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/concurrentG1Refine.hpp" 33 #include "gc/g1/concurrentG1RefineThread.hpp" 34 #include "gc/g1/concurrentMarkThread.inline.hpp" 35 #include "gc/g1/g1Allocator.inline.hpp" 36 #include "gc/g1/g1CollectedHeap.inline.hpp" 37 #include "gc/g1/g1CollectionSet.hpp" 38 #include "gc/g1/g1CollectorPolicy.hpp" 39 #include "gc/g1/g1CollectorState.hpp" 40 #include "gc/g1/g1EvacStats.inline.hpp" 41 #include "gc/g1/g1GCPhaseTimes.hpp" 42 #include "gc/g1/g1HeapSizingPolicy.hpp" 43 #include "gc/g1/g1HeapTransition.hpp" 44 #include "gc/g1/g1HeapVerifier.hpp" 45 #include "gc/g1/g1HotCardCache.hpp" 46 #include "gc/g1/g1MarkSweep.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/g1StringDedup.hpp" 55 #include "gc/g1/g1YCTypes.hpp" 56 #include "gc/g1/heapRegion.inline.hpp" 57 #include "gc/g1/heapRegionRemSet.hpp" 58 #include "gc/g1/heapRegionSet.inline.hpp" 59 #include "gc/g1/suspendibleThreadSet.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/referenceProcessor.inline.hpp" 71 #include "gc/shared/taskqueue.inline.hpp" 72 #include "logging/log.hpp" 73 #include "memory/allocation.hpp" 74 #include "memory/iterator.hpp" 75 #include "memory/resourceArea.hpp" 76 #include "oops/oop.inline.hpp" 77 #include "prims/resolvedMethodTable.hpp" 78 #include "runtime/atomic.hpp" 79 #include "runtime/init.hpp" 80 #include "runtime/orderAccess.inline.hpp" 81 #include "runtime/vmThread.hpp" 82 #include "utilities/globalDefinitions.hpp" 83 #include "utilities/stack.inline.hpp" 84 85 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 86 87 // INVARIANTS/NOTES 88 // 89 // All allocation activity covered by the G1CollectedHeap interface is 90 // serialized by acquiring the HeapLock. This happens in mem_allocate 91 // and allocate_new_tlab, which are the "entry" points to the 92 // allocation code from the rest of the JVM. (Note that this does not 93 // apply to TLAB allocation, which is not part of this interface: it 94 // is done by clients of this interface.) 95 96 // Local to this file. 97 98 class RefineCardTableEntryClosure: public CardTableEntryClosure { 99 bool _concurrent; 100 public: 101 RefineCardTableEntryClosure() : _concurrent(true) { } 102 103 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 104 G1CollectedHeap::heap()->g1_rem_set()->refine_card_concurrently(card_ptr, worker_i); 105 106 if (_concurrent && SuspendibleThreadSet::should_yield()) { 107 // Caller will actually yield. 108 return false; 109 } 110 // Otherwise, we finished successfully; return true. 111 return true; 112 } 113 114 void set_concurrent(bool b) { _concurrent = b; } 115 }; 116 117 118 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 119 private: 120 size_t _num_dirtied; 121 G1CollectedHeap* _g1h; 122 G1SATBCardTableLoggingModRefBS* _g1_bs; 123 124 HeapRegion* region_for_card(jbyte* card_ptr) const { 125 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 126 } 127 128 bool will_become_free(HeapRegion* hr) const { 129 // A region will be freed by free_collection_set if the region is in the 130 // collection set and has not had an evacuation failure. 131 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 132 } 133 134 public: 135 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 136 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 137 138 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 139 HeapRegion* hr = region_for_card(card_ptr); 140 141 // Should only dirty cards in regions that won't be freed. 142 if (!will_become_free(hr)) { 143 *card_ptr = CardTableModRefBS::dirty_card_val(); 144 _num_dirtied++; 145 } 146 147 return true; 148 } 149 150 size_t num_dirtied() const { return _num_dirtied; } 151 }; 152 153 154 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 155 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 156 } 157 158 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 159 // The from card cache is not the memory that is actually committed. So we cannot 160 // take advantage of the zero_filled parameter. 161 reset_from_card_cache(start_idx, num_regions); 162 } 163 164 // Returns true if the reference points to an object that 165 // can move in an incremental collection. 166 bool G1CollectedHeap::is_scavengable(const void* p) { 167 HeapRegion* hr = heap_region_containing(p); 168 return !hr->is_pinned(); 169 } 170 171 // Private methods. 172 173 HeapRegion* 174 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 175 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 176 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 177 if (!_secondary_free_list.is_empty()) { 178 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 179 "secondary_free_list has %u entries", 180 _secondary_free_list.length()); 181 // It looks as if there are free regions available on the 182 // secondary_free_list. Let's move them to the free_list and try 183 // again to allocate from it. 184 append_secondary_free_list(); 185 186 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 187 "empty we should have moved at least one entry to the free_list"); 188 HeapRegion* res = _hrm.allocate_free_region(is_old); 189 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 190 "allocated " HR_FORMAT " from secondary_free_list", 191 HR_FORMAT_PARAMS(res)); 192 return res; 193 } 194 195 // Wait here until we get notified either when (a) there are no 196 // more free regions coming or (b) some regions have been moved on 197 // the secondary_free_list. 198 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 199 } 200 201 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 202 "could not allocate from secondary_free_list"); 203 return NULL; 204 } 205 206 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 207 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 208 "the only time we use this to allocate a humongous region is " 209 "when we are allocating a single humongous region"); 210 211 HeapRegion* res; 212 if (G1StressConcRegionFreeing) { 213 if (!_secondary_free_list.is_empty()) { 214 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 215 "forced to look at the secondary_free_list"); 216 res = new_region_try_secondary_free_list(is_old); 217 if (res != NULL) { 218 return res; 219 } 220 } 221 } 222 223 res = _hrm.allocate_free_region(is_old); 224 225 if (res == NULL) { 226 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 227 "res == NULL, trying the secondary_free_list"); 228 res = new_region_try_secondary_free_list(is_old); 229 } 230 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 231 // Currently, only attempts to allocate GC alloc regions set 232 // do_expand to true. So, we should only reach here during a 233 // safepoint. If this assumption changes we might have to 234 // reconsider the use of _expand_heap_after_alloc_failure. 235 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 236 237 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 238 word_size * HeapWordSize); 239 240 if (expand(word_size * HeapWordSize)) { 241 // Given that expand() succeeded in expanding the heap, and we 242 // always expand the heap by an amount aligned to the heap 243 // region size, the free list should in theory not be empty. 244 // In either case allocate_free_region() will check for NULL. 245 res = _hrm.allocate_free_region(is_old); 246 } else { 247 _expand_heap_after_alloc_failure = false; 248 } 249 } 250 return res; 251 } 252 253 HeapWord* 254 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 255 uint num_regions, 256 size_t word_size, 257 AllocationContext_t context) { 258 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 259 assert(is_humongous(word_size), "word_size should be humongous"); 260 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 261 262 // Index of last region in the series. 263 uint last = first + num_regions - 1; 264 265 // We need to initialize the region(s) we just discovered. This is 266 // a bit tricky given that it can happen concurrently with 267 // refinement threads refining cards on these regions and 268 // potentially wanting to refine the BOT as they are scanning 269 // those cards (this can happen shortly after a cleanup; see CR 270 // 6991377). So we have to set up the region(s) carefully and in 271 // a specific order. 272 273 // The word size sum of all the regions we will allocate. 274 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 275 assert(word_size <= word_size_sum, "sanity"); 276 277 // This will be the "starts humongous" region. 278 HeapRegion* first_hr = region_at(first); 279 // The header of the new object will be placed at the bottom of 280 // the first region. 281 HeapWord* new_obj = first_hr->bottom(); 282 // This will be the new top of the new object. 283 HeapWord* obj_top = new_obj + word_size; 284 285 // First, we need to zero the header of the space that we will be 286 // allocating. When we update top further down, some refinement 287 // threads might try to scan the region. By zeroing the header we 288 // ensure that any thread that will try to scan the region will 289 // come across the zero klass word and bail out. 290 // 291 // NOTE: It would not have been correct to have used 292 // CollectedHeap::fill_with_object() and make the space look like 293 // an int array. The thread that is doing the allocation will 294 // later update the object header to a potentially different array 295 // type and, for a very short period of time, the klass and length 296 // fields will be inconsistent. This could cause a refinement 297 // thread to calculate the object size incorrectly. 298 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 299 300 // Next, pad out the unused tail of the last region with filler 301 // objects, for improved usage accounting. 302 // How many words we use for filler objects. 303 size_t word_fill_size = word_size_sum - word_size; 304 305 // How many words memory we "waste" which cannot hold a filler object. 306 size_t words_not_fillable = 0; 307 308 if (word_fill_size >= min_fill_size()) { 309 fill_with_objects(obj_top, word_fill_size); 310 } else if (word_fill_size > 0) { 311 // We have space to fill, but we cannot fit an object there. 312 words_not_fillable = word_fill_size; 313 word_fill_size = 0; 314 } 315 316 // We will set up the first region as "starts humongous". This 317 // will also update the BOT covering all the regions to reflect 318 // that there is a single object that starts at the bottom of the 319 // first region. 320 first_hr->set_starts_humongous(obj_top, word_fill_size); 321 first_hr->set_allocation_context(context); 322 // Then, if there are any, we will set up the "continues 323 // humongous" regions. 324 HeapRegion* hr = NULL; 325 for (uint i = first + 1; i <= last; ++i) { 326 hr = region_at(i); 327 hr->set_continues_humongous(first_hr); 328 hr->set_allocation_context(context); 329 } 330 331 // Up to this point no concurrent thread would have been able to 332 // do any scanning on any region in this series. All the top 333 // fields still point to bottom, so the intersection between 334 // [bottom,top] and [card_start,card_end] will be empty. Before we 335 // update the top fields, we'll do a storestore to make sure that 336 // no thread sees the update to top before the zeroing of the 337 // object header and the BOT initialization. 338 OrderAccess::storestore(); 339 340 // Now, we will update the top fields of the "continues humongous" 341 // regions except the last one. 342 for (uint i = first; i < last; ++i) { 343 hr = region_at(i); 344 hr->set_top(hr->end()); 345 } 346 347 hr = region_at(last); 348 // If we cannot fit a filler object, we must set top to the end 349 // of the humongous object, otherwise we cannot iterate the heap 350 // and the BOT will not be complete. 351 hr->set_top(hr->end() - words_not_fillable); 352 353 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 354 "obj_top should be in last region"); 355 356 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 357 358 assert(words_not_fillable == 0 || 359 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 360 "Miscalculation in humongous allocation"); 361 362 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 363 364 for (uint i = first; i <= last; ++i) { 365 hr = region_at(i); 366 _humongous_set.add(hr); 367 _hr_printer.alloc(hr); 368 } 369 370 return new_obj; 371 } 372 373 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 374 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 375 return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 376 } 377 378 // If could fit into free regions w/o expansion, try. 379 // Otherwise, if can expand, do so. 380 // Otherwise, if using ex regions might help, try with ex given back. 381 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 382 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 383 384 _verifier->verify_region_sets_optional(); 385 386 uint first = G1_NO_HRM_INDEX; 387 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 388 389 if (obj_regions == 1) { 390 // Only one region to allocate, try to use a fast path by directly allocating 391 // from the free lists. Do not try to expand here, we will potentially do that 392 // later. 393 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 394 if (hr != NULL) { 395 first = hr->hrm_index(); 396 } 397 } else { 398 // We can't allocate humongous regions spanning more than one region while 399 // cleanupComplete() is running, since some of the regions we find to be 400 // empty might not yet be added to the free list. It is not straightforward 401 // to know in which list they are on so that we can remove them. We only 402 // need to do this if we need to allocate more than one region to satisfy the 403 // current humongous allocation request. If we are only allocating one region 404 // we use the one-region region allocation code (see above), that already 405 // potentially waits for regions from the secondary free list. 406 wait_while_free_regions_coming(); 407 append_secondary_free_list_if_not_empty_with_lock(); 408 409 // Policy: Try only empty regions (i.e. already committed first). Maybe we 410 // are lucky enough to find some. 411 first = _hrm.find_contiguous_only_empty(obj_regions); 412 if (first != G1_NO_HRM_INDEX) { 413 _hrm.allocate_free_regions_starting_at(first, obj_regions); 414 } 415 } 416 417 if (first == G1_NO_HRM_INDEX) { 418 // Policy: We could not find enough regions for the humongous object in the 419 // free list. Look through the heap to find a mix of free and uncommitted regions. 420 // If so, try expansion. 421 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 422 if (first != G1_NO_HRM_INDEX) { 423 // We found something. Make sure these regions are committed, i.e. expand 424 // the heap. Alternatively we could do a defragmentation GC. 425 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 426 word_size * HeapWordSize); 427 428 _hrm.expand_at(first, obj_regions, workers()); 429 g1_policy()->record_new_heap_size(num_regions()); 430 431 #ifdef ASSERT 432 for (uint i = first; i < first + obj_regions; ++i) { 433 HeapRegion* hr = region_at(i); 434 assert(hr->is_free(), "sanity"); 435 assert(hr->is_empty(), "sanity"); 436 assert(is_on_master_free_list(hr), "sanity"); 437 } 438 #endif 439 _hrm.allocate_free_regions_starting_at(first, obj_regions); 440 } else { 441 // Policy: Potentially trigger a defragmentation GC. 442 } 443 } 444 445 HeapWord* result = NULL; 446 if (first != G1_NO_HRM_INDEX) { 447 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 448 word_size, context); 449 assert(result != NULL, "it should always return a valid result"); 450 451 // A successful humongous object allocation changes the used space 452 // information of the old generation so we need to recalculate the 453 // sizes and update the jstat counters here. 454 g1mm()->update_sizes(); 455 } 456 457 _verifier->verify_region_sets_optional(); 458 459 return result; 460 } 461 462 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 463 assert_heap_not_locked_and_not_at_safepoint(); 464 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 465 466 uint dummy_gc_count_before; 467 uint dummy_gclocker_retry_count = 0; 468 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 469 } 470 471 HeapWord* 472 G1CollectedHeap::mem_allocate(size_t word_size, 473 bool* gc_overhead_limit_was_exceeded) { 474 assert_heap_not_locked_and_not_at_safepoint(); 475 476 // Loop until the allocation is satisfied, or unsatisfied after GC. 477 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 478 uint gc_count_before; 479 480 HeapWord* result = NULL; 481 if (!is_humongous(word_size)) { 482 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 483 } else { 484 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 485 } 486 if (result != NULL) { 487 return result; 488 } 489 490 // Create the garbage collection operation... 491 VM_G1CollectForAllocation op(gc_count_before, word_size); 492 op.set_allocation_context(AllocationContext::current()); 493 494 // ...and get the VM thread to execute it. 495 VMThread::execute(&op); 496 497 if (op.prologue_succeeded() && op.pause_succeeded()) { 498 // If the operation was successful we'll return the result even 499 // if it is NULL. If the allocation attempt failed immediately 500 // after a Full GC, it's unlikely we'll be able to allocate now. 501 HeapWord* result = op.result(); 502 if (result != NULL && !is_humongous(word_size)) { 503 // Allocations that take place on VM operations do not do any 504 // card dirtying and we have to do it here. We only have to do 505 // this for non-humongous allocations, though. 506 dirty_young_block(result, word_size); 507 } 508 return result; 509 } else { 510 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 511 return NULL; 512 } 513 assert(op.result() == NULL, 514 "the result should be NULL if the VM op did not succeed"); 515 } 516 517 // Give a warning if we seem to be looping forever. 518 if ((QueuedAllocationWarningCount > 0) && 519 (try_count % QueuedAllocationWarningCount == 0)) { 520 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count); 521 } 522 } 523 524 ShouldNotReachHere(); 525 return NULL; 526 } 527 528 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 529 AllocationContext_t context, 530 uint* gc_count_before_ret, 531 uint* gclocker_retry_count_ret) { 532 // Make sure you read the note in attempt_allocation_humongous(). 533 534 assert_heap_not_locked_and_not_at_safepoint(); 535 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 536 "be called for humongous allocation requests"); 537 538 // We should only get here after the first-level allocation attempt 539 // (attempt_allocation()) failed to allocate. 540 541 // We will loop until a) we manage to successfully perform the 542 // allocation or b) we successfully schedule a collection which 543 // fails to perform the allocation. b) is the only case when we'll 544 // return NULL. 545 HeapWord* result = NULL; 546 for (int try_count = 1; /* we'll return */; try_count += 1) { 547 bool should_try_gc; 548 uint gc_count_before; 549 550 { 551 MutexLockerEx x(Heap_lock); 552 result = _allocator->attempt_allocation_locked(word_size, context); 553 if (result != NULL) { 554 return result; 555 } 556 557 if (GCLocker::is_active_and_needs_gc()) { 558 if (g1_policy()->can_expand_young_list()) { 559 // No need for an ergo verbose message here, 560 // can_expand_young_list() does this when it returns true. 561 result = _allocator->attempt_allocation_force(word_size, context); 562 if (result != NULL) { 563 return result; 564 } 565 } 566 should_try_gc = false; 567 } else { 568 // The GCLocker may not be active but the GCLocker initiated 569 // GC may not yet have been performed (GCLocker::needs_gc() 570 // returns true). In this case we do not try this GC and 571 // wait until the GCLocker initiated GC is performed, and 572 // then retry the allocation. 573 if (GCLocker::needs_gc()) { 574 should_try_gc = false; 575 } else { 576 // Read the GC count while still holding the Heap_lock. 577 gc_count_before = total_collections(); 578 should_try_gc = true; 579 } 580 } 581 } 582 583 if (should_try_gc) { 584 bool succeeded; 585 result = do_collection_pause(word_size, gc_count_before, &succeeded, 586 GCCause::_g1_inc_collection_pause); 587 if (result != NULL) { 588 assert(succeeded, "only way to get back a non-NULL result"); 589 return result; 590 } 591 592 if (succeeded) { 593 // If we get here we successfully scheduled a collection which 594 // failed to allocate. No point in trying to allocate 595 // further. We'll just return NULL. 596 MutexLockerEx x(Heap_lock); 597 *gc_count_before_ret = total_collections(); 598 return NULL; 599 } 600 } else { 601 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 602 MutexLockerEx x(Heap_lock); 603 *gc_count_before_ret = total_collections(); 604 return NULL; 605 } 606 // The GCLocker is either active or the GCLocker initiated 607 // GC has not yet been performed. Stall until it is and 608 // then retry the allocation. 609 GCLocker::stall_until_clear(); 610 (*gclocker_retry_count_ret) += 1; 611 } 612 613 // We can reach here if we were unsuccessful in scheduling a 614 // collection (because another thread beat us to it) or if we were 615 // stalled due to the GC locker. In either can we should retry the 616 // allocation attempt in case another thread successfully 617 // performed a collection and reclaimed enough space. We do the 618 // first attempt (without holding the Heap_lock) here and the 619 // follow-on attempt will be at the start of the next loop 620 // iteration (after taking the Heap_lock). 621 result = _allocator->attempt_allocation(word_size, context); 622 if (result != NULL) { 623 return result; 624 } 625 626 // Give a warning if we seem to be looping forever. 627 if ((QueuedAllocationWarningCount > 0) && 628 (try_count % QueuedAllocationWarningCount == 0)) { 629 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() " 630 "retries %d times", try_count); 631 } 632 } 633 634 ShouldNotReachHere(); 635 return NULL; 636 } 637 638 void G1CollectedHeap::begin_archive_alloc_range() { 639 assert_at_safepoint(true /* should_be_vm_thread */); 640 if (_archive_allocator == NULL) { 641 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 642 } 643 } 644 645 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 646 // Allocations in archive regions cannot be of a size that would be considered 647 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 648 // may be different at archive-restore time. 649 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 650 } 651 652 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 653 assert_at_safepoint(true /* should_be_vm_thread */); 654 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 655 if (is_archive_alloc_too_large(word_size)) { 656 return NULL; 657 } 658 return _archive_allocator->archive_mem_allocate(word_size); 659 } 660 661 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 662 size_t end_alignment_in_bytes) { 663 assert_at_safepoint(true /* should_be_vm_thread */); 664 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 665 666 // Call complete_archive to do the real work, filling in the MemRegion 667 // array with the archive regions. 668 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 669 delete _archive_allocator; 670 _archive_allocator = NULL; 671 } 672 673 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 674 assert(ranges != NULL, "MemRegion array NULL"); 675 assert(count != 0, "No MemRegions provided"); 676 MemRegion reserved = _hrm.reserved(); 677 for (size_t i = 0; i < count; i++) { 678 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 679 return false; 680 } 681 } 682 return true; 683 } 684 685 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 686 assert(!is_init_completed(), "Expect to be called at JVM init time"); 687 assert(ranges != NULL, "MemRegion array NULL"); 688 assert(count != 0, "No MemRegions provided"); 689 MutexLockerEx x(Heap_lock); 690 691 MemRegion reserved = _hrm.reserved(); 692 HeapWord* prev_last_addr = NULL; 693 HeapRegion* prev_last_region = NULL; 694 695 // Temporarily disable pretouching of heap pages. This interface is used 696 // when mmap'ing archived heap data in, so pre-touching is wasted. 697 FlagSetting fs(AlwaysPreTouch, false); 698 699 // Enable archive object checking used by G1MarkSweep. We have to let it know 700 // about each archive range, so that objects in those ranges aren't marked. 701 G1ArchiveAllocator::enable_archive_object_check(); 702 703 // For each specified MemRegion range, allocate the corresponding G1 704 // regions and mark them as archive regions. We expect the ranges in 705 // ascending starting address order, without overlap. 706 for (size_t i = 0; i < count; i++) { 707 MemRegion curr_range = ranges[i]; 708 HeapWord* start_address = curr_range.start(); 709 size_t word_size = curr_range.word_size(); 710 HeapWord* last_address = curr_range.last(); 711 size_t commits = 0; 712 713 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 714 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 715 p2i(start_address), p2i(last_address)); 716 guarantee(start_address > prev_last_addr, 717 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 718 p2i(start_address), p2i(prev_last_addr)); 719 prev_last_addr = last_address; 720 721 // Check for ranges that start in the same G1 region in which the previous 722 // range ended, and adjust the start address so we don't try to allocate 723 // the same region again. If the current range is entirely within that 724 // region, skip it, just adjusting the recorded top. 725 HeapRegion* start_region = _hrm.addr_to_region(start_address); 726 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 727 start_address = start_region->end(); 728 if (start_address > last_address) { 729 increase_used(word_size * HeapWordSize); 730 start_region->set_top(last_address + 1); 731 continue; 732 } 733 start_region->set_top(start_address); 734 curr_range = MemRegion(start_address, last_address + 1); 735 start_region = _hrm.addr_to_region(start_address); 736 } 737 738 // Perform the actual region allocation, exiting if it fails. 739 // Then note how much new space we have allocated. 740 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 741 return false; 742 } 743 increase_used(word_size * HeapWordSize); 744 if (commits != 0) { 745 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 746 HeapRegion::GrainWords * HeapWordSize * commits); 747 748 } 749 750 // Mark each G1 region touched by the range as archive, add it to the old set, 751 // and set the allocation context and top. 752 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 753 HeapRegion* last_region = _hrm.addr_to_region(last_address); 754 prev_last_region = last_region; 755 756 while (curr_region != NULL) { 757 assert(curr_region->is_empty() && !curr_region->is_pinned(), 758 "Region already in use (index %u)", curr_region->hrm_index()); 759 curr_region->set_allocation_context(AllocationContext::system()); 760 curr_region->set_archive(); 761 _hr_printer.alloc(curr_region); 762 _old_set.add(curr_region); 763 if (curr_region != last_region) { 764 curr_region->set_top(curr_region->end()); 765 curr_region = _hrm.next_region_in_heap(curr_region); 766 } else { 767 curr_region->set_top(last_address + 1); 768 curr_region = NULL; 769 } 770 } 771 772 // Notify mark-sweep of the archive range. 773 G1ArchiveAllocator::set_range_archive(curr_range, true); 774 } 775 return true; 776 } 777 778 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 779 assert(!is_init_completed(), "Expect to be called at JVM init time"); 780 assert(ranges != NULL, "MemRegion array NULL"); 781 assert(count != 0, "No MemRegions provided"); 782 MemRegion reserved = _hrm.reserved(); 783 HeapWord *prev_last_addr = NULL; 784 HeapRegion* prev_last_region = NULL; 785 786 // For each MemRegion, create filler objects, if needed, in the G1 regions 787 // that contain the address range. The address range actually within the 788 // MemRegion will not be modified. That is assumed to have been initialized 789 // elsewhere, probably via an mmap of archived heap data. 790 MutexLockerEx x(Heap_lock); 791 for (size_t i = 0; i < count; i++) { 792 HeapWord* start_address = ranges[i].start(); 793 HeapWord* last_address = ranges[i].last(); 794 795 assert(reserved.contains(start_address) && reserved.contains(last_address), 796 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 797 p2i(start_address), p2i(last_address)); 798 assert(start_address > prev_last_addr, 799 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 800 p2i(start_address), p2i(prev_last_addr)); 801 802 HeapRegion* start_region = _hrm.addr_to_region(start_address); 803 HeapRegion* last_region = _hrm.addr_to_region(last_address); 804 HeapWord* bottom_address = start_region->bottom(); 805 806 // Check for a range beginning in the same region in which the 807 // previous one ended. 808 if (start_region == prev_last_region) { 809 bottom_address = prev_last_addr + 1; 810 } 811 812 // Verify that the regions were all marked as archive regions by 813 // alloc_archive_regions. 814 HeapRegion* curr_region = start_region; 815 while (curr_region != NULL) { 816 guarantee(curr_region->is_archive(), 817 "Expected archive region at index %u", curr_region->hrm_index()); 818 if (curr_region != last_region) { 819 curr_region = _hrm.next_region_in_heap(curr_region); 820 } else { 821 curr_region = NULL; 822 } 823 } 824 825 prev_last_addr = last_address; 826 prev_last_region = last_region; 827 828 // Fill the memory below the allocated range with dummy object(s), 829 // if the region bottom does not match the range start, or if the previous 830 // range ended within the same G1 region, and there is a gap. 831 if (start_address != bottom_address) { 832 size_t fill_size = pointer_delta(start_address, bottom_address); 833 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 834 increase_used(fill_size * HeapWordSize); 835 } 836 } 837 } 838 839 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 840 uint* gc_count_before_ret, 841 uint* gclocker_retry_count_ret) { 842 assert_heap_not_locked_and_not_at_safepoint(); 843 assert(!is_humongous(word_size), "attempt_allocation() should not " 844 "be called for humongous allocation requests"); 845 846 AllocationContext_t context = AllocationContext::current(); 847 HeapWord* result = _allocator->attempt_allocation(word_size, context); 848 849 if (result == NULL) { 850 result = attempt_allocation_slow(word_size, 851 context, 852 gc_count_before_ret, 853 gclocker_retry_count_ret); 854 } 855 assert_heap_not_locked(); 856 if (result != NULL) { 857 dirty_young_block(result, word_size); 858 } 859 return result; 860 } 861 862 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 863 assert(!is_init_completed(), "Expect to be called at JVM init time"); 864 assert(ranges != NULL, "MemRegion array NULL"); 865 assert(count != 0, "No MemRegions provided"); 866 MemRegion reserved = _hrm.reserved(); 867 HeapWord* prev_last_addr = NULL; 868 HeapRegion* prev_last_region = NULL; 869 size_t size_used = 0; 870 size_t uncommitted_regions = 0; 871 872 // For each Memregion, free the G1 regions that constitute it, and 873 // notify mark-sweep that the range is no longer to be considered 'archive.' 874 MutexLockerEx x(Heap_lock); 875 for (size_t i = 0; i < count; i++) { 876 HeapWord* start_address = ranges[i].start(); 877 HeapWord* last_address = ranges[i].last(); 878 879 assert(reserved.contains(start_address) && reserved.contains(last_address), 880 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 881 p2i(start_address), p2i(last_address)); 882 assert(start_address > prev_last_addr, 883 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 884 p2i(start_address), p2i(prev_last_addr)); 885 size_used += ranges[i].byte_size(); 886 prev_last_addr = last_address; 887 888 HeapRegion* start_region = _hrm.addr_to_region(start_address); 889 HeapRegion* last_region = _hrm.addr_to_region(last_address); 890 891 // Check for ranges that start in the same G1 region in which the previous 892 // range ended, and adjust the start address so we don't try to free 893 // the same region again. If the current range is entirely within that 894 // region, skip it. 895 if (start_region == prev_last_region) { 896 start_address = start_region->end(); 897 if (start_address > last_address) { 898 continue; 899 } 900 start_region = _hrm.addr_to_region(start_address); 901 } 902 prev_last_region = last_region; 903 904 // After verifying that each region was marked as an archive region by 905 // alloc_archive_regions, set it free and empty and uncommit it. 906 HeapRegion* curr_region = start_region; 907 while (curr_region != NULL) { 908 guarantee(curr_region->is_archive(), 909 "Expected archive region at index %u", curr_region->hrm_index()); 910 uint curr_index = curr_region->hrm_index(); 911 _old_set.remove(curr_region); 912 curr_region->set_free(); 913 curr_region->set_top(curr_region->bottom()); 914 if (curr_region != last_region) { 915 curr_region = _hrm.next_region_in_heap(curr_region); 916 } else { 917 curr_region = NULL; 918 } 919 _hrm.shrink_at(curr_index, 1); 920 uncommitted_regions++; 921 } 922 923 // Notify mark-sweep that this is no longer an archive range. 924 G1ArchiveAllocator::set_range_archive(ranges[i], false); 925 } 926 927 if (uncommitted_regions != 0) { 928 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 929 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 930 } 931 decrease_used(size_used); 932 } 933 934 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 935 uint* gc_count_before_ret, 936 uint* gclocker_retry_count_ret) { 937 // The structure of this method has a lot of similarities to 938 // attempt_allocation_slow(). The reason these two were not merged 939 // into a single one is that such a method would require several "if 940 // allocation is not humongous do this, otherwise do that" 941 // conditional paths which would obscure its flow. In fact, an early 942 // version of this code did use a unified method which was harder to 943 // follow and, as a result, it had subtle bugs that were hard to 944 // track down. So keeping these two methods separate allows each to 945 // be more readable. It will be good to keep these two in sync as 946 // much as possible. 947 948 assert_heap_not_locked_and_not_at_safepoint(); 949 assert(is_humongous(word_size), "attempt_allocation_humongous() " 950 "should only be called for humongous allocations"); 951 952 // Humongous objects can exhaust the heap quickly, so we should check if we 953 // need to start a marking cycle at each humongous object allocation. We do 954 // the check before we do the actual allocation. The reason for doing it 955 // before the allocation is that we avoid having to keep track of the newly 956 // allocated memory while we do a GC. 957 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 958 word_size)) { 959 collect(GCCause::_g1_humongous_allocation); 960 } 961 962 // We will loop until a) we manage to successfully perform the 963 // allocation or b) we successfully schedule a collection which 964 // fails to perform the allocation. b) is the only case when we'll 965 // return NULL. 966 HeapWord* result = NULL; 967 for (int try_count = 1; /* we'll return */; try_count += 1) { 968 bool should_try_gc; 969 uint gc_count_before; 970 971 { 972 MutexLockerEx x(Heap_lock); 973 974 // Given that humongous objects are not allocated in young 975 // regions, we'll first try to do the allocation without doing a 976 // collection hoping that there's enough space in the heap. 977 result = humongous_obj_allocate(word_size, AllocationContext::current()); 978 if (result != NULL) { 979 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 980 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 981 return result; 982 } 983 984 if (GCLocker::is_active_and_needs_gc()) { 985 should_try_gc = false; 986 } else { 987 // The GCLocker may not be active but the GCLocker initiated 988 // GC may not yet have been performed (GCLocker::needs_gc() 989 // returns true). In this case we do not try this GC and 990 // wait until the GCLocker initiated GC is performed, and 991 // then retry the allocation. 992 if (GCLocker::needs_gc()) { 993 should_try_gc = false; 994 } else { 995 // Read the GC count while still holding the Heap_lock. 996 gc_count_before = total_collections(); 997 should_try_gc = true; 998 } 999 } 1000 } 1001 1002 if (should_try_gc) { 1003 // If we failed to allocate the humongous object, we should try to 1004 // do a collection pause (if we're allowed) in case it reclaims 1005 // enough space for the allocation to succeed after the pause. 1006 1007 bool succeeded; 1008 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1009 GCCause::_g1_humongous_allocation); 1010 if (result != NULL) { 1011 assert(succeeded, "only way to get back a non-NULL result"); 1012 return result; 1013 } 1014 1015 if (succeeded) { 1016 // If we get here we successfully scheduled a collection which 1017 // failed to allocate. No point in trying to allocate 1018 // further. We'll just return NULL. 1019 MutexLockerEx x(Heap_lock); 1020 *gc_count_before_ret = total_collections(); 1021 return NULL; 1022 } 1023 } else { 1024 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1025 MutexLockerEx x(Heap_lock); 1026 *gc_count_before_ret = total_collections(); 1027 return NULL; 1028 } 1029 // The GCLocker is either active or the GCLocker initiated 1030 // GC has not yet been performed. Stall until it is and 1031 // then retry the allocation. 1032 GCLocker::stall_until_clear(); 1033 (*gclocker_retry_count_ret) += 1; 1034 } 1035 1036 // We can reach here if we were unsuccessful in scheduling a 1037 // collection (because another thread beat us to it) or if we were 1038 // stalled due to the GC locker. In either can we should retry the 1039 // allocation attempt in case another thread successfully 1040 // performed a collection and reclaimed enough space. Give a 1041 // warning if we seem to be looping forever. 1042 1043 if ((QueuedAllocationWarningCount > 0) && 1044 (try_count % QueuedAllocationWarningCount == 0)) { 1045 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() " 1046 "retries %d times", try_count); 1047 } 1048 } 1049 1050 ShouldNotReachHere(); 1051 return NULL; 1052 } 1053 1054 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1055 AllocationContext_t context, 1056 bool expect_null_mutator_alloc_region) { 1057 assert_at_safepoint(true /* should_be_vm_thread */); 1058 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1059 "the current alloc region was unexpectedly found to be non-NULL"); 1060 1061 if (!is_humongous(word_size)) { 1062 return _allocator->attempt_allocation_locked(word_size, context); 1063 } else { 1064 HeapWord* result = humongous_obj_allocate(word_size, context); 1065 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1066 collector_state()->set_initiate_conc_mark_if_possible(true); 1067 } 1068 return result; 1069 } 1070 1071 ShouldNotReachHere(); 1072 } 1073 1074 class PostMCRemSetClearClosure: public HeapRegionClosure { 1075 G1CollectedHeap* _g1h; 1076 ModRefBarrierSet* _mr_bs; 1077 public: 1078 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1079 _g1h(g1h), _mr_bs(mr_bs) {} 1080 1081 bool doHeapRegion(HeapRegion* r) { 1082 HeapRegionRemSet* hrrs = r->rem_set(); 1083 1084 _g1h->reset_gc_time_stamps(r); 1085 1086 if (r->is_continues_humongous()) { 1087 // We'll assert that the strong code root list and RSet is empty 1088 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1089 assert(hrrs->occupied() == 0, "RSet should be empty"); 1090 } else { 1091 hrrs->clear(); 1092 } 1093 // You might think here that we could clear just the cards 1094 // corresponding to the used region. But no: if we leave a dirty card 1095 // in a region we might allocate into, then it would prevent that card 1096 // from being enqueued, and cause it to be missed. 1097 // Re: the performance cost: we shouldn't be doing full GC anyway! 1098 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1099 1100 return false; 1101 } 1102 }; 1103 1104 void G1CollectedHeap::clear_rsets_post_compaction() { 1105 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1106 heap_region_iterate(&rs_clear); 1107 } 1108 1109 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1110 G1CollectedHeap* _g1h; 1111 RebuildRSOopClosure _cl; 1112 public: 1113 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1114 _cl(g1->g1_rem_set(), worker_i), 1115 _g1h(g1) 1116 { } 1117 1118 bool doHeapRegion(HeapRegion* r) { 1119 if (!r->is_continues_humongous()) { 1120 _cl.set_from(r); 1121 r->oop_iterate(&_cl); 1122 } 1123 return false; 1124 } 1125 }; 1126 1127 class ParRebuildRSTask: public AbstractGangTask { 1128 G1CollectedHeap* _g1; 1129 HeapRegionClaimer _hrclaimer; 1130 1131 public: 1132 ParRebuildRSTask(G1CollectedHeap* g1) : 1133 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1134 1135 void work(uint worker_id) { 1136 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1137 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1138 } 1139 }; 1140 1141 class PostCompactionPrinterClosure: public HeapRegionClosure { 1142 private: 1143 G1HRPrinter* _hr_printer; 1144 public: 1145 bool doHeapRegion(HeapRegion* hr) { 1146 assert(!hr->is_young(), "not expecting to find young regions"); 1147 _hr_printer->post_compaction(hr); 1148 return false; 1149 } 1150 1151 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1152 : _hr_printer(hr_printer) { } 1153 }; 1154 1155 void G1CollectedHeap::print_hrm_post_compaction() { 1156 if (_hr_printer.is_active()) { 1157 PostCompactionPrinterClosure cl(hr_printer()); 1158 heap_region_iterate(&cl); 1159 } 1160 1161 } 1162 1163 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1164 bool clear_all_soft_refs) { 1165 assert_at_safepoint(true /* should_be_vm_thread */); 1166 1167 if (GCLocker::check_active_before_gc()) { 1168 return false; 1169 } 1170 1171 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1172 gc_timer->register_gc_start(); 1173 1174 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1175 GCIdMark gc_id_mark; 1176 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1177 1178 SvcGCMarker sgcm(SvcGCMarker::FULL); 1179 ResourceMark rm; 1180 1181 print_heap_before_gc(); 1182 print_heap_regions(); 1183 trace_heap_before_gc(gc_tracer); 1184 1185 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1186 1187 _verifier->verify_region_sets_optional(); 1188 1189 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1190 collector_policy()->should_clear_all_soft_refs(); 1191 1192 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1193 1194 { 1195 IsGCActiveMark x; 1196 1197 // Timing 1198 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1199 GCTraceCPUTime tcpu; 1200 1201 { 1202 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1203 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1204 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1205 1206 G1HeapTransition heap_transition(this); 1207 g1_policy()->record_full_collection_start(); 1208 1209 // Note: When we have a more flexible GC logging framework that 1210 // allows us to add optional attributes to a GC log record we 1211 // could consider timing and reporting how long we wait in the 1212 // following two methods. 1213 wait_while_free_regions_coming(); 1214 // If we start the compaction before the CM threads finish 1215 // scanning the root regions we might trip them over as we'll 1216 // be moving objects / updating references. So let's wait until 1217 // they are done. By telling them to abort, they should complete 1218 // early. 1219 _cm->root_regions()->abort(); 1220 _cm->root_regions()->wait_until_scan_finished(); 1221 append_secondary_free_list_if_not_empty_with_lock(); 1222 1223 gc_prologue(true); 1224 increment_total_collections(true /* full gc */); 1225 increment_old_marking_cycles_started(); 1226 1227 assert(used() == recalculate_used(), "Should be equal"); 1228 1229 _verifier->verify_before_gc(); 1230 1231 _verifier->check_bitmaps("Full GC Start"); 1232 pre_full_gc_dump(gc_timer); 1233 1234 #if defined(COMPILER2) || INCLUDE_JVMCI 1235 DerivedPointerTable::clear(); 1236 #endif 1237 1238 // Disable discovery and empty the discovered lists 1239 // for the CM ref processor. 1240 ref_processor_cm()->disable_discovery(); 1241 ref_processor_cm()->abandon_partial_discovery(); 1242 ref_processor_cm()->verify_no_references_recorded(); 1243 1244 // Abandon current iterations of concurrent marking and concurrent 1245 // refinement, if any are in progress. 1246 concurrent_mark()->abort(); 1247 1248 // Make sure we'll choose a new allocation region afterwards. 1249 _allocator->release_mutator_alloc_region(); 1250 _allocator->abandon_gc_alloc_regions(); 1251 g1_rem_set()->cleanupHRRS(); 1252 1253 // We may have added regions to the current incremental collection 1254 // set between the last GC or pause and now. We need to clear the 1255 // incremental collection set and then start rebuilding it afresh 1256 // after this full GC. 1257 abandon_collection_set(collection_set()); 1258 1259 tear_down_region_sets(false /* free_list_only */); 1260 collector_state()->set_gcs_are_young(true); 1261 1262 // See the comments in g1CollectedHeap.hpp and 1263 // G1CollectedHeap::ref_processing_init() about 1264 // how reference processing currently works in G1. 1265 1266 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1267 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1268 1269 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1270 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1271 1272 ref_processor_stw()->enable_discovery(); 1273 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1274 1275 // Do collection work 1276 { 1277 HandleMark hm; // Discard invalid handles created during gc 1278 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1279 } 1280 1281 assert(num_free_regions() == 0, "we should not have added any free regions"); 1282 rebuild_region_sets(false /* free_list_only */); 1283 1284 // Enqueue any discovered reference objects that have 1285 // not been removed from the discovered lists. 1286 ref_processor_stw()->enqueue_discovered_references(); 1287 1288 #if defined(COMPILER2) || INCLUDE_JVMCI 1289 DerivedPointerTable::update_pointers(); 1290 #endif 1291 1292 MemoryService::track_memory_usage(); 1293 1294 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1295 ref_processor_stw()->verify_no_references_recorded(); 1296 1297 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1298 ClassLoaderDataGraph::purge(); 1299 MetaspaceAux::verify_metrics(); 1300 1301 // Note: since we've just done a full GC, concurrent 1302 // marking is no longer active. Therefore we need not 1303 // re-enable reference discovery for the CM ref processor. 1304 // That will be done at the start of the next marking cycle. 1305 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1306 ref_processor_cm()->verify_no_references_recorded(); 1307 1308 reset_gc_time_stamp(); 1309 // Since everything potentially moved, we will clear all remembered 1310 // sets, and clear all cards. Later we will rebuild remembered 1311 // sets. We will also reset the GC time stamps of the regions. 1312 clear_rsets_post_compaction(); 1313 check_gc_time_stamps(); 1314 1315 resize_if_necessary_after_full_collection(); 1316 1317 // We should do this after we potentially resize the heap so 1318 // that all the COMMIT / UNCOMMIT events are generated before 1319 // the compaction events. 1320 print_hrm_post_compaction(); 1321 1322 if (_hot_card_cache->use_cache()) { 1323 _hot_card_cache->reset_card_counts(); 1324 _hot_card_cache->reset_hot_cache(); 1325 } 1326 1327 // Rebuild remembered sets of all regions. 1328 uint n_workers = 1329 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1330 workers()->active_workers(), 1331 Threads::number_of_non_daemon_threads()); 1332 workers()->update_active_workers(n_workers); 1333 log_info(gc,task)("Using %u workers of %u to rebuild remembered set", n_workers, workers()->total_workers()); 1334 1335 ParRebuildRSTask rebuild_rs_task(this); 1336 workers()->run_task(&rebuild_rs_task); 1337 1338 // Rebuild the strong code root lists for each region 1339 rebuild_strong_code_roots(); 1340 1341 if (true) { // FIXME 1342 MetaspaceGC::compute_new_size(); 1343 } 1344 1345 #ifdef TRACESPINNING 1346 ParallelTaskTerminator::print_termination_counts(); 1347 #endif 1348 1349 // Discard all rset updates 1350 JavaThread::dirty_card_queue_set().abandon_logs(); 1351 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1352 1353 // At this point there should be no regions in the 1354 // entire heap tagged as young. 1355 assert(check_young_list_empty(), "young list should be empty at this point"); 1356 1357 // Update the number of full collections that have been completed. 1358 increment_old_marking_cycles_completed(false /* concurrent */); 1359 1360 _hrm.verify_optional(); 1361 _verifier->verify_region_sets_optional(); 1362 1363 _verifier->verify_after_gc(); 1364 1365 // Clear the previous marking bitmap, if needed for bitmap verification. 1366 // Note we cannot do this when we clear the next marking bitmap in 1367 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1368 // objects marked during a full GC against the previous bitmap. 1369 // But we need to clear it before calling check_bitmaps below since 1370 // the full GC has compacted objects and updated TAMS but not updated 1371 // the prev bitmap. 1372 if (G1VerifyBitmaps) { 1373 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1374 _cm->clear_prev_bitmap(workers()); 1375 } 1376 _verifier->check_bitmaps("Full GC End"); 1377 1378 start_new_collection_set(); 1379 1380 _allocator->init_mutator_alloc_region(); 1381 1382 g1_policy()->record_full_collection_end(); 1383 1384 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1385 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1386 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1387 // before any GC notifications are raised. 1388 g1mm()->update_sizes(); 1389 1390 gc_epilogue(true); 1391 1392 heap_transition.print(); 1393 1394 print_heap_after_gc(); 1395 print_heap_regions(); 1396 trace_heap_after_gc(gc_tracer); 1397 1398 post_full_gc_dump(gc_timer); 1399 } 1400 1401 gc_timer->register_gc_end(); 1402 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1403 } 1404 1405 return true; 1406 } 1407 1408 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1409 // Currently, there is no facility in the do_full_collection(bool) API to notify 1410 // the caller that the collection did not succeed (e.g., because it was locked 1411 // out by the GC locker). So, right now, we'll ignore the return value. 1412 bool dummy = do_full_collection(true, /* explicit_gc */ 1413 clear_all_soft_refs); 1414 } 1415 1416 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1417 // Include bytes that will be pre-allocated to support collections, as "used". 1418 const size_t used_after_gc = used(); 1419 const size_t capacity_after_gc = capacity(); 1420 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1421 1422 // This is enforced in arguments.cpp. 1423 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1424 "otherwise the code below doesn't make sense"); 1425 1426 // We don't have floating point command-line arguments 1427 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1428 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1429 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1430 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1431 1432 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1433 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1434 1435 // We have to be careful here as these two calculations can overflow 1436 // 32-bit size_t's. 1437 double used_after_gc_d = (double) used_after_gc; 1438 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1439 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1440 1441 // Let's make sure that they are both under the max heap size, which 1442 // by default will make them fit into a size_t. 1443 double desired_capacity_upper_bound = (double) max_heap_size; 1444 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1445 desired_capacity_upper_bound); 1446 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1447 desired_capacity_upper_bound); 1448 1449 // We can now safely turn them into size_t's. 1450 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1451 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1452 1453 // This assert only makes sense here, before we adjust them 1454 // with respect to the min and max heap size. 1455 assert(minimum_desired_capacity <= maximum_desired_capacity, 1456 "minimum_desired_capacity = " SIZE_FORMAT ", " 1457 "maximum_desired_capacity = " SIZE_FORMAT, 1458 minimum_desired_capacity, maximum_desired_capacity); 1459 1460 // Should not be greater than the heap max size. No need to adjust 1461 // it with respect to the heap min size as it's a lower bound (i.e., 1462 // we'll try to make the capacity larger than it, not smaller). 1463 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1464 // Should not be less than the heap min size. No need to adjust it 1465 // with respect to the heap max size as it's an upper bound (i.e., 1466 // we'll try to make the capacity smaller than it, not greater). 1467 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1468 1469 if (capacity_after_gc < minimum_desired_capacity) { 1470 // Don't expand unless it's significant 1471 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1472 1473 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1474 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1475 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1476 1477 expand(expand_bytes, _workers); 1478 1479 // No expansion, now see if we want to shrink 1480 } else if (capacity_after_gc > maximum_desired_capacity) { 1481 // Capacity too large, compute shrinking size 1482 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1483 1484 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1485 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1486 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1487 1488 shrink(shrink_bytes); 1489 } 1490 } 1491 1492 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1493 AllocationContext_t context, 1494 bool do_gc, 1495 bool clear_all_soft_refs, 1496 bool expect_null_mutator_alloc_region, 1497 bool* gc_succeeded) { 1498 *gc_succeeded = true; 1499 // Let's attempt the allocation first. 1500 HeapWord* result = 1501 attempt_allocation_at_safepoint(word_size, 1502 context, 1503 expect_null_mutator_alloc_region); 1504 if (result != NULL) { 1505 assert(*gc_succeeded, "sanity"); 1506 return result; 1507 } 1508 1509 // In a G1 heap, we're supposed to keep allocation from failing by 1510 // incremental pauses. Therefore, at least for now, we'll favor 1511 // expansion over collection. (This might change in the future if we can 1512 // do something smarter than full collection to satisfy a failed alloc.) 1513 result = expand_and_allocate(word_size, context); 1514 if (result != NULL) { 1515 assert(*gc_succeeded, "sanity"); 1516 return result; 1517 } 1518 1519 if (do_gc) { 1520 // Expansion didn't work, we'll try to do a Full GC. 1521 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1522 clear_all_soft_refs); 1523 } 1524 1525 return NULL; 1526 } 1527 1528 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1529 AllocationContext_t context, 1530 bool* succeeded) { 1531 assert_at_safepoint(true /* should_be_vm_thread */); 1532 1533 // Attempts to allocate followed by Full GC. 1534 HeapWord* result = 1535 satisfy_failed_allocation_helper(word_size, 1536 context, 1537 true, /* do_gc */ 1538 false, /* clear_all_soft_refs */ 1539 false, /* expect_null_mutator_alloc_region */ 1540 succeeded); 1541 1542 if (result != NULL || !*succeeded) { 1543 return result; 1544 } 1545 1546 // Attempts to allocate followed by Full GC that will collect all soft references. 1547 result = satisfy_failed_allocation_helper(word_size, 1548 context, 1549 true, /* do_gc */ 1550 true, /* clear_all_soft_refs */ 1551 true, /* expect_null_mutator_alloc_region */ 1552 succeeded); 1553 1554 if (result != NULL || !*succeeded) { 1555 return result; 1556 } 1557 1558 // Attempts to allocate, no GC 1559 result = satisfy_failed_allocation_helper(word_size, 1560 context, 1561 false, /* do_gc */ 1562 false, /* clear_all_soft_refs */ 1563 true, /* expect_null_mutator_alloc_region */ 1564 succeeded); 1565 1566 if (result != NULL) { 1567 assert(*succeeded, "sanity"); 1568 return result; 1569 } 1570 1571 assert(!collector_policy()->should_clear_all_soft_refs(), 1572 "Flag should have been handled and cleared prior to this point"); 1573 1574 // What else? We might try synchronous finalization later. If the total 1575 // space available is large enough for the allocation, then a more 1576 // complete compaction phase than we've tried so far might be 1577 // appropriate. 1578 assert(*succeeded, "sanity"); 1579 return NULL; 1580 } 1581 1582 // Attempting to expand the heap sufficiently 1583 // to support an allocation of the given "word_size". If 1584 // successful, perform the allocation and return the address of the 1585 // allocated block, or else "NULL". 1586 1587 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1588 assert_at_safepoint(true /* should_be_vm_thread */); 1589 1590 _verifier->verify_region_sets_optional(); 1591 1592 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1593 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1594 word_size * HeapWordSize); 1595 1596 1597 if (expand(expand_bytes, _workers)) { 1598 _hrm.verify_optional(); 1599 _verifier->verify_region_sets_optional(); 1600 return attempt_allocation_at_safepoint(word_size, 1601 context, 1602 false /* expect_null_mutator_alloc_region */); 1603 } 1604 return NULL; 1605 } 1606 1607 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1608 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1609 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1610 HeapRegion::GrainBytes); 1611 1612 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1613 expand_bytes, aligned_expand_bytes); 1614 1615 if (is_maximal_no_gc()) { 1616 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1617 return false; 1618 } 1619 1620 double expand_heap_start_time_sec = os::elapsedTime(); 1621 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1622 assert(regions_to_expand > 0, "Must expand by at least one region"); 1623 1624 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers); 1625 if (expand_time_ms != NULL) { 1626 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1627 } 1628 1629 if (expanded_by > 0) { 1630 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1631 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1632 g1_policy()->record_new_heap_size(num_regions()); 1633 } else { 1634 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1635 1636 // The expansion of the virtual storage space was unsuccessful. 1637 // Let's see if it was because we ran out of swap. 1638 if (G1ExitOnExpansionFailure && 1639 _hrm.available() >= regions_to_expand) { 1640 // We had head room... 1641 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1642 } 1643 } 1644 return regions_to_expand > 0; 1645 } 1646 1647 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1648 size_t aligned_shrink_bytes = 1649 ReservedSpace::page_align_size_down(shrink_bytes); 1650 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1651 HeapRegion::GrainBytes); 1652 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1653 1654 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1655 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1656 1657 1658 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", 1659 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1660 if (num_regions_removed > 0) { 1661 g1_policy()->record_new_heap_size(num_regions()); 1662 } else { 1663 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1664 } 1665 } 1666 1667 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1668 _verifier->verify_region_sets_optional(); 1669 1670 // We should only reach here at the end of a Full GC which means we 1671 // should not not be holding to any GC alloc regions. The method 1672 // below will make sure of that and do any remaining clean up. 1673 _allocator->abandon_gc_alloc_regions(); 1674 1675 // Instead of tearing down / rebuilding the free lists here, we 1676 // could instead use the remove_all_pending() method on free_list to 1677 // remove only the ones that we need to remove. 1678 tear_down_region_sets(true /* free_list_only */); 1679 shrink_helper(shrink_bytes); 1680 rebuild_region_sets(true /* free_list_only */); 1681 1682 _hrm.verify_optional(); 1683 _verifier->verify_region_sets_optional(); 1684 } 1685 1686 // Public methods. 1687 1688 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1689 CollectedHeap(), 1690 _collector_policy(collector_policy), 1691 _g1_policy(create_g1_policy()), 1692 _collection_set(this, _g1_policy), 1693 _dirty_card_queue_set(false), 1694 _is_alive_closure_cm(this), 1695 _is_alive_closure_stw(this), 1696 _ref_processor_cm(NULL), 1697 _ref_processor_stw(NULL), 1698 _bot(NULL), 1699 _hot_card_cache(NULL), 1700 _g1_rem_set(NULL), 1701 _cg1r(NULL), 1702 _g1mm(NULL), 1703 _refine_cte_cl(NULL), 1704 _preserved_marks_set(true /* in_c_heap */), 1705 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1706 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1707 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1708 _humongous_reclaim_candidates(), 1709 _has_humongous_reclaim_candidates(false), 1710 _archive_allocator(NULL), 1711 _free_regions_coming(false), 1712 _gc_time_stamp(0), 1713 _summary_bytes_used(0), 1714 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1715 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1716 _expand_heap_after_alloc_failure(true), 1717 _old_marking_cycles_started(0), 1718 _old_marking_cycles_completed(0), 1719 _in_cset_fast_test(), 1720 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1721 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) { 1722 1723 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1724 /* are_GC_task_threads */true, 1725 /* are_ConcurrentGC_threads */false); 1726 _workers->initialize_workers(); 1727 _verifier = new G1HeapVerifier(this); 1728 1729 _allocator = G1Allocator::create_allocator(this); 1730 1731 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1732 1733 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1734 1735 // Override the default _filler_array_max_size so that no humongous filler 1736 // objects are created. 1737 _filler_array_max_size = _humongous_object_threshold_in_words; 1738 1739 uint n_queues = ParallelGCThreads; 1740 _task_queues = new RefToScanQueueSet(n_queues); 1741 1742 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1743 1744 for (uint i = 0; i < n_queues; i++) { 1745 RefToScanQueue* q = new RefToScanQueue(); 1746 q->initialize(); 1747 _task_queues->register_queue(i, q); 1748 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1749 } 1750 1751 // Initialize the G1EvacuationFailureALot counters and flags. 1752 NOT_PRODUCT(reset_evacuation_should_fail();) 1753 1754 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1755 } 1756 1757 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1758 size_t size, 1759 size_t translation_factor) { 1760 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1761 // Allocate a new reserved space, preferring to use large pages. 1762 ReservedSpace rs(size, preferred_page_size); 1763 G1RegionToSpaceMapper* result = 1764 G1RegionToSpaceMapper::create_mapper(rs, 1765 size, 1766 rs.alignment(), 1767 HeapRegion::GrainBytes, 1768 translation_factor, 1769 mtGC); 1770 1771 os::trace_page_sizes_for_requested_size(description, 1772 size, 1773 preferred_page_size, 1774 rs.alignment(), 1775 rs.base(), 1776 rs.size()); 1777 1778 return result; 1779 } 1780 1781 jint G1CollectedHeap::initialize() { 1782 CollectedHeap::pre_initialize(); 1783 os::enable_vtime(); 1784 1785 // Necessary to satisfy locking discipline assertions. 1786 1787 MutexLocker x(Heap_lock); 1788 1789 // While there are no constraints in the GC code that HeapWordSize 1790 // be any particular value, there are multiple other areas in the 1791 // system which believe this to be true (e.g. oop->object_size in some 1792 // cases incorrectly returns the size in wordSize units rather than 1793 // HeapWordSize). 1794 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1795 1796 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1797 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1798 size_t heap_alignment = collector_policy()->heap_alignment(); 1799 1800 // Ensure that the sizes are properly aligned. 1801 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1802 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1803 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1804 1805 _refine_cte_cl = new RefineCardTableEntryClosure(); 1806 1807 jint ecode = JNI_OK; 1808 _cg1r = ConcurrentG1Refine::create(_refine_cte_cl, &ecode); 1809 if (_cg1r == NULL) { 1810 return ecode; 1811 } 1812 1813 // Reserve the maximum. 1814 1815 // When compressed oops are enabled, the preferred heap base 1816 // is calculated by subtracting the requested size from the 1817 // 32Gb boundary and using the result as the base address for 1818 // heap reservation. If the requested size is not aligned to 1819 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1820 // into the ReservedHeapSpace constructor) then the actual 1821 // base of the reserved heap may end up differing from the 1822 // address that was requested (i.e. the preferred heap base). 1823 // If this happens then we could end up using a non-optimal 1824 // compressed oops mode. 1825 1826 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1827 heap_alignment); 1828 1829 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1830 1831 // Create the barrier set for the entire reserved region. 1832 G1SATBCardTableLoggingModRefBS* bs 1833 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1834 bs->initialize(); 1835 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1836 set_barrier_set(bs); 1837 1838 // Create the hot card cache. 1839 _hot_card_cache = new G1HotCardCache(this); 1840 1841 // Also create a G1 rem set. 1842 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache); 1843 1844 // Carve out the G1 part of the heap. 1845 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1846 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1847 G1RegionToSpaceMapper* heap_storage = 1848 G1RegionToSpaceMapper::create_mapper(g1_rs, 1849 g1_rs.size(), 1850 page_size, 1851 HeapRegion::GrainBytes, 1852 1, 1853 mtJavaHeap); 1854 os::trace_page_sizes("Heap", 1855 collector_policy()->min_heap_byte_size(), 1856 max_byte_size, 1857 page_size, 1858 heap_rs.base(), 1859 heap_rs.size()); 1860 heap_storage->set_mapping_changed_listener(&_listener); 1861 1862 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1863 G1RegionToSpaceMapper* bot_storage = 1864 create_aux_memory_mapper("Block Offset Table", 1865 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1866 G1BlockOffsetTable::heap_map_factor()); 1867 1868 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1869 G1RegionToSpaceMapper* cardtable_storage = 1870 create_aux_memory_mapper("Card Table", 1871 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1872 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1873 1874 G1RegionToSpaceMapper* card_counts_storage = 1875 create_aux_memory_mapper("Card Counts Table", 1876 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1877 G1CardCounts::heap_map_factor()); 1878 1879 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1880 G1RegionToSpaceMapper* prev_bitmap_storage = 1881 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1882 G1RegionToSpaceMapper* next_bitmap_storage = 1883 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1884 1885 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1886 g1_barrier_set()->initialize(cardtable_storage); 1887 // Do later initialization work for concurrent refinement. 1888 _hot_card_cache->initialize(card_counts_storage); 1889 1890 // 6843694 - ensure that the maximum region index can fit 1891 // in the remembered set structures. 1892 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1893 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1894 1895 g1_rem_set()->initialize(max_capacity(), max_regions()); 1896 1897 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1898 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1899 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1900 "too many cards per region"); 1901 1902 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1903 1904 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1905 1906 { 1907 HeapWord* start = _hrm.reserved().start(); 1908 HeapWord* end = _hrm.reserved().end(); 1909 size_t granularity = HeapRegion::GrainBytes; 1910 1911 _in_cset_fast_test.initialize(start, end, granularity); 1912 _humongous_reclaim_candidates.initialize(start, end, granularity); 1913 } 1914 1915 // Create the G1ConcurrentMark data structure and thread. 1916 // (Must do this late, so that "max_regions" is defined.) 1917 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1918 if (_cm == NULL || !_cm->completed_initialization()) { 1919 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1920 return JNI_ENOMEM; 1921 } 1922 _cmThread = _cm->cmThread(); 1923 1924 // Now expand into the initial heap size. 1925 if (!expand(init_byte_size, _workers)) { 1926 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1927 return JNI_ENOMEM; 1928 } 1929 1930 // Perform any initialization actions delegated to the policy. 1931 g1_policy()->init(this, &_collection_set); 1932 1933 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1934 SATB_Q_FL_lock, 1935 G1SATBProcessCompletedThreshold, 1936 Shared_SATB_Q_lock); 1937 1938 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 1939 DirtyCardQ_CBL_mon, 1940 DirtyCardQ_FL_lock, 1941 (int)concurrent_g1_refine()->yellow_zone(), 1942 (int)concurrent_g1_refine()->red_zone(), 1943 Shared_DirtyCardQ_lock, 1944 NULL, // fl_owner 1945 true); // init_free_ids 1946 1947 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 1948 DirtyCardQ_CBL_mon, 1949 DirtyCardQ_FL_lock, 1950 -1, // never trigger processing 1951 -1, // no limit on length 1952 Shared_DirtyCardQ_lock, 1953 &JavaThread::dirty_card_queue_set()); 1954 1955 // Here we allocate the dummy HeapRegion that is required by the 1956 // G1AllocRegion class. 1957 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1958 1959 // We'll re-use the same region whether the alloc region will 1960 // require BOT updates or not and, if it doesn't, then a non-young 1961 // region will complain that it cannot support allocations without 1962 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1963 dummy_region->set_eden(); 1964 // Make sure it's full. 1965 dummy_region->set_top(dummy_region->end()); 1966 G1AllocRegion::setup(this, dummy_region); 1967 1968 _allocator->init_mutator_alloc_region(); 1969 1970 // Do create of the monitoring and management support so that 1971 // values in the heap have been properly initialized. 1972 _g1mm = new G1MonitoringSupport(this); 1973 1974 G1StringDedup::initialize(); 1975 1976 _preserved_marks_set.init(ParallelGCThreads); 1977 1978 _collection_set.initialize(max_regions()); 1979 1980 return JNI_OK; 1981 } 1982 1983 void G1CollectedHeap::stop() { 1984 // Stop all concurrent threads. We do this to make sure these threads 1985 // do not continue to execute and access resources (e.g. logging) 1986 // that are destroyed during shutdown. 1987 _cg1r->stop(); 1988 _cmThread->stop(); 1989 if (G1StringDedup::is_enabled()) { 1990 G1StringDedup::stop(); 1991 } 1992 } 1993 1994 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1995 return HeapRegion::max_region_size(); 1996 } 1997 1998 void G1CollectedHeap::post_initialize() { 1999 ref_processing_init(); 2000 } 2001 2002 void G1CollectedHeap::ref_processing_init() { 2003 // Reference processing in G1 currently works as follows: 2004 // 2005 // * There are two reference processor instances. One is 2006 // used to record and process discovered references 2007 // during concurrent marking; the other is used to 2008 // record and process references during STW pauses 2009 // (both full and incremental). 2010 // * Both ref processors need to 'span' the entire heap as 2011 // the regions in the collection set may be dotted around. 2012 // 2013 // * For the concurrent marking ref processor: 2014 // * Reference discovery is enabled at initial marking. 2015 // * Reference discovery is disabled and the discovered 2016 // references processed etc during remarking. 2017 // * Reference discovery is MT (see below). 2018 // * Reference discovery requires a barrier (see below). 2019 // * Reference processing may or may not be MT 2020 // (depending on the value of ParallelRefProcEnabled 2021 // and ParallelGCThreads). 2022 // * A full GC disables reference discovery by the CM 2023 // ref processor and abandons any entries on it's 2024 // discovered lists. 2025 // 2026 // * For the STW processor: 2027 // * Non MT discovery is enabled at the start of a full GC. 2028 // * Processing and enqueueing during a full GC is non-MT. 2029 // * During a full GC, references are processed after marking. 2030 // 2031 // * Discovery (may or may not be MT) is enabled at the start 2032 // of an incremental evacuation pause. 2033 // * References are processed near the end of a STW evacuation pause. 2034 // * For both types of GC: 2035 // * Discovery is atomic - i.e. not concurrent. 2036 // * Reference discovery will not need a barrier. 2037 2038 MemRegion mr = reserved_region(); 2039 2040 // Concurrent Mark ref processor 2041 _ref_processor_cm = 2042 new ReferenceProcessor(mr, // span 2043 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2044 // mt processing 2045 ParallelGCThreads, 2046 // degree of mt processing 2047 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2048 // mt discovery 2049 MAX2(ParallelGCThreads, ConcGCThreads), 2050 // degree of mt discovery 2051 false, 2052 // Reference discovery is not atomic 2053 &_is_alive_closure_cm); 2054 // is alive closure 2055 // (for efficiency/performance) 2056 2057 // STW ref processor 2058 _ref_processor_stw = 2059 new ReferenceProcessor(mr, // span 2060 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2061 // mt processing 2062 ParallelGCThreads, 2063 // degree of mt processing 2064 (ParallelGCThreads > 1), 2065 // mt discovery 2066 ParallelGCThreads, 2067 // degree of mt discovery 2068 true, 2069 // Reference discovery is atomic 2070 &_is_alive_closure_stw); 2071 // is alive closure 2072 // (for efficiency/performance) 2073 } 2074 2075 CollectorPolicy* G1CollectedHeap::collector_policy() const { 2076 return _collector_policy; 2077 } 2078 2079 size_t G1CollectedHeap::capacity() const { 2080 return _hrm.length() * HeapRegion::GrainBytes; 2081 } 2082 2083 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2084 hr->reset_gc_time_stamp(); 2085 } 2086 2087 #ifndef PRODUCT 2088 2089 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2090 private: 2091 unsigned _gc_time_stamp; 2092 bool _failures; 2093 2094 public: 2095 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2096 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2097 2098 virtual bool doHeapRegion(HeapRegion* hr) { 2099 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2100 if (_gc_time_stamp != region_gc_time_stamp) { 2101 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 2102 region_gc_time_stamp, _gc_time_stamp); 2103 _failures = true; 2104 } 2105 return false; 2106 } 2107 2108 bool failures() { return _failures; } 2109 }; 2110 2111 void G1CollectedHeap::check_gc_time_stamps() { 2112 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2113 heap_region_iterate(&cl); 2114 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2115 } 2116 #endif // PRODUCT 2117 2118 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2119 _hot_card_cache->drain(cl, worker_i); 2120 } 2121 2122 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2123 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2124 size_t n_completed_buffers = 0; 2125 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2126 n_completed_buffers++; 2127 } 2128 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2129 dcqs.clear_n_completed_buffers(); 2130 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2131 } 2132 2133 // Computes the sum of the storage used by the various regions. 2134 size_t G1CollectedHeap::used() const { 2135 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2136 if (_archive_allocator != NULL) { 2137 result += _archive_allocator->used(); 2138 } 2139 return result; 2140 } 2141 2142 size_t G1CollectedHeap::used_unlocked() const { 2143 return _summary_bytes_used; 2144 } 2145 2146 class SumUsedClosure: public HeapRegionClosure { 2147 size_t _used; 2148 public: 2149 SumUsedClosure() : _used(0) {} 2150 bool doHeapRegion(HeapRegion* r) { 2151 _used += r->used(); 2152 return false; 2153 } 2154 size_t result() { return _used; } 2155 }; 2156 2157 size_t G1CollectedHeap::recalculate_used() const { 2158 double recalculate_used_start = os::elapsedTime(); 2159 2160 SumUsedClosure blk; 2161 heap_region_iterate(&blk); 2162 2163 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2164 return blk.result(); 2165 } 2166 2167 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2168 switch (cause) { 2169 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2170 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2171 case GCCause::_update_allocation_context_stats_inc: return true; 2172 case GCCause::_wb_conc_mark: return true; 2173 default : return false; 2174 } 2175 } 2176 2177 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2178 switch (cause) { 2179 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2180 case GCCause::_g1_humongous_allocation: return true; 2181 default: return is_user_requested_concurrent_full_gc(cause); 2182 } 2183 } 2184 2185 #ifndef PRODUCT 2186 void G1CollectedHeap::allocate_dummy_regions() { 2187 // Let's fill up most of the region 2188 size_t word_size = HeapRegion::GrainWords - 1024; 2189 // And as a result the region we'll allocate will be humongous. 2190 guarantee(is_humongous(word_size), "sanity"); 2191 2192 // _filler_array_max_size is set to humongous object threshold 2193 // but temporarily change it to use CollectedHeap::fill_with_object(). 2194 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2195 2196 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2197 // Let's use the existing mechanism for the allocation 2198 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2199 AllocationContext::system()); 2200 if (dummy_obj != NULL) { 2201 MemRegion mr(dummy_obj, word_size); 2202 CollectedHeap::fill_with_object(mr); 2203 } else { 2204 // If we can't allocate once, we probably cannot allocate 2205 // again. Let's get out of the loop. 2206 break; 2207 } 2208 } 2209 } 2210 #endif // !PRODUCT 2211 2212 void G1CollectedHeap::increment_old_marking_cycles_started() { 2213 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2214 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2215 "Wrong marking cycle count (started: %d, completed: %d)", 2216 _old_marking_cycles_started, _old_marking_cycles_completed); 2217 2218 _old_marking_cycles_started++; 2219 } 2220 2221 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2222 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2223 2224 // We assume that if concurrent == true, then the caller is a 2225 // concurrent thread that was joined the Suspendible Thread 2226 // Set. If there's ever a cheap way to check this, we should add an 2227 // assert here. 2228 2229 // Given that this method is called at the end of a Full GC or of a 2230 // concurrent cycle, and those can be nested (i.e., a Full GC can 2231 // interrupt a concurrent cycle), the number of full collections 2232 // completed should be either one (in the case where there was no 2233 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2234 // behind the number of full collections started. 2235 2236 // This is the case for the inner caller, i.e. a Full GC. 2237 assert(concurrent || 2238 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2239 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2240 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2241 "is inconsistent with _old_marking_cycles_completed = %u", 2242 _old_marking_cycles_started, _old_marking_cycles_completed); 2243 2244 // This is the case for the outer caller, i.e. the concurrent cycle. 2245 assert(!concurrent || 2246 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2247 "for outer caller (concurrent cycle): " 2248 "_old_marking_cycles_started = %u " 2249 "is inconsistent with _old_marking_cycles_completed = %u", 2250 _old_marking_cycles_started, _old_marking_cycles_completed); 2251 2252 _old_marking_cycles_completed += 1; 2253 2254 // We need to clear the "in_progress" flag in the CM thread before 2255 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2256 // is set) so that if a waiter requests another System.gc() it doesn't 2257 // incorrectly see that a marking cycle is still in progress. 2258 if (concurrent) { 2259 _cmThread->set_idle(); 2260 } 2261 2262 // This notify_all() will ensure that a thread that called 2263 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2264 // and it's waiting for a full GC to finish will be woken up. It is 2265 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2266 FullGCCount_lock->notify_all(); 2267 } 2268 2269 void G1CollectedHeap::collect(GCCause::Cause cause) { 2270 assert_heap_not_locked(); 2271 2272 uint gc_count_before; 2273 uint old_marking_count_before; 2274 uint full_gc_count_before; 2275 bool retry_gc; 2276 2277 do { 2278 retry_gc = false; 2279 2280 { 2281 MutexLocker ml(Heap_lock); 2282 2283 // Read the GC count while holding the Heap_lock 2284 gc_count_before = total_collections(); 2285 full_gc_count_before = total_full_collections(); 2286 old_marking_count_before = _old_marking_cycles_started; 2287 } 2288 2289 if (should_do_concurrent_full_gc(cause)) { 2290 // Schedule an initial-mark evacuation pause that will start a 2291 // concurrent cycle. We're setting word_size to 0 which means that 2292 // we are not requesting a post-GC allocation. 2293 VM_G1IncCollectionPause op(gc_count_before, 2294 0, /* word_size */ 2295 true, /* should_initiate_conc_mark */ 2296 g1_policy()->max_pause_time_ms(), 2297 cause); 2298 op.set_allocation_context(AllocationContext::current()); 2299 2300 VMThread::execute(&op); 2301 if (!op.pause_succeeded()) { 2302 if (old_marking_count_before == _old_marking_cycles_started) { 2303 retry_gc = op.should_retry_gc(); 2304 } else { 2305 // A Full GC happened while we were trying to schedule the 2306 // initial-mark GC. No point in starting a new cycle given 2307 // that the whole heap was collected anyway. 2308 } 2309 2310 if (retry_gc) { 2311 if (GCLocker::is_active_and_needs_gc()) { 2312 GCLocker::stall_until_clear(); 2313 } 2314 } 2315 } 2316 } else { 2317 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2318 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2319 2320 // Schedule a standard evacuation pause. We're setting word_size 2321 // to 0 which means that we are not requesting a post-GC allocation. 2322 VM_G1IncCollectionPause op(gc_count_before, 2323 0, /* word_size */ 2324 false, /* should_initiate_conc_mark */ 2325 g1_policy()->max_pause_time_ms(), 2326 cause); 2327 VMThread::execute(&op); 2328 } else { 2329 // Schedule a Full GC. 2330 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2331 VMThread::execute(&op); 2332 } 2333 } 2334 } while (retry_gc); 2335 } 2336 2337 bool G1CollectedHeap::is_in(const void* p) const { 2338 if (_hrm.reserved().contains(p)) { 2339 // Given that we know that p is in the reserved space, 2340 // heap_region_containing() should successfully 2341 // return the containing region. 2342 HeapRegion* hr = heap_region_containing(p); 2343 return hr->is_in(p); 2344 } else { 2345 return false; 2346 } 2347 } 2348 2349 #ifdef ASSERT 2350 bool G1CollectedHeap::is_in_exact(const void* p) const { 2351 bool contains = reserved_region().contains(p); 2352 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2353 if (contains && available) { 2354 return true; 2355 } else { 2356 return false; 2357 } 2358 } 2359 #endif 2360 2361 // Iteration functions. 2362 2363 // Iterates an ObjectClosure over all objects within a HeapRegion. 2364 2365 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2366 ObjectClosure* _cl; 2367 public: 2368 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2369 bool doHeapRegion(HeapRegion* r) { 2370 if (!r->is_continues_humongous()) { 2371 r->object_iterate(_cl); 2372 } 2373 return false; 2374 } 2375 }; 2376 2377 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2378 IterateObjectClosureRegionClosure blk(cl); 2379 heap_region_iterate(&blk); 2380 } 2381 2382 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2383 _hrm.iterate(cl); 2384 } 2385 2386 void G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2387 uint worker_id, 2388 HeapRegionClaimer *hrclaimer) const { 2389 _hrm.par_iterate(cl, worker_id, hrclaimer); 2390 } 2391 2392 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2393 _collection_set.iterate(cl); 2394 } 2395 2396 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2397 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2398 } 2399 2400 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2401 HeapRegion* result = _hrm.next_region_in_heap(from); 2402 while (result != NULL && result->is_pinned()) { 2403 result = _hrm.next_region_in_heap(result); 2404 } 2405 return result; 2406 } 2407 2408 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2409 HeapRegion* hr = heap_region_containing(addr); 2410 return hr->block_start(addr); 2411 } 2412 2413 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2414 HeapRegion* hr = heap_region_containing(addr); 2415 return hr->block_size(addr); 2416 } 2417 2418 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2419 HeapRegion* hr = heap_region_containing(addr); 2420 return hr->block_is_obj(addr); 2421 } 2422 2423 bool G1CollectedHeap::supports_tlab_allocation() const { 2424 return true; 2425 } 2426 2427 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2428 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2429 } 2430 2431 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2432 return _eden.length() * HeapRegion::GrainBytes; 2433 } 2434 2435 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2436 // must be equal to the humongous object limit. 2437 size_t G1CollectedHeap::max_tlab_size() const { 2438 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2439 } 2440 2441 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2442 AllocationContext_t context = AllocationContext::current(); 2443 return _allocator->unsafe_max_tlab_alloc(context); 2444 } 2445 2446 size_t G1CollectedHeap::max_capacity() const { 2447 return _hrm.reserved().byte_size(); 2448 } 2449 2450 jlong G1CollectedHeap::millis_since_last_gc() { 2451 // See the notes in GenCollectedHeap::millis_since_last_gc() 2452 // for more information about the implementation. 2453 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2454 _g1_policy->collection_pause_end_millis(); 2455 if (ret_val < 0) { 2456 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2457 ". returning zero instead.", ret_val); 2458 return 0; 2459 } 2460 return ret_val; 2461 } 2462 2463 void G1CollectedHeap::prepare_for_verify() { 2464 _verifier->prepare_for_verify(); 2465 } 2466 2467 void G1CollectedHeap::verify(VerifyOption vo) { 2468 _verifier->verify(vo); 2469 } 2470 2471 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2472 return true; 2473 } 2474 2475 const char* const* G1CollectedHeap::concurrent_phases() const { 2476 return _cmThread->concurrent_phases(); 2477 } 2478 2479 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2480 return _cmThread->request_concurrent_phase(phase); 2481 } 2482 2483 class PrintRegionClosure: public HeapRegionClosure { 2484 outputStream* _st; 2485 public: 2486 PrintRegionClosure(outputStream* st) : _st(st) {} 2487 bool doHeapRegion(HeapRegion* r) { 2488 r->print_on(_st); 2489 return false; 2490 } 2491 }; 2492 2493 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2494 const HeapRegion* hr, 2495 const VerifyOption vo) const { 2496 switch (vo) { 2497 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2498 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2499 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 2500 default: ShouldNotReachHere(); 2501 } 2502 return false; // keep some compilers happy 2503 } 2504 2505 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2506 const VerifyOption vo) const { 2507 switch (vo) { 2508 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2509 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2510 case VerifyOption_G1UseMarkWord: { 2511 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 2512 return !obj->is_gc_marked() && !hr->is_archive(); 2513 } 2514 default: ShouldNotReachHere(); 2515 } 2516 return false; // keep some compilers happy 2517 } 2518 2519 void G1CollectedHeap::print_heap_regions() const { 2520 Log(gc, heap, region) log; 2521 if (log.is_trace()) { 2522 ResourceMark rm; 2523 print_regions_on(log.trace_stream()); 2524 } 2525 } 2526 2527 void G1CollectedHeap::print_on(outputStream* st) const { 2528 st->print(" %-20s", "garbage-first heap"); 2529 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2530 capacity()/K, used_unlocked()/K); 2531 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 2532 p2i(_hrm.reserved().start()), 2533 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 2534 p2i(_hrm.reserved().end())); 2535 st->cr(); 2536 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2537 uint young_regions = young_regions_count(); 2538 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2539 (size_t) young_regions * HeapRegion::GrainBytes / K); 2540 uint survivor_regions = survivor_regions_count(); 2541 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2542 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2543 st->cr(); 2544 MetaspaceAux::print_on(st); 2545 } 2546 2547 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2548 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2549 "HS=humongous(starts), HC=humongous(continues), " 2550 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2551 "AC=allocation context, " 2552 "TAMS=top-at-mark-start (previous, next)"); 2553 PrintRegionClosure blk(st); 2554 heap_region_iterate(&blk); 2555 } 2556 2557 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2558 print_on(st); 2559 2560 // Print the per-region information. 2561 print_regions_on(st); 2562 } 2563 2564 void G1CollectedHeap::print_on_error(outputStream* st) const { 2565 this->CollectedHeap::print_on_error(st); 2566 2567 if (_cm != NULL) { 2568 st->cr(); 2569 _cm->print_on_error(st); 2570 } 2571 } 2572 2573 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2574 workers()->print_worker_threads_on(st); 2575 _cmThread->print_on(st); 2576 st->cr(); 2577 _cm->print_worker_threads_on(st); 2578 _cg1r->print_worker_threads_on(st); // also prints the sample thread 2579 if (G1StringDedup::is_enabled()) { 2580 G1StringDedup::print_worker_threads_on(st); 2581 } 2582 } 2583 2584 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2585 workers()->threads_do(tc); 2586 tc->do_thread(_cmThread); 2587 _cm->threads_do(tc); 2588 _cg1r->threads_do(tc); // also iterates over the sample thread 2589 if (G1StringDedup::is_enabled()) { 2590 G1StringDedup::threads_do(tc); 2591 } 2592 } 2593 2594 void G1CollectedHeap::print_tracing_info() const { 2595 g1_rem_set()->print_summary_info(); 2596 concurrent_mark()->print_summary_info(); 2597 } 2598 2599 #ifndef PRODUCT 2600 // Helpful for debugging RSet issues. 2601 2602 class PrintRSetsClosure : public HeapRegionClosure { 2603 private: 2604 const char* _msg; 2605 size_t _occupied_sum; 2606 2607 public: 2608 bool doHeapRegion(HeapRegion* r) { 2609 HeapRegionRemSet* hrrs = r->rem_set(); 2610 size_t occupied = hrrs->occupied(); 2611 _occupied_sum += occupied; 2612 2613 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2614 if (occupied == 0) { 2615 tty->print_cr(" RSet is empty"); 2616 } else { 2617 hrrs->print(); 2618 } 2619 tty->print_cr("----------"); 2620 return false; 2621 } 2622 2623 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2624 tty->cr(); 2625 tty->print_cr("========================================"); 2626 tty->print_cr("%s", msg); 2627 tty->cr(); 2628 } 2629 2630 ~PrintRSetsClosure() { 2631 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2632 tty->print_cr("========================================"); 2633 tty->cr(); 2634 } 2635 }; 2636 2637 void G1CollectedHeap::print_cset_rsets() { 2638 PrintRSetsClosure cl("Printing CSet RSets"); 2639 collection_set_iterate(&cl); 2640 } 2641 2642 void G1CollectedHeap::print_all_rsets() { 2643 PrintRSetsClosure cl("Printing All RSets");; 2644 heap_region_iterate(&cl); 2645 } 2646 #endif // PRODUCT 2647 2648 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2649 2650 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2651 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2652 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2653 2654 size_t eden_capacity_bytes = 2655 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2656 2657 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2658 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2659 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2660 } 2661 2662 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2663 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2664 stats->unused(), stats->used(), stats->region_end_waste(), 2665 stats->regions_filled(), stats->direct_allocated(), 2666 stats->failure_used(), stats->failure_waste()); 2667 } 2668 2669 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2670 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2671 gc_tracer->report_gc_heap_summary(when, heap_summary); 2672 2673 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2674 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2675 } 2676 2677 G1CollectedHeap* G1CollectedHeap::heap() { 2678 CollectedHeap* heap = Universe::heap(); 2679 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2680 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2681 return (G1CollectedHeap*)heap; 2682 } 2683 2684 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 2685 // always_do_update_barrier = false; 2686 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2687 2688 double start = os::elapsedTime(); 2689 // Fill TLAB's and such 2690 accumulate_statistics_all_tlabs(); 2691 ensure_parsability(true); 2692 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2693 2694 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2695 } 2696 2697 void G1CollectedHeap::gc_epilogue(bool full) { 2698 // we are at the end of the GC. Total collections has already been increased. 2699 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2700 2701 // FIXME: what is this about? 2702 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2703 // is set. 2704 #if defined(COMPILER2) || INCLUDE_JVMCI 2705 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2706 #endif 2707 // always_do_update_barrier = true; 2708 2709 double start = os::elapsedTime(); 2710 resize_all_tlabs(); 2711 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2712 2713 allocation_context_stats().update(full); 2714 2715 // We have just completed a GC. Update the soft reference 2716 // policy with the new heap occupancy 2717 Universe::update_heap_info_at_gc(); 2718 } 2719 2720 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2721 uint gc_count_before, 2722 bool* succeeded, 2723 GCCause::Cause gc_cause) { 2724 assert_heap_not_locked_and_not_at_safepoint(); 2725 VM_G1IncCollectionPause op(gc_count_before, 2726 word_size, 2727 false, /* should_initiate_conc_mark */ 2728 g1_policy()->max_pause_time_ms(), 2729 gc_cause); 2730 2731 op.set_allocation_context(AllocationContext::current()); 2732 VMThread::execute(&op); 2733 2734 HeapWord* result = op.result(); 2735 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2736 assert(result == NULL || ret_succeeded, 2737 "the result should be NULL if the VM did not succeed"); 2738 *succeeded = ret_succeeded; 2739 2740 assert_heap_not_locked(); 2741 return result; 2742 } 2743 2744 void 2745 G1CollectedHeap::doConcurrentMark() { 2746 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2747 if (!_cmThread->in_progress()) { 2748 _cmThread->set_started(); 2749 CGC_lock->notify(); 2750 } 2751 } 2752 2753 size_t G1CollectedHeap::pending_card_num() { 2754 size_t extra_cards = 0; 2755 JavaThread *curr = Threads::first(); 2756 while (curr != NULL) { 2757 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2758 extra_cards += dcq.size(); 2759 curr = curr->next(); 2760 } 2761 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2762 size_t buffer_size = dcqs.buffer_size(); 2763 size_t buffer_num = dcqs.completed_buffers_num(); 2764 2765 return buffer_size * buffer_num + extra_cards; 2766 } 2767 2768 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2769 private: 2770 size_t _total_humongous; 2771 size_t _candidate_humongous; 2772 2773 DirtyCardQueue _dcq; 2774 2775 // We don't nominate objects with many remembered set entries, on 2776 // the assumption that such objects are likely still live. 2777 bool is_remset_small(HeapRegion* region) const { 2778 HeapRegionRemSet* const rset = region->rem_set(); 2779 return G1EagerReclaimHumongousObjectsWithStaleRefs 2780 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2781 : rset->is_empty(); 2782 } 2783 2784 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2785 assert(region->is_starts_humongous(), "Must start a humongous object"); 2786 2787 oop obj = oop(region->bottom()); 2788 2789 // Dead objects cannot be eager reclaim candidates. Due to class 2790 // unloading it is unsafe to query their classes so we return early. 2791 if (heap->is_obj_dead(obj, region)) { 2792 return false; 2793 } 2794 2795 // Candidate selection must satisfy the following constraints 2796 // while concurrent marking is in progress: 2797 // 2798 // * In order to maintain SATB invariants, an object must not be 2799 // reclaimed if it was allocated before the start of marking and 2800 // has not had its references scanned. Such an object must have 2801 // its references (including type metadata) scanned to ensure no 2802 // live objects are missed by the marking process. Objects 2803 // allocated after the start of concurrent marking don't need to 2804 // be scanned. 2805 // 2806 // * An object must not be reclaimed if it is on the concurrent 2807 // mark stack. Objects allocated after the start of concurrent 2808 // marking are never pushed on the mark stack. 2809 // 2810 // Nominating only objects allocated after the start of concurrent 2811 // marking is sufficient to meet both constraints. This may miss 2812 // some objects that satisfy the constraints, but the marking data 2813 // structures don't support efficiently performing the needed 2814 // additional tests or scrubbing of the mark stack. 2815 // 2816 // However, we presently only nominate is_typeArray() objects. 2817 // A humongous object containing references induces remembered 2818 // set entries on other regions. In order to reclaim such an 2819 // object, those remembered sets would need to be cleaned up. 2820 // 2821 // We also treat is_typeArray() objects specially, allowing them 2822 // to be reclaimed even if allocated before the start of 2823 // concurrent mark. For this we rely on mark stack insertion to 2824 // exclude is_typeArray() objects, preventing reclaiming an object 2825 // that is in the mark stack. We also rely on the metadata for 2826 // such objects to be built-in and so ensured to be kept live. 2827 // Frequent allocation and drop of large binary blobs is an 2828 // important use case for eager reclaim, and this special handling 2829 // may reduce needed headroom. 2830 2831 return obj->is_typeArray() && is_remset_small(region); 2832 } 2833 2834 public: 2835 RegisterHumongousWithInCSetFastTestClosure() 2836 : _total_humongous(0), 2837 _candidate_humongous(0), 2838 _dcq(&JavaThread::dirty_card_queue_set()) { 2839 } 2840 2841 virtual bool doHeapRegion(HeapRegion* r) { 2842 if (!r->is_starts_humongous()) { 2843 return false; 2844 } 2845 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2846 2847 bool is_candidate = humongous_region_is_candidate(g1h, r); 2848 uint rindex = r->hrm_index(); 2849 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2850 if (is_candidate) { 2851 _candidate_humongous++; 2852 g1h->register_humongous_region_with_cset(rindex); 2853 // Is_candidate already filters out humongous object with large remembered sets. 2854 // If we have a humongous object with a few remembered sets, we simply flush these 2855 // remembered set entries into the DCQS. That will result in automatic 2856 // re-evaluation of their remembered set entries during the following evacuation 2857 // phase. 2858 if (!r->rem_set()->is_empty()) { 2859 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2860 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2861 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 2862 HeapRegionRemSetIterator hrrs(r->rem_set()); 2863 size_t card_index; 2864 while (hrrs.has_next(card_index)) { 2865 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 2866 // The remembered set might contain references to already freed 2867 // regions. Filter out such entries to avoid failing card table 2868 // verification. 2869 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 2870 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 2871 *card_ptr = CardTableModRefBS::dirty_card_val(); 2872 _dcq.enqueue(card_ptr); 2873 } 2874 } 2875 } 2876 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2877 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2878 hrrs.n_yielded(), r->rem_set()->occupied()); 2879 r->rem_set()->clear_locked(); 2880 } 2881 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2882 } 2883 _total_humongous++; 2884 2885 return false; 2886 } 2887 2888 size_t total_humongous() const { return _total_humongous; } 2889 size_t candidate_humongous() const { return _candidate_humongous; } 2890 2891 void flush_rem_set_entries() { _dcq.flush(); } 2892 }; 2893 2894 void G1CollectedHeap::register_humongous_regions_with_cset() { 2895 if (!G1EagerReclaimHumongousObjects) { 2896 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2897 return; 2898 } 2899 double time = os::elapsed_counter(); 2900 2901 // Collect reclaim candidate information and register candidates with cset. 2902 RegisterHumongousWithInCSetFastTestClosure cl; 2903 heap_region_iterate(&cl); 2904 2905 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2906 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2907 cl.total_humongous(), 2908 cl.candidate_humongous()); 2909 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2910 2911 // Finally flush all remembered set entries to re-check into the global DCQS. 2912 cl.flush_rem_set_entries(); 2913 } 2914 2915 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2916 public: 2917 bool doHeapRegion(HeapRegion* hr) { 2918 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2919 hr->verify_rem_set(); 2920 } 2921 return false; 2922 } 2923 }; 2924 2925 uint G1CollectedHeap::num_task_queues() const { 2926 return _task_queues->size(); 2927 } 2928 2929 #if TASKQUEUE_STATS 2930 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2931 st->print_raw_cr("GC Task Stats"); 2932 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2933 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2934 } 2935 2936 void G1CollectedHeap::print_taskqueue_stats() const { 2937 if (!log_is_enabled(Trace, gc, task, stats)) { 2938 return; 2939 } 2940 Log(gc, task, stats) log; 2941 ResourceMark rm; 2942 outputStream* st = log.trace_stream(); 2943 2944 print_taskqueue_stats_hdr(st); 2945 2946 TaskQueueStats totals; 2947 const uint n = num_task_queues(); 2948 for (uint i = 0; i < n; ++i) { 2949 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2950 totals += task_queue(i)->stats; 2951 } 2952 st->print_raw("tot "); totals.print(st); st->cr(); 2953 2954 DEBUG_ONLY(totals.verify()); 2955 } 2956 2957 void G1CollectedHeap::reset_taskqueue_stats() { 2958 const uint n = num_task_queues(); 2959 for (uint i = 0; i < n; ++i) { 2960 task_queue(i)->stats.reset(); 2961 } 2962 } 2963 #endif // TASKQUEUE_STATS 2964 2965 void G1CollectedHeap::wait_for_root_region_scanning() { 2966 double scan_wait_start = os::elapsedTime(); 2967 // We have to wait until the CM threads finish scanning the 2968 // root regions as it's the only way to ensure that all the 2969 // objects on them have been correctly scanned before we start 2970 // moving them during the GC. 2971 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2972 double wait_time_ms = 0.0; 2973 if (waited) { 2974 double scan_wait_end = os::elapsedTime(); 2975 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2976 } 2977 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2978 } 2979 2980 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2981 private: 2982 G1HRPrinter* _hr_printer; 2983 public: 2984 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2985 2986 virtual bool doHeapRegion(HeapRegion* r) { 2987 _hr_printer->cset(r); 2988 return false; 2989 } 2990 }; 2991 2992 void G1CollectedHeap::start_new_collection_set() { 2993 collection_set()->start_incremental_building(); 2994 2995 clear_cset_fast_test(); 2996 2997 guarantee(_eden.length() == 0, "eden should have been cleared"); 2998 g1_policy()->transfer_survivors_to_cset(survivor()); 2999 } 3000 3001 bool 3002 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3003 assert_at_safepoint(true /* should_be_vm_thread */); 3004 guarantee(!is_gc_active(), "collection is not reentrant"); 3005 3006 if (GCLocker::check_active_before_gc()) { 3007 return false; 3008 } 3009 3010 _gc_timer_stw->register_gc_start(); 3011 3012 GCIdMark gc_id_mark; 3013 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3014 3015 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3016 ResourceMark rm; 3017 3018 g1_policy()->note_gc_start(); 3019 3020 wait_for_root_region_scanning(); 3021 3022 print_heap_before_gc(); 3023 print_heap_regions(); 3024 trace_heap_before_gc(_gc_tracer_stw); 3025 3026 _verifier->verify_region_sets_optional(); 3027 _verifier->verify_dirty_young_regions(); 3028 3029 // We should not be doing initial mark unless the conc mark thread is running 3030 if (!_cmThread->should_terminate()) { 3031 // This call will decide whether this pause is an initial-mark 3032 // pause. If it is, during_initial_mark_pause() will return true 3033 // for the duration of this pause. 3034 g1_policy()->decide_on_conc_mark_initiation(); 3035 } 3036 3037 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3038 assert(!collector_state()->during_initial_mark_pause() || 3039 collector_state()->gcs_are_young(), "sanity"); 3040 3041 // We also do not allow mixed GCs during marking. 3042 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3043 3044 // Record whether this pause is an initial mark. When the current 3045 // thread has completed its logging output and it's safe to signal 3046 // the CM thread, the flag's value in the policy has been reset. 3047 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3048 3049 // Inner scope for scope based logging, timers, and stats collection 3050 { 3051 EvacuationInfo evacuation_info; 3052 3053 if (collector_state()->during_initial_mark_pause()) { 3054 // We are about to start a marking cycle, so we increment the 3055 // full collection counter. 3056 increment_old_marking_cycles_started(); 3057 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 3058 } 3059 3060 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3061 3062 GCTraceCPUTime tcpu; 3063 3064 FormatBuffer<> gc_string("Pause "); 3065 if (collector_state()->during_initial_mark_pause()) { 3066 gc_string.append("Initial Mark"); 3067 } else if (collector_state()->gcs_are_young()) { 3068 gc_string.append("Young"); 3069 } else { 3070 gc_string.append("Mixed"); 3071 } 3072 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 3073 3074 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3075 workers()->active_workers(), 3076 Threads::number_of_non_daemon_threads()); 3077 workers()->update_active_workers(active_workers); 3078 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 3079 3080 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3081 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3082 3083 // If the secondary_free_list is not empty, append it to the 3084 // free_list. No need to wait for the cleanup operation to finish; 3085 // the region allocation code will check the secondary_free_list 3086 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3087 // set, skip this step so that the region allocation code has to 3088 // get entries from the secondary_free_list. 3089 if (!G1StressConcRegionFreeing) { 3090 append_secondary_free_list_if_not_empty_with_lock(); 3091 } 3092 3093 G1HeapTransition heap_transition(this); 3094 size_t heap_used_bytes_before_gc = used(); 3095 3096 // Don't dynamically change the number of GC threads this early. A value of 3097 // 0 is used to indicate serial work. When parallel work is done, 3098 // it will be set. 3099 3100 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3101 IsGCActiveMark x; 3102 3103 gc_prologue(false); 3104 increment_total_collections(false /* full gc */); 3105 increment_gc_time_stamp(); 3106 3107 if (VerifyRememberedSets) { 3108 log_info(gc, verify)("[Verifying RemSets before GC]"); 3109 VerifyRegionRemSetClosure v_cl; 3110 heap_region_iterate(&v_cl); 3111 } 3112 3113 _verifier->verify_before_gc(); 3114 3115 _verifier->check_bitmaps("GC Start"); 3116 3117 #if defined(COMPILER2) || INCLUDE_JVMCI 3118 DerivedPointerTable::clear(); 3119 #endif 3120 3121 // Please see comment in g1CollectedHeap.hpp and 3122 // G1CollectedHeap::ref_processing_init() to see how 3123 // reference processing currently works in G1. 3124 3125 // Enable discovery in the STW reference processor 3126 if (g1_policy()->should_process_references()) { 3127 ref_processor_stw()->enable_discovery(); 3128 } else { 3129 ref_processor_stw()->disable_discovery(); 3130 } 3131 3132 { 3133 // We want to temporarily turn off discovery by the 3134 // CM ref processor, if necessary, and turn it back on 3135 // on again later if we do. Using a scoped 3136 // NoRefDiscovery object will do this. 3137 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3138 3139 // Forget the current alloc region (we might even choose it to be part 3140 // of the collection set!). 3141 _allocator->release_mutator_alloc_region(); 3142 3143 // This timing is only used by the ergonomics to handle our pause target. 3144 // It is unclear why this should not include the full pause. We will 3145 // investigate this in CR 7178365. 3146 // 3147 // Preserving the old comment here if that helps the investigation: 3148 // 3149 // The elapsed time induced by the start time below deliberately elides 3150 // the possible verification above. 3151 double sample_start_time_sec = os::elapsedTime(); 3152 3153 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3154 3155 if (collector_state()->during_initial_mark_pause()) { 3156 concurrent_mark()->checkpointRootsInitialPre(); 3157 } 3158 3159 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 3160 3161 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3162 3163 // Make sure the remembered sets are up to date. This needs to be 3164 // done before register_humongous_regions_with_cset(), because the 3165 // remembered sets are used there to choose eager reclaim candidates. 3166 // If the remembered sets are not up to date we might miss some 3167 // entries that need to be handled. 3168 g1_rem_set()->cleanupHRRS(); 3169 3170 register_humongous_regions_with_cset(); 3171 3172 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3173 3174 // We call this after finalize_cset() to 3175 // ensure that the CSet has been finalized. 3176 _cm->verify_no_cset_oops(); 3177 3178 if (_hr_printer.is_active()) { 3179 G1PrintCollectionSetClosure cl(&_hr_printer); 3180 _collection_set.iterate(&cl); 3181 } 3182 3183 // Initialize the GC alloc regions. 3184 _allocator->init_gc_alloc_regions(evacuation_info); 3185 3186 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3187 pre_evacuate_collection_set(); 3188 3189 // Actually do the work... 3190 evacuate_collection_set(evacuation_info, &per_thread_states); 3191 3192 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3193 3194 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3195 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 3196 3197 eagerly_reclaim_humongous_regions(); 3198 3199 record_obj_copy_mem_stats(); 3200 _survivor_evac_stats.adjust_desired_plab_sz(); 3201 _old_evac_stats.adjust_desired_plab_sz(); 3202 3203 double start = os::elapsedTime(); 3204 start_new_collection_set(); 3205 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 3206 3207 if (evacuation_failed()) { 3208 set_used(recalculate_used()); 3209 if (_archive_allocator != NULL) { 3210 _archive_allocator->clear_used(); 3211 } 3212 for (uint i = 0; i < ParallelGCThreads; i++) { 3213 if (_evacuation_failed_info_array[i].has_failed()) { 3214 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3215 } 3216 } 3217 } else { 3218 // The "used" of the the collection set have already been subtracted 3219 // when they were freed. Add in the bytes evacuated. 3220 increase_used(g1_policy()->bytes_copied_during_gc()); 3221 } 3222 3223 if (collector_state()->during_initial_mark_pause()) { 3224 // We have to do this before we notify the CM threads that 3225 // they can start working to make sure that all the 3226 // appropriate initialization is done on the CM object. 3227 concurrent_mark()->checkpointRootsInitialPost(); 3228 collector_state()->set_mark_in_progress(true); 3229 // Note that we don't actually trigger the CM thread at 3230 // this point. We do that later when we're sure that 3231 // the current thread has completed its logging output. 3232 } 3233 3234 allocate_dummy_regions(); 3235 3236 _allocator->init_mutator_alloc_region(); 3237 3238 { 3239 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3240 if (expand_bytes > 0) { 3241 size_t bytes_before = capacity(); 3242 // No need for an ergo logging here, 3243 // expansion_amount() does this when it returns a value > 0. 3244 double expand_ms; 3245 if (!expand(expand_bytes, _workers, &expand_ms)) { 3246 // We failed to expand the heap. Cannot do anything about it. 3247 } 3248 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3249 } 3250 } 3251 3252 // We redo the verification but now wrt to the new CSet which 3253 // has just got initialized after the previous CSet was freed. 3254 _cm->verify_no_cset_oops(); 3255 3256 // This timing is only used by the ergonomics to handle our pause target. 3257 // It is unclear why this should not include the full pause. We will 3258 // investigate this in CR 7178365. 3259 double sample_end_time_sec = os::elapsedTime(); 3260 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3261 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScannedCards); 3262 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3263 3264 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3265 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3266 3267 MemoryService::track_memory_usage(); 3268 3269 // In prepare_for_verify() below we'll need to scan the deferred 3270 // update buffers to bring the RSets up-to-date if 3271 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3272 // the update buffers we'll probably need to scan cards on the 3273 // regions we just allocated to (i.e., the GC alloc 3274 // regions). However, during the last GC we called 3275 // set_saved_mark() on all the GC alloc regions, so card 3276 // scanning might skip the [saved_mark_word()...top()] area of 3277 // those regions (i.e., the area we allocated objects into 3278 // during the last GC). But it shouldn't. Given that 3279 // saved_mark_word() is conditional on whether the GC time stamp 3280 // on the region is current or not, by incrementing the GC time 3281 // stamp here we invalidate all the GC time stamps on all the 3282 // regions and saved_mark_word() will simply return top() for 3283 // all the regions. This is a nicer way of ensuring this rather 3284 // than iterating over the regions and fixing them. In fact, the 3285 // GC time stamp increment here also ensures that 3286 // saved_mark_word() will return top() between pauses, i.e., 3287 // during concurrent refinement. So we don't need the 3288 // is_gc_active() check to decided which top to use when 3289 // scanning cards (see CR 7039627). 3290 increment_gc_time_stamp(); 3291 3292 if (VerifyRememberedSets) { 3293 log_info(gc, verify)("[Verifying RemSets after GC]"); 3294 VerifyRegionRemSetClosure v_cl; 3295 heap_region_iterate(&v_cl); 3296 } 3297 3298 _verifier->verify_after_gc(); 3299 _verifier->check_bitmaps("GC End"); 3300 3301 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3302 ref_processor_stw()->verify_no_references_recorded(); 3303 3304 // CM reference discovery will be re-enabled if necessary. 3305 } 3306 3307 #ifdef TRACESPINNING 3308 ParallelTaskTerminator::print_termination_counts(); 3309 #endif 3310 3311 gc_epilogue(false); 3312 } 3313 3314 // Print the remainder of the GC log output. 3315 if (evacuation_failed()) { 3316 log_info(gc)("To-space exhausted"); 3317 } 3318 3319 g1_policy()->print_phases(); 3320 heap_transition.print(); 3321 3322 // It is not yet to safe to tell the concurrent mark to 3323 // start as we have some optional output below. We don't want the 3324 // output from the concurrent mark thread interfering with this 3325 // logging output either. 3326 3327 _hrm.verify_optional(); 3328 _verifier->verify_region_sets_optional(); 3329 3330 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3331 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3332 3333 print_heap_after_gc(); 3334 print_heap_regions(); 3335 trace_heap_after_gc(_gc_tracer_stw); 3336 3337 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3338 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3339 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3340 // before any GC notifications are raised. 3341 g1mm()->update_sizes(); 3342 3343 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3344 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3345 _gc_timer_stw->register_gc_end(); 3346 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3347 } 3348 // It should now be safe to tell the concurrent mark thread to start 3349 // without its logging output interfering with the logging output 3350 // that came from the pause. 3351 3352 if (should_start_conc_mark) { 3353 // CAUTION: after the doConcurrentMark() call below, 3354 // the concurrent marking thread(s) could be running 3355 // concurrently with us. Make sure that anything after 3356 // this point does not assume that we are the only GC thread 3357 // running. Note: of course, the actual marking work will 3358 // not start until the safepoint itself is released in 3359 // SuspendibleThreadSet::desynchronize(). 3360 doConcurrentMark(); 3361 } 3362 3363 return true; 3364 } 3365 3366 void G1CollectedHeap::remove_self_forwarding_pointers() { 3367 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3368 workers()->run_task(&rsfp_task); 3369 } 3370 3371 void G1CollectedHeap::restore_after_evac_failure() { 3372 double remove_self_forwards_start = os::elapsedTime(); 3373 3374 remove_self_forwarding_pointers(); 3375 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3376 _preserved_marks_set.restore(&task_executor); 3377 3378 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3379 } 3380 3381 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3382 if (!_evacuation_failed) { 3383 _evacuation_failed = true; 3384 } 3385 3386 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3387 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3388 } 3389 3390 bool G1ParEvacuateFollowersClosure::offer_termination() { 3391 G1ParScanThreadState* const pss = par_scan_state(); 3392 start_term_time(); 3393 const bool res = terminator()->offer_termination(); 3394 end_term_time(); 3395 return res; 3396 } 3397 3398 void G1ParEvacuateFollowersClosure::do_void() { 3399 G1ParScanThreadState* const pss = par_scan_state(); 3400 pss->trim_queue(); 3401 do { 3402 pss->steal_and_trim_queue(queues()); 3403 } while (!offer_termination()); 3404 } 3405 3406 class G1ParTask : public AbstractGangTask { 3407 protected: 3408 G1CollectedHeap* _g1h; 3409 G1ParScanThreadStateSet* _pss; 3410 RefToScanQueueSet* _queues; 3411 G1RootProcessor* _root_processor; 3412 ParallelTaskTerminator _terminator; 3413 uint _n_workers; 3414 3415 public: 3416 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3417 : AbstractGangTask("G1 collection"), 3418 _g1h(g1h), 3419 _pss(per_thread_states), 3420 _queues(task_queues), 3421 _root_processor(root_processor), 3422 _terminator(n_workers, _queues), 3423 _n_workers(n_workers) 3424 {} 3425 3426 void work(uint worker_id) { 3427 if (worker_id >= _n_workers) return; // no work needed this round 3428 3429 double start_sec = os::elapsedTime(); 3430 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3431 3432 { 3433 ResourceMark rm; 3434 HandleMark hm; 3435 3436 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3437 3438 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3439 pss->set_ref_processor(rp); 3440 3441 double start_strong_roots_sec = os::elapsedTime(); 3442 3443 _root_processor->evacuate_roots(pss->closures(), worker_id); 3444 3445 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3446 // treating the nmethods visited to act as roots for concurrent marking. 3447 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3448 // objects copied by the current evacuation. 3449 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, 3450 pss->closures()->weak_codeblobs(), 3451 worker_id); 3452 3453 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3454 3455 double term_sec = 0.0; 3456 size_t evac_term_attempts = 0; 3457 { 3458 double start = os::elapsedTime(); 3459 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3460 evac.do_void(); 3461 3462 evac_term_attempts = evac.term_attempts(); 3463 term_sec = evac.term_time(); 3464 double elapsed_sec = os::elapsedTime() - start; 3465 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3466 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3467 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3468 } 3469 3470 assert(pss->queue_is_empty(), "should be empty"); 3471 3472 if (log_is_enabled(Debug, gc, task, stats)) { 3473 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3474 size_t lab_waste; 3475 size_t lab_undo_waste; 3476 pss->waste(lab_waste, lab_undo_waste); 3477 _g1h->print_termination_stats(worker_id, 3478 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3479 strong_roots_sec * 1000.0, /* strong roots time */ 3480 term_sec * 1000.0, /* evac term time */ 3481 evac_term_attempts, /* evac term attempts */ 3482 lab_waste, /* alloc buffer waste */ 3483 lab_undo_waste /* undo waste */ 3484 ); 3485 } 3486 3487 // Close the inner scope so that the ResourceMark and HandleMark 3488 // destructors are executed here and are included as part of the 3489 // "GC Worker Time". 3490 } 3491 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3492 } 3493 }; 3494 3495 void G1CollectedHeap::print_termination_stats_hdr() { 3496 log_debug(gc, task, stats)("GC Termination Stats"); 3497 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3498 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3499 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3500 } 3501 3502 void G1CollectedHeap::print_termination_stats(uint worker_id, 3503 double elapsed_ms, 3504 double strong_roots_ms, 3505 double term_ms, 3506 size_t term_attempts, 3507 size_t alloc_buffer_waste, 3508 size_t undo_waste) const { 3509 log_debug(gc, task, stats) 3510 ("%3d %9.2f %9.2f %6.2f " 3511 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3512 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3513 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3514 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3515 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3516 alloc_buffer_waste * HeapWordSize / K, 3517 undo_waste * HeapWordSize / K); 3518 } 3519 3520 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3521 private: 3522 BoolObjectClosure* _is_alive; 3523 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3524 3525 int _initial_string_table_size; 3526 int _initial_symbol_table_size; 3527 3528 bool _process_strings; 3529 int _strings_processed; 3530 int _strings_removed; 3531 3532 bool _process_symbols; 3533 int _symbols_processed; 3534 int _symbols_removed; 3535 3536 bool _process_string_dedup; 3537 3538 public: 3539 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3540 AbstractGangTask("String/Symbol Unlinking"), 3541 _is_alive(is_alive), 3542 _dedup_closure(is_alive, NULL, false), 3543 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3544 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3545 _process_string_dedup(process_string_dedup) { 3546 3547 _initial_string_table_size = StringTable::the_table()->table_size(); 3548 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3549 if (process_strings) { 3550 StringTable::clear_parallel_claimed_index(); 3551 } 3552 if (process_symbols) { 3553 SymbolTable::clear_parallel_claimed_index(); 3554 } 3555 } 3556 3557 ~G1StringAndSymbolCleaningTask() { 3558 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3559 "claim value %d after unlink less than initial string table size %d", 3560 StringTable::parallel_claimed_index(), _initial_string_table_size); 3561 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3562 "claim value %d after unlink less than initial symbol table size %d", 3563 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3564 3565 log_info(gc, stringtable)( 3566 "Cleaned string and symbol table, " 3567 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3568 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3569 strings_processed(), strings_removed(), 3570 symbols_processed(), symbols_removed()); 3571 } 3572 3573 void work(uint worker_id) { 3574 int strings_processed = 0; 3575 int strings_removed = 0; 3576 int symbols_processed = 0; 3577 int symbols_removed = 0; 3578 if (_process_strings) { 3579 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3580 Atomic::add(strings_processed, &_strings_processed); 3581 Atomic::add(strings_removed, &_strings_removed); 3582 } 3583 if (_process_symbols) { 3584 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3585 Atomic::add(symbols_processed, &_symbols_processed); 3586 Atomic::add(symbols_removed, &_symbols_removed); 3587 } 3588 if (_process_string_dedup) { 3589 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3590 } 3591 } 3592 3593 size_t strings_processed() const { return (size_t)_strings_processed; } 3594 size_t strings_removed() const { return (size_t)_strings_removed; } 3595 3596 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3597 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3598 }; 3599 3600 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3601 private: 3602 static Monitor* _lock; 3603 3604 BoolObjectClosure* const _is_alive; 3605 const bool _unloading_occurred; 3606 const uint _num_workers; 3607 3608 // Variables used to claim nmethods. 3609 CompiledMethod* _first_nmethod; 3610 volatile CompiledMethod* _claimed_nmethod; 3611 3612 // The list of nmethods that need to be processed by the second pass. 3613 volatile CompiledMethod* _postponed_list; 3614 volatile uint _num_entered_barrier; 3615 3616 public: 3617 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3618 _is_alive(is_alive), 3619 _unloading_occurred(unloading_occurred), 3620 _num_workers(num_workers), 3621 _first_nmethod(NULL), 3622 _claimed_nmethod(NULL), 3623 _postponed_list(NULL), 3624 _num_entered_barrier(0) 3625 { 3626 CompiledMethod::increase_unloading_clock(); 3627 // Get first alive nmethod 3628 CompiledMethodIterator iter = CompiledMethodIterator(); 3629 if(iter.next_alive()) { 3630 _first_nmethod = iter.method(); 3631 } 3632 _claimed_nmethod = (volatile CompiledMethod*)_first_nmethod; 3633 } 3634 3635 ~G1CodeCacheUnloadingTask() { 3636 CodeCache::verify_clean_inline_caches(); 3637 3638 CodeCache::set_needs_cache_clean(false); 3639 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3640 3641 CodeCache::verify_icholder_relocations(); 3642 } 3643 3644 private: 3645 void add_to_postponed_list(CompiledMethod* nm) { 3646 CompiledMethod* old; 3647 do { 3648 old = (CompiledMethod*)_postponed_list; 3649 nm->set_unloading_next(old); 3650 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 3651 } 3652 3653 void clean_nmethod(CompiledMethod* nm) { 3654 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3655 3656 if (postponed) { 3657 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3658 add_to_postponed_list(nm); 3659 } 3660 3661 // Mark that this thread has been cleaned/unloaded. 3662 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3663 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3664 } 3665 3666 void clean_nmethod_postponed(CompiledMethod* nm) { 3667 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3668 } 3669 3670 static const int MaxClaimNmethods = 16; 3671 3672 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3673 CompiledMethod* first; 3674 CompiledMethodIterator last; 3675 3676 do { 3677 *num_claimed_nmethods = 0; 3678 3679 first = (CompiledMethod*)_claimed_nmethod; 3680 last = CompiledMethodIterator(first); 3681 3682 if (first != NULL) { 3683 3684 for (int i = 0; i < MaxClaimNmethods; i++) { 3685 if (!last.next_alive()) { 3686 break; 3687 } 3688 claimed_nmethods[i] = last.method(); 3689 (*num_claimed_nmethods)++; 3690 } 3691 } 3692 3693 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 3694 } 3695 3696 CompiledMethod* claim_postponed_nmethod() { 3697 CompiledMethod* claim; 3698 CompiledMethod* next; 3699 3700 do { 3701 claim = (CompiledMethod*)_postponed_list; 3702 if (claim == NULL) { 3703 return NULL; 3704 } 3705 3706 next = claim->unloading_next(); 3707 3708 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 3709 3710 return claim; 3711 } 3712 3713 public: 3714 // Mark that we're done with the first pass of nmethod cleaning. 3715 void barrier_mark(uint worker_id) { 3716 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3717 _num_entered_barrier++; 3718 if (_num_entered_barrier == _num_workers) { 3719 ml.notify_all(); 3720 } 3721 } 3722 3723 // See if we have to wait for the other workers to 3724 // finish their first-pass nmethod cleaning work. 3725 void barrier_wait(uint worker_id) { 3726 if (_num_entered_barrier < _num_workers) { 3727 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3728 while (_num_entered_barrier < _num_workers) { 3729 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3730 } 3731 } 3732 } 3733 3734 // Cleaning and unloading of nmethods. Some work has to be postponed 3735 // to the second pass, when we know which nmethods survive. 3736 void work_first_pass(uint worker_id) { 3737 // The first nmethods is claimed by the first worker. 3738 if (worker_id == 0 && _first_nmethod != NULL) { 3739 clean_nmethod(_first_nmethod); 3740 _first_nmethod = NULL; 3741 } 3742 3743 int num_claimed_nmethods; 3744 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3745 3746 while (true) { 3747 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3748 3749 if (num_claimed_nmethods == 0) { 3750 break; 3751 } 3752 3753 for (int i = 0; i < num_claimed_nmethods; i++) { 3754 clean_nmethod(claimed_nmethods[i]); 3755 } 3756 } 3757 } 3758 3759 void work_second_pass(uint worker_id) { 3760 CompiledMethod* nm; 3761 // Take care of postponed nmethods. 3762 while ((nm = claim_postponed_nmethod()) != NULL) { 3763 clean_nmethod_postponed(nm); 3764 } 3765 } 3766 }; 3767 3768 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3769 3770 class G1KlassCleaningTask : public StackObj { 3771 BoolObjectClosure* _is_alive; 3772 volatile jint _clean_klass_tree_claimed; 3773 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3774 3775 public: 3776 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3777 _is_alive(is_alive), 3778 _clean_klass_tree_claimed(0), 3779 _klass_iterator() { 3780 } 3781 3782 private: 3783 bool claim_clean_klass_tree_task() { 3784 if (_clean_klass_tree_claimed) { 3785 return false; 3786 } 3787 3788 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 3789 } 3790 3791 InstanceKlass* claim_next_klass() { 3792 Klass* klass; 3793 do { 3794 klass =_klass_iterator.next_klass(); 3795 } while (klass != NULL && !klass->is_instance_klass()); 3796 3797 // this can be null so don't call InstanceKlass::cast 3798 return static_cast<InstanceKlass*>(klass); 3799 } 3800 3801 public: 3802 3803 void clean_klass(InstanceKlass* ik) { 3804 ik->clean_weak_instanceklass_links(_is_alive); 3805 } 3806 3807 void work() { 3808 ResourceMark rm; 3809 3810 // One worker will clean the subklass/sibling klass tree. 3811 if (claim_clean_klass_tree_task()) { 3812 Klass::clean_subklass_tree(_is_alive); 3813 } 3814 3815 // All workers will help cleaning the classes, 3816 InstanceKlass* klass; 3817 while ((klass = claim_next_klass()) != NULL) { 3818 clean_klass(klass); 3819 } 3820 } 3821 }; 3822 3823 class G1ResolvedMethodCleaningTask : public StackObj { 3824 BoolObjectClosure* _is_alive; 3825 volatile jint _resolved_method_task_claimed; 3826 public: 3827 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) : 3828 _is_alive(is_alive), _resolved_method_task_claimed(0) {} 3829 3830 bool claim_resolved_method_task() { 3831 if (_resolved_method_task_claimed) { 3832 return false; 3833 } 3834 return Atomic::cmpxchg(1, (jint*)&_resolved_method_task_claimed, 0) == 0; 3835 } 3836 3837 // These aren't big, one thread can do it all. 3838 void work() { 3839 if (claim_resolved_method_task()) { 3840 ResolvedMethodTable::unlink(_is_alive); 3841 } 3842 } 3843 }; 3844 3845 3846 // To minimize the remark pause times, the tasks below are done in parallel. 3847 class G1ParallelCleaningTask : public AbstractGangTask { 3848 private: 3849 G1StringAndSymbolCleaningTask _string_symbol_task; 3850 G1CodeCacheUnloadingTask _code_cache_task; 3851 G1KlassCleaningTask _klass_cleaning_task; 3852 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task; 3853 3854 public: 3855 // The constructor is run in the VMThread. 3856 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3857 AbstractGangTask("Parallel Cleaning"), 3858 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3859 _code_cache_task(num_workers, is_alive, unloading_occurred), 3860 _klass_cleaning_task(is_alive), 3861 _resolved_method_cleaning_task(is_alive) { 3862 } 3863 3864 // The parallel work done by all worker threads. 3865 void work(uint worker_id) { 3866 // Do first pass of code cache cleaning. 3867 _code_cache_task.work_first_pass(worker_id); 3868 3869 // Let the threads mark that the first pass is done. 3870 _code_cache_task.barrier_mark(worker_id); 3871 3872 // Clean the Strings and Symbols. 3873 _string_symbol_task.work(worker_id); 3874 3875 // Clean unreferenced things in the ResolvedMethodTable 3876 _resolved_method_cleaning_task.work(); 3877 3878 // Wait for all workers to finish the first code cache cleaning pass. 3879 _code_cache_task.barrier_wait(worker_id); 3880 3881 // Do the second code cache cleaning work, which realize on 3882 // the liveness information gathered during the first pass. 3883 _code_cache_task.work_second_pass(worker_id); 3884 3885 // Clean all klasses that were not unloaded. 3886 _klass_cleaning_task.work(); 3887 } 3888 }; 3889 3890 3891 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3892 bool class_unloading_occurred) { 3893 uint n_workers = workers()->active_workers(); 3894 3895 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3896 workers()->run_task(&g1_unlink_task); 3897 } 3898 3899 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3900 bool process_strings, 3901 bool process_symbols, 3902 bool process_string_dedup) { 3903 if (!process_strings && !process_symbols && !process_string_dedup) { 3904 // Nothing to clean. 3905 return; 3906 } 3907 3908 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3909 workers()->run_task(&g1_unlink_task); 3910 3911 } 3912 3913 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3914 private: 3915 DirtyCardQueueSet* _queue; 3916 G1CollectedHeap* _g1h; 3917 public: 3918 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3919 _queue(queue), _g1h(g1h) { } 3920 3921 virtual void work(uint worker_id) { 3922 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3923 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3924 3925 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3926 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3927 3928 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3929 } 3930 }; 3931 3932 void G1CollectedHeap::redirty_logged_cards() { 3933 double redirty_logged_cards_start = os::elapsedTime(); 3934 3935 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3936 dirty_card_queue_set().reset_for_par_iteration(); 3937 workers()->run_task(&redirty_task); 3938 3939 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 3940 dcq.merge_bufferlists(&dirty_card_queue_set()); 3941 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3942 3943 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3944 } 3945 3946 // Weak Reference Processing support 3947 3948 // An always "is_alive" closure that is used to preserve referents. 3949 // If the object is non-null then it's alive. Used in the preservation 3950 // of referent objects that are pointed to by reference objects 3951 // discovered by the CM ref processor. 3952 class G1AlwaysAliveClosure: public BoolObjectClosure { 3953 G1CollectedHeap* _g1; 3954 public: 3955 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3956 bool do_object_b(oop p) { 3957 if (p != NULL) { 3958 return true; 3959 } 3960 return false; 3961 } 3962 }; 3963 3964 bool G1STWIsAliveClosure::do_object_b(oop p) { 3965 // An object is reachable if it is outside the collection set, 3966 // or is inside and copied. 3967 return !_g1->is_in_cset(p) || p->is_forwarded(); 3968 } 3969 3970 // Non Copying Keep Alive closure 3971 class G1KeepAliveClosure: public OopClosure { 3972 G1CollectedHeap* _g1; 3973 public: 3974 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3975 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3976 void do_oop(oop* p) { 3977 oop obj = *p; 3978 assert(obj != NULL, "the caller should have filtered out NULL values"); 3979 3980 const InCSetState cset_state = _g1->in_cset_state(obj); 3981 if (!cset_state.is_in_cset_or_humongous()) { 3982 return; 3983 } 3984 if (cset_state.is_in_cset()) { 3985 assert( obj->is_forwarded(), "invariant" ); 3986 *p = obj->forwardee(); 3987 } else { 3988 assert(!obj->is_forwarded(), "invariant" ); 3989 assert(cset_state.is_humongous(), 3990 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3991 _g1->set_humongous_is_live(obj); 3992 } 3993 } 3994 }; 3995 3996 // Copying Keep Alive closure - can be called from both 3997 // serial and parallel code as long as different worker 3998 // threads utilize different G1ParScanThreadState instances 3999 // and different queues. 4000 4001 class G1CopyingKeepAliveClosure: public OopClosure { 4002 G1CollectedHeap* _g1h; 4003 OopClosure* _copy_non_heap_obj_cl; 4004 G1ParScanThreadState* _par_scan_state; 4005 4006 public: 4007 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4008 OopClosure* non_heap_obj_cl, 4009 G1ParScanThreadState* pss): 4010 _g1h(g1h), 4011 _copy_non_heap_obj_cl(non_heap_obj_cl), 4012 _par_scan_state(pss) 4013 {} 4014 4015 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4016 virtual void do_oop( oop* p) { do_oop_work(p); } 4017 4018 template <class T> void do_oop_work(T* p) { 4019 oop obj = oopDesc::load_decode_heap_oop(p); 4020 4021 if (_g1h->is_in_cset_or_humongous(obj)) { 4022 // If the referent object has been forwarded (either copied 4023 // to a new location or to itself in the event of an 4024 // evacuation failure) then we need to update the reference 4025 // field and, if both reference and referent are in the G1 4026 // heap, update the RSet for the referent. 4027 // 4028 // If the referent has not been forwarded then we have to keep 4029 // it alive by policy. Therefore we have copy the referent. 4030 // 4031 // If the reference field is in the G1 heap then we can push 4032 // on the PSS queue. When the queue is drained (after each 4033 // phase of reference processing) the object and it's followers 4034 // will be copied, the reference field set to point to the 4035 // new location, and the RSet updated. Otherwise we need to 4036 // use the the non-heap or metadata closures directly to copy 4037 // the referent object and update the pointer, while avoiding 4038 // updating the RSet. 4039 4040 if (_g1h->is_in_g1_reserved(p)) { 4041 _par_scan_state->push_on_queue(p); 4042 } else { 4043 assert(!Metaspace::contains((const void*)p), 4044 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4045 _copy_non_heap_obj_cl->do_oop(p); 4046 } 4047 } 4048 } 4049 }; 4050 4051 // Serial drain queue closure. Called as the 'complete_gc' 4052 // closure for each discovered list in some of the 4053 // reference processing phases. 4054 4055 class G1STWDrainQueueClosure: public VoidClosure { 4056 protected: 4057 G1CollectedHeap* _g1h; 4058 G1ParScanThreadState* _par_scan_state; 4059 4060 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4061 4062 public: 4063 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4064 _g1h(g1h), 4065 _par_scan_state(pss) 4066 { } 4067 4068 void do_void() { 4069 G1ParScanThreadState* const pss = par_scan_state(); 4070 pss->trim_queue(); 4071 } 4072 }; 4073 4074 // Parallel Reference Processing closures 4075 4076 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4077 // processing during G1 evacuation pauses. 4078 4079 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4080 private: 4081 G1CollectedHeap* _g1h; 4082 G1ParScanThreadStateSet* _pss; 4083 RefToScanQueueSet* _queues; 4084 WorkGang* _workers; 4085 uint _active_workers; 4086 4087 public: 4088 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4089 G1ParScanThreadStateSet* per_thread_states, 4090 WorkGang* workers, 4091 RefToScanQueueSet *task_queues, 4092 uint n_workers) : 4093 _g1h(g1h), 4094 _pss(per_thread_states), 4095 _queues(task_queues), 4096 _workers(workers), 4097 _active_workers(n_workers) 4098 { 4099 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 4100 } 4101 4102 // Executes the given task using concurrent marking worker threads. 4103 virtual void execute(ProcessTask& task); 4104 virtual void execute(EnqueueTask& task); 4105 }; 4106 4107 // Gang task for possibly parallel reference processing 4108 4109 class G1STWRefProcTaskProxy: public AbstractGangTask { 4110 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4111 ProcessTask& _proc_task; 4112 G1CollectedHeap* _g1h; 4113 G1ParScanThreadStateSet* _pss; 4114 RefToScanQueueSet* _task_queues; 4115 ParallelTaskTerminator* _terminator; 4116 4117 public: 4118 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4119 G1CollectedHeap* g1h, 4120 G1ParScanThreadStateSet* per_thread_states, 4121 RefToScanQueueSet *task_queues, 4122 ParallelTaskTerminator* terminator) : 4123 AbstractGangTask("Process reference objects in parallel"), 4124 _proc_task(proc_task), 4125 _g1h(g1h), 4126 _pss(per_thread_states), 4127 _task_queues(task_queues), 4128 _terminator(terminator) 4129 {} 4130 4131 virtual void work(uint worker_id) { 4132 // The reference processing task executed by a single worker. 4133 ResourceMark rm; 4134 HandleMark hm; 4135 4136 G1STWIsAliveClosure is_alive(_g1h); 4137 4138 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4139 pss->set_ref_processor(NULL); 4140 4141 // Keep alive closure. 4142 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4143 4144 // Complete GC closure 4145 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4146 4147 // Call the reference processing task's work routine. 4148 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4149 4150 // Note we cannot assert that the refs array is empty here as not all 4151 // of the processing tasks (specifically phase2 - pp2_work) execute 4152 // the complete_gc closure (which ordinarily would drain the queue) so 4153 // the queue may not be empty. 4154 } 4155 }; 4156 4157 // Driver routine for parallel reference processing. 4158 // Creates an instance of the ref processing gang 4159 // task and has the worker threads execute it. 4160 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4161 assert(_workers != NULL, "Need parallel worker threads."); 4162 4163 ParallelTaskTerminator terminator(_active_workers, _queues); 4164 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4165 4166 _workers->run_task(&proc_task_proxy); 4167 } 4168 4169 // Gang task for parallel reference enqueueing. 4170 4171 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4172 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4173 EnqueueTask& _enq_task; 4174 4175 public: 4176 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4177 AbstractGangTask("Enqueue reference objects in parallel"), 4178 _enq_task(enq_task) 4179 { } 4180 4181 virtual void work(uint worker_id) { 4182 _enq_task.work(worker_id); 4183 } 4184 }; 4185 4186 // Driver routine for parallel reference enqueueing. 4187 // Creates an instance of the ref enqueueing gang 4188 // task and has the worker threads execute it. 4189 4190 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4191 assert(_workers != NULL, "Need parallel worker threads."); 4192 4193 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4194 4195 _workers->run_task(&enq_task_proxy); 4196 } 4197 4198 // End of weak reference support closures 4199 4200 // Abstract task used to preserve (i.e. copy) any referent objects 4201 // that are in the collection set and are pointed to by reference 4202 // objects discovered by the CM ref processor. 4203 4204 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4205 protected: 4206 G1CollectedHeap* _g1h; 4207 G1ParScanThreadStateSet* _pss; 4208 RefToScanQueueSet* _queues; 4209 ParallelTaskTerminator _terminator; 4210 uint _n_workers; 4211 4212 public: 4213 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4214 AbstractGangTask("ParPreserveCMReferents"), 4215 _g1h(g1h), 4216 _pss(per_thread_states), 4217 _queues(task_queues), 4218 _terminator(workers, _queues), 4219 _n_workers(workers) 4220 { 4221 g1h->ref_processor_cm()->set_active_mt_degree(workers); 4222 } 4223 4224 void work(uint worker_id) { 4225 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4226 4227 ResourceMark rm; 4228 HandleMark hm; 4229 4230 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4231 pss->set_ref_processor(NULL); 4232 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4233 4234 // Is alive closure 4235 G1AlwaysAliveClosure always_alive(_g1h); 4236 4237 // Copying keep alive closure. Applied to referent objects that need 4238 // to be copied. 4239 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4240 4241 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4242 4243 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4244 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4245 4246 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4247 // So this must be true - but assert just in case someone decides to 4248 // change the worker ids. 4249 assert(worker_id < limit, "sanity"); 4250 assert(!rp->discovery_is_atomic(), "check this code"); 4251 4252 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4253 for (uint idx = worker_id; idx < limit; idx += stride) { 4254 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4255 4256 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4257 while (iter.has_next()) { 4258 // Since discovery is not atomic for the CM ref processor, we 4259 // can see some null referent objects. 4260 iter.load_ptrs(DEBUG_ONLY(true)); 4261 oop ref = iter.obj(); 4262 4263 // This will filter nulls. 4264 if (iter.is_referent_alive()) { 4265 iter.make_referent_alive(); 4266 } 4267 iter.move_to_next(); 4268 } 4269 } 4270 4271 // Drain the queue - which may cause stealing 4272 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4273 drain_queue.do_void(); 4274 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4275 assert(pss->queue_is_empty(), "should be"); 4276 } 4277 }; 4278 4279 void G1CollectedHeap::process_weak_jni_handles() { 4280 double ref_proc_start = os::elapsedTime(); 4281 4282 G1STWIsAliveClosure is_alive(this); 4283 G1KeepAliveClosure keep_alive(this); 4284 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 4285 4286 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4287 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4288 } 4289 4290 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4291 // Any reference objects, in the collection set, that were 'discovered' 4292 // by the CM ref processor should have already been copied (either by 4293 // applying the external root copy closure to the discovered lists, or 4294 // by following an RSet entry). 4295 // 4296 // But some of the referents, that are in the collection set, that these 4297 // reference objects point to may not have been copied: the STW ref 4298 // processor would have seen that the reference object had already 4299 // been 'discovered' and would have skipped discovering the reference, 4300 // but would not have treated the reference object as a regular oop. 4301 // As a result the copy closure would not have been applied to the 4302 // referent object. 4303 // 4304 // We need to explicitly copy these referent objects - the references 4305 // will be processed at the end of remarking. 4306 // 4307 // We also need to do this copying before we process the reference 4308 // objects discovered by the STW ref processor in case one of these 4309 // referents points to another object which is also referenced by an 4310 // object discovered by the STW ref processor. 4311 double preserve_cm_referents_time = 0.0; 4312 4313 // To avoid spawning task when there is no work to do, check that 4314 // a concurrent cycle is active and that some references have been 4315 // discovered. 4316 if (concurrent_mark()->cmThread()->during_cycle() && 4317 ref_processor_cm()->has_discovered_references()) { 4318 double preserve_cm_referents_start = os::elapsedTime(); 4319 uint no_of_gc_workers = workers()->active_workers(); 4320 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4321 per_thread_states, 4322 no_of_gc_workers, 4323 _task_queues); 4324 workers()->run_task(&keep_cm_referents); 4325 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4326 } 4327 4328 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4329 } 4330 4331 // Weak Reference processing during an evacuation pause (part 1). 4332 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4333 double ref_proc_start = os::elapsedTime(); 4334 4335 ReferenceProcessor* rp = _ref_processor_stw; 4336 assert(rp->discovery_enabled(), "should have been enabled"); 4337 4338 // Closure to test whether a referent is alive. 4339 G1STWIsAliveClosure is_alive(this); 4340 4341 // Even when parallel reference processing is enabled, the processing 4342 // of JNI refs is serial and performed serially by the current thread 4343 // rather than by a worker. The following PSS will be used for processing 4344 // JNI refs. 4345 4346 // Use only a single queue for this PSS. 4347 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4348 pss->set_ref_processor(NULL); 4349 assert(pss->queue_is_empty(), "pre-condition"); 4350 4351 // Keep alive closure. 4352 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4353 4354 // Serial Complete GC closure 4355 G1STWDrainQueueClosure drain_queue(this, pss); 4356 4357 // Setup the soft refs policy... 4358 rp->setup_policy(false); 4359 4360 ReferenceProcessorStats stats; 4361 if (!rp->processing_is_mt()) { 4362 // Serial reference processing... 4363 stats = rp->process_discovered_references(&is_alive, 4364 &keep_alive, 4365 &drain_queue, 4366 NULL, 4367 _gc_timer_stw); 4368 } else { 4369 uint no_of_gc_workers = workers()->active_workers(); 4370 4371 // Parallel reference processing 4372 assert(no_of_gc_workers <= rp->max_num_q(), 4373 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4374 no_of_gc_workers, rp->max_num_q()); 4375 4376 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4377 stats = rp->process_discovered_references(&is_alive, 4378 &keep_alive, 4379 &drain_queue, 4380 &par_task_executor, 4381 _gc_timer_stw); 4382 } 4383 4384 _gc_tracer_stw->report_gc_reference_stats(stats); 4385 4386 // We have completed copying any necessary live referent objects. 4387 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4388 4389 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4390 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4391 } 4392 4393 // Weak Reference processing during an evacuation pause (part 2). 4394 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4395 double ref_enq_start = os::elapsedTime(); 4396 4397 ReferenceProcessor* rp = _ref_processor_stw; 4398 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4399 4400 // Now enqueue any remaining on the discovered lists on to 4401 // the pending list. 4402 if (!rp->processing_is_mt()) { 4403 // Serial reference processing... 4404 rp->enqueue_discovered_references(); 4405 } else { 4406 // Parallel reference enqueueing 4407 4408 uint n_workers = workers()->active_workers(); 4409 4410 assert(n_workers <= rp->max_num_q(), 4411 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4412 n_workers, rp->max_num_q()); 4413 4414 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4415 rp->enqueue_discovered_references(&par_task_executor); 4416 } 4417 4418 rp->verify_no_references_recorded(); 4419 assert(!rp->discovery_enabled(), "should have been disabled"); 4420 4421 // FIXME 4422 // CM's reference processing also cleans up the string and symbol tables. 4423 // Should we do that here also? We could, but it is a serial operation 4424 // and could significantly increase the pause time. 4425 4426 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4427 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4428 } 4429 4430 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4431 double merge_pss_time_start = os::elapsedTime(); 4432 per_thread_states->flush(); 4433 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4434 } 4435 4436 void G1CollectedHeap::pre_evacuate_collection_set() { 4437 _expand_heap_after_alloc_failure = true; 4438 _evacuation_failed = false; 4439 4440 // Disable the hot card cache. 4441 _hot_card_cache->reset_hot_cache_claimed_index(); 4442 _hot_card_cache->set_use_cache(false); 4443 4444 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4445 _preserved_marks_set.assert_empty(); 4446 4447 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4448 4449 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4450 if (collector_state()->during_initial_mark_pause()) { 4451 double start_clear_claimed_marks = os::elapsedTime(); 4452 4453 ClassLoaderDataGraph::clear_claimed_marks(); 4454 4455 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4456 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4457 } 4458 } 4459 4460 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4461 // Should G1EvacuationFailureALot be in effect for this GC? 4462 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4463 4464 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4465 4466 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4467 4468 double start_par_time_sec = os::elapsedTime(); 4469 double end_par_time_sec; 4470 4471 { 4472 const uint n_workers = workers()->active_workers(); 4473 G1RootProcessor root_processor(this, n_workers); 4474 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4475 4476 print_termination_stats_hdr(); 4477 4478 workers()->run_task(&g1_par_task); 4479 end_par_time_sec = os::elapsedTime(); 4480 4481 // Closing the inner scope will execute the destructor 4482 // for the G1RootProcessor object. We record the current 4483 // elapsed time before closing the scope so that time 4484 // taken for the destructor is NOT included in the 4485 // reported parallel time. 4486 } 4487 4488 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4489 phase_times->record_par_time(par_time_ms); 4490 4491 double code_root_fixup_time_ms = 4492 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4493 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4494 } 4495 4496 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4497 // Process any discovered reference objects - we have 4498 // to do this _before_ we retire the GC alloc regions 4499 // as we may have to copy some 'reachable' referent 4500 // objects (and their reachable sub-graphs) that were 4501 // not copied during the pause. 4502 if (g1_policy()->should_process_references()) { 4503 preserve_cm_referents(per_thread_states); 4504 process_discovered_references(per_thread_states); 4505 } else { 4506 ref_processor_stw()->verify_no_references_recorded(); 4507 process_weak_jni_handles(); 4508 } 4509 4510 if (G1StringDedup::is_enabled()) { 4511 double fixup_start = os::elapsedTime(); 4512 4513 G1STWIsAliveClosure is_alive(this); 4514 G1KeepAliveClosure keep_alive(this); 4515 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4516 4517 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4518 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4519 } 4520 4521 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4522 4523 if (evacuation_failed()) { 4524 restore_after_evac_failure(); 4525 4526 // Reset the G1EvacuationFailureALot counters and flags 4527 // Note: the values are reset only when an actual 4528 // evacuation failure occurs. 4529 NOT_PRODUCT(reset_evacuation_should_fail();) 4530 } 4531 4532 _preserved_marks_set.assert_empty(); 4533 4534 // Enqueue any remaining references remaining on the STW 4535 // reference processor's discovered lists. We need to do 4536 // this after the card table is cleaned (and verified) as 4537 // the act of enqueueing entries on to the pending list 4538 // will log these updates (and dirty their associated 4539 // cards). We need these updates logged to update any 4540 // RSets. 4541 if (g1_policy()->should_process_references()) { 4542 enqueue_discovered_references(per_thread_states); 4543 } else { 4544 g1_policy()->phase_times()->record_ref_enq_time(0); 4545 } 4546 4547 _allocator->release_gc_alloc_regions(evacuation_info); 4548 4549 merge_per_thread_state_info(per_thread_states); 4550 4551 // Reset and re-enable the hot card cache. 4552 // Note the counts for the cards in the regions in the 4553 // collection set are reset when the collection set is freed. 4554 _hot_card_cache->reset_hot_cache(); 4555 _hot_card_cache->set_use_cache(true); 4556 4557 purge_code_root_memory(); 4558 4559 redirty_logged_cards(); 4560 #if defined(COMPILER2) || INCLUDE_JVMCI 4561 double start = os::elapsedTime(); 4562 DerivedPointerTable::update_pointers(); 4563 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4564 #endif 4565 g1_policy()->print_age_table(); 4566 } 4567 4568 void G1CollectedHeap::record_obj_copy_mem_stats() { 4569 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4570 4571 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4572 create_g1_evac_summary(&_old_evac_stats)); 4573 } 4574 4575 void G1CollectedHeap::free_region(HeapRegion* hr, 4576 FreeRegionList* free_list, 4577 bool skip_remset, 4578 bool skip_hot_card_cache, 4579 bool locked) { 4580 assert(!hr->is_free(), "the region should not be free"); 4581 assert(!hr->is_empty(), "the region should not be empty"); 4582 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4583 assert(free_list != NULL, "pre-condition"); 4584 4585 if (G1VerifyBitmaps) { 4586 MemRegion mr(hr->bottom(), hr->end()); 4587 concurrent_mark()->clearRangePrevBitmap(mr); 4588 } 4589 4590 // Clear the card counts for this region. 4591 // Note: we only need to do this if the region is not young 4592 // (since we don't refine cards in young regions). 4593 if (!skip_hot_card_cache && !hr->is_young()) { 4594 _hot_card_cache->reset_card_counts(hr); 4595 } 4596 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4597 free_list->add_ordered(hr); 4598 } 4599 4600 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4601 FreeRegionList* free_list, 4602 bool skip_remset) { 4603 assert(hr->is_humongous(), "this is only for humongous regions"); 4604 assert(free_list != NULL, "pre-condition"); 4605 hr->clear_humongous(); 4606 free_region(hr, free_list, skip_remset); 4607 } 4608 4609 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4610 const uint humongous_regions_removed) { 4611 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4612 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4613 _old_set.bulk_remove(old_regions_removed); 4614 _humongous_set.bulk_remove(humongous_regions_removed); 4615 } 4616 4617 } 4618 4619 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4620 assert(list != NULL, "list can't be null"); 4621 if (!list->is_empty()) { 4622 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4623 _hrm.insert_list_into_free_list(list); 4624 } 4625 } 4626 4627 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4628 decrease_used(bytes); 4629 } 4630 4631 class G1ParScrubRemSetTask: public AbstractGangTask { 4632 protected: 4633 G1RemSet* _g1rs; 4634 HeapRegionClaimer _hrclaimer; 4635 4636 public: 4637 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) : 4638 AbstractGangTask("G1 ScrubRS"), 4639 _g1rs(g1_rs), 4640 _hrclaimer(num_workers) { 4641 } 4642 4643 void work(uint worker_id) { 4644 _g1rs->scrub(worker_id, &_hrclaimer); 4645 } 4646 }; 4647 4648 void G1CollectedHeap::scrub_rem_set() { 4649 uint num_workers = workers()->active_workers(); 4650 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers); 4651 workers()->run_task(&g1_par_scrub_rs_task); 4652 } 4653 4654 class G1FreeCollectionSetTask : public AbstractGangTask { 4655 private: 4656 4657 // Closure applied to all regions in the collection set to do work that needs to 4658 // be done serially in a single thread. 4659 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4660 private: 4661 EvacuationInfo* _evacuation_info; 4662 const size_t* _surviving_young_words; 4663 4664 // Bytes used in successfully evacuated regions before the evacuation. 4665 size_t _before_used_bytes; 4666 // Bytes used in unsucessfully evacuated regions before the evacuation 4667 size_t _after_used_bytes; 4668 4669 size_t _bytes_allocated_in_old_since_last_gc; 4670 4671 size_t _failure_used_words; 4672 size_t _failure_waste_words; 4673 4674 FreeRegionList _local_free_list; 4675 public: 4676 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4677 HeapRegionClosure(), 4678 _evacuation_info(evacuation_info), 4679 _surviving_young_words(surviving_young_words), 4680 _before_used_bytes(0), 4681 _after_used_bytes(0), 4682 _bytes_allocated_in_old_since_last_gc(0), 4683 _failure_used_words(0), 4684 _failure_waste_words(0), 4685 _local_free_list("Local Region List for CSet Freeing") { 4686 } 4687 4688 virtual bool doHeapRegion(HeapRegion* r) { 4689 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4690 4691 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4692 g1h->clear_in_cset(r); 4693 4694 if (r->is_young()) { 4695 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4696 "Young index %d is wrong for region %u of type %s with %u young regions", 4697 r->young_index_in_cset(), 4698 r->hrm_index(), 4699 r->get_type_str(), 4700 g1h->collection_set()->young_region_length()); 4701 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4702 r->record_surv_words_in_group(words_survived); 4703 } 4704 4705 if (!r->evacuation_failed()) { 4706 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4707 _before_used_bytes += r->used(); 4708 g1h->free_region(r, 4709 &_local_free_list, 4710 true, /* skip_remset */ 4711 true, /* skip_hot_card_cache */ 4712 true /* locked */); 4713 } else { 4714 r->uninstall_surv_rate_group(); 4715 r->set_young_index_in_cset(-1); 4716 r->set_evacuation_failed(false); 4717 // When moving a young gen region to old gen, we "allocate" that whole region 4718 // there. This is in addition to any already evacuated objects. Notify the 4719 // policy about that. 4720 // Old gen regions do not cause an additional allocation: both the objects 4721 // still in the region and the ones already moved are accounted for elsewhere. 4722 if (r->is_young()) { 4723 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4724 } 4725 // The region is now considered to be old. 4726 r->set_old(); 4727 // Do some allocation statistics accounting. Regions that failed evacuation 4728 // are always made old, so there is no need to update anything in the young 4729 // gen statistics, but we need to update old gen statistics. 4730 size_t used_words = r->marked_bytes() / HeapWordSize; 4731 4732 _failure_used_words += used_words; 4733 _failure_waste_words += HeapRegion::GrainWords - used_words; 4734 4735 g1h->old_set_add(r); 4736 _after_used_bytes += r->used(); 4737 } 4738 return false; 4739 } 4740 4741 void complete_work() { 4742 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4743 4744 _evacuation_info->set_regions_freed(_local_free_list.length()); 4745 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4746 4747 g1h->prepend_to_freelist(&_local_free_list); 4748 g1h->decrement_summary_bytes(_before_used_bytes); 4749 4750 G1Policy* policy = g1h->g1_policy(); 4751 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4752 4753 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4754 } 4755 }; 4756 4757 G1CollectionSet* _collection_set; 4758 G1SerialFreeCollectionSetClosure _cl; 4759 const size_t* _surviving_young_words; 4760 4761 size_t _rs_lengths; 4762 4763 volatile jint _serial_work_claim; 4764 4765 struct WorkItem { 4766 uint region_idx; 4767 bool is_young; 4768 bool evacuation_failed; 4769 4770 WorkItem(HeapRegion* r) { 4771 region_idx = r->hrm_index(); 4772 is_young = r->is_young(); 4773 evacuation_failed = r->evacuation_failed(); 4774 } 4775 }; 4776 4777 volatile size_t _parallel_work_claim; 4778 size_t _num_work_items; 4779 WorkItem* _work_items; 4780 4781 void do_serial_work() { 4782 // Need to grab the lock to be allowed to modify the old region list. 4783 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4784 _collection_set->iterate(&_cl); 4785 } 4786 4787 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4788 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4789 4790 HeapRegion* r = g1h->region_at(region_idx); 4791 assert(!g1h->is_on_master_free_list(r), "sanity"); 4792 4793 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4794 4795 if (!is_young) { 4796 g1h->_hot_card_cache->reset_card_counts(r); 4797 } 4798 4799 if (!evacuation_failed) { 4800 r->rem_set()->clear_locked(); 4801 } 4802 } 4803 4804 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4805 private: 4806 size_t _cur_idx; 4807 WorkItem* _work_items; 4808 public: 4809 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4810 4811 virtual bool doHeapRegion(HeapRegion* r) { 4812 _work_items[_cur_idx++] = WorkItem(r); 4813 return false; 4814 } 4815 }; 4816 4817 void prepare_work() { 4818 G1PrepareFreeCollectionSetClosure cl(_work_items); 4819 _collection_set->iterate(&cl); 4820 } 4821 4822 void complete_work() { 4823 _cl.complete_work(); 4824 4825 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4826 policy->record_max_rs_lengths(_rs_lengths); 4827 policy->cset_regions_freed(); 4828 } 4829 public: 4830 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4831 AbstractGangTask("G1 Free Collection Set"), 4832 _cl(evacuation_info, surviving_young_words), 4833 _collection_set(collection_set), 4834 _surviving_young_words(surviving_young_words), 4835 _serial_work_claim(0), 4836 _rs_lengths(0), 4837 _parallel_work_claim(0), 4838 _num_work_items(collection_set->region_length()), 4839 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4840 prepare_work(); 4841 } 4842 4843 ~G1FreeCollectionSetTask() { 4844 complete_work(); 4845 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4846 } 4847 4848 // Chunk size for work distribution. The chosen value has been determined experimentally 4849 // to be a good tradeoff between overhead and achievable parallelism. 4850 static uint chunk_size() { return 32; } 4851 4852 virtual void work(uint worker_id) { 4853 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4854 4855 // Claim serial work. 4856 if (_serial_work_claim == 0) { 4857 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4858 if (value == 0) { 4859 double serial_time = os::elapsedTime(); 4860 do_serial_work(); 4861 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4862 } 4863 } 4864 4865 // Start parallel work. 4866 double young_time = 0.0; 4867 bool has_young_time = false; 4868 double non_young_time = 0.0; 4869 bool has_non_young_time = false; 4870 4871 while (true) { 4872 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4873 size_t cur = end - chunk_size(); 4874 4875 if (cur >= _num_work_items) { 4876 break; 4877 } 4878 4879 double start_time = os::elapsedTime(); 4880 4881 end = MIN2(end, _num_work_items); 4882 4883 for (; cur < end; cur++) { 4884 bool is_young = _work_items[cur].is_young; 4885 4886 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4887 4888 double end_time = os::elapsedTime(); 4889 double time_taken = end_time - start_time; 4890 if (is_young) { 4891 young_time += time_taken; 4892 has_young_time = true; 4893 } else { 4894 non_young_time += time_taken; 4895 has_non_young_time = true; 4896 } 4897 start_time = end_time; 4898 } 4899 } 4900 4901 if (has_young_time) { 4902 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4903 } 4904 if (has_non_young_time) { 4905 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time); 4906 } 4907 } 4908 }; 4909 4910 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4911 _eden.clear(); 4912 4913 double free_cset_start_time = os::elapsedTime(); 4914 4915 { 4916 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4917 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4918 4919 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4920 4921 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4922 cl.name(), 4923 num_workers, 4924 _collection_set.region_length()); 4925 workers()->run_task(&cl, num_workers); 4926 } 4927 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4928 4929 collection_set->clear(); 4930 } 4931 4932 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4933 private: 4934 FreeRegionList* _free_region_list; 4935 HeapRegionSet* _proxy_set; 4936 uint _humongous_objects_reclaimed; 4937 uint _humongous_regions_reclaimed; 4938 size_t _freed_bytes; 4939 public: 4940 4941 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4942 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4943 } 4944 4945 virtual bool doHeapRegion(HeapRegion* r) { 4946 if (!r->is_starts_humongous()) { 4947 return false; 4948 } 4949 4950 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4951 4952 oop obj = (oop)r->bottom(); 4953 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 4954 4955 // The following checks whether the humongous object is live are sufficient. 4956 // The main additional check (in addition to having a reference from the roots 4957 // or the young gen) is whether the humongous object has a remembered set entry. 4958 // 4959 // A humongous object cannot be live if there is no remembered set for it 4960 // because: 4961 // - there can be no references from within humongous starts regions referencing 4962 // the object because we never allocate other objects into them. 4963 // (I.e. there are no intra-region references that may be missed by the 4964 // remembered set) 4965 // - as soon there is a remembered set entry to the humongous starts region 4966 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4967 // until the end of a concurrent mark. 4968 // 4969 // It is not required to check whether the object has been found dead by marking 4970 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4971 // all objects allocated during that time are considered live. 4972 // SATB marking is even more conservative than the remembered set. 4973 // So if at this point in the collection there is no remembered set entry, 4974 // nobody has a reference to it. 4975 // At the start of collection we flush all refinement logs, and remembered sets 4976 // are completely up-to-date wrt to references to the humongous object. 4977 // 4978 // Other implementation considerations: 4979 // - never consider object arrays at this time because they would pose 4980 // considerable effort for cleaning up the the remembered sets. This is 4981 // required because stale remembered sets might reference locations that 4982 // are currently allocated into. 4983 uint region_idx = r->hrm_index(); 4984 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4985 !r->rem_set()->is_empty()) { 4986 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", 4987 region_idx, 4988 (size_t)obj->size() * HeapWordSize, 4989 p2i(r->bottom()), 4990 r->rem_set()->occupied(), 4991 r->rem_set()->strong_code_roots_list_length(), 4992 next_bitmap->isMarked(r->bottom()), 4993 g1h->is_humongous_reclaim_candidate(region_idx), 4994 obj->is_typeArray() 4995 ); 4996 return false; 4997 } 4998 4999 guarantee(obj->is_typeArray(), 5000 "Only eagerly reclaiming type arrays is supported, but the object " 5001 PTR_FORMAT " is not.", p2i(r->bottom())); 5002 5003 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", 5004 region_idx, 5005 (size_t)obj->size() * HeapWordSize, 5006 p2i(r->bottom()), 5007 r->rem_set()->occupied(), 5008 r->rem_set()->strong_code_roots_list_length(), 5009 next_bitmap->isMarked(r->bottom()), 5010 g1h->is_humongous_reclaim_candidate(region_idx), 5011 obj->is_typeArray() 5012 ); 5013 5014 // Need to clear mark bit of the humongous object if already set. 5015 if (next_bitmap->isMarked(r->bottom())) { 5016 next_bitmap->clear(r->bottom()); 5017 } 5018 _humongous_objects_reclaimed++; 5019 do { 5020 HeapRegion* next = g1h->next_region_in_humongous(r); 5021 _freed_bytes += r->used(); 5022 r->set_containing_set(NULL); 5023 _humongous_regions_reclaimed++; 5024 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ ); 5025 r = next; 5026 } while (r != NULL); 5027 5028 return false; 5029 } 5030 5031 uint humongous_objects_reclaimed() { 5032 return _humongous_objects_reclaimed; 5033 } 5034 5035 uint humongous_regions_reclaimed() { 5036 return _humongous_regions_reclaimed; 5037 } 5038 5039 size_t bytes_freed() const { 5040 return _freed_bytes; 5041 } 5042 }; 5043 5044 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 5045 assert_at_safepoint(true); 5046 5047 if (!G1EagerReclaimHumongousObjects || 5048 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 5049 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5050 return; 5051 } 5052 5053 double start_time = os::elapsedTime(); 5054 5055 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5056 5057 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5058 heap_region_iterate(&cl); 5059 5060 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 5061 5062 G1HRPrinter* hrp = hr_printer(); 5063 if (hrp->is_active()) { 5064 FreeRegionListIterator iter(&local_cleanup_list); 5065 while (iter.more_available()) { 5066 HeapRegion* hr = iter.get_next(); 5067 hrp->cleanup(hr); 5068 } 5069 } 5070 5071 prepend_to_freelist(&local_cleanup_list); 5072 decrement_summary_bytes(cl.bytes_freed()); 5073 5074 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5075 cl.humongous_objects_reclaimed()); 5076 } 5077 5078 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 5079 public: 5080 virtual bool doHeapRegion(HeapRegion* r) { 5081 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 5082 G1CollectedHeap::heap()->clear_in_cset(r); 5083 r->set_young_index_in_cset(-1); 5084 return false; 5085 } 5086 }; 5087 5088 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 5089 G1AbandonCollectionSetClosure cl; 5090 collection_set->iterate(&cl); 5091 5092 collection_set->clear(); 5093 collection_set->stop_incremental_building(); 5094 } 5095 5096 void G1CollectedHeap::set_free_regions_coming() { 5097 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 5098 5099 assert(!free_regions_coming(), "pre-condition"); 5100 _free_regions_coming = true; 5101 } 5102 5103 void G1CollectedHeap::reset_free_regions_coming() { 5104 assert(free_regions_coming(), "pre-condition"); 5105 5106 { 5107 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5108 _free_regions_coming = false; 5109 SecondaryFreeList_lock->notify_all(); 5110 } 5111 5112 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 5113 } 5114 5115 void G1CollectedHeap::wait_while_free_regions_coming() { 5116 // Most of the time we won't have to wait, so let's do a quick test 5117 // first before we take the lock. 5118 if (!free_regions_coming()) { 5119 return; 5120 } 5121 5122 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 5123 5124 { 5125 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5126 while (free_regions_coming()) { 5127 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5128 } 5129 } 5130 5131 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 5132 } 5133 5134 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5135 return _allocator->is_retained_old_region(hr); 5136 } 5137 5138 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5139 _eden.add(hr); 5140 _g1_policy->set_region_eden(hr); 5141 } 5142 5143 #ifdef ASSERT 5144 5145 class NoYoungRegionsClosure: public HeapRegionClosure { 5146 private: 5147 bool _success; 5148 public: 5149 NoYoungRegionsClosure() : _success(true) { } 5150 bool doHeapRegion(HeapRegion* r) { 5151 if (r->is_young()) { 5152 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5153 p2i(r->bottom()), p2i(r->end())); 5154 _success = false; 5155 } 5156 return false; 5157 } 5158 bool success() { return _success; } 5159 }; 5160 5161 bool G1CollectedHeap::check_young_list_empty() { 5162 bool ret = (young_regions_count() == 0); 5163 5164 NoYoungRegionsClosure closure; 5165 heap_region_iterate(&closure); 5166 ret = ret && closure.success(); 5167 5168 return ret; 5169 } 5170 5171 #endif // ASSERT 5172 5173 class TearDownRegionSetsClosure : public HeapRegionClosure { 5174 private: 5175 HeapRegionSet *_old_set; 5176 5177 public: 5178 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5179 5180 bool doHeapRegion(HeapRegion* r) { 5181 if (r->is_old()) { 5182 _old_set->remove(r); 5183 } else if(r->is_young()) { 5184 r->uninstall_surv_rate_group(); 5185 } else { 5186 // We ignore free regions, we'll empty the free list afterwards. 5187 // We ignore humongous regions, we're not tearing down the 5188 // humongous regions set. 5189 assert(r->is_free() || r->is_humongous(), 5190 "it cannot be another type"); 5191 } 5192 return false; 5193 } 5194 5195 ~TearDownRegionSetsClosure() { 5196 assert(_old_set->is_empty(), "post-condition"); 5197 } 5198 }; 5199 5200 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5201 assert_at_safepoint(true /* should_be_vm_thread */); 5202 5203 if (!free_list_only) { 5204 TearDownRegionSetsClosure cl(&_old_set); 5205 heap_region_iterate(&cl); 5206 5207 // Note that emptying the _young_list is postponed and instead done as 5208 // the first step when rebuilding the regions sets again. The reason for 5209 // this is that during a full GC string deduplication needs to know if 5210 // a collected region was young or old when the full GC was initiated. 5211 } 5212 _hrm.remove_all_free_regions(); 5213 } 5214 5215 void G1CollectedHeap::increase_used(size_t bytes) { 5216 _summary_bytes_used += bytes; 5217 } 5218 5219 void G1CollectedHeap::decrease_used(size_t bytes) { 5220 assert(_summary_bytes_used >= bytes, 5221 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5222 _summary_bytes_used, bytes); 5223 _summary_bytes_used -= bytes; 5224 } 5225 5226 void G1CollectedHeap::set_used(size_t bytes) { 5227 _summary_bytes_used = bytes; 5228 } 5229 5230 class RebuildRegionSetsClosure : public HeapRegionClosure { 5231 private: 5232 bool _free_list_only; 5233 HeapRegionSet* _old_set; 5234 HeapRegionManager* _hrm; 5235 size_t _total_used; 5236 5237 public: 5238 RebuildRegionSetsClosure(bool free_list_only, 5239 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5240 _free_list_only(free_list_only), 5241 _old_set(old_set), _hrm(hrm), _total_used(0) { 5242 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5243 if (!free_list_only) { 5244 assert(_old_set->is_empty(), "pre-condition"); 5245 } 5246 } 5247 5248 bool doHeapRegion(HeapRegion* r) { 5249 if (r->is_empty()) { 5250 // Add free regions to the free list 5251 r->set_free(); 5252 r->set_allocation_context(AllocationContext::system()); 5253 _hrm->insert_into_free_list(r); 5254 } else if (!_free_list_only) { 5255 5256 if (r->is_humongous()) { 5257 // We ignore humongous regions. We left the humongous set unchanged. 5258 } else { 5259 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 5260 // We now consider all regions old, so register as such. Leave 5261 // archive regions set that way, however, while still adding 5262 // them to the old set. 5263 if (!r->is_archive()) { 5264 r->set_old(); 5265 } 5266 _old_set->add(r); 5267 } 5268 _total_used += r->used(); 5269 } 5270 5271 return false; 5272 } 5273 5274 size_t total_used() { 5275 return _total_used; 5276 } 5277 }; 5278 5279 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5280 assert_at_safepoint(true /* should_be_vm_thread */); 5281 5282 if (!free_list_only) { 5283 _eden.clear(); 5284 _survivor.clear(); 5285 } 5286 5287 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5288 heap_region_iterate(&cl); 5289 5290 if (!free_list_only) { 5291 set_used(cl.total_used()); 5292 if (_archive_allocator != NULL) { 5293 _archive_allocator->clear_used(); 5294 } 5295 } 5296 assert(used_unlocked() == recalculate_used(), 5297 "inconsistent used_unlocked(), " 5298 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5299 used_unlocked(), recalculate_used()); 5300 } 5301 5302 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 5303 _refine_cte_cl->set_concurrent(concurrent); 5304 } 5305 5306 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5307 HeapRegion* hr = heap_region_containing(p); 5308 return hr->is_in(p); 5309 } 5310 5311 // Methods for the mutator alloc region 5312 5313 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5314 bool force) { 5315 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5316 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 5317 if (force || should_allocate) { 5318 HeapRegion* new_alloc_region = new_region(word_size, 5319 false /* is_old */, 5320 false /* do_expand */); 5321 if (new_alloc_region != NULL) { 5322 set_region_short_lived_locked(new_alloc_region); 5323 _hr_printer.alloc(new_alloc_region, !should_allocate); 5324 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5325 return new_alloc_region; 5326 } 5327 } 5328 return NULL; 5329 } 5330 5331 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5332 size_t allocated_bytes) { 5333 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5334 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5335 5336 collection_set()->add_eden_region(alloc_region); 5337 increase_used(allocated_bytes); 5338 _hr_printer.retire(alloc_region); 5339 // We update the eden sizes here, when the region is retired, 5340 // instead of when it's allocated, since this is the point that its 5341 // used space has been recored in _summary_bytes_used. 5342 g1mm()->update_eden_size(); 5343 } 5344 5345 // Methods for the GC alloc regions 5346 5347 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 5348 if (dest.is_old()) { 5349 return true; 5350 } else { 5351 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 5352 } 5353 } 5354 5355 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 5356 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5357 5358 if (!has_more_regions(dest)) { 5359 return NULL; 5360 } 5361 5362 const bool is_survivor = dest.is_young(); 5363 5364 HeapRegion* new_alloc_region = new_region(word_size, 5365 !is_survivor, 5366 true /* do_expand */); 5367 if (new_alloc_region != NULL) { 5368 // We really only need to do this for old regions given that we 5369 // should never scan survivors. But it doesn't hurt to do it 5370 // for survivors too. 5371 new_alloc_region->record_timestamp(); 5372 if (is_survivor) { 5373 new_alloc_region->set_survivor(); 5374 _survivor.add(new_alloc_region); 5375 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5376 } else { 5377 new_alloc_region->set_old(); 5378 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5379 } 5380 _hr_printer.alloc(new_alloc_region); 5381 bool during_im = collector_state()->during_initial_mark_pause(); 5382 new_alloc_region->note_start_of_copying(during_im); 5383 return new_alloc_region; 5384 } 5385 return NULL; 5386 } 5387 5388 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5389 size_t allocated_bytes, 5390 InCSetState dest) { 5391 bool during_im = collector_state()->during_initial_mark_pause(); 5392 alloc_region->note_end_of_copying(during_im); 5393 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5394 if (dest.is_old()) { 5395 _old_set.add(alloc_region); 5396 } 5397 _hr_printer.retire(alloc_region); 5398 } 5399 5400 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5401 bool expanded = false; 5402 uint index = _hrm.find_highest_free(&expanded); 5403 5404 if (index != G1_NO_HRM_INDEX) { 5405 if (expanded) { 5406 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5407 HeapRegion::GrainWords * HeapWordSize); 5408 } 5409 _hrm.allocate_free_regions_starting_at(index, 1); 5410 return region_at(index); 5411 } 5412 return NULL; 5413 } 5414 5415 // Optimized nmethod scanning 5416 5417 class RegisterNMethodOopClosure: public OopClosure { 5418 G1CollectedHeap* _g1h; 5419 nmethod* _nm; 5420 5421 template <class T> void do_oop_work(T* p) { 5422 T heap_oop = oopDesc::load_heap_oop(p); 5423 if (!oopDesc::is_null(heap_oop)) { 5424 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5425 HeapRegion* hr = _g1h->heap_region_containing(obj); 5426 assert(!hr->is_continues_humongous(), 5427 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5428 " starting at " HR_FORMAT, 5429 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5430 5431 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5432 hr->add_strong_code_root_locked(_nm); 5433 } 5434 } 5435 5436 public: 5437 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5438 _g1h(g1h), _nm(nm) {} 5439 5440 void do_oop(oop* p) { do_oop_work(p); } 5441 void do_oop(narrowOop* p) { do_oop_work(p); } 5442 }; 5443 5444 class UnregisterNMethodOopClosure: public OopClosure { 5445 G1CollectedHeap* _g1h; 5446 nmethod* _nm; 5447 5448 template <class T> void do_oop_work(T* p) { 5449 T heap_oop = oopDesc::load_heap_oop(p); 5450 if (!oopDesc::is_null(heap_oop)) { 5451 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5452 HeapRegion* hr = _g1h->heap_region_containing(obj); 5453 assert(!hr->is_continues_humongous(), 5454 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5455 " starting at " HR_FORMAT, 5456 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5457 5458 hr->remove_strong_code_root(_nm); 5459 } 5460 } 5461 5462 public: 5463 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5464 _g1h(g1h), _nm(nm) {} 5465 5466 void do_oop(oop* p) { do_oop_work(p); } 5467 void do_oop(narrowOop* p) { do_oop_work(p); } 5468 }; 5469 5470 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5471 CollectedHeap::register_nmethod(nm); 5472 5473 guarantee(nm != NULL, "sanity"); 5474 RegisterNMethodOopClosure reg_cl(this, nm); 5475 nm->oops_do(®_cl); 5476 } 5477 5478 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5479 CollectedHeap::unregister_nmethod(nm); 5480 5481 guarantee(nm != NULL, "sanity"); 5482 UnregisterNMethodOopClosure reg_cl(this, nm); 5483 nm->oops_do(®_cl, true); 5484 } 5485 5486 void G1CollectedHeap::purge_code_root_memory() { 5487 double purge_start = os::elapsedTime(); 5488 G1CodeRootSet::purge(); 5489 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5490 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5491 } 5492 5493 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5494 G1CollectedHeap* _g1h; 5495 5496 public: 5497 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5498 _g1h(g1h) {} 5499 5500 void do_code_blob(CodeBlob* cb) { 5501 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5502 if (nm == NULL) { 5503 return; 5504 } 5505 5506 if (ScavengeRootsInCode) { 5507 _g1h->register_nmethod(nm); 5508 } 5509 } 5510 }; 5511 5512 void G1CollectedHeap::rebuild_strong_code_roots() { 5513 RebuildStrongCodeRootClosure blob_cl(this); 5514 CodeCache::blobs_do(&blob_cl); 5515 }