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