1 /* 2 * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/metadataOnStackMark.hpp" 27 #include "classfile/stringTable.hpp" 28 #include "classfile/symbolTable.hpp" 29 #include "code/codeCache.hpp" 30 #include "code/icBuffer.hpp" 31 #include "gc/g1/bufferingOopClosure.hpp" 32 #include "gc/g1/concurrentMarkThread.inline.hpp" 33 #include "gc/g1/g1Allocator.inline.hpp" 34 #include "gc/g1/g1CollectedHeap.inline.hpp" 35 #include "gc/g1/g1CollectionSet.hpp" 36 #include "gc/g1/g1CollectorPolicy.hpp" 37 #include "gc/g1/g1CollectorState.hpp" 38 #include "gc/g1/g1ConcurrentRefine.hpp" 39 #include "gc/g1/g1ConcurrentRefineThread.hpp" 40 #include "gc/g1/g1EvacStats.inline.hpp" 41 #include "gc/g1/g1FullCollector.hpp" 42 #include "gc/g1/g1GCPhaseTimes.hpp" 43 #include "gc/g1/g1HeapSizingPolicy.hpp" 44 #include "gc/g1/g1HeapTransition.hpp" 45 #include "gc/g1/g1HeapVerifier.hpp" 46 #include "gc/g1/g1HotCardCache.hpp" 47 #include "gc/g1/g1MemoryPool.hpp" 48 #include "gc/g1/g1OopClosures.inline.hpp" 49 #include "gc/g1/g1ParScanThreadState.inline.hpp" 50 #include "gc/g1/g1Policy.hpp" 51 #include "gc/g1/g1RegionToSpaceMapper.hpp" 52 #include "gc/g1/g1RemSet.hpp" 53 #include "gc/g1/g1RootClosures.hpp" 54 #include "gc/g1/g1RootProcessor.hpp" 55 #include "gc/g1/g1StringDedup.hpp" 56 #include "gc/g1/g1YCTypes.hpp" 57 #include "gc/g1/g1YoungRemSetSamplingThread.hpp" 58 #include "gc/g1/heapRegion.inline.hpp" 59 #include "gc/g1/heapRegionRemSet.hpp" 60 #include "gc/g1/heapRegionSet.inline.hpp" 61 #include "gc/g1/vm_operations_g1.hpp" 62 #include "gc/shared/gcHeapSummary.hpp" 63 #include "gc/shared/gcId.hpp" 64 #include "gc/shared/gcLocker.inline.hpp" 65 #include "gc/shared/gcTimer.hpp" 66 #include "gc/shared/gcTrace.hpp" 67 #include "gc/shared/gcTraceTime.inline.hpp" 68 #include "gc/shared/generationSpec.hpp" 69 #include "gc/shared/isGCActiveMark.hpp" 70 #include "gc/shared/preservedMarks.inline.hpp" 71 #include "gc/shared/suspendibleThreadSet.hpp" 72 #include "gc/shared/referenceProcessor.inline.hpp" 73 #include "gc/shared/taskqueue.inline.hpp" 74 #include "gc/shared/weakProcessor.hpp" 75 #include "logging/log.hpp" 76 #include "memory/allocation.hpp" 77 #include "memory/iterator.hpp" 78 #include "memory/resourceArea.hpp" 79 #include "oops/oop.inline.hpp" 80 #include "prims/resolvedMethodTable.hpp" 81 #include "runtime/atomic.hpp" 82 #include "runtime/init.hpp" 83 #include "runtime/orderAccess.inline.hpp" 84 #include "runtime/threadSMR.hpp" 85 #include "runtime/vmThread.hpp" 86 #include "utilities/align.hpp" 87 #include "utilities/globalDefinitions.hpp" 88 #include "utilities/stack.inline.hpp" 89 90 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 91 92 // INVARIANTS/NOTES 93 // 94 // All allocation activity covered by the G1CollectedHeap interface is 95 // serialized by acquiring the HeapLock. This happens in mem_allocate 96 // and allocate_new_tlab, which are the "entry" points to the 97 // allocation code from the rest of the JVM. (Note that this does not 98 // apply to TLAB allocation, which is not part of this interface: it 99 // is done by clients of this interface.) 100 101 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 102 private: 103 size_t _num_dirtied; 104 G1CollectedHeap* _g1h; 105 G1SATBCardTableLoggingModRefBS* _g1_bs; 106 107 HeapRegion* region_for_card(jbyte* card_ptr) const { 108 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 109 } 110 111 bool will_become_free(HeapRegion* hr) const { 112 // A region will be freed by free_collection_set if the region is in the 113 // collection set and has not had an evacuation failure. 114 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 115 } 116 117 public: 118 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 119 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 120 121 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 122 HeapRegion* hr = region_for_card(card_ptr); 123 124 // Should only dirty cards in regions that won't be freed. 125 if (!will_become_free(hr)) { 126 *card_ptr = CardTableModRefBS::dirty_card_val(); 127 _num_dirtied++; 128 } 129 130 return true; 131 } 132 133 size_t num_dirtied() const { return _num_dirtied; } 134 }; 135 136 137 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 138 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 139 } 140 141 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 142 // The from card cache is not the memory that is actually committed. So we cannot 143 // take advantage of the zero_filled parameter. 144 reset_from_card_cache(start_idx, num_regions); 145 } 146 147 148 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 149 MemRegion mr) { 150 return new HeapRegion(hrs_index, bot(), mr); 151 } 152 153 // Private methods. 154 155 HeapRegion* 156 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 157 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 158 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 159 if (!_secondary_free_list.is_empty()) { 160 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 161 "secondary_free_list has %u entries", 162 _secondary_free_list.length()); 163 // It looks as if there are free regions available on the 164 // secondary_free_list. Let's move them to the free_list and try 165 // again to allocate from it. 166 append_secondary_free_list(); 167 168 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 169 "empty we should have moved at least one entry to the free_list"); 170 HeapRegion* res = _hrm.allocate_free_region(is_old); 171 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 172 "allocated " HR_FORMAT " from secondary_free_list", 173 HR_FORMAT_PARAMS(res)); 174 return res; 175 } 176 177 // Wait here until we get notified either when (a) there are no 178 // more free regions coming or (b) some regions have been moved on 179 // the secondary_free_list. 180 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 181 } 182 183 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 184 "could not allocate from secondary_free_list"); 185 return NULL; 186 } 187 188 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 189 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 190 "the only time we use this to allocate a humongous region is " 191 "when we are allocating a single humongous region"); 192 193 HeapRegion* res; 194 if (G1StressConcRegionFreeing) { 195 if (!_secondary_free_list.is_empty()) { 196 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 197 "forced to look at the secondary_free_list"); 198 res = new_region_try_secondary_free_list(is_old); 199 if (res != NULL) { 200 return res; 201 } 202 } 203 } 204 205 res = _hrm.allocate_free_region(is_old); 206 207 if (res == NULL) { 208 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 209 "res == NULL, trying the secondary_free_list"); 210 res = new_region_try_secondary_free_list(is_old); 211 } 212 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 213 // Currently, only attempts to allocate GC alloc regions set 214 // do_expand to true. So, we should only reach here during a 215 // safepoint. If this assumption changes we might have to 216 // reconsider the use of _expand_heap_after_alloc_failure. 217 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 218 219 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 220 word_size * HeapWordSize); 221 222 if (expand(word_size * HeapWordSize)) { 223 // Given that expand() succeeded in expanding the heap, and we 224 // always expand the heap by an amount aligned to the heap 225 // region size, the free list should in theory not be empty. 226 // In either case allocate_free_region() will check for NULL. 227 res = _hrm.allocate_free_region(is_old); 228 } else { 229 _expand_heap_after_alloc_failure = false; 230 } 231 } 232 return res; 233 } 234 235 HeapWord* 236 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 237 uint num_regions, 238 size_t word_size, 239 AllocationContext_t context) { 240 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 241 assert(is_humongous(word_size), "word_size should be humongous"); 242 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 243 244 // Index of last region in the series. 245 uint last = first + num_regions - 1; 246 247 // We need to initialize the region(s) we just discovered. This is 248 // a bit tricky given that it can happen concurrently with 249 // refinement threads refining cards on these regions and 250 // potentially wanting to refine the BOT as they are scanning 251 // those cards (this can happen shortly after a cleanup; see CR 252 // 6991377). So we have to set up the region(s) carefully and in 253 // a specific order. 254 255 // The word size sum of all the regions we will allocate. 256 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 257 assert(word_size <= word_size_sum, "sanity"); 258 259 // This will be the "starts humongous" region. 260 HeapRegion* first_hr = region_at(first); 261 // The header of the new object will be placed at the bottom of 262 // the first region. 263 HeapWord* new_obj = first_hr->bottom(); 264 // This will be the new top of the new object. 265 HeapWord* obj_top = new_obj + word_size; 266 267 // First, we need to zero the header of the space that we will be 268 // allocating. When we update top further down, some refinement 269 // threads might try to scan the region. By zeroing the header we 270 // ensure that any thread that will try to scan the region will 271 // come across the zero klass word and bail out. 272 // 273 // NOTE: It would not have been correct to have used 274 // CollectedHeap::fill_with_object() and make the space look like 275 // an int array. The thread that is doing the allocation will 276 // later update the object header to a potentially different array 277 // type and, for a very short period of time, the klass and length 278 // fields will be inconsistent. This could cause a refinement 279 // thread to calculate the object size incorrectly. 280 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 281 282 // Next, pad out the unused tail of the last region with filler 283 // objects, for improved usage accounting. 284 // How many words we use for filler objects. 285 size_t word_fill_size = word_size_sum - word_size; 286 287 // How many words memory we "waste" which cannot hold a filler object. 288 size_t words_not_fillable = 0; 289 290 if (word_fill_size >= min_fill_size()) { 291 fill_with_objects(obj_top, word_fill_size); 292 } else if (word_fill_size > 0) { 293 // We have space to fill, but we cannot fit an object there. 294 words_not_fillable = word_fill_size; 295 word_fill_size = 0; 296 } 297 298 // We will set up the first region as "starts humongous". This 299 // will also update the BOT covering all the regions to reflect 300 // that there is a single object that starts at the bottom of the 301 // first region. 302 first_hr->set_starts_humongous(obj_top, word_fill_size); 303 first_hr->set_allocation_context(context); 304 // Then, if there are any, we will set up the "continues 305 // humongous" regions. 306 HeapRegion* hr = NULL; 307 for (uint i = first + 1; i <= last; ++i) { 308 hr = region_at(i); 309 hr->set_continues_humongous(first_hr); 310 hr->set_allocation_context(context); 311 } 312 313 // Up to this point no concurrent thread would have been able to 314 // do any scanning on any region in this series. All the top 315 // fields still point to bottom, so the intersection between 316 // [bottom,top] and [card_start,card_end] will be empty. Before we 317 // update the top fields, we'll do a storestore to make sure that 318 // no thread sees the update to top before the zeroing of the 319 // object header and the BOT initialization. 320 OrderAccess::storestore(); 321 322 // Now, we will update the top fields of the "continues humongous" 323 // regions except the last one. 324 for (uint i = first; i < last; ++i) { 325 hr = region_at(i); 326 hr->set_top(hr->end()); 327 } 328 329 hr = region_at(last); 330 // If we cannot fit a filler object, we must set top to the end 331 // of the humongous object, otherwise we cannot iterate the heap 332 // and the BOT will not be complete. 333 hr->set_top(hr->end() - words_not_fillable); 334 335 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 336 "obj_top should be in last region"); 337 338 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 339 340 assert(words_not_fillable == 0 || 341 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 342 "Miscalculation in humongous allocation"); 343 344 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 345 346 for (uint i = first; i <= last; ++i) { 347 hr = region_at(i); 348 _humongous_set.add(hr); 349 _hr_printer.alloc(hr); 350 } 351 352 return new_obj; 353 } 354 355 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 356 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 357 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 358 } 359 360 // If could fit into free regions w/o expansion, try. 361 // Otherwise, if can expand, do so. 362 // Otherwise, if using ex regions might help, try with ex given back. 363 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 364 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 365 366 _verifier->verify_region_sets_optional(); 367 368 uint first = G1_NO_HRM_INDEX; 369 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 370 371 if (obj_regions == 1) { 372 // Only one region to allocate, try to use a fast path by directly allocating 373 // from the free lists. Do not try to expand here, we will potentially do that 374 // later. 375 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 376 if (hr != NULL) { 377 first = hr->hrm_index(); 378 } 379 } else { 380 // We can't allocate humongous regions spanning more than one region while 381 // cleanupComplete() is running, since some of the regions we find to be 382 // empty might not yet be added to the free list. It is not straightforward 383 // to know in which list they are on so that we can remove them. We only 384 // need to do this if we need to allocate more than one region to satisfy the 385 // current humongous allocation request. If we are only allocating one region 386 // we use the one-region region allocation code (see above), that already 387 // potentially waits for regions from the secondary free list. 388 wait_while_free_regions_coming(); 389 append_secondary_free_list_if_not_empty_with_lock(); 390 391 // Policy: Try only empty regions (i.e. already committed first). Maybe we 392 // are lucky enough to find some. 393 first = _hrm.find_contiguous_only_empty(obj_regions); 394 if (first != G1_NO_HRM_INDEX) { 395 _hrm.allocate_free_regions_starting_at(first, obj_regions); 396 } 397 } 398 399 if (first == G1_NO_HRM_INDEX) { 400 // Policy: We could not find enough regions for the humongous object in the 401 // free list. Look through the heap to find a mix of free and uncommitted regions. 402 // If so, try expansion. 403 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 404 if (first != G1_NO_HRM_INDEX) { 405 // We found something. Make sure these regions are committed, i.e. expand 406 // the heap. Alternatively we could do a defragmentation GC. 407 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 408 word_size * HeapWordSize); 409 410 _hrm.expand_at(first, obj_regions, workers()); 411 g1_policy()->record_new_heap_size(num_regions()); 412 413 #ifdef ASSERT 414 for (uint i = first; i < first + obj_regions; ++i) { 415 HeapRegion* hr = region_at(i); 416 assert(hr->is_free(), "sanity"); 417 assert(hr->is_empty(), "sanity"); 418 assert(is_on_master_free_list(hr), "sanity"); 419 } 420 #endif 421 _hrm.allocate_free_regions_starting_at(first, obj_regions); 422 } else { 423 // Policy: Potentially trigger a defragmentation GC. 424 } 425 } 426 427 HeapWord* result = NULL; 428 if (first != G1_NO_HRM_INDEX) { 429 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 430 word_size, context); 431 assert(result != NULL, "it should always return a valid result"); 432 433 // A successful humongous object allocation changes the used space 434 // information of the old generation so we need to recalculate the 435 // sizes and update the jstat counters here. 436 g1mm()->update_sizes(); 437 } 438 439 _verifier->verify_region_sets_optional(); 440 441 return result; 442 } 443 444 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 445 assert_heap_not_locked_and_not_at_safepoint(); 446 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 447 448 uint dummy_gc_count_before; 449 uint dummy_gclocker_retry_count = 0; 450 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 451 } 452 453 HeapWord* 454 G1CollectedHeap::mem_allocate(size_t word_size, 455 bool* gc_overhead_limit_was_exceeded) { 456 assert_heap_not_locked_and_not_at_safepoint(); 457 458 // Loop until the allocation is satisfied, or unsatisfied after GC. 459 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 460 uint gc_count_before; 461 462 HeapWord* result = NULL; 463 if (!is_humongous(word_size)) { 464 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 465 } else { 466 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 467 } 468 if (result != NULL) { 469 return result; 470 } 471 472 // Create the garbage collection operation... 473 VM_G1CollectForAllocation op(gc_count_before, word_size); 474 op.set_allocation_context(AllocationContext::current()); 475 476 // ...and get the VM thread to execute it. 477 VMThread::execute(&op); 478 479 if (op.prologue_succeeded() && op.pause_succeeded()) { 480 // If the operation was successful we'll return the result even 481 // if it is NULL. If the allocation attempt failed immediately 482 // after a Full GC, it's unlikely we'll be able to allocate now. 483 HeapWord* result = op.result(); 484 if (result != NULL && !is_humongous(word_size)) { 485 // Allocations that take place on VM operations do not do any 486 // card dirtying and we have to do it here. We only have to do 487 // this for non-humongous allocations, though. 488 dirty_young_block(result, word_size); 489 } 490 return result; 491 } else { 492 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 493 return NULL; 494 } 495 assert(op.result() == NULL, 496 "the result should be NULL if the VM op did not succeed"); 497 } 498 499 // Give a warning if we seem to be looping forever. 500 if ((QueuedAllocationWarningCount > 0) && 501 (try_count % QueuedAllocationWarningCount == 0)) { 502 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count); 503 } 504 } 505 506 ShouldNotReachHere(); 507 return NULL; 508 } 509 510 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 511 AllocationContext_t context, 512 uint* gc_count_before_ret, 513 uint* gclocker_retry_count_ret) { 514 // Make sure you read the note in attempt_allocation_humongous(). 515 516 assert_heap_not_locked_and_not_at_safepoint(); 517 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 518 "be called for humongous allocation requests"); 519 520 // We should only get here after the first-level allocation attempt 521 // (attempt_allocation()) failed to allocate. 522 523 // We will loop until a) we manage to successfully perform the 524 // allocation or b) we successfully schedule a collection which 525 // fails to perform the allocation. b) is the only case when we'll 526 // return NULL. 527 HeapWord* result = NULL; 528 for (int try_count = 1; /* we'll return */; try_count += 1) { 529 bool should_try_gc; 530 uint gc_count_before; 531 532 { 533 MutexLockerEx x(Heap_lock); 534 result = _allocator->attempt_allocation_locked(word_size, context); 535 if (result != NULL) { 536 return result; 537 } 538 539 if (GCLocker::is_active_and_needs_gc()) { 540 if (g1_policy()->can_expand_young_list()) { 541 // No need for an ergo verbose message here, 542 // can_expand_young_list() does this when it returns true. 543 result = _allocator->attempt_allocation_force(word_size, context); 544 if (result != NULL) { 545 return result; 546 } 547 } 548 should_try_gc = false; 549 } else { 550 // The GCLocker may not be active but the GCLocker initiated 551 // GC may not yet have been performed (GCLocker::needs_gc() 552 // returns true). In this case we do not try this GC and 553 // wait until the GCLocker initiated GC is performed, and 554 // then retry the allocation. 555 if (GCLocker::needs_gc()) { 556 should_try_gc = false; 557 } else { 558 // Read the GC count while still holding the Heap_lock. 559 gc_count_before = total_collections(); 560 should_try_gc = true; 561 } 562 } 563 } 564 565 if (should_try_gc) { 566 bool succeeded; 567 result = do_collection_pause(word_size, gc_count_before, &succeeded, 568 GCCause::_g1_inc_collection_pause); 569 if (result != NULL) { 570 assert(succeeded, "only way to get back a non-NULL result"); 571 return result; 572 } 573 574 if (succeeded) { 575 // If we get here we successfully scheduled a collection which 576 // failed to allocate. No point in trying to allocate 577 // further. We'll just return NULL. 578 MutexLockerEx x(Heap_lock); 579 *gc_count_before_ret = total_collections(); 580 return NULL; 581 } 582 } else { 583 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 584 MutexLockerEx x(Heap_lock); 585 *gc_count_before_ret = total_collections(); 586 return NULL; 587 } 588 // The GCLocker is either active or the GCLocker initiated 589 // GC has not yet been performed. Stall until it is and 590 // then retry the allocation. 591 GCLocker::stall_until_clear(); 592 (*gclocker_retry_count_ret) += 1; 593 } 594 595 // We can reach here if we were unsuccessful in scheduling a 596 // collection (because another thread beat us to it) or if we were 597 // stalled due to the GC locker. In either can we should retry the 598 // allocation attempt in case another thread successfully 599 // performed a collection and reclaimed enough space. We do the 600 // first attempt (without holding the Heap_lock) here and the 601 // follow-on attempt will be at the start of the next loop 602 // iteration (after taking the Heap_lock). 603 result = _allocator->attempt_allocation(word_size, context); 604 if (result != NULL) { 605 return result; 606 } 607 608 // Give a warning if we seem to be looping forever. 609 if ((QueuedAllocationWarningCount > 0) && 610 (try_count % QueuedAllocationWarningCount == 0)) { 611 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() " 612 "retries %d times", try_count); 613 } 614 } 615 616 ShouldNotReachHere(); 617 return NULL; 618 } 619 620 void G1CollectedHeap::begin_archive_alloc_range(bool open) { 621 assert_at_safepoint(true /* should_be_vm_thread */); 622 if (_archive_allocator == NULL) { 623 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open); 624 } 625 } 626 627 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 628 // Allocations in archive regions cannot be of a size that would be considered 629 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 630 // may be different at archive-restore time. 631 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 632 } 633 634 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 635 assert_at_safepoint(true /* should_be_vm_thread */); 636 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 637 if (is_archive_alloc_too_large(word_size)) { 638 return NULL; 639 } 640 return _archive_allocator->archive_mem_allocate(word_size); 641 } 642 643 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 644 size_t end_alignment_in_bytes) { 645 assert_at_safepoint(true /* should_be_vm_thread */); 646 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 647 648 // Call complete_archive to do the real work, filling in the MemRegion 649 // array with the archive regions. 650 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 651 delete _archive_allocator; 652 _archive_allocator = NULL; 653 } 654 655 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 656 assert(ranges != NULL, "MemRegion array NULL"); 657 assert(count != 0, "No MemRegions provided"); 658 MemRegion reserved = _hrm.reserved(); 659 for (size_t i = 0; i < count; i++) { 660 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 661 return false; 662 } 663 } 664 return true; 665 } 666 667 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, 668 size_t count, 669 bool open) { 670 assert(!is_init_completed(), "Expect to be called at JVM init time"); 671 assert(ranges != NULL, "MemRegion array NULL"); 672 assert(count != 0, "No MemRegions provided"); 673 MutexLockerEx x(Heap_lock); 674 675 MemRegion reserved = _hrm.reserved(); 676 HeapWord* prev_last_addr = NULL; 677 HeapRegion* prev_last_region = NULL; 678 679 // Temporarily disable pretouching of heap pages. This interface is used 680 // when mmap'ing archived heap data in, so pre-touching is wasted. 681 FlagSetting fs(AlwaysPreTouch, false); 682 683 // Enable archive object checking used by G1MarkSweep. We have to let it know 684 // about each archive range, so that objects in those ranges aren't marked. 685 G1ArchiveAllocator::enable_archive_object_check(); 686 687 // For each specified MemRegion range, allocate the corresponding G1 688 // regions and mark them as archive regions. We expect the ranges 689 // in ascending starting address order, without overlap. 690 for (size_t i = 0; i < count; i++) { 691 MemRegion curr_range = ranges[i]; 692 HeapWord* start_address = curr_range.start(); 693 size_t word_size = curr_range.word_size(); 694 HeapWord* last_address = curr_range.last(); 695 size_t commits = 0; 696 697 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 698 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 699 p2i(start_address), p2i(last_address)); 700 guarantee(start_address > prev_last_addr, 701 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 702 p2i(start_address), p2i(prev_last_addr)); 703 prev_last_addr = last_address; 704 705 // Check for ranges that start in the same G1 region in which the previous 706 // range ended, and adjust the start address so we don't try to allocate 707 // the same region again. If the current range is entirely within that 708 // region, skip it, just adjusting the recorded top. 709 HeapRegion* start_region = _hrm.addr_to_region(start_address); 710 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 711 start_address = start_region->end(); 712 if (start_address > last_address) { 713 increase_used(word_size * HeapWordSize); 714 start_region->set_top(last_address + 1); 715 continue; 716 } 717 start_region->set_top(start_address); 718 curr_range = MemRegion(start_address, last_address + 1); 719 start_region = _hrm.addr_to_region(start_address); 720 } 721 722 // Perform the actual region allocation, exiting if it fails. 723 // Then note how much new space we have allocated. 724 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 725 return false; 726 } 727 increase_used(word_size * HeapWordSize); 728 if (commits != 0) { 729 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 730 HeapRegion::GrainWords * HeapWordSize * commits); 731 732 } 733 734 // Mark each G1 region touched by the range as archive, add it to 735 // the old set, and set the allocation context and top. 736 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 737 HeapRegion* last_region = _hrm.addr_to_region(last_address); 738 prev_last_region = last_region; 739 740 while (curr_region != NULL) { 741 assert(curr_region->is_empty() && !curr_region->is_pinned(), 742 "Region already in use (index %u)", curr_region->hrm_index()); 743 curr_region->set_allocation_context(AllocationContext::system()); 744 if (open) { 745 curr_region->set_open_archive(); 746 } else { 747 curr_region->set_closed_archive(); 748 } 749 _hr_printer.alloc(curr_region); 750 _old_set.add(curr_region); 751 HeapWord* top; 752 HeapRegion* next_region; 753 if (curr_region != last_region) { 754 top = curr_region->end(); 755 next_region = _hrm.next_region_in_heap(curr_region); 756 } else { 757 top = last_address + 1; 758 next_region = NULL; 759 } 760 curr_region->set_top(top); 761 curr_region->set_first_dead(top); 762 curr_region->set_end_of_live(top); 763 curr_region = next_region; 764 } 765 766 // Notify mark-sweep of the archive 767 G1ArchiveAllocator::set_range_archive(curr_range, open); 768 } 769 return true; 770 } 771 772 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 773 assert(!is_init_completed(), "Expect to be called at JVM init time"); 774 assert(ranges != NULL, "MemRegion array NULL"); 775 assert(count != 0, "No MemRegions provided"); 776 MemRegion reserved = _hrm.reserved(); 777 HeapWord *prev_last_addr = NULL; 778 HeapRegion* prev_last_region = NULL; 779 780 // For each MemRegion, create filler objects, if needed, in the G1 regions 781 // that contain the address range. The address range actually within the 782 // MemRegion will not be modified. That is assumed to have been initialized 783 // elsewhere, probably via an mmap of archived heap data. 784 MutexLockerEx x(Heap_lock); 785 for (size_t i = 0; i < count; i++) { 786 HeapWord* start_address = ranges[i].start(); 787 HeapWord* last_address = ranges[i].last(); 788 789 assert(reserved.contains(start_address) && reserved.contains(last_address), 790 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 791 p2i(start_address), p2i(last_address)); 792 assert(start_address > prev_last_addr, 793 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 794 p2i(start_address), p2i(prev_last_addr)); 795 796 HeapRegion* start_region = _hrm.addr_to_region(start_address); 797 HeapRegion* last_region = _hrm.addr_to_region(last_address); 798 HeapWord* bottom_address = start_region->bottom(); 799 800 // Check for a range beginning in the same region in which the 801 // previous one ended. 802 if (start_region == prev_last_region) { 803 bottom_address = prev_last_addr + 1; 804 } 805 806 // Verify that the regions were all marked as archive regions by 807 // alloc_archive_regions. 808 HeapRegion* curr_region = start_region; 809 while (curr_region != NULL) { 810 guarantee(curr_region->is_archive(), 811 "Expected archive region at index %u", curr_region->hrm_index()); 812 if (curr_region != last_region) { 813 curr_region = _hrm.next_region_in_heap(curr_region); 814 } else { 815 curr_region = NULL; 816 } 817 } 818 819 prev_last_addr = last_address; 820 prev_last_region = last_region; 821 822 // Fill the memory below the allocated range with dummy object(s), 823 // if the region bottom does not match the range start, or if the previous 824 // range ended within the same G1 region, and there is a gap. 825 if (start_address != bottom_address) { 826 size_t fill_size = pointer_delta(start_address, bottom_address); 827 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 828 increase_used(fill_size * HeapWordSize); 829 } 830 } 831 } 832 833 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 834 uint* gc_count_before_ret, 835 uint* gclocker_retry_count_ret) { 836 assert_heap_not_locked_and_not_at_safepoint(); 837 assert(!is_humongous(word_size), "attempt_allocation() should not " 838 "be called for humongous allocation requests"); 839 840 AllocationContext_t context = AllocationContext::current(); 841 HeapWord* result = _allocator->attempt_allocation(word_size, context); 842 843 if (result == NULL) { 844 result = attempt_allocation_slow(word_size, 845 context, 846 gc_count_before_ret, 847 gclocker_retry_count_ret); 848 } 849 assert_heap_not_locked(); 850 if (result != NULL) { 851 dirty_young_block(result, word_size); 852 } 853 return result; 854 } 855 856 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 857 assert(!is_init_completed(), "Expect to be called at JVM init time"); 858 assert(ranges != NULL, "MemRegion array NULL"); 859 assert(count != 0, "No MemRegions provided"); 860 MemRegion reserved = _hrm.reserved(); 861 HeapWord* prev_last_addr = NULL; 862 HeapRegion* prev_last_region = NULL; 863 size_t size_used = 0; 864 size_t uncommitted_regions = 0; 865 866 // For each Memregion, free the G1 regions that constitute it, and 867 // notify mark-sweep that the range is no longer to be considered 'archive.' 868 MutexLockerEx x(Heap_lock); 869 for (size_t i = 0; i < count; i++) { 870 HeapWord* start_address = ranges[i].start(); 871 HeapWord* last_address = ranges[i].last(); 872 873 assert(reserved.contains(start_address) && reserved.contains(last_address), 874 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 875 p2i(start_address), p2i(last_address)); 876 assert(start_address > prev_last_addr, 877 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 878 p2i(start_address), p2i(prev_last_addr)); 879 size_used += ranges[i].byte_size(); 880 prev_last_addr = last_address; 881 882 HeapRegion* start_region = _hrm.addr_to_region(start_address); 883 HeapRegion* last_region = _hrm.addr_to_region(last_address); 884 885 // Check for ranges that start in the same G1 region in which the previous 886 // range ended, and adjust the start address so we don't try to free 887 // the same region again. If the current range is entirely within that 888 // region, skip it. 889 if (start_region == prev_last_region) { 890 start_address = start_region->end(); 891 if (start_address > last_address) { 892 continue; 893 } 894 start_region = _hrm.addr_to_region(start_address); 895 } 896 prev_last_region = last_region; 897 898 // After verifying that each region was marked as an archive region by 899 // alloc_archive_regions, set it free and empty and uncommit it. 900 HeapRegion* curr_region = start_region; 901 while (curr_region != NULL) { 902 guarantee(curr_region->is_archive(), 903 "Expected archive region at index %u", curr_region->hrm_index()); 904 uint curr_index = curr_region->hrm_index(); 905 _old_set.remove(curr_region); 906 curr_region->set_free(); 907 curr_region->set_top(curr_region->bottom()); 908 if (curr_region != last_region) { 909 curr_region = _hrm.next_region_in_heap(curr_region); 910 } else { 911 curr_region = NULL; 912 } 913 _hrm.shrink_at(curr_index, 1); 914 uncommitted_regions++; 915 } 916 917 // Notify mark-sweep that this is no longer an archive range. 918 G1ArchiveAllocator::set_range_archive(ranges[i], false); 919 } 920 921 if (uncommitted_regions != 0) { 922 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 923 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 924 } 925 decrease_used(size_used); 926 } 927 928 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 929 uint* gc_count_before_ret, 930 uint* gclocker_retry_count_ret) { 931 // The structure of this method has a lot of similarities to 932 // attempt_allocation_slow(). The reason these two were not merged 933 // into a single one is that such a method would require several "if 934 // allocation is not humongous do this, otherwise do that" 935 // conditional paths which would obscure its flow. In fact, an early 936 // version of this code did use a unified method which was harder to 937 // follow and, as a result, it had subtle bugs that were hard to 938 // track down. So keeping these two methods separate allows each to 939 // be more readable. It will be good to keep these two in sync as 940 // much as possible. 941 942 assert_heap_not_locked_and_not_at_safepoint(); 943 assert(is_humongous(word_size), "attempt_allocation_humongous() " 944 "should only be called for humongous allocations"); 945 946 // Humongous objects can exhaust the heap quickly, so we should check if we 947 // need to start a marking cycle at each humongous object allocation. We do 948 // the check before we do the actual allocation. The reason for doing it 949 // before the allocation is that we avoid having to keep track of the newly 950 // allocated memory while we do a GC. 951 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 952 word_size)) { 953 collect(GCCause::_g1_humongous_allocation); 954 } 955 956 // We will loop until a) we manage to successfully perform the 957 // allocation or b) we successfully schedule a collection which 958 // fails to perform the allocation. b) is the only case when we'll 959 // return NULL. 960 HeapWord* result = NULL; 961 for (int try_count = 1; /* we'll return */; try_count += 1) { 962 bool should_try_gc; 963 uint gc_count_before; 964 965 { 966 MutexLockerEx x(Heap_lock); 967 968 // Given that humongous objects are not allocated in young 969 // regions, we'll first try to do the allocation without doing a 970 // collection hoping that there's enough space in the heap. 971 result = humongous_obj_allocate(word_size, AllocationContext::current()); 972 if (result != NULL) { 973 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 974 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 975 return result; 976 } 977 978 if (GCLocker::is_active_and_needs_gc()) { 979 should_try_gc = false; 980 } else { 981 // The GCLocker may not be active but the GCLocker initiated 982 // GC may not yet have been performed (GCLocker::needs_gc() 983 // returns true). In this case we do not try this GC and 984 // wait until the GCLocker initiated GC is performed, and 985 // then retry the allocation. 986 if (GCLocker::needs_gc()) { 987 should_try_gc = false; 988 } else { 989 // Read the GC count while still holding the Heap_lock. 990 gc_count_before = total_collections(); 991 should_try_gc = true; 992 } 993 } 994 } 995 996 if (should_try_gc) { 997 // If we failed to allocate the humongous object, we should try to 998 // do a collection pause (if we're allowed) in case it reclaims 999 // enough space for the allocation to succeed after the pause. 1000 1001 bool succeeded; 1002 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1003 GCCause::_g1_humongous_allocation); 1004 if (result != NULL) { 1005 assert(succeeded, "only way to get back a non-NULL result"); 1006 return result; 1007 } 1008 1009 if (succeeded) { 1010 // If we get here we successfully scheduled a collection which 1011 // failed to allocate. No point in trying to allocate 1012 // further. We'll just return NULL. 1013 MutexLockerEx x(Heap_lock); 1014 *gc_count_before_ret = total_collections(); 1015 return NULL; 1016 } 1017 } else { 1018 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1019 MutexLockerEx x(Heap_lock); 1020 *gc_count_before_ret = total_collections(); 1021 return NULL; 1022 } 1023 // The GCLocker is either active or the GCLocker initiated 1024 // GC has not yet been performed. Stall until it is and 1025 // then retry the allocation. 1026 GCLocker::stall_until_clear(); 1027 (*gclocker_retry_count_ret) += 1; 1028 } 1029 1030 // We can reach here if we were unsuccessful in scheduling a 1031 // collection (because another thread beat us to it) or if we were 1032 // stalled due to the GC locker. In either can we should retry the 1033 // allocation attempt in case another thread successfully 1034 // performed a collection and reclaimed enough space. Give a 1035 // warning if we seem to be looping forever. 1036 1037 if ((QueuedAllocationWarningCount > 0) && 1038 (try_count % QueuedAllocationWarningCount == 0)) { 1039 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() " 1040 "retries %d times", try_count); 1041 } 1042 } 1043 1044 ShouldNotReachHere(); 1045 return NULL; 1046 } 1047 1048 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1049 AllocationContext_t context, 1050 bool expect_null_mutator_alloc_region) { 1051 assert_at_safepoint(true /* should_be_vm_thread */); 1052 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1053 "the current alloc region was unexpectedly found to be non-NULL"); 1054 1055 if (!is_humongous(word_size)) { 1056 return _allocator->attempt_allocation_locked(word_size, context); 1057 } else { 1058 HeapWord* result = humongous_obj_allocate(word_size, context); 1059 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1060 collector_state()->set_initiate_conc_mark_if_possible(true); 1061 } 1062 return result; 1063 } 1064 1065 ShouldNotReachHere(); 1066 } 1067 1068 class PostCompactionPrinterClosure: public HeapRegionClosure { 1069 private: 1070 G1HRPrinter* _hr_printer; 1071 public: 1072 bool doHeapRegion(HeapRegion* hr) { 1073 assert(!hr->is_young(), "not expecting to find young regions"); 1074 _hr_printer->post_compaction(hr); 1075 return false; 1076 } 1077 1078 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1079 : _hr_printer(hr_printer) { } 1080 }; 1081 1082 void G1CollectedHeap::print_hrm_post_compaction() { 1083 if (_hr_printer.is_active()) { 1084 PostCompactionPrinterClosure cl(hr_printer()); 1085 heap_region_iterate(&cl); 1086 } 1087 1088 } 1089 1090 void G1CollectedHeap::abort_concurrent_cycle() { 1091 // Note: When we have a more flexible GC logging framework that 1092 // allows us to add optional attributes to a GC log record we 1093 // could consider timing and reporting how long we wait in the 1094 // following two methods. 1095 wait_while_free_regions_coming(); 1096 // If we start the compaction before the CM threads finish 1097 // scanning the root regions we might trip them over as we'll 1098 // be moving objects / updating references. So let's wait until 1099 // they are done. By telling them to abort, they should complete 1100 // early. 1101 _cm->root_regions()->abort(); 1102 _cm->root_regions()->wait_until_scan_finished(); 1103 append_secondary_free_list_if_not_empty_with_lock(); 1104 1105 // Disable discovery and empty the discovered lists 1106 // for the CM ref processor. 1107 ref_processor_cm()->disable_discovery(); 1108 ref_processor_cm()->abandon_partial_discovery(); 1109 ref_processor_cm()->verify_no_references_recorded(); 1110 1111 // Abandon current iterations of concurrent marking and concurrent 1112 // refinement, if any are in progress. 1113 concurrent_mark()->abort(); 1114 } 1115 1116 void G1CollectedHeap::prepare_heap_for_full_collection() { 1117 // Make sure we'll choose a new allocation region afterwards. 1118 _allocator->release_mutator_alloc_region(); 1119 _allocator->abandon_gc_alloc_regions(); 1120 g1_rem_set()->cleanupHRRS(); 1121 1122 // We may have added regions to the current incremental collection 1123 // set between the last GC or pause and now. We need to clear the 1124 // incremental collection set and then start rebuilding it afresh 1125 // after this full GC. 1126 abandon_collection_set(collection_set()); 1127 1128 tear_down_region_sets(false /* free_list_only */); 1129 collector_state()->set_gcs_are_young(true); 1130 } 1131 1132 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1133 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1134 assert(used() == recalculate_used(), "Should be equal"); 1135 _verifier->verify_region_sets_optional(); 1136 _verifier->verify_before_gc(); 1137 _verifier->check_bitmaps("Full GC Start"); 1138 } 1139 1140 void G1CollectedHeap::prepare_heap_for_mutators() { 1141 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1142 ClassLoaderDataGraph::purge(); 1143 MetaspaceAux::verify_metrics(); 1144 1145 // Prepare heap for normal collections. 1146 assert(num_free_regions() == 0, "we should not have added any free regions"); 1147 rebuild_region_sets(false /* free_list_only */); 1148 abort_refinement(); 1149 resize_if_necessary_after_full_collection(); 1150 1151 // Rebuild the strong code root lists for each region 1152 rebuild_strong_code_roots(); 1153 1154 // Start a new incremental collection set for the next pause 1155 start_new_collection_set(); 1156 1157 _allocator->init_mutator_alloc_region(); 1158 1159 // Post collection state updates. 1160 MetaspaceGC::compute_new_size(); 1161 } 1162 1163 void G1CollectedHeap::abort_refinement() { 1164 if (_hot_card_cache->use_cache()) { 1165 _hot_card_cache->reset_hot_cache(); 1166 } 1167 1168 // Discard all remembered set updates. 1169 JavaThread::dirty_card_queue_set().abandon_logs(); 1170 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1171 } 1172 1173 void G1CollectedHeap::verify_after_full_collection() { 1174 check_gc_time_stamps(); 1175 _hrm.verify_optional(); 1176 _verifier->verify_region_sets_optional(); 1177 _verifier->verify_after_gc(); 1178 // Clear the previous marking bitmap, if needed for bitmap verification. 1179 // Note we cannot do this when we clear the next marking bitmap in 1180 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1181 // objects marked during a full GC against the previous bitmap. 1182 // But we need to clear it before calling check_bitmaps below since 1183 // the full GC has compacted objects and updated TAMS but not updated 1184 // the prev bitmap. 1185 if (G1VerifyBitmaps) { 1186 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1187 _cm->clear_prev_bitmap(workers()); 1188 } 1189 _verifier->check_bitmaps("Full GC End"); 1190 1191 // At this point there should be no regions in the 1192 // entire heap tagged as young. 1193 assert(check_young_list_empty(), "young list should be empty at this point"); 1194 1195 // Note: since we've just done a full GC, concurrent 1196 // marking is no longer active. Therefore we need not 1197 // re-enable reference discovery for the CM ref processor. 1198 // That will be done at the start of the next marking cycle. 1199 // We also know that the STW processor should no longer 1200 // discover any new references. 1201 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1202 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1203 ref_processor_stw()->verify_no_references_recorded(); 1204 ref_processor_cm()->verify_no_references_recorded(); 1205 } 1206 1207 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1208 // Post collection logging. 1209 // We should do this after we potentially resize the heap so 1210 // that all the COMMIT / UNCOMMIT events are generated before 1211 // the compaction events. 1212 print_hrm_post_compaction(); 1213 heap_transition->print(); 1214 print_heap_after_gc(); 1215 print_heap_regions(); 1216 #ifdef TRACESPINNING 1217 ParallelTaskTerminator::print_termination_counts(); 1218 #endif 1219 } 1220 1221 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1222 bool clear_all_soft_refs) { 1223 assert_at_safepoint(true /* should_be_vm_thread */); 1224 1225 if (GCLocker::check_active_before_gc()) { 1226 // Full GC was not completed. 1227 return false; 1228 } 1229 1230 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1231 collector_policy()->should_clear_all_soft_refs(); 1232 1233 G1FullCollector collector(this, &_full_gc_mem_mgr, explicit_gc, do_clear_all_soft_refs); 1234 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1235 1236 collector.prepare_collection(); 1237 collector.collect(); 1238 collector.complete_collection(); 1239 1240 // Full collection was successfully completed. 1241 return true; 1242 } 1243 1244 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1245 // Currently, there is no facility in the do_full_collection(bool) API to notify 1246 // the caller that the collection did not succeed (e.g., because it was locked 1247 // out by the GC locker). So, right now, we'll ignore the return value. 1248 bool dummy = do_full_collection(true, /* explicit_gc */ 1249 clear_all_soft_refs); 1250 } 1251 1252 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1253 // Capacity, free and used after the GC counted as full regions to 1254 // include the waste in the following calculations. 1255 const size_t capacity_after_gc = capacity(); 1256 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes(); 1257 1258 // This is enforced in arguments.cpp. 1259 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1260 "otherwise the code below doesn't make sense"); 1261 1262 // We don't have floating point command-line arguments 1263 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1264 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1265 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1266 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1267 1268 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1269 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1270 1271 // We have to be careful here as these two calculations can overflow 1272 // 32-bit size_t's. 1273 double used_after_gc_d = (double) used_after_gc; 1274 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1275 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1276 1277 // Let's make sure that they are both under the max heap size, which 1278 // by default will make them fit into a size_t. 1279 double desired_capacity_upper_bound = (double) max_heap_size; 1280 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1281 desired_capacity_upper_bound); 1282 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1283 desired_capacity_upper_bound); 1284 1285 // We can now safely turn them into size_t's. 1286 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1287 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1288 1289 // This assert only makes sense here, before we adjust them 1290 // with respect to the min and max heap size. 1291 assert(minimum_desired_capacity <= maximum_desired_capacity, 1292 "minimum_desired_capacity = " SIZE_FORMAT ", " 1293 "maximum_desired_capacity = " SIZE_FORMAT, 1294 minimum_desired_capacity, maximum_desired_capacity); 1295 1296 // Should not be greater than the heap max size. No need to adjust 1297 // it with respect to the heap min size as it's a lower bound (i.e., 1298 // we'll try to make the capacity larger than it, not smaller). 1299 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1300 // Should not be less than the heap min size. No need to adjust it 1301 // with respect to the heap max size as it's an upper bound (i.e., 1302 // we'll try to make the capacity smaller than it, not greater). 1303 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1304 1305 if (capacity_after_gc < minimum_desired_capacity) { 1306 // Don't expand unless it's significant 1307 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1308 1309 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1310 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1311 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1312 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio); 1313 1314 expand(expand_bytes, _workers); 1315 1316 // No expansion, now see if we want to shrink 1317 } else if (capacity_after_gc > maximum_desired_capacity) { 1318 // Capacity too large, compute shrinking size 1319 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1320 1321 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1322 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1323 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1324 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio); 1325 1326 shrink(shrink_bytes); 1327 } 1328 } 1329 1330 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1331 AllocationContext_t context, 1332 bool do_gc, 1333 bool clear_all_soft_refs, 1334 bool expect_null_mutator_alloc_region, 1335 bool* gc_succeeded) { 1336 *gc_succeeded = true; 1337 // Let's attempt the allocation first. 1338 HeapWord* result = 1339 attempt_allocation_at_safepoint(word_size, 1340 context, 1341 expect_null_mutator_alloc_region); 1342 if (result != NULL) { 1343 assert(*gc_succeeded, "sanity"); 1344 return result; 1345 } 1346 1347 // In a G1 heap, we're supposed to keep allocation from failing by 1348 // incremental pauses. Therefore, at least for now, we'll favor 1349 // expansion over collection. (This might change in the future if we can 1350 // do something smarter than full collection to satisfy a failed alloc.) 1351 result = expand_and_allocate(word_size, context); 1352 if (result != NULL) { 1353 assert(*gc_succeeded, "sanity"); 1354 return result; 1355 } 1356 1357 if (do_gc) { 1358 // Expansion didn't work, we'll try to do a Full GC. 1359 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1360 clear_all_soft_refs); 1361 } 1362 1363 return NULL; 1364 } 1365 1366 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1367 AllocationContext_t context, 1368 bool* succeeded) { 1369 assert_at_safepoint(true /* should_be_vm_thread */); 1370 1371 // Attempts to allocate followed by Full GC. 1372 HeapWord* result = 1373 satisfy_failed_allocation_helper(word_size, 1374 context, 1375 true, /* do_gc */ 1376 false, /* clear_all_soft_refs */ 1377 false, /* expect_null_mutator_alloc_region */ 1378 succeeded); 1379 1380 if (result != NULL || !*succeeded) { 1381 return result; 1382 } 1383 1384 // Attempts to allocate followed by Full GC that will collect all soft references. 1385 result = satisfy_failed_allocation_helper(word_size, 1386 context, 1387 true, /* do_gc */ 1388 true, /* clear_all_soft_refs */ 1389 true, /* expect_null_mutator_alloc_region */ 1390 succeeded); 1391 1392 if (result != NULL || !*succeeded) { 1393 return result; 1394 } 1395 1396 // Attempts to allocate, no GC 1397 result = satisfy_failed_allocation_helper(word_size, 1398 context, 1399 false, /* do_gc */ 1400 false, /* clear_all_soft_refs */ 1401 true, /* expect_null_mutator_alloc_region */ 1402 succeeded); 1403 1404 if (result != NULL) { 1405 assert(*succeeded, "sanity"); 1406 return result; 1407 } 1408 1409 assert(!collector_policy()->should_clear_all_soft_refs(), 1410 "Flag should have been handled and cleared prior to this point"); 1411 1412 // What else? We might try synchronous finalization later. If the total 1413 // space available is large enough for the allocation, then a more 1414 // complete compaction phase than we've tried so far might be 1415 // appropriate. 1416 assert(*succeeded, "sanity"); 1417 return NULL; 1418 } 1419 1420 // Attempting to expand the heap sufficiently 1421 // to support an allocation of the given "word_size". If 1422 // successful, perform the allocation and return the address of the 1423 // allocated block, or else "NULL". 1424 1425 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1426 assert_at_safepoint(true /* should_be_vm_thread */); 1427 1428 _verifier->verify_region_sets_optional(); 1429 1430 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1431 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1432 word_size * HeapWordSize); 1433 1434 1435 if (expand(expand_bytes, _workers)) { 1436 _hrm.verify_optional(); 1437 _verifier->verify_region_sets_optional(); 1438 return attempt_allocation_at_safepoint(word_size, 1439 context, 1440 false /* expect_null_mutator_alloc_region */); 1441 } 1442 return NULL; 1443 } 1444 1445 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1446 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1447 aligned_expand_bytes = align_up(aligned_expand_bytes, 1448 HeapRegion::GrainBytes); 1449 1450 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1451 expand_bytes, aligned_expand_bytes); 1452 1453 if (is_maximal_no_gc()) { 1454 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1455 return false; 1456 } 1457 1458 double expand_heap_start_time_sec = os::elapsedTime(); 1459 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1460 assert(regions_to_expand > 0, "Must expand by at least one region"); 1461 1462 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers); 1463 if (expand_time_ms != NULL) { 1464 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1465 } 1466 1467 if (expanded_by > 0) { 1468 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1469 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1470 g1_policy()->record_new_heap_size(num_regions()); 1471 } else { 1472 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1473 1474 // The expansion of the virtual storage space was unsuccessful. 1475 // Let's see if it was because we ran out of swap. 1476 if (G1ExitOnExpansionFailure && 1477 _hrm.available() >= regions_to_expand) { 1478 // We had head room... 1479 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1480 } 1481 } 1482 return regions_to_expand > 0; 1483 } 1484 1485 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1486 size_t aligned_shrink_bytes = 1487 ReservedSpace::page_align_size_down(shrink_bytes); 1488 aligned_shrink_bytes = align_down(aligned_shrink_bytes, 1489 HeapRegion::GrainBytes); 1490 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1491 1492 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1493 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1494 1495 1496 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", 1497 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1498 if (num_regions_removed > 0) { 1499 g1_policy()->record_new_heap_size(num_regions()); 1500 } else { 1501 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1502 } 1503 } 1504 1505 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1506 _verifier->verify_region_sets_optional(); 1507 1508 // We should only reach here at the end of a Full GC which means we 1509 // should not not be holding to any GC alloc regions. The method 1510 // below will make sure of that and do any remaining clean up. 1511 _allocator->abandon_gc_alloc_regions(); 1512 1513 // Instead of tearing down / rebuilding the free lists here, we 1514 // could instead use the remove_all_pending() method on free_list to 1515 // remove only the ones that we need to remove. 1516 tear_down_region_sets(true /* free_list_only */); 1517 shrink_helper(shrink_bytes); 1518 rebuild_region_sets(true /* free_list_only */); 1519 1520 _hrm.verify_optional(); 1521 _verifier->verify_region_sets_optional(); 1522 } 1523 1524 // Public methods. 1525 1526 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1527 CollectedHeap(), 1528 _young_gen_sampling_thread(NULL), 1529 _collector_policy(collector_policy), 1530 _mem_mgr("G1 Young Generation", "end of minor GC"), 1531 _full_gc_mem_mgr("G1 Old Generation", "end of major GC"), 1532 _eden_pool(NULL), 1533 _survivor_pool(NULL), 1534 _old_pool(NULL), 1535 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1536 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1537 _g1_policy(create_g1_policy(_gc_timer_stw)), 1538 _collection_set(this, _g1_policy), 1539 _dirty_card_queue_set(false), 1540 _is_alive_closure_cm(this), 1541 _is_alive_closure_stw(this), 1542 _ref_processor_cm(NULL), 1543 _ref_processor_stw(NULL), 1544 _bot(NULL), 1545 _hot_card_cache(NULL), 1546 _g1_rem_set(NULL), 1547 _cr(NULL), 1548 _g1mm(NULL), 1549 _preserved_marks_set(true /* in_c_heap */), 1550 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1551 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1552 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1553 _humongous_reclaim_candidates(), 1554 _has_humongous_reclaim_candidates(false), 1555 _archive_allocator(NULL), 1556 _free_regions_coming(false), 1557 _gc_time_stamp(0), 1558 _summary_bytes_used(0), 1559 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1560 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1561 _expand_heap_after_alloc_failure(true), 1562 _old_marking_cycles_started(0), 1563 _old_marking_cycles_completed(0), 1564 _in_cset_fast_test() { 1565 1566 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1567 /* are_GC_task_threads */true, 1568 /* are_ConcurrentGC_threads */false); 1569 _workers->initialize_workers(); 1570 _verifier = new G1HeapVerifier(this); 1571 1572 _allocator = G1Allocator::create_allocator(this); 1573 1574 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1575 1576 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1577 1578 // Override the default _filler_array_max_size so that no humongous filler 1579 // objects are created. 1580 _filler_array_max_size = _humongous_object_threshold_in_words; 1581 1582 uint n_queues = ParallelGCThreads; 1583 _task_queues = new RefToScanQueueSet(n_queues); 1584 1585 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1586 1587 for (uint i = 0; i < n_queues; i++) { 1588 RefToScanQueue* q = new RefToScanQueue(); 1589 q->initialize(); 1590 _task_queues->register_queue(i, q); 1591 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1592 } 1593 1594 // Initialize the G1EvacuationFailureALot counters and flags. 1595 NOT_PRODUCT(reset_evacuation_should_fail();) 1596 1597 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1598 } 1599 1600 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1601 size_t size, 1602 size_t translation_factor) { 1603 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1604 // Allocate a new reserved space, preferring to use large pages. 1605 ReservedSpace rs(size, preferred_page_size); 1606 G1RegionToSpaceMapper* result = 1607 G1RegionToSpaceMapper::create_mapper(rs, 1608 size, 1609 rs.alignment(), 1610 HeapRegion::GrainBytes, 1611 translation_factor, 1612 mtGC); 1613 1614 os::trace_page_sizes_for_requested_size(description, 1615 size, 1616 preferred_page_size, 1617 rs.alignment(), 1618 rs.base(), 1619 rs.size()); 1620 1621 return result; 1622 } 1623 1624 jint G1CollectedHeap::initialize_concurrent_refinement() { 1625 jint ecode = JNI_OK; 1626 _cr = G1ConcurrentRefine::create(&ecode); 1627 return ecode; 1628 } 1629 1630 jint G1CollectedHeap::initialize_young_gen_sampling_thread() { 1631 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread(); 1632 if (_young_gen_sampling_thread->osthread() == NULL) { 1633 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread"); 1634 return JNI_ENOMEM; 1635 } 1636 return JNI_OK; 1637 } 1638 1639 jint G1CollectedHeap::initialize() { 1640 CollectedHeap::pre_initialize(); 1641 os::enable_vtime(); 1642 1643 // Necessary to satisfy locking discipline assertions. 1644 1645 MutexLocker x(Heap_lock); 1646 1647 // While there are no constraints in the GC code that HeapWordSize 1648 // be any particular value, there are multiple other areas in the 1649 // system which believe this to be true (e.g. oop->object_size in some 1650 // cases incorrectly returns the size in wordSize units rather than 1651 // HeapWordSize). 1652 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1653 1654 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1655 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1656 size_t heap_alignment = collector_policy()->heap_alignment(); 1657 1658 // Ensure that the sizes are properly aligned. 1659 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1660 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1661 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1662 1663 // Reserve the maximum. 1664 1665 // When compressed oops are enabled, the preferred heap base 1666 // is calculated by subtracting the requested size from the 1667 // 32Gb boundary and using the result as the base address for 1668 // heap reservation. If the requested size is not aligned to 1669 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1670 // into the ReservedHeapSpace constructor) then the actual 1671 // base of the reserved heap may end up differing from the 1672 // address that was requested (i.e. the preferred heap base). 1673 // If this happens then we could end up using a non-optimal 1674 // compressed oops mode. 1675 1676 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1677 heap_alignment); 1678 1679 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1680 1681 // Create the barrier set for the entire reserved region. 1682 G1SATBCardTableLoggingModRefBS* bs 1683 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1684 bs->initialize(); 1685 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1686 set_barrier_set(bs); 1687 1688 // Create the hot card cache. 1689 _hot_card_cache = new G1HotCardCache(this); 1690 1691 // Carve out the G1 part of the heap. 1692 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1693 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1694 G1RegionToSpaceMapper* heap_storage = 1695 G1RegionToSpaceMapper::create_mapper(g1_rs, 1696 g1_rs.size(), 1697 page_size, 1698 HeapRegion::GrainBytes, 1699 1, 1700 mtJavaHeap); 1701 os::trace_page_sizes("Heap", 1702 collector_policy()->min_heap_byte_size(), 1703 max_byte_size, 1704 page_size, 1705 heap_rs.base(), 1706 heap_rs.size()); 1707 heap_storage->set_mapping_changed_listener(&_listener); 1708 1709 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1710 G1RegionToSpaceMapper* bot_storage = 1711 create_aux_memory_mapper("Block Offset Table", 1712 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1713 G1BlockOffsetTable::heap_map_factor()); 1714 1715 G1RegionToSpaceMapper* cardtable_storage = 1716 create_aux_memory_mapper("Card Table", 1717 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1718 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1719 1720 G1RegionToSpaceMapper* card_counts_storage = 1721 create_aux_memory_mapper("Card Counts Table", 1722 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1723 G1CardCounts::heap_map_factor()); 1724 1725 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1726 G1RegionToSpaceMapper* prev_bitmap_storage = 1727 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1728 G1RegionToSpaceMapper* next_bitmap_storage = 1729 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1730 1731 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1732 g1_barrier_set()->initialize(cardtable_storage); 1733 // Do later initialization work for concurrent refinement. 1734 _hot_card_cache->initialize(card_counts_storage); 1735 1736 // 6843694 - ensure that the maximum region index can fit 1737 // in the remembered set structures. 1738 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1739 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1740 1741 // Also create a G1 rem set. 1742 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache); 1743 _g1_rem_set->initialize(max_capacity(), max_regions()); 1744 1745 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1746 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1747 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1748 "too many cards per region"); 1749 1750 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1751 1752 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1753 1754 { 1755 HeapWord* start = _hrm.reserved().start(); 1756 HeapWord* end = _hrm.reserved().end(); 1757 size_t granularity = HeapRegion::GrainBytes; 1758 1759 _in_cset_fast_test.initialize(start, end, granularity); 1760 _humongous_reclaim_candidates.initialize(start, end, granularity); 1761 } 1762 1763 // Create the G1ConcurrentMark data structure and thread. 1764 // (Must do this late, so that "max_regions" is defined.) 1765 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1766 if (_cm == NULL || !_cm->completed_initialization()) { 1767 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1768 return JNI_ENOMEM; 1769 } 1770 _cmThread = _cm->cm_thread(); 1771 1772 // Now expand into the initial heap size. 1773 if (!expand(init_byte_size, _workers)) { 1774 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1775 return JNI_ENOMEM; 1776 } 1777 1778 // Perform any initialization actions delegated to the policy. 1779 g1_policy()->init(this, &_collection_set); 1780 1781 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1782 SATB_Q_FL_lock, 1783 G1SATBProcessCompletedThreshold, 1784 Shared_SATB_Q_lock); 1785 1786 jint ecode = initialize_concurrent_refinement(); 1787 if (ecode != JNI_OK) { 1788 return ecode; 1789 } 1790 1791 ecode = initialize_young_gen_sampling_thread(); 1792 if (ecode != JNI_OK) { 1793 return ecode; 1794 } 1795 1796 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1797 DirtyCardQ_FL_lock, 1798 (int)concurrent_refine()->yellow_zone(), 1799 (int)concurrent_refine()->red_zone(), 1800 Shared_DirtyCardQ_lock, 1801 NULL, // fl_owner 1802 true); // init_free_ids 1803 1804 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1805 DirtyCardQ_FL_lock, 1806 -1, // never trigger processing 1807 -1, // no limit on length 1808 Shared_DirtyCardQ_lock, 1809 &JavaThread::dirty_card_queue_set()); 1810 1811 // Here we allocate the dummy HeapRegion that is required by the 1812 // G1AllocRegion class. 1813 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1814 1815 // We'll re-use the same region whether the alloc region will 1816 // require BOT updates or not and, if it doesn't, then a non-young 1817 // region will complain that it cannot support allocations without 1818 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1819 dummy_region->set_eden(); 1820 // Make sure it's full. 1821 dummy_region->set_top(dummy_region->end()); 1822 G1AllocRegion::setup(this, dummy_region); 1823 1824 _allocator->init_mutator_alloc_region(); 1825 1826 // Do create of the monitoring and management support so that 1827 // values in the heap have been properly initialized. 1828 _g1mm = new G1MonitoringSupport(this); 1829 1830 _eden_pool = new G1EdenPool(this); 1831 _survivor_pool = new G1SurvivorPool(this); 1832 _old_pool = new G1OldGenPool(this); 1833 1834 _full_gc_mem_mgr.add_pool(_eden_pool); 1835 _full_gc_mem_mgr.add_pool(_survivor_pool); 1836 _full_gc_mem_mgr.add_pool(_old_pool); 1837 1838 _mem_mgr.add_pool(_eden_pool); 1839 _mem_mgr.add_pool(_survivor_pool); 1840 1841 G1StringDedup::initialize(); 1842 1843 _preserved_marks_set.init(ParallelGCThreads); 1844 1845 _collection_set.initialize(max_regions()); 1846 1847 return JNI_OK; 1848 } 1849 1850 void G1CollectedHeap::stop() { 1851 // Stop all concurrent threads. We do this to make sure these threads 1852 // do not continue to execute and access resources (e.g. logging) 1853 // that are destroyed during shutdown. 1854 _cr->stop(); 1855 _young_gen_sampling_thread->stop(); 1856 _cmThread->stop(); 1857 if (G1StringDedup::is_enabled()) { 1858 G1StringDedup::stop(); 1859 } 1860 } 1861 1862 void G1CollectedHeap::safepoint_synchronize_begin() { 1863 SuspendibleThreadSet::synchronize(); 1864 } 1865 1866 void G1CollectedHeap::safepoint_synchronize_end() { 1867 SuspendibleThreadSet::desynchronize(); 1868 } 1869 1870 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1871 return HeapRegion::max_region_size(); 1872 } 1873 1874 void G1CollectedHeap::post_initialize() { 1875 ref_processing_init(); 1876 } 1877 1878 void G1CollectedHeap::ref_processing_init() { 1879 // Reference processing in G1 currently works as follows: 1880 // 1881 // * There are two reference processor instances. One is 1882 // used to record and process discovered references 1883 // during concurrent marking; the other is used to 1884 // record and process references during STW pauses 1885 // (both full and incremental). 1886 // * Both ref processors need to 'span' the entire heap as 1887 // the regions in the collection set may be dotted around. 1888 // 1889 // * For the concurrent marking ref processor: 1890 // * Reference discovery is enabled at initial marking. 1891 // * Reference discovery is disabled and the discovered 1892 // references processed etc during remarking. 1893 // * Reference discovery is MT (see below). 1894 // * Reference discovery requires a barrier (see below). 1895 // * Reference processing may or may not be MT 1896 // (depending on the value of ParallelRefProcEnabled 1897 // and ParallelGCThreads). 1898 // * A full GC disables reference discovery by the CM 1899 // ref processor and abandons any entries on it's 1900 // discovered lists. 1901 // 1902 // * For the STW processor: 1903 // * Non MT discovery is enabled at the start of a full GC. 1904 // * Processing and enqueueing during a full GC is non-MT. 1905 // * During a full GC, references are processed after marking. 1906 // 1907 // * Discovery (may or may not be MT) is enabled at the start 1908 // of an incremental evacuation pause. 1909 // * References are processed near the end of a STW evacuation pause. 1910 // * For both types of GC: 1911 // * Discovery is atomic - i.e. not concurrent. 1912 // * Reference discovery will not need a barrier. 1913 1914 MemRegion mr = reserved_region(); 1915 1916 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1); 1917 1918 // Concurrent Mark ref processor 1919 _ref_processor_cm = 1920 new ReferenceProcessor(mr, // span 1921 mt_processing, 1922 // mt processing 1923 ParallelGCThreads, 1924 // degree of mt processing 1925 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 1926 // mt discovery 1927 MAX2(ParallelGCThreads, ConcGCThreads), 1928 // degree of mt discovery 1929 false, 1930 // Reference discovery is not atomic 1931 &_is_alive_closure_cm); 1932 // is alive closure 1933 // (for efficiency/performance) 1934 1935 // STW ref processor 1936 _ref_processor_stw = 1937 new ReferenceProcessor(mr, // span 1938 mt_processing, 1939 // mt processing 1940 ParallelGCThreads, 1941 // degree of mt processing 1942 (ParallelGCThreads > 1), 1943 // mt discovery 1944 ParallelGCThreads, 1945 // degree of mt discovery 1946 true, 1947 // Reference discovery is atomic 1948 &_is_alive_closure_stw); 1949 // is alive closure 1950 // (for efficiency/performance) 1951 } 1952 1953 CollectorPolicy* G1CollectedHeap::collector_policy() const { 1954 return _collector_policy; 1955 } 1956 1957 size_t G1CollectedHeap::capacity() const { 1958 return _hrm.length() * HeapRegion::GrainBytes; 1959 } 1960 1961 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const { 1962 return _hrm.total_free_bytes(); 1963 } 1964 1965 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 1966 hr->reset_gc_time_stamp(); 1967 } 1968 1969 #ifndef PRODUCT 1970 1971 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 1972 private: 1973 unsigned _gc_time_stamp; 1974 bool _failures; 1975 1976 public: 1977 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 1978 _gc_time_stamp(gc_time_stamp), _failures(false) { } 1979 1980 virtual bool doHeapRegion(HeapRegion* hr) { 1981 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 1982 if (_gc_time_stamp != region_gc_time_stamp) { 1983 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 1984 region_gc_time_stamp, _gc_time_stamp); 1985 _failures = true; 1986 } 1987 return false; 1988 } 1989 1990 bool failures() { return _failures; } 1991 }; 1992 1993 void G1CollectedHeap::check_gc_time_stamps() { 1994 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 1995 heap_region_iterate(&cl); 1996 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 1997 } 1998 #endif // PRODUCT 1999 2000 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2001 _hot_card_cache->drain(cl, worker_i); 2002 } 2003 2004 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2005 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2006 size_t n_completed_buffers = 0; 2007 while (dcqs.apply_closure_during_gc(cl, worker_i)) { 2008 n_completed_buffers++; 2009 } 2010 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2011 dcqs.clear_n_completed_buffers(); 2012 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2013 } 2014 2015 // Computes the sum of the storage used by the various regions. 2016 size_t G1CollectedHeap::used() const { 2017 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2018 if (_archive_allocator != NULL) { 2019 result += _archive_allocator->used(); 2020 } 2021 return result; 2022 } 2023 2024 size_t G1CollectedHeap::used_unlocked() const { 2025 return _summary_bytes_used; 2026 } 2027 2028 class SumUsedClosure: public HeapRegionClosure { 2029 size_t _used; 2030 public: 2031 SumUsedClosure() : _used(0) {} 2032 bool doHeapRegion(HeapRegion* r) { 2033 _used += r->used(); 2034 return false; 2035 } 2036 size_t result() { return _used; } 2037 }; 2038 2039 size_t G1CollectedHeap::recalculate_used() const { 2040 double recalculate_used_start = os::elapsedTime(); 2041 2042 SumUsedClosure blk; 2043 heap_region_iterate(&blk); 2044 2045 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2046 return blk.result(); 2047 } 2048 2049 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2050 switch (cause) { 2051 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2052 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2053 case GCCause::_update_allocation_context_stats_inc: return true; 2054 case GCCause::_wb_conc_mark: return true; 2055 default : return false; 2056 } 2057 } 2058 2059 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2060 switch (cause) { 2061 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2062 case GCCause::_g1_humongous_allocation: return true; 2063 default: return is_user_requested_concurrent_full_gc(cause); 2064 } 2065 } 2066 2067 #ifndef PRODUCT 2068 void G1CollectedHeap::allocate_dummy_regions() { 2069 // Let's fill up most of the region 2070 size_t word_size = HeapRegion::GrainWords - 1024; 2071 // And as a result the region we'll allocate will be humongous. 2072 guarantee(is_humongous(word_size), "sanity"); 2073 2074 // _filler_array_max_size is set to humongous object threshold 2075 // but temporarily change it to use CollectedHeap::fill_with_object(). 2076 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2077 2078 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2079 // Let's use the existing mechanism for the allocation 2080 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2081 AllocationContext::system()); 2082 if (dummy_obj != NULL) { 2083 MemRegion mr(dummy_obj, word_size); 2084 CollectedHeap::fill_with_object(mr); 2085 } else { 2086 // If we can't allocate once, we probably cannot allocate 2087 // again. Let's get out of the loop. 2088 break; 2089 } 2090 } 2091 } 2092 #endif // !PRODUCT 2093 2094 void G1CollectedHeap::increment_old_marking_cycles_started() { 2095 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2096 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2097 "Wrong marking cycle count (started: %d, completed: %d)", 2098 _old_marking_cycles_started, _old_marking_cycles_completed); 2099 2100 _old_marking_cycles_started++; 2101 } 2102 2103 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2104 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2105 2106 // We assume that if concurrent == true, then the caller is a 2107 // concurrent thread that was joined the Suspendible Thread 2108 // Set. If there's ever a cheap way to check this, we should add an 2109 // assert here. 2110 2111 // Given that this method is called at the end of a Full GC or of a 2112 // concurrent cycle, and those can be nested (i.e., a Full GC can 2113 // interrupt a concurrent cycle), the number of full collections 2114 // completed should be either one (in the case where there was no 2115 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2116 // behind the number of full collections started. 2117 2118 // This is the case for the inner caller, i.e. a Full GC. 2119 assert(concurrent || 2120 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2121 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2122 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2123 "is inconsistent with _old_marking_cycles_completed = %u", 2124 _old_marking_cycles_started, _old_marking_cycles_completed); 2125 2126 // This is the case for the outer caller, i.e. the concurrent cycle. 2127 assert(!concurrent || 2128 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2129 "for outer caller (concurrent cycle): " 2130 "_old_marking_cycles_started = %u " 2131 "is inconsistent with _old_marking_cycles_completed = %u", 2132 _old_marking_cycles_started, _old_marking_cycles_completed); 2133 2134 _old_marking_cycles_completed += 1; 2135 2136 // We need to clear the "in_progress" flag in the CM thread before 2137 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2138 // is set) so that if a waiter requests another System.gc() it doesn't 2139 // incorrectly see that a marking cycle is still in progress. 2140 if (concurrent) { 2141 _cmThread->set_idle(); 2142 } 2143 2144 // This notify_all() will ensure that a thread that called 2145 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2146 // and it's waiting for a full GC to finish will be woken up. It is 2147 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2148 FullGCCount_lock->notify_all(); 2149 } 2150 2151 void G1CollectedHeap::collect(GCCause::Cause cause) { 2152 assert_heap_not_locked(); 2153 2154 uint gc_count_before; 2155 uint old_marking_count_before; 2156 uint full_gc_count_before; 2157 bool retry_gc; 2158 2159 do { 2160 retry_gc = false; 2161 2162 { 2163 MutexLocker ml(Heap_lock); 2164 2165 // Read the GC count while holding the Heap_lock 2166 gc_count_before = total_collections(); 2167 full_gc_count_before = total_full_collections(); 2168 old_marking_count_before = _old_marking_cycles_started; 2169 } 2170 2171 if (should_do_concurrent_full_gc(cause)) { 2172 // Schedule an initial-mark evacuation pause that will start a 2173 // concurrent cycle. We're setting word_size to 0 which means that 2174 // we are not requesting a post-GC allocation. 2175 VM_G1IncCollectionPause op(gc_count_before, 2176 0, /* word_size */ 2177 true, /* should_initiate_conc_mark */ 2178 g1_policy()->max_pause_time_ms(), 2179 cause); 2180 op.set_allocation_context(AllocationContext::current()); 2181 2182 VMThread::execute(&op); 2183 if (!op.pause_succeeded()) { 2184 if (old_marking_count_before == _old_marking_cycles_started) { 2185 retry_gc = op.should_retry_gc(); 2186 } else { 2187 // A Full GC happened while we were trying to schedule the 2188 // initial-mark GC. No point in starting a new cycle given 2189 // that the whole heap was collected anyway. 2190 } 2191 2192 if (retry_gc) { 2193 if (GCLocker::is_active_and_needs_gc()) { 2194 GCLocker::stall_until_clear(); 2195 } 2196 } 2197 } 2198 } else { 2199 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2200 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2201 2202 // Schedule a standard evacuation pause. We're setting word_size 2203 // to 0 which means that we are not requesting a post-GC allocation. 2204 VM_G1IncCollectionPause op(gc_count_before, 2205 0, /* word_size */ 2206 false, /* should_initiate_conc_mark */ 2207 g1_policy()->max_pause_time_ms(), 2208 cause); 2209 VMThread::execute(&op); 2210 } else { 2211 // Schedule a Full GC. 2212 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2213 VMThread::execute(&op); 2214 } 2215 } 2216 } while (retry_gc); 2217 } 2218 2219 bool G1CollectedHeap::is_in(const void* p) const { 2220 if (_hrm.reserved().contains(p)) { 2221 // Given that we know that p is in the reserved space, 2222 // heap_region_containing() should successfully 2223 // return the containing region. 2224 HeapRegion* hr = heap_region_containing(p); 2225 return hr->is_in(p); 2226 } else { 2227 return false; 2228 } 2229 } 2230 2231 #ifdef ASSERT 2232 bool G1CollectedHeap::is_in_exact(const void* p) const { 2233 bool contains = reserved_region().contains(p); 2234 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2235 if (contains && available) { 2236 return true; 2237 } else { 2238 return false; 2239 } 2240 } 2241 #endif 2242 2243 // Iteration functions. 2244 2245 // Iterates an ObjectClosure over all objects within a HeapRegion. 2246 2247 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2248 ObjectClosure* _cl; 2249 public: 2250 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2251 bool doHeapRegion(HeapRegion* r) { 2252 if (!r->is_continues_humongous()) { 2253 r->object_iterate(_cl); 2254 } 2255 return false; 2256 } 2257 }; 2258 2259 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2260 IterateObjectClosureRegionClosure blk(cl); 2261 heap_region_iterate(&blk); 2262 } 2263 2264 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2265 _hrm.iterate(cl); 2266 } 2267 2268 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl, 2269 HeapRegionClaimer *hrclaimer, 2270 uint worker_id) const { 2271 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id)); 2272 } 2273 2274 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl, 2275 HeapRegionClaimer *hrclaimer) const { 2276 _hrm.par_iterate(cl, hrclaimer, 0); 2277 } 2278 2279 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2280 _collection_set.iterate(cl); 2281 } 2282 2283 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2284 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2285 } 2286 2287 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2288 HeapRegion* hr = heap_region_containing(addr); 2289 return hr->block_start(addr); 2290 } 2291 2292 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2293 HeapRegion* hr = heap_region_containing(addr); 2294 return hr->block_size(addr); 2295 } 2296 2297 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2298 HeapRegion* hr = heap_region_containing(addr); 2299 return hr->block_is_obj(addr); 2300 } 2301 2302 bool G1CollectedHeap::supports_tlab_allocation() const { 2303 return true; 2304 } 2305 2306 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2307 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2308 } 2309 2310 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2311 return _eden.length() * HeapRegion::GrainBytes; 2312 } 2313 2314 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2315 // must be equal to the humongous object limit. 2316 size_t G1CollectedHeap::max_tlab_size() const { 2317 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2318 } 2319 2320 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2321 AllocationContext_t context = AllocationContext::current(); 2322 return _allocator->unsafe_max_tlab_alloc(context); 2323 } 2324 2325 size_t G1CollectedHeap::max_capacity() const { 2326 return _hrm.reserved().byte_size(); 2327 } 2328 2329 jlong G1CollectedHeap::millis_since_last_gc() { 2330 // See the notes in GenCollectedHeap::millis_since_last_gc() 2331 // for more information about the implementation. 2332 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2333 _g1_policy->collection_pause_end_millis(); 2334 if (ret_val < 0) { 2335 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2336 ". returning zero instead.", ret_val); 2337 return 0; 2338 } 2339 return ret_val; 2340 } 2341 2342 void G1CollectedHeap::prepare_for_verify() { 2343 _verifier->prepare_for_verify(); 2344 } 2345 2346 void G1CollectedHeap::verify(VerifyOption vo) { 2347 _verifier->verify(vo); 2348 } 2349 2350 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2351 return true; 2352 } 2353 2354 const char* const* G1CollectedHeap::concurrent_phases() const { 2355 return _cmThread->concurrent_phases(); 2356 } 2357 2358 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2359 return _cmThread->request_concurrent_phase(phase); 2360 } 2361 2362 class PrintRegionClosure: public HeapRegionClosure { 2363 outputStream* _st; 2364 public: 2365 PrintRegionClosure(outputStream* st) : _st(st) {} 2366 bool doHeapRegion(HeapRegion* r) { 2367 r->print_on(_st); 2368 return false; 2369 } 2370 }; 2371 2372 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2373 const HeapRegion* hr, 2374 const VerifyOption vo) const { 2375 switch (vo) { 2376 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2377 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2378 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr); 2379 default: ShouldNotReachHere(); 2380 } 2381 return false; // keep some compilers happy 2382 } 2383 2384 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2385 const VerifyOption vo) const { 2386 switch (vo) { 2387 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2388 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2389 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj); 2390 default: ShouldNotReachHere(); 2391 } 2392 return false; // keep some compilers happy 2393 } 2394 2395 void G1CollectedHeap::print_heap_regions() const { 2396 LogTarget(Trace, gc, heap, region) lt; 2397 if (lt.is_enabled()) { 2398 LogStream ls(lt); 2399 print_regions_on(&ls); 2400 } 2401 } 2402 2403 void G1CollectedHeap::print_on(outputStream* st) const { 2404 st->print(" %-20s", "garbage-first heap"); 2405 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2406 capacity()/K, used_unlocked()/K); 2407 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")", 2408 p2i(_hrm.reserved().start()), 2409 p2i(_hrm.reserved().end())); 2410 st->cr(); 2411 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2412 uint young_regions = young_regions_count(); 2413 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2414 (size_t) young_regions * HeapRegion::GrainBytes / K); 2415 uint survivor_regions = survivor_regions_count(); 2416 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2417 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2418 st->cr(); 2419 MetaspaceAux::print_on(st); 2420 } 2421 2422 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2423 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2424 "HS=humongous(starts), HC=humongous(continues), " 2425 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2426 "AC=allocation context, " 2427 "TAMS=top-at-mark-start (previous, next)"); 2428 PrintRegionClosure blk(st); 2429 heap_region_iterate(&blk); 2430 } 2431 2432 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2433 print_on(st); 2434 2435 // Print the per-region information. 2436 print_regions_on(st); 2437 } 2438 2439 void G1CollectedHeap::print_on_error(outputStream* st) const { 2440 this->CollectedHeap::print_on_error(st); 2441 2442 if (_cm != NULL) { 2443 st->cr(); 2444 _cm->print_on_error(st); 2445 } 2446 } 2447 2448 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2449 workers()->print_worker_threads_on(st); 2450 _cmThread->print_on(st); 2451 st->cr(); 2452 _cm->print_worker_threads_on(st); 2453 _cr->print_threads_on(st); 2454 _young_gen_sampling_thread->print_on(st); 2455 if (G1StringDedup::is_enabled()) { 2456 G1StringDedup::print_worker_threads_on(st); 2457 } 2458 } 2459 2460 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2461 workers()->threads_do(tc); 2462 tc->do_thread(_cmThread); 2463 _cm->threads_do(tc); 2464 _cr->threads_do(tc); 2465 tc->do_thread(_young_gen_sampling_thread); 2466 if (G1StringDedup::is_enabled()) { 2467 G1StringDedup::threads_do(tc); 2468 } 2469 } 2470 2471 void G1CollectedHeap::print_tracing_info() const { 2472 g1_rem_set()->print_summary_info(); 2473 concurrent_mark()->print_summary_info(); 2474 } 2475 2476 #ifndef PRODUCT 2477 // Helpful for debugging RSet issues. 2478 2479 class PrintRSetsClosure : public HeapRegionClosure { 2480 private: 2481 const char* _msg; 2482 size_t _occupied_sum; 2483 2484 public: 2485 bool doHeapRegion(HeapRegion* r) { 2486 HeapRegionRemSet* hrrs = r->rem_set(); 2487 size_t occupied = hrrs->occupied(); 2488 _occupied_sum += occupied; 2489 2490 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2491 if (occupied == 0) { 2492 tty->print_cr(" RSet is empty"); 2493 } else { 2494 hrrs->print(); 2495 } 2496 tty->print_cr("----------"); 2497 return false; 2498 } 2499 2500 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2501 tty->cr(); 2502 tty->print_cr("========================================"); 2503 tty->print_cr("%s", msg); 2504 tty->cr(); 2505 } 2506 2507 ~PrintRSetsClosure() { 2508 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2509 tty->print_cr("========================================"); 2510 tty->cr(); 2511 } 2512 }; 2513 2514 void G1CollectedHeap::print_cset_rsets() { 2515 PrintRSetsClosure cl("Printing CSet RSets"); 2516 collection_set_iterate(&cl); 2517 } 2518 2519 void G1CollectedHeap::print_all_rsets() { 2520 PrintRSetsClosure cl("Printing All RSets");; 2521 heap_region_iterate(&cl); 2522 } 2523 #endif // PRODUCT 2524 2525 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2526 2527 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2528 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2529 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2530 2531 size_t eden_capacity_bytes = 2532 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2533 2534 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2535 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2536 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2537 } 2538 2539 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2540 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2541 stats->unused(), stats->used(), stats->region_end_waste(), 2542 stats->regions_filled(), stats->direct_allocated(), 2543 stats->failure_used(), stats->failure_waste()); 2544 } 2545 2546 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2547 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2548 gc_tracer->report_gc_heap_summary(when, heap_summary); 2549 2550 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2551 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2552 } 2553 2554 G1CollectedHeap* G1CollectedHeap::heap() { 2555 CollectedHeap* heap = Universe::heap(); 2556 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2557 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2558 return (G1CollectedHeap*)heap; 2559 } 2560 2561 void G1CollectedHeap::gc_prologue(bool full) { 2562 // always_do_update_barrier = false; 2563 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2564 2565 // This summary needs to be printed before incrementing total collections. 2566 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2567 2568 // Update common counters. 2569 increment_total_collections(full /* full gc */); 2570 if (full) { 2571 increment_old_marking_cycles_started(); 2572 reset_gc_time_stamp(); 2573 } else { 2574 increment_gc_time_stamp(); 2575 } 2576 2577 // Fill TLAB's and such 2578 double start = os::elapsedTime(); 2579 accumulate_statistics_all_tlabs(); 2580 ensure_parsability(true); 2581 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2582 } 2583 2584 void G1CollectedHeap::gc_epilogue(bool full) { 2585 // Update common counters. 2586 if (full) { 2587 // Update the number of full collections that have been completed. 2588 increment_old_marking_cycles_completed(false /* concurrent */); 2589 } 2590 2591 // We are at the end of the GC. Total collections has already been increased. 2592 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2593 2594 // FIXME: what is this about? 2595 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2596 // is set. 2597 #if COMPILER2_OR_JVMCI 2598 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2599 #endif 2600 // always_do_update_barrier = true; 2601 2602 double start = os::elapsedTime(); 2603 resize_all_tlabs(); 2604 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2605 2606 allocation_context_stats().update(full); 2607 2608 MemoryService::track_memory_usage(); 2609 // We have just completed a GC. Update the soft reference 2610 // policy with the new heap occupancy 2611 Universe::update_heap_info_at_gc(); 2612 } 2613 2614 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2615 uint gc_count_before, 2616 bool* succeeded, 2617 GCCause::Cause gc_cause) { 2618 assert_heap_not_locked_and_not_at_safepoint(); 2619 VM_G1IncCollectionPause op(gc_count_before, 2620 word_size, 2621 false, /* should_initiate_conc_mark */ 2622 g1_policy()->max_pause_time_ms(), 2623 gc_cause); 2624 2625 op.set_allocation_context(AllocationContext::current()); 2626 VMThread::execute(&op); 2627 2628 HeapWord* result = op.result(); 2629 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2630 assert(result == NULL || ret_succeeded, 2631 "the result should be NULL if the VM did not succeed"); 2632 *succeeded = ret_succeeded; 2633 2634 assert_heap_not_locked(); 2635 return result; 2636 } 2637 2638 void 2639 G1CollectedHeap::doConcurrentMark() { 2640 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2641 if (!_cmThread->in_progress()) { 2642 _cmThread->set_started(); 2643 CGC_lock->notify(); 2644 } 2645 } 2646 2647 size_t G1CollectedHeap::pending_card_num() { 2648 size_t extra_cards = 0; 2649 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) { 2650 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2651 extra_cards += dcq.size(); 2652 } 2653 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2654 size_t buffer_size = dcqs.buffer_size(); 2655 size_t buffer_num = dcqs.completed_buffers_num(); 2656 2657 return buffer_size * buffer_num + extra_cards; 2658 } 2659 2660 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2661 private: 2662 size_t _total_humongous; 2663 size_t _candidate_humongous; 2664 2665 DirtyCardQueue _dcq; 2666 2667 // We don't nominate objects with many remembered set entries, on 2668 // the assumption that such objects are likely still live. 2669 bool is_remset_small(HeapRegion* region) const { 2670 HeapRegionRemSet* const rset = region->rem_set(); 2671 return G1EagerReclaimHumongousObjectsWithStaleRefs 2672 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2673 : rset->is_empty(); 2674 } 2675 2676 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2677 assert(region->is_starts_humongous(), "Must start a humongous object"); 2678 2679 oop obj = oop(region->bottom()); 2680 2681 // Dead objects cannot be eager reclaim candidates. Due to class 2682 // unloading it is unsafe to query their classes so we return early. 2683 if (heap->is_obj_dead(obj, region)) { 2684 return false; 2685 } 2686 2687 // Candidate selection must satisfy the following constraints 2688 // while concurrent marking is in progress: 2689 // 2690 // * In order to maintain SATB invariants, an object must not be 2691 // reclaimed if it was allocated before the start of marking and 2692 // has not had its references scanned. Such an object must have 2693 // its references (including type metadata) scanned to ensure no 2694 // live objects are missed by the marking process. Objects 2695 // allocated after the start of concurrent marking don't need to 2696 // be scanned. 2697 // 2698 // * An object must not be reclaimed if it is on the concurrent 2699 // mark stack. Objects allocated after the start of concurrent 2700 // marking are never pushed on the mark stack. 2701 // 2702 // Nominating only objects allocated after the start of concurrent 2703 // marking is sufficient to meet both constraints. This may miss 2704 // some objects that satisfy the constraints, but the marking data 2705 // structures don't support efficiently performing the needed 2706 // additional tests or scrubbing of the mark stack. 2707 // 2708 // However, we presently only nominate is_typeArray() objects. 2709 // A humongous object containing references induces remembered 2710 // set entries on other regions. In order to reclaim such an 2711 // object, those remembered sets would need to be cleaned up. 2712 // 2713 // We also treat is_typeArray() objects specially, allowing them 2714 // to be reclaimed even if allocated before the start of 2715 // concurrent mark. For this we rely on mark stack insertion to 2716 // exclude is_typeArray() objects, preventing reclaiming an object 2717 // that is in the mark stack. We also rely on the metadata for 2718 // such objects to be built-in and so ensured to be kept live. 2719 // Frequent allocation and drop of large binary blobs is an 2720 // important use case for eager reclaim, and this special handling 2721 // may reduce needed headroom. 2722 2723 return obj->is_typeArray() && is_remset_small(region); 2724 } 2725 2726 public: 2727 RegisterHumongousWithInCSetFastTestClosure() 2728 : _total_humongous(0), 2729 _candidate_humongous(0), 2730 _dcq(&JavaThread::dirty_card_queue_set()) { 2731 } 2732 2733 virtual bool doHeapRegion(HeapRegion* r) { 2734 if (!r->is_starts_humongous()) { 2735 return false; 2736 } 2737 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2738 2739 bool is_candidate = humongous_region_is_candidate(g1h, r); 2740 uint rindex = r->hrm_index(); 2741 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2742 if (is_candidate) { 2743 _candidate_humongous++; 2744 g1h->register_humongous_region_with_cset(rindex); 2745 // Is_candidate already filters out humongous object with large remembered sets. 2746 // If we have a humongous object with a few remembered sets, we simply flush these 2747 // remembered set entries into the DCQS. That will result in automatic 2748 // re-evaluation of their remembered set entries during the following evacuation 2749 // phase. 2750 if (!r->rem_set()->is_empty()) { 2751 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2752 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2753 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 2754 HeapRegionRemSetIterator hrrs(r->rem_set()); 2755 size_t card_index; 2756 while (hrrs.has_next(card_index)) { 2757 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 2758 // The remembered set might contain references to already freed 2759 // regions. Filter out such entries to avoid failing card table 2760 // verification. 2761 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 2762 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 2763 *card_ptr = CardTableModRefBS::dirty_card_val(); 2764 _dcq.enqueue(card_ptr); 2765 } 2766 } 2767 } 2768 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2769 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2770 hrrs.n_yielded(), r->rem_set()->occupied()); 2771 r->rem_set()->clear_locked(); 2772 } 2773 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2774 } 2775 _total_humongous++; 2776 2777 return false; 2778 } 2779 2780 size_t total_humongous() const { return _total_humongous; } 2781 size_t candidate_humongous() const { return _candidate_humongous; } 2782 2783 void flush_rem_set_entries() { _dcq.flush(); } 2784 }; 2785 2786 void G1CollectedHeap::register_humongous_regions_with_cset() { 2787 if (!G1EagerReclaimHumongousObjects) { 2788 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2789 return; 2790 } 2791 double time = os::elapsed_counter(); 2792 2793 // Collect reclaim candidate information and register candidates with cset. 2794 RegisterHumongousWithInCSetFastTestClosure cl; 2795 heap_region_iterate(&cl); 2796 2797 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2798 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2799 cl.total_humongous(), 2800 cl.candidate_humongous()); 2801 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2802 2803 // Finally flush all remembered set entries to re-check into the global DCQS. 2804 cl.flush_rem_set_entries(); 2805 } 2806 2807 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2808 public: 2809 bool doHeapRegion(HeapRegion* hr) { 2810 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2811 hr->verify_rem_set(); 2812 } 2813 return false; 2814 } 2815 }; 2816 2817 uint G1CollectedHeap::num_task_queues() const { 2818 return _task_queues->size(); 2819 } 2820 2821 #if TASKQUEUE_STATS 2822 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2823 st->print_raw_cr("GC Task Stats"); 2824 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2825 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2826 } 2827 2828 void G1CollectedHeap::print_taskqueue_stats() const { 2829 if (!log_is_enabled(Trace, gc, task, stats)) { 2830 return; 2831 } 2832 Log(gc, task, stats) log; 2833 ResourceMark rm; 2834 LogStream ls(log.trace()); 2835 outputStream* st = &ls; 2836 2837 print_taskqueue_stats_hdr(st); 2838 2839 TaskQueueStats totals; 2840 const uint n = num_task_queues(); 2841 for (uint i = 0; i < n; ++i) { 2842 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2843 totals += task_queue(i)->stats; 2844 } 2845 st->print_raw("tot "); totals.print(st); st->cr(); 2846 2847 DEBUG_ONLY(totals.verify()); 2848 } 2849 2850 void G1CollectedHeap::reset_taskqueue_stats() { 2851 const uint n = num_task_queues(); 2852 for (uint i = 0; i < n; ++i) { 2853 task_queue(i)->stats.reset(); 2854 } 2855 } 2856 #endif // TASKQUEUE_STATS 2857 2858 void G1CollectedHeap::wait_for_root_region_scanning() { 2859 double scan_wait_start = os::elapsedTime(); 2860 // We have to wait until the CM threads finish scanning the 2861 // root regions as it's the only way to ensure that all the 2862 // objects on them have been correctly scanned before we start 2863 // moving them during the GC. 2864 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2865 double wait_time_ms = 0.0; 2866 if (waited) { 2867 double scan_wait_end = os::elapsedTime(); 2868 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2869 } 2870 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2871 } 2872 2873 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2874 private: 2875 G1HRPrinter* _hr_printer; 2876 public: 2877 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2878 2879 virtual bool doHeapRegion(HeapRegion* r) { 2880 _hr_printer->cset(r); 2881 return false; 2882 } 2883 }; 2884 2885 void G1CollectedHeap::start_new_collection_set() { 2886 collection_set()->start_incremental_building(); 2887 2888 clear_cset_fast_test(); 2889 2890 guarantee(_eden.length() == 0, "eden should have been cleared"); 2891 g1_policy()->transfer_survivors_to_cset(survivor()); 2892 } 2893 2894 bool 2895 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2896 assert_at_safepoint(true /* should_be_vm_thread */); 2897 guarantee(!is_gc_active(), "collection is not reentrant"); 2898 2899 if (GCLocker::check_active_before_gc()) { 2900 return false; 2901 } 2902 2903 _gc_timer_stw->register_gc_start(); 2904 2905 GCIdMark gc_id_mark; 2906 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2907 2908 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2909 ResourceMark rm; 2910 2911 g1_policy()->note_gc_start(); 2912 2913 wait_for_root_region_scanning(); 2914 2915 print_heap_before_gc(); 2916 print_heap_regions(); 2917 trace_heap_before_gc(_gc_tracer_stw); 2918 2919 _verifier->verify_region_sets_optional(); 2920 _verifier->verify_dirty_young_regions(); 2921 2922 // We should not be doing initial mark unless the conc mark thread is running 2923 if (!_cmThread->should_terminate()) { 2924 // This call will decide whether this pause is an initial-mark 2925 // pause. If it is, during_initial_mark_pause() will return true 2926 // for the duration of this pause. 2927 g1_policy()->decide_on_conc_mark_initiation(); 2928 } 2929 2930 // We do not allow initial-mark to be piggy-backed on a mixed GC. 2931 assert(!collector_state()->during_initial_mark_pause() || 2932 collector_state()->gcs_are_young(), "sanity"); 2933 2934 // We also do not allow mixed GCs during marking. 2935 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 2936 2937 // Record whether this pause is an initial mark. When the current 2938 // thread has completed its logging output and it's safe to signal 2939 // the CM thread, the flag's value in the policy has been reset. 2940 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 2941 2942 // Inner scope for scope based logging, timers, and stats collection 2943 { 2944 EvacuationInfo evacuation_info; 2945 2946 if (collector_state()->during_initial_mark_pause()) { 2947 // We are about to start a marking cycle, so we increment the 2948 // full collection counter. 2949 increment_old_marking_cycles_started(); 2950 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 2951 } 2952 2953 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 2954 2955 GCTraceCPUTime tcpu; 2956 2957 FormatBuffer<> gc_string("Pause "); 2958 if (collector_state()->during_initial_mark_pause()) { 2959 gc_string.append("Initial Mark"); 2960 } else if (collector_state()->gcs_are_young()) { 2961 gc_string.append("Young"); 2962 } else { 2963 gc_string.append("Mixed"); 2964 } 2965 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 2966 2967 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 2968 workers()->active_workers(), 2969 Threads::number_of_non_daemon_threads()); 2970 workers()->update_active_workers(active_workers); 2971 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 2972 2973 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 2974 TraceMemoryManagerStats tms(&_mem_mgr, gc_cause()); 2975 2976 // If the secondary_free_list is not empty, append it to the 2977 // free_list. No need to wait for the cleanup operation to finish; 2978 // the region allocation code will check the secondary_free_list 2979 // and wait if necessary. If the G1StressConcRegionFreeing flag is 2980 // set, skip this step so that the region allocation code has to 2981 // get entries from the secondary_free_list. 2982 if (!G1StressConcRegionFreeing) { 2983 append_secondary_free_list_if_not_empty_with_lock(); 2984 } 2985 2986 G1HeapTransition heap_transition(this); 2987 size_t heap_used_bytes_before_gc = used(); 2988 2989 // Don't dynamically change the number of GC threads this early. A value of 2990 // 0 is used to indicate serial work. When parallel work is done, 2991 // it will be set. 2992 2993 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 2994 IsGCActiveMark x; 2995 2996 gc_prologue(false); 2997 2998 if (VerifyRememberedSets) { 2999 log_info(gc, verify)("[Verifying RemSets before GC]"); 3000 VerifyRegionRemSetClosure v_cl; 3001 heap_region_iterate(&v_cl); 3002 } 3003 3004 _verifier->verify_before_gc(); 3005 3006 _verifier->check_bitmaps("GC Start"); 3007 3008 #if COMPILER2_OR_JVMCI 3009 DerivedPointerTable::clear(); 3010 #endif 3011 3012 // Please see comment in g1CollectedHeap.hpp and 3013 // G1CollectedHeap::ref_processing_init() to see how 3014 // reference processing currently works in G1. 3015 3016 // Enable discovery in the STW reference processor 3017 if (g1_policy()->should_process_references()) { 3018 ref_processor_stw()->enable_discovery(); 3019 } else { 3020 ref_processor_stw()->disable_discovery(); 3021 } 3022 3023 { 3024 // We want to temporarily turn off discovery by the 3025 // CM ref processor, if necessary, and turn it back on 3026 // on again later if we do. Using a scoped 3027 // NoRefDiscovery object will do this. 3028 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3029 3030 // Forget the current alloc region (we might even choose it to be part 3031 // of the collection set!). 3032 _allocator->release_mutator_alloc_region(); 3033 3034 // This timing is only used by the ergonomics to handle our pause target. 3035 // It is unclear why this should not include the full pause. We will 3036 // investigate this in CR 7178365. 3037 // 3038 // Preserving the old comment here if that helps the investigation: 3039 // 3040 // The elapsed time induced by the start time below deliberately elides 3041 // the possible verification above. 3042 double sample_start_time_sec = os::elapsedTime(); 3043 3044 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3045 3046 if (collector_state()->during_initial_mark_pause()) { 3047 concurrent_mark()->checkpoint_roots_initial_pre(); 3048 } 3049 3050 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 3051 3052 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3053 3054 // Make sure the remembered sets are up to date. This needs to be 3055 // done before register_humongous_regions_with_cset(), because the 3056 // remembered sets are used there to choose eager reclaim candidates. 3057 // If the remembered sets are not up to date we might miss some 3058 // entries that need to be handled. 3059 g1_rem_set()->cleanupHRRS(); 3060 3061 register_humongous_regions_with_cset(); 3062 3063 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3064 3065 // We call this after finalize_cset() to 3066 // ensure that the CSet has been finalized. 3067 _cm->verify_no_cset_oops(); 3068 3069 if (_hr_printer.is_active()) { 3070 G1PrintCollectionSetClosure cl(&_hr_printer); 3071 _collection_set.iterate(&cl); 3072 } 3073 3074 // Initialize the GC alloc regions. 3075 _allocator->init_gc_alloc_regions(evacuation_info); 3076 3077 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3078 pre_evacuate_collection_set(); 3079 3080 // Actually do the work... 3081 evacuate_collection_set(evacuation_info, &per_thread_states); 3082 3083 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3084 3085 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3086 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 3087 3088 eagerly_reclaim_humongous_regions(); 3089 3090 record_obj_copy_mem_stats(); 3091 _survivor_evac_stats.adjust_desired_plab_sz(); 3092 _old_evac_stats.adjust_desired_plab_sz(); 3093 3094 double start = os::elapsedTime(); 3095 start_new_collection_set(); 3096 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 3097 3098 if (evacuation_failed()) { 3099 set_used(recalculate_used()); 3100 if (_archive_allocator != NULL) { 3101 _archive_allocator->clear_used(); 3102 } 3103 for (uint i = 0; i < ParallelGCThreads; i++) { 3104 if (_evacuation_failed_info_array[i].has_failed()) { 3105 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3106 } 3107 } 3108 } else { 3109 // The "used" of the the collection set have already been subtracted 3110 // when they were freed. Add in the bytes evacuated. 3111 increase_used(g1_policy()->bytes_copied_during_gc()); 3112 } 3113 3114 if (collector_state()->during_initial_mark_pause()) { 3115 // We have to do this before we notify the CM threads that 3116 // they can start working to make sure that all the 3117 // appropriate initialization is done on the CM object. 3118 concurrent_mark()->checkpoint_roots_initial_post(); 3119 collector_state()->set_mark_in_progress(true); 3120 // Note that we don't actually trigger the CM thread at 3121 // this point. We do that later when we're sure that 3122 // the current thread has completed its logging output. 3123 } 3124 3125 allocate_dummy_regions(); 3126 3127 _allocator->init_mutator_alloc_region(); 3128 3129 { 3130 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3131 if (expand_bytes > 0) { 3132 size_t bytes_before = capacity(); 3133 // No need for an ergo logging here, 3134 // expansion_amount() does this when it returns a value > 0. 3135 double expand_ms; 3136 if (!expand(expand_bytes, _workers, &expand_ms)) { 3137 // We failed to expand the heap. Cannot do anything about it. 3138 } 3139 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3140 } 3141 } 3142 3143 // We redo the verification but now wrt to the new CSet which 3144 // has just got initialized after the previous CSet was freed. 3145 _cm->verify_no_cset_oops(); 3146 3147 // This timing is only used by the ergonomics to handle our pause target. 3148 // It is unclear why this should not include the full pause. We will 3149 // investigate this in CR 7178365. 3150 double sample_end_time_sec = os::elapsedTime(); 3151 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3152 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards); 3153 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3154 3155 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3156 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3157 3158 if (VerifyRememberedSets) { 3159 log_info(gc, verify)("[Verifying RemSets after GC]"); 3160 VerifyRegionRemSetClosure v_cl; 3161 heap_region_iterate(&v_cl); 3162 } 3163 3164 _verifier->verify_after_gc(); 3165 _verifier->check_bitmaps("GC End"); 3166 3167 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3168 ref_processor_stw()->verify_no_references_recorded(); 3169 3170 // CM reference discovery will be re-enabled if necessary. 3171 } 3172 3173 #ifdef TRACESPINNING 3174 ParallelTaskTerminator::print_termination_counts(); 3175 #endif 3176 3177 gc_epilogue(false); 3178 } 3179 3180 // Print the remainder of the GC log output. 3181 if (evacuation_failed()) { 3182 log_info(gc)("To-space exhausted"); 3183 } 3184 3185 g1_policy()->print_phases(); 3186 heap_transition.print(); 3187 3188 // It is not yet to safe to tell the concurrent mark to 3189 // start as we have some optional output below. We don't want the 3190 // output from the concurrent mark thread interfering with this 3191 // logging output either. 3192 3193 _hrm.verify_optional(); 3194 _verifier->verify_region_sets_optional(); 3195 3196 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3197 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3198 3199 print_heap_after_gc(); 3200 print_heap_regions(); 3201 trace_heap_after_gc(_gc_tracer_stw); 3202 3203 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3204 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3205 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3206 // before any GC notifications are raised. 3207 g1mm()->update_sizes(); 3208 3209 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3210 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3211 _gc_timer_stw->register_gc_end(); 3212 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3213 } 3214 // It should now be safe to tell the concurrent mark thread to start 3215 // without its logging output interfering with the logging output 3216 // that came from the pause. 3217 3218 if (should_start_conc_mark) { 3219 // CAUTION: after the doConcurrentMark() call below, 3220 // the concurrent marking thread(s) could be running 3221 // concurrently with us. Make sure that anything after 3222 // this point does not assume that we are the only GC thread 3223 // running. Note: of course, the actual marking work will 3224 // not start until the safepoint itself is released in 3225 // SuspendibleThreadSet::desynchronize(). 3226 doConcurrentMark(); 3227 } 3228 3229 return true; 3230 } 3231 3232 void G1CollectedHeap::remove_self_forwarding_pointers() { 3233 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3234 workers()->run_task(&rsfp_task); 3235 } 3236 3237 void G1CollectedHeap::restore_after_evac_failure() { 3238 double remove_self_forwards_start = os::elapsedTime(); 3239 3240 remove_self_forwarding_pointers(); 3241 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3242 _preserved_marks_set.restore(&task_executor); 3243 3244 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3245 } 3246 3247 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3248 if (!_evacuation_failed) { 3249 _evacuation_failed = true; 3250 } 3251 3252 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3253 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3254 } 3255 3256 bool G1ParEvacuateFollowersClosure::offer_termination() { 3257 G1ParScanThreadState* const pss = par_scan_state(); 3258 start_term_time(); 3259 const bool res = terminator()->offer_termination(); 3260 end_term_time(); 3261 return res; 3262 } 3263 3264 void G1ParEvacuateFollowersClosure::do_void() { 3265 G1ParScanThreadState* const pss = par_scan_state(); 3266 pss->trim_queue(); 3267 do { 3268 pss->steal_and_trim_queue(queues()); 3269 } while (!offer_termination()); 3270 } 3271 3272 class G1ParTask : public AbstractGangTask { 3273 protected: 3274 G1CollectedHeap* _g1h; 3275 G1ParScanThreadStateSet* _pss; 3276 RefToScanQueueSet* _queues; 3277 G1RootProcessor* _root_processor; 3278 ParallelTaskTerminator _terminator; 3279 uint _n_workers; 3280 3281 public: 3282 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3283 : AbstractGangTask("G1 collection"), 3284 _g1h(g1h), 3285 _pss(per_thread_states), 3286 _queues(task_queues), 3287 _root_processor(root_processor), 3288 _terminator(n_workers, _queues), 3289 _n_workers(n_workers) 3290 {} 3291 3292 void work(uint worker_id) { 3293 if (worker_id >= _n_workers) return; // no work needed this round 3294 3295 double start_sec = os::elapsedTime(); 3296 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3297 3298 { 3299 ResourceMark rm; 3300 HandleMark hm; 3301 3302 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3303 3304 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3305 pss->set_ref_processor(rp); 3306 3307 double start_strong_roots_sec = os::elapsedTime(); 3308 3309 _root_processor->evacuate_roots(pss->closures(), worker_id); 3310 3311 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3312 // treating the nmethods visited to act as roots for concurrent marking. 3313 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3314 // objects copied by the current evacuation. 3315 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, 3316 pss->closures()->weak_codeblobs(), 3317 worker_id); 3318 3319 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3320 3321 double term_sec = 0.0; 3322 size_t evac_term_attempts = 0; 3323 { 3324 double start = os::elapsedTime(); 3325 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3326 evac.do_void(); 3327 3328 evac_term_attempts = evac.term_attempts(); 3329 term_sec = evac.term_time(); 3330 double elapsed_sec = os::elapsedTime() - start; 3331 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3332 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3333 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3334 } 3335 3336 assert(pss->queue_is_empty(), "should be empty"); 3337 3338 if (log_is_enabled(Debug, gc, task, stats)) { 3339 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3340 size_t lab_waste; 3341 size_t lab_undo_waste; 3342 pss->waste(lab_waste, lab_undo_waste); 3343 _g1h->print_termination_stats(worker_id, 3344 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3345 strong_roots_sec * 1000.0, /* strong roots time */ 3346 term_sec * 1000.0, /* evac term time */ 3347 evac_term_attempts, /* evac term attempts */ 3348 lab_waste, /* alloc buffer waste */ 3349 lab_undo_waste /* undo waste */ 3350 ); 3351 } 3352 3353 // Close the inner scope so that the ResourceMark and HandleMark 3354 // destructors are executed here and are included as part of the 3355 // "GC Worker Time". 3356 } 3357 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3358 } 3359 }; 3360 3361 void G1CollectedHeap::print_termination_stats_hdr() { 3362 log_debug(gc, task, stats)("GC Termination Stats"); 3363 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3364 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3365 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3366 } 3367 3368 void G1CollectedHeap::print_termination_stats(uint worker_id, 3369 double elapsed_ms, 3370 double strong_roots_ms, 3371 double term_ms, 3372 size_t term_attempts, 3373 size_t alloc_buffer_waste, 3374 size_t undo_waste) const { 3375 log_debug(gc, task, stats) 3376 ("%3d %9.2f %9.2f %6.2f " 3377 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3378 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3379 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3380 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3381 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3382 alloc_buffer_waste * HeapWordSize / K, 3383 undo_waste * HeapWordSize / K); 3384 } 3385 3386 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3387 private: 3388 BoolObjectClosure* _is_alive; 3389 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3390 3391 int _initial_string_table_size; 3392 int _initial_symbol_table_size; 3393 3394 bool _process_strings; 3395 int _strings_processed; 3396 int _strings_removed; 3397 3398 bool _process_symbols; 3399 int _symbols_processed; 3400 int _symbols_removed; 3401 3402 bool _process_string_dedup; 3403 3404 public: 3405 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3406 AbstractGangTask("String/Symbol Unlinking"), 3407 _is_alive(is_alive), 3408 _dedup_closure(is_alive, NULL, false), 3409 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3410 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3411 _process_string_dedup(process_string_dedup) { 3412 3413 _initial_string_table_size = StringTable::the_table()->table_size(); 3414 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3415 if (process_strings) { 3416 StringTable::clear_parallel_claimed_index(); 3417 } 3418 if (process_symbols) { 3419 SymbolTable::clear_parallel_claimed_index(); 3420 } 3421 } 3422 3423 ~G1StringAndSymbolCleaningTask() { 3424 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3425 "claim value %d after unlink less than initial string table size %d", 3426 StringTable::parallel_claimed_index(), _initial_string_table_size); 3427 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3428 "claim value %d after unlink less than initial symbol table size %d", 3429 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3430 3431 log_info(gc, stringtable)( 3432 "Cleaned string and symbol table, " 3433 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3434 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3435 strings_processed(), strings_removed(), 3436 symbols_processed(), symbols_removed()); 3437 } 3438 3439 void work(uint worker_id) { 3440 int strings_processed = 0; 3441 int strings_removed = 0; 3442 int symbols_processed = 0; 3443 int symbols_removed = 0; 3444 if (_process_strings) { 3445 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3446 Atomic::add(strings_processed, &_strings_processed); 3447 Atomic::add(strings_removed, &_strings_removed); 3448 } 3449 if (_process_symbols) { 3450 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3451 Atomic::add(symbols_processed, &_symbols_processed); 3452 Atomic::add(symbols_removed, &_symbols_removed); 3453 } 3454 if (_process_string_dedup) { 3455 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3456 } 3457 } 3458 3459 size_t strings_processed() const { return (size_t)_strings_processed; } 3460 size_t strings_removed() const { return (size_t)_strings_removed; } 3461 3462 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3463 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3464 }; 3465 3466 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3467 private: 3468 static Monitor* _lock; 3469 3470 BoolObjectClosure* const _is_alive; 3471 const bool _unloading_occurred; 3472 const uint _num_workers; 3473 3474 // Variables used to claim nmethods. 3475 CompiledMethod* _first_nmethod; 3476 CompiledMethod* volatile _claimed_nmethod; 3477 3478 // The list of nmethods that need to be processed by the second pass. 3479 CompiledMethod* volatile _postponed_list; 3480 volatile uint _num_entered_barrier; 3481 3482 public: 3483 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3484 _is_alive(is_alive), 3485 _unloading_occurred(unloading_occurred), 3486 _num_workers(num_workers), 3487 _first_nmethod(NULL), 3488 _claimed_nmethod(NULL), 3489 _postponed_list(NULL), 3490 _num_entered_barrier(0) 3491 { 3492 CompiledMethod::increase_unloading_clock(); 3493 // Get first alive nmethod 3494 CompiledMethodIterator iter = CompiledMethodIterator(); 3495 if(iter.next_alive()) { 3496 _first_nmethod = iter.method(); 3497 } 3498 _claimed_nmethod = _first_nmethod; 3499 } 3500 3501 ~G1CodeCacheUnloadingTask() { 3502 CodeCache::verify_clean_inline_caches(); 3503 3504 CodeCache::set_needs_cache_clean(false); 3505 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3506 3507 CodeCache::verify_icholder_relocations(); 3508 } 3509 3510 private: 3511 void add_to_postponed_list(CompiledMethod* nm) { 3512 CompiledMethod* old; 3513 do { 3514 old = _postponed_list; 3515 nm->set_unloading_next(old); 3516 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old); 3517 } 3518 3519 void clean_nmethod(CompiledMethod* nm) { 3520 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3521 3522 if (postponed) { 3523 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3524 add_to_postponed_list(nm); 3525 } 3526 3527 // Mark that this thread has been cleaned/unloaded. 3528 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3529 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3530 } 3531 3532 void clean_nmethod_postponed(CompiledMethod* nm) { 3533 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3534 } 3535 3536 static const int MaxClaimNmethods = 16; 3537 3538 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3539 CompiledMethod* first; 3540 CompiledMethodIterator last; 3541 3542 do { 3543 *num_claimed_nmethods = 0; 3544 3545 first = _claimed_nmethod; 3546 last = CompiledMethodIterator(first); 3547 3548 if (first != NULL) { 3549 3550 for (int i = 0; i < MaxClaimNmethods; i++) { 3551 if (!last.next_alive()) { 3552 break; 3553 } 3554 claimed_nmethods[i] = last.method(); 3555 (*num_claimed_nmethods)++; 3556 } 3557 } 3558 3559 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first); 3560 } 3561 3562 CompiledMethod* claim_postponed_nmethod() { 3563 CompiledMethod* claim; 3564 CompiledMethod* next; 3565 3566 do { 3567 claim = _postponed_list; 3568 if (claim == NULL) { 3569 return NULL; 3570 } 3571 3572 next = claim->unloading_next(); 3573 3574 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim); 3575 3576 return claim; 3577 } 3578 3579 public: 3580 // Mark that we're done with the first pass of nmethod cleaning. 3581 void barrier_mark(uint worker_id) { 3582 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3583 _num_entered_barrier++; 3584 if (_num_entered_barrier == _num_workers) { 3585 ml.notify_all(); 3586 } 3587 } 3588 3589 // See if we have to wait for the other workers to 3590 // finish their first-pass nmethod cleaning work. 3591 void barrier_wait(uint worker_id) { 3592 if (_num_entered_barrier < _num_workers) { 3593 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3594 while (_num_entered_barrier < _num_workers) { 3595 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3596 } 3597 } 3598 } 3599 3600 // Cleaning and unloading of nmethods. Some work has to be postponed 3601 // to the second pass, when we know which nmethods survive. 3602 void work_first_pass(uint worker_id) { 3603 // The first nmethods is claimed by the first worker. 3604 if (worker_id == 0 && _first_nmethod != NULL) { 3605 clean_nmethod(_first_nmethod); 3606 _first_nmethod = NULL; 3607 } 3608 3609 int num_claimed_nmethods; 3610 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3611 3612 while (true) { 3613 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3614 3615 if (num_claimed_nmethods == 0) { 3616 break; 3617 } 3618 3619 for (int i = 0; i < num_claimed_nmethods; i++) { 3620 clean_nmethod(claimed_nmethods[i]); 3621 } 3622 } 3623 } 3624 3625 void work_second_pass(uint worker_id) { 3626 CompiledMethod* nm; 3627 // Take care of postponed nmethods. 3628 while ((nm = claim_postponed_nmethod()) != NULL) { 3629 clean_nmethod_postponed(nm); 3630 } 3631 } 3632 }; 3633 3634 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3635 3636 class G1KlassCleaningTask : public StackObj { 3637 BoolObjectClosure* _is_alive; 3638 volatile int _clean_klass_tree_claimed; 3639 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3640 3641 public: 3642 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3643 _is_alive(is_alive), 3644 _clean_klass_tree_claimed(0), 3645 _klass_iterator() { 3646 } 3647 3648 private: 3649 bool claim_clean_klass_tree_task() { 3650 if (_clean_klass_tree_claimed) { 3651 return false; 3652 } 3653 3654 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0; 3655 } 3656 3657 InstanceKlass* claim_next_klass() { 3658 Klass* klass; 3659 do { 3660 klass =_klass_iterator.next_klass(); 3661 } while (klass != NULL && !klass->is_instance_klass()); 3662 3663 // this can be null so don't call InstanceKlass::cast 3664 return static_cast<InstanceKlass*>(klass); 3665 } 3666 3667 public: 3668 3669 void clean_klass(InstanceKlass* ik) { 3670 ik->clean_weak_instanceklass_links(_is_alive); 3671 } 3672 3673 void work() { 3674 ResourceMark rm; 3675 3676 // One worker will clean the subklass/sibling klass tree. 3677 if (claim_clean_klass_tree_task()) { 3678 Klass::clean_subklass_tree(_is_alive); 3679 } 3680 3681 // All workers will help cleaning the classes, 3682 InstanceKlass* klass; 3683 while ((klass = claim_next_klass()) != NULL) { 3684 clean_klass(klass); 3685 } 3686 } 3687 }; 3688 3689 class G1ResolvedMethodCleaningTask : public StackObj { 3690 BoolObjectClosure* _is_alive; 3691 volatile int _resolved_method_task_claimed; 3692 public: 3693 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) : 3694 _is_alive(is_alive), _resolved_method_task_claimed(0) {} 3695 3696 bool claim_resolved_method_task() { 3697 if (_resolved_method_task_claimed) { 3698 return false; 3699 } 3700 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0; 3701 } 3702 3703 // These aren't big, one thread can do it all. 3704 void work() { 3705 if (claim_resolved_method_task()) { 3706 ResolvedMethodTable::unlink(_is_alive); 3707 } 3708 } 3709 }; 3710 3711 3712 // To minimize the remark pause times, the tasks below are done in parallel. 3713 class G1ParallelCleaningTask : public AbstractGangTask { 3714 private: 3715 G1StringAndSymbolCleaningTask _string_symbol_task; 3716 G1CodeCacheUnloadingTask _code_cache_task; 3717 G1KlassCleaningTask _klass_cleaning_task; 3718 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task; 3719 3720 public: 3721 // The constructor is run in the VMThread. 3722 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3723 AbstractGangTask("Parallel Cleaning"), 3724 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3725 _code_cache_task(num_workers, is_alive, unloading_occurred), 3726 _klass_cleaning_task(is_alive), 3727 _resolved_method_cleaning_task(is_alive) { 3728 } 3729 3730 // The parallel work done by all worker threads. 3731 void work(uint worker_id) { 3732 // Do first pass of code cache cleaning. 3733 _code_cache_task.work_first_pass(worker_id); 3734 3735 // Let the threads mark that the first pass is done. 3736 _code_cache_task.barrier_mark(worker_id); 3737 3738 // Clean the Strings and Symbols. 3739 _string_symbol_task.work(worker_id); 3740 3741 // Clean unreferenced things in the ResolvedMethodTable 3742 _resolved_method_cleaning_task.work(); 3743 3744 // Wait for all workers to finish the first code cache cleaning pass. 3745 _code_cache_task.barrier_wait(worker_id); 3746 3747 // Do the second code cache cleaning work, which realize on 3748 // the liveness information gathered during the first pass. 3749 _code_cache_task.work_second_pass(worker_id); 3750 3751 // Clean all klasses that were not unloaded. 3752 _klass_cleaning_task.work(); 3753 } 3754 }; 3755 3756 3757 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3758 bool class_unloading_occurred) { 3759 uint n_workers = workers()->active_workers(); 3760 3761 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3762 workers()->run_task(&g1_unlink_task); 3763 } 3764 3765 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3766 bool process_strings, 3767 bool process_symbols, 3768 bool process_string_dedup) { 3769 if (!process_strings && !process_symbols && !process_string_dedup) { 3770 // Nothing to clean. 3771 return; 3772 } 3773 3774 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3775 workers()->run_task(&g1_unlink_task); 3776 3777 } 3778 3779 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3780 private: 3781 DirtyCardQueueSet* _queue; 3782 G1CollectedHeap* _g1h; 3783 public: 3784 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3785 _queue(queue), _g1h(g1h) { } 3786 3787 virtual void work(uint worker_id) { 3788 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3789 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3790 3791 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3792 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3793 3794 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3795 } 3796 }; 3797 3798 void G1CollectedHeap::redirty_logged_cards() { 3799 double redirty_logged_cards_start = os::elapsedTime(); 3800 3801 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3802 dirty_card_queue_set().reset_for_par_iteration(); 3803 workers()->run_task(&redirty_task); 3804 3805 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 3806 dcq.merge_bufferlists(&dirty_card_queue_set()); 3807 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3808 3809 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3810 } 3811 3812 // Weak Reference Processing support 3813 3814 // An always "is_alive" closure that is used to preserve referents. 3815 // If the object is non-null then it's alive. Used in the preservation 3816 // of referent objects that are pointed to by reference objects 3817 // discovered by the CM ref processor. 3818 class G1AlwaysAliveClosure: public BoolObjectClosure { 3819 G1CollectedHeap* _g1; 3820 public: 3821 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3822 bool do_object_b(oop p) { 3823 if (p != NULL) { 3824 return true; 3825 } 3826 return false; 3827 } 3828 }; 3829 3830 bool G1STWIsAliveClosure::do_object_b(oop p) { 3831 // An object is reachable if it is outside the collection set, 3832 // or is inside and copied. 3833 return !_g1->is_in_cset(p) || p->is_forwarded(); 3834 } 3835 3836 // Non Copying Keep Alive closure 3837 class G1KeepAliveClosure: public OopClosure { 3838 G1CollectedHeap* _g1; 3839 public: 3840 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3841 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3842 void do_oop(oop* p) { 3843 oop obj = *p; 3844 assert(obj != NULL, "the caller should have filtered out NULL values"); 3845 3846 const InCSetState cset_state = _g1->in_cset_state(obj); 3847 if (!cset_state.is_in_cset_or_humongous()) { 3848 return; 3849 } 3850 if (cset_state.is_in_cset()) { 3851 assert( obj->is_forwarded(), "invariant" ); 3852 *p = obj->forwardee(); 3853 } else { 3854 assert(!obj->is_forwarded(), "invariant" ); 3855 assert(cset_state.is_humongous(), 3856 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3857 _g1->set_humongous_is_live(obj); 3858 } 3859 } 3860 }; 3861 3862 // Copying Keep Alive closure - can be called from both 3863 // serial and parallel code as long as different worker 3864 // threads utilize different G1ParScanThreadState instances 3865 // and different queues. 3866 3867 class G1CopyingKeepAliveClosure: public OopClosure { 3868 G1CollectedHeap* _g1h; 3869 OopClosure* _copy_non_heap_obj_cl; 3870 G1ParScanThreadState* _par_scan_state; 3871 3872 public: 3873 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3874 OopClosure* non_heap_obj_cl, 3875 G1ParScanThreadState* pss): 3876 _g1h(g1h), 3877 _copy_non_heap_obj_cl(non_heap_obj_cl), 3878 _par_scan_state(pss) 3879 {} 3880 3881 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3882 virtual void do_oop( oop* p) { do_oop_work(p); } 3883 3884 template <class T> void do_oop_work(T* p) { 3885 oop obj = oopDesc::load_decode_heap_oop(p); 3886 3887 if (_g1h->is_in_cset_or_humongous(obj)) { 3888 // If the referent object has been forwarded (either copied 3889 // to a new location or to itself in the event of an 3890 // evacuation failure) then we need to update the reference 3891 // field and, if both reference and referent are in the G1 3892 // heap, update the RSet for the referent. 3893 // 3894 // If the referent has not been forwarded then we have to keep 3895 // it alive by policy. Therefore we have copy the referent. 3896 // 3897 // If the reference field is in the G1 heap then we can push 3898 // on the PSS queue. When the queue is drained (after each 3899 // phase of reference processing) the object and it's followers 3900 // will be copied, the reference field set to point to the 3901 // new location, and the RSet updated. Otherwise we need to 3902 // use the the non-heap or metadata closures directly to copy 3903 // the referent object and update the pointer, while avoiding 3904 // updating the RSet. 3905 3906 if (_g1h->is_in_g1_reserved(p)) { 3907 _par_scan_state->push_on_queue(p); 3908 } else { 3909 assert(!Metaspace::contains((const void*)p), 3910 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 3911 _copy_non_heap_obj_cl->do_oop(p); 3912 } 3913 } 3914 } 3915 }; 3916 3917 // Serial drain queue closure. Called as the 'complete_gc' 3918 // closure for each discovered list in some of the 3919 // reference processing phases. 3920 3921 class G1STWDrainQueueClosure: public VoidClosure { 3922 protected: 3923 G1CollectedHeap* _g1h; 3924 G1ParScanThreadState* _par_scan_state; 3925 3926 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3927 3928 public: 3929 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3930 _g1h(g1h), 3931 _par_scan_state(pss) 3932 { } 3933 3934 void do_void() { 3935 G1ParScanThreadState* const pss = par_scan_state(); 3936 pss->trim_queue(); 3937 } 3938 }; 3939 3940 // Parallel Reference Processing closures 3941 3942 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3943 // processing during G1 evacuation pauses. 3944 3945 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3946 private: 3947 G1CollectedHeap* _g1h; 3948 G1ParScanThreadStateSet* _pss; 3949 RefToScanQueueSet* _queues; 3950 WorkGang* _workers; 3951 uint _active_workers; 3952 3953 public: 3954 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3955 G1ParScanThreadStateSet* per_thread_states, 3956 WorkGang* workers, 3957 RefToScanQueueSet *task_queues, 3958 uint n_workers) : 3959 _g1h(g1h), 3960 _pss(per_thread_states), 3961 _queues(task_queues), 3962 _workers(workers), 3963 _active_workers(n_workers) 3964 { 3965 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 3966 } 3967 3968 // Executes the given task using concurrent marking worker threads. 3969 virtual void execute(ProcessTask& task); 3970 virtual void execute(EnqueueTask& task); 3971 }; 3972 3973 // Gang task for possibly parallel reference processing 3974 3975 class G1STWRefProcTaskProxy: public AbstractGangTask { 3976 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 3977 ProcessTask& _proc_task; 3978 G1CollectedHeap* _g1h; 3979 G1ParScanThreadStateSet* _pss; 3980 RefToScanQueueSet* _task_queues; 3981 ParallelTaskTerminator* _terminator; 3982 3983 public: 3984 G1STWRefProcTaskProxy(ProcessTask& proc_task, 3985 G1CollectedHeap* g1h, 3986 G1ParScanThreadStateSet* per_thread_states, 3987 RefToScanQueueSet *task_queues, 3988 ParallelTaskTerminator* terminator) : 3989 AbstractGangTask("Process reference objects in parallel"), 3990 _proc_task(proc_task), 3991 _g1h(g1h), 3992 _pss(per_thread_states), 3993 _task_queues(task_queues), 3994 _terminator(terminator) 3995 {} 3996 3997 virtual void work(uint worker_id) { 3998 // The reference processing task executed by a single worker. 3999 ResourceMark rm; 4000 HandleMark hm; 4001 4002 G1STWIsAliveClosure is_alive(_g1h); 4003 4004 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4005 pss->set_ref_processor(NULL); 4006 4007 // Keep alive closure. 4008 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4009 4010 // Complete GC closure 4011 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4012 4013 // Call the reference processing task's work routine. 4014 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4015 4016 // Note we cannot assert that the refs array is empty here as not all 4017 // of the processing tasks (specifically phase2 - pp2_work) execute 4018 // the complete_gc closure (which ordinarily would drain the queue) so 4019 // the queue may not be empty. 4020 } 4021 }; 4022 4023 // Driver routine for parallel reference processing. 4024 // Creates an instance of the ref processing gang 4025 // task and has the worker threads execute it. 4026 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4027 assert(_workers != NULL, "Need parallel worker threads."); 4028 4029 ParallelTaskTerminator terminator(_active_workers, _queues); 4030 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4031 4032 _workers->run_task(&proc_task_proxy); 4033 } 4034 4035 // Gang task for parallel reference enqueueing. 4036 4037 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4038 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4039 EnqueueTask& _enq_task; 4040 4041 public: 4042 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4043 AbstractGangTask("Enqueue reference objects in parallel"), 4044 _enq_task(enq_task) 4045 { } 4046 4047 virtual void work(uint worker_id) { 4048 _enq_task.work(worker_id); 4049 } 4050 }; 4051 4052 // Driver routine for parallel reference enqueueing. 4053 // Creates an instance of the ref enqueueing gang 4054 // task and has the worker threads execute it. 4055 4056 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4057 assert(_workers != NULL, "Need parallel worker threads."); 4058 4059 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4060 4061 _workers->run_task(&enq_task_proxy); 4062 } 4063 4064 // End of weak reference support closures 4065 4066 // Abstract task used to preserve (i.e. copy) any referent objects 4067 // that are in the collection set and are pointed to by reference 4068 // objects discovered by the CM ref processor. 4069 4070 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4071 protected: 4072 G1CollectedHeap* _g1h; 4073 G1ParScanThreadStateSet* _pss; 4074 RefToScanQueueSet* _queues; 4075 ParallelTaskTerminator _terminator; 4076 uint _n_workers; 4077 4078 public: 4079 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4080 AbstractGangTask("ParPreserveCMReferents"), 4081 _g1h(g1h), 4082 _pss(per_thread_states), 4083 _queues(task_queues), 4084 _terminator(workers, _queues), 4085 _n_workers(workers) 4086 { 4087 g1h->ref_processor_cm()->set_active_mt_degree(workers); 4088 } 4089 4090 void work(uint worker_id) { 4091 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4092 4093 ResourceMark rm; 4094 HandleMark hm; 4095 4096 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4097 pss->set_ref_processor(NULL); 4098 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4099 4100 // Is alive closure 4101 G1AlwaysAliveClosure always_alive(_g1h); 4102 4103 // Copying keep alive closure. Applied to referent objects that need 4104 // to be copied. 4105 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4106 4107 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4108 4109 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4110 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4111 4112 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4113 // So this must be true - but assert just in case someone decides to 4114 // change the worker ids. 4115 assert(worker_id < limit, "sanity"); 4116 assert(!rp->discovery_is_atomic(), "check this code"); 4117 4118 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4119 for (uint idx = worker_id; idx < limit; idx += stride) { 4120 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4121 4122 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4123 while (iter.has_next()) { 4124 // Since discovery is not atomic for the CM ref processor, we 4125 // can see some null referent objects. 4126 iter.load_ptrs(DEBUG_ONLY(true)); 4127 oop ref = iter.obj(); 4128 4129 // This will filter nulls. 4130 if (iter.is_referent_alive()) { 4131 iter.make_referent_alive(); 4132 } 4133 iter.move_to_next(); 4134 } 4135 } 4136 4137 // Drain the queue - which may cause stealing 4138 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4139 drain_queue.do_void(); 4140 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4141 assert(pss->queue_is_empty(), "should be"); 4142 } 4143 }; 4144 4145 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4146 // Any reference objects, in the collection set, that were 'discovered' 4147 // by the CM ref processor should have already been copied (either by 4148 // applying the external root copy closure to the discovered lists, or 4149 // by following an RSet entry). 4150 // 4151 // But some of the referents, that are in the collection set, that these 4152 // reference objects point to may not have been copied: the STW ref 4153 // processor would have seen that the reference object had already 4154 // been 'discovered' and would have skipped discovering the reference, 4155 // but would not have treated the reference object as a regular oop. 4156 // As a result the copy closure would not have been applied to the 4157 // referent object. 4158 // 4159 // We need to explicitly copy these referent objects - the references 4160 // will be processed at the end of remarking. 4161 // 4162 // We also need to do this copying before we process the reference 4163 // objects discovered by the STW ref processor in case one of these 4164 // referents points to another object which is also referenced by an 4165 // object discovered by the STW ref processor. 4166 double preserve_cm_referents_time = 0.0; 4167 4168 // To avoid spawning task when there is no work to do, check that 4169 // a concurrent cycle is active and that some references have been 4170 // discovered. 4171 if (concurrent_mark()->cm_thread()->during_cycle() && 4172 ref_processor_cm()->has_discovered_references()) { 4173 double preserve_cm_referents_start = os::elapsedTime(); 4174 uint no_of_gc_workers = workers()->active_workers(); 4175 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4176 per_thread_states, 4177 no_of_gc_workers, 4178 _task_queues); 4179 workers()->run_task(&keep_cm_referents); 4180 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4181 } 4182 4183 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4184 } 4185 4186 // Weak Reference processing during an evacuation pause (part 1). 4187 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4188 double ref_proc_start = os::elapsedTime(); 4189 4190 ReferenceProcessor* rp = _ref_processor_stw; 4191 assert(rp->discovery_enabled(), "should have been enabled"); 4192 4193 // Closure to test whether a referent is alive. 4194 G1STWIsAliveClosure is_alive(this); 4195 4196 // Even when parallel reference processing is enabled, the processing 4197 // of JNI refs is serial and performed serially by the current thread 4198 // rather than by a worker. The following PSS will be used for processing 4199 // JNI refs. 4200 4201 // Use only a single queue for this PSS. 4202 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4203 pss->set_ref_processor(NULL); 4204 assert(pss->queue_is_empty(), "pre-condition"); 4205 4206 // Keep alive closure. 4207 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4208 4209 // Serial Complete GC closure 4210 G1STWDrainQueueClosure drain_queue(this, pss); 4211 4212 // Setup the soft refs policy... 4213 rp->setup_policy(false); 4214 4215 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4216 4217 ReferenceProcessorStats stats; 4218 if (!rp->processing_is_mt()) { 4219 // Serial reference processing... 4220 stats = rp->process_discovered_references(&is_alive, 4221 &keep_alive, 4222 &drain_queue, 4223 NULL, 4224 pt); 4225 } else { 4226 uint no_of_gc_workers = workers()->active_workers(); 4227 4228 // Parallel reference processing 4229 assert(no_of_gc_workers <= rp->max_num_q(), 4230 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4231 no_of_gc_workers, rp->max_num_q()); 4232 4233 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4234 stats = rp->process_discovered_references(&is_alive, 4235 &keep_alive, 4236 &drain_queue, 4237 &par_task_executor, 4238 pt); 4239 } 4240 4241 _gc_tracer_stw->report_gc_reference_stats(stats); 4242 4243 // We have completed copying any necessary live referent objects. 4244 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4245 4246 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4247 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4248 } 4249 4250 // Weak Reference processing during an evacuation pause (part 2). 4251 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4252 double ref_enq_start = os::elapsedTime(); 4253 4254 ReferenceProcessor* rp = _ref_processor_stw; 4255 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4256 4257 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4258 4259 // Now enqueue any remaining on the discovered lists on to 4260 // the pending list. 4261 if (!rp->processing_is_mt()) { 4262 // Serial reference processing... 4263 rp->enqueue_discovered_references(NULL, pt); 4264 } else { 4265 // Parallel reference enqueueing 4266 4267 uint n_workers = workers()->active_workers(); 4268 4269 assert(n_workers <= rp->max_num_q(), 4270 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4271 n_workers, rp->max_num_q()); 4272 4273 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4274 rp->enqueue_discovered_references(&par_task_executor, pt); 4275 } 4276 4277 rp->verify_no_references_recorded(); 4278 assert(!rp->discovery_enabled(), "should have been disabled"); 4279 4280 // If during an initial mark pause we install a pending list head which is not otherwise reachable 4281 // ensure that it is marked in the bitmap for concurrent marking to discover. 4282 if (collector_state()->during_initial_mark_pause()) { 4283 oop pll_head = Universe::reference_pending_list(); 4284 if (pll_head != NULL) { 4285 _cm->mark_in_next_bitmap(pll_head); 4286 } 4287 } 4288 4289 // FIXME 4290 // CM's reference processing also cleans up the string and symbol tables. 4291 // Should we do that here also? We could, but it is a serial operation 4292 // and could significantly increase the pause time. 4293 4294 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4295 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4296 } 4297 4298 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4299 double merge_pss_time_start = os::elapsedTime(); 4300 per_thread_states->flush(); 4301 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4302 } 4303 4304 void G1CollectedHeap::pre_evacuate_collection_set() { 4305 _expand_heap_after_alloc_failure = true; 4306 _evacuation_failed = false; 4307 4308 // Disable the hot card cache. 4309 _hot_card_cache->reset_hot_cache_claimed_index(); 4310 _hot_card_cache->set_use_cache(false); 4311 4312 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4313 _preserved_marks_set.assert_empty(); 4314 4315 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4316 4317 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4318 if (collector_state()->during_initial_mark_pause()) { 4319 double start_clear_claimed_marks = os::elapsedTime(); 4320 4321 ClassLoaderDataGraph::clear_claimed_marks(); 4322 4323 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4324 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4325 } 4326 } 4327 4328 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4329 // Should G1EvacuationFailureALot be in effect for this GC? 4330 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4331 4332 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4333 4334 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4335 4336 double start_par_time_sec = os::elapsedTime(); 4337 double end_par_time_sec; 4338 4339 { 4340 const uint n_workers = workers()->active_workers(); 4341 G1RootProcessor root_processor(this, n_workers); 4342 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4343 4344 print_termination_stats_hdr(); 4345 4346 workers()->run_task(&g1_par_task); 4347 end_par_time_sec = os::elapsedTime(); 4348 4349 // Closing the inner scope will execute the destructor 4350 // for the G1RootProcessor object. We record the current 4351 // elapsed time before closing the scope so that time 4352 // taken for the destructor is NOT included in the 4353 // reported parallel time. 4354 } 4355 4356 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4357 phase_times->record_par_time(par_time_ms); 4358 4359 double code_root_fixup_time_ms = 4360 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4361 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4362 } 4363 4364 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4365 // Process any discovered reference objects - we have 4366 // to do this _before_ we retire the GC alloc regions 4367 // as we may have to copy some 'reachable' referent 4368 // objects (and their reachable sub-graphs) that were 4369 // not copied during the pause. 4370 if (g1_policy()->should_process_references()) { 4371 preserve_cm_referents(per_thread_states); 4372 process_discovered_references(per_thread_states); 4373 } else { 4374 ref_processor_stw()->verify_no_references_recorded(); 4375 } 4376 4377 G1STWIsAliveClosure is_alive(this); 4378 G1KeepAliveClosure keep_alive(this); 4379 4380 { 4381 double start = os::elapsedTime(); 4382 4383 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 4384 4385 double time_ms = (os::elapsedTime() - start) * 1000.0; 4386 g1_policy()->phase_times()->record_ref_proc_time(time_ms); 4387 } 4388 4389 if (G1StringDedup::is_enabled()) { 4390 double fixup_start = os::elapsedTime(); 4391 4392 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4393 4394 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4395 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4396 } 4397 4398 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4399 4400 if (evacuation_failed()) { 4401 restore_after_evac_failure(); 4402 4403 // Reset the G1EvacuationFailureALot counters and flags 4404 // Note: the values are reset only when an actual 4405 // evacuation failure occurs. 4406 NOT_PRODUCT(reset_evacuation_should_fail();) 4407 } 4408 4409 _preserved_marks_set.assert_empty(); 4410 4411 // Enqueue any remaining references remaining on the STW 4412 // reference processor's discovered lists. We need to do 4413 // this after the card table is cleaned (and verified) as 4414 // the act of enqueueing entries on to the pending list 4415 // will log these updates (and dirty their associated 4416 // cards). We need these updates logged to update any 4417 // RSets. 4418 if (g1_policy()->should_process_references()) { 4419 enqueue_discovered_references(per_thread_states); 4420 } else { 4421 g1_policy()->phase_times()->record_ref_enq_time(0); 4422 } 4423 4424 _allocator->release_gc_alloc_regions(evacuation_info); 4425 4426 merge_per_thread_state_info(per_thread_states); 4427 4428 // Reset and re-enable the hot card cache. 4429 // Note the counts for the cards in the regions in the 4430 // collection set are reset when the collection set is freed. 4431 _hot_card_cache->reset_hot_cache(); 4432 _hot_card_cache->set_use_cache(true); 4433 4434 purge_code_root_memory(); 4435 4436 redirty_logged_cards(); 4437 #if COMPILER2_OR_JVMCI 4438 double start = os::elapsedTime(); 4439 DerivedPointerTable::update_pointers(); 4440 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4441 #endif 4442 g1_policy()->print_age_table(); 4443 } 4444 4445 void G1CollectedHeap::record_obj_copy_mem_stats() { 4446 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4447 4448 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4449 create_g1_evac_summary(&_old_evac_stats)); 4450 } 4451 4452 void G1CollectedHeap::free_region(HeapRegion* hr, 4453 FreeRegionList* free_list, 4454 bool skip_remset, 4455 bool skip_hot_card_cache, 4456 bool locked) { 4457 assert(!hr->is_free(), "the region should not be free"); 4458 assert(!hr->is_empty(), "the region should not be empty"); 4459 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4460 assert(free_list != NULL, "pre-condition"); 4461 4462 if (G1VerifyBitmaps) { 4463 MemRegion mr(hr->bottom(), hr->end()); 4464 concurrent_mark()->clear_range_in_prev_bitmap(mr); 4465 } 4466 4467 // Clear the card counts for this region. 4468 // Note: we only need to do this if the region is not young 4469 // (since we don't refine cards in young regions). 4470 if (!skip_hot_card_cache && !hr->is_young()) { 4471 _hot_card_cache->reset_card_counts(hr); 4472 } 4473 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4474 free_list->add_ordered(hr); 4475 } 4476 4477 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4478 FreeRegionList* free_list, 4479 bool skip_remset) { 4480 assert(hr->is_humongous(), "this is only for humongous regions"); 4481 assert(free_list != NULL, "pre-condition"); 4482 hr->clear_humongous(); 4483 free_region(hr, free_list, skip_remset); 4484 } 4485 4486 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4487 const uint humongous_regions_removed) { 4488 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4489 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4490 _old_set.bulk_remove(old_regions_removed); 4491 _humongous_set.bulk_remove(humongous_regions_removed); 4492 } 4493 4494 } 4495 4496 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4497 assert(list != NULL, "list can't be null"); 4498 if (!list->is_empty()) { 4499 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4500 _hrm.insert_list_into_free_list(list); 4501 } 4502 } 4503 4504 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4505 decrease_used(bytes); 4506 } 4507 4508 class G1ParScrubRemSetTask: public AbstractGangTask { 4509 protected: 4510 G1RemSet* _g1rs; 4511 HeapRegionClaimer _hrclaimer; 4512 4513 public: 4514 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) : 4515 AbstractGangTask("G1 ScrubRS"), 4516 _g1rs(g1_rs), 4517 _hrclaimer(num_workers) { 4518 } 4519 4520 void work(uint worker_id) { 4521 _g1rs->scrub(worker_id, &_hrclaimer); 4522 } 4523 }; 4524 4525 void G1CollectedHeap::scrub_rem_set() { 4526 uint num_workers = workers()->active_workers(); 4527 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers); 4528 workers()->run_task(&g1_par_scrub_rs_task); 4529 } 4530 4531 class G1FreeCollectionSetTask : public AbstractGangTask { 4532 private: 4533 4534 // Closure applied to all regions in the collection set to do work that needs to 4535 // be done serially in a single thread. 4536 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4537 private: 4538 EvacuationInfo* _evacuation_info; 4539 const size_t* _surviving_young_words; 4540 4541 // Bytes used in successfully evacuated regions before the evacuation. 4542 size_t _before_used_bytes; 4543 // Bytes used in unsucessfully evacuated regions before the evacuation 4544 size_t _after_used_bytes; 4545 4546 size_t _bytes_allocated_in_old_since_last_gc; 4547 4548 size_t _failure_used_words; 4549 size_t _failure_waste_words; 4550 4551 FreeRegionList _local_free_list; 4552 public: 4553 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4554 HeapRegionClosure(), 4555 _evacuation_info(evacuation_info), 4556 _surviving_young_words(surviving_young_words), 4557 _before_used_bytes(0), 4558 _after_used_bytes(0), 4559 _bytes_allocated_in_old_since_last_gc(0), 4560 _failure_used_words(0), 4561 _failure_waste_words(0), 4562 _local_free_list("Local Region List for CSet Freeing") { 4563 } 4564 4565 virtual bool doHeapRegion(HeapRegion* r) { 4566 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4567 4568 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4569 g1h->clear_in_cset(r); 4570 4571 if (r->is_young()) { 4572 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4573 "Young index %d is wrong for region %u of type %s with %u young regions", 4574 r->young_index_in_cset(), 4575 r->hrm_index(), 4576 r->get_type_str(), 4577 g1h->collection_set()->young_region_length()); 4578 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4579 r->record_surv_words_in_group(words_survived); 4580 } 4581 4582 if (!r->evacuation_failed()) { 4583 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4584 _before_used_bytes += r->used(); 4585 g1h->free_region(r, 4586 &_local_free_list, 4587 true, /* skip_remset */ 4588 true, /* skip_hot_card_cache */ 4589 true /* locked */); 4590 } else { 4591 r->uninstall_surv_rate_group(); 4592 r->set_young_index_in_cset(-1); 4593 r->set_evacuation_failed(false); 4594 // When moving a young gen region to old gen, we "allocate" that whole region 4595 // there. This is in addition to any already evacuated objects. Notify the 4596 // policy about that. 4597 // Old gen regions do not cause an additional allocation: both the objects 4598 // still in the region and the ones already moved are accounted for elsewhere. 4599 if (r->is_young()) { 4600 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4601 } 4602 // The region is now considered to be old. 4603 r->set_old(); 4604 // Do some allocation statistics accounting. Regions that failed evacuation 4605 // are always made old, so there is no need to update anything in the young 4606 // gen statistics, but we need to update old gen statistics. 4607 size_t used_words = r->marked_bytes() / HeapWordSize; 4608 4609 _failure_used_words += used_words; 4610 _failure_waste_words += HeapRegion::GrainWords - used_words; 4611 4612 g1h->old_set_add(r); 4613 _after_used_bytes += r->used(); 4614 } 4615 return false; 4616 } 4617 4618 void complete_work() { 4619 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4620 4621 _evacuation_info->set_regions_freed(_local_free_list.length()); 4622 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4623 4624 g1h->prepend_to_freelist(&_local_free_list); 4625 g1h->decrement_summary_bytes(_before_used_bytes); 4626 4627 G1Policy* policy = g1h->g1_policy(); 4628 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4629 4630 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4631 } 4632 }; 4633 4634 G1CollectionSet* _collection_set; 4635 G1SerialFreeCollectionSetClosure _cl; 4636 const size_t* _surviving_young_words; 4637 4638 size_t _rs_lengths; 4639 4640 volatile jint _serial_work_claim; 4641 4642 struct WorkItem { 4643 uint region_idx; 4644 bool is_young; 4645 bool evacuation_failed; 4646 4647 WorkItem(HeapRegion* r) { 4648 region_idx = r->hrm_index(); 4649 is_young = r->is_young(); 4650 evacuation_failed = r->evacuation_failed(); 4651 } 4652 }; 4653 4654 volatile size_t _parallel_work_claim; 4655 size_t _num_work_items; 4656 WorkItem* _work_items; 4657 4658 void do_serial_work() { 4659 // Need to grab the lock to be allowed to modify the old region list. 4660 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4661 _collection_set->iterate(&_cl); 4662 } 4663 4664 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4665 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4666 4667 HeapRegion* r = g1h->region_at(region_idx); 4668 assert(!g1h->is_on_master_free_list(r), "sanity"); 4669 4670 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4671 4672 if (!is_young) { 4673 g1h->_hot_card_cache->reset_card_counts(r); 4674 } 4675 4676 if (!evacuation_failed) { 4677 r->rem_set()->clear_locked(); 4678 } 4679 } 4680 4681 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4682 private: 4683 size_t _cur_idx; 4684 WorkItem* _work_items; 4685 public: 4686 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4687 4688 virtual bool doHeapRegion(HeapRegion* r) { 4689 _work_items[_cur_idx++] = WorkItem(r); 4690 return false; 4691 } 4692 }; 4693 4694 void prepare_work() { 4695 G1PrepareFreeCollectionSetClosure cl(_work_items); 4696 _collection_set->iterate(&cl); 4697 } 4698 4699 void complete_work() { 4700 _cl.complete_work(); 4701 4702 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4703 policy->record_max_rs_lengths(_rs_lengths); 4704 policy->cset_regions_freed(); 4705 } 4706 public: 4707 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4708 AbstractGangTask("G1 Free Collection Set"), 4709 _cl(evacuation_info, surviving_young_words), 4710 _collection_set(collection_set), 4711 _surviving_young_words(surviving_young_words), 4712 _serial_work_claim(0), 4713 _rs_lengths(0), 4714 _parallel_work_claim(0), 4715 _num_work_items(collection_set->region_length()), 4716 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4717 prepare_work(); 4718 } 4719 4720 ~G1FreeCollectionSetTask() { 4721 complete_work(); 4722 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4723 } 4724 4725 // Chunk size for work distribution. The chosen value has been determined experimentally 4726 // to be a good tradeoff between overhead and achievable parallelism. 4727 static uint chunk_size() { return 32; } 4728 4729 virtual void work(uint worker_id) { 4730 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4731 4732 // Claim serial work. 4733 if (_serial_work_claim == 0) { 4734 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4735 if (value == 0) { 4736 double serial_time = os::elapsedTime(); 4737 do_serial_work(); 4738 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4739 } 4740 } 4741 4742 // Start parallel work. 4743 double young_time = 0.0; 4744 bool has_young_time = false; 4745 double non_young_time = 0.0; 4746 bool has_non_young_time = false; 4747 4748 while (true) { 4749 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4750 size_t cur = end - chunk_size(); 4751 4752 if (cur >= _num_work_items) { 4753 break; 4754 } 4755 4756 double start_time = os::elapsedTime(); 4757 4758 end = MIN2(end, _num_work_items); 4759 4760 for (; cur < end; cur++) { 4761 bool is_young = _work_items[cur].is_young; 4762 4763 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4764 4765 double end_time = os::elapsedTime(); 4766 double time_taken = end_time - start_time; 4767 if (is_young) { 4768 young_time += time_taken; 4769 has_young_time = true; 4770 } else { 4771 non_young_time += time_taken; 4772 has_non_young_time = true; 4773 } 4774 start_time = end_time; 4775 } 4776 } 4777 4778 if (has_young_time) { 4779 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4780 } 4781 if (has_non_young_time) { 4782 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time); 4783 } 4784 } 4785 }; 4786 4787 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4788 _eden.clear(); 4789 4790 double free_cset_start_time = os::elapsedTime(); 4791 4792 { 4793 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4794 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4795 4796 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4797 4798 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4799 cl.name(), 4800 num_workers, 4801 _collection_set.region_length()); 4802 workers()->run_task(&cl, num_workers); 4803 } 4804 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4805 4806 collection_set->clear(); 4807 } 4808 4809 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4810 private: 4811 FreeRegionList* _free_region_list; 4812 HeapRegionSet* _proxy_set; 4813 uint _humongous_objects_reclaimed; 4814 uint _humongous_regions_reclaimed; 4815 size_t _freed_bytes; 4816 public: 4817 4818 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4819 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4820 } 4821 4822 virtual bool doHeapRegion(HeapRegion* r) { 4823 if (!r->is_starts_humongous()) { 4824 return false; 4825 } 4826 4827 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4828 4829 oop obj = (oop)r->bottom(); 4830 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap(); 4831 4832 // The following checks whether the humongous object is live are sufficient. 4833 // The main additional check (in addition to having a reference from the roots 4834 // or the young gen) is whether the humongous object has a remembered set entry. 4835 // 4836 // A humongous object cannot be live if there is no remembered set for it 4837 // because: 4838 // - there can be no references from within humongous starts regions referencing 4839 // the object because we never allocate other objects into them. 4840 // (I.e. there are no intra-region references that may be missed by the 4841 // remembered set) 4842 // - as soon there is a remembered set entry to the humongous starts region 4843 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4844 // until the end of a concurrent mark. 4845 // 4846 // It is not required to check whether the object has been found dead by marking 4847 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4848 // all objects allocated during that time are considered live. 4849 // SATB marking is even more conservative than the remembered set. 4850 // So if at this point in the collection there is no remembered set entry, 4851 // nobody has a reference to it. 4852 // At the start of collection we flush all refinement logs, and remembered sets 4853 // are completely up-to-date wrt to references to the humongous object. 4854 // 4855 // Other implementation considerations: 4856 // - never consider object arrays at this time because they would pose 4857 // considerable effort for cleaning up the the remembered sets. This is 4858 // required because stale remembered sets might reference locations that 4859 // are currently allocated into. 4860 uint region_idx = r->hrm_index(); 4861 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4862 !r->rem_set()->is_empty()) { 4863 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", 4864 region_idx, 4865 (size_t)obj->size() * HeapWordSize, 4866 p2i(r->bottom()), 4867 r->rem_set()->occupied(), 4868 r->rem_set()->strong_code_roots_list_length(), 4869 next_bitmap->is_marked(r->bottom()), 4870 g1h->is_humongous_reclaim_candidate(region_idx), 4871 obj->is_typeArray() 4872 ); 4873 return false; 4874 } 4875 4876 guarantee(obj->is_typeArray(), 4877 "Only eagerly reclaiming type arrays is supported, but the object " 4878 PTR_FORMAT " is not.", p2i(r->bottom())); 4879 4880 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", 4881 region_idx, 4882 (size_t)obj->size() * HeapWordSize, 4883 p2i(r->bottom()), 4884 r->rem_set()->occupied(), 4885 r->rem_set()->strong_code_roots_list_length(), 4886 next_bitmap->is_marked(r->bottom()), 4887 g1h->is_humongous_reclaim_candidate(region_idx), 4888 obj->is_typeArray() 4889 ); 4890 4891 // Need to clear mark bit of the humongous object if already set. 4892 if (next_bitmap->is_marked(r->bottom())) { 4893 next_bitmap->clear(r->bottom()); 4894 } 4895 _humongous_objects_reclaimed++; 4896 do { 4897 HeapRegion* next = g1h->next_region_in_humongous(r); 4898 _freed_bytes += r->used(); 4899 r->set_containing_set(NULL); 4900 _humongous_regions_reclaimed++; 4901 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ ); 4902 r = next; 4903 } while (r != NULL); 4904 4905 return false; 4906 } 4907 4908 uint humongous_objects_reclaimed() { 4909 return _humongous_objects_reclaimed; 4910 } 4911 4912 uint humongous_regions_reclaimed() { 4913 return _humongous_regions_reclaimed; 4914 } 4915 4916 size_t bytes_freed() const { 4917 return _freed_bytes; 4918 } 4919 }; 4920 4921 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4922 assert_at_safepoint(true); 4923 4924 if (!G1EagerReclaimHumongousObjects || 4925 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4926 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4927 return; 4928 } 4929 4930 double start_time = os::elapsedTime(); 4931 4932 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4933 4934 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4935 heap_region_iterate(&cl); 4936 4937 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4938 4939 G1HRPrinter* hrp = hr_printer(); 4940 if (hrp->is_active()) { 4941 FreeRegionListIterator iter(&local_cleanup_list); 4942 while (iter.more_available()) { 4943 HeapRegion* hr = iter.get_next(); 4944 hrp->cleanup(hr); 4945 } 4946 } 4947 4948 prepend_to_freelist(&local_cleanup_list); 4949 decrement_summary_bytes(cl.bytes_freed()); 4950 4951 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4952 cl.humongous_objects_reclaimed()); 4953 } 4954 4955 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4956 public: 4957 virtual bool doHeapRegion(HeapRegion* r) { 4958 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4959 G1CollectedHeap::heap()->clear_in_cset(r); 4960 r->set_young_index_in_cset(-1); 4961 return false; 4962 } 4963 }; 4964 4965 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4966 G1AbandonCollectionSetClosure cl; 4967 collection_set->iterate(&cl); 4968 4969 collection_set->clear(); 4970 collection_set->stop_incremental_building(); 4971 } 4972 4973 void G1CollectedHeap::set_free_regions_coming() { 4974 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 4975 4976 assert(!free_regions_coming(), "pre-condition"); 4977 _free_regions_coming = true; 4978 } 4979 4980 void G1CollectedHeap::reset_free_regions_coming() { 4981 assert(free_regions_coming(), "pre-condition"); 4982 4983 { 4984 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 4985 _free_regions_coming = false; 4986 SecondaryFreeList_lock->notify_all(); 4987 } 4988 4989 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 4990 } 4991 4992 void G1CollectedHeap::wait_while_free_regions_coming() { 4993 // Most of the time we won't have to wait, so let's do a quick test 4994 // first before we take the lock. 4995 if (!free_regions_coming()) { 4996 return; 4997 } 4998 4999 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 5000 5001 { 5002 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5003 while (free_regions_coming()) { 5004 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5005 } 5006 } 5007 5008 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 5009 } 5010 5011 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5012 return _allocator->is_retained_old_region(hr); 5013 } 5014 5015 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5016 _eden.add(hr); 5017 _g1_policy->set_region_eden(hr); 5018 } 5019 5020 #ifdef ASSERT 5021 5022 class NoYoungRegionsClosure: public HeapRegionClosure { 5023 private: 5024 bool _success; 5025 public: 5026 NoYoungRegionsClosure() : _success(true) { } 5027 bool doHeapRegion(HeapRegion* r) { 5028 if (r->is_young()) { 5029 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5030 p2i(r->bottom()), p2i(r->end())); 5031 _success = false; 5032 } 5033 return false; 5034 } 5035 bool success() { return _success; } 5036 }; 5037 5038 bool G1CollectedHeap::check_young_list_empty() { 5039 bool ret = (young_regions_count() == 0); 5040 5041 NoYoungRegionsClosure closure; 5042 heap_region_iterate(&closure); 5043 ret = ret && closure.success(); 5044 5045 return ret; 5046 } 5047 5048 #endif // ASSERT 5049 5050 class TearDownRegionSetsClosure : public HeapRegionClosure { 5051 private: 5052 HeapRegionSet *_old_set; 5053 5054 public: 5055 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5056 5057 bool doHeapRegion(HeapRegion* r) { 5058 if (r->is_old()) { 5059 _old_set->remove(r); 5060 } else if(r->is_young()) { 5061 r->uninstall_surv_rate_group(); 5062 } else { 5063 // We ignore free regions, we'll empty the free list afterwards. 5064 // We ignore humongous regions, we're not tearing down the 5065 // humongous regions set. 5066 assert(r->is_free() || r->is_humongous(), 5067 "it cannot be another type"); 5068 } 5069 return false; 5070 } 5071 5072 ~TearDownRegionSetsClosure() { 5073 assert(_old_set->is_empty(), "post-condition"); 5074 } 5075 }; 5076 5077 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5078 assert_at_safepoint(true /* should_be_vm_thread */); 5079 5080 if (!free_list_only) { 5081 TearDownRegionSetsClosure cl(&_old_set); 5082 heap_region_iterate(&cl); 5083 5084 // Note that emptying the _young_list is postponed and instead done as 5085 // the first step when rebuilding the regions sets again. The reason for 5086 // this is that during a full GC string deduplication needs to know if 5087 // a collected region was young or old when the full GC was initiated. 5088 } 5089 _hrm.remove_all_free_regions(); 5090 } 5091 5092 void G1CollectedHeap::increase_used(size_t bytes) { 5093 _summary_bytes_used += bytes; 5094 } 5095 5096 void G1CollectedHeap::decrease_used(size_t bytes) { 5097 assert(_summary_bytes_used >= bytes, 5098 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5099 _summary_bytes_used, bytes); 5100 _summary_bytes_used -= bytes; 5101 } 5102 5103 void G1CollectedHeap::set_used(size_t bytes) { 5104 _summary_bytes_used = bytes; 5105 } 5106 5107 class RebuildRegionSetsClosure : public HeapRegionClosure { 5108 private: 5109 bool _free_list_only; 5110 HeapRegionSet* _old_set; 5111 HeapRegionManager* _hrm; 5112 size_t _total_used; 5113 5114 public: 5115 RebuildRegionSetsClosure(bool free_list_only, 5116 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5117 _free_list_only(free_list_only), 5118 _old_set(old_set), _hrm(hrm), _total_used(0) { 5119 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5120 if (!free_list_only) { 5121 assert(_old_set->is_empty(), "pre-condition"); 5122 } 5123 } 5124 5125 bool doHeapRegion(HeapRegion* r) { 5126 if (r->is_empty()) { 5127 // Add free regions to the free list 5128 r->set_free(); 5129 r->set_allocation_context(AllocationContext::system()); 5130 _hrm->insert_into_free_list(r); 5131 } else if (!_free_list_only) { 5132 5133 if (r->is_humongous()) { 5134 // We ignore humongous regions. We left the humongous set unchanged. 5135 } else { 5136 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 5137 // We now move all (non-humongous, non-old) regions to old gen, and register them as such. 5138 r->move_to_old(); 5139 _old_set->add(r); 5140 } 5141 _total_used += r->used(); 5142 } 5143 5144 return false; 5145 } 5146 5147 size_t total_used() { 5148 return _total_used; 5149 } 5150 }; 5151 5152 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5153 assert_at_safepoint(true /* should_be_vm_thread */); 5154 5155 if (!free_list_only) { 5156 _eden.clear(); 5157 _survivor.clear(); 5158 } 5159 5160 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5161 heap_region_iterate(&cl); 5162 5163 if (!free_list_only) { 5164 set_used(cl.total_used()); 5165 if (_archive_allocator != NULL) { 5166 _archive_allocator->clear_used(); 5167 } 5168 } 5169 assert(used_unlocked() == recalculate_used(), 5170 "inconsistent used_unlocked(), " 5171 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5172 used_unlocked(), recalculate_used()); 5173 } 5174 5175 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5176 HeapRegion* hr = heap_region_containing(p); 5177 return hr->is_in(p); 5178 } 5179 5180 // Methods for the mutator alloc region 5181 5182 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5183 bool force) { 5184 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5185 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 5186 if (force || should_allocate) { 5187 HeapRegion* new_alloc_region = new_region(word_size, 5188 false /* is_old */, 5189 false /* do_expand */); 5190 if (new_alloc_region != NULL) { 5191 set_region_short_lived_locked(new_alloc_region); 5192 _hr_printer.alloc(new_alloc_region, !should_allocate); 5193 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5194 return new_alloc_region; 5195 } 5196 } 5197 return NULL; 5198 } 5199 5200 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5201 size_t allocated_bytes) { 5202 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5203 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5204 5205 collection_set()->add_eden_region(alloc_region); 5206 increase_used(allocated_bytes); 5207 _hr_printer.retire(alloc_region); 5208 // We update the eden sizes here, when the region is retired, 5209 // instead of when it's allocated, since this is the point that its 5210 // used space has been recored in _summary_bytes_used. 5211 g1mm()->update_eden_size(); 5212 } 5213 5214 // Methods for the GC alloc regions 5215 5216 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 5217 if (dest.is_old()) { 5218 return true; 5219 } else { 5220 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 5221 } 5222 } 5223 5224 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 5225 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5226 5227 if (!has_more_regions(dest)) { 5228 return NULL; 5229 } 5230 5231 const bool is_survivor = dest.is_young(); 5232 5233 HeapRegion* new_alloc_region = new_region(word_size, 5234 !is_survivor, 5235 true /* do_expand */); 5236 if (new_alloc_region != NULL) { 5237 // We really only need to do this for old regions given that we 5238 // should never scan survivors. But it doesn't hurt to do it 5239 // for survivors too. 5240 new_alloc_region->record_timestamp(); 5241 if (is_survivor) { 5242 new_alloc_region->set_survivor(); 5243 _survivor.add(new_alloc_region); 5244 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5245 } else { 5246 new_alloc_region->set_old(); 5247 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5248 } 5249 _hr_printer.alloc(new_alloc_region); 5250 bool during_im = collector_state()->during_initial_mark_pause(); 5251 new_alloc_region->note_start_of_copying(during_im); 5252 return new_alloc_region; 5253 } 5254 return NULL; 5255 } 5256 5257 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5258 size_t allocated_bytes, 5259 InCSetState dest) { 5260 bool during_im = collector_state()->during_initial_mark_pause(); 5261 alloc_region->note_end_of_copying(during_im); 5262 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5263 if (dest.is_old()) { 5264 _old_set.add(alloc_region); 5265 } 5266 _hr_printer.retire(alloc_region); 5267 } 5268 5269 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5270 bool expanded = false; 5271 uint index = _hrm.find_highest_free(&expanded); 5272 5273 if (index != G1_NO_HRM_INDEX) { 5274 if (expanded) { 5275 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5276 HeapRegion::GrainWords * HeapWordSize); 5277 } 5278 _hrm.allocate_free_regions_starting_at(index, 1); 5279 return region_at(index); 5280 } 5281 return NULL; 5282 } 5283 5284 // Optimized nmethod scanning 5285 5286 class RegisterNMethodOopClosure: public OopClosure { 5287 G1CollectedHeap* _g1h; 5288 nmethod* _nm; 5289 5290 template <class T> void do_oop_work(T* p) { 5291 T heap_oop = oopDesc::load_heap_oop(p); 5292 if (!oopDesc::is_null(heap_oop)) { 5293 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5294 HeapRegion* hr = _g1h->heap_region_containing(obj); 5295 assert(!hr->is_continues_humongous(), 5296 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5297 " starting at " HR_FORMAT, 5298 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5299 5300 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5301 hr->add_strong_code_root_locked(_nm); 5302 } 5303 } 5304 5305 public: 5306 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5307 _g1h(g1h), _nm(nm) {} 5308 5309 void do_oop(oop* p) { do_oop_work(p); } 5310 void do_oop(narrowOop* p) { do_oop_work(p); } 5311 }; 5312 5313 class UnregisterNMethodOopClosure: public OopClosure { 5314 G1CollectedHeap* _g1h; 5315 nmethod* _nm; 5316 5317 template <class T> void do_oop_work(T* p) { 5318 T heap_oop = oopDesc::load_heap_oop(p); 5319 if (!oopDesc::is_null(heap_oop)) { 5320 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5321 HeapRegion* hr = _g1h->heap_region_containing(obj); 5322 assert(!hr->is_continues_humongous(), 5323 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5324 " starting at " HR_FORMAT, 5325 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5326 5327 hr->remove_strong_code_root(_nm); 5328 } 5329 } 5330 5331 public: 5332 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5333 _g1h(g1h), _nm(nm) {} 5334 5335 void do_oop(oop* p) { do_oop_work(p); } 5336 void do_oop(narrowOop* p) { do_oop_work(p); } 5337 }; 5338 5339 // Returns true if the reference points to an object that 5340 // can move in an incremental collection. 5341 bool G1CollectedHeap::is_scavengable(oop obj) { 5342 HeapRegion* hr = heap_region_containing(obj); 5343 return !hr->is_pinned(); 5344 } 5345 5346 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5347 guarantee(nm != NULL, "sanity"); 5348 RegisterNMethodOopClosure reg_cl(this, nm); 5349 nm->oops_do(®_cl); 5350 } 5351 5352 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5353 guarantee(nm != NULL, "sanity"); 5354 UnregisterNMethodOopClosure reg_cl(this, nm); 5355 nm->oops_do(®_cl, true); 5356 } 5357 5358 void G1CollectedHeap::purge_code_root_memory() { 5359 double purge_start = os::elapsedTime(); 5360 G1CodeRootSet::purge(); 5361 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5362 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5363 } 5364 5365 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5366 G1CollectedHeap* _g1h; 5367 5368 public: 5369 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5370 _g1h(g1h) {} 5371 5372 void do_code_blob(CodeBlob* cb) { 5373 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5374 if (nm == NULL) { 5375 return; 5376 } 5377 5378 if (ScavengeRootsInCode) { 5379 _g1h->register_nmethod(nm); 5380 } 5381 } 5382 }; 5383 5384 void G1CollectedHeap::rebuild_strong_code_roots() { 5385 RebuildStrongCodeRootClosure blob_cl(this); 5386 CodeCache::blobs_do(&blob_cl); 5387 } 5388 5389 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() { 5390 GrowableArray<GCMemoryManager*> memory_managers(2); 5391 memory_managers.append(&_mem_mgr); 5392 memory_managers.append(&_full_gc_mem_mgr); 5393 return memory_managers; 5394 } 5395 5396 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() { 5397 GrowableArray<MemoryPool*> memory_pools(3); 5398 memory_pools.append(_eden_pool); 5399 memory_pools.append(_survivor_pool); 5400 memory_pools.append(_old_pool); 5401 return memory_pools; 5402 }