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/g1ErgoVerbose.hpp" 39 #include "gc/g1/g1EvacFailure.hpp" 40 #include "gc/g1/g1EvacStats.inline.hpp" 41 #include "gc/g1/g1GCPhaseTimes.hpp" 42 #include "gc/g1/g1Log.hpp" 43 #include "gc/g1/g1MarkSweep.hpp" 44 #include "gc/g1/g1OopClosures.inline.hpp" 45 #include "gc/g1/g1ParScanThreadState.inline.hpp" 46 #include "gc/g1/g1RegionToSpaceMapper.hpp" 47 #include "gc/g1/g1RemSet.inline.hpp" 48 #include "gc/g1/g1RootClosures.hpp" 49 #include "gc/g1/g1RootProcessor.hpp" 50 #include "gc/g1/g1StringDedup.hpp" 51 #include "gc/g1/g1YCTypes.hpp" 52 #include "gc/g1/heapRegion.inline.hpp" 53 #include "gc/g1/heapRegionRemSet.hpp" 54 #include "gc/g1/heapRegionSet.inline.hpp" 55 #include "gc/g1/suspendibleThreadSet.hpp" 56 #include "gc/g1/vm_operations_g1.hpp" 57 #include "gc/shared/gcHeapSummary.hpp" 58 #include "gc/shared/gcId.hpp" 59 #include "gc/shared/gcLocker.inline.hpp" 60 #include "gc/shared/gcTimer.hpp" 61 #include "gc/shared/gcTrace.hpp" 62 #include "gc/shared/gcTraceTime.hpp" 63 #include "gc/shared/generationSpec.hpp" 64 #include "gc/shared/isGCActiveMark.hpp" 65 #include "gc/shared/referenceProcessor.hpp" 66 #include "gc/shared/taskqueue.inline.hpp" 67 #include "memory/allocation.hpp" 68 #include "memory/iterator.hpp" 69 #include "oops/oop.inline.hpp" 70 #include "runtime/atomic.inline.hpp" 71 #include "runtime/init.hpp" 72 #include "runtime/orderAccess.inline.hpp" 73 #include "runtime/vmThread.hpp" 74 #include "utilities/globalDefinitions.hpp" 75 #include "utilities/stack.inline.hpp" 76 77 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 78 79 // INVARIANTS/NOTES 80 // 81 // All allocation activity covered by the G1CollectedHeap interface is 82 // serialized by acquiring the HeapLock. This happens in mem_allocate 83 // and allocate_new_tlab, which are the "entry" points to the 84 // allocation code from the rest of the JVM. (Note that this does not 85 // apply to TLAB allocation, which is not part of this interface: it 86 // is done by clients of this interface.) 87 88 // Local to this file. 89 90 class RefineCardTableEntryClosure: public CardTableEntryClosure { 91 bool _concurrent; 92 public: 93 RefineCardTableEntryClosure() : _concurrent(true) { } 94 95 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 96 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false); 97 // This path is executed by the concurrent refine or mutator threads, 98 // concurrently, and so we do not care if card_ptr contains references 99 // that point into the collection set. 100 assert(!oops_into_cset, "should be"); 101 102 if (_concurrent && SuspendibleThreadSet::should_yield()) { 103 // Caller will actually yield. 104 return false; 105 } 106 // Otherwise, we finished successfully; return true. 107 return true; 108 } 109 110 void set_concurrent(bool b) { _concurrent = b; } 111 }; 112 113 114 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 115 private: 116 size_t _num_processed; 117 118 public: 119 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { } 120 121 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 122 *card_ptr = CardTableModRefBS::dirty_card_val(); 123 _num_processed++; 124 return true; 125 } 126 127 size_t num_processed() const { return _num_processed; } 128 }; 129 130 131 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 132 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 133 } 134 135 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 136 // The from card cache is not the memory that is actually committed. So we cannot 137 // take advantage of the zero_filled parameter. 138 reset_from_card_cache(start_idx, num_regions); 139 } 140 141 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 142 { 143 // Claim the right to put the region on the dirty cards region list 144 // by installing a self pointer. 145 HeapRegion* next = hr->get_next_dirty_cards_region(); 146 if (next == NULL) { 147 HeapRegion* res = (HeapRegion*) 148 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 149 NULL); 150 if (res == NULL) { 151 HeapRegion* head; 152 do { 153 // Put the region to the dirty cards region list. 154 head = _dirty_cards_region_list; 155 next = (HeapRegion*) 156 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 157 if (next == head) { 158 assert(hr->get_next_dirty_cards_region() == hr, 159 "hr->get_next_dirty_cards_region() != hr"); 160 if (next == NULL) { 161 // The last region in the list points to itself. 162 hr->set_next_dirty_cards_region(hr); 163 } else { 164 hr->set_next_dirty_cards_region(next); 165 } 166 } 167 } while (next != head); 168 } 169 } 170 } 171 172 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 173 { 174 HeapRegion* head; 175 HeapRegion* hr; 176 do { 177 head = _dirty_cards_region_list; 178 if (head == NULL) { 179 return NULL; 180 } 181 HeapRegion* new_head = head->get_next_dirty_cards_region(); 182 if (head == new_head) { 183 // The last region. 184 new_head = NULL; 185 } 186 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 187 head); 188 } while (hr != head); 189 assert(hr != NULL, "invariant"); 190 hr->set_next_dirty_cards_region(NULL); 191 return hr; 192 } 193 194 // Returns true if the reference points to an object that 195 // can move in an incremental collection. 196 bool G1CollectedHeap::is_scavengable(const void* p) { 197 HeapRegion* hr = heap_region_containing(p); 198 return !hr->is_pinned(); 199 } 200 201 // Private methods. 202 203 HeapRegion* 204 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 205 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 206 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 207 if (!_secondary_free_list.is_empty()) { 208 if (G1ConcRegionFreeingVerbose) { 209 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 210 "secondary_free_list has %u entries", 211 _secondary_free_list.length()); 212 } 213 // It looks as if there are free regions available on the 214 // secondary_free_list. Let's move them to the free_list and try 215 // again to allocate from it. 216 append_secondary_free_list(); 217 218 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 219 "empty we should have moved at least one entry to the free_list"); 220 HeapRegion* res = _hrm.allocate_free_region(is_old); 221 if (G1ConcRegionFreeingVerbose) { 222 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 223 "allocated " HR_FORMAT " from secondary_free_list", 224 HR_FORMAT_PARAMS(res)); 225 } 226 return res; 227 } 228 229 // Wait here until we get notified either when (a) there are no 230 // more free regions coming or (b) some regions have been moved on 231 // the secondary_free_list. 232 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 233 } 234 235 if (G1ConcRegionFreeingVerbose) { 236 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 237 "could not allocate from secondary_free_list"); 238 } 239 return NULL; 240 } 241 242 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 243 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 244 "the only time we use this to allocate a humongous region is " 245 "when we are allocating a single humongous region"); 246 247 HeapRegion* res; 248 if (G1StressConcRegionFreeing) { 249 if (!_secondary_free_list.is_empty()) { 250 if (G1ConcRegionFreeingVerbose) { 251 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 252 "forced to look at the secondary_free_list"); 253 } 254 res = new_region_try_secondary_free_list(is_old); 255 if (res != NULL) { 256 return res; 257 } 258 } 259 } 260 261 res = _hrm.allocate_free_region(is_old); 262 263 if (res == NULL) { 264 if (G1ConcRegionFreeingVerbose) { 265 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 266 "res == NULL, trying the secondary_free_list"); 267 } 268 res = new_region_try_secondary_free_list(is_old); 269 } 270 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 271 // Currently, only attempts to allocate GC alloc regions set 272 // do_expand to true. So, we should only reach here during a 273 // safepoint. If this assumption changes we might have to 274 // reconsider the use of _expand_heap_after_alloc_failure. 275 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 276 277 ergo_verbose1(ErgoHeapSizing, 278 "attempt heap expansion", 279 ergo_format_reason("region allocation request failed") 280 ergo_format_byte("allocation request"), 281 word_size * HeapWordSize); 282 if (expand(word_size * HeapWordSize)) { 283 // Given that expand() succeeded in expanding the heap, and we 284 // always expand the heap by an amount aligned to the heap 285 // region size, the free list should in theory not be empty. 286 // In either case allocate_free_region() will check for NULL. 287 res = _hrm.allocate_free_region(is_old); 288 } else { 289 _expand_heap_after_alloc_failure = false; 290 } 291 } 292 return res; 293 } 294 295 HeapWord* 296 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 297 uint num_regions, 298 size_t word_size, 299 AllocationContext_t context) { 300 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 301 assert(is_humongous(word_size), "word_size should be humongous"); 302 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 303 304 // Index of last region in the series + 1. 305 uint last = first + num_regions; 306 307 // We need to initialize the region(s) we just discovered. This is 308 // a bit tricky given that it can happen concurrently with 309 // refinement threads refining cards on these regions and 310 // potentially wanting to refine the BOT as they are scanning 311 // those cards (this can happen shortly after a cleanup; see CR 312 // 6991377). So we have to set up the region(s) carefully and in 313 // a specific order. 314 315 // The word size sum of all the regions we will allocate. 316 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 317 assert(word_size <= word_size_sum, "sanity"); 318 319 // This will be the "starts humongous" region. 320 HeapRegion* first_hr = region_at(first); 321 // The header of the new object will be placed at the bottom of 322 // the first region. 323 HeapWord* new_obj = first_hr->bottom(); 324 // This will be the new top of the new object. 325 HeapWord* obj_top = new_obj + word_size; 326 327 // First, we need to zero the header of the space that we will be 328 // allocating. When we update top further down, some refinement 329 // threads might try to scan the region. By zeroing the header we 330 // ensure that any thread that will try to scan the region will 331 // come across the zero klass word and bail out. 332 // 333 // NOTE: It would not have been correct to have used 334 // CollectedHeap::fill_with_object() and make the space look like 335 // an int array. The thread that is doing the allocation will 336 // later update the object header to a potentially different array 337 // type and, for a very short period of time, the klass and length 338 // fields will be inconsistent. This could cause a refinement 339 // thread to calculate the object size incorrectly. 340 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 341 342 size_t fill_size = word_size_sum - word_size; 343 if (fill_size > 0) { 344 fill_with_objects(obj_top, fill_size); 345 } 346 347 // We will set up the first region as "starts humongous". This 348 // will also update the BOT covering all the regions to reflect 349 // that there is a single object that starts at the bottom of the 350 // first region. 351 first_hr->set_starts_humongous(first_hr->bottom() + word_size_sum); 352 first_hr->set_allocation_context(context); 353 // Then, if there are any, we will set up the "continues 354 // humongous" regions. 355 HeapRegion* hr = NULL; 356 for (uint i = first + 1; i < last; ++i) { 357 hr = region_at(i); 358 hr->set_continues_humongous(first_hr); 359 hr->set_allocation_context(context); 360 } 361 362 // Up to this point no concurrent thread would have been able to 363 // do any scanning on any region in this series. All the top 364 // fields still point to bottom, so the intersection between 365 // [bottom,top] and [card_start,card_end] will be empty. Before we 366 // update the top fields, we'll do a storestore to make sure that 367 // no thread sees the update to top before the zeroing of the 368 // object header and the BOT initialization. 369 OrderAccess::storestore(); 370 371 // Now that the BOT and the object header have been initialized, 372 // we can update top of the "starts humongous" region. 373 first_hr->set_top(first_hr->end()); 374 if (_hr_printer.is_active()) { 375 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, first_hr->end()); 376 } 377 378 // Now, we will update the top fields of the "continues humongous" 379 // regions. 380 hr = NULL; 381 for (uint i = first + 1; i < last; ++i) { 382 hr = region_at(i); 383 hr->set_top(hr->end()); 384 if (_hr_printer.is_active()) { 385 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 386 } 387 } 388 389 assert(hr == NULL || (hr->bottom() < obj_top && obj_top <= hr->end()), 390 "obj_top should be in last region"); 391 392 check_bitmaps("Humongous Region Allocation", first_hr); 393 394 increase_used(word_size_sum * HeapWordSize); 395 396 for (uint i = first; i < last; ++i) { 397 _humongous_set.add(region_at(i)); 398 } 399 400 return new_obj; 401 } 402 403 // If could fit into free regions w/o expansion, try. 404 // Otherwise, if can expand, do so. 405 // Otherwise, if using ex regions might help, try with ex given back. 406 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 407 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 408 409 verify_region_sets_optional(); 410 411 uint first = G1_NO_HRM_INDEX; 412 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords); 413 414 if (obj_regions == 1) { 415 // Only one region to allocate, try to use a fast path by directly allocating 416 // from the free lists. Do not try to expand here, we will potentially do that 417 // later. 418 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 419 if (hr != NULL) { 420 first = hr->hrm_index(); 421 } 422 } else { 423 // We can't allocate humongous regions spanning more than one region while 424 // cleanupComplete() is running, since some of the regions we find to be 425 // empty might not yet be added to the free list. It is not straightforward 426 // to know in which list they are on so that we can remove them. We only 427 // need to do this if we need to allocate more than one region to satisfy the 428 // current humongous allocation request. If we are only allocating one region 429 // we use the one-region region allocation code (see above), that already 430 // potentially waits for regions from the secondary free list. 431 wait_while_free_regions_coming(); 432 append_secondary_free_list_if_not_empty_with_lock(); 433 434 // Policy: Try only empty regions (i.e. already committed first). Maybe we 435 // are lucky enough to find some. 436 first = _hrm.find_contiguous_only_empty(obj_regions); 437 if (first != G1_NO_HRM_INDEX) { 438 _hrm.allocate_free_regions_starting_at(first, obj_regions); 439 } 440 } 441 442 if (first == G1_NO_HRM_INDEX) { 443 // Policy: We could not find enough regions for the humongous object in the 444 // free list. Look through the heap to find a mix of free and uncommitted regions. 445 // If so, try expansion. 446 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 447 if (first != G1_NO_HRM_INDEX) { 448 // We found something. Make sure these regions are committed, i.e. expand 449 // the heap. Alternatively we could do a defragmentation GC. 450 ergo_verbose1(ErgoHeapSizing, 451 "attempt heap expansion", 452 ergo_format_reason("humongous allocation request failed") 453 ergo_format_byte("allocation request"), 454 word_size * HeapWordSize); 455 456 _hrm.expand_at(first, obj_regions); 457 g1_policy()->record_new_heap_size(num_regions()); 458 459 #ifdef ASSERT 460 for (uint i = first; i < first + obj_regions; ++i) { 461 HeapRegion* hr = region_at(i); 462 assert(hr->is_free(), "sanity"); 463 assert(hr->is_empty(), "sanity"); 464 assert(is_on_master_free_list(hr), "sanity"); 465 } 466 #endif 467 _hrm.allocate_free_regions_starting_at(first, obj_regions); 468 } else { 469 // Policy: Potentially trigger a defragmentation GC. 470 } 471 } 472 473 HeapWord* result = NULL; 474 if (first != G1_NO_HRM_INDEX) { 475 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 476 word_size, context); 477 assert(result != NULL, "it should always return a valid result"); 478 479 // A successful humongous object allocation changes the used space 480 // information of the old generation so we need to recalculate the 481 // sizes and update the jstat counters here. 482 g1mm()->update_sizes(); 483 } 484 485 verify_region_sets_optional(); 486 487 return result; 488 } 489 490 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 491 assert_heap_not_locked_and_not_at_safepoint(); 492 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 493 494 uint dummy_gc_count_before; 495 uint dummy_gclocker_retry_count = 0; 496 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 497 } 498 499 HeapWord* 500 G1CollectedHeap::mem_allocate(size_t word_size, 501 bool* gc_overhead_limit_was_exceeded) { 502 assert_heap_not_locked_and_not_at_safepoint(); 503 504 // Loop until the allocation is satisfied, or unsatisfied after GC. 505 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 506 uint gc_count_before; 507 508 HeapWord* result = NULL; 509 if (!is_humongous(word_size)) { 510 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 511 } else { 512 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 513 } 514 if (result != NULL) { 515 return result; 516 } 517 518 // Create the garbage collection operation... 519 VM_G1CollectForAllocation op(gc_count_before, word_size); 520 op.set_allocation_context(AllocationContext::current()); 521 522 // ...and get the VM thread to execute it. 523 VMThread::execute(&op); 524 525 if (op.prologue_succeeded() && op.pause_succeeded()) { 526 // If the operation was successful we'll return the result even 527 // if it is NULL. If the allocation attempt failed immediately 528 // after a Full GC, it's unlikely we'll be able to allocate now. 529 HeapWord* result = op.result(); 530 if (result != NULL && !is_humongous(word_size)) { 531 // Allocations that take place on VM operations do not do any 532 // card dirtying and we have to do it here. We only have to do 533 // this for non-humongous allocations, though. 534 dirty_young_block(result, word_size); 535 } 536 return result; 537 } else { 538 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 539 return NULL; 540 } 541 assert(op.result() == NULL, 542 "the result should be NULL if the VM op did not succeed"); 543 } 544 545 // Give a warning if we seem to be looping forever. 546 if ((QueuedAllocationWarningCount > 0) && 547 (try_count % QueuedAllocationWarningCount == 0)) { 548 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 549 } 550 } 551 552 ShouldNotReachHere(); 553 return NULL; 554 } 555 556 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 557 AllocationContext_t context, 558 uint* gc_count_before_ret, 559 uint* gclocker_retry_count_ret) { 560 // Make sure you read the note in attempt_allocation_humongous(). 561 562 assert_heap_not_locked_and_not_at_safepoint(); 563 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 564 "be called for humongous allocation requests"); 565 566 // We should only get here after the first-level allocation attempt 567 // (attempt_allocation()) failed to allocate. 568 569 // We will loop until a) we manage to successfully perform the 570 // allocation or b) we successfully schedule a collection which 571 // fails to perform the allocation. b) is the only case when we'll 572 // return NULL. 573 HeapWord* result = NULL; 574 for (int try_count = 1; /* we'll return */; try_count += 1) { 575 bool should_try_gc; 576 uint gc_count_before; 577 578 { 579 MutexLockerEx x(Heap_lock); 580 result = _allocator->attempt_allocation_locked(word_size, context); 581 if (result != NULL) { 582 return result; 583 } 584 585 if (GC_locker::is_active_and_needs_gc()) { 586 if (g1_policy()->can_expand_young_list()) { 587 // No need for an ergo verbose message here, 588 // can_expand_young_list() does this when it returns true. 589 result = _allocator->attempt_allocation_force(word_size, context); 590 if (result != NULL) { 591 return result; 592 } 593 } 594 should_try_gc = false; 595 } else { 596 // The GCLocker may not be active but the GCLocker initiated 597 // GC may not yet have been performed (GCLocker::needs_gc() 598 // returns true). In this case we do not try this GC and 599 // wait until the GCLocker initiated GC is performed, and 600 // then retry the allocation. 601 if (GC_locker::needs_gc()) { 602 should_try_gc = false; 603 } else { 604 // Read the GC count while still holding the Heap_lock. 605 gc_count_before = total_collections(); 606 should_try_gc = true; 607 } 608 } 609 } 610 611 if (should_try_gc) { 612 bool succeeded; 613 result = do_collection_pause(word_size, gc_count_before, &succeeded, 614 GCCause::_g1_inc_collection_pause); 615 if (result != NULL) { 616 assert(succeeded, "only way to get back a non-NULL result"); 617 return result; 618 } 619 620 if (succeeded) { 621 // If we get here we successfully scheduled a collection which 622 // failed to allocate. No point in trying to allocate 623 // further. We'll just return NULL. 624 MutexLockerEx x(Heap_lock); 625 *gc_count_before_ret = total_collections(); 626 return NULL; 627 } 628 } else { 629 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 630 MutexLockerEx x(Heap_lock); 631 *gc_count_before_ret = total_collections(); 632 return NULL; 633 } 634 // The GCLocker is either active or the GCLocker initiated 635 // GC has not yet been performed. Stall until it is and 636 // then retry the allocation. 637 GC_locker::stall_until_clear(); 638 (*gclocker_retry_count_ret) += 1; 639 } 640 641 // We can reach here if we were unsuccessful in scheduling a 642 // collection (because another thread beat us to it) or if we were 643 // stalled due to the GC locker. In either can we should retry the 644 // allocation attempt in case another thread successfully 645 // performed a collection and reclaimed enough space. We do the 646 // first attempt (without holding the Heap_lock) here and the 647 // follow-on attempt will be at the start of the next loop 648 // iteration (after taking the Heap_lock). 649 result = _allocator->attempt_allocation(word_size, context); 650 if (result != NULL) { 651 return result; 652 } 653 654 // Give a warning if we seem to be looping forever. 655 if ((QueuedAllocationWarningCount > 0) && 656 (try_count % QueuedAllocationWarningCount == 0)) { 657 warning("G1CollectedHeap::attempt_allocation_slow() " 658 "retries %d times", try_count); 659 } 660 } 661 662 ShouldNotReachHere(); 663 return NULL; 664 } 665 666 void G1CollectedHeap::begin_archive_alloc_range() { 667 assert_at_safepoint(true /* should_be_vm_thread */); 668 if (_archive_allocator == NULL) { 669 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 670 } 671 } 672 673 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 674 // Allocations in archive regions cannot be of a size that would be considered 675 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 676 // may be different at archive-restore time. 677 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 678 } 679 680 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 681 assert_at_safepoint(true /* should_be_vm_thread */); 682 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 683 if (is_archive_alloc_too_large(word_size)) { 684 return NULL; 685 } 686 return _archive_allocator->archive_mem_allocate(word_size); 687 } 688 689 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 690 size_t end_alignment_in_bytes) { 691 assert_at_safepoint(true /* should_be_vm_thread */); 692 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 693 694 // Call complete_archive to do the real work, filling in the MemRegion 695 // array with the archive regions. 696 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 697 delete _archive_allocator; 698 _archive_allocator = NULL; 699 } 700 701 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 702 assert(ranges != NULL, "MemRegion array NULL"); 703 assert(count != 0, "No MemRegions provided"); 704 MemRegion reserved = _hrm.reserved(); 705 for (size_t i = 0; i < count; i++) { 706 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 707 return false; 708 } 709 } 710 return true; 711 } 712 713 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 714 assert(!is_init_completed(), "Expect to be called at JVM init time"); 715 assert(ranges != NULL, "MemRegion array NULL"); 716 assert(count != 0, "No MemRegions provided"); 717 MutexLockerEx x(Heap_lock); 718 719 MemRegion reserved = _hrm.reserved(); 720 HeapWord* prev_last_addr = NULL; 721 HeapRegion* prev_last_region = NULL; 722 723 // Temporarily disable pretouching of heap pages. This interface is used 724 // when mmap'ing archived heap data in, so pre-touching is wasted. 725 FlagSetting fs(AlwaysPreTouch, false); 726 727 // Enable archive object checking in G1MarkSweep. We have to let it know 728 // about each archive range, so that objects in those ranges aren't marked. 729 G1MarkSweep::enable_archive_object_check(); 730 731 // For each specified MemRegion range, allocate the corresponding G1 732 // regions and mark them as archive regions. We expect the ranges in 733 // ascending starting address order, without overlap. 734 for (size_t i = 0; i < count; i++) { 735 MemRegion curr_range = ranges[i]; 736 HeapWord* start_address = curr_range.start(); 737 size_t word_size = curr_range.word_size(); 738 HeapWord* last_address = curr_range.last(); 739 size_t commits = 0; 740 741 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 742 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 743 p2i(start_address), p2i(last_address)); 744 guarantee(start_address > prev_last_addr, 745 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 746 p2i(start_address), p2i(prev_last_addr)); 747 prev_last_addr = last_address; 748 749 // Check for ranges that start in the same G1 region in which the previous 750 // range ended, and adjust the start address so we don't try to allocate 751 // the same region again. If the current range is entirely within that 752 // region, skip it, just adjusting the recorded top. 753 HeapRegion* start_region = _hrm.addr_to_region(start_address); 754 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 755 start_address = start_region->end(); 756 if (start_address > last_address) { 757 increase_used(word_size * HeapWordSize); 758 start_region->set_top(last_address + 1); 759 continue; 760 } 761 start_region->set_top(start_address); 762 curr_range = MemRegion(start_address, last_address + 1); 763 start_region = _hrm.addr_to_region(start_address); 764 } 765 766 // Perform the actual region allocation, exiting if it fails. 767 // Then note how much new space we have allocated. 768 if (!_hrm.allocate_containing_regions(curr_range, &commits)) { 769 return false; 770 } 771 increase_used(word_size * HeapWordSize); 772 if (commits != 0) { 773 ergo_verbose1(ErgoHeapSizing, 774 "attempt heap expansion", 775 ergo_format_reason("allocate archive regions") 776 ergo_format_byte("total size"), 777 HeapRegion::GrainWords * HeapWordSize * commits); 778 } 779 780 // Mark each G1 region touched by the range as archive, add it to the old set, 781 // and set the allocation context and top. 782 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 783 HeapRegion* last_region = _hrm.addr_to_region(last_address); 784 prev_last_region = last_region; 785 786 while (curr_region != NULL) { 787 assert(curr_region->is_empty() && !curr_region->is_pinned(), 788 "Region already in use (index %u)", curr_region->hrm_index()); 789 _hr_printer.alloc(curr_region, G1HRPrinter::Archive); 790 curr_region->set_allocation_context(AllocationContext::system()); 791 curr_region->set_archive(); 792 _old_set.add(curr_region); 793 if (curr_region != last_region) { 794 curr_region->set_top(curr_region->end()); 795 curr_region = _hrm.next_region_in_heap(curr_region); 796 } else { 797 curr_region->set_top(last_address + 1); 798 curr_region = NULL; 799 } 800 } 801 802 // Notify mark-sweep of the archive range. 803 G1MarkSweep::set_range_archive(curr_range, true); 804 } 805 return true; 806 } 807 808 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 809 assert(!is_init_completed(), "Expect to be called at JVM init time"); 810 assert(ranges != NULL, "MemRegion array NULL"); 811 assert(count != 0, "No MemRegions provided"); 812 MemRegion reserved = _hrm.reserved(); 813 HeapWord *prev_last_addr = NULL; 814 HeapRegion* prev_last_region = NULL; 815 816 // For each MemRegion, create filler objects, if needed, in the G1 regions 817 // that contain the address range. The address range actually within the 818 // MemRegion will not be modified. That is assumed to have been initialized 819 // elsewhere, probably via an mmap of archived heap data. 820 MutexLockerEx x(Heap_lock); 821 for (size_t i = 0; i < count; i++) { 822 HeapWord* start_address = ranges[i].start(); 823 HeapWord* last_address = ranges[i].last(); 824 825 assert(reserved.contains(start_address) && reserved.contains(last_address), 826 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 827 p2i(start_address), p2i(last_address)); 828 assert(start_address > prev_last_addr, 829 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 830 p2i(start_address), p2i(prev_last_addr)); 831 832 HeapRegion* start_region = _hrm.addr_to_region(start_address); 833 HeapRegion* last_region = _hrm.addr_to_region(last_address); 834 HeapWord* bottom_address = start_region->bottom(); 835 836 // Check for a range beginning in the same region in which the 837 // previous one ended. 838 if (start_region == prev_last_region) { 839 bottom_address = prev_last_addr + 1; 840 } 841 842 // Verify that the regions were all marked as archive regions by 843 // alloc_archive_regions. 844 HeapRegion* curr_region = start_region; 845 while (curr_region != NULL) { 846 guarantee(curr_region->is_archive(), 847 "Expected archive region at index %u", curr_region->hrm_index()); 848 if (curr_region != last_region) { 849 curr_region = _hrm.next_region_in_heap(curr_region); 850 } else { 851 curr_region = NULL; 852 } 853 } 854 855 prev_last_addr = last_address; 856 prev_last_region = last_region; 857 858 // Fill the memory below the allocated range with dummy object(s), 859 // if the region bottom does not match the range start, or if the previous 860 // range ended within the same G1 region, and there is a gap. 861 if (start_address != bottom_address) { 862 size_t fill_size = pointer_delta(start_address, bottom_address); 863 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 864 increase_used(fill_size * HeapWordSize); 865 } 866 } 867 } 868 869 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 870 uint* gc_count_before_ret, 871 uint* gclocker_retry_count_ret) { 872 assert_heap_not_locked_and_not_at_safepoint(); 873 assert(!is_humongous(word_size), "attempt_allocation() should not " 874 "be called for humongous allocation requests"); 875 876 AllocationContext_t context = AllocationContext::current(); 877 HeapWord* result = _allocator->attempt_allocation(word_size, context); 878 879 if (result == NULL) { 880 result = attempt_allocation_slow(word_size, 881 context, 882 gc_count_before_ret, 883 gclocker_retry_count_ret); 884 } 885 assert_heap_not_locked(); 886 if (result != NULL) { 887 dirty_young_block(result, word_size); 888 } 889 return result; 890 } 891 892 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 893 assert(!is_init_completed(), "Expect to be called at JVM init time"); 894 assert(ranges != NULL, "MemRegion array NULL"); 895 assert(count != 0, "No MemRegions provided"); 896 MemRegion reserved = _hrm.reserved(); 897 HeapWord* prev_last_addr = NULL; 898 HeapRegion* prev_last_region = NULL; 899 size_t size_used = 0; 900 size_t uncommitted_regions = 0; 901 902 // For each Memregion, free the G1 regions that constitute it, and 903 // notify mark-sweep that the range is no longer to be considered 'archive.' 904 MutexLockerEx x(Heap_lock); 905 for (size_t i = 0; i < count; i++) { 906 HeapWord* start_address = ranges[i].start(); 907 HeapWord* last_address = ranges[i].last(); 908 909 assert(reserved.contains(start_address) && reserved.contains(last_address), 910 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 911 p2i(start_address), p2i(last_address)); 912 assert(start_address > prev_last_addr, 913 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 914 p2i(start_address), p2i(prev_last_addr)); 915 size_used += ranges[i].byte_size(); 916 prev_last_addr = last_address; 917 918 HeapRegion* start_region = _hrm.addr_to_region(start_address); 919 HeapRegion* last_region = _hrm.addr_to_region(last_address); 920 921 // Check for ranges that start in the same G1 region in which the previous 922 // range ended, and adjust the start address so we don't try to free 923 // the same region again. If the current range is entirely within that 924 // region, skip it. 925 if (start_region == prev_last_region) { 926 start_address = start_region->end(); 927 if (start_address > last_address) { 928 continue; 929 } 930 start_region = _hrm.addr_to_region(start_address); 931 } 932 prev_last_region = last_region; 933 934 // After verifying that each region was marked as an archive region by 935 // alloc_archive_regions, set it free and empty and uncommit it. 936 HeapRegion* curr_region = start_region; 937 while (curr_region != NULL) { 938 guarantee(curr_region->is_archive(), 939 "Expected archive region at index %u", curr_region->hrm_index()); 940 uint curr_index = curr_region->hrm_index(); 941 _old_set.remove(curr_region); 942 curr_region->set_free(); 943 curr_region->set_top(curr_region->bottom()); 944 if (curr_region != last_region) { 945 curr_region = _hrm.next_region_in_heap(curr_region); 946 } else { 947 curr_region = NULL; 948 } 949 _hrm.shrink_at(curr_index, 1); 950 uncommitted_regions++; 951 } 952 953 // Notify mark-sweep that this is no longer an archive range. 954 G1MarkSweep::set_range_archive(ranges[i], false); 955 } 956 957 if (uncommitted_regions != 0) { 958 ergo_verbose1(ErgoHeapSizing, 959 "attempt heap shrinking", 960 ergo_format_reason("uncommitted archive regions") 961 ergo_format_byte("total size"), 962 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 963 } 964 decrease_used(size_used); 965 } 966 967 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 968 uint* gc_count_before_ret, 969 uint* gclocker_retry_count_ret) { 970 // The structure of this method has a lot of similarities to 971 // attempt_allocation_slow(). The reason these two were not merged 972 // into a single one is that such a method would require several "if 973 // allocation is not humongous do this, otherwise do that" 974 // conditional paths which would obscure its flow. In fact, an early 975 // version of this code did use a unified method which was harder to 976 // follow and, as a result, it had subtle bugs that were hard to 977 // track down. So keeping these two methods separate allows each to 978 // be more readable. It will be good to keep these two in sync as 979 // much as possible. 980 981 assert_heap_not_locked_and_not_at_safepoint(); 982 assert(is_humongous(word_size), "attempt_allocation_humongous() " 983 "should only be called for humongous allocations"); 984 985 // Humongous objects can exhaust the heap quickly, so we should check if we 986 // need to start a marking cycle at each humongous object allocation. We do 987 // the check before we do the actual allocation. The reason for doing it 988 // before the allocation is that we avoid having to keep track of the newly 989 // allocated memory while we do a GC. 990 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 991 word_size)) { 992 collect(GCCause::_g1_humongous_allocation); 993 } 994 995 // We will loop until a) we manage to successfully perform the 996 // allocation or b) we successfully schedule a collection which 997 // fails to perform the allocation. b) is the only case when we'll 998 // return NULL. 999 HeapWord* result = NULL; 1000 for (int try_count = 1; /* we'll return */; try_count += 1) { 1001 bool should_try_gc; 1002 uint gc_count_before; 1003 1004 { 1005 MutexLockerEx x(Heap_lock); 1006 1007 // Given that humongous objects are not allocated in young 1008 // regions, we'll first try to do the allocation without doing a 1009 // collection hoping that there's enough space in the heap. 1010 result = humongous_obj_allocate(word_size, AllocationContext::current()); 1011 if (result != NULL) { 1012 return result; 1013 } 1014 1015 if (GC_locker::is_active_and_needs_gc()) { 1016 should_try_gc = false; 1017 } else { 1018 // The GCLocker may not be active but the GCLocker initiated 1019 // GC may not yet have been performed (GCLocker::needs_gc() 1020 // returns true). In this case we do not try this GC and 1021 // wait until the GCLocker initiated GC is performed, and 1022 // then retry the allocation. 1023 if (GC_locker::needs_gc()) { 1024 should_try_gc = false; 1025 } else { 1026 // Read the GC count while still holding the Heap_lock. 1027 gc_count_before = total_collections(); 1028 should_try_gc = true; 1029 } 1030 } 1031 } 1032 1033 if (should_try_gc) { 1034 // If we failed to allocate the humongous object, we should try to 1035 // do a collection pause (if we're allowed) in case it reclaims 1036 // enough space for the allocation to succeed after the pause. 1037 1038 bool succeeded; 1039 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1040 GCCause::_g1_humongous_allocation); 1041 if (result != NULL) { 1042 assert(succeeded, "only way to get back a non-NULL result"); 1043 return result; 1044 } 1045 1046 if (succeeded) { 1047 // If we get here we successfully scheduled a collection which 1048 // failed to allocate. No point in trying to allocate 1049 // further. We'll just return NULL. 1050 MutexLockerEx x(Heap_lock); 1051 *gc_count_before_ret = total_collections(); 1052 return NULL; 1053 } 1054 } else { 1055 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1056 MutexLockerEx x(Heap_lock); 1057 *gc_count_before_ret = total_collections(); 1058 return NULL; 1059 } 1060 // The GCLocker is either active or the GCLocker initiated 1061 // GC has not yet been performed. Stall until it is and 1062 // then retry the allocation. 1063 GC_locker::stall_until_clear(); 1064 (*gclocker_retry_count_ret) += 1; 1065 } 1066 1067 // We can reach here if we were unsuccessful in scheduling a 1068 // collection (because another thread beat us to it) or if we were 1069 // stalled due to the GC locker. In either can we should retry the 1070 // allocation attempt in case another thread successfully 1071 // performed a collection and reclaimed enough space. Give a 1072 // warning if we seem to be looping forever. 1073 1074 if ((QueuedAllocationWarningCount > 0) && 1075 (try_count % QueuedAllocationWarningCount == 0)) { 1076 warning("G1CollectedHeap::attempt_allocation_humongous() " 1077 "retries %d times", try_count); 1078 } 1079 } 1080 1081 ShouldNotReachHere(); 1082 return NULL; 1083 } 1084 1085 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1086 AllocationContext_t context, 1087 bool expect_null_mutator_alloc_region) { 1088 assert_at_safepoint(true /* should_be_vm_thread */); 1089 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1090 "the current alloc region was unexpectedly found to be non-NULL"); 1091 1092 if (!is_humongous(word_size)) { 1093 return _allocator->attempt_allocation_locked(word_size, context); 1094 } else { 1095 HeapWord* result = humongous_obj_allocate(word_size, context); 1096 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1097 collector_state()->set_initiate_conc_mark_if_possible(true); 1098 } 1099 return result; 1100 } 1101 1102 ShouldNotReachHere(); 1103 } 1104 1105 class PostMCRemSetClearClosure: public HeapRegionClosure { 1106 G1CollectedHeap* _g1h; 1107 ModRefBarrierSet* _mr_bs; 1108 public: 1109 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1110 _g1h(g1h), _mr_bs(mr_bs) {} 1111 1112 bool doHeapRegion(HeapRegion* r) { 1113 HeapRegionRemSet* hrrs = r->rem_set(); 1114 1115 _g1h->reset_gc_time_stamps(r); 1116 1117 if (r->is_continues_humongous()) { 1118 // We'll assert that the strong code root list and RSet is empty 1119 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1120 assert(hrrs->occupied() == 0, "RSet should be empty"); 1121 } else { 1122 hrrs->clear(); 1123 } 1124 // You might think here that we could clear just the cards 1125 // corresponding to the used region. But no: if we leave a dirty card 1126 // in a region we might allocate into, then it would prevent that card 1127 // from being enqueued, and cause it to be missed. 1128 // Re: the performance cost: we shouldn't be doing full GC anyway! 1129 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1130 1131 return false; 1132 } 1133 }; 1134 1135 void G1CollectedHeap::clear_rsets_post_compaction() { 1136 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1137 heap_region_iterate(&rs_clear); 1138 } 1139 1140 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1141 G1CollectedHeap* _g1h; 1142 UpdateRSOopClosure _cl; 1143 public: 1144 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1145 _cl(g1->g1_rem_set(), worker_i), 1146 _g1h(g1) 1147 { } 1148 1149 bool doHeapRegion(HeapRegion* r) { 1150 if (!r->is_continues_humongous()) { 1151 _cl.set_from(r); 1152 r->oop_iterate(&_cl); 1153 } 1154 return false; 1155 } 1156 }; 1157 1158 class ParRebuildRSTask: public AbstractGangTask { 1159 G1CollectedHeap* _g1; 1160 HeapRegionClaimer _hrclaimer; 1161 1162 public: 1163 ParRebuildRSTask(G1CollectedHeap* g1) : 1164 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1165 1166 void work(uint worker_id) { 1167 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1168 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1169 } 1170 }; 1171 1172 class PostCompactionPrinterClosure: public HeapRegionClosure { 1173 private: 1174 G1HRPrinter* _hr_printer; 1175 public: 1176 bool doHeapRegion(HeapRegion* hr) { 1177 assert(!hr->is_young(), "not expecting to find young regions"); 1178 if (hr->is_free()) { 1179 // We only generate output for non-empty regions. 1180 } else if (hr->is_starts_humongous()) { 1181 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1182 } else if (hr->is_continues_humongous()) { 1183 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1184 } else if (hr->is_archive()) { 1185 _hr_printer->post_compaction(hr, G1HRPrinter::Archive); 1186 } else if (hr->is_old()) { 1187 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1188 } else { 1189 ShouldNotReachHere(); 1190 } 1191 return false; 1192 } 1193 1194 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1195 : _hr_printer(hr_printer) { } 1196 }; 1197 1198 void G1CollectedHeap::print_hrm_post_compaction() { 1199 PostCompactionPrinterClosure cl(hr_printer()); 1200 heap_region_iterate(&cl); 1201 } 1202 1203 bool G1CollectedHeap::do_collection(bool explicit_gc, 1204 bool clear_all_soft_refs, 1205 size_t word_size) { 1206 assert_at_safepoint(true /* should_be_vm_thread */); 1207 1208 if (GC_locker::check_active_before_gc()) { 1209 return false; 1210 } 1211 1212 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1213 gc_timer->register_gc_start(); 1214 1215 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1216 GCIdMark gc_id_mark; 1217 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1218 1219 SvcGCMarker sgcm(SvcGCMarker::FULL); 1220 ResourceMark rm; 1221 1222 G1Log::update_level(); 1223 print_heap_before_gc(); 1224 trace_heap_before_gc(gc_tracer); 1225 1226 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1227 1228 verify_region_sets_optional(); 1229 1230 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1231 collector_policy()->should_clear_all_soft_refs(); 1232 1233 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1234 1235 { 1236 IsGCActiveMark x; 1237 1238 // Timing 1239 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1240 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 1241 1242 { 1243 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL); 1244 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1245 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1246 1247 g1_policy()->record_full_collection_start(); 1248 1249 // Note: When we have a more flexible GC logging framework that 1250 // allows us to add optional attributes to a GC log record we 1251 // could consider timing and reporting how long we wait in the 1252 // following two methods. 1253 wait_while_free_regions_coming(); 1254 // If we start the compaction before the CM threads finish 1255 // scanning the root regions we might trip them over as we'll 1256 // be moving objects / updating references. So let's wait until 1257 // they are done. By telling them to abort, they should complete 1258 // early. 1259 _cm->root_regions()->abort(); 1260 _cm->root_regions()->wait_until_scan_finished(); 1261 append_secondary_free_list_if_not_empty_with_lock(); 1262 1263 gc_prologue(true); 1264 increment_total_collections(true /* full gc */); 1265 increment_old_marking_cycles_started(); 1266 1267 assert(used() == recalculate_used(), "Should be equal"); 1268 1269 verify_before_gc(); 1270 1271 check_bitmaps("Full GC Start"); 1272 pre_full_gc_dump(gc_timer); 1273 1274 #if defined(COMPILER2) || INCLUDE_JVMCI 1275 DerivedPointerTable::clear(); 1276 #endif 1277 1278 // Disable discovery and empty the discovered lists 1279 // for the CM ref processor. 1280 ref_processor_cm()->disable_discovery(); 1281 ref_processor_cm()->abandon_partial_discovery(); 1282 ref_processor_cm()->verify_no_references_recorded(); 1283 1284 // Abandon current iterations of concurrent marking and concurrent 1285 // refinement, if any are in progress. We have to do this before 1286 // wait_until_scan_finished() below. 1287 concurrent_mark()->abort(); 1288 1289 // Make sure we'll choose a new allocation region afterwards. 1290 _allocator->release_mutator_alloc_region(); 1291 _allocator->abandon_gc_alloc_regions(); 1292 g1_rem_set()->cleanupHRRS(); 1293 1294 // We should call this after we retire any currently active alloc 1295 // regions so that all the ALLOC / RETIRE events are generated 1296 // before the start GC event. 1297 _hr_printer.start_gc(true /* full */, (size_t) total_collections()); 1298 1299 // We may have added regions to the current incremental collection 1300 // set between the last GC or pause and now. We need to clear the 1301 // incremental collection set and then start rebuilding it afresh 1302 // after this full GC. 1303 abandon_collection_set(g1_policy()->inc_cset_head()); 1304 g1_policy()->clear_incremental_cset(); 1305 g1_policy()->stop_incremental_cset_building(); 1306 1307 tear_down_region_sets(false /* free_list_only */); 1308 collector_state()->set_gcs_are_young(true); 1309 1310 // See the comments in g1CollectedHeap.hpp and 1311 // G1CollectedHeap::ref_processing_init() about 1312 // how reference processing currently works in G1. 1313 1314 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1315 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1316 1317 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1318 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1319 1320 ref_processor_stw()->enable_discovery(); 1321 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1322 1323 // Do collection work 1324 { 1325 HandleMark hm; // Discard invalid handles created during gc 1326 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1327 } 1328 1329 assert(num_free_regions() == 0, "we should not have added any free regions"); 1330 rebuild_region_sets(false /* free_list_only */); 1331 1332 // Enqueue any discovered reference objects that have 1333 // not been removed from the discovered lists. 1334 ref_processor_stw()->enqueue_discovered_references(); 1335 1336 #if defined(COMPILER2) || INCLUDE_JVMCI 1337 DerivedPointerTable::update_pointers(); 1338 #endif 1339 1340 MemoryService::track_memory_usage(); 1341 1342 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1343 ref_processor_stw()->verify_no_references_recorded(); 1344 1345 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1346 ClassLoaderDataGraph::purge(); 1347 MetaspaceAux::verify_metrics(); 1348 1349 // Note: since we've just done a full GC, concurrent 1350 // marking is no longer active. Therefore we need not 1351 // re-enable reference discovery for the CM ref processor. 1352 // That will be done at the start of the next marking cycle. 1353 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1354 ref_processor_cm()->verify_no_references_recorded(); 1355 1356 reset_gc_time_stamp(); 1357 // Since everything potentially moved, we will clear all remembered 1358 // sets, and clear all cards. Later we will rebuild remembered 1359 // sets. We will also reset the GC time stamps of the regions. 1360 clear_rsets_post_compaction(); 1361 check_gc_time_stamps(); 1362 1363 // Resize the heap if necessary. 1364 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); 1365 1366 if (_hr_printer.is_active()) { 1367 // We should do this after we potentially resize the heap so 1368 // that all the COMMIT / UNCOMMIT events are generated before 1369 // the end GC event. 1370 1371 print_hrm_post_compaction(); 1372 _hr_printer.end_gc(true /* full */, (size_t) total_collections()); 1373 } 1374 1375 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1376 if (hot_card_cache->use_cache()) { 1377 hot_card_cache->reset_card_counts(); 1378 hot_card_cache->reset_hot_cache(); 1379 } 1380 1381 // Rebuild remembered sets of all regions. 1382 uint n_workers = 1383 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1384 workers()->active_workers(), 1385 Threads::number_of_non_daemon_threads()); 1386 workers()->set_active_workers(n_workers); 1387 1388 ParRebuildRSTask rebuild_rs_task(this); 1389 workers()->run_task(&rebuild_rs_task); 1390 1391 // Rebuild the strong code root lists for each region 1392 rebuild_strong_code_roots(); 1393 1394 if (true) { // FIXME 1395 MetaspaceGC::compute_new_size(); 1396 } 1397 1398 #ifdef TRACESPINNING 1399 ParallelTaskTerminator::print_termination_counts(); 1400 #endif 1401 1402 // Discard all rset updates 1403 JavaThread::dirty_card_queue_set().abandon_logs(); 1404 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1405 1406 _young_list->reset_sampled_info(); 1407 // At this point there should be no regions in the 1408 // entire heap tagged as young. 1409 assert(check_young_list_empty(true /* check_heap */), 1410 "young list should be empty at this point"); 1411 1412 // Update the number of full collections that have been completed. 1413 increment_old_marking_cycles_completed(false /* concurrent */); 1414 1415 _hrm.verify_optional(); 1416 verify_region_sets_optional(); 1417 1418 verify_after_gc(); 1419 1420 // Clear the previous marking bitmap, if needed for bitmap verification. 1421 // Note we cannot do this when we clear the next marking bitmap in 1422 // ConcurrentMark::abort() above since VerifyDuringGC verifies the 1423 // objects marked during a full GC against the previous bitmap. 1424 // But we need to clear it before calling check_bitmaps below since 1425 // the full GC has compacted objects and updated TAMS but not updated 1426 // the prev bitmap. 1427 if (G1VerifyBitmaps) { 1428 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll(); 1429 } 1430 check_bitmaps("Full GC End"); 1431 1432 // Start a new incremental collection set for the next pause 1433 assert(g1_policy()->collection_set() == NULL, "must be"); 1434 g1_policy()->start_incremental_cset_building(); 1435 1436 clear_cset_fast_test(); 1437 1438 _allocator->init_mutator_alloc_region(); 1439 1440 g1_policy()->record_full_collection_end(); 1441 1442 if (G1Log::fine()) { 1443 g1_policy()->print_heap_transition(); 1444 } 1445 1446 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1447 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1448 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1449 // before any GC notifications are raised. 1450 g1mm()->update_sizes(); 1451 1452 gc_epilogue(true); 1453 } 1454 1455 if (G1Log::finer()) { 1456 g1_policy()->print_detailed_heap_transition(true /* full */); 1457 } 1458 1459 print_heap_after_gc(); 1460 trace_heap_after_gc(gc_tracer); 1461 1462 post_full_gc_dump(gc_timer); 1463 1464 gc_timer->register_gc_end(); 1465 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1466 } 1467 1468 return true; 1469 } 1470 1471 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1472 // do_collection() will return whether it succeeded in performing 1473 // the GC. Currently, there is no facility on the 1474 // do_full_collection() API to notify the caller than the collection 1475 // did not succeed (e.g., because it was locked out by the GC 1476 // locker). So, right now, we'll ignore the return value. 1477 bool dummy = do_collection(true, /* explicit_gc */ 1478 clear_all_soft_refs, 1479 0 /* word_size */); 1480 } 1481 1482 // This code is mostly copied from TenuredGeneration. 1483 void 1484 G1CollectedHeap:: 1485 resize_if_necessary_after_full_collection(size_t word_size) { 1486 // Include the current allocation, if any, and bytes that will be 1487 // pre-allocated to support collections, as "used". 1488 const size_t used_after_gc = used(); 1489 const size_t capacity_after_gc = capacity(); 1490 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1491 1492 // This is enforced in arguments.cpp. 1493 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1494 "otherwise the code below doesn't make sense"); 1495 1496 // We don't have floating point command-line arguments 1497 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1498 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1499 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1500 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1501 1502 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1503 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1504 1505 // We have to be careful here as these two calculations can overflow 1506 // 32-bit size_t's. 1507 double used_after_gc_d = (double) used_after_gc; 1508 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1509 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1510 1511 // Let's make sure that they are both under the max heap size, which 1512 // by default will make them fit into a size_t. 1513 double desired_capacity_upper_bound = (double) max_heap_size; 1514 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1515 desired_capacity_upper_bound); 1516 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1517 desired_capacity_upper_bound); 1518 1519 // We can now safely turn them into size_t's. 1520 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1521 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1522 1523 // This assert only makes sense here, before we adjust them 1524 // with respect to the min and max heap size. 1525 assert(minimum_desired_capacity <= maximum_desired_capacity, 1526 "minimum_desired_capacity = " SIZE_FORMAT ", " 1527 "maximum_desired_capacity = " SIZE_FORMAT, 1528 minimum_desired_capacity, maximum_desired_capacity); 1529 1530 // Should not be greater than the heap max size. No need to adjust 1531 // it with respect to the heap min size as it's a lower bound (i.e., 1532 // we'll try to make the capacity larger than it, not smaller). 1533 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1534 // Should not be less than the heap min size. No need to adjust it 1535 // with respect to the heap max size as it's an upper bound (i.e., 1536 // we'll try to make the capacity smaller than it, not greater). 1537 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1538 1539 if (capacity_after_gc < minimum_desired_capacity) { 1540 // Don't expand unless it's significant 1541 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1542 ergo_verbose4(ErgoHeapSizing, 1543 "attempt heap expansion", 1544 ergo_format_reason("capacity lower than " 1545 "min desired capacity after Full GC") 1546 ergo_format_byte("capacity") 1547 ergo_format_byte("occupancy") 1548 ergo_format_byte_perc("min desired capacity"), 1549 capacity_after_gc, used_after_gc, 1550 minimum_desired_capacity, (double) MinHeapFreeRatio); 1551 expand(expand_bytes); 1552 1553 // No expansion, now see if we want to shrink 1554 } else if (capacity_after_gc > maximum_desired_capacity) { 1555 // Capacity too large, compute shrinking size 1556 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1557 ergo_verbose4(ErgoHeapSizing, 1558 "attempt heap shrinking", 1559 ergo_format_reason("capacity higher than " 1560 "max desired capacity after Full GC") 1561 ergo_format_byte("capacity") 1562 ergo_format_byte("occupancy") 1563 ergo_format_byte_perc("max desired capacity"), 1564 capacity_after_gc, used_after_gc, 1565 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1566 shrink(shrink_bytes); 1567 } 1568 } 1569 1570 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1571 AllocationContext_t context, 1572 bool do_gc, 1573 bool clear_all_soft_refs, 1574 bool expect_null_mutator_alloc_region, 1575 bool* gc_succeeded) { 1576 *gc_succeeded = true; 1577 // Let's attempt the allocation first. 1578 HeapWord* result = 1579 attempt_allocation_at_safepoint(word_size, 1580 context, 1581 expect_null_mutator_alloc_region); 1582 if (result != NULL) { 1583 assert(*gc_succeeded, "sanity"); 1584 return result; 1585 } 1586 1587 // In a G1 heap, we're supposed to keep allocation from failing by 1588 // incremental pauses. Therefore, at least for now, we'll favor 1589 // expansion over collection. (This might change in the future if we can 1590 // do something smarter than full collection to satisfy a failed alloc.) 1591 result = expand_and_allocate(word_size, context); 1592 if (result != NULL) { 1593 assert(*gc_succeeded, "sanity"); 1594 return result; 1595 } 1596 1597 if (do_gc) { 1598 // Expansion didn't work, we'll try to do a Full GC. 1599 *gc_succeeded = do_collection(false, /* explicit_gc */ 1600 clear_all_soft_refs, 1601 word_size); 1602 } 1603 1604 return NULL; 1605 } 1606 1607 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1608 AllocationContext_t context, 1609 bool* succeeded) { 1610 assert_at_safepoint(true /* should_be_vm_thread */); 1611 1612 // Attempts to allocate followed by Full GC. 1613 HeapWord* result = 1614 satisfy_failed_allocation_helper(word_size, 1615 context, 1616 true, /* do_gc */ 1617 false, /* clear_all_soft_refs */ 1618 false, /* expect_null_mutator_alloc_region */ 1619 succeeded); 1620 1621 if (result != NULL || !*succeeded) { 1622 return result; 1623 } 1624 1625 // Attempts to allocate followed by Full GC that will collect all soft references. 1626 result = satisfy_failed_allocation_helper(word_size, 1627 context, 1628 true, /* do_gc */ 1629 true, /* clear_all_soft_refs */ 1630 true, /* expect_null_mutator_alloc_region */ 1631 succeeded); 1632 1633 if (result != NULL || !*succeeded) { 1634 return result; 1635 } 1636 1637 // Attempts to allocate, no GC 1638 result = satisfy_failed_allocation_helper(word_size, 1639 context, 1640 false, /* do_gc */ 1641 false, /* clear_all_soft_refs */ 1642 true, /* expect_null_mutator_alloc_region */ 1643 succeeded); 1644 1645 if (result != NULL) { 1646 assert(*succeeded, "sanity"); 1647 return result; 1648 } 1649 1650 assert(!collector_policy()->should_clear_all_soft_refs(), 1651 "Flag should have been handled and cleared prior to this point"); 1652 1653 // What else? We might try synchronous finalization later. If the total 1654 // space available is large enough for the allocation, then a more 1655 // complete compaction phase than we've tried so far might be 1656 // appropriate. 1657 assert(*succeeded, "sanity"); 1658 return NULL; 1659 } 1660 1661 // Attempting to expand the heap sufficiently 1662 // to support an allocation of the given "word_size". If 1663 // successful, perform the allocation and return the address of the 1664 // allocated block, or else "NULL". 1665 1666 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1667 assert_at_safepoint(true /* should_be_vm_thread */); 1668 1669 verify_region_sets_optional(); 1670 1671 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1672 ergo_verbose1(ErgoHeapSizing, 1673 "attempt heap expansion", 1674 ergo_format_reason("allocation request failed") 1675 ergo_format_byte("allocation request"), 1676 word_size * HeapWordSize); 1677 if (expand(expand_bytes)) { 1678 _hrm.verify_optional(); 1679 verify_region_sets_optional(); 1680 return attempt_allocation_at_safepoint(word_size, 1681 context, 1682 false /* expect_null_mutator_alloc_region */); 1683 } 1684 return NULL; 1685 } 1686 1687 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) { 1688 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1689 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1690 HeapRegion::GrainBytes); 1691 ergo_verbose2(ErgoHeapSizing, 1692 "expand the heap", 1693 ergo_format_byte("requested expansion amount") 1694 ergo_format_byte("attempted expansion amount"), 1695 expand_bytes, aligned_expand_bytes); 1696 1697 if (is_maximal_no_gc()) { 1698 ergo_verbose0(ErgoHeapSizing, 1699 "did not expand the heap", 1700 ergo_format_reason("heap already fully expanded")); 1701 return false; 1702 } 1703 1704 double expand_heap_start_time_sec = os::elapsedTime(); 1705 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1706 assert(regions_to_expand > 0, "Must expand by at least one region"); 1707 1708 uint expanded_by = _hrm.expand_by(regions_to_expand); 1709 if (expand_time_ms != NULL) { 1710 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1711 } 1712 1713 if (expanded_by > 0) { 1714 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1715 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1716 g1_policy()->record_new_heap_size(num_regions()); 1717 } else { 1718 ergo_verbose0(ErgoHeapSizing, 1719 "did not expand the heap", 1720 ergo_format_reason("heap expansion operation failed")); 1721 // The expansion of the virtual storage space was unsuccessful. 1722 // Let's see if it was because we ran out of swap. 1723 if (G1ExitOnExpansionFailure && 1724 _hrm.available() >= regions_to_expand) { 1725 // We had head room... 1726 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1727 } 1728 } 1729 return regions_to_expand > 0; 1730 } 1731 1732 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1733 size_t aligned_shrink_bytes = 1734 ReservedSpace::page_align_size_down(shrink_bytes); 1735 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1736 HeapRegion::GrainBytes); 1737 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1738 1739 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1740 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1741 1742 ergo_verbose3(ErgoHeapSizing, 1743 "shrink the heap", 1744 ergo_format_byte("requested shrinking amount") 1745 ergo_format_byte("aligned shrinking amount") 1746 ergo_format_byte("attempted shrinking amount"), 1747 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1748 if (num_regions_removed > 0) { 1749 g1_policy()->record_new_heap_size(num_regions()); 1750 } else { 1751 ergo_verbose0(ErgoHeapSizing, 1752 "did not shrink the heap", 1753 ergo_format_reason("heap shrinking operation failed")); 1754 } 1755 } 1756 1757 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1758 verify_region_sets_optional(); 1759 1760 // We should only reach here at the end of a Full GC which means we 1761 // should not not be holding to any GC alloc regions. The method 1762 // below will make sure of that and do any remaining clean up. 1763 _allocator->abandon_gc_alloc_regions(); 1764 1765 // Instead of tearing down / rebuilding the free lists here, we 1766 // could instead use the remove_all_pending() method on free_list to 1767 // remove only the ones that we need to remove. 1768 tear_down_region_sets(true /* free_list_only */); 1769 shrink_helper(shrink_bytes); 1770 rebuild_region_sets(true /* free_list_only */); 1771 1772 _hrm.verify_optional(); 1773 verify_region_sets_optional(); 1774 } 1775 1776 // Public methods. 1777 1778 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1779 CollectedHeap(), 1780 _g1_policy(policy_), 1781 _dirty_card_queue_set(false), 1782 _is_alive_closure_cm(this), 1783 _is_alive_closure_stw(this), 1784 _ref_processor_cm(NULL), 1785 _ref_processor_stw(NULL), 1786 _bot_shared(NULL), 1787 _cg1r(NULL), 1788 _g1mm(NULL), 1789 _refine_cte_cl(NULL), 1790 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1791 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1792 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1793 _humongous_reclaim_candidates(), 1794 _has_humongous_reclaim_candidates(false), 1795 _archive_allocator(NULL), 1796 _free_regions_coming(false), 1797 _young_list(new YoungList(this)), 1798 _gc_time_stamp(0), 1799 _summary_bytes_used(0), 1800 _survivor_evac_stats(YoungPLABSize, PLABWeight), 1801 _old_evac_stats(OldPLABSize, PLABWeight), 1802 _expand_heap_after_alloc_failure(true), 1803 _old_marking_cycles_started(0), 1804 _old_marking_cycles_completed(0), 1805 _heap_summary_sent(false), 1806 _in_cset_fast_test(), 1807 _dirty_cards_region_list(NULL), 1808 _worker_cset_start_region(NULL), 1809 _worker_cset_start_region_time_stamp(NULL), 1810 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1811 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1812 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1813 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1814 1815 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1816 /* are_GC_task_threads */true, 1817 /* are_ConcurrentGC_threads */false); 1818 _workers->initialize_workers(); 1819 1820 _allocator = G1Allocator::create_allocator(this); 1821 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1822 1823 // Override the default _filler_array_max_size so that no humongous filler 1824 // objects are created. 1825 _filler_array_max_size = _humongous_object_threshold_in_words; 1826 1827 uint n_queues = ParallelGCThreads; 1828 _task_queues = new RefToScanQueueSet(n_queues); 1829 1830 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1831 assert(n_rem_sets > 0, "Invariant."); 1832 1833 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1834 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC); 1835 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1836 1837 for (uint i = 0; i < n_queues; i++) { 1838 RefToScanQueue* q = new RefToScanQueue(); 1839 q->initialize(); 1840 _task_queues->register_queue(i, q); 1841 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1842 } 1843 clear_cset_start_regions(); 1844 1845 // Initialize the G1EvacuationFailureALot counters and flags. 1846 NOT_PRODUCT(reset_evacuation_should_fail();) 1847 1848 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1849 } 1850 1851 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1852 size_t size, 1853 size_t translation_factor) { 1854 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1855 // Allocate a new reserved space, preferring to use large pages. 1856 ReservedSpace rs(size, preferred_page_size); 1857 G1RegionToSpaceMapper* result = 1858 G1RegionToSpaceMapper::create_mapper(rs, 1859 size, 1860 rs.alignment(), 1861 HeapRegion::GrainBytes, 1862 translation_factor, 1863 mtGC); 1864 if (TracePageSizes) { 1865 gclog_or_tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT, 1866 description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size); 1867 } 1868 return result; 1869 } 1870 1871 jint G1CollectedHeap::initialize() { 1872 CollectedHeap::pre_initialize(); 1873 os::enable_vtime(); 1874 1875 G1Log::init(); 1876 1877 // Necessary to satisfy locking discipline assertions. 1878 1879 MutexLocker x(Heap_lock); 1880 1881 // We have to initialize the printer before committing the heap, as 1882 // it will be used then. 1883 _hr_printer.set_active(G1PrintHeapRegions); 1884 1885 // While there are no constraints in the GC code that HeapWordSize 1886 // be any particular value, there are multiple other areas in the 1887 // system which believe this to be true (e.g. oop->object_size in some 1888 // cases incorrectly returns the size in wordSize units rather than 1889 // HeapWordSize). 1890 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1891 1892 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1893 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1894 size_t heap_alignment = collector_policy()->heap_alignment(); 1895 1896 // Ensure that the sizes are properly aligned. 1897 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1898 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1899 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1900 1901 _refine_cte_cl = new RefineCardTableEntryClosure(); 1902 1903 jint ecode = JNI_OK; 1904 _cg1r = ConcurrentG1Refine::create(this, _refine_cte_cl, &ecode); 1905 if (_cg1r == NULL) { 1906 return ecode; 1907 } 1908 1909 // Reserve the maximum. 1910 1911 // When compressed oops are enabled, the preferred heap base 1912 // is calculated by subtracting the requested size from the 1913 // 32Gb boundary and using the result as the base address for 1914 // heap reservation. If the requested size is not aligned to 1915 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1916 // into the ReservedHeapSpace constructor) then the actual 1917 // base of the reserved heap may end up differing from the 1918 // address that was requested (i.e. the preferred heap base). 1919 // If this happens then we could end up using a non-optimal 1920 // compressed oops mode. 1921 1922 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1923 heap_alignment); 1924 1925 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1926 1927 // Create the barrier set for the entire reserved region. 1928 G1SATBCardTableLoggingModRefBS* bs 1929 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1930 bs->initialize(); 1931 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1932 set_barrier_set(bs); 1933 1934 // Also create a G1 rem set. 1935 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 1936 1937 // Carve out the G1 part of the heap. 1938 1939 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1940 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1941 G1RegionToSpaceMapper* heap_storage = 1942 G1RegionToSpaceMapper::create_mapper(g1_rs, 1943 g1_rs.size(), 1944 page_size, 1945 HeapRegion::GrainBytes, 1946 1, 1947 mtJavaHeap); 1948 os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(), 1949 max_byte_size, page_size, 1950 heap_rs.base(), 1951 heap_rs.size()); 1952 heap_storage->set_mapping_changed_listener(&_listener); 1953 1954 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1955 G1RegionToSpaceMapper* bot_storage = 1956 create_aux_memory_mapper("Block offset table", 1957 G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize), 1958 G1BlockOffsetSharedArray::heap_map_factor()); 1959 1960 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1961 G1RegionToSpaceMapper* cardtable_storage = 1962 create_aux_memory_mapper("Card table", 1963 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1964 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1965 1966 G1RegionToSpaceMapper* card_counts_storage = 1967 create_aux_memory_mapper("Card counts table", 1968 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1969 G1CardCounts::heap_map_factor()); 1970 1971 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size()); 1972 G1RegionToSpaceMapper* prev_bitmap_storage = 1973 create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1974 G1RegionToSpaceMapper* next_bitmap_storage = 1975 create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1976 1977 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1978 g1_barrier_set()->initialize(cardtable_storage); 1979 // Do later initialization work for concurrent refinement. 1980 _cg1r->init(card_counts_storage); 1981 1982 // 6843694 - ensure that the maximum region index can fit 1983 // in the remembered set structures. 1984 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1985 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1986 1987 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1988 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1989 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1990 "too many cards per region"); 1991 1992 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1993 1994 _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage); 1995 1996 { 1997 HeapWord* start = _hrm.reserved().start(); 1998 HeapWord* end = _hrm.reserved().end(); 1999 size_t granularity = HeapRegion::GrainBytes; 2000 2001 _in_cset_fast_test.initialize(start, end, granularity); 2002 _humongous_reclaim_candidates.initialize(start, end, granularity); 2003 } 2004 2005 // Create the ConcurrentMark data structure and thread. 2006 // (Must do this late, so that "max_regions" is defined.) 2007 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 2008 if (_cm == NULL || !_cm->completed_initialization()) { 2009 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 2010 return JNI_ENOMEM; 2011 } 2012 _cmThread = _cm->cmThread(); 2013 2014 // Initialize the from_card cache structure of HeapRegionRemSet. 2015 HeapRegionRemSet::init_heap(max_regions()); 2016 2017 // Now expand into the initial heap size. 2018 if (!expand(init_byte_size)) { 2019 vm_shutdown_during_initialization("Failed to allocate initial heap."); 2020 return JNI_ENOMEM; 2021 } 2022 2023 // Perform any initialization actions delegated to the policy. 2024 g1_policy()->init(); 2025 2026 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2027 SATB_Q_FL_lock, 2028 G1SATBProcessCompletedThreshold, 2029 Shared_SATB_Q_lock); 2030 2031 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 2032 DirtyCardQ_CBL_mon, 2033 DirtyCardQ_FL_lock, 2034 concurrent_g1_refine()->yellow_zone(), 2035 concurrent_g1_refine()->red_zone(), 2036 Shared_DirtyCardQ_lock); 2037 2038 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 2039 DirtyCardQ_CBL_mon, 2040 DirtyCardQ_FL_lock, 2041 -1, // never trigger processing 2042 -1, // no limit on length 2043 Shared_DirtyCardQ_lock, 2044 &JavaThread::dirty_card_queue_set()); 2045 2046 // Here we allocate the dummy HeapRegion that is required by the 2047 // G1AllocRegion class. 2048 HeapRegion* dummy_region = _hrm.get_dummy_region(); 2049 2050 // We'll re-use the same region whether the alloc region will 2051 // require BOT updates or not and, if it doesn't, then a non-young 2052 // region will complain that it cannot support allocations without 2053 // BOT updates. So we'll tag the dummy region as eden to avoid that. 2054 dummy_region->set_eden(); 2055 // Make sure it's full. 2056 dummy_region->set_top(dummy_region->end()); 2057 G1AllocRegion::setup(this, dummy_region); 2058 2059 _allocator->init_mutator_alloc_region(); 2060 2061 // Do create of the monitoring and management support so that 2062 // values in the heap have been properly initialized. 2063 _g1mm = new G1MonitoringSupport(this); 2064 2065 G1StringDedup::initialize(); 2066 2067 _preserved_objs = NEW_C_HEAP_ARRAY(OopAndMarkOopStack, ParallelGCThreads, mtGC); 2068 for (uint i = 0; i < ParallelGCThreads; i++) { 2069 new (&_preserved_objs[i]) OopAndMarkOopStack(); 2070 } 2071 2072 return JNI_OK; 2073 } 2074 2075 void G1CollectedHeap::stop() { 2076 // Stop all concurrent threads. We do this to make sure these threads 2077 // do not continue to execute and access resources (e.g. gclog_or_tty) 2078 // that are destroyed during shutdown. 2079 _cg1r->stop(); 2080 _cmThread->stop(); 2081 if (G1StringDedup::is_enabled()) { 2082 G1StringDedup::stop(); 2083 } 2084 } 2085 2086 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2087 return HeapRegion::max_region_size(); 2088 } 2089 2090 void G1CollectedHeap::post_initialize() { 2091 CollectedHeap::post_initialize(); 2092 ref_processing_init(); 2093 } 2094 2095 void G1CollectedHeap::ref_processing_init() { 2096 // Reference processing in G1 currently works as follows: 2097 // 2098 // * There are two reference processor instances. One is 2099 // used to record and process discovered references 2100 // during concurrent marking; the other is used to 2101 // record and process references during STW pauses 2102 // (both full and incremental). 2103 // * Both ref processors need to 'span' the entire heap as 2104 // the regions in the collection set may be dotted around. 2105 // 2106 // * For the concurrent marking ref processor: 2107 // * Reference discovery is enabled at initial marking. 2108 // * Reference discovery is disabled and the discovered 2109 // references processed etc during remarking. 2110 // * Reference discovery is MT (see below). 2111 // * Reference discovery requires a barrier (see below). 2112 // * Reference processing may or may not be MT 2113 // (depending on the value of ParallelRefProcEnabled 2114 // and ParallelGCThreads). 2115 // * A full GC disables reference discovery by the CM 2116 // ref processor and abandons any entries on it's 2117 // discovered lists. 2118 // 2119 // * For the STW processor: 2120 // * Non MT discovery is enabled at the start of a full GC. 2121 // * Processing and enqueueing during a full GC is non-MT. 2122 // * During a full GC, references are processed after marking. 2123 // 2124 // * Discovery (may or may not be MT) is enabled at the start 2125 // of an incremental evacuation pause. 2126 // * References are processed near the end of a STW evacuation pause. 2127 // * For both types of GC: 2128 // * Discovery is atomic - i.e. not concurrent. 2129 // * Reference discovery will not need a barrier. 2130 2131 MemRegion mr = reserved_region(); 2132 2133 // Concurrent Mark ref processor 2134 _ref_processor_cm = 2135 new ReferenceProcessor(mr, // span 2136 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2137 // mt processing 2138 ParallelGCThreads, 2139 // degree of mt processing 2140 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2141 // mt discovery 2142 MAX2(ParallelGCThreads, ConcGCThreads), 2143 // degree of mt discovery 2144 false, 2145 // Reference discovery is not atomic 2146 &_is_alive_closure_cm); 2147 // is alive closure 2148 // (for efficiency/performance) 2149 2150 // STW ref processor 2151 _ref_processor_stw = 2152 new ReferenceProcessor(mr, // span 2153 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2154 // mt processing 2155 ParallelGCThreads, 2156 // degree of mt processing 2157 (ParallelGCThreads > 1), 2158 // mt discovery 2159 ParallelGCThreads, 2160 // degree of mt discovery 2161 true, 2162 // Reference discovery is atomic 2163 &_is_alive_closure_stw); 2164 // is alive closure 2165 // (for efficiency/performance) 2166 } 2167 2168 CollectorPolicy* G1CollectedHeap::collector_policy() const { 2169 return g1_policy(); 2170 } 2171 2172 size_t G1CollectedHeap::capacity() const { 2173 return _hrm.length() * HeapRegion::GrainBytes; 2174 } 2175 2176 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2177 hr->reset_gc_time_stamp(); 2178 } 2179 2180 #ifndef PRODUCT 2181 2182 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2183 private: 2184 unsigned _gc_time_stamp; 2185 bool _failures; 2186 2187 public: 2188 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2189 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2190 2191 virtual bool doHeapRegion(HeapRegion* hr) { 2192 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2193 if (_gc_time_stamp != region_gc_time_stamp) { 2194 gclog_or_tty->print_cr("Region " HR_FORMAT " has GC time stamp = %d, " 2195 "expected %d", HR_FORMAT_PARAMS(hr), 2196 region_gc_time_stamp, _gc_time_stamp); 2197 _failures = true; 2198 } 2199 return false; 2200 } 2201 2202 bool failures() { return _failures; } 2203 }; 2204 2205 void G1CollectedHeap::check_gc_time_stamps() { 2206 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2207 heap_region_iterate(&cl); 2208 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2209 } 2210 #endif // PRODUCT 2211 2212 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2213 _cg1r->hot_card_cache()->drain(cl, worker_i); 2214 } 2215 2216 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2217 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2218 size_t n_completed_buffers = 0; 2219 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2220 n_completed_buffers++; 2221 } 2222 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2223 dcqs.clear_n_completed_buffers(); 2224 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2225 } 2226 2227 // Computes the sum of the storage used by the various regions. 2228 size_t G1CollectedHeap::used() const { 2229 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2230 if (_archive_allocator != NULL) { 2231 result += _archive_allocator->used(); 2232 } 2233 return result; 2234 } 2235 2236 size_t G1CollectedHeap::used_unlocked() const { 2237 return _summary_bytes_used; 2238 } 2239 2240 class SumUsedClosure: public HeapRegionClosure { 2241 size_t _used; 2242 public: 2243 SumUsedClosure() : _used(0) {} 2244 bool doHeapRegion(HeapRegion* r) { 2245 _used += r->used(); 2246 return false; 2247 } 2248 size_t result() { return _used; } 2249 }; 2250 2251 size_t G1CollectedHeap::recalculate_used() const { 2252 double recalculate_used_start = os::elapsedTime(); 2253 2254 SumUsedClosure blk; 2255 heap_region_iterate(&blk); 2256 2257 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2258 return blk.result(); 2259 } 2260 2261 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2262 switch (cause) { 2263 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2264 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2265 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2266 case GCCause::_g1_humongous_allocation: return true; 2267 case GCCause::_update_allocation_context_stats_inc: return true; 2268 case GCCause::_wb_conc_mark: return true; 2269 default: return false; 2270 } 2271 } 2272 2273 #ifndef PRODUCT 2274 void G1CollectedHeap::allocate_dummy_regions() { 2275 // Let's fill up most of the region 2276 size_t word_size = HeapRegion::GrainWords - 1024; 2277 // And as a result the region we'll allocate will be humongous. 2278 guarantee(is_humongous(word_size), "sanity"); 2279 2280 // _filler_array_max_size is set to humongous object threshold 2281 // but temporarily change it to use CollectedHeap::fill_with_object(). 2282 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2283 2284 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2285 // Let's use the existing mechanism for the allocation 2286 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2287 AllocationContext::system()); 2288 if (dummy_obj != NULL) { 2289 MemRegion mr(dummy_obj, word_size); 2290 CollectedHeap::fill_with_object(mr); 2291 } else { 2292 // If we can't allocate once, we probably cannot allocate 2293 // again. Let's get out of the loop. 2294 break; 2295 } 2296 } 2297 } 2298 #endif // !PRODUCT 2299 2300 void G1CollectedHeap::increment_old_marking_cycles_started() { 2301 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2302 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2303 "Wrong marking cycle count (started: %d, completed: %d)", 2304 _old_marking_cycles_started, _old_marking_cycles_completed); 2305 2306 _old_marking_cycles_started++; 2307 } 2308 2309 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2310 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2311 2312 // We assume that if concurrent == true, then the caller is a 2313 // concurrent thread that was joined the Suspendible Thread 2314 // Set. If there's ever a cheap way to check this, we should add an 2315 // assert here. 2316 2317 // Given that this method is called at the end of a Full GC or of a 2318 // concurrent cycle, and those can be nested (i.e., a Full GC can 2319 // interrupt a concurrent cycle), the number of full collections 2320 // completed should be either one (in the case where there was no 2321 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2322 // behind the number of full collections started. 2323 2324 // This is the case for the inner caller, i.e. a Full GC. 2325 assert(concurrent || 2326 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2327 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2328 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2329 "is inconsistent with _old_marking_cycles_completed = %u", 2330 _old_marking_cycles_started, _old_marking_cycles_completed); 2331 2332 // This is the case for the outer caller, i.e. the concurrent cycle. 2333 assert(!concurrent || 2334 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2335 "for outer caller (concurrent cycle): " 2336 "_old_marking_cycles_started = %u " 2337 "is inconsistent with _old_marking_cycles_completed = %u", 2338 _old_marking_cycles_started, _old_marking_cycles_completed); 2339 2340 _old_marking_cycles_completed += 1; 2341 2342 // We need to clear the "in_progress" flag in the CM thread before 2343 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2344 // is set) so that if a waiter requests another System.gc() it doesn't 2345 // incorrectly see that a marking cycle is still in progress. 2346 if (concurrent) { 2347 _cmThread->set_idle(); 2348 } 2349 2350 // This notify_all() will ensure that a thread that called 2351 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2352 // and it's waiting for a full GC to finish will be woken up. It is 2353 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2354 FullGCCount_lock->notify_all(); 2355 } 2356 2357 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2358 GCIdMarkAndRestore conc_gc_id_mark; 2359 collector_state()->set_concurrent_cycle_started(true); 2360 _gc_timer_cm->register_gc_start(start_time); 2361 2362 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2363 trace_heap_before_gc(_gc_tracer_cm); 2364 _cmThread->set_gc_id(GCId::current()); 2365 } 2366 2367 void G1CollectedHeap::register_concurrent_cycle_end() { 2368 if (collector_state()->concurrent_cycle_started()) { 2369 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2370 if (_cm->has_aborted()) { 2371 _gc_tracer_cm->report_concurrent_mode_failure(); 2372 } 2373 2374 _gc_timer_cm->register_gc_end(); 2375 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2376 2377 // Clear state variables to prepare for the next concurrent cycle. 2378 collector_state()->set_concurrent_cycle_started(false); 2379 _heap_summary_sent = false; 2380 } 2381 } 2382 2383 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2384 if (collector_state()->concurrent_cycle_started()) { 2385 // This function can be called when: 2386 // the cleanup pause is run 2387 // the concurrent cycle is aborted before the cleanup pause. 2388 // the concurrent cycle is aborted after the cleanup pause, 2389 // but before the concurrent cycle end has been registered. 2390 // Make sure that we only send the heap information once. 2391 if (!_heap_summary_sent) { 2392 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2393 trace_heap_after_gc(_gc_tracer_cm); 2394 _heap_summary_sent = true; 2395 } 2396 } 2397 } 2398 2399 void G1CollectedHeap::collect(GCCause::Cause cause) { 2400 assert_heap_not_locked(); 2401 2402 uint gc_count_before; 2403 uint old_marking_count_before; 2404 uint full_gc_count_before; 2405 bool retry_gc; 2406 2407 do { 2408 retry_gc = false; 2409 2410 { 2411 MutexLocker ml(Heap_lock); 2412 2413 // Read the GC count while holding the Heap_lock 2414 gc_count_before = total_collections(); 2415 full_gc_count_before = total_full_collections(); 2416 old_marking_count_before = _old_marking_cycles_started; 2417 } 2418 2419 if (should_do_concurrent_full_gc(cause)) { 2420 // Schedule an initial-mark evacuation pause that will start a 2421 // concurrent cycle. We're setting word_size to 0 which means that 2422 // we are not requesting a post-GC allocation. 2423 VM_G1IncCollectionPause op(gc_count_before, 2424 0, /* word_size */ 2425 true, /* should_initiate_conc_mark */ 2426 g1_policy()->max_pause_time_ms(), 2427 cause); 2428 op.set_allocation_context(AllocationContext::current()); 2429 2430 VMThread::execute(&op); 2431 if (!op.pause_succeeded()) { 2432 if (old_marking_count_before == _old_marking_cycles_started) { 2433 retry_gc = op.should_retry_gc(); 2434 } else { 2435 // A Full GC happened while we were trying to schedule the 2436 // initial-mark GC. No point in starting a new cycle given 2437 // that the whole heap was collected anyway. 2438 } 2439 2440 if (retry_gc) { 2441 if (GC_locker::is_active_and_needs_gc()) { 2442 GC_locker::stall_until_clear(); 2443 } 2444 } 2445 } 2446 } else { 2447 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2448 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2449 2450 // Schedule a standard evacuation pause. We're setting word_size 2451 // to 0 which means that we are not requesting a post-GC allocation. 2452 VM_G1IncCollectionPause op(gc_count_before, 2453 0, /* word_size */ 2454 false, /* should_initiate_conc_mark */ 2455 g1_policy()->max_pause_time_ms(), 2456 cause); 2457 VMThread::execute(&op); 2458 } else { 2459 // Schedule a Full GC. 2460 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2461 VMThread::execute(&op); 2462 } 2463 } 2464 } while (retry_gc); 2465 } 2466 2467 bool G1CollectedHeap::is_in(const void* p) const { 2468 if (_hrm.reserved().contains(p)) { 2469 // Given that we know that p is in the reserved space, 2470 // heap_region_containing() should successfully 2471 // return the containing region. 2472 HeapRegion* hr = heap_region_containing(p); 2473 return hr->is_in(p); 2474 } else { 2475 return false; 2476 } 2477 } 2478 2479 #ifdef ASSERT 2480 bool G1CollectedHeap::is_in_exact(const void* p) const { 2481 bool contains = reserved_region().contains(p); 2482 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2483 if (contains && available) { 2484 return true; 2485 } else { 2486 return false; 2487 } 2488 } 2489 #endif 2490 2491 bool G1CollectedHeap::obj_in_cs(oop obj) { 2492 HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj); 2493 return r != NULL && r->in_collection_set(); 2494 } 2495 2496 // Iteration functions. 2497 2498 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2499 2500 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2501 ExtendedOopClosure* _cl; 2502 public: 2503 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2504 bool doHeapRegion(HeapRegion* r) { 2505 if (!r->is_continues_humongous()) { 2506 r->oop_iterate(_cl); 2507 } 2508 return false; 2509 } 2510 }; 2511 2512 // Iterates an ObjectClosure over all objects within a HeapRegion. 2513 2514 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2515 ObjectClosure* _cl; 2516 public: 2517 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2518 bool doHeapRegion(HeapRegion* r) { 2519 if (!r->is_continues_humongous()) { 2520 r->object_iterate(_cl); 2521 } 2522 return false; 2523 } 2524 }; 2525 2526 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2527 IterateObjectClosureRegionClosure blk(cl); 2528 heap_region_iterate(&blk); 2529 } 2530 2531 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2532 _hrm.iterate(cl); 2533 } 2534 2535 void 2536 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2537 uint worker_id, 2538 HeapRegionClaimer *hrclaimer, 2539 bool concurrent) const { 2540 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2541 } 2542 2543 // Clear the cached CSet starting regions and (more importantly) 2544 // the time stamps. Called when we reset the GC time stamp. 2545 void G1CollectedHeap::clear_cset_start_regions() { 2546 assert(_worker_cset_start_region != NULL, "sanity"); 2547 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2548 2549 for (uint i = 0; i < ParallelGCThreads; i++) { 2550 _worker_cset_start_region[i] = NULL; 2551 _worker_cset_start_region_time_stamp[i] = 0; 2552 } 2553 } 2554 2555 // Given the id of a worker, obtain or calculate a suitable 2556 // starting region for iterating over the current collection set. 2557 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2558 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2559 2560 HeapRegion* result = NULL; 2561 unsigned gc_time_stamp = get_gc_time_stamp(); 2562 2563 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2564 // Cached starting region for current worker was set 2565 // during the current pause - so it's valid. 2566 // Note: the cached starting heap region may be NULL 2567 // (when the collection set is empty). 2568 result = _worker_cset_start_region[worker_i]; 2569 assert(result == NULL || result->in_collection_set(), "sanity"); 2570 return result; 2571 } 2572 2573 // The cached entry was not valid so let's calculate 2574 // a suitable starting heap region for this worker. 2575 2576 // We want the parallel threads to start their collection 2577 // set iteration at different collection set regions to 2578 // avoid contention. 2579 // If we have: 2580 // n collection set regions 2581 // p threads 2582 // Then thread t will start at region floor ((t * n) / p) 2583 2584 result = g1_policy()->collection_set(); 2585 uint cs_size = g1_policy()->cset_region_length(); 2586 uint active_workers = workers()->active_workers(); 2587 2588 uint end_ind = (cs_size * worker_i) / active_workers; 2589 uint start_ind = 0; 2590 2591 if (worker_i > 0 && 2592 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2593 // Previous workers starting region is valid 2594 // so let's iterate from there 2595 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2596 result = _worker_cset_start_region[worker_i - 1]; 2597 } 2598 2599 for (uint i = start_ind; i < end_ind; i++) { 2600 result = result->next_in_collection_set(); 2601 } 2602 2603 // Note: the calculated starting heap region may be NULL 2604 // (when the collection set is empty). 2605 assert(result == NULL || result->in_collection_set(), "sanity"); 2606 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2607 "should be updated only once per pause"); 2608 _worker_cset_start_region[worker_i] = result; 2609 OrderAccess::storestore(); 2610 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2611 return result; 2612 } 2613 2614 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2615 HeapRegion* r = g1_policy()->collection_set(); 2616 while (r != NULL) { 2617 HeapRegion* next = r->next_in_collection_set(); 2618 if (cl->doHeapRegion(r)) { 2619 cl->incomplete(); 2620 return; 2621 } 2622 r = next; 2623 } 2624 } 2625 2626 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2627 HeapRegionClosure *cl) { 2628 if (r == NULL) { 2629 // The CSet is empty so there's nothing to do. 2630 return; 2631 } 2632 2633 assert(r->in_collection_set(), 2634 "Start region must be a member of the collection set."); 2635 HeapRegion* cur = r; 2636 while (cur != NULL) { 2637 HeapRegion* next = cur->next_in_collection_set(); 2638 if (cl->doHeapRegion(cur) && false) { 2639 cl->incomplete(); 2640 return; 2641 } 2642 cur = next; 2643 } 2644 cur = g1_policy()->collection_set(); 2645 while (cur != r) { 2646 HeapRegion* next = cur->next_in_collection_set(); 2647 if (cl->doHeapRegion(cur) && false) { 2648 cl->incomplete(); 2649 return; 2650 } 2651 cur = next; 2652 } 2653 } 2654 2655 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2656 HeapRegion* result = _hrm.next_region_in_heap(from); 2657 while (result != NULL && result->is_pinned()) { 2658 result = _hrm.next_region_in_heap(result); 2659 } 2660 return result; 2661 } 2662 2663 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2664 HeapRegion* hr = heap_region_containing(addr); 2665 return hr->block_start(addr); 2666 } 2667 2668 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2669 HeapRegion* hr = heap_region_containing(addr); 2670 return hr->block_size(addr); 2671 } 2672 2673 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2674 HeapRegion* hr = heap_region_containing(addr); 2675 return hr->block_is_obj(addr); 2676 } 2677 2678 bool G1CollectedHeap::supports_tlab_allocation() const { 2679 return true; 2680 } 2681 2682 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2683 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2684 } 2685 2686 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2687 return young_list()->eden_used_bytes(); 2688 } 2689 2690 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2691 // must be equal to the humongous object limit. 2692 size_t G1CollectedHeap::max_tlab_size() const { 2693 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2694 } 2695 2696 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2697 AllocationContext_t context = AllocationContext::current(); 2698 return _allocator->unsafe_max_tlab_alloc(context); 2699 } 2700 2701 size_t G1CollectedHeap::max_capacity() const { 2702 return _hrm.reserved().byte_size(); 2703 } 2704 2705 jlong G1CollectedHeap::millis_since_last_gc() { 2706 // assert(false, "NYI"); 2707 return 0; 2708 } 2709 2710 void G1CollectedHeap::prepare_for_verify() { 2711 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2712 ensure_parsability(false); 2713 } 2714 g1_rem_set()->prepare_for_verify(); 2715 } 2716 2717 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 2718 VerifyOption vo) { 2719 switch (vo) { 2720 case VerifyOption_G1UsePrevMarking: 2721 return hr->obj_allocated_since_prev_marking(obj); 2722 case VerifyOption_G1UseNextMarking: 2723 return hr->obj_allocated_since_next_marking(obj); 2724 case VerifyOption_G1UseMarkWord: 2725 return false; 2726 default: 2727 ShouldNotReachHere(); 2728 } 2729 return false; // keep some compilers happy 2730 } 2731 2732 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 2733 switch (vo) { 2734 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 2735 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 2736 case VerifyOption_G1UseMarkWord: return NULL; 2737 default: ShouldNotReachHere(); 2738 } 2739 return NULL; // keep some compilers happy 2740 } 2741 2742 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 2743 switch (vo) { 2744 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 2745 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 2746 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 2747 default: ShouldNotReachHere(); 2748 } 2749 return false; // keep some compilers happy 2750 } 2751 2752 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 2753 switch (vo) { 2754 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 2755 case VerifyOption_G1UseNextMarking: return "NTAMS"; 2756 case VerifyOption_G1UseMarkWord: return "NONE"; 2757 default: ShouldNotReachHere(); 2758 } 2759 return NULL; // keep some compilers happy 2760 } 2761 2762 class VerifyRootsClosure: public OopClosure { 2763 private: 2764 G1CollectedHeap* _g1h; 2765 VerifyOption _vo; 2766 bool _failures; 2767 public: 2768 // _vo == UsePrevMarking -> use "prev" marking information, 2769 // _vo == UseNextMarking -> use "next" marking information, 2770 // _vo == UseMarkWord -> use mark word from object header. 2771 VerifyRootsClosure(VerifyOption vo) : 2772 _g1h(G1CollectedHeap::heap()), 2773 _vo(vo), 2774 _failures(false) { } 2775 2776 bool failures() { return _failures; } 2777 2778 template <class T> void do_oop_nv(T* p) { 2779 T heap_oop = oopDesc::load_heap_oop(p); 2780 if (!oopDesc::is_null(heap_oop)) { 2781 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2782 if (_g1h->is_obj_dead_cond(obj, _vo)) { 2783 gclog_or_tty->print_cr("Root location " PTR_FORMAT " " 2784 "points to dead obj " PTR_FORMAT, p2i(p), p2i(obj)); 2785 if (_vo == VerifyOption_G1UseMarkWord) { 2786 gclog_or_tty->print_cr(" Mark word: " INTPTR_FORMAT, (intptr_t)obj->mark()); 2787 } 2788 obj->print_on(gclog_or_tty); 2789 _failures = true; 2790 } 2791 } 2792 } 2793 2794 void do_oop(oop* p) { do_oop_nv(p); } 2795 void do_oop(narrowOop* p) { do_oop_nv(p); } 2796 }; 2797 2798 class G1VerifyCodeRootOopClosure: public OopClosure { 2799 G1CollectedHeap* _g1h; 2800 OopClosure* _root_cl; 2801 nmethod* _nm; 2802 VerifyOption _vo; 2803 bool _failures; 2804 2805 template <class T> void do_oop_work(T* p) { 2806 // First verify that this root is live 2807 _root_cl->do_oop(p); 2808 2809 if (!G1VerifyHeapRegionCodeRoots) { 2810 // We're not verifying the code roots attached to heap region. 2811 return; 2812 } 2813 2814 // Don't check the code roots during marking verification in a full GC 2815 if (_vo == VerifyOption_G1UseMarkWord) { 2816 return; 2817 } 2818 2819 // Now verify that the current nmethod (which contains p) is 2820 // in the code root list of the heap region containing the 2821 // object referenced by p. 2822 2823 T heap_oop = oopDesc::load_heap_oop(p); 2824 if (!oopDesc::is_null(heap_oop)) { 2825 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2826 2827 // Now fetch the region containing the object 2828 HeapRegion* hr = _g1h->heap_region_containing(obj); 2829 HeapRegionRemSet* hrrs = hr->rem_set(); 2830 // Verify that the strong code root list for this region 2831 // contains the nmethod 2832 if (!hrrs->strong_code_roots_list_contains(_nm)) { 2833 gclog_or_tty->print_cr("Code root location " PTR_FORMAT " " 2834 "from nmethod " PTR_FORMAT " not in strong " 2835 "code roots for region [" PTR_FORMAT "," PTR_FORMAT ")", 2836 p2i(p), p2i(_nm), p2i(hr->bottom()), p2i(hr->end())); 2837 _failures = true; 2838 } 2839 } 2840 } 2841 2842 public: 2843 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo): 2844 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {} 2845 2846 void do_oop(oop* p) { do_oop_work(p); } 2847 void do_oop(narrowOop* p) { do_oop_work(p); } 2848 2849 void set_nmethod(nmethod* nm) { _nm = nm; } 2850 bool failures() { return _failures; } 2851 }; 2852 2853 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure { 2854 G1VerifyCodeRootOopClosure* _oop_cl; 2855 2856 public: 2857 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl): 2858 _oop_cl(oop_cl) {} 2859 2860 void do_code_blob(CodeBlob* cb) { 2861 nmethod* nm = cb->as_nmethod_or_null(); 2862 if (nm != NULL) { 2863 _oop_cl->set_nmethod(nm); 2864 nm->oops_do(_oop_cl); 2865 } 2866 } 2867 }; 2868 2869 class YoungRefCounterClosure : public OopClosure { 2870 G1CollectedHeap* _g1h; 2871 int _count; 2872 public: 2873 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 2874 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 2875 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 2876 2877 int count() { return _count; } 2878 void reset_count() { _count = 0; }; 2879 }; 2880 2881 class VerifyKlassClosure: public KlassClosure { 2882 YoungRefCounterClosure _young_ref_counter_closure; 2883 OopClosure *_oop_closure; 2884 public: 2885 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 2886 void do_klass(Klass* k) { 2887 k->oops_do(_oop_closure); 2888 2889 _young_ref_counter_closure.reset_count(); 2890 k->oops_do(&_young_ref_counter_closure); 2891 if (_young_ref_counter_closure.count() > 0) { 2892 guarantee(k->has_modified_oops(), "Klass " PTR_FORMAT ", has young refs but is not dirty.", p2i(k)); 2893 } 2894 } 2895 }; 2896 2897 class VerifyLivenessOopClosure: public OopClosure { 2898 G1CollectedHeap* _g1h; 2899 VerifyOption _vo; 2900 public: 2901 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 2902 _g1h(g1h), _vo(vo) 2903 { } 2904 void do_oop(narrowOop *p) { do_oop_work(p); } 2905 void do_oop( oop *p) { do_oop_work(p); } 2906 2907 template <class T> void do_oop_work(T *p) { 2908 oop obj = oopDesc::load_decode_heap_oop(p); 2909 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 2910 "Dead object referenced by a not dead object"); 2911 } 2912 }; 2913 2914 class VerifyObjsInRegionClosure: public ObjectClosure { 2915 private: 2916 G1CollectedHeap* _g1h; 2917 size_t _live_bytes; 2918 HeapRegion *_hr; 2919 VerifyOption _vo; 2920 public: 2921 // _vo == UsePrevMarking -> use "prev" marking information, 2922 // _vo == UseNextMarking -> use "next" marking information, 2923 // _vo == UseMarkWord -> use mark word from object header. 2924 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 2925 : _live_bytes(0), _hr(hr), _vo(vo) { 2926 _g1h = G1CollectedHeap::heap(); 2927 } 2928 void do_object(oop o) { 2929 VerifyLivenessOopClosure isLive(_g1h, _vo); 2930 assert(o != NULL, "Huh?"); 2931 if (!_g1h->is_obj_dead_cond(o, _vo)) { 2932 // If the object is alive according to the mark word, 2933 // then verify that the marking information agrees. 2934 // Note we can't verify the contra-positive of the 2935 // above: if the object is dead (according to the mark 2936 // word), it may not be marked, or may have been marked 2937 // but has since became dead, or may have been allocated 2938 // since the last marking. 2939 if (_vo == VerifyOption_G1UseMarkWord) { 2940 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 2941 } 2942 2943 o->oop_iterate_no_header(&isLive); 2944 if (!_hr->obj_allocated_since_prev_marking(o)) { 2945 size_t obj_size = o->size(); // Make sure we don't overflow 2946 _live_bytes += (obj_size * HeapWordSize); 2947 } 2948 } 2949 } 2950 size_t live_bytes() { return _live_bytes; } 2951 }; 2952 2953 class VerifyArchiveOopClosure: public OopClosure { 2954 public: 2955 VerifyArchiveOopClosure(HeapRegion *hr) { } 2956 void do_oop(narrowOop *p) { do_oop_work(p); } 2957 void do_oop( oop *p) { do_oop_work(p); } 2958 2959 template <class T> void do_oop_work(T *p) { 2960 oop obj = oopDesc::load_decode_heap_oop(p); 2961 guarantee(obj == NULL || G1MarkSweep::in_archive_range(obj), 2962 "Archive object at " PTR_FORMAT " references a non-archive object at " PTR_FORMAT, 2963 p2i(p), p2i(obj)); 2964 } 2965 }; 2966 2967 class VerifyArchiveRegionClosure: public ObjectClosure { 2968 public: 2969 VerifyArchiveRegionClosure(HeapRegion *hr) { } 2970 // Verify that all object pointers are to archive regions. 2971 void do_object(oop o) { 2972 VerifyArchiveOopClosure checkOop(NULL); 2973 assert(o != NULL, "Should not be here for NULL oops"); 2974 o->oop_iterate_no_header(&checkOop); 2975 } 2976 }; 2977 2978 class VerifyRegionClosure: public HeapRegionClosure { 2979 private: 2980 bool _par; 2981 VerifyOption _vo; 2982 bool _failures; 2983 public: 2984 // _vo == UsePrevMarking -> use "prev" marking information, 2985 // _vo == UseNextMarking -> use "next" marking information, 2986 // _vo == UseMarkWord -> use mark word from object header. 2987 VerifyRegionClosure(bool par, VerifyOption vo) 2988 : _par(par), 2989 _vo(vo), 2990 _failures(false) {} 2991 2992 bool failures() { 2993 return _failures; 2994 } 2995 2996 bool doHeapRegion(HeapRegion* r) { 2997 // For archive regions, verify there are no heap pointers to 2998 // non-pinned regions. For all others, verify liveness info. 2999 if (r->is_archive()) { 3000 VerifyArchiveRegionClosure verify_oop_pointers(r); 3001 r->object_iterate(&verify_oop_pointers); 3002 return true; 3003 } 3004 if (!r->is_continues_humongous()) { 3005 bool failures = false; 3006 r->verify(_vo, &failures); 3007 if (failures) { 3008 _failures = true; 3009 } else if (!r->is_starts_humongous()) { 3010 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 3011 r->object_iterate(¬_dead_yet_cl); 3012 if (_vo != VerifyOption_G1UseNextMarking) { 3013 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 3014 gclog_or_tty->print_cr("[" PTR_FORMAT "," PTR_FORMAT "] " 3015 "max_live_bytes " SIZE_FORMAT " " 3016 "< calculated " SIZE_FORMAT, 3017 p2i(r->bottom()), p2i(r->end()), 3018 r->max_live_bytes(), 3019 not_dead_yet_cl.live_bytes()); 3020 _failures = true; 3021 } 3022 } else { 3023 // When vo == UseNextMarking we cannot currently do a sanity 3024 // check on the live bytes as the calculation has not been 3025 // finalized yet. 3026 } 3027 } 3028 } 3029 return false; // stop the region iteration if we hit a failure 3030 } 3031 }; 3032 3033 // This is the task used for parallel verification of the heap regions 3034 3035 class G1ParVerifyTask: public AbstractGangTask { 3036 private: 3037 G1CollectedHeap* _g1h; 3038 VerifyOption _vo; 3039 bool _failures; 3040 HeapRegionClaimer _hrclaimer; 3041 3042 public: 3043 // _vo == UsePrevMarking -> use "prev" marking information, 3044 // _vo == UseNextMarking -> use "next" marking information, 3045 // _vo == UseMarkWord -> use mark word from object header. 3046 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3047 AbstractGangTask("Parallel verify task"), 3048 _g1h(g1h), 3049 _vo(vo), 3050 _failures(false), 3051 _hrclaimer(g1h->workers()->active_workers()) {} 3052 3053 bool failures() { 3054 return _failures; 3055 } 3056 3057 void work(uint worker_id) { 3058 HandleMark hm; 3059 VerifyRegionClosure blk(true, _vo); 3060 _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer); 3061 if (blk.failures()) { 3062 _failures = true; 3063 } 3064 } 3065 }; 3066 3067 void G1CollectedHeap::verify(bool silent, VerifyOption vo) { 3068 if (SafepointSynchronize::is_at_safepoint()) { 3069 assert(Thread::current()->is_VM_thread(), 3070 "Expected to be executed serially by the VM thread at this point"); 3071 3072 if (!silent) { gclog_or_tty->print("Roots "); } 3073 VerifyRootsClosure rootsCl(vo); 3074 VerifyKlassClosure klassCl(this, &rootsCl); 3075 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false); 3076 3077 // We apply the relevant closures to all the oops in the 3078 // system dictionary, class loader data graph, the string table 3079 // and the nmethods in the code cache. 3080 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo); 3081 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl); 3082 3083 { 3084 G1RootProcessor root_processor(this, 1); 3085 root_processor.process_all_roots(&rootsCl, 3086 &cldCl, 3087 &blobsCl); 3088 } 3089 3090 bool failures = rootsCl.failures() || codeRootsCl.failures(); 3091 3092 if (vo != VerifyOption_G1UseMarkWord) { 3093 // If we're verifying during a full GC then the region sets 3094 // will have been torn down at the start of the GC. Therefore 3095 // verifying the region sets will fail. So we only verify 3096 // the region sets when not in a full GC. 3097 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3098 verify_region_sets(); 3099 } 3100 3101 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3102 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3103 3104 G1ParVerifyTask task(this, vo); 3105 workers()->run_task(&task); 3106 if (task.failures()) { 3107 failures = true; 3108 } 3109 3110 } else { 3111 VerifyRegionClosure blk(false, vo); 3112 heap_region_iterate(&blk); 3113 if (blk.failures()) { 3114 failures = true; 3115 } 3116 } 3117 3118 if (G1StringDedup::is_enabled()) { 3119 if (!silent) gclog_or_tty->print("StrDedup "); 3120 G1StringDedup::verify(); 3121 } 3122 3123 if (failures) { 3124 gclog_or_tty->print_cr("Heap:"); 3125 // It helps to have the per-region information in the output to 3126 // help us track down what went wrong. This is why we call 3127 // print_extended_on() instead of print_on(). 3128 print_extended_on(gclog_or_tty); 3129 gclog_or_tty->cr(); 3130 gclog_or_tty->flush(); 3131 } 3132 guarantee(!failures, "there should not have been any failures"); 3133 } else { 3134 if (!silent) { 3135 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet"); 3136 if (G1StringDedup::is_enabled()) { 3137 gclog_or_tty->print(", StrDedup"); 3138 } 3139 gclog_or_tty->print(") "); 3140 } 3141 } 3142 } 3143 3144 void G1CollectedHeap::verify(bool silent) { 3145 verify(silent, VerifyOption_G1UsePrevMarking); 3146 } 3147 3148 double G1CollectedHeap::verify(bool guard, const char* msg) { 3149 double verify_time_ms = 0.0; 3150 3151 if (guard && total_collections() >= VerifyGCStartAt) { 3152 double verify_start = os::elapsedTime(); 3153 HandleMark hm; // Discard invalid handles created during verification 3154 prepare_for_verify(); 3155 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 3156 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 3157 } 3158 3159 return verify_time_ms; 3160 } 3161 3162 void G1CollectedHeap::verify_before_gc() { 3163 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:"); 3164 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 3165 } 3166 3167 void G1CollectedHeap::verify_after_gc() { 3168 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:"); 3169 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 3170 } 3171 3172 class PrintRegionClosure: public HeapRegionClosure { 3173 outputStream* _st; 3174 public: 3175 PrintRegionClosure(outputStream* st) : _st(st) {} 3176 bool doHeapRegion(HeapRegion* r) { 3177 r->print_on(_st); 3178 return false; 3179 } 3180 }; 3181 3182 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3183 const HeapRegion* hr, 3184 const VerifyOption vo) const { 3185 switch (vo) { 3186 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 3187 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 3188 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 3189 default: ShouldNotReachHere(); 3190 } 3191 return false; // keep some compilers happy 3192 } 3193 3194 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3195 const VerifyOption vo) const { 3196 switch (vo) { 3197 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 3198 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 3199 case VerifyOption_G1UseMarkWord: { 3200 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 3201 return !obj->is_gc_marked() && !hr->is_archive(); 3202 } 3203 default: ShouldNotReachHere(); 3204 } 3205 return false; // keep some compilers happy 3206 } 3207 3208 void G1CollectedHeap::print_on(outputStream* st) const { 3209 st->print(" %-20s", "garbage-first heap"); 3210 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3211 capacity()/K, used_unlocked()/K); 3212 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 3213 p2i(_hrm.reserved().start()), 3214 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 3215 p2i(_hrm.reserved().end())); 3216 st->cr(); 3217 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3218 uint young_regions = _young_list->length(); 3219 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3220 (size_t) young_regions * HeapRegion::GrainBytes / K); 3221 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3222 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3223 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3224 st->cr(); 3225 MetaspaceAux::print_on(st); 3226 } 3227 3228 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3229 print_on(st); 3230 3231 // Print the per-region information. 3232 st->cr(); 3233 st->print_cr("Heap Regions: (E=young(eden), S=young(survivor), O=old, " 3234 "HS=humongous(starts), HC=humongous(continues), " 3235 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 3236 "PTAMS=previous top-at-mark-start, " 3237 "NTAMS=next top-at-mark-start)"); 3238 PrintRegionClosure blk(st); 3239 heap_region_iterate(&blk); 3240 } 3241 3242 void G1CollectedHeap::print_on_error(outputStream* st) const { 3243 this->CollectedHeap::print_on_error(st); 3244 3245 if (_cm != NULL) { 3246 st->cr(); 3247 _cm->print_on_error(st); 3248 } 3249 } 3250 3251 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3252 workers()->print_worker_threads_on(st); 3253 _cmThread->print_on(st); 3254 st->cr(); 3255 _cm->print_worker_threads_on(st); 3256 _cg1r->print_worker_threads_on(st); 3257 if (G1StringDedup::is_enabled()) { 3258 G1StringDedup::print_worker_threads_on(st); 3259 } 3260 } 3261 3262 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3263 workers()->threads_do(tc); 3264 tc->do_thread(_cmThread); 3265 _cg1r->threads_do(tc); 3266 if (G1StringDedup::is_enabled()) { 3267 G1StringDedup::threads_do(tc); 3268 } 3269 } 3270 3271 void G1CollectedHeap::print_tracing_info() const { 3272 // We'll overload this to mean "trace GC pause statistics." 3273 if (TraceYoungGenTime || TraceOldGenTime) { 3274 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3275 // to that. 3276 g1_policy()->print_tracing_info(); 3277 } 3278 if (G1SummarizeRSetStats) { 3279 g1_rem_set()->print_summary_info(); 3280 } 3281 if (G1SummarizeConcMark) { 3282 concurrent_mark()->print_summary_info(); 3283 } 3284 g1_policy()->print_yg_surv_rate_info(); 3285 } 3286 3287 #ifndef PRODUCT 3288 // Helpful for debugging RSet issues. 3289 3290 class PrintRSetsClosure : public HeapRegionClosure { 3291 private: 3292 const char* _msg; 3293 size_t _occupied_sum; 3294 3295 public: 3296 bool doHeapRegion(HeapRegion* r) { 3297 HeapRegionRemSet* hrrs = r->rem_set(); 3298 size_t occupied = hrrs->occupied(); 3299 _occupied_sum += occupied; 3300 3301 gclog_or_tty->print_cr("Printing RSet for region " HR_FORMAT, 3302 HR_FORMAT_PARAMS(r)); 3303 if (occupied == 0) { 3304 gclog_or_tty->print_cr(" RSet is empty"); 3305 } else { 3306 hrrs->print(); 3307 } 3308 gclog_or_tty->print_cr("----------"); 3309 return false; 3310 } 3311 3312 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3313 gclog_or_tty->cr(); 3314 gclog_or_tty->print_cr("========================================"); 3315 gclog_or_tty->print_cr("%s", msg); 3316 gclog_or_tty->cr(); 3317 } 3318 3319 ~PrintRSetsClosure() { 3320 gclog_or_tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 3321 gclog_or_tty->print_cr("========================================"); 3322 gclog_or_tty->cr(); 3323 } 3324 }; 3325 3326 void G1CollectedHeap::print_cset_rsets() { 3327 PrintRSetsClosure cl("Printing CSet RSets"); 3328 collection_set_iterate(&cl); 3329 } 3330 3331 void G1CollectedHeap::print_all_rsets() { 3332 PrintRSetsClosure cl("Printing All RSets");; 3333 heap_region_iterate(&cl); 3334 } 3335 #endif // PRODUCT 3336 3337 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 3338 YoungList* young_list = heap()->young_list(); 3339 3340 size_t eden_used_bytes = young_list->eden_used_bytes(); 3341 size_t survivor_used_bytes = young_list->survivor_used_bytes(); 3342 3343 size_t eden_capacity_bytes = 3344 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 3345 3346 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 3347 return G1HeapSummary(heap_summary, used(), eden_used_bytes, eden_capacity_bytes, survivor_used_bytes); 3348 } 3349 3350 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 3351 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 3352 stats->unused(), stats->used(), stats->region_end_waste(), 3353 stats->regions_filled(), stats->direct_allocated(), 3354 stats->failure_used(), stats->failure_waste()); 3355 } 3356 3357 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 3358 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 3359 gc_tracer->report_gc_heap_summary(when, heap_summary); 3360 3361 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 3362 gc_tracer->report_metaspace_summary(when, metaspace_summary); 3363 } 3364 3365 3366 G1CollectedHeap* G1CollectedHeap::heap() { 3367 CollectedHeap* heap = Universe::heap(); 3368 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 3369 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 3370 return (G1CollectedHeap*)heap; 3371 } 3372 3373 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3374 // always_do_update_barrier = false; 3375 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3376 // Fill TLAB's and such 3377 accumulate_statistics_all_tlabs(); 3378 ensure_parsability(true); 3379 3380 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) && 3381 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 3382 g1_rem_set()->print_periodic_summary_info("Before GC RS summary"); 3383 } 3384 } 3385 3386 void G1CollectedHeap::gc_epilogue(bool full) { 3387 3388 if (G1SummarizeRSetStats && 3389 (G1SummarizeRSetStatsPeriod > 0) && 3390 // we are at the end of the GC. Total collections has already been increased. 3391 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) { 3392 g1_rem_set()->print_periodic_summary_info("After GC RS summary"); 3393 } 3394 3395 // FIXME: what is this about? 3396 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3397 // is set. 3398 #if defined(COMPILER2) || INCLUDE_JVMCI 3399 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 3400 #endif 3401 // always_do_update_barrier = true; 3402 3403 resize_all_tlabs(); 3404 allocation_context_stats().update(full); 3405 3406 // We have just completed a GC. Update the soft reference 3407 // policy with the new heap occupancy 3408 Universe::update_heap_info_at_gc(); 3409 } 3410 3411 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3412 uint gc_count_before, 3413 bool* succeeded, 3414 GCCause::Cause gc_cause) { 3415 assert_heap_not_locked_and_not_at_safepoint(); 3416 g1_policy()->record_stop_world_start(); 3417 VM_G1IncCollectionPause op(gc_count_before, 3418 word_size, 3419 false, /* should_initiate_conc_mark */ 3420 g1_policy()->max_pause_time_ms(), 3421 gc_cause); 3422 3423 op.set_allocation_context(AllocationContext::current()); 3424 VMThread::execute(&op); 3425 3426 HeapWord* result = op.result(); 3427 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3428 assert(result == NULL || ret_succeeded, 3429 "the result should be NULL if the VM did not succeed"); 3430 *succeeded = ret_succeeded; 3431 3432 assert_heap_not_locked(); 3433 return result; 3434 } 3435 3436 void 3437 G1CollectedHeap::doConcurrentMark() { 3438 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3439 if (!_cmThread->in_progress()) { 3440 _cmThread->set_started(); 3441 CGC_lock->notify(); 3442 } 3443 } 3444 3445 size_t G1CollectedHeap::pending_card_num() { 3446 size_t extra_cards = 0; 3447 JavaThread *curr = Threads::first(); 3448 while (curr != NULL) { 3449 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3450 extra_cards += dcq.size(); 3451 curr = curr->next(); 3452 } 3453 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3454 size_t buffer_size = dcqs.buffer_size(); 3455 size_t buffer_num = dcqs.completed_buffers_num(); 3456 3457 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3458 // in bytes - not the number of 'entries'. We need to convert 3459 // into a number of cards. 3460 return (buffer_size * buffer_num + extra_cards) / oopSize; 3461 } 3462 3463 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 3464 private: 3465 size_t _total_humongous; 3466 size_t _candidate_humongous; 3467 3468 DirtyCardQueue _dcq; 3469 3470 // We don't nominate objects with many remembered set entries, on 3471 // the assumption that such objects are likely still live. 3472 bool is_remset_small(HeapRegion* region) const { 3473 HeapRegionRemSet* const rset = region->rem_set(); 3474 return G1EagerReclaimHumongousObjectsWithStaleRefs 3475 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 3476 : rset->is_empty(); 3477 } 3478 3479 bool is_typeArray_region(HeapRegion* region) const { 3480 return oop(region->bottom())->is_typeArray(); 3481 } 3482 3483 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 3484 assert(region->is_starts_humongous(), "Must start a humongous object"); 3485 3486 // Candidate selection must satisfy the following constraints 3487 // while concurrent marking is in progress: 3488 // 3489 // * In order to maintain SATB invariants, an object must not be 3490 // reclaimed if it was allocated before the start of marking and 3491 // has not had its references scanned. Such an object must have 3492 // its references (including type metadata) scanned to ensure no 3493 // live objects are missed by the marking process. Objects 3494 // allocated after the start of concurrent marking don't need to 3495 // be scanned. 3496 // 3497 // * An object must not be reclaimed if it is on the concurrent 3498 // mark stack. Objects allocated after the start of concurrent 3499 // marking are never pushed on the mark stack. 3500 // 3501 // Nominating only objects allocated after the start of concurrent 3502 // marking is sufficient to meet both constraints. This may miss 3503 // some objects that satisfy the constraints, but the marking data 3504 // structures don't support efficiently performing the needed 3505 // additional tests or scrubbing of the mark stack. 3506 // 3507 // However, we presently only nominate is_typeArray() objects. 3508 // A humongous object containing references induces remembered 3509 // set entries on other regions. In order to reclaim such an 3510 // object, those remembered sets would need to be cleaned up. 3511 // 3512 // We also treat is_typeArray() objects specially, allowing them 3513 // to be reclaimed even if allocated before the start of 3514 // concurrent mark. For this we rely on mark stack insertion to 3515 // exclude is_typeArray() objects, preventing reclaiming an object 3516 // that is in the mark stack. We also rely on the metadata for 3517 // such objects to be built-in and so ensured to be kept live. 3518 // Frequent allocation and drop of large binary blobs is an 3519 // important use case for eager reclaim, and this special handling 3520 // may reduce needed headroom. 3521 3522 return is_typeArray_region(region) && is_remset_small(region); 3523 } 3524 3525 public: 3526 RegisterHumongousWithInCSetFastTestClosure() 3527 : _total_humongous(0), 3528 _candidate_humongous(0), 3529 _dcq(&JavaThread::dirty_card_queue_set()) { 3530 } 3531 3532 virtual bool doHeapRegion(HeapRegion* r) { 3533 if (!r->is_starts_humongous()) { 3534 return false; 3535 } 3536 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3537 3538 bool is_candidate = humongous_region_is_candidate(g1h, r); 3539 uint rindex = r->hrm_index(); 3540 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 3541 if (is_candidate) { 3542 _candidate_humongous++; 3543 g1h->register_humongous_region_with_cset(rindex); 3544 // Is_candidate already filters out humongous object with large remembered sets. 3545 // If we have a humongous object with a few remembered sets, we simply flush these 3546 // remembered set entries into the DCQS. That will result in automatic 3547 // re-evaluation of their remembered set entries during the following evacuation 3548 // phase. 3549 if (!r->rem_set()->is_empty()) { 3550 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 3551 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 3552 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 3553 HeapRegionRemSetIterator hrrs(r->rem_set()); 3554 size_t card_index; 3555 while (hrrs.has_next(card_index)) { 3556 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 3557 // The remembered set might contain references to already freed 3558 // regions. Filter out such entries to avoid failing card table 3559 // verification. 3560 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 3561 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 3562 *card_ptr = CardTableModRefBS::dirty_card_val(); 3563 _dcq.enqueue(card_ptr); 3564 } 3565 } 3566 } 3567 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 3568 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 3569 hrrs.n_yielded(), r->rem_set()->occupied()); 3570 r->rem_set()->clear_locked(); 3571 } 3572 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 3573 } 3574 _total_humongous++; 3575 3576 return false; 3577 } 3578 3579 size_t total_humongous() const { return _total_humongous; } 3580 size_t candidate_humongous() const { return _candidate_humongous; } 3581 3582 void flush_rem_set_entries() { _dcq.flush(); } 3583 }; 3584 3585 void G1CollectedHeap::register_humongous_regions_with_cset() { 3586 if (!G1EagerReclaimHumongousObjects) { 3587 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 3588 return; 3589 } 3590 double time = os::elapsed_counter(); 3591 3592 // Collect reclaim candidate information and register candidates with cset. 3593 RegisterHumongousWithInCSetFastTestClosure cl; 3594 heap_region_iterate(&cl); 3595 3596 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 3597 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 3598 cl.total_humongous(), 3599 cl.candidate_humongous()); 3600 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3601 3602 // Finally flush all remembered set entries to re-check into the global DCQS. 3603 cl.flush_rem_set_entries(); 3604 } 3605 3606 #ifdef ASSERT 3607 class VerifyCSetClosure: public HeapRegionClosure { 3608 public: 3609 bool doHeapRegion(HeapRegion* hr) { 3610 // Here we check that the CSet region's RSet is ready for parallel 3611 // iteration. The fields that we'll verify are only manipulated 3612 // when the region is part of a CSet and is collected. Afterwards, 3613 // we reset these fields when we clear the region's RSet (when the 3614 // region is freed) so they are ready when the region is 3615 // re-allocated. The only exception to this is if there's an 3616 // evacuation failure and instead of freeing the region we leave 3617 // it in the heap. In that case, we reset these fields during 3618 // evacuation failure handling. 3619 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3620 3621 // Here's a good place to add any other checks we'd like to 3622 // perform on CSet regions. 3623 return false; 3624 } 3625 }; 3626 #endif // ASSERT 3627 3628 uint G1CollectedHeap::num_task_queues() const { 3629 return _task_queues->size(); 3630 } 3631 3632 #if TASKQUEUE_STATS 3633 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3634 st->print_raw_cr("GC Task Stats"); 3635 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3636 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3637 } 3638 3639 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3640 print_taskqueue_stats_hdr(st); 3641 3642 TaskQueueStats totals; 3643 const uint n = num_task_queues(); 3644 for (uint i = 0; i < n; ++i) { 3645 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 3646 totals += task_queue(i)->stats; 3647 } 3648 st->print_raw("tot "); totals.print(st); st->cr(); 3649 3650 DEBUG_ONLY(totals.verify()); 3651 } 3652 3653 void G1CollectedHeap::reset_taskqueue_stats() { 3654 const uint n = num_task_queues(); 3655 for (uint i = 0; i < n; ++i) { 3656 task_queue(i)->stats.reset(); 3657 } 3658 } 3659 #endif // TASKQUEUE_STATS 3660 3661 void G1CollectedHeap::log_gc_header() { 3662 if (!G1Log::fine()) { 3663 return; 3664 } 3665 3666 gclog_or_tty->gclog_stamp(); 3667 3668 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) 3669 .append(collector_state()->gcs_are_young() ? "(young)" : "(mixed)") 3670 .append(collector_state()->during_initial_mark_pause() ? " (initial-mark)" : ""); 3671 3672 gclog_or_tty->print("[%s", (const char*)gc_cause_str); 3673 } 3674 3675 void G1CollectedHeap::log_gc_footer(double pause_time_sec) { 3676 if (!G1Log::fine()) { 3677 return; 3678 } 3679 3680 if (G1Log::finer()) { 3681 if (evacuation_failed()) { 3682 gclog_or_tty->print(" (to-space exhausted)"); 3683 } 3684 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3685 g1_policy()->print_phases(pause_time_sec); 3686 g1_policy()->print_detailed_heap_transition(); 3687 } else { 3688 if (evacuation_failed()) { 3689 gclog_or_tty->print("--"); 3690 } 3691 g1_policy()->print_heap_transition(); 3692 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3693 } 3694 gclog_or_tty->flush(); 3695 } 3696 3697 void G1CollectedHeap::wait_for_root_region_scanning() { 3698 double scan_wait_start = os::elapsedTime(); 3699 // We have to wait until the CM threads finish scanning the 3700 // root regions as it's the only way to ensure that all the 3701 // objects on them have been correctly scanned before we start 3702 // moving them during the GC. 3703 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3704 double wait_time_ms = 0.0; 3705 if (waited) { 3706 double scan_wait_end = os::elapsedTime(); 3707 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3708 } 3709 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3710 } 3711 3712 bool 3713 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3714 assert_at_safepoint(true /* should_be_vm_thread */); 3715 guarantee(!is_gc_active(), "collection is not reentrant"); 3716 3717 if (GC_locker::check_active_before_gc()) { 3718 return false; 3719 } 3720 3721 _gc_timer_stw->register_gc_start(); 3722 3723 GCIdMark gc_id_mark; 3724 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3725 3726 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3727 ResourceMark rm; 3728 3729 wait_for_root_region_scanning(); 3730 3731 G1Log::update_level(); 3732 print_heap_before_gc(); 3733 trace_heap_before_gc(_gc_tracer_stw); 3734 3735 verify_region_sets_optional(); 3736 verify_dirty_young_regions(); 3737 3738 // This call will decide whether this pause is an initial-mark 3739 // pause. If it is, during_initial_mark_pause() will return true 3740 // for the duration of this pause. 3741 g1_policy()->decide_on_conc_mark_initiation(); 3742 3743 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3744 assert(!collector_state()->during_initial_mark_pause() || 3745 collector_state()->gcs_are_young(), "sanity"); 3746 3747 // We also do not allow mixed GCs during marking. 3748 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3749 3750 // Record whether this pause is an initial mark. When the current 3751 // thread has completed its logging output and it's safe to signal 3752 // the CM thread, the flag's value in the policy has been reset. 3753 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3754 3755 // Inner scope for scope based logging, timers, and stats collection 3756 { 3757 EvacuationInfo evacuation_info; 3758 3759 if (collector_state()->during_initial_mark_pause()) { 3760 // We are about to start a marking cycle, so we increment the 3761 // full collection counter. 3762 increment_old_marking_cycles_started(); 3763 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3764 } 3765 3766 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3767 3768 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 3769 3770 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3771 workers()->active_workers(), 3772 Threads::number_of_non_daemon_threads()); 3773 workers()->set_active_workers(active_workers); 3774 3775 double pause_start_sec = os::elapsedTime(); 3776 g1_policy()->note_gc_start(active_workers); 3777 log_gc_header(); 3778 3779 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3780 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3781 3782 // If the secondary_free_list is not empty, append it to the 3783 // free_list. No need to wait for the cleanup operation to finish; 3784 // the region allocation code will check the secondary_free_list 3785 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3786 // set, skip this step so that the region allocation code has to 3787 // get entries from the secondary_free_list. 3788 if (!G1StressConcRegionFreeing) { 3789 append_secondary_free_list_if_not_empty_with_lock(); 3790 } 3791 3792 assert(check_young_list_well_formed(), "young list should be well formed"); 3793 3794 // Don't dynamically change the number of GC threads this early. A value of 3795 // 0 is used to indicate serial work. When parallel work is done, 3796 // it will be set. 3797 3798 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3799 IsGCActiveMark x; 3800 3801 gc_prologue(false); 3802 increment_total_collections(false /* full gc */); 3803 increment_gc_time_stamp(); 3804 3805 verify_before_gc(); 3806 3807 check_bitmaps("GC Start"); 3808 3809 #if defined(COMPILER2) || INCLUDE_JVMCI 3810 DerivedPointerTable::clear(); 3811 #endif 3812 3813 // Please see comment in g1CollectedHeap.hpp and 3814 // G1CollectedHeap::ref_processing_init() to see how 3815 // reference processing currently works in G1. 3816 3817 // Enable discovery in the STW reference processor 3818 ref_processor_stw()->enable_discovery(); 3819 3820 { 3821 // We want to temporarily turn off discovery by the 3822 // CM ref processor, if necessary, and turn it back on 3823 // on again later if we do. Using a scoped 3824 // NoRefDiscovery object will do this. 3825 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3826 3827 // Forget the current alloc region (we might even choose it to be part 3828 // of the collection set!). 3829 _allocator->release_mutator_alloc_region(); 3830 3831 // We should call this after we retire the mutator alloc 3832 // region(s) so that all the ALLOC / RETIRE events are generated 3833 // before the start GC event. 3834 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 3835 3836 // This timing is only used by the ergonomics to handle our pause target. 3837 // It is unclear why this should not include the full pause. We will 3838 // investigate this in CR 7178365. 3839 // 3840 // Preserving the old comment here if that helps the investigation: 3841 // 3842 // The elapsed time induced by the start time below deliberately elides 3843 // the possible verification above. 3844 double sample_start_time_sec = os::elapsedTime(); 3845 3846 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3847 3848 if (collector_state()->during_initial_mark_pause()) { 3849 concurrent_mark()->checkpointRootsInitialPre(); 3850 } 3851 3852 double time_remaining_ms = g1_policy()->finalize_young_cset_part(target_pause_time_ms); 3853 g1_policy()->finalize_old_cset_part(time_remaining_ms); 3854 3855 evacuation_info.set_collectionset_regions(g1_policy()->cset_region_length()); 3856 3857 // Make sure the remembered sets are up to date. This needs to be 3858 // done before register_humongous_regions_with_cset(), because the 3859 // remembered sets are used there to choose eager reclaim candidates. 3860 // If the remembered sets are not up to date we might miss some 3861 // entries that need to be handled. 3862 g1_rem_set()->cleanupHRRS(); 3863 3864 register_humongous_regions_with_cset(); 3865 3866 assert(check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3867 3868 _cm->note_start_of_gc(); 3869 // We call this after finalize_cset() to 3870 // ensure that the CSet has been finalized. 3871 _cm->verify_no_cset_oops(); 3872 3873 if (_hr_printer.is_active()) { 3874 HeapRegion* hr = g1_policy()->collection_set(); 3875 while (hr != NULL) { 3876 _hr_printer.cset(hr); 3877 hr = hr->next_in_collection_set(); 3878 } 3879 } 3880 3881 #ifdef ASSERT 3882 VerifyCSetClosure cl; 3883 collection_set_iterate(&cl); 3884 #endif // ASSERT 3885 3886 // Initialize the GC alloc regions. 3887 _allocator->init_gc_alloc_regions(evacuation_info); 3888 3889 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), g1_policy()->young_cset_region_length()); 3890 pre_evacuate_collection_set(); 3891 3892 // Actually do the work... 3893 evacuate_collection_set(evacuation_info, &per_thread_states); 3894 3895 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3896 3897 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3898 free_collection_set(g1_policy()->collection_set(), evacuation_info, surviving_young_words); 3899 3900 eagerly_reclaim_humongous_regions(); 3901 3902 g1_policy()->clear_collection_set(); 3903 3904 // Start a new incremental collection set for the next pause. 3905 g1_policy()->start_incremental_cset_building(); 3906 3907 clear_cset_fast_test(); 3908 3909 _young_list->reset_sampled_info(); 3910 3911 // Don't check the whole heap at this point as the 3912 // GC alloc regions from this pause have been tagged 3913 // as survivors and moved on to the survivor list. 3914 // Survivor regions will fail the !is_young() check. 3915 assert(check_young_list_empty(false /* check_heap */), 3916 "young list should be empty"); 3917 3918 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3919 _young_list->first_survivor_region(), 3920 _young_list->last_survivor_region()); 3921 3922 _young_list->reset_auxilary_lists(); 3923 3924 if (evacuation_failed()) { 3925 set_used(recalculate_used()); 3926 if (_archive_allocator != NULL) { 3927 _archive_allocator->clear_used(); 3928 } 3929 for (uint i = 0; i < ParallelGCThreads; i++) { 3930 if (_evacuation_failed_info_array[i].has_failed()) { 3931 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3932 } 3933 } 3934 } else { 3935 // The "used" of the the collection set have already been subtracted 3936 // when they were freed. Add in the bytes evacuated. 3937 increase_used(g1_policy()->bytes_copied_during_gc()); 3938 } 3939 3940 if (collector_state()->during_initial_mark_pause()) { 3941 // We have to do this before we notify the CM threads that 3942 // they can start working to make sure that all the 3943 // appropriate initialization is done on the CM object. 3944 concurrent_mark()->checkpointRootsInitialPost(); 3945 collector_state()->set_mark_in_progress(true); 3946 // Note that we don't actually trigger the CM thread at 3947 // this point. We do that later when we're sure that 3948 // the current thread has completed its logging output. 3949 } 3950 3951 allocate_dummy_regions(); 3952 3953 _allocator->init_mutator_alloc_region(); 3954 3955 { 3956 size_t expand_bytes = g1_policy()->expansion_amount(); 3957 if (expand_bytes > 0) { 3958 size_t bytes_before = capacity(); 3959 // No need for an ergo verbose message here, 3960 // expansion_amount() does this when it returns a value > 0. 3961 double expand_ms; 3962 if (!expand(expand_bytes, &expand_ms)) { 3963 // We failed to expand the heap. Cannot do anything about it. 3964 } 3965 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3966 } 3967 } 3968 3969 // We redo the verification but now wrt to the new CSet which 3970 // has just got initialized after the previous CSet was freed. 3971 _cm->verify_no_cset_oops(); 3972 _cm->note_end_of_gc(); 3973 3974 // This timing is only used by the ergonomics to handle our pause target. 3975 // It is unclear why this should not include the full pause. We will 3976 // investigate this in CR 7178365. 3977 double sample_end_time_sec = os::elapsedTime(); 3978 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3979 size_t total_cards_scanned = per_thread_states.total_cards_scanned(); 3980 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned); 3981 3982 evacuation_info.set_collectionset_used_before(g1_policy()->collection_set_bytes_used_before()); 3983 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3984 3985 MemoryService::track_memory_usage(); 3986 3987 // In prepare_for_verify() below we'll need to scan the deferred 3988 // update buffers to bring the RSets up-to-date if 3989 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3990 // the update buffers we'll probably need to scan cards on the 3991 // regions we just allocated to (i.e., the GC alloc 3992 // regions). However, during the last GC we called 3993 // set_saved_mark() on all the GC alloc regions, so card 3994 // scanning might skip the [saved_mark_word()...top()] area of 3995 // those regions (i.e., the area we allocated objects into 3996 // during the last GC). But it shouldn't. Given that 3997 // saved_mark_word() is conditional on whether the GC time stamp 3998 // on the region is current or not, by incrementing the GC time 3999 // stamp here we invalidate all the GC time stamps on all the 4000 // regions and saved_mark_word() will simply return top() for 4001 // all the regions. This is a nicer way of ensuring this rather 4002 // than iterating over the regions and fixing them. In fact, the 4003 // GC time stamp increment here also ensures that 4004 // saved_mark_word() will return top() between pauses, i.e., 4005 // during concurrent refinement. So we don't need the 4006 // is_gc_active() check to decided which top to use when 4007 // scanning cards (see CR 7039627). 4008 increment_gc_time_stamp(); 4009 4010 verify_after_gc(); 4011 check_bitmaps("GC End"); 4012 4013 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 4014 ref_processor_stw()->verify_no_references_recorded(); 4015 4016 // CM reference discovery will be re-enabled if necessary. 4017 } 4018 4019 // We should do this after we potentially expand the heap so 4020 // that all the COMMIT events are generated before the end GC 4021 // event, and after we retire the GC alloc regions so that all 4022 // RETIRE events are generated before the end GC event. 4023 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 4024 4025 #ifdef TRACESPINNING 4026 ParallelTaskTerminator::print_termination_counts(); 4027 #endif 4028 4029 gc_epilogue(false); 4030 } 4031 4032 // Print the remainder of the GC log output. 4033 log_gc_footer(os::elapsedTime() - pause_start_sec); 4034 4035 // It is not yet to safe to tell the concurrent mark to 4036 // start as we have some optional output below. We don't want the 4037 // output from the concurrent mark thread interfering with this 4038 // logging output either. 4039 4040 _hrm.verify_optional(); 4041 verify_region_sets_optional(); 4042 4043 TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats()); 4044 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 4045 4046 print_heap_after_gc(); 4047 trace_heap_after_gc(_gc_tracer_stw); 4048 4049 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 4050 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 4051 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 4052 // before any GC notifications are raised. 4053 g1mm()->update_sizes(); 4054 4055 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 4056 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 4057 _gc_timer_stw->register_gc_end(); 4058 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 4059 } 4060 // It should now be safe to tell the concurrent mark thread to start 4061 // without its logging output interfering with the logging output 4062 // that came from the pause. 4063 4064 if (should_start_conc_mark) { 4065 // CAUTION: after the doConcurrentMark() call below, 4066 // the concurrent marking thread(s) could be running 4067 // concurrently with us. Make sure that anything after 4068 // this point does not assume that we are the only GC thread 4069 // running. Note: of course, the actual marking work will 4070 // not start until the safepoint itself is released in 4071 // SuspendibleThreadSet::desynchronize(). 4072 doConcurrentMark(); 4073 } 4074 4075 return true; 4076 } 4077 4078 void G1CollectedHeap::remove_self_forwarding_pointers() { 4079 double remove_self_forwards_start = os::elapsedTime(); 4080 4081 G1ParRemoveSelfForwardPtrsTask rsfp_task; 4082 workers()->run_task(&rsfp_task); 4083 4084 // Now restore saved marks, if any. 4085 for (uint i = 0; i < ParallelGCThreads; i++) { 4086 OopAndMarkOopStack& cur = _preserved_objs[i]; 4087 while (!cur.is_empty()) { 4088 OopAndMarkOop elem = cur.pop(); 4089 elem.set_mark(); 4090 } 4091 cur.clear(true); 4092 } 4093 4094 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 4095 } 4096 4097 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 4098 if (!_evacuation_failed) { 4099 _evacuation_failed = true; 4100 } 4101 4102 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 4103 4104 // We want to call the "for_promotion_failure" version only in the 4105 // case of a promotion failure. 4106 if (m->must_be_preserved_for_promotion_failure(obj)) { 4107 OopAndMarkOop elem(obj, m); 4108 _preserved_objs[worker_id].push(elem); 4109 } 4110 } 4111 4112 class G1ParEvacuateFollowersClosure : public VoidClosure { 4113 private: 4114 double _start_term; 4115 double _term_time; 4116 size_t _term_attempts; 4117 4118 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); } 4119 void end_term_time() { _term_time += os::elapsedTime() - _start_term; } 4120 protected: 4121 G1CollectedHeap* _g1h; 4122 G1ParScanThreadState* _par_scan_state; 4123 RefToScanQueueSet* _queues; 4124 ParallelTaskTerminator* _terminator; 4125 4126 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4127 RefToScanQueueSet* queues() { return _queues; } 4128 ParallelTaskTerminator* terminator() { return _terminator; } 4129 4130 public: 4131 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4132 G1ParScanThreadState* par_scan_state, 4133 RefToScanQueueSet* queues, 4134 ParallelTaskTerminator* terminator) 4135 : _g1h(g1h), _par_scan_state(par_scan_state), 4136 _queues(queues), _terminator(terminator), 4137 _start_term(0.0), _term_time(0.0), _term_attempts(0) {} 4138 4139 void do_void(); 4140 4141 double term_time() const { return _term_time; } 4142 size_t term_attempts() const { return _term_attempts; } 4143 4144 private: 4145 inline bool offer_termination(); 4146 }; 4147 4148 bool G1ParEvacuateFollowersClosure::offer_termination() { 4149 G1ParScanThreadState* const pss = par_scan_state(); 4150 start_term_time(); 4151 const bool res = terminator()->offer_termination(); 4152 end_term_time(); 4153 return res; 4154 } 4155 4156 void G1ParEvacuateFollowersClosure::do_void() { 4157 G1ParScanThreadState* const pss = par_scan_state(); 4158 pss->trim_queue(); 4159 do { 4160 pss->steal_and_trim_queue(queues()); 4161 } while (!offer_termination()); 4162 } 4163 4164 class G1ParTask : public AbstractGangTask { 4165 protected: 4166 G1CollectedHeap* _g1h; 4167 G1ParScanThreadStateSet* _pss; 4168 RefToScanQueueSet* _queues; 4169 G1RootProcessor* _root_processor; 4170 ParallelTaskTerminator _terminator; 4171 uint _n_workers; 4172 4173 public: 4174 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 4175 : AbstractGangTask("G1 collection"), 4176 _g1h(g1h), 4177 _pss(per_thread_states), 4178 _queues(task_queues), 4179 _root_processor(root_processor), 4180 _terminator(n_workers, _queues), 4181 _n_workers(n_workers) 4182 {} 4183 4184 void work(uint worker_id) { 4185 if (worker_id >= _n_workers) return; // no work needed this round 4186 4187 double start_sec = os::elapsedTime(); 4188 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 4189 4190 { 4191 ResourceMark rm; 4192 HandleMark hm; 4193 4194 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4195 4196 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4197 pss->set_ref_processor(rp); 4198 4199 double start_strong_roots_sec = os::elapsedTime(); 4200 4201 _root_processor->evacuate_roots(pss->closures(), worker_id); 4202 4203 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss); 4204 4205 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 4206 // treating the nmethods visited to act as roots for concurrent marking. 4207 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 4208 // objects copied by the current evacuation. 4209 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl, 4210 pss->closures()->weak_codeblobs(), 4211 worker_id); 4212 4213 _pss->add_cards_scanned(worker_id, cards_scanned); 4214 4215 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 4216 4217 double term_sec = 0.0; 4218 size_t evac_term_attempts = 0; 4219 { 4220 double start = os::elapsedTime(); 4221 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 4222 evac.do_void(); 4223 4224 evac_term_attempts = evac.term_attempts(); 4225 term_sec = evac.term_time(); 4226 double elapsed_sec = os::elapsedTime() - start; 4227 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 4228 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 4229 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 4230 } 4231 4232 assert(pss->queue_is_empty(), "should be empty"); 4233 4234 if (PrintTerminationStats) { 4235 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 4236 size_t lab_waste; 4237 size_t lab_undo_waste; 4238 pss->waste(lab_waste, lab_undo_waste); 4239 _g1h->print_termination_stats(gclog_or_tty, 4240 worker_id, 4241 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 4242 strong_roots_sec * 1000.0, /* strong roots time */ 4243 term_sec * 1000.0, /* evac term time */ 4244 evac_term_attempts, /* evac term attempts */ 4245 lab_waste, /* alloc buffer waste */ 4246 lab_undo_waste /* undo waste */ 4247 ); 4248 } 4249 4250 // Close the inner scope so that the ResourceMark and HandleMark 4251 // destructors are executed here and are included as part of the 4252 // "GC Worker Time". 4253 } 4254 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 4255 } 4256 }; 4257 4258 void G1CollectedHeap::print_termination_stats_hdr(outputStream* const st) { 4259 st->print_raw_cr("GC Termination Stats"); 4260 st->print_raw_cr(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 4261 st->print_raw_cr("thr ms ms % ms % attempts total alloc undo"); 4262 st->print_raw_cr("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 4263 } 4264 4265 void G1CollectedHeap::print_termination_stats(outputStream* const st, 4266 uint worker_id, 4267 double elapsed_ms, 4268 double strong_roots_ms, 4269 double term_ms, 4270 size_t term_attempts, 4271 size_t alloc_buffer_waste, 4272 size_t undo_waste) const { 4273 st->print_cr("%3d %9.2f %9.2f %6.2f " 4274 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 4275 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 4276 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 4277 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 4278 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 4279 alloc_buffer_waste * HeapWordSize / K, 4280 undo_waste * HeapWordSize / K); 4281 } 4282 4283 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 4284 private: 4285 BoolObjectClosure* _is_alive; 4286 int _initial_string_table_size; 4287 int _initial_symbol_table_size; 4288 4289 bool _process_strings; 4290 int _strings_processed; 4291 int _strings_removed; 4292 4293 bool _process_symbols; 4294 int _symbols_processed; 4295 int _symbols_removed; 4296 4297 public: 4298 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 4299 AbstractGangTask("String/Symbol Unlinking"), 4300 _is_alive(is_alive), 4301 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 4302 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 4303 4304 _initial_string_table_size = StringTable::the_table()->table_size(); 4305 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 4306 if (process_strings) { 4307 StringTable::clear_parallel_claimed_index(); 4308 } 4309 if (process_symbols) { 4310 SymbolTable::clear_parallel_claimed_index(); 4311 } 4312 } 4313 4314 ~G1StringSymbolTableUnlinkTask() { 4315 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 4316 "claim value %d after unlink less than initial string table size %d", 4317 StringTable::parallel_claimed_index(), _initial_string_table_size); 4318 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 4319 "claim value %d after unlink less than initial symbol table size %d", 4320 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 4321 4322 if (G1TraceStringSymbolTableScrubbing) { 4323 gclog_or_tty->print_cr("Cleaned string and symbol table, " 4324 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 4325 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 4326 strings_processed(), strings_removed(), 4327 symbols_processed(), symbols_removed()); 4328 } 4329 } 4330 4331 void work(uint worker_id) { 4332 int strings_processed = 0; 4333 int strings_removed = 0; 4334 int symbols_processed = 0; 4335 int symbols_removed = 0; 4336 if (_process_strings) { 4337 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 4338 Atomic::add(strings_processed, &_strings_processed); 4339 Atomic::add(strings_removed, &_strings_removed); 4340 } 4341 if (_process_symbols) { 4342 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 4343 Atomic::add(symbols_processed, &_symbols_processed); 4344 Atomic::add(symbols_removed, &_symbols_removed); 4345 } 4346 } 4347 4348 size_t strings_processed() const { return (size_t)_strings_processed; } 4349 size_t strings_removed() const { return (size_t)_strings_removed; } 4350 4351 size_t symbols_processed() const { return (size_t)_symbols_processed; } 4352 size_t symbols_removed() const { return (size_t)_symbols_removed; } 4353 }; 4354 4355 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 4356 private: 4357 static Monitor* _lock; 4358 4359 BoolObjectClosure* const _is_alive; 4360 const bool _unloading_occurred; 4361 const uint _num_workers; 4362 4363 // Variables used to claim nmethods. 4364 nmethod* _first_nmethod; 4365 volatile nmethod* _claimed_nmethod; 4366 4367 // The list of nmethods that need to be processed by the second pass. 4368 volatile nmethod* _postponed_list; 4369 volatile uint _num_entered_barrier; 4370 4371 public: 4372 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 4373 _is_alive(is_alive), 4374 _unloading_occurred(unloading_occurred), 4375 _num_workers(num_workers), 4376 _first_nmethod(NULL), 4377 _claimed_nmethod(NULL), 4378 _postponed_list(NULL), 4379 _num_entered_barrier(0) 4380 { 4381 nmethod::increase_unloading_clock(); 4382 // Get first alive nmethod 4383 NMethodIterator iter = NMethodIterator(); 4384 if(iter.next_alive()) { 4385 _first_nmethod = iter.method(); 4386 } 4387 _claimed_nmethod = (volatile nmethod*)_first_nmethod; 4388 } 4389 4390 ~G1CodeCacheUnloadingTask() { 4391 CodeCache::verify_clean_inline_caches(); 4392 4393 CodeCache::set_needs_cache_clean(false); 4394 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 4395 4396 CodeCache::verify_icholder_relocations(); 4397 } 4398 4399 private: 4400 void add_to_postponed_list(nmethod* nm) { 4401 nmethod* old; 4402 do { 4403 old = (nmethod*)_postponed_list; 4404 nm->set_unloading_next(old); 4405 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 4406 } 4407 4408 void clean_nmethod(nmethod* nm) { 4409 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 4410 4411 if (postponed) { 4412 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 4413 add_to_postponed_list(nm); 4414 } 4415 4416 // Mark that this thread has been cleaned/unloaded. 4417 // After this call, it will be safe to ask if this nmethod was unloaded or not. 4418 nm->set_unloading_clock(nmethod::global_unloading_clock()); 4419 } 4420 4421 void clean_nmethod_postponed(nmethod* nm) { 4422 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 4423 } 4424 4425 static const int MaxClaimNmethods = 16; 4426 4427 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) { 4428 nmethod* first; 4429 NMethodIterator last; 4430 4431 do { 4432 *num_claimed_nmethods = 0; 4433 4434 first = (nmethod*)_claimed_nmethod; 4435 last = NMethodIterator(first); 4436 4437 if (first != NULL) { 4438 4439 for (int i = 0; i < MaxClaimNmethods; i++) { 4440 if (!last.next_alive()) { 4441 break; 4442 } 4443 claimed_nmethods[i] = last.method(); 4444 (*num_claimed_nmethods)++; 4445 } 4446 } 4447 4448 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 4449 } 4450 4451 nmethod* claim_postponed_nmethod() { 4452 nmethod* claim; 4453 nmethod* next; 4454 4455 do { 4456 claim = (nmethod*)_postponed_list; 4457 if (claim == NULL) { 4458 return NULL; 4459 } 4460 4461 next = claim->unloading_next(); 4462 4463 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 4464 4465 return claim; 4466 } 4467 4468 public: 4469 // Mark that we're done with the first pass of nmethod cleaning. 4470 void barrier_mark(uint worker_id) { 4471 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4472 _num_entered_barrier++; 4473 if (_num_entered_barrier == _num_workers) { 4474 ml.notify_all(); 4475 } 4476 } 4477 4478 // See if we have to wait for the other workers to 4479 // finish their first-pass nmethod cleaning work. 4480 void barrier_wait(uint worker_id) { 4481 if (_num_entered_barrier < _num_workers) { 4482 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4483 while (_num_entered_barrier < _num_workers) { 4484 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 4485 } 4486 } 4487 } 4488 4489 // Cleaning and unloading of nmethods. Some work has to be postponed 4490 // to the second pass, when we know which nmethods survive. 4491 void work_first_pass(uint worker_id) { 4492 // The first nmethods is claimed by the first worker. 4493 if (worker_id == 0 && _first_nmethod != NULL) { 4494 clean_nmethod(_first_nmethod); 4495 _first_nmethod = NULL; 4496 } 4497 4498 int num_claimed_nmethods; 4499 nmethod* claimed_nmethods[MaxClaimNmethods]; 4500 4501 while (true) { 4502 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 4503 4504 if (num_claimed_nmethods == 0) { 4505 break; 4506 } 4507 4508 for (int i = 0; i < num_claimed_nmethods; i++) { 4509 clean_nmethod(claimed_nmethods[i]); 4510 } 4511 } 4512 } 4513 4514 void work_second_pass(uint worker_id) { 4515 nmethod* nm; 4516 // Take care of postponed nmethods. 4517 while ((nm = claim_postponed_nmethod()) != NULL) { 4518 clean_nmethod_postponed(nm); 4519 } 4520 } 4521 }; 4522 4523 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 4524 4525 class G1KlassCleaningTask : public StackObj { 4526 BoolObjectClosure* _is_alive; 4527 volatile jint _clean_klass_tree_claimed; 4528 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 4529 4530 public: 4531 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 4532 _is_alive(is_alive), 4533 _clean_klass_tree_claimed(0), 4534 _klass_iterator() { 4535 } 4536 4537 private: 4538 bool claim_clean_klass_tree_task() { 4539 if (_clean_klass_tree_claimed) { 4540 return false; 4541 } 4542 4543 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 4544 } 4545 4546 InstanceKlass* claim_next_klass() { 4547 Klass* klass; 4548 do { 4549 klass =_klass_iterator.next_klass(); 4550 } while (klass != NULL && !klass->is_instance_klass()); 4551 4552 // this can be null so don't call InstanceKlass::cast 4553 return static_cast<InstanceKlass*>(klass); 4554 } 4555 4556 public: 4557 4558 void clean_klass(InstanceKlass* ik) { 4559 ik->clean_weak_instanceklass_links(_is_alive); 4560 } 4561 4562 void work() { 4563 ResourceMark rm; 4564 4565 // One worker will clean the subklass/sibling klass tree. 4566 if (claim_clean_klass_tree_task()) { 4567 Klass::clean_subklass_tree(_is_alive); 4568 } 4569 4570 // All workers will help cleaning the classes, 4571 InstanceKlass* klass; 4572 while ((klass = claim_next_klass()) != NULL) { 4573 clean_klass(klass); 4574 } 4575 } 4576 }; 4577 4578 // To minimize the remark pause times, the tasks below are done in parallel. 4579 class G1ParallelCleaningTask : public AbstractGangTask { 4580 private: 4581 G1StringSymbolTableUnlinkTask _string_symbol_task; 4582 G1CodeCacheUnloadingTask _code_cache_task; 4583 G1KlassCleaningTask _klass_cleaning_task; 4584 4585 public: 4586 // The constructor is run in the VMThread. 4587 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 4588 AbstractGangTask("Parallel Cleaning"), 4589 _string_symbol_task(is_alive, process_strings, process_symbols), 4590 _code_cache_task(num_workers, is_alive, unloading_occurred), 4591 _klass_cleaning_task(is_alive) { 4592 } 4593 4594 // The parallel work done by all worker threads. 4595 void work(uint worker_id) { 4596 // Do first pass of code cache cleaning. 4597 _code_cache_task.work_first_pass(worker_id); 4598 4599 // Let the threads mark that the first pass is done. 4600 _code_cache_task.barrier_mark(worker_id); 4601 4602 // Clean the Strings and Symbols. 4603 _string_symbol_task.work(worker_id); 4604 4605 // Wait for all workers to finish the first code cache cleaning pass. 4606 _code_cache_task.barrier_wait(worker_id); 4607 4608 // Do the second code cache cleaning work, which realize on 4609 // the liveness information gathered during the first pass. 4610 _code_cache_task.work_second_pass(worker_id); 4611 4612 // Clean all klasses that were not unloaded. 4613 _klass_cleaning_task.work(); 4614 } 4615 }; 4616 4617 4618 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 4619 bool process_strings, 4620 bool process_symbols, 4621 bool class_unloading_occurred) { 4622 uint n_workers = workers()->active_workers(); 4623 4624 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 4625 n_workers, class_unloading_occurred); 4626 workers()->run_task(&g1_unlink_task); 4627 } 4628 4629 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 4630 bool process_strings, bool process_symbols) { 4631 { 4632 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 4633 workers()->run_task(&g1_unlink_task); 4634 } 4635 4636 if (G1StringDedup::is_enabled()) { 4637 G1StringDedup::unlink(is_alive); 4638 } 4639 } 4640 4641 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 4642 private: 4643 DirtyCardQueueSet* _queue; 4644 public: 4645 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { } 4646 4647 virtual void work(uint worker_id) { 4648 G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4649 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 4650 4651 RedirtyLoggedCardTableEntryClosure cl; 4652 _queue->par_apply_closure_to_all_completed_buffers(&cl); 4653 4654 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed()); 4655 } 4656 }; 4657 4658 void G1CollectedHeap::redirty_logged_cards() { 4659 double redirty_logged_cards_start = os::elapsedTime(); 4660 4661 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set()); 4662 dirty_card_queue_set().reset_for_par_iteration(); 4663 workers()->run_task(&redirty_task); 4664 4665 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 4666 dcq.merge_bufferlists(&dirty_card_queue_set()); 4667 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 4668 4669 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 4670 } 4671 4672 // Weak Reference Processing support 4673 4674 // An always "is_alive" closure that is used to preserve referents. 4675 // If the object is non-null then it's alive. Used in the preservation 4676 // of referent objects that are pointed to by reference objects 4677 // discovered by the CM ref processor. 4678 class G1AlwaysAliveClosure: public BoolObjectClosure { 4679 G1CollectedHeap* _g1; 4680 public: 4681 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4682 bool do_object_b(oop p) { 4683 if (p != NULL) { 4684 return true; 4685 } 4686 return false; 4687 } 4688 }; 4689 4690 bool G1STWIsAliveClosure::do_object_b(oop p) { 4691 // An object is reachable if it is outside the collection set, 4692 // or is inside and copied. 4693 return !_g1->is_in_cset(p) || p->is_forwarded(); 4694 } 4695 4696 // Non Copying Keep Alive closure 4697 class G1KeepAliveClosure: public OopClosure { 4698 G1CollectedHeap* _g1; 4699 public: 4700 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4701 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 4702 void do_oop(oop* p) { 4703 oop obj = *p; 4704 assert(obj != NULL, "the caller should have filtered out NULL values"); 4705 4706 const InCSetState cset_state = _g1->in_cset_state(obj); 4707 if (!cset_state.is_in_cset_or_humongous()) { 4708 return; 4709 } 4710 if (cset_state.is_in_cset()) { 4711 assert( obj->is_forwarded(), "invariant" ); 4712 *p = obj->forwardee(); 4713 } else { 4714 assert(!obj->is_forwarded(), "invariant" ); 4715 assert(cset_state.is_humongous(), 4716 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 4717 _g1->set_humongous_is_live(obj); 4718 } 4719 } 4720 }; 4721 4722 // Copying Keep Alive closure - can be called from both 4723 // serial and parallel code as long as different worker 4724 // threads utilize different G1ParScanThreadState instances 4725 // and different queues. 4726 4727 class G1CopyingKeepAliveClosure: public OopClosure { 4728 G1CollectedHeap* _g1h; 4729 OopClosure* _copy_non_heap_obj_cl; 4730 G1ParScanThreadState* _par_scan_state; 4731 4732 public: 4733 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4734 OopClosure* non_heap_obj_cl, 4735 G1ParScanThreadState* pss): 4736 _g1h(g1h), 4737 _copy_non_heap_obj_cl(non_heap_obj_cl), 4738 _par_scan_state(pss) 4739 {} 4740 4741 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4742 virtual void do_oop( oop* p) { do_oop_work(p); } 4743 4744 template <class T> void do_oop_work(T* p) { 4745 oop obj = oopDesc::load_decode_heap_oop(p); 4746 4747 if (_g1h->is_in_cset_or_humongous(obj)) { 4748 // If the referent object has been forwarded (either copied 4749 // to a new location or to itself in the event of an 4750 // evacuation failure) then we need to update the reference 4751 // field and, if both reference and referent are in the G1 4752 // heap, update the RSet for the referent. 4753 // 4754 // If the referent has not been forwarded then we have to keep 4755 // it alive by policy. Therefore we have copy the referent. 4756 // 4757 // If the reference field is in the G1 heap then we can push 4758 // on the PSS queue. When the queue is drained (after each 4759 // phase of reference processing) the object and it's followers 4760 // will be copied, the reference field set to point to the 4761 // new location, and the RSet updated. Otherwise we need to 4762 // use the the non-heap or metadata closures directly to copy 4763 // the referent object and update the pointer, while avoiding 4764 // updating the RSet. 4765 4766 if (_g1h->is_in_g1_reserved(p)) { 4767 _par_scan_state->push_on_queue(p); 4768 } else { 4769 assert(!Metaspace::contains((const void*)p), 4770 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4771 _copy_non_heap_obj_cl->do_oop(p); 4772 } 4773 } 4774 } 4775 }; 4776 4777 // Serial drain queue closure. Called as the 'complete_gc' 4778 // closure for each discovered list in some of the 4779 // reference processing phases. 4780 4781 class G1STWDrainQueueClosure: public VoidClosure { 4782 protected: 4783 G1CollectedHeap* _g1h; 4784 G1ParScanThreadState* _par_scan_state; 4785 4786 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4787 4788 public: 4789 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4790 _g1h(g1h), 4791 _par_scan_state(pss) 4792 { } 4793 4794 void do_void() { 4795 G1ParScanThreadState* const pss = par_scan_state(); 4796 pss->trim_queue(); 4797 } 4798 }; 4799 4800 // Parallel Reference Processing closures 4801 4802 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4803 // processing during G1 evacuation pauses. 4804 4805 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4806 private: 4807 G1CollectedHeap* _g1h; 4808 G1ParScanThreadStateSet* _pss; 4809 RefToScanQueueSet* _queues; 4810 WorkGang* _workers; 4811 uint _active_workers; 4812 4813 public: 4814 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4815 G1ParScanThreadStateSet* per_thread_states, 4816 WorkGang* workers, 4817 RefToScanQueueSet *task_queues, 4818 uint n_workers) : 4819 _g1h(g1h), 4820 _pss(per_thread_states), 4821 _queues(task_queues), 4822 _workers(workers), 4823 _active_workers(n_workers) 4824 { 4825 assert(n_workers > 0, "shouldn't call this otherwise"); 4826 } 4827 4828 // Executes the given task using concurrent marking worker threads. 4829 virtual void execute(ProcessTask& task); 4830 virtual void execute(EnqueueTask& task); 4831 }; 4832 4833 // Gang task for possibly parallel reference processing 4834 4835 class G1STWRefProcTaskProxy: public AbstractGangTask { 4836 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4837 ProcessTask& _proc_task; 4838 G1CollectedHeap* _g1h; 4839 G1ParScanThreadStateSet* _pss; 4840 RefToScanQueueSet* _task_queues; 4841 ParallelTaskTerminator* _terminator; 4842 4843 public: 4844 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4845 G1CollectedHeap* g1h, 4846 G1ParScanThreadStateSet* per_thread_states, 4847 RefToScanQueueSet *task_queues, 4848 ParallelTaskTerminator* terminator) : 4849 AbstractGangTask("Process reference objects in parallel"), 4850 _proc_task(proc_task), 4851 _g1h(g1h), 4852 _pss(per_thread_states), 4853 _task_queues(task_queues), 4854 _terminator(terminator) 4855 {} 4856 4857 virtual void work(uint worker_id) { 4858 // The reference processing task executed by a single worker. 4859 ResourceMark rm; 4860 HandleMark hm; 4861 4862 G1STWIsAliveClosure is_alive(_g1h); 4863 4864 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4865 pss->set_ref_processor(NULL); 4866 4867 // Keep alive closure. 4868 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4869 4870 // Complete GC closure 4871 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4872 4873 // Call the reference processing task's work routine. 4874 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4875 4876 // Note we cannot assert that the refs array is empty here as not all 4877 // of the processing tasks (specifically phase2 - pp2_work) execute 4878 // the complete_gc closure (which ordinarily would drain the queue) so 4879 // the queue may not be empty. 4880 } 4881 }; 4882 4883 // Driver routine for parallel reference processing. 4884 // Creates an instance of the ref processing gang 4885 // task and has the worker threads execute it. 4886 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4887 assert(_workers != NULL, "Need parallel worker threads."); 4888 4889 ParallelTaskTerminator terminator(_active_workers, _queues); 4890 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4891 4892 _workers->run_task(&proc_task_proxy); 4893 } 4894 4895 // Gang task for parallel reference enqueueing. 4896 4897 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4898 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4899 EnqueueTask& _enq_task; 4900 4901 public: 4902 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4903 AbstractGangTask("Enqueue reference objects in parallel"), 4904 _enq_task(enq_task) 4905 { } 4906 4907 virtual void work(uint worker_id) { 4908 _enq_task.work(worker_id); 4909 } 4910 }; 4911 4912 // Driver routine for parallel reference enqueueing. 4913 // Creates an instance of the ref enqueueing gang 4914 // task and has the worker threads execute it. 4915 4916 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4917 assert(_workers != NULL, "Need parallel worker threads."); 4918 4919 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4920 4921 _workers->run_task(&enq_task_proxy); 4922 } 4923 4924 // End of weak reference support closures 4925 4926 // Abstract task used to preserve (i.e. copy) any referent objects 4927 // that are in the collection set and are pointed to by reference 4928 // objects discovered by the CM ref processor. 4929 4930 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4931 protected: 4932 G1CollectedHeap* _g1h; 4933 G1ParScanThreadStateSet* _pss; 4934 RefToScanQueueSet* _queues; 4935 ParallelTaskTerminator _terminator; 4936 uint _n_workers; 4937 4938 public: 4939 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4940 AbstractGangTask("ParPreserveCMReferents"), 4941 _g1h(g1h), 4942 _pss(per_thread_states), 4943 _queues(task_queues), 4944 _terminator(workers, _queues), 4945 _n_workers(workers) 4946 { } 4947 4948 void work(uint worker_id) { 4949 ResourceMark rm; 4950 HandleMark hm; 4951 4952 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4953 pss->set_ref_processor(NULL); 4954 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4955 4956 // Is alive closure 4957 G1AlwaysAliveClosure always_alive(_g1h); 4958 4959 // Copying keep alive closure. Applied to referent objects that need 4960 // to be copied. 4961 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4962 4963 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4964 4965 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4966 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4967 4968 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4969 // So this must be true - but assert just in case someone decides to 4970 // change the worker ids. 4971 assert(worker_id < limit, "sanity"); 4972 assert(!rp->discovery_is_atomic(), "check this code"); 4973 4974 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4975 for (uint idx = worker_id; idx < limit; idx += stride) { 4976 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4977 4978 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4979 while (iter.has_next()) { 4980 // Since discovery is not atomic for the CM ref processor, we 4981 // can see some null referent objects. 4982 iter.load_ptrs(DEBUG_ONLY(true)); 4983 oop ref = iter.obj(); 4984 4985 // This will filter nulls. 4986 if (iter.is_referent_alive()) { 4987 iter.make_referent_alive(); 4988 } 4989 iter.move_to_next(); 4990 } 4991 } 4992 4993 // Drain the queue - which may cause stealing 4994 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4995 drain_queue.do_void(); 4996 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4997 assert(pss->queue_is_empty(), "should be"); 4998 } 4999 }; 5000 5001 // Weak Reference processing during an evacuation pause (part 1). 5002 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 5003 double ref_proc_start = os::elapsedTime(); 5004 5005 ReferenceProcessor* rp = _ref_processor_stw; 5006 assert(rp->discovery_enabled(), "should have been enabled"); 5007 5008 // Any reference objects, in the collection set, that were 'discovered' 5009 // by the CM ref processor should have already been copied (either by 5010 // applying the external root copy closure to the discovered lists, or 5011 // by following an RSet entry). 5012 // 5013 // But some of the referents, that are in the collection set, that these 5014 // reference objects point to may not have been copied: the STW ref 5015 // processor would have seen that the reference object had already 5016 // been 'discovered' and would have skipped discovering the reference, 5017 // but would not have treated the reference object as a regular oop. 5018 // As a result the copy closure would not have been applied to the 5019 // referent object. 5020 // 5021 // We need to explicitly copy these referent objects - the references 5022 // will be processed at the end of remarking. 5023 // 5024 // We also need to do this copying before we process the reference 5025 // objects discovered by the STW ref processor in case one of these 5026 // referents points to another object which is also referenced by an 5027 // object discovered by the STW ref processor. 5028 5029 uint no_of_gc_workers = workers()->active_workers(); 5030 5031 G1ParPreserveCMReferentsTask keep_cm_referents(this, 5032 per_thread_states, 5033 no_of_gc_workers, 5034 _task_queues); 5035 5036 workers()->run_task(&keep_cm_referents); 5037 5038 // Closure to test whether a referent is alive. 5039 G1STWIsAliveClosure is_alive(this); 5040 5041 // Even when parallel reference processing is enabled, the processing 5042 // of JNI refs is serial and performed serially by the current thread 5043 // rather than by a worker. The following PSS will be used for processing 5044 // JNI refs. 5045 5046 // Use only a single queue for this PSS. 5047 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 5048 pss->set_ref_processor(NULL); 5049 assert(pss->queue_is_empty(), "pre-condition"); 5050 5051 // Keep alive closure. 5052 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 5053 5054 // Serial Complete GC closure 5055 G1STWDrainQueueClosure drain_queue(this, pss); 5056 5057 // Setup the soft refs policy... 5058 rp->setup_policy(false); 5059 5060 ReferenceProcessorStats stats; 5061 if (!rp->processing_is_mt()) { 5062 // Serial reference processing... 5063 stats = rp->process_discovered_references(&is_alive, 5064 &keep_alive, 5065 &drain_queue, 5066 NULL, 5067 _gc_timer_stw); 5068 } else { 5069 // Parallel reference processing 5070 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5071 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5072 5073 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 5074 stats = rp->process_discovered_references(&is_alive, 5075 &keep_alive, 5076 &drain_queue, 5077 &par_task_executor, 5078 _gc_timer_stw); 5079 } 5080 5081 _gc_tracer_stw->report_gc_reference_stats(stats); 5082 5083 // We have completed copying any necessary live referent objects. 5084 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 5085 5086 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5087 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 5088 } 5089 5090 // Weak Reference processing during an evacuation pause (part 2). 5091 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 5092 double ref_enq_start = os::elapsedTime(); 5093 5094 ReferenceProcessor* rp = _ref_processor_stw; 5095 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5096 5097 // Now enqueue any remaining on the discovered lists on to 5098 // the pending list. 5099 if (!rp->processing_is_mt()) { 5100 // Serial reference processing... 5101 rp->enqueue_discovered_references(); 5102 } else { 5103 // Parallel reference enqueueing 5104 5105 uint n_workers = workers()->active_workers(); 5106 5107 assert(rp->num_q() == n_workers, "sanity"); 5108 assert(n_workers <= rp->max_num_q(), "sanity"); 5109 5110 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 5111 rp->enqueue_discovered_references(&par_task_executor); 5112 } 5113 5114 rp->verify_no_references_recorded(); 5115 assert(!rp->discovery_enabled(), "should have been disabled"); 5116 5117 // FIXME 5118 // CM's reference processing also cleans up the string and symbol tables. 5119 // Should we do that here also? We could, but it is a serial operation 5120 // and could significantly increase the pause time. 5121 5122 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5123 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5124 } 5125 5126 void G1CollectedHeap::pre_evacuate_collection_set() { 5127 _expand_heap_after_alloc_failure = true; 5128 _evacuation_failed = false; 5129 5130 // Disable the hot card cache. 5131 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5132 hot_card_cache->reset_hot_cache_claimed_index(); 5133 hot_card_cache->set_use_cache(false); 5134 5135 } 5136 5137 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 5138 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5139 5140 // Should G1EvacuationFailureALot be in effect for this GC? 5141 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5142 5143 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5144 double start_par_time_sec = os::elapsedTime(); 5145 double end_par_time_sec; 5146 5147 { 5148 const uint n_workers = workers()->active_workers(); 5149 G1RootProcessor root_processor(this, n_workers); 5150 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 5151 // InitialMark needs claim bits to keep track of the marked-through CLDs. 5152 if (collector_state()->during_initial_mark_pause()) { 5153 ClassLoaderDataGraph::clear_claimed_marks(); 5154 } 5155 5156 // The individual threads will set their evac-failure closures. 5157 if (PrintTerminationStats) { 5158 print_termination_stats_hdr(gclog_or_tty); 5159 } 5160 5161 workers()->run_task(&g1_par_task); 5162 end_par_time_sec = os::elapsedTime(); 5163 5164 // Closing the inner scope will execute the destructor 5165 // for the G1RootProcessor object. We record the current 5166 // elapsed time before closing the scope so that time 5167 // taken for the destructor is NOT included in the 5168 // reported parallel time. 5169 } 5170 5171 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 5172 5173 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5174 phase_times->record_par_time(par_time_ms); 5175 5176 double code_root_fixup_time_ms = 5177 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5178 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 5179 5180 // Process any discovered reference objects - we have 5181 // to do this _before_ we retire the GC alloc regions 5182 // as we may have to copy some 'reachable' referent 5183 // objects (and their reachable sub-graphs) that were 5184 // not copied during the pause. 5185 process_discovered_references(per_thread_states); 5186 5187 if (G1StringDedup::is_enabled()) { 5188 double fixup_start = os::elapsedTime(); 5189 5190 G1STWIsAliveClosure is_alive(this); 5191 G1KeepAliveClosure keep_alive(this); 5192 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times); 5193 5194 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 5195 phase_times->record_string_dedup_fixup_time(fixup_time_ms); 5196 } 5197 5198 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5199 5200 if (evacuation_failed()) { 5201 remove_self_forwarding_pointers(); 5202 5203 // Reset the G1EvacuationFailureALot counters and flags 5204 // Note: the values are reset only when an actual 5205 // evacuation failure occurs. 5206 NOT_PRODUCT(reset_evacuation_should_fail();) 5207 } 5208 5209 // Enqueue any remaining references remaining on the STW 5210 // reference processor's discovered lists. We need to do 5211 // this after the card table is cleaned (and verified) as 5212 // the act of enqueueing entries on to the pending list 5213 // will log these updates (and dirty their associated 5214 // cards). We need these updates logged to update any 5215 // RSets. 5216 enqueue_discovered_references(per_thread_states); 5217 } 5218 5219 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 5220 _allocator->release_gc_alloc_regions(evacuation_info); 5221 5222 per_thread_states->flush(); 5223 5224 record_obj_copy_mem_stats(); 5225 5226 _survivor_evac_stats.adjust_desired_plab_sz(); 5227 _old_evac_stats.adjust_desired_plab_sz(); 5228 5229 // Reset and re-enable the hot card cache. 5230 // Note the counts for the cards in the regions in the 5231 // collection set are reset when the collection set is freed. 5232 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5233 hot_card_cache->reset_hot_cache(); 5234 hot_card_cache->set_use_cache(true); 5235 5236 purge_code_root_memory(); 5237 5238 redirty_logged_cards(); 5239 #if defined(COMPILER2) || INCLUDE_JVMCI 5240 DerivedPointerTable::update_pointers(); 5241 #endif 5242 } 5243 5244 void G1CollectedHeap::record_obj_copy_mem_stats() { 5245 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 5246 create_g1_evac_summary(&_old_evac_stats)); 5247 } 5248 5249 void G1CollectedHeap::free_region(HeapRegion* hr, 5250 FreeRegionList* free_list, 5251 bool par, 5252 bool locked) { 5253 assert(!hr->is_free(), "the region should not be free"); 5254 assert(!hr->is_empty(), "the region should not be empty"); 5255 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 5256 assert(free_list != NULL, "pre-condition"); 5257 5258 if (G1VerifyBitmaps) { 5259 MemRegion mr(hr->bottom(), hr->end()); 5260 concurrent_mark()->clearRangePrevBitmap(mr); 5261 } 5262 5263 // Clear the card counts for this region. 5264 // Note: we only need to do this if the region is not young 5265 // (since we don't refine cards in young regions). 5266 if (!hr->is_young()) { 5267 _cg1r->hot_card_cache()->reset_card_counts(hr); 5268 } 5269 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 5270 free_list->add_ordered(hr); 5271 } 5272 5273 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5274 FreeRegionList* free_list, 5275 bool par) { 5276 assert(hr->is_humongous(), "this is only for humongous regions"); 5277 assert(free_list != NULL, "pre-condition"); 5278 hr->clear_humongous(); 5279 free_region(hr, free_list, par); 5280 } 5281 5282 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, 5283 const HeapRegionSetCount& humongous_regions_removed) { 5284 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) { 5285 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5286 _old_set.bulk_remove(old_regions_removed); 5287 _humongous_set.bulk_remove(humongous_regions_removed); 5288 } 5289 5290 } 5291 5292 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 5293 assert(list != NULL, "list can't be null"); 5294 if (!list->is_empty()) { 5295 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 5296 _hrm.insert_list_into_free_list(list); 5297 } 5298 } 5299 5300 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 5301 decrease_used(bytes); 5302 } 5303 5304 class G1ParCleanupCTTask : public AbstractGangTask { 5305 G1SATBCardTableModRefBS* _ct_bs; 5306 G1CollectedHeap* _g1h; 5307 HeapRegion* volatile _su_head; 5308 public: 5309 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 5310 G1CollectedHeap* g1h) : 5311 AbstractGangTask("G1 Par Cleanup CT Task"), 5312 _ct_bs(ct_bs), _g1h(g1h) { } 5313 5314 void work(uint worker_id) { 5315 HeapRegion* r; 5316 while (r = _g1h->pop_dirty_cards_region()) { 5317 clear_cards(r); 5318 } 5319 } 5320 5321 void clear_cards(HeapRegion* r) { 5322 // Cards of the survivors should have already been dirtied. 5323 if (!r->is_survivor()) { 5324 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 5325 } 5326 } 5327 }; 5328 5329 #ifndef PRODUCT 5330 class G1VerifyCardTableCleanup: public HeapRegionClosure { 5331 G1CollectedHeap* _g1h; 5332 G1SATBCardTableModRefBS* _ct_bs; 5333 public: 5334 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs) 5335 : _g1h(g1h), _ct_bs(ct_bs) { } 5336 virtual bool doHeapRegion(HeapRegion* r) { 5337 if (r->is_survivor()) { 5338 _g1h->verify_dirty_region(r); 5339 } else { 5340 _g1h->verify_not_dirty_region(r); 5341 } 5342 return false; 5343 } 5344 }; 5345 5346 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 5347 // All of the region should be clean. 5348 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5349 MemRegion mr(hr->bottom(), hr->end()); 5350 ct_bs->verify_not_dirty_region(mr); 5351 } 5352 5353 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 5354 // We cannot guarantee that [bottom(),end()] is dirty. Threads 5355 // dirty allocated blocks as they allocate them. The thread that 5356 // retires each region and replaces it with a new one will do a 5357 // maximal allocation to fill in [pre_dummy_top(),end()] but will 5358 // not dirty that area (one less thing to have to do while holding 5359 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 5360 // is dirty. 5361 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5362 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 5363 if (hr->is_young()) { 5364 ct_bs->verify_g1_young_region(mr); 5365 } else { 5366 ct_bs->verify_dirty_region(mr); 5367 } 5368 } 5369 5370 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 5371 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5372 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 5373 verify_dirty_region(hr); 5374 } 5375 } 5376 5377 void G1CollectedHeap::verify_dirty_young_regions() { 5378 verify_dirty_young_list(_young_list->first_region()); 5379 } 5380 5381 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 5382 HeapWord* tams, HeapWord* end) { 5383 guarantee(tams <= end, 5384 "tams: " PTR_FORMAT " end: " PTR_FORMAT, p2i(tams), p2i(end)); 5385 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end); 5386 if (result < end) { 5387 gclog_or_tty->cr(); 5388 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: " PTR_FORMAT, 5389 bitmap_name, p2i(result)); 5390 gclog_or_tty->print_cr("## %s tams: " PTR_FORMAT " end: " PTR_FORMAT, 5391 bitmap_name, p2i(tams), p2i(end)); 5392 return false; 5393 } 5394 return true; 5395 } 5396 5397 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) { 5398 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap(); 5399 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap(); 5400 5401 HeapWord* bottom = hr->bottom(); 5402 HeapWord* ptams = hr->prev_top_at_mark_start(); 5403 HeapWord* ntams = hr->next_top_at_mark_start(); 5404 HeapWord* end = hr->end(); 5405 5406 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end); 5407 5408 bool res_n = true; 5409 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window 5410 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap 5411 // if we happen to be in that state. 5412 if (collector_state()->mark_in_progress() || !_cmThread->in_progress()) { 5413 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end); 5414 } 5415 if (!res_p || !res_n) { 5416 gclog_or_tty->print_cr("#### Bitmap verification failed for " HR_FORMAT, 5417 HR_FORMAT_PARAMS(hr)); 5418 gclog_or_tty->print_cr("#### Caller: %s", caller); 5419 return false; 5420 } 5421 return true; 5422 } 5423 5424 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) { 5425 if (!G1VerifyBitmaps) return; 5426 5427 guarantee(verify_bitmaps(caller, hr), "bitmap verification"); 5428 } 5429 5430 class G1VerifyBitmapClosure : public HeapRegionClosure { 5431 private: 5432 const char* _caller; 5433 G1CollectedHeap* _g1h; 5434 bool _failures; 5435 5436 public: 5437 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) : 5438 _caller(caller), _g1h(g1h), _failures(false) { } 5439 5440 bool failures() { return _failures; } 5441 5442 virtual bool doHeapRegion(HeapRegion* hr) { 5443 bool result = _g1h->verify_bitmaps(_caller, hr); 5444 if (!result) { 5445 _failures = true; 5446 } 5447 return false; 5448 } 5449 }; 5450 5451 void G1CollectedHeap::check_bitmaps(const char* caller) { 5452 if (!G1VerifyBitmaps) return; 5453 5454 G1VerifyBitmapClosure cl(caller, this); 5455 heap_region_iterate(&cl); 5456 guarantee(!cl.failures(), "bitmap verification"); 5457 } 5458 5459 class G1CheckCSetFastTableClosure : public HeapRegionClosure { 5460 private: 5461 bool _failures; 5462 public: 5463 G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { } 5464 5465 virtual bool doHeapRegion(HeapRegion* hr) { 5466 uint i = hr->hrm_index(); 5467 InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i); 5468 if (hr->is_humongous()) { 5469 if (hr->in_collection_set()) { 5470 gclog_or_tty->print_cr("\n## humongous region %u in CSet", i); 5471 _failures = true; 5472 return true; 5473 } 5474 if (cset_state.is_in_cset()) { 5475 gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i); 5476 _failures = true; 5477 return true; 5478 } 5479 if (hr->is_continues_humongous() && cset_state.is_humongous()) { 5480 gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i); 5481 _failures = true; 5482 return true; 5483 } 5484 } else { 5485 if (cset_state.is_humongous()) { 5486 gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i); 5487 _failures = true; 5488 return true; 5489 } 5490 if (hr->in_collection_set() != cset_state.is_in_cset()) { 5491 gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u", 5492 hr->in_collection_set(), cset_state.value(), i); 5493 _failures = true; 5494 return true; 5495 } 5496 if (cset_state.is_in_cset()) { 5497 if (hr->is_young() != (cset_state.is_young())) { 5498 gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u", 5499 hr->is_young(), cset_state.value(), i); 5500 _failures = true; 5501 return true; 5502 } 5503 if (hr->is_old() != (cset_state.is_old())) { 5504 gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u", 5505 hr->is_old(), cset_state.value(), i); 5506 _failures = true; 5507 return true; 5508 } 5509 } 5510 } 5511 return false; 5512 } 5513 5514 bool failures() const { return _failures; } 5515 }; 5516 5517 bool G1CollectedHeap::check_cset_fast_test() { 5518 G1CheckCSetFastTableClosure cl; 5519 _hrm.iterate(&cl); 5520 return !cl.failures(); 5521 } 5522 #endif // PRODUCT 5523 5524 void G1CollectedHeap::cleanUpCardTable() { 5525 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5526 double start = os::elapsedTime(); 5527 5528 { 5529 // Iterate over the dirty cards region list. 5530 G1ParCleanupCTTask cleanup_task(ct_bs, this); 5531 5532 workers()->run_task(&cleanup_task); 5533 #ifndef PRODUCT 5534 if (G1VerifyCTCleanup || VerifyAfterGC) { 5535 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 5536 heap_region_iterate(&cleanup_verifier); 5537 } 5538 #endif 5539 } 5540 5541 double elapsed = os::elapsedTime() - start; 5542 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 5543 } 5544 5545 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 5546 size_t pre_used = 0; 5547 FreeRegionList local_free_list("Local List for CSet Freeing"); 5548 5549 double young_time_ms = 0.0; 5550 double non_young_time_ms = 0.0; 5551 5552 // Since the collection set is a superset of the the young list, 5553 // all we need to do to clear the young list is clear its 5554 // head and length, and unlink any young regions in the code below 5555 _young_list->clear(); 5556 5557 G1CollectorPolicy* policy = g1_policy(); 5558 5559 double start_sec = os::elapsedTime(); 5560 bool non_young = true; 5561 5562 HeapRegion* cur = cs_head; 5563 int age_bound = -1; 5564 size_t rs_lengths = 0; 5565 5566 while (cur != NULL) { 5567 assert(!is_on_master_free_list(cur), "sanity"); 5568 if (non_young) { 5569 if (cur->is_young()) { 5570 double end_sec = os::elapsedTime(); 5571 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5572 non_young_time_ms += elapsed_ms; 5573 5574 start_sec = os::elapsedTime(); 5575 non_young = false; 5576 } 5577 } else { 5578 if (!cur->is_young()) { 5579 double end_sec = os::elapsedTime(); 5580 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5581 young_time_ms += elapsed_ms; 5582 5583 start_sec = os::elapsedTime(); 5584 non_young = true; 5585 } 5586 } 5587 5588 rs_lengths += cur->rem_set()->occupied_locked(); 5589 5590 HeapRegion* next = cur->next_in_collection_set(); 5591 assert(cur->in_collection_set(), "bad CS"); 5592 cur->set_next_in_collection_set(NULL); 5593 clear_in_cset(cur); 5594 5595 if (cur->is_young()) { 5596 int index = cur->young_index_in_cset(); 5597 assert(index != -1, "invariant"); 5598 assert((uint) index < policy->young_cset_region_length(), "invariant"); 5599 size_t words_survived = surviving_young_words[index]; 5600 cur->record_surv_words_in_group(words_survived); 5601 5602 // At this point the we have 'popped' cur from the collection set 5603 // (linked via next_in_collection_set()) but it is still in the 5604 // young list (linked via next_young_region()). Clear the 5605 // _next_young_region field. 5606 cur->set_next_young_region(NULL); 5607 } else { 5608 int index = cur->young_index_in_cset(); 5609 assert(index == -1, "invariant"); 5610 } 5611 5612 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 5613 (!cur->is_young() && cur->young_index_in_cset() == -1), 5614 "invariant" ); 5615 5616 if (!cur->evacuation_failed()) { 5617 MemRegion used_mr = cur->used_region(); 5618 5619 // And the region is empty. 5620 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 5621 pre_used += cur->used(); 5622 free_region(cur, &local_free_list, false /* par */, true /* locked */); 5623 } else { 5624 cur->uninstall_surv_rate_group(); 5625 if (cur->is_young()) { 5626 cur->set_young_index_in_cset(-1); 5627 } 5628 cur->set_evacuation_failed(false); 5629 // The region is now considered to be old. 5630 cur->set_old(); 5631 // Do some allocation statistics accounting. Regions that failed evacuation 5632 // are always made old, so there is no need to update anything in the young 5633 // gen statistics, but we need to update old gen statistics. 5634 size_t used_words = cur->marked_bytes() / HeapWordSize; 5635 _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words); 5636 _old_set.add(cur); 5637 evacuation_info.increment_collectionset_used_after(cur->used()); 5638 } 5639 cur = next; 5640 } 5641 5642 evacuation_info.set_regions_freed(local_free_list.length()); 5643 policy->record_max_rs_lengths(rs_lengths); 5644 policy->cset_regions_freed(); 5645 5646 double end_sec = os::elapsedTime(); 5647 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5648 5649 if (non_young) { 5650 non_young_time_ms += elapsed_ms; 5651 } else { 5652 young_time_ms += elapsed_ms; 5653 } 5654 5655 prepend_to_freelist(&local_free_list); 5656 decrement_summary_bytes(pre_used); 5657 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 5658 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 5659 } 5660 5661 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 5662 private: 5663 FreeRegionList* _free_region_list; 5664 HeapRegionSet* _proxy_set; 5665 HeapRegionSetCount _humongous_regions_removed; 5666 size_t _freed_bytes; 5667 public: 5668 5669 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 5670 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) { 5671 } 5672 5673 virtual bool doHeapRegion(HeapRegion* r) { 5674 if (!r->is_starts_humongous()) { 5675 return false; 5676 } 5677 5678 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 5679 5680 oop obj = (oop)r->bottom(); 5681 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 5682 5683 // The following checks whether the humongous object is live are sufficient. 5684 // The main additional check (in addition to having a reference from the roots 5685 // or the young gen) is whether the humongous object has a remembered set entry. 5686 // 5687 // A humongous object cannot be live if there is no remembered set for it 5688 // because: 5689 // - there can be no references from within humongous starts regions referencing 5690 // the object because we never allocate other objects into them. 5691 // (I.e. there are no intra-region references that may be missed by the 5692 // remembered set) 5693 // - as soon there is a remembered set entry to the humongous starts region 5694 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 5695 // until the end of a concurrent mark. 5696 // 5697 // It is not required to check whether the object has been found dead by marking 5698 // or not, in fact it would prevent reclamation within a concurrent cycle, as 5699 // all objects allocated during that time are considered live. 5700 // SATB marking is even more conservative than the remembered set. 5701 // So if at this point in the collection there is no remembered set entry, 5702 // nobody has a reference to it. 5703 // At the start of collection we flush all refinement logs, and remembered sets 5704 // are completely up-to-date wrt to references to the humongous object. 5705 // 5706 // Other implementation considerations: 5707 // - never consider object arrays at this time because they would pose 5708 // considerable effort for cleaning up the the remembered sets. This is 5709 // required because stale remembered sets might reference locations that 5710 // are currently allocated into. 5711 uint region_idx = r->hrm_index(); 5712 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 5713 !r->rem_set()->is_empty()) { 5714 5715 if (G1TraceEagerReclaimHumongousObjects) { 5716 gclog_or_tty->print_cr("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", 5717 region_idx, 5718 (size_t)obj->size() * HeapWordSize, 5719 p2i(r->bottom()), 5720 r->rem_set()->occupied(), 5721 r->rem_set()->strong_code_roots_list_length(), 5722 next_bitmap->isMarked(r->bottom()), 5723 g1h->is_humongous_reclaim_candidate(region_idx), 5724 obj->is_typeArray() 5725 ); 5726 } 5727 5728 return false; 5729 } 5730 5731 guarantee(obj->is_typeArray(), 5732 "Only eagerly reclaiming type arrays is supported, but the object " 5733 PTR_FORMAT " is not.", p2i(r->bottom())); 5734 5735 if (G1TraceEagerReclaimHumongousObjects) { 5736 gclog_or_tty->print_cr("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", 5737 region_idx, 5738 (size_t)obj->size() * HeapWordSize, 5739 p2i(r->bottom()), 5740 r->rem_set()->occupied(), 5741 r->rem_set()->strong_code_roots_list_length(), 5742 next_bitmap->isMarked(r->bottom()), 5743 g1h->is_humongous_reclaim_candidate(region_idx), 5744 obj->is_typeArray() 5745 ); 5746 } 5747 // Need to clear mark bit of the humongous object if already set. 5748 if (next_bitmap->isMarked(r->bottom())) { 5749 next_bitmap->clear(r->bottom()); 5750 } 5751 do { 5752 HeapRegion* next = g1h->next_region_in_humongous(r); 5753 _freed_bytes += r->used(); 5754 r->set_containing_set(NULL); 5755 _humongous_regions_removed.increment(1u, r->capacity()); 5756 g1h->free_humongous_region(r, _free_region_list, false); 5757 r = next; 5758 } while (r != NULL); 5759 5760 return false; 5761 } 5762 5763 HeapRegionSetCount& humongous_free_count() { 5764 return _humongous_regions_removed; 5765 } 5766 5767 size_t bytes_freed() const { 5768 return _freed_bytes; 5769 } 5770 5771 size_t humongous_reclaimed() const { 5772 return _humongous_regions_removed.length(); 5773 } 5774 }; 5775 5776 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 5777 assert_at_safepoint(true); 5778 5779 if (!G1EagerReclaimHumongousObjects || 5780 (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) { 5781 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5782 return; 5783 } 5784 5785 double start_time = os::elapsedTime(); 5786 5787 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5788 5789 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5790 heap_region_iterate(&cl); 5791 5792 HeapRegionSetCount empty_set; 5793 remove_from_old_sets(empty_set, cl.humongous_free_count()); 5794 5795 G1HRPrinter* hrp = hr_printer(); 5796 if (hrp->is_active()) { 5797 FreeRegionListIterator iter(&local_cleanup_list); 5798 while (iter.more_available()) { 5799 HeapRegion* hr = iter.get_next(); 5800 hrp->cleanup(hr); 5801 } 5802 } 5803 5804 prepend_to_freelist(&local_cleanup_list); 5805 decrement_summary_bytes(cl.bytes_freed()); 5806 5807 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5808 cl.humongous_reclaimed()); 5809 } 5810 5811 // This routine is similar to the above but does not record 5812 // any policy statistics or update free lists; we are abandoning 5813 // the current incremental collection set in preparation of a 5814 // full collection. After the full GC we will start to build up 5815 // the incremental collection set again. 5816 // This is only called when we're doing a full collection 5817 // and is immediately followed by the tearing down of the young list. 5818 5819 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 5820 HeapRegion* cur = cs_head; 5821 5822 while (cur != NULL) { 5823 HeapRegion* next = cur->next_in_collection_set(); 5824 assert(cur->in_collection_set(), "bad CS"); 5825 cur->set_next_in_collection_set(NULL); 5826 clear_in_cset(cur); 5827 cur->set_young_index_in_cset(-1); 5828 cur = next; 5829 } 5830 } 5831 5832 void G1CollectedHeap::set_free_regions_coming() { 5833 if (G1ConcRegionFreeingVerbose) { 5834 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 5835 "setting free regions coming"); 5836 } 5837 5838 assert(!free_regions_coming(), "pre-condition"); 5839 _free_regions_coming = true; 5840 } 5841 5842 void G1CollectedHeap::reset_free_regions_coming() { 5843 assert(free_regions_coming(), "pre-condition"); 5844 5845 { 5846 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5847 _free_regions_coming = false; 5848 SecondaryFreeList_lock->notify_all(); 5849 } 5850 5851 if (G1ConcRegionFreeingVerbose) { 5852 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 5853 "reset free regions coming"); 5854 } 5855 } 5856 5857 void G1CollectedHeap::wait_while_free_regions_coming() { 5858 // Most of the time we won't have to wait, so let's do a quick test 5859 // first before we take the lock. 5860 if (!free_regions_coming()) { 5861 return; 5862 } 5863 5864 if (G1ConcRegionFreeingVerbose) { 5865 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 5866 "waiting for free regions"); 5867 } 5868 5869 { 5870 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5871 while (free_regions_coming()) { 5872 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5873 } 5874 } 5875 5876 if (G1ConcRegionFreeingVerbose) { 5877 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 5878 "done waiting for free regions"); 5879 } 5880 } 5881 5882 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5883 return _allocator->is_retained_old_region(hr); 5884 } 5885 5886 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5887 _young_list->push_region(hr); 5888 } 5889 5890 class NoYoungRegionsClosure: public HeapRegionClosure { 5891 private: 5892 bool _success; 5893 public: 5894 NoYoungRegionsClosure() : _success(true) { } 5895 bool doHeapRegion(HeapRegion* r) { 5896 if (r->is_young()) { 5897 gclog_or_tty->print_cr("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5898 p2i(r->bottom()), p2i(r->end())); 5899 _success = false; 5900 } 5901 return false; 5902 } 5903 bool success() { return _success; } 5904 }; 5905 5906 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 5907 bool ret = _young_list->check_list_empty(check_sample); 5908 5909 if (check_heap) { 5910 NoYoungRegionsClosure closure; 5911 heap_region_iterate(&closure); 5912 ret = ret && closure.success(); 5913 } 5914 5915 return ret; 5916 } 5917 5918 class TearDownRegionSetsClosure : public HeapRegionClosure { 5919 private: 5920 HeapRegionSet *_old_set; 5921 5922 public: 5923 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5924 5925 bool doHeapRegion(HeapRegion* r) { 5926 if (r->is_old()) { 5927 _old_set->remove(r); 5928 } else { 5929 // We ignore free regions, we'll empty the free list afterwards. 5930 // We ignore young regions, we'll empty the young list afterwards. 5931 // We ignore humongous regions, we're not tearing down the 5932 // humongous regions set. 5933 assert(r->is_free() || r->is_young() || r->is_humongous(), 5934 "it cannot be another type"); 5935 } 5936 return false; 5937 } 5938 5939 ~TearDownRegionSetsClosure() { 5940 assert(_old_set->is_empty(), "post-condition"); 5941 } 5942 }; 5943 5944 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5945 assert_at_safepoint(true /* should_be_vm_thread */); 5946 5947 if (!free_list_only) { 5948 TearDownRegionSetsClosure cl(&_old_set); 5949 heap_region_iterate(&cl); 5950 5951 // Note that emptying the _young_list is postponed and instead done as 5952 // the first step when rebuilding the regions sets again. The reason for 5953 // this is that during a full GC string deduplication needs to know if 5954 // a collected region was young or old when the full GC was initiated. 5955 } 5956 _hrm.remove_all_free_regions(); 5957 } 5958 5959 void G1CollectedHeap::increase_used(size_t bytes) { 5960 _summary_bytes_used += bytes; 5961 } 5962 5963 void G1CollectedHeap::decrease_used(size_t bytes) { 5964 assert(_summary_bytes_used >= bytes, 5965 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5966 _summary_bytes_used, bytes); 5967 _summary_bytes_used -= bytes; 5968 } 5969 5970 void G1CollectedHeap::set_used(size_t bytes) { 5971 _summary_bytes_used = bytes; 5972 } 5973 5974 class RebuildRegionSetsClosure : public HeapRegionClosure { 5975 private: 5976 bool _free_list_only; 5977 HeapRegionSet* _old_set; 5978 HeapRegionManager* _hrm; 5979 size_t _total_used; 5980 5981 public: 5982 RebuildRegionSetsClosure(bool free_list_only, 5983 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5984 _free_list_only(free_list_only), 5985 _old_set(old_set), _hrm(hrm), _total_used(0) { 5986 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5987 if (!free_list_only) { 5988 assert(_old_set->is_empty(), "pre-condition"); 5989 } 5990 } 5991 5992 bool doHeapRegion(HeapRegion* r) { 5993 if (r->is_empty()) { 5994 // Add free regions to the free list 5995 r->set_free(); 5996 r->set_allocation_context(AllocationContext::system()); 5997 _hrm->insert_into_free_list(r); 5998 } else if (!_free_list_only) { 5999 assert(!r->is_young(), "we should not come across young regions"); 6000 6001 if (r->is_humongous()) { 6002 // We ignore humongous regions. We left the humongous set unchanged. 6003 } else { 6004 // Objects that were compacted would have ended up on regions 6005 // that were previously old or free. Archive regions (which are 6006 // old) will not have been touched. 6007 assert(r->is_free() || r->is_old(), "invariant"); 6008 // We now consider them old, so register as such. Leave 6009 // archive regions set that way, however, while still adding 6010 // them to the old set. 6011 if (!r->is_archive()) { 6012 r->set_old(); 6013 } 6014 _old_set->add(r); 6015 } 6016 _total_used += r->used(); 6017 } 6018 6019 return false; 6020 } 6021 6022 size_t total_used() { 6023 return _total_used; 6024 } 6025 }; 6026 6027 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6028 assert_at_safepoint(true /* should_be_vm_thread */); 6029 6030 if (!free_list_only) { 6031 _young_list->empty_list(); 6032 } 6033 6034 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 6035 heap_region_iterate(&cl); 6036 6037 if (!free_list_only) { 6038 set_used(cl.total_used()); 6039 if (_archive_allocator != NULL) { 6040 _archive_allocator->clear_used(); 6041 } 6042 } 6043 assert(used_unlocked() == recalculate_used(), 6044 "inconsistent used_unlocked(), " 6045 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 6046 used_unlocked(), recalculate_used()); 6047 } 6048 6049 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6050 _refine_cte_cl->set_concurrent(concurrent); 6051 } 6052 6053 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6054 HeapRegion* hr = heap_region_containing(p); 6055 return hr->is_in(p); 6056 } 6057 6058 // Methods for the mutator alloc region 6059 6060 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6061 bool force) { 6062 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6063 assert(!force || g1_policy()->can_expand_young_list(), 6064 "if force is true we should be able to expand the young list"); 6065 bool young_list_full = g1_policy()->is_young_list_full(); 6066 if (force || !young_list_full) { 6067 HeapRegion* new_alloc_region = new_region(word_size, 6068 false /* is_old */, 6069 false /* do_expand */); 6070 if (new_alloc_region != NULL) { 6071 set_region_short_lived_locked(new_alloc_region); 6072 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6073 check_bitmaps("Mutator Region Allocation", new_alloc_region); 6074 return new_alloc_region; 6075 } 6076 } 6077 return NULL; 6078 } 6079 6080 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6081 size_t allocated_bytes) { 6082 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6083 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 6084 6085 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6086 increase_used(allocated_bytes); 6087 _hr_printer.retire(alloc_region); 6088 // We update the eden sizes here, when the region is retired, 6089 // instead of when it's allocated, since this is the point that its 6090 // used space has been recored in _summary_bytes_used. 6091 g1mm()->update_eden_size(); 6092 } 6093 6094 // Methods for the GC alloc regions 6095 6096 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6097 uint count, 6098 InCSetState dest) { 6099 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6100 6101 if (count < g1_policy()->max_regions(dest)) { 6102 const bool is_survivor = (dest.is_young()); 6103 HeapRegion* new_alloc_region = new_region(word_size, 6104 !is_survivor, 6105 true /* do_expand */); 6106 if (new_alloc_region != NULL) { 6107 // We really only need to do this for old regions given that we 6108 // should never scan survivors. But it doesn't hurt to do it 6109 // for survivors too. 6110 new_alloc_region->record_timestamp(); 6111 if (is_survivor) { 6112 new_alloc_region->set_survivor(); 6113 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6114 check_bitmaps("Survivor Region Allocation", new_alloc_region); 6115 } else { 6116 new_alloc_region->set_old(); 6117 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6118 check_bitmaps("Old Region Allocation", new_alloc_region); 6119 } 6120 bool during_im = collector_state()->during_initial_mark_pause(); 6121 new_alloc_region->note_start_of_copying(during_im); 6122 return new_alloc_region; 6123 } 6124 } 6125 return NULL; 6126 } 6127 6128 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6129 size_t allocated_bytes, 6130 InCSetState dest) { 6131 bool during_im = collector_state()->during_initial_mark_pause(); 6132 alloc_region->note_end_of_copying(during_im); 6133 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6134 if (dest.is_young()) { 6135 young_list()->add_survivor_region(alloc_region); 6136 } else { 6137 _old_set.add(alloc_region); 6138 } 6139 _hr_printer.retire(alloc_region); 6140 } 6141 6142 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 6143 bool expanded = false; 6144 uint index = _hrm.find_highest_free(&expanded); 6145 6146 if (index != G1_NO_HRM_INDEX) { 6147 if (expanded) { 6148 ergo_verbose1(ErgoHeapSizing, 6149 "attempt heap expansion", 6150 ergo_format_reason("requested address range outside heap bounds") 6151 ergo_format_byte("region size"), 6152 HeapRegion::GrainWords * HeapWordSize); 6153 } 6154 _hrm.allocate_free_regions_starting_at(index, 1); 6155 return region_at(index); 6156 } 6157 return NULL; 6158 } 6159 6160 // Heap region set verification 6161 6162 class VerifyRegionListsClosure : public HeapRegionClosure { 6163 private: 6164 HeapRegionSet* _old_set; 6165 HeapRegionSet* _humongous_set; 6166 HeapRegionManager* _hrm; 6167 6168 public: 6169 HeapRegionSetCount _old_count; 6170 HeapRegionSetCount _humongous_count; 6171 HeapRegionSetCount _free_count; 6172 6173 VerifyRegionListsClosure(HeapRegionSet* old_set, 6174 HeapRegionSet* humongous_set, 6175 HeapRegionManager* hrm) : 6176 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm), 6177 _old_count(), _humongous_count(), _free_count(){ } 6178 6179 bool doHeapRegion(HeapRegion* hr) { 6180 if (hr->is_young()) { 6181 // TODO 6182 } else if (hr->is_humongous()) { 6183 assert(hr->containing_set() == _humongous_set, "Heap region %u is humongous but not in humongous set.", hr->hrm_index()); 6184 _humongous_count.increment(1u, hr->capacity()); 6185 } else if (hr->is_empty()) { 6186 assert(_hrm->is_free(hr), "Heap region %u is empty but not on the free list.", hr->hrm_index()); 6187 _free_count.increment(1u, hr->capacity()); 6188 } else if (hr->is_old()) { 6189 assert(hr->containing_set() == _old_set, "Heap region %u is old but not in the old set.", hr->hrm_index()); 6190 _old_count.increment(1u, hr->capacity()); 6191 } else { 6192 // There are no other valid region types. Check for one invalid 6193 // one we can identify: pinned without old or humongous set. 6194 assert(!hr->is_pinned(), "Heap region %u is pinned but not old (archive) or humongous.", hr->hrm_index()); 6195 ShouldNotReachHere(); 6196 } 6197 return false; 6198 } 6199 6200 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) { 6201 guarantee(old_set->length() == _old_count.length(), "Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()); 6202 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), "Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6203 old_set->total_capacity_bytes(), _old_count.capacity()); 6204 6205 guarantee(humongous_set->length() == _humongous_count.length(), "Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()); 6206 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), "Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6207 humongous_set->total_capacity_bytes(), _humongous_count.capacity()); 6208 6209 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()); 6210 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), "Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6211 free_list->total_capacity_bytes(), _free_count.capacity()); 6212 } 6213 }; 6214 6215 void G1CollectedHeap::verify_region_sets() { 6216 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6217 6218 // First, check the explicit lists. 6219 _hrm.verify(); 6220 { 6221 // Given that a concurrent operation might be adding regions to 6222 // the secondary free list we have to take the lock before 6223 // verifying it. 6224 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6225 _secondary_free_list.verify_list(); 6226 } 6227 6228 // If a concurrent region freeing operation is in progress it will 6229 // be difficult to correctly attributed any free regions we come 6230 // across to the correct free list given that they might belong to 6231 // one of several (free_list, secondary_free_list, any local lists, 6232 // etc.). So, if that's the case we will skip the rest of the 6233 // verification operation. Alternatively, waiting for the concurrent 6234 // operation to complete will have a non-trivial effect on the GC's 6235 // operation (no concurrent operation will last longer than the 6236 // interval between two calls to verification) and it might hide 6237 // any issues that we would like to catch during testing. 6238 if (free_regions_coming()) { 6239 return; 6240 } 6241 6242 // Make sure we append the secondary_free_list on the free_list so 6243 // that all free regions we will come across can be safely 6244 // attributed to the free_list. 6245 append_secondary_free_list_if_not_empty_with_lock(); 6246 6247 // Finally, make sure that the region accounting in the lists is 6248 // consistent with what we see in the heap. 6249 6250 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm); 6251 heap_region_iterate(&cl); 6252 cl.verify_counts(&_old_set, &_humongous_set, &_hrm); 6253 } 6254 6255 // Optimized nmethod scanning 6256 6257 class RegisterNMethodOopClosure: public OopClosure { 6258 G1CollectedHeap* _g1h; 6259 nmethod* _nm; 6260 6261 template <class T> void do_oop_work(T* p) { 6262 T heap_oop = oopDesc::load_heap_oop(p); 6263 if (!oopDesc::is_null(heap_oop)) { 6264 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6265 HeapRegion* hr = _g1h->heap_region_containing(obj); 6266 assert(!hr->is_continues_humongous(), 6267 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6268 " starting at " HR_FORMAT, 6269 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 6270 6271 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 6272 hr->add_strong_code_root_locked(_nm); 6273 } 6274 } 6275 6276 public: 6277 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6278 _g1h(g1h), _nm(nm) {} 6279 6280 void do_oop(oop* p) { do_oop_work(p); } 6281 void do_oop(narrowOop* p) { do_oop_work(p); } 6282 }; 6283 6284 class UnregisterNMethodOopClosure: public OopClosure { 6285 G1CollectedHeap* _g1h; 6286 nmethod* _nm; 6287 6288 template <class T> void do_oop_work(T* p) { 6289 T heap_oop = oopDesc::load_heap_oop(p); 6290 if (!oopDesc::is_null(heap_oop)) { 6291 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6292 HeapRegion* hr = _g1h->heap_region_containing(obj); 6293 assert(!hr->is_continues_humongous(), 6294 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6295 " starting at " HR_FORMAT, 6296 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 6297 6298 hr->remove_strong_code_root(_nm); 6299 } 6300 } 6301 6302 public: 6303 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6304 _g1h(g1h), _nm(nm) {} 6305 6306 void do_oop(oop* p) { do_oop_work(p); } 6307 void do_oop(narrowOop* p) { do_oop_work(p); } 6308 }; 6309 6310 void G1CollectedHeap::register_nmethod(nmethod* nm) { 6311 CollectedHeap::register_nmethod(nm); 6312 6313 guarantee(nm != NULL, "sanity"); 6314 RegisterNMethodOopClosure reg_cl(this, nm); 6315 nm->oops_do(®_cl); 6316 } 6317 6318 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 6319 CollectedHeap::unregister_nmethod(nm); 6320 6321 guarantee(nm != NULL, "sanity"); 6322 UnregisterNMethodOopClosure reg_cl(this, nm); 6323 nm->oops_do(®_cl, true); 6324 } 6325 6326 void G1CollectedHeap::purge_code_root_memory() { 6327 double purge_start = os::elapsedTime(); 6328 G1CodeRootSet::purge(); 6329 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 6330 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 6331 } 6332 6333 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 6334 G1CollectedHeap* _g1h; 6335 6336 public: 6337 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 6338 _g1h(g1h) {} 6339 6340 void do_code_blob(CodeBlob* cb) { 6341 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 6342 if (nm == NULL) { 6343 return; 6344 } 6345 6346 if (ScavengeRootsInCode) { 6347 _g1h->register_nmethod(nm); 6348 } 6349 } 6350 }; 6351 6352 void G1CollectedHeap::rebuild_strong_code_roots() { 6353 RebuildStrongCodeRootClosure blob_cl(this); 6354 CodeCache::blobs_do(&blob_cl); 6355 }