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/init.hpp" 79 #include "runtime/orderAccess.inline.hpp" 80 #include "runtime/vmThread.hpp" 81 #include "utilities/globalDefinitions.hpp" 82 #include "utilities/stack.inline.hpp" 83 84 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 85 86 // INVARIANTS/NOTES 87 // 88 // All allocation activity covered by the G1CollectedHeap interface is 89 // serialized by acquiring the HeapLock. This happens in mem_allocate 90 // and allocate_new_tlab, which are the "entry" points to the 91 // allocation code from the rest of the JVM. (Note that this does not 92 // apply to TLAB allocation, which is not part of this interface: it 93 // is done by clients of this interface.) 94 95 // Local to this file. 96 97 class RefineCardTableEntryClosure: public CardTableEntryClosure { 98 bool _concurrent; 99 public: 100 RefineCardTableEntryClosure() : _concurrent(true) { } 101 102 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 103 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, NULL); 104 // This path is executed by the concurrent refine or mutator threads, 105 // concurrently, and so we do not care if card_ptr contains references 106 // that point into the collection set. 107 assert(!oops_into_cset, "should be"); 108 109 if (_concurrent && SuspendibleThreadSet::should_yield()) { 110 // Caller will actually yield. 111 return false; 112 } 113 // Otherwise, we finished successfully; return true. 114 return true; 115 } 116 117 void set_concurrent(bool b) { _concurrent = b; } 118 }; 119 120 121 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 122 private: 123 size_t _num_dirtied; 124 G1CollectedHeap* _g1h; 125 G1SATBCardTableLoggingModRefBS* _g1_bs; 126 127 HeapRegion* region_for_card(jbyte* card_ptr) const { 128 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 129 } 130 131 bool will_become_free(HeapRegion* hr) const { 132 // A region will be freed by free_collection_set if the region is in the 133 // collection set and has not had an evacuation failure. 134 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 135 } 136 137 public: 138 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 139 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 140 141 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 142 HeapRegion* hr = region_for_card(card_ptr); 143 144 // Should only dirty cards in regions that won't be freed. 145 if (!will_become_free(hr)) { 146 *card_ptr = CardTableModRefBS::dirty_card_val(); 147 _num_dirtied++; 148 } 149 150 return true; 151 } 152 153 size_t num_dirtied() const { return _num_dirtied; } 154 }; 155 156 157 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 158 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 159 } 160 161 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 162 // The from card cache is not the memory that is actually committed. So we cannot 163 // take advantage of the zero_filled parameter. 164 reset_from_card_cache(start_idx, num_regions); 165 } 166 167 // Returns true if the reference points to an object that 168 // can move in an incremental collection. 169 bool G1CollectedHeap::is_scavengable(const void* p) { 170 HeapRegion* hr = heap_region_containing(p); 171 return !hr->is_pinned(); 172 } 173 174 // Private methods. 175 176 HeapRegion* 177 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 178 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 179 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 180 if (!_secondary_free_list.is_empty()) { 181 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 182 "secondary_free_list has %u entries", 183 _secondary_free_list.length()); 184 // It looks as if there are free regions available on the 185 // secondary_free_list. Let's move them to the free_list and try 186 // again to allocate from it. 187 append_secondary_free_list(); 188 189 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 190 "empty we should have moved at least one entry to the free_list"); 191 HeapRegion* res = _hrm.allocate_free_region(is_old); 192 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 193 "allocated " HR_FORMAT " from secondary_free_list", 194 HR_FORMAT_PARAMS(res)); 195 return res; 196 } 197 198 // Wait here until we get notified either when (a) there are no 199 // more free regions coming or (b) some regions have been moved on 200 // the secondary_free_list. 201 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 202 } 203 204 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 205 "could not allocate from secondary_free_list"); 206 return NULL; 207 } 208 209 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 210 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 211 "the only time we use this to allocate a humongous region is " 212 "when we are allocating a single humongous region"); 213 214 HeapRegion* res; 215 if (G1StressConcRegionFreeing) { 216 if (!_secondary_free_list.is_empty()) { 217 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 218 "forced to look at the secondary_free_list"); 219 res = new_region_try_secondary_free_list(is_old); 220 if (res != NULL) { 221 return res; 222 } 223 } 224 } 225 226 res = _hrm.allocate_free_region(is_old); 227 228 if (res == NULL) { 229 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 230 "res == NULL, trying the secondary_free_list"); 231 res = new_region_try_secondary_free_list(is_old); 232 } 233 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 234 // Currently, only attempts to allocate GC alloc regions set 235 // do_expand to true. So, we should only reach here during a 236 // safepoint. If this assumption changes we might have to 237 // reconsider the use of _expand_heap_after_alloc_failure. 238 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 239 240 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 241 word_size * HeapWordSize); 242 243 if (expand(word_size * HeapWordSize)) { 244 // Given that expand() succeeded in expanding the heap, and we 245 // always expand the heap by an amount aligned to the heap 246 // region size, the free list should in theory not be empty. 247 // In either case allocate_free_region() will check for NULL. 248 res = _hrm.allocate_free_region(is_old); 249 } else { 250 _expand_heap_after_alloc_failure = false; 251 } 252 } 253 return res; 254 } 255 256 HeapWord* 257 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 258 uint num_regions, 259 size_t word_size, 260 AllocationContext_t context) { 261 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 262 assert(is_humongous(word_size), "word_size should be humongous"); 263 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 264 265 // Index of last region in the series. 266 uint last = first + num_regions - 1; 267 268 // We need to initialize the region(s) we just discovered. This is 269 // a bit tricky given that it can happen concurrently with 270 // refinement threads refining cards on these regions and 271 // potentially wanting to refine the BOT as they are scanning 272 // those cards (this can happen shortly after a cleanup; see CR 273 // 6991377). So we have to set up the region(s) carefully and in 274 // a specific order. 275 276 // The word size sum of all the regions we will allocate. 277 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 278 assert(word_size <= word_size_sum, "sanity"); 279 280 // This will be the "starts humongous" region. 281 HeapRegion* first_hr = region_at(first); 282 // The header of the new object will be placed at the bottom of 283 // the first region. 284 HeapWord* new_obj = first_hr->bottom(); 285 // This will be the new top of the new object. 286 HeapWord* obj_top = new_obj + word_size; 287 288 // First, we need to zero the header of the space that we will be 289 // allocating. When we update top further down, some refinement 290 // threads might try to scan the region. By zeroing the header we 291 // ensure that any thread that will try to scan the region will 292 // come across the zero klass word and bail out. 293 // 294 // NOTE: It would not have been correct to have used 295 // CollectedHeap::fill_with_object() and make the space look like 296 // an int array. The thread that is doing the allocation will 297 // later update the object header to a potentially different array 298 // type and, for a very short period of time, the klass and length 299 // fields will be inconsistent. This could cause a refinement 300 // thread to calculate the object size incorrectly. 301 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 302 303 // Next, pad out the unused tail of the last region with filler 304 // objects, for improved usage accounting. 305 // How many words we use for filler objects. 306 size_t word_fill_size = word_size_sum - word_size; 307 308 // How many words memory we "waste" which cannot hold a filler object. 309 size_t words_not_fillable = 0; 310 311 if (word_fill_size >= min_fill_size()) { 312 fill_with_objects(obj_top, word_fill_size); 313 } else if (word_fill_size > 0) { 314 // We have space to fill, but we cannot fit an object there. 315 words_not_fillable = word_fill_size; 316 word_fill_size = 0; 317 } 318 319 // We will set up the first region as "starts humongous". This 320 // will also update the BOT covering all the regions to reflect 321 // that there is a single object that starts at the bottom of the 322 // first region. 323 first_hr->set_starts_humongous(obj_top, word_fill_size); 324 first_hr->set_allocation_context(context); 325 // Then, if there are any, we will set up the "continues 326 // humongous" regions. 327 HeapRegion* hr = NULL; 328 for (uint i = first + 1; i <= last; ++i) { 329 hr = region_at(i); 330 hr->set_continues_humongous(first_hr); 331 hr->set_allocation_context(context); 332 } 333 334 // Up to this point no concurrent thread would have been able to 335 // do any scanning on any region in this series. All the top 336 // fields still point to bottom, so the intersection between 337 // [bottom,top] and [card_start,card_end] will be empty. Before we 338 // update the top fields, we'll do a storestore to make sure that 339 // no thread sees the update to top before the zeroing of the 340 // object header and the BOT initialization. 341 OrderAccess::storestore(); 342 343 // Now, we will update the top fields of the "continues humongous" 344 // regions except the last one. 345 for (uint i = first; i < last; ++i) { 346 hr = region_at(i); 347 hr->set_top(hr->end()); 348 } 349 350 hr = region_at(last); 351 // If we cannot fit a filler object, we must set top to the end 352 // of the humongous object, otherwise we cannot iterate the heap 353 // and the BOT will not be complete. 354 hr->set_top(hr->end() - words_not_fillable); 355 356 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 357 "obj_top should be in last region"); 358 359 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 360 361 assert(words_not_fillable == 0 || 362 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 363 "Miscalculation in humongous allocation"); 364 365 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 366 367 for (uint i = first; i <= last; ++i) { 368 hr = region_at(i); 369 _humongous_set.add(hr); 370 _hr_printer.alloc(hr); 371 } 372 373 return new_obj; 374 } 375 376 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 377 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 378 return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 379 } 380 381 // If could fit into free regions w/o expansion, try. 382 // Otherwise, if can expand, do so. 383 // Otherwise, if using ex regions might help, try with ex given back. 384 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 385 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 386 387 _verifier->verify_region_sets_optional(); 388 389 uint first = G1_NO_HRM_INDEX; 390 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 391 392 if (obj_regions == 1) { 393 // Only one region to allocate, try to use a fast path by directly allocating 394 // from the free lists. Do not try to expand here, we will potentially do that 395 // later. 396 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 397 if (hr != NULL) { 398 first = hr->hrm_index(); 399 } 400 } else { 401 // We can't allocate humongous regions spanning more than one region while 402 // cleanupComplete() is running, since some of the regions we find to be 403 // empty might not yet be added to the free list. It is not straightforward 404 // to know in which list they are on so that we can remove them. We only 405 // need to do this if we need to allocate more than one region to satisfy the 406 // current humongous allocation request. If we are only allocating one region 407 // we use the one-region region allocation code (see above), that already 408 // potentially waits for regions from the secondary free list. 409 wait_while_free_regions_coming(); 410 append_secondary_free_list_if_not_empty_with_lock(); 411 412 // Policy: Try only empty regions (i.e. already committed first). Maybe we 413 // are lucky enough to find some. 414 first = _hrm.find_contiguous_only_empty(obj_regions); 415 if (first != G1_NO_HRM_INDEX) { 416 _hrm.allocate_free_regions_starting_at(first, obj_regions); 417 } 418 } 419 420 if (first == G1_NO_HRM_INDEX) { 421 // Policy: We could not find enough regions for the humongous object in the 422 // free list. Look through the heap to find a mix of free and uncommitted regions. 423 // If so, try expansion. 424 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 425 if (first != G1_NO_HRM_INDEX) { 426 // We found something. Make sure these regions are committed, i.e. expand 427 // the heap. Alternatively we could do a defragmentation GC. 428 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 429 word_size * HeapWordSize); 430 431 _hrm.expand_at(first, obj_regions, workers()); 432 g1_policy()->record_new_heap_size(num_regions()); 433 434 #ifdef ASSERT 435 for (uint i = first; i < first + obj_regions; ++i) { 436 HeapRegion* hr = region_at(i); 437 assert(hr->is_free(), "sanity"); 438 assert(hr->is_empty(), "sanity"); 439 assert(is_on_master_free_list(hr), "sanity"); 440 } 441 #endif 442 _hrm.allocate_free_regions_starting_at(first, obj_regions); 443 } else { 444 // Policy: Potentially trigger a defragmentation GC. 445 } 446 } 447 448 HeapWord* result = NULL; 449 if (first != G1_NO_HRM_INDEX) { 450 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 451 word_size, context); 452 assert(result != NULL, "it should always return a valid result"); 453 454 // A successful humongous object allocation changes the used space 455 // information of the old generation so we need to recalculate the 456 // sizes and update the jstat counters here. 457 g1mm()->update_sizes(); 458 } 459 460 _verifier->verify_region_sets_optional(); 461 462 return result; 463 } 464 465 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 466 assert_heap_not_locked_and_not_at_safepoint(); 467 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 468 469 uint dummy_gc_count_before; 470 uint dummy_gclocker_retry_count = 0; 471 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 472 } 473 474 HeapWord* 475 G1CollectedHeap::mem_allocate(size_t word_size, 476 bool* gc_overhead_limit_was_exceeded) { 477 assert_heap_not_locked_and_not_at_safepoint(); 478 479 // Loop until the allocation is satisfied, or unsatisfied after GC. 480 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 481 uint gc_count_before; 482 483 HeapWord* result = NULL; 484 if (!is_humongous(word_size)) { 485 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 486 } else { 487 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 488 } 489 if (result != NULL) { 490 return result; 491 } 492 493 // Create the garbage collection operation... 494 VM_G1CollectForAllocation op(gc_count_before, word_size); 495 op.set_allocation_context(AllocationContext::current()); 496 497 // ...and get the VM thread to execute it. 498 VMThread::execute(&op); 499 500 if (op.prologue_succeeded() && op.pause_succeeded()) { 501 // If the operation was successful we'll return the result even 502 // if it is NULL. If the allocation attempt failed immediately 503 // after a Full GC, it's unlikely we'll be able to allocate now. 504 HeapWord* result = op.result(); 505 if (result != NULL && !is_humongous(word_size)) { 506 // Allocations that take place on VM operations do not do any 507 // card dirtying and we have to do it here. We only have to do 508 // this for non-humongous allocations, though. 509 dirty_young_block(result, word_size); 510 } 511 return result; 512 } else { 513 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 514 return NULL; 515 } 516 assert(op.result() == NULL, 517 "the result should be NULL if the VM op did not succeed"); 518 } 519 520 // Give a warning if we seem to be looping forever. 521 if ((QueuedAllocationWarningCount > 0) && 522 (try_count % QueuedAllocationWarningCount == 0)) { 523 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count); 524 } 525 } 526 527 ShouldNotReachHere(); 528 return NULL; 529 } 530 531 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 532 AllocationContext_t context, 533 uint* gc_count_before_ret, 534 uint* gclocker_retry_count_ret) { 535 // Make sure you read the note in attempt_allocation_humongous(). 536 537 assert_heap_not_locked_and_not_at_safepoint(); 538 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 539 "be called for humongous allocation requests"); 540 541 // We should only get here after the first-level allocation attempt 542 // (attempt_allocation()) failed to allocate. 543 544 // We will loop until a) we manage to successfully perform the 545 // allocation or b) we successfully schedule a collection which 546 // fails to perform the allocation. b) is the only case when we'll 547 // return NULL. 548 HeapWord* result = NULL; 549 for (int try_count = 1; /* we'll return */; try_count += 1) { 550 bool should_try_gc; 551 uint gc_count_before; 552 553 { 554 MutexLockerEx x(Heap_lock); 555 result = _allocator->attempt_allocation_locked(word_size, context); 556 if (result != NULL) { 557 return result; 558 } 559 560 if (GCLocker::is_active_and_needs_gc()) { 561 if (g1_policy()->can_expand_young_list()) { 562 // No need for an ergo verbose message here, 563 // can_expand_young_list() does this when it returns true. 564 result = _allocator->attempt_allocation_force(word_size, context); 565 if (result != NULL) { 566 return result; 567 } 568 } 569 should_try_gc = false; 570 } else { 571 // The GCLocker may not be active but the GCLocker initiated 572 // GC may not yet have been performed (GCLocker::needs_gc() 573 // returns true). In this case we do not try this GC and 574 // wait until the GCLocker initiated GC is performed, and 575 // then retry the allocation. 576 if (GCLocker::needs_gc()) { 577 should_try_gc = false; 578 } else { 579 // Read the GC count while still holding the Heap_lock. 580 gc_count_before = total_collections(); 581 should_try_gc = true; 582 } 583 } 584 } 585 586 if (should_try_gc) { 587 bool succeeded; 588 result = do_collection_pause(word_size, gc_count_before, &succeeded, 589 GCCause::_g1_inc_collection_pause); 590 if (result != NULL) { 591 assert(succeeded, "only way to get back a non-NULL result"); 592 return result; 593 } 594 595 if (succeeded) { 596 // If we get here we successfully scheduled a collection which 597 // failed to allocate. No point in trying to allocate 598 // further. We'll just return NULL. 599 MutexLockerEx x(Heap_lock); 600 *gc_count_before_ret = total_collections(); 601 return NULL; 602 } 603 } else { 604 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 605 MutexLockerEx x(Heap_lock); 606 *gc_count_before_ret = total_collections(); 607 return NULL; 608 } 609 // The GCLocker is either active or the GCLocker initiated 610 // GC has not yet been performed. Stall until it is and 611 // then retry the allocation. 612 GCLocker::stall_until_clear(); 613 (*gclocker_retry_count_ret) += 1; 614 } 615 616 // We can reach here if we were unsuccessful in scheduling a 617 // collection (because another thread beat us to it) or if we were 618 // stalled due to the GC locker. In either can we should retry the 619 // allocation attempt in case another thread successfully 620 // performed a collection and reclaimed enough space. We do the 621 // first attempt (without holding the Heap_lock) here and the 622 // follow-on attempt will be at the start of the next loop 623 // iteration (after taking the Heap_lock). 624 result = _allocator->attempt_allocation(word_size, context); 625 if (result != NULL) { 626 return result; 627 } 628 629 // Give a warning if we seem to be looping forever. 630 if ((QueuedAllocationWarningCount > 0) && 631 (try_count % QueuedAllocationWarningCount == 0)) { 632 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() " 633 "retries %d times", try_count); 634 } 635 } 636 637 ShouldNotReachHere(); 638 return NULL; 639 } 640 641 void G1CollectedHeap::begin_archive_alloc_range() { 642 assert_at_safepoint(true /* should_be_vm_thread */); 643 if (_archive_allocator == NULL) { 644 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 645 } 646 } 647 648 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 649 // Allocations in archive regions cannot be of a size that would be considered 650 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 651 // may be different at archive-restore time. 652 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 653 } 654 655 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 656 assert_at_safepoint(true /* should_be_vm_thread */); 657 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 658 if (is_archive_alloc_too_large(word_size)) { 659 return NULL; 660 } 661 return _archive_allocator->archive_mem_allocate(word_size); 662 } 663 664 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 665 size_t end_alignment_in_bytes) { 666 assert_at_safepoint(true /* should_be_vm_thread */); 667 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 668 669 // Call complete_archive to do the real work, filling in the MemRegion 670 // array with the archive regions. 671 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 672 delete _archive_allocator; 673 _archive_allocator = NULL; 674 } 675 676 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 677 assert(ranges != NULL, "MemRegion array NULL"); 678 assert(count != 0, "No MemRegions provided"); 679 MemRegion reserved = _hrm.reserved(); 680 for (size_t i = 0; i < count; i++) { 681 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 682 return false; 683 } 684 } 685 return true; 686 } 687 688 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 689 assert(!is_init_completed(), "Expect to be called at JVM init time"); 690 assert(ranges != NULL, "MemRegion array NULL"); 691 assert(count != 0, "No MemRegions provided"); 692 MutexLockerEx x(Heap_lock); 693 694 MemRegion reserved = _hrm.reserved(); 695 HeapWord* prev_last_addr = NULL; 696 HeapRegion* prev_last_region = NULL; 697 698 // Temporarily disable pretouching of heap pages. This interface is used 699 // when mmap'ing archived heap data in, so pre-touching is wasted. 700 FlagSetting fs(AlwaysPreTouch, false); 701 702 // Enable archive object checking used by G1MarkSweep. We have to let it know 703 // about each archive range, so that objects in those ranges aren't marked. 704 G1ArchiveAllocator::enable_archive_object_check(); 705 706 // For each specified MemRegion range, allocate the corresponding G1 707 // regions and mark them as archive regions. We expect the ranges in 708 // ascending starting address order, without overlap. 709 for (size_t i = 0; i < count; i++) { 710 MemRegion curr_range = ranges[i]; 711 HeapWord* start_address = curr_range.start(); 712 size_t word_size = curr_range.word_size(); 713 HeapWord* last_address = curr_range.last(); 714 size_t commits = 0; 715 716 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 717 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 718 p2i(start_address), p2i(last_address)); 719 guarantee(start_address > prev_last_addr, 720 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 721 p2i(start_address), p2i(prev_last_addr)); 722 prev_last_addr = last_address; 723 724 // Check for ranges that start in the same G1 region in which the previous 725 // range ended, and adjust the start address so we don't try to allocate 726 // the same region again. If the current range is entirely within that 727 // region, skip it, just adjusting the recorded top. 728 HeapRegion* start_region = _hrm.addr_to_region(start_address); 729 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 730 start_address = start_region->end(); 731 if (start_address > last_address) { 732 increase_used(word_size * HeapWordSize); 733 start_region->set_top(last_address + 1); 734 continue; 735 } 736 start_region->set_top(start_address); 737 curr_range = MemRegion(start_address, last_address + 1); 738 start_region = _hrm.addr_to_region(start_address); 739 } 740 741 // Perform the actual region allocation, exiting if it fails. 742 // Then note how much new space we have allocated. 743 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 744 return false; 745 } 746 increase_used(word_size * HeapWordSize); 747 if (commits != 0) { 748 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 749 HeapRegion::GrainWords * HeapWordSize * commits); 750 751 } 752 753 // Mark each G1 region touched by the range as archive, add it to the old set, 754 // and set the allocation context and top. 755 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 756 HeapRegion* last_region = _hrm.addr_to_region(last_address); 757 prev_last_region = last_region; 758 759 while (curr_region != NULL) { 760 assert(curr_region->is_empty() && !curr_region->is_pinned(), 761 "Region already in use (index %u)", curr_region->hrm_index()); 762 curr_region->set_allocation_context(AllocationContext::system()); 763 curr_region->set_archive(); 764 _hr_printer.alloc(curr_region); 765 _old_set.add(curr_region); 766 if (curr_region != last_region) { 767 curr_region->set_top(curr_region->end()); 768 curr_region = _hrm.next_region_in_heap(curr_region); 769 } else { 770 curr_region->set_top(last_address + 1); 771 curr_region = NULL; 772 } 773 } 774 775 // Notify mark-sweep of the archive range. 776 G1ArchiveAllocator::set_range_archive(curr_range, true); 777 } 778 return true; 779 } 780 781 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 782 assert(!is_init_completed(), "Expect to be called at JVM init time"); 783 assert(ranges != NULL, "MemRegion array NULL"); 784 assert(count != 0, "No MemRegions provided"); 785 MemRegion reserved = _hrm.reserved(); 786 HeapWord *prev_last_addr = NULL; 787 HeapRegion* prev_last_region = NULL; 788 789 // For each MemRegion, create filler objects, if needed, in the G1 regions 790 // that contain the address range. The address range actually within the 791 // MemRegion will not be modified. That is assumed to have been initialized 792 // elsewhere, probably via an mmap of archived heap data. 793 MutexLockerEx x(Heap_lock); 794 for (size_t i = 0; i < count; i++) { 795 HeapWord* start_address = ranges[i].start(); 796 HeapWord* last_address = ranges[i].last(); 797 798 assert(reserved.contains(start_address) && reserved.contains(last_address), 799 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 800 p2i(start_address), p2i(last_address)); 801 assert(start_address > prev_last_addr, 802 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 803 p2i(start_address), p2i(prev_last_addr)); 804 805 HeapRegion* start_region = _hrm.addr_to_region(start_address); 806 HeapRegion* last_region = _hrm.addr_to_region(last_address); 807 HeapWord* bottom_address = start_region->bottom(); 808 809 // Check for a range beginning in the same region in which the 810 // previous one ended. 811 if (start_region == prev_last_region) { 812 bottom_address = prev_last_addr + 1; 813 } 814 815 // Verify that the regions were all marked as archive regions by 816 // alloc_archive_regions. 817 HeapRegion* curr_region = start_region; 818 while (curr_region != NULL) { 819 guarantee(curr_region->is_archive(), 820 "Expected archive region at index %u", curr_region->hrm_index()); 821 if (curr_region != last_region) { 822 curr_region = _hrm.next_region_in_heap(curr_region); 823 } else { 824 curr_region = NULL; 825 } 826 } 827 828 prev_last_addr = last_address; 829 prev_last_region = last_region; 830 831 // Fill the memory below the allocated range with dummy object(s), 832 // if the region bottom does not match the range start, or if the previous 833 // range ended within the same G1 region, and there is a gap. 834 if (start_address != bottom_address) { 835 size_t fill_size = pointer_delta(start_address, bottom_address); 836 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 837 increase_used(fill_size * HeapWordSize); 838 } 839 } 840 } 841 842 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 843 uint* gc_count_before_ret, 844 uint* gclocker_retry_count_ret) { 845 assert_heap_not_locked_and_not_at_safepoint(); 846 assert(!is_humongous(word_size), "attempt_allocation() should not " 847 "be called for humongous allocation requests"); 848 849 AllocationContext_t context = AllocationContext::current(); 850 HeapWord* result = _allocator->attempt_allocation(word_size, context); 851 852 if (result == NULL) { 853 result = attempt_allocation_slow(word_size, 854 context, 855 gc_count_before_ret, 856 gclocker_retry_count_ret); 857 } 858 assert_heap_not_locked(); 859 if (result != NULL) { 860 dirty_young_block(result, word_size); 861 } 862 return result; 863 } 864 865 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 866 assert(!is_init_completed(), "Expect to be called at JVM init time"); 867 assert(ranges != NULL, "MemRegion array NULL"); 868 assert(count != 0, "No MemRegions provided"); 869 MemRegion reserved = _hrm.reserved(); 870 HeapWord* prev_last_addr = NULL; 871 HeapRegion* prev_last_region = NULL; 872 size_t size_used = 0; 873 size_t uncommitted_regions = 0; 874 875 // For each Memregion, free the G1 regions that constitute it, and 876 // notify mark-sweep that the range is no longer to be considered 'archive.' 877 MutexLockerEx x(Heap_lock); 878 for (size_t i = 0; i < count; i++) { 879 HeapWord* start_address = ranges[i].start(); 880 HeapWord* last_address = ranges[i].last(); 881 882 assert(reserved.contains(start_address) && reserved.contains(last_address), 883 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 884 p2i(start_address), p2i(last_address)); 885 assert(start_address > prev_last_addr, 886 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 887 p2i(start_address), p2i(prev_last_addr)); 888 size_used += ranges[i].byte_size(); 889 prev_last_addr = last_address; 890 891 HeapRegion* start_region = _hrm.addr_to_region(start_address); 892 HeapRegion* last_region = _hrm.addr_to_region(last_address); 893 894 // Check for ranges that start in the same G1 region in which the previous 895 // range ended, and adjust the start address so we don't try to free 896 // the same region again. If the current range is entirely within that 897 // region, skip it. 898 if (start_region == prev_last_region) { 899 start_address = start_region->end(); 900 if (start_address > last_address) { 901 continue; 902 } 903 start_region = _hrm.addr_to_region(start_address); 904 } 905 prev_last_region = last_region; 906 907 // After verifying that each region was marked as an archive region by 908 // alloc_archive_regions, set it free and empty and uncommit it. 909 HeapRegion* curr_region = start_region; 910 while (curr_region != NULL) { 911 guarantee(curr_region->is_archive(), 912 "Expected archive region at index %u", curr_region->hrm_index()); 913 uint curr_index = curr_region->hrm_index(); 914 _old_set.remove(curr_region); 915 curr_region->set_free(); 916 curr_region->set_top(curr_region->bottom()); 917 if (curr_region != last_region) { 918 curr_region = _hrm.next_region_in_heap(curr_region); 919 } else { 920 curr_region = NULL; 921 } 922 _hrm.shrink_at(curr_index, 1); 923 uncommitted_regions++; 924 } 925 926 // Notify mark-sweep that this is no longer an archive range. 927 G1ArchiveAllocator::set_range_archive(ranges[i], false); 928 } 929 930 if (uncommitted_regions != 0) { 931 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 932 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 933 } 934 decrease_used(size_used); 935 } 936 937 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 938 uint* gc_count_before_ret, 939 uint* gclocker_retry_count_ret) { 940 // The structure of this method has a lot of similarities to 941 // attempt_allocation_slow(). The reason these two were not merged 942 // into a single one is that such a method would require several "if 943 // allocation is not humongous do this, otherwise do that" 944 // conditional paths which would obscure its flow. In fact, an early 945 // version of this code did use a unified method which was harder to 946 // follow and, as a result, it had subtle bugs that were hard to 947 // track down. So keeping these two methods separate allows each to 948 // be more readable. It will be good to keep these two in sync as 949 // much as possible. 950 951 assert_heap_not_locked_and_not_at_safepoint(); 952 assert(is_humongous(word_size), "attempt_allocation_humongous() " 953 "should only be called for humongous allocations"); 954 955 // Humongous objects can exhaust the heap quickly, so we should check if we 956 // need to start a marking cycle at each humongous object allocation. We do 957 // the check before we do the actual allocation. The reason for doing it 958 // before the allocation is that we avoid having to keep track of the newly 959 // allocated memory while we do a GC. 960 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 961 word_size)) { 962 collect(GCCause::_g1_humongous_allocation); 963 } 964 965 // We will loop until a) we manage to successfully perform the 966 // allocation or b) we successfully schedule a collection which 967 // fails to perform the allocation. b) is the only case when we'll 968 // return NULL. 969 HeapWord* result = NULL; 970 for (int try_count = 1; /* we'll return */; try_count += 1) { 971 bool should_try_gc; 972 uint gc_count_before; 973 974 { 975 MutexLockerEx x(Heap_lock); 976 977 // Given that humongous objects are not allocated in young 978 // regions, we'll first try to do the allocation without doing a 979 // collection hoping that there's enough space in the heap. 980 result = humongous_obj_allocate(word_size, AllocationContext::current()); 981 if (result != NULL) { 982 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 983 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 984 return result; 985 } 986 987 if (GCLocker::is_active_and_needs_gc()) { 988 should_try_gc = false; 989 } else { 990 // The GCLocker may not be active but the GCLocker initiated 991 // GC may not yet have been performed (GCLocker::needs_gc() 992 // returns true). In this case we do not try this GC and 993 // wait until the GCLocker initiated GC is performed, and 994 // then retry the allocation. 995 if (GCLocker::needs_gc()) { 996 should_try_gc = false; 997 } else { 998 // Read the GC count while still holding the Heap_lock. 999 gc_count_before = total_collections(); 1000 should_try_gc = true; 1001 } 1002 } 1003 } 1004 1005 if (should_try_gc) { 1006 // If we failed to allocate the humongous object, we should try to 1007 // do a collection pause (if we're allowed) in case it reclaims 1008 // enough space for the allocation to succeed after the pause. 1009 1010 bool succeeded; 1011 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1012 GCCause::_g1_humongous_allocation); 1013 if (result != NULL) { 1014 assert(succeeded, "only way to get back a non-NULL result"); 1015 return result; 1016 } 1017 1018 if (succeeded) { 1019 // If we get here we successfully scheduled a collection which 1020 // failed to allocate. No point in trying to allocate 1021 // further. We'll just return NULL. 1022 MutexLockerEx x(Heap_lock); 1023 *gc_count_before_ret = total_collections(); 1024 return NULL; 1025 } 1026 } else { 1027 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1028 MutexLockerEx x(Heap_lock); 1029 *gc_count_before_ret = total_collections(); 1030 return NULL; 1031 } 1032 // The GCLocker is either active or the GCLocker initiated 1033 // GC has not yet been performed. Stall until it is and 1034 // then retry the allocation. 1035 GCLocker::stall_until_clear(); 1036 (*gclocker_retry_count_ret) += 1; 1037 } 1038 1039 // We can reach here if we were unsuccessful in scheduling a 1040 // collection (because another thread beat us to it) or if we were 1041 // stalled due to the GC locker. In either can we should retry the 1042 // allocation attempt in case another thread successfully 1043 // performed a collection and reclaimed enough space. Give a 1044 // warning if we seem to be looping forever. 1045 1046 if ((QueuedAllocationWarningCount > 0) && 1047 (try_count % QueuedAllocationWarningCount == 0)) { 1048 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() " 1049 "retries %d times", try_count); 1050 } 1051 } 1052 1053 ShouldNotReachHere(); 1054 return NULL; 1055 } 1056 1057 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1058 AllocationContext_t context, 1059 bool expect_null_mutator_alloc_region) { 1060 assert_at_safepoint(true /* should_be_vm_thread */); 1061 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1062 "the current alloc region was unexpectedly found to be non-NULL"); 1063 1064 if (!is_humongous(word_size)) { 1065 return _allocator->attempt_allocation_locked(word_size, context); 1066 } else { 1067 HeapWord* result = humongous_obj_allocate(word_size, context); 1068 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1069 collector_state()->set_initiate_conc_mark_if_possible(true); 1070 } 1071 return result; 1072 } 1073 1074 ShouldNotReachHere(); 1075 } 1076 1077 class PostMCRemSetClearClosure: public HeapRegionClosure { 1078 G1CollectedHeap* _g1h; 1079 ModRefBarrierSet* _mr_bs; 1080 public: 1081 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1082 _g1h(g1h), _mr_bs(mr_bs) {} 1083 1084 bool doHeapRegion(HeapRegion* r) { 1085 HeapRegionRemSet* hrrs = r->rem_set(); 1086 1087 _g1h->reset_gc_time_stamps(r); 1088 1089 if (r->is_continues_humongous()) { 1090 // We'll assert that the strong code root list and RSet is empty 1091 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1092 assert(hrrs->occupied() == 0, "RSet should be empty"); 1093 } else { 1094 hrrs->clear(); 1095 } 1096 // You might think here that we could clear just the cards 1097 // corresponding to the used region. But no: if we leave a dirty card 1098 // in a region we might allocate into, then it would prevent that card 1099 // from being enqueued, and cause it to be missed. 1100 // Re: the performance cost: we shouldn't be doing full GC anyway! 1101 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1102 1103 return false; 1104 } 1105 }; 1106 1107 void G1CollectedHeap::clear_rsets_post_compaction() { 1108 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1109 heap_region_iterate(&rs_clear); 1110 } 1111 1112 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1113 G1CollectedHeap* _g1h; 1114 UpdateRSOopClosure _cl; 1115 public: 1116 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1117 _cl(g1->g1_rem_set(), worker_i), 1118 _g1h(g1) 1119 { } 1120 1121 bool doHeapRegion(HeapRegion* r) { 1122 if (!r->is_continues_humongous()) { 1123 _cl.set_from(r); 1124 r->oop_iterate(&_cl); 1125 } 1126 return false; 1127 } 1128 }; 1129 1130 class ParRebuildRSTask: public AbstractGangTask { 1131 G1CollectedHeap* _g1; 1132 HeapRegionClaimer _hrclaimer; 1133 1134 public: 1135 ParRebuildRSTask(G1CollectedHeap* g1) : 1136 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1137 1138 void work(uint worker_id) { 1139 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1140 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1141 } 1142 }; 1143 1144 class PostCompactionPrinterClosure: public HeapRegionClosure { 1145 private: 1146 G1HRPrinter* _hr_printer; 1147 public: 1148 bool doHeapRegion(HeapRegion* hr) { 1149 assert(!hr->is_young(), "not expecting to find young regions"); 1150 _hr_printer->post_compaction(hr); 1151 return false; 1152 } 1153 1154 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1155 : _hr_printer(hr_printer) { } 1156 }; 1157 1158 void G1CollectedHeap::print_hrm_post_compaction() { 1159 if (_hr_printer.is_active()) { 1160 PostCompactionPrinterClosure cl(hr_printer()); 1161 heap_region_iterate(&cl); 1162 } 1163 1164 } 1165 1166 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1167 bool clear_all_soft_refs) { 1168 assert_at_safepoint(true /* should_be_vm_thread */); 1169 1170 if (GCLocker::check_active_before_gc()) { 1171 return false; 1172 } 1173 1174 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1175 gc_timer->register_gc_start(); 1176 1177 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1178 GCIdMark gc_id_mark; 1179 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1180 1181 SvcGCMarker sgcm(SvcGCMarker::FULL); 1182 ResourceMark rm; 1183 1184 print_heap_before_gc(); 1185 print_heap_regions(); 1186 trace_heap_before_gc(gc_tracer); 1187 1188 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1189 1190 _verifier->verify_region_sets_optional(); 1191 1192 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1193 collector_policy()->should_clear_all_soft_refs(); 1194 1195 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1196 1197 { 1198 IsGCActiveMark x; 1199 1200 // Timing 1201 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1202 GCTraceCPUTime tcpu; 1203 1204 { 1205 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1206 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1207 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1208 1209 G1HeapTransition heap_transition(this); 1210 g1_policy()->record_full_collection_start(); 1211 1212 // Note: When we have a more flexible GC logging framework that 1213 // allows us to add optional attributes to a GC log record we 1214 // could consider timing and reporting how long we wait in the 1215 // following two methods. 1216 wait_while_free_regions_coming(); 1217 // If we start the compaction before the CM threads finish 1218 // scanning the root regions we might trip them over as we'll 1219 // be moving objects / updating references. So let's wait until 1220 // they are done. By telling them to abort, they should complete 1221 // early. 1222 _cm->root_regions()->abort(); 1223 _cm->root_regions()->wait_until_scan_finished(); 1224 append_secondary_free_list_if_not_empty_with_lock(); 1225 1226 gc_prologue(true); 1227 increment_total_collections(true /* full gc */); 1228 increment_old_marking_cycles_started(); 1229 1230 assert(used() == recalculate_used(), "Should be equal"); 1231 1232 _verifier->verify_before_gc(); 1233 1234 _verifier->check_bitmaps("Full GC Start"); 1235 pre_full_gc_dump(gc_timer); 1236 1237 #if defined(COMPILER2) || INCLUDE_JVMCI 1238 DerivedPointerTable::clear(); 1239 #endif 1240 1241 // Disable discovery and empty the discovered lists 1242 // for the CM ref processor. 1243 ref_processor_cm()->disable_discovery(); 1244 ref_processor_cm()->abandon_partial_discovery(); 1245 ref_processor_cm()->verify_no_references_recorded(); 1246 1247 // Abandon current iterations of concurrent marking and concurrent 1248 // refinement, if any are in progress. 1249 concurrent_mark()->abort(); 1250 1251 // Make sure we'll choose a new allocation region afterwards. 1252 _allocator->release_mutator_alloc_region(); 1253 _allocator->abandon_gc_alloc_regions(); 1254 g1_rem_set()->cleanupHRRS(); 1255 1256 // We may have added regions to the current incremental collection 1257 // set between the last GC or pause and now. We need to clear the 1258 // incremental collection set and then start rebuilding it afresh 1259 // after this full GC. 1260 abandon_collection_set(collection_set()); 1261 1262 tear_down_region_sets(false /* free_list_only */); 1263 collector_state()->set_gcs_are_young(true); 1264 1265 // See the comments in g1CollectedHeap.hpp and 1266 // G1CollectedHeap::ref_processing_init() about 1267 // how reference processing currently works in G1. 1268 1269 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1270 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1271 1272 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1273 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1274 1275 ref_processor_stw()->enable_discovery(); 1276 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1277 1278 // Do collection work 1279 { 1280 HandleMark hm; // Discard invalid handles created during gc 1281 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1282 } 1283 1284 assert(num_free_regions() == 0, "we should not have added any free regions"); 1285 rebuild_region_sets(false /* free_list_only */); 1286 1287 // Enqueue any discovered reference objects that have 1288 // not been removed from the discovered lists. 1289 ref_processor_stw()->enqueue_discovered_references(); 1290 1291 #if defined(COMPILER2) || INCLUDE_JVMCI 1292 DerivedPointerTable::update_pointers(); 1293 #endif 1294 1295 MemoryService::track_memory_usage(); 1296 1297 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1298 ref_processor_stw()->verify_no_references_recorded(); 1299 1300 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1301 ClassLoaderDataGraph::purge(); 1302 MetaspaceAux::verify_metrics(); 1303 1304 // Note: since we've just done a full GC, concurrent 1305 // marking is no longer active. Therefore we need not 1306 // re-enable reference discovery for the CM ref processor. 1307 // That will be done at the start of the next marking cycle. 1308 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1309 ref_processor_cm()->verify_no_references_recorded(); 1310 1311 reset_gc_time_stamp(); 1312 // Since everything potentially moved, we will clear all remembered 1313 // sets, and clear all cards. Later we will rebuild remembered 1314 // sets. We will also reset the GC time stamps of the regions. 1315 clear_rsets_post_compaction(); 1316 check_gc_time_stamps(); 1317 1318 resize_if_necessary_after_full_collection(); 1319 1320 // We should do this after we potentially resize the heap so 1321 // that all the COMMIT / UNCOMMIT events are generated before 1322 // the compaction events. 1323 print_hrm_post_compaction(); 1324 1325 if (_hot_card_cache->use_cache()) { 1326 _hot_card_cache->reset_card_counts(); 1327 _hot_card_cache->reset_hot_cache(); 1328 } 1329 1330 // Rebuild remembered sets of all regions. 1331 uint n_workers = 1332 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1333 workers()->active_workers(), 1334 Threads::number_of_non_daemon_threads()); 1335 workers()->update_active_workers(n_workers); 1336 log_info(gc,task)("Using %u workers of %u to rebuild remembered set", n_workers, workers()->total_workers()); 1337 1338 ParRebuildRSTask rebuild_rs_task(this); 1339 workers()->run_task(&rebuild_rs_task); 1340 1341 // Rebuild the strong code root lists for each region 1342 rebuild_strong_code_roots(); 1343 1344 if (true) { // FIXME 1345 MetaspaceGC::compute_new_size(); 1346 } 1347 1348 #ifdef TRACESPINNING 1349 ParallelTaskTerminator::print_termination_counts(); 1350 #endif 1351 1352 // Discard all rset updates 1353 JavaThread::dirty_card_queue_set().abandon_logs(); 1354 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1355 1356 // At this point there should be no regions in the 1357 // entire heap tagged as young. 1358 assert(check_young_list_empty(), "young list should be empty at this point"); 1359 1360 // Update the number of full collections that have been completed. 1361 increment_old_marking_cycles_completed(false /* concurrent */); 1362 1363 _hrm.verify_optional(); 1364 _verifier->verify_region_sets_optional(); 1365 1366 _verifier->verify_after_gc(); 1367 1368 // Clear the previous marking bitmap, if needed for bitmap verification. 1369 // Note we cannot do this when we clear the next marking bitmap in 1370 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1371 // objects marked during a full GC against the previous bitmap. 1372 // But we need to clear it before calling check_bitmaps below since 1373 // the full GC has compacted objects and updated TAMS but not updated 1374 // the prev bitmap. 1375 if (G1VerifyBitmaps) { 1376 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1377 _cm->clear_prev_bitmap(workers()); 1378 } 1379 _verifier->check_bitmaps("Full GC End"); 1380 1381 start_new_collection_set(); 1382 1383 _allocator->init_mutator_alloc_region(); 1384 1385 g1_policy()->record_full_collection_end(); 1386 1387 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1388 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1389 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1390 // before any GC notifications are raised. 1391 g1mm()->update_sizes(); 1392 1393 gc_epilogue(true); 1394 1395 heap_transition.print(); 1396 1397 print_heap_after_gc(); 1398 print_heap_regions(); 1399 trace_heap_after_gc(gc_tracer); 1400 1401 post_full_gc_dump(gc_timer); 1402 } 1403 1404 gc_timer->register_gc_end(); 1405 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1406 } 1407 1408 return true; 1409 } 1410 1411 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1412 // Currently, there is no facility in the do_full_collection(bool) API to notify 1413 // the caller that the collection did not succeed (e.g., because it was locked 1414 // out by the GC locker). So, right now, we'll ignore the return value. 1415 bool dummy = do_full_collection(true, /* explicit_gc */ 1416 clear_all_soft_refs); 1417 } 1418 1419 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1420 // Include bytes that will be pre-allocated to support collections, as "used". 1421 const size_t used_after_gc = used(); 1422 const size_t capacity_after_gc = capacity(); 1423 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1424 1425 // This is enforced in arguments.cpp. 1426 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1427 "otherwise the code below doesn't make sense"); 1428 1429 // We don't have floating point command-line arguments 1430 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1431 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1432 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1433 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1434 1435 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1436 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1437 1438 // We have to be careful here as these two calculations can overflow 1439 // 32-bit size_t's. 1440 double used_after_gc_d = (double) used_after_gc; 1441 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1442 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1443 1444 // Let's make sure that they are both under the max heap size, which 1445 // by default will make them fit into a size_t. 1446 double desired_capacity_upper_bound = (double) max_heap_size; 1447 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1448 desired_capacity_upper_bound); 1449 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1450 desired_capacity_upper_bound); 1451 1452 // We can now safely turn them into size_t's. 1453 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1454 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1455 1456 // This assert only makes sense here, before we adjust them 1457 // with respect to the min and max heap size. 1458 assert(minimum_desired_capacity <= maximum_desired_capacity, 1459 "minimum_desired_capacity = " SIZE_FORMAT ", " 1460 "maximum_desired_capacity = " SIZE_FORMAT, 1461 minimum_desired_capacity, maximum_desired_capacity); 1462 1463 // Should not be greater than the heap max size. No need to adjust 1464 // it with respect to the heap min size as it's a lower bound (i.e., 1465 // we'll try to make the capacity larger than it, not smaller). 1466 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1467 // Should not be less than the heap min size. No need to adjust it 1468 // with respect to the heap max size as it's an upper bound (i.e., 1469 // we'll try to make the capacity smaller than it, not greater). 1470 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1471 1472 if (capacity_after_gc < minimum_desired_capacity) { 1473 // Don't expand unless it's significant 1474 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1475 1476 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1477 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1478 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1479 1480 expand(expand_bytes, _workers); 1481 1482 // No expansion, now see if we want to shrink 1483 } else if (capacity_after_gc > maximum_desired_capacity) { 1484 // Capacity too large, compute shrinking size 1485 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1486 1487 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1488 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1489 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1490 1491 shrink(shrink_bytes); 1492 } 1493 } 1494 1495 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1496 AllocationContext_t context, 1497 bool do_gc, 1498 bool clear_all_soft_refs, 1499 bool expect_null_mutator_alloc_region, 1500 bool* gc_succeeded) { 1501 *gc_succeeded = true; 1502 // Let's attempt the allocation first. 1503 HeapWord* result = 1504 attempt_allocation_at_safepoint(word_size, 1505 context, 1506 expect_null_mutator_alloc_region); 1507 if (result != NULL) { 1508 assert(*gc_succeeded, "sanity"); 1509 return result; 1510 } 1511 1512 // In a G1 heap, we're supposed to keep allocation from failing by 1513 // incremental pauses. Therefore, at least for now, we'll favor 1514 // expansion over collection. (This might change in the future if we can 1515 // do something smarter than full collection to satisfy a failed alloc.) 1516 result = expand_and_allocate(word_size, context); 1517 if (result != NULL) { 1518 assert(*gc_succeeded, "sanity"); 1519 return result; 1520 } 1521 1522 if (do_gc) { 1523 // Expansion didn't work, we'll try to do a Full GC. 1524 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1525 clear_all_soft_refs); 1526 } 1527 1528 return NULL; 1529 } 1530 1531 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1532 AllocationContext_t context, 1533 bool* succeeded) { 1534 assert_at_safepoint(true /* should_be_vm_thread */); 1535 1536 // Attempts to allocate followed by Full GC. 1537 HeapWord* result = 1538 satisfy_failed_allocation_helper(word_size, 1539 context, 1540 true, /* do_gc */ 1541 false, /* clear_all_soft_refs */ 1542 false, /* expect_null_mutator_alloc_region */ 1543 succeeded); 1544 1545 if (result != NULL || !*succeeded) { 1546 return result; 1547 } 1548 1549 // Attempts to allocate followed by Full GC that will collect all soft references. 1550 result = satisfy_failed_allocation_helper(word_size, 1551 context, 1552 true, /* do_gc */ 1553 true, /* clear_all_soft_refs */ 1554 true, /* expect_null_mutator_alloc_region */ 1555 succeeded); 1556 1557 if (result != NULL || !*succeeded) { 1558 return result; 1559 } 1560 1561 // Attempts to allocate, no GC 1562 result = satisfy_failed_allocation_helper(word_size, 1563 context, 1564 false, /* do_gc */ 1565 false, /* clear_all_soft_refs */ 1566 true, /* expect_null_mutator_alloc_region */ 1567 succeeded); 1568 1569 if (result != NULL) { 1570 assert(*succeeded, "sanity"); 1571 return result; 1572 } 1573 1574 assert(!collector_policy()->should_clear_all_soft_refs(), 1575 "Flag should have been handled and cleared prior to this point"); 1576 1577 // What else? We might try synchronous finalization later. If the total 1578 // space available is large enough for the allocation, then a more 1579 // complete compaction phase than we've tried so far might be 1580 // appropriate. 1581 assert(*succeeded, "sanity"); 1582 return NULL; 1583 } 1584 1585 // Attempting to expand the heap sufficiently 1586 // to support an allocation of the given "word_size". If 1587 // successful, perform the allocation and return the address of the 1588 // allocated block, or else "NULL". 1589 1590 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1591 assert_at_safepoint(true /* should_be_vm_thread */); 1592 1593 _verifier->verify_region_sets_optional(); 1594 1595 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1596 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1597 word_size * HeapWordSize); 1598 1599 1600 if (expand(expand_bytes, _workers)) { 1601 _hrm.verify_optional(); 1602 _verifier->verify_region_sets_optional(); 1603 return attempt_allocation_at_safepoint(word_size, 1604 context, 1605 false /* expect_null_mutator_alloc_region */); 1606 } 1607 return NULL; 1608 } 1609 1610 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1611 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1612 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1613 HeapRegion::GrainBytes); 1614 1615 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1616 expand_bytes, aligned_expand_bytes); 1617 1618 if (is_maximal_no_gc()) { 1619 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1620 return false; 1621 } 1622 1623 double expand_heap_start_time_sec = os::elapsedTime(); 1624 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1625 assert(regions_to_expand > 0, "Must expand by at least one region"); 1626 1627 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers); 1628 if (expand_time_ms != NULL) { 1629 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1630 } 1631 1632 if (expanded_by > 0) { 1633 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1634 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1635 g1_policy()->record_new_heap_size(num_regions()); 1636 } else { 1637 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1638 1639 // The expansion of the virtual storage space was unsuccessful. 1640 // Let's see if it was because we ran out of swap. 1641 if (G1ExitOnExpansionFailure && 1642 _hrm.available() >= regions_to_expand) { 1643 // We had head room... 1644 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1645 } 1646 } 1647 return regions_to_expand > 0; 1648 } 1649 1650 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1651 size_t aligned_shrink_bytes = 1652 ReservedSpace::page_align_size_down(shrink_bytes); 1653 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1654 HeapRegion::GrainBytes); 1655 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1656 1657 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1658 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1659 1660 1661 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", 1662 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1663 if (num_regions_removed > 0) { 1664 g1_policy()->record_new_heap_size(num_regions()); 1665 } else { 1666 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1667 } 1668 } 1669 1670 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1671 _verifier->verify_region_sets_optional(); 1672 1673 // We should only reach here at the end of a Full GC which means we 1674 // should not not be holding to any GC alloc regions. The method 1675 // below will make sure of that and do any remaining clean up. 1676 _allocator->abandon_gc_alloc_regions(); 1677 1678 // Instead of tearing down / rebuilding the free lists here, we 1679 // could instead use the remove_all_pending() method on free_list to 1680 // remove only the ones that we need to remove. 1681 tear_down_region_sets(true /* free_list_only */); 1682 shrink_helper(shrink_bytes); 1683 rebuild_region_sets(true /* free_list_only */); 1684 1685 _hrm.verify_optional(); 1686 _verifier->verify_region_sets_optional(); 1687 } 1688 1689 // Public methods. 1690 1691 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1692 CollectedHeap(), 1693 _collector_policy(collector_policy), 1694 _g1_policy(create_g1_policy()), 1695 _collection_set(this, _g1_policy), 1696 _dirty_card_queue_set(false), 1697 _is_alive_closure_cm(this), 1698 _is_alive_closure_stw(this), 1699 _ref_processor_cm(NULL), 1700 _ref_processor_stw(NULL), 1701 _bot(NULL), 1702 _hot_card_cache(NULL), 1703 _g1_rem_set(NULL), 1704 _cg1r(NULL), 1705 _g1mm(NULL), 1706 _refine_cte_cl(NULL), 1707 _preserved_marks_set(true /* in_c_heap */), 1708 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1709 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1710 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1711 _humongous_reclaim_candidates(), 1712 _has_humongous_reclaim_candidates(false), 1713 _archive_allocator(NULL), 1714 _free_regions_coming(false), 1715 _gc_time_stamp(0), 1716 _summary_bytes_used(0), 1717 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1718 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1719 _expand_heap_after_alloc_failure(true), 1720 _old_marking_cycles_started(0), 1721 _old_marking_cycles_completed(0), 1722 _in_cset_fast_test(), 1723 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1724 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) { 1725 1726 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1727 /* are_GC_task_threads */true, 1728 /* are_ConcurrentGC_threads */false); 1729 _workers->initialize_workers(); 1730 _verifier = new G1HeapVerifier(this); 1731 1732 _allocator = G1Allocator::create_allocator(this); 1733 1734 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1735 1736 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1737 1738 // Override the default _filler_array_max_size so that no humongous filler 1739 // objects are created. 1740 _filler_array_max_size = _humongous_object_threshold_in_words; 1741 1742 uint n_queues = ParallelGCThreads; 1743 _task_queues = new RefToScanQueueSet(n_queues); 1744 1745 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1746 1747 for (uint i = 0; i < n_queues; i++) { 1748 RefToScanQueue* q = new RefToScanQueue(); 1749 q->initialize(); 1750 _task_queues->register_queue(i, q); 1751 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1752 } 1753 1754 // Initialize the G1EvacuationFailureALot counters and flags. 1755 NOT_PRODUCT(reset_evacuation_should_fail();) 1756 1757 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1758 } 1759 1760 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1761 size_t size, 1762 size_t translation_factor) { 1763 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1764 // Allocate a new reserved space, preferring to use large pages. 1765 ReservedSpace rs(size, preferred_page_size); 1766 G1RegionToSpaceMapper* result = 1767 G1RegionToSpaceMapper::create_mapper(rs, 1768 size, 1769 rs.alignment(), 1770 HeapRegion::GrainBytes, 1771 translation_factor, 1772 mtGC); 1773 1774 os::trace_page_sizes_for_requested_size(description, 1775 size, 1776 preferred_page_size, 1777 rs.alignment(), 1778 rs.base(), 1779 rs.size()); 1780 1781 return result; 1782 } 1783 1784 jint G1CollectedHeap::initialize() { 1785 CollectedHeap::pre_initialize(); 1786 os::enable_vtime(); 1787 1788 // Necessary to satisfy locking discipline assertions. 1789 1790 MutexLocker x(Heap_lock); 1791 1792 // While there are no constraints in the GC code that HeapWordSize 1793 // be any particular value, there are multiple other areas in the 1794 // system which believe this to be true (e.g. oop->object_size in some 1795 // cases incorrectly returns the size in wordSize units rather than 1796 // HeapWordSize). 1797 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1798 1799 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1800 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1801 size_t heap_alignment = collector_policy()->heap_alignment(); 1802 1803 // Ensure that the sizes are properly aligned. 1804 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1805 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1806 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1807 1808 _refine_cte_cl = new RefineCardTableEntryClosure(); 1809 1810 jint ecode = JNI_OK; 1811 _cg1r = ConcurrentG1Refine::create(_refine_cte_cl, &ecode); 1812 if (_cg1r == NULL) { 1813 return ecode; 1814 } 1815 1816 // Reserve the maximum. 1817 1818 // When compressed oops are enabled, the preferred heap base 1819 // is calculated by subtracting the requested size from the 1820 // 32Gb boundary and using the result as the base address for 1821 // heap reservation. If the requested size is not aligned to 1822 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1823 // into the ReservedHeapSpace constructor) then the actual 1824 // base of the reserved heap may end up differing from the 1825 // address that was requested (i.e. the preferred heap base). 1826 // If this happens then we could end up using a non-optimal 1827 // compressed oops mode. 1828 1829 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1830 heap_alignment); 1831 1832 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1833 1834 // Create the barrier set for the entire reserved region. 1835 G1SATBCardTableLoggingModRefBS* bs 1836 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1837 bs->initialize(); 1838 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1839 set_barrier_set(bs); 1840 1841 // Create the hot card cache. 1842 _hot_card_cache = new G1HotCardCache(this); 1843 1844 // Also create a G1 rem set. 1845 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache); 1846 1847 // Carve out the G1 part of the heap. 1848 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1849 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1850 G1RegionToSpaceMapper* heap_storage = 1851 G1RegionToSpaceMapper::create_mapper(g1_rs, 1852 g1_rs.size(), 1853 page_size, 1854 HeapRegion::GrainBytes, 1855 1, 1856 mtJavaHeap); 1857 os::trace_page_sizes("Heap", 1858 collector_policy()->min_heap_byte_size(), 1859 max_byte_size, 1860 page_size, 1861 heap_rs.base(), 1862 heap_rs.size()); 1863 heap_storage->set_mapping_changed_listener(&_listener); 1864 1865 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1866 G1RegionToSpaceMapper* bot_storage = 1867 create_aux_memory_mapper("Block Offset Table", 1868 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1869 G1BlockOffsetTable::heap_map_factor()); 1870 1871 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1872 G1RegionToSpaceMapper* cardtable_storage = 1873 create_aux_memory_mapper("Card Table", 1874 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1875 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1876 1877 G1RegionToSpaceMapper* card_counts_storage = 1878 create_aux_memory_mapper("Card Counts Table", 1879 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1880 G1CardCounts::heap_map_factor()); 1881 1882 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1883 G1RegionToSpaceMapper* prev_bitmap_storage = 1884 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1885 G1RegionToSpaceMapper* next_bitmap_storage = 1886 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1887 1888 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1889 g1_barrier_set()->initialize(cardtable_storage); 1890 // Do later initialization work for concurrent refinement. 1891 _hot_card_cache->initialize(card_counts_storage); 1892 1893 // 6843694 - ensure that the maximum region index can fit 1894 // in the remembered set structures. 1895 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1896 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1897 1898 g1_rem_set()->initialize(max_capacity(), max_regions()); 1899 1900 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1901 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1902 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1903 "too many cards per region"); 1904 1905 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1906 1907 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1908 1909 { 1910 HeapWord* start = _hrm.reserved().start(); 1911 HeapWord* end = _hrm.reserved().end(); 1912 size_t granularity = HeapRegion::GrainBytes; 1913 1914 _in_cset_fast_test.initialize(start, end, granularity); 1915 _humongous_reclaim_candidates.initialize(start, end, granularity); 1916 } 1917 1918 // Create the G1ConcurrentMark data structure and thread. 1919 // (Must do this late, so that "max_regions" is defined.) 1920 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1921 if (_cm == NULL || !_cm->completed_initialization()) { 1922 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1923 return JNI_ENOMEM; 1924 } 1925 _cmThread = _cm->cmThread(); 1926 1927 // Now expand into the initial heap size. 1928 if (!expand(init_byte_size, _workers)) { 1929 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1930 return JNI_ENOMEM; 1931 } 1932 1933 // Perform any initialization actions delegated to the policy. 1934 g1_policy()->init(this, &_collection_set); 1935 1936 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1937 SATB_Q_FL_lock, 1938 G1SATBProcessCompletedThreshold, 1939 Shared_SATB_Q_lock); 1940 1941 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 1942 DirtyCardQ_CBL_mon, 1943 DirtyCardQ_FL_lock, 1944 (int)concurrent_g1_refine()->yellow_zone(), 1945 (int)concurrent_g1_refine()->red_zone(), 1946 Shared_DirtyCardQ_lock, 1947 NULL, // fl_owner 1948 true); // init_free_ids 1949 1950 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 1951 DirtyCardQ_CBL_mon, 1952 DirtyCardQ_FL_lock, 1953 -1, // never trigger processing 1954 -1, // no limit on length 1955 Shared_DirtyCardQ_lock, 1956 &JavaThread::dirty_card_queue_set()); 1957 1958 // Here we allocate the dummy HeapRegion that is required by the 1959 // G1AllocRegion class. 1960 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1961 1962 // We'll re-use the same region whether the alloc region will 1963 // require BOT updates or not and, if it doesn't, then a non-young 1964 // region will complain that it cannot support allocations without 1965 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1966 dummy_region->set_eden(); 1967 // Make sure it's full. 1968 dummy_region->set_top(dummy_region->end()); 1969 G1AllocRegion::setup(this, dummy_region); 1970 1971 _allocator->init_mutator_alloc_region(); 1972 1973 // Do create of the monitoring and management support so that 1974 // values in the heap have been properly initialized. 1975 _g1mm = new G1MonitoringSupport(this); 1976 1977 G1StringDedup::initialize(); 1978 1979 _preserved_marks_set.init(ParallelGCThreads); 1980 1981 _collection_set.initialize(max_regions()); 1982 1983 return JNI_OK; 1984 } 1985 1986 void G1CollectedHeap::stop() { 1987 // Stop all concurrent threads. We do this to make sure these threads 1988 // do not continue to execute and access resources (e.g. logging) 1989 // that are destroyed during shutdown. 1990 _cg1r->stop(); 1991 _cmThread->stop(); 1992 if (G1StringDedup::is_enabled()) { 1993 G1StringDedup::stop(); 1994 } 1995 } 1996 1997 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1998 return HeapRegion::max_region_size(); 1999 } 2000 2001 void G1CollectedHeap::post_initialize() { 2002 ref_processing_init(); 2003 } 2004 2005 void G1CollectedHeap::ref_processing_init() { 2006 // Reference processing in G1 currently works as follows: 2007 // 2008 // * There are two reference processor instances. One is 2009 // used to record and process discovered references 2010 // during concurrent marking; the other is used to 2011 // record and process references during STW pauses 2012 // (both full and incremental). 2013 // * Both ref processors need to 'span' the entire heap as 2014 // the regions in the collection set may be dotted around. 2015 // 2016 // * For the concurrent marking ref processor: 2017 // * Reference discovery is enabled at initial marking. 2018 // * Reference discovery is disabled and the discovered 2019 // references processed etc during remarking. 2020 // * Reference discovery is MT (see below). 2021 // * Reference discovery requires a barrier (see below). 2022 // * Reference processing may or may not be MT 2023 // (depending on the value of ParallelRefProcEnabled 2024 // and ParallelGCThreads). 2025 // * A full GC disables reference discovery by the CM 2026 // ref processor and abandons any entries on it's 2027 // discovered lists. 2028 // 2029 // * For the STW processor: 2030 // * Non MT discovery is enabled at the start of a full GC. 2031 // * Processing and enqueueing during a full GC is non-MT. 2032 // * During a full GC, references are processed after marking. 2033 // 2034 // * Discovery (may or may not be MT) is enabled at the start 2035 // of an incremental evacuation pause. 2036 // * References are processed near the end of a STW evacuation pause. 2037 // * For both types of GC: 2038 // * Discovery is atomic - i.e. not concurrent. 2039 // * Reference discovery will not need a barrier. 2040 2041 MemRegion mr = reserved_region(); 2042 2043 // Concurrent Mark ref processor 2044 _ref_processor_cm = 2045 new ReferenceProcessor(mr, // span 2046 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2047 // mt processing 2048 ParallelGCThreads, 2049 // degree of mt processing 2050 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2051 // mt discovery 2052 MAX2(ParallelGCThreads, ConcGCThreads), 2053 // degree of mt discovery 2054 false, 2055 // Reference discovery is not atomic 2056 &_is_alive_closure_cm); 2057 // is alive closure 2058 // (for efficiency/performance) 2059 2060 // STW ref processor 2061 _ref_processor_stw = 2062 new ReferenceProcessor(mr, // span 2063 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2064 // mt processing 2065 ParallelGCThreads, 2066 // degree of mt processing 2067 (ParallelGCThreads > 1), 2068 // mt discovery 2069 ParallelGCThreads, 2070 // degree of mt discovery 2071 true, 2072 // Reference discovery is atomic 2073 &_is_alive_closure_stw); 2074 // is alive closure 2075 // (for efficiency/performance) 2076 } 2077 2078 CollectorPolicy* G1CollectedHeap::collector_policy() const { 2079 return _collector_policy; 2080 } 2081 2082 size_t G1CollectedHeap::capacity() const { 2083 return _hrm.length() * HeapRegion::GrainBytes; 2084 } 2085 2086 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2087 hr->reset_gc_time_stamp(); 2088 } 2089 2090 #ifndef PRODUCT 2091 2092 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2093 private: 2094 unsigned _gc_time_stamp; 2095 bool _failures; 2096 2097 public: 2098 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2099 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2100 2101 virtual bool doHeapRegion(HeapRegion* hr) { 2102 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2103 if (_gc_time_stamp != region_gc_time_stamp) { 2104 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 2105 region_gc_time_stamp, _gc_time_stamp); 2106 _failures = true; 2107 } 2108 return false; 2109 } 2110 2111 bool failures() { return _failures; } 2112 }; 2113 2114 void G1CollectedHeap::check_gc_time_stamps() { 2115 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2116 heap_region_iterate(&cl); 2117 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2118 } 2119 #endif // PRODUCT 2120 2121 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2122 _hot_card_cache->drain(cl, worker_i); 2123 } 2124 2125 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2126 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2127 size_t n_completed_buffers = 0; 2128 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2129 n_completed_buffers++; 2130 } 2131 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2132 dcqs.clear_n_completed_buffers(); 2133 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2134 } 2135 2136 // Computes the sum of the storage used by the various regions. 2137 size_t G1CollectedHeap::used() const { 2138 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2139 if (_archive_allocator != NULL) { 2140 result += _archive_allocator->used(); 2141 } 2142 return result; 2143 } 2144 2145 size_t G1CollectedHeap::used_unlocked() const { 2146 return _summary_bytes_used; 2147 } 2148 2149 class SumUsedClosure: public HeapRegionClosure { 2150 size_t _used; 2151 public: 2152 SumUsedClosure() : _used(0) {} 2153 bool doHeapRegion(HeapRegion* r) { 2154 _used += r->used(); 2155 return false; 2156 } 2157 size_t result() { return _used; } 2158 }; 2159 2160 size_t G1CollectedHeap::recalculate_used() const { 2161 double recalculate_used_start = os::elapsedTime(); 2162 2163 SumUsedClosure blk; 2164 heap_region_iterate(&blk); 2165 2166 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2167 return blk.result(); 2168 } 2169 2170 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2171 switch (cause) { 2172 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2173 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2174 case GCCause::_update_allocation_context_stats_inc: return true; 2175 case GCCause::_wb_conc_mark: return true; 2176 default : return false; 2177 } 2178 } 2179 2180 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2181 switch (cause) { 2182 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2183 case GCCause::_g1_humongous_allocation: return true; 2184 default: return is_user_requested_concurrent_full_gc(cause); 2185 } 2186 } 2187 2188 #ifndef PRODUCT 2189 void G1CollectedHeap::allocate_dummy_regions() { 2190 // Let's fill up most of the region 2191 size_t word_size = HeapRegion::GrainWords - 1024; 2192 // And as a result the region we'll allocate will be humongous. 2193 guarantee(is_humongous(word_size), "sanity"); 2194 2195 // _filler_array_max_size is set to humongous object threshold 2196 // but temporarily change it to use CollectedHeap::fill_with_object(). 2197 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2198 2199 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2200 // Let's use the existing mechanism for the allocation 2201 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2202 AllocationContext::system()); 2203 if (dummy_obj != NULL) { 2204 MemRegion mr(dummy_obj, word_size); 2205 CollectedHeap::fill_with_object(mr); 2206 } else { 2207 // If we can't allocate once, we probably cannot allocate 2208 // again. Let's get out of the loop. 2209 break; 2210 } 2211 } 2212 } 2213 #endif // !PRODUCT 2214 2215 void G1CollectedHeap::increment_old_marking_cycles_started() { 2216 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2217 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2218 "Wrong marking cycle count (started: %d, completed: %d)", 2219 _old_marking_cycles_started, _old_marking_cycles_completed); 2220 2221 _old_marking_cycles_started++; 2222 } 2223 2224 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2225 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2226 2227 // We assume that if concurrent == true, then the caller is a 2228 // concurrent thread that was joined the Suspendible Thread 2229 // Set. If there's ever a cheap way to check this, we should add an 2230 // assert here. 2231 2232 // Given that this method is called at the end of a Full GC or of a 2233 // concurrent cycle, and those can be nested (i.e., a Full GC can 2234 // interrupt a concurrent cycle), the number of full collections 2235 // completed should be either one (in the case where there was no 2236 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2237 // behind the number of full collections started. 2238 2239 // This is the case for the inner caller, i.e. a Full GC. 2240 assert(concurrent || 2241 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2242 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2243 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2244 "is inconsistent with _old_marking_cycles_completed = %u", 2245 _old_marking_cycles_started, _old_marking_cycles_completed); 2246 2247 // This is the case for the outer caller, i.e. the concurrent cycle. 2248 assert(!concurrent || 2249 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2250 "for outer caller (concurrent cycle): " 2251 "_old_marking_cycles_started = %u " 2252 "is inconsistent with _old_marking_cycles_completed = %u", 2253 _old_marking_cycles_started, _old_marking_cycles_completed); 2254 2255 _old_marking_cycles_completed += 1; 2256 2257 // We need to clear the "in_progress" flag in the CM thread before 2258 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2259 // is set) so that if a waiter requests another System.gc() it doesn't 2260 // incorrectly see that a marking cycle is still in progress. 2261 if (concurrent) { 2262 _cmThread->set_idle(); 2263 } 2264 2265 // This notify_all() will ensure that a thread that called 2266 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2267 // and it's waiting for a full GC to finish will be woken up. It is 2268 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2269 FullGCCount_lock->notify_all(); 2270 } 2271 2272 void G1CollectedHeap::collect(GCCause::Cause cause) { 2273 assert_heap_not_locked(); 2274 2275 uint gc_count_before; 2276 uint old_marking_count_before; 2277 uint full_gc_count_before; 2278 bool retry_gc; 2279 2280 do { 2281 retry_gc = false; 2282 2283 { 2284 MutexLocker ml(Heap_lock); 2285 2286 // Read the GC count while holding the Heap_lock 2287 gc_count_before = total_collections(); 2288 full_gc_count_before = total_full_collections(); 2289 old_marking_count_before = _old_marking_cycles_started; 2290 } 2291 2292 if (should_do_concurrent_full_gc(cause)) { 2293 // Schedule an initial-mark evacuation pause that will start a 2294 // concurrent cycle. We're setting word_size to 0 which means that 2295 // we are not requesting a post-GC allocation. 2296 VM_G1IncCollectionPause op(gc_count_before, 2297 0, /* word_size */ 2298 true, /* should_initiate_conc_mark */ 2299 g1_policy()->max_pause_time_ms(), 2300 cause); 2301 op.set_allocation_context(AllocationContext::current()); 2302 2303 VMThread::execute(&op); 2304 if (!op.pause_succeeded()) { 2305 if (old_marking_count_before == _old_marking_cycles_started) { 2306 retry_gc = op.should_retry_gc(); 2307 } else { 2308 // A Full GC happened while we were trying to schedule the 2309 // initial-mark GC. No point in starting a new cycle given 2310 // that the whole heap was collected anyway. 2311 } 2312 2313 if (retry_gc) { 2314 if (GCLocker::is_active_and_needs_gc()) { 2315 GCLocker::stall_until_clear(); 2316 } 2317 } 2318 } 2319 } else { 2320 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2321 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2322 2323 // Schedule a standard evacuation pause. We're setting word_size 2324 // to 0 which means that we are not requesting a post-GC allocation. 2325 VM_G1IncCollectionPause op(gc_count_before, 2326 0, /* word_size */ 2327 false, /* should_initiate_conc_mark */ 2328 g1_policy()->max_pause_time_ms(), 2329 cause); 2330 VMThread::execute(&op); 2331 } else { 2332 // Schedule a Full GC. 2333 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2334 VMThread::execute(&op); 2335 } 2336 } 2337 } while (retry_gc); 2338 } 2339 2340 bool G1CollectedHeap::is_in(const void* p) const { 2341 if (_hrm.reserved().contains(p)) { 2342 // Given that we know that p is in the reserved space, 2343 // heap_region_containing() should successfully 2344 // return the containing region. 2345 HeapRegion* hr = heap_region_containing(p); 2346 return hr->is_in(p); 2347 } else { 2348 return false; 2349 } 2350 } 2351 2352 #ifdef ASSERT 2353 bool G1CollectedHeap::is_in_exact(const void* p) const { 2354 bool contains = reserved_region().contains(p); 2355 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2356 if (contains && available) { 2357 return true; 2358 } else { 2359 return false; 2360 } 2361 } 2362 #endif 2363 2364 // Iteration functions. 2365 2366 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2367 2368 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2369 ExtendedOopClosure* _cl; 2370 public: 2371 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2372 bool doHeapRegion(HeapRegion* r) { 2373 if (!r->is_continues_humongous()) { 2374 r->oop_iterate(_cl); 2375 } 2376 return false; 2377 } 2378 }; 2379 2380 // Iterates an ObjectClosure over all objects within a HeapRegion. 2381 2382 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2383 ObjectClosure* _cl; 2384 public: 2385 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2386 bool doHeapRegion(HeapRegion* r) { 2387 if (!r->is_continues_humongous()) { 2388 r->object_iterate(_cl); 2389 } 2390 return false; 2391 } 2392 }; 2393 2394 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2395 IterateObjectClosureRegionClosure blk(cl); 2396 heap_region_iterate(&blk); 2397 } 2398 2399 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2400 _hrm.iterate(cl); 2401 } 2402 2403 void 2404 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2405 uint worker_id, 2406 HeapRegionClaimer *hrclaimer, 2407 bool concurrent) const { 2408 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2409 } 2410 2411 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2412 _collection_set.iterate(cl); 2413 } 2414 2415 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2416 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2417 } 2418 2419 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2420 HeapRegion* result = _hrm.next_region_in_heap(from); 2421 while (result != NULL && result->is_pinned()) { 2422 result = _hrm.next_region_in_heap(result); 2423 } 2424 return result; 2425 } 2426 2427 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2428 HeapRegion* hr = heap_region_containing(addr); 2429 return hr->block_start(addr); 2430 } 2431 2432 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2433 HeapRegion* hr = heap_region_containing(addr); 2434 return hr->block_size(addr); 2435 } 2436 2437 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2438 HeapRegion* hr = heap_region_containing(addr); 2439 return hr->block_is_obj(addr); 2440 } 2441 2442 bool G1CollectedHeap::supports_tlab_allocation() const { 2443 return true; 2444 } 2445 2446 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2447 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2448 } 2449 2450 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2451 return _eden.length() * HeapRegion::GrainBytes; 2452 } 2453 2454 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2455 // must be equal to the humongous object limit. 2456 size_t G1CollectedHeap::max_tlab_size() const { 2457 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2458 } 2459 2460 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2461 AllocationContext_t context = AllocationContext::current(); 2462 return _allocator->unsafe_max_tlab_alloc(context); 2463 } 2464 2465 size_t G1CollectedHeap::max_capacity() const { 2466 return _hrm.reserved().byte_size(); 2467 } 2468 2469 jlong G1CollectedHeap::millis_since_last_gc() { 2470 // See the notes in GenCollectedHeap::millis_since_last_gc() 2471 // for more information about the implementation. 2472 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2473 _g1_policy->collection_pause_end_millis(); 2474 if (ret_val < 0) { 2475 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2476 ". returning zero instead.", ret_val); 2477 return 0; 2478 } 2479 return ret_val; 2480 } 2481 2482 void G1CollectedHeap::prepare_for_verify() { 2483 _verifier->prepare_for_verify(); 2484 } 2485 2486 void G1CollectedHeap::verify(VerifyOption vo) { 2487 _verifier->verify(vo); 2488 } 2489 2490 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2491 return true; 2492 } 2493 2494 const char* const* G1CollectedHeap::concurrent_phases() const { 2495 return _cmThread->concurrent_phases(); 2496 } 2497 2498 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2499 return _cmThread->request_concurrent_phase(phase); 2500 } 2501 2502 class PrintRegionClosure: public HeapRegionClosure { 2503 outputStream* _st; 2504 public: 2505 PrintRegionClosure(outputStream* st) : _st(st) {} 2506 bool doHeapRegion(HeapRegion* r) { 2507 r->print_on(_st); 2508 return false; 2509 } 2510 }; 2511 2512 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2513 const HeapRegion* hr, 2514 const VerifyOption vo) const { 2515 switch (vo) { 2516 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2517 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2518 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 2519 default: ShouldNotReachHere(); 2520 } 2521 return false; // keep some compilers happy 2522 } 2523 2524 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2525 const VerifyOption vo) const { 2526 switch (vo) { 2527 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2528 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2529 case VerifyOption_G1UseMarkWord: { 2530 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 2531 return !obj->is_gc_marked() && !hr->is_archive(); 2532 } 2533 default: ShouldNotReachHere(); 2534 } 2535 return false; // keep some compilers happy 2536 } 2537 2538 void G1CollectedHeap::print_heap_regions() const { 2539 Log(gc, heap, region) log; 2540 if (log.is_trace()) { 2541 ResourceMark rm; 2542 print_regions_on(log.trace_stream()); 2543 } 2544 } 2545 2546 void G1CollectedHeap::print_on(outputStream* st) const { 2547 st->print(" %-20s", "garbage-first heap"); 2548 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2549 capacity()/K, used_unlocked()/K); 2550 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 2551 p2i(_hrm.reserved().start()), 2552 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 2553 p2i(_hrm.reserved().end())); 2554 st->cr(); 2555 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2556 uint young_regions = young_regions_count(); 2557 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2558 (size_t) young_regions * HeapRegion::GrainBytes / K); 2559 uint survivor_regions = survivor_regions_count(); 2560 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2561 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2562 st->cr(); 2563 MetaspaceAux::print_on(st); 2564 } 2565 2566 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2567 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2568 "HS=humongous(starts), HC=humongous(continues), " 2569 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2570 "AC=allocation context, " 2571 "TAMS=top-at-mark-start (previous, next)"); 2572 PrintRegionClosure blk(st); 2573 heap_region_iterate(&blk); 2574 } 2575 2576 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2577 print_on(st); 2578 2579 // Print the per-region information. 2580 print_regions_on(st); 2581 } 2582 2583 void G1CollectedHeap::print_on_error(outputStream* st) const { 2584 this->CollectedHeap::print_on_error(st); 2585 2586 if (_cm != NULL) { 2587 st->cr(); 2588 _cm->print_on_error(st); 2589 } 2590 } 2591 2592 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2593 workers()->print_worker_threads_on(st); 2594 _cmThread->print_on(st); 2595 st->cr(); 2596 _cm->print_worker_threads_on(st); 2597 _cg1r->print_worker_threads_on(st); // also prints the sample thread 2598 if (G1StringDedup::is_enabled()) { 2599 G1StringDedup::print_worker_threads_on(st); 2600 } 2601 } 2602 2603 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2604 workers()->threads_do(tc); 2605 tc->do_thread(_cmThread); 2606 _cm->threads_do(tc); 2607 _cg1r->threads_do(tc); // also iterates over the sample thread 2608 if (G1StringDedup::is_enabled()) { 2609 G1StringDedup::threads_do(tc); 2610 } 2611 } 2612 2613 void G1CollectedHeap::print_tracing_info() const { 2614 g1_rem_set()->print_summary_info(); 2615 concurrent_mark()->print_summary_info(); 2616 } 2617 2618 #ifndef PRODUCT 2619 // Helpful for debugging RSet issues. 2620 2621 class PrintRSetsClosure : public HeapRegionClosure { 2622 private: 2623 const char* _msg; 2624 size_t _occupied_sum; 2625 2626 public: 2627 bool doHeapRegion(HeapRegion* r) { 2628 HeapRegionRemSet* hrrs = r->rem_set(); 2629 size_t occupied = hrrs->occupied(); 2630 _occupied_sum += occupied; 2631 2632 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2633 if (occupied == 0) { 2634 tty->print_cr(" RSet is empty"); 2635 } else { 2636 hrrs->print(); 2637 } 2638 tty->print_cr("----------"); 2639 return false; 2640 } 2641 2642 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2643 tty->cr(); 2644 tty->print_cr("========================================"); 2645 tty->print_cr("%s", msg); 2646 tty->cr(); 2647 } 2648 2649 ~PrintRSetsClosure() { 2650 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2651 tty->print_cr("========================================"); 2652 tty->cr(); 2653 } 2654 }; 2655 2656 void G1CollectedHeap::print_cset_rsets() { 2657 PrintRSetsClosure cl("Printing CSet RSets"); 2658 collection_set_iterate(&cl); 2659 } 2660 2661 void G1CollectedHeap::print_all_rsets() { 2662 PrintRSetsClosure cl("Printing All RSets");; 2663 heap_region_iterate(&cl); 2664 } 2665 #endif // PRODUCT 2666 2667 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2668 2669 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2670 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2671 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2672 2673 size_t eden_capacity_bytes = 2674 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2675 2676 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2677 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2678 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2679 } 2680 2681 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2682 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2683 stats->unused(), stats->used(), stats->region_end_waste(), 2684 stats->regions_filled(), stats->direct_allocated(), 2685 stats->failure_used(), stats->failure_waste()); 2686 } 2687 2688 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2689 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2690 gc_tracer->report_gc_heap_summary(when, heap_summary); 2691 2692 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2693 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2694 } 2695 2696 G1CollectedHeap* G1CollectedHeap::heap() { 2697 CollectedHeap* heap = Universe::heap(); 2698 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2699 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2700 return (G1CollectedHeap*)heap; 2701 } 2702 2703 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 2704 // always_do_update_barrier = false; 2705 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2706 2707 double start = os::elapsedTime(); 2708 // Fill TLAB's and such 2709 accumulate_statistics_all_tlabs(); 2710 ensure_parsability(true); 2711 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2712 2713 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2714 } 2715 2716 void G1CollectedHeap::gc_epilogue(bool full) { 2717 // we are at the end of the GC. Total collections has already been increased. 2718 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2719 2720 // FIXME: what is this about? 2721 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2722 // is set. 2723 #if defined(COMPILER2) || INCLUDE_JVMCI 2724 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2725 #endif 2726 // always_do_update_barrier = true; 2727 2728 double start = os::elapsedTime(); 2729 resize_all_tlabs(); 2730 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2731 2732 allocation_context_stats().update(full); 2733 2734 // We have just completed a GC. Update the soft reference 2735 // policy with the new heap occupancy 2736 Universe::update_heap_info_at_gc(); 2737 } 2738 2739 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2740 uint gc_count_before, 2741 bool* succeeded, 2742 GCCause::Cause gc_cause) { 2743 assert_heap_not_locked_and_not_at_safepoint(); 2744 VM_G1IncCollectionPause op(gc_count_before, 2745 word_size, 2746 false, /* should_initiate_conc_mark */ 2747 g1_policy()->max_pause_time_ms(), 2748 gc_cause); 2749 2750 op.set_allocation_context(AllocationContext::current()); 2751 VMThread::execute(&op); 2752 2753 HeapWord* result = op.result(); 2754 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2755 assert(result == NULL || ret_succeeded, 2756 "the result should be NULL if the VM did not succeed"); 2757 *succeeded = ret_succeeded; 2758 2759 assert_heap_not_locked(); 2760 return result; 2761 } 2762 2763 void 2764 G1CollectedHeap::doConcurrentMark() { 2765 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2766 if (!_cmThread->in_progress()) { 2767 _cmThread->set_started(); 2768 CGC_lock->notify(); 2769 } 2770 } 2771 2772 size_t G1CollectedHeap::pending_card_num() { 2773 size_t extra_cards = 0; 2774 JavaThread *curr = Threads::first(); 2775 while (curr != NULL) { 2776 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2777 extra_cards += dcq.size(); 2778 curr = curr->next(); 2779 } 2780 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2781 size_t buffer_size = dcqs.buffer_size(); 2782 size_t buffer_num = dcqs.completed_buffers_num(); 2783 2784 return buffer_size * buffer_num + extra_cards; 2785 } 2786 2787 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2788 private: 2789 size_t _total_humongous; 2790 size_t _candidate_humongous; 2791 2792 DirtyCardQueue _dcq; 2793 2794 // We don't nominate objects with many remembered set entries, on 2795 // the assumption that such objects are likely still live. 2796 bool is_remset_small(HeapRegion* region) const { 2797 HeapRegionRemSet* const rset = region->rem_set(); 2798 return G1EagerReclaimHumongousObjectsWithStaleRefs 2799 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2800 : rset->is_empty(); 2801 } 2802 2803 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2804 assert(region->is_starts_humongous(), "Must start a humongous object"); 2805 2806 oop obj = oop(region->bottom()); 2807 2808 // Dead objects cannot be eager reclaim candidates. Due to class 2809 // unloading it is unsafe to query their classes so we return early. 2810 if (heap->is_obj_dead(obj, region)) { 2811 return false; 2812 } 2813 2814 // Candidate selection must satisfy the following constraints 2815 // while concurrent marking is in progress: 2816 // 2817 // * In order to maintain SATB invariants, an object must not be 2818 // reclaimed if it was allocated before the start of marking and 2819 // has not had its references scanned. Such an object must have 2820 // its references (including type metadata) scanned to ensure no 2821 // live objects are missed by the marking process. Objects 2822 // allocated after the start of concurrent marking don't need to 2823 // be scanned. 2824 // 2825 // * An object must not be reclaimed if it is on the concurrent 2826 // mark stack. Objects allocated after the start of concurrent 2827 // marking are never pushed on the mark stack. 2828 // 2829 // Nominating only objects allocated after the start of concurrent 2830 // marking is sufficient to meet both constraints. This may miss 2831 // some objects that satisfy the constraints, but the marking data 2832 // structures don't support efficiently performing the needed 2833 // additional tests or scrubbing of the mark stack. 2834 // 2835 // However, we presently only nominate is_typeArray() objects. 2836 // A humongous object containing references induces remembered 2837 // set entries on other regions. In order to reclaim such an 2838 // object, those remembered sets would need to be cleaned up. 2839 // 2840 // We also treat is_typeArray() objects specially, allowing them 2841 // to be reclaimed even if allocated before the start of 2842 // concurrent mark. For this we rely on mark stack insertion to 2843 // exclude is_typeArray() objects, preventing reclaiming an object 2844 // that is in the mark stack. We also rely on the metadata for 2845 // such objects to be built-in and so ensured to be kept live. 2846 // Frequent allocation and drop of large binary blobs is an 2847 // important use case for eager reclaim, and this special handling 2848 // may reduce needed headroom. 2849 2850 return obj->is_typeArray() && is_remset_small(region); 2851 } 2852 2853 public: 2854 RegisterHumongousWithInCSetFastTestClosure() 2855 : _total_humongous(0), 2856 _candidate_humongous(0), 2857 _dcq(&JavaThread::dirty_card_queue_set()) { 2858 } 2859 2860 virtual bool doHeapRegion(HeapRegion* r) { 2861 if (!r->is_starts_humongous()) { 2862 return false; 2863 } 2864 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2865 2866 bool is_candidate = humongous_region_is_candidate(g1h, r); 2867 uint rindex = r->hrm_index(); 2868 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2869 if (is_candidate) { 2870 _candidate_humongous++; 2871 g1h->register_humongous_region_with_cset(rindex); 2872 // Is_candidate already filters out humongous object with large remembered sets. 2873 // If we have a humongous object with a few remembered sets, we simply flush these 2874 // remembered set entries into the DCQS. That will result in automatic 2875 // re-evaluation of their remembered set entries during the following evacuation 2876 // phase. 2877 if (!r->rem_set()->is_empty()) { 2878 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2879 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2880 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 2881 HeapRegionRemSetIterator hrrs(r->rem_set()); 2882 size_t card_index; 2883 while (hrrs.has_next(card_index)) { 2884 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 2885 // The remembered set might contain references to already freed 2886 // regions. Filter out such entries to avoid failing card table 2887 // verification. 2888 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 2889 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 2890 *card_ptr = CardTableModRefBS::dirty_card_val(); 2891 _dcq.enqueue(card_ptr); 2892 } 2893 } 2894 } 2895 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2896 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2897 hrrs.n_yielded(), r->rem_set()->occupied()); 2898 r->rem_set()->clear_locked(); 2899 } 2900 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2901 } 2902 _total_humongous++; 2903 2904 return false; 2905 } 2906 2907 size_t total_humongous() const { return _total_humongous; } 2908 size_t candidate_humongous() const { return _candidate_humongous; } 2909 2910 void flush_rem_set_entries() { _dcq.flush(); } 2911 }; 2912 2913 void G1CollectedHeap::register_humongous_regions_with_cset() { 2914 if (!G1EagerReclaimHumongousObjects) { 2915 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2916 return; 2917 } 2918 double time = os::elapsed_counter(); 2919 2920 // Collect reclaim candidate information and register candidates with cset. 2921 RegisterHumongousWithInCSetFastTestClosure cl; 2922 heap_region_iterate(&cl); 2923 2924 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2925 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2926 cl.total_humongous(), 2927 cl.candidate_humongous()); 2928 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2929 2930 // Finally flush all remembered set entries to re-check into the global DCQS. 2931 cl.flush_rem_set_entries(); 2932 } 2933 2934 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2935 public: 2936 bool doHeapRegion(HeapRegion* hr) { 2937 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2938 hr->verify_rem_set(); 2939 } 2940 return false; 2941 } 2942 }; 2943 2944 uint G1CollectedHeap::num_task_queues() const { 2945 return _task_queues->size(); 2946 } 2947 2948 #if TASKQUEUE_STATS 2949 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2950 st->print_raw_cr("GC Task Stats"); 2951 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2952 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2953 } 2954 2955 void G1CollectedHeap::print_taskqueue_stats() const { 2956 if (!log_is_enabled(Trace, gc, task, stats)) { 2957 return; 2958 } 2959 Log(gc, task, stats) log; 2960 ResourceMark rm; 2961 outputStream* st = log.trace_stream(); 2962 2963 print_taskqueue_stats_hdr(st); 2964 2965 TaskQueueStats totals; 2966 const uint n = num_task_queues(); 2967 for (uint i = 0; i < n; ++i) { 2968 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2969 totals += task_queue(i)->stats; 2970 } 2971 st->print_raw("tot "); totals.print(st); st->cr(); 2972 2973 DEBUG_ONLY(totals.verify()); 2974 } 2975 2976 void G1CollectedHeap::reset_taskqueue_stats() { 2977 const uint n = num_task_queues(); 2978 for (uint i = 0; i < n; ++i) { 2979 task_queue(i)->stats.reset(); 2980 } 2981 } 2982 #endif // TASKQUEUE_STATS 2983 2984 void G1CollectedHeap::wait_for_root_region_scanning() { 2985 double scan_wait_start = os::elapsedTime(); 2986 // We have to wait until the CM threads finish scanning the 2987 // root regions as it's the only way to ensure that all the 2988 // objects on them have been correctly scanned before we start 2989 // moving them during the GC. 2990 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2991 double wait_time_ms = 0.0; 2992 if (waited) { 2993 double scan_wait_end = os::elapsedTime(); 2994 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2995 } 2996 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2997 } 2998 2999 class G1PrintCollectionSetClosure : public HeapRegionClosure { 3000 private: 3001 G1HRPrinter* _hr_printer; 3002 public: 3003 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 3004 3005 virtual bool doHeapRegion(HeapRegion* r) { 3006 _hr_printer->cset(r); 3007 return false; 3008 } 3009 }; 3010 3011 void G1CollectedHeap::start_new_collection_set() { 3012 collection_set()->start_incremental_building(); 3013 3014 clear_cset_fast_test(); 3015 3016 guarantee(_eden.length() == 0, "eden should have been cleared"); 3017 g1_policy()->transfer_survivors_to_cset(survivor()); 3018 } 3019 3020 bool 3021 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3022 assert_at_safepoint(true /* should_be_vm_thread */); 3023 guarantee(!is_gc_active(), "collection is not reentrant"); 3024 3025 if (GCLocker::check_active_before_gc()) { 3026 return false; 3027 } 3028 3029 _gc_timer_stw->register_gc_start(); 3030 3031 GCIdMark gc_id_mark; 3032 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3033 3034 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3035 ResourceMark rm; 3036 3037 g1_policy()->note_gc_start(); 3038 3039 wait_for_root_region_scanning(); 3040 3041 print_heap_before_gc(); 3042 print_heap_regions(); 3043 trace_heap_before_gc(_gc_tracer_stw); 3044 3045 _verifier->verify_region_sets_optional(); 3046 _verifier->verify_dirty_young_regions(); 3047 3048 // We should not be doing initial mark unless the conc mark thread is running 3049 if (!_cmThread->should_terminate()) { 3050 // This call will decide whether this pause is an initial-mark 3051 // pause. If it is, during_initial_mark_pause() will return true 3052 // for the duration of this pause. 3053 g1_policy()->decide_on_conc_mark_initiation(); 3054 } 3055 3056 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3057 assert(!collector_state()->during_initial_mark_pause() || 3058 collector_state()->gcs_are_young(), "sanity"); 3059 3060 // We also do not allow mixed GCs during marking. 3061 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3062 3063 // Record whether this pause is an initial mark. When the current 3064 // thread has completed its logging output and it's safe to signal 3065 // the CM thread, the flag's value in the policy has been reset. 3066 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3067 3068 // Inner scope for scope based logging, timers, and stats collection 3069 { 3070 EvacuationInfo evacuation_info; 3071 3072 if (collector_state()->during_initial_mark_pause()) { 3073 // We are about to start a marking cycle, so we increment the 3074 // full collection counter. 3075 increment_old_marking_cycles_started(); 3076 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 3077 } 3078 3079 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3080 3081 GCTraceCPUTime tcpu; 3082 3083 FormatBuffer<> gc_string("Pause "); 3084 if (collector_state()->during_initial_mark_pause()) { 3085 gc_string.append("Initial Mark"); 3086 } else if (collector_state()->gcs_are_young()) { 3087 gc_string.append("Young"); 3088 } else { 3089 gc_string.append("Mixed"); 3090 } 3091 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 3092 3093 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3094 workers()->active_workers(), 3095 Threads::number_of_non_daemon_threads()); 3096 workers()->update_active_workers(active_workers); 3097 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 3098 3099 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3100 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3101 3102 // If the secondary_free_list is not empty, append it to the 3103 // free_list. No need to wait for the cleanup operation to finish; 3104 // the region allocation code will check the secondary_free_list 3105 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3106 // set, skip this step so that the region allocation code has to 3107 // get entries from the secondary_free_list. 3108 if (!G1StressConcRegionFreeing) { 3109 append_secondary_free_list_if_not_empty_with_lock(); 3110 } 3111 3112 G1HeapTransition heap_transition(this); 3113 size_t heap_used_bytes_before_gc = used(); 3114 3115 // Don't dynamically change the number of GC threads this early. A value of 3116 // 0 is used to indicate serial work. When parallel work is done, 3117 // it will be set. 3118 3119 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3120 IsGCActiveMark x; 3121 3122 gc_prologue(false); 3123 increment_total_collections(false /* full gc */); 3124 increment_gc_time_stamp(); 3125 3126 if (VerifyRememberedSets) { 3127 log_info(gc, verify)("[Verifying RemSets before GC]"); 3128 VerifyRegionRemSetClosure v_cl; 3129 heap_region_iterate(&v_cl); 3130 } 3131 3132 _verifier->verify_before_gc(); 3133 3134 _verifier->check_bitmaps("GC Start"); 3135 3136 #if defined(COMPILER2) || INCLUDE_JVMCI 3137 DerivedPointerTable::clear(); 3138 #endif 3139 3140 // Please see comment in g1CollectedHeap.hpp and 3141 // G1CollectedHeap::ref_processing_init() to see how 3142 // reference processing currently works in G1. 3143 3144 // Enable discovery in the STW reference processor 3145 if (g1_policy()->should_process_references()) { 3146 ref_processor_stw()->enable_discovery(); 3147 } else { 3148 ref_processor_stw()->disable_discovery(); 3149 } 3150 3151 { 3152 // We want to temporarily turn off discovery by the 3153 // CM ref processor, if necessary, and turn it back on 3154 // on again later if we do. Using a scoped 3155 // NoRefDiscovery object will do this. 3156 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3157 3158 // Forget the current alloc region (we might even choose it to be part 3159 // of the collection set!). 3160 _allocator->release_mutator_alloc_region(); 3161 3162 // This timing is only used by the ergonomics to handle our pause target. 3163 // It is unclear why this should not include the full pause. We will 3164 // investigate this in CR 7178365. 3165 // 3166 // Preserving the old comment here if that helps the investigation: 3167 // 3168 // The elapsed time induced by the start time below deliberately elides 3169 // the possible verification above. 3170 double sample_start_time_sec = os::elapsedTime(); 3171 3172 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3173 3174 if (collector_state()->during_initial_mark_pause()) { 3175 concurrent_mark()->checkpointRootsInitialPre(); 3176 } 3177 3178 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 3179 3180 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3181 3182 // Make sure the remembered sets are up to date. This needs to be 3183 // done before register_humongous_regions_with_cset(), because the 3184 // remembered sets are used there to choose eager reclaim candidates. 3185 // If the remembered sets are not up to date we might miss some 3186 // entries that need to be handled. 3187 g1_rem_set()->cleanupHRRS(); 3188 3189 register_humongous_regions_with_cset(); 3190 3191 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3192 3193 // We call this after finalize_cset() to 3194 // ensure that the CSet has been finalized. 3195 _cm->verify_no_cset_oops(); 3196 3197 if (_hr_printer.is_active()) { 3198 G1PrintCollectionSetClosure cl(&_hr_printer); 3199 _collection_set.iterate(&cl); 3200 } 3201 3202 // Initialize the GC alloc regions. 3203 _allocator->init_gc_alloc_regions(evacuation_info); 3204 3205 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3206 pre_evacuate_collection_set(); 3207 3208 // Actually do the work... 3209 evacuate_collection_set(evacuation_info, &per_thread_states); 3210 3211 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3212 3213 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3214 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 3215 3216 eagerly_reclaim_humongous_regions(); 3217 3218 record_obj_copy_mem_stats(); 3219 _survivor_evac_stats.adjust_desired_plab_sz(); 3220 _old_evac_stats.adjust_desired_plab_sz(); 3221 3222 double start = os::elapsedTime(); 3223 start_new_collection_set(); 3224 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 3225 3226 if (evacuation_failed()) { 3227 set_used(recalculate_used()); 3228 if (_archive_allocator != NULL) { 3229 _archive_allocator->clear_used(); 3230 } 3231 for (uint i = 0; i < ParallelGCThreads; i++) { 3232 if (_evacuation_failed_info_array[i].has_failed()) { 3233 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3234 } 3235 } 3236 } else { 3237 // The "used" of the the collection set have already been subtracted 3238 // when they were freed. Add in the bytes evacuated. 3239 increase_used(g1_policy()->bytes_copied_during_gc()); 3240 } 3241 3242 if (collector_state()->during_initial_mark_pause()) { 3243 // We have to do this before we notify the CM threads that 3244 // they can start working to make sure that all the 3245 // appropriate initialization is done on the CM object. 3246 concurrent_mark()->checkpointRootsInitialPost(); 3247 collector_state()->set_mark_in_progress(true); 3248 // Note that we don't actually trigger the CM thread at 3249 // this point. We do that later when we're sure that 3250 // the current thread has completed its logging output. 3251 } 3252 3253 allocate_dummy_regions(); 3254 3255 _allocator->init_mutator_alloc_region(); 3256 3257 { 3258 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3259 if (expand_bytes > 0) { 3260 size_t bytes_before = capacity(); 3261 // No need for an ergo logging here, 3262 // expansion_amount() does this when it returns a value > 0. 3263 double expand_ms; 3264 if (!expand(expand_bytes, _workers, &expand_ms)) { 3265 // We failed to expand the heap. Cannot do anything about it. 3266 } 3267 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3268 } 3269 } 3270 3271 // We redo the verification but now wrt to the new CSet which 3272 // has just got initialized after the previous CSet was freed. 3273 _cm->verify_no_cset_oops(); 3274 3275 // This timing is only used by the ergonomics to handle our pause target. 3276 // It is unclear why this should not include the full pause. We will 3277 // investigate this in CR 7178365. 3278 double sample_end_time_sec = os::elapsedTime(); 3279 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3280 size_t total_cards_scanned = per_thread_states.total_cards_scanned(); 3281 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3282 3283 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3284 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3285 3286 MemoryService::track_memory_usage(); 3287 3288 // In prepare_for_verify() below we'll need to scan the deferred 3289 // update buffers to bring the RSets up-to-date if 3290 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3291 // the update buffers we'll probably need to scan cards on the 3292 // regions we just allocated to (i.e., the GC alloc 3293 // regions). However, during the last GC we called 3294 // set_saved_mark() on all the GC alloc regions, so card 3295 // scanning might skip the [saved_mark_word()...top()] area of 3296 // those regions (i.e., the area we allocated objects into 3297 // during the last GC). But it shouldn't. Given that 3298 // saved_mark_word() is conditional on whether the GC time stamp 3299 // on the region is current or not, by incrementing the GC time 3300 // stamp here we invalidate all the GC time stamps on all the 3301 // regions and saved_mark_word() will simply return top() for 3302 // all the regions. This is a nicer way of ensuring this rather 3303 // than iterating over the regions and fixing them. In fact, the 3304 // GC time stamp increment here also ensures that 3305 // saved_mark_word() will return top() between pauses, i.e., 3306 // during concurrent refinement. So we don't need the 3307 // is_gc_active() check to decided which top to use when 3308 // scanning cards (see CR 7039627). 3309 increment_gc_time_stamp(); 3310 3311 if (VerifyRememberedSets) { 3312 log_info(gc, verify)("[Verifying RemSets after GC]"); 3313 VerifyRegionRemSetClosure v_cl; 3314 heap_region_iterate(&v_cl); 3315 } 3316 3317 _verifier->verify_after_gc(); 3318 _verifier->check_bitmaps("GC End"); 3319 3320 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3321 ref_processor_stw()->verify_no_references_recorded(); 3322 3323 // CM reference discovery will be re-enabled if necessary. 3324 } 3325 3326 #ifdef TRACESPINNING 3327 ParallelTaskTerminator::print_termination_counts(); 3328 #endif 3329 3330 gc_epilogue(false); 3331 } 3332 3333 // Print the remainder of the GC log output. 3334 if (evacuation_failed()) { 3335 log_info(gc)("To-space exhausted"); 3336 } 3337 3338 g1_policy()->print_phases(); 3339 heap_transition.print(); 3340 3341 // It is not yet to safe to tell the concurrent mark to 3342 // start as we have some optional output below. We don't want the 3343 // output from the concurrent mark thread interfering with this 3344 // logging output either. 3345 3346 _hrm.verify_optional(); 3347 _verifier->verify_region_sets_optional(); 3348 3349 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3350 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3351 3352 print_heap_after_gc(); 3353 print_heap_regions(); 3354 trace_heap_after_gc(_gc_tracer_stw); 3355 3356 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3357 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3358 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3359 // before any GC notifications are raised. 3360 g1mm()->update_sizes(); 3361 3362 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3363 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3364 _gc_timer_stw->register_gc_end(); 3365 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3366 } 3367 // It should now be safe to tell the concurrent mark thread to start 3368 // without its logging output interfering with the logging output 3369 // that came from the pause. 3370 3371 if (should_start_conc_mark) { 3372 // CAUTION: after the doConcurrentMark() call below, 3373 // the concurrent marking thread(s) could be running 3374 // concurrently with us. Make sure that anything after 3375 // this point does not assume that we are the only GC thread 3376 // running. Note: of course, the actual marking work will 3377 // not start until the safepoint itself is released in 3378 // SuspendibleThreadSet::desynchronize(). 3379 doConcurrentMark(); 3380 } 3381 3382 return true; 3383 } 3384 3385 void G1CollectedHeap::remove_self_forwarding_pointers() { 3386 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3387 workers()->run_task(&rsfp_task); 3388 } 3389 3390 void G1CollectedHeap::restore_after_evac_failure() { 3391 double remove_self_forwards_start = os::elapsedTime(); 3392 3393 remove_self_forwarding_pointers(); 3394 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3395 _preserved_marks_set.restore(&task_executor); 3396 3397 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3398 } 3399 3400 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3401 if (!_evacuation_failed) { 3402 _evacuation_failed = true; 3403 } 3404 3405 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3406 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3407 } 3408 3409 bool G1ParEvacuateFollowersClosure::offer_termination() { 3410 G1ParScanThreadState* const pss = par_scan_state(); 3411 start_term_time(); 3412 const bool res = terminator()->offer_termination(); 3413 end_term_time(); 3414 return res; 3415 } 3416 3417 void G1ParEvacuateFollowersClosure::do_void() { 3418 G1ParScanThreadState* const pss = par_scan_state(); 3419 pss->trim_queue(); 3420 do { 3421 pss->steal_and_trim_queue(queues()); 3422 } while (!offer_termination()); 3423 } 3424 3425 class G1ParTask : public AbstractGangTask { 3426 protected: 3427 G1CollectedHeap* _g1h; 3428 G1ParScanThreadStateSet* _pss; 3429 RefToScanQueueSet* _queues; 3430 G1RootProcessor* _root_processor; 3431 ParallelTaskTerminator _terminator; 3432 uint _n_workers; 3433 3434 public: 3435 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3436 : AbstractGangTask("G1 collection"), 3437 _g1h(g1h), 3438 _pss(per_thread_states), 3439 _queues(task_queues), 3440 _root_processor(root_processor), 3441 _terminator(n_workers, _queues), 3442 _n_workers(n_workers) 3443 {} 3444 3445 void work(uint worker_id) { 3446 if (worker_id >= _n_workers) return; // no work needed this round 3447 3448 double start_sec = os::elapsedTime(); 3449 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3450 3451 { 3452 ResourceMark rm; 3453 HandleMark hm; 3454 3455 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3456 3457 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3458 pss->set_ref_processor(rp); 3459 3460 double start_strong_roots_sec = os::elapsedTime(); 3461 3462 _root_processor->evacuate_roots(pss->closures(), worker_id); 3463 3464 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss); 3465 3466 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3467 // treating the nmethods visited to act as roots for concurrent marking. 3468 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3469 // objects copied by the current evacuation. 3470 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl, 3471 pss->closures()->weak_codeblobs(), 3472 worker_id); 3473 3474 _pss->add_cards_scanned(worker_id, cards_scanned); 3475 3476 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3477 3478 double term_sec = 0.0; 3479 size_t evac_term_attempts = 0; 3480 { 3481 double start = os::elapsedTime(); 3482 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3483 evac.do_void(); 3484 3485 evac_term_attempts = evac.term_attempts(); 3486 term_sec = evac.term_time(); 3487 double elapsed_sec = os::elapsedTime() - start; 3488 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3489 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3490 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3491 } 3492 3493 assert(pss->queue_is_empty(), "should be empty"); 3494 3495 if (log_is_enabled(Debug, gc, task, stats)) { 3496 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3497 size_t lab_waste; 3498 size_t lab_undo_waste; 3499 pss->waste(lab_waste, lab_undo_waste); 3500 _g1h->print_termination_stats(worker_id, 3501 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3502 strong_roots_sec * 1000.0, /* strong roots time */ 3503 term_sec * 1000.0, /* evac term time */ 3504 evac_term_attempts, /* evac term attempts */ 3505 lab_waste, /* alloc buffer waste */ 3506 lab_undo_waste /* undo waste */ 3507 ); 3508 } 3509 3510 // Close the inner scope so that the ResourceMark and HandleMark 3511 // destructors are executed here and are included as part of the 3512 // "GC Worker Time". 3513 } 3514 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3515 } 3516 }; 3517 3518 void G1CollectedHeap::print_termination_stats_hdr() { 3519 log_debug(gc, task, stats)("GC Termination Stats"); 3520 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3521 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3522 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3523 } 3524 3525 void G1CollectedHeap::print_termination_stats(uint worker_id, 3526 double elapsed_ms, 3527 double strong_roots_ms, 3528 double term_ms, 3529 size_t term_attempts, 3530 size_t alloc_buffer_waste, 3531 size_t undo_waste) const { 3532 log_debug(gc, task, stats) 3533 ("%3d %9.2f %9.2f %6.2f " 3534 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3535 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3536 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3537 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3538 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3539 alloc_buffer_waste * HeapWordSize / K, 3540 undo_waste * HeapWordSize / K); 3541 } 3542 3543 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3544 private: 3545 BoolObjectClosure* _is_alive; 3546 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3547 3548 int _initial_string_table_size; 3549 int _initial_symbol_table_size; 3550 3551 bool _process_strings; 3552 int _strings_processed; 3553 int _strings_removed; 3554 3555 bool _process_symbols; 3556 int _symbols_processed; 3557 int _symbols_removed; 3558 3559 bool _process_string_dedup; 3560 3561 public: 3562 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3563 AbstractGangTask("String/Symbol Unlinking"), 3564 _is_alive(is_alive), 3565 _dedup_closure(is_alive, NULL, false), 3566 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3567 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3568 _process_string_dedup(process_string_dedup) { 3569 3570 _initial_string_table_size = StringTable::the_table()->table_size(); 3571 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3572 if (process_strings) { 3573 StringTable::clear_parallel_claimed_index(); 3574 } 3575 if (process_symbols) { 3576 SymbolTable::clear_parallel_claimed_index(); 3577 } 3578 } 3579 3580 ~G1StringAndSymbolCleaningTask() { 3581 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3582 "claim value %d after unlink less than initial string table size %d", 3583 StringTable::parallel_claimed_index(), _initial_string_table_size); 3584 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3585 "claim value %d after unlink less than initial symbol table size %d", 3586 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3587 3588 log_info(gc, stringtable)( 3589 "Cleaned string and symbol table, " 3590 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3591 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3592 strings_processed(), strings_removed(), 3593 symbols_processed(), symbols_removed()); 3594 } 3595 3596 void work(uint worker_id) { 3597 int strings_processed = 0; 3598 int strings_removed = 0; 3599 int symbols_processed = 0; 3600 int symbols_removed = 0; 3601 if (_process_strings) { 3602 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3603 Atomic::add(strings_processed, &_strings_processed); 3604 Atomic::add(strings_removed, &_strings_removed); 3605 } 3606 if (_process_symbols) { 3607 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3608 Atomic::add(symbols_processed, &_symbols_processed); 3609 Atomic::add(symbols_removed, &_symbols_removed); 3610 } 3611 if (_process_string_dedup) { 3612 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3613 } 3614 } 3615 3616 size_t strings_processed() const { return (size_t)_strings_processed; } 3617 size_t strings_removed() const { return (size_t)_strings_removed; } 3618 3619 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3620 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3621 }; 3622 3623 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3624 private: 3625 static Monitor* _lock; 3626 3627 BoolObjectClosure* const _is_alive; 3628 const bool _unloading_occurred; 3629 const uint _num_workers; 3630 3631 // Variables used to claim nmethods. 3632 CompiledMethod* _first_nmethod; 3633 volatile CompiledMethod* _claimed_nmethod; 3634 3635 // The list of nmethods that need to be processed by the second pass. 3636 volatile CompiledMethod* _postponed_list; 3637 volatile uint _num_entered_barrier; 3638 3639 public: 3640 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3641 _is_alive(is_alive), 3642 _unloading_occurred(unloading_occurred), 3643 _num_workers(num_workers), 3644 _first_nmethod(NULL), 3645 _claimed_nmethod(NULL), 3646 _postponed_list(NULL), 3647 _num_entered_barrier(0) 3648 { 3649 CompiledMethod::increase_unloading_clock(); 3650 // Get first alive nmethod 3651 CompiledMethodIterator iter = CompiledMethodIterator(); 3652 if(iter.next_alive()) { 3653 _first_nmethod = iter.method(); 3654 } 3655 _claimed_nmethod = (volatile CompiledMethod*)_first_nmethod; 3656 } 3657 3658 ~G1CodeCacheUnloadingTask() { 3659 CodeCache::verify_clean_inline_caches(); 3660 3661 CodeCache::set_needs_cache_clean(false); 3662 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3663 3664 CodeCache::verify_icholder_relocations(); 3665 } 3666 3667 private: 3668 void add_to_postponed_list(CompiledMethod* nm) { 3669 CompiledMethod* old; 3670 do { 3671 old = (CompiledMethod*)_postponed_list; 3672 nm->set_unloading_next(old); 3673 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 3674 } 3675 3676 void clean_nmethod(CompiledMethod* nm) { 3677 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3678 3679 if (postponed) { 3680 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3681 add_to_postponed_list(nm); 3682 } 3683 3684 // Mark that this thread has been cleaned/unloaded. 3685 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3686 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3687 } 3688 3689 void clean_nmethod_postponed(CompiledMethod* nm) { 3690 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3691 } 3692 3693 static const int MaxClaimNmethods = 16; 3694 3695 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3696 CompiledMethod* first; 3697 CompiledMethodIterator last; 3698 3699 do { 3700 *num_claimed_nmethods = 0; 3701 3702 first = (CompiledMethod*)_claimed_nmethod; 3703 last = CompiledMethodIterator(first); 3704 3705 if (first != NULL) { 3706 3707 for (int i = 0; i < MaxClaimNmethods; i++) { 3708 if (!last.next_alive()) { 3709 break; 3710 } 3711 claimed_nmethods[i] = last.method(); 3712 (*num_claimed_nmethods)++; 3713 } 3714 } 3715 3716 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 3717 } 3718 3719 CompiledMethod* claim_postponed_nmethod() { 3720 CompiledMethod* claim; 3721 CompiledMethod* next; 3722 3723 do { 3724 claim = (CompiledMethod*)_postponed_list; 3725 if (claim == NULL) { 3726 return NULL; 3727 } 3728 3729 next = claim->unloading_next(); 3730 3731 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 3732 3733 return claim; 3734 } 3735 3736 public: 3737 // Mark that we're done with the first pass of nmethod cleaning. 3738 void barrier_mark(uint worker_id) { 3739 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3740 _num_entered_barrier++; 3741 if (_num_entered_barrier == _num_workers) { 3742 ml.notify_all(); 3743 } 3744 } 3745 3746 // See if we have to wait for the other workers to 3747 // finish their first-pass nmethod cleaning work. 3748 void barrier_wait(uint worker_id) { 3749 if (_num_entered_barrier < _num_workers) { 3750 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3751 while (_num_entered_barrier < _num_workers) { 3752 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3753 } 3754 } 3755 } 3756 3757 // Cleaning and unloading of nmethods. Some work has to be postponed 3758 // to the second pass, when we know which nmethods survive. 3759 void work_first_pass(uint worker_id) { 3760 // The first nmethods is claimed by the first worker. 3761 if (worker_id == 0 && _first_nmethod != NULL) { 3762 clean_nmethod(_first_nmethod); 3763 _first_nmethod = NULL; 3764 } 3765 3766 int num_claimed_nmethods; 3767 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3768 3769 while (true) { 3770 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3771 3772 if (num_claimed_nmethods == 0) { 3773 break; 3774 } 3775 3776 for (int i = 0; i < num_claimed_nmethods; i++) { 3777 clean_nmethod(claimed_nmethods[i]); 3778 } 3779 } 3780 } 3781 3782 void work_second_pass(uint worker_id) { 3783 CompiledMethod* nm; 3784 // Take care of postponed nmethods. 3785 while ((nm = claim_postponed_nmethod()) != NULL) { 3786 clean_nmethod_postponed(nm); 3787 } 3788 } 3789 }; 3790 3791 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3792 3793 class G1KlassCleaningTask : public StackObj { 3794 BoolObjectClosure* _is_alive; 3795 volatile jint _clean_klass_tree_claimed; 3796 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3797 3798 public: 3799 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3800 _is_alive(is_alive), 3801 _clean_klass_tree_claimed(0), 3802 _klass_iterator() { 3803 } 3804 3805 private: 3806 bool claim_clean_klass_tree_task() { 3807 if (_clean_klass_tree_claimed) { 3808 return false; 3809 } 3810 3811 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 3812 } 3813 3814 InstanceKlass* claim_next_klass() { 3815 Klass* klass; 3816 do { 3817 klass =_klass_iterator.next_klass(); 3818 } while (klass != NULL && !klass->is_instance_klass()); 3819 3820 // this can be null so don't call InstanceKlass::cast 3821 return static_cast<InstanceKlass*>(klass); 3822 } 3823 3824 public: 3825 3826 void clean_klass(InstanceKlass* ik) { 3827 ik->clean_weak_instanceklass_links(_is_alive); 3828 } 3829 3830 void work() { 3831 ResourceMark rm; 3832 3833 // One worker will clean the subklass/sibling klass tree. 3834 if (claim_clean_klass_tree_task()) { 3835 Klass::clean_subklass_tree(_is_alive); 3836 } 3837 3838 // All workers will help cleaning the classes, 3839 InstanceKlass* klass; 3840 while ((klass = claim_next_klass()) != NULL) { 3841 clean_klass(klass); 3842 } 3843 } 3844 }; 3845 3846 // To minimize the remark pause times, the tasks below are done in parallel. 3847 class G1ParallelCleaningTask : public AbstractGangTask { 3848 private: 3849 G1StringAndSymbolCleaningTask _string_symbol_task; 3850 G1CodeCacheUnloadingTask _code_cache_task; 3851 G1KlassCleaningTask _klass_cleaning_task; 3852 3853 public: 3854 // The constructor is run in the VMThread. 3855 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3856 AbstractGangTask("Parallel Cleaning"), 3857 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3858 _code_cache_task(num_workers, is_alive, unloading_occurred), 3859 _klass_cleaning_task(is_alive) { 3860 } 3861 3862 // The parallel work done by all worker threads. 3863 void work(uint worker_id) { 3864 // Do first pass of code cache cleaning. 3865 _code_cache_task.work_first_pass(worker_id); 3866 3867 // Let the threads mark that the first pass is done. 3868 _code_cache_task.barrier_mark(worker_id); 3869 3870 // Clean the Strings and Symbols. 3871 _string_symbol_task.work(worker_id); 3872 3873 // Wait for all workers to finish the first code cache cleaning pass. 3874 _code_cache_task.barrier_wait(worker_id); 3875 3876 // Do the second code cache cleaning work, which realize on 3877 // the liveness information gathered during the first pass. 3878 _code_cache_task.work_second_pass(worker_id); 3879 3880 // Clean all klasses that were not unloaded. 3881 _klass_cleaning_task.work(); 3882 } 3883 }; 3884 3885 3886 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3887 bool class_unloading_occurred) { 3888 uint n_workers = workers()->active_workers(); 3889 3890 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3891 workers()->run_task(&g1_unlink_task); 3892 } 3893 3894 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3895 bool process_strings, 3896 bool process_symbols, 3897 bool process_string_dedup) { 3898 if (!process_strings && !process_symbols && !process_string_dedup) { 3899 // Nothing to clean. 3900 return; 3901 } 3902 3903 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3904 workers()->run_task(&g1_unlink_task); 3905 3906 } 3907 3908 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3909 private: 3910 DirtyCardQueueSet* _queue; 3911 G1CollectedHeap* _g1h; 3912 public: 3913 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3914 _queue(queue), _g1h(g1h) { } 3915 3916 virtual void work(uint worker_id) { 3917 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3918 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3919 3920 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3921 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3922 3923 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3924 } 3925 }; 3926 3927 void G1CollectedHeap::redirty_logged_cards() { 3928 double redirty_logged_cards_start = os::elapsedTime(); 3929 3930 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3931 dirty_card_queue_set().reset_for_par_iteration(); 3932 workers()->run_task(&redirty_task); 3933 3934 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 3935 dcq.merge_bufferlists(&dirty_card_queue_set()); 3936 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3937 3938 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3939 } 3940 3941 // Weak Reference Processing support 3942 3943 // An always "is_alive" closure that is used to preserve referents. 3944 // If the object is non-null then it's alive. Used in the preservation 3945 // of referent objects that are pointed to by reference objects 3946 // discovered by the CM ref processor. 3947 class G1AlwaysAliveClosure: public BoolObjectClosure { 3948 G1CollectedHeap* _g1; 3949 public: 3950 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3951 bool do_object_b(oop p) { 3952 if (p != NULL) { 3953 return true; 3954 } 3955 return false; 3956 } 3957 }; 3958 3959 bool G1STWIsAliveClosure::do_object_b(oop p) { 3960 // An object is reachable if it is outside the collection set, 3961 // or is inside and copied. 3962 return !_g1->is_in_cset(p) || p->is_forwarded(); 3963 } 3964 3965 // Non Copying Keep Alive closure 3966 class G1KeepAliveClosure: public OopClosure { 3967 G1CollectedHeap* _g1; 3968 public: 3969 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3970 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3971 void do_oop(oop* p) { 3972 oop obj = *p; 3973 assert(obj != NULL, "the caller should have filtered out NULL values"); 3974 3975 const InCSetState cset_state = _g1->in_cset_state(obj); 3976 if (!cset_state.is_in_cset_or_humongous()) { 3977 return; 3978 } 3979 if (cset_state.is_in_cset()) { 3980 assert( obj->is_forwarded(), "invariant" ); 3981 *p = obj->forwardee(); 3982 } else { 3983 assert(!obj->is_forwarded(), "invariant" ); 3984 assert(cset_state.is_humongous(), 3985 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3986 _g1->set_humongous_is_live(obj); 3987 } 3988 } 3989 }; 3990 3991 // Copying Keep Alive closure - can be called from both 3992 // serial and parallel code as long as different worker 3993 // threads utilize different G1ParScanThreadState instances 3994 // and different queues. 3995 3996 class G1CopyingKeepAliveClosure: public OopClosure { 3997 G1CollectedHeap* _g1h; 3998 OopClosure* _copy_non_heap_obj_cl; 3999 G1ParScanThreadState* _par_scan_state; 4000 4001 public: 4002 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4003 OopClosure* non_heap_obj_cl, 4004 G1ParScanThreadState* pss): 4005 _g1h(g1h), 4006 _copy_non_heap_obj_cl(non_heap_obj_cl), 4007 _par_scan_state(pss) 4008 {} 4009 4010 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4011 virtual void do_oop( oop* p) { do_oop_work(p); } 4012 4013 template <class T> void do_oop_work(T* p) { 4014 oop obj = oopDesc::load_decode_heap_oop(p); 4015 4016 if (_g1h->is_in_cset_or_humongous(obj)) { 4017 // If the referent object has been forwarded (either copied 4018 // to a new location or to itself in the event of an 4019 // evacuation failure) then we need to update the reference 4020 // field and, if both reference and referent are in the G1 4021 // heap, update the RSet for the referent. 4022 // 4023 // If the referent has not been forwarded then we have to keep 4024 // it alive by policy. Therefore we have copy the referent. 4025 // 4026 // If the reference field is in the G1 heap then we can push 4027 // on the PSS queue. When the queue is drained (after each 4028 // phase of reference processing) the object and it's followers 4029 // will be copied, the reference field set to point to the 4030 // new location, and the RSet updated. Otherwise we need to 4031 // use the the non-heap or metadata closures directly to copy 4032 // the referent object and update the pointer, while avoiding 4033 // updating the RSet. 4034 4035 if (_g1h->is_in_g1_reserved(p)) { 4036 _par_scan_state->push_on_queue(p); 4037 } else { 4038 assert(!Metaspace::contains((const void*)p), 4039 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4040 _copy_non_heap_obj_cl->do_oop(p); 4041 } 4042 } 4043 } 4044 }; 4045 4046 // Serial drain queue closure. Called as the 'complete_gc' 4047 // closure for each discovered list in some of the 4048 // reference processing phases. 4049 4050 class G1STWDrainQueueClosure: public VoidClosure { 4051 protected: 4052 G1CollectedHeap* _g1h; 4053 G1ParScanThreadState* _par_scan_state; 4054 4055 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4056 4057 public: 4058 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4059 _g1h(g1h), 4060 _par_scan_state(pss) 4061 { } 4062 4063 void do_void() { 4064 G1ParScanThreadState* const pss = par_scan_state(); 4065 pss->trim_queue(); 4066 } 4067 }; 4068 4069 // Parallel Reference Processing closures 4070 4071 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4072 // processing during G1 evacuation pauses. 4073 4074 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4075 private: 4076 G1CollectedHeap* _g1h; 4077 G1ParScanThreadStateSet* _pss; 4078 RefToScanQueueSet* _queues; 4079 WorkGang* _workers; 4080 uint _active_workers; 4081 4082 public: 4083 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4084 G1ParScanThreadStateSet* per_thread_states, 4085 WorkGang* workers, 4086 RefToScanQueueSet *task_queues, 4087 uint n_workers) : 4088 _g1h(g1h), 4089 _pss(per_thread_states), 4090 _queues(task_queues), 4091 _workers(workers), 4092 _active_workers(n_workers) 4093 { 4094 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 4095 } 4096 4097 // Executes the given task using concurrent marking worker threads. 4098 virtual void execute(ProcessTask& task); 4099 virtual void execute(EnqueueTask& task); 4100 }; 4101 4102 // Gang task for possibly parallel reference processing 4103 4104 class G1STWRefProcTaskProxy: public AbstractGangTask { 4105 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4106 ProcessTask& _proc_task; 4107 G1CollectedHeap* _g1h; 4108 G1ParScanThreadStateSet* _pss; 4109 RefToScanQueueSet* _task_queues; 4110 ParallelTaskTerminator* _terminator; 4111 4112 public: 4113 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4114 G1CollectedHeap* g1h, 4115 G1ParScanThreadStateSet* per_thread_states, 4116 RefToScanQueueSet *task_queues, 4117 ParallelTaskTerminator* terminator) : 4118 AbstractGangTask("Process reference objects in parallel"), 4119 _proc_task(proc_task), 4120 _g1h(g1h), 4121 _pss(per_thread_states), 4122 _task_queues(task_queues), 4123 _terminator(terminator) 4124 {} 4125 4126 virtual void work(uint worker_id) { 4127 // The reference processing task executed by a single worker. 4128 ResourceMark rm; 4129 HandleMark hm; 4130 4131 G1STWIsAliveClosure is_alive(_g1h); 4132 4133 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4134 pss->set_ref_processor(NULL); 4135 4136 // Keep alive closure. 4137 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4138 4139 // Complete GC closure 4140 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4141 4142 // Call the reference processing task's work routine. 4143 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4144 4145 // Note we cannot assert that the refs array is empty here as not all 4146 // of the processing tasks (specifically phase2 - pp2_work) execute 4147 // the complete_gc closure (which ordinarily would drain the queue) so 4148 // the queue may not be empty. 4149 } 4150 }; 4151 4152 // Driver routine for parallel reference processing. 4153 // Creates an instance of the ref processing gang 4154 // task and has the worker threads execute it. 4155 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4156 assert(_workers != NULL, "Need parallel worker threads."); 4157 4158 ParallelTaskTerminator terminator(_active_workers, _queues); 4159 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4160 4161 _workers->run_task(&proc_task_proxy); 4162 } 4163 4164 // Gang task for parallel reference enqueueing. 4165 4166 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4167 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4168 EnqueueTask& _enq_task; 4169 4170 public: 4171 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4172 AbstractGangTask("Enqueue reference objects in parallel"), 4173 _enq_task(enq_task) 4174 { } 4175 4176 virtual void work(uint worker_id) { 4177 _enq_task.work(worker_id); 4178 } 4179 }; 4180 4181 // Driver routine for parallel reference enqueueing. 4182 // Creates an instance of the ref enqueueing gang 4183 // task and has the worker threads execute it. 4184 4185 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4186 assert(_workers != NULL, "Need parallel worker threads."); 4187 4188 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4189 4190 _workers->run_task(&enq_task_proxy); 4191 } 4192 4193 // End of weak reference support closures 4194 4195 // Abstract task used to preserve (i.e. copy) any referent objects 4196 // that are in the collection set and are pointed to by reference 4197 // objects discovered by the CM ref processor. 4198 4199 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4200 protected: 4201 G1CollectedHeap* _g1h; 4202 G1ParScanThreadStateSet* _pss; 4203 RefToScanQueueSet* _queues; 4204 ParallelTaskTerminator _terminator; 4205 uint _n_workers; 4206 4207 public: 4208 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4209 AbstractGangTask("ParPreserveCMReferents"), 4210 _g1h(g1h), 4211 _pss(per_thread_states), 4212 _queues(task_queues), 4213 _terminator(workers, _queues), 4214 _n_workers(workers) 4215 { 4216 g1h->ref_processor_cm()->set_active_mt_degree(workers); 4217 } 4218 4219 void work(uint worker_id) { 4220 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4221 4222 ResourceMark rm; 4223 HandleMark hm; 4224 4225 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4226 pss->set_ref_processor(NULL); 4227 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4228 4229 // Is alive closure 4230 G1AlwaysAliveClosure always_alive(_g1h); 4231 4232 // Copying keep alive closure. Applied to referent objects that need 4233 // to be copied. 4234 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4235 4236 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4237 4238 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4239 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4240 4241 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4242 // So this must be true - but assert just in case someone decides to 4243 // change the worker ids. 4244 assert(worker_id < limit, "sanity"); 4245 assert(!rp->discovery_is_atomic(), "check this code"); 4246 4247 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4248 for (uint idx = worker_id; idx < limit; idx += stride) { 4249 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4250 4251 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4252 while (iter.has_next()) { 4253 // Since discovery is not atomic for the CM ref processor, we 4254 // can see some null referent objects. 4255 iter.load_ptrs(DEBUG_ONLY(true)); 4256 oop ref = iter.obj(); 4257 4258 // This will filter nulls. 4259 if (iter.is_referent_alive()) { 4260 iter.make_referent_alive(); 4261 } 4262 iter.move_to_next(); 4263 } 4264 } 4265 4266 // Drain the queue - which may cause stealing 4267 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4268 drain_queue.do_void(); 4269 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4270 assert(pss->queue_is_empty(), "should be"); 4271 } 4272 }; 4273 4274 void G1CollectedHeap::process_weak_jni_handles() { 4275 double ref_proc_start = os::elapsedTime(); 4276 4277 G1STWIsAliveClosure is_alive(this); 4278 G1KeepAliveClosure keep_alive(this); 4279 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 4280 4281 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4282 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4283 } 4284 4285 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4286 // Any reference objects, in the collection set, that were 'discovered' 4287 // by the CM ref processor should have already been copied (either by 4288 // applying the external root copy closure to the discovered lists, or 4289 // by following an RSet entry). 4290 // 4291 // But some of the referents, that are in the collection set, that these 4292 // reference objects point to may not have been copied: the STW ref 4293 // processor would have seen that the reference object had already 4294 // been 'discovered' and would have skipped discovering the reference, 4295 // but would not have treated the reference object as a regular oop. 4296 // As a result the copy closure would not have been applied to the 4297 // referent object. 4298 // 4299 // We need to explicitly copy these referent objects - the references 4300 // will be processed at the end of remarking. 4301 // 4302 // We also need to do this copying before we process the reference 4303 // objects discovered by the STW ref processor in case one of these 4304 // referents points to another object which is also referenced by an 4305 // object discovered by the STW ref processor. 4306 double preserve_cm_referents_time = 0.0; 4307 4308 // To avoid spawning task when there is no work to do, check that 4309 // a concurrent cycle is active and that some references have been 4310 // discovered. 4311 if (concurrent_mark()->cmThread()->during_cycle() && 4312 ref_processor_cm()->has_discovered_references()) { 4313 double preserve_cm_referents_start = os::elapsedTime(); 4314 uint no_of_gc_workers = workers()->active_workers(); 4315 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4316 per_thread_states, 4317 no_of_gc_workers, 4318 _task_queues); 4319 workers()->run_task(&keep_cm_referents); 4320 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4321 } 4322 4323 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4324 } 4325 4326 // Weak Reference processing during an evacuation pause (part 1). 4327 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4328 double ref_proc_start = os::elapsedTime(); 4329 4330 ReferenceProcessor* rp = _ref_processor_stw; 4331 assert(rp->discovery_enabled(), "should have been enabled"); 4332 4333 // Closure to test whether a referent is alive. 4334 G1STWIsAliveClosure is_alive(this); 4335 4336 // Even when parallel reference processing is enabled, the processing 4337 // of JNI refs is serial and performed serially by the current thread 4338 // rather than by a worker. The following PSS will be used for processing 4339 // JNI refs. 4340 4341 // Use only a single queue for this PSS. 4342 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4343 pss->set_ref_processor(NULL); 4344 assert(pss->queue_is_empty(), "pre-condition"); 4345 4346 // Keep alive closure. 4347 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4348 4349 // Serial Complete GC closure 4350 G1STWDrainQueueClosure drain_queue(this, pss); 4351 4352 // Setup the soft refs policy... 4353 rp->setup_policy(false); 4354 4355 ReferenceProcessorStats stats; 4356 if (!rp->processing_is_mt()) { 4357 // Serial reference processing... 4358 stats = rp->process_discovered_references(&is_alive, 4359 &keep_alive, 4360 &drain_queue, 4361 NULL, 4362 _gc_timer_stw); 4363 } else { 4364 uint no_of_gc_workers = workers()->active_workers(); 4365 4366 // Parallel reference processing 4367 assert(no_of_gc_workers <= rp->max_num_q(), 4368 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4369 no_of_gc_workers, rp->max_num_q()); 4370 4371 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4372 stats = rp->process_discovered_references(&is_alive, 4373 &keep_alive, 4374 &drain_queue, 4375 &par_task_executor, 4376 _gc_timer_stw); 4377 } 4378 4379 _gc_tracer_stw->report_gc_reference_stats(stats); 4380 4381 // We have completed copying any necessary live referent objects. 4382 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4383 4384 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4385 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4386 } 4387 4388 // Weak Reference processing during an evacuation pause (part 2). 4389 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4390 double ref_enq_start = os::elapsedTime(); 4391 4392 ReferenceProcessor* rp = _ref_processor_stw; 4393 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4394 4395 // Now enqueue any remaining on the discovered lists on to 4396 // the pending list. 4397 if (!rp->processing_is_mt()) { 4398 // Serial reference processing... 4399 rp->enqueue_discovered_references(); 4400 } else { 4401 // Parallel reference enqueueing 4402 4403 uint n_workers = workers()->active_workers(); 4404 4405 assert(n_workers <= rp->max_num_q(), 4406 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4407 n_workers, rp->max_num_q()); 4408 4409 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4410 rp->enqueue_discovered_references(&par_task_executor); 4411 } 4412 4413 rp->verify_no_references_recorded(); 4414 assert(!rp->discovery_enabled(), "should have been disabled"); 4415 4416 // FIXME 4417 // CM's reference processing also cleans up the string and symbol tables. 4418 // Should we do that here also? We could, but it is a serial operation 4419 // and could significantly increase the pause time. 4420 4421 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4422 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4423 } 4424 4425 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4426 double merge_pss_time_start = os::elapsedTime(); 4427 per_thread_states->flush(); 4428 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4429 } 4430 4431 void G1CollectedHeap::pre_evacuate_collection_set() { 4432 _expand_heap_after_alloc_failure = true; 4433 _evacuation_failed = false; 4434 4435 // Disable the hot card cache. 4436 _hot_card_cache->reset_hot_cache_claimed_index(); 4437 _hot_card_cache->set_use_cache(false); 4438 4439 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4440 _preserved_marks_set.assert_empty(); 4441 4442 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4443 4444 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4445 if (collector_state()->during_initial_mark_pause()) { 4446 double start_clear_claimed_marks = os::elapsedTime(); 4447 4448 ClassLoaderDataGraph::clear_claimed_marks(); 4449 4450 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4451 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4452 } 4453 } 4454 4455 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4456 // Should G1EvacuationFailureALot be in effect for this GC? 4457 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4458 4459 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4460 4461 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4462 4463 double start_par_time_sec = os::elapsedTime(); 4464 double end_par_time_sec; 4465 4466 { 4467 const uint n_workers = workers()->active_workers(); 4468 G1RootProcessor root_processor(this, n_workers); 4469 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4470 4471 print_termination_stats_hdr(); 4472 4473 workers()->run_task(&g1_par_task); 4474 end_par_time_sec = os::elapsedTime(); 4475 4476 // Closing the inner scope will execute the destructor 4477 // for the G1RootProcessor object. We record the current 4478 // elapsed time before closing the scope so that time 4479 // taken for the destructor is NOT included in the 4480 // reported parallel time. 4481 } 4482 4483 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4484 phase_times->record_par_time(par_time_ms); 4485 4486 double code_root_fixup_time_ms = 4487 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4488 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4489 } 4490 4491 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4492 // Process any discovered reference objects - we have 4493 // to do this _before_ we retire the GC alloc regions 4494 // as we may have to copy some 'reachable' referent 4495 // objects (and their reachable sub-graphs) that were 4496 // not copied during the pause. 4497 if (g1_policy()->should_process_references()) { 4498 preserve_cm_referents(per_thread_states); 4499 process_discovered_references(per_thread_states); 4500 } else { 4501 ref_processor_stw()->verify_no_references_recorded(); 4502 process_weak_jni_handles(); 4503 } 4504 4505 if (G1StringDedup::is_enabled()) { 4506 double fixup_start = os::elapsedTime(); 4507 4508 G1STWIsAliveClosure is_alive(this); 4509 G1KeepAliveClosure keep_alive(this); 4510 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4511 4512 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4513 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4514 } 4515 4516 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4517 4518 if (evacuation_failed()) { 4519 restore_after_evac_failure(); 4520 4521 // Reset the G1EvacuationFailureALot counters and flags 4522 // Note: the values are reset only when an actual 4523 // evacuation failure occurs. 4524 NOT_PRODUCT(reset_evacuation_should_fail();) 4525 } 4526 4527 _preserved_marks_set.assert_empty(); 4528 4529 // Enqueue any remaining references remaining on the STW 4530 // reference processor's discovered lists. We need to do 4531 // this after the card table is cleaned (and verified) as 4532 // the act of enqueueing entries on to the pending list 4533 // will log these updates (and dirty their associated 4534 // cards). We need these updates logged to update any 4535 // RSets. 4536 if (g1_policy()->should_process_references()) { 4537 enqueue_discovered_references(per_thread_states); 4538 } else { 4539 g1_policy()->phase_times()->record_ref_enq_time(0); 4540 } 4541 4542 _allocator->release_gc_alloc_regions(evacuation_info); 4543 4544 merge_per_thread_state_info(per_thread_states); 4545 4546 // Reset and re-enable the hot card cache. 4547 // Note the counts for the cards in the regions in the 4548 // collection set are reset when the collection set is freed. 4549 _hot_card_cache->reset_hot_cache(); 4550 _hot_card_cache->set_use_cache(true); 4551 4552 purge_code_root_memory(); 4553 4554 redirty_logged_cards(); 4555 #if defined(COMPILER2) || INCLUDE_JVMCI 4556 double start = os::elapsedTime(); 4557 DerivedPointerTable::update_pointers(); 4558 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4559 #endif 4560 g1_policy()->print_age_table(); 4561 } 4562 4563 void G1CollectedHeap::record_obj_copy_mem_stats() { 4564 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4565 4566 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4567 create_g1_evac_summary(&_old_evac_stats)); 4568 } 4569 4570 void G1CollectedHeap::free_region(HeapRegion* hr, 4571 FreeRegionList* free_list, 4572 bool skip_remset, 4573 bool skip_hot_card_cache, 4574 bool locked) { 4575 assert(!hr->is_free(), "the region should not be free"); 4576 assert(!hr->is_empty(), "the region should not be empty"); 4577 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4578 assert(free_list != NULL, "pre-condition"); 4579 4580 if (G1VerifyBitmaps) { 4581 MemRegion mr(hr->bottom(), hr->end()); 4582 concurrent_mark()->clearRangePrevBitmap(mr); 4583 } 4584 4585 // Clear the card counts for this region. 4586 // Note: we only need to do this if the region is not young 4587 // (since we don't refine cards in young regions). 4588 if (!skip_hot_card_cache && !hr->is_young()) { 4589 _hot_card_cache->reset_card_counts(hr); 4590 } 4591 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4592 free_list->add_ordered(hr); 4593 } 4594 4595 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4596 FreeRegionList* free_list, 4597 bool skip_remset) { 4598 assert(hr->is_humongous(), "this is only for humongous regions"); 4599 assert(free_list != NULL, "pre-condition"); 4600 hr->clear_humongous(); 4601 free_region(hr, free_list, skip_remset); 4602 } 4603 4604 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4605 const uint humongous_regions_removed) { 4606 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4607 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4608 _old_set.bulk_remove(old_regions_removed); 4609 _humongous_set.bulk_remove(humongous_regions_removed); 4610 } 4611 4612 } 4613 4614 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4615 assert(list != NULL, "list can't be null"); 4616 if (!list->is_empty()) { 4617 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4618 _hrm.insert_list_into_free_list(list); 4619 } 4620 } 4621 4622 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4623 decrease_used(bytes); 4624 } 4625 4626 class G1ParScrubRemSetTask: public AbstractGangTask { 4627 protected: 4628 G1RemSet* _g1rs; 4629 HeapRegionClaimer _hrclaimer; 4630 4631 public: 4632 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) : 4633 AbstractGangTask("G1 ScrubRS"), 4634 _g1rs(g1_rs), 4635 _hrclaimer(num_workers) { 4636 } 4637 4638 void work(uint worker_id) { 4639 _g1rs->scrub(worker_id, &_hrclaimer); 4640 } 4641 }; 4642 4643 void G1CollectedHeap::scrub_rem_set() { 4644 uint num_workers = workers()->active_workers(); 4645 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers); 4646 workers()->run_task(&g1_par_scrub_rs_task); 4647 } 4648 4649 class G1FreeCollectionSetTask : public AbstractGangTask { 4650 private: 4651 4652 // Closure applied to all regions in the collection set to do work that needs to 4653 // be done serially in a single thread. 4654 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4655 private: 4656 EvacuationInfo* _evacuation_info; 4657 const size_t* _surviving_young_words; 4658 4659 // Bytes used in successfully evacuated regions before the evacuation. 4660 size_t _before_used_bytes; 4661 // Bytes used in unsucessfully evacuated regions before the evacuation 4662 size_t _after_used_bytes; 4663 4664 size_t _bytes_allocated_in_old_since_last_gc; 4665 4666 size_t _failure_used_words; 4667 size_t _failure_waste_words; 4668 4669 FreeRegionList _local_free_list; 4670 public: 4671 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4672 HeapRegionClosure(), 4673 _evacuation_info(evacuation_info), 4674 _surviving_young_words(surviving_young_words), 4675 _before_used_bytes(0), 4676 _after_used_bytes(0), 4677 _bytes_allocated_in_old_since_last_gc(0), 4678 _failure_used_words(0), 4679 _failure_waste_words(0), 4680 _local_free_list("Local Region List for CSet Freeing") { 4681 } 4682 4683 virtual bool doHeapRegion(HeapRegion* r) { 4684 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4685 4686 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4687 g1h->clear_in_cset(r); 4688 4689 if (r->is_young()) { 4690 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4691 "Young index %d is wrong for region %u of type %s with %u young regions", 4692 r->young_index_in_cset(), 4693 r->hrm_index(), 4694 r->get_type_str(), 4695 g1h->collection_set()->young_region_length()); 4696 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4697 r->record_surv_words_in_group(words_survived); 4698 } 4699 4700 if (!r->evacuation_failed()) { 4701 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4702 _before_used_bytes += r->used(); 4703 g1h->free_region(r, 4704 &_local_free_list, 4705 true, /* skip_remset */ 4706 true, /* skip_hot_card_cache */ 4707 true /* locked */); 4708 } else { 4709 r->uninstall_surv_rate_group(); 4710 r->set_young_index_in_cset(-1); 4711 r->set_evacuation_failed(false); 4712 // When moving a young gen region to old gen, we "allocate" that whole region 4713 // there. This is in addition to any already evacuated objects. Notify the 4714 // policy about that. 4715 // Old gen regions do not cause an additional allocation: both the objects 4716 // still in the region and the ones already moved are accounted for elsewhere. 4717 if (r->is_young()) { 4718 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4719 } 4720 // The region is now considered to be old. 4721 r->set_old(); 4722 // Do some allocation statistics accounting. Regions that failed evacuation 4723 // are always made old, so there is no need to update anything in the young 4724 // gen statistics, but we need to update old gen statistics. 4725 size_t used_words = r->marked_bytes() / HeapWordSize; 4726 4727 _failure_used_words += used_words; 4728 _failure_waste_words += HeapRegion::GrainWords - used_words; 4729 4730 g1h->old_set_add(r); 4731 _after_used_bytes += r->used(); 4732 } 4733 return false; 4734 } 4735 4736 void complete_work() { 4737 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4738 4739 _evacuation_info->set_regions_freed(_local_free_list.length()); 4740 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4741 4742 g1h->prepend_to_freelist(&_local_free_list); 4743 g1h->decrement_summary_bytes(_before_used_bytes); 4744 4745 G1Policy* policy = g1h->g1_policy(); 4746 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4747 4748 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4749 } 4750 }; 4751 4752 G1CollectionSet* _collection_set; 4753 G1SerialFreeCollectionSetClosure _cl; 4754 const size_t* _surviving_young_words; 4755 4756 size_t _rs_lengths; 4757 4758 volatile jint _serial_work_claim; 4759 4760 struct WorkItem { 4761 uint region_idx; 4762 bool is_young; 4763 bool evacuation_failed; 4764 4765 WorkItem(HeapRegion* r) { 4766 region_idx = r->hrm_index(); 4767 is_young = r->is_young(); 4768 evacuation_failed = r->evacuation_failed(); 4769 } 4770 }; 4771 4772 volatile size_t _parallel_work_claim; 4773 size_t _num_work_items; 4774 WorkItem* _work_items; 4775 4776 void do_serial_work() { 4777 // Need to grab the lock to be allowed to modify the old region list. 4778 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4779 _collection_set->iterate(&_cl); 4780 } 4781 4782 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4783 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4784 4785 HeapRegion* r = g1h->region_at(region_idx); 4786 assert(!g1h->is_on_master_free_list(r), "sanity"); 4787 4788 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4789 4790 if (!is_young) { 4791 g1h->_hot_card_cache->reset_card_counts(r); 4792 } 4793 4794 if (!evacuation_failed) { 4795 r->rem_set()->clear_locked(); 4796 } 4797 } 4798 4799 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4800 private: 4801 size_t _cur_idx; 4802 WorkItem* _work_items; 4803 public: 4804 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4805 4806 virtual bool doHeapRegion(HeapRegion* r) { 4807 _work_items[_cur_idx++] = WorkItem(r); 4808 return false; 4809 } 4810 }; 4811 4812 void prepare_work() { 4813 G1PrepareFreeCollectionSetClosure cl(_work_items); 4814 _collection_set->iterate(&cl); 4815 } 4816 4817 void complete_work() { 4818 _cl.complete_work(); 4819 4820 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4821 policy->record_max_rs_lengths(_rs_lengths); 4822 policy->cset_regions_freed(); 4823 } 4824 public: 4825 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4826 AbstractGangTask("G1 Free Collection Set"), 4827 _cl(evacuation_info, surviving_young_words), 4828 _collection_set(collection_set), 4829 _surviving_young_words(surviving_young_words), 4830 _serial_work_claim(0), 4831 _rs_lengths(0), 4832 _parallel_work_claim(0), 4833 _num_work_items(collection_set->region_length()), 4834 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4835 prepare_work(); 4836 } 4837 4838 ~G1FreeCollectionSetTask() { 4839 complete_work(); 4840 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4841 } 4842 4843 // Chunk size for work distribution. The chosen value has been determined experimentally 4844 // to be a good tradeoff between overhead and achievable parallelism. 4845 static uint chunk_size() { return 32; } 4846 4847 virtual void work(uint worker_id) { 4848 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4849 4850 // Claim serial work. 4851 if (_serial_work_claim == 0) { 4852 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4853 if (value == 0) { 4854 double serial_time = os::elapsedTime(); 4855 do_serial_work(); 4856 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4857 } 4858 } 4859 4860 // Start parallel work. 4861 double young_time = 0.0; 4862 bool has_young_time = false; 4863 double non_young_time = 0.0; 4864 bool has_non_young_time = false; 4865 4866 while (true) { 4867 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4868 size_t cur = end - chunk_size(); 4869 4870 if (cur >= _num_work_items) { 4871 break; 4872 } 4873 4874 double start_time = os::elapsedTime(); 4875 4876 end = MIN2(end, _num_work_items); 4877 4878 for (; cur < end; cur++) { 4879 bool is_young = _work_items[cur].is_young; 4880 4881 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4882 4883 double end_time = os::elapsedTime(); 4884 double time_taken = end_time - start_time; 4885 if (is_young) { 4886 young_time += time_taken; 4887 has_young_time = true; 4888 } else { 4889 non_young_time += time_taken; 4890 has_non_young_time = true; 4891 } 4892 start_time = end_time; 4893 } 4894 } 4895 4896 if (has_young_time) { 4897 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4898 } 4899 if (has_non_young_time) { 4900 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time); 4901 } 4902 } 4903 }; 4904 4905 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4906 _eden.clear(); 4907 4908 double free_cset_start_time = os::elapsedTime(); 4909 4910 { 4911 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4912 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4913 4914 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4915 4916 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4917 cl.name(), 4918 num_workers, 4919 _collection_set.region_length()); 4920 workers()->run_task(&cl, num_workers); 4921 } 4922 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4923 4924 collection_set->clear(); 4925 } 4926 4927 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4928 private: 4929 FreeRegionList* _free_region_list; 4930 HeapRegionSet* _proxy_set; 4931 uint _humongous_objects_reclaimed; 4932 uint _humongous_regions_reclaimed; 4933 size_t _freed_bytes; 4934 public: 4935 4936 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4937 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4938 } 4939 4940 virtual bool doHeapRegion(HeapRegion* r) { 4941 if (!r->is_starts_humongous()) { 4942 return false; 4943 } 4944 4945 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4946 4947 oop obj = (oop)r->bottom(); 4948 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 4949 4950 // The following checks whether the humongous object is live are sufficient. 4951 // The main additional check (in addition to having a reference from the roots 4952 // or the young gen) is whether the humongous object has a remembered set entry. 4953 // 4954 // A humongous object cannot be live if there is no remembered set for it 4955 // because: 4956 // - there can be no references from within humongous starts regions referencing 4957 // the object because we never allocate other objects into them. 4958 // (I.e. there are no intra-region references that may be missed by the 4959 // remembered set) 4960 // - as soon there is a remembered set entry to the humongous starts region 4961 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4962 // until the end of a concurrent mark. 4963 // 4964 // It is not required to check whether the object has been found dead by marking 4965 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4966 // all objects allocated during that time are considered live. 4967 // SATB marking is even more conservative than the remembered set. 4968 // So if at this point in the collection there is no remembered set entry, 4969 // nobody has a reference to it. 4970 // At the start of collection we flush all refinement logs, and remembered sets 4971 // are completely up-to-date wrt to references to the humongous object. 4972 // 4973 // Other implementation considerations: 4974 // - never consider object arrays at this time because they would pose 4975 // considerable effort for cleaning up the the remembered sets. This is 4976 // required because stale remembered sets might reference locations that 4977 // are currently allocated into. 4978 uint region_idx = r->hrm_index(); 4979 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4980 !r->rem_set()->is_empty()) { 4981 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", 4982 region_idx, 4983 (size_t)obj->size() * HeapWordSize, 4984 p2i(r->bottom()), 4985 r->rem_set()->occupied(), 4986 r->rem_set()->strong_code_roots_list_length(), 4987 next_bitmap->isMarked(r->bottom()), 4988 g1h->is_humongous_reclaim_candidate(region_idx), 4989 obj->is_typeArray() 4990 ); 4991 return false; 4992 } 4993 4994 guarantee(obj->is_typeArray(), 4995 "Only eagerly reclaiming type arrays is supported, but the object " 4996 PTR_FORMAT " is not.", p2i(r->bottom())); 4997 4998 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", 4999 region_idx, 5000 (size_t)obj->size() * HeapWordSize, 5001 p2i(r->bottom()), 5002 r->rem_set()->occupied(), 5003 r->rem_set()->strong_code_roots_list_length(), 5004 next_bitmap->isMarked(r->bottom()), 5005 g1h->is_humongous_reclaim_candidate(region_idx), 5006 obj->is_typeArray() 5007 ); 5008 5009 // Need to clear mark bit of the humongous object if already set. 5010 if (next_bitmap->isMarked(r->bottom())) { 5011 next_bitmap->clear(r->bottom()); 5012 } 5013 _humongous_objects_reclaimed++; 5014 do { 5015 HeapRegion* next = g1h->next_region_in_humongous(r); 5016 _freed_bytes += r->used(); 5017 r->set_containing_set(NULL); 5018 _humongous_regions_reclaimed++; 5019 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ ); 5020 r = next; 5021 } while (r != NULL); 5022 5023 return false; 5024 } 5025 5026 uint humongous_objects_reclaimed() { 5027 return _humongous_objects_reclaimed; 5028 } 5029 5030 uint humongous_regions_reclaimed() { 5031 return _humongous_regions_reclaimed; 5032 } 5033 5034 size_t bytes_freed() const { 5035 return _freed_bytes; 5036 } 5037 }; 5038 5039 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 5040 assert_at_safepoint(true); 5041 5042 if (!G1EagerReclaimHumongousObjects || 5043 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 5044 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5045 return; 5046 } 5047 5048 double start_time = os::elapsedTime(); 5049 5050 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5051 5052 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5053 heap_region_iterate(&cl); 5054 5055 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 5056 5057 G1HRPrinter* hrp = hr_printer(); 5058 if (hrp->is_active()) { 5059 FreeRegionListIterator iter(&local_cleanup_list); 5060 while (iter.more_available()) { 5061 HeapRegion* hr = iter.get_next(); 5062 hrp->cleanup(hr); 5063 } 5064 } 5065 5066 prepend_to_freelist(&local_cleanup_list); 5067 decrement_summary_bytes(cl.bytes_freed()); 5068 5069 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5070 cl.humongous_objects_reclaimed()); 5071 } 5072 5073 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 5074 public: 5075 virtual bool doHeapRegion(HeapRegion* r) { 5076 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 5077 G1CollectedHeap::heap()->clear_in_cset(r); 5078 r->set_young_index_in_cset(-1); 5079 return false; 5080 } 5081 }; 5082 5083 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 5084 G1AbandonCollectionSetClosure cl; 5085 collection_set->iterate(&cl); 5086 5087 collection_set->clear(); 5088 collection_set->stop_incremental_building(); 5089 } 5090 5091 void G1CollectedHeap::set_free_regions_coming() { 5092 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 5093 5094 assert(!free_regions_coming(), "pre-condition"); 5095 _free_regions_coming = true; 5096 } 5097 5098 void G1CollectedHeap::reset_free_regions_coming() { 5099 assert(free_regions_coming(), "pre-condition"); 5100 5101 { 5102 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5103 _free_regions_coming = false; 5104 SecondaryFreeList_lock->notify_all(); 5105 } 5106 5107 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 5108 } 5109 5110 void G1CollectedHeap::wait_while_free_regions_coming() { 5111 // Most of the time we won't have to wait, so let's do a quick test 5112 // first before we take the lock. 5113 if (!free_regions_coming()) { 5114 return; 5115 } 5116 5117 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 5118 5119 { 5120 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5121 while (free_regions_coming()) { 5122 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5123 } 5124 } 5125 5126 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 5127 } 5128 5129 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5130 return _allocator->is_retained_old_region(hr); 5131 } 5132 5133 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5134 _eden.add(hr); 5135 _g1_policy->set_region_eden(hr); 5136 } 5137 5138 #ifdef ASSERT 5139 5140 class NoYoungRegionsClosure: public HeapRegionClosure { 5141 private: 5142 bool _success; 5143 public: 5144 NoYoungRegionsClosure() : _success(true) { } 5145 bool doHeapRegion(HeapRegion* r) { 5146 if (r->is_young()) { 5147 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5148 p2i(r->bottom()), p2i(r->end())); 5149 _success = false; 5150 } 5151 return false; 5152 } 5153 bool success() { return _success; } 5154 }; 5155 5156 bool G1CollectedHeap::check_young_list_empty() { 5157 bool ret = (young_regions_count() == 0); 5158 5159 NoYoungRegionsClosure closure; 5160 heap_region_iterate(&closure); 5161 ret = ret && closure.success(); 5162 5163 return ret; 5164 } 5165 5166 #endif // ASSERT 5167 5168 class TearDownRegionSetsClosure : public HeapRegionClosure { 5169 private: 5170 HeapRegionSet *_old_set; 5171 5172 public: 5173 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5174 5175 bool doHeapRegion(HeapRegion* r) { 5176 if (r->is_old()) { 5177 _old_set->remove(r); 5178 } else if(r->is_young()) { 5179 r->uninstall_surv_rate_group(); 5180 } else { 5181 // We ignore free regions, we'll empty the free list afterwards. 5182 // We ignore humongous regions, we're not tearing down the 5183 // humongous regions set. 5184 assert(r->is_free() || r->is_humongous(), 5185 "it cannot be another type"); 5186 } 5187 return false; 5188 } 5189 5190 ~TearDownRegionSetsClosure() { 5191 assert(_old_set->is_empty(), "post-condition"); 5192 } 5193 }; 5194 5195 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5196 assert_at_safepoint(true /* should_be_vm_thread */); 5197 5198 if (!free_list_only) { 5199 TearDownRegionSetsClosure cl(&_old_set); 5200 heap_region_iterate(&cl); 5201 5202 // Note that emptying the _young_list is postponed and instead done as 5203 // the first step when rebuilding the regions sets again. The reason for 5204 // this is that during a full GC string deduplication needs to know if 5205 // a collected region was young or old when the full GC was initiated. 5206 } 5207 _hrm.remove_all_free_regions(); 5208 } 5209 5210 void G1CollectedHeap::increase_used(size_t bytes) { 5211 _summary_bytes_used += bytes; 5212 } 5213 5214 void G1CollectedHeap::decrease_used(size_t bytes) { 5215 assert(_summary_bytes_used >= bytes, 5216 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5217 _summary_bytes_used, bytes); 5218 _summary_bytes_used -= bytes; 5219 } 5220 5221 void G1CollectedHeap::set_used(size_t bytes) { 5222 _summary_bytes_used = bytes; 5223 } 5224 5225 class RebuildRegionSetsClosure : public HeapRegionClosure { 5226 private: 5227 bool _free_list_only; 5228 HeapRegionSet* _old_set; 5229 HeapRegionManager* _hrm; 5230 size_t _total_used; 5231 5232 public: 5233 RebuildRegionSetsClosure(bool free_list_only, 5234 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5235 _free_list_only(free_list_only), 5236 _old_set(old_set), _hrm(hrm), _total_used(0) { 5237 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5238 if (!free_list_only) { 5239 assert(_old_set->is_empty(), "pre-condition"); 5240 } 5241 } 5242 5243 bool doHeapRegion(HeapRegion* r) { 5244 if (r->is_empty()) { 5245 // Add free regions to the free list 5246 r->set_free(); 5247 r->set_allocation_context(AllocationContext::system()); 5248 _hrm->insert_into_free_list(r); 5249 } else if (!_free_list_only) { 5250 5251 if (r->is_humongous()) { 5252 // We ignore humongous regions. We left the humongous set unchanged. 5253 } else { 5254 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 5255 // We now consider all regions old, so register as such. Leave 5256 // archive regions set that way, however, while still adding 5257 // them to the old set. 5258 if (!r->is_archive()) { 5259 r->set_old(); 5260 } 5261 _old_set->add(r); 5262 } 5263 _total_used += r->used(); 5264 } 5265 5266 return false; 5267 } 5268 5269 size_t total_used() { 5270 return _total_used; 5271 } 5272 }; 5273 5274 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5275 assert_at_safepoint(true /* should_be_vm_thread */); 5276 5277 if (!free_list_only) { 5278 _eden.clear(); 5279 _survivor.clear(); 5280 } 5281 5282 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5283 heap_region_iterate(&cl); 5284 5285 if (!free_list_only) { 5286 set_used(cl.total_used()); 5287 if (_archive_allocator != NULL) { 5288 _archive_allocator->clear_used(); 5289 } 5290 } 5291 assert(used_unlocked() == recalculate_used(), 5292 "inconsistent used_unlocked(), " 5293 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5294 used_unlocked(), recalculate_used()); 5295 } 5296 5297 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 5298 _refine_cte_cl->set_concurrent(concurrent); 5299 } 5300 5301 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5302 HeapRegion* hr = heap_region_containing(p); 5303 return hr->is_in(p); 5304 } 5305 5306 // Methods for the mutator alloc region 5307 5308 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5309 bool force) { 5310 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5311 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 5312 if (force || should_allocate) { 5313 HeapRegion* new_alloc_region = new_region(word_size, 5314 false /* is_old */, 5315 false /* do_expand */); 5316 if (new_alloc_region != NULL) { 5317 set_region_short_lived_locked(new_alloc_region); 5318 _hr_printer.alloc(new_alloc_region, !should_allocate); 5319 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5320 return new_alloc_region; 5321 } 5322 } 5323 return NULL; 5324 } 5325 5326 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5327 size_t allocated_bytes) { 5328 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5329 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5330 5331 collection_set()->add_eden_region(alloc_region); 5332 increase_used(allocated_bytes); 5333 _hr_printer.retire(alloc_region); 5334 // We update the eden sizes here, when the region is retired, 5335 // instead of when it's allocated, since this is the point that its 5336 // used space has been recored in _summary_bytes_used. 5337 g1mm()->update_eden_size(); 5338 } 5339 5340 // Methods for the GC alloc regions 5341 5342 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 5343 if (dest.is_old()) { 5344 return true; 5345 } else { 5346 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 5347 } 5348 } 5349 5350 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 5351 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5352 5353 if (!has_more_regions(dest)) { 5354 return NULL; 5355 } 5356 5357 const bool is_survivor = dest.is_young(); 5358 5359 HeapRegion* new_alloc_region = new_region(word_size, 5360 !is_survivor, 5361 true /* do_expand */); 5362 if (new_alloc_region != NULL) { 5363 // We really only need to do this for old regions given that we 5364 // should never scan survivors. But it doesn't hurt to do it 5365 // for survivors too. 5366 new_alloc_region->record_timestamp(); 5367 if (is_survivor) { 5368 new_alloc_region->set_survivor(); 5369 _survivor.add(new_alloc_region); 5370 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5371 } else { 5372 new_alloc_region->set_old(); 5373 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5374 } 5375 _hr_printer.alloc(new_alloc_region); 5376 bool during_im = collector_state()->during_initial_mark_pause(); 5377 new_alloc_region->note_start_of_copying(during_im); 5378 return new_alloc_region; 5379 } 5380 return NULL; 5381 } 5382 5383 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5384 size_t allocated_bytes, 5385 InCSetState dest) { 5386 bool during_im = collector_state()->during_initial_mark_pause(); 5387 alloc_region->note_end_of_copying(during_im); 5388 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5389 if (dest.is_old()) { 5390 _old_set.add(alloc_region); 5391 } 5392 _hr_printer.retire(alloc_region); 5393 } 5394 5395 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5396 bool expanded = false; 5397 uint index = _hrm.find_highest_free(&expanded); 5398 5399 if (index != G1_NO_HRM_INDEX) { 5400 if (expanded) { 5401 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5402 HeapRegion::GrainWords * HeapWordSize); 5403 } 5404 _hrm.allocate_free_regions_starting_at(index, 1); 5405 return region_at(index); 5406 } 5407 return NULL; 5408 } 5409 5410 // Optimized nmethod scanning 5411 5412 class RegisterNMethodOopClosure: public OopClosure { 5413 G1CollectedHeap* _g1h; 5414 nmethod* _nm; 5415 5416 template <class T> void do_oop_work(T* p) { 5417 T heap_oop = oopDesc::load_heap_oop(p); 5418 if (!oopDesc::is_null(heap_oop)) { 5419 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5420 HeapRegion* hr = _g1h->heap_region_containing(obj); 5421 assert(!hr->is_continues_humongous(), 5422 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5423 " starting at " HR_FORMAT, 5424 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5425 5426 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5427 hr->add_strong_code_root_locked(_nm); 5428 } 5429 } 5430 5431 public: 5432 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5433 _g1h(g1h), _nm(nm) {} 5434 5435 void do_oop(oop* p) { do_oop_work(p); } 5436 void do_oop(narrowOop* p) { do_oop_work(p); } 5437 }; 5438 5439 class UnregisterNMethodOopClosure: public OopClosure { 5440 G1CollectedHeap* _g1h; 5441 nmethod* _nm; 5442 5443 template <class T> void do_oop_work(T* p) { 5444 T heap_oop = oopDesc::load_heap_oop(p); 5445 if (!oopDesc::is_null(heap_oop)) { 5446 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5447 HeapRegion* hr = _g1h->heap_region_containing(obj); 5448 assert(!hr->is_continues_humongous(), 5449 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5450 " starting at " HR_FORMAT, 5451 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5452 5453 hr->remove_strong_code_root(_nm); 5454 } 5455 } 5456 5457 public: 5458 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5459 _g1h(g1h), _nm(nm) {} 5460 5461 void do_oop(oop* p) { do_oop_work(p); } 5462 void do_oop(narrowOop* p) { do_oop_work(p); } 5463 }; 5464 5465 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5466 CollectedHeap::register_nmethod(nm); 5467 5468 guarantee(nm != NULL, "sanity"); 5469 RegisterNMethodOopClosure reg_cl(this, nm); 5470 nm->oops_do(®_cl); 5471 } 5472 5473 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5474 CollectedHeap::unregister_nmethod(nm); 5475 5476 guarantee(nm != NULL, "sanity"); 5477 UnregisterNMethodOopClosure reg_cl(this, nm); 5478 nm->oops_do(®_cl, true); 5479 } 5480 5481 void G1CollectedHeap::purge_code_root_memory() { 5482 double purge_start = os::elapsedTime(); 5483 G1CodeRootSet::purge(); 5484 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5485 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5486 } 5487 5488 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5489 G1CollectedHeap* _g1h; 5490 5491 public: 5492 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5493 _g1h(g1h) {} 5494 5495 void do_code_blob(CodeBlob* cb) { 5496 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5497 if (nm == NULL) { 5498 return; 5499 } 5500 5501 if (ScavengeRootsInCode) { 5502 _g1h->register_nmethod(nm); 5503 } 5504 } 5505 }; 5506 5507 void G1CollectedHeap::rebuild_strong_code_roots() { 5508 RebuildStrongCodeRootClosure blob_cl(this); 5509 CodeCache::blobs_do(&blob_cl); 5510 }