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 Log(gc, heap, region) log; 2499 if (log.is_trace()) { 2500 ResourceMark rm; 2501 print_regions_on(log.trace_stream()); 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 outputStream* st = log.trace_stream(); 2921 2922 print_taskqueue_stats_hdr(st); 2923 2924 TaskQueueStats totals; 2925 const uint n = num_task_queues(); 2926 for (uint i = 0; i < n; ++i) { 2927 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2928 totals += task_queue(i)->stats; 2929 } 2930 st->print_raw("tot "); totals.print(st); st->cr(); 2931 2932 DEBUG_ONLY(totals.verify()); 2933 } 2934 2935 void G1CollectedHeap::reset_taskqueue_stats() { 2936 const uint n = num_task_queues(); 2937 for (uint i = 0; i < n; ++i) { 2938 task_queue(i)->stats.reset(); 2939 } 2940 } 2941 #endif // TASKQUEUE_STATS 2942 2943 void G1CollectedHeap::wait_for_root_region_scanning() { 2944 double scan_wait_start = os::elapsedTime(); 2945 // We have to wait until the CM threads finish scanning the 2946 // root regions as it's the only way to ensure that all the 2947 // objects on them have been correctly scanned before we start 2948 // moving them during the GC. 2949 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2950 double wait_time_ms = 0.0; 2951 if (waited) { 2952 double scan_wait_end = os::elapsedTime(); 2953 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2954 } 2955 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2956 } 2957 2958 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2959 private: 2960 G1HRPrinter* _hr_printer; 2961 public: 2962 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2963 2964 virtual bool doHeapRegion(HeapRegion* r) { 2965 _hr_printer->cset(r); 2966 return false; 2967 } 2968 }; 2969 2970 void G1CollectedHeap::start_new_collection_set() { 2971 collection_set()->start_incremental_building(); 2972 2973 clear_cset_fast_test(); 2974 2975 guarantee(_eden.length() == 0, "eden should have been cleared"); 2976 g1_policy()->transfer_survivors_to_cset(survivor()); 2977 } 2978 2979 bool 2980 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2981 assert_at_safepoint(true /* should_be_vm_thread */); 2982 guarantee(!is_gc_active(), "collection is not reentrant"); 2983 2984 if (GCLocker::check_active_before_gc()) { 2985 return false; 2986 } 2987 2988 _gc_timer_stw->register_gc_start(); 2989 2990 GCIdMark gc_id_mark; 2991 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2992 2993 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2994 ResourceMark rm; 2995 2996 g1_policy()->note_gc_start(); 2997 2998 wait_for_root_region_scanning(); 2999 3000 print_heap_before_gc(); 3001 print_heap_regions(); 3002 trace_heap_before_gc(_gc_tracer_stw); 3003 3004 _verifier->verify_region_sets_optional(); 3005 _verifier->verify_dirty_young_regions(); 3006 3007 // We should not be doing initial mark unless the conc mark thread is running 3008 if (!_cmThread->should_terminate()) { 3009 // This call will decide whether this pause is an initial-mark 3010 // pause. If it is, during_initial_mark_pause() will return true 3011 // for the duration of this pause. 3012 g1_policy()->decide_on_conc_mark_initiation(); 3013 } 3014 3015 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3016 assert(!collector_state()->during_initial_mark_pause() || 3017 collector_state()->gcs_are_young(), "sanity"); 3018 3019 // We also do not allow mixed GCs during marking. 3020 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3021 3022 // Record whether this pause is an initial mark. When the current 3023 // thread has completed its logging output and it's safe to signal 3024 // the CM thread, the flag's value in the policy has been reset. 3025 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3026 3027 // Inner scope for scope based logging, timers, and stats collection 3028 { 3029 EvacuationInfo evacuation_info; 3030 3031 if (collector_state()->during_initial_mark_pause()) { 3032 // We are about to start a marking cycle, so we increment the 3033 // full collection counter. 3034 increment_old_marking_cycles_started(); 3035 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 3036 } 3037 3038 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3039 3040 GCTraceCPUTime tcpu; 3041 3042 FormatBuffer<> gc_string("Pause "); 3043 if (collector_state()->during_initial_mark_pause()) { 3044 gc_string.append("Initial Mark"); 3045 } else if (collector_state()->gcs_are_young()) { 3046 gc_string.append("Young"); 3047 } else { 3048 gc_string.append("Mixed"); 3049 } 3050 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 3051 3052 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3053 workers()->active_workers(), 3054 Threads::number_of_non_daemon_threads()); 3055 workers()->update_active_workers(active_workers); 3056 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 3057 3058 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3059 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3060 3061 // If the secondary_free_list is not empty, append it to the 3062 // free_list. No need to wait for the cleanup operation to finish; 3063 // the region allocation code will check the secondary_free_list 3064 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3065 // set, skip this step so that the region allocation code has to 3066 // get entries from the secondary_free_list. 3067 if (!G1StressConcRegionFreeing) { 3068 append_secondary_free_list_if_not_empty_with_lock(); 3069 } 3070 3071 G1HeapTransition heap_transition(this); 3072 size_t heap_used_bytes_before_gc = used(); 3073 3074 // Don't dynamically change the number of GC threads this early. A value of 3075 // 0 is used to indicate serial work. When parallel work is done, 3076 // it will be set. 3077 3078 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3079 IsGCActiveMark x; 3080 3081 gc_prologue(false); 3082 increment_total_collections(false /* full gc */); 3083 increment_gc_time_stamp(); 3084 3085 if (VerifyRememberedSets) { 3086 log_info(gc, verify)("[Verifying RemSets before GC]"); 3087 VerifyRegionRemSetClosure v_cl; 3088 heap_region_iterate(&v_cl); 3089 } 3090 3091 _verifier->verify_before_gc(); 3092 3093 _verifier->check_bitmaps("GC Start"); 3094 3095 #if defined(COMPILER2) || INCLUDE_JVMCI 3096 DerivedPointerTable::clear(); 3097 #endif 3098 3099 // Please see comment in g1CollectedHeap.hpp and 3100 // G1CollectedHeap::ref_processing_init() to see how 3101 // reference processing currently works in G1. 3102 3103 // Enable discovery in the STW reference processor 3104 if (g1_policy()->should_process_references()) { 3105 ref_processor_stw()->enable_discovery(); 3106 } else { 3107 ref_processor_stw()->disable_discovery(); 3108 } 3109 3110 { 3111 // We want to temporarily turn off discovery by the 3112 // CM ref processor, if necessary, and turn it back on 3113 // on again later if we do. Using a scoped 3114 // NoRefDiscovery object will do this. 3115 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3116 3117 // Forget the current alloc region (we might even choose it to be part 3118 // of the collection set!). 3119 _allocator->release_mutator_alloc_region(); 3120 3121 // This timing is only used by the ergonomics to handle our pause target. 3122 // It is unclear why this should not include the full pause. We will 3123 // investigate this in CR 7178365. 3124 // 3125 // Preserving the old comment here if that helps the investigation: 3126 // 3127 // The elapsed time induced by the start time below deliberately elides 3128 // the possible verification above. 3129 double sample_start_time_sec = os::elapsedTime(); 3130 3131 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3132 3133 if (collector_state()->during_initial_mark_pause()) { 3134 concurrent_mark()->checkpointRootsInitialPre(); 3135 } 3136 3137 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 3138 3139 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3140 3141 // Make sure the remembered sets are up to date. This needs to be 3142 // done before register_humongous_regions_with_cset(), because the 3143 // remembered sets are used there to choose eager reclaim candidates. 3144 // If the remembered sets are not up to date we might miss some 3145 // entries that need to be handled. 3146 g1_rem_set()->cleanupHRRS(); 3147 3148 register_humongous_regions_with_cset(); 3149 3150 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3151 3152 // We call this after finalize_cset() to 3153 // ensure that the CSet has been finalized. 3154 _cm->verify_no_cset_oops(); 3155 3156 if (_hr_printer.is_active()) { 3157 G1PrintCollectionSetClosure cl(&_hr_printer); 3158 _collection_set.iterate(&cl); 3159 } 3160 3161 // Initialize the GC alloc regions. 3162 _allocator->init_gc_alloc_regions(evacuation_info); 3163 3164 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3165 pre_evacuate_collection_set(); 3166 3167 // Actually do the work... 3168 evacuate_collection_set(evacuation_info, &per_thread_states); 3169 3170 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3171 3172 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3173 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 3174 3175 eagerly_reclaim_humongous_regions(); 3176 3177 record_obj_copy_mem_stats(); 3178 _survivor_evac_stats.adjust_desired_plab_sz(); 3179 _old_evac_stats.adjust_desired_plab_sz(); 3180 3181 double start = os::elapsedTime(); 3182 start_new_collection_set(); 3183 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 3184 3185 if (evacuation_failed()) { 3186 set_used(recalculate_used()); 3187 if (_archive_allocator != NULL) { 3188 _archive_allocator->clear_used(); 3189 } 3190 for (uint i = 0; i < ParallelGCThreads; i++) { 3191 if (_evacuation_failed_info_array[i].has_failed()) { 3192 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3193 } 3194 } 3195 } else { 3196 // The "used" of the the collection set have already been subtracted 3197 // when they were freed. Add in the bytes evacuated. 3198 increase_used(g1_policy()->bytes_copied_during_gc()); 3199 } 3200 3201 if (collector_state()->during_initial_mark_pause()) { 3202 // We have to do this before we notify the CM threads that 3203 // they can start working to make sure that all the 3204 // appropriate initialization is done on the CM object. 3205 concurrent_mark()->checkpointRootsInitialPost(); 3206 collector_state()->set_mark_in_progress(true); 3207 // Note that we don't actually trigger the CM thread at 3208 // this point. We do that later when we're sure that 3209 // the current thread has completed its logging output. 3210 } 3211 3212 allocate_dummy_regions(); 3213 3214 _allocator->init_mutator_alloc_region(); 3215 3216 { 3217 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3218 if (expand_bytes > 0) { 3219 size_t bytes_before = capacity(); 3220 // No need for an ergo logging here, 3221 // expansion_amount() does this when it returns a value > 0. 3222 double expand_ms; 3223 if (!expand(expand_bytes, _workers, &expand_ms)) { 3224 // We failed to expand the heap. Cannot do anything about it. 3225 } 3226 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3227 } 3228 } 3229 3230 // We redo the verification but now wrt to the new CSet which 3231 // has just got initialized after the previous CSet was freed. 3232 _cm->verify_no_cset_oops(); 3233 3234 // This timing is only used by the ergonomics to handle our pause target. 3235 // It is unclear why this should not include the full pause. We will 3236 // investigate this in CR 7178365. 3237 double sample_end_time_sec = os::elapsedTime(); 3238 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3239 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScannedCards); 3240 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3241 3242 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3243 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3244 3245 MemoryService::track_memory_usage(); 3246 3247 if (VerifyRememberedSets) { 3248 log_info(gc, verify)("[Verifying RemSets after GC]"); 3249 VerifyRegionRemSetClosure v_cl; 3250 heap_region_iterate(&v_cl); 3251 } 3252 3253 _verifier->verify_after_gc(); 3254 _verifier->check_bitmaps("GC End"); 3255 3256 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3257 ref_processor_stw()->verify_no_references_recorded(); 3258 3259 // CM reference discovery will be re-enabled if necessary. 3260 } 3261 3262 #ifdef TRACESPINNING 3263 ParallelTaskTerminator::print_termination_counts(); 3264 #endif 3265 3266 gc_epilogue(false); 3267 } 3268 3269 // Print the remainder of the GC log output. 3270 if (evacuation_failed()) { 3271 log_info(gc)("To-space exhausted"); 3272 } 3273 3274 g1_policy()->print_phases(); 3275 heap_transition.print(); 3276 3277 // It is not yet to safe to tell the concurrent mark to 3278 // start as we have some optional output below. We don't want the 3279 // output from the concurrent mark thread interfering with this 3280 // logging output either. 3281 3282 _hrm.verify_optional(); 3283 _verifier->verify_region_sets_optional(); 3284 3285 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3286 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3287 3288 print_heap_after_gc(); 3289 print_heap_regions(); 3290 trace_heap_after_gc(_gc_tracer_stw); 3291 3292 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3293 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3294 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3295 // before any GC notifications are raised. 3296 g1mm()->update_sizes(); 3297 3298 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3299 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3300 _gc_timer_stw->register_gc_end(); 3301 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3302 } 3303 // It should now be safe to tell the concurrent mark thread to start 3304 // without its logging output interfering with the logging output 3305 // that came from the pause. 3306 3307 if (should_start_conc_mark) { 3308 // CAUTION: after the doConcurrentMark() call below, 3309 // the concurrent marking thread(s) could be running 3310 // concurrently with us. Make sure that anything after 3311 // this point does not assume that we are the only GC thread 3312 // running. Note: of course, the actual marking work will 3313 // not start until the safepoint itself is released in 3314 // SuspendibleThreadSet::desynchronize(). 3315 doConcurrentMark(); 3316 } 3317 3318 return true; 3319 } 3320 3321 void G1CollectedHeap::remove_self_forwarding_pointers() { 3322 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3323 workers()->run_task(&rsfp_task); 3324 } 3325 3326 void G1CollectedHeap::restore_after_evac_failure() { 3327 double remove_self_forwards_start = os::elapsedTime(); 3328 3329 remove_self_forwarding_pointers(); 3330 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3331 _preserved_marks_set.restore(&task_executor); 3332 3333 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3334 } 3335 3336 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3337 if (!_evacuation_failed) { 3338 _evacuation_failed = true; 3339 } 3340 3341 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3342 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3343 } 3344 3345 bool G1ParEvacuateFollowersClosure::offer_termination() { 3346 G1ParScanThreadState* const pss = par_scan_state(); 3347 start_term_time(); 3348 const bool res = terminator()->offer_termination(); 3349 end_term_time(); 3350 return res; 3351 } 3352 3353 void G1ParEvacuateFollowersClosure::do_void() { 3354 G1ParScanThreadState* const pss = par_scan_state(); 3355 pss->trim_queue(); 3356 do { 3357 pss->steal_and_trim_queue(queues()); 3358 } while (!offer_termination()); 3359 } 3360 3361 class G1ParTask : public AbstractGangTask { 3362 protected: 3363 G1CollectedHeap* _g1h; 3364 G1ParScanThreadStateSet* _pss; 3365 RefToScanQueueSet* _queues; 3366 G1RootProcessor* _root_processor; 3367 ParallelTaskTerminator _terminator; 3368 uint _n_workers; 3369 3370 public: 3371 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3372 : AbstractGangTask("G1 collection"), 3373 _g1h(g1h), 3374 _pss(per_thread_states), 3375 _queues(task_queues), 3376 _root_processor(root_processor), 3377 _terminator(n_workers, _queues), 3378 _n_workers(n_workers) 3379 {} 3380 3381 void work(uint worker_id) { 3382 if (worker_id >= _n_workers) return; // no work needed this round 3383 3384 double start_sec = os::elapsedTime(); 3385 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3386 3387 { 3388 ResourceMark rm; 3389 HandleMark hm; 3390 3391 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3392 3393 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3394 pss->set_ref_processor(rp); 3395 3396 double start_strong_roots_sec = os::elapsedTime(); 3397 3398 _root_processor->evacuate_roots(pss->closures(), worker_id); 3399 3400 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3401 // treating the nmethods visited to act as roots for concurrent marking. 3402 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3403 // objects copied by the current evacuation. 3404 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, 3405 pss->closures()->weak_codeblobs(), 3406 worker_id); 3407 3408 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3409 3410 double term_sec = 0.0; 3411 size_t evac_term_attempts = 0; 3412 { 3413 double start = os::elapsedTime(); 3414 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3415 evac.do_void(); 3416 3417 evac_term_attempts = evac.term_attempts(); 3418 term_sec = evac.term_time(); 3419 double elapsed_sec = os::elapsedTime() - start; 3420 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3421 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3422 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3423 } 3424 3425 assert(pss->queue_is_empty(), "should be empty"); 3426 3427 if (log_is_enabled(Debug, gc, task, stats)) { 3428 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3429 size_t lab_waste; 3430 size_t lab_undo_waste; 3431 pss->waste(lab_waste, lab_undo_waste); 3432 _g1h->print_termination_stats(worker_id, 3433 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3434 strong_roots_sec * 1000.0, /* strong roots time */ 3435 term_sec * 1000.0, /* evac term time */ 3436 evac_term_attempts, /* evac term attempts */ 3437 lab_waste, /* alloc buffer waste */ 3438 lab_undo_waste /* undo waste */ 3439 ); 3440 } 3441 3442 // Close the inner scope so that the ResourceMark and HandleMark 3443 // destructors are executed here and are included as part of the 3444 // "GC Worker Time". 3445 } 3446 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3447 } 3448 }; 3449 3450 void G1CollectedHeap::print_termination_stats_hdr() { 3451 log_debug(gc, task, stats)("GC Termination Stats"); 3452 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3453 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3454 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3455 } 3456 3457 void G1CollectedHeap::print_termination_stats(uint worker_id, 3458 double elapsed_ms, 3459 double strong_roots_ms, 3460 double term_ms, 3461 size_t term_attempts, 3462 size_t alloc_buffer_waste, 3463 size_t undo_waste) const { 3464 log_debug(gc, task, stats) 3465 ("%3d %9.2f %9.2f %6.2f " 3466 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3467 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3468 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3469 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3470 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3471 alloc_buffer_waste * HeapWordSize / K, 3472 undo_waste * HeapWordSize / K); 3473 } 3474 3475 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3476 private: 3477 BoolObjectClosure* _is_alive; 3478 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3479 3480 int _initial_string_table_size; 3481 int _initial_symbol_table_size; 3482 3483 bool _process_strings; 3484 int _strings_processed; 3485 int _strings_removed; 3486 3487 bool _process_symbols; 3488 int _symbols_processed; 3489 int _symbols_removed; 3490 3491 bool _process_string_dedup; 3492 3493 public: 3494 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3495 AbstractGangTask("String/Symbol Unlinking"), 3496 _is_alive(is_alive), 3497 _dedup_closure(is_alive, NULL, false), 3498 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3499 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3500 _process_string_dedup(process_string_dedup) { 3501 3502 _initial_string_table_size = StringTable::the_table()->table_size(); 3503 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3504 if (process_strings) { 3505 StringTable::clear_parallel_claimed_index(); 3506 } 3507 if (process_symbols) { 3508 SymbolTable::clear_parallel_claimed_index(); 3509 } 3510 } 3511 3512 ~G1StringAndSymbolCleaningTask() { 3513 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3514 "claim value %d after unlink less than initial string table size %d", 3515 StringTable::parallel_claimed_index(), _initial_string_table_size); 3516 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3517 "claim value %d after unlink less than initial symbol table size %d", 3518 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3519 3520 log_info(gc, stringtable)( 3521 "Cleaned string and symbol table, " 3522 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3523 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3524 strings_processed(), strings_removed(), 3525 symbols_processed(), symbols_removed()); 3526 } 3527 3528 void work(uint worker_id) { 3529 int strings_processed = 0; 3530 int strings_removed = 0; 3531 int symbols_processed = 0; 3532 int symbols_removed = 0; 3533 if (_process_strings) { 3534 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3535 Atomic::add(strings_processed, &_strings_processed); 3536 Atomic::add(strings_removed, &_strings_removed); 3537 } 3538 if (_process_symbols) { 3539 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3540 Atomic::add(symbols_processed, &_symbols_processed); 3541 Atomic::add(symbols_removed, &_symbols_removed); 3542 } 3543 if (_process_string_dedup) { 3544 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3545 } 3546 } 3547 3548 size_t strings_processed() const { return (size_t)_strings_processed; } 3549 size_t strings_removed() const { return (size_t)_strings_removed; } 3550 3551 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3552 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3553 }; 3554 3555 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3556 private: 3557 static Monitor* _lock; 3558 3559 BoolObjectClosure* const _is_alive; 3560 const bool _unloading_occurred; 3561 const uint _num_workers; 3562 3563 // Variables used to claim nmethods. 3564 CompiledMethod* _first_nmethod; 3565 volatile CompiledMethod* _claimed_nmethod; 3566 3567 // The list of nmethods that need to be processed by the second pass. 3568 volatile CompiledMethod* _postponed_list; 3569 volatile uint _num_entered_barrier; 3570 3571 public: 3572 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3573 _is_alive(is_alive), 3574 _unloading_occurred(unloading_occurred), 3575 _num_workers(num_workers), 3576 _first_nmethod(NULL), 3577 _claimed_nmethod(NULL), 3578 _postponed_list(NULL), 3579 _num_entered_barrier(0) 3580 { 3581 CompiledMethod::increase_unloading_clock(); 3582 // Get first alive nmethod 3583 CompiledMethodIterator iter = CompiledMethodIterator(); 3584 if(iter.next_alive()) { 3585 _first_nmethod = iter.method(); 3586 } 3587 _claimed_nmethod = (volatile CompiledMethod*)_first_nmethod; 3588 } 3589 3590 ~G1CodeCacheUnloadingTask() { 3591 CodeCache::verify_clean_inline_caches(); 3592 3593 CodeCache::set_needs_cache_clean(false); 3594 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3595 3596 CodeCache::verify_icholder_relocations(); 3597 } 3598 3599 private: 3600 void add_to_postponed_list(CompiledMethod* nm) { 3601 CompiledMethod* old; 3602 do { 3603 old = (CompiledMethod*)_postponed_list; 3604 nm->set_unloading_next(old); 3605 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 3606 } 3607 3608 void clean_nmethod(CompiledMethod* nm) { 3609 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3610 3611 if (postponed) { 3612 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3613 add_to_postponed_list(nm); 3614 } 3615 3616 // Mark that this thread has been cleaned/unloaded. 3617 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3618 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3619 } 3620 3621 void clean_nmethod_postponed(CompiledMethod* nm) { 3622 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3623 } 3624 3625 static const int MaxClaimNmethods = 16; 3626 3627 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3628 CompiledMethod* first; 3629 CompiledMethodIterator last; 3630 3631 do { 3632 *num_claimed_nmethods = 0; 3633 3634 first = (CompiledMethod*)_claimed_nmethod; 3635 last = CompiledMethodIterator(first); 3636 3637 if (first != NULL) { 3638 3639 for (int i = 0; i < MaxClaimNmethods; i++) { 3640 if (!last.next_alive()) { 3641 break; 3642 } 3643 claimed_nmethods[i] = last.method(); 3644 (*num_claimed_nmethods)++; 3645 } 3646 } 3647 3648 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 3649 } 3650 3651 CompiledMethod* claim_postponed_nmethod() { 3652 CompiledMethod* claim; 3653 CompiledMethod* next; 3654 3655 do { 3656 claim = (CompiledMethod*)_postponed_list; 3657 if (claim == NULL) { 3658 return NULL; 3659 } 3660 3661 next = claim->unloading_next(); 3662 3663 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 3664 3665 return claim; 3666 } 3667 3668 public: 3669 // Mark that we're done with the first pass of nmethod cleaning. 3670 void barrier_mark(uint worker_id) { 3671 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3672 _num_entered_barrier++; 3673 if (_num_entered_barrier == _num_workers) { 3674 ml.notify_all(); 3675 } 3676 } 3677 3678 // See if we have to wait for the other workers to 3679 // finish their first-pass nmethod cleaning work. 3680 void barrier_wait(uint worker_id) { 3681 if (_num_entered_barrier < _num_workers) { 3682 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3683 while (_num_entered_barrier < _num_workers) { 3684 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3685 } 3686 } 3687 } 3688 3689 // Cleaning and unloading of nmethods. Some work has to be postponed 3690 // to the second pass, when we know which nmethods survive. 3691 void work_first_pass(uint worker_id) { 3692 // The first nmethods is claimed by the first worker. 3693 if (worker_id == 0 && _first_nmethod != NULL) { 3694 clean_nmethod(_first_nmethod); 3695 _first_nmethod = NULL; 3696 } 3697 3698 int num_claimed_nmethods; 3699 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3700 3701 while (true) { 3702 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3703 3704 if (num_claimed_nmethods == 0) { 3705 break; 3706 } 3707 3708 for (int i = 0; i < num_claimed_nmethods; i++) { 3709 clean_nmethod(claimed_nmethods[i]); 3710 } 3711 } 3712 } 3713 3714 void work_second_pass(uint worker_id) { 3715 CompiledMethod* nm; 3716 // Take care of postponed nmethods. 3717 while ((nm = claim_postponed_nmethod()) != NULL) { 3718 clean_nmethod_postponed(nm); 3719 } 3720 } 3721 }; 3722 3723 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3724 3725 class G1KlassCleaningTask : public StackObj { 3726 BoolObjectClosure* _is_alive; 3727 volatile jint _clean_klass_tree_claimed; 3728 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3729 3730 public: 3731 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3732 _is_alive(is_alive), 3733 _clean_klass_tree_claimed(0), 3734 _klass_iterator() { 3735 } 3736 3737 private: 3738 bool claim_clean_klass_tree_task() { 3739 if (_clean_klass_tree_claimed) { 3740 return false; 3741 } 3742 3743 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 3744 } 3745 3746 InstanceKlass* claim_next_klass() { 3747 Klass* klass; 3748 do { 3749 klass =_klass_iterator.next_klass(); 3750 } while (klass != NULL && !klass->is_instance_klass()); 3751 3752 // this can be null so don't call InstanceKlass::cast 3753 return static_cast<InstanceKlass*>(klass); 3754 } 3755 3756 public: 3757 3758 void clean_klass(InstanceKlass* ik) { 3759 ik->clean_weak_instanceklass_links(_is_alive); 3760 } 3761 3762 void work() { 3763 ResourceMark rm; 3764 3765 // One worker will clean the subklass/sibling klass tree. 3766 if (claim_clean_klass_tree_task()) { 3767 Klass::clean_subklass_tree(_is_alive); 3768 } 3769 3770 // All workers will help cleaning the classes, 3771 InstanceKlass* klass; 3772 while ((klass = claim_next_klass()) != NULL) { 3773 clean_klass(klass); 3774 } 3775 } 3776 }; 3777 3778 class G1ResolvedMethodCleaningTask : public StackObj { 3779 BoolObjectClosure* _is_alive; 3780 volatile jint _resolved_method_task_claimed; 3781 public: 3782 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) : 3783 _is_alive(is_alive), _resolved_method_task_claimed(0) {} 3784 3785 bool claim_resolved_method_task() { 3786 if (_resolved_method_task_claimed) { 3787 return false; 3788 } 3789 return Atomic::cmpxchg(1, (jint*)&_resolved_method_task_claimed, 0) == 0; 3790 } 3791 3792 // These aren't big, one thread can do it all. 3793 void work() { 3794 if (claim_resolved_method_task()) { 3795 ResolvedMethodTable::unlink(_is_alive); 3796 } 3797 } 3798 }; 3799 3800 3801 // To minimize the remark pause times, the tasks below are done in parallel. 3802 class G1ParallelCleaningTask : public AbstractGangTask { 3803 private: 3804 G1StringAndSymbolCleaningTask _string_symbol_task; 3805 G1CodeCacheUnloadingTask _code_cache_task; 3806 G1KlassCleaningTask _klass_cleaning_task; 3807 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task; 3808 3809 public: 3810 // The constructor is run in the VMThread. 3811 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3812 AbstractGangTask("Parallel Cleaning"), 3813 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3814 _code_cache_task(num_workers, is_alive, unloading_occurred), 3815 _klass_cleaning_task(is_alive), 3816 _resolved_method_cleaning_task(is_alive) { 3817 } 3818 3819 // The parallel work done by all worker threads. 3820 void work(uint worker_id) { 3821 // Do first pass of code cache cleaning. 3822 _code_cache_task.work_first_pass(worker_id); 3823 3824 // Let the threads mark that the first pass is done. 3825 _code_cache_task.barrier_mark(worker_id); 3826 3827 // Clean the Strings and Symbols. 3828 _string_symbol_task.work(worker_id); 3829 3830 // Clean unreferenced things in the ResolvedMethodTable 3831 _resolved_method_cleaning_task.work(); 3832 3833 // Wait for all workers to finish the first code cache cleaning pass. 3834 _code_cache_task.barrier_wait(worker_id); 3835 3836 // Do the second code cache cleaning work, which realize on 3837 // the liveness information gathered during the first pass. 3838 _code_cache_task.work_second_pass(worker_id); 3839 3840 // Clean all klasses that were not unloaded. 3841 _klass_cleaning_task.work(); 3842 } 3843 }; 3844 3845 3846 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3847 bool class_unloading_occurred) { 3848 uint n_workers = workers()->active_workers(); 3849 3850 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3851 workers()->run_task(&g1_unlink_task); 3852 } 3853 3854 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3855 bool process_strings, 3856 bool process_symbols, 3857 bool process_string_dedup) { 3858 if (!process_strings && !process_symbols && !process_string_dedup) { 3859 // Nothing to clean. 3860 return; 3861 } 3862 3863 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3864 workers()->run_task(&g1_unlink_task); 3865 3866 } 3867 3868 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3869 private: 3870 DirtyCardQueueSet* _queue; 3871 G1CollectedHeap* _g1h; 3872 public: 3873 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3874 _queue(queue), _g1h(g1h) { } 3875 3876 virtual void work(uint worker_id) { 3877 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3878 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3879 3880 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3881 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3882 3883 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3884 } 3885 }; 3886 3887 void G1CollectedHeap::redirty_logged_cards() { 3888 double redirty_logged_cards_start = os::elapsedTime(); 3889 3890 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3891 dirty_card_queue_set().reset_for_par_iteration(); 3892 workers()->run_task(&redirty_task); 3893 3894 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 3895 dcq.merge_bufferlists(&dirty_card_queue_set()); 3896 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3897 3898 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3899 } 3900 3901 // Weak Reference Processing support 3902 3903 // An always "is_alive" closure that is used to preserve referents. 3904 // If the object is non-null then it's alive. Used in the preservation 3905 // of referent objects that are pointed to by reference objects 3906 // discovered by the CM ref processor. 3907 class G1AlwaysAliveClosure: public BoolObjectClosure { 3908 G1CollectedHeap* _g1; 3909 public: 3910 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3911 bool do_object_b(oop p) { 3912 if (p != NULL) { 3913 return true; 3914 } 3915 return false; 3916 } 3917 }; 3918 3919 bool G1STWIsAliveClosure::do_object_b(oop p) { 3920 // An object is reachable if it is outside the collection set, 3921 // or is inside and copied. 3922 return !_g1->is_in_cset(p) || p->is_forwarded(); 3923 } 3924 3925 // Non Copying Keep Alive closure 3926 class G1KeepAliveClosure: public OopClosure { 3927 G1CollectedHeap* _g1; 3928 public: 3929 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3930 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3931 void do_oop(oop* p) { 3932 oop obj = *p; 3933 assert(obj != NULL, "the caller should have filtered out NULL values"); 3934 3935 const InCSetState cset_state = _g1->in_cset_state(obj); 3936 if (!cset_state.is_in_cset_or_humongous()) { 3937 return; 3938 } 3939 if (cset_state.is_in_cset()) { 3940 assert( obj->is_forwarded(), "invariant" ); 3941 *p = obj->forwardee(); 3942 } else { 3943 assert(!obj->is_forwarded(), "invariant" ); 3944 assert(cset_state.is_humongous(), 3945 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3946 _g1->set_humongous_is_live(obj); 3947 } 3948 } 3949 }; 3950 3951 // Copying Keep Alive closure - can be called from both 3952 // serial and parallel code as long as different worker 3953 // threads utilize different G1ParScanThreadState instances 3954 // and different queues. 3955 3956 class G1CopyingKeepAliveClosure: public OopClosure { 3957 G1CollectedHeap* _g1h; 3958 OopClosure* _copy_non_heap_obj_cl; 3959 G1ParScanThreadState* _par_scan_state; 3960 3961 public: 3962 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3963 OopClosure* non_heap_obj_cl, 3964 G1ParScanThreadState* pss): 3965 _g1h(g1h), 3966 _copy_non_heap_obj_cl(non_heap_obj_cl), 3967 _par_scan_state(pss) 3968 {} 3969 3970 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3971 virtual void do_oop( oop* p) { do_oop_work(p); } 3972 3973 template <class T> void do_oop_work(T* p) { 3974 oop obj = oopDesc::load_decode_heap_oop(p); 3975 3976 if (_g1h->is_in_cset_or_humongous(obj)) { 3977 // If the referent object has been forwarded (either copied 3978 // to a new location or to itself in the event of an 3979 // evacuation failure) then we need to update the reference 3980 // field and, if both reference and referent are in the G1 3981 // heap, update the RSet for the referent. 3982 // 3983 // If the referent has not been forwarded then we have to keep 3984 // it alive by policy. Therefore we have copy the referent. 3985 // 3986 // If the reference field is in the G1 heap then we can push 3987 // on the PSS queue. When the queue is drained (after each 3988 // phase of reference processing) the object and it's followers 3989 // will be copied, the reference field set to point to the 3990 // new location, and the RSet updated. Otherwise we need to 3991 // use the the non-heap or metadata closures directly to copy 3992 // the referent object and update the pointer, while avoiding 3993 // updating the RSet. 3994 3995 if (_g1h->is_in_g1_reserved(p)) { 3996 _par_scan_state->push_on_queue(p); 3997 } else { 3998 assert(!Metaspace::contains((const void*)p), 3999 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4000 _copy_non_heap_obj_cl->do_oop(p); 4001 } 4002 } 4003 } 4004 }; 4005 4006 // Serial drain queue closure. Called as the 'complete_gc' 4007 // closure for each discovered list in some of the 4008 // reference processing phases. 4009 4010 class G1STWDrainQueueClosure: public VoidClosure { 4011 protected: 4012 G1CollectedHeap* _g1h; 4013 G1ParScanThreadState* _par_scan_state; 4014 4015 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4016 4017 public: 4018 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4019 _g1h(g1h), 4020 _par_scan_state(pss) 4021 { } 4022 4023 void do_void() { 4024 G1ParScanThreadState* const pss = par_scan_state(); 4025 pss->trim_queue(); 4026 } 4027 }; 4028 4029 // Parallel Reference Processing closures 4030 4031 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4032 // processing during G1 evacuation pauses. 4033 4034 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4035 private: 4036 G1CollectedHeap* _g1h; 4037 G1ParScanThreadStateSet* _pss; 4038 RefToScanQueueSet* _queues; 4039 WorkGang* _workers; 4040 uint _active_workers; 4041 4042 public: 4043 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4044 G1ParScanThreadStateSet* per_thread_states, 4045 WorkGang* workers, 4046 RefToScanQueueSet *task_queues, 4047 uint n_workers) : 4048 _g1h(g1h), 4049 _pss(per_thread_states), 4050 _queues(task_queues), 4051 _workers(workers), 4052 _active_workers(n_workers) 4053 { 4054 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 4055 } 4056 4057 // Executes the given task using concurrent marking worker threads. 4058 virtual void execute(ProcessTask& task); 4059 virtual void execute(EnqueueTask& task); 4060 }; 4061 4062 // Gang task for possibly parallel reference processing 4063 4064 class G1STWRefProcTaskProxy: public AbstractGangTask { 4065 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4066 ProcessTask& _proc_task; 4067 G1CollectedHeap* _g1h; 4068 G1ParScanThreadStateSet* _pss; 4069 RefToScanQueueSet* _task_queues; 4070 ParallelTaskTerminator* _terminator; 4071 4072 public: 4073 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4074 G1CollectedHeap* g1h, 4075 G1ParScanThreadStateSet* per_thread_states, 4076 RefToScanQueueSet *task_queues, 4077 ParallelTaskTerminator* terminator) : 4078 AbstractGangTask("Process reference objects in parallel"), 4079 _proc_task(proc_task), 4080 _g1h(g1h), 4081 _pss(per_thread_states), 4082 _task_queues(task_queues), 4083 _terminator(terminator) 4084 {} 4085 4086 virtual void work(uint worker_id) { 4087 // The reference processing task executed by a single worker. 4088 ResourceMark rm; 4089 HandleMark hm; 4090 4091 G1STWIsAliveClosure is_alive(_g1h); 4092 4093 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4094 pss->set_ref_processor(NULL); 4095 4096 // Keep alive closure. 4097 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4098 4099 // Complete GC closure 4100 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4101 4102 // Call the reference processing task's work routine. 4103 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4104 4105 // Note we cannot assert that the refs array is empty here as not all 4106 // of the processing tasks (specifically phase2 - pp2_work) execute 4107 // the complete_gc closure (which ordinarily would drain the queue) so 4108 // the queue may not be empty. 4109 } 4110 }; 4111 4112 // Driver routine for parallel reference processing. 4113 // Creates an instance of the ref processing gang 4114 // task and has the worker threads execute it. 4115 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4116 assert(_workers != NULL, "Need parallel worker threads."); 4117 4118 ParallelTaskTerminator terminator(_active_workers, _queues); 4119 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4120 4121 _workers->run_task(&proc_task_proxy); 4122 } 4123 4124 // Gang task for parallel reference enqueueing. 4125 4126 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4127 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4128 EnqueueTask& _enq_task; 4129 4130 public: 4131 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4132 AbstractGangTask("Enqueue reference objects in parallel"), 4133 _enq_task(enq_task) 4134 { } 4135 4136 virtual void work(uint worker_id) { 4137 _enq_task.work(worker_id); 4138 } 4139 }; 4140 4141 // Driver routine for parallel reference enqueueing. 4142 // Creates an instance of the ref enqueueing gang 4143 // task and has the worker threads execute it. 4144 4145 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4146 assert(_workers != NULL, "Need parallel worker threads."); 4147 4148 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4149 4150 _workers->run_task(&enq_task_proxy); 4151 } 4152 4153 // End of weak reference support closures 4154 4155 // Abstract task used to preserve (i.e. copy) any referent objects 4156 // that are in the collection set and are pointed to by reference 4157 // objects discovered by the CM ref processor. 4158 4159 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4160 protected: 4161 G1CollectedHeap* _g1h; 4162 G1ParScanThreadStateSet* _pss; 4163 RefToScanQueueSet* _queues; 4164 ParallelTaskTerminator _terminator; 4165 uint _n_workers; 4166 4167 public: 4168 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4169 AbstractGangTask("ParPreserveCMReferents"), 4170 _g1h(g1h), 4171 _pss(per_thread_states), 4172 _queues(task_queues), 4173 _terminator(workers, _queues), 4174 _n_workers(workers) 4175 { 4176 g1h->ref_processor_cm()->set_active_mt_degree(workers); 4177 } 4178 4179 void work(uint worker_id) { 4180 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4181 4182 ResourceMark rm; 4183 HandleMark hm; 4184 4185 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4186 pss->set_ref_processor(NULL); 4187 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4188 4189 // Is alive closure 4190 G1AlwaysAliveClosure always_alive(_g1h); 4191 4192 // Copying keep alive closure. Applied to referent objects that need 4193 // to be copied. 4194 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4195 4196 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4197 4198 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4199 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4200 4201 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4202 // So this must be true - but assert just in case someone decides to 4203 // change the worker ids. 4204 assert(worker_id < limit, "sanity"); 4205 assert(!rp->discovery_is_atomic(), "check this code"); 4206 4207 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4208 for (uint idx = worker_id; idx < limit; idx += stride) { 4209 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4210 4211 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4212 while (iter.has_next()) { 4213 // Since discovery is not atomic for the CM ref processor, we 4214 // can see some null referent objects. 4215 iter.load_ptrs(DEBUG_ONLY(true)); 4216 oop ref = iter.obj(); 4217 4218 // This will filter nulls. 4219 if (iter.is_referent_alive()) { 4220 iter.make_referent_alive(); 4221 } 4222 iter.move_to_next(); 4223 } 4224 } 4225 4226 // Drain the queue - which may cause stealing 4227 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4228 drain_queue.do_void(); 4229 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4230 assert(pss->queue_is_empty(), "should be"); 4231 } 4232 }; 4233 4234 void G1CollectedHeap::process_weak_jni_handles() { 4235 double ref_proc_start = os::elapsedTime(); 4236 4237 G1STWIsAliveClosure is_alive(this); 4238 G1KeepAliveClosure keep_alive(this); 4239 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 4240 4241 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4242 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4243 } 4244 4245 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4246 // Any reference objects, in the collection set, that were 'discovered' 4247 // by the CM ref processor should have already been copied (either by 4248 // applying the external root copy closure to the discovered lists, or 4249 // by following an RSet entry). 4250 // 4251 // But some of the referents, that are in the collection set, that these 4252 // reference objects point to may not have been copied: the STW ref 4253 // processor would have seen that the reference object had already 4254 // been 'discovered' and would have skipped discovering the reference, 4255 // but would not have treated the reference object as a regular oop. 4256 // As a result the copy closure would not have been applied to the 4257 // referent object. 4258 // 4259 // We need to explicitly copy these referent objects - the references 4260 // will be processed at the end of remarking. 4261 // 4262 // We also need to do this copying before we process the reference 4263 // objects discovered by the STW ref processor in case one of these 4264 // referents points to another object which is also referenced by an 4265 // object discovered by the STW ref processor. 4266 double preserve_cm_referents_time = 0.0; 4267 4268 // To avoid spawning task when there is no work to do, check that 4269 // a concurrent cycle is active and that some references have been 4270 // discovered. 4271 if (concurrent_mark()->cmThread()->during_cycle() && 4272 ref_processor_cm()->has_discovered_references()) { 4273 double preserve_cm_referents_start = os::elapsedTime(); 4274 uint no_of_gc_workers = workers()->active_workers(); 4275 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4276 per_thread_states, 4277 no_of_gc_workers, 4278 _task_queues); 4279 workers()->run_task(&keep_cm_referents); 4280 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4281 } 4282 4283 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4284 } 4285 4286 // Weak Reference processing during an evacuation pause (part 1). 4287 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4288 double ref_proc_start = os::elapsedTime(); 4289 4290 ReferenceProcessor* rp = _ref_processor_stw; 4291 assert(rp->discovery_enabled(), "should have been enabled"); 4292 4293 // Closure to test whether a referent is alive. 4294 G1STWIsAliveClosure is_alive(this); 4295 4296 // Even when parallel reference processing is enabled, the processing 4297 // of JNI refs is serial and performed serially by the current thread 4298 // rather than by a worker. The following PSS will be used for processing 4299 // JNI refs. 4300 4301 // Use only a single queue for this PSS. 4302 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4303 pss->set_ref_processor(NULL); 4304 assert(pss->queue_is_empty(), "pre-condition"); 4305 4306 // Keep alive closure. 4307 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4308 4309 // Serial Complete GC closure 4310 G1STWDrainQueueClosure drain_queue(this, pss); 4311 4312 // Setup the soft refs policy... 4313 rp->setup_policy(false); 4314 4315 ReferenceProcessorStats stats; 4316 if (!rp->processing_is_mt()) { 4317 // Serial reference processing... 4318 stats = rp->process_discovered_references(&is_alive, 4319 &keep_alive, 4320 &drain_queue, 4321 NULL, 4322 _gc_timer_stw); 4323 } else { 4324 uint no_of_gc_workers = workers()->active_workers(); 4325 4326 // Parallel reference processing 4327 assert(no_of_gc_workers <= rp->max_num_q(), 4328 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4329 no_of_gc_workers, rp->max_num_q()); 4330 4331 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4332 stats = rp->process_discovered_references(&is_alive, 4333 &keep_alive, 4334 &drain_queue, 4335 &par_task_executor, 4336 _gc_timer_stw); 4337 } 4338 4339 _gc_tracer_stw->report_gc_reference_stats(stats); 4340 4341 // We have completed copying any necessary live referent objects. 4342 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4343 4344 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4345 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4346 } 4347 4348 // Weak Reference processing during an evacuation pause (part 2). 4349 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4350 double ref_enq_start = os::elapsedTime(); 4351 4352 ReferenceProcessor* rp = _ref_processor_stw; 4353 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4354 4355 // Now enqueue any remaining on the discovered lists on to 4356 // the pending list. 4357 if (!rp->processing_is_mt()) { 4358 // Serial reference processing... 4359 rp->enqueue_discovered_references(); 4360 } else { 4361 // Parallel reference enqueueing 4362 4363 uint n_workers = workers()->active_workers(); 4364 4365 assert(n_workers <= rp->max_num_q(), 4366 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4367 n_workers, rp->max_num_q()); 4368 4369 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4370 rp->enqueue_discovered_references(&par_task_executor); 4371 } 4372 4373 rp->verify_no_references_recorded(); 4374 assert(!rp->discovery_enabled(), "should have been disabled"); 4375 4376 // FIXME 4377 // CM's reference processing also cleans up the string and symbol tables. 4378 // Should we do that here also? We could, but it is a serial operation 4379 // and could significantly increase the pause time. 4380 4381 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4382 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4383 } 4384 4385 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4386 double merge_pss_time_start = os::elapsedTime(); 4387 per_thread_states->flush(); 4388 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4389 } 4390 4391 void G1CollectedHeap::pre_evacuate_collection_set() { 4392 _expand_heap_after_alloc_failure = true; 4393 _evacuation_failed = false; 4394 4395 // Disable the hot card cache. 4396 _hot_card_cache->reset_hot_cache_claimed_index(); 4397 _hot_card_cache->set_use_cache(false); 4398 4399 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4400 _preserved_marks_set.assert_empty(); 4401 4402 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4403 4404 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4405 if (collector_state()->during_initial_mark_pause()) { 4406 double start_clear_claimed_marks = os::elapsedTime(); 4407 4408 ClassLoaderDataGraph::clear_claimed_marks(); 4409 4410 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4411 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4412 } 4413 } 4414 4415 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4416 // Should G1EvacuationFailureALot be in effect for this GC? 4417 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4418 4419 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4420 4421 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4422 4423 double start_par_time_sec = os::elapsedTime(); 4424 double end_par_time_sec; 4425 4426 { 4427 const uint n_workers = workers()->active_workers(); 4428 G1RootProcessor root_processor(this, n_workers); 4429 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4430 4431 print_termination_stats_hdr(); 4432 4433 workers()->run_task(&g1_par_task); 4434 end_par_time_sec = os::elapsedTime(); 4435 4436 // Closing the inner scope will execute the destructor 4437 // for the G1RootProcessor object. We record the current 4438 // elapsed time before closing the scope so that time 4439 // taken for the destructor is NOT included in the 4440 // reported parallel time. 4441 } 4442 4443 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4444 phase_times->record_par_time(par_time_ms); 4445 4446 double code_root_fixup_time_ms = 4447 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4448 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4449 } 4450 4451 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4452 // Process any discovered reference objects - we have 4453 // to do this _before_ we retire the GC alloc regions 4454 // as we may have to copy some 'reachable' referent 4455 // objects (and their reachable sub-graphs) that were 4456 // not copied during the pause. 4457 if (g1_policy()->should_process_references()) { 4458 preserve_cm_referents(per_thread_states); 4459 process_discovered_references(per_thread_states); 4460 } else { 4461 ref_processor_stw()->verify_no_references_recorded(); 4462 process_weak_jni_handles(); 4463 } 4464 4465 if (G1StringDedup::is_enabled()) { 4466 double fixup_start = os::elapsedTime(); 4467 4468 G1STWIsAliveClosure is_alive(this); 4469 G1KeepAliveClosure keep_alive(this); 4470 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4471 4472 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4473 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4474 } 4475 4476 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4477 4478 if (evacuation_failed()) { 4479 restore_after_evac_failure(); 4480 4481 // Reset the G1EvacuationFailureALot counters and flags 4482 // Note: the values are reset only when an actual 4483 // evacuation failure occurs. 4484 NOT_PRODUCT(reset_evacuation_should_fail();) 4485 } 4486 4487 _preserved_marks_set.assert_empty(); 4488 4489 // Enqueue any remaining references remaining on the STW 4490 // reference processor's discovered lists. We need to do 4491 // this after the card table is cleaned (and verified) as 4492 // the act of enqueueing entries on to the pending list 4493 // will log these updates (and dirty their associated 4494 // cards). We need these updates logged to update any 4495 // RSets. 4496 if (g1_policy()->should_process_references()) { 4497 enqueue_discovered_references(per_thread_states); 4498 } else { 4499 g1_policy()->phase_times()->record_ref_enq_time(0); 4500 } 4501 4502 _allocator->release_gc_alloc_regions(evacuation_info); 4503 4504 merge_per_thread_state_info(per_thread_states); 4505 4506 // Reset and re-enable the hot card cache. 4507 // Note the counts for the cards in the regions in the 4508 // collection set are reset when the collection set is freed. 4509 _hot_card_cache->reset_hot_cache(); 4510 _hot_card_cache->set_use_cache(true); 4511 4512 purge_code_root_memory(); 4513 4514 redirty_logged_cards(); 4515 #if defined(COMPILER2) || INCLUDE_JVMCI 4516 double start = os::elapsedTime(); 4517 DerivedPointerTable::update_pointers(); 4518 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4519 #endif 4520 g1_policy()->print_age_table(); 4521 } 4522 4523 void G1CollectedHeap::record_obj_copy_mem_stats() { 4524 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4525 4526 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4527 create_g1_evac_summary(&_old_evac_stats)); 4528 } 4529 4530 void G1CollectedHeap::free_region(HeapRegion* hr, 4531 FreeRegionList* free_list, 4532 bool skip_remset, 4533 bool skip_hot_card_cache, 4534 bool locked) { 4535 assert(!hr->is_free(), "the region should not be free"); 4536 assert(!hr->is_empty(), "the region should not be empty"); 4537 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4538 assert(free_list != NULL, "pre-condition"); 4539 4540 if (G1VerifyBitmaps) { 4541 MemRegion mr(hr->bottom(), hr->end()); 4542 concurrent_mark()->clearRangePrevBitmap(mr); 4543 } 4544 4545 // Clear the card counts for this region. 4546 // Note: we only need to do this if the region is not young 4547 // (since we don't refine cards in young regions). 4548 if (!skip_hot_card_cache && !hr->is_young()) { 4549 _hot_card_cache->reset_card_counts(hr); 4550 } 4551 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4552 free_list->add_ordered(hr); 4553 } 4554 4555 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4556 FreeRegionList* free_list, 4557 bool skip_remset) { 4558 assert(hr->is_humongous(), "this is only for humongous regions"); 4559 assert(free_list != NULL, "pre-condition"); 4560 hr->clear_humongous(); 4561 free_region(hr, free_list, skip_remset); 4562 } 4563 4564 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4565 const uint humongous_regions_removed) { 4566 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4567 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4568 _old_set.bulk_remove(old_regions_removed); 4569 _humongous_set.bulk_remove(humongous_regions_removed); 4570 } 4571 4572 } 4573 4574 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4575 assert(list != NULL, "list can't be null"); 4576 if (!list->is_empty()) { 4577 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4578 _hrm.insert_list_into_free_list(list); 4579 } 4580 } 4581 4582 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4583 decrease_used(bytes); 4584 } 4585 4586 class G1ParScrubRemSetTask: public AbstractGangTask { 4587 protected: 4588 G1RemSet* _g1rs; 4589 HeapRegionClaimer _hrclaimer; 4590 4591 public: 4592 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) : 4593 AbstractGangTask("G1 ScrubRS"), 4594 _g1rs(g1_rs), 4595 _hrclaimer(num_workers) { 4596 } 4597 4598 void work(uint worker_id) { 4599 _g1rs->scrub(worker_id, &_hrclaimer); 4600 } 4601 }; 4602 4603 void G1CollectedHeap::scrub_rem_set() { 4604 uint num_workers = workers()->active_workers(); 4605 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers); 4606 workers()->run_task(&g1_par_scrub_rs_task); 4607 } 4608 4609 class G1FreeCollectionSetTask : public AbstractGangTask { 4610 private: 4611 4612 // Closure applied to all regions in the collection set to do work that needs to 4613 // be done serially in a single thread. 4614 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4615 private: 4616 EvacuationInfo* _evacuation_info; 4617 const size_t* _surviving_young_words; 4618 4619 // Bytes used in successfully evacuated regions before the evacuation. 4620 size_t _before_used_bytes; 4621 // Bytes used in unsucessfully evacuated regions before the evacuation 4622 size_t _after_used_bytes; 4623 4624 size_t _bytes_allocated_in_old_since_last_gc; 4625 4626 size_t _failure_used_words; 4627 size_t _failure_waste_words; 4628 4629 FreeRegionList _local_free_list; 4630 public: 4631 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4632 HeapRegionClosure(), 4633 _evacuation_info(evacuation_info), 4634 _surviving_young_words(surviving_young_words), 4635 _before_used_bytes(0), 4636 _after_used_bytes(0), 4637 _bytes_allocated_in_old_since_last_gc(0), 4638 _failure_used_words(0), 4639 _failure_waste_words(0), 4640 _local_free_list("Local Region List for CSet Freeing") { 4641 } 4642 4643 virtual bool doHeapRegion(HeapRegion* r) { 4644 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4645 4646 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4647 g1h->clear_in_cset(r); 4648 4649 if (r->is_young()) { 4650 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4651 "Young index %d is wrong for region %u of type %s with %u young regions", 4652 r->young_index_in_cset(), 4653 r->hrm_index(), 4654 r->get_type_str(), 4655 g1h->collection_set()->young_region_length()); 4656 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4657 r->record_surv_words_in_group(words_survived); 4658 } 4659 4660 if (!r->evacuation_failed()) { 4661 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4662 _before_used_bytes += r->used(); 4663 g1h->free_region(r, 4664 &_local_free_list, 4665 true, /* skip_remset */ 4666 true, /* skip_hot_card_cache */ 4667 true /* locked */); 4668 } else { 4669 r->uninstall_surv_rate_group(); 4670 r->set_young_index_in_cset(-1); 4671 r->set_evacuation_failed(false); 4672 // When moving a young gen region to old gen, we "allocate" that whole region 4673 // there. This is in addition to any already evacuated objects. Notify the 4674 // policy about that. 4675 // Old gen regions do not cause an additional allocation: both the objects 4676 // still in the region and the ones already moved are accounted for elsewhere. 4677 if (r->is_young()) { 4678 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4679 } 4680 // The region is now considered to be old. 4681 r->set_old(); 4682 // Do some allocation statistics accounting. Regions that failed evacuation 4683 // are always made old, so there is no need to update anything in the young 4684 // gen statistics, but we need to update old gen statistics. 4685 size_t used_words = r->marked_bytes() / HeapWordSize; 4686 4687 _failure_used_words += used_words; 4688 _failure_waste_words += HeapRegion::GrainWords - used_words; 4689 4690 g1h->old_set_add(r); 4691 _after_used_bytes += r->used(); 4692 } 4693 return false; 4694 } 4695 4696 void complete_work() { 4697 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4698 4699 _evacuation_info->set_regions_freed(_local_free_list.length()); 4700 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4701 4702 g1h->prepend_to_freelist(&_local_free_list); 4703 g1h->decrement_summary_bytes(_before_used_bytes); 4704 4705 G1Policy* policy = g1h->g1_policy(); 4706 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4707 4708 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4709 } 4710 }; 4711 4712 G1CollectionSet* _collection_set; 4713 G1SerialFreeCollectionSetClosure _cl; 4714 const size_t* _surviving_young_words; 4715 4716 size_t _rs_lengths; 4717 4718 volatile jint _serial_work_claim; 4719 4720 struct WorkItem { 4721 uint region_idx; 4722 bool is_young; 4723 bool evacuation_failed; 4724 4725 WorkItem(HeapRegion* r) { 4726 region_idx = r->hrm_index(); 4727 is_young = r->is_young(); 4728 evacuation_failed = r->evacuation_failed(); 4729 } 4730 }; 4731 4732 volatile size_t _parallel_work_claim; 4733 size_t _num_work_items; 4734 WorkItem* _work_items; 4735 4736 void do_serial_work() { 4737 // Need to grab the lock to be allowed to modify the old region list. 4738 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4739 _collection_set->iterate(&_cl); 4740 } 4741 4742 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4743 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4744 4745 HeapRegion* r = g1h->region_at(region_idx); 4746 assert(!g1h->is_on_master_free_list(r), "sanity"); 4747 4748 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4749 4750 if (!is_young) { 4751 g1h->_hot_card_cache->reset_card_counts(r); 4752 } 4753 4754 if (!evacuation_failed) { 4755 r->rem_set()->clear_locked(); 4756 } 4757 } 4758 4759 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4760 private: 4761 size_t _cur_idx; 4762 WorkItem* _work_items; 4763 public: 4764 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4765 4766 virtual bool doHeapRegion(HeapRegion* r) { 4767 _work_items[_cur_idx++] = WorkItem(r); 4768 return false; 4769 } 4770 }; 4771 4772 void prepare_work() { 4773 G1PrepareFreeCollectionSetClosure cl(_work_items); 4774 _collection_set->iterate(&cl); 4775 } 4776 4777 void complete_work() { 4778 _cl.complete_work(); 4779 4780 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4781 policy->record_max_rs_lengths(_rs_lengths); 4782 policy->cset_regions_freed(); 4783 } 4784 public: 4785 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4786 AbstractGangTask("G1 Free Collection Set"), 4787 _cl(evacuation_info, surviving_young_words), 4788 _collection_set(collection_set), 4789 _surviving_young_words(surviving_young_words), 4790 _serial_work_claim(0), 4791 _rs_lengths(0), 4792 _parallel_work_claim(0), 4793 _num_work_items(collection_set->region_length()), 4794 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4795 prepare_work(); 4796 } 4797 4798 ~G1FreeCollectionSetTask() { 4799 complete_work(); 4800 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4801 } 4802 4803 // Chunk size for work distribution. The chosen value has been determined experimentally 4804 // to be a good tradeoff between overhead and achievable parallelism. 4805 static uint chunk_size() { return 32; } 4806 4807 virtual void work(uint worker_id) { 4808 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4809 4810 // Claim serial work. 4811 if (_serial_work_claim == 0) { 4812 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4813 if (value == 0) { 4814 double serial_time = os::elapsedTime(); 4815 do_serial_work(); 4816 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4817 } 4818 } 4819 4820 // Start parallel work. 4821 double young_time = 0.0; 4822 bool has_young_time = false; 4823 double non_young_time = 0.0; 4824 bool has_non_young_time = false; 4825 4826 while (true) { 4827 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4828 size_t cur = end - chunk_size(); 4829 4830 if (cur >= _num_work_items) { 4831 break; 4832 } 4833 4834 double start_time = os::elapsedTime(); 4835 4836 end = MIN2(end, _num_work_items); 4837 4838 for (; cur < end; cur++) { 4839 bool is_young = _work_items[cur].is_young; 4840 4841 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4842 4843 double end_time = os::elapsedTime(); 4844 double time_taken = end_time - start_time; 4845 if (is_young) { 4846 young_time += time_taken; 4847 has_young_time = true; 4848 } else { 4849 non_young_time += time_taken; 4850 has_non_young_time = true; 4851 } 4852 start_time = end_time; 4853 } 4854 } 4855 4856 if (has_young_time) { 4857 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4858 } 4859 if (has_non_young_time) { 4860 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time); 4861 } 4862 } 4863 }; 4864 4865 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4866 _eden.clear(); 4867 4868 double free_cset_start_time = os::elapsedTime(); 4869 4870 { 4871 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4872 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4873 4874 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4875 4876 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4877 cl.name(), 4878 num_workers, 4879 _collection_set.region_length()); 4880 workers()->run_task(&cl, num_workers); 4881 } 4882 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4883 4884 collection_set->clear(); 4885 } 4886 4887 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4888 private: 4889 FreeRegionList* _free_region_list; 4890 HeapRegionSet* _proxy_set; 4891 uint _humongous_objects_reclaimed; 4892 uint _humongous_regions_reclaimed; 4893 size_t _freed_bytes; 4894 public: 4895 4896 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4897 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4898 } 4899 4900 virtual bool doHeapRegion(HeapRegion* r) { 4901 if (!r->is_starts_humongous()) { 4902 return false; 4903 } 4904 4905 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4906 4907 oop obj = (oop)r->bottom(); 4908 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 4909 4910 // The following checks whether the humongous object is live are sufficient. 4911 // The main additional check (in addition to having a reference from the roots 4912 // or the young gen) is whether the humongous object has a remembered set entry. 4913 // 4914 // A humongous object cannot be live if there is no remembered set for it 4915 // because: 4916 // - there can be no references from within humongous starts regions referencing 4917 // the object because we never allocate other objects into them. 4918 // (I.e. there are no intra-region references that may be missed by the 4919 // remembered set) 4920 // - as soon there is a remembered set entry to the humongous starts region 4921 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4922 // until the end of a concurrent mark. 4923 // 4924 // It is not required to check whether the object has been found dead by marking 4925 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4926 // all objects allocated during that time are considered live. 4927 // SATB marking is even more conservative than the remembered set. 4928 // So if at this point in the collection there is no remembered set entry, 4929 // nobody has a reference to it. 4930 // At the start of collection we flush all refinement logs, and remembered sets 4931 // are completely up-to-date wrt to references to the humongous object. 4932 // 4933 // Other implementation considerations: 4934 // - never consider object arrays at this time because they would pose 4935 // considerable effort for cleaning up the the remembered sets. This is 4936 // required because stale remembered sets might reference locations that 4937 // are currently allocated into. 4938 uint region_idx = r->hrm_index(); 4939 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4940 !r->rem_set()->is_empty()) { 4941 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", 4942 region_idx, 4943 (size_t)obj->size() * HeapWordSize, 4944 p2i(r->bottom()), 4945 r->rem_set()->occupied(), 4946 r->rem_set()->strong_code_roots_list_length(), 4947 next_bitmap->isMarked(r->bottom()), 4948 g1h->is_humongous_reclaim_candidate(region_idx), 4949 obj->is_typeArray() 4950 ); 4951 return false; 4952 } 4953 4954 guarantee(obj->is_typeArray(), 4955 "Only eagerly reclaiming type arrays is supported, but the object " 4956 PTR_FORMAT " is not.", p2i(r->bottom())); 4957 4958 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", 4959 region_idx, 4960 (size_t)obj->size() * HeapWordSize, 4961 p2i(r->bottom()), 4962 r->rem_set()->occupied(), 4963 r->rem_set()->strong_code_roots_list_length(), 4964 next_bitmap->isMarked(r->bottom()), 4965 g1h->is_humongous_reclaim_candidate(region_idx), 4966 obj->is_typeArray() 4967 ); 4968 4969 // Need to clear mark bit of the humongous object if already set. 4970 if (next_bitmap->isMarked(r->bottom())) { 4971 next_bitmap->clear(r->bottom()); 4972 } 4973 _humongous_objects_reclaimed++; 4974 do { 4975 HeapRegion* next = g1h->next_region_in_humongous(r); 4976 _freed_bytes += r->used(); 4977 r->set_containing_set(NULL); 4978 _humongous_regions_reclaimed++; 4979 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ ); 4980 r = next; 4981 } while (r != NULL); 4982 4983 return false; 4984 } 4985 4986 uint humongous_objects_reclaimed() { 4987 return _humongous_objects_reclaimed; 4988 } 4989 4990 uint humongous_regions_reclaimed() { 4991 return _humongous_regions_reclaimed; 4992 } 4993 4994 size_t bytes_freed() const { 4995 return _freed_bytes; 4996 } 4997 }; 4998 4999 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 5000 assert_at_safepoint(true); 5001 5002 if (!G1EagerReclaimHumongousObjects || 5003 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 5004 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5005 return; 5006 } 5007 5008 double start_time = os::elapsedTime(); 5009 5010 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5011 5012 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5013 heap_region_iterate(&cl); 5014 5015 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 5016 5017 G1HRPrinter* hrp = hr_printer(); 5018 if (hrp->is_active()) { 5019 FreeRegionListIterator iter(&local_cleanup_list); 5020 while (iter.more_available()) { 5021 HeapRegion* hr = iter.get_next(); 5022 hrp->cleanup(hr); 5023 } 5024 } 5025 5026 prepend_to_freelist(&local_cleanup_list); 5027 decrement_summary_bytes(cl.bytes_freed()); 5028 5029 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5030 cl.humongous_objects_reclaimed()); 5031 } 5032 5033 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 5034 public: 5035 virtual bool doHeapRegion(HeapRegion* r) { 5036 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 5037 G1CollectedHeap::heap()->clear_in_cset(r); 5038 r->set_young_index_in_cset(-1); 5039 return false; 5040 } 5041 }; 5042 5043 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 5044 G1AbandonCollectionSetClosure cl; 5045 collection_set->iterate(&cl); 5046 5047 collection_set->clear(); 5048 collection_set->stop_incremental_building(); 5049 } 5050 5051 void G1CollectedHeap::set_free_regions_coming() { 5052 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 5053 5054 assert(!free_regions_coming(), "pre-condition"); 5055 _free_regions_coming = true; 5056 } 5057 5058 void G1CollectedHeap::reset_free_regions_coming() { 5059 assert(free_regions_coming(), "pre-condition"); 5060 5061 { 5062 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5063 _free_regions_coming = false; 5064 SecondaryFreeList_lock->notify_all(); 5065 } 5066 5067 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 5068 } 5069 5070 void G1CollectedHeap::wait_while_free_regions_coming() { 5071 // Most of the time we won't have to wait, so let's do a quick test 5072 // first before we take the lock. 5073 if (!free_regions_coming()) { 5074 return; 5075 } 5076 5077 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 5078 5079 { 5080 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5081 while (free_regions_coming()) { 5082 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5083 } 5084 } 5085 5086 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 5087 } 5088 5089 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5090 return _allocator->is_retained_old_region(hr); 5091 } 5092 5093 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5094 _eden.add(hr); 5095 _g1_policy->set_region_eden(hr); 5096 } 5097 5098 #ifdef ASSERT 5099 5100 class NoYoungRegionsClosure: public HeapRegionClosure { 5101 private: 5102 bool _success; 5103 public: 5104 NoYoungRegionsClosure() : _success(true) { } 5105 bool doHeapRegion(HeapRegion* r) { 5106 if (r->is_young()) { 5107 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5108 p2i(r->bottom()), p2i(r->end())); 5109 _success = false; 5110 } 5111 return false; 5112 } 5113 bool success() { return _success; } 5114 }; 5115 5116 bool G1CollectedHeap::check_young_list_empty() { 5117 bool ret = (young_regions_count() == 0); 5118 5119 NoYoungRegionsClosure closure; 5120 heap_region_iterate(&closure); 5121 ret = ret && closure.success(); 5122 5123 return ret; 5124 } 5125 5126 #endif // ASSERT 5127 5128 class TearDownRegionSetsClosure : public HeapRegionClosure { 5129 private: 5130 HeapRegionSet *_old_set; 5131 5132 public: 5133 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5134 5135 bool doHeapRegion(HeapRegion* r) { 5136 if (r->is_old()) { 5137 _old_set->remove(r); 5138 } else if(r->is_young()) { 5139 r->uninstall_surv_rate_group(); 5140 } else { 5141 // We ignore free regions, we'll empty the free list afterwards. 5142 // We ignore humongous regions, we're not tearing down the 5143 // humongous regions set. 5144 assert(r->is_free() || r->is_humongous(), 5145 "it cannot be another type"); 5146 } 5147 return false; 5148 } 5149 5150 ~TearDownRegionSetsClosure() { 5151 assert(_old_set->is_empty(), "post-condition"); 5152 } 5153 }; 5154 5155 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5156 assert_at_safepoint(true /* should_be_vm_thread */); 5157 5158 if (!free_list_only) { 5159 TearDownRegionSetsClosure cl(&_old_set); 5160 heap_region_iterate(&cl); 5161 5162 // Note that emptying the _young_list is postponed and instead done as 5163 // the first step when rebuilding the regions sets again. The reason for 5164 // this is that during a full GC string deduplication needs to know if 5165 // a collected region was young or old when the full GC was initiated. 5166 } 5167 _hrm.remove_all_free_regions(); 5168 } 5169 5170 void G1CollectedHeap::increase_used(size_t bytes) { 5171 _summary_bytes_used += bytes; 5172 } 5173 5174 void G1CollectedHeap::decrease_used(size_t bytes) { 5175 assert(_summary_bytes_used >= bytes, 5176 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5177 _summary_bytes_used, bytes); 5178 _summary_bytes_used -= bytes; 5179 } 5180 5181 void G1CollectedHeap::set_used(size_t bytes) { 5182 _summary_bytes_used = bytes; 5183 } 5184 5185 class RebuildRegionSetsClosure : public HeapRegionClosure { 5186 private: 5187 bool _free_list_only; 5188 HeapRegionSet* _old_set; 5189 HeapRegionManager* _hrm; 5190 size_t _total_used; 5191 5192 public: 5193 RebuildRegionSetsClosure(bool free_list_only, 5194 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5195 _free_list_only(free_list_only), 5196 _old_set(old_set), _hrm(hrm), _total_used(0) { 5197 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5198 if (!free_list_only) { 5199 assert(_old_set->is_empty(), "pre-condition"); 5200 } 5201 } 5202 5203 bool doHeapRegion(HeapRegion* r) { 5204 if (r->is_empty()) { 5205 // Add free regions to the free list 5206 r->set_free(); 5207 r->set_allocation_context(AllocationContext::system()); 5208 _hrm->insert_into_free_list(r); 5209 } else if (!_free_list_only) { 5210 5211 if (r->is_humongous()) { 5212 // We ignore humongous regions. We left the humongous set unchanged. 5213 } else { 5214 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 5215 // We now consider all regions old, so register as such. Leave 5216 // archive regions set that way, however, while still adding 5217 // them to the old set. 5218 if (!r->is_archive()) { 5219 r->set_old(); 5220 } 5221 _old_set->add(r); 5222 } 5223 _total_used += r->used(); 5224 } 5225 5226 return false; 5227 } 5228 5229 size_t total_used() { 5230 return _total_used; 5231 } 5232 }; 5233 5234 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5235 assert_at_safepoint(true /* should_be_vm_thread */); 5236 5237 if (!free_list_only) { 5238 _eden.clear(); 5239 _survivor.clear(); 5240 } 5241 5242 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5243 heap_region_iterate(&cl); 5244 5245 if (!free_list_only) { 5246 set_used(cl.total_used()); 5247 if (_archive_allocator != NULL) { 5248 _archive_allocator->clear_used(); 5249 } 5250 } 5251 assert(used_unlocked() == recalculate_used(), 5252 "inconsistent used_unlocked(), " 5253 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5254 used_unlocked(), recalculate_used()); 5255 } 5256 5257 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5258 HeapRegion* hr = heap_region_containing(p); 5259 return hr->is_in(p); 5260 } 5261 5262 // Methods for the mutator alloc region 5263 5264 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5265 bool force) { 5266 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5267 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 5268 if (force || should_allocate) { 5269 HeapRegion* new_alloc_region = new_region(word_size, 5270 false /* is_old */, 5271 false /* do_expand */); 5272 if (new_alloc_region != NULL) { 5273 set_region_short_lived_locked(new_alloc_region); 5274 _hr_printer.alloc(new_alloc_region, !should_allocate); 5275 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5276 return new_alloc_region; 5277 } 5278 } 5279 return NULL; 5280 } 5281 5282 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5283 size_t allocated_bytes) { 5284 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5285 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5286 5287 collection_set()->add_eden_region(alloc_region); 5288 increase_used(allocated_bytes); 5289 _hr_printer.retire(alloc_region); 5290 // We update the eden sizes here, when the region is retired, 5291 // instead of when it's allocated, since this is the point that its 5292 // used space has been recored in _summary_bytes_used. 5293 g1mm()->update_eden_size(); 5294 } 5295 5296 // Methods for the GC alloc regions 5297 5298 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 5299 if (dest.is_old()) { 5300 return true; 5301 } else { 5302 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 5303 } 5304 } 5305 5306 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 5307 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5308 5309 if (!has_more_regions(dest)) { 5310 return NULL; 5311 } 5312 5313 const bool is_survivor = dest.is_young(); 5314 5315 HeapRegion* new_alloc_region = new_region(word_size, 5316 !is_survivor, 5317 true /* do_expand */); 5318 if (new_alloc_region != NULL) { 5319 // We really only need to do this for old regions given that we 5320 // should never scan survivors. But it doesn't hurt to do it 5321 // for survivors too. 5322 new_alloc_region->record_timestamp(); 5323 if (is_survivor) { 5324 new_alloc_region->set_survivor(); 5325 _survivor.add(new_alloc_region); 5326 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5327 } else { 5328 new_alloc_region->set_old(); 5329 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5330 } 5331 _hr_printer.alloc(new_alloc_region); 5332 bool during_im = collector_state()->during_initial_mark_pause(); 5333 new_alloc_region->note_start_of_copying(during_im); 5334 return new_alloc_region; 5335 } 5336 return NULL; 5337 } 5338 5339 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5340 size_t allocated_bytes, 5341 InCSetState dest) { 5342 bool during_im = collector_state()->during_initial_mark_pause(); 5343 alloc_region->note_end_of_copying(during_im); 5344 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5345 if (dest.is_old()) { 5346 _old_set.add(alloc_region); 5347 } 5348 _hr_printer.retire(alloc_region); 5349 } 5350 5351 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5352 bool expanded = false; 5353 uint index = _hrm.find_highest_free(&expanded); 5354 5355 if (index != G1_NO_HRM_INDEX) { 5356 if (expanded) { 5357 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5358 HeapRegion::GrainWords * HeapWordSize); 5359 } 5360 _hrm.allocate_free_regions_starting_at(index, 1); 5361 return region_at(index); 5362 } 5363 return NULL; 5364 } 5365 5366 // Optimized nmethod scanning 5367 5368 class RegisterNMethodOopClosure: public OopClosure { 5369 G1CollectedHeap* _g1h; 5370 nmethod* _nm; 5371 5372 template <class T> void do_oop_work(T* p) { 5373 T heap_oop = oopDesc::load_heap_oop(p); 5374 if (!oopDesc::is_null(heap_oop)) { 5375 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5376 HeapRegion* hr = _g1h->heap_region_containing(obj); 5377 assert(!hr->is_continues_humongous(), 5378 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5379 " starting at " HR_FORMAT, 5380 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5381 5382 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5383 hr->add_strong_code_root_locked(_nm); 5384 } 5385 } 5386 5387 public: 5388 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5389 _g1h(g1h), _nm(nm) {} 5390 5391 void do_oop(oop* p) { do_oop_work(p); } 5392 void do_oop(narrowOop* p) { do_oop_work(p); } 5393 }; 5394 5395 class UnregisterNMethodOopClosure: public OopClosure { 5396 G1CollectedHeap* _g1h; 5397 nmethod* _nm; 5398 5399 template <class T> void do_oop_work(T* p) { 5400 T heap_oop = oopDesc::load_heap_oop(p); 5401 if (!oopDesc::is_null(heap_oop)) { 5402 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5403 HeapRegion* hr = _g1h->heap_region_containing(obj); 5404 assert(!hr->is_continues_humongous(), 5405 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5406 " starting at " HR_FORMAT, 5407 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5408 5409 hr->remove_strong_code_root(_nm); 5410 } 5411 } 5412 5413 public: 5414 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5415 _g1h(g1h), _nm(nm) {} 5416 5417 void do_oop(oop* p) { do_oop_work(p); } 5418 void do_oop(narrowOop* p) { do_oop_work(p); } 5419 }; 5420 5421 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5422 assert_locked_or_safepoint(CodeCache_lock); 5423 guarantee(nm != NULL, "sanity"); 5424 RegisterNMethodOopClosure reg_cl(this, nm); 5425 nm->oops_do(®_cl); 5426 } 5427 5428 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5429 assert_locked_or_safepoint(CodeCache_lock); 5430 guarantee(nm != NULL, "sanity"); 5431 UnregisterNMethodOopClosure reg_cl(this, nm); 5432 nm->oops_do(®_cl, true); 5433 } 5434 5435 void G1CollectedHeap::purge_code_root_memory() { 5436 double purge_start = os::elapsedTime(); 5437 G1CodeRootSet::purge(); 5438 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5439 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5440 } 5441 5442 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5443 G1CollectedHeap* _g1h; 5444 5445 public: 5446 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5447 _g1h(g1h) {} 5448 5449 void do_code_blob(CodeBlob* cb) { 5450 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5451 if (nm == NULL) { 5452 return; 5453 } 5454 5455 if (ScavengeRootsInCode) { 5456 _g1h->register_nmethod(nm); 5457 } 5458 } 5459 }; 5460 5461 void G1CollectedHeap::rebuild_strong_code_roots() { 5462 RebuildStrongCodeRootClosure blob_cl(this); 5463 CodeCache::blobs_do(&blob_cl); 5464 }