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