1 /* 2 * Copyright (c) 2001, 2017, 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/heapMonitoring.hpp" 79 #include "runtime/init.hpp" 80 #include "runtime/orderAccess.inline.hpp" 81 #include "runtime/vmThread.hpp" 82 #include "utilities/globalDefinitions.hpp" 83 #include "utilities/stack.inline.hpp" 84 85 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 86 87 // INVARIANTS/NOTES 88 // 89 // All allocation activity covered by the G1CollectedHeap interface is 90 // serialized by acquiring the HeapLock. This happens in mem_allocate 91 // and allocate_new_tlab, which are the "entry" points to the 92 // allocation code from the rest of the JVM. (Note that this does not 93 // apply to TLAB allocation, which is not part of this interface: it 94 // is done by clients of this interface.) 95 96 // Local to this file. 97 98 class RefineCardTableEntryClosure: public CardTableEntryClosure { 99 bool _concurrent; 100 public: 101 RefineCardTableEntryClosure() : _concurrent(true) { } 102 103 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 104 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, NULL); 105 // This path is executed by the concurrent refine or mutator threads, 106 // concurrently, and so we do not care if card_ptr contains references 107 // that point into the collection set. 108 assert(!oops_into_cset, "should be"); 109 110 if (_concurrent && SuspendibleThreadSet::should_yield()) { 111 // Caller will actually yield. 112 return false; 113 } 114 // Otherwise, we finished successfully; return true. 115 return true; 116 } 117 118 void set_concurrent(bool b) { _concurrent = b; } 119 }; 120 121 122 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 123 private: 124 size_t _num_dirtied; 125 G1CollectedHeap* _g1h; 126 G1SATBCardTableLoggingModRefBS* _g1_bs; 127 128 HeapRegion* region_for_card(jbyte* card_ptr) const { 129 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 130 } 131 132 bool will_become_free(HeapRegion* hr) const { 133 // A region will be freed by free_collection_set if the region is in the 134 // collection set and has not had an evacuation failure. 135 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 136 } 137 138 public: 139 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 140 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 141 142 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 143 HeapRegion* hr = region_for_card(card_ptr); 144 145 // Should only dirty cards in regions that won't be freed. 146 if (!will_become_free(hr)) { 147 *card_ptr = CardTableModRefBS::dirty_card_val(); 148 _num_dirtied++; 149 } 150 151 return true; 152 } 153 154 size_t num_dirtied() const { return _num_dirtied; } 155 }; 156 157 158 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 159 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 160 } 161 162 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 163 // The from card cache is not the memory that is actually committed. So we cannot 164 // take advantage of the zero_filled parameter. 165 reset_from_card_cache(start_idx, num_regions); 166 } 167 168 // Returns true if the reference points to an object that 169 // can move in an incremental collection. 170 bool G1CollectedHeap::is_scavengable(const void* p) { 171 HeapRegion* hr = heap_region_containing(p); 172 return !hr->is_pinned(); 173 } 174 175 // Private methods. 176 177 HeapRegion* 178 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 179 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 180 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 181 if (!_secondary_free_list.is_empty()) { 182 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 183 "secondary_free_list has %u entries", 184 _secondary_free_list.length()); 185 // It looks as if there are free regions available on the 186 // secondary_free_list. Let's move them to the free_list and try 187 // again to allocate from it. 188 append_secondary_free_list(); 189 190 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 191 "empty we should have moved at least one entry to the free_list"); 192 HeapRegion* res = _hrm.allocate_free_region(is_old); 193 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 194 "allocated " HR_FORMAT " from secondary_free_list", 195 HR_FORMAT_PARAMS(res)); 196 return res; 197 } 198 199 // Wait here until we get notified either when (a) there are no 200 // more free regions coming or (b) some regions have been moved on 201 // the secondary_free_list. 202 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 203 } 204 205 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 206 "could not allocate from secondary_free_list"); 207 return NULL; 208 } 209 210 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 211 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 212 "the only time we use this to allocate a humongous region is " 213 "when we are allocating a single humongous region"); 214 215 HeapRegion* res; 216 if (G1StressConcRegionFreeing) { 217 if (!_secondary_free_list.is_empty()) { 218 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 219 "forced to look at the secondary_free_list"); 220 res = new_region_try_secondary_free_list(is_old); 221 if (res != NULL) { 222 return res; 223 } 224 } 225 } 226 227 res = _hrm.allocate_free_region(is_old); 228 229 if (res == NULL) { 230 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 231 "res == NULL, trying the secondary_free_list"); 232 res = new_region_try_secondary_free_list(is_old); 233 } 234 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 235 // Currently, only attempts to allocate GC alloc regions set 236 // do_expand to true. So, we should only reach here during a 237 // safepoint. If this assumption changes we might have to 238 // reconsider the use of _expand_heap_after_alloc_failure. 239 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 240 241 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 242 word_size * HeapWordSize); 243 244 if (expand(word_size * HeapWordSize)) { 245 // Given that expand() succeeded in expanding the heap, and we 246 // always expand the heap by an amount aligned to the heap 247 // region size, the free list should in theory not be empty. 248 // In either case allocate_free_region() will check for NULL. 249 res = _hrm.allocate_free_region(is_old); 250 } else { 251 _expand_heap_after_alloc_failure = false; 252 } 253 } 254 return res; 255 } 256 257 HeapWord* 258 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 259 uint num_regions, 260 size_t word_size, 261 AllocationContext_t context) { 262 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 263 assert(is_humongous(word_size), "word_size should be humongous"); 264 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 265 266 // Index of last region in the series. 267 uint last = first + num_regions - 1; 268 269 // We need to initialize the region(s) we just discovered. This is 270 // a bit tricky given that it can happen concurrently with 271 // refinement threads refining cards on these regions and 272 // potentially wanting to refine the BOT as they are scanning 273 // those cards (this can happen shortly after a cleanup; see CR 274 // 6991377). So we have to set up the region(s) carefully and in 275 // a specific order. 276 277 // The word size sum of all the regions we will allocate. 278 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 279 assert(word_size <= word_size_sum, "sanity"); 280 281 // This will be the "starts humongous" region. 282 HeapRegion* first_hr = region_at(first); 283 // The header of the new object will be placed at the bottom of 284 // the first region. 285 HeapWord* new_obj = first_hr->bottom(); 286 // This will be the new top of the new object. 287 HeapWord* obj_top = new_obj + word_size; 288 289 // First, we need to zero the header of the space that we will be 290 // allocating. When we update top further down, some refinement 291 // threads might try to scan the region. By zeroing the header we 292 // ensure that any thread that will try to scan the region will 293 // come across the zero klass word and bail out. 294 // 295 // NOTE: It would not have been correct to have used 296 // CollectedHeap::fill_with_object() and make the space look like 297 // an int array. The thread that is doing the allocation will 298 // later update the object header to a potentially different array 299 // type and, for a very short period of time, the klass and length 300 // fields will be inconsistent. This could cause a refinement 301 // thread to calculate the object size incorrectly. 302 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 303 304 // Next, pad out the unused tail of the last region with filler 305 // objects, for improved usage accounting. 306 // How many words we use for filler objects. 307 size_t word_fill_size = word_size_sum - word_size; 308 309 // How many words memory we "waste" which cannot hold a filler object. 310 size_t words_not_fillable = 0; 311 312 if (word_fill_size >= min_fill_size()) { 313 fill_with_objects(obj_top, word_fill_size); 314 } else if (word_fill_size > 0) { 315 // We have space to fill, but we cannot fit an object there. 316 words_not_fillable = word_fill_size; 317 word_fill_size = 0; 318 } 319 320 // We will set up the first region as "starts humongous". This 321 // will also update the BOT covering all the regions to reflect 322 // that there is a single object that starts at the bottom of the 323 // first region. 324 first_hr->set_starts_humongous(obj_top, word_fill_size); 325 first_hr->set_allocation_context(context); 326 // Then, if there are any, we will set up the "continues 327 // humongous" regions. 328 HeapRegion* hr = NULL; 329 for (uint i = first + 1; i <= last; ++i) { 330 hr = region_at(i); 331 hr->set_continues_humongous(first_hr); 332 hr->set_allocation_context(context); 333 } 334 335 // Up to this point no concurrent thread would have been able to 336 // do any scanning on any region in this series. All the top 337 // fields still point to bottom, so the intersection between 338 // [bottom,top] and [card_start,card_end] will be empty. Before we 339 // update the top fields, we'll do a storestore to make sure that 340 // no thread sees the update to top before the zeroing of the 341 // object header and the BOT initialization. 342 OrderAccess::storestore(); 343 344 // Now, we will update the top fields of the "continues humongous" 345 // regions except the last one. 346 for (uint i = first; i < last; ++i) { 347 hr = region_at(i); 348 hr->set_top(hr->end()); 349 } 350 351 hr = region_at(last); 352 // If we cannot fit a filler object, we must set top to the end 353 // of the humongous object, otherwise we cannot iterate the heap 354 // and the BOT will not be complete. 355 hr->set_top(hr->end() - words_not_fillable); 356 357 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 358 "obj_top should be in last region"); 359 360 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 361 362 assert(words_not_fillable == 0 || 363 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 364 "Miscalculation in humongous allocation"); 365 366 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 367 368 for (uint i = first; i <= last; ++i) { 369 hr = region_at(i); 370 _humongous_set.add(hr); 371 _hr_printer.alloc(hr); 372 } 373 374 return new_obj; 375 } 376 377 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 378 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 379 return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 380 } 381 382 // If could fit into free regions w/o expansion, try. 383 // Otherwise, if can expand, do so. 384 // Otherwise, if using ex regions might help, try with ex given back. 385 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 386 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 387 388 _verifier->verify_region_sets_optional(); 389 390 uint first = G1_NO_HRM_INDEX; 391 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 392 393 if (obj_regions == 1) { 394 // Only one region to allocate, try to use a fast path by directly allocating 395 // from the free lists. Do not try to expand here, we will potentially do that 396 // later. 397 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 398 if (hr != NULL) { 399 first = hr->hrm_index(); 400 } 401 } else { 402 // We can't allocate humongous regions spanning more than one region while 403 // cleanupComplete() is running, since some of the regions we find to be 404 // empty might not yet be added to the free list. It is not straightforward 405 // to know in which list they are on so that we can remove them. We only 406 // need to do this if we need to allocate more than one region to satisfy the 407 // current humongous allocation request. If we are only allocating one region 408 // we use the one-region region allocation code (see above), that already 409 // potentially waits for regions from the secondary free list. 410 wait_while_free_regions_coming(); 411 append_secondary_free_list_if_not_empty_with_lock(); 412 413 // Policy: Try only empty regions (i.e. already committed first). Maybe we 414 // are lucky enough to find some. 415 first = _hrm.find_contiguous_only_empty(obj_regions); 416 if (first != G1_NO_HRM_INDEX) { 417 _hrm.allocate_free_regions_starting_at(first, obj_regions); 418 } 419 } 420 421 if (first == G1_NO_HRM_INDEX) { 422 // Policy: We could not find enough regions for the humongous object in the 423 // free list. Look through the heap to find a mix of free and uncommitted regions. 424 // If so, try expansion. 425 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 426 if (first != G1_NO_HRM_INDEX) { 427 // We found something. Make sure these regions are committed, i.e. expand 428 // the heap. Alternatively we could do a defragmentation GC. 429 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 430 word_size * HeapWordSize); 431 432 _hrm.expand_at(first, obj_regions, workers()); 433 g1_policy()->record_new_heap_size(num_regions()); 434 435 #ifdef ASSERT 436 for (uint i = first; i < first + obj_regions; ++i) { 437 HeapRegion* hr = region_at(i); 438 assert(hr->is_free(), "sanity"); 439 assert(hr->is_empty(), "sanity"); 440 assert(is_on_master_free_list(hr), "sanity"); 441 } 442 #endif 443 _hrm.allocate_free_regions_starting_at(first, obj_regions); 444 } else { 445 // Policy: Potentially trigger a defragmentation GC. 446 } 447 } 448 449 HeapWord* result = NULL; 450 if (first != G1_NO_HRM_INDEX) { 451 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 452 word_size, context); 453 assert(result != NULL, "it should always return a valid result"); 454 455 // A successful humongous object allocation changes the used space 456 // information of the old generation so we need to recalculate the 457 // sizes and update the jstat counters here. 458 g1mm()->update_sizes(); 459 } 460 461 _verifier->verify_region_sets_optional(); 462 463 return result; 464 } 465 466 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 467 assert_heap_not_locked_and_not_at_safepoint(); 468 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 469 470 uint dummy_gc_count_before; 471 uint dummy_gclocker_retry_count = 0; 472 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 473 } 474 475 HeapWord* 476 G1CollectedHeap::mem_allocate(size_t word_size, 477 bool* gc_overhead_limit_was_exceeded) { 478 assert_heap_not_locked_and_not_at_safepoint(); 479 480 // Loop until the allocation is satisfied, or unsatisfied after GC. 481 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 482 uint gc_count_before; 483 484 HeapWord* result = NULL; 485 if (!is_humongous(word_size)) { 486 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 487 } else { 488 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 489 } 490 if (result != NULL) { 491 return result; 492 } 493 494 // Create the garbage collection operation... 495 VM_G1CollectForAllocation op(gc_count_before, word_size); 496 op.set_allocation_context(AllocationContext::current()); 497 498 // ...and get the VM thread to execute it. 499 VMThread::execute(&op); 500 501 if (op.prologue_succeeded() && op.pause_succeeded()) { 502 // If the operation was successful we'll return the result even 503 // if it is NULL. If the allocation attempt failed immediately 504 // after a Full GC, it's unlikely we'll be able to allocate now. 505 HeapWord* result = op.result(); 506 if (result != NULL && !is_humongous(word_size)) { 507 // Allocations that take place on VM operations do not do any 508 // card dirtying and we have to do it here. We only have to do 509 // this for non-humongous allocations, though. 510 dirty_young_block(result, word_size); 511 } 512 return result; 513 } else { 514 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 515 return NULL; 516 } 517 assert(op.result() == NULL, 518 "the result should be NULL if the VM op did not succeed"); 519 } 520 521 // Give a warning if we seem to be looping forever. 522 if ((QueuedAllocationWarningCount > 0) && 523 (try_count % QueuedAllocationWarningCount == 0)) { 524 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count); 525 } 526 } 527 528 ShouldNotReachHere(); 529 return NULL; 530 } 531 532 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 533 AllocationContext_t context, 534 uint* gc_count_before_ret, 535 uint* gclocker_retry_count_ret) { 536 // Make sure you read the note in attempt_allocation_humongous(). 537 538 assert_heap_not_locked_and_not_at_safepoint(); 539 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 540 "be called for humongous allocation requests"); 541 542 // We should only get here after the first-level allocation attempt 543 // (attempt_allocation()) failed to allocate. 544 545 // We will loop until a) we manage to successfully perform the 546 // allocation or b) we successfully schedule a collection which 547 // fails to perform the allocation. b) is the only case when we'll 548 // return NULL. 549 HeapWord* result = NULL; 550 for (int try_count = 1; /* we'll return */; try_count += 1) { 551 bool should_try_gc; 552 uint gc_count_before; 553 554 { 555 MutexLockerEx x(Heap_lock); 556 result = _allocator->attempt_allocation_locked(word_size, context); 557 if (result != NULL) { 558 return result; 559 } 560 561 if (GCLocker::is_active_and_needs_gc()) { 562 if (g1_policy()->can_expand_young_list()) { 563 // No need for an ergo verbose message here, 564 // can_expand_young_list() does this when it returns true. 565 result = _allocator->attempt_allocation_force(word_size, context); 566 if (result != NULL) { 567 return result; 568 } 569 } 570 should_try_gc = false; 571 } else { 572 // The GCLocker may not be active but the GCLocker initiated 573 // GC may not yet have been performed (GCLocker::needs_gc() 574 // returns true). In this case we do not try this GC and 575 // wait until the GCLocker initiated GC is performed, and 576 // then retry the allocation. 577 if (GCLocker::needs_gc()) { 578 should_try_gc = false; 579 } else { 580 // Read the GC count while still holding the Heap_lock. 581 gc_count_before = total_collections(); 582 should_try_gc = true; 583 } 584 } 585 } 586 587 if (should_try_gc) { 588 bool succeeded; 589 result = do_collection_pause(word_size, gc_count_before, &succeeded, 590 GCCause::_g1_inc_collection_pause); 591 if (result != NULL) { 592 assert(succeeded, "only way to get back a non-NULL result"); 593 return result; 594 } 595 596 if (succeeded) { 597 // If we get here we successfully scheduled a collection which 598 // failed to allocate. No point in trying to allocate 599 // further. We'll just return NULL. 600 MutexLockerEx x(Heap_lock); 601 *gc_count_before_ret = total_collections(); 602 return NULL; 603 } 604 } else { 605 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 606 MutexLockerEx x(Heap_lock); 607 *gc_count_before_ret = total_collections(); 608 return NULL; 609 } 610 // The GCLocker is either active or the GCLocker initiated 611 // GC has not yet been performed. Stall until it is and 612 // then retry the allocation. 613 GCLocker::stall_until_clear(); 614 (*gclocker_retry_count_ret) += 1; 615 } 616 617 // We can reach here if we were unsuccessful in scheduling a 618 // collection (because another thread beat us to it) or if we were 619 // stalled due to the GC locker. In either can we should retry the 620 // allocation attempt in case another thread successfully 621 // performed a collection and reclaimed enough space. We do the 622 // first attempt (without holding the Heap_lock) here and the 623 // follow-on attempt will be at the start of the next loop 624 // iteration (after taking the Heap_lock). 625 result = _allocator->attempt_allocation(word_size, context); 626 if (result != NULL) { 627 return result; 628 } 629 630 // Give a warning if we seem to be looping forever. 631 if ((QueuedAllocationWarningCount > 0) && 632 (try_count % QueuedAllocationWarningCount == 0)) { 633 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() " 634 "retries %d times", try_count); 635 } 636 } 637 638 ShouldNotReachHere(); 639 return NULL; 640 } 641 642 void G1CollectedHeap::begin_archive_alloc_range() { 643 assert_at_safepoint(true /* should_be_vm_thread */); 644 if (_archive_allocator == NULL) { 645 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 646 } 647 } 648 649 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 650 // Allocations in archive regions cannot be of a size that would be considered 651 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 652 // may be different at archive-restore time. 653 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 654 } 655 656 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 657 assert_at_safepoint(true /* should_be_vm_thread */); 658 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 659 if (is_archive_alloc_too_large(word_size)) { 660 return NULL; 661 } 662 return _archive_allocator->archive_mem_allocate(word_size); 663 } 664 665 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 666 size_t end_alignment_in_bytes) { 667 assert_at_safepoint(true /* should_be_vm_thread */); 668 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 669 670 // Call complete_archive to do the real work, filling in the MemRegion 671 // array with the archive regions. 672 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 673 delete _archive_allocator; 674 _archive_allocator = NULL; 675 } 676 677 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 678 assert(ranges != NULL, "MemRegion array NULL"); 679 assert(count != 0, "No MemRegions provided"); 680 MemRegion reserved = _hrm.reserved(); 681 for (size_t i = 0; i < count; i++) { 682 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 683 return false; 684 } 685 } 686 return true; 687 } 688 689 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 690 assert(!is_init_completed(), "Expect to be called at JVM init time"); 691 assert(ranges != NULL, "MemRegion array NULL"); 692 assert(count != 0, "No MemRegions provided"); 693 MutexLockerEx x(Heap_lock); 694 695 MemRegion reserved = _hrm.reserved(); 696 HeapWord* prev_last_addr = NULL; 697 HeapRegion* prev_last_region = NULL; 698 699 // Temporarily disable pretouching of heap pages. This interface is used 700 // when mmap'ing archived heap data in, so pre-touching is wasted. 701 FlagSetting fs(AlwaysPreTouch, false); 702 703 // Enable archive object checking used by G1MarkSweep. We have to let it know 704 // about each archive range, so that objects in those ranges aren't marked. 705 G1ArchiveAllocator::enable_archive_object_check(); 706 707 // For each specified MemRegion range, allocate the corresponding G1 708 // regions and mark them as archive regions. We expect the ranges in 709 // ascending starting address order, without overlap. 710 for (size_t i = 0; i < count; i++) { 711 MemRegion curr_range = ranges[i]; 712 HeapWord* start_address = curr_range.start(); 713 size_t word_size = curr_range.word_size(); 714 HeapWord* last_address = curr_range.last(); 715 size_t commits = 0; 716 717 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 718 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 719 p2i(start_address), p2i(last_address)); 720 guarantee(start_address > prev_last_addr, 721 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 722 p2i(start_address), p2i(prev_last_addr)); 723 prev_last_addr = last_address; 724 725 // Check for ranges that start in the same G1 region in which the previous 726 // range ended, and adjust the start address so we don't try to allocate 727 // the same region again. If the current range is entirely within that 728 // region, skip it, just adjusting the recorded top. 729 HeapRegion* start_region = _hrm.addr_to_region(start_address); 730 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 731 start_address = start_region->end(); 732 if (start_address > last_address) { 733 increase_used(word_size * HeapWordSize); 734 start_region->set_top(last_address + 1); 735 continue; 736 } 737 start_region->set_top(start_address); 738 curr_range = MemRegion(start_address, last_address + 1); 739 start_region = _hrm.addr_to_region(start_address); 740 } 741 742 // Perform the actual region allocation, exiting if it fails. 743 // Then note how much new space we have allocated. 744 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 745 return false; 746 } 747 increase_used(word_size * HeapWordSize); 748 if (commits != 0) { 749 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 750 HeapRegion::GrainWords * HeapWordSize * commits); 751 752 } 753 754 // Mark each G1 region touched by the range as archive, add it to the old set, 755 // and set the allocation context and top. 756 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 757 HeapRegion* last_region = _hrm.addr_to_region(last_address); 758 prev_last_region = last_region; 759 760 while (curr_region != NULL) { 761 assert(curr_region->is_empty() && !curr_region->is_pinned(), 762 "Region already in use (index %u)", curr_region->hrm_index()); 763 curr_region->set_allocation_context(AllocationContext::system()); 764 curr_region->set_archive(); 765 _hr_printer.alloc(curr_region); 766 _old_set.add(curr_region); 767 if (curr_region != last_region) { 768 curr_region->set_top(curr_region->end()); 769 curr_region = _hrm.next_region_in_heap(curr_region); 770 } else { 771 curr_region->set_top(last_address + 1); 772 curr_region = NULL; 773 } 774 } 775 776 // Notify mark-sweep of the archive range. 777 G1ArchiveAllocator::set_range_archive(curr_range, true); 778 } 779 return true; 780 } 781 782 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 783 assert(!is_init_completed(), "Expect to be called at JVM init time"); 784 assert(ranges != NULL, "MemRegion array NULL"); 785 assert(count != 0, "No MemRegions provided"); 786 MemRegion reserved = _hrm.reserved(); 787 HeapWord *prev_last_addr = NULL; 788 HeapRegion* prev_last_region = NULL; 789 790 // For each MemRegion, create filler objects, if needed, in the G1 regions 791 // that contain the address range. The address range actually within the 792 // MemRegion will not be modified. That is assumed to have been initialized 793 // elsewhere, probably via an mmap of archived heap data. 794 MutexLockerEx x(Heap_lock); 795 for (size_t i = 0; i < count; i++) { 796 HeapWord* start_address = ranges[i].start(); 797 HeapWord* last_address = ranges[i].last(); 798 799 assert(reserved.contains(start_address) && reserved.contains(last_address), 800 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 801 p2i(start_address), p2i(last_address)); 802 assert(start_address > prev_last_addr, 803 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 804 p2i(start_address), p2i(prev_last_addr)); 805 806 HeapRegion* start_region = _hrm.addr_to_region(start_address); 807 HeapRegion* last_region = _hrm.addr_to_region(last_address); 808 HeapWord* bottom_address = start_region->bottom(); 809 810 // Check for a range beginning in the same region in which the 811 // previous one ended. 812 if (start_region == prev_last_region) { 813 bottom_address = prev_last_addr + 1; 814 } 815 816 // Verify that the regions were all marked as archive regions by 817 // alloc_archive_regions. 818 HeapRegion* curr_region = start_region; 819 while (curr_region != NULL) { 820 guarantee(curr_region->is_archive(), 821 "Expected archive region at index %u", curr_region->hrm_index()); 822 if (curr_region != last_region) { 823 curr_region = _hrm.next_region_in_heap(curr_region); 824 } else { 825 curr_region = NULL; 826 } 827 } 828 829 prev_last_addr = last_address; 830 prev_last_region = last_region; 831 832 // Fill the memory below the allocated range with dummy object(s), 833 // if the region bottom does not match the range start, or if the previous 834 // range ended within the same G1 region, and there is a gap. 835 if (start_address != bottom_address) { 836 size_t fill_size = pointer_delta(start_address, bottom_address); 837 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 838 increase_used(fill_size * HeapWordSize); 839 } 840 } 841 } 842 843 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 844 uint* gc_count_before_ret, 845 uint* gclocker_retry_count_ret) { 846 assert_heap_not_locked_and_not_at_safepoint(); 847 assert(!is_humongous(word_size), "attempt_allocation() should not " 848 "be called for humongous allocation requests"); 849 850 AllocationContext_t context = AllocationContext::current(); 851 HeapWord* result = _allocator->attempt_allocation(word_size, context); 852 853 if (result == NULL) { 854 result = attempt_allocation_slow(word_size, 855 context, 856 gc_count_before_ret, 857 gclocker_retry_count_ret); 858 } 859 assert_heap_not_locked(); 860 if (result != NULL) { 861 dirty_young_block(result, word_size); 862 } 863 return result; 864 } 865 866 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 867 assert(!is_init_completed(), "Expect to be called at JVM init time"); 868 assert(ranges != NULL, "MemRegion array NULL"); 869 assert(count != 0, "No MemRegions provided"); 870 MemRegion reserved = _hrm.reserved(); 871 HeapWord* prev_last_addr = NULL; 872 HeapRegion* prev_last_region = NULL; 873 size_t size_used = 0; 874 size_t uncommitted_regions = 0; 875 876 // For each Memregion, free the G1 regions that constitute it, and 877 // notify mark-sweep that the range is no longer to be considered 'archive.' 878 MutexLockerEx x(Heap_lock); 879 for (size_t i = 0; i < count; i++) { 880 HeapWord* start_address = ranges[i].start(); 881 HeapWord* last_address = ranges[i].last(); 882 883 assert(reserved.contains(start_address) && reserved.contains(last_address), 884 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 885 p2i(start_address), p2i(last_address)); 886 assert(start_address > prev_last_addr, 887 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 888 p2i(start_address), p2i(prev_last_addr)); 889 size_used += ranges[i].byte_size(); 890 prev_last_addr = last_address; 891 892 HeapRegion* start_region = _hrm.addr_to_region(start_address); 893 HeapRegion* last_region = _hrm.addr_to_region(last_address); 894 895 // Check for ranges that start in the same G1 region in which the previous 896 // range ended, and adjust the start address so we don't try to free 897 // the same region again. If the current range is entirely within that 898 // region, skip it. 899 if (start_region == prev_last_region) { 900 start_address = start_region->end(); 901 if (start_address > last_address) { 902 continue; 903 } 904 start_region = _hrm.addr_to_region(start_address); 905 } 906 prev_last_region = last_region; 907 908 // After verifying that each region was marked as an archive region by 909 // alloc_archive_regions, set it free and empty and uncommit it. 910 HeapRegion* curr_region = start_region; 911 while (curr_region != NULL) { 912 guarantee(curr_region->is_archive(), 913 "Expected archive region at index %u", curr_region->hrm_index()); 914 uint curr_index = curr_region->hrm_index(); 915 _old_set.remove(curr_region); 916 curr_region->set_free(); 917 curr_region->set_top(curr_region->bottom()); 918 if (curr_region != last_region) { 919 curr_region = _hrm.next_region_in_heap(curr_region); 920 } else { 921 curr_region = NULL; 922 } 923 _hrm.shrink_at(curr_index, 1); 924 uncommitted_regions++; 925 } 926 927 // Notify mark-sweep that this is no longer an archive range. 928 G1ArchiveAllocator::set_range_archive(ranges[i], false); 929 } 930 931 if (uncommitted_regions != 0) { 932 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 933 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 934 } 935 decrease_used(size_used); 936 } 937 938 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 939 uint* gc_count_before_ret, 940 uint* gclocker_retry_count_ret) { 941 // The structure of this method has a lot of similarities to 942 // attempt_allocation_slow(). The reason these two were not merged 943 // into a single one is that such a method would require several "if 944 // allocation is not humongous do this, otherwise do that" 945 // conditional paths which would obscure its flow. In fact, an early 946 // version of this code did use a unified method which was harder to 947 // follow and, as a result, it had subtle bugs that were hard to 948 // track down. So keeping these two methods separate allows each to 949 // be more readable. It will be good to keep these two in sync as 950 // much as possible. 951 952 assert_heap_not_locked_and_not_at_safepoint(); 953 assert(is_humongous(word_size), "attempt_allocation_humongous() " 954 "should only be called for humongous allocations"); 955 956 // Humongous objects can exhaust the heap quickly, so we should check if we 957 // need to start a marking cycle at each humongous object allocation. We do 958 // the check before we do the actual allocation. The reason for doing it 959 // before the allocation is that we avoid having to keep track of the newly 960 // allocated memory while we do a GC. 961 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 962 word_size)) { 963 collect(GCCause::_g1_humongous_allocation); 964 } 965 966 // We will loop until a) we manage to successfully perform the 967 // allocation or b) we successfully schedule a collection which 968 // fails to perform the allocation. b) is the only case when we'll 969 // return NULL. 970 HeapWord* result = NULL; 971 for (int try_count = 1; /* we'll return */; try_count += 1) { 972 bool should_try_gc; 973 uint gc_count_before; 974 975 { 976 MutexLockerEx x(Heap_lock); 977 978 // Given that humongous objects are not allocated in young 979 // regions, we'll first try to do the allocation without doing a 980 // collection hoping that there's enough space in the heap. 981 result = humongous_obj_allocate(word_size, AllocationContext::current()); 982 if (result != NULL) { 983 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 984 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 985 return result; 986 } 987 988 if (GCLocker::is_active_and_needs_gc()) { 989 should_try_gc = false; 990 } else { 991 // The GCLocker may not be active but the GCLocker initiated 992 // GC may not yet have been performed (GCLocker::needs_gc() 993 // returns true). In this case we do not try this GC and 994 // wait until the GCLocker initiated GC is performed, and 995 // then retry the allocation. 996 if (GCLocker::needs_gc()) { 997 should_try_gc = false; 998 } else { 999 // Read the GC count while still holding the Heap_lock. 1000 gc_count_before = total_collections(); 1001 should_try_gc = true; 1002 } 1003 } 1004 } 1005 1006 if (should_try_gc) { 1007 // If we failed to allocate the humongous object, we should try to 1008 // do a collection pause (if we're allowed) in case it reclaims 1009 // enough space for the allocation to succeed after the pause. 1010 1011 bool succeeded; 1012 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1013 GCCause::_g1_humongous_allocation); 1014 if (result != NULL) { 1015 assert(succeeded, "only way to get back a non-NULL result"); 1016 return result; 1017 } 1018 1019 if (succeeded) { 1020 // If we get here we successfully scheduled a collection which 1021 // failed to allocate. No point in trying to allocate 1022 // further. We'll just return NULL. 1023 MutexLockerEx x(Heap_lock); 1024 *gc_count_before_ret = total_collections(); 1025 return NULL; 1026 } 1027 } else { 1028 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1029 MutexLockerEx x(Heap_lock); 1030 *gc_count_before_ret = total_collections(); 1031 return NULL; 1032 } 1033 // The GCLocker is either active or the GCLocker initiated 1034 // GC has not yet been performed. Stall until it is and 1035 // then retry the allocation. 1036 GCLocker::stall_until_clear(); 1037 (*gclocker_retry_count_ret) += 1; 1038 } 1039 1040 // We can reach here if we were unsuccessful in scheduling a 1041 // collection (because another thread beat us to it) or if we were 1042 // stalled due to the GC locker. In either can we should retry the 1043 // allocation attempt in case another thread successfully 1044 // performed a collection and reclaimed enough space. Give a 1045 // warning if we seem to be looping forever. 1046 1047 if ((QueuedAllocationWarningCount > 0) && 1048 (try_count % QueuedAllocationWarningCount == 0)) { 1049 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() " 1050 "retries %d times", try_count); 1051 } 1052 } 1053 1054 ShouldNotReachHere(); 1055 return NULL; 1056 } 1057 1058 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1059 AllocationContext_t context, 1060 bool expect_null_mutator_alloc_region) { 1061 assert_at_safepoint(true /* should_be_vm_thread */); 1062 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1063 "the current alloc region was unexpectedly found to be non-NULL"); 1064 1065 if (!is_humongous(word_size)) { 1066 return _allocator->attempt_allocation_locked(word_size, context); 1067 } else { 1068 HeapWord* result = humongous_obj_allocate(word_size, context); 1069 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1070 collector_state()->set_initiate_conc_mark_if_possible(true); 1071 } 1072 return result; 1073 } 1074 1075 ShouldNotReachHere(); 1076 } 1077 1078 class PostMCRemSetClearClosure: public HeapRegionClosure { 1079 G1CollectedHeap* _g1h; 1080 ModRefBarrierSet* _mr_bs; 1081 public: 1082 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1083 _g1h(g1h), _mr_bs(mr_bs) {} 1084 1085 bool doHeapRegion(HeapRegion* r) { 1086 HeapRegionRemSet* hrrs = r->rem_set(); 1087 1088 _g1h->reset_gc_time_stamps(r); 1089 1090 if (r->is_continues_humongous()) { 1091 // We'll assert that the strong code root list and RSet is empty 1092 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1093 assert(hrrs->occupied() == 0, "RSet should be empty"); 1094 } else { 1095 hrrs->clear(); 1096 } 1097 // You might think here that we could clear just the cards 1098 // corresponding to the used region. But no: if we leave a dirty card 1099 // in a region we might allocate into, then it would prevent that card 1100 // from being enqueued, and cause it to be missed. 1101 // Re: the performance cost: we shouldn't be doing full GC anyway! 1102 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1103 1104 return false; 1105 } 1106 }; 1107 1108 void G1CollectedHeap::clear_rsets_post_compaction() { 1109 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1110 heap_region_iterate(&rs_clear); 1111 } 1112 1113 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1114 G1CollectedHeap* _g1h; 1115 UpdateRSOopClosure _cl; 1116 public: 1117 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1118 _cl(g1->g1_rem_set(), worker_i), 1119 _g1h(g1) 1120 { } 1121 1122 bool doHeapRegion(HeapRegion* r) { 1123 if (!r->is_continues_humongous()) { 1124 _cl.set_from(r); 1125 r->oop_iterate(&_cl); 1126 } 1127 return false; 1128 } 1129 }; 1130 1131 class ParRebuildRSTask: public AbstractGangTask { 1132 G1CollectedHeap* _g1; 1133 HeapRegionClaimer _hrclaimer; 1134 1135 public: 1136 ParRebuildRSTask(G1CollectedHeap* g1) : 1137 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1138 1139 void work(uint worker_id) { 1140 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1141 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1142 } 1143 }; 1144 1145 class PostCompactionPrinterClosure: public HeapRegionClosure { 1146 private: 1147 G1HRPrinter* _hr_printer; 1148 public: 1149 bool doHeapRegion(HeapRegion* hr) { 1150 assert(!hr->is_young(), "not expecting to find young regions"); 1151 _hr_printer->post_compaction(hr); 1152 return false; 1153 } 1154 1155 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1156 : _hr_printer(hr_printer) { } 1157 }; 1158 1159 void G1CollectedHeap::print_hrm_post_compaction() { 1160 if (_hr_printer.is_active()) { 1161 PostCompactionPrinterClosure cl(hr_printer()); 1162 heap_region_iterate(&cl); 1163 } 1164 1165 } 1166 1167 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1168 bool clear_all_soft_refs) { 1169 assert_at_safepoint(true /* should_be_vm_thread */); 1170 1171 if (GCLocker::check_active_before_gc()) { 1172 return false; 1173 } 1174 1175 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1176 gc_timer->register_gc_start(); 1177 1178 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1179 GCIdMark gc_id_mark; 1180 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1181 1182 SvcGCMarker sgcm(SvcGCMarker::FULL); 1183 ResourceMark rm; 1184 1185 print_heap_before_gc(); 1186 print_heap_regions(); 1187 trace_heap_before_gc(gc_tracer); 1188 1189 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1190 1191 _verifier->verify_region_sets_optional(); 1192 1193 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1194 collector_policy()->should_clear_all_soft_refs(); 1195 1196 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1197 1198 { 1199 IsGCActiveMark x; 1200 1201 // Timing 1202 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1203 GCTraceCPUTime tcpu; 1204 1205 { 1206 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1207 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1208 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1209 1210 G1HeapTransition heap_transition(this); 1211 g1_policy()->record_full_collection_start(); 1212 1213 // Note: When we have a more flexible GC logging framework that 1214 // allows us to add optional attributes to a GC log record we 1215 // could consider timing and reporting how long we wait in the 1216 // following two methods. 1217 wait_while_free_regions_coming(); 1218 // If we start the compaction before the CM threads finish 1219 // scanning the root regions we might trip them over as we'll 1220 // be moving objects / updating references. So let's wait until 1221 // they are done. By telling them to abort, they should complete 1222 // early. 1223 _cm->root_regions()->abort(); 1224 _cm->root_regions()->wait_until_scan_finished(); 1225 append_secondary_free_list_if_not_empty_with_lock(); 1226 1227 gc_prologue(true); 1228 increment_total_collections(true /* full gc */); 1229 increment_old_marking_cycles_started(); 1230 1231 assert(used() == recalculate_used(), "Should be equal"); 1232 1233 _verifier->verify_before_gc(); 1234 1235 _verifier->check_bitmaps("Full GC Start"); 1236 pre_full_gc_dump(gc_timer); 1237 1238 #if defined(COMPILER2) || INCLUDE_JVMCI 1239 DerivedPointerTable::clear(); 1240 #endif 1241 1242 // Disable discovery and empty the discovered lists 1243 // for the CM ref processor. 1244 ref_processor_cm()->disable_discovery(); 1245 ref_processor_cm()->abandon_partial_discovery(); 1246 ref_processor_cm()->verify_no_references_recorded(); 1247 1248 // Abandon current iterations of concurrent marking and concurrent 1249 // refinement, if any are in progress. 1250 concurrent_mark()->abort(); 1251 1252 // Make sure we'll choose a new allocation region afterwards. 1253 _allocator->release_mutator_alloc_region(); 1254 _allocator->abandon_gc_alloc_regions(); 1255 g1_rem_set()->cleanupHRRS(); 1256 1257 // We may have added regions to the current incremental collection 1258 // set between the last GC or pause and now. We need to clear the 1259 // incremental collection set and then start rebuilding it afresh 1260 // after this full GC. 1261 abandon_collection_set(collection_set()); 1262 1263 tear_down_region_sets(false /* free_list_only */); 1264 collector_state()->set_gcs_are_young(true); 1265 1266 // See the comments in g1CollectedHeap.hpp and 1267 // G1CollectedHeap::ref_processing_init() about 1268 // how reference processing currently works in G1. 1269 1270 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1271 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1272 1273 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1274 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1275 1276 ref_processor_stw()->enable_discovery(); 1277 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1278 1279 // Do collection work 1280 { 1281 HandleMark hm; // Discard invalid handles created during gc 1282 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1283 } 1284 1285 assert(num_free_regions() == 0, "we should not have added any free regions"); 1286 rebuild_region_sets(false /* free_list_only */); 1287 1288 // Enqueue any discovered reference objects that have 1289 // not been removed from the discovered lists. 1290 ref_processor_stw()->enqueue_discovered_references(); 1291 1292 #if defined(COMPILER2) || INCLUDE_JVMCI 1293 DerivedPointerTable::update_pointers(); 1294 #endif 1295 1296 MemoryService::track_memory_usage(); 1297 1298 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1299 ref_processor_stw()->verify_no_references_recorded(); 1300 1301 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1302 ClassLoaderDataGraph::purge(); 1303 MetaspaceAux::verify_metrics(); 1304 1305 // Note: since we've just done a full GC, concurrent 1306 // marking is no longer active. Therefore we need not 1307 // re-enable reference discovery for the CM ref processor. 1308 // That will be done at the start of the next marking cycle. 1309 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1310 ref_processor_cm()->verify_no_references_recorded(); 1311 1312 reset_gc_time_stamp(); 1313 // Since everything potentially moved, we will clear all remembered 1314 // sets, and clear all cards. Later we will rebuild remembered 1315 // sets. We will also reset the GC time stamps of the regions. 1316 clear_rsets_post_compaction(); 1317 check_gc_time_stamps(); 1318 1319 resize_if_necessary_after_full_collection(); 1320 1321 // We should do this after we potentially resize the heap so 1322 // that all the COMMIT / UNCOMMIT events are generated before 1323 // the compaction events. 1324 print_hrm_post_compaction(); 1325 1326 if (_hot_card_cache->use_cache()) { 1327 _hot_card_cache->reset_card_counts(); 1328 _hot_card_cache->reset_hot_cache(); 1329 } 1330 1331 // Rebuild remembered sets of all regions. 1332 uint n_workers = 1333 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1334 workers()->active_workers(), 1335 Threads::number_of_non_daemon_threads()); 1336 workers()->update_active_workers(n_workers); 1337 log_info(gc,task)("Using %u workers of %u to rebuild remembered set", n_workers, workers()->total_workers()); 1338 1339 ParRebuildRSTask rebuild_rs_task(this); 1340 workers()->run_task(&rebuild_rs_task); 1341 1342 // Rebuild the strong code root lists for each region 1343 rebuild_strong_code_roots(); 1344 1345 if (true) { // FIXME 1346 MetaspaceGC::compute_new_size(); 1347 } 1348 1349 #ifdef TRACESPINNING 1350 ParallelTaskTerminator::print_termination_counts(); 1351 #endif 1352 1353 // Discard all rset updates 1354 JavaThread::dirty_card_queue_set().abandon_logs(); 1355 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1356 1357 // At this point there should be no regions in the 1358 // entire heap tagged as young. 1359 assert(check_young_list_empty(), "young list should be empty at this point"); 1360 1361 // Update the number of full collections that have been completed. 1362 increment_old_marking_cycles_completed(false /* concurrent */); 1363 1364 _hrm.verify_optional(); 1365 _verifier->verify_region_sets_optional(); 1366 1367 _verifier->verify_after_gc(); 1368 1369 // Clear the previous marking bitmap, if needed for bitmap verification. 1370 // Note we cannot do this when we clear the next marking bitmap in 1371 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1372 // objects marked during a full GC against the previous bitmap. 1373 // But we need to clear it before calling check_bitmaps below since 1374 // the full GC has compacted objects and updated TAMS but not updated 1375 // the prev bitmap. 1376 if (G1VerifyBitmaps) { 1377 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1378 _cm->clear_prev_bitmap(workers()); 1379 } 1380 _verifier->check_bitmaps("Full GC End"); 1381 1382 start_new_collection_set(); 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, _workers); 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, _workers)) { 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, WorkGang* pretouch_workers, 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, pretouch_workers); 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, _workers)) { 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 // Iteration functions. 2366 2367 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2368 2369 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2370 ExtendedOopClosure* _cl; 2371 public: 2372 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2373 bool doHeapRegion(HeapRegion* r) { 2374 if (!r->is_continues_humongous()) { 2375 r->oop_iterate(_cl); 2376 } 2377 return false; 2378 } 2379 }; 2380 2381 // Iterates an ObjectClosure over all objects within a HeapRegion. 2382 2383 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2384 ObjectClosure* _cl; 2385 public: 2386 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2387 bool doHeapRegion(HeapRegion* r) { 2388 if (!r->is_continues_humongous()) { 2389 r->object_iterate(_cl); 2390 } 2391 return false; 2392 } 2393 }; 2394 2395 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2396 IterateObjectClosureRegionClosure blk(cl); 2397 heap_region_iterate(&blk); 2398 } 2399 2400 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2401 _hrm.iterate(cl); 2402 } 2403 2404 void 2405 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2406 uint worker_id, 2407 HeapRegionClaimer *hrclaimer, 2408 bool concurrent) const { 2409 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2410 } 2411 2412 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2413 _collection_set.iterate(cl); 2414 } 2415 2416 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2417 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2418 } 2419 2420 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2421 HeapRegion* result = _hrm.next_region_in_heap(from); 2422 while (result != NULL && result->is_pinned()) { 2423 result = _hrm.next_region_in_heap(result); 2424 } 2425 return result; 2426 } 2427 2428 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2429 HeapRegion* hr = heap_region_containing(addr); 2430 return hr->block_start(addr); 2431 } 2432 2433 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2434 HeapRegion* hr = heap_region_containing(addr); 2435 return hr->block_size(addr); 2436 } 2437 2438 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2439 HeapRegion* hr = heap_region_containing(addr); 2440 return hr->block_is_obj(addr); 2441 } 2442 2443 bool G1CollectedHeap::supports_tlab_allocation() const { 2444 return true; 2445 } 2446 2447 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2448 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2449 } 2450 2451 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2452 return _eden.length() * HeapRegion::GrainBytes; 2453 } 2454 2455 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2456 // must be equal to the humongous object limit. 2457 size_t G1CollectedHeap::max_tlab_size() const { 2458 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2459 } 2460 2461 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2462 AllocationContext_t context = AllocationContext::current(); 2463 return _allocator->unsafe_max_tlab_alloc(context); 2464 } 2465 2466 size_t G1CollectedHeap::max_capacity() const { 2467 return _hrm.reserved().byte_size(); 2468 } 2469 2470 jlong G1CollectedHeap::millis_since_last_gc() { 2471 // See the notes in GenCollectedHeap::millis_since_last_gc() 2472 // for more information about the implementation. 2473 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2474 _g1_policy->collection_pause_end_millis(); 2475 if (ret_val < 0) { 2476 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2477 ". returning zero instead.", ret_val); 2478 return 0; 2479 } 2480 return ret_val; 2481 } 2482 2483 void G1CollectedHeap::prepare_for_verify() { 2484 _verifier->prepare_for_verify(); 2485 } 2486 2487 void G1CollectedHeap::verify(VerifyOption vo) { 2488 _verifier->verify(vo); 2489 } 2490 2491 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2492 return true; 2493 } 2494 2495 const char* const* G1CollectedHeap::concurrent_phases() const { 2496 return _cmThread->concurrent_phases(); 2497 } 2498 2499 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2500 return _cmThread->request_concurrent_phase(phase); 2501 } 2502 2503 class PrintRegionClosure: public HeapRegionClosure { 2504 outputStream* _st; 2505 public: 2506 PrintRegionClosure(outputStream* st) : _st(st) {} 2507 bool doHeapRegion(HeapRegion* r) { 2508 r->print_on(_st); 2509 return false; 2510 } 2511 }; 2512 2513 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2514 const HeapRegion* hr, 2515 const VerifyOption vo) const { 2516 switch (vo) { 2517 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2518 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2519 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 2520 default: ShouldNotReachHere(); 2521 } 2522 return false; // keep some compilers happy 2523 } 2524 2525 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2526 const VerifyOption vo) const { 2527 switch (vo) { 2528 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2529 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2530 case VerifyOption_G1UseMarkWord: { 2531 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 2532 return !obj->is_gc_marked() && !hr->is_archive(); 2533 } 2534 default: ShouldNotReachHere(); 2535 } 2536 return false; // keep some compilers happy 2537 } 2538 2539 void G1CollectedHeap::print_heap_regions() const { 2540 Log(gc, heap, region) log; 2541 if (log.is_trace()) { 2542 ResourceMark rm; 2543 print_regions_on(log.trace_stream()); 2544 } 2545 } 2546 2547 void G1CollectedHeap::print_on(outputStream* st) const { 2548 st->print(" %-20s", "garbage-first heap"); 2549 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2550 capacity()/K, used_unlocked()/K); 2551 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 2552 p2i(_hrm.reserved().start()), 2553 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 2554 p2i(_hrm.reserved().end())); 2555 st->cr(); 2556 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2557 uint young_regions = young_regions_count(); 2558 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2559 (size_t) young_regions * HeapRegion::GrainBytes / K); 2560 uint survivor_regions = survivor_regions_count(); 2561 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2562 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2563 st->cr(); 2564 MetaspaceAux::print_on(st); 2565 } 2566 2567 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2568 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2569 "HS=humongous(starts), HC=humongous(continues), " 2570 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2571 "AC=allocation context, " 2572 "TAMS=top-at-mark-start (previous, next)"); 2573 PrintRegionClosure blk(st); 2574 heap_region_iterate(&blk); 2575 } 2576 2577 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2578 print_on(st); 2579 2580 // Print the per-region information. 2581 print_regions_on(st); 2582 } 2583 2584 void G1CollectedHeap::print_on_error(outputStream* st) const { 2585 this->CollectedHeap::print_on_error(st); 2586 2587 if (_cm != NULL) { 2588 st->cr(); 2589 _cm->print_on_error(st); 2590 } 2591 } 2592 2593 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2594 workers()->print_worker_threads_on(st); 2595 _cmThread->print_on(st); 2596 st->cr(); 2597 _cm->print_worker_threads_on(st); 2598 _cg1r->print_worker_threads_on(st); // also prints the sample thread 2599 if (G1StringDedup::is_enabled()) { 2600 G1StringDedup::print_worker_threads_on(st); 2601 } 2602 } 2603 2604 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2605 workers()->threads_do(tc); 2606 tc->do_thread(_cmThread); 2607 _cm->threads_do(tc); 2608 _cg1r->threads_do(tc); // also iterates over the sample thread 2609 if (G1StringDedup::is_enabled()) { 2610 G1StringDedup::threads_do(tc); 2611 } 2612 } 2613 2614 void G1CollectedHeap::print_tracing_info() const { 2615 g1_rem_set()->print_summary_info(); 2616 concurrent_mark()->print_summary_info(); 2617 } 2618 2619 #ifndef PRODUCT 2620 // Helpful for debugging RSet issues. 2621 2622 class PrintRSetsClosure : public HeapRegionClosure { 2623 private: 2624 const char* _msg; 2625 size_t _occupied_sum; 2626 2627 public: 2628 bool doHeapRegion(HeapRegion* r) { 2629 HeapRegionRemSet* hrrs = r->rem_set(); 2630 size_t occupied = hrrs->occupied(); 2631 _occupied_sum += occupied; 2632 2633 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2634 if (occupied == 0) { 2635 tty->print_cr(" RSet is empty"); 2636 } else { 2637 hrrs->print(); 2638 } 2639 tty->print_cr("----------"); 2640 return false; 2641 } 2642 2643 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2644 tty->cr(); 2645 tty->print_cr("========================================"); 2646 tty->print_cr("%s", msg); 2647 tty->cr(); 2648 } 2649 2650 ~PrintRSetsClosure() { 2651 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2652 tty->print_cr("========================================"); 2653 tty->cr(); 2654 } 2655 }; 2656 2657 void G1CollectedHeap::print_cset_rsets() { 2658 PrintRSetsClosure cl("Printing CSet RSets"); 2659 collection_set_iterate(&cl); 2660 } 2661 2662 void G1CollectedHeap::print_all_rsets() { 2663 PrintRSetsClosure cl("Printing All RSets");; 2664 heap_region_iterate(&cl); 2665 } 2666 #endif // PRODUCT 2667 2668 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2669 2670 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2671 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2672 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2673 2674 size_t eden_capacity_bytes = 2675 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2676 2677 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2678 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2679 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2680 } 2681 2682 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2683 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2684 stats->unused(), stats->used(), stats->region_end_waste(), 2685 stats->regions_filled(), stats->direct_allocated(), 2686 stats->failure_used(), stats->failure_waste()); 2687 } 2688 2689 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2690 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2691 gc_tracer->report_gc_heap_summary(when, heap_summary); 2692 2693 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2694 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2695 } 2696 2697 G1CollectedHeap* G1CollectedHeap::heap() { 2698 CollectedHeap* heap = Universe::heap(); 2699 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2700 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2701 return (G1CollectedHeap*)heap; 2702 } 2703 2704 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 2705 // always_do_update_barrier = false; 2706 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2707 2708 double start = os::elapsedTime(); 2709 // Fill TLAB's and such 2710 accumulate_statistics_all_tlabs(); 2711 ensure_parsability(true); 2712 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2713 2714 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2715 } 2716 2717 void G1CollectedHeap::gc_epilogue(bool full) { 2718 // we are at the end of the GC. Total collections has already been increased. 2719 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2720 2721 // FIXME: what is this about? 2722 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2723 // is set. 2724 #if defined(COMPILER2) || INCLUDE_JVMCI 2725 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2726 #endif 2727 // always_do_update_barrier = true; 2728 2729 double start = os::elapsedTime(); 2730 resize_all_tlabs(); 2731 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2732 2733 allocation_context_stats().update(full); 2734 2735 // We have just completed a GC. Update the soft reference 2736 // policy with the new heap occupancy 2737 Universe::update_heap_info_at_gc(); 2738 } 2739 2740 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2741 uint gc_count_before, 2742 bool* succeeded, 2743 GCCause::Cause gc_cause) { 2744 assert_heap_not_locked_and_not_at_safepoint(); 2745 VM_G1IncCollectionPause op(gc_count_before, 2746 word_size, 2747 false, /* should_initiate_conc_mark */ 2748 g1_policy()->max_pause_time_ms(), 2749 gc_cause); 2750 2751 op.set_allocation_context(AllocationContext::current()); 2752 VMThread::execute(&op); 2753 2754 HeapWord* result = op.result(); 2755 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2756 assert(result == NULL || ret_succeeded, 2757 "the result should be NULL if the VM did not succeed"); 2758 *succeeded = ret_succeeded; 2759 2760 assert_heap_not_locked(); 2761 return result; 2762 } 2763 2764 void 2765 G1CollectedHeap::doConcurrentMark() { 2766 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2767 if (!_cmThread->in_progress()) { 2768 _cmThread->set_started(); 2769 CGC_lock->notify(); 2770 } 2771 } 2772 2773 size_t G1CollectedHeap::pending_card_num() { 2774 size_t extra_cards = 0; 2775 JavaThread *curr = Threads::first(); 2776 while (curr != NULL) { 2777 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2778 extra_cards += dcq.size(); 2779 curr = curr->next(); 2780 } 2781 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2782 size_t buffer_size = dcqs.buffer_size(); 2783 size_t buffer_num = dcqs.completed_buffers_num(); 2784 2785 return buffer_size * buffer_num + extra_cards; 2786 } 2787 2788 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2789 private: 2790 size_t _total_humongous; 2791 size_t _candidate_humongous; 2792 2793 DirtyCardQueue _dcq; 2794 2795 // We don't nominate objects with many remembered set entries, on 2796 // the assumption that such objects are likely still live. 2797 bool is_remset_small(HeapRegion* region) const { 2798 HeapRegionRemSet* const rset = region->rem_set(); 2799 return G1EagerReclaimHumongousObjectsWithStaleRefs 2800 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2801 : rset->is_empty(); 2802 } 2803 2804 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2805 assert(region->is_starts_humongous(), "Must start a humongous object"); 2806 2807 oop obj = oop(region->bottom()); 2808 2809 // Dead objects cannot be eager reclaim candidates. Due to class 2810 // unloading it is unsafe to query their classes so we return early. 2811 if (heap->is_obj_dead(obj, region)) { 2812 return false; 2813 } 2814 2815 // Candidate selection must satisfy the following constraints 2816 // while concurrent marking is in progress: 2817 // 2818 // * In order to maintain SATB invariants, an object must not be 2819 // reclaimed if it was allocated before the start of marking and 2820 // has not had its references scanned. Such an object must have 2821 // its references (including type metadata) scanned to ensure no 2822 // live objects are missed by the marking process. Objects 2823 // allocated after the start of concurrent marking don't need to 2824 // be scanned. 2825 // 2826 // * An object must not be reclaimed if it is on the concurrent 2827 // mark stack. Objects allocated after the start of concurrent 2828 // marking are never pushed on the mark stack. 2829 // 2830 // Nominating only objects allocated after the start of concurrent 2831 // marking is sufficient to meet both constraints. This may miss 2832 // some objects that satisfy the constraints, but the marking data 2833 // structures don't support efficiently performing the needed 2834 // additional tests or scrubbing of the mark stack. 2835 // 2836 // However, we presently only nominate is_typeArray() objects. 2837 // A humongous object containing references induces remembered 2838 // set entries on other regions. In order to reclaim such an 2839 // object, those remembered sets would need to be cleaned up. 2840 // 2841 // We also treat is_typeArray() objects specially, allowing them 2842 // to be reclaimed even if allocated before the start of 2843 // concurrent mark. For this we rely on mark stack insertion to 2844 // exclude is_typeArray() objects, preventing reclaiming an object 2845 // that is in the mark stack. We also rely on the metadata for 2846 // such objects to be built-in and so ensured to be kept live. 2847 // Frequent allocation and drop of large binary blobs is an 2848 // important use case for eager reclaim, and this special handling 2849 // may reduce needed headroom. 2850 2851 return obj->is_typeArray() && is_remset_small(region); 2852 } 2853 2854 public: 2855 RegisterHumongousWithInCSetFastTestClosure() 2856 : _total_humongous(0), 2857 _candidate_humongous(0), 2858 _dcq(&JavaThread::dirty_card_queue_set()) { 2859 } 2860 2861 virtual bool doHeapRegion(HeapRegion* r) { 2862 if (!r->is_starts_humongous()) { 2863 return false; 2864 } 2865 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2866 2867 bool is_candidate = humongous_region_is_candidate(g1h, r); 2868 uint rindex = r->hrm_index(); 2869 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2870 if (is_candidate) { 2871 _candidate_humongous++; 2872 g1h->register_humongous_region_with_cset(rindex); 2873 // Is_candidate already filters out humongous object with large remembered sets. 2874 // If we have a humongous object with a few remembered sets, we simply flush these 2875 // remembered set entries into the DCQS. That will result in automatic 2876 // re-evaluation of their remembered set entries during the following evacuation 2877 // phase. 2878 if (!r->rem_set()->is_empty()) { 2879 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2880 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2881 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 2882 HeapRegionRemSetIterator hrrs(r->rem_set()); 2883 size_t card_index; 2884 while (hrrs.has_next(card_index)) { 2885 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 2886 // The remembered set might contain references to already freed 2887 // regions. Filter out such entries to avoid failing card table 2888 // verification. 2889 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 2890 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 2891 *card_ptr = CardTableModRefBS::dirty_card_val(); 2892 _dcq.enqueue(card_ptr); 2893 } 2894 } 2895 } 2896 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2897 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2898 hrrs.n_yielded(), r->rem_set()->occupied()); 2899 r->rem_set()->clear_locked(); 2900 } 2901 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2902 } 2903 _total_humongous++; 2904 2905 return false; 2906 } 2907 2908 size_t total_humongous() const { return _total_humongous; } 2909 size_t candidate_humongous() const { return _candidate_humongous; } 2910 2911 void flush_rem_set_entries() { _dcq.flush(); } 2912 }; 2913 2914 void G1CollectedHeap::register_humongous_regions_with_cset() { 2915 if (!G1EagerReclaimHumongousObjects) { 2916 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2917 return; 2918 } 2919 double time = os::elapsed_counter(); 2920 2921 // Collect reclaim candidate information and register candidates with cset. 2922 RegisterHumongousWithInCSetFastTestClosure cl; 2923 heap_region_iterate(&cl); 2924 2925 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2926 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2927 cl.total_humongous(), 2928 cl.candidate_humongous()); 2929 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2930 2931 // Finally flush all remembered set entries to re-check into the global DCQS. 2932 cl.flush_rem_set_entries(); 2933 } 2934 2935 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2936 public: 2937 bool doHeapRegion(HeapRegion* hr) { 2938 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2939 hr->verify_rem_set(); 2940 } 2941 return false; 2942 } 2943 }; 2944 2945 uint G1CollectedHeap::num_task_queues() const { 2946 return _task_queues->size(); 2947 } 2948 2949 #if TASKQUEUE_STATS 2950 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2951 st->print_raw_cr("GC Task Stats"); 2952 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2953 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2954 } 2955 2956 void G1CollectedHeap::print_taskqueue_stats() const { 2957 if (!log_is_enabled(Trace, gc, task, stats)) { 2958 return; 2959 } 2960 Log(gc, task, stats) log; 2961 ResourceMark rm; 2962 outputStream* st = log.trace_stream(); 2963 2964 print_taskqueue_stats_hdr(st); 2965 2966 TaskQueueStats totals; 2967 const uint n = num_task_queues(); 2968 for (uint i = 0; i < n; ++i) { 2969 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2970 totals += task_queue(i)->stats; 2971 } 2972 st->print_raw("tot "); totals.print(st); st->cr(); 2973 2974 DEBUG_ONLY(totals.verify()); 2975 } 2976 2977 void G1CollectedHeap::reset_taskqueue_stats() { 2978 const uint n = num_task_queues(); 2979 for (uint i = 0; i < n; ++i) { 2980 task_queue(i)->stats.reset(); 2981 } 2982 } 2983 #endif // TASKQUEUE_STATS 2984 2985 void G1CollectedHeap::wait_for_root_region_scanning() { 2986 double scan_wait_start = os::elapsedTime(); 2987 // We have to wait until the CM threads finish scanning the 2988 // root regions as it's the only way to ensure that all the 2989 // objects on them have been correctly scanned before we start 2990 // moving them during the GC. 2991 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2992 double wait_time_ms = 0.0; 2993 if (waited) { 2994 double scan_wait_end = os::elapsedTime(); 2995 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2996 } 2997 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2998 } 2999 3000 class G1PrintCollectionSetClosure : public HeapRegionClosure { 3001 private: 3002 G1HRPrinter* _hr_printer; 3003 public: 3004 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 3005 3006 virtual bool doHeapRegion(HeapRegion* r) { 3007 _hr_printer->cset(r); 3008 return false; 3009 } 3010 }; 3011 3012 void G1CollectedHeap::start_new_collection_set() { 3013 collection_set()->start_incremental_building(); 3014 3015 clear_cset_fast_test(); 3016 3017 guarantee(_eden.length() == 0, "eden should have been cleared"); 3018 g1_policy()->transfer_survivors_to_cset(survivor()); 3019 } 3020 3021 bool 3022 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3023 assert_at_safepoint(true /* should_be_vm_thread */); 3024 guarantee(!is_gc_active(), "collection is not reentrant"); 3025 3026 if (GCLocker::check_active_before_gc()) { 3027 return false; 3028 } 3029 3030 _gc_timer_stw->register_gc_start(); 3031 3032 GCIdMark gc_id_mark; 3033 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3034 3035 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3036 ResourceMark rm; 3037 3038 g1_policy()->note_gc_start(); 3039 3040 wait_for_root_region_scanning(); 3041 3042 print_heap_before_gc(); 3043 print_heap_regions(); 3044 trace_heap_before_gc(_gc_tracer_stw); 3045 3046 _verifier->verify_region_sets_optional(); 3047 _verifier->verify_dirty_young_regions(); 3048 3049 // We should not be doing initial mark unless the conc mark thread is running 3050 if (!_cmThread->should_terminate()) { 3051 // This call will decide whether this pause is an initial-mark 3052 // pause. If it is, during_initial_mark_pause() will return true 3053 // for the duration of this pause. 3054 g1_policy()->decide_on_conc_mark_initiation(); 3055 } 3056 3057 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3058 assert(!collector_state()->during_initial_mark_pause() || 3059 collector_state()->gcs_are_young(), "sanity"); 3060 3061 // We also do not allow mixed GCs during marking. 3062 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3063 3064 // Record whether this pause is an initial mark. When the current 3065 // thread has completed its logging output and it's safe to signal 3066 // the CM thread, the flag's value in the policy has been reset. 3067 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3068 3069 // Inner scope for scope based logging, timers, and stats collection 3070 { 3071 EvacuationInfo evacuation_info; 3072 3073 if (collector_state()->during_initial_mark_pause()) { 3074 // We are about to start a marking cycle, so we increment the 3075 // full collection counter. 3076 increment_old_marking_cycles_started(); 3077 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 3078 } 3079 3080 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3081 3082 GCTraceCPUTime tcpu; 3083 3084 FormatBuffer<> gc_string("Pause "); 3085 if (collector_state()->during_initial_mark_pause()) { 3086 gc_string.append("Initial Mark"); 3087 } else if (collector_state()->gcs_are_young()) { 3088 gc_string.append("Young"); 3089 } else { 3090 gc_string.append("Mixed"); 3091 } 3092 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 3093 3094 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3095 workers()->active_workers(), 3096 Threads::number_of_non_daemon_threads()); 3097 workers()->update_active_workers(active_workers); 3098 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 3099 3100 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3101 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3102 3103 // If the secondary_free_list is not empty, append it to the 3104 // free_list. No need to wait for the cleanup operation to finish; 3105 // the region allocation code will check the secondary_free_list 3106 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3107 // set, skip this step so that the region allocation code has to 3108 // get entries from the secondary_free_list. 3109 if (!G1StressConcRegionFreeing) { 3110 append_secondary_free_list_if_not_empty_with_lock(); 3111 } 3112 3113 G1HeapTransition heap_transition(this); 3114 size_t heap_used_bytes_before_gc = used(); 3115 3116 // Don't dynamically change the number of GC threads this early. A value of 3117 // 0 is used to indicate serial work. When parallel work is done, 3118 // it will be set. 3119 3120 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3121 IsGCActiveMark x; 3122 3123 gc_prologue(false); 3124 increment_total_collections(false /* full gc */); 3125 increment_gc_time_stamp(); 3126 3127 if (VerifyRememberedSets) { 3128 log_info(gc, verify)("[Verifying RemSets before GC]"); 3129 VerifyRegionRemSetClosure v_cl; 3130 heap_region_iterate(&v_cl); 3131 } 3132 3133 _verifier->verify_before_gc(); 3134 3135 _verifier->check_bitmaps("GC Start"); 3136 3137 #if defined(COMPILER2) || INCLUDE_JVMCI 3138 DerivedPointerTable::clear(); 3139 #endif 3140 3141 // Please see comment in g1CollectedHeap.hpp and 3142 // G1CollectedHeap::ref_processing_init() to see how 3143 // reference processing currently works in G1. 3144 3145 // Enable discovery in the STW reference processor 3146 if (g1_policy()->should_process_references()) { 3147 ref_processor_stw()->enable_discovery(); 3148 } else { 3149 ref_processor_stw()->disable_discovery(); 3150 } 3151 3152 { 3153 // We want to temporarily turn off discovery by the 3154 // CM ref processor, if necessary, and turn it back on 3155 // on again later if we do. Using a scoped 3156 // NoRefDiscovery object will do this. 3157 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3158 3159 // Forget the current alloc region (we might even choose it to be part 3160 // of the collection set!). 3161 _allocator->release_mutator_alloc_region(); 3162 3163 // This timing is only used by the ergonomics to handle our pause target. 3164 // It is unclear why this should not include the full pause. We will 3165 // investigate this in CR 7178365. 3166 // 3167 // Preserving the old comment here if that helps the investigation: 3168 // 3169 // The elapsed time induced by the start time below deliberately elides 3170 // the possible verification above. 3171 double sample_start_time_sec = os::elapsedTime(); 3172 3173 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3174 3175 if (collector_state()->during_initial_mark_pause()) { 3176 concurrent_mark()->checkpointRootsInitialPre(); 3177 } 3178 3179 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 3180 3181 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3182 3183 // Make sure the remembered sets are up to date. This needs to be 3184 // done before register_humongous_regions_with_cset(), because the 3185 // remembered sets are used there to choose eager reclaim candidates. 3186 // If the remembered sets are not up to date we might miss some 3187 // entries that need to be handled. 3188 g1_rem_set()->cleanupHRRS(); 3189 3190 register_humongous_regions_with_cset(); 3191 3192 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3193 3194 // We call this after finalize_cset() to 3195 // ensure that the CSet has been finalized. 3196 _cm->verify_no_cset_oops(); 3197 3198 if (_hr_printer.is_active()) { 3199 G1PrintCollectionSetClosure cl(&_hr_printer); 3200 _collection_set.iterate(&cl); 3201 } 3202 3203 // Initialize the GC alloc regions. 3204 _allocator->init_gc_alloc_regions(evacuation_info); 3205 3206 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3207 pre_evacuate_collection_set(); 3208 3209 // Actually do the work... 3210 evacuate_collection_set(evacuation_info, &per_thread_states); 3211 3212 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3213 3214 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3215 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 3216 3217 eagerly_reclaim_humongous_regions(); 3218 3219 record_obj_copy_mem_stats(); 3220 _survivor_evac_stats.adjust_desired_plab_sz(); 3221 _old_evac_stats.adjust_desired_plab_sz(); 3222 3223 double start = os::elapsedTime(); 3224 start_new_collection_set(); 3225 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 3226 3227 if (evacuation_failed()) { 3228 set_used(recalculate_used()); 3229 if (_archive_allocator != NULL) { 3230 _archive_allocator->clear_used(); 3231 } 3232 for (uint i = 0; i < ParallelGCThreads; i++) { 3233 if (_evacuation_failed_info_array[i].has_failed()) { 3234 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3235 } 3236 } 3237 } else { 3238 // The "used" of the the collection set have already been subtracted 3239 // when they were freed. Add in the bytes evacuated. 3240 increase_used(g1_policy()->bytes_copied_during_gc()); 3241 } 3242 3243 if (collector_state()->during_initial_mark_pause()) { 3244 // We have to do this before we notify the CM threads that 3245 // they can start working to make sure that all the 3246 // appropriate initialization is done on the CM object. 3247 concurrent_mark()->checkpointRootsInitialPost(); 3248 collector_state()->set_mark_in_progress(true); 3249 // Note that we don't actually trigger the CM thread at 3250 // this point. We do that later when we're sure that 3251 // the current thread has completed its logging output. 3252 } 3253 3254 allocate_dummy_regions(); 3255 3256 _allocator->init_mutator_alloc_region(); 3257 3258 { 3259 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3260 if (expand_bytes > 0) { 3261 size_t bytes_before = capacity(); 3262 // No need for an ergo logging here, 3263 // expansion_amount() does this when it returns a value > 0. 3264 double expand_ms; 3265 if (!expand(expand_bytes, _workers, &expand_ms)) { 3266 // We failed to expand the heap. Cannot do anything about it. 3267 } 3268 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3269 } 3270 } 3271 3272 // We redo the verification but now wrt to the new CSet which 3273 // has just got initialized after the previous CSet was freed. 3274 _cm->verify_no_cset_oops(); 3275 3276 // This timing is only used by the ergonomics to handle our pause target. 3277 // It is unclear why this should not include the full pause. We will 3278 // investigate this in CR 7178365. 3279 double sample_end_time_sec = os::elapsedTime(); 3280 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3281 size_t total_cards_scanned = per_thread_states.total_cards_scanned(); 3282 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3283 3284 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3285 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3286 3287 MemoryService::track_memory_usage(); 3288 3289 // In prepare_for_verify() below we'll need to scan the deferred 3290 // update buffers to bring the RSets up-to-date if 3291 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3292 // the update buffers we'll probably need to scan cards on the 3293 // regions we just allocated to (i.e., the GC alloc 3294 // regions). However, during the last GC we called 3295 // set_saved_mark() on all the GC alloc regions, so card 3296 // scanning might skip the [saved_mark_word()...top()] area of 3297 // those regions (i.e., the area we allocated objects into 3298 // during the last GC). But it shouldn't. Given that 3299 // saved_mark_word() is conditional on whether the GC time stamp 3300 // on the region is current or not, by incrementing the GC time 3301 // stamp here we invalidate all the GC time stamps on all the 3302 // regions and saved_mark_word() will simply return top() for 3303 // all the regions. This is a nicer way of ensuring this rather 3304 // than iterating over the regions and fixing them. In fact, the 3305 // GC time stamp increment here also ensures that 3306 // saved_mark_word() will return top() between pauses, i.e., 3307 // during concurrent refinement. So we don't need the 3308 // is_gc_active() check to decided which top to use when 3309 // scanning cards (see CR 7039627). 3310 increment_gc_time_stamp(); 3311 3312 if (VerifyRememberedSets) { 3313 log_info(gc, verify)("[Verifying RemSets after GC]"); 3314 VerifyRegionRemSetClosure v_cl; 3315 heap_region_iterate(&v_cl); 3316 } 3317 3318 _verifier->verify_after_gc(); 3319 _verifier->check_bitmaps("GC End"); 3320 3321 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3322 ref_processor_stw()->verify_no_references_recorded(); 3323 3324 // CM reference discovery will be re-enabled if necessary. 3325 } 3326 3327 #ifdef TRACESPINNING 3328 ParallelTaskTerminator::print_termination_counts(); 3329 #endif 3330 3331 gc_epilogue(false); 3332 } 3333 3334 // Print the remainder of the GC log output. 3335 if (evacuation_failed()) { 3336 log_info(gc)("To-space exhausted"); 3337 } 3338 3339 g1_policy()->print_phases(); 3340 heap_transition.print(); 3341 3342 // It is not yet to safe to tell the concurrent mark to 3343 // start as we have some optional output below. We don't want the 3344 // output from the concurrent mark thread interfering with this 3345 // logging output either. 3346 3347 _hrm.verify_optional(); 3348 _verifier->verify_region_sets_optional(); 3349 3350 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3351 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3352 3353 print_heap_after_gc(); 3354 print_heap_regions(); 3355 trace_heap_after_gc(_gc_tracer_stw); 3356 3357 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3358 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3359 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3360 // before any GC notifications are raised. 3361 g1mm()->update_sizes(); 3362 3363 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3364 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3365 _gc_timer_stw->register_gc_end(); 3366 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3367 } 3368 // It should now be safe to tell the concurrent mark thread to start 3369 // without its logging output interfering with the logging output 3370 // that came from the pause. 3371 3372 if (should_start_conc_mark) { 3373 // CAUTION: after the doConcurrentMark() call below, 3374 // the concurrent marking thread(s) could be running 3375 // concurrently with us. Make sure that anything after 3376 // this point does not assume that we are the only GC thread 3377 // running. Note: of course, the actual marking work will 3378 // not start until the safepoint itself is released in 3379 // SuspendibleThreadSet::desynchronize(). 3380 doConcurrentMark(); 3381 } 3382 3383 return true; 3384 } 3385 3386 void G1CollectedHeap::remove_self_forwarding_pointers() { 3387 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3388 workers()->run_task(&rsfp_task); 3389 } 3390 3391 void G1CollectedHeap::restore_after_evac_failure() { 3392 double remove_self_forwards_start = os::elapsedTime(); 3393 3394 remove_self_forwarding_pointers(); 3395 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3396 _preserved_marks_set.restore(&task_executor); 3397 3398 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3399 } 3400 3401 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3402 if (!_evacuation_failed) { 3403 _evacuation_failed = true; 3404 } 3405 3406 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3407 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3408 } 3409 3410 bool G1ParEvacuateFollowersClosure::offer_termination() { 3411 G1ParScanThreadState* const pss = par_scan_state(); 3412 start_term_time(); 3413 const bool res = terminator()->offer_termination(); 3414 end_term_time(); 3415 return res; 3416 } 3417 3418 void G1ParEvacuateFollowersClosure::do_void() { 3419 G1ParScanThreadState* const pss = par_scan_state(); 3420 pss->trim_queue(); 3421 do { 3422 pss->steal_and_trim_queue(queues()); 3423 } while (!offer_termination()); 3424 } 3425 3426 class G1ParTask : public AbstractGangTask { 3427 protected: 3428 G1CollectedHeap* _g1h; 3429 G1ParScanThreadStateSet* _pss; 3430 RefToScanQueueSet* _queues; 3431 G1RootProcessor* _root_processor; 3432 ParallelTaskTerminator _terminator; 3433 uint _n_workers; 3434 3435 public: 3436 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3437 : AbstractGangTask("G1 collection"), 3438 _g1h(g1h), 3439 _pss(per_thread_states), 3440 _queues(task_queues), 3441 _root_processor(root_processor), 3442 _terminator(n_workers, _queues), 3443 _n_workers(n_workers) 3444 {} 3445 3446 void work(uint worker_id) { 3447 if (worker_id >= _n_workers) return; // no work needed this round 3448 3449 double start_sec = os::elapsedTime(); 3450 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3451 3452 { 3453 ResourceMark rm; 3454 HandleMark hm; 3455 3456 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3457 3458 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3459 pss->set_ref_processor(rp); 3460 3461 double start_strong_roots_sec = os::elapsedTime(); 3462 3463 _root_processor->evacuate_roots(pss->closures(), worker_id); 3464 3465 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss); 3466 3467 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3468 // treating the nmethods visited to act as roots for concurrent marking. 3469 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3470 // objects copied by the current evacuation. 3471 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl, 3472 pss->closures()->weak_codeblobs(), 3473 worker_id); 3474 3475 _pss->add_cards_scanned(worker_id, cards_scanned); 3476 3477 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3478 3479 double term_sec = 0.0; 3480 size_t evac_term_attempts = 0; 3481 { 3482 double start = os::elapsedTime(); 3483 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3484 evac.do_void(); 3485 3486 evac_term_attempts = evac.term_attempts(); 3487 term_sec = evac.term_time(); 3488 double elapsed_sec = os::elapsedTime() - start; 3489 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3490 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3491 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3492 } 3493 3494 assert(pss->queue_is_empty(), "should be empty"); 3495 3496 if (log_is_enabled(Debug, gc, task, stats)) { 3497 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3498 size_t lab_waste; 3499 size_t lab_undo_waste; 3500 pss->waste(lab_waste, lab_undo_waste); 3501 _g1h->print_termination_stats(worker_id, 3502 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3503 strong_roots_sec * 1000.0, /* strong roots time */ 3504 term_sec * 1000.0, /* evac term time */ 3505 evac_term_attempts, /* evac term attempts */ 3506 lab_waste, /* alloc buffer waste */ 3507 lab_undo_waste /* undo waste */ 3508 ); 3509 } 3510 3511 // Close the inner scope so that the ResourceMark and HandleMark 3512 // destructors are executed here and are included as part of the 3513 // "GC Worker Time". 3514 } 3515 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3516 } 3517 }; 3518 3519 void G1CollectedHeap::print_termination_stats_hdr() { 3520 log_debug(gc, task, stats)("GC Termination Stats"); 3521 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3522 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3523 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3524 } 3525 3526 void G1CollectedHeap::print_termination_stats(uint worker_id, 3527 double elapsed_ms, 3528 double strong_roots_ms, 3529 double term_ms, 3530 size_t term_attempts, 3531 size_t alloc_buffer_waste, 3532 size_t undo_waste) const { 3533 log_debug(gc, task, stats) 3534 ("%3d %9.2f %9.2f %6.2f " 3535 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3536 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3537 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3538 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3539 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3540 alloc_buffer_waste * HeapWordSize / K, 3541 undo_waste * HeapWordSize / K); 3542 } 3543 3544 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3545 private: 3546 BoolObjectClosure* _is_alive; 3547 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3548 3549 int _initial_string_table_size; 3550 int _initial_symbol_table_size; 3551 3552 bool _process_strings; 3553 int _strings_processed; 3554 int _strings_removed; 3555 3556 bool _process_symbols; 3557 int _symbols_processed; 3558 int _symbols_removed; 3559 3560 bool _process_string_dedup; 3561 3562 public: 3563 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3564 AbstractGangTask("String/Symbol Unlinking"), 3565 _is_alive(is_alive), 3566 _dedup_closure(is_alive, NULL, false), 3567 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3568 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3569 _process_string_dedup(process_string_dedup) { 3570 3571 _initial_string_table_size = StringTable::the_table()->table_size(); 3572 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3573 if (process_strings) { 3574 StringTable::clear_parallel_claimed_index(); 3575 } 3576 if (process_symbols) { 3577 SymbolTable::clear_parallel_claimed_index(); 3578 } 3579 } 3580 3581 ~G1StringAndSymbolCleaningTask() { 3582 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3583 "claim value %d after unlink less than initial string table size %d", 3584 StringTable::parallel_claimed_index(), _initial_string_table_size); 3585 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3586 "claim value %d after unlink less than initial symbol table size %d", 3587 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3588 3589 log_info(gc, stringtable)( 3590 "Cleaned string and symbol table, " 3591 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3592 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3593 strings_processed(), strings_removed(), 3594 symbols_processed(), symbols_removed()); 3595 } 3596 3597 void work(uint worker_id) { 3598 int strings_processed = 0; 3599 int strings_removed = 0; 3600 int symbols_processed = 0; 3601 int symbols_removed = 0; 3602 if (_process_strings) { 3603 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3604 Atomic::add(strings_processed, &_strings_processed); 3605 Atomic::add(strings_removed, &_strings_removed); 3606 } 3607 if (_process_symbols) { 3608 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3609 Atomic::add(symbols_processed, &_symbols_processed); 3610 Atomic::add(symbols_removed, &_symbols_removed); 3611 } 3612 if (_process_string_dedup) { 3613 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3614 } 3615 } 3616 3617 size_t strings_processed() const { return (size_t)_strings_processed; } 3618 size_t strings_removed() const { return (size_t)_strings_removed; } 3619 3620 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3621 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3622 }; 3623 3624 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3625 private: 3626 static Monitor* _lock; 3627 3628 BoolObjectClosure* const _is_alive; 3629 const bool _unloading_occurred; 3630 const uint _num_workers; 3631 3632 // Variables used to claim nmethods. 3633 CompiledMethod* _first_nmethod; 3634 volatile CompiledMethod* _claimed_nmethod; 3635 3636 // The list of nmethods that need to be processed by the second pass. 3637 volatile CompiledMethod* _postponed_list; 3638 volatile uint _num_entered_barrier; 3639 3640 public: 3641 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3642 _is_alive(is_alive), 3643 _unloading_occurred(unloading_occurred), 3644 _num_workers(num_workers), 3645 _first_nmethod(NULL), 3646 _claimed_nmethod(NULL), 3647 _postponed_list(NULL), 3648 _num_entered_barrier(0) 3649 { 3650 CompiledMethod::increase_unloading_clock(); 3651 // Get first alive nmethod 3652 CompiledMethodIterator iter = CompiledMethodIterator(); 3653 if(iter.next_alive()) { 3654 _first_nmethod = iter.method(); 3655 } 3656 _claimed_nmethod = (volatile CompiledMethod*)_first_nmethod; 3657 } 3658 3659 ~G1CodeCacheUnloadingTask() { 3660 CodeCache::verify_clean_inline_caches(); 3661 3662 CodeCache::set_needs_cache_clean(false); 3663 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3664 3665 CodeCache::verify_icholder_relocations(); 3666 } 3667 3668 private: 3669 void add_to_postponed_list(CompiledMethod* nm) { 3670 CompiledMethod* old; 3671 do { 3672 old = (CompiledMethod*)_postponed_list; 3673 nm->set_unloading_next(old); 3674 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 3675 } 3676 3677 void clean_nmethod(CompiledMethod* nm) { 3678 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3679 3680 if (postponed) { 3681 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3682 add_to_postponed_list(nm); 3683 } 3684 3685 // Mark that this thread has been cleaned/unloaded. 3686 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3687 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3688 } 3689 3690 void clean_nmethod_postponed(CompiledMethod* nm) { 3691 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3692 } 3693 3694 static const int MaxClaimNmethods = 16; 3695 3696 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3697 CompiledMethod* first; 3698 CompiledMethodIterator last; 3699 3700 do { 3701 *num_claimed_nmethods = 0; 3702 3703 first = (CompiledMethod*)_claimed_nmethod; 3704 last = CompiledMethodIterator(first); 3705 3706 if (first != NULL) { 3707 3708 for (int i = 0; i < MaxClaimNmethods; i++) { 3709 if (!last.next_alive()) { 3710 break; 3711 } 3712 claimed_nmethods[i] = last.method(); 3713 (*num_claimed_nmethods)++; 3714 } 3715 } 3716 3717 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 3718 } 3719 3720 CompiledMethod* claim_postponed_nmethod() { 3721 CompiledMethod* claim; 3722 CompiledMethod* next; 3723 3724 do { 3725 claim = (CompiledMethod*)_postponed_list; 3726 if (claim == NULL) { 3727 return NULL; 3728 } 3729 3730 next = claim->unloading_next(); 3731 3732 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 3733 3734 return claim; 3735 } 3736 3737 public: 3738 // Mark that we're done with the first pass of nmethod cleaning. 3739 void barrier_mark(uint worker_id) { 3740 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3741 _num_entered_barrier++; 3742 if (_num_entered_barrier == _num_workers) { 3743 ml.notify_all(); 3744 } 3745 } 3746 3747 // See if we have to wait for the other workers to 3748 // finish their first-pass nmethod cleaning work. 3749 void barrier_wait(uint worker_id) { 3750 if (_num_entered_barrier < _num_workers) { 3751 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3752 while (_num_entered_barrier < _num_workers) { 3753 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3754 } 3755 } 3756 } 3757 3758 // Cleaning and unloading of nmethods. Some work has to be postponed 3759 // to the second pass, when we know which nmethods survive. 3760 void work_first_pass(uint worker_id) { 3761 // The first nmethods is claimed by the first worker. 3762 if (worker_id == 0 && _first_nmethod != NULL) { 3763 clean_nmethod(_first_nmethod); 3764 _first_nmethod = NULL; 3765 } 3766 3767 int num_claimed_nmethods; 3768 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3769 3770 while (true) { 3771 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3772 3773 if (num_claimed_nmethods == 0) { 3774 break; 3775 } 3776 3777 for (int i = 0; i < num_claimed_nmethods; i++) { 3778 clean_nmethod(claimed_nmethods[i]); 3779 } 3780 } 3781 } 3782 3783 void work_second_pass(uint worker_id) { 3784 CompiledMethod* nm; 3785 // Take care of postponed nmethods. 3786 while ((nm = claim_postponed_nmethod()) != NULL) { 3787 clean_nmethod_postponed(nm); 3788 } 3789 } 3790 }; 3791 3792 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3793 3794 class G1KlassCleaningTask : public StackObj { 3795 BoolObjectClosure* _is_alive; 3796 volatile jint _clean_klass_tree_claimed; 3797 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3798 3799 public: 3800 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3801 _is_alive(is_alive), 3802 _clean_klass_tree_claimed(0), 3803 _klass_iterator() { 3804 } 3805 3806 private: 3807 bool claim_clean_klass_tree_task() { 3808 if (_clean_klass_tree_claimed) { 3809 return false; 3810 } 3811 3812 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 3813 } 3814 3815 InstanceKlass* claim_next_klass() { 3816 Klass* klass; 3817 do { 3818 klass =_klass_iterator.next_klass(); 3819 } while (klass != NULL && !klass->is_instance_klass()); 3820 3821 // this can be null so don't call InstanceKlass::cast 3822 return static_cast<InstanceKlass*>(klass); 3823 } 3824 3825 public: 3826 3827 void clean_klass(InstanceKlass* ik) { 3828 ik->clean_weak_instanceklass_links(_is_alive); 3829 } 3830 3831 void work() { 3832 ResourceMark rm; 3833 3834 // One worker will clean the subklass/sibling klass tree. 3835 if (claim_clean_klass_tree_task()) { 3836 Klass::clean_subklass_tree(_is_alive); 3837 } 3838 3839 // All workers will help cleaning the classes, 3840 InstanceKlass* klass; 3841 while ((klass = claim_next_klass()) != NULL) { 3842 clean_klass(klass); 3843 } 3844 } 3845 }; 3846 3847 // To minimize the remark pause times, the tasks below are done in parallel. 3848 class G1ParallelCleaningTask : public AbstractGangTask { 3849 private: 3850 G1StringAndSymbolCleaningTask _string_symbol_task; 3851 G1CodeCacheUnloadingTask _code_cache_task; 3852 G1KlassCleaningTask _klass_cleaning_task; 3853 3854 public: 3855 // The constructor is run in the VMThread. 3856 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3857 AbstractGangTask("Parallel Cleaning"), 3858 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3859 _code_cache_task(num_workers, is_alive, unloading_occurred), 3860 _klass_cleaning_task(is_alive) { 3861 } 3862 3863 // The parallel work done by all worker threads. 3864 void work(uint worker_id) { 3865 // Do first pass of code cache cleaning. 3866 _code_cache_task.work_first_pass(worker_id); 3867 3868 // Let the threads mark that the first pass is done. 3869 _code_cache_task.barrier_mark(worker_id); 3870 3871 // Clean the Strings and Symbols. 3872 _string_symbol_task.work(worker_id); 3873 3874 // Wait for all workers to finish the first code cache cleaning pass. 3875 _code_cache_task.barrier_wait(worker_id); 3876 3877 // Do the second code cache cleaning work, which realize on 3878 // the liveness information gathered during the first pass. 3879 _code_cache_task.work_second_pass(worker_id); 3880 3881 // Clean all klasses that were not unloaded. 3882 _klass_cleaning_task.work(); 3883 } 3884 }; 3885 3886 3887 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3888 bool class_unloading_occurred) { 3889 uint n_workers = workers()->active_workers(); 3890 3891 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3892 workers()->run_task(&g1_unlink_task); 3893 } 3894 3895 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3896 bool process_strings, 3897 bool process_symbols, 3898 bool process_string_dedup) { 3899 if (!process_strings && !process_symbols && !process_string_dedup) { 3900 // Nothing to clean. 3901 return; 3902 } 3903 3904 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3905 workers()->run_task(&g1_unlink_task); 3906 3907 } 3908 3909 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3910 private: 3911 DirtyCardQueueSet* _queue; 3912 G1CollectedHeap* _g1h; 3913 public: 3914 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3915 _queue(queue), _g1h(g1h) { } 3916 3917 virtual void work(uint worker_id) { 3918 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3919 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3920 3921 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3922 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3923 3924 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3925 } 3926 }; 3927 3928 void G1CollectedHeap::redirty_logged_cards() { 3929 double redirty_logged_cards_start = os::elapsedTime(); 3930 3931 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3932 dirty_card_queue_set().reset_for_par_iteration(); 3933 workers()->run_task(&redirty_task); 3934 3935 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 3936 dcq.merge_bufferlists(&dirty_card_queue_set()); 3937 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3938 3939 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3940 } 3941 3942 // Weak Reference Processing support 3943 3944 // An always "is_alive" closure that is used to preserve referents. 3945 // If the object is non-null then it's alive. Used in the preservation 3946 // of referent objects that are pointed to by reference objects 3947 // discovered by the CM ref processor. 3948 class G1AlwaysAliveClosure: public BoolObjectClosure { 3949 G1CollectedHeap* _g1; 3950 public: 3951 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3952 bool do_object_b(oop p) { 3953 if (p != NULL) { 3954 return true; 3955 } 3956 return false; 3957 } 3958 }; 3959 3960 bool G1STWIsAliveClosure::do_object_b(oop p) { 3961 // An object is reachable if it is outside the collection set, 3962 // or is inside and copied. 3963 return !_g1->is_in_cset(p) || p->is_forwarded(); 3964 } 3965 3966 // Non Copying Keep Alive closure 3967 class G1KeepAliveClosure: public OopClosure { 3968 G1CollectedHeap* _g1; 3969 public: 3970 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3971 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3972 void do_oop(oop* p) { 3973 oop obj = *p; 3974 assert(obj != NULL, "the caller should have filtered out NULL values"); 3975 3976 const InCSetState cset_state = _g1->in_cset_state(obj); 3977 if (!cset_state.is_in_cset_or_humongous()) { 3978 return; 3979 } 3980 if (cset_state.is_in_cset()) { 3981 assert( obj->is_forwarded(), "invariant" ); 3982 *p = obj->forwardee(); 3983 } else { 3984 assert(!obj->is_forwarded(), "invariant" ); 3985 assert(cset_state.is_humongous(), 3986 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3987 _g1->set_humongous_is_live(obj); 3988 } 3989 } 3990 }; 3991 3992 // Copying Keep Alive closure - can be called from both 3993 // serial and parallel code as long as different worker 3994 // threads utilize different G1ParScanThreadState instances 3995 // and different queues. 3996 3997 class G1CopyingKeepAliveClosure: public OopClosure { 3998 G1CollectedHeap* _g1h; 3999 OopClosure* _copy_non_heap_obj_cl; 4000 G1ParScanThreadState* _par_scan_state; 4001 4002 public: 4003 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4004 OopClosure* non_heap_obj_cl, 4005 G1ParScanThreadState* pss): 4006 _g1h(g1h), 4007 _copy_non_heap_obj_cl(non_heap_obj_cl), 4008 _par_scan_state(pss) 4009 {} 4010 4011 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4012 virtual void do_oop( oop* p) { do_oop_work(p); } 4013 4014 template <class T> void do_oop_work(T* p) { 4015 oop obj = oopDesc::load_decode_heap_oop(p); 4016 4017 if (_g1h->is_in_cset_or_humongous(obj)) { 4018 // If the referent object has been forwarded (either copied 4019 // to a new location or to itself in the event of an 4020 // evacuation failure) then we need to update the reference 4021 // field and, if both reference and referent are in the G1 4022 // heap, update the RSet for the referent. 4023 // 4024 // If the referent has not been forwarded then we have to keep 4025 // it alive by policy. Therefore we have copy the referent. 4026 // 4027 // If the reference field is in the G1 heap then we can push 4028 // on the PSS queue. When the queue is drained (after each 4029 // phase of reference processing) the object and it's followers 4030 // will be copied, the reference field set to point to the 4031 // new location, and the RSet updated. Otherwise we need to 4032 // use the the non-heap or metadata closures directly to copy 4033 // the referent object and update the pointer, while avoiding 4034 // updating the RSet. 4035 4036 if (_g1h->is_in_g1_reserved(p)) { 4037 _par_scan_state->push_on_queue(p); 4038 } else { 4039 assert(!Metaspace::contains((const void*)p), 4040 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4041 _copy_non_heap_obj_cl->do_oop(p); 4042 } 4043 } 4044 } 4045 }; 4046 4047 // Serial drain queue closure. Called as the 'complete_gc' 4048 // closure for each discovered list in some of the 4049 // reference processing phases. 4050 4051 class G1STWDrainQueueClosure: public VoidClosure { 4052 protected: 4053 G1CollectedHeap* _g1h; 4054 G1ParScanThreadState* _par_scan_state; 4055 4056 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4057 4058 public: 4059 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4060 _g1h(g1h), 4061 _par_scan_state(pss) 4062 { } 4063 4064 void do_void() { 4065 G1ParScanThreadState* const pss = par_scan_state(); 4066 pss->trim_queue(); 4067 } 4068 }; 4069 4070 // Parallel Reference Processing closures 4071 4072 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4073 // processing during G1 evacuation pauses. 4074 4075 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4076 private: 4077 G1CollectedHeap* _g1h; 4078 G1ParScanThreadStateSet* _pss; 4079 RefToScanQueueSet* _queues; 4080 WorkGang* _workers; 4081 uint _active_workers; 4082 4083 public: 4084 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4085 G1ParScanThreadStateSet* per_thread_states, 4086 WorkGang* workers, 4087 RefToScanQueueSet *task_queues, 4088 uint n_workers) : 4089 _g1h(g1h), 4090 _pss(per_thread_states), 4091 _queues(task_queues), 4092 _workers(workers), 4093 _active_workers(n_workers) 4094 { 4095 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 4096 } 4097 4098 // Executes the given task using concurrent marking worker threads. 4099 virtual void execute(ProcessTask& task); 4100 virtual void execute(EnqueueTask& task); 4101 }; 4102 4103 // Gang task for possibly parallel reference processing 4104 4105 class G1STWRefProcTaskProxy: public AbstractGangTask { 4106 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4107 ProcessTask& _proc_task; 4108 G1CollectedHeap* _g1h; 4109 G1ParScanThreadStateSet* _pss; 4110 RefToScanQueueSet* _task_queues; 4111 ParallelTaskTerminator* _terminator; 4112 4113 public: 4114 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4115 G1CollectedHeap* g1h, 4116 G1ParScanThreadStateSet* per_thread_states, 4117 RefToScanQueueSet *task_queues, 4118 ParallelTaskTerminator* terminator) : 4119 AbstractGangTask("Process reference objects in parallel"), 4120 _proc_task(proc_task), 4121 _g1h(g1h), 4122 _pss(per_thread_states), 4123 _task_queues(task_queues), 4124 _terminator(terminator) 4125 {} 4126 4127 virtual void work(uint worker_id) { 4128 // The reference processing task executed by a single worker. 4129 ResourceMark rm; 4130 HandleMark hm; 4131 4132 G1STWIsAliveClosure is_alive(_g1h); 4133 4134 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4135 pss->set_ref_processor(NULL); 4136 4137 // Keep alive closure. 4138 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4139 4140 // Complete GC closure 4141 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4142 4143 // Call the reference processing task's work routine. 4144 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4145 4146 // Note we cannot assert that the refs array is empty here as not all 4147 // of the processing tasks (specifically phase2 - pp2_work) execute 4148 // the complete_gc closure (which ordinarily would drain the queue) so 4149 // the queue may not be empty. 4150 } 4151 }; 4152 4153 // Driver routine for parallel reference processing. 4154 // Creates an instance of the ref processing gang 4155 // task and has the worker threads execute it. 4156 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4157 assert(_workers != NULL, "Need parallel worker threads."); 4158 4159 ParallelTaskTerminator terminator(_active_workers, _queues); 4160 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4161 4162 _workers->run_task(&proc_task_proxy); 4163 } 4164 4165 // Gang task for parallel reference enqueueing. 4166 4167 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4168 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4169 EnqueueTask& _enq_task; 4170 4171 public: 4172 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4173 AbstractGangTask("Enqueue reference objects in parallel"), 4174 _enq_task(enq_task) 4175 { } 4176 4177 virtual void work(uint worker_id) { 4178 _enq_task.work(worker_id); 4179 } 4180 }; 4181 4182 // Driver routine for parallel reference enqueueing. 4183 // Creates an instance of the ref enqueueing gang 4184 // task and has the worker threads execute it. 4185 4186 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4187 assert(_workers != NULL, "Need parallel worker threads."); 4188 4189 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4190 4191 _workers->run_task(&enq_task_proxy); 4192 } 4193 4194 // End of weak reference support closures 4195 4196 // Abstract task used to preserve (i.e. copy) any referent objects 4197 // that are in the collection set and are pointed to by reference 4198 // objects discovered by the CM ref processor. 4199 4200 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4201 protected: 4202 G1CollectedHeap* _g1h; 4203 G1ParScanThreadStateSet* _pss; 4204 RefToScanQueueSet* _queues; 4205 ParallelTaskTerminator _terminator; 4206 uint _n_workers; 4207 4208 public: 4209 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4210 AbstractGangTask("ParPreserveCMReferents"), 4211 _g1h(g1h), 4212 _pss(per_thread_states), 4213 _queues(task_queues), 4214 _terminator(workers, _queues), 4215 _n_workers(workers) 4216 { 4217 g1h->ref_processor_cm()->set_active_mt_degree(workers); 4218 } 4219 4220 void work(uint worker_id) { 4221 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4222 4223 ResourceMark rm; 4224 HandleMark hm; 4225 4226 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4227 pss->set_ref_processor(NULL); 4228 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4229 4230 // Is alive closure 4231 G1AlwaysAliveClosure always_alive(_g1h); 4232 4233 // Copying keep alive closure. Applied to referent objects that need 4234 // to be copied. 4235 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4236 4237 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4238 4239 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4240 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4241 4242 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4243 // So this must be true - but assert just in case someone decides to 4244 // change the worker ids. 4245 assert(worker_id < limit, "sanity"); 4246 assert(!rp->discovery_is_atomic(), "check this code"); 4247 4248 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4249 for (uint idx = worker_id; idx < limit; idx += stride) { 4250 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4251 4252 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4253 while (iter.has_next()) { 4254 // Since discovery is not atomic for the CM ref processor, we 4255 // can see some null referent objects. 4256 iter.load_ptrs(DEBUG_ONLY(true)); 4257 oop ref = iter.obj(); 4258 4259 // This will filter nulls. 4260 if (iter.is_referent_alive()) { 4261 iter.make_referent_alive(); 4262 } 4263 iter.move_to_next(); 4264 } 4265 } 4266 4267 // Drain the queue - which may cause stealing 4268 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4269 drain_queue.do_void(); 4270 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4271 assert(pss->queue_is_empty(), "should be"); 4272 } 4273 }; 4274 4275 void G1CollectedHeap::process_weak_jni_handles() { 4276 double ref_proc_start = os::elapsedTime(); 4277 4278 G1STWIsAliveClosure is_alive(this); 4279 G1KeepAliveClosure keep_alive(this); 4280 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 4281 4282 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4283 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4284 } 4285 4286 void G1CollectedHeap::process_heap_monitoring() { 4287 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : heap monitoring"); 4288 G1STWIsAliveClosure is_alive(this); 4289 G1KeepAliveClosure keep_alive(this); 4290 HeapMonitoring::weak_oops_do(NULL, &is_alive, &keep_alive, NULL); 4291 } 4292 4293 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4294 // Any reference objects, in the collection set, that were 'discovered' 4295 // by the CM ref processor should have already been copied (either by 4296 // applying the external root copy closure to the discovered lists, or 4297 // by following an RSet entry). 4298 // 4299 // But some of the referents, that are in the collection set, that these 4300 // reference objects point to may not have been copied: the STW ref 4301 // processor would have seen that the reference object had already 4302 // been 'discovered' and would have skipped discovering the reference, 4303 // but would not have treated the reference object as a regular oop. 4304 // As a result the copy closure would not have been applied to the 4305 // referent object. 4306 // 4307 // We need to explicitly copy these referent objects - the references 4308 // will be processed at the end of remarking. 4309 // 4310 // We also need to do this copying before we process the reference 4311 // objects discovered by the STW ref processor in case one of these 4312 // referents points to another object which is also referenced by an 4313 // object discovered by the STW ref processor. 4314 double preserve_cm_referents_time = 0.0; 4315 4316 // To avoid spawning task when there is no work to do, check that 4317 // a concurrent cycle is active and that some references have been 4318 // discovered. 4319 if (concurrent_mark()->cmThread()->during_cycle() && 4320 ref_processor_cm()->has_discovered_references()) { 4321 double preserve_cm_referents_start = os::elapsedTime(); 4322 uint no_of_gc_workers = workers()->active_workers(); 4323 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4324 per_thread_states, 4325 no_of_gc_workers, 4326 _task_queues); 4327 workers()->run_task(&keep_cm_referents); 4328 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4329 } 4330 4331 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4332 } 4333 4334 // Weak Reference processing during an evacuation pause (part 1). 4335 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4336 double ref_proc_start = os::elapsedTime(); 4337 4338 ReferenceProcessor* rp = _ref_processor_stw; 4339 assert(rp->discovery_enabled(), "should have been enabled"); 4340 4341 // Closure to test whether a referent is alive. 4342 G1STWIsAliveClosure is_alive(this); 4343 4344 // Even when parallel reference processing is enabled, the processing 4345 // of JNI refs is serial and performed serially by the current thread 4346 // rather than by a worker. The following PSS will be used for processing 4347 // JNI refs. 4348 4349 // Use only a single queue for this PSS. 4350 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4351 pss->set_ref_processor(NULL); 4352 assert(pss->queue_is_empty(), "pre-condition"); 4353 4354 // Keep alive closure. 4355 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4356 4357 // Serial Complete GC closure 4358 G1STWDrainQueueClosure drain_queue(this, pss); 4359 4360 // Setup the soft refs policy... 4361 rp->setup_policy(false); 4362 4363 ReferenceProcessorStats stats; 4364 if (!rp->processing_is_mt()) { 4365 // Serial reference processing... 4366 stats = rp->process_discovered_references(&is_alive, 4367 &keep_alive, 4368 &drain_queue, 4369 NULL, 4370 _gc_timer_stw); 4371 } else { 4372 uint no_of_gc_workers = workers()->active_workers(); 4373 4374 // Parallel reference processing 4375 assert(no_of_gc_workers <= rp->max_num_q(), 4376 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4377 no_of_gc_workers, rp->max_num_q()); 4378 4379 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4380 stats = rp->process_discovered_references(&is_alive, 4381 &keep_alive, 4382 &drain_queue, 4383 &par_task_executor, 4384 _gc_timer_stw); 4385 } 4386 4387 _gc_tracer_stw->report_gc_reference_stats(stats); 4388 4389 // We have completed copying any necessary live referent objects. 4390 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4391 4392 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4393 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4394 } 4395 4396 // Weak Reference processing during an evacuation pause (part 2). 4397 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4398 double ref_enq_start = os::elapsedTime(); 4399 4400 ReferenceProcessor* rp = _ref_processor_stw; 4401 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4402 4403 // Now enqueue any remaining on the discovered lists on to 4404 // the pending list. 4405 if (!rp->processing_is_mt()) { 4406 // Serial reference processing... 4407 rp->enqueue_discovered_references(); 4408 } else { 4409 // Parallel reference enqueueing 4410 4411 uint n_workers = workers()->active_workers(); 4412 4413 assert(n_workers <= rp->max_num_q(), 4414 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4415 n_workers, rp->max_num_q()); 4416 4417 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4418 rp->enqueue_discovered_references(&par_task_executor); 4419 } 4420 4421 rp->verify_no_references_recorded(); 4422 assert(!rp->discovery_enabled(), "should have been disabled"); 4423 4424 // FIXME 4425 // CM's reference processing also cleans up the string and symbol tables. 4426 // Should we do that here also? We could, but it is a serial operation 4427 // and could significantly increase the pause time. 4428 4429 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4430 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4431 } 4432 4433 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4434 double merge_pss_time_start = os::elapsedTime(); 4435 per_thread_states->flush(); 4436 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4437 } 4438 4439 void G1CollectedHeap::pre_evacuate_collection_set() { 4440 _expand_heap_after_alloc_failure = true; 4441 _evacuation_failed = false; 4442 4443 // Disable the hot card cache. 4444 _hot_card_cache->reset_hot_cache_claimed_index(); 4445 _hot_card_cache->set_use_cache(false); 4446 4447 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4448 _preserved_marks_set.assert_empty(); 4449 4450 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4451 4452 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4453 if (collector_state()->during_initial_mark_pause()) { 4454 double start_clear_claimed_marks = os::elapsedTime(); 4455 4456 ClassLoaderDataGraph::clear_claimed_marks(); 4457 4458 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4459 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4460 } 4461 } 4462 4463 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4464 // Should G1EvacuationFailureALot be in effect for this GC? 4465 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4466 4467 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4468 4469 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4470 4471 double start_par_time_sec = os::elapsedTime(); 4472 double end_par_time_sec; 4473 4474 { 4475 const uint n_workers = workers()->active_workers(); 4476 G1RootProcessor root_processor(this, n_workers); 4477 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4478 4479 print_termination_stats_hdr(); 4480 4481 workers()->run_task(&g1_par_task); 4482 end_par_time_sec = os::elapsedTime(); 4483 4484 // Closing the inner scope will execute the destructor 4485 // for the G1RootProcessor object. We record the current 4486 // elapsed time before closing the scope so that time 4487 // taken for the destructor is NOT included in the 4488 // reported parallel time. 4489 } 4490 4491 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4492 phase_times->record_par_time(par_time_ms); 4493 4494 double code_root_fixup_time_ms = 4495 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4496 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4497 } 4498 4499 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4500 // Process any discovered reference objects - we have 4501 // to do this _before_ we retire the GC alloc regions 4502 // as we may have to copy some 'reachable' referent 4503 // objects (and their reachable sub-graphs) that were 4504 // not copied during the pause. 4505 if (g1_policy()->should_process_references()) { 4506 preserve_cm_referents(per_thread_states); 4507 process_discovered_references(per_thread_states); 4508 } else { 4509 ref_processor_stw()->verify_no_references_recorded(); 4510 process_weak_jni_handles(); 4511 process_heap_monitoring(); 4512 } 4513 4514 if (G1StringDedup::is_enabled()) { 4515 double fixup_start = os::elapsedTime(); 4516 4517 G1STWIsAliveClosure is_alive(this); 4518 G1KeepAliveClosure keep_alive(this); 4519 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4520 4521 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4522 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4523 } 4524 4525 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4526 4527 if (evacuation_failed()) { 4528 restore_after_evac_failure(); 4529 4530 // Reset the G1EvacuationFailureALot counters and flags 4531 // Note: the values are reset only when an actual 4532 // evacuation failure occurs. 4533 NOT_PRODUCT(reset_evacuation_should_fail();) 4534 } 4535 4536 _preserved_marks_set.assert_empty(); 4537 4538 // Enqueue any remaining references remaining on the STW 4539 // reference processor's discovered lists. We need to do 4540 // this after the card table is cleaned (and verified) as 4541 // the act of enqueueing entries on to the pending list 4542 // will log these updates (and dirty their associated 4543 // cards). We need these updates logged to update any 4544 // RSets. 4545 if (g1_policy()->should_process_references()) { 4546 enqueue_discovered_references(per_thread_states); 4547 } else { 4548 g1_policy()->phase_times()->record_ref_enq_time(0); 4549 } 4550 4551 _allocator->release_gc_alloc_regions(evacuation_info); 4552 4553 merge_per_thread_state_info(per_thread_states); 4554 4555 // Reset and re-enable the hot card cache. 4556 // Note the counts for the cards in the regions in the 4557 // collection set are reset when the collection set is freed. 4558 _hot_card_cache->reset_hot_cache(); 4559 _hot_card_cache->set_use_cache(true); 4560 4561 purge_code_root_memory(); 4562 4563 redirty_logged_cards(); 4564 #if defined(COMPILER2) || INCLUDE_JVMCI 4565 double start = os::elapsedTime(); 4566 DerivedPointerTable::update_pointers(); 4567 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4568 #endif 4569 g1_policy()->print_age_table(); 4570 } 4571 4572 void G1CollectedHeap::record_obj_copy_mem_stats() { 4573 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4574 4575 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4576 create_g1_evac_summary(&_old_evac_stats)); 4577 } 4578 4579 void G1CollectedHeap::free_region(HeapRegion* hr, 4580 FreeRegionList* free_list, 4581 bool skip_remset, 4582 bool skip_hot_card_cache, 4583 bool locked) { 4584 assert(!hr->is_free(), "the region should not be free"); 4585 assert(!hr->is_empty(), "the region should not be empty"); 4586 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4587 assert(free_list != NULL, "pre-condition"); 4588 4589 if (G1VerifyBitmaps) { 4590 MemRegion mr(hr->bottom(), hr->end()); 4591 concurrent_mark()->clearRangePrevBitmap(mr); 4592 } 4593 4594 // Clear the card counts for this region. 4595 // Note: we only need to do this if the region is not young 4596 // (since we don't refine cards in young regions). 4597 if (!skip_hot_card_cache && !hr->is_young()) { 4598 _hot_card_cache->reset_card_counts(hr); 4599 } 4600 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4601 free_list->add_ordered(hr); 4602 } 4603 4604 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4605 FreeRegionList* free_list, 4606 bool skip_remset) { 4607 assert(hr->is_humongous(), "this is only for humongous regions"); 4608 assert(free_list != NULL, "pre-condition"); 4609 hr->clear_humongous(); 4610 free_region(hr, free_list, skip_remset); 4611 } 4612 4613 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4614 const uint humongous_regions_removed) { 4615 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4616 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4617 _old_set.bulk_remove(old_regions_removed); 4618 _humongous_set.bulk_remove(humongous_regions_removed); 4619 } 4620 4621 } 4622 4623 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4624 assert(list != NULL, "list can't be null"); 4625 if (!list->is_empty()) { 4626 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4627 _hrm.insert_list_into_free_list(list); 4628 } 4629 } 4630 4631 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4632 decrease_used(bytes); 4633 } 4634 4635 class G1ParScrubRemSetTask: public AbstractGangTask { 4636 protected: 4637 G1RemSet* _g1rs; 4638 HeapRegionClaimer _hrclaimer; 4639 4640 public: 4641 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) : 4642 AbstractGangTask("G1 ScrubRS"), 4643 _g1rs(g1_rs), 4644 _hrclaimer(num_workers) { 4645 } 4646 4647 void work(uint worker_id) { 4648 _g1rs->scrub(worker_id, &_hrclaimer); 4649 } 4650 }; 4651 4652 void G1CollectedHeap::scrub_rem_set() { 4653 uint num_workers = workers()->active_workers(); 4654 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers); 4655 workers()->run_task(&g1_par_scrub_rs_task); 4656 } 4657 4658 class G1FreeCollectionSetTask : public AbstractGangTask { 4659 private: 4660 4661 // Closure applied to all regions in the collection set to do work that needs to 4662 // be done serially in a single thread. 4663 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4664 private: 4665 EvacuationInfo* _evacuation_info; 4666 const size_t* _surviving_young_words; 4667 4668 // Bytes used in successfully evacuated regions before the evacuation. 4669 size_t _before_used_bytes; 4670 // Bytes used in unsucessfully evacuated regions before the evacuation 4671 size_t _after_used_bytes; 4672 4673 size_t _bytes_allocated_in_old_since_last_gc; 4674 4675 size_t _failure_used_words; 4676 size_t _failure_waste_words; 4677 4678 FreeRegionList _local_free_list; 4679 public: 4680 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4681 HeapRegionClosure(), 4682 _evacuation_info(evacuation_info), 4683 _surviving_young_words(surviving_young_words), 4684 _before_used_bytes(0), 4685 _after_used_bytes(0), 4686 _bytes_allocated_in_old_since_last_gc(0), 4687 _failure_used_words(0), 4688 _failure_waste_words(0), 4689 _local_free_list("Local Region List for CSet Freeing") { 4690 } 4691 4692 virtual bool doHeapRegion(HeapRegion* r) { 4693 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4694 4695 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4696 g1h->clear_in_cset(r); 4697 4698 if (r->is_young()) { 4699 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4700 "Young index %d is wrong for region %u of type %s with %u young regions", 4701 r->young_index_in_cset(), 4702 r->hrm_index(), 4703 r->get_type_str(), 4704 g1h->collection_set()->young_region_length()); 4705 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4706 r->record_surv_words_in_group(words_survived); 4707 } 4708 4709 if (!r->evacuation_failed()) { 4710 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4711 _before_used_bytes += r->used(); 4712 g1h->free_region(r, 4713 &_local_free_list, 4714 true, /* skip_remset */ 4715 true, /* skip_hot_card_cache */ 4716 true /* locked */); 4717 } else { 4718 r->uninstall_surv_rate_group(); 4719 r->set_young_index_in_cset(-1); 4720 r->set_evacuation_failed(false); 4721 // When moving a young gen region to old gen, we "allocate" that whole region 4722 // there. This is in addition to any already evacuated objects. Notify the 4723 // policy about that. 4724 // Old gen regions do not cause an additional allocation: both the objects 4725 // still in the region and the ones already moved are accounted for elsewhere. 4726 if (r->is_young()) { 4727 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4728 } 4729 // The region is now considered to be old. 4730 r->set_old(); 4731 // Do some allocation statistics accounting. Regions that failed evacuation 4732 // are always made old, so there is no need to update anything in the young 4733 // gen statistics, but we need to update old gen statistics. 4734 size_t used_words = r->marked_bytes() / HeapWordSize; 4735 4736 _failure_used_words += used_words; 4737 _failure_waste_words += HeapRegion::GrainWords - used_words; 4738 4739 g1h->old_set_add(r); 4740 _after_used_bytes += r->used(); 4741 } 4742 return false; 4743 } 4744 4745 void complete_work() { 4746 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4747 4748 _evacuation_info->set_regions_freed(_local_free_list.length()); 4749 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4750 4751 g1h->prepend_to_freelist(&_local_free_list); 4752 g1h->decrement_summary_bytes(_before_used_bytes); 4753 4754 G1Policy* policy = g1h->g1_policy(); 4755 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4756 4757 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4758 } 4759 }; 4760 4761 G1CollectionSet* _collection_set; 4762 G1SerialFreeCollectionSetClosure _cl; 4763 const size_t* _surviving_young_words; 4764 4765 size_t _rs_lengths; 4766 4767 volatile jint _serial_work_claim; 4768 4769 struct WorkItem { 4770 uint region_idx; 4771 bool is_young; 4772 bool evacuation_failed; 4773 4774 WorkItem(HeapRegion* r) { 4775 region_idx = r->hrm_index(); 4776 is_young = r->is_young(); 4777 evacuation_failed = r->evacuation_failed(); 4778 } 4779 }; 4780 4781 volatile size_t _parallel_work_claim; 4782 size_t _num_work_items; 4783 WorkItem* _work_items; 4784 4785 void do_serial_work() { 4786 // Need to grab the lock to be allowed to modify the old region list. 4787 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4788 _collection_set->iterate(&_cl); 4789 } 4790 4791 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4792 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4793 4794 HeapRegion* r = g1h->region_at(region_idx); 4795 assert(!g1h->is_on_master_free_list(r), "sanity"); 4796 4797 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4798 4799 if (!is_young) { 4800 g1h->_hot_card_cache->reset_card_counts(r); 4801 } 4802 4803 if (!evacuation_failed) { 4804 r->rem_set()->clear_locked(); 4805 } 4806 } 4807 4808 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4809 private: 4810 size_t _cur_idx; 4811 WorkItem* _work_items; 4812 public: 4813 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4814 4815 virtual bool doHeapRegion(HeapRegion* r) { 4816 _work_items[_cur_idx++] = WorkItem(r); 4817 return false; 4818 } 4819 }; 4820 4821 void prepare_work() { 4822 G1PrepareFreeCollectionSetClosure cl(_work_items); 4823 _collection_set->iterate(&cl); 4824 } 4825 4826 void complete_work() { 4827 _cl.complete_work(); 4828 4829 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4830 policy->record_max_rs_lengths(_rs_lengths); 4831 policy->cset_regions_freed(); 4832 } 4833 public: 4834 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4835 AbstractGangTask("G1 Free Collection Set"), 4836 _cl(evacuation_info, surviving_young_words), 4837 _collection_set(collection_set), 4838 _surviving_young_words(surviving_young_words), 4839 _serial_work_claim(0), 4840 _rs_lengths(0), 4841 _parallel_work_claim(0), 4842 _num_work_items(collection_set->region_length()), 4843 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4844 prepare_work(); 4845 } 4846 4847 ~G1FreeCollectionSetTask() { 4848 complete_work(); 4849 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4850 } 4851 4852 // Chunk size for work distribution. The chosen value has been determined experimentally 4853 // to be a good tradeoff between overhead and achievable parallelism. 4854 static uint chunk_size() { return 32; } 4855 4856 virtual void work(uint worker_id) { 4857 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4858 4859 // Claim serial work. 4860 if (_serial_work_claim == 0) { 4861 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4862 if (value == 0) { 4863 double serial_time = os::elapsedTime(); 4864 do_serial_work(); 4865 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4866 } 4867 } 4868 4869 // Start parallel work. 4870 double young_time = 0.0; 4871 bool has_young_time = false; 4872 double non_young_time = 0.0; 4873 bool has_non_young_time = false; 4874 4875 while (true) { 4876 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4877 size_t cur = end - chunk_size(); 4878 4879 if (cur >= _num_work_items) { 4880 break; 4881 } 4882 4883 double start_time = os::elapsedTime(); 4884 4885 end = MIN2(end, _num_work_items); 4886 4887 for (; cur < end; cur++) { 4888 bool is_young = _work_items[cur].is_young; 4889 4890 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4891 4892 double end_time = os::elapsedTime(); 4893 double time_taken = end_time - start_time; 4894 if (is_young) { 4895 young_time += time_taken; 4896 has_young_time = true; 4897 } else { 4898 non_young_time += time_taken; 4899 has_non_young_time = true; 4900 } 4901 start_time = end_time; 4902 } 4903 } 4904 4905 if (has_young_time) { 4906 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4907 } 4908 if (has_non_young_time) { 4909 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time); 4910 } 4911 } 4912 }; 4913 4914 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4915 _eden.clear(); 4916 4917 double free_cset_start_time = os::elapsedTime(); 4918 4919 { 4920 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4921 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4922 4923 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4924 4925 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4926 cl.name(), 4927 num_workers, 4928 _collection_set.region_length()); 4929 workers()->run_task(&cl, num_workers); 4930 } 4931 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4932 4933 collection_set->clear(); 4934 } 4935 4936 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4937 private: 4938 FreeRegionList* _free_region_list; 4939 HeapRegionSet* _proxy_set; 4940 uint _humongous_objects_reclaimed; 4941 uint _humongous_regions_reclaimed; 4942 size_t _freed_bytes; 4943 public: 4944 4945 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4946 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4947 } 4948 4949 virtual bool doHeapRegion(HeapRegion* r) { 4950 if (!r->is_starts_humongous()) { 4951 return false; 4952 } 4953 4954 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4955 4956 oop obj = (oop)r->bottom(); 4957 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 4958 4959 // The following checks whether the humongous object is live are sufficient. 4960 // The main additional check (in addition to having a reference from the roots 4961 // or the young gen) is whether the humongous object has a remembered set entry. 4962 // 4963 // A humongous object cannot be live if there is no remembered set for it 4964 // because: 4965 // - there can be no references from within humongous starts regions referencing 4966 // the object because we never allocate other objects into them. 4967 // (I.e. there are no intra-region references that may be missed by the 4968 // remembered set) 4969 // - as soon there is a remembered set entry to the humongous starts region 4970 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4971 // until the end of a concurrent mark. 4972 // 4973 // It is not required to check whether the object has been found dead by marking 4974 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4975 // all objects allocated during that time are considered live. 4976 // SATB marking is even more conservative than the remembered set. 4977 // So if at this point in the collection there is no remembered set entry, 4978 // nobody has a reference to it. 4979 // At the start of collection we flush all refinement logs, and remembered sets 4980 // are completely up-to-date wrt to references to the humongous object. 4981 // 4982 // Other implementation considerations: 4983 // - never consider object arrays at this time because they would pose 4984 // considerable effort for cleaning up the the remembered sets. This is 4985 // required because stale remembered sets might reference locations that 4986 // are currently allocated into. 4987 uint region_idx = r->hrm_index(); 4988 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4989 !r->rem_set()->is_empty()) { 4990 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", 4991 region_idx, 4992 (size_t)obj->size() * HeapWordSize, 4993 p2i(r->bottom()), 4994 r->rem_set()->occupied(), 4995 r->rem_set()->strong_code_roots_list_length(), 4996 next_bitmap->isMarked(r->bottom()), 4997 g1h->is_humongous_reclaim_candidate(region_idx), 4998 obj->is_typeArray() 4999 ); 5000 return false; 5001 } 5002 5003 guarantee(obj->is_typeArray(), 5004 "Only eagerly reclaiming type arrays is supported, but the object " 5005 PTR_FORMAT " is not.", p2i(r->bottom())); 5006 5007 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", 5008 region_idx, 5009 (size_t)obj->size() * HeapWordSize, 5010 p2i(r->bottom()), 5011 r->rem_set()->occupied(), 5012 r->rem_set()->strong_code_roots_list_length(), 5013 next_bitmap->isMarked(r->bottom()), 5014 g1h->is_humongous_reclaim_candidate(region_idx), 5015 obj->is_typeArray() 5016 ); 5017 5018 // Need to clear mark bit of the humongous object if already set. 5019 if (next_bitmap->isMarked(r->bottom())) { 5020 next_bitmap->clear(r->bottom()); 5021 } 5022 _humongous_objects_reclaimed++; 5023 do { 5024 HeapRegion* next = g1h->next_region_in_humongous(r); 5025 _freed_bytes += r->used(); 5026 r->set_containing_set(NULL); 5027 _humongous_regions_reclaimed++; 5028 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ ); 5029 r = next; 5030 } while (r != NULL); 5031 5032 return false; 5033 } 5034 5035 uint humongous_objects_reclaimed() { 5036 return _humongous_objects_reclaimed; 5037 } 5038 5039 uint humongous_regions_reclaimed() { 5040 return _humongous_regions_reclaimed; 5041 } 5042 5043 size_t bytes_freed() const { 5044 return _freed_bytes; 5045 } 5046 }; 5047 5048 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 5049 assert_at_safepoint(true); 5050 5051 if (!G1EagerReclaimHumongousObjects || 5052 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 5053 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5054 return; 5055 } 5056 5057 double start_time = os::elapsedTime(); 5058 5059 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5060 5061 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5062 heap_region_iterate(&cl); 5063 5064 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 5065 5066 G1HRPrinter* hrp = hr_printer(); 5067 if (hrp->is_active()) { 5068 FreeRegionListIterator iter(&local_cleanup_list); 5069 while (iter.more_available()) { 5070 HeapRegion* hr = iter.get_next(); 5071 hrp->cleanup(hr); 5072 } 5073 } 5074 5075 prepend_to_freelist(&local_cleanup_list); 5076 decrement_summary_bytes(cl.bytes_freed()); 5077 5078 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5079 cl.humongous_objects_reclaimed()); 5080 } 5081 5082 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 5083 public: 5084 virtual bool doHeapRegion(HeapRegion* r) { 5085 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 5086 G1CollectedHeap::heap()->clear_in_cset(r); 5087 r->set_young_index_in_cset(-1); 5088 return false; 5089 } 5090 }; 5091 5092 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 5093 G1AbandonCollectionSetClosure cl; 5094 collection_set->iterate(&cl); 5095 5096 collection_set->clear(); 5097 collection_set->stop_incremental_building(); 5098 } 5099 5100 void G1CollectedHeap::set_free_regions_coming() { 5101 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 5102 5103 assert(!free_regions_coming(), "pre-condition"); 5104 _free_regions_coming = true; 5105 } 5106 5107 void G1CollectedHeap::reset_free_regions_coming() { 5108 assert(free_regions_coming(), "pre-condition"); 5109 5110 { 5111 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5112 _free_regions_coming = false; 5113 SecondaryFreeList_lock->notify_all(); 5114 } 5115 5116 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 5117 } 5118 5119 void G1CollectedHeap::wait_while_free_regions_coming() { 5120 // Most of the time we won't have to wait, so let's do a quick test 5121 // first before we take the lock. 5122 if (!free_regions_coming()) { 5123 return; 5124 } 5125 5126 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 5127 5128 { 5129 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5130 while (free_regions_coming()) { 5131 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5132 } 5133 } 5134 5135 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 5136 } 5137 5138 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5139 return _allocator->is_retained_old_region(hr); 5140 } 5141 5142 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5143 _eden.add(hr); 5144 _g1_policy->set_region_eden(hr); 5145 } 5146 5147 #ifdef ASSERT 5148 5149 class NoYoungRegionsClosure: public HeapRegionClosure { 5150 private: 5151 bool _success; 5152 public: 5153 NoYoungRegionsClosure() : _success(true) { } 5154 bool doHeapRegion(HeapRegion* r) { 5155 if (r->is_young()) { 5156 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5157 p2i(r->bottom()), p2i(r->end())); 5158 _success = false; 5159 } 5160 return false; 5161 } 5162 bool success() { return _success; } 5163 }; 5164 5165 bool G1CollectedHeap::check_young_list_empty() { 5166 bool ret = (young_regions_count() == 0); 5167 5168 NoYoungRegionsClosure closure; 5169 heap_region_iterate(&closure); 5170 ret = ret && closure.success(); 5171 5172 return ret; 5173 } 5174 5175 #endif // ASSERT 5176 5177 class TearDownRegionSetsClosure : public HeapRegionClosure { 5178 private: 5179 HeapRegionSet *_old_set; 5180 5181 public: 5182 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5183 5184 bool doHeapRegion(HeapRegion* r) { 5185 if (r->is_old()) { 5186 _old_set->remove(r); 5187 } else if(r->is_young()) { 5188 r->uninstall_surv_rate_group(); 5189 } else { 5190 // We ignore free regions, we'll empty the free list afterwards. 5191 // We ignore humongous regions, we're not tearing down the 5192 // humongous regions set. 5193 assert(r->is_free() || r->is_humongous(), 5194 "it cannot be another type"); 5195 } 5196 return false; 5197 } 5198 5199 ~TearDownRegionSetsClosure() { 5200 assert(_old_set->is_empty(), "post-condition"); 5201 } 5202 }; 5203 5204 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5205 assert_at_safepoint(true /* should_be_vm_thread */); 5206 5207 if (!free_list_only) { 5208 TearDownRegionSetsClosure cl(&_old_set); 5209 heap_region_iterate(&cl); 5210 5211 // Note that emptying the _young_list is postponed and instead done as 5212 // the first step when rebuilding the regions sets again. The reason for 5213 // this is that during a full GC string deduplication needs to know if 5214 // a collected region was young or old when the full GC was initiated. 5215 } 5216 _hrm.remove_all_free_regions(); 5217 } 5218 5219 void G1CollectedHeap::increase_used(size_t bytes) { 5220 _summary_bytes_used += bytes; 5221 } 5222 5223 void G1CollectedHeap::decrease_used(size_t bytes) { 5224 assert(_summary_bytes_used >= bytes, 5225 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5226 _summary_bytes_used, bytes); 5227 _summary_bytes_used -= bytes; 5228 } 5229 5230 void G1CollectedHeap::set_used(size_t bytes) { 5231 _summary_bytes_used = bytes; 5232 } 5233 5234 class RebuildRegionSetsClosure : public HeapRegionClosure { 5235 private: 5236 bool _free_list_only; 5237 HeapRegionSet* _old_set; 5238 HeapRegionManager* _hrm; 5239 size_t _total_used; 5240 5241 public: 5242 RebuildRegionSetsClosure(bool free_list_only, 5243 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5244 _free_list_only(free_list_only), 5245 _old_set(old_set), _hrm(hrm), _total_used(0) { 5246 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5247 if (!free_list_only) { 5248 assert(_old_set->is_empty(), "pre-condition"); 5249 } 5250 } 5251 5252 bool doHeapRegion(HeapRegion* r) { 5253 if (r->is_empty()) { 5254 // Add free regions to the free list 5255 r->set_free(); 5256 r->set_allocation_context(AllocationContext::system()); 5257 _hrm->insert_into_free_list(r); 5258 } else if (!_free_list_only) { 5259 5260 if (r->is_humongous()) { 5261 // We ignore humongous regions. We left the humongous set unchanged. 5262 } else { 5263 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 5264 // We now consider all regions old, so register as such. Leave 5265 // archive regions set that way, however, while still adding 5266 // them to the old set. 5267 if (!r->is_archive()) { 5268 r->set_old(); 5269 } 5270 _old_set->add(r); 5271 } 5272 _total_used += r->used(); 5273 } 5274 5275 return false; 5276 } 5277 5278 size_t total_used() { 5279 return _total_used; 5280 } 5281 }; 5282 5283 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5284 assert_at_safepoint(true /* should_be_vm_thread */); 5285 5286 if (!free_list_only) { 5287 _eden.clear(); 5288 _survivor.clear(); 5289 } 5290 5291 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5292 heap_region_iterate(&cl); 5293 5294 if (!free_list_only) { 5295 set_used(cl.total_used()); 5296 if (_archive_allocator != NULL) { 5297 _archive_allocator->clear_used(); 5298 } 5299 } 5300 assert(used_unlocked() == recalculate_used(), 5301 "inconsistent used_unlocked(), " 5302 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5303 used_unlocked(), recalculate_used()); 5304 } 5305 5306 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 5307 _refine_cte_cl->set_concurrent(concurrent); 5308 } 5309 5310 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5311 HeapRegion* hr = heap_region_containing(p); 5312 return hr->is_in(p); 5313 } 5314 5315 // Methods for the mutator alloc region 5316 5317 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5318 bool force) { 5319 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5320 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 5321 if (force || should_allocate) { 5322 HeapRegion* new_alloc_region = new_region(word_size, 5323 false /* is_old */, 5324 false /* do_expand */); 5325 if (new_alloc_region != NULL) { 5326 set_region_short_lived_locked(new_alloc_region); 5327 _hr_printer.alloc(new_alloc_region, !should_allocate); 5328 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5329 return new_alloc_region; 5330 } 5331 } 5332 return NULL; 5333 } 5334 5335 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5336 size_t allocated_bytes) { 5337 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5338 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5339 5340 collection_set()->add_eden_region(alloc_region); 5341 increase_used(allocated_bytes); 5342 _hr_printer.retire(alloc_region); 5343 // We update the eden sizes here, when the region is retired, 5344 // instead of when it's allocated, since this is the point that its 5345 // used space has been recored in _summary_bytes_used. 5346 g1mm()->update_eden_size(); 5347 } 5348 5349 // Methods for the GC alloc regions 5350 5351 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 5352 if (dest.is_old()) { 5353 return true; 5354 } else { 5355 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 5356 } 5357 } 5358 5359 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 5360 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5361 5362 if (!has_more_regions(dest)) { 5363 return NULL; 5364 } 5365 5366 const bool is_survivor = dest.is_young(); 5367 5368 HeapRegion* new_alloc_region = new_region(word_size, 5369 !is_survivor, 5370 true /* do_expand */); 5371 if (new_alloc_region != NULL) { 5372 // We really only need to do this for old regions given that we 5373 // should never scan survivors. But it doesn't hurt to do it 5374 // for survivors too. 5375 new_alloc_region->record_timestamp(); 5376 if (is_survivor) { 5377 new_alloc_region->set_survivor(); 5378 _survivor.add(new_alloc_region); 5379 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5380 } else { 5381 new_alloc_region->set_old(); 5382 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5383 } 5384 _hr_printer.alloc(new_alloc_region); 5385 bool during_im = collector_state()->during_initial_mark_pause(); 5386 new_alloc_region->note_start_of_copying(during_im); 5387 return new_alloc_region; 5388 } 5389 return NULL; 5390 } 5391 5392 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5393 size_t allocated_bytes, 5394 InCSetState dest) { 5395 bool during_im = collector_state()->during_initial_mark_pause(); 5396 alloc_region->note_end_of_copying(during_im); 5397 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5398 if (dest.is_old()) { 5399 _old_set.add(alloc_region); 5400 } 5401 _hr_printer.retire(alloc_region); 5402 } 5403 5404 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5405 bool expanded = false; 5406 uint index = _hrm.find_highest_free(&expanded); 5407 5408 if (index != G1_NO_HRM_INDEX) { 5409 if (expanded) { 5410 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5411 HeapRegion::GrainWords * HeapWordSize); 5412 } 5413 _hrm.allocate_free_regions_starting_at(index, 1); 5414 return region_at(index); 5415 } 5416 return NULL; 5417 } 5418 5419 // Optimized nmethod scanning 5420 5421 class RegisterNMethodOopClosure: public OopClosure { 5422 G1CollectedHeap* _g1h; 5423 nmethod* _nm; 5424 5425 template <class T> void do_oop_work(T* p) { 5426 T heap_oop = oopDesc::load_heap_oop(p); 5427 if (!oopDesc::is_null(heap_oop)) { 5428 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5429 HeapRegion* hr = _g1h->heap_region_containing(obj); 5430 assert(!hr->is_continues_humongous(), 5431 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5432 " starting at " HR_FORMAT, 5433 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5434 5435 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5436 hr->add_strong_code_root_locked(_nm); 5437 } 5438 } 5439 5440 public: 5441 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5442 _g1h(g1h), _nm(nm) {} 5443 5444 void do_oop(oop* p) { do_oop_work(p); } 5445 void do_oop(narrowOop* p) { do_oop_work(p); } 5446 }; 5447 5448 class UnregisterNMethodOopClosure: public OopClosure { 5449 G1CollectedHeap* _g1h; 5450 nmethod* _nm; 5451 5452 template <class T> void do_oop_work(T* p) { 5453 T heap_oop = oopDesc::load_heap_oop(p); 5454 if (!oopDesc::is_null(heap_oop)) { 5455 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5456 HeapRegion* hr = _g1h->heap_region_containing(obj); 5457 assert(!hr->is_continues_humongous(), 5458 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5459 " starting at " HR_FORMAT, 5460 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5461 5462 hr->remove_strong_code_root(_nm); 5463 } 5464 } 5465 5466 public: 5467 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5468 _g1h(g1h), _nm(nm) {} 5469 5470 void do_oop(oop* p) { do_oop_work(p); } 5471 void do_oop(narrowOop* p) { do_oop_work(p); } 5472 }; 5473 5474 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5475 CollectedHeap::register_nmethod(nm); 5476 5477 guarantee(nm != NULL, "sanity"); 5478 RegisterNMethodOopClosure reg_cl(this, nm); 5479 nm->oops_do(®_cl); 5480 } 5481 5482 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5483 CollectedHeap::unregister_nmethod(nm); 5484 5485 guarantee(nm != NULL, "sanity"); 5486 UnregisterNMethodOopClosure reg_cl(this, nm); 5487 nm->oops_do(®_cl, true); 5488 } 5489 5490 void G1CollectedHeap::purge_code_root_memory() { 5491 double purge_start = os::elapsedTime(); 5492 G1CodeRootSet::purge(); 5493 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5494 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5495 } 5496 5497 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5498 G1CollectedHeap* _g1h; 5499 5500 public: 5501 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5502 _g1h(g1h) {} 5503 5504 void do_code_blob(CodeBlob* cb) { 5505 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5506 if (nm == NULL) { 5507 return; 5508 } 5509 5510 if (ScavengeRootsInCode) { 5511 _g1h->register_nmethod(nm); 5512 } 5513 } 5514 }; 5515 5516 void G1CollectedHeap::rebuild_strong_code_roots() { 5517 RebuildStrongCodeRootClosure blob_cl(this); 5518 CodeCache::blobs_do(&blob_cl); 5519 }