1 /* 2 * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/metadataOnStackMark.hpp" 27 #include "classfile/stringTable.hpp" 28 #include "classfile/symbolTable.hpp" 29 #include "code/codeCache.hpp" 30 #include "code/icBuffer.hpp" 31 #include "gc/g1/bufferingOopClosure.hpp" 32 #include "gc/g1/concurrentMarkThread.inline.hpp" 33 #include "gc/g1/g1Allocator.inline.hpp" 34 #include "gc/g1/g1CollectedHeap.inline.hpp" 35 #include "gc/g1/g1CollectionSet.hpp" 36 #include "gc/g1/g1CollectorPolicy.hpp" 37 #include "gc/g1/g1CollectorState.hpp" 38 #include "gc/g1/g1ConcurrentRefine.hpp" 39 #include "gc/g1/g1ConcurrentRefineThread.hpp" 40 #include "gc/g1/g1EvacStats.inline.hpp" 41 #include "gc/g1/g1FullCollector.hpp" 42 #include "gc/g1/g1GCPhaseTimes.hpp" 43 #include "gc/g1/g1HeapSizingPolicy.hpp" 44 #include "gc/g1/g1HeapTransition.hpp" 45 #include "gc/g1/g1HeapVerifier.hpp" 46 #include "gc/g1/g1HotCardCache.hpp" 47 #include "gc/g1/g1OopClosures.inline.hpp" 48 #include "gc/g1/g1ParScanThreadState.inline.hpp" 49 #include "gc/g1/g1Policy.hpp" 50 #include "gc/g1/g1RegionToSpaceMapper.hpp" 51 #include "gc/g1/g1RemSet.hpp" 52 #include "gc/g1/g1RootClosures.hpp" 53 #include "gc/g1/g1RootProcessor.hpp" 54 #include "gc/g1/g1StringDedup.hpp" 55 #include "gc/g1/g1YCTypes.hpp" 56 #include "gc/g1/g1YoungRemSetSamplingThread.hpp" 57 #include "gc/g1/heapRegion.inline.hpp" 58 #include "gc/g1/heapRegionRemSet.hpp" 59 #include "gc/g1/heapRegionSet.inline.hpp" 60 #include "gc/g1/vm_operations_g1.hpp" 61 #include "gc/shared/gcHeapSummary.hpp" 62 #include "gc/shared/gcId.hpp" 63 #include "gc/shared/gcLocker.inline.hpp" 64 #include "gc/shared/gcTimer.hpp" 65 #include "gc/shared/gcTrace.hpp" 66 #include "gc/shared/gcTraceTime.inline.hpp" 67 #include "gc/shared/generationSpec.hpp" 68 #include "gc/shared/isGCActiveMark.hpp" 69 #include "gc/shared/preservedMarks.inline.hpp" 70 #include "gc/shared/suspendibleThreadSet.hpp" 71 #include "gc/shared/referenceProcessor.inline.hpp" 72 #include "gc/shared/taskqueue.inline.hpp" 73 #include "gc/shared/weakProcessor.hpp" 74 #include "logging/log.hpp" 75 #include "memory/allocation.hpp" 76 #include "memory/iterator.hpp" 77 #include "memory/resourceArea.hpp" 78 #include "oops/oop.inline.hpp" 79 #include "prims/resolvedMethodTable.hpp" 80 #include "runtime/atomic.hpp" 81 #include "runtime/init.hpp" 82 #include "runtime/orderAccess.inline.hpp" 83 #include "runtime/threadSMR.hpp" 84 #include "runtime/vmThread.hpp" 85 #include "utilities/align.hpp" 86 #include "utilities/globalDefinitions.hpp" 87 #include "utilities/stack.inline.hpp" 88 89 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 90 91 // INVARIANTS/NOTES 92 // 93 // All allocation activity covered by the G1CollectedHeap interface is 94 // serialized by acquiring the HeapLock. This happens in mem_allocate 95 // and allocate_new_tlab, which are the "entry" points to the 96 // allocation code from the rest of the JVM. (Note that this does not 97 // apply to TLAB allocation, which is not part of this interface: it 98 // is done by clients of this interface.) 99 100 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 101 private: 102 size_t _num_dirtied; 103 G1CollectedHeap* _g1h; 104 G1SATBCardTableLoggingModRefBS* _g1_bs; 105 106 HeapRegion* region_for_card(jbyte* card_ptr) const { 107 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 108 } 109 110 bool will_become_free(HeapRegion* hr) const { 111 // A region will be freed by free_collection_set if the region is in the 112 // collection set and has not had an evacuation failure. 113 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 114 } 115 116 public: 117 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 118 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 119 120 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 121 HeapRegion* hr = region_for_card(card_ptr); 122 123 // Should only dirty cards in regions that won't be freed. 124 if (!will_become_free(hr)) { 125 *card_ptr = CardTableModRefBS::dirty_card_val(); 126 _num_dirtied++; 127 } 128 129 return true; 130 } 131 132 size_t num_dirtied() const { return _num_dirtied; } 133 }; 134 135 136 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 137 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 138 } 139 140 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 141 // The from card cache is not the memory that is actually committed. So we cannot 142 // take advantage of the zero_filled parameter. 143 reset_from_card_cache(start_idx, num_regions); 144 } 145 146 147 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 148 MemRegion mr) { 149 return new HeapRegion(hrs_index, bot(), mr); 150 } 151 152 // Private methods. 153 154 HeapRegion* 155 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 156 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 157 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 158 if (!_secondary_free_list.is_empty()) { 159 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 160 "secondary_free_list has %u entries", 161 _secondary_free_list.length()); 162 // It looks as if there are free regions available on the 163 // secondary_free_list. Let's move them to the free_list and try 164 // again to allocate from it. 165 append_secondary_free_list(); 166 167 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 168 "empty we should have moved at least one entry to the free_list"); 169 HeapRegion* res = _hrm.allocate_free_region(is_old); 170 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 171 "allocated " HR_FORMAT " from secondary_free_list", 172 HR_FORMAT_PARAMS(res)); 173 return res; 174 } 175 176 // Wait here until we get notified either when (a) there are no 177 // more free regions coming or (b) some regions have been moved on 178 // the secondary_free_list. 179 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 180 } 181 182 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 183 "could not allocate from secondary_free_list"); 184 return NULL; 185 } 186 187 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 188 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 189 "the only time we use this to allocate a humongous region is " 190 "when we are allocating a single humongous region"); 191 192 HeapRegion* res; 193 if (G1StressConcRegionFreeing) { 194 if (!_secondary_free_list.is_empty()) { 195 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 196 "forced to look at the secondary_free_list"); 197 res = new_region_try_secondary_free_list(is_old); 198 if (res != NULL) { 199 return res; 200 } 201 } 202 } 203 204 res = _hrm.allocate_free_region(is_old); 205 206 if (res == NULL) { 207 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 208 "res == NULL, trying the secondary_free_list"); 209 res = new_region_try_secondary_free_list(is_old); 210 } 211 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 212 // Currently, only attempts to allocate GC alloc regions set 213 // do_expand to true. So, we should only reach here during a 214 // safepoint. If this assumption changes we might have to 215 // reconsider the use of _expand_heap_after_alloc_failure. 216 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 217 218 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 219 word_size * HeapWordSize); 220 221 if (expand(word_size * HeapWordSize)) { 222 // Given that expand() succeeded in expanding the heap, and we 223 // always expand the heap by an amount aligned to the heap 224 // region size, the free list should in theory not be empty. 225 // In either case allocate_free_region() will check for NULL. 226 res = _hrm.allocate_free_region(is_old); 227 } else { 228 _expand_heap_after_alloc_failure = false; 229 } 230 } 231 return res; 232 } 233 234 HeapWord* 235 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 236 uint num_regions, 237 size_t word_size, 238 AllocationContext_t context) { 239 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 240 assert(is_humongous(word_size), "word_size should be humongous"); 241 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 242 243 // Index of last region in the series. 244 uint last = first + num_regions - 1; 245 246 // We need to initialize the region(s) we just discovered. This is 247 // a bit tricky given that it can happen concurrently with 248 // refinement threads refining cards on these regions and 249 // potentially wanting to refine the BOT as they are scanning 250 // those cards (this can happen shortly after a cleanup; see CR 251 // 6991377). So we have to set up the region(s) carefully and in 252 // a specific order. 253 254 // The word size sum of all the regions we will allocate. 255 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 256 assert(word_size <= word_size_sum, "sanity"); 257 258 // This will be the "starts humongous" region. 259 HeapRegion* first_hr = region_at(first); 260 // The header of the new object will be placed at the bottom of 261 // the first region. 262 HeapWord* new_obj = first_hr->bottom(); 263 // This will be the new top of the new object. 264 HeapWord* obj_top = new_obj + word_size; 265 266 // First, we need to zero the header of the space that we will be 267 // allocating. When we update top further down, some refinement 268 // threads might try to scan the region. By zeroing the header we 269 // ensure that any thread that will try to scan the region will 270 // come across the zero klass word and bail out. 271 // 272 // NOTE: It would not have been correct to have used 273 // CollectedHeap::fill_with_object() and make the space look like 274 // an int array. The thread that is doing the allocation will 275 // later update the object header to a potentially different array 276 // type and, for a very short period of time, the klass and length 277 // fields will be inconsistent. This could cause a refinement 278 // thread to calculate the object size incorrectly. 279 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 280 281 // Next, pad out the unused tail of the last region with filler 282 // objects, for improved usage accounting. 283 // How many words we use for filler objects. 284 size_t word_fill_size = word_size_sum - word_size; 285 286 // How many words memory we "waste" which cannot hold a filler object. 287 size_t words_not_fillable = 0; 288 289 if (word_fill_size >= min_fill_size()) { 290 fill_with_objects(obj_top, word_fill_size); 291 } else if (word_fill_size > 0) { 292 // We have space to fill, but we cannot fit an object there. 293 words_not_fillable = word_fill_size; 294 word_fill_size = 0; 295 } 296 297 // We will set up the first region as "starts humongous". This 298 // will also update the BOT covering all the regions to reflect 299 // that there is a single object that starts at the bottom of the 300 // first region. 301 first_hr->set_starts_humongous(obj_top, word_fill_size); 302 first_hr->set_allocation_context(context); 303 // Then, if there are any, we will set up the "continues 304 // humongous" regions. 305 HeapRegion* hr = NULL; 306 for (uint i = first + 1; i <= last; ++i) { 307 hr = region_at(i); 308 hr->set_continues_humongous(first_hr); 309 hr->set_allocation_context(context); 310 } 311 312 // Up to this point no concurrent thread would have been able to 313 // do any scanning on any region in this series. All the top 314 // fields still point to bottom, so the intersection between 315 // [bottom,top] and [card_start,card_end] will be empty. Before we 316 // update the top fields, we'll do a storestore to make sure that 317 // no thread sees the update to top before the zeroing of the 318 // object header and the BOT initialization. 319 OrderAccess::storestore(); 320 321 // Now, we will update the top fields of the "continues humongous" 322 // regions except the last one. 323 for (uint i = first; i < last; ++i) { 324 hr = region_at(i); 325 hr->set_top(hr->end()); 326 } 327 328 hr = region_at(last); 329 // If we cannot fit a filler object, we must set top to the end 330 // of the humongous object, otherwise we cannot iterate the heap 331 // and the BOT will not be complete. 332 hr->set_top(hr->end() - words_not_fillable); 333 334 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 335 "obj_top should be in last region"); 336 337 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 338 339 assert(words_not_fillable == 0 || 340 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 341 "Miscalculation in humongous allocation"); 342 343 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 344 345 for (uint i = first; i <= last; ++i) { 346 hr = region_at(i); 347 _humongous_set.add(hr); 348 _hr_printer.alloc(hr); 349 } 350 351 return new_obj; 352 } 353 354 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 355 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 356 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 357 } 358 359 // If could fit into free regions w/o expansion, try. 360 // Otherwise, if can expand, do so. 361 // Otherwise, if using ex regions might help, try with ex given back. 362 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 363 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 364 365 _verifier->verify_region_sets_optional(); 366 367 uint first = G1_NO_HRM_INDEX; 368 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 369 370 if (obj_regions == 1) { 371 // Only one region to allocate, try to use a fast path by directly allocating 372 // from the free lists. Do not try to expand here, we will potentially do that 373 // later. 374 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 375 if (hr != NULL) { 376 first = hr->hrm_index(); 377 } 378 } else { 379 // We can't allocate humongous regions spanning more than one region while 380 // cleanupComplete() is running, since some of the regions we find to be 381 // empty might not yet be added to the free list. It is not straightforward 382 // to know in which list they are on so that we can remove them. We only 383 // need to do this if we need to allocate more than one region to satisfy the 384 // current humongous allocation request. If we are only allocating one region 385 // we use the one-region region allocation code (see above), that already 386 // potentially waits for regions from the secondary free list. 387 wait_while_free_regions_coming(); 388 append_secondary_free_list_if_not_empty_with_lock(); 389 390 // Policy: Try only empty regions (i.e. already committed first). Maybe we 391 // are lucky enough to find some. 392 first = _hrm.find_contiguous_only_empty(obj_regions); 393 if (first != G1_NO_HRM_INDEX) { 394 _hrm.allocate_free_regions_starting_at(first, obj_regions); 395 } 396 } 397 398 if (first == G1_NO_HRM_INDEX) { 399 // Policy: We could not find enough regions for the humongous object in the 400 // free list. Look through the heap to find a mix of free and uncommitted regions. 401 // If so, try expansion. 402 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 403 if (first != G1_NO_HRM_INDEX) { 404 // We found something. Make sure these regions are committed, i.e. expand 405 // the heap. Alternatively we could do a defragmentation GC. 406 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 407 word_size * HeapWordSize); 408 409 _hrm.expand_at(first, obj_regions, workers()); 410 g1_policy()->record_new_heap_size(num_regions()); 411 412 #ifdef ASSERT 413 for (uint i = first; i < first + obj_regions; ++i) { 414 HeapRegion* hr = region_at(i); 415 assert(hr->is_free(), "sanity"); 416 assert(hr->is_empty(), "sanity"); 417 assert(is_on_master_free_list(hr), "sanity"); 418 } 419 #endif 420 _hrm.allocate_free_regions_starting_at(first, obj_regions); 421 } else { 422 // Policy: Potentially trigger a defragmentation GC. 423 } 424 } 425 426 HeapWord* result = NULL; 427 if (first != G1_NO_HRM_INDEX) { 428 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 429 word_size, context); 430 assert(result != NULL, "it should always return a valid result"); 431 432 // A successful humongous object allocation changes the used space 433 // information of the old generation so we need to recalculate the 434 // sizes and update the jstat counters here. 435 g1mm()->update_sizes(); 436 } 437 438 _verifier->verify_region_sets_optional(); 439 440 return result; 441 } 442 443 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 444 assert_heap_not_locked_and_not_at_safepoint(); 445 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 446 447 uint dummy_gc_count_before; 448 uint dummy_gclocker_retry_count = 0; 449 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 450 } 451 452 HeapWord* 453 G1CollectedHeap::mem_allocate(size_t word_size, 454 bool* gc_overhead_limit_was_exceeded) { 455 assert_heap_not_locked_and_not_at_safepoint(); 456 457 // Loop until the allocation is satisfied, or unsatisfied after GC. 458 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 459 uint gc_count_before; 460 461 HeapWord* result = NULL; 462 if (!is_humongous(word_size)) { 463 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 464 } else { 465 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 466 } 467 if (result != NULL) { 468 return result; 469 } 470 471 // Create the garbage collection operation... 472 VM_G1CollectForAllocation op(gc_count_before, word_size); 473 op.set_allocation_context(AllocationContext::current()); 474 475 // ...and get the VM thread to execute it. 476 VMThread::execute(&op); 477 478 if (op.prologue_succeeded() && op.pause_succeeded()) { 479 // If the operation was successful we'll return the result even 480 // if it is NULL. If the allocation attempt failed immediately 481 // after a Full GC, it's unlikely we'll be able to allocate now. 482 HeapWord* result = op.result(); 483 if (result != NULL && !is_humongous(word_size)) { 484 // Allocations that take place on VM operations do not do any 485 // card dirtying and we have to do it here. We only have to do 486 // this for non-humongous allocations, though. 487 dirty_young_block(result, word_size); 488 } 489 return result; 490 } else { 491 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 492 return NULL; 493 } 494 assert(op.result() == NULL, 495 "the result should be NULL if the VM op did not succeed"); 496 } 497 498 // Give a warning if we seem to be looping forever. 499 if ((QueuedAllocationWarningCount > 0) && 500 (try_count % QueuedAllocationWarningCount == 0)) { 501 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count); 502 } 503 } 504 505 ShouldNotReachHere(); 506 return NULL; 507 } 508 509 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 510 AllocationContext_t context, 511 uint* gc_count_before_ret, 512 uint* gclocker_retry_count_ret) { 513 // Make sure you read the note in attempt_allocation_humongous(). 514 515 assert_heap_not_locked_and_not_at_safepoint(); 516 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 517 "be called for humongous allocation requests"); 518 519 // We should only get here after the first-level allocation attempt 520 // (attempt_allocation()) failed to allocate. 521 522 // We will loop until a) we manage to successfully perform the 523 // allocation or b) we successfully schedule a collection which 524 // fails to perform the allocation. b) is the only case when we'll 525 // return NULL. 526 HeapWord* result = NULL; 527 for (int try_count = 1; /* we'll return */; try_count += 1) { 528 bool should_try_gc; 529 uint gc_count_before; 530 531 { 532 MutexLockerEx x(Heap_lock); 533 result = _allocator->attempt_allocation_locked(word_size, context); 534 if (result != NULL) { 535 return result; 536 } 537 538 if (GCLocker::is_active_and_needs_gc()) { 539 if (g1_policy()->can_expand_young_list()) { 540 // No need for an ergo verbose message here, 541 // can_expand_young_list() does this when it returns true. 542 result = _allocator->attempt_allocation_force(word_size, context); 543 if (result != NULL) { 544 return result; 545 } 546 } 547 should_try_gc = false; 548 } else { 549 // The GCLocker may not be active but the GCLocker initiated 550 // GC may not yet have been performed (GCLocker::needs_gc() 551 // returns true). In this case we do not try this GC and 552 // wait until the GCLocker initiated GC is performed, and 553 // then retry the allocation. 554 if (GCLocker::needs_gc()) { 555 should_try_gc = false; 556 } else { 557 // Read the GC count while still holding the Heap_lock. 558 gc_count_before = total_collections(); 559 should_try_gc = true; 560 } 561 } 562 } 563 564 if (should_try_gc) { 565 bool succeeded; 566 result = do_collection_pause(word_size, gc_count_before, &succeeded, 567 GCCause::_g1_inc_collection_pause); 568 if (result != NULL) { 569 assert(succeeded, "only way to get back a non-NULL result"); 570 return result; 571 } 572 573 if (succeeded) { 574 // If we get here we successfully scheduled a collection which 575 // failed to allocate. No point in trying to allocate 576 // further. We'll just return NULL. 577 MutexLockerEx x(Heap_lock); 578 *gc_count_before_ret = total_collections(); 579 return NULL; 580 } 581 } else { 582 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 583 MutexLockerEx x(Heap_lock); 584 *gc_count_before_ret = total_collections(); 585 return NULL; 586 } 587 // The GCLocker is either active or the GCLocker initiated 588 // GC has not yet been performed. Stall until it is and 589 // then retry the allocation. 590 GCLocker::stall_until_clear(); 591 (*gclocker_retry_count_ret) += 1; 592 } 593 594 // We can reach here if we were unsuccessful in scheduling a 595 // collection (because another thread beat us to it) or if we were 596 // stalled due to the GC locker. In either can we should retry the 597 // allocation attempt in case another thread successfully 598 // performed a collection and reclaimed enough space. We do the 599 // first attempt (without holding the Heap_lock) here and the 600 // follow-on attempt will be at the start of the next loop 601 // iteration (after taking the Heap_lock). 602 result = _allocator->attempt_allocation(word_size, context); 603 if (result != NULL) { 604 return result; 605 } 606 607 // Give a warning if we seem to be looping forever. 608 if ((QueuedAllocationWarningCount > 0) && 609 (try_count % QueuedAllocationWarningCount == 0)) { 610 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() " 611 "retries %d times", try_count); 612 } 613 } 614 615 ShouldNotReachHere(); 616 return NULL; 617 } 618 619 void G1CollectedHeap::begin_archive_alloc_range(bool open) { 620 assert_at_safepoint(true /* should_be_vm_thread */); 621 if (_archive_allocator == NULL) { 622 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open); 623 } 624 } 625 626 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 627 // Allocations in archive regions cannot be of a size that would be considered 628 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 629 // may be different at archive-restore time. 630 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 631 } 632 633 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 634 assert_at_safepoint(true /* should_be_vm_thread */); 635 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 636 if (is_archive_alloc_too_large(word_size)) { 637 return NULL; 638 } 639 return _archive_allocator->archive_mem_allocate(word_size); 640 } 641 642 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 643 size_t end_alignment_in_bytes) { 644 assert_at_safepoint(true /* should_be_vm_thread */); 645 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 646 647 // Call complete_archive to do the real work, filling in the MemRegion 648 // array with the archive regions. 649 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 650 delete _archive_allocator; 651 _archive_allocator = NULL; 652 } 653 654 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 655 assert(ranges != NULL, "MemRegion array NULL"); 656 assert(count != 0, "No MemRegions provided"); 657 MemRegion reserved = _hrm.reserved(); 658 for (size_t i = 0; i < count; i++) { 659 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 660 return false; 661 } 662 } 663 return true; 664 } 665 666 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, 667 size_t count, 668 bool open) { 669 assert(!is_init_completed(), "Expect to be called at JVM init time"); 670 assert(ranges != NULL, "MemRegion array NULL"); 671 assert(count != 0, "No MemRegions provided"); 672 MutexLockerEx x(Heap_lock); 673 674 MemRegion reserved = _hrm.reserved(); 675 HeapWord* prev_last_addr = NULL; 676 HeapRegion* prev_last_region = NULL; 677 678 // Temporarily disable pretouching of heap pages. This interface is used 679 // when mmap'ing archived heap data in, so pre-touching is wasted. 680 FlagSetting fs(AlwaysPreTouch, false); 681 682 // Enable archive object checking used by G1MarkSweep. We have to let it know 683 // about each archive range, so that objects in those ranges aren't marked. 684 G1ArchiveAllocator::enable_archive_object_check(); 685 686 // For each specified MemRegion range, allocate the corresponding G1 687 // regions and mark them as archive regions. We expect the ranges 688 // in ascending starting address order, without overlap. 689 for (size_t i = 0; i < count; i++) { 690 MemRegion curr_range = ranges[i]; 691 HeapWord* start_address = curr_range.start(); 692 size_t word_size = curr_range.word_size(); 693 HeapWord* last_address = curr_range.last(); 694 size_t commits = 0; 695 696 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 697 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 698 p2i(start_address), p2i(last_address)); 699 guarantee(start_address > prev_last_addr, 700 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 701 p2i(start_address), p2i(prev_last_addr)); 702 prev_last_addr = last_address; 703 704 // Check for ranges that start in the same G1 region in which the previous 705 // range ended, and adjust the start address so we don't try to allocate 706 // the same region again. If the current range is entirely within that 707 // region, skip it, just adjusting the recorded top. 708 HeapRegion* start_region = _hrm.addr_to_region(start_address); 709 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 710 start_address = start_region->end(); 711 if (start_address > last_address) { 712 increase_used(word_size * HeapWordSize); 713 start_region->set_top(last_address + 1); 714 continue; 715 } 716 start_region->set_top(start_address); 717 curr_range = MemRegion(start_address, last_address + 1); 718 start_region = _hrm.addr_to_region(start_address); 719 } 720 721 // Perform the actual region allocation, exiting if it fails. 722 // Then note how much new space we have allocated. 723 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 724 return false; 725 } 726 increase_used(word_size * HeapWordSize); 727 if (commits != 0) { 728 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 729 HeapRegion::GrainWords * HeapWordSize * commits); 730 731 } 732 733 // Mark each G1 region touched by the range as archive, add it to 734 // the old set, and set the allocation context and top. 735 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 736 HeapRegion* last_region = _hrm.addr_to_region(last_address); 737 prev_last_region = last_region; 738 739 while (curr_region != NULL) { 740 assert(curr_region->is_empty() && !curr_region->is_pinned(), 741 "Region already in use (index %u)", curr_region->hrm_index()); 742 curr_region->set_allocation_context(AllocationContext::system()); 743 if (open) { 744 curr_region->set_open_archive(); 745 } else { 746 curr_region->set_closed_archive(); 747 } 748 _hr_printer.alloc(curr_region); 749 _old_set.add(curr_region); 750 HeapWord* top; 751 HeapRegion* next_region; 752 if (curr_region != last_region) { 753 top = curr_region->end(); 754 next_region = _hrm.next_region_in_heap(curr_region); 755 } else { 756 top = last_address + 1; 757 next_region = NULL; 758 } 759 curr_region->set_top(top); 760 curr_region->set_first_dead(top); 761 curr_region->set_end_of_live(top); 762 curr_region = next_region; 763 } 764 765 // Notify mark-sweep of the archive 766 G1ArchiveAllocator::set_range_archive(curr_range, open); 767 } 768 return true; 769 } 770 771 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 772 assert(!is_init_completed(), "Expect to be called at JVM init time"); 773 assert(ranges != NULL, "MemRegion array NULL"); 774 assert(count != 0, "No MemRegions provided"); 775 MemRegion reserved = _hrm.reserved(); 776 HeapWord *prev_last_addr = NULL; 777 HeapRegion* prev_last_region = NULL; 778 779 // For each MemRegion, create filler objects, if needed, in the G1 regions 780 // that contain the address range. The address range actually within the 781 // MemRegion will not be modified. That is assumed to have been initialized 782 // elsewhere, probably via an mmap of archived heap data. 783 MutexLockerEx x(Heap_lock); 784 for (size_t i = 0; i < count; i++) { 785 HeapWord* start_address = ranges[i].start(); 786 HeapWord* last_address = ranges[i].last(); 787 788 assert(reserved.contains(start_address) && reserved.contains(last_address), 789 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 790 p2i(start_address), p2i(last_address)); 791 assert(start_address > prev_last_addr, 792 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 793 p2i(start_address), p2i(prev_last_addr)); 794 795 HeapRegion* start_region = _hrm.addr_to_region(start_address); 796 HeapRegion* last_region = _hrm.addr_to_region(last_address); 797 HeapWord* bottom_address = start_region->bottom(); 798 799 // Check for a range beginning in the same region in which the 800 // previous one ended. 801 if (start_region == prev_last_region) { 802 bottom_address = prev_last_addr + 1; 803 } 804 805 // Verify that the regions were all marked as archive regions by 806 // alloc_archive_regions. 807 HeapRegion* curr_region = start_region; 808 while (curr_region != NULL) { 809 guarantee(curr_region->is_archive(), 810 "Expected archive region at index %u", curr_region->hrm_index()); 811 if (curr_region != last_region) { 812 curr_region = _hrm.next_region_in_heap(curr_region); 813 } else { 814 curr_region = NULL; 815 } 816 } 817 818 prev_last_addr = last_address; 819 prev_last_region = last_region; 820 821 // Fill the memory below the allocated range with dummy object(s), 822 // if the region bottom does not match the range start, or if the previous 823 // range ended within the same G1 region, and there is a gap. 824 if (start_address != bottom_address) { 825 size_t fill_size = pointer_delta(start_address, bottom_address); 826 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 827 increase_used(fill_size * HeapWordSize); 828 } 829 } 830 } 831 832 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 833 uint* gc_count_before_ret, 834 uint* gclocker_retry_count_ret) { 835 assert_heap_not_locked_and_not_at_safepoint(); 836 assert(!is_humongous(word_size), "attempt_allocation() should not " 837 "be called for humongous allocation requests"); 838 839 AllocationContext_t context = AllocationContext::current(); 840 HeapWord* result = _allocator->attempt_allocation(word_size, context); 841 842 if (result == NULL) { 843 result = attempt_allocation_slow(word_size, 844 context, 845 gc_count_before_ret, 846 gclocker_retry_count_ret); 847 } 848 assert_heap_not_locked(); 849 if (result != NULL) { 850 dirty_young_block(result, word_size); 851 } 852 return result; 853 } 854 855 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 856 assert(!is_init_completed(), "Expect to be called at JVM init time"); 857 assert(ranges != NULL, "MemRegion array NULL"); 858 assert(count != 0, "No MemRegions provided"); 859 MemRegion reserved = _hrm.reserved(); 860 HeapWord* prev_last_addr = NULL; 861 HeapRegion* prev_last_region = NULL; 862 size_t size_used = 0; 863 size_t uncommitted_regions = 0; 864 865 // For each Memregion, free the G1 regions that constitute it, and 866 // notify mark-sweep that the range is no longer to be considered 'archive.' 867 MutexLockerEx x(Heap_lock); 868 for (size_t i = 0; i < count; i++) { 869 HeapWord* start_address = ranges[i].start(); 870 HeapWord* last_address = ranges[i].last(); 871 872 assert(reserved.contains(start_address) && reserved.contains(last_address), 873 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 874 p2i(start_address), p2i(last_address)); 875 assert(start_address > prev_last_addr, 876 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 877 p2i(start_address), p2i(prev_last_addr)); 878 size_used += ranges[i].byte_size(); 879 prev_last_addr = last_address; 880 881 HeapRegion* start_region = _hrm.addr_to_region(start_address); 882 HeapRegion* last_region = _hrm.addr_to_region(last_address); 883 884 // Check for ranges that start in the same G1 region in which the previous 885 // range ended, and adjust the start address so we don't try to free 886 // the same region again. If the current range is entirely within that 887 // region, skip it. 888 if (start_region == prev_last_region) { 889 start_address = start_region->end(); 890 if (start_address > last_address) { 891 continue; 892 } 893 start_region = _hrm.addr_to_region(start_address); 894 } 895 prev_last_region = last_region; 896 897 // After verifying that each region was marked as an archive region by 898 // alloc_archive_regions, set it free and empty and uncommit it. 899 HeapRegion* curr_region = start_region; 900 while (curr_region != NULL) { 901 guarantee(curr_region->is_archive(), 902 "Expected archive region at index %u", curr_region->hrm_index()); 903 uint curr_index = curr_region->hrm_index(); 904 _old_set.remove(curr_region); 905 curr_region->set_free(); 906 curr_region->set_top(curr_region->bottom()); 907 if (curr_region != last_region) { 908 curr_region = _hrm.next_region_in_heap(curr_region); 909 } else { 910 curr_region = NULL; 911 } 912 _hrm.shrink_at(curr_index, 1); 913 uncommitted_regions++; 914 } 915 916 // Notify mark-sweep that this is no longer an archive range. 917 G1ArchiveAllocator::set_range_archive(ranges[i], false); 918 } 919 920 if (uncommitted_regions != 0) { 921 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 922 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 923 } 924 decrease_used(size_used); 925 } 926 927 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 928 uint* gc_count_before_ret, 929 uint* gclocker_retry_count_ret) { 930 // The structure of this method has a lot of similarities to 931 // attempt_allocation_slow(). The reason these two were not merged 932 // into a single one is that such a method would require several "if 933 // allocation is not humongous do this, otherwise do that" 934 // conditional paths which would obscure its flow. In fact, an early 935 // version of this code did use a unified method which was harder to 936 // follow and, as a result, it had subtle bugs that were hard to 937 // track down. So keeping these two methods separate allows each to 938 // be more readable. It will be good to keep these two in sync as 939 // much as possible. 940 941 assert_heap_not_locked_and_not_at_safepoint(); 942 assert(is_humongous(word_size), "attempt_allocation_humongous() " 943 "should only be called for humongous allocations"); 944 945 // Humongous objects can exhaust the heap quickly, so we should check if we 946 // need to start a marking cycle at each humongous object allocation. We do 947 // the check before we do the actual allocation. The reason for doing it 948 // before the allocation is that we avoid having to keep track of the newly 949 // allocated memory while we do a GC. 950 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 951 word_size)) { 952 collect(GCCause::_g1_humongous_allocation); 953 } 954 955 // We will loop until a) we manage to successfully perform the 956 // allocation or b) we successfully schedule a collection which 957 // fails to perform the allocation. b) is the only case when we'll 958 // return NULL. 959 HeapWord* result = NULL; 960 for (int try_count = 1; /* we'll return */; try_count += 1) { 961 bool should_try_gc; 962 uint gc_count_before; 963 964 { 965 MutexLockerEx x(Heap_lock); 966 967 // Given that humongous objects are not allocated in young 968 // regions, we'll first try to do the allocation without doing a 969 // collection hoping that there's enough space in the heap. 970 result = humongous_obj_allocate(word_size, AllocationContext::current()); 971 if (result != NULL) { 972 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 973 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 974 return result; 975 } 976 977 if (GCLocker::is_active_and_needs_gc()) { 978 should_try_gc = false; 979 } else { 980 // The GCLocker may not be active but the GCLocker initiated 981 // GC may not yet have been performed (GCLocker::needs_gc() 982 // returns true). In this case we do not try this GC and 983 // wait until the GCLocker initiated GC is performed, and 984 // then retry the allocation. 985 if (GCLocker::needs_gc()) { 986 should_try_gc = false; 987 } else { 988 // Read the GC count while still holding the Heap_lock. 989 gc_count_before = total_collections(); 990 should_try_gc = true; 991 } 992 } 993 } 994 995 if (should_try_gc) { 996 // If we failed to allocate the humongous object, we should try to 997 // do a collection pause (if we're allowed) in case it reclaims 998 // enough space for the allocation to succeed after the pause. 999 1000 bool succeeded; 1001 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1002 GCCause::_g1_humongous_allocation); 1003 if (result != NULL) { 1004 assert(succeeded, "only way to get back a non-NULL result"); 1005 return result; 1006 } 1007 1008 if (succeeded) { 1009 // If we get here we successfully scheduled a collection which 1010 // failed to allocate. No point in trying to allocate 1011 // further. We'll just return NULL. 1012 MutexLockerEx x(Heap_lock); 1013 *gc_count_before_ret = total_collections(); 1014 return NULL; 1015 } 1016 } else { 1017 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1018 MutexLockerEx x(Heap_lock); 1019 *gc_count_before_ret = total_collections(); 1020 return NULL; 1021 } 1022 // The GCLocker is either active or the GCLocker initiated 1023 // GC has not yet been performed. Stall until it is and 1024 // then retry the allocation. 1025 GCLocker::stall_until_clear(); 1026 (*gclocker_retry_count_ret) += 1; 1027 } 1028 1029 // We can reach here if we were unsuccessful in scheduling a 1030 // collection (because another thread beat us to it) or if we were 1031 // stalled due to the GC locker. In either can we should retry the 1032 // allocation attempt in case another thread successfully 1033 // performed a collection and reclaimed enough space. Give a 1034 // warning if we seem to be looping forever. 1035 1036 if ((QueuedAllocationWarningCount > 0) && 1037 (try_count % QueuedAllocationWarningCount == 0)) { 1038 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() " 1039 "retries %d times", try_count); 1040 } 1041 } 1042 1043 ShouldNotReachHere(); 1044 return NULL; 1045 } 1046 1047 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1048 AllocationContext_t context, 1049 bool expect_null_mutator_alloc_region) { 1050 assert_at_safepoint(true /* should_be_vm_thread */); 1051 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1052 "the current alloc region was unexpectedly found to be non-NULL"); 1053 1054 if (!is_humongous(word_size)) { 1055 return _allocator->attempt_allocation_locked(word_size, context); 1056 } else { 1057 HeapWord* result = humongous_obj_allocate(word_size, context); 1058 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1059 collector_state()->set_initiate_conc_mark_if_possible(true); 1060 } 1061 return result; 1062 } 1063 1064 ShouldNotReachHere(); 1065 } 1066 1067 class PostCompactionPrinterClosure: public HeapRegionClosure { 1068 private: 1069 G1HRPrinter* _hr_printer; 1070 public: 1071 bool doHeapRegion(HeapRegion* hr) { 1072 assert(!hr->is_young(), "not expecting to find young regions"); 1073 _hr_printer->post_compaction(hr); 1074 return false; 1075 } 1076 1077 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1078 : _hr_printer(hr_printer) { } 1079 }; 1080 1081 void G1CollectedHeap::print_hrm_post_compaction() { 1082 if (_hr_printer.is_active()) { 1083 PostCompactionPrinterClosure cl(hr_printer()); 1084 heap_region_iterate(&cl); 1085 } 1086 } 1087 1088 void G1CollectedHeap::abort_concurrent_cycle() { 1089 // Note: When we have a more flexible GC logging framework that 1090 // allows us to add optional attributes to a GC log record we 1091 // could consider timing and reporting how long we wait in the 1092 // following two methods. 1093 wait_while_free_regions_coming(); 1094 // If we start the compaction before the CM threads finish 1095 // scanning the root regions we might trip them over as we'll 1096 // be moving objects / updating references. So let's wait until 1097 // they are done. By telling them to abort, they should complete 1098 // early. 1099 _cm->root_regions()->abort(); 1100 _cm->root_regions()->wait_until_scan_finished(); 1101 append_secondary_free_list_if_not_empty_with_lock(); 1102 1103 // Disable discovery and empty the discovered lists 1104 // for the CM ref processor. 1105 ref_processor_cm()->disable_discovery(); 1106 ref_processor_cm()->abandon_partial_discovery(); 1107 ref_processor_cm()->verify_no_references_recorded(); 1108 1109 // Abandon current iterations of concurrent marking and concurrent 1110 // refinement, if any are in progress. 1111 concurrent_mark()->abort(); 1112 } 1113 1114 void G1CollectedHeap::prepare_heap_for_full_collection() { 1115 // Make sure we'll choose a new allocation region afterwards. 1116 _allocator->release_mutator_alloc_region(); 1117 _allocator->abandon_gc_alloc_regions(); 1118 g1_rem_set()->cleanupHRRS(); 1119 1120 // We may have added regions to the current incremental collection 1121 // set between the last GC or pause and now. We need to clear the 1122 // incremental collection set and then start rebuilding it afresh 1123 // after this full GC. 1124 abandon_collection_set(collection_set()); 1125 1126 tear_down_region_sets(false /* free_list_only */); 1127 collector_state()->set_gcs_are_young(true); 1128 } 1129 1130 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1131 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1132 assert(used() == recalculate_used(), "Should be equal"); 1133 _verifier->verify_region_sets_optional(); 1134 _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull); 1135 _verifier->check_bitmaps("Full GC Start"); 1136 } 1137 1138 void G1CollectedHeap::prepare_heap_for_mutators() { 1139 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1140 ClassLoaderDataGraph::purge(); 1141 MetaspaceAux::verify_metrics(); 1142 1143 // Prepare heap for normal collections. 1144 assert(num_free_regions() == 0, "we should not have added any free regions"); 1145 rebuild_region_sets(false /* free_list_only */); 1146 abort_refinement(); 1147 resize_if_necessary_after_full_collection(); 1148 1149 // Rebuild the strong code root lists for each region 1150 rebuild_strong_code_roots(); 1151 1152 // Start a new incremental collection set for the next pause 1153 start_new_collection_set(); 1154 1155 _allocator->init_mutator_alloc_region(); 1156 1157 // Post collection state updates. 1158 MetaspaceGC::compute_new_size(); 1159 } 1160 1161 void G1CollectedHeap::abort_refinement() { 1162 if (_hot_card_cache->use_cache()) { 1163 _hot_card_cache->reset_hot_cache(); 1164 } 1165 1166 // Discard all remembered set updates. 1167 JavaThread::dirty_card_queue_set().abandon_logs(); 1168 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1169 } 1170 1171 void G1CollectedHeap::verify_after_full_collection() { 1172 check_gc_time_stamps(); 1173 _hrm.verify_optional(); 1174 _verifier->verify_region_sets_optional(); 1175 _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull); 1176 // Clear the previous marking bitmap, if needed for bitmap verification. 1177 // Note we cannot do this when we clear the next marking bitmap in 1178 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1179 // objects marked during a full GC against the previous bitmap. 1180 // But we need to clear it before calling check_bitmaps below since 1181 // the full GC has compacted objects and updated TAMS but not updated 1182 // the prev bitmap. 1183 if (G1VerifyBitmaps) { 1184 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1185 _cm->clear_prev_bitmap(workers()); 1186 } 1187 _verifier->check_bitmaps("Full GC End"); 1188 1189 // At this point there should be no regions in the 1190 // entire heap tagged as young. 1191 assert(check_young_list_empty(), "young list should be empty at this point"); 1192 1193 // Note: since we've just done a full GC, concurrent 1194 // marking is no longer active. Therefore we need not 1195 // re-enable reference discovery for the CM ref processor. 1196 // That will be done at the start of the next marking cycle. 1197 // We also know that the STW processor should no longer 1198 // discover any new references. 1199 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1200 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1201 ref_processor_stw()->verify_no_references_recorded(); 1202 ref_processor_cm()->verify_no_references_recorded(); 1203 } 1204 1205 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1206 // Post collection logging. 1207 // We should do this after we potentially resize the heap so 1208 // that all the COMMIT / UNCOMMIT events are generated before 1209 // the compaction events. 1210 print_hrm_post_compaction(); 1211 heap_transition->print(); 1212 print_heap_after_gc(); 1213 print_heap_regions(); 1214 #ifdef TRACESPINNING 1215 ParallelTaskTerminator::print_termination_counts(); 1216 #endif 1217 } 1218 1219 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1220 bool clear_all_soft_refs) { 1221 assert_at_safepoint(true /* should_be_vm_thread */); 1222 1223 if (GCLocker::check_active_before_gc()) { 1224 // Full GC was not completed. 1225 return false; 1226 } 1227 1228 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1229 collector_policy()->should_clear_all_soft_refs(); 1230 1231 G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs); 1232 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1233 1234 collector.prepare_collection(); 1235 collector.collect(); 1236 collector.complete_collection(); 1237 1238 // Full collection was successfully completed. 1239 return true; 1240 } 1241 1242 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1243 // Currently, there is no facility in the do_full_collection(bool) API to notify 1244 // the caller that the collection did not succeed (e.g., because it was locked 1245 // out by the GC locker). So, right now, we'll ignore the return value. 1246 bool dummy = do_full_collection(true, /* explicit_gc */ 1247 clear_all_soft_refs); 1248 } 1249 1250 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1251 // Capacity, free and used after the GC counted as full regions to 1252 // include the waste in the following calculations. 1253 const size_t capacity_after_gc = capacity(); 1254 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes(); 1255 1256 // This is enforced in arguments.cpp. 1257 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1258 "otherwise the code below doesn't make sense"); 1259 1260 // We don't have floating point command-line arguments 1261 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1262 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1263 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1264 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1265 1266 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1267 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1268 1269 // We have to be careful here as these two calculations can overflow 1270 // 32-bit size_t's. 1271 double used_after_gc_d = (double) used_after_gc; 1272 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1273 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1274 1275 // Let's make sure that they are both under the max heap size, which 1276 // by default will make them fit into a size_t. 1277 double desired_capacity_upper_bound = (double) max_heap_size; 1278 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1279 desired_capacity_upper_bound); 1280 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1281 desired_capacity_upper_bound); 1282 1283 // We can now safely turn them into size_t's. 1284 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1285 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1286 1287 // This assert only makes sense here, before we adjust them 1288 // with respect to the min and max heap size. 1289 assert(minimum_desired_capacity <= maximum_desired_capacity, 1290 "minimum_desired_capacity = " SIZE_FORMAT ", " 1291 "maximum_desired_capacity = " SIZE_FORMAT, 1292 minimum_desired_capacity, maximum_desired_capacity); 1293 1294 // Should not be greater than the heap max size. No need to adjust 1295 // it with respect to the heap min size as it's a lower bound (i.e., 1296 // we'll try to make the capacity larger than it, not smaller). 1297 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1298 // Should not be less than the heap min size. No need to adjust it 1299 // with respect to the heap max size as it's an upper bound (i.e., 1300 // we'll try to make the capacity smaller than it, not greater). 1301 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1302 1303 if (capacity_after_gc < minimum_desired_capacity) { 1304 // Don't expand unless it's significant 1305 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1306 1307 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1308 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1309 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1310 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio); 1311 1312 expand(expand_bytes, _workers); 1313 1314 // No expansion, now see if we want to shrink 1315 } else if (capacity_after_gc > maximum_desired_capacity) { 1316 // Capacity too large, compute shrinking size 1317 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1318 1319 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1320 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B " 1321 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1322 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio); 1323 1324 shrink(shrink_bytes); 1325 } 1326 } 1327 1328 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1329 AllocationContext_t context, 1330 bool do_gc, 1331 bool clear_all_soft_refs, 1332 bool expect_null_mutator_alloc_region, 1333 bool* gc_succeeded) { 1334 *gc_succeeded = true; 1335 // Let's attempt the allocation first. 1336 HeapWord* result = 1337 attempt_allocation_at_safepoint(word_size, 1338 context, 1339 expect_null_mutator_alloc_region); 1340 if (result != NULL) { 1341 assert(*gc_succeeded, "sanity"); 1342 return result; 1343 } 1344 1345 // In a G1 heap, we're supposed to keep allocation from failing by 1346 // incremental pauses. Therefore, at least for now, we'll favor 1347 // expansion over collection. (This might change in the future if we can 1348 // do something smarter than full collection to satisfy a failed alloc.) 1349 result = expand_and_allocate(word_size, context); 1350 if (result != NULL) { 1351 assert(*gc_succeeded, "sanity"); 1352 return result; 1353 } 1354 1355 if (do_gc) { 1356 // Expansion didn't work, we'll try to do a Full GC. 1357 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1358 clear_all_soft_refs); 1359 } 1360 1361 return NULL; 1362 } 1363 1364 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1365 AllocationContext_t context, 1366 bool* succeeded) { 1367 assert_at_safepoint(true /* should_be_vm_thread */); 1368 1369 // Attempts to allocate followed by Full GC. 1370 HeapWord* result = 1371 satisfy_failed_allocation_helper(word_size, 1372 context, 1373 true, /* do_gc */ 1374 false, /* clear_all_soft_refs */ 1375 false, /* expect_null_mutator_alloc_region */ 1376 succeeded); 1377 1378 if (result != NULL || !*succeeded) { 1379 return result; 1380 } 1381 1382 // Attempts to allocate followed by Full GC that will collect all soft references. 1383 result = satisfy_failed_allocation_helper(word_size, 1384 context, 1385 true, /* do_gc */ 1386 true, /* clear_all_soft_refs */ 1387 true, /* expect_null_mutator_alloc_region */ 1388 succeeded); 1389 1390 if (result != NULL || !*succeeded) { 1391 return result; 1392 } 1393 1394 // Attempts to allocate, no GC 1395 result = satisfy_failed_allocation_helper(word_size, 1396 context, 1397 false, /* do_gc */ 1398 false, /* clear_all_soft_refs */ 1399 true, /* expect_null_mutator_alloc_region */ 1400 succeeded); 1401 1402 if (result != NULL) { 1403 assert(*succeeded, "sanity"); 1404 return result; 1405 } 1406 1407 assert(!collector_policy()->should_clear_all_soft_refs(), 1408 "Flag should have been handled and cleared prior to this point"); 1409 1410 // What else? We might try synchronous finalization later. If the total 1411 // space available is large enough for the allocation, then a more 1412 // complete compaction phase than we've tried so far might be 1413 // appropriate. 1414 assert(*succeeded, "sanity"); 1415 return NULL; 1416 } 1417 1418 // Attempting to expand the heap sufficiently 1419 // to support an allocation of the given "word_size". If 1420 // successful, perform the allocation and return the address of the 1421 // allocated block, or else "NULL". 1422 1423 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1424 assert_at_safepoint(true /* should_be_vm_thread */); 1425 1426 _verifier->verify_region_sets_optional(); 1427 1428 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1429 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1430 word_size * HeapWordSize); 1431 1432 1433 if (expand(expand_bytes, _workers)) { 1434 _hrm.verify_optional(); 1435 _verifier->verify_region_sets_optional(); 1436 return attempt_allocation_at_safepoint(word_size, 1437 context, 1438 false /* expect_null_mutator_alloc_region */); 1439 } 1440 return NULL; 1441 } 1442 1443 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1444 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1445 aligned_expand_bytes = align_up(aligned_expand_bytes, 1446 HeapRegion::GrainBytes); 1447 1448 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1449 expand_bytes, aligned_expand_bytes); 1450 1451 if (is_maximal_no_gc()) { 1452 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1453 return false; 1454 } 1455 1456 double expand_heap_start_time_sec = os::elapsedTime(); 1457 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1458 assert(regions_to_expand > 0, "Must expand by at least one region"); 1459 1460 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers); 1461 if (expand_time_ms != NULL) { 1462 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1463 } 1464 1465 if (expanded_by > 0) { 1466 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1467 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1468 g1_policy()->record_new_heap_size(num_regions()); 1469 } else { 1470 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1471 1472 // The expansion of the virtual storage space was unsuccessful. 1473 // Let's see if it was because we ran out of swap. 1474 if (G1ExitOnExpansionFailure && 1475 _hrm.available() >= regions_to_expand) { 1476 // We had head room... 1477 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1478 } 1479 } 1480 return regions_to_expand > 0; 1481 } 1482 1483 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1484 size_t aligned_shrink_bytes = 1485 ReservedSpace::page_align_size_down(shrink_bytes); 1486 aligned_shrink_bytes = align_down(aligned_shrink_bytes, 1487 HeapRegion::GrainBytes); 1488 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1489 1490 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1491 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1492 1493 1494 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", 1495 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1496 if (num_regions_removed > 0) { 1497 g1_policy()->record_new_heap_size(num_regions()); 1498 } else { 1499 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1500 } 1501 } 1502 1503 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1504 _verifier->verify_region_sets_optional(); 1505 1506 // We should only reach here at the end of a Full GC which means we 1507 // should not not be holding to any GC alloc regions. The method 1508 // below will make sure of that and do any remaining clean up. 1509 _allocator->abandon_gc_alloc_regions(); 1510 1511 // Instead of tearing down / rebuilding the free lists here, we 1512 // could instead use the remove_all_pending() method on free_list to 1513 // remove only the ones that we need to remove. 1514 tear_down_region_sets(true /* free_list_only */); 1515 shrink_helper(shrink_bytes); 1516 rebuild_region_sets(true /* free_list_only */); 1517 1518 _hrm.verify_optional(); 1519 _verifier->verify_region_sets_optional(); 1520 } 1521 1522 // Public methods. 1523 1524 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1525 CollectedHeap(), 1526 _young_gen_sampling_thread(NULL), 1527 _collector_policy(collector_policy), 1528 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1529 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1530 _g1_policy(create_g1_policy(_gc_timer_stw)), 1531 _collection_set(this, _g1_policy), 1532 _dirty_card_queue_set(false), 1533 _is_alive_closure_cm(this), 1534 _is_alive_closure_stw(this), 1535 _ref_processor_cm(NULL), 1536 _ref_processor_stw(NULL), 1537 _bot(NULL), 1538 _hot_card_cache(NULL), 1539 _g1_rem_set(NULL), 1540 _cr(NULL), 1541 _g1mm(NULL), 1542 _preserved_marks_set(true /* in_c_heap */), 1543 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1544 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1545 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1546 _humongous_reclaim_candidates(), 1547 _has_humongous_reclaim_candidates(false), 1548 _archive_allocator(NULL), 1549 _free_regions_coming(false), 1550 _gc_time_stamp(0), 1551 _summary_bytes_used(0), 1552 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1553 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1554 _expand_heap_after_alloc_failure(true), 1555 _old_marking_cycles_started(0), 1556 _old_marking_cycles_completed(0), 1557 _in_cset_fast_test() { 1558 1559 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1560 /* are_GC_task_threads */true, 1561 /* are_ConcurrentGC_threads */false); 1562 _workers->initialize_workers(); 1563 _verifier = new G1HeapVerifier(this); 1564 1565 _allocator = G1Allocator::create_allocator(this); 1566 1567 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1568 1569 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1570 1571 // Override the default _filler_array_max_size so that no humongous filler 1572 // objects are created. 1573 _filler_array_max_size = _humongous_object_threshold_in_words; 1574 1575 uint n_queues = ParallelGCThreads; 1576 _task_queues = new RefToScanQueueSet(n_queues); 1577 1578 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1579 1580 for (uint i = 0; i < n_queues; i++) { 1581 RefToScanQueue* q = new RefToScanQueue(); 1582 q->initialize(); 1583 _task_queues->register_queue(i, q); 1584 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1585 } 1586 1587 // Initialize the G1EvacuationFailureALot counters and flags. 1588 NOT_PRODUCT(reset_evacuation_should_fail();) 1589 1590 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1591 } 1592 1593 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1594 size_t size, 1595 size_t translation_factor) { 1596 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1597 // Allocate a new reserved space, preferring to use large pages. 1598 ReservedSpace rs(size, preferred_page_size); 1599 G1RegionToSpaceMapper* result = 1600 G1RegionToSpaceMapper::create_mapper(rs, 1601 size, 1602 rs.alignment(), 1603 HeapRegion::GrainBytes, 1604 translation_factor, 1605 mtGC); 1606 1607 os::trace_page_sizes_for_requested_size(description, 1608 size, 1609 preferred_page_size, 1610 rs.alignment(), 1611 rs.base(), 1612 rs.size()); 1613 1614 return result; 1615 } 1616 1617 jint G1CollectedHeap::initialize_concurrent_refinement() { 1618 jint ecode = JNI_OK; 1619 _cr = G1ConcurrentRefine::create(&ecode); 1620 return ecode; 1621 } 1622 1623 jint G1CollectedHeap::initialize_young_gen_sampling_thread() { 1624 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread(); 1625 if (_young_gen_sampling_thread->osthread() == NULL) { 1626 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread"); 1627 return JNI_ENOMEM; 1628 } 1629 return JNI_OK; 1630 } 1631 1632 jint G1CollectedHeap::initialize() { 1633 CollectedHeap::pre_initialize(); 1634 os::enable_vtime(); 1635 1636 // Necessary to satisfy locking discipline assertions. 1637 1638 MutexLocker x(Heap_lock); 1639 1640 // While there are no constraints in the GC code that HeapWordSize 1641 // be any particular value, there are multiple other areas in the 1642 // system which believe this to be true (e.g. oop->object_size in some 1643 // cases incorrectly returns the size in wordSize units rather than 1644 // HeapWordSize). 1645 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1646 1647 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1648 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1649 size_t heap_alignment = collector_policy()->heap_alignment(); 1650 1651 // Ensure that the sizes are properly aligned. 1652 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1653 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1654 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1655 1656 // Reserve the maximum. 1657 1658 // When compressed oops are enabled, the preferred heap base 1659 // is calculated by subtracting the requested size from the 1660 // 32Gb boundary and using the result as the base address for 1661 // heap reservation. If the requested size is not aligned to 1662 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1663 // into the ReservedHeapSpace constructor) then the actual 1664 // base of the reserved heap may end up differing from the 1665 // address that was requested (i.e. the preferred heap base). 1666 // If this happens then we could end up using a non-optimal 1667 // compressed oops mode. 1668 1669 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1670 heap_alignment); 1671 1672 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1673 1674 // Create the barrier set for the entire reserved region. 1675 G1SATBCardTableLoggingModRefBS* bs 1676 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1677 bs->initialize(); 1678 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1679 set_barrier_set(bs); 1680 1681 // Create the hot card cache. 1682 _hot_card_cache = new G1HotCardCache(this); 1683 1684 // Carve out the G1 part of the heap. 1685 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1686 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1687 G1RegionToSpaceMapper* heap_storage = 1688 G1RegionToSpaceMapper::create_mapper(g1_rs, 1689 g1_rs.size(), 1690 page_size, 1691 HeapRegion::GrainBytes, 1692 1, 1693 mtJavaHeap); 1694 os::trace_page_sizes("Heap", 1695 collector_policy()->min_heap_byte_size(), 1696 max_byte_size, 1697 page_size, 1698 heap_rs.base(), 1699 heap_rs.size()); 1700 heap_storage->set_mapping_changed_listener(&_listener); 1701 1702 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1703 G1RegionToSpaceMapper* bot_storage = 1704 create_aux_memory_mapper("Block Offset Table", 1705 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1706 G1BlockOffsetTable::heap_map_factor()); 1707 1708 G1RegionToSpaceMapper* cardtable_storage = 1709 create_aux_memory_mapper("Card Table", 1710 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1711 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1712 1713 G1RegionToSpaceMapper* card_counts_storage = 1714 create_aux_memory_mapper("Card Counts Table", 1715 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1716 G1CardCounts::heap_map_factor()); 1717 1718 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1719 G1RegionToSpaceMapper* prev_bitmap_storage = 1720 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1721 G1RegionToSpaceMapper* next_bitmap_storage = 1722 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1723 1724 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1725 g1_barrier_set()->initialize(cardtable_storage); 1726 // Do later initialization work for concurrent refinement. 1727 _hot_card_cache->initialize(card_counts_storage); 1728 1729 // 6843694 - ensure that the maximum region index can fit 1730 // in the remembered set structures. 1731 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1732 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1733 1734 // Also create a G1 rem set. 1735 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache); 1736 _g1_rem_set->initialize(max_capacity(), max_regions()); 1737 1738 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1739 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1740 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1741 "too many cards per region"); 1742 1743 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1744 1745 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1746 1747 { 1748 HeapWord* start = _hrm.reserved().start(); 1749 HeapWord* end = _hrm.reserved().end(); 1750 size_t granularity = HeapRegion::GrainBytes; 1751 1752 _in_cset_fast_test.initialize(start, end, granularity); 1753 _humongous_reclaim_candidates.initialize(start, end, granularity); 1754 } 1755 1756 // Create the G1ConcurrentMark data structure and thread. 1757 // (Must do this late, so that "max_regions" is defined.) 1758 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1759 if (_cm == NULL || !_cm->completed_initialization()) { 1760 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1761 return JNI_ENOMEM; 1762 } 1763 _cmThread = _cm->cm_thread(); 1764 1765 // Now expand into the initial heap size. 1766 if (!expand(init_byte_size, _workers)) { 1767 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1768 return JNI_ENOMEM; 1769 } 1770 1771 // Perform any initialization actions delegated to the policy. 1772 g1_policy()->init(this, &_collection_set); 1773 1774 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1775 SATB_Q_FL_lock, 1776 G1SATBProcessCompletedThreshold, 1777 Shared_SATB_Q_lock); 1778 1779 jint ecode = initialize_concurrent_refinement(); 1780 if (ecode != JNI_OK) { 1781 return ecode; 1782 } 1783 1784 ecode = initialize_young_gen_sampling_thread(); 1785 if (ecode != JNI_OK) { 1786 return ecode; 1787 } 1788 1789 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1790 DirtyCardQ_FL_lock, 1791 (int)concurrent_refine()->yellow_zone(), 1792 (int)concurrent_refine()->red_zone(), 1793 Shared_DirtyCardQ_lock, 1794 NULL, // fl_owner 1795 true); // init_free_ids 1796 1797 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1798 DirtyCardQ_FL_lock, 1799 -1, // never trigger processing 1800 -1, // no limit on length 1801 Shared_DirtyCardQ_lock, 1802 &JavaThread::dirty_card_queue_set()); 1803 1804 // Here we allocate the dummy HeapRegion that is required by the 1805 // G1AllocRegion class. 1806 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1807 1808 // We'll re-use the same region whether the alloc region will 1809 // require BOT updates or not and, if it doesn't, then a non-young 1810 // region will complain that it cannot support allocations without 1811 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1812 dummy_region->set_eden(); 1813 // Make sure it's full. 1814 dummy_region->set_top(dummy_region->end()); 1815 G1AllocRegion::setup(this, dummy_region); 1816 1817 _allocator->init_mutator_alloc_region(); 1818 1819 // Do create of the monitoring and management support so that 1820 // values in the heap have been properly initialized. 1821 _g1mm = new G1MonitoringSupport(this); 1822 1823 G1StringDedup::initialize(); 1824 1825 _preserved_marks_set.init(ParallelGCThreads); 1826 1827 _collection_set.initialize(max_regions()); 1828 1829 return JNI_OK; 1830 } 1831 1832 void G1CollectedHeap::stop() { 1833 // Stop all concurrent threads. We do this to make sure these threads 1834 // do not continue to execute and access resources (e.g. logging) 1835 // that are destroyed during shutdown. 1836 _cr->stop(); 1837 _young_gen_sampling_thread->stop(); 1838 _cmThread->stop(); 1839 if (G1StringDedup::is_enabled()) { 1840 G1StringDedup::stop(); 1841 } 1842 } 1843 1844 void G1CollectedHeap::safepoint_synchronize_begin() { 1845 SuspendibleThreadSet::synchronize(); 1846 } 1847 1848 void G1CollectedHeap::safepoint_synchronize_end() { 1849 SuspendibleThreadSet::desynchronize(); 1850 } 1851 1852 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1853 return HeapRegion::max_region_size(); 1854 } 1855 1856 void G1CollectedHeap::post_initialize() { 1857 ref_processing_init(); 1858 } 1859 1860 void G1CollectedHeap::ref_processing_init() { 1861 // Reference processing in G1 currently works as follows: 1862 // 1863 // * There are two reference processor instances. One is 1864 // used to record and process discovered references 1865 // during concurrent marking; the other is used to 1866 // record and process references during STW pauses 1867 // (both full and incremental). 1868 // * Both ref processors need to 'span' the entire heap as 1869 // the regions in the collection set may be dotted around. 1870 // 1871 // * For the concurrent marking ref processor: 1872 // * Reference discovery is enabled at initial marking. 1873 // * Reference discovery is disabled and the discovered 1874 // references processed etc during remarking. 1875 // * Reference discovery is MT (see below). 1876 // * Reference discovery requires a barrier (see below). 1877 // * Reference processing may or may not be MT 1878 // (depending on the value of ParallelRefProcEnabled 1879 // and ParallelGCThreads). 1880 // * A full GC disables reference discovery by the CM 1881 // ref processor and abandons any entries on it's 1882 // discovered lists. 1883 // 1884 // * For the STW processor: 1885 // * Non MT discovery is enabled at the start of a full GC. 1886 // * Processing and enqueueing during a full GC is non-MT. 1887 // * During a full GC, references are processed after marking. 1888 // 1889 // * Discovery (may or may not be MT) is enabled at the start 1890 // of an incremental evacuation pause. 1891 // * References are processed near the end of a STW evacuation pause. 1892 // * For both types of GC: 1893 // * Discovery is atomic - i.e. not concurrent. 1894 // * Reference discovery will not need a barrier. 1895 1896 MemRegion mr = reserved_region(); 1897 1898 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1); 1899 1900 // Concurrent Mark ref processor 1901 _ref_processor_cm = 1902 new ReferenceProcessor(mr, // span 1903 mt_processing, 1904 // mt processing 1905 ParallelGCThreads, 1906 // degree of mt processing 1907 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 1908 // mt discovery 1909 MAX2(ParallelGCThreads, ConcGCThreads), 1910 // degree of mt discovery 1911 false, 1912 // Reference discovery is not atomic 1913 &_is_alive_closure_cm); 1914 // is alive closure 1915 // (for efficiency/performance) 1916 1917 // STW ref processor 1918 _ref_processor_stw = 1919 new ReferenceProcessor(mr, // span 1920 mt_processing, 1921 // mt processing 1922 ParallelGCThreads, 1923 // degree of mt processing 1924 (ParallelGCThreads > 1), 1925 // mt discovery 1926 ParallelGCThreads, 1927 // degree of mt discovery 1928 true, 1929 // Reference discovery is atomic 1930 &_is_alive_closure_stw); 1931 // is alive closure 1932 // (for efficiency/performance) 1933 } 1934 1935 CollectorPolicy* G1CollectedHeap::collector_policy() const { 1936 return _collector_policy; 1937 } 1938 1939 size_t G1CollectedHeap::capacity() const { 1940 return _hrm.length() * HeapRegion::GrainBytes; 1941 } 1942 1943 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const { 1944 return _hrm.total_free_bytes(); 1945 } 1946 1947 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 1948 hr->reset_gc_time_stamp(); 1949 } 1950 1951 #ifndef PRODUCT 1952 1953 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 1954 private: 1955 unsigned _gc_time_stamp; 1956 bool _failures; 1957 1958 public: 1959 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 1960 _gc_time_stamp(gc_time_stamp), _failures(false) { } 1961 1962 virtual bool doHeapRegion(HeapRegion* hr) { 1963 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 1964 if (_gc_time_stamp != region_gc_time_stamp) { 1965 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 1966 region_gc_time_stamp, _gc_time_stamp); 1967 _failures = true; 1968 } 1969 return false; 1970 } 1971 1972 bool failures() { return _failures; } 1973 }; 1974 1975 void G1CollectedHeap::check_gc_time_stamps() { 1976 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 1977 heap_region_iterate(&cl); 1978 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 1979 } 1980 #endif // PRODUCT 1981 1982 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 1983 _hot_card_cache->drain(cl, worker_i); 1984 } 1985 1986 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 1987 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 1988 size_t n_completed_buffers = 0; 1989 while (dcqs.apply_closure_during_gc(cl, worker_i)) { 1990 n_completed_buffers++; 1991 } 1992 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 1993 dcqs.clear_n_completed_buffers(); 1994 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 1995 } 1996 1997 // Computes the sum of the storage used by the various regions. 1998 size_t G1CollectedHeap::used() const { 1999 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2000 if (_archive_allocator != NULL) { 2001 result += _archive_allocator->used(); 2002 } 2003 return result; 2004 } 2005 2006 size_t G1CollectedHeap::used_unlocked() const { 2007 return _summary_bytes_used; 2008 } 2009 2010 class SumUsedClosure: public HeapRegionClosure { 2011 size_t _used; 2012 public: 2013 SumUsedClosure() : _used(0) {} 2014 bool doHeapRegion(HeapRegion* r) { 2015 _used += r->used(); 2016 return false; 2017 } 2018 size_t result() { return _used; } 2019 }; 2020 2021 size_t G1CollectedHeap::recalculate_used() const { 2022 double recalculate_used_start = os::elapsedTime(); 2023 2024 SumUsedClosure blk; 2025 heap_region_iterate(&blk); 2026 2027 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2028 return blk.result(); 2029 } 2030 2031 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2032 switch (cause) { 2033 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2034 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2035 case GCCause::_update_allocation_context_stats_inc: return true; 2036 case GCCause::_wb_conc_mark: return true; 2037 default : return false; 2038 } 2039 } 2040 2041 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2042 switch (cause) { 2043 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2044 case GCCause::_g1_humongous_allocation: return true; 2045 default: return is_user_requested_concurrent_full_gc(cause); 2046 } 2047 } 2048 2049 #ifndef PRODUCT 2050 void G1CollectedHeap::allocate_dummy_regions() { 2051 // Let's fill up most of the region 2052 size_t word_size = HeapRegion::GrainWords - 1024; 2053 // And as a result the region we'll allocate will be humongous. 2054 guarantee(is_humongous(word_size), "sanity"); 2055 2056 // _filler_array_max_size is set to humongous object threshold 2057 // but temporarily change it to use CollectedHeap::fill_with_object(). 2058 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2059 2060 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2061 // Let's use the existing mechanism for the allocation 2062 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2063 AllocationContext::system()); 2064 if (dummy_obj != NULL) { 2065 MemRegion mr(dummy_obj, word_size); 2066 CollectedHeap::fill_with_object(mr); 2067 } else { 2068 // If we can't allocate once, we probably cannot allocate 2069 // again. Let's get out of the loop. 2070 break; 2071 } 2072 } 2073 } 2074 #endif // !PRODUCT 2075 2076 void G1CollectedHeap::increment_old_marking_cycles_started() { 2077 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2078 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2079 "Wrong marking cycle count (started: %d, completed: %d)", 2080 _old_marking_cycles_started, _old_marking_cycles_completed); 2081 2082 _old_marking_cycles_started++; 2083 } 2084 2085 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2086 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2087 2088 // We assume that if concurrent == true, then the caller is a 2089 // concurrent thread that was joined the Suspendible Thread 2090 // Set. If there's ever a cheap way to check this, we should add an 2091 // assert here. 2092 2093 // Given that this method is called at the end of a Full GC or of a 2094 // concurrent cycle, and those can be nested (i.e., a Full GC can 2095 // interrupt a concurrent cycle), the number of full collections 2096 // completed should be either one (in the case where there was no 2097 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2098 // behind the number of full collections started. 2099 2100 // This is the case for the inner caller, i.e. a Full GC. 2101 assert(concurrent || 2102 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2103 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2104 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2105 "is inconsistent with _old_marking_cycles_completed = %u", 2106 _old_marking_cycles_started, _old_marking_cycles_completed); 2107 2108 // This is the case for the outer caller, i.e. the concurrent cycle. 2109 assert(!concurrent || 2110 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2111 "for outer caller (concurrent cycle): " 2112 "_old_marking_cycles_started = %u " 2113 "is inconsistent with _old_marking_cycles_completed = %u", 2114 _old_marking_cycles_started, _old_marking_cycles_completed); 2115 2116 _old_marking_cycles_completed += 1; 2117 2118 // We need to clear the "in_progress" flag in the CM thread before 2119 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2120 // is set) so that if a waiter requests another System.gc() it doesn't 2121 // incorrectly see that a marking cycle is still in progress. 2122 if (concurrent) { 2123 _cmThread->set_idle(); 2124 } 2125 2126 // This notify_all() will ensure that a thread that called 2127 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2128 // and it's waiting for a full GC to finish will be woken up. It is 2129 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2130 FullGCCount_lock->notify_all(); 2131 } 2132 2133 void G1CollectedHeap::collect(GCCause::Cause cause) { 2134 assert_heap_not_locked(); 2135 2136 uint gc_count_before; 2137 uint old_marking_count_before; 2138 uint full_gc_count_before; 2139 bool retry_gc; 2140 2141 do { 2142 retry_gc = false; 2143 2144 { 2145 MutexLocker ml(Heap_lock); 2146 2147 // Read the GC count while holding the Heap_lock 2148 gc_count_before = total_collections(); 2149 full_gc_count_before = total_full_collections(); 2150 old_marking_count_before = _old_marking_cycles_started; 2151 } 2152 2153 if (should_do_concurrent_full_gc(cause)) { 2154 // Schedule an initial-mark evacuation pause that will start a 2155 // concurrent cycle. We're setting word_size to 0 which means that 2156 // we are not requesting a post-GC allocation. 2157 VM_G1IncCollectionPause op(gc_count_before, 2158 0, /* word_size */ 2159 true, /* should_initiate_conc_mark */ 2160 g1_policy()->max_pause_time_ms(), 2161 cause); 2162 op.set_allocation_context(AllocationContext::current()); 2163 2164 VMThread::execute(&op); 2165 if (!op.pause_succeeded()) { 2166 if (old_marking_count_before == _old_marking_cycles_started) { 2167 retry_gc = op.should_retry_gc(); 2168 } else { 2169 // A Full GC happened while we were trying to schedule the 2170 // initial-mark GC. No point in starting a new cycle given 2171 // that the whole heap was collected anyway. 2172 } 2173 2174 if (retry_gc) { 2175 if (GCLocker::is_active_and_needs_gc()) { 2176 GCLocker::stall_until_clear(); 2177 } 2178 } 2179 } 2180 } else { 2181 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2182 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2183 2184 // Schedule a standard evacuation pause. We're setting word_size 2185 // to 0 which means that we are not requesting a post-GC allocation. 2186 VM_G1IncCollectionPause op(gc_count_before, 2187 0, /* word_size */ 2188 false, /* should_initiate_conc_mark */ 2189 g1_policy()->max_pause_time_ms(), 2190 cause); 2191 VMThread::execute(&op); 2192 } else { 2193 // Schedule a Full GC. 2194 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2195 VMThread::execute(&op); 2196 } 2197 } 2198 } while (retry_gc); 2199 } 2200 2201 bool G1CollectedHeap::is_in(const void* p) const { 2202 if (_hrm.reserved().contains(p)) { 2203 // Given that we know that p is in the reserved space, 2204 // heap_region_containing() should successfully 2205 // return the containing region. 2206 HeapRegion* hr = heap_region_containing(p); 2207 return hr->is_in(p); 2208 } else { 2209 return false; 2210 } 2211 } 2212 2213 #ifdef ASSERT 2214 bool G1CollectedHeap::is_in_exact(const void* p) const { 2215 bool contains = reserved_region().contains(p); 2216 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2217 if (contains && available) { 2218 return true; 2219 } else { 2220 return false; 2221 } 2222 } 2223 #endif 2224 2225 // Iteration functions. 2226 2227 // Iterates an ObjectClosure over all objects within a HeapRegion. 2228 2229 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2230 ObjectClosure* _cl; 2231 public: 2232 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2233 bool doHeapRegion(HeapRegion* r) { 2234 if (!r->is_continues_humongous()) { 2235 r->object_iterate(_cl); 2236 } 2237 return false; 2238 } 2239 }; 2240 2241 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2242 IterateObjectClosureRegionClosure blk(cl); 2243 heap_region_iterate(&blk); 2244 } 2245 2246 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2247 _hrm.iterate(cl); 2248 } 2249 2250 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl, 2251 HeapRegionClaimer *hrclaimer, 2252 uint worker_id) const { 2253 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id)); 2254 } 2255 2256 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl, 2257 HeapRegionClaimer *hrclaimer) const { 2258 _hrm.par_iterate(cl, hrclaimer, 0); 2259 } 2260 2261 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2262 _collection_set.iterate(cl); 2263 } 2264 2265 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2266 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2267 } 2268 2269 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2270 HeapRegion* hr = heap_region_containing(addr); 2271 return hr->block_start(addr); 2272 } 2273 2274 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2275 HeapRegion* hr = heap_region_containing(addr); 2276 return hr->block_size(addr); 2277 } 2278 2279 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2280 HeapRegion* hr = heap_region_containing(addr); 2281 return hr->block_is_obj(addr); 2282 } 2283 2284 bool G1CollectedHeap::supports_tlab_allocation() const { 2285 return true; 2286 } 2287 2288 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2289 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2290 } 2291 2292 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2293 return _eden.length() * HeapRegion::GrainBytes; 2294 } 2295 2296 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2297 // must be equal to the humongous object limit. 2298 size_t G1CollectedHeap::max_tlab_size() const { 2299 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2300 } 2301 2302 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2303 AllocationContext_t context = AllocationContext::current(); 2304 return _allocator->unsafe_max_tlab_alloc(context); 2305 } 2306 2307 size_t G1CollectedHeap::max_capacity() const { 2308 return _hrm.reserved().byte_size(); 2309 } 2310 2311 jlong G1CollectedHeap::millis_since_last_gc() { 2312 // See the notes in GenCollectedHeap::millis_since_last_gc() 2313 // for more information about the implementation. 2314 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2315 _g1_policy->collection_pause_end_millis(); 2316 if (ret_val < 0) { 2317 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2318 ". returning zero instead.", ret_val); 2319 return 0; 2320 } 2321 return ret_val; 2322 } 2323 2324 void G1CollectedHeap::prepare_for_verify() { 2325 _verifier->prepare_for_verify(); 2326 } 2327 2328 void G1CollectedHeap::verify(VerifyOption vo) { 2329 _verifier->verify(vo); 2330 } 2331 2332 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2333 return true; 2334 } 2335 2336 const char* const* G1CollectedHeap::concurrent_phases() const { 2337 return _cmThread->concurrent_phases(); 2338 } 2339 2340 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2341 return _cmThread->request_concurrent_phase(phase); 2342 } 2343 2344 class PrintRegionClosure: public HeapRegionClosure { 2345 outputStream* _st; 2346 public: 2347 PrintRegionClosure(outputStream* st) : _st(st) {} 2348 bool doHeapRegion(HeapRegion* r) { 2349 r->print_on(_st); 2350 return false; 2351 } 2352 }; 2353 2354 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2355 const HeapRegion* hr, 2356 const VerifyOption vo) const { 2357 switch (vo) { 2358 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2359 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2360 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr); 2361 default: ShouldNotReachHere(); 2362 } 2363 return false; // keep some compilers happy 2364 } 2365 2366 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2367 const VerifyOption vo) const { 2368 switch (vo) { 2369 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2370 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2371 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj); 2372 default: ShouldNotReachHere(); 2373 } 2374 return false; // keep some compilers happy 2375 } 2376 2377 void G1CollectedHeap::print_heap_regions() const { 2378 LogTarget(Trace, gc, heap, region) lt; 2379 if (lt.is_enabled()) { 2380 LogStream ls(lt); 2381 print_regions_on(&ls); 2382 } 2383 } 2384 2385 void G1CollectedHeap::print_on(outputStream* st) const { 2386 st->print(" %-20s", "garbage-first heap"); 2387 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2388 capacity()/K, used_unlocked()/K); 2389 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")", 2390 p2i(_hrm.reserved().start()), 2391 p2i(_hrm.reserved().end())); 2392 st->cr(); 2393 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2394 uint young_regions = young_regions_count(); 2395 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2396 (size_t) young_regions * HeapRegion::GrainBytes / K); 2397 uint survivor_regions = survivor_regions_count(); 2398 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2399 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2400 st->cr(); 2401 MetaspaceAux::print_on(st); 2402 } 2403 2404 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2405 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2406 "HS=humongous(starts), HC=humongous(continues), " 2407 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2408 "AC=allocation context, " 2409 "TAMS=top-at-mark-start (previous, next)"); 2410 PrintRegionClosure blk(st); 2411 heap_region_iterate(&blk); 2412 } 2413 2414 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2415 print_on(st); 2416 2417 // Print the per-region information. 2418 print_regions_on(st); 2419 } 2420 2421 void G1CollectedHeap::print_on_error(outputStream* st) const { 2422 this->CollectedHeap::print_on_error(st); 2423 2424 if (_cm != NULL) { 2425 st->cr(); 2426 _cm->print_on_error(st); 2427 } 2428 } 2429 2430 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2431 workers()->print_worker_threads_on(st); 2432 _cmThread->print_on(st); 2433 st->cr(); 2434 _cm->print_worker_threads_on(st); 2435 _cr->print_threads_on(st); 2436 _young_gen_sampling_thread->print_on(st); 2437 if (G1StringDedup::is_enabled()) { 2438 G1StringDedup::print_worker_threads_on(st); 2439 } 2440 } 2441 2442 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2443 workers()->threads_do(tc); 2444 tc->do_thread(_cmThread); 2445 _cm->threads_do(tc); 2446 _cr->threads_do(tc); 2447 tc->do_thread(_young_gen_sampling_thread); 2448 if (G1StringDedup::is_enabled()) { 2449 G1StringDedup::threads_do(tc); 2450 } 2451 } 2452 2453 void G1CollectedHeap::print_tracing_info() const { 2454 g1_rem_set()->print_summary_info(); 2455 concurrent_mark()->print_summary_info(); 2456 } 2457 2458 #ifndef PRODUCT 2459 // Helpful for debugging RSet issues. 2460 2461 class PrintRSetsClosure : public HeapRegionClosure { 2462 private: 2463 const char* _msg; 2464 size_t _occupied_sum; 2465 2466 public: 2467 bool doHeapRegion(HeapRegion* r) { 2468 HeapRegionRemSet* hrrs = r->rem_set(); 2469 size_t occupied = hrrs->occupied(); 2470 _occupied_sum += occupied; 2471 2472 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2473 if (occupied == 0) { 2474 tty->print_cr(" RSet is empty"); 2475 } else { 2476 hrrs->print(); 2477 } 2478 tty->print_cr("----------"); 2479 return false; 2480 } 2481 2482 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2483 tty->cr(); 2484 tty->print_cr("========================================"); 2485 tty->print_cr("%s", msg); 2486 tty->cr(); 2487 } 2488 2489 ~PrintRSetsClosure() { 2490 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2491 tty->print_cr("========================================"); 2492 tty->cr(); 2493 } 2494 }; 2495 2496 void G1CollectedHeap::print_cset_rsets() { 2497 PrintRSetsClosure cl("Printing CSet RSets"); 2498 collection_set_iterate(&cl); 2499 } 2500 2501 void G1CollectedHeap::print_all_rsets() { 2502 PrintRSetsClosure cl("Printing All RSets");; 2503 heap_region_iterate(&cl); 2504 } 2505 #endif // PRODUCT 2506 2507 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2508 2509 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2510 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2511 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2512 2513 size_t eden_capacity_bytes = 2514 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2515 2516 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2517 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2518 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2519 } 2520 2521 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2522 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2523 stats->unused(), stats->used(), stats->region_end_waste(), 2524 stats->regions_filled(), stats->direct_allocated(), 2525 stats->failure_used(), stats->failure_waste()); 2526 } 2527 2528 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2529 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2530 gc_tracer->report_gc_heap_summary(when, heap_summary); 2531 2532 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2533 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2534 } 2535 2536 G1CollectedHeap* G1CollectedHeap::heap() { 2537 CollectedHeap* heap = Universe::heap(); 2538 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2539 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2540 return (G1CollectedHeap*)heap; 2541 } 2542 2543 void G1CollectedHeap::gc_prologue(bool full) { 2544 // always_do_update_barrier = false; 2545 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2546 2547 // This summary needs to be printed before incrementing total collections. 2548 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2549 2550 // Update common counters. 2551 increment_total_collections(full /* full gc */); 2552 if (full) { 2553 increment_old_marking_cycles_started(); 2554 reset_gc_time_stamp(); 2555 } else { 2556 increment_gc_time_stamp(); 2557 } 2558 2559 // Fill TLAB's and such 2560 double start = os::elapsedTime(); 2561 accumulate_statistics_all_tlabs(); 2562 ensure_parsability(true); 2563 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2564 } 2565 2566 void G1CollectedHeap::gc_epilogue(bool full) { 2567 // Update common counters. 2568 if (full) { 2569 // Update the number of full collections that have been completed. 2570 increment_old_marking_cycles_completed(false /* concurrent */); 2571 } 2572 2573 // We are at the end of the GC. Total collections has already been increased. 2574 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2575 2576 // FIXME: what is this about? 2577 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2578 // is set. 2579 #if COMPILER2_OR_JVMCI 2580 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2581 #endif 2582 // always_do_update_barrier = true; 2583 2584 double start = os::elapsedTime(); 2585 resize_all_tlabs(); 2586 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2587 2588 allocation_context_stats().update(full); 2589 2590 MemoryService::track_memory_usage(); 2591 // We have just completed a GC. Update the soft reference 2592 // policy with the new heap occupancy 2593 Universe::update_heap_info_at_gc(); 2594 } 2595 2596 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2597 uint gc_count_before, 2598 bool* succeeded, 2599 GCCause::Cause gc_cause) { 2600 assert_heap_not_locked_and_not_at_safepoint(); 2601 VM_G1IncCollectionPause op(gc_count_before, 2602 word_size, 2603 false, /* should_initiate_conc_mark */ 2604 g1_policy()->max_pause_time_ms(), 2605 gc_cause); 2606 2607 op.set_allocation_context(AllocationContext::current()); 2608 VMThread::execute(&op); 2609 2610 HeapWord* result = op.result(); 2611 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2612 assert(result == NULL || ret_succeeded, 2613 "the result should be NULL if the VM did not succeed"); 2614 *succeeded = ret_succeeded; 2615 2616 assert_heap_not_locked(); 2617 return result; 2618 } 2619 2620 void 2621 G1CollectedHeap::doConcurrentMark() { 2622 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2623 if (!_cmThread->in_progress()) { 2624 _cmThread->set_started(); 2625 CGC_lock->notify(); 2626 } 2627 } 2628 2629 size_t G1CollectedHeap::pending_card_num() { 2630 size_t extra_cards = 0; 2631 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) { 2632 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2633 extra_cards += dcq.size(); 2634 } 2635 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2636 size_t buffer_size = dcqs.buffer_size(); 2637 size_t buffer_num = dcqs.completed_buffers_num(); 2638 2639 return buffer_size * buffer_num + extra_cards; 2640 } 2641 2642 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2643 private: 2644 size_t _total_humongous; 2645 size_t _candidate_humongous; 2646 2647 DirtyCardQueue _dcq; 2648 2649 // We don't nominate objects with many remembered set entries, on 2650 // the assumption that such objects are likely still live. 2651 bool is_remset_small(HeapRegion* region) const { 2652 HeapRegionRemSet* const rset = region->rem_set(); 2653 return G1EagerReclaimHumongousObjectsWithStaleRefs 2654 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2655 : rset->is_empty(); 2656 } 2657 2658 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2659 assert(region->is_starts_humongous(), "Must start a humongous object"); 2660 2661 oop obj = oop(region->bottom()); 2662 2663 // Dead objects cannot be eager reclaim candidates. Due to class 2664 // unloading it is unsafe to query their classes so we return early. 2665 if (heap->is_obj_dead(obj, region)) { 2666 return false; 2667 } 2668 2669 // Candidate selection must satisfy the following constraints 2670 // while concurrent marking is in progress: 2671 // 2672 // * In order to maintain SATB invariants, an object must not be 2673 // reclaimed if it was allocated before the start of marking and 2674 // has not had its references scanned. Such an object must have 2675 // its references (including type metadata) scanned to ensure no 2676 // live objects are missed by the marking process. Objects 2677 // allocated after the start of concurrent marking don't need to 2678 // be scanned. 2679 // 2680 // * An object must not be reclaimed if it is on the concurrent 2681 // mark stack. Objects allocated after the start of concurrent 2682 // marking are never pushed on the mark stack. 2683 // 2684 // Nominating only objects allocated after the start of concurrent 2685 // marking is sufficient to meet both constraints. This may miss 2686 // some objects that satisfy the constraints, but the marking data 2687 // structures don't support efficiently performing the needed 2688 // additional tests or scrubbing of the mark stack. 2689 // 2690 // However, we presently only nominate is_typeArray() objects. 2691 // A humongous object containing references induces remembered 2692 // set entries on other regions. In order to reclaim such an 2693 // object, those remembered sets would need to be cleaned up. 2694 // 2695 // We also treat is_typeArray() objects specially, allowing them 2696 // to be reclaimed even if allocated before the start of 2697 // concurrent mark. For this we rely on mark stack insertion to 2698 // exclude is_typeArray() objects, preventing reclaiming an object 2699 // that is in the mark stack. We also rely on the metadata for 2700 // such objects to be built-in and so ensured to be kept live. 2701 // Frequent allocation and drop of large binary blobs is an 2702 // important use case for eager reclaim, and this special handling 2703 // may reduce needed headroom. 2704 2705 return obj->is_typeArray() && is_remset_small(region); 2706 } 2707 2708 public: 2709 RegisterHumongousWithInCSetFastTestClosure() 2710 : _total_humongous(0), 2711 _candidate_humongous(0), 2712 _dcq(&JavaThread::dirty_card_queue_set()) { 2713 } 2714 2715 virtual bool doHeapRegion(HeapRegion* r) { 2716 if (!r->is_starts_humongous()) { 2717 return false; 2718 } 2719 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2720 2721 bool is_candidate = humongous_region_is_candidate(g1h, r); 2722 uint rindex = r->hrm_index(); 2723 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2724 if (is_candidate) { 2725 _candidate_humongous++; 2726 g1h->register_humongous_region_with_cset(rindex); 2727 // Is_candidate already filters out humongous object with large remembered sets. 2728 // If we have a humongous object with a few remembered sets, we simply flush these 2729 // remembered set entries into the DCQS. That will result in automatic 2730 // re-evaluation of their remembered set entries during the following evacuation 2731 // phase. 2732 if (!r->rem_set()->is_empty()) { 2733 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2734 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2735 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 2736 HeapRegionRemSetIterator hrrs(r->rem_set()); 2737 size_t card_index; 2738 while (hrrs.has_next(card_index)) { 2739 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 2740 // The remembered set might contain references to already freed 2741 // regions. Filter out such entries to avoid failing card table 2742 // verification. 2743 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 2744 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 2745 *card_ptr = CardTableModRefBS::dirty_card_val(); 2746 _dcq.enqueue(card_ptr); 2747 } 2748 } 2749 } 2750 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2751 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2752 hrrs.n_yielded(), r->rem_set()->occupied()); 2753 r->rem_set()->clear_locked(); 2754 } 2755 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2756 } 2757 _total_humongous++; 2758 2759 return false; 2760 } 2761 2762 size_t total_humongous() const { return _total_humongous; } 2763 size_t candidate_humongous() const { return _candidate_humongous; } 2764 2765 void flush_rem_set_entries() { _dcq.flush(); } 2766 }; 2767 2768 void G1CollectedHeap::register_humongous_regions_with_cset() { 2769 if (!G1EagerReclaimHumongousObjects) { 2770 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2771 return; 2772 } 2773 double time = os::elapsed_counter(); 2774 2775 // Collect reclaim candidate information and register candidates with cset. 2776 RegisterHumongousWithInCSetFastTestClosure cl; 2777 heap_region_iterate(&cl); 2778 2779 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2780 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2781 cl.total_humongous(), 2782 cl.candidate_humongous()); 2783 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2784 2785 // Finally flush all remembered set entries to re-check into the global DCQS. 2786 cl.flush_rem_set_entries(); 2787 } 2788 2789 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2790 public: 2791 bool doHeapRegion(HeapRegion* hr) { 2792 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2793 hr->verify_rem_set(); 2794 } 2795 return false; 2796 } 2797 }; 2798 2799 uint G1CollectedHeap::num_task_queues() const { 2800 return _task_queues->size(); 2801 } 2802 2803 #if TASKQUEUE_STATS 2804 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2805 st->print_raw_cr("GC Task Stats"); 2806 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2807 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2808 } 2809 2810 void G1CollectedHeap::print_taskqueue_stats() const { 2811 if (!log_is_enabled(Trace, gc, task, stats)) { 2812 return; 2813 } 2814 Log(gc, task, stats) log; 2815 ResourceMark rm; 2816 LogStream ls(log.trace()); 2817 outputStream* st = &ls; 2818 2819 print_taskqueue_stats_hdr(st); 2820 2821 TaskQueueStats totals; 2822 const uint n = num_task_queues(); 2823 for (uint i = 0; i < n; ++i) { 2824 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2825 totals += task_queue(i)->stats; 2826 } 2827 st->print_raw("tot "); totals.print(st); st->cr(); 2828 2829 DEBUG_ONLY(totals.verify()); 2830 } 2831 2832 void G1CollectedHeap::reset_taskqueue_stats() { 2833 const uint n = num_task_queues(); 2834 for (uint i = 0; i < n; ++i) { 2835 task_queue(i)->stats.reset(); 2836 } 2837 } 2838 #endif // TASKQUEUE_STATS 2839 2840 void G1CollectedHeap::wait_for_root_region_scanning() { 2841 double scan_wait_start = os::elapsedTime(); 2842 // We have to wait until the CM threads finish scanning the 2843 // root regions as it's the only way to ensure that all the 2844 // objects on them have been correctly scanned before we start 2845 // moving them during the GC. 2846 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2847 double wait_time_ms = 0.0; 2848 if (waited) { 2849 double scan_wait_end = os::elapsedTime(); 2850 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2851 } 2852 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2853 } 2854 2855 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2856 private: 2857 G1HRPrinter* _hr_printer; 2858 public: 2859 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2860 2861 virtual bool doHeapRegion(HeapRegion* r) { 2862 _hr_printer->cset(r); 2863 return false; 2864 } 2865 }; 2866 2867 void G1CollectedHeap::start_new_collection_set() { 2868 collection_set()->start_incremental_building(); 2869 2870 clear_cset_fast_test(); 2871 2872 guarantee(_eden.length() == 0, "eden should have been cleared"); 2873 g1_policy()->transfer_survivors_to_cset(survivor()); 2874 } 2875 2876 bool 2877 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2878 assert_at_safepoint(true /* should_be_vm_thread */); 2879 guarantee(!is_gc_active(), "collection is not reentrant"); 2880 2881 if (GCLocker::check_active_before_gc()) { 2882 return false; 2883 } 2884 2885 _gc_timer_stw->register_gc_start(); 2886 2887 GCIdMark gc_id_mark; 2888 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2889 2890 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2891 ResourceMark rm; 2892 2893 g1_policy()->note_gc_start(); 2894 2895 wait_for_root_region_scanning(); 2896 2897 print_heap_before_gc(); 2898 print_heap_regions(); 2899 trace_heap_before_gc(_gc_tracer_stw); 2900 2901 _verifier->verify_region_sets_optional(); 2902 _verifier->verify_dirty_young_regions(); 2903 2904 // We should not be doing initial mark unless the conc mark thread is running 2905 if (!_cmThread->should_terminate()) { 2906 // This call will decide whether this pause is an initial-mark 2907 // pause. If it is, during_initial_mark_pause() will return true 2908 // for the duration of this pause. 2909 g1_policy()->decide_on_conc_mark_initiation(); 2910 } 2911 2912 // We do not allow initial-mark to be piggy-backed on a mixed GC. 2913 assert(!collector_state()->during_initial_mark_pause() || 2914 collector_state()->gcs_are_young(), "sanity"); 2915 2916 // We also do not allow mixed GCs during marking. 2917 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 2918 2919 // Record whether this pause is an initial mark. When the current 2920 // thread has completed its logging output and it's safe to signal 2921 // the CM thread, the flag's value in the policy has been reset. 2922 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 2923 2924 // Inner scope for scope based logging, timers, and stats collection 2925 { 2926 EvacuationInfo evacuation_info; 2927 2928 if (collector_state()->during_initial_mark_pause()) { 2929 // We are about to start a marking cycle, so we increment the 2930 // full collection counter. 2931 increment_old_marking_cycles_started(); 2932 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 2933 } 2934 2935 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 2936 2937 GCTraceCPUTime tcpu; 2938 2939 G1HeapVerifier::G1VerifyType verify_type; 2940 FormatBuffer<> gc_string("Pause "); 2941 if (collector_state()->during_initial_mark_pause()) { 2942 gc_string.append("Initial Mark"); 2943 verify_type = G1HeapVerifier::G1VerifyInitialMark; 2944 } else if (collector_state()->gcs_are_young()) { 2945 gc_string.append("Young"); 2946 verify_type = G1HeapVerifier::G1VerifyYoungOnly; 2947 } else { 2948 gc_string.append("Mixed"); 2949 verify_type = G1HeapVerifier::G1VerifyMixed; 2950 } 2951 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 2952 2953 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 2954 workers()->active_workers(), 2955 Threads::number_of_non_daemon_threads()); 2956 workers()->update_active_workers(active_workers); 2957 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 2958 2959 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 2960 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 2961 2962 // If the secondary_free_list is not empty, append it to the 2963 // free_list. No need to wait for the cleanup operation to finish; 2964 // the region allocation code will check the secondary_free_list 2965 // and wait if necessary. If the G1StressConcRegionFreeing flag is 2966 // set, skip this step so that the region allocation code has to 2967 // get entries from the secondary_free_list. 2968 if (!G1StressConcRegionFreeing) { 2969 append_secondary_free_list_if_not_empty_with_lock(); 2970 } 2971 2972 G1HeapTransition heap_transition(this); 2973 size_t heap_used_bytes_before_gc = used(); 2974 2975 // Don't dynamically change the number of GC threads this early. A value of 2976 // 0 is used to indicate serial work. When parallel work is done, 2977 // it will be set. 2978 2979 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 2980 IsGCActiveMark x; 2981 2982 gc_prologue(false); 2983 2984 if (VerifyRememberedSets) { 2985 log_info(gc, verify)("[Verifying RemSets before GC]"); 2986 VerifyRegionRemSetClosure v_cl; 2987 heap_region_iterate(&v_cl); 2988 } 2989 2990 _verifier->verify_before_gc(verify_type); 2991 2992 _verifier->check_bitmaps("GC Start"); 2993 2994 #if COMPILER2_OR_JVMCI 2995 DerivedPointerTable::clear(); 2996 #endif 2997 2998 // Please see comment in g1CollectedHeap.hpp and 2999 // G1CollectedHeap::ref_processing_init() to see how 3000 // reference processing currently works in G1. 3001 3002 // Enable discovery in the STW reference processor 3003 if (g1_policy()->should_process_references()) { 3004 ref_processor_stw()->enable_discovery(); 3005 } else { 3006 ref_processor_stw()->disable_discovery(); 3007 } 3008 3009 { 3010 // We want to temporarily turn off discovery by the 3011 // CM ref processor, if necessary, and turn it back on 3012 // on again later if we do. Using a scoped 3013 // NoRefDiscovery object will do this. 3014 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3015 3016 // Forget the current alloc region (we might even choose it to be part 3017 // of the collection set!). 3018 _allocator->release_mutator_alloc_region(); 3019 3020 // This timing is only used by the ergonomics to handle our pause target. 3021 // It is unclear why this should not include the full pause. We will 3022 // investigate this in CR 7178365. 3023 // 3024 // Preserving the old comment here if that helps the investigation: 3025 // 3026 // The elapsed time induced by the start time below deliberately elides 3027 // the possible verification above. 3028 double sample_start_time_sec = os::elapsedTime(); 3029 3030 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3031 3032 if (collector_state()->during_initial_mark_pause()) { 3033 concurrent_mark()->checkpoint_roots_initial_pre(); 3034 } 3035 3036 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 3037 3038 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3039 3040 // Make sure the remembered sets are up to date. This needs to be 3041 // done before register_humongous_regions_with_cset(), because the 3042 // remembered sets are used there to choose eager reclaim candidates. 3043 // If the remembered sets are not up to date we might miss some 3044 // entries that need to be handled. 3045 g1_rem_set()->cleanupHRRS(); 3046 3047 register_humongous_regions_with_cset(); 3048 3049 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3050 3051 // We call this after finalize_cset() to 3052 // ensure that the CSet has been finalized. 3053 _cm->verify_no_cset_oops(); 3054 3055 if (_hr_printer.is_active()) { 3056 G1PrintCollectionSetClosure cl(&_hr_printer); 3057 _collection_set.iterate(&cl); 3058 } 3059 3060 // Initialize the GC alloc regions. 3061 _allocator->init_gc_alloc_regions(evacuation_info); 3062 3063 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3064 pre_evacuate_collection_set(); 3065 3066 // Actually do the work... 3067 evacuate_collection_set(evacuation_info, &per_thread_states); 3068 3069 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3070 3071 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3072 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 3073 3074 eagerly_reclaim_humongous_regions(); 3075 3076 record_obj_copy_mem_stats(); 3077 _survivor_evac_stats.adjust_desired_plab_sz(); 3078 _old_evac_stats.adjust_desired_plab_sz(); 3079 3080 double start = os::elapsedTime(); 3081 start_new_collection_set(); 3082 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 3083 3084 if (evacuation_failed()) { 3085 set_used(recalculate_used()); 3086 if (_archive_allocator != NULL) { 3087 _archive_allocator->clear_used(); 3088 } 3089 for (uint i = 0; i < ParallelGCThreads; i++) { 3090 if (_evacuation_failed_info_array[i].has_failed()) { 3091 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3092 } 3093 } 3094 } else { 3095 // The "used" of the the collection set have already been subtracted 3096 // when they were freed. Add in the bytes evacuated. 3097 increase_used(g1_policy()->bytes_copied_during_gc()); 3098 } 3099 3100 if (collector_state()->during_initial_mark_pause()) { 3101 // We have to do this before we notify the CM threads that 3102 // they can start working to make sure that all the 3103 // appropriate initialization is done on the CM object. 3104 concurrent_mark()->checkpoint_roots_initial_post(); 3105 collector_state()->set_mark_in_progress(true); 3106 // Note that we don't actually trigger the CM thread at 3107 // this point. We do that later when we're sure that 3108 // the current thread has completed its logging output. 3109 } 3110 3111 allocate_dummy_regions(); 3112 3113 _allocator->init_mutator_alloc_region(); 3114 3115 { 3116 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3117 if (expand_bytes > 0) { 3118 size_t bytes_before = capacity(); 3119 // No need for an ergo logging here, 3120 // expansion_amount() does this when it returns a value > 0. 3121 double expand_ms; 3122 if (!expand(expand_bytes, _workers, &expand_ms)) { 3123 // We failed to expand the heap. Cannot do anything about it. 3124 } 3125 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3126 } 3127 } 3128 3129 // We redo the verification but now wrt to the new CSet which 3130 // has just got initialized after the previous CSet was freed. 3131 _cm->verify_no_cset_oops(); 3132 3133 // This timing is only used by the ergonomics to handle our pause target. 3134 // It is unclear why this should not include the full pause. We will 3135 // investigate this in CR 7178365. 3136 double sample_end_time_sec = os::elapsedTime(); 3137 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3138 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards); 3139 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3140 3141 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3142 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3143 3144 if (VerifyRememberedSets) { 3145 log_info(gc, verify)("[Verifying RemSets after GC]"); 3146 VerifyRegionRemSetClosure v_cl; 3147 heap_region_iterate(&v_cl); 3148 } 3149 3150 _verifier->verify_after_gc(verify_type); 3151 _verifier->check_bitmaps("GC End"); 3152 3153 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3154 ref_processor_stw()->verify_no_references_recorded(); 3155 3156 // CM reference discovery will be re-enabled if necessary. 3157 } 3158 3159 #ifdef TRACESPINNING 3160 ParallelTaskTerminator::print_termination_counts(); 3161 #endif 3162 3163 gc_epilogue(false); 3164 } 3165 3166 // Print the remainder of the GC log output. 3167 if (evacuation_failed()) { 3168 log_info(gc)("To-space exhausted"); 3169 } 3170 3171 g1_policy()->print_phases(); 3172 heap_transition.print(); 3173 3174 // It is not yet to safe to tell the concurrent mark to 3175 // start as we have some optional output below. We don't want the 3176 // output from the concurrent mark thread interfering with this 3177 // logging output either. 3178 3179 _hrm.verify_optional(); 3180 _verifier->verify_region_sets_optional(); 3181 3182 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3183 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3184 3185 print_heap_after_gc(); 3186 print_heap_regions(); 3187 trace_heap_after_gc(_gc_tracer_stw); 3188 3189 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3190 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3191 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3192 // before any GC notifications are raised. 3193 g1mm()->update_sizes(); 3194 3195 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3196 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3197 _gc_timer_stw->register_gc_end(); 3198 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3199 } 3200 // It should now be safe to tell the concurrent mark thread to start 3201 // without its logging output interfering with the logging output 3202 // that came from the pause. 3203 3204 if (should_start_conc_mark) { 3205 // CAUTION: after the doConcurrentMark() call below, 3206 // the concurrent marking thread(s) could be running 3207 // concurrently with us. Make sure that anything after 3208 // this point does not assume that we are the only GC thread 3209 // running. Note: of course, the actual marking work will 3210 // not start until the safepoint itself is released in 3211 // SuspendibleThreadSet::desynchronize(). 3212 doConcurrentMark(); 3213 } 3214 3215 return true; 3216 } 3217 3218 void G1CollectedHeap::remove_self_forwarding_pointers() { 3219 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3220 workers()->run_task(&rsfp_task); 3221 } 3222 3223 void G1CollectedHeap::restore_after_evac_failure() { 3224 double remove_self_forwards_start = os::elapsedTime(); 3225 3226 remove_self_forwarding_pointers(); 3227 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3228 _preserved_marks_set.restore(&task_executor); 3229 3230 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3231 } 3232 3233 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3234 if (!_evacuation_failed) { 3235 _evacuation_failed = true; 3236 } 3237 3238 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3239 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3240 } 3241 3242 bool G1ParEvacuateFollowersClosure::offer_termination() { 3243 G1ParScanThreadState* const pss = par_scan_state(); 3244 start_term_time(); 3245 const bool res = terminator()->offer_termination(); 3246 end_term_time(); 3247 return res; 3248 } 3249 3250 void G1ParEvacuateFollowersClosure::do_void() { 3251 G1ParScanThreadState* const pss = par_scan_state(); 3252 pss->trim_queue(); 3253 do { 3254 pss->steal_and_trim_queue(queues()); 3255 } while (!offer_termination()); 3256 } 3257 3258 class G1ParTask : public AbstractGangTask { 3259 protected: 3260 G1CollectedHeap* _g1h; 3261 G1ParScanThreadStateSet* _pss; 3262 RefToScanQueueSet* _queues; 3263 G1RootProcessor* _root_processor; 3264 ParallelTaskTerminator _terminator; 3265 uint _n_workers; 3266 3267 public: 3268 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3269 : AbstractGangTask("G1 collection"), 3270 _g1h(g1h), 3271 _pss(per_thread_states), 3272 _queues(task_queues), 3273 _root_processor(root_processor), 3274 _terminator(n_workers, _queues), 3275 _n_workers(n_workers) 3276 {} 3277 3278 void work(uint worker_id) { 3279 if (worker_id >= _n_workers) return; // no work needed this round 3280 3281 double start_sec = os::elapsedTime(); 3282 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3283 3284 { 3285 ResourceMark rm; 3286 HandleMark hm; 3287 3288 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3289 3290 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3291 pss->set_ref_processor(rp); 3292 3293 double start_strong_roots_sec = os::elapsedTime(); 3294 3295 _root_processor->evacuate_roots(pss->closures(), worker_id); 3296 3297 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3298 // treating the nmethods visited to act as roots for concurrent marking. 3299 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3300 // objects copied by the current evacuation. 3301 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, 3302 pss->closures()->weak_codeblobs(), 3303 worker_id); 3304 3305 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3306 3307 double term_sec = 0.0; 3308 size_t evac_term_attempts = 0; 3309 { 3310 double start = os::elapsedTime(); 3311 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3312 evac.do_void(); 3313 3314 evac_term_attempts = evac.term_attempts(); 3315 term_sec = evac.term_time(); 3316 double elapsed_sec = os::elapsedTime() - start; 3317 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3318 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3319 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3320 } 3321 3322 assert(pss->queue_is_empty(), "should be empty"); 3323 3324 if (log_is_enabled(Debug, gc, task, stats)) { 3325 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3326 size_t lab_waste; 3327 size_t lab_undo_waste; 3328 pss->waste(lab_waste, lab_undo_waste); 3329 _g1h->print_termination_stats(worker_id, 3330 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3331 strong_roots_sec * 1000.0, /* strong roots time */ 3332 term_sec * 1000.0, /* evac term time */ 3333 evac_term_attempts, /* evac term attempts */ 3334 lab_waste, /* alloc buffer waste */ 3335 lab_undo_waste /* undo waste */ 3336 ); 3337 } 3338 3339 // Close the inner scope so that the ResourceMark and HandleMark 3340 // destructors are executed here and are included as part of the 3341 // "GC Worker Time". 3342 } 3343 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3344 } 3345 }; 3346 3347 void G1CollectedHeap::print_termination_stats_hdr() { 3348 log_debug(gc, task, stats)("GC Termination Stats"); 3349 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3350 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3351 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3352 } 3353 3354 void G1CollectedHeap::print_termination_stats(uint worker_id, 3355 double elapsed_ms, 3356 double strong_roots_ms, 3357 double term_ms, 3358 size_t term_attempts, 3359 size_t alloc_buffer_waste, 3360 size_t undo_waste) const { 3361 log_debug(gc, task, stats) 3362 ("%3d %9.2f %9.2f %6.2f " 3363 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3364 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3365 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3366 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3367 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3368 alloc_buffer_waste * HeapWordSize / K, 3369 undo_waste * HeapWordSize / K); 3370 } 3371 3372 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3373 private: 3374 BoolObjectClosure* _is_alive; 3375 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3376 3377 int _initial_string_table_size; 3378 int _initial_symbol_table_size; 3379 3380 bool _process_strings; 3381 int _strings_processed; 3382 int _strings_removed; 3383 3384 bool _process_symbols; 3385 int _symbols_processed; 3386 int _symbols_removed; 3387 3388 bool _process_string_dedup; 3389 3390 public: 3391 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3392 AbstractGangTask("String/Symbol Unlinking"), 3393 _is_alive(is_alive), 3394 _dedup_closure(is_alive, NULL, false), 3395 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3396 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3397 _process_string_dedup(process_string_dedup) { 3398 3399 _initial_string_table_size = StringTable::the_table()->table_size(); 3400 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3401 if (process_strings) { 3402 StringTable::clear_parallel_claimed_index(); 3403 } 3404 if (process_symbols) { 3405 SymbolTable::clear_parallel_claimed_index(); 3406 } 3407 } 3408 3409 ~G1StringAndSymbolCleaningTask() { 3410 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3411 "claim value %d after unlink less than initial string table size %d", 3412 StringTable::parallel_claimed_index(), _initial_string_table_size); 3413 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3414 "claim value %d after unlink less than initial symbol table size %d", 3415 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3416 3417 log_info(gc, stringtable)( 3418 "Cleaned string and symbol table, " 3419 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3420 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3421 strings_processed(), strings_removed(), 3422 symbols_processed(), symbols_removed()); 3423 } 3424 3425 void work(uint worker_id) { 3426 int strings_processed = 0; 3427 int strings_removed = 0; 3428 int symbols_processed = 0; 3429 int symbols_removed = 0; 3430 if (_process_strings) { 3431 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3432 Atomic::add(strings_processed, &_strings_processed); 3433 Atomic::add(strings_removed, &_strings_removed); 3434 } 3435 if (_process_symbols) { 3436 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3437 Atomic::add(symbols_processed, &_symbols_processed); 3438 Atomic::add(symbols_removed, &_symbols_removed); 3439 } 3440 if (_process_string_dedup) { 3441 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3442 } 3443 } 3444 3445 size_t strings_processed() const { return (size_t)_strings_processed; } 3446 size_t strings_removed() const { return (size_t)_strings_removed; } 3447 3448 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3449 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3450 }; 3451 3452 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3453 private: 3454 static Monitor* _lock; 3455 3456 BoolObjectClosure* const _is_alive; 3457 const bool _unloading_occurred; 3458 const uint _num_workers; 3459 3460 // Variables used to claim nmethods. 3461 CompiledMethod* _first_nmethod; 3462 CompiledMethod* volatile _claimed_nmethod; 3463 3464 // The list of nmethods that need to be processed by the second pass. 3465 CompiledMethod* volatile _postponed_list; 3466 volatile uint _num_entered_barrier; 3467 3468 public: 3469 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3470 _is_alive(is_alive), 3471 _unloading_occurred(unloading_occurred), 3472 _num_workers(num_workers), 3473 _first_nmethod(NULL), 3474 _claimed_nmethod(NULL), 3475 _postponed_list(NULL), 3476 _num_entered_barrier(0) 3477 { 3478 CompiledMethod::increase_unloading_clock(); 3479 // Get first alive nmethod 3480 CompiledMethodIterator iter = CompiledMethodIterator(); 3481 if(iter.next_alive()) { 3482 _first_nmethod = iter.method(); 3483 } 3484 _claimed_nmethod = _first_nmethod; 3485 } 3486 3487 ~G1CodeCacheUnloadingTask() { 3488 CodeCache::verify_clean_inline_caches(); 3489 3490 CodeCache::set_needs_cache_clean(false); 3491 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3492 3493 CodeCache::verify_icholder_relocations(); 3494 } 3495 3496 private: 3497 void add_to_postponed_list(CompiledMethod* nm) { 3498 CompiledMethod* old; 3499 do { 3500 old = _postponed_list; 3501 nm->set_unloading_next(old); 3502 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old); 3503 } 3504 3505 void clean_nmethod(CompiledMethod* nm) { 3506 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3507 3508 if (postponed) { 3509 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3510 add_to_postponed_list(nm); 3511 } 3512 3513 // Mark that this thread has been cleaned/unloaded. 3514 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3515 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3516 } 3517 3518 void clean_nmethod_postponed(CompiledMethod* nm) { 3519 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3520 } 3521 3522 static const int MaxClaimNmethods = 16; 3523 3524 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3525 CompiledMethod* first; 3526 CompiledMethodIterator last; 3527 3528 do { 3529 *num_claimed_nmethods = 0; 3530 3531 first = _claimed_nmethod; 3532 last = CompiledMethodIterator(first); 3533 3534 if (first != NULL) { 3535 3536 for (int i = 0; i < MaxClaimNmethods; i++) { 3537 if (!last.next_alive()) { 3538 break; 3539 } 3540 claimed_nmethods[i] = last.method(); 3541 (*num_claimed_nmethods)++; 3542 } 3543 } 3544 3545 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first); 3546 } 3547 3548 CompiledMethod* claim_postponed_nmethod() { 3549 CompiledMethod* claim; 3550 CompiledMethod* next; 3551 3552 do { 3553 claim = _postponed_list; 3554 if (claim == NULL) { 3555 return NULL; 3556 } 3557 3558 next = claim->unloading_next(); 3559 3560 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim); 3561 3562 return claim; 3563 } 3564 3565 public: 3566 // Mark that we're done with the first pass of nmethod cleaning. 3567 void barrier_mark(uint worker_id) { 3568 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3569 _num_entered_barrier++; 3570 if (_num_entered_barrier == _num_workers) { 3571 ml.notify_all(); 3572 } 3573 } 3574 3575 // See if we have to wait for the other workers to 3576 // finish their first-pass nmethod cleaning work. 3577 void barrier_wait(uint worker_id) { 3578 if (_num_entered_barrier < _num_workers) { 3579 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3580 while (_num_entered_barrier < _num_workers) { 3581 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3582 } 3583 } 3584 } 3585 3586 // Cleaning and unloading of nmethods. Some work has to be postponed 3587 // to the second pass, when we know which nmethods survive. 3588 void work_first_pass(uint worker_id) { 3589 // The first nmethods is claimed by the first worker. 3590 if (worker_id == 0 && _first_nmethod != NULL) { 3591 clean_nmethod(_first_nmethod); 3592 _first_nmethod = NULL; 3593 } 3594 3595 int num_claimed_nmethods; 3596 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3597 3598 while (true) { 3599 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3600 3601 if (num_claimed_nmethods == 0) { 3602 break; 3603 } 3604 3605 for (int i = 0; i < num_claimed_nmethods; i++) { 3606 clean_nmethod(claimed_nmethods[i]); 3607 } 3608 } 3609 } 3610 3611 void work_second_pass(uint worker_id) { 3612 CompiledMethod* nm; 3613 // Take care of postponed nmethods. 3614 while ((nm = claim_postponed_nmethod()) != NULL) { 3615 clean_nmethod_postponed(nm); 3616 } 3617 } 3618 }; 3619 3620 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3621 3622 class G1KlassCleaningTask : public StackObj { 3623 BoolObjectClosure* _is_alive; 3624 volatile int _clean_klass_tree_claimed; 3625 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3626 3627 public: 3628 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3629 _is_alive(is_alive), 3630 _clean_klass_tree_claimed(0), 3631 _klass_iterator() { 3632 } 3633 3634 private: 3635 bool claim_clean_klass_tree_task() { 3636 if (_clean_klass_tree_claimed) { 3637 return false; 3638 } 3639 3640 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0; 3641 } 3642 3643 InstanceKlass* claim_next_klass() { 3644 Klass* klass; 3645 do { 3646 klass =_klass_iterator.next_klass(); 3647 } while (klass != NULL && !klass->is_instance_klass()); 3648 3649 // this can be null so don't call InstanceKlass::cast 3650 return static_cast<InstanceKlass*>(klass); 3651 } 3652 3653 public: 3654 3655 void clean_klass(InstanceKlass* ik) { 3656 ik->clean_weak_instanceklass_links(_is_alive); 3657 } 3658 3659 void work() { 3660 ResourceMark rm; 3661 3662 // One worker will clean the subklass/sibling klass tree. 3663 if (claim_clean_klass_tree_task()) { 3664 Klass::clean_subklass_tree(_is_alive); 3665 } 3666 3667 // All workers will help cleaning the classes, 3668 InstanceKlass* klass; 3669 while ((klass = claim_next_klass()) != NULL) { 3670 clean_klass(klass); 3671 } 3672 } 3673 }; 3674 3675 class G1ResolvedMethodCleaningTask : public StackObj { 3676 BoolObjectClosure* _is_alive; 3677 volatile int _resolved_method_task_claimed; 3678 public: 3679 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) : 3680 _is_alive(is_alive), _resolved_method_task_claimed(0) {} 3681 3682 bool claim_resolved_method_task() { 3683 if (_resolved_method_task_claimed) { 3684 return false; 3685 } 3686 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0; 3687 } 3688 3689 // These aren't big, one thread can do it all. 3690 void work() { 3691 if (claim_resolved_method_task()) { 3692 ResolvedMethodTable::unlink(_is_alive); 3693 } 3694 } 3695 }; 3696 3697 3698 // To minimize the remark pause times, the tasks below are done in parallel. 3699 class G1ParallelCleaningTask : public AbstractGangTask { 3700 private: 3701 G1StringAndSymbolCleaningTask _string_symbol_task; 3702 G1CodeCacheUnloadingTask _code_cache_task; 3703 G1KlassCleaningTask _klass_cleaning_task; 3704 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task; 3705 3706 public: 3707 // The constructor is run in the VMThread. 3708 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3709 AbstractGangTask("Parallel Cleaning"), 3710 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3711 _code_cache_task(num_workers, is_alive, unloading_occurred), 3712 _klass_cleaning_task(is_alive), 3713 _resolved_method_cleaning_task(is_alive) { 3714 } 3715 3716 // The parallel work done by all worker threads. 3717 void work(uint worker_id) { 3718 // Do first pass of code cache cleaning. 3719 _code_cache_task.work_first_pass(worker_id); 3720 3721 // Let the threads mark that the first pass is done. 3722 _code_cache_task.barrier_mark(worker_id); 3723 3724 // Clean the Strings and Symbols. 3725 _string_symbol_task.work(worker_id); 3726 3727 // Clean unreferenced things in the ResolvedMethodTable 3728 _resolved_method_cleaning_task.work(); 3729 3730 // Wait for all workers to finish the first code cache cleaning pass. 3731 _code_cache_task.barrier_wait(worker_id); 3732 3733 // Do the second code cache cleaning work, which realize on 3734 // the liveness information gathered during the first pass. 3735 _code_cache_task.work_second_pass(worker_id); 3736 3737 // Clean all klasses that were not unloaded. 3738 _klass_cleaning_task.work(); 3739 } 3740 }; 3741 3742 3743 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3744 bool class_unloading_occurred) { 3745 uint n_workers = workers()->active_workers(); 3746 3747 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3748 workers()->run_task(&g1_unlink_task); 3749 } 3750 3751 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3752 bool process_strings, 3753 bool process_symbols, 3754 bool process_string_dedup) { 3755 if (!process_strings && !process_symbols && !process_string_dedup) { 3756 // Nothing to clean. 3757 return; 3758 } 3759 3760 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3761 workers()->run_task(&g1_unlink_task); 3762 3763 } 3764 3765 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3766 private: 3767 DirtyCardQueueSet* _queue; 3768 G1CollectedHeap* _g1h; 3769 public: 3770 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3771 _queue(queue), _g1h(g1h) { } 3772 3773 virtual void work(uint worker_id) { 3774 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3775 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3776 3777 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3778 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3779 3780 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3781 } 3782 }; 3783 3784 void G1CollectedHeap::redirty_logged_cards() { 3785 double redirty_logged_cards_start = os::elapsedTime(); 3786 3787 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3788 dirty_card_queue_set().reset_for_par_iteration(); 3789 workers()->run_task(&redirty_task); 3790 3791 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 3792 dcq.merge_bufferlists(&dirty_card_queue_set()); 3793 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3794 3795 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3796 } 3797 3798 // Weak Reference Processing support 3799 3800 // An always "is_alive" closure that is used to preserve referents. 3801 // If the object is non-null then it's alive. Used in the preservation 3802 // of referent objects that are pointed to by reference objects 3803 // discovered by the CM ref processor. 3804 class G1AlwaysAliveClosure: public BoolObjectClosure { 3805 G1CollectedHeap* _g1; 3806 public: 3807 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3808 bool do_object_b(oop p) { 3809 if (p != NULL) { 3810 return true; 3811 } 3812 return false; 3813 } 3814 }; 3815 3816 bool G1STWIsAliveClosure::do_object_b(oop p) { 3817 // An object is reachable if it is outside the collection set, 3818 // or is inside and copied. 3819 return !_g1->is_in_cset(p) || p->is_forwarded(); 3820 } 3821 3822 // Non Copying Keep Alive closure 3823 class G1KeepAliveClosure: public OopClosure { 3824 G1CollectedHeap* _g1; 3825 public: 3826 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3827 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3828 void do_oop(oop* p) { 3829 oop obj = *p; 3830 assert(obj != NULL, "the caller should have filtered out NULL values"); 3831 3832 const InCSetState cset_state = _g1->in_cset_state(obj); 3833 if (!cset_state.is_in_cset_or_humongous()) { 3834 return; 3835 } 3836 if (cset_state.is_in_cset()) { 3837 assert( obj->is_forwarded(), "invariant" ); 3838 *p = obj->forwardee(); 3839 } else { 3840 assert(!obj->is_forwarded(), "invariant" ); 3841 assert(cset_state.is_humongous(), 3842 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3843 _g1->set_humongous_is_live(obj); 3844 } 3845 } 3846 }; 3847 3848 // Copying Keep Alive closure - can be called from both 3849 // serial and parallel code as long as different worker 3850 // threads utilize different G1ParScanThreadState instances 3851 // and different queues. 3852 3853 class G1CopyingKeepAliveClosure: public OopClosure { 3854 G1CollectedHeap* _g1h; 3855 OopClosure* _copy_non_heap_obj_cl; 3856 G1ParScanThreadState* _par_scan_state; 3857 3858 public: 3859 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3860 OopClosure* non_heap_obj_cl, 3861 G1ParScanThreadState* pss): 3862 _g1h(g1h), 3863 _copy_non_heap_obj_cl(non_heap_obj_cl), 3864 _par_scan_state(pss) 3865 {} 3866 3867 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3868 virtual void do_oop( oop* p) { do_oop_work(p); } 3869 3870 template <class T> void do_oop_work(T* p) { 3871 oop obj = oopDesc::load_decode_heap_oop(p); 3872 3873 if (_g1h->is_in_cset_or_humongous(obj)) { 3874 // If the referent object has been forwarded (either copied 3875 // to a new location or to itself in the event of an 3876 // evacuation failure) then we need to update the reference 3877 // field and, if both reference and referent are in the G1 3878 // heap, update the RSet for the referent. 3879 // 3880 // If the referent has not been forwarded then we have to keep 3881 // it alive by policy. Therefore we have copy the referent. 3882 // 3883 // If the reference field is in the G1 heap then we can push 3884 // on the PSS queue. When the queue is drained (after each 3885 // phase of reference processing) the object and it's followers 3886 // will be copied, the reference field set to point to the 3887 // new location, and the RSet updated. Otherwise we need to 3888 // use the the non-heap or metadata closures directly to copy 3889 // the referent object and update the pointer, while avoiding 3890 // updating the RSet. 3891 3892 if (_g1h->is_in_g1_reserved(p)) { 3893 _par_scan_state->push_on_queue(p); 3894 } else { 3895 assert(!Metaspace::contains((const void*)p), 3896 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 3897 _copy_non_heap_obj_cl->do_oop(p); 3898 } 3899 } 3900 } 3901 }; 3902 3903 // Serial drain queue closure. Called as the 'complete_gc' 3904 // closure for each discovered list in some of the 3905 // reference processing phases. 3906 3907 class G1STWDrainQueueClosure: public VoidClosure { 3908 protected: 3909 G1CollectedHeap* _g1h; 3910 G1ParScanThreadState* _par_scan_state; 3911 3912 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3913 3914 public: 3915 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3916 _g1h(g1h), 3917 _par_scan_state(pss) 3918 { } 3919 3920 void do_void() { 3921 G1ParScanThreadState* const pss = par_scan_state(); 3922 pss->trim_queue(); 3923 } 3924 }; 3925 3926 // Parallel Reference Processing closures 3927 3928 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3929 // processing during G1 evacuation pauses. 3930 3931 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3932 private: 3933 G1CollectedHeap* _g1h; 3934 G1ParScanThreadStateSet* _pss; 3935 RefToScanQueueSet* _queues; 3936 WorkGang* _workers; 3937 uint _active_workers; 3938 3939 public: 3940 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3941 G1ParScanThreadStateSet* per_thread_states, 3942 WorkGang* workers, 3943 RefToScanQueueSet *task_queues, 3944 uint n_workers) : 3945 _g1h(g1h), 3946 _pss(per_thread_states), 3947 _queues(task_queues), 3948 _workers(workers), 3949 _active_workers(n_workers) 3950 { 3951 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 3952 } 3953 3954 // Executes the given task using concurrent marking worker threads. 3955 virtual void execute(ProcessTask& task); 3956 virtual void execute(EnqueueTask& task); 3957 }; 3958 3959 // Gang task for possibly parallel reference processing 3960 3961 class G1STWRefProcTaskProxy: public AbstractGangTask { 3962 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 3963 ProcessTask& _proc_task; 3964 G1CollectedHeap* _g1h; 3965 G1ParScanThreadStateSet* _pss; 3966 RefToScanQueueSet* _task_queues; 3967 ParallelTaskTerminator* _terminator; 3968 3969 public: 3970 G1STWRefProcTaskProxy(ProcessTask& proc_task, 3971 G1CollectedHeap* g1h, 3972 G1ParScanThreadStateSet* per_thread_states, 3973 RefToScanQueueSet *task_queues, 3974 ParallelTaskTerminator* terminator) : 3975 AbstractGangTask("Process reference objects in parallel"), 3976 _proc_task(proc_task), 3977 _g1h(g1h), 3978 _pss(per_thread_states), 3979 _task_queues(task_queues), 3980 _terminator(terminator) 3981 {} 3982 3983 virtual void work(uint worker_id) { 3984 // The reference processing task executed by a single worker. 3985 ResourceMark rm; 3986 HandleMark hm; 3987 3988 G1STWIsAliveClosure is_alive(_g1h); 3989 3990 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3991 pss->set_ref_processor(NULL); 3992 3993 // Keep alive closure. 3994 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 3995 3996 // Complete GC closure 3997 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 3998 3999 // Call the reference processing task's work routine. 4000 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4001 4002 // Note we cannot assert that the refs array is empty here as not all 4003 // of the processing tasks (specifically phase2 - pp2_work) execute 4004 // the complete_gc closure (which ordinarily would drain the queue) so 4005 // the queue may not be empty. 4006 } 4007 }; 4008 4009 // Driver routine for parallel reference processing. 4010 // Creates an instance of the ref processing gang 4011 // task and has the worker threads execute it. 4012 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4013 assert(_workers != NULL, "Need parallel worker threads."); 4014 4015 ParallelTaskTerminator terminator(_active_workers, _queues); 4016 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4017 4018 _workers->run_task(&proc_task_proxy); 4019 } 4020 4021 // Gang task for parallel reference enqueueing. 4022 4023 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4024 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4025 EnqueueTask& _enq_task; 4026 4027 public: 4028 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4029 AbstractGangTask("Enqueue reference objects in parallel"), 4030 _enq_task(enq_task) 4031 { } 4032 4033 virtual void work(uint worker_id) { 4034 _enq_task.work(worker_id); 4035 } 4036 }; 4037 4038 // Driver routine for parallel reference enqueueing. 4039 // Creates an instance of the ref enqueueing gang 4040 // task and has the worker threads execute it. 4041 4042 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4043 assert(_workers != NULL, "Need parallel worker threads."); 4044 4045 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4046 4047 _workers->run_task(&enq_task_proxy); 4048 } 4049 4050 // End of weak reference support closures 4051 4052 // Abstract task used to preserve (i.e. copy) any referent objects 4053 // that are in the collection set and are pointed to by reference 4054 // objects discovered by the CM ref processor. 4055 4056 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4057 protected: 4058 G1CollectedHeap* _g1h; 4059 G1ParScanThreadStateSet* _pss; 4060 RefToScanQueueSet* _queues; 4061 ParallelTaskTerminator _terminator; 4062 uint _n_workers; 4063 4064 public: 4065 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4066 AbstractGangTask("ParPreserveCMReferents"), 4067 _g1h(g1h), 4068 _pss(per_thread_states), 4069 _queues(task_queues), 4070 _terminator(workers, _queues), 4071 _n_workers(workers) 4072 { 4073 g1h->ref_processor_cm()->set_active_mt_degree(workers); 4074 } 4075 4076 void work(uint worker_id) { 4077 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4078 4079 ResourceMark rm; 4080 HandleMark hm; 4081 4082 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4083 pss->set_ref_processor(NULL); 4084 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4085 4086 // Is alive closure 4087 G1AlwaysAliveClosure always_alive(_g1h); 4088 4089 // Copying keep alive closure. Applied to referent objects that need 4090 // to be copied. 4091 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4092 4093 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4094 4095 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4096 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4097 4098 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4099 // So this must be true - but assert just in case someone decides to 4100 // change the worker ids. 4101 assert(worker_id < limit, "sanity"); 4102 assert(!rp->discovery_is_atomic(), "check this code"); 4103 4104 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4105 for (uint idx = worker_id; idx < limit; idx += stride) { 4106 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4107 4108 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4109 while (iter.has_next()) { 4110 // Since discovery is not atomic for the CM ref processor, we 4111 // can see some null referent objects. 4112 iter.load_ptrs(DEBUG_ONLY(true)); 4113 oop ref = iter.obj(); 4114 4115 // This will filter nulls. 4116 if (iter.is_referent_alive()) { 4117 iter.make_referent_alive(); 4118 } 4119 iter.move_to_next(); 4120 } 4121 } 4122 4123 // Drain the queue - which may cause stealing 4124 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4125 drain_queue.do_void(); 4126 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4127 assert(pss->queue_is_empty(), "should be"); 4128 } 4129 }; 4130 4131 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4132 // Any reference objects, in the collection set, that were 'discovered' 4133 // by the CM ref processor should have already been copied (either by 4134 // applying the external root copy closure to the discovered lists, or 4135 // by following an RSet entry). 4136 // 4137 // But some of the referents, that are in the collection set, that these 4138 // reference objects point to may not have been copied: the STW ref 4139 // processor would have seen that the reference object had already 4140 // been 'discovered' and would have skipped discovering the reference, 4141 // but would not have treated the reference object as a regular oop. 4142 // As a result the copy closure would not have been applied to the 4143 // referent object. 4144 // 4145 // We need to explicitly copy these referent objects - the references 4146 // will be processed at the end of remarking. 4147 // 4148 // We also need to do this copying before we process the reference 4149 // objects discovered by the STW ref processor in case one of these 4150 // referents points to another object which is also referenced by an 4151 // object discovered by the STW ref processor. 4152 double preserve_cm_referents_time = 0.0; 4153 4154 // To avoid spawning task when there is no work to do, check that 4155 // a concurrent cycle is active and that some references have been 4156 // discovered. 4157 if (concurrent_mark()->cm_thread()->during_cycle() && 4158 ref_processor_cm()->has_discovered_references()) { 4159 double preserve_cm_referents_start = os::elapsedTime(); 4160 uint no_of_gc_workers = workers()->active_workers(); 4161 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4162 per_thread_states, 4163 no_of_gc_workers, 4164 _task_queues); 4165 workers()->run_task(&keep_cm_referents); 4166 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4167 } 4168 4169 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4170 } 4171 4172 // Weak Reference processing during an evacuation pause (part 1). 4173 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4174 double ref_proc_start = os::elapsedTime(); 4175 4176 ReferenceProcessor* rp = _ref_processor_stw; 4177 assert(rp->discovery_enabled(), "should have been enabled"); 4178 4179 // Closure to test whether a referent is alive. 4180 G1STWIsAliveClosure is_alive(this); 4181 4182 // Even when parallel reference processing is enabled, the processing 4183 // of JNI refs is serial and performed serially by the current thread 4184 // rather than by a worker. The following PSS will be used for processing 4185 // JNI refs. 4186 4187 // Use only a single queue for this PSS. 4188 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4189 pss->set_ref_processor(NULL); 4190 assert(pss->queue_is_empty(), "pre-condition"); 4191 4192 // Keep alive closure. 4193 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4194 4195 // Serial Complete GC closure 4196 G1STWDrainQueueClosure drain_queue(this, pss); 4197 4198 // Setup the soft refs policy... 4199 rp->setup_policy(false); 4200 4201 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4202 4203 ReferenceProcessorStats stats; 4204 if (!rp->processing_is_mt()) { 4205 // Serial reference processing... 4206 stats = rp->process_discovered_references(&is_alive, 4207 &keep_alive, 4208 &drain_queue, 4209 NULL, 4210 pt); 4211 } else { 4212 uint no_of_gc_workers = workers()->active_workers(); 4213 4214 // Parallel reference processing 4215 assert(no_of_gc_workers <= rp->max_num_q(), 4216 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4217 no_of_gc_workers, rp->max_num_q()); 4218 4219 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4220 stats = rp->process_discovered_references(&is_alive, 4221 &keep_alive, 4222 &drain_queue, 4223 &par_task_executor, 4224 pt); 4225 } 4226 4227 _gc_tracer_stw->report_gc_reference_stats(stats); 4228 4229 // We have completed copying any necessary live referent objects. 4230 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4231 4232 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4233 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4234 } 4235 4236 // Weak Reference processing during an evacuation pause (part 2). 4237 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4238 double ref_enq_start = os::elapsedTime(); 4239 4240 ReferenceProcessor* rp = _ref_processor_stw; 4241 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4242 4243 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4244 4245 // Now enqueue any remaining on the discovered lists on to 4246 // the pending list. 4247 if (!rp->processing_is_mt()) { 4248 // Serial reference processing... 4249 rp->enqueue_discovered_references(NULL, pt); 4250 } else { 4251 // Parallel reference enqueueing 4252 4253 uint n_workers = workers()->active_workers(); 4254 4255 assert(n_workers <= rp->max_num_q(), 4256 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4257 n_workers, rp->max_num_q()); 4258 4259 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4260 rp->enqueue_discovered_references(&par_task_executor, pt); 4261 } 4262 4263 rp->verify_no_references_recorded(); 4264 assert(!rp->discovery_enabled(), "should have been disabled"); 4265 4266 // If during an initial mark pause we install a pending list head which is not otherwise reachable 4267 // ensure that it is marked in the bitmap for concurrent marking to discover. 4268 if (collector_state()->during_initial_mark_pause()) { 4269 oop pll_head = Universe::reference_pending_list(); 4270 if (pll_head != NULL) { 4271 _cm->mark_in_next_bitmap(pll_head); 4272 } 4273 } 4274 4275 // FIXME 4276 // CM's reference processing also cleans up the string and symbol tables. 4277 // Should we do that here also? We could, but it is a serial operation 4278 // and could significantly increase the pause time. 4279 4280 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4281 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4282 } 4283 4284 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4285 double merge_pss_time_start = os::elapsedTime(); 4286 per_thread_states->flush(); 4287 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4288 } 4289 4290 void G1CollectedHeap::pre_evacuate_collection_set() { 4291 _expand_heap_after_alloc_failure = true; 4292 _evacuation_failed = false; 4293 4294 // Disable the hot card cache. 4295 _hot_card_cache->reset_hot_cache_claimed_index(); 4296 _hot_card_cache->set_use_cache(false); 4297 4298 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4299 _preserved_marks_set.assert_empty(); 4300 4301 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4302 4303 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4304 if (collector_state()->during_initial_mark_pause()) { 4305 double start_clear_claimed_marks = os::elapsedTime(); 4306 4307 ClassLoaderDataGraph::clear_claimed_marks(); 4308 4309 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4310 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4311 } 4312 } 4313 4314 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4315 // Should G1EvacuationFailureALot be in effect for this GC? 4316 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4317 4318 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4319 4320 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4321 4322 double start_par_time_sec = os::elapsedTime(); 4323 double end_par_time_sec; 4324 4325 { 4326 const uint n_workers = workers()->active_workers(); 4327 G1RootProcessor root_processor(this, n_workers); 4328 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4329 4330 print_termination_stats_hdr(); 4331 4332 workers()->run_task(&g1_par_task); 4333 end_par_time_sec = os::elapsedTime(); 4334 4335 // Closing the inner scope will execute the destructor 4336 // for the G1RootProcessor object. We record the current 4337 // elapsed time before closing the scope so that time 4338 // taken for the destructor is NOT included in the 4339 // reported parallel time. 4340 } 4341 4342 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4343 phase_times->record_par_time(par_time_ms); 4344 4345 double code_root_fixup_time_ms = 4346 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4347 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4348 } 4349 4350 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4351 // Process any discovered reference objects - we have 4352 // to do this _before_ we retire the GC alloc regions 4353 // as we may have to copy some 'reachable' referent 4354 // objects (and their reachable sub-graphs) that were 4355 // not copied during the pause. 4356 if (g1_policy()->should_process_references()) { 4357 preserve_cm_referents(per_thread_states); 4358 process_discovered_references(per_thread_states); 4359 } else { 4360 ref_processor_stw()->verify_no_references_recorded(); 4361 } 4362 4363 G1STWIsAliveClosure is_alive(this); 4364 G1KeepAliveClosure keep_alive(this); 4365 4366 { 4367 double start = os::elapsedTime(); 4368 4369 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 4370 4371 double time_ms = (os::elapsedTime() - start) * 1000.0; 4372 g1_policy()->phase_times()->record_ref_proc_time(time_ms); 4373 } 4374 4375 if (G1StringDedup::is_enabled()) { 4376 double fixup_start = os::elapsedTime(); 4377 4378 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4379 4380 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4381 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4382 } 4383 4384 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4385 4386 if (evacuation_failed()) { 4387 restore_after_evac_failure(); 4388 4389 // Reset the G1EvacuationFailureALot counters and flags 4390 // Note: the values are reset only when an actual 4391 // evacuation failure occurs. 4392 NOT_PRODUCT(reset_evacuation_should_fail();) 4393 } 4394 4395 _preserved_marks_set.assert_empty(); 4396 4397 // Enqueue any remaining references remaining on the STW 4398 // reference processor's discovered lists. We need to do 4399 // this after the card table is cleaned (and verified) as 4400 // the act of enqueueing entries on to the pending list 4401 // will log these updates (and dirty their associated 4402 // cards). We need these updates logged to update any 4403 // RSets. 4404 if (g1_policy()->should_process_references()) { 4405 enqueue_discovered_references(per_thread_states); 4406 } else { 4407 g1_policy()->phase_times()->record_ref_enq_time(0); 4408 } 4409 4410 _allocator->release_gc_alloc_regions(evacuation_info); 4411 4412 merge_per_thread_state_info(per_thread_states); 4413 4414 // Reset and re-enable the hot card cache. 4415 // Note the counts for the cards in the regions in the 4416 // collection set are reset when the collection set is freed. 4417 _hot_card_cache->reset_hot_cache(); 4418 _hot_card_cache->set_use_cache(true); 4419 4420 purge_code_root_memory(); 4421 4422 redirty_logged_cards(); 4423 #if COMPILER2_OR_JVMCI 4424 double start = os::elapsedTime(); 4425 DerivedPointerTable::update_pointers(); 4426 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4427 #endif 4428 g1_policy()->print_age_table(); 4429 } 4430 4431 void G1CollectedHeap::record_obj_copy_mem_stats() { 4432 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4433 4434 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4435 create_g1_evac_summary(&_old_evac_stats)); 4436 } 4437 4438 void G1CollectedHeap::free_region(HeapRegion* hr, 4439 FreeRegionList* free_list, 4440 bool skip_remset, 4441 bool skip_hot_card_cache, 4442 bool locked) { 4443 assert(!hr->is_free(), "the region should not be free"); 4444 assert(!hr->is_empty(), "the region should not be empty"); 4445 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4446 assert(free_list != NULL, "pre-condition"); 4447 4448 if (G1VerifyBitmaps) { 4449 MemRegion mr(hr->bottom(), hr->end()); 4450 concurrent_mark()->clear_range_in_prev_bitmap(mr); 4451 } 4452 4453 // Clear the card counts for this region. 4454 // Note: we only need to do this if the region is not young 4455 // (since we don't refine cards in young regions). 4456 if (!skip_hot_card_cache && !hr->is_young()) { 4457 _hot_card_cache->reset_card_counts(hr); 4458 } 4459 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4460 free_list->add_ordered(hr); 4461 } 4462 4463 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4464 FreeRegionList* free_list, 4465 bool skip_remset) { 4466 assert(hr->is_humongous(), "this is only for humongous regions"); 4467 assert(free_list != NULL, "pre-condition"); 4468 hr->clear_humongous(); 4469 free_region(hr, free_list, skip_remset); 4470 } 4471 4472 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4473 const uint humongous_regions_removed) { 4474 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4475 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4476 _old_set.bulk_remove(old_regions_removed); 4477 _humongous_set.bulk_remove(humongous_regions_removed); 4478 } 4479 4480 } 4481 4482 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4483 assert(list != NULL, "list can't be null"); 4484 if (!list->is_empty()) { 4485 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4486 _hrm.insert_list_into_free_list(list); 4487 } 4488 } 4489 4490 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4491 decrease_used(bytes); 4492 } 4493 4494 class G1ParScrubRemSetTask: public AbstractGangTask { 4495 protected: 4496 G1RemSet* _g1rs; 4497 HeapRegionClaimer _hrclaimer; 4498 4499 public: 4500 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) : 4501 AbstractGangTask("G1 ScrubRS"), 4502 _g1rs(g1_rs), 4503 _hrclaimer(num_workers) { 4504 } 4505 4506 void work(uint worker_id) { 4507 _g1rs->scrub(worker_id, &_hrclaimer); 4508 } 4509 }; 4510 4511 void G1CollectedHeap::scrub_rem_set() { 4512 uint num_workers = workers()->active_workers(); 4513 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers); 4514 workers()->run_task(&g1_par_scrub_rs_task); 4515 } 4516 4517 class G1FreeCollectionSetTask : public AbstractGangTask { 4518 private: 4519 4520 // Closure applied to all regions in the collection set to do work that needs to 4521 // be done serially in a single thread. 4522 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4523 private: 4524 EvacuationInfo* _evacuation_info; 4525 const size_t* _surviving_young_words; 4526 4527 // Bytes used in successfully evacuated regions before the evacuation. 4528 size_t _before_used_bytes; 4529 // Bytes used in unsucessfully evacuated regions before the evacuation 4530 size_t _after_used_bytes; 4531 4532 size_t _bytes_allocated_in_old_since_last_gc; 4533 4534 size_t _failure_used_words; 4535 size_t _failure_waste_words; 4536 4537 FreeRegionList _local_free_list; 4538 public: 4539 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4540 HeapRegionClosure(), 4541 _evacuation_info(evacuation_info), 4542 _surviving_young_words(surviving_young_words), 4543 _before_used_bytes(0), 4544 _after_used_bytes(0), 4545 _bytes_allocated_in_old_since_last_gc(0), 4546 _failure_used_words(0), 4547 _failure_waste_words(0), 4548 _local_free_list("Local Region List for CSet Freeing") { 4549 } 4550 4551 virtual bool doHeapRegion(HeapRegion* r) { 4552 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4553 4554 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4555 g1h->clear_in_cset(r); 4556 4557 if (r->is_young()) { 4558 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4559 "Young index %d is wrong for region %u of type %s with %u young regions", 4560 r->young_index_in_cset(), 4561 r->hrm_index(), 4562 r->get_type_str(), 4563 g1h->collection_set()->young_region_length()); 4564 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4565 r->record_surv_words_in_group(words_survived); 4566 } 4567 4568 if (!r->evacuation_failed()) { 4569 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4570 _before_used_bytes += r->used(); 4571 g1h->free_region(r, 4572 &_local_free_list, 4573 true, /* skip_remset */ 4574 true, /* skip_hot_card_cache */ 4575 true /* locked */); 4576 } else { 4577 r->uninstall_surv_rate_group(); 4578 r->set_young_index_in_cset(-1); 4579 r->set_evacuation_failed(false); 4580 // When moving a young gen region to old gen, we "allocate" that whole region 4581 // there. This is in addition to any already evacuated objects. Notify the 4582 // policy about that. 4583 // Old gen regions do not cause an additional allocation: both the objects 4584 // still in the region and the ones already moved are accounted for elsewhere. 4585 if (r->is_young()) { 4586 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4587 } 4588 // The region is now considered to be old. 4589 r->set_old(); 4590 // Do some allocation statistics accounting. Regions that failed evacuation 4591 // are always made old, so there is no need to update anything in the young 4592 // gen statistics, but we need to update old gen statistics. 4593 size_t used_words = r->marked_bytes() / HeapWordSize; 4594 4595 _failure_used_words += used_words; 4596 _failure_waste_words += HeapRegion::GrainWords - used_words; 4597 4598 g1h->old_set_add(r); 4599 _after_used_bytes += r->used(); 4600 } 4601 return false; 4602 } 4603 4604 void complete_work() { 4605 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4606 4607 _evacuation_info->set_regions_freed(_local_free_list.length()); 4608 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4609 4610 g1h->prepend_to_freelist(&_local_free_list); 4611 g1h->decrement_summary_bytes(_before_used_bytes); 4612 4613 G1Policy* policy = g1h->g1_policy(); 4614 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4615 4616 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4617 } 4618 }; 4619 4620 G1CollectionSet* _collection_set; 4621 G1SerialFreeCollectionSetClosure _cl; 4622 const size_t* _surviving_young_words; 4623 4624 size_t _rs_lengths; 4625 4626 volatile jint _serial_work_claim; 4627 4628 struct WorkItem { 4629 uint region_idx; 4630 bool is_young; 4631 bool evacuation_failed; 4632 4633 WorkItem(HeapRegion* r) { 4634 region_idx = r->hrm_index(); 4635 is_young = r->is_young(); 4636 evacuation_failed = r->evacuation_failed(); 4637 } 4638 }; 4639 4640 volatile size_t _parallel_work_claim; 4641 size_t _num_work_items; 4642 WorkItem* _work_items; 4643 4644 void do_serial_work() { 4645 // Need to grab the lock to be allowed to modify the old region list. 4646 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4647 _collection_set->iterate(&_cl); 4648 } 4649 4650 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4651 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4652 4653 HeapRegion* r = g1h->region_at(region_idx); 4654 assert(!g1h->is_on_master_free_list(r), "sanity"); 4655 4656 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4657 4658 if (!is_young) { 4659 g1h->_hot_card_cache->reset_card_counts(r); 4660 } 4661 4662 if (!evacuation_failed) { 4663 r->rem_set()->clear_locked(); 4664 } 4665 } 4666 4667 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4668 private: 4669 size_t _cur_idx; 4670 WorkItem* _work_items; 4671 public: 4672 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4673 4674 virtual bool doHeapRegion(HeapRegion* r) { 4675 _work_items[_cur_idx++] = WorkItem(r); 4676 return false; 4677 } 4678 }; 4679 4680 void prepare_work() { 4681 G1PrepareFreeCollectionSetClosure cl(_work_items); 4682 _collection_set->iterate(&cl); 4683 } 4684 4685 void complete_work() { 4686 _cl.complete_work(); 4687 4688 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4689 policy->record_max_rs_lengths(_rs_lengths); 4690 policy->cset_regions_freed(); 4691 } 4692 public: 4693 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4694 AbstractGangTask("G1 Free Collection Set"), 4695 _cl(evacuation_info, surviving_young_words), 4696 _collection_set(collection_set), 4697 _surviving_young_words(surviving_young_words), 4698 _serial_work_claim(0), 4699 _rs_lengths(0), 4700 _parallel_work_claim(0), 4701 _num_work_items(collection_set->region_length()), 4702 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4703 prepare_work(); 4704 } 4705 4706 ~G1FreeCollectionSetTask() { 4707 complete_work(); 4708 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4709 } 4710 4711 // Chunk size for work distribution. The chosen value has been determined experimentally 4712 // to be a good tradeoff between overhead and achievable parallelism. 4713 static uint chunk_size() { return 32; } 4714 4715 virtual void work(uint worker_id) { 4716 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4717 4718 // Claim serial work. 4719 if (_serial_work_claim == 0) { 4720 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4721 if (value == 0) { 4722 double serial_time = os::elapsedTime(); 4723 do_serial_work(); 4724 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4725 } 4726 } 4727 4728 // Start parallel work. 4729 double young_time = 0.0; 4730 bool has_young_time = false; 4731 double non_young_time = 0.0; 4732 bool has_non_young_time = false; 4733 4734 while (true) { 4735 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4736 size_t cur = end - chunk_size(); 4737 4738 if (cur >= _num_work_items) { 4739 break; 4740 } 4741 4742 double start_time = os::elapsedTime(); 4743 4744 end = MIN2(end, _num_work_items); 4745 4746 for (; cur < end; cur++) { 4747 bool is_young = _work_items[cur].is_young; 4748 4749 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4750 4751 double end_time = os::elapsedTime(); 4752 double time_taken = end_time - start_time; 4753 if (is_young) { 4754 young_time += time_taken; 4755 has_young_time = true; 4756 } else { 4757 non_young_time += time_taken; 4758 has_non_young_time = true; 4759 } 4760 start_time = end_time; 4761 } 4762 } 4763 4764 if (has_young_time) { 4765 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4766 } 4767 if (has_non_young_time) { 4768 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time); 4769 } 4770 } 4771 }; 4772 4773 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4774 _eden.clear(); 4775 4776 double free_cset_start_time = os::elapsedTime(); 4777 4778 { 4779 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4780 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4781 4782 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4783 4784 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4785 cl.name(), 4786 num_workers, 4787 _collection_set.region_length()); 4788 workers()->run_task(&cl, num_workers); 4789 } 4790 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4791 4792 collection_set->clear(); 4793 } 4794 4795 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4796 private: 4797 FreeRegionList* _free_region_list; 4798 HeapRegionSet* _proxy_set; 4799 uint _humongous_objects_reclaimed; 4800 uint _humongous_regions_reclaimed; 4801 size_t _freed_bytes; 4802 public: 4803 4804 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4805 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4806 } 4807 4808 virtual bool doHeapRegion(HeapRegion* r) { 4809 if (!r->is_starts_humongous()) { 4810 return false; 4811 } 4812 4813 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4814 4815 oop obj = (oop)r->bottom(); 4816 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap(); 4817 4818 // The following checks whether the humongous object is live are sufficient. 4819 // The main additional check (in addition to having a reference from the roots 4820 // or the young gen) is whether the humongous object has a remembered set entry. 4821 // 4822 // A humongous object cannot be live if there is no remembered set for it 4823 // because: 4824 // - there can be no references from within humongous starts regions referencing 4825 // the object because we never allocate other objects into them. 4826 // (I.e. there are no intra-region references that may be missed by the 4827 // remembered set) 4828 // - as soon there is a remembered set entry to the humongous starts region 4829 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4830 // until the end of a concurrent mark. 4831 // 4832 // It is not required to check whether the object has been found dead by marking 4833 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4834 // all objects allocated during that time are considered live. 4835 // SATB marking is even more conservative than the remembered set. 4836 // So if at this point in the collection there is no remembered set entry, 4837 // nobody has a reference to it. 4838 // At the start of collection we flush all refinement logs, and remembered sets 4839 // are completely up-to-date wrt to references to the humongous object. 4840 // 4841 // Other implementation considerations: 4842 // - never consider object arrays at this time because they would pose 4843 // considerable effort for cleaning up the the remembered sets. This is 4844 // required because stale remembered sets might reference locations that 4845 // are currently allocated into. 4846 uint region_idx = r->hrm_index(); 4847 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4848 !r->rem_set()->is_empty()) { 4849 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", 4850 region_idx, 4851 (size_t)obj->size() * HeapWordSize, 4852 p2i(r->bottom()), 4853 r->rem_set()->occupied(), 4854 r->rem_set()->strong_code_roots_list_length(), 4855 next_bitmap->is_marked(r->bottom()), 4856 g1h->is_humongous_reclaim_candidate(region_idx), 4857 obj->is_typeArray() 4858 ); 4859 return false; 4860 } 4861 4862 guarantee(obj->is_typeArray(), 4863 "Only eagerly reclaiming type arrays is supported, but the object " 4864 PTR_FORMAT " is not.", p2i(r->bottom())); 4865 4866 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", 4867 region_idx, 4868 (size_t)obj->size() * HeapWordSize, 4869 p2i(r->bottom()), 4870 r->rem_set()->occupied(), 4871 r->rem_set()->strong_code_roots_list_length(), 4872 next_bitmap->is_marked(r->bottom()), 4873 g1h->is_humongous_reclaim_candidate(region_idx), 4874 obj->is_typeArray() 4875 ); 4876 4877 // Need to clear mark bit of the humongous object if already set. 4878 if (next_bitmap->is_marked(r->bottom())) { 4879 next_bitmap->clear(r->bottom()); 4880 } 4881 _humongous_objects_reclaimed++; 4882 do { 4883 HeapRegion* next = g1h->next_region_in_humongous(r); 4884 _freed_bytes += r->used(); 4885 r->set_containing_set(NULL); 4886 _humongous_regions_reclaimed++; 4887 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ ); 4888 r = next; 4889 } while (r != NULL); 4890 4891 return false; 4892 } 4893 4894 uint humongous_objects_reclaimed() { 4895 return _humongous_objects_reclaimed; 4896 } 4897 4898 uint humongous_regions_reclaimed() { 4899 return _humongous_regions_reclaimed; 4900 } 4901 4902 size_t bytes_freed() const { 4903 return _freed_bytes; 4904 } 4905 }; 4906 4907 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4908 assert_at_safepoint(true); 4909 4910 if (!G1EagerReclaimHumongousObjects || 4911 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4912 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4913 return; 4914 } 4915 4916 double start_time = os::elapsedTime(); 4917 4918 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4919 4920 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4921 heap_region_iterate(&cl); 4922 4923 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4924 4925 G1HRPrinter* hrp = hr_printer(); 4926 if (hrp->is_active()) { 4927 FreeRegionListIterator iter(&local_cleanup_list); 4928 while (iter.more_available()) { 4929 HeapRegion* hr = iter.get_next(); 4930 hrp->cleanup(hr); 4931 } 4932 } 4933 4934 prepend_to_freelist(&local_cleanup_list); 4935 decrement_summary_bytes(cl.bytes_freed()); 4936 4937 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4938 cl.humongous_objects_reclaimed()); 4939 } 4940 4941 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4942 public: 4943 virtual bool doHeapRegion(HeapRegion* r) { 4944 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4945 G1CollectedHeap::heap()->clear_in_cset(r); 4946 r->set_young_index_in_cset(-1); 4947 return false; 4948 } 4949 }; 4950 4951 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4952 G1AbandonCollectionSetClosure cl; 4953 collection_set->iterate(&cl); 4954 4955 collection_set->clear(); 4956 collection_set->stop_incremental_building(); 4957 } 4958 4959 void G1CollectedHeap::set_free_regions_coming() { 4960 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 4961 4962 assert(!free_regions_coming(), "pre-condition"); 4963 _free_regions_coming = true; 4964 } 4965 4966 void G1CollectedHeap::reset_free_regions_coming() { 4967 assert(free_regions_coming(), "pre-condition"); 4968 4969 { 4970 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 4971 _free_regions_coming = false; 4972 SecondaryFreeList_lock->notify_all(); 4973 } 4974 4975 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 4976 } 4977 4978 void G1CollectedHeap::wait_while_free_regions_coming() { 4979 // Most of the time we won't have to wait, so let's do a quick test 4980 // first before we take the lock. 4981 if (!free_regions_coming()) { 4982 return; 4983 } 4984 4985 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 4986 4987 { 4988 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 4989 while (free_regions_coming()) { 4990 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 4991 } 4992 } 4993 4994 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 4995 } 4996 4997 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 4998 return _allocator->is_retained_old_region(hr); 4999 } 5000 5001 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5002 _eden.add(hr); 5003 _g1_policy->set_region_eden(hr); 5004 } 5005 5006 #ifdef ASSERT 5007 5008 class NoYoungRegionsClosure: public HeapRegionClosure { 5009 private: 5010 bool _success; 5011 public: 5012 NoYoungRegionsClosure() : _success(true) { } 5013 bool doHeapRegion(HeapRegion* r) { 5014 if (r->is_young()) { 5015 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5016 p2i(r->bottom()), p2i(r->end())); 5017 _success = false; 5018 } 5019 return false; 5020 } 5021 bool success() { return _success; } 5022 }; 5023 5024 bool G1CollectedHeap::check_young_list_empty() { 5025 bool ret = (young_regions_count() == 0); 5026 5027 NoYoungRegionsClosure closure; 5028 heap_region_iterate(&closure); 5029 ret = ret && closure.success(); 5030 5031 return ret; 5032 } 5033 5034 #endif // ASSERT 5035 5036 class TearDownRegionSetsClosure : public HeapRegionClosure { 5037 private: 5038 HeapRegionSet *_old_set; 5039 5040 public: 5041 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5042 5043 bool doHeapRegion(HeapRegion* r) { 5044 if (r->is_old()) { 5045 _old_set->remove(r); 5046 } else if(r->is_young()) { 5047 r->uninstall_surv_rate_group(); 5048 } else { 5049 // We ignore free regions, we'll empty the free list afterwards. 5050 // We ignore humongous regions, we're not tearing down the 5051 // humongous regions set. 5052 assert(r->is_free() || r->is_humongous(), 5053 "it cannot be another type"); 5054 } 5055 return false; 5056 } 5057 5058 ~TearDownRegionSetsClosure() { 5059 assert(_old_set->is_empty(), "post-condition"); 5060 } 5061 }; 5062 5063 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5064 assert_at_safepoint(true /* should_be_vm_thread */); 5065 5066 if (!free_list_only) { 5067 TearDownRegionSetsClosure cl(&_old_set); 5068 heap_region_iterate(&cl); 5069 5070 // Note that emptying the _young_list is postponed and instead done as 5071 // the first step when rebuilding the regions sets again. The reason for 5072 // this is that during a full GC string deduplication needs to know if 5073 // a collected region was young or old when the full GC was initiated. 5074 } 5075 _hrm.remove_all_free_regions(); 5076 } 5077 5078 void G1CollectedHeap::increase_used(size_t bytes) { 5079 _summary_bytes_used += bytes; 5080 } 5081 5082 void G1CollectedHeap::decrease_used(size_t bytes) { 5083 assert(_summary_bytes_used >= bytes, 5084 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5085 _summary_bytes_used, bytes); 5086 _summary_bytes_used -= bytes; 5087 } 5088 5089 void G1CollectedHeap::set_used(size_t bytes) { 5090 _summary_bytes_used = bytes; 5091 } 5092 5093 class RebuildRegionSetsClosure : public HeapRegionClosure { 5094 private: 5095 bool _free_list_only; 5096 HeapRegionSet* _old_set; 5097 HeapRegionManager* _hrm; 5098 size_t _total_used; 5099 5100 public: 5101 RebuildRegionSetsClosure(bool free_list_only, 5102 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5103 _free_list_only(free_list_only), 5104 _old_set(old_set), _hrm(hrm), _total_used(0) { 5105 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5106 if (!free_list_only) { 5107 assert(_old_set->is_empty(), "pre-condition"); 5108 } 5109 } 5110 5111 bool doHeapRegion(HeapRegion* r) { 5112 if (r->is_empty()) { 5113 // Add free regions to the free list 5114 r->set_free(); 5115 r->set_allocation_context(AllocationContext::system()); 5116 _hrm->insert_into_free_list(r); 5117 } else if (!_free_list_only) { 5118 5119 if (r->is_humongous()) { 5120 // We ignore humongous regions. We left the humongous set unchanged. 5121 } else { 5122 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 5123 // We now move all (non-humongous, non-old) regions to old gen, and register them as such. 5124 r->move_to_old(); 5125 _old_set->add(r); 5126 } 5127 _total_used += r->used(); 5128 } 5129 5130 return false; 5131 } 5132 5133 size_t total_used() { 5134 return _total_used; 5135 } 5136 }; 5137 5138 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5139 assert_at_safepoint(true /* should_be_vm_thread */); 5140 5141 if (!free_list_only) { 5142 _eden.clear(); 5143 _survivor.clear(); 5144 } 5145 5146 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5147 heap_region_iterate(&cl); 5148 5149 if (!free_list_only) { 5150 set_used(cl.total_used()); 5151 if (_archive_allocator != NULL) { 5152 _archive_allocator->clear_used(); 5153 } 5154 } 5155 assert(used_unlocked() == recalculate_used(), 5156 "inconsistent used_unlocked(), " 5157 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5158 used_unlocked(), recalculate_used()); 5159 } 5160 5161 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5162 HeapRegion* hr = heap_region_containing(p); 5163 return hr->is_in(p); 5164 } 5165 5166 // Methods for the mutator alloc region 5167 5168 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5169 bool force) { 5170 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5171 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 5172 if (force || should_allocate) { 5173 HeapRegion* new_alloc_region = new_region(word_size, 5174 false /* is_old */, 5175 false /* do_expand */); 5176 if (new_alloc_region != NULL) { 5177 set_region_short_lived_locked(new_alloc_region); 5178 _hr_printer.alloc(new_alloc_region, !should_allocate); 5179 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5180 return new_alloc_region; 5181 } 5182 } 5183 return NULL; 5184 } 5185 5186 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5187 size_t allocated_bytes) { 5188 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5189 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5190 5191 collection_set()->add_eden_region(alloc_region); 5192 increase_used(allocated_bytes); 5193 _hr_printer.retire(alloc_region); 5194 // We update the eden sizes here, when the region is retired, 5195 // instead of when it's allocated, since this is the point that its 5196 // used space has been recored in _summary_bytes_used. 5197 g1mm()->update_eden_size(); 5198 } 5199 5200 // Methods for the GC alloc regions 5201 5202 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 5203 if (dest.is_old()) { 5204 return true; 5205 } else { 5206 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 5207 } 5208 } 5209 5210 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 5211 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5212 5213 if (!has_more_regions(dest)) { 5214 return NULL; 5215 } 5216 5217 const bool is_survivor = dest.is_young(); 5218 5219 HeapRegion* new_alloc_region = new_region(word_size, 5220 !is_survivor, 5221 true /* do_expand */); 5222 if (new_alloc_region != NULL) { 5223 // We really only need to do this for old regions given that we 5224 // should never scan survivors. But it doesn't hurt to do it 5225 // for survivors too. 5226 new_alloc_region->record_timestamp(); 5227 if (is_survivor) { 5228 new_alloc_region->set_survivor(); 5229 _survivor.add(new_alloc_region); 5230 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5231 } else { 5232 new_alloc_region->set_old(); 5233 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5234 } 5235 _hr_printer.alloc(new_alloc_region); 5236 bool during_im = collector_state()->during_initial_mark_pause(); 5237 new_alloc_region->note_start_of_copying(during_im); 5238 return new_alloc_region; 5239 } 5240 return NULL; 5241 } 5242 5243 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5244 size_t allocated_bytes, 5245 InCSetState dest) { 5246 bool during_im = collector_state()->during_initial_mark_pause(); 5247 alloc_region->note_end_of_copying(during_im); 5248 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5249 if (dest.is_old()) { 5250 _old_set.add(alloc_region); 5251 } 5252 _hr_printer.retire(alloc_region); 5253 } 5254 5255 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5256 bool expanded = false; 5257 uint index = _hrm.find_highest_free(&expanded); 5258 5259 if (index != G1_NO_HRM_INDEX) { 5260 if (expanded) { 5261 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5262 HeapRegion::GrainWords * HeapWordSize); 5263 } 5264 _hrm.allocate_free_regions_starting_at(index, 1); 5265 return region_at(index); 5266 } 5267 return NULL; 5268 } 5269 5270 // Optimized nmethod scanning 5271 5272 class RegisterNMethodOopClosure: public OopClosure { 5273 G1CollectedHeap* _g1h; 5274 nmethod* _nm; 5275 5276 template <class T> void do_oop_work(T* p) { 5277 T heap_oop = oopDesc::load_heap_oop(p); 5278 if (!oopDesc::is_null(heap_oop)) { 5279 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5280 HeapRegion* hr = _g1h->heap_region_containing(obj); 5281 assert(!hr->is_continues_humongous(), 5282 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5283 " starting at " HR_FORMAT, 5284 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5285 5286 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5287 hr->add_strong_code_root_locked(_nm); 5288 } 5289 } 5290 5291 public: 5292 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5293 _g1h(g1h), _nm(nm) {} 5294 5295 void do_oop(oop* p) { do_oop_work(p); } 5296 void do_oop(narrowOop* p) { do_oop_work(p); } 5297 }; 5298 5299 class UnregisterNMethodOopClosure: public OopClosure { 5300 G1CollectedHeap* _g1h; 5301 nmethod* _nm; 5302 5303 template <class T> void do_oop_work(T* p) { 5304 T heap_oop = oopDesc::load_heap_oop(p); 5305 if (!oopDesc::is_null(heap_oop)) { 5306 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5307 HeapRegion* hr = _g1h->heap_region_containing(obj); 5308 assert(!hr->is_continues_humongous(), 5309 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5310 " starting at " HR_FORMAT, 5311 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5312 5313 hr->remove_strong_code_root(_nm); 5314 } 5315 } 5316 5317 public: 5318 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5319 _g1h(g1h), _nm(nm) {} 5320 5321 void do_oop(oop* p) { do_oop_work(p); } 5322 void do_oop(narrowOop* p) { do_oop_work(p); } 5323 }; 5324 5325 // Returns true if the reference points to an object that 5326 // can move in an incremental collection. 5327 bool G1CollectedHeap::is_scavengable(oop obj) { 5328 HeapRegion* hr = heap_region_containing(obj); 5329 return !hr->is_pinned(); 5330 } 5331 5332 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5333 guarantee(nm != NULL, "sanity"); 5334 RegisterNMethodOopClosure reg_cl(this, nm); 5335 nm->oops_do(®_cl); 5336 } 5337 5338 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5339 guarantee(nm != NULL, "sanity"); 5340 UnregisterNMethodOopClosure reg_cl(this, nm); 5341 nm->oops_do(®_cl, true); 5342 } 5343 5344 void G1CollectedHeap::purge_code_root_memory() { 5345 double purge_start = os::elapsedTime(); 5346 G1CodeRootSet::purge(); 5347 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5348 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5349 } 5350 5351 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5352 G1CollectedHeap* _g1h; 5353 5354 public: 5355 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5356 _g1h(g1h) {} 5357 5358 void do_code_blob(CodeBlob* cb) { 5359 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5360 if (nm == NULL) { 5361 return; 5362 } 5363 5364 if (ScavengeRootsInCode) { 5365 _g1h->register_nmethod(nm); 5366 } 5367 } 5368 }; 5369 5370 void G1CollectedHeap::rebuild_strong_code_roots() { 5371 RebuildStrongCodeRootClosure blob_cl(this); 5372 CodeCache::blobs_do(&blob_cl); 5373 }