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 "classfile/symbolTable.hpp" 29 #include "code/codeCache.hpp" 30 #include "code/icBuffer.hpp" 31 #include "gc/g1/bufferingOopClosure.hpp" 32 #include "gc/g1/concurrentG1Refine.hpp" 33 #include "gc/g1/concurrentG1RefineThread.hpp" 34 #include "gc/g1/concurrentMarkThread.inline.hpp" 35 #include "gc/g1/g1Allocator.inline.hpp" 36 #include "gc/g1/g1CollectedHeap.inline.hpp" 37 #include "gc/g1/g1CollectorPolicy.hpp" 38 #include "gc/g1/g1CollectorState.hpp" 39 #include "gc/g1/g1EvacStats.inline.hpp" 40 #include "gc/g1/g1GCPhaseTimes.hpp" 41 #include "gc/g1/g1MarkSweep.hpp" 42 #include "gc/g1/g1OopClosures.inline.hpp" 43 #include "gc/g1/g1ParScanThreadState.inline.hpp" 44 #include "gc/g1/g1RegionToSpaceMapper.hpp" 45 #include "gc/g1/g1RemSet.inline.hpp" 46 #include "gc/g1/g1RootClosures.hpp" 47 #include "gc/g1/g1RootProcessor.hpp" 48 #include "gc/g1/g1StringDedup.hpp" 49 #include "gc/g1/g1YCTypes.hpp" 50 #include "gc/g1/heapRegion.inline.hpp" 51 #include "gc/g1/heapRegionRemSet.hpp" 52 #include "gc/g1/heapRegionSet.inline.hpp" 53 #include "gc/g1/suspendibleThreadSet.hpp" 54 #include "gc/g1/vm_operations_g1.hpp" 55 #include "gc/shared/gcHeapSummary.hpp" 56 #include "gc/shared/gcId.hpp" 57 #include "gc/shared/gcLocker.inline.hpp" 58 #include "gc/shared/gcTimer.hpp" 59 #include "gc/shared/gcTrace.hpp" 60 #include "gc/shared/gcTraceTime.inline.hpp" 61 #include "gc/shared/generationSpec.hpp" 62 #include "gc/shared/isGCActiveMark.hpp" 63 #include "gc/shared/referenceProcessor.hpp" 64 #include "gc/shared/taskqueue.inline.hpp" 65 #include "logging/log.hpp" 66 #include "memory/allocation.hpp" 67 #include "memory/iterator.hpp" 68 #include "oops/oop.inline.hpp" 69 #include "runtime/atomic.inline.hpp" 70 #include "runtime/init.hpp" 71 #include "runtime/orderAccess.inline.hpp" 72 #include "runtime/vmThread.hpp" 73 #include "utilities/globalDefinitions.hpp" 74 #include "utilities/stack.inline.hpp" 75 76 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 77 78 // INVARIANTS/NOTES 79 // 80 // All allocation activity covered by the G1CollectedHeap interface is 81 // serialized by acquiring the HeapLock. This happens in mem_allocate 82 // and allocate_new_tlab, which are the "entry" points to the 83 // allocation code from the rest of the JVM. (Note that this does not 84 // apply to TLAB allocation, which is not part of this interface: it 85 // is done by clients of this interface.) 86 87 // Local to this file. 88 89 class RefineCardTableEntryClosure: public CardTableEntryClosure { 90 bool _concurrent; 91 public: 92 RefineCardTableEntryClosure() : _concurrent(true) { } 93 94 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 95 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false); 96 // This path is executed by the concurrent refine or mutator threads, 97 // concurrently, and so we do not care if card_ptr contains references 98 // that point into the collection set. 99 assert(!oops_into_cset, "should be"); 100 101 if (_concurrent && SuspendibleThreadSet::should_yield()) { 102 // Caller will actually yield. 103 return false; 104 } 105 // Otherwise, we finished successfully; return true. 106 return true; 107 } 108 109 void set_concurrent(bool b) { _concurrent = b; } 110 }; 111 112 113 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 114 private: 115 size_t _num_dirtied; 116 G1CollectedHeap* _g1h; 117 G1SATBCardTableLoggingModRefBS* _g1_bs; 118 119 HeapRegion* region_for_card(jbyte* card_ptr) const { 120 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 121 } 122 123 bool will_become_free(HeapRegion* hr) const { 124 // A region will be freed by free_collection_set if the region is in the 125 // collection set and has not had an evacuation failure. 126 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 127 } 128 129 public: 130 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 131 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 132 133 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 134 HeapRegion* hr = region_for_card(card_ptr); 135 136 // Should only dirty cards in regions that won't be freed. 137 if (!will_become_free(hr)) { 138 *card_ptr = CardTableModRefBS::dirty_card_val(); 139 _num_dirtied++; 140 } 141 142 return true; 143 } 144 145 size_t num_dirtied() const { return _num_dirtied; } 146 }; 147 148 149 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 150 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 151 } 152 153 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 154 // The from card cache is not the memory that is actually committed. So we cannot 155 // take advantage of the zero_filled parameter. 156 reset_from_card_cache(start_idx, num_regions); 157 } 158 159 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 160 { 161 // Claim the right to put the region on the dirty cards region list 162 // by installing a self pointer. 163 HeapRegion* next = hr->get_next_dirty_cards_region(); 164 if (next == NULL) { 165 HeapRegion* res = (HeapRegion*) 166 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 167 NULL); 168 if (res == NULL) { 169 HeapRegion* head; 170 do { 171 // Put the region to the dirty cards region list. 172 head = _dirty_cards_region_list; 173 next = (HeapRegion*) 174 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 175 if (next == head) { 176 assert(hr->get_next_dirty_cards_region() == hr, 177 "hr->get_next_dirty_cards_region() != hr"); 178 if (next == NULL) { 179 // The last region in the list points to itself. 180 hr->set_next_dirty_cards_region(hr); 181 } else { 182 hr->set_next_dirty_cards_region(next); 183 } 184 } 185 } while (next != head); 186 } 187 } 188 } 189 190 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 191 { 192 HeapRegion* head; 193 HeapRegion* hr; 194 do { 195 head = _dirty_cards_region_list; 196 if (head == NULL) { 197 return NULL; 198 } 199 HeapRegion* new_head = head->get_next_dirty_cards_region(); 200 if (head == new_head) { 201 // The last region. 202 new_head = NULL; 203 } 204 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 205 head); 206 } while (hr != head); 207 assert(hr != NULL, "invariant"); 208 hr->set_next_dirty_cards_region(NULL); 209 return hr; 210 } 211 212 // Returns true if the reference points to an object that 213 // can move in an incremental collection. 214 bool G1CollectedHeap::is_scavengable(const void* p) { 215 HeapRegion* hr = heap_region_containing(p); 216 return !hr->is_pinned(); 217 } 218 219 // Private methods. 220 221 HeapRegion* 222 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 223 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 224 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 225 if (!_secondary_free_list.is_empty()) { 226 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 227 "secondary_free_list has %u entries", 228 _secondary_free_list.length()); 229 // It looks as if there are free regions available on the 230 // secondary_free_list. Let's move them to the free_list and try 231 // again to allocate from it. 232 append_secondary_free_list(); 233 234 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 235 "empty we should have moved at least one entry to the free_list"); 236 HeapRegion* res = _hrm.allocate_free_region(is_old); 237 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 238 "allocated " HR_FORMAT " from secondary_free_list", 239 HR_FORMAT_PARAMS(res)); 240 return res; 241 } 242 243 // Wait here until we get notified either when (a) there are no 244 // more free regions coming or (b) some regions have been moved on 245 // the secondary_free_list. 246 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 247 } 248 249 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 250 "could not allocate from secondary_free_list"); 251 return NULL; 252 } 253 254 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 255 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 256 "the only time we use this to allocate a humongous region is " 257 "when we are allocating a single humongous region"); 258 259 HeapRegion* res; 260 if (G1StressConcRegionFreeing) { 261 if (!_secondary_free_list.is_empty()) { 262 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 263 "forced to look at the secondary_free_list"); 264 res = new_region_try_secondary_free_list(is_old); 265 if (res != NULL) { 266 return res; 267 } 268 } 269 } 270 271 res = _hrm.allocate_free_region(is_old); 272 273 if (res == NULL) { 274 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 275 "res == NULL, trying the secondary_free_list"); 276 res = new_region_try_secondary_free_list(is_old); 277 } 278 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 279 // Currently, only attempts to allocate GC alloc regions set 280 // do_expand to true. So, we should only reach here during a 281 // safepoint. If this assumption changes we might have to 282 // reconsider the use of _expand_heap_after_alloc_failure. 283 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 284 285 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 286 word_size * HeapWordSize); 287 288 if (expand(word_size * HeapWordSize)) { 289 // Given that expand() succeeded in expanding the heap, and we 290 // always expand the heap by an amount aligned to the heap 291 // region size, the free list should in theory not be empty. 292 // In either case allocate_free_region() will check for NULL. 293 res = _hrm.allocate_free_region(is_old); 294 } else { 295 _expand_heap_after_alloc_failure = false; 296 } 297 } 298 return res; 299 } 300 301 HeapWord* 302 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 303 uint num_regions, 304 size_t word_size, 305 AllocationContext_t context) { 306 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 307 assert(is_humongous(word_size), "word_size should be humongous"); 308 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 309 310 // Index of last region in the series. 311 uint last = first + num_regions - 1; 312 313 // We need to initialize the region(s) we just discovered. This is 314 // a bit tricky given that it can happen concurrently with 315 // refinement threads refining cards on these regions and 316 // potentially wanting to refine the BOT as they are scanning 317 // those cards (this can happen shortly after a cleanup; see CR 318 // 6991377). So we have to set up the region(s) carefully and in 319 // a specific order. 320 321 // The word size sum of all the regions we will allocate. 322 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 323 assert(word_size <= word_size_sum, "sanity"); 324 325 // This will be the "starts humongous" region. 326 HeapRegion* first_hr = region_at(first); 327 // The header of the new object will be placed at the bottom of 328 // the first region. 329 HeapWord* new_obj = first_hr->bottom(); 330 // This will be the new top of the new object. 331 HeapWord* obj_top = new_obj + word_size; 332 333 // First, we need to zero the header of the space that we will be 334 // allocating. When we update top further down, some refinement 335 // threads might try to scan the region. By zeroing the header we 336 // ensure that any thread that will try to scan the region will 337 // come across the zero klass word and bail out. 338 // 339 // NOTE: It would not have been correct to have used 340 // CollectedHeap::fill_with_object() and make the space look like 341 // an int array. The thread that is doing the allocation will 342 // later update the object header to a potentially different array 343 // type and, for a very short period of time, the klass and length 344 // fields will be inconsistent. This could cause a refinement 345 // thread to calculate the object size incorrectly. 346 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 347 348 // How many words we use for filler objects. 349 size_t word_fill_size = word_size_sum - word_size; 350 351 // How many words memory we "waste" which cannot hold a filler object. 352 size_t words_not_fillable = 0; 353 354 if (word_fill_size >= min_fill_size()) { 355 fill_with_objects(obj_top, word_fill_size); 356 } else if (word_fill_size > 0) { 357 // We have space to fill, but we cannot fit an object there. 358 words_not_fillable = word_fill_size; 359 word_fill_size = 0; 360 } 361 362 // We will set up the first region as "starts humongous". This 363 // will also update the BOT covering all the regions to reflect 364 // that there is a single object that starts at the bottom of the 365 // first region. 366 first_hr->set_starts_humongous(obj_top, word_fill_size); 367 first_hr->set_allocation_context(context); 368 // Then, if there are any, we will set up the "continues 369 // humongous" regions. 370 HeapRegion* hr = NULL; 371 for (uint i = first + 1; i <= last; ++i) { 372 hr = region_at(i); 373 hr->set_continues_humongous(first_hr); 374 hr->set_allocation_context(context); 375 } 376 377 // Up to this point no concurrent thread would have been able to 378 // do any scanning on any region in this series. All the top 379 // fields still point to bottom, so the intersection between 380 // [bottom,top] and [card_start,card_end] will be empty. Before we 381 // update the top fields, we'll do a storestore to make sure that 382 // no thread sees the update to top before the zeroing of the 383 // object header and the BOT initialization. 384 OrderAccess::storestore(); 385 386 // Now, we will update the top fields of the "continues humongous" 387 // regions except the last one. 388 for (uint i = first; i < last; ++i) { 389 hr = region_at(i); 390 hr->set_top(hr->end()); 391 } 392 393 hr = region_at(last); 394 // If we cannot fit a filler object, we must set top to the end 395 // of the humongous object, otherwise we cannot iterate the heap 396 // and the BOT will not be complete. 397 hr->set_top(hr->end() - words_not_fillable); 398 399 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 400 "obj_top should be in last region"); 401 402 check_bitmaps("Humongous Region Allocation", first_hr); 403 404 assert(words_not_fillable == 0 || 405 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 406 "Miscalculation in humongous allocation"); 407 408 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 409 410 for (uint i = first; i <= last; ++i) { 411 hr = region_at(i); 412 _humongous_set.add(hr); 413 if (i == first) { 414 _hr_printer.alloc(G1HRPrinter::StartsHumongous, hr, hr->top()); 415 } else { 416 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->top()); 417 } 418 } 419 420 return new_obj; 421 } 422 423 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 424 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 425 return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 426 } 427 428 // If could fit into free regions w/o expansion, try. 429 // Otherwise, if can expand, do so. 430 // Otherwise, if using ex regions might help, try with ex given back. 431 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 432 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 433 434 verify_region_sets_optional(); 435 436 uint first = G1_NO_HRM_INDEX; 437 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 438 439 if (obj_regions == 1) { 440 // Only one region to allocate, try to use a fast path by directly allocating 441 // from the free lists. Do not try to expand here, we will potentially do that 442 // later. 443 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 444 if (hr != NULL) { 445 first = hr->hrm_index(); 446 } 447 } else { 448 // We can't allocate humongous regions spanning more than one region while 449 // cleanupComplete() is running, since some of the regions we find to be 450 // empty might not yet be added to the free list. It is not straightforward 451 // to know in which list they are on so that we can remove them. We only 452 // need to do this if we need to allocate more than one region to satisfy the 453 // current humongous allocation request. If we are only allocating one region 454 // we use the one-region region allocation code (see above), that already 455 // potentially waits for regions from the secondary free list. 456 wait_while_free_regions_coming(); 457 append_secondary_free_list_if_not_empty_with_lock(); 458 459 // Policy: Try only empty regions (i.e. already committed first). Maybe we 460 // are lucky enough to find some. 461 first = _hrm.find_contiguous_only_empty(obj_regions); 462 if (first != G1_NO_HRM_INDEX) { 463 _hrm.allocate_free_regions_starting_at(first, obj_regions); 464 } 465 } 466 467 if (first == G1_NO_HRM_INDEX) { 468 // Policy: We could not find enough regions for the humongous object in the 469 // free list. Look through the heap to find a mix of free and uncommitted regions. 470 // If so, try expansion. 471 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 472 if (first != G1_NO_HRM_INDEX) { 473 // We found something. Make sure these regions are committed, i.e. expand 474 // the heap. Alternatively we could do a defragmentation GC. 475 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 476 word_size * HeapWordSize); 477 478 479 _hrm.expand_at(first, obj_regions); 480 g1_policy()->record_new_heap_size(num_regions()); 481 482 #ifdef ASSERT 483 for (uint i = first; i < first + obj_regions; ++i) { 484 HeapRegion* hr = region_at(i); 485 assert(hr->is_free(), "sanity"); 486 assert(hr->is_empty(), "sanity"); 487 assert(is_on_master_free_list(hr), "sanity"); 488 } 489 #endif 490 _hrm.allocate_free_regions_starting_at(first, obj_regions); 491 } else { 492 // Policy: Potentially trigger a defragmentation GC. 493 } 494 } 495 496 HeapWord* result = NULL; 497 if (first != G1_NO_HRM_INDEX) { 498 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 499 word_size, context); 500 assert(result != NULL, "it should always return a valid result"); 501 502 // A successful humongous object allocation changes the used space 503 // information of the old generation so we need to recalculate the 504 // sizes and update the jstat counters here. 505 g1mm()->update_sizes(); 506 } 507 508 verify_region_sets_optional(); 509 510 return result; 511 } 512 513 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 514 assert_heap_not_locked_and_not_at_safepoint(); 515 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 516 517 uint dummy_gc_count_before; 518 uint dummy_gclocker_retry_count = 0; 519 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 520 } 521 522 HeapWord* 523 G1CollectedHeap::mem_allocate(size_t word_size, 524 bool* gc_overhead_limit_was_exceeded) { 525 assert_heap_not_locked_and_not_at_safepoint(); 526 527 // Loop until the allocation is satisfied, or unsatisfied after GC. 528 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 529 uint gc_count_before; 530 531 HeapWord* result = NULL; 532 if (!is_humongous(word_size)) { 533 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 534 } else { 535 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 536 } 537 if (result != NULL) { 538 return result; 539 } 540 541 // Create the garbage collection operation... 542 VM_G1CollectForAllocation op(gc_count_before, word_size); 543 op.set_allocation_context(AllocationContext::current()); 544 545 // ...and get the VM thread to execute it. 546 VMThread::execute(&op); 547 548 if (op.prologue_succeeded() && op.pause_succeeded()) { 549 // If the operation was successful we'll return the result even 550 // if it is NULL. If the allocation attempt failed immediately 551 // after a Full GC, it's unlikely we'll be able to allocate now. 552 HeapWord* result = op.result(); 553 if (result != NULL && !is_humongous(word_size)) { 554 // Allocations that take place on VM operations do not do any 555 // card dirtying and we have to do it here. We only have to do 556 // this for non-humongous allocations, though. 557 dirty_young_block(result, word_size); 558 } 559 return result; 560 } else { 561 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 562 return NULL; 563 } 564 assert(op.result() == NULL, 565 "the result should be NULL if the VM op did not succeed"); 566 } 567 568 // Give a warning if we seem to be looping forever. 569 if ((QueuedAllocationWarningCount > 0) && 570 (try_count % QueuedAllocationWarningCount == 0)) { 571 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 572 } 573 } 574 575 ShouldNotReachHere(); 576 return NULL; 577 } 578 579 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 580 AllocationContext_t context, 581 uint* gc_count_before_ret, 582 uint* gclocker_retry_count_ret) { 583 // Make sure you read the note in attempt_allocation_humongous(). 584 585 assert_heap_not_locked_and_not_at_safepoint(); 586 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 587 "be called for humongous allocation requests"); 588 589 // We should only get here after the first-level allocation attempt 590 // (attempt_allocation()) failed to allocate. 591 592 // We will loop until a) we manage to successfully perform the 593 // allocation or b) we successfully schedule a collection which 594 // fails to perform the allocation. b) is the only case when we'll 595 // return NULL. 596 HeapWord* result = NULL; 597 for (int try_count = 1; /* we'll return */; try_count += 1) { 598 bool should_try_gc; 599 uint gc_count_before; 600 601 { 602 MutexLockerEx x(Heap_lock); 603 result = _allocator->attempt_allocation_locked(word_size, context); 604 if (result != NULL) { 605 return result; 606 } 607 608 if (GC_locker::is_active_and_needs_gc()) { 609 if (g1_policy()->can_expand_young_list()) { 610 // No need for an ergo verbose message here, 611 // can_expand_young_list() does this when it returns true. 612 result = _allocator->attempt_allocation_force(word_size, context); 613 if (result != NULL) { 614 return result; 615 } 616 } 617 should_try_gc = false; 618 } else { 619 // The GCLocker may not be active but the GCLocker initiated 620 // GC may not yet have been performed (GCLocker::needs_gc() 621 // returns true). In this case we do not try this GC and 622 // wait until the GCLocker initiated GC is performed, and 623 // then retry the allocation. 624 if (GC_locker::needs_gc()) { 625 should_try_gc = false; 626 } else { 627 // Read the GC count while still holding the Heap_lock. 628 gc_count_before = total_collections(); 629 should_try_gc = true; 630 } 631 } 632 } 633 634 if (should_try_gc) { 635 bool succeeded; 636 result = do_collection_pause(word_size, gc_count_before, &succeeded, 637 GCCause::_g1_inc_collection_pause); 638 if (result != NULL) { 639 assert(succeeded, "only way to get back a non-NULL result"); 640 return result; 641 } 642 643 if (succeeded) { 644 // If we get here we successfully scheduled a collection which 645 // failed to allocate. No point in trying to allocate 646 // further. We'll just return NULL. 647 MutexLockerEx x(Heap_lock); 648 *gc_count_before_ret = total_collections(); 649 return NULL; 650 } 651 } else { 652 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 653 MutexLockerEx x(Heap_lock); 654 *gc_count_before_ret = total_collections(); 655 return NULL; 656 } 657 // The GCLocker is either active or the GCLocker initiated 658 // GC has not yet been performed. Stall until it is and 659 // then retry the allocation. 660 GC_locker::stall_until_clear(); 661 (*gclocker_retry_count_ret) += 1; 662 } 663 664 // We can reach here if we were unsuccessful in scheduling a 665 // collection (because another thread beat us to it) or if we were 666 // stalled due to the GC locker. In either can we should retry the 667 // allocation attempt in case another thread successfully 668 // performed a collection and reclaimed enough space. We do the 669 // first attempt (without holding the Heap_lock) here and the 670 // follow-on attempt will be at the start of the next loop 671 // iteration (after taking the Heap_lock). 672 result = _allocator->attempt_allocation(word_size, context); 673 if (result != NULL) { 674 return result; 675 } 676 677 // Give a warning if we seem to be looping forever. 678 if ((QueuedAllocationWarningCount > 0) && 679 (try_count % QueuedAllocationWarningCount == 0)) { 680 warning("G1CollectedHeap::attempt_allocation_slow() " 681 "retries %d times", try_count); 682 } 683 } 684 685 ShouldNotReachHere(); 686 return NULL; 687 } 688 689 void G1CollectedHeap::begin_archive_alloc_range() { 690 assert_at_safepoint(true /* should_be_vm_thread */); 691 if (_archive_allocator == NULL) { 692 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 693 } 694 } 695 696 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 697 // Allocations in archive regions cannot be of a size that would be considered 698 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 699 // may be different at archive-restore time. 700 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 701 } 702 703 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 704 assert_at_safepoint(true /* should_be_vm_thread */); 705 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 706 if (is_archive_alloc_too_large(word_size)) { 707 return NULL; 708 } 709 return _archive_allocator->archive_mem_allocate(word_size); 710 } 711 712 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 713 size_t end_alignment_in_bytes) { 714 assert_at_safepoint(true /* should_be_vm_thread */); 715 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 716 717 // Call complete_archive to do the real work, filling in the MemRegion 718 // array with the archive regions. 719 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 720 delete _archive_allocator; 721 _archive_allocator = NULL; 722 } 723 724 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 725 assert(ranges != NULL, "MemRegion array NULL"); 726 assert(count != 0, "No MemRegions provided"); 727 MemRegion reserved = _hrm.reserved(); 728 for (size_t i = 0; i < count; i++) { 729 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 730 return false; 731 } 732 } 733 return true; 734 } 735 736 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 737 assert(!is_init_completed(), "Expect to be called at JVM init time"); 738 assert(ranges != NULL, "MemRegion array NULL"); 739 assert(count != 0, "No MemRegions provided"); 740 MutexLockerEx x(Heap_lock); 741 742 MemRegion reserved = _hrm.reserved(); 743 HeapWord* prev_last_addr = NULL; 744 HeapRegion* prev_last_region = NULL; 745 746 // Temporarily disable pretouching of heap pages. This interface is used 747 // when mmap'ing archived heap data in, so pre-touching is wasted. 748 FlagSetting fs(AlwaysPreTouch, false); 749 750 // Enable archive object checking in G1MarkSweep. We have to let it know 751 // about each archive range, so that objects in those ranges aren't marked. 752 G1MarkSweep::enable_archive_object_check(); 753 754 // For each specified MemRegion range, allocate the corresponding G1 755 // regions and mark them as archive regions. We expect the ranges in 756 // ascending starting address order, without overlap. 757 for (size_t i = 0; i < count; i++) { 758 MemRegion curr_range = ranges[i]; 759 HeapWord* start_address = curr_range.start(); 760 size_t word_size = curr_range.word_size(); 761 HeapWord* last_address = curr_range.last(); 762 size_t commits = 0; 763 764 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 765 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 766 p2i(start_address), p2i(last_address)); 767 guarantee(start_address > prev_last_addr, 768 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 769 p2i(start_address), p2i(prev_last_addr)); 770 prev_last_addr = last_address; 771 772 // Check for ranges that start in the same G1 region in which the previous 773 // range ended, and adjust the start address so we don't try to allocate 774 // the same region again. If the current range is entirely within that 775 // region, skip it, just adjusting the recorded top. 776 HeapRegion* start_region = _hrm.addr_to_region(start_address); 777 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 778 start_address = start_region->end(); 779 if (start_address > last_address) { 780 increase_used(word_size * HeapWordSize); 781 start_region->set_top(last_address + 1); 782 continue; 783 } 784 start_region->set_top(start_address); 785 curr_range = MemRegion(start_address, last_address + 1); 786 start_region = _hrm.addr_to_region(start_address); 787 } 788 789 // Perform the actual region allocation, exiting if it fails. 790 // Then note how much new space we have allocated. 791 if (!_hrm.allocate_containing_regions(curr_range, &commits)) { 792 return false; 793 } 794 increase_used(word_size * HeapWordSize); 795 if (commits != 0) { 796 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 797 HeapRegion::GrainWords * HeapWordSize * commits); 798 799 } 800 801 // Mark each G1 region touched by the range as archive, add it to the old set, 802 // and set the allocation context and top. 803 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 804 HeapRegion* last_region = _hrm.addr_to_region(last_address); 805 prev_last_region = last_region; 806 807 while (curr_region != NULL) { 808 assert(curr_region->is_empty() && !curr_region->is_pinned(), 809 "Region already in use (index %u)", curr_region->hrm_index()); 810 _hr_printer.alloc(curr_region, G1HRPrinter::Archive); 811 curr_region->set_allocation_context(AllocationContext::system()); 812 curr_region->set_archive(); 813 _old_set.add(curr_region); 814 if (curr_region != last_region) { 815 curr_region->set_top(curr_region->end()); 816 curr_region = _hrm.next_region_in_heap(curr_region); 817 } else { 818 curr_region->set_top(last_address + 1); 819 curr_region = NULL; 820 } 821 } 822 823 // Notify mark-sweep of the archive range. 824 G1MarkSweep::set_range_archive(curr_range, true); 825 } 826 return true; 827 } 828 829 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 830 assert(!is_init_completed(), "Expect to be called at JVM init time"); 831 assert(ranges != NULL, "MemRegion array NULL"); 832 assert(count != 0, "No MemRegions provided"); 833 MemRegion reserved = _hrm.reserved(); 834 HeapWord *prev_last_addr = NULL; 835 HeapRegion* prev_last_region = NULL; 836 837 // For each MemRegion, create filler objects, if needed, in the G1 regions 838 // that contain the address range. The address range actually within the 839 // MemRegion will not be modified. That is assumed to have been initialized 840 // elsewhere, probably via an mmap of archived heap data. 841 MutexLockerEx x(Heap_lock); 842 for (size_t i = 0; i < count; i++) { 843 HeapWord* start_address = ranges[i].start(); 844 HeapWord* last_address = ranges[i].last(); 845 846 assert(reserved.contains(start_address) && reserved.contains(last_address), 847 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 848 p2i(start_address), p2i(last_address)); 849 assert(start_address > prev_last_addr, 850 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 851 p2i(start_address), p2i(prev_last_addr)); 852 853 HeapRegion* start_region = _hrm.addr_to_region(start_address); 854 HeapRegion* last_region = _hrm.addr_to_region(last_address); 855 HeapWord* bottom_address = start_region->bottom(); 856 857 // Check for a range beginning in the same region in which the 858 // previous one ended. 859 if (start_region == prev_last_region) { 860 bottom_address = prev_last_addr + 1; 861 } 862 863 // Verify that the regions were all marked as archive regions by 864 // alloc_archive_regions. 865 HeapRegion* curr_region = start_region; 866 while (curr_region != NULL) { 867 guarantee(curr_region->is_archive(), 868 "Expected archive region at index %u", curr_region->hrm_index()); 869 if (curr_region != last_region) { 870 curr_region = _hrm.next_region_in_heap(curr_region); 871 } else { 872 curr_region = NULL; 873 } 874 } 875 876 prev_last_addr = last_address; 877 prev_last_region = last_region; 878 879 // Fill the memory below the allocated range with dummy object(s), 880 // if the region bottom does not match the range start, or if the previous 881 // range ended within the same G1 region, and there is a gap. 882 if (start_address != bottom_address) { 883 size_t fill_size = pointer_delta(start_address, bottom_address); 884 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 885 increase_used(fill_size * HeapWordSize); 886 } 887 } 888 } 889 890 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 891 uint* gc_count_before_ret, 892 uint* gclocker_retry_count_ret) { 893 assert_heap_not_locked_and_not_at_safepoint(); 894 assert(!is_humongous(word_size), "attempt_allocation() should not " 895 "be called for humongous allocation requests"); 896 897 AllocationContext_t context = AllocationContext::current(); 898 HeapWord* result = _allocator->attempt_allocation(word_size, context); 899 900 if (result == NULL) { 901 result = attempt_allocation_slow(word_size, 902 context, 903 gc_count_before_ret, 904 gclocker_retry_count_ret); 905 } 906 assert_heap_not_locked(); 907 if (result != NULL) { 908 dirty_young_block(result, word_size); 909 } 910 return result; 911 } 912 913 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 914 assert(!is_init_completed(), "Expect to be called at JVM init time"); 915 assert(ranges != NULL, "MemRegion array NULL"); 916 assert(count != 0, "No MemRegions provided"); 917 MemRegion reserved = _hrm.reserved(); 918 HeapWord* prev_last_addr = NULL; 919 HeapRegion* prev_last_region = NULL; 920 size_t size_used = 0; 921 size_t uncommitted_regions = 0; 922 923 // For each Memregion, free the G1 regions that constitute it, and 924 // notify mark-sweep that the range is no longer to be considered 'archive.' 925 MutexLockerEx x(Heap_lock); 926 for (size_t i = 0; i < count; i++) { 927 HeapWord* start_address = ranges[i].start(); 928 HeapWord* last_address = ranges[i].last(); 929 930 assert(reserved.contains(start_address) && reserved.contains(last_address), 931 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 932 p2i(start_address), p2i(last_address)); 933 assert(start_address > prev_last_addr, 934 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 935 p2i(start_address), p2i(prev_last_addr)); 936 size_used += ranges[i].byte_size(); 937 prev_last_addr = last_address; 938 939 HeapRegion* start_region = _hrm.addr_to_region(start_address); 940 HeapRegion* last_region = _hrm.addr_to_region(last_address); 941 942 // Check for ranges that start in the same G1 region in which the previous 943 // range ended, and adjust the start address so we don't try to free 944 // the same region again. If the current range is entirely within that 945 // region, skip it. 946 if (start_region == prev_last_region) { 947 start_address = start_region->end(); 948 if (start_address > last_address) { 949 continue; 950 } 951 start_region = _hrm.addr_to_region(start_address); 952 } 953 prev_last_region = last_region; 954 955 // After verifying that each region was marked as an archive region by 956 // alloc_archive_regions, set it free and empty and uncommit it. 957 HeapRegion* curr_region = start_region; 958 while (curr_region != NULL) { 959 guarantee(curr_region->is_archive(), 960 "Expected archive region at index %u", curr_region->hrm_index()); 961 uint curr_index = curr_region->hrm_index(); 962 _old_set.remove(curr_region); 963 curr_region->set_free(); 964 curr_region->set_top(curr_region->bottom()); 965 if (curr_region != last_region) { 966 curr_region = _hrm.next_region_in_heap(curr_region); 967 } else { 968 curr_region = NULL; 969 } 970 _hrm.shrink_at(curr_index, 1); 971 uncommitted_regions++; 972 } 973 974 // Notify mark-sweep that this is no longer an archive range. 975 G1MarkSweep::set_range_archive(ranges[i], false); 976 } 977 978 if (uncommitted_regions != 0) { 979 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 980 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 981 } 982 decrease_used(size_used); 983 } 984 985 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 986 uint* gc_count_before_ret, 987 uint* gclocker_retry_count_ret) { 988 // The structure of this method has a lot of similarities to 989 // attempt_allocation_slow(). The reason these two were not merged 990 // into a single one is that such a method would require several "if 991 // allocation is not humongous do this, otherwise do that" 992 // conditional paths which would obscure its flow. In fact, an early 993 // version of this code did use a unified method which was harder to 994 // follow and, as a result, it had subtle bugs that were hard to 995 // track down. So keeping these two methods separate allows each to 996 // be more readable. It will be good to keep these two in sync as 997 // much as possible. 998 999 assert_heap_not_locked_and_not_at_safepoint(); 1000 assert(is_humongous(word_size), "attempt_allocation_humongous() " 1001 "should only be called for humongous allocations"); 1002 1003 // Humongous objects can exhaust the heap quickly, so we should check if we 1004 // need to start a marking cycle at each humongous object allocation. We do 1005 // the check before we do the actual allocation. The reason for doing it 1006 // before the allocation is that we avoid having to keep track of the newly 1007 // allocated memory while we do a GC. 1008 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 1009 word_size)) { 1010 collect(GCCause::_g1_humongous_allocation); 1011 } 1012 1013 // We will loop until a) we manage to successfully perform the 1014 // allocation or b) we successfully schedule a collection which 1015 // fails to perform the allocation. b) is the only case when we'll 1016 // return NULL. 1017 HeapWord* result = NULL; 1018 for (int try_count = 1; /* we'll return */; try_count += 1) { 1019 bool should_try_gc; 1020 uint gc_count_before; 1021 1022 { 1023 MutexLockerEx x(Heap_lock); 1024 1025 // Given that humongous objects are not allocated in young 1026 // regions, we'll first try to do the allocation without doing a 1027 // collection hoping that there's enough space in the heap. 1028 result = humongous_obj_allocate(word_size, AllocationContext::current()); 1029 if (result != NULL) { 1030 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 1031 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 1032 return result; 1033 } 1034 1035 if (GC_locker::is_active_and_needs_gc()) { 1036 should_try_gc = false; 1037 } else { 1038 // The GCLocker may not be active but the GCLocker initiated 1039 // GC may not yet have been performed (GCLocker::needs_gc() 1040 // returns true). In this case we do not try this GC and 1041 // wait until the GCLocker initiated GC is performed, and 1042 // then retry the allocation. 1043 if (GC_locker::needs_gc()) { 1044 should_try_gc = false; 1045 } else { 1046 // Read the GC count while still holding the Heap_lock. 1047 gc_count_before = total_collections(); 1048 should_try_gc = true; 1049 } 1050 } 1051 } 1052 1053 if (should_try_gc) { 1054 // If we failed to allocate the humongous object, we should try to 1055 // do a collection pause (if we're allowed) in case it reclaims 1056 // enough space for the allocation to succeed after the pause. 1057 1058 bool succeeded; 1059 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1060 GCCause::_g1_humongous_allocation); 1061 if (result != NULL) { 1062 assert(succeeded, "only way to get back a non-NULL result"); 1063 return result; 1064 } 1065 1066 if (succeeded) { 1067 // If we get here we successfully scheduled a collection which 1068 // failed to allocate. No point in trying to allocate 1069 // further. We'll just return NULL. 1070 MutexLockerEx x(Heap_lock); 1071 *gc_count_before_ret = total_collections(); 1072 return NULL; 1073 } 1074 } else { 1075 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1076 MutexLockerEx x(Heap_lock); 1077 *gc_count_before_ret = total_collections(); 1078 return NULL; 1079 } 1080 // The GCLocker is either active or the GCLocker initiated 1081 // GC has not yet been performed. Stall until it is and 1082 // then retry the allocation. 1083 GC_locker::stall_until_clear(); 1084 (*gclocker_retry_count_ret) += 1; 1085 } 1086 1087 // We can reach here if we were unsuccessful in scheduling a 1088 // collection (because another thread beat us to it) or if we were 1089 // stalled due to the GC locker. In either can we should retry the 1090 // allocation attempt in case another thread successfully 1091 // performed a collection and reclaimed enough space. Give a 1092 // warning if we seem to be looping forever. 1093 1094 if ((QueuedAllocationWarningCount > 0) && 1095 (try_count % QueuedAllocationWarningCount == 0)) { 1096 warning("G1CollectedHeap::attempt_allocation_humongous() " 1097 "retries %d times", try_count); 1098 } 1099 } 1100 1101 ShouldNotReachHere(); 1102 return NULL; 1103 } 1104 1105 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1106 AllocationContext_t context, 1107 bool expect_null_mutator_alloc_region) { 1108 assert_at_safepoint(true /* should_be_vm_thread */); 1109 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1110 "the current alloc region was unexpectedly found to be non-NULL"); 1111 1112 if (!is_humongous(word_size)) { 1113 return _allocator->attempt_allocation_locked(word_size, context); 1114 } else { 1115 HeapWord* result = humongous_obj_allocate(word_size, context); 1116 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1117 collector_state()->set_initiate_conc_mark_if_possible(true); 1118 } 1119 return result; 1120 } 1121 1122 ShouldNotReachHere(); 1123 } 1124 1125 class PostMCRemSetClearClosure: public HeapRegionClosure { 1126 G1CollectedHeap* _g1h; 1127 ModRefBarrierSet* _mr_bs; 1128 public: 1129 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1130 _g1h(g1h), _mr_bs(mr_bs) {} 1131 1132 bool doHeapRegion(HeapRegion* r) { 1133 HeapRegionRemSet* hrrs = r->rem_set(); 1134 1135 _g1h->reset_gc_time_stamps(r); 1136 1137 if (r->is_continues_humongous()) { 1138 // We'll assert that the strong code root list and RSet is empty 1139 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1140 assert(hrrs->occupied() == 0, "RSet should be empty"); 1141 } else { 1142 hrrs->clear(); 1143 } 1144 // You might think here that we could clear just the cards 1145 // corresponding to the used region. But no: if we leave a dirty card 1146 // in a region we might allocate into, then it would prevent that card 1147 // from being enqueued, and cause it to be missed. 1148 // Re: the performance cost: we shouldn't be doing full GC anyway! 1149 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1150 1151 return false; 1152 } 1153 }; 1154 1155 void G1CollectedHeap::clear_rsets_post_compaction() { 1156 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1157 heap_region_iterate(&rs_clear); 1158 } 1159 1160 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1161 G1CollectedHeap* _g1h; 1162 UpdateRSOopClosure _cl; 1163 public: 1164 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1165 _cl(g1->g1_rem_set(), worker_i), 1166 _g1h(g1) 1167 { } 1168 1169 bool doHeapRegion(HeapRegion* r) { 1170 if (!r->is_continues_humongous()) { 1171 _cl.set_from(r); 1172 r->oop_iterate(&_cl); 1173 } 1174 return false; 1175 } 1176 }; 1177 1178 class ParRebuildRSTask: public AbstractGangTask { 1179 G1CollectedHeap* _g1; 1180 HeapRegionClaimer _hrclaimer; 1181 1182 public: 1183 ParRebuildRSTask(G1CollectedHeap* g1) : 1184 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1185 1186 void work(uint worker_id) { 1187 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1188 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1189 } 1190 }; 1191 1192 class PostCompactionPrinterClosure: public HeapRegionClosure { 1193 private: 1194 G1HRPrinter* _hr_printer; 1195 public: 1196 bool doHeapRegion(HeapRegion* hr) { 1197 assert(!hr->is_young(), "not expecting to find young regions"); 1198 if (hr->is_free()) { 1199 // We only generate output for non-empty regions. 1200 } else if (hr->is_starts_humongous()) { 1201 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1202 } else if (hr->is_continues_humongous()) { 1203 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1204 } else if (hr->is_archive()) { 1205 _hr_printer->post_compaction(hr, G1HRPrinter::Archive); 1206 } else if (hr->is_old()) { 1207 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1208 } else { 1209 ShouldNotReachHere(); 1210 } 1211 return false; 1212 } 1213 1214 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1215 : _hr_printer(hr_printer) { } 1216 }; 1217 1218 void G1CollectedHeap::print_hrm_post_compaction() { 1219 if (_hr_printer.is_active()) { 1220 PostCompactionPrinterClosure cl(hr_printer()); 1221 heap_region_iterate(&cl); 1222 } 1223 1224 } 1225 1226 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1227 bool clear_all_soft_refs) { 1228 assert_at_safepoint(true /* should_be_vm_thread */); 1229 1230 if (GC_locker::check_active_before_gc()) { 1231 return false; 1232 } 1233 1234 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1235 gc_timer->register_gc_start(); 1236 1237 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1238 GCIdMark gc_id_mark; 1239 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1240 1241 SvcGCMarker sgcm(SvcGCMarker::FULL); 1242 ResourceMark rm; 1243 1244 print_heap_before_gc(); 1245 trace_heap_before_gc(gc_tracer); 1246 1247 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1248 1249 verify_region_sets_optional(); 1250 1251 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1252 collector_policy()->should_clear_all_soft_refs(); 1253 1254 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1255 1256 { 1257 IsGCActiveMark x; 1258 1259 // Timing 1260 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1261 GCTraceCPUTime tcpu; 1262 1263 { 1264 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1265 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1266 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1267 1268 g1_policy()->record_full_collection_start(); 1269 1270 // Note: When we have a more flexible GC logging framework that 1271 // allows us to add optional attributes to a GC log record we 1272 // could consider timing and reporting how long we wait in the 1273 // following two methods. 1274 wait_while_free_regions_coming(); 1275 // If we start the compaction before the CM threads finish 1276 // scanning the root regions we might trip them over as we'll 1277 // be moving objects / updating references. So let's wait until 1278 // they are done. By telling them to abort, they should complete 1279 // early. 1280 _cm->root_regions()->abort(); 1281 _cm->root_regions()->wait_until_scan_finished(); 1282 append_secondary_free_list_if_not_empty_with_lock(); 1283 1284 gc_prologue(true); 1285 increment_total_collections(true /* full gc */); 1286 increment_old_marking_cycles_started(); 1287 1288 assert(used() == recalculate_used(), "Should be equal"); 1289 1290 verify_before_gc(); 1291 1292 check_bitmaps("Full GC Start"); 1293 pre_full_gc_dump(gc_timer); 1294 1295 #if defined(COMPILER2) || INCLUDE_JVMCI 1296 DerivedPointerTable::clear(); 1297 #endif 1298 1299 // Disable discovery and empty the discovered lists 1300 // for the CM ref processor. 1301 ref_processor_cm()->disable_discovery(); 1302 ref_processor_cm()->abandon_partial_discovery(); 1303 ref_processor_cm()->verify_no_references_recorded(); 1304 1305 // Abandon current iterations of concurrent marking and concurrent 1306 // refinement, if any are in progress. We have to do this before 1307 // wait_until_scan_finished() below. 1308 concurrent_mark()->abort(); 1309 1310 // Make sure we'll choose a new allocation region afterwards. 1311 _allocator->release_mutator_alloc_region(); 1312 _allocator->abandon_gc_alloc_regions(); 1313 g1_rem_set()->cleanupHRRS(); 1314 1315 // We may have added regions to the current incremental collection 1316 // set between the last GC or pause and now. We need to clear the 1317 // incremental collection set and then start rebuilding it afresh 1318 // after this full GC. 1319 abandon_collection_set(g1_policy()->inc_cset_head()); 1320 g1_policy()->clear_incremental_cset(); 1321 g1_policy()->stop_incremental_cset_building(); 1322 1323 tear_down_region_sets(false /* free_list_only */); 1324 collector_state()->set_gcs_are_young(true); 1325 1326 // See the comments in g1CollectedHeap.hpp and 1327 // G1CollectedHeap::ref_processing_init() about 1328 // how reference processing currently works in G1. 1329 1330 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1331 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1332 1333 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1334 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1335 1336 ref_processor_stw()->enable_discovery(); 1337 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1338 1339 // Do collection work 1340 { 1341 HandleMark hm; // Discard invalid handles created during gc 1342 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1343 } 1344 1345 assert(num_free_regions() == 0, "we should not have added any free regions"); 1346 rebuild_region_sets(false /* free_list_only */); 1347 1348 // Enqueue any discovered reference objects that have 1349 // not been removed from the discovered lists. 1350 ref_processor_stw()->enqueue_discovered_references(); 1351 1352 #if defined(COMPILER2) || INCLUDE_JVMCI 1353 DerivedPointerTable::update_pointers(); 1354 #endif 1355 1356 MemoryService::track_memory_usage(); 1357 1358 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1359 ref_processor_stw()->verify_no_references_recorded(); 1360 1361 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1362 ClassLoaderDataGraph::purge(); 1363 MetaspaceAux::verify_metrics(); 1364 1365 // Note: since we've just done a full GC, concurrent 1366 // marking is no longer active. Therefore we need not 1367 // re-enable reference discovery for the CM ref processor. 1368 // That will be done at the start of the next marking cycle. 1369 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1370 ref_processor_cm()->verify_no_references_recorded(); 1371 1372 reset_gc_time_stamp(); 1373 // Since everything potentially moved, we will clear all remembered 1374 // sets, and clear all cards. Later we will rebuild remembered 1375 // sets. We will also reset the GC time stamps of the regions. 1376 clear_rsets_post_compaction(); 1377 check_gc_time_stamps(); 1378 1379 resize_if_necessary_after_full_collection(); 1380 1381 // We should do this after we potentially resize the heap so 1382 // that all the COMMIT / UNCOMMIT events are generated before 1383 // the compaction events. 1384 print_hrm_post_compaction(); 1385 1386 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1387 if (hot_card_cache->use_cache()) { 1388 hot_card_cache->reset_card_counts(); 1389 hot_card_cache->reset_hot_cache(); 1390 } 1391 1392 // Rebuild remembered sets of all regions. 1393 uint n_workers = 1394 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1395 workers()->active_workers(), 1396 Threads::number_of_non_daemon_threads()); 1397 workers()->set_active_workers(n_workers); 1398 1399 ParRebuildRSTask rebuild_rs_task(this); 1400 workers()->run_task(&rebuild_rs_task); 1401 1402 // Rebuild the strong code root lists for each region 1403 rebuild_strong_code_roots(); 1404 1405 if (true) { // FIXME 1406 MetaspaceGC::compute_new_size(); 1407 } 1408 1409 #ifdef TRACESPINNING 1410 ParallelTaskTerminator::print_termination_counts(); 1411 #endif 1412 1413 // Discard all rset updates 1414 JavaThread::dirty_card_queue_set().abandon_logs(); 1415 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1416 1417 _young_list->reset_sampled_info(); 1418 // At this point there should be no regions in the 1419 // entire heap tagged as young. 1420 assert(check_young_list_empty(true /* check_heap */), 1421 "young list should be empty at this point"); 1422 1423 // Update the number of full collections that have been completed. 1424 increment_old_marking_cycles_completed(false /* concurrent */); 1425 1426 _hrm.verify_optional(); 1427 verify_region_sets_optional(); 1428 1429 verify_after_gc(); 1430 1431 // Clear the previous marking bitmap, if needed for bitmap verification. 1432 // Note we cannot do this when we clear the next marking bitmap in 1433 // ConcurrentMark::abort() above since VerifyDuringGC verifies the 1434 // objects marked during a full GC against the previous bitmap. 1435 // But we need to clear it before calling check_bitmaps below since 1436 // the full GC has compacted objects and updated TAMS but not updated 1437 // the prev bitmap. 1438 if (G1VerifyBitmaps) { 1439 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll(); 1440 } 1441 check_bitmaps("Full GC End"); 1442 1443 // Start a new incremental collection set for the next pause 1444 assert(g1_policy()->collection_set() == NULL, "must be"); 1445 g1_policy()->start_incremental_cset_building(); 1446 1447 clear_cset_fast_test(); 1448 1449 _allocator->init_mutator_alloc_region(); 1450 1451 g1_policy()->record_full_collection_end(); 1452 1453 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1454 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1455 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1456 // before any GC notifications are raised. 1457 g1mm()->update_sizes(); 1458 1459 gc_epilogue(true); 1460 } 1461 1462 g1_policy()->print_detailed_heap_transition(); 1463 1464 print_heap_after_gc(); 1465 trace_heap_after_gc(gc_tracer); 1466 1467 post_full_gc_dump(gc_timer); 1468 1469 gc_timer->register_gc_end(); 1470 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1471 } 1472 1473 return true; 1474 } 1475 1476 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1477 // Currently, there is no facility in the do_full_collection(bool) API to notify 1478 // the caller that the collection did not succeed (e.g., because it was locked 1479 // out by the GC locker). So, right now, we'll ignore the return value. 1480 bool dummy = do_full_collection(true, /* explicit_gc */ 1481 clear_all_soft_refs); 1482 } 1483 1484 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1485 // Include bytes that will be pre-allocated to support collections, as "used". 1486 const size_t used_after_gc = used(); 1487 const size_t capacity_after_gc = capacity(); 1488 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1489 1490 // This is enforced in arguments.cpp. 1491 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1492 "otherwise the code below doesn't make sense"); 1493 1494 // We don't have floating point command-line arguments 1495 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1496 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1497 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1498 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1499 1500 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1501 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1502 1503 // We have to be careful here as these two calculations can overflow 1504 // 32-bit size_t's. 1505 double used_after_gc_d = (double) used_after_gc; 1506 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1507 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1508 1509 // Let's make sure that they are both under the max heap size, which 1510 // by default will make them fit into a size_t. 1511 double desired_capacity_upper_bound = (double) max_heap_size; 1512 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1513 desired_capacity_upper_bound); 1514 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1515 desired_capacity_upper_bound); 1516 1517 // We can now safely turn them into size_t's. 1518 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1519 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1520 1521 // This assert only makes sense here, before we adjust them 1522 // with respect to the min and max heap size. 1523 assert(minimum_desired_capacity <= maximum_desired_capacity, 1524 "minimum_desired_capacity = " SIZE_FORMAT ", " 1525 "maximum_desired_capacity = " SIZE_FORMAT, 1526 minimum_desired_capacity, maximum_desired_capacity); 1527 1528 // Should not be greater than the heap max size. No need to adjust 1529 // it with respect to the heap min size as it's a lower bound (i.e., 1530 // we'll try to make the capacity larger than it, not smaller). 1531 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1532 // Should not be less than the heap min size. No need to adjust it 1533 // with respect to the heap max size as it's an upper bound (i.e., 1534 // we'll try to make the capacity smaller than it, not greater). 1535 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1536 1537 if (capacity_after_gc < minimum_desired_capacity) { 1538 // Don't expand unless it's significant 1539 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1540 1541 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1542 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1543 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1544 1545 expand(expand_bytes); 1546 1547 // No expansion, now see if we want to shrink 1548 } else if (capacity_after_gc > maximum_desired_capacity) { 1549 // Capacity too large, compute shrinking size 1550 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1551 1552 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1553 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1554 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1555 1556 shrink(shrink_bytes); 1557 } 1558 } 1559 1560 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1561 AllocationContext_t context, 1562 bool do_gc, 1563 bool clear_all_soft_refs, 1564 bool expect_null_mutator_alloc_region, 1565 bool* gc_succeeded) { 1566 *gc_succeeded = true; 1567 // Let's attempt the allocation first. 1568 HeapWord* result = 1569 attempt_allocation_at_safepoint(word_size, 1570 context, 1571 expect_null_mutator_alloc_region); 1572 if (result != NULL) { 1573 assert(*gc_succeeded, "sanity"); 1574 return result; 1575 } 1576 1577 // In a G1 heap, we're supposed to keep allocation from failing by 1578 // incremental pauses. Therefore, at least for now, we'll favor 1579 // expansion over collection. (This might change in the future if we can 1580 // do something smarter than full collection to satisfy a failed alloc.) 1581 result = expand_and_allocate(word_size, context); 1582 if (result != NULL) { 1583 assert(*gc_succeeded, "sanity"); 1584 return result; 1585 } 1586 1587 if (do_gc) { 1588 // Expansion didn't work, we'll try to do a Full GC. 1589 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1590 clear_all_soft_refs); 1591 } 1592 1593 return NULL; 1594 } 1595 1596 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1597 AllocationContext_t context, 1598 bool* succeeded) { 1599 assert_at_safepoint(true /* should_be_vm_thread */); 1600 1601 // Attempts to allocate followed by Full GC. 1602 HeapWord* result = 1603 satisfy_failed_allocation_helper(word_size, 1604 context, 1605 true, /* do_gc */ 1606 false, /* clear_all_soft_refs */ 1607 false, /* expect_null_mutator_alloc_region */ 1608 succeeded); 1609 1610 if (result != NULL || !*succeeded) { 1611 return result; 1612 } 1613 1614 // Attempts to allocate followed by Full GC that will collect all soft references. 1615 result = satisfy_failed_allocation_helper(word_size, 1616 context, 1617 true, /* do_gc */ 1618 true, /* clear_all_soft_refs */ 1619 true, /* expect_null_mutator_alloc_region */ 1620 succeeded); 1621 1622 if (result != NULL || !*succeeded) { 1623 return result; 1624 } 1625 1626 // Attempts to allocate, no GC 1627 result = satisfy_failed_allocation_helper(word_size, 1628 context, 1629 false, /* do_gc */ 1630 false, /* clear_all_soft_refs */ 1631 true, /* expect_null_mutator_alloc_region */ 1632 succeeded); 1633 1634 if (result != NULL) { 1635 assert(*succeeded, "sanity"); 1636 return result; 1637 } 1638 1639 assert(!collector_policy()->should_clear_all_soft_refs(), 1640 "Flag should have been handled and cleared prior to this point"); 1641 1642 // What else? We might try synchronous finalization later. If the total 1643 // space available is large enough for the allocation, then a more 1644 // complete compaction phase than we've tried so far might be 1645 // appropriate. 1646 assert(*succeeded, "sanity"); 1647 return NULL; 1648 } 1649 1650 // Attempting to expand the heap sufficiently 1651 // to support an allocation of the given "word_size". If 1652 // successful, perform the allocation and return the address of the 1653 // allocated block, or else "NULL". 1654 1655 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1656 assert_at_safepoint(true /* should_be_vm_thread */); 1657 1658 verify_region_sets_optional(); 1659 1660 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1661 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1662 word_size * HeapWordSize); 1663 1664 1665 if (expand(expand_bytes)) { 1666 _hrm.verify_optional(); 1667 verify_region_sets_optional(); 1668 return attempt_allocation_at_safepoint(word_size, 1669 context, 1670 false /* expect_null_mutator_alloc_region */); 1671 } 1672 return NULL; 1673 } 1674 1675 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) { 1676 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1677 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1678 HeapRegion::GrainBytes); 1679 1680 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B", 1681 expand_bytes, aligned_expand_bytes); 1682 1683 if (is_maximal_no_gc()) { 1684 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1685 return false; 1686 } 1687 1688 double expand_heap_start_time_sec = os::elapsedTime(); 1689 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1690 assert(regions_to_expand > 0, "Must expand by at least one region"); 1691 1692 uint expanded_by = _hrm.expand_by(regions_to_expand); 1693 if (expand_time_ms != NULL) { 1694 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1695 } 1696 1697 if (expanded_by > 0) { 1698 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1699 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1700 g1_policy()->record_new_heap_size(num_regions()); 1701 } else { 1702 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1703 1704 // The expansion of the virtual storage space was unsuccessful. 1705 // Let's see if it was because we ran out of swap. 1706 if (G1ExitOnExpansionFailure && 1707 _hrm.available() >= regions_to_expand) { 1708 // We had head room... 1709 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1710 } 1711 } 1712 return regions_to_expand > 0; 1713 } 1714 1715 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1716 size_t aligned_shrink_bytes = 1717 ReservedSpace::page_align_size_down(shrink_bytes); 1718 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1719 HeapRegion::GrainBytes); 1720 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1721 1722 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1723 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1724 1725 1726 log_debug(gc, ergo, heap)("Shrink the heap. requested shrinking amount: " SIZE_FORMAT "B aligned shrinking amount: " SIZE_FORMAT "B attempted shrinking amount: " SIZE_FORMAT "B", 1727 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1728 if (num_regions_removed > 0) { 1729 g1_policy()->record_new_heap_size(num_regions()); 1730 } else { 1731 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1732 } 1733 } 1734 1735 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1736 verify_region_sets_optional(); 1737 1738 // We should only reach here at the end of a Full GC which means we 1739 // should not not be holding to any GC alloc regions. The method 1740 // below will make sure of that and do any remaining clean up. 1741 _allocator->abandon_gc_alloc_regions(); 1742 1743 // Instead of tearing down / rebuilding the free lists here, we 1744 // could instead use the remove_all_pending() method on free_list to 1745 // remove only the ones that we need to remove. 1746 tear_down_region_sets(true /* free_list_only */); 1747 shrink_helper(shrink_bytes); 1748 rebuild_region_sets(true /* free_list_only */); 1749 1750 _hrm.verify_optional(); 1751 verify_region_sets_optional(); 1752 } 1753 1754 // Public methods. 1755 1756 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1757 CollectedHeap(), 1758 _g1_policy(policy_), 1759 _dirty_card_queue_set(false), 1760 _is_alive_closure_cm(this), 1761 _is_alive_closure_stw(this), 1762 _ref_processor_cm(NULL), 1763 _ref_processor_stw(NULL), 1764 _bot_shared(NULL), 1765 _cg1r(NULL), 1766 _g1mm(NULL), 1767 _refine_cte_cl(NULL), 1768 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1769 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1770 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1771 _humongous_reclaim_candidates(), 1772 _has_humongous_reclaim_candidates(false), 1773 _archive_allocator(NULL), 1774 _free_regions_coming(false), 1775 _young_list(new YoungList(this)), 1776 _gc_time_stamp(0), 1777 _summary_bytes_used(0), 1778 _survivor_evac_stats(YoungPLABSize, PLABWeight), 1779 _old_evac_stats(OldPLABSize, PLABWeight), 1780 _expand_heap_after_alloc_failure(true), 1781 _old_marking_cycles_started(0), 1782 _old_marking_cycles_completed(0), 1783 _heap_summary_sent(false), 1784 _in_cset_fast_test(), 1785 _dirty_cards_region_list(NULL), 1786 _worker_cset_start_region(NULL), 1787 _worker_cset_start_region_time_stamp(NULL), 1788 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1789 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1790 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1791 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1792 1793 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1794 /* are_GC_task_threads */true, 1795 /* are_ConcurrentGC_threads */false); 1796 _workers->initialize_workers(); 1797 1798 _allocator = G1Allocator::create_allocator(this); 1799 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1800 1801 // Override the default _filler_array_max_size so that no humongous filler 1802 // objects are created. 1803 _filler_array_max_size = _humongous_object_threshold_in_words; 1804 1805 uint n_queues = ParallelGCThreads; 1806 _task_queues = new RefToScanQueueSet(n_queues); 1807 1808 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1809 assert(n_rem_sets > 0, "Invariant."); 1810 1811 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1812 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC); 1813 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1814 1815 for (uint i = 0; i < n_queues; i++) { 1816 RefToScanQueue* q = new RefToScanQueue(); 1817 q->initialize(); 1818 _task_queues->register_queue(i, q); 1819 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1820 } 1821 clear_cset_start_regions(); 1822 1823 // Initialize the G1EvacuationFailureALot counters and flags. 1824 NOT_PRODUCT(reset_evacuation_should_fail();) 1825 1826 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1827 } 1828 1829 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1830 size_t size, 1831 size_t translation_factor) { 1832 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1833 // Allocate a new reserved space, preferring to use large pages. 1834 ReservedSpace rs(size, preferred_page_size); 1835 G1RegionToSpaceMapper* result = 1836 G1RegionToSpaceMapper::create_mapper(rs, 1837 size, 1838 rs.alignment(), 1839 HeapRegion::GrainBytes, 1840 translation_factor, 1841 mtGC); 1842 if (TracePageSizes) { 1843 tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT, 1844 description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size); 1845 } 1846 return result; 1847 } 1848 1849 jint G1CollectedHeap::initialize() { 1850 CollectedHeap::pre_initialize(); 1851 os::enable_vtime(); 1852 1853 // Necessary to satisfy locking discipline assertions. 1854 1855 MutexLocker x(Heap_lock); 1856 1857 // While there are no constraints in the GC code that HeapWordSize 1858 // be any particular value, there are multiple other areas in the 1859 // system which believe this to be true (e.g. oop->object_size in some 1860 // cases incorrectly returns the size in wordSize units rather than 1861 // HeapWordSize). 1862 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1863 1864 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1865 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1866 size_t heap_alignment = collector_policy()->heap_alignment(); 1867 1868 // Ensure that the sizes are properly aligned. 1869 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1870 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1871 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1872 1873 _refine_cte_cl = new RefineCardTableEntryClosure(); 1874 1875 jint ecode = JNI_OK; 1876 _cg1r = ConcurrentG1Refine::create(this, _refine_cte_cl, &ecode); 1877 if (_cg1r == NULL) { 1878 return ecode; 1879 } 1880 1881 // Reserve the maximum. 1882 1883 // When compressed oops are enabled, the preferred heap base 1884 // is calculated by subtracting the requested size from the 1885 // 32Gb boundary and using the result as the base address for 1886 // heap reservation. If the requested size is not aligned to 1887 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1888 // into the ReservedHeapSpace constructor) then the actual 1889 // base of the reserved heap may end up differing from the 1890 // address that was requested (i.e. the preferred heap base). 1891 // If this happens then we could end up using a non-optimal 1892 // compressed oops mode. 1893 1894 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1895 heap_alignment); 1896 1897 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1898 1899 // Create the barrier set for the entire reserved region. 1900 G1SATBCardTableLoggingModRefBS* bs 1901 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1902 bs->initialize(); 1903 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1904 set_barrier_set(bs); 1905 1906 // Also create a G1 rem set. 1907 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 1908 1909 // Carve out the G1 part of the heap. 1910 1911 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1912 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1913 G1RegionToSpaceMapper* heap_storage = 1914 G1RegionToSpaceMapper::create_mapper(g1_rs, 1915 g1_rs.size(), 1916 page_size, 1917 HeapRegion::GrainBytes, 1918 1, 1919 mtJavaHeap); 1920 os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(), 1921 max_byte_size, page_size, 1922 heap_rs.base(), 1923 heap_rs.size()); 1924 heap_storage->set_mapping_changed_listener(&_listener); 1925 1926 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1927 G1RegionToSpaceMapper* bot_storage = 1928 create_aux_memory_mapper("Block offset table", 1929 G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize), 1930 G1BlockOffsetSharedArray::heap_map_factor()); 1931 1932 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1933 G1RegionToSpaceMapper* cardtable_storage = 1934 create_aux_memory_mapper("Card table", 1935 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1936 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1937 1938 G1RegionToSpaceMapper* card_counts_storage = 1939 create_aux_memory_mapper("Card counts table", 1940 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1941 G1CardCounts::heap_map_factor()); 1942 1943 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size()); 1944 G1RegionToSpaceMapper* prev_bitmap_storage = 1945 create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1946 G1RegionToSpaceMapper* next_bitmap_storage = 1947 create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1948 1949 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1950 g1_barrier_set()->initialize(cardtable_storage); 1951 // Do later initialization work for concurrent refinement. 1952 _cg1r->init(card_counts_storage); 1953 1954 // 6843694 - ensure that the maximum region index can fit 1955 // in the remembered set structures. 1956 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1957 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1958 1959 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1960 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1961 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1962 "too many cards per region"); 1963 1964 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1965 1966 _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage); 1967 1968 { 1969 HeapWord* start = _hrm.reserved().start(); 1970 HeapWord* end = _hrm.reserved().end(); 1971 size_t granularity = HeapRegion::GrainBytes; 1972 1973 _in_cset_fast_test.initialize(start, end, granularity); 1974 _humongous_reclaim_candidates.initialize(start, end, granularity); 1975 } 1976 1977 // Create the ConcurrentMark data structure and thread. 1978 // (Must do this late, so that "max_regions" is defined.) 1979 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1980 if (_cm == NULL || !_cm->completed_initialization()) { 1981 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 1982 return JNI_ENOMEM; 1983 } 1984 _cmThread = _cm->cmThread(); 1985 1986 // Initialize the from_card cache structure of HeapRegionRemSet. 1987 HeapRegionRemSet::init_heap(max_regions()); 1988 1989 // Now expand into the initial heap size. 1990 if (!expand(init_byte_size)) { 1991 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1992 return JNI_ENOMEM; 1993 } 1994 1995 // Perform any initialization actions delegated to the policy. 1996 g1_policy()->init(); 1997 1998 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1999 SATB_Q_FL_lock, 2000 G1SATBProcessCompletedThreshold, 2001 Shared_SATB_Q_lock); 2002 2003 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 2004 DirtyCardQ_CBL_mon, 2005 DirtyCardQ_FL_lock, 2006 concurrent_g1_refine()->yellow_zone(), 2007 concurrent_g1_refine()->red_zone(), 2008 Shared_DirtyCardQ_lock); 2009 2010 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 2011 DirtyCardQ_CBL_mon, 2012 DirtyCardQ_FL_lock, 2013 -1, // never trigger processing 2014 -1, // no limit on length 2015 Shared_DirtyCardQ_lock, 2016 &JavaThread::dirty_card_queue_set()); 2017 2018 // Here we allocate the dummy HeapRegion that is required by the 2019 // G1AllocRegion class. 2020 HeapRegion* dummy_region = _hrm.get_dummy_region(); 2021 2022 // We'll re-use the same region whether the alloc region will 2023 // require BOT updates or not and, if it doesn't, then a non-young 2024 // region will complain that it cannot support allocations without 2025 // BOT updates. So we'll tag the dummy region as eden to avoid that. 2026 dummy_region->set_eden(); 2027 // Make sure it's full. 2028 dummy_region->set_top(dummy_region->end()); 2029 G1AllocRegion::setup(this, dummy_region); 2030 2031 _allocator->init_mutator_alloc_region(); 2032 2033 // Do create of the monitoring and management support so that 2034 // values in the heap have been properly initialized. 2035 _g1mm = new G1MonitoringSupport(this); 2036 2037 G1StringDedup::initialize(); 2038 2039 _preserved_objs = NEW_C_HEAP_ARRAY(OopAndMarkOopStack, ParallelGCThreads, mtGC); 2040 for (uint i = 0; i < ParallelGCThreads; i++) { 2041 new (&_preserved_objs[i]) OopAndMarkOopStack(); 2042 } 2043 2044 return JNI_OK; 2045 } 2046 2047 void G1CollectedHeap::stop() { 2048 // Stop all concurrent threads. We do this to make sure these threads 2049 // do not continue to execute and access resources (e.g. logging) 2050 // that are destroyed during shutdown. 2051 _cg1r->stop(); 2052 _cmThread->stop(); 2053 if (G1StringDedup::is_enabled()) { 2054 G1StringDedup::stop(); 2055 } 2056 } 2057 2058 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2059 return HeapRegion::max_region_size(); 2060 } 2061 2062 void G1CollectedHeap::post_initialize() { 2063 CollectedHeap::post_initialize(); 2064 ref_processing_init(); 2065 } 2066 2067 void G1CollectedHeap::ref_processing_init() { 2068 // Reference processing in G1 currently works as follows: 2069 // 2070 // * There are two reference processor instances. One is 2071 // used to record and process discovered references 2072 // during concurrent marking; the other is used to 2073 // record and process references during STW pauses 2074 // (both full and incremental). 2075 // * Both ref processors need to 'span' the entire heap as 2076 // the regions in the collection set may be dotted around. 2077 // 2078 // * For the concurrent marking ref processor: 2079 // * Reference discovery is enabled at initial marking. 2080 // * Reference discovery is disabled and the discovered 2081 // references processed etc during remarking. 2082 // * Reference discovery is MT (see below). 2083 // * Reference discovery requires a barrier (see below). 2084 // * Reference processing may or may not be MT 2085 // (depending on the value of ParallelRefProcEnabled 2086 // and ParallelGCThreads). 2087 // * A full GC disables reference discovery by the CM 2088 // ref processor and abandons any entries on it's 2089 // discovered lists. 2090 // 2091 // * For the STW processor: 2092 // * Non MT discovery is enabled at the start of a full GC. 2093 // * Processing and enqueueing during a full GC is non-MT. 2094 // * During a full GC, references are processed after marking. 2095 // 2096 // * Discovery (may or may not be MT) is enabled at the start 2097 // of an incremental evacuation pause. 2098 // * References are processed near the end of a STW evacuation pause. 2099 // * For both types of GC: 2100 // * Discovery is atomic - i.e. not concurrent. 2101 // * Reference discovery will not need a barrier. 2102 2103 MemRegion mr = reserved_region(); 2104 2105 // Concurrent Mark ref processor 2106 _ref_processor_cm = 2107 new ReferenceProcessor(mr, // span 2108 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2109 // mt processing 2110 ParallelGCThreads, 2111 // degree of mt processing 2112 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2113 // mt discovery 2114 MAX2(ParallelGCThreads, ConcGCThreads), 2115 // degree of mt discovery 2116 false, 2117 // Reference discovery is not atomic 2118 &_is_alive_closure_cm); 2119 // is alive closure 2120 // (for efficiency/performance) 2121 2122 // STW ref processor 2123 _ref_processor_stw = 2124 new ReferenceProcessor(mr, // span 2125 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2126 // mt processing 2127 ParallelGCThreads, 2128 // degree of mt processing 2129 (ParallelGCThreads > 1), 2130 // mt discovery 2131 ParallelGCThreads, 2132 // degree of mt discovery 2133 true, 2134 // Reference discovery is atomic 2135 &_is_alive_closure_stw); 2136 // is alive closure 2137 // (for efficiency/performance) 2138 } 2139 2140 CollectorPolicy* G1CollectedHeap::collector_policy() const { 2141 return g1_policy(); 2142 } 2143 2144 size_t G1CollectedHeap::capacity() const { 2145 return _hrm.length() * HeapRegion::GrainBytes; 2146 } 2147 2148 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2149 hr->reset_gc_time_stamp(); 2150 } 2151 2152 #ifndef PRODUCT 2153 2154 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2155 private: 2156 unsigned _gc_time_stamp; 2157 bool _failures; 2158 2159 public: 2160 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2161 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2162 2163 virtual bool doHeapRegion(HeapRegion* hr) { 2164 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2165 if (_gc_time_stamp != region_gc_time_stamp) { 2166 log_info(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 2167 region_gc_time_stamp, _gc_time_stamp); 2168 _failures = true; 2169 } 2170 return false; 2171 } 2172 2173 bool failures() { return _failures; } 2174 }; 2175 2176 void G1CollectedHeap::check_gc_time_stamps() { 2177 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2178 heap_region_iterate(&cl); 2179 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2180 } 2181 #endif // PRODUCT 2182 2183 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2184 _cg1r->hot_card_cache()->drain(cl, worker_i); 2185 } 2186 2187 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2188 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2189 size_t n_completed_buffers = 0; 2190 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2191 n_completed_buffers++; 2192 } 2193 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2194 dcqs.clear_n_completed_buffers(); 2195 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2196 } 2197 2198 // Computes the sum of the storage used by the various regions. 2199 size_t G1CollectedHeap::used() const { 2200 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2201 if (_archive_allocator != NULL) { 2202 result += _archive_allocator->used(); 2203 } 2204 return result; 2205 } 2206 2207 size_t G1CollectedHeap::used_unlocked() const { 2208 return _summary_bytes_used; 2209 } 2210 2211 class SumUsedClosure: public HeapRegionClosure { 2212 size_t _used; 2213 public: 2214 SumUsedClosure() : _used(0) {} 2215 bool doHeapRegion(HeapRegion* r) { 2216 _used += r->used(); 2217 return false; 2218 } 2219 size_t result() { return _used; } 2220 }; 2221 2222 size_t G1CollectedHeap::recalculate_used() const { 2223 double recalculate_used_start = os::elapsedTime(); 2224 2225 SumUsedClosure blk; 2226 heap_region_iterate(&blk); 2227 2228 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2229 return blk.result(); 2230 } 2231 2232 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2233 switch (cause) { 2234 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2235 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2236 case GCCause::_update_allocation_context_stats_inc: return true; 2237 case GCCause::_wb_conc_mark: return true; 2238 default : return false; 2239 } 2240 } 2241 2242 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2243 switch (cause) { 2244 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2245 case GCCause::_g1_humongous_allocation: return true; 2246 default: return is_user_requested_concurrent_full_gc(cause); 2247 } 2248 } 2249 2250 #ifndef PRODUCT 2251 void G1CollectedHeap::allocate_dummy_regions() { 2252 // Let's fill up most of the region 2253 size_t word_size = HeapRegion::GrainWords - 1024; 2254 // And as a result the region we'll allocate will be humongous. 2255 guarantee(is_humongous(word_size), "sanity"); 2256 2257 // _filler_array_max_size is set to humongous object threshold 2258 // but temporarily change it to use CollectedHeap::fill_with_object(). 2259 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2260 2261 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2262 // Let's use the existing mechanism for the allocation 2263 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2264 AllocationContext::system()); 2265 if (dummy_obj != NULL) { 2266 MemRegion mr(dummy_obj, word_size); 2267 CollectedHeap::fill_with_object(mr); 2268 } else { 2269 // If we can't allocate once, we probably cannot allocate 2270 // again. Let's get out of the loop. 2271 break; 2272 } 2273 } 2274 } 2275 #endif // !PRODUCT 2276 2277 void G1CollectedHeap::increment_old_marking_cycles_started() { 2278 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2279 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2280 "Wrong marking cycle count (started: %d, completed: %d)", 2281 _old_marking_cycles_started, _old_marking_cycles_completed); 2282 2283 _old_marking_cycles_started++; 2284 } 2285 2286 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2287 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2288 2289 // We assume that if concurrent == true, then the caller is a 2290 // concurrent thread that was joined the Suspendible Thread 2291 // Set. If there's ever a cheap way to check this, we should add an 2292 // assert here. 2293 2294 // Given that this method is called at the end of a Full GC or of a 2295 // concurrent cycle, and those can be nested (i.e., a Full GC can 2296 // interrupt a concurrent cycle), the number of full collections 2297 // completed should be either one (in the case where there was no 2298 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2299 // behind the number of full collections started. 2300 2301 // This is the case for the inner caller, i.e. a Full GC. 2302 assert(concurrent || 2303 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2304 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2305 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2306 "is inconsistent with _old_marking_cycles_completed = %u", 2307 _old_marking_cycles_started, _old_marking_cycles_completed); 2308 2309 // This is the case for the outer caller, i.e. the concurrent cycle. 2310 assert(!concurrent || 2311 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2312 "for outer caller (concurrent cycle): " 2313 "_old_marking_cycles_started = %u " 2314 "is inconsistent with _old_marking_cycles_completed = %u", 2315 _old_marking_cycles_started, _old_marking_cycles_completed); 2316 2317 _old_marking_cycles_completed += 1; 2318 2319 // We need to clear the "in_progress" flag in the CM thread before 2320 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2321 // is set) so that if a waiter requests another System.gc() it doesn't 2322 // incorrectly see that a marking cycle is still in progress. 2323 if (concurrent) { 2324 _cmThread->set_idle(); 2325 } 2326 2327 // This notify_all() will ensure that a thread that called 2328 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2329 // and it's waiting for a full GC to finish will be woken up. It is 2330 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2331 FullGCCount_lock->notify_all(); 2332 } 2333 2334 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2335 GCIdMarkAndRestore conc_gc_id_mark; 2336 collector_state()->set_concurrent_cycle_started(true); 2337 _gc_timer_cm->register_gc_start(start_time); 2338 2339 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2340 trace_heap_before_gc(_gc_tracer_cm); 2341 _cmThread->set_gc_id(GCId::current()); 2342 } 2343 2344 void G1CollectedHeap::register_concurrent_cycle_end() { 2345 if (collector_state()->concurrent_cycle_started()) { 2346 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2347 if (_cm->has_aborted()) { 2348 _gc_tracer_cm->report_concurrent_mode_failure(); 2349 } 2350 2351 _gc_timer_cm->register_gc_end(); 2352 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2353 2354 // Clear state variables to prepare for the next concurrent cycle. 2355 collector_state()->set_concurrent_cycle_started(false); 2356 _heap_summary_sent = false; 2357 } 2358 } 2359 2360 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2361 if (collector_state()->concurrent_cycle_started()) { 2362 // This function can be called when: 2363 // the cleanup pause is run 2364 // the concurrent cycle is aborted before the cleanup pause. 2365 // the concurrent cycle is aborted after the cleanup pause, 2366 // but before the concurrent cycle end has been registered. 2367 // Make sure that we only send the heap information once. 2368 if (!_heap_summary_sent) { 2369 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2370 trace_heap_after_gc(_gc_tracer_cm); 2371 _heap_summary_sent = true; 2372 } 2373 } 2374 } 2375 2376 void G1CollectedHeap::collect(GCCause::Cause cause) { 2377 assert_heap_not_locked(); 2378 2379 uint gc_count_before; 2380 uint old_marking_count_before; 2381 uint full_gc_count_before; 2382 bool retry_gc; 2383 2384 do { 2385 retry_gc = false; 2386 2387 { 2388 MutexLocker ml(Heap_lock); 2389 2390 // Read the GC count while holding the Heap_lock 2391 gc_count_before = total_collections(); 2392 full_gc_count_before = total_full_collections(); 2393 old_marking_count_before = _old_marking_cycles_started; 2394 } 2395 2396 if (should_do_concurrent_full_gc(cause)) { 2397 // Schedule an initial-mark evacuation pause that will start a 2398 // concurrent cycle. We're setting word_size to 0 which means that 2399 // we are not requesting a post-GC allocation. 2400 VM_G1IncCollectionPause op(gc_count_before, 2401 0, /* word_size */ 2402 true, /* should_initiate_conc_mark */ 2403 g1_policy()->max_pause_time_ms(), 2404 cause); 2405 op.set_allocation_context(AllocationContext::current()); 2406 2407 VMThread::execute(&op); 2408 if (!op.pause_succeeded()) { 2409 if (old_marking_count_before == _old_marking_cycles_started) { 2410 retry_gc = op.should_retry_gc(); 2411 } else { 2412 // A Full GC happened while we were trying to schedule the 2413 // initial-mark GC. No point in starting a new cycle given 2414 // that the whole heap was collected anyway. 2415 } 2416 2417 if (retry_gc) { 2418 if (GC_locker::is_active_and_needs_gc()) { 2419 GC_locker::stall_until_clear(); 2420 } 2421 } 2422 } 2423 } else { 2424 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2425 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2426 2427 // Schedule a standard evacuation pause. We're setting word_size 2428 // to 0 which means that we are not requesting a post-GC allocation. 2429 VM_G1IncCollectionPause op(gc_count_before, 2430 0, /* word_size */ 2431 false, /* should_initiate_conc_mark */ 2432 g1_policy()->max_pause_time_ms(), 2433 cause); 2434 VMThread::execute(&op); 2435 } else { 2436 // Schedule a Full GC. 2437 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2438 VMThread::execute(&op); 2439 } 2440 } 2441 } while (retry_gc); 2442 } 2443 2444 bool G1CollectedHeap::is_in(const void* p) const { 2445 if (_hrm.reserved().contains(p)) { 2446 // Given that we know that p is in the reserved space, 2447 // heap_region_containing() should successfully 2448 // return the containing region. 2449 HeapRegion* hr = heap_region_containing(p); 2450 return hr->is_in(p); 2451 } else { 2452 return false; 2453 } 2454 } 2455 2456 #ifdef ASSERT 2457 bool G1CollectedHeap::is_in_exact(const void* p) const { 2458 bool contains = reserved_region().contains(p); 2459 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2460 if (contains && available) { 2461 return true; 2462 } else { 2463 return false; 2464 } 2465 } 2466 #endif 2467 2468 bool G1CollectedHeap::obj_in_cs(oop obj) { 2469 HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj); 2470 return r != NULL && r->in_collection_set(); 2471 } 2472 2473 // Iteration functions. 2474 2475 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2476 2477 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2478 ExtendedOopClosure* _cl; 2479 public: 2480 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2481 bool doHeapRegion(HeapRegion* r) { 2482 if (!r->is_continues_humongous()) { 2483 r->oop_iterate(_cl); 2484 } 2485 return false; 2486 } 2487 }; 2488 2489 // Iterates an ObjectClosure over all objects within a HeapRegion. 2490 2491 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2492 ObjectClosure* _cl; 2493 public: 2494 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2495 bool doHeapRegion(HeapRegion* r) { 2496 if (!r->is_continues_humongous()) { 2497 r->object_iterate(_cl); 2498 } 2499 return false; 2500 } 2501 }; 2502 2503 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2504 IterateObjectClosureRegionClosure blk(cl); 2505 heap_region_iterate(&blk); 2506 } 2507 2508 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2509 _hrm.iterate(cl); 2510 } 2511 2512 void 2513 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2514 uint worker_id, 2515 HeapRegionClaimer *hrclaimer, 2516 bool concurrent) const { 2517 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2518 } 2519 2520 // Clear the cached CSet starting regions and (more importantly) 2521 // the time stamps. Called when we reset the GC time stamp. 2522 void G1CollectedHeap::clear_cset_start_regions() { 2523 assert(_worker_cset_start_region != NULL, "sanity"); 2524 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2525 2526 for (uint i = 0; i < ParallelGCThreads; i++) { 2527 _worker_cset_start_region[i] = NULL; 2528 _worker_cset_start_region_time_stamp[i] = 0; 2529 } 2530 } 2531 2532 // Given the id of a worker, obtain or calculate a suitable 2533 // starting region for iterating over the current collection set. 2534 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2535 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2536 2537 HeapRegion* result = NULL; 2538 unsigned gc_time_stamp = get_gc_time_stamp(); 2539 2540 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2541 // Cached starting region for current worker was set 2542 // during the current pause - so it's valid. 2543 // Note: the cached starting heap region may be NULL 2544 // (when the collection set is empty). 2545 result = _worker_cset_start_region[worker_i]; 2546 assert(result == NULL || result->in_collection_set(), "sanity"); 2547 return result; 2548 } 2549 2550 // The cached entry was not valid so let's calculate 2551 // a suitable starting heap region for this worker. 2552 2553 // We want the parallel threads to start their collection 2554 // set iteration at different collection set regions to 2555 // avoid contention. 2556 // If we have: 2557 // n collection set regions 2558 // p threads 2559 // Then thread t will start at region floor ((t * n) / p) 2560 2561 result = g1_policy()->collection_set(); 2562 uint cs_size = g1_policy()->cset_region_length(); 2563 uint active_workers = workers()->active_workers(); 2564 2565 uint end_ind = (cs_size * worker_i) / active_workers; 2566 uint start_ind = 0; 2567 2568 if (worker_i > 0 && 2569 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2570 // Previous workers starting region is valid 2571 // so let's iterate from there 2572 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2573 result = _worker_cset_start_region[worker_i - 1]; 2574 } 2575 2576 for (uint i = start_ind; i < end_ind; i++) { 2577 result = result->next_in_collection_set(); 2578 } 2579 2580 // Note: the calculated starting heap region may be NULL 2581 // (when the collection set is empty). 2582 assert(result == NULL || result->in_collection_set(), "sanity"); 2583 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2584 "should be updated only once per pause"); 2585 _worker_cset_start_region[worker_i] = result; 2586 OrderAccess::storestore(); 2587 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2588 return result; 2589 } 2590 2591 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2592 HeapRegion* r = g1_policy()->collection_set(); 2593 while (r != NULL) { 2594 HeapRegion* next = r->next_in_collection_set(); 2595 if (cl->doHeapRegion(r)) { 2596 cl->incomplete(); 2597 return; 2598 } 2599 r = next; 2600 } 2601 } 2602 2603 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2604 HeapRegionClosure *cl) { 2605 if (r == NULL) { 2606 // The CSet is empty so there's nothing to do. 2607 return; 2608 } 2609 2610 assert(r->in_collection_set(), 2611 "Start region must be a member of the collection set."); 2612 HeapRegion* cur = r; 2613 while (cur != NULL) { 2614 HeapRegion* next = cur->next_in_collection_set(); 2615 if (cl->doHeapRegion(cur) && false) { 2616 cl->incomplete(); 2617 return; 2618 } 2619 cur = next; 2620 } 2621 cur = g1_policy()->collection_set(); 2622 while (cur != r) { 2623 HeapRegion* next = cur->next_in_collection_set(); 2624 if (cl->doHeapRegion(cur) && false) { 2625 cl->incomplete(); 2626 return; 2627 } 2628 cur = next; 2629 } 2630 } 2631 2632 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2633 HeapRegion* result = _hrm.next_region_in_heap(from); 2634 while (result != NULL && result->is_pinned()) { 2635 result = _hrm.next_region_in_heap(result); 2636 } 2637 return result; 2638 } 2639 2640 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2641 HeapRegion* hr = heap_region_containing(addr); 2642 return hr->block_start(addr); 2643 } 2644 2645 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2646 HeapRegion* hr = heap_region_containing(addr); 2647 return hr->block_size(addr); 2648 } 2649 2650 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2651 HeapRegion* hr = heap_region_containing(addr); 2652 return hr->block_is_obj(addr); 2653 } 2654 2655 bool G1CollectedHeap::supports_tlab_allocation() const { 2656 return true; 2657 } 2658 2659 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2660 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2661 } 2662 2663 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2664 return young_list()->eden_used_bytes(); 2665 } 2666 2667 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2668 // must be equal to the humongous object limit. 2669 size_t G1CollectedHeap::max_tlab_size() const { 2670 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2671 } 2672 2673 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2674 AllocationContext_t context = AllocationContext::current(); 2675 return _allocator->unsafe_max_tlab_alloc(context); 2676 } 2677 2678 size_t G1CollectedHeap::max_capacity() const { 2679 return _hrm.reserved().byte_size(); 2680 } 2681 2682 jlong G1CollectedHeap::millis_since_last_gc() { 2683 // assert(false, "NYI"); 2684 return 0; 2685 } 2686 2687 void G1CollectedHeap::prepare_for_verify() { 2688 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2689 ensure_parsability(false); 2690 } 2691 g1_rem_set()->prepare_for_verify(); 2692 } 2693 2694 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 2695 VerifyOption vo) { 2696 switch (vo) { 2697 case VerifyOption_G1UsePrevMarking: 2698 return hr->obj_allocated_since_prev_marking(obj); 2699 case VerifyOption_G1UseNextMarking: 2700 return hr->obj_allocated_since_next_marking(obj); 2701 case VerifyOption_G1UseMarkWord: 2702 return false; 2703 default: 2704 ShouldNotReachHere(); 2705 } 2706 return false; // keep some compilers happy 2707 } 2708 2709 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 2710 switch (vo) { 2711 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 2712 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 2713 case VerifyOption_G1UseMarkWord: return NULL; 2714 default: ShouldNotReachHere(); 2715 } 2716 return NULL; // keep some compilers happy 2717 } 2718 2719 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 2720 switch (vo) { 2721 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 2722 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 2723 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 2724 default: ShouldNotReachHere(); 2725 } 2726 return false; // keep some compilers happy 2727 } 2728 2729 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 2730 switch (vo) { 2731 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 2732 case VerifyOption_G1UseNextMarking: return "NTAMS"; 2733 case VerifyOption_G1UseMarkWord: return "NONE"; 2734 default: ShouldNotReachHere(); 2735 } 2736 return NULL; // keep some compilers happy 2737 } 2738 2739 class VerifyRootsClosure: public OopClosure { 2740 private: 2741 G1CollectedHeap* _g1h; 2742 VerifyOption _vo; 2743 bool _failures; 2744 public: 2745 // _vo == UsePrevMarking -> use "prev" marking information, 2746 // _vo == UseNextMarking -> use "next" marking information, 2747 // _vo == UseMarkWord -> use mark word from object header. 2748 VerifyRootsClosure(VerifyOption vo) : 2749 _g1h(G1CollectedHeap::heap()), 2750 _vo(vo), 2751 _failures(false) { } 2752 2753 bool failures() { return _failures; } 2754 2755 template <class T> void do_oop_nv(T* p) { 2756 T heap_oop = oopDesc::load_heap_oop(p); 2757 if (!oopDesc::is_null(heap_oop)) { 2758 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2759 if (_g1h->is_obj_dead_cond(obj, _vo)) { 2760 LogHandle(gc, verify) log; 2761 log.info("Root location " PTR_FORMAT " points to dead obj " PTR_FORMAT, p2i(p), p2i(obj)); 2762 if (_vo == VerifyOption_G1UseMarkWord) { 2763 log.info(" Mark word: " PTR_FORMAT, p2i(obj->mark())); 2764 } 2765 ResourceMark rm; 2766 obj->print_on(log.info_stream()); 2767 _failures = true; 2768 } 2769 } 2770 } 2771 2772 void do_oop(oop* p) { do_oop_nv(p); } 2773 void do_oop(narrowOop* p) { do_oop_nv(p); } 2774 }; 2775 2776 class G1VerifyCodeRootOopClosure: public OopClosure { 2777 G1CollectedHeap* _g1h; 2778 OopClosure* _root_cl; 2779 nmethod* _nm; 2780 VerifyOption _vo; 2781 bool _failures; 2782 2783 template <class T> void do_oop_work(T* p) { 2784 // First verify that this root is live 2785 _root_cl->do_oop(p); 2786 2787 if (!G1VerifyHeapRegionCodeRoots) { 2788 // We're not verifying the code roots attached to heap region. 2789 return; 2790 } 2791 2792 // Don't check the code roots during marking verification in a full GC 2793 if (_vo == VerifyOption_G1UseMarkWord) { 2794 return; 2795 } 2796 2797 // Now verify that the current nmethod (which contains p) is 2798 // in the code root list of the heap region containing the 2799 // object referenced by p. 2800 2801 T heap_oop = oopDesc::load_heap_oop(p); 2802 if (!oopDesc::is_null(heap_oop)) { 2803 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2804 2805 // Now fetch the region containing the object 2806 HeapRegion* hr = _g1h->heap_region_containing(obj); 2807 HeapRegionRemSet* hrrs = hr->rem_set(); 2808 // Verify that the strong code root list for this region 2809 // contains the nmethod 2810 if (!hrrs->strong_code_roots_list_contains(_nm)) { 2811 log_info(gc, verify)("Code root location " PTR_FORMAT " " 2812 "from nmethod " PTR_FORMAT " not in strong " 2813 "code roots for region [" PTR_FORMAT "," PTR_FORMAT ")", 2814 p2i(p), p2i(_nm), p2i(hr->bottom()), p2i(hr->end())); 2815 _failures = true; 2816 } 2817 } 2818 } 2819 2820 public: 2821 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo): 2822 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {} 2823 2824 void do_oop(oop* p) { do_oop_work(p); } 2825 void do_oop(narrowOop* p) { do_oop_work(p); } 2826 2827 void set_nmethod(nmethod* nm) { _nm = nm; } 2828 bool failures() { return _failures; } 2829 }; 2830 2831 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure { 2832 G1VerifyCodeRootOopClosure* _oop_cl; 2833 2834 public: 2835 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl): 2836 _oop_cl(oop_cl) {} 2837 2838 void do_code_blob(CodeBlob* cb) { 2839 nmethod* nm = cb->as_nmethod_or_null(); 2840 if (nm != NULL) { 2841 _oop_cl->set_nmethod(nm); 2842 nm->oops_do(_oop_cl); 2843 } 2844 } 2845 }; 2846 2847 class YoungRefCounterClosure : public OopClosure { 2848 G1CollectedHeap* _g1h; 2849 int _count; 2850 public: 2851 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 2852 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 2853 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 2854 2855 int count() { return _count; } 2856 void reset_count() { _count = 0; }; 2857 }; 2858 2859 class VerifyKlassClosure: public KlassClosure { 2860 YoungRefCounterClosure _young_ref_counter_closure; 2861 OopClosure *_oop_closure; 2862 public: 2863 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 2864 void do_klass(Klass* k) { 2865 k->oops_do(_oop_closure); 2866 2867 _young_ref_counter_closure.reset_count(); 2868 k->oops_do(&_young_ref_counter_closure); 2869 if (_young_ref_counter_closure.count() > 0) { 2870 guarantee(k->has_modified_oops(), "Klass " PTR_FORMAT ", has young refs but is not dirty.", p2i(k)); 2871 } 2872 } 2873 }; 2874 2875 class VerifyLivenessOopClosure: public OopClosure { 2876 G1CollectedHeap* _g1h; 2877 VerifyOption _vo; 2878 public: 2879 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 2880 _g1h(g1h), _vo(vo) 2881 { } 2882 void do_oop(narrowOop *p) { do_oop_work(p); } 2883 void do_oop( oop *p) { do_oop_work(p); } 2884 2885 template <class T> void do_oop_work(T *p) { 2886 oop obj = oopDesc::load_decode_heap_oop(p); 2887 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 2888 "Dead object referenced by a not dead object"); 2889 } 2890 }; 2891 2892 class VerifyObjsInRegionClosure: public ObjectClosure { 2893 private: 2894 G1CollectedHeap* _g1h; 2895 size_t _live_bytes; 2896 HeapRegion *_hr; 2897 VerifyOption _vo; 2898 public: 2899 // _vo == UsePrevMarking -> use "prev" marking information, 2900 // _vo == UseNextMarking -> use "next" marking information, 2901 // _vo == UseMarkWord -> use mark word from object header. 2902 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 2903 : _live_bytes(0), _hr(hr), _vo(vo) { 2904 _g1h = G1CollectedHeap::heap(); 2905 } 2906 void do_object(oop o) { 2907 VerifyLivenessOopClosure isLive(_g1h, _vo); 2908 assert(o != NULL, "Huh?"); 2909 if (!_g1h->is_obj_dead_cond(o, _vo)) { 2910 // If the object is alive according to the mark word, 2911 // then verify that the marking information agrees. 2912 // Note we can't verify the contra-positive of the 2913 // above: if the object is dead (according to the mark 2914 // word), it may not be marked, or may have been marked 2915 // but has since became dead, or may have been allocated 2916 // since the last marking. 2917 if (_vo == VerifyOption_G1UseMarkWord) { 2918 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 2919 } 2920 2921 o->oop_iterate_no_header(&isLive); 2922 if (!_hr->obj_allocated_since_prev_marking(o)) { 2923 size_t obj_size = o->size(); // Make sure we don't overflow 2924 _live_bytes += (obj_size * HeapWordSize); 2925 } 2926 } 2927 } 2928 size_t live_bytes() { return _live_bytes; } 2929 }; 2930 2931 class VerifyArchiveOopClosure: public OopClosure { 2932 public: 2933 VerifyArchiveOopClosure(HeapRegion *hr) { } 2934 void do_oop(narrowOop *p) { do_oop_work(p); } 2935 void do_oop( oop *p) { do_oop_work(p); } 2936 2937 template <class T> void do_oop_work(T *p) { 2938 oop obj = oopDesc::load_decode_heap_oop(p); 2939 guarantee(obj == NULL || G1MarkSweep::in_archive_range(obj), 2940 "Archive object at " PTR_FORMAT " references a non-archive object at " PTR_FORMAT, 2941 p2i(p), p2i(obj)); 2942 } 2943 }; 2944 2945 class VerifyArchiveRegionClosure: public ObjectClosure { 2946 public: 2947 VerifyArchiveRegionClosure(HeapRegion *hr) { } 2948 // Verify that all object pointers are to archive regions. 2949 void do_object(oop o) { 2950 VerifyArchiveOopClosure checkOop(NULL); 2951 assert(o != NULL, "Should not be here for NULL oops"); 2952 o->oop_iterate_no_header(&checkOop); 2953 } 2954 }; 2955 2956 class VerifyRegionClosure: public HeapRegionClosure { 2957 private: 2958 bool _par; 2959 VerifyOption _vo; 2960 bool _failures; 2961 public: 2962 // _vo == UsePrevMarking -> use "prev" marking information, 2963 // _vo == UseNextMarking -> use "next" marking information, 2964 // _vo == UseMarkWord -> use mark word from object header. 2965 VerifyRegionClosure(bool par, VerifyOption vo) 2966 : _par(par), 2967 _vo(vo), 2968 _failures(false) {} 2969 2970 bool failures() { 2971 return _failures; 2972 } 2973 2974 bool doHeapRegion(HeapRegion* r) { 2975 // For archive regions, verify there are no heap pointers to 2976 // non-pinned regions. For all others, verify liveness info. 2977 if (r->is_archive()) { 2978 VerifyArchiveRegionClosure verify_oop_pointers(r); 2979 r->object_iterate(&verify_oop_pointers); 2980 return true; 2981 } 2982 if (!r->is_continues_humongous()) { 2983 bool failures = false; 2984 r->verify(_vo, &failures); 2985 if (failures) { 2986 _failures = true; 2987 } else if (!r->is_starts_humongous()) { 2988 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 2989 r->object_iterate(¬_dead_yet_cl); 2990 if (_vo != VerifyOption_G1UseNextMarking) { 2991 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 2992 log_info(gc, verify)("[" PTR_FORMAT "," PTR_FORMAT "] max_live_bytes " SIZE_FORMAT " < calculated " SIZE_FORMAT, 2993 p2i(r->bottom()), p2i(r->end()), r->max_live_bytes(), not_dead_yet_cl.live_bytes()); 2994 _failures = true; 2995 } 2996 } else { 2997 // When vo == UseNextMarking we cannot currently do a sanity 2998 // check on the live bytes as the calculation has not been 2999 // finalized yet. 3000 } 3001 } 3002 } 3003 return false; // stop the region iteration if we hit a failure 3004 } 3005 }; 3006 3007 // This is the task used for parallel verification of the heap regions 3008 3009 class G1ParVerifyTask: public AbstractGangTask { 3010 private: 3011 G1CollectedHeap* _g1h; 3012 VerifyOption _vo; 3013 bool _failures; 3014 HeapRegionClaimer _hrclaimer; 3015 3016 public: 3017 // _vo == UsePrevMarking -> use "prev" marking information, 3018 // _vo == UseNextMarking -> use "next" marking information, 3019 // _vo == UseMarkWord -> use mark word from object header. 3020 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3021 AbstractGangTask("Parallel verify task"), 3022 _g1h(g1h), 3023 _vo(vo), 3024 _failures(false), 3025 _hrclaimer(g1h->workers()->active_workers()) {} 3026 3027 bool failures() { 3028 return _failures; 3029 } 3030 3031 void work(uint worker_id) { 3032 HandleMark hm; 3033 VerifyRegionClosure blk(true, _vo); 3034 _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer); 3035 if (blk.failures()) { 3036 _failures = true; 3037 } 3038 } 3039 }; 3040 3041 void G1CollectedHeap::verify(VerifyOption vo) { 3042 if (!SafepointSynchronize::is_at_safepoint()) { 3043 log_info(gc, verify)("Skipping verification. Not at safepoint."); 3044 } 3045 3046 assert(Thread::current()->is_VM_thread(), 3047 "Expected to be executed serially by the VM thread at this point"); 3048 3049 log_debug(gc, verify)("Roots"); 3050 VerifyRootsClosure rootsCl(vo); 3051 VerifyKlassClosure klassCl(this, &rootsCl); 3052 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false); 3053 3054 // We apply the relevant closures to all the oops in the 3055 // system dictionary, class loader data graph, the string table 3056 // and the nmethods in the code cache. 3057 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo); 3058 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl); 3059 3060 { 3061 G1RootProcessor root_processor(this, 1); 3062 root_processor.process_all_roots(&rootsCl, 3063 &cldCl, 3064 &blobsCl); 3065 } 3066 3067 bool failures = rootsCl.failures() || codeRootsCl.failures(); 3068 3069 if (vo != VerifyOption_G1UseMarkWord) { 3070 // If we're verifying during a full GC then the region sets 3071 // will have been torn down at the start of the GC. Therefore 3072 // verifying the region sets will fail. So we only verify 3073 // the region sets when not in a full GC. 3074 log_debug(gc, verify)("HeapRegionSets"); 3075 verify_region_sets(); 3076 } 3077 3078 log_debug(gc, verify)("HeapRegions"); 3079 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3080 3081 G1ParVerifyTask task(this, vo); 3082 workers()->run_task(&task); 3083 if (task.failures()) { 3084 failures = true; 3085 } 3086 3087 } else { 3088 VerifyRegionClosure blk(false, vo); 3089 heap_region_iterate(&blk); 3090 if (blk.failures()) { 3091 failures = true; 3092 } 3093 } 3094 3095 if (G1StringDedup::is_enabled()) { 3096 log_debug(gc, verify)("StrDedup"); 3097 G1StringDedup::verify(); 3098 } 3099 3100 if (failures) { 3101 log_info(gc, verify)("Heap after failed verification:"); 3102 // It helps to have the per-region information in the output to 3103 // help us track down what went wrong. This is why we call 3104 // print_extended_on() instead of print_on(). 3105 LogHandle(gc, verify) log; 3106 ResourceMark rm; 3107 print_extended_on(log.info_stream()); 3108 } 3109 guarantee(!failures, "there should not have been any failures"); 3110 } 3111 3112 double G1CollectedHeap::verify(bool guard, const char* msg) { 3113 double verify_time_ms = 0.0; 3114 3115 if (guard && total_collections() >= VerifyGCStartAt) { 3116 double verify_start = os::elapsedTime(); 3117 HandleMark hm; // Discard invalid handles created during verification 3118 prepare_for_verify(); 3119 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 3120 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 3121 } 3122 3123 return verify_time_ms; 3124 } 3125 3126 void G1CollectedHeap::verify_before_gc() { 3127 double verify_time_ms = verify(VerifyBeforeGC, "Before GC"); 3128 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 3129 } 3130 3131 void G1CollectedHeap::verify_after_gc() { 3132 double verify_time_ms = verify(VerifyAfterGC, "After GC"); 3133 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 3134 } 3135 3136 class PrintRegionClosure: public HeapRegionClosure { 3137 outputStream* _st; 3138 public: 3139 PrintRegionClosure(outputStream* st) : _st(st) {} 3140 bool doHeapRegion(HeapRegion* r) { 3141 r->print_on(_st); 3142 return false; 3143 } 3144 }; 3145 3146 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3147 const HeapRegion* hr, 3148 const VerifyOption vo) const { 3149 switch (vo) { 3150 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 3151 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 3152 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 3153 default: ShouldNotReachHere(); 3154 } 3155 return false; // keep some compilers happy 3156 } 3157 3158 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3159 const VerifyOption vo) const { 3160 switch (vo) { 3161 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 3162 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 3163 case VerifyOption_G1UseMarkWord: { 3164 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 3165 return !obj->is_gc_marked() && !hr->is_archive(); 3166 } 3167 default: ShouldNotReachHere(); 3168 } 3169 return false; // keep some compilers happy 3170 } 3171 3172 void G1CollectedHeap::print_on(outputStream* st) const { 3173 st->print(" %-20s", "garbage-first heap"); 3174 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3175 capacity()/K, used_unlocked()/K); 3176 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 3177 p2i(_hrm.reserved().start()), 3178 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 3179 p2i(_hrm.reserved().end())); 3180 st->cr(); 3181 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3182 uint young_regions = _young_list->length(); 3183 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3184 (size_t) young_regions * HeapRegion::GrainBytes / K); 3185 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3186 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3187 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3188 st->cr(); 3189 MetaspaceAux::print_on(st); 3190 } 3191 3192 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3193 print_on(st); 3194 3195 // Print the per-region information. 3196 st->cr(); 3197 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 3198 "HS=humongous(starts), HC=humongous(continues), " 3199 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 3200 "AC=allocation context, " 3201 "TAMS=top-at-mark-start (previous, next)"); 3202 PrintRegionClosure blk(st); 3203 heap_region_iterate(&blk); 3204 } 3205 3206 void G1CollectedHeap::print_on_error(outputStream* st) const { 3207 this->CollectedHeap::print_on_error(st); 3208 3209 if (_cm != NULL) { 3210 st->cr(); 3211 _cm->print_on_error(st); 3212 } 3213 } 3214 3215 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3216 workers()->print_worker_threads_on(st); 3217 _cmThread->print_on(st); 3218 st->cr(); 3219 _cm->print_worker_threads_on(st); 3220 _cg1r->print_worker_threads_on(st); 3221 if (G1StringDedup::is_enabled()) { 3222 G1StringDedup::print_worker_threads_on(st); 3223 } 3224 } 3225 3226 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3227 workers()->threads_do(tc); 3228 tc->do_thread(_cmThread); 3229 _cg1r->threads_do(tc); 3230 if (G1StringDedup::is_enabled()) { 3231 G1StringDedup::threads_do(tc); 3232 } 3233 } 3234 3235 void G1CollectedHeap::print_tracing_info() const { 3236 // We'll overload this to mean "trace GC pause statistics." 3237 if (TraceYoungGenTime || TraceOldGenTime) { 3238 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3239 // to that. 3240 g1_policy()->print_tracing_info(); 3241 } 3242 g1_rem_set()->print_summary_info(); 3243 concurrent_mark()->print_summary_info(); 3244 g1_policy()->print_yg_surv_rate_info(); 3245 } 3246 3247 #ifndef PRODUCT 3248 // Helpful for debugging RSet issues. 3249 3250 class PrintRSetsClosure : public HeapRegionClosure { 3251 private: 3252 const char* _msg; 3253 size_t _occupied_sum; 3254 3255 public: 3256 bool doHeapRegion(HeapRegion* r) { 3257 HeapRegionRemSet* hrrs = r->rem_set(); 3258 size_t occupied = hrrs->occupied(); 3259 _occupied_sum += occupied; 3260 3261 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 3262 if (occupied == 0) { 3263 tty->print_cr(" RSet is empty"); 3264 } else { 3265 hrrs->print(); 3266 } 3267 tty->print_cr("----------"); 3268 return false; 3269 } 3270 3271 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3272 tty->cr(); 3273 tty->print_cr("========================================"); 3274 tty->print_cr("%s", msg); 3275 tty->cr(); 3276 } 3277 3278 ~PrintRSetsClosure() { 3279 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 3280 tty->print_cr("========================================"); 3281 tty->cr(); 3282 } 3283 }; 3284 3285 void G1CollectedHeap::print_cset_rsets() { 3286 PrintRSetsClosure cl("Printing CSet RSets"); 3287 collection_set_iterate(&cl); 3288 } 3289 3290 void G1CollectedHeap::print_all_rsets() { 3291 PrintRSetsClosure cl("Printing All RSets");; 3292 heap_region_iterate(&cl); 3293 } 3294 #endif // PRODUCT 3295 3296 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 3297 YoungList* young_list = heap()->young_list(); 3298 3299 size_t eden_used_bytes = young_list->eden_used_bytes(); 3300 size_t survivor_used_bytes = young_list->survivor_used_bytes(); 3301 3302 size_t eden_capacity_bytes = 3303 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 3304 3305 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 3306 return G1HeapSummary(heap_summary, used(), eden_used_bytes, eden_capacity_bytes, survivor_used_bytes); 3307 } 3308 3309 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 3310 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 3311 stats->unused(), stats->used(), stats->region_end_waste(), 3312 stats->regions_filled(), stats->direct_allocated(), 3313 stats->failure_used(), stats->failure_waste()); 3314 } 3315 3316 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 3317 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 3318 gc_tracer->report_gc_heap_summary(when, heap_summary); 3319 3320 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 3321 gc_tracer->report_metaspace_summary(when, metaspace_summary); 3322 } 3323 3324 3325 G1CollectedHeap* G1CollectedHeap::heap() { 3326 CollectedHeap* heap = Universe::heap(); 3327 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 3328 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 3329 return (G1CollectedHeap*)heap; 3330 } 3331 3332 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3333 // always_do_update_barrier = false; 3334 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3335 // Fill TLAB's and such 3336 accumulate_statistics_all_tlabs(); 3337 ensure_parsability(true); 3338 3339 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 3340 } 3341 3342 void G1CollectedHeap::gc_epilogue(bool full) { 3343 // we are at the end of the GC. Total collections has already been increased. 3344 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 3345 3346 // FIXME: what is this about? 3347 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3348 // is set. 3349 #if defined(COMPILER2) || INCLUDE_JVMCI 3350 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 3351 #endif 3352 // always_do_update_barrier = true; 3353 3354 resize_all_tlabs(); 3355 allocation_context_stats().update(full); 3356 3357 // We have just completed a GC. Update the soft reference 3358 // policy with the new heap occupancy 3359 Universe::update_heap_info_at_gc(); 3360 } 3361 3362 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3363 uint gc_count_before, 3364 bool* succeeded, 3365 GCCause::Cause gc_cause) { 3366 assert_heap_not_locked_and_not_at_safepoint(); 3367 g1_policy()->record_stop_world_start(); 3368 VM_G1IncCollectionPause op(gc_count_before, 3369 word_size, 3370 false, /* should_initiate_conc_mark */ 3371 g1_policy()->max_pause_time_ms(), 3372 gc_cause); 3373 3374 op.set_allocation_context(AllocationContext::current()); 3375 VMThread::execute(&op); 3376 3377 HeapWord* result = op.result(); 3378 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3379 assert(result == NULL || ret_succeeded, 3380 "the result should be NULL if the VM did not succeed"); 3381 *succeeded = ret_succeeded; 3382 3383 assert_heap_not_locked(); 3384 return result; 3385 } 3386 3387 void 3388 G1CollectedHeap::doConcurrentMark() { 3389 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3390 if (!_cmThread->in_progress()) { 3391 _cmThread->set_started(); 3392 CGC_lock->notify(); 3393 } 3394 } 3395 3396 size_t G1CollectedHeap::pending_card_num() { 3397 size_t extra_cards = 0; 3398 JavaThread *curr = Threads::first(); 3399 while (curr != NULL) { 3400 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3401 extra_cards += dcq.size(); 3402 curr = curr->next(); 3403 } 3404 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3405 size_t buffer_size = dcqs.buffer_size(); 3406 size_t buffer_num = dcqs.completed_buffers_num(); 3407 3408 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3409 // in bytes - not the number of 'entries'. We need to convert 3410 // into a number of cards. 3411 return (buffer_size * buffer_num + extra_cards) / oopSize; 3412 } 3413 3414 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 3415 private: 3416 size_t _total_humongous; 3417 size_t _candidate_humongous; 3418 3419 DirtyCardQueue _dcq; 3420 3421 // We don't nominate objects with many remembered set entries, on 3422 // the assumption that such objects are likely still live. 3423 bool is_remset_small(HeapRegion* region) const { 3424 HeapRegionRemSet* const rset = region->rem_set(); 3425 return G1EagerReclaimHumongousObjectsWithStaleRefs 3426 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 3427 : rset->is_empty(); 3428 } 3429 3430 bool is_typeArray_region(HeapRegion* region) const { 3431 return oop(region->bottom())->is_typeArray(); 3432 } 3433 3434 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 3435 assert(region->is_starts_humongous(), "Must start a humongous object"); 3436 3437 // Candidate selection must satisfy the following constraints 3438 // while concurrent marking is in progress: 3439 // 3440 // * In order to maintain SATB invariants, an object must not be 3441 // reclaimed if it was allocated before the start of marking and 3442 // has not had its references scanned. Such an object must have 3443 // its references (including type metadata) scanned to ensure no 3444 // live objects are missed by the marking process. Objects 3445 // allocated after the start of concurrent marking don't need to 3446 // be scanned. 3447 // 3448 // * An object must not be reclaimed if it is on the concurrent 3449 // mark stack. Objects allocated after the start of concurrent 3450 // marking are never pushed on the mark stack. 3451 // 3452 // Nominating only objects allocated after the start of concurrent 3453 // marking is sufficient to meet both constraints. This may miss 3454 // some objects that satisfy the constraints, but the marking data 3455 // structures don't support efficiently performing the needed 3456 // additional tests or scrubbing of the mark stack. 3457 // 3458 // However, we presently only nominate is_typeArray() objects. 3459 // A humongous object containing references induces remembered 3460 // set entries on other regions. In order to reclaim such an 3461 // object, those remembered sets would need to be cleaned up. 3462 // 3463 // We also treat is_typeArray() objects specially, allowing them 3464 // to be reclaimed even if allocated before the start of 3465 // concurrent mark. For this we rely on mark stack insertion to 3466 // exclude is_typeArray() objects, preventing reclaiming an object 3467 // that is in the mark stack. We also rely on the metadata for 3468 // such objects to be built-in and so ensured to be kept live. 3469 // Frequent allocation and drop of large binary blobs is an 3470 // important use case for eager reclaim, and this special handling 3471 // may reduce needed headroom. 3472 3473 return is_typeArray_region(region) && is_remset_small(region); 3474 } 3475 3476 public: 3477 RegisterHumongousWithInCSetFastTestClosure() 3478 : _total_humongous(0), 3479 _candidate_humongous(0), 3480 _dcq(&JavaThread::dirty_card_queue_set()) { 3481 } 3482 3483 virtual bool doHeapRegion(HeapRegion* r) { 3484 if (!r->is_starts_humongous()) { 3485 return false; 3486 } 3487 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3488 3489 bool is_candidate = humongous_region_is_candidate(g1h, r); 3490 uint rindex = r->hrm_index(); 3491 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 3492 if (is_candidate) { 3493 _candidate_humongous++; 3494 g1h->register_humongous_region_with_cset(rindex); 3495 // Is_candidate already filters out humongous object with large remembered sets. 3496 // If we have a humongous object with a few remembered sets, we simply flush these 3497 // remembered set entries into the DCQS. That will result in automatic 3498 // re-evaluation of their remembered set entries during the following evacuation 3499 // phase. 3500 if (!r->rem_set()->is_empty()) { 3501 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 3502 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 3503 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 3504 HeapRegionRemSetIterator hrrs(r->rem_set()); 3505 size_t card_index; 3506 while (hrrs.has_next(card_index)) { 3507 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 3508 // The remembered set might contain references to already freed 3509 // regions. Filter out such entries to avoid failing card table 3510 // verification. 3511 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 3512 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 3513 *card_ptr = CardTableModRefBS::dirty_card_val(); 3514 _dcq.enqueue(card_ptr); 3515 } 3516 } 3517 } 3518 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 3519 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 3520 hrrs.n_yielded(), r->rem_set()->occupied()); 3521 r->rem_set()->clear_locked(); 3522 } 3523 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 3524 } 3525 _total_humongous++; 3526 3527 return false; 3528 } 3529 3530 size_t total_humongous() const { return _total_humongous; } 3531 size_t candidate_humongous() const { return _candidate_humongous; } 3532 3533 void flush_rem_set_entries() { _dcq.flush(); } 3534 }; 3535 3536 void G1CollectedHeap::register_humongous_regions_with_cset() { 3537 if (!G1EagerReclaimHumongousObjects) { 3538 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 3539 return; 3540 } 3541 double time = os::elapsed_counter(); 3542 3543 // Collect reclaim candidate information and register candidates with cset. 3544 RegisterHumongousWithInCSetFastTestClosure cl; 3545 heap_region_iterate(&cl); 3546 3547 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 3548 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 3549 cl.total_humongous(), 3550 cl.candidate_humongous()); 3551 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3552 3553 // Finally flush all remembered set entries to re-check into the global DCQS. 3554 cl.flush_rem_set_entries(); 3555 } 3556 3557 #ifdef ASSERT 3558 class VerifyCSetClosure: public HeapRegionClosure { 3559 public: 3560 bool doHeapRegion(HeapRegion* hr) { 3561 // Here we check that the CSet region's RSet is ready for parallel 3562 // iteration. The fields that we'll verify are only manipulated 3563 // when the region is part of a CSet and is collected. Afterwards, 3564 // we reset these fields when we clear the region's RSet (when the 3565 // region is freed) so they are ready when the region is 3566 // re-allocated. The only exception to this is if there's an 3567 // evacuation failure and instead of freeing the region we leave 3568 // it in the heap. In that case, we reset these fields during 3569 // evacuation failure handling. 3570 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3571 3572 // Here's a good place to add any other checks we'd like to 3573 // perform on CSet regions. 3574 return false; 3575 } 3576 }; 3577 #endif // ASSERT 3578 3579 uint G1CollectedHeap::num_task_queues() const { 3580 return _task_queues->size(); 3581 } 3582 3583 #if TASKQUEUE_STATS 3584 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3585 st->print_raw_cr("GC Task Stats"); 3586 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3587 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3588 } 3589 3590 void G1CollectedHeap::print_taskqueue_stats() const { 3591 if (!develop_log_is_enabled(Trace, gc, task, stats)) { 3592 return; 3593 } 3594 LogHandle(gc, task, stats) log; 3595 ResourceMark rm; 3596 outputStream* st = log.trace_stream(); 3597 3598 print_taskqueue_stats_hdr(st); 3599 3600 TaskQueueStats totals; 3601 const uint n = num_task_queues(); 3602 for (uint i = 0; i < n; ++i) { 3603 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 3604 totals += task_queue(i)->stats; 3605 } 3606 st->print_raw("tot "); totals.print(st); st->cr(); 3607 3608 DEBUG_ONLY(totals.verify()); 3609 } 3610 3611 void G1CollectedHeap::reset_taskqueue_stats() { 3612 const uint n = num_task_queues(); 3613 for (uint i = 0; i < n; ++i) { 3614 task_queue(i)->stats.reset(); 3615 } 3616 } 3617 #endif // TASKQUEUE_STATS 3618 3619 void G1CollectedHeap::log_gc_footer(jlong pause_time_counter) { 3620 if (evacuation_failed()) { 3621 log_info(gc)("To-space exhausted"); 3622 } 3623 3624 double pause_time_ms = TimeHelper::counter_to_millis(pause_time_counter); 3625 g1_policy()->print_phases(pause_time_ms); 3626 3627 g1_policy()->print_detailed_heap_transition(); 3628 } 3629 3630 3631 void G1CollectedHeap::wait_for_root_region_scanning() { 3632 double scan_wait_start = os::elapsedTime(); 3633 // We have to wait until the CM threads finish scanning the 3634 // root regions as it's the only way to ensure that all the 3635 // objects on them have been correctly scanned before we start 3636 // moving them during the GC. 3637 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3638 double wait_time_ms = 0.0; 3639 if (waited) { 3640 double scan_wait_end = os::elapsedTime(); 3641 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3642 } 3643 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3644 } 3645 3646 bool 3647 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3648 assert_at_safepoint(true /* should_be_vm_thread */); 3649 guarantee(!is_gc_active(), "collection is not reentrant"); 3650 3651 if (GC_locker::check_active_before_gc()) { 3652 return false; 3653 } 3654 3655 _gc_timer_stw->register_gc_start(); 3656 3657 GCIdMark gc_id_mark; 3658 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3659 3660 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3661 ResourceMark rm; 3662 3663 wait_for_root_region_scanning(); 3664 3665 print_heap_before_gc(); 3666 trace_heap_before_gc(_gc_tracer_stw); 3667 3668 verify_region_sets_optional(); 3669 verify_dirty_young_regions(); 3670 3671 // This call will decide whether this pause is an initial-mark 3672 // pause. If it is, during_initial_mark_pause() will return true 3673 // for the duration of this pause. 3674 g1_policy()->decide_on_conc_mark_initiation(); 3675 3676 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3677 assert(!collector_state()->during_initial_mark_pause() || 3678 collector_state()->gcs_are_young(), "sanity"); 3679 3680 // We also do not allow mixed GCs during marking. 3681 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3682 3683 // Record whether this pause is an initial mark. When the current 3684 // thread has completed its logging output and it's safe to signal 3685 // the CM thread, the flag's value in the policy has been reset. 3686 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3687 3688 // Inner scope for scope based logging, timers, and stats collection 3689 { 3690 EvacuationInfo evacuation_info; 3691 3692 if (collector_state()->during_initial_mark_pause()) { 3693 // We are about to start a marking cycle, so we increment the 3694 // full collection counter. 3695 increment_old_marking_cycles_started(); 3696 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3697 } 3698 3699 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3700 3701 GCTraceCPUTime tcpu; 3702 3703 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3704 workers()->active_workers(), 3705 Threads::number_of_non_daemon_threads()); 3706 workers()->set_active_workers(active_workers); 3707 FormatBuffer<> gc_string("Pause "); 3708 if (collector_state()->during_initial_mark_pause()) { 3709 gc_string.append("Initial Mark"); 3710 } else if (collector_state()->gcs_are_young()) { 3711 gc_string.append("Young"); 3712 } else { 3713 gc_string.append("Mixed"); 3714 } 3715 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 3716 3717 double pause_start_sec = os::elapsedTime(); 3718 jlong pause_start_counter = os::elapsed_counter(); 3719 g1_policy()->note_gc_start(active_workers); 3720 3721 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3722 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3723 3724 // If the secondary_free_list is not empty, append it to the 3725 // free_list. No need to wait for the cleanup operation to finish; 3726 // the region allocation code will check the secondary_free_list 3727 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3728 // set, skip this step so that the region allocation code has to 3729 // get entries from the secondary_free_list. 3730 if (!G1StressConcRegionFreeing) { 3731 append_secondary_free_list_if_not_empty_with_lock(); 3732 } 3733 3734 assert(check_young_list_well_formed(), "young list should be well formed"); 3735 3736 // Don't dynamically change the number of GC threads this early. A value of 3737 // 0 is used to indicate serial work. When parallel work is done, 3738 // it will be set. 3739 3740 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3741 IsGCActiveMark x; 3742 3743 gc_prologue(false); 3744 increment_total_collections(false /* full gc */); 3745 increment_gc_time_stamp(); 3746 3747 verify_before_gc(); 3748 3749 check_bitmaps("GC Start"); 3750 3751 #if defined(COMPILER2) || INCLUDE_JVMCI 3752 DerivedPointerTable::clear(); 3753 #endif 3754 3755 // Please see comment in g1CollectedHeap.hpp and 3756 // G1CollectedHeap::ref_processing_init() to see how 3757 // reference processing currently works in G1. 3758 3759 // Enable discovery in the STW reference processor 3760 if (g1_policy()->should_process_references()) { 3761 ref_processor_stw()->enable_discovery(); 3762 } else { 3763 ref_processor_stw()->disable_discovery(); 3764 } 3765 3766 { 3767 // We want to temporarily turn off discovery by the 3768 // CM ref processor, if necessary, and turn it back on 3769 // on again later if we do. Using a scoped 3770 // NoRefDiscovery object will do this. 3771 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3772 3773 // Forget the current alloc region (we might even choose it to be part 3774 // of the collection set!). 3775 _allocator->release_mutator_alloc_region(); 3776 3777 // This timing is only used by the ergonomics to handle our pause target. 3778 // It is unclear why this should not include the full pause. We will 3779 // investigate this in CR 7178365. 3780 // 3781 // Preserving the old comment here if that helps the investigation: 3782 // 3783 // The elapsed time induced by the start time below deliberately elides 3784 // the possible verification above. 3785 double sample_start_time_sec = os::elapsedTime(); 3786 3787 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3788 3789 if (collector_state()->during_initial_mark_pause()) { 3790 concurrent_mark()->checkpointRootsInitialPre(); 3791 } 3792 3793 double time_remaining_ms = g1_policy()->finalize_young_cset_part(target_pause_time_ms); 3794 g1_policy()->finalize_old_cset_part(time_remaining_ms); 3795 3796 evacuation_info.set_collectionset_regions(g1_policy()->cset_region_length()); 3797 3798 // Make sure the remembered sets are up to date. This needs to be 3799 // done before register_humongous_regions_with_cset(), because the 3800 // remembered sets are used there to choose eager reclaim candidates. 3801 // If the remembered sets are not up to date we might miss some 3802 // entries that need to be handled. 3803 g1_rem_set()->cleanupHRRS(); 3804 3805 register_humongous_regions_with_cset(); 3806 3807 assert(check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3808 3809 _cm->note_start_of_gc(); 3810 // We call this after finalize_cset() to 3811 // ensure that the CSet has been finalized. 3812 _cm->verify_no_cset_oops(); 3813 3814 if (_hr_printer.is_active()) { 3815 HeapRegion* hr = g1_policy()->collection_set(); 3816 while (hr != NULL) { 3817 _hr_printer.cset(hr); 3818 hr = hr->next_in_collection_set(); 3819 } 3820 } 3821 3822 #ifdef ASSERT 3823 VerifyCSetClosure cl; 3824 collection_set_iterate(&cl); 3825 #endif // ASSERT 3826 3827 // Initialize the GC alloc regions. 3828 _allocator->init_gc_alloc_regions(evacuation_info); 3829 3830 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), g1_policy()->young_cset_region_length()); 3831 pre_evacuate_collection_set(); 3832 3833 // Actually do the work... 3834 evacuate_collection_set(evacuation_info, &per_thread_states); 3835 3836 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3837 3838 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3839 free_collection_set(g1_policy()->collection_set(), evacuation_info, surviving_young_words); 3840 3841 eagerly_reclaim_humongous_regions(); 3842 3843 g1_policy()->clear_collection_set(); 3844 3845 // Start a new incremental collection set for the next pause. 3846 g1_policy()->start_incremental_cset_building(); 3847 3848 clear_cset_fast_test(); 3849 3850 _young_list->reset_sampled_info(); 3851 3852 // Don't check the whole heap at this point as the 3853 // GC alloc regions from this pause have been tagged 3854 // as survivors and moved on to the survivor list. 3855 // Survivor regions will fail the !is_young() check. 3856 assert(check_young_list_empty(false /* check_heap */), 3857 "young list should be empty"); 3858 3859 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3860 _young_list->first_survivor_region(), 3861 _young_list->last_survivor_region()); 3862 3863 _young_list->reset_auxilary_lists(); 3864 3865 if (evacuation_failed()) { 3866 set_used(recalculate_used()); 3867 if (_archive_allocator != NULL) { 3868 _archive_allocator->clear_used(); 3869 } 3870 for (uint i = 0; i < ParallelGCThreads; i++) { 3871 if (_evacuation_failed_info_array[i].has_failed()) { 3872 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3873 } 3874 } 3875 } else { 3876 // The "used" of the the collection set have already been subtracted 3877 // when they were freed. Add in the bytes evacuated. 3878 increase_used(g1_policy()->bytes_copied_during_gc()); 3879 } 3880 3881 if (collector_state()->during_initial_mark_pause()) { 3882 // We have to do this before we notify the CM threads that 3883 // they can start working to make sure that all the 3884 // appropriate initialization is done on the CM object. 3885 concurrent_mark()->checkpointRootsInitialPost(); 3886 collector_state()->set_mark_in_progress(true); 3887 // Note that we don't actually trigger the CM thread at 3888 // this point. We do that later when we're sure that 3889 // the current thread has completed its logging output. 3890 } 3891 3892 allocate_dummy_regions(); 3893 3894 _allocator->init_mutator_alloc_region(); 3895 3896 { 3897 size_t expand_bytes = g1_policy()->expansion_amount(); 3898 if (expand_bytes > 0) { 3899 size_t bytes_before = capacity(); 3900 // No need for an ergo logging here, 3901 // expansion_amount() does this when it returns a value > 0. 3902 double expand_ms; 3903 if (!expand(expand_bytes, &expand_ms)) { 3904 // We failed to expand the heap. Cannot do anything about it. 3905 } 3906 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3907 } 3908 } 3909 3910 // We redo the verification but now wrt to the new CSet which 3911 // has just got initialized after the previous CSet was freed. 3912 _cm->verify_no_cset_oops(); 3913 _cm->note_end_of_gc(); 3914 3915 // This timing is only used by the ergonomics to handle our pause target. 3916 // It is unclear why this should not include the full pause. We will 3917 // investigate this in CR 7178365. 3918 double sample_end_time_sec = os::elapsedTime(); 3919 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3920 size_t total_cards_scanned = per_thread_states.total_cards_scanned(); 3921 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned); 3922 3923 evacuation_info.set_collectionset_used_before(g1_policy()->collection_set_bytes_used_before()); 3924 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3925 3926 MemoryService::track_memory_usage(); 3927 3928 // In prepare_for_verify() below we'll need to scan the deferred 3929 // update buffers to bring the RSets up-to-date if 3930 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3931 // the update buffers we'll probably need to scan cards on the 3932 // regions we just allocated to (i.e., the GC alloc 3933 // regions). However, during the last GC we called 3934 // set_saved_mark() on all the GC alloc regions, so card 3935 // scanning might skip the [saved_mark_word()...top()] area of 3936 // those regions (i.e., the area we allocated objects into 3937 // during the last GC). But it shouldn't. Given that 3938 // saved_mark_word() is conditional on whether the GC time stamp 3939 // on the region is current or not, by incrementing the GC time 3940 // stamp here we invalidate all the GC time stamps on all the 3941 // regions and saved_mark_word() will simply return top() for 3942 // all the regions. This is a nicer way of ensuring this rather 3943 // than iterating over the regions and fixing them. In fact, the 3944 // GC time stamp increment here also ensures that 3945 // saved_mark_word() will return top() between pauses, i.e., 3946 // during concurrent refinement. So we don't need the 3947 // is_gc_active() check to decided which top to use when 3948 // scanning cards (see CR 7039627). 3949 increment_gc_time_stamp(); 3950 3951 verify_after_gc(); 3952 check_bitmaps("GC End"); 3953 3954 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3955 ref_processor_stw()->verify_no_references_recorded(); 3956 3957 // CM reference discovery will be re-enabled if necessary. 3958 } 3959 3960 #ifdef TRACESPINNING 3961 ParallelTaskTerminator::print_termination_counts(); 3962 #endif 3963 3964 gc_epilogue(false); 3965 } 3966 3967 // Print the remainder of the GC log output. 3968 log_gc_footer(os::elapsed_counter() - pause_start_counter); 3969 3970 // It is not yet to safe to tell the concurrent mark to 3971 // start as we have some optional output below. We don't want the 3972 // output from the concurrent mark thread interfering with this 3973 // logging output either. 3974 3975 _hrm.verify_optional(); 3976 verify_region_sets_optional(); 3977 3978 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3979 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3980 3981 print_heap_after_gc(); 3982 trace_heap_after_gc(_gc_tracer_stw); 3983 3984 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3985 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3986 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3987 // before any GC notifications are raised. 3988 g1mm()->update_sizes(); 3989 3990 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3991 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3992 _gc_timer_stw->register_gc_end(); 3993 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3994 } 3995 // It should now be safe to tell the concurrent mark thread to start 3996 // without its logging output interfering with the logging output 3997 // that came from the pause. 3998 3999 if (should_start_conc_mark) { 4000 // CAUTION: after the doConcurrentMark() call below, 4001 // the concurrent marking thread(s) could be running 4002 // concurrently with us. Make sure that anything after 4003 // this point does not assume that we are the only GC thread 4004 // running. Note: of course, the actual marking work will 4005 // not start until the safepoint itself is released in 4006 // SuspendibleThreadSet::desynchronize(). 4007 doConcurrentMark(); 4008 } 4009 4010 return true; 4011 } 4012 4013 void G1CollectedHeap::restore_preserved_marks() { 4014 G1RestorePreservedMarksTask rpm_task(_preserved_objs); 4015 workers()->run_task(&rpm_task); 4016 } 4017 4018 void G1CollectedHeap::remove_self_forwarding_pointers() { 4019 G1ParRemoveSelfForwardPtrsTask rsfp_task; 4020 workers()->run_task(&rsfp_task); 4021 } 4022 4023 void G1CollectedHeap::restore_after_evac_failure() { 4024 double remove_self_forwards_start = os::elapsedTime(); 4025 4026 remove_self_forwarding_pointers(); 4027 restore_preserved_marks(); 4028 4029 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 4030 } 4031 4032 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 4033 if (!_evacuation_failed) { 4034 _evacuation_failed = true; 4035 } 4036 4037 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 4038 4039 // We want to call the "for_promotion_failure" version only in the 4040 // case of a promotion failure. 4041 if (m->must_be_preserved_for_promotion_failure(obj)) { 4042 OopAndMarkOop elem(obj, m); 4043 _preserved_objs[worker_id].push(elem); 4044 } 4045 } 4046 4047 bool G1ParEvacuateFollowersClosure::offer_termination() { 4048 G1ParScanThreadState* const pss = par_scan_state(); 4049 start_term_time(); 4050 const bool res = terminator()->offer_termination(); 4051 end_term_time(); 4052 return res; 4053 } 4054 4055 void G1ParEvacuateFollowersClosure::do_void() { 4056 G1ParScanThreadState* const pss = par_scan_state(); 4057 pss->trim_queue(); 4058 do { 4059 pss->steal_and_trim_queue(queues()); 4060 } while (!offer_termination()); 4061 } 4062 4063 class G1ParTask : public AbstractGangTask { 4064 protected: 4065 G1CollectedHeap* _g1h; 4066 G1ParScanThreadStateSet* _pss; 4067 RefToScanQueueSet* _queues; 4068 G1RootProcessor* _root_processor; 4069 ParallelTaskTerminator _terminator; 4070 uint _n_workers; 4071 4072 public: 4073 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 4074 : AbstractGangTask("G1 collection"), 4075 _g1h(g1h), 4076 _pss(per_thread_states), 4077 _queues(task_queues), 4078 _root_processor(root_processor), 4079 _terminator(n_workers, _queues), 4080 _n_workers(n_workers) 4081 {} 4082 4083 void work(uint worker_id) { 4084 if (worker_id >= _n_workers) return; // no work needed this round 4085 4086 double start_sec = os::elapsedTime(); 4087 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 4088 4089 { 4090 ResourceMark rm; 4091 HandleMark hm; 4092 4093 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4094 4095 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4096 pss->set_ref_processor(rp); 4097 4098 double start_strong_roots_sec = os::elapsedTime(); 4099 4100 _root_processor->evacuate_roots(pss->closures(), worker_id); 4101 4102 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss); 4103 4104 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 4105 // treating the nmethods visited to act as roots for concurrent marking. 4106 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 4107 // objects copied by the current evacuation. 4108 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl, 4109 pss->closures()->weak_codeblobs(), 4110 worker_id); 4111 4112 _pss->add_cards_scanned(worker_id, cards_scanned); 4113 4114 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 4115 4116 double term_sec = 0.0; 4117 size_t evac_term_attempts = 0; 4118 { 4119 double start = os::elapsedTime(); 4120 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 4121 evac.do_void(); 4122 4123 evac_term_attempts = evac.term_attempts(); 4124 term_sec = evac.term_time(); 4125 double elapsed_sec = os::elapsedTime() - start; 4126 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 4127 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 4128 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 4129 } 4130 4131 assert(pss->queue_is_empty(), "should be empty"); 4132 4133 if (log_is_enabled(Debug, gc, task, stats)) { 4134 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 4135 size_t lab_waste; 4136 size_t lab_undo_waste; 4137 pss->waste(lab_waste, lab_undo_waste); 4138 _g1h->print_termination_stats(worker_id, 4139 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 4140 strong_roots_sec * 1000.0, /* strong roots time */ 4141 term_sec * 1000.0, /* evac term time */ 4142 evac_term_attempts, /* evac term attempts */ 4143 lab_waste, /* alloc buffer waste */ 4144 lab_undo_waste /* undo waste */ 4145 ); 4146 } 4147 4148 // Close the inner scope so that the ResourceMark and HandleMark 4149 // destructors are executed here and are included as part of the 4150 // "GC Worker Time". 4151 } 4152 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 4153 } 4154 }; 4155 4156 void G1CollectedHeap::print_termination_stats_hdr() { 4157 log_debug(gc, task, stats)("GC Termination Stats"); 4158 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 4159 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 4160 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 4161 } 4162 4163 void G1CollectedHeap::print_termination_stats(uint worker_id, 4164 double elapsed_ms, 4165 double strong_roots_ms, 4166 double term_ms, 4167 size_t term_attempts, 4168 size_t alloc_buffer_waste, 4169 size_t undo_waste) const { 4170 log_debug(gc, task, stats) 4171 ("%3d %9.2f %9.2f %6.2f " 4172 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 4173 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 4174 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 4175 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 4176 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 4177 alloc_buffer_waste * HeapWordSize / K, 4178 undo_waste * HeapWordSize / K); 4179 } 4180 4181 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 4182 private: 4183 BoolObjectClosure* _is_alive; 4184 int _initial_string_table_size; 4185 int _initial_symbol_table_size; 4186 4187 bool _process_strings; 4188 int _strings_processed; 4189 int _strings_removed; 4190 4191 bool _process_symbols; 4192 int _symbols_processed; 4193 int _symbols_removed; 4194 4195 public: 4196 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 4197 AbstractGangTask("String/Symbol Unlinking"), 4198 _is_alive(is_alive), 4199 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 4200 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 4201 4202 _initial_string_table_size = StringTable::the_table()->table_size(); 4203 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 4204 if (process_strings) { 4205 StringTable::clear_parallel_claimed_index(); 4206 } 4207 if (process_symbols) { 4208 SymbolTable::clear_parallel_claimed_index(); 4209 } 4210 } 4211 4212 ~G1StringSymbolTableUnlinkTask() { 4213 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 4214 "claim value %d after unlink less than initial string table size %d", 4215 StringTable::parallel_claimed_index(), _initial_string_table_size); 4216 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 4217 "claim value %d after unlink less than initial symbol table size %d", 4218 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 4219 4220 log_debug(gc, stringdedup)("Cleaned string and symbol table, " 4221 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 4222 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 4223 strings_processed(), strings_removed(), 4224 symbols_processed(), symbols_removed()); 4225 } 4226 4227 void work(uint worker_id) { 4228 int strings_processed = 0; 4229 int strings_removed = 0; 4230 int symbols_processed = 0; 4231 int symbols_removed = 0; 4232 if (_process_strings) { 4233 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 4234 Atomic::add(strings_processed, &_strings_processed); 4235 Atomic::add(strings_removed, &_strings_removed); 4236 } 4237 if (_process_symbols) { 4238 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 4239 Atomic::add(symbols_processed, &_symbols_processed); 4240 Atomic::add(symbols_removed, &_symbols_removed); 4241 } 4242 } 4243 4244 size_t strings_processed() const { return (size_t)_strings_processed; } 4245 size_t strings_removed() const { return (size_t)_strings_removed; } 4246 4247 size_t symbols_processed() const { return (size_t)_symbols_processed; } 4248 size_t symbols_removed() const { return (size_t)_symbols_removed; } 4249 }; 4250 4251 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 4252 private: 4253 static Monitor* _lock; 4254 4255 BoolObjectClosure* const _is_alive; 4256 const bool _unloading_occurred; 4257 const uint _num_workers; 4258 4259 // Variables used to claim nmethods. 4260 nmethod* _first_nmethod; 4261 volatile nmethod* _claimed_nmethod; 4262 4263 // The list of nmethods that need to be processed by the second pass. 4264 volatile nmethod* _postponed_list; 4265 volatile uint _num_entered_barrier; 4266 4267 public: 4268 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 4269 _is_alive(is_alive), 4270 _unloading_occurred(unloading_occurred), 4271 _num_workers(num_workers), 4272 _first_nmethod(NULL), 4273 _claimed_nmethod(NULL), 4274 _postponed_list(NULL), 4275 _num_entered_barrier(0) 4276 { 4277 nmethod::increase_unloading_clock(); 4278 // Get first alive nmethod 4279 NMethodIterator iter = NMethodIterator(); 4280 if(iter.next_alive()) { 4281 _first_nmethod = iter.method(); 4282 } 4283 _claimed_nmethod = (volatile nmethod*)_first_nmethod; 4284 } 4285 4286 ~G1CodeCacheUnloadingTask() { 4287 CodeCache::verify_clean_inline_caches(); 4288 4289 CodeCache::set_needs_cache_clean(false); 4290 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 4291 4292 CodeCache::verify_icholder_relocations(); 4293 } 4294 4295 private: 4296 void add_to_postponed_list(nmethod* nm) { 4297 nmethod* old; 4298 do { 4299 old = (nmethod*)_postponed_list; 4300 nm->set_unloading_next(old); 4301 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 4302 } 4303 4304 void clean_nmethod(nmethod* nm) { 4305 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 4306 4307 if (postponed) { 4308 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 4309 add_to_postponed_list(nm); 4310 } 4311 4312 // Mark that this thread has been cleaned/unloaded. 4313 // After this call, it will be safe to ask if this nmethod was unloaded or not. 4314 nm->set_unloading_clock(nmethod::global_unloading_clock()); 4315 } 4316 4317 void clean_nmethod_postponed(nmethod* nm) { 4318 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 4319 } 4320 4321 static const int MaxClaimNmethods = 16; 4322 4323 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) { 4324 nmethod* first; 4325 NMethodIterator last; 4326 4327 do { 4328 *num_claimed_nmethods = 0; 4329 4330 first = (nmethod*)_claimed_nmethod; 4331 last = NMethodIterator(first); 4332 4333 if (first != NULL) { 4334 4335 for (int i = 0; i < MaxClaimNmethods; i++) { 4336 if (!last.next_alive()) { 4337 break; 4338 } 4339 claimed_nmethods[i] = last.method(); 4340 (*num_claimed_nmethods)++; 4341 } 4342 } 4343 4344 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 4345 } 4346 4347 nmethod* claim_postponed_nmethod() { 4348 nmethod* claim; 4349 nmethod* next; 4350 4351 do { 4352 claim = (nmethod*)_postponed_list; 4353 if (claim == NULL) { 4354 return NULL; 4355 } 4356 4357 next = claim->unloading_next(); 4358 4359 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 4360 4361 return claim; 4362 } 4363 4364 public: 4365 // Mark that we're done with the first pass of nmethod cleaning. 4366 void barrier_mark(uint worker_id) { 4367 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4368 _num_entered_barrier++; 4369 if (_num_entered_barrier == _num_workers) { 4370 ml.notify_all(); 4371 } 4372 } 4373 4374 // See if we have to wait for the other workers to 4375 // finish their first-pass nmethod cleaning work. 4376 void barrier_wait(uint worker_id) { 4377 if (_num_entered_barrier < _num_workers) { 4378 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4379 while (_num_entered_barrier < _num_workers) { 4380 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 4381 } 4382 } 4383 } 4384 4385 // Cleaning and unloading of nmethods. Some work has to be postponed 4386 // to the second pass, when we know which nmethods survive. 4387 void work_first_pass(uint worker_id) { 4388 // The first nmethods is claimed by the first worker. 4389 if (worker_id == 0 && _first_nmethod != NULL) { 4390 clean_nmethod(_first_nmethod); 4391 _first_nmethod = NULL; 4392 } 4393 4394 int num_claimed_nmethods; 4395 nmethod* claimed_nmethods[MaxClaimNmethods]; 4396 4397 while (true) { 4398 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 4399 4400 if (num_claimed_nmethods == 0) { 4401 break; 4402 } 4403 4404 for (int i = 0; i < num_claimed_nmethods; i++) { 4405 clean_nmethod(claimed_nmethods[i]); 4406 } 4407 } 4408 } 4409 4410 void work_second_pass(uint worker_id) { 4411 nmethod* nm; 4412 // Take care of postponed nmethods. 4413 while ((nm = claim_postponed_nmethod()) != NULL) { 4414 clean_nmethod_postponed(nm); 4415 } 4416 } 4417 }; 4418 4419 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 4420 4421 class G1KlassCleaningTask : public StackObj { 4422 BoolObjectClosure* _is_alive; 4423 volatile jint _clean_klass_tree_claimed; 4424 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 4425 4426 public: 4427 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 4428 _is_alive(is_alive), 4429 _clean_klass_tree_claimed(0), 4430 _klass_iterator() { 4431 } 4432 4433 private: 4434 bool claim_clean_klass_tree_task() { 4435 if (_clean_klass_tree_claimed) { 4436 return false; 4437 } 4438 4439 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 4440 } 4441 4442 InstanceKlass* claim_next_klass() { 4443 Klass* klass; 4444 do { 4445 klass =_klass_iterator.next_klass(); 4446 } while (klass != NULL && !klass->is_instance_klass()); 4447 4448 // this can be null so don't call InstanceKlass::cast 4449 return static_cast<InstanceKlass*>(klass); 4450 } 4451 4452 public: 4453 4454 void clean_klass(InstanceKlass* ik) { 4455 ik->clean_weak_instanceklass_links(_is_alive); 4456 } 4457 4458 void work() { 4459 ResourceMark rm; 4460 4461 // One worker will clean the subklass/sibling klass tree. 4462 if (claim_clean_klass_tree_task()) { 4463 Klass::clean_subklass_tree(_is_alive); 4464 } 4465 4466 // All workers will help cleaning the classes, 4467 InstanceKlass* klass; 4468 while ((klass = claim_next_klass()) != NULL) { 4469 clean_klass(klass); 4470 } 4471 } 4472 }; 4473 4474 // To minimize the remark pause times, the tasks below are done in parallel. 4475 class G1ParallelCleaningTask : public AbstractGangTask { 4476 private: 4477 G1StringSymbolTableUnlinkTask _string_symbol_task; 4478 G1CodeCacheUnloadingTask _code_cache_task; 4479 G1KlassCleaningTask _klass_cleaning_task; 4480 4481 public: 4482 // The constructor is run in the VMThread. 4483 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 4484 AbstractGangTask("Parallel Cleaning"), 4485 _string_symbol_task(is_alive, process_strings, process_symbols), 4486 _code_cache_task(num_workers, is_alive, unloading_occurred), 4487 _klass_cleaning_task(is_alive) { 4488 } 4489 4490 // The parallel work done by all worker threads. 4491 void work(uint worker_id) { 4492 // Do first pass of code cache cleaning. 4493 _code_cache_task.work_first_pass(worker_id); 4494 4495 // Let the threads mark that the first pass is done. 4496 _code_cache_task.barrier_mark(worker_id); 4497 4498 // Clean the Strings and Symbols. 4499 _string_symbol_task.work(worker_id); 4500 4501 // Wait for all workers to finish the first code cache cleaning pass. 4502 _code_cache_task.barrier_wait(worker_id); 4503 4504 // Do the second code cache cleaning work, which realize on 4505 // the liveness information gathered during the first pass. 4506 _code_cache_task.work_second_pass(worker_id); 4507 4508 // Clean all klasses that were not unloaded. 4509 _klass_cleaning_task.work(); 4510 } 4511 }; 4512 4513 4514 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 4515 bool process_strings, 4516 bool process_symbols, 4517 bool class_unloading_occurred) { 4518 uint n_workers = workers()->active_workers(); 4519 4520 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 4521 n_workers, class_unloading_occurred); 4522 workers()->run_task(&g1_unlink_task); 4523 } 4524 4525 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 4526 bool process_strings, bool process_symbols) { 4527 { 4528 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 4529 workers()->run_task(&g1_unlink_task); 4530 } 4531 4532 if (G1StringDedup::is_enabled()) { 4533 G1StringDedup::unlink(is_alive); 4534 } 4535 } 4536 4537 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 4538 private: 4539 DirtyCardQueueSet* _queue; 4540 G1CollectedHeap* _g1h; 4541 public: 4542 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 4543 _queue(queue), _g1h(g1h) { } 4544 4545 virtual void work(uint worker_id) { 4546 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 4547 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 4548 4549 RedirtyLoggedCardTableEntryClosure cl(_g1h); 4550 _queue->par_apply_closure_to_all_completed_buffers(&cl); 4551 4552 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 4553 } 4554 }; 4555 4556 void G1CollectedHeap::redirty_logged_cards() { 4557 double redirty_logged_cards_start = os::elapsedTime(); 4558 4559 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 4560 dirty_card_queue_set().reset_for_par_iteration(); 4561 workers()->run_task(&redirty_task); 4562 4563 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 4564 dcq.merge_bufferlists(&dirty_card_queue_set()); 4565 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 4566 4567 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 4568 } 4569 4570 // Weak Reference Processing support 4571 4572 // An always "is_alive" closure that is used to preserve referents. 4573 // If the object is non-null then it's alive. Used in the preservation 4574 // of referent objects that are pointed to by reference objects 4575 // discovered by the CM ref processor. 4576 class G1AlwaysAliveClosure: public BoolObjectClosure { 4577 G1CollectedHeap* _g1; 4578 public: 4579 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4580 bool do_object_b(oop p) { 4581 if (p != NULL) { 4582 return true; 4583 } 4584 return false; 4585 } 4586 }; 4587 4588 bool G1STWIsAliveClosure::do_object_b(oop p) { 4589 // An object is reachable if it is outside the collection set, 4590 // or is inside and copied. 4591 return !_g1->is_in_cset(p) || p->is_forwarded(); 4592 } 4593 4594 // Non Copying Keep Alive closure 4595 class G1KeepAliveClosure: public OopClosure { 4596 G1CollectedHeap* _g1; 4597 public: 4598 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4599 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 4600 void do_oop(oop* p) { 4601 oop obj = *p; 4602 assert(obj != NULL, "the caller should have filtered out NULL values"); 4603 4604 const InCSetState cset_state = _g1->in_cset_state(obj); 4605 if (!cset_state.is_in_cset_or_humongous()) { 4606 return; 4607 } 4608 if (cset_state.is_in_cset()) { 4609 assert( obj->is_forwarded(), "invariant" ); 4610 *p = obj->forwardee(); 4611 } else { 4612 assert(!obj->is_forwarded(), "invariant" ); 4613 assert(cset_state.is_humongous(), 4614 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 4615 _g1->set_humongous_is_live(obj); 4616 } 4617 } 4618 }; 4619 4620 // Copying Keep Alive closure - can be called from both 4621 // serial and parallel code as long as different worker 4622 // threads utilize different G1ParScanThreadState instances 4623 // and different queues. 4624 4625 class G1CopyingKeepAliveClosure: public OopClosure { 4626 G1CollectedHeap* _g1h; 4627 OopClosure* _copy_non_heap_obj_cl; 4628 G1ParScanThreadState* _par_scan_state; 4629 4630 public: 4631 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4632 OopClosure* non_heap_obj_cl, 4633 G1ParScanThreadState* pss): 4634 _g1h(g1h), 4635 _copy_non_heap_obj_cl(non_heap_obj_cl), 4636 _par_scan_state(pss) 4637 {} 4638 4639 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4640 virtual void do_oop( oop* p) { do_oop_work(p); } 4641 4642 template <class T> void do_oop_work(T* p) { 4643 oop obj = oopDesc::load_decode_heap_oop(p); 4644 4645 if (_g1h->is_in_cset_or_humongous(obj)) { 4646 // If the referent object has been forwarded (either copied 4647 // to a new location or to itself in the event of an 4648 // evacuation failure) then we need to update the reference 4649 // field and, if both reference and referent are in the G1 4650 // heap, update the RSet for the referent. 4651 // 4652 // If the referent has not been forwarded then we have to keep 4653 // it alive by policy. Therefore we have copy the referent. 4654 // 4655 // If the reference field is in the G1 heap then we can push 4656 // on the PSS queue. When the queue is drained (after each 4657 // phase of reference processing) the object and it's followers 4658 // will be copied, the reference field set to point to the 4659 // new location, and the RSet updated. Otherwise we need to 4660 // use the the non-heap or metadata closures directly to copy 4661 // the referent object and update the pointer, while avoiding 4662 // updating the RSet. 4663 4664 if (_g1h->is_in_g1_reserved(p)) { 4665 _par_scan_state->push_on_queue(p); 4666 } else { 4667 assert(!Metaspace::contains((const void*)p), 4668 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4669 _copy_non_heap_obj_cl->do_oop(p); 4670 } 4671 } 4672 } 4673 }; 4674 4675 // Serial drain queue closure. Called as the 'complete_gc' 4676 // closure for each discovered list in some of the 4677 // reference processing phases. 4678 4679 class G1STWDrainQueueClosure: public VoidClosure { 4680 protected: 4681 G1CollectedHeap* _g1h; 4682 G1ParScanThreadState* _par_scan_state; 4683 4684 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4685 4686 public: 4687 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4688 _g1h(g1h), 4689 _par_scan_state(pss) 4690 { } 4691 4692 void do_void() { 4693 G1ParScanThreadState* const pss = par_scan_state(); 4694 pss->trim_queue(); 4695 } 4696 }; 4697 4698 // Parallel Reference Processing closures 4699 4700 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4701 // processing during G1 evacuation pauses. 4702 4703 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4704 private: 4705 G1CollectedHeap* _g1h; 4706 G1ParScanThreadStateSet* _pss; 4707 RefToScanQueueSet* _queues; 4708 WorkGang* _workers; 4709 uint _active_workers; 4710 4711 public: 4712 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4713 G1ParScanThreadStateSet* per_thread_states, 4714 WorkGang* workers, 4715 RefToScanQueueSet *task_queues, 4716 uint n_workers) : 4717 _g1h(g1h), 4718 _pss(per_thread_states), 4719 _queues(task_queues), 4720 _workers(workers), 4721 _active_workers(n_workers) 4722 { 4723 assert(n_workers > 0, "shouldn't call this otherwise"); 4724 } 4725 4726 // Executes the given task using concurrent marking worker threads. 4727 virtual void execute(ProcessTask& task); 4728 virtual void execute(EnqueueTask& task); 4729 }; 4730 4731 // Gang task for possibly parallel reference processing 4732 4733 class G1STWRefProcTaskProxy: public AbstractGangTask { 4734 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4735 ProcessTask& _proc_task; 4736 G1CollectedHeap* _g1h; 4737 G1ParScanThreadStateSet* _pss; 4738 RefToScanQueueSet* _task_queues; 4739 ParallelTaskTerminator* _terminator; 4740 4741 public: 4742 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4743 G1CollectedHeap* g1h, 4744 G1ParScanThreadStateSet* per_thread_states, 4745 RefToScanQueueSet *task_queues, 4746 ParallelTaskTerminator* terminator) : 4747 AbstractGangTask("Process reference objects in parallel"), 4748 _proc_task(proc_task), 4749 _g1h(g1h), 4750 _pss(per_thread_states), 4751 _task_queues(task_queues), 4752 _terminator(terminator) 4753 {} 4754 4755 virtual void work(uint worker_id) { 4756 // The reference processing task executed by a single worker. 4757 ResourceMark rm; 4758 HandleMark hm; 4759 4760 G1STWIsAliveClosure is_alive(_g1h); 4761 4762 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4763 pss->set_ref_processor(NULL); 4764 4765 // Keep alive closure. 4766 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4767 4768 // Complete GC closure 4769 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4770 4771 // Call the reference processing task's work routine. 4772 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4773 4774 // Note we cannot assert that the refs array is empty here as not all 4775 // of the processing tasks (specifically phase2 - pp2_work) execute 4776 // the complete_gc closure (which ordinarily would drain the queue) so 4777 // the queue may not be empty. 4778 } 4779 }; 4780 4781 // Driver routine for parallel reference processing. 4782 // Creates an instance of the ref processing gang 4783 // task and has the worker threads execute it. 4784 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4785 assert(_workers != NULL, "Need parallel worker threads."); 4786 4787 ParallelTaskTerminator terminator(_active_workers, _queues); 4788 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4789 4790 _workers->run_task(&proc_task_proxy); 4791 } 4792 4793 // Gang task for parallel reference enqueueing. 4794 4795 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4796 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4797 EnqueueTask& _enq_task; 4798 4799 public: 4800 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4801 AbstractGangTask("Enqueue reference objects in parallel"), 4802 _enq_task(enq_task) 4803 { } 4804 4805 virtual void work(uint worker_id) { 4806 _enq_task.work(worker_id); 4807 } 4808 }; 4809 4810 // Driver routine for parallel reference enqueueing. 4811 // Creates an instance of the ref enqueueing gang 4812 // task and has the worker threads execute it. 4813 4814 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4815 assert(_workers != NULL, "Need parallel worker threads."); 4816 4817 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4818 4819 _workers->run_task(&enq_task_proxy); 4820 } 4821 4822 // End of weak reference support closures 4823 4824 // Abstract task used to preserve (i.e. copy) any referent objects 4825 // that are in the collection set and are pointed to by reference 4826 // objects discovered by the CM ref processor. 4827 4828 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4829 protected: 4830 G1CollectedHeap* _g1h; 4831 G1ParScanThreadStateSet* _pss; 4832 RefToScanQueueSet* _queues; 4833 ParallelTaskTerminator _terminator; 4834 uint _n_workers; 4835 4836 public: 4837 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4838 AbstractGangTask("ParPreserveCMReferents"), 4839 _g1h(g1h), 4840 _pss(per_thread_states), 4841 _queues(task_queues), 4842 _terminator(workers, _queues), 4843 _n_workers(workers) 4844 { } 4845 4846 void work(uint worker_id) { 4847 ResourceMark rm; 4848 HandleMark hm; 4849 4850 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4851 pss->set_ref_processor(NULL); 4852 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4853 4854 // Is alive closure 4855 G1AlwaysAliveClosure always_alive(_g1h); 4856 4857 // Copying keep alive closure. Applied to referent objects that need 4858 // to be copied. 4859 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4860 4861 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4862 4863 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4864 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4865 4866 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4867 // So this must be true - but assert just in case someone decides to 4868 // change the worker ids. 4869 assert(worker_id < limit, "sanity"); 4870 assert(!rp->discovery_is_atomic(), "check this code"); 4871 4872 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4873 for (uint idx = worker_id; idx < limit; idx += stride) { 4874 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4875 4876 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4877 while (iter.has_next()) { 4878 // Since discovery is not atomic for the CM ref processor, we 4879 // can see some null referent objects. 4880 iter.load_ptrs(DEBUG_ONLY(true)); 4881 oop ref = iter.obj(); 4882 4883 // This will filter nulls. 4884 if (iter.is_referent_alive()) { 4885 iter.make_referent_alive(); 4886 } 4887 iter.move_to_next(); 4888 } 4889 } 4890 4891 // Drain the queue - which may cause stealing 4892 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4893 drain_queue.do_void(); 4894 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4895 assert(pss->queue_is_empty(), "should be"); 4896 } 4897 }; 4898 4899 void G1CollectedHeap::process_weak_jni_handles() { 4900 double ref_proc_start = os::elapsedTime(); 4901 4902 G1STWIsAliveClosure is_alive(this); 4903 G1KeepAliveClosure keep_alive(this); 4904 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 4905 4906 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4907 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4908 } 4909 4910 // Weak Reference processing during an evacuation pause (part 1). 4911 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4912 double ref_proc_start = os::elapsedTime(); 4913 4914 ReferenceProcessor* rp = _ref_processor_stw; 4915 assert(rp->discovery_enabled(), "should have been enabled"); 4916 4917 // Any reference objects, in the collection set, that were 'discovered' 4918 // by the CM ref processor should have already been copied (either by 4919 // applying the external root copy closure to the discovered lists, or 4920 // by following an RSet entry). 4921 // 4922 // But some of the referents, that are in the collection set, that these 4923 // reference objects point to may not have been copied: the STW ref 4924 // processor would have seen that the reference object had already 4925 // been 'discovered' and would have skipped discovering the reference, 4926 // but would not have treated the reference object as a regular oop. 4927 // As a result the copy closure would not have been applied to the 4928 // referent object. 4929 // 4930 // We need to explicitly copy these referent objects - the references 4931 // will be processed at the end of remarking. 4932 // 4933 // We also need to do this copying before we process the reference 4934 // objects discovered by the STW ref processor in case one of these 4935 // referents points to another object which is also referenced by an 4936 // object discovered by the STW ref processor. 4937 4938 uint no_of_gc_workers = workers()->active_workers(); 4939 4940 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4941 per_thread_states, 4942 no_of_gc_workers, 4943 _task_queues); 4944 4945 workers()->run_task(&keep_cm_referents); 4946 4947 // Closure to test whether a referent is alive. 4948 G1STWIsAliveClosure is_alive(this); 4949 4950 // Even when parallel reference processing is enabled, the processing 4951 // of JNI refs is serial and performed serially by the current thread 4952 // rather than by a worker. The following PSS will be used for processing 4953 // JNI refs. 4954 4955 // Use only a single queue for this PSS. 4956 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4957 pss->set_ref_processor(NULL); 4958 assert(pss->queue_is_empty(), "pre-condition"); 4959 4960 // Keep alive closure. 4961 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4962 4963 // Serial Complete GC closure 4964 G1STWDrainQueueClosure drain_queue(this, pss); 4965 4966 // Setup the soft refs policy... 4967 rp->setup_policy(false); 4968 4969 ReferenceProcessorStats stats; 4970 if (!rp->processing_is_mt()) { 4971 // Serial reference processing... 4972 stats = rp->process_discovered_references(&is_alive, 4973 &keep_alive, 4974 &drain_queue, 4975 NULL, 4976 _gc_timer_stw); 4977 } else { 4978 // Parallel reference processing 4979 assert(rp->num_q() == no_of_gc_workers, "sanity"); 4980 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 4981 4982 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4983 stats = rp->process_discovered_references(&is_alive, 4984 &keep_alive, 4985 &drain_queue, 4986 &par_task_executor, 4987 _gc_timer_stw); 4988 } 4989 4990 _gc_tracer_stw->report_gc_reference_stats(stats); 4991 4992 // We have completed copying any necessary live referent objects. 4993 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4994 4995 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4996 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4997 } 4998 4999 // Weak Reference processing during an evacuation pause (part 2). 5000 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 5001 double ref_enq_start = os::elapsedTime(); 5002 5003 ReferenceProcessor* rp = _ref_processor_stw; 5004 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5005 5006 // Now enqueue any remaining on the discovered lists on to 5007 // the pending list. 5008 if (!rp->processing_is_mt()) { 5009 // Serial reference processing... 5010 rp->enqueue_discovered_references(); 5011 } else { 5012 // Parallel reference enqueueing 5013 5014 uint n_workers = workers()->active_workers(); 5015 5016 assert(rp->num_q() == n_workers, "sanity"); 5017 assert(n_workers <= rp->max_num_q(), "sanity"); 5018 5019 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 5020 rp->enqueue_discovered_references(&par_task_executor); 5021 } 5022 5023 rp->verify_no_references_recorded(); 5024 assert(!rp->discovery_enabled(), "should have been disabled"); 5025 5026 // FIXME 5027 // CM's reference processing also cleans up the string and symbol tables. 5028 // Should we do that here also? We could, but it is a serial operation 5029 // and could significantly increase the pause time. 5030 5031 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5032 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5033 } 5034 5035 void G1CollectedHeap::pre_evacuate_collection_set() { 5036 _expand_heap_after_alloc_failure = true; 5037 _evacuation_failed = false; 5038 5039 // Disable the hot card cache. 5040 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5041 hot_card_cache->reset_hot_cache_claimed_index(); 5042 hot_card_cache->set_use_cache(false); 5043 5044 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5045 } 5046 5047 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 5048 // Should G1EvacuationFailureALot be in effect for this GC? 5049 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5050 5051 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5052 double start_par_time_sec = os::elapsedTime(); 5053 double end_par_time_sec; 5054 5055 { 5056 const uint n_workers = workers()->active_workers(); 5057 G1RootProcessor root_processor(this, n_workers); 5058 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 5059 // InitialMark needs claim bits to keep track of the marked-through CLDs. 5060 if (collector_state()->during_initial_mark_pause()) { 5061 ClassLoaderDataGraph::clear_claimed_marks(); 5062 } 5063 5064 print_termination_stats_hdr(); 5065 5066 workers()->run_task(&g1_par_task); 5067 end_par_time_sec = os::elapsedTime(); 5068 5069 // Closing the inner scope will execute the destructor 5070 // for the G1RootProcessor object. We record the current 5071 // elapsed time before closing the scope so that time 5072 // taken for the destructor is NOT included in the 5073 // reported parallel time. 5074 } 5075 5076 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 5077 5078 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5079 phase_times->record_par_time(par_time_ms); 5080 5081 double code_root_fixup_time_ms = 5082 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5083 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 5084 } 5085 5086 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 5087 // Process any discovered reference objects - we have 5088 // to do this _before_ we retire the GC alloc regions 5089 // as we may have to copy some 'reachable' referent 5090 // objects (and their reachable sub-graphs) that were 5091 // not copied during the pause. 5092 if (g1_policy()->should_process_references()) { 5093 process_discovered_references(per_thread_states); 5094 } else { 5095 ref_processor_stw()->verify_no_references_recorded(); 5096 process_weak_jni_handles(); 5097 } 5098 5099 if (G1StringDedup::is_enabled()) { 5100 double fixup_start = os::elapsedTime(); 5101 5102 G1STWIsAliveClosure is_alive(this); 5103 G1KeepAliveClosure keep_alive(this); 5104 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 5105 5106 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 5107 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 5108 } 5109 5110 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5111 5112 if (evacuation_failed()) { 5113 restore_after_evac_failure(); 5114 5115 // Reset the G1EvacuationFailureALot counters and flags 5116 // Note: the values are reset only when an actual 5117 // evacuation failure occurs. 5118 NOT_PRODUCT(reset_evacuation_should_fail();) 5119 } 5120 5121 // Enqueue any remaining references remaining on the STW 5122 // reference processor's discovered lists. We need to do 5123 // this after the card table is cleaned (and verified) as 5124 // the act of enqueueing entries on to the pending list 5125 // will log these updates (and dirty their associated 5126 // cards). We need these updates logged to update any 5127 // RSets. 5128 if (g1_policy()->should_process_references()) { 5129 enqueue_discovered_references(per_thread_states); 5130 } else { 5131 g1_policy()->phase_times()->record_ref_enq_time(0); 5132 } 5133 5134 _allocator->release_gc_alloc_regions(evacuation_info); 5135 5136 per_thread_states->flush(); 5137 5138 record_obj_copy_mem_stats(); 5139 5140 _survivor_evac_stats.adjust_desired_plab_sz(); 5141 _old_evac_stats.adjust_desired_plab_sz(); 5142 5143 // Reset and re-enable the hot card cache. 5144 // Note the counts for the cards in the regions in the 5145 // collection set are reset when the collection set is freed. 5146 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5147 hot_card_cache->reset_hot_cache(); 5148 hot_card_cache->set_use_cache(true); 5149 5150 purge_code_root_memory(); 5151 5152 redirty_logged_cards(); 5153 #if defined(COMPILER2) || INCLUDE_JVMCI 5154 DerivedPointerTable::update_pointers(); 5155 #endif 5156 } 5157 5158 void G1CollectedHeap::record_obj_copy_mem_stats() { 5159 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 5160 5161 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 5162 create_g1_evac_summary(&_old_evac_stats)); 5163 } 5164 5165 void G1CollectedHeap::free_region(HeapRegion* hr, 5166 FreeRegionList* free_list, 5167 bool par, 5168 bool locked) { 5169 assert(!hr->is_free(), "the region should not be free"); 5170 assert(!hr->is_empty(), "the region should not be empty"); 5171 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 5172 assert(free_list != NULL, "pre-condition"); 5173 5174 if (G1VerifyBitmaps) { 5175 MemRegion mr(hr->bottom(), hr->end()); 5176 concurrent_mark()->clearRangePrevBitmap(mr); 5177 } 5178 5179 // Clear the card counts for this region. 5180 // Note: we only need to do this if the region is not young 5181 // (since we don't refine cards in young regions). 5182 if (!hr->is_young()) { 5183 _cg1r->hot_card_cache()->reset_card_counts(hr); 5184 } 5185 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 5186 free_list->add_ordered(hr); 5187 } 5188 5189 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5190 FreeRegionList* free_list, 5191 bool par) { 5192 assert(hr->is_humongous(), "this is only for humongous regions"); 5193 assert(free_list != NULL, "pre-condition"); 5194 hr->clear_humongous(); 5195 free_region(hr, free_list, par); 5196 } 5197 5198 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 5199 const uint humongous_regions_removed) { 5200 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 5201 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5202 _old_set.bulk_remove(old_regions_removed); 5203 _humongous_set.bulk_remove(humongous_regions_removed); 5204 } 5205 5206 } 5207 5208 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 5209 assert(list != NULL, "list can't be null"); 5210 if (!list->is_empty()) { 5211 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 5212 _hrm.insert_list_into_free_list(list); 5213 } 5214 } 5215 5216 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 5217 decrease_used(bytes); 5218 } 5219 5220 class G1ParCleanupCTTask : public AbstractGangTask { 5221 G1SATBCardTableModRefBS* _ct_bs; 5222 G1CollectedHeap* _g1h; 5223 HeapRegion* volatile _su_head; 5224 public: 5225 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 5226 G1CollectedHeap* g1h) : 5227 AbstractGangTask("G1 Par Cleanup CT Task"), 5228 _ct_bs(ct_bs), _g1h(g1h) { } 5229 5230 void work(uint worker_id) { 5231 HeapRegion* r; 5232 while (r = _g1h->pop_dirty_cards_region()) { 5233 clear_cards(r); 5234 } 5235 } 5236 5237 void clear_cards(HeapRegion* r) { 5238 // Cards of the survivors should have already been dirtied. 5239 if (!r->is_survivor()) { 5240 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 5241 } 5242 } 5243 }; 5244 5245 #ifndef PRODUCT 5246 class G1VerifyCardTableCleanup: public HeapRegionClosure { 5247 G1CollectedHeap* _g1h; 5248 G1SATBCardTableModRefBS* _ct_bs; 5249 public: 5250 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs) 5251 : _g1h(g1h), _ct_bs(ct_bs) { } 5252 virtual bool doHeapRegion(HeapRegion* r) { 5253 if (r->is_survivor()) { 5254 _g1h->verify_dirty_region(r); 5255 } else { 5256 _g1h->verify_not_dirty_region(r); 5257 } 5258 return false; 5259 } 5260 }; 5261 5262 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 5263 // All of the region should be clean. 5264 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5265 MemRegion mr(hr->bottom(), hr->end()); 5266 ct_bs->verify_not_dirty_region(mr); 5267 } 5268 5269 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 5270 // We cannot guarantee that [bottom(),end()] is dirty. Threads 5271 // dirty allocated blocks as they allocate them. The thread that 5272 // retires each region and replaces it with a new one will do a 5273 // maximal allocation to fill in [pre_dummy_top(),end()] but will 5274 // not dirty that area (one less thing to have to do while holding 5275 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 5276 // is dirty. 5277 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5278 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 5279 if (hr->is_young()) { 5280 ct_bs->verify_g1_young_region(mr); 5281 } else { 5282 ct_bs->verify_dirty_region(mr); 5283 } 5284 } 5285 5286 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 5287 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5288 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 5289 verify_dirty_region(hr); 5290 } 5291 } 5292 5293 void G1CollectedHeap::verify_dirty_young_regions() { 5294 verify_dirty_young_list(_young_list->first_region()); 5295 } 5296 5297 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 5298 HeapWord* tams, HeapWord* end) { 5299 guarantee(tams <= end, 5300 "tams: " PTR_FORMAT " end: " PTR_FORMAT, p2i(tams), p2i(end)); 5301 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end); 5302 if (result < end) { 5303 log_info(gc, verify)("## wrong marked address on %s bitmap: " PTR_FORMAT, bitmap_name, p2i(result)); 5304 log_info(gc, verify)("## %s tams: " PTR_FORMAT " end: " PTR_FORMAT, bitmap_name, p2i(tams), p2i(end)); 5305 return false; 5306 } 5307 return true; 5308 } 5309 5310 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) { 5311 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap(); 5312 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap(); 5313 5314 HeapWord* bottom = hr->bottom(); 5315 HeapWord* ptams = hr->prev_top_at_mark_start(); 5316 HeapWord* ntams = hr->next_top_at_mark_start(); 5317 HeapWord* end = hr->end(); 5318 5319 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end); 5320 5321 bool res_n = true; 5322 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window 5323 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap 5324 // if we happen to be in that state. 5325 if (collector_state()->mark_in_progress() || !_cmThread->in_progress()) { 5326 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end); 5327 } 5328 if (!res_p || !res_n) { 5329 log_info(gc, verify)("#### Bitmap verification failed for " HR_FORMAT, HR_FORMAT_PARAMS(hr)); 5330 log_info(gc, verify)("#### Caller: %s", caller); 5331 return false; 5332 } 5333 return true; 5334 } 5335 5336 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) { 5337 if (!G1VerifyBitmaps) return; 5338 5339 guarantee(verify_bitmaps(caller, hr), "bitmap verification"); 5340 } 5341 5342 class G1VerifyBitmapClosure : public HeapRegionClosure { 5343 private: 5344 const char* _caller; 5345 G1CollectedHeap* _g1h; 5346 bool _failures; 5347 5348 public: 5349 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) : 5350 _caller(caller), _g1h(g1h), _failures(false) { } 5351 5352 bool failures() { return _failures; } 5353 5354 virtual bool doHeapRegion(HeapRegion* hr) { 5355 bool result = _g1h->verify_bitmaps(_caller, hr); 5356 if (!result) { 5357 _failures = true; 5358 } 5359 return false; 5360 } 5361 }; 5362 5363 void G1CollectedHeap::check_bitmaps(const char* caller) { 5364 if (!G1VerifyBitmaps) return; 5365 5366 G1VerifyBitmapClosure cl(caller, this); 5367 heap_region_iterate(&cl); 5368 guarantee(!cl.failures(), "bitmap verification"); 5369 } 5370 5371 class G1CheckCSetFastTableClosure : public HeapRegionClosure { 5372 private: 5373 bool _failures; 5374 public: 5375 G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { } 5376 5377 virtual bool doHeapRegion(HeapRegion* hr) { 5378 uint i = hr->hrm_index(); 5379 InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i); 5380 if (hr->is_humongous()) { 5381 if (hr->in_collection_set()) { 5382 log_info(gc, verify)("## humongous region %u in CSet", i); 5383 _failures = true; 5384 return true; 5385 } 5386 if (cset_state.is_in_cset()) { 5387 log_info(gc, verify)("## inconsistent cset state " CSETSTATE_FORMAT " for humongous region %u", cset_state.value(), i); 5388 _failures = true; 5389 return true; 5390 } 5391 if (hr->is_continues_humongous() && cset_state.is_humongous()) { 5392 log_info(gc, verify)("## inconsistent cset state " CSETSTATE_FORMAT " for continues humongous region %u", cset_state.value(), i); 5393 _failures = true; 5394 return true; 5395 } 5396 } else { 5397 if (cset_state.is_humongous()) { 5398 log_info(gc, verify)("## inconsistent cset state " CSETSTATE_FORMAT " for non-humongous region %u", cset_state.value(), i); 5399 _failures = true; 5400 return true; 5401 } 5402 if (hr->in_collection_set() != cset_state.is_in_cset()) { 5403 log_info(gc, verify)("## in CSet %d / cset state " CSETSTATE_FORMAT " inconsistency for region %u", 5404 hr->in_collection_set(), cset_state.value(), i); 5405 _failures = true; 5406 return true; 5407 } 5408 if (cset_state.is_in_cset()) { 5409 if (hr->is_young() != (cset_state.is_young())) { 5410 log_info(gc, verify)("## is_young %d / cset state " CSETSTATE_FORMAT " inconsistency for region %u", 5411 hr->is_young(), cset_state.value(), i); 5412 _failures = true; 5413 return true; 5414 } 5415 if (hr->is_old() != (cset_state.is_old())) { 5416 log_info(gc, verify)("## is_old %d / cset state " CSETSTATE_FORMAT " inconsistency for region %u", 5417 hr->is_old(), cset_state.value(), i); 5418 _failures = true; 5419 return true; 5420 } 5421 } 5422 } 5423 return false; 5424 } 5425 5426 bool failures() const { return _failures; } 5427 }; 5428 5429 bool G1CollectedHeap::check_cset_fast_test() { 5430 G1CheckCSetFastTableClosure cl; 5431 _hrm.iterate(&cl); 5432 return !cl.failures(); 5433 } 5434 #endif // PRODUCT 5435 5436 void G1CollectedHeap::cleanUpCardTable() { 5437 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5438 double start = os::elapsedTime(); 5439 5440 { 5441 // Iterate over the dirty cards region list. 5442 G1ParCleanupCTTask cleanup_task(ct_bs, this); 5443 5444 workers()->run_task(&cleanup_task); 5445 #ifndef PRODUCT 5446 if (G1VerifyCTCleanup || VerifyAfterGC) { 5447 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 5448 heap_region_iterate(&cleanup_verifier); 5449 } 5450 #endif 5451 } 5452 5453 double elapsed = os::elapsedTime() - start; 5454 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 5455 } 5456 5457 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 5458 size_t pre_used = 0; 5459 FreeRegionList local_free_list("Local List for CSet Freeing"); 5460 5461 double young_time_ms = 0.0; 5462 double non_young_time_ms = 0.0; 5463 5464 // Since the collection set is a superset of the the young list, 5465 // all we need to do to clear the young list is clear its 5466 // head and length, and unlink any young regions in the code below 5467 _young_list->clear(); 5468 5469 G1CollectorPolicy* policy = g1_policy(); 5470 5471 double start_sec = os::elapsedTime(); 5472 bool non_young = true; 5473 5474 HeapRegion* cur = cs_head; 5475 int age_bound = -1; 5476 size_t rs_lengths = 0; 5477 5478 while (cur != NULL) { 5479 assert(!is_on_master_free_list(cur), "sanity"); 5480 if (non_young) { 5481 if (cur->is_young()) { 5482 double end_sec = os::elapsedTime(); 5483 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5484 non_young_time_ms += elapsed_ms; 5485 5486 start_sec = os::elapsedTime(); 5487 non_young = false; 5488 } 5489 } else { 5490 if (!cur->is_young()) { 5491 double end_sec = os::elapsedTime(); 5492 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5493 young_time_ms += elapsed_ms; 5494 5495 start_sec = os::elapsedTime(); 5496 non_young = true; 5497 } 5498 } 5499 5500 rs_lengths += cur->rem_set()->occupied_locked(); 5501 5502 HeapRegion* next = cur->next_in_collection_set(); 5503 assert(cur->in_collection_set(), "bad CS"); 5504 cur->set_next_in_collection_set(NULL); 5505 clear_in_cset(cur); 5506 5507 if (cur->is_young()) { 5508 int index = cur->young_index_in_cset(); 5509 assert(index != -1, "invariant"); 5510 assert((uint) index < policy->young_cset_region_length(), "invariant"); 5511 size_t words_survived = surviving_young_words[index]; 5512 cur->record_surv_words_in_group(words_survived); 5513 5514 // At this point the we have 'popped' cur from the collection set 5515 // (linked via next_in_collection_set()) but it is still in the 5516 // young list (linked via next_young_region()). Clear the 5517 // _next_young_region field. 5518 cur->set_next_young_region(NULL); 5519 } else { 5520 int index = cur->young_index_in_cset(); 5521 assert(index == -1, "invariant"); 5522 } 5523 5524 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 5525 (!cur->is_young() && cur->young_index_in_cset() == -1), 5526 "invariant" ); 5527 5528 if (!cur->evacuation_failed()) { 5529 MemRegion used_mr = cur->used_region(); 5530 5531 // And the region is empty. 5532 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 5533 pre_used += cur->used(); 5534 free_region(cur, &local_free_list, false /* par */, true /* locked */); 5535 } else { 5536 cur->uninstall_surv_rate_group(); 5537 if (cur->is_young()) { 5538 cur->set_young_index_in_cset(-1); 5539 } 5540 cur->set_evacuation_failed(false); 5541 // When moving a young gen region to old gen, we "allocate" that whole region 5542 // there. This is in addition to any already evacuated objects. Notify the 5543 // policy about that. 5544 // Old gen regions do not cause an additional allocation: both the objects 5545 // still in the region and the ones already moved are accounted for elsewhere. 5546 if (cur->is_young()) { 5547 policy->add_bytes_allocated_in_old_since_last_gc(HeapRegion::GrainBytes); 5548 } 5549 // The region is now considered to be old. 5550 cur->set_old(); 5551 // Do some allocation statistics accounting. Regions that failed evacuation 5552 // are always made old, so there is no need to update anything in the young 5553 // gen statistics, but we need to update old gen statistics. 5554 size_t used_words = cur->marked_bytes() / HeapWordSize; 5555 _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words); 5556 _old_set.add(cur); 5557 evacuation_info.increment_collectionset_used_after(cur->used()); 5558 } 5559 cur = next; 5560 } 5561 5562 evacuation_info.set_regions_freed(local_free_list.length()); 5563 policy->record_max_rs_lengths(rs_lengths); 5564 policy->cset_regions_freed(); 5565 5566 double end_sec = os::elapsedTime(); 5567 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5568 5569 if (non_young) { 5570 non_young_time_ms += elapsed_ms; 5571 } else { 5572 young_time_ms += elapsed_ms; 5573 } 5574 5575 prepend_to_freelist(&local_free_list); 5576 decrement_summary_bytes(pre_used); 5577 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 5578 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 5579 } 5580 5581 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 5582 private: 5583 FreeRegionList* _free_region_list; 5584 HeapRegionSet* _proxy_set; 5585 uint _humongous_regions_removed; 5586 size_t _freed_bytes; 5587 public: 5588 5589 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 5590 _free_region_list(free_region_list), _humongous_regions_removed(0), _freed_bytes(0) { 5591 } 5592 5593 virtual bool doHeapRegion(HeapRegion* r) { 5594 if (!r->is_starts_humongous()) { 5595 return false; 5596 } 5597 5598 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 5599 5600 oop obj = (oop)r->bottom(); 5601 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 5602 5603 // The following checks whether the humongous object is live are sufficient. 5604 // The main additional check (in addition to having a reference from the roots 5605 // or the young gen) is whether the humongous object has a remembered set entry. 5606 // 5607 // A humongous object cannot be live if there is no remembered set for it 5608 // because: 5609 // - there can be no references from within humongous starts regions referencing 5610 // the object because we never allocate other objects into them. 5611 // (I.e. there are no intra-region references that may be missed by the 5612 // remembered set) 5613 // - as soon there is a remembered set entry to the humongous starts region 5614 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 5615 // until the end of a concurrent mark. 5616 // 5617 // It is not required to check whether the object has been found dead by marking 5618 // or not, in fact it would prevent reclamation within a concurrent cycle, as 5619 // all objects allocated during that time are considered live. 5620 // SATB marking is even more conservative than the remembered set. 5621 // So if at this point in the collection there is no remembered set entry, 5622 // nobody has a reference to it. 5623 // At the start of collection we flush all refinement logs, and remembered sets 5624 // are completely up-to-date wrt to references to the humongous object. 5625 // 5626 // Other implementation considerations: 5627 // - never consider object arrays at this time because they would pose 5628 // considerable effort for cleaning up the the remembered sets. This is 5629 // required because stale remembered sets might reference locations that 5630 // are currently allocated into. 5631 uint region_idx = r->hrm_index(); 5632 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 5633 !r->rem_set()->is_empty()) { 5634 log_debug(gc, humongous)("Live humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d", 5635 region_idx, 5636 (size_t)obj->size() * HeapWordSize, 5637 p2i(r->bottom()), 5638 r->rem_set()->occupied(), 5639 r->rem_set()->strong_code_roots_list_length(), 5640 next_bitmap->isMarked(r->bottom()), 5641 g1h->is_humongous_reclaim_candidate(region_idx), 5642 obj->is_typeArray() 5643 ); 5644 return false; 5645 } 5646 5647 guarantee(obj->is_typeArray(), 5648 "Only eagerly reclaiming type arrays is supported, but the object " 5649 PTR_FORMAT " is not.", p2i(r->bottom())); 5650 5651 log_debug(gc, humongous)("Dead humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d", 5652 region_idx, 5653 (size_t)obj->size() * HeapWordSize, 5654 p2i(r->bottom()), 5655 r->rem_set()->occupied(), 5656 r->rem_set()->strong_code_roots_list_length(), 5657 next_bitmap->isMarked(r->bottom()), 5658 g1h->is_humongous_reclaim_candidate(region_idx), 5659 obj->is_typeArray() 5660 ); 5661 5662 // Need to clear mark bit of the humongous object if already set. 5663 if (next_bitmap->isMarked(r->bottom())) { 5664 next_bitmap->clear(r->bottom()); 5665 } 5666 do { 5667 HeapRegion* next = g1h->next_region_in_humongous(r); 5668 _freed_bytes += r->used(); 5669 r->set_containing_set(NULL); 5670 _humongous_regions_removed++; 5671 g1h->free_humongous_region(r, _free_region_list, false); 5672 r = next; 5673 } while (r != NULL); 5674 5675 return false; 5676 } 5677 5678 uint humongous_free_count() { 5679 return _humongous_regions_removed; 5680 } 5681 5682 size_t bytes_freed() const { 5683 return _freed_bytes; 5684 } 5685 }; 5686 5687 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 5688 assert_at_safepoint(true); 5689 5690 if (!G1EagerReclaimHumongousObjects || 5691 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 5692 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5693 return; 5694 } 5695 5696 double start_time = os::elapsedTime(); 5697 5698 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5699 5700 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5701 heap_region_iterate(&cl); 5702 5703 remove_from_old_sets(0, cl.humongous_free_count()); 5704 5705 G1HRPrinter* hrp = hr_printer(); 5706 if (hrp->is_active()) { 5707 FreeRegionListIterator iter(&local_cleanup_list); 5708 while (iter.more_available()) { 5709 HeapRegion* hr = iter.get_next(); 5710 hrp->cleanup(hr); 5711 } 5712 } 5713 5714 prepend_to_freelist(&local_cleanup_list); 5715 decrement_summary_bytes(cl.bytes_freed()); 5716 5717 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5718 cl.humongous_free_count()); 5719 } 5720 5721 // This routine is similar to the above but does not record 5722 // any policy statistics or update free lists; we are abandoning 5723 // the current incremental collection set in preparation of a 5724 // full collection. After the full GC we will start to build up 5725 // the incremental collection set again. 5726 // This is only called when we're doing a full collection 5727 // and is immediately followed by the tearing down of the young list. 5728 5729 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 5730 HeapRegion* cur = cs_head; 5731 5732 while (cur != NULL) { 5733 HeapRegion* next = cur->next_in_collection_set(); 5734 assert(cur->in_collection_set(), "bad CS"); 5735 cur->set_next_in_collection_set(NULL); 5736 clear_in_cset(cur); 5737 cur->set_young_index_in_cset(-1); 5738 cur = next; 5739 } 5740 } 5741 5742 void G1CollectedHeap::set_free_regions_coming() { 5743 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 5744 5745 assert(!free_regions_coming(), "pre-condition"); 5746 _free_regions_coming = true; 5747 } 5748 5749 void G1CollectedHeap::reset_free_regions_coming() { 5750 assert(free_regions_coming(), "pre-condition"); 5751 5752 { 5753 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5754 _free_regions_coming = false; 5755 SecondaryFreeList_lock->notify_all(); 5756 } 5757 5758 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 5759 } 5760 5761 void G1CollectedHeap::wait_while_free_regions_coming() { 5762 // Most of the time we won't have to wait, so let's do a quick test 5763 // first before we take the lock. 5764 if (!free_regions_coming()) { 5765 return; 5766 } 5767 5768 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 5769 5770 { 5771 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5772 while (free_regions_coming()) { 5773 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5774 } 5775 } 5776 5777 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 5778 } 5779 5780 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5781 return _allocator->is_retained_old_region(hr); 5782 } 5783 5784 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5785 _young_list->push_region(hr); 5786 } 5787 5788 class NoYoungRegionsClosure: public HeapRegionClosure { 5789 private: 5790 bool _success; 5791 public: 5792 NoYoungRegionsClosure() : _success(true) { } 5793 bool doHeapRegion(HeapRegion* r) { 5794 if (r->is_young()) { 5795 log_info(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5796 p2i(r->bottom()), p2i(r->end())); 5797 _success = false; 5798 } 5799 return false; 5800 } 5801 bool success() { return _success; } 5802 }; 5803 5804 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 5805 bool ret = _young_list->check_list_empty(check_sample); 5806 5807 if (check_heap) { 5808 NoYoungRegionsClosure closure; 5809 heap_region_iterate(&closure); 5810 ret = ret && closure.success(); 5811 } 5812 5813 return ret; 5814 } 5815 5816 class TearDownRegionSetsClosure : public HeapRegionClosure { 5817 private: 5818 HeapRegionSet *_old_set; 5819 5820 public: 5821 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5822 5823 bool doHeapRegion(HeapRegion* r) { 5824 if (r->is_old()) { 5825 _old_set->remove(r); 5826 } else { 5827 // We ignore free regions, we'll empty the free list afterwards. 5828 // We ignore young regions, we'll empty the young list afterwards. 5829 // We ignore humongous regions, we're not tearing down the 5830 // humongous regions set. 5831 assert(r->is_free() || r->is_young() || r->is_humongous(), 5832 "it cannot be another type"); 5833 } 5834 return false; 5835 } 5836 5837 ~TearDownRegionSetsClosure() { 5838 assert(_old_set->is_empty(), "post-condition"); 5839 } 5840 }; 5841 5842 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5843 assert_at_safepoint(true /* should_be_vm_thread */); 5844 5845 if (!free_list_only) { 5846 TearDownRegionSetsClosure cl(&_old_set); 5847 heap_region_iterate(&cl); 5848 5849 // Note that emptying the _young_list is postponed and instead done as 5850 // the first step when rebuilding the regions sets again. The reason for 5851 // this is that during a full GC string deduplication needs to know if 5852 // a collected region was young or old when the full GC was initiated. 5853 } 5854 _hrm.remove_all_free_regions(); 5855 } 5856 5857 void G1CollectedHeap::increase_used(size_t bytes) { 5858 _summary_bytes_used += bytes; 5859 } 5860 5861 void G1CollectedHeap::decrease_used(size_t bytes) { 5862 assert(_summary_bytes_used >= bytes, 5863 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5864 _summary_bytes_used, bytes); 5865 _summary_bytes_used -= bytes; 5866 } 5867 5868 void G1CollectedHeap::set_used(size_t bytes) { 5869 _summary_bytes_used = bytes; 5870 } 5871 5872 class RebuildRegionSetsClosure : public HeapRegionClosure { 5873 private: 5874 bool _free_list_only; 5875 HeapRegionSet* _old_set; 5876 HeapRegionManager* _hrm; 5877 size_t _total_used; 5878 5879 public: 5880 RebuildRegionSetsClosure(bool free_list_only, 5881 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5882 _free_list_only(free_list_only), 5883 _old_set(old_set), _hrm(hrm), _total_used(0) { 5884 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5885 if (!free_list_only) { 5886 assert(_old_set->is_empty(), "pre-condition"); 5887 } 5888 } 5889 5890 bool doHeapRegion(HeapRegion* r) { 5891 if (r->is_empty()) { 5892 // Add free regions to the free list 5893 r->set_free(); 5894 r->set_allocation_context(AllocationContext::system()); 5895 _hrm->insert_into_free_list(r); 5896 } else if (!_free_list_only) { 5897 assert(!r->is_young(), "we should not come across young regions"); 5898 5899 if (r->is_humongous()) { 5900 // We ignore humongous regions. We left the humongous set unchanged. 5901 } else { 5902 // Objects that were compacted would have ended up on regions 5903 // that were previously old or free. Archive regions (which are 5904 // old) will not have been touched. 5905 assert(r->is_free() || r->is_old(), "invariant"); 5906 // We now consider them old, so register as such. Leave 5907 // archive regions set that way, however, while still adding 5908 // them to the old set. 5909 if (!r->is_archive()) { 5910 r->set_old(); 5911 } 5912 _old_set->add(r); 5913 } 5914 _total_used += r->used(); 5915 } 5916 5917 return false; 5918 } 5919 5920 size_t total_used() { 5921 return _total_used; 5922 } 5923 }; 5924 5925 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5926 assert_at_safepoint(true /* should_be_vm_thread */); 5927 5928 if (!free_list_only) { 5929 _young_list->empty_list(); 5930 } 5931 5932 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5933 heap_region_iterate(&cl); 5934 5935 if (!free_list_only) { 5936 set_used(cl.total_used()); 5937 if (_archive_allocator != NULL) { 5938 _archive_allocator->clear_used(); 5939 } 5940 } 5941 assert(used_unlocked() == recalculate_used(), 5942 "inconsistent used_unlocked(), " 5943 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5944 used_unlocked(), recalculate_used()); 5945 } 5946 5947 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 5948 _refine_cte_cl->set_concurrent(concurrent); 5949 } 5950 5951 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5952 HeapRegion* hr = heap_region_containing(p); 5953 return hr->is_in(p); 5954 } 5955 5956 // Methods for the mutator alloc region 5957 5958 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5959 bool force) { 5960 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5961 assert(!force || g1_policy()->can_expand_young_list(), 5962 "if force is true we should be able to expand the young list"); 5963 bool young_list_full = g1_policy()->is_young_list_full(); 5964 if (force || !young_list_full) { 5965 HeapRegion* new_alloc_region = new_region(word_size, 5966 false /* is_old */, 5967 false /* do_expand */); 5968 if (new_alloc_region != NULL) { 5969 set_region_short_lived_locked(new_alloc_region); 5970 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 5971 check_bitmaps("Mutator Region Allocation", new_alloc_region); 5972 return new_alloc_region; 5973 } 5974 } 5975 return NULL; 5976 } 5977 5978 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5979 size_t allocated_bytes) { 5980 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5981 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5982 5983 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 5984 increase_used(allocated_bytes); 5985 _hr_printer.retire(alloc_region); 5986 // We update the eden sizes here, when the region is retired, 5987 // instead of when it's allocated, since this is the point that its 5988 // used space has been recored in _summary_bytes_used. 5989 g1mm()->update_eden_size(); 5990 } 5991 5992 // Methods for the GC alloc regions 5993 5994 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 5995 uint count, 5996 InCSetState dest) { 5997 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5998 5999 if (count < g1_policy()->max_regions(dest)) { 6000 const bool is_survivor = (dest.is_young()); 6001 HeapRegion* new_alloc_region = new_region(word_size, 6002 !is_survivor, 6003 true /* do_expand */); 6004 if (new_alloc_region != NULL) { 6005 // We really only need to do this for old regions given that we 6006 // should never scan survivors. But it doesn't hurt to do it 6007 // for survivors too. 6008 new_alloc_region->record_timestamp(); 6009 if (is_survivor) { 6010 new_alloc_region->set_survivor(); 6011 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6012 check_bitmaps("Survivor Region Allocation", new_alloc_region); 6013 } else { 6014 new_alloc_region->set_old(); 6015 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6016 check_bitmaps("Old Region Allocation", new_alloc_region); 6017 } 6018 bool during_im = collector_state()->during_initial_mark_pause(); 6019 new_alloc_region->note_start_of_copying(during_im); 6020 return new_alloc_region; 6021 } 6022 } 6023 return NULL; 6024 } 6025 6026 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6027 size_t allocated_bytes, 6028 InCSetState dest) { 6029 bool during_im = collector_state()->during_initial_mark_pause(); 6030 alloc_region->note_end_of_copying(during_im); 6031 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6032 if (dest.is_young()) { 6033 young_list()->add_survivor_region(alloc_region); 6034 } else { 6035 _old_set.add(alloc_region); 6036 } 6037 _hr_printer.retire(alloc_region); 6038 } 6039 6040 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 6041 bool expanded = false; 6042 uint index = _hrm.find_highest_free(&expanded); 6043 6044 if (index != G1_NO_HRM_INDEX) { 6045 if (expanded) { 6046 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 6047 HeapRegion::GrainWords * HeapWordSize); 6048 } 6049 _hrm.allocate_free_regions_starting_at(index, 1); 6050 return region_at(index); 6051 } 6052 return NULL; 6053 } 6054 6055 // Heap region set verification 6056 6057 class VerifyRegionListsClosure : public HeapRegionClosure { 6058 private: 6059 HeapRegionSet* _old_set; 6060 HeapRegionSet* _humongous_set; 6061 HeapRegionManager* _hrm; 6062 6063 public: 6064 uint _old_count; 6065 uint _humongous_count; 6066 uint _free_count; 6067 6068 VerifyRegionListsClosure(HeapRegionSet* old_set, 6069 HeapRegionSet* humongous_set, 6070 HeapRegionManager* hrm) : 6071 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm), 6072 _old_count(), _humongous_count(), _free_count(){ } 6073 6074 bool doHeapRegion(HeapRegion* hr) { 6075 if (hr->is_young()) { 6076 // TODO 6077 } else if (hr->is_humongous()) { 6078 assert(hr->containing_set() == _humongous_set, "Heap region %u is humongous but not in humongous set.", hr->hrm_index()); 6079 _humongous_count++; 6080 } else if (hr->is_empty()) { 6081 assert(_hrm->is_free(hr), "Heap region %u is empty but not on the free list.", hr->hrm_index()); 6082 _free_count++; 6083 } else if (hr->is_old()) { 6084 assert(hr->containing_set() == _old_set, "Heap region %u is old but not in the old set.", hr->hrm_index()); 6085 _old_count++; 6086 } else { 6087 // There are no other valid region types. Check for one invalid 6088 // one we can identify: pinned without old or humongous set. 6089 assert(!hr->is_pinned(), "Heap region %u is pinned but not old (archive) or humongous.", hr->hrm_index()); 6090 ShouldNotReachHere(); 6091 } 6092 return false; 6093 } 6094 6095 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) { 6096 guarantee(old_set->length() == _old_count, "Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count); 6097 guarantee(humongous_set->length() == _humongous_count, "Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count); 6098 guarantee(free_list->num_free_regions() == _free_count, "Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count); 6099 } 6100 }; 6101 6102 void G1CollectedHeap::verify_region_sets() { 6103 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6104 6105 // First, check the explicit lists. 6106 _hrm.verify(); 6107 { 6108 // Given that a concurrent operation might be adding regions to 6109 // the secondary free list we have to take the lock before 6110 // verifying it. 6111 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6112 _secondary_free_list.verify_list(); 6113 } 6114 6115 // If a concurrent region freeing operation is in progress it will 6116 // be difficult to correctly attributed any free regions we come 6117 // across to the correct free list given that they might belong to 6118 // one of several (free_list, secondary_free_list, any local lists, 6119 // etc.). So, if that's the case we will skip the rest of the 6120 // verification operation. Alternatively, waiting for the concurrent 6121 // operation to complete will have a non-trivial effect on the GC's 6122 // operation (no concurrent operation will last longer than the 6123 // interval between two calls to verification) and it might hide 6124 // any issues that we would like to catch during testing. 6125 if (free_regions_coming()) { 6126 return; 6127 } 6128 6129 // Make sure we append the secondary_free_list on the free_list so 6130 // that all free regions we will come across can be safely 6131 // attributed to the free_list. 6132 append_secondary_free_list_if_not_empty_with_lock(); 6133 6134 // Finally, make sure that the region accounting in the lists is 6135 // consistent with what we see in the heap. 6136 6137 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm); 6138 heap_region_iterate(&cl); 6139 cl.verify_counts(&_old_set, &_humongous_set, &_hrm); 6140 } 6141 6142 // Optimized nmethod scanning 6143 6144 class RegisterNMethodOopClosure: public OopClosure { 6145 G1CollectedHeap* _g1h; 6146 nmethod* _nm; 6147 6148 template <class T> void do_oop_work(T* p) { 6149 T heap_oop = oopDesc::load_heap_oop(p); 6150 if (!oopDesc::is_null(heap_oop)) { 6151 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6152 HeapRegion* hr = _g1h->heap_region_containing(obj); 6153 assert(!hr->is_continues_humongous(), 6154 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6155 " starting at " HR_FORMAT, 6156 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 6157 6158 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 6159 hr->add_strong_code_root_locked(_nm); 6160 } 6161 } 6162 6163 public: 6164 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6165 _g1h(g1h), _nm(nm) {} 6166 6167 void do_oop(oop* p) { do_oop_work(p); } 6168 void do_oop(narrowOop* p) { do_oop_work(p); } 6169 }; 6170 6171 class UnregisterNMethodOopClosure: public OopClosure { 6172 G1CollectedHeap* _g1h; 6173 nmethod* _nm; 6174 6175 template <class T> void do_oop_work(T* p) { 6176 T heap_oop = oopDesc::load_heap_oop(p); 6177 if (!oopDesc::is_null(heap_oop)) { 6178 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6179 HeapRegion* hr = _g1h->heap_region_containing(obj); 6180 assert(!hr->is_continues_humongous(), 6181 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6182 " starting at " HR_FORMAT, 6183 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 6184 6185 hr->remove_strong_code_root(_nm); 6186 } 6187 } 6188 6189 public: 6190 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6191 _g1h(g1h), _nm(nm) {} 6192 6193 void do_oop(oop* p) { do_oop_work(p); } 6194 void do_oop(narrowOop* p) { do_oop_work(p); } 6195 }; 6196 6197 void G1CollectedHeap::register_nmethod(nmethod* nm) { 6198 CollectedHeap::register_nmethod(nm); 6199 6200 guarantee(nm != NULL, "sanity"); 6201 RegisterNMethodOopClosure reg_cl(this, nm); 6202 nm->oops_do(®_cl); 6203 } 6204 6205 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 6206 CollectedHeap::unregister_nmethod(nm); 6207 6208 guarantee(nm != NULL, "sanity"); 6209 UnregisterNMethodOopClosure reg_cl(this, nm); 6210 nm->oops_do(®_cl, true); 6211 } 6212 6213 void G1CollectedHeap::purge_code_root_memory() { 6214 double purge_start = os::elapsedTime(); 6215 G1CodeRootSet::purge(); 6216 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 6217 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 6218 } 6219 6220 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 6221 G1CollectedHeap* _g1h; 6222 6223 public: 6224 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 6225 _g1h(g1h) {} 6226 6227 void do_code_blob(CodeBlob* cb) { 6228 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 6229 if (nm == NULL) { 6230 return; 6231 } 6232 6233 if (ScavengeRootsInCode) { 6234 _g1h->register_nmethod(nm); 6235 } 6236 } 6237 }; 6238 6239 void G1CollectedHeap::rebuild_strong_code_roots() { 6240 RebuildStrongCodeRootClosure blob_cl(this); 6241 CodeCache::blobs_do(&blob_cl); 6242 }