1 /* 2 * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/metadataOnStackMark.hpp" 27 #include "classfile/stringTable.hpp" 28 #include "classfile/symbolTable.hpp" 29 #include "code/codeCache.hpp" 30 #include "code/icBuffer.hpp" 31 #include "gc/g1/bufferingOopClosure.hpp" 32 #include "gc/g1/concurrentG1Refine.hpp" 33 #include "gc/g1/concurrentG1RefineThread.hpp" 34 #include "gc/g1/concurrentMarkThread.inline.hpp" 35 #include "gc/g1/g1Allocator.inline.hpp" 36 #include "gc/g1/g1CollectedHeap.inline.hpp" 37 #include "gc/g1/g1CollectionSet.hpp" 38 #include "gc/g1/g1CollectorPolicy.hpp" 39 #include "gc/g1/g1CollectorState.hpp" 40 #include "gc/g1/g1EvacStats.inline.hpp" 41 #include "gc/g1/g1GCPhaseTimes.hpp" 42 #include "gc/g1/g1HeapSizingPolicy.hpp" 43 #include "gc/g1/g1HeapTransition.hpp" 44 #include "gc/g1/g1HeapVerifier.hpp" 45 #include "gc/g1/g1HotCardCache.hpp" 46 #include "gc/g1/g1MarkSweep.hpp" 47 #include "gc/g1/g1OopClosures.inline.hpp" 48 #include "gc/g1/g1ParScanThreadState.inline.hpp" 49 #include "gc/g1/g1Policy.hpp" 50 #include "gc/g1/g1RegionToSpaceMapper.hpp" 51 #include "gc/g1/g1RemSet.inline.hpp" 52 #include "gc/g1/g1RootClosures.hpp" 53 #include "gc/g1/g1RootProcessor.hpp" 54 #include "gc/g1/g1StringDedup.hpp" 55 #include "gc/g1/g1YCTypes.hpp" 56 #include "gc/g1/heapRegion.inline.hpp" 57 #include "gc/g1/heapRegionRemSet.hpp" 58 #include "gc/g1/heapRegionSet.inline.hpp" 59 #include "gc/g1/suspendibleThreadSet.hpp" 60 #include "gc/g1/vm_operations_g1.hpp" 61 #include "gc/shared/gcHeapSummary.hpp" 62 #include "gc/shared/gcId.hpp" 63 #include "gc/shared/gcLocker.inline.hpp" 64 #include "gc/shared/gcTimer.hpp" 65 #include "gc/shared/gcTrace.hpp" 66 #include "gc/shared/gcTraceTime.inline.hpp" 67 #include "gc/shared/generationSpec.hpp" 68 #include "gc/shared/isGCActiveMark.hpp" 69 #include "gc/shared/preservedMarks.inline.hpp" 70 #include "gc/shared/referenceProcessor.inline.hpp" 71 #include "gc/shared/taskqueue.inline.hpp" 72 #include "logging/log.hpp" 73 #include "memory/allocation.hpp" 74 #include "memory/iterator.hpp" 75 #include "memory/resourceArea.hpp" 76 #include "oops/oop.inline.hpp" 77 #include "runtime/atomic.inline.hpp" 78 #include "runtime/init.hpp" 79 #include "runtime/orderAccess.inline.hpp" 80 #include "runtime/vmThread.hpp" 81 #include "utilities/globalDefinitions.hpp" 82 #include "utilities/stack.inline.hpp" 83 84 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 85 86 // INVARIANTS/NOTES 87 // 88 // All allocation activity covered by the G1CollectedHeap interface is 89 // serialized by acquiring the HeapLock. This happens in mem_allocate 90 // and allocate_new_tlab, which are the "entry" points to the 91 // allocation code from the rest of the JVM. (Note that this does not 92 // apply to TLAB allocation, which is not part of this interface: it 93 // is done by clients of this interface.) 94 95 // Local to this file. 96 97 class RefineCardTableEntryClosure: public CardTableEntryClosure { 98 bool _concurrent; 99 public: 100 RefineCardTableEntryClosure() : _concurrent(true) { } 101 102 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 103 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, NULL); 104 // This path is executed by the concurrent refine or mutator threads, 105 // concurrently, and so we do not care if card_ptr contains references 106 // that point into the collection set. 107 assert(!oops_into_cset, "should be"); 108 109 if (_concurrent && SuspendibleThreadSet::should_yield()) { 110 // Caller will actually yield. 111 return false; 112 } 113 // Otherwise, we finished successfully; return true. 114 return true; 115 } 116 117 void set_concurrent(bool b) { _concurrent = b; } 118 }; 119 120 121 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 122 private: 123 size_t _num_dirtied; 124 G1CollectedHeap* _g1h; 125 G1SATBCardTableLoggingModRefBS* _g1_bs; 126 127 HeapRegion* region_for_card(jbyte* card_ptr) const { 128 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 129 } 130 131 bool will_become_free(HeapRegion* hr) const { 132 // A region will be freed by free_collection_set if the region is in the 133 // collection set and has not had an evacuation failure. 134 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 135 } 136 137 public: 138 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 139 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 140 141 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 142 HeapRegion* hr = region_for_card(card_ptr); 143 144 // Should only dirty cards in regions that won't be freed. 145 if (!will_become_free(hr)) { 146 *card_ptr = CardTableModRefBS::dirty_card_val(); 147 _num_dirtied++; 148 } 149 150 return true; 151 } 152 153 size_t num_dirtied() const { return _num_dirtied; } 154 }; 155 156 157 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 158 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 159 } 160 161 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 162 // The from card cache is not the memory that is actually committed. So we cannot 163 // take advantage of the zero_filled parameter. 164 reset_from_card_cache(start_idx, num_regions); 165 } 166 167 // Returns true if the reference points to an object that 168 // can move in an incremental collection. 169 bool G1CollectedHeap::is_scavengable(const void* p) { 170 HeapRegion* hr = heap_region_containing(p); 171 return !hr->is_pinned(); 172 } 173 174 // Private methods. 175 176 HeapRegion* 177 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 178 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 179 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 180 if (!_secondary_free_list.is_empty()) { 181 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 182 "secondary_free_list has %u entries", 183 _secondary_free_list.length()); 184 // It looks as if there are free regions available on the 185 // secondary_free_list. Let's move them to the free_list and try 186 // again to allocate from it. 187 append_secondary_free_list(); 188 189 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 190 "empty we should have moved at least one entry to the free_list"); 191 HeapRegion* res = _hrm.allocate_free_region(is_old); 192 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 193 "allocated " HR_FORMAT " from secondary_free_list", 194 HR_FORMAT_PARAMS(res)); 195 return res; 196 } 197 198 // Wait here until we get notified either when (a) there are no 199 // more free regions coming or (b) some regions have been moved on 200 // the secondary_free_list. 201 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 202 } 203 204 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 205 "could not allocate from secondary_free_list"); 206 return NULL; 207 } 208 209 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 210 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 211 "the only time we use this to allocate a humongous region is " 212 "when we are allocating a single humongous region"); 213 214 HeapRegion* res; 215 if (G1StressConcRegionFreeing) { 216 if (!_secondary_free_list.is_empty()) { 217 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 218 "forced to look at the secondary_free_list"); 219 res = new_region_try_secondary_free_list(is_old); 220 if (res != NULL) { 221 return res; 222 } 223 } 224 } 225 226 res = _hrm.allocate_free_region(is_old); 227 228 if (res == NULL) { 229 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 230 "res == NULL, trying the secondary_free_list"); 231 res = new_region_try_secondary_free_list(is_old); 232 } 233 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 234 // Currently, only attempts to allocate GC alloc regions set 235 // do_expand to true. So, we should only reach here during a 236 // safepoint. If this assumption changes we might have to 237 // reconsider the use of _expand_heap_after_alloc_failure. 238 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 239 240 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 241 word_size * HeapWordSize); 242 243 if (expand(word_size * HeapWordSize)) { 244 // Given that expand() succeeded in expanding the heap, and we 245 // always expand the heap by an amount aligned to the heap 246 // region size, the free list should in theory not be empty. 247 // In either case allocate_free_region() will check for NULL. 248 res = _hrm.allocate_free_region(is_old); 249 } else { 250 _expand_heap_after_alloc_failure = false; 251 } 252 } 253 return res; 254 } 255 256 HeapWord* 257 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 258 uint num_regions, 259 size_t word_size, 260 AllocationContext_t context) { 261 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 262 assert(is_humongous(word_size), "word_size should be humongous"); 263 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 264 265 // Index of last region in the series. 266 uint last = first + num_regions - 1; 267 268 // We need to initialize the region(s) we just discovered. This is 269 // a bit tricky given that it can happen concurrently with 270 // refinement threads refining cards on these regions and 271 // potentially wanting to refine the BOT as they are scanning 272 // those cards (this can happen shortly after a cleanup; see CR 273 // 6991377). So we have to set up the region(s) carefully and in 274 // a specific order. 275 276 // The word size sum of all the regions we will allocate. 277 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 278 assert(word_size <= word_size_sum, "sanity"); 279 280 // This will be the "starts humongous" region. 281 HeapRegion* first_hr = region_at(first); 282 // The header of the new object will be placed at the bottom of 283 // the first region. 284 HeapWord* new_obj = first_hr->bottom(); 285 // This will be the new top of the new object. 286 HeapWord* obj_top = new_obj + word_size; 287 288 // First, we need to zero the header of the space that we will be 289 // allocating. When we update top further down, some refinement 290 // threads might try to scan the region. By zeroing the header we 291 // ensure that any thread that will try to scan the region will 292 // come across the zero klass word and bail out. 293 // 294 // NOTE: It would not have been correct to have used 295 // CollectedHeap::fill_with_object() and make the space look like 296 // an int array. The thread that is doing the allocation will 297 // later update the object header to a potentially different array 298 // type and, for a very short period of time, the klass and length 299 // fields will be inconsistent. This could cause a refinement 300 // thread to calculate the object size incorrectly. 301 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 302 303 // How many words we use for filler objects. 304 size_t word_fill_size = word_size_sum - word_size; 305 306 // How many words memory we "waste" which cannot hold a filler object. 307 size_t words_not_fillable = 0; 308 309 if (word_fill_size >= min_fill_size()) { 310 fill_with_objects(obj_top, word_fill_size); 311 } else if (word_fill_size > 0) { 312 // We have space to fill, but we cannot fit an object there. 313 words_not_fillable = word_fill_size; 314 word_fill_size = 0; 315 } 316 317 // We will set up the first region as "starts humongous". This 318 // will also update the BOT covering all the regions to reflect 319 // that there is a single object that starts at the bottom of the 320 // first region. 321 first_hr->set_starts_humongous(obj_top, word_fill_size); 322 first_hr->set_allocation_context(context); 323 // Then, if there are any, we will set up the "continues 324 // humongous" regions. 325 HeapRegion* hr = NULL; 326 for (uint i = first + 1; i <= last; ++i) { 327 hr = region_at(i); 328 hr->set_continues_humongous(first_hr); 329 hr->set_allocation_context(context); 330 } 331 332 // Up to this point no concurrent thread would have been able to 333 // do any scanning on any region in this series. All the top 334 // fields still point to bottom, so the intersection between 335 // [bottom,top] and [card_start,card_end] will be empty. Before we 336 // update the top fields, we'll do a storestore to make sure that 337 // no thread sees the update to top before the zeroing of the 338 // object header and the BOT initialization. 339 OrderAccess::storestore(); 340 341 // Now, we will update the top fields of the "continues humongous" 342 // regions except the last one. 343 for (uint i = first; i < last; ++i) { 344 hr = region_at(i); 345 hr->set_top(hr->end()); 346 } 347 348 hr = region_at(last); 349 // If we cannot fit a filler object, we must set top to the end 350 // of the humongous object, otherwise we cannot iterate the heap 351 // and the BOT will not be complete. 352 hr->set_top(hr->end() - words_not_fillable); 353 354 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 355 "obj_top should be in last region"); 356 357 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 358 359 assert(words_not_fillable == 0 || 360 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 361 "Miscalculation in humongous allocation"); 362 363 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 364 365 for (uint i = first; i <= last; ++i) { 366 hr = region_at(i); 367 _humongous_set.add(hr); 368 _hr_printer.alloc(hr); 369 } 370 371 return new_obj; 372 } 373 374 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 375 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 376 return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 377 } 378 379 // If could fit into free regions w/o expansion, try. 380 // Otherwise, if can expand, do so. 381 // Otherwise, if using ex regions might help, try with ex given back. 382 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 383 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 384 385 _verifier->verify_region_sets_optional(); 386 387 uint first = G1_NO_HRM_INDEX; 388 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 389 390 if (obj_regions == 1) { 391 // Only one region to allocate, try to use a fast path by directly allocating 392 // from the free lists. Do not try to expand here, we will potentially do that 393 // later. 394 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 395 if (hr != NULL) { 396 first = hr->hrm_index(); 397 } 398 } else { 399 // We can't allocate humongous regions spanning more than one region while 400 // cleanupComplete() is running, since some of the regions we find to be 401 // empty might not yet be added to the free list. It is not straightforward 402 // to know in which list they are on so that we can remove them. We only 403 // need to do this if we need to allocate more than one region to satisfy the 404 // current humongous allocation request. If we are only allocating one region 405 // we use the one-region region allocation code (see above), that already 406 // potentially waits for regions from the secondary free list. 407 wait_while_free_regions_coming(); 408 append_secondary_free_list_if_not_empty_with_lock(); 409 410 // Policy: Try only empty regions (i.e. already committed first). Maybe we 411 // are lucky enough to find some. 412 first = _hrm.find_contiguous_only_empty(obj_regions); 413 if (first != G1_NO_HRM_INDEX) { 414 _hrm.allocate_free_regions_starting_at(first, obj_regions); 415 } 416 } 417 418 if (first == G1_NO_HRM_INDEX) { 419 // Policy: We could not find enough regions for the humongous object in the 420 // free list. Look through the heap to find a mix of free and uncommitted regions. 421 // If so, try expansion. 422 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 423 if (first != G1_NO_HRM_INDEX) { 424 // We found something. Make sure these regions are committed, i.e. expand 425 // the heap. Alternatively we could do a defragmentation GC. 426 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 427 word_size * HeapWordSize); 428 429 430 _hrm.expand_at(first, obj_regions); 431 g1_policy()->record_new_heap_size(num_regions()); 432 433 #ifdef ASSERT 434 for (uint i = first; i < first + obj_regions; ++i) { 435 HeapRegion* hr = region_at(i); 436 assert(hr->is_free(), "sanity"); 437 assert(hr->is_empty(), "sanity"); 438 assert(is_on_master_free_list(hr), "sanity"); 439 } 440 #endif 441 _hrm.allocate_free_regions_starting_at(first, obj_regions); 442 } else { 443 // Policy: Potentially trigger a defragmentation GC. 444 } 445 } 446 447 HeapWord* result = NULL; 448 if (first != G1_NO_HRM_INDEX) { 449 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 450 word_size, context); 451 assert(result != NULL, "it should always return a valid result"); 452 453 // A successful humongous object allocation changes the used space 454 // information of the old generation so we need to recalculate the 455 // sizes and update the jstat counters here. 456 g1mm()->update_sizes(); 457 } 458 459 _verifier->verify_region_sets_optional(); 460 461 return result; 462 } 463 464 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 465 assert_heap_not_locked_and_not_at_safepoint(); 466 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 467 468 uint dummy_gc_count_before; 469 uint dummy_gclocker_retry_count = 0; 470 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 471 } 472 473 HeapWord* 474 G1CollectedHeap::mem_allocate(size_t word_size, 475 bool* gc_overhead_limit_was_exceeded) { 476 assert_heap_not_locked_and_not_at_safepoint(); 477 478 // Loop until the allocation is satisfied, or unsatisfied after GC. 479 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 480 uint gc_count_before; 481 482 HeapWord* result = NULL; 483 if (!is_humongous(word_size)) { 484 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 485 } else { 486 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 487 } 488 if (result != NULL) { 489 return result; 490 } 491 492 // Create the garbage collection operation... 493 VM_G1CollectForAllocation op(gc_count_before, word_size); 494 op.set_allocation_context(AllocationContext::current()); 495 496 // ...and get the VM thread to execute it. 497 VMThread::execute(&op); 498 499 if (op.prologue_succeeded() && op.pause_succeeded()) { 500 // If the operation was successful we'll return the result even 501 // if it is NULL. If the allocation attempt failed immediately 502 // after a Full GC, it's unlikely we'll be able to allocate now. 503 HeapWord* result = op.result(); 504 if (result != NULL && !is_humongous(word_size)) { 505 // Allocations that take place on VM operations do not do any 506 // card dirtying and we have to do it here. We only have to do 507 // this for non-humongous allocations, though. 508 dirty_young_block(result, word_size); 509 } 510 return result; 511 } else { 512 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 513 return NULL; 514 } 515 assert(op.result() == NULL, 516 "the result should be NULL if the VM op did not succeed"); 517 } 518 519 // Give a warning if we seem to be looping forever. 520 if ((QueuedAllocationWarningCount > 0) && 521 (try_count % QueuedAllocationWarningCount == 0)) { 522 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count); 523 } 524 } 525 526 ShouldNotReachHere(); 527 return NULL; 528 } 529 530 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 531 AllocationContext_t context, 532 uint* gc_count_before_ret, 533 uint* gclocker_retry_count_ret) { 534 // Make sure you read the note in attempt_allocation_humongous(). 535 536 assert_heap_not_locked_and_not_at_safepoint(); 537 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 538 "be called for humongous allocation requests"); 539 540 // We should only get here after the first-level allocation attempt 541 // (attempt_allocation()) failed to allocate. 542 543 // We will loop until a) we manage to successfully perform the 544 // allocation or b) we successfully schedule a collection which 545 // fails to perform the allocation. b) is the only case when we'll 546 // return NULL. 547 HeapWord* result = NULL; 548 for (int try_count = 1; /* we'll return */; try_count += 1) { 549 bool should_try_gc; 550 uint gc_count_before; 551 552 { 553 MutexLockerEx x(Heap_lock); 554 result = _allocator->attempt_allocation_locked(word_size, context); 555 if (result != NULL) { 556 return result; 557 } 558 559 if (GCLocker::is_active_and_needs_gc()) { 560 if (g1_policy()->can_expand_young_list()) { 561 // No need for an ergo verbose message here, 562 // can_expand_young_list() does this when it returns true. 563 result = _allocator->attempt_allocation_force(word_size, context); 564 if (result != NULL) { 565 return result; 566 } 567 } 568 should_try_gc = false; 569 } else { 570 // The GCLocker may not be active but the GCLocker initiated 571 // GC may not yet have been performed (GCLocker::needs_gc() 572 // returns true). In this case we do not try this GC and 573 // wait until the GCLocker initiated GC is performed, and 574 // then retry the allocation. 575 if (GCLocker::needs_gc()) { 576 should_try_gc = false; 577 } else { 578 // Read the GC count while still holding the Heap_lock. 579 gc_count_before = total_collections(); 580 should_try_gc = true; 581 } 582 } 583 } 584 585 if (should_try_gc) { 586 bool succeeded; 587 result = do_collection_pause(word_size, gc_count_before, &succeeded, 588 GCCause::_g1_inc_collection_pause); 589 if (result != NULL) { 590 assert(succeeded, "only way to get back a non-NULL result"); 591 return result; 592 } 593 594 if (succeeded) { 595 // If we get here we successfully scheduled a collection which 596 // failed to allocate. No point in trying to allocate 597 // further. We'll just return NULL. 598 MutexLockerEx x(Heap_lock); 599 *gc_count_before_ret = total_collections(); 600 return NULL; 601 } 602 } else { 603 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 604 MutexLockerEx x(Heap_lock); 605 *gc_count_before_ret = total_collections(); 606 return NULL; 607 } 608 // The GCLocker is either active or the GCLocker initiated 609 // GC has not yet been performed. Stall until it is and 610 // then retry the allocation. 611 GCLocker::stall_until_clear(); 612 (*gclocker_retry_count_ret) += 1; 613 } 614 615 // We can reach here if we were unsuccessful in scheduling a 616 // collection (because another thread beat us to it) or if we were 617 // stalled due to the GC locker. In either can we should retry the 618 // allocation attempt in case another thread successfully 619 // performed a collection and reclaimed enough space. We do the 620 // first attempt (without holding the Heap_lock) here and the 621 // follow-on attempt will be at the start of the next loop 622 // iteration (after taking the Heap_lock). 623 result = _allocator->attempt_allocation(word_size, context); 624 if (result != NULL) { 625 return result; 626 } 627 628 // Give a warning if we seem to be looping forever. 629 if ((QueuedAllocationWarningCount > 0) && 630 (try_count % QueuedAllocationWarningCount == 0)) { 631 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() " 632 "retries %d times", try_count); 633 } 634 } 635 636 ShouldNotReachHere(); 637 return NULL; 638 } 639 640 void G1CollectedHeap::begin_archive_alloc_range() { 641 assert_at_safepoint(true /* should_be_vm_thread */); 642 if (_archive_allocator == NULL) { 643 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 644 } 645 } 646 647 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 648 // Allocations in archive regions cannot be of a size that would be considered 649 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 650 // may be different at archive-restore time. 651 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 652 } 653 654 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 655 assert_at_safepoint(true /* should_be_vm_thread */); 656 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 657 if (is_archive_alloc_too_large(word_size)) { 658 return NULL; 659 } 660 return _archive_allocator->archive_mem_allocate(word_size); 661 } 662 663 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 664 size_t end_alignment_in_bytes) { 665 assert_at_safepoint(true /* should_be_vm_thread */); 666 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 667 668 // Call complete_archive to do the real work, filling in the MemRegion 669 // array with the archive regions. 670 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 671 delete _archive_allocator; 672 _archive_allocator = NULL; 673 } 674 675 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 676 assert(ranges != NULL, "MemRegion array NULL"); 677 assert(count != 0, "No MemRegions provided"); 678 MemRegion reserved = _hrm.reserved(); 679 for (size_t i = 0; i < count; i++) { 680 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 681 return false; 682 } 683 } 684 return true; 685 } 686 687 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 688 assert(!is_init_completed(), "Expect to be called at JVM init time"); 689 assert(ranges != NULL, "MemRegion array NULL"); 690 assert(count != 0, "No MemRegions provided"); 691 MutexLockerEx x(Heap_lock); 692 693 MemRegion reserved = _hrm.reserved(); 694 HeapWord* prev_last_addr = NULL; 695 HeapRegion* prev_last_region = NULL; 696 697 // Temporarily disable pretouching of heap pages. This interface is used 698 // when mmap'ing archived heap data in, so pre-touching is wasted. 699 FlagSetting fs(AlwaysPreTouch, false); 700 701 // Enable archive object checking in G1MarkSweep. We have to let it know 702 // about each archive range, so that objects in those ranges aren't marked. 703 G1MarkSweep::enable_archive_object_check(); 704 705 // For each specified MemRegion range, allocate the corresponding G1 706 // regions and mark them as archive regions. We expect the ranges in 707 // ascending starting address order, without overlap. 708 for (size_t i = 0; i < count; i++) { 709 MemRegion curr_range = ranges[i]; 710 HeapWord* start_address = curr_range.start(); 711 size_t word_size = curr_range.word_size(); 712 HeapWord* last_address = curr_range.last(); 713 size_t commits = 0; 714 715 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 716 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 717 p2i(start_address), p2i(last_address)); 718 guarantee(start_address > prev_last_addr, 719 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 720 p2i(start_address), p2i(prev_last_addr)); 721 prev_last_addr = last_address; 722 723 // Check for ranges that start in the same G1 region in which the previous 724 // range ended, and adjust the start address so we don't try to allocate 725 // the same region again. If the current range is entirely within that 726 // region, skip it, just adjusting the recorded top. 727 HeapRegion* start_region = _hrm.addr_to_region(start_address); 728 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 729 start_address = start_region->end(); 730 if (start_address > last_address) { 731 increase_used(word_size * HeapWordSize); 732 start_region->set_top(last_address + 1); 733 continue; 734 } 735 start_region->set_top(start_address); 736 curr_range = MemRegion(start_address, last_address + 1); 737 start_region = _hrm.addr_to_region(start_address); 738 } 739 740 // Perform the actual region allocation, exiting if it fails. 741 // Then note how much new space we have allocated. 742 if (!_hrm.allocate_containing_regions(curr_range, &commits)) { 743 return false; 744 } 745 increase_used(word_size * HeapWordSize); 746 if (commits != 0) { 747 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 748 HeapRegion::GrainWords * HeapWordSize * commits); 749 750 } 751 752 // Mark each G1 region touched by the range as archive, add it to the old set, 753 // and set the allocation context and top. 754 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 755 HeapRegion* last_region = _hrm.addr_to_region(last_address); 756 prev_last_region = last_region; 757 758 while (curr_region != NULL) { 759 assert(curr_region->is_empty() && !curr_region->is_pinned(), 760 "Region already in use (index %u)", curr_region->hrm_index()); 761 curr_region->set_allocation_context(AllocationContext::system()); 762 curr_region->set_archive(); 763 _hr_printer.alloc(curr_region); 764 _old_set.add(curr_region); 765 if (curr_region != last_region) { 766 curr_region->set_top(curr_region->end()); 767 curr_region = _hrm.next_region_in_heap(curr_region); 768 } else { 769 curr_region->set_top(last_address + 1); 770 curr_region = NULL; 771 } 772 } 773 774 // Notify mark-sweep of the archive range. 775 G1MarkSweep::set_range_archive(curr_range, true); 776 } 777 return true; 778 } 779 780 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 781 assert(!is_init_completed(), "Expect to be called at JVM init time"); 782 assert(ranges != NULL, "MemRegion array NULL"); 783 assert(count != 0, "No MemRegions provided"); 784 MemRegion reserved = _hrm.reserved(); 785 HeapWord *prev_last_addr = NULL; 786 HeapRegion* prev_last_region = NULL; 787 788 // For each MemRegion, create filler objects, if needed, in the G1 regions 789 // that contain the address range. The address range actually within the 790 // MemRegion will not be modified. That is assumed to have been initialized 791 // elsewhere, probably via an mmap of archived heap data. 792 MutexLockerEx x(Heap_lock); 793 for (size_t i = 0; i < count; i++) { 794 HeapWord* start_address = ranges[i].start(); 795 HeapWord* last_address = ranges[i].last(); 796 797 assert(reserved.contains(start_address) && reserved.contains(last_address), 798 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 799 p2i(start_address), p2i(last_address)); 800 assert(start_address > prev_last_addr, 801 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 802 p2i(start_address), p2i(prev_last_addr)); 803 804 HeapRegion* start_region = _hrm.addr_to_region(start_address); 805 HeapRegion* last_region = _hrm.addr_to_region(last_address); 806 HeapWord* bottom_address = start_region->bottom(); 807 808 // Check for a range beginning in the same region in which the 809 // previous one ended. 810 if (start_region == prev_last_region) { 811 bottom_address = prev_last_addr + 1; 812 } 813 814 // Verify that the regions were all marked as archive regions by 815 // alloc_archive_regions. 816 HeapRegion* curr_region = start_region; 817 while (curr_region != NULL) { 818 guarantee(curr_region->is_archive(), 819 "Expected archive region at index %u", curr_region->hrm_index()); 820 if (curr_region != last_region) { 821 curr_region = _hrm.next_region_in_heap(curr_region); 822 } else { 823 curr_region = NULL; 824 } 825 } 826 827 prev_last_addr = last_address; 828 prev_last_region = last_region; 829 830 // Fill the memory below the allocated range with dummy object(s), 831 // if the region bottom does not match the range start, or if the previous 832 // range ended within the same G1 region, and there is a gap. 833 if (start_address != bottom_address) { 834 size_t fill_size = pointer_delta(start_address, bottom_address); 835 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 836 increase_used(fill_size * HeapWordSize); 837 } 838 } 839 } 840 841 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 842 uint* gc_count_before_ret, 843 uint* gclocker_retry_count_ret) { 844 assert_heap_not_locked_and_not_at_safepoint(); 845 assert(!is_humongous(word_size), "attempt_allocation() should not " 846 "be called for humongous allocation requests"); 847 848 AllocationContext_t context = AllocationContext::current(); 849 HeapWord* result = _allocator->attempt_allocation(word_size, context); 850 851 if (result == NULL) { 852 result = attempt_allocation_slow(word_size, 853 context, 854 gc_count_before_ret, 855 gclocker_retry_count_ret); 856 } 857 assert_heap_not_locked(); 858 if (result != NULL) { 859 dirty_young_block(result, word_size); 860 } 861 return result; 862 } 863 864 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 865 assert(!is_init_completed(), "Expect to be called at JVM init time"); 866 assert(ranges != NULL, "MemRegion array NULL"); 867 assert(count != 0, "No MemRegions provided"); 868 MemRegion reserved = _hrm.reserved(); 869 HeapWord* prev_last_addr = NULL; 870 HeapRegion* prev_last_region = NULL; 871 size_t size_used = 0; 872 size_t uncommitted_regions = 0; 873 874 // For each Memregion, free the G1 regions that constitute it, and 875 // notify mark-sweep that the range is no longer to be considered 'archive.' 876 MutexLockerEx x(Heap_lock); 877 for (size_t i = 0; i < count; i++) { 878 HeapWord* start_address = ranges[i].start(); 879 HeapWord* last_address = ranges[i].last(); 880 881 assert(reserved.contains(start_address) && reserved.contains(last_address), 882 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 883 p2i(start_address), p2i(last_address)); 884 assert(start_address > prev_last_addr, 885 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 886 p2i(start_address), p2i(prev_last_addr)); 887 size_used += ranges[i].byte_size(); 888 prev_last_addr = last_address; 889 890 HeapRegion* start_region = _hrm.addr_to_region(start_address); 891 HeapRegion* last_region = _hrm.addr_to_region(last_address); 892 893 // Check for ranges that start in the same G1 region in which the previous 894 // range ended, and adjust the start address so we don't try to free 895 // the same region again. If the current range is entirely within that 896 // region, skip it. 897 if (start_region == prev_last_region) { 898 start_address = start_region->end(); 899 if (start_address > last_address) { 900 continue; 901 } 902 start_region = _hrm.addr_to_region(start_address); 903 } 904 prev_last_region = last_region; 905 906 // After verifying that each region was marked as an archive region by 907 // alloc_archive_regions, set it free and empty and uncommit it. 908 HeapRegion* curr_region = start_region; 909 while (curr_region != NULL) { 910 guarantee(curr_region->is_archive(), 911 "Expected archive region at index %u", curr_region->hrm_index()); 912 uint curr_index = curr_region->hrm_index(); 913 _old_set.remove(curr_region); 914 curr_region->set_free(); 915 curr_region->set_top(curr_region->bottom()); 916 if (curr_region != last_region) { 917 curr_region = _hrm.next_region_in_heap(curr_region); 918 } else { 919 curr_region = NULL; 920 } 921 _hrm.shrink_at(curr_index, 1); 922 uncommitted_regions++; 923 } 924 925 // Notify mark-sweep that this is no longer an archive range. 926 G1MarkSweep::set_range_archive(ranges[i], false); 927 } 928 929 if (uncommitted_regions != 0) { 930 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 931 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 932 } 933 decrease_used(size_used); 934 } 935 936 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 937 uint* gc_count_before_ret, 938 uint* gclocker_retry_count_ret) { 939 // The structure of this method has a lot of similarities to 940 // attempt_allocation_slow(). The reason these two were not merged 941 // into a single one is that such a method would require several "if 942 // allocation is not humongous do this, otherwise do that" 943 // conditional paths which would obscure its flow. In fact, an early 944 // version of this code did use a unified method which was harder to 945 // follow and, as a result, it had subtle bugs that were hard to 946 // track down. So keeping these two methods separate allows each to 947 // be more readable. It will be good to keep these two in sync as 948 // much as possible. 949 950 assert_heap_not_locked_and_not_at_safepoint(); 951 assert(is_humongous(word_size), "attempt_allocation_humongous() " 952 "should only be called for humongous allocations"); 953 954 // Humongous objects can exhaust the heap quickly, so we should check if we 955 // need to start a marking cycle at each humongous object allocation. We do 956 // the check before we do the actual allocation. The reason for doing it 957 // before the allocation is that we avoid having to keep track of the newly 958 // allocated memory while we do a GC. 959 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 960 word_size)) { 961 collect(GCCause::_g1_humongous_allocation); 962 } 963 964 // We will loop until a) we manage to successfully perform the 965 // allocation or b) we successfully schedule a collection which 966 // fails to perform the allocation. b) is the only case when we'll 967 // return NULL. 968 HeapWord* result = NULL; 969 for (int try_count = 1; /* we'll return */; try_count += 1) { 970 bool should_try_gc; 971 uint gc_count_before; 972 973 { 974 MutexLockerEx x(Heap_lock); 975 976 // Given that humongous objects are not allocated in young 977 // regions, we'll first try to do the allocation without doing a 978 // collection hoping that there's enough space in the heap. 979 result = humongous_obj_allocate(word_size, AllocationContext::current()); 980 if (result != NULL) { 981 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 982 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 983 return result; 984 } 985 986 if (GCLocker::is_active_and_needs_gc()) { 987 should_try_gc = false; 988 } else { 989 // The GCLocker may not be active but the GCLocker initiated 990 // GC may not yet have been performed (GCLocker::needs_gc() 991 // returns true). In this case we do not try this GC and 992 // wait until the GCLocker initiated GC is performed, and 993 // then retry the allocation. 994 if (GCLocker::needs_gc()) { 995 should_try_gc = false; 996 } else { 997 // Read the GC count while still holding the Heap_lock. 998 gc_count_before = total_collections(); 999 should_try_gc = true; 1000 } 1001 } 1002 } 1003 1004 if (should_try_gc) { 1005 // If we failed to allocate the humongous object, we should try to 1006 // do a collection pause (if we're allowed) in case it reclaims 1007 // enough space for the allocation to succeed after the pause. 1008 1009 bool succeeded; 1010 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1011 GCCause::_g1_humongous_allocation); 1012 if (result != NULL) { 1013 assert(succeeded, "only way to get back a non-NULL result"); 1014 return result; 1015 } 1016 1017 if (succeeded) { 1018 // If we get here we successfully scheduled a collection which 1019 // failed to allocate. No point in trying to allocate 1020 // further. We'll just return NULL. 1021 MutexLockerEx x(Heap_lock); 1022 *gc_count_before_ret = total_collections(); 1023 return NULL; 1024 } 1025 } else { 1026 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1027 MutexLockerEx x(Heap_lock); 1028 *gc_count_before_ret = total_collections(); 1029 return NULL; 1030 } 1031 // The GCLocker is either active or the GCLocker initiated 1032 // GC has not yet been performed. Stall until it is and 1033 // then retry the allocation. 1034 GCLocker::stall_until_clear(); 1035 (*gclocker_retry_count_ret) += 1; 1036 } 1037 1038 // We can reach here if we were unsuccessful in scheduling a 1039 // collection (because another thread beat us to it) or if we were 1040 // stalled due to the GC locker. In either can we should retry the 1041 // allocation attempt in case another thread successfully 1042 // performed a collection and reclaimed enough space. Give a 1043 // warning if we seem to be looping forever. 1044 1045 if ((QueuedAllocationWarningCount > 0) && 1046 (try_count % QueuedAllocationWarningCount == 0)) { 1047 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() " 1048 "retries %d times", try_count); 1049 } 1050 } 1051 1052 ShouldNotReachHere(); 1053 return NULL; 1054 } 1055 1056 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1057 AllocationContext_t context, 1058 bool expect_null_mutator_alloc_region) { 1059 assert_at_safepoint(true /* should_be_vm_thread */); 1060 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1061 "the current alloc region was unexpectedly found to be non-NULL"); 1062 1063 if (!is_humongous(word_size)) { 1064 return _allocator->attempt_allocation_locked(word_size, context); 1065 } else { 1066 HeapWord* result = humongous_obj_allocate(word_size, context); 1067 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1068 collector_state()->set_initiate_conc_mark_if_possible(true); 1069 } 1070 return result; 1071 } 1072 1073 ShouldNotReachHere(); 1074 } 1075 1076 class PostMCRemSetClearClosure: public HeapRegionClosure { 1077 G1CollectedHeap* _g1h; 1078 ModRefBarrierSet* _mr_bs; 1079 public: 1080 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1081 _g1h(g1h), _mr_bs(mr_bs) {} 1082 1083 bool doHeapRegion(HeapRegion* r) { 1084 HeapRegionRemSet* hrrs = r->rem_set(); 1085 1086 _g1h->reset_gc_time_stamps(r); 1087 1088 if (r->is_continues_humongous()) { 1089 // We'll assert that the strong code root list and RSet is empty 1090 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1091 assert(hrrs->occupied() == 0, "RSet should be empty"); 1092 } else { 1093 hrrs->clear(); 1094 } 1095 // You might think here that we could clear just the cards 1096 // corresponding to the used region. But no: if we leave a dirty card 1097 // in a region we might allocate into, then it would prevent that card 1098 // from being enqueued, and cause it to be missed. 1099 // Re: the performance cost: we shouldn't be doing full GC anyway! 1100 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1101 1102 return false; 1103 } 1104 }; 1105 1106 void G1CollectedHeap::clear_rsets_post_compaction() { 1107 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1108 heap_region_iterate(&rs_clear); 1109 } 1110 1111 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1112 G1CollectedHeap* _g1h; 1113 UpdateRSOopClosure _cl; 1114 public: 1115 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1116 _cl(g1->g1_rem_set(), worker_i), 1117 _g1h(g1) 1118 { } 1119 1120 bool doHeapRegion(HeapRegion* r) { 1121 if (!r->is_continues_humongous()) { 1122 _cl.set_from(r); 1123 r->oop_iterate(&_cl); 1124 } 1125 return false; 1126 } 1127 }; 1128 1129 class ParRebuildRSTask: public AbstractGangTask { 1130 G1CollectedHeap* _g1; 1131 HeapRegionClaimer _hrclaimer; 1132 1133 public: 1134 ParRebuildRSTask(G1CollectedHeap* g1) : 1135 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1136 1137 void work(uint worker_id) { 1138 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1139 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1140 } 1141 }; 1142 1143 class PostCompactionPrinterClosure: public HeapRegionClosure { 1144 private: 1145 G1HRPrinter* _hr_printer; 1146 public: 1147 bool doHeapRegion(HeapRegion* hr) { 1148 assert(!hr->is_young(), "not expecting to find young regions"); 1149 _hr_printer->post_compaction(hr); 1150 return false; 1151 } 1152 1153 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1154 : _hr_printer(hr_printer) { } 1155 }; 1156 1157 void G1CollectedHeap::print_hrm_post_compaction() { 1158 if (_hr_printer.is_active()) { 1159 PostCompactionPrinterClosure cl(hr_printer()); 1160 heap_region_iterate(&cl); 1161 } 1162 1163 } 1164 1165 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1166 bool clear_all_soft_refs) { 1167 assert_at_safepoint(true /* should_be_vm_thread */); 1168 1169 if (GCLocker::check_active_before_gc()) { 1170 return false; 1171 } 1172 1173 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1174 gc_timer->register_gc_start(); 1175 1176 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1177 GCIdMark gc_id_mark; 1178 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1179 1180 SvcGCMarker sgcm(SvcGCMarker::FULL); 1181 ResourceMark rm; 1182 1183 print_heap_before_gc(); 1184 print_heap_regions(); 1185 trace_heap_before_gc(gc_tracer); 1186 1187 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1188 1189 _verifier->verify_region_sets_optional(); 1190 1191 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1192 collector_policy()->should_clear_all_soft_refs(); 1193 1194 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1195 1196 { 1197 IsGCActiveMark x; 1198 1199 // Timing 1200 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1201 GCTraceCPUTime tcpu; 1202 1203 { 1204 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1205 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1206 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1207 1208 G1HeapTransition heap_transition(this); 1209 g1_policy()->record_full_collection_start(); 1210 1211 // Note: When we have a more flexible GC logging framework that 1212 // allows us to add optional attributes to a GC log record we 1213 // could consider timing and reporting how long we wait in the 1214 // following two methods. 1215 wait_while_free_regions_coming(); 1216 // If we start the compaction before the CM threads finish 1217 // scanning the root regions we might trip them over as we'll 1218 // be moving objects / updating references. So let's wait until 1219 // they are done. By telling them to abort, they should complete 1220 // early. 1221 _cm->root_regions()->abort(); 1222 _cm->root_regions()->wait_until_scan_finished(); 1223 append_secondary_free_list_if_not_empty_with_lock(); 1224 1225 gc_prologue(true); 1226 increment_total_collections(true /* full gc */); 1227 increment_old_marking_cycles_started(); 1228 1229 assert(used() == recalculate_used(), "Should be equal"); 1230 1231 _verifier->verify_before_gc(); 1232 1233 _verifier->check_bitmaps("Full GC Start"); 1234 pre_full_gc_dump(gc_timer); 1235 1236 #if defined(COMPILER2) || INCLUDE_JVMCI 1237 DerivedPointerTable::clear(); 1238 #endif 1239 1240 // Disable discovery and empty the discovered lists 1241 // for the CM ref processor. 1242 ref_processor_cm()->disable_discovery(); 1243 ref_processor_cm()->abandon_partial_discovery(); 1244 ref_processor_cm()->verify_no_references_recorded(); 1245 1246 // Abandon current iterations of concurrent marking and concurrent 1247 // refinement, if any are in progress. 1248 concurrent_mark()->abort(); 1249 1250 // Make sure we'll choose a new allocation region afterwards. 1251 _allocator->release_mutator_alloc_region(); 1252 _allocator->abandon_gc_alloc_regions(); 1253 g1_rem_set()->cleanupHRRS(); 1254 1255 // We may have added regions to the current incremental collection 1256 // set between the last GC or pause and now. We need to clear the 1257 // incremental collection set and then start rebuilding it afresh 1258 // after this full GC. 1259 abandon_collection_set(collection_set()->inc_head()); 1260 collection_set()->clear_incremental(); 1261 collection_set()->stop_incremental_building(); 1262 1263 tear_down_region_sets(false /* free_list_only */); 1264 collector_state()->set_gcs_are_young(true); 1265 1266 // See the comments in g1CollectedHeap.hpp and 1267 // G1CollectedHeap::ref_processing_init() about 1268 // how reference processing currently works in G1. 1269 1270 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1271 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1272 1273 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1274 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1275 1276 ref_processor_stw()->enable_discovery(); 1277 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1278 1279 // Do collection work 1280 { 1281 HandleMark hm; // Discard invalid handles created during gc 1282 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1283 } 1284 1285 assert(num_free_regions() == 0, "we should not have added any free regions"); 1286 rebuild_region_sets(false /* free_list_only */); 1287 1288 // Enqueue any discovered reference objects that have 1289 // not been removed from the discovered lists. 1290 ref_processor_stw()->enqueue_discovered_references(); 1291 1292 #if defined(COMPILER2) || INCLUDE_JVMCI 1293 DerivedPointerTable::update_pointers(); 1294 #endif 1295 1296 MemoryService::track_memory_usage(); 1297 1298 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1299 ref_processor_stw()->verify_no_references_recorded(); 1300 1301 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1302 ClassLoaderDataGraph::purge(); 1303 MetaspaceAux::verify_metrics(); 1304 1305 // Note: since we've just done a full GC, concurrent 1306 // marking is no longer active. Therefore we need not 1307 // re-enable reference discovery for the CM ref processor. 1308 // That will be done at the start of the next marking cycle. 1309 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1310 ref_processor_cm()->verify_no_references_recorded(); 1311 1312 reset_gc_time_stamp(); 1313 // Since everything potentially moved, we will clear all remembered 1314 // sets, and clear all cards. Later we will rebuild remembered 1315 // sets. We will also reset the GC time stamps of the regions. 1316 clear_rsets_post_compaction(); 1317 check_gc_time_stamps(); 1318 1319 resize_if_necessary_after_full_collection(); 1320 1321 // We should do this after we potentially resize the heap so 1322 // that all the COMMIT / UNCOMMIT events are generated before 1323 // the compaction events. 1324 print_hrm_post_compaction(); 1325 1326 if (_hot_card_cache->use_cache()) { 1327 _hot_card_cache->reset_card_counts(); 1328 _hot_card_cache->reset_hot_cache(); 1329 } 1330 1331 // Rebuild remembered sets of all regions. 1332 uint n_workers = 1333 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1334 workers()->active_workers(), 1335 Threads::number_of_non_daemon_threads()); 1336 workers()->set_active_workers(n_workers); 1337 1338 ParRebuildRSTask rebuild_rs_task(this); 1339 workers()->run_task(&rebuild_rs_task); 1340 1341 // Rebuild the strong code root lists for each region 1342 rebuild_strong_code_roots(); 1343 1344 if (true) { // FIXME 1345 MetaspaceGC::compute_new_size(); 1346 } 1347 1348 #ifdef TRACESPINNING 1349 ParallelTaskTerminator::print_termination_counts(); 1350 #endif 1351 1352 // Discard all rset updates 1353 JavaThread::dirty_card_queue_set().abandon_logs(); 1354 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1355 1356 // At this point there should be no regions in the 1357 // entire heap tagged as young. 1358 assert(check_young_list_empty(), "young list should be empty at this point"); 1359 1360 // Update the number of full collections that have been completed. 1361 increment_old_marking_cycles_completed(false /* concurrent */); 1362 1363 _hrm.verify_optional(); 1364 _verifier->verify_region_sets_optional(); 1365 1366 _verifier->verify_after_gc(); 1367 1368 // Clear the previous marking bitmap, if needed for bitmap verification. 1369 // Note we cannot do this when we clear the next marking bitmap in 1370 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1371 // objects marked during a full GC against the previous bitmap. 1372 // But we need to clear it before calling check_bitmaps below since 1373 // the full GC has compacted objects and updated TAMS but not updated 1374 // the prev bitmap. 1375 if (G1VerifyBitmaps) { 1376 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1377 _cm->clear_prev_bitmap(workers()); 1378 } 1379 _verifier->check_bitmaps("Full GC End"); 1380 1381 // Start a new incremental collection set for the next pause 1382 assert(collection_set()->head() == NULL, "must be"); 1383 collection_set()->start_incremental_building(); 1384 1385 clear_cset_fast_test(); 1386 1387 _allocator->init_mutator_alloc_region(); 1388 1389 g1_policy()->record_full_collection_end(); 1390 1391 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1392 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1393 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1394 // before any GC notifications are raised. 1395 g1mm()->update_sizes(); 1396 1397 gc_epilogue(true); 1398 1399 heap_transition.print(); 1400 1401 print_heap_after_gc(); 1402 print_heap_regions(); 1403 trace_heap_after_gc(gc_tracer); 1404 1405 post_full_gc_dump(gc_timer); 1406 } 1407 1408 gc_timer->register_gc_end(); 1409 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1410 } 1411 1412 return true; 1413 } 1414 1415 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1416 // Currently, there is no facility in the do_full_collection(bool) API to notify 1417 // the caller that the collection did not succeed (e.g., because it was locked 1418 // out by the GC locker). So, right now, we'll ignore the return value. 1419 bool dummy = do_full_collection(true, /* explicit_gc */ 1420 clear_all_soft_refs); 1421 } 1422 1423 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1424 // Include bytes that will be pre-allocated to support collections, as "used". 1425 const size_t used_after_gc = used(); 1426 const size_t capacity_after_gc = capacity(); 1427 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1428 1429 // This is enforced in arguments.cpp. 1430 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1431 "otherwise the code below doesn't make sense"); 1432 1433 // We don't have floating point command-line arguments 1434 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1435 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1436 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1437 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1438 1439 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1440 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1441 1442 // We have to be careful here as these two calculations can overflow 1443 // 32-bit size_t's. 1444 double used_after_gc_d = (double) used_after_gc; 1445 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1446 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1447 1448 // Let's make sure that they are both under the max heap size, which 1449 // by default will make them fit into a size_t. 1450 double desired_capacity_upper_bound = (double) max_heap_size; 1451 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1452 desired_capacity_upper_bound); 1453 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1454 desired_capacity_upper_bound); 1455 1456 // We can now safely turn them into size_t's. 1457 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1458 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1459 1460 // This assert only makes sense here, before we adjust them 1461 // with respect to the min and max heap size. 1462 assert(minimum_desired_capacity <= maximum_desired_capacity, 1463 "minimum_desired_capacity = " SIZE_FORMAT ", " 1464 "maximum_desired_capacity = " SIZE_FORMAT, 1465 minimum_desired_capacity, maximum_desired_capacity); 1466 1467 // Should not be greater than the heap max size. No need to adjust 1468 // it with respect to the heap min size as it's a lower bound (i.e., 1469 // we'll try to make the capacity larger than it, not smaller). 1470 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1471 // Should not be less than the heap min size. No need to adjust it 1472 // with respect to the heap max size as it's an upper bound (i.e., 1473 // we'll try to make the capacity smaller than it, not greater). 1474 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1475 1476 if (capacity_after_gc < minimum_desired_capacity) { 1477 // Don't expand unless it's significant 1478 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1479 1480 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1481 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1482 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1483 1484 expand(expand_bytes); 1485 1486 // No expansion, now see if we want to shrink 1487 } else if (capacity_after_gc > maximum_desired_capacity) { 1488 // Capacity too large, compute shrinking size 1489 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1490 1491 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1492 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1493 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1494 1495 shrink(shrink_bytes); 1496 } 1497 } 1498 1499 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1500 AllocationContext_t context, 1501 bool do_gc, 1502 bool clear_all_soft_refs, 1503 bool expect_null_mutator_alloc_region, 1504 bool* gc_succeeded) { 1505 *gc_succeeded = true; 1506 // Let's attempt the allocation first. 1507 HeapWord* result = 1508 attempt_allocation_at_safepoint(word_size, 1509 context, 1510 expect_null_mutator_alloc_region); 1511 if (result != NULL) { 1512 assert(*gc_succeeded, "sanity"); 1513 return result; 1514 } 1515 1516 // In a G1 heap, we're supposed to keep allocation from failing by 1517 // incremental pauses. Therefore, at least for now, we'll favor 1518 // expansion over collection. (This might change in the future if we can 1519 // do something smarter than full collection to satisfy a failed alloc.) 1520 result = expand_and_allocate(word_size, context); 1521 if (result != NULL) { 1522 assert(*gc_succeeded, "sanity"); 1523 return result; 1524 } 1525 1526 if (do_gc) { 1527 // Expansion didn't work, we'll try to do a Full GC. 1528 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1529 clear_all_soft_refs); 1530 } 1531 1532 return NULL; 1533 } 1534 1535 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1536 AllocationContext_t context, 1537 bool* succeeded) { 1538 assert_at_safepoint(true /* should_be_vm_thread */); 1539 1540 // Attempts to allocate followed by Full GC. 1541 HeapWord* result = 1542 satisfy_failed_allocation_helper(word_size, 1543 context, 1544 true, /* do_gc */ 1545 false, /* clear_all_soft_refs */ 1546 false, /* expect_null_mutator_alloc_region */ 1547 succeeded); 1548 1549 if (result != NULL || !*succeeded) { 1550 return result; 1551 } 1552 1553 // Attempts to allocate followed by Full GC that will collect all soft references. 1554 result = satisfy_failed_allocation_helper(word_size, 1555 context, 1556 true, /* do_gc */ 1557 true, /* clear_all_soft_refs */ 1558 true, /* expect_null_mutator_alloc_region */ 1559 succeeded); 1560 1561 if (result != NULL || !*succeeded) { 1562 return result; 1563 } 1564 1565 // Attempts to allocate, no GC 1566 result = satisfy_failed_allocation_helper(word_size, 1567 context, 1568 false, /* do_gc */ 1569 false, /* clear_all_soft_refs */ 1570 true, /* expect_null_mutator_alloc_region */ 1571 succeeded); 1572 1573 if (result != NULL) { 1574 assert(*succeeded, "sanity"); 1575 return result; 1576 } 1577 1578 assert(!collector_policy()->should_clear_all_soft_refs(), 1579 "Flag should have been handled and cleared prior to this point"); 1580 1581 // What else? We might try synchronous finalization later. If the total 1582 // space available is large enough for the allocation, then a more 1583 // complete compaction phase than we've tried so far might be 1584 // appropriate. 1585 assert(*succeeded, "sanity"); 1586 return NULL; 1587 } 1588 1589 // Attempting to expand the heap sufficiently 1590 // to support an allocation of the given "word_size". If 1591 // successful, perform the allocation and return the address of the 1592 // allocated block, or else "NULL". 1593 1594 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1595 assert_at_safepoint(true /* should_be_vm_thread */); 1596 1597 _verifier->verify_region_sets_optional(); 1598 1599 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1600 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1601 word_size * HeapWordSize); 1602 1603 1604 if (expand(expand_bytes)) { 1605 _hrm.verify_optional(); 1606 _verifier->verify_region_sets_optional(); 1607 return attempt_allocation_at_safepoint(word_size, 1608 context, 1609 false /* expect_null_mutator_alloc_region */); 1610 } 1611 return NULL; 1612 } 1613 1614 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) { 1615 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1616 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1617 HeapRegion::GrainBytes); 1618 1619 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B", 1620 expand_bytes, aligned_expand_bytes); 1621 1622 if (is_maximal_no_gc()) { 1623 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1624 return false; 1625 } 1626 1627 double expand_heap_start_time_sec = os::elapsedTime(); 1628 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1629 assert(regions_to_expand > 0, "Must expand by at least one region"); 1630 1631 uint expanded_by = _hrm.expand_by(regions_to_expand); 1632 if (expand_time_ms != NULL) { 1633 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1634 } 1635 1636 if (expanded_by > 0) { 1637 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1638 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1639 g1_policy()->record_new_heap_size(num_regions()); 1640 } else { 1641 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1642 1643 // The expansion of the virtual storage space was unsuccessful. 1644 // Let's see if it was because we ran out of swap. 1645 if (G1ExitOnExpansionFailure && 1646 _hrm.available() >= regions_to_expand) { 1647 // We had head room... 1648 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1649 } 1650 } 1651 return regions_to_expand > 0; 1652 } 1653 1654 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1655 size_t aligned_shrink_bytes = 1656 ReservedSpace::page_align_size_down(shrink_bytes); 1657 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1658 HeapRegion::GrainBytes); 1659 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1660 1661 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1662 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1663 1664 1665 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", 1666 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1667 if (num_regions_removed > 0) { 1668 g1_policy()->record_new_heap_size(num_regions()); 1669 } else { 1670 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1671 } 1672 } 1673 1674 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1675 _verifier->verify_region_sets_optional(); 1676 1677 // We should only reach here at the end of a Full GC which means we 1678 // should not not be holding to any GC alloc regions. The method 1679 // below will make sure of that and do any remaining clean up. 1680 _allocator->abandon_gc_alloc_regions(); 1681 1682 // Instead of tearing down / rebuilding the free lists here, we 1683 // could instead use the remove_all_pending() method on free_list to 1684 // remove only the ones that we need to remove. 1685 tear_down_region_sets(true /* free_list_only */); 1686 shrink_helper(shrink_bytes); 1687 rebuild_region_sets(true /* free_list_only */); 1688 1689 _hrm.verify_optional(); 1690 _verifier->verify_region_sets_optional(); 1691 } 1692 1693 // Public methods. 1694 1695 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1696 CollectedHeap(), 1697 _collector_policy(collector_policy), 1698 _g1_policy(create_g1_policy()), 1699 _collection_set(this, _g1_policy), 1700 _dirty_card_queue_set(false), 1701 _is_alive_closure_cm(this), 1702 _is_alive_closure_stw(this), 1703 _ref_processor_cm(NULL), 1704 _ref_processor_stw(NULL), 1705 _bot(NULL), 1706 _hot_card_cache(NULL), 1707 _g1_rem_set(NULL), 1708 _cg1r(NULL), 1709 _g1mm(NULL), 1710 _refine_cte_cl(NULL), 1711 _preserved_marks_set(true /* in_c_heap */), 1712 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1713 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1714 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1715 _humongous_reclaim_candidates(), 1716 _has_humongous_reclaim_candidates(false), 1717 _archive_allocator(NULL), 1718 _free_regions_coming(false), 1719 _gc_time_stamp(0), 1720 _summary_bytes_used(0), 1721 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1722 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1723 _expand_heap_after_alloc_failure(true), 1724 _old_marking_cycles_started(0), 1725 _old_marking_cycles_completed(0), 1726 _in_cset_fast_test(), 1727 _worker_cset_start_region(NULL), 1728 _worker_cset_start_region_time_stamp(NULL), 1729 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1730 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) { 1731 1732 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1733 /* are_GC_task_threads */true, 1734 /* are_ConcurrentGC_threads */false); 1735 _workers->initialize_workers(); 1736 _verifier = new G1HeapVerifier(this); 1737 1738 _allocator = G1Allocator::create_allocator(this); 1739 1740 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1741 1742 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1743 1744 // Override the default _filler_array_max_size so that no humongous filler 1745 // objects are created. 1746 _filler_array_max_size = _humongous_object_threshold_in_words; 1747 1748 uint n_queues = ParallelGCThreads; 1749 _task_queues = new RefToScanQueueSet(n_queues); 1750 1751 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1752 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC); 1753 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1754 1755 for (uint i = 0; i < n_queues; i++) { 1756 RefToScanQueue* q = new RefToScanQueue(); 1757 q->initialize(); 1758 _task_queues->register_queue(i, q); 1759 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1760 } 1761 clear_cset_start_regions(); 1762 1763 // Initialize the G1EvacuationFailureALot counters and flags. 1764 NOT_PRODUCT(reset_evacuation_should_fail();) 1765 1766 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1767 } 1768 1769 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1770 size_t size, 1771 size_t translation_factor) { 1772 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1773 // Allocate a new reserved space, preferring to use large pages. 1774 ReservedSpace rs(size, preferred_page_size); 1775 G1RegionToSpaceMapper* result = 1776 G1RegionToSpaceMapper::create_mapper(rs, 1777 size, 1778 rs.alignment(), 1779 HeapRegion::GrainBytes, 1780 translation_factor, 1781 mtGC); 1782 1783 os::trace_page_sizes_for_requested_size(description, 1784 size, 1785 preferred_page_size, 1786 rs.alignment(), 1787 rs.base(), 1788 rs.size()); 1789 1790 return result; 1791 } 1792 1793 jint G1CollectedHeap::initialize() { 1794 CollectedHeap::pre_initialize(); 1795 os::enable_vtime(); 1796 1797 // Necessary to satisfy locking discipline assertions. 1798 1799 MutexLocker x(Heap_lock); 1800 1801 // While there are no constraints in the GC code that HeapWordSize 1802 // be any particular value, there are multiple other areas in the 1803 // system which believe this to be true (e.g. oop->object_size in some 1804 // cases incorrectly returns the size in wordSize units rather than 1805 // HeapWordSize). 1806 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1807 1808 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1809 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1810 size_t heap_alignment = collector_policy()->heap_alignment(); 1811 1812 // Ensure that the sizes are properly aligned. 1813 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1814 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1815 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1816 1817 _refine_cte_cl = new RefineCardTableEntryClosure(); 1818 1819 jint ecode = JNI_OK; 1820 _cg1r = ConcurrentG1Refine::create(_refine_cte_cl, &ecode); 1821 if (_cg1r == NULL) { 1822 return ecode; 1823 } 1824 1825 // Reserve the maximum. 1826 1827 // When compressed oops are enabled, the preferred heap base 1828 // is calculated by subtracting the requested size from the 1829 // 32Gb boundary and using the result as the base address for 1830 // heap reservation. If the requested size is not aligned to 1831 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1832 // into the ReservedHeapSpace constructor) then the actual 1833 // base of the reserved heap may end up differing from the 1834 // address that was requested (i.e. the preferred heap base). 1835 // If this happens then we could end up using a non-optimal 1836 // compressed oops mode. 1837 1838 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1839 heap_alignment); 1840 1841 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1842 1843 // Create the barrier set for the entire reserved region. 1844 G1SATBCardTableLoggingModRefBS* bs 1845 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1846 bs->initialize(); 1847 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1848 set_barrier_set(bs); 1849 1850 // Create the hot card cache. 1851 _hot_card_cache = new G1HotCardCache(this); 1852 1853 // Also create a G1 rem set. 1854 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache); 1855 1856 // Carve out the G1 part of the heap. 1857 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1858 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1859 G1RegionToSpaceMapper* heap_storage = 1860 G1RegionToSpaceMapper::create_mapper(g1_rs, 1861 g1_rs.size(), 1862 page_size, 1863 HeapRegion::GrainBytes, 1864 1, 1865 mtJavaHeap); 1866 os::trace_page_sizes("Heap", 1867 collector_policy()->min_heap_byte_size(), 1868 max_byte_size, 1869 page_size, 1870 heap_rs.base(), 1871 heap_rs.size()); 1872 heap_storage->set_mapping_changed_listener(&_listener); 1873 1874 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1875 G1RegionToSpaceMapper* bot_storage = 1876 create_aux_memory_mapper("Block Offset Table", 1877 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1878 G1BlockOffsetTable::heap_map_factor()); 1879 1880 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1881 G1RegionToSpaceMapper* cardtable_storage = 1882 create_aux_memory_mapper("Card Table", 1883 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1884 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1885 1886 G1RegionToSpaceMapper* card_counts_storage = 1887 create_aux_memory_mapper("Card Counts Table", 1888 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1889 G1CardCounts::heap_map_factor()); 1890 1891 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1892 G1RegionToSpaceMapper* prev_bitmap_storage = 1893 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1894 G1RegionToSpaceMapper* next_bitmap_storage = 1895 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1896 1897 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1898 g1_barrier_set()->initialize(cardtable_storage); 1899 // Do later initialization work for concurrent refinement. 1900 _hot_card_cache->initialize(card_counts_storage); 1901 1902 // 6843694 - ensure that the maximum region index can fit 1903 // in the remembered set structures. 1904 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1905 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1906 1907 g1_rem_set()->initialize(max_capacity(), max_regions()); 1908 1909 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1910 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1911 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1912 "too many cards per region"); 1913 1914 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1915 1916 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1917 1918 { 1919 HeapWord* start = _hrm.reserved().start(); 1920 HeapWord* end = _hrm.reserved().end(); 1921 size_t granularity = HeapRegion::GrainBytes; 1922 1923 _in_cset_fast_test.initialize(start, end, granularity); 1924 _humongous_reclaim_candidates.initialize(start, end, granularity); 1925 } 1926 1927 // Create the G1ConcurrentMark data structure and thread. 1928 // (Must do this late, so that "max_regions" is defined.) 1929 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1930 if (_cm == NULL || !_cm->completed_initialization()) { 1931 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1932 return JNI_ENOMEM; 1933 } 1934 _cmThread = _cm->cmThread(); 1935 1936 // Now expand into the initial heap size. 1937 if (!expand(init_byte_size)) { 1938 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1939 return JNI_ENOMEM; 1940 } 1941 1942 // Perform any initialization actions delegated to the policy. 1943 g1_policy()->init(this, &_collection_set); 1944 1945 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1946 SATB_Q_FL_lock, 1947 G1SATBProcessCompletedThreshold, 1948 Shared_SATB_Q_lock); 1949 1950 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 1951 DirtyCardQ_CBL_mon, 1952 DirtyCardQ_FL_lock, 1953 (int)concurrent_g1_refine()->yellow_zone(), 1954 (int)concurrent_g1_refine()->red_zone(), 1955 Shared_DirtyCardQ_lock, 1956 NULL, // fl_owner 1957 true); // init_free_ids 1958 1959 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 1960 DirtyCardQ_CBL_mon, 1961 DirtyCardQ_FL_lock, 1962 -1, // never trigger processing 1963 -1, // no limit on length 1964 Shared_DirtyCardQ_lock, 1965 &JavaThread::dirty_card_queue_set()); 1966 1967 // Here we allocate the dummy HeapRegion that is required by the 1968 // G1AllocRegion class. 1969 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1970 1971 // We'll re-use the same region whether the alloc region will 1972 // require BOT updates or not and, if it doesn't, then a non-young 1973 // region will complain that it cannot support allocations without 1974 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1975 dummy_region->set_eden(); 1976 // Make sure it's full. 1977 dummy_region->set_top(dummy_region->end()); 1978 G1AllocRegion::setup(this, dummy_region); 1979 1980 _allocator->init_mutator_alloc_region(); 1981 1982 // Do create of the monitoring and management support so that 1983 // values in the heap have been properly initialized. 1984 _g1mm = new G1MonitoringSupport(this); 1985 1986 G1StringDedup::initialize(); 1987 1988 _preserved_marks_set.init(ParallelGCThreads); 1989 1990 return JNI_OK; 1991 } 1992 1993 void G1CollectedHeap::stop() { 1994 // Stop all concurrent threads. We do this to make sure these threads 1995 // do not continue to execute and access resources (e.g. logging) 1996 // that are destroyed during shutdown. 1997 _cg1r->stop(); 1998 _cmThread->stop(); 1999 if (G1StringDedup::is_enabled()) { 2000 G1StringDedup::stop(); 2001 } 2002 } 2003 2004 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2005 return HeapRegion::max_region_size(); 2006 } 2007 2008 void G1CollectedHeap::post_initialize() { 2009 ref_processing_init(); 2010 } 2011 2012 void G1CollectedHeap::ref_processing_init() { 2013 // Reference processing in G1 currently works as follows: 2014 // 2015 // * There are two reference processor instances. One is 2016 // used to record and process discovered references 2017 // during concurrent marking; the other is used to 2018 // record and process references during STW pauses 2019 // (both full and incremental). 2020 // * Both ref processors need to 'span' the entire heap as 2021 // the regions in the collection set may be dotted around. 2022 // 2023 // * For the concurrent marking ref processor: 2024 // * Reference discovery is enabled at initial marking. 2025 // * Reference discovery is disabled and the discovered 2026 // references processed etc during remarking. 2027 // * Reference discovery is MT (see below). 2028 // * Reference discovery requires a barrier (see below). 2029 // * Reference processing may or may not be MT 2030 // (depending on the value of ParallelRefProcEnabled 2031 // and ParallelGCThreads). 2032 // * A full GC disables reference discovery by the CM 2033 // ref processor and abandons any entries on it's 2034 // discovered lists. 2035 // 2036 // * For the STW processor: 2037 // * Non MT discovery is enabled at the start of a full GC. 2038 // * Processing and enqueueing during a full GC is non-MT. 2039 // * During a full GC, references are processed after marking. 2040 // 2041 // * Discovery (may or may not be MT) is enabled at the start 2042 // of an incremental evacuation pause. 2043 // * References are processed near the end of a STW evacuation pause. 2044 // * For both types of GC: 2045 // * Discovery is atomic - i.e. not concurrent. 2046 // * Reference discovery will not need a barrier. 2047 2048 MemRegion mr = reserved_region(); 2049 2050 // Concurrent Mark ref processor 2051 _ref_processor_cm = 2052 new ReferenceProcessor(mr, // span 2053 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2054 // mt processing 2055 ParallelGCThreads, 2056 // degree of mt processing 2057 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2058 // mt discovery 2059 MAX2(ParallelGCThreads, ConcGCThreads), 2060 // degree of mt discovery 2061 false, 2062 // Reference discovery is not atomic 2063 &_is_alive_closure_cm); 2064 // is alive closure 2065 // (for efficiency/performance) 2066 2067 // STW ref processor 2068 _ref_processor_stw = 2069 new ReferenceProcessor(mr, // span 2070 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2071 // mt processing 2072 ParallelGCThreads, 2073 // degree of mt processing 2074 (ParallelGCThreads > 1), 2075 // mt discovery 2076 ParallelGCThreads, 2077 // degree of mt discovery 2078 true, 2079 // Reference discovery is atomic 2080 &_is_alive_closure_stw); 2081 // is alive closure 2082 // (for efficiency/performance) 2083 } 2084 2085 CollectorPolicy* G1CollectedHeap::collector_policy() const { 2086 return _collector_policy; 2087 } 2088 2089 size_t G1CollectedHeap::capacity() const { 2090 return _hrm.length() * HeapRegion::GrainBytes; 2091 } 2092 2093 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2094 hr->reset_gc_time_stamp(); 2095 } 2096 2097 #ifndef PRODUCT 2098 2099 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2100 private: 2101 unsigned _gc_time_stamp; 2102 bool _failures; 2103 2104 public: 2105 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2106 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2107 2108 virtual bool doHeapRegion(HeapRegion* hr) { 2109 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2110 if (_gc_time_stamp != region_gc_time_stamp) { 2111 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 2112 region_gc_time_stamp, _gc_time_stamp); 2113 _failures = true; 2114 } 2115 return false; 2116 } 2117 2118 bool failures() { return _failures; } 2119 }; 2120 2121 void G1CollectedHeap::check_gc_time_stamps() { 2122 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2123 heap_region_iterate(&cl); 2124 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2125 } 2126 #endif // PRODUCT 2127 2128 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2129 _hot_card_cache->drain(cl, worker_i); 2130 } 2131 2132 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2133 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2134 size_t n_completed_buffers = 0; 2135 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2136 n_completed_buffers++; 2137 } 2138 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2139 dcqs.clear_n_completed_buffers(); 2140 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2141 } 2142 2143 // Computes the sum of the storage used by the various regions. 2144 size_t G1CollectedHeap::used() const { 2145 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2146 if (_archive_allocator != NULL) { 2147 result += _archive_allocator->used(); 2148 } 2149 return result; 2150 } 2151 2152 size_t G1CollectedHeap::used_unlocked() const { 2153 return _summary_bytes_used; 2154 } 2155 2156 class SumUsedClosure: public HeapRegionClosure { 2157 size_t _used; 2158 public: 2159 SumUsedClosure() : _used(0) {} 2160 bool doHeapRegion(HeapRegion* r) { 2161 _used += r->used(); 2162 return false; 2163 } 2164 size_t result() { return _used; } 2165 }; 2166 2167 size_t G1CollectedHeap::recalculate_used() const { 2168 double recalculate_used_start = os::elapsedTime(); 2169 2170 SumUsedClosure blk; 2171 heap_region_iterate(&blk); 2172 2173 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2174 return blk.result(); 2175 } 2176 2177 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2178 switch (cause) { 2179 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2180 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2181 case GCCause::_update_allocation_context_stats_inc: return true; 2182 case GCCause::_wb_conc_mark: return true; 2183 default : return false; 2184 } 2185 } 2186 2187 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2188 switch (cause) { 2189 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2190 case GCCause::_g1_humongous_allocation: return true; 2191 default: return is_user_requested_concurrent_full_gc(cause); 2192 } 2193 } 2194 2195 #ifndef PRODUCT 2196 void G1CollectedHeap::allocate_dummy_regions() { 2197 // Let's fill up most of the region 2198 size_t word_size = HeapRegion::GrainWords - 1024; 2199 // And as a result the region we'll allocate will be humongous. 2200 guarantee(is_humongous(word_size), "sanity"); 2201 2202 // _filler_array_max_size is set to humongous object threshold 2203 // but temporarily change it to use CollectedHeap::fill_with_object(). 2204 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2205 2206 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2207 // Let's use the existing mechanism for the allocation 2208 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2209 AllocationContext::system()); 2210 if (dummy_obj != NULL) { 2211 MemRegion mr(dummy_obj, word_size); 2212 CollectedHeap::fill_with_object(mr); 2213 } else { 2214 // If we can't allocate once, we probably cannot allocate 2215 // again. Let's get out of the loop. 2216 break; 2217 } 2218 } 2219 } 2220 #endif // !PRODUCT 2221 2222 void G1CollectedHeap::increment_old_marking_cycles_started() { 2223 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2224 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2225 "Wrong marking cycle count (started: %d, completed: %d)", 2226 _old_marking_cycles_started, _old_marking_cycles_completed); 2227 2228 _old_marking_cycles_started++; 2229 } 2230 2231 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2232 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2233 2234 // We assume that if concurrent == true, then the caller is a 2235 // concurrent thread that was joined the Suspendible Thread 2236 // Set. If there's ever a cheap way to check this, we should add an 2237 // assert here. 2238 2239 // Given that this method is called at the end of a Full GC or of a 2240 // concurrent cycle, and those can be nested (i.e., a Full GC can 2241 // interrupt a concurrent cycle), the number of full collections 2242 // completed should be either one (in the case where there was no 2243 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2244 // behind the number of full collections started. 2245 2246 // This is the case for the inner caller, i.e. a Full GC. 2247 assert(concurrent || 2248 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2249 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2250 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2251 "is inconsistent with _old_marking_cycles_completed = %u", 2252 _old_marking_cycles_started, _old_marking_cycles_completed); 2253 2254 // This is the case for the outer caller, i.e. the concurrent cycle. 2255 assert(!concurrent || 2256 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2257 "for outer caller (concurrent cycle): " 2258 "_old_marking_cycles_started = %u " 2259 "is inconsistent with _old_marking_cycles_completed = %u", 2260 _old_marking_cycles_started, _old_marking_cycles_completed); 2261 2262 _old_marking_cycles_completed += 1; 2263 2264 // We need to clear the "in_progress" flag in the CM thread before 2265 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2266 // is set) so that if a waiter requests another System.gc() it doesn't 2267 // incorrectly see that a marking cycle is still in progress. 2268 if (concurrent) { 2269 _cmThread->set_idle(); 2270 } 2271 2272 // This notify_all() will ensure that a thread that called 2273 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2274 // and it's waiting for a full GC to finish will be woken up. It is 2275 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2276 FullGCCount_lock->notify_all(); 2277 } 2278 2279 void G1CollectedHeap::collect(GCCause::Cause cause) { 2280 assert_heap_not_locked(); 2281 2282 uint gc_count_before; 2283 uint old_marking_count_before; 2284 uint full_gc_count_before; 2285 bool retry_gc; 2286 2287 do { 2288 retry_gc = false; 2289 2290 { 2291 MutexLocker ml(Heap_lock); 2292 2293 // Read the GC count while holding the Heap_lock 2294 gc_count_before = total_collections(); 2295 full_gc_count_before = total_full_collections(); 2296 old_marking_count_before = _old_marking_cycles_started; 2297 } 2298 2299 if (should_do_concurrent_full_gc(cause)) { 2300 // Schedule an initial-mark evacuation pause that will start a 2301 // concurrent cycle. We're setting word_size to 0 which means that 2302 // we are not requesting a post-GC allocation. 2303 VM_G1IncCollectionPause op(gc_count_before, 2304 0, /* word_size */ 2305 true, /* should_initiate_conc_mark */ 2306 g1_policy()->max_pause_time_ms(), 2307 cause); 2308 op.set_allocation_context(AllocationContext::current()); 2309 2310 VMThread::execute(&op); 2311 if (!op.pause_succeeded()) { 2312 if (old_marking_count_before == _old_marking_cycles_started) { 2313 retry_gc = op.should_retry_gc(); 2314 } else { 2315 // A Full GC happened while we were trying to schedule the 2316 // initial-mark GC. No point in starting a new cycle given 2317 // that the whole heap was collected anyway. 2318 } 2319 2320 if (retry_gc) { 2321 if (GCLocker::is_active_and_needs_gc()) { 2322 GCLocker::stall_until_clear(); 2323 } 2324 } 2325 } 2326 } else { 2327 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2328 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2329 2330 // Schedule a standard evacuation pause. We're setting word_size 2331 // to 0 which means that we are not requesting a post-GC allocation. 2332 VM_G1IncCollectionPause op(gc_count_before, 2333 0, /* word_size */ 2334 false, /* should_initiate_conc_mark */ 2335 g1_policy()->max_pause_time_ms(), 2336 cause); 2337 VMThread::execute(&op); 2338 } else { 2339 // Schedule a Full GC. 2340 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2341 VMThread::execute(&op); 2342 } 2343 } 2344 } while (retry_gc); 2345 } 2346 2347 bool G1CollectedHeap::is_in(const void* p) const { 2348 if (_hrm.reserved().contains(p)) { 2349 // Given that we know that p is in the reserved space, 2350 // heap_region_containing() should successfully 2351 // return the containing region. 2352 HeapRegion* hr = heap_region_containing(p); 2353 return hr->is_in(p); 2354 } else { 2355 return false; 2356 } 2357 } 2358 2359 #ifdef ASSERT 2360 bool G1CollectedHeap::is_in_exact(const void* p) const { 2361 bool contains = reserved_region().contains(p); 2362 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2363 if (contains && available) { 2364 return true; 2365 } else { 2366 return false; 2367 } 2368 } 2369 #endif 2370 2371 bool G1CollectedHeap::obj_in_cs(oop obj) { 2372 HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj); 2373 return r != NULL && r->in_collection_set(); 2374 } 2375 2376 // Iteration functions. 2377 2378 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2379 2380 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2381 ExtendedOopClosure* _cl; 2382 public: 2383 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2384 bool doHeapRegion(HeapRegion* r) { 2385 if (!r->is_continues_humongous()) { 2386 r->oop_iterate(_cl); 2387 } 2388 return false; 2389 } 2390 }; 2391 2392 // Iterates an ObjectClosure over all objects within a HeapRegion. 2393 2394 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2395 ObjectClosure* _cl; 2396 public: 2397 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2398 bool doHeapRegion(HeapRegion* r) { 2399 if (!r->is_continues_humongous()) { 2400 r->object_iterate(_cl); 2401 } 2402 return false; 2403 } 2404 }; 2405 2406 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2407 IterateObjectClosureRegionClosure blk(cl); 2408 heap_region_iterate(&blk); 2409 } 2410 2411 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2412 _hrm.iterate(cl); 2413 } 2414 2415 void 2416 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2417 uint worker_id, 2418 HeapRegionClaimer *hrclaimer, 2419 bool concurrent) const { 2420 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2421 } 2422 2423 // Clear the cached CSet starting regions and (more importantly) 2424 // the time stamps. Called when we reset the GC time stamp. 2425 void G1CollectedHeap::clear_cset_start_regions() { 2426 assert(_worker_cset_start_region != NULL, "sanity"); 2427 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2428 2429 for (uint i = 0; i < ParallelGCThreads; i++) { 2430 _worker_cset_start_region[i] = NULL; 2431 _worker_cset_start_region_time_stamp[i] = 0; 2432 } 2433 } 2434 2435 // Given the id of a worker, obtain or calculate a suitable 2436 // starting region for iterating over the current collection set. 2437 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2438 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2439 2440 HeapRegion* result = NULL; 2441 unsigned gc_time_stamp = get_gc_time_stamp(); 2442 2443 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2444 // Cached starting region for current worker was set 2445 // during the current pause - so it's valid. 2446 // Note: the cached starting heap region may be NULL 2447 // (when the collection set is empty). 2448 result = _worker_cset_start_region[worker_i]; 2449 assert(result == NULL || result->in_collection_set(), "sanity"); 2450 return result; 2451 } 2452 2453 // The cached entry was not valid so let's calculate 2454 // a suitable starting heap region for this worker. 2455 2456 // We want the parallel threads to start their collection 2457 // set iteration at different collection set regions to 2458 // avoid contention. 2459 // If we have: 2460 // n collection set regions 2461 // p threads 2462 // Then thread t will start at region floor ((t * n) / p) 2463 2464 result = collection_set()->head(); 2465 uint cs_size = collection_set()->region_length(); 2466 uint active_workers = workers()->active_workers(); 2467 2468 uint end_ind = (cs_size * worker_i) / active_workers; 2469 uint start_ind = 0; 2470 2471 if (worker_i > 0 && 2472 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2473 // Previous workers starting region is valid 2474 // so let's iterate from there 2475 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2476 OrderAccess::loadload(); 2477 result = _worker_cset_start_region[worker_i - 1]; 2478 } 2479 2480 for (uint i = start_ind; i < end_ind; i++) { 2481 result = result->next_in_collection_set(); 2482 } 2483 2484 // Note: the calculated starting heap region may be NULL 2485 // (when the collection set is empty). 2486 assert(result == NULL || result->in_collection_set(), "sanity"); 2487 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2488 "should be updated only once per pause"); 2489 _worker_cset_start_region[worker_i] = result; 2490 OrderAccess::storestore(); 2491 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2492 return result; 2493 } 2494 2495 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2496 HeapRegion* r = collection_set()->head(); 2497 while (r != NULL) { 2498 HeapRegion* next = r->next_in_collection_set(); 2499 if (cl->doHeapRegion(r)) { 2500 cl->incomplete(); 2501 return; 2502 } 2503 r = next; 2504 } 2505 } 2506 2507 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2508 HeapRegionClosure *cl) { 2509 if (r == NULL) { 2510 // The CSet is empty so there's nothing to do. 2511 return; 2512 } 2513 2514 assert(r->in_collection_set(), 2515 "Start region must be a member of the collection set."); 2516 HeapRegion* cur = r; 2517 while (cur != NULL) { 2518 HeapRegion* next = cur->next_in_collection_set(); 2519 if (cl->doHeapRegion(cur) && false) { 2520 cl->incomplete(); 2521 return; 2522 } 2523 cur = next; 2524 } 2525 cur = collection_set()->head(); 2526 while (cur != r) { 2527 HeapRegion* next = cur->next_in_collection_set(); 2528 if (cl->doHeapRegion(cur) && false) { 2529 cl->incomplete(); 2530 return; 2531 } 2532 cur = next; 2533 } 2534 } 2535 2536 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2537 HeapRegion* result = _hrm.next_region_in_heap(from); 2538 while (result != NULL && result->is_pinned()) { 2539 result = _hrm.next_region_in_heap(result); 2540 } 2541 return result; 2542 } 2543 2544 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2545 HeapRegion* hr = heap_region_containing(addr); 2546 return hr->block_start(addr); 2547 } 2548 2549 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2550 HeapRegion* hr = heap_region_containing(addr); 2551 return hr->block_size(addr); 2552 } 2553 2554 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2555 HeapRegion* hr = heap_region_containing(addr); 2556 return hr->block_is_obj(addr); 2557 } 2558 2559 bool G1CollectedHeap::supports_tlab_allocation() const { 2560 return true; 2561 } 2562 2563 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2564 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2565 } 2566 2567 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2568 return _eden.length() * HeapRegion::GrainBytes; 2569 } 2570 2571 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2572 // must be equal to the humongous object limit. 2573 size_t G1CollectedHeap::max_tlab_size() const { 2574 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2575 } 2576 2577 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2578 AllocationContext_t context = AllocationContext::current(); 2579 return _allocator->unsafe_max_tlab_alloc(context); 2580 } 2581 2582 size_t G1CollectedHeap::max_capacity() const { 2583 return _hrm.reserved().byte_size(); 2584 } 2585 2586 jlong G1CollectedHeap::millis_since_last_gc() { 2587 // assert(false, "NYI"); 2588 return 0; 2589 } 2590 2591 void G1CollectedHeap::prepare_for_verify() { 2592 _verifier->prepare_for_verify(); 2593 } 2594 2595 void G1CollectedHeap::verify(VerifyOption vo) { 2596 _verifier->verify(vo); 2597 } 2598 2599 class PrintRegionClosure: public HeapRegionClosure { 2600 outputStream* _st; 2601 public: 2602 PrintRegionClosure(outputStream* st) : _st(st) {} 2603 bool doHeapRegion(HeapRegion* r) { 2604 r->print_on(_st); 2605 return false; 2606 } 2607 }; 2608 2609 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2610 const HeapRegion* hr, 2611 const VerifyOption vo) const { 2612 switch (vo) { 2613 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2614 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2615 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 2616 default: ShouldNotReachHere(); 2617 } 2618 return false; // keep some compilers happy 2619 } 2620 2621 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2622 const VerifyOption vo) const { 2623 switch (vo) { 2624 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2625 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2626 case VerifyOption_G1UseMarkWord: { 2627 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 2628 return !obj->is_gc_marked() && !hr->is_archive(); 2629 } 2630 default: ShouldNotReachHere(); 2631 } 2632 return false; // keep some compilers happy 2633 } 2634 2635 void G1CollectedHeap::print_heap_regions() const { 2636 Log(gc, heap, region) log; 2637 if (log.is_trace()) { 2638 ResourceMark rm; 2639 print_regions_on(log.trace_stream()); 2640 } 2641 } 2642 2643 void G1CollectedHeap::print_on(outputStream* st) const { 2644 st->print(" %-20s", "garbage-first heap"); 2645 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2646 capacity()/K, used_unlocked()/K); 2647 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 2648 p2i(_hrm.reserved().start()), 2649 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 2650 p2i(_hrm.reserved().end())); 2651 st->cr(); 2652 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2653 uint young_regions = young_regions_count(); 2654 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2655 (size_t) young_regions * HeapRegion::GrainBytes / K); 2656 uint survivor_regions = survivor_regions_count(); 2657 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2658 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2659 st->cr(); 2660 MetaspaceAux::print_on(st); 2661 } 2662 2663 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2664 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2665 "HS=humongous(starts), HC=humongous(continues), " 2666 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2667 "AC=allocation context, " 2668 "TAMS=top-at-mark-start (previous, next)"); 2669 PrintRegionClosure blk(st); 2670 heap_region_iterate(&blk); 2671 } 2672 2673 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2674 print_on(st); 2675 2676 // Print the per-region information. 2677 print_regions_on(st); 2678 } 2679 2680 void G1CollectedHeap::print_on_error(outputStream* st) const { 2681 this->CollectedHeap::print_on_error(st); 2682 2683 if (_cm != NULL) { 2684 st->cr(); 2685 _cm->print_on_error(st); 2686 } 2687 } 2688 2689 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2690 workers()->print_worker_threads_on(st); 2691 _cmThread->print_on(st); 2692 st->cr(); 2693 _cm->print_worker_threads_on(st); 2694 _cg1r->print_worker_threads_on(st); // also prints the sample thread 2695 if (G1StringDedup::is_enabled()) { 2696 G1StringDedup::print_worker_threads_on(st); 2697 } 2698 } 2699 2700 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2701 workers()->threads_do(tc); 2702 tc->do_thread(_cmThread); 2703 _cm->threads_do(tc); 2704 _cg1r->threads_do(tc); // also iterates over the sample thread 2705 if (G1StringDedup::is_enabled()) { 2706 G1StringDedup::threads_do(tc); 2707 } 2708 } 2709 2710 void G1CollectedHeap::print_tracing_info() const { 2711 g1_rem_set()->print_summary_info(); 2712 concurrent_mark()->print_summary_info(); 2713 } 2714 2715 #ifndef PRODUCT 2716 // Helpful for debugging RSet issues. 2717 2718 class PrintRSetsClosure : public HeapRegionClosure { 2719 private: 2720 const char* _msg; 2721 size_t _occupied_sum; 2722 2723 public: 2724 bool doHeapRegion(HeapRegion* r) { 2725 HeapRegionRemSet* hrrs = r->rem_set(); 2726 size_t occupied = hrrs->occupied(); 2727 _occupied_sum += occupied; 2728 2729 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2730 if (occupied == 0) { 2731 tty->print_cr(" RSet is empty"); 2732 } else { 2733 hrrs->print(); 2734 } 2735 tty->print_cr("----------"); 2736 return false; 2737 } 2738 2739 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2740 tty->cr(); 2741 tty->print_cr("========================================"); 2742 tty->print_cr("%s", msg); 2743 tty->cr(); 2744 } 2745 2746 ~PrintRSetsClosure() { 2747 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2748 tty->print_cr("========================================"); 2749 tty->cr(); 2750 } 2751 }; 2752 2753 void G1CollectedHeap::print_cset_rsets() { 2754 PrintRSetsClosure cl("Printing CSet RSets"); 2755 collection_set_iterate(&cl); 2756 } 2757 2758 void G1CollectedHeap::print_all_rsets() { 2759 PrintRSetsClosure cl("Printing All RSets");; 2760 heap_region_iterate(&cl); 2761 } 2762 #endif // PRODUCT 2763 2764 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2765 2766 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2767 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2768 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2769 2770 size_t eden_capacity_bytes = 2771 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2772 2773 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2774 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2775 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2776 } 2777 2778 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2779 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2780 stats->unused(), stats->used(), stats->region_end_waste(), 2781 stats->regions_filled(), stats->direct_allocated(), 2782 stats->failure_used(), stats->failure_waste()); 2783 } 2784 2785 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2786 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2787 gc_tracer->report_gc_heap_summary(when, heap_summary); 2788 2789 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2790 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2791 } 2792 2793 G1CollectedHeap* G1CollectedHeap::heap() { 2794 CollectedHeap* heap = Universe::heap(); 2795 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2796 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2797 return (G1CollectedHeap*)heap; 2798 } 2799 2800 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 2801 // always_do_update_barrier = false; 2802 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2803 // Fill TLAB's and such 2804 accumulate_statistics_all_tlabs(); 2805 ensure_parsability(true); 2806 2807 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2808 } 2809 2810 void G1CollectedHeap::gc_epilogue(bool full) { 2811 // we are at the end of the GC. Total collections has already been increased. 2812 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2813 2814 // FIXME: what is this about? 2815 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2816 // is set. 2817 #if defined(COMPILER2) || INCLUDE_JVMCI 2818 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2819 #endif 2820 // always_do_update_barrier = true; 2821 2822 resize_all_tlabs(); 2823 allocation_context_stats().update(full); 2824 2825 // We have just completed a GC. Update the soft reference 2826 // policy with the new heap occupancy 2827 Universe::update_heap_info_at_gc(); 2828 } 2829 2830 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2831 uint gc_count_before, 2832 bool* succeeded, 2833 GCCause::Cause gc_cause) { 2834 assert_heap_not_locked_and_not_at_safepoint(); 2835 VM_G1IncCollectionPause op(gc_count_before, 2836 word_size, 2837 false, /* should_initiate_conc_mark */ 2838 g1_policy()->max_pause_time_ms(), 2839 gc_cause); 2840 2841 op.set_allocation_context(AllocationContext::current()); 2842 VMThread::execute(&op); 2843 2844 HeapWord* result = op.result(); 2845 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2846 assert(result == NULL || ret_succeeded, 2847 "the result should be NULL if the VM did not succeed"); 2848 *succeeded = ret_succeeded; 2849 2850 assert_heap_not_locked(); 2851 return result; 2852 } 2853 2854 void 2855 G1CollectedHeap::doConcurrentMark() { 2856 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2857 if (!_cmThread->in_progress()) { 2858 _cmThread->set_started(); 2859 CGC_lock->notify(); 2860 } 2861 } 2862 2863 size_t G1CollectedHeap::pending_card_num() { 2864 size_t extra_cards = 0; 2865 JavaThread *curr = Threads::first(); 2866 while (curr != NULL) { 2867 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2868 extra_cards += dcq.size(); 2869 curr = curr->next(); 2870 } 2871 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2872 size_t buffer_size = dcqs.buffer_size(); 2873 size_t buffer_num = dcqs.completed_buffers_num(); 2874 2875 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 2876 // in bytes - not the number of 'entries'. We need to convert 2877 // into a number of cards. 2878 return (buffer_size * buffer_num + extra_cards) / oopSize; 2879 } 2880 2881 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2882 private: 2883 size_t _total_humongous; 2884 size_t _candidate_humongous; 2885 2886 DirtyCardQueue _dcq; 2887 2888 // We don't nominate objects with many remembered set entries, on 2889 // the assumption that such objects are likely still live. 2890 bool is_remset_small(HeapRegion* region) const { 2891 HeapRegionRemSet* const rset = region->rem_set(); 2892 return G1EagerReclaimHumongousObjectsWithStaleRefs 2893 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2894 : rset->is_empty(); 2895 } 2896 2897 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2898 assert(region->is_starts_humongous(), "Must start a humongous object"); 2899 2900 oop obj = oop(region->bottom()); 2901 2902 // Dead objects cannot be eager reclaim candidates. Due to class 2903 // unloading it is unsafe to query their classes so we return early. 2904 if (heap->is_obj_dead(obj, region)) { 2905 return false; 2906 } 2907 2908 // Candidate selection must satisfy the following constraints 2909 // while concurrent marking is in progress: 2910 // 2911 // * In order to maintain SATB invariants, an object must not be 2912 // reclaimed if it was allocated before the start of marking and 2913 // has not had its references scanned. Such an object must have 2914 // its references (including type metadata) scanned to ensure no 2915 // live objects are missed by the marking process. Objects 2916 // allocated after the start of concurrent marking don't need to 2917 // be scanned. 2918 // 2919 // * An object must not be reclaimed if it is on the concurrent 2920 // mark stack. Objects allocated after the start of concurrent 2921 // marking are never pushed on the mark stack. 2922 // 2923 // Nominating only objects allocated after the start of concurrent 2924 // marking is sufficient to meet both constraints. This may miss 2925 // some objects that satisfy the constraints, but the marking data 2926 // structures don't support efficiently performing the needed 2927 // additional tests or scrubbing of the mark stack. 2928 // 2929 // However, we presently only nominate is_typeArray() objects. 2930 // A humongous object containing references induces remembered 2931 // set entries on other regions. In order to reclaim such an 2932 // object, those remembered sets would need to be cleaned up. 2933 // 2934 // We also treat is_typeArray() objects specially, allowing them 2935 // to be reclaimed even if allocated before the start of 2936 // concurrent mark. For this we rely on mark stack insertion to 2937 // exclude is_typeArray() objects, preventing reclaiming an object 2938 // that is in the mark stack. We also rely on the metadata for 2939 // such objects to be built-in and so ensured to be kept live. 2940 // Frequent allocation and drop of large binary blobs is an 2941 // important use case for eager reclaim, and this special handling 2942 // may reduce needed headroom. 2943 2944 return obj->is_typeArray() && is_remset_small(region); 2945 } 2946 2947 public: 2948 RegisterHumongousWithInCSetFastTestClosure() 2949 : _total_humongous(0), 2950 _candidate_humongous(0), 2951 _dcq(&JavaThread::dirty_card_queue_set()) { 2952 } 2953 2954 virtual bool doHeapRegion(HeapRegion* r) { 2955 if (!r->is_starts_humongous()) { 2956 return false; 2957 } 2958 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2959 2960 bool is_candidate = humongous_region_is_candidate(g1h, r); 2961 uint rindex = r->hrm_index(); 2962 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2963 if (is_candidate) { 2964 _candidate_humongous++; 2965 g1h->register_humongous_region_with_cset(rindex); 2966 // Is_candidate already filters out humongous object with large remembered sets. 2967 // If we have a humongous object with a few remembered sets, we simply flush these 2968 // remembered set entries into the DCQS. That will result in automatic 2969 // re-evaluation of their remembered set entries during the following evacuation 2970 // phase. 2971 if (!r->rem_set()->is_empty()) { 2972 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2973 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2974 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 2975 HeapRegionRemSetIterator hrrs(r->rem_set()); 2976 size_t card_index; 2977 while (hrrs.has_next(card_index)) { 2978 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 2979 // The remembered set might contain references to already freed 2980 // regions. Filter out such entries to avoid failing card table 2981 // verification. 2982 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 2983 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 2984 *card_ptr = CardTableModRefBS::dirty_card_val(); 2985 _dcq.enqueue(card_ptr); 2986 } 2987 } 2988 } 2989 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2990 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2991 hrrs.n_yielded(), r->rem_set()->occupied()); 2992 r->rem_set()->clear_locked(); 2993 } 2994 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2995 } 2996 _total_humongous++; 2997 2998 return false; 2999 } 3000 3001 size_t total_humongous() const { return _total_humongous; } 3002 size_t candidate_humongous() const { return _candidate_humongous; } 3003 3004 void flush_rem_set_entries() { _dcq.flush(); } 3005 }; 3006 3007 void G1CollectedHeap::register_humongous_regions_with_cset() { 3008 if (!G1EagerReclaimHumongousObjects) { 3009 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 3010 return; 3011 } 3012 double time = os::elapsed_counter(); 3013 3014 // Collect reclaim candidate information and register candidates with cset. 3015 RegisterHumongousWithInCSetFastTestClosure cl; 3016 heap_region_iterate(&cl); 3017 3018 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 3019 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 3020 cl.total_humongous(), 3021 cl.candidate_humongous()); 3022 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3023 3024 // Finally flush all remembered set entries to re-check into the global DCQS. 3025 cl.flush_rem_set_entries(); 3026 } 3027 3028 class VerifyRegionRemSetClosure : public HeapRegionClosure { 3029 public: 3030 bool doHeapRegion(HeapRegion* hr) { 3031 if (!hr->is_archive() && !hr->is_continues_humongous()) { 3032 hr->verify_rem_set(); 3033 } 3034 return false; 3035 } 3036 }; 3037 3038 uint G1CollectedHeap::num_task_queues() const { 3039 return _task_queues->size(); 3040 } 3041 3042 #if TASKQUEUE_STATS 3043 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3044 st->print_raw_cr("GC Task Stats"); 3045 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3046 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3047 } 3048 3049 void G1CollectedHeap::print_taskqueue_stats() const { 3050 if (!log_is_enabled(Trace, gc, task, stats)) { 3051 return; 3052 } 3053 Log(gc, task, stats) log; 3054 ResourceMark rm; 3055 outputStream* st = log.trace_stream(); 3056 3057 print_taskqueue_stats_hdr(st); 3058 3059 TaskQueueStats totals; 3060 const uint n = num_task_queues(); 3061 for (uint i = 0; i < n; ++i) { 3062 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 3063 totals += task_queue(i)->stats; 3064 } 3065 st->print_raw("tot "); totals.print(st); st->cr(); 3066 3067 DEBUG_ONLY(totals.verify()); 3068 } 3069 3070 void G1CollectedHeap::reset_taskqueue_stats() { 3071 const uint n = num_task_queues(); 3072 for (uint i = 0; i < n; ++i) { 3073 task_queue(i)->stats.reset(); 3074 } 3075 } 3076 #endif // TASKQUEUE_STATS 3077 3078 void G1CollectedHeap::wait_for_root_region_scanning() { 3079 double scan_wait_start = os::elapsedTime(); 3080 // We have to wait until the CM threads finish scanning the 3081 // root regions as it's the only way to ensure that all the 3082 // objects on them have been correctly scanned before we start 3083 // moving them during the GC. 3084 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3085 double wait_time_ms = 0.0; 3086 if (waited) { 3087 double scan_wait_end = os::elapsedTime(); 3088 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3089 } 3090 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3091 } 3092 3093 bool 3094 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3095 assert_at_safepoint(true /* should_be_vm_thread */); 3096 guarantee(!is_gc_active(), "collection is not reentrant"); 3097 3098 if (GCLocker::check_active_before_gc()) { 3099 return false; 3100 } 3101 3102 _gc_timer_stw->register_gc_start(); 3103 3104 GCIdMark gc_id_mark; 3105 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3106 3107 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3108 ResourceMark rm; 3109 3110 g1_policy()->note_gc_start(); 3111 3112 wait_for_root_region_scanning(); 3113 3114 print_heap_before_gc(); 3115 print_heap_regions(); 3116 trace_heap_before_gc(_gc_tracer_stw); 3117 3118 _verifier->verify_region_sets_optional(); 3119 _verifier->verify_dirty_young_regions(); 3120 3121 // We should not be doing initial mark unless the conc mark thread is running 3122 if (!_cmThread->should_terminate()) { 3123 // This call will decide whether this pause is an initial-mark 3124 // pause. If it is, during_initial_mark_pause() will return true 3125 // for the duration of this pause. 3126 g1_policy()->decide_on_conc_mark_initiation(); 3127 } 3128 3129 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3130 assert(!collector_state()->during_initial_mark_pause() || 3131 collector_state()->gcs_are_young(), "sanity"); 3132 3133 // We also do not allow mixed GCs during marking. 3134 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3135 3136 // Record whether this pause is an initial mark. When the current 3137 // thread has completed its logging output and it's safe to signal 3138 // the CM thread, the flag's value in the policy has been reset. 3139 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3140 3141 // Inner scope for scope based logging, timers, and stats collection 3142 { 3143 EvacuationInfo evacuation_info; 3144 3145 if (collector_state()->during_initial_mark_pause()) { 3146 // We are about to start a marking cycle, so we increment the 3147 // full collection counter. 3148 increment_old_marking_cycles_started(); 3149 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 3150 } 3151 3152 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3153 3154 GCTraceCPUTime tcpu; 3155 3156 FormatBuffer<> gc_string("Pause "); 3157 if (collector_state()->during_initial_mark_pause()) { 3158 gc_string.append("Initial Mark"); 3159 } else if (collector_state()->gcs_are_young()) { 3160 gc_string.append("Young"); 3161 } else { 3162 gc_string.append("Mixed"); 3163 } 3164 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 3165 3166 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3167 workers()->active_workers(), 3168 Threads::number_of_non_daemon_threads()); 3169 workers()->set_active_workers(active_workers); 3170 3171 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3172 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3173 3174 // If the secondary_free_list is not empty, append it to the 3175 // free_list. No need to wait for the cleanup operation to finish; 3176 // the region allocation code will check the secondary_free_list 3177 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3178 // set, skip this step so that the region allocation code has to 3179 // get entries from the secondary_free_list. 3180 if (!G1StressConcRegionFreeing) { 3181 append_secondary_free_list_if_not_empty_with_lock(); 3182 } 3183 3184 G1HeapTransition heap_transition(this); 3185 size_t heap_used_bytes_before_gc = used(); 3186 3187 // Don't dynamically change the number of GC threads this early. A value of 3188 // 0 is used to indicate serial work. When parallel work is done, 3189 // it will be set. 3190 3191 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3192 IsGCActiveMark x; 3193 3194 gc_prologue(false); 3195 increment_total_collections(false /* full gc */); 3196 increment_gc_time_stamp(); 3197 3198 if (VerifyRememberedSets) { 3199 log_info(gc, verify)("[Verifying RemSets before GC]"); 3200 VerifyRegionRemSetClosure v_cl; 3201 heap_region_iterate(&v_cl); 3202 } 3203 3204 _verifier->verify_before_gc(); 3205 3206 _verifier->check_bitmaps("GC Start"); 3207 3208 #if defined(COMPILER2) || INCLUDE_JVMCI 3209 DerivedPointerTable::clear(); 3210 #endif 3211 3212 // Please see comment in g1CollectedHeap.hpp and 3213 // G1CollectedHeap::ref_processing_init() to see how 3214 // reference processing currently works in G1. 3215 3216 // Enable discovery in the STW reference processor 3217 if (g1_policy()->should_process_references()) { 3218 ref_processor_stw()->enable_discovery(); 3219 } else { 3220 ref_processor_stw()->disable_discovery(); 3221 } 3222 3223 { 3224 // We want to temporarily turn off discovery by the 3225 // CM ref processor, if necessary, and turn it back on 3226 // on again later if we do. Using a scoped 3227 // NoRefDiscovery object will do this. 3228 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3229 3230 // Forget the current alloc region (we might even choose it to be part 3231 // of the collection set!). 3232 _allocator->release_mutator_alloc_region(); 3233 3234 // This timing is only used by the ergonomics to handle our pause target. 3235 // It is unclear why this should not include the full pause. We will 3236 // investigate this in CR 7178365. 3237 // 3238 // Preserving the old comment here if that helps the investigation: 3239 // 3240 // The elapsed time induced by the start time below deliberately elides 3241 // the possible verification above. 3242 double sample_start_time_sec = os::elapsedTime(); 3243 3244 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3245 3246 if (collector_state()->during_initial_mark_pause()) { 3247 concurrent_mark()->checkpointRootsInitialPre(); 3248 } 3249 3250 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 3251 3252 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3253 3254 // Make sure the remembered sets are up to date. This needs to be 3255 // done before register_humongous_regions_with_cset(), because the 3256 // remembered sets are used there to choose eager reclaim candidates. 3257 // If the remembered sets are not up to date we might miss some 3258 // entries that need to be handled. 3259 g1_rem_set()->cleanupHRRS(); 3260 3261 register_humongous_regions_with_cset(); 3262 3263 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3264 3265 _cm->note_start_of_gc(); 3266 // We call this after finalize_cset() to 3267 // ensure that the CSet has been finalized. 3268 _cm->verify_no_cset_oops(); 3269 3270 if (_hr_printer.is_active()) { 3271 HeapRegion* hr = collection_set()->head(); 3272 while (hr != NULL) { 3273 _hr_printer.cset(hr); 3274 hr = hr->next_in_collection_set(); 3275 } 3276 } 3277 3278 // Initialize the GC alloc regions. 3279 _allocator->init_gc_alloc_regions(evacuation_info); 3280 3281 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3282 pre_evacuate_collection_set(); 3283 3284 // Actually do the work... 3285 evacuate_collection_set(evacuation_info, &per_thread_states); 3286 3287 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3288 3289 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3290 free_collection_set(collection_set()->head(), evacuation_info, surviving_young_words); 3291 3292 eagerly_reclaim_humongous_regions(); 3293 3294 collection_set()->clear_head(); 3295 3296 record_obj_copy_mem_stats(); 3297 _survivor_evac_stats.adjust_desired_plab_sz(); 3298 _old_evac_stats.adjust_desired_plab_sz(); 3299 3300 // Start a new incremental collection set for the next pause. 3301 collection_set()->start_incremental_building(); 3302 3303 clear_cset_fast_test(); 3304 3305 guarantee(_eden.length() == 0, "eden should have been cleared"); 3306 g1_policy()->transfer_survivors_to_cset(survivor()); 3307 3308 if (evacuation_failed()) { 3309 set_used(recalculate_used()); 3310 if (_archive_allocator != NULL) { 3311 _archive_allocator->clear_used(); 3312 } 3313 for (uint i = 0; i < ParallelGCThreads; i++) { 3314 if (_evacuation_failed_info_array[i].has_failed()) { 3315 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3316 } 3317 } 3318 } else { 3319 // The "used" of the the collection set have already been subtracted 3320 // when they were freed. Add in the bytes evacuated. 3321 increase_used(g1_policy()->bytes_copied_during_gc()); 3322 } 3323 3324 if (collector_state()->during_initial_mark_pause()) { 3325 // We have to do this before we notify the CM threads that 3326 // they can start working to make sure that all the 3327 // appropriate initialization is done on the CM object. 3328 concurrent_mark()->checkpointRootsInitialPost(); 3329 collector_state()->set_mark_in_progress(true); 3330 // Note that we don't actually trigger the CM thread at 3331 // this point. We do that later when we're sure that 3332 // the current thread has completed its logging output. 3333 } 3334 3335 allocate_dummy_regions(); 3336 3337 _allocator->init_mutator_alloc_region(); 3338 3339 { 3340 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3341 if (expand_bytes > 0) { 3342 size_t bytes_before = capacity(); 3343 // No need for an ergo logging here, 3344 // expansion_amount() does this when it returns a value > 0. 3345 double expand_ms; 3346 if (!expand(expand_bytes, &expand_ms)) { 3347 // We failed to expand the heap. Cannot do anything about it. 3348 } 3349 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3350 } 3351 } 3352 3353 // We redo the verification but now wrt to the new CSet which 3354 // has just got initialized after the previous CSet was freed. 3355 _cm->verify_no_cset_oops(); 3356 _cm->note_end_of_gc(); 3357 3358 // This timing is only used by the ergonomics to handle our pause target. 3359 // It is unclear why this should not include the full pause. We will 3360 // investigate this in CR 7178365. 3361 double sample_end_time_sec = os::elapsedTime(); 3362 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3363 size_t total_cards_scanned = per_thread_states.total_cards_scanned(); 3364 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3365 3366 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3367 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3368 3369 MemoryService::track_memory_usage(); 3370 3371 // In prepare_for_verify() below we'll need to scan the deferred 3372 // update buffers to bring the RSets up-to-date if 3373 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3374 // the update buffers we'll probably need to scan cards on the 3375 // regions we just allocated to (i.e., the GC alloc 3376 // regions). However, during the last GC we called 3377 // set_saved_mark() on all the GC alloc regions, so card 3378 // scanning might skip the [saved_mark_word()...top()] area of 3379 // those regions (i.e., the area we allocated objects into 3380 // during the last GC). But it shouldn't. Given that 3381 // saved_mark_word() is conditional on whether the GC time stamp 3382 // on the region is current or not, by incrementing the GC time 3383 // stamp here we invalidate all the GC time stamps on all the 3384 // regions and saved_mark_word() will simply return top() for 3385 // all the regions. This is a nicer way of ensuring this rather 3386 // than iterating over the regions and fixing them. In fact, the 3387 // GC time stamp increment here also ensures that 3388 // saved_mark_word() will return top() between pauses, i.e., 3389 // during concurrent refinement. So we don't need the 3390 // is_gc_active() check to decided which top to use when 3391 // scanning cards (see CR 7039627). 3392 increment_gc_time_stamp(); 3393 3394 if (VerifyRememberedSets) { 3395 log_info(gc, verify)("[Verifying RemSets after GC]"); 3396 VerifyRegionRemSetClosure v_cl; 3397 heap_region_iterate(&v_cl); 3398 } 3399 3400 _verifier->verify_after_gc(); 3401 _verifier->check_bitmaps("GC End"); 3402 3403 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3404 ref_processor_stw()->verify_no_references_recorded(); 3405 3406 // CM reference discovery will be re-enabled if necessary. 3407 } 3408 3409 #ifdef TRACESPINNING 3410 ParallelTaskTerminator::print_termination_counts(); 3411 #endif 3412 3413 gc_epilogue(false); 3414 } 3415 3416 // Print the remainder of the GC log output. 3417 if (evacuation_failed()) { 3418 log_info(gc)("To-space exhausted"); 3419 } 3420 3421 g1_policy()->print_phases(); 3422 heap_transition.print(); 3423 3424 // It is not yet to safe to tell the concurrent mark to 3425 // start as we have some optional output below. We don't want the 3426 // output from the concurrent mark thread interfering with this 3427 // logging output either. 3428 3429 _hrm.verify_optional(); 3430 _verifier->verify_region_sets_optional(); 3431 3432 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3433 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3434 3435 print_heap_after_gc(); 3436 print_heap_regions(); 3437 trace_heap_after_gc(_gc_tracer_stw); 3438 3439 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3440 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3441 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3442 // before any GC notifications are raised. 3443 g1mm()->update_sizes(); 3444 3445 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3446 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3447 _gc_timer_stw->register_gc_end(); 3448 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3449 } 3450 // It should now be safe to tell the concurrent mark thread to start 3451 // without its logging output interfering with the logging output 3452 // that came from the pause. 3453 3454 if (should_start_conc_mark) { 3455 // CAUTION: after the doConcurrentMark() call below, 3456 // the concurrent marking thread(s) could be running 3457 // concurrently with us. Make sure that anything after 3458 // this point does not assume that we are the only GC thread 3459 // running. Note: of course, the actual marking work will 3460 // not start until the safepoint itself is released in 3461 // SuspendibleThreadSet::desynchronize(). 3462 doConcurrentMark(); 3463 } 3464 3465 return true; 3466 } 3467 3468 void G1CollectedHeap::remove_self_forwarding_pointers() { 3469 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3470 workers()->run_task(&rsfp_task); 3471 } 3472 3473 void G1CollectedHeap::restore_after_evac_failure() { 3474 double remove_self_forwards_start = os::elapsedTime(); 3475 3476 remove_self_forwarding_pointers(); 3477 _preserved_marks_set.restore(workers()); 3478 3479 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3480 } 3481 3482 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3483 if (!_evacuation_failed) { 3484 _evacuation_failed = true; 3485 } 3486 3487 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3488 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3489 } 3490 3491 bool G1ParEvacuateFollowersClosure::offer_termination() { 3492 G1ParScanThreadState* const pss = par_scan_state(); 3493 start_term_time(); 3494 const bool res = terminator()->offer_termination(); 3495 end_term_time(); 3496 return res; 3497 } 3498 3499 void G1ParEvacuateFollowersClosure::do_void() { 3500 G1ParScanThreadState* const pss = par_scan_state(); 3501 pss->trim_queue(); 3502 do { 3503 pss->steal_and_trim_queue(queues()); 3504 } while (!offer_termination()); 3505 } 3506 3507 class G1ParTask : public AbstractGangTask { 3508 protected: 3509 G1CollectedHeap* _g1h; 3510 G1ParScanThreadStateSet* _pss; 3511 RefToScanQueueSet* _queues; 3512 G1RootProcessor* _root_processor; 3513 ParallelTaskTerminator _terminator; 3514 uint _n_workers; 3515 3516 public: 3517 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3518 : AbstractGangTask("G1 collection"), 3519 _g1h(g1h), 3520 _pss(per_thread_states), 3521 _queues(task_queues), 3522 _root_processor(root_processor), 3523 _terminator(n_workers, _queues), 3524 _n_workers(n_workers) 3525 {} 3526 3527 void work(uint worker_id) { 3528 if (worker_id >= _n_workers) return; // no work needed this round 3529 3530 double start_sec = os::elapsedTime(); 3531 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3532 3533 { 3534 ResourceMark rm; 3535 HandleMark hm; 3536 3537 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3538 3539 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3540 pss->set_ref_processor(rp); 3541 3542 double start_strong_roots_sec = os::elapsedTime(); 3543 3544 _root_processor->evacuate_roots(pss->closures(), worker_id); 3545 3546 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss); 3547 3548 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3549 // treating the nmethods visited to act as roots for concurrent marking. 3550 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3551 // objects copied by the current evacuation. 3552 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl, 3553 pss->closures()->weak_codeblobs(), 3554 worker_id); 3555 3556 _pss->add_cards_scanned(worker_id, cards_scanned); 3557 3558 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3559 3560 double term_sec = 0.0; 3561 size_t evac_term_attempts = 0; 3562 { 3563 double start = os::elapsedTime(); 3564 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3565 evac.do_void(); 3566 3567 evac_term_attempts = evac.term_attempts(); 3568 term_sec = evac.term_time(); 3569 double elapsed_sec = os::elapsedTime() - start; 3570 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3571 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3572 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3573 } 3574 3575 assert(pss->queue_is_empty(), "should be empty"); 3576 3577 if (log_is_enabled(Debug, gc, task, stats)) { 3578 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3579 size_t lab_waste; 3580 size_t lab_undo_waste; 3581 pss->waste(lab_waste, lab_undo_waste); 3582 _g1h->print_termination_stats(worker_id, 3583 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3584 strong_roots_sec * 1000.0, /* strong roots time */ 3585 term_sec * 1000.0, /* evac term time */ 3586 evac_term_attempts, /* evac term attempts */ 3587 lab_waste, /* alloc buffer waste */ 3588 lab_undo_waste /* undo waste */ 3589 ); 3590 } 3591 3592 // Close the inner scope so that the ResourceMark and HandleMark 3593 // destructors are executed here and are included as part of the 3594 // "GC Worker Time". 3595 } 3596 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3597 } 3598 }; 3599 3600 void G1CollectedHeap::print_termination_stats_hdr() { 3601 log_debug(gc, task, stats)("GC Termination Stats"); 3602 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3603 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3604 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3605 } 3606 3607 void G1CollectedHeap::print_termination_stats(uint worker_id, 3608 double elapsed_ms, 3609 double strong_roots_ms, 3610 double term_ms, 3611 size_t term_attempts, 3612 size_t alloc_buffer_waste, 3613 size_t undo_waste) const { 3614 log_debug(gc, task, stats) 3615 ("%3d %9.2f %9.2f %6.2f " 3616 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3617 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3618 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3619 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3620 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3621 alloc_buffer_waste * HeapWordSize / K, 3622 undo_waste * HeapWordSize / K); 3623 } 3624 3625 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 3626 private: 3627 BoolObjectClosure* _is_alive; 3628 int _initial_string_table_size; 3629 int _initial_symbol_table_size; 3630 3631 bool _process_strings; 3632 int _strings_processed; 3633 int _strings_removed; 3634 3635 bool _process_symbols; 3636 int _symbols_processed; 3637 int _symbols_removed; 3638 3639 public: 3640 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 3641 AbstractGangTask("String/Symbol Unlinking"), 3642 _is_alive(is_alive), 3643 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3644 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 3645 3646 _initial_string_table_size = StringTable::the_table()->table_size(); 3647 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3648 if (process_strings) { 3649 StringTable::clear_parallel_claimed_index(); 3650 } 3651 if (process_symbols) { 3652 SymbolTable::clear_parallel_claimed_index(); 3653 } 3654 } 3655 3656 ~G1StringSymbolTableUnlinkTask() { 3657 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3658 "claim value %d after unlink less than initial string table size %d", 3659 StringTable::parallel_claimed_index(), _initial_string_table_size); 3660 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3661 "claim value %d after unlink less than initial symbol table size %d", 3662 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3663 3664 log_info(gc, stringtable)( 3665 "Cleaned string and symbol table, " 3666 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3667 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3668 strings_processed(), strings_removed(), 3669 symbols_processed(), symbols_removed()); 3670 } 3671 3672 void work(uint worker_id) { 3673 int strings_processed = 0; 3674 int strings_removed = 0; 3675 int symbols_processed = 0; 3676 int symbols_removed = 0; 3677 if (_process_strings) { 3678 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3679 Atomic::add(strings_processed, &_strings_processed); 3680 Atomic::add(strings_removed, &_strings_removed); 3681 } 3682 if (_process_symbols) { 3683 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3684 Atomic::add(symbols_processed, &_symbols_processed); 3685 Atomic::add(symbols_removed, &_symbols_removed); 3686 } 3687 } 3688 3689 size_t strings_processed() const { return (size_t)_strings_processed; } 3690 size_t strings_removed() const { return (size_t)_strings_removed; } 3691 3692 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3693 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3694 }; 3695 3696 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3697 private: 3698 static Monitor* _lock; 3699 3700 BoolObjectClosure* const _is_alive; 3701 const bool _unloading_occurred; 3702 const uint _num_workers; 3703 3704 // Variables used to claim nmethods. 3705 CompiledMethod* _first_nmethod; 3706 volatile CompiledMethod* _claimed_nmethod; 3707 3708 // The list of nmethods that need to be processed by the second pass. 3709 volatile CompiledMethod* _postponed_list; 3710 volatile uint _num_entered_barrier; 3711 3712 public: 3713 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3714 _is_alive(is_alive), 3715 _unloading_occurred(unloading_occurred), 3716 _num_workers(num_workers), 3717 _first_nmethod(NULL), 3718 _claimed_nmethod(NULL), 3719 _postponed_list(NULL), 3720 _num_entered_barrier(0) 3721 { 3722 CompiledMethod::increase_unloading_clock(); 3723 // Get first alive nmethod 3724 CompiledMethodIterator iter = CompiledMethodIterator(); 3725 if(iter.next_alive()) { 3726 _first_nmethod = iter.method(); 3727 } 3728 _claimed_nmethod = (volatile CompiledMethod*)_first_nmethod; 3729 } 3730 3731 ~G1CodeCacheUnloadingTask() { 3732 CodeCache::verify_clean_inline_caches(); 3733 3734 CodeCache::set_needs_cache_clean(false); 3735 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3736 3737 CodeCache::verify_icholder_relocations(); 3738 } 3739 3740 private: 3741 void add_to_postponed_list(CompiledMethod* nm) { 3742 CompiledMethod* old; 3743 do { 3744 old = (CompiledMethod*)_postponed_list; 3745 nm->set_unloading_next(old); 3746 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 3747 } 3748 3749 void clean_nmethod(CompiledMethod* nm) { 3750 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3751 3752 if (postponed) { 3753 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3754 add_to_postponed_list(nm); 3755 } 3756 3757 // Mark that this thread has been cleaned/unloaded. 3758 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3759 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3760 } 3761 3762 void clean_nmethod_postponed(CompiledMethod* nm) { 3763 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3764 } 3765 3766 static const int MaxClaimNmethods = 16; 3767 3768 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3769 CompiledMethod* first; 3770 CompiledMethodIterator last; 3771 3772 do { 3773 *num_claimed_nmethods = 0; 3774 3775 first = (CompiledMethod*)_claimed_nmethod; 3776 last = CompiledMethodIterator(first); 3777 3778 if (first != NULL) { 3779 3780 for (int i = 0; i < MaxClaimNmethods; i++) { 3781 if (!last.next_alive()) { 3782 break; 3783 } 3784 claimed_nmethods[i] = last.method(); 3785 (*num_claimed_nmethods)++; 3786 } 3787 } 3788 3789 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 3790 } 3791 3792 CompiledMethod* claim_postponed_nmethod() { 3793 CompiledMethod* claim; 3794 CompiledMethod* next; 3795 3796 do { 3797 claim = (CompiledMethod*)_postponed_list; 3798 if (claim == NULL) { 3799 return NULL; 3800 } 3801 3802 next = claim->unloading_next(); 3803 3804 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 3805 3806 return claim; 3807 } 3808 3809 public: 3810 // Mark that we're done with the first pass of nmethod cleaning. 3811 void barrier_mark(uint worker_id) { 3812 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3813 _num_entered_barrier++; 3814 if (_num_entered_barrier == _num_workers) { 3815 ml.notify_all(); 3816 } 3817 } 3818 3819 // See if we have to wait for the other workers to 3820 // finish their first-pass nmethod cleaning work. 3821 void barrier_wait(uint worker_id) { 3822 if (_num_entered_barrier < _num_workers) { 3823 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3824 while (_num_entered_barrier < _num_workers) { 3825 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3826 } 3827 } 3828 } 3829 3830 // Cleaning and unloading of nmethods. Some work has to be postponed 3831 // to the second pass, when we know which nmethods survive. 3832 void work_first_pass(uint worker_id) { 3833 // The first nmethods is claimed by the first worker. 3834 if (worker_id == 0 && _first_nmethod != NULL) { 3835 clean_nmethod(_first_nmethod); 3836 _first_nmethod = NULL; 3837 } 3838 3839 int num_claimed_nmethods; 3840 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3841 3842 while (true) { 3843 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3844 3845 if (num_claimed_nmethods == 0) { 3846 break; 3847 } 3848 3849 for (int i = 0; i < num_claimed_nmethods; i++) { 3850 clean_nmethod(claimed_nmethods[i]); 3851 } 3852 } 3853 } 3854 3855 void work_second_pass(uint worker_id) { 3856 CompiledMethod* nm; 3857 // Take care of postponed nmethods. 3858 while ((nm = claim_postponed_nmethod()) != NULL) { 3859 clean_nmethod_postponed(nm); 3860 } 3861 } 3862 }; 3863 3864 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3865 3866 class G1KlassCleaningTask : public StackObj { 3867 BoolObjectClosure* _is_alive; 3868 volatile jint _clean_klass_tree_claimed; 3869 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3870 3871 public: 3872 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3873 _is_alive(is_alive), 3874 _clean_klass_tree_claimed(0), 3875 _klass_iterator() { 3876 } 3877 3878 private: 3879 bool claim_clean_klass_tree_task() { 3880 if (_clean_klass_tree_claimed) { 3881 return false; 3882 } 3883 3884 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 3885 } 3886 3887 InstanceKlass* claim_next_klass() { 3888 Klass* klass; 3889 do { 3890 klass =_klass_iterator.next_klass(); 3891 } while (klass != NULL && !klass->is_instance_klass()); 3892 3893 // this can be null so don't call InstanceKlass::cast 3894 return static_cast<InstanceKlass*>(klass); 3895 } 3896 3897 public: 3898 3899 void clean_klass(InstanceKlass* ik) { 3900 ik->clean_weak_instanceklass_links(_is_alive); 3901 } 3902 3903 void work() { 3904 ResourceMark rm; 3905 3906 // One worker will clean the subklass/sibling klass tree. 3907 if (claim_clean_klass_tree_task()) { 3908 Klass::clean_subklass_tree(_is_alive); 3909 } 3910 3911 // All workers will help cleaning the classes, 3912 InstanceKlass* klass; 3913 while ((klass = claim_next_klass()) != NULL) { 3914 clean_klass(klass); 3915 } 3916 } 3917 }; 3918 3919 // To minimize the remark pause times, the tasks below are done in parallel. 3920 class G1ParallelCleaningTask : public AbstractGangTask { 3921 private: 3922 G1StringSymbolTableUnlinkTask _string_symbol_task; 3923 G1CodeCacheUnloadingTask _code_cache_task; 3924 G1KlassCleaningTask _klass_cleaning_task; 3925 3926 public: 3927 // The constructor is run in the VMThread. 3928 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 3929 AbstractGangTask("Parallel Cleaning"), 3930 _string_symbol_task(is_alive, process_strings, process_symbols), 3931 _code_cache_task(num_workers, is_alive, unloading_occurred), 3932 _klass_cleaning_task(is_alive) { 3933 } 3934 3935 // The parallel work done by all worker threads. 3936 void work(uint worker_id) { 3937 // Do first pass of code cache cleaning. 3938 _code_cache_task.work_first_pass(worker_id); 3939 3940 // Let the threads mark that the first pass is done. 3941 _code_cache_task.barrier_mark(worker_id); 3942 3943 // Clean the Strings and Symbols. 3944 _string_symbol_task.work(worker_id); 3945 3946 // Wait for all workers to finish the first code cache cleaning pass. 3947 _code_cache_task.barrier_wait(worker_id); 3948 3949 // Do the second code cache cleaning work, which realize on 3950 // the liveness information gathered during the first pass. 3951 _code_cache_task.work_second_pass(worker_id); 3952 3953 // Clean all klasses that were not unloaded. 3954 _klass_cleaning_task.work(); 3955 } 3956 }; 3957 3958 3959 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 3960 bool process_strings, 3961 bool process_symbols, 3962 bool class_unloading_occurred) { 3963 uint n_workers = workers()->active_workers(); 3964 3965 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 3966 n_workers, class_unloading_occurred); 3967 workers()->run_task(&g1_unlink_task); 3968 } 3969 3970 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 3971 bool process_strings, bool process_symbols) { 3972 { // Timing scope 3973 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 3974 workers()->run_task(&g1_unlink_task); 3975 } 3976 } 3977 3978 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3979 private: 3980 DirtyCardQueueSet* _queue; 3981 G1CollectedHeap* _g1h; 3982 public: 3983 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3984 _queue(queue), _g1h(g1h) { } 3985 3986 virtual void work(uint worker_id) { 3987 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3988 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3989 3990 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3991 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3992 3993 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3994 } 3995 }; 3996 3997 void G1CollectedHeap::redirty_logged_cards() { 3998 double redirty_logged_cards_start = os::elapsedTime(); 3999 4000 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 4001 dirty_card_queue_set().reset_for_par_iteration(); 4002 workers()->run_task(&redirty_task); 4003 4004 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 4005 dcq.merge_bufferlists(&dirty_card_queue_set()); 4006 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 4007 4008 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 4009 } 4010 4011 // Weak Reference Processing support 4012 4013 // An always "is_alive" closure that is used to preserve referents. 4014 // If the object is non-null then it's alive. Used in the preservation 4015 // of referent objects that are pointed to by reference objects 4016 // discovered by the CM ref processor. 4017 class G1AlwaysAliveClosure: public BoolObjectClosure { 4018 G1CollectedHeap* _g1; 4019 public: 4020 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4021 bool do_object_b(oop p) { 4022 if (p != NULL) { 4023 return true; 4024 } 4025 return false; 4026 } 4027 }; 4028 4029 bool G1STWIsAliveClosure::do_object_b(oop p) { 4030 // An object is reachable if it is outside the collection set, 4031 // or is inside and copied. 4032 return !_g1->is_in_cset(p) || p->is_forwarded(); 4033 } 4034 4035 // Non Copying Keep Alive closure 4036 class G1KeepAliveClosure: public OopClosure { 4037 G1CollectedHeap* _g1; 4038 public: 4039 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4040 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 4041 void do_oop(oop* p) { 4042 oop obj = *p; 4043 assert(obj != NULL, "the caller should have filtered out NULL values"); 4044 4045 const InCSetState cset_state = _g1->in_cset_state(obj); 4046 if (!cset_state.is_in_cset_or_humongous()) { 4047 return; 4048 } 4049 if (cset_state.is_in_cset()) { 4050 assert( obj->is_forwarded(), "invariant" ); 4051 *p = obj->forwardee(); 4052 } else { 4053 assert(!obj->is_forwarded(), "invariant" ); 4054 assert(cset_state.is_humongous(), 4055 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 4056 _g1->set_humongous_is_live(obj); 4057 } 4058 } 4059 }; 4060 4061 // Copying Keep Alive closure - can be called from both 4062 // serial and parallel code as long as different worker 4063 // threads utilize different G1ParScanThreadState instances 4064 // and different queues. 4065 4066 class G1CopyingKeepAliveClosure: public OopClosure { 4067 G1CollectedHeap* _g1h; 4068 OopClosure* _copy_non_heap_obj_cl; 4069 G1ParScanThreadState* _par_scan_state; 4070 4071 public: 4072 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4073 OopClosure* non_heap_obj_cl, 4074 G1ParScanThreadState* pss): 4075 _g1h(g1h), 4076 _copy_non_heap_obj_cl(non_heap_obj_cl), 4077 _par_scan_state(pss) 4078 {} 4079 4080 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4081 virtual void do_oop( oop* p) { do_oop_work(p); } 4082 4083 template <class T> void do_oop_work(T* p) { 4084 oop obj = oopDesc::load_decode_heap_oop(p); 4085 4086 if (_g1h->is_in_cset_or_humongous(obj)) { 4087 // If the referent object has been forwarded (either copied 4088 // to a new location or to itself in the event of an 4089 // evacuation failure) then we need to update the reference 4090 // field and, if both reference and referent are in the G1 4091 // heap, update the RSet for the referent. 4092 // 4093 // If the referent has not been forwarded then we have to keep 4094 // it alive by policy. Therefore we have copy the referent. 4095 // 4096 // If the reference field is in the G1 heap then we can push 4097 // on the PSS queue. When the queue is drained (after each 4098 // phase of reference processing) the object and it's followers 4099 // will be copied, the reference field set to point to the 4100 // new location, and the RSet updated. Otherwise we need to 4101 // use the the non-heap or metadata closures directly to copy 4102 // the referent object and update the pointer, while avoiding 4103 // updating the RSet. 4104 4105 if (_g1h->is_in_g1_reserved(p)) { 4106 _par_scan_state->push_on_queue(p); 4107 } else { 4108 assert(!Metaspace::contains((const void*)p), 4109 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4110 _copy_non_heap_obj_cl->do_oop(p); 4111 } 4112 } 4113 } 4114 }; 4115 4116 // Serial drain queue closure. Called as the 'complete_gc' 4117 // closure for each discovered list in some of the 4118 // reference processing phases. 4119 4120 class G1STWDrainQueueClosure: public VoidClosure { 4121 protected: 4122 G1CollectedHeap* _g1h; 4123 G1ParScanThreadState* _par_scan_state; 4124 4125 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4126 4127 public: 4128 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4129 _g1h(g1h), 4130 _par_scan_state(pss) 4131 { } 4132 4133 void do_void() { 4134 G1ParScanThreadState* const pss = par_scan_state(); 4135 pss->trim_queue(); 4136 } 4137 }; 4138 4139 // Parallel Reference Processing closures 4140 4141 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4142 // processing during G1 evacuation pauses. 4143 4144 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4145 private: 4146 G1CollectedHeap* _g1h; 4147 G1ParScanThreadStateSet* _pss; 4148 RefToScanQueueSet* _queues; 4149 WorkGang* _workers; 4150 uint _active_workers; 4151 4152 public: 4153 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4154 G1ParScanThreadStateSet* per_thread_states, 4155 WorkGang* workers, 4156 RefToScanQueueSet *task_queues, 4157 uint n_workers) : 4158 _g1h(g1h), 4159 _pss(per_thread_states), 4160 _queues(task_queues), 4161 _workers(workers), 4162 _active_workers(n_workers) 4163 { 4164 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 4165 } 4166 4167 // Executes the given task using concurrent marking worker threads. 4168 virtual void execute(ProcessTask& task); 4169 virtual void execute(EnqueueTask& task); 4170 }; 4171 4172 // Gang task for possibly parallel reference processing 4173 4174 class G1STWRefProcTaskProxy: public AbstractGangTask { 4175 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4176 ProcessTask& _proc_task; 4177 G1CollectedHeap* _g1h; 4178 G1ParScanThreadStateSet* _pss; 4179 RefToScanQueueSet* _task_queues; 4180 ParallelTaskTerminator* _terminator; 4181 4182 public: 4183 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4184 G1CollectedHeap* g1h, 4185 G1ParScanThreadStateSet* per_thread_states, 4186 RefToScanQueueSet *task_queues, 4187 ParallelTaskTerminator* terminator) : 4188 AbstractGangTask("Process reference objects in parallel"), 4189 _proc_task(proc_task), 4190 _g1h(g1h), 4191 _pss(per_thread_states), 4192 _task_queues(task_queues), 4193 _terminator(terminator) 4194 {} 4195 4196 virtual void work(uint worker_id) { 4197 // The reference processing task executed by a single worker. 4198 ResourceMark rm; 4199 HandleMark hm; 4200 4201 G1STWIsAliveClosure is_alive(_g1h); 4202 4203 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4204 pss->set_ref_processor(NULL); 4205 4206 // Keep alive closure. 4207 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4208 4209 // Complete GC closure 4210 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4211 4212 // Call the reference processing task's work routine. 4213 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4214 4215 // Note we cannot assert that the refs array is empty here as not all 4216 // of the processing tasks (specifically phase2 - pp2_work) execute 4217 // the complete_gc closure (which ordinarily would drain the queue) so 4218 // the queue may not be empty. 4219 } 4220 }; 4221 4222 // Driver routine for parallel reference processing. 4223 // Creates an instance of the ref processing gang 4224 // task and has the worker threads execute it. 4225 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4226 assert(_workers != NULL, "Need parallel worker threads."); 4227 4228 ParallelTaskTerminator terminator(_active_workers, _queues); 4229 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4230 4231 _workers->run_task(&proc_task_proxy); 4232 } 4233 4234 // Gang task for parallel reference enqueueing. 4235 4236 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4237 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4238 EnqueueTask& _enq_task; 4239 4240 public: 4241 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4242 AbstractGangTask("Enqueue reference objects in parallel"), 4243 _enq_task(enq_task) 4244 { } 4245 4246 virtual void work(uint worker_id) { 4247 _enq_task.work(worker_id); 4248 } 4249 }; 4250 4251 // Driver routine for parallel reference enqueueing. 4252 // Creates an instance of the ref enqueueing gang 4253 // task and has the worker threads execute it. 4254 4255 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4256 assert(_workers != NULL, "Need parallel worker threads."); 4257 4258 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4259 4260 _workers->run_task(&enq_task_proxy); 4261 } 4262 4263 // End of weak reference support closures 4264 4265 // Abstract task used to preserve (i.e. copy) any referent objects 4266 // that are in the collection set and are pointed to by reference 4267 // objects discovered by the CM ref processor. 4268 4269 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4270 protected: 4271 G1CollectedHeap* _g1h; 4272 G1ParScanThreadStateSet* _pss; 4273 RefToScanQueueSet* _queues; 4274 ParallelTaskTerminator _terminator; 4275 uint _n_workers; 4276 4277 public: 4278 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4279 AbstractGangTask("ParPreserveCMReferents"), 4280 _g1h(g1h), 4281 _pss(per_thread_states), 4282 _queues(task_queues), 4283 _terminator(workers, _queues), 4284 _n_workers(workers) 4285 { 4286 g1h->ref_processor_cm()->set_active_mt_degree(workers); 4287 } 4288 4289 void work(uint worker_id) { 4290 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4291 4292 ResourceMark rm; 4293 HandleMark hm; 4294 4295 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4296 pss->set_ref_processor(NULL); 4297 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4298 4299 // Is alive closure 4300 G1AlwaysAliveClosure always_alive(_g1h); 4301 4302 // Copying keep alive closure. Applied to referent objects that need 4303 // to be copied. 4304 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4305 4306 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4307 4308 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4309 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4310 4311 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4312 // So this must be true - but assert just in case someone decides to 4313 // change the worker ids. 4314 assert(worker_id < limit, "sanity"); 4315 assert(!rp->discovery_is_atomic(), "check this code"); 4316 4317 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4318 for (uint idx = worker_id; idx < limit; idx += stride) { 4319 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4320 4321 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4322 while (iter.has_next()) { 4323 // Since discovery is not atomic for the CM ref processor, we 4324 // can see some null referent objects. 4325 iter.load_ptrs(DEBUG_ONLY(true)); 4326 oop ref = iter.obj(); 4327 4328 // This will filter nulls. 4329 if (iter.is_referent_alive()) { 4330 iter.make_referent_alive(); 4331 } 4332 iter.move_to_next(); 4333 } 4334 } 4335 4336 // Drain the queue - which may cause stealing 4337 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4338 drain_queue.do_void(); 4339 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4340 assert(pss->queue_is_empty(), "should be"); 4341 } 4342 }; 4343 4344 void G1CollectedHeap::process_weak_jni_handles() { 4345 double ref_proc_start = os::elapsedTime(); 4346 4347 G1STWIsAliveClosure is_alive(this); 4348 G1KeepAliveClosure keep_alive(this); 4349 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 4350 4351 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4352 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4353 } 4354 4355 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4356 // Any reference objects, in the collection set, that were 'discovered' 4357 // by the CM ref processor should have already been copied (either by 4358 // applying the external root copy closure to the discovered lists, or 4359 // by following an RSet entry). 4360 // 4361 // But some of the referents, that are in the collection set, that these 4362 // reference objects point to may not have been copied: the STW ref 4363 // processor would have seen that the reference object had already 4364 // been 'discovered' and would have skipped discovering the reference, 4365 // but would not have treated the reference object as a regular oop. 4366 // As a result the copy closure would not have been applied to the 4367 // referent object. 4368 // 4369 // We need to explicitly copy these referent objects - the references 4370 // will be processed at the end of remarking. 4371 // 4372 // We also need to do this copying before we process the reference 4373 // objects discovered by the STW ref processor in case one of these 4374 // referents points to another object which is also referenced by an 4375 // object discovered by the STW ref processor. 4376 double preserve_cm_referents_time = 0.0; 4377 4378 // To avoid spawning task when there is no work to do, check that 4379 // a concurrent cycle is active and that some references have been 4380 // discovered. 4381 if (concurrent_mark()->cmThread()->during_cycle() && 4382 ref_processor_cm()->has_discovered_references()) { 4383 double preserve_cm_referents_start = os::elapsedTime(); 4384 uint no_of_gc_workers = workers()->active_workers(); 4385 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4386 per_thread_states, 4387 no_of_gc_workers, 4388 _task_queues); 4389 workers()->run_task(&keep_cm_referents); 4390 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4391 } 4392 4393 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4394 } 4395 4396 // Weak Reference processing during an evacuation pause (part 1). 4397 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4398 double ref_proc_start = os::elapsedTime(); 4399 4400 ReferenceProcessor* rp = _ref_processor_stw; 4401 assert(rp->discovery_enabled(), "should have been enabled"); 4402 4403 // Closure to test whether a referent is alive. 4404 G1STWIsAliveClosure is_alive(this); 4405 4406 // Even when parallel reference processing is enabled, the processing 4407 // of JNI refs is serial and performed serially by the current thread 4408 // rather than by a worker. The following PSS will be used for processing 4409 // JNI refs. 4410 4411 // Use only a single queue for this PSS. 4412 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4413 pss->set_ref_processor(NULL); 4414 assert(pss->queue_is_empty(), "pre-condition"); 4415 4416 // Keep alive closure. 4417 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4418 4419 // Serial Complete GC closure 4420 G1STWDrainQueueClosure drain_queue(this, pss); 4421 4422 // Setup the soft refs policy... 4423 rp->setup_policy(false); 4424 4425 ReferenceProcessorStats stats; 4426 if (!rp->processing_is_mt()) { 4427 // Serial reference processing... 4428 stats = rp->process_discovered_references(&is_alive, 4429 &keep_alive, 4430 &drain_queue, 4431 NULL, 4432 _gc_timer_stw); 4433 } else { 4434 uint no_of_gc_workers = workers()->active_workers(); 4435 4436 // Parallel reference processing 4437 assert(no_of_gc_workers <= rp->max_num_q(), 4438 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4439 no_of_gc_workers, rp->max_num_q()); 4440 4441 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4442 stats = rp->process_discovered_references(&is_alive, 4443 &keep_alive, 4444 &drain_queue, 4445 &par_task_executor, 4446 _gc_timer_stw); 4447 } 4448 4449 _gc_tracer_stw->report_gc_reference_stats(stats); 4450 4451 // We have completed copying any necessary live referent objects. 4452 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4453 4454 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4455 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4456 } 4457 4458 // Weak Reference processing during an evacuation pause (part 2). 4459 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4460 double ref_enq_start = os::elapsedTime(); 4461 4462 ReferenceProcessor* rp = _ref_processor_stw; 4463 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4464 4465 // Now enqueue any remaining on the discovered lists on to 4466 // the pending list. 4467 if (!rp->processing_is_mt()) { 4468 // Serial reference processing... 4469 rp->enqueue_discovered_references(); 4470 } else { 4471 // Parallel reference enqueueing 4472 4473 uint n_workers = workers()->active_workers(); 4474 4475 assert(n_workers <= rp->max_num_q(), 4476 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4477 n_workers, rp->max_num_q()); 4478 4479 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4480 rp->enqueue_discovered_references(&par_task_executor); 4481 } 4482 4483 rp->verify_no_references_recorded(); 4484 assert(!rp->discovery_enabled(), "should have been disabled"); 4485 4486 // FIXME 4487 // CM's reference processing also cleans up the string and symbol tables. 4488 // Should we do that here also? We could, but it is a serial operation 4489 // and could significantly increase the pause time. 4490 4491 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4492 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4493 } 4494 4495 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4496 double merge_pss_time_start = os::elapsedTime(); 4497 per_thread_states->flush(); 4498 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4499 } 4500 4501 void G1CollectedHeap::pre_evacuate_collection_set() { 4502 _expand_heap_after_alloc_failure = true; 4503 _evacuation_failed = false; 4504 4505 // Disable the hot card cache. 4506 _hot_card_cache->reset_hot_cache_claimed_index(); 4507 _hot_card_cache->set_use_cache(false); 4508 4509 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4510 _preserved_marks_set.assert_empty(); 4511 } 4512 4513 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4514 // Should G1EvacuationFailureALot be in effect for this GC? 4515 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4516 4517 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4518 double start_par_time_sec = os::elapsedTime(); 4519 double end_par_time_sec; 4520 4521 { 4522 const uint n_workers = workers()->active_workers(); 4523 G1RootProcessor root_processor(this, n_workers); 4524 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4525 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4526 if (collector_state()->during_initial_mark_pause()) { 4527 ClassLoaderDataGraph::clear_claimed_marks(); 4528 } 4529 4530 print_termination_stats_hdr(); 4531 4532 workers()->run_task(&g1_par_task); 4533 end_par_time_sec = os::elapsedTime(); 4534 4535 // Closing the inner scope will execute the destructor 4536 // for the G1RootProcessor object. We record the current 4537 // elapsed time before closing the scope so that time 4538 // taken for the destructor is NOT included in the 4539 // reported parallel time. 4540 } 4541 4542 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4543 4544 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4545 phase_times->record_par_time(par_time_ms); 4546 4547 double code_root_fixup_time_ms = 4548 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4549 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4550 } 4551 4552 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4553 // Process any discovered reference objects - we have 4554 // to do this _before_ we retire the GC alloc regions 4555 // as we may have to copy some 'reachable' referent 4556 // objects (and their reachable sub-graphs) that were 4557 // not copied during the pause. 4558 if (g1_policy()->should_process_references()) { 4559 preserve_cm_referents(per_thread_states); 4560 process_discovered_references(per_thread_states); 4561 } else { 4562 ref_processor_stw()->verify_no_references_recorded(); 4563 process_weak_jni_handles(); 4564 } 4565 4566 if (G1StringDedup::is_enabled()) { 4567 double fixup_start = os::elapsedTime(); 4568 4569 G1STWIsAliveClosure is_alive(this); 4570 G1KeepAliveClosure keep_alive(this); 4571 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4572 4573 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4574 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4575 } 4576 4577 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4578 4579 if (evacuation_failed()) { 4580 restore_after_evac_failure(); 4581 4582 // Reset the G1EvacuationFailureALot counters and flags 4583 // Note: the values are reset only when an actual 4584 // evacuation failure occurs. 4585 NOT_PRODUCT(reset_evacuation_should_fail();) 4586 } 4587 4588 _preserved_marks_set.assert_empty(); 4589 4590 // Enqueue any remaining references remaining on the STW 4591 // reference processor's discovered lists. We need to do 4592 // this after the card table is cleaned (and verified) as 4593 // the act of enqueueing entries on to the pending list 4594 // will log these updates (and dirty their associated 4595 // cards). We need these updates logged to update any 4596 // RSets. 4597 if (g1_policy()->should_process_references()) { 4598 enqueue_discovered_references(per_thread_states); 4599 } else { 4600 g1_policy()->phase_times()->record_ref_enq_time(0); 4601 } 4602 4603 _allocator->release_gc_alloc_regions(evacuation_info); 4604 4605 merge_per_thread_state_info(per_thread_states); 4606 4607 // Reset and re-enable the hot card cache. 4608 // Note the counts for the cards in the regions in the 4609 // collection set are reset when the collection set is freed. 4610 _hot_card_cache->reset_hot_cache(); 4611 _hot_card_cache->set_use_cache(true); 4612 4613 purge_code_root_memory(); 4614 4615 redirty_logged_cards(); 4616 #if defined(COMPILER2) || INCLUDE_JVMCI 4617 DerivedPointerTable::update_pointers(); 4618 #endif 4619 } 4620 4621 void G1CollectedHeap::record_obj_copy_mem_stats() { 4622 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4623 4624 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4625 create_g1_evac_summary(&_old_evac_stats)); 4626 } 4627 4628 void G1CollectedHeap::free_region(HeapRegion* hr, 4629 FreeRegionList* free_list, 4630 bool par, 4631 bool locked) { 4632 assert(!hr->is_free(), "the region should not be free"); 4633 assert(!hr->is_empty(), "the region should not be empty"); 4634 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4635 assert(free_list != NULL, "pre-condition"); 4636 4637 if (G1VerifyBitmaps) { 4638 MemRegion mr(hr->bottom(), hr->end()); 4639 concurrent_mark()->clearRangePrevBitmap(mr); 4640 } 4641 4642 // Clear the card counts for this region. 4643 // Note: we only need to do this if the region is not young 4644 // (since we don't refine cards in young regions). 4645 if (!hr->is_young()) { 4646 _hot_card_cache->reset_card_counts(hr); 4647 } 4648 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 4649 free_list->add_ordered(hr); 4650 } 4651 4652 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4653 FreeRegionList* free_list, 4654 bool par) { 4655 assert(hr->is_humongous(), "this is only for humongous regions"); 4656 assert(free_list != NULL, "pre-condition"); 4657 hr->clear_humongous(); 4658 free_region(hr, free_list, par); 4659 } 4660 4661 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4662 const uint humongous_regions_removed) { 4663 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4664 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4665 _old_set.bulk_remove(old_regions_removed); 4666 _humongous_set.bulk_remove(humongous_regions_removed); 4667 } 4668 4669 } 4670 4671 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4672 assert(list != NULL, "list can't be null"); 4673 if (!list->is_empty()) { 4674 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4675 _hrm.insert_list_into_free_list(list); 4676 } 4677 } 4678 4679 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4680 decrease_used(bytes); 4681 } 4682 4683 class G1ParScrubRemSetTask: public AbstractGangTask { 4684 protected: 4685 G1RemSet* _g1rs; 4686 HeapRegionClaimer _hrclaimer; 4687 4688 public: 4689 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) : 4690 AbstractGangTask("G1 ScrubRS"), 4691 _g1rs(g1_rs), 4692 _hrclaimer(num_workers) { 4693 } 4694 4695 void work(uint worker_id) { 4696 _g1rs->scrub(worker_id, &_hrclaimer); 4697 } 4698 }; 4699 4700 void G1CollectedHeap::scrub_rem_set() { 4701 uint num_workers = workers()->active_workers(); 4702 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers); 4703 workers()->run_task(&g1_par_scrub_rs_task); 4704 } 4705 4706 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4707 size_t pre_used = 0; 4708 FreeRegionList local_free_list("Local List for CSet Freeing"); 4709 4710 double young_time_ms = 0.0; 4711 double non_young_time_ms = 0.0; 4712 4713 _eden.clear(); 4714 4715 G1Policy* policy = g1_policy(); 4716 4717 double start_sec = os::elapsedTime(); 4718 bool non_young = true; 4719 4720 HeapRegion* cur = cs_head; 4721 int age_bound = -1; 4722 size_t rs_lengths = 0; 4723 4724 while (cur != NULL) { 4725 assert(!is_on_master_free_list(cur), "sanity"); 4726 if (non_young) { 4727 if (cur->is_young()) { 4728 double end_sec = os::elapsedTime(); 4729 double elapsed_ms = (end_sec - start_sec) * 1000.0; 4730 non_young_time_ms += elapsed_ms; 4731 4732 start_sec = os::elapsedTime(); 4733 non_young = false; 4734 } 4735 } else { 4736 if (!cur->is_young()) { 4737 double end_sec = os::elapsedTime(); 4738 double elapsed_ms = (end_sec - start_sec) * 1000.0; 4739 young_time_ms += elapsed_ms; 4740 4741 start_sec = os::elapsedTime(); 4742 non_young = true; 4743 } 4744 } 4745 4746 rs_lengths += cur->rem_set()->occupied_locked(); 4747 4748 HeapRegion* next = cur->next_in_collection_set(); 4749 assert(cur->in_collection_set(), "bad CS"); 4750 cur->set_next_in_collection_set(NULL); 4751 clear_in_cset(cur); 4752 4753 if (cur->is_young()) { 4754 int index = cur->young_index_in_cset(); 4755 assert(index != -1, "invariant"); 4756 assert((uint) index < collection_set()->young_region_length(), "invariant"); 4757 size_t words_survived = surviving_young_words[index]; 4758 cur->record_surv_words_in_group(words_survived); 4759 4760 } else { 4761 int index = cur->young_index_in_cset(); 4762 assert(index == -1, "invariant"); 4763 } 4764 4765 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 4766 (!cur->is_young() && cur->young_index_in_cset() == -1), 4767 "invariant" ); 4768 4769 if (!cur->evacuation_failed()) { 4770 MemRegion used_mr = cur->used_region(); 4771 4772 // And the region is empty. 4773 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 4774 pre_used += cur->used(); 4775 free_region(cur, &local_free_list, false /* par */, true /* locked */); 4776 } else { 4777 cur->uninstall_surv_rate_group(); 4778 if (cur->is_young()) { 4779 cur->set_young_index_in_cset(-1); 4780 } 4781 cur->set_evacuation_failed(false); 4782 // When moving a young gen region to old gen, we "allocate" that whole region 4783 // there. This is in addition to any already evacuated objects. Notify the 4784 // policy about that. 4785 // Old gen regions do not cause an additional allocation: both the objects 4786 // still in the region and the ones already moved are accounted for elsewhere. 4787 if (cur->is_young()) { 4788 policy->add_bytes_allocated_in_old_since_last_gc(HeapRegion::GrainBytes); 4789 } 4790 // The region is now considered to be old. 4791 cur->set_old(); 4792 // Do some allocation statistics accounting. Regions that failed evacuation 4793 // are always made old, so there is no need to update anything in the young 4794 // gen statistics, but we need to update old gen statistics. 4795 size_t used_words = cur->marked_bytes() / HeapWordSize; 4796 _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words); 4797 _old_set.add(cur); 4798 evacuation_info.increment_collectionset_used_after(cur->used()); 4799 } 4800 cur = next; 4801 } 4802 4803 evacuation_info.set_regions_freed(local_free_list.length()); 4804 policy->record_max_rs_lengths(rs_lengths); 4805 policy->cset_regions_freed(); 4806 4807 double end_sec = os::elapsedTime(); 4808 double elapsed_ms = (end_sec - start_sec) * 1000.0; 4809 4810 if (non_young) { 4811 non_young_time_ms += elapsed_ms; 4812 } else { 4813 young_time_ms += elapsed_ms; 4814 } 4815 4816 prepend_to_freelist(&local_free_list); 4817 decrement_summary_bytes(pre_used); 4818 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 4819 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 4820 } 4821 4822 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4823 private: 4824 FreeRegionList* _free_region_list; 4825 HeapRegionSet* _proxy_set; 4826 uint _humongous_regions_removed; 4827 size_t _freed_bytes; 4828 public: 4829 4830 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4831 _free_region_list(free_region_list), _humongous_regions_removed(0), _freed_bytes(0) { 4832 } 4833 4834 virtual bool doHeapRegion(HeapRegion* r) { 4835 if (!r->is_starts_humongous()) { 4836 return false; 4837 } 4838 4839 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4840 4841 oop obj = (oop)r->bottom(); 4842 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 4843 4844 // The following checks whether the humongous object is live are sufficient. 4845 // The main additional check (in addition to having a reference from the roots 4846 // or the young gen) is whether the humongous object has a remembered set entry. 4847 // 4848 // A humongous object cannot be live if there is no remembered set for it 4849 // because: 4850 // - there can be no references from within humongous starts regions referencing 4851 // the object because we never allocate other objects into them. 4852 // (I.e. there are no intra-region references that may be missed by the 4853 // remembered set) 4854 // - as soon there is a remembered set entry to the humongous starts region 4855 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4856 // until the end of a concurrent mark. 4857 // 4858 // It is not required to check whether the object has been found dead by marking 4859 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4860 // all objects allocated during that time are considered live. 4861 // SATB marking is even more conservative than the remembered set. 4862 // So if at this point in the collection there is no remembered set entry, 4863 // nobody has a reference to it. 4864 // At the start of collection we flush all refinement logs, and remembered sets 4865 // are completely up-to-date wrt to references to the humongous object. 4866 // 4867 // Other implementation considerations: 4868 // - never consider object arrays at this time because they would pose 4869 // considerable effort for cleaning up the the remembered sets. This is 4870 // required because stale remembered sets might reference locations that 4871 // are currently allocated into. 4872 uint region_idx = r->hrm_index(); 4873 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4874 !r->rem_set()->is_empty()) { 4875 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", 4876 region_idx, 4877 (size_t)obj->size() * HeapWordSize, 4878 p2i(r->bottom()), 4879 r->rem_set()->occupied(), 4880 r->rem_set()->strong_code_roots_list_length(), 4881 next_bitmap->isMarked(r->bottom()), 4882 g1h->is_humongous_reclaim_candidate(region_idx), 4883 obj->is_typeArray() 4884 ); 4885 return false; 4886 } 4887 4888 guarantee(obj->is_typeArray(), 4889 "Only eagerly reclaiming type arrays is supported, but the object " 4890 PTR_FORMAT " is not.", p2i(r->bottom())); 4891 4892 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", 4893 region_idx, 4894 (size_t)obj->size() * HeapWordSize, 4895 p2i(r->bottom()), 4896 r->rem_set()->occupied(), 4897 r->rem_set()->strong_code_roots_list_length(), 4898 next_bitmap->isMarked(r->bottom()), 4899 g1h->is_humongous_reclaim_candidate(region_idx), 4900 obj->is_typeArray() 4901 ); 4902 4903 // Need to clear mark bit of the humongous object if already set. 4904 if (next_bitmap->isMarked(r->bottom())) { 4905 next_bitmap->clear(r->bottom()); 4906 } 4907 do { 4908 HeapRegion* next = g1h->next_region_in_humongous(r); 4909 _freed_bytes += r->used(); 4910 r->set_containing_set(NULL); 4911 _humongous_regions_removed++; 4912 g1h->free_humongous_region(r, _free_region_list, false); 4913 r = next; 4914 } while (r != NULL); 4915 4916 return false; 4917 } 4918 4919 uint humongous_free_count() { 4920 return _humongous_regions_removed; 4921 } 4922 4923 size_t bytes_freed() const { 4924 return _freed_bytes; 4925 } 4926 }; 4927 4928 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4929 assert_at_safepoint(true); 4930 4931 if (!G1EagerReclaimHumongousObjects || 4932 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4933 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4934 return; 4935 } 4936 4937 double start_time = os::elapsedTime(); 4938 4939 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4940 4941 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4942 heap_region_iterate(&cl); 4943 4944 remove_from_old_sets(0, cl.humongous_free_count()); 4945 4946 G1HRPrinter* hrp = hr_printer(); 4947 if (hrp->is_active()) { 4948 FreeRegionListIterator iter(&local_cleanup_list); 4949 while (iter.more_available()) { 4950 HeapRegion* hr = iter.get_next(); 4951 hrp->cleanup(hr); 4952 } 4953 } 4954 4955 prepend_to_freelist(&local_cleanup_list); 4956 decrement_summary_bytes(cl.bytes_freed()); 4957 4958 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4959 cl.humongous_free_count()); 4960 } 4961 4962 // This routine is similar to the above but does not record 4963 // any policy statistics or update free lists; we are abandoning 4964 // the current incremental collection set in preparation of a 4965 // full collection. After the full GC we will start to build up 4966 // the incremental collection set again. 4967 // This is only called when we're doing a full collection 4968 // and is immediately followed by the tearing down of the young list. 4969 4970 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 4971 HeapRegion* cur = cs_head; 4972 4973 while (cur != NULL) { 4974 HeapRegion* next = cur->next_in_collection_set(); 4975 assert(cur->in_collection_set(), "bad CS"); 4976 cur->set_next_in_collection_set(NULL); 4977 clear_in_cset(cur); 4978 cur->set_young_index_in_cset(-1); 4979 cur = next; 4980 } 4981 } 4982 4983 void G1CollectedHeap::set_free_regions_coming() { 4984 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 4985 4986 assert(!free_regions_coming(), "pre-condition"); 4987 _free_regions_coming = true; 4988 } 4989 4990 void G1CollectedHeap::reset_free_regions_coming() { 4991 assert(free_regions_coming(), "pre-condition"); 4992 4993 { 4994 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 4995 _free_regions_coming = false; 4996 SecondaryFreeList_lock->notify_all(); 4997 } 4998 4999 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 5000 } 5001 5002 void G1CollectedHeap::wait_while_free_regions_coming() { 5003 // Most of the time we won't have to wait, so let's do a quick test 5004 // first before we take the lock. 5005 if (!free_regions_coming()) { 5006 return; 5007 } 5008 5009 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 5010 5011 { 5012 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5013 while (free_regions_coming()) { 5014 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5015 } 5016 } 5017 5018 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 5019 } 5020 5021 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5022 return _allocator->is_retained_old_region(hr); 5023 } 5024 5025 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5026 _eden.add(hr); 5027 _g1_policy->set_region_eden(hr); 5028 } 5029 5030 #ifdef ASSERT 5031 5032 class NoYoungRegionsClosure: public HeapRegionClosure { 5033 private: 5034 bool _success; 5035 public: 5036 NoYoungRegionsClosure() : _success(true) { } 5037 bool doHeapRegion(HeapRegion* r) { 5038 if (r->is_young()) { 5039 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5040 p2i(r->bottom()), p2i(r->end())); 5041 _success = false; 5042 } 5043 return false; 5044 } 5045 bool success() { return _success; } 5046 }; 5047 5048 bool G1CollectedHeap::check_young_list_empty() { 5049 bool ret = (young_regions_count() == 0); 5050 5051 NoYoungRegionsClosure closure; 5052 heap_region_iterate(&closure); 5053 ret = ret && closure.success(); 5054 5055 return ret; 5056 } 5057 5058 #endif // ASSERT 5059 5060 class TearDownRegionSetsClosure : public HeapRegionClosure { 5061 private: 5062 HeapRegionSet *_old_set; 5063 5064 public: 5065 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5066 5067 bool doHeapRegion(HeapRegion* r) { 5068 if (r->is_old()) { 5069 _old_set->remove(r); 5070 } else if(r->is_young()) { 5071 r->uninstall_surv_rate_group(); 5072 } else { 5073 // We ignore free regions, we'll empty the free list afterwards. 5074 // We ignore humongous regions, we're not tearing down the 5075 // humongous regions set. 5076 assert(r->is_free() || r->is_humongous(), 5077 "it cannot be another type"); 5078 } 5079 return false; 5080 } 5081 5082 ~TearDownRegionSetsClosure() { 5083 assert(_old_set->is_empty(), "post-condition"); 5084 } 5085 }; 5086 5087 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5088 assert_at_safepoint(true /* should_be_vm_thread */); 5089 5090 if (!free_list_only) { 5091 TearDownRegionSetsClosure cl(&_old_set); 5092 heap_region_iterate(&cl); 5093 5094 // Note that emptying the _young_list is postponed and instead done as 5095 // the first step when rebuilding the regions sets again. The reason for 5096 // this is that during a full GC string deduplication needs to know if 5097 // a collected region was young or old when the full GC was initiated. 5098 } 5099 _hrm.remove_all_free_regions(); 5100 } 5101 5102 void G1CollectedHeap::increase_used(size_t bytes) { 5103 _summary_bytes_used += bytes; 5104 } 5105 5106 void G1CollectedHeap::decrease_used(size_t bytes) { 5107 assert(_summary_bytes_used >= bytes, 5108 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5109 _summary_bytes_used, bytes); 5110 _summary_bytes_used -= bytes; 5111 } 5112 5113 void G1CollectedHeap::set_used(size_t bytes) { 5114 _summary_bytes_used = bytes; 5115 } 5116 5117 class RebuildRegionSetsClosure : public HeapRegionClosure { 5118 private: 5119 bool _free_list_only; 5120 HeapRegionSet* _old_set; 5121 HeapRegionManager* _hrm; 5122 size_t _total_used; 5123 5124 public: 5125 RebuildRegionSetsClosure(bool free_list_only, 5126 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5127 _free_list_only(free_list_only), 5128 _old_set(old_set), _hrm(hrm), _total_used(0) { 5129 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5130 if (!free_list_only) { 5131 assert(_old_set->is_empty(), "pre-condition"); 5132 } 5133 } 5134 5135 bool doHeapRegion(HeapRegion* r) { 5136 if (r->is_empty()) { 5137 // Add free regions to the free list 5138 r->set_free(); 5139 r->set_allocation_context(AllocationContext::system()); 5140 _hrm->insert_into_free_list(r); 5141 } else if (!_free_list_only) { 5142 5143 if (r->is_humongous()) { 5144 // We ignore humongous regions. We left the humongous set unchanged. 5145 } else { 5146 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 5147 // We now consider all regions old, so register as such. Leave 5148 // archive regions set that way, however, while still adding 5149 // them to the old set. 5150 if (!r->is_archive()) { 5151 r->set_old(); 5152 } 5153 _old_set->add(r); 5154 } 5155 _total_used += r->used(); 5156 } 5157 5158 return false; 5159 } 5160 5161 size_t total_used() { 5162 return _total_used; 5163 } 5164 }; 5165 5166 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5167 assert_at_safepoint(true /* should_be_vm_thread */); 5168 5169 if (!free_list_only) { 5170 _eden.clear(); 5171 _survivor.clear(); 5172 } 5173 5174 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5175 heap_region_iterate(&cl); 5176 5177 if (!free_list_only) { 5178 set_used(cl.total_used()); 5179 if (_archive_allocator != NULL) { 5180 _archive_allocator->clear_used(); 5181 } 5182 } 5183 assert(used_unlocked() == recalculate_used(), 5184 "inconsistent used_unlocked(), " 5185 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5186 used_unlocked(), recalculate_used()); 5187 } 5188 5189 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 5190 _refine_cte_cl->set_concurrent(concurrent); 5191 } 5192 5193 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5194 HeapRegion* hr = heap_region_containing(p); 5195 return hr->is_in(p); 5196 } 5197 5198 // Methods for the mutator alloc region 5199 5200 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5201 bool force) { 5202 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5203 assert(!force || g1_policy()->can_expand_young_list(), 5204 "if force is true we should be able to expand the young list"); 5205 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 5206 if (force || should_allocate) { 5207 HeapRegion* new_alloc_region = new_region(word_size, 5208 false /* is_old */, 5209 false /* do_expand */); 5210 if (new_alloc_region != NULL) { 5211 set_region_short_lived_locked(new_alloc_region); 5212 _hr_printer.alloc(new_alloc_region, !should_allocate); 5213 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5214 return new_alloc_region; 5215 } 5216 } 5217 return NULL; 5218 } 5219 5220 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5221 size_t allocated_bytes) { 5222 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5223 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5224 5225 collection_set()->add_eden_region(alloc_region); 5226 increase_used(allocated_bytes); 5227 _hr_printer.retire(alloc_region); 5228 // We update the eden sizes here, when the region is retired, 5229 // instead of when it's allocated, since this is the point that its 5230 // used space has been recored in _summary_bytes_used. 5231 g1mm()->update_eden_size(); 5232 } 5233 5234 // Methods for the GC alloc regions 5235 5236 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 5237 if (dest.is_old()) { 5238 return true; 5239 } else { 5240 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 5241 } 5242 } 5243 5244 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 5245 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5246 5247 if (!has_more_regions(dest)) { 5248 return NULL; 5249 } 5250 5251 const bool is_survivor = dest.is_young(); 5252 5253 HeapRegion* new_alloc_region = new_region(word_size, 5254 !is_survivor, 5255 true /* do_expand */); 5256 if (new_alloc_region != NULL) { 5257 // We really only need to do this for old regions given that we 5258 // should never scan survivors. But it doesn't hurt to do it 5259 // for survivors too. 5260 new_alloc_region->record_timestamp(); 5261 if (is_survivor) { 5262 new_alloc_region->set_survivor(); 5263 _survivor.add(new_alloc_region); 5264 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5265 } else { 5266 new_alloc_region->set_old(); 5267 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5268 } 5269 _hr_printer.alloc(new_alloc_region); 5270 bool during_im = collector_state()->during_initial_mark_pause(); 5271 new_alloc_region->note_start_of_copying(during_im); 5272 return new_alloc_region; 5273 } 5274 return NULL; 5275 } 5276 5277 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5278 size_t allocated_bytes, 5279 InCSetState dest) { 5280 bool during_im = collector_state()->during_initial_mark_pause(); 5281 alloc_region->note_end_of_copying(during_im); 5282 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5283 if (dest.is_old()) { 5284 _old_set.add(alloc_region); 5285 } 5286 _hr_printer.retire(alloc_region); 5287 } 5288 5289 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5290 bool expanded = false; 5291 uint index = _hrm.find_highest_free(&expanded); 5292 5293 if (index != G1_NO_HRM_INDEX) { 5294 if (expanded) { 5295 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5296 HeapRegion::GrainWords * HeapWordSize); 5297 } 5298 _hrm.allocate_free_regions_starting_at(index, 1); 5299 return region_at(index); 5300 } 5301 return NULL; 5302 } 5303 5304 // Optimized nmethod scanning 5305 5306 class RegisterNMethodOopClosure: public OopClosure { 5307 G1CollectedHeap* _g1h; 5308 nmethod* _nm; 5309 5310 template <class T> void do_oop_work(T* p) { 5311 T heap_oop = oopDesc::load_heap_oop(p); 5312 if (!oopDesc::is_null(heap_oop)) { 5313 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5314 HeapRegion* hr = _g1h->heap_region_containing(obj); 5315 assert(!hr->is_continues_humongous(), 5316 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5317 " starting at " HR_FORMAT, 5318 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5319 5320 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5321 hr->add_strong_code_root_locked(_nm); 5322 } 5323 } 5324 5325 public: 5326 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5327 _g1h(g1h), _nm(nm) {} 5328 5329 void do_oop(oop* p) { do_oop_work(p); } 5330 void do_oop(narrowOop* p) { do_oop_work(p); } 5331 }; 5332 5333 class UnregisterNMethodOopClosure: public OopClosure { 5334 G1CollectedHeap* _g1h; 5335 nmethod* _nm; 5336 5337 template <class T> void do_oop_work(T* p) { 5338 T heap_oop = oopDesc::load_heap_oop(p); 5339 if (!oopDesc::is_null(heap_oop)) { 5340 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5341 HeapRegion* hr = _g1h->heap_region_containing(obj); 5342 assert(!hr->is_continues_humongous(), 5343 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5344 " starting at " HR_FORMAT, 5345 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5346 5347 hr->remove_strong_code_root(_nm); 5348 } 5349 } 5350 5351 public: 5352 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5353 _g1h(g1h), _nm(nm) {} 5354 5355 void do_oop(oop* p) { do_oop_work(p); } 5356 void do_oop(narrowOop* p) { do_oop_work(p); } 5357 }; 5358 5359 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5360 CollectedHeap::register_nmethod(nm); 5361 5362 guarantee(nm != NULL, "sanity"); 5363 RegisterNMethodOopClosure reg_cl(this, nm); 5364 nm->oops_do(®_cl); 5365 } 5366 5367 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5368 CollectedHeap::unregister_nmethod(nm); 5369 5370 guarantee(nm != NULL, "sanity"); 5371 UnregisterNMethodOopClosure reg_cl(this, nm); 5372 nm->oops_do(®_cl, true); 5373 } 5374 5375 void G1CollectedHeap::purge_code_root_memory() { 5376 double purge_start = os::elapsedTime(); 5377 G1CodeRootSet::purge(); 5378 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5379 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5380 } 5381 5382 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5383 G1CollectedHeap* _g1h; 5384 5385 public: 5386 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5387 _g1h(g1h) {} 5388 5389 void do_code_blob(CodeBlob* cb) { 5390 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5391 if (nm == NULL) { 5392 return; 5393 } 5394 5395 if (ScavengeRootsInCode) { 5396 _g1h->register_nmethod(nm); 5397 } 5398 } 5399 }; 5400 5401 void G1CollectedHeap::rebuild_strong_code_roots() { 5402 RebuildStrongCodeRootClosure blob_cl(this); 5403 CodeCache::blobs_do(&blob_cl); 5404 }