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/g1FullGCScope.hpp" 43 #include "gc/g1/g1GCPhaseTimes.hpp" 44 #include "gc/g1/g1HeapSizingPolicy.hpp" 45 #include "gc/g1/g1HeapTransition.hpp" 46 #include "gc/g1/g1HeapVerifier.hpp" 47 #include "gc/g1/g1HotCardCache.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/vmThread.hpp" 85 #include "utilities/align.hpp" 86 #include "utilities/globalDefinitions.hpp" 87 #include "utilities/stack.inline.hpp" 88 89 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 90 91 // INVARIANTS/NOTES 92 // 93 // All allocation activity covered by the G1CollectedHeap interface is 94 // serialized by acquiring the HeapLock. This happens in mem_allocate 95 // and allocate_new_tlab, which are the "entry" points to the 96 // allocation code from the rest of the JVM. (Note that this does not 97 // apply to TLAB allocation, which is not part of this interface: it 98 // is done by clients of this interface.) 99 100 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 101 private: 102 size_t _num_dirtied; 103 G1CollectedHeap* _g1h; 104 G1SATBCardTableLoggingModRefBS* _g1_bs; 105 106 HeapRegion* region_for_card(jbyte* card_ptr) const { 107 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 108 } 109 110 bool will_become_free(HeapRegion* hr) const { 111 // A region will be freed by free_collection_set if the region is in the 112 // collection set and has not had an evacuation failure. 113 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 114 } 115 116 public: 117 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 118 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 119 120 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 121 HeapRegion* hr = region_for_card(card_ptr); 122 123 // Should only dirty cards in regions that won't be freed. 124 if (!will_become_free(hr)) { 125 *card_ptr = CardTableModRefBS::dirty_card_val(); 126 _num_dirtied++; 127 } 128 129 return true; 130 } 131 132 size_t num_dirtied() const { return _num_dirtied; } 133 }; 134 135 136 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 137 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 138 } 139 140 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 141 // The from card cache is not the memory that is actually committed. So we cannot 142 // take advantage of the zero_filled parameter. 143 reset_from_card_cache(start_idx, num_regions); 144 } 145 146 147 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 148 MemRegion mr) { 149 return new HeapRegion(hrs_index, bot(), mr); 150 } 151 152 // Private methods. 153 154 HeapRegion* 155 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 156 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 157 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 158 if (!_secondary_free_list.is_empty()) { 159 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 160 "secondary_free_list has %u entries", 161 _secondary_free_list.length()); 162 // It looks as if there are free regions available on the 163 // secondary_free_list. Let's move them to the free_list and try 164 // again to allocate from it. 165 append_secondary_free_list(); 166 167 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 168 "empty we should have moved at least one entry to the free_list"); 169 HeapRegion* res = _hrm.allocate_free_region(is_old); 170 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 171 "allocated " HR_FORMAT " from secondary_free_list", 172 HR_FORMAT_PARAMS(res)); 173 return res; 174 } 175 176 // Wait here until we get notified either when (a) there are no 177 // more free regions coming or (b) some regions have been moved on 178 // the secondary_free_list. 179 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 180 } 181 182 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 183 "could not allocate from secondary_free_list"); 184 return NULL; 185 } 186 187 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 188 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 189 "the only time we use this to allocate a humongous region is " 190 "when we are allocating a single humongous region"); 191 192 HeapRegion* res; 193 if (G1StressConcRegionFreeing) { 194 if (!_secondary_free_list.is_empty()) { 195 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 196 "forced to look at the secondary_free_list"); 197 res = new_region_try_secondary_free_list(is_old); 198 if (res != NULL) { 199 return res; 200 } 201 } 202 } 203 204 res = _hrm.allocate_free_region(is_old); 205 206 if (res == NULL) { 207 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 208 "res == NULL, trying the secondary_free_list"); 209 res = new_region_try_secondary_free_list(is_old); 210 } 211 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 212 // Currently, only attempts to allocate GC alloc regions set 213 // do_expand to true. So, we should only reach here during a 214 // safepoint. If this assumption changes we might have to 215 // reconsider the use of _expand_heap_after_alloc_failure. 216 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 217 218 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 219 word_size * HeapWordSize); 220 221 if (expand(word_size * HeapWordSize)) { 222 // Given that expand() succeeded in expanding the heap, and we 223 // always expand the heap by an amount aligned to the heap 224 // region size, the free list should in theory not be empty. 225 // In either case allocate_free_region() will check for NULL. 226 res = _hrm.allocate_free_region(is_old); 227 } else { 228 _expand_heap_after_alloc_failure = false; 229 } 230 } 231 return res; 232 } 233 234 HeapWord* 235 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 236 uint num_regions, 237 size_t word_size, 238 AllocationContext_t context) { 239 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 240 assert(is_humongous(word_size), "word_size should be humongous"); 241 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 242 243 // Index of last region in the series. 244 uint last = first + num_regions - 1; 245 246 // We need to initialize the region(s) we just discovered. This is 247 // a bit tricky given that it can happen concurrently with 248 // refinement threads refining cards on these regions and 249 // potentially wanting to refine the BOT as they are scanning 250 // those cards (this can happen shortly after a cleanup; see CR 251 // 6991377). So we have to set up the region(s) carefully and in 252 // a specific order. 253 254 // The word size sum of all the regions we will allocate. 255 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 256 assert(word_size <= word_size_sum, "sanity"); 257 258 // This will be the "starts humongous" region. 259 HeapRegion* first_hr = region_at(first); 260 // The header of the new object will be placed at the bottom of 261 // the first region. 262 HeapWord* new_obj = first_hr->bottom(); 263 // This will be the new top of the new object. 264 HeapWord* obj_top = new_obj + word_size; 265 266 // First, we need to zero the header of the space that we will be 267 // allocating. When we update top further down, some refinement 268 // threads might try to scan the region. By zeroing the header we 269 // ensure that any thread that will try to scan the region will 270 // come across the zero klass word and bail out. 271 // 272 // NOTE: It would not have been correct to have used 273 // CollectedHeap::fill_with_object() and make the space look like 274 // an int array. The thread that is doing the allocation will 275 // later update the object header to a potentially different array 276 // type and, for a very short period of time, the klass and length 277 // fields will be inconsistent. This could cause a refinement 278 // thread to calculate the object size incorrectly. 279 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 280 281 // Next, pad out the unused tail of the last region with filler 282 // objects, for improved usage accounting. 283 // How many words we use for filler objects. 284 size_t word_fill_size = word_size_sum - word_size; 285 286 // How many words memory we "waste" which cannot hold a filler object. 287 size_t words_not_fillable = 0; 288 289 if (word_fill_size >= min_fill_size()) { 290 fill_with_objects(obj_top, word_fill_size); 291 } else if (word_fill_size > 0) { 292 // We have space to fill, but we cannot fit an object there. 293 words_not_fillable = word_fill_size; 294 word_fill_size = 0; 295 } 296 297 // We will set up the first region as "starts humongous". This 298 // will also update the BOT covering all the regions to reflect 299 // that there is a single object that starts at the bottom of the 300 // first region. 301 first_hr->set_starts_humongous(obj_top, word_fill_size); 302 first_hr->set_allocation_context(context); 303 // Then, if there are any, we will set up the "continues 304 // humongous" regions. 305 HeapRegion* hr = NULL; 306 for (uint i = first + 1; i <= last; ++i) { 307 hr = region_at(i); 308 hr->set_continues_humongous(first_hr); 309 hr->set_allocation_context(context); 310 } 311 312 // Up to this point no concurrent thread would have been able to 313 // do any scanning on any region in this series. All the top 314 // fields still point to bottom, so the intersection between 315 // [bottom,top] and [card_start,card_end] will be empty. Before we 316 // update the top fields, we'll do a storestore to make sure that 317 // no thread sees the update to top before the zeroing of the 318 // object header and the BOT initialization. 319 OrderAccess::storestore(); 320 321 // Now, we will update the top fields of the "continues humongous" 322 // regions except the last one. 323 for (uint i = first; i < last; ++i) { 324 hr = region_at(i); 325 hr->set_top(hr->end()); 326 } 327 328 hr = region_at(last); 329 // If we cannot fit a filler object, we must set top to the end 330 // of the humongous object, otherwise we cannot iterate the heap 331 // and the BOT will not be complete. 332 hr->set_top(hr->end() - words_not_fillable); 333 334 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 335 "obj_top should be in last region"); 336 337 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 338 339 assert(words_not_fillable == 0 || 340 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 341 "Miscalculation in humongous allocation"); 342 343 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 344 345 for (uint i = first; i <= last; ++i) { 346 hr = region_at(i); 347 _humongous_set.add(hr); 348 _hr_printer.alloc(hr); 349 } 350 351 return new_obj; 352 } 353 354 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 355 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 356 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 357 } 358 359 // If could fit into free regions w/o expansion, try. 360 // Otherwise, if can expand, do so. 361 // Otherwise, if using ex regions might help, try with ex given back. 362 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 363 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 364 365 _verifier->verify_region_sets_optional(); 366 367 uint first = G1_NO_HRM_INDEX; 368 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 369 370 if (obj_regions == 1) { 371 // Only one region to allocate, try to use a fast path by directly allocating 372 // from the free lists. Do not try to expand here, we will potentially do that 373 // later. 374 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 375 if (hr != NULL) { 376 first = hr->hrm_index(); 377 } 378 } else { 379 // We can't allocate humongous regions spanning more than one region while 380 // cleanupComplete() is running, since some of the regions we find to be 381 // empty might not yet be added to the free list. It is not straightforward 382 // to know in which list they are on so that we can remove them. We only 383 // need to do this if we need to allocate more than one region to satisfy the 384 // current humongous allocation request. If we are only allocating one region 385 // we use the one-region region allocation code (see above), that already 386 // potentially waits for regions from the secondary free list. 387 wait_while_free_regions_coming(); 388 append_secondary_free_list_if_not_empty_with_lock(); 389 390 // Policy: Try only empty regions (i.e. already committed first). Maybe we 391 // are lucky enough to find some. 392 first = _hrm.find_contiguous_only_empty(obj_regions); 393 if (first != G1_NO_HRM_INDEX) { 394 _hrm.allocate_free_regions_starting_at(first, obj_regions); 395 } 396 } 397 398 if (first == G1_NO_HRM_INDEX) { 399 // Policy: We could not find enough regions for the humongous object in the 400 // free list. Look through the heap to find a mix of free and uncommitted regions. 401 // If so, try expansion. 402 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 403 if (first != G1_NO_HRM_INDEX) { 404 // We found something. Make sure these regions are committed, i.e. expand 405 // the heap. Alternatively we could do a defragmentation GC. 406 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 407 word_size * HeapWordSize); 408 409 _hrm.expand_at(first, obj_regions, workers()); 410 g1_policy()->record_new_heap_size(num_regions()); 411 412 #ifdef ASSERT 413 for (uint i = first; i < first + obj_regions; ++i) { 414 HeapRegion* hr = region_at(i); 415 assert(hr->is_free(), "sanity"); 416 assert(hr->is_empty(), "sanity"); 417 assert(is_on_master_free_list(hr), "sanity"); 418 } 419 #endif 420 _hrm.allocate_free_regions_starting_at(first, obj_regions); 421 } else { 422 // Policy: Potentially trigger a defragmentation GC. 423 } 424 } 425 426 HeapWord* result = NULL; 427 if (first != G1_NO_HRM_INDEX) { 428 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 429 word_size, context); 430 assert(result != NULL, "it should always return a valid result"); 431 432 // A successful humongous object allocation changes the used space 433 // information of the old generation so we need to recalculate the 434 // sizes and update the jstat counters here. 435 g1mm()->update_sizes(); 436 } 437 438 _verifier->verify_region_sets_optional(); 439 440 return result; 441 } 442 443 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 444 assert_heap_not_locked_and_not_at_safepoint(); 445 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 446 447 uint dummy_gc_count_before; 448 uint dummy_gclocker_retry_count = 0; 449 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 450 } 451 452 HeapWord* 453 G1CollectedHeap::mem_allocate(size_t word_size, 454 bool* gc_overhead_limit_was_exceeded) { 455 assert_heap_not_locked_and_not_at_safepoint(); 456 457 // Loop until the allocation is satisfied, or unsatisfied after GC. 458 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 459 uint gc_count_before; 460 461 HeapWord* result = NULL; 462 if (!is_humongous(word_size)) { 463 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 464 } else { 465 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 466 } 467 if (result != NULL) { 468 return result; 469 } 470 471 // Create the garbage collection operation... 472 VM_G1CollectForAllocation op(gc_count_before, word_size); 473 op.set_allocation_context(AllocationContext::current()); 474 475 // ...and get the VM thread to execute it. 476 VMThread::execute(&op); 477 478 if (op.prologue_succeeded() && op.pause_succeeded()) { 479 // If the operation was successful we'll return the result even 480 // if it is NULL. If the allocation attempt failed immediately 481 // after a Full GC, it's unlikely we'll be able to allocate now. 482 HeapWord* result = op.result(); 483 if (result != NULL && !is_humongous(word_size)) { 484 // Allocations that take place on VM operations do not do any 485 // card dirtying and we have to do it here. We only have to do 486 // this for non-humongous allocations, though. 487 dirty_young_block(result, word_size); 488 } 489 return result; 490 } else { 491 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 492 return NULL; 493 } 494 assert(op.result() == NULL, 495 "the result should be NULL if the VM op did not succeed"); 496 } 497 498 // Give a warning if we seem to be looping forever. 499 if ((QueuedAllocationWarningCount > 0) && 500 (try_count % QueuedAllocationWarningCount == 0)) { 501 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count); 502 } 503 } 504 505 ShouldNotReachHere(); 506 return NULL; 507 } 508 509 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 510 AllocationContext_t context, 511 uint* gc_count_before_ret, 512 uint* gclocker_retry_count_ret) { 513 // Make sure you read the note in attempt_allocation_humongous(). 514 515 assert_heap_not_locked_and_not_at_safepoint(); 516 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 517 "be called for humongous allocation requests"); 518 519 // We should only get here after the first-level allocation attempt 520 // (attempt_allocation()) failed to allocate. 521 522 // We will loop until a) we manage to successfully perform the 523 // allocation or b) we successfully schedule a collection which 524 // fails to perform the allocation. b) is the only case when we'll 525 // return NULL. 526 HeapWord* result = NULL; 527 for (int try_count = 1; /* we'll return */; try_count += 1) { 528 bool should_try_gc; 529 uint gc_count_before; 530 531 { 532 MutexLockerEx x(Heap_lock); 533 result = _allocator->attempt_allocation_locked(word_size, context); 534 if (result != NULL) { 535 return result; 536 } 537 538 if (GCLocker::is_active_and_needs_gc()) { 539 if (g1_policy()->can_expand_young_list()) { 540 // No need for an ergo verbose message here, 541 // can_expand_young_list() does this when it returns true. 542 result = _allocator->attempt_allocation_force(word_size, context); 543 if (result != NULL) { 544 return result; 545 } 546 } 547 should_try_gc = false; 548 } else { 549 // The GCLocker may not be active but the GCLocker initiated 550 // GC may not yet have been performed (GCLocker::needs_gc() 551 // returns true). In this case we do not try this GC and 552 // wait until the GCLocker initiated GC is performed, and 553 // then retry the allocation. 554 if (GCLocker::needs_gc()) { 555 should_try_gc = false; 556 } else { 557 // Read the GC count while still holding the Heap_lock. 558 gc_count_before = total_collections(); 559 should_try_gc = true; 560 } 561 } 562 } 563 564 if (should_try_gc) { 565 bool succeeded; 566 result = do_collection_pause(word_size, gc_count_before, &succeeded, 567 GCCause::_g1_inc_collection_pause); 568 if (result != NULL) { 569 assert(succeeded, "only way to get back a non-NULL result"); 570 return result; 571 } 572 573 if (succeeded) { 574 // If we get here we successfully scheduled a collection which 575 // failed to allocate. No point in trying to allocate 576 // further. We'll just return NULL. 577 MutexLockerEx x(Heap_lock); 578 *gc_count_before_ret = total_collections(); 579 return NULL; 580 } 581 } else { 582 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 583 MutexLockerEx x(Heap_lock); 584 *gc_count_before_ret = total_collections(); 585 return NULL; 586 } 587 // The GCLocker is either active or the GCLocker initiated 588 // GC has not yet been performed. Stall until it is and 589 // then retry the allocation. 590 GCLocker::stall_until_clear(); 591 (*gclocker_retry_count_ret) += 1; 592 } 593 594 // We can reach here if we were unsuccessful in scheduling a 595 // collection (because another thread beat us to it) or if we were 596 // stalled due to the GC locker. In either can we should retry the 597 // allocation attempt in case another thread successfully 598 // performed a collection and reclaimed enough space. We do the 599 // first attempt (without holding the Heap_lock) here and the 600 // follow-on attempt will be at the start of the next loop 601 // iteration (after taking the Heap_lock). 602 result = _allocator->attempt_allocation(word_size, context); 603 if (result != NULL) { 604 return result; 605 } 606 607 // Give a warning if we seem to be looping forever. 608 if ((QueuedAllocationWarningCount > 0) && 609 (try_count % QueuedAllocationWarningCount == 0)) { 610 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() " 611 "retries %d times", try_count); 612 } 613 } 614 615 ShouldNotReachHere(); 616 return NULL; 617 } 618 619 void G1CollectedHeap::begin_archive_alloc_range(bool open) { 620 assert_at_safepoint(true /* should_be_vm_thread */); 621 if (_archive_allocator == NULL) { 622 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open); 623 } 624 } 625 626 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 627 // Allocations in archive regions cannot be of a size that would be considered 628 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 629 // may be different at archive-restore time. 630 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 631 } 632 633 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 634 assert_at_safepoint(true /* should_be_vm_thread */); 635 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 636 if (is_archive_alloc_too_large(word_size)) { 637 return NULL; 638 } 639 return _archive_allocator->archive_mem_allocate(word_size); 640 } 641 642 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 643 size_t end_alignment_in_bytes) { 644 assert_at_safepoint(true /* should_be_vm_thread */); 645 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 646 647 // Call complete_archive to do the real work, filling in the MemRegion 648 // array with the archive regions. 649 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 650 delete _archive_allocator; 651 _archive_allocator = NULL; 652 } 653 654 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 655 assert(ranges != NULL, "MemRegion array NULL"); 656 assert(count != 0, "No MemRegions provided"); 657 MemRegion reserved = _hrm.reserved(); 658 for (size_t i = 0; i < count; i++) { 659 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 660 return false; 661 } 662 } 663 return true; 664 } 665 666 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, 667 size_t count, 668 bool open) { 669 assert(!is_init_completed(), "Expect to be called at JVM init time"); 670 assert(ranges != NULL, "MemRegion array NULL"); 671 assert(count != 0, "No MemRegions provided"); 672 MutexLockerEx x(Heap_lock); 673 674 MemRegion reserved = _hrm.reserved(); 675 HeapWord* prev_last_addr = NULL; 676 HeapRegion* prev_last_region = NULL; 677 678 // Temporarily disable pretouching of heap pages. This interface is used 679 // when mmap'ing archived heap data in, so pre-touching is wasted. 680 FlagSetting fs(AlwaysPreTouch, false); 681 682 // Enable archive object checking used by G1MarkSweep. We have to let it know 683 // about each archive range, so that objects in those ranges aren't marked. 684 G1ArchiveAllocator::enable_archive_object_check(); 685 686 // For each specified MemRegion range, allocate the corresponding G1 687 // regions and mark them as archive regions. We expect the ranges 688 // in ascending starting address order, without overlap. 689 for (size_t i = 0; i < count; i++) { 690 MemRegion curr_range = ranges[i]; 691 HeapWord* start_address = curr_range.start(); 692 size_t word_size = curr_range.word_size(); 693 HeapWord* last_address = curr_range.last(); 694 size_t commits = 0; 695 696 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 697 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 698 p2i(start_address), p2i(last_address)); 699 guarantee(start_address > prev_last_addr, 700 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 701 p2i(start_address), p2i(prev_last_addr)); 702 prev_last_addr = last_address; 703 704 // Check for ranges that start in the same G1 region in which the previous 705 // range ended, and adjust the start address so we don't try to allocate 706 // the same region again. If the current range is entirely within that 707 // region, skip it, just adjusting the recorded top. 708 HeapRegion* start_region = _hrm.addr_to_region(start_address); 709 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 710 start_address = start_region->end(); 711 if (start_address > last_address) { 712 increase_used(word_size * HeapWordSize); 713 start_region->set_top(last_address + 1); 714 continue; 715 } 716 start_region->set_top(start_address); 717 curr_range = MemRegion(start_address, last_address + 1); 718 start_region = _hrm.addr_to_region(start_address); 719 } 720 721 // Perform the actual region allocation, exiting if it fails. 722 // Then note how much new space we have allocated. 723 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 724 return false; 725 } 726 increase_used(word_size * HeapWordSize); 727 if (commits != 0) { 728 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 729 HeapRegion::GrainWords * HeapWordSize * commits); 730 731 } 732 733 // Mark each G1 region touched by the range as archive, add it to 734 // the old set, and set the allocation context and top. 735 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 736 HeapRegion* last_region = _hrm.addr_to_region(last_address); 737 prev_last_region = last_region; 738 739 while (curr_region != NULL) { 740 assert(curr_region->is_empty() && !curr_region->is_pinned(), 741 "Region already in use (index %u)", curr_region->hrm_index()); 742 curr_region->set_allocation_context(AllocationContext::system()); 743 if (open) { 744 curr_region->set_open_archive(); 745 } else { 746 curr_region->set_closed_archive(); 747 } 748 _hr_printer.alloc(curr_region); 749 _old_set.add(curr_region); 750 HeapWord* top; 751 HeapRegion* next_region; 752 if (curr_region != last_region) { 753 top = curr_region->end(); 754 next_region = _hrm.next_region_in_heap(curr_region); 755 } else { 756 top = last_address + 1; 757 next_region = NULL; 758 } 759 curr_region->set_top(top); 760 curr_region->set_first_dead(top); 761 curr_region->set_end_of_live(top); 762 curr_region = next_region; 763 } 764 765 // Notify mark-sweep of the archive 766 G1ArchiveAllocator::set_range_archive(curr_range, open); 767 } 768 return true; 769 } 770 771 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 772 assert(!is_init_completed(), "Expect to be called at JVM init time"); 773 assert(ranges != NULL, "MemRegion array NULL"); 774 assert(count != 0, "No MemRegions provided"); 775 MemRegion reserved = _hrm.reserved(); 776 HeapWord *prev_last_addr = NULL; 777 HeapRegion* prev_last_region = NULL; 778 779 // For each MemRegion, create filler objects, if needed, in the G1 regions 780 // that contain the address range. The address range actually within the 781 // MemRegion will not be modified. That is assumed to have been initialized 782 // elsewhere, probably via an mmap of archived heap data. 783 MutexLockerEx x(Heap_lock); 784 for (size_t i = 0; i < count; i++) { 785 HeapWord* start_address = ranges[i].start(); 786 HeapWord* last_address = ranges[i].last(); 787 788 assert(reserved.contains(start_address) && reserved.contains(last_address), 789 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 790 p2i(start_address), p2i(last_address)); 791 assert(start_address > prev_last_addr, 792 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 793 p2i(start_address), p2i(prev_last_addr)); 794 795 HeapRegion* start_region = _hrm.addr_to_region(start_address); 796 HeapRegion* last_region = _hrm.addr_to_region(last_address); 797 HeapWord* bottom_address = start_region->bottom(); 798 799 // Check for a range beginning in the same region in which the 800 // previous one ended. 801 if (start_region == prev_last_region) { 802 bottom_address = prev_last_addr + 1; 803 } 804 805 // Verify that the regions were all marked as archive regions by 806 // alloc_archive_regions. 807 HeapRegion* curr_region = start_region; 808 while (curr_region != NULL) { 809 guarantee(curr_region->is_archive(), 810 "Expected archive region at index %u", curr_region->hrm_index()); 811 if (curr_region != last_region) { 812 curr_region = _hrm.next_region_in_heap(curr_region); 813 } else { 814 curr_region = NULL; 815 } 816 } 817 818 prev_last_addr = last_address; 819 prev_last_region = last_region; 820 821 // Fill the memory below the allocated range with dummy object(s), 822 // if the region bottom does not match the range start, or if the previous 823 // range ended within the same G1 region, and there is a gap. 824 if (start_address != bottom_address) { 825 size_t fill_size = pointer_delta(start_address, bottom_address); 826 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 827 increase_used(fill_size * HeapWordSize); 828 } 829 } 830 } 831 832 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 833 uint* gc_count_before_ret, 834 uint* gclocker_retry_count_ret) { 835 assert_heap_not_locked_and_not_at_safepoint(); 836 assert(!is_humongous(word_size), "attempt_allocation() should not " 837 "be called for humongous allocation requests"); 838 839 AllocationContext_t context = AllocationContext::current(); 840 HeapWord* result = _allocator->attempt_allocation(word_size, context); 841 842 if (result == NULL) { 843 result = attempt_allocation_slow(word_size, 844 context, 845 gc_count_before_ret, 846 gclocker_retry_count_ret); 847 } 848 assert_heap_not_locked(); 849 if (result != NULL) { 850 dirty_young_block(result, word_size); 851 } 852 return result; 853 } 854 855 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 856 assert(!is_init_completed(), "Expect to be called at JVM init time"); 857 assert(ranges != NULL, "MemRegion array NULL"); 858 assert(count != 0, "No MemRegions provided"); 859 MemRegion reserved = _hrm.reserved(); 860 HeapWord* prev_last_addr = NULL; 861 HeapRegion* prev_last_region = NULL; 862 size_t size_used = 0; 863 size_t uncommitted_regions = 0; 864 865 // For each Memregion, free the G1 regions that constitute it, and 866 // notify mark-sweep that the range is no longer to be considered 'archive.' 867 MutexLockerEx x(Heap_lock); 868 for (size_t i = 0; i < count; i++) { 869 HeapWord* start_address = ranges[i].start(); 870 HeapWord* last_address = ranges[i].last(); 871 872 assert(reserved.contains(start_address) && reserved.contains(last_address), 873 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 874 p2i(start_address), p2i(last_address)); 875 assert(start_address > prev_last_addr, 876 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 877 p2i(start_address), p2i(prev_last_addr)); 878 size_used += ranges[i].byte_size(); 879 prev_last_addr = last_address; 880 881 HeapRegion* start_region = _hrm.addr_to_region(start_address); 882 HeapRegion* last_region = _hrm.addr_to_region(last_address); 883 884 // Check for ranges that start in the same G1 region in which the previous 885 // range ended, and adjust the start address so we don't try to free 886 // the same region again. If the current range is entirely within that 887 // region, skip it. 888 if (start_region == prev_last_region) { 889 start_address = start_region->end(); 890 if (start_address > last_address) { 891 continue; 892 } 893 start_region = _hrm.addr_to_region(start_address); 894 } 895 prev_last_region = last_region; 896 897 // After verifying that each region was marked as an archive region by 898 // alloc_archive_regions, set it free and empty and uncommit it. 899 HeapRegion* curr_region = start_region; 900 while (curr_region != NULL) { 901 guarantee(curr_region->is_archive(), 902 "Expected archive region at index %u", curr_region->hrm_index()); 903 uint curr_index = curr_region->hrm_index(); 904 _old_set.remove(curr_region); 905 curr_region->set_free(); 906 curr_region->set_top(curr_region->bottom()); 907 if (curr_region != last_region) { 908 curr_region = _hrm.next_region_in_heap(curr_region); 909 } else { 910 curr_region = NULL; 911 } 912 _hrm.shrink_at(curr_index, 1); 913 uncommitted_regions++; 914 } 915 916 // Notify mark-sweep that this is no longer an archive range. 917 G1ArchiveAllocator::set_range_archive(ranges[i], false); 918 } 919 920 if (uncommitted_regions != 0) { 921 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 922 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 923 } 924 decrease_used(size_used); 925 } 926 927 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 928 uint* gc_count_before_ret, 929 uint* gclocker_retry_count_ret) { 930 // The structure of this method has a lot of similarities to 931 // attempt_allocation_slow(). The reason these two were not merged 932 // into a single one is that such a method would require several "if 933 // allocation is not humongous do this, otherwise do that" 934 // conditional paths which would obscure its flow. In fact, an early 935 // version of this code did use a unified method which was harder to 936 // follow and, as a result, it had subtle bugs that were hard to 937 // track down. So keeping these two methods separate allows each to 938 // be more readable. It will be good to keep these two in sync as 939 // much as possible. 940 941 assert_heap_not_locked_and_not_at_safepoint(); 942 assert(is_humongous(word_size), "attempt_allocation_humongous() " 943 "should only be called for humongous allocations"); 944 945 // Humongous objects can exhaust the heap quickly, so we should check if we 946 // need to start a marking cycle at each humongous object allocation. We do 947 // the check before we do the actual allocation. The reason for doing it 948 // before the allocation is that we avoid having to keep track of the newly 949 // allocated memory while we do a GC. 950 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 951 word_size)) { 952 collect(GCCause::_g1_humongous_allocation); 953 } 954 955 // We will loop until a) we manage to successfully perform the 956 // allocation or b) we successfully schedule a collection which 957 // fails to perform the allocation. b) is the only case when we'll 958 // return NULL. 959 HeapWord* result = NULL; 960 for (int try_count = 1; /* we'll return */; try_count += 1) { 961 bool should_try_gc; 962 uint gc_count_before; 963 964 { 965 MutexLockerEx x(Heap_lock); 966 967 // Given that humongous objects are not allocated in young 968 // regions, we'll first try to do the allocation without doing a 969 // collection hoping that there's enough space in the heap. 970 result = humongous_obj_allocate(word_size, AllocationContext::current()); 971 if (result != NULL) { 972 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 973 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 974 return result; 975 } 976 977 if (GCLocker::is_active_and_needs_gc()) { 978 should_try_gc = false; 979 } else { 980 // The GCLocker may not be active but the GCLocker initiated 981 // GC may not yet have been performed (GCLocker::needs_gc() 982 // returns true). In this case we do not try this GC and 983 // wait until the GCLocker initiated GC is performed, and 984 // then retry the allocation. 985 if (GCLocker::needs_gc()) { 986 should_try_gc = false; 987 } else { 988 // Read the GC count while still holding the Heap_lock. 989 gc_count_before = total_collections(); 990 should_try_gc = true; 991 } 992 } 993 } 994 995 if (should_try_gc) { 996 // If we failed to allocate the humongous object, we should try to 997 // do a collection pause (if we're allowed) in case it reclaims 998 // enough space for the allocation to succeed after the pause. 999 1000 bool succeeded; 1001 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1002 GCCause::_g1_humongous_allocation); 1003 if (result != NULL) { 1004 assert(succeeded, "only way to get back a non-NULL result"); 1005 return result; 1006 } 1007 1008 if (succeeded) { 1009 // If we get here we successfully scheduled a collection which 1010 // failed to allocate. No point in trying to allocate 1011 // further. We'll just return NULL. 1012 MutexLockerEx x(Heap_lock); 1013 *gc_count_before_ret = total_collections(); 1014 return NULL; 1015 } 1016 } else { 1017 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1018 MutexLockerEx x(Heap_lock); 1019 *gc_count_before_ret = total_collections(); 1020 return NULL; 1021 } 1022 // The GCLocker is either active or the GCLocker initiated 1023 // GC has not yet been performed. Stall until it is and 1024 // then retry the allocation. 1025 GCLocker::stall_until_clear(); 1026 (*gclocker_retry_count_ret) += 1; 1027 } 1028 1029 // We can reach here if we were unsuccessful in scheduling a 1030 // collection (because another thread beat us to it) or if we were 1031 // stalled due to the GC locker. In either can we should retry the 1032 // allocation attempt in case another thread successfully 1033 // performed a collection and reclaimed enough space. Give a 1034 // warning if we seem to be looping forever. 1035 1036 if ((QueuedAllocationWarningCount > 0) && 1037 (try_count % QueuedAllocationWarningCount == 0)) { 1038 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() " 1039 "retries %d times", try_count); 1040 } 1041 } 1042 1043 ShouldNotReachHere(); 1044 return NULL; 1045 } 1046 1047 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1048 AllocationContext_t context, 1049 bool expect_null_mutator_alloc_region) { 1050 assert_at_safepoint(true /* should_be_vm_thread */); 1051 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1052 "the current alloc region was unexpectedly found to be non-NULL"); 1053 1054 if (!is_humongous(word_size)) { 1055 return _allocator->attempt_allocation_locked(word_size, context); 1056 } else { 1057 HeapWord* result = humongous_obj_allocate(word_size, context); 1058 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1059 collector_state()->set_initiate_conc_mark_if_possible(true); 1060 } 1061 return result; 1062 } 1063 1064 ShouldNotReachHere(); 1065 } 1066 1067 class PostCompactionPrinterClosure: public HeapRegionClosure { 1068 private: 1069 G1HRPrinter* _hr_printer; 1070 public: 1071 bool doHeapRegion(HeapRegion* hr) { 1072 assert(!hr->is_young(), "not expecting to find young regions"); 1073 _hr_printer->post_compaction(hr); 1074 return false; 1075 } 1076 1077 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1078 : _hr_printer(hr_printer) { } 1079 }; 1080 1081 void G1CollectedHeap::print_hrm_post_compaction() { 1082 if (_hr_printer.is_active()) { 1083 PostCompactionPrinterClosure cl(hr_printer()); 1084 heap_region_iterate(&cl); 1085 } 1086 1087 } 1088 1089 void G1CollectedHeap::abort_concurrent_cycle() { 1090 // Note: When we have a more flexible GC logging framework that 1091 // allows us to add optional attributes to a GC log record we 1092 // could consider timing and reporting how long we wait in the 1093 // following two methods. 1094 wait_while_free_regions_coming(); 1095 // If we start the compaction before the CM threads finish 1096 // scanning the root regions we might trip them over as we'll 1097 // be moving objects / updating references. So let's wait until 1098 // they are done. By telling them to abort, they should complete 1099 // early. 1100 _cm->root_regions()->abort(); 1101 _cm->root_regions()->wait_until_scan_finished(); 1102 append_secondary_free_list_if_not_empty_with_lock(); 1103 1104 // Disable discovery and empty the discovered lists 1105 // for the CM ref processor. 1106 ref_processor_cm()->disable_discovery(); 1107 ref_processor_cm()->abandon_partial_discovery(); 1108 ref_processor_cm()->verify_no_references_recorded(); 1109 1110 // Abandon current iterations of concurrent marking and concurrent 1111 // refinement, if any are in progress. 1112 concurrent_mark()->abort(); 1113 } 1114 1115 void G1CollectedHeap::prepare_heap_for_full_collection() { 1116 // Make sure we'll choose a new allocation region afterwards. 1117 _allocator->release_mutator_alloc_region(); 1118 _allocator->abandon_gc_alloc_regions(); 1119 g1_rem_set()->cleanupHRRS(); 1120 1121 // We may have added regions to the current incremental collection 1122 // set between the last GC or pause and now. We need to clear the 1123 // incremental collection set and then start rebuilding it afresh 1124 // after this full GC. 1125 abandon_collection_set(collection_set()); 1126 1127 tear_down_region_sets(false /* free_list_only */); 1128 collector_state()->set_gcs_are_young(true); 1129 } 1130 1131 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1132 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1133 assert(used() == recalculate_used(), "Should be equal"); 1134 _verifier->verify_region_sets_optional(); 1135 _verifier->verify_before_gc(); 1136 _verifier->check_bitmaps("Full GC Start"); 1137 } 1138 1139 void G1CollectedHeap::prepare_heap_for_mutators() { 1140 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1141 ClassLoaderDataGraph::purge(); 1142 MetaspaceAux::verify_metrics(); 1143 1144 // Prepare heap for normal collections. 1145 assert(num_free_regions() == 0, "we should not have added any free regions"); 1146 rebuild_region_sets(false /* free_list_only */); 1147 abort_refinement(); 1148 resize_if_necessary_after_full_collection(); 1149 1150 // Rebuild the strong code root lists for each region 1151 rebuild_strong_code_roots(); 1152 1153 // Start a new incremental collection set for the next pause 1154 start_new_collection_set(); 1155 1156 _allocator->init_mutator_alloc_region(); 1157 1158 // Post collection state updates. 1159 MetaspaceGC::compute_new_size(); 1160 } 1161 1162 void G1CollectedHeap::abort_refinement() { 1163 if (_hot_card_cache->use_cache()) { 1164 _hot_card_cache->reset_hot_cache(); 1165 } 1166 1167 // Discard all remembered set updates. 1168 JavaThread::dirty_card_queue_set().abandon_logs(); 1169 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1170 } 1171 1172 void G1CollectedHeap::verify_after_full_collection() { 1173 check_gc_time_stamps(); 1174 _hrm.verify_optional(); 1175 _verifier->verify_region_sets_optional(); 1176 _verifier->verify_after_gc(); 1177 // Clear the previous marking bitmap, if needed for bitmap verification. 1178 // Note we cannot do this when we clear the next marking bitmap in 1179 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1180 // objects marked during a full GC against the previous bitmap. 1181 // But we need to clear it before calling check_bitmaps below since 1182 // the full GC has compacted objects and updated TAMS but not updated 1183 // the prev bitmap. 1184 if (G1VerifyBitmaps) { 1185 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1186 _cm->clear_prev_bitmap(workers()); 1187 } 1188 _verifier->check_bitmaps("Full GC End"); 1189 1190 // At this point there should be no regions in the 1191 // entire heap tagged as young. 1192 assert(check_young_list_empty(), "young list should be empty at this point"); 1193 1194 // Note: since we've just done a full GC, concurrent 1195 // marking is no longer active. Therefore we need not 1196 // re-enable reference discovery for the CM ref processor. 1197 // That will be done at the start of the next marking cycle. 1198 // We also know that the STW processor should no longer 1199 // discover any new references. 1200 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1201 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1202 ref_processor_stw()->verify_no_references_recorded(); 1203 ref_processor_cm()->verify_no_references_recorded(); 1204 } 1205 1206 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1207 // Post collection logging. 1208 // We should do this after we potentially resize the heap so 1209 // that all the COMMIT / UNCOMMIT events are generated before 1210 // the compaction events. 1211 print_hrm_post_compaction(); 1212 heap_transition->print(); 1213 print_heap_after_gc(); 1214 print_heap_regions(); 1215 #ifdef TRACESPINNING 1216 ParallelTaskTerminator::print_termination_counts(); 1217 #endif 1218 } 1219 1220 void G1CollectedHeap::do_full_collection_inner(G1FullGCScope* scope) { 1221 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1222 g1_policy()->record_full_collection_start(); 1223 1224 print_heap_before_gc(); 1225 print_heap_regions(); 1226 1227 abort_concurrent_cycle(); 1228 verify_before_full_collection(scope->is_explicit_gc()); 1229 1230 gc_prologue(true); 1231 prepare_heap_for_full_collection(); 1232 1233 G1FullCollector collector(scope, ref_processor_stw(), concurrent_mark()->next_mark_bitmap(), workers()->active_workers()); 1234 collector.prepare_collection(); 1235 collector.collect(); 1236 collector.complete_collection(); 1237 1238 prepare_heap_for_mutators(); 1239 1240 g1_policy()->record_full_collection_end(); 1241 gc_epilogue(true); 1242 1243 verify_after_full_collection(); 1244 1245 print_heap_after_full_collection(scope->heap_transition()); 1246 } 1247 1248 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1249 bool clear_all_soft_refs) { 1250 assert_at_safepoint(true /* should_be_vm_thread */); 1251 1252 if (GCLocker::check_active_before_gc()) { 1253 // Full GC was not completed. 1254 return false; 1255 } 1256 1257 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1258 collector_policy()->should_clear_all_soft_refs(); 1259 1260 G1FullGCScope scope(explicit_gc, do_clear_all_soft_refs); 1261 do_full_collection_inner(&scope); 1262 1263 // Full collection was successfully completed. 1264 return true; 1265 } 1266 1267 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1268 // Currently, there is no facility in the do_full_collection(bool) API to notify 1269 // the caller that the collection did not succeed (e.g., because it was locked 1270 // out by the GC locker). So, right now, we'll ignore the return value. 1271 bool dummy = do_full_collection(true, /* explicit_gc */ 1272 clear_all_soft_refs); 1273 } 1274 1275 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1276 // Capacity, free and used after the GC counted as full regions to 1277 // include the waste in the following calculations. 1278 const size_t capacity_after_gc = capacity(); 1279 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes(); 1280 1281 // This is enforced in arguments.cpp. 1282 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1283 "otherwise the code below doesn't make sense"); 1284 1285 // We don't have floating point command-line arguments 1286 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1287 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1288 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1289 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1290 1291 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1292 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1293 1294 // We have to be careful here as these two calculations can overflow 1295 // 32-bit size_t's. 1296 double used_after_gc_d = (double) used_after_gc; 1297 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1298 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1299 1300 // Let's make sure that they are both under the max heap size, which 1301 // by default will make them fit into a size_t. 1302 double desired_capacity_upper_bound = (double) max_heap_size; 1303 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1304 desired_capacity_upper_bound); 1305 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1306 desired_capacity_upper_bound); 1307 1308 // We can now safely turn them into size_t's. 1309 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1310 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1311 1312 // This assert only makes sense here, before we adjust them 1313 // with respect to the min and max heap size. 1314 assert(minimum_desired_capacity <= maximum_desired_capacity, 1315 "minimum_desired_capacity = " SIZE_FORMAT ", " 1316 "maximum_desired_capacity = " SIZE_FORMAT, 1317 minimum_desired_capacity, maximum_desired_capacity); 1318 1319 // Should not be greater than the heap max size. No need to adjust 1320 // it with respect to the heap min size as it's a lower bound (i.e., 1321 // we'll try to make the capacity larger than it, not smaller). 1322 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1323 // Should not be less than the heap min size. No need to adjust it 1324 // with respect to the heap max size as it's an upper bound (i.e., 1325 // we'll try to make the capacity smaller than it, not greater). 1326 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1327 1328 if (capacity_after_gc < minimum_desired_capacity) { 1329 // Don't expand unless it's significant 1330 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1331 1332 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1333 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1334 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1335 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio); 1336 1337 expand(expand_bytes, _workers); 1338 1339 // No expansion, now see if we want to shrink 1340 } else if (capacity_after_gc > maximum_desired_capacity) { 1341 // Capacity too large, compute shrinking size 1342 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1343 1344 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1345 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1346 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1347 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio); 1348 1349 shrink(shrink_bytes); 1350 } 1351 } 1352 1353 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1354 AllocationContext_t context, 1355 bool do_gc, 1356 bool clear_all_soft_refs, 1357 bool expect_null_mutator_alloc_region, 1358 bool* gc_succeeded) { 1359 *gc_succeeded = true; 1360 // Let's attempt the allocation first. 1361 HeapWord* result = 1362 attempt_allocation_at_safepoint(word_size, 1363 context, 1364 expect_null_mutator_alloc_region); 1365 if (result != NULL) { 1366 assert(*gc_succeeded, "sanity"); 1367 return result; 1368 } 1369 1370 // In a G1 heap, we're supposed to keep allocation from failing by 1371 // incremental pauses. Therefore, at least for now, we'll favor 1372 // expansion over collection. (This might change in the future if we can 1373 // do something smarter than full collection to satisfy a failed alloc.) 1374 result = expand_and_allocate(word_size, context); 1375 if (result != NULL) { 1376 assert(*gc_succeeded, "sanity"); 1377 return result; 1378 } 1379 1380 if (do_gc) { 1381 // Expansion didn't work, we'll try to do a Full GC. 1382 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1383 clear_all_soft_refs); 1384 } 1385 1386 return NULL; 1387 } 1388 1389 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1390 AllocationContext_t context, 1391 bool* succeeded) { 1392 assert_at_safepoint(true /* should_be_vm_thread */); 1393 1394 // Attempts to allocate followed by Full GC. 1395 HeapWord* result = 1396 satisfy_failed_allocation_helper(word_size, 1397 context, 1398 true, /* do_gc */ 1399 false, /* clear_all_soft_refs */ 1400 false, /* expect_null_mutator_alloc_region */ 1401 succeeded); 1402 1403 if (result != NULL || !*succeeded) { 1404 return result; 1405 } 1406 1407 // Attempts to allocate followed by Full GC that will collect all soft references. 1408 result = satisfy_failed_allocation_helper(word_size, 1409 context, 1410 true, /* do_gc */ 1411 true, /* clear_all_soft_refs */ 1412 true, /* expect_null_mutator_alloc_region */ 1413 succeeded); 1414 1415 if (result != NULL || !*succeeded) { 1416 return result; 1417 } 1418 1419 // Attempts to allocate, no GC 1420 result = satisfy_failed_allocation_helper(word_size, 1421 context, 1422 false, /* do_gc */ 1423 false, /* clear_all_soft_refs */ 1424 true, /* expect_null_mutator_alloc_region */ 1425 succeeded); 1426 1427 if (result != NULL) { 1428 assert(*succeeded, "sanity"); 1429 return result; 1430 } 1431 1432 assert(!collector_policy()->should_clear_all_soft_refs(), 1433 "Flag should have been handled and cleared prior to this point"); 1434 1435 // What else? We might try synchronous finalization later. If the total 1436 // space available is large enough for the allocation, then a more 1437 // complete compaction phase than we've tried so far might be 1438 // appropriate. 1439 assert(*succeeded, "sanity"); 1440 return NULL; 1441 } 1442 1443 // Attempting to expand the heap sufficiently 1444 // to support an allocation of the given "word_size". If 1445 // successful, perform the allocation and return the address of the 1446 // allocated block, or else "NULL". 1447 1448 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1449 assert_at_safepoint(true /* should_be_vm_thread */); 1450 1451 _verifier->verify_region_sets_optional(); 1452 1453 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1454 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1455 word_size * HeapWordSize); 1456 1457 1458 if (expand(expand_bytes, _workers)) { 1459 _hrm.verify_optional(); 1460 _verifier->verify_region_sets_optional(); 1461 return attempt_allocation_at_safepoint(word_size, 1462 context, 1463 false /* expect_null_mutator_alloc_region */); 1464 } 1465 return NULL; 1466 } 1467 1468 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1469 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1470 aligned_expand_bytes = align_up(aligned_expand_bytes, 1471 HeapRegion::GrainBytes); 1472 1473 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1474 expand_bytes, aligned_expand_bytes); 1475 1476 if (is_maximal_no_gc()) { 1477 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1478 return false; 1479 } 1480 1481 double expand_heap_start_time_sec = os::elapsedTime(); 1482 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1483 assert(regions_to_expand > 0, "Must expand by at least one region"); 1484 1485 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers); 1486 if (expand_time_ms != NULL) { 1487 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1488 } 1489 1490 if (expanded_by > 0) { 1491 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1492 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1493 g1_policy()->record_new_heap_size(num_regions()); 1494 } else { 1495 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1496 1497 // The expansion of the virtual storage space was unsuccessful. 1498 // Let's see if it was because we ran out of swap. 1499 if (G1ExitOnExpansionFailure && 1500 _hrm.available() >= regions_to_expand) { 1501 // We had head room... 1502 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1503 } 1504 } 1505 return regions_to_expand > 0; 1506 } 1507 1508 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1509 size_t aligned_shrink_bytes = 1510 ReservedSpace::page_align_size_down(shrink_bytes); 1511 aligned_shrink_bytes = align_down(aligned_shrink_bytes, 1512 HeapRegion::GrainBytes); 1513 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1514 1515 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1516 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1517 1518 1519 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", 1520 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1521 if (num_regions_removed > 0) { 1522 g1_policy()->record_new_heap_size(num_regions()); 1523 } else { 1524 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1525 } 1526 } 1527 1528 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1529 _verifier->verify_region_sets_optional(); 1530 1531 // We should only reach here at the end of a Full GC which means we 1532 // should not not be holding to any GC alloc regions. The method 1533 // below will make sure of that and do any remaining clean up. 1534 _allocator->abandon_gc_alloc_regions(); 1535 1536 // Instead of tearing down / rebuilding the free lists here, we 1537 // could instead use the remove_all_pending() method on free_list to 1538 // remove only the ones that we need to remove. 1539 tear_down_region_sets(true /* free_list_only */); 1540 shrink_helper(shrink_bytes); 1541 rebuild_region_sets(true /* free_list_only */); 1542 1543 _hrm.verify_optional(); 1544 _verifier->verify_region_sets_optional(); 1545 } 1546 1547 // Public methods. 1548 1549 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1550 CollectedHeap(), 1551 _young_gen_sampling_thread(NULL), 1552 _collector_policy(collector_policy), 1553 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1554 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1555 _g1_policy(create_g1_policy(_gc_timer_stw)), 1556 _collection_set(this, _g1_policy), 1557 _dirty_card_queue_set(false), 1558 _is_alive_closure_cm(this), 1559 _is_alive_closure_stw(this), 1560 _ref_processor_cm(NULL), 1561 _ref_processor_stw(NULL), 1562 _bot(NULL), 1563 _hot_card_cache(NULL), 1564 _g1_rem_set(NULL), 1565 _cr(NULL), 1566 _g1mm(NULL), 1567 _preserved_marks_set(true /* in_c_heap */), 1568 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1569 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1570 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1571 _humongous_reclaim_candidates(), 1572 _has_humongous_reclaim_candidates(false), 1573 _archive_allocator(NULL), 1574 _free_regions_coming(false), 1575 _gc_time_stamp(0), 1576 _summary_bytes_used(0), 1577 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1578 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1579 _expand_heap_after_alloc_failure(true), 1580 _old_marking_cycles_started(0), 1581 _old_marking_cycles_completed(0), 1582 _in_cset_fast_test() { 1583 1584 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1585 /* are_GC_task_threads */true, 1586 /* are_ConcurrentGC_threads */false); 1587 _workers->initialize_workers(); 1588 _verifier = new G1HeapVerifier(this); 1589 1590 _allocator = G1Allocator::create_allocator(this); 1591 1592 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1593 1594 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1595 1596 // Override the default _filler_array_max_size so that no humongous filler 1597 // objects are created. 1598 _filler_array_max_size = _humongous_object_threshold_in_words; 1599 1600 uint n_queues = ParallelGCThreads; 1601 _task_queues = new RefToScanQueueSet(n_queues); 1602 1603 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1604 1605 for (uint i = 0; i < n_queues; i++) { 1606 RefToScanQueue* q = new RefToScanQueue(); 1607 q->initialize(); 1608 _task_queues->register_queue(i, q); 1609 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1610 } 1611 1612 // Initialize the G1EvacuationFailureALot counters and flags. 1613 NOT_PRODUCT(reset_evacuation_should_fail();) 1614 1615 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1616 } 1617 1618 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1619 size_t size, 1620 size_t translation_factor) { 1621 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1622 // Allocate a new reserved space, preferring to use large pages. 1623 ReservedSpace rs(size, preferred_page_size); 1624 G1RegionToSpaceMapper* result = 1625 G1RegionToSpaceMapper::create_mapper(rs, 1626 size, 1627 rs.alignment(), 1628 HeapRegion::GrainBytes, 1629 translation_factor, 1630 mtGC); 1631 1632 os::trace_page_sizes_for_requested_size(description, 1633 size, 1634 preferred_page_size, 1635 rs.alignment(), 1636 rs.base(), 1637 rs.size()); 1638 1639 return result; 1640 } 1641 1642 jint G1CollectedHeap::initialize_concurrent_refinement() { 1643 jint ecode = JNI_OK; 1644 _cr = G1ConcurrentRefine::create(&ecode); 1645 return ecode; 1646 } 1647 1648 jint G1CollectedHeap::initialize_young_gen_sampling_thread() { 1649 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread(); 1650 if (_young_gen_sampling_thread->osthread() == NULL) { 1651 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread"); 1652 return JNI_ENOMEM; 1653 } 1654 return JNI_OK; 1655 } 1656 1657 jint G1CollectedHeap::initialize() { 1658 CollectedHeap::pre_initialize(); 1659 os::enable_vtime(); 1660 1661 // Necessary to satisfy locking discipline assertions. 1662 1663 MutexLocker x(Heap_lock); 1664 1665 // While there are no constraints in the GC code that HeapWordSize 1666 // be any particular value, there are multiple other areas in the 1667 // system which believe this to be true (e.g. oop->object_size in some 1668 // cases incorrectly returns the size in wordSize units rather than 1669 // HeapWordSize). 1670 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1671 1672 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1673 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1674 size_t heap_alignment = collector_policy()->heap_alignment(); 1675 1676 // Ensure that the sizes are properly aligned. 1677 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1678 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1679 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1680 1681 // Reserve the maximum. 1682 1683 // When compressed oops are enabled, the preferred heap base 1684 // is calculated by subtracting the requested size from the 1685 // 32Gb boundary and using the result as the base address for 1686 // heap reservation. If the requested size is not aligned to 1687 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1688 // into the ReservedHeapSpace constructor) then the actual 1689 // base of the reserved heap may end up differing from the 1690 // address that was requested (i.e. the preferred heap base). 1691 // If this happens then we could end up using a non-optimal 1692 // compressed oops mode. 1693 1694 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1695 heap_alignment); 1696 1697 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1698 1699 // Create the barrier set for the entire reserved region. 1700 G1SATBCardTableLoggingModRefBS* bs 1701 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1702 bs->initialize(); 1703 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1704 set_barrier_set(bs); 1705 1706 // Create the hot card cache. 1707 _hot_card_cache = new G1HotCardCache(this); 1708 1709 // Carve out the G1 part of the heap. 1710 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1711 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1712 G1RegionToSpaceMapper* heap_storage = 1713 G1RegionToSpaceMapper::create_mapper(g1_rs, 1714 g1_rs.size(), 1715 page_size, 1716 HeapRegion::GrainBytes, 1717 1, 1718 mtJavaHeap); 1719 os::trace_page_sizes("Heap", 1720 collector_policy()->min_heap_byte_size(), 1721 max_byte_size, 1722 page_size, 1723 heap_rs.base(), 1724 heap_rs.size()); 1725 heap_storage->set_mapping_changed_listener(&_listener); 1726 1727 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1728 G1RegionToSpaceMapper* bot_storage = 1729 create_aux_memory_mapper("Block Offset Table", 1730 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1731 G1BlockOffsetTable::heap_map_factor()); 1732 1733 G1RegionToSpaceMapper* cardtable_storage = 1734 create_aux_memory_mapper("Card Table", 1735 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1736 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1737 1738 G1RegionToSpaceMapper* card_counts_storage = 1739 create_aux_memory_mapper("Card Counts Table", 1740 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1741 G1CardCounts::heap_map_factor()); 1742 1743 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1744 G1RegionToSpaceMapper* prev_bitmap_storage = 1745 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1746 G1RegionToSpaceMapper* next_bitmap_storage = 1747 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1748 1749 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1750 g1_barrier_set()->initialize(cardtable_storage); 1751 // Do later initialization work for concurrent refinement. 1752 _hot_card_cache->initialize(card_counts_storage); 1753 1754 // 6843694 - ensure that the maximum region index can fit 1755 // in the remembered set structures. 1756 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1757 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1758 1759 // Also create a G1 rem set. 1760 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache); 1761 _g1_rem_set->initialize(max_capacity(), max_regions()); 1762 1763 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1764 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1765 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1766 "too many cards per region"); 1767 1768 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1769 1770 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1771 1772 { 1773 HeapWord* start = _hrm.reserved().start(); 1774 HeapWord* end = _hrm.reserved().end(); 1775 size_t granularity = HeapRegion::GrainBytes; 1776 1777 _in_cset_fast_test.initialize(start, end, granularity); 1778 _humongous_reclaim_candidates.initialize(start, end, granularity); 1779 } 1780 1781 // Create the G1ConcurrentMark data structure and thread. 1782 // (Must do this late, so that "max_regions" is defined.) 1783 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1784 if (_cm == NULL || !_cm->completed_initialization()) { 1785 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1786 return JNI_ENOMEM; 1787 } 1788 _cmThread = _cm->cm_thread(); 1789 1790 // Now expand into the initial heap size. 1791 if (!expand(init_byte_size, _workers)) { 1792 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1793 return JNI_ENOMEM; 1794 } 1795 1796 // Perform any initialization actions delegated to the policy. 1797 g1_policy()->init(this, &_collection_set); 1798 1799 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1800 SATB_Q_FL_lock, 1801 G1SATBProcessCompletedThreshold, 1802 Shared_SATB_Q_lock); 1803 1804 jint ecode = initialize_concurrent_refinement(); 1805 if (ecode != JNI_OK) { 1806 return ecode; 1807 } 1808 1809 ecode = initialize_young_gen_sampling_thread(); 1810 if (ecode != JNI_OK) { 1811 return ecode; 1812 } 1813 1814 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1815 DirtyCardQ_FL_lock, 1816 (int)concurrent_refine()->yellow_zone(), 1817 (int)concurrent_refine()->red_zone(), 1818 Shared_DirtyCardQ_lock, 1819 NULL, // fl_owner 1820 true); // init_free_ids 1821 1822 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1823 DirtyCardQ_FL_lock, 1824 -1, // never trigger processing 1825 -1, // no limit on length 1826 Shared_DirtyCardQ_lock, 1827 &JavaThread::dirty_card_queue_set()); 1828 1829 // Here we allocate the dummy HeapRegion that is required by the 1830 // G1AllocRegion class. 1831 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1832 1833 // We'll re-use the same region whether the alloc region will 1834 // require BOT updates or not and, if it doesn't, then a non-young 1835 // region will complain that it cannot support allocations without 1836 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1837 dummy_region->set_eden(); 1838 // Make sure it's full. 1839 dummy_region->set_top(dummy_region->end()); 1840 G1AllocRegion::setup(this, dummy_region); 1841 1842 _allocator->init_mutator_alloc_region(); 1843 1844 // Do create of the monitoring and management support so that 1845 // values in the heap have been properly initialized. 1846 _g1mm = new G1MonitoringSupport(this); 1847 1848 G1StringDedup::initialize(); 1849 1850 _preserved_marks_set.init(ParallelGCThreads); 1851 1852 _collection_set.initialize(max_regions()); 1853 1854 return JNI_OK; 1855 } 1856 1857 void G1CollectedHeap::stop() { 1858 // Stop all concurrent threads. We do this to make sure these threads 1859 // do not continue to execute and access resources (e.g. logging) 1860 // that are destroyed during shutdown. 1861 _cr->stop(); 1862 _young_gen_sampling_thread->stop(); 1863 _cmThread->stop(); 1864 if (G1StringDedup::is_enabled()) { 1865 G1StringDedup::stop(); 1866 } 1867 } 1868 1869 void G1CollectedHeap::safepoint_synchronize_begin() { 1870 SuspendibleThreadSet::synchronize(); 1871 } 1872 1873 void G1CollectedHeap::safepoint_synchronize_end() { 1874 SuspendibleThreadSet::desynchronize(); 1875 } 1876 1877 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1878 return HeapRegion::max_region_size(); 1879 } 1880 1881 void G1CollectedHeap::post_initialize() { 1882 ref_processing_init(); 1883 } 1884 1885 void G1CollectedHeap::ref_processing_init() { 1886 // Reference processing in G1 currently works as follows: 1887 // 1888 // * There are two reference processor instances. One is 1889 // used to record and process discovered references 1890 // during concurrent marking; the other is used to 1891 // record and process references during STW pauses 1892 // (both full and incremental). 1893 // * Both ref processors need to 'span' the entire heap as 1894 // the regions in the collection set may be dotted around. 1895 // 1896 // * For the concurrent marking ref processor: 1897 // * Reference discovery is enabled at initial marking. 1898 // * Reference discovery is disabled and the discovered 1899 // references processed etc during remarking. 1900 // * Reference discovery is MT (see below). 1901 // * Reference discovery requires a barrier (see below). 1902 // * Reference processing may or may not be MT 1903 // (depending on the value of ParallelRefProcEnabled 1904 // and ParallelGCThreads). 1905 // * A full GC disables reference discovery by the CM 1906 // ref processor and abandons any entries on it's 1907 // discovered lists. 1908 // 1909 // * For the STW processor: 1910 // * Non MT discovery is enabled at the start of a full GC. 1911 // * Processing and enqueueing during a full GC is non-MT. 1912 // * During a full GC, references are processed after marking. 1913 // 1914 // * Discovery (may or may not be MT) is enabled at the start 1915 // of an incremental evacuation pause. 1916 // * References are processed near the end of a STW evacuation pause. 1917 // * For both types of GC: 1918 // * Discovery is atomic - i.e. not concurrent. 1919 // * Reference discovery will not need a barrier. 1920 1921 MemRegion mr = reserved_region(); 1922 1923 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1); 1924 1925 // Concurrent Mark ref processor 1926 _ref_processor_cm = 1927 new ReferenceProcessor(mr, // span 1928 mt_processing, 1929 // mt processing 1930 ParallelGCThreads, 1931 // degree of mt processing 1932 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 1933 // mt discovery 1934 MAX2(ParallelGCThreads, ConcGCThreads), 1935 // degree of mt discovery 1936 false, 1937 // Reference discovery is not atomic 1938 &_is_alive_closure_cm); 1939 // is alive closure 1940 // (for efficiency/performance) 1941 1942 // STW ref processor 1943 _ref_processor_stw = 1944 new ReferenceProcessor(mr, // span 1945 mt_processing, 1946 // mt processing 1947 ParallelGCThreads, 1948 // degree of mt processing 1949 (ParallelGCThreads > 1), 1950 // mt discovery 1951 ParallelGCThreads, 1952 // degree of mt discovery 1953 true, 1954 // Reference discovery is atomic 1955 &_is_alive_closure_stw); 1956 // is alive closure 1957 // (for efficiency/performance) 1958 } 1959 1960 CollectorPolicy* G1CollectedHeap::collector_policy() const { 1961 return _collector_policy; 1962 } 1963 1964 size_t G1CollectedHeap::capacity() const { 1965 return _hrm.length() * HeapRegion::GrainBytes; 1966 } 1967 1968 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const { 1969 return _hrm.total_free_bytes(); 1970 } 1971 1972 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 1973 hr->reset_gc_time_stamp(); 1974 } 1975 1976 #ifndef PRODUCT 1977 1978 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 1979 private: 1980 unsigned _gc_time_stamp; 1981 bool _failures; 1982 1983 public: 1984 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 1985 _gc_time_stamp(gc_time_stamp), _failures(false) { } 1986 1987 virtual bool doHeapRegion(HeapRegion* hr) { 1988 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 1989 if (_gc_time_stamp != region_gc_time_stamp) { 1990 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 1991 region_gc_time_stamp, _gc_time_stamp); 1992 _failures = true; 1993 } 1994 return false; 1995 } 1996 1997 bool failures() { return _failures; } 1998 }; 1999 2000 void G1CollectedHeap::check_gc_time_stamps() { 2001 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2002 heap_region_iterate(&cl); 2003 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2004 } 2005 #endif // PRODUCT 2006 2007 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2008 _hot_card_cache->drain(cl, worker_i); 2009 } 2010 2011 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2012 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2013 size_t n_completed_buffers = 0; 2014 while (dcqs.apply_closure_during_gc(cl, worker_i)) { 2015 n_completed_buffers++; 2016 } 2017 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2018 dcqs.clear_n_completed_buffers(); 2019 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2020 } 2021 2022 // Computes the sum of the storage used by the various regions. 2023 size_t G1CollectedHeap::used() const { 2024 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2025 if (_archive_allocator != NULL) { 2026 result += _archive_allocator->used(); 2027 } 2028 return result; 2029 } 2030 2031 size_t G1CollectedHeap::used_unlocked() const { 2032 return _summary_bytes_used; 2033 } 2034 2035 class SumUsedClosure: public HeapRegionClosure { 2036 size_t _used; 2037 public: 2038 SumUsedClosure() : _used(0) {} 2039 bool doHeapRegion(HeapRegion* r) { 2040 _used += r->used(); 2041 return false; 2042 } 2043 size_t result() { return _used; } 2044 }; 2045 2046 size_t G1CollectedHeap::recalculate_used() const { 2047 double recalculate_used_start = os::elapsedTime(); 2048 2049 SumUsedClosure blk; 2050 heap_region_iterate(&blk); 2051 2052 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2053 return blk.result(); 2054 } 2055 2056 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2057 switch (cause) { 2058 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2059 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2060 case GCCause::_update_allocation_context_stats_inc: return true; 2061 case GCCause::_wb_conc_mark: return true; 2062 default : return false; 2063 } 2064 } 2065 2066 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2067 switch (cause) { 2068 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2069 case GCCause::_g1_humongous_allocation: return true; 2070 default: return is_user_requested_concurrent_full_gc(cause); 2071 } 2072 } 2073 2074 #ifndef PRODUCT 2075 void G1CollectedHeap::allocate_dummy_regions() { 2076 // Let's fill up most of the region 2077 size_t word_size = HeapRegion::GrainWords - 1024; 2078 // And as a result the region we'll allocate will be humongous. 2079 guarantee(is_humongous(word_size), "sanity"); 2080 2081 // _filler_array_max_size is set to humongous object threshold 2082 // but temporarily change it to use CollectedHeap::fill_with_object(). 2083 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2084 2085 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2086 // Let's use the existing mechanism for the allocation 2087 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2088 AllocationContext::system()); 2089 if (dummy_obj != NULL) { 2090 MemRegion mr(dummy_obj, word_size); 2091 CollectedHeap::fill_with_object(mr); 2092 } else { 2093 // If we can't allocate once, we probably cannot allocate 2094 // again. Let's get out of the loop. 2095 break; 2096 } 2097 } 2098 } 2099 #endif // !PRODUCT 2100 2101 void G1CollectedHeap::increment_old_marking_cycles_started() { 2102 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2103 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2104 "Wrong marking cycle count (started: %d, completed: %d)", 2105 _old_marking_cycles_started, _old_marking_cycles_completed); 2106 2107 _old_marking_cycles_started++; 2108 } 2109 2110 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2111 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2112 2113 // We assume that if concurrent == true, then the caller is a 2114 // concurrent thread that was joined the Suspendible Thread 2115 // Set. If there's ever a cheap way to check this, we should add an 2116 // assert here. 2117 2118 // Given that this method is called at the end of a Full GC or of a 2119 // concurrent cycle, and those can be nested (i.e., a Full GC can 2120 // interrupt a concurrent cycle), the number of full collections 2121 // completed should be either one (in the case where there was no 2122 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2123 // behind the number of full collections started. 2124 2125 // This is the case for the inner caller, i.e. a Full GC. 2126 assert(concurrent || 2127 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2128 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2129 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2130 "is inconsistent with _old_marking_cycles_completed = %u", 2131 _old_marking_cycles_started, _old_marking_cycles_completed); 2132 2133 // This is the case for the outer caller, i.e. the concurrent cycle. 2134 assert(!concurrent || 2135 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2136 "for outer caller (concurrent cycle): " 2137 "_old_marking_cycles_started = %u " 2138 "is inconsistent with _old_marking_cycles_completed = %u", 2139 _old_marking_cycles_started, _old_marking_cycles_completed); 2140 2141 _old_marking_cycles_completed += 1; 2142 2143 // We need to clear the "in_progress" flag in the CM thread before 2144 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2145 // is set) so that if a waiter requests another System.gc() it doesn't 2146 // incorrectly see that a marking cycle is still in progress. 2147 if (concurrent) { 2148 _cmThread->set_idle(); 2149 } 2150 2151 // This notify_all() will ensure that a thread that called 2152 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2153 // and it's waiting for a full GC to finish will be woken up. It is 2154 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2155 FullGCCount_lock->notify_all(); 2156 } 2157 2158 void G1CollectedHeap::collect(GCCause::Cause cause) { 2159 assert_heap_not_locked(); 2160 2161 uint gc_count_before; 2162 uint old_marking_count_before; 2163 uint full_gc_count_before; 2164 bool retry_gc; 2165 2166 do { 2167 retry_gc = false; 2168 2169 { 2170 MutexLocker ml(Heap_lock); 2171 2172 // Read the GC count while holding the Heap_lock 2173 gc_count_before = total_collections(); 2174 full_gc_count_before = total_full_collections(); 2175 old_marking_count_before = _old_marking_cycles_started; 2176 } 2177 2178 if (should_do_concurrent_full_gc(cause)) { 2179 // Schedule an initial-mark evacuation pause that will start a 2180 // concurrent cycle. We're setting word_size to 0 which means that 2181 // we are not requesting a post-GC allocation. 2182 VM_G1IncCollectionPause op(gc_count_before, 2183 0, /* word_size */ 2184 true, /* should_initiate_conc_mark */ 2185 g1_policy()->max_pause_time_ms(), 2186 cause); 2187 op.set_allocation_context(AllocationContext::current()); 2188 2189 VMThread::execute(&op); 2190 if (!op.pause_succeeded()) { 2191 if (old_marking_count_before == _old_marking_cycles_started) { 2192 retry_gc = op.should_retry_gc(); 2193 } else { 2194 // A Full GC happened while we were trying to schedule the 2195 // initial-mark GC. No point in starting a new cycle given 2196 // that the whole heap was collected anyway. 2197 } 2198 2199 if (retry_gc) { 2200 if (GCLocker::is_active_and_needs_gc()) { 2201 GCLocker::stall_until_clear(); 2202 } 2203 } 2204 } 2205 } else { 2206 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2207 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2208 2209 // Schedule a standard evacuation pause. We're setting word_size 2210 // to 0 which means that we are not requesting a post-GC allocation. 2211 VM_G1IncCollectionPause op(gc_count_before, 2212 0, /* word_size */ 2213 false, /* should_initiate_conc_mark */ 2214 g1_policy()->max_pause_time_ms(), 2215 cause); 2216 VMThread::execute(&op); 2217 } else { 2218 // Schedule a Full GC. 2219 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2220 VMThread::execute(&op); 2221 } 2222 } 2223 } while (retry_gc); 2224 } 2225 2226 bool G1CollectedHeap::is_in(const void* p) const { 2227 if (_hrm.reserved().contains(p)) { 2228 // Given that we know that p is in the reserved space, 2229 // heap_region_containing() should successfully 2230 // return the containing region. 2231 HeapRegion* hr = heap_region_containing(p); 2232 return hr->is_in(p); 2233 } else { 2234 return false; 2235 } 2236 } 2237 2238 #ifdef ASSERT 2239 bool G1CollectedHeap::is_in_exact(const void* p) const { 2240 bool contains = reserved_region().contains(p); 2241 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2242 if (contains && available) { 2243 return true; 2244 } else { 2245 return false; 2246 } 2247 } 2248 #endif 2249 2250 // Iteration functions. 2251 2252 // Iterates an ObjectClosure over all objects within a HeapRegion. 2253 2254 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2255 ObjectClosure* _cl; 2256 public: 2257 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2258 bool doHeapRegion(HeapRegion* r) { 2259 if (!r->is_continues_humongous()) { 2260 r->object_iterate(_cl); 2261 } 2262 return false; 2263 } 2264 }; 2265 2266 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2267 IterateObjectClosureRegionClosure blk(cl); 2268 heap_region_iterate(&blk); 2269 } 2270 2271 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2272 _hrm.iterate(cl); 2273 } 2274 2275 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl, 2276 HeapRegionClaimer *hrclaimer, 2277 uint worker_id) const { 2278 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id)); 2279 } 2280 2281 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl, 2282 HeapRegionClaimer *hrclaimer) const { 2283 _hrm.par_iterate(cl, hrclaimer, 0); 2284 } 2285 2286 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2287 _collection_set.iterate(cl); 2288 } 2289 2290 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2291 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2292 } 2293 2294 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2295 HeapRegion* hr = heap_region_containing(addr); 2296 return hr->block_start(addr); 2297 } 2298 2299 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2300 HeapRegion* hr = heap_region_containing(addr); 2301 return hr->block_size(addr); 2302 } 2303 2304 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2305 HeapRegion* hr = heap_region_containing(addr); 2306 return hr->block_is_obj(addr); 2307 } 2308 2309 bool G1CollectedHeap::supports_tlab_allocation() const { 2310 return true; 2311 } 2312 2313 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2314 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2315 } 2316 2317 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2318 return _eden.length() * HeapRegion::GrainBytes; 2319 } 2320 2321 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2322 // must be equal to the humongous object limit. 2323 size_t G1CollectedHeap::max_tlab_size() const { 2324 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2325 } 2326 2327 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2328 AllocationContext_t context = AllocationContext::current(); 2329 return _allocator->unsafe_max_tlab_alloc(context); 2330 } 2331 2332 size_t G1CollectedHeap::max_capacity() const { 2333 return _hrm.reserved().byte_size(); 2334 } 2335 2336 jlong G1CollectedHeap::millis_since_last_gc() { 2337 // See the notes in GenCollectedHeap::millis_since_last_gc() 2338 // for more information about the implementation. 2339 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2340 _g1_policy->collection_pause_end_millis(); 2341 if (ret_val < 0) { 2342 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2343 ". returning zero instead.", ret_val); 2344 return 0; 2345 } 2346 return ret_val; 2347 } 2348 2349 void G1CollectedHeap::prepare_for_verify() { 2350 _verifier->prepare_for_verify(); 2351 } 2352 2353 void G1CollectedHeap::verify(VerifyOption vo) { 2354 _verifier->verify(vo); 2355 } 2356 2357 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2358 return true; 2359 } 2360 2361 const char* const* G1CollectedHeap::concurrent_phases() const { 2362 return _cmThread->concurrent_phases(); 2363 } 2364 2365 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2366 return _cmThread->request_concurrent_phase(phase); 2367 } 2368 2369 class PrintRegionClosure: public HeapRegionClosure { 2370 outputStream* _st; 2371 public: 2372 PrintRegionClosure(outputStream* st) : _st(st) {} 2373 bool doHeapRegion(HeapRegion* r) { 2374 r->print_on(_st); 2375 return false; 2376 } 2377 }; 2378 2379 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2380 const HeapRegion* hr, 2381 const VerifyOption vo) const { 2382 switch (vo) { 2383 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2384 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2385 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr); 2386 default: ShouldNotReachHere(); 2387 } 2388 return false; // keep some compilers happy 2389 } 2390 2391 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2392 const VerifyOption vo) const { 2393 switch (vo) { 2394 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2395 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2396 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj); 2397 default: ShouldNotReachHere(); 2398 } 2399 return false; // keep some compilers happy 2400 } 2401 2402 void G1CollectedHeap::print_heap_regions() const { 2403 LogTarget(Trace, gc, heap, region) lt; 2404 if (lt.is_enabled()) { 2405 LogStream ls(lt); 2406 print_regions_on(&ls); 2407 } 2408 } 2409 2410 void G1CollectedHeap::print_on(outputStream* st) const { 2411 st->print(" %-20s", "garbage-first heap"); 2412 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2413 capacity()/K, used_unlocked()/K); 2414 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")", 2415 p2i(_hrm.reserved().start()), 2416 p2i(_hrm.reserved().end())); 2417 st->cr(); 2418 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2419 uint young_regions = young_regions_count(); 2420 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2421 (size_t) young_regions * HeapRegion::GrainBytes / K); 2422 uint survivor_regions = survivor_regions_count(); 2423 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2424 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2425 st->cr(); 2426 MetaspaceAux::print_on(st); 2427 } 2428 2429 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2430 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2431 "HS=humongous(starts), HC=humongous(continues), " 2432 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2433 "AC=allocation context, " 2434 "TAMS=top-at-mark-start (previous, next)"); 2435 PrintRegionClosure blk(st); 2436 heap_region_iterate(&blk); 2437 } 2438 2439 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2440 print_on(st); 2441 2442 // Print the per-region information. 2443 print_regions_on(st); 2444 } 2445 2446 void G1CollectedHeap::print_on_error(outputStream* st) const { 2447 this->CollectedHeap::print_on_error(st); 2448 2449 if (_cm != NULL) { 2450 st->cr(); 2451 _cm->print_on_error(st); 2452 } 2453 } 2454 2455 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2456 workers()->print_worker_threads_on(st); 2457 _cmThread->print_on(st); 2458 st->cr(); 2459 _cm->print_worker_threads_on(st); 2460 _cr->print_threads_on(st); 2461 _young_gen_sampling_thread->print_on(st); 2462 if (G1StringDedup::is_enabled()) { 2463 G1StringDedup::print_worker_threads_on(st); 2464 } 2465 } 2466 2467 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2468 workers()->threads_do(tc); 2469 tc->do_thread(_cmThread); 2470 _cm->threads_do(tc); 2471 _cr->threads_do(tc); 2472 tc->do_thread(_young_gen_sampling_thread); 2473 if (G1StringDedup::is_enabled()) { 2474 G1StringDedup::threads_do(tc); 2475 } 2476 } 2477 2478 void G1CollectedHeap::print_tracing_info() const { 2479 g1_rem_set()->print_summary_info(); 2480 concurrent_mark()->print_summary_info(); 2481 } 2482 2483 #ifndef PRODUCT 2484 // Helpful for debugging RSet issues. 2485 2486 class PrintRSetsClosure : public HeapRegionClosure { 2487 private: 2488 const char* _msg; 2489 size_t _occupied_sum; 2490 2491 public: 2492 bool doHeapRegion(HeapRegion* r) { 2493 HeapRegionRemSet* hrrs = r->rem_set(); 2494 size_t occupied = hrrs->occupied(); 2495 _occupied_sum += occupied; 2496 2497 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2498 if (occupied == 0) { 2499 tty->print_cr(" RSet is empty"); 2500 } else { 2501 hrrs->print(); 2502 } 2503 tty->print_cr("----------"); 2504 return false; 2505 } 2506 2507 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2508 tty->cr(); 2509 tty->print_cr("========================================"); 2510 tty->print_cr("%s", msg); 2511 tty->cr(); 2512 } 2513 2514 ~PrintRSetsClosure() { 2515 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2516 tty->print_cr("========================================"); 2517 tty->cr(); 2518 } 2519 }; 2520 2521 void G1CollectedHeap::print_cset_rsets() { 2522 PrintRSetsClosure cl("Printing CSet RSets"); 2523 collection_set_iterate(&cl); 2524 } 2525 2526 void G1CollectedHeap::print_all_rsets() { 2527 PrintRSetsClosure cl("Printing All RSets");; 2528 heap_region_iterate(&cl); 2529 } 2530 #endif // PRODUCT 2531 2532 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2533 2534 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2535 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2536 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2537 2538 size_t eden_capacity_bytes = 2539 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2540 2541 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2542 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2543 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2544 } 2545 2546 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2547 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2548 stats->unused(), stats->used(), stats->region_end_waste(), 2549 stats->regions_filled(), stats->direct_allocated(), 2550 stats->failure_used(), stats->failure_waste()); 2551 } 2552 2553 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2554 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2555 gc_tracer->report_gc_heap_summary(when, heap_summary); 2556 2557 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2558 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2559 } 2560 2561 G1CollectedHeap* G1CollectedHeap::heap() { 2562 CollectedHeap* heap = Universe::heap(); 2563 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2564 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2565 return (G1CollectedHeap*)heap; 2566 } 2567 2568 void G1CollectedHeap::gc_prologue(bool full) { 2569 // always_do_update_barrier = false; 2570 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2571 2572 // This summary needs to be printed before incrementing total collections. 2573 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2574 2575 // Update common counters. 2576 increment_total_collections(full /* full gc */); 2577 if (full) { 2578 increment_old_marking_cycles_started(); 2579 reset_gc_time_stamp(); 2580 } else { 2581 increment_gc_time_stamp(); 2582 } 2583 2584 // Fill TLAB's and such 2585 double start = os::elapsedTime(); 2586 accumulate_statistics_all_tlabs(); 2587 ensure_parsability(true); 2588 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2589 } 2590 2591 void G1CollectedHeap::gc_epilogue(bool full) { 2592 // Update common counters. 2593 if (full) { 2594 // Update the number of full collections that have been completed. 2595 increment_old_marking_cycles_completed(false /* concurrent */); 2596 } 2597 2598 // We are at the end of the GC. Total collections has already been increased. 2599 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2600 2601 // FIXME: what is this about? 2602 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2603 // is set. 2604 #if COMPILER2_OR_JVMCI 2605 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2606 #endif 2607 // always_do_update_barrier = true; 2608 2609 double start = os::elapsedTime(); 2610 resize_all_tlabs(); 2611 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2612 2613 allocation_context_stats().update(full); 2614 2615 MemoryService::track_memory_usage(); 2616 // We have just completed a GC. Update the soft reference 2617 // policy with the new heap occupancy 2618 Universe::update_heap_info_at_gc(); 2619 } 2620 2621 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2622 uint gc_count_before, 2623 bool* succeeded, 2624 GCCause::Cause gc_cause) { 2625 assert_heap_not_locked_and_not_at_safepoint(); 2626 VM_G1IncCollectionPause op(gc_count_before, 2627 word_size, 2628 false, /* should_initiate_conc_mark */ 2629 g1_policy()->max_pause_time_ms(), 2630 gc_cause); 2631 2632 op.set_allocation_context(AllocationContext::current()); 2633 VMThread::execute(&op); 2634 2635 HeapWord* result = op.result(); 2636 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2637 assert(result == NULL || ret_succeeded, 2638 "the result should be NULL if the VM did not succeed"); 2639 *succeeded = ret_succeeded; 2640 2641 assert_heap_not_locked(); 2642 return result; 2643 } 2644 2645 void 2646 G1CollectedHeap::doConcurrentMark() { 2647 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2648 if (!_cmThread->in_progress()) { 2649 _cmThread->set_started(); 2650 CGC_lock->notify(); 2651 } 2652 } 2653 2654 size_t G1CollectedHeap::pending_card_num() { 2655 size_t extra_cards = 0; 2656 JavaThread *curr = Threads::first(); 2657 while (curr != NULL) { 2658 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2659 extra_cards += dcq.size(); 2660 curr = curr->next(); 2661 } 2662 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2663 size_t buffer_size = dcqs.buffer_size(); 2664 size_t buffer_num = dcqs.completed_buffers_num(); 2665 2666 return buffer_size * buffer_num + extra_cards; 2667 } 2668 2669 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2670 private: 2671 size_t _total_humongous; 2672 size_t _candidate_humongous; 2673 2674 DirtyCardQueue _dcq; 2675 2676 // We don't nominate objects with many remembered set entries, on 2677 // the assumption that such objects are likely still live. 2678 bool is_remset_small(HeapRegion* region) const { 2679 HeapRegionRemSet* const rset = region->rem_set(); 2680 return G1EagerReclaimHumongousObjectsWithStaleRefs 2681 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2682 : rset->is_empty(); 2683 } 2684 2685 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2686 assert(region->is_starts_humongous(), "Must start a humongous object"); 2687 2688 oop obj = oop(region->bottom()); 2689 2690 // Dead objects cannot be eager reclaim candidates. Due to class 2691 // unloading it is unsafe to query their classes so we return early. 2692 if (heap->is_obj_dead(obj, region)) { 2693 return false; 2694 } 2695 2696 // Candidate selection must satisfy the following constraints 2697 // while concurrent marking is in progress: 2698 // 2699 // * In order to maintain SATB invariants, an object must not be 2700 // reclaimed if it was allocated before the start of marking and 2701 // has not had its references scanned. Such an object must have 2702 // its references (including type metadata) scanned to ensure no 2703 // live objects are missed by the marking process. Objects 2704 // allocated after the start of concurrent marking don't need to 2705 // be scanned. 2706 // 2707 // * An object must not be reclaimed if it is on the concurrent 2708 // mark stack. Objects allocated after the start of concurrent 2709 // marking are never pushed on the mark stack. 2710 // 2711 // Nominating only objects allocated after the start of concurrent 2712 // marking is sufficient to meet both constraints. This may miss 2713 // some objects that satisfy the constraints, but the marking data 2714 // structures don't support efficiently performing the needed 2715 // additional tests or scrubbing of the mark stack. 2716 // 2717 // However, we presently only nominate is_typeArray() objects. 2718 // A humongous object containing references induces remembered 2719 // set entries on other regions. In order to reclaim such an 2720 // object, those remembered sets would need to be cleaned up. 2721 // 2722 // We also treat is_typeArray() objects specially, allowing them 2723 // to be reclaimed even if allocated before the start of 2724 // concurrent mark. For this we rely on mark stack insertion to 2725 // exclude is_typeArray() objects, preventing reclaiming an object 2726 // that is in the mark stack. We also rely on the metadata for 2727 // such objects to be built-in and so ensured to be kept live. 2728 // Frequent allocation and drop of large binary blobs is an 2729 // important use case for eager reclaim, and this special handling 2730 // may reduce needed headroom. 2731 2732 return obj->is_typeArray() && is_remset_small(region); 2733 } 2734 2735 public: 2736 RegisterHumongousWithInCSetFastTestClosure() 2737 : _total_humongous(0), 2738 _candidate_humongous(0), 2739 _dcq(&JavaThread::dirty_card_queue_set()) { 2740 } 2741 2742 virtual bool doHeapRegion(HeapRegion* r) { 2743 if (!r->is_starts_humongous()) { 2744 return false; 2745 } 2746 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2747 2748 bool is_candidate = humongous_region_is_candidate(g1h, r); 2749 uint rindex = r->hrm_index(); 2750 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2751 if (is_candidate) { 2752 _candidate_humongous++; 2753 g1h->register_humongous_region_with_cset(rindex); 2754 // Is_candidate already filters out humongous object with large remembered sets. 2755 // If we have a humongous object with a few remembered sets, we simply flush these 2756 // remembered set entries into the DCQS. That will result in automatic 2757 // re-evaluation of their remembered set entries during the following evacuation 2758 // phase. 2759 if (!r->rem_set()->is_empty()) { 2760 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2761 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2762 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 2763 HeapRegionRemSetIterator hrrs(r->rem_set()); 2764 size_t card_index; 2765 while (hrrs.has_next(card_index)) { 2766 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 2767 // The remembered set might contain references to already freed 2768 // regions. Filter out such entries to avoid failing card table 2769 // verification. 2770 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 2771 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 2772 *card_ptr = CardTableModRefBS::dirty_card_val(); 2773 _dcq.enqueue(card_ptr); 2774 } 2775 } 2776 } 2777 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2778 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2779 hrrs.n_yielded(), r->rem_set()->occupied()); 2780 r->rem_set()->clear_locked(); 2781 } 2782 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2783 } 2784 _total_humongous++; 2785 2786 return false; 2787 } 2788 2789 size_t total_humongous() const { return _total_humongous; } 2790 size_t candidate_humongous() const { return _candidate_humongous; } 2791 2792 void flush_rem_set_entries() { _dcq.flush(); } 2793 }; 2794 2795 void G1CollectedHeap::register_humongous_regions_with_cset() { 2796 if (!G1EagerReclaimHumongousObjects) { 2797 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2798 return; 2799 } 2800 double time = os::elapsed_counter(); 2801 2802 // Collect reclaim candidate information and register candidates with cset. 2803 RegisterHumongousWithInCSetFastTestClosure cl; 2804 heap_region_iterate(&cl); 2805 2806 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2807 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2808 cl.total_humongous(), 2809 cl.candidate_humongous()); 2810 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2811 2812 // Finally flush all remembered set entries to re-check into the global DCQS. 2813 cl.flush_rem_set_entries(); 2814 } 2815 2816 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2817 public: 2818 bool doHeapRegion(HeapRegion* hr) { 2819 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2820 hr->verify_rem_set(); 2821 } 2822 return false; 2823 } 2824 }; 2825 2826 uint G1CollectedHeap::num_task_queues() const { 2827 return _task_queues->size(); 2828 } 2829 2830 #if TASKQUEUE_STATS 2831 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2832 st->print_raw_cr("GC Task Stats"); 2833 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2834 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2835 } 2836 2837 void G1CollectedHeap::print_taskqueue_stats() const { 2838 if (!log_is_enabled(Trace, gc, task, stats)) { 2839 return; 2840 } 2841 Log(gc, task, stats) log; 2842 ResourceMark rm; 2843 LogStream ls(log.trace()); 2844 outputStream* st = &ls; 2845 2846 print_taskqueue_stats_hdr(st); 2847 2848 TaskQueueStats totals; 2849 const uint n = num_task_queues(); 2850 for (uint i = 0; i < n; ++i) { 2851 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2852 totals += task_queue(i)->stats; 2853 } 2854 st->print_raw("tot "); totals.print(st); st->cr(); 2855 2856 DEBUG_ONLY(totals.verify()); 2857 } 2858 2859 void G1CollectedHeap::reset_taskqueue_stats() { 2860 const uint n = num_task_queues(); 2861 for (uint i = 0; i < n; ++i) { 2862 task_queue(i)->stats.reset(); 2863 } 2864 } 2865 #endif // TASKQUEUE_STATS 2866 2867 void G1CollectedHeap::wait_for_root_region_scanning() { 2868 double scan_wait_start = os::elapsedTime(); 2869 // We have to wait until the CM threads finish scanning the 2870 // root regions as it's the only way to ensure that all the 2871 // objects on them have been correctly scanned before we start 2872 // moving them during the GC. 2873 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2874 double wait_time_ms = 0.0; 2875 if (waited) { 2876 double scan_wait_end = os::elapsedTime(); 2877 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2878 } 2879 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2880 } 2881 2882 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2883 private: 2884 G1HRPrinter* _hr_printer; 2885 public: 2886 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2887 2888 virtual bool doHeapRegion(HeapRegion* r) { 2889 _hr_printer->cset(r); 2890 return false; 2891 } 2892 }; 2893 2894 void G1CollectedHeap::start_new_collection_set() { 2895 collection_set()->start_incremental_building(); 2896 2897 clear_cset_fast_test(); 2898 2899 guarantee(_eden.length() == 0, "eden should have been cleared"); 2900 g1_policy()->transfer_survivors_to_cset(survivor()); 2901 } 2902 2903 bool 2904 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2905 assert_at_safepoint(true /* should_be_vm_thread */); 2906 guarantee(!is_gc_active(), "collection is not reentrant"); 2907 2908 if (GCLocker::check_active_before_gc()) { 2909 return false; 2910 } 2911 2912 _gc_timer_stw->register_gc_start(); 2913 2914 GCIdMark gc_id_mark; 2915 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2916 2917 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2918 ResourceMark rm; 2919 2920 g1_policy()->note_gc_start(); 2921 2922 wait_for_root_region_scanning(); 2923 2924 print_heap_before_gc(); 2925 print_heap_regions(); 2926 trace_heap_before_gc(_gc_tracer_stw); 2927 2928 _verifier->verify_region_sets_optional(); 2929 _verifier->verify_dirty_young_regions(); 2930 2931 // We should not be doing initial mark unless the conc mark thread is running 2932 if (!_cmThread->should_terminate()) { 2933 // This call will decide whether this pause is an initial-mark 2934 // pause. If it is, during_initial_mark_pause() will return true 2935 // for the duration of this pause. 2936 g1_policy()->decide_on_conc_mark_initiation(); 2937 } 2938 2939 // We do not allow initial-mark to be piggy-backed on a mixed GC. 2940 assert(!collector_state()->during_initial_mark_pause() || 2941 collector_state()->gcs_are_young(), "sanity"); 2942 2943 // We also do not allow mixed GCs during marking. 2944 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 2945 2946 // Record whether this pause is an initial mark. When the current 2947 // thread has completed its logging output and it's safe to signal 2948 // the CM thread, the flag's value in the policy has been reset. 2949 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 2950 2951 // Inner scope for scope based logging, timers, and stats collection 2952 { 2953 EvacuationInfo evacuation_info; 2954 2955 if (collector_state()->during_initial_mark_pause()) { 2956 // We are about to start a marking cycle, so we increment the 2957 // full collection counter. 2958 increment_old_marking_cycles_started(); 2959 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 2960 } 2961 2962 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 2963 2964 GCTraceCPUTime tcpu; 2965 2966 FormatBuffer<> gc_string("Pause "); 2967 if (collector_state()->during_initial_mark_pause()) { 2968 gc_string.append("Initial Mark"); 2969 } else if (collector_state()->gcs_are_young()) { 2970 gc_string.append("Young"); 2971 } else { 2972 gc_string.append("Mixed"); 2973 } 2974 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 2975 2976 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 2977 workers()->active_workers(), 2978 Threads::number_of_non_daemon_threads()); 2979 workers()->update_active_workers(active_workers); 2980 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 2981 2982 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 2983 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 2984 2985 // If the secondary_free_list is not empty, append it to the 2986 // free_list. No need to wait for the cleanup operation to finish; 2987 // the region allocation code will check the secondary_free_list 2988 // and wait if necessary. If the G1StressConcRegionFreeing flag is 2989 // set, skip this step so that the region allocation code has to 2990 // get entries from the secondary_free_list. 2991 if (!G1StressConcRegionFreeing) { 2992 append_secondary_free_list_if_not_empty_with_lock(); 2993 } 2994 2995 G1HeapTransition heap_transition(this); 2996 size_t heap_used_bytes_before_gc = used(); 2997 2998 // Don't dynamically change the number of GC threads this early. A value of 2999 // 0 is used to indicate serial work. When parallel work is done, 3000 // it will be set. 3001 3002 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3003 IsGCActiveMark x; 3004 3005 gc_prologue(false); 3006 3007 if (VerifyRememberedSets) { 3008 log_info(gc, verify)("[Verifying RemSets before GC]"); 3009 VerifyRegionRemSetClosure v_cl; 3010 heap_region_iterate(&v_cl); 3011 } 3012 3013 _verifier->verify_before_gc(); 3014 3015 _verifier->check_bitmaps("GC Start"); 3016 3017 #if COMPILER2_OR_JVMCI 3018 DerivedPointerTable::clear(); 3019 #endif 3020 3021 // Please see comment in g1CollectedHeap.hpp and 3022 // G1CollectedHeap::ref_processing_init() to see how 3023 // reference processing currently works in G1. 3024 3025 // Enable discovery in the STW reference processor 3026 if (g1_policy()->should_process_references()) { 3027 ref_processor_stw()->enable_discovery(); 3028 } else { 3029 ref_processor_stw()->disable_discovery(); 3030 } 3031 3032 { 3033 // We want to temporarily turn off discovery by the 3034 // CM ref processor, if necessary, and turn it back on 3035 // on again later if we do. Using a scoped 3036 // NoRefDiscovery object will do this. 3037 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3038 3039 // Forget the current alloc region (we might even choose it to be part 3040 // of the collection set!). 3041 _allocator->release_mutator_alloc_region(); 3042 3043 // This timing is only used by the ergonomics to handle our pause target. 3044 // It is unclear why this should not include the full pause. We will 3045 // investigate this in CR 7178365. 3046 // 3047 // Preserving the old comment here if that helps the investigation: 3048 // 3049 // The elapsed time induced by the start time below deliberately elides 3050 // the possible verification above. 3051 double sample_start_time_sec = os::elapsedTime(); 3052 3053 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3054 3055 if (collector_state()->during_initial_mark_pause()) { 3056 concurrent_mark()->checkpoint_roots_initial_pre(); 3057 } 3058 3059 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 3060 3061 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3062 3063 // Make sure the remembered sets are up to date. This needs to be 3064 // done before register_humongous_regions_with_cset(), because the 3065 // remembered sets are used there to choose eager reclaim candidates. 3066 // If the remembered sets are not up to date we might miss some 3067 // entries that need to be handled. 3068 g1_rem_set()->cleanupHRRS(); 3069 3070 register_humongous_regions_with_cset(); 3071 3072 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3073 3074 // We call this after finalize_cset() to 3075 // ensure that the CSet has been finalized. 3076 _cm->verify_no_cset_oops(); 3077 3078 if (_hr_printer.is_active()) { 3079 G1PrintCollectionSetClosure cl(&_hr_printer); 3080 _collection_set.iterate(&cl); 3081 } 3082 3083 // Initialize the GC alloc regions. 3084 _allocator->init_gc_alloc_regions(evacuation_info); 3085 3086 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3087 pre_evacuate_collection_set(); 3088 3089 // Actually do the work... 3090 evacuate_collection_set(evacuation_info, &per_thread_states); 3091 3092 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3093 3094 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3095 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 3096 3097 eagerly_reclaim_humongous_regions(); 3098 3099 record_obj_copy_mem_stats(); 3100 _survivor_evac_stats.adjust_desired_plab_sz(); 3101 _old_evac_stats.adjust_desired_plab_sz(); 3102 3103 double start = os::elapsedTime(); 3104 start_new_collection_set(); 3105 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 3106 3107 if (evacuation_failed()) { 3108 set_used(recalculate_used()); 3109 if (_archive_allocator != NULL) { 3110 _archive_allocator->clear_used(); 3111 } 3112 for (uint i = 0; i < ParallelGCThreads; i++) { 3113 if (_evacuation_failed_info_array[i].has_failed()) { 3114 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3115 } 3116 } 3117 } else { 3118 // The "used" of the the collection set have already been subtracted 3119 // when they were freed. Add in the bytes evacuated. 3120 increase_used(g1_policy()->bytes_copied_during_gc()); 3121 } 3122 3123 if (collector_state()->during_initial_mark_pause()) { 3124 // We have to do this before we notify the CM threads that 3125 // they can start working to make sure that all the 3126 // appropriate initialization is done on the CM object. 3127 concurrent_mark()->checkpoint_roots_initial_post(); 3128 collector_state()->set_mark_in_progress(true); 3129 // Note that we don't actually trigger the CM thread at 3130 // this point. We do that later when we're sure that 3131 // the current thread has completed its logging output. 3132 } 3133 3134 allocate_dummy_regions(); 3135 3136 _allocator->init_mutator_alloc_region(); 3137 3138 { 3139 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3140 if (expand_bytes > 0) { 3141 size_t bytes_before = capacity(); 3142 // No need for an ergo logging here, 3143 // expansion_amount() does this when it returns a value > 0. 3144 double expand_ms; 3145 if (!expand(expand_bytes, _workers, &expand_ms)) { 3146 // We failed to expand the heap. Cannot do anything about it. 3147 } 3148 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3149 } 3150 } 3151 3152 // We redo the verification but now wrt to the new CSet which 3153 // has just got initialized after the previous CSet was freed. 3154 _cm->verify_no_cset_oops(); 3155 3156 // This timing is only used by the ergonomics to handle our pause target. 3157 // It is unclear why this should not include the full pause. We will 3158 // investigate this in CR 7178365. 3159 double sample_end_time_sec = os::elapsedTime(); 3160 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3161 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards); 3162 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3163 3164 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3165 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3166 3167 if (VerifyRememberedSets) { 3168 log_info(gc, verify)("[Verifying RemSets after GC]"); 3169 VerifyRegionRemSetClosure v_cl; 3170 heap_region_iterate(&v_cl); 3171 } 3172 3173 _verifier->verify_after_gc(); 3174 _verifier->check_bitmaps("GC End"); 3175 3176 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3177 ref_processor_stw()->verify_no_references_recorded(); 3178 3179 // CM reference discovery will be re-enabled if necessary. 3180 } 3181 3182 #ifdef TRACESPINNING 3183 ParallelTaskTerminator::print_termination_counts(); 3184 #endif 3185 3186 gc_epilogue(false); 3187 } 3188 3189 // Print the remainder of the GC log output. 3190 if (evacuation_failed()) { 3191 log_info(gc)("To-space exhausted"); 3192 } 3193 3194 g1_policy()->print_phases(); 3195 heap_transition.print(); 3196 3197 // It is not yet to safe to tell the concurrent mark to 3198 // start as we have some optional output below. We don't want the 3199 // output from the concurrent mark thread interfering with this 3200 // logging output either. 3201 3202 _hrm.verify_optional(); 3203 _verifier->verify_region_sets_optional(); 3204 3205 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3206 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3207 3208 print_heap_after_gc(); 3209 print_heap_regions(); 3210 trace_heap_after_gc(_gc_tracer_stw); 3211 3212 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3213 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3214 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3215 // before any GC notifications are raised. 3216 g1mm()->update_sizes(); 3217 3218 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3219 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3220 _gc_timer_stw->register_gc_end(); 3221 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3222 } 3223 // It should now be safe to tell the concurrent mark thread to start 3224 // without its logging output interfering with the logging output 3225 // that came from the pause. 3226 3227 if (should_start_conc_mark) { 3228 // CAUTION: after the doConcurrentMark() call below, 3229 // the concurrent marking thread(s) could be running 3230 // concurrently with us. Make sure that anything after 3231 // this point does not assume that we are the only GC thread 3232 // running. Note: of course, the actual marking work will 3233 // not start until the safepoint itself is released in 3234 // SuspendibleThreadSet::desynchronize(). 3235 doConcurrentMark(); 3236 } 3237 3238 return true; 3239 } 3240 3241 void G1CollectedHeap::remove_self_forwarding_pointers() { 3242 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3243 workers()->run_task(&rsfp_task); 3244 } 3245 3246 void G1CollectedHeap::restore_after_evac_failure() { 3247 double remove_self_forwards_start = os::elapsedTime(); 3248 3249 remove_self_forwarding_pointers(); 3250 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3251 _preserved_marks_set.restore(&task_executor); 3252 3253 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3254 } 3255 3256 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3257 if (!_evacuation_failed) { 3258 _evacuation_failed = true; 3259 } 3260 3261 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3262 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3263 } 3264 3265 bool G1ParEvacuateFollowersClosure::offer_termination() { 3266 G1ParScanThreadState* const pss = par_scan_state(); 3267 start_term_time(); 3268 const bool res = terminator()->offer_termination(); 3269 end_term_time(); 3270 return res; 3271 } 3272 3273 void G1ParEvacuateFollowersClosure::do_void() { 3274 G1ParScanThreadState* const pss = par_scan_state(); 3275 pss->trim_queue(); 3276 do { 3277 pss->steal_and_trim_queue(queues()); 3278 } while (!offer_termination()); 3279 } 3280 3281 class G1ParTask : public AbstractGangTask { 3282 protected: 3283 G1CollectedHeap* _g1h; 3284 G1ParScanThreadStateSet* _pss; 3285 RefToScanQueueSet* _queues; 3286 G1RootProcessor* _root_processor; 3287 ParallelTaskTerminator _terminator; 3288 uint _n_workers; 3289 3290 public: 3291 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3292 : AbstractGangTask("G1 collection"), 3293 _g1h(g1h), 3294 _pss(per_thread_states), 3295 _queues(task_queues), 3296 _root_processor(root_processor), 3297 _terminator(n_workers, _queues), 3298 _n_workers(n_workers) 3299 {} 3300 3301 void work(uint worker_id) { 3302 if (worker_id >= _n_workers) return; // no work needed this round 3303 3304 double start_sec = os::elapsedTime(); 3305 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3306 3307 { 3308 ResourceMark rm; 3309 HandleMark hm; 3310 3311 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3312 3313 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3314 pss->set_ref_processor(rp); 3315 3316 double start_strong_roots_sec = os::elapsedTime(); 3317 3318 _root_processor->evacuate_roots(pss->closures(), worker_id); 3319 3320 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3321 // treating the nmethods visited to act as roots for concurrent marking. 3322 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3323 // objects copied by the current evacuation. 3324 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, 3325 pss->closures()->weak_codeblobs(), 3326 worker_id); 3327 3328 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3329 3330 double term_sec = 0.0; 3331 size_t evac_term_attempts = 0; 3332 { 3333 double start = os::elapsedTime(); 3334 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3335 evac.do_void(); 3336 3337 evac_term_attempts = evac.term_attempts(); 3338 term_sec = evac.term_time(); 3339 double elapsed_sec = os::elapsedTime() - start; 3340 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3341 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3342 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3343 } 3344 3345 assert(pss->queue_is_empty(), "should be empty"); 3346 3347 if (log_is_enabled(Debug, gc, task, stats)) { 3348 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3349 size_t lab_waste; 3350 size_t lab_undo_waste; 3351 pss->waste(lab_waste, lab_undo_waste); 3352 _g1h->print_termination_stats(worker_id, 3353 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3354 strong_roots_sec * 1000.0, /* strong roots time */ 3355 term_sec * 1000.0, /* evac term time */ 3356 evac_term_attempts, /* evac term attempts */ 3357 lab_waste, /* alloc buffer waste */ 3358 lab_undo_waste /* undo waste */ 3359 ); 3360 } 3361 3362 // Close the inner scope so that the ResourceMark and HandleMark 3363 // destructors are executed here and are included as part of the 3364 // "GC Worker Time". 3365 } 3366 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3367 } 3368 }; 3369 3370 void G1CollectedHeap::print_termination_stats_hdr() { 3371 log_debug(gc, task, stats)("GC Termination Stats"); 3372 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3373 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3374 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3375 } 3376 3377 void G1CollectedHeap::print_termination_stats(uint worker_id, 3378 double elapsed_ms, 3379 double strong_roots_ms, 3380 double term_ms, 3381 size_t term_attempts, 3382 size_t alloc_buffer_waste, 3383 size_t undo_waste) const { 3384 log_debug(gc, task, stats) 3385 ("%3d %9.2f %9.2f %6.2f " 3386 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3387 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3388 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3389 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3390 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3391 alloc_buffer_waste * HeapWordSize / K, 3392 undo_waste * HeapWordSize / K); 3393 } 3394 3395 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3396 private: 3397 BoolObjectClosure* _is_alive; 3398 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3399 3400 int _initial_string_table_size; 3401 int _initial_symbol_table_size; 3402 3403 bool _process_strings; 3404 int _strings_processed; 3405 int _strings_removed; 3406 3407 bool _process_symbols; 3408 int _symbols_processed; 3409 int _symbols_removed; 3410 3411 bool _process_string_dedup; 3412 3413 public: 3414 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3415 AbstractGangTask("String/Symbol Unlinking"), 3416 _is_alive(is_alive), 3417 _dedup_closure(is_alive, NULL, false), 3418 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3419 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3420 _process_string_dedup(process_string_dedup) { 3421 3422 _initial_string_table_size = StringTable::the_table()->table_size(); 3423 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3424 if (process_strings) { 3425 StringTable::clear_parallel_claimed_index(); 3426 } 3427 if (process_symbols) { 3428 SymbolTable::clear_parallel_claimed_index(); 3429 } 3430 } 3431 3432 ~G1StringAndSymbolCleaningTask() { 3433 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3434 "claim value %d after unlink less than initial string table size %d", 3435 StringTable::parallel_claimed_index(), _initial_string_table_size); 3436 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3437 "claim value %d after unlink less than initial symbol table size %d", 3438 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3439 3440 log_info(gc, stringtable)( 3441 "Cleaned string and symbol table, " 3442 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3443 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3444 strings_processed(), strings_removed(), 3445 symbols_processed(), symbols_removed()); 3446 } 3447 3448 void work(uint worker_id) { 3449 int strings_processed = 0; 3450 int strings_removed = 0; 3451 int symbols_processed = 0; 3452 int symbols_removed = 0; 3453 if (_process_strings) { 3454 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3455 Atomic::add(strings_processed, &_strings_processed); 3456 Atomic::add(strings_removed, &_strings_removed); 3457 } 3458 if (_process_symbols) { 3459 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3460 Atomic::add(symbols_processed, &_symbols_processed); 3461 Atomic::add(symbols_removed, &_symbols_removed); 3462 } 3463 if (_process_string_dedup) { 3464 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3465 } 3466 } 3467 3468 size_t strings_processed() const { return (size_t)_strings_processed; } 3469 size_t strings_removed() const { return (size_t)_strings_removed; } 3470 3471 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3472 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3473 }; 3474 3475 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3476 private: 3477 static Monitor* _lock; 3478 3479 BoolObjectClosure* const _is_alive; 3480 const bool _unloading_occurred; 3481 const uint _num_workers; 3482 3483 // Variables used to claim nmethods. 3484 CompiledMethod* _first_nmethod; 3485 CompiledMethod* volatile _claimed_nmethod; 3486 3487 // The list of nmethods that need to be processed by the second pass. 3488 CompiledMethod* volatile _postponed_list; 3489 volatile uint _num_entered_barrier; 3490 3491 public: 3492 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3493 _is_alive(is_alive), 3494 _unloading_occurred(unloading_occurred), 3495 _num_workers(num_workers), 3496 _first_nmethod(NULL), 3497 _claimed_nmethod(NULL), 3498 _postponed_list(NULL), 3499 _num_entered_barrier(0) 3500 { 3501 CompiledMethod::increase_unloading_clock(); 3502 // Get first alive nmethod 3503 CompiledMethodIterator iter = CompiledMethodIterator(); 3504 if(iter.next_alive()) { 3505 _first_nmethod = iter.method(); 3506 } 3507 _claimed_nmethod = _first_nmethod; 3508 } 3509 3510 ~G1CodeCacheUnloadingTask() { 3511 CodeCache::verify_clean_inline_caches(); 3512 3513 CodeCache::set_needs_cache_clean(false); 3514 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3515 3516 CodeCache::verify_icholder_relocations(); 3517 } 3518 3519 private: 3520 void add_to_postponed_list(CompiledMethod* nm) { 3521 CompiledMethod* old; 3522 do { 3523 old = _postponed_list; 3524 nm->set_unloading_next(old); 3525 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old); 3526 } 3527 3528 void clean_nmethod(CompiledMethod* nm) { 3529 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3530 3531 if (postponed) { 3532 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3533 add_to_postponed_list(nm); 3534 } 3535 3536 // Mark that this thread has been cleaned/unloaded. 3537 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3538 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3539 } 3540 3541 void clean_nmethod_postponed(CompiledMethod* nm) { 3542 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3543 } 3544 3545 static const int MaxClaimNmethods = 16; 3546 3547 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3548 CompiledMethod* first; 3549 CompiledMethodIterator last; 3550 3551 do { 3552 *num_claimed_nmethods = 0; 3553 3554 first = _claimed_nmethod; 3555 last = CompiledMethodIterator(first); 3556 3557 if (first != NULL) { 3558 3559 for (int i = 0; i < MaxClaimNmethods; i++) { 3560 if (!last.next_alive()) { 3561 break; 3562 } 3563 claimed_nmethods[i] = last.method(); 3564 (*num_claimed_nmethods)++; 3565 } 3566 } 3567 3568 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first); 3569 } 3570 3571 CompiledMethod* claim_postponed_nmethod() { 3572 CompiledMethod* claim; 3573 CompiledMethod* next; 3574 3575 do { 3576 claim = _postponed_list; 3577 if (claim == NULL) { 3578 return NULL; 3579 } 3580 3581 next = claim->unloading_next(); 3582 3583 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim); 3584 3585 return claim; 3586 } 3587 3588 public: 3589 // Mark that we're done with the first pass of nmethod cleaning. 3590 void barrier_mark(uint worker_id) { 3591 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3592 _num_entered_barrier++; 3593 if (_num_entered_barrier == _num_workers) { 3594 ml.notify_all(); 3595 } 3596 } 3597 3598 // See if we have to wait for the other workers to 3599 // finish their first-pass nmethod cleaning work. 3600 void barrier_wait(uint worker_id) { 3601 if (_num_entered_barrier < _num_workers) { 3602 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3603 while (_num_entered_barrier < _num_workers) { 3604 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3605 } 3606 } 3607 } 3608 3609 // Cleaning and unloading of nmethods. Some work has to be postponed 3610 // to the second pass, when we know which nmethods survive. 3611 void work_first_pass(uint worker_id) { 3612 // The first nmethods is claimed by the first worker. 3613 if (worker_id == 0 && _first_nmethod != NULL) { 3614 clean_nmethod(_first_nmethod); 3615 _first_nmethod = NULL; 3616 } 3617 3618 int num_claimed_nmethods; 3619 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3620 3621 while (true) { 3622 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3623 3624 if (num_claimed_nmethods == 0) { 3625 break; 3626 } 3627 3628 for (int i = 0; i < num_claimed_nmethods; i++) { 3629 clean_nmethod(claimed_nmethods[i]); 3630 } 3631 } 3632 } 3633 3634 void work_second_pass(uint worker_id) { 3635 CompiledMethod* nm; 3636 // Take care of postponed nmethods. 3637 while ((nm = claim_postponed_nmethod()) != NULL) { 3638 clean_nmethod_postponed(nm); 3639 } 3640 } 3641 }; 3642 3643 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3644 3645 class G1KlassCleaningTask : public StackObj { 3646 BoolObjectClosure* _is_alive; 3647 volatile int _clean_klass_tree_claimed; 3648 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3649 3650 public: 3651 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3652 _is_alive(is_alive), 3653 _clean_klass_tree_claimed(0), 3654 _klass_iterator() { 3655 } 3656 3657 private: 3658 bool claim_clean_klass_tree_task() { 3659 if (_clean_klass_tree_claimed) { 3660 return false; 3661 } 3662 3663 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0; 3664 } 3665 3666 InstanceKlass* claim_next_klass() { 3667 Klass* klass; 3668 do { 3669 klass =_klass_iterator.next_klass(); 3670 } while (klass != NULL && !klass->is_instance_klass()); 3671 3672 // this can be null so don't call InstanceKlass::cast 3673 return static_cast<InstanceKlass*>(klass); 3674 } 3675 3676 public: 3677 3678 void clean_klass(InstanceKlass* ik) { 3679 ik->clean_weak_instanceklass_links(_is_alive); 3680 } 3681 3682 void work() { 3683 ResourceMark rm; 3684 3685 // One worker will clean the subklass/sibling klass tree. 3686 if (claim_clean_klass_tree_task()) { 3687 Klass::clean_subklass_tree(_is_alive); 3688 } 3689 3690 // All workers will help cleaning the classes, 3691 InstanceKlass* klass; 3692 while ((klass = claim_next_klass()) != NULL) { 3693 clean_klass(klass); 3694 } 3695 } 3696 }; 3697 3698 class G1ResolvedMethodCleaningTask : public StackObj { 3699 BoolObjectClosure* _is_alive; 3700 volatile int _resolved_method_task_claimed; 3701 public: 3702 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) : 3703 _is_alive(is_alive), _resolved_method_task_claimed(0) {} 3704 3705 bool claim_resolved_method_task() { 3706 if (_resolved_method_task_claimed) { 3707 return false; 3708 } 3709 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0; 3710 } 3711 3712 // These aren't big, one thread can do it all. 3713 void work() { 3714 if (claim_resolved_method_task()) { 3715 ResolvedMethodTable::unlink(_is_alive); 3716 } 3717 } 3718 }; 3719 3720 3721 // To minimize the remark pause times, the tasks below are done in parallel. 3722 class G1ParallelCleaningTask : public AbstractGangTask { 3723 private: 3724 G1StringAndSymbolCleaningTask _string_symbol_task; 3725 G1CodeCacheUnloadingTask _code_cache_task; 3726 G1KlassCleaningTask _klass_cleaning_task; 3727 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task; 3728 3729 public: 3730 // The constructor is run in the VMThread. 3731 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3732 AbstractGangTask("Parallel Cleaning"), 3733 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3734 _code_cache_task(num_workers, is_alive, unloading_occurred), 3735 _klass_cleaning_task(is_alive), 3736 _resolved_method_cleaning_task(is_alive) { 3737 } 3738 3739 // The parallel work done by all worker threads. 3740 void work(uint worker_id) { 3741 // Do first pass of code cache cleaning. 3742 _code_cache_task.work_first_pass(worker_id); 3743 3744 // Let the threads mark that the first pass is done. 3745 _code_cache_task.barrier_mark(worker_id); 3746 3747 // Clean the Strings and Symbols. 3748 _string_symbol_task.work(worker_id); 3749 3750 // Clean unreferenced things in the ResolvedMethodTable 3751 _resolved_method_cleaning_task.work(); 3752 3753 // Wait for all workers to finish the first code cache cleaning pass. 3754 _code_cache_task.barrier_wait(worker_id); 3755 3756 // Do the second code cache cleaning work, which realize on 3757 // the liveness information gathered during the first pass. 3758 _code_cache_task.work_second_pass(worker_id); 3759 3760 // Clean all klasses that were not unloaded. 3761 _klass_cleaning_task.work(); 3762 } 3763 }; 3764 3765 3766 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3767 bool class_unloading_occurred) { 3768 uint n_workers = workers()->active_workers(); 3769 3770 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3771 workers()->run_task(&g1_unlink_task); 3772 } 3773 3774 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3775 bool process_strings, 3776 bool process_symbols, 3777 bool process_string_dedup) { 3778 if (!process_strings && !process_symbols && !process_string_dedup) { 3779 // Nothing to clean. 3780 return; 3781 } 3782 3783 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3784 workers()->run_task(&g1_unlink_task); 3785 3786 } 3787 3788 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3789 private: 3790 DirtyCardQueueSet* _queue; 3791 G1CollectedHeap* _g1h; 3792 public: 3793 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3794 _queue(queue), _g1h(g1h) { } 3795 3796 virtual void work(uint worker_id) { 3797 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3798 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3799 3800 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3801 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3802 3803 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3804 } 3805 }; 3806 3807 void G1CollectedHeap::redirty_logged_cards() { 3808 double redirty_logged_cards_start = os::elapsedTime(); 3809 3810 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3811 dirty_card_queue_set().reset_for_par_iteration(); 3812 workers()->run_task(&redirty_task); 3813 3814 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 3815 dcq.merge_bufferlists(&dirty_card_queue_set()); 3816 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3817 3818 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3819 } 3820 3821 // Weak Reference Processing support 3822 3823 // An always "is_alive" closure that is used to preserve referents. 3824 // If the object is non-null then it's alive. Used in the preservation 3825 // of referent objects that are pointed to by reference objects 3826 // discovered by the CM ref processor. 3827 class G1AlwaysAliveClosure: public BoolObjectClosure { 3828 G1CollectedHeap* _g1; 3829 public: 3830 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3831 bool do_object_b(oop p) { 3832 if (p != NULL) { 3833 return true; 3834 } 3835 return false; 3836 } 3837 }; 3838 3839 bool G1STWIsAliveClosure::do_object_b(oop p) { 3840 // An object is reachable if it is outside the collection set, 3841 // or is inside and copied. 3842 return !_g1->is_in_cset(p) || p->is_forwarded(); 3843 } 3844 3845 // Non Copying Keep Alive closure 3846 class G1KeepAliveClosure: public OopClosure { 3847 G1CollectedHeap* _g1; 3848 public: 3849 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3850 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3851 void do_oop(oop* p) { 3852 oop obj = *p; 3853 assert(obj != NULL, "the caller should have filtered out NULL values"); 3854 3855 const InCSetState cset_state = _g1->in_cset_state(obj); 3856 if (!cset_state.is_in_cset_or_humongous()) { 3857 return; 3858 } 3859 if (cset_state.is_in_cset()) { 3860 assert( obj->is_forwarded(), "invariant" ); 3861 *p = obj->forwardee(); 3862 } else { 3863 assert(!obj->is_forwarded(), "invariant" ); 3864 assert(cset_state.is_humongous(), 3865 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3866 _g1->set_humongous_is_live(obj); 3867 } 3868 } 3869 }; 3870 3871 // Copying Keep Alive closure - can be called from both 3872 // serial and parallel code as long as different worker 3873 // threads utilize different G1ParScanThreadState instances 3874 // and different queues. 3875 3876 class G1CopyingKeepAliveClosure: public OopClosure { 3877 G1CollectedHeap* _g1h; 3878 OopClosure* _copy_non_heap_obj_cl; 3879 G1ParScanThreadState* _par_scan_state; 3880 3881 public: 3882 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3883 OopClosure* non_heap_obj_cl, 3884 G1ParScanThreadState* pss): 3885 _g1h(g1h), 3886 _copy_non_heap_obj_cl(non_heap_obj_cl), 3887 _par_scan_state(pss) 3888 {} 3889 3890 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3891 virtual void do_oop( oop* p) { do_oop_work(p); } 3892 3893 template <class T> void do_oop_work(T* p) { 3894 oop obj = oopDesc::load_decode_heap_oop(p); 3895 3896 if (_g1h->is_in_cset_or_humongous(obj)) { 3897 // If the referent object has been forwarded (either copied 3898 // to a new location or to itself in the event of an 3899 // evacuation failure) then we need to update the reference 3900 // field and, if both reference and referent are in the G1 3901 // heap, update the RSet for the referent. 3902 // 3903 // If the referent has not been forwarded then we have to keep 3904 // it alive by policy. Therefore we have copy the referent. 3905 // 3906 // If the reference field is in the G1 heap then we can push 3907 // on the PSS queue. When the queue is drained (after each 3908 // phase of reference processing) the object and it's followers 3909 // will be copied, the reference field set to point to the 3910 // new location, and the RSet updated. Otherwise we need to 3911 // use the the non-heap or metadata closures directly to copy 3912 // the referent object and update the pointer, while avoiding 3913 // updating the RSet. 3914 3915 if (_g1h->is_in_g1_reserved(p)) { 3916 _par_scan_state->push_on_queue(p); 3917 } else { 3918 assert(!Metaspace::contains((const void*)p), 3919 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 3920 _copy_non_heap_obj_cl->do_oop(p); 3921 } 3922 } 3923 } 3924 }; 3925 3926 // Serial drain queue closure. Called as the 'complete_gc' 3927 // closure for each discovered list in some of the 3928 // reference processing phases. 3929 3930 class G1STWDrainQueueClosure: public VoidClosure { 3931 protected: 3932 G1CollectedHeap* _g1h; 3933 G1ParScanThreadState* _par_scan_state; 3934 3935 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3936 3937 public: 3938 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3939 _g1h(g1h), 3940 _par_scan_state(pss) 3941 { } 3942 3943 void do_void() { 3944 G1ParScanThreadState* const pss = par_scan_state(); 3945 pss->trim_queue(); 3946 } 3947 }; 3948 3949 // Parallel Reference Processing closures 3950 3951 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3952 // processing during G1 evacuation pauses. 3953 3954 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3955 private: 3956 G1CollectedHeap* _g1h; 3957 G1ParScanThreadStateSet* _pss; 3958 RefToScanQueueSet* _queues; 3959 WorkGang* _workers; 3960 uint _active_workers; 3961 3962 public: 3963 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3964 G1ParScanThreadStateSet* per_thread_states, 3965 WorkGang* workers, 3966 RefToScanQueueSet *task_queues, 3967 uint n_workers) : 3968 _g1h(g1h), 3969 _pss(per_thread_states), 3970 _queues(task_queues), 3971 _workers(workers), 3972 _active_workers(n_workers) 3973 { 3974 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 3975 } 3976 3977 // Executes the given task using concurrent marking worker threads. 3978 virtual void execute(ProcessTask& task); 3979 virtual void execute(EnqueueTask& task); 3980 }; 3981 3982 // Gang task for possibly parallel reference processing 3983 3984 class G1STWRefProcTaskProxy: public AbstractGangTask { 3985 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 3986 ProcessTask& _proc_task; 3987 G1CollectedHeap* _g1h; 3988 G1ParScanThreadStateSet* _pss; 3989 RefToScanQueueSet* _task_queues; 3990 ParallelTaskTerminator* _terminator; 3991 3992 public: 3993 G1STWRefProcTaskProxy(ProcessTask& proc_task, 3994 G1CollectedHeap* g1h, 3995 G1ParScanThreadStateSet* per_thread_states, 3996 RefToScanQueueSet *task_queues, 3997 ParallelTaskTerminator* terminator) : 3998 AbstractGangTask("Process reference objects in parallel"), 3999 _proc_task(proc_task), 4000 _g1h(g1h), 4001 _pss(per_thread_states), 4002 _task_queues(task_queues), 4003 _terminator(terminator) 4004 {} 4005 4006 virtual void work(uint worker_id) { 4007 // The reference processing task executed by a single worker. 4008 ResourceMark rm; 4009 HandleMark hm; 4010 4011 G1STWIsAliveClosure is_alive(_g1h); 4012 4013 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4014 pss->set_ref_processor(NULL); 4015 4016 // Keep alive closure. 4017 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4018 4019 // Complete GC closure 4020 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4021 4022 // Call the reference processing task's work routine. 4023 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4024 4025 // Note we cannot assert that the refs array is empty here as not all 4026 // of the processing tasks (specifically phase2 - pp2_work) execute 4027 // the complete_gc closure (which ordinarily would drain the queue) so 4028 // the queue may not be empty. 4029 } 4030 }; 4031 4032 // Driver routine for parallel reference processing. 4033 // Creates an instance of the ref processing gang 4034 // task and has the worker threads execute it. 4035 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4036 assert(_workers != NULL, "Need parallel worker threads."); 4037 4038 ParallelTaskTerminator terminator(_active_workers, _queues); 4039 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4040 4041 _workers->run_task(&proc_task_proxy); 4042 } 4043 4044 // Gang task for parallel reference enqueueing. 4045 4046 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4047 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4048 EnqueueTask& _enq_task; 4049 4050 public: 4051 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4052 AbstractGangTask("Enqueue reference objects in parallel"), 4053 _enq_task(enq_task) 4054 { } 4055 4056 virtual void work(uint worker_id) { 4057 _enq_task.work(worker_id); 4058 } 4059 }; 4060 4061 // Driver routine for parallel reference enqueueing. 4062 // Creates an instance of the ref enqueueing gang 4063 // task and has the worker threads execute it. 4064 4065 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4066 assert(_workers != NULL, "Need parallel worker threads."); 4067 4068 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4069 4070 _workers->run_task(&enq_task_proxy); 4071 } 4072 4073 // End of weak reference support closures 4074 4075 // Abstract task used to preserve (i.e. copy) any referent objects 4076 // that are in the collection set and are pointed to by reference 4077 // objects discovered by the CM ref processor. 4078 4079 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4080 protected: 4081 G1CollectedHeap* _g1h; 4082 G1ParScanThreadStateSet* _pss; 4083 RefToScanQueueSet* _queues; 4084 ParallelTaskTerminator _terminator; 4085 uint _n_workers; 4086 4087 public: 4088 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4089 AbstractGangTask("ParPreserveCMReferents"), 4090 _g1h(g1h), 4091 _pss(per_thread_states), 4092 _queues(task_queues), 4093 _terminator(workers, _queues), 4094 _n_workers(workers) 4095 { 4096 g1h->ref_processor_cm()->set_active_mt_degree(workers); 4097 } 4098 4099 void work(uint worker_id) { 4100 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4101 4102 ResourceMark rm; 4103 HandleMark hm; 4104 4105 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4106 pss->set_ref_processor(NULL); 4107 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4108 4109 // Is alive closure 4110 G1AlwaysAliveClosure always_alive(_g1h); 4111 4112 // Copying keep alive closure. Applied to referent objects that need 4113 // to be copied. 4114 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4115 4116 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4117 4118 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4119 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4120 4121 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4122 // So this must be true - but assert just in case someone decides to 4123 // change the worker ids. 4124 assert(worker_id < limit, "sanity"); 4125 assert(!rp->discovery_is_atomic(), "check this code"); 4126 4127 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4128 for (uint idx = worker_id; idx < limit; idx += stride) { 4129 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4130 4131 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4132 while (iter.has_next()) { 4133 // Since discovery is not atomic for the CM ref processor, we 4134 // can see some null referent objects. 4135 iter.load_ptrs(DEBUG_ONLY(true)); 4136 oop ref = iter.obj(); 4137 4138 // This will filter nulls. 4139 if (iter.is_referent_alive()) { 4140 iter.make_referent_alive(); 4141 } 4142 iter.move_to_next(); 4143 } 4144 } 4145 4146 // Drain the queue - which may cause stealing 4147 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4148 drain_queue.do_void(); 4149 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4150 assert(pss->queue_is_empty(), "should be"); 4151 } 4152 }; 4153 4154 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4155 // Any reference objects, in the collection set, that were 'discovered' 4156 // by the CM ref processor should have already been copied (either by 4157 // applying the external root copy closure to the discovered lists, or 4158 // by following an RSet entry). 4159 // 4160 // But some of the referents, that are in the collection set, that these 4161 // reference objects point to may not have been copied: the STW ref 4162 // processor would have seen that the reference object had already 4163 // been 'discovered' and would have skipped discovering the reference, 4164 // but would not have treated the reference object as a regular oop. 4165 // As a result the copy closure would not have been applied to the 4166 // referent object. 4167 // 4168 // We need to explicitly copy these referent objects - the references 4169 // will be processed at the end of remarking. 4170 // 4171 // We also need to do this copying before we process the reference 4172 // objects discovered by the STW ref processor in case one of these 4173 // referents points to another object which is also referenced by an 4174 // object discovered by the STW ref processor. 4175 double preserve_cm_referents_time = 0.0; 4176 4177 // To avoid spawning task when there is no work to do, check that 4178 // a concurrent cycle is active and that some references have been 4179 // discovered. 4180 if (concurrent_mark()->cm_thread()->during_cycle() && 4181 ref_processor_cm()->has_discovered_references()) { 4182 double preserve_cm_referents_start = os::elapsedTime(); 4183 uint no_of_gc_workers = workers()->active_workers(); 4184 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4185 per_thread_states, 4186 no_of_gc_workers, 4187 _task_queues); 4188 workers()->run_task(&keep_cm_referents); 4189 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4190 } 4191 4192 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4193 } 4194 4195 // Weak Reference processing during an evacuation pause (part 1). 4196 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4197 double ref_proc_start = os::elapsedTime(); 4198 4199 ReferenceProcessor* rp = _ref_processor_stw; 4200 assert(rp->discovery_enabled(), "should have been enabled"); 4201 4202 // Closure to test whether a referent is alive. 4203 G1STWIsAliveClosure is_alive(this); 4204 4205 // Even when parallel reference processing is enabled, the processing 4206 // of JNI refs is serial and performed serially by the current thread 4207 // rather than by a worker. The following PSS will be used for processing 4208 // JNI refs. 4209 4210 // Use only a single queue for this PSS. 4211 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4212 pss->set_ref_processor(NULL); 4213 assert(pss->queue_is_empty(), "pre-condition"); 4214 4215 // Keep alive closure. 4216 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4217 4218 // Serial Complete GC closure 4219 G1STWDrainQueueClosure drain_queue(this, pss); 4220 4221 // Setup the soft refs policy... 4222 rp->setup_policy(false); 4223 4224 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4225 4226 ReferenceProcessorStats stats; 4227 if (!rp->processing_is_mt()) { 4228 // Serial reference processing... 4229 stats = rp->process_discovered_references(&is_alive, 4230 &keep_alive, 4231 &drain_queue, 4232 NULL, 4233 pt); 4234 } else { 4235 uint no_of_gc_workers = workers()->active_workers(); 4236 4237 // Parallel reference processing 4238 assert(no_of_gc_workers <= rp->max_num_q(), 4239 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4240 no_of_gc_workers, rp->max_num_q()); 4241 4242 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4243 stats = rp->process_discovered_references(&is_alive, 4244 &keep_alive, 4245 &drain_queue, 4246 &par_task_executor, 4247 pt); 4248 } 4249 4250 _gc_tracer_stw->report_gc_reference_stats(stats); 4251 4252 // We have completed copying any necessary live referent objects. 4253 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4254 4255 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4256 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4257 } 4258 4259 // Weak Reference processing during an evacuation pause (part 2). 4260 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4261 double ref_enq_start = os::elapsedTime(); 4262 4263 ReferenceProcessor* rp = _ref_processor_stw; 4264 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4265 4266 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4267 4268 // Now enqueue any remaining on the discovered lists on to 4269 // the pending list. 4270 if (!rp->processing_is_mt()) { 4271 // Serial reference processing... 4272 rp->enqueue_discovered_references(NULL, pt); 4273 } else { 4274 // Parallel reference enqueueing 4275 4276 uint n_workers = workers()->active_workers(); 4277 4278 assert(n_workers <= rp->max_num_q(), 4279 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4280 n_workers, rp->max_num_q()); 4281 4282 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4283 rp->enqueue_discovered_references(&par_task_executor, pt); 4284 } 4285 4286 rp->verify_no_references_recorded(); 4287 assert(!rp->discovery_enabled(), "should have been disabled"); 4288 4289 // If during an initial mark pause we install a pending list head which is not otherwise reachable 4290 // ensure that it is marked in the bitmap for concurrent marking to discover. 4291 if (collector_state()->during_initial_mark_pause()) { 4292 oop pll_head = Universe::reference_pending_list(); 4293 if (pll_head != NULL) { 4294 _cm->mark_in_next_bitmap(pll_head); 4295 } 4296 } 4297 4298 // FIXME 4299 // CM's reference processing also cleans up the string and symbol tables. 4300 // Should we do that here also? We could, but it is a serial operation 4301 // and could significantly increase the pause time. 4302 4303 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4304 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4305 } 4306 4307 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4308 double merge_pss_time_start = os::elapsedTime(); 4309 per_thread_states->flush(); 4310 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4311 } 4312 4313 void G1CollectedHeap::pre_evacuate_collection_set() { 4314 _expand_heap_after_alloc_failure = true; 4315 _evacuation_failed = false; 4316 4317 // Disable the hot card cache. 4318 _hot_card_cache->reset_hot_cache_claimed_index(); 4319 _hot_card_cache->set_use_cache(false); 4320 4321 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4322 _preserved_marks_set.assert_empty(); 4323 4324 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4325 4326 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4327 if (collector_state()->during_initial_mark_pause()) { 4328 double start_clear_claimed_marks = os::elapsedTime(); 4329 4330 ClassLoaderDataGraph::clear_claimed_marks(); 4331 4332 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4333 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4334 } 4335 } 4336 4337 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4338 // Should G1EvacuationFailureALot be in effect for this GC? 4339 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4340 4341 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4342 4343 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4344 4345 double start_par_time_sec = os::elapsedTime(); 4346 double end_par_time_sec; 4347 4348 { 4349 const uint n_workers = workers()->active_workers(); 4350 G1RootProcessor root_processor(this, n_workers); 4351 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4352 4353 print_termination_stats_hdr(); 4354 4355 workers()->run_task(&g1_par_task); 4356 end_par_time_sec = os::elapsedTime(); 4357 4358 // Closing the inner scope will execute the destructor 4359 // for the G1RootProcessor object. We record the current 4360 // elapsed time before closing the scope so that time 4361 // taken for the destructor is NOT included in the 4362 // reported parallel time. 4363 } 4364 4365 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4366 phase_times->record_par_time(par_time_ms); 4367 4368 double code_root_fixup_time_ms = 4369 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4370 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4371 } 4372 4373 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4374 // Process any discovered reference objects - we have 4375 // to do this _before_ we retire the GC alloc regions 4376 // as we may have to copy some 'reachable' referent 4377 // objects (and their reachable sub-graphs) that were 4378 // not copied during the pause. 4379 if (g1_policy()->should_process_references()) { 4380 preserve_cm_referents(per_thread_states); 4381 process_discovered_references(per_thread_states); 4382 } else { 4383 ref_processor_stw()->verify_no_references_recorded(); 4384 } 4385 4386 G1STWIsAliveClosure is_alive(this); 4387 G1KeepAliveClosure keep_alive(this); 4388 4389 { 4390 double start = os::elapsedTime(); 4391 4392 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 4393 4394 double time_ms = (os::elapsedTime() - start) * 1000.0; 4395 g1_policy()->phase_times()->record_ref_proc_time(time_ms); 4396 } 4397 4398 if (G1StringDedup::is_enabled()) { 4399 double fixup_start = os::elapsedTime(); 4400 4401 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4402 4403 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4404 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4405 } 4406 4407 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4408 4409 if (evacuation_failed()) { 4410 restore_after_evac_failure(); 4411 4412 // Reset the G1EvacuationFailureALot counters and flags 4413 // Note: the values are reset only when an actual 4414 // evacuation failure occurs. 4415 NOT_PRODUCT(reset_evacuation_should_fail();) 4416 } 4417 4418 _preserved_marks_set.assert_empty(); 4419 4420 // Enqueue any remaining references remaining on the STW 4421 // reference processor's discovered lists. We need to do 4422 // this after the card table is cleaned (and verified) as 4423 // the act of enqueueing entries on to the pending list 4424 // will log these updates (and dirty their associated 4425 // cards). We need these updates logged to update any 4426 // RSets. 4427 if (g1_policy()->should_process_references()) { 4428 enqueue_discovered_references(per_thread_states); 4429 } else { 4430 g1_policy()->phase_times()->record_ref_enq_time(0); 4431 } 4432 4433 _allocator->release_gc_alloc_regions(evacuation_info); 4434 4435 merge_per_thread_state_info(per_thread_states); 4436 4437 // Reset and re-enable the hot card cache. 4438 // Note the counts for the cards in the regions in the 4439 // collection set are reset when the collection set is freed. 4440 _hot_card_cache->reset_hot_cache(); 4441 _hot_card_cache->set_use_cache(true); 4442 4443 purge_code_root_memory(); 4444 4445 redirty_logged_cards(); 4446 #if COMPILER2_OR_JVMCI 4447 double start = os::elapsedTime(); 4448 DerivedPointerTable::update_pointers(); 4449 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4450 #endif 4451 g1_policy()->print_age_table(); 4452 } 4453 4454 void G1CollectedHeap::record_obj_copy_mem_stats() { 4455 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4456 4457 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4458 create_g1_evac_summary(&_old_evac_stats)); 4459 } 4460 4461 void G1CollectedHeap::free_region(HeapRegion* hr, 4462 FreeRegionList* free_list, 4463 bool skip_remset, 4464 bool skip_hot_card_cache, 4465 bool locked) { 4466 assert(!hr->is_free(), "the region should not be free"); 4467 assert(!hr->is_empty(), "the region should not be empty"); 4468 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4469 assert(free_list != NULL, "pre-condition"); 4470 4471 if (G1VerifyBitmaps) { 4472 MemRegion mr(hr->bottom(), hr->end()); 4473 concurrent_mark()->clear_range_in_prev_bitmap(mr); 4474 } 4475 4476 // Clear the card counts for this region. 4477 // Note: we only need to do this if the region is not young 4478 // (since we don't refine cards in young regions). 4479 if (!skip_hot_card_cache && !hr->is_young()) { 4480 _hot_card_cache->reset_card_counts(hr); 4481 } 4482 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4483 free_list->add_ordered(hr); 4484 } 4485 4486 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4487 FreeRegionList* free_list, 4488 bool skip_remset) { 4489 assert(hr->is_humongous(), "this is only for humongous regions"); 4490 assert(free_list != NULL, "pre-condition"); 4491 hr->clear_humongous(); 4492 free_region(hr, free_list, skip_remset); 4493 } 4494 4495 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4496 const uint humongous_regions_removed) { 4497 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4498 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4499 _old_set.bulk_remove(old_regions_removed); 4500 _humongous_set.bulk_remove(humongous_regions_removed); 4501 } 4502 4503 } 4504 4505 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4506 assert(list != NULL, "list can't be null"); 4507 if (!list->is_empty()) { 4508 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4509 _hrm.insert_list_into_free_list(list); 4510 } 4511 } 4512 4513 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4514 decrease_used(bytes); 4515 } 4516 4517 class G1ParScrubRemSetTask: public AbstractGangTask { 4518 protected: 4519 G1RemSet* _g1rs; 4520 HeapRegionClaimer _hrclaimer; 4521 4522 public: 4523 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) : 4524 AbstractGangTask("G1 ScrubRS"), 4525 _g1rs(g1_rs), 4526 _hrclaimer(num_workers) { 4527 } 4528 4529 void work(uint worker_id) { 4530 _g1rs->scrub(worker_id, &_hrclaimer); 4531 } 4532 }; 4533 4534 void G1CollectedHeap::scrub_rem_set() { 4535 uint num_workers = workers()->active_workers(); 4536 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers); 4537 workers()->run_task(&g1_par_scrub_rs_task); 4538 } 4539 4540 class G1FreeCollectionSetTask : public AbstractGangTask { 4541 private: 4542 4543 // Closure applied to all regions in the collection set to do work that needs to 4544 // be done serially in a single thread. 4545 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4546 private: 4547 EvacuationInfo* _evacuation_info; 4548 const size_t* _surviving_young_words; 4549 4550 // Bytes used in successfully evacuated regions before the evacuation. 4551 size_t _before_used_bytes; 4552 // Bytes used in unsucessfully evacuated regions before the evacuation 4553 size_t _after_used_bytes; 4554 4555 size_t _bytes_allocated_in_old_since_last_gc; 4556 4557 size_t _failure_used_words; 4558 size_t _failure_waste_words; 4559 4560 FreeRegionList _local_free_list; 4561 public: 4562 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4563 HeapRegionClosure(), 4564 _evacuation_info(evacuation_info), 4565 _surviving_young_words(surviving_young_words), 4566 _before_used_bytes(0), 4567 _after_used_bytes(0), 4568 _bytes_allocated_in_old_since_last_gc(0), 4569 _failure_used_words(0), 4570 _failure_waste_words(0), 4571 _local_free_list("Local Region List for CSet Freeing") { 4572 } 4573 4574 virtual bool doHeapRegion(HeapRegion* r) { 4575 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4576 4577 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4578 g1h->clear_in_cset(r); 4579 4580 if (r->is_young()) { 4581 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4582 "Young index %d is wrong for region %u of type %s with %u young regions", 4583 r->young_index_in_cset(), 4584 r->hrm_index(), 4585 r->get_type_str(), 4586 g1h->collection_set()->young_region_length()); 4587 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4588 r->record_surv_words_in_group(words_survived); 4589 } 4590 4591 if (!r->evacuation_failed()) { 4592 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4593 _before_used_bytes += r->used(); 4594 g1h->free_region(r, 4595 &_local_free_list, 4596 true, /* skip_remset */ 4597 true, /* skip_hot_card_cache */ 4598 true /* locked */); 4599 } else { 4600 r->uninstall_surv_rate_group(); 4601 r->set_young_index_in_cset(-1); 4602 r->set_evacuation_failed(false); 4603 // When moving a young gen region to old gen, we "allocate" that whole region 4604 // there. This is in addition to any already evacuated objects. Notify the 4605 // policy about that. 4606 // Old gen regions do not cause an additional allocation: both the objects 4607 // still in the region and the ones already moved are accounted for elsewhere. 4608 if (r->is_young()) { 4609 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4610 } 4611 // The region is now considered to be old. 4612 r->set_old(); 4613 // Do some allocation statistics accounting. Regions that failed evacuation 4614 // are always made old, so there is no need to update anything in the young 4615 // gen statistics, but we need to update old gen statistics. 4616 size_t used_words = r->marked_bytes() / HeapWordSize; 4617 4618 _failure_used_words += used_words; 4619 _failure_waste_words += HeapRegion::GrainWords - used_words; 4620 4621 g1h->old_set_add(r); 4622 _after_used_bytes += r->used(); 4623 } 4624 return false; 4625 } 4626 4627 void complete_work() { 4628 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4629 4630 _evacuation_info->set_regions_freed(_local_free_list.length()); 4631 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4632 4633 g1h->prepend_to_freelist(&_local_free_list); 4634 g1h->decrement_summary_bytes(_before_used_bytes); 4635 4636 G1Policy* policy = g1h->g1_policy(); 4637 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4638 4639 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4640 } 4641 }; 4642 4643 G1CollectionSet* _collection_set; 4644 G1SerialFreeCollectionSetClosure _cl; 4645 const size_t* _surviving_young_words; 4646 4647 size_t _rs_lengths; 4648 4649 volatile jint _serial_work_claim; 4650 4651 struct WorkItem { 4652 uint region_idx; 4653 bool is_young; 4654 bool evacuation_failed; 4655 4656 WorkItem(HeapRegion* r) { 4657 region_idx = r->hrm_index(); 4658 is_young = r->is_young(); 4659 evacuation_failed = r->evacuation_failed(); 4660 } 4661 }; 4662 4663 volatile size_t _parallel_work_claim; 4664 size_t _num_work_items; 4665 WorkItem* _work_items; 4666 4667 void do_serial_work() { 4668 // Need to grab the lock to be allowed to modify the old region list. 4669 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4670 _collection_set->iterate(&_cl); 4671 } 4672 4673 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4674 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4675 4676 HeapRegion* r = g1h->region_at(region_idx); 4677 assert(!g1h->is_on_master_free_list(r), "sanity"); 4678 4679 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4680 4681 if (!is_young) { 4682 g1h->_hot_card_cache->reset_card_counts(r); 4683 } 4684 4685 if (!evacuation_failed) { 4686 r->rem_set()->clear_locked(); 4687 } 4688 } 4689 4690 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4691 private: 4692 size_t _cur_idx; 4693 WorkItem* _work_items; 4694 public: 4695 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4696 4697 virtual bool doHeapRegion(HeapRegion* r) { 4698 _work_items[_cur_idx++] = WorkItem(r); 4699 return false; 4700 } 4701 }; 4702 4703 void prepare_work() { 4704 G1PrepareFreeCollectionSetClosure cl(_work_items); 4705 _collection_set->iterate(&cl); 4706 } 4707 4708 void complete_work() { 4709 _cl.complete_work(); 4710 4711 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4712 policy->record_max_rs_lengths(_rs_lengths); 4713 policy->cset_regions_freed(); 4714 } 4715 public: 4716 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4717 AbstractGangTask("G1 Free Collection Set"), 4718 _cl(evacuation_info, surviving_young_words), 4719 _collection_set(collection_set), 4720 _surviving_young_words(surviving_young_words), 4721 _serial_work_claim(0), 4722 _rs_lengths(0), 4723 _parallel_work_claim(0), 4724 _num_work_items(collection_set->region_length()), 4725 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4726 prepare_work(); 4727 } 4728 4729 ~G1FreeCollectionSetTask() { 4730 complete_work(); 4731 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4732 } 4733 4734 // Chunk size for work distribution. The chosen value has been determined experimentally 4735 // to be a good tradeoff between overhead and achievable parallelism. 4736 static uint chunk_size() { return 32; } 4737 4738 virtual void work(uint worker_id) { 4739 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4740 4741 // Claim serial work. 4742 if (_serial_work_claim == 0) { 4743 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4744 if (value == 0) { 4745 double serial_time = os::elapsedTime(); 4746 do_serial_work(); 4747 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4748 } 4749 } 4750 4751 // Start parallel work. 4752 double young_time = 0.0; 4753 bool has_young_time = false; 4754 double non_young_time = 0.0; 4755 bool has_non_young_time = false; 4756 4757 while (true) { 4758 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4759 size_t cur = end - chunk_size(); 4760 4761 if (cur >= _num_work_items) { 4762 break; 4763 } 4764 4765 double start_time = os::elapsedTime(); 4766 4767 end = MIN2(end, _num_work_items); 4768 4769 for (; cur < end; cur++) { 4770 bool is_young = _work_items[cur].is_young; 4771 4772 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4773 4774 double end_time = os::elapsedTime(); 4775 double time_taken = end_time - start_time; 4776 if (is_young) { 4777 young_time += time_taken; 4778 has_young_time = true; 4779 } else { 4780 non_young_time += time_taken; 4781 has_non_young_time = true; 4782 } 4783 start_time = end_time; 4784 } 4785 } 4786 4787 if (has_young_time) { 4788 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4789 } 4790 if (has_non_young_time) { 4791 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time); 4792 } 4793 } 4794 }; 4795 4796 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4797 _eden.clear(); 4798 4799 double free_cset_start_time = os::elapsedTime(); 4800 4801 { 4802 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4803 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4804 4805 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4806 4807 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4808 cl.name(), 4809 num_workers, 4810 _collection_set.region_length()); 4811 workers()->run_task(&cl, num_workers); 4812 } 4813 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4814 4815 collection_set->clear(); 4816 } 4817 4818 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4819 private: 4820 FreeRegionList* _free_region_list; 4821 HeapRegionSet* _proxy_set; 4822 uint _humongous_objects_reclaimed; 4823 uint _humongous_regions_reclaimed; 4824 size_t _freed_bytes; 4825 public: 4826 4827 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4828 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4829 } 4830 4831 virtual bool doHeapRegion(HeapRegion* r) { 4832 if (!r->is_starts_humongous()) { 4833 return false; 4834 } 4835 4836 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4837 4838 oop obj = (oop)r->bottom(); 4839 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap(); 4840 4841 // The following checks whether the humongous object is live are sufficient. 4842 // The main additional check (in addition to having a reference from the roots 4843 // or the young gen) is whether the humongous object has a remembered set entry. 4844 // 4845 // A humongous object cannot be live if there is no remembered set for it 4846 // because: 4847 // - there can be no references from within humongous starts regions referencing 4848 // the object because we never allocate other objects into them. 4849 // (I.e. there are no intra-region references that may be missed by the 4850 // remembered set) 4851 // - as soon there is a remembered set entry to the humongous starts region 4852 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4853 // until the end of a concurrent mark. 4854 // 4855 // It is not required to check whether the object has been found dead by marking 4856 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4857 // all objects allocated during that time are considered live. 4858 // SATB marking is even more conservative than the remembered set. 4859 // So if at this point in the collection there is no remembered set entry, 4860 // nobody has a reference to it. 4861 // At the start of collection we flush all refinement logs, and remembered sets 4862 // are completely up-to-date wrt to references to the humongous object. 4863 // 4864 // Other implementation considerations: 4865 // - never consider object arrays at this time because they would pose 4866 // considerable effort for cleaning up the the remembered sets. This is 4867 // required because stale remembered sets might reference locations that 4868 // are currently allocated into. 4869 uint region_idx = r->hrm_index(); 4870 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4871 !r->rem_set()->is_empty()) { 4872 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", 4873 region_idx, 4874 (size_t)obj->size() * HeapWordSize, 4875 p2i(r->bottom()), 4876 r->rem_set()->occupied(), 4877 r->rem_set()->strong_code_roots_list_length(), 4878 next_bitmap->is_marked(r->bottom()), 4879 g1h->is_humongous_reclaim_candidate(region_idx), 4880 obj->is_typeArray() 4881 ); 4882 return false; 4883 } 4884 4885 guarantee(obj->is_typeArray(), 4886 "Only eagerly reclaiming type arrays is supported, but the object " 4887 PTR_FORMAT " is not.", p2i(r->bottom())); 4888 4889 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", 4890 region_idx, 4891 (size_t)obj->size() * HeapWordSize, 4892 p2i(r->bottom()), 4893 r->rem_set()->occupied(), 4894 r->rem_set()->strong_code_roots_list_length(), 4895 next_bitmap->is_marked(r->bottom()), 4896 g1h->is_humongous_reclaim_candidate(region_idx), 4897 obj->is_typeArray() 4898 ); 4899 4900 // Need to clear mark bit of the humongous object if already set. 4901 if (next_bitmap->is_marked(r->bottom())) { 4902 next_bitmap->clear(r->bottom()); 4903 } 4904 _humongous_objects_reclaimed++; 4905 do { 4906 HeapRegion* next = g1h->next_region_in_humongous(r); 4907 _freed_bytes += r->used(); 4908 r->set_containing_set(NULL); 4909 _humongous_regions_reclaimed++; 4910 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ ); 4911 r = next; 4912 } while (r != NULL); 4913 4914 return false; 4915 } 4916 4917 uint humongous_objects_reclaimed() { 4918 return _humongous_objects_reclaimed; 4919 } 4920 4921 uint humongous_regions_reclaimed() { 4922 return _humongous_regions_reclaimed; 4923 } 4924 4925 size_t bytes_freed() const { 4926 return _freed_bytes; 4927 } 4928 }; 4929 4930 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4931 assert_at_safepoint(true); 4932 4933 if (!G1EagerReclaimHumongousObjects || 4934 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4935 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4936 return; 4937 } 4938 4939 double start_time = os::elapsedTime(); 4940 4941 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4942 4943 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4944 heap_region_iterate(&cl); 4945 4946 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4947 4948 G1HRPrinter* hrp = hr_printer(); 4949 if (hrp->is_active()) { 4950 FreeRegionListIterator iter(&local_cleanup_list); 4951 while (iter.more_available()) { 4952 HeapRegion* hr = iter.get_next(); 4953 hrp->cleanup(hr); 4954 } 4955 } 4956 4957 prepend_to_freelist(&local_cleanup_list); 4958 decrement_summary_bytes(cl.bytes_freed()); 4959 4960 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4961 cl.humongous_objects_reclaimed()); 4962 } 4963 4964 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4965 public: 4966 virtual bool doHeapRegion(HeapRegion* r) { 4967 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4968 G1CollectedHeap::heap()->clear_in_cset(r); 4969 r->set_young_index_in_cset(-1); 4970 return false; 4971 } 4972 }; 4973 4974 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4975 G1AbandonCollectionSetClosure cl; 4976 collection_set->iterate(&cl); 4977 4978 collection_set->clear(); 4979 collection_set->stop_incremental_building(); 4980 } 4981 4982 void G1CollectedHeap::set_free_regions_coming() { 4983 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 4984 4985 assert(!free_regions_coming(), "pre-condition"); 4986 _free_regions_coming = true; 4987 } 4988 4989 void G1CollectedHeap::reset_free_regions_coming() { 4990 assert(free_regions_coming(), "pre-condition"); 4991 4992 { 4993 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 4994 _free_regions_coming = false; 4995 SecondaryFreeList_lock->notify_all(); 4996 } 4997 4998 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 4999 } 5000 5001 void G1CollectedHeap::wait_while_free_regions_coming() { 5002 // Most of the time we won't have to wait, so let's do a quick test 5003 // first before we take the lock. 5004 if (!free_regions_coming()) { 5005 return; 5006 } 5007 5008 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 5009 5010 { 5011 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5012 while (free_regions_coming()) { 5013 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5014 } 5015 } 5016 5017 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 5018 } 5019 5020 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5021 return _allocator->is_retained_old_region(hr); 5022 } 5023 5024 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5025 _eden.add(hr); 5026 _g1_policy->set_region_eden(hr); 5027 } 5028 5029 #ifdef ASSERT 5030 5031 class NoYoungRegionsClosure: public HeapRegionClosure { 5032 private: 5033 bool _success; 5034 public: 5035 NoYoungRegionsClosure() : _success(true) { } 5036 bool doHeapRegion(HeapRegion* r) { 5037 if (r->is_young()) { 5038 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5039 p2i(r->bottom()), p2i(r->end())); 5040 _success = false; 5041 } 5042 return false; 5043 } 5044 bool success() { return _success; } 5045 }; 5046 5047 bool G1CollectedHeap::check_young_list_empty() { 5048 bool ret = (young_regions_count() == 0); 5049 5050 NoYoungRegionsClosure closure; 5051 heap_region_iterate(&closure); 5052 ret = ret && closure.success(); 5053 5054 return ret; 5055 } 5056 5057 #endif // ASSERT 5058 5059 class TearDownRegionSetsClosure : public HeapRegionClosure { 5060 private: 5061 HeapRegionSet *_old_set; 5062 5063 public: 5064 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5065 5066 bool doHeapRegion(HeapRegion* r) { 5067 if (r->is_old()) { 5068 _old_set->remove(r); 5069 } else if(r->is_young()) { 5070 r->uninstall_surv_rate_group(); 5071 } else { 5072 // We ignore free regions, we'll empty the free list afterwards. 5073 // We ignore humongous regions, we're not tearing down the 5074 // humongous regions set. 5075 assert(r->is_free() || r->is_humongous(), 5076 "it cannot be another type"); 5077 } 5078 return false; 5079 } 5080 5081 ~TearDownRegionSetsClosure() { 5082 assert(_old_set->is_empty(), "post-condition"); 5083 } 5084 }; 5085 5086 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5087 assert_at_safepoint(true /* should_be_vm_thread */); 5088 5089 if (!free_list_only) { 5090 TearDownRegionSetsClosure cl(&_old_set); 5091 heap_region_iterate(&cl); 5092 5093 // Note that emptying the _young_list is postponed and instead done as 5094 // the first step when rebuilding the regions sets again. The reason for 5095 // this is that during a full GC string deduplication needs to know if 5096 // a collected region was young or old when the full GC was initiated. 5097 } 5098 _hrm.remove_all_free_regions(); 5099 } 5100 5101 void G1CollectedHeap::increase_used(size_t bytes) { 5102 _summary_bytes_used += bytes; 5103 } 5104 5105 void G1CollectedHeap::decrease_used(size_t bytes) { 5106 assert(_summary_bytes_used >= bytes, 5107 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5108 _summary_bytes_used, bytes); 5109 _summary_bytes_used -= bytes; 5110 } 5111 5112 void G1CollectedHeap::set_used(size_t bytes) { 5113 _summary_bytes_used = bytes; 5114 } 5115 5116 class RebuildRegionSetsClosure : public HeapRegionClosure { 5117 private: 5118 bool _free_list_only; 5119 HeapRegionSet* _old_set; 5120 HeapRegionManager* _hrm; 5121 size_t _total_used; 5122 5123 public: 5124 RebuildRegionSetsClosure(bool free_list_only, 5125 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5126 _free_list_only(free_list_only), 5127 _old_set(old_set), _hrm(hrm), _total_used(0) { 5128 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5129 if (!free_list_only) { 5130 assert(_old_set->is_empty(), "pre-condition"); 5131 } 5132 } 5133 5134 bool doHeapRegion(HeapRegion* r) { 5135 if (r->is_empty()) { 5136 // Add free regions to the free list 5137 r->set_free(); 5138 r->set_allocation_context(AllocationContext::system()); 5139 _hrm->insert_into_free_list(r); 5140 } else if (!_free_list_only) { 5141 5142 if (r->is_humongous()) { 5143 // We ignore humongous regions. We left the humongous set unchanged. 5144 } else { 5145 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 5146 // We now move all (non-humongous, non-old) regions to old gen, and register them as such. 5147 r->move_to_old(); 5148 _old_set->add(r); 5149 } 5150 _total_used += r->used(); 5151 } 5152 5153 return false; 5154 } 5155 5156 size_t total_used() { 5157 return _total_used; 5158 } 5159 }; 5160 5161 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5162 assert_at_safepoint(true /* should_be_vm_thread */); 5163 5164 if (!free_list_only) { 5165 _eden.clear(); 5166 _survivor.clear(); 5167 } 5168 5169 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5170 heap_region_iterate(&cl); 5171 5172 if (!free_list_only) { 5173 set_used(cl.total_used()); 5174 if (_archive_allocator != NULL) { 5175 _archive_allocator->clear_used(); 5176 } 5177 } 5178 assert(used_unlocked() == recalculate_used(), 5179 "inconsistent used_unlocked(), " 5180 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5181 used_unlocked(), recalculate_used()); 5182 } 5183 5184 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5185 HeapRegion* hr = heap_region_containing(p); 5186 return hr->is_in(p); 5187 } 5188 5189 // Methods for the mutator alloc region 5190 5191 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5192 bool force) { 5193 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5194 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 5195 if (force || should_allocate) { 5196 HeapRegion* new_alloc_region = new_region(word_size, 5197 false /* is_old */, 5198 false /* do_expand */); 5199 if (new_alloc_region != NULL) { 5200 set_region_short_lived_locked(new_alloc_region); 5201 _hr_printer.alloc(new_alloc_region, !should_allocate); 5202 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5203 return new_alloc_region; 5204 } 5205 } 5206 return NULL; 5207 } 5208 5209 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5210 size_t allocated_bytes) { 5211 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5212 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5213 5214 collection_set()->add_eden_region(alloc_region); 5215 increase_used(allocated_bytes); 5216 _hr_printer.retire(alloc_region); 5217 // We update the eden sizes here, when the region is retired, 5218 // instead of when it's allocated, since this is the point that its 5219 // used space has been recored in _summary_bytes_used. 5220 g1mm()->update_eden_size(); 5221 } 5222 5223 // Methods for the GC alloc regions 5224 5225 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 5226 if (dest.is_old()) { 5227 return true; 5228 } else { 5229 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 5230 } 5231 } 5232 5233 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 5234 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5235 5236 if (!has_more_regions(dest)) { 5237 return NULL; 5238 } 5239 5240 const bool is_survivor = dest.is_young(); 5241 5242 HeapRegion* new_alloc_region = new_region(word_size, 5243 !is_survivor, 5244 true /* do_expand */); 5245 if (new_alloc_region != NULL) { 5246 // We really only need to do this for old regions given that we 5247 // should never scan survivors. But it doesn't hurt to do it 5248 // for survivors too. 5249 new_alloc_region->record_timestamp(); 5250 if (is_survivor) { 5251 new_alloc_region->set_survivor(); 5252 _survivor.add(new_alloc_region); 5253 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5254 } else { 5255 new_alloc_region->set_old(); 5256 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5257 } 5258 _hr_printer.alloc(new_alloc_region); 5259 bool during_im = collector_state()->during_initial_mark_pause(); 5260 new_alloc_region->note_start_of_copying(during_im); 5261 return new_alloc_region; 5262 } 5263 return NULL; 5264 } 5265 5266 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5267 size_t allocated_bytes, 5268 InCSetState dest) { 5269 bool during_im = collector_state()->during_initial_mark_pause(); 5270 alloc_region->note_end_of_copying(during_im); 5271 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5272 if (dest.is_old()) { 5273 _old_set.add(alloc_region); 5274 } 5275 _hr_printer.retire(alloc_region); 5276 } 5277 5278 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5279 bool expanded = false; 5280 uint index = _hrm.find_highest_free(&expanded); 5281 5282 if (index != G1_NO_HRM_INDEX) { 5283 if (expanded) { 5284 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5285 HeapRegion::GrainWords * HeapWordSize); 5286 } 5287 _hrm.allocate_free_regions_starting_at(index, 1); 5288 return region_at(index); 5289 } 5290 return NULL; 5291 } 5292 5293 // Optimized nmethod scanning 5294 5295 class RegisterNMethodOopClosure: public OopClosure { 5296 G1CollectedHeap* _g1h; 5297 nmethod* _nm; 5298 5299 template <class T> void do_oop_work(T* p) { 5300 T heap_oop = oopDesc::load_heap_oop(p); 5301 if (!oopDesc::is_null(heap_oop)) { 5302 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5303 HeapRegion* hr = _g1h->heap_region_containing(obj); 5304 assert(!hr->is_continues_humongous(), 5305 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5306 " starting at " HR_FORMAT, 5307 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5308 5309 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5310 hr->add_strong_code_root_locked(_nm); 5311 } 5312 } 5313 5314 public: 5315 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5316 _g1h(g1h), _nm(nm) {} 5317 5318 void do_oop(oop* p) { do_oop_work(p); } 5319 void do_oop(narrowOop* p) { do_oop_work(p); } 5320 }; 5321 5322 class UnregisterNMethodOopClosure: public OopClosure { 5323 G1CollectedHeap* _g1h; 5324 nmethod* _nm; 5325 5326 template <class T> void do_oop_work(T* p) { 5327 T heap_oop = oopDesc::load_heap_oop(p); 5328 if (!oopDesc::is_null(heap_oop)) { 5329 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5330 HeapRegion* hr = _g1h->heap_region_containing(obj); 5331 assert(!hr->is_continues_humongous(), 5332 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5333 " starting at " HR_FORMAT, 5334 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5335 5336 hr->remove_strong_code_root(_nm); 5337 } 5338 } 5339 5340 public: 5341 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5342 _g1h(g1h), _nm(nm) {} 5343 5344 void do_oop(oop* p) { do_oop_work(p); } 5345 void do_oop(narrowOop* p) { do_oop_work(p); } 5346 }; 5347 5348 // Returns true if the reference points to an object that 5349 // can move in an incremental collection. 5350 bool G1CollectedHeap::is_scavengable(oop obj) { 5351 HeapRegion* hr = heap_region_containing(obj); 5352 return !hr->is_pinned(); 5353 } 5354 5355 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5356 guarantee(nm != NULL, "sanity"); 5357 RegisterNMethodOopClosure reg_cl(this, nm); 5358 nm->oops_do(®_cl); 5359 } 5360 5361 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5362 guarantee(nm != NULL, "sanity"); 5363 UnregisterNMethodOopClosure reg_cl(this, nm); 5364 nm->oops_do(®_cl, true); 5365 } 5366 5367 void G1CollectedHeap::purge_code_root_memory() { 5368 double purge_start = os::elapsedTime(); 5369 G1CodeRootSet::purge(); 5370 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5371 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5372 } 5373 5374 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5375 G1CollectedHeap* _g1h; 5376 5377 public: 5378 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5379 _g1h(g1h) {} 5380 5381 void do_code_blob(CodeBlob* cb) { 5382 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5383 if (nm == NULL) { 5384 return; 5385 } 5386 5387 if (ScavengeRootsInCode) { 5388 _g1h->register_nmethod(nm); 5389 } 5390 } 5391 }; 5392 5393 void G1CollectedHeap::rebuild_strong_code_roots() { 5394 RebuildStrongCodeRootClosure blob_cl(this); 5395 CodeCache::blobs_do(&blob_cl); 5396 }