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_memory_manager, 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 _memory_manager("G1 Young Generation", "end of minor GC"), 1531 _full_gc_memory_manager("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 G1StringDedup::initialize(); 1831 1832 _preserved_marks_set.init(ParallelGCThreads); 1833 1834 _collection_set.initialize(max_regions()); 1835 1836 return JNI_OK; 1837 } 1838 1839 void G1CollectedHeap::initialize_serviceability() { 1840 _eden_pool = new G1EdenPool(this); 1841 _survivor_pool = new G1SurvivorPool(this); 1842 _old_pool = new G1OldGenPool(this); 1843 1844 _full_gc_memory_manager.add_pool(_eden_pool); 1845 _full_gc_memory_manager.add_pool(_survivor_pool); 1846 _full_gc_memory_manager.add_pool(_old_pool); 1847 1848 _memory_manager.add_pool(_eden_pool); 1849 _memory_manager.add_pool(_survivor_pool); 1850 1851 } 1852 1853 void G1CollectedHeap::stop() { 1854 // Stop all concurrent threads. We do this to make sure these threads 1855 // do not continue to execute and access resources (e.g. logging) 1856 // that are destroyed during shutdown. 1857 _cr->stop(); 1858 _young_gen_sampling_thread->stop(); 1859 _cmThread->stop(); 1860 if (G1StringDedup::is_enabled()) { 1861 G1StringDedup::stop(); 1862 } 1863 } 1864 1865 void G1CollectedHeap::safepoint_synchronize_begin() { 1866 SuspendibleThreadSet::synchronize(); 1867 } 1868 1869 void G1CollectedHeap::safepoint_synchronize_end() { 1870 SuspendibleThreadSet::desynchronize(); 1871 } 1872 1873 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1874 return HeapRegion::max_region_size(); 1875 } 1876 1877 void G1CollectedHeap::post_initialize() { 1878 CollectedHeap::post_initialize(); 1879 ref_processing_init(); 1880 } 1881 1882 void G1CollectedHeap::ref_processing_init() { 1883 // Reference processing in G1 currently works as follows: 1884 // 1885 // * There are two reference processor instances. One is 1886 // used to record and process discovered references 1887 // during concurrent marking; the other is used to 1888 // record and process references during STW pauses 1889 // (both full and incremental). 1890 // * Both ref processors need to 'span' the entire heap as 1891 // the regions in the collection set may be dotted around. 1892 // 1893 // * For the concurrent marking ref processor: 1894 // * Reference discovery is enabled at initial marking. 1895 // * Reference discovery is disabled and the discovered 1896 // references processed etc during remarking. 1897 // * Reference discovery is MT (see below). 1898 // * Reference discovery requires a barrier (see below). 1899 // * Reference processing may or may not be MT 1900 // (depending on the value of ParallelRefProcEnabled 1901 // and ParallelGCThreads). 1902 // * A full GC disables reference discovery by the CM 1903 // ref processor and abandons any entries on it's 1904 // discovered lists. 1905 // 1906 // * For the STW processor: 1907 // * Non MT discovery is enabled at the start of a full GC. 1908 // * Processing and enqueueing during a full GC is non-MT. 1909 // * During a full GC, references are processed after marking. 1910 // 1911 // * Discovery (may or may not be MT) is enabled at the start 1912 // of an incremental evacuation pause. 1913 // * References are processed near the end of a STW evacuation pause. 1914 // * For both types of GC: 1915 // * Discovery is atomic - i.e. not concurrent. 1916 // * Reference discovery will not need a barrier. 1917 1918 MemRegion mr = reserved_region(); 1919 1920 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1); 1921 1922 // Concurrent Mark ref processor 1923 _ref_processor_cm = 1924 new ReferenceProcessor(mr, // span 1925 mt_processing, 1926 // mt processing 1927 ParallelGCThreads, 1928 // degree of mt processing 1929 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 1930 // mt discovery 1931 MAX2(ParallelGCThreads, ConcGCThreads), 1932 // degree of mt discovery 1933 false, 1934 // Reference discovery is not atomic 1935 &_is_alive_closure_cm); 1936 // is alive closure 1937 // (for efficiency/performance) 1938 1939 // STW ref processor 1940 _ref_processor_stw = 1941 new ReferenceProcessor(mr, // span 1942 mt_processing, 1943 // mt processing 1944 ParallelGCThreads, 1945 // degree of mt processing 1946 (ParallelGCThreads > 1), 1947 // mt discovery 1948 ParallelGCThreads, 1949 // degree of mt discovery 1950 true, 1951 // Reference discovery is atomic 1952 &_is_alive_closure_stw); 1953 // is alive closure 1954 // (for efficiency/performance) 1955 } 1956 1957 CollectorPolicy* G1CollectedHeap::collector_policy() const { 1958 return _collector_policy; 1959 } 1960 1961 size_t G1CollectedHeap::capacity() const { 1962 return _hrm.length() * HeapRegion::GrainBytes; 1963 } 1964 1965 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const { 1966 return _hrm.total_free_bytes(); 1967 } 1968 1969 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 1970 hr->reset_gc_time_stamp(); 1971 } 1972 1973 #ifndef PRODUCT 1974 1975 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 1976 private: 1977 unsigned _gc_time_stamp; 1978 bool _failures; 1979 1980 public: 1981 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 1982 _gc_time_stamp(gc_time_stamp), _failures(false) { } 1983 1984 virtual bool doHeapRegion(HeapRegion* hr) { 1985 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 1986 if (_gc_time_stamp != region_gc_time_stamp) { 1987 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 1988 region_gc_time_stamp, _gc_time_stamp); 1989 _failures = true; 1990 } 1991 return false; 1992 } 1993 1994 bool failures() { return _failures; } 1995 }; 1996 1997 void G1CollectedHeap::check_gc_time_stamps() { 1998 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 1999 heap_region_iterate(&cl); 2000 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2001 } 2002 #endif // PRODUCT 2003 2004 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2005 _hot_card_cache->drain(cl, worker_i); 2006 } 2007 2008 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2009 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2010 size_t n_completed_buffers = 0; 2011 while (dcqs.apply_closure_during_gc(cl, worker_i)) { 2012 n_completed_buffers++; 2013 } 2014 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2015 dcqs.clear_n_completed_buffers(); 2016 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2017 } 2018 2019 // Computes the sum of the storage used by the various regions. 2020 size_t G1CollectedHeap::used() const { 2021 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2022 if (_archive_allocator != NULL) { 2023 result += _archive_allocator->used(); 2024 } 2025 return result; 2026 } 2027 2028 size_t G1CollectedHeap::used_unlocked() const { 2029 return _summary_bytes_used; 2030 } 2031 2032 class SumUsedClosure: public HeapRegionClosure { 2033 size_t _used; 2034 public: 2035 SumUsedClosure() : _used(0) {} 2036 bool doHeapRegion(HeapRegion* r) { 2037 _used += r->used(); 2038 return false; 2039 } 2040 size_t result() { return _used; } 2041 }; 2042 2043 size_t G1CollectedHeap::recalculate_used() const { 2044 double recalculate_used_start = os::elapsedTime(); 2045 2046 SumUsedClosure blk; 2047 heap_region_iterate(&blk); 2048 2049 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2050 return blk.result(); 2051 } 2052 2053 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2054 switch (cause) { 2055 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2056 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2057 case GCCause::_update_allocation_context_stats_inc: return true; 2058 case GCCause::_wb_conc_mark: return true; 2059 default : return false; 2060 } 2061 } 2062 2063 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2064 switch (cause) { 2065 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2066 case GCCause::_g1_humongous_allocation: return true; 2067 default: return is_user_requested_concurrent_full_gc(cause); 2068 } 2069 } 2070 2071 #ifndef PRODUCT 2072 void G1CollectedHeap::allocate_dummy_regions() { 2073 // Let's fill up most of the region 2074 size_t word_size = HeapRegion::GrainWords - 1024; 2075 // And as a result the region we'll allocate will be humongous. 2076 guarantee(is_humongous(word_size), "sanity"); 2077 2078 // _filler_array_max_size is set to humongous object threshold 2079 // but temporarily change it to use CollectedHeap::fill_with_object(). 2080 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2081 2082 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2083 // Let's use the existing mechanism for the allocation 2084 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2085 AllocationContext::system()); 2086 if (dummy_obj != NULL) { 2087 MemRegion mr(dummy_obj, word_size); 2088 CollectedHeap::fill_with_object(mr); 2089 } else { 2090 // If we can't allocate once, we probably cannot allocate 2091 // again. Let's get out of the loop. 2092 break; 2093 } 2094 } 2095 } 2096 #endif // !PRODUCT 2097 2098 void G1CollectedHeap::increment_old_marking_cycles_started() { 2099 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2100 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2101 "Wrong marking cycle count (started: %d, completed: %d)", 2102 _old_marking_cycles_started, _old_marking_cycles_completed); 2103 2104 _old_marking_cycles_started++; 2105 } 2106 2107 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2108 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2109 2110 // We assume that if concurrent == true, then the caller is a 2111 // concurrent thread that was joined the Suspendible Thread 2112 // Set. If there's ever a cheap way to check this, we should add an 2113 // assert here. 2114 2115 // Given that this method is called at the end of a Full GC or of a 2116 // concurrent cycle, and those can be nested (i.e., a Full GC can 2117 // interrupt a concurrent cycle), the number of full collections 2118 // completed should be either one (in the case where there was no 2119 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2120 // behind the number of full collections started. 2121 2122 // This is the case for the inner caller, i.e. a Full GC. 2123 assert(concurrent || 2124 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2125 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2126 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2127 "is inconsistent with _old_marking_cycles_completed = %u", 2128 _old_marking_cycles_started, _old_marking_cycles_completed); 2129 2130 // This is the case for the outer caller, i.e. the concurrent cycle. 2131 assert(!concurrent || 2132 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2133 "for outer caller (concurrent cycle): " 2134 "_old_marking_cycles_started = %u " 2135 "is inconsistent with _old_marking_cycles_completed = %u", 2136 _old_marking_cycles_started, _old_marking_cycles_completed); 2137 2138 _old_marking_cycles_completed += 1; 2139 2140 // We need to clear the "in_progress" flag in the CM thread before 2141 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2142 // is set) so that if a waiter requests another System.gc() it doesn't 2143 // incorrectly see that a marking cycle is still in progress. 2144 if (concurrent) { 2145 _cmThread->set_idle(); 2146 } 2147 2148 // This notify_all() will ensure that a thread that called 2149 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2150 // and it's waiting for a full GC to finish will be woken up. It is 2151 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2152 FullGCCount_lock->notify_all(); 2153 } 2154 2155 void G1CollectedHeap::collect(GCCause::Cause cause) { 2156 assert_heap_not_locked(); 2157 2158 uint gc_count_before; 2159 uint old_marking_count_before; 2160 uint full_gc_count_before; 2161 bool retry_gc; 2162 2163 do { 2164 retry_gc = false; 2165 2166 { 2167 MutexLocker ml(Heap_lock); 2168 2169 // Read the GC count while holding the Heap_lock 2170 gc_count_before = total_collections(); 2171 full_gc_count_before = total_full_collections(); 2172 old_marking_count_before = _old_marking_cycles_started; 2173 } 2174 2175 if (should_do_concurrent_full_gc(cause)) { 2176 // Schedule an initial-mark evacuation pause that will start a 2177 // concurrent cycle. We're setting word_size to 0 which means that 2178 // we are not requesting a post-GC allocation. 2179 VM_G1IncCollectionPause op(gc_count_before, 2180 0, /* word_size */ 2181 true, /* should_initiate_conc_mark */ 2182 g1_policy()->max_pause_time_ms(), 2183 cause); 2184 op.set_allocation_context(AllocationContext::current()); 2185 2186 VMThread::execute(&op); 2187 if (!op.pause_succeeded()) { 2188 if (old_marking_count_before == _old_marking_cycles_started) { 2189 retry_gc = op.should_retry_gc(); 2190 } else { 2191 // A Full GC happened while we were trying to schedule the 2192 // initial-mark GC. No point in starting a new cycle given 2193 // that the whole heap was collected anyway. 2194 } 2195 2196 if (retry_gc) { 2197 if (GCLocker::is_active_and_needs_gc()) { 2198 GCLocker::stall_until_clear(); 2199 } 2200 } 2201 } 2202 } else { 2203 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2204 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2205 2206 // Schedule a standard evacuation pause. We're setting word_size 2207 // to 0 which means that we are not requesting a post-GC allocation. 2208 VM_G1IncCollectionPause op(gc_count_before, 2209 0, /* word_size */ 2210 false, /* should_initiate_conc_mark */ 2211 g1_policy()->max_pause_time_ms(), 2212 cause); 2213 VMThread::execute(&op); 2214 } else { 2215 // Schedule a Full GC. 2216 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2217 VMThread::execute(&op); 2218 } 2219 } 2220 } while (retry_gc); 2221 } 2222 2223 bool G1CollectedHeap::is_in(const void* p) const { 2224 if (_hrm.reserved().contains(p)) { 2225 // Given that we know that p is in the reserved space, 2226 // heap_region_containing() should successfully 2227 // return the containing region. 2228 HeapRegion* hr = heap_region_containing(p); 2229 return hr->is_in(p); 2230 } else { 2231 return false; 2232 } 2233 } 2234 2235 #ifdef ASSERT 2236 bool G1CollectedHeap::is_in_exact(const void* p) const { 2237 bool contains = reserved_region().contains(p); 2238 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2239 if (contains && available) { 2240 return true; 2241 } else { 2242 return false; 2243 } 2244 } 2245 #endif 2246 2247 // Iteration functions. 2248 2249 // Iterates an ObjectClosure over all objects within a HeapRegion. 2250 2251 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2252 ObjectClosure* _cl; 2253 public: 2254 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2255 bool doHeapRegion(HeapRegion* r) { 2256 if (!r->is_continues_humongous()) { 2257 r->object_iterate(_cl); 2258 } 2259 return false; 2260 } 2261 }; 2262 2263 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2264 IterateObjectClosureRegionClosure blk(cl); 2265 heap_region_iterate(&blk); 2266 } 2267 2268 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2269 _hrm.iterate(cl); 2270 } 2271 2272 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl, 2273 HeapRegionClaimer *hrclaimer, 2274 uint worker_id) const { 2275 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id)); 2276 } 2277 2278 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl, 2279 HeapRegionClaimer *hrclaimer) const { 2280 _hrm.par_iterate(cl, hrclaimer, 0); 2281 } 2282 2283 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2284 _collection_set.iterate(cl); 2285 } 2286 2287 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2288 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2289 } 2290 2291 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2292 HeapRegion* hr = heap_region_containing(addr); 2293 return hr->block_start(addr); 2294 } 2295 2296 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2297 HeapRegion* hr = heap_region_containing(addr); 2298 return hr->block_size(addr); 2299 } 2300 2301 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2302 HeapRegion* hr = heap_region_containing(addr); 2303 return hr->block_is_obj(addr); 2304 } 2305 2306 bool G1CollectedHeap::supports_tlab_allocation() const { 2307 return true; 2308 } 2309 2310 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2311 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2312 } 2313 2314 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2315 return _eden.length() * HeapRegion::GrainBytes; 2316 } 2317 2318 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2319 // must be equal to the humongous object limit. 2320 size_t G1CollectedHeap::max_tlab_size() const { 2321 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2322 } 2323 2324 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2325 AllocationContext_t context = AllocationContext::current(); 2326 return _allocator->unsafe_max_tlab_alloc(context); 2327 } 2328 2329 size_t G1CollectedHeap::max_capacity() const { 2330 return _hrm.reserved().byte_size(); 2331 } 2332 2333 jlong G1CollectedHeap::millis_since_last_gc() { 2334 // See the notes in GenCollectedHeap::millis_since_last_gc() 2335 // for more information about the implementation. 2336 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2337 _g1_policy->collection_pause_end_millis(); 2338 if (ret_val < 0) { 2339 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2340 ". returning zero instead.", ret_val); 2341 return 0; 2342 } 2343 return ret_val; 2344 } 2345 2346 void G1CollectedHeap::prepare_for_verify() { 2347 _verifier->prepare_for_verify(); 2348 } 2349 2350 void G1CollectedHeap::verify(VerifyOption vo) { 2351 _verifier->verify(vo); 2352 } 2353 2354 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2355 return true; 2356 } 2357 2358 const char* const* G1CollectedHeap::concurrent_phases() const { 2359 return _cmThread->concurrent_phases(); 2360 } 2361 2362 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2363 return _cmThread->request_concurrent_phase(phase); 2364 } 2365 2366 class PrintRegionClosure: public HeapRegionClosure { 2367 outputStream* _st; 2368 public: 2369 PrintRegionClosure(outputStream* st) : _st(st) {} 2370 bool doHeapRegion(HeapRegion* r) { 2371 r->print_on(_st); 2372 return false; 2373 } 2374 }; 2375 2376 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2377 const HeapRegion* hr, 2378 const VerifyOption vo) const { 2379 switch (vo) { 2380 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2381 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2382 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr); 2383 default: ShouldNotReachHere(); 2384 } 2385 return false; // keep some compilers happy 2386 } 2387 2388 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2389 const VerifyOption vo) const { 2390 switch (vo) { 2391 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2392 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2393 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj); 2394 default: ShouldNotReachHere(); 2395 } 2396 return false; // keep some compilers happy 2397 } 2398 2399 void G1CollectedHeap::print_heap_regions() const { 2400 LogTarget(Trace, gc, heap, region) lt; 2401 if (lt.is_enabled()) { 2402 LogStream ls(lt); 2403 print_regions_on(&ls); 2404 } 2405 } 2406 2407 void G1CollectedHeap::print_on(outputStream* st) const { 2408 st->print(" %-20s", "garbage-first heap"); 2409 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2410 capacity()/K, used_unlocked()/K); 2411 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")", 2412 p2i(_hrm.reserved().start()), 2413 p2i(_hrm.reserved().end())); 2414 st->cr(); 2415 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2416 uint young_regions = young_regions_count(); 2417 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2418 (size_t) young_regions * HeapRegion::GrainBytes / K); 2419 uint survivor_regions = survivor_regions_count(); 2420 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2421 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2422 st->cr(); 2423 MetaspaceAux::print_on(st); 2424 } 2425 2426 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2427 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2428 "HS=humongous(starts), HC=humongous(continues), " 2429 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2430 "AC=allocation context, " 2431 "TAMS=top-at-mark-start (previous, next)"); 2432 PrintRegionClosure blk(st); 2433 heap_region_iterate(&blk); 2434 } 2435 2436 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2437 print_on(st); 2438 2439 // Print the per-region information. 2440 print_regions_on(st); 2441 } 2442 2443 void G1CollectedHeap::print_on_error(outputStream* st) const { 2444 this->CollectedHeap::print_on_error(st); 2445 2446 if (_cm != NULL) { 2447 st->cr(); 2448 _cm->print_on_error(st); 2449 } 2450 } 2451 2452 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2453 workers()->print_worker_threads_on(st); 2454 _cmThread->print_on(st); 2455 st->cr(); 2456 _cm->print_worker_threads_on(st); 2457 _cr->print_threads_on(st); 2458 _young_gen_sampling_thread->print_on(st); 2459 if (G1StringDedup::is_enabled()) { 2460 G1StringDedup::print_worker_threads_on(st); 2461 } 2462 } 2463 2464 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2465 workers()->threads_do(tc); 2466 tc->do_thread(_cmThread); 2467 _cm->threads_do(tc); 2468 _cr->threads_do(tc); 2469 tc->do_thread(_young_gen_sampling_thread); 2470 if (G1StringDedup::is_enabled()) { 2471 G1StringDedup::threads_do(tc); 2472 } 2473 } 2474 2475 void G1CollectedHeap::print_tracing_info() const { 2476 g1_rem_set()->print_summary_info(); 2477 concurrent_mark()->print_summary_info(); 2478 } 2479 2480 #ifndef PRODUCT 2481 // Helpful for debugging RSet issues. 2482 2483 class PrintRSetsClosure : public HeapRegionClosure { 2484 private: 2485 const char* _msg; 2486 size_t _occupied_sum; 2487 2488 public: 2489 bool doHeapRegion(HeapRegion* r) { 2490 HeapRegionRemSet* hrrs = r->rem_set(); 2491 size_t occupied = hrrs->occupied(); 2492 _occupied_sum += occupied; 2493 2494 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2495 if (occupied == 0) { 2496 tty->print_cr(" RSet is empty"); 2497 } else { 2498 hrrs->print(); 2499 } 2500 tty->print_cr("----------"); 2501 return false; 2502 } 2503 2504 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2505 tty->cr(); 2506 tty->print_cr("========================================"); 2507 tty->print_cr("%s", msg); 2508 tty->cr(); 2509 } 2510 2511 ~PrintRSetsClosure() { 2512 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2513 tty->print_cr("========================================"); 2514 tty->cr(); 2515 } 2516 }; 2517 2518 void G1CollectedHeap::print_cset_rsets() { 2519 PrintRSetsClosure cl("Printing CSet RSets"); 2520 collection_set_iterate(&cl); 2521 } 2522 2523 void G1CollectedHeap::print_all_rsets() { 2524 PrintRSetsClosure cl("Printing All RSets");; 2525 heap_region_iterate(&cl); 2526 } 2527 #endif // PRODUCT 2528 2529 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2530 2531 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2532 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2533 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2534 2535 size_t eden_capacity_bytes = 2536 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2537 2538 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2539 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2540 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2541 } 2542 2543 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2544 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2545 stats->unused(), stats->used(), stats->region_end_waste(), 2546 stats->regions_filled(), stats->direct_allocated(), 2547 stats->failure_used(), stats->failure_waste()); 2548 } 2549 2550 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2551 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2552 gc_tracer->report_gc_heap_summary(when, heap_summary); 2553 2554 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2555 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2556 } 2557 2558 G1CollectedHeap* G1CollectedHeap::heap() { 2559 CollectedHeap* heap = Universe::heap(); 2560 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2561 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2562 return (G1CollectedHeap*)heap; 2563 } 2564 2565 void G1CollectedHeap::gc_prologue(bool full) { 2566 // always_do_update_barrier = false; 2567 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2568 2569 // This summary needs to be printed before incrementing total collections. 2570 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2571 2572 // Update common counters. 2573 increment_total_collections(full /* full gc */); 2574 if (full) { 2575 increment_old_marking_cycles_started(); 2576 reset_gc_time_stamp(); 2577 } else { 2578 increment_gc_time_stamp(); 2579 } 2580 2581 // Fill TLAB's and such 2582 double start = os::elapsedTime(); 2583 accumulate_statistics_all_tlabs(); 2584 ensure_parsability(true); 2585 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2586 } 2587 2588 void G1CollectedHeap::gc_epilogue(bool full) { 2589 // Update common counters. 2590 if (full) { 2591 // Update the number of full collections that have been completed. 2592 increment_old_marking_cycles_completed(false /* concurrent */); 2593 } 2594 2595 // We are at the end of the GC. Total collections has already been increased. 2596 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2597 2598 // FIXME: what is this about? 2599 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2600 // is set. 2601 #if COMPILER2_OR_JVMCI 2602 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2603 #endif 2604 // always_do_update_barrier = true; 2605 2606 double start = os::elapsedTime(); 2607 resize_all_tlabs(); 2608 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2609 2610 allocation_context_stats().update(full); 2611 2612 MemoryService::track_memory_usage(); 2613 // We have just completed a GC. Update the soft reference 2614 // policy with the new heap occupancy 2615 Universe::update_heap_info_at_gc(); 2616 } 2617 2618 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2619 uint gc_count_before, 2620 bool* succeeded, 2621 GCCause::Cause gc_cause) { 2622 assert_heap_not_locked_and_not_at_safepoint(); 2623 VM_G1IncCollectionPause op(gc_count_before, 2624 word_size, 2625 false, /* should_initiate_conc_mark */ 2626 g1_policy()->max_pause_time_ms(), 2627 gc_cause); 2628 2629 op.set_allocation_context(AllocationContext::current()); 2630 VMThread::execute(&op); 2631 2632 HeapWord* result = op.result(); 2633 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2634 assert(result == NULL || ret_succeeded, 2635 "the result should be NULL if the VM did not succeed"); 2636 *succeeded = ret_succeeded; 2637 2638 assert_heap_not_locked(); 2639 return result; 2640 } 2641 2642 void 2643 G1CollectedHeap::doConcurrentMark() { 2644 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2645 if (!_cmThread->in_progress()) { 2646 _cmThread->set_started(); 2647 CGC_lock->notify(); 2648 } 2649 } 2650 2651 size_t G1CollectedHeap::pending_card_num() { 2652 size_t extra_cards = 0; 2653 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) { 2654 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2655 extra_cards += dcq.size(); 2656 } 2657 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2658 size_t buffer_size = dcqs.buffer_size(); 2659 size_t buffer_num = dcqs.completed_buffers_num(); 2660 2661 return buffer_size * buffer_num + extra_cards; 2662 } 2663 2664 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2665 private: 2666 size_t _total_humongous; 2667 size_t _candidate_humongous; 2668 2669 DirtyCardQueue _dcq; 2670 2671 // We don't nominate objects with many remembered set entries, on 2672 // the assumption that such objects are likely still live. 2673 bool is_remset_small(HeapRegion* region) const { 2674 HeapRegionRemSet* const rset = region->rem_set(); 2675 return G1EagerReclaimHumongousObjectsWithStaleRefs 2676 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2677 : rset->is_empty(); 2678 } 2679 2680 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2681 assert(region->is_starts_humongous(), "Must start a humongous object"); 2682 2683 oop obj = oop(region->bottom()); 2684 2685 // Dead objects cannot be eager reclaim candidates. Due to class 2686 // unloading it is unsafe to query their classes so we return early. 2687 if (heap->is_obj_dead(obj, region)) { 2688 return false; 2689 } 2690 2691 // Candidate selection must satisfy the following constraints 2692 // while concurrent marking is in progress: 2693 // 2694 // * In order to maintain SATB invariants, an object must not be 2695 // reclaimed if it was allocated before the start of marking and 2696 // has not had its references scanned. Such an object must have 2697 // its references (including type metadata) scanned to ensure no 2698 // live objects are missed by the marking process. Objects 2699 // allocated after the start of concurrent marking don't need to 2700 // be scanned. 2701 // 2702 // * An object must not be reclaimed if it is on the concurrent 2703 // mark stack. Objects allocated after the start of concurrent 2704 // marking are never pushed on the mark stack. 2705 // 2706 // Nominating only objects allocated after the start of concurrent 2707 // marking is sufficient to meet both constraints. This may miss 2708 // some objects that satisfy the constraints, but the marking data 2709 // structures don't support efficiently performing the needed 2710 // additional tests or scrubbing of the mark stack. 2711 // 2712 // However, we presently only nominate is_typeArray() objects. 2713 // A humongous object containing references induces remembered 2714 // set entries on other regions. In order to reclaim such an 2715 // object, those remembered sets would need to be cleaned up. 2716 // 2717 // We also treat is_typeArray() objects specially, allowing them 2718 // to be reclaimed even if allocated before the start of 2719 // concurrent mark. For this we rely on mark stack insertion to 2720 // exclude is_typeArray() objects, preventing reclaiming an object 2721 // that is in the mark stack. We also rely on the metadata for 2722 // such objects to be built-in and so ensured to be kept live. 2723 // Frequent allocation and drop of large binary blobs is an 2724 // important use case for eager reclaim, and this special handling 2725 // may reduce needed headroom. 2726 2727 return obj->is_typeArray() && is_remset_small(region); 2728 } 2729 2730 public: 2731 RegisterHumongousWithInCSetFastTestClosure() 2732 : _total_humongous(0), 2733 _candidate_humongous(0), 2734 _dcq(&JavaThread::dirty_card_queue_set()) { 2735 } 2736 2737 virtual bool doHeapRegion(HeapRegion* r) { 2738 if (!r->is_starts_humongous()) { 2739 return false; 2740 } 2741 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2742 2743 bool is_candidate = humongous_region_is_candidate(g1h, r); 2744 uint rindex = r->hrm_index(); 2745 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2746 if (is_candidate) { 2747 _candidate_humongous++; 2748 g1h->register_humongous_region_with_cset(rindex); 2749 // Is_candidate already filters out humongous object with large remembered sets. 2750 // If we have a humongous object with a few remembered sets, we simply flush these 2751 // remembered set entries into the DCQS. That will result in automatic 2752 // re-evaluation of their remembered set entries during the following evacuation 2753 // phase. 2754 if (!r->rem_set()->is_empty()) { 2755 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2756 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2757 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 2758 HeapRegionRemSetIterator hrrs(r->rem_set()); 2759 size_t card_index; 2760 while (hrrs.has_next(card_index)) { 2761 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 2762 // The remembered set might contain references to already freed 2763 // regions. Filter out such entries to avoid failing card table 2764 // verification. 2765 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 2766 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 2767 *card_ptr = CardTableModRefBS::dirty_card_val(); 2768 _dcq.enqueue(card_ptr); 2769 } 2770 } 2771 } 2772 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2773 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2774 hrrs.n_yielded(), r->rem_set()->occupied()); 2775 r->rem_set()->clear_locked(); 2776 } 2777 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2778 } 2779 _total_humongous++; 2780 2781 return false; 2782 } 2783 2784 size_t total_humongous() const { return _total_humongous; } 2785 size_t candidate_humongous() const { return _candidate_humongous; } 2786 2787 void flush_rem_set_entries() { _dcq.flush(); } 2788 }; 2789 2790 void G1CollectedHeap::register_humongous_regions_with_cset() { 2791 if (!G1EagerReclaimHumongousObjects) { 2792 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2793 return; 2794 } 2795 double time = os::elapsed_counter(); 2796 2797 // Collect reclaim candidate information and register candidates with cset. 2798 RegisterHumongousWithInCSetFastTestClosure cl; 2799 heap_region_iterate(&cl); 2800 2801 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2802 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2803 cl.total_humongous(), 2804 cl.candidate_humongous()); 2805 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2806 2807 // Finally flush all remembered set entries to re-check into the global DCQS. 2808 cl.flush_rem_set_entries(); 2809 } 2810 2811 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2812 public: 2813 bool doHeapRegion(HeapRegion* hr) { 2814 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2815 hr->verify_rem_set(); 2816 } 2817 return false; 2818 } 2819 }; 2820 2821 uint G1CollectedHeap::num_task_queues() const { 2822 return _task_queues->size(); 2823 } 2824 2825 #if TASKQUEUE_STATS 2826 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2827 st->print_raw_cr("GC Task Stats"); 2828 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2829 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2830 } 2831 2832 void G1CollectedHeap::print_taskqueue_stats() const { 2833 if (!log_is_enabled(Trace, gc, task, stats)) { 2834 return; 2835 } 2836 Log(gc, task, stats) log; 2837 ResourceMark rm; 2838 LogStream ls(log.trace()); 2839 outputStream* st = &ls; 2840 2841 print_taskqueue_stats_hdr(st); 2842 2843 TaskQueueStats totals; 2844 const uint n = num_task_queues(); 2845 for (uint i = 0; i < n; ++i) { 2846 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2847 totals += task_queue(i)->stats; 2848 } 2849 st->print_raw("tot "); totals.print(st); st->cr(); 2850 2851 DEBUG_ONLY(totals.verify()); 2852 } 2853 2854 void G1CollectedHeap::reset_taskqueue_stats() { 2855 const uint n = num_task_queues(); 2856 for (uint i = 0; i < n; ++i) { 2857 task_queue(i)->stats.reset(); 2858 } 2859 } 2860 #endif // TASKQUEUE_STATS 2861 2862 void G1CollectedHeap::wait_for_root_region_scanning() { 2863 double scan_wait_start = os::elapsedTime(); 2864 // We have to wait until the CM threads finish scanning the 2865 // root regions as it's the only way to ensure that all the 2866 // objects on them have been correctly scanned before we start 2867 // moving them during the GC. 2868 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2869 double wait_time_ms = 0.0; 2870 if (waited) { 2871 double scan_wait_end = os::elapsedTime(); 2872 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2873 } 2874 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2875 } 2876 2877 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2878 private: 2879 G1HRPrinter* _hr_printer; 2880 public: 2881 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2882 2883 virtual bool doHeapRegion(HeapRegion* r) { 2884 _hr_printer->cset(r); 2885 return false; 2886 } 2887 }; 2888 2889 void G1CollectedHeap::start_new_collection_set() { 2890 collection_set()->start_incremental_building(); 2891 2892 clear_cset_fast_test(); 2893 2894 guarantee(_eden.length() == 0, "eden should have been cleared"); 2895 g1_policy()->transfer_survivors_to_cset(survivor()); 2896 } 2897 2898 bool 2899 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2900 assert_at_safepoint(true /* should_be_vm_thread */); 2901 guarantee(!is_gc_active(), "collection is not reentrant"); 2902 2903 if (GCLocker::check_active_before_gc()) { 2904 return false; 2905 } 2906 2907 _gc_timer_stw->register_gc_start(); 2908 2909 GCIdMark gc_id_mark; 2910 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2911 2912 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2913 ResourceMark rm; 2914 2915 g1_policy()->note_gc_start(); 2916 2917 wait_for_root_region_scanning(); 2918 2919 print_heap_before_gc(); 2920 print_heap_regions(); 2921 trace_heap_before_gc(_gc_tracer_stw); 2922 2923 _verifier->verify_region_sets_optional(); 2924 _verifier->verify_dirty_young_regions(); 2925 2926 // We should not be doing initial mark unless the conc mark thread is running 2927 if (!_cmThread->should_terminate()) { 2928 // This call will decide whether this pause is an initial-mark 2929 // pause. If it is, during_initial_mark_pause() will return true 2930 // for the duration of this pause. 2931 g1_policy()->decide_on_conc_mark_initiation(); 2932 } 2933 2934 // We do not allow initial-mark to be piggy-backed on a mixed GC. 2935 assert(!collector_state()->during_initial_mark_pause() || 2936 collector_state()->gcs_are_young(), "sanity"); 2937 2938 // We also do not allow mixed GCs during marking. 2939 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 2940 2941 // Record whether this pause is an initial mark. When the current 2942 // thread has completed its logging output and it's safe to signal 2943 // the CM thread, the flag's value in the policy has been reset. 2944 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 2945 2946 // Inner scope for scope based logging, timers, and stats collection 2947 { 2948 EvacuationInfo evacuation_info; 2949 2950 if (collector_state()->during_initial_mark_pause()) { 2951 // We are about to start a marking cycle, so we increment the 2952 // full collection counter. 2953 increment_old_marking_cycles_started(); 2954 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 2955 } 2956 2957 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 2958 2959 GCTraceCPUTime tcpu; 2960 2961 FormatBuffer<> gc_string("Pause "); 2962 if (collector_state()->during_initial_mark_pause()) { 2963 gc_string.append("Initial Mark"); 2964 } else if (collector_state()->gcs_are_young()) { 2965 gc_string.append("Young"); 2966 } else { 2967 gc_string.append("Mixed"); 2968 } 2969 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 2970 2971 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 2972 workers()->active_workers(), 2973 Threads::number_of_non_daemon_threads()); 2974 workers()->update_active_workers(active_workers); 2975 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 2976 2977 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 2978 TraceMemoryManagerStats tms(&_memory_manager, gc_cause()); 2979 2980 // If the secondary_free_list is not empty, append it to the 2981 // free_list. No need to wait for the cleanup operation to finish; 2982 // the region allocation code will check the secondary_free_list 2983 // and wait if necessary. If the G1StressConcRegionFreeing flag is 2984 // set, skip this step so that the region allocation code has to 2985 // get entries from the secondary_free_list. 2986 if (!G1StressConcRegionFreeing) { 2987 append_secondary_free_list_if_not_empty_with_lock(); 2988 } 2989 2990 G1HeapTransition heap_transition(this); 2991 size_t heap_used_bytes_before_gc = used(); 2992 2993 // Don't dynamically change the number of GC threads this early. A value of 2994 // 0 is used to indicate serial work. When parallel work is done, 2995 // it will be set. 2996 2997 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 2998 IsGCActiveMark x; 2999 3000 gc_prologue(false); 3001 3002 if (VerifyRememberedSets) { 3003 log_info(gc, verify)("[Verifying RemSets before GC]"); 3004 VerifyRegionRemSetClosure v_cl; 3005 heap_region_iterate(&v_cl); 3006 } 3007 3008 _verifier->verify_before_gc(); 3009 3010 _verifier->check_bitmaps("GC Start"); 3011 3012 #if COMPILER2_OR_JVMCI 3013 DerivedPointerTable::clear(); 3014 #endif 3015 3016 // Please see comment in g1CollectedHeap.hpp and 3017 // G1CollectedHeap::ref_processing_init() to see how 3018 // reference processing currently works in G1. 3019 3020 // Enable discovery in the STW reference processor 3021 if (g1_policy()->should_process_references()) { 3022 ref_processor_stw()->enable_discovery(); 3023 } else { 3024 ref_processor_stw()->disable_discovery(); 3025 } 3026 3027 { 3028 // We want to temporarily turn off discovery by the 3029 // CM ref processor, if necessary, and turn it back on 3030 // on again later if we do. Using a scoped 3031 // NoRefDiscovery object will do this. 3032 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3033 3034 // Forget the current alloc region (we might even choose it to be part 3035 // of the collection set!). 3036 _allocator->release_mutator_alloc_region(); 3037 3038 // This timing is only used by the ergonomics to handle our pause target. 3039 // It is unclear why this should not include the full pause. We will 3040 // investigate this in CR 7178365. 3041 // 3042 // Preserving the old comment here if that helps the investigation: 3043 // 3044 // The elapsed time induced by the start time below deliberately elides 3045 // the possible verification above. 3046 double sample_start_time_sec = os::elapsedTime(); 3047 3048 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3049 3050 if (collector_state()->during_initial_mark_pause()) { 3051 concurrent_mark()->checkpoint_roots_initial_pre(); 3052 } 3053 3054 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 3055 3056 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3057 3058 // Make sure the remembered sets are up to date. This needs to be 3059 // done before register_humongous_regions_with_cset(), because the 3060 // remembered sets are used there to choose eager reclaim candidates. 3061 // If the remembered sets are not up to date we might miss some 3062 // entries that need to be handled. 3063 g1_rem_set()->cleanupHRRS(); 3064 3065 register_humongous_regions_with_cset(); 3066 3067 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3068 3069 // We call this after finalize_cset() to 3070 // ensure that the CSet has been finalized. 3071 _cm->verify_no_cset_oops(); 3072 3073 if (_hr_printer.is_active()) { 3074 G1PrintCollectionSetClosure cl(&_hr_printer); 3075 _collection_set.iterate(&cl); 3076 } 3077 3078 // Initialize the GC alloc regions. 3079 _allocator->init_gc_alloc_regions(evacuation_info); 3080 3081 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3082 pre_evacuate_collection_set(); 3083 3084 // Actually do the work... 3085 evacuate_collection_set(evacuation_info, &per_thread_states); 3086 3087 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3088 3089 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3090 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 3091 3092 eagerly_reclaim_humongous_regions(); 3093 3094 record_obj_copy_mem_stats(); 3095 _survivor_evac_stats.adjust_desired_plab_sz(); 3096 _old_evac_stats.adjust_desired_plab_sz(); 3097 3098 double start = os::elapsedTime(); 3099 start_new_collection_set(); 3100 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 3101 3102 if (evacuation_failed()) { 3103 set_used(recalculate_used()); 3104 if (_archive_allocator != NULL) { 3105 _archive_allocator->clear_used(); 3106 } 3107 for (uint i = 0; i < ParallelGCThreads; i++) { 3108 if (_evacuation_failed_info_array[i].has_failed()) { 3109 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3110 } 3111 } 3112 } else { 3113 // The "used" of the the collection set have already been subtracted 3114 // when they were freed. Add in the bytes evacuated. 3115 increase_used(g1_policy()->bytes_copied_during_gc()); 3116 } 3117 3118 if (collector_state()->during_initial_mark_pause()) { 3119 // We have to do this before we notify the CM threads that 3120 // they can start working to make sure that all the 3121 // appropriate initialization is done on the CM object. 3122 concurrent_mark()->checkpoint_roots_initial_post(); 3123 collector_state()->set_mark_in_progress(true); 3124 // Note that we don't actually trigger the CM thread at 3125 // this point. We do that later when we're sure that 3126 // the current thread has completed its logging output. 3127 } 3128 3129 allocate_dummy_regions(); 3130 3131 _allocator->init_mutator_alloc_region(); 3132 3133 { 3134 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3135 if (expand_bytes > 0) { 3136 size_t bytes_before = capacity(); 3137 // No need for an ergo logging here, 3138 // expansion_amount() does this when it returns a value > 0. 3139 double expand_ms; 3140 if (!expand(expand_bytes, _workers, &expand_ms)) { 3141 // We failed to expand the heap. Cannot do anything about it. 3142 } 3143 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3144 } 3145 } 3146 3147 // We redo the verification but now wrt to the new CSet which 3148 // has just got initialized after the previous CSet was freed. 3149 _cm->verify_no_cset_oops(); 3150 3151 // This timing is only used by the ergonomics to handle our pause target. 3152 // It is unclear why this should not include the full pause. We will 3153 // investigate this in CR 7178365. 3154 double sample_end_time_sec = os::elapsedTime(); 3155 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3156 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards); 3157 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3158 3159 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3160 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3161 3162 if (VerifyRememberedSets) { 3163 log_info(gc, verify)("[Verifying RemSets after GC]"); 3164 VerifyRegionRemSetClosure v_cl; 3165 heap_region_iterate(&v_cl); 3166 } 3167 3168 _verifier->verify_after_gc(); 3169 _verifier->check_bitmaps("GC End"); 3170 3171 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3172 ref_processor_stw()->verify_no_references_recorded(); 3173 3174 // CM reference discovery will be re-enabled if necessary. 3175 } 3176 3177 #ifdef TRACESPINNING 3178 ParallelTaskTerminator::print_termination_counts(); 3179 #endif 3180 3181 gc_epilogue(false); 3182 } 3183 3184 // Print the remainder of the GC log output. 3185 if (evacuation_failed()) { 3186 log_info(gc)("To-space exhausted"); 3187 } 3188 3189 g1_policy()->print_phases(); 3190 heap_transition.print(); 3191 3192 // It is not yet to safe to tell the concurrent mark to 3193 // start as we have some optional output below. We don't want the 3194 // output from the concurrent mark thread interfering with this 3195 // logging output either. 3196 3197 _hrm.verify_optional(); 3198 _verifier->verify_region_sets_optional(); 3199 3200 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3201 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3202 3203 print_heap_after_gc(); 3204 print_heap_regions(); 3205 trace_heap_after_gc(_gc_tracer_stw); 3206 3207 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3208 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3209 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3210 // before any GC notifications are raised. 3211 g1mm()->update_sizes(); 3212 3213 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3214 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3215 _gc_timer_stw->register_gc_end(); 3216 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3217 } 3218 // It should now be safe to tell the concurrent mark thread to start 3219 // without its logging output interfering with the logging output 3220 // that came from the pause. 3221 3222 if (should_start_conc_mark) { 3223 // CAUTION: after the doConcurrentMark() call below, 3224 // the concurrent marking thread(s) could be running 3225 // concurrently with us. Make sure that anything after 3226 // this point does not assume that we are the only GC thread 3227 // running. Note: of course, the actual marking work will 3228 // not start until the safepoint itself is released in 3229 // SuspendibleThreadSet::desynchronize(). 3230 doConcurrentMark(); 3231 } 3232 3233 return true; 3234 } 3235 3236 void G1CollectedHeap::remove_self_forwarding_pointers() { 3237 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3238 workers()->run_task(&rsfp_task); 3239 } 3240 3241 void G1CollectedHeap::restore_after_evac_failure() { 3242 double remove_self_forwards_start = os::elapsedTime(); 3243 3244 remove_self_forwarding_pointers(); 3245 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3246 _preserved_marks_set.restore(&task_executor); 3247 3248 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3249 } 3250 3251 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3252 if (!_evacuation_failed) { 3253 _evacuation_failed = true; 3254 } 3255 3256 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3257 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3258 } 3259 3260 bool G1ParEvacuateFollowersClosure::offer_termination() { 3261 G1ParScanThreadState* const pss = par_scan_state(); 3262 start_term_time(); 3263 const bool res = terminator()->offer_termination(); 3264 end_term_time(); 3265 return res; 3266 } 3267 3268 void G1ParEvacuateFollowersClosure::do_void() { 3269 G1ParScanThreadState* const pss = par_scan_state(); 3270 pss->trim_queue(); 3271 do { 3272 pss->steal_and_trim_queue(queues()); 3273 } while (!offer_termination()); 3274 } 3275 3276 class G1ParTask : public AbstractGangTask { 3277 protected: 3278 G1CollectedHeap* _g1h; 3279 G1ParScanThreadStateSet* _pss; 3280 RefToScanQueueSet* _queues; 3281 G1RootProcessor* _root_processor; 3282 ParallelTaskTerminator _terminator; 3283 uint _n_workers; 3284 3285 public: 3286 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3287 : AbstractGangTask("G1 collection"), 3288 _g1h(g1h), 3289 _pss(per_thread_states), 3290 _queues(task_queues), 3291 _root_processor(root_processor), 3292 _terminator(n_workers, _queues), 3293 _n_workers(n_workers) 3294 {} 3295 3296 void work(uint worker_id) { 3297 if (worker_id >= _n_workers) return; // no work needed this round 3298 3299 double start_sec = os::elapsedTime(); 3300 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3301 3302 { 3303 ResourceMark rm; 3304 HandleMark hm; 3305 3306 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3307 3308 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3309 pss->set_ref_processor(rp); 3310 3311 double start_strong_roots_sec = os::elapsedTime(); 3312 3313 _root_processor->evacuate_roots(pss->closures(), worker_id); 3314 3315 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3316 // treating the nmethods visited to act as roots for concurrent marking. 3317 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3318 // objects copied by the current evacuation. 3319 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, 3320 pss->closures()->weak_codeblobs(), 3321 worker_id); 3322 3323 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3324 3325 double term_sec = 0.0; 3326 size_t evac_term_attempts = 0; 3327 { 3328 double start = os::elapsedTime(); 3329 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3330 evac.do_void(); 3331 3332 evac_term_attempts = evac.term_attempts(); 3333 term_sec = evac.term_time(); 3334 double elapsed_sec = os::elapsedTime() - start; 3335 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3336 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3337 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3338 } 3339 3340 assert(pss->queue_is_empty(), "should be empty"); 3341 3342 if (log_is_enabled(Debug, gc, task, stats)) { 3343 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3344 size_t lab_waste; 3345 size_t lab_undo_waste; 3346 pss->waste(lab_waste, lab_undo_waste); 3347 _g1h->print_termination_stats(worker_id, 3348 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3349 strong_roots_sec * 1000.0, /* strong roots time */ 3350 term_sec * 1000.0, /* evac term time */ 3351 evac_term_attempts, /* evac term attempts */ 3352 lab_waste, /* alloc buffer waste */ 3353 lab_undo_waste /* undo waste */ 3354 ); 3355 } 3356 3357 // Close the inner scope so that the ResourceMark and HandleMark 3358 // destructors are executed here and are included as part of the 3359 // "GC Worker Time". 3360 } 3361 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3362 } 3363 }; 3364 3365 void G1CollectedHeap::print_termination_stats_hdr() { 3366 log_debug(gc, task, stats)("GC Termination Stats"); 3367 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3368 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3369 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3370 } 3371 3372 void G1CollectedHeap::print_termination_stats(uint worker_id, 3373 double elapsed_ms, 3374 double strong_roots_ms, 3375 double term_ms, 3376 size_t term_attempts, 3377 size_t alloc_buffer_waste, 3378 size_t undo_waste) const { 3379 log_debug(gc, task, stats) 3380 ("%3d %9.2f %9.2f %6.2f " 3381 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3382 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3383 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3384 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3385 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3386 alloc_buffer_waste * HeapWordSize / K, 3387 undo_waste * HeapWordSize / K); 3388 } 3389 3390 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3391 private: 3392 BoolObjectClosure* _is_alive; 3393 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3394 3395 int _initial_string_table_size; 3396 int _initial_symbol_table_size; 3397 3398 bool _process_strings; 3399 int _strings_processed; 3400 int _strings_removed; 3401 3402 bool _process_symbols; 3403 int _symbols_processed; 3404 int _symbols_removed; 3405 3406 bool _process_string_dedup; 3407 3408 public: 3409 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3410 AbstractGangTask("String/Symbol Unlinking"), 3411 _is_alive(is_alive), 3412 _dedup_closure(is_alive, NULL, false), 3413 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3414 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3415 _process_string_dedup(process_string_dedup) { 3416 3417 _initial_string_table_size = StringTable::the_table()->table_size(); 3418 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3419 if (process_strings) { 3420 StringTable::clear_parallel_claimed_index(); 3421 } 3422 if (process_symbols) { 3423 SymbolTable::clear_parallel_claimed_index(); 3424 } 3425 } 3426 3427 ~G1StringAndSymbolCleaningTask() { 3428 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3429 "claim value %d after unlink less than initial string table size %d", 3430 StringTable::parallel_claimed_index(), _initial_string_table_size); 3431 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3432 "claim value %d after unlink less than initial symbol table size %d", 3433 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3434 3435 log_info(gc, stringtable)( 3436 "Cleaned string and symbol table, " 3437 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3438 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3439 strings_processed(), strings_removed(), 3440 symbols_processed(), symbols_removed()); 3441 } 3442 3443 void work(uint worker_id) { 3444 int strings_processed = 0; 3445 int strings_removed = 0; 3446 int symbols_processed = 0; 3447 int symbols_removed = 0; 3448 if (_process_strings) { 3449 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3450 Atomic::add(strings_processed, &_strings_processed); 3451 Atomic::add(strings_removed, &_strings_removed); 3452 } 3453 if (_process_symbols) { 3454 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3455 Atomic::add(symbols_processed, &_symbols_processed); 3456 Atomic::add(symbols_removed, &_symbols_removed); 3457 } 3458 if (_process_string_dedup) { 3459 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3460 } 3461 } 3462 3463 size_t strings_processed() const { return (size_t)_strings_processed; } 3464 size_t strings_removed() const { return (size_t)_strings_removed; } 3465 3466 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3467 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3468 }; 3469 3470 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3471 private: 3472 static Monitor* _lock; 3473 3474 BoolObjectClosure* const _is_alive; 3475 const bool _unloading_occurred; 3476 const uint _num_workers; 3477 3478 // Variables used to claim nmethods. 3479 CompiledMethod* _first_nmethod; 3480 CompiledMethod* volatile _claimed_nmethod; 3481 3482 // The list of nmethods that need to be processed by the second pass. 3483 CompiledMethod* volatile _postponed_list; 3484 volatile uint _num_entered_barrier; 3485 3486 public: 3487 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3488 _is_alive(is_alive), 3489 _unloading_occurred(unloading_occurred), 3490 _num_workers(num_workers), 3491 _first_nmethod(NULL), 3492 _claimed_nmethod(NULL), 3493 _postponed_list(NULL), 3494 _num_entered_barrier(0) 3495 { 3496 CompiledMethod::increase_unloading_clock(); 3497 // Get first alive nmethod 3498 CompiledMethodIterator iter = CompiledMethodIterator(); 3499 if(iter.next_alive()) { 3500 _first_nmethod = iter.method(); 3501 } 3502 _claimed_nmethod = _first_nmethod; 3503 } 3504 3505 ~G1CodeCacheUnloadingTask() { 3506 CodeCache::verify_clean_inline_caches(); 3507 3508 CodeCache::set_needs_cache_clean(false); 3509 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3510 3511 CodeCache::verify_icholder_relocations(); 3512 } 3513 3514 private: 3515 void add_to_postponed_list(CompiledMethod* nm) { 3516 CompiledMethod* old; 3517 do { 3518 old = _postponed_list; 3519 nm->set_unloading_next(old); 3520 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old); 3521 } 3522 3523 void clean_nmethod(CompiledMethod* nm) { 3524 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3525 3526 if (postponed) { 3527 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3528 add_to_postponed_list(nm); 3529 } 3530 3531 // Mark that this thread has been cleaned/unloaded. 3532 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3533 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3534 } 3535 3536 void clean_nmethod_postponed(CompiledMethod* nm) { 3537 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3538 } 3539 3540 static const int MaxClaimNmethods = 16; 3541 3542 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3543 CompiledMethod* first; 3544 CompiledMethodIterator last; 3545 3546 do { 3547 *num_claimed_nmethods = 0; 3548 3549 first = _claimed_nmethod; 3550 last = CompiledMethodIterator(first); 3551 3552 if (first != NULL) { 3553 3554 for (int i = 0; i < MaxClaimNmethods; i++) { 3555 if (!last.next_alive()) { 3556 break; 3557 } 3558 claimed_nmethods[i] = last.method(); 3559 (*num_claimed_nmethods)++; 3560 } 3561 } 3562 3563 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first); 3564 } 3565 3566 CompiledMethod* claim_postponed_nmethod() { 3567 CompiledMethod* claim; 3568 CompiledMethod* next; 3569 3570 do { 3571 claim = _postponed_list; 3572 if (claim == NULL) { 3573 return NULL; 3574 } 3575 3576 next = claim->unloading_next(); 3577 3578 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim); 3579 3580 return claim; 3581 } 3582 3583 public: 3584 // Mark that we're done with the first pass of nmethod cleaning. 3585 void barrier_mark(uint worker_id) { 3586 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3587 _num_entered_barrier++; 3588 if (_num_entered_barrier == _num_workers) { 3589 ml.notify_all(); 3590 } 3591 } 3592 3593 // See if we have to wait for the other workers to 3594 // finish their first-pass nmethod cleaning work. 3595 void barrier_wait(uint worker_id) { 3596 if (_num_entered_barrier < _num_workers) { 3597 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3598 while (_num_entered_barrier < _num_workers) { 3599 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3600 } 3601 } 3602 } 3603 3604 // Cleaning and unloading of nmethods. Some work has to be postponed 3605 // to the second pass, when we know which nmethods survive. 3606 void work_first_pass(uint worker_id) { 3607 // The first nmethods is claimed by the first worker. 3608 if (worker_id == 0 && _first_nmethod != NULL) { 3609 clean_nmethod(_first_nmethod); 3610 _first_nmethod = NULL; 3611 } 3612 3613 int num_claimed_nmethods; 3614 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3615 3616 while (true) { 3617 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3618 3619 if (num_claimed_nmethods == 0) { 3620 break; 3621 } 3622 3623 for (int i = 0; i < num_claimed_nmethods; i++) { 3624 clean_nmethod(claimed_nmethods[i]); 3625 } 3626 } 3627 } 3628 3629 void work_second_pass(uint worker_id) { 3630 CompiledMethod* nm; 3631 // Take care of postponed nmethods. 3632 while ((nm = claim_postponed_nmethod()) != NULL) { 3633 clean_nmethod_postponed(nm); 3634 } 3635 } 3636 }; 3637 3638 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3639 3640 class G1KlassCleaningTask : public StackObj { 3641 BoolObjectClosure* _is_alive; 3642 volatile int _clean_klass_tree_claimed; 3643 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3644 3645 public: 3646 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3647 _is_alive(is_alive), 3648 _clean_klass_tree_claimed(0), 3649 _klass_iterator() { 3650 } 3651 3652 private: 3653 bool claim_clean_klass_tree_task() { 3654 if (_clean_klass_tree_claimed) { 3655 return false; 3656 } 3657 3658 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0; 3659 } 3660 3661 InstanceKlass* claim_next_klass() { 3662 Klass* klass; 3663 do { 3664 klass =_klass_iterator.next_klass(); 3665 } while (klass != NULL && !klass->is_instance_klass()); 3666 3667 // this can be null so don't call InstanceKlass::cast 3668 return static_cast<InstanceKlass*>(klass); 3669 } 3670 3671 public: 3672 3673 void clean_klass(InstanceKlass* ik) { 3674 ik->clean_weak_instanceklass_links(_is_alive); 3675 } 3676 3677 void work() { 3678 ResourceMark rm; 3679 3680 // One worker will clean the subklass/sibling klass tree. 3681 if (claim_clean_klass_tree_task()) { 3682 Klass::clean_subklass_tree(_is_alive); 3683 } 3684 3685 // All workers will help cleaning the classes, 3686 InstanceKlass* klass; 3687 while ((klass = claim_next_klass()) != NULL) { 3688 clean_klass(klass); 3689 } 3690 } 3691 }; 3692 3693 class G1ResolvedMethodCleaningTask : public StackObj { 3694 BoolObjectClosure* _is_alive; 3695 volatile int _resolved_method_task_claimed; 3696 public: 3697 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) : 3698 _is_alive(is_alive), _resolved_method_task_claimed(0) {} 3699 3700 bool claim_resolved_method_task() { 3701 if (_resolved_method_task_claimed) { 3702 return false; 3703 } 3704 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0; 3705 } 3706 3707 // These aren't big, one thread can do it all. 3708 void work() { 3709 if (claim_resolved_method_task()) { 3710 ResolvedMethodTable::unlink(_is_alive); 3711 } 3712 } 3713 }; 3714 3715 3716 // To minimize the remark pause times, the tasks below are done in parallel. 3717 class G1ParallelCleaningTask : public AbstractGangTask { 3718 private: 3719 G1StringAndSymbolCleaningTask _string_symbol_task; 3720 G1CodeCacheUnloadingTask _code_cache_task; 3721 G1KlassCleaningTask _klass_cleaning_task; 3722 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task; 3723 3724 public: 3725 // The constructor is run in the VMThread. 3726 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3727 AbstractGangTask("Parallel Cleaning"), 3728 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3729 _code_cache_task(num_workers, is_alive, unloading_occurred), 3730 _klass_cleaning_task(is_alive), 3731 _resolved_method_cleaning_task(is_alive) { 3732 } 3733 3734 // The parallel work done by all worker threads. 3735 void work(uint worker_id) { 3736 // Do first pass of code cache cleaning. 3737 _code_cache_task.work_first_pass(worker_id); 3738 3739 // Let the threads mark that the first pass is done. 3740 _code_cache_task.barrier_mark(worker_id); 3741 3742 // Clean the Strings and Symbols. 3743 _string_symbol_task.work(worker_id); 3744 3745 // Clean unreferenced things in the ResolvedMethodTable 3746 _resolved_method_cleaning_task.work(); 3747 3748 // Wait for all workers to finish the first code cache cleaning pass. 3749 _code_cache_task.barrier_wait(worker_id); 3750 3751 // Do the second code cache cleaning work, which realize on 3752 // the liveness information gathered during the first pass. 3753 _code_cache_task.work_second_pass(worker_id); 3754 3755 // Clean all klasses that were not unloaded. 3756 _klass_cleaning_task.work(); 3757 } 3758 }; 3759 3760 3761 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3762 bool class_unloading_occurred) { 3763 uint n_workers = workers()->active_workers(); 3764 3765 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3766 workers()->run_task(&g1_unlink_task); 3767 } 3768 3769 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3770 bool process_strings, 3771 bool process_symbols, 3772 bool process_string_dedup) { 3773 if (!process_strings && !process_symbols && !process_string_dedup) { 3774 // Nothing to clean. 3775 return; 3776 } 3777 3778 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3779 workers()->run_task(&g1_unlink_task); 3780 3781 } 3782 3783 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3784 private: 3785 DirtyCardQueueSet* _queue; 3786 G1CollectedHeap* _g1h; 3787 public: 3788 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3789 _queue(queue), _g1h(g1h) { } 3790 3791 virtual void work(uint worker_id) { 3792 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3793 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3794 3795 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3796 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3797 3798 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3799 } 3800 }; 3801 3802 void G1CollectedHeap::redirty_logged_cards() { 3803 double redirty_logged_cards_start = os::elapsedTime(); 3804 3805 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3806 dirty_card_queue_set().reset_for_par_iteration(); 3807 workers()->run_task(&redirty_task); 3808 3809 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 3810 dcq.merge_bufferlists(&dirty_card_queue_set()); 3811 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3812 3813 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3814 } 3815 3816 // Weak Reference Processing support 3817 3818 // An always "is_alive" closure that is used to preserve referents. 3819 // If the object is non-null then it's alive. Used in the preservation 3820 // of referent objects that are pointed to by reference objects 3821 // discovered by the CM ref processor. 3822 class G1AlwaysAliveClosure: public BoolObjectClosure { 3823 G1CollectedHeap* _g1; 3824 public: 3825 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3826 bool do_object_b(oop p) { 3827 if (p != NULL) { 3828 return true; 3829 } 3830 return false; 3831 } 3832 }; 3833 3834 bool G1STWIsAliveClosure::do_object_b(oop p) { 3835 // An object is reachable if it is outside the collection set, 3836 // or is inside and copied. 3837 return !_g1->is_in_cset(p) || p->is_forwarded(); 3838 } 3839 3840 // Non Copying Keep Alive closure 3841 class G1KeepAliveClosure: public OopClosure { 3842 G1CollectedHeap* _g1; 3843 public: 3844 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3845 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3846 void do_oop(oop* p) { 3847 oop obj = *p; 3848 assert(obj != NULL, "the caller should have filtered out NULL values"); 3849 3850 const InCSetState cset_state = _g1->in_cset_state(obj); 3851 if (!cset_state.is_in_cset_or_humongous()) { 3852 return; 3853 } 3854 if (cset_state.is_in_cset()) { 3855 assert( obj->is_forwarded(), "invariant" ); 3856 *p = obj->forwardee(); 3857 } else { 3858 assert(!obj->is_forwarded(), "invariant" ); 3859 assert(cset_state.is_humongous(), 3860 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3861 _g1->set_humongous_is_live(obj); 3862 } 3863 } 3864 }; 3865 3866 // Copying Keep Alive closure - can be called from both 3867 // serial and parallel code as long as different worker 3868 // threads utilize different G1ParScanThreadState instances 3869 // and different queues. 3870 3871 class G1CopyingKeepAliveClosure: public OopClosure { 3872 G1CollectedHeap* _g1h; 3873 OopClosure* _copy_non_heap_obj_cl; 3874 G1ParScanThreadState* _par_scan_state; 3875 3876 public: 3877 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3878 OopClosure* non_heap_obj_cl, 3879 G1ParScanThreadState* pss): 3880 _g1h(g1h), 3881 _copy_non_heap_obj_cl(non_heap_obj_cl), 3882 _par_scan_state(pss) 3883 {} 3884 3885 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3886 virtual void do_oop( oop* p) { do_oop_work(p); } 3887 3888 template <class T> void do_oop_work(T* p) { 3889 oop obj = oopDesc::load_decode_heap_oop(p); 3890 3891 if (_g1h->is_in_cset_or_humongous(obj)) { 3892 // If the referent object has been forwarded (either copied 3893 // to a new location or to itself in the event of an 3894 // evacuation failure) then we need to update the reference 3895 // field and, if both reference and referent are in the G1 3896 // heap, update the RSet for the referent. 3897 // 3898 // If the referent has not been forwarded then we have to keep 3899 // it alive by policy. Therefore we have copy the referent. 3900 // 3901 // If the reference field is in the G1 heap then we can push 3902 // on the PSS queue. When the queue is drained (after each 3903 // phase of reference processing) the object and it's followers 3904 // will be copied, the reference field set to point to the 3905 // new location, and the RSet updated. Otherwise we need to 3906 // use the the non-heap or metadata closures directly to copy 3907 // the referent object and update the pointer, while avoiding 3908 // updating the RSet. 3909 3910 if (_g1h->is_in_g1_reserved(p)) { 3911 _par_scan_state->push_on_queue(p); 3912 } else { 3913 assert(!Metaspace::contains((const void*)p), 3914 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 3915 _copy_non_heap_obj_cl->do_oop(p); 3916 } 3917 } 3918 } 3919 }; 3920 3921 // Serial drain queue closure. Called as the 'complete_gc' 3922 // closure for each discovered list in some of the 3923 // reference processing phases. 3924 3925 class G1STWDrainQueueClosure: public VoidClosure { 3926 protected: 3927 G1CollectedHeap* _g1h; 3928 G1ParScanThreadState* _par_scan_state; 3929 3930 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3931 3932 public: 3933 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3934 _g1h(g1h), 3935 _par_scan_state(pss) 3936 { } 3937 3938 void do_void() { 3939 G1ParScanThreadState* const pss = par_scan_state(); 3940 pss->trim_queue(); 3941 } 3942 }; 3943 3944 // Parallel Reference Processing closures 3945 3946 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3947 // processing during G1 evacuation pauses. 3948 3949 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3950 private: 3951 G1CollectedHeap* _g1h; 3952 G1ParScanThreadStateSet* _pss; 3953 RefToScanQueueSet* _queues; 3954 WorkGang* _workers; 3955 uint _active_workers; 3956 3957 public: 3958 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3959 G1ParScanThreadStateSet* per_thread_states, 3960 WorkGang* workers, 3961 RefToScanQueueSet *task_queues, 3962 uint n_workers) : 3963 _g1h(g1h), 3964 _pss(per_thread_states), 3965 _queues(task_queues), 3966 _workers(workers), 3967 _active_workers(n_workers) 3968 { 3969 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 3970 } 3971 3972 // Executes the given task using concurrent marking worker threads. 3973 virtual void execute(ProcessTask& task); 3974 virtual void execute(EnqueueTask& task); 3975 }; 3976 3977 // Gang task for possibly parallel reference processing 3978 3979 class G1STWRefProcTaskProxy: public AbstractGangTask { 3980 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 3981 ProcessTask& _proc_task; 3982 G1CollectedHeap* _g1h; 3983 G1ParScanThreadStateSet* _pss; 3984 RefToScanQueueSet* _task_queues; 3985 ParallelTaskTerminator* _terminator; 3986 3987 public: 3988 G1STWRefProcTaskProxy(ProcessTask& proc_task, 3989 G1CollectedHeap* g1h, 3990 G1ParScanThreadStateSet* per_thread_states, 3991 RefToScanQueueSet *task_queues, 3992 ParallelTaskTerminator* terminator) : 3993 AbstractGangTask("Process reference objects in parallel"), 3994 _proc_task(proc_task), 3995 _g1h(g1h), 3996 _pss(per_thread_states), 3997 _task_queues(task_queues), 3998 _terminator(terminator) 3999 {} 4000 4001 virtual void work(uint worker_id) { 4002 // The reference processing task executed by a single worker. 4003 ResourceMark rm; 4004 HandleMark hm; 4005 4006 G1STWIsAliveClosure is_alive(_g1h); 4007 4008 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4009 pss->set_ref_processor(NULL); 4010 4011 // Keep alive closure. 4012 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4013 4014 // Complete GC closure 4015 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4016 4017 // Call the reference processing task's work routine. 4018 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4019 4020 // Note we cannot assert that the refs array is empty here as not all 4021 // of the processing tasks (specifically phase2 - pp2_work) execute 4022 // the complete_gc closure (which ordinarily would drain the queue) so 4023 // the queue may not be empty. 4024 } 4025 }; 4026 4027 // Driver routine for parallel reference processing. 4028 // Creates an instance of the ref processing gang 4029 // task and has the worker threads execute it. 4030 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4031 assert(_workers != NULL, "Need parallel worker threads."); 4032 4033 ParallelTaskTerminator terminator(_active_workers, _queues); 4034 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4035 4036 _workers->run_task(&proc_task_proxy); 4037 } 4038 4039 // Gang task for parallel reference enqueueing. 4040 4041 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4042 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4043 EnqueueTask& _enq_task; 4044 4045 public: 4046 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4047 AbstractGangTask("Enqueue reference objects in parallel"), 4048 _enq_task(enq_task) 4049 { } 4050 4051 virtual void work(uint worker_id) { 4052 _enq_task.work(worker_id); 4053 } 4054 }; 4055 4056 // Driver routine for parallel reference enqueueing. 4057 // Creates an instance of the ref enqueueing gang 4058 // task and has the worker threads execute it. 4059 4060 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4061 assert(_workers != NULL, "Need parallel worker threads."); 4062 4063 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4064 4065 _workers->run_task(&enq_task_proxy); 4066 } 4067 4068 // End of weak reference support closures 4069 4070 // Abstract task used to preserve (i.e. copy) any referent objects 4071 // that are in the collection set and are pointed to by reference 4072 // objects discovered by the CM ref processor. 4073 4074 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4075 protected: 4076 G1CollectedHeap* _g1h; 4077 G1ParScanThreadStateSet* _pss; 4078 RefToScanQueueSet* _queues; 4079 ParallelTaskTerminator _terminator; 4080 uint _n_workers; 4081 4082 public: 4083 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4084 AbstractGangTask("ParPreserveCMReferents"), 4085 _g1h(g1h), 4086 _pss(per_thread_states), 4087 _queues(task_queues), 4088 _terminator(workers, _queues), 4089 _n_workers(workers) 4090 { 4091 g1h->ref_processor_cm()->set_active_mt_degree(workers); 4092 } 4093 4094 void work(uint worker_id) { 4095 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4096 4097 ResourceMark rm; 4098 HandleMark hm; 4099 4100 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4101 pss->set_ref_processor(NULL); 4102 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4103 4104 // Is alive closure 4105 G1AlwaysAliveClosure always_alive(_g1h); 4106 4107 // Copying keep alive closure. Applied to referent objects that need 4108 // to be copied. 4109 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4110 4111 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4112 4113 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4114 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4115 4116 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4117 // So this must be true - but assert just in case someone decides to 4118 // change the worker ids. 4119 assert(worker_id < limit, "sanity"); 4120 assert(!rp->discovery_is_atomic(), "check this code"); 4121 4122 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4123 for (uint idx = worker_id; idx < limit; idx += stride) { 4124 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4125 4126 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4127 while (iter.has_next()) { 4128 // Since discovery is not atomic for the CM ref processor, we 4129 // can see some null referent objects. 4130 iter.load_ptrs(DEBUG_ONLY(true)); 4131 oop ref = iter.obj(); 4132 4133 // This will filter nulls. 4134 if (iter.is_referent_alive()) { 4135 iter.make_referent_alive(); 4136 } 4137 iter.move_to_next(); 4138 } 4139 } 4140 4141 // Drain the queue - which may cause stealing 4142 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4143 drain_queue.do_void(); 4144 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4145 assert(pss->queue_is_empty(), "should be"); 4146 } 4147 }; 4148 4149 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4150 // Any reference objects, in the collection set, that were 'discovered' 4151 // by the CM ref processor should have already been copied (either by 4152 // applying the external root copy closure to the discovered lists, or 4153 // by following an RSet entry). 4154 // 4155 // But some of the referents, that are in the collection set, that these 4156 // reference objects point to may not have been copied: the STW ref 4157 // processor would have seen that the reference object had already 4158 // been 'discovered' and would have skipped discovering the reference, 4159 // but would not have treated the reference object as a regular oop. 4160 // As a result the copy closure would not have been applied to the 4161 // referent object. 4162 // 4163 // We need to explicitly copy these referent objects - the references 4164 // will be processed at the end of remarking. 4165 // 4166 // We also need to do this copying before we process the reference 4167 // objects discovered by the STW ref processor in case one of these 4168 // referents points to another object which is also referenced by an 4169 // object discovered by the STW ref processor. 4170 double preserve_cm_referents_time = 0.0; 4171 4172 // To avoid spawning task when there is no work to do, check that 4173 // a concurrent cycle is active and that some references have been 4174 // discovered. 4175 if (concurrent_mark()->cm_thread()->during_cycle() && 4176 ref_processor_cm()->has_discovered_references()) { 4177 double preserve_cm_referents_start = os::elapsedTime(); 4178 uint no_of_gc_workers = workers()->active_workers(); 4179 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4180 per_thread_states, 4181 no_of_gc_workers, 4182 _task_queues); 4183 workers()->run_task(&keep_cm_referents); 4184 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4185 } 4186 4187 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4188 } 4189 4190 // Weak Reference processing during an evacuation pause (part 1). 4191 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4192 double ref_proc_start = os::elapsedTime(); 4193 4194 ReferenceProcessor* rp = _ref_processor_stw; 4195 assert(rp->discovery_enabled(), "should have been enabled"); 4196 4197 // Closure to test whether a referent is alive. 4198 G1STWIsAliveClosure is_alive(this); 4199 4200 // Even when parallel reference processing is enabled, the processing 4201 // of JNI refs is serial and performed serially by the current thread 4202 // rather than by a worker. The following PSS will be used for processing 4203 // JNI refs. 4204 4205 // Use only a single queue for this PSS. 4206 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4207 pss->set_ref_processor(NULL); 4208 assert(pss->queue_is_empty(), "pre-condition"); 4209 4210 // Keep alive closure. 4211 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4212 4213 // Serial Complete GC closure 4214 G1STWDrainQueueClosure drain_queue(this, pss); 4215 4216 // Setup the soft refs policy... 4217 rp->setup_policy(false); 4218 4219 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4220 4221 ReferenceProcessorStats stats; 4222 if (!rp->processing_is_mt()) { 4223 // Serial reference processing... 4224 stats = rp->process_discovered_references(&is_alive, 4225 &keep_alive, 4226 &drain_queue, 4227 NULL, 4228 pt); 4229 } else { 4230 uint no_of_gc_workers = workers()->active_workers(); 4231 4232 // Parallel reference processing 4233 assert(no_of_gc_workers <= rp->max_num_q(), 4234 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4235 no_of_gc_workers, rp->max_num_q()); 4236 4237 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4238 stats = rp->process_discovered_references(&is_alive, 4239 &keep_alive, 4240 &drain_queue, 4241 &par_task_executor, 4242 pt); 4243 } 4244 4245 _gc_tracer_stw->report_gc_reference_stats(stats); 4246 4247 // We have completed copying any necessary live referent objects. 4248 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4249 4250 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4251 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4252 } 4253 4254 // Weak Reference processing during an evacuation pause (part 2). 4255 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4256 double ref_enq_start = os::elapsedTime(); 4257 4258 ReferenceProcessor* rp = _ref_processor_stw; 4259 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4260 4261 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4262 4263 // Now enqueue any remaining on the discovered lists on to 4264 // the pending list. 4265 if (!rp->processing_is_mt()) { 4266 // Serial reference processing... 4267 rp->enqueue_discovered_references(NULL, pt); 4268 } else { 4269 // Parallel reference enqueueing 4270 4271 uint n_workers = workers()->active_workers(); 4272 4273 assert(n_workers <= rp->max_num_q(), 4274 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4275 n_workers, rp->max_num_q()); 4276 4277 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4278 rp->enqueue_discovered_references(&par_task_executor, pt); 4279 } 4280 4281 rp->verify_no_references_recorded(); 4282 assert(!rp->discovery_enabled(), "should have been disabled"); 4283 4284 // If during an initial mark pause we install a pending list head which is not otherwise reachable 4285 // ensure that it is marked in the bitmap for concurrent marking to discover. 4286 if (collector_state()->during_initial_mark_pause()) { 4287 oop pll_head = Universe::reference_pending_list(); 4288 if (pll_head != NULL) { 4289 _cm->mark_in_next_bitmap(pll_head); 4290 } 4291 } 4292 4293 // FIXME 4294 // CM's reference processing also cleans up the string and symbol tables. 4295 // Should we do that here also? We could, but it is a serial operation 4296 // and could significantly increase the pause time. 4297 4298 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4299 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4300 } 4301 4302 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4303 double merge_pss_time_start = os::elapsedTime(); 4304 per_thread_states->flush(); 4305 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4306 } 4307 4308 void G1CollectedHeap::pre_evacuate_collection_set() { 4309 _expand_heap_after_alloc_failure = true; 4310 _evacuation_failed = false; 4311 4312 // Disable the hot card cache. 4313 _hot_card_cache->reset_hot_cache_claimed_index(); 4314 _hot_card_cache->set_use_cache(false); 4315 4316 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4317 _preserved_marks_set.assert_empty(); 4318 4319 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4320 4321 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4322 if (collector_state()->during_initial_mark_pause()) { 4323 double start_clear_claimed_marks = os::elapsedTime(); 4324 4325 ClassLoaderDataGraph::clear_claimed_marks(); 4326 4327 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4328 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4329 } 4330 } 4331 4332 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4333 // Should G1EvacuationFailureALot be in effect for this GC? 4334 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4335 4336 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4337 4338 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4339 4340 double start_par_time_sec = os::elapsedTime(); 4341 double end_par_time_sec; 4342 4343 { 4344 const uint n_workers = workers()->active_workers(); 4345 G1RootProcessor root_processor(this, n_workers); 4346 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4347 4348 print_termination_stats_hdr(); 4349 4350 workers()->run_task(&g1_par_task); 4351 end_par_time_sec = os::elapsedTime(); 4352 4353 // Closing the inner scope will execute the destructor 4354 // for the G1RootProcessor object. We record the current 4355 // elapsed time before closing the scope so that time 4356 // taken for the destructor is NOT included in the 4357 // reported parallel time. 4358 } 4359 4360 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4361 phase_times->record_par_time(par_time_ms); 4362 4363 double code_root_fixup_time_ms = 4364 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4365 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4366 } 4367 4368 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4369 // Process any discovered reference objects - we have 4370 // to do this _before_ we retire the GC alloc regions 4371 // as we may have to copy some 'reachable' referent 4372 // objects (and their reachable sub-graphs) that were 4373 // not copied during the pause. 4374 if (g1_policy()->should_process_references()) { 4375 preserve_cm_referents(per_thread_states); 4376 process_discovered_references(per_thread_states); 4377 } else { 4378 ref_processor_stw()->verify_no_references_recorded(); 4379 } 4380 4381 G1STWIsAliveClosure is_alive(this); 4382 G1KeepAliveClosure keep_alive(this); 4383 4384 { 4385 double start = os::elapsedTime(); 4386 4387 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 4388 4389 double time_ms = (os::elapsedTime() - start) * 1000.0; 4390 g1_policy()->phase_times()->record_ref_proc_time(time_ms); 4391 } 4392 4393 if (G1StringDedup::is_enabled()) { 4394 double fixup_start = os::elapsedTime(); 4395 4396 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4397 4398 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4399 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4400 } 4401 4402 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4403 4404 if (evacuation_failed()) { 4405 restore_after_evac_failure(); 4406 4407 // Reset the G1EvacuationFailureALot counters and flags 4408 // Note: the values are reset only when an actual 4409 // evacuation failure occurs. 4410 NOT_PRODUCT(reset_evacuation_should_fail();) 4411 } 4412 4413 _preserved_marks_set.assert_empty(); 4414 4415 // Enqueue any remaining references remaining on the STW 4416 // reference processor's discovered lists. We need to do 4417 // this after the card table is cleaned (and verified) as 4418 // the act of enqueueing entries on to the pending list 4419 // will log these updates (and dirty their associated 4420 // cards). We need these updates logged to update any 4421 // RSets. 4422 if (g1_policy()->should_process_references()) { 4423 enqueue_discovered_references(per_thread_states); 4424 } else { 4425 g1_policy()->phase_times()->record_ref_enq_time(0); 4426 } 4427 4428 _allocator->release_gc_alloc_regions(evacuation_info); 4429 4430 merge_per_thread_state_info(per_thread_states); 4431 4432 // Reset and re-enable the hot card cache. 4433 // Note the counts for the cards in the regions in the 4434 // collection set are reset when the collection set is freed. 4435 _hot_card_cache->reset_hot_cache(); 4436 _hot_card_cache->set_use_cache(true); 4437 4438 purge_code_root_memory(); 4439 4440 redirty_logged_cards(); 4441 #if COMPILER2_OR_JVMCI 4442 double start = os::elapsedTime(); 4443 DerivedPointerTable::update_pointers(); 4444 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4445 #endif 4446 g1_policy()->print_age_table(); 4447 } 4448 4449 void G1CollectedHeap::record_obj_copy_mem_stats() { 4450 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4451 4452 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4453 create_g1_evac_summary(&_old_evac_stats)); 4454 } 4455 4456 void G1CollectedHeap::free_region(HeapRegion* hr, 4457 FreeRegionList* free_list, 4458 bool skip_remset, 4459 bool skip_hot_card_cache, 4460 bool locked) { 4461 assert(!hr->is_free(), "the region should not be free"); 4462 assert(!hr->is_empty(), "the region should not be empty"); 4463 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4464 assert(free_list != NULL, "pre-condition"); 4465 4466 if (G1VerifyBitmaps) { 4467 MemRegion mr(hr->bottom(), hr->end()); 4468 concurrent_mark()->clear_range_in_prev_bitmap(mr); 4469 } 4470 4471 // Clear the card counts for this region. 4472 // Note: we only need to do this if the region is not young 4473 // (since we don't refine cards in young regions). 4474 if (!skip_hot_card_cache && !hr->is_young()) { 4475 _hot_card_cache->reset_card_counts(hr); 4476 } 4477 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4478 free_list->add_ordered(hr); 4479 } 4480 4481 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4482 FreeRegionList* free_list, 4483 bool skip_remset) { 4484 assert(hr->is_humongous(), "this is only for humongous regions"); 4485 assert(free_list != NULL, "pre-condition"); 4486 hr->clear_humongous(); 4487 free_region(hr, free_list, skip_remset); 4488 } 4489 4490 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4491 const uint humongous_regions_removed) { 4492 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4493 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4494 _old_set.bulk_remove(old_regions_removed); 4495 _humongous_set.bulk_remove(humongous_regions_removed); 4496 } 4497 4498 } 4499 4500 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4501 assert(list != NULL, "list can't be null"); 4502 if (!list->is_empty()) { 4503 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4504 _hrm.insert_list_into_free_list(list); 4505 } 4506 } 4507 4508 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4509 decrease_used(bytes); 4510 } 4511 4512 class G1ParScrubRemSetTask: public AbstractGangTask { 4513 protected: 4514 G1RemSet* _g1rs; 4515 HeapRegionClaimer _hrclaimer; 4516 4517 public: 4518 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) : 4519 AbstractGangTask("G1 ScrubRS"), 4520 _g1rs(g1_rs), 4521 _hrclaimer(num_workers) { 4522 } 4523 4524 void work(uint worker_id) { 4525 _g1rs->scrub(worker_id, &_hrclaimer); 4526 } 4527 }; 4528 4529 void G1CollectedHeap::scrub_rem_set() { 4530 uint num_workers = workers()->active_workers(); 4531 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers); 4532 workers()->run_task(&g1_par_scrub_rs_task); 4533 } 4534 4535 class G1FreeCollectionSetTask : public AbstractGangTask { 4536 private: 4537 4538 // Closure applied to all regions in the collection set to do work that needs to 4539 // be done serially in a single thread. 4540 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4541 private: 4542 EvacuationInfo* _evacuation_info; 4543 const size_t* _surviving_young_words; 4544 4545 // Bytes used in successfully evacuated regions before the evacuation. 4546 size_t _before_used_bytes; 4547 // Bytes used in unsucessfully evacuated regions before the evacuation 4548 size_t _after_used_bytes; 4549 4550 size_t _bytes_allocated_in_old_since_last_gc; 4551 4552 size_t _failure_used_words; 4553 size_t _failure_waste_words; 4554 4555 FreeRegionList _local_free_list; 4556 public: 4557 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4558 HeapRegionClosure(), 4559 _evacuation_info(evacuation_info), 4560 _surviving_young_words(surviving_young_words), 4561 _before_used_bytes(0), 4562 _after_used_bytes(0), 4563 _bytes_allocated_in_old_since_last_gc(0), 4564 _failure_used_words(0), 4565 _failure_waste_words(0), 4566 _local_free_list("Local Region List for CSet Freeing") { 4567 } 4568 4569 virtual bool doHeapRegion(HeapRegion* r) { 4570 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4571 4572 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4573 g1h->clear_in_cset(r); 4574 4575 if (r->is_young()) { 4576 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4577 "Young index %d is wrong for region %u of type %s with %u young regions", 4578 r->young_index_in_cset(), 4579 r->hrm_index(), 4580 r->get_type_str(), 4581 g1h->collection_set()->young_region_length()); 4582 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4583 r->record_surv_words_in_group(words_survived); 4584 } 4585 4586 if (!r->evacuation_failed()) { 4587 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4588 _before_used_bytes += r->used(); 4589 g1h->free_region(r, 4590 &_local_free_list, 4591 true, /* skip_remset */ 4592 true, /* skip_hot_card_cache */ 4593 true /* locked */); 4594 } else { 4595 r->uninstall_surv_rate_group(); 4596 r->set_young_index_in_cset(-1); 4597 r->set_evacuation_failed(false); 4598 // When moving a young gen region to old gen, we "allocate" that whole region 4599 // there. This is in addition to any already evacuated objects. Notify the 4600 // policy about that. 4601 // Old gen regions do not cause an additional allocation: both the objects 4602 // still in the region and the ones already moved are accounted for elsewhere. 4603 if (r->is_young()) { 4604 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4605 } 4606 // The region is now considered to be old. 4607 r->set_old(); 4608 // Do some allocation statistics accounting. Regions that failed evacuation 4609 // are always made old, so there is no need to update anything in the young 4610 // gen statistics, but we need to update old gen statistics. 4611 size_t used_words = r->marked_bytes() / HeapWordSize; 4612 4613 _failure_used_words += used_words; 4614 _failure_waste_words += HeapRegion::GrainWords - used_words; 4615 4616 g1h->old_set_add(r); 4617 _after_used_bytes += r->used(); 4618 } 4619 return false; 4620 } 4621 4622 void complete_work() { 4623 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4624 4625 _evacuation_info->set_regions_freed(_local_free_list.length()); 4626 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4627 4628 g1h->prepend_to_freelist(&_local_free_list); 4629 g1h->decrement_summary_bytes(_before_used_bytes); 4630 4631 G1Policy* policy = g1h->g1_policy(); 4632 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4633 4634 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4635 } 4636 }; 4637 4638 G1CollectionSet* _collection_set; 4639 G1SerialFreeCollectionSetClosure _cl; 4640 const size_t* _surviving_young_words; 4641 4642 size_t _rs_lengths; 4643 4644 volatile jint _serial_work_claim; 4645 4646 struct WorkItem { 4647 uint region_idx; 4648 bool is_young; 4649 bool evacuation_failed; 4650 4651 WorkItem(HeapRegion* r) { 4652 region_idx = r->hrm_index(); 4653 is_young = r->is_young(); 4654 evacuation_failed = r->evacuation_failed(); 4655 } 4656 }; 4657 4658 volatile size_t _parallel_work_claim; 4659 size_t _num_work_items; 4660 WorkItem* _work_items; 4661 4662 void do_serial_work() { 4663 // Need to grab the lock to be allowed to modify the old region list. 4664 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4665 _collection_set->iterate(&_cl); 4666 } 4667 4668 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4669 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4670 4671 HeapRegion* r = g1h->region_at(region_idx); 4672 assert(!g1h->is_on_master_free_list(r), "sanity"); 4673 4674 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4675 4676 if (!is_young) { 4677 g1h->_hot_card_cache->reset_card_counts(r); 4678 } 4679 4680 if (!evacuation_failed) { 4681 r->rem_set()->clear_locked(); 4682 } 4683 } 4684 4685 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4686 private: 4687 size_t _cur_idx; 4688 WorkItem* _work_items; 4689 public: 4690 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4691 4692 virtual bool doHeapRegion(HeapRegion* r) { 4693 _work_items[_cur_idx++] = WorkItem(r); 4694 return false; 4695 } 4696 }; 4697 4698 void prepare_work() { 4699 G1PrepareFreeCollectionSetClosure cl(_work_items); 4700 _collection_set->iterate(&cl); 4701 } 4702 4703 void complete_work() { 4704 _cl.complete_work(); 4705 4706 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4707 policy->record_max_rs_lengths(_rs_lengths); 4708 policy->cset_regions_freed(); 4709 } 4710 public: 4711 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4712 AbstractGangTask("G1 Free Collection Set"), 4713 _cl(evacuation_info, surviving_young_words), 4714 _collection_set(collection_set), 4715 _surviving_young_words(surviving_young_words), 4716 _serial_work_claim(0), 4717 _rs_lengths(0), 4718 _parallel_work_claim(0), 4719 _num_work_items(collection_set->region_length()), 4720 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4721 prepare_work(); 4722 } 4723 4724 ~G1FreeCollectionSetTask() { 4725 complete_work(); 4726 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4727 } 4728 4729 // Chunk size for work distribution. The chosen value has been determined experimentally 4730 // to be a good tradeoff between overhead and achievable parallelism. 4731 static uint chunk_size() { return 32; } 4732 4733 virtual void work(uint worker_id) { 4734 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4735 4736 // Claim serial work. 4737 if (_serial_work_claim == 0) { 4738 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4739 if (value == 0) { 4740 double serial_time = os::elapsedTime(); 4741 do_serial_work(); 4742 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4743 } 4744 } 4745 4746 // Start parallel work. 4747 double young_time = 0.0; 4748 bool has_young_time = false; 4749 double non_young_time = 0.0; 4750 bool has_non_young_time = false; 4751 4752 while (true) { 4753 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4754 size_t cur = end - chunk_size(); 4755 4756 if (cur >= _num_work_items) { 4757 break; 4758 } 4759 4760 double start_time = os::elapsedTime(); 4761 4762 end = MIN2(end, _num_work_items); 4763 4764 for (; cur < end; cur++) { 4765 bool is_young = _work_items[cur].is_young; 4766 4767 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4768 4769 double end_time = os::elapsedTime(); 4770 double time_taken = end_time - start_time; 4771 if (is_young) { 4772 young_time += time_taken; 4773 has_young_time = true; 4774 } else { 4775 non_young_time += time_taken; 4776 has_non_young_time = true; 4777 } 4778 start_time = end_time; 4779 } 4780 } 4781 4782 if (has_young_time) { 4783 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4784 } 4785 if (has_non_young_time) { 4786 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time); 4787 } 4788 } 4789 }; 4790 4791 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4792 _eden.clear(); 4793 4794 double free_cset_start_time = os::elapsedTime(); 4795 4796 { 4797 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4798 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4799 4800 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4801 4802 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4803 cl.name(), 4804 num_workers, 4805 _collection_set.region_length()); 4806 workers()->run_task(&cl, num_workers); 4807 } 4808 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4809 4810 collection_set->clear(); 4811 } 4812 4813 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4814 private: 4815 FreeRegionList* _free_region_list; 4816 HeapRegionSet* _proxy_set; 4817 uint _humongous_objects_reclaimed; 4818 uint _humongous_regions_reclaimed; 4819 size_t _freed_bytes; 4820 public: 4821 4822 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4823 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4824 } 4825 4826 virtual bool doHeapRegion(HeapRegion* r) { 4827 if (!r->is_starts_humongous()) { 4828 return false; 4829 } 4830 4831 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4832 4833 oop obj = (oop)r->bottom(); 4834 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap(); 4835 4836 // The following checks whether the humongous object is live are sufficient. 4837 // The main additional check (in addition to having a reference from the roots 4838 // or the young gen) is whether the humongous object has a remembered set entry. 4839 // 4840 // A humongous object cannot be live if there is no remembered set for it 4841 // because: 4842 // - there can be no references from within humongous starts regions referencing 4843 // the object because we never allocate other objects into them. 4844 // (I.e. there are no intra-region references that may be missed by the 4845 // remembered set) 4846 // - as soon there is a remembered set entry to the humongous starts region 4847 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4848 // until the end of a concurrent mark. 4849 // 4850 // It is not required to check whether the object has been found dead by marking 4851 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4852 // all objects allocated during that time are considered live. 4853 // SATB marking is even more conservative than the remembered set. 4854 // So if at this point in the collection there is no remembered set entry, 4855 // nobody has a reference to it. 4856 // At the start of collection we flush all refinement logs, and remembered sets 4857 // are completely up-to-date wrt to references to the humongous object. 4858 // 4859 // Other implementation considerations: 4860 // - never consider object arrays at this time because they would pose 4861 // considerable effort for cleaning up the the remembered sets. This is 4862 // required because stale remembered sets might reference locations that 4863 // are currently allocated into. 4864 uint region_idx = r->hrm_index(); 4865 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4866 !r->rem_set()->is_empty()) { 4867 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", 4868 region_idx, 4869 (size_t)obj->size() * HeapWordSize, 4870 p2i(r->bottom()), 4871 r->rem_set()->occupied(), 4872 r->rem_set()->strong_code_roots_list_length(), 4873 next_bitmap->is_marked(r->bottom()), 4874 g1h->is_humongous_reclaim_candidate(region_idx), 4875 obj->is_typeArray() 4876 ); 4877 return false; 4878 } 4879 4880 guarantee(obj->is_typeArray(), 4881 "Only eagerly reclaiming type arrays is supported, but the object " 4882 PTR_FORMAT " is not.", p2i(r->bottom())); 4883 4884 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", 4885 region_idx, 4886 (size_t)obj->size() * HeapWordSize, 4887 p2i(r->bottom()), 4888 r->rem_set()->occupied(), 4889 r->rem_set()->strong_code_roots_list_length(), 4890 next_bitmap->is_marked(r->bottom()), 4891 g1h->is_humongous_reclaim_candidate(region_idx), 4892 obj->is_typeArray() 4893 ); 4894 4895 // Need to clear mark bit of the humongous object if already set. 4896 if (next_bitmap->is_marked(r->bottom())) { 4897 next_bitmap->clear(r->bottom()); 4898 } 4899 _humongous_objects_reclaimed++; 4900 do { 4901 HeapRegion* next = g1h->next_region_in_humongous(r); 4902 _freed_bytes += r->used(); 4903 r->set_containing_set(NULL); 4904 _humongous_regions_reclaimed++; 4905 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ ); 4906 r = next; 4907 } while (r != NULL); 4908 4909 return false; 4910 } 4911 4912 uint humongous_objects_reclaimed() { 4913 return _humongous_objects_reclaimed; 4914 } 4915 4916 uint humongous_regions_reclaimed() { 4917 return _humongous_regions_reclaimed; 4918 } 4919 4920 size_t bytes_freed() const { 4921 return _freed_bytes; 4922 } 4923 }; 4924 4925 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4926 assert_at_safepoint(true); 4927 4928 if (!G1EagerReclaimHumongousObjects || 4929 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4930 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4931 return; 4932 } 4933 4934 double start_time = os::elapsedTime(); 4935 4936 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4937 4938 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4939 heap_region_iterate(&cl); 4940 4941 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4942 4943 G1HRPrinter* hrp = hr_printer(); 4944 if (hrp->is_active()) { 4945 FreeRegionListIterator iter(&local_cleanup_list); 4946 while (iter.more_available()) { 4947 HeapRegion* hr = iter.get_next(); 4948 hrp->cleanup(hr); 4949 } 4950 } 4951 4952 prepend_to_freelist(&local_cleanup_list); 4953 decrement_summary_bytes(cl.bytes_freed()); 4954 4955 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4956 cl.humongous_objects_reclaimed()); 4957 } 4958 4959 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4960 public: 4961 virtual bool doHeapRegion(HeapRegion* r) { 4962 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4963 G1CollectedHeap::heap()->clear_in_cset(r); 4964 r->set_young_index_in_cset(-1); 4965 return false; 4966 } 4967 }; 4968 4969 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4970 G1AbandonCollectionSetClosure cl; 4971 collection_set->iterate(&cl); 4972 4973 collection_set->clear(); 4974 collection_set->stop_incremental_building(); 4975 } 4976 4977 void G1CollectedHeap::set_free_regions_coming() { 4978 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 4979 4980 assert(!free_regions_coming(), "pre-condition"); 4981 _free_regions_coming = true; 4982 } 4983 4984 void G1CollectedHeap::reset_free_regions_coming() { 4985 assert(free_regions_coming(), "pre-condition"); 4986 4987 { 4988 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 4989 _free_regions_coming = false; 4990 SecondaryFreeList_lock->notify_all(); 4991 } 4992 4993 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 4994 } 4995 4996 void G1CollectedHeap::wait_while_free_regions_coming() { 4997 // Most of the time we won't have to wait, so let's do a quick test 4998 // first before we take the lock. 4999 if (!free_regions_coming()) { 5000 return; 5001 } 5002 5003 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 5004 5005 { 5006 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5007 while (free_regions_coming()) { 5008 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5009 } 5010 } 5011 5012 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 5013 } 5014 5015 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5016 return _allocator->is_retained_old_region(hr); 5017 } 5018 5019 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5020 _eden.add(hr); 5021 _g1_policy->set_region_eden(hr); 5022 } 5023 5024 #ifdef ASSERT 5025 5026 class NoYoungRegionsClosure: public HeapRegionClosure { 5027 private: 5028 bool _success; 5029 public: 5030 NoYoungRegionsClosure() : _success(true) { } 5031 bool doHeapRegion(HeapRegion* r) { 5032 if (r->is_young()) { 5033 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5034 p2i(r->bottom()), p2i(r->end())); 5035 _success = false; 5036 } 5037 return false; 5038 } 5039 bool success() { return _success; } 5040 }; 5041 5042 bool G1CollectedHeap::check_young_list_empty() { 5043 bool ret = (young_regions_count() == 0); 5044 5045 NoYoungRegionsClosure closure; 5046 heap_region_iterate(&closure); 5047 ret = ret && closure.success(); 5048 5049 return ret; 5050 } 5051 5052 #endif // ASSERT 5053 5054 class TearDownRegionSetsClosure : public HeapRegionClosure { 5055 private: 5056 HeapRegionSet *_old_set; 5057 5058 public: 5059 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5060 5061 bool doHeapRegion(HeapRegion* r) { 5062 if (r->is_old()) { 5063 _old_set->remove(r); 5064 } else if(r->is_young()) { 5065 r->uninstall_surv_rate_group(); 5066 } else { 5067 // We ignore free regions, we'll empty the free list afterwards. 5068 // We ignore humongous regions, we're not tearing down the 5069 // humongous regions set. 5070 assert(r->is_free() || r->is_humongous(), 5071 "it cannot be another type"); 5072 } 5073 return false; 5074 } 5075 5076 ~TearDownRegionSetsClosure() { 5077 assert(_old_set->is_empty(), "post-condition"); 5078 } 5079 }; 5080 5081 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5082 assert_at_safepoint(true /* should_be_vm_thread */); 5083 5084 if (!free_list_only) { 5085 TearDownRegionSetsClosure cl(&_old_set); 5086 heap_region_iterate(&cl); 5087 5088 // Note that emptying the _young_list is postponed and instead done as 5089 // the first step when rebuilding the regions sets again. The reason for 5090 // this is that during a full GC string deduplication needs to know if 5091 // a collected region was young or old when the full GC was initiated. 5092 } 5093 _hrm.remove_all_free_regions(); 5094 } 5095 5096 void G1CollectedHeap::increase_used(size_t bytes) { 5097 _summary_bytes_used += bytes; 5098 } 5099 5100 void G1CollectedHeap::decrease_used(size_t bytes) { 5101 assert(_summary_bytes_used >= bytes, 5102 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5103 _summary_bytes_used, bytes); 5104 _summary_bytes_used -= bytes; 5105 } 5106 5107 void G1CollectedHeap::set_used(size_t bytes) { 5108 _summary_bytes_used = bytes; 5109 } 5110 5111 class RebuildRegionSetsClosure : public HeapRegionClosure { 5112 private: 5113 bool _free_list_only; 5114 HeapRegionSet* _old_set; 5115 HeapRegionManager* _hrm; 5116 size_t _total_used; 5117 5118 public: 5119 RebuildRegionSetsClosure(bool free_list_only, 5120 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5121 _free_list_only(free_list_only), 5122 _old_set(old_set), _hrm(hrm), _total_used(0) { 5123 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5124 if (!free_list_only) { 5125 assert(_old_set->is_empty(), "pre-condition"); 5126 } 5127 } 5128 5129 bool doHeapRegion(HeapRegion* r) { 5130 if (r->is_empty()) { 5131 // Add free regions to the free list 5132 r->set_free(); 5133 r->set_allocation_context(AllocationContext::system()); 5134 _hrm->insert_into_free_list(r); 5135 } else if (!_free_list_only) { 5136 5137 if (r->is_humongous()) { 5138 // We ignore humongous regions. We left the humongous set unchanged. 5139 } else { 5140 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 5141 // We now move all (non-humongous, non-old) regions to old gen, and register them as such. 5142 r->move_to_old(); 5143 _old_set->add(r); 5144 } 5145 _total_used += r->used(); 5146 } 5147 5148 return false; 5149 } 5150 5151 size_t total_used() { 5152 return _total_used; 5153 } 5154 }; 5155 5156 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5157 assert_at_safepoint(true /* should_be_vm_thread */); 5158 5159 if (!free_list_only) { 5160 _eden.clear(); 5161 _survivor.clear(); 5162 } 5163 5164 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5165 heap_region_iterate(&cl); 5166 5167 if (!free_list_only) { 5168 set_used(cl.total_used()); 5169 if (_archive_allocator != NULL) { 5170 _archive_allocator->clear_used(); 5171 } 5172 } 5173 assert(used_unlocked() == recalculate_used(), 5174 "inconsistent used_unlocked(), " 5175 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5176 used_unlocked(), recalculate_used()); 5177 } 5178 5179 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5180 HeapRegion* hr = heap_region_containing(p); 5181 return hr->is_in(p); 5182 } 5183 5184 // Methods for the mutator alloc region 5185 5186 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5187 bool force) { 5188 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5189 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 5190 if (force || should_allocate) { 5191 HeapRegion* new_alloc_region = new_region(word_size, 5192 false /* is_old */, 5193 false /* do_expand */); 5194 if (new_alloc_region != NULL) { 5195 set_region_short_lived_locked(new_alloc_region); 5196 _hr_printer.alloc(new_alloc_region, !should_allocate); 5197 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5198 return new_alloc_region; 5199 } 5200 } 5201 return NULL; 5202 } 5203 5204 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5205 size_t allocated_bytes) { 5206 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5207 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5208 5209 collection_set()->add_eden_region(alloc_region); 5210 increase_used(allocated_bytes); 5211 _hr_printer.retire(alloc_region); 5212 // We update the eden sizes here, when the region is retired, 5213 // instead of when it's allocated, since this is the point that its 5214 // used space has been recored in _summary_bytes_used. 5215 g1mm()->update_eden_size(); 5216 } 5217 5218 // Methods for the GC alloc regions 5219 5220 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 5221 if (dest.is_old()) { 5222 return true; 5223 } else { 5224 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 5225 } 5226 } 5227 5228 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 5229 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5230 5231 if (!has_more_regions(dest)) { 5232 return NULL; 5233 } 5234 5235 const bool is_survivor = dest.is_young(); 5236 5237 HeapRegion* new_alloc_region = new_region(word_size, 5238 !is_survivor, 5239 true /* do_expand */); 5240 if (new_alloc_region != NULL) { 5241 // We really only need to do this for old regions given that we 5242 // should never scan survivors. But it doesn't hurt to do it 5243 // for survivors too. 5244 new_alloc_region->record_timestamp(); 5245 if (is_survivor) { 5246 new_alloc_region->set_survivor(); 5247 _survivor.add(new_alloc_region); 5248 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5249 } else { 5250 new_alloc_region->set_old(); 5251 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5252 } 5253 _hr_printer.alloc(new_alloc_region); 5254 bool during_im = collector_state()->during_initial_mark_pause(); 5255 new_alloc_region->note_start_of_copying(during_im); 5256 return new_alloc_region; 5257 } 5258 return NULL; 5259 } 5260 5261 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5262 size_t allocated_bytes, 5263 InCSetState dest) { 5264 bool during_im = collector_state()->during_initial_mark_pause(); 5265 alloc_region->note_end_of_copying(during_im); 5266 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5267 if (dest.is_old()) { 5268 _old_set.add(alloc_region); 5269 } 5270 _hr_printer.retire(alloc_region); 5271 } 5272 5273 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5274 bool expanded = false; 5275 uint index = _hrm.find_highest_free(&expanded); 5276 5277 if (index != G1_NO_HRM_INDEX) { 5278 if (expanded) { 5279 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5280 HeapRegion::GrainWords * HeapWordSize); 5281 } 5282 _hrm.allocate_free_regions_starting_at(index, 1); 5283 return region_at(index); 5284 } 5285 return NULL; 5286 } 5287 5288 // Optimized nmethod scanning 5289 5290 class RegisterNMethodOopClosure: public OopClosure { 5291 G1CollectedHeap* _g1h; 5292 nmethod* _nm; 5293 5294 template <class T> void do_oop_work(T* p) { 5295 T heap_oop = oopDesc::load_heap_oop(p); 5296 if (!oopDesc::is_null(heap_oop)) { 5297 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5298 HeapRegion* hr = _g1h->heap_region_containing(obj); 5299 assert(!hr->is_continues_humongous(), 5300 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5301 " starting at " HR_FORMAT, 5302 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5303 5304 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5305 hr->add_strong_code_root_locked(_nm); 5306 } 5307 } 5308 5309 public: 5310 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5311 _g1h(g1h), _nm(nm) {} 5312 5313 void do_oop(oop* p) { do_oop_work(p); } 5314 void do_oop(narrowOop* p) { do_oop_work(p); } 5315 }; 5316 5317 class UnregisterNMethodOopClosure: public OopClosure { 5318 G1CollectedHeap* _g1h; 5319 nmethod* _nm; 5320 5321 template <class T> void do_oop_work(T* p) { 5322 T heap_oop = oopDesc::load_heap_oop(p); 5323 if (!oopDesc::is_null(heap_oop)) { 5324 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5325 HeapRegion* hr = _g1h->heap_region_containing(obj); 5326 assert(!hr->is_continues_humongous(), 5327 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5328 " starting at " HR_FORMAT, 5329 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5330 5331 hr->remove_strong_code_root(_nm); 5332 } 5333 } 5334 5335 public: 5336 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5337 _g1h(g1h), _nm(nm) {} 5338 5339 void do_oop(oop* p) { do_oop_work(p); } 5340 void do_oop(narrowOop* p) { do_oop_work(p); } 5341 }; 5342 5343 // Returns true if the reference points to an object that 5344 // can move in an incremental collection. 5345 bool G1CollectedHeap::is_scavengable(oop obj) { 5346 HeapRegion* hr = heap_region_containing(obj); 5347 return !hr->is_pinned(); 5348 } 5349 5350 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5351 guarantee(nm != NULL, "sanity"); 5352 RegisterNMethodOopClosure reg_cl(this, nm); 5353 nm->oops_do(®_cl); 5354 } 5355 5356 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5357 guarantee(nm != NULL, "sanity"); 5358 UnregisterNMethodOopClosure reg_cl(this, nm); 5359 nm->oops_do(®_cl, true); 5360 } 5361 5362 void G1CollectedHeap::purge_code_root_memory() { 5363 double purge_start = os::elapsedTime(); 5364 G1CodeRootSet::purge(); 5365 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5366 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5367 } 5368 5369 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5370 G1CollectedHeap* _g1h; 5371 5372 public: 5373 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5374 _g1h(g1h) {} 5375 5376 void do_code_blob(CodeBlob* cb) { 5377 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5378 if (nm == NULL) { 5379 return; 5380 } 5381 5382 if (ScavengeRootsInCode) { 5383 _g1h->register_nmethod(nm); 5384 } 5385 } 5386 }; 5387 5388 void G1CollectedHeap::rebuild_strong_code_roots() { 5389 RebuildStrongCodeRootClosure blob_cl(this); 5390 CodeCache::blobs_do(&blob_cl); 5391 } 5392 5393 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() { 5394 GrowableArray<GCMemoryManager*> memory_managers(2); 5395 memory_managers.append(&_memory_manager); 5396 memory_managers.append(&_full_gc_memory_manager); 5397 return memory_managers; 5398 } 5399 5400 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() { 5401 GrowableArray<MemoryPool*> memory_pools(3); 5402 memory_pools.append(_eden_pool); 5403 memory_pools.append(_survivor_pool); 5404 memory_pools.append(_old_pool); 5405 return memory_pools; 5406 }