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/g1FullGCScope.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.inline.hpp" 52 #include "gc/g1/g1RootClosures.hpp" 53 #include "gc/g1/g1RootProcessor.hpp" 54 #include "gc/g1/g1SerialFullCollector.hpp" 55 #include "gc/g1/g1StringDedup.hpp" 56 #include "gc/g1/g1YCTypes.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/vmThread.hpp" 84 #include "utilities/align.hpp" 85 #include "utilities/globalDefinitions.hpp" 86 #include "utilities/stack.inline.hpp" 87 88 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 89 90 // INVARIANTS/NOTES 91 // 92 // All allocation activity covered by the G1CollectedHeap interface is 93 // serialized by acquiring the HeapLock. This happens in mem_allocate 94 // and allocate_new_tlab, which are the "entry" points to the 95 // allocation code from the rest of the JVM. (Note that this does not 96 // apply to TLAB allocation, which is not part of this interface: it 97 // is done by clients of this interface.) 98 99 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 100 private: 101 size_t _num_dirtied; 102 G1CollectedHeap* _g1h; 103 G1SATBCardTableLoggingModRefBS* _g1_bs; 104 105 HeapRegion* region_for_card(jbyte* card_ptr) const { 106 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 107 } 108 109 bool will_become_free(HeapRegion* hr) const { 110 // A region will be freed by free_collection_set if the region is in the 111 // collection set and has not had an evacuation failure. 112 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 113 } 114 115 public: 116 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 117 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 118 119 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 120 HeapRegion* hr = region_for_card(card_ptr); 121 122 // Should only dirty cards in regions that won't be freed. 123 if (!will_become_free(hr)) { 124 *card_ptr = CardTableModRefBS::dirty_card_val(); 125 _num_dirtied++; 126 } 127 128 return true; 129 } 130 131 size_t num_dirtied() const { return _num_dirtied; } 132 }; 133 134 135 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 136 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 137 } 138 139 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 140 // The from card cache is not the memory that is actually committed. So we cannot 141 // take advantage of the zero_filled parameter. 142 reset_from_card_cache(start_idx, num_regions); 143 } 144 145 // Private methods. 146 147 HeapRegion* 148 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 149 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 150 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 151 if (!_secondary_free_list.is_empty()) { 152 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 153 "secondary_free_list has %u entries", 154 _secondary_free_list.length()); 155 // It looks as if there are free regions available on the 156 // secondary_free_list. Let's move them to the free_list and try 157 // again to allocate from it. 158 append_secondary_free_list(); 159 160 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 161 "empty we should have moved at least one entry to the free_list"); 162 HeapRegion* res = _hrm.allocate_free_region(is_old); 163 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 164 "allocated " HR_FORMAT " from secondary_free_list", 165 HR_FORMAT_PARAMS(res)); 166 return res; 167 } 168 169 // Wait here until we get notified either when (a) there are no 170 // more free regions coming or (b) some regions have been moved on 171 // the secondary_free_list. 172 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 173 } 174 175 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 176 "could not allocate from secondary_free_list"); 177 return NULL; 178 } 179 180 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 181 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 182 "the only time we use this to allocate a humongous region is " 183 "when we are allocating a single humongous region"); 184 185 HeapRegion* res; 186 if (G1StressConcRegionFreeing) { 187 if (!_secondary_free_list.is_empty()) { 188 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 189 "forced to look at the secondary_free_list"); 190 res = new_region_try_secondary_free_list(is_old); 191 if (res != NULL) { 192 return res; 193 } 194 } 195 } 196 197 res = _hrm.allocate_free_region(is_old); 198 199 if (res == NULL) { 200 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 201 "res == NULL, trying the secondary_free_list"); 202 res = new_region_try_secondary_free_list(is_old); 203 } 204 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 205 // Currently, only attempts to allocate GC alloc regions set 206 // do_expand to true. So, we should only reach here during a 207 // safepoint. If this assumption changes we might have to 208 // reconsider the use of _expand_heap_after_alloc_failure. 209 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 210 211 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 212 word_size * HeapWordSize); 213 214 if (expand(word_size * HeapWordSize)) { 215 // Given that expand() succeeded in expanding the heap, and we 216 // always expand the heap by an amount aligned to the heap 217 // region size, the free list should in theory not be empty. 218 // In either case allocate_free_region() will check for NULL. 219 res = _hrm.allocate_free_region(is_old); 220 } else { 221 _expand_heap_after_alloc_failure = false; 222 } 223 } 224 return res; 225 } 226 227 HeapWord* 228 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 229 uint num_regions, 230 size_t word_size, 231 AllocationContext_t context) { 232 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 233 assert(is_humongous(word_size), "word_size should be humongous"); 234 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 235 236 // Index of last region in the series. 237 uint last = first + num_regions - 1; 238 239 // We need to initialize the region(s) we just discovered. This is 240 // a bit tricky given that it can happen concurrently with 241 // refinement threads refining cards on these regions and 242 // potentially wanting to refine the BOT as they are scanning 243 // those cards (this can happen shortly after a cleanup; see CR 244 // 6991377). So we have to set up the region(s) carefully and in 245 // a specific order. 246 247 // The word size sum of all the regions we will allocate. 248 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 249 assert(word_size <= word_size_sum, "sanity"); 250 251 // This will be the "starts humongous" region. 252 HeapRegion* first_hr = region_at(first); 253 // The header of the new object will be placed at the bottom of 254 // the first region. 255 HeapWord* new_obj = first_hr->bottom(); 256 // This will be the new top of the new object. 257 HeapWord* obj_top = new_obj + word_size; 258 259 // First, we need to zero the header of the space that we will be 260 // allocating. When we update top further down, some refinement 261 // threads might try to scan the region. By zeroing the header we 262 // ensure that any thread that will try to scan the region will 263 // come across the zero klass word and bail out. 264 // 265 // NOTE: It would not have been correct to have used 266 // CollectedHeap::fill_with_object() and make the space look like 267 // an int array. The thread that is doing the allocation will 268 // later update the object header to a potentially different array 269 // type and, for a very short period of time, the klass and length 270 // fields will be inconsistent. This could cause a refinement 271 // thread to calculate the object size incorrectly. 272 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 273 274 // Next, pad out the unused tail of the last region with filler 275 // objects, for improved usage accounting. 276 // How many words we use for filler objects. 277 size_t word_fill_size = word_size_sum - word_size; 278 279 // How many words memory we "waste" which cannot hold a filler object. 280 size_t words_not_fillable = 0; 281 282 if (word_fill_size >= min_fill_size()) { 283 fill_with_objects(obj_top, word_fill_size); 284 } else if (word_fill_size > 0) { 285 // We have space to fill, but we cannot fit an object there. 286 words_not_fillable = word_fill_size; 287 word_fill_size = 0; 288 } 289 290 // We will set up the first region as "starts humongous". This 291 // will also update the BOT covering all the regions to reflect 292 // that there is a single object that starts at the bottom of the 293 // first region. 294 first_hr->set_starts_humongous(obj_top, word_fill_size); 295 first_hr->set_allocation_context(context); 296 // Then, if there are any, we will set up the "continues 297 // humongous" regions. 298 HeapRegion* hr = NULL; 299 for (uint i = first + 1; i <= last; ++i) { 300 hr = region_at(i); 301 hr->set_continues_humongous(first_hr); 302 hr->set_allocation_context(context); 303 } 304 305 // Up to this point no concurrent thread would have been able to 306 // do any scanning on any region in this series. All the top 307 // fields still point to bottom, so the intersection between 308 // [bottom,top] and [card_start,card_end] will be empty. Before we 309 // update the top fields, we'll do a storestore to make sure that 310 // no thread sees the update to top before the zeroing of the 311 // object header and the BOT initialization. 312 OrderAccess::storestore(); 313 314 // Now, we will update the top fields of the "continues humongous" 315 // regions except the last one. 316 for (uint i = first; i < last; ++i) { 317 hr = region_at(i); 318 hr->set_top(hr->end()); 319 } 320 321 hr = region_at(last); 322 // If we cannot fit a filler object, we must set top to the end 323 // of the humongous object, otherwise we cannot iterate the heap 324 // and the BOT will not be complete. 325 hr->set_top(hr->end() - words_not_fillable); 326 327 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 328 "obj_top should be in last region"); 329 330 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 331 332 assert(words_not_fillable == 0 || 333 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 334 "Miscalculation in humongous allocation"); 335 336 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 337 338 for (uint i = first; i <= last; ++i) { 339 hr = region_at(i); 340 _humongous_set.add(hr); 341 _hr_printer.alloc(hr); 342 } 343 344 return new_obj; 345 } 346 347 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 348 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 349 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 350 } 351 352 // If could fit into free regions w/o expansion, try. 353 // Otherwise, if can expand, do so. 354 // Otherwise, if using ex regions might help, try with ex given back. 355 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 356 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 357 358 _verifier->verify_region_sets_optional(); 359 360 uint first = G1_NO_HRM_INDEX; 361 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 362 363 if (obj_regions == 1) { 364 // Only one region to allocate, try to use a fast path by directly allocating 365 // from the free lists. Do not try to expand here, we will potentially do that 366 // later. 367 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 368 if (hr != NULL) { 369 first = hr->hrm_index(); 370 } 371 } else { 372 // We can't allocate humongous regions spanning more than one region while 373 // cleanupComplete() is running, since some of the regions we find to be 374 // empty might not yet be added to the free list. It is not straightforward 375 // to know in which list they are on so that we can remove them. We only 376 // need to do this if we need to allocate more than one region to satisfy the 377 // current humongous allocation request. If we are only allocating one region 378 // we use the one-region region allocation code (see above), that already 379 // potentially waits for regions from the secondary free list. 380 wait_while_free_regions_coming(); 381 append_secondary_free_list_if_not_empty_with_lock(); 382 383 // Policy: Try only empty regions (i.e. already committed first). Maybe we 384 // are lucky enough to find some. 385 first = _hrm.find_contiguous_only_empty(obj_regions); 386 if (first != G1_NO_HRM_INDEX) { 387 _hrm.allocate_free_regions_starting_at(first, obj_regions); 388 } 389 } 390 391 if (first == G1_NO_HRM_INDEX) { 392 // Policy: We could not find enough regions for the humongous object in the 393 // free list. Look through the heap to find a mix of free and uncommitted regions. 394 // If so, try expansion. 395 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 396 if (first != G1_NO_HRM_INDEX) { 397 // We found something. Make sure these regions are committed, i.e. expand 398 // the heap. Alternatively we could do a defragmentation GC. 399 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 400 word_size * HeapWordSize); 401 402 _hrm.expand_at(first, obj_regions, workers()); 403 g1_policy()->record_new_heap_size(num_regions()); 404 405 #ifdef ASSERT 406 for (uint i = first; i < first + obj_regions; ++i) { 407 HeapRegion* hr = region_at(i); 408 assert(hr->is_free(), "sanity"); 409 assert(hr->is_empty(), "sanity"); 410 assert(is_on_master_free_list(hr), "sanity"); 411 } 412 #endif 413 _hrm.allocate_free_regions_starting_at(first, obj_regions); 414 } else { 415 // Policy: Potentially trigger a defragmentation GC. 416 } 417 } 418 419 HeapWord* result = NULL; 420 if (first != G1_NO_HRM_INDEX) { 421 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 422 word_size, context); 423 assert(result != NULL, "it should always return a valid result"); 424 425 // A successful humongous object allocation changes the used space 426 // information of the old generation so we need to recalculate the 427 // sizes and update the jstat counters here. 428 g1mm()->update_sizes(); 429 } 430 431 _verifier->verify_region_sets_optional(); 432 433 return result; 434 } 435 436 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 437 assert_heap_not_locked_and_not_at_safepoint(); 438 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 439 440 uint dummy_gc_count_before; 441 uint dummy_gclocker_retry_count = 0; 442 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 443 } 444 445 HeapWord* 446 G1CollectedHeap::mem_allocate(size_t word_size, 447 bool* gc_overhead_limit_was_exceeded) { 448 assert_heap_not_locked_and_not_at_safepoint(); 449 450 // Loop until the allocation is satisfied, or unsatisfied after GC. 451 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 452 uint gc_count_before; 453 454 HeapWord* result = NULL; 455 if (!is_humongous(word_size)) { 456 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 457 } else { 458 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 459 } 460 if (result != NULL) { 461 return result; 462 } 463 464 // Create the garbage collection operation... 465 VM_G1CollectForAllocation op(gc_count_before, word_size); 466 op.set_allocation_context(AllocationContext::current()); 467 468 // ...and get the VM thread to execute it. 469 VMThread::execute(&op); 470 471 if (op.prologue_succeeded() && op.pause_succeeded()) { 472 // If the operation was successful we'll return the result even 473 // if it is NULL. If the allocation attempt failed immediately 474 // after a Full GC, it's unlikely we'll be able to allocate now. 475 HeapWord* result = op.result(); 476 if (result != NULL && !is_humongous(word_size)) { 477 // Allocations that take place on VM operations do not do any 478 // card dirtying and we have to do it here. We only have to do 479 // this for non-humongous allocations, though. 480 dirty_young_block(result, word_size); 481 } 482 return result; 483 } else { 484 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 485 return NULL; 486 } 487 assert(op.result() == NULL, 488 "the result should be NULL if the VM op did not succeed"); 489 } 490 491 // Give a warning if we seem to be looping forever. 492 if ((QueuedAllocationWarningCount > 0) && 493 (try_count % QueuedAllocationWarningCount == 0)) { 494 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count); 495 } 496 } 497 498 ShouldNotReachHere(); 499 return NULL; 500 } 501 502 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 503 AllocationContext_t context, 504 uint* gc_count_before_ret, 505 uint* gclocker_retry_count_ret) { 506 // Make sure you read the note in attempt_allocation_humongous(). 507 508 assert_heap_not_locked_and_not_at_safepoint(); 509 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 510 "be called for humongous allocation requests"); 511 512 // We should only get here after the first-level allocation attempt 513 // (attempt_allocation()) failed to allocate. 514 515 // We will loop until a) we manage to successfully perform the 516 // allocation or b) we successfully schedule a collection which 517 // fails to perform the allocation. b) is the only case when we'll 518 // return NULL. 519 HeapWord* result = NULL; 520 for (int try_count = 1; /* we'll return */; try_count += 1) { 521 bool should_try_gc; 522 uint gc_count_before; 523 524 { 525 MutexLockerEx x(Heap_lock); 526 result = _allocator->attempt_allocation_locked(word_size, context); 527 if (result != NULL) { 528 return result; 529 } 530 531 if (GCLocker::is_active_and_needs_gc()) { 532 if (g1_policy()->can_expand_young_list()) { 533 // No need for an ergo verbose message here, 534 // can_expand_young_list() does this when it returns true. 535 result = _allocator->attempt_allocation_force(word_size, context); 536 if (result != NULL) { 537 return result; 538 } 539 } 540 should_try_gc = false; 541 } else { 542 // The GCLocker may not be active but the GCLocker initiated 543 // GC may not yet have been performed (GCLocker::needs_gc() 544 // returns true). In this case we do not try this GC and 545 // wait until the GCLocker initiated GC is performed, and 546 // then retry the allocation. 547 if (GCLocker::needs_gc()) { 548 should_try_gc = false; 549 } else { 550 // Read the GC count while still holding the Heap_lock. 551 gc_count_before = total_collections(); 552 should_try_gc = true; 553 } 554 } 555 } 556 557 if (should_try_gc) { 558 bool succeeded; 559 result = do_collection_pause(word_size, gc_count_before, &succeeded, 560 GCCause::_g1_inc_collection_pause); 561 if (result != NULL) { 562 assert(succeeded, "only way to get back a non-NULL result"); 563 return result; 564 } 565 566 if (succeeded) { 567 // If we get here we successfully scheduled a collection which 568 // failed to allocate. No point in trying to allocate 569 // further. We'll just return NULL. 570 MutexLockerEx x(Heap_lock); 571 *gc_count_before_ret = total_collections(); 572 return NULL; 573 } 574 } else { 575 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 576 MutexLockerEx x(Heap_lock); 577 *gc_count_before_ret = total_collections(); 578 return NULL; 579 } 580 // The GCLocker is either active or the GCLocker initiated 581 // GC has not yet been performed. Stall until it is and 582 // then retry the allocation. 583 GCLocker::stall_until_clear(); 584 (*gclocker_retry_count_ret) += 1; 585 } 586 587 // We can reach here if we were unsuccessful in scheduling a 588 // collection (because another thread beat us to it) or if we were 589 // stalled due to the GC locker. In either can we should retry the 590 // allocation attempt in case another thread successfully 591 // performed a collection and reclaimed enough space. We do the 592 // first attempt (without holding the Heap_lock) here and the 593 // follow-on attempt will be at the start of the next loop 594 // iteration (after taking the Heap_lock). 595 result = _allocator->attempt_allocation(word_size, context); 596 if (result != NULL) { 597 return result; 598 } 599 600 // Give a warning if we seem to be looping forever. 601 if ((QueuedAllocationWarningCount > 0) && 602 (try_count % QueuedAllocationWarningCount == 0)) { 603 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() " 604 "retries %d times", try_count); 605 } 606 } 607 608 ShouldNotReachHere(); 609 return NULL; 610 } 611 612 void G1CollectedHeap::begin_archive_alloc_range(bool open) { 613 assert_at_safepoint(true /* should_be_vm_thread */); 614 if (_archive_allocator == NULL) { 615 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open); 616 } 617 } 618 619 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 620 // Allocations in archive regions cannot be of a size that would be considered 621 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 622 // may be different at archive-restore time. 623 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 624 } 625 626 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 627 assert_at_safepoint(true /* should_be_vm_thread */); 628 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 629 if (is_archive_alloc_too_large(word_size)) { 630 return NULL; 631 } 632 return _archive_allocator->archive_mem_allocate(word_size); 633 } 634 635 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 636 size_t end_alignment_in_bytes) { 637 assert_at_safepoint(true /* should_be_vm_thread */); 638 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 639 640 // Call complete_archive to do the real work, filling in the MemRegion 641 // array with the archive regions. 642 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 643 delete _archive_allocator; 644 _archive_allocator = NULL; 645 } 646 647 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 648 assert(ranges != NULL, "MemRegion array NULL"); 649 assert(count != 0, "No MemRegions provided"); 650 MemRegion reserved = _hrm.reserved(); 651 for (size_t i = 0; i < count; i++) { 652 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 653 return false; 654 } 655 } 656 return true; 657 } 658 659 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, 660 size_t count, 661 bool open) { 662 assert(!is_init_completed(), "Expect to be called at JVM init time"); 663 assert(ranges != NULL, "MemRegion array NULL"); 664 assert(count != 0, "No MemRegions provided"); 665 MutexLockerEx x(Heap_lock); 666 667 MemRegion reserved = _hrm.reserved(); 668 HeapWord* prev_last_addr = NULL; 669 HeapRegion* prev_last_region = NULL; 670 671 // Temporarily disable pretouching of heap pages. This interface is used 672 // when mmap'ing archived heap data in, so pre-touching is wasted. 673 FlagSetting fs(AlwaysPreTouch, false); 674 675 // Enable archive object checking used by G1MarkSweep. We have to let it know 676 // about each archive range, so that objects in those ranges aren't marked. 677 G1ArchiveAllocator::enable_archive_object_check(); 678 679 // For each specified MemRegion range, allocate the corresponding G1 680 // regions and mark them as archive regions. We expect the ranges 681 // in ascending starting address order, without overlap. 682 for (size_t i = 0; i < count; i++) { 683 MemRegion curr_range = ranges[i]; 684 HeapWord* start_address = curr_range.start(); 685 size_t word_size = curr_range.word_size(); 686 HeapWord* last_address = curr_range.last(); 687 size_t commits = 0; 688 689 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 690 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 691 p2i(start_address), p2i(last_address)); 692 guarantee(start_address > prev_last_addr, 693 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 694 p2i(start_address), p2i(prev_last_addr)); 695 prev_last_addr = last_address; 696 697 // Check for ranges that start in the same G1 region in which the previous 698 // range ended, and adjust the start address so we don't try to allocate 699 // the same region again. If the current range is entirely within that 700 // region, skip it, just adjusting the recorded top. 701 HeapRegion* start_region = _hrm.addr_to_region(start_address); 702 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 703 start_address = start_region->end(); 704 if (start_address > last_address) { 705 increase_used(word_size * HeapWordSize); 706 start_region->set_top(last_address + 1); 707 continue; 708 } 709 start_region->set_top(start_address); 710 curr_range = MemRegion(start_address, last_address + 1); 711 start_region = _hrm.addr_to_region(start_address); 712 } 713 714 // Perform the actual region allocation, exiting if it fails. 715 // Then note how much new space we have allocated. 716 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 717 return false; 718 } 719 increase_used(word_size * HeapWordSize); 720 if (commits != 0) { 721 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 722 HeapRegion::GrainWords * HeapWordSize * commits); 723 724 } 725 726 // Mark each G1 region touched by the range as archive, add it to 727 // the old set, and set the allocation context and top. 728 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 729 HeapRegion* last_region = _hrm.addr_to_region(last_address); 730 prev_last_region = last_region; 731 732 while (curr_region != NULL) { 733 assert(curr_region->is_empty() && !curr_region->is_pinned(), 734 "Region already in use (index %u)", curr_region->hrm_index()); 735 curr_region->set_allocation_context(AllocationContext::system()); 736 if (open) { 737 curr_region->set_open_archive(); 738 } else { 739 curr_region->set_closed_archive(); 740 } 741 _hr_printer.alloc(curr_region); 742 _old_set.add(curr_region); 743 HeapWord* top; 744 HeapRegion* next_region; 745 if (curr_region != last_region) { 746 top = curr_region->end(); 747 next_region = _hrm.next_region_in_heap(curr_region); 748 } else { 749 top = last_address + 1; 750 next_region = NULL; 751 } 752 curr_region->set_top(top); 753 curr_region->set_first_dead(top); 754 curr_region->set_end_of_live(top); 755 curr_region = next_region; 756 } 757 758 // Notify mark-sweep of the archive 759 G1ArchiveAllocator::set_range_archive(curr_range, open); 760 } 761 return true; 762 } 763 764 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 765 assert(!is_init_completed(), "Expect to be called at JVM init time"); 766 assert(ranges != NULL, "MemRegion array NULL"); 767 assert(count != 0, "No MemRegions provided"); 768 MemRegion reserved = _hrm.reserved(); 769 HeapWord *prev_last_addr = NULL; 770 HeapRegion* prev_last_region = NULL; 771 772 // For each MemRegion, create filler objects, if needed, in the G1 regions 773 // that contain the address range. The address range actually within the 774 // MemRegion will not be modified. That is assumed to have been initialized 775 // elsewhere, probably via an mmap of archived heap data. 776 MutexLockerEx x(Heap_lock); 777 for (size_t i = 0; i < count; i++) { 778 HeapWord* start_address = ranges[i].start(); 779 HeapWord* last_address = ranges[i].last(); 780 781 assert(reserved.contains(start_address) && reserved.contains(last_address), 782 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 783 p2i(start_address), p2i(last_address)); 784 assert(start_address > prev_last_addr, 785 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 786 p2i(start_address), p2i(prev_last_addr)); 787 788 HeapRegion* start_region = _hrm.addr_to_region(start_address); 789 HeapRegion* last_region = _hrm.addr_to_region(last_address); 790 HeapWord* bottom_address = start_region->bottom(); 791 792 // Check for a range beginning in the same region in which the 793 // previous one ended. 794 if (start_region == prev_last_region) { 795 bottom_address = prev_last_addr + 1; 796 } 797 798 // Verify that the regions were all marked as archive regions by 799 // alloc_archive_regions. 800 HeapRegion* curr_region = start_region; 801 while (curr_region != NULL) { 802 guarantee(curr_region->is_archive(), 803 "Expected archive region at index %u", curr_region->hrm_index()); 804 if (curr_region != last_region) { 805 curr_region = _hrm.next_region_in_heap(curr_region); 806 } else { 807 curr_region = NULL; 808 } 809 } 810 811 prev_last_addr = last_address; 812 prev_last_region = last_region; 813 814 // Fill the memory below the allocated range with dummy object(s), 815 // if the region bottom does not match the range start, or if the previous 816 // range ended within the same G1 region, and there is a gap. 817 if (start_address != bottom_address) { 818 size_t fill_size = pointer_delta(start_address, bottom_address); 819 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 820 increase_used(fill_size * HeapWordSize); 821 } 822 } 823 } 824 825 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 826 uint* gc_count_before_ret, 827 uint* gclocker_retry_count_ret) { 828 assert_heap_not_locked_and_not_at_safepoint(); 829 assert(!is_humongous(word_size), "attempt_allocation() should not " 830 "be called for humongous allocation requests"); 831 832 AllocationContext_t context = AllocationContext::current(); 833 HeapWord* result = _allocator->attempt_allocation(word_size, context); 834 835 if (result == NULL) { 836 result = attempt_allocation_slow(word_size, 837 context, 838 gc_count_before_ret, 839 gclocker_retry_count_ret); 840 } 841 assert_heap_not_locked(); 842 if (result != NULL) { 843 dirty_young_block(result, word_size); 844 } 845 return result; 846 } 847 848 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 849 assert(!is_init_completed(), "Expect to be called at JVM init time"); 850 assert(ranges != NULL, "MemRegion array NULL"); 851 assert(count != 0, "No MemRegions provided"); 852 MemRegion reserved = _hrm.reserved(); 853 HeapWord* prev_last_addr = NULL; 854 HeapRegion* prev_last_region = NULL; 855 size_t size_used = 0; 856 size_t uncommitted_regions = 0; 857 858 // For each Memregion, free the G1 regions that constitute it, and 859 // notify mark-sweep that the range is no longer to be considered 'archive.' 860 MutexLockerEx x(Heap_lock); 861 for (size_t i = 0; i < count; i++) { 862 HeapWord* start_address = ranges[i].start(); 863 HeapWord* last_address = ranges[i].last(); 864 865 assert(reserved.contains(start_address) && reserved.contains(last_address), 866 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 867 p2i(start_address), p2i(last_address)); 868 assert(start_address > prev_last_addr, 869 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 870 p2i(start_address), p2i(prev_last_addr)); 871 size_used += ranges[i].byte_size(); 872 prev_last_addr = last_address; 873 874 HeapRegion* start_region = _hrm.addr_to_region(start_address); 875 HeapRegion* last_region = _hrm.addr_to_region(last_address); 876 877 // Check for ranges that start in the same G1 region in which the previous 878 // range ended, and adjust the start address so we don't try to free 879 // the same region again. If the current range is entirely within that 880 // region, skip it. 881 if (start_region == prev_last_region) { 882 start_address = start_region->end(); 883 if (start_address > last_address) { 884 continue; 885 } 886 start_region = _hrm.addr_to_region(start_address); 887 } 888 prev_last_region = last_region; 889 890 // After verifying that each region was marked as an archive region by 891 // alloc_archive_regions, set it free and empty and uncommit it. 892 HeapRegion* curr_region = start_region; 893 while (curr_region != NULL) { 894 guarantee(curr_region->is_archive(), 895 "Expected archive region at index %u", curr_region->hrm_index()); 896 uint curr_index = curr_region->hrm_index(); 897 _old_set.remove(curr_region); 898 curr_region->set_free(); 899 curr_region->set_top(curr_region->bottom()); 900 if (curr_region != last_region) { 901 curr_region = _hrm.next_region_in_heap(curr_region); 902 } else { 903 curr_region = NULL; 904 } 905 _hrm.shrink_at(curr_index, 1); 906 uncommitted_regions++; 907 } 908 909 // Notify mark-sweep that this is no longer an archive range. 910 G1ArchiveAllocator::set_range_archive(ranges[i], false); 911 } 912 913 if (uncommitted_regions != 0) { 914 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 915 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 916 } 917 decrease_used(size_used); 918 } 919 920 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 921 uint* gc_count_before_ret, 922 uint* gclocker_retry_count_ret) { 923 // The structure of this method has a lot of similarities to 924 // attempt_allocation_slow(). The reason these two were not merged 925 // into a single one is that such a method would require several "if 926 // allocation is not humongous do this, otherwise do that" 927 // conditional paths which would obscure its flow. In fact, an early 928 // version of this code did use a unified method which was harder to 929 // follow and, as a result, it had subtle bugs that were hard to 930 // track down. So keeping these two methods separate allows each to 931 // be more readable. It will be good to keep these two in sync as 932 // much as possible. 933 934 assert_heap_not_locked_and_not_at_safepoint(); 935 assert(is_humongous(word_size), "attempt_allocation_humongous() " 936 "should only be called for humongous allocations"); 937 938 // Humongous objects can exhaust the heap quickly, so we should check if we 939 // need to start a marking cycle at each humongous object allocation. We do 940 // the check before we do the actual allocation. The reason for doing it 941 // before the allocation is that we avoid having to keep track of the newly 942 // allocated memory while we do a GC. 943 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 944 word_size)) { 945 collect(GCCause::_g1_humongous_allocation); 946 } 947 948 // We will loop until a) we manage to successfully perform the 949 // allocation or b) we successfully schedule a collection which 950 // fails to perform the allocation. b) is the only case when we'll 951 // return NULL. 952 HeapWord* result = NULL; 953 for (int try_count = 1; /* we'll return */; try_count += 1) { 954 bool should_try_gc; 955 uint gc_count_before; 956 957 { 958 MutexLockerEx x(Heap_lock); 959 960 // Given that humongous objects are not allocated in young 961 // regions, we'll first try to do the allocation without doing a 962 // collection hoping that there's enough space in the heap. 963 result = humongous_obj_allocate(word_size, AllocationContext::current()); 964 if (result != NULL) { 965 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 966 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 967 return result; 968 } 969 970 if (GCLocker::is_active_and_needs_gc()) { 971 should_try_gc = false; 972 } else { 973 // The GCLocker may not be active but the GCLocker initiated 974 // GC may not yet have been performed (GCLocker::needs_gc() 975 // returns true). In this case we do not try this GC and 976 // wait until the GCLocker initiated GC is performed, and 977 // then retry the allocation. 978 if (GCLocker::needs_gc()) { 979 should_try_gc = false; 980 } else { 981 // Read the GC count while still holding the Heap_lock. 982 gc_count_before = total_collections(); 983 should_try_gc = true; 984 } 985 } 986 } 987 988 if (should_try_gc) { 989 // If we failed to allocate the humongous object, we should try to 990 // do a collection pause (if we're allowed) in case it reclaims 991 // enough space for the allocation to succeed after the pause. 992 993 bool succeeded; 994 result = do_collection_pause(word_size, gc_count_before, &succeeded, 995 GCCause::_g1_humongous_allocation); 996 if (result != NULL) { 997 assert(succeeded, "only way to get back a non-NULL result"); 998 return result; 999 } 1000 1001 if (succeeded) { 1002 // If we get here we successfully scheduled a collection which 1003 // failed to allocate. No point in trying to allocate 1004 // further. We'll just return NULL. 1005 MutexLockerEx x(Heap_lock); 1006 *gc_count_before_ret = total_collections(); 1007 return NULL; 1008 } 1009 } else { 1010 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1011 MutexLockerEx x(Heap_lock); 1012 *gc_count_before_ret = total_collections(); 1013 return NULL; 1014 } 1015 // The GCLocker is either active or the GCLocker initiated 1016 // GC has not yet been performed. Stall until it is and 1017 // then retry the allocation. 1018 GCLocker::stall_until_clear(); 1019 (*gclocker_retry_count_ret) += 1; 1020 } 1021 1022 // We can reach here if we were unsuccessful in scheduling a 1023 // collection (because another thread beat us to it) or if we were 1024 // stalled due to the GC locker. In either can we should retry the 1025 // allocation attempt in case another thread successfully 1026 // performed a collection and reclaimed enough space. Give a 1027 // warning if we seem to be looping forever. 1028 1029 if ((QueuedAllocationWarningCount > 0) && 1030 (try_count % QueuedAllocationWarningCount == 0)) { 1031 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() " 1032 "retries %d times", try_count); 1033 } 1034 } 1035 1036 ShouldNotReachHere(); 1037 return NULL; 1038 } 1039 1040 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1041 AllocationContext_t context, 1042 bool expect_null_mutator_alloc_region) { 1043 assert_at_safepoint(true /* should_be_vm_thread */); 1044 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1045 "the current alloc region was unexpectedly found to be non-NULL"); 1046 1047 if (!is_humongous(word_size)) { 1048 return _allocator->attempt_allocation_locked(word_size, context); 1049 } else { 1050 HeapWord* result = humongous_obj_allocate(word_size, context); 1051 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1052 collector_state()->set_initiate_conc_mark_if_possible(true); 1053 } 1054 return result; 1055 } 1056 1057 ShouldNotReachHere(); 1058 } 1059 1060 class PostCompactionPrinterClosure: public HeapRegionClosure { 1061 private: 1062 G1HRPrinter* _hr_printer; 1063 public: 1064 bool doHeapRegion(HeapRegion* hr) { 1065 assert(!hr->is_young(), "not expecting to find young regions"); 1066 _hr_printer->post_compaction(hr); 1067 return false; 1068 } 1069 1070 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1071 : _hr_printer(hr_printer) { } 1072 }; 1073 1074 void G1CollectedHeap::print_hrm_post_compaction() { 1075 if (_hr_printer.is_active()) { 1076 PostCompactionPrinterClosure cl(hr_printer()); 1077 heap_region_iterate(&cl); 1078 } 1079 1080 } 1081 1082 void G1CollectedHeap::abort_concurrent_cycle() { 1083 // Note: When we have a more flexible GC logging framework that 1084 // allows us to add optional attributes to a GC log record we 1085 // could consider timing and reporting how long we wait in the 1086 // following two methods. 1087 wait_while_free_regions_coming(); 1088 // If we start the compaction before the CM threads finish 1089 // scanning the root regions we might trip them over as we'll 1090 // be moving objects / updating references. So let's wait until 1091 // they are done. By telling them to abort, they should complete 1092 // early. 1093 _cm->root_regions()->abort(); 1094 _cm->root_regions()->wait_until_scan_finished(); 1095 append_secondary_free_list_if_not_empty_with_lock(); 1096 1097 // Disable discovery and empty the discovered lists 1098 // for the CM ref processor. 1099 ref_processor_cm()->disable_discovery(); 1100 ref_processor_cm()->abandon_partial_discovery(); 1101 ref_processor_cm()->verify_no_references_recorded(); 1102 1103 // Abandon current iterations of concurrent marking and concurrent 1104 // refinement, if any are in progress. 1105 concurrent_mark()->abort(); 1106 } 1107 1108 void G1CollectedHeap::prepare_heap_for_full_collection() { 1109 // Make sure we'll choose a new allocation region afterwards. 1110 _allocator->release_mutator_alloc_region(); 1111 _allocator->abandon_gc_alloc_regions(); 1112 g1_rem_set()->cleanupHRRS(); 1113 1114 // We may have added regions to the current incremental collection 1115 // set between the last GC or pause and now. We need to clear the 1116 // incremental collection set and then start rebuilding it afresh 1117 // after this full GC. 1118 abandon_collection_set(collection_set()); 1119 1120 tear_down_region_sets(false /* free_list_only */); 1121 collector_state()->set_gcs_are_young(true); 1122 } 1123 1124 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1125 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1126 assert(used() == recalculate_used(), "Should be equal"); 1127 _verifier->verify_region_sets_optional(); 1128 _verifier->verify_before_gc(); 1129 _verifier->check_bitmaps("Full GC Start"); 1130 } 1131 1132 void G1CollectedHeap::prepare_heap_for_mutators() { 1133 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1134 ClassLoaderDataGraph::purge(); 1135 MetaspaceAux::verify_metrics(); 1136 1137 // Prepare heap for normal collections. 1138 assert(num_free_regions() == 0, "we should not have added any free regions"); 1139 rebuild_region_sets(false /* free_list_only */); 1140 abort_refinement(); 1141 resize_if_necessary_after_full_collection(); 1142 1143 // Rebuild the strong code root lists for each region 1144 rebuild_strong_code_roots(); 1145 1146 // Start a new incremental collection set for the next pause 1147 start_new_collection_set(); 1148 1149 _allocator->init_mutator_alloc_region(); 1150 1151 // Post collection state updates. 1152 MetaspaceGC::compute_new_size(); 1153 } 1154 1155 void G1CollectedHeap::abort_refinement() { 1156 if (_hot_card_cache->use_cache()) { 1157 _hot_card_cache->reset_card_counts(); 1158 _hot_card_cache->reset_hot_cache(); 1159 } 1160 1161 // Discard all remembered set updates. 1162 JavaThread::dirty_card_queue_set().abandon_logs(); 1163 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1164 } 1165 1166 void G1CollectedHeap::verify_after_full_collection() { 1167 check_gc_time_stamps(); 1168 _hrm.verify_optional(); 1169 _verifier->verify_region_sets_optional(); 1170 _verifier->verify_after_gc(); 1171 // Clear the previous marking bitmap, if needed for bitmap verification. 1172 // Note we cannot do this when we clear the next marking bitmap in 1173 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1174 // objects marked during a full GC against the previous bitmap. 1175 // But we need to clear it before calling check_bitmaps below since 1176 // the full GC has compacted objects and updated TAMS but not updated 1177 // the prev bitmap. 1178 if (G1VerifyBitmaps) { 1179 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1180 _cm->clear_prev_bitmap(workers()); 1181 } 1182 _verifier->check_bitmaps("Full GC End"); 1183 1184 // At this point there should be no regions in the 1185 // entire heap tagged as young. 1186 assert(check_young_list_empty(), "young list should be empty at this point"); 1187 1188 // Note: since we've just done a full GC, concurrent 1189 // marking is no longer active. Therefore we need not 1190 // re-enable reference discovery for the CM ref processor. 1191 // That will be done at the start of the next marking cycle. 1192 // We also know that the STW processor should no longer 1193 // discover any new references. 1194 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1195 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1196 ref_processor_stw()->verify_no_references_recorded(); 1197 ref_processor_cm()->verify_no_references_recorded(); 1198 } 1199 1200 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1201 print_hrm_post_compaction(); 1202 heap_transition->print(); 1203 print_heap_after_gc(); 1204 print_heap_regions(); 1205 #ifdef TRACESPINNING 1206 ParallelTaskTerminator::print_termination_counts(); 1207 #endif 1208 } 1209 1210 void G1CollectedHeap::do_full_collection_inner(G1FullGCScope* scope) { 1211 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1212 g1_policy()->record_full_collection_start(); 1213 1214 print_heap_before_gc(); 1215 print_heap_regions(); 1216 1217 abort_concurrent_cycle(); 1218 verify_before_full_collection(scope->is_explicit_gc()); 1219 1220 gc_prologue(true); 1221 prepare_heap_for_full_collection(); 1222 1223 G1SerialFullCollector serial(scope, ref_processor_stw()); 1224 serial.prepare_collection(); 1225 serial.collect(); 1226 serial.complete_collection(); 1227 1228 prepare_heap_for_mutators(); 1229 1230 g1_policy()->record_full_collection_end(); 1231 gc_epilogue(true); 1232 1233 // Post collection verification. 1234 verify_after_full_collection(); 1235 1236 // Post collection logging. 1237 // We should do this after we potentially resize the heap so 1238 // that all the COMMIT / UNCOMMIT events are generated before 1239 // the compaction events. 1240 print_heap_after_full_collection(scope->heap_transition()); 1241 } 1242 1243 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1244 bool clear_all_soft_refs) { 1245 assert_at_safepoint(true /* should_be_vm_thread */); 1246 1247 if (GCLocker::check_active_before_gc()) { 1248 // Full GC was not completed. 1249 return false; 1250 } 1251 1252 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1253 collector_policy()->should_clear_all_soft_refs(); 1254 1255 G1FullGCScope scope(explicit_gc, do_clear_all_soft_refs); 1256 do_full_collection_inner(&scope); 1257 1258 // Full collection was successfully completed. 1259 return true; 1260 } 1261 1262 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1263 // Currently, there is no facility in the do_full_collection(bool) API to notify 1264 // the caller that the collection did not succeed (e.g., because it was locked 1265 // out by the GC locker). So, right now, we'll ignore the return value. 1266 bool dummy = do_full_collection(true, /* explicit_gc */ 1267 clear_all_soft_refs); 1268 } 1269 1270 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1271 // Include bytes that will be pre-allocated to support collections, as "used". 1272 const size_t used_after_gc = used(); 1273 const size_t capacity_after_gc = capacity(); 1274 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1275 1276 // This is enforced in arguments.cpp. 1277 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1278 "otherwise the code below doesn't make sense"); 1279 1280 // We don't have floating point command-line arguments 1281 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1282 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1283 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1284 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1285 1286 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1287 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1288 1289 // We have to be careful here as these two calculations can overflow 1290 // 32-bit size_t's. 1291 double used_after_gc_d = (double) used_after_gc; 1292 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1293 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1294 1295 // Let's make sure that they are both under the max heap size, which 1296 // by default will make them fit into a size_t. 1297 double desired_capacity_upper_bound = (double) max_heap_size; 1298 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1299 desired_capacity_upper_bound); 1300 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1301 desired_capacity_upper_bound); 1302 1303 // We can now safely turn them into size_t's. 1304 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1305 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1306 1307 // This assert only makes sense here, before we adjust them 1308 // with respect to the min and max heap size. 1309 assert(minimum_desired_capacity <= maximum_desired_capacity, 1310 "minimum_desired_capacity = " SIZE_FORMAT ", " 1311 "maximum_desired_capacity = " SIZE_FORMAT, 1312 minimum_desired_capacity, maximum_desired_capacity); 1313 1314 // Should not be greater than the heap max size. No need to adjust 1315 // it with respect to the heap min size as it's a lower bound (i.e., 1316 // we'll try to make the capacity larger than it, not smaller). 1317 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1318 // Should not be less than the heap min size. No need to adjust it 1319 // with respect to the heap max size as it's an upper bound (i.e., 1320 // we'll try to make the capacity smaller than it, not greater). 1321 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1322 1323 if (capacity_after_gc < minimum_desired_capacity) { 1324 // Don't expand unless it's significant 1325 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1326 1327 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1328 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1329 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1330 1331 expand(expand_bytes, _workers); 1332 1333 // No expansion, now see if we want to shrink 1334 } else if (capacity_after_gc > maximum_desired_capacity) { 1335 // Capacity too large, compute shrinking size 1336 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1337 1338 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1339 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1340 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1341 1342 shrink(shrink_bytes); 1343 } 1344 } 1345 1346 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1347 AllocationContext_t context, 1348 bool do_gc, 1349 bool clear_all_soft_refs, 1350 bool expect_null_mutator_alloc_region, 1351 bool* gc_succeeded) { 1352 *gc_succeeded = true; 1353 // Let's attempt the allocation first. 1354 HeapWord* result = 1355 attempt_allocation_at_safepoint(word_size, 1356 context, 1357 expect_null_mutator_alloc_region); 1358 if (result != NULL) { 1359 assert(*gc_succeeded, "sanity"); 1360 return result; 1361 } 1362 1363 // In a G1 heap, we're supposed to keep allocation from failing by 1364 // incremental pauses. Therefore, at least for now, we'll favor 1365 // expansion over collection. (This might change in the future if we can 1366 // do something smarter than full collection to satisfy a failed alloc.) 1367 result = expand_and_allocate(word_size, context); 1368 if (result != NULL) { 1369 assert(*gc_succeeded, "sanity"); 1370 return result; 1371 } 1372 1373 if (do_gc) { 1374 // Expansion didn't work, we'll try to do a Full GC. 1375 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1376 clear_all_soft_refs); 1377 } 1378 1379 return NULL; 1380 } 1381 1382 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1383 AllocationContext_t context, 1384 bool* succeeded) { 1385 assert_at_safepoint(true /* should_be_vm_thread */); 1386 1387 // Attempts to allocate followed by Full GC. 1388 HeapWord* result = 1389 satisfy_failed_allocation_helper(word_size, 1390 context, 1391 true, /* do_gc */ 1392 false, /* clear_all_soft_refs */ 1393 false, /* expect_null_mutator_alloc_region */ 1394 succeeded); 1395 1396 if (result != NULL || !*succeeded) { 1397 return result; 1398 } 1399 1400 // Attempts to allocate followed by Full GC that will collect all soft references. 1401 result = satisfy_failed_allocation_helper(word_size, 1402 context, 1403 true, /* do_gc */ 1404 true, /* clear_all_soft_refs */ 1405 true, /* expect_null_mutator_alloc_region */ 1406 succeeded); 1407 1408 if (result != NULL || !*succeeded) { 1409 return result; 1410 } 1411 1412 // Attempts to allocate, no GC 1413 result = satisfy_failed_allocation_helper(word_size, 1414 context, 1415 false, /* do_gc */ 1416 false, /* clear_all_soft_refs */ 1417 true, /* expect_null_mutator_alloc_region */ 1418 succeeded); 1419 1420 if (result != NULL) { 1421 assert(*succeeded, "sanity"); 1422 return result; 1423 } 1424 1425 assert(!collector_policy()->should_clear_all_soft_refs(), 1426 "Flag should have been handled and cleared prior to this point"); 1427 1428 // What else? We might try synchronous finalization later. If the total 1429 // space available is large enough for the allocation, then a more 1430 // complete compaction phase than we've tried so far might be 1431 // appropriate. 1432 assert(*succeeded, "sanity"); 1433 return NULL; 1434 } 1435 1436 // Attempting to expand the heap sufficiently 1437 // to support an allocation of the given "word_size". If 1438 // successful, perform the allocation and return the address of the 1439 // allocated block, or else "NULL". 1440 1441 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1442 assert_at_safepoint(true /* should_be_vm_thread */); 1443 1444 _verifier->verify_region_sets_optional(); 1445 1446 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1447 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1448 word_size * HeapWordSize); 1449 1450 1451 if (expand(expand_bytes, _workers)) { 1452 _hrm.verify_optional(); 1453 _verifier->verify_region_sets_optional(); 1454 return attempt_allocation_at_safepoint(word_size, 1455 context, 1456 false /* expect_null_mutator_alloc_region */); 1457 } 1458 return NULL; 1459 } 1460 1461 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1462 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1463 aligned_expand_bytes = align_up(aligned_expand_bytes, 1464 HeapRegion::GrainBytes); 1465 1466 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1467 expand_bytes, aligned_expand_bytes); 1468 1469 if (is_maximal_no_gc()) { 1470 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1471 return false; 1472 } 1473 1474 double expand_heap_start_time_sec = os::elapsedTime(); 1475 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1476 assert(regions_to_expand > 0, "Must expand by at least one region"); 1477 1478 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers); 1479 if (expand_time_ms != NULL) { 1480 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1481 } 1482 1483 if (expanded_by > 0) { 1484 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1485 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1486 g1_policy()->record_new_heap_size(num_regions()); 1487 } else { 1488 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1489 1490 // The expansion of the virtual storage space was unsuccessful. 1491 // Let's see if it was because we ran out of swap. 1492 if (G1ExitOnExpansionFailure && 1493 _hrm.available() >= regions_to_expand) { 1494 // We had head room... 1495 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1496 } 1497 } 1498 return regions_to_expand > 0; 1499 } 1500 1501 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1502 size_t aligned_shrink_bytes = 1503 ReservedSpace::page_align_size_down(shrink_bytes); 1504 aligned_shrink_bytes = align_down(aligned_shrink_bytes, 1505 HeapRegion::GrainBytes); 1506 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1507 1508 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1509 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1510 1511 1512 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", 1513 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1514 if (num_regions_removed > 0) { 1515 g1_policy()->record_new_heap_size(num_regions()); 1516 } else { 1517 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1518 } 1519 } 1520 1521 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1522 _verifier->verify_region_sets_optional(); 1523 1524 // We should only reach here at the end of a Full GC which means we 1525 // should not not be holding to any GC alloc regions. The method 1526 // below will make sure of that and do any remaining clean up. 1527 _allocator->abandon_gc_alloc_regions(); 1528 1529 // Instead of tearing down / rebuilding the free lists here, we 1530 // could instead use the remove_all_pending() method on free_list to 1531 // remove only the ones that we need to remove. 1532 tear_down_region_sets(true /* free_list_only */); 1533 shrink_helper(shrink_bytes); 1534 rebuild_region_sets(true /* free_list_only */); 1535 1536 _hrm.verify_optional(); 1537 _verifier->verify_region_sets_optional(); 1538 } 1539 1540 // Public methods. 1541 1542 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1543 CollectedHeap(), 1544 _collector_policy(collector_policy), 1545 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1546 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1547 _g1_policy(create_g1_policy(_gc_timer_stw)), 1548 _collection_set(this, _g1_policy), 1549 _dirty_card_queue_set(false), 1550 _is_alive_closure_cm(this), 1551 _is_alive_closure_stw(this), 1552 _ref_processor_cm(NULL), 1553 _ref_processor_stw(NULL), 1554 _bot(NULL), 1555 _hot_card_cache(NULL), 1556 _g1_rem_set(NULL), 1557 _cr(NULL), 1558 _g1mm(NULL), 1559 _preserved_marks_set(true /* in_c_heap */), 1560 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1561 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1562 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1563 _humongous_reclaim_candidates(), 1564 _has_humongous_reclaim_candidates(false), 1565 _archive_allocator(NULL), 1566 _free_regions_coming(false), 1567 _gc_time_stamp(0), 1568 _summary_bytes_used(0), 1569 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1570 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1571 _expand_heap_after_alloc_failure(true), 1572 _old_marking_cycles_started(0), 1573 _old_marking_cycles_completed(0), 1574 _in_cset_fast_test() { 1575 1576 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1577 /* are_GC_task_threads */true, 1578 /* are_ConcurrentGC_threads */false); 1579 _workers->initialize_workers(); 1580 _verifier = new G1HeapVerifier(this); 1581 1582 _allocator = G1Allocator::create_allocator(this); 1583 1584 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1585 1586 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1587 1588 // Override the default _filler_array_max_size so that no humongous filler 1589 // objects are created. 1590 _filler_array_max_size = _humongous_object_threshold_in_words; 1591 1592 uint n_queues = ParallelGCThreads; 1593 _task_queues = new RefToScanQueueSet(n_queues); 1594 1595 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1596 1597 for (uint i = 0; i < n_queues; i++) { 1598 RefToScanQueue* q = new RefToScanQueue(); 1599 q->initialize(); 1600 _task_queues->register_queue(i, q); 1601 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1602 } 1603 1604 // Initialize the G1EvacuationFailureALot counters and flags. 1605 NOT_PRODUCT(reset_evacuation_should_fail();) 1606 1607 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1608 } 1609 1610 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1611 size_t size, 1612 size_t translation_factor) { 1613 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1614 // Allocate a new reserved space, preferring to use large pages. 1615 ReservedSpace rs(size, preferred_page_size); 1616 G1RegionToSpaceMapper* result = 1617 G1RegionToSpaceMapper::create_mapper(rs, 1618 size, 1619 rs.alignment(), 1620 HeapRegion::GrainBytes, 1621 translation_factor, 1622 mtGC); 1623 1624 os::trace_page_sizes_for_requested_size(description, 1625 size, 1626 preferred_page_size, 1627 rs.alignment(), 1628 rs.base(), 1629 rs.size()); 1630 1631 return result; 1632 } 1633 1634 jint G1CollectedHeap::initialize_concurrent_refinement() { 1635 jint ecode = JNI_OK; 1636 _cr = G1ConcurrentRefine::create(&ecode); 1637 return ecode; 1638 } 1639 1640 jint G1CollectedHeap::initialize() { 1641 CollectedHeap::pre_initialize(); 1642 os::enable_vtime(); 1643 1644 // Necessary to satisfy locking discipline assertions. 1645 1646 MutexLocker x(Heap_lock); 1647 1648 // While there are no constraints in the GC code that HeapWordSize 1649 // be any particular value, there are multiple other areas in the 1650 // system which believe this to be true (e.g. oop->object_size in some 1651 // cases incorrectly returns the size in wordSize units rather than 1652 // HeapWordSize). 1653 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1654 1655 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1656 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1657 size_t heap_alignment = collector_policy()->heap_alignment(); 1658 1659 // Ensure that the sizes are properly aligned. 1660 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1661 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1662 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1663 1664 // Reserve the maximum. 1665 1666 // When compressed oops are enabled, the preferred heap base 1667 // is calculated by subtracting the requested size from the 1668 // 32Gb boundary and using the result as the base address for 1669 // heap reservation. If the requested size is not aligned to 1670 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1671 // into the ReservedHeapSpace constructor) then the actual 1672 // base of the reserved heap may end up differing from the 1673 // address that was requested (i.e. the preferred heap base). 1674 // If this happens then we could end up using a non-optimal 1675 // compressed oops mode. 1676 1677 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1678 heap_alignment); 1679 1680 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1681 1682 // Create the barrier set for the entire reserved region. 1683 G1SATBCardTableLoggingModRefBS* bs 1684 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1685 bs->initialize(); 1686 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1687 set_barrier_set(bs); 1688 1689 // Create the hot card cache. 1690 _hot_card_cache = new G1HotCardCache(this); 1691 1692 // Carve out the G1 part of the heap. 1693 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1694 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1695 G1RegionToSpaceMapper* heap_storage = 1696 G1RegionToSpaceMapper::create_mapper(g1_rs, 1697 g1_rs.size(), 1698 page_size, 1699 HeapRegion::GrainBytes, 1700 1, 1701 mtJavaHeap); 1702 os::trace_page_sizes("Heap", 1703 collector_policy()->min_heap_byte_size(), 1704 max_byte_size, 1705 page_size, 1706 heap_rs.base(), 1707 heap_rs.size()); 1708 heap_storage->set_mapping_changed_listener(&_listener); 1709 1710 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1711 G1RegionToSpaceMapper* bot_storage = 1712 create_aux_memory_mapper("Block Offset Table", 1713 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1714 G1BlockOffsetTable::heap_map_factor()); 1715 1716 G1RegionToSpaceMapper* cardtable_storage = 1717 create_aux_memory_mapper("Card Table", 1718 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1719 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1720 1721 G1RegionToSpaceMapper* card_counts_storage = 1722 create_aux_memory_mapper("Card Counts Table", 1723 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1724 G1CardCounts::heap_map_factor()); 1725 1726 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1727 G1RegionToSpaceMapper* prev_bitmap_storage = 1728 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1729 G1RegionToSpaceMapper* next_bitmap_storage = 1730 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1731 1732 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1733 g1_barrier_set()->initialize(cardtable_storage); 1734 // Do later initialization work for concurrent refinement. 1735 _hot_card_cache->initialize(card_counts_storage); 1736 1737 // 6843694 - ensure that the maximum region index can fit 1738 // in the remembered set structures. 1739 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1740 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1741 1742 // Also create a G1 rem set. 1743 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache); 1744 _g1_rem_set->initialize(max_capacity(), max_regions()); 1745 1746 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1747 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1748 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1749 "too many cards per region"); 1750 1751 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1752 1753 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1754 1755 { 1756 HeapWord* start = _hrm.reserved().start(); 1757 HeapWord* end = _hrm.reserved().end(); 1758 size_t granularity = HeapRegion::GrainBytes; 1759 1760 _in_cset_fast_test.initialize(start, end, granularity); 1761 _humongous_reclaim_candidates.initialize(start, end, granularity); 1762 } 1763 1764 // Create the G1ConcurrentMark data structure and thread. 1765 // (Must do this late, so that "max_regions" is defined.) 1766 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1767 if (_cm == NULL || !_cm->completed_initialization()) { 1768 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1769 return JNI_ENOMEM; 1770 } 1771 _cmThread = _cm->cm_thread(); 1772 1773 // Now expand into the initial heap size. 1774 if (!expand(init_byte_size, _workers)) { 1775 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1776 return JNI_ENOMEM; 1777 } 1778 1779 // Perform any initialization actions delegated to the policy. 1780 g1_policy()->init(this, &_collection_set); 1781 1782 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1783 SATB_Q_FL_lock, 1784 G1SATBProcessCompletedThreshold, 1785 Shared_SATB_Q_lock); 1786 1787 jint ecode = initialize_concurrent_refinement(); 1788 if (ecode != JNI_OK) { 1789 return ecode; 1790 } 1791 1792 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1793 DirtyCardQ_FL_lock, 1794 (int)concurrent_refine()->yellow_zone(), 1795 (int)concurrent_refine()->red_zone(), 1796 Shared_DirtyCardQ_lock, 1797 NULL, // fl_owner 1798 true); // init_free_ids 1799 1800 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1801 DirtyCardQ_FL_lock, 1802 -1, // never trigger processing 1803 -1, // no limit on length 1804 Shared_DirtyCardQ_lock, 1805 &JavaThread::dirty_card_queue_set()); 1806 1807 // Here we allocate the dummy HeapRegion that is required by the 1808 // G1AllocRegion class. 1809 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1810 1811 // We'll re-use the same region whether the alloc region will 1812 // require BOT updates or not and, if it doesn't, then a non-young 1813 // region will complain that it cannot support allocations without 1814 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1815 dummy_region->set_eden(); 1816 // Make sure it's full. 1817 dummy_region->set_top(dummy_region->end()); 1818 G1AllocRegion::setup(this, dummy_region); 1819 1820 _allocator->init_mutator_alloc_region(); 1821 1822 // Do create of the monitoring and management support so that 1823 // values in the heap have been properly initialized. 1824 _g1mm = new G1MonitoringSupport(this); 1825 1826 G1StringDedup::initialize(); 1827 1828 _preserved_marks_set.init(ParallelGCThreads); 1829 1830 _collection_set.initialize(max_regions()); 1831 1832 return JNI_OK; 1833 } 1834 1835 void G1CollectedHeap::stop() { 1836 // Stop all concurrent threads. We do this to make sure these threads 1837 // do not continue to execute and access resources (e.g. logging) 1838 // that are destroyed during shutdown. 1839 _cr->stop(); 1840 _cmThread->stop(); 1841 if (G1StringDedup::is_enabled()) { 1842 G1StringDedup::stop(); 1843 } 1844 } 1845 1846 void G1CollectedHeap::safepoint_synchronize_begin() { 1847 SuspendibleThreadSet::synchronize(); 1848 } 1849 1850 void G1CollectedHeap::safepoint_synchronize_end() { 1851 SuspendibleThreadSet::desynchronize(); 1852 } 1853 1854 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1855 return HeapRegion::max_region_size(); 1856 } 1857 1858 void G1CollectedHeap::post_initialize() { 1859 ref_processing_init(); 1860 } 1861 1862 void G1CollectedHeap::ref_processing_init() { 1863 // Reference processing in G1 currently works as follows: 1864 // 1865 // * There are two reference processor instances. One is 1866 // used to record and process discovered references 1867 // during concurrent marking; the other is used to 1868 // record and process references during STW pauses 1869 // (both full and incremental). 1870 // * Both ref processors need to 'span' the entire heap as 1871 // the regions in the collection set may be dotted around. 1872 // 1873 // * For the concurrent marking ref processor: 1874 // * Reference discovery is enabled at initial marking. 1875 // * Reference discovery is disabled and the discovered 1876 // references processed etc during remarking. 1877 // * Reference discovery is MT (see below). 1878 // * Reference discovery requires a barrier (see below). 1879 // * Reference processing may or may not be MT 1880 // (depending on the value of ParallelRefProcEnabled 1881 // and ParallelGCThreads). 1882 // * A full GC disables reference discovery by the CM 1883 // ref processor and abandons any entries on it's 1884 // discovered lists. 1885 // 1886 // * For the STW processor: 1887 // * Non MT discovery is enabled at the start of a full GC. 1888 // * Processing and enqueueing during a full GC is non-MT. 1889 // * During a full GC, references are processed after marking. 1890 // 1891 // * Discovery (may or may not be MT) is enabled at the start 1892 // of an incremental evacuation pause. 1893 // * References are processed near the end of a STW evacuation pause. 1894 // * For both types of GC: 1895 // * Discovery is atomic - i.e. not concurrent. 1896 // * Reference discovery will not need a barrier. 1897 1898 MemRegion mr = reserved_region(); 1899 1900 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1); 1901 1902 // Concurrent Mark ref processor 1903 _ref_processor_cm = 1904 new ReferenceProcessor(mr, // span 1905 mt_processing, 1906 // mt processing 1907 ParallelGCThreads, 1908 // degree of mt processing 1909 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 1910 // mt discovery 1911 MAX2(ParallelGCThreads, ConcGCThreads), 1912 // degree of mt discovery 1913 false, 1914 // Reference discovery is not atomic 1915 &_is_alive_closure_cm); 1916 // is alive closure 1917 // (for efficiency/performance) 1918 1919 // STW ref processor 1920 _ref_processor_stw = 1921 new ReferenceProcessor(mr, // span 1922 mt_processing, 1923 // mt processing 1924 ParallelGCThreads, 1925 // degree of mt processing 1926 (ParallelGCThreads > 1), 1927 // mt discovery 1928 ParallelGCThreads, 1929 // degree of mt discovery 1930 true, 1931 // Reference discovery is atomic 1932 &_is_alive_closure_stw); 1933 // is alive closure 1934 // (for efficiency/performance) 1935 } 1936 1937 CollectorPolicy* G1CollectedHeap::collector_policy() const { 1938 return _collector_policy; 1939 } 1940 1941 size_t G1CollectedHeap::capacity() const { 1942 return _hrm.length() * HeapRegion::GrainBytes; 1943 } 1944 1945 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 1946 hr->reset_gc_time_stamp(); 1947 } 1948 1949 #ifndef PRODUCT 1950 1951 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 1952 private: 1953 unsigned _gc_time_stamp; 1954 bool _failures; 1955 1956 public: 1957 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 1958 _gc_time_stamp(gc_time_stamp), _failures(false) { } 1959 1960 virtual bool doHeapRegion(HeapRegion* hr) { 1961 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 1962 if (_gc_time_stamp != region_gc_time_stamp) { 1963 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 1964 region_gc_time_stamp, _gc_time_stamp); 1965 _failures = true; 1966 } 1967 return false; 1968 } 1969 1970 bool failures() { return _failures; } 1971 }; 1972 1973 void G1CollectedHeap::check_gc_time_stamps() { 1974 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 1975 heap_region_iterate(&cl); 1976 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 1977 } 1978 #endif // PRODUCT 1979 1980 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 1981 _hot_card_cache->drain(cl, worker_i); 1982 } 1983 1984 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 1985 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 1986 size_t n_completed_buffers = 0; 1987 while (dcqs.apply_closure_during_gc(cl, worker_i)) { 1988 n_completed_buffers++; 1989 } 1990 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 1991 dcqs.clear_n_completed_buffers(); 1992 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 1993 } 1994 1995 // Computes the sum of the storage used by the various regions. 1996 size_t G1CollectedHeap::used() const { 1997 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 1998 if (_archive_allocator != NULL) { 1999 result += _archive_allocator->used(); 2000 } 2001 return result; 2002 } 2003 2004 size_t G1CollectedHeap::used_unlocked() const { 2005 return _summary_bytes_used; 2006 } 2007 2008 class SumUsedClosure: public HeapRegionClosure { 2009 size_t _used; 2010 public: 2011 SumUsedClosure() : _used(0) {} 2012 bool doHeapRegion(HeapRegion* r) { 2013 _used += r->used(); 2014 return false; 2015 } 2016 size_t result() { return _used; } 2017 }; 2018 2019 size_t G1CollectedHeap::recalculate_used() const { 2020 double recalculate_used_start = os::elapsedTime(); 2021 2022 SumUsedClosure blk; 2023 heap_region_iterate(&blk); 2024 2025 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2026 return blk.result(); 2027 } 2028 2029 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2030 switch (cause) { 2031 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2032 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2033 case GCCause::_update_allocation_context_stats_inc: return true; 2034 case GCCause::_wb_conc_mark: return true; 2035 default : return false; 2036 } 2037 } 2038 2039 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2040 switch (cause) { 2041 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2042 case GCCause::_g1_humongous_allocation: return true; 2043 default: return is_user_requested_concurrent_full_gc(cause); 2044 } 2045 } 2046 2047 #ifndef PRODUCT 2048 void G1CollectedHeap::allocate_dummy_regions() { 2049 // Let's fill up most of the region 2050 size_t word_size = HeapRegion::GrainWords - 1024; 2051 // And as a result the region we'll allocate will be humongous. 2052 guarantee(is_humongous(word_size), "sanity"); 2053 2054 // _filler_array_max_size is set to humongous object threshold 2055 // but temporarily change it to use CollectedHeap::fill_with_object(). 2056 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2057 2058 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2059 // Let's use the existing mechanism for the allocation 2060 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2061 AllocationContext::system()); 2062 if (dummy_obj != NULL) { 2063 MemRegion mr(dummy_obj, word_size); 2064 CollectedHeap::fill_with_object(mr); 2065 } else { 2066 // If we can't allocate once, we probably cannot allocate 2067 // again. Let's get out of the loop. 2068 break; 2069 } 2070 } 2071 } 2072 #endif // !PRODUCT 2073 2074 void G1CollectedHeap::increment_old_marking_cycles_started() { 2075 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2076 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2077 "Wrong marking cycle count (started: %d, completed: %d)", 2078 _old_marking_cycles_started, _old_marking_cycles_completed); 2079 2080 _old_marking_cycles_started++; 2081 } 2082 2083 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2084 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2085 2086 // We assume that if concurrent == true, then the caller is a 2087 // concurrent thread that was joined the Suspendible Thread 2088 // Set. If there's ever a cheap way to check this, we should add an 2089 // assert here. 2090 2091 // Given that this method is called at the end of a Full GC or of a 2092 // concurrent cycle, and those can be nested (i.e., a Full GC can 2093 // interrupt a concurrent cycle), the number of full collections 2094 // completed should be either one (in the case where there was no 2095 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2096 // behind the number of full collections started. 2097 2098 // This is the case for the inner caller, i.e. a Full GC. 2099 assert(concurrent || 2100 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2101 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2102 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2103 "is inconsistent with _old_marking_cycles_completed = %u", 2104 _old_marking_cycles_started, _old_marking_cycles_completed); 2105 2106 // This is the case for the outer caller, i.e. the concurrent cycle. 2107 assert(!concurrent || 2108 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2109 "for outer caller (concurrent cycle): " 2110 "_old_marking_cycles_started = %u " 2111 "is inconsistent with _old_marking_cycles_completed = %u", 2112 _old_marking_cycles_started, _old_marking_cycles_completed); 2113 2114 _old_marking_cycles_completed += 1; 2115 2116 // We need to clear the "in_progress" flag in the CM thread before 2117 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2118 // is set) so that if a waiter requests another System.gc() it doesn't 2119 // incorrectly see that a marking cycle is still in progress. 2120 if (concurrent) { 2121 _cmThread->set_idle(); 2122 } 2123 2124 // This notify_all() will ensure that a thread that called 2125 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2126 // and it's waiting for a full GC to finish will be woken up. It is 2127 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2128 FullGCCount_lock->notify_all(); 2129 } 2130 2131 void G1CollectedHeap::collect(GCCause::Cause cause) { 2132 assert_heap_not_locked(); 2133 2134 uint gc_count_before; 2135 uint old_marking_count_before; 2136 uint full_gc_count_before; 2137 bool retry_gc; 2138 2139 do { 2140 retry_gc = false; 2141 2142 { 2143 MutexLocker ml(Heap_lock); 2144 2145 // Read the GC count while holding the Heap_lock 2146 gc_count_before = total_collections(); 2147 full_gc_count_before = total_full_collections(); 2148 old_marking_count_before = _old_marking_cycles_started; 2149 } 2150 2151 if (should_do_concurrent_full_gc(cause)) { 2152 // Schedule an initial-mark evacuation pause that will start a 2153 // concurrent cycle. We're setting word_size to 0 which means that 2154 // we are not requesting a post-GC allocation. 2155 VM_G1IncCollectionPause op(gc_count_before, 2156 0, /* word_size */ 2157 true, /* should_initiate_conc_mark */ 2158 g1_policy()->max_pause_time_ms(), 2159 cause); 2160 op.set_allocation_context(AllocationContext::current()); 2161 2162 VMThread::execute(&op); 2163 if (!op.pause_succeeded()) { 2164 if (old_marking_count_before == _old_marking_cycles_started) { 2165 retry_gc = op.should_retry_gc(); 2166 } else { 2167 // A Full GC happened while we were trying to schedule the 2168 // initial-mark GC. No point in starting a new cycle given 2169 // that the whole heap was collected anyway. 2170 } 2171 2172 if (retry_gc) { 2173 if (GCLocker::is_active_and_needs_gc()) { 2174 GCLocker::stall_until_clear(); 2175 } 2176 } 2177 } 2178 } else { 2179 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2180 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2181 2182 // Schedule a standard evacuation pause. We're setting word_size 2183 // to 0 which means that we are not requesting a post-GC allocation. 2184 VM_G1IncCollectionPause op(gc_count_before, 2185 0, /* word_size */ 2186 false, /* should_initiate_conc_mark */ 2187 g1_policy()->max_pause_time_ms(), 2188 cause); 2189 VMThread::execute(&op); 2190 } else { 2191 // Schedule a Full GC. 2192 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2193 VMThread::execute(&op); 2194 } 2195 } 2196 } while (retry_gc); 2197 } 2198 2199 bool G1CollectedHeap::is_in(const void* p) const { 2200 if (_hrm.reserved().contains(p)) { 2201 // Given that we know that p is in the reserved space, 2202 // heap_region_containing() should successfully 2203 // return the containing region. 2204 HeapRegion* hr = heap_region_containing(p); 2205 return hr->is_in(p); 2206 } else { 2207 return false; 2208 } 2209 } 2210 2211 #ifdef ASSERT 2212 bool G1CollectedHeap::is_in_exact(const void* p) const { 2213 bool contains = reserved_region().contains(p); 2214 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2215 if (contains && available) { 2216 return true; 2217 } else { 2218 return false; 2219 } 2220 } 2221 #endif 2222 2223 // Iteration functions. 2224 2225 // Iterates an ObjectClosure over all objects within a HeapRegion. 2226 2227 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2228 ObjectClosure* _cl; 2229 public: 2230 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2231 bool doHeapRegion(HeapRegion* r) { 2232 if (!r->is_continues_humongous()) { 2233 r->object_iterate(_cl); 2234 } 2235 return false; 2236 } 2237 }; 2238 2239 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2240 IterateObjectClosureRegionClosure blk(cl); 2241 heap_region_iterate(&blk); 2242 } 2243 2244 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2245 _hrm.iterate(cl); 2246 } 2247 2248 void G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2249 uint worker_id, 2250 HeapRegionClaimer *hrclaimer) const { 2251 _hrm.par_iterate(cl, worker_id, hrclaimer); 2252 } 2253 2254 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2255 _collection_set.iterate(cl); 2256 } 2257 2258 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2259 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2260 } 2261 2262 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2263 HeapRegion* result = _hrm.next_region_in_heap(from); 2264 while (result != NULL && result->is_pinned()) { 2265 result = _hrm.next_region_in_heap(result); 2266 } 2267 return result; 2268 } 2269 2270 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2271 HeapRegion* hr = heap_region_containing(addr); 2272 return hr->block_start(addr); 2273 } 2274 2275 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2276 HeapRegion* hr = heap_region_containing(addr); 2277 return hr->block_size(addr); 2278 } 2279 2280 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2281 HeapRegion* hr = heap_region_containing(addr); 2282 return hr->block_is_obj(addr); 2283 } 2284 2285 bool G1CollectedHeap::supports_tlab_allocation() const { 2286 return true; 2287 } 2288 2289 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2290 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2291 } 2292 2293 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2294 return _eden.length() * HeapRegion::GrainBytes; 2295 } 2296 2297 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2298 // must be equal to the humongous object limit. 2299 size_t G1CollectedHeap::max_tlab_size() const { 2300 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2301 } 2302 2303 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2304 AllocationContext_t context = AllocationContext::current(); 2305 return _allocator->unsafe_max_tlab_alloc(context); 2306 } 2307 2308 size_t G1CollectedHeap::max_capacity() const { 2309 return _hrm.reserved().byte_size(); 2310 } 2311 2312 jlong G1CollectedHeap::millis_since_last_gc() { 2313 // See the notes in GenCollectedHeap::millis_since_last_gc() 2314 // for more information about the implementation. 2315 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2316 _g1_policy->collection_pause_end_millis(); 2317 if (ret_val < 0) { 2318 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2319 ". returning zero instead.", ret_val); 2320 return 0; 2321 } 2322 return ret_val; 2323 } 2324 2325 void G1CollectedHeap::prepare_for_verify() { 2326 _verifier->prepare_for_verify(); 2327 } 2328 2329 void G1CollectedHeap::verify(VerifyOption vo) { 2330 _verifier->verify(vo); 2331 } 2332 2333 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2334 return true; 2335 } 2336 2337 const char* const* G1CollectedHeap::concurrent_phases() const { 2338 return _cmThread->concurrent_phases(); 2339 } 2340 2341 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2342 return _cmThread->request_concurrent_phase(phase); 2343 } 2344 2345 class PrintRegionClosure: public HeapRegionClosure { 2346 outputStream* _st; 2347 public: 2348 PrintRegionClosure(outputStream* st) : _st(st) {} 2349 bool doHeapRegion(HeapRegion* r) { 2350 r->print_on(_st); 2351 return false; 2352 } 2353 }; 2354 2355 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2356 const HeapRegion* hr, 2357 const VerifyOption vo) const { 2358 switch (vo) { 2359 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2360 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2361 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 2362 default: ShouldNotReachHere(); 2363 } 2364 return false; // keep some compilers happy 2365 } 2366 2367 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2368 const VerifyOption vo) const { 2369 switch (vo) { 2370 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2371 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2372 case VerifyOption_G1UseMarkWord: { 2373 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 2374 return !obj->is_gc_marked() && !hr->is_archive(); 2375 } 2376 default: ShouldNotReachHere(); 2377 } 2378 return false; // keep some compilers happy 2379 } 2380 2381 void G1CollectedHeap::print_heap_regions() const { 2382 LogTarget(Trace, gc, heap, region) lt; 2383 if (lt.is_enabled()) { 2384 LogStream ls(lt); 2385 print_regions_on(&ls); 2386 } 2387 } 2388 2389 void G1CollectedHeap::print_on(outputStream* st) const { 2390 st->print(" %-20s", "garbage-first heap"); 2391 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2392 capacity()/K, used_unlocked()/K); 2393 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")", 2394 p2i(_hrm.reserved().start()), 2395 p2i(_hrm.reserved().end())); 2396 st->cr(); 2397 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2398 uint young_regions = young_regions_count(); 2399 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2400 (size_t) young_regions * HeapRegion::GrainBytes / K); 2401 uint survivor_regions = survivor_regions_count(); 2402 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2403 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2404 st->cr(); 2405 MetaspaceAux::print_on(st); 2406 } 2407 2408 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2409 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2410 "HS=humongous(starts), HC=humongous(continues), " 2411 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2412 "AC=allocation context, " 2413 "TAMS=top-at-mark-start (previous, next)"); 2414 PrintRegionClosure blk(st); 2415 heap_region_iterate(&blk); 2416 } 2417 2418 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2419 print_on(st); 2420 2421 // Print the per-region information. 2422 print_regions_on(st); 2423 } 2424 2425 void G1CollectedHeap::print_on_error(outputStream* st) const { 2426 this->CollectedHeap::print_on_error(st); 2427 2428 if (_cm != NULL) { 2429 st->cr(); 2430 _cm->print_on_error(st); 2431 } 2432 } 2433 2434 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2435 workers()->print_worker_threads_on(st); 2436 _cmThread->print_on(st); 2437 st->cr(); 2438 _cm->print_worker_threads_on(st); 2439 _cr->print_worker_threads_on(st); // also prints the sample thread 2440 if (G1StringDedup::is_enabled()) { 2441 G1StringDedup::print_worker_threads_on(st); 2442 } 2443 } 2444 2445 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2446 workers()->threads_do(tc); 2447 tc->do_thread(_cmThread); 2448 _cm->threads_do(tc); 2449 _cr->threads_do(tc); // also iterates over the sample thread 2450 if (G1StringDedup::is_enabled()) { 2451 G1StringDedup::threads_do(tc); 2452 } 2453 } 2454 2455 void G1CollectedHeap::print_tracing_info() const { 2456 g1_rem_set()->print_summary_info(); 2457 concurrent_mark()->print_summary_info(); 2458 } 2459 2460 #ifndef PRODUCT 2461 // Helpful for debugging RSet issues. 2462 2463 class PrintRSetsClosure : public HeapRegionClosure { 2464 private: 2465 const char* _msg; 2466 size_t _occupied_sum; 2467 2468 public: 2469 bool doHeapRegion(HeapRegion* r) { 2470 HeapRegionRemSet* hrrs = r->rem_set(); 2471 size_t occupied = hrrs->occupied(); 2472 _occupied_sum += occupied; 2473 2474 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2475 if (occupied == 0) { 2476 tty->print_cr(" RSet is empty"); 2477 } else { 2478 hrrs->print(); 2479 } 2480 tty->print_cr("----------"); 2481 return false; 2482 } 2483 2484 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2485 tty->cr(); 2486 tty->print_cr("========================================"); 2487 tty->print_cr("%s", msg); 2488 tty->cr(); 2489 } 2490 2491 ~PrintRSetsClosure() { 2492 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2493 tty->print_cr("========================================"); 2494 tty->cr(); 2495 } 2496 }; 2497 2498 void G1CollectedHeap::print_cset_rsets() { 2499 PrintRSetsClosure cl("Printing CSet RSets"); 2500 collection_set_iterate(&cl); 2501 } 2502 2503 void G1CollectedHeap::print_all_rsets() { 2504 PrintRSetsClosure cl("Printing All RSets");; 2505 heap_region_iterate(&cl); 2506 } 2507 #endif // PRODUCT 2508 2509 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2510 2511 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2512 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2513 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2514 2515 size_t eden_capacity_bytes = 2516 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2517 2518 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2519 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2520 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2521 } 2522 2523 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2524 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2525 stats->unused(), stats->used(), stats->region_end_waste(), 2526 stats->regions_filled(), stats->direct_allocated(), 2527 stats->failure_used(), stats->failure_waste()); 2528 } 2529 2530 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2531 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2532 gc_tracer->report_gc_heap_summary(when, heap_summary); 2533 2534 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2535 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2536 } 2537 2538 G1CollectedHeap* G1CollectedHeap::heap() { 2539 CollectedHeap* heap = Universe::heap(); 2540 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2541 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2542 return (G1CollectedHeap*)heap; 2543 } 2544 2545 void G1CollectedHeap::gc_prologue(bool full) { 2546 // always_do_update_barrier = false; 2547 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2548 2549 // This summary needs to be printed before incrementing total collections. 2550 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2551 2552 // Update common counters. 2553 increment_total_collections(full /* full gc */); 2554 if (full) { 2555 increment_old_marking_cycles_started(); 2556 reset_gc_time_stamp(); 2557 } else { 2558 increment_gc_time_stamp(); 2559 } 2560 2561 // Fill TLAB's and such 2562 double start = os::elapsedTime(); 2563 accumulate_statistics_all_tlabs(); 2564 ensure_parsability(true); 2565 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2566 } 2567 2568 void G1CollectedHeap::gc_epilogue(bool full) { 2569 // Update common counters. 2570 if (full) { 2571 // Update the number of full collections that have been completed. 2572 increment_old_marking_cycles_completed(false /* concurrent */); 2573 } 2574 2575 // We are at the end of the GC. Total collections has already been increased. 2576 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2577 2578 // FIXME: what is this about? 2579 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2580 // is set. 2581 #if defined(COMPILER2) || INCLUDE_JVMCI 2582 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2583 #endif 2584 // always_do_update_barrier = true; 2585 2586 double start = os::elapsedTime(); 2587 resize_all_tlabs(); 2588 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2589 2590 allocation_context_stats().update(full); 2591 2592 MemoryService::track_memory_usage(); 2593 // We have just completed a GC. Update the soft reference 2594 // policy with the new heap occupancy 2595 Universe::update_heap_info_at_gc(); 2596 } 2597 2598 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2599 uint gc_count_before, 2600 bool* succeeded, 2601 GCCause::Cause gc_cause) { 2602 assert_heap_not_locked_and_not_at_safepoint(); 2603 VM_G1IncCollectionPause op(gc_count_before, 2604 word_size, 2605 false, /* should_initiate_conc_mark */ 2606 g1_policy()->max_pause_time_ms(), 2607 gc_cause); 2608 2609 op.set_allocation_context(AllocationContext::current()); 2610 VMThread::execute(&op); 2611 2612 HeapWord* result = op.result(); 2613 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2614 assert(result == NULL || ret_succeeded, 2615 "the result should be NULL if the VM did not succeed"); 2616 *succeeded = ret_succeeded; 2617 2618 assert_heap_not_locked(); 2619 return result; 2620 } 2621 2622 void 2623 G1CollectedHeap::doConcurrentMark() { 2624 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2625 if (!_cmThread->in_progress()) { 2626 _cmThread->set_started(); 2627 CGC_lock->notify(); 2628 } 2629 } 2630 2631 size_t G1CollectedHeap::pending_card_num() { 2632 size_t extra_cards = 0; 2633 JavaThread *curr = Threads::first(); 2634 while (curr != NULL) { 2635 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2636 extra_cards += dcq.size(); 2637 curr = curr->next(); 2638 } 2639 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2640 size_t buffer_size = dcqs.buffer_size(); 2641 size_t buffer_num = dcqs.completed_buffers_num(); 2642 2643 return buffer_size * buffer_num + extra_cards; 2644 } 2645 2646 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2647 private: 2648 size_t _total_humongous; 2649 size_t _candidate_humongous; 2650 2651 DirtyCardQueue _dcq; 2652 2653 // We don't nominate objects with many remembered set entries, on 2654 // the assumption that such objects are likely still live. 2655 bool is_remset_small(HeapRegion* region) const { 2656 HeapRegionRemSet* const rset = region->rem_set(); 2657 return G1EagerReclaimHumongousObjectsWithStaleRefs 2658 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2659 : rset->is_empty(); 2660 } 2661 2662 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2663 assert(region->is_starts_humongous(), "Must start a humongous object"); 2664 2665 oop obj = oop(region->bottom()); 2666 2667 // Dead objects cannot be eager reclaim candidates. Due to class 2668 // unloading it is unsafe to query their classes so we return early. 2669 if (heap->is_obj_dead(obj, region)) { 2670 return false; 2671 } 2672 2673 // Candidate selection must satisfy the following constraints 2674 // while concurrent marking is in progress: 2675 // 2676 // * In order to maintain SATB invariants, an object must not be 2677 // reclaimed if it was allocated before the start of marking and 2678 // has not had its references scanned. Such an object must have 2679 // its references (including type metadata) scanned to ensure no 2680 // live objects are missed by the marking process. Objects 2681 // allocated after the start of concurrent marking don't need to 2682 // be scanned. 2683 // 2684 // * An object must not be reclaimed if it is on the concurrent 2685 // mark stack. Objects allocated after the start of concurrent 2686 // marking are never pushed on the mark stack. 2687 // 2688 // Nominating only objects allocated after the start of concurrent 2689 // marking is sufficient to meet both constraints. This may miss 2690 // some objects that satisfy the constraints, but the marking data 2691 // structures don't support efficiently performing the needed 2692 // additional tests or scrubbing of the mark stack. 2693 // 2694 // However, we presently only nominate is_typeArray() objects. 2695 // A humongous object containing references induces remembered 2696 // set entries on other regions. In order to reclaim such an 2697 // object, those remembered sets would need to be cleaned up. 2698 // 2699 // We also treat is_typeArray() objects specially, allowing them 2700 // to be reclaimed even if allocated before the start of 2701 // concurrent mark. For this we rely on mark stack insertion to 2702 // exclude is_typeArray() objects, preventing reclaiming an object 2703 // that is in the mark stack. We also rely on the metadata for 2704 // such objects to be built-in and so ensured to be kept live. 2705 // Frequent allocation and drop of large binary blobs is an 2706 // important use case for eager reclaim, and this special handling 2707 // may reduce needed headroom. 2708 2709 return obj->is_typeArray() && is_remset_small(region); 2710 } 2711 2712 public: 2713 RegisterHumongousWithInCSetFastTestClosure() 2714 : _total_humongous(0), 2715 _candidate_humongous(0), 2716 _dcq(&JavaThread::dirty_card_queue_set()) { 2717 } 2718 2719 virtual bool doHeapRegion(HeapRegion* r) { 2720 if (!r->is_starts_humongous()) { 2721 return false; 2722 } 2723 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2724 2725 bool is_candidate = humongous_region_is_candidate(g1h, r); 2726 uint rindex = r->hrm_index(); 2727 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2728 if (is_candidate) { 2729 _candidate_humongous++; 2730 g1h->register_humongous_region_with_cset(rindex); 2731 // Is_candidate already filters out humongous object with large remembered sets. 2732 // If we have a humongous object with a few remembered sets, we simply flush these 2733 // remembered set entries into the DCQS. That will result in automatic 2734 // re-evaluation of their remembered set entries during the following evacuation 2735 // phase. 2736 if (!r->rem_set()->is_empty()) { 2737 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2738 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2739 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 2740 HeapRegionRemSetIterator hrrs(r->rem_set()); 2741 size_t card_index; 2742 while (hrrs.has_next(card_index)) { 2743 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 2744 // The remembered set might contain references to already freed 2745 // regions. Filter out such entries to avoid failing card table 2746 // verification. 2747 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 2748 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 2749 *card_ptr = CardTableModRefBS::dirty_card_val(); 2750 _dcq.enqueue(card_ptr); 2751 } 2752 } 2753 } 2754 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2755 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2756 hrrs.n_yielded(), r->rem_set()->occupied()); 2757 r->rem_set()->clear_locked(); 2758 } 2759 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2760 } 2761 _total_humongous++; 2762 2763 return false; 2764 } 2765 2766 size_t total_humongous() const { return _total_humongous; } 2767 size_t candidate_humongous() const { return _candidate_humongous; } 2768 2769 void flush_rem_set_entries() { _dcq.flush(); } 2770 }; 2771 2772 void G1CollectedHeap::register_humongous_regions_with_cset() { 2773 if (!G1EagerReclaimHumongousObjects) { 2774 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2775 return; 2776 } 2777 double time = os::elapsed_counter(); 2778 2779 // Collect reclaim candidate information and register candidates with cset. 2780 RegisterHumongousWithInCSetFastTestClosure cl; 2781 heap_region_iterate(&cl); 2782 2783 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2784 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2785 cl.total_humongous(), 2786 cl.candidate_humongous()); 2787 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2788 2789 // Finally flush all remembered set entries to re-check into the global DCQS. 2790 cl.flush_rem_set_entries(); 2791 } 2792 2793 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2794 public: 2795 bool doHeapRegion(HeapRegion* hr) { 2796 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2797 hr->verify_rem_set(); 2798 } 2799 return false; 2800 } 2801 }; 2802 2803 uint G1CollectedHeap::num_task_queues() const { 2804 return _task_queues->size(); 2805 } 2806 2807 #if TASKQUEUE_STATS 2808 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2809 st->print_raw_cr("GC Task Stats"); 2810 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2811 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2812 } 2813 2814 void G1CollectedHeap::print_taskqueue_stats() const { 2815 if (!log_is_enabled(Trace, gc, task, stats)) { 2816 return; 2817 } 2818 Log(gc, task, stats) log; 2819 ResourceMark rm; 2820 LogStream ls(log.trace()); 2821 outputStream* st = &ls; 2822 2823 print_taskqueue_stats_hdr(st); 2824 2825 TaskQueueStats totals; 2826 const uint n = num_task_queues(); 2827 for (uint i = 0; i < n; ++i) { 2828 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2829 totals += task_queue(i)->stats; 2830 } 2831 st->print_raw("tot "); totals.print(st); st->cr(); 2832 2833 DEBUG_ONLY(totals.verify()); 2834 } 2835 2836 void G1CollectedHeap::reset_taskqueue_stats() { 2837 const uint n = num_task_queues(); 2838 for (uint i = 0; i < n; ++i) { 2839 task_queue(i)->stats.reset(); 2840 } 2841 } 2842 #endif // TASKQUEUE_STATS 2843 2844 void G1CollectedHeap::wait_for_root_region_scanning() { 2845 double scan_wait_start = os::elapsedTime(); 2846 // We have to wait until the CM threads finish scanning the 2847 // root regions as it's the only way to ensure that all the 2848 // objects on them have been correctly scanned before we start 2849 // moving them during the GC. 2850 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2851 double wait_time_ms = 0.0; 2852 if (waited) { 2853 double scan_wait_end = os::elapsedTime(); 2854 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2855 } 2856 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2857 } 2858 2859 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2860 private: 2861 G1HRPrinter* _hr_printer; 2862 public: 2863 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2864 2865 virtual bool doHeapRegion(HeapRegion* r) { 2866 _hr_printer->cset(r); 2867 return false; 2868 } 2869 }; 2870 2871 void G1CollectedHeap::start_new_collection_set() { 2872 collection_set()->start_incremental_building(); 2873 2874 clear_cset_fast_test(); 2875 2876 guarantee(_eden.length() == 0, "eden should have been cleared"); 2877 g1_policy()->transfer_survivors_to_cset(survivor()); 2878 } 2879 2880 bool 2881 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2882 assert_at_safepoint(true /* should_be_vm_thread */); 2883 guarantee(!is_gc_active(), "collection is not reentrant"); 2884 2885 if (GCLocker::check_active_before_gc()) { 2886 return false; 2887 } 2888 2889 _gc_timer_stw->register_gc_start(); 2890 2891 GCIdMark gc_id_mark; 2892 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2893 2894 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2895 ResourceMark rm; 2896 2897 g1_policy()->note_gc_start(); 2898 2899 wait_for_root_region_scanning(); 2900 2901 print_heap_before_gc(); 2902 print_heap_regions(); 2903 trace_heap_before_gc(_gc_tracer_stw); 2904 2905 _verifier->verify_region_sets_optional(); 2906 _verifier->verify_dirty_young_regions(); 2907 2908 // We should not be doing initial mark unless the conc mark thread is running 2909 if (!_cmThread->should_terminate()) { 2910 // This call will decide whether this pause is an initial-mark 2911 // pause. If it is, during_initial_mark_pause() will return true 2912 // for the duration of this pause. 2913 g1_policy()->decide_on_conc_mark_initiation(); 2914 } 2915 2916 // We do not allow initial-mark to be piggy-backed on a mixed GC. 2917 assert(!collector_state()->during_initial_mark_pause() || 2918 collector_state()->gcs_are_young(), "sanity"); 2919 2920 // We also do not allow mixed GCs during marking. 2921 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 2922 2923 // Record whether this pause is an initial mark. When the current 2924 // thread has completed its logging output and it's safe to signal 2925 // the CM thread, the flag's value in the policy has been reset. 2926 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 2927 2928 // Inner scope for scope based logging, timers, and stats collection 2929 { 2930 EvacuationInfo evacuation_info; 2931 2932 if (collector_state()->during_initial_mark_pause()) { 2933 // We are about to start a marking cycle, so we increment the 2934 // full collection counter. 2935 increment_old_marking_cycles_started(); 2936 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 2937 } 2938 2939 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 2940 2941 GCTraceCPUTime tcpu; 2942 2943 FormatBuffer<> gc_string("Pause "); 2944 if (collector_state()->during_initial_mark_pause()) { 2945 gc_string.append("Initial Mark"); 2946 } else if (collector_state()->gcs_are_young()) { 2947 gc_string.append("Young"); 2948 } else { 2949 gc_string.append("Mixed"); 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(); 2991 2992 _verifier->check_bitmaps("GC Start"); 2993 2994 #if defined(COMPILER2) || INCLUDE_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(); 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 defined(COMPILER2) || INCLUDE_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 }