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5907 assert_at_safepoint(true /* should_be_vm_thread */); 5908 5909 if (!free_list_only) { 5910 _young_list->empty_list(); 5911 } 5912 5913 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5914 heap_region_iterate(&cl); 5915 5916 if (!free_list_only) { 5917 set_used(cl.total_used()); 5918 if (_archive_allocator != NULL) { 5919 _archive_allocator->clear_used(); 5920 } 5921 } 5922 assert(used_unlocked() == recalculate_used(), 5923 "inconsistent used_unlocked(), " 5924 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5925 used_unlocked(), recalculate_used()); 5926 } 5927 5928 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 5929 _refine_cte_cl->set_concurrent(concurrent); 5930 } 5931 5932 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5933 HeapRegion* hr = heap_region_containing(p); 5934 return hr->is_in(p); 5935 } 5936 5937 // Methods for the mutator alloc region 5938 5939 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5940 bool force) { 5941 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5942 assert(!force || g1_policy()->can_expand_young_list(), 5943 "if force is true we should be able to expand the young list"); 5944 bool young_list_full = g1_policy()->is_young_list_full(); 5945 if (force || !young_list_full) { 5946 HeapRegion* new_alloc_region = new_region(word_size, 5947 false /* is_old */, 5948 false /* do_expand */); 5949 if (new_alloc_region != NULL) { 5950 set_region_short_lived_locked(new_alloc_region); 5951 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 5952 check_bitmaps("Mutator Region Allocation", new_alloc_region); 5953 return new_alloc_region; 5954 } 5955 } 5956 return NULL; 5957 } 5958 5959 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5960 size_t allocated_bytes) { 5961 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5962 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5963 5964 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 5965 increase_used(allocated_bytes); 5966 _hr_printer.retire(alloc_region); 5967 // We update the eden sizes here, when the region is retired, 5968 // instead of when it's allocated, since this is the point that its 5969 // used space has been recored in _summary_bytes_used. 5970 g1mm()->update_eden_size(); 5971 } 5972 5973 // Methods for the GC alloc regions 5974 5975 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 5976 uint count, 5977 InCSetState dest) { 5978 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5979 5980 if (count < g1_policy()->max_regions(dest)) { 5981 const bool is_survivor = (dest.is_young()); 5982 HeapRegion* new_alloc_region = new_region(word_size, 5983 !is_survivor, 5984 true /* do_expand */); 5985 if (new_alloc_region != NULL) { 5986 // We really only need to do this for old regions given that we 5987 // should never scan survivors. But it doesn't hurt to do it 5988 // for survivors too. 5989 new_alloc_region->record_timestamp(); 5990 if (is_survivor) { 5991 new_alloc_region->set_survivor(); 5992 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 5993 check_bitmaps("Survivor Region Allocation", new_alloc_region); 5994 } else { 5995 new_alloc_region->set_old(); 5996 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 5997 check_bitmaps("Old Region Allocation", new_alloc_region); 5998 } 5999 bool during_im = collector_state()->during_initial_mark_pause(); 6000 new_alloc_region->note_start_of_copying(during_im); 6001 return new_alloc_region; 6002 } 6003 } 6004 return NULL; 6005 } 6006 6007 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6008 size_t allocated_bytes, 6009 InCSetState dest) { 6010 bool during_im = collector_state()->during_initial_mark_pause(); 6011 alloc_region->note_end_of_copying(during_im); 6012 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6013 if (dest.is_young()) { 6014 young_list()->add_survivor_region(alloc_region); 6015 } else { 6016 _old_set.add(alloc_region); 6017 } 6018 _hr_printer.retire(alloc_region); 6019 } 6020 6021 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 6022 bool expanded = false; 6023 uint index = _hrm.find_highest_free(&expanded); 6024 6025 if (index != G1_NO_HRM_INDEX) { 6026 if (expanded) { 6027 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 6028 HeapRegion::GrainWords * HeapWordSize); 6029 } 6030 _hrm.allocate_free_regions_starting_at(index, 1); 6031 return region_at(index); 6032 } 6033 return NULL; 6034 } 6035 6036 // Heap region set verification 6037 6038 class VerifyRegionListsClosure : public HeapRegionClosure { 6039 private: 6040 HeapRegionSet* _old_set; 6041 HeapRegionSet* _humongous_set; 6042 HeapRegionManager* _hrm; 6043 6044 public: 6045 HeapRegionSetCount _old_count; 6046 HeapRegionSetCount _humongous_count; 6047 HeapRegionSetCount _free_count; 6048 6049 VerifyRegionListsClosure(HeapRegionSet* old_set, 6050 HeapRegionSet* humongous_set, 6051 HeapRegionManager* hrm) : 6052 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm), 6053 _old_count(), _humongous_count(), _free_count(){ } 6054 6055 bool doHeapRegion(HeapRegion* hr) { 6056 if (hr->is_young()) { 6057 // TODO 6058 } else if (hr->is_humongous()) { 6059 assert(hr->containing_set() == _humongous_set, "Heap region %u is humongous but not in humongous set.", hr->hrm_index()); 6060 _humongous_count.increment(1u, hr->capacity()); 6061 } else if (hr->is_empty()) { 6062 assert(_hrm->is_free(hr), "Heap region %u is empty but not on the free list.", hr->hrm_index()); 6063 _free_count.increment(1u, hr->capacity()); 6064 } else if (hr->is_old()) { 6065 assert(hr->containing_set() == _old_set, "Heap region %u is old but not in the old set.", hr->hrm_index()); 6066 _old_count.increment(1u, hr->capacity()); 6067 } else { 6068 // There are no other valid region types. Check for one invalid 6069 // one we can identify: pinned without old or humongous set. 6070 assert(!hr->is_pinned(), "Heap region %u is pinned but not old (archive) or humongous.", hr->hrm_index()); 6071 ShouldNotReachHere(); 6072 } 6073 return false; 6074 } 6075 6076 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) { 6077 guarantee(old_set->length() == _old_count.length(), "Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()); 6078 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), "Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6079 old_set->total_capacity_bytes(), _old_count.capacity()); 6080 6081 guarantee(humongous_set->length() == _humongous_count.length(), "Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()); 6082 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), "Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6083 humongous_set->total_capacity_bytes(), _humongous_count.capacity()); 6084 6085 guarantee(free_list->num_free_regions() == _free_count.length(), "Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count.length()); 6086 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), "Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6087 free_list->total_capacity_bytes(), _free_count.capacity()); 6088 } 6089 }; 6090 6091 void G1CollectedHeap::verify_region_sets() { 6092 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6093 6094 // First, check the explicit lists. 6095 _hrm.verify(); 6096 { 6097 // Given that a concurrent operation might be adding regions to 6098 // the secondary free list we have to take the lock before 6099 // verifying it. 6100 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6101 _secondary_free_list.verify_list(); 6102 } 6103 6104 // If a concurrent region freeing operation is in progress it will 6105 // be difficult to correctly attributed any free regions we come 6106 // across to the correct free list given that they might belong to 6107 // one of several (free_list, secondary_free_list, any local lists, 6108 // etc.). So, if that's the case we will skip the rest of the 6109 // verification operation. Alternatively, waiting for the concurrent 6110 // operation to complete will have a non-trivial effect on the GC's 6111 // operation (no concurrent operation will last longer than the 6112 // interval between two calls to verification) and it might hide 6113 // any issues that we would like to catch during testing. 6114 if (free_regions_coming()) { 6115 return; 6116 } 6117 6118 // Make sure we append the secondary_free_list on the free_list so 6119 // that all free regions we will come across can be safely 6120 // attributed to the free_list. 6121 append_secondary_free_list_if_not_empty_with_lock(); 6122 6123 // Finally, make sure that the region accounting in the lists is 6124 // consistent with what we see in the heap. 6125 6126 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm); 6127 heap_region_iterate(&cl); 6128 cl.verify_counts(&_old_set, &_humongous_set, &_hrm); 6129 } 6130 6131 // Optimized nmethod scanning 6132 6133 class RegisterNMethodOopClosure: public OopClosure { 6134 G1CollectedHeap* _g1h; 6135 nmethod* _nm; 6136 6137 template <class T> void do_oop_work(T* p) { 6138 T heap_oop = oopDesc::load_heap_oop(p); 6139 if (!oopDesc::is_null(heap_oop)) { 6140 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6141 HeapRegion* hr = _g1h->heap_region_containing(obj); 6142 assert(!hr->is_continues_humongous(), 6143 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6144 " starting at " HR_FORMAT, 6145 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 6146 6147 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 6148 hr->add_strong_code_root_locked(_nm); 6149 } 6150 } 6151 6152 public: 6153 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6154 _g1h(g1h), _nm(nm) {} 6155 6156 void do_oop(oop* p) { do_oop_work(p); } 6157 void do_oop(narrowOop* p) { do_oop_work(p); } 6158 }; 6159 6160 class UnregisterNMethodOopClosure: public OopClosure { 6161 G1CollectedHeap* _g1h; 6162 nmethod* _nm; 6163 6164 template <class T> void do_oop_work(T* p) { 6165 T heap_oop = oopDesc::load_heap_oop(p); 6166 if (!oopDesc::is_null(heap_oop)) { 6167 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6168 HeapRegion* hr = _g1h->heap_region_containing(obj); 6169 assert(!hr->is_continues_humongous(), 6170 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6171 " starting at " HR_FORMAT, 6172 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 6173 6174 hr->remove_strong_code_root(_nm); 6175 } 6176 } 6177 6178 public: 6179 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6180 _g1h(g1h), _nm(nm) {} 6181 6182 void do_oop(oop* p) { do_oop_work(p); } 6183 void do_oop(narrowOop* p) { do_oop_work(p); } 6184 }; 6185 6186 void G1CollectedHeap::register_nmethod(nmethod* nm) { 6187 CollectedHeap::register_nmethod(nm); 6188 6189 guarantee(nm != NULL, "sanity"); 6190 RegisterNMethodOopClosure reg_cl(this, nm); 6191 nm->oops_do(®_cl); 6192 } 6193 6194 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 6195 CollectedHeap::unregister_nmethod(nm); 6196 6197 guarantee(nm != NULL, "sanity"); 6198 UnregisterNMethodOopClosure reg_cl(this, nm); 6199 nm->oops_do(®_cl, true); 6200 } 6201 6202 void G1CollectedHeap::purge_code_root_memory() { 6203 double purge_start = os::elapsedTime(); 6204 G1CodeRootSet::purge(); 6205 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 6206 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 6207 } 6208 6209 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 6210 G1CollectedHeap* _g1h; 6211 6212 public: 6213 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 6214 _g1h(g1h) {} 6215 6216 void do_code_blob(CodeBlob* cb) { 6217 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 6218 if (nm == NULL) { 6219 return; 6220 } 6221 6222 if (ScavengeRootsInCode) { 6223 _g1h->register_nmethod(nm); 6224 } 6225 } 6226 }; 6227 6228 void G1CollectedHeap::rebuild_strong_code_roots() { 6229 RebuildStrongCodeRootClosure blob_cl(this); 6230 CodeCache::blobs_do(&blob_cl); 6231 }