1 /* 2 * Copyright (c) 2001, 2016, 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/g1CollectionSet.hpp" 38 #include "gc/g1/g1CollectorPolicy.hpp" 39 #include "gc/g1/g1CollectorState.hpp" 40 #include "gc/g1/g1EvacStats.inline.hpp" 41 #include "gc/g1/g1GCPhaseTimes.hpp" 42 #include "gc/g1/g1HeapSizingPolicy.hpp" 43 #include "gc/g1/g1HeapTransition.hpp" 44 #include "gc/g1/g1HeapVerifier.hpp" 45 #include "gc/g1/g1HotCardCache.hpp" 46 #include "gc/g1/g1MarkSweep.hpp" 47 #include "gc/g1/g1OopClosures.inline.hpp" 48 #include "gc/g1/g1ParScanThreadState.inline.hpp" 49 #include "gc/g1/g1Policy.hpp" 50 #include "gc/g1/g1RegionToSpaceMapper.hpp" 51 #include "gc/g1/g1RemSet.inline.hpp" 52 #include "gc/g1/g1RootClosures.hpp" 53 #include "gc/g1/g1RootProcessor.hpp" 54 #include "gc/g1/g1StringDedup.hpp" 55 #include "gc/g1/g1YCTypes.hpp" 56 #include "gc/g1/heapRegion.inline.hpp" 57 #include "gc/g1/heapRegionRemSet.hpp" 58 #include "gc/g1/heapRegionSet.inline.hpp" 59 #include "gc/g1/suspendibleThreadSet.hpp" 60 #include "gc/g1/vm_operations_g1.hpp" 61 #include "gc/shared/gcHeapSummary.hpp" 62 #include "gc/shared/gcId.hpp" 63 #include "gc/shared/gcLocker.inline.hpp" 64 #include "gc/shared/gcTimer.hpp" 65 #include "gc/shared/gcTrace.hpp" 66 #include "gc/shared/gcTraceTime.inline.hpp" 67 #include "gc/shared/generationSpec.hpp" 68 #include "gc/shared/isGCActiveMark.hpp" 69 #include "gc/shared/preservedMarks.inline.hpp" 70 #include "gc/shared/referenceProcessor.inline.hpp" 71 #include "gc/shared/taskqueue.inline.hpp" 72 #include "logging/log.hpp" 73 #include "memory/allocation.hpp" 74 #include "memory/iterator.hpp" 75 #include "memory/resourceArea.hpp" 76 #include "oops/oop.inline.hpp" 77 #include "runtime/atomic.hpp" 78 #include "runtime/init.hpp" 79 #include "runtime/orderAccess.inline.hpp" 80 #include "runtime/vmThread.hpp" 81 #include "utilities/globalDefinitions.hpp" 82 #include "utilities/stack.inline.hpp" 83 84 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 85 86 // INVARIANTS/NOTES 87 // 88 // All allocation activity covered by the G1CollectedHeap interface is 89 // serialized by acquiring the HeapLock. This happens in mem_allocate 90 // and allocate_new_tlab, which are the "entry" points to the 91 // allocation code from the rest of the JVM. (Note that this does not 92 // apply to TLAB allocation, which is not part of this interface: it 93 // is done by clients of this interface.) 94 95 // Local to this file. 96 97 class RefineCardTableEntryClosure: public CardTableEntryClosure { 98 bool _concurrent; 99 public: 100 RefineCardTableEntryClosure() : _concurrent(true) { } 101 102 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 103 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, NULL); 104 // This path is executed by the concurrent refine or mutator threads, 105 // concurrently, and so we do not care if card_ptr contains references 106 // that point into the collection set. 107 assert(!oops_into_cset, "should be"); 108 109 if (_concurrent && SuspendibleThreadSet::should_yield()) { 110 // Caller will actually yield. 111 return false; 112 } 113 // Otherwise, we finished successfully; return true. 114 return true; 115 } 116 117 void set_concurrent(bool b) { _concurrent = b; } 118 }; 119 120 121 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 122 private: 123 size_t _num_dirtied; 124 G1CollectedHeap* _g1h; 125 G1SATBCardTableLoggingModRefBS* _g1_bs; 126 127 HeapRegion* region_for_card(jbyte* card_ptr) const { 128 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 129 } 130 131 bool will_become_free(HeapRegion* hr) const { 132 // A region will be freed by free_collection_set if the region is in the 133 // collection set and has not had an evacuation failure. 134 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 135 } 136 137 public: 138 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 139 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 140 141 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 142 HeapRegion* hr = region_for_card(card_ptr); 143 144 // Should only dirty cards in regions that won't be freed. 145 if (!will_become_free(hr)) { 146 *card_ptr = CardTableModRefBS::dirty_card_val(); 147 _num_dirtied++; 148 } 149 150 return true; 151 } 152 153 size_t num_dirtied() const { return _num_dirtied; } 154 }; 155 156 157 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 158 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 159 } 160 161 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 162 // The from card cache is not the memory that is actually committed. So we cannot 163 // take advantage of the zero_filled parameter. 164 reset_from_card_cache(start_idx, num_regions); 165 } 166 167 // Returns true if the reference points to an object that 168 // can move in an incremental collection. 169 bool G1CollectedHeap::is_scavengable(const void* p) { 170 HeapRegion* hr = heap_region_containing(p); 171 return !hr->is_pinned(); 172 } 173 174 // Private methods. 175 176 HeapRegion* 177 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 178 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 179 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 180 if (!_secondary_free_list.is_empty()) { 181 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 182 "secondary_free_list has %u entries", 183 _secondary_free_list.length()); 184 // It looks as if there are free regions available on the 185 // secondary_free_list. Let's move them to the free_list and try 186 // again to allocate from it. 187 append_secondary_free_list(); 188 189 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 190 "empty we should have moved at least one entry to the free_list"); 191 HeapRegion* res = _hrm.allocate_free_region(is_old); 192 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 193 "allocated " HR_FORMAT " from secondary_free_list", 194 HR_FORMAT_PARAMS(res)); 195 return res; 196 } 197 198 // Wait here until we get notified either when (a) there are no 199 // more free regions coming or (b) some regions have been moved on 200 // the secondary_free_list. 201 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 202 } 203 204 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 205 "could not allocate from secondary_free_list"); 206 return NULL; 207 } 208 209 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 210 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 211 "the only time we use this to allocate a humongous region is " 212 "when we are allocating a single humongous region"); 213 214 HeapRegion* res; 215 if (G1StressConcRegionFreeing) { 216 if (!_secondary_free_list.is_empty()) { 217 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 218 "forced to look at the secondary_free_list"); 219 res = new_region_try_secondary_free_list(is_old); 220 if (res != NULL) { 221 return res; 222 } 223 } 224 } 225 226 res = _hrm.allocate_free_region(is_old); 227 228 if (res == NULL) { 229 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 230 "res == NULL, trying the secondary_free_list"); 231 res = new_region_try_secondary_free_list(is_old); 232 } 233 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 234 // Currently, only attempts to allocate GC alloc regions set 235 // do_expand to true. So, we should only reach here during a 236 // safepoint. If this assumption changes we might have to 237 // reconsider the use of _expand_heap_after_alloc_failure. 238 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 239 240 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 241 word_size * HeapWordSize); 242 243 if (expand(word_size * HeapWordSize)) { 244 // Given that expand() succeeded in expanding the heap, and we 245 // always expand the heap by an amount aligned to the heap 246 // region size, the free list should in theory not be empty. 247 // In either case allocate_free_region() will check for NULL. 248 res = _hrm.allocate_free_region(is_old); 249 } else { 250 _expand_heap_after_alloc_failure = false; 251 } 252 } 253 return res; 254 } 255 256 HeapWord* 257 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 258 uint num_regions, 259 size_t word_size, 260 AllocationContext_t context) { 261 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 262 assert(is_humongous(word_size), "word_size should be humongous"); 263 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 264 265 // Index of last region in the series. 266 uint last = first + num_regions - 1; 267 268 // We need to initialize the region(s) we just discovered. This is 269 // a bit tricky given that it can happen concurrently with 270 // refinement threads refining cards on these regions and 271 // potentially wanting to refine the BOT as they are scanning 272 // those cards (this can happen shortly after a cleanup; see CR 273 // 6991377). So we have to set up the region(s) carefully and in 274 // a specific order. 275 276 // The word size sum of all the regions we will allocate. 277 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 278 assert(word_size <= word_size_sum, "sanity"); 279 280 // This will be the "starts humongous" region. 281 HeapRegion* first_hr = region_at(first); 282 // The header of the new object will be placed at the bottom of 283 // the first region. 284 HeapWord* new_obj = first_hr->bottom(); 285 // This will be the new top of the new object. 286 HeapWord* obj_top = new_obj + word_size; 287 288 // First, we need to zero the header of the space that we will be 289 // allocating. When we update top further down, some refinement 290 // threads might try to scan the region. By zeroing the header we 291 // ensure that any thread that will try to scan the region will 292 // come across the zero klass word and bail out. 293 // 294 // NOTE: It would not have been correct to have used 295 // CollectedHeap::fill_with_object() and make the space look like 296 // an int array. The thread that is doing the allocation will 297 // later update the object header to a potentially different array 298 // type and, for a very short period of time, the klass and length 299 // fields will be inconsistent. This could cause a refinement 300 // thread to calculate the object size incorrectly. 301 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 302 303 // How many words we use for filler objects. 304 size_t word_fill_size = word_size_sum - word_size; 305 306 // How many words memory we "waste" which cannot hold a filler object. 307 size_t words_not_fillable = 0; 308 309 if (word_fill_size >= min_fill_size()) { 310 fill_with_objects(obj_top, word_fill_size); 311 } else if (word_fill_size > 0) { 312 // We have space to fill, but we cannot fit an object there. 313 words_not_fillable = word_fill_size; 314 word_fill_size = 0; 315 } 316 317 // We will set up the first region as "starts humongous". This 318 // will also update the BOT covering all the regions to reflect 319 // that there is a single object that starts at the bottom of the 320 // first region. 321 first_hr->set_starts_humongous(obj_top, word_fill_size); 322 first_hr->set_allocation_context(context); 323 // Then, if there are any, we will set up the "continues 324 // humongous" regions. 325 HeapRegion* hr = NULL; 326 for (uint i = first + 1; i <= last; ++i) { 327 hr = region_at(i); 328 hr->set_continues_humongous(first_hr); 329 hr->set_allocation_context(context); 330 } 331 332 // Up to this point no concurrent thread would have been able to 333 // do any scanning on any region in this series. All the top 334 // fields still point to bottom, so the intersection between 335 // [bottom,top] and [card_start,card_end] will be empty. Before we 336 // update the top fields, we'll do a storestore to make sure that 337 // no thread sees the update to top before the zeroing of the 338 // object header and the BOT initialization. 339 OrderAccess::storestore(); 340 341 // Now, we will update the top fields of the "continues humongous" 342 // regions except the last one. 343 for (uint i = first; i < last; ++i) { 344 hr = region_at(i); 345 hr->set_top(hr->end()); 346 } 347 348 hr = region_at(last); 349 // If we cannot fit a filler object, we must set top to the end 350 // of the humongous object, otherwise we cannot iterate the heap 351 // and the BOT will not be complete. 352 hr->set_top(hr->end() - words_not_fillable); 353 354 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 355 "obj_top should be in last region"); 356 357 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 358 359 assert(words_not_fillable == 0 || 360 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 361 "Miscalculation in humongous allocation"); 362 363 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 364 365 for (uint i = first; i <= last; ++i) { 366 hr = region_at(i); 367 _humongous_set.add(hr); 368 _hr_printer.alloc(hr); 369 } 370 371 return new_obj; 372 } 373 374 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 375 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 376 return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 377 } 378 379 // If could fit into free regions w/o expansion, try. 380 // Otherwise, if can expand, do so. 381 // Otherwise, if using ex regions might help, try with ex given back. 382 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 383 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 384 385 _verifier->verify_region_sets_optional(); 386 387 uint first = G1_NO_HRM_INDEX; 388 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 389 390 if (obj_regions == 1) { 391 // Only one region to allocate, try to use a fast path by directly allocating 392 // from the free lists. Do not try to expand here, we will potentially do that 393 // later. 394 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 395 if (hr != NULL) { 396 first = hr->hrm_index(); 397 } 398 } else { 399 // We can't allocate humongous regions spanning more than one region while 400 // cleanupComplete() is running, since some of the regions we find to be 401 // empty might not yet be added to the free list. It is not straightforward 402 // to know in which list they are on so that we can remove them. We only 403 // need to do this if we need to allocate more than one region to satisfy the 404 // current humongous allocation request. If we are only allocating one region 405 // we use the one-region region allocation code (see above), that already 406 // potentially waits for regions from the secondary free list. 407 wait_while_free_regions_coming(); 408 append_secondary_free_list_if_not_empty_with_lock(); 409 410 // Policy: Try only empty regions (i.e. already committed first). Maybe we 411 // are lucky enough to find some. 412 first = _hrm.find_contiguous_only_empty(obj_regions); 413 if (first != G1_NO_HRM_INDEX) { 414 _hrm.allocate_free_regions_starting_at(first, obj_regions); 415 } 416 } 417 418 if (first == G1_NO_HRM_INDEX) { 419 // Policy: We could not find enough regions for the humongous object in the 420 // free list. Look through the heap to find a mix of free and uncommitted regions. 421 // If so, try expansion. 422 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 423 if (first != G1_NO_HRM_INDEX) { 424 // We found something. Make sure these regions are committed, i.e. expand 425 // the heap. Alternatively we could do a defragmentation GC. 426 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 427 word_size * HeapWordSize); 428 429 430 _hrm.expand_at(first, obj_regions); 431 g1_policy()->record_new_heap_size(num_regions()); 432 433 #ifdef ASSERT 434 for (uint i = first; i < first + obj_regions; ++i) { 435 HeapRegion* hr = region_at(i); 436 assert(hr->is_free(), "sanity"); 437 assert(hr->is_empty(), "sanity"); 438 assert(is_on_master_free_list(hr), "sanity"); 439 } 440 #endif 441 _hrm.allocate_free_regions_starting_at(first, obj_regions); 442 } else { 443 // Policy: Potentially trigger a defragmentation GC. 444 } 445 } 446 447 HeapWord* result = NULL; 448 if (first != G1_NO_HRM_INDEX) { 449 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 450 word_size, context); 451 assert(result != NULL, "it should always return a valid result"); 452 453 // A successful humongous object allocation changes the used space 454 // information of the old generation so we need to recalculate the 455 // sizes and update the jstat counters here. 456 g1mm()->update_sizes(); 457 } 458 459 _verifier->verify_region_sets_optional(); 460 461 return result; 462 } 463 464 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 465 assert_heap_not_locked_and_not_at_safepoint(); 466 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 467 468 uint dummy_gc_count_before; 469 uint dummy_gclocker_retry_count = 0; 470 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 471 } 472 473 HeapWord* 474 G1CollectedHeap::mem_allocate(size_t word_size, 475 bool* gc_overhead_limit_was_exceeded) { 476 assert_heap_not_locked_and_not_at_safepoint(); 477 478 // Loop until the allocation is satisfied, or unsatisfied after GC. 479 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 480 uint gc_count_before; 481 482 HeapWord* result = NULL; 483 if (!is_humongous(word_size)) { 484 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 485 } else { 486 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 487 } 488 if (result != NULL) { 489 return result; 490 } 491 492 // Create the garbage collection operation... 493 VM_G1CollectForAllocation op(gc_count_before, word_size); 494 op.set_allocation_context(AllocationContext::current()); 495 496 // ...and get the VM thread to execute it. 497 VMThread::execute(&op); 498 499 if (op.prologue_succeeded() && op.pause_succeeded()) { 500 // If the operation was successful we'll return the result even 501 // if it is NULL. If the allocation attempt failed immediately 502 // after a Full GC, it's unlikely we'll be able to allocate now. 503 HeapWord* result = op.result(); 504 if (result != NULL && !is_humongous(word_size)) { 505 // Allocations that take place on VM operations do not do any 506 // card dirtying and we have to do it here. We only have to do 507 // this for non-humongous allocations, though. 508 dirty_young_block(result, word_size); 509 } 510 return result; 511 } else { 512 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 513 return NULL; 514 } 515 assert(op.result() == NULL, 516 "the result should be NULL if the VM op did not succeed"); 517 } 518 519 // Give a warning if we seem to be looping forever. 520 if ((QueuedAllocationWarningCount > 0) && 521 (try_count % QueuedAllocationWarningCount == 0)) { 522 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count); 523 } 524 } 525 526 ShouldNotReachHere(); 527 return NULL; 528 } 529 530 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 531 AllocationContext_t context, 532 uint* gc_count_before_ret, 533 uint* gclocker_retry_count_ret) { 534 // Make sure you read the note in attempt_allocation_humongous(). 535 536 assert_heap_not_locked_and_not_at_safepoint(); 537 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 538 "be called for humongous allocation requests"); 539 540 // We should only get here after the first-level allocation attempt 541 // (attempt_allocation()) failed to allocate. 542 543 // We will loop until a) we manage to successfully perform the 544 // allocation or b) we successfully schedule a collection which 545 // fails to perform the allocation. b) is the only case when we'll 546 // return NULL. 547 HeapWord* result = NULL; 548 for (int try_count = 1; /* we'll return */; try_count += 1) { 549 bool should_try_gc; 550 uint gc_count_before; 551 552 { 553 MutexLockerEx x(Heap_lock); 554 result = _allocator->attempt_allocation_locked(word_size, context); 555 if (result != NULL) { 556 return result; 557 } 558 559 if (GCLocker::is_active_and_needs_gc()) { 560 if (g1_policy()->can_expand_young_list()) { 561 // No need for an ergo verbose message here, 562 // can_expand_young_list() does this when it returns true. 563 result = _allocator->attempt_allocation_force(word_size, context); 564 if (result != NULL) { 565 return result; 566 } 567 } 568 should_try_gc = false; 569 } else { 570 // The GCLocker may not be active but the GCLocker initiated 571 // GC may not yet have been performed (GCLocker::needs_gc() 572 // returns true). In this case we do not try this GC and 573 // wait until the GCLocker initiated GC is performed, and 574 // then retry the allocation. 575 if (GCLocker::needs_gc()) { 576 should_try_gc = false; 577 } else { 578 // Read the GC count while still holding the Heap_lock. 579 gc_count_before = total_collections(); 580 should_try_gc = true; 581 } 582 } 583 } 584 585 if (should_try_gc) { 586 bool succeeded; 587 result = do_collection_pause(word_size, gc_count_before, &succeeded, 588 GCCause::_g1_inc_collection_pause); 589 if (result != NULL) { 590 assert(succeeded, "only way to get back a non-NULL result"); 591 return result; 592 } 593 594 if (succeeded) { 595 // If we get here we successfully scheduled a collection which 596 // failed to allocate. No point in trying to allocate 597 // further. We'll just return NULL. 598 MutexLockerEx x(Heap_lock); 599 *gc_count_before_ret = total_collections(); 600 return NULL; 601 } 602 } else { 603 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 604 MutexLockerEx x(Heap_lock); 605 *gc_count_before_ret = total_collections(); 606 return NULL; 607 } 608 // The GCLocker is either active or the GCLocker initiated 609 // GC has not yet been performed. Stall until it is and 610 // then retry the allocation. 611 GCLocker::stall_until_clear(); 612 (*gclocker_retry_count_ret) += 1; 613 } 614 615 // We can reach here if we were unsuccessful in scheduling a 616 // collection (because another thread beat us to it) or if we were 617 // stalled due to the GC locker. In either can we should retry the 618 // allocation attempt in case another thread successfully 619 // performed a collection and reclaimed enough space. We do the 620 // first attempt (without holding the Heap_lock) here and the 621 // follow-on attempt will be at the start of the next loop 622 // iteration (after taking the Heap_lock). 623 result = _allocator->attempt_allocation(word_size, context); 624 if (result != NULL) { 625 return result; 626 } 627 628 // Give a warning if we seem to be looping forever. 629 if ((QueuedAllocationWarningCount > 0) && 630 (try_count % QueuedAllocationWarningCount == 0)) { 631 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() " 632 "retries %d times", try_count); 633 } 634 } 635 636 ShouldNotReachHere(); 637 return NULL; 638 } 639 640 void G1CollectedHeap::begin_archive_alloc_range() { 641 assert_at_safepoint(true /* should_be_vm_thread */); 642 if (_archive_allocator == NULL) { 643 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 644 } 645 } 646 647 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 648 // Allocations in archive regions cannot be of a size that would be considered 649 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 650 // may be different at archive-restore time. 651 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 652 } 653 654 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 655 assert_at_safepoint(true /* should_be_vm_thread */); 656 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 657 if (is_archive_alloc_too_large(word_size)) { 658 return NULL; 659 } 660 return _archive_allocator->archive_mem_allocate(word_size); 661 } 662 663 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 664 size_t end_alignment_in_bytes) { 665 assert_at_safepoint(true /* should_be_vm_thread */); 666 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 667 668 // Call complete_archive to do the real work, filling in the MemRegion 669 // array with the archive regions. 670 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 671 delete _archive_allocator; 672 _archive_allocator = NULL; 673 } 674 675 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 676 assert(ranges != NULL, "MemRegion array NULL"); 677 assert(count != 0, "No MemRegions provided"); 678 MemRegion reserved = _hrm.reserved(); 679 for (size_t i = 0; i < count; i++) { 680 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 681 return false; 682 } 683 } 684 return true; 685 } 686 687 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 688 assert(!is_init_completed(), "Expect to be called at JVM init time"); 689 assert(ranges != NULL, "MemRegion array NULL"); 690 assert(count != 0, "No MemRegions provided"); 691 MutexLockerEx x(Heap_lock); 692 693 MemRegion reserved = _hrm.reserved(); 694 HeapWord* prev_last_addr = NULL; 695 HeapRegion* prev_last_region = NULL; 696 697 // Temporarily disable pretouching of heap pages. This interface is used 698 // when mmap'ing archived heap data in, so pre-touching is wasted. 699 FlagSetting fs(AlwaysPreTouch, false); 700 701 // Enable archive object checking in G1MarkSweep. We have to let it know 702 // about each archive range, so that objects in those ranges aren't marked. 703 G1MarkSweep::enable_archive_object_check(); 704 705 // For each specified MemRegion range, allocate the corresponding G1 706 // regions and mark them as archive regions. We expect the ranges in 707 // ascending starting address order, without overlap. 708 for (size_t i = 0; i < count; i++) { 709 MemRegion curr_range = ranges[i]; 710 HeapWord* start_address = curr_range.start(); 711 size_t word_size = curr_range.word_size(); 712 HeapWord* last_address = curr_range.last(); 713 size_t commits = 0; 714 715 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 716 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 717 p2i(start_address), p2i(last_address)); 718 guarantee(start_address > prev_last_addr, 719 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 720 p2i(start_address), p2i(prev_last_addr)); 721 prev_last_addr = last_address; 722 723 // Check for ranges that start in the same G1 region in which the previous 724 // range ended, and adjust the start address so we don't try to allocate 725 // the same region again. If the current range is entirely within that 726 // region, skip it, just adjusting the recorded top. 727 HeapRegion* start_region = _hrm.addr_to_region(start_address); 728 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 729 start_address = start_region->end(); 730 if (start_address > last_address) { 731 increase_used(word_size * HeapWordSize); 732 start_region->set_top(last_address + 1); 733 continue; 734 } 735 start_region->set_top(start_address); 736 curr_range = MemRegion(start_address, last_address + 1); 737 start_region = _hrm.addr_to_region(start_address); 738 } 739 740 // Perform the actual region allocation, exiting if it fails. 741 // Then note how much new space we have allocated. 742 if (!_hrm.allocate_containing_regions(curr_range, &commits)) { 743 return false; 744 } 745 increase_used(word_size * HeapWordSize); 746 if (commits != 0) { 747 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 748 HeapRegion::GrainWords * HeapWordSize * commits); 749 750 } 751 752 // Mark each G1 region touched by the range as archive, add it to the old set, 753 // and set the allocation context and top. 754 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 755 HeapRegion* last_region = _hrm.addr_to_region(last_address); 756 prev_last_region = last_region; 757 758 while (curr_region != NULL) { 759 assert(curr_region->is_empty() && !curr_region->is_pinned(), 760 "Region already in use (index %u)", curr_region->hrm_index()); 761 curr_region->set_allocation_context(AllocationContext::system()); 762 curr_region->set_archive(); 763 _hr_printer.alloc(curr_region); 764 _old_set.add(curr_region); 765 if (curr_region != last_region) { 766 curr_region->set_top(curr_region->end()); 767 curr_region = _hrm.next_region_in_heap(curr_region); 768 } else { 769 curr_region->set_top(last_address + 1); 770 curr_region = NULL; 771 } 772 } 773 774 // Notify mark-sweep of the archive range. 775 G1MarkSweep::set_range_archive(curr_range, true); 776 } 777 return true; 778 } 779 780 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 781 assert(!is_init_completed(), "Expect to be called at JVM init time"); 782 assert(ranges != NULL, "MemRegion array NULL"); 783 assert(count != 0, "No MemRegions provided"); 784 MemRegion reserved = _hrm.reserved(); 785 HeapWord *prev_last_addr = NULL; 786 HeapRegion* prev_last_region = NULL; 787 788 // For each MemRegion, create filler objects, if needed, in the G1 regions 789 // that contain the address range. The address range actually within the 790 // MemRegion will not be modified. That is assumed to have been initialized 791 // elsewhere, probably via an mmap of archived heap data. 792 MutexLockerEx x(Heap_lock); 793 for (size_t i = 0; i < count; i++) { 794 HeapWord* start_address = ranges[i].start(); 795 HeapWord* last_address = ranges[i].last(); 796 797 assert(reserved.contains(start_address) && reserved.contains(last_address), 798 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 799 p2i(start_address), p2i(last_address)); 800 assert(start_address > prev_last_addr, 801 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 802 p2i(start_address), p2i(prev_last_addr)); 803 804 HeapRegion* start_region = _hrm.addr_to_region(start_address); 805 HeapRegion* last_region = _hrm.addr_to_region(last_address); 806 HeapWord* bottom_address = start_region->bottom(); 807 808 // Check for a range beginning in the same region in which the 809 // previous one ended. 810 if (start_region == prev_last_region) { 811 bottom_address = prev_last_addr + 1; 812 } 813 814 // Verify that the regions were all marked as archive regions by 815 // alloc_archive_regions. 816 HeapRegion* curr_region = start_region; 817 while (curr_region != NULL) { 818 guarantee(curr_region->is_archive(), 819 "Expected archive region at index %u", curr_region->hrm_index()); 820 if (curr_region != last_region) { 821 curr_region = _hrm.next_region_in_heap(curr_region); 822 } else { 823 curr_region = NULL; 824 } 825 } 826 827 prev_last_addr = last_address; 828 prev_last_region = last_region; 829 830 // Fill the memory below the allocated range with dummy object(s), 831 // if the region bottom does not match the range start, or if the previous 832 // range ended within the same G1 region, and there is a gap. 833 if (start_address != bottom_address) { 834 size_t fill_size = pointer_delta(start_address, bottom_address); 835 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 836 increase_used(fill_size * HeapWordSize); 837 } 838 } 839 } 840 841 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 842 uint* gc_count_before_ret, 843 uint* gclocker_retry_count_ret) { 844 assert_heap_not_locked_and_not_at_safepoint(); 845 assert(!is_humongous(word_size), "attempt_allocation() should not " 846 "be called for humongous allocation requests"); 847 848 AllocationContext_t context = AllocationContext::current(); 849 HeapWord* result = _allocator->attempt_allocation(word_size, context); 850 851 if (result == NULL) { 852 result = attempt_allocation_slow(word_size, 853 context, 854 gc_count_before_ret, 855 gclocker_retry_count_ret); 856 } 857 assert_heap_not_locked(); 858 if (result != NULL) { 859 dirty_young_block(result, word_size); 860 } 861 return result; 862 } 863 864 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 865 assert(!is_init_completed(), "Expect to be called at JVM init time"); 866 assert(ranges != NULL, "MemRegion array NULL"); 867 assert(count != 0, "No MemRegions provided"); 868 MemRegion reserved = _hrm.reserved(); 869 HeapWord* prev_last_addr = NULL; 870 HeapRegion* prev_last_region = NULL; 871 size_t size_used = 0; 872 size_t uncommitted_regions = 0; 873 874 // For each Memregion, free the G1 regions that constitute it, and 875 // notify mark-sweep that the range is no longer to be considered 'archive.' 876 MutexLockerEx x(Heap_lock); 877 for (size_t i = 0; i < count; i++) { 878 HeapWord* start_address = ranges[i].start(); 879 HeapWord* last_address = ranges[i].last(); 880 881 assert(reserved.contains(start_address) && reserved.contains(last_address), 882 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 883 p2i(start_address), p2i(last_address)); 884 assert(start_address > prev_last_addr, 885 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 886 p2i(start_address), p2i(prev_last_addr)); 887 size_used += ranges[i].byte_size(); 888 prev_last_addr = last_address; 889 890 HeapRegion* start_region = _hrm.addr_to_region(start_address); 891 HeapRegion* last_region = _hrm.addr_to_region(last_address); 892 893 // Check for ranges that start in the same G1 region in which the previous 894 // range ended, and adjust the start address so we don't try to free 895 // the same region again. If the current range is entirely within that 896 // region, skip it. 897 if (start_region == prev_last_region) { 898 start_address = start_region->end(); 899 if (start_address > last_address) { 900 continue; 901 } 902 start_region = _hrm.addr_to_region(start_address); 903 } 904 prev_last_region = last_region; 905 906 // After verifying that each region was marked as an archive region by 907 // alloc_archive_regions, set it free and empty and uncommit it. 908 HeapRegion* curr_region = start_region; 909 while (curr_region != NULL) { 910 guarantee(curr_region->is_archive(), 911 "Expected archive region at index %u", curr_region->hrm_index()); 912 uint curr_index = curr_region->hrm_index(); 913 _old_set.remove(curr_region); 914 curr_region->set_free(); 915 curr_region->set_top(curr_region->bottom()); 916 if (curr_region != last_region) { 917 curr_region = _hrm.next_region_in_heap(curr_region); 918 } else { 919 curr_region = NULL; 920 } 921 _hrm.shrink_at(curr_index, 1); 922 uncommitted_regions++; 923 } 924 925 // Notify mark-sweep that this is no longer an archive range. 926 G1MarkSweep::set_range_archive(ranges[i], false); 927 } 928 929 if (uncommitted_regions != 0) { 930 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 931 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 932 } 933 decrease_used(size_used); 934 } 935 936 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 937 uint* gc_count_before_ret, 938 uint* gclocker_retry_count_ret) { 939 // The structure of this method has a lot of similarities to 940 // attempt_allocation_slow(). The reason these two were not merged 941 // into a single one is that such a method would require several "if 942 // allocation is not humongous do this, otherwise do that" 943 // conditional paths which would obscure its flow. In fact, an early 944 // version of this code did use a unified method which was harder to 945 // follow and, as a result, it had subtle bugs that were hard to 946 // track down. So keeping these two methods separate allows each to 947 // be more readable. It will be good to keep these two in sync as 948 // much as possible. 949 950 assert_heap_not_locked_and_not_at_safepoint(); 951 assert(is_humongous(word_size), "attempt_allocation_humongous() " 952 "should only be called for humongous allocations"); 953 954 // Humongous objects can exhaust the heap quickly, so we should check if we 955 // need to start a marking cycle at each humongous object allocation. We do 956 // the check before we do the actual allocation. The reason for doing it 957 // before the allocation is that we avoid having to keep track of the newly 958 // allocated memory while we do a GC. 959 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 960 word_size)) { 961 collect(GCCause::_g1_humongous_allocation); 962 } 963 964 // We will loop until a) we manage to successfully perform the 965 // allocation or b) we successfully schedule a collection which 966 // fails to perform the allocation. b) is the only case when we'll 967 // return NULL. 968 HeapWord* result = NULL; 969 for (int try_count = 1; /* we'll return */; try_count += 1) { 970 bool should_try_gc; 971 uint gc_count_before; 972 973 { 974 MutexLockerEx x(Heap_lock); 975 976 // Given that humongous objects are not allocated in young 977 // regions, we'll first try to do the allocation without doing a 978 // collection hoping that there's enough space in the heap. 979 result = humongous_obj_allocate(word_size, AllocationContext::current()); 980 if (result != NULL) { 981 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 982 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 983 return result; 984 } 985 986 if (GCLocker::is_active_and_needs_gc()) { 987 should_try_gc = false; 988 } else { 989 // The GCLocker may not be active but the GCLocker initiated 990 // GC may not yet have been performed (GCLocker::needs_gc() 991 // returns true). In this case we do not try this GC and 992 // wait until the GCLocker initiated GC is performed, and 993 // then retry the allocation. 994 if (GCLocker::needs_gc()) { 995 should_try_gc = false; 996 } else { 997 // Read the GC count while still holding the Heap_lock. 998 gc_count_before = total_collections(); 999 should_try_gc = true; 1000 } 1001 } 1002 } 1003 1004 if (should_try_gc) { 1005 // If we failed to allocate the humongous object, we should try to 1006 // do a collection pause (if we're allowed) in case it reclaims 1007 // enough space for the allocation to succeed after the pause. 1008 1009 bool succeeded; 1010 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1011 GCCause::_g1_humongous_allocation); 1012 if (result != NULL) { 1013 assert(succeeded, "only way to get back a non-NULL result"); 1014 return result; 1015 } 1016 1017 if (succeeded) { 1018 // If we get here we successfully scheduled a collection which 1019 // failed to allocate. No point in trying to allocate 1020 // further. We'll just return NULL. 1021 MutexLockerEx x(Heap_lock); 1022 *gc_count_before_ret = total_collections(); 1023 return NULL; 1024 } 1025 } else { 1026 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1027 MutexLockerEx x(Heap_lock); 1028 *gc_count_before_ret = total_collections(); 1029 return NULL; 1030 } 1031 // The GCLocker is either active or the GCLocker initiated 1032 // GC has not yet been performed. Stall until it is and 1033 // then retry the allocation. 1034 GCLocker::stall_until_clear(); 1035 (*gclocker_retry_count_ret) += 1; 1036 } 1037 1038 // We can reach here if we were unsuccessful in scheduling a 1039 // collection (because another thread beat us to it) or if we were 1040 // stalled due to the GC locker. In either can we should retry the 1041 // allocation attempt in case another thread successfully 1042 // performed a collection and reclaimed enough space. Give a 1043 // warning if we seem to be looping forever. 1044 1045 if ((QueuedAllocationWarningCount > 0) && 1046 (try_count % QueuedAllocationWarningCount == 0)) { 1047 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() " 1048 "retries %d times", try_count); 1049 } 1050 } 1051 1052 ShouldNotReachHere(); 1053 return NULL; 1054 } 1055 1056 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1057 AllocationContext_t context, 1058 bool expect_null_mutator_alloc_region) { 1059 assert_at_safepoint(true /* should_be_vm_thread */); 1060 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1061 "the current alloc region was unexpectedly found to be non-NULL"); 1062 1063 if (!is_humongous(word_size)) { 1064 return _allocator->attempt_allocation_locked(word_size, context); 1065 } else { 1066 HeapWord* result = humongous_obj_allocate(word_size, context); 1067 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1068 collector_state()->set_initiate_conc_mark_if_possible(true); 1069 } 1070 return result; 1071 } 1072 1073 ShouldNotReachHere(); 1074 } 1075 1076 class PostMCRemSetClearClosure: public HeapRegionClosure { 1077 G1CollectedHeap* _g1h; 1078 ModRefBarrierSet* _mr_bs; 1079 public: 1080 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1081 _g1h(g1h), _mr_bs(mr_bs) {} 1082 1083 bool doHeapRegion(HeapRegion* r) { 1084 HeapRegionRemSet* hrrs = r->rem_set(); 1085 1086 _g1h->reset_gc_time_stamps(r); 1087 1088 if (r->is_continues_humongous()) { 1089 // We'll assert that the strong code root list and RSet is empty 1090 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1091 assert(hrrs->occupied() == 0, "RSet should be empty"); 1092 } else { 1093 hrrs->clear(); 1094 } 1095 // You might think here that we could clear just the cards 1096 // corresponding to the used region. But no: if we leave a dirty card 1097 // in a region we might allocate into, then it would prevent that card 1098 // from being enqueued, and cause it to be missed. 1099 // Re: the performance cost: we shouldn't be doing full GC anyway! 1100 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1101 1102 return false; 1103 } 1104 }; 1105 1106 void G1CollectedHeap::clear_rsets_post_compaction() { 1107 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1108 heap_region_iterate(&rs_clear); 1109 } 1110 1111 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1112 G1CollectedHeap* _g1h; 1113 UpdateRSOopClosure _cl; 1114 public: 1115 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1116 _cl(g1->g1_rem_set(), worker_i), 1117 _g1h(g1) 1118 { } 1119 1120 bool doHeapRegion(HeapRegion* r) { 1121 if (!r->is_continues_humongous()) { 1122 _cl.set_from(r); 1123 r->oop_iterate(&_cl); 1124 } 1125 return false; 1126 } 1127 }; 1128 1129 class ParRebuildRSTask: public AbstractGangTask { 1130 G1CollectedHeap* _g1; 1131 HeapRegionClaimer _hrclaimer; 1132 1133 public: 1134 ParRebuildRSTask(G1CollectedHeap* g1) : 1135 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1136 1137 void work(uint worker_id) { 1138 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1139 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1140 } 1141 }; 1142 1143 class PostCompactionPrinterClosure: public HeapRegionClosure { 1144 private: 1145 G1HRPrinter* _hr_printer; 1146 public: 1147 bool doHeapRegion(HeapRegion* hr) { 1148 assert(!hr->is_young(), "not expecting to find young regions"); 1149 _hr_printer->post_compaction(hr); 1150 return false; 1151 } 1152 1153 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1154 : _hr_printer(hr_printer) { } 1155 }; 1156 1157 void G1CollectedHeap::print_hrm_post_compaction() { 1158 if (_hr_printer.is_active()) { 1159 PostCompactionPrinterClosure cl(hr_printer()); 1160 heap_region_iterate(&cl); 1161 } 1162 1163 } 1164 1165 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1166 bool clear_all_soft_refs) { 1167 assert_at_safepoint(true /* should_be_vm_thread */); 1168 1169 if (GCLocker::check_active_before_gc()) { 1170 return false; 1171 } 1172 1173 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1174 gc_timer->register_gc_start(); 1175 1176 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1177 GCIdMark gc_id_mark; 1178 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1179 1180 SvcGCMarker sgcm(SvcGCMarker::FULL); 1181 ResourceMark rm; 1182 1183 print_heap_before_gc(); 1184 print_heap_regions(); 1185 trace_heap_before_gc(gc_tracer); 1186 1187 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1188 1189 _verifier->verify_region_sets_optional(); 1190 1191 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1192 collector_policy()->should_clear_all_soft_refs(); 1193 1194 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1195 1196 { 1197 IsGCActiveMark x; 1198 1199 // Timing 1200 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1201 GCTraceCPUTime tcpu; 1202 1203 { 1204 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1205 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1206 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1207 1208 G1HeapTransition heap_transition(this); 1209 g1_policy()->record_full_collection_start(); 1210 1211 // Note: When we have a more flexible GC logging framework that 1212 // allows us to add optional attributes to a GC log record we 1213 // could consider timing and reporting how long we wait in the 1214 // following two methods. 1215 wait_while_free_regions_coming(); 1216 // If we start the compaction before the CM threads finish 1217 // scanning the root regions we might trip them over as we'll 1218 // be moving objects / updating references. So let's wait until 1219 // they are done. By telling them to abort, they should complete 1220 // early. 1221 _cm->root_regions()->abort(); 1222 _cm->root_regions()->wait_until_scan_finished(); 1223 append_secondary_free_list_if_not_empty_with_lock(); 1224 1225 gc_prologue(true); 1226 increment_total_collections(true /* full gc */); 1227 increment_old_marking_cycles_started(); 1228 1229 assert(used() == recalculate_used(), "Should be equal"); 1230 1231 _verifier->verify_before_gc(); 1232 1233 _verifier->check_bitmaps("Full GC Start"); 1234 pre_full_gc_dump(gc_timer); 1235 1236 #if defined(COMPILER2) || INCLUDE_JVMCI 1237 DerivedPointerTable::clear(); 1238 #endif 1239 1240 // Disable discovery and empty the discovered lists 1241 // for the CM ref processor. 1242 ref_processor_cm()->disable_discovery(); 1243 ref_processor_cm()->abandon_partial_discovery(); 1244 ref_processor_cm()->verify_no_references_recorded(); 1245 1246 // Abandon current iterations of concurrent marking and concurrent 1247 // refinement, if any are in progress. 1248 concurrent_mark()->abort(); 1249 1250 // Make sure we'll choose a new allocation region afterwards. 1251 _allocator->release_mutator_alloc_region(); 1252 _allocator->abandon_gc_alloc_regions(); 1253 g1_rem_set()->cleanupHRRS(); 1254 1255 // We may have added regions to the current incremental collection 1256 // set between the last GC or pause and now. We need to clear the 1257 // incremental collection set and then start rebuilding it afresh 1258 // after this full GC. 1259 abandon_collection_set(collection_set()); 1260 1261 tear_down_region_sets(false /* free_list_only */); 1262 collector_state()->set_gcs_are_young(true); 1263 1264 // See the comments in g1CollectedHeap.hpp and 1265 // G1CollectedHeap::ref_processing_init() about 1266 // how reference processing currently works in G1. 1267 1268 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1269 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1270 1271 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1272 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1273 1274 ref_processor_stw()->enable_discovery(); 1275 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1276 1277 // Do collection work 1278 { 1279 HandleMark hm; // Discard invalid handles created during gc 1280 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1281 } 1282 1283 assert(num_free_regions() == 0, "we should not have added any free regions"); 1284 rebuild_region_sets(false /* free_list_only */); 1285 1286 // Enqueue any discovered reference objects that have 1287 // not been removed from the discovered lists. 1288 ref_processor_stw()->enqueue_discovered_references(); 1289 1290 #if defined(COMPILER2) || INCLUDE_JVMCI 1291 DerivedPointerTable::update_pointers(); 1292 #endif 1293 1294 MemoryService::track_memory_usage(); 1295 1296 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1297 ref_processor_stw()->verify_no_references_recorded(); 1298 1299 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1300 ClassLoaderDataGraph::purge(); 1301 MetaspaceAux::verify_metrics(); 1302 1303 // Note: since we've just done a full GC, concurrent 1304 // marking is no longer active. Therefore we need not 1305 // re-enable reference discovery for the CM ref processor. 1306 // That will be done at the start of the next marking cycle. 1307 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1308 ref_processor_cm()->verify_no_references_recorded(); 1309 1310 reset_gc_time_stamp(); 1311 // Since everything potentially moved, we will clear all remembered 1312 // sets, and clear all cards. Later we will rebuild remembered 1313 // sets. We will also reset the GC time stamps of the regions. 1314 clear_rsets_post_compaction(); 1315 check_gc_time_stamps(); 1316 1317 resize_if_necessary_after_full_collection(); 1318 1319 // We should do this after we potentially resize the heap so 1320 // that all the COMMIT / UNCOMMIT events are generated before 1321 // the compaction events. 1322 print_hrm_post_compaction(); 1323 1324 if (_hot_card_cache->use_cache()) { 1325 _hot_card_cache->reset_card_counts(); 1326 _hot_card_cache->reset_hot_cache(); 1327 } 1328 1329 // Rebuild remembered sets of all regions. 1330 uint n_workers = 1331 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1332 workers()->active_workers(), 1333 Threads::number_of_non_daemon_threads()); 1334 workers()->update_active_workers(n_workers); 1335 1336 ParRebuildRSTask rebuild_rs_task(this); 1337 workers()->run_task(&rebuild_rs_task); 1338 1339 // Rebuild the strong code root lists for each region 1340 rebuild_strong_code_roots(); 1341 1342 if (true) { // FIXME 1343 MetaspaceGC::compute_new_size(); 1344 } 1345 1346 #ifdef TRACESPINNING 1347 ParallelTaskTerminator::print_termination_counts(); 1348 #endif 1349 1350 // Discard all rset updates 1351 JavaThread::dirty_card_queue_set().abandon_logs(); 1352 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1353 1354 // At this point there should be no regions in the 1355 // entire heap tagged as young. 1356 assert(check_young_list_empty(), "young list should be empty at this point"); 1357 1358 // Update the number of full collections that have been completed. 1359 increment_old_marking_cycles_completed(false /* concurrent */); 1360 1361 _hrm.verify_optional(); 1362 _verifier->verify_region_sets_optional(); 1363 1364 _verifier->verify_after_gc(); 1365 1366 // Clear the previous marking bitmap, if needed for bitmap verification. 1367 // Note we cannot do this when we clear the next marking bitmap in 1368 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1369 // objects marked during a full GC against the previous bitmap. 1370 // But we need to clear it before calling check_bitmaps below since 1371 // the full GC has compacted objects and updated TAMS but not updated 1372 // the prev bitmap. 1373 if (G1VerifyBitmaps) { 1374 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1375 _cm->clear_prev_bitmap(workers()); 1376 } 1377 _verifier->check_bitmaps("Full GC End"); 1378 1379 // Start a new incremental collection set for the next pause 1380 collection_set()->start_incremental_building(); 1381 1382 clear_cset_fast_test(); 1383 1384 _allocator->init_mutator_alloc_region(); 1385 1386 g1_policy()->record_full_collection_end(); 1387 1388 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1389 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1390 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1391 // before any GC notifications are raised. 1392 g1mm()->update_sizes(); 1393 1394 gc_epilogue(true); 1395 1396 heap_transition.print(); 1397 1398 print_heap_after_gc(); 1399 print_heap_regions(); 1400 trace_heap_after_gc(gc_tracer); 1401 1402 post_full_gc_dump(gc_timer); 1403 } 1404 1405 gc_timer->register_gc_end(); 1406 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1407 } 1408 1409 return true; 1410 } 1411 1412 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1413 // Currently, there is no facility in the do_full_collection(bool) API to notify 1414 // the caller that the collection did not succeed (e.g., because it was locked 1415 // out by the GC locker). So, right now, we'll ignore the return value. 1416 bool dummy = do_full_collection(true, /* explicit_gc */ 1417 clear_all_soft_refs); 1418 } 1419 1420 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1421 // Include bytes that will be pre-allocated to support collections, as "used". 1422 const size_t used_after_gc = used(); 1423 const size_t capacity_after_gc = capacity(); 1424 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1425 1426 // This is enforced in arguments.cpp. 1427 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1428 "otherwise the code below doesn't make sense"); 1429 1430 // We don't have floating point command-line arguments 1431 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1432 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1433 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1434 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1435 1436 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1437 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1438 1439 // We have to be careful here as these two calculations can overflow 1440 // 32-bit size_t's. 1441 double used_after_gc_d = (double) used_after_gc; 1442 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1443 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1444 1445 // Let's make sure that they are both under the max heap size, which 1446 // by default will make them fit into a size_t. 1447 double desired_capacity_upper_bound = (double) max_heap_size; 1448 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1449 desired_capacity_upper_bound); 1450 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1451 desired_capacity_upper_bound); 1452 1453 // We can now safely turn them into size_t's. 1454 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1455 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1456 1457 // This assert only makes sense here, before we adjust them 1458 // with respect to the min and max heap size. 1459 assert(minimum_desired_capacity <= maximum_desired_capacity, 1460 "minimum_desired_capacity = " SIZE_FORMAT ", " 1461 "maximum_desired_capacity = " SIZE_FORMAT, 1462 minimum_desired_capacity, maximum_desired_capacity); 1463 1464 // Should not be greater than the heap max size. No need to adjust 1465 // it with respect to the heap min size as it's a lower bound (i.e., 1466 // we'll try to make the capacity larger than it, not smaller). 1467 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1468 // Should not be less than the heap min size. No need to adjust it 1469 // with respect to the heap max size as it's an upper bound (i.e., 1470 // we'll try to make the capacity smaller than it, not greater). 1471 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1472 1473 if (capacity_after_gc < minimum_desired_capacity) { 1474 // Don't expand unless it's significant 1475 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1476 1477 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1478 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1479 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1480 1481 expand(expand_bytes); 1482 1483 // No expansion, now see if we want to shrink 1484 } else if (capacity_after_gc > maximum_desired_capacity) { 1485 // Capacity too large, compute shrinking size 1486 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1487 1488 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1489 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1490 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1491 1492 shrink(shrink_bytes); 1493 } 1494 } 1495 1496 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1497 AllocationContext_t context, 1498 bool do_gc, 1499 bool clear_all_soft_refs, 1500 bool expect_null_mutator_alloc_region, 1501 bool* gc_succeeded) { 1502 *gc_succeeded = true; 1503 // Let's attempt the allocation first. 1504 HeapWord* result = 1505 attempt_allocation_at_safepoint(word_size, 1506 context, 1507 expect_null_mutator_alloc_region); 1508 if (result != NULL) { 1509 assert(*gc_succeeded, "sanity"); 1510 return result; 1511 } 1512 1513 // In a G1 heap, we're supposed to keep allocation from failing by 1514 // incremental pauses. Therefore, at least for now, we'll favor 1515 // expansion over collection. (This might change in the future if we can 1516 // do something smarter than full collection to satisfy a failed alloc.) 1517 result = expand_and_allocate(word_size, context); 1518 if (result != NULL) { 1519 assert(*gc_succeeded, "sanity"); 1520 return result; 1521 } 1522 1523 if (do_gc) { 1524 // Expansion didn't work, we'll try to do a Full GC. 1525 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1526 clear_all_soft_refs); 1527 } 1528 1529 return NULL; 1530 } 1531 1532 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1533 AllocationContext_t context, 1534 bool* succeeded) { 1535 assert_at_safepoint(true /* should_be_vm_thread */); 1536 1537 // Attempts to allocate followed by Full GC. 1538 HeapWord* result = 1539 satisfy_failed_allocation_helper(word_size, 1540 context, 1541 true, /* do_gc */ 1542 false, /* clear_all_soft_refs */ 1543 false, /* expect_null_mutator_alloc_region */ 1544 succeeded); 1545 1546 if (result != NULL || !*succeeded) { 1547 return result; 1548 } 1549 1550 // Attempts to allocate followed by Full GC that will collect all soft references. 1551 result = satisfy_failed_allocation_helper(word_size, 1552 context, 1553 true, /* do_gc */ 1554 true, /* clear_all_soft_refs */ 1555 true, /* expect_null_mutator_alloc_region */ 1556 succeeded); 1557 1558 if (result != NULL || !*succeeded) { 1559 return result; 1560 } 1561 1562 // Attempts to allocate, no GC 1563 result = satisfy_failed_allocation_helper(word_size, 1564 context, 1565 false, /* do_gc */ 1566 false, /* clear_all_soft_refs */ 1567 true, /* expect_null_mutator_alloc_region */ 1568 succeeded); 1569 1570 if (result != NULL) { 1571 assert(*succeeded, "sanity"); 1572 return result; 1573 } 1574 1575 assert(!collector_policy()->should_clear_all_soft_refs(), 1576 "Flag should have been handled and cleared prior to this point"); 1577 1578 // What else? We might try synchronous finalization later. If the total 1579 // space available is large enough for the allocation, then a more 1580 // complete compaction phase than we've tried so far might be 1581 // appropriate. 1582 assert(*succeeded, "sanity"); 1583 return NULL; 1584 } 1585 1586 // Attempting to expand the heap sufficiently 1587 // to support an allocation of the given "word_size". If 1588 // successful, perform the allocation and return the address of the 1589 // allocated block, or else "NULL". 1590 1591 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1592 assert_at_safepoint(true /* should_be_vm_thread */); 1593 1594 _verifier->verify_region_sets_optional(); 1595 1596 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1597 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1598 word_size * HeapWordSize); 1599 1600 1601 if (expand(expand_bytes)) { 1602 _hrm.verify_optional(); 1603 _verifier->verify_region_sets_optional(); 1604 return attempt_allocation_at_safepoint(word_size, 1605 context, 1606 false /* expect_null_mutator_alloc_region */); 1607 } 1608 return NULL; 1609 } 1610 1611 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) { 1612 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1613 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1614 HeapRegion::GrainBytes); 1615 1616 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B", 1617 expand_bytes, aligned_expand_bytes); 1618 1619 if (is_maximal_no_gc()) { 1620 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1621 return false; 1622 } 1623 1624 double expand_heap_start_time_sec = os::elapsedTime(); 1625 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1626 assert(regions_to_expand > 0, "Must expand by at least one region"); 1627 1628 uint expanded_by = _hrm.expand_by(regions_to_expand); 1629 if (expand_time_ms != NULL) { 1630 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1631 } 1632 1633 if (expanded_by > 0) { 1634 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1635 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1636 g1_policy()->record_new_heap_size(num_regions()); 1637 } else { 1638 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1639 1640 // The expansion of the virtual storage space was unsuccessful. 1641 // Let's see if it was because we ran out of swap. 1642 if (G1ExitOnExpansionFailure && 1643 _hrm.available() >= regions_to_expand) { 1644 // We had head room... 1645 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1646 } 1647 } 1648 return regions_to_expand > 0; 1649 } 1650 1651 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1652 size_t aligned_shrink_bytes = 1653 ReservedSpace::page_align_size_down(shrink_bytes); 1654 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1655 HeapRegion::GrainBytes); 1656 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1657 1658 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1659 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1660 1661 1662 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", 1663 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1664 if (num_regions_removed > 0) { 1665 g1_policy()->record_new_heap_size(num_regions()); 1666 } else { 1667 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1668 } 1669 } 1670 1671 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1672 _verifier->verify_region_sets_optional(); 1673 1674 // We should only reach here at the end of a Full GC which means we 1675 // should not not be holding to any GC alloc regions. The method 1676 // below will make sure of that and do any remaining clean up. 1677 _allocator->abandon_gc_alloc_regions(); 1678 1679 // Instead of tearing down / rebuilding the free lists here, we 1680 // could instead use the remove_all_pending() method on free_list to 1681 // remove only the ones that we need to remove. 1682 tear_down_region_sets(true /* free_list_only */); 1683 shrink_helper(shrink_bytes); 1684 rebuild_region_sets(true /* free_list_only */); 1685 1686 _hrm.verify_optional(); 1687 _verifier->verify_region_sets_optional(); 1688 } 1689 1690 // Public methods. 1691 1692 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1693 CollectedHeap(), 1694 _collector_policy(collector_policy), 1695 _g1_policy(create_g1_policy()), 1696 _collection_set(this, _g1_policy), 1697 _dirty_card_queue_set(false), 1698 _is_alive_closure_cm(this), 1699 _is_alive_closure_stw(this), 1700 _ref_processor_cm(NULL), 1701 _ref_processor_stw(NULL), 1702 _bot(NULL), 1703 _hot_card_cache(NULL), 1704 _g1_rem_set(NULL), 1705 _cg1r(NULL), 1706 _g1mm(NULL), 1707 _refine_cte_cl(NULL), 1708 _preserved_marks_set(true /* in_c_heap */), 1709 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1710 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1711 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1712 _humongous_reclaim_candidates(), 1713 _has_humongous_reclaim_candidates(false), 1714 _archive_allocator(NULL), 1715 _free_regions_coming(false), 1716 _gc_time_stamp(0), 1717 _summary_bytes_used(0), 1718 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1719 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1720 _expand_heap_after_alloc_failure(true), 1721 _old_marking_cycles_started(0), 1722 _old_marking_cycles_completed(0), 1723 _in_cset_fast_test(), 1724 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1725 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) { 1726 1727 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1728 /* are_GC_task_threads */true, 1729 /* are_ConcurrentGC_threads */false); 1730 _workers->initialize_workers(); 1731 _verifier = new G1HeapVerifier(this); 1732 1733 _allocator = G1Allocator::create_allocator(this); 1734 1735 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1736 1737 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1738 1739 // Override the default _filler_array_max_size so that no humongous filler 1740 // objects are created. 1741 _filler_array_max_size = _humongous_object_threshold_in_words; 1742 1743 uint n_queues = ParallelGCThreads; 1744 _task_queues = new RefToScanQueueSet(n_queues); 1745 1746 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1747 1748 for (uint i = 0; i < n_queues; i++) { 1749 RefToScanQueue* q = new RefToScanQueue(); 1750 q->initialize(); 1751 _task_queues->register_queue(i, q); 1752 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1753 } 1754 1755 // Initialize the G1EvacuationFailureALot counters and flags. 1756 NOT_PRODUCT(reset_evacuation_should_fail();) 1757 1758 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1759 } 1760 1761 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1762 size_t size, 1763 size_t translation_factor) { 1764 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1765 // Allocate a new reserved space, preferring to use large pages. 1766 ReservedSpace rs(size, preferred_page_size); 1767 G1RegionToSpaceMapper* result = 1768 G1RegionToSpaceMapper::create_mapper(rs, 1769 size, 1770 rs.alignment(), 1771 HeapRegion::GrainBytes, 1772 translation_factor, 1773 mtGC); 1774 1775 os::trace_page_sizes_for_requested_size(description, 1776 size, 1777 preferred_page_size, 1778 rs.alignment(), 1779 rs.base(), 1780 rs.size()); 1781 1782 return result; 1783 } 1784 1785 jint G1CollectedHeap::initialize() { 1786 CollectedHeap::pre_initialize(); 1787 os::enable_vtime(); 1788 1789 // Necessary to satisfy locking discipline assertions. 1790 1791 MutexLocker x(Heap_lock); 1792 1793 // While there are no constraints in the GC code that HeapWordSize 1794 // be any particular value, there are multiple other areas in the 1795 // system which believe this to be true (e.g. oop->object_size in some 1796 // cases incorrectly returns the size in wordSize units rather than 1797 // HeapWordSize). 1798 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1799 1800 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1801 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1802 size_t heap_alignment = collector_policy()->heap_alignment(); 1803 1804 // Ensure that the sizes are properly aligned. 1805 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1806 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1807 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1808 1809 _refine_cte_cl = new RefineCardTableEntryClosure(); 1810 1811 jint ecode = JNI_OK; 1812 _cg1r = ConcurrentG1Refine::create(_refine_cte_cl, &ecode); 1813 if (_cg1r == NULL) { 1814 return ecode; 1815 } 1816 1817 // Reserve the maximum. 1818 1819 // When compressed oops are enabled, the preferred heap base 1820 // is calculated by subtracting the requested size from the 1821 // 32Gb boundary and using the result as the base address for 1822 // heap reservation. If the requested size is not aligned to 1823 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1824 // into the ReservedHeapSpace constructor) then the actual 1825 // base of the reserved heap may end up differing from the 1826 // address that was requested (i.e. the preferred heap base). 1827 // If this happens then we could end up using a non-optimal 1828 // compressed oops mode. 1829 1830 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1831 heap_alignment); 1832 1833 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1834 1835 // Create the barrier set for the entire reserved region. 1836 G1SATBCardTableLoggingModRefBS* bs 1837 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1838 bs->initialize(); 1839 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1840 set_barrier_set(bs); 1841 1842 // Create the hot card cache. 1843 _hot_card_cache = new G1HotCardCache(this); 1844 1845 // Also create a G1 rem set. 1846 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache); 1847 1848 // Carve out the G1 part of the heap. 1849 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1850 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1851 G1RegionToSpaceMapper* heap_storage = 1852 G1RegionToSpaceMapper::create_mapper(g1_rs, 1853 g1_rs.size(), 1854 page_size, 1855 HeapRegion::GrainBytes, 1856 1, 1857 mtJavaHeap); 1858 os::trace_page_sizes("Heap", 1859 collector_policy()->min_heap_byte_size(), 1860 max_byte_size, 1861 page_size, 1862 heap_rs.base(), 1863 heap_rs.size()); 1864 heap_storage->set_mapping_changed_listener(&_listener); 1865 1866 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1867 G1RegionToSpaceMapper* bot_storage = 1868 create_aux_memory_mapper("Block Offset Table", 1869 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1870 G1BlockOffsetTable::heap_map_factor()); 1871 1872 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1873 G1RegionToSpaceMapper* cardtable_storage = 1874 create_aux_memory_mapper("Card Table", 1875 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1876 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1877 1878 G1RegionToSpaceMapper* card_counts_storage = 1879 create_aux_memory_mapper("Card Counts Table", 1880 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1881 G1CardCounts::heap_map_factor()); 1882 1883 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1884 G1RegionToSpaceMapper* prev_bitmap_storage = 1885 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1886 G1RegionToSpaceMapper* next_bitmap_storage = 1887 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1888 1889 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1890 g1_barrier_set()->initialize(cardtable_storage); 1891 // Do later initialization work for concurrent refinement. 1892 _hot_card_cache->initialize(card_counts_storage); 1893 1894 // 6843694 - ensure that the maximum region index can fit 1895 // in the remembered set structures. 1896 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1897 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1898 1899 g1_rem_set()->initialize(max_capacity(), max_regions()); 1900 1901 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1902 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1903 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1904 "too many cards per region"); 1905 1906 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1907 1908 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1909 1910 { 1911 HeapWord* start = _hrm.reserved().start(); 1912 HeapWord* end = _hrm.reserved().end(); 1913 size_t granularity = HeapRegion::GrainBytes; 1914 1915 _in_cset_fast_test.initialize(start, end, granularity); 1916 _humongous_reclaim_candidates.initialize(start, end, granularity); 1917 } 1918 1919 // Create the G1ConcurrentMark data structure and thread. 1920 // (Must do this late, so that "max_regions" is defined.) 1921 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1922 if (_cm == NULL || !_cm->completed_initialization()) { 1923 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1924 return JNI_ENOMEM; 1925 } 1926 _cmThread = _cm->cmThread(); 1927 1928 // Now expand into the initial heap size. 1929 if (!expand(init_byte_size)) { 1930 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1931 return JNI_ENOMEM; 1932 } 1933 1934 // Perform any initialization actions delegated to the policy. 1935 g1_policy()->init(this, &_collection_set); 1936 1937 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1938 SATB_Q_FL_lock, 1939 G1SATBProcessCompletedThreshold, 1940 Shared_SATB_Q_lock); 1941 1942 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 1943 DirtyCardQ_CBL_mon, 1944 DirtyCardQ_FL_lock, 1945 (int)concurrent_g1_refine()->yellow_zone(), 1946 (int)concurrent_g1_refine()->red_zone(), 1947 Shared_DirtyCardQ_lock, 1948 NULL, // fl_owner 1949 true); // init_free_ids 1950 1951 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 1952 DirtyCardQ_CBL_mon, 1953 DirtyCardQ_FL_lock, 1954 -1, // never trigger processing 1955 -1, // no limit on length 1956 Shared_DirtyCardQ_lock, 1957 &JavaThread::dirty_card_queue_set()); 1958 1959 // Here we allocate the dummy HeapRegion that is required by the 1960 // G1AllocRegion class. 1961 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1962 1963 // We'll re-use the same region whether the alloc region will 1964 // require BOT updates or not and, if it doesn't, then a non-young 1965 // region will complain that it cannot support allocations without 1966 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1967 dummy_region->set_eden(); 1968 // Make sure it's full. 1969 dummy_region->set_top(dummy_region->end()); 1970 G1AllocRegion::setup(this, dummy_region); 1971 1972 _allocator->init_mutator_alloc_region(); 1973 1974 // Do create of the monitoring and management support so that 1975 // values in the heap have been properly initialized. 1976 _g1mm = new G1MonitoringSupport(this); 1977 1978 G1StringDedup::initialize(); 1979 1980 _preserved_marks_set.init(ParallelGCThreads); 1981 1982 _collection_set.initialize(max_regions()); 1983 1984 return JNI_OK; 1985 } 1986 1987 void G1CollectedHeap::stop() { 1988 // Stop all concurrent threads. We do this to make sure these threads 1989 // do not continue to execute and access resources (e.g. logging) 1990 // that are destroyed during shutdown. 1991 _cg1r->stop(); 1992 _cmThread->stop(); 1993 if (G1StringDedup::is_enabled()) { 1994 G1StringDedup::stop(); 1995 } 1996 } 1997 1998 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1999 return HeapRegion::max_region_size(); 2000 } 2001 2002 void G1CollectedHeap::post_initialize() { 2003 ref_processing_init(); 2004 } 2005 2006 void G1CollectedHeap::ref_processing_init() { 2007 // Reference processing in G1 currently works as follows: 2008 // 2009 // * There are two reference processor instances. One is 2010 // used to record and process discovered references 2011 // during concurrent marking; the other is used to 2012 // record and process references during STW pauses 2013 // (both full and incremental). 2014 // * Both ref processors need to 'span' the entire heap as 2015 // the regions in the collection set may be dotted around. 2016 // 2017 // * For the concurrent marking ref processor: 2018 // * Reference discovery is enabled at initial marking. 2019 // * Reference discovery is disabled and the discovered 2020 // references processed etc during remarking. 2021 // * Reference discovery is MT (see below). 2022 // * Reference discovery requires a barrier (see below). 2023 // * Reference processing may or may not be MT 2024 // (depending on the value of ParallelRefProcEnabled 2025 // and ParallelGCThreads). 2026 // * A full GC disables reference discovery by the CM 2027 // ref processor and abandons any entries on it's 2028 // discovered lists. 2029 // 2030 // * For the STW processor: 2031 // * Non MT discovery is enabled at the start of a full GC. 2032 // * Processing and enqueueing during a full GC is non-MT. 2033 // * During a full GC, references are processed after marking. 2034 // 2035 // * Discovery (may or may not be MT) is enabled at the start 2036 // of an incremental evacuation pause. 2037 // * References are processed near the end of a STW evacuation pause. 2038 // * For both types of GC: 2039 // * Discovery is atomic - i.e. not concurrent. 2040 // * Reference discovery will not need a barrier. 2041 2042 MemRegion mr = reserved_region(); 2043 2044 // Concurrent Mark ref processor 2045 _ref_processor_cm = 2046 new ReferenceProcessor(mr, // span 2047 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2048 // mt processing 2049 ParallelGCThreads, 2050 // degree of mt processing 2051 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2052 // mt discovery 2053 MAX2(ParallelGCThreads, ConcGCThreads), 2054 // degree of mt discovery 2055 false, 2056 // Reference discovery is not atomic 2057 &_is_alive_closure_cm); 2058 // is alive closure 2059 // (for efficiency/performance) 2060 2061 // STW ref processor 2062 _ref_processor_stw = 2063 new ReferenceProcessor(mr, // span 2064 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2065 // mt processing 2066 ParallelGCThreads, 2067 // degree of mt processing 2068 (ParallelGCThreads > 1), 2069 // mt discovery 2070 ParallelGCThreads, 2071 // degree of mt discovery 2072 true, 2073 // Reference discovery is atomic 2074 &_is_alive_closure_stw); 2075 // is alive closure 2076 // (for efficiency/performance) 2077 } 2078 2079 CollectorPolicy* G1CollectedHeap::collector_policy() const { 2080 return _collector_policy; 2081 } 2082 2083 size_t G1CollectedHeap::capacity() const { 2084 return _hrm.length() * HeapRegion::GrainBytes; 2085 } 2086 2087 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2088 hr->reset_gc_time_stamp(); 2089 } 2090 2091 #ifndef PRODUCT 2092 2093 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2094 private: 2095 unsigned _gc_time_stamp; 2096 bool _failures; 2097 2098 public: 2099 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2100 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2101 2102 virtual bool doHeapRegion(HeapRegion* hr) { 2103 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2104 if (_gc_time_stamp != region_gc_time_stamp) { 2105 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 2106 region_gc_time_stamp, _gc_time_stamp); 2107 _failures = true; 2108 } 2109 return false; 2110 } 2111 2112 bool failures() { return _failures; } 2113 }; 2114 2115 void G1CollectedHeap::check_gc_time_stamps() { 2116 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2117 heap_region_iterate(&cl); 2118 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2119 } 2120 #endif // PRODUCT 2121 2122 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2123 _hot_card_cache->drain(cl, worker_i); 2124 } 2125 2126 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2127 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2128 size_t n_completed_buffers = 0; 2129 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2130 n_completed_buffers++; 2131 } 2132 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2133 dcqs.clear_n_completed_buffers(); 2134 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2135 } 2136 2137 // Computes the sum of the storage used by the various regions. 2138 size_t G1CollectedHeap::used() const { 2139 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2140 if (_archive_allocator != NULL) { 2141 result += _archive_allocator->used(); 2142 } 2143 return result; 2144 } 2145 2146 size_t G1CollectedHeap::used_unlocked() const { 2147 return _summary_bytes_used; 2148 } 2149 2150 class SumUsedClosure: public HeapRegionClosure { 2151 size_t _used; 2152 public: 2153 SumUsedClosure() : _used(0) {} 2154 bool doHeapRegion(HeapRegion* r) { 2155 _used += r->used(); 2156 return false; 2157 } 2158 size_t result() { return _used; } 2159 }; 2160 2161 size_t G1CollectedHeap::recalculate_used() const { 2162 double recalculate_used_start = os::elapsedTime(); 2163 2164 SumUsedClosure blk; 2165 heap_region_iterate(&blk); 2166 2167 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2168 return blk.result(); 2169 } 2170 2171 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2172 switch (cause) { 2173 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2174 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2175 case GCCause::_update_allocation_context_stats_inc: return true; 2176 case GCCause::_wb_conc_mark: return true; 2177 default : return false; 2178 } 2179 } 2180 2181 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2182 switch (cause) { 2183 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2184 case GCCause::_g1_humongous_allocation: return true; 2185 default: return is_user_requested_concurrent_full_gc(cause); 2186 } 2187 } 2188 2189 #ifndef PRODUCT 2190 void G1CollectedHeap::allocate_dummy_regions() { 2191 // Let's fill up most of the region 2192 size_t word_size = HeapRegion::GrainWords - 1024; 2193 // And as a result the region we'll allocate will be humongous. 2194 guarantee(is_humongous(word_size), "sanity"); 2195 2196 // _filler_array_max_size is set to humongous object threshold 2197 // but temporarily change it to use CollectedHeap::fill_with_object(). 2198 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2199 2200 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2201 // Let's use the existing mechanism for the allocation 2202 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2203 AllocationContext::system()); 2204 if (dummy_obj != NULL) { 2205 MemRegion mr(dummy_obj, word_size); 2206 CollectedHeap::fill_with_object(mr); 2207 } else { 2208 // If we can't allocate once, we probably cannot allocate 2209 // again. Let's get out of the loop. 2210 break; 2211 } 2212 } 2213 } 2214 #endif // !PRODUCT 2215 2216 void G1CollectedHeap::increment_old_marking_cycles_started() { 2217 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2218 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2219 "Wrong marking cycle count (started: %d, completed: %d)", 2220 _old_marking_cycles_started, _old_marking_cycles_completed); 2221 2222 _old_marking_cycles_started++; 2223 } 2224 2225 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2226 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2227 2228 // We assume that if concurrent == true, then the caller is a 2229 // concurrent thread that was joined the Suspendible Thread 2230 // Set. If there's ever a cheap way to check this, we should add an 2231 // assert here. 2232 2233 // Given that this method is called at the end of a Full GC or of a 2234 // concurrent cycle, and those can be nested (i.e., a Full GC can 2235 // interrupt a concurrent cycle), the number of full collections 2236 // completed should be either one (in the case where there was no 2237 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2238 // behind the number of full collections started. 2239 2240 // This is the case for the inner caller, i.e. a Full GC. 2241 assert(concurrent || 2242 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2243 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2244 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2245 "is inconsistent with _old_marking_cycles_completed = %u", 2246 _old_marking_cycles_started, _old_marking_cycles_completed); 2247 2248 // This is the case for the outer caller, i.e. the concurrent cycle. 2249 assert(!concurrent || 2250 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2251 "for outer caller (concurrent cycle): " 2252 "_old_marking_cycles_started = %u " 2253 "is inconsistent with _old_marking_cycles_completed = %u", 2254 _old_marking_cycles_started, _old_marking_cycles_completed); 2255 2256 _old_marking_cycles_completed += 1; 2257 2258 // We need to clear the "in_progress" flag in the CM thread before 2259 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2260 // is set) so that if a waiter requests another System.gc() it doesn't 2261 // incorrectly see that a marking cycle is still in progress. 2262 if (concurrent) { 2263 _cmThread->set_idle(); 2264 } 2265 2266 // This notify_all() will ensure that a thread that called 2267 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2268 // and it's waiting for a full GC to finish will be woken up. It is 2269 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2270 FullGCCount_lock->notify_all(); 2271 } 2272 2273 void G1CollectedHeap::collect(GCCause::Cause cause) { 2274 assert_heap_not_locked(); 2275 2276 uint gc_count_before; 2277 uint old_marking_count_before; 2278 uint full_gc_count_before; 2279 bool retry_gc; 2280 2281 do { 2282 retry_gc = false; 2283 2284 { 2285 MutexLocker ml(Heap_lock); 2286 2287 // Read the GC count while holding the Heap_lock 2288 gc_count_before = total_collections(); 2289 full_gc_count_before = total_full_collections(); 2290 old_marking_count_before = _old_marking_cycles_started; 2291 } 2292 2293 if (should_do_concurrent_full_gc(cause)) { 2294 // Schedule an initial-mark evacuation pause that will start a 2295 // concurrent cycle. We're setting word_size to 0 which means that 2296 // we are not requesting a post-GC allocation. 2297 VM_G1IncCollectionPause op(gc_count_before, 2298 0, /* word_size */ 2299 true, /* should_initiate_conc_mark */ 2300 g1_policy()->max_pause_time_ms(), 2301 cause); 2302 op.set_allocation_context(AllocationContext::current()); 2303 2304 VMThread::execute(&op); 2305 if (!op.pause_succeeded()) { 2306 if (old_marking_count_before == _old_marking_cycles_started) { 2307 retry_gc = op.should_retry_gc(); 2308 } else { 2309 // A Full GC happened while we were trying to schedule the 2310 // initial-mark GC. No point in starting a new cycle given 2311 // that the whole heap was collected anyway. 2312 } 2313 2314 if (retry_gc) { 2315 if (GCLocker::is_active_and_needs_gc()) { 2316 GCLocker::stall_until_clear(); 2317 } 2318 } 2319 } 2320 } else { 2321 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2322 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2323 2324 // Schedule a standard evacuation pause. We're setting word_size 2325 // to 0 which means that we are not requesting a post-GC allocation. 2326 VM_G1IncCollectionPause op(gc_count_before, 2327 0, /* word_size */ 2328 false, /* should_initiate_conc_mark */ 2329 g1_policy()->max_pause_time_ms(), 2330 cause); 2331 VMThread::execute(&op); 2332 } else { 2333 // Schedule a Full GC. 2334 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2335 VMThread::execute(&op); 2336 } 2337 } 2338 } while (retry_gc); 2339 } 2340 2341 bool G1CollectedHeap::is_in(const void* p) const { 2342 if (_hrm.reserved().contains(p)) { 2343 // Given that we know that p is in the reserved space, 2344 // heap_region_containing() should successfully 2345 // return the containing region. 2346 HeapRegion* hr = heap_region_containing(p); 2347 return hr->is_in(p); 2348 } else { 2349 return false; 2350 } 2351 } 2352 2353 #ifdef ASSERT 2354 bool G1CollectedHeap::is_in_exact(const void* p) const { 2355 bool contains = reserved_region().contains(p); 2356 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2357 if (contains && available) { 2358 return true; 2359 } else { 2360 return false; 2361 } 2362 } 2363 #endif 2364 2365 bool G1CollectedHeap::obj_in_cs(oop obj) { 2366 HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj); 2367 return r != NULL && r->in_collection_set(); 2368 } 2369 2370 // Iteration functions. 2371 2372 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2373 2374 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2375 ExtendedOopClosure* _cl; 2376 public: 2377 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2378 bool doHeapRegion(HeapRegion* r) { 2379 if (!r->is_continues_humongous()) { 2380 r->oop_iterate(_cl); 2381 } 2382 return false; 2383 } 2384 }; 2385 2386 // Iterates an ObjectClosure over all objects within a HeapRegion. 2387 2388 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2389 ObjectClosure* _cl; 2390 public: 2391 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2392 bool doHeapRegion(HeapRegion* r) { 2393 if (!r->is_continues_humongous()) { 2394 r->object_iterate(_cl); 2395 } 2396 return false; 2397 } 2398 }; 2399 2400 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2401 IterateObjectClosureRegionClosure blk(cl); 2402 heap_region_iterate(&blk); 2403 } 2404 2405 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2406 _hrm.iterate(cl); 2407 } 2408 2409 void 2410 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2411 uint worker_id, 2412 HeapRegionClaimer *hrclaimer, 2413 bool concurrent) const { 2414 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2415 } 2416 2417 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2418 _collection_set.iterate(cl); 2419 } 2420 2421 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2422 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2423 } 2424 2425 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2426 HeapRegion* result = _hrm.next_region_in_heap(from); 2427 while (result != NULL && result->is_pinned()) { 2428 result = _hrm.next_region_in_heap(result); 2429 } 2430 return result; 2431 } 2432 2433 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2434 HeapRegion* hr = heap_region_containing(addr); 2435 return hr->block_start(addr); 2436 } 2437 2438 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2439 HeapRegion* hr = heap_region_containing(addr); 2440 return hr->block_size(addr); 2441 } 2442 2443 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2444 HeapRegion* hr = heap_region_containing(addr); 2445 return hr->block_is_obj(addr); 2446 } 2447 2448 bool G1CollectedHeap::supports_tlab_allocation() const { 2449 return true; 2450 } 2451 2452 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2453 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2454 } 2455 2456 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2457 return _eden.length() * HeapRegion::GrainBytes; 2458 } 2459 2460 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2461 // must be equal to the humongous object limit. 2462 size_t G1CollectedHeap::max_tlab_size() const { 2463 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2464 } 2465 2466 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2467 AllocationContext_t context = AllocationContext::current(); 2468 return _allocator->unsafe_max_tlab_alloc(context); 2469 } 2470 2471 size_t G1CollectedHeap::max_capacity() const { 2472 return _hrm.reserved().byte_size(); 2473 } 2474 2475 jlong G1CollectedHeap::millis_since_last_gc() { 2476 // See the notes in GenCollectedHeap::millis_since_last_gc() 2477 // for more information about the implementation. 2478 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2479 _g1_policy->full_collection_end_millis(); 2480 if (ret_val < 0) { 2481 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2482 ". returning zero instead.", ret_val); 2483 return 0; 2484 } 2485 return ret_val; 2486 } 2487 2488 void G1CollectedHeap::prepare_for_verify() { 2489 _verifier->prepare_for_verify(); 2490 } 2491 2492 void G1CollectedHeap::verify(VerifyOption vo) { 2493 _verifier->verify(vo); 2494 } 2495 2496 class PrintRegionClosure: public HeapRegionClosure { 2497 outputStream* _st; 2498 public: 2499 PrintRegionClosure(outputStream* st) : _st(st) {} 2500 bool doHeapRegion(HeapRegion* r) { 2501 r->print_on(_st); 2502 return false; 2503 } 2504 }; 2505 2506 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2507 const HeapRegion* hr, 2508 const VerifyOption vo) const { 2509 switch (vo) { 2510 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2511 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2512 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 2513 default: ShouldNotReachHere(); 2514 } 2515 return false; // keep some compilers happy 2516 } 2517 2518 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2519 const VerifyOption vo) const { 2520 switch (vo) { 2521 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2522 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2523 case VerifyOption_G1UseMarkWord: { 2524 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 2525 return !obj->is_gc_marked() && !hr->is_archive(); 2526 } 2527 default: ShouldNotReachHere(); 2528 } 2529 return false; // keep some compilers happy 2530 } 2531 2532 void G1CollectedHeap::print_heap_regions() const { 2533 Log(gc, heap, region) log; 2534 if (log.is_trace()) { 2535 ResourceMark rm; 2536 print_regions_on(log.trace_stream()); 2537 } 2538 } 2539 2540 void G1CollectedHeap::print_on(outputStream* st) const { 2541 st->print(" %-20s", "garbage-first heap"); 2542 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2543 capacity()/K, used_unlocked()/K); 2544 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 2545 p2i(_hrm.reserved().start()), 2546 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 2547 p2i(_hrm.reserved().end())); 2548 st->cr(); 2549 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2550 uint young_regions = young_regions_count(); 2551 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2552 (size_t) young_regions * HeapRegion::GrainBytes / K); 2553 uint survivor_regions = survivor_regions_count(); 2554 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2555 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2556 st->cr(); 2557 MetaspaceAux::print_on(st); 2558 } 2559 2560 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2561 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2562 "HS=humongous(starts), HC=humongous(continues), " 2563 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2564 "AC=allocation context, " 2565 "TAMS=top-at-mark-start (previous, next)"); 2566 PrintRegionClosure blk(st); 2567 heap_region_iterate(&blk); 2568 } 2569 2570 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2571 print_on(st); 2572 2573 // Print the per-region information. 2574 print_regions_on(st); 2575 } 2576 2577 void G1CollectedHeap::print_on_error(outputStream* st) const { 2578 this->CollectedHeap::print_on_error(st); 2579 2580 if (_cm != NULL) { 2581 st->cr(); 2582 _cm->print_on_error(st); 2583 } 2584 } 2585 2586 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2587 workers()->print_worker_threads_on(st); 2588 _cmThread->print_on(st); 2589 st->cr(); 2590 _cm->print_worker_threads_on(st); 2591 _cg1r->print_worker_threads_on(st); // also prints the sample thread 2592 if (G1StringDedup::is_enabled()) { 2593 G1StringDedup::print_worker_threads_on(st); 2594 } 2595 } 2596 2597 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2598 workers()->threads_do(tc); 2599 tc->do_thread(_cmThread); 2600 _cm->threads_do(tc); 2601 _cg1r->threads_do(tc); // also iterates over the sample thread 2602 if (G1StringDedup::is_enabled()) { 2603 G1StringDedup::threads_do(tc); 2604 } 2605 } 2606 2607 void G1CollectedHeap::print_tracing_info() const { 2608 g1_rem_set()->print_summary_info(); 2609 concurrent_mark()->print_summary_info(); 2610 } 2611 2612 #ifndef PRODUCT 2613 // Helpful for debugging RSet issues. 2614 2615 class PrintRSetsClosure : public HeapRegionClosure { 2616 private: 2617 const char* _msg; 2618 size_t _occupied_sum; 2619 2620 public: 2621 bool doHeapRegion(HeapRegion* r) { 2622 HeapRegionRemSet* hrrs = r->rem_set(); 2623 size_t occupied = hrrs->occupied(); 2624 _occupied_sum += occupied; 2625 2626 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2627 if (occupied == 0) { 2628 tty->print_cr(" RSet is empty"); 2629 } else { 2630 hrrs->print(); 2631 } 2632 tty->print_cr("----------"); 2633 return false; 2634 } 2635 2636 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2637 tty->cr(); 2638 tty->print_cr("========================================"); 2639 tty->print_cr("%s", msg); 2640 tty->cr(); 2641 } 2642 2643 ~PrintRSetsClosure() { 2644 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2645 tty->print_cr("========================================"); 2646 tty->cr(); 2647 } 2648 }; 2649 2650 void G1CollectedHeap::print_cset_rsets() { 2651 PrintRSetsClosure cl("Printing CSet RSets"); 2652 collection_set_iterate(&cl); 2653 } 2654 2655 void G1CollectedHeap::print_all_rsets() { 2656 PrintRSetsClosure cl("Printing All RSets");; 2657 heap_region_iterate(&cl); 2658 } 2659 #endif // PRODUCT 2660 2661 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2662 2663 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2664 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2665 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2666 2667 size_t eden_capacity_bytes = 2668 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2669 2670 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2671 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2672 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2673 } 2674 2675 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2676 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2677 stats->unused(), stats->used(), stats->region_end_waste(), 2678 stats->regions_filled(), stats->direct_allocated(), 2679 stats->failure_used(), stats->failure_waste()); 2680 } 2681 2682 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2683 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2684 gc_tracer->report_gc_heap_summary(when, heap_summary); 2685 2686 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2687 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2688 } 2689 2690 G1CollectedHeap* G1CollectedHeap::heap() { 2691 CollectedHeap* heap = Universe::heap(); 2692 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2693 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2694 return (G1CollectedHeap*)heap; 2695 } 2696 2697 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 2698 // always_do_update_barrier = false; 2699 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2700 // Fill TLAB's and such 2701 accumulate_statistics_all_tlabs(); 2702 ensure_parsability(true); 2703 2704 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2705 } 2706 2707 void G1CollectedHeap::gc_epilogue(bool full) { 2708 // we are at the end of the GC. Total collections has already been increased. 2709 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2710 2711 // FIXME: what is this about? 2712 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2713 // is set. 2714 #if defined(COMPILER2) || INCLUDE_JVMCI 2715 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2716 #endif 2717 // always_do_update_barrier = true; 2718 2719 resize_all_tlabs(); 2720 allocation_context_stats().update(full); 2721 2722 // We have just completed a GC. Update the soft reference 2723 // policy with the new heap occupancy 2724 Universe::update_heap_info_at_gc(); 2725 } 2726 2727 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2728 uint gc_count_before, 2729 bool* succeeded, 2730 GCCause::Cause gc_cause) { 2731 assert_heap_not_locked_and_not_at_safepoint(); 2732 VM_G1IncCollectionPause op(gc_count_before, 2733 word_size, 2734 false, /* should_initiate_conc_mark */ 2735 g1_policy()->max_pause_time_ms(), 2736 gc_cause); 2737 2738 op.set_allocation_context(AllocationContext::current()); 2739 VMThread::execute(&op); 2740 2741 HeapWord* result = op.result(); 2742 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2743 assert(result == NULL || ret_succeeded, 2744 "the result should be NULL if the VM did not succeed"); 2745 *succeeded = ret_succeeded; 2746 2747 assert_heap_not_locked(); 2748 return result; 2749 } 2750 2751 void 2752 G1CollectedHeap::doConcurrentMark() { 2753 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2754 if (!_cmThread->in_progress()) { 2755 _cmThread->set_started(); 2756 CGC_lock->notify(); 2757 } 2758 } 2759 2760 size_t G1CollectedHeap::pending_card_num() { 2761 size_t extra_cards = 0; 2762 JavaThread *curr = Threads::first(); 2763 while (curr != NULL) { 2764 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2765 extra_cards += dcq.size(); 2766 curr = curr->next(); 2767 } 2768 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2769 size_t buffer_size = dcqs.buffer_size(); 2770 size_t buffer_num = dcqs.completed_buffers_num(); 2771 2772 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 2773 // in bytes - not the number of 'entries'. We need to convert 2774 // into a number of cards. 2775 return (buffer_size * buffer_num + extra_cards) / oopSize; 2776 } 2777 2778 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2779 private: 2780 size_t _total_humongous; 2781 size_t _candidate_humongous; 2782 2783 DirtyCardQueue _dcq; 2784 2785 // We don't nominate objects with many remembered set entries, on 2786 // the assumption that such objects are likely still live. 2787 bool is_remset_small(HeapRegion* region) const { 2788 HeapRegionRemSet* const rset = region->rem_set(); 2789 return G1EagerReclaimHumongousObjectsWithStaleRefs 2790 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2791 : rset->is_empty(); 2792 } 2793 2794 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2795 assert(region->is_starts_humongous(), "Must start a humongous object"); 2796 2797 oop obj = oop(region->bottom()); 2798 2799 // Dead objects cannot be eager reclaim candidates. Due to class 2800 // unloading it is unsafe to query their classes so we return early. 2801 if (heap->is_obj_dead(obj, region)) { 2802 return false; 2803 } 2804 2805 // Candidate selection must satisfy the following constraints 2806 // while concurrent marking is in progress: 2807 // 2808 // * In order to maintain SATB invariants, an object must not be 2809 // reclaimed if it was allocated before the start of marking and 2810 // has not had its references scanned. Such an object must have 2811 // its references (including type metadata) scanned to ensure no 2812 // live objects are missed by the marking process. Objects 2813 // allocated after the start of concurrent marking don't need to 2814 // be scanned. 2815 // 2816 // * An object must not be reclaimed if it is on the concurrent 2817 // mark stack. Objects allocated after the start of concurrent 2818 // marking are never pushed on the mark stack. 2819 // 2820 // Nominating only objects allocated after the start of concurrent 2821 // marking is sufficient to meet both constraints. This may miss 2822 // some objects that satisfy the constraints, but the marking data 2823 // structures don't support efficiently performing the needed 2824 // additional tests or scrubbing of the mark stack. 2825 // 2826 // However, we presently only nominate is_typeArray() objects. 2827 // A humongous object containing references induces remembered 2828 // set entries on other regions. In order to reclaim such an 2829 // object, those remembered sets would need to be cleaned up. 2830 // 2831 // We also treat is_typeArray() objects specially, allowing them 2832 // to be reclaimed even if allocated before the start of 2833 // concurrent mark. For this we rely on mark stack insertion to 2834 // exclude is_typeArray() objects, preventing reclaiming an object 2835 // that is in the mark stack. We also rely on the metadata for 2836 // such objects to be built-in and so ensured to be kept live. 2837 // Frequent allocation and drop of large binary blobs is an 2838 // important use case for eager reclaim, and this special handling 2839 // may reduce needed headroom. 2840 2841 return obj->is_typeArray() && is_remset_small(region); 2842 } 2843 2844 public: 2845 RegisterHumongousWithInCSetFastTestClosure() 2846 : _total_humongous(0), 2847 _candidate_humongous(0), 2848 _dcq(&JavaThread::dirty_card_queue_set()) { 2849 } 2850 2851 virtual bool doHeapRegion(HeapRegion* r) { 2852 if (!r->is_starts_humongous()) { 2853 return false; 2854 } 2855 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2856 2857 bool is_candidate = humongous_region_is_candidate(g1h, r); 2858 uint rindex = r->hrm_index(); 2859 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2860 if (is_candidate) { 2861 _candidate_humongous++; 2862 g1h->register_humongous_region_with_cset(rindex); 2863 // Is_candidate already filters out humongous object with large remembered sets. 2864 // If we have a humongous object with a few remembered sets, we simply flush these 2865 // remembered set entries into the DCQS. That will result in automatic 2866 // re-evaluation of their remembered set entries during the following evacuation 2867 // phase. 2868 if (!r->rem_set()->is_empty()) { 2869 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2870 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2871 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 2872 HeapRegionRemSetIterator hrrs(r->rem_set()); 2873 size_t card_index; 2874 while (hrrs.has_next(card_index)) { 2875 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 2876 // The remembered set might contain references to already freed 2877 // regions. Filter out such entries to avoid failing card table 2878 // verification. 2879 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 2880 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 2881 *card_ptr = CardTableModRefBS::dirty_card_val(); 2882 _dcq.enqueue(card_ptr); 2883 } 2884 } 2885 } 2886 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2887 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2888 hrrs.n_yielded(), r->rem_set()->occupied()); 2889 r->rem_set()->clear_locked(); 2890 } 2891 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2892 } 2893 _total_humongous++; 2894 2895 return false; 2896 } 2897 2898 size_t total_humongous() const { return _total_humongous; } 2899 size_t candidate_humongous() const { return _candidate_humongous; } 2900 2901 void flush_rem_set_entries() { _dcq.flush(); } 2902 }; 2903 2904 void G1CollectedHeap::register_humongous_regions_with_cset() { 2905 if (!G1EagerReclaimHumongousObjects) { 2906 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2907 return; 2908 } 2909 double time = os::elapsed_counter(); 2910 2911 // Collect reclaim candidate information and register candidates with cset. 2912 RegisterHumongousWithInCSetFastTestClosure cl; 2913 heap_region_iterate(&cl); 2914 2915 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2916 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2917 cl.total_humongous(), 2918 cl.candidate_humongous()); 2919 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2920 2921 // Finally flush all remembered set entries to re-check into the global DCQS. 2922 cl.flush_rem_set_entries(); 2923 } 2924 2925 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2926 public: 2927 bool doHeapRegion(HeapRegion* hr) { 2928 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2929 hr->verify_rem_set(); 2930 } 2931 return false; 2932 } 2933 }; 2934 2935 uint G1CollectedHeap::num_task_queues() const { 2936 return _task_queues->size(); 2937 } 2938 2939 #if TASKQUEUE_STATS 2940 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2941 st->print_raw_cr("GC Task Stats"); 2942 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2943 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2944 } 2945 2946 void G1CollectedHeap::print_taskqueue_stats() const { 2947 if (!log_is_enabled(Trace, gc, task, stats)) { 2948 return; 2949 } 2950 Log(gc, task, stats) log; 2951 ResourceMark rm; 2952 outputStream* st = log.trace_stream(); 2953 2954 print_taskqueue_stats_hdr(st); 2955 2956 TaskQueueStats totals; 2957 const uint n = num_task_queues(); 2958 for (uint i = 0; i < n; ++i) { 2959 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2960 totals += task_queue(i)->stats; 2961 } 2962 st->print_raw("tot "); totals.print(st); st->cr(); 2963 2964 DEBUG_ONLY(totals.verify()); 2965 } 2966 2967 void G1CollectedHeap::reset_taskqueue_stats() { 2968 const uint n = num_task_queues(); 2969 for (uint i = 0; i < n; ++i) { 2970 task_queue(i)->stats.reset(); 2971 } 2972 } 2973 #endif // TASKQUEUE_STATS 2974 2975 void G1CollectedHeap::wait_for_root_region_scanning() { 2976 double scan_wait_start = os::elapsedTime(); 2977 // We have to wait until the CM threads finish scanning the 2978 // root regions as it's the only way to ensure that all the 2979 // objects on them have been correctly scanned before we start 2980 // moving them during the GC. 2981 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2982 double wait_time_ms = 0.0; 2983 if (waited) { 2984 double scan_wait_end = os::elapsedTime(); 2985 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2986 } 2987 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2988 } 2989 2990 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2991 private: 2992 G1HRPrinter* _hr_printer; 2993 public: 2994 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2995 2996 virtual bool doHeapRegion(HeapRegion* r) { 2997 _hr_printer->cset(r); 2998 return false; 2999 } 3000 }; 3001 3002 bool 3003 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3004 assert_at_safepoint(true /* should_be_vm_thread */); 3005 guarantee(!is_gc_active(), "collection is not reentrant"); 3006 3007 if (GCLocker::check_active_before_gc()) { 3008 return false; 3009 } 3010 3011 _gc_timer_stw->register_gc_start(); 3012 3013 GCIdMark gc_id_mark; 3014 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3015 3016 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3017 ResourceMark rm; 3018 3019 g1_policy()->note_gc_start(); 3020 3021 wait_for_root_region_scanning(); 3022 3023 print_heap_before_gc(); 3024 print_heap_regions(); 3025 trace_heap_before_gc(_gc_tracer_stw); 3026 3027 _verifier->verify_region_sets_optional(); 3028 _verifier->verify_dirty_young_regions(); 3029 3030 // We should not be doing initial mark unless the conc mark thread is running 3031 if (!_cmThread->should_terminate()) { 3032 // This call will decide whether this pause is an initial-mark 3033 // pause. If it is, during_initial_mark_pause() will return true 3034 // for the duration of this pause. 3035 g1_policy()->decide_on_conc_mark_initiation(); 3036 } 3037 3038 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3039 assert(!collector_state()->during_initial_mark_pause() || 3040 collector_state()->gcs_are_young(), "sanity"); 3041 3042 // We also do not allow mixed GCs during marking. 3043 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3044 3045 // Record whether this pause is an initial mark. When the current 3046 // thread has completed its logging output and it's safe to signal 3047 // the CM thread, the flag's value in the policy has been reset. 3048 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3049 3050 // Inner scope for scope based logging, timers, and stats collection 3051 { 3052 EvacuationInfo evacuation_info; 3053 3054 if (collector_state()->during_initial_mark_pause()) { 3055 // We are about to start a marking cycle, so we increment the 3056 // full collection counter. 3057 increment_old_marking_cycles_started(); 3058 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 3059 } 3060 3061 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3062 3063 GCTraceCPUTime tcpu; 3064 3065 FormatBuffer<> gc_string("Pause "); 3066 if (collector_state()->during_initial_mark_pause()) { 3067 gc_string.append("Initial Mark"); 3068 } else if (collector_state()->gcs_are_young()) { 3069 gc_string.append("Young"); 3070 } else { 3071 gc_string.append("Mixed"); 3072 } 3073 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 3074 3075 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3076 workers()->active_workers(), 3077 Threads::number_of_non_daemon_threads()); 3078 workers()->update_active_workers(active_workers); 3079 3080 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3081 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3082 3083 // If the secondary_free_list is not empty, append it to the 3084 // free_list. No need to wait for the cleanup operation to finish; 3085 // the region allocation code will check the secondary_free_list 3086 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3087 // set, skip this step so that the region allocation code has to 3088 // get entries from the secondary_free_list. 3089 if (!G1StressConcRegionFreeing) { 3090 append_secondary_free_list_if_not_empty_with_lock(); 3091 } 3092 3093 G1HeapTransition heap_transition(this); 3094 size_t heap_used_bytes_before_gc = used(); 3095 3096 // Don't dynamically change the number of GC threads this early. A value of 3097 // 0 is used to indicate serial work. When parallel work is done, 3098 // it will be set. 3099 3100 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3101 IsGCActiveMark x; 3102 3103 gc_prologue(false); 3104 increment_total_collections(false /* full gc */); 3105 increment_gc_time_stamp(); 3106 3107 if (VerifyRememberedSets) { 3108 log_info(gc, verify)("[Verifying RemSets before GC]"); 3109 VerifyRegionRemSetClosure v_cl; 3110 heap_region_iterate(&v_cl); 3111 } 3112 3113 _verifier->verify_before_gc(); 3114 3115 _verifier->check_bitmaps("GC Start"); 3116 3117 #if defined(COMPILER2) || INCLUDE_JVMCI 3118 DerivedPointerTable::clear(); 3119 #endif 3120 3121 // Please see comment in g1CollectedHeap.hpp and 3122 // G1CollectedHeap::ref_processing_init() to see how 3123 // reference processing currently works in G1. 3124 3125 // Enable discovery in the STW reference processor 3126 if (g1_policy()->should_process_references()) { 3127 ref_processor_stw()->enable_discovery(); 3128 } else { 3129 ref_processor_stw()->disable_discovery(); 3130 } 3131 3132 { 3133 // We want to temporarily turn off discovery by the 3134 // CM ref processor, if necessary, and turn it back on 3135 // on again later if we do. Using a scoped 3136 // NoRefDiscovery object will do this. 3137 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3138 3139 // Forget the current alloc region (we might even choose it to be part 3140 // of the collection set!). 3141 _allocator->release_mutator_alloc_region(); 3142 3143 // This timing is only used by the ergonomics to handle our pause target. 3144 // It is unclear why this should not include the full pause. We will 3145 // investigate this in CR 7178365. 3146 // 3147 // Preserving the old comment here if that helps the investigation: 3148 // 3149 // The elapsed time induced by the start time below deliberately elides 3150 // the possible verification above. 3151 double sample_start_time_sec = os::elapsedTime(); 3152 3153 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3154 3155 if (collector_state()->during_initial_mark_pause()) { 3156 concurrent_mark()->checkpointRootsInitialPre(); 3157 } 3158 3159 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 3160 3161 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3162 3163 // Make sure the remembered sets are up to date. This needs to be 3164 // done before register_humongous_regions_with_cset(), because the 3165 // remembered sets are used there to choose eager reclaim candidates. 3166 // If the remembered sets are not up to date we might miss some 3167 // entries that need to be handled. 3168 g1_rem_set()->cleanupHRRS(); 3169 3170 register_humongous_regions_with_cset(); 3171 3172 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3173 3174 _cm->note_start_of_gc(); 3175 // We call this after finalize_cset() to 3176 // ensure that the CSet has been finalized. 3177 _cm->verify_no_cset_oops(); 3178 3179 if (_hr_printer.is_active()) { 3180 G1PrintCollectionSetClosure cl(&_hr_printer); 3181 _collection_set.iterate(&cl); 3182 } 3183 3184 // Initialize the GC alloc regions. 3185 _allocator->init_gc_alloc_regions(evacuation_info); 3186 3187 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3188 pre_evacuate_collection_set(); 3189 3190 // Actually do the work... 3191 evacuate_collection_set(evacuation_info, &per_thread_states); 3192 3193 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3194 3195 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3196 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 3197 3198 eagerly_reclaim_humongous_regions(); 3199 3200 record_obj_copy_mem_stats(); 3201 _survivor_evac_stats.adjust_desired_plab_sz(); 3202 _old_evac_stats.adjust_desired_plab_sz(); 3203 3204 // Start a new incremental collection set for the next pause. 3205 collection_set()->start_incremental_building(); 3206 3207 clear_cset_fast_test(); 3208 3209 guarantee(_eden.length() == 0, "eden should have been cleared"); 3210 g1_policy()->transfer_survivors_to_cset(survivor()); 3211 3212 if (evacuation_failed()) { 3213 set_used(recalculate_used()); 3214 if (_archive_allocator != NULL) { 3215 _archive_allocator->clear_used(); 3216 } 3217 for (uint i = 0; i < ParallelGCThreads; i++) { 3218 if (_evacuation_failed_info_array[i].has_failed()) { 3219 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3220 } 3221 } 3222 } else { 3223 // The "used" of the the collection set have already been subtracted 3224 // when they were freed. Add in the bytes evacuated. 3225 increase_used(g1_policy()->bytes_copied_during_gc()); 3226 } 3227 3228 if (collector_state()->during_initial_mark_pause()) { 3229 // We have to do this before we notify the CM threads that 3230 // they can start working to make sure that all the 3231 // appropriate initialization is done on the CM object. 3232 concurrent_mark()->checkpointRootsInitialPost(); 3233 collector_state()->set_mark_in_progress(true); 3234 // Note that we don't actually trigger the CM thread at 3235 // this point. We do that later when we're sure that 3236 // the current thread has completed its logging output. 3237 } 3238 3239 allocate_dummy_regions(); 3240 3241 _allocator->init_mutator_alloc_region(); 3242 3243 { 3244 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3245 if (expand_bytes > 0) { 3246 size_t bytes_before = capacity(); 3247 // No need for an ergo logging here, 3248 // expansion_amount() does this when it returns a value > 0. 3249 double expand_ms; 3250 if (!expand(expand_bytes, &expand_ms)) { 3251 // We failed to expand the heap. Cannot do anything about it. 3252 } 3253 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3254 } 3255 } 3256 3257 // We redo the verification but now wrt to the new CSet which 3258 // has just got initialized after the previous CSet was freed. 3259 _cm->verify_no_cset_oops(); 3260 _cm->note_end_of_gc(); 3261 3262 // This timing is only used by the ergonomics to handle our pause target. 3263 // It is unclear why this should not include the full pause. We will 3264 // investigate this in CR 7178365. 3265 double sample_end_time_sec = os::elapsedTime(); 3266 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3267 size_t total_cards_scanned = per_thread_states.total_cards_scanned(); 3268 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3269 3270 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3271 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3272 3273 MemoryService::track_memory_usage(); 3274 3275 // In prepare_for_verify() below we'll need to scan the deferred 3276 // update buffers to bring the RSets up-to-date if 3277 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3278 // the update buffers we'll probably need to scan cards on the 3279 // regions we just allocated to (i.e., the GC alloc 3280 // regions). However, during the last GC we called 3281 // set_saved_mark() on all the GC alloc regions, so card 3282 // scanning might skip the [saved_mark_word()...top()] area of 3283 // those regions (i.e., the area we allocated objects into 3284 // during the last GC). But it shouldn't. Given that 3285 // saved_mark_word() is conditional on whether the GC time stamp 3286 // on the region is current or not, by incrementing the GC time 3287 // stamp here we invalidate all the GC time stamps on all the 3288 // regions and saved_mark_word() will simply return top() for 3289 // all the regions. This is a nicer way of ensuring this rather 3290 // than iterating over the regions and fixing them. In fact, the 3291 // GC time stamp increment here also ensures that 3292 // saved_mark_word() will return top() between pauses, i.e., 3293 // during concurrent refinement. So we don't need the 3294 // is_gc_active() check to decided which top to use when 3295 // scanning cards (see CR 7039627). 3296 increment_gc_time_stamp(); 3297 3298 if (VerifyRememberedSets) { 3299 log_info(gc, verify)("[Verifying RemSets after GC]"); 3300 VerifyRegionRemSetClosure v_cl; 3301 heap_region_iterate(&v_cl); 3302 } 3303 3304 _verifier->verify_after_gc(); 3305 _verifier->check_bitmaps("GC End"); 3306 3307 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3308 ref_processor_stw()->verify_no_references_recorded(); 3309 3310 // CM reference discovery will be re-enabled if necessary. 3311 } 3312 3313 #ifdef TRACESPINNING 3314 ParallelTaskTerminator::print_termination_counts(); 3315 #endif 3316 3317 gc_epilogue(false); 3318 } 3319 3320 // Print the remainder of the GC log output. 3321 if (evacuation_failed()) { 3322 log_info(gc)("To-space exhausted"); 3323 } 3324 3325 g1_policy()->print_phases(); 3326 heap_transition.print(); 3327 3328 // It is not yet to safe to tell the concurrent mark to 3329 // start as we have some optional output below. We don't want the 3330 // output from the concurrent mark thread interfering with this 3331 // logging output either. 3332 3333 _hrm.verify_optional(); 3334 _verifier->verify_region_sets_optional(); 3335 3336 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3337 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3338 3339 print_heap_after_gc(); 3340 print_heap_regions(); 3341 trace_heap_after_gc(_gc_tracer_stw); 3342 3343 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3344 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3345 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3346 // before any GC notifications are raised. 3347 g1mm()->update_sizes(); 3348 3349 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3350 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3351 _gc_timer_stw->register_gc_end(); 3352 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3353 } 3354 // It should now be safe to tell the concurrent mark thread to start 3355 // without its logging output interfering with the logging output 3356 // that came from the pause. 3357 3358 if (should_start_conc_mark) { 3359 // CAUTION: after the doConcurrentMark() call below, 3360 // the concurrent marking thread(s) could be running 3361 // concurrently with us. Make sure that anything after 3362 // this point does not assume that we are the only GC thread 3363 // running. Note: of course, the actual marking work will 3364 // not start until the safepoint itself is released in 3365 // SuspendibleThreadSet::desynchronize(). 3366 doConcurrentMark(); 3367 } 3368 3369 return true; 3370 } 3371 3372 void G1CollectedHeap::remove_self_forwarding_pointers() { 3373 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3374 workers()->run_task(&rsfp_task); 3375 } 3376 3377 void G1CollectedHeap::restore_after_evac_failure() { 3378 double remove_self_forwards_start = os::elapsedTime(); 3379 3380 remove_self_forwarding_pointers(); 3381 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3382 _preserved_marks_set.restore(&task_executor); 3383 3384 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3385 } 3386 3387 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3388 if (!_evacuation_failed) { 3389 _evacuation_failed = true; 3390 } 3391 3392 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3393 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3394 } 3395 3396 bool G1ParEvacuateFollowersClosure::offer_termination() { 3397 G1ParScanThreadState* const pss = par_scan_state(); 3398 start_term_time(); 3399 const bool res = terminator()->offer_termination(); 3400 end_term_time(); 3401 return res; 3402 } 3403 3404 void G1ParEvacuateFollowersClosure::do_void() { 3405 G1ParScanThreadState* const pss = par_scan_state(); 3406 pss->trim_queue(); 3407 do { 3408 pss->steal_and_trim_queue(queues()); 3409 } while (!offer_termination()); 3410 } 3411 3412 class G1ParTask : public AbstractGangTask { 3413 protected: 3414 G1CollectedHeap* _g1h; 3415 G1ParScanThreadStateSet* _pss; 3416 RefToScanQueueSet* _queues; 3417 G1RootProcessor* _root_processor; 3418 ParallelTaskTerminator _terminator; 3419 uint _n_workers; 3420 3421 public: 3422 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3423 : AbstractGangTask("G1 collection"), 3424 _g1h(g1h), 3425 _pss(per_thread_states), 3426 _queues(task_queues), 3427 _root_processor(root_processor), 3428 _terminator(n_workers, _queues), 3429 _n_workers(n_workers) 3430 {} 3431 3432 void work(uint worker_id) { 3433 if (worker_id >= _n_workers) return; // no work needed this round 3434 3435 double start_sec = os::elapsedTime(); 3436 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3437 3438 { 3439 ResourceMark rm; 3440 HandleMark hm; 3441 3442 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3443 3444 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3445 pss->set_ref_processor(rp); 3446 3447 double start_strong_roots_sec = os::elapsedTime(); 3448 3449 _root_processor->evacuate_roots(pss->closures(), worker_id); 3450 3451 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss); 3452 3453 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3454 // treating the nmethods visited to act as roots for concurrent marking. 3455 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3456 // objects copied by the current evacuation. 3457 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl, 3458 pss->closures()->weak_codeblobs(), 3459 worker_id); 3460 3461 _pss->add_cards_scanned(worker_id, cards_scanned); 3462 3463 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3464 3465 double term_sec = 0.0; 3466 size_t evac_term_attempts = 0; 3467 { 3468 double start = os::elapsedTime(); 3469 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3470 evac.do_void(); 3471 3472 evac_term_attempts = evac.term_attempts(); 3473 term_sec = evac.term_time(); 3474 double elapsed_sec = os::elapsedTime() - start; 3475 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3476 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3477 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3478 } 3479 3480 assert(pss->queue_is_empty(), "should be empty"); 3481 3482 if (log_is_enabled(Debug, gc, task, stats)) { 3483 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3484 size_t lab_waste; 3485 size_t lab_undo_waste; 3486 pss->waste(lab_waste, lab_undo_waste); 3487 _g1h->print_termination_stats(worker_id, 3488 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3489 strong_roots_sec * 1000.0, /* strong roots time */ 3490 term_sec * 1000.0, /* evac term time */ 3491 evac_term_attempts, /* evac term attempts */ 3492 lab_waste, /* alloc buffer waste */ 3493 lab_undo_waste /* undo waste */ 3494 ); 3495 } 3496 3497 // Close the inner scope so that the ResourceMark and HandleMark 3498 // destructors are executed here and are included as part of the 3499 // "GC Worker Time". 3500 } 3501 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3502 } 3503 }; 3504 3505 void G1CollectedHeap::print_termination_stats_hdr() { 3506 log_debug(gc, task, stats)("GC Termination Stats"); 3507 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3508 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3509 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3510 } 3511 3512 void G1CollectedHeap::print_termination_stats(uint worker_id, 3513 double elapsed_ms, 3514 double strong_roots_ms, 3515 double term_ms, 3516 size_t term_attempts, 3517 size_t alloc_buffer_waste, 3518 size_t undo_waste) const { 3519 log_debug(gc, task, stats) 3520 ("%3d %9.2f %9.2f %6.2f " 3521 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3522 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3523 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3524 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3525 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3526 alloc_buffer_waste * HeapWordSize / K, 3527 undo_waste * HeapWordSize / K); 3528 } 3529 3530 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 3531 private: 3532 BoolObjectClosure* _is_alive; 3533 int _initial_string_table_size; 3534 int _initial_symbol_table_size; 3535 3536 bool _process_strings; 3537 int _strings_processed; 3538 int _strings_removed; 3539 3540 bool _process_symbols; 3541 int _symbols_processed; 3542 int _symbols_removed; 3543 3544 public: 3545 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 3546 AbstractGangTask("String/Symbol Unlinking"), 3547 _is_alive(is_alive), 3548 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3549 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 3550 3551 _initial_string_table_size = StringTable::the_table()->table_size(); 3552 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3553 if (process_strings) { 3554 StringTable::clear_parallel_claimed_index(); 3555 } 3556 if (process_symbols) { 3557 SymbolTable::clear_parallel_claimed_index(); 3558 } 3559 } 3560 3561 ~G1StringSymbolTableUnlinkTask() { 3562 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3563 "claim value %d after unlink less than initial string table size %d", 3564 StringTable::parallel_claimed_index(), _initial_string_table_size); 3565 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3566 "claim value %d after unlink less than initial symbol table size %d", 3567 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3568 3569 log_info(gc, stringtable)( 3570 "Cleaned string and symbol table, " 3571 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3572 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3573 strings_processed(), strings_removed(), 3574 symbols_processed(), symbols_removed()); 3575 } 3576 3577 void work(uint worker_id) { 3578 int strings_processed = 0; 3579 int strings_removed = 0; 3580 int symbols_processed = 0; 3581 int symbols_removed = 0; 3582 if (_process_strings) { 3583 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3584 Atomic::add(strings_processed, &_strings_processed); 3585 Atomic::add(strings_removed, &_strings_removed); 3586 } 3587 if (_process_symbols) { 3588 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3589 Atomic::add(symbols_processed, &_symbols_processed); 3590 Atomic::add(symbols_removed, &_symbols_removed); 3591 } 3592 } 3593 3594 size_t strings_processed() const { return (size_t)_strings_processed; } 3595 size_t strings_removed() const { return (size_t)_strings_removed; } 3596 3597 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3598 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3599 }; 3600 3601 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3602 private: 3603 static Monitor* _lock; 3604 3605 BoolObjectClosure* const _is_alive; 3606 const bool _unloading_occurred; 3607 const uint _num_workers; 3608 3609 // Variables used to claim nmethods. 3610 CompiledMethod* _first_nmethod; 3611 volatile CompiledMethod* _claimed_nmethod; 3612 3613 // The list of nmethods that need to be processed by the second pass. 3614 volatile CompiledMethod* _postponed_list; 3615 volatile uint _num_entered_barrier; 3616 3617 public: 3618 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3619 _is_alive(is_alive), 3620 _unloading_occurred(unloading_occurred), 3621 _num_workers(num_workers), 3622 _first_nmethod(NULL), 3623 _claimed_nmethod(NULL), 3624 _postponed_list(NULL), 3625 _num_entered_barrier(0) 3626 { 3627 CompiledMethod::increase_unloading_clock(); 3628 // Get first alive nmethod 3629 CompiledMethodIterator iter = CompiledMethodIterator(); 3630 if(iter.next_alive()) { 3631 _first_nmethod = iter.method(); 3632 } 3633 _claimed_nmethod = (volatile CompiledMethod*)_first_nmethod; 3634 } 3635 3636 ~G1CodeCacheUnloadingTask() { 3637 CodeCache::verify_clean_inline_caches(); 3638 3639 CodeCache::set_needs_cache_clean(false); 3640 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3641 3642 CodeCache::verify_icholder_relocations(); 3643 } 3644 3645 private: 3646 void add_to_postponed_list(CompiledMethod* nm) { 3647 CompiledMethod* old; 3648 do { 3649 old = (CompiledMethod*)_postponed_list; 3650 nm->set_unloading_next(old); 3651 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 3652 } 3653 3654 void clean_nmethod(CompiledMethod* nm) { 3655 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3656 3657 if (postponed) { 3658 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3659 add_to_postponed_list(nm); 3660 } 3661 3662 // Mark that this thread has been cleaned/unloaded. 3663 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3664 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3665 } 3666 3667 void clean_nmethod_postponed(CompiledMethod* nm) { 3668 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3669 } 3670 3671 static const int MaxClaimNmethods = 16; 3672 3673 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3674 CompiledMethod* first; 3675 CompiledMethodIterator last; 3676 3677 do { 3678 *num_claimed_nmethods = 0; 3679 3680 first = (CompiledMethod*)_claimed_nmethod; 3681 last = CompiledMethodIterator(first); 3682 3683 if (first != NULL) { 3684 3685 for (int i = 0; i < MaxClaimNmethods; i++) { 3686 if (!last.next_alive()) { 3687 break; 3688 } 3689 claimed_nmethods[i] = last.method(); 3690 (*num_claimed_nmethods)++; 3691 } 3692 } 3693 3694 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 3695 } 3696 3697 CompiledMethod* claim_postponed_nmethod() { 3698 CompiledMethod* claim; 3699 CompiledMethod* next; 3700 3701 do { 3702 claim = (CompiledMethod*)_postponed_list; 3703 if (claim == NULL) { 3704 return NULL; 3705 } 3706 3707 next = claim->unloading_next(); 3708 3709 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 3710 3711 return claim; 3712 } 3713 3714 public: 3715 // Mark that we're done with the first pass of nmethod cleaning. 3716 void barrier_mark(uint worker_id) { 3717 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3718 _num_entered_barrier++; 3719 if (_num_entered_barrier == _num_workers) { 3720 ml.notify_all(); 3721 } 3722 } 3723 3724 // See if we have to wait for the other workers to 3725 // finish their first-pass nmethod cleaning work. 3726 void barrier_wait(uint worker_id) { 3727 if (_num_entered_barrier < _num_workers) { 3728 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3729 while (_num_entered_barrier < _num_workers) { 3730 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3731 } 3732 } 3733 } 3734 3735 // Cleaning and unloading of nmethods. Some work has to be postponed 3736 // to the second pass, when we know which nmethods survive. 3737 void work_first_pass(uint worker_id) { 3738 // The first nmethods is claimed by the first worker. 3739 if (worker_id == 0 && _first_nmethod != NULL) { 3740 clean_nmethod(_first_nmethod); 3741 _first_nmethod = NULL; 3742 } 3743 3744 int num_claimed_nmethods; 3745 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3746 3747 while (true) { 3748 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3749 3750 if (num_claimed_nmethods == 0) { 3751 break; 3752 } 3753 3754 for (int i = 0; i < num_claimed_nmethods; i++) { 3755 clean_nmethod(claimed_nmethods[i]); 3756 } 3757 } 3758 } 3759 3760 void work_second_pass(uint worker_id) { 3761 CompiledMethod* nm; 3762 // Take care of postponed nmethods. 3763 while ((nm = claim_postponed_nmethod()) != NULL) { 3764 clean_nmethod_postponed(nm); 3765 } 3766 } 3767 }; 3768 3769 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3770 3771 class G1KlassCleaningTask : public StackObj { 3772 BoolObjectClosure* _is_alive; 3773 volatile jint _clean_klass_tree_claimed; 3774 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3775 3776 public: 3777 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3778 _is_alive(is_alive), 3779 _clean_klass_tree_claimed(0), 3780 _klass_iterator() { 3781 } 3782 3783 private: 3784 bool claim_clean_klass_tree_task() { 3785 if (_clean_klass_tree_claimed) { 3786 return false; 3787 } 3788 3789 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 3790 } 3791 3792 InstanceKlass* claim_next_klass() { 3793 Klass* klass; 3794 do { 3795 klass =_klass_iterator.next_klass(); 3796 } while (klass != NULL && !klass->is_instance_klass()); 3797 3798 // this can be null so don't call InstanceKlass::cast 3799 return static_cast<InstanceKlass*>(klass); 3800 } 3801 3802 public: 3803 3804 void clean_klass(InstanceKlass* ik) { 3805 ik->clean_weak_instanceklass_links(_is_alive); 3806 } 3807 3808 void work() { 3809 ResourceMark rm; 3810 3811 // One worker will clean the subklass/sibling klass tree. 3812 if (claim_clean_klass_tree_task()) { 3813 Klass::clean_subklass_tree(_is_alive); 3814 } 3815 3816 // All workers will help cleaning the classes, 3817 InstanceKlass* klass; 3818 while ((klass = claim_next_klass()) != NULL) { 3819 clean_klass(klass); 3820 } 3821 } 3822 }; 3823 3824 // To minimize the remark pause times, the tasks below are done in parallel. 3825 class G1ParallelCleaningTask : public AbstractGangTask { 3826 private: 3827 G1StringSymbolTableUnlinkTask _string_symbol_task; 3828 G1CodeCacheUnloadingTask _code_cache_task; 3829 G1KlassCleaningTask _klass_cleaning_task; 3830 3831 public: 3832 // The constructor is run in the VMThread. 3833 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 3834 AbstractGangTask("Parallel Cleaning"), 3835 _string_symbol_task(is_alive, process_strings, process_symbols), 3836 _code_cache_task(num_workers, is_alive, unloading_occurred), 3837 _klass_cleaning_task(is_alive) { 3838 } 3839 3840 // The parallel work done by all worker threads. 3841 void work(uint worker_id) { 3842 // Do first pass of code cache cleaning. 3843 _code_cache_task.work_first_pass(worker_id); 3844 3845 // Let the threads mark that the first pass is done. 3846 _code_cache_task.barrier_mark(worker_id); 3847 3848 // Clean the Strings and Symbols. 3849 _string_symbol_task.work(worker_id); 3850 3851 // Wait for all workers to finish the first code cache cleaning pass. 3852 _code_cache_task.barrier_wait(worker_id); 3853 3854 // Do the second code cache cleaning work, which realize on 3855 // the liveness information gathered during the first pass. 3856 _code_cache_task.work_second_pass(worker_id); 3857 3858 // Clean all klasses that were not unloaded. 3859 _klass_cleaning_task.work(); 3860 } 3861 }; 3862 3863 3864 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 3865 bool process_strings, 3866 bool process_symbols, 3867 bool class_unloading_occurred) { 3868 uint n_workers = workers()->active_workers(); 3869 3870 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 3871 n_workers, class_unloading_occurred); 3872 workers()->run_task(&g1_unlink_task); 3873 } 3874 3875 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 3876 bool process_strings, bool process_symbols) { 3877 { // Timing scope 3878 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 3879 workers()->run_task(&g1_unlink_task); 3880 } 3881 } 3882 3883 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3884 private: 3885 DirtyCardQueueSet* _queue; 3886 G1CollectedHeap* _g1h; 3887 public: 3888 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3889 _queue(queue), _g1h(g1h) { } 3890 3891 virtual void work(uint worker_id) { 3892 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3893 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3894 3895 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3896 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3897 3898 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3899 } 3900 }; 3901 3902 void G1CollectedHeap::redirty_logged_cards() { 3903 double redirty_logged_cards_start = os::elapsedTime(); 3904 3905 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3906 dirty_card_queue_set().reset_for_par_iteration(); 3907 workers()->run_task(&redirty_task); 3908 3909 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 3910 dcq.merge_bufferlists(&dirty_card_queue_set()); 3911 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3912 3913 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3914 } 3915 3916 // Weak Reference Processing support 3917 3918 // An always "is_alive" closure that is used to preserve referents. 3919 // If the object is non-null then it's alive. Used in the preservation 3920 // of referent objects that are pointed to by reference objects 3921 // discovered by the CM ref processor. 3922 class G1AlwaysAliveClosure: public BoolObjectClosure { 3923 G1CollectedHeap* _g1; 3924 public: 3925 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3926 bool do_object_b(oop p) { 3927 if (p != NULL) { 3928 return true; 3929 } 3930 return false; 3931 } 3932 }; 3933 3934 bool G1STWIsAliveClosure::do_object_b(oop p) { 3935 // An object is reachable if it is outside the collection set, 3936 // or is inside and copied. 3937 return !_g1->is_in_cset(p) || p->is_forwarded(); 3938 } 3939 3940 // Non Copying Keep Alive closure 3941 class G1KeepAliveClosure: public OopClosure { 3942 G1CollectedHeap* _g1; 3943 public: 3944 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3945 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3946 void do_oop(oop* p) { 3947 oop obj = *p; 3948 assert(obj != NULL, "the caller should have filtered out NULL values"); 3949 3950 const InCSetState cset_state = _g1->in_cset_state(obj); 3951 if (!cset_state.is_in_cset_or_humongous()) { 3952 return; 3953 } 3954 if (cset_state.is_in_cset()) { 3955 assert( obj->is_forwarded(), "invariant" ); 3956 *p = obj->forwardee(); 3957 } else { 3958 assert(!obj->is_forwarded(), "invariant" ); 3959 assert(cset_state.is_humongous(), 3960 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3961 _g1->set_humongous_is_live(obj); 3962 } 3963 } 3964 }; 3965 3966 // Copying Keep Alive closure - can be called from both 3967 // serial and parallel code as long as different worker 3968 // threads utilize different G1ParScanThreadState instances 3969 // and different queues. 3970 3971 class G1CopyingKeepAliveClosure: public OopClosure { 3972 G1CollectedHeap* _g1h; 3973 OopClosure* _copy_non_heap_obj_cl; 3974 G1ParScanThreadState* _par_scan_state; 3975 3976 public: 3977 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3978 OopClosure* non_heap_obj_cl, 3979 G1ParScanThreadState* pss): 3980 _g1h(g1h), 3981 _copy_non_heap_obj_cl(non_heap_obj_cl), 3982 _par_scan_state(pss) 3983 {} 3984 3985 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3986 virtual void do_oop( oop* p) { do_oop_work(p); } 3987 3988 template <class T> void do_oop_work(T* p) { 3989 oop obj = oopDesc::load_decode_heap_oop(p); 3990 3991 if (_g1h->is_in_cset_or_humongous(obj)) { 3992 // If the referent object has been forwarded (either copied 3993 // to a new location or to itself in the event of an 3994 // evacuation failure) then we need to update the reference 3995 // field and, if both reference and referent are in the G1 3996 // heap, update the RSet for the referent. 3997 // 3998 // If the referent has not been forwarded then we have to keep 3999 // it alive by policy. Therefore we have copy the referent. 4000 // 4001 // If the reference field is in the G1 heap then we can push 4002 // on the PSS queue. When the queue is drained (after each 4003 // phase of reference processing) the object and it's followers 4004 // will be copied, the reference field set to point to the 4005 // new location, and the RSet updated. Otherwise we need to 4006 // use the the non-heap or metadata closures directly to copy 4007 // the referent object and update the pointer, while avoiding 4008 // updating the RSet. 4009 4010 if (_g1h->is_in_g1_reserved(p)) { 4011 _par_scan_state->push_on_queue(p); 4012 } else { 4013 assert(!Metaspace::contains((const void*)p), 4014 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4015 _copy_non_heap_obj_cl->do_oop(p); 4016 } 4017 } 4018 } 4019 }; 4020 4021 // Serial drain queue closure. Called as the 'complete_gc' 4022 // closure for each discovered list in some of the 4023 // reference processing phases. 4024 4025 class G1STWDrainQueueClosure: public VoidClosure { 4026 protected: 4027 G1CollectedHeap* _g1h; 4028 G1ParScanThreadState* _par_scan_state; 4029 4030 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4031 4032 public: 4033 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4034 _g1h(g1h), 4035 _par_scan_state(pss) 4036 { } 4037 4038 void do_void() { 4039 G1ParScanThreadState* const pss = par_scan_state(); 4040 pss->trim_queue(); 4041 } 4042 }; 4043 4044 // Parallel Reference Processing closures 4045 4046 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4047 // processing during G1 evacuation pauses. 4048 4049 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4050 private: 4051 G1CollectedHeap* _g1h; 4052 G1ParScanThreadStateSet* _pss; 4053 RefToScanQueueSet* _queues; 4054 WorkGang* _workers; 4055 uint _active_workers; 4056 4057 public: 4058 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4059 G1ParScanThreadStateSet* per_thread_states, 4060 WorkGang* workers, 4061 RefToScanQueueSet *task_queues, 4062 uint n_workers) : 4063 _g1h(g1h), 4064 _pss(per_thread_states), 4065 _queues(task_queues), 4066 _workers(workers), 4067 _active_workers(n_workers) 4068 { 4069 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 4070 } 4071 4072 // Executes the given task using concurrent marking worker threads. 4073 virtual void execute(ProcessTask& task); 4074 virtual void execute(EnqueueTask& task); 4075 }; 4076 4077 // Gang task for possibly parallel reference processing 4078 4079 class G1STWRefProcTaskProxy: public AbstractGangTask { 4080 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4081 ProcessTask& _proc_task; 4082 G1CollectedHeap* _g1h; 4083 G1ParScanThreadStateSet* _pss; 4084 RefToScanQueueSet* _task_queues; 4085 ParallelTaskTerminator* _terminator; 4086 4087 public: 4088 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4089 G1CollectedHeap* g1h, 4090 G1ParScanThreadStateSet* per_thread_states, 4091 RefToScanQueueSet *task_queues, 4092 ParallelTaskTerminator* terminator) : 4093 AbstractGangTask("Process reference objects in parallel"), 4094 _proc_task(proc_task), 4095 _g1h(g1h), 4096 _pss(per_thread_states), 4097 _task_queues(task_queues), 4098 _terminator(terminator) 4099 {} 4100 4101 virtual void work(uint worker_id) { 4102 // The reference processing task executed by a single worker. 4103 ResourceMark rm; 4104 HandleMark hm; 4105 4106 G1STWIsAliveClosure is_alive(_g1h); 4107 4108 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4109 pss->set_ref_processor(NULL); 4110 4111 // Keep alive closure. 4112 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4113 4114 // Complete GC closure 4115 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4116 4117 // Call the reference processing task's work routine. 4118 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4119 4120 // Note we cannot assert that the refs array is empty here as not all 4121 // of the processing tasks (specifically phase2 - pp2_work) execute 4122 // the complete_gc closure (which ordinarily would drain the queue) so 4123 // the queue may not be empty. 4124 } 4125 }; 4126 4127 // Driver routine for parallel reference processing. 4128 // Creates an instance of the ref processing gang 4129 // task and has the worker threads execute it. 4130 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4131 assert(_workers != NULL, "Need parallel worker threads."); 4132 4133 ParallelTaskTerminator terminator(_active_workers, _queues); 4134 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4135 4136 _workers->run_task(&proc_task_proxy); 4137 } 4138 4139 // Gang task for parallel reference enqueueing. 4140 4141 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4142 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4143 EnqueueTask& _enq_task; 4144 4145 public: 4146 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4147 AbstractGangTask("Enqueue reference objects in parallel"), 4148 _enq_task(enq_task) 4149 { } 4150 4151 virtual void work(uint worker_id) { 4152 _enq_task.work(worker_id); 4153 } 4154 }; 4155 4156 // Driver routine for parallel reference enqueueing. 4157 // Creates an instance of the ref enqueueing gang 4158 // task and has the worker threads execute it. 4159 4160 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4161 assert(_workers != NULL, "Need parallel worker threads."); 4162 4163 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4164 4165 _workers->run_task(&enq_task_proxy); 4166 } 4167 4168 // End of weak reference support closures 4169 4170 // Abstract task used to preserve (i.e. copy) any referent objects 4171 // that are in the collection set and are pointed to by reference 4172 // objects discovered by the CM ref processor. 4173 4174 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4175 protected: 4176 G1CollectedHeap* _g1h; 4177 G1ParScanThreadStateSet* _pss; 4178 RefToScanQueueSet* _queues; 4179 ParallelTaskTerminator _terminator; 4180 uint _n_workers; 4181 4182 public: 4183 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4184 AbstractGangTask("ParPreserveCMReferents"), 4185 _g1h(g1h), 4186 _pss(per_thread_states), 4187 _queues(task_queues), 4188 _terminator(workers, _queues), 4189 _n_workers(workers) 4190 { 4191 g1h->ref_processor_cm()->set_active_mt_degree(workers); 4192 } 4193 4194 void work(uint worker_id) { 4195 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4196 4197 ResourceMark rm; 4198 HandleMark hm; 4199 4200 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4201 pss->set_ref_processor(NULL); 4202 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4203 4204 // Is alive closure 4205 G1AlwaysAliveClosure always_alive(_g1h); 4206 4207 // Copying keep alive closure. Applied to referent objects that need 4208 // to be copied. 4209 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4210 4211 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4212 4213 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4214 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4215 4216 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4217 // So this must be true - but assert just in case someone decides to 4218 // change the worker ids. 4219 assert(worker_id < limit, "sanity"); 4220 assert(!rp->discovery_is_atomic(), "check this code"); 4221 4222 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4223 for (uint idx = worker_id; idx < limit; idx += stride) { 4224 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4225 4226 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4227 while (iter.has_next()) { 4228 // Since discovery is not atomic for the CM ref processor, we 4229 // can see some null referent objects. 4230 iter.load_ptrs(DEBUG_ONLY(true)); 4231 oop ref = iter.obj(); 4232 4233 // This will filter nulls. 4234 if (iter.is_referent_alive()) { 4235 iter.make_referent_alive(); 4236 } 4237 iter.move_to_next(); 4238 } 4239 } 4240 4241 // Drain the queue - which may cause stealing 4242 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4243 drain_queue.do_void(); 4244 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4245 assert(pss->queue_is_empty(), "should be"); 4246 } 4247 }; 4248 4249 void G1CollectedHeap::process_weak_jni_handles() { 4250 double ref_proc_start = os::elapsedTime(); 4251 4252 G1STWIsAliveClosure is_alive(this); 4253 G1KeepAliveClosure keep_alive(this); 4254 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 4255 4256 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4257 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4258 } 4259 4260 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4261 // Any reference objects, in the collection set, that were 'discovered' 4262 // by the CM ref processor should have already been copied (either by 4263 // applying the external root copy closure to the discovered lists, or 4264 // by following an RSet entry). 4265 // 4266 // But some of the referents, that are in the collection set, that these 4267 // reference objects point to may not have been copied: the STW ref 4268 // processor would have seen that the reference object had already 4269 // been 'discovered' and would have skipped discovering the reference, 4270 // but would not have treated the reference object as a regular oop. 4271 // As a result the copy closure would not have been applied to the 4272 // referent object. 4273 // 4274 // We need to explicitly copy these referent objects - the references 4275 // will be processed at the end of remarking. 4276 // 4277 // We also need to do this copying before we process the reference 4278 // objects discovered by the STW ref processor in case one of these 4279 // referents points to another object which is also referenced by an 4280 // object discovered by the STW ref processor. 4281 double preserve_cm_referents_time = 0.0; 4282 4283 // To avoid spawning task when there is no work to do, check that 4284 // a concurrent cycle is active and that some references have been 4285 // discovered. 4286 if (concurrent_mark()->cmThread()->during_cycle() && 4287 ref_processor_cm()->has_discovered_references()) { 4288 double preserve_cm_referents_start = os::elapsedTime(); 4289 uint no_of_gc_workers = workers()->active_workers(); 4290 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4291 per_thread_states, 4292 no_of_gc_workers, 4293 _task_queues); 4294 workers()->run_task(&keep_cm_referents); 4295 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4296 } 4297 4298 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4299 } 4300 4301 // Weak Reference processing during an evacuation pause (part 1). 4302 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4303 double ref_proc_start = os::elapsedTime(); 4304 4305 ReferenceProcessor* rp = _ref_processor_stw; 4306 assert(rp->discovery_enabled(), "should have been enabled"); 4307 4308 // Closure to test whether a referent is alive. 4309 G1STWIsAliveClosure is_alive(this); 4310 4311 // Even when parallel reference processing is enabled, the processing 4312 // of JNI refs is serial and performed serially by the current thread 4313 // rather than by a worker. The following PSS will be used for processing 4314 // JNI refs. 4315 4316 // Use only a single queue for this PSS. 4317 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4318 pss->set_ref_processor(NULL); 4319 assert(pss->queue_is_empty(), "pre-condition"); 4320 4321 // Keep alive closure. 4322 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4323 4324 // Serial Complete GC closure 4325 G1STWDrainQueueClosure drain_queue(this, pss); 4326 4327 // Setup the soft refs policy... 4328 rp->setup_policy(false); 4329 4330 ReferenceProcessorStats stats; 4331 if (!rp->processing_is_mt()) { 4332 // Serial reference processing... 4333 stats = rp->process_discovered_references(&is_alive, 4334 &keep_alive, 4335 &drain_queue, 4336 NULL, 4337 _gc_timer_stw); 4338 } else { 4339 uint no_of_gc_workers = workers()->active_workers(); 4340 4341 // Parallel reference processing 4342 assert(no_of_gc_workers <= rp->max_num_q(), 4343 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4344 no_of_gc_workers, rp->max_num_q()); 4345 4346 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4347 stats = rp->process_discovered_references(&is_alive, 4348 &keep_alive, 4349 &drain_queue, 4350 &par_task_executor, 4351 _gc_timer_stw); 4352 } 4353 4354 _gc_tracer_stw->report_gc_reference_stats(stats); 4355 4356 // We have completed copying any necessary live referent objects. 4357 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4358 4359 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4360 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4361 } 4362 4363 // Weak Reference processing during an evacuation pause (part 2). 4364 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4365 double ref_enq_start = os::elapsedTime(); 4366 4367 ReferenceProcessor* rp = _ref_processor_stw; 4368 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4369 4370 // Now enqueue any remaining on the discovered lists on to 4371 // the pending list. 4372 if (!rp->processing_is_mt()) { 4373 // Serial reference processing... 4374 rp->enqueue_discovered_references(); 4375 } else { 4376 // Parallel reference enqueueing 4377 4378 uint n_workers = workers()->active_workers(); 4379 4380 assert(n_workers <= rp->max_num_q(), 4381 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4382 n_workers, rp->max_num_q()); 4383 4384 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4385 rp->enqueue_discovered_references(&par_task_executor); 4386 } 4387 4388 rp->verify_no_references_recorded(); 4389 assert(!rp->discovery_enabled(), "should have been disabled"); 4390 4391 // FIXME 4392 // CM's reference processing also cleans up the string and symbol tables. 4393 // Should we do that here also? We could, but it is a serial operation 4394 // and could significantly increase the pause time. 4395 4396 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4397 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4398 } 4399 4400 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4401 double merge_pss_time_start = os::elapsedTime(); 4402 per_thread_states->flush(); 4403 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4404 } 4405 4406 void G1CollectedHeap::pre_evacuate_collection_set() { 4407 _expand_heap_after_alloc_failure = true; 4408 _evacuation_failed = false; 4409 4410 // Disable the hot card cache. 4411 _hot_card_cache->reset_hot_cache_claimed_index(); 4412 _hot_card_cache->set_use_cache(false); 4413 4414 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4415 _preserved_marks_set.assert_empty(); 4416 } 4417 4418 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4419 // Should G1EvacuationFailureALot be in effect for this GC? 4420 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4421 4422 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4423 double start_par_time_sec = os::elapsedTime(); 4424 double end_par_time_sec; 4425 4426 { 4427 const uint n_workers = workers()->active_workers(); 4428 G1RootProcessor root_processor(this, n_workers); 4429 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4430 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4431 if (collector_state()->during_initial_mark_pause()) { 4432 ClassLoaderDataGraph::clear_claimed_marks(); 4433 } 4434 4435 print_termination_stats_hdr(); 4436 4437 workers()->run_task(&g1_par_task); 4438 end_par_time_sec = os::elapsedTime(); 4439 4440 // Closing the inner scope will execute the destructor 4441 // for the G1RootProcessor object. We record the current 4442 // elapsed time before closing the scope so that time 4443 // taken for the destructor is NOT included in the 4444 // reported parallel time. 4445 } 4446 4447 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4448 4449 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4450 phase_times->record_par_time(par_time_ms); 4451 4452 double code_root_fixup_time_ms = 4453 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4454 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4455 } 4456 4457 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4458 // Process any discovered reference objects - we have 4459 // to do this _before_ we retire the GC alloc regions 4460 // as we may have to copy some 'reachable' referent 4461 // objects (and their reachable sub-graphs) that were 4462 // not copied during the pause. 4463 if (g1_policy()->should_process_references()) { 4464 preserve_cm_referents(per_thread_states); 4465 process_discovered_references(per_thread_states); 4466 } else { 4467 ref_processor_stw()->verify_no_references_recorded(); 4468 process_weak_jni_handles(); 4469 } 4470 4471 if (G1StringDedup::is_enabled()) { 4472 double fixup_start = os::elapsedTime(); 4473 4474 G1STWIsAliveClosure is_alive(this); 4475 G1KeepAliveClosure keep_alive(this); 4476 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4477 4478 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4479 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4480 } 4481 4482 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4483 4484 if (evacuation_failed()) { 4485 restore_after_evac_failure(); 4486 4487 // Reset the G1EvacuationFailureALot counters and flags 4488 // Note: the values are reset only when an actual 4489 // evacuation failure occurs. 4490 NOT_PRODUCT(reset_evacuation_should_fail();) 4491 } 4492 4493 _preserved_marks_set.assert_empty(); 4494 4495 // Enqueue any remaining references remaining on the STW 4496 // reference processor's discovered lists. We need to do 4497 // this after the card table is cleaned (and verified) as 4498 // the act of enqueueing entries on to the pending list 4499 // will log these updates (and dirty their associated 4500 // cards). We need these updates logged to update any 4501 // RSets. 4502 if (g1_policy()->should_process_references()) { 4503 enqueue_discovered_references(per_thread_states); 4504 } else { 4505 g1_policy()->phase_times()->record_ref_enq_time(0); 4506 } 4507 4508 _allocator->release_gc_alloc_regions(evacuation_info); 4509 4510 merge_per_thread_state_info(per_thread_states); 4511 4512 // Reset and re-enable the hot card cache. 4513 // Note the counts for the cards in the regions in the 4514 // collection set are reset when the collection set is freed. 4515 _hot_card_cache->reset_hot_cache(); 4516 _hot_card_cache->set_use_cache(true); 4517 4518 purge_code_root_memory(); 4519 4520 redirty_logged_cards(); 4521 #if defined(COMPILER2) || INCLUDE_JVMCI 4522 DerivedPointerTable::update_pointers(); 4523 #endif 4524 } 4525 4526 void G1CollectedHeap::record_obj_copy_mem_stats() { 4527 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4528 4529 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4530 create_g1_evac_summary(&_old_evac_stats)); 4531 } 4532 4533 void G1CollectedHeap::free_region(HeapRegion* hr, 4534 FreeRegionList* free_list, 4535 bool skip_remset, 4536 bool skip_hot_card_cache, 4537 bool locked) { 4538 assert(!hr->is_free(), "the region should not be free"); 4539 assert(!hr->is_empty(), "the region should not be empty"); 4540 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4541 assert(free_list != NULL, "pre-condition"); 4542 4543 if (G1VerifyBitmaps) { 4544 MemRegion mr(hr->bottom(), hr->end()); 4545 concurrent_mark()->clearRangePrevBitmap(mr); 4546 } 4547 4548 // Clear the card counts for this region. 4549 // Note: we only need to do this if the region is not young 4550 // (since we don't refine cards in young regions). 4551 if (!skip_hot_card_cache && !hr->is_young()) { 4552 _hot_card_cache->reset_card_counts(hr); 4553 } 4554 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4555 free_list->add_ordered(hr); 4556 } 4557 4558 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4559 FreeRegionList* free_list, 4560 bool skip_remset) { 4561 assert(hr->is_humongous(), "this is only for humongous regions"); 4562 assert(free_list != NULL, "pre-condition"); 4563 hr->clear_humongous(); 4564 free_region(hr, free_list, skip_remset); 4565 } 4566 4567 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4568 const uint humongous_regions_removed) { 4569 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4570 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4571 _old_set.bulk_remove(old_regions_removed); 4572 _humongous_set.bulk_remove(humongous_regions_removed); 4573 } 4574 4575 } 4576 4577 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4578 assert(list != NULL, "list can't be null"); 4579 if (!list->is_empty()) { 4580 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4581 _hrm.insert_list_into_free_list(list); 4582 } 4583 } 4584 4585 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4586 decrease_used(bytes); 4587 } 4588 4589 class G1ParScrubRemSetTask: public AbstractGangTask { 4590 protected: 4591 G1RemSet* _g1rs; 4592 HeapRegionClaimer _hrclaimer; 4593 4594 public: 4595 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) : 4596 AbstractGangTask("G1 ScrubRS"), 4597 _g1rs(g1_rs), 4598 _hrclaimer(num_workers) { 4599 } 4600 4601 void work(uint worker_id) { 4602 _g1rs->scrub(worker_id, &_hrclaimer); 4603 } 4604 }; 4605 4606 void G1CollectedHeap::scrub_rem_set() { 4607 uint num_workers = workers()->active_workers(); 4608 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers); 4609 workers()->run_task(&g1_par_scrub_rs_task); 4610 } 4611 4612 class G1FreeCollectionSetTask : public AbstractGangTask { 4613 private: 4614 4615 // Closure applied to all regions in the collection set to do work that needs to 4616 // be done serially in a single thread. 4617 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4618 private: 4619 EvacuationInfo* _evacuation_info; 4620 const size_t* _surviving_young_words; 4621 4622 // Bytes used in successfully evacuated regions before the evacuation. 4623 size_t _before_used_bytes; 4624 // Bytes used in unsucessfully evacuated regions before the evacuation 4625 size_t _after_used_bytes; 4626 4627 size_t _bytes_allocated_in_old_since_last_gc; 4628 4629 size_t _failure_used_words; 4630 size_t _failure_waste_words; 4631 4632 FreeRegionList _local_free_list; 4633 public: 4634 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4635 HeapRegionClosure(), 4636 _evacuation_info(evacuation_info), 4637 _surviving_young_words(surviving_young_words), 4638 _before_used_bytes(0), 4639 _after_used_bytes(0), 4640 _bytes_allocated_in_old_since_last_gc(0), 4641 _failure_used_words(0), 4642 _failure_waste_words(0), 4643 _local_free_list("Local Region List for CSet Freeing") { 4644 } 4645 4646 virtual bool doHeapRegion(HeapRegion* r) { 4647 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4648 4649 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4650 g1h->clear_in_cset(r); 4651 4652 if (r->is_young()) { 4653 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4654 "Young index %d is wrong for region %u of type %s with %u young regions", 4655 r->young_index_in_cset(), 4656 r->hrm_index(), 4657 r->get_type_str(), 4658 g1h->collection_set()->young_region_length()); 4659 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4660 r->record_surv_words_in_group(words_survived); 4661 } 4662 4663 if (!r->evacuation_failed()) { 4664 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4665 _before_used_bytes += r->used(); 4666 g1h->free_region(r, 4667 &_local_free_list, 4668 true, /* skip_remset */ 4669 true, /* skip_hot_card_cache */ 4670 true /* locked */); 4671 } else { 4672 r->uninstall_surv_rate_group(); 4673 r->set_young_index_in_cset(-1); 4674 r->set_evacuation_failed(false); 4675 // When moving a young gen region to old gen, we "allocate" that whole region 4676 // there. This is in addition to any already evacuated objects. Notify the 4677 // policy about that. 4678 // Old gen regions do not cause an additional allocation: both the objects 4679 // still in the region and the ones already moved are accounted for elsewhere. 4680 if (r->is_young()) { 4681 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4682 } 4683 // The region is now considered to be old. 4684 r->set_old(); 4685 // Do some allocation statistics accounting. Regions that failed evacuation 4686 // are always made old, so there is no need to update anything in the young 4687 // gen statistics, but we need to update old gen statistics. 4688 size_t used_words = r->marked_bytes() / HeapWordSize; 4689 4690 _failure_used_words += used_words; 4691 _failure_waste_words += HeapRegion::GrainWords - used_words; 4692 4693 g1h->old_set_add(r); 4694 _after_used_bytes += r->used(); 4695 } 4696 return false; 4697 } 4698 4699 void complete_work() { 4700 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4701 4702 _evacuation_info->set_regions_freed(_local_free_list.length()); 4703 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4704 4705 g1h->prepend_to_freelist(&_local_free_list); 4706 g1h->decrement_summary_bytes(_before_used_bytes); 4707 4708 G1Policy* policy = g1h->g1_policy(); 4709 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4710 4711 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4712 } 4713 }; 4714 4715 G1CollectionSet* _collection_set; 4716 G1SerialFreeCollectionSetClosure _cl; 4717 const size_t* _surviving_young_words; 4718 4719 size_t _rs_lengths; 4720 4721 volatile jint _serial_work_claim; 4722 4723 struct WorkItem { 4724 uint region_idx; 4725 bool is_young; 4726 bool evacuation_failed; 4727 4728 WorkItem(HeapRegion* r) { 4729 region_idx = r->hrm_index(); 4730 is_young = r->is_young(); 4731 evacuation_failed = r->evacuation_failed(); 4732 } 4733 }; 4734 4735 volatile size_t _parallel_work_claim; 4736 size_t _num_work_items; 4737 WorkItem* _work_items; 4738 4739 void do_serial_work() { 4740 // Need to grab the lock to be allowed to modify the old region list. 4741 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4742 _collection_set->iterate(&_cl); 4743 } 4744 4745 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4746 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4747 4748 HeapRegion* r = g1h->region_at(region_idx); 4749 assert(!g1h->is_on_master_free_list(r), "sanity"); 4750 4751 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4752 4753 if (!is_young) { 4754 g1h->_hot_card_cache->reset_card_counts(r); 4755 } 4756 4757 if (!evacuation_failed) { 4758 r->rem_set()->clear_locked(); 4759 } 4760 } 4761 4762 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4763 private: 4764 size_t _cur_idx; 4765 WorkItem* _work_items; 4766 public: 4767 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4768 4769 virtual bool doHeapRegion(HeapRegion* r) { 4770 _work_items[_cur_idx++] = WorkItem(r); 4771 return false; 4772 } 4773 }; 4774 4775 void prepare_work() { 4776 G1PrepareFreeCollectionSetClosure cl(_work_items); 4777 _collection_set->iterate(&cl); 4778 } 4779 4780 void complete_work() { 4781 _cl.complete_work(); 4782 4783 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4784 policy->record_max_rs_lengths(_rs_lengths); 4785 policy->cset_regions_freed(); 4786 } 4787 public: 4788 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4789 AbstractGangTask("G1 Free Collection Set"), 4790 _cl(evacuation_info, surviving_young_words), 4791 _collection_set(collection_set), 4792 _surviving_young_words(surviving_young_words), 4793 _serial_work_claim(0), 4794 _rs_lengths(0), 4795 _parallel_work_claim(0), 4796 _num_work_items(collection_set->region_length()), 4797 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4798 prepare_work(); 4799 } 4800 4801 ~G1FreeCollectionSetTask() { 4802 complete_work(); 4803 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4804 } 4805 4806 // Chunk size for work distribution. The chosen value has been determined experimentally 4807 // to be a good tradeoff between overhead and achievable parallelism. 4808 static uint chunk_size() { return 32; } 4809 4810 virtual void work(uint worker_id) { 4811 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4812 4813 // Claim serial work. 4814 if (_serial_work_claim == 0) { 4815 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4816 if (value == 0) { 4817 double serial_time = os::elapsedTime(); 4818 do_serial_work(); 4819 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4820 } 4821 } 4822 4823 // Start parallel work. 4824 double young_time = 0.0; 4825 bool has_young_time = false; 4826 double non_young_time = 0.0; 4827 bool has_non_young_time = false; 4828 4829 while (true) { 4830 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4831 size_t cur = end - chunk_size(); 4832 4833 if (cur >= _num_work_items) { 4834 break; 4835 } 4836 4837 double start_time = os::elapsedTime(); 4838 4839 end = MIN2(end, _num_work_items); 4840 4841 for (; cur < end; cur++) { 4842 bool is_young = _work_items[cur].is_young; 4843 4844 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4845 4846 double end_time = os::elapsedTime(); 4847 double time_taken = end_time - start_time; 4848 if (is_young) { 4849 young_time += time_taken; 4850 has_young_time = true; 4851 } else { 4852 non_young_time += time_taken; 4853 has_non_young_time = true; 4854 } 4855 start_time = end_time; 4856 } 4857 } 4858 4859 if (has_young_time) { 4860 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4861 } 4862 if (has_non_young_time) { 4863 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time); 4864 } 4865 } 4866 }; 4867 4868 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4869 _eden.clear(); 4870 4871 double free_cset_start_time = os::elapsedTime(); 4872 4873 { 4874 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4875 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4876 4877 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4878 4879 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4880 cl.name(), 4881 num_workers, 4882 _collection_set.region_length()); 4883 workers()->run_task(&cl, num_workers); 4884 } 4885 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4886 4887 collection_set->clear(); 4888 } 4889 4890 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4891 private: 4892 FreeRegionList* _free_region_list; 4893 HeapRegionSet* _proxy_set; 4894 uint _humongous_regions_removed; 4895 size_t _freed_bytes; 4896 public: 4897 4898 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4899 _free_region_list(free_region_list), _humongous_regions_removed(0), _freed_bytes(0) { 4900 } 4901 4902 virtual bool doHeapRegion(HeapRegion* r) { 4903 if (!r->is_starts_humongous()) { 4904 return false; 4905 } 4906 4907 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4908 4909 oop obj = (oop)r->bottom(); 4910 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 4911 4912 // The following checks whether the humongous object is live are sufficient. 4913 // The main additional check (in addition to having a reference from the roots 4914 // or the young gen) is whether the humongous object has a remembered set entry. 4915 // 4916 // A humongous object cannot be live if there is no remembered set for it 4917 // because: 4918 // - there can be no references from within humongous starts regions referencing 4919 // the object because we never allocate other objects into them. 4920 // (I.e. there are no intra-region references that may be missed by the 4921 // remembered set) 4922 // - as soon there is a remembered set entry to the humongous starts region 4923 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4924 // until the end of a concurrent mark. 4925 // 4926 // It is not required to check whether the object has been found dead by marking 4927 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4928 // all objects allocated during that time are considered live. 4929 // SATB marking is even more conservative than the remembered set. 4930 // So if at this point in the collection there is no remembered set entry, 4931 // nobody has a reference to it. 4932 // At the start of collection we flush all refinement logs, and remembered sets 4933 // are completely up-to-date wrt to references to the humongous object. 4934 // 4935 // Other implementation considerations: 4936 // - never consider object arrays at this time because they would pose 4937 // considerable effort for cleaning up the the remembered sets. This is 4938 // required because stale remembered sets might reference locations that 4939 // are currently allocated into. 4940 uint region_idx = r->hrm_index(); 4941 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4942 !r->rem_set()->is_empty()) { 4943 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", 4944 region_idx, 4945 (size_t)obj->size() * HeapWordSize, 4946 p2i(r->bottom()), 4947 r->rem_set()->occupied(), 4948 r->rem_set()->strong_code_roots_list_length(), 4949 next_bitmap->isMarked(r->bottom()), 4950 g1h->is_humongous_reclaim_candidate(region_idx), 4951 obj->is_typeArray() 4952 ); 4953 return false; 4954 } 4955 4956 guarantee(obj->is_typeArray(), 4957 "Only eagerly reclaiming type arrays is supported, but the object " 4958 PTR_FORMAT " is not.", p2i(r->bottom())); 4959 4960 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", 4961 region_idx, 4962 (size_t)obj->size() * HeapWordSize, 4963 p2i(r->bottom()), 4964 r->rem_set()->occupied(), 4965 r->rem_set()->strong_code_roots_list_length(), 4966 next_bitmap->isMarked(r->bottom()), 4967 g1h->is_humongous_reclaim_candidate(region_idx), 4968 obj->is_typeArray() 4969 ); 4970 4971 // Need to clear mark bit of the humongous object if already set. 4972 if (next_bitmap->isMarked(r->bottom())) { 4973 next_bitmap->clear(r->bottom()); 4974 } 4975 do { 4976 HeapRegion* next = g1h->next_region_in_humongous(r); 4977 _freed_bytes += r->used(); 4978 r->set_containing_set(NULL); 4979 _humongous_regions_removed++; 4980 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ ); 4981 r = next; 4982 } while (r != NULL); 4983 4984 return false; 4985 } 4986 4987 uint humongous_free_count() { 4988 return _humongous_regions_removed; 4989 } 4990 4991 size_t bytes_freed() const { 4992 return _freed_bytes; 4993 } 4994 }; 4995 4996 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4997 assert_at_safepoint(true); 4998 4999 if (!G1EagerReclaimHumongousObjects || 5000 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 5001 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5002 return; 5003 } 5004 5005 double start_time = os::elapsedTime(); 5006 5007 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5008 5009 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5010 heap_region_iterate(&cl); 5011 5012 remove_from_old_sets(0, cl.humongous_free_count()); 5013 5014 G1HRPrinter* hrp = hr_printer(); 5015 if (hrp->is_active()) { 5016 FreeRegionListIterator iter(&local_cleanup_list); 5017 while (iter.more_available()) { 5018 HeapRegion* hr = iter.get_next(); 5019 hrp->cleanup(hr); 5020 } 5021 } 5022 5023 prepend_to_freelist(&local_cleanup_list); 5024 decrement_summary_bytes(cl.bytes_freed()); 5025 5026 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5027 cl.humongous_free_count()); 5028 } 5029 5030 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 5031 public: 5032 virtual bool doHeapRegion(HeapRegion* r) { 5033 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 5034 G1CollectedHeap::heap()->clear_in_cset(r); 5035 r->set_young_index_in_cset(-1); 5036 return false; 5037 } 5038 }; 5039 5040 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 5041 G1AbandonCollectionSetClosure cl; 5042 collection_set->iterate(&cl); 5043 5044 collection_set->clear(); 5045 collection_set->stop_incremental_building(); 5046 } 5047 5048 void G1CollectedHeap::set_free_regions_coming() { 5049 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 5050 5051 assert(!free_regions_coming(), "pre-condition"); 5052 _free_regions_coming = true; 5053 } 5054 5055 void G1CollectedHeap::reset_free_regions_coming() { 5056 assert(free_regions_coming(), "pre-condition"); 5057 5058 { 5059 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5060 _free_regions_coming = false; 5061 SecondaryFreeList_lock->notify_all(); 5062 } 5063 5064 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 5065 } 5066 5067 void G1CollectedHeap::wait_while_free_regions_coming() { 5068 // Most of the time we won't have to wait, so let's do a quick test 5069 // first before we take the lock. 5070 if (!free_regions_coming()) { 5071 return; 5072 } 5073 5074 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 5075 5076 { 5077 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5078 while (free_regions_coming()) { 5079 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5080 } 5081 } 5082 5083 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 5084 } 5085 5086 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5087 return _allocator->is_retained_old_region(hr); 5088 } 5089 5090 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5091 _eden.add(hr); 5092 _g1_policy->set_region_eden(hr); 5093 } 5094 5095 #ifdef ASSERT 5096 5097 class NoYoungRegionsClosure: public HeapRegionClosure { 5098 private: 5099 bool _success; 5100 public: 5101 NoYoungRegionsClosure() : _success(true) { } 5102 bool doHeapRegion(HeapRegion* r) { 5103 if (r->is_young()) { 5104 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5105 p2i(r->bottom()), p2i(r->end())); 5106 _success = false; 5107 } 5108 return false; 5109 } 5110 bool success() { return _success; } 5111 }; 5112 5113 bool G1CollectedHeap::check_young_list_empty() { 5114 bool ret = (young_regions_count() == 0); 5115 5116 NoYoungRegionsClosure closure; 5117 heap_region_iterate(&closure); 5118 ret = ret && closure.success(); 5119 5120 return ret; 5121 } 5122 5123 #endif // ASSERT 5124 5125 class TearDownRegionSetsClosure : public HeapRegionClosure { 5126 private: 5127 HeapRegionSet *_old_set; 5128 5129 public: 5130 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5131 5132 bool doHeapRegion(HeapRegion* r) { 5133 if (r->is_old()) { 5134 _old_set->remove(r); 5135 } else if(r->is_young()) { 5136 r->uninstall_surv_rate_group(); 5137 } else { 5138 // We ignore free regions, we'll empty the free list afterwards. 5139 // We ignore humongous regions, we're not tearing down the 5140 // humongous regions set. 5141 assert(r->is_free() || r->is_humongous(), 5142 "it cannot be another type"); 5143 } 5144 return false; 5145 } 5146 5147 ~TearDownRegionSetsClosure() { 5148 assert(_old_set->is_empty(), "post-condition"); 5149 } 5150 }; 5151 5152 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5153 assert_at_safepoint(true /* should_be_vm_thread */); 5154 5155 if (!free_list_only) { 5156 TearDownRegionSetsClosure cl(&_old_set); 5157 heap_region_iterate(&cl); 5158 5159 // Note that emptying the _young_list is postponed and instead done as 5160 // the first step when rebuilding the regions sets again. The reason for 5161 // this is that during a full GC string deduplication needs to know if 5162 // a collected region was young or old when the full GC was initiated. 5163 } 5164 _hrm.remove_all_free_regions(); 5165 } 5166 5167 void G1CollectedHeap::increase_used(size_t bytes) { 5168 _summary_bytes_used += bytes; 5169 } 5170 5171 void G1CollectedHeap::decrease_used(size_t bytes) { 5172 assert(_summary_bytes_used >= bytes, 5173 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5174 _summary_bytes_used, bytes); 5175 _summary_bytes_used -= bytes; 5176 } 5177 5178 void G1CollectedHeap::set_used(size_t bytes) { 5179 _summary_bytes_used = bytes; 5180 } 5181 5182 class RebuildRegionSetsClosure : public HeapRegionClosure { 5183 private: 5184 bool _free_list_only; 5185 HeapRegionSet* _old_set; 5186 HeapRegionManager* _hrm; 5187 size_t _total_used; 5188 5189 public: 5190 RebuildRegionSetsClosure(bool free_list_only, 5191 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5192 _free_list_only(free_list_only), 5193 _old_set(old_set), _hrm(hrm), _total_used(0) { 5194 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5195 if (!free_list_only) { 5196 assert(_old_set->is_empty(), "pre-condition"); 5197 } 5198 } 5199 5200 bool doHeapRegion(HeapRegion* r) { 5201 if (r->is_empty()) { 5202 // Add free regions to the free list 5203 r->set_free(); 5204 r->set_allocation_context(AllocationContext::system()); 5205 _hrm->insert_into_free_list(r); 5206 } else if (!_free_list_only) { 5207 5208 if (r->is_humongous()) { 5209 // We ignore humongous regions. We left the humongous set unchanged. 5210 } else { 5211 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 5212 // We now consider all regions old, so register as such. Leave 5213 // archive regions set that way, however, while still adding 5214 // them to the old set. 5215 if (!r->is_archive()) { 5216 r->set_old(); 5217 } 5218 _old_set->add(r); 5219 } 5220 _total_used += r->used(); 5221 } 5222 5223 return false; 5224 } 5225 5226 size_t total_used() { 5227 return _total_used; 5228 } 5229 }; 5230 5231 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5232 assert_at_safepoint(true /* should_be_vm_thread */); 5233 5234 if (!free_list_only) { 5235 _eden.clear(); 5236 _survivor.clear(); 5237 } 5238 5239 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5240 heap_region_iterate(&cl); 5241 5242 if (!free_list_only) { 5243 set_used(cl.total_used()); 5244 if (_archive_allocator != NULL) { 5245 _archive_allocator->clear_used(); 5246 } 5247 } 5248 assert(used_unlocked() == recalculate_used(), 5249 "inconsistent used_unlocked(), " 5250 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5251 used_unlocked(), recalculate_used()); 5252 } 5253 5254 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 5255 _refine_cte_cl->set_concurrent(concurrent); 5256 } 5257 5258 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5259 HeapRegion* hr = heap_region_containing(p); 5260 return hr->is_in(p); 5261 } 5262 5263 // Methods for the mutator alloc region 5264 5265 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5266 bool force) { 5267 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5268 assert(!force || g1_policy()->can_expand_young_list(), 5269 "if force is true we should be able to expand the young list"); 5270 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 5271 if (force || should_allocate) { 5272 HeapRegion* new_alloc_region = new_region(word_size, 5273 false /* is_old */, 5274 false /* do_expand */); 5275 if (new_alloc_region != NULL) { 5276 set_region_short_lived_locked(new_alloc_region); 5277 _hr_printer.alloc(new_alloc_region, !should_allocate); 5278 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5279 return new_alloc_region; 5280 } 5281 } 5282 return NULL; 5283 } 5284 5285 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5286 size_t allocated_bytes) { 5287 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5288 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5289 5290 collection_set()->add_eden_region(alloc_region); 5291 increase_used(allocated_bytes); 5292 _hr_printer.retire(alloc_region); 5293 // We update the eden sizes here, when the region is retired, 5294 // instead of when it's allocated, since this is the point that its 5295 // used space has been recored in _summary_bytes_used. 5296 g1mm()->update_eden_size(); 5297 } 5298 5299 // Methods for the GC alloc regions 5300 5301 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 5302 if (dest.is_old()) { 5303 return true; 5304 } else { 5305 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 5306 } 5307 } 5308 5309 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 5310 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5311 5312 if (!has_more_regions(dest)) { 5313 return NULL; 5314 } 5315 5316 const bool is_survivor = dest.is_young(); 5317 5318 HeapRegion* new_alloc_region = new_region(word_size, 5319 !is_survivor, 5320 true /* do_expand */); 5321 if (new_alloc_region != NULL) { 5322 // We really only need to do this for old regions given that we 5323 // should never scan survivors. But it doesn't hurt to do it 5324 // for survivors too. 5325 new_alloc_region->record_timestamp(); 5326 if (is_survivor) { 5327 new_alloc_region->set_survivor(); 5328 _survivor.add(new_alloc_region); 5329 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5330 } else { 5331 new_alloc_region->set_old(); 5332 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5333 } 5334 _hr_printer.alloc(new_alloc_region); 5335 bool during_im = collector_state()->during_initial_mark_pause(); 5336 new_alloc_region->note_start_of_copying(during_im); 5337 return new_alloc_region; 5338 } 5339 return NULL; 5340 } 5341 5342 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5343 size_t allocated_bytes, 5344 InCSetState dest) { 5345 bool during_im = collector_state()->during_initial_mark_pause(); 5346 alloc_region->note_end_of_copying(during_im); 5347 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5348 if (dest.is_old()) { 5349 _old_set.add(alloc_region); 5350 } 5351 _hr_printer.retire(alloc_region); 5352 } 5353 5354 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5355 bool expanded = false; 5356 uint index = _hrm.find_highest_free(&expanded); 5357 5358 if (index != G1_NO_HRM_INDEX) { 5359 if (expanded) { 5360 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5361 HeapRegion::GrainWords * HeapWordSize); 5362 } 5363 _hrm.allocate_free_regions_starting_at(index, 1); 5364 return region_at(index); 5365 } 5366 return NULL; 5367 } 5368 5369 // Optimized nmethod scanning 5370 5371 class RegisterNMethodOopClosure: public OopClosure { 5372 G1CollectedHeap* _g1h; 5373 nmethod* _nm; 5374 5375 template <class T> void do_oop_work(T* p) { 5376 T heap_oop = oopDesc::load_heap_oop(p); 5377 if (!oopDesc::is_null(heap_oop)) { 5378 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5379 HeapRegion* hr = _g1h->heap_region_containing(obj); 5380 assert(!hr->is_continues_humongous(), 5381 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5382 " starting at " HR_FORMAT, 5383 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5384 5385 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5386 hr->add_strong_code_root_locked(_nm); 5387 } 5388 } 5389 5390 public: 5391 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5392 _g1h(g1h), _nm(nm) {} 5393 5394 void do_oop(oop* p) { do_oop_work(p); } 5395 void do_oop(narrowOop* p) { do_oop_work(p); } 5396 }; 5397 5398 class UnregisterNMethodOopClosure: public OopClosure { 5399 G1CollectedHeap* _g1h; 5400 nmethod* _nm; 5401 5402 template <class T> void do_oop_work(T* p) { 5403 T heap_oop = oopDesc::load_heap_oop(p); 5404 if (!oopDesc::is_null(heap_oop)) { 5405 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5406 HeapRegion* hr = _g1h->heap_region_containing(obj); 5407 assert(!hr->is_continues_humongous(), 5408 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5409 " starting at " HR_FORMAT, 5410 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5411 5412 hr->remove_strong_code_root(_nm); 5413 } 5414 } 5415 5416 public: 5417 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5418 _g1h(g1h), _nm(nm) {} 5419 5420 void do_oop(oop* p) { do_oop_work(p); } 5421 void do_oop(narrowOop* p) { do_oop_work(p); } 5422 }; 5423 5424 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5425 CollectedHeap::register_nmethod(nm); 5426 5427 guarantee(nm != NULL, "sanity"); 5428 RegisterNMethodOopClosure reg_cl(this, nm); 5429 nm->oops_do(®_cl); 5430 } 5431 5432 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5433 CollectedHeap::unregister_nmethod(nm); 5434 5435 guarantee(nm != NULL, "sanity"); 5436 UnregisterNMethodOopClosure reg_cl(this, nm); 5437 nm->oops_do(®_cl, true); 5438 } 5439 5440 void G1CollectedHeap::purge_code_root_memory() { 5441 double purge_start = os::elapsedTime(); 5442 G1CodeRootSet::purge(); 5443 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5444 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5445 } 5446 5447 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5448 G1CollectedHeap* _g1h; 5449 5450 public: 5451 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5452 _g1h(g1h) {} 5453 5454 void do_code_blob(CodeBlob* cb) { 5455 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5456 if (nm == NULL) { 5457 return; 5458 } 5459 5460 if (ScavengeRootsInCode) { 5461 _g1h->register_nmethod(nm); 5462 } 5463 } 5464 }; 5465 5466 void G1CollectedHeap::rebuild_strong_code_roots() { 5467 RebuildStrongCodeRootClosure blob_cl(this); 5468 CodeCache::blobs_do(&blob_cl); 5469 }