1 /* 2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/metadataOnStackMark.hpp" 27 #include "classfile/stringTable.hpp" 28 #include "code/codeCache.hpp" 29 #include "code/icBuffer.hpp" 30 #include "gc/g1/bufferingOopClosure.hpp" 31 #include "gc/g1/concurrentG1Refine.hpp" 32 #include "gc/g1/concurrentG1RefineThread.hpp" 33 #include "gc/g1/concurrentMarkThread.inline.hpp" 34 #include "gc/g1/g1Allocator.inline.hpp" 35 #include "gc/g1/g1CollectedHeap.inline.hpp" 36 #include "gc/g1/g1CollectorPolicy.hpp" 37 #include "gc/g1/g1CollectorState.hpp" 38 #include "gc/g1/g1ErgoVerbose.hpp" 39 #include "gc/g1/g1EvacFailure.hpp" 40 #include "gc/g1/g1EvacStats.inline.hpp" 41 #include "gc/g1/g1GCPhaseTimes.hpp" 42 #include "gc/g1/g1Log.hpp" 43 #include "gc/g1/g1MarkSweep.hpp" 44 #include "gc/g1/g1OopClosures.inline.hpp" 45 #include "gc/g1/g1ParScanThreadState.inline.hpp" 46 #include "gc/g1/g1RegionToSpaceMapper.hpp" 47 #include "gc/g1/g1RemSet.inline.hpp" 48 #include "gc/g1/g1RootClosures.hpp" 49 #include "gc/g1/g1RootProcessor.hpp" 50 #include "gc/g1/g1StringDedup.hpp" 51 #include "gc/g1/g1YCTypes.hpp" 52 #include "gc/g1/heapRegion.inline.hpp" 53 #include "gc/g1/heapRegionRemSet.hpp" 54 #include "gc/g1/heapRegionSet.inline.hpp" 55 #include "gc/g1/suspendibleThreadSet.hpp" 56 #include "gc/g1/vm_operations_g1.hpp" 57 #include "gc/shared/gcHeapSummary.hpp" 58 #include "gc/shared/gcId.hpp" 59 #include "gc/shared/gcLocker.inline.hpp" 60 #include "gc/shared/gcTimer.hpp" 61 #include "gc/shared/gcTrace.hpp" 62 #include "gc/shared/gcTraceTime.hpp" 63 #include "gc/shared/generationSpec.hpp" 64 #include "gc/shared/isGCActiveMark.hpp" 65 #include "gc/shared/referenceProcessor.hpp" 66 #include "gc/shared/taskqueue.inline.hpp" 67 #include "memory/allocation.hpp" 68 #include "memory/iterator.hpp" 69 #include "oops/oop.inline.hpp" 70 #include "runtime/atomic.inline.hpp" 71 #include "runtime/init.hpp" 72 #include "runtime/orderAccess.inline.hpp" 73 #include "runtime/vmThread.hpp" 74 #include "utilities/globalDefinitions.hpp" 75 #include "utilities/stack.inline.hpp" 76 77 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 78 79 // INVARIANTS/NOTES 80 // 81 // All allocation activity covered by the G1CollectedHeap interface is 82 // serialized by acquiring the HeapLock. This happens in mem_allocate 83 // and allocate_new_tlab, which are the "entry" points to the 84 // allocation code from the rest of the JVM. (Note that this does not 85 // apply to TLAB allocation, which is not part of this interface: it 86 // is done by clients of this interface.) 87 88 // Local to this file. 89 90 class RefineCardTableEntryClosure: public CardTableEntryClosure { 91 bool _concurrent; 92 public: 93 RefineCardTableEntryClosure() : _concurrent(true) { } 94 95 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 96 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false); 97 // This path is executed by the concurrent refine or mutator threads, 98 // concurrently, and so we do not care if card_ptr contains references 99 // that point into the collection set. 100 assert(!oops_into_cset, "should be"); 101 102 if (_concurrent && SuspendibleThreadSet::should_yield()) { 103 // Caller will actually yield. 104 return false; 105 } 106 // Otherwise, we finished successfully; return true. 107 return true; 108 } 109 110 void set_concurrent(bool b) { _concurrent = b; } 111 }; 112 113 114 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 115 private: 116 size_t _num_processed; 117 118 public: 119 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { } 120 121 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 122 *card_ptr = CardTableModRefBS::dirty_card_val(); 123 _num_processed++; 124 return true; 125 } 126 127 size_t num_processed() const { return _num_processed; } 128 }; 129 130 131 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 132 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 133 } 134 135 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 136 // The from card cache is not the memory that is actually committed. So we cannot 137 // take advantage of the zero_filled parameter. 138 reset_from_card_cache(start_idx, num_regions); 139 } 140 141 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 142 { 143 // Claim the right to put the region on the dirty cards region list 144 // by installing a self pointer. 145 HeapRegion* next = hr->get_next_dirty_cards_region(); 146 if (next == NULL) { 147 HeapRegion* res = (HeapRegion*) 148 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 149 NULL); 150 if (res == NULL) { 151 HeapRegion* head; 152 do { 153 // Put the region to the dirty cards region list. 154 head = _dirty_cards_region_list; 155 next = (HeapRegion*) 156 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 157 if (next == head) { 158 assert(hr->get_next_dirty_cards_region() == hr, 159 "hr->get_next_dirty_cards_region() != hr"); 160 if (next == NULL) { 161 // The last region in the list points to itself. 162 hr->set_next_dirty_cards_region(hr); 163 } else { 164 hr->set_next_dirty_cards_region(next); 165 } 166 } 167 } while (next != head); 168 } 169 } 170 } 171 172 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 173 { 174 HeapRegion* head; 175 HeapRegion* hr; 176 do { 177 head = _dirty_cards_region_list; 178 if (head == NULL) { 179 return NULL; 180 } 181 HeapRegion* new_head = head->get_next_dirty_cards_region(); 182 if (head == new_head) { 183 // The last region. 184 new_head = NULL; 185 } 186 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 187 head); 188 } while (hr != head); 189 assert(hr != NULL, "invariant"); 190 hr->set_next_dirty_cards_region(NULL); 191 return hr; 192 } 193 194 // Returns true if the reference points to an object that 195 // can move in an incremental collection. 196 bool G1CollectedHeap::is_scavengable(const void* p) { 197 HeapRegion* hr = heap_region_containing(p); 198 return !hr->is_pinned(); 199 } 200 201 // Private methods. 202 203 HeapRegion* 204 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 205 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 206 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 207 if (!_secondary_free_list.is_empty()) { 208 if (G1ConcRegionFreeingVerbose) { 209 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 210 "secondary_free_list has %u entries", 211 _secondary_free_list.length()); 212 } 213 // It looks as if there are free regions available on the 214 // secondary_free_list. Let's move them to the free_list and try 215 // again to allocate from it. 216 append_secondary_free_list(); 217 218 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 219 "empty we should have moved at least one entry to the free_list"); 220 HeapRegion* res = _hrm.allocate_free_region(is_old); 221 if (G1ConcRegionFreeingVerbose) { 222 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 223 "allocated " HR_FORMAT " from secondary_free_list", 224 HR_FORMAT_PARAMS(res)); 225 } 226 return res; 227 } 228 229 // Wait here until we get notified either when (a) there are no 230 // more free regions coming or (b) some regions have been moved on 231 // the secondary_free_list. 232 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 233 } 234 235 if (G1ConcRegionFreeingVerbose) { 236 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 237 "could not allocate from secondary_free_list"); 238 } 239 return NULL; 240 } 241 242 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 243 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 244 "the only time we use this to allocate a humongous region is " 245 "when we are allocating a single humongous region"); 246 247 HeapRegion* res; 248 if (G1StressConcRegionFreeing) { 249 if (!_secondary_free_list.is_empty()) { 250 if (G1ConcRegionFreeingVerbose) { 251 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 252 "forced to look at the secondary_free_list"); 253 } 254 res = new_region_try_secondary_free_list(is_old); 255 if (res != NULL) { 256 return res; 257 } 258 } 259 } 260 261 res = _hrm.allocate_free_region(is_old); 262 263 if (res == NULL) { 264 if (G1ConcRegionFreeingVerbose) { 265 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 266 "res == NULL, trying the secondary_free_list"); 267 } 268 res = new_region_try_secondary_free_list(is_old); 269 } 270 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 271 // Currently, only attempts to allocate GC alloc regions set 272 // do_expand to true. So, we should only reach here during a 273 // safepoint. If this assumption changes we might have to 274 // reconsider the use of _expand_heap_after_alloc_failure. 275 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 276 277 ergo_verbose1(ErgoHeapSizing, 278 "attempt heap expansion", 279 ergo_format_reason("region allocation request failed") 280 ergo_format_byte("allocation request"), 281 word_size * HeapWordSize); 282 if (expand(word_size * HeapWordSize)) { 283 // Given that expand() succeeded in expanding the heap, and we 284 // always expand the heap by an amount aligned to the heap 285 // region size, the free list should in theory not be empty. 286 // In either case allocate_free_region() will check for NULL. 287 res = _hrm.allocate_free_region(is_old); 288 } else { 289 _expand_heap_after_alloc_failure = false; 290 } 291 } 292 return res; 293 } 294 295 HeapWord* 296 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 297 uint num_regions, 298 size_t word_size, 299 AllocationContext_t context) { 300 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 301 assert(is_humongous(word_size), "word_size should be humongous"); 302 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 303 304 // Index of last region in the series + 1. 305 uint last = first + num_regions; 306 307 // We need to initialize the region(s) we just discovered. This is 308 // a bit tricky given that it can happen concurrently with 309 // refinement threads refining cards on these regions and 310 // potentially wanting to refine the BOT as they are scanning 311 // those cards (this can happen shortly after a cleanup; see CR 312 // 6991377). So we have to set up the region(s) carefully and in 313 // a specific order. 314 315 // The word size sum of all the regions we will allocate. 316 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 317 assert(word_size <= word_size_sum, "sanity"); 318 319 // This will be the "starts humongous" region. 320 HeapRegion* first_hr = region_at(first); 321 // The header of the new object will be placed at the bottom of 322 // the first region. 323 HeapWord* new_obj = first_hr->bottom(); 324 // This will be the new top of the new object. 325 HeapWord* obj_top = new_obj + word_size; 326 327 // First, we need to zero the header of the space that we will be 328 // allocating. When we update top further down, some refinement 329 // threads might try to scan the region. By zeroing the header we 330 // ensure that any thread that will try to scan the region will 331 // come across the zero klass word and bail out. 332 // 333 // NOTE: It would not have been correct to have used 334 // CollectedHeap::fill_with_object() and make the space look like 335 // an int array. The thread that is doing the allocation will 336 // later update the object header to a potentially different array 337 // type and, for a very short period of time, the klass and length 338 // fields will be inconsistent. This could cause a refinement 339 // thread to calculate the object size incorrectly. 340 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 341 342 // We will set up the first region as "starts humongous". This 343 // will also update the BOT covering all the regions to reflect 344 // that there is a single object that starts at the bottom of the 345 // first region. 346 first_hr->set_starts_humongous(obj_top); 347 first_hr->set_allocation_context(context); 348 // Then, if there are any, we will set up the "continues 349 // humongous" regions. 350 HeapRegion* hr = NULL; 351 for (uint i = first + 1; i < last; ++i) { 352 hr = region_at(i); 353 hr->set_continues_humongous(first_hr); 354 hr->set_allocation_context(context); 355 } 356 357 // Up to this point no concurrent thread would have been able to 358 // do any scanning on any region in this series. All the top 359 // fields still point to bottom, so the intersection between 360 // [bottom,top] and [card_start,card_end] will be empty. Before we 361 // update the top fields, we'll do a storestore to make sure that 362 // no thread sees the update to top before the zeroing of the 363 // object header and the BOT initialization. 364 OrderAccess::storestore(); 365 366 // Now that the BOT and the object header have been initialized, 367 // we can update top of the "starts humongous" region. 368 first_hr->set_top(MIN2(first_hr->end(), obj_top)); 369 if (_hr_printer.is_active()) { 370 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, first_hr->top()); 371 } 372 373 // Now, we will update the top fields of the "continues humongous" 374 // regions. 375 hr = NULL; 376 for (uint i = first + 1; i < last; ++i) { 377 hr = region_at(i); 378 if ((i + 1) == last) { 379 // last continues humongous region 380 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 381 "new_top should fall on this region"); 382 hr->set_top(obj_top); 383 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, obj_top); 384 } else { 385 // not last one 386 assert(obj_top > hr->end(), "obj_top should be above this region"); 387 hr->set_top(hr->end()); 388 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 389 } 390 } 391 // If we have continues humongous regions (hr != NULL), its top should 392 // match obj_top. 393 assert(hr == NULL || (hr->top() == obj_top), "sanity"); 394 check_bitmaps("Humongous Region Allocation", first_hr); 395 396 increase_used(word_size * HeapWordSize); 397 398 for (uint i = first; i < last; ++i) { 399 _humongous_set.add(region_at(i)); 400 } 401 402 return new_obj; 403 } 404 405 // If could fit into free regions w/o expansion, try. 406 // Otherwise, if can expand, do so. 407 // Otherwise, if using ex regions might help, try with ex given back. 408 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 409 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 410 411 verify_region_sets_optional(); 412 413 uint first = G1_NO_HRM_INDEX; 414 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords); 415 416 if (obj_regions == 1) { 417 // Only one region to allocate, try to use a fast path by directly allocating 418 // from the free lists. Do not try to expand here, we will potentially do that 419 // later. 420 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 421 if (hr != NULL) { 422 first = hr->hrm_index(); 423 } 424 } else { 425 // We can't allocate humongous regions spanning more than one region while 426 // cleanupComplete() is running, since some of the regions we find to be 427 // empty might not yet be added to the free list. It is not straightforward 428 // to know in which list they are on so that we can remove them. We only 429 // need to do this if we need to allocate more than one region to satisfy the 430 // current humongous allocation request. If we are only allocating one region 431 // we use the one-region region allocation code (see above), that already 432 // potentially waits for regions from the secondary free list. 433 wait_while_free_regions_coming(); 434 append_secondary_free_list_if_not_empty_with_lock(); 435 436 // Policy: Try only empty regions (i.e. already committed first). Maybe we 437 // are lucky enough to find some. 438 first = _hrm.find_contiguous_only_empty(obj_regions); 439 if (first != G1_NO_HRM_INDEX) { 440 _hrm.allocate_free_regions_starting_at(first, obj_regions); 441 } 442 } 443 444 if (first == G1_NO_HRM_INDEX) { 445 // Policy: We could not find enough regions for the humongous object in the 446 // free list. Look through the heap to find a mix of free and uncommitted regions. 447 // If so, try expansion. 448 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 449 if (first != G1_NO_HRM_INDEX) { 450 // We found something. Make sure these regions are committed, i.e. expand 451 // the heap. Alternatively we could do a defragmentation GC. 452 ergo_verbose1(ErgoHeapSizing, 453 "attempt heap expansion", 454 ergo_format_reason("humongous allocation request failed") 455 ergo_format_byte("allocation request"), 456 word_size * HeapWordSize); 457 458 _hrm.expand_at(first, obj_regions); 459 g1_policy()->record_new_heap_size(num_regions()); 460 461 #ifdef ASSERT 462 for (uint i = first; i < first + obj_regions; ++i) { 463 HeapRegion* hr = region_at(i); 464 assert(hr->is_free(), "sanity"); 465 assert(hr->is_empty(), "sanity"); 466 assert(is_on_master_free_list(hr), "sanity"); 467 } 468 #endif 469 _hrm.allocate_free_regions_starting_at(first, obj_regions); 470 } else { 471 // Policy: Potentially trigger a defragmentation GC. 472 } 473 } 474 475 HeapWord* result = NULL; 476 if (first != G1_NO_HRM_INDEX) { 477 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 478 word_size, context); 479 assert(result != NULL, "it should always return a valid result"); 480 481 // A successful humongous object allocation changes the used space 482 // information of the old generation so we need to recalculate the 483 // sizes and update the jstat counters here. 484 g1mm()->update_sizes(); 485 } 486 487 verify_region_sets_optional(); 488 489 return result; 490 } 491 492 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 493 assert_heap_not_locked_and_not_at_safepoint(); 494 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 495 496 uint dummy_gc_count_before; 497 uint dummy_gclocker_retry_count = 0; 498 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 499 } 500 501 HeapWord* 502 G1CollectedHeap::mem_allocate(size_t word_size, 503 bool* gc_overhead_limit_was_exceeded) { 504 assert_heap_not_locked_and_not_at_safepoint(); 505 506 // Loop until the allocation is satisfied, or unsatisfied after GC. 507 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 508 uint gc_count_before; 509 510 HeapWord* result = NULL; 511 if (!is_humongous(word_size)) { 512 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 513 } else { 514 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 515 } 516 if (result != NULL) { 517 return result; 518 } 519 520 // Create the garbage collection operation... 521 VM_G1CollectForAllocation op(gc_count_before, word_size); 522 op.set_allocation_context(AllocationContext::current()); 523 524 // ...and get the VM thread to execute it. 525 VMThread::execute(&op); 526 527 if (op.prologue_succeeded() && op.pause_succeeded()) { 528 // If the operation was successful we'll return the result even 529 // if it is NULL. If the allocation attempt failed immediately 530 // after a Full GC, it's unlikely we'll be able to allocate now. 531 HeapWord* result = op.result(); 532 if (result != NULL && !is_humongous(word_size)) { 533 // Allocations that take place on VM operations do not do any 534 // card dirtying and we have to do it here. We only have to do 535 // this for non-humongous allocations, though. 536 dirty_young_block(result, word_size); 537 } 538 return result; 539 } else { 540 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 541 return NULL; 542 } 543 assert(op.result() == NULL, 544 "the result should be NULL if the VM op did not succeed"); 545 } 546 547 // Give a warning if we seem to be looping forever. 548 if ((QueuedAllocationWarningCount > 0) && 549 (try_count % QueuedAllocationWarningCount == 0)) { 550 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 551 } 552 } 553 554 ShouldNotReachHere(); 555 return NULL; 556 } 557 558 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 559 AllocationContext_t context, 560 uint* gc_count_before_ret, 561 uint* gclocker_retry_count_ret) { 562 // Make sure you read the note in attempt_allocation_humongous(). 563 564 assert_heap_not_locked_and_not_at_safepoint(); 565 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 566 "be called for humongous allocation requests"); 567 568 // We should only get here after the first-level allocation attempt 569 // (attempt_allocation()) failed to allocate. 570 571 // We will loop until a) we manage to successfully perform the 572 // allocation or b) we successfully schedule a collection which 573 // fails to perform the allocation. b) is the only case when we'll 574 // return NULL. 575 HeapWord* result = NULL; 576 for (int try_count = 1; /* we'll return */; try_count += 1) { 577 bool should_try_gc; 578 uint gc_count_before; 579 580 { 581 MutexLockerEx x(Heap_lock); 582 result = _allocator->attempt_allocation_locked(word_size, context); 583 if (result != NULL) { 584 return result; 585 } 586 587 if (GC_locker::is_active_and_needs_gc()) { 588 if (g1_policy()->can_expand_young_list()) { 589 // No need for an ergo verbose message here, 590 // can_expand_young_list() does this when it returns true. 591 result = _allocator->attempt_allocation_force(word_size, context); 592 if (result != NULL) { 593 return result; 594 } 595 } 596 should_try_gc = false; 597 } else { 598 // The GCLocker may not be active but the GCLocker initiated 599 // GC may not yet have been performed (GCLocker::needs_gc() 600 // returns true). In this case we do not try this GC and 601 // wait until the GCLocker initiated GC is performed, and 602 // then retry the allocation. 603 if (GC_locker::needs_gc()) { 604 should_try_gc = false; 605 } else { 606 // Read the GC count while still holding the Heap_lock. 607 gc_count_before = total_collections(); 608 should_try_gc = true; 609 } 610 } 611 } 612 613 if (should_try_gc) { 614 bool succeeded; 615 result = do_collection_pause(word_size, gc_count_before, &succeeded, 616 GCCause::_g1_inc_collection_pause); 617 if (result != NULL) { 618 assert(succeeded, "only way to get back a non-NULL result"); 619 return result; 620 } 621 622 if (succeeded) { 623 // If we get here we successfully scheduled a collection which 624 // failed to allocate. No point in trying to allocate 625 // further. We'll just return NULL. 626 MutexLockerEx x(Heap_lock); 627 *gc_count_before_ret = total_collections(); 628 return NULL; 629 } 630 } else { 631 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 632 MutexLockerEx x(Heap_lock); 633 *gc_count_before_ret = total_collections(); 634 return NULL; 635 } 636 // The GCLocker is either active or the GCLocker initiated 637 // GC has not yet been performed. Stall until it is and 638 // then retry the allocation. 639 GC_locker::stall_until_clear(); 640 (*gclocker_retry_count_ret) += 1; 641 } 642 643 // We can reach here if we were unsuccessful in scheduling a 644 // collection (because another thread beat us to it) or if we were 645 // stalled due to the GC locker. In either can we should retry the 646 // allocation attempt in case another thread successfully 647 // performed a collection and reclaimed enough space. We do the 648 // first attempt (without holding the Heap_lock) here and the 649 // follow-on attempt will be at the start of the next loop 650 // iteration (after taking the Heap_lock). 651 result = _allocator->attempt_allocation(word_size, context); 652 if (result != NULL) { 653 return result; 654 } 655 656 // Give a warning if we seem to be looping forever. 657 if ((QueuedAllocationWarningCount > 0) && 658 (try_count % QueuedAllocationWarningCount == 0)) { 659 warning("G1CollectedHeap::attempt_allocation_slow() " 660 "retries %d times", try_count); 661 } 662 } 663 664 ShouldNotReachHere(); 665 return NULL; 666 } 667 668 void G1CollectedHeap::begin_archive_alloc_range() { 669 assert_at_safepoint(true /* should_be_vm_thread */); 670 if (_archive_allocator == NULL) { 671 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 672 } 673 } 674 675 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 676 // Allocations in archive regions cannot be of a size that would be considered 677 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 678 // may be different at archive-restore time. 679 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 680 } 681 682 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 683 assert_at_safepoint(true /* should_be_vm_thread */); 684 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 685 if (is_archive_alloc_too_large(word_size)) { 686 return NULL; 687 } 688 return _archive_allocator->archive_mem_allocate(word_size); 689 } 690 691 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 692 size_t end_alignment_in_bytes) { 693 assert_at_safepoint(true /* should_be_vm_thread */); 694 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 695 696 // Call complete_archive to do the real work, filling in the MemRegion 697 // array with the archive regions. 698 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 699 delete _archive_allocator; 700 _archive_allocator = NULL; 701 } 702 703 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 704 assert(ranges != NULL, "MemRegion array NULL"); 705 assert(count != 0, "No MemRegions provided"); 706 MemRegion reserved = _hrm.reserved(); 707 for (size_t i = 0; i < count; i++) { 708 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 709 return false; 710 } 711 } 712 return true; 713 } 714 715 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 716 assert(!is_init_completed(), "Expect to be called at JVM init time"); 717 assert(ranges != NULL, "MemRegion array NULL"); 718 assert(count != 0, "No MemRegions provided"); 719 MutexLockerEx x(Heap_lock); 720 721 MemRegion reserved = _hrm.reserved(); 722 HeapWord* prev_last_addr = NULL; 723 HeapRegion* prev_last_region = NULL; 724 725 // Temporarily disable pretouching of heap pages. This interface is used 726 // when mmap'ing archived heap data in, so pre-touching is wasted. 727 FlagSetting fs(AlwaysPreTouch, false); 728 729 // Enable archive object checking in G1MarkSweep. We have to let it know 730 // about each archive range, so that objects in those ranges aren't marked. 731 G1MarkSweep::enable_archive_object_check(); 732 733 // For each specified MemRegion range, allocate the corresponding G1 734 // regions and mark them as archive regions. We expect the ranges in 735 // ascending starting address order, without overlap. 736 for (size_t i = 0; i < count; i++) { 737 MemRegion curr_range = ranges[i]; 738 HeapWord* start_address = curr_range.start(); 739 size_t word_size = curr_range.word_size(); 740 HeapWord* last_address = curr_range.last(); 741 size_t commits = 0; 742 743 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 744 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 745 p2i(start_address), p2i(last_address)); 746 guarantee(start_address > prev_last_addr, 747 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 748 p2i(start_address), p2i(prev_last_addr)); 749 prev_last_addr = last_address; 750 751 // Check for ranges that start in the same G1 region in which the previous 752 // range ended, and adjust the start address so we don't try to allocate 753 // the same region again. If the current range is entirely within that 754 // region, skip it, just adjusting the recorded top. 755 HeapRegion* start_region = _hrm.addr_to_region(start_address); 756 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 757 start_address = start_region->end(); 758 if (start_address > last_address) { 759 increase_used(word_size * HeapWordSize); 760 start_region->set_top(last_address + 1); 761 continue; 762 } 763 start_region->set_top(start_address); 764 curr_range = MemRegion(start_address, last_address + 1); 765 start_region = _hrm.addr_to_region(start_address); 766 } 767 768 // Perform the actual region allocation, exiting if it fails. 769 // Then note how much new space we have allocated. 770 if (!_hrm.allocate_containing_regions(curr_range, &commits)) { 771 return false; 772 } 773 increase_used(word_size * HeapWordSize); 774 if (commits != 0) { 775 ergo_verbose1(ErgoHeapSizing, 776 "attempt heap expansion", 777 ergo_format_reason("allocate archive regions") 778 ergo_format_byte("total size"), 779 HeapRegion::GrainWords * HeapWordSize * commits); 780 } 781 782 // Mark each G1 region touched by the range as archive, add it to the old set, 783 // and set the allocation context and top. 784 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 785 HeapRegion* last_region = _hrm.addr_to_region(last_address); 786 prev_last_region = last_region; 787 788 while (curr_region != NULL) { 789 assert(curr_region->is_empty() && !curr_region->is_pinned(), 790 "Region already in use (index %u)", curr_region->hrm_index()); 791 _hr_printer.alloc(curr_region, G1HRPrinter::Archive); 792 curr_region->set_allocation_context(AllocationContext::system()); 793 curr_region->set_archive(); 794 _old_set.add(curr_region); 795 if (curr_region != last_region) { 796 curr_region->set_top(curr_region->end()); 797 curr_region = _hrm.next_region_in_heap(curr_region); 798 } else { 799 curr_region->set_top(last_address + 1); 800 curr_region = NULL; 801 } 802 } 803 804 // Notify mark-sweep of the archive range. 805 G1MarkSweep::set_range_archive(curr_range, true); 806 } 807 return true; 808 } 809 810 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 811 assert(!is_init_completed(), "Expect to be called at JVM init time"); 812 assert(ranges != NULL, "MemRegion array NULL"); 813 assert(count != 0, "No MemRegions provided"); 814 MemRegion reserved = _hrm.reserved(); 815 HeapWord *prev_last_addr = NULL; 816 HeapRegion* prev_last_region = NULL; 817 818 // For each MemRegion, create filler objects, if needed, in the G1 regions 819 // that contain the address range. The address range actually within the 820 // MemRegion will not be modified. That is assumed to have been initialized 821 // elsewhere, probably via an mmap of archived heap data. 822 MutexLockerEx x(Heap_lock); 823 for (size_t i = 0; i < count; i++) { 824 HeapWord* start_address = ranges[i].start(); 825 HeapWord* last_address = ranges[i].last(); 826 827 assert(reserved.contains(start_address) && reserved.contains(last_address), 828 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 829 p2i(start_address), p2i(last_address)); 830 assert(start_address > prev_last_addr, 831 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 832 p2i(start_address), p2i(prev_last_addr)); 833 834 HeapRegion* start_region = _hrm.addr_to_region(start_address); 835 HeapRegion* last_region = _hrm.addr_to_region(last_address); 836 HeapWord* bottom_address = start_region->bottom(); 837 838 // Check for a range beginning in the same region in which the 839 // previous one ended. 840 if (start_region == prev_last_region) { 841 bottom_address = prev_last_addr + 1; 842 } 843 844 // Verify that the regions were all marked as archive regions by 845 // alloc_archive_regions. 846 HeapRegion* curr_region = start_region; 847 while (curr_region != NULL) { 848 guarantee(curr_region->is_archive(), 849 "Expected archive region at index %u", curr_region->hrm_index()); 850 if (curr_region != last_region) { 851 curr_region = _hrm.next_region_in_heap(curr_region); 852 } else { 853 curr_region = NULL; 854 } 855 } 856 857 prev_last_addr = last_address; 858 prev_last_region = last_region; 859 860 // Fill the memory below the allocated range with dummy object(s), 861 // if the region bottom does not match the range start, or if the previous 862 // range ended within the same G1 region, and there is a gap. 863 if (start_address != bottom_address) { 864 size_t fill_size = pointer_delta(start_address, bottom_address); 865 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 866 increase_used(fill_size * HeapWordSize); 867 } 868 } 869 } 870 871 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 872 uint* gc_count_before_ret, 873 uint* gclocker_retry_count_ret) { 874 assert_heap_not_locked_and_not_at_safepoint(); 875 assert(!is_humongous(word_size), "attempt_allocation() should not " 876 "be called for humongous allocation requests"); 877 878 AllocationContext_t context = AllocationContext::current(); 879 HeapWord* result = _allocator->attempt_allocation(word_size, context); 880 881 if (result == NULL) { 882 result = attempt_allocation_slow(word_size, 883 context, 884 gc_count_before_ret, 885 gclocker_retry_count_ret); 886 } 887 assert_heap_not_locked(); 888 if (result != NULL) { 889 dirty_young_block(result, word_size); 890 } 891 return result; 892 } 893 894 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 895 assert(!is_init_completed(), "Expect to be called at JVM init time"); 896 assert(ranges != NULL, "MemRegion array NULL"); 897 assert(count != 0, "No MemRegions provided"); 898 MemRegion reserved = _hrm.reserved(); 899 HeapWord* prev_last_addr = NULL; 900 HeapRegion* prev_last_region = NULL; 901 size_t size_used = 0; 902 size_t uncommitted_regions = 0; 903 904 // For each Memregion, free the G1 regions that constitute it, and 905 // notify mark-sweep that the range is no longer to be considered 'archive.' 906 MutexLockerEx x(Heap_lock); 907 for (size_t i = 0; i < count; i++) { 908 HeapWord* start_address = ranges[i].start(); 909 HeapWord* last_address = ranges[i].last(); 910 911 assert(reserved.contains(start_address) && reserved.contains(last_address), 912 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 913 p2i(start_address), p2i(last_address)); 914 assert(start_address > prev_last_addr, 915 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 916 p2i(start_address), p2i(prev_last_addr)); 917 size_used += ranges[i].byte_size(); 918 prev_last_addr = last_address; 919 920 HeapRegion* start_region = _hrm.addr_to_region(start_address); 921 HeapRegion* last_region = _hrm.addr_to_region(last_address); 922 923 // Check for ranges that start in the same G1 region in which the previous 924 // range ended, and adjust the start address so we don't try to free 925 // the same region again. If the current range is entirely within that 926 // region, skip it. 927 if (start_region == prev_last_region) { 928 start_address = start_region->end(); 929 if (start_address > last_address) { 930 continue; 931 } 932 start_region = _hrm.addr_to_region(start_address); 933 } 934 prev_last_region = last_region; 935 936 // After verifying that each region was marked as an archive region by 937 // alloc_archive_regions, set it free and empty and uncommit it. 938 HeapRegion* curr_region = start_region; 939 while (curr_region != NULL) { 940 guarantee(curr_region->is_archive(), 941 "Expected archive region at index %u", curr_region->hrm_index()); 942 uint curr_index = curr_region->hrm_index(); 943 _old_set.remove(curr_region); 944 curr_region->set_free(); 945 curr_region->set_top(curr_region->bottom()); 946 if (curr_region != last_region) { 947 curr_region = _hrm.next_region_in_heap(curr_region); 948 } else { 949 curr_region = NULL; 950 } 951 _hrm.shrink_at(curr_index, 1); 952 uncommitted_regions++; 953 } 954 955 // Notify mark-sweep that this is no longer an archive range. 956 G1MarkSweep::set_range_archive(ranges[i], false); 957 } 958 959 if (uncommitted_regions != 0) { 960 ergo_verbose1(ErgoHeapSizing, 961 "attempt heap shrinking", 962 ergo_format_reason("uncommitted archive regions") 963 ergo_format_byte("total size"), 964 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 965 } 966 decrease_used(size_used); 967 } 968 969 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 970 uint* gc_count_before_ret, 971 uint* gclocker_retry_count_ret) { 972 // The structure of this method has a lot of similarities to 973 // attempt_allocation_slow(). The reason these two were not merged 974 // into a single one is that such a method would require several "if 975 // allocation is not humongous do this, otherwise do that" 976 // conditional paths which would obscure its flow. In fact, an early 977 // version of this code did use a unified method which was harder to 978 // follow and, as a result, it had subtle bugs that were hard to 979 // track down. So keeping these two methods separate allows each to 980 // be more readable. It will be good to keep these two in sync as 981 // much as possible. 982 983 assert_heap_not_locked_and_not_at_safepoint(); 984 assert(is_humongous(word_size), "attempt_allocation_humongous() " 985 "should only be called for humongous allocations"); 986 987 // Humongous objects can exhaust the heap quickly, so we should check if we 988 // need to start a marking cycle at each humongous object allocation. We do 989 // the check before we do the actual allocation. The reason for doing it 990 // before the allocation is that we avoid having to keep track of the newly 991 // allocated memory while we do a GC. 992 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 993 word_size)) { 994 collect(GCCause::_g1_humongous_allocation); 995 } 996 997 // We will loop until a) we manage to successfully perform the 998 // allocation or b) we successfully schedule a collection which 999 // fails to perform the allocation. b) is the only case when we'll 1000 // return NULL. 1001 HeapWord* result = NULL; 1002 for (int try_count = 1; /* we'll return */; try_count += 1) { 1003 bool should_try_gc; 1004 uint gc_count_before; 1005 1006 { 1007 MutexLockerEx x(Heap_lock); 1008 1009 // Given that humongous objects are not allocated in young 1010 // regions, we'll first try to do the allocation without doing a 1011 // collection hoping that there's enough space in the heap. 1012 result = humongous_obj_allocate(word_size, AllocationContext::current()); 1013 if (result != NULL) { 1014 return result; 1015 } 1016 1017 if (GC_locker::is_active_and_needs_gc()) { 1018 should_try_gc = false; 1019 } else { 1020 // The GCLocker may not be active but the GCLocker initiated 1021 // GC may not yet have been performed (GCLocker::needs_gc() 1022 // returns true). In this case we do not try this GC and 1023 // wait until the GCLocker initiated GC is performed, and 1024 // then retry the allocation. 1025 if (GC_locker::needs_gc()) { 1026 should_try_gc = false; 1027 } else { 1028 // Read the GC count while still holding the Heap_lock. 1029 gc_count_before = total_collections(); 1030 should_try_gc = true; 1031 } 1032 } 1033 } 1034 1035 if (should_try_gc) { 1036 // If we failed to allocate the humongous object, we should try to 1037 // do a collection pause (if we're allowed) in case it reclaims 1038 // enough space for the allocation to succeed after the pause. 1039 1040 bool succeeded; 1041 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1042 GCCause::_g1_humongous_allocation); 1043 if (result != NULL) { 1044 assert(succeeded, "only way to get back a non-NULL result"); 1045 return result; 1046 } 1047 1048 if (succeeded) { 1049 // If we get here we successfully scheduled a collection which 1050 // failed to allocate. No point in trying to allocate 1051 // further. We'll just return NULL. 1052 MutexLockerEx x(Heap_lock); 1053 *gc_count_before_ret = total_collections(); 1054 return NULL; 1055 } 1056 } else { 1057 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1058 MutexLockerEx x(Heap_lock); 1059 *gc_count_before_ret = total_collections(); 1060 return NULL; 1061 } 1062 // The GCLocker is either active or the GCLocker initiated 1063 // GC has not yet been performed. Stall until it is and 1064 // then retry the allocation. 1065 GC_locker::stall_until_clear(); 1066 (*gclocker_retry_count_ret) += 1; 1067 } 1068 1069 // We can reach here if we were unsuccessful in scheduling a 1070 // collection (because another thread beat us to it) or if we were 1071 // stalled due to the GC locker. In either can we should retry the 1072 // allocation attempt in case another thread successfully 1073 // performed a collection and reclaimed enough space. Give a 1074 // warning if we seem to be looping forever. 1075 1076 if ((QueuedAllocationWarningCount > 0) && 1077 (try_count % QueuedAllocationWarningCount == 0)) { 1078 warning("G1CollectedHeap::attempt_allocation_humongous() " 1079 "retries %d times", try_count); 1080 } 1081 } 1082 1083 ShouldNotReachHere(); 1084 return NULL; 1085 } 1086 1087 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1088 AllocationContext_t context, 1089 bool expect_null_mutator_alloc_region) { 1090 assert_at_safepoint(true /* should_be_vm_thread */); 1091 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1092 "the current alloc region was unexpectedly found to be non-NULL"); 1093 1094 if (!is_humongous(word_size)) { 1095 return _allocator->attempt_allocation_locked(word_size, context); 1096 } else { 1097 HeapWord* result = humongous_obj_allocate(word_size, context); 1098 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1099 collector_state()->set_initiate_conc_mark_if_possible(true); 1100 } 1101 return result; 1102 } 1103 1104 ShouldNotReachHere(); 1105 } 1106 1107 class PostMCRemSetClearClosure: public HeapRegionClosure { 1108 G1CollectedHeap* _g1h; 1109 ModRefBarrierSet* _mr_bs; 1110 public: 1111 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1112 _g1h(g1h), _mr_bs(mr_bs) {} 1113 1114 bool doHeapRegion(HeapRegion* r) { 1115 HeapRegionRemSet* hrrs = r->rem_set(); 1116 1117 _g1h->reset_gc_time_stamps(r); 1118 1119 if (r->is_continues_humongous()) { 1120 // We'll assert that the strong code root list and RSet is empty 1121 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1122 assert(hrrs->occupied() == 0, "RSet should be empty"); 1123 } else { 1124 hrrs->clear(); 1125 } 1126 // You might think here that we could clear just the cards 1127 // corresponding to the used region. But no: if we leave a dirty card 1128 // in a region we might allocate into, then it would prevent that card 1129 // from being enqueued, and cause it to be missed. 1130 // Re: the performance cost: we shouldn't be doing full GC anyway! 1131 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1132 1133 return false; 1134 } 1135 }; 1136 1137 void G1CollectedHeap::clear_rsets_post_compaction() { 1138 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1139 heap_region_iterate(&rs_clear); 1140 } 1141 1142 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1143 G1CollectedHeap* _g1h; 1144 UpdateRSOopClosure _cl; 1145 public: 1146 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1147 _cl(g1->g1_rem_set(), worker_i), 1148 _g1h(g1) 1149 { } 1150 1151 bool doHeapRegion(HeapRegion* r) { 1152 if (!r->is_continues_humongous()) { 1153 _cl.set_from(r); 1154 r->oop_iterate(&_cl); 1155 } 1156 return false; 1157 } 1158 }; 1159 1160 class ParRebuildRSTask: public AbstractGangTask { 1161 G1CollectedHeap* _g1; 1162 HeapRegionClaimer _hrclaimer; 1163 1164 public: 1165 ParRebuildRSTask(G1CollectedHeap* g1) : 1166 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1167 1168 void work(uint worker_id) { 1169 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1170 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1171 } 1172 }; 1173 1174 class PostCompactionPrinterClosure: public HeapRegionClosure { 1175 private: 1176 G1HRPrinter* _hr_printer; 1177 public: 1178 bool doHeapRegion(HeapRegion* hr) { 1179 assert(!hr->is_young(), "not expecting to find young regions"); 1180 if (hr->is_free()) { 1181 // We only generate output for non-empty regions. 1182 } else if (hr->is_starts_humongous()) { 1183 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1184 } else if (hr->is_continues_humongous()) { 1185 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1186 } else if (hr->is_archive()) { 1187 _hr_printer->post_compaction(hr, G1HRPrinter::Archive); 1188 } else if (hr->is_old()) { 1189 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1190 } else { 1191 ShouldNotReachHere(); 1192 } 1193 return false; 1194 } 1195 1196 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1197 : _hr_printer(hr_printer) { } 1198 }; 1199 1200 void G1CollectedHeap::print_hrm_post_compaction() { 1201 PostCompactionPrinterClosure cl(hr_printer()); 1202 heap_region_iterate(&cl); 1203 } 1204 1205 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1206 bool clear_all_soft_refs) { 1207 assert_at_safepoint(true /* should_be_vm_thread */); 1208 1209 if (GC_locker::check_active_before_gc()) { 1210 return false; 1211 } 1212 1213 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1214 gc_timer->register_gc_start(); 1215 1216 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1217 GCIdMark gc_id_mark; 1218 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1219 1220 SvcGCMarker sgcm(SvcGCMarker::FULL); 1221 ResourceMark rm; 1222 1223 G1Log::update_level(); 1224 print_heap_before_gc(); 1225 trace_heap_before_gc(gc_tracer); 1226 1227 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1228 1229 verify_region_sets_optional(); 1230 1231 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1232 collector_policy()->should_clear_all_soft_refs(); 1233 1234 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1235 1236 { 1237 IsGCActiveMark x; 1238 1239 // Timing 1240 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1241 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 1242 1243 { 1244 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL); 1245 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1246 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1247 1248 g1_policy()->record_full_collection_start(); 1249 1250 // Note: When we have a more flexible GC logging framework that 1251 // allows us to add optional attributes to a GC log record we 1252 // could consider timing and reporting how long we wait in the 1253 // following two methods. 1254 wait_while_free_regions_coming(); 1255 // If we start the compaction before the CM threads finish 1256 // scanning the root regions we might trip them over as we'll 1257 // be moving objects / updating references. So let's wait until 1258 // they are done. By telling them to abort, they should complete 1259 // early. 1260 _cm->root_regions()->abort(); 1261 _cm->root_regions()->wait_until_scan_finished(); 1262 append_secondary_free_list_if_not_empty_with_lock(); 1263 1264 gc_prologue(true); 1265 increment_total_collections(true /* full gc */); 1266 increment_old_marking_cycles_started(); 1267 1268 assert(used() == recalculate_used(), "Should be equal"); 1269 1270 verify_before_gc(); 1271 1272 check_bitmaps("Full GC Start"); 1273 pre_full_gc_dump(gc_timer); 1274 1275 #if defined(COMPILER2) || INCLUDE_JVMCI 1276 DerivedPointerTable::clear(); 1277 #endif 1278 1279 // Disable discovery and empty the discovered lists 1280 // for the CM ref processor. 1281 ref_processor_cm()->disable_discovery(); 1282 ref_processor_cm()->abandon_partial_discovery(); 1283 ref_processor_cm()->verify_no_references_recorded(); 1284 1285 // Abandon current iterations of concurrent marking and concurrent 1286 // refinement, if any are in progress. We have to do this before 1287 // wait_until_scan_finished() below. 1288 concurrent_mark()->abort(); 1289 1290 // Make sure we'll choose a new allocation region afterwards. 1291 _allocator->release_mutator_alloc_region(); 1292 _allocator->abandon_gc_alloc_regions(); 1293 g1_rem_set()->cleanupHRRS(); 1294 1295 // We should call this after we retire any currently active alloc 1296 // regions so that all the ALLOC / RETIRE events are generated 1297 // before the start GC event. 1298 _hr_printer.start_gc(true /* full */, (size_t) total_collections()); 1299 1300 // We may have added regions to the current incremental collection 1301 // set between the last GC or pause and now. We need to clear the 1302 // incremental collection set and then start rebuilding it afresh 1303 // after this full GC. 1304 abandon_collection_set(g1_policy()->inc_cset_head()); 1305 g1_policy()->clear_incremental_cset(); 1306 g1_policy()->stop_incremental_cset_building(); 1307 1308 tear_down_region_sets(false /* free_list_only */); 1309 collector_state()->set_gcs_are_young(true); 1310 1311 // See the comments in g1CollectedHeap.hpp and 1312 // G1CollectedHeap::ref_processing_init() about 1313 // how reference processing currently works in G1. 1314 1315 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1316 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1317 1318 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1319 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1320 1321 ref_processor_stw()->enable_discovery(); 1322 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1323 1324 // Do collection work 1325 { 1326 HandleMark hm; // Discard invalid handles created during gc 1327 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1328 } 1329 1330 assert(num_free_regions() == 0, "we should not have added any free regions"); 1331 rebuild_region_sets(false /* free_list_only */); 1332 1333 // Enqueue any discovered reference objects that have 1334 // not been removed from the discovered lists. 1335 ref_processor_stw()->enqueue_discovered_references(); 1336 1337 #if defined(COMPILER2) || INCLUDE_JVMCI 1338 DerivedPointerTable::update_pointers(); 1339 #endif 1340 1341 MemoryService::track_memory_usage(); 1342 1343 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1344 ref_processor_stw()->verify_no_references_recorded(); 1345 1346 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1347 ClassLoaderDataGraph::purge(); 1348 MetaspaceAux::verify_metrics(); 1349 1350 // Note: since we've just done a full GC, concurrent 1351 // marking is no longer active. Therefore we need not 1352 // re-enable reference discovery for the CM ref processor. 1353 // That will be done at the start of the next marking cycle. 1354 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1355 ref_processor_cm()->verify_no_references_recorded(); 1356 1357 reset_gc_time_stamp(); 1358 // Since everything potentially moved, we will clear all remembered 1359 // sets, and clear all cards. Later we will rebuild remembered 1360 // sets. We will also reset the GC time stamps of the regions. 1361 clear_rsets_post_compaction(); 1362 check_gc_time_stamps(); 1363 1364 resize_if_necessary_after_full_collection(); 1365 1366 if (_hr_printer.is_active()) { 1367 // We should do this after we potentially resize the heap so 1368 // that all the COMMIT / UNCOMMIT events are generated before 1369 // the end GC event. 1370 1371 print_hrm_post_compaction(); 1372 _hr_printer.end_gc(true /* full */, (size_t) total_collections()); 1373 } 1374 1375 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1376 if (hot_card_cache->use_cache()) { 1377 hot_card_cache->reset_card_counts(); 1378 hot_card_cache->reset_hot_cache(); 1379 } 1380 1381 // Rebuild remembered sets of all regions. 1382 uint n_workers = 1383 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1384 workers()->active_workers(), 1385 Threads::number_of_non_daemon_threads()); 1386 workers()->set_active_workers(n_workers); 1387 1388 ParRebuildRSTask rebuild_rs_task(this); 1389 workers()->run_task(&rebuild_rs_task); 1390 1391 // Rebuild the strong code root lists for each region 1392 rebuild_strong_code_roots(); 1393 1394 if (true) { // FIXME 1395 MetaspaceGC::compute_new_size(); 1396 } 1397 1398 #ifdef TRACESPINNING 1399 ParallelTaskTerminator::print_termination_counts(); 1400 #endif 1401 1402 // Discard all rset updates 1403 JavaThread::dirty_card_queue_set().abandon_logs(); 1404 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1405 1406 _young_list->reset_sampled_info(); 1407 // At this point there should be no regions in the 1408 // entire heap tagged as young. 1409 assert(check_young_list_empty(true /* check_heap */), 1410 "young list should be empty at this point"); 1411 1412 // Update the number of full collections that have been completed. 1413 increment_old_marking_cycles_completed(false /* concurrent */); 1414 1415 _hrm.verify_optional(); 1416 verify_region_sets_optional(); 1417 1418 verify_after_gc(); 1419 1420 // Clear the previous marking bitmap, if needed for bitmap verification. 1421 // Note we cannot do this when we clear the next marking bitmap in 1422 // ConcurrentMark::abort() above since VerifyDuringGC verifies the 1423 // objects marked during a full GC against the previous bitmap. 1424 // But we need to clear it before calling check_bitmaps below since 1425 // the full GC has compacted objects and updated TAMS but not updated 1426 // the prev bitmap. 1427 if (G1VerifyBitmaps) { 1428 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll(); 1429 } 1430 check_bitmaps("Full GC End"); 1431 1432 // Start a new incremental collection set for the next pause 1433 assert(g1_policy()->collection_set() == NULL, "must be"); 1434 g1_policy()->start_incremental_cset_building(); 1435 1436 clear_cset_fast_test(); 1437 1438 _allocator->init_mutator_alloc_region(); 1439 1440 g1_policy()->record_full_collection_end(); 1441 1442 if (G1Log::fine()) { 1443 g1_policy()->print_heap_transition(); 1444 } 1445 1446 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1447 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1448 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1449 // before any GC notifications are raised. 1450 g1mm()->update_sizes(); 1451 1452 gc_epilogue(true); 1453 } 1454 1455 if (G1Log::finer()) { 1456 g1_policy()->print_detailed_heap_transition(true /* full */); 1457 } 1458 1459 print_heap_after_gc(); 1460 trace_heap_after_gc(gc_tracer); 1461 1462 post_full_gc_dump(gc_timer); 1463 1464 gc_timer->register_gc_end(); 1465 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1466 } 1467 1468 return true; 1469 } 1470 1471 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1472 // Currently, there is no facility in the do_full_collection(bool) API to notify 1473 // the caller that the collection did not succeed (e.g., because it was locked 1474 // out by the GC locker). So, right now, we'll ignore the return value. 1475 bool dummy = do_full_collection(true, /* explicit_gc */ 1476 clear_all_soft_refs); 1477 } 1478 1479 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1480 // Include bytes that will be pre-allocated to support collections, as "used". 1481 const size_t used_after_gc = used(); 1482 const size_t capacity_after_gc = capacity(); 1483 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1484 1485 // This is enforced in arguments.cpp. 1486 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1487 "otherwise the code below doesn't make sense"); 1488 1489 // We don't have floating point command-line arguments 1490 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1491 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1492 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1493 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1494 1495 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1496 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1497 1498 // We have to be careful here as these two calculations can overflow 1499 // 32-bit size_t's. 1500 double used_after_gc_d = (double) used_after_gc; 1501 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1502 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1503 1504 // Let's make sure that they are both under the max heap size, which 1505 // by default will make them fit into a size_t. 1506 double desired_capacity_upper_bound = (double) max_heap_size; 1507 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1508 desired_capacity_upper_bound); 1509 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1510 desired_capacity_upper_bound); 1511 1512 // We can now safely turn them into size_t's. 1513 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1514 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1515 1516 // This assert only makes sense here, before we adjust them 1517 // with respect to the min and max heap size. 1518 assert(minimum_desired_capacity <= maximum_desired_capacity, 1519 "minimum_desired_capacity = " SIZE_FORMAT ", " 1520 "maximum_desired_capacity = " SIZE_FORMAT, 1521 minimum_desired_capacity, maximum_desired_capacity); 1522 1523 // Should not be greater than the heap max size. No need to adjust 1524 // it with respect to the heap min size as it's a lower bound (i.e., 1525 // we'll try to make the capacity larger than it, not smaller). 1526 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1527 // Should not be less than the heap min size. No need to adjust it 1528 // with respect to the heap max size as it's an upper bound (i.e., 1529 // we'll try to make the capacity smaller than it, not greater). 1530 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1531 1532 if (capacity_after_gc < minimum_desired_capacity) { 1533 // Don't expand unless it's significant 1534 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1535 ergo_verbose4(ErgoHeapSizing, 1536 "attempt heap expansion", 1537 ergo_format_reason("capacity lower than " 1538 "min desired capacity after Full GC") 1539 ergo_format_byte("capacity") 1540 ergo_format_byte("occupancy") 1541 ergo_format_byte_perc("min desired capacity"), 1542 capacity_after_gc, used_after_gc, 1543 minimum_desired_capacity, (double) MinHeapFreeRatio); 1544 expand(expand_bytes); 1545 1546 // No expansion, now see if we want to shrink 1547 } else if (capacity_after_gc > maximum_desired_capacity) { 1548 // Capacity too large, compute shrinking size 1549 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1550 ergo_verbose4(ErgoHeapSizing, 1551 "attempt heap shrinking", 1552 ergo_format_reason("capacity higher than " 1553 "max desired capacity after Full GC") 1554 ergo_format_byte("capacity") 1555 ergo_format_byte("occupancy") 1556 ergo_format_byte_perc("max desired capacity"), 1557 capacity_after_gc, used_after_gc, 1558 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1559 shrink(shrink_bytes); 1560 } 1561 } 1562 1563 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1564 AllocationContext_t context, 1565 bool do_gc, 1566 bool clear_all_soft_refs, 1567 bool expect_null_mutator_alloc_region, 1568 bool* gc_succeeded) { 1569 *gc_succeeded = true; 1570 // Let's attempt the allocation first. 1571 HeapWord* result = 1572 attempt_allocation_at_safepoint(word_size, 1573 context, 1574 expect_null_mutator_alloc_region); 1575 if (result != NULL) { 1576 assert(*gc_succeeded, "sanity"); 1577 return result; 1578 } 1579 1580 // In a G1 heap, we're supposed to keep allocation from failing by 1581 // incremental pauses. Therefore, at least for now, we'll favor 1582 // expansion over collection. (This might change in the future if we can 1583 // do something smarter than full collection to satisfy a failed alloc.) 1584 result = expand_and_allocate(word_size, context); 1585 if (result != NULL) { 1586 assert(*gc_succeeded, "sanity"); 1587 return result; 1588 } 1589 1590 if (do_gc) { 1591 // Expansion didn't work, we'll try to do a Full GC. 1592 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1593 clear_all_soft_refs); 1594 } 1595 1596 return NULL; 1597 } 1598 1599 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1600 AllocationContext_t context, 1601 bool* succeeded) { 1602 assert_at_safepoint(true /* should_be_vm_thread */); 1603 1604 // Attempts to allocate followed by Full GC. 1605 HeapWord* result = 1606 satisfy_failed_allocation_helper(word_size, 1607 context, 1608 true, /* do_gc */ 1609 false, /* clear_all_soft_refs */ 1610 false, /* expect_null_mutator_alloc_region */ 1611 succeeded); 1612 1613 if (result != NULL || !*succeeded) { 1614 return result; 1615 } 1616 1617 // Attempts to allocate followed by Full GC that will collect all soft references. 1618 result = satisfy_failed_allocation_helper(word_size, 1619 context, 1620 true, /* do_gc */ 1621 true, /* clear_all_soft_refs */ 1622 true, /* expect_null_mutator_alloc_region */ 1623 succeeded); 1624 1625 if (result != NULL || !*succeeded) { 1626 return result; 1627 } 1628 1629 // Attempts to allocate, no GC 1630 result = satisfy_failed_allocation_helper(word_size, 1631 context, 1632 false, /* do_gc */ 1633 false, /* clear_all_soft_refs */ 1634 true, /* expect_null_mutator_alloc_region */ 1635 succeeded); 1636 1637 if (result != NULL) { 1638 assert(*succeeded, "sanity"); 1639 return result; 1640 } 1641 1642 assert(!collector_policy()->should_clear_all_soft_refs(), 1643 "Flag should have been handled and cleared prior to this point"); 1644 1645 // What else? We might try synchronous finalization later. If the total 1646 // space available is large enough for the allocation, then a more 1647 // complete compaction phase than we've tried so far might be 1648 // appropriate. 1649 assert(*succeeded, "sanity"); 1650 return NULL; 1651 } 1652 1653 // Attempting to expand the heap sufficiently 1654 // to support an allocation of the given "word_size". If 1655 // successful, perform the allocation and return the address of the 1656 // allocated block, or else "NULL". 1657 1658 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1659 assert_at_safepoint(true /* should_be_vm_thread */); 1660 1661 verify_region_sets_optional(); 1662 1663 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1664 ergo_verbose1(ErgoHeapSizing, 1665 "attempt heap expansion", 1666 ergo_format_reason("allocation request failed") 1667 ergo_format_byte("allocation request"), 1668 word_size * HeapWordSize); 1669 if (expand(expand_bytes)) { 1670 _hrm.verify_optional(); 1671 verify_region_sets_optional(); 1672 return attempt_allocation_at_safepoint(word_size, 1673 context, 1674 false /* expect_null_mutator_alloc_region */); 1675 } 1676 return NULL; 1677 } 1678 1679 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) { 1680 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1681 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1682 HeapRegion::GrainBytes); 1683 ergo_verbose2(ErgoHeapSizing, 1684 "expand the heap", 1685 ergo_format_byte("requested expansion amount") 1686 ergo_format_byte("attempted expansion amount"), 1687 expand_bytes, aligned_expand_bytes); 1688 1689 if (is_maximal_no_gc()) { 1690 ergo_verbose0(ErgoHeapSizing, 1691 "did not expand the heap", 1692 ergo_format_reason("heap already fully expanded")); 1693 return false; 1694 } 1695 1696 double expand_heap_start_time_sec = os::elapsedTime(); 1697 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1698 assert(regions_to_expand > 0, "Must expand by at least one region"); 1699 1700 uint expanded_by = _hrm.expand_by(regions_to_expand); 1701 if (expand_time_ms != NULL) { 1702 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1703 } 1704 1705 if (expanded_by > 0) { 1706 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1707 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1708 g1_policy()->record_new_heap_size(num_regions()); 1709 } else { 1710 ergo_verbose0(ErgoHeapSizing, 1711 "did not expand the heap", 1712 ergo_format_reason("heap expansion operation failed")); 1713 // The expansion of the virtual storage space was unsuccessful. 1714 // Let's see if it was because we ran out of swap. 1715 if (G1ExitOnExpansionFailure && 1716 _hrm.available() >= regions_to_expand) { 1717 // We had head room... 1718 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1719 } 1720 } 1721 return regions_to_expand > 0; 1722 } 1723 1724 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1725 size_t aligned_shrink_bytes = 1726 ReservedSpace::page_align_size_down(shrink_bytes); 1727 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1728 HeapRegion::GrainBytes); 1729 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1730 1731 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1732 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1733 1734 ergo_verbose3(ErgoHeapSizing, 1735 "shrink the heap", 1736 ergo_format_byte("requested shrinking amount") 1737 ergo_format_byte("aligned shrinking amount") 1738 ergo_format_byte("attempted shrinking amount"), 1739 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1740 if (num_regions_removed > 0) { 1741 g1_policy()->record_new_heap_size(num_regions()); 1742 } else { 1743 ergo_verbose0(ErgoHeapSizing, 1744 "did not shrink the heap", 1745 ergo_format_reason("heap shrinking operation failed")); 1746 } 1747 } 1748 1749 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1750 verify_region_sets_optional(); 1751 1752 // We should only reach here at the end of a Full GC which means we 1753 // should not not be holding to any GC alloc regions. The method 1754 // below will make sure of that and do any remaining clean up. 1755 _allocator->abandon_gc_alloc_regions(); 1756 1757 // Instead of tearing down / rebuilding the free lists here, we 1758 // could instead use the remove_all_pending() method on free_list to 1759 // remove only the ones that we need to remove. 1760 tear_down_region_sets(true /* free_list_only */); 1761 shrink_helper(shrink_bytes); 1762 rebuild_region_sets(true /* free_list_only */); 1763 1764 _hrm.verify_optional(); 1765 verify_region_sets_optional(); 1766 } 1767 1768 // Public methods. 1769 1770 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1771 CollectedHeap(), 1772 _g1_policy(policy_), 1773 _dirty_card_queue_set(false), 1774 _is_alive_closure_cm(this), 1775 _is_alive_closure_stw(this), 1776 _ref_processor_cm(NULL), 1777 _ref_processor_stw(NULL), 1778 _bot_shared(NULL), 1779 _cg1r(NULL), 1780 _g1mm(NULL), 1781 _refine_cte_cl(NULL), 1782 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1783 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1784 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1785 _humongous_reclaim_candidates(), 1786 _has_humongous_reclaim_candidates(false), 1787 _archive_allocator(NULL), 1788 _free_regions_coming(false), 1789 _young_list(new YoungList(this)), 1790 _gc_time_stamp(0), 1791 _summary_bytes_used(0), 1792 _survivor_evac_stats(YoungPLABSize, PLABWeight), 1793 _old_evac_stats(OldPLABSize, PLABWeight), 1794 _expand_heap_after_alloc_failure(true), 1795 _old_marking_cycles_started(0), 1796 _old_marking_cycles_completed(0), 1797 _heap_summary_sent(false), 1798 _in_cset_fast_test(), 1799 _dirty_cards_region_list(NULL), 1800 _worker_cset_start_region(NULL), 1801 _worker_cset_start_region_time_stamp(NULL), 1802 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1803 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1804 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1805 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1806 1807 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1808 /* are_GC_task_threads */true, 1809 /* are_ConcurrentGC_threads */false); 1810 _workers->initialize_workers(); 1811 1812 _allocator = G1Allocator::create_allocator(this); 1813 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1814 1815 // Override the default _filler_array_max_size so that no humongous filler 1816 // objects are created. 1817 _filler_array_max_size = _humongous_object_threshold_in_words; 1818 1819 uint n_queues = ParallelGCThreads; 1820 _task_queues = new RefToScanQueueSet(n_queues); 1821 1822 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1823 assert(n_rem_sets > 0, "Invariant."); 1824 1825 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1826 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC); 1827 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1828 1829 for (uint i = 0; i < n_queues; i++) { 1830 RefToScanQueue* q = new RefToScanQueue(); 1831 q->initialize(); 1832 _task_queues->register_queue(i, q); 1833 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1834 } 1835 clear_cset_start_regions(); 1836 1837 // Initialize the G1EvacuationFailureALot counters and flags. 1838 NOT_PRODUCT(reset_evacuation_should_fail();) 1839 1840 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1841 } 1842 1843 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1844 size_t size, 1845 size_t translation_factor) { 1846 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1847 // Allocate a new reserved space, preferring to use large pages. 1848 ReservedSpace rs(size, preferred_page_size); 1849 G1RegionToSpaceMapper* result = 1850 G1RegionToSpaceMapper::create_mapper(rs, 1851 size, 1852 rs.alignment(), 1853 HeapRegion::GrainBytes, 1854 translation_factor, 1855 mtGC); 1856 if (TracePageSizes) { 1857 gclog_or_tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT, 1858 description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size); 1859 } 1860 return result; 1861 } 1862 1863 jint G1CollectedHeap::initialize() { 1864 CollectedHeap::pre_initialize(); 1865 os::enable_vtime(); 1866 1867 G1Log::init(); 1868 1869 // Necessary to satisfy locking discipline assertions. 1870 1871 MutexLocker x(Heap_lock); 1872 1873 // We have to initialize the printer before committing the heap, as 1874 // it will be used then. 1875 _hr_printer.set_active(G1PrintHeapRegions); 1876 1877 // While there are no constraints in the GC code that HeapWordSize 1878 // be any particular value, there are multiple other areas in the 1879 // system which believe this to be true (e.g. oop->object_size in some 1880 // cases incorrectly returns the size in wordSize units rather than 1881 // HeapWordSize). 1882 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1883 1884 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1885 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1886 size_t heap_alignment = collector_policy()->heap_alignment(); 1887 1888 // Ensure that the sizes are properly aligned. 1889 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1890 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1891 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1892 1893 _refine_cte_cl = new RefineCardTableEntryClosure(); 1894 1895 jint ecode = JNI_OK; 1896 _cg1r = ConcurrentG1Refine::create(this, _refine_cte_cl, &ecode); 1897 if (_cg1r == NULL) { 1898 return ecode; 1899 } 1900 1901 // Reserve the maximum. 1902 1903 // When compressed oops are enabled, the preferred heap base 1904 // is calculated by subtracting the requested size from the 1905 // 32Gb boundary and using the result as the base address for 1906 // heap reservation. If the requested size is not aligned to 1907 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1908 // into the ReservedHeapSpace constructor) then the actual 1909 // base of the reserved heap may end up differing from the 1910 // address that was requested (i.e. the preferred heap base). 1911 // If this happens then we could end up using a non-optimal 1912 // compressed oops mode. 1913 1914 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1915 heap_alignment); 1916 1917 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1918 1919 // Create the barrier set for the entire reserved region. 1920 G1SATBCardTableLoggingModRefBS* bs 1921 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1922 bs->initialize(); 1923 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1924 set_barrier_set(bs); 1925 1926 // Also create a G1 rem set. 1927 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 1928 1929 // Carve out the G1 part of the heap. 1930 1931 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1932 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1933 G1RegionToSpaceMapper* heap_storage = 1934 G1RegionToSpaceMapper::create_mapper(g1_rs, 1935 g1_rs.size(), 1936 page_size, 1937 HeapRegion::GrainBytes, 1938 1, 1939 mtJavaHeap); 1940 os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(), 1941 max_byte_size, page_size, 1942 heap_rs.base(), 1943 heap_rs.size()); 1944 heap_storage->set_mapping_changed_listener(&_listener); 1945 1946 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1947 G1RegionToSpaceMapper* bot_storage = 1948 create_aux_memory_mapper("Block offset table", 1949 G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize), 1950 G1BlockOffsetSharedArray::heap_map_factor()); 1951 1952 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1953 G1RegionToSpaceMapper* cardtable_storage = 1954 create_aux_memory_mapper("Card table", 1955 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1956 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1957 1958 G1RegionToSpaceMapper* card_counts_storage = 1959 create_aux_memory_mapper("Card counts table", 1960 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1961 G1CardCounts::heap_map_factor()); 1962 1963 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size()); 1964 G1RegionToSpaceMapper* prev_bitmap_storage = 1965 create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1966 G1RegionToSpaceMapper* next_bitmap_storage = 1967 create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1968 1969 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1970 g1_barrier_set()->initialize(cardtable_storage); 1971 // Do later initialization work for concurrent refinement. 1972 _cg1r->init(card_counts_storage); 1973 1974 // 6843694 - ensure that the maximum region index can fit 1975 // in the remembered set structures. 1976 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1977 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1978 1979 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1980 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1981 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1982 "too many cards per region"); 1983 1984 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1985 1986 _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage); 1987 1988 { 1989 HeapWord* start = _hrm.reserved().start(); 1990 HeapWord* end = _hrm.reserved().end(); 1991 size_t granularity = HeapRegion::GrainBytes; 1992 1993 _in_cset_fast_test.initialize(start, end, granularity); 1994 _humongous_reclaim_candidates.initialize(start, end, granularity); 1995 } 1996 1997 // Create the ConcurrentMark data structure and thread. 1998 // (Must do this late, so that "max_regions" is defined.) 1999 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 2000 if (_cm == NULL || !_cm->completed_initialization()) { 2001 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 2002 return JNI_ENOMEM; 2003 } 2004 _cmThread = _cm->cmThread(); 2005 2006 // Initialize the from_card cache structure of HeapRegionRemSet. 2007 HeapRegionRemSet::init_heap(max_regions()); 2008 2009 // Now expand into the initial heap size. 2010 if (!expand(init_byte_size)) { 2011 vm_shutdown_during_initialization("Failed to allocate initial heap."); 2012 return JNI_ENOMEM; 2013 } 2014 2015 // Perform any initialization actions delegated to the policy. 2016 g1_policy()->init(); 2017 2018 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2019 SATB_Q_FL_lock, 2020 G1SATBProcessCompletedThreshold, 2021 Shared_SATB_Q_lock); 2022 2023 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 2024 DirtyCardQ_CBL_mon, 2025 DirtyCardQ_FL_lock, 2026 concurrent_g1_refine()->yellow_zone(), 2027 concurrent_g1_refine()->red_zone(), 2028 Shared_DirtyCardQ_lock); 2029 2030 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 2031 DirtyCardQ_CBL_mon, 2032 DirtyCardQ_FL_lock, 2033 -1, // never trigger processing 2034 -1, // no limit on length 2035 Shared_DirtyCardQ_lock, 2036 &JavaThread::dirty_card_queue_set()); 2037 2038 // Here we allocate the dummy HeapRegion that is required by the 2039 // G1AllocRegion class. 2040 HeapRegion* dummy_region = _hrm.get_dummy_region(); 2041 2042 // We'll re-use the same region whether the alloc region will 2043 // require BOT updates or not and, if it doesn't, then a non-young 2044 // region will complain that it cannot support allocations without 2045 // BOT updates. So we'll tag the dummy region as eden to avoid that. 2046 dummy_region->set_eden(); 2047 // Make sure it's full. 2048 dummy_region->set_top(dummy_region->end()); 2049 G1AllocRegion::setup(this, dummy_region); 2050 2051 _allocator->init_mutator_alloc_region(); 2052 2053 // Do create of the monitoring and management support so that 2054 // values in the heap have been properly initialized. 2055 _g1mm = new G1MonitoringSupport(this); 2056 2057 G1StringDedup::initialize(); 2058 2059 _preserved_objs = NEW_C_HEAP_ARRAY(OopAndMarkOopStack, ParallelGCThreads, mtGC); 2060 for (uint i = 0; i < ParallelGCThreads; i++) { 2061 new (&_preserved_objs[i]) OopAndMarkOopStack(); 2062 } 2063 2064 return JNI_OK; 2065 } 2066 2067 void G1CollectedHeap::stop() { 2068 // Stop all concurrent threads. We do this to make sure these threads 2069 // do not continue to execute and access resources (e.g. gclog_or_tty) 2070 // that are destroyed during shutdown. 2071 _cg1r->stop(); 2072 _cmThread->stop(); 2073 if (G1StringDedup::is_enabled()) { 2074 G1StringDedup::stop(); 2075 } 2076 } 2077 2078 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2079 return HeapRegion::max_region_size(); 2080 } 2081 2082 void G1CollectedHeap::post_initialize() { 2083 CollectedHeap::post_initialize(); 2084 ref_processing_init(); 2085 } 2086 2087 void G1CollectedHeap::ref_processing_init() { 2088 // Reference processing in G1 currently works as follows: 2089 // 2090 // * There are two reference processor instances. One is 2091 // used to record and process discovered references 2092 // during concurrent marking; the other is used to 2093 // record and process references during STW pauses 2094 // (both full and incremental). 2095 // * Both ref processors need to 'span' the entire heap as 2096 // the regions in the collection set may be dotted around. 2097 // 2098 // * For the concurrent marking ref processor: 2099 // * Reference discovery is enabled at initial marking. 2100 // * Reference discovery is disabled and the discovered 2101 // references processed etc during remarking. 2102 // * Reference discovery is MT (see below). 2103 // * Reference discovery requires a barrier (see below). 2104 // * Reference processing may or may not be MT 2105 // (depending on the value of ParallelRefProcEnabled 2106 // and ParallelGCThreads). 2107 // * A full GC disables reference discovery by the CM 2108 // ref processor and abandons any entries on it's 2109 // discovered lists. 2110 // 2111 // * For the STW processor: 2112 // * Non MT discovery is enabled at the start of a full GC. 2113 // * Processing and enqueueing during a full GC is non-MT. 2114 // * During a full GC, references are processed after marking. 2115 // 2116 // * Discovery (may or may not be MT) is enabled at the start 2117 // of an incremental evacuation pause. 2118 // * References are processed near the end of a STW evacuation pause. 2119 // * For both types of GC: 2120 // * Discovery is atomic - i.e. not concurrent. 2121 // * Reference discovery will not need a barrier. 2122 2123 MemRegion mr = reserved_region(); 2124 2125 // Concurrent Mark ref processor 2126 _ref_processor_cm = 2127 new ReferenceProcessor(mr, // span 2128 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2129 // mt processing 2130 ParallelGCThreads, 2131 // degree of mt processing 2132 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2133 // mt discovery 2134 MAX2(ParallelGCThreads, ConcGCThreads), 2135 // degree of mt discovery 2136 false, 2137 // Reference discovery is not atomic 2138 &_is_alive_closure_cm); 2139 // is alive closure 2140 // (for efficiency/performance) 2141 2142 // STW ref processor 2143 _ref_processor_stw = 2144 new ReferenceProcessor(mr, // span 2145 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2146 // mt processing 2147 ParallelGCThreads, 2148 // degree of mt processing 2149 (ParallelGCThreads > 1), 2150 // mt discovery 2151 ParallelGCThreads, 2152 // degree of mt discovery 2153 true, 2154 // Reference discovery is atomic 2155 &_is_alive_closure_stw); 2156 // is alive closure 2157 // (for efficiency/performance) 2158 } 2159 2160 CollectorPolicy* G1CollectedHeap::collector_policy() const { 2161 return g1_policy(); 2162 } 2163 2164 size_t G1CollectedHeap::capacity() const { 2165 return _hrm.length() * HeapRegion::GrainBytes; 2166 } 2167 2168 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2169 hr->reset_gc_time_stamp(); 2170 } 2171 2172 #ifndef PRODUCT 2173 2174 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2175 private: 2176 unsigned _gc_time_stamp; 2177 bool _failures; 2178 2179 public: 2180 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2181 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2182 2183 virtual bool doHeapRegion(HeapRegion* hr) { 2184 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2185 if (_gc_time_stamp != region_gc_time_stamp) { 2186 gclog_or_tty->print_cr("Region " HR_FORMAT " has GC time stamp = %d, " 2187 "expected %d", HR_FORMAT_PARAMS(hr), 2188 region_gc_time_stamp, _gc_time_stamp); 2189 _failures = true; 2190 } 2191 return false; 2192 } 2193 2194 bool failures() { return _failures; } 2195 }; 2196 2197 void G1CollectedHeap::check_gc_time_stamps() { 2198 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2199 heap_region_iterate(&cl); 2200 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2201 } 2202 #endif // PRODUCT 2203 2204 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2205 _cg1r->hot_card_cache()->drain(cl, worker_i); 2206 } 2207 2208 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2209 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2210 size_t n_completed_buffers = 0; 2211 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2212 n_completed_buffers++; 2213 } 2214 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2215 dcqs.clear_n_completed_buffers(); 2216 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2217 } 2218 2219 // Computes the sum of the storage used by the various regions. 2220 size_t G1CollectedHeap::used() const { 2221 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2222 if (_archive_allocator != NULL) { 2223 result += _archive_allocator->used(); 2224 } 2225 return result; 2226 } 2227 2228 size_t G1CollectedHeap::used_unlocked() const { 2229 return _summary_bytes_used; 2230 } 2231 2232 class SumUsedClosure: public HeapRegionClosure { 2233 size_t _used; 2234 public: 2235 SumUsedClosure() : _used(0) {} 2236 bool doHeapRegion(HeapRegion* r) { 2237 _used += r->used(); 2238 return false; 2239 } 2240 size_t result() { return _used; } 2241 }; 2242 2243 size_t G1CollectedHeap::recalculate_used() const { 2244 double recalculate_used_start = os::elapsedTime(); 2245 2246 SumUsedClosure blk; 2247 heap_region_iterate(&blk); 2248 2249 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2250 return blk.result(); 2251 } 2252 2253 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2254 switch (cause) { 2255 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2256 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2257 case GCCause::_update_allocation_context_stats_inc: return true; 2258 case GCCause::_wb_conc_mark: return true; 2259 default : return false; 2260 } 2261 } 2262 2263 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2264 switch (cause) { 2265 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2266 case GCCause::_g1_humongous_allocation: return true; 2267 default: return is_user_requested_concurrent_full_gc(cause); 2268 } 2269 } 2270 2271 #ifndef PRODUCT 2272 void G1CollectedHeap::allocate_dummy_regions() { 2273 // Let's fill up most of the region 2274 size_t word_size = HeapRegion::GrainWords - 1024; 2275 // And as a result the region we'll allocate will be humongous. 2276 guarantee(is_humongous(word_size), "sanity"); 2277 2278 // _filler_array_max_size is set to humongous object threshold 2279 // but temporarily change it to use CollectedHeap::fill_with_object(). 2280 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2281 2282 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2283 // Let's use the existing mechanism for the allocation 2284 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2285 AllocationContext::system()); 2286 if (dummy_obj != NULL) { 2287 MemRegion mr(dummy_obj, word_size); 2288 CollectedHeap::fill_with_object(mr); 2289 } else { 2290 // If we can't allocate once, we probably cannot allocate 2291 // again. Let's get out of the loop. 2292 break; 2293 } 2294 } 2295 } 2296 #endif // !PRODUCT 2297 2298 void G1CollectedHeap::increment_old_marking_cycles_started() { 2299 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2300 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2301 "Wrong marking cycle count (started: %d, completed: %d)", 2302 _old_marking_cycles_started, _old_marking_cycles_completed); 2303 2304 _old_marking_cycles_started++; 2305 } 2306 2307 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2308 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2309 2310 // We assume that if concurrent == true, then the caller is a 2311 // concurrent thread that was joined the Suspendible Thread 2312 // Set. If there's ever a cheap way to check this, we should add an 2313 // assert here. 2314 2315 // Given that this method is called at the end of a Full GC or of a 2316 // concurrent cycle, and those can be nested (i.e., a Full GC can 2317 // interrupt a concurrent cycle), the number of full collections 2318 // completed should be either one (in the case where there was no 2319 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2320 // behind the number of full collections started. 2321 2322 // This is the case for the inner caller, i.e. a Full GC. 2323 assert(concurrent || 2324 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2325 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2326 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2327 "is inconsistent with _old_marking_cycles_completed = %u", 2328 _old_marking_cycles_started, _old_marking_cycles_completed); 2329 2330 // This is the case for the outer caller, i.e. the concurrent cycle. 2331 assert(!concurrent || 2332 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2333 "for outer caller (concurrent cycle): " 2334 "_old_marking_cycles_started = %u " 2335 "is inconsistent with _old_marking_cycles_completed = %u", 2336 _old_marking_cycles_started, _old_marking_cycles_completed); 2337 2338 _old_marking_cycles_completed += 1; 2339 2340 // We need to clear the "in_progress" flag in the CM thread before 2341 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2342 // is set) so that if a waiter requests another System.gc() it doesn't 2343 // incorrectly see that a marking cycle is still in progress. 2344 if (concurrent) { 2345 _cmThread->set_idle(); 2346 } 2347 2348 // This notify_all() will ensure that a thread that called 2349 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2350 // and it's waiting for a full GC to finish will be woken up. It is 2351 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2352 FullGCCount_lock->notify_all(); 2353 } 2354 2355 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2356 GCIdMarkAndRestore conc_gc_id_mark; 2357 collector_state()->set_concurrent_cycle_started(true); 2358 _gc_timer_cm->register_gc_start(start_time); 2359 2360 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2361 trace_heap_before_gc(_gc_tracer_cm); 2362 _cmThread->set_gc_id(GCId::current()); 2363 } 2364 2365 void G1CollectedHeap::register_concurrent_cycle_end() { 2366 if (collector_state()->concurrent_cycle_started()) { 2367 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2368 if (_cm->has_aborted()) { 2369 _gc_tracer_cm->report_concurrent_mode_failure(); 2370 } 2371 2372 _gc_timer_cm->register_gc_end(); 2373 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2374 2375 // Clear state variables to prepare for the next concurrent cycle. 2376 collector_state()->set_concurrent_cycle_started(false); 2377 _heap_summary_sent = false; 2378 } 2379 } 2380 2381 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2382 if (collector_state()->concurrent_cycle_started()) { 2383 // This function can be called when: 2384 // the cleanup pause is run 2385 // the concurrent cycle is aborted before the cleanup pause. 2386 // the concurrent cycle is aborted after the cleanup pause, 2387 // but before the concurrent cycle end has been registered. 2388 // Make sure that we only send the heap information once. 2389 if (!_heap_summary_sent) { 2390 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2391 trace_heap_after_gc(_gc_tracer_cm); 2392 _heap_summary_sent = true; 2393 } 2394 } 2395 } 2396 2397 void G1CollectedHeap::collect(GCCause::Cause cause) { 2398 assert_heap_not_locked(); 2399 2400 uint gc_count_before; 2401 uint old_marking_count_before; 2402 uint full_gc_count_before; 2403 bool retry_gc; 2404 2405 do { 2406 retry_gc = false; 2407 2408 { 2409 MutexLocker ml(Heap_lock); 2410 2411 // Read the GC count while holding the Heap_lock 2412 gc_count_before = total_collections(); 2413 full_gc_count_before = total_full_collections(); 2414 old_marking_count_before = _old_marking_cycles_started; 2415 } 2416 2417 if (should_do_concurrent_full_gc(cause)) { 2418 // Schedule an initial-mark evacuation pause that will start a 2419 // concurrent cycle. We're setting word_size to 0 which means that 2420 // we are not requesting a post-GC allocation. 2421 VM_G1IncCollectionPause op(gc_count_before, 2422 0, /* word_size */ 2423 true, /* should_initiate_conc_mark */ 2424 g1_policy()->max_pause_time_ms(), 2425 cause); 2426 op.set_allocation_context(AllocationContext::current()); 2427 2428 VMThread::execute(&op); 2429 if (!op.pause_succeeded()) { 2430 if (old_marking_count_before == _old_marking_cycles_started) { 2431 retry_gc = op.should_retry_gc(); 2432 } else { 2433 // A Full GC happened while we were trying to schedule the 2434 // initial-mark GC. No point in starting a new cycle given 2435 // that the whole heap was collected anyway. 2436 } 2437 2438 if (retry_gc) { 2439 if (GC_locker::is_active_and_needs_gc()) { 2440 GC_locker::stall_until_clear(); 2441 } 2442 } 2443 } 2444 } else { 2445 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2446 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2447 2448 // Schedule a standard evacuation pause. We're setting word_size 2449 // to 0 which means that we are not requesting a post-GC allocation. 2450 VM_G1IncCollectionPause op(gc_count_before, 2451 0, /* word_size */ 2452 false, /* should_initiate_conc_mark */ 2453 g1_policy()->max_pause_time_ms(), 2454 cause); 2455 VMThread::execute(&op); 2456 } else { 2457 // Schedule a Full GC. 2458 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2459 VMThread::execute(&op); 2460 } 2461 } 2462 } while (retry_gc); 2463 } 2464 2465 bool G1CollectedHeap::is_in(const void* p) const { 2466 if (_hrm.reserved().contains(p)) { 2467 // Given that we know that p is in the reserved space, 2468 // heap_region_containing() should successfully 2469 // return the containing region. 2470 HeapRegion* hr = heap_region_containing(p); 2471 return hr->is_in(p); 2472 } else { 2473 return false; 2474 } 2475 } 2476 2477 #ifdef ASSERT 2478 bool G1CollectedHeap::is_in_exact(const void* p) const { 2479 bool contains = reserved_region().contains(p); 2480 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2481 if (contains && available) { 2482 return true; 2483 } else { 2484 return false; 2485 } 2486 } 2487 #endif 2488 2489 bool G1CollectedHeap::obj_in_cs(oop obj) { 2490 HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj); 2491 return r != NULL && r->in_collection_set(); 2492 } 2493 2494 // Iteration functions. 2495 2496 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2497 2498 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2499 ExtendedOopClosure* _cl; 2500 public: 2501 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2502 bool doHeapRegion(HeapRegion* r) { 2503 if (!r->is_continues_humongous()) { 2504 r->oop_iterate(_cl); 2505 } 2506 return false; 2507 } 2508 }; 2509 2510 // Iterates an ObjectClosure over all objects within a HeapRegion. 2511 2512 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2513 ObjectClosure* _cl; 2514 public: 2515 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2516 bool doHeapRegion(HeapRegion* r) { 2517 if (!r->is_continues_humongous()) { 2518 r->object_iterate(_cl); 2519 } 2520 return false; 2521 } 2522 }; 2523 2524 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2525 IterateObjectClosureRegionClosure blk(cl); 2526 heap_region_iterate(&blk); 2527 } 2528 2529 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2530 _hrm.iterate(cl); 2531 } 2532 2533 void 2534 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2535 uint worker_id, 2536 HeapRegionClaimer *hrclaimer, 2537 bool concurrent) const { 2538 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2539 } 2540 2541 // Clear the cached CSet starting regions and (more importantly) 2542 // the time stamps. Called when we reset the GC time stamp. 2543 void G1CollectedHeap::clear_cset_start_regions() { 2544 assert(_worker_cset_start_region != NULL, "sanity"); 2545 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2546 2547 for (uint i = 0; i < ParallelGCThreads; i++) { 2548 _worker_cset_start_region[i] = NULL; 2549 _worker_cset_start_region_time_stamp[i] = 0; 2550 } 2551 } 2552 2553 // Given the id of a worker, obtain or calculate a suitable 2554 // starting region for iterating over the current collection set. 2555 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2556 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2557 2558 HeapRegion* result = NULL; 2559 unsigned gc_time_stamp = get_gc_time_stamp(); 2560 2561 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2562 // Cached starting region for current worker was set 2563 // during the current pause - so it's valid. 2564 // Note: the cached starting heap region may be NULL 2565 // (when the collection set is empty). 2566 result = _worker_cset_start_region[worker_i]; 2567 assert(result == NULL || result->in_collection_set(), "sanity"); 2568 return result; 2569 } 2570 2571 // The cached entry was not valid so let's calculate 2572 // a suitable starting heap region for this worker. 2573 2574 // We want the parallel threads to start their collection 2575 // set iteration at different collection set regions to 2576 // avoid contention. 2577 // If we have: 2578 // n collection set regions 2579 // p threads 2580 // Then thread t will start at region floor ((t * n) / p) 2581 2582 result = g1_policy()->collection_set(); 2583 uint cs_size = g1_policy()->cset_region_length(); 2584 uint active_workers = workers()->active_workers(); 2585 2586 uint end_ind = (cs_size * worker_i) / active_workers; 2587 uint start_ind = 0; 2588 2589 if (worker_i > 0 && 2590 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2591 // Previous workers starting region is valid 2592 // so let's iterate from there 2593 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2594 result = _worker_cset_start_region[worker_i - 1]; 2595 } 2596 2597 for (uint i = start_ind; i < end_ind; i++) { 2598 result = result->next_in_collection_set(); 2599 } 2600 2601 // Note: the calculated starting heap region may be NULL 2602 // (when the collection set is empty). 2603 assert(result == NULL || result->in_collection_set(), "sanity"); 2604 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2605 "should be updated only once per pause"); 2606 _worker_cset_start_region[worker_i] = result; 2607 OrderAccess::storestore(); 2608 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2609 return result; 2610 } 2611 2612 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2613 HeapRegion* r = g1_policy()->collection_set(); 2614 while (r != NULL) { 2615 HeapRegion* next = r->next_in_collection_set(); 2616 if (cl->doHeapRegion(r)) { 2617 cl->incomplete(); 2618 return; 2619 } 2620 r = next; 2621 } 2622 } 2623 2624 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2625 HeapRegionClosure *cl) { 2626 if (r == NULL) { 2627 // The CSet is empty so there's nothing to do. 2628 return; 2629 } 2630 2631 assert(r->in_collection_set(), 2632 "Start region must be a member of the collection set."); 2633 HeapRegion* cur = r; 2634 while (cur != NULL) { 2635 HeapRegion* next = cur->next_in_collection_set(); 2636 if (cl->doHeapRegion(cur) && false) { 2637 cl->incomplete(); 2638 return; 2639 } 2640 cur = next; 2641 } 2642 cur = g1_policy()->collection_set(); 2643 while (cur != r) { 2644 HeapRegion* next = cur->next_in_collection_set(); 2645 if (cl->doHeapRegion(cur) && false) { 2646 cl->incomplete(); 2647 return; 2648 } 2649 cur = next; 2650 } 2651 } 2652 2653 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2654 HeapRegion* result = _hrm.next_region_in_heap(from); 2655 while (result != NULL && result->is_pinned()) { 2656 result = _hrm.next_region_in_heap(result); 2657 } 2658 return result; 2659 } 2660 2661 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2662 HeapRegion* hr = heap_region_containing(addr); 2663 return hr->block_start(addr); 2664 } 2665 2666 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2667 HeapRegion* hr = heap_region_containing(addr); 2668 return hr->block_size(addr); 2669 } 2670 2671 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2672 HeapRegion* hr = heap_region_containing(addr); 2673 return hr->block_is_obj(addr); 2674 } 2675 2676 bool G1CollectedHeap::supports_tlab_allocation() const { 2677 return true; 2678 } 2679 2680 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2681 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2682 } 2683 2684 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2685 return young_list()->eden_used_bytes(); 2686 } 2687 2688 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2689 // must be equal to the humongous object limit. 2690 size_t G1CollectedHeap::max_tlab_size() const { 2691 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2692 } 2693 2694 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2695 AllocationContext_t context = AllocationContext::current(); 2696 return _allocator->unsafe_max_tlab_alloc(context); 2697 } 2698 2699 size_t G1CollectedHeap::max_capacity() const { 2700 return _hrm.reserved().byte_size(); 2701 } 2702 2703 jlong G1CollectedHeap::millis_since_last_gc() { 2704 // assert(false, "NYI"); 2705 return 0; 2706 } 2707 2708 void G1CollectedHeap::prepare_for_verify() { 2709 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2710 ensure_parsability(false); 2711 } 2712 g1_rem_set()->prepare_for_verify(); 2713 } 2714 2715 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 2716 VerifyOption vo) { 2717 switch (vo) { 2718 case VerifyOption_G1UsePrevMarking: 2719 return hr->obj_allocated_since_prev_marking(obj); 2720 case VerifyOption_G1UseNextMarking: 2721 return hr->obj_allocated_since_next_marking(obj); 2722 case VerifyOption_G1UseMarkWord: 2723 return false; 2724 default: 2725 ShouldNotReachHere(); 2726 } 2727 return false; // keep some compilers happy 2728 } 2729 2730 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 2731 switch (vo) { 2732 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 2733 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 2734 case VerifyOption_G1UseMarkWord: return NULL; 2735 default: ShouldNotReachHere(); 2736 } 2737 return NULL; // keep some compilers happy 2738 } 2739 2740 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 2741 switch (vo) { 2742 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 2743 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 2744 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 2745 default: ShouldNotReachHere(); 2746 } 2747 return false; // keep some compilers happy 2748 } 2749 2750 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 2751 switch (vo) { 2752 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 2753 case VerifyOption_G1UseNextMarking: return "NTAMS"; 2754 case VerifyOption_G1UseMarkWord: return "NONE"; 2755 default: ShouldNotReachHere(); 2756 } 2757 return NULL; // keep some compilers happy 2758 } 2759 2760 class VerifyRootsClosure: public OopClosure { 2761 private: 2762 G1CollectedHeap* _g1h; 2763 VerifyOption _vo; 2764 bool _failures; 2765 public: 2766 // _vo == UsePrevMarking -> use "prev" marking information, 2767 // _vo == UseNextMarking -> use "next" marking information, 2768 // _vo == UseMarkWord -> use mark word from object header. 2769 VerifyRootsClosure(VerifyOption vo) : 2770 _g1h(G1CollectedHeap::heap()), 2771 _vo(vo), 2772 _failures(false) { } 2773 2774 bool failures() { return _failures; } 2775 2776 template <class T> void do_oop_nv(T* p) { 2777 T heap_oop = oopDesc::load_heap_oop(p); 2778 if (!oopDesc::is_null(heap_oop)) { 2779 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2780 if (_g1h->is_obj_dead_cond(obj, _vo)) { 2781 gclog_or_tty->print_cr("Root location " PTR_FORMAT " " 2782 "points to dead obj " PTR_FORMAT, p2i(p), p2i(obj)); 2783 if (_vo == VerifyOption_G1UseMarkWord) { 2784 gclog_or_tty->print_cr(" Mark word: " INTPTR_FORMAT, (intptr_t)obj->mark()); 2785 } 2786 obj->print_on(gclog_or_tty); 2787 _failures = true; 2788 } 2789 } 2790 } 2791 2792 void do_oop(oop* p) { do_oop_nv(p); } 2793 void do_oop(narrowOop* p) { do_oop_nv(p); } 2794 }; 2795 2796 class G1VerifyCodeRootOopClosure: public OopClosure { 2797 G1CollectedHeap* _g1h; 2798 OopClosure* _root_cl; 2799 nmethod* _nm; 2800 VerifyOption _vo; 2801 bool _failures; 2802 2803 template <class T> void do_oop_work(T* p) { 2804 // First verify that this root is live 2805 _root_cl->do_oop(p); 2806 2807 if (!G1VerifyHeapRegionCodeRoots) { 2808 // We're not verifying the code roots attached to heap region. 2809 return; 2810 } 2811 2812 // Don't check the code roots during marking verification in a full GC 2813 if (_vo == VerifyOption_G1UseMarkWord) { 2814 return; 2815 } 2816 2817 // Now verify that the current nmethod (which contains p) is 2818 // in the code root list of the heap region containing the 2819 // object referenced by p. 2820 2821 T heap_oop = oopDesc::load_heap_oop(p); 2822 if (!oopDesc::is_null(heap_oop)) { 2823 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2824 2825 // Now fetch the region containing the object 2826 HeapRegion* hr = _g1h->heap_region_containing(obj); 2827 HeapRegionRemSet* hrrs = hr->rem_set(); 2828 // Verify that the strong code root list for this region 2829 // contains the nmethod 2830 if (!hrrs->strong_code_roots_list_contains(_nm)) { 2831 gclog_or_tty->print_cr("Code root location " PTR_FORMAT " " 2832 "from nmethod " PTR_FORMAT " not in strong " 2833 "code roots for region [" PTR_FORMAT "," PTR_FORMAT ")", 2834 p2i(p), p2i(_nm), p2i(hr->bottom()), p2i(hr->end())); 2835 _failures = true; 2836 } 2837 } 2838 } 2839 2840 public: 2841 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo): 2842 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {} 2843 2844 void do_oop(oop* p) { do_oop_work(p); } 2845 void do_oop(narrowOop* p) { do_oop_work(p); } 2846 2847 void set_nmethod(nmethod* nm) { _nm = nm; } 2848 bool failures() { return _failures; } 2849 }; 2850 2851 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure { 2852 G1VerifyCodeRootOopClosure* _oop_cl; 2853 2854 public: 2855 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl): 2856 _oop_cl(oop_cl) {} 2857 2858 void do_code_blob(CodeBlob* cb) { 2859 nmethod* nm = cb->as_nmethod_or_null(); 2860 if (nm != NULL) { 2861 _oop_cl->set_nmethod(nm); 2862 nm->oops_do(_oop_cl); 2863 } 2864 } 2865 }; 2866 2867 class YoungRefCounterClosure : public OopClosure { 2868 G1CollectedHeap* _g1h; 2869 int _count; 2870 public: 2871 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 2872 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 2873 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 2874 2875 int count() { return _count; } 2876 void reset_count() { _count = 0; }; 2877 }; 2878 2879 class VerifyKlassClosure: public KlassClosure { 2880 YoungRefCounterClosure _young_ref_counter_closure; 2881 OopClosure *_oop_closure; 2882 public: 2883 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 2884 void do_klass(Klass* k) { 2885 k->oops_do(_oop_closure); 2886 2887 _young_ref_counter_closure.reset_count(); 2888 k->oops_do(&_young_ref_counter_closure); 2889 if (_young_ref_counter_closure.count() > 0) { 2890 guarantee(k->has_modified_oops(), "Klass " PTR_FORMAT ", has young refs but is not dirty.", p2i(k)); 2891 } 2892 } 2893 }; 2894 2895 class VerifyLivenessOopClosure: public OopClosure { 2896 G1CollectedHeap* _g1h; 2897 VerifyOption _vo; 2898 public: 2899 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 2900 _g1h(g1h), _vo(vo) 2901 { } 2902 void do_oop(narrowOop *p) { do_oop_work(p); } 2903 void do_oop( oop *p) { do_oop_work(p); } 2904 2905 template <class T> void do_oop_work(T *p) { 2906 oop obj = oopDesc::load_decode_heap_oop(p); 2907 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 2908 "Dead object referenced by a not dead object"); 2909 } 2910 }; 2911 2912 class VerifyObjsInRegionClosure: public ObjectClosure { 2913 private: 2914 G1CollectedHeap* _g1h; 2915 size_t _live_bytes; 2916 HeapRegion *_hr; 2917 VerifyOption _vo; 2918 public: 2919 // _vo == UsePrevMarking -> use "prev" marking information, 2920 // _vo == UseNextMarking -> use "next" marking information, 2921 // _vo == UseMarkWord -> use mark word from object header. 2922 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 2923 : _live_bytes(0), _hr(hr), _vo(vo) { 2924 _g1h = G1CollectedHeap::heap(); 2925 } 2926 void do_object(oop o) { 2927 VerifyLivenessOopClosure isLive(_g1h, _vo); 2928 assert(o != NULL, "Huh?"); 2929 if (!_g1h->is_obj_dead_cond(o, _vo)) { 2930 // If the object is alive according to the mark word, 2931 // then verify that the marking information agrees. 2932 // Note we can't verify the contra-positive of the 2933 // above: if the object is dead (according to the mark 2934 // word), it may not be marked, or may have been marked 2935 // but has since became dead, or may have been allocated 2936 // since the last marking. 2937 if (_vo == VerifyOption_G1UseMarkWord) { 2938 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 2939 } 2940 2941 o->oop_iterate_no_header(&isLive); 2942 if (!_hr->obj_allocated_since_prev_marking(o)) { 2943 size_t obj_size = o->size(); // Make sure we don't overflow 2944 _live_bytes += (obj_size * HeapWordSize); 2945 } 2946 } 2947 } 2948 size_t live_bytes() { return _live_bytes; } 2949 }; 2950 2951 class VerifyArchiveOopClosure: public OopClosure { 2952 public: 2953 VerifyArchiveOopClosure(HeapRegion *hr) { } 2954 void do_oop(narrowOop *p) { do_oop_work(p); } 2955 void do_oop( oop *p) { do_oop_work(p); } 2956 2957 template <class T> void do_oop_work(T *p) { 2958 oop obj = oopDesc::load_decode_heap_oop(p); 2959 guarantee(obj == NULL || G1MarkSweep::in_archive_range(obj), 2960 "Archive object at " PTR_FORMAT " references a non-archive object at " PTR_FORMAT, 2961 p2i(p), p2i(obj)); 2962 } 2963 }; 2964 2965 class VerifyArchiveRegionClosure: public ObjectClosure { 2966 public: 2967 VerifyArchiveRegionClosure(HeapRegion *hr) { } 2968 // Verify that all object pointers are to archive regions. 2969 void do_object(oop o) { 2970 VerifyArchiveOopClosure checkOop(NULL); 2971 assert(o != NULL, "Should not be here for NULL oops"); 2972 o->oop_iterate_no_header(&checkOop); 2973 } 2974 }; 2975 2976 class VerifyRegionClosure: public HeapRegionClosure { 2977 private: 2978 bool _par; 2979 VerifyOption _vo; 2980 bool _failures; 2981 public: 2982 // _vo == UsePrevMarking -> use "prev" marking information, 2983 // _vo == UseNextMarking -> use "next" marking information, 2984 // _vo == UseMarkWord -> use mark word from object header. 2985 VerifyRegionClosure(bool par, VerifyOption vo) 2986 : _par(par), 2987 _vo(vo), 2988 _failures(false) {} 2989 2990 bool failures() { 2991 return _failures; 2992 } 2993 2994 bool doHeapRegion(HeapRegion* r) { 2995 // For archive regions, verify there are no heap pointers to 2996 // non-pinned regions. For all others, verify liveness info. 2997 if (r->is_archive()) { 2998 VerifyArchiveRegionClosure verify_oop_pointers(r); 2999 r->object_iterate(&verify_oop_pointers); 3000 return true; 3001 } 3002 if (!r->is_continues_humongous()) { 3003 bool failures = false; 3004 r->verify(_vo, &failures); 3005 if (failures) { 3006 _failures = true; 3007 } else if (!r->is_starts_humongous()) { 3008 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 3009 r->object_iterate(¬_dead_yet_cl); 3010 if (_vo != VerifyOption_G1UseNextMarking) { 3011 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 3012 gclog_or_tty->print_cr("[" PTR_FORMAT "," PTR_FORMAT "] " 3013 "max_live_bytes " SIZE_FORMAT " " 3014 "< calculated " SIZE_FORMAT, 3015 p2i(r->bottom()), p2i(r->end()), 3016 r->max_live_bytes(), 3017 not_dead_yet_cl.live_bytes()); 3018 _failures = true; 3019 } 3020 } else { 3021 // When vo == UseNextMarking we cannot currently do a sanity 3022 // check on the live bytes as the calculation has not been 3023 // finalized yet. 3024 } 3025 } 3026 } 3027 return false; // stop the region iteration if we hit a failure 3028 } 3029 }; 3030 3031 // This is the task used for parallel verification of the heap regions 3032 3033 class G1ParVerifyTask: public AbstractGangTask { 3034 private: 3035 G1CollectedHeap* _g1h; 3036 VerifyOption _vo; 3037 bool _failures; 3038 HeapRegionClaimer _hrclaimer; 3039 3040 public: 3041 // _vo == UsePrevMarking -> use "prev" marking information, 3042 // _vo == UseNextMarking -> use "next" marking information, 3043 // _vo == UseMarkWord -> use mark word from object header. 3044 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3045 AbstractGangTask("Parallel verify task"), 3046 _g1h(g1h), 3047 _vo(vo), 3048 _failures(false), 3049 _hrclaimer(g1h->workers()->active_workers()) {} 3050 3051 bool failures() { 3052 return _failures; 3053 } 3054 3055 void work(uint worker_id) { 3056 HandleMark hm; 3057 VerifyRegionClosure blk(true, _vo); 3058 _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer); 3059 if (blk.failures()) { 3060 _failures = true; 3061 } 3062 } 3063 }; 3064 3065 void G1CollectedHeap::verify(bool silent, VerifyOption vo) { 3066 if (SafepointSynchronize::is_at_safepoint()) { 3067 assert(Thread::current()->is_VM_thread(), 3068 "Expected to be executed serially by the VM thread at this point"); 3069 3070 if (!silent) { gclog_or_tty->print("Roots "); } 3071 VerifyRootsClosure rootsCl(vo); 3072 VerifyKlassClosure klassCl(this, &rootsCl); 3073 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false); 3074 3075 // We apply the relevant closures to all the oops in the 3076 // system dictionary, class loader data graph, the string table 3077 // and the nmethods in the code cache. 3078 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo); 3079 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl); 3080 3081 { 3082 G1RootProcessor root_processor(this, 1); 3083 root_processor.process_all_roots(&rootsCl, 3084 &cldCl, 3085 &blobsCl); 3086 } 3087 3088 bool failures = rootsCl.failures() || codeRootsCl.failures(); 3089 3090 if (vo != VerifyOption_G1UseMarkWord) { 3091 // If we're verifying during a full GC then the region sets 3092 // will have been torn down at the start of the GC. Therefore 3093 // verifying the region sets will fail. So we only verify 3094 // the region sets when not in a full GC. 3095 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3096 verify_region_sets(); 3097 } 3098 3099 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3100 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3101 3102 G1ParVerifyTask task(this, vo); 3103 workers()->run_task(&task); 3104 if (task.failures()) { 3105 failures = true; 3106 } 3107 3108 } else { 3109 VerifyRegionClosure blk(false, vo); 3110 heap_region_iterate(&blk); 3111 if (blk.failures()) { 3112 failures = true; 3113 } 3114 } 3115 3116 if (G1StringDedup::is_enabled()) { 3117 if (!silent) gclog_or_tty->print("StrDedup "); 3118 G1StringDedup::verify(); 3119 } 3120 3121 if (failures) { 3122 gclog_or_tty->print_cr("Heap:"); 3123 // It helps to have the per-region information in the output to 3124 // help us track down what went wrong. This is why we call 3125 // print_extended_on() instead of print_on(). 3126 print_extended_on(gclog_or_tty); 3127 gclog_or_tty->cr(); 3128 gclog_or_tty->flush(); 3129 } 3130 guarantee(!failures, "there should not have been any failures"); 3131 } else { 3132 if (!silent) { 3133 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet"); 3134 if (G1StringDedup::is_enabled()) { 3135 gclog_or_tty->print(", StrDedup"); 3136 } 3137 gclog_or_tty->print(") "); 3138 } 3139 } 3140 } 3141 3142 void G1CollectedHeap::verify(bool silent) { 3143 verify(silent, VerifyOption_G1UsePrevMarking); 3144 } 3145 3146 double G1CollectedHeap::verify(bool guard, const char* msg) { 3147 double verify_time_ms = 0.0; 3148 3149 if (guard && total_collections() >= VerifyGCStartAt) { 3150 double verify_start = os::elapsedTime(); 3151 HandleMark hm; // Discard invalid handles created during verification 3152 prepare_for_verify(); 3153 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 3154 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 3155 } 3156 3157 return verify_time_ms; 3158 } 3159 3160 void G1CollectedHeap::verify_before_gc() { 3161 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:"); 3162 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 3163 } 3164 3165 void G1CollectedHeap::verify_after_gc() { 3166 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:"); 3167 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 3168 } 3169 3170 class PrintRegionClosure: public HeapRegionClosure { 3171 outputStream* _st; 3172 public: 3173 PrintRegionClosure(outputStream* st) : _st(st) {} 3174 bool doHeapRegion(HeapRegion* r) { 3175 r->print_on(_st); 3176 return false; 3177 } 3178 }; 3179 3180 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3181 const HeapRegion* hr, 3182 const VerifyOption vo) const { 3183 switch (vo) { 3184 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 3185 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 3186 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 3187 default: ShouldNotReachHere(); 3188 } 3189 return false; // keep some compilers happy 3190 } 3191 3192 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3193 const VerifyOption vo) const { 3194 switch (vo) { 3195 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 3196 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 3197 case VerifyOption_G1UseMarkWord: { 3198 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 3199 return !obj->is_gc_marked() && !hr->is_archive(); 3200 } 3201 default: ShouldNotReachHere(); 3202 } 3203 return false; // keep some compilers happy 3204 } 3205 3206 void G1CollectedHeap::print_on(outputStream* st) const { 3207 st->print(" %-20s", "garbage-first heap"); 3208 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3209 capacity()/K, used_unlocked()/K); 3210 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 3211 p2i(_hrm.reserved().start()), 3212 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 3213 p2i(_hrm.reserved().end())); 3214 st->cr(); 3215 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3216 uint young_regions = _young_list->length(); 3217 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3218 (size_t) young_regions * HeapRegion::GrainBytes / K); 3219 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3220 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3221 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3222 st->cr(); 3223 MetaspaceAux::print_on(st); 3224 } 3225 3226 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3227 print_on(st); 3228 3229 // Print the per-region information. 3230 st->cr(); 3231 st->print_cr("Heap Regions: (E=young(eden), S=young(survivor), O=old, " 3232 "HS=humongous(starts), HC=humongous(continues), " 3233 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 3234 "PTAMS=previous top-at-mark-start, " 3235 "NTAMS=next top-at-mark-start)"); 3236 PrintRegionClosure blk(st); 3237 heap_region_iterate(&blk); 3238 } 3239 3240 void G1CollectedHeap::print_on_error(outputStream* st) const { 3241 this->CollectedHeap::print_on_error(st); 3242 3243 if (_cm != NULL) { 3244 st->cr(); 3245 _cm->print_on_error(st); 3246 } 3247 } 3248 3249 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3250 workers()->print_worker_threads_on(st); 3251 _cmThread->print_on(st); 3252 st->cr(); 3253 _cm->print_worker_threads_on(st); 3254 _cg1r->print_worker_threads_on(st); 3255 if (G1StringDedup::is_enabled()) { 3256 G1StringDedup::print_worker_threads_on(st); 3257 } 3258 } 3259 3260 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3261 workers()->threads_do(tc); 3262 tc->do_thread(_cmThread); 3263 _cg1r->threads_do(tc); 3264 if (G1StringDedup::is_enabled()) { 3265 G1StringDedup::threads_do(tc); 3266 } 3267 } 3268 3269 void G1CollectedHeap::print_tracing_info() const { 3270 // We'll overload this to mean "trace GC pause statistics." 3271 if (TraceYoungGenTime || TraceOldGenTime) { 3272 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3273 // to that. 3274 g1_policy()->print_tracing_info(); 3275 } 3276 if (G1SummarizeRSetStats) { 3277 g1_rem_set()->print_summary_info(); 3278 } 3279 if (G1SummarizeConcMark) { 3280 concurrent_mark()->print_summary_info(); 3281 } 3282 g1_policy()->print_yg_surv_rate_info(); 3283 } 3284 3285 #ifndef PRODUCT 3286 // Helpful for debugging RSet issues. 3287 3288 class PrintRSetsClosure : public HeapRegionClosure { 3289 private: 3290 const char* _msg; 3291 size_t _occupied_sum; 3292 3293 public: 3294 bool doHeapRegion(HeapRegion* r) { 3295 HeapRegionRemSet* hrrs = r->rem_set(); 3296 size_t occupied = hrrs->occupied(); 3297 _occupied_sum += occupied; 3298 3299 gclog_or_tty->print_cr("Printing RSet for region " HR_FORMAT, 3300 HR_FORMAT_PARAMS(r)); 3301 if (occupied == 0) { 3302 gclog_or_tty->print_cr(" RSet is empty"); 3303 } else { 3304 hrrs->print(); 3305 } 3306 gclog_or_tty->print_cr("----------"); 3307 return false; 3308 } 3309 3310 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3311 gclog_or_tty->cr(); 3312 gclog_or_tty->print_cr("========================================"); 3313 gclog_or_tty->print_cr("%s", msg); 3314 gclog_or_tty->cr(); 3315 } 3316 3317 ~PrintRSetsClosure() { 3318 gclog_or_tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 3319 gclog_or_tty->print_cr("========================================"); 3320 gclog_or_tty->cr(); 3321 } 3322 }; 3323 3324 void G1CollectedHeap::print_cset_rsets() { 3325 PrintRSetsClosure cl("Printing CSet RSets"); 3326 collection_set_iterate(&cl); 3327 } 3328 3329 void G1CollectedHeap::print_all_rsets() { 3330 PrintRSetsClosure cl("Printing All RSets");; 3331 heap_region_iterate(&cl); 3332 } 3333 #endif // PRODUCT 3334 3335 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 3336 YoungList* young_list = heap()->young_list(); 3337 3338 size_t eden_used_bytes = young_list->eden_used_bytes(); 3339 size_t survivor_used_bytes = young_list->survivor_used_bytes(); 3340 3341 size_t eden_capacity_bytes = 3342 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 3343 3344 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 3345 return G1HeapSummary(heap_summary, used(), eden_used_bytes, eden_capacity_bytes, survivor_used_bytes); 3346 } 3347 3348 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 3349 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 3350 stats->unused(), stats->used(), stats->region_end_waste(), 3351 stats->regions_filled(), stats->direct_allocated(), 3352 stats->failure_used(), stats->failure_waste()); 3353 } 3354 3355 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 3356 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 3357 gc_tracer->report_gc_heap_summary(when, heap_summary); 3358 3359 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 3360 gc_tracer->report_metaspace_summary(when, metaspace_summary); 3361 } 3362 3363 3364 G1CollectedHeap* G1CollectedHeap::heap() { 3365 CollectedHeap* heap = Universe::heap(); 3366 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 3367 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 3368 return (G1CollectedHeap*)heap; 3369 } 3370 3371 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3372 // always_do_update_barrier = false; 3373 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3374 // Fill TLAB's and such 3375 accumulate_statistics_all_tlabs(); 3376 ensure_parsability(true); 3377 3378 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) && 3379 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 3380 g1_rem_set()->print_periodic_summary_info("Before GC RS summary"); 3381 } 3382 } 3383 3384 void G1CollectedHeap::gc_epilogue(bool full) { 3385 3386 if (G1SummarizeRSetStats && 3387 (G1SummarizeRSetStatsPeriod > 0) && 3388 // we are at the end of the GC. Total collections has already been increased. 3389 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) { 3390 g1_rem_set()->print_periodic_summary_info("After GC RS summary"); 3391 } 3392 3393 // FIXME: what is this about? 3394 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3395 // is set. 3396 #if defined(COMPILER2) || INCLUDE_JVMCI 3397 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 3398 #endif 3399 // always_do_update_barrier = true; 3400 3401 resize_all_tlabs(); 3402 allocation_context_stats().update(full); 3403 3404 // We have just completed a GC. Update the soft reference 3405 // policy with the new heap occupancy 3406 Universe::update_heap_info_at_gc(); 3407 } 3408 3409 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3410 uint gc_count_before, 3411 bool* succeeded, 3412 GCCause::Cause gc_cause) { 3413 assert_heap_not_locked_and_not_at_safepoint(); 3414 g1_policy()->record_stop_world_start(); 3415 VM_G1IncCollectionPause op(gc_count_before, 3416 word_size, 3417 false, /* should_initiate_conc_mark */ 3418 g1_policy()->max_pause_time_ms(), 3419 gc_cause); 3420 3421 op.set_allocation_context(AllocationContext::current()); 3422 VMThread::execute(&op); 3423 3424 HeapWord* result = op.result(); 3425 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3426 assert(result == NULL || ret_succeeded, 3427 "the result should be NULL if the VM did not succeed"); 3428 *succeeded = ret_succeeded; 3429 3430 assert_heap_not_locked(); 3431 return result; 3432 } 3433 3434 void 3435 G1CollectedHeap::doConcurrentMark() { 3436 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3437 if (!_cmThread->in_progress()) { 3438 _cmThread->set_started(); 3439 CGC_lock->notify(); 3440 } 3441 } 3442 3443 size_t G1CollectedHeap::pending_card_num() { 3444 size_t extra_cards = 0; 3445 JavaThread *curr = Threads::first(); 3446 while (curr != NULL) { 3447 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3448 extra_cards += dcq.size(); 3449 curr = curr->next(); 3450 } 3451 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3452 size_t buffer_size = dcqs.buffer_size(); 3453 size_t buffer_num = dcqs.completed_buffers_num(); 3454 3455 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3456 // in bytes - not the number of 'entries'. We need to convert 3457 // into a number of cards. 3458 return (buffer_size * buffer_num + extra_cards) / oopSize; 3459 } 3460 3461 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 3462 private: 3463 size_t _total_humongous; 3464 size_t _candidate_humongous; 3465 3466 DirtyCardQueue _dcq; 3467 3468 // We don't nominate objects with many remembered set entries, on 3469 // the assumption that such objects are likely still live. 3470 bool is_remset_small(HeapRegion* region) const { 3471 HeapRegionRemSet* const rset = region->rem_set(); 3472 return G1EagerReclaimHumongousObjectsWithStaleRefs 3473 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 3474 : rset->is_empty(); 3475 } 3476 3477 bool is_typeArray_region(HeapRegion* region) const { 3478 return oop(region->bottom())->is_typeArray(); 3479 } 3480 3481 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 3482 assert(region->is_starts_humongous(), "Must start a humongous object"); 3483 3484 // Candidate selection must satisfy the following constraints 3485 // while concurrent marking is in progress: 3486 // 3487 // * In order to maintain SATB invariants, an object must not be 3488 // reclaimed if it was allocated before the start of marking and 3489 // has not had its references scanned. Such an object must have 3490 // its references (including type metadata) scanned to ensure no 3491 // live objects are missed by the marking process. Objects 3492 // allocated after the start of concurrent marking don't need to 3493 // be scanned. 3494 // 3495 // * An object must not be reclaimed if it is on the concurrent 3496 // mark stack. Objects allocated after the start of concurrent 3497 // marking are never pushed on the mark stack. 3498 // 3499 // Nominating only objects allocated after the start of concurrent 3500 // marking is sufficient to meet both constraints. This may miss 3501 // some objects that satisfy the constraints, but the marking data 3502 // structures don't support efficiently performing the needed 3503 // additional tests or scrubbing of the mark stack. 3504 // 3505 // However, we presently only nominate is_typeArray() objects. 3506 // A humongous object containing references induces remembered 3507 // set entries on other regions. In order to reclaim such an 3508 // object, those remembered sets would need to be cleaned up. 3509 // 3510 // We also treat is_typeArray() objects specially, allowing them 3511 // to be reclaimed even if allocated before the start of 3512 // concurrent mark. For this we rely on mark stack insertion to 3513 // exclude is_typeArray() objects, preventing reclaiming an object 3514 // that is in the mark stack. We also rely on the metadata for 3515 // such objects to be built-in and so ensured to be kept live. 3516 // Frequent allocation and drop of large binary blobs is an 3517 // important use case for eager reclaim, and this special handling 3518 // may reduce needed headroom. 3519 3520 return is_typeArray_region(region) && is_remset_small(region); 3521 } 3522 3523 public: 3524 RegisterHumongousWithInCSetFastTestClosure() 3525 : _total_humongous(0), 3526 _candidate_humongous(0), 3527 _dcq(&JavaThread::dirty_card_queue_set()) { 3528 } 3529 3530 virtual bool doHeapRegion(HeapRegion* r) { 3531 if (!r->is_starts_humongous()) { 3532 return false; 3533 } 3534 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3535 3536 bool is_candidate = humongous_region_is_candidate(g1h, r); 3537 uint rindex = r->hrm_index(); 3538 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 3539 if (is_candidate) { 3540 _candidate_humongous++; 3541 g1h->register_humongous_region_with_cset(rindex); 3542 // Is_candidate already filters out humongous object with large remembered sets. 3543 // If we have a humongous object with a few remembered sets, we simply flush these 3544 // remembered set entries into the DCQS. That will result in automatic 3545 // re-evaluation of their remembered set entries during the following evacuation 3546 // phase. 3547 if (!r->rem_set()->is_empty()) { 3548 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 3549 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 3550 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 3551 HeapRegionRemSetIterator hrrs(r->rem_set()); 3552 size_t card_index; 3553 while (hrrs.has_next(card_index)) { 3554 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 3555 // The remembered set might contain references to already freed 3556 // regions. Filter out such entries to avoid failing card table 3557 // verification. 3558 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 3559 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 3560 *card_ptr = CardTableModRefBS::dirty_card_val(); 3561 _dcq.enqueue(card_ptr); 3562 } 3563 } 3564 } 3565 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 3566 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 3567 hrrs.n_yielded(), r->rem_set()->occupied()); 3568 r->rem_set()->clear_locked(); 3569 } 3570 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 3571 } 3572 _total_humongous++; 3573 3574 return false; 3575 } 3576 3577 size_t total_humongous() const { return _total_humongous; } 3578 size_t candidate_humongous() const { return _candidate_humongous; } 3579 3580 void flush_rem_set_entries() { _dcq.flush(); } 3581 }; 3582 3583 void G1CollectedHeap::register_humongous_regions_with_cset() { 3584 if (!G1EagerReclaimHumongousObjects) { 3585 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 3586 return; 3587 } 3588 double time = os::elapsed_counter(); 3589 3590 // Collect reclaim candidate information and register candidates with cset. 3591 RegisterHumongousWithInCSetFastTestClosure cl; 3592 heap_region_iterate(&cl); 3593 3594 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 3595 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 3596 cl.total_humongous(), 3597 cl.candidate_humongous()); 3598 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3599 3600 // Finally flush all remembered set entries to re-check into the global DCQS. 3601 cl.flush_rem_set_entries(); 3602 } 3603 3604 #ifdef ASSERT 3605 class VerifyCSetClosure: public HeapRegionClosure { 3606 public: 3607 bool doHeapRegion(HeapRegion* hr) { 3608 // Here we check that the CSet region's RSet is ready for parallel 3609 // iteration. The fields that we'll verify are only manipulated 3610 // when the region is part of a CSet and is collected. Afterwards, 3611 // we reset these fields when we clear the region's RSet (when the 3612 // region is freed) so they are ready when the region is 3613 // re-allocated. The only exception to this is if there's an 3614 // evacuation failure and instead of freeing the region we leave 3615 // it in the heap. In that case, we reset these fields during 3616 // evacuation failure handling. 3617 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3618 3619 // Here's a good place to add any other checks we'd like to 3620 // perform on CSet regions. 3621 return false; 3622 } 3623 }; 3624 #endif // ASSERT 3625 3626 uint G1CollectedHeap::num_task_queues() const { 3627 return _task_queues->size(); 3628 } 3629 3630 #if TASKQUEUE_STATS 3631 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3632 st->print_raw_cr("GC Task Stats"); 3633 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3634 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3635 } 3636 3637 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3638 print_taskqueue_stats_hdr(st); 3639 3640 TaskQueueStats totals; 3641 const uint n = num_task_queues(); 3642 for (uint i = 0; i < n; ++i) { 3643 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 3644 totals += task_queue(i)->stats; 3645 } 3646 st->print_raw("tot "); totals.print(st); st->cr(); 3647 3648 DEBUG_ONLY(totals.verify()); 3649 } 3650 3651 void G1CollectedHeap::reset_taskqueue_stats() { 3652 const uint n = num_task_queues(); 3653 for (uint i = 0; i < n; ++i) { 3654 task_queue(i)->stats.reset(); 3655 } 3656 } 3657 #endif // TASKQUEUE_STATS 3658 3659 void G1CollectedHeap::log_gc_header() { 3660 if (!G1Log::fine()) { 3661 return; 3662 } 3663 3664 gclog_or_tty->gclog_stamp(); 3665 3666 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) 3667 .append(collector_state()->gcs_are_young() ? "(young)" : "(mixed)") 3668 .append(collector_state()->during_initial_mark_pause() ? " (initial-mark)" : ""); 3669 3670 gclog_or_tty->print("[%s", (const char*)gc_cause_str); 3671 } 3672 3673 void G1CollectedHeap::log_gc_footer(double pause_time_sec) { 3674 if (!G1Log::fine()) { 3675 return; 3676 } 3677 3678 if (G1Log::finer()) { 3679 if (evacuation_failed()) { 3680 gclog_or_tty->print(" (to-space exhausted)"); 3681 } 3682 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3683 g1_policy()->print_phases(pause_time_sec); 3684 g1_policy()->print_detailed_heap_transition(); 3685 } else { 3686 if (evacuation_failed()) { 3687 gclog_or_tty->print("--"); 3688 } 3689 g1_policy()->print_heap_transition(); 3690 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3691 } 3692 gclog_or_tty->flush(); 3693 } 3694 3695 void G1CollectedHeap::wait_for_root_region_scanning() { 3696 double scan_wait_start = os::elapsedTime(); 3697 // We have to wait until the CM threads finish scanning the 3698 // root regions as it's the only way to ensure that all the 3699 // objects on them have been correctly scanned before we start 3700 // moving them during the GC. 3701 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3702 double wait_time_ms = 0.0; 3703 if (waited) { 3704 double scan_wait_end = os::elapsedTime(); 3705 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3706 } 3707 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3708 } 3709 3710 bool 3711 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3712 assert_at_safepoint(true /* should_be_vm_thread */); 3713 guarantee(!is_gc_active(), "collection is not reentrant"); 3714 3715 if (GC_locker::check_active_before_gc()) { 3716 return false; 3717 } 3718 3719 _gc_timer_stw->register_gc_start(); 3720 3721 GCIdMark gc_id_mark; 3722 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3723 3724 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3725 ResourceMark rm; 3726 3727 wait_for_root_region_scanning(); 3728 3729 G1Log::update_level(); 3730 print_heap_before_gc(); 3731 trace_heap_before_gc(_gc_tracer_stw); 3732 3733 verify_region_sets_optional(); 3734 verify_dirty_young_regions(); 3735 3736 // This call will decide whether this pause is an initial-mark 3737 // pause. If it is, during_initial_mark_pause() will return true 3738 // for the duration of this pause. 3739 g1_policy()->decide_on_conc_mark_initiation(); 3740 3741 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3742 assert(!collector_state()->during_initial_mark_pause() || 3743 collector_state()->gcs_are_young(), "sanity"); 3744 3745 // We also do not allow mixed GCs during marking. 3746 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3747 3748 // Record whether this pause is an initial mark. When the current 3749 // thread has completed its logging output and it's safe to signal 3750 // the CM thread, the flag's value in the policy has been reset. 3751 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3752 3753 // Inner scope for scope based logging, timers, and stats collection 3754 { 3755 EvacuationInfo evacuation_info; 3756 3757 if (collector_state()->during_initial_mark_pause()) { 3758 // We are about to start a marking cycle, so we increment the 3759 // full collection counter. 3760 increment_old_marking_cycles_started(); 3761 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3762 } 3763 3764 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3765 3766 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 3767 3768 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3769 workers()->active_workers(), 3770 Threads::number_of_non_daemon_threads()); 3771 workers()->set_active_workers(active_workers); 3772 3773 double pause_start_sec = os::elapsedTime(); 3774 g1_policy()->note_gc_start(active_workers); 3775 log_gc_header(); 3776 3777 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3778 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3779 3780 // If the secondary_free_list is not empty, append it to the 3781 // free_list. No need to wait for the cleanup operation to finish; 3782 // the region allocation code will check the secondary_free_list 3783 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3784 // set, skip this step so that the region allocation code has to 3785 // get entries from the secondary_free_list. 3786 if (!G1StressConcRegionFreeing) { 3787 append_secondary_free_list_if_not_empty_with_lock(); 3788 } 3789 3790 assert(check_young_list_well_formed(), "young list should be well formed"); 3791 3792 // Don't dynamically change the number of GC threads this early. A value of 3793 // 0 is used to indicate serial work. When parallel work is done, 3794 // it will be set. 3795 3796 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3797 IsGCActiveMark x; 3798 3799 gc_prologue(false); 3800 increment_total_collections(false /* full gc */); 3801 increment_gc_time_stamp(); 3802 3803 verify_before_gc(); 3804 3805 check_bitmaps("GC Start"); 3806 3807 #if defined(COMPILER2) || INCLUDE_JVMCI 3808 DerivedPointerTable::clear(); 3809 #endif 3810 3811 // Please see comment in g1CollectedHeap.hpp and 3812 // G1CollectedHeap::ref_processing_init() to see how 3813 // reference processing currently works in G1. 3814 3815 // Enable discovery in the STW reference processor 3816 ref_processor_stw()->enable_discovery(); 3817 3818 { 3819 // We want to temporarily turn off discovery by the 3820 // CM ref processor, if necessary, and turn it back on 3821 // on again later if we do. Using a scoped 3822 // NoRefDiscovery object will do this. 3823 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3824 3825 // Forget the current alloc region (we might even choose it to be part 3826 // of the collection set!). 3827 _allocator->release_mutator_alloc_region(); 3828 3829 // We should call this after we retire the mutator alloc 3830 // region(s) so that all the ALLOC / RETIRE events are generated 3831 // before the start GC event. 3832 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 3833 3834 // This timing is only used by the ergonomics to handle our pause target. 3835 // It is unclear why this should not include the full pause. We will 3836 // investigate this in CR 7178365. 3837 // 3838 // Preserving the old comment here if that helps the investigation: 3839 // 3840 // The elapsed time induced by the start time below deliberately elides 3841 // the possible verification above. 3842 double sample_start_time_sec = os::elapsedTime(); 3843 3844 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3845 3846 if (collector_state()->during_initial_mark_pause()) { 3847 concurrent_mark()->checkpointRootsInitialPre(); 3848 } 3849 3850 double time_remaining_ms = g1_policy()->finalize_young_cset_part(target_pause_time_ms); 3851 g1_policy()->finalize_old_cset_part(time_remaining_ms); 3852 3853 evacuation_info.set_collectionset_regions(g1_policy()->cset_region_length()); 3854 3855 // Make sure the remembered sets are up to date. This needs to be 3856 // done before register_humongous_regions_with_cset(), because the 3857 // remembered sets are used there to choose eager reclaim candidates. 3858 // If the remembered sets are not up to date we might miss some 3859 // entries that need to be handled. 3860 g1_rem_set()->cleanupHRRS(); 3861 3862 register_humongous_regions_with_cset(); 3863 3864 assert(check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3865 3866 _cm->note_start_of_gc(); 3867 // We call this after finalize_cset() to 3868 // ensure that the CSet has been finalized. 3869 _cm->verify_no_cset_oops(); 3870 3871 if (_hr_printer.is_active()) { 3872 HeapRegion* hr = g1_policy()->collection_set(); 3873 while (hr != NULL) { 3874 _hr_printer.cset(hr); 3875 hr = hr->next_in_collection_set(); 3876 } 3877 } 3878 3879 #ifdef ASSERT 3880 VerifyCSetClosure cl; 3881 collection_set_iterate(&cl); 3882 #endif // ASSERT 3883 3884 // Initialize the GC alloc regions. 3885 _allocator->init_gc_alloc_regions(evacuation_info); 3886 3887 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), g1_policy()->young_cset_region_length()); 3888 pre_evacuate_collection_set(); 3889 3890 // Actually do the work... 3891 evacuate_collection_set(evacuation_info, &per_thread_states); 3892 3893 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3894 3895 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3896 free_collection_set(g1_policy()->collection_set(), evacuation_info, surviving_young_words); 3897 3898 eagerly_reclaim_humongous_regions(); 3899 3900 g1_policy()->clear_collection_set(); 3901 3902 // Start a new incremental collection set for the next pause. 3903 g1_policy()->start_incremental_cset_building(); 3904 3905 clear_cset_fast_test(); 3906 3907 _young_list->reset_sampled_info(); 3908 3909 // Don't check the whole heap at this point as the 3910 // GC alloc regions from this pause have been tagged 3911 // as survivors and moved on to the survivor list. 3912 // Survivor regions will fail the !is_young() check. 3913 assert(check_young_list_empty(false /* check_heap */), 3914 "young list should be empty"); 3915 3916 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3917 _young_list->first_survivor_region(), 3918 _young_list->last_survivor_region()); 3919 3920 _young_list->reset_auxilary_lists(); 3921 3922 if (evacuation_failed()) { 3923 set_used(recalculate_used()); 3924 if (_archive_allocator != NULL) { 3925 _archive_allocator->clear_used(); 3926 } 3927 for (uint i = 0; i < ParallelGCThreads; i++) { 3928 if (_evacuation_failed_info_array[i].has_failed()) { 3929 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3930 } 3931 } 3932 } else { 3933 // The "used" of the the collection set have already been subtracted 3934 // when they were freed. Add in the bytes evacuated. 3935 increase_used(g1_policy()->bytes_copied_during_gc()); 3936 } 3937 3938 if (collector_state()->during_initial_mark_pause()) { 3939 // We have to do this before we notify the CM threads that 3940 // they can start working to make sure that all the 3941 // appropriate initialization is done on the CM object. 3942 concurrent_mark()->checkpointRootsInitialPost(); 3943 collector_state()->set_mark_in_progress(true); 3944 // Note that we don't actually trigger the CM thread at 3945 // this point. We do that later when we're sure that 3946 // the current thread has completed its logging output. 3947 } 3948 3949 allocate_dummy_regions(); 3950 3951 _allocator->init_mutator_alloc_region(); 3952 3953 { 3954 size_t expand_bytes = g1_policy()->expansion_amount(); 3955 if (expand_bytes > 0) { 3956 size_t bytes_before = capacity(); 3957 // No need for an ergo verbose message here, 3958 // expansion_amount() does this when it returns a value > 0. 3959 double expand_ms; 3960 if (!expand(expand_bytes, &expand_ms)) { 3961 // We failed to expand the heap. Cannot do anything about it. 3962 } 3963 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3964 } 3965 } 3966 3967 // We redo the verification but now wrt to the new CSet which 3968 // has just got initialized after the previous CSet was freed. 3969 _cm->verify_no_cset_oops(); 3970 _cm->note_end_of_gc(); 3971 3972 // This timing is only used by the ergonomics to handle our pause target. 3973 // It is unclear why this should not include the full pause. We will 3974 // investigate this in CR 7178365. 3975 double sample_end_time_sec = os::elapsedTime(); 3976 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3977 size_t total_cards_scanned = per_thread_states.total_cards_scanned(); 3978 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned); 3979 3980 evacuation_info.set_collectionset_used_before(g1_policy()->collection_set_bytes_used_before()); 3981 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3982 3983 MemoryService::track_memory_usage(); 3984 3985 // In prepare_for_verify() below we'll need to scan the deferred 3986 // update buffers to bring the RSets up-to-date if 3987 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3988 // the update buffers we'll probably need to scan cards on the 3989 // regions we just allocated to (i.e., the GC alloc 3990 // regions). However, during the last GC we called 3991 // set_saved_mark() on all the GC alloc regions, so card 3992 // scanning might skip the [saved_mark_word()...top()] area of 3993 // those regions (i.e., the area we allocated objects into 3994 // during the last GC). But it shouldn't. Given that 3995 // saved_mark_word() is conditional on whether the GC time stamp 3996 // on the region is current or not, by incrementing the GC time 3997 // stamp here we invalidate all the GC time stamps on all the 3998 // regions and saved_mark_word() will simply return top() for 3999 // all the regions. This is a nicer way of ensuring this rather 4000 // than iterating over the regions and fixing them. In fact, the 4001 // GC time stamp increment here also ensures that 4002 // saved_mark_word() will return top() between pauses, i.e., 4003 // during concurrent refinement. So we don't need the 4004 // is_gc_active() check to decided which top to use when 4005 // scanning cards (see CR 7039627). 4006 increment_gc_time_stamp(); 4007 4008 verify_after_gc(); 4009 check_bitmaps("GC End"); 4010 4011 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 4012 ref_processor_stw()->verify_no_references_recorded(); 4013 4014 // CM reference discovery will be re-enabled if necessary. 4015 } 4016 4017 // We should do this after we potentially expand the heap so 4018 // that all the COMMIT events are generated before the end GC 4019 // event, and after we retire the GC alloc regions so that all 4020 // RETIRE events are generated before the end GC event. 4021 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 4022 4023 #ifdef TRACESPINNING 4024 ParallelTaskTerminator::print_termination_counts(); 4025 #endif 4026 4027 gc_epilogue(false); 4028 } 4029 4030 // Print the remainder of the GC log output. 4031 log_gc_footer(os::elapsedTime() - pause_start_sec); 4032 4033 // It is not yet to safe to tell the concurrent mark to 4034 // start as we have some optional output below. We don't want the 4035 // output from the concurrent mark thread interfering with this 4036 // logging output either. 4037 4038 _hrm.verify_optional(); 4039 verify_region_sets_optional(); 4040 4041 TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats()); 4042 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 4043 4044 print_heap_after_gc(); 4045 trace_heap_after_gc(_gc_tracer_stw); 4046 4047 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 4048 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 4049 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 4050 // before any GC notifications are raised. 4051 g1mm()->update_sizes(); 4052 4053 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 4054 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 4055 _gc_timer_stw->register_gc_end(); 4056 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 4057 } 4058 // It should now be safe to tell the concurrent mark thread to start 4059 // without its logging output interfering with the logging output 4060 // that came from the pause. 4061 4062 if (should_start_conc_mark) { 4063 // CAUTION: after the doConcurrentMark() call below, 4064 // the concurrent marking thread(s) could be running 4065 // concurrently with us. Make sure that anything after 4066 // this point does not assume that we are the only GC thread 4067 // running. Note: of course, the actual marking work will 4068 // not start until the safepoint itself is released in 4069 // SuspendibleThreadSet::desynchronize(). 4070 doConcurrentMark(); 4071 } 4072 4073 return true; 4074 } 4075 4076 void G1CollectedHeap::remove_self_forwarding_pointers() { 4077 double remove_self_forwards_start = os::elapsedTime(); 4078 4079 G1ParRemoveSelfForwardPtrsTask rsfp_task; 4080 workers()->run_task(&rsfp_task); 4081 4082 // Now restore saved marks, if any. 4083 for (uint i = 0; i < ParallelGCThreads; i++) { 4084 OopAndMarkOopStack& cur = _preserved_objs[i]; 4085 while (!cur.is_empty()) { 4086 OopAndMarkOop elem = cur.pop(); 4087 elem.set_mark(); 4088 } 4089 cur.clear(true); 4090 } 4091 4092 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 4093 } 4094 4095 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 4096 if (!_evacuation_failed) { 4097 _evacuation_failed = true; 4098 } 4099 4100 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 4101 4102 // We want to call the "for_promotion_failure" version only in the 4103 // case of a promotion failure. 4104 if (m->must_be_preserved_for_promotion_failure(obj)) { 4105 OopAndMarkOop elem(obj, m); 4106 _preserved_objs[worker_id].push(elem); 4107 } 4108 } 4109 4110 class G1ParEvacuateFollowersClosure : public VoidClosure { 4111 private: 4112 double _start_term; 4113 double _term_time; 4114 size_t _term_attempts; 4115 4116 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); } 4117 void end_term_time() { _term_time += os::elapsedTime() - _start_term; } 4118 protected: 4119 G1CollectedHeap* _g1h; 4120 G1ParScanThreadState* _par_scan_state; 4121 RefToScanQueueSet* _queues; 4122 ParallelTaskTerminator* _terminator; 4123 4124 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4125 RefToScanQueueSet* queues() { return _queues; } 4126 ParallelTaskTerminator* terminator() { return _terminator; } 4127 4128 public: 4129 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4130 G1ParScanThreadState* par_scan_state, 4131 RefToScanQueueSet* queues, 4132 ParallelTaskTerminator* terminator) 4133 : _g1h(g1h), _par_scan_state(par_scan_state), 4134 _queues(queues), _terminator(terminator), 4135 _start_term(0.0), _term_time(0.0), _term_attempts(0) {} 4136 4137 void do_void(); 4138 4139 double term_time() const { return _term_time; } 4140 size_t term_attempts() const { return _term_attempts; } 4141 4142 private: 4143 inline bool offer_termination(); 4144 }; 4145 4146 bool G1ParEvacuateFollowersClosure::offer_termination() { 4147 G1ParScanThreadState* const pss = par_scan_state(); 4148 start_term_time(); 4149 const bool res = terminator()->offer_termination(); 4150 end_term_time(); 4151 return res; 4152 } 4153 4154 void G1ParEvacuateFollowersClosure::do_void() { 4155 G1ParScanThreadState* const pss = par_scan_state(); 4156 pss->trim_queue(); 4157 do { 4158 pss->steal_and_trim_queue(queues()); 4159 } while (!offer_termination()); 4160 } 4161 4162 class G1ParTask : public AbstractGangTask { 4163 protected: 4164 G1CollectedHeap* _g1h; 4165 G1ParScanThreadStateSet* _pss; 4166 RefToScanQueueSet* _queues; 4167 G1RootProcessor* _root_processor; 4168 ParallelTaskTerminator _terminator; 4169 uint _n_workers; 4170 4171 public: 4172 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 4173 : AbstractGangTask("G1 collection"), 4174 _g1h(g1h), 4175 _pss(per_thread_states), 4176 _queues(task_queues), 4177 _root_processor(root_processor), 4178 _terminator(n_workers, _queues), 4179 _n_workers(n_workers) 4180 {} 4181 4182 void work(uint worker_id) { 4183 if (worker_id >= _n_workers) return; // no work needed this round 4184 4185 double start_sec = os::elapsedTime(); 4186 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 4187 4188 { 4189 ResourceMark rm; 4190 HandleMark hm; 4191 4192 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4193 4194 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4195 pss->set_ref_processor(rp); 4196 4197 double start_strong_roots_sec = os::elapsedTime(); 4198 4199 _root_processor->evacuate_roots(pss->closures(), worker_id); 4200 4201 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss); 4202 4203 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 4204 // treating the nmethods visited to act as roots for concurrent marking. 4205 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 4206 // objects copied by the current evacuation. 4207 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl, 4208 pss->closures()->weak_codeblobs(), 4209 worker_id); 4210 4211 _pss->add_cards_scanned(worker_id, cards_scanned); 4212 4213 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 4214 4215 double term_sec = 0.0; 4216 size_t evac_term_attempts = 0; 4217 { 4218 double start = os::elapsedTime(); 4219 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 4220 evac.do_void(); 4221 4222 evac_term_attempts = evac.term_attempts(); 4223 term_sec = evac.term_time(); 4224 double elapsed_sec = os::elapsedTime() - start; 4225 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 4226 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 4227 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 4228 } 4229 4230 assert(pss->queue_is_empty(), "should be empty"); 4231 4232 if (PrintTerminationStats) { 4233 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 4234 size_t lab_waste; 4235 size_t lab_undo_waste; 4236 pss->waste(lab_waste, lab_undo_waste); 4237 _g1h->print_termination_stats(gclog_or_tty, 4238 worker_id, 4239 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 4240 strong_roots_sec * 1000.0, /* strong roots time */ 4241 term_sec * 1000.0, /* evac term time */ 4242 evac_term_attempts, /* evac term attempts */ 4243 lab_waste, /* alloc buffer waste */ 4244 lab_undo_waste /* undo waste */ 4245 ); 4246 } 4247 4248 // Close the inner scope so that the ResourceMark and HandleMark 4249 // destructors are executed here and are included as part of the 4250 // "GC Worker Time". 4251 } 4252 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 4253 } 4254 }; 4255 4256 void G1CollectedHeap::print_termination_stats_hdr(outputStream* const st) { 4257 st->print_raw_cr("GC Termination Stats"); 4258 st->print_raw_cr(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 4259 st->print_raw_cr("thr ms ms % ms % attempts total alloc undo"); 4260 st->print_raw_cr("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 4261 } 4262 4263 void G1CollectedHeap::print_termination_stats(outputStream* const st, 4264 uint worker_id, 4265 double elapsed_ms, 4266 double strong_roots_ms, 4267 double term_ms, 4268 size_t term_attempts, 4269 size_t alloc_buffer_waste, 4270 size_t undo_waste) const { 4271 st->print_cr("%3d %9.2f %9.2f %6.2f " 4272 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 4273 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 4274 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 4275 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 4276 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 4277 alloc_buffer_waste * HeapWordSize / K, 4278 undo_waste * HeapWordSize / K); 4279 } 4280 4281 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 4282 private: 4283 BoolObjectClosure* _is_alive; 4284 int _initial_string_table_size; 4285 int _initial_symbol_table_size; 4286 4287 bool _process_strings; 4288 int _strings_processed; 4289 int _strings_removed; 4290 4291 bool _process_symbols; 4292 int _symbols_processed; 4293 int _symbols_removed; 4294 4295 public: 4296 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 4297 AbstractGangTask("String/Symbol Unlinking"), 4298 _is_alive(is_alive), 4299 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 4300 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 4301 4302 _initial_string_table_size = StringTable::the_table()->table_size(); 4303 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 4304 if (process_strings) { 4305 StringTable::clear_parallel_claimed_index(); 4306 } 4307 if (process_symbols) { 4308 SymbolTable::clear_parallel_claimed_index(); 4309 } 4310 } 4311 4312 ~G1StringSymbolTableUnlinkTask() { 4313 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 4314 "claim value %d after unlink less than initial string table size %d", 4315 StringTable::parallel_claimed_index(), _initial_string_table_size); 4316 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 4317 "claim value %d after unlink less than initial symbol table size %d", 4318 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 4319 4320 if (G1TraceStringSymbolTableScrubbing) { 4321 gclog_or_tty->print_cr("Cleaned string and symbol table, " 4322 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 4323 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 4324 strings_processed(), strings_removed(), 4325 symbols_processed(), symbols_removed()); 4326 } 4327 } 4328 4329 void work(uint worker_id) { 4330 int strings_processed = 0; 4331 int strings_removed = 0; 4332 int symbols_processed = 0; 4333 int symbols_removed = 0; 4334 if (_process_strings) { 4335 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 4336 Atomic::add(strings_processed, &_strings_processed); 4337 Atomic::add(strings_removed, &_strings_removed); 4338 } 4339 if (_process_symbols) { 4340 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 4341 Atomic::add(symbols_processed, &_symbols_processed); 4342 Atomic::add(symbols_removed, &_symbols_removed); 4343 } 4344 } 4345 4346 size_t strings_processed() const { return (size_t)_strings_processed; } 4347 size_t strings_removed() const { return (size_t)_strings_removed; } 4348 4349 size_t symbols_processed() const { return (size_t)_symbols_processed; } 4350 size_t symbols_removed() const { return (size_t)_symbols_removed; } 4351 }; 4352 4353 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 4354 private: 4355 static Monitor* _lock; 4356 4357 BoolObjectClosure* const _is_alive; 4358 const bool _unloading_occurred; 4359 const uint _num_workers; 4360 4361 // Variables used to claim nmethods. 4362 nmethod* _first_nmethod; 4363 volatile nmethod* _claimed_nmethod; 4364 4365 // The list of nmethods that need to be processed by the second pass. 4366 volatile nmethod* _postponed_list; 4367 volatile uint _num_entered_barrier; 4368 4369 public: 4370 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 4371 _is_alive(is_alive), 4372 _unloading_occurred(unloading_occurred), 4373 _num_workers(num_workers), 4374 _first_nmethod(NULL), 4375 _claimed_nmethod(NULL), 4376 _postponed_list(NULL), 4377 _num_entered_barrier(0) 4378 { 4379 nmethod::increase_unloading_clock(); 4380 // Get first alive nmethod 4381 NMethodIterator iter = NMethodIterator(); 4382 if(iter.next_alive()) { 4383 _first_nmethod = iter.method(); 4384 } 4385 _claimed_nmethod = (volatile nmethod*)_first_nmethod; 4386 } 4387 4388 ~G1CodeCacheUnloadingTask() { 4389 CodeCache::verify_clean_inline_caches(); 4390 4391 CodeCache::set_needs_cache_clean(false); 4392 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 4393 4394 CodeCache::verify_icholder_relocations(); 4395 } 4396 4397 private: 4398 void add_to_postponed_list(nmethod* nm) { 4399 nmethod* old; 4400 do { 4401 old = (nmethod*)_postponed_list; 4402 nm->set_unloading_next(old); 4403 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 4404 } 4405 4406 void clean_nmethod(nmethod* nm) { 4407 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 4408 4409 if (postponed) { 4410 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 4411 add_to_postponed_list(nm); 4412 } 4413 4414 // Mark that this thread has been cleaned/unloaded. 4415 // After this call, it will be safe to ask if this nmethod was unloaded or not. 4416 nm->set_unloading_clock(nmethod::global_unloading_clock()); 4417 } 4418 4419 void clean_nmethod_postponed(nmethod* nm) { 4420 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 4421 } 4422 4423 static const int MaxClaimNmethods = 16; 4424 4425 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) { 4426 nmethod* first; 4427 NMethodIterator last; 4428 4429 do { 4430 *num_claimed_nmethods = 0; 4431 4432 first = (nmethod*)_claimed_nmethod; 4433 last = NMethodIterator(first); 4434 4435 if (first != NULL) { 4436 4437 for (int i = 0; i < MaxClaimNmethods; i++) { 4438 if (!last.next_alive()) { 4439 break; 4440 } 4441 claimed_nmethods[i] = last.method(); 4442 (*num_claimed_nmethods)++; 4443 } 4444 } 4445 4446 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 4447 } 4448 4449 nmethod* claim_postponed_nmethod() { 4450 nmethod* claim; 4451 nmethod* next; 4452 4453 do { 4454 claim = (nmethod*)_postponed_list; 4455 if (claim == NULL) { 4456 return NULL; 4457 } 4458 4459 next = claim->unloading_next(); 4460 4461 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 4462 4463 return claim; 4464 } 4465 4466 public: 4467 // Mark that we're done with the first pass of nmethod cleaning. 4468 void barrier_mark(uint worker_id) { 4469 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4470 _num_entered_barrier++; 4471 if (_num_entered_barrier == _num_workers) { 4472 ml.notify_all(); 4473 } 4474 } 4475 4476 // See if we have to wait for the other workers to 4477 // finish their first-pass nmethod cleaning work. 4478 void barrier_wait(uint worker_id) { 4479 if (_num_entered_barrier < _num_workers) { 4480 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4481 while (_num_entered_barrier < _num_workers) { 4482 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 4483 } 4484 } 4485 } 4486 4487 // Cleaning and unloading of nmethods. Some work has to be postponed 4488 // to the second pass, when we know which nmethods survive. 4489 void work_first_pass(uint worker_id) { 4490 // The first nmethods is claimed by the first worker. 4491 if (worker_id == 0 && _first_nmethod != NULL) { 4492 clean_nmethod(_first_nmethod); 4493 _first_nmethod = NULL; 4494 } 4495 4496 int num_claimed_nmethods; 4497 nmethod* claimed_nmethods[MaxClaimNmethods]; 4498 4499 while (true) { 4500 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 4501 4502 if (num_claimed_nmethods == 0) { 4503 break; 4504 } 4505 4506 for (int i = 0; i < num_claimed_nmethods; i++) { 4507 clean_nmethod(claimed_nmethods[i]); 4508 } 4509 } 4510 } 4511 4512 void work_second_pass(uint worker_id) { 4513 nmethod* nm; 4514 // Take care of postponed nmethods. 4515 while ((nm = claim_postponed_nmethod()) != NULL) { 4516 clean_nmethod_postponed(nm); 4517 } 4518 } 4519 }; 4520 4521 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 4522 4523 class G1KlassCleaningTask : public StackObj { 4524 BoolObjectClosure* _is_alive; 4525 volatile jint _clean_klass_tree_claimed; 4526 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 4527 4528 public: 4529 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 4530 _is_alive(is_alive), 4531 _clean_klass_tree_claimed(0), 4532 _klass_iterator() { 4533 } 4534 4535 private: 4536 bool claim_clean_klass_tree_task() { 4537 if (_clean_klass_tree_claimed) { 4538 return false; 4539 } 4540 4541 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 4542 } 4543 4544 InstanceKlass* claim_next_klass() { 4545 Klass* klass; 4546 do { 4547 klass =_klass_iterator.next_klass(); 4548 } while (klass != NULL && !klass->is_instance_klass()); 4549 4550 // this can be null so don't call InstanceKlass::cast 4551 return static_cast<InstanceKlass*>(klass); 4552 } 4553 4554 public: 4555 4556 void clean_klass(InstanceKlass* ik) { 4557 ik->clean_weak_instanceklass_links(_is_alive); 4558 } 4559 4560 void work() { 4561 ResourceMark rm; 4562 4563 // One worker will clean the subklass/sibling klass tree. 4564 if (claim_clean_klass_tree_task()) { 4565 Klass::clean_subklass_tree(_is_alive); 4566 } 4567 4568 // All workers will help cleaning the classes, 4569 InstanceKlass* klass; 4570 while ((klass = claim_next_klass()) != NULL) { 4571 clean_klass(klass); 4572 } 4573 } 4574 }; 4575 4576 // To minimize the remark pause times, the tasks below are done in parallel. 4577 class G1ParallelCleaningTask : public AbstractGangTask { 4578 private: 4579 G1StringSymbolTableUnlinkTask _string_symbol_task; 4580 G1CodeCacheUnloadingTask _code_cache_task; 4581 G1KlassCleaningTask _klass_cleaning_task; 4582 4583 public: 4584 // The constructor is run in the VMThread. 4585 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 4586 AbstractGangTask("Parallel Cleaning"), 4587 _string_symbol_task(is_alive, process_strings, process_symbols), 4588 _code_cache_task(num_workers, is_alive, unloading_occurred), 4589 _klass_cleaning_task(is_alive) { 4590 } 4591 4592 // The parallel work done by all worker threads. 4593 void work(uint worker_id) { 4594 // Do first pass of code cache cleaning. 4595 _code_cache_task.work_first_pass(worker_id); 4596 4597 // Let the threads mark that the first pass is done. 4598 _code_cache_task.barrier_mark(worker_id); 4599 4600 // Clean the Strings and Symbols. 4601 _string_symbol_task.work(worker_id); 4602 4603 // Wait for all workers to finish the first code cache cleaning pass. 4604 _code_cache_task.barrier_wait(worker_id); 4605 4606 // Do the second code cache cleaning work, which realize on 4607 // the liveness information gathered during the first pass. 4608 _code_cache_task.work_second_pass(worker_id); 4609 4610 // Clean all klasses that were not unloaded. 4611 _klass_cleaning_task.work(); 4612 } 4613 }; 4614 4615 4616 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 4617 bool process_strings, 4618 bool process_symbols, 4619 bool class_unloading_occurred) { 4620 uint n_workers = workers()->active_workers(); 4621 4622 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 4623 n_workers, class_unloading_occurred); 4624 workers()->run_task(&g1_unlink_task); 4625 } 4626 4627 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 4628 bool process_strings, bool process_symbols) { 4629 { 4630 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 4631 workers()->run_task(&g1_unlink_task); 4632 } 4633 4634 if (G1StringDedup::is_enabled()) { 4635 G1StringDedup::unlink(is_alive); 4636 } 4637 } 4638 4639 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 4640 private: 4641 DirtyCardQueueSet* _queue; 4642 public: 4643 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { } 4644 4645 virtual void work(uint worker_id) { 4646 G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4647 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 4648 4649 RedirtyLoggedCardTableEntryClosure cl; 4650 _queue->par_apply_closure_to_all_completed_buffers(&cl); 4651 4652 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed()); 4653 } 4654 }; 4655 4656 void G1CollectedHeap::redirty_logged_cards() { 4657 double redirty_logged_cards_start = os::elapsedTime(); 4658 4659 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set()); 4660 dirty_card_queue_set().reset_for_par_iteration(); 4661 workers()->run_task(&redirty_task); 4662 4663 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 4664 dcq.merge_bufferlists(&dirty_card_queue_set()); 4665 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 4666 4667 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 4668 } 4669 4670 // Weak Reference Processing support 4671 4672 // An always "is_alive" closure that is used to preserve referents. 4673 // If the object is non-null then it's alive. Used in the preservation 4674 // of referent objects that are pointed to by reference objects 4675 // discovered by the CM ref processor. 4676 class G1AlwaysAliveClosure: public BoolObjectClosure { 4677 G1CollectedHeap* _g1; 4678 public: 4679 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4680 bool do_object_b(oop p) { 4681 if (p != NULL) { 4682 return true; 4683 } 4684 return false; 4685 } 4686 }; 4687 4688 bool G1STWIsAliveClosure::do_object_b(oop p) { 4689 // An object is reachable if it is outside the collection set, 4690 // or is inside and copied. 4691 return !_g1->is_in_cset(p) || p->is_forwarded(); 4692 } 4693 4694 // Non Copying Keep Alive closure 4695 class G1KeepAliveClosure: public OopClosure { 4696 G1CollectedHeap* _g1; 4697 public: 4698 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4699 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 4700 void do_oop(oop* p) { 4701 oop obj = *p; 4702 assert(obj != NULL, "the caller should have filtered out NULL values"); 4703 4704 const InCSetState cset_state = _g1->in_cset_state(obj); 4705 if (!cset_state.is_in_cset_or_humongous()) { 4706 return; 4707 } 4708 if (cset_state.is_in_cset()) { 4709 assert( obj->is_forwarded(), "invariant" ); 4710 *p = obj->forwardee(); 4711 } else { 4712 assert(!obj->is_forwarded(), "invariant" ); 4713 assert(cset_state.is_humongous(), 4714 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 4715 _g1->set_humongous_is_live(obj); 4716 } 4717 } 4718 }; 4719 4720 // Copying Keep Alive closure - can be called from both 4721 // serial and parallel code as long as different worker 4722 // threads utilize different G1ParScanThreadState instances 4723 // and different queues. 4724 4725 class G1CopyingKeepAliveClosure: public OopClosure { 4726 G1CollectedHeap* _g1h; 4727 OopClosure* _copy_non_heap_obj_cl; 4728 G1ParScanThreadState* _par_scan_state; 4729 4730 public: 4731 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4732 OopClosure* non_heap_obj_cl, 4733 G1ParScanThreadState* pss): 4734 _g1h(g1h), 4735 _copy_non_heap_obj_cl(non_heap_obj_cl), 4736 _par_scan_state(pss) 4737 {} 4738 4739 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4740 virtual void do_oop( oop* p) { do_oop_work(p); } 4741 4742 template <class T> void do_oop_work(T* p) { 4743 oop obj = oopDesc::load_decode_heap_oop(p); 4744 4745 if (_g1h->is_in_cset_or_humongous(obj)) { 4746 // If the referent object has been forwarded (either copied 4747 // to a new location or to itself in the event of an 4748 // evacuation failure) then we need to update the reference 4749 // field and, if both reference and referent are in the G1 4750 // heap, update the RSet for the referent. 4751 // 4752 // If the referent has not been forwarded then we have to keep 4753 // it alive by policy. Therefore we have copy the referent. 4754 // 4755 // If the reference field is in the G1 heap then we can push 4756 // on the PSS queue. When the queue is drained (after each 4757 // phase of reference processing) the object and it's followers 4758 // will be copied, the reference field set to point to the 4759 // new location, and the RSet updated. Otherwise we need to 4760 // use the the non-heap or metadata closures directly to copy 4761 // the referent object and update the pointer, while avoiding 4762 // updating the RSet. 4763 4764 if (_g1h->is_in_g1_reserved(p)) { 4765 _par_scan_state->push_on_queue(p); 4766 } else { 4767 assert(!Metaspace::contains((const void*)p), 4768 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4769 _copy_non_heap_obj_cl->do_oop(p); 4770 } 4771 } 4772 } 4773 }; 4774 4775 // Serial drain queue closure. Called as the 'complete_gc' 4776 // closure for each discovered list in some of the 4777 // reference processing phases. 4778 4779 class G1STWDrainQueueClosure: public VoidClosure { 4780 protected: 4781 G1CollectedHeap* _g1h; 4782 G1ParScanThreadState* _par_scan_state; 4783 4784 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4785 4786 public: 4787 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4788 _g1h(g1h), 4789 _par_scan_state(pss) 4790 { } 4791 4792 void do_void() { 4793 G1ParScanThreadState* const pss = par_scan_state(); 4794 pss->trim_queue(); 4795 } 4796 }; 4797 4798 // Parallel Reference Processing closures 4799 4800 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4801 // processing during G1 evacuation pauses. 4802 4803 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4804 private: 4805 G1CollectedHeap* _g1h; 4806 G1ParScanThreadStateSet* _pss; 4807 RefToScanQueueSet* _queues; 4808 WorkGang* _workers; 4809 uint _active_workers; 4810 4811 public: 4812 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4813 G1ParScanThreadStateSet* per_thread_states, 4814 WorkGang* workers, 4815 RefToScanQueueSet *task_queues, 4816 uint n_workers) : 4817 _g1h(g1h), 4818 _pss(per_thread_states), 4819 _queues(task_queues), 4820 _workers(workers), 4821 _active_workers(n_workers) 4822 { 4823 assert(n_workers > 0, "shouldn't call this otherwise"); 4824 } 4825 4826 // Executes the given task using concurrent marking worker threads. 4827 virtual void execute(ProcessTask& task); 4828 virtual void execute(EnqueueTask& task); 4829 }; 4830 4831 // Gang task for possibly parallel reference processing 4832 4833 class G1STWRefProcTaskProxy: public AbstractGangTask { 4834 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4835 ProcessTask& _proc_task; 4836 G1CollectedHeap* _g1h; 4837 G1ParScanThreadStateSet* _pss; 4838 RefToScanQueueSet* _task_queues; 4839 ParallelTaskTerminator* _terminator; 4840 4841 public: 4842 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4843 G1CollectedHeap* g1h, 4844 G1ParScanThreadStateSet* per_thread_states, 4845 RefToScanQueueSet *task_queues, 4846 ParallelTaskTerminator* terminator) : 4847 AbstractGangTask("Process reference objects in parallel"), 4848 _proc_task(proc_task), 4849 _g1h(g1h), 4850 _pss(per_thread_states), 4851 _task_queues(task_queues), 4852 _terminator(terminator) 4853 {} 4854 4855 virtual void work(uint worker_id) { 4856 // The reference processing task executed by a single worker. 4857 ResourceMark rm; 4858 HandleMark hm; 4859 4860 G1STWIsAliveClosure is_alive(_g1h); 4861 4862 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4863 pss->set_ref_processor(NULL); 4864 4865 // Keep alive closure. 4866 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4867 4868 // Complete GC closure 4869 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4870 4871 // Call the reference processing task's work routine. 4872 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4873 4874 // Note we cannot assert that the refs array is empty here as not all 4875 // of the processing tasks (specifically phase2 - pp2_work) execute 4876 // the complete_gc closure (which ordinarily would drain the queue) so 4877 // the queue may not be empty. 4878 } 4879 }; 4880 4881 // Driver routine for parallel reference processing. 4882 // Creates an instance of the ref processing gang 4883 // task and has the worker threads execute it. 4884 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4885 assert(_workers != NULL, "Need parallel worker threads."); 4886 4887 ParallelTaskTerminator terminator(_active_workers, _queues); 4888 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4889 4890 _workers->run_task(&proc_task_proxy); 4891 } 4892 4893 // Gang task for parallel reference enqueueing. 4894 4895 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4896 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4897 EnqueueTask& _enq_task; 4898 4899 public: 4900 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4901 AbstractGangTask("Enqueue reference objects in parallel"), 4902 _enq_task(enq_task) 4903 { } 4904 4905 virtual void work(uint worker_id) { 4906 _enq_task.work(worker_id); 4907 } 4908 }; 4909 4910 // Driver routine for parallel reference enqueueing. 4911 // Creates an instance of the ref enqueueing gang 4912 // task and has the worker threads execute it. 4913 4914 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4915 assert(_workers != NULL, "Need parallel worker threads."); 4916 4917 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4918 4919 _workers->run_task(&enq_task_proxy); 4920 } 4921 4922 // End of weak reference support closures 4923 4924 // Abstract task used to preserve (i.e. copy) any referent objects 4925 // that are in the collection set and are pointed to by reference 4926 // objects discovered by the CM ref processor. 4927 4928 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4929 protected: 4930 G1CollectedHeap* _g1h; 4931 G1ParScanThreadStateSet* _pss; 4932 RefToScanQueueSet* _queues; 4933 ParallelTaskTerminator _terminator; 4934 uint _n_workers; 4935 4936 public: 4937 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4938 AbstractGangTask("ParPreserveCMReferents"), 4939 _g1h(g1h), 4940 _pss(per_thread_states), 4941 _queues(task_queues), 4942 _terminator(workers, _queues), 4943 _n_workers(workers) 4944 { } 4945 4946 void work(uint worker_id) { 4947 ResourceMark rm; 4948 HandleMark hm; 4949 4950 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4951 pss->set_ref_processor(NULL); 4952 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4953 4954 // Is alive closure 4955 G1AlwaysAliveClosure always_alive(_g1h); 4956 4957 // Copying keep alive closure. Applied to referent objects that need 4958 // to be copied. 4959 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4960 4961 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4962 4963 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4964 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4965 4966 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4967 // So this must be true - but assert just in case someone decides to 4968 // change the worker ids. 4969 assert(worker_id < limit, "sanity"); 4970 assert(!rp->discovery_is_atomic(), "check this code"); 4971 4972 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4973 for (uint idx = worker_id; idx < limit; idx += stride) { 4974 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4975 4976 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4977 while (iter.has_next()) { 4978 // Since discovery is not atomic for the CM ref processor, we 4979 // can see some null referent objects. 4980 iter.load_ptrs(DEBUG_ONLY(true)); 4981 oop ref = iter.obj(); 4982 4983 // This will filter nulls. 4984 if (iter.is_referent_alive()) { 4985 iter.make_referent_alive(); 4986 } 4987 iter.move_to_next(); 4988 } 4989 } 4990 4991 // Drain the queue - which may cause stealing 4992 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4993 drain_queue.do_void(); 4994 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4995 assert(pss->queue_is_empty(), "should be"); 4996 } 4997 }; 4998 4999 // Weak Reference processing during an evacuation pause (part 1). 5000 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 5001 double ref_proc_start = os::elapsedTime(); 5002 5003 ReferenceProcessor* rp = _ref_processor_stw; 5004 assert(rp->discovery_enabled(), "should have been enabled"); 5005 5006 // Any reference objects, in the collection set, that were 'discovered' 5007 // by the CM ref processor should have already been copied (either by 5008 // applying the external root copy closure to the discovered lists, or 5009 // by following an RSet entry). 5010 // 5011 // But some of the referents, that are in the collection set, that these 5012 // reference objects point to may not have been copied: the STW ref 5013 // processor would have seen that the reference object had already 5014 // been 'discovered' and would have skipped discovering the reference, 5015 // but would not have treated the reference object as a regular oop. 5016 // As a result the copy closure would not have been applied to the 5017 // referent object. 5018 // 5019 // We need to explicitly copy these referent objects - the references 5020 // will be processed at the end of remarking. 5021 // 5022 // We also need to do this copying before we process the reference 5023 // objects discovered by the STW ref processor in case one of these 5024 // referents points to another object which is also referenced by an 5025 // object discovered by the STW ref processor. 5026 5027 uint no_of_gc_workers = workers()->active_workers(); 5028 5029 G1ParPreserveCMReferentsTask keep_cm_referents(this, 5030 per_thread_states, 5031 no_of_gc_workers, 5032 _task_queues); 5033 5034 workers()->run_task(&keep_cm_referents); 5035 5036 // Closure to test whether a referent is alive. 5037 G1STWIsAliveClosure is_alive(this); 5038 5039 // Even when parallel reference processing is enabled, the processing 5040 // of JNI refs is serial and performed serially by the current thread 5041 // rather than by a worker. The following PSS will be used for processing 5042 // JNI refs. 5043 5044 // Use only a single queue for this PSS. 5045 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 5046 pss->set_ref_processor(NULL); 5047 assert(pss->queue_is_empty(), "pre-condition"); 5048 5049 // Keep alive closure. 5050 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 5051 5052 // Serial Complete GC closure 5053 G1STWDrainQueueClosure drain_queue(this, pss); 5054 5055 // Setup the soft refs policy... 5056 rp->setup_policy(false); 5057 5058 ReferenceProcessorStats stats; 5059 if (!rp->processing_is_mt()) { 5060 // Serial reference processing... 5061 stats = rp->process_discovered_references(&is_alive, 5062 &keep_alive, 5063 &drain_queue, 5064 NULL, 5065 _gc_timer_stw); 5066 } else { 5067 // Parallel reference processing 5068 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5069 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5070 5071 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 5072 stats = rp->process_discovered_references(&is_alive, 5073 &keep_alive, 5074 &drain_queue, 5075 &par_task_executor, 5076 _gc_timer_stw); 5077 } 5078 5079 _gc_tracer_stw->report_gc_reference_stats(stats); 5080 5081 // We have completed copying any necessary live referent objects. 5082 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 5083 5084 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5085 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 5086 } 5087 5088 // Weak Reference processing during an evacuation pause (part 2). 5089 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 5090 double ref_enq_start = os::elapsedTime(); 5091 5092 ReferenceProcessor* rp = _ref_processor_stw; 5093 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5094 5095 // Now enqueue any remaining on the discovered lists on to 5096 // the pending list. 5097 if (!rp->processing_is_mt()) { 5098 // Serial reference processing... 5099 rp->enqueue_discovered_references(); 5100 } else { 5101 // Parallel reference enqueueing 5102 5103 uint n_workers = workers()->active_workers(); 5104 5105 assert(rp->num_q() == n_workers, "sanity"); 5106 assert(n_workers <= rp->max_num_q(), "sanity"); 5107 5108 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 5109 rp->enqueue_discovered_references(&par_task_executor); 5110 } 5111 5112 rp->verify_no_references_recorded(); 5113 assert(!rp->discovery_enabled(), "should have been disabled"); 5114 5115 // FIXME 5116 // CM's reference processing also cleans up the string and symbol tables. 5117 // Should we do that here also? We could, but it is a serial operation 5118 // and could significantly increase the pause time. 5119 5120 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5121 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5122 } 5123 5124 void G1CollectedHeap::pre_evacuate_collection_set() { 5125 _expand_heap_after_alloc_failure = true; 5126 _evacuation_failed = false; 5127 5128 // Disable the hot card cache. 5129 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5130 hot_card_cache->reset_hot_cache_claimed_index(); 5131 hot_card_cache->set_use_cache(false); 5132 5133 } 5134 5135 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 5136 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5137 5138 // Should G1EvacuationFailureALot be in effect for this GC? 5139 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5140 5141 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5142 double start_par_time_sec = os::elapsedTime(); 5143 double end_par_time_sec; 5144 5145 { 5146 const uint n_workers = workers()->active_workers(); 5147 G1RootProcessor root_processor(this, n_workers); 5148 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 5149 // InitialMark needs claim bits to keep track of the marked-through CLDs. 5150 if (collector_state()->during_initial_mark_pause()) { 5151 ClassLoaderDataGraph::clear_claimed_marks(); 5152 } 5153 5154 // The individual threads will set their evac-failure closures. 5155 if (PrintTerminationStats) { 5156 print_termination_stats_hdr(gclog_or_tty); 5157 } 5158 5159 workers()->run_task(&g1_par_task); 5160 end_par_time_sec = os::elapsedTime(); 5161 5162 // Closing the inner scope will execute the destructor 5163 // for the G1RootProcessor object. We record the current 5164 // elapsed time before closing the scope so that time 5165 // taken for the destructor is NOT included in the 5166 // reported parallel time. 5167 } 5168 5169 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 5170 5171 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5172 phase_times->record_par_time(par_time_ms); 5173 5174 double code_root_fixup_time_ms = 5175 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5176 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 5177 5178 // Process any discovered reference objects - we have 5179 // to do this _before_ we retire the GC alloc regions 5180 // as we may have to copy some 'reachable' referent 5181 // objects (and their reachable sub-graphs) that were 5182 // not copied during the pause. 5183 process_discovered_references(per_thread_states); 5184 5185 if (G1StringDedup::is_enabled()) { 5186 double fixup_start = os::elapsedTime(); 5187 5188 G1STWIsAliveClosure is_alive(this); 5189 G1KeepAliveClosure keep_alive(this); 5190 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times); 5191 5192 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 5193 phase_times->record_string_dedup_fixup_time(fixup_time_ms); 5194 } 5195 5196 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5197 5198 if (evacuation_failed()) { 5199 remove_self_forwarding_pointers(); 5200 5201 // Reset the G1EvacuationFailureALot counters and flags 5202 // Note: the values are reset only when an actual 5203 // evacuation failure occurs. 5204 NOT_PRODUCT(reset_evacuation_should_fail();) 5205 } 5206 5207 // Enqueue any remaining references remaining on the STW 5208 // reference processor's discovered lists. We need to do 5209 // this after the card table is cleaned (and verified) as 5210 // the act of enqueueing entries on to the pending list 5211 // will log these updates (and dirty their associated 5212 // cards). We need these updates logged to update any 5213 // RSets. 5214 enqueue_discovered_references(per_thread_states); 5215 } 5216 5217 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 5218 _allocator->release_gc_alloc_regions(evacuation_info); 5219 5220 per_thread_states->flush(); 5221 5222 record_obj_copy_mem_stats(); 5223 5224 _survivor_evac_stats.adjust_desired_plab_sz(); 5225 _old_evac_stats.adjust_desired_plab_sz(); 5226 5227 // Reset and re-enable the hot card cache. 5228 // Note the counts for the cards in the regions in the 5229 // collection set are reset when the collection set is freed. 5230 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5231 hot_card_cache->reset_hot_cache(); 5232 hot_card_cache->set_use_cache(true); 5233 5234 purge_code_root_memory(); 5235 5236 redirty_logged_cards(); 5237 #if defined(COMPILER2) || INCLUDE_JVMCI 5238 DerivedPointerTable::update_pointers(); 5239 #endif 5240 } 5241 5242 void G1CollectedHeap::record_obj_copy_mem_stats() { 5243 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 5244 create_g1_evac_summary(&_old_evac_stats)); 5245 } 5246 5247 void G1CollectedHeap::free_region(HeapRegion* hr, 5248 FreeRegionList* free_list, 5249 bool par, 5250 bool locked) { 5251 assert(!hr->is_free(), "the region should not be free"); 5252 assert(!hr->is_empty(), "the region should not be empty"); 5253 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 5254 assert(free_list != NULL, "pre-condition"); 5255 5256 if (G1VerifyBitmaps) { 5257 MemRegion mr(hr->bottom(), hr->end()); 5258 concurrent_mark()->clearRangePrevBitmap(mr); 5259 } 5260 5261 // Clear the card counts for this region. 5262 // Note: we only need to do this if the region is not young 5263 // (since we don't refine cards in young regions). 5264 if (!hr->is_young()) { 5265 _cg1r->hot_card_cache()->reset_card_counts(hr); 5266 } 5267 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 5268 free_list->add_ordered(hr); 5269 } 5270 5271 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5272 FreeRegionList* free_list, 5273 bool par) { 5274 assert(hr->is_humongous(), "this is only for humongous regions"); 5275 assert(free_list != NULL, "pre-condition"); 5276 hr->clear_humongous(); 5277 free_region(hr, free_list, par); 5278 } 5279 5280 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, 5281 const HeapRegionSetCount& humongous_regions_removed) { 5282 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) { 5283 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5284 _old_set.bulk_remove(old_regions_removed); 5285 _humongous_set.bulk_remove(humongous_regions_removed); 5286 } 5287 5288 } 5289 5290 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 5291 assert(list != NULL, "list can't be null"); 5292 if (!list->is_empty()) { 5293 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 5294 _hrm.insert_list_into_free_list(list); 5295 } 5296 } 5297 5298 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 5299 decrease_used(bytes); 5300 } 5301 5302 class G1ParCleanupCTTask : public AbstractGangTask { 5303 G1SATBCardTableModRefBS* _ct_bs; 5304 G1CollectedHeap* _g1h; 5305 HeapRegion* volatile _su_head; 5306 public: 5307 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 5308 G1CollectedHeap* g1h) : 5309 AbstractGangTask("G1 Par Cleanup CT Task"), 5310 _ct_bs(ct_bs), _g1h(g1h) { } 5311 5312 void work(uint worker_id) { 5313 HeapRegion* r; 5314 while (r = _g1h->pop_dirty_cards_region()) { 5315 clear_cards(r); 5316 } 5317 } 5318 5319 void clear_cards(HeapRegion* r) { 5320 // Cards of the survivors should have already been dirtied. 5321 if (!r->is_survivor()) { 5322 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 5323 } 5324 } 5325 }; 5326 5327 #ifndef PRODUCT 5328 class G1VerifyCardTableCleanup: public HeapRegionClosure { 5329 G1CollectedHeap* _g1h; 5330 G1SATBCardTableModRefBS* _ct_bs; 5331 public: 5332 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs) 5333 : _g1h(g1h), _ct_bs(ct_bs) { } 5334 virtual bool doHeapRegion(HeapRegion* r) { 5335 if (r->is_survivor()) { 5336 _g1h->verify_dirty_region(r); 5337 } else { 5338 _g1h->verify_not_dirty_region(r); 5339 } 5340 return false; 5341 } 5342 }; 5343 5344 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 5345 // All of the region should be clean. 5346 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5347 MemRegion mr(hr->bottom(), hr->end()); 5348 ct_bs->verify_not_dirty_region(mr); 5349 } 5350 5351 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 5352 // We cannot guarantee that [bottom(),end()] is dirty. Threads 5353 // dirty allocated blocks as they allocate them. The thread that 5354 // retires each region and replaces it with a new one will do a 5355 // maximal allocation to fill in [pre_dummy_top(),end()] but will 5356 // not dirty that area (one less thing to have to do while holding 5357 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 5358 // is dirty. 5359 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5360 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 5361 if (hr->is_young()) { 5362 ct_bs->verify_g1_young_region(mr); 5363 } else { 5364 ct_bs->verify_dirty_region(mr); 5365 } 5366 } 5367 5368 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 5369 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5370 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 5371 verify_dirty_region(hr); 5372 } 5373 } 5374 5375 void G1CollectedHeap::verify_dirty_young_regions() { 5376 verify_dirty_young_list(_young_list->first_region()); 5377 } 5378 5379 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 5380 HeapWord* tams, HeapWord* end) { 5381 guarantee(tams <= end, 5382 "tams: " PTR_FORMAT " end: " PTR_FORMAT, p2i(tams), p2i(end)); 5383 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end); 5384 if (result < end) { 5385 gclog_or_tty->cr(); 5386 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: " PTR_FORMAT, 5387 bitmap_name, p2i(result)); 5388 gclog_or_tty->print_cr("## %s tams: " PTR_FORMAT " end: " PTR_FORMAT, 5389 bitmap_name, p2i(tams), p2i(end)); 5390 return false; 5391 } 5392 return true; 5393 } 5394 5395 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) { 5396 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap(); 5397 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap(); 5398 5399 HeapWord* bottom = hr->bottom(); 5400 HeapWord* ptams = hr->prev_top_at_mark_start(); 5401 HeapWord* ntams = hr->next_top_at_mark_start(); 5402 HeapWord* end = hr->end(); 5403 5404 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end); 5405 5406 bool res_n = true; 5407 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window 5408 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap 5409 // if we happen to be in that state. 5410 if (collector_state()->mark_in_progress() || !_cmThread->in_progress()) { 5411 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end); 5412 } 5413 if (!res_p || !res_n) { 5414 gclog_or_tty->print_cr("#### Bitmap verification failed for " HR_FORMAT, 5415 HR_FORMAT_PARAMS(hr)); 5416 gclog_or_tty->print_cr("#### Caller: %s", caller); 5417 return false; 5418 } 5419 return true; 5420 } 5421 5422 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) { 5423 if (!G1VerifyBitmaps) return; 5424 5425 guarantee(verify_bitmaps(caller, hr), "bitmap verification"); 5426 } 5427 5428 class G1VerifyBitmapClosure : public HeapRegionClosure { 5429 private: 5430 const char* _caller; 5431 G1CollectedHeap* _g1h; 5432 bool _failures; 5433 5434 public: 5435 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) : 5436 _caller(caller), _g1h(g1h), _failures(false) { } 5437 5438 bool failures() { return _failures; } 5439 5440 virtual bool doHeapRegion(HeapRegion* hr) { 5441 bool result = _g1h->verify_bitmaps(_caller, hr); 5442 if (!result) { 5443 _failures = true; 5444 } 5445 return false; 5446 } 5447 }; 5448 5449 void G1CollectedHeap::check_bitmaps(const char* caller) { 5450 if (!G1VerifyBitmaps) return; 5451 5452 G1VerifyBitmapClosure cl(caller, this); 5453 heap_region_iterate(&cl); 5454 guarantee(!cl.failures(), "bitmap verification"); 5455 } 5456 5457 class G1CheckCSetFastTableClosure : public HeapRegionClosure { 5458 private: 5459 bool _failures; 5460 public: 5461 G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { } 5462 5463 virtual bool doHeapRegion(HeapRegion* hr) { 5464 uint i = hr->hrm_index(); 5465 InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i); 5466 if (hr->is_humongous()) { 5467 if (hr->in_collection_set()) { 5468 gclog_or_tty->print_cr("\n## humongous region %u in CSet", i); 5469 _failures = true; 5470 return true; 5471 } 5472 if (cset_state.is_in_cset()) { 5473 gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i); 5474 _failures = true; 5475 return true; 5476 } 5477 if (hr->is_continues_humongous() && cset_state.is_humongous()) { 5478 gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i); 5479 _failures = true; 5480 return true; 5481 } 5482 } else { 5483 if (cset_state.is_humongous()) { 5484 gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i); 5485 _failures = true; 5486 return true; 5487 } 5488 if (hr->in_collection_set() != cset_state.is_in_cset()) { 5489 gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u", 5490 hr->in_collection_set(), cset_state.value(), i); 5491 _failures = true; 5492 return true; 5493 } 5494 if (cset_state.is_in_cset()) { 5495 if (hr->is_young() != (cset_state.is_young())) { 5496 gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u", 5497 hr->is_young(), cset_state.value(), i); 5498 _failures = true; 5499 return true; 5500 } 5501 if (hr->is_old() != (cset_state.is_old())) { 5502 gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u", 5503 hr->is_old(), cset_state.value(), i); 5504 _failures = true; 5505 return true; 5506 } 5507 } 5508 } 5509 return false; 5510 } 5511 5512 bool failures() const { return _failures; } 5513 }; 5514 5515 bool G1CollectedHeap::check_cset_fast_test() { 5516 G1CheckCSetFastTableClosure cl; 5517 _hrm.iterate(&cl); 5518 return !cl.failures(); 5519 } 5520 #endif // PRODUCT 5521 5522 void G1CollectedHeap::cleanUpCardTable() { 5523 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5524 double start = os::elapsedTime(); 5525 5526 { 5527 // Iterate over the dirty cards region list. 5528 G1ParCleanupCTTask cleanup_task(ct_bs, this); 5529 5530 workers()->run_task(&cleanup_task); 5531 #ifndef PRODUCT 5532 if (G1VerifyCTCleanup || VerifyAfterGC) { 5533 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 5534 heap_region_iterate(&cleanup_verifier); 5535 } 5536 #endif 5537 } 5538 5539 double elapsed = os::elapsedTime() - start; 5540 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 5541 } 5542 5543 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 5544 size_t pre_used = 0; 5545 FreeRegionList local_free_list("Local List for CSet Freeing"); 5546 5547 double young_time_ms = 0.0; 5548 double non_young_time_ms = 0.0; 5549 5550 // Since the collection set is a superset of the the young list, 5551 // all we need to do to clear the young list is clear its 5552 // head and length, and unlink any young regions in the code below 5553 _young_list->clear(); 5554 5555 G1CollectorPolicy* policy = g1_policy(); 5556 5557 double start_sec = os::elapsedTime(); 5558 bool non_young = true; 5559 5560 HeapRegion* cur = cs_head; 5561 int age_bound = -1; 5562 size_t rs_lengths = 0; 5563 5564 while (cur != NULL) { 5565 assert(!is_on_master_free_list(cur), "sanity"); 5566 if (non_young) { 5567 if (cur->is_young()) { 5568 double end_sec = os::elapsedTime(); 5569 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5570 non_young_time_ms += elapsed_ms; 5571 5572 start_sec = os::elapsedTime(); 5573 non_young = false; 5574 } 5575 } else { 5576 if (!cur->is_young()) { 5577 double end_sec = os::elapsedTime(); 5578 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5579 young_time_ms += elapsed_ms; 5580 5581 start_sec = os::elapsedTime(); 5582 non_young = true; 5583 } 5584 } 5585 5586 rs_lengths += cur->rem_set()->occupied_locked(); 5587 5588 HeapRegion* next = cur->next_in_collection_set(); 5589 assert(cur->in_collection_set(), "bad CS"); 5590 cur->set_next_in_collection_set(NULL); 5591 clear_in_cset(cur); 5592 5593 if (cur->is_young()) { 5594 int index = cur->young_index_in_cset(); 5595 assert(index != -1, "invariant"); 5596 assert((uint) index < policy->young_cset_region_length(), "invariant"); 5597 size_t words_survived = surviving_young_words[index]; 5598 cur->record_surv_words_in_group(words_survived); 5599 5600 // At this point the we have 'popped' cur from the collection set 5601 // (linked via next_in_collection_set()) but it is still in the 5602 // young list (linked via next_young_region()). Clear the 5603 // _next_young_region field. 5604 cur->set_next_young_region(NULL); 5605 } else { 5606 int index = cur->young_index_in_cset(); 5607 assert(index == -1, "invariant"); 5608 } 5609 5610 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 5611 (!cur->is_young() && cur->young_index_in_cset() == -1), 5612 "invariant" ); 5613 5614 if (!cur->evacuation_failed()) { 5615 MemRegion used_mr = cur->used_region(); 5616 5617 // And the region is empty. 5618 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 5619 pre_used += cur->used(); 5620 free_region(cur, &local_free_list, false /* par */, true /* locked */); 5621 } else { 5622 cur->uninstall_surv_rate_group(); 5623 if (cur->is_young()) { 5624 cur->set_young_index_in_cset(-1); 5625 } 5626 cur->set_evacuation_failed(false); 5627 // The region is now considered to be old. 5628 cur->set_old(); 5629 // Do some allocation statistics accounting. Regions that failed evacuation 5630 // are always made old, so there is no need to update anything in the young 5631 // gen statistics, but we need to update old gen statistics. 5632 size_t used_words = cur->marked_bytes() / HeapWordSize; 5633 _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words); 5634 _old_set.add(cur); 5635 evacuation_info.increment_collectionset_used_after(cur->used()); 5636 } 5637 cur = next; 5638 } 5639 5640 evacuation_info.set_regions_freed(local_free_list.length()); 5641 policy->record_max_rs_lengths(rs_lengths); 5642 policy->cset_regions_freed(); 5643 5644 double end_sec = os::elapsedTime(); 5645 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5646 5647 if (non_young) { 5648 non_young_time_ms += elapsed_ms; 5649 } else { 5650 young_time_ms += elapsed_ms; 5651 } 5652 5653 prepend_to_freelist(&local_free_list); 5654 decrement_summary_bytes(pre_used); 5655 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 5656 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 5657 } 5658 5659 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 5660 private: 5661 FreeRegionList* _free_region_list; 5662 HeapRegionSet* _proxy_set; 5663 HeapRegionSetCount _humongous_regions_removed; 5664 size_t _freed_bytes; 5665 public: 5666 5667 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 5668 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) { 5669 } 5670 5671 virtual bool doHeapRegion(HeapRegion* r) { 5672 if (!r->is_starts_humongous()) { 5673 return false; 5674 } 5675 5676 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 5677 5678 oop obj = (oop)r->bottom(); 5679 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 5680 5681 // The following checks whether the humongous object is live are sufficient. 5682 // The main additional check (in addition to having a reference from the roots 5683 // or the young gen) is whether the humongous object has a remembered set entry. 5684 // 5685 // A humongous object cannot be live if there is no remembered set for it 5686 // because: 5687 // - there can be no references from within humongous starts regions referencing 5688 // the object because we never allocate other objects into them. 5689 // (I.e. there are no intra-region references that may be missed by the 5690 // remembered set) 5691 // - as soon there is a remembered set entry to the humongous starts region 5692 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 5693 // until the end of a concurrent mark. 5694 // 5695 // It is not required to check whether the object has been found dead by marking 5696 // or not, in fact it would prevent reclamation within a concurrent cycle, as 5697 // all objects allocated during that time are considered live. 5698 // SATB marking is even more conservative than the remembered set. 5699 // So if at this point in the collection there is no remembered set entry, 5700 // nobody has a reference to it. 5701 // At the start of collection we flush all refinement logs, and remembered sets 5702 // are completely up-to-date wrt to references to the humongous object. 5703 // 5704 // Other implementation considerations: 5705 // - never consider object arrays at this time because they would pose 5706 // considerable effort for cleaning up the the remembered sets. This is 5707 // required because stale remembered sets might reference locations that 5708 // are currently allocated into. 5709 uint region_idx = r->hrm_index(); 5710 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 5711 !r->rem_set()->is_empty()) { 5712 5713 if (G1TraceEagerReclaimHumongousObjects) { 5714 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", 5715 region_idx, 5716 (size_t)obj->size() * HeapWordSize, 5717 p2i(r->bottom()), 5718 r->rem_set()->occupied(), 5719 r->rem_set()->strong_code_roots_list_length(), 5720 next_bitmap->isMarked(r->bottom()), 5721 g1h->is_humongous_reclaim_candidate(region_idx), 5722 obj->is_typeArray() 5723 ); 5724 } 5725 5726 return false; 5727 } 5728 5729 guarantee(obj->is_typeArray(), 5730 "Only eagerly reclaiming type arrays is supported, but the object " 5731 PTR_FORMAT " is not.", p2i(r->bottom())); 5732 5733 if (G1TraceEagerReclaimHumongousObjects) { 5734 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", 5735 region_idx, 5736 (size_t)obj->size() * HeapWordSize, 5737 p2i(r->bottom()), 5738 r->rem_set()->occupied(), 5739 r->rem_set()->strong_code_roots_list_length(), 5740 next_bitmap->isMarked(r->bottom()), 5741 g1h->is_humongous_reclaim_candidate(region_idx), 5742 obj->is_typeArray() 5743 ); 5744 } 5745 // Need to clear mark bit of the humongous object if already set. 5746 if (next_bitmap->isMarked(r->bottom())) { 5747 next_bitmap->clear(r->bottom()); 5748 } 5749 do { 5750 HeapRegion* next = g1h->next_region_in_humongous(r); 5751 _freed_bytes += r->used(); 5752 r->set_containing_set(NULL); 5753 _humongous_regions_removed.increment(1u, r->capacity()); 5754 g1h->free_humongous_region(r, _free_region_list, false); 5755 r = next; 5756 } while (r != NULL); 5757 5758 return false; 5759 } 5760 5761 HeapRegionSetCount& humongous_free_count() { 5762 return _humongous_regions_removed; 5763 } 5764 5765 size_t bytes_freed() const { 5766 return _freed_bytes; 5767 } 5768 5769 size_t humongous_reclaimed() const { 5770 return _humongous_regions_removed.length(); 5771 } 5772 }; 5773 5774 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 5775 assert_at_safepoint(true); 5776 5777 if (!G1EagerReclaimHumongousObjects || 5778 (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) { 5779 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5780 return; 5781 } 5782 5783 double start_time = os::elapsedTime(); 5784 5785 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5786 5787 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5788 heap_region_iterate(&cl); 5789 5790 HeapRegionSetCount empty_set; 5791 remove_from_old_sets(empty_set, cl.humongous_free_count()); 5792 5793 G1HRPrinter* hrp = hr_printer(); 5794 if (hrp->is_active()) { 5795 FreeRegionListIterator iter(&local_cleanup_list); 5796 while (iter.more_available()) { 5797 HeapRegion* hr = iter.get_next(); 5798 hrp->cleanup(hr); 5799 } 5800 } 5801 5802 prepend_to_freelist(&local_cleanup_list); 5803 decrement_summary_bytes(cl.bytes_freed()); 5804 5805 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5806 cl.humongous_reclaimed()); 5807 } 5808 5809 // This routine is similar to the above but does not record 5810 // any policy statistics or update free lists; we are abandoning 5811 // the current incremental collection set in preparation of a 5812 // full collection. After the full GC we will start to build up 5813 // the incremental collection set again. 5814 // This is only called when we're doing a full collection 5815 // and is immediately followed by the tearing down of the young list. 5816 5817 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 5818 HeapRegion* cur = cs_head; 5819 5820 while (cur != NULL) { 5821 HeapRegion* next = cur->next_in_collection_set(); 5822 assert(cur->in_collection_set(), "bad CS"); 5823 cur->set_next_in_collection_set(NULL); 5824 clear_in_cset(cur); 5825 cur->set_young_index_in_cset(-1); 5826 cur = next; 5827 } 5828 } 5829 5830 void G1CollectedHeap::set_free_regions_coming() { 5831 if (G1ConcRegionFreeingVerbose) { 5832 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 5833 "setting free regions coming"); 5834 } 5835 5836 assert(!free_regions_coming(), "pre-condition"); 5837 _free_regions_coming = true; 5838 } 5839 5840 void G1CollectedHeap::reset_free_regions_coming() { 5841 assert(free_regions_coming(), "pre-condition"); 5842 5843 { 5844 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5845 _free_regions_coming = false; 5846 SecondaryFreeList_lock->notify_all(); 5847 } 5848 5849 if (G1ConcRegionFreeingVerbose) { 5850 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 5851 "reset free regions coming"); 5852 } 5853 } 5854 5855 void G1CollectedHeap::wait_while_free_regions_coming() { 5856 // Most of the time we won't have to wait, so let's do a quick test 5857 // first before we take the lock. 5858 if (!free_regions_coming()) { 5859 return; 5860 } 5861 5862 if (G1ConcRegionFreeingVerbose) { 5863 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 5864 "waiting for free regions"); 5865 } 5866 5867 { 5868 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5869 while (free_regions_coming()) { 5870 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5871 } 5872 } 5873 5874 if (G1ConcRegionFreeingVerbose) { 5875 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 5876 "done waiting for free regions"); 5877 } 5878 } 5879 5880 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5881 return _allocator->is_retained_old_region(hr); 5882 } 5883 5884 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5885 _young_list->push_region(hr); 5886 } 5887 5888 class NoYoungRegionsClosure: public HeapRegionClosure { 5889 private: 5890 bool _success; 5891 public: 5892 NoYoungRegionsClosure() : _success(true) { } 5893 bool doHeapRegion(HeapRegion* r) { 5894 if (r->is_young()) { 5895 gclog_or_tty->print_cr("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5896 p2i(r->bottom()), p2i(r->end())); 5897 _success = false; 5898 } 5899 return false; 5900 } 5901 bool success() { return _success; } 5902 }; 5903 5904 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 5905 bool ret = _young_list->check_list_empty(check_sample); 5906 5907 if (check_heap) { 5908 NoYoungRegionsClosure closure; 5909 heap_region_iterate(&closure); 5910 ret = ret && closure.success(); 5911 } 5912 5913 return ret; 5914 } 5915 5916 class TearDownRegionSetsClosure : public HeapRegionClosure { 5917 private: 5918 HeapRegionSet *_old_set; 5919 5920 public: 5921 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5922 5923 bool doHeapRegion(HeapRegion* r) { 5924 if (r->is_old()) { 5925 _old_set->remove(r); 5926 } else { 5927 // We ignore free regions, we'll empty the free list afterwards. 5928 // We ignore young regions, we'll empty the young list afterwards. 5929 // We ignore humongous regions, we're not tearing down the 5930 // humongous regions set. 5931 assert(r->is_free() || r->is_young() || r->is_humongous(), 5932 "it cannot be another type"); 5933 } 5934 return false; 5935 } 5936 5937 ~TearDownRegionSetsClosure() { 5938 assert(_old_set->is_empty(), "post-condition"); 5939 } 5940 }; 5941 5942 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5943 assert_at_safepoint(true /* should_be_vm_thread */); 5944 5945 if (!free_list_only) { 5946 TearDownRegionSetsClosure cl(&_old_set); 5947 heap_region_iterate(&cl); 5948 5949 // Note that emptying the _young_list is postponed and instead done as 5950 // the first step when rebuilding the regions sets again. The reason for 5951 // this is that during a full GC string deduplication needs to know if 5952 // a collected region was young or old when the full GC was initiated. 5953 } 5954 _hrm.remove_all_free_regions(); 5955 } 5956 5957 void G1CollectedHeap::increase_used(size_t bytes) { 5958 _summary_bytes_used += bytes; 5959 } 5960 5961 void G1CollectedHeap::decrease_used(size_t bytes) { 5962 assert(_summary_bytes_used >= bytes, 5963 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5964 _summary_bytes_used, bytes); 5965 _summary_bytes_used -= bytes; 5966 } 5967 5968 void G1CollectedHeap::set_used(size_t bytes) { 5969 _summary_bytes_used = bytes; 5970 } 5971 5972 class RebuildRegionSetsClosure : public HeapRegionClosure { 5973 private: 5974 bool _free_list_only; 5975 HeapRegionSet* _old_set; 5976 HeapRegionManager* _hrm; 5977 size_t _total_used; 5978 5979 public: 5980 RebuildRegionSetsClosure(bool free_list_only, 5981 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5982 _free_list_only(free_list_only), 5983 _old_set(old_set), _hrm(hrm), _total_used(0) { 5984 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5985 if (!free_list_only) { 5986 assert(_old_set->is_empty(), "pre-condition"); 5987 } 5988 } 5989 5990 bool doHeapRegion(HeapRegion* r) { 5991 if (r->is_empty()) { 5992 // Add free regions to the free list 5993 r->set_free(); 5994 r->set_allocation_context(AllocationContext::system()); 5995 _hrm->insert_into_free_list(r); 5996 } else if (!_free_list_only) { 5997 assert(!r->is_young(), "we should not come across young regions"); 5998 5999 if (r->is_humongous()) { 6000 // We ignore humongous regions. We left the humongous set unchanged. 6001 } else { 6002 // Objects that were compacted would have ended up on regions 6003 // that were previously old or free. Archive regions (which are 6004 // old) will not have been touched. 6005 assert(r->is_free() || r->is_old(), "invariant"); 6006 // We now consider them old, so register as such. Leave 6007 // archive regions set that way, however, while still adding 6008 // them to the old set. 6009 if (!r->is_archive()) { 6010 r->set_old(); 6011 } 6012 _old_set->add(r); 6013 } 6014 _total_used += r->used(); 6015 } 6016 6017 return false; 6018 } 6019 6020 size_t total_used() { 6021 return _total_used; 6022 } 6023 }; 6024 6025 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6026 assert_at_safepoint(true /* should_be_vm_thread */); 6027 6028 if (!free_list_only) { 6029 _young_list->empty_list(); 6030 } 6031 6032 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 6033 heap_region_iterate(&cl); 6034 6035 if (!free_list_only) { 6036 set_used(cl.total_used()); 6037 if (_archive_allocator != NULL) { 6038 _archive_allocator->clear_used(); 6039 } 6040 } 6041 assert(used_unlocked() == recalculate_used(), 6042 "inconsistent used_unlocked(), " 6043 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 6044 used_unlocked(), recalculate_used()); 6045 } 6046 6047 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6048 _refine_cte_cl->set_concurrent(concurrent); 6049 } 6050 6051 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6052 HeapRegion* hr = heap_region_containing(p); 6053 return hr->is_in(p); 6054 } 6055 6056 // Methods for the mutator alloc region 6057 6058 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6059 bool force) { 6060 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6061 assert(!force || g1_policy()->can_expand_young_list(), 6062 "if force is true we should be able to expand the young list"); 6063 bool young_list_full = g1_policy()->is_young_list_full(); 6064 if (force || !young_list_full) { 6065 HeapRegion* new_alloc_region = new_region(word_size, 6066 false /* is_old */, 6067 false /* do_expand */); 6068 if (new_alloc_region != NULL) { 6069 set_region_short_lived_locked(new_alloc_region); 6070 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6071 check_bitmaps("Mutator Region Allocation", new_alloc_region); 6072 return new_alloc_region; 6073 } 6074 } 6075 return NULL; 6076 } 6077 6078 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6079 size_t allocated_bytes) { 6080 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6081 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 6082 6083 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6084 increase_used(allocated_bytes); 6085 _hr_printer.retire(alloc_region); 6086 // We update the eden sizes here, when the region is retired, 6087 // instead of when it's allocated, since this is the point that its 6088 // used space has been recored in _summary_bytes_used. 6089 g1mm()->update_eden_size(); 6090 } 6091 6092 // Methods for the GC alloc regions 6093 6094 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6095 uint count, 6096 InCSetState dest) { 6097 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6098 6099 if (count < g1_policy()->max_regions(dest)) { 6100 const bool is_survivor = (dest.is_young()); 6101 HeapRegion* new_alloc_region = new_region(word_size, 6102 !is_survivor, 6103 true /* do_expand */); 6104 if (new_alloc_region != NULL) { 6105 // We really only need to do this for old regions given that we 6106 // should never scan survivors. But it doesn't hurt to do it 6107 // for survivors too. 6108 new_alloc_region->record_timestamp(); 6109 if (is_survivor) { 6110 new_alloc_region->set_survivor(); 6111 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6112 check_bitmaps("Survivor Region Allocation", new_alloc_region); 6113 } else { 6114 new_alloc_region->set_old(); 6115 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6116 check_bitmaps("Old Region Allocation", new_alloc_region); 6117 } 6118 bool during_im = collector_state()->during_initial_mark_pause(); 6119 new_alloc_region->note_start_of_copying(during_im); 6120 return new_alloc_region; 6121 } 6122 } 6123 return NULL; 6124 } 6125 6126 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6127 size_t allocated_bytes, 6128 InCSetState dest) { 6129 bool during_im = collector_state()->during_initial_mark_pause(); 6130 alloc_region->note_end_of_copying(during_im); 6131 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6132 if (dest.is_young()) { 6133 young_list()->add_survivor_region(alloc_region); 6134 } else { 6135 _old_set.add(alloc_region); 6136 } 6137 _hr_printer.retire(alloc_region); 6138 } 6139 6140 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 6141 bool expanded = false; 6142 uint index = _hrm.find_highest_free(&expanded); 6143 6144 if (index != G1_NO_HRM_INDEX) { 6145 if (expanded) { 6146 ergo_verbose1(ErgoHeapSizing, 6147 "attempt heap expansion", 6148 ergo_format_reason("requested address range outside heap bounds") 6149 ergo_format_byte("region size"), 6150 HeapRegion::GrainWords * HeapWordSize); 6151 } 6152 _hrm.allocate_free_regions_starting_at(index, 1); 6153 return region_at(index); 6154 } 6155 return NULL; 6156 } 6157 6158 // Heap region set verification 6159 6160 class VerifyRegionListsClosure : public HeapRegionClosure { 6161 private: 6162 HeapRegionSet* _old_set; 6163 HeapRegionSet* _humongous_set; 6164 HeapRegionManager* _hrm; 6165 6166 public: 6167 HeapRegionSetCount _old_count; 6168 HeapRegionSetCount _humongous_count; 6169 HeapRegionSetCount _free_count; 6170 6171 VerifyRegionListsClosure(HeapRegionSet* old_set, 6172 HeapRegionSet* humongous_set, 6173 HeapRegionManager* hrm) : 6174 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm), 6175 _old_count(), _humongous_count(), _free_count(){ } 6176 6177 bool doHeapRegion(HeapRegion* hr) { 6178 if (hr->is_young()) { 6179 // TODO 6180 } else if (hr->is_humongous()) { 6181 assert(hr->containing_set() == _humongous_set, "Heap region %u is humongous but not in humongous set.", hr->hrm_index()); 6182 _humongous_count.increment(1u, hr->capacity()); 6183 } else if (hr->is_empty()) { 6184 assert(_hrm->is_free(hr), "Heap region %u is empty but not on the free list.", hr->hrm_index()); 6185 _free_count.increment(1u, hr->capacity()); 6186 } else if (hr->is_old()) { 6187 assert(hr->containing_set() == _old_set, "Heap region %u is old but not in the old set.", hr->hrm_index()); 6188 _old_count.increment(1u, hr->capacity()); 6189 } else { 6190 // There are no other valid region types. Check for one invalid 6191 // one we can identify: pinned without old or humongous set. 6192 assert(!hr->is_pinned(), "Heap region %u is pinned but not old (archive) or humongous.", hr->hrm_index()); 6193 ShouldNotReachHere(); 6194 } 6195 return false; 6196 } 6197 6198 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) { 6199 guarantee(old_set->length() == _old_count.length(), "Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()); 6200 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), "Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6201 old_set->total_capacity_bytes(), _old_count.capacity()); 6202 6203 guarantee(humongous_set->length() == _humongous_count.length(), "Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()); 6204 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), "Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6205 humongous_set->total_capacity_bytes(), _humongous_count.capacity()); 6206 6207 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()); 6208 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), "Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6209 free_list->total_capacity_bytes(), _free_count.capacity()); 6210 } 6211 }; 6212 6213 void G1CollectedHeap::verify_region_sets() { 6214 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6215 6216 // First, check the explicit lists. 6217 _hrm.verify(); 6218 { 6219 // Given that a concurrent operation might be adding regions to 6220 // the secondary free list we have to take the lock before 6221 // verifying it. 6222 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6223 _secondary_free_list.verify_list(); 6224 } 6225 6226 // If a concurrent region freeing operation is in progress it will 6227 // be difficult to correctly attributed any free regions we come 6228 // across to the correct free list given that they might belong to 6229 // one of several (free_list, secondary_free_list, any local lists, 6230 // etc.). So, if that's the case we will skip the rest of the 6231 // verification operation. Alternatively, waiting for the concurrent 6232 // operation to complete will have a non-trivial effect on the GC's 6233 // operation (no concurrent operation will last longer than the 6234 // interval between two calls to verification) and it might hide 6235 // any issues that we would like to catch during testing. 6236 if (free_regions_coming()) { 6237 return; 6238 } 6239 6240 // Make sure we append the secondary_free_list on the free_list so 6241 // that all free regions we will come across can be safely 6242 // attributed to the free_list. 6243 append_secondary_free_list_if_not_empty_with_lock(); 6244 6245 // Finally, make sure that the region accounting in the lists is 6246 // consistent with what we see in the heap. 6247 6248 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm); 6249 heap_region_iterate(&cl); 6250 cl.verify_counts(&_old_set, &_humongous_set, &_hrm); 6251 } 6252 6253 // Optimized nmethod scanning 6254 6255 class RegisterNMethodOopClosure: public OopClosure { 6256 G1CollectedHeap* _g1h; 6257 nmethod* _nm; 6258 6259 template <class T> void do_oop_work(T* p) { 6260 T heap_oop = oopDesc::load_heap_oop(p); 6261 if (!oopDesc::is_null(heap_oop)) { 6262 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6263 HeapRegion* hr = _g1h->heap_region_containing(obj); 6264 assert(!hr->is_continues_humongous(), 6265 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6266 " starting at " HR_FORMAT, 6267 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 6268 6269 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 6270 hr->add_strong_code_root_locked(_nm); 6271 } 6272 } 6273 6274 public: 6275 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6276 _g1h(g1h), _nm(nm) {} 6277 6278 void do_oop(oop* p) { do_oop_work(p); } 6279 void do_oop(narrowOop* p) { do_oop_work(p); } 6280 }; 6281 6282 class UnregisterNMethodOopClosure: public OopClosure { 6283 G1CollectedHeap* _g1h; 6284 nmethod* _nm; 6285 6286 template <class T> void do_oop_work(T* p) { 6287 T heap_oop = oopDesc::load_heap_oop(p); 6288 if (!oopDesc::is_null(heap_oop)) { 6289 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6290 HeapRegion* hr = _g1h->heap_region_containing(obj); 6291 assert(!hr->is_continues_humongous(), 6292 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6293 " starting at " HR_FORMAT, 6294 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 6295 6296 hr->remove_strong_code_root(_nm); 6297 } 6298 } 6299 6300 public: 6301 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6302 _g1h(g1h), _nm(nm) {} 6303 6304 void do_oop(oop* p) { do_oop_work(p); } 6305 void do_oop(narrowOop* p) { do_oop_work(p); } 6306 }; 6307 6308 void G1CollectedHeap::register_nmethod(nmethod* nm) { 6309 CollectedHeap::register_nmethod(nm); 6310 6311 guarantee(nm != NULL, "sanity"); 6312 RegisterNMethodOopClosure reg_cl(this, nm); 6313 nm->oops_do(®_cl); 6314 } 6315 6316 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 6317 CollectedHeap::unregister_nmethod(nm); 6318 6319 guarantee(nm != NULL, "sanity"); 6320 UnregisterNMethodOopClosure reg_cl(this, nm); 6321 nm->oops_do(®_cl, true); 6322 } 6323 6324 void G1CollectedHeap::purge_code_root_memory() { 6325 double purge_start = os::elapsedTime(); 6326 G1CodeRootSet::purge(); 6327 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 6328 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 6329 } 6330 6331 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 6332 G1CollectedHeap* _g1h; 6333 6334 public: 6335 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 6336 _g1h(g1h) {} 6337 6338 void do_code_blob(CodeBlob* cb) { 6339 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 6340 if (nm == NULL) { 6341 return; 6342 } 6343 6344 if (ScavengeRootsInCode) { 6345 _g1h->register_nmethod(nm); 6346 } 6347 } 6348 }; 6349 6350 void G1CollectedHeap::rebuild_strong_code_roots() { 6351 RebuildStrongCodeRootClosure blob_cl(this); 6352 CodeCache::blobs_do(&blob_cl); 6353 }