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