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/g1GCPhaseTimes.hpp" 41 #include "gc/g1/g1Log.hpp" 42 #include "gc/g1/g1MarkSweep.hpp" 43 #include "gc/g1/g1OopClosures.inline.hpp" 44 #include "gc/g1/g1ParScanThreadState.inline.hpp" 45 #include "gc/g1/g1RegionToSpaceMapper.hpp" 46 #include "gc/g1/g1RemSet.inline.hpp" 47 #include "gc/g1/g1RootClosures.hpp" 48 #include "gc/g1/g1RootProcessor.hpp" 49 #include "gc/g1/g1StringDedup.hpp" 50 #include "gc/g1/g1YCTypes.hpp" 51 #include "gc/g1/heapRegion.inline.hpp" 52 #include "gc/g1/heapRegionRemSet.hpp" 53 #include "gc/g1/heapRegionSet.inline.hpp" 54 #include "gc/g1/suspendibleThreadSet.hpp" 55 #include "gc/g1/vm_operations_g1.hpp" 56 #include "gc/shared/gcHeapSummary.hpp" 57 #include "gc/shared/gcId.hpp" 58 #include "gc/shared/gcLocker.inline.hpp" 59 #include "gc/shared/gcTimer.hpp" 60 #include "gc/shared/gcTrace.hpp" 61 #include "gc/shared/gcTraceTime.hpp" 62 #include "gc/shared/generationSpec.hpp" 63 #include "gc/shared/isGCActiveMark.hpp" 64 #include "gc/shared/referenceProcessor.hpp" 65 #include "gc/shared/taskqueue.inline.hpp" 66 #include "memory/allocation.hpp" 67 #include "memory/iterator.hpp" 68 #include "oops/oop.inline.hpp" 69 #include "runtime/atomic.inline.hpp" 70 #include "runtime/init.hpp" 71 #include "runtime/orderAccess.inline.hpp" 72 #include "runtime/vmThread.hpp" 73 #include "utilities/globalDefinitions.hpp" 74 #include "utilities/stack.inline.hpp" 75 76 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 77 78 // INVARIANTS/NOTES 79 // 80 // All allocation activity covered by the G1CollectedHeap interface is 81 // serialized by acquiring the HeapLock. This happens in mem_allocate 82 // and allocate_new_tlab, which are the "entry" points to the 83 // allocation code from the rest of the JVM. (Note that this does not 84 // apply to TLAB allocation, which is not part of this interface: it 85 // is done by clients of this interface.) 86 87 // Local to this file. 88 89 class RefineCardTableEntryClosure: public CardTableEntryClosure { 90 bool _concurrent; 91 public: 92 RefineCardTableEntryClosure() : _concurrent(true) { } 93 94 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 95 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false); 96 // This path is executed by the concurrent refine or mutator threads, 97 // concurrently, and so we do not care if card_ptr contains references 98 // that point into the collection set. 99 assert(!oops_into_cset, "should be"); 100 101 if (_concurrent && SuspendibleThreadSet::should_yield()) { 102 // Caller will actually yield. 103 return false; 104 } 105 // Otherwise, we finished successfully; return true. 106 return true; 107 } 108 109 void set_concurrent(bool b) { _concurrent = b; } 110 }; 111 112 113 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 114 private: 115 size_t _num_processed; 116 117 public: 118 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { } 119 120 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 121 *card_ptr = CardTableModRefBS::dirty_card_val(); 122 _num_processed++; 123 return true; 124 } 125 126 size_t num_processed() const { return _num_processed; } 127 }; 128 129 130 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 131 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 132 } 133 134 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 135 // The from card cache is not the memory that is actually committed. So we cannot 136 // take advantage of the zero_filled parameter. 137 reset_from_card_cache(start_idx, num_regions); 138 } 139 140 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 141 { 142 // Claim the right to put the region on the dirty cards region list 143 // by installing a self pointer. 144 HeapRegion* next = hr->get_next_dirty_cards_region(); 145 if (next == NULL) { 146 HeapRegion* res = (HeapRegion*) 147 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 148 NULL); 149 if (res == NULL) { 150 HeapRegion* head; 151 do { 152 // Put the region to the dirty cards region list. 153 head = _dirty_cards_region_list; 154 next = (HeapRegion*) 155 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 156 if (next == head) { 157 assert(hr->get_next_dirty_cards_region() == hr, 158 "hr->get_next_dirty_cards_region() != hr"); 159 if (next == NULL) { 160 // The last region in the list points to itself. 161 hr->set_next_dirty_cards_region(hr); 162 } else { 163 hr->set_next_dirty_cards_region(next); 164 } 165 } 166 } while (next != head); 167 } 168 } 169 } 170 171 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 172 { 173 HeapRegion* head; 174 HeapRegion* hr; 175 do { 176 head = _dirty_cards_region_list; 177 if (head == NULL) { 178 return NULL; 179 } 180 HeapRegion* new_head = head->get_next_dirty_cards_region(); 181 if (head == new_head) { 182 // The last region. 183 new_head = NULL; 184 } 185 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 186 head); 187 } while (hr != head); 188 assert(hr != NULL, "invariant"); 189 hr->set_next_dirty_cards_region(NULL); 190 return hr; 191 } 192 193 // Returns true if the reference points to an object that 194 // can move in an incremental collection. 195 bool G1CollectedHeap::is_scavengable(const void* p) { 196 HeapRegion* hr = heap_region_containing(p); 197 return !hr->is_pinned(); 198 } 199 200 // Private methods. 201 202 HeapRegion* 203 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 204 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 205 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 206 if (!_secondary_free_list.is_empty()) { 207 if (G1ConcRegionFreeingVerbose) { 208 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 209 "secondary_free_list has %u entries", 210 _secondary_free_list.length()); 211 } 212 // It looks as if there are free regions available on the 213 // secondary_free_list. Let's move them to the free_list and try 214 // again to allocate from it. 215 append_secondary_free_list(); 216 217 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 218 "empty we should have moved at least one entry to the free_list"); 219 HeapRegion* res = _hrm.allocate_free_region(is_old); 220 if (G1ConcRegionFreeingVerbose) { 221 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 222 "allocated " HR_FORMAT " from secondary_free_list", 223 HR_FORMAT_PARAMS(res)); 224 } 225 return res; 226 } 227 228 // Wait here until we get notified either when (a) there are no 229 // more free regions coming or (b) some regions have been moved on 230 // the secondary_free_list. 231 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 232 } 233 234 if (G1ConcRegionFreeingVerbose) { 235 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 236 "could not allocate from secondary_free_list"); 237 } 238 return NULL; 239 } 240 241 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 242 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 243 "the only time we use this to allocate a humongous region is " 244 "when we are allocating a single humongous region"); 245 246 HeapRegion* res; 247 if (G1StressConcRegionFreeing) { 248 if (!_secondary_free_list.is_empty()) { 249 if (G1ConcRegionFreeingVerbose) { 250 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 251 "forced to look at the secondary_free_list"); 252 } 253 res = new_region_try_secondary_free_list(is_old); 254 if (res != NULL) { 255 return res; 256 } 257 } 258 } 259 260 res = _hrm.allocate_free_region(is_old); 261 262 if (res == NULL) { 263 if (G1ConcRegionFreeingVerbose) { 264 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 265 "res == NULL, trying the secondary_free_list"); 266 } 267 res = new_region_try_secondary_free_list(is_old); 268 } 269 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 270 // Currently, only attempts to allocate GC alloc regions set 271 // do_expand to true. So, we should only reach here during a 272 // safepoint. If this assumption changes we might have to 273 // reconsider the use of _expand_heap_after_alloc_failure. 274 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 275 276 ergo_verbose1(ErgoHeapSizing, 277 "attempt heap expansion", 278 ergo_format_reason("region allocation request failed") 279 ergo_format_byte("allocation request"), 280 word_size * HeapWordSize); 281 if (expand(word_size * HeapWordSize)) { 282 // Given that expand() succeeded in expanding the heap, and we 283 // always expand the heap by an amount aligned to the heap 284 // region size, the free list should in theory not be empty. 285 // In either case allocate_free_region() will check for NULL. 286 res = _hrm.allocate_free_region(is_old); 287 } else { 288 _expand_heap_after_alloc_failure = false; 289 } 290 } 291 return res; 292 } 293 294 HeapWord* 295 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 296 uint num_regions, 297 size_t word_size, 298 AllocationContext_t context) { 299 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 300 assert(is_humongous(word_size), "word_size should be humongous"); 301 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 302 303 // Index of last region in the series + 1. 304 uint last = first + num_regions; 305 306 // We need to initialize the region(s) we just discovered. This is 307 // a bit tricky given that it can happen concurrently with 308 // refinement threads refining cards on these regions and 309 // potentially wanting to refine the BOT as they are scanning 310 // those cards (this can happen shortly after a cleanup; see CR 311 // 6991377). So we have to set up the region(s) carefully and in 312 // a specific order. 313 314 // The word size sum of all the regions we will allocate. 315 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 316 assert(word_size <= word_size_sum, "sanity"); 317 318 // This will be the "starts humongous" region. 319 HeapRegion* first_hr = region_at(first); 320 // The header of the new object will be placed at the bottom of 321 // the first region. 322 HeapWord* new_obj = first_hr->bottom(); 323 // This will be the new top of the new object. 324 HeapWord* obj_top = new_obj + word_size; 325 326 // First, we need to zero the header of the space that we will be 327 // allocating. When we update top further down, some refinement 328 // threads might try to scan the region. By zeroing the header we 329 // ensure that any thread that will try to scan the region will 330 // come across the zero klass word and bail out. 331 // 332 // NOTE: It would not have been correct to have used 333 // CollectedHeap::fill_with_object() and make the space look like 334 // an int array. The thread that is doing the allocation will 335 // later update the object header to a potentially different array 336 // type and, for a very short period of time, the klass and length 337 // fields will be inconsistent. This could cause a refinement 338 // thread to calculate the object size incorrectly. 339 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 340 341 // We will set up the first region as "starts humongous". This 342 // will also update the BOT covering all the regions to reflect 343 // that there is a single object that starts at the bottom of the 344 // first region. 345 first_hr->set_starts_humongous(obj_top); 346 first_hr->set_allocation_context(context); 347 // Then, if there are any, we will set up the "continues 348 // humongous" regions. 349 HeapRegion* hr = NULL; 350 for (uint i = first + 1; i < last; ++i) { 351 hr = region_at(i); 352 hr->set_continues_humongous(first_hr); 353 hr->set_allocation_context(context); 354 } 355 356 // Up to this point no concurrent thread would have been able to 357 // do any scanning on any region in this series. All the top 358 // fields still point to bottom, so the intersection between 359 // [bottom,top] and [card_start,card_end] will be empty. Before we 360 // update the top fields, we'll do a storestore to make sure that 361 // no thread sees the update to top before the zeroing of the 362 // object header and the BOT initialization. 363 OrderAccess::storestore(); 364 365 // Now that the BOT and the object header have been initialized, 366 // we can update top of the "starts humongous" region. 367 first_hr->set_top(MIN2(first_hr->end(), obj_top)); 368 if (_hr_printer.is_active()) { 369 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, first_hr->top()); 370 } 371 372 // Now, we will update the top fields of the "continues humongous" 373 // regions. 374 hr = NULL; 375 for (uint i = first + 1; i < last; ++i) { 376 hr = region_at(i); 377 if ((i + 1) == last) { 378 // last continues humongous region 379 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 380 "new_top should fall on this region"); 381 hr->set_top(obj_top); 382 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, obj_top); 383 } else { 384 // not last one 385 assert(obj_top > hr->end(), "obj_top should be above this region"); 386 hr->set_top(hr->end()); 387 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 388 } 389 } 390 // If we have continues humongous regions (hr != NULL), its top should 391 // match obj_top. 392 assert(hr == NULL || (hr->top() == obj_top), "sanity"); 393 check_bitmaps("Humongous Region Allocation", first_hr); 394 395 increase_used(word_size * HeapWordSize); 396 397 for (uint i = first; i < last; ++i) { 398 _humongous_set.add(region_at(i)); 399 } 400 401 return new_obj; 402 } 403 404 // If could fit into free regions w/o expansion, try. 405 // Otherwise, if can expand, do so. 406 // Otherwise, if using ex regions might help, try with ex given back. 407 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 408 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 409 410 verify_region_sets_optional(); 411 412 uint first = G1_NO_HRM_INDEX; 413 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords); 414 415 if (obj_regions == 1) { 416 // Only one region to allocate, try to use a fast path by directly allocating 417 // from the free lists. Do not try to expand here, we will potentially do that 418 // later. 419 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 420 if (hr != NULL) { 421 first = hr->hrm_index(); 422 } 423 } else { 424 // We can't allocate humongous regions spanning more than one region while 425 // cleanupComplete() is running, since some of the regions we find to be 426 // empty might not yet be added to the free list. It is not straightforward 427 // to know in which list they are on so that we can remove them. We only 428 // need to do this if we need to allocate more than one region to satisfy the 429 // current humongous allocation request. If we are only allocating one region 430 // we use the one-region region allocation code (see above), that already 431 // potentially waits for regions from the secondary free list. 432 wait_while_free_regions_coming(); 433 append_secondary_free_list_if_not_empty_with_lock(); 434 435 // Policy: Try only empty regions (i.e. already committed first). Maybe we 436 // are lucky enough to find some. 437 first = _hrm.find_contiguous_only_empty(obj_regions); 438 if (first != G1_NO_HRM_INDEX) { 439 _hrm.allocate_free_regions_starting_at(first, obj_regions); 440 } 441 } 442 443 if (first == G1_NO_HRM_INDEX) { 444 // Policy: We could not find enough regions for the humongous object in the 445 // free list. Look through the heap to find a mix of free and uncommitted regions. 446 // If so, try expansion. 447 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 448 if (first != G1_NO_HRM_INDEX) { 449 // We found something. Make sure these regions are committed, i.e. expand 450 // the heap. Alternatively we could do a defragmentation GC. 451 ergo_verbose1(ErgoHeapSizing, 452 "attempt heap expansion", 453 ergo_format_reason("humongous allocation request failed") 454 ergo_format_byte("allocation request"), 455 word_size * HeapWordSize); 456 457 _hrm.expand_at(first, obj_regions); 458 g1_policy()->record_new_heap_size(num_regions()); 459 460 #ifdef ASSERT 461 for (uint i = first; i < first + obj_regions; ++i) { 462 HeapRegion* hr = region_at(i); 463 assert(hr->is_free(), "sanity"); 464 assert(hr->is_empty(), "sanity"); 465 assert(is_on_master_free_list(hr), "sanity"); 466 } 467 #endif 468 _hrm.allocate_free_regions_starting_at(first, obj_regions); 469 } else { 470 // Policy: Potentially trigger a defragmentation GC. 471 } 472 } 473 474 HeapWord* result = NULL; 475 if (first != G1_NO_HRM_INDEX) { 476 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 477 word_size, context); 478 assert(result != NULL, "it should always return a valid result"); 479 480 // A successful humongous object allocation changes the used space 481 // information of the old generation so we need to recalculate the 482 // sizes and update the jstat counters here. 483 g1mm()->update_sizes(); 484 } 485 486 verify_region_sets_optional(); 487 488 return result; 489 } 490 491 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 492 assert_heap_not_locked_and_not_at_safepoint(); 493 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 494 495 uint dummy_gc_count_before; 496 uint dummy_gclocker_retry_count = 0; 497 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 498 } 499 500 HeapWord* 501 G1CollectedHeap::mem_allocate(size_t word_size, 502 bool* gc_overhead_limit_was_exceeded) { 503 assert_heap_not_locked_and_not_at_safepoint(); 504 505 // Loop until the allocation is satisfied, or unsatisfied after GC. 506 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 507 uint gc_count_before; 508 509 HeapWord* result = NULL; 510 if (!is_humongous(word_size)) { 511 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 512 } else { 513 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 514 } 515 if (result != NULL) { 516 return result; 517 } 518 519 // Create the garbage collection operation... 520 VM_G1CollectForAllocation op(gc_count_before, word_size); 521 op.set_allocation_context(AllocationContext::current()); 522 523 // ...and get the VM thread to execute it. 524 VMThread::execute(&op); 525 526 if (op.prologue_succeeded() && op.pause_succeeded()) { 527 // If the operation was successful we'll return the result even 528 // if it is NULL. If the allocation attempt failed immediately 529 // after a Full GC, it's unlikely we'll be able to allocate now. 530 HeapWord* result = op.result(); 531 if (result != NULL && !is_humongous(word_size)) { 532 // Allocations that take place on VM operations do not do any 533 // card dirtying and we have to do it here. We only have to do 534 // this for non-humongous allocations, though. 535 dirty_young_block(result, word_size); 536 } 537 return result; 538 } else { 539 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 540 return NULL; 541 } 542 assert(op.result() == NULL, 543 "the result should be NULL if the VM op did not succeed"); 544 } 545 546 // Give a warning if we seem to be looping forever. 547 if ((QueuedAllocationWarningCount > 0) && 548 (try_count % QueuedAllocationWarningCount == 0)) { 549 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 550 } 551 } 552 553 ShouldNotReachHere(); 554 return NULL; 555 } 556 557 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 558 AllocationContext_t context, 559 uint* gc_count_before_ret, 560 uint* gclocker_retry_count_ret) { 561 // Make sure you read the note in attempt_allocation_humongous(). 562 563 assert_heap_not_locked_and_not_at_safepoint(); 564 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 565 "be called for humongous allocation requests"); 566 567 // We should only get here after the first-level allocation attempt 568 // (attempt_allocation()) failed to allocate. 569 570 // We will loop until a) we manage to successfully perform the 571 // allocation or b) we successfully schedule a collection which 572 // fails to perform the allocation. b) is the only case when we'll 573 // return NULL. 574 HeapWord* result = NULL; 575 for (int try_count = 1; /* we'll return */; try_count += 1) { 576 bool should_try_gc; 577 uint gc_count_before; 578 579 { 580 MutexLockerEx x(Heap_lock); 581 result = _allocator->attempt_allocation_locked(word_size, context); 582 if (result != NULL) { 583 return result; 584 } 585 586 if (GC_locker::is_active_and_needs_gc()) { 587 if (g1_policy()->can_expand_young_list()) { 588 // No need for an ergo verbose message here, 589 // can_expand_young_list() does this when it returns true. 590 result = _allocator->attempt_allocation_force(word_size, context); 591 if (result != NULL) { 592 return result; 593 } 594 } 595 should_try_gc = false; 596 } else { 597 // The GCLocker may not be active but the GCLocker initiated 598 // GC may not yet have been performed (GCLocker::needs_gc() 599 // returns true). In this case we do not try this GC and 600 // wait until the GCLocker initiated GC is performed, and 601 // then retry the allocation. 602 if (GC_locker::needs_gc()) { 603 should_try_gc = false; 604 } else { 605 // Read the GC count while still holding the Heap_lock. 606 gc_count_before = total_collections(); 607 should_try_gc = true; 608 } 609 } 610 } 611 612 if (should_try_gc) { 613 bool succeeded; 614 result = do_collection_pause(word_size, gc_count_before, &succeeded, 615 GCCause::_g1_inc_collection_pause); 616 if (result != NULL) { 617 assert(succeeded, "only way to get back a non-NULL result"); 618 return result; 619 } 620 621 if (succeeded) { 622 // If we get here we successfully scheduled a collection which 623 // failed to allocate. No point in trying to allocate 624 // further. We'll just return NULL. 625 MutexLockerEx x(Heap_lock); 626 *gc_count_before_ret = total_collections(); 627 return NULL; 628 } 629 } else { 630 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 631 MutexLockerEx x(Heap_lock); 632 *gc_count_before_ret = total_collections(); 633 return NULL; 634 } 635 // The GCLocker is either active or the GCLocker initiated 636 // GC has not yet been performed. Stall until it is and 637 // then retry the allocation. 638 GC_locker::stall_until_clear(); 639 (*gclocker_retry_count_ret) += 1; 640 } 641 642 // We can reach here if we were unsuccessful in scheduling a 643 // collection (because another thread beat us to it) or if we were 644 // stalled due to the GC locker. In either can we should retry the 645 // allocation attempt in case another thread successfully 646 // performed a collection and reclaimed enough space. We do the 647 // first attempt (without holding the Heap_lock) here and the 648 // follow-on attempt will be at the start of the next loop 649 // iteration (after taking the Heap_lock). 650 result = _allocator->attempt_allocation(word_size, context); 651 if (result != NULL) { 652 return result; 653 } 654 655 // Give a warning if we seem to be looping forever. 656 if ((QueuedAllocationWarningCount > 0) && 657 (try_count % QueuedAllocationWarningCount == 0)) { 658 warning("G1CollectedHeap::attempt_allocation_slow() " 659 "retries %d times", try_count); 660 } 661 } 662 663 ShouldNotReachHere(); 664 return NULL; 665 } 666 667 void G1CollectedHeap::begin_archive_alloc_range() { 668 assert_at_safepoint(true /* should_be_vm_thread */); 669 if (_archive_allocator == NULL) { 670 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 671 } 672 } 673 674 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 675 // Allocations in archive regions cannot be of a size that would be considered 676 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 677 // may be different at archive-restore time. 678 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 679 } 680 681 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 682 assert_at_safepoint(true /* should_be_vm_thread */); 683 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 684 if (is_archive_alloc_too_large(word_size)) { 685 return NULL; 686 } 687 return _archive_allocator->archive_mem_allocate(word_size); 688 } 689 690 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 691 size_t end_alignment_in_bytes) { 692 assert_at_safepoint(true /* should_be_vm_thread */); 693 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 694 695 // Call complete_archive to do the real work, filling in the MemRegion 696 // array with the archive regions. 697 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 698 delete _archive_allocator; 699 _archive_allocator = NULL; 700 } 701 702 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 703 assert(ranges != NULL, "MemRegion array NULL"); 704 assert(count != 0, "No MemRegions provided"); 705 MemRegion reserved = _hrm.reserved(); 706 for (size_t i = 0; i < count; i++) { 707 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 708 return false; 709 } 710 } 711 return true; 712 } 713 714 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 715 assert(!is_init_completed(), "Expect to be called at JVM init time"); 716 assert(ranges != NULL, "MemRegion array NULL"); 717 assert(count != 0, "No MemRegions provided"); 718 MutexLockerEx x(Heap_lock); 719 720 MemRegion reserved = _hrm.reserved(); 721 HeapWord* prev_last_addr = NULL; 722 HeapRegion* prev_last_region = NULL; 723 724 // Temporarily disable pretouching of heap pages. This interface is used 725 // when mmap'ing archived heap data in, so pre-touching is wasted. 726 FlagSetting fs(AlwaysPreTouch, false); 727 728 // Enable archive object checking in G1MarkSweep. We have to let it know 729 // about each archive range, so that objects in those ranges aren't marked. 730 G1MarkSweep::enable_archive_object_check(); 731 732 // For each specified MemRegion range, allocate the corresponding G1 733 // regions and mark them as archive regions. We expect the ranges in 734 // ascending starting address order, without overlap. 735 for (size_t i = 0; i < count; i++) { 736 MemRegion curr_range = ranges[i]; 737 HeapWord* start_address = curr_range.start(); 738 size_t word_size = curr_range.word_size(); 739 HeapWord* last_address = curr_range.last(); 740 size_t commits = 0; 741 742 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 743 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 744 p2i(start_address), p2i(last_address)); 745 guarantee(start_address > prev_last_addr, 746 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 747 p2i(start_address), p2i(prev_last_addr)); 748 prev_last_addr = last_address; 749 750 // Check for ranges that start in the same G1 region in which the previous 751 // range ended, and adjust the start address so we don't try to allocate 752 // the same region again. If the current range is entirely within that 753 // region, skip it, just adjusting the recorded top. 754 HeapRegion* start_region = _hrm.addr_to_region(start_address); 755 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 756 start_address = start_region->end(); 757 if (start_address > last_address) { 758 increase_used(word_size * HeapWordSize); 759 start_region->set_top(last_address + 1); 760 continue; 761 } 762 start_region->set_top(start_address); 763 curr_range = MemRegion(start_address, last_address + 1); 764 start_region = _hrm.addr_to_region(start_address); 765 } 766 767 // Perform the actual region allocation, exiting if it fails. 768 // Then note how much new space we have allocated. 769 if (!_hrm.allocate_containing_regions(curr_range, &commits)) { 770 return false; 771 } 772 increase_used(word_size * HeapWordSize); 773 if (commits != 0) { 774 ergo_verbose1(ErgoHeapSizing, 775 "attempt heap expansion", 776 ergo_format_reason("allocate archive regions") 777 ergo_format_byte("total size"), 778 HeapRegion::GrainWords * HeapWordSize * commits); 779 } 780 781 // Mark each G1 region touched by the range as archive, add it to the old set, 782 // and set the allocation context and top. 783 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 784 HeapRegion* last_region = _hrm.addr_to_region(last_address); 785 prev_last_region = last_region; 786 787 while (curr_region != NULL) { 788 assert(curr_region->is_empty() && !curr_region->is_pinned(), 789 "Region already in use (index %u)", curr_region->hrm_index()); 790 _hr_printer.alloc(curr_region, G1HRPrinter::Archive); 791 curr_region->set_allocation_context(AllocationContext::system()); 792 curr_region->set_archive(); 793 _old_set.add(curr_region); 794 if (curr_region != last_region) { 795 curr_region->set_top(curr_region->end()); 796 curr_region = _hrm.next_region_in_heap(curr_region); 797 } else { 798 curr_region->set_top(last_address + 1); 799 curr_region = NULL; 800 } 801 } 802 803 // Notify mark-sweep of the archive range. 804 G1MarkSweep::set_range_archive(curr_range, true); 805 } 806 return true; 807 } 808 809 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 810 assert(!is_init_completed(), "Expect to be called at JVM init time"); 811 assert(ranges != NULL, "MemRegion array NULL"); 812 assert(count != 0, "No MemRegions provided"); 813 MemRegion reserved = _hrm.reserved(); 814 HeapWord *prev_last_addr = NULL; 815 HeapRegion* prev_last_region = NULL; 816 817 // For each MemRegion, create filler objects, if needed, in the G1 regions 818 // that contain the address range. The address range actually within the 819 // MemRegion will not be modified. That is assumed to have been initialized 820 // elsewhere, probably via an mmap of archived heap data. 821 MutexLockerEx x(Heap_lock); 822 for (size_t i = 0; i < count; i++) { 823 HeapWord* start_address = ranges[i].start(); 824 HeapWord* last_address = ranges[i].last(); 825 826 assert(reserved.contains(start_address) && reserved.contains(last_address), 827 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 828 p2i(start_address), p2i(last_address)); 829 assert(start_address > prev_last_addr, 830 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 831 p2i(start_address), p2i(prev_last_addr)); 832 833 HeapRegion* start_region = _hrm.addr_to_region(start_address); 834 HeapRegion* last_region = _hrm.addr_to_region(last_address); 835 HeapWord* bottom_address = start_region->bottom(); 836 837 // Check for a range beginning in the same region in which the 838 // previous one ended. 839 if (start_region == prev_last_region) { 840 bottom_address = prev_last_addr + 1; 841 } 842 843 // Verify that the regions were all marked as archive regions by 844 // alloc_archive_regions. 845 HeapRegion* curr_region = start_region; 846 while (curr_region != NULL) { 847 guarantee(curr_region->is_archive(), 848 "Expected archive region at index %u", curr_region->hrm_index()); 849 if (curr_region != last_region) { 850 curr_region = _hrm.next_region_in_heap(curr_region); 851 } else { 852 curr_region = NULL; 853 } 854 } 855 856 prev_last_addr = last_address; 857 prev_last_region = last_region; 858 859 // Fill the memory below the allocated range with dummy object(s), 860 // if the region bottom does not match the range start, or if the previous 861 // range ended within the same G1 region, and there is a gap. 862 if (start_address != bottom_address) { 863 size_t fill_size = pointer_delta(start_address, bottom_address); 864 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 865 increase_used(fill_size * HeapWordSize); 866 } 867 } 868 } 869 870 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 871 uint* gc_count_before_ret, 872 uint* gclocker_retry_count_ret) { 873 assert_heap_not_locked_and_not_at_safepoint(); 874 assert(!is_humongous(word_size), "attempt_allocation() should not " 875 "be called for humongous allocation requests"); 876 877 AllocationContext_t context = AllocationContext::current(); 878 HeapWord* result = _allocator->attempt_allocation(word_size, context); 879 880 if (result == NULL) { 881 result = attempt_allocation_slow(word_size, 882 context, 883 gc_count_before_ret, 884 gclocker_retry_count_ret); 885 } 886 assert_heap_not_locked(); 887 if (result != NULL) { 888 dirty_young_block(result, word_size); 889 } 890 return result; 891 } 892 893 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 894 assert(!is_init_completed(), "Expect to be called at JVM init time"); 895 assert(ranges != NULL, "MemRegion array NULL"); 896 assert(count != 0, "No MemRegions provided"); 897 MemRegion reserved = _hrm.reserved(); 898 HeapWord* prev_last_addr = NULL; 899 HeapRegion* prev_last_region = NULL; 900 size_t size_used = 0; 901 size_t uncommitted_regions = 0; 902 903 // For each Memregion, free the G1 regions that constitute it, and 904 // notify mark-sweep that the range is no longer to be considered 'archive.' 905 MutexLockerEx x(Heap_lock); 906 for (size_t i = 0; i < count; i++) { 907 HeapWord* start_address = ranges[i].start(); 908 HeapWord* last_address = ranges[i].last(); 909 910 assert(reserved.contains(start_address) && reserved.contains(last_address), 911 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 912 p2i(start_address), p2i(last_address)); 913 assert(start_address > prev_last_addr, 914 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 915 p2i(start_address), p2i(prev_last_addr)); 916 size_used += ranges[i].byte_size(); 917 prev_last_addr = last_address; 918 919 HeapRegion* start_region = _hrm.addr_to_region(start_address); 920 HeapRegion* last_region = _hrm.addr_to_region(last_address); 921 922 // Check for ranges that start in the same G1 region in which the previous 923 // range ended, and adjust the start address so we don't try to free 924 // the same region again. If the current range is entirely within that 925 // region, skip it. 926 if (start_region == prev_last_region) { 927 start_address = start_region->end(); 928 if (start_address > last_address) { 929 continue; 930 } 931 start_region = _hrm.addr_to_region(start_address); 932 } 933 prev_last_region = last_region; 934 935 // After verifying that each region was marked as an archive region by 936 // alloc_archive_regions, set it free and empty and uncommit it. 937 HeapRegion* curr_region = start_region; 938 while (curr_region != NULL) { 939 guarantee(curr_region->is_archive(), 940 "Expected archive region at index %u", curr_region->hrm_index()); 941 uint curr_index = curr_region->hrm_index(); 942 _old_set.remove(curr_region); 943 curr_region->set_free(); 944 curr_region->set_top(curr_region->bottom()); 945 if (curr_region != last_region) { 946 curr_region = _hrm.next_region_in_heap(curr_region); 947 } else { 948 curr_region = NULL; 949 } 950 _hrm.shrink_at(curr_index, 1); 951 uncommitted_regions++; 952 } 953 954 // Notify mark-sweep that this is no longer an archive range. 955 G1MarkSweep::set_range_archive(ranges[i], false); 956 } 957 958 if (uncommitted_regions != 0) { 959 ergo_verbose1(ErgoHeapSizing, 960 "attempt heap shrinking", 961 ergo_format_reason("uncommitted archive regions") 962 ergo_format_byte("total size"), 963 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 964 } 965 decrease_used(size_used); 966 } 967 968 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 969 uint* gc_count_before_ret, 970 uint* gclocker_retry_count_ret) { 971 // The structure of this method has a lot of similarities to 972 // attempt_allocation_slow(). The reason these two were not merged 973 // into a single one is that such a method would require several "if 974 // allocation is not humongous do this, otherwise do that" 975 // conditional paths which would obscure its flow. In fact, an early 976 // version of this code did use a unified method which was harder to 977 // follow and, as a result, it had subtle bugs that were hard to 978 // track down. So keeping these two methods separate allows each to 979 // be more readable. It will be good to keep these two in sync as 980 // much as possible. 981 982 assert_heap_not_locked_and_not_at_safepoint(); 983 assert(is_humongous(word_size), "attempt_allocation_humongous() " 984 "should only be called for humongous allocations"); 985 986 // Humongous objects can exhaust the heap quickly, so we should check if we 987 // need to start a marking cycle at each humongous object allocation. We do 988 // the check before we do the actual allocation. The reason for doing it 989 // before the allocation is that we avoid having to keep track of the newly 990 // allocated memory while we do a GC. 991 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 992 word_size)) { 993 collect(GCCause::_g1_humongous_allocation); 994 } 995 996 // We will loop until a) we manage to successfully perform the 997 // allocation or b) we successfully schedule a collection which 998 // fails to perform the allocation. b) is the only case when we'll 999 // return NULL. 1000 HeapWord* result = NULL; 1001 for (int try_count = 1; /* we'll return */; try_count += 1) { 1002 bool should_try_gc; 1003 uint gc_count_before; 1004 1005 { 1006 MutexLockerEx x(Heap_lock); 1007 1008 // Given that humongous objects are not allocated in young 1009 // regions, we'll first try to do the allocation without doing a 1010 // collection hoping that there's enough space in the heap. 1011 result = humongous_obj_allocate(word_size, AllocationContext::current()); 1012 if (result != NULL) { 1013 return result; 1014 } 1015 1016 if (GC_locker::is_active_and_needs_gc()) { 1017 should_try_gc = false; 1018 } else { 1019 // The GCLocker may not be active but the GCLocker initiated 1020 // GC may not yet have been performed (GCLocker::needs_gc() 1021 // returns true). In this case we do not try this GC and 1022 // wait until the GCLocker initiated GC is performed, and 1023 // then retry the allocation. 1024 if (GC_locker::needs_gc()) { 1025 should_try_gc = false; 1026 } else { 1027 // Read the GC count while still holding the Heap_lock. 1028 gc_count_before = total_collections(); 1029 should_try_gc = true; 1030 } 1031 } 1032 } 1033 1034 if (should_try_gc) { 1035 // If we failed to allocate the humongous object, we should try to 1036 // do a collection pause (if we're allowed) in case it reclaims 1037 // enough space for the allocation to succeed after the pause. 1038 1039 bool succeeded; 1040 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1041 GCCause::_g1_humongous_allocation); 1042 if (result != NULL) { 1043 assert(succeeded, "only way to get back a non-NULL result"); 1044 return result; 1045 } 1046 1047 if (succeeded) { 1048 // If we get here we successfully scheduled a collection which 1049 // failed to allocate. No point in trying to allocate 1050 // further. We'll just return NULL. 1051 MutexLockerEx x(Heap_lock); 1052 *gc_count_before_ret = total_collections(); 1053 return NULL; 1054 } 1055 } else { 1056 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1057 MutexLockerEx x(Heap_lock); 1058 *gc_count_before_ret = total_collections(); 1059 return NULL; 1060 } 1061 // The GCLocker is either active or the GCLocker initiated 1062 // GC has not yet been performed. Stall until it is and 1063 // then retry the allocation. 1064 GC_locker::stall_until_clear(); 1065 (*gclocker_retry_count_ret) += 1; 1066 } 1067 1068 // We can reach here if we were unsuccessful in scheduling a 1069 // collection (because another thread beat us to it) or if we were 1070 // stalled due to the GC locker. In either can we should retry the 1071 // allocation attempt in case another thread successfully 1072 // performed a collection and reclaimed enough space. Give a 1073 // warning if we seem to be looping forever. 1074 1075 if ((QueuedAllocationWarningCount > 0) && 1076 (try_count % QueuedAllocationWarningCount == 0)) { 1077 warning("G1CollectedHeap::attempt_allocation_humongous() " 1078 "retries %d times", try_count); 1079 } 1080 } 1081 1082 ShouldNotReachHere(); 1083 return NULL; 1084 } 1085 1086 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1087 AllocationContext_t context, 1088 bool expect_null_mutator_alloc_region) { 1089 assert_at_safepoint(true /* should_be_vm_thread */); 1090 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1091 "the current alloc region was unexpectedly found to be non-NULL"); 1092 1093 if (!is_humongous(word_size)) { 1094 return _allocator->attempt_allocation_locked(word_size, context); 1095 } else { 1096 HeapWord* result = humongous_obj_allocate(word_size, context); 1097 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1098 collector_state()->set_initiate_conc_mark_if_possible(true); 1099 } 1100 return result; 1101 } 1102 1103 ShouldNotReachHere(); 1104 } 1105 1106 class PostMCRemSetClearClosure: public HeapRegionClosure { 1107 G1CollectedHeap* _g1h; 1108 ModRefBarrierSet* _mr_bs; 1109 public: 1110 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1111 _g1h(g1h), _mr_bs(mr_bs) {} 1112 1113 bool doHeapRegion(HeapRegion* r) { 1114 HeapRegionRemSet* hrrs = r->rem_set(); 1115 1116 _g1h->reset_gc_time_stamps(r); 1117 1118 if (r->is_continues_humongous()) { 1119 // We'll assert that the strong code root list and RSet is empty 1120 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1121 assert(hrrs->occupied() == 0, "RSet should be empty"); 1122 } else { 1123 hrrs->clear(); 1124 } 1125 // You might think here that we could clear just the cards 1126 // corresponding to the used region. But no: if we leave a dirty card 1127 // in a region we might allocate into, then it would prevent that card 1128 // from being enqueued, and cause it to be missed. 1129 // Re: the performance cost: we shouldn't be doing full GC anyway! 1130 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1131 1132 return false; 1133 } 1134 }; 1135 1136 void G1CollectedHeap::clear_rsets_post_compaction() { 1137 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1138 heap_region_iterate(&rs_clear); 1139 } 1140 1141 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1142 G1CollectedHeap* _g1h; 1143 UpdateRSOopClosure _cl; 1144 public: 1145 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1146 _cl(g1->g1_rem_set(), worker_i), 1147 _g1h(g1) 1148 { } 1149 1150 bool doHeapRegion(HeapRegion* r) { 1151 if (!r->is_continues_humongous()) { 1152 _cl.set_from(r); 1153 r->oop_iterate(&_cl); 1154 } 1155 return false; 1156 } 1157 }; 1158 1159 class ParRebuildRSTask: public AbstractGangTask { 1160 G1CollectedHeap* _g1; 1161 HeapRegionClaimer _hrclaimer; 1162 1163 public: 1164 ParRebuildRSTask(G1CollectedHeap* g1) : 1165 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1166 1167 void work(uint worker_id) { 1168 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1169 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1170 } 1171 }; 1172 1173 class PostCompactionPrinterClosure: public HeapRegionClosure { 1174 private: 1175 G1HRPrinter* _hr_printer; 1176 public: 1177 bool doHeapRegion(HeapRegion* hr) { 1178 assert(!hr->is_young(), "not expecting to find young regions"); 1179 if (hr->is_free()) { 1180 // We only generate output for non-empty regions. 1181 } else if (hr->is_starts_humongous()) { 1182 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1183 } else if (hr->is_continues_humongous()) { 1184 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1185 } else if (hr->is_archive()) { 1186 _hr_printer->post_compaction(hr, G1HRPrinter::Archive); 1187 } else if (hr->is_old()) { 1188 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1189 } else { 1190 ShouldNotReachHere(); 1191 } 1192 return false; 1193 } 1194 1195 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1196 : _hr_printer(hr_printer) { } 1197 }; 1198 1199 void G1CollectedHeap::print_hrm_post_compaction() { 1200 PostCompactionPrinterClosure cl(hr_printer()); 1201 heap_region_iterate(&cl); 1202 } 1203 1204 bool G1CollectedHeap::do_collection(bool explicit_gc, 1205 bool clear_all_soft_refs, 1206 size_t word_size) { 1207 assert_at_safepoint(true /* should_be_vm_thread */); 1208 1209 if (GC_locker::check_active_before_gc()) { 1210 return false; 1211 } 1212 1213 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1214 gc_timer->register_gc_start(); 1215 1216 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1217 GCIdMark gc_id_mark; 1218 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1219 1220 SvcGCMarker sgcm(SvcGCMarker::FULL); 1221 ResourceMark rm; 1222 1223 G1Log::update_level(); 1224 print_heap_before_gc(); 1225 trace_heap_before_gc(gc_tracer); 1226 1227 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1228 1229 verify_region_sets_optional(); 1230 1231 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1232 collector_policy()->should_clear_all_soft_refs(); 1233 1234 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1235 1236 { 1237 IsGCActiveMark x; 1238 1239 // Timing 1240 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1241 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 1242 1243 { 1244 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL); 1245 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1246 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1247 1248 g1_policy()->record_full_collection_start(); 1249 1250 // Note: When we have a more flexible GC logging framework that 1251 // allows us to add optional attributes to a GC log record we 1252 // could consider timing and reporting how long we wait in the 1253 // following two methods. 1254 wait_while_free_regions_coming(); 1255 // If we start the compaction before the CM threads finish 1256 // scanning the root regions we might trip them over as we'll 1257 // be moving objects / updating references. So let's wait until 1258 // they are done. By telling them to abort, they should complete 1259 // early. 1260 _cm->root_regions()->abort(); 1261 _cm->root_regions()->wait_until_scan_finished(); 1262 append_secondary_free_list_if_not_empty_with_lock(); 1263 1264 gc_prologue(true); 1265 increment_total_collections(true /* full gc */); 1266 increment_old_marking_cycles_started(); 1267 1268 assert(used() == recalculate_used(), "Should be equal"); 1269 1270 verify_before_gc(); 1271 1272 check_bitmaps("Full GC Start"); 1273 pre_full_gc_dump(gc_timer); 1274 1275 #if defined(COMPILER2) || INCLUDE_JVMCI 1276 DerivedPointerTable::clear(); 1277 #endif 1278 1279 // Disable discovery and empty the discovered lists 1280 // for the CM ref processor. 1281 ref_processor_cm()->disable_discovery(); 1282 ref_processor_cm()->abandon_partial_discovery(); 1283 ref_processor_cm()->verify_no_references_recorded(); 1284 1285 // Abandon current iterations of concurrent marking and concurrent 1286 // refinement, if any are in progress. We have to do this before 1287 // wait_until_scan_finished() below. 1288 concurrent_mark()->abort(); 1289 1290 // Make sure we'll choose a new allocation region afterwards. 1291 _allocator->release_mutator_alloc_region(); 1292 _allocator->abandon_gc_alloc_regions(); 1293 g1_rem_set()->cleanupHRRS(); 1294 1295 // We should call this after we retire any currently active alloc 1296 // regions so that all the ALLOC / RETIRE events are generated 1297 // before the start GC event. 1298 _hr_printer.start_gc(true /* full */, (size_t) total_collections()); 1299 1300 // We may have added regions to the current incremental collection 1301 // set between the last GC or pause and now. We need to clear the 1302 // incremental collection set and then start rebuilding it afresh 1303 // after this full GC. 1304 abandon_collection_set(g1_policy()->inc_cset_head()); 1305 g1_policy()->clear_incremental_cset(); 1306 g1_policy()->stop_incremental_cset_building(); 1307 1308 tear_down_region_sets(false /* free_list_only */); 1309 collector_state()->set_gcs_are_young(true); 1310 1311 // See the comments in g1CollectedHeap.hpp and 1312 // G1CollectedHeap::ref_processing_init() about 1313 // how reference processing currently works in G1. 1314 1315 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1316 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1317 1318 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1319 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1320 1321 ref_processor_stw()->enable_discovery(); 1322 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1323 1324 // Do collection work 1325 { 1326 HandleMark hm; // Discard invalid handles created during gc 1327 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1328 } 1329 1330 assert(num_free_regions() == 0, "we should not have added any free regions"); 1331 rebuild_region_sets(false /* free_list_only */); 1332 1333 // Enqueue any discovered reference objects that have 1334 // not been removed from the discovered lists. 1335 ref_processor_stw()->enqueue_discovered_references(); 1336 1337 #if defined(COMPILER2) || INCLUDE_JVMCI 1338 DerivedPointerTable::update_pointers(); 1339 #endif 1340 1341 MemoryService::track_memory_usage(); 1342 1343 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1344 ref_processor_stw()->verify_no_references_recorded(); 1345 1346 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1347 ClassLoaderDataGraph::purge(); 1348 MetaspaceAux::verify_metrics(); 1349 1350 // Note: since we've just done a full GC, concurrent 1351 // marking is no longer active. Therefore we need not 1352 // re-enable reference discovery for the CM ref processor. 1353 // That will be done at the start of the next marking cycle. 1354 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1355 ref_processor_cm()->verify_no_references_recorded(); 1356 1357 reset_gc_time_stamp(); 1358 // Since everything potentially moved, we will clear all remembered 1359 // sets, and clear all cards. Later we will rebuild remembered 1360 // sets. We will also reset the GC time stamps of the regions. 1361 clear_rsets_post_compaction(); 1362 check_gc_time_stamps(); 1363 1364 // Resize the heap if necessary. 1365 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); 1366 1367 if (_hr_printer.is_active()) { 1368 // We should do this after we potentially resize the heap so 1369 // that all the COMMIT / UNCOMMIT events are generated before 1370 // the end GC event. 1371 1372 print_hrm_post_compaction(); 1373 _hr_printer.end_gc(true /* full */, (size_t) total_collections()); 1374 } 1375 1376 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1377 if (hot_card_cache->use_cache()) { 1378 hot_card_cache->reset_card_counts(); 1379 hot_card_cache->reset_hot_cache(); 1380 } 1381 1382 // Rebuild remembered sets of all regions. 1383 uint n_workers = 1384 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1385 workers()->active_workers(), 1386 Threads::number_of_non_daemon_threads()); 1387 workers()->set_active_workers(n_workers); 1388 1389 ParRebuildRSTask rebuild_rs_task(this); 1390 workers()->run_task(&rebuild_rs_task); 1391 1392 // Rebuild the strong code root lists for each region 1393 rebuild_strong_code_roots(); 1394 1395 if (true) { // FIXME 1396 MetaspaceGC::compute_new_size(); 1397 } 1398 1399 #ifdef TRACESPINNING 1400 ParallelTaskTerminator::print_termination_counts(); 1401 #endif 1402 1403 // Discard all rset updates 1404 JavaThread::dirty_card_queue_set().abandon_logs(); 1405 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1406 1407 _young_list->reset_sampled_info(); 1408 // At this point there should be no regions in the 1409 // entire heap tagged as young. 1410 assert(check_young_list_empty(true /* check_heap */), 1411 "young list should be empty at this point"); 1412 1413 // Update the number of full collections that have been completed. 1414 increment_old_marking_cycles_completed(false /* concurrent */); 1415 1416 _hrm.verify_optional(); 1417 verify_region_sets_optional(); 1418 1419 verify_after_gc(); 1420 1421 // Clear the previous marking bitmap, if needed for bitmap verification. 1422 // Note we cannot do this when we clear the next marking bitmap in 1423 // ConcurrentMark::abort() above since VerifyDuringGC verifies the 1424 // objects marked during a full GC against the previous bitmap. 1425 // But we need to clear it before calling check_bitmaps below since 1426 // the full GC has compacted objects and updated TAMS but not updated 1427 // the prev bitmap. 1428 if (G1VerifyBitmaps) { 1429 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll(); 1430 } 1431 check_bitmaps("Full GC End"); 1432 1433 // Start a new incremental collection set for the next pause 1434 assert(g1_policy()->collection_set() == NULL, "must be"); 1435 g1_policy()->start_incremental_cset_building(); 1436 1437 clear_cset_fast_test(); 1438 1439 _allocator->init_mutator_alloc_region(); 1440 1441 g1_policy()->record_full_collection_end(); 1442 1443 if (G1Log::fine()) { 1444 g1_policy()->print_heap_transition(); 1445 } 1446 1447 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1448 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1449 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1450 // before any GC notifications are raised. 1451 g1mm()->update_sizes(); 1452 1453 gc_epilogue(true); 1454 } 1455 1456 if (G1Log::finer()) { 1457 g1_policy()->print_detailed_heap_transition(true /* full */); 1458 } 1459 1460 print_heap_after_gc(); 1461 trace_heap_after_gc(gc_tracer); 1462 1463 post_full_gc_dump(gc_timer); 1464 1465 gc_timer->register_gc_end(); 1466 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1467 } 1468 1469 return true; 1470 } 1471 1472 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1473 // do_collection() will return whether it succeeded in performing 1474 // the GC. Currently, there is no facility on the 1475 // do_full_collection() API to notify the caller than the collection 1476 // did not succeed (e.g., because it was locked out by the GC 1477 // locker). So, right now, we'll ignore the return value. 1478 bool dummy = do_collection(true, /* explicit_gc */ 1479 clear_all_soft_refs, 1480 0 /* word_size */); 1481 } 1482 1483 // This code is mostly copied from TenuredGeneration. 1484 void 1485 G1CollectedHeap:: 1486 resize_if_necessary_after_full_collection(size_t word_size) { 1487 // Include the current allocation, if any, and bytes that will be 1488 // pre-allocated to support collections, as "used". 1489 const size_t used_after_gc = used(); 1490 const size_t capacity_after_gc = capacity(); 1491 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1492 1493 // This is enforced in arguments.cpp. 1494 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1495 "otherwise the code below doesn't make sense"); 1496 1497 // We don't have floating point command-line arguments 1498 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1499 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1500 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1501 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1502 1503 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1504 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1505 1506 // We have to be careful here as these two calculations can overflow 1507 // 32-bit size_t's. 1508 double used_after_gc_d = (double) used_after_gc; 1509 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1510 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1511 1512 // Let's make sure that they are both under the max heap size, which 1513 // by default will make them fit into a size_t. 1514 double desired_capacity_upper_bound = (double) max_heap_size; 1515 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1516 desired_capacity_upper_bound); 1517 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1518 desired_capacity_upper_bound); 1519 1520 // We can now safely turn them into size_t's. 1521 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1522 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1523 1524 // This assert only makes sense here, before we adjust them 1525 // with respect to the min and max heap size. 1526 assert(minimum_desired_capacity <= maximum_desired_capacity, 1527 "minimum_desired_capacity = " SIZE_FORMAT ", " 1528 "maximum_desired_capacity = " SIZE_FORMAT, 1529 minimum_desired_capacity, maximum_desired_capacity); 1530 1531 // Should not be greater than the heap max size. No need to adjust 1532 // it with respect to the heap min size as it's a lower bound (i.e., 1533 // we'll try to make the capacity larger than it, not smaller). 1534 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1535 // Should not be less than the heap min size. No need to adjust it 1536 // with respect to the heap max size as it's an upper bound (i.e., 1537 // we'll try to make the capacity smaller than it, not greater). 1538 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1539 1540 if (capacity_after_gc < minimum_desired_capacity) { 1541 // Don't expand unless it's significant 1542 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1543 ergo_verbose4(ErgoHeapSizing, 1544 "attempt heap expansion", 1545 ergo_format_reason("capacity lower than " 1546 "min desired capacity after Full GC") 1547 ergo_format_byte("capacity") 1548 ergo_format_byte("occupancy") 1549 ergo_format_byte_perc("min desired capacity"), 1550 capacity_after_gc, used_after_gc, 1551 minimum_desired_capacity, (double) MinHeapFreeRatio); 1552 expand(expand_bytes); 1553 1554 // No expansion, now see if we want to shrink 1555 } else if (capacity_after_gc > maximum_desired_capacity) { 1556 // Capacity too large, compute shrinking size 1557 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1558 ergo_verbose4(ErgoHeapSizing, 1559 "attempt heap shrinking", 1560 ergo_format_reason("capacity higher than " 1561 "max desired capacity after Full GC") 1562 ergo_format_byte("capacity") 1563 ergo_format_byte("occupancy") 1564 ergo_format_byte_perc("max desired capacity"), 1565 capacity_after_gc, used_after_gc, 1566 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1567 shrink(shrink_bytes); 1568 } 1569 } 1570 1571 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1572 AllocationContext_t context, 1573 bool do_gc, 1574 bool clear_all_soft_refs, 1575 bool expect_null_mutator_alloc_region, 1576 bool* gc_succeeded) { 1577 *gc_succeeded = true; 1578 // Let's attempt the allocation first. 1579 HeapWord* result = 1580 attempt_allocation_at_safepoint(word_size, 1581 context, 1582 expect_null_mutator_alloc_region); 1583 if (result != NULL) { 1584 assert(*gc_succeeded, "sanity"); 1585 return result; 1586 } 1587 1588 // In a G1 heap, we're supposed to keep allocation from failing by 1589 // incremental pauses. Therefore, at least for now, we'll favor 1590 // expansion over collection. (This might change in the future if we can 1591 // do something smarter than full collection to satisfy a failed alloc.) 1592 result = expand_and_allocate(word_size, context); 1593 if (result != NULL) { 1594 assert(*gc_succeeded, "sanity"); 1595 return result; 1596 } 1597 1598 if (do_gc) { 1599 // Expansion didn't work, we'll try to do a Full GC. 1600 *gc_succeeded = do_collection(false, /* explicit_gc */ 1601 clear_all_soft_refs, 1602 word_size); 1603 } 1604 1605 return NULL; 1606 } 1607 1608 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1609 AllocationContext_t context, 1610 bool* succeeded) { 1611 assert_at_safepoint(true /* should_be_vm_thread */); 1612 1613 // Attempts to allocate followed by Full GC. 1614 HeapWord* result = 1615 satisfy_failed_allocation_helper(word_size, 1616 context, 1617 true, /* do_gc */ 1618 false, /* clear_all_soft_refs */ 1619 false, /* expect_null_mutator_alloc_region */ 1620 succeeded); 1621 1622 if (result != NULL || !*succeeded) { 1623 return result; 1624 } 1625 1626 // Attempts to allocate followed by Full GC that will collect all soft references. 1627 result = satisfy_failed_allocation_helper(word_size, 1628 context, 1629 true, /* do_gc */ 1630 true, /* clear_all_soft_refs */ 1631 true, /* expect_null_mutator_alloc_region */ 1632 succeeded); 1633 1634 if (result != NULL || !*succeeded) { 1635 return result; 1636 } 1637 1638 // Attempts to allocate, no GC 1639 result = satisfy_failed_allocation_helper(word_size, 1640 context, 1641 false, /* do_gc */ 1642 false, /* clear_all_soft_refs */ 1643 true, /* expect_null_mutator_alloc_region */ 1644 succeeded); 1645 1646 if (result != NULL) { 1647 assert(*succeeded, "sanity"); 1648 return result; 1649 } 1650 1651 assert(!collector_policy()->should_clear_all_soft_refs(), 1652 "Flag should have been handled and cleared prior to this point"); 1653 1654 // What else? We might try synchronous finalization later. If the total 1655 // space available is large enough for the allocation, then a more 1656 // complete compaction phase than we've tried so far might be 1657 // appropriate. 1658 assert(*succeeded, "sanity"); 1659 return NULL; 1660 } 1661 1662 // Attempting to expand the heap sufficiently 1663 // to support an allocation of the given "word_size". If 1664 // successful, perform the allocation and return the address of the 1665 // allocated block, or else "NULL". 1666 1667 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1668 assert_at_safepoint(true /* should_be_vm_thread */); 1669 1670 verify_region_sets_optional(); 1671 1672 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1673 ergo_verbose1(ErgoHeapSizing, 1674 "attempt heap expansion", 1675 ergo_format_reason("allocation request failed") 1676 ergo_format_byte("allocation request"), 1677 word_size * HeapWordSize); 1678 if (expand(expand_bytes)) { 1679 _hrm.verify_optional(); 1680 verify_region_sets_optional(); 1681 return attempt_allocation_at_safepoint(word_size, 1682 context, 1683 false /* expect_null_mutator_alloc_region */); 1684 } 1685 return NULL; 1686 } 1687 1688 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) { 1689 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1690 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1691 HeapRegion::GrainBytes); 1692 ergo_verbose2(ErgoHeapSizing, 1693 "expand the heap", 1694 ergo_format_byte("requested expansion amount") 1695 ergo_format_byte("attempted expansion amount"), 1696 expand_bytes, aligned_expand_bytes); 1697 1698 if (is_maximal_no_gc()) { 1699 ergo_verbose0(ErgoHeapSizing, 1700 "did not expand the heap", 1701 ergo_format_reason("heap already fully expanded")); 1702 return false; 1703 } 1704 1705 double expand_heap_start_time_sec = os::elapsedTime(); 1706 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1707 assert(regions_to_expand > 0, "Must expand by at least one region"); 1708 1709 uint expanded_by = _hrm.expand_by(regions_to_expand); 1710 if (expand_time_ms != NULL) { 1711 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1712 } 1713 1714 if (expanded_by > 0) { 1715 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1716 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1717 g1_policy()->record_new_heap_size(num_regions()); 1718 } else { 1719 ergo_verbose0(ErgoHeapSizing, 1720 "did not expand the heap", 1721 ergo_format_reason("heap expansion operation failed")); 1722 // The expansion of the virtual storage space was unsuccessful. 1723 // Let's see if it was because we ran out of swap. 1724 if (G1ExitOnExpansionFailure && 1725 _hrm.available() >= regions_to_expand) { 1726 // We had head room... 1727 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1728 } 1729 } 1730 return regions_to_expand > 0; 1731 } 1732 1733 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1734 size_t aligned_shrink_bytes = 1735 ReservedSpace::page_align_size_down(shrink_bytes); 1736 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1737 HeapRegion::GrainBytes); 1738 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1739 1740 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1741 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1742 1743 ergo_verbose3(ErgoHeapSizing, 1744 "shrink the heap", 1745 ergo_format_byte("requested shrinking amount") 1746 ergo_format_byte("aligned shrinking amount") 1747 ergo_format_byte("attempted shrinking amount"), 1748 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1749 if (num_regions_removed > 0) { 1750 g1_policy()->record_new_heap_size(num_regions()); 1751 } else { 1752 ergo_verbose0(ErgoHeapSizing, 1753 "did not shrink the heap", 1754 ergo_format_reason("heap shrinking operation failed")); 1755 } 1756 } 1757 1758 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1759 verify_region_sets_optional(); 1760 1761 // We should only reach here at the end of a Full GC which means we 1762 // should not not be holding to any GC alloc regions. The method 1763 // below will make sure of that and do any remaining clean up. 1764 _allocator->abandon_gc_alloc_regions(); 1765 1766 // Instead of tearing down / rebuilding the free lists here, we 1767 // could instead use the remove_all_pending() method on free_list to 1768 // remove only the ones that we need to remove. 1769 tear_down_region_sets(true /* free_list_only */); 1770 shrink_helper(shrink_bytes); 1771 rebuild_region_sets(true /* free_list_only */); 1772 1773 _hrm.verify_optional(); 1774 verify_region_sets_optional(); 1775 } 1776 1777 // Public methods. 1778 1779 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1780 CollectedHeap(), 1781 _g1_policy(policy_), 1782 _dirty_card_queue_set(false), 1783 _is_alive_closure_cm(this), 1784 _is_alive_closure_stw(this), 1785 _ref_processor_cm(NULL), 1786 _ref_processor_stw(NULL), 1787 _bot_shared(NULL), 1788 _cg1r(NULL), 1789 _g1mm(NULL), 1790 _refine_cte_cl(NULL), 1791 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1792 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1793 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1794 _humongous_reclaim_candidates(), 1795 _has_humongous_reclaim_candidates(false), 1796 _archive_allocator(NULL), 1797 _free_regions_coming(false), 1798 _young_list(new YoungList(this)), 1799 _gc_time_stamp(0), 1800 _summary_bytes_used(0), 1801 _survivor_evac_stats(YoungPLABSize, PLABWeight), 1802 _old_evac_stats(OldPLABSize, PLABWeight), 1803 _expand_heap_after_alloc_failure(true), 1804 _old_marking_cycles_started(0), 1805 _old_marking_cycles_completed(0), 1806 _heap_summary_sent(false), 1807 _in_cset_fast_test(), 1808 _dirty_cards_region_list(NULL), 1809 _worker_cset_start_region(NULL), 1810 _worker_cset_start_region_time_stamp(NULL), 1811 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1812 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1813 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1814 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1815 1816 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1817 /* are_GC_task_threads */true, 1818 /* are_ConcurrentGC_threads */false); 1819 _workers->initialize_workers(); 1820 1821 _allocator = G1Allocator::create_allocator(this); 1822 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1823 1824 // Override the default _filler_array_max_size so that no humongous filler 1825 // objects are created. 1826 _filler_array_max_size = _humongous_object_threshold_in_words; 1827 1828 uint n_queues = ParallelGCThreads; 1829 _task_queues = new RefToScanQueueSet(n_queues); 1830 1831 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1832 assert(n_rem_sets > 0, "Invariant."); 1833 1834 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1835 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC); 1836 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1837 1838 for (uint i = 0; i < n_queues; i++) { 1839 RefToScanQueue* q = new RefToScanQueue(); 1840 q->initialize(); 1841 _task_queues->register_queue(i, q); 1842 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1843 } 1844 clear_cset_start_regions(); 1845 1846 // Initialize the G1EvacuationFailureALot counters and flags. 1847 NOT_PRODUCT(reset_evacuation_should_fail();) 1848 1849 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1850 } 1851 1852 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1853 size_t size, 1854 size_t translation_factor) { 1855 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1856 // Allocate a new reserved space, preferring to use large pages. 1857 ReservedSpace rs(size, preferred_page_size); 1858 G1RegionToSpaceMapper* result = 1859 G1RegionToSpaceMapper::create_mapper(rs, 1860 size, 1861 rs.alignment(), 1862 HeapRegion::GrainBytes, 1863 translation_factor, 1864 mtGC); 1865 if (TracePageSizes) { 1866 gclog_or_tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT, 1867 description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size); 1868 } 1869 return result; 1870 } 1871 1872 jint G1CollectedHeap::initialize() { 1873 CollectedHeap::pre_initialize(); 1874 os::enable_vtime(); 1875 1876 G1Log::init(); 1877 1878 // Necessary to satisfy locking discipline assertions. 1879 1880 MutexLocker x(Heap_lock); 1881 1882 // We have to initialize the printer before committing the heap, as 1883 // it will be used then. 1884 _hr_printer.set_active(G1PrintHeapRegions); 1885 1886 // While there are no constraints in the GC code that HeapWordSize 1887 // be any particular value, there are multiple other areas in the 1888 // system which believe this to be true (e.g. oop->object_size in some 1889 // cases incorrectly returns the size in wordSize units rather than 1890 // HeapWordSize). 1891 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1892 1893 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1894 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1895 size_t heap_alignment = collector_policy()->heap_alignment(); 1896 1897 // Ensure that the sizes are properly aligned. 1898 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1899 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1900 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1901 1902 _refine_cte_cl = new RefineCardTableEntryClosure(); 1903 1904 jint ecode = JNI_OK; 1905 _cg1r = ConcurrentG1Refine::create(this, _refine_cte_cl, &ecode); 1906 if (_cg1r == NULL) { 1907 return ecode; 1908 } 1909 1910 // Reserve the maximum. 1911 1912 // When compressed oops are enabled, the preferred heap base 1913 // is calculated by subtracting the requested size from the 1914 // 32Gb boundary and using the result as the base address for 1915 // heap reservation. If the requested size is not aligned to 1916 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1917 // into the ReservedHeapSpace constructor) then the actual 1918 // base of the reserved heap may end up differing from the 1919 // address that was requested (i.e. the preferred heap base). 1920 // If this happens then we could end up using a non-optimal 1921 // compressed oops mode. 1922 1923 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1924 heap_alignment); 1925 1926 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1927 1928 // Create the barrier set for the entire reserved region. 1929 G1SATBCardTableLoggingModRefBS* bs 1930 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1931 bs->initialize(); 1932 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1933 set_barrier_set(bs); 1934 1935 // Also create a G1 rem set. 1936 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 1937 1938 // Carve out the G1 part of the heap. 1939 1940 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1941 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1942 G1RegionToSpaceMapper* heap_storage = 1943 G1RegionToSpaceMapper::create_mapper(g1_rs, 1944 g1_rs.size(), 1945 page_size, 1946 HeapRegion::GrainBytes, 1947 1, 1948 mtJavaHeap); 1949 os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(), 1950 max_byte_size, page_size, 1951 heap_rs.base(), 1952 heap_rs.size()); 1953 heap_storage->set_mapping_changed_listener(&_listener); 1954 1955 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1956 G1RegionToSpaceMapper* bot_storage = 1957 create_aux_memory_mapper("Block offset table", 1958 G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize), 1959 G1BlockOffsetSharedArray::heap_map_factor()); 1960 1961 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1962 G1RegionToSpaceMapper* cardtable_storage = 1963 create_aux_memory_mapper("Card table", 1964 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1965 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1966 1967 G1RegionToSpaceMapper* card_counts_storage = 1968 create_aux_memory_mapper("Card counts table", 1969 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1970 G1CardCounts::heap_map_factor()); 1971 1972 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size()); 1973 G1RegionToSpaceMapper* prev_bitmap_storage = 1974 create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1975 G1RegionToSpaceMapper* next_bitmap_storage = 1976 create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1977 1978 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1979 g1_barrier_set()->initialize(cardtable_storage); 1980 // Do later initialization work for concurrent refinement. 1981 _cg1r->init(card_counts_storage); 1982 1983 // 6843694 - ensure that the maximum region index can fit 1984 // in the remembered set structures. 1985 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1986 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1987 1988 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1989 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1990 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1991 "too many cards per region"); 1992 1993 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1994 1995 _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage); 1996 1997 { 1998 HeapWord* start = _hrm.reserved().start(); 1999 HeapWord* end = _hrm.reserved().end(); 2000 size_t granularity = HeapRegion::GrainBytes; 2001 2002 _in_cset_fast_test.initialize(start, end, granularity); 2003 _humongous_reclaim_candidates.initialize(start, end, granularity); 2004 } 2005 2006 // Create the ConcurrentMark data structure and thread. 2007 // (Must do this late, so that "max_regions" is defined.) 2008 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 2009 if (_cm == NULL || !_cm->completed_initialization()) { 2010 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 2011 return JNI_ENOMEM; 2012 } 2013 _cmThread = _cm->cmThread(); 2014 2015 // Initialize the from_card cache structure of HeapRegionRemSet. 2016 HeapRegionRemSet::init_heap(max_regions()); 2017 2018 // Now expand into the initial heap size. 2019 if (!expand(init_byte_size)) { 2020 vm_shutdown_during_initialization("Failed to allocate initial heap."); 2021 return JNI_ENOMEM; 2022 } 2023 2024 // Perform any initialization actions delegated to the policy. 2025 g1_policy()->init(); 2026 2027 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2028 SATB_Q_FL_lock, 2029 G1SATBProcessCompletedThreshold, 2030 Shared_SATB_Q_lock); 2031 2032 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 2033 DirtyCardQ_CBL_mon, 2034 DirtyCardQ_FL_lock, 2035 concurrent_g1_refine()->yellow_zone(), 2036 concurrent_g1_refine()->red_zone(), 2037 Shared_DirtyCardQ_lock); 2038 2039 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 2040 DirtyCardQ_CBL_mon, 2041 DirtyCardQ_FL_lock, 2042 -1, // never trigger processing 2043 -1, // no limit on length 2044 Shared_DirtyCardQ_lock, 2045 &JavaThread::dirty_card_queue_set()); 2046 2047 // Here we allocate the dummy HeapRegion that is required by the 2048 // G1AllocRegion class. 2049 HeapRegion* dummy_region = _hrm.get_dummy_region(); 2050 2051 // We'll re-use the same region whether the alloc region will 2052 // require BOT updates or not and, if it doesn't, then a non-young 2053 // region will complain that it cannot support allocations without 2054 // BOT updates. So we'll tag the dummy region as eden to avoid that. 2055 dummy_region->set_eden(); 2056 // Make sure it's full. 2057 dummy_region->set_top(dummy_region->end()); 2058 G1AllocRegion::setup(this, dummy_region); 2059 2060 _allocator->init_mutator_alloc_region(); 2061 2062 // Do create of the monitoring and management support so that 2063 // values in the heap have been properly initialized. 2064 _g1mm = new G1MonitoringSupport(this); 2065 2066 G1StringDedup::initialize(); 2067 2068 _preserved_objs = NEW_C_HEAP_ARRAY(OopAndMarkOopStack, ParallelGCThreads, mtGC); 2069 for (uint i = 0; i < ParallelGCThreads; i++) { 2070 new (&_preserved_objs[i]) OopAndMarkOopStack(); 2071 } 2072 2073 return JNI_OK; 2074 } 2075 2076 void G1CollectedHeap::stop() { 2077 // Stop all concurrent threads. We do this to make sure these threads 2078 // do not continue to execute and access resources (e.g. gclog_or_tty) 2079 // that are destroyed during shutdown. 2080 _cg1r->stop(); 2081 _cmThread->stop(); 2082 if (G1StringDedup::is_enabled()) { 2083 G1StringDedup::stop(); 2084 } 2085 } 2086 2087 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2088 return HeapRegion::max_region_size(); 2089 } 2090 2091 void G1CollectedHeap::post_initialize() { 2092 CollectedHeap::post_initialize(); 2093 ref_processing_init(); 2094 } 2095 2096 void G1CollectedHeap::ref_processing_init() { 2097 // Reference processing in G1 currently works as follows: 2098 // 2099 // * There are two reference processor instances. One is 2100 // used to record and process discovered references 2101 // during concurrent marking; the other is used to 2102 // record and process references during STW pauses 2103 // (both full and incremental). 2104 // * Both ref processors need to 'span' the entire heap as 2105 // the regions in the collection set may be dotted around. 2106 // 2107 // * For the concurrent marking ref processor: 2108 // * Reference discovery is enabled at initial marking. 2109 // * Reference discovery is disabled and the discovered 2110 // references processed etc during remarking. 2111 // * Reference discovery is MT (see below). 2112 // * Reference discovery requires a barrier (see below). 2113 // * Reference processing may or may not be MT 2114 // (depending on the value of ParallelRefProcEnabled 2115 // and ParallelGCThreads). 2116 // * A full GC disables reference discovery by the CM 2117 // ref processor and abandons any entries on it's 2118 // discovered lists. 2119 // 2120 // * For the STW processor: 2121 // * Non MT discovery is enabled at the start of a full GC. 2122 // * Processing and enqueueing during a full GC is non-MT. 2123 // * During a full GC, references are processed after marking. 2124 // 2125 // * Discovery (may or may not be MT) is enabled at the start 2126 // of an incremental evacuation pause. 2127 // * References are processed near the end of a STW evacuation pause. 2128 // * For both types of GC: 2129 // * Discovery is atomic - i.e. not concurrent. 2130 // * Reference discovery will not need a barrier. 2131 2132 MemRegion mr = reserved_region(); 2133 2134 // Concurrent Mark ref processor 2135 _ref_processor_cm = 2136 new ReferenceProcessor(mr, // span 2137 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2138 // mt processing 2139 ParallelGCThreads, 2140 // degree of mt processing 2141 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2142 // mt discovery 2143 MAX2(ParallelGCThreads, ConcGCThreads), 2144 // degree of mt discovery 2145 false, 2146 // Reference discovery is not atomic 2147 &_is_alive_closure_cm); 2148 // is alive closure 2149 // (for efficiency/performance) 2150 2151 // STW ref processor 2152 _ref_processor_stw = 2153 new ReferenceProcessor(mr, // span 2154 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2155 // mt processing 2156 ParallelGCThreads, 2157 // degree of mt processing 2158 (ParallelGCThreads > 1), 2159 // mt discovery 2160 ParallelGCThreads, 2161 // degree of mt discovery 2162 true, 2163 // Reference discovery is atomic 2164 &_is_alive_closure_stw); 2165 // is alive closure 2166 // (for efficiency/performance) 2167 } 2168 2169 CollectorPolicy* G1CollectedHeap::collector_policy() const { 2170 return g1_policy(); 2171 } 2172 2173 size_t G1CollectedHeap::capacity() const { 2174 return _hrm.length() * HeapRegion::GrainBytes; 2175 } 2176 2177 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2178 hr->reset_gc_time_stamp(); 2179 } 2180 2181 #ifndef PRODUCT 2182 2183 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2184 private: 2185 unsigned _gc_time_stamp; 2186 bool _failures; 2187 2188 public: 2189 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2190 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2191 2192 virtual bool doHeapRegion(HeapRegion* hr) { 2193 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2194 if (_gc_time_stamp != region_gc_time_stamp) { 2195 gclog_or_tty->print_cr("Region " HR_FORMAT " has GC time stamp = %d, " 2196 "expected %d", HR_FORMAT_PARAMS(hr), 2197 region_gc_time_stamp, _gc_time_stamp); 2198 _failures = true; 2199 } 2200 return false; 2201 } 2202 2203 bool failures() { return _failures; } 2204 }; 2205 2206 void G1CollectedHeap::check_gc_time_stamps() { 2207 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2208 heap_region_iterate(&cl); 2209 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2210 } 2211 #endif // PRODUCT 2212 2213 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2214 _cg1r->hot_card_cache()->drain(cl, worker_i); 2215 } 2216 2217 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2218 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2219 size_t n_completed_buffers = 0; 2220 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2221 n_completed_buffers++; 2222 } 2223 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2224 dcqs.clear_n_completed_buffers(); 2225 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2226 } 2227 2228 // Computes the sum of the storage used by the various regions. 2229 size_t G1CollectedHeap::used() const { 2230 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2231 if (_archive_allocator != NULL) { 2232 result += _archive_allocator->used(); 2233 } 2234 return result; 2235 } 2236 2237 size_t G1CollectedHeap::used_unlocked() const { 2238 return _summary_bytes_used; 2239 } 2240 2241 class SumUsedClosure: public HeapRegionClosure { 2242 size_t _used; 2243 public: 2244 SumUsedClosure() : _used(0) {} 2245 bool doHeapRegion(HeapRegion* r) { 2246 _used += r->used(); 2247 return false; 2248 } 2249 size_t result() { return _used; } 2250 }; 2251 2252 size_t G1CollectedHeap::recalculate_used() const { 2253 double recalculate_used_start = os::elapsedTime(); 2254 2255 SumUsedClosure blk; 2256 heap_region_iterate(&blk); 2257 2258 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2259 return blk.result(); 2260 } 2261 2262 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2263 switch (cause) { 2264 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2265 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2266 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2267 case GCCause::_g1_humongous_allocation: return true; 2268 case GCCause::_update_allocation_context_stats_inc: return true; 2269 case GCCause::_wb_conc_mark: return true; 2270 default: return false; 2271 } 2272 } 2273 2274 #ifndef PRODUCT 2275 void G1CollectedHeap::allocate_dummy_regions() { 2276 // Let's fill up most of the region 2277 size_t word_size = HeapRegion::GrainWords - 1024; 2278 // And as a result the region we'll allocate will be humongous. 2279 guarantee(is_humongous(word_size), "sanity"); 2280 2281 // _filler_array_max_size is set to humongous object threshold 2282 // but temporarily change it to use CollectedHeap::fill_with_object(). 2283 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2284 2285 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2286 // Let's use the existing mechanism for the allocation 2287 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2288 AllocationContext::system()); 2289 if (dummy_obj != NULL) { 2290 MemRegion mr(dummy_obj, word_size); 2291 CollectedHeap::fill_with_object(mr); 2292 } else { 2293 // If we can't allocate once, we probably cannot allocate 2294 // again. Let's get out of the loop. 2295 break; 2296 } 2297 } 2298 } 2299 #endif // !PRODUCT 2300 2301 void G1CollectedHeap::increment_old_marking_cycles_started() { 2302 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2303 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2304 "Wrong marking cycle count (started: %d, completed: %d)", 2305 _old_marking_cycles_started, _old_marking_cycles_completed); 2306 2307 _old_marking_cycles_started++; 2308 } 2309 2310 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2311 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2312 2313 // We assume that if concurrent == true, then the caller is a 2314 // concurrent thread that was joined the Suspendible Thread 2315 // Set. If there's ever a cheap way to check this, we should add an 2316 // assert here. 2317 2318 // Given that this method is called at the end of a Full GC or of a 2319 // concurrent cycle, and those can be nested (i.e., a Full GC can 2320 // interrupt a concurrent cycle), the number of full collections 2321 // completed should be either one (in the case where there was no 2322 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2323 // behind the number of full collections started. 2324 2325 // This is the case for the inner caller, i.e. a Full GC. 2326 assert(concurrent || 2327 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2328 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2329 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2330 "is inconsistent with _old_marking_cycles_completed = %u", 2331 _old_marking_cycles_started, _old_marking_cycles_completed); 2332 2333 // This is the case for the outer caller, i.e. the concurrent cycle. 2334 assert(!concurrent || 2335 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2336 "for outer caller (concurrent cycle): " 2337 "_old_marking_cycles_started = %u " 2338 "is inconsistent with _old_marking_cycles_completed = %u", 2339 _old_marking_cycles_started, _old_marking_cycles_completed); 2340 2341 _old_marking_cycles_completed += 1; 2342 2343 // We need to clear the "in_progress" flag in the CM thread before 2344 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2345 // is set) so that if a waiter requests another System.gc() it doesn't 2346 // incorrectly see that a marking cycle is still in progress. 2347 if (concurrent) { 2348 _cmThread->set_idle(); 2349 } 2350 2351 // This notify_all() will ensure that a thread that called 2352 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2353 // and it's waiting for a full GC to finish will be woken up. It is 2354 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2355 FullGCCount_lock->notify_all(); 2356 } 2357 2358 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2359 GCIdMarkAndRestore conc_gc_id_mark; 2360 collector_state()->set_concurrent_cycle_started(true); 2361 _gc_timer_cm->register_gc_start(start_time); 2362 2363 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2364 trace_heap_before_gc(_gc_tracer_cm); 2365 _cmThread->set_gc_id(GCId::current()); 2366 } 2367 2368 void G1CollectedHeap::register_concurrent_cycle_end() { 2369 if (collector_state()->concurrent_cycle_started()) { 2370 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2371 if (_cm->has_aborted()) { 2372 _gc_tracer_cm->report_concurrent_mode_failure(); 2373 } 2374 2375 _gc_timer_cm->register_gc_end(); 2376 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2377 2378 // Clear state variables to prepare for the next concurrent cycle. 2379 collector_state()->set_concurrent_cycle_started(false); 2380 _heap_summary_sent = false; 2381 } 2382 } 2383 2384 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2385 if (collector_state()->concurrent_cycle_started()) { 2386 // This function can be called when: 2387 // the cleanup pause is run 2388 // the concurrent cycle is aborted before the cleanup pause. 2389 // the concurrent cycle is aborted after the cleanup pause, 2390 // but before the concurrent cycle end has been registered. 2391 // Make sure that we only send the heap information once. 2392 if (!_heap_summary_sent) { 2393 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2394 trace_heap_after_gc(_gc_tracer_cm); 2395 _heap_summary_sent = true; 2396 } 2397 } 2398 } 2399 2400 void G1CollectedHeap::collect(GCCause::Cause cause) { 2401 assert_heap_not_locked(); 2402 2403 uint gc_count_before; 2404 uint old_marking_count_before; 2405 uint full_gc_count_before; 2406 bool retry_gc; 2407 2408 do { 2409 retry_gc = false; 2410 2411 { 2412 MutexLocker ml(Heap_lock); 2413 2414 // Read the GC count while holding the Heap_lock 2415 gc_count_before = total_collections(); 2416 full_gc_count_before = total_full_collections(); 2417 old_marking_count_before = _old_marking_cycles_started; 2418 } 2419 2420 if (should_do_concurrent_full_gc(cause)) { 2421 // Schedule an initial-mark evacuation pause that will start a 2422 // concurrent cycle. We're setting word_size to 0 which means that 2423 // we are not requesting a post-GC allocation. 2424 VM_G1IncCollectionPause op(gc_count_before, 2425 0, /* word_size */ 2426 true, /* should_initiate_conc_mark */ 2427 g1_policy()->max_pause_time_ms(), 2428 cause); 2429 op.set_allocation_context(AllocationContext::current()); 2430 2431 VMThread::execute(&op); 2432 if (!op.pause_succeeded()) { 2433 if (old_marking_count_before == _old_marking_cycles_started) { 2434 retry_gc = op.should_retry_gc(); 2435 } else { 2436 // A Full GC happened while we were trying to schedule the 2437 // initial-mark GC. No point in starting a new cycle given 2438 // that the whole heap was collected anyway. 2439 } 2440 2441 if (retry_gc) { 2442 if (GC_locker::is_active_and_needs_gc()) { 2443 GC_locker::stall_until_clear(); 2444 } 2445 } 2446 } 2447 } else { 2448 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2449 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2450 2451 // Schedule a standard evacuation pause. We're setting word_size 2452 // to 0 which means that we are not requesting a post-GC allocation. 2453 VM_G1IncCollectionPause op(gc_count_before, 2454 0, /* word_size */ 2455 false, /* should_initiate_conc_mark */ 2456 g1_policy()->max_pause_time_ms(), 2457 cause); 2458 VMThread::execute(&op); 2459 } else { 2460 // Schedule a Full GC. 2461 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2462 VMThread::execute(&op); 2463 } 2464 } 2465 } while (retry_gc); 2466 } 2467 2468 bool G1CollectedHeap::is_in(const void* p) const { 2469 if (_hrm.reserved().contains(p)) { 2470 // Given that we know that p is in the reserved space, 2471 // heap_region_containing() should successfully 2472 // return the containing region. 2473 HeapRegion* hr = heap_region_containing(p); 2474 return hr->is_in(p); 2475 } else { 2476 return false; 2477 } 2478 } 2479 2480 #ifdef ASSERT 2481 bool G1CollectedHeap::is_in_exact(const void* p) const { 2482 bool contains = reserved_region().contains(p); 2483 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2484 if (contains && available) { 2485 return true; 2486 } else { 2487 return false; 2488 } 2489 } 2490 #endif 2491 2492 bool G1CollectedHeap::obj_in_cs(oop obj) { 2493 HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj); 2494 return r != NULL && r->in_collection_set(); 2495 } 2496 2497 // Iteration functions. 2498 2499 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2500 2501 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2502 ExtendedOopClosure* _cl; 2503 public: 2504 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2505 bool doHeapRegion(HeapRegion* r) { 2506 if (!r->is_continues_humongous()) { 2507 r->oop_iterate(_cl); 2508 } 2509 return false; 2510 } 2511 }; 2512 2513 // Iterates an ObjectClosure over all objects within a HeapRegion. 2514 2515 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2516 ObjectClosure* _cl; 2517 public: 2518 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2519 bool doHeapRegion(HeapRegion* r) { 2520 if (!r->is_continues_humongous()) { 2521 r->object_iterate(_cl); 2522 } 2523 return false; 2524 } 2525 }; 2526 2527 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2528 IterateObjectClosureRegionClosure blk(cl); 2529 heap_region_iterate(&blk); 2530 } 2531 2532 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2533 _hrm.iterate(cl); 2534 } 2535 2536 void 2537 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2538 uint worker_id, 2539 HeapRegionClaimer *hrclaimer, 2540 bool concurrent) const { 2541 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2542 } 2543 2544 // Clear the cached CSet starting regions and (more importantly) 2545 // the time stamps. Called when we reset the GC time stamp. 2546 void G1CollectedHeap::clear_cset_start_regions() { 2547 assert(_worker_cset_start_region != NULL, "sanity"); 2548 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2549 2550 for (uint i = 0; i < ParallelGCThreads; i++) { 2551 _worker_cset_start_region[i] = NULL; 2552 _worker_cset_start_region_time_stamp[i] = 0; 2553 } 2554 } 2555 2556 // Given the id of a worker, obtain or calculate a suitable 2557 // starting region for iterating over the current collection set. 2558 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2559 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2560 2561 HeapRegion* result = NULL; 2562 unsigned gc_time_stamp = get_gc_time_stamp(); 2563 2564 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2565 // Cached starting region for current worker was set 2566 // during the current pause - so it's valid. 2567 // Note: the cached starting heap region may be NULL 2568 // (when the collection set is empty). 2569 result = _worker_cset_start_region[worker_i]; 2570 assert(result == NULL || result->in_collection_set(), "sanity"); 2571 return result; 2572 } 2573 2574 // The cached entry was not valid so let's calculate 2575 // a suitable starting heap region for this worker. 2576 2577 // We want the parallel threads to start their collection 2578 // set iteration at different collection set regions to 2579 // avoid contention. 2580 // If we have: 2581 // n collection set regions 2582 // p threads 2583 // Then thread t will start at region floor ((t * n) / p) 2584 2585 result = g1_policy()->collection_set(); 2586 uint cs_size = g1_policy()->cset_region_length(); 2587 uint active_workers = workers()->active_workers(); 2588 2589 uint end_ind = (cs_size * worker_i) / active_workers; 2590 uint start_ind = 0; 2591 2592 if (worker_i > 0 && 2593 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2594 // Previous workers starting region is valid 2595 // so let's iterate from there 2596 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2597 result = _worker_cset_start_region[worker_i - 1]; 2598 } 2599 2600 for (uint i = start_ind; i < end_ind; i++) { 2601 result = result->next_in_collection_set(); 2602 } 2603 2604 // Note: the calculated starting heap region may be NULL 2605 // (when the collection set is empty). 2606 assert(result == NULL || result->in_collection_set(), "sanity"); 2607 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2608 "should be updated only once per pause"); 2609 _worker_cset_start_region[worker_i] = result; 2610 OrderAccess::storestore(); 2611 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2612 return result; 2613 } 2614 2615 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2616 HeapRegion* r = g1_policy()->collection_set(); 2617 while (r != NULL) { 2618 HeapRegion* next = r->next_in_collection_set(); 2619 if (cl->doHeapRegion(r)) { 2620 cl->incomplete(); 2621 return; 2622 } 2623 r = next; 2624 } 2625 } 2626 2627 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2628 HeapRegionClosure *cl) { 2629 if (r == NULL) { 2630 // The CSet is empty so there's nothing to do. 2631 return; 2632 } 2633 2634 assert(r->in_collection_set(), 2635 "Start region must be a member of the collection set."); 2636 HeapRegion* cur = r; 2637 while (cur != NULL) { 2638 HeapRegion* next = cur->next_in_collection_set(); 2639 if (cl->doHeapRegion(cur) && false) { 2640 cl->incomplete(); 2641 return; 2642 } 2643 cur = next; 2644 } 2645 cur = g1_policy()->collection_set(); 2646 while (cur != r) { 2647 HeapRegion* next = cur->next_in_collection_set(); 2648 if (cl->doHeapRegion(cur) && false) { 2649 cl->incomplete(); 2650 return; 2651 } 2652 cur = next; 2653 } 2654 } 2655 2656 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2657 HeapRegion* result = _hrm.next_region_in_heap(from); 2658 while (result != NULL && result->is_pinned()) { 2659 result = _hrm.next_region_in_heap(result); 2660 } 2661 return result; 2662 } 2663 2664 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2665 HeapRegion* hr = heap_region_containing(addr); 2666 return hr->block_start(addr); 2667 } 2668 2669 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2670 HeapRegion* hr = heap_region_containing(addr); 2671 return hr->block_size(addr); 2672 } 2673 2674 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2675 HeapRegion* hr = heap_region_containing(addr); 2676 return hr->block_is_obj(addr); 2677 } 2678 2679 bool G1CollectedHeap::supports_tlab_allocation() const { 2680 return true; 2681 } 2682 2683 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2684 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2685 } 2686 2687 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2688 return young_list()->eden_used_bytes(); 2689 } 2690 2691 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2692 // must be equal to the humongous object limit. 2693 size_t G1CollectedHeap::max_tlab_size() const { 2694 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2695 } 2696 2697 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2698 AllocationContext_t context = AllocationContext::current(); 2699 return _allocator->unsafe_max_tlab_alloc(context); 2700 } 2701 2702 size_t G1CollectedHeap::max_capacity() const { 2703 return _hrm.reserved().byte_size(); 2704 } 2705 2706 jlong G1CollectedHeap::millis_since_last_gc() { 2707 // assert(false, "NYI"); 2708 return 0; 2709 } 2710 2711 void G1CollectedHeap::prepare_for_verify() { 2712 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2713 ensure_parsability(false); 2714 } 2715 g1_rem_set()->prepare_for_verify(); 2716 } 2717 2718 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 2719 VerifyOption vo) { 2720 switch (vo) { 2721 case VerifyOption_G1UsePrevMarking: 2722 return hr->obj_allocated_since_prev_marking(obj); 2723 case VerifyOption_G1UseNextMarking: 2724 return hr->obj_allocated_since_next_marking(obj); 2725 case VerifyOption_G1UseMarkWord: 2726 return false; 2727 default: 2728 ShouldNotReachHere(); 2729 } 2730 return false; // keep some compilers happy 2731 } 2732 2733 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 2734 switch (vo) { 2735 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 2736 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 2737 case VerifyOption_G1UseMarkWord: return NULL; 2738 default: ShouldNotReachHere(); 2739 } 2740 return NULL; // keep some compilers happy 2741 } 2742 2743 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 2744 switch (vo) { 2745 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 2746 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 2747 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 2748 default: ShouldNotReachHere(); 2749 } 2750 return false; // keep some compilers happy 2751 } 2752 2753 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 2754 switch (vo) { 2755 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 2756 case VerifyOption_G1UseNextMarking: return "NTAMS"; 2757 case VerifyOption_G1UseMarkWord: return "NONE"; 2758 default: ShouldNotReachHere(); 2759 } 2760 return NULL; // keep some compilers happy 2761 } 2762 2763 class VerifyRootsClosure: public OopClosure { 2764 private: 2765 G1CollectedHeap* _g1h; 2766 VerifyOption _vo; 2767 bool _failures; 2768 public: 2769 // _vo == UsePrevMarking -> use "prev" marking information, 2770 // _vo == UseNextMarking -> use "next" marking information, 2771 // _vo == UseMarkWord -> use mark word from object header. 2772 VerifyRootsClosure(VerifyOption vo) : 2773 _g1h(G1CollectedHeap::heap()), 2774 _vo(vo), 2775 _failures(false) { } 2776 2777 bool failures() { return _failures; } 2778 2779 template <class T> void do_oop_nv(T* p) { 2780 T heap_oop = oopDesc::load_heap_oop(p); 2781 if (!oopDesc::is_null(heap_oop)) { 2782 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2783 if (_g1h->is_obj_dead_cond(obj, _vo)) { 2784 gclog_or_tty->print_cr("Root location " PTR_FORMAT " " 2785 "points to dead obj " PTR_FORMAT, p2i(p), p2i(obj)); 2786 if (_vo == VerifyOption_G1UseMarkWord) { 2787 gclog_or_tty->print_cr(" Mark word: " INTPTR_FORMAT, (intptr_t)obj->mark()); 2788 } 2789 obj->print_on(gclog_or_tty); 2790 _failures = true; 2791 } 2792 } 2793 } 2794 2795 void do_oop(oop* p) { do_oop_nv(p); } 2796 void do_oop(narrowOop* p) { do_oop_nv(p); } 2797 }; 2798 2799 class G1VerifyCodeRootOopClosure: public OopClosure { 2800 G1CollectedHeap* _g1h; 2801 OopClosure* _root_cl; 2802 nmethod* _nm; 2803 VerifyOption _vo; 2804 bool _failures; 2805 2806 template <class T> void do_oop_work(T* p) { 2807 // First verify that this root is live 2808 _root_cl->do_oop(p); 2809 2810 if (!G1VerifyHeapRegionCodeRoots) { 2811 // We're not verifying the code roots attached to heap region. 2812 return; 2813 } 2814 2815 // Don't check the code roots during marking verification in a full GC 2816 if (_vo == VerifyOption_G1UseMarkWord) { 2817 return; 2818 } 2819 2820 // Now verify that the current nmethod (which contains p) is 2821 // in the code root list of the heap region containing the 2822 // object referenced by p. 2823 2824 T heap_oop = oopDesc::load_heap_oop(p); 2825 if (!oopDesc::is_null(heap_oop)) { 2826 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2827 2828 // Now fetch the region containing the object 2829 HeapRegion* hr = _g1h->heap_region_containing(obj); 2830 HeapRegionRemSet* hrrs = hr->rem_set(); 2831 // Verify that the strong code root list for this region 2832 // contains the nmethod 2833 if (!hrrs->strong_code_roots_list_contains(_nm)) { 2834 gclog_or_tty->print_cr("Code root location " PTR_FORMAT " " 2835 "from nmethod " PTR_FORMAT " not in strong " 2836 "code roots for region [" PTR_FORMAT "," PTR_FORMAT ")", 2837 p2i(p), p2i(_nm), p2i(hr->bottom()), p2i(hr->end())); 2838 _failures = true; 2839 } 2840 } 2841 } 2842 2843 public: 2844 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo): 2845 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {} 2846 2847 void do_oop(oop* p) { do_oop_work(p); } 2848 void do_oop(narrowOop* p) { do_oop_work(p); } 2849 2850 void set_nmethod(nmethod* nm) { _nm = nm; } 2851 bool failures() { return _failures; } 2852 }; 2853 2854 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure { 2855 G1VerifyCodeRootOopClosure* _oop_cl; 2856 2857 public: 2858 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl): 2859 _oop_cl(oop_cl) {} 2860 2861 void do_code_blob(CodeBlob* cb) { 2862 nmethod* nm = cb->as_nmethod_or_null(); 2863 if (nm != NULL) { 2864 _oop_cl->set_nmethod(nm); 2865 nm->oops_do(_oop_cl); 2866 } 2867 } 2868 }; 2869 2870 class YoungRefCounterClosure : public OopClosure { 2871 G1CollectedHeap* _g1h; 2872 int _count; 2873 public: 2874 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 2875 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 2876 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 2877 2878 int count() { return _count; } 2879 void reset_count() { _count = 0; }; 2880 }; 2881 2882 class VerifyKlassClosure: public KlassClosure { 2883 YoungRefCounterClosure _young_ref_counter_closure; 2884 OopClosure *_oop_closure; 2885 public: 2886 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 2887 void do_klass(Klass* k) { 2888 k->oops_do(_oop_closure); 2889 2890 _young_ref_counter_closure.reset_count(); 2891 k->oops_do(&_young_ref_counter_closure); 2892 if (_young_ref_counter_closure.count() > 0) { 2893 guarantee(k->has_modified_oops(), "Klass " PTR_FORMAT ", has young refs but is not dirty.", p2i(k)); 2894 } 2895 } 2896 }; 2897 2898 class VerifyLivenessOopClosure: public OopClosure { 2899 G1CollectedHeap* _g1h; 2900 VerifyOption _vo; 2901 public: 2902 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 2903 _g1h(g1h), _vo(vo) 2904 { } 2905 void do_oop(narrowOop *p) { do_oop_work(p); } 2906 void do_oop( oop *p) { do_oop_work(p); } 2907 2908 template <class T> void do_oop_work(T *p) { 2909 oop obj = oopDesc::load_decode_heap_oop(p); 2910 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 2911 "Dead object referenced by a not dead object"); 2912 } 2913 }; 2914 2915 class VerifyObjsInRegionClosure: public ObjectClosure { 2916 private: 2917 G1CollectedHeap* _g1h; 2918 size_t _live_bytes; 2919 HeapRegion *_hr; 2920 VerifyOption _vo; 2921 public: 2922 // _vo == UsePrevMarking -> use "prev" marking information, 2923 // _vo == UseNextMarking -> use "next" marking information, 2924 // _vo == UseMarkWord -> use mark word from object header. 2925 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 2926 : _live_bytes(0), _hr(hr), _vo(vo) { 2927 _g1h = G1CollectedHeap::heap(); 2928 } 2929 void do_object(oop o) { 2930 VerifyLivenessOopClosure isLive(_g1h, _vo); 2931 assert(o != NULL, "Huh?"); 2932 if (!_g1h->is_obj_dead_cond(o, _vo)) { 2933 // If the object is alive according to the mark word, 2934 // then verify that the marking information agrees. 2935 // Note we can't verify the contra-positive of the 2936 // above: if the object is dead (according to the mark 2937 // word), it may not be marked, or may have been marked 2938 // but has since became dead, or may have been allocated 2939 // since the last marking. 2940 if (_vo == VerifyOption_G1UseMarkWord) { 2941 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 2942 } 2943 2944 o->oop_iterate_no_header(&isLive); 2945 if (!_hr->obj_allocated_since_prev_marking(o)) { 2946 size_t obj_size = o->size(); // Make sure we don't overflow 2947 _live_bytes += (obj_size * HeapWordSize); 2948 } 2949 } 2950 } 2951 size_t live_bytes() { return _live_bytes; } 2952 }; 2953 2954 class VerifyArchiveOopClosure: public OopClosure { 2955 public: 2956 VerifyArchiveOopClosure(HeapRegion *hr) { } 2957 void do_oop(narrowOop *p) { do_oop_work(p); } 2958 void do_oop( oop *p) { do_oop_work(p); } 2959 2960 template <class T> void do_oop_work(T *p) { 2961 oop obj = oopDesc::load_decode_heap_oop(p); 2962 guarantee(obj == NULL || G1MarkSweep::in_archive_range(obj), 2963 "Archive object at " PTR_FORMAT " references a non-archive object at " PTR_FORMAT, 2964 p2i(p), p2i(obj)); 2965 } 2966 }; 2967 2968 class VerifyArchiveRegionClosure: public ObjectClosure { 2969 public: 2970 VerifyArchiveRegionClosure(HeapRegion *hr) { } 2971 // Verify that all object pointers are to archive regions. 2972 void do_object(oop o) { 2973 VerifyArchiveOopClosure checkOop(NULL); 2974 assert(o != NULL, "Should not be here for NULL oops"); 2975 o->oop_iterate_no_header(&checkOop); 2976 } 2977 }; 2978 2979 class VerifyRegionClosure: public HeapRegionClosure { 2980 private: 2981 bool _par; 2982 VerifyOption _vo; 2983 bool _failures; 2984 public: 2985 // _vo == UsePrevMarking -> use "prev" marking information, 2986 // _vo == UseNextMarking -> use "next" marking information, 2987 // _vo == UseMarkWord -> use mark word from object header. 2988 VerifyRegionClosure(bool par, VerifyOption vo) 2989 : _par(par), 2990 _vo(vo), 2991 _failures(false) {} 2992 2993 bool failures() { 2994 return _failures; 2995 } 2996 2997 bool doHeapRegion(HeapRegion* r) { 2998 // For archive regions, verify there are no heap pointers to 2999 // non-pinned regions. For all others, verify liveness info. 3000 if (r->is_archive()) { 3001 VerifyArchiveRegionClosure verify_oop_pointers(r); 3002 r->object_iterate(&verify_oop_pointers); 3003 return true; 3004 } 3005 if (!r->is_continues_humongous()) { 3006 bool failures = false; 3007 r->verify(_vo, &failures); 3008 if (failures) { 3009 _failures = true; 3010 } else if (!r->is_starts_humongous()) { 3011 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 3012 r->object_iterate(¬_dead_yet_cl); 3013 if (_vo != VerifyOption_G1UseNextMarking) { 3014 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 3015 gclog_or_tty->print_cr("[" PTR_FORMAT "," PTR_FORMAT "] " 3016 "max_live_bytes " SIZE_FORMAT " " 3017 "< calculated " SIZE_FORMAT, 3018 p2i(r->bottom()), p2i(r->end()), 3019 r->max_live_bytes(), 3020 not_dead_yet_cl.live_bytes()); 3021 _failures = true; 3022 } 3023 } else { 3024 // When vo == UseNextMarking we cannot currently do a sanity 3025 // check on the live bytes as the calculation has not been 3026 // finalized yet. 3027 } 3028 } 3029 } 3030 return false; // stop the region iteration if we hit a failure 3031 } 3032 }; 3033 3034 // This is the task used for parallel verification of the heap regions 3035 3036 class G1ParVerifyTask: public AbstractGangTask { 3037 private: 3038 G1CollectedHeap* _g1h; 3039 VerifyOption _vo; 3040 bool _failures; 3041 HeapRegionClaimer _hrclaimer; 3042 3043 public: 3044 // _vo == UsePrevMarking -> use "prev" marking information, 3045 // _vo == UseNextMarking -> use "next" marking information, 3046 // _vo == UseMarkWord -> use mark word from object header. 3047 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3048 AbstractGangTask("Parallel verify task"), 3049 _g1h(g1h), 3050 _vo(vo), 3051 _failures(false), 3052 _hrclaimer(g1h->workers()->active_workers()) {} 3053 3054 bool failures() { 3055 return _failures; 3056 } 3057 3058 void work(uint worker_id) { 3059 HandleMark hm; 3060 VerifyRegionClosure blk(true, _vo); 3061 _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer); 3062 if (blk.failures()) { 3063 _failures = true; 3064 } 3065 } 3066 }; 3067 3068 void G1CollectedHeap::verify(bool silent, VerifyOption vo) { 3069 if (SafepointSynchronize::is_at_safepoint()) { 3070 assert(Thread::current()->is_VM_thread(), 3071 "Expected to be executed serially by the VM thread at this point"); 3072 3073 if (!silent) { gclog_or_tty->print("Roots "); } 3074 VerifyRootsClosure rootsCl(vo); 3075 VerifyKlassClosure klassCl(this, &rootsCl); 3076 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false); 3077 3078 // We apply the relevant closures to all the oops in the 3079 // system dictionary, class loader data graph, the string table 3080 // and the nmethods in the code cache. 3081 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo); 3082 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl); 3083 3084 { 3085 G1RootProcessor root_processor(this, 1); 3086 root_processor.process_all_roots(&rootsCl, 3087 &cldCl, 3088 &blobsCl); 3089 } 3090 3091 bool failures = rootsCl.failures() || codeRootsCl.failures(); 3092 3093 if (vo != VerifyOption_G1UseMarkWord) { 3094 // If we're verifying during a full GC then the region sets 3095 // will have been torn down at the start of the GC. Therefore 3096 // verifying the region sets will fail. So we only verify 3097 // the region sets when not in a full GC. 3098 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3099 verify_region_sets(); 3100 } 3101 3102 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3103 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3104 3105 G1ParVerifyTask task(this, vo); 3106 workers()->run_task(&task); 3107 if (task.failures()) { 3108 failures = true; 3109 } 3110 3111 } else { 3112 VerifyRegionClosure blk(false, vo); 3113 heap_region_iterate(&blk); 3114 if (blk.failures()) { 3115 failures = true; 3116 } 3117 } 3118 3119 if (G1StringDedup::is_enabled()) { 3120 if (!silent) gclog_or_tty->print("StrDedup "); 3121 G1StringDedup::verify(); 3122 } 3123 3124 if (failures) { 3125 gclog_or_tty->print_cr("Heap:"); 3126 // It helps to have the per-region information in the output to 3127 // help us track down what went wrong. This is why we call 3128 // print_extended_on() instead of print_on(). 3129 print_extended_on(gclog_or_tty); 3130 gclog_or_tty->cr(); 3131 gclog_or_tty->flush(); 3132 } 3133 guarantee(!failures, "there should not have been any failures"); 3134 } else { 3135 if (!silent) { 3136 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet"); 3137 if (G1StringDedup::is_enabled()) { 3138 gclog_or_tty->print(", StrDedup"); 3139 } 3140 gclog_or_tty->print(") "); 3141 } 3142 } 3143 } 3144 3145 void G1CollectedHeap::verify(bool silent) { 3146 verify(silent, VerifyOption_G1UsePrevMarking); 3147 } 3148 3149 double G1CollectedHeap::verify(bool guard, const char* msg) { 3150 double verify_time_ms = 0.0; 3151 3152 if (guard && total_collections() >= VerifyGCStartAt) { 3153 double verify_start = os::elapsedTime(); 3154 HandleMark hm; // Discard invalid handles created during verification 3155 prepare_for_verify(); 3156 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 3157 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 3158 } 3159 3160 return verify_time_ms; 3161 } 3162 3163 void G1CollectedHeap::verify_before_gc() { 3164 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:"); 3165 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 3166 } 3167 3168 void G1CollectedHeap::verify_after_gc() { 3169 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:"); 3170 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 3171 } 3172 3173 class PrintRegionClosure: public HeapRegionClosure { 3174 outputStream* _st; 3175 public: 3176 PrintRegionClosure(outputStream* st) : _st(st) {} 3177 bool doHeapRegion(HeapRegion* r) { 3178 r->print_on(_st); 3179 return false; 3180 } 3181 }; 3182 3183 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3184 const HeapRegion* hr, 3185 const VerifyOption vo) const { 3186 switch (vo) { 3187 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 3188 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 3189 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 3190 default: ShouldNotReachHere(); 3191 } 3192 return false; // keep some compilers happy 3193 } 3194 3195 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3196 const VerifyOption vo) const { 3197 switch (vo) { 3198 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 3199 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 3200 case VerifyOption_G1UseMarkWord: { 3201 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 3202 return !obj->is_gc_marked() && !hr->is_archive(); 3203 } 3204 default: ShouldNotReachHere(); 3205 } 3206 return false; // keep some compilers happy 3207 } 3208 3209 void G1CollectedHeap::print_on(outputStream* st) const { 3210 st->print(" %-20s", "garbage-first heap"); 3211 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3212 capacity()/K, used_unlocked()/K); 3213 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 3214 p2i(_hrm.reserved().start()), 3215 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 3216 p2i(_hrm.reserved().end())); 3217 st->cr(); 3218 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3219 uint young_regions = _young_list->length(); 3220 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3221 (size_t) young_regions * HeapRegion::GrainBytes / K); 3222 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3223 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3224 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3225 st->cr(); 3226 MetaspaceAux::print_on(st); 3227 } 3228 3229 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3230 print_on(st); 3231 3232 // Print the per-region information. 3233 st->cr(); 3234 st->print_cr("Heap Regions: (E=young(eden), S=young(survivor), O=old, " 3235 "HS=humongous(starts), HC=humongous(continues), " 3236 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 3237 "PTAMS=previous top-at-mark-start, " 3238 "NTAMS=next top-at-mark-start)"); 3239 PrintRegionClosure blk(st); 3240 heap_region_iterate(&blk); 3241 } 3242 3243 void G1CollectedHeap::print_on_error(outputStream* st) const { 3244 this->CollectedHeap::print_on_error(st); 3245 3246 if (_cm != NULL) { 3247 st->cr(); 3248 _cm->print_on_error(st); 3249 } 3250 } 3251 3252 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3253 workers()->print_worker_threads_on(st); 3254 _cmThread->print_on(st); 3255 st->cr(); 3256 _cm->print_worker_threads_on(st); 3257 _cg1r->print_worker_threads_on(st); 3258 if (G1StringDedup::is_enabled()) { 3259 G1StringDedup::print_worker_threads_on(st); 3260 } 3261 } 3262 3263 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3264 workers()->threads_do(tc); 3265 tc->do_thread(_cmThread); 3266 _cg1r->threads_do(tc); 3267 if (G1StringDedup::is_enabled()) { 3268 G1StringDedup::threads_do(tc); 3269 } 3270 } 3271 3272 void G1CollectedHeap::print_tracing_info() const { 3273 // We'll overload this to mean "trace GC pause statistics." 3274 if (TraceYoungGenTime || TraceOldGenTime) { 3275 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3276 // to that. 3277 g1_policy()->print_tracing_info(); 3278 } 3279 if (G1SummarizeRSetStats) { 3280 g1_rem_set()->print_summary_info(); 3281 } 3282 if (G1SummarizeConcMark) { 3283 concurrent_mark()->print_summary_info(); 3284 } 3285 g1_policy()->print_yg_surv_rate_info(); 3286 } 3287 3288 #ifndef PRODUCT 3289 // Helpful for debugging RSet issues. 3290 3291 class PrintRSetsClosure : public HeapRegionClosure { 3292 private: 3293 const char* _msg; 3294 size_t _occupied_sum; 3295 3296 public: 3297 bool doHeapRegion(HeapRegion* r) { 3298 HeapRegionRemSet* hrrs = r->rem_set(); 3299 size_t occupied = hrrs->occupied(); 3300 _occupied_sum += occupied; 3301 3302 gclog_or_tty->print_cr("Printing RSet for region " HR_FORMAT, 3303 HR_FORMAT_PARAMS(r)); 3304 if (occupied == 0) { 3305 gclog_or_tty->print_cr(" RSet is empty"); 3306 } else { 3307 hrrs->print(); 3308 } 3309 gclog_or_tty->print_cr("----------"); 3310 return false; 3311 } 3312 3313 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3314 gclog_or_tty->cr(); 3315 gclog_or_tty->print_cr("========================================"); 3316 gclog_or_tty->print_cr("%s", msg); 3317 gclog_or_tty->cr(); 3318 } 3319 3320 ~PrintRSetsClosure() { 3321 gclog_or_tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 3322 gclog_or_tty->print_cr("========================================"); 3323 gclog_or_tty->cr(); 3324 } 3325 }; 3326 3327 void G1CollectedHeap::print_cset_rsets() { 3328 PrintRSetsClosure cl("Printing CSet RSets"); 3329 collection_set_iterate(&cl); 3330 } 3331 3332 void G1CollectedHeap::print_all_rsets() { 3333 PrintRSetsClosure cl("Printing All RSets");; 3334 heap_region_iterate(&cl); 3335 } 3336 #endif // PRODUCT 3337 3338 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 3339 YoungList* young_list = heap()->young_list(); 3340 3341 size_t eden_used_bytes = young_list->eden_used_bytes(); 3342 size_t survivor_used_bytes = young_list->survivor_used_bytes(); 3343 3344 size_t eden_capacity_bytes = 3345 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 3346 3347 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 3348 return G1HeapSummary(heap_summary, used(), eden_used_bytes, eden_capacity_bytes, survivor_used_bytes); 3349 } 3350 3351 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 3352 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 3353 stats->unused(), stats->used(), stats->region_end_waste(), 3354 stats->regions_filled(), stats->direct_allocated(), 3355 stats->failure_used(), stats->failure_waste()); 3356 } 3357 3358 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 3359 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 3360 gc_tracer->report_gc_heap_summary(when, heap_summary); 3361 3362 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 3363 gc_tracer->report_metaspace_summary(when, metaspace_summary); 3364 } 3365 3366 3367 G1CollectedHeap* G1CollectedHeap::heap() { 3368 CollectedHeap* heap = Universe::heap(); 3369 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 3370 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 3371 return (G1CollectedHeap*)heap; 3372 } 3373 3374 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3375 // always_do_update_barrier = false; 3376 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3377 // Fill TLAB's and such 3378 accumulate_statistics_all_tlabs(); 3379 ensure_parsability(true); 3380 3381 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) && 3382 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 3383 g1_rem_set()->print_periodic_summary_info("Before GC RS summary"); 3384 } 3385 } 3386 3387 void G1CollectedHeap::gc_epilogue(bool full) { 3388 3389 if (G1SummarizeRSetStats && 3390 (G1SummarizeRSetStatsPeriod > 0) && 3391 // we are at the end of the GC. Total collections has already been increased. 3392 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) { 3393 g1_rem_set()->print_periodic_summary_info("After GC RS summary"); 3394 } 3395 3396 // FIXME: what is this about? 3397 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3398 // is set. 3399 #if defined(COMPILER2) || INCLUDE_JVMCI 3400 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 3401 #endif 3402 // always_do_update_barrier = true; 3403 3404 resize_all_tlabs(); 3405 allocation_context_stats().update(full); 3406 3407 // We have just completed a GC. Update the soft reference 3408 // policy with the new heap occupancy 3409 Universe::update_heap_info_at_gc(); 3410 } 3411 3412 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3413 uint gc_count_before, 3414 bool* succeeded, 3415 GCCause::Cause gc_cause) { 3416 assert_heap_not_locked_and_not_at_safepoint(); 3417 g1_policy()->record_stop_world_start(); 3418 VM_G1IncCollectionPause op(gc_count_before, 3419 word_size, 3420 false, /* should_initiate_conc_mark */ 3421 g1_policy()->max_pause_time_ms(), 3422 gc_cause); 3423 3424 op.set_allocation_context(AllocationContext::current()); 3425 VMThread::execute(&op); 3426 3427 HeapWord* result = op.result(); 3428 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3429 assert(result == NULL || ret_succeeded, 3430 "the result should be NULL if the VM did not succeed"); 3431 *succeeded = ret_succeeded; 3432 3433 assert_heap_not_locked(); 3434 return result; 3435 } 3436 3437 void 3438 G1CollectedHeap::doConcurrentMark() { 3439 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3440 if (!_cmThread->in_progress()) { 3441 _cmThread->set_started(); 3442 CGC_lock->notify(); 3443 } 3444 } 3445 3446 size_t G1CollectedHeap::pending_card_num() { 3447 size_t extra_cards = 0; 3448 JavaThread *curr = Threads::first(); 3449 while (curr != NULL) { 3450 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3451 extra_cards += dcq.size(); 3452 curr = curr->next(); 3453 } 3454 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3455 size_t buffer_size = dcqs.buffer_size(); 3456 size_t buffer_num = dcqs.completed_buffers_num(); 3457 3458 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3459 // in bytes - not the number of 'entries'. We need to convert 3460 // into a number of cards. 3461 return (buffer_size * buffer_num + extra_cards) / oopSize; 3462 } 3463 3464 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 3465 private: 3466 size_t _total_humongous; 3467 size_t _candidate_humongous; 3468 3469 DirtyCardQueue _dcq; 3470 3471 // We don't nominate objects with many remembered set entries, on 3472 // the assumption that such objects are likely still live. 3473 bool is_remset_small(HeapRegion* region) const { 3474 HeapRegionRemSet* const rset = region->rem_set(); 3475 return G1EagerReclaimHumongousObjectsWithStaleRefs 3476 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 3477 : rset->is_empty(); 3478 } 3479 3480 bool is_typeArray_region(HeapRegion* region) const { 3481 return oop(region->bottom())->is_typeArray(); 3482 } 3483 3484 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 3485 assert(region->is_starts_humongous(), "Must start a humongous object"); 3486 3487 // Candidate selection must satisfy the following constraints 3488 // while concurrent marking is in progress: 3489 // 3490 // * In order to maintain SATB invariants, an object must not be 3491 // reclaimed if it was allocated before the start of marking and 3492 // has not had its references scanned. Such an object must have 3493 // its references (including type metadata) scanned to ensure no 3494 // live objects are missed by the marking process. Objects 3495 // allocated after the start of concurrent marking don't need to 3496 // be scanned. 3497 // 3498 // * An object must not be reclaimed if it is on the concurrent 3499 // mark stack. Objects allocated after the start of concurrent 3500 // marking are never pushed on the mark stack. 3501 // 3502 // Nominating only objects allocated after the start of concurrent 3503 // marking is sufficient to meet both constraints. This may miss 3504 // some objects that satisfy the constraints, but the marking data 3505 // structures don't support efficiently performing the needed 3506 // additional tests or scrubbing of the mark stack. 3507 // 3508 // However, we presently only nominate is_typeArray() objects. 3509 // A humongous object containing references induces remembered 3510 // set entries on other regions. In order to reclaim such an 3511 // object, those remembered sets would need to be cleaned up. 3512 // 3513 // We also treat is_typeArray() objects specially, allowing them 3514 // to be reclaimed even if allocated before the start of 3515 // concurrent mark. For this we rely on mark stack insertion to 3516 // exclude is_typeArray() objects, preventing reclaiming an object 3517 // that is in the mark stack. We also rely on the metadata for 3518 // such objects to be built-in and so ensured to be kept live. 3519 // Frequent allocation and drop of large binary blobs is an 3520 // important use case for eager reclaim, and this special handling 3521 // may reduce needed headroom. 3522 3523 return is_typeArray_region(region) && is_remset_small(region); 3524 } 3525 3526 public: 3527 RegisterHumongousWithInCSetFastTestClosure() 3528 : _total_humongous(0), 3529 _candidate_humongous(0), 3530 _dcq(&JavaThread::dirty_card_queue_set()) { 3531 } 3532 3533 virtual bool doHeapRegion(HeapRegion* r) { 3534 if (!r->is_starts_humongous()) { 3535 return false; 3536 } 3537 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3538 3539 bool is_candidate = humongous_region_is_candidate(g1h, r); 3540 uint rindex = r->hrm_index(); 3541 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 3542 if (is_candidate) { 3543 _candidate_humongous++; 3544 g1h->register_humongous_region_with_cset(rindex); 3545 // Is_candidate already filters out humongous object with large remembered sets. 3546 // If we have a humongous object with a few remembered sets, we simply flush these 3547 // remembered set entries into the DCQS. That will result in automatic 3548 // re-evaluation of their remembered set entries during the following evacuation 3549 // phase. 3550 if (!r->rem_set()->is_empty()) { 3551 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 3552 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 3553 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 3554 HeapRegionRemSetIterator hrrs(r->rem_set()); 3555 size_t card_index; 3556 while (hrrs.has_next(card_index)) { 3557 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 3558 // The remembered set might contain references to already freed 3559 // regions. Filter out such entries to avoid failing card table 3560 // verification. 3561 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 3562 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 3563 *card_ptr = CardTableModRefBS::dirty_card_val(); 3564 _dcq.enqueue(card_ptr); 3565 } 3566 } 3567 } 3568 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 3569 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 3570 hrrs.n_yielded(), r->rem_set()->occupied()); 3571 r->rem_set()->clear_locked(); 3572 } 3573 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 3574 } 3575 _total_humongous++; 3576 3577 return false; 3578 } 3579 3580 size_t total_humongous() const { return _total_humongous; } 3581 size_t candidate_humongous() const { return _candidate_humongous; } 3582 3583 void flush_rem_set_entries() { _dcq.flush(); } 3584 }; 3585 3586 void G1CollectedHeap::register_humongous_regions_with_cset() { 3587 if (!G1EagerReclaimHumongousObjects) { 3588 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 3589 return; 3590 } 3591 double time = os::elapsed_counter(); 3592 3593 // Collect reclaim candidate information and register candidates with cset. 3594 RegisterHumongousWithInCSetFastTestClosure cl; 3595 heap_region_iterate(&cl); 3596 3597 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 3598 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 3599 cl.total_humongous(), 3600 cl.candidate_humongous()); 3601 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3602 3603 // Finally flush all remembered set entries to re-check into the global DCQS. 3604 cl.flush_rem_set_entries(); 3605 } 3606 3607 #ifdef ASSERT 3608 class VerifyCSetClosure: public HeapRegionClosure { 3609 public: 3610 bool doHeapRegion(HeapRegion* hr) { 3611 // Here we check that the CSet region's RSet is ready for parallel 3612 // iteration. The fields that we'll verify are only manipulated 3613 // when the region is part of a CSet and is collected. Afterwards, 3614 // we reset these fields when we clear the region's RSet (when the 3615 // region is freed) so they are ready when the region is 3616 // re-allocated. The only exception to this is if there's an 3617 // evacuation failure and instead of freeing the region we leave 3618 // it in the heap. In that case, we reset these fields during 3619 // evacuation failure handling. 3620 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3621 3622 // Here's a good place to add any other checks we'd like to 3623 // perform on CSet regions. 3624 return false; 3625 } 3626 }; 3627 #endif // ASSERT 3628 3629 uint G1CollectedHeap::num_task_queues() const { 3630 return _task_queues->size(); 3631 } 3632 3633 #if TASKQUEUE_STATS 3634 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3635 st->print_raw_cr("GC Task Stats"); 3636 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3637 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3638 } 3639 3640 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3641 print_taskqueue_stats_hdr(st); 3642 3643 TaskQueueStats totals; 3644 const uint n = num_task_queues(); 3645 for (uint i = 0; i < n; ++i) { 3646 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 3647 totals += task_queue(i)->stats; 3648 } 3649 st->print_raw("tot "); totals.print(st); st->cr(); 3650 3651 DEBUG_ONLY(totals.verify()); 3652 } 3653 3654 void G1CollectedHeap::reset_taskqueue_stats() { 3655 const uint n = num_task_queues(); 3656 for (uint i = 0; i < n; ++i) { 3657 task_queue(i)->stats.reset(); 3658 } 3659 } 3660 #endif // TASKQUEUE_STATS 3661 3662 void G1CollectedHeap::log_gc_header() { 3663 if (!G1Log::fine()) { 3664 return; 3665 } 3666 3667 gclog_or_tty->gclog_stamp(); 3668 3669 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) 3670 .append(collector_state()->gcs_are_young() ? "(young)" : "(mixed)") 3671 .append(collector_state()->during_initial_mark_pause() ? " (initial-mark)" : ""); 3672 3673 gclog_or_tty->print("[%s", (const char*)gc_cause_str); 3674 } 3675 3676 void G1CollectedHeap::log_gc_footer(double pause_time_sec) { 3677 if (!G1Log::fine()) { 3678 return; 3679 } 3680 3681 if (G1Log::finer()) { 3682 if (evacuation_failed()) { 3683 gclog_or_tty->print(" (to-space exhausted)"); 3684 } 3685 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3686 g1_policy()->print_phases(pause_time_sec); 3687 g1_policy()->print_detailed_heap_transition(); 3688 } else { 3689 if (evacuation_failed()) { 3690 gclog_or_tty->print("--"); 3691 } 3692 g1_policy()->print_heap_transition(); 3693 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3694 } 3695 gclog_or_tty->flush(); 3696 } 3697 3698 void G1CollectedHeap::wait_for_root_region_scanning() { 3699 double scan_wait_start = os::elapsedTime(); 3700 // We have to wait until the CM threads finish scanning the 3701 // root regions as it's the only way to ensure that all the 3702 // objects on them have been correctly scanned before we start 3703 // moving them during the GC. 3704 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3705 double wait_time_ms = 0.0; 3706 if (waited) { 3707 double scan_wait_end = os::elapsedTime(); 3708 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3709 } 3710 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3711 } 3712 3713 bool 3714 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3715 assert_at_safepoint(true /* should_be_vm_thread */); 3716 guarantee(!is_gc_active(), "collection is not reentrant"); 3717 3718 if (GC_locker::check_active_before_gc()) { 3719 return false; 3720 } 3721 3722 _gc_timer_stw->register_gc_start(); 3723 3724 GCIdMark gc_id_mark; 3725 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3726 3727 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3728 ResourceMark rm; 3729 3730 wait_for_root_region_scanning(); 3731 3732 G1Log::update_level(); 3733 print_heap_before_gc(); 3734 trace_heap_before_gc(_gc_tracer_stw); 3735 3736 verify_region_sets_optional(); 3737 verify_dirty_young_regions(); 3738 3739 // This call will decide whether this pause is an initial-mark 3740 // pause. If it is, during_initial_mark_pause() will return true 3741 // for the duration of this pause. 3742 g1_policy()->decide_on_conc_mark_initiation(); 3743 3744 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3745 assert(!collector_state()->during_initial_mark_pause() || 3746 collector_state()->gcs_are_young(), "sanity"); 3747 3748 // We also do not allow mixed GCs during marking. 3749 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3750 3751 // Record whether this pause is an initial mark. When the current 3752 // thread has completed its logging output and it's safe to signal 3753 // the CM thread, the flag's value in the policy has been reset. 3754 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3755 3756 // Inner scope for scope based logging, timers, and stats collection 3757 { 3758 EvacuationInfo evacuation_info; 3759 3760 if (collector_state()->during_initial_mark_pause()) { 3761 // We are about to start a marking cycle, so we increment the 3762 // full collection counter. 3763 increment_old_marking_cycles_started(); 3764 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3765 } 3766 3767 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3768 3769 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 3770 3771 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3772 workers()->active_workers(), 3773 Threads::number_of_non_daemon_threads()); 3774 workers()->set_active_workers(active_workers); 3775 3776 double pause_start_sec = os::elapsedTime(); 3777 g1_policy()->note_gc_start(active_workers); 3778 log_gc_header(); 3779 3780 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3781 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3782 3783 // If the secondary_free_list is not empty, append it to the 3784 // free_list. No need to wait for the cleanup operation to finish; 3785 // the region allocation code will check the secondary_free_list 3786 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3787 // set, skip this step so that the region allocation code has to 3788 // get entries from the secondary_free_list. 3789 if (!G1StressConcRegionFreeing) { 3790 append_secondary_free_list_if_not_empty_with_lock(); 3791 } 3792 3793 assert(check_young_list_well_formed(), "young list should be well formed"); 3794 3795 // Don't dynamically change the number of GC threads this early. A value of 3796 // 0 is used to indicate serial work. When parallel work is done, 3797 // it will be set. 3798 3799 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3800 IsGCActiveMark x; 3801 3802 gc_prologue(false); 3803 increment_total_collections(false /* full gc */); 3804 increment_gc_time_stamp(); 3805 3806 verify_before_gc(); 3807 3808 check_bitmaps("GC Start"); 3809 3810 #if defined(COMPILER2) || INCLUDE_JVMCI 3811 DerivedPointerTable::clear(); 3812 #endif 3813 3814 // Please see comment in g1CollectedHeap.hpp and 3815 // G1CollectedHeap::ref_processing_init() to see how 3816 // reference processing currently works in G1. 3817 3818 // Enable discovery in the STW reference processor 3819 ref_processor_stw()->enable_discovery(); 3820 3821 { 3822 // We want to temporarily turn off discovery by the 3823 // CM ref processor, if necessary, and turn it back on 3824 // on again later if we do. Using a scoped 3825 // NoRefDiscovery object will do this. 3826 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3827 3828 // Forget the current alloc region (we might even choose it to be part 3829 // of the collection set!). 3830 _allocator->release_mutator_alloc_region(); 3831 3832 // We should call this after we retire the mutator alloc 3833 // region(s) so that all the ALLOC / RETIRE events are generated 3834 // before the start GC event. 3835 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 3836 3837 // This timing is only used by the ergonomics to handle our pause target. 3838 // It is unclear why this should not include the full pause. We will 3839 // investigate this in CR 7178365. 3840 // 3841 // Preserving the old comment here if that helps the investigation: 3842 // 3843 // The elapsed time induced by the start time below deliberately elides 3844 // the possible verification above. 3845 double sample_start_time_sec = os::elapsedTime(); 3846 3847 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3848 3849 if (collector_state()->during_initial_mark_pause()) { 3850 concurrent_mark()->checkpointRootsInitialPre(); 3851 } 3852 3853 double time_remaining_ms = g1_policy()->finalize_young_cset_part(target_pause_time_ms); 3854 g1_policy()->finalize_old_cset_part(time_remaining_ms); 3855 3856 evacuation_info.set_collectionset_regions(g1_policy()->cset_region_length()); 3857 3858 // Make sure the remembered sets are up to date. This needs to be 3859 // done before register_humongous_regions_with_cset(), because the 3860 // remembered sets are used there to choose eager reclaim candidates. 3861 // If the remembered sets are not up to date we might miss some 3862 // entries that need to be handled. 3863 g1_rem_set()->cleanupHRRS(); 3864 3865 register_humongous_regions_with_cset(); 3866 3867 assert(check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3868 3869 _cm->note_start_of_gc(); 3870 // We call this after finalize_cset() to 3871 // ensure that the CSet has been finalized. 3872 _cm->verify_no_cset_oops(); 3873 3874 if (_hr_printer.is_active()) { 3875 HeapRegion* hr = g1_policy()->collection_set(); 3876 while (hr != NULL) { 3877 _hr_printer.cset(hr); 3878 hr = hr->next_in_collection_set(); 3879 } 3880 } 3881 3882 #ifdef ASSERT 3883 VerifyCSetClosure cl; 3884 collection_set_iterate(&cl); 3885 #endif // ASSERT 3886 3887 // Initialize the GC alloc regions. 3888 _allocator->init_gc_alloc_regions(evacuation_info); 3889 3890 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), g1_policy()->young_cset_region_length()); 3891 pre_evacuate_collection_set(); 3892 3893 // Actually do the work... 3894 evacuate_collection_set(evacuation_info, &per_thread_states); 3895 3896 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3897 3898 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3899 free_collection_set(g1_policy()->collection_set(), evacuation_info, surviving_young_words); 3900 3901 eagerly_reclaim_humongous_regions(); 3902 3903 g1_policy()->clear_collection_set(); 3904 3905 // Start a new incremental collection set for the next pause. 3906 g1_policy()->start_incremental_cset_building(); 3907 3908 clear_cset_fast_test(); 3909 3910 _young_list->reset_sampled_info(); 3911 3912 // Don't check the whole heap at this point as the 3913 // GC alloc regions from this pause have been tagged 3914 // as survivors and moved on to the survivor list. 3915 // Survivor regions will fail the !is_young() check. 3916 assert(check_young_list_empty(false /* check_heap */), 3917 "young list should be empty"); 3918 3919 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3920 _young_list->first_survivor_region(), 3921 _young_list->last_survivor_region()); 3922 3923 _young_list->reset_auxilary_lists(); 3924 3925 if (evacuation_failed()) { 3926 set_used(recalculate_used()); 3927 if (_archive_allocator != NULL) { 3928 _archive_allocator->clear_used(); 3929 } 3930 for (uint i = 0; i < ParallelGCThreads; i++) { 3931 if (_evacuation_failed_info_array[i].has_failed()) { 3932 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3933 } 3934 } 3935 } else { 3936 // The "used" of the the collection set have already been subtracted 3937 // when they were freed. Add in the bytes evacuated. 3938 increase_used(g1_policy()->bytes_copied_during_gc()); 3939 } 3940 3941 if (collector_state()->during_initial_mark_pause()) { 3942 // We have to do this before we notify the CM threads that 3943 // they can start working to make sure that all the 3944 // appropriate initialization is done on the CM object. 3945 concurrent_mark()->checkpointRootsInitialPost(); 3946 collector_state()->set_mark_in_progress(true); 3947 // Note that we don't actually trigger the CM thread at 3948 // this point. We do that later when we're sure that 3949 // the current thread has completed its logging output. 3950 } 3951 3952 allocate_dummy_regions(); 3953 3954 _allocator->init_mutator_alloc_region(); 3955 3956 { 3957 size_t expand_bytes = g1_policy()->expansion_amount(); 3958 if (expand_bytes > 0) { 3959 size_t bytes_before = capacity(); 3960 // No need for an ergo verbose message here, 3961 // expansion_amount() does this when it returns a value > 0. 3962 double expand_ms; 3963 if (!expand(expand_bytes, &expand_ms)) { 3964 // We failed to expand the heap. Cannot do anything about it. 3965 } 3966 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3967 } 3968 } 3969 3970 // We redo the verification but now wrt to the new CSet which 3971 // has just got initialized after the previous CSet was freed. 3972 _cm->verify_no_cset_oops(); 3973 _cm->note_end_of_gc(); 3974 3975 // This timing is only used by the ergonomics to handle our pause target. 3976 // It is unclear why this should not include the full pause. We will 3977 // investigate this in CR 7178365. 3978 double sample_end_time_sec = os::elapsedTime(); 3979 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3980 size_t total_cards_scanned = per_thread_states.total_cards_scanned(); 3981 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned); 3982 3983 evacuation_info.set_collectionset_used_before(g1_policy()->collection_set_bytes_used_before()); 3984 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3985 3986 MemoryService::track_memory_usage(); 3987 3988 // In prepare_for_verify() below we'll need to scan the deferred 3989 // update buffers to bring the RSets up-to-date if 3990 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3991 // the update buffers we'll probably need to scan cards on the 3992 // regions we just allocated to (i.e., the GC alloc 3993 // regions). However, during the last GC we called 3994 // set_saved_mark() on all the GC alloc regions, so card 3995 // scanning might skip the [saved_mark_word()...top()] area of 3996 // those regions (i.e., the area we allocated objects into 3997 // during the last GC). But it shouldn't. Given that 3998 // saved_mark_word() is conditional on whether the GC time stamp 3999 // on the region is current or not, by incrementing the GC time 4000 // stamp here we invalidate all the GC time stamps on all the 4001 // regions and saved_mark_word() will simply return top() for 4002 // all the regions. This is a nicer way of ensuring this rather 4003 // than iterating over the regions and fixing them. In fact, the 4004 // GC time stamp increment here also ensures that 4005 // saved_mark_word() will return top() between pauses, i.e., 4006 // during concurrent refinement. So we don't need the 4007 // is_gc_active() check to decided which top to use when 4008 // scanning cards (see CR 7039627). 4009 increment_gc_time_stamp(); 4010 4011 verify_after_gc(); 4012 check_bitmaps("GC End"); 4013 4014 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 4015 ref_processor_stw()->verify_no_references_recorded(); 4016 4017 // CM reference discovery will be re-enabled if necessary. 4018 } 4019 4020 // We should do this after we potentially expand the heap so 4021 // that all the COMMIT events are generated before the end GC 4022 // event, and after we retire the GC alloc regions so that all 4023 // RETIRE events are generated before the end GC event. 4024 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 4025 4026 #ifdef TRACESPINNING 4027 ParallelTaskTerminator::print_termination_counts(); 4028 #endif 4029 4030 gc_epilogue(false); 4031 } 4032 4033 // Print the remainder of the GC log output. 4034 log_gc_footer(os::elapsedTime() - pause_start_sec); 4035 4036 // It is not yet to safe to tell the concurrent mark to 4037 // start as we have some optional output below. We don't want the 4038 // output from the concurrent mark thread interfering with this 4039 // logging output either. 4040 4041 _hrm.verify_optional(); 4042 verify_region_sets_optional(); 4043 4044 TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats()); 4045 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 4046 4047 print_heap_after_gc(); 4048 trace_heap_after_gc(_gc_tracer_stw); 4049 4050 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 4051 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 4052 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 4053 // before any GC notifications are raised. 4054 g1mm()->update_sizes(); 4055 4056 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 4057 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 4058 _gc_timer_stw->register_gc_end(); 4059 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 4060 } 4061 // It should now be safe to tell the concurrent mark thread to start 4062 // without its logging output interfering with the logging output 4063 // that came from the pause. 4064 4065 if (should_start_conc_mark) { 4066 // CAUTION: after the doConcurrentMark() call below, 4067 // the concurrent marking thread(s) could be running 4068 // concurrently with us. Make sure that anything after 4069 // this point does not assume that we are the only GC thread 4070 // running. Note: of course, the actual marking work will 4071 // not start until the safepoint itself is released in 4072 // SuspendibleThreadSet::desynchronize(). 4073 doConcurrentMark(); 4074 } 4075 4076 return true; 4077 } 4078 4079 void G1CollectedHeap::remove_self_forwarding_pointers() { 4080 double remove_self_forwards_start = os::elapsedTime(); 4081 4082 G1ParRemoveSelfForwardPtrsTask rsfp_task; 4083 workers()->run_task(&rsfp_task); 4084 4085 // Now restore saved marks, if any. 4086 for (uint i = 0; i < ParallelGCThreads; i++) { 4087 OopAndMarkOopStack& cur = _preserved_objs[i]; 4088 while (!cur.is_empty()) { 4089 OopAndMarkOop elem = cur.pop(); 4090 elem.set_mark(); 4091 } 4092 cur.clear(true); 4093 } 4094 4095 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 4096 } 4097 4098 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 4099 if (!_evacuation_failed) { 4100 _evacuation_failed = true; 4101 } 4102 4103 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 4104 4105 // We want to call the "for_promotion_failure" version only in the 4106 // case of a promotion failure. 4107 if (m->must_be_preserved_for_promotion_failure(obj)) { 4108 OopAndMarkOop elem(obj, m); 4109 _preserved_objs[worker_id].push(elem); 4110 } 4111 } 4112 4113 class G1ParEvacuateFollowersClosure : public VoidClosure { 4114 private: 4115 double _start_term; 4116 double _term_time; 4117 size_t _term_attempts; 4118 4119 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); } 4120 void end_term_time() { _term_time += os::elapsedTime() - _start_term; } 4121 protected: 4122 G1CollectedHeap* _g1h; 4123 G1ParScanThreadState* _par_scan_state; 4124 RefToScanQueueSet* _queues; 4125 ParallelTaskTerminator* _terminator; 4126 4127 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4128 RefToScanQueueSet* queues() { return _queues; } 4129 ParallelTaskTerminator* terminator() { return _terminator; } 4130 4131 public: 4132 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4133 G1ParScanThreadState* par_scan_state, 4134 RefToScanQueueSet* queues, 4135 ParallelTaskTerminator* terminator) 4136 : _g1h(g1h), _par_scan_state(par_scan_state), 4137 _queues(queues), _terminator(terminator), 4138 _start_term(0.0), _term_time(0.0), _term_attempts(0) {} 4139 4140 void do_void(); 4141 4142 double term_time() const { return _term_time; } 4143 size_t term_attempts() const { return _term_attempts; } 4144 4145 private: 4146 inline bool offer_termination(); 4147 }; 4148 4149 bool G1ParEvacuateFollowersClosure::offer_termination() { 4150 G1ParScanThreadState* const pss = par_scan_state(); 4151 start_term_time(); 4152 const bool res = terminator()->offer_termination(); 4153 end_term_time(); 4154 return res; 4155 } 4156 4157 void G1ParEvacuateFollowersClosure::do_void() { 4158 G1ParScanThreadState* const pss = par_scan_state(); 4159 pss->trim_queue(); 4160 do { 4161 pss->steal_and_trim_queue(queues()); 4162 } while (!offer_termination()); 4163 } 4164 4165 class G1ParTask : public AbstractGangTask { 4166 protected: 4167 G1CollectedHeap* _g1h; 4168 G1ParScanThreadStateSet* _pss; 4169 RefToScanQueueSet* _queues; 4170 G1RootProcessor* _root_processor; 4171 ParallelTaskTerminator _terminator; 4172 uint _n_workers; 4173 4174 public: 4175 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 4176 : AbstractGangTask("G1 collection"), 4177 _g1h(g1h), 4178 _pss(per_thread_states), 4179 _queues(task_queues), 4180 _root_processor(root_processor), 4181 _terminator(n_workers, _queues), 4182 _n_workers(n_workers) 4183 {} 4184 4185 void work(uint worker_id) { 4186 if (worker_id >= _n_workers) return; // no work needed this round 4187 4188 double start_sec = os::elapsedTime(); 4189 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 4190 4191 { 4192 ResourceMark rm; 4193 HandleMark hm; 4194 4195 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4196 4197 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4198 pss->set_ref_processor(rp); 4199 4200 double start_strong_roots_sec = os::elapsedTime(); 4201 4202 _root_processor->evacuate_roots(pss->closures(), worker_id); 4203 4204 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss); 4205 4206 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 4207 // treating the nmethods visited to act as roots for concurrent marking. 4208 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 4209 // objects copied by the current evacuation. 4210 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl, 4211 pss->closures()->weak_codeblobs(), 4212 worker_id); 4213 4214 _pss->add_cards_scanned(worker_id, cards_scanned); 4215 4216 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 4217 4218 double term_sec = 0.0; 4219 size_t evac_term_attempts = 0; 4220 { 4221 double start = os::elapsedTime(); 4222 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 4223 evac.do_void(); 4224 4225 evac_term_attempts = evac.term_attempts(); 4226 term_sec = evac.term_time(); 4227 double elapsed_sec = os::elapsedTime() - start; 4228 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 4229 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 4230 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 4231 } 4232 4233 assert(pss->queue_is_empty(), "should be empty"); 4234 4235 if (PrintTerminationStats) { 4236 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 4237 size_t lab_waste; 4238 size_t lab_undo_waste; 4239 pss->waste(lab_waste, lab_undo_waste); 4240 _g1h->print_termination_stats(gclog_or_tty, 4241 worker_id, 4242 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 4243 strong_roots_sec * 1000.0, /* strong roots time */ 4244 term_sec * 1000.0, /* evac term time */ 4245 evac_term_attempts, /* evac term attempts */ 4246 lab_waste, /* alloc buffer waste */ 4247 lab_undo_waste /* undo waste */ 4248 ); 4249 } 4250 4251 // Close the inner scope so that the ResourceMark and HandleMark 4252 // destructors are executed here and are included as part of the 4253 // "GC Worker Time". 4254 } 4255 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 4256 } 4257 }; 4258 4259 void G1CollectedHeap::print_termination_stats_hdr(outputStream* const st) { 4260 st->print_raw_cr("GC Termination Stats"); 4261 st->print_raw_cr(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 4262 st->print_raw_cr("thr ms ms % ms % attempts total alloc undo"); 4263 st->print_raw_cr("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 4264 } 4265 4266 void G1CollectedHeap::print_termination_stats(outputStream* const st, 4267 uint worker_id, 4268 double elapsed_ms, 4269 double strong_roots_ms, 4270 double term_ms, 4271 size_t term_attempts, 4272 size_t alloc_buffer_waste, 4273 size_t undo_waste) const { 4274 st->print_cr("%3d %9.2f %9.2f %6.2f " 4275 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 4276 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 4277 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 4278 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 4279 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 4280 alloc_buffer_waste * HeapWordSize / K, 4281 undo_waste * HeapWordSize / K); 4282 } 4283 4284 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 4285 private: 4286 BoolObjectClosure* _is_alive; 4287 int _initial_string_table_size; 4288 int _initial_symbol_table_size; 4289 4290 bool _process_strings; 4291 int _strings_processed; 4292 int _strings_removed; 4293 4294 bool _process_symbols; 4295 int _symbols_processed; 4296 int _symbols_removed; 4297 4298 public: 4299 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 4300 AbstractGangTask("String/Symbol Unlinking"), 4301 _is_alive(is_alive), 4302 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 4303 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 4304 4305 _initial_string_table_size = StringTable::the_table()->table_size(); 4306 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 4307 if (process_strings) { 4308 StringTable::clear_parallel_claimed_index(); 4309 } 4310 if (process_symbols) { 4311 SymbolTable::clear_parallel_claimed_index(); 4312 } 4313 } 4314 4315 ~G1StringSymbolTableUnlinkTask() { 4316 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 4317 "claim value %d after unlink less than initial string table size %d", 4318 StringTable::parallel_claimed_index(), _initial_string_table_size); 4319 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 4320 "claim value %d after unlink less than initial symbol table size %d", 4321 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 4322 4323 if (G1TraceStringSymbolTableScrubbing) { 4324 gclog_or_tty->print_cr("Cleaned string and symbol table, " 4325 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 4326 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 4327 strings_processed(), strings_removed(), 4328 symbols_processed(), symbols_removed()); 4329 } 4330 } 4331 4332 void work(uint worker_id) { 4333 int strings_processed = 0; 4334 int strings_removed = 0; 4335 int symbols_processed = 0; 4336 int symbols_removed = 0; 4337 if (_process_strings) { 4338 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 4339 Atomic::add(strings_processed, &_strings_processed); 4340 Atomic::add(strings_removed, &_strings_removed); 4341 } 4342 if (_process_symbols) { 4343 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 4344 Atomic::add(symbols_processed, &_symbols_processed); 4345 Atomic::add(symbols_removed, &_symbols_removed); 4346 } 4347 } 4348 4349 size_t strings_processed() const { return (size_t)_strings_processed; } 4350 size_t strings_removed() const { return (size_t)_strings_removed; } 4351 4352 size_t symbols_processed() const { return (size_t)_symbols_processed; } 4353 size_t symbols_removed() const { return (size_t)_symbols_removed; } 4354 }; 4355 4356 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 4357 private: 4358 static Monitor* _lock; 4359 4360 BoolObjectClosure* const _is_alive; 4361 const bool _unloading_occurred; 4362 const uint _num_workers; 4363 4364 // Variables used to claim nmethods. 4365 nmethod* _first_nmethod; 4366 volatile nmethod* _claimed_nmethod; 4367 4368 // The list of nmethods that need to be processed by the second pass. 4369 volatile nmethod* _postponed_list; 4370 volatile uint _num_entered_barrier; 4371 4372 public: 4373 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 4374 _is_alive(is_alive), 4375 _unloading_occurred(unloading_occurred), 4376 _num_workers(num_workers), 4377 _first_nmethod(NULL), 4378 _claimed_nmethod(NULL), 4379 _postponed_list(NULL), 4380 _num_entered_barrier(0) 4381 { 4382 nmethod::increase_unloading_clock(); 4383 // Get first alive nmethod 4384 NMethodIterator iter = NMethodIterator(); 4385 if(iter.next_alive()) { 4386 _first_nmethod = iter.method(); 4387 } 4388 _claimed_nmethod = (volatile nmethod*)_first_nmethod; 4389 } 4390 4391 ~G1CodeCacheUnloadingTask() { 4392 CodeCache::verify_clean_inline_caches(); 4393 4394 CodeCache::set_needs_cache_clean(false); 4395 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 4396 4397 CodeCache::verify_icholder_relocations(); 4398 } 4399 4400 private: 4401 void add_to_postponed_list(nmethod* nm) { 4402 nmethod* old; 4403 do { 4404 old = (nmethod*)_postponed_list; 4405 nm->set_unloading_next(old); 4406 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 4407 } 4408 4409 void clean_nmethod(nmethod* nm) { 4410 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 4411 4412 if (postponed) { 4413 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 4414 add_to_postponed_list(nm); 4415 } 4416 4417 // Mark that this thread has been cleaned/unloaded. 4418 // After this call, it will be safe to ask if this nmethod was unloaded or not. 4419 nm->set_unloading_clock(nmethod::global_unloading_clock()); 4420 } 4421 4422 void clean_nmethod_postponed(nmethod* nm) { 4423 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 4424 } 4425 4426 static const int MaxClaimNmethods = 16; 4427 4428 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) { 4429 nmethod* first; 4430 NMethodIterator last; 4431 4432 do { 4433 *num_claimed_nmethods = 0; 4434 4435 first = (nmethod*)_claimed_nmethod; 4436 last = NMethodIterator(first); 4437 4438 if (first != NULL) { 4439 4440 for (int i = 0; i < MaxClaimNmethods; i++) { 4441 if (!last.next_alive()) { 4442 break; 4443 } 4444 claimed_nmethods[i] = last.method(); 4445 (*num_claimed_nmethods)++; 4446 } 4447 } 4448 4449 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 4450 } 4451 4452 nmethod* claim_postponed_nmethod() { 4453 nmethod* claim; 4454 nmethod* next; 4455 4456 do { 4457 claim = (nmethod*)_postponed_list; 4458 if (claim == NULL) { 4459 return NULL; 4460 } 4461 4462 next = claim->unloading_next(); 4463 4464 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 4465 4466 return claim; 4467 } 4468 4469 public: 4470 // Mark that we're done with the first pass of nmethod cleaning. 4471 void barrier_mark(uint worker_id) { 4472 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4473 _num_entered_barrier++; 4474 if (_num_entered_barrier == _num_workers) { 4475 ml.notify_all(); 4476 } 4477 } 4478 4479 // See if we have to wait for the other workers to 4480 // finish their first-pass nmethod cleaning work. 4481 void barrier_wait(uint worker_id) { 4482 if (_num_entered_barrier < _num_workers) { 4483 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4484 while (_num_entered_barrier < _num_workers) { 4485 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 4486 } 4487 } 4488 } 4489 4490 // Cleaning and unloading of nmethods. Some work has to be postponed 4491 // to the second pass, when we know which nmethods survive. 4492 void work_first_pass(uint worker_id) { 4493 // The first nmethods is claimed by the first worker. 4494 if (worker_id == 0 && _first_nmethod != NULL) { 4495 clean_nmethod(_first_nmethod); 4496 _first_nmethod = NULL; 4497 } 4498 4499 int num_claimed_nmethods; 4500 nmethod* claimed_nmethods[MaxClaimNmethods]; 4501 4502 while (true) { 4503 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 4504 4505 if (num_claimed_nmethods == 0) { 4506 break; 4507 } 4508 4509 for (int i = 0; i < num_claimed_nmethods; i++) { 4510 clean_nmethod(claimed_nmethods[i]); 4511 } 4512 } 4513 } 4514 4515 void work_second_pass(uint worker_id) { 4516 nmethod* nm; 4517 // Take care of postponed nmethods. 4518 while ((nm = claim_postponed_nmethod()) != NULL) { 4519 clean_nmethod_postponed(nm); 4520 } 4521 } 4522 }; 4523 4524 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 4525 4526 class G1KlassCleaningTask : public StackObj { 4527 BoolObjectClosure* _is_alive; 4528 volatile jint _clean_klass_tree_claimed; 4529 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 4530 4531 public: 4532 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 4533 _is_alive(is_alive), 4534 _clean_klass_tree_claimed(0), 4535 _klass_iterator() { 4536 } 4537 4538 private: 4539 bool claim_clean_klass_tree_task() { 4540 if (_clean_klass_tree_claimed) { 4541 return false; 4542 } 4543 4544 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 4545 } 4546 4547 InstanceKlass* claim_next_klass() { 4548 Klass* klass; 4549 do { 4550 klass =_klass_iterator.next_klass(); 4551 } while (klass != NULL && !klass->is_instance_klass()); 4552 4553 // this can be null so don't call InstanceKlass::cast 4554 return static_cast<InstanceKlass*>(klass); 4555 } 4556 4557 public: 4558 4559 void clean_klass(InstanceKlass* ik) { 4560 ik->clean_weak_instanceklass_links(_is_alive); 4561 } 4562 4563 void work() { 4564 ResourceMark rm; 4565 4566 // One worker will clean the subklass/sibling klass tree. 4567 if (claim_clean_klass_tree_task()) { 4568 Klass::clean_subklass_tree(_is_alive); 4569 } 4570 4571 // All workers will help cleaning the classes, 4572 InstanceKlass* klass; 4573 while ((klass = claim_next_klass()) != NULL) { 4574 clean_klass(klass); 4575 } 4576 } 4577 }; 4578 4579 // To minimize the remark pause times, the tasks below are done in parallel. 4580 class G1ParallelCleaningTask : public AbstractGangTask { 4581 private: 4582 G1StringSymbolTableUnlinkTask _string_symbol_task; 4583 G1CodeCacheUnloadingTask _code_cache_task; 4584 G1KlassCleaningTask _klass_cleaning_task; 4585 4586 public: 4587 // The constructor is run in the VMThread. 4588 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 4589 AbstractGangTask("Parallel Cleaning"), 4590 _string_symbol_task(is_alive, process_strings, process_symbols), 4591 _code_cache_task(num_workers, is_alive, unloading_occurred), 4592 _klass_cleaning_task(is_alive) { 4593 } 4594 4595 // The parallel work done by all worker threads. 4596 void work(uint worker_id) { 4597 // Do first pass of code cache cleaning. 4598 _code_cache_task.work_first_pass(worker_id); 4599 4600 // Let the threads mark that the first pass is done. 4601 _code_cache_task.barrier_mark(worker_id); 4602 4603 // Clean the Strings and Symbols. 4604 _string_symbol_task.work(worker_id); 4605 4606 // Wait for all workers to finish the first code cache cleaning pass. 4607 _code_cache_task.barrier_wait(worker_id); 4608 4609 // Do the second code cache cleaning work, which realize on 4610 // the liveness information gathered during the first pass. 4611 _code_cache_task.work_second_pass(worker_id); 4612 4613 // Clean all klasses that were not unloaded. 4614 _klass_cleaning_task.work(); 4615 } 4616 }; 4617 4618 4619 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 4620 bool process_strings, 4621 bool process_symbols, 4622 bool class_unloading_occurred) { 4623 uint n_workers = workers()->active_workers(); 4624 4625 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 4626 n_workers, class_unloading_occurred); 4627 workers()->run_task(&g1_unlink_task); 4628 } 4629 4630 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 4631 bool process_strings, bool process_symbols) { 4632 { 4633 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 4634 workers()->run_task(&g1_unlink_task); 4635 } 4636 4637 if (G1StringDedup::is_enabled()) { 4638 G1StringDedup::unlink(is_alive); 4639 } 4640 } 4641 4642 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 4643 private: 4644 DirtyCardQueueSet* _queue; 4645 public: 4646 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { } 4647 4648 virtual void work(uint worker_id) { 4649 G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4650 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 4651 4652 RedirtyLoggedCardTableEntryClosure cl; 4653 _queue->par_apply_closure_to_all_completed_buffers(&cl); 4654 4655 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed()); 4656 } 4657 }; 4658 4659 void G1CollectedHeap::redirty_logged_cards() { 4660 double redirty_logged_cards_start = os::elapsedTime(); 4661 4662 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set()); 4663 dirty_card_queue_set().reset_for_par_iteration(); 4664 workers()->run_task(&redirty_task); 4665 4666 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 4667 dcq.merge_bufferlists(&dirty_card_queue_set()); 4668 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 4669 4670 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 4671 } 4672 4673 // Weak Reference Processing support 4674 4675 // An always "is_alive" closure that is used to preserve referents. 4676 // If the object is non-null then it's alive. Used in the preservation 4677 // of referent objects that are pointed to by reference objects 4678 // discovered by the CM ref processor. 4679 class G1AlwaysAliveClosure: public BoolObjectClosure { 4680 G1CollectedHeap* _g1; 4681 public: 4682 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4683 bool do_object_b(oop p) { 4684 if (p != NULL) { 4685 return true; 4686 } 4687 return false; 4688 } 4689 }; 4690 4691 bool G1STWIsAliveClosure::do_object_b(oop p) { 4692 // An object is reachable if it is outside the collection set, 4693 // or is inside and copied. 4694 return !_g1->is_in_cset(p) || p->is_forwarded(); 4695 } 4696 4697 // Non Copying Keep Alive closure 4698 class G1KeepAliveClosure: public OopClosure { 4699 G1CollectedHeap* _g1; 4700 public: 4701 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4702 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 4703 void do_oop(oop* p) { 4704 oop obj = *p; 4705 assert(obj != NULL, "the caller should have filtered out NULL values"); 4706 4707 const InCSetState cset_state = _g1->in_cset_state(obj); 4708 if (!cset_state.is_in_cset_or_humongous()) { 4709 return; 4710 } 4711 if (cset_state.is_in_cset()) { 4712 assert( obj->is_forwarded(), "invariant" ); 4713 *p = obj->forwardee(); 4714 } else { 4715 assert(!obj->is_forwarded(), "invariant" ); 4716 assert(cset_state.is_humongous(), 4717 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 4718 _g1->set_humongous_is_live(obj); 4719 } 4720 } 4721 }; 4722 4723 // Copying Keep Alive closure - can be called from both 4724 // serial and parallel code as long as different worker 4725 // threads utilize different G1ParScanThreadState instances 4726 // and different queues. 4727 4728 class G1CopyingKeepAliveClosure: public OopClosure { 4729 G1CollectedHeap* _g1h; 4730 OopClosure* _copy_non_heap_obj_cl; 4731 G1ParScanThreadState* _par_scan_state; 4732 4733 public: 4734 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4735 OopClosure* non_heap_obj_cl, 4736 G1ParScanThreadState* pss): 4737 _g1h(g1h), 4738 _copy_non_heap_obj_cl(non_heap_obj_cl), 4739 _par_scan_state(pss) 4740 {} 4741 4742 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4743 virtual void do_oop( oop* p) { do_oop_work(p); } 4744 4745 template <class T> void do_oop_work(T* p) { 4746 oop obj = oopDesc::load_decode_heap_oop(p); 4747 4748 if (_g1h->is_in_cset_or_humongous(obj)) { 4749 // If the referent object has been forwarded (either copied 4750 // to a new location or to itself in the event of an 4751 // evacuation failure) then we need to update the reference 4752 // field and, if both reference and referent are in the G1 4753 // heap, update the RSet for the referent. 4754 // 4755 // If the referent has not been forwarded then we have to keep 4756 // it alive by policy. Therefore we have copy the referent. 4757 // 4758 // If the reference field is in the G1 heap then we can push 4759 // on the PSS queue. When the queue is drained (after each 4760 // phase of reference processing) the object and it's followers 4761 // will be copied, the reference field set to point to the 4762 // new location, and the RSet updated. Otherwise we need to 4763 // use the the non-heap or metadata closures directly to copy 4764 // the referent object and update the pointer, while avoiding 4765 // updating the RSet. 4766 4767 if (_g1h->is_in_g1_reserved(p)) { 4768 _par_scan_state->push_on_queue(p); 4769 } else { 4770 assert(!Metaspace::contains((const void*)p), 4771 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4772 _copy_non_heap_obj_cl->do_oop(p); 4773 } 4774 } 4775 } 4776 }; 4777 4778 // Serial drain queue closure. Called as the 'complete_gc' 4779 // closure for each discovered list in some of the 4780 // reference processing phases. 4781 4782 class G1STWDrainQueueClosure: public VoidClosure { 4783 protected: 4784 G1CollectedHeap* _g1h; 4785 G1ParScanThreadState* _par_scan_state; 4786 4787 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4788 4789 public: 4790 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4791 _g1h(g1h), 4792 _par_scan_state(pss) 4793 { } 4794 4795 void do_void() { 4796 G1ParScanThreadState* const pss = par_scan_state(); 4797 pss->trim_queue(); 4798 } 4799 }; 4800 4801 // Parallel Reference Processing closures 4802 4803 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4804 // processing during G1 evacuation pauses. 4805 4806 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4807 private: 4808 G1CollectedHeap* _g1h; 4809 G1ParScanThreadStateSet* _pss; 4810 RefToScanQueueSet* _queues; 4811 WorkGang* _workers; 4812 uint _active_workers; 4813 4814 public: 4815 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4816 G1ParScanThreadStateSet* per_thread_states, 4817 WorkGang* workers, 4818 RefToScanQueueSet *task_queues, 4819 uint n_workers) : 4820 _g1h(g1h), 4821 _pss(per_thread_states), 4822 _queues(task_queues), 4823 _workers(workers), 4824 _active_workers(n_workers) 4825 { 4826 assert(n_workers > 0, "shouldn't call this otherwise"); 4827 } 4828 4829 // Executes the given task using concurrent marking worker threads. 4830 virtual void execute(ProcessTask& task); 4831 virtual void execute(EnqueueTask& task); 4832 }; 4833 4834 // Gang task for possibly parallel reference processing 4835 4836 class G1STWRefProcTaskProxy: public AbstractGangTask { 4837 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4838 ProcessTask& _proc_task; 4839 G1CollectedHeap* _g1h; 4840 G1ParScanThreadStateSet* _pss; 4841 RefToScanQueueSet* _task_queues; 4842 ParallelTaskTerminator* _terminator; 4843 4844 public: 4845 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4846 G1CollectedHeap* g1h, 4847 G1ParScanThreadStateSet* per_thread_states, 4848 RefToScanQueueSet *task_queues, 4849 ParallelTaskTerminator* terminator) : 4850 AbstractGangTask("Process reference objects in parallel"), 4851 _proc_task(proc_task), 4852 _g1h(g1h), 4853 _pss(per_thread_states), 4854 _task_queues(task_queues), 4855 _terminator(terminator) 4856 {} 4857 4858 virtual void work(uint worker_id) { 4859 // The reference processing task executed by a single worker. 4860 ResourceMark rm; 4861 HandleMark hm; 4862 4863 G1STWIsAliveClosure is_alive(_g1h); 4864 4865 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4866 pss->set_ref_processor(NULL); 4867 4868 // Keep alive closure. 4869 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4870 4871 // Complete GC closure 4872 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4873 4874 // Call the reference processing task's work routine. 4875 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4876 4877 // Note we cannot assert that the refs array is empty here as not all 4878 // of the processing tasks (specifically phase2 - pp2_work) execute 4879 // the complete_gc closure (which ordinarily would drain the queue) so 4880 // the queue may not be empty. 4881 } 4882 }; 4883 4884 // Driver routine for parallel reference processing. 4885 // Creates an instance of the ref processing gang 4886 // task and has the worker threads execute it. 4887 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4888 assert(_workers != NULL, "Need parallel worker threads."); 4889 4890 ParallelTaskTerminator terminator(_active_workers, _queues); 4891 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4892 4893 _workers->run_task(&proc_task_proxy); 4894 } 4895 4896 // Gang task for parallel reference enqueueing. 4897 4898 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4899 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4900 EnqueueTask& _enq_task; 4901 4902 public: 4903 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4904 AbstractGangTask("Enqueue reference objects in parallel"), 4905 _enq_task(enq_task) 4906 { } 4907 4908 virtual void work(uint worker_id) { 4909 _enq_task.work(worker_id); 4910 } 4911 }; 4912 4913 // Driver routine for parallel reference enqueueing. 4914 // Creates an instance of the ref enqueueing gang 4915 // task and has the worker threads execute it. 4916 4917 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4918 assert(_workers != NULL, "Need parallel worker threads."); 4919 4920 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4921 4922 _workers->run_task(&enq_task_proxy); 4923 } 4924 4925 // End of weak reference support closures 4926 4927 // Abstract task used to preserve (i.e. copy) any referent objects 4928 // that are in the collection set and are pointed to by reference 4929 // objects discovered by the CM ref processor. 4930 4931 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4932 protected: 4933 G1CollectedHeap* _g1h; 4934 G1ParScanThreadStateSet* _pss; 4935 RefToScanQueueSet* _queues; 4936 ParallelTaskTerminator _terminator; 4937 uint _n_workers; 4938 4939 public: 4940 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4941 AbstractGangTask("ParPreserveCMReferents"), 4942 _g1h(g1h), 4943 _pss(per_thread_states), 4944 _queues(task_queues), 4945 _terminator(workers, _queues), 4946 _n_workers(workers) 4947 { } 4948 4949 void work(uint worker_id) { 4950 ResourceMark rm; 4951 HandleMark hm; 4952 4953 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4954 pss->set_ref_processor(NULL); 4955 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4956 4957 // Is alive closure 4958 G1AlwaysAliveClosure always_alive(_g1h); 4959 4960 // Copying keep alive closure. Applied to referent objects that need 4961 // to be copied. 4962 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4963 4964 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4965 4966 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4967 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4968 4969 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4970 // So this must be true - but assert just in case someone decides to 4971 // change the worker ids. 4972 assert(worker_id < limit, "sanity"); 4973 assert(!rp->discovery_is_atomic(), "check this code"); 4974 4975 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4976 for (uint idx = worker_id; idx < limit; idx += stride) { 4977 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4978 4979 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4980 while (iter.has_next()) { 4981 // Since discovery is not atomic for the CM ref processor, we 4982 // can see some null referent objects. 4983 iter.load_ptrs(DEBUG_ONLY(true)); 4984 oop ref = iter.obj(); 4985 4986 // This will filter nulls. 4987 if (iter.is_referent_alive()) { 4988 iter.make_referent_alive(); 4989 } 4990 iter.move_to_next(); 4991 } 4992 } 4993 4994 // Drain the queue - which may cause stealing 4995 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4996 drain_queue.do_void(); 4997 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4998 assert(pss->queue_is_empty(), "should be"); 4999 } 5000 }; 5001 5002 // Weak Reference processing during an evacuation pause (part 1). 5003 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 5004 double ref_proc_start = os::elapsedTime(); 5005 5006 ReferenceProcessor* rp = _ref_processor_stw; 5007 assert(rp->discovery_enabled(), "should have been enabled"); 5008 5009 // Any reference objects, in the collection set, that were 'discovered' 5010 // by the CM ref processor should have already been copied (either by 5011 // applying the external root copy closure to the discovered lists, or 5012 // by following an RSet entry). 5013 // 5014 // But some of the referents, that are in the collection set, that these 5015 // reference objects point to may not have been copied: the STW ref 5016 // processor would have seen that the reference object had already 5017 // been 'discovered' and would have skipped discovering the reference, 5018 // but would not have treated the reference object as a regular oop. 5019 // As a result the copy closure would not have been applied to the 5020 // referent object. 5021 // 5022 // We need to explicitly copy these referent objects - the references 5023 // will be processed at the end of remarking. 5024 // 5025 // We also need to do this copying before we process the reference 5026 // objects discovered by the STW ref processor in case one of these 5027 // referents points to another object which is also referenced by an 5028 // object discovered by the STW ref processor. 5029 5030 uint no_of_gc_workers = workers()->active_workers(); 5031 5032 G1ParPreserveCMReferentsTask keep_cm_referents(this, 5033 per_thread_states, 5034 no_of_gc_workers, 5035 _task_queues); 5036 5037 workers()->run_task(&keep_cm_referents); 5038 5039 // Closure to test whether a referent is alive. 5040 G1STWIsAliveClosure is_alive(this); 5041 5042 // Even when parallel reference processing is enabled, the processing 5043 // of JNI refs is serial and performed serially by the current thread 5044 // rather than by a worker. The following PSS will be used for processing 5045 // JNI refs. 5046 5047 // Use only a single queue for this PSS. 5048 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 5049 pss->set_ref_processor(NULL); 5050 assert(pss->queue_is_empty(), "pre-condition"); 5051 5052 // Keep alive closure. 5053 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 5054 5055 // Serial Complete GC closure 5056 G1STWDrainQueueClosure drain_queue(this, pss); 5057 5058 // Setup the soft refs policy... 5059 rp->setup_policy(false); 5060 5061 ReferenceProcessorStats stats; 5062 if (!rp->processing_is_mt()) { 5063 // Serial reference processing... 5064 stats = rp->process_discovered_references(&is_alive, 5065 &keep_alive, 5066 &drain_queue, 5067 NULL, 5068 _gc_timer_stw); 5069 } else { 5070 // Parallel reference processing 5071 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5072 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5073 5074 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 5075 stats = rp->process_discovered_references(&is_alive, 5076 &keep_alive, 5077 &drain_queue, 5078 &par_task_executor, 5079 _gc_timer_stw); 5080 } 5081 5082 _gc_tracer_stw->report_gc_reference_stats(stats); 5083 5084 // We have completed copying any necessary live referent objects. 5085 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 5086 5087 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5088 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 5089 } 5090 5091 // Weak Reference processing during an evacuation pause (part 2). 5092 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 5093 double ref_enq_start = os::elapsedTime(); 5094 5095 ReferenceProcessor* rp = _ref_processor_stw; 5096 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5097 5098 // Now enqueue any remaining on the discovered lists on to 5099 // the pending list. 5100 if (!rp->processing_is_mt()) { 5101 // Serial reference processing... 5102 rp->enqueue_discovered_references(); 5103 } else { 5104 // Parallel reference enqueueing 5105 5106 uint n_workers = workers()->active_workers(); 5107 5108 assert(rp->num_q() == n_workers, "sanity"); 5109 assert(n_workers <= rp->max_num_q(), "sanity"); 5110 5111 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 5112 rp->enqueue_discovered_references(&par_task_executor); 5113 } 5114 5115 rp->verify_no_references_recorded(); 5116 assert(!rp->discovery_enabled(), "should have been disabled"); 5117 5118 // FIXME 5119 // CM's reference processing also cleans up the string and symbol tables. 5120 // Should we do that here also? We could, but it is a serial operation 5121 // and could significantly increase the pause time. 5122 5123 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5124 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5125 } 5126 5127 void G1CollectedHeap::pre_evacuate_collection_set() { 5128 _expand_heap_after_alloc_failure = true; 5129 _evacuation_failed = false; 5130 5131 // Disable the hot card cache. 5132 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5133 hot_card_cache->reset_hot_cache_claimed_index(); 5134 hot_card_cache->set_use_cache(false); 5135 5136 } 5137 5138 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 5139 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5140 5141 // Should G1EvacuationFailureALot be in effect for this GC? 5142 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5143 5144 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5145 double start_par_time_sec = os::elapsedTime(); 5146 double end_par_time_sec; 5147 5148 { 5149 const uint n_workers = workers()->active_workers(); 5150 G1RootProcessor root_processor(this, n_workers); 5151 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 5152 // InitialMark needs claim bits to keep track of the marked-through CLDs. 5153 if (collector_state()->during_initial_mark_pause()) { 5154 ClassLoaderDataGraph::clear_claimed_marks(); 5155 } 5156 5157 // The individual threads will set their evac-failure closures. 5158 if (PrintTerminationStats) { 5159 print_termination_stats_hdr(gclog_or_tty); 5160 } 5161 5162 workers()->run_task(&g1_par_task); 5163 end_par_time_sec = os::elapsedTime(); 5164 5165 // Closing the inner scope will execute the destructor 5166 // for the G1RootProcessor object. We record the current 5167 // elapsed time before closing the scope so that time 5168 // taken for the destructor is NOT included in the 5169 // reported parallel time. 5170 } 5171 5172 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 5173 5174 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5175 phase_times->record_par_time(par_time_ms); 5176 5177 double code_root_fixup_time_ms = 5178 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5179 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 5180 5181 // Process any discovered reference objects - we have 5182 // to do this _before_ we retire the GC alloc regions 5183 // as we may have to copy some 'reachable' referent 5184 // objects (and their reachable sub-graphs) that were 5185 // not copied during the pause. 5186 process_discovered_references(per_thread_states); 5187 5188 if (G1StringDedup::is_enabled()) { 5189 double fixup_start = os::elapsedTime(); 5190 5191 G1STWIsAliveClosure is_alive(this); 5192 G1KeepAliveClosure keep_alive(this); 5193 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times); 5194 5195 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 5196 phase_times->record_string_dedup_fixup_time(fixup_time_ms); 5197 } 5198 5199 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5200 5201 if (evacuation_failed()) { 5202 remove_self_forwarding_pointers(); 5203 5204 // Reset the G1EvacuationFailureALot counters and flags 5205 // Note: the values are reset only when an actual 5206 // evacuation failure occurs. 5207 NOT_PRODUCT(reset_evacuation_should_fail();) 5208 } 5209 5210 // Enqueue any remaining references remaining on the STW 5211 // reference processor's discovered lists. We need to do 5212 // this after the card table is cleaned (and verified) as 5213 // the act of enqueueing entries on to the pending list 5214 // will log these updates (and dirty their associated 5215 // cards). We need these updates logged to update any 5216 // RSets. 5217 enqueue_discovered_references(per_thread_states); 5218 } 5219 5220 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 5221 _allocator->release_gc_alloc_regions(evacuation_info); 5222 5223 per_thread_states->flush(); 5224 5225 record_obj_copy_mem_stats(); 5226 5227 _survivor_evac_stats.adjust_desired_plab_sz(); 5228 _old_evac_stats.adjust_desired_plab_sz(); 5229 5230 // Reset and re-enable the hot card cache. 5231 // Note the counts for the cards in the regions in the 5232 // collection set are reset when the collection set is freed. 5233 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5234 hot_card_cache->reset_hot_cache(); 5235 hot_card_cache->set_use_cache(true); 5236 5237 purge_code_root_memory(); 5238 5239 redirty_logged_cards(); 5240 #if defined(COMPILER2) || INCLUDE_JVMCI 5241 DerivedPointerTable::update_pointers(); 5242 #endif 5243 } 5244 5245 void G1CollectedHeap::record_obj_copy_mem_stats() { 5246 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 5247 create_g1_evac_summary(&_old_evac_stats)); 5248 } 5249 5250 void G1CollectedHeap::free_region(HeapRegion* hr, 5251 FreeRegionList* free_list, 5252 bool par, 5253 bool locked) { 5254 assert(!hr->is_free(), "the region should not be free"); 5255 assert(!hr->is_empty(), "the region should not be empty"); 5256 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 5257 assert(free_list != NULL, "pre-condition"); 5258 5259 if (G1VerifyBitmaps) { 5260 MemRegion mr(hr->bottom(), hr->end()); 5261 concurrent_mark()->clearRangePrevBitmap(mr); 5262 } 5263 5264 // Clear the card counts for this region. 5265 // Note: we only need to do this if the region is not young 5266 // (since we don't refine cards in young regions). 5267 if (!hr->is_young()) { 5268 _cg1r->hot_card_cache()->reset_card_counts(hr); 5269 } 5270 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 5271 free_list->add_ordered(hr); 5272 } 5273 5274 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5275 FreeRegionList* free_list, 5276 bool par) { 5277 assert(hr->is_humongous(), "this is only for humongous regions"); 5278 assert(free_list != NULL, "pre-condition"); 5279 hr->clear_humongous(); 5280 free_region(hr, free_list, par); 5281 } 5282 5283 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, 5284 const HeapRegionSetCount& humongous_regions_removed) { 5285 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) { 5286 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5287 _old_set.bulk_remove(old_regions_removed); 5288 _humongous_set.bulk_remove(humongous_regions_removed); 5289 } 5290 5291 } 5292 5293 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 5294 assert(list != NULL, "list can't be null"); 5295 if (!list->is_empty()) { 5296 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 5297 _hrm.insert_list_into_free_list(list); 5298 } 5299 } 5300 5301 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 5302 decrease_used(bytes); 5303 } 5304 5305 class G1ParCleanupCTTask : public AbstractGangTask { 5306 G1SATBCardTableModRefBS* _ct_bs; 5307 G1CollectedHeap* _g1h; 5308 HeapRegion* volatile _su_head; 5309 public: 5310 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 5311 G1CollectedHeap* g1h) : 5312 AbstractGangTask("G1 Par Cleanup CT Task"), 5313 _ct_bs(ct_bs), _g1h(g1h) { } 5314 5315 void work(uint worker_id) { 5316 HeapRegion* r; 5317 while (r = _g1h->pop_dirty_cards_region()) { 5318 clear_cards(r); 5319 } 5320 } 5321 5322 void clear_cards(HeapRegion* r) { 5323 // Cards of the survivors should have already been dirtied. 5324 if (!r->is_survivor()) { 5325 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 5326 } 5327 } 5328 }; 5329 5330 #ifndef PRODUCT 5331 class G1VerifyCardTableCleanup: public HeapRegionClosure { 5332 G1CollectedHeap* _g1h; 5333 G1SATBCardTableModRefBS* _ct_bs; 5334 public: 5335 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs) 5336 : _g1h(g1h), _ct_bs(ct_bs) { } 5337 virtual bool doHeapRegion(HeapRegion* r) { 5338 if (r->is_survivor()) { 5339 _g1h->verify_dirty_region(r); 5340 } else { 5341 _g1h->verify_not_dirty_region(r); 5342 } 5343 return false; 5344 } 5345 }; 5346 5347 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 5348 // All of the region should be clean. 5349 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5350 MemRegion mr(hr->bottom(), hr->end()); 5351 ct_bs->verify_not_dirty_region(mr); 5352 } 5353 5354 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 5355 // We cannot guarantee that [bottom(),end()] is dirty. Threads 5356 // dirty allocated blocks as they allocate them. The thread that 5357 // retires each region and replaces it with a new one will do a 5358 // maximal allocation to fill in [pre_dummy_top(),end()] but will 5359 // not dirty that area (one less thing to have to do while holding 5360 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 5361 // is dirty. 5362 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5363 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 5364 if (hr->is_young()) { 5365 ct_bs->verify_g1_young_region(mr); 5366 } else { 5367 ct_bs->verify_dirty_region(mr); 5368 } 5369 } 5370 5371 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 5372 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5373 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 5374 verify_dirty_region(hr); 5375 } 5376 } 5377 5378 void G1CollectedHeap::verify_dirty_young_regions() { 5379 verify_dirty_young_list(_young_list->first_region()); 5380 } 5381 5382 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 5383 HeapWord* tams, HeapWord* end) { 5384 guarantee(tams <= end, 5385 "tams: " PTR_FORMAT " end: " PTR_FORMAT, p2i(tams), p2i(end)); 5386 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end); 5387 if (result < end) { 5388 gclog_or_tty->cr(); 5389 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: " PTR_FORMAT, 5390 bitmap_name, p2i(result)); 5391 gclog_or_tty->print_cr("## %s tams: " PTR_FORMAT " end: " PTR_FORMAT, 5392 bitmap_name, p2i(tams), p2i(end)); 5393 return false; 5394 } 5395 return true; 5396 } 5397 5398 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) { 5399 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap(); 5400 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap(); 5401 5402 HeapWord* bottom = hr->bottom(); 5403 HeapWord* ptams = hr->prev_top_at_mark_start(); 5404 HeapWord* ntams = hr->next_top_at_mark_start(); 5405 HeapWord* end = hr->end(); 5406 5407 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end); 5408 5409 bool res_n = true; 5410 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window 5411 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap 5412 // if we happen to be in that state. 5413 if (collector_state()->mark_in_progress() || !_cmThread->in_progress()) { 5414 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end); 5415 } 5416 if (!res_p || !res_n) { 5417 gclog_or_tty->print_cr("#### Bitmap verification failed for " HR_FORMAT, 5418 HR_FORMAT_PARAMS(hr)); 5419 gclog_or_tty->print_cr("#### Caller: %s", caller); 5420 return false; 5421 } 5422 return true; 5423 } 5424 5425 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) { 5426 if (!G1VerifyBitmaps) return; 5427 5428 guarantee(verify_bitmaps(caller, hr), "bitmap verification"); 5429 } 5430 5431 class G1VerifyBitmapClosure : public HeapRegionClosure { 5432 private: 5433 const char* _caller; 5434 G1CollectedHeap* _g1h; 5435 bool _failures; 5436 5437 public: 5438 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) : 5439 _caller(caller), _g1h(g1h), _failures(false) { } 5440 5441 bool failures() { return _failures; } 5442 5443 virtual bool doHeapRegion(HeapRegion* hr) { 5444 bool result = _g1h->verify_bitmaps(_caller, hr); 5445 if (!result) { 5446 _failures = true; 5447 } 5448 return false; 5449 } 5450 }; 5451 5452 void G1CollectedHeap::check_bitmaps(const char* caller) { 5453 if (!G1VerifyBitmaps) return; 5454 5455 G1VerifyBitmapClosure cl(caller, this); 5456 heap_region_iterate(&cl); 5457 guarantee(!cl.failures(), "bitmap verification"); 5458 } 5459 5460 class G1CheckCSetFastTableClosure : public HeapRegionClosure { 5461 private: 5462 bool _failures; 5463 public: 5464 G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { } 5465 5466 virtual bool doHeapRegion(HeapRegion* hr) { 5467 uint i = hr->hrm_index(); 5468 InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i); 5469 if (hr->is_humongous()) { 5470 if (hr->in_collection_set()) { 5471 gclog_or_tty->print_cr("\n## humongous region %u in CSet", i); 5472 _failures = true; 5473 return true; 5474 } 5475 if (cset_state.is_in_cset()) { 5476 gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i); 5477 _failures = true; 5478 return true; 5479 } 5480 if (hr->is_continues_humongous() && cset_state.is_humongous()) { 5481 gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i); 5482 _failures = true; 5483 return true; 5484 } 5485 } else { 5486 if (cset_state.is_humongous()) { 5487 gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i); 5488 _failures = true; 5489 return true; 5490 } 5491 if (hr->in_collection_set() != cset_state.is_in_cset()) { 5492 gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u", 5493 hr->in_collection_set(), cset_state.value(), i); 5494 _failures = true; 5495 return true; 5496 } 5497 if (cset_state.is_in_cset()) { 5498 if (hr->is_young() != (cset_state.is_young())) { 5499 gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u", 5500 hr->is_young(), cset_state.value(), i); 5501 _failures = true; 5502 return true; 5503 } 5504 if (hr->is_old() != (cset_state.is_old())) { 5505 gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u", 5506 hr->is_old(), cset_state.value(), i); 5507 _failures = true; 5508 return true; 5509 } 5510 } 5511 } 5512 return false; 5513 } 5514 5515 bool failures() const { return _failures; } 5516 }; 5517 5518 bool G1CollectedHeap::check_cset_fast_test() { 5519 G1CheckCSetFastTableClosure cl; 5520 _hrm.iterate(&cl); 5521 return !cl.failures(); 5522 } 5523 #endif // PRODUCT 5524 5525 void G1CollectedHeap::cleanUpCardTable() { 5526 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5527 double start = os::elapsedTime(); 5528 5529 { 5530 // Iterate over the dirty cards region list. 5531 G1ParCleanupCTTask cleanup_task(ct_bs, this); 5532 5533 workers()->run_task(&cleanup_task); 5534 #ifndef PRODUCT 5535 if (G1VerifyCTCleanup || VerifyAfterGC) { 5536 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 5537 heap_region_iterate(&cleanup_verifier); 5538 } 5539 #endif 5540 } 5541 5542 double elapsed = os::elapsedTime() - start; 5543 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 5544 } 5545 5546 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 5547 size_t pre_used = 0; 5548 FreeRegionList local_free_list("Local List for CSet Freeing"); 5549 5550 double young_time_ms = 0.0; 5551 double non_young_time_ms = 0.0; 5552 5553 // Since the collection set is a superset of the the young list, 5554 // all we need to do to clear the young list is clear its 5555 // head and length, and unlink any young regions in the code below 5556 _young_list->clear(); 5557 5558 G1CollectorPolicy* policy = g1_policy(); 5559 5560 double start_sec = os::elapsedTime(); 5561 bool non_young = true; 5562 5563 HeapRegion* cur = cs_head; 5564 int age_bound = -1; 5565 size_t rs_lengths = 0; 5566 5567 while (cur != NULL) { 5568 assert(!is_on_master_free_list(cur), "sanity"); 5569 if (non_young) { 5570 if (cur->is_young()) { 5571 double end_sec = os::elapsedTime(); 5572 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5573 non_young_time_ms += elapsed_ms; 5574 5575 start_sec = os::elapsedTime(); 5576 non_young = false; 5577 } 5578 } else { 5579 if (!cur->is_young()) { 5580 double end_sec = os::elapsedTime(); 5581 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5582 young_time_ms += elapsed_ms; 5583 5584 start_sec = os::elapsedTime(); 5585 non_young = true; 5586 } 5587 } 5588 5589 rs_lengths += cur->rem_set()->occupied_locked(); 5590 5591 HeapRegion* next = cur->next_in_collection_set(); 5592 assert(cur->in_collection_set(), "bad CS"); 5593 cur->set_next_in_collection_set(NULL); 5594 clear_in_cset(cur); 5595 5596 if (cur->is_young()) { 5597 int index = cur->young_index_in_cset(); 5598 assert(index != -1, "invariant"); 5599 assert((uint) index < policy->young_cset_region_length(), "invariant"); 5600 size_t words_survived = surviving_young_words[index]; 5601 cur->record_surv_words_in_group(words_survived); 5602 5603 // At this point the we have 'popped' cur from the collection set 5604 // (linked via next_in_collection_set()) but it is still in the 5605 // young list (linked via next_young_region()). Clear the 5606 // _next_young_region field. 5607 cur->set_next_young_region(NULL); 5608 } else { 5609 int index = cur->young_index_in_cset(); 5610 assert(index == -1, "invariant"); 5611 } 5612 5613 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 5614 (!cur->is_young() && cur->young_index_in_cset() == -1), 5615 "invariant" ); 5616 5617 if (!cur->evacuation_failed()) { 5618 MemRegion used_mr = cur->used_region(); 5619 5620 // And the region is empty. 5621 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 5622 pre_used += cur->used(); 5623 free_region(cur, &local_free_list, false /* par */, true /* locked */); 5624 } else { 5625 cur->uninstall_surv_rate_group(); 5626 if (cur->is_young()) { 5627 cur->set_young_index_in_cset(-1); 5628 } 5629 cur->set_evacuation_failed(false); 5630 // The region is now considered to be old. 5631 cur->set_old(); 5632 // Do some allocation statistics accounting. Regions that failed evacuation 5633 // are always made old, so there is no need to update anything in the young 5634 // gen statistics, but we need to update old gen statistics. 5635 size_t used_words = cur->marked_bytes() / HeapWordSize; 5636 _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words); 5637 _old_set.add(cur); 5638 evacuation_info.increment_collectionset_used_after(cur->used()); 5639 } 5640 cur = next; 5641 } 5642 5643 evacuation_info.set_regions_freed(local_free_list.length()); 5644 policy->record_max_rs_lengths(rs_lengths); 5645 policy->cset_regions_freed(); 5646 5647 double end_sec = os::elapsedTime(); 5648 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5649 5650 if (non_young) { 5651 non_young_time_ms += elapsed_ms; 5652 } else { 5653 young_time_ms += elapsed_ms; 5654 } 5655 5656 prepend_to_freelist(&local_free_list); 5657 decrement_summary_bytes(pre_used); 5658 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 5659 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 5660 } 5661 5662 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 5663 private: 5664 FreeRegionList* _free_region_list; 5665 HeapRegionSet* _proxy_set; 5666 HeapRegionSetCount _humongous_regions_removed; 5667 size_t _freed_bytes; 5668 public: 5669 5670 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 5671 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) { 5672 } 5673 5674 virtual bool doHeapRegion(HeapRegion* r) { 5675 if (!r->is_starts_humongous()) { 5676 return false; 5677 } 5678 5679 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 5680 5681 oop obj = (oop)r->bottom(); 5682 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 5683 5684 // The following checks whether the humongous object is live are sufficient. 5685 // The main additional check (in addition to having a reference from the roots 5686 // or the young gen) is whether the humongous object has a remembered set entry. 5687 // 5688 // A humongous object cannot be live if there is no remembered set for it 5689 // because: 5690 // - there can be no references from within humongous starts regions referencing 5691 // the object because we never allocate other objects into them. 5692 // (I.e. there are no intra-region references that may be missed by the 5693 // remembered set) 5694 // - as soon there is a remembered set entry to the humongous starts region 5695 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 5696 // until the end of a concurrent mark. 5697 // 5698 // It is not required to check whether the object has been found dead by marking 5699 // or not, in fact it would prevent reclamation within a concurrent cycle, as 5700 // all objects allocated during that time are considered live. 5701 // SATB marking is even more conservative than the remembered set. 5702 // So if at this point in the collection there is no remembered set entry, 5703 // nobody has a reference to it. 5704 // At the start of collection we flush all refinement logs, and remembered sets 5705 // are completely up-to-date wrt to references to the humongous object. 5706 // 5707 // Other implementation considerations: 5708 // - never consider object arrays at this time because they would pose 5709 // considerable effort for cleaning up the the remembered sets. This is 5710 // required because stale remembered sets might reference locations that 5711 // are currently allocated into. 5712 uint region_idx = r->hrm_index(); 5713 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 5714 !r->rem_set()->is_empty()) { 5715 5716 if (G1TraceEagerReclaimHumongousObjects) { 5717 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", 5718 region_idx, 5719 (size_t)obj->size() * HeapWordSize, 5720 p2i(r->bottom()), 5721 r->rem_set()->occupied(), 5722 r->rem_set()->strong_code_roots_list_length(), 5723 next_bitmap->isMarked(r->bottom()), 5724 g1h->is_humongous_reclaim_candidate(region_idx), 5725 obj->is_typeArray() 5726 ); 5727 } 5728 5729 return false; 5730 } 5731 5732 guarantee(obj->is_typeArray(), 5733 "Only eagerly reclaiming type arrays is supported, but the object " 5734 PTR_FORMAT " is not.", p2i(r->bottom())); 5735 5736 if (G1TraceEagerReclaimHumongousObjects) { 5737 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", 5738 region_idx, 5739 (size_t)obj->size() * HeapWordSize, 5740 p2i(r->bottom()), 5741 r->rem_set()->occupied(), 5742 r->rem_set()->strong_code_roots_list_length(), 5743 next_bitmap->isMarked(r->bottom()), 5744 g1h->is_humongous_reclaim_candidate(region_idx), 5745 obj->is_typeArray() 5746 ); 5747 } 5748 // Need to clear mark bit of the humongous object if already set. 5749 if (next_bitmap->isMarked(r->bottom())) { 5750 next_bitmap->clear(r->bottom()); 5751 } 5752 do { 5753 HeapRegion* next = g1h->next_region_in_humongous(r); 5754 _freed_bytes += r->used(); 5755 r->set_containing_set(NULL); 5756 _humongous_regions_removed.increment(1u, r->capacity()); 5757 g1h->free_humongous_region(r, _free_region_list, false); 5758 r = next; 5759 } while (r != NULL); 5760 5761 return false; 5762 } 5763 5764 HeapRegionSetCount& humongous_free_count() { 5765 return _humongous_regions_removed; 5766 } 5767 5768 size_t bytes_freed() const { 5769 return _freed_bytes; 5770 } 5771 5772 size_t humongous_reclaimed() const { 5773 return _humongous_regions_removed.length(); 5774 } 5775 }; 5776 5777 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 5778 assert_at_safepoint(true); 5779 5780 if (!G1EagerReclaimHumongousObjects || 5781 (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) { 5782 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5783 return; 5784 } 5785 5786 double start_time = os::elapsedTime(); 5787 5788 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5789 5790 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5791 heap_region_iterate(&cl); 5792 5793 HeapRegionSetCount empty_set; 5794 remove_from_old_sets(empty_set, cl.humongous_free_count()); 5795 5796 G1HRPrinter* hrp = hr_printer(); 5797 if (hrp->is_active()) { 5798 FreeRegionListIterator iter(&local_cleanup_list); 5799 while (iter.more_available()) { 5800 HeapRegion* hr = iter.get_next(); 5801 hrp->cleanup(hr); 5802 } 5803 } 5804 5805 prepend_to_freelist(&local_cleanup_list); 5806 decrement_summary_bytes(cl.bytes_freed()); 5807 5808 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5809 cl.humongous_reclaimed()); 5810 } 5811 5812 // This routine is similar to the above but does not record 5813 // any policy statistics or update free lists; we are abandoning 5814 // the current incremental collection set in preparation of a 5815 // full collection. After the full GC we will start to build up 5816 // the incremental collection set again. 5817 // This is only called when we're doing a full collection 5818 // and is immediately followed by the tearing down of the young list. 5819 5820 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 5821 HeapRegion* cur = cs_head; 5822 5823 while (cur != NULL) { 5824 HeapRegion* next = cur->next_in_collection_set(); 5825 assert(cur->in_collection_set(), "bad CS"); 5826 cur->set_next_in_collection_set(NULL); 5827 clear_in_cset(cur); 5828 cur->set_young_index_in_cset(-1); 5829 cur = next; 5830 } 5831 } 5832 5833 void G1CollectedHeap::set_free_regions_coming() { 5834 if (G1ConcRegionFreeingVerbose) { 5835 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 5836 "setting free regions coming"); 5837 } 5838 5839 assert(!free_regions_coming(), "pre-condition"); 5840 _free_regions_coming = true; 5841 } 5842 5843 void G1CollectedHeap::reset_free_regions_coming() { 5844 assert(free_regions_coming(), "pre-condition"); 5845 5846 { 5847 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5848 _free_regions_coming = false; 5849 SecondaryFreeList_lock->notify_all(); 5850 } 5851 5852 if (G1ConcRegionFreeingVerbose) { 5853 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 5854 "reset free regions coming"); 5855 } 5856 } 5857 5858 void G1CollectedHeap::wait_while_free_regions_coming() { 5859 // Most of the time we won't have to wait, so let's do a quick test 5860 // first before we take the lock. 5861 if (!free_regions_coming()) { 5862 return; 5863 } 5864 5865 if (G1ConcRegionFreeingVerbose) { 5866 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 5867 "waiting for free regions"); 5868 } 5869 5870 { 5871 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5872 while (free_regions_coming()) { 5873 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5874 } 5875 } 5876 5877 if (G1ConcRegionFreeingVerbose) { 5878 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 5879 "done waiting for free regions"); 5880 } 5881 } 5882 5883 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5884 return _allocator->is_retained_old_region(hr); 5885 } 5886 5887 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5888 _young_list->push_region(hr); 5889 } 5890 5891 class NoYoungRegionsClosure: public HeapRegionClosure { 5892 private: 5893 bool _success; 5894 public: 5895 NoYoungRegionsClosure() : _success(true) { } 5896 bool doHeapRegion(HeapRegion* r) { 5897 if (r->is_young()) { 5898 gclog_or_tty->print_cr("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5899 p2i(r->bottom()), p2i(r->end())); 5900 _success = false; 5901 } 5902 return false; 5903 } 5904 bool success() { return _success; } 5905 }; 5906 5907 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 5908 bool ret = _young_list->check_list_empty(check_sample); 5909 5910 if (check_heap) { 5911 NoYoungRegionsClosure closure; 5912 heap_region_iterate(&closure); 5913 ret = ret && closure.success(); 5914 } 5915 5916 return ret; 5917 } 5918 5919 class TearDownRegionSetsClosure : public HeapRegionClosure { 5920 private: 5921 HeapRegionSet *_old_set; 5922 5923 public: 5924 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5925 5926 bool doHeapRegion(HeapRegion* r) { 5927 if (r->is_old()) { 5928 _old_set->remove(r); 5929 } else { 5930 // We ignore free regions, we'll empty the free list afterwards. 5931 // We ignore young regions, we'll empty the young list afterwards. 5932 // We ignore humongous regions, we're not tearing down the 5933 // humongous regions set. 5934 assert(r->is_free() || r->is_young() || r->is_humongous(), 5935 "it cannot be another type"); 5936 } 5937 return false; 5938 } 5939 5940 ~TearDownRegionSetsClosure() { 5941 assert(_old_set->is_empty(), "post-condition"); 5942 } 5943 }; 5944 5945 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5946 assert_at_safepoint(true /* should_be_vm_thread */); 5947 5948 if (!free_list_only) { 5949 TearDownRegionSetsClosure cl(&_old_set); 5950 heap_region_iterate(&cl); 5951 5952 // Note that emptying the _young_list is postponed and instead done as 5953 // the first step when rebuilding the regions sets again. The reason for 5954 // this is that during a full GC string deduplication needs to know if 5955 // a collected region was young or old when the full GC was initiated. 5956 } 5957 _hrm.remove_all_free_regions(); 5958 } 5959 5960 void G1CollectedHeap::increase_used(size_t bytes) { 5961 _summary_bytes_used += bytes; 5962 } 5963 5964 void G1CollectedHeap::decrease_used(size_t bytes) { 5965 assert(_summary_bytes_used >= bytes, 5966 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5967 _summary_bytes_used, bytes); 5968 _summary_bytes_used -= bytes; 5969 } 5970 5971 void G1CollectedHeap::set_used(size_t bytes) { 5972 _summary_bytes_used = bytes; 5973 } 5974 5975 class RebuildRegionSetsClosure : public HeapRegionClosure { 5976 private: 5977 bool _free_list_only; 5978 HeapRegionSet* _old_set; 5979 HeapRegionManager* _hrm; 5980 size_t _total_used; 5981 5982 public: 5983 RebuildRegionSetsClosure(bool free_list_only, 5984 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5985 _free_list_only(free_list_only), 5986 _old_set(old_set), _hrm(hrm), _total_used(0) { 5987 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5988 if (!free_list_only) { 5989 assert(_old_set->is_empty(), "pre-condition"); 5990 } 5991 } 5992 5993 bool doHeapRegion(HeapRegion* r) { 5994 if (r->is_empty()) { 5995 // Add free regions to the free list 5996 r->set_free(); 5997 r->set_allocation_context(AllocationContext::system()); 5998 _hrm->insert_into_free_list(r); 5999 } else if (!_free_list_only) { 6000 assert(!r->is_young(), "we should not come across young regions"); 6001 6002 if (r->is_humongous()) { 6003 // We ignore humongous regions. We left the humongous set unchanged. 6004 } else { 6005 // Objects that were compacted would have ended up on regions 6006 // that were previously old or free. Archive regions (which are 6007 // old) will not have been touched. 6008 assert(r->is_free() || r->is_old(), "invariant"); 6009 // We now consider them old, so register as such. Leave 6010 // archive regions set that way, however, while still adding 6011 // them to the old set. 6012 if (!r->is_archive()) { 6013 r->set_old(); 6014 } 6015 _old_set->add(r); 6016 } 6017 _total_used += r->used(); 6018 } 6019 6020 return false; 6021 } 6022 6023 size_t total_used() { 6024 return _total_used; 6025 } 6026 }; 6027 6028 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6029 assert_at_safepoint(true /* should_be_vm_thread */); 6030 6031 if (!free_list_only) { 6032 _young_list->empty_list(); 6033 } 6034 6035 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 6036 heap_region_iterate(&cl); 6037 6038 if (!free_list_only) { 6039 set_used(cl.total_used()); 6040 if (_archive_allocator != NULL) { 6041 _archive_allocator->clear_used(); 6042 } 6043 } 6044 assert(used_unlocked() == recalculate_used(), 6045 "inconsistent used_unlocked(), " 6046 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 6047 used_unlocked(), recalculate_used()); 6048 } 6049 6050 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6051 _refine_cte_cl->set_concurrent(concurrent); 6052 } 6053 6054 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6055 HeapRegion* hr = heap_region_containing(p); 6056 return hr->is_in(p); 6057 } 6058 6059 // Methods for the mutator alloc region 6060 6061 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6062 bool force) { 6063 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6064 assert(!force || g1_policy()->can_expand_young_list(), 6065 "if force is true we should be able to expand the young list"); 6066 bool young_list_full = g1_policy()->is_young_list_full(); 6067 if (force || !young_list_full) { 6068 HeapRegion* new_alloc_region = new_region(word_size, 6069 false /* is_old */, 6070 false /* do_expand */); 6071 if (new_alloc_region != NULL) { 6072 set_region_short_lived_locked(new_alloc_region); 6073 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6074 check_bitmaps("Mutator Region Allocation", new_alloc_region); 6075 return new_alloc_region; 6076 } 6077 } 6078 return NULL; 6079 } 6080 6081 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6082 size_t allocated_bytes) { 6083 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6084 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 6085 6086 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6087 increase_used(allocated_bytes); 6088 _hr_printer.retire(alloc_region); 6089 // We update the eden sizes here, when the region is retired, 6090 // instead of when it's allocated, since this is the point that its 6091 // used space has been recored in _summary_bytes_used. 6092 g1mm()->update_eden_size(); 6093 } 6094 6095 // Methods for the GC alloc regions 6096 6097 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6098 uint count, 6099 InCSetState dest) { 6100 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6101 6102 if (count < g1_policy()->max_regions(dest)) { 6103 const bool is_survivor = (dest.is_young()); 6104 HeapRegion* new_alloc_region = new_region(word_size, 6105 !is_survivor, 6106 true /* do_expand */); 6107 if (new_alloc_region != NULL) { 6108 // We really only need to do this for old regions given that we 6109 // should never scan survivors. But it doesn't hurt to do it 6110 // for survivors too. 6111 new_alloc_region->record_timestamp(); 6112 if (is_survivor) { 6113 new_alloc_region->set_survivor(); 6114 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6115 check_bitmaps("Survivor Region Allocation", new_alloc_region); 6116 } else { 6117 new_alloc_region->set_old(); 6118 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6119 check_bitmaps("Old Region Allocation", new_alloc_region); 6120 } 6121 bool during_im = collector_state()->during_initial_mark_pause(); 6122 new_alloc_region->note_start_of_copying(during_im); 6123 return new_alloc_region; 6124 } 6125 } 6126 return NULL; 6127 } 6128 6129 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6130 size_t allocated_bytes, 6131 InCSetState dest) { 6132 bool during_im = collector_state()->during_initial_mark_pause(); 6133 alloc_region->note_end_of_copying(during_im); 6134 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6135 if (dest.is_young()) { 6136 young_list()->add_survivor_region(alloc_region); 6137 } else { 6138 _old_set.add(alloc_region); 6139 } 6140 _hr_printer.retire(alloc_region); 6141 } 6142 6143 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 6144 bool expanded = false; 6145 uint index = _hrm.find_highest_free(&expanded); 6146 6147 if (index != G1_NO_HRM_INDEX) { 6148 if (expanded) { 6149 ergo_verbose1(ErgoHeapSizing, 6150 "attempt heap expansion", 6151 ergo_format_reason("requested address range outside heap bounds") 6152 ergo_format_byte("region size"), 6153 HeapRegion::GrainWords * HeapWordSize); 6154 } 6155 _hrm.allocate_free_regions_starting_at(index, 1); 6156 return region_at(index); 6157 } 6158 return NULL; 6159 } 6160 6161 // Heap region set verification 6162 6163 class VerifyRegionListsClosure : public HeapRegionClosure { 6164 private: 6165 HeapRegionSet* _old_set; 6166 HeapRegionSet* _humongous_set; 6167 HeapRegionManager* _hrm; 6168 6169 public: 6170 HeapRegionSetCount _old_count; 6171 HeapRegionSetCount _humongous_count; 6172 HeapRegionSetCount _free_count; 6173 6174 VerifyRegionListsClosure(HeapRegionSet* old_set, 6175 HeapRegionSet* humongous_set, 6176 HeapRegionManager* hrm) : 6177 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm), 6178 _old_count(), _humongous_count(), _free_count(){ } 6179 6180 bool doHeapRegion(HeapRegion* hr) { 6181 if (hr->is_young()) { 6182 // TODO 6183 } else if (hr->is_humongous()) { 6184 assert(hr->containing_set() == _humongous_set, "Heap region %u is humongous but not in humongous set.", hr->hrm_index()); 6185 _humongous_count.increment(1u, hr->capacity()); 6186 } else if (hr->is_empty()) { 6187 assert(_hrm->is_free(hr), "Heap region %u is empty but not on the free list.", hr->hrm_index()); 6188 _free_count.increment(1u, hr->capacity()); 6189 } else if (hr->is_old()) { 6190 assert(hr->containing_set() == _old_set, "Heap region %u is old but not in the old set.", hr->hrm_index()); 6191 _old_count.increment(1u, hr->capacity()); 6192 } else { 6193 // There are no other valid region types. Check for one invalid 6194 // one we can identify: pinned without old or humongous set. 6195 assert(!hr->is_pinned(), "Heap region %u is pinned but not old (archive) or humongous.", hr->hrm_index()); 6196 ShouldNotReachHere(); 6197 } 6198 return false; 6199 } 6200 6201 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) { 6202 guarantee(old_set->length() == _old_count.length(), "Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()); 6203 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), "Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6204 old_set->total_capacity_bytes(), _old_count.capacity()); 6205 6206 guarantee(humongous_set->length() == _humongous_count.length(), "Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()); 6207 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), "Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6208 humongous_set->total_capacity_bytes(), _humongous_count.capacity()); 6209 6210 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()); 6211 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), "Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6212 free_list->total_capacity_bytes(), _free_count.capacity()); 6213 } 6214 }; 6215 6216 void G1CollectedHeap::verify_region_sets() { 6217 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6218 6219 // First, check the explicit lists. 6220 _hrm.verify(); 6221 { 6222 // Given that a concurrent operation might be adding regions to 6223 // the secondary free list we have to take the lock before 6224 // verifying it. 6225 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6226 _secondary_free_list.verify_list(); 6227 } 6228 6229 // If a concurrent region freeing operation is in progress it will 6230 // be difficult to correctly attributed any free regions we come 6231 // across to the correct free list given that they might belong to 6232 // one of several (free_list, secondary_free_list, any local lists, 6233 // etc.). So, if that's the case we will skip the rest of the 6234 // verification operation. Alternatively, waiting for the concurrent 6235 // operation to complete will have a non-trivial effect on the GC's 6236 // operation (no concurrent operation will last longer than the 6237 // interval between two calls to verification) and it might hide 6238 // any issues that we would like to catch during testing. 6239 if (free_regions_coming()) { 6240 return; 6241 } 6242 6243 // Make sure we append the secondary_free_list on the free_list so 6244 // that all free regions we will come across can be safely 6245 // attributed to the free_list. 6246 append_secondary_free_list_if_not_empty_with_lock(); 6247 6248 // Finally, make sure that the region accounting in the lists is 6249 // consistent with what we see in the heap. 6250 6251 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm); 6252 heap_region_iterate(&cl); 6253 cl.verify_counts(&_old_set, &_humongous_set, &_hrm); 6254 } 6255 6256 // Optimized nmethod scanning 6257 6258 class RegisterNMethodOopClosure: public OopClosure { 6259 G1CollectedHeap* _g1h; 6260 nmethod* _nm; 6261 6262 template <class T> void do_oop_work(T* p) { 6263 T heap_oop = oopDesc::load_heap_oop(p); 6264 if (!oopDesc::is_null(heap_oop)) { 6265 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6266 HeapRegion* hr = _g1h->heap_region_containing(obj); 6267 assert(!hr->is_continues_humongous(), 6268 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6269 " starting at " HR_FORMAT, 6270 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 6271 6272 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 6273 hr->add_strong_code_root_locked(_nm); 6274 } 6275 } 6276 6277 public: 6278 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6279 _g1h(g1h), _nm(nm) {} 6280 6281 void do_oop(oop* p) { do_oop_work(p); } 6282 void do_oop(narrowOop* p) { do_oop_work(p); } 6283 }; 6284 6285 class UnregisterNMethodOopClosure: public OopClosure { 6286 G1CollectedHeap* _g1h; 6287 nmethod* _nm; 6288 6289 template <class T> void do_oop_work(T* p) { 6290 T heap_oop = oopDesc::load_heap_oop(p); 6291 if (!oopDesc::is_null(heap_oop)) { 6292 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6293 HeapRegion* hr = _g1h->heap_region_containing(obj); 6294 assert(!hr->is_continues_humongous(), 6295 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6296 " starting at " HR_FORMAT, 6297 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 6298 6299 hr->remove_strong_code_root(_nm); 6300 } 6301 } 6302 6303 public: 6304 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6305 _g1h(g1h), _nm(nm) {} 6306 6307 void do_oop(oop* p) { do_oop_work(p); } 6308 void do_oop(narrowOop* p) { do_oop_work(p); } 6309 }; 6310 6311 void G1CollectedHeap::register_nmethod(nmethod* nm) { 6312 CollectedHeap::register_nmethod(nm); 6313 6314 guarantee(nm != NULL, "sanity"); 6315 RegisterNMethodOopClosure reg_cl(this, nm); 6316 nm->oops_do(®_cl); 6317 } 6318 6319 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 6320 CollectedHeap::unregister_nmethod(nm); 6321 6322 guarantee(nm != NULL, "sanity"); 6323 UnregisterNMethodOopClosure reg_cl(this, nm); 6324 nm->oops_do(®_cl, true); 6325 } 6326 6327 void G1CollectedHeap::purge_code_root_memory() { 6328 double purge_start = os::elapsedTime(); 6329 G1CodeRootSet::purge(); 6330 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 6331 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 6332 } 6333 6334 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 6335 G1CollectedHeap* _g1h; 6336 6337 public: 6338 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 6339 _g1h(g1h) {} 6340 6341 void do_code_blob(CodeBlob* cb) { 6342 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 6343 if (nm == NULL) { 6344 return; 6345 } 6346 6347 if (ScavengeRootsInCode) { 6348 _g1h->register_nmethod(nm); 6349 } 6350 } 6351 }; 6352 6353 void G1CollectedHeap::rebuild_strong_code_roots() { 6354 RebuildStrongCodeRootClosure blob_cl(this); 6355 CodeCache::blobs_do(&blob_cl); 6356 }