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