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/g1FullGCScope.hpp" 42 #include "gc/g1/g1GCPhaseTimes.hpp" 43 #include "gc/g1/g1HeapSizingPolicy.hpp" 44 #include "gc/g1/g1HeapTransition.hpp" 45 #include "gc/g1/g1HeapVerifier.hpp" 46 #include "gc/g1/g1HotCardCache.hpp" 47 #include "gc/g1/g1OopClosures.inline.hpp" 48 #include "gc/g1/g1ParScanThreadState.inline.hpp" 49 #include "gc/g1/g1Policy.hpp" 50 #include "gc/g1/g1RegionToSpaceMapper.hpp" 51 #include "gc/g1/g1RemSet.inline.hpp" 52 #include "gc/g1/g1RootClosures.hpp" 53 #include "gc/g1/g1RootProcessor.hpp" 54 #include "gc/g1/g1SerialFullCollector.hpp" 55 #include "gc/g1/g1StringDedup.hpp" 56 #include "gc/g1/g1YCTypes.hpp" 57 #include "gc/g1/heapRegion.inline.hpp" 58 #include "gc/g1/heapRegionRemSet.hpp" 59 #include "gc/g1/heapRegionSet.inline.hpp" 60 #include "gc/g1/suspendibleThreadSet.hpp" 61 #include "gc/g1/vm_operations_g1.hpp" 62 #include "gc/shared/gcHeapSummary.hpp" 63 #include "gc/shared/gcId.hpp" 64 #include "gc/shared/gcLocker.inline.hpp" 65 #include "gc/shared/gcTimer.hpp" 66 #include "gc/shared/gcTrace.hpp" 67 #include "gc/shared/gcTraceTime.inline.hpp" 68 #include "gc/shared/generationSpec.hpp" 69 #include "gc/shared/isGCActiveMark.hpp" 70 #include "gc/shared/preservedMarks.inline.hpp" 71 #include "gc/shared/referenceProcessor.inline.hpp" 72 #include "gc/shared/taskqueue.inline.hpp" 73 #include "logging/log.hpp" 74 #include "memory/allocation.hpp" 75 #include "memory/iterator.hpp" 76 #include "memory/resourceArea.hpp" 77 #include "oops/oop.inline.hpp" 78 #include "prims/resolvedMethodTable.hpp" 79 #include "runtime/atomic.hpp" 80 #include "runtime/init.hpp" 81 #include "runtime/orderAccess.inline.hpp" 82 #include "runtime/vmThread.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 // Local to this file. 98 99 class RefineCardTableEntryClosure: public CardTableEntryClosure { 100 bool _concurrent; 101 public: 102 RefineCardTableEntryClosure() : _concurrent(true) { } 103 104 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 105 G1CollectedHeap::heap()->g1_rem_set()->refine_card_concurrently(card_ptr, worker_i); 106 107 if (_concurrent && SuspendibleThreadSet::should_yield()) { 108 // Caller will actually yield. 109 return false; 110 } 111 // Otherwise, we finished successfully; return true. 112 return true; 113 } 114 115 void set_concurrent(bool b) { _concurrent = b; } 116 }; 117 118 119 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 120 private: 121 size_t _num_dirtied; 122 G1CollectedHeap* _g1h; 123 G1SATBCardTableLoggingModRefBS* _g1_bs; 124 125 HeapRegion* region_for_card(jbyte* card_ptr) const { 126 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 127 } 128 129 bool will_become_free(HeapRegion* hr) const { 130 // A region will be freed by free_collection_set if the region is in the 131 // collection set and has not had an evacuation failure. 132 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 133 } 134 135 public: 136 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 137 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 138 139 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 140 HeapRegion* hr = region_for_card(card_ptr); 141 142 // Should only dirty cards in regions that won't be freed. 143 if (!will_become_free(hr)) { 144 *card_ptr = CardTableModRefBS::dirty_card_val(); 145 _num_dirtied++; 146 } 147 148 return true; 149 } 150 151 size_t num_dirtied() const { return _num_dirtied; } 152 }; 153 154 155 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 156 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 157 } 158 159 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 160 // The from card cache is not the memory that is actually committed. So we cannot 161 // take advantage of the zero_filled parameter. 162 reset_from_card_cache(start_idx, num_regions); 163 } 164 165 // Returns true if the reference points to an object that 166 // can move in an incremental collection. 167 bool G1CollectedHeap::is_scavengable(const void* p) { 168 HeapRegion* hr = heap_region_containing(p); 169 return !hr->is_pinned(); 170 } 171 172 // Private methods. 173 174 HeapRegion* 175 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 176 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 177 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 178 if (!_secondary_free_list.is_empty()) { 179 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 180 "secondary_free_list has %u entries", 181 _secondary_free_list.length()); 182 // It looks as if there are free regions available on the 183 // secondary_free_list. Let's move them to the free_list and try 184 // again to allocate from it. 185 append_secondary_free_list(); 186 187 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 188 "empty we should have moved at least one entry to the free_list"); 189 HeapRegion* res = _hrm.allocate_free_region(is_old); 190 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 191 "allocated " HR_FORMAT " from secondary_free_list", 192 HR_FORMAT_PARAMS(res)); 193 return res; 194 } 195 196 // Wait here until we get notified either when (a) there are no 197 // more free regions coming or (b) some regions have been moved on 198 // the secondary_free_list. 199 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 200 } 201 202 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 203 "could not allocate from secondary_free_list"); 204 return NULL; 205 } 206 207 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 208 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 209 "the only time we use this to allocate a humongous region is " 210 "when we are allocating a single humongous region"); 211 212 HeapRegion* res; 213 if (G1StressConcRegionFreeing) { 214 if (!_secondary_free_list.is_empty()) { 215 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 216 "forced to look at the secondary_free_list"); 217 res = new_region_try_secondary_free_list(is_old); 218 if (res != NULL) { 219 return res; 220 } 221 } 222 } 223 224 res = _hrm.allocate_free_region(is_old); 225 226 if (res == NULL) { 227 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 228 "res == NULL, trying the secondary_free_list"); 229 res = new_region_try_secondary_free_list(is_old); 230 } 231 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 232 // Currently, only attempts to allocate GC alloc regions set 233 // do_expand to true. So, we should only reach here during a 234 // safepoint. If this assumption changes we might have to 235 // reconsider the use of _expand_heap_after_alloc_failure. 236 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 237 238 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 239 word_size * HeapWordSize); 240 241 if (expand(word_size * HeapWordSize)) { 242 // Given that expand() succeeded in expanding the heap, and we 243 // always expand the heap by an amount aligned to the heap 244 // region size, the free list should in theory not be empty. 245 // In either case allocate_free_region() will check for NULL. 246 res = _hrm.allocate_free_region(is_old); 247 } else { 248 _expand_heap_after_alloc_failure = false; 249 } 250 } 251 return res; 252 } 253 254 HeapWord* 255 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 256 uint num_regions, 257 size_t word_size, 258 AllocationContext_t context) { 259 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 260 assert(is_humongous(word_size), "word_size should be humongous"); 261 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 262 263 // Index of last region in the series. 264 uint last = first + num_regions - 1; 265 266 // We need to initialize the region(s) we just discovered. This is 267 // a bit tricky given that it can happen concurrently with 268 // refinement threads refining cards on these regions and 269 // potentially wanting to refine the BOT as they are scanning 270 // those cards (this can happen shortly after a cleanup; see CR 271 // 6991377). So we have to set up the region(s) carefully and in 272 // a specific order. 273 274 // The word size sum of all the regions we will allocate. 275 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 276 assert(word_size <= word_size_sum, "sanity"); 277 278 // This will be the "starts humongous" region. 279 HeapRegion* first_hr = region_at(first); 280 // The header of the new object will be placed at the bottom of 281 // the first region. 282 HeapWord* new_obj = first_hr->bottom(); 283 // This will be the new top of the new object. 284 HeapWord* obj_top = new_obj + word_size; 285 286 // First, we need to zero the header of the space that we will be 287 // allocating. When we update top further down, some refinement 288 // threads might try to scan the region. By zeroing the header we 289 // ensure that any thread that will try to scan the region will 290 // come across the zero klass word and bail out. 291 // 292 // NOTE: It would not have been correct to have used 293 // CollectedHeap::fill_with_object() and make the space look like 294 // an int array. The thread that is doing the allocation will 295 // later update the object header to a potentially different array 296 // type and, for a very short period of time, the klass and length 297 // fields will be inconsistent. This could cause a refinement 298 // thread to calculate the object size incorrectly. 299 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 300 301 // Next, pad out the unused tail of the last region with filler 302 // objects, for improved usage accounting. 303 // How many words we use for filler objects. 304 size_t word_fill_size = word_size_sum - word_size; 305 306 // How many words memory we "waste" which cannot hold a filler object. 307 size_t words_not_fillable = 0; 308 309 if (word_fill_size >= min_fill_size()) { 310 fill_with_objects(obj_top, word_fill_size); 311 } else if (word_fill_size > 0) { 312 // We have space to fill, but we cannot fit an object there. 313 words_not_fillable = word_fill_size; 314 word_fill_size = 0; 315 } 316 317 // We will set up the first region as "starts humongous". This 318 // will also update the BOT covering all the regions to reflect 319 // that there is a single object that starts at the bottom of the 320 // first region. 321 first_hr->set_starts_humongous(obj_top, word_fill_size); 322 first_hr->set_allocation_context(context); 323 // Then, if there are any, we will set up the "continues 324 // humongous" regions. 325 HeapRegion* hr = NULL; 326 for (uint i = first + 1; i <= last; ++i) { 327 hr = region_at(i); 328 hr->set_continues_humongous(first_hr); 329 hr->set_allocation_context(context); 330 } 331 332 // Up to this point no concurrent thread would have been able to 333 // do any scanning on any region in this series. All the top 334 // fields still point to bottom, so the intersection between 335 // [bottom,top] and [card_start,card_end] will be empty. Before we 336 // update the top fields, we'll do a storestore to make sure that 337 // no thread sees the update to top before the zeroing of the 338 // object header and the BOT initialization. 339 OrderAccess::storestore(); 340 341 // Now, we will update the top fields of the "continues humongous" 342 // regions except the last one. 343 for (uint i = first; i < last; ++i) { 344 hr = region_at(i); 345 hr->set_top(hr->end()); 346 } 347 348 hr = region_at(last); 349 // If we cannot fit a filler object, we must set top to the end 350 // of the humongous object, otherwise we cannot iterate the heap 351 // and the BOT will not be complete. 352 hr->set_top(hr->end() - words_not_fillable); 353 354 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 355 "obj_top should be in last region"); 356 357 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 358 359 assert(words_not_fillable == 0 || 360 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 361 "Miscalculation in humongous allocation"); 362 363 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 364 365 for (uint i = first; i <= last; ++i) { 366 hr = region_at(i); 367 _humongous_set.add(hr); 368 _hr_printer.alloc(hr); 369 } 370 371 return new_obj; 372 } 373 374 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 375 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 376 return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 377 } 378 379 // If could fit into free regions w/o expansion, try. 380 // Otherwise, if can expand, do so. 381 // Otherwise, if using ex regions might help, try with ex given back. 382 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 383 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 384 385 _verifier->verify_region_sets_optional(); 386 387 uint first = G1_NO_HRM_INDEX; 388 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 389 390 if (obj_regions == 1) { 391 // Only one region to allocate, try to use a fast path by directly allocating 392 // from the free lists. Do not try to expand here, we will potentially do that 393 // later. 394 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 395 if (hr != NULL) { 396 first = hr->hrm_index(); 397 } 398 } else { 399 // We can't allocate humongous regions spanning more than one region while 400 // cleanupComplete() is running, since some of the regions we find to be 401 // empty might not yet be added to the free list. It is not straightforward 402 // to know in which list they are on so that we can remove them. We only 403 // need to do this if we need to allocate more than one region to satisfy the 404 // current humongous allocation request. If we are only allocating one region 405 // we use the one-region region allocation code (see above), that already 406 // potentially waits for regions from the secondary free list. 407 wait_while_free_regions_coming(); 408 append_secondary_free_list_if_not_empty_with_lock(); 409 410 // Policy: Try only empty regions (i.e. already committed first). Maybe we 411 // are lucky enough to find some. 412 first = _hrm.find_contiguous_only_empty(obj_regions); 413 if (first != G1_NO_HRM_INDEX) { 414 _hrm.allocate_free_regions_starting_at(first, obj_regions); 415 } 416 } 417 418 if (first == G1_NO_HRM_INDEX) { 419 // Policy: We could not find enough regions for the humongous object in the 420 // free list. Look through the heap to find a mix of free and uncommitted regions. 421 // If so, try expansion. 422 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 423 if (first != G1_NO_HRM_INDEX) { 424 // We found something. Make sure these regions are committed, i.e. expand 425 // the heap. Alternatively we could do a defragmentation GC. 426 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 427 word_size * HeapWordSize); 428 429 _hrm.expand_at(first, obj_regions, workers()); 430 g1_policy()->record_new_heap_size(num_regions()); 431 432 #ifdef ASSERT 433 for (uint i = first; i < first + obj_regions; ++i) { 434 HeapRegion* hr = region_at(i); 435 assert(hr->is_free(), "sanity"); 436 assert(hr->is_empty(), "sanity"); 437 assert(is_on_master_free_list(hr), "sanity"); 438 } 439 #endif 440 _hrm.allocate_free_regions_starting_at(first, obj_regions); 441 } else { 442 // Policy: Potentially trigger a defragmentation GC. 443 } 444 } 445 446 HeapWord* result = NULL; 447 if (first != G1_NO_HRM_INDEX) { 448 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 449 word_size, context); 450 assert(result != NULL, "it should always return a valid result"); 451 452 // A successful humongous object allocation changes the used space 453 // information of the old generation so we need to recalculate the 454 // sizes and update the jstat counters here. 455 g1mm()->update_sizes(); 456 } 457 458 _verifier->verify_region_sets_optional(); 459 460 return result; 461 } 462 463 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 464 assert_heap_not_locked_and_not_at_safepoint(); 465 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 466 467 uint dummy_gc_count_before; 468 uint dummy_gclocker_retry_count = 0; 469 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 470 } 471 472 HeapWord* 473 G1CollectedHeap::mem_allocate(size_t word_size, 474 bool* gc_overhead_limit_was_exceeded) { 475 assert_heap_not_locked_and_not_at_safepoint(); 476 477 // Loop until the allocation is satisfied, or unsatisfied after GC. 478 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 479 uint gc_count_before; 480 481 HeapWord* result = NULL; 482 if (!is_humongous(word_size)) { 483 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 484 } else { 485 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 486 } 487 if (result != NULL) { 488 return result; 489 } 490 491 // Create the garbage collection operation... 492 VM_G1CollectForAllocation op(gc_count_before, word_size); 493 op.set_allocation_context(AllocationContext::current()); 494 495 // ...and get the VM thread to execute it. 496 VMThread::execute(&op); 497 498 if (op.prologue_succeeded() && op.pause_succeeded()) { 499 // If the operation was successful we'll return the result even 500 // if it is NULL. If the allocation attempt failed immediately 501 // after a Full GC, it's unlikely we'll be able to allocate now. 502 HeapWord* result = op.result(); 503 if (result != NULL && !is_humongous(word_size)) { 504 // Allocations that take place on VM operations do not do any 505 // card dirtying and we have to do it here. We only have to do 506 // this for non-humongous allocations, though. 507 dirty_young_block(result, word_size); 508 } 509 return result; 510 } else { 511 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 512 return NULL; 513 } 514 assert(op.result() == NULL, 515 "the result should be NULL if the VM op did not succeed"); 516 } 517 518 // Give a warning if we seem to be looping forever. 519 if ((QueuedAllocationWarningCount > 0) && 520 (try_count % QueuedAllocationWarningCount == 0)) { 521 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count); 522 } 523 } 524 525 ShouldNotReachHere(); 526 return NULL; 527 } 528 529 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 530 AllocationContext_t context, 531 uint* gc_count_before_ret, 532 uint* gclocker_retry_count_ret) { 533 // Make sure you read the note in attempt_allocation_humongous(). 534 535 assert_heap_not_locked_and_not_at_safepoint(); 536 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 537 "be called for humongous allocation requests"); 538 539 // We should only get here after the first-level allocation attempt 540 // (attempt_allocation()) failed to allocate. 541 542 // We will loop until a) we manage to successfully perform the 543 // allocation or b) we successfully schedule a collection which 544 // fails to perform the allocation. b) is the only case when we'll 545 // return NULL. 546 HeapWord* result = NULL; 547 for (int try_count = 1; /* we'll return */; try_count += 1) { 548 bool should_try_gc; 549 uint gc_count_before; 550 551 { 552 MutexLockerEx x(Heap_lock); 553 result = _allocator->attempt_allocation_locked(word_size, context); 554 if (result != NULL) { 555 return result; 556 } 557 558 if (GCLocker::is_active_and_needs_gc()) { 559 if (g1_policy()->can_expand_young_list()) { 560 // No need for an ergo verbose message here, 561 // can_expand_young_list() does this when it returns true. 562 result = _allocator->attempt_allocation_force(word_size, context); 563 if (result != NULL) { 564 return result; 565 } 566 } 567 should_try_gc = false; 568 } else { 569 // The GCLocker may not be active but the GCLocker initiated 570 // GC may not yet have been performed (GCLocker::needs_gc() 571 // returns true). In this case we do not try this GC and 572 // wait until the GCLocker initiated GC is performed, and 573 // then retry the allocation. 574 if (GCLocker::needs_gc()) { 575 should_try_gc = false; 576 } else { 577 // Read the GC count while still holding the Heap_lock. 578 gc_count_before = total_collections(); 579 should_try_gc = true; 580 } 581 } 582 } 583 584 if (should_try_gc) { 585 bool succeeded; 586 result = do_collection_pause(word_size, gc_count_before, &succeeded, 587 GCCause::_g1_inc_collection_pause); 588 if (result != NULL) { 589 assert(succeeded, "only way to get back a non-NULL result"); 590 return result; 591 } 592 593 if (succeeded) { 594 // If we get here we successfully scheduled a collection which 595 // failed to allocate. No point in trying to allocate 596 // further. We'll just return NULL. 597 MutexLockerEx x(Heap_lock); 598 *gc_count_before_ret = total_collections(); 599 return NULL; 600 } 601 } else { 602 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 603 MutexLockerEx x(Heap_lock); 604 *gc_count_before_ret = total_collections(); 605 return NULL; 606 } 607 // The GCLocker is either active or the GCLocker initiated 608 // GC has not yet been performed. Stall until it is and 609 // then retry the allocation. 610 GCLocker::stall_until_clear(); 611 (*gclocker_retry_count_ret) += 1; 612 } 613 614 // We can reach here if we were unsuccessful in scheduling a 615 // collection (because another thread beat us to it) or if we were 616 // stalled due to the GC locker. In either can we should retry the 617 // allocation attempt in case another thread successfully 618 // performed a collection and reclaimed enough space. We do the 619 // first attempt (without holding the Heap_lock) here and the 620 // follow-on attempt will be at the start of the next loop 621 // iteration (after taking the Heap_lock). 622 result = _allocator->attempt_allocation(word_size, context); 623 if (result != NULL) { 624 return result; 625 } 626 627 // Give a warning if we seem to be looping forever. 628 if ((QueuedAllocationWarningCount > 0) && 629 (try_count % QueuedAllocationWarningCount == 0)) { 630 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() " 631 "retries %d times", try_count); 632 } 633 } 634 635 ShouldNotReachHere(); 636 return NULL; 637 } 638 639 void G1CollectedHeap::begin_archive_alloc_range() { 640 assert_at_safepoint(true /* should_be_vm_thread */); 641 if (_archive_allocator == NULL) { 642 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 643 } 644 } 645 646 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 647 // Allocations in archive regions cannot be of a size that would be considered 648 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 649 // may be different at archive-restore time. 650 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 651 } 652 653 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 654 assert_at_safepoint(true /* should_be_vm_thread */); 655 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 656 if (is_archive_alloc_too_large(word_size)) { 657 return NULL; 658 } 659 return _archive_allocator->archive_mem_allocate(word_size); 660 } 661 662 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 663 size_t end_alignment_in_bytes) { 664 assert_at_safepoint(true /* should_be_vm_thread */); 665 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 666 667 // Call complete_archive to do the real work, filling in the MemRegion 668 // array with the archive regions. 669 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 670 delete _archive_allocator; 671 _archive_allocator = NULL; 672 } 673 674 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 675 assert(ranges != NULL, "MemRegion array NULL"); 676 assert(count != 0, "No MemRegions provided"); 677 MemRegion reserved = _hrm.reserved(); 678 for (size_t i = 0; i < count; i++) { 679 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 680 return false; 681 } 682 } 683 return true; 684 } 685 686 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 687 assert(!is_init_completed(), "Expect to be called at JVM init time"); 688 assert(ranges != NULL, "MemRegion array NULL"); 689 assert(count != 0, "No MemRegions provided"); 690 MutexLockerEx x(Heap_lock); 691 692 MemRegion reserved = _hrm.reserved(); 693 HeapWord* prev_last_addr = NULL; 694 HeapRegion* prev_last_region = NULL; 695 696 // Temporarily disable pretouching of heap pages. This interface is used 697 // when mmap'ing archived heap data in, so pre-touching is wasted. 698 FlagSetting fs(AlwaysPreTouch, false); 699 700 // Enable archive object checking used by G1MarkSweep. We have to let it know 701 // about each archive range, so that objects in those ranges aren't marked. 702 G1ArchiveAllocator::enable_archive_object_check(); 703 704 // For each specified MemRegion range, allocate the corresponding G1 705 // regions and mark them as archive regions. We expect the ranges in 706 // ascending starting address order, without overlap. 707 for (size_t i = 0; i < count; i++) { 708 MemRegion curr_range = ranges[i]; 709 HeapWord* start_address = curr_range.start(); 710 size_t word_size = curr_range.word_size(); 711 HeapWord* last_address = curr_range.last(); 712 size_t commits = 0; 713 714 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 715 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 716 p2i(start_address), p2i(last_address)); 717 guarantee(start_address > prev_last_addr, 718 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 719 p2i(start_address), p2i(prev_last_addr)); 720 prev_last_addr = last_address; 721 722 // Check for ranges that start in the same G1 region in which the previous 723 // range ended, and adjust the start address so we don't try to allocate 724 // the same region again. If the current range is entirely within that 725 // region, skip it, just adjusting the recorded top. 726 HeapRegion* start_region = _hrm.addr_to_region(start_address); 727 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 728 start_address = start_region->end(); 729 if (start_address > last_address) { 730 increase_used(word_size * HeapWordSize); 731 start_region->set_top(last_address + 1); 732 continue; 733 } 734 start_region->set_top(start_address); 735 curr_range = MemRegion(start_address, last_address + 1); 736 start_region = _hrm.addr_to_region(start_address); 737 } 738 739 // Perform the actual region allocation, exiting if it fails. 740 // Then note how much new space we have allocated. 741 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 742 return false; 743 } 744 increase_used(word_size * HeapWordSize); 745 if (commits != 0) { 746 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 747 HeapRegion::GrainWords * HeapWordSize * commits); 748 749 } 750 751 // Mark each G1 region touched by the range as archive, add it to the old set, 752 // and set the allocation context and top. 753 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 754 HeapRegion* last_region = _hrm.addr_to_region(last_address); 755 prev_last_region = last_region; 756 757 while (curr_region != NULL) { 758 assert(curr_region->is_empty() && !curr_region->is_pinned(), 759 "Region already in use (index %u)", curr_region->hrm_index()); 760 curr_region->set_allocation_context(AllocationContext::system()); 761 curr_region->set_archive(); 762 _hr_printer.alloc(curr_region); 763 _old_set.add(curr_region); 764 if (curr_region != last_region) { 765 curr_region->set_top(curr_region->end()); 766 curr_region = _hrm.next_region_in_heap(curr_region); 767 } else { 768 curr_region->set_top(last_address + 1); 769 curr_region = NULL; 770 } 771 } 772 773 // Notify mark-sweep of the archive range. 774 G1ArchiveAllocator::set_range_archive(curr_range, true); 775 } 776 return true; 777 } 778 779 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 780 assert(!is_init_completed(), "Expect to be called at JVM init time"); 781 assert(ranges != NULL, "MemRegion array NULL"); 782 assert(count != 0, "No MemRegions provided"); 783 MemRegion reserved = _hrm.reserved(); 784 HeapWord *prev_last_addr = NULL; 785 HeapRegion* prev_last_region = NULL; 786 787 // For each MemRegion, create filler objects, if needed, in the G1 regions 788 // that contain the address range. The address range actually within the 789 // MemRegion will not be modified. That is assumed to have been initialized 790 // elsewhere, probably via an mmap of archived heap data. 791 MutexLockerEx x(Heap_lock); 792 for (size_t i = 0; i < count; i++) { 793 HeapWord* start_address = ranges[i].start(); 794 HeapWord* last_address = ranges[i].last(); 795 796 assert(reserved.contains(start_address) && reserved.contains(last_address), 797 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 798 p2i(start_address), p2i(last_address)); 799 assert(start_address > prev_last_addr, 800 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 801 p2i(start_address), p2i(prev_last_addr)); 802 803 HeapRegion* start_region = _hrm.addr_to_region(start_address); 804 HeapRegion* last_region = _hrm.addr_to_region(last_address); 805 HeapWord* bottom_address = start_region->bottom(); 806 807 // Check for a range beginning in the same region in which the 808 // previous one ended. 809 if (start_region == prev_last_region) { 810 bottom_address = prev_last_addr + 1; 811 } 812 813 // Verify that the regions were all marked as archive regions by 814 // alloc_archive_regions. 815 HeapRegion* curr_region = start_region; 816 while (curr_region != NULL) { 817 guarantee(curr_region->is_archive(), 818 "Expected archive region at index %u", curr_region->hrm_index()); 819 if (curr_region != last_region) { 820 curr_region = _hrm.next_region_in_heap(curr_region); 821 } else { 822 curr_region = NULL; 823 } 824 } 825 826 prev_last_addr = last_address; 827 prev_last_region = last_region; 828 829 // Fill the memory below the allocated range with dummy object(s), 830 // if the region bottom does not match the range start, or if the previous 831 // range ended within the same G1 region, and there is a gap. 832 if (start_address != bottom_address) { 833 size_t fill_size = pointer_delta(start_address, bottom_address); 834 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 835 increase_used(fill_size * HeapWordSize); 836 } 837 } 838 } 839 840 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 841 uint* gc_count_before_ret, 842 uint* gclocker_retry_count_ret) { 843 assert_heap_not_locked_and_not_at_safepoint(); 844 assert(!is_humongous(word_size), "attempt_allocation() should not " 845 "be called for humongous allocation requests"); 846 847 AllocationContext_t context = AllocationContext::current(); 848 HeapWord* result = _allocator->attempt_allocation(word_size, context); 849 850 if (result == NULL) { 851 result = attempt_allocation_slow(word_size, 852 context, 853 gc_count_before_ret, 854 gclocker_retry_count_ret); 855 } 856 assert_heap_not_locked(); 857 if (result != NULL) { 858 dirty_young_block(result, word_size); 859 } 860 return result; 861 } 862 863 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 864 assert(!is_init_completed(), "Expect to be called at JVM init time"); 865 assert(ranges != NULL, "MemRegion array NULL"); 866 assert(count != 0, "No MemRegions provided"); 867 MemRegion reserved = _hrm.reserved(); 868 HeapWord* prev_last_addr = NULL; 869 HeapRegion* prev_last_region = NULL; 870 size_t size_used = 0; 871 size_t uncommitted_regions = 0; 872 873 // For each Memregion, free the G1 regions that constitute it, and 874 // notify mark-sweep that the range is no longer to be considered 'archive.' 875 MutexLockerEx x(Heap_lock); 876 for (size_t i = 0; i < count; i++) { 877 HeapWord* start_address = ranges[i].start(); 878 HeapWord* last_address = ranges[i].last(); 879 880 assert(reserved.contains(start_address) && reserved.contains(last_address), 881 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 882 p2i(start_address), p2i(last_address)); 883 assert(start_address > prev_last_addr, 884 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 885 p2i(start_address), p2i(prev_last_addr)); 886 size_used += ranges[i].byte_size(); 887 prev_last_addr = last_address; 888 889 HeapRegion* start_region = _hrm.addr_to_region(start_address); 890 HeapRegion* last_region = _hrm.addr_to_region(last_address); 891 892 // Check for ranges that start in the same G1 region in which the previous 893 // range ended, and adjust the start address so we don't try to free 894 // the same region again. If the current range is entirely within that 895 // region, skip it. 896 if (start_region == prev_last_region) { 897 start_address = start_region->end(); 898 if (start_address > last_address) { 899 continue; 900 } 901 start_region = _hrm.addr_to_region(start_address); 902 } 903 prev_last_region = last_region; 904 905 // After verifying that each region was marked as an archive region by 906 // alloc_archive_regions, set it free and empty and uncommit it. 907 HeapRegion* curr_region = start_region; 908 while (curr_region != NULL) { 909 guarantee(curr_region->is_archive(), 910 "Expected archive region at index %u", curr_region->hrm_index()); 911 uint curr_index = curr_region->hrm_index(); 912 _old_set.remove(curr_region); 913 curr_region->set_free(); 914 curr_region->set_top(curr_region->bottom()); 915 if (curr_region != last_region) { 916 curr_region = _hrm.next_region_in_heap(curr_region); 917 } else { 918 curr_region = NULL; 919 } 920 _hrm.shrink_at(curr_index, 1); 921 uncommitted_regions++; 922 } 923 924 // Notify mark-sweep that this is no longer an archive range. 925 G1ArchiveAllocator::set_range_archive(ranges[i], false); 926 } 927 928 if (uncommitted_regions != 0) { 929 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 930 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 931 } 932 decrease_used(size_used); 933 } 934 935 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 936 uint* gc_count_before_ret, 937 uint* gclocker_retry_count_ret) { 938 // The structure of this method has a lot of similarities to 939 // attempt_allocation_slow(). The reason these two were not merged 940 // into a single one is that such a method would require several "if 941 // allocation is not humongous do this, otherwise do that" 942 // conditional paths which would obscure its flow. In fact, an early 943 // version of this code did use a unified method which was harder to 944 // follow and, as a result, it had subtle bugs that were hard to 945 // track down. So keeping these two methods separate allows each to 946 // be more readable. It will be good to keep these two in sync as 947 // much as possible. 948 949 assert_heap_not_locked_and_not_at_safepoint(); 950 assert(is_humongous(word_size), "attempt_allocation_humongous() " 951 "should only be called for humongous allocations"); 952 953 // Humongous objects can exhaust the heap quickly, so we should check if we 954 // need to start a marking cycle at each humongous object allocation. We do 955 // the check before we do the actual allocation. The reason for doing it 956 // before the allocation is that we avoid having to keep track of the newly 957 // allocated memory while we do a GC. 958 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 959 word_size)) { 960 collect(GCCause::_g1_humongous_allocation); 961 } 962 963 // We will loop until a) we manage to successfully perform the 964 // allocation or b) we successfully schedule a collection which 965 // fails to perform the allocation. b) is the only case when we'll 966 // return NULL. 967 HeapWord* result = NULL; 968 for (int try_count = 1; /* we'll return */; try_count += 1) { 969 bool should_try_gc; 970 uint gc_count_before; 971 972 { 973 MutexLockerEx x(Heap_lock); 974 975 // Given that humongous objects are not allocated in young 976 // regions, we'll first try to do the allocation without doing a 977 // collection hoping that there's enough space in the heap. 978 result = humongous_obj_allocate(word_size, AllocationContext::current()); 979 if (result != NULL) { 980 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 981 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 982 return result; 983 } 984 985 if (GCLocker::is_active_and_needs_gc()) { 986 should_try_gc = false; 987 } else { 988 // The GCLocker may not be active but the GCLocker initiated 989 // GC may not yet have been performed (GCLocker::needs_gc() 990 // returns true). In this case we do not try this GC and 991 // wait until the GCLocker initiated GC is performed, and 992 // then retry the allocation. 993 if (GCLocker::needs_gc()) { 994 should_try_gc = false; 995 } else { 996 // Read the GC count while still holding the Heap_lock. 997 gc_count_before = total_collections(); 998 should_try_gc = true; 999 } 1000 } 1001 } 1002 1003 if (should_try_gc) { 1004 // If we failed to allocate the humongous object, we should try to 1005 // do a collection pause (if we're allowed) in case it reclaims 1006 // enough space for the allocation to succeed after the pause. 1007 1008 bool succeeded; 1009 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1010 GCCause::_g1_humongous_allocation); 1011 if (result != NULL) { 1012 assert(succeeded, "only way to get back a non-NULL result"); 1013 return result; 1014 } 1015 1016 if (succeeded) { 1017 // If we get here we successfully scheduled a collection which 1018 // failed to allocate. No point in trying to allocate 1019 // further. We'll just return NULL. 1020 MutexLockerEx x(Heap_lock); 1021 *gc_count_before_ret = total_collections(); 1022 return NULL; 1023 } 1024 } else { 1025 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1026 MutexLockerEx x(Heap_lock); 1027 *gc_count_before_ret = total_collections(); 1028 return NULL; 1029 } 1030 // The GCLocker is either active or the GCLocker initiated 1031 // GC has not yet been performed. Stall until it is and 1032 // then retry the allocation. 1033 GCLocker::stall_until_clear(); 1034 (*gclocker_retry_count_ret) += 1; 1035 } 1036 1037 // We can reach here if we were unsuccessful in scheduling a 1038 // collection (because another thread beat us to it) or if we were 1039 // stalled due to the GC locker. In either can we should retry the 1040 // allocation attempt in case another thread successfully 1041 // performed a collection and reclaimed enough space. Give a 1042 // warning if we seem to be looping forever. 1043 1044 if ((QueuedAllocationWarningCount > 0) && 1045 (try_count % QueuedAllocationWarningCount == 0)) { 1046 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() " 1047 "retries %d times", try_count); 1048 } 1049 } 1050 1051 ShouldNotReachHere(); 1052 return NULL; 1053 } 1054 1055 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1056 AllocationContext_t context, 1057 bool expect_null_mutator_alloc_region) { 1058 assert_at_safepoint(true /* should_be_vm_thread */); 1059 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1060 "the current alloc region was unexpectedly found to be non-NULL"); 1061 1062 if (!is_humongous(word_size)) { 1063 return _allocator->attempt_allocation_locked(word_size, context); 1064 } else { 1065 HeapWord* result = humongous_obj_allocate(word_size, context); 1066 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1067 collector_state()->set_initiate_conc_mark_if_possible(true); 1068 } 1069 return result; 1070 } 1071 1072 ShouldNotReachHere(); 1073 } 1074 1075 class PostCompactionPrinterClosure: public HeapRegionClosure { 1076 private: 1077 G1HRPrinter* _hr_printer; 1078 public: 1079 bool doHeapRegion(HeapRegion* hr) { 1080 assert(!hr->is_young(), "not expecting to find young regions"); 1081 _hr_printer->post_compaction(hr); 1082 return false; 1083 } 1084 1085 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1086 : _hr_printer(hr_printer) { } 1087 }; 1088 1089 void G1CollectedHeap::print_hrm_post_compaction() { 1090 if (_hr_printer.is_active()) { 1091 PostCompactionPrinterClosure cl(hr_printer()); 1092 heap_region_iterate(&cl); 1093 } 1094 1095 } 1096 1097 void G1CollectedHeap::abort_concurrent_cycle() { 1098 // Note: When we have a more flexible GC logging framework that 1099 // allows us to add optional attributes to a GC log record we 1100 // could consider timing and reporting how long we wait in the 1101 // following two methods. 1102 wait_while_free_regions_coming(); 1103 // If we start the compaction before the CM threads finish 1104 // scanning the root regions we might trip them over as we'll 1105 // be moving objects / updating references. So let's wait until 1106 // they are done. By telling them to abort, they should complete 1107 // early. 1108 _cm->root_regions()->abort(); 1109 _cm->root_regions()->wait_until_scan_finished(); 1110 append_secondary_free_list_if_not_empty_with_lock(); 1111 1112 // Disable discovery and empty the discovered lists 1113 // for the CM ref processor. 1114 ref_processor_cm()->disable_discovery(); 1115 ref_processor_cm()->abandon_partial_discovery(); 1116 ref_processor_cm()->verify_no_references_recorded(); 1117 1118 // Abandon current iterations of concurrent marking and concurrent 1119 // refinement, if any are in progress. 1120 concurrent_mark()->abort(); 1121 } 1122 1123 void G1CollectedHeap::prepare_heap_for_full_collection() { 1124 // Make sure we'll choose a new allocation region afterwards. 1125 _allocator->release_mutator_alloc_region(); 1126 _allocator->abandon_gc_alloc_regions(); 1127 g1_rem_set()->cleanupHRRS(); 1128 1129 // We may have added regions to the current incremental collection 1130 // set between the last GC or pause and now. We need to clear the 1131 // incremental collection set and then start rebuilding it afresh 1132 // after this full GC. 1133 abandon_collection_set(collection_set()); 1134 1135 tear_down_region_sets(false /* free_list_only */); 1136 collector_state()->set_gcs_are_young(true); 1137 } 1138 1139 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1140 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1141 assert(used() == recalculate_used(), "Should be equal"); 1142 _verifier->verify_region_sets_optional(); 1143 _verifier->verify_before_gc(); 1144 _verifier->check_bitmaps("Full GC Start"); 1145 } 1146 1147 void G1CollectedHeap::prepare_heap_for_mutators() { 1148 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1149 ClassLoaderDataGraph::purge(); 1150 MetaspaceAux::verify_metrics(); 1151 1152 // Prepare heap for normal collections. 1153 assert(num_free_regions() == 0, "we should not have added any free regions"); 1154 rebuild_region_sets(false /* free_list_only */); 1155 abort_refinement(); 1156 resize_if_necessary_after_full_collection(); 1157 1158 // Rebuild the strong code root lists for each region 1159 rebuild_strong_code_roots(); 1160 1161 // Start a new incremental collection set for the next pause 1162 start_new_collection_set(); 1163 1164 _allocator->init_mutator_alloc_region(); 1165 1166 // Post collection state updates. 1167 MetaspaceGC::compute_new_size(); 1168 } 1169 1170 void G1CollectedHeap::abort_refinement() { 1171 if (_hot_card_cache->use_cache()) { 1172 _hot_card_cache->reset_card_counts(); 1173 _hot_card_cache->reset_hot_cache(); 1174 } 1175 1176 // Discard all remembered set updates. 1177 JavaThread::dirty_card_queue_set().abandon_logs(); 1178 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1179 } 1180 1181 void G1CollectedHeap::verify_after_full_collection() { 1182 check_gc_time_stamps(); 1183 _hrm.verify_optional(); 1184 _verifier->verify_region_sets_optional(); 1185 _verifier->verify_after_gc(); 1186 // Clear the previous marking bitmap, if needed for bitmap verification. 1187 // Note we cannot do this when we clear the next marking bitmap in 1188 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1189 // objects marked during a full GC against the previous bitmap. 1190 // But we need to clear it before calling check_bitmaps below since 1191 // the full GC has compacted objects and updated TAMS but not updated 1192 // the prev bitmap. 1193 if (G1VerifyBitmaps) { 1194 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1195 _cm->clear_prev_bitmap(workers()); 1196 } 1197 _verifier->check_bitmaps("Full GC End"); 1198 1199 // At this point there should be no regions in the 1200 // entire heap tagged as young. 1201 assert(check_young_list_empty(), "young list should be empty at this point"); 1202 1203 // Note: since we've just done a full GC, concurrent 1204 // marking is no longer active. Therefore we need not 1205 // re-enable reference discovery for the CM ref processor. 1206 // That will be done at the start of the next marking cycle. 1207 // We also know that the STW processor should no longer 1208 // discover any new references. 1209 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1210 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1211 ref_processor_stw()->verify_no_references_recorded(); 1212 ref_processor_cm()->verify_no_references_recorded(); 1213 } 1214 1215 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1216 print_hrm_post_compaction(); 1217 heap_transition->print(); 1218 print_heap_after_gc(); 1219 print_heap_regions(); 1220 #ifdef TRACESPINNING 1221 ParallelTaskTerminator::print_termination_counts(); 1222 #endif 1223 } 1224 1225 void G1CollectedHeap::do_full_collection_inner(G1FullGCScope* scope) { 1226 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1227 g1_policy()->record_full_collection_start(); 1228 1229 print_heap_before_gc(); 1230 print_heap_regions(); 1231 1232 abort_concurrent_cycle(); 1233 verify_before_full_collection(scope->is_explicit_gc()); 1234 1235 gc_prologue(true); 1236 prepare_heap_for_full_collection(); 1237 1238 G1SerialFullCollector serial(scope, ref_processor_stw()); 1239 serial.prepare_collection(); 1240 serial.collect(); 1241 serial.complete_collection(); 1242 1243 prepare_heap_for_mutators(); 1244 1245 g1_policy()->record_full_collection_end(); 1246 gc_epilogue(true); 1247 1248 // Post collection verification. 1249 verify_after_full_collection(); 1250 1251 // Post collection logging. 1252 // We should do this after we potentially resize the heap so 1253 // that all the COMMIT / UNCOMMIT events are generated before 1254 // the compaction events. 1255 print_heap_after_full_collection(scope->heap_transition()); 1256 } 1257 1258 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1259 bool clear_all_soft_refs) { 1260 assert_at_safepoint(true /* should_be_vm_thread */); 1261 1262 if (GCLocker::check_active_before_gc()) { 1263 // Full GC was not completed. 1264 return false; 1265 } 1266 1267 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1268 collector_policy()->should_clear_all_soft_refs(); 1269 1270 G1FullGCScope scope(explicit_gc, do_clear_all_soft_refs); 1271 do_full_collection_inner(&scope); 1272 1273 // Full collection was successfully completed. 1274 return true; 1275 } 1276 1277 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1278 // Currently, there is no facility in the do_full_collection(bool) API to notify 1279 // the caller that the collection did not succeed (e.g., because it was locked 1280 // out by the GC locker). So, right now, we'll ignore the return value. 1281 bool dummy = do_full_collection(true, /* explicit_gc */ 1282 clear_all_soft_refs); 1283 } 1284 1285 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1286 // Include bytes that will be pre-allocated to support collections, as "used". 1287 const size_t used_after_gc = used(); 1288 const size_t capacity_after_gc = capacity(); 1289 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1290 1291 // This is enforced in arguments.cpp. 1292 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1293 "otherwise the code below doesn't make sense"); 1294 1295 // We don't have floating point command-line arguments 1296 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1297 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1298 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1299 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1300 1301 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1302 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1303 1304 // We have to be careful here as these two calculations can overflow 1305 // 32-bit size_t's. 1306 double used_after_gc_d = (double) used_after_gc; 1307 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1308 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1309 1310 // Let's make sure that they are both under the max heap size, which 1311 // by default will make them fit into a size_t. 1312 double desired_capacity_upper_bound = (double) max_heap_size; 1313 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1314 desired_capacity_upper_bound); 1315 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1316 desired_capacity_upper_bound); 1317 1318 // We can now safely turn them into size_t's. 1319 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1320 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1321 1322 // This assert only makes sense here, before we adjust them 1323 // with respect to the min and max heap size. 1324 assert(minimum_desired_capacity <= maximum_desired_capacity, 1325 "minimum_desired_capacity = " SIZE_FORMAT ", " 1326 "maximum_desired_capacity = " SIZE_FORMAT, 1327 minimum_desired_capacity, maximum_desired_capacity); 1328 1329 // Should not be greater than the heap max size. No need to adjust 1330 // it with respect to the heap min size as it's a lower bound (i.e., 1331 // we'll try to make the capacity larger than it, not smaller). 1332 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1333 // Should not be less than the heap min size. No need to adjust it 1334 // with respect to the heap max size as it's an upper bound (i.e., 1335 // we'll try to make the capacity smaller than it, not greater). 1336 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1337 1338 if (capacity_after_gc < minimum_desired_capacity) { 1339 // Don't expand unless it's significant 1340 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1341 1342 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1343 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1344 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1345 1346 expand(expand_bytes, _workers); 1347 1348 // No expansion, now see if we want to shrink 1349 } else if (capacity_after_gc > maximum_desired_capacity) { 1350 // Capacity too large, compute shrinking size 1351 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1352 1353 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1354 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1355 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1356 1357 shrink(shrink_bytes); 1358 } 1359 } 1360 1361 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1362 AllocationContext_t context, 1363 bool do_gc, 1364 bool clear_all_soft_refs, 1365 bool expect_null_mutator_alloc_region, 1366 bool* gc_succeeded) { 1367 *gc_succeeded = true; 1368 // Let's attempt the allocation first. 1369 HeapWord* result = 1370 attempt_allocation_at_safepoint(word_size, 1371 context, 1372 expect_null_mutator_alloc_region); 1373 if (result != NULL) { 1374 assert(*gc_succeeded, "sanity"); 1375 return result; 1376 } 1377 1378 // In a G1 heap, we're supposed to keep allocation from failing by 1379 // incremental pauses. Therefore, at least for now, we'll favor 1380 // expansion over collection. (This might change in the future if we can 1381 // do something smarter than full collection to satisfy a failed alloc.) 1382 result = expand_and_allocate(word_size, context); 1383 if (result != NULL) { 1384 assert(*gc_succeeded, "sanity"); 1385 return result; 1386 } 1387 1388 if (do_gc) { 1389 // Expansion didn't work, we'll try to do a Full GC. 1390 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1391 clear_all_soft_refs); 1392 } 1393 1394 return NULL; 1395 } 1396 1397 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1398 AllocationContext_t context, 1399 bool* succeeded) { 1400 assert_at_safepoint(true /* should_be_vm_thread */); 1401 1402 // Attempts to allocate followed by Full GC. 1403 HeapWord* result = 1404 satisfy_failed_allocation_helper(word_size, 1405 context, 1406 true, /* do_gc */ 1407 false, /* clear_all_soft_refs */ 1408 false, /* expect_null_mutator_alloc_region */ 1409 succeeded); 1410 1411 if (result != NULL || !*succeeded) { 1412 return result; 1413 } 1414 1415 // Attempts to allocate followed by Full GC that will collect all soft references. 1416 result = satisfy_failed_allocation_helper(word_size, 1417 context, 1418 true, /* do_gc */ 1419 true, /* clear_all_soft_refs */ 1420 true, /* expect_null_mutator_alloc_region */ 1421 succeeded); 1422 1423 if (result != NULL || !*succeeded) { 1424 return result; 1425 } 1426 1427 // Attempts to allocate, no GC 1428 result = satisfy_failed_allocation_helper(word_size, 1429 context, 1430 false, /* do_gc */ 1431 false, /* clear_all_soft_refs */ 1432 true, /* expect_null_mutator_alloc_region */ 1433 succeeded); 1434 1435 if (result != NULL) { 1436 assert(*succeeded, "sanity"); 1437 return result; 1438 } 1439 1440 assert(!collector_policy()->should_clear_all_soft_refs(), 1441 "Flag should have been handled and cleared prior to this point"); 1442 1443 // What else? We might try synchronous finalization later. If the total 1444 // space available is large enough for the allocation, then a more 1445 // complete compaction phase than we've tried so far might be 1446 // appropriate. 1447 assert(*succeeded, "sanity"); 1448 return NULL; 1449 } 1450 1451 // Attempting to expand the heap sufficiently 1452 // to support an allocation of the given "word_size". If 1453 // successful, perform the allocation and return the address of the 1454 // allocated block, or else "NULL". 1455 1456 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1457 assert_at_safepoint(true /* should_be_vm_thread */); 1458 1459 _verifier->verify_region_sets_optional(); 1460 1461 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1462 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1463 word_size * HeapWordSize); 1464 1465 1466 if (expand(expand_bytes, _workers)) { 1467 _hrm.verify_optional(); 1468 _verifier->verify_region_sets_optional(); 1469 return attempt_allocation_at_safepoint(word_size, 1470 context, 1471 false /* expect_null_mutator_alloc_region */); 1472 } 1473 return NULL; 1474 } 1475 1476 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1477 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1478 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1479 HeapRegion::GrainBytes); 1480 1481 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1482 expand_bytes, aligned_expand_bytes); 1483 1484 if (is_maximal_no_gc()) { 1485 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1486 return false; 1487 } 1488 1489 double expand_heap_start_time_sec = os::elapsedTime(); 1490 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1491 assert(regions_to_expand > 0, "Must expand by at least one region"); 1492 1493 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers); 1494 if (expand_time_ms != NULL) { 1495 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1496 } 1497 1498 if (expanded_by > 0) { 1499 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1500 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1501 g1_policy()->record_new_heap_size(num_regions()); 1502 } else { 1503 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1504 1505 // The expansion of the virtual storage space was unsuccessful. 1506 // Let's see if it was because we ran out of swap. 1507 if (G1ExitOnExpansionFailure && 1508 _hrm.available() >= regions_to_expand) { 1509 // We had head room... 1510 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1511 } 1512 } 1513 return regions_to_expand > 0; 1514 } 1515 1516 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1517 size_t aligned_shrink_bytes = 1518 ReservedSpace::page_align_size_down(shrink_bytes); 1519 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1520 HeapRegion::GrainBytes); 1521 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1522 1523 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1524 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1525 1526 1527 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", 1528 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1529 if (num_regions_removed > 0) { 1530 g1_policy()->record_new_heap_size(num_regions()); 1531 } else { 1532 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1533 } 1534 } 1535 1536 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1537 _verifier->verify_region_sets_optional(); 1538 1539 // We should only reach here at the end of a Full GC which means we 1540 // should not not be holding to any GC alloc regions. The method 1541 // below will make sure of that and do any remaining clean up. 1542 _allocator->abandon_gc_alloc_regions(); 1543 1544 // Instead of tearing down / rebuilding the free lists here, we 1545 // could instead use the remove_all_pending() method on free_list to 1546 // remove only the ones that we need to remove. 1547 tear_down_region_sets(true /* free_list_only */); 1548 shrink_helper(shrink_bytes); 1549 rebuild_region_sets(true /* free_list_only */); 1550 1551 _hrm.verify_optional(); 1552 _verifier->verify_region_sets_optional(); 1553 } 1554 1555 // Public methods. 1556 1557 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1558 CollectedHeap(), 1559 _collector_policy(collector_policy), 1560 _g1_policy(create_g1_policy()), 1561 _collection_set(this, _g1_policy), 1562 _dirty_card_queue_set(false), 1563 _is_alive_closure_cm(this), 1564 _is_alive_closure_stw(this), 1565 _ref_processor_cm(NULL), 1566 _ref_processor_stw(NULL), 1567 _bot(NULL), 1568 _hot_card_cache(NULL), 1569 _g1_rem_set(NULL), 1570 _cg1r(NULL), 1571 _g1mm(NULL), 1572 _refine_cte_cl(NULL), 1573 _preserved_marks_set(true /* in_c_heap */), 1574 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1575 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1576 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1577 _humongous_reclaim_candidates(), 1578 _has_humongous_reclaim_candidates(false), 1579 _archive_allocator(NULL), 1580 _free_regions_coming(false), 1581 _gc_time_stamp(0), 1582 _summary_bytes_used(0), 1583 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1584 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1585 _expand_heap_after_alloc_failure(true), 1586 _old_marking_cycles_started(0), 1587 _old_marking_cycles_completed(0), 1588 _in_cset_fast_test(), 1589 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1590 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) { 1591 1592 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1593 /* are_GC_task_threads */true, 1594 /* are_ConcurrentGC_threads */false); 1595 _workers->initialize_workers(); 1596 _verifier = new G1HeapVerifier(this); 1597 1598 _allocator = G1Allocator::create_allocator(this); 1599 1600 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1601 1602 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1603 1604 // Override the default _filler_array_max_size so that no humongous filler 1605 // objects are created. 1606 _filler_array_max_size = _humongous_object_threshold_in_words; 1607 1608 uint n_queues = ParallelGCThreads; 1609 _task_queues = new RefToScanQueueSet(n_queues); 1610 1611 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1612 1613 for (uint i = 0; i < n_queues; i++) { 1614 RefToScanQueue* q = new RefToScanQueue(); 1615 q->initialize(); 1616 _task_queues->register_queue(i, q); 1617 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1618 } 1619 1620 // Initialize the G1EvacuationFailureALot counters and flags. 1621 NOT_PRODUCT(reset_evacuation_should_fail();) 1622 1623 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1624 } 1625 1626 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1627 size_t size, 1628 size_t translation_factor) { 1629 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1630 // Allocate a new reserved space, preferring to use large pages. 1631 ReservedSpace rs(size, preferred_page_size); 1632 G1RegionToSpaceMapper* result = 1633 G1RegionToSpaceMapper::create_mapper(rs, 1634 size, 1635 rs.alignment(), 1636 HeapRegion::GrainBytes, 1637 translation_factor, 1638 mtGC); 1639 1640 os::trace_page_sizes_for_requested_size(description, 1641 size, 1642 preferred_page_size, 1643 rs.alignment(), 1644 rs.base(), 1645 rs.size()); 1646 1647 return result; 1648 } 1649 1650 jint G1CollectedHeap::initialize() { 1651 CollectedHeap::pre_initialize(); 1652 os::enable_vtime(); 1653 1654 // Necessary to satisfy locking discipline assertions. 1655 1656 MutexLocker x(Heap_lock); 1657 1658 // While there are no constraints in the GC code that HeapWordSize 1659 // be any particular value, there are multiple other areas in the 1660 // system which believe this to be true (e.g. oop->object_size in some 1661 // cases incorrectly returns the size in wordSize units rather than 1662 // HeapWordSize). 1663 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1664 1665 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1666 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1667 size_t heap_alignment = collector_policy()->heap_alignment(); 1668 1669 // Ensure that the sizes are properly aligned. 1670 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1671 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1672 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1673 1674 _refine_cte_cl = new RefineCardTableEntryClosure(); 1675 1676 jint ecode = JNI_OK; 1677 _cg1r = ConcurrentG1Refine::create(_refine_cte_cl, &ecode); 1678 if (_cg1r == NULL) { 1679 return ecode; 1680 } 1681 1682 // Reserve the maximum. 1683 1684 // When compressed oops are enabled, the preferred heap base 1685 // is calculated by subtracting the requested size from the 1686 // 32Gb boundary and using the result as the base address for 1687 // heap reservation. If the requested size is not aligned to 1688 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1689 // into the ReservedHeapSpace constructor) then the actual 1690 // base of the reserved heap may end up differing from the 1691 // address that was requested (i.e. the preferred heap base). 1692 // If this happens then we could end up using a non-optimal 1693 // compressed oops mode. 1694 1695 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1696 heap_alignment); 1697 1698 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1699 1700 // Create the barrier set for the entire reserved region. 1701 G1SATBCardTableLoggingModRefBS* bs 1702 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1703 bs->initialize(); 1704 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1705 set_barrier_set(bs); 1706 1707 // Create the hot card cache. 1708 _hot_card_cache = new G1HotCardCache(this); 1709 1710 // Also create a G1 rem set. 1711 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache); 1712 1713 // Carve out the G1 part of the heap. 1714 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1715 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1716 G1RegionToSpaceMapper* heap_storage = 1717 G1RegionToSpaceMapper::create_mapper(g1_rs, 1718 g1_rs.size(), 1719 page_size, 1720 HeapRegion::GrainBytes, 1721 1, 1722 mtJavaHeap); 1723 os::trace_page_sizes("Heap", 1724 collector_policy()->min_heap_byte_size(), 1725 max_byte_size, 1726 page_size, 1727 heap_rs.base(), 1728 heap_rs.size()); 1729 heap_storage->set_mapping_changed_listener(&_listener); 1730 1731 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1732 G1RegionToSpaceMapper* bot_storage = 1733 create_aux_memory_mapper("Block Offset Table", 1734 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1735 G1BlockOffsetTable::heap_map_factor()); 1736 1737 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1738 G1RegionToSpaceMapper* cardtable_storage = 1739 create_aux_memory_mapper("Card Table", 1740 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1741 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1742 1743 G1RegionToSpaceMapper* card_counts_storage = 1744 create_aux_memory_mapper("Card Counts Table", 1745 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1746 G1CardCounts::heap_map_factor()); 1747 1748 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1749 G1RegionToSpaceMapper* prev_bitmap_storage = 1750 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1751 G1RegionToSpaceMapper* next_bitmap_storage = 1752 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1753 1754 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1755 g1_barrier_set()->initialize(cardtable_storage); 1756 // Do later initialization work for concurrent refinement. 1757 _hot_card_cache->initialize(card_counts_storage); 1758 1759 // 6843694 - ensure that the maximum region index can fit 1760 // in the remembered set structures. 1761 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1762 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1763 1764 g1_rem_set()->initialize(max_capacity(), max_regions()); 1765 1766 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1767 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1768 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1769 "too many cards per region"); 1770 1771 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1772 1773 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1774 1775 { 1776 HeapWord* start = _hrm.reserved().start(); 1777 HeapWord* end = _hrm.reserved().end(); 1778 size_t granularity = HeapRegion::GrainBytes; 1779 1780 _in_cset_fast_test.initialize(start, end, granularity); 1781 _humongous_reclaim_candidates.initialize(start, end, granularity); 1782 } 1783 1784 // Create the G1ConcurrentMark data structure and thread. 1785 // (Must do this late, so that "max_regions" is defined.) 1786 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1787 if (_cm == NULL || !_cm->completed_initialization()) { 1788 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1789 return JNI_ENOMEM; 1790 } 1791 _cmThread = _cm->cmThread(); 1792 1793 // Now expand into the initial heap size. 1794 if (!expand(init_byte_size, _workers)) { 1795 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1796 return JNI_ENOMEM; 1797 } 1798 1799 // Perform any initialization actions delegated to the policy. 1800 g1_policy()->init(this, &_collection_set); 1801 1802 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1803 SATB_Q_FL_lock, 1804 G1SATBProcessCompletedThreshold, 1805 Shared_SATB_Q_lock); 1806 1807 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 1808 DirtyCardQ_CBL_mon, 1809 DirtyCardQ_FL_lock, 1810 (int)concurrent_g1_refine()->yellow_zone(), 1811 (int)concurrent_g1_refine()->red_zone(), 1812 Shared_DirtyCardQ_lock, 1813 NULL, // fl_owner 1814 true); // init_free_ids 1815 1816 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 1817 DirtyCardQ_CBL_mon, 1818 DirtyCardQ_FL_lock, 1819 -1, // never trigger processing 1820 -1, // no limit on length 1821 Shared_DirtyCardQ_lock, 1822 &JavaThread::dirty_card_queue_set()); 1823 1824 // Here we allocate the dummy HeapRegion that is required by the 1825 // G1AllocRegion class. 1826 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1827 1828 // We'll re-use the same region whether the alloc region will 1829 // require BOT updates or not and, if it doesn't, then a non-young 1830 // region will complain that it cannot support allocations without 1831 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1832 dummy_region->set_eden(); 1833 // Make sure it's full. 1834 dummy_region->set_top(dummy_region->end()); 1835 G1AllocRegion::setup(this, dummy_region); 1836 1837 _allocator->init_mutator_alloc_region(); 1838 1839 // Do create of the monitoring and management support so that 1840 // values in the heap have been properly initialized. 1841 _g1mm = new G1MonitoringSupport(this); 1842 1843 G1StringDedup::initialize(); 1844 1845 _preserved_marks_set.init(ParallelGCThreads); 1846 1847 _collection_set.initialize(max_regions()); 1848 1849 return JNI_OK; 1850 } 1851 1852 void G1CollectedHeap::stop() { 1853 // Stop all concurrent threads. We do this to make sure these threads 1854 // do not continue to execute and access resources (e.g. logging) 1855 // that are destroyed during shutdown. 1856 _cg1r->stop(); 1857 _cmThread->stop(); 1858 if (G1StringDedup::is_enabled()) { 1859 G1StringDedup::stop(); 1860 } 1861 } 1862 1863 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1864 return HeapRegion::max_region_size(); 1865 } 1866 1867 void G1CollectedHeap::post_initialize() { 1868 ref_processing_init(); 1869 } 1870 1871 void G1CollectedHeap::ref_processing_init() { 1872 // Reference processing in G1 currently works as follows: 1873 // 1874 // * There are two reference processor instances. One is 1875 // used to record and process discovered references 1876 // during concurrent marking; the other is used to 1877 // record and process references during STW pauses 1878 // (both full and incremental). 1879 // * Both ref processors need to 'span' the entire heap as 1880 // the regions in the collection set may be dotted around. 1881 // 1882 // * For the concurrent marking ref processor: 1883 // * Reference discovery is enabled at initial marking. 1884 // * Reference discovery is disabled and the discovered 1885 // references processed etc during remarking. 1886 // * Reference discovery is MT (see below). 1887 // * Reference discovery requires a barrier (see below). 1888 // * Reference processing may or may not be MT 1889 // (depending on the value of ParallelRefProcEnabled 1890 // and ParallelGCThreads). 1891 // * A full GC disables reference discovery by the CM 1892 // ref processor and abandons any entries on it's 1893 // discovered lists. 1894 // 1895 // * For the STW processor: 1896 // * Non MT discovery is enabled at the start of a full GC. 1897 // * Processing and enqueueing during a full GC is non-MT. 1898 // * During a full GC, references are processed after marking. 1899 // 1900 // * Discovery (may or may not be MT) is enabled at the start 1901 // of an incremental evacuation pause. 1902 // * References are processed near the end of a STW evacuation pause. 1903 // * For both types of GC: 1904 // * Discovery is atomic - i.e. not concurrent. 1905 // * Reference discovery will not need a barrier. 1906 1907 MemRegion mr = reserved_region(); 1908 1909 // Concurrent Mark ref processor 1910 _ref_processor_cm = 1911 new ReferenceProcessor(mr, // span 1912 ParallelRefProcEnabled && (ParallelGCThreads > 1), 1913 // mt processing 1914 ParallelGCThreads, 1915 // degree of mt processing 1916 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 1917 // mt discovery 1918 MAX2(ParallelGCThreads, ConcGCThreads), 1919 // degree of mt discovery 1920 false, 1921 // Reference discovery is not atomic 1922 &_is_alive_closure_cm); 1923 // is alive closure 1924 // (for efficiency/performance) 1925 1926 // STW ref processor 1927 _ref_processor_stw = 1928 new ReferenceProcessor(mr, // span 1929 ParallelRefProcEnabled && (ParallelGCThreads > 1), 1930 // mt processing 1931 ParallelGCThreads, 1932 // degree of mt processing 1933 (ParallelGCThreads > 1), 1934 // mt discovery 1935 ParallelGCThreads, 1936 // degree of mt discovery 1937 true, 1938 // Reference discovery is atomic 1939 &_is_alive_closure_stw); 1940 // is alive closure 1941 // (for efficiency/performance) 1942 } 1943 1944 CollectorPolicy* G1CollectedHeap::collector_policy() const { 1945 return _collector_policy; 1946 } 1947 1948 size_t G1CollectedHeap::capacity() const { 1949 return _hrm.length() * HeapRegion::GrainBytes; 1950 } 1951 1952 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 1953 hr->reset_gc_time_stamp(); 1954 } 1955 1956 #ifndef PRODUCT 1957 1958 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 1959 private: 1960 unsigned _gc_time_stamp; 1961 bool _failures; 1962 1963 public: 1964 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 1965 _gc_time_stamp(gc_time_stamp), _failures(false) { } 1966 1967 virtual bool doHeapRegion(HeapRegion* hr) { 1968 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 1969 if (_gc_time_stamp != region_gc_time_stamp) { 1970 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 1971 region_gc_time_stamp, _gc_time_stamp); 1972 _failures = true; 1973 } 1974 return false; 1975 } 1976 1977 bool failures() { return _failures; } 1978 }; 1979 1980 void G1CollectedHeap::check_gc_time_stamps() { 1981 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 1982 heap_region_iterate(&cl); 1983 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 1984 } 1985 #endif // PRODUCT 1986 1987 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 1988 _hot_card_cache->drain(cl, worker_i); 1989 } 1990 1991 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 1992 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 1993 size_t n_completed_buffers = 0; 1994 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 1995 n_completed_buffers++; 1996 } 1997 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 1998 dcqs.clear_n_completed_buffers(); 1999 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2000 } 2001 2002 // Computes the sum of the storage used by the various regions. 2003 size_t G1CollectedHeap::used() const { 2004 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2005 if (_archive_allocator != NULL) { 2006 result += _archive_allocator->used(); 2007 } 2008 return result; 2009 } 2010 2011 size_t G1CollectedHeap::used_unlocked() const { 2012 return _summary_bytes_used; 2013 } 2014 2015 class SumUsedClosure: public HeapRegionClosure { 2016 size_t _used; 2017 public: 2018 SumUsedClosure() : _used(0) {} 2019 bool doHeapRegion(HeapRegion* r) { 2020 _used += r->used(); 2021 return false; 2022 } 2023 size_t result() { return _used; } 2024 }; 2025 2026 size_t G1CollectedHeap::recalculate_used() const { 2027 double recalculate_used_start = os::elapsedTime(); 2028 2029 SumUsedClosure blk; 2030 heap_region_iterate(&blk); 2031 2032 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2033 return blk.result(); 2034 } 2035 2036 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2037 switch (cause) { 2038 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2039 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2040 case GCCause::_update_allocation_context_stats_inc: return true; 2041 case GCCause::_wb_conc_mark: return true; 2042 default : return false; 2043 } 2044 } 2045 2046 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2047 switch (cause) { 2048 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2049 case GCCause::_g1_humongous_allocation: return true; 2050 default: return is_user_requested_concurrent_full_gc(cause); 2051 } 2052 } 2053 2054 #ifndef PRODUCT 2055 void G1CollectedHeap::allocate_dummy_regions() { 2056 // Let's fill up most of the region 2057 size_t word_size = HeapRegion::GrainWords - 1024; 2058 // And as a result the region we'll allocate will be humongous. 2059 guarantee(is_humongous(word_size), "sanity"); 2060 2061 // _filler_array_max_size is set to humongous object threshold 2062 // but temporarily change it to use CollectedHeap::fill_with_object(). 2063 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2064 2065 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2066 // Let's use the existing mechanism for the allocation 2067 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2068 AllocationContext::system()); 2069 if (dummy_obj != NULL) { 2070 MemRegion mr(dummy_obj, word_size); 2071 CollectedHeap::fill_with_object(mr); 2072 } else { 2073 // If we can't allocate once, we probably cannot allocate 2074 // again. Let's get out of the loop. 2075 break; 2076 } 2077 } 2078 } 2079 #endif // !PRODUCT 2080 2081 void G1CollectedHeap::increment_old_marking_cycles_started() { 2082 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2083 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2084 "Wrong marking cycle count (started: %d, completed: %d)", 2085 _old_marking_cycles_started, _old_marking_cycles_completed); 2086 2087 _old_marking_cycles_started++; 2088 } 2089 2090 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2091 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2092 2093 // We assume that if concurrent == true, then the caller is a 2094 // concurrent thread that was joined the Suspendible Thread 2095 // Set. If there's ever a cheap way to check this, we should add an 2096 // assert here. 2097 2098 // Given that this method is called at the end of a Full GC or of a 2099 // concurrent cycle, and those can be nested (i.e., a Full GC can 2100 // interrupt a concurrent cycle), the number of full collections 2101 // completed should be either one (in the case where there was no 2102 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2103 // behind the number of full collections started. 2104 2105 // This is the case for the inner caller, i.e. a Full GC. 2106 assert(concurrent || 2107 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2108 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2109 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2110 "is inconsistent with _old_marking_cycles_completed = %u", 2111 _old_marking_cycles_started, _old_marking_cycles_completed); 2112 2113 // This is the case for the outer caller, i.e. the concurrent cycle. 2114 assert(!concurrent || 2115 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2116 "for outer caller (concurrent cycle): " 2117 "_old_marking_cycles_started = %u " 2118 "is inconsistent with _old_marking_cycles_completed = %u", 2119 _old_marking_cycles_started, _old_marking_cycles_completed); 2120 2121 _old_marking_cycles_completed += 1; 2122 2123 // We need to clear the "in_progress" flag in the CM thread before 2124 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2125 // is set) so that if a waiter requests another System.gc() it doesn't 2126 // incorrectly see that a marking cycle is still in progress. 2127 if (concurrent) { 2128 _cmThread->set_idle(); 2129 } 2130 2131 // This notify_all() will ensure that a thread that called 2132 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2133 // and it's waiting for a full GC to finish will be woken up. It is 2134 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2135 FullGCCount_lock->notify_all(); 2136 } 2137 2138 void G1CollectedHeap::collect(GCCause::Cause cause) { 2139 assert_heap_not_locked(); 2140 2141 uint gc_count_before; 2142 uint old_marking_count_before; 2143 uint full_gc_count_before; 2144 bool retry_gc; 2145 2146 do { 2147 retry_gc = false; 2148 2149 { 2150 MutexLocker ml(Heap_lock); 2151 2152 // Read the GC count while holding the Heap_lock 2153 gc_count_before = total_collections(); 2154 full_gc_count_before = total_full_collections(); 2155 old_marking_count_before = _old_marking_cycles_started; 2156 } 2157 2158 if (should_do_concurrent_full_gc(cause)) { 2159 // Schedule an initial-mark evacuation pause that will start a 2160 // concurrent cycle. We're setting word_size to 0 which means that 2161 // we are not requesting a post-GC allocation. 2162 VM_G1IncCollectionPause op(gc_count_before, 2163 0, /* word_size */ 2164 true, /* should_initiate_conc_mark */ 2165 g1_policy()->max_pause_time_ms(), 2166 cause); 2167 op.set_allocation_context(AllocationContext::current()); 2168 2169 VMThread::execute(&op); 2170 if (!op.pause_succeeded()) { 2171 if (old_marking_count_before == _old_marking_cycles_started) { 2172 retry_gc = op.should_retry_gc(); 2173 } else { 2174 // A Full GC happened while we were trying to schedule the 2175 // initial-mark GC. No point in starting a new cycle given 2176 // that the whole heap was collected anyway. 2177 } 2178 2179 if (retry_gc) { 2180 if (GCLocker::is_active_and_needs_gc()) { 2181 GCLocker::stall_until_clear(); 2182 } 2183 } 2184 } 2185 } else { 2186 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2187 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2188 2189 // Schedule a standard evacuation pause. We're setting word_size 2190 // to 0 which means that we are not requesting a post-GC allocation. 2191 VM_G1IncCollectionPause op(gc_count_before, 2192 0, /* word_size */ 2193 false, /* should_initiate_conc_mark */ 2194 g1_policy()->max_pause_time_ms(), 2195 cause); 2196 VMThread::execute(&op); 2197 } else { 2198 // Schedule a Full GC. 2199 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2200 VMThread::execute(&op); 2201 } 2202 } 2203 } while (retry_gc); 2204 } 2205 2206 bool G1CollectedHeap::is_in(const void* p) const { 2207 if (_hrm.reserved().contains(p)) { 2208 // Given that we know that p is in the reserved space, 2209 // heap_region_containing() should successfully 2210 // return the containing region. 2211 HeapRegion* hr = heap_region_containing(p); 2212 return hr->is_in(p); 2213 } else { 2214 return false; 2215 } 2216 } 2217 2218 #ifdef ASSERT 2219 bool G1CollectedHeap::is_in_exact(const void* p) const { 2220 bool contains = reserved_region().contains(p); 2221 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2222 if (contains && available) { 2223 return true; 2224 } else { 2225 return false; 2226 } 2227 } 2228 #endif 2229 2230 // Iteration functions. 2231 2232 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2233 2234 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2235 ExtendedOopClosure* _cl; 2236 public: 2237 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2238 bool doHeapRegion(HeapRegion* r) { 2239 if (!r->is_continues_humongous()) { 2240 r->oop_iterate(_cl); 2241 } 2242 return false; 2243 } 2244 }; 2245 2246 // Iterates an ObjectClosure over all objects within a HeapRegion. 2247 2248 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2249 ObjectClosure* _cl; 2250 public: 2251 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2252 bool doHeapRegion(HeapRegion* r) { 2253 if (!r->is_continues_humongous()) { 2254 r->object_iterate(_cl); 2255 } 2256 return false; 2257 } 2258 }; 2259 2260 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2261 IterateObjectClosureRegionClosure blk(cl); 2262 heap_region_iterate(&blk); 2263 } 2264 2265 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2266 _hrm.iterate(cl); 2267 } 2268 2269 void 2270 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2271 uint worker_id, 2272 HeapRegionClaimer *hrclaimer, 2273 bool concurrent) const { 2274 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2275 } 2276 2277 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2278 _collection_set.iterate(cl); 2279 } 2280 2281 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2282 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2283 } 2284 2285 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2286 HeapRegion* result = _hrm.next_region_in_heap(from); 2287 while (result != NULL && result->is_pinned()) { 2288 result = _hrm.next_region_in_heap(result); 2289 } 2290 return result; 2291 } 2292 2293 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2294 HeapRegion* hr = heap_region_containing(addr); 2295 return hr->block_start(addr); 2296 } 2297 2298 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2299 HeapRegion* hr = heap_region_containing(addr); 2300 return hr->block_size(addr); 2301 } 2302 2303 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2304 HeapRegion* hr = heap_region_containing(addr); 2305 return hr->block_is_obj(addr); 2306 } 2307 2308 bool G1CollectedHeap::supports_tlab_allocation() const { 2309 return true; 2310 } 2311 2312 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2313 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2314 } 2315 2316 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2317 return _eden.length() * HeapRegion::GrainBytes; 2318 } 2319 2320 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2321 // must be equal to the humongous object limit. 2322 size_t G1CollectedHeap::max_tlab_size() const { 2323 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2324 } 2325 2326 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2327 AllocationContext_t context = AllocationContext::current(); 2328 return _allocator->unsafe_max_tlab_alloc(context); 2329 } 2330 2331 size_t G1CollectedHeap::max_capacity() const { 2332 return _hrm.reserved().byte_size(); 2333 } 2334 2335 jlong G1CollectedHeap::millis_since_last_gc() { 2336 // See the notes in GenCollectedHeap::millis_since_last_gc() 2337 // for more information about the implementation. 2338 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2339 _g1_policy->collection_pause_end_millis(); 2340 if (ret_val < 0) { 2341 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2342 ". returning zero instead.", ret_val); 2343 return 0; 2344 } 2345 return ret_val; 2346 } 2347 2348 void G1CollectedHeap::prepare_for_verify() { 2349 _verifier->prepare_for_verify(); 2350 } 2351 2352 void G1CollectedHeap::verify(VerifyOption vo) { 2353 _verifier->verify(vo); 2354 } 2355 2356 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2357 return true; 2358 } 2359 2360 const char* const* G1CollectedHeap::concurrent_phases() const { 2361 return _cmThread->concurrent_phases(); 2362 } 2363 2364 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2365 return _cmThread->request_concurrent_phase(phase); 2366 } 2367 2368 class PrintRegionClosure: public HeapRegionClosure { 2369 outputStream* _st; 2370 public: 2371 PrintRegionClosure(outputStream* st) : _st(st) {} 2372 bool doHeapRegion(HeapRegion* r) { 2373 r->print_on(_st); 2374 return false; 2375 } 2376 }; 2377 2378 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2379 const HeapRegion* hr, 2380 const VerifyOption vo) const { 2381 switch (vo) { 2382 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2383 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2384 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 2385 default: ShouldNotReachHere(); 2386 } 2387 return false; // keep some compilers happy 2388 } 2389 2390 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2391 const VerifyOption vo) const { 2392 switch (vo) { 2393 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2394 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2395 case VerifyOption_G1UseMarkWord: { 2396 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 2397 return !obj->is_gc_marked() && !hr->is_archive(); 2398 } 2399 default: ShouldNotReachHere(); 2400 } 2401 return false; // keep some compilers happy 2402 } 2403 2404 void G1CollectedHeap::print_heap_regions() const { 2405 Log(gc, heap, region) log; 2406 if (log.is_trace()) { 2407 ResourceMark rm; 2408 print_regions_on(log.trace_stream()); 2409 } 2410 } 2411 2412 void G1CollectedHeap::print_on(outputStream* st) const { 2413 st->print(" %-20s", "garbage-first heap"); 2414 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2415 capacity()/K, used_unlocked()/K); 2416 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 2417 p2i(_hrm.reserved().start()), 2418 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 2419 p2i(_hrm.reserved().end())); 2420 st->cr(); 2421 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2422 uint young_regions = young_regions_count(); 2423 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2424 (size_t) young_regions * HeapRegion::GrainBytes / K); 2425 uint survivor_regions = survivor_regions_count(); 2426 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2427 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2428 st->cr(); 2429 MetaspaceAux::print_on(st); 2430 } 2431 2432 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2433 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2434 "HS=humongous(starts), HC=humongous(continues), " 2435 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2436 "AC=allocation context, " 2437 "TAMS=top-at-mark-start (previous, next)"); 2438 PrintRegionClosure blk(st); 2439 heap_region_iterate(&blk); 2440 } 2441 2442 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2443 print_on(st); 2444 2445 // Print the per-region information. 2446 print_regions_on(st); 2447 } 2448 2449 void G1CollectedHeap::print_on_error(outputStream* st) const { 2450 this->CollectedHeap::print_on_error(st); 2451 2452 if (_cm != NULL) { 2453 st->cr(); 2454 _cm->print_on_error(st); 2455 } 2456 } 2457 2458 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2459 workers()->print_worker_threads_on(st); 2460 _cmThread->print_on(st); 2461 st->cr(); 2462 _cm->print_worker_threads_on(st); 2463 _cg1r->print_worker_threads_on(st); // also prints the sample thread 2464 if (G1StringDedup::is_enabled()) { 2465 G1StringDedup::print_worker_threads_on(st); 2466 } 2467 } 2468 2469 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2470 workers()->threads_do(tc); 2471 tc->do_thread(_cmThread); 2472 _cm->threads_do(tc); 2473 _cg1r->threads_do(tc); // also iterates over the sample thread 2474 if (G1StringDedup::is_enabled()) { 2475 G1StringDedup::threads_do(tc); 2476 } 2477 } 2478 2479 void G1CollectedHeap::print_tracing_info() const { 2480 g1_rem_set()->print_summary_info(); 2481 concurrent_mark()->print_summary_info(); 2482 } 2483 2484 #ifndef PRODUCT 2485 // Helpful for debugging RSet issues. 2486 2487 class PrintRSetsClosure : public HeapRegionClosure { 2488 private: 2489 const char* _msg; 2490 size_t _occupied_sum; 2491 2492 public: 2493 bool doHeapRegion(HeapRegion* r) { 2494 HeapRegionRemSet* hrrs = r->rem_set(); 2495 size_t occupied = hrrs->occupied(); 2496 _occupied_sum += occupied; 2497 2498 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2499 if (occupied == 0) { 2500 tty->print_cr(" RSet is empty"); 2501 } else { 2502 hrrs->print(); 2503 } 2504 tty->print_cr("----------"); 2505 return false; 2506 } 2507 2508 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2509 tty->cr(); 2510 tty->print_cr("========================================"); 2511 tty->print_cr("%s", msg); 2512 tty->cr(); 2513 } 2514 2515 ~PrintRSetsClosure() { 2516 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2517 tty->print_cr("========================================"); 2518 tty->cr(); 2519 } 2520 }; 2521 2522 void G1CollectedHeap::print_cset_rsets() { 2523 PrintRSetsClosure cl("Printing CSet RSets"); 2524 collection_set_iterate(&cl); 2525 } 2526 2527 void G1CollectedHeap::print_all_rsets() { 2528 PrintRSetsClosure cl("Printing All RSets");; 2529 heap_region_iterate(&cl); 2530 } 2531 #endif // PRODUCT 2532 2533 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2534 2535 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2536 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2537 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2538 2539 size_t eden_capacity_bytes = 2540 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2541 2542 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2543 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2544 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2545 } 2546 2547 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2548 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2549 stats->unused(), stats->used(), stats->region_end_waste(), 2550 stats->regions_filled(), stats->direct_allocated(), 2551 stats->failure_used(), stats->failure_waste()); 2552 } 2553 2554 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2555 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2556 gc_tracer->report_gc_heap_summary(when, heap_summary); 2557 2558 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2559 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2560 } 2561 2562 G1CollectedHeap* G1CollectedHeap::heap() { 2563 CollectedHeap* heap = Universe::heap(); 2564 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2565 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2566 return (G1CollectedHeap*)heap; 2567 } 2568 2569 void G1CollectedHeap::gc_prologue(bool full) { 2570 // always_do_update_barrier = false; 2571 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2572 2573 // This summary needs to be printed before incrementing total collections. 2574 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2575 2576 // Update common counters. 2577 increment_total_collections(full /* full gc */); 2578 if (full) { 2579 increment_old_marking_cycles_started(); 2580 reset_gc_time_stamp(); 2581 } else { 2582 increment_gc_time_stamp(); 2583 } 2584 2585 // Fill TLAB's and such 2586 double start = os::elapsedTime(); 2587 accumulate_statistics_all_tlabs(); 2588 ensure_parsability(true); 2589 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2590 } 2591 2592 void G1CollectedHeap::gc_epilogue(bool full) { 2593 // Update common counters. 2594 if (full) { 2595 // Update the number of full collections that have been completed. 2596 increment_old_marking_cycles_completed(false /* concurrent */); 2597 } 2598 2599 // We are at the end of the GC. Total collections has already been increased. 2600 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2601 2602 // FIXME: what is this about? 2603 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2604 // is set. 2605 #if defined(COMPILER2) || INCLUDE_JVMCI 2606 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2607 #endif 2608 // always_do_update_barrier = true; 2609 2610 double start = os::elapsedTime(); 2611 resize_all_tlabs(); 2612 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2613 2614 allocation_context_stats().update(full); 2615 2616 MemoryService::track_memory_usage(); 2617 // We have just completed a GC. Update the soft reference 2618 // policy with the new heap occupancy 2619 Universe::update_heap_info_at_gc(); 2620 } 2621 2622 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2623 uint gc_count_before, 2624 bool* succeeded, 2625 GCCause::Cause gc_cause) { 2626 assert_heap_not_locked_and_not_at_safepoint(); 2627 VM_G1IncCollectionPause op(gc_count_before, 2628 word_size, 2629 false, /* should_initiate_conc_mark */ 2630 g1_policy()->max_pause_time_ms(), 2631 gc_cause); 2632 2633 op.set_allocation_context(AllocationContext::current()); 2634 VMThread::execute(&op); 2635 2636 HeapWord* result = op.result(); 2637 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2638 assert(result == NULL || ret_succeeded, 2639 "the result should be NULL if the VM did not succeed"); 2640 *succeeded = ret_succeeded; 2641 2642 assert_heap_not_locked(); 2643 return result; 2644 } 2645 2646 void 2647 G1CollectedHeap::doConcurrentMark() { 2648 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2649 if (!_cmThread->in_progress()) { 2650 _cmThread->set_started(); 2651 CGC_lock->notify(); 2652 } 2653 } 2654 2655 size_t G1CollectedHeap::pending_card_num() { 2656 size_t extra_cards = 0; 2657 JavaThread *curr = Threads::first(); 2658 while (curr != NULL) { 2659 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2660 extra_cards += dcq.size(); 2661 curr = curr->next(); 2662 } 2663 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2664 size_t buffer_size = dcqs.buffer_size(); 2665 size_t buffer_num = dcqs.completed_buffers_num(); 2666 2667 return buffer_size * buffer_num + extra_cards; 2668 } 2669 2670 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2671 private: 2672 size_t _total_humongous; 2673 size_t _candidate_humongous; 2674 2675 DirtyCardQueue _dcq; 2676 2677 // We don't nominate objects with many remembered set entries, on 2678 // the assumption that such objects are likely still live. 2679 bool is_remset_small(HeapRegion* region) const { 2680 HeapRegionRemSet* const rset = region->rem_set(); 2681 return G1EagerReclaimHumongousObjectsWithStaleRefs 2682 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2683 : rset->is_empty(); 2684 } 2685 2686 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2687 assert(region->is_starts_humongous(), "Must start a humongous object"); 2688 2689 oop obj = oop(region->bottom()); 2690 2691 // Dead objects cannot be eager reclaim candidates. Due to class 2692 // unloading it is unsafe to query their classes so we return early. 2693 if (heap->is_obj_dead(obj, region)) { 2694 return false; 2695 } 2696 2697 // Candidate selection must satisfy the following constraints 2698 // while concurrent marking is in progress: 2699 // 2700 // * In order to maintain SATB invariants, an object must not be 2701 // reclaimed if it was allocated before the start of marking and 2702 // has not had its references scanned. Such an object must have 2703 // its references (including type metadata) scanned to ensure no 2704 // live objects are missed by the marking process. Objects 2705 // allocated after the start of concurrent marking don't need to 2706 // be scanned. 2707 // 2708 // * An object must not be reclaimed if it is on the concurrent 2709 // mark stack. Objects allocated after the start of concurrent 2710 // marking are never pushed on the mark stack. 2711 // 2712 // Nominating only objects allocated after the start of concurrent 2713 // marking is sufficient to meet both constraints. This may miss 2714 // some objects that satisfy the constraints, but the marking data 2715 // structures don't support efficiently performing the needed 2716 // additional tests or scrubbing of the mark stack. 2717 // 2718 // However, we presently only nominate is_typeArray() objects. 2719 // A humongous object containing references induces remembered 2720 // set entries on other regions. In order to reclaim such an 2721 // object, those remembered sets would need to be cleaned up. 2722 // 2723 // We also treat is_typeArray() objects specially, allowing them 2724 // to be reclaimed even if allocated before the start of 2725 // concurrent mark. For this we rely on mark stack insertion to 2726 // exclude is_typeArray() objects, preventing reclaiming an object 2727 // that is in the mark stack. We also rely on the metadata for 2728 // such objects to be built-in and so ensured to be kept live. 2729 // Frequent allocation and drop of large binary blobs is an 2730 // important use case for eager reclaim, and this special handling 2731 // may reduce needed headroom. 2732 2733 return obj->is_typeArray() && is_remset_small(region); 2734 } 2735 2736 public: 2737 RegisterHumongousWithInCSetFastTestClosure() 2738 : _total_humongous(0), 2739 _candidate_humongous(0), 2740 _dcq(&JavaThread::dirty_card_queue_set()) { 2741 } 2742 2743 virtual bool doHeapRegion(HeapRegion* r) { 2744 if (!r->is_starts_humongous()) { 2745 return false; 2746 } 2747 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2748 2749 bool is_candidate = humongous_region_is_candidate(g1h, r); 2750 uint rindex = r->hrm_index(); 2751 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2752 if (is_candidate) { 2753 _candidate_humongous++; 2754 g1h->register_humongous_region_with_cset(rindex); 2755 // Is_candidate already filters out humongous object with large remembered sets. 2756 // If we have a humongous object with a few remembered sets, we simply flush these 2757 // remembered set entries into the DCQS. That will result in automatic 2758 // re-evaluation of their remembered set entries during the following evacuation 2759 // phase. 2760 if (!r->rem_set()->is_empty()) { 2761 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2762 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2763 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 2764 HeapRegionRemSetIterator hrrs(r->rem_set()); 2765 size_t card_index; 2766 while (hrrs.has_next(card_index)) { 2767 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 2768 // The remembered set might contain references to already freed 2769 // regions. Filter out such entries to avoid failing card table 2770 // verification. 2771 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 2772 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 2773 *card_ptr = CardTableModRefBS::dirty_card_val(); 2774 _dcq.enqueue(card_ptr); 2775 } 2776 } 2777 } 2778 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2779 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2780 hrrs.n_yielded(), r->rem_set()->occupied()); 2781 r->rem_set()->clear_locked(); 2782 } 2783 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2784 } 2785 _total_humongous++; 2786 2787 return false; 2788 } 2789 2790 size_t total_humongous() const { return _total_humongous; } 2791 size_t candidate_humongous() const { return _candidate_humongous; } 2792 2793 void flush_rem_set_entries() { _dcq.flush(); } 2794 }; 2795 2796 void G1CollectedHeap::register_humongous_regions_with_cset() { 2797 if (!G1EagerReclaimHumongousObjects) { 2798 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2799 return; 2800 } 2801 double time = os::elapsed_counter(); 2802 2803 // Collect reclaim candidate information and register candidates with cset. 2804 RegisterHumongousWithInCSetFastTestClosure cl; 2805 heap_region_iterate(&cl); 2806 2807 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2808 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2809 cl.total_humongous(), 2810 cl.candidate_humongous()); 2811 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2812 2813 // Finally flush all remembered set entries to re-check into the global DCQS. 2814 cl.flush_rem_set_entries(); 2815 } 2816 2817 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2818 public: 2819 bool doHeapRegion(HeapRegion* hr) { 2820 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2821 hr->verify_rem_set(); 2822 } 2823 return false; 2824 } 2825 }; 2826 2827 uint G1CollectedHeap::num_task_queues() const { 2828 return _task_queues->size(); 2829 } 2830 2831 #if TASKQUEUE_STATS 2832 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2833 st->print_raw_cr("GC Task Stats"); 2834 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2835 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2836 } 2837 2838 void G1CollectedHeap::print_taskqueue_stats() const { 2839 if (!log_is_enabled(Trace, gc, task, stats)) { 2840 return; 2841 } 2842 Log(gc, task, stats) log; 2843 ResourceMark rm; 2844 outputStream* st = log.trace_stream(); 2845 2846 print_taskqueue_stats_hdr(st); 2847 2848 TaskQueueStats totals; 2849 const uint n = num_task_queues(); 2850 for (uint i = 0; i < n; ++i) { 2851 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2852 totals += task_queue(i)->stats; 2853 } 2854 st->print_raw("tot "); totals.print(st); st->cr(); 2855 2856 DEBUG_ONLY(totals.verify()); 2857 } 2858 2859 void G1CollectedHeap::reset_taskqueue_stats() { 2860 const uint n = num_task_queues(); 2861 for (uint i = 0; i < n; ++i) { 2862 task_queue(i)->stats.reset(); 2863 } 2864 } 2865 #endif // TASKQUEUE_STATS 2866 2867 void G1CollectedHeap::wait_for_root_region_scanning() { 2868 double scan_wait_start = os::elapsedTime(); 2869 // We have to wait until the CM threads finish scanning the 2870 // root regions as it's the only way to ensure that all the 2871 // objects on them have been correctly scanned before we start 2872 // moving them during the GC. 2873 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2874 double wait_time_ms = 0.0; 2875 if (waited) { 2876 double scan_wait_end = os::elapsedTime(); 2877 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2878 } 2879 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2880 } 2881 2882 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2883 private: 2884 G1HRPrinter* _hr_printer; 2885 public: 2886 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2887 2888 virtual bool doHeapRegion(HeapRegion* r) { 2889 _hr_printer->cset(r); 2890 return false; 2891 } 2892 }; 2893 2894 void G1CollectedHeap::start_new_collection_set() { 2895 collection_set()->start_incremental_building(); 2896 2897 clear_cset_fast_test(); 2898 2899 guarantee(_eden.length() == 0, "eden should have been cleared"); 2900 g1_policy()->transfer_survivors_to_cset(survivor()); 2901 } 2902 2903 bool 2904 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2905 assert_at_safepoint(true /* should_be_vm_thread */); 2906 guarantee(!is_gc_active(), "collection is not reentrant"); 2907 2908 if (GCLocker::check_active_before_gc()) { 2909 return false; 2910 } 2911 2912 _gc_timer_stw->register_gc_start(); 2913 2914 GCIdMark gc_id_mark; 2915 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2916 2917 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2918 ResourceMark rm; 2919 2920 g1_policy()->note_gc_start(); 2921 2922 wait_for_root_region_scanning(); 2923 2924 print_heap_before_gc(); 2925 print_heap_regions(); 2926 trace_heap_before_gc(_gc_tracer_stw); 2927 2928 _verifier->verify_region_sets_optional(); 2929 _verifier->verify_dirty_young_regions(); 2930 2931 // We should not be doing initial mark unless the conc mark thread is running 2932 if (!_cmThread->should_terminate()) { 2933 // This call will decide whether this pause is an initial-mark 2934 // pause. If it is, during_initial_mark_pause() will return true 2935 // for the duration of this pause. 2936 g1_policy()->decide_on_conc_mark_initiation(); 2937 } 2938 2939 // We do not allow initial-mark to be piggy-backed on a mixed GC. 2940 assert(!collector_state()->during_initial_mark_pause() || 2941 collector_state()->gcs_are_young(), "sanity"); 2942 2943 // We also do not allow mixed GCs during marking. 2944 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 2945 2946 // Record whether this pause is an initial mark. When the current 2947 // thread has completed its logging output and it's safe to signal 2948 // the CM thread, the flag's value in the policy has been reset. 2949 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 2950 2951 // Inner scope for scope based logging, timers, and stats collection 2952 { 2953 EvacuationInfo evacuation_info; 2954 2955 if (collector_state()->during_initial_mark_pause()) { 2956 // We are about to start a marking cycle, so we increment the 2957 // full collection counter. 2958 increment_old_marking_cycles_started(); 2959 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 2960 } 2961 2962 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 2963 2964 GCTraceCPUTime tcpu; 2965 2966 FormatBuffer<> gc_string("Pause "); 2967 if (collector_state()->during_initial_mark_pause()) { 2968 gc_string.append("Initial Mark"); 2969 } else if (collector_state()->gcs_are_young()) { 2970 gc_string.append("Young"); 2971 } else { 2972 gc_string.append("Mixed"); 2973 } 2974 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 2975 2976 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 2977 workers()->active_workers(), 2978 Threads::number_of_non_daemon_threads()); 2979 workers()->update_active_workers(active_workers); 2980 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 2981 2982 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 2983 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 2984 2985 // If the secondary_free_list is not empty, append it to the 2986 // free_list. No need to wait for the cleanup operation to finish; 2987 // the region allocation code will check the secondary_free_list 2988 // and wait if necessary. If the G1StressConcRegionFreeing flag is 2989 // set, skip this step so that the region allocation code has to 2990 // get entries from the secondary_free_list. 2991 if (!G1StressConcRegionFreeing) { 2992 append_secondary_free_list_if_not_empty_with_lock(); 2993 } 2994 2995 G1HeapTransition heap_transition(this); 2996 size_t heap_used_bytes_before_gc = used(); 2997 2998 // Don't dynamically change the number of GC threads this early. A value of 2999 // 0 is used to indicate serial work. When parallel work is done, 3000 // it will be set. 3001 3002 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3003 IsGCActiveMark x; 3004 3005 gc_prologue(false); 3006 3007 if (VerifyRememberedSets) { 3008 log_info(gc, verify)("[Verifying RemSets before GC]"); 3009 VerifyRegionRemSetClosure v_cl; 3010 heap_region_iterate(&v_cl); 3011 } 3012 3013 _verifier->verify_before_gc(); 3014 3015 _verifier->check_bitmaps("GC Start"); 3016 3017 #if defined(COMPILER2) || INCLUDE_JVMCI 3018 DerivedPointerTable::clear(); 3019 #endif 3020 3021 // Please see comment in g1CollectedHeap.hpp and 3022 // G1CollectedHeap::ref_processing_init() to see how 3023 // reference processing currently works in G1. 3024 3025 // Enable discovery in the STW reference processor 3026 if (g1_policy()->should_process_references()) { 3027 ref_processor_stw()->enable_discovery(); 3028 } else { 3029 ref_processor_stw()->disable_discovery(); 3030 } 3031 3032 { 3033 // We want to temporarily turn off discovery by the 3034 // CM ref processor, if necessary, and turn it back on 3035 // on again later if we do. Using a scoped 3036 // NoRefDiscovery object will do this. 3037 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3038 3039 // Forget the current alloc region (we might even choose it to be part 3040 // of the collection set!). 3041 _allocator->release_mutator_alloc_region(); 3042 3043 // This timing is only used by the ergonomics to handle our pause target. 3044 // It is unclear why this should not include the full pause. We will 3045 // investigate this in CR 7178365. 3046 // 3047 // Preserving the old comment here if that helps the investigation: 3048 // 3049 // The elapsed time induced by the start time below deliberately elides 3050 // the possible verification above. 3051 double sample_start_time_sec = os::elapsedTime(); 3052 3053 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3054 3055 if (collector_state()->during_initial_mark_pause()) { 3056 concurrent_mark()->checkpointRootsInitialPre(); 3057 } 3058 3059 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 3060 3061 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3062 3063 // Make sure the remembered sets are up to date. This needs to be 3064 // done before register_humongous_regions_with_cset(), because the 3065 // remembered sets are used there to choose eager reclaim candidates. 3066 // If the remembered sets are not up to date we might miss some 3067 // entries that need to be handled. 3068 g1_rem_set()->cleanupHRRS(); 3069 3070 register_humongous_regions_with_cset(); 3071 3072 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3073 3074 // We call this after finalize_cset() to 3075 // ensure that the CSet has been finalized. 3076 _cm->verify_no_cset_oops(); 3077 3078 if (_hr_printer.is_active()) { 3079 G1PrintCollectionSetClosure cl(&_hr_printer); 3080 _collection_set.iterate(&cl); 3081 } 3082 3083 // Initialize the GC alloc regions. 3084 _allocator->init_gc_alloc_regions(evacuation_info); 3085 3086 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3087 pre_evacuate_collection_set(); 3088 3089 // Actually do the work... 3090 evacuate_collection_set(evacuation_info, &per_thread_states); 3091 3092 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3093 3094 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3095 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 3096 3097 eagerly_reclaim_humongous_regions(); 3098 3099 record_obj_copy_mem_stats(); 3100 _survivor_evac_stats.adjust_desired_plab_sz(); 3101 _old_evac_stats.adjust_desired_plab_sz(); 3102 3103 double start = os::elapsedTime(); 3104 start_new_collection_set(); 3105 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 3106 3107 if (evacuation_failed()) { 3108 set_used(recalculate_used()); 3109 if (_archive_allocator != NULL) { 3110 _archive_allocator->clear_used(); 3111 } 3112 for (uint i = 0; i < ParallelGCThreads; i++) { 3113 if (_evacuation_failed_info_array[i].has_failed()) { 3114 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3115 } 3116 } 3117 } else { 3118 // The "used" of the the collection set have already been subtracted 3119 // when they were freed. Add in the bytes evacuated. 3120 increase_used(g1_policy()->bytes_copied_during_gc()); 3121 } 3122 3123 if (collector_state()->during_initial_mark_pause()) { 3124 // We have to do this before we notify the CM threads that 3125 // they can start working to make sure that all the 3126 // appropriate initialization is done on the CM object. 3127 concurrent_mark()->checkpointRootsInitialPost(); 3128 collector_state()->set_mark_in_progress(true); 3129 // Note that we don't actually trigger the CM thread at 3130 // this point. We do that later when we're sure that 3131 // the current thread has completed its logging output. 3132 } 3133 3134 allocate_dummy_regions(); 3135 3136 _allocator->init_mutator_alloc_region(); 3137 3138 { 3139 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3140 if (expand_bytes > 0) { 3141 size_t bytes_before = capacity(); 3142 // No need for an ergo logging here, 3143 // expansion_amount() does this when it returns a value > 0. 3144 double expand_ms; 3145 if (!expand(expand_bytes, _workers, &expand_ms)) { 3146 // We failed to expand the heap. Cannot do anything about it. 3147 } 3148 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3149 } 3150 } 3151 3152 // We redo the verification but now wrt to the new CSet which 3153 // has just got initialized after the previous CSet was freed. 3154 _cm->verify_no_cset_oops(); 3155 3156 // This timing is only used by the ergonomics to handle our pause target. 3157 // It is unclear why this should not include the full pause. We will 3158 // investigate this in CR 7178365. 3159 double sample_end_time_sec = os::elapsedTime(); 3160 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3161 size_t total_cards_scanned = per_thread_states.total_cards_scanned(); 3162 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3163 3164 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3165 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3166 3167 // In prepare_for_verify() below we'll need to scan the deferred 3168 // update buffers to bring the RSets up-to-date if 3169 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3170 // the update buffers we'll probably need to scan cards on the 3171 // regions we just allocated to (i.e., the GC alloc 3172 // regions). However, during the last GC we called 3173 // set_saved_mark() on all the GC alloc regions, so card 3174 // scanning might skip the [saved_mark_word()...top()] area of 3175 // those regions (i.e., the area we allocated objects into 3176 // during the last GC). But it shouldn't. Given that 3177 // saved_mark_word() is conditional on whether the GC time stamp 3178 // on the region is current or not, by incrementing the GC time 3179 // stamp here we invalidate all the GC time stamps on all the 3180 // regions and saved_mark_word() will simply return top() for 3181 // all the regions. This is a nicer way of ensuring this rather 3182 // than iterating over the regions and fixing them. In fact, the 3183 // GC time stamp increment here also ensures that 3184 // saved_mark_word() will return top() between pauses, i.e., 3185 // during concurrent refinement. So we don't need the 3186 // is_gc_active() check to decided which top to use when 3187 // scanning cards (see CR 7039627). 3188 increment_gc_time_stamp(); 3189 3190 if (VerifyRememberedSets) { 3191 log_info(gc, verify)("[Verifying RemSets after GC]"); 3192 VerifyRegionRemSetClosure v_cl; 3193 heap_region_iterate(&v_cl); 3194 } 3195 3196 _verifier->verify_after_gc(); 3197 _verifier->check_bitmaps("GC End"); 3198 3199 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3200 ref_processor_stw()->verify_no_references_recorded(); 3201 3202 // CM reference discovery will be re-enabled if necessary. 3203 } 3204 3205 #ifdef TRACESPINNING 3206 ParallelTaskTerminator::print_termination_counts(); 3207 #endif 3208 3209 gc_epilogue(false); 3210 } 3211 3212 // Print the remainder of the GC log output. 3213 if (evacuation_failed()) { 3214 log_info(gc)("To-space exhausted"); 3215 } 3216 3217 g1_policy()->print_phases(); 3218 heap_transition.print(); 3219 3220 // It is not yet to safe to tell the concurrent mark to 3221 // start as we have some optional output below. We don't want the 3222 // output from the concurrent mark thread interfering with this 3223 // logging output either. 3224 3225 _hrm.verify_optional(); 3226 _verifier->verify_region_sets_optional(); 3227 3228 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3229 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3230 3231 print_heap_after_gc(); 3232 print_heap_regions(); 3233 trace_heap_after_gc(_gc_tracer_stw); 3234 3235 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3236 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3237 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3238 // before any GC notifications are raised. 3239 g1mm()->update_sizes(); 3240 3241 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3242 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3243 _gc_timer_stw->register_gc_end(); 3244 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3245 } 3246 // It should now be safe to tell the concurrent mark thread to start 3247 // without its logging output interfering with the logging output 3248 // that came from the pause. 3249 3250 if (should_start_conc_mark) { 3251 // CAUTION: after the doConcurrentMark() call below, 3252 // the concurrent marking thread(s) could be running 3253 // concurrently with us. Make sure that anything after 3254 // this point does not assume that we are the only GC thread 3255 // running. Note: of course, the actual marking work will 3256 // not start until the safepoint itself is released in 3257 // SuspendibleThreadSet::desynchronize(). 3258 doConcurrentMark(); 3259 } 3260 3261 return true; 3262 } 3263 3264 void G1CollectedHeap::remove_self_forwarding_pointers() { 3265 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3266 workers()->run_task(&rsfp_task); 3267 } 3268 3269 void G1CollectedHeap::restore_after_evac_failure() { 3270 double remove_self_forwards_start = os::elapsedTime(); 3271 3272 remove_self_forwarding_pointers(); 3273 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3274 _preserved_marks_set.restore(&task_executor); 3275 3276 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3277 } 3278 3279 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3280 if (!_evacuation_failed) { 3281 _evacuation_failed = true; 3282 } 3283 3284 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3285 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3286 } 3287 3288 bool G1ParEvacuateFollowersClosure::offer_termination() { 3289 G1ParScanThreadState* const pss = par_scan_state(); 3290 start_term_time(); 3291 const bool res = terminator()->offer_termination(); 3292 end_term_time(); 3293 return res; 3294 } 3295 3296 void G1ParEvacuateFollowersClosure::do_void() { 3297 G1ParScanThreadState* const pss = par_scan_state(); 3298 pss->trim_queue(); 3299 do { 3300 pss->steal_and_trim_queue(queues()); 3301 } while (!offer_termination()); 3302 } 3303 3304 class G1ParTask : public AbstractGangTask { 3305 protected: 3306 G1CollectedHeap* _g1h; 3307 G1ParScanThreadStateSet* _pss; 3308 RefToScanQueueSet* _queues; 3309 G1RootProcessor* _root_processor; 3310 ParallelTaskTerminator _terminator; 3311 uint _n_workers; 3312 3313 public: 3314 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3315 : AbstractGangTask("G1 collection"), 3316 _g1h(g1h), 3317 _pss(per_thread_states), 3318 _queues(task_queues), 3319 _root_processor(root_processor), 3320 _terminator(n_workers, _queues), 3321 _n_workers(n_workers) 3322 {} 3323 3324 void work(uint worker_id) { 3325 if (worker_id >= _n_workers) return; // no work needed this round 3326 3327 double start_sec = os::elapsedTime(); 3328 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3329 3330 { 3331 ResourceMark rm; 3332 HandleMark hm; 3333 3334 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3335 3336 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3337 pss->set_ref_processor(rp); 3338 3339 double start_strong_roots_sec = os::elapsedTime(); 3340 3341 _root_processor->evacuate_roots(pss->closures(), worker_id); 3342 3343 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss); 3344 3345 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3346 // treating the nmethods visited to act as roots for concurrent marking. 3347 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3348 // objects copied by the current evacuation. 3349 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl, 3350 pss->closures()->weak_codeblobs(), 3351 worker_id); 3352 3353 _pss->add_cards_scanned(worker_id, cards_scanned); 3354 3355 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3356 3357 double term_sec = 0.0; 3358 size_t evac_term_attempts = 0; 3359 { 3360 double start = os::elapsedTime(); 3361 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3362 evac.do_void(); 3363 3364 evac_term_attempts = evac.term_attempts(); 3365 term_sec = evac.term_time(); 3366 double elapsed_sec = os::elapsedTime() - start; 3367 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3368 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3369 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3370 } 3371 3372 assert(pss->queue_is_empty(), "should be empty"); 3373 3374 if (log_is_enabled(Debug, gc, task, stats)) { 3375 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3376 size_t lab_waste; 3377 size_t lab_undo_waste; 3378 pss->waste(lab_waste, lab_undo_waste); 3379 _g1h->print_termination_stats(worker_id, 3380 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3381 strong_roots_sec * 1000.0, /* strong roots time */ 3382 term_sec * 1000.0, /* evac term time */ 3383 evac_term_attempts, /* evac term attempts */ 3384 lab_waste, /* alloc buffer waste */ 3385 lab_undo_waste /* undo waste */ 3386 ); 3387 } 3388 3389 // Close the inner scope so that the ResourceMark and HandleMark 3390 // destructors are executed here and are included as part of the 3391 // "GC Worker Time". 3392 } 3393 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3394 } 3395 }; 3396 3397 void G1CollectedHeap::print_termination_stats_hdr() { 3398 log_debug(gc, task, stats)("GC Termination Stats"); 3399 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3400 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3401 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3402 } 3403 3404 void G1CollectedHeap::print_termination_stats(uint worker_id, 3405 double elapsed_ms, 3406 double strong_roots_ms, 3407 double term_ms, 3408 size_t term_attempts, 3409 size_t alloc_buffer_waste, 3410 size_t undo_waste) const { 3411 log_debug(gc, task, stats) 3412 ("%3d %9.2f %9.2f %6.2f " 3413 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3414 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3415 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3416 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3417 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3418 alloc_buffer_waste * HeapWordSize / K, 3419 undo_waste * HeapWordSize / K); 3420 } 3421 3422 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3423 private: 3424 BoolObjectClosure* _is_alive; 3425 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3426 3427 int _initial_string_table_size; 3428 int _initial_symbol_table_size; 3429 3430 bool _process_strings; 3431 int _strings_processed; 3432 int _strings_removed; 3433 3434 bool _process_symbols; 3435 int _symbols_processed; 3436 int _symbols_removed; 3437 3438 bool _process_string_dedup; 3439 3440 public: 3441 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3442 AbstractGangTask("String/Symbol Unlinking"), 3443 _is_alive(is_alive), 3444 _dedup_closure(is_alive, NULL, false), 3445 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3446 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3447 _process_string_dedup(process_string_dedup) { 3448 3449 _initial_string_table_size = StringTable::the_table()->table_size(); 3450 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3451 if (process_strings) { 3452 StringTable::clear_parallel_claimed_index(); 3453 } 3454 if (process_symbols) { 3455 SymbolTable::clear_parallel_claimed_index(); 3456 } 3457 } 3458 3459 ~G1StringAndSymbolCleaningTask() { 3460 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3461 "claim value %d after unlink less than initial string table size %d", 3462 StringTable::parallel_claimed_index(), _initial_string_table_size); 3463 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3464 "claim value %d after unlink less than initial symbol table size %d", 3465 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3466 3467 log_info(gc, stringtable)( 3468 "Cleaned string and symbol table, " 3469 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3470 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3471 strings_processed(), strings_removed(), 3472 symbols_processed(), symbols_removed()); 3473 } 3474 3475 void work(uint worker_id) { 3476 int strings_processed = 0; 3477 int strings_removed = 0; 3478 int symbols_processed = 0; 3479 int symbols_removed = 0; 3480 if (_process_strings) { 3481 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3482 Atomic::add(strings_processed, &_strings_processed); 3483 Atomic::add(strings_removed, &_strings_removed); 3484 } 3485 if (_process_symbols) { 3486 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3487 Atomic::add(symbols_processed, &_symbols_processed); 3488 Atomic::add(symbols_removed, &_symbols_removed); 3489 } 3490 if (_process_string_dedup) { 3491 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3492 } 3493 } 3494 3495 size_t strings_processed() const { return (size_t)_strings_processed; } 3496 size_t strings_removed() const { return (size_t)_strings_removed; } 3497 3498 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3499 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3500 }; 3501 3502 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3503 private: 3504 static Monitor* _lock; 3505 3506 BoolObjectClosure* const _is_alive; 3507 const bool _unloading_occurred; 3508 const uint _num_workers; 3509 3510 // Variables used to claim nmethods. 3511 CompiledMethod* _first_nmethod; 3512 volatile CompiledMethod* _claimed_nmethod; 3513 3514 // The list of nmethods that need to be processed by the second pass. 3515 volatile CompiledMethod* _postponed_list; 3516 volatile uint _num_entered_barrier; 3517 3518 public: 3519 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3520 _is_alive(is_alive), 3521 _unloading_occurred(unloading_occurred), 3522 _num_workers(num_workers), 3523 _first_nmethod(NULL), 3524 _claimed_nmethod(NULL), 3525 _postponed_list(NULL), 3526 _num_entered_barrier(0) 3527 { 3528 CompiledMethod::increase_unloading_clock(); 3529 // Get first alive nmethod 3530 CompiledMethodIterator iter = CompiledMethodIterator(); 3531 if(iter.next_alive()) { 3532 _first_nmethod = iter.method(); 3533 } 3534 _claimed_nmethod = (volatile CompiledMethod*)_first_nmethod; 3535 } 3536 3537 ~G1CodeCacheUnloadingTask() { 3538 CodeCache::verify_clean_inline_caches(); 3539 3540 CodeCache::set_needs_cache_clean(false); 3541 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3542 3543 CodeCache::verify_icholder_relocations(); 3544 } 3545 3546 private: 3547 void add_to_postponed_list(CompiledMethod* nm) { 3548 CompiledMethod* old; 3549 do { 3550 old = (CompiledMethod*)_postponed_list; 3551 nm->set_unloading_next(old); 3552 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 3553 } 3554 3555 void clean_nmethod(CompiledMethod* nm) { 3556 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3557 3558 if (postponed) { 3559 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3560 add_to_postponed_list(nm); 3561 } 3562 3563 // Mark that this thread has been cleaned/unloaded. 3564 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3565 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3566 } 3567 3568 void clean_nmethod_postponed(CompiledMethod* nm) { 3569 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3570 } 3571 3572 static const int MaxClaimNmethods = 16; 3573 3574 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3575 CompiledMethod* first; 3576 CompiledMethodIterator last; 3577 3578 do { 3579 *num_claimed_nmethods = 0; 3580 3581 first = (CompiledMethod*)_claimed_nmethod; 3582 last = CompiledMethodIterator(first); 3583 3584 if (first != NULL) { 3585 3586 for (int i = 0; i < MaxClaimNmethods; i++) { 3587 if (!last.next_alive()) { 3588 break; 3589 } 3590 claimed_nmethods[i] = last.method(); 3591 (*num_claimed_nmethods)++; 3592 } 3593 } 3594 3595 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 3596 } 3597 3598 CompiledMethod* claim_postponed_nmethod() { 3599 CompiledMethod* claim; 3600 CompiledMethod* next; 3601 3602 do { 3603 claim = (CompiledMethod*)_postponed_list; 3604 if (claim == NULL) { 3605 return NULL; 3606 } 3607 3608 next = claim->unloading_next(); 3609 3610 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 3611 3612 return claim; 3613 } 3614 3615 public: 3616 // Mark that we're done with the first pass of nmethod cleaning. 3617 void barrier_mark(uint worker_id) { 3618 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3619 _num_entered_barrier++; 3620 if (_num_entered_barrier == _num_workers) { 3621 ml.notify_all(); 3622 } 3623 } 3624 3625 // See if we have to wait for the other workers to 3626 // finish their first-pass nmethod cleaning work. 3627 void barrier_wait(uint worker_id) { 3628 if (_num_entered_barrier < _num_workers) { 3629 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3630 while (_num_entered_barrier < _num_workers) { 3631 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3632 } 3633 } 3634 } 3635 3636 // Cleaning and unloading of nmethods. Some work has to be postponed 3637 // to the second pass, when we know which nmethods survive. 3638 void work_first_pass(uint worker_id) { 3639 // The first nmethods is claimed by the first worker. 3640 if (worker_id == 0 && _first_nmethod != NULL) { 3641 clean_nmethod(_first_nmethod); 3642 _first_nmethod = NULL; 3643 } 3644 3645 int num_claimed_nmethods; 3646 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3647 3648 while (true) { 3649 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3650 3651 if (num_claimed_nmethods == 0) { 3652 break; 3653 } 3654 3655 for (int i = 0; i < num_claimed_nmethods; i++) { 3656 clean_nmethod(claimed_nmethods[i]); 3657 } 3658 } 3659 } 3660 3661 void work_second_pass(uint worker_id) { 3662 CompiledMethod* nm; 3663 // Take care of postponed nmethods. 3664 while ((nm = claim_postponed_nmethod()) != NULL) { 3665 clean_nmethod_postponed(nm); 3666 } 3667 } 3668 }; 3669 3670 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3671 3672 class G1KlassCleaningTask : public StackObj { 3673 BoolObjectClosure* _is_alive; 3674 volatile jint _clean_klass_tree_claimed; 3675 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3676 3677 public: 3678 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3679 _is_alive(is_alive), 3680 _clean_klass_tree_claimed(0), 3681 _klass_iterator() { 3682 } 3683 3684 private: 3685 bool claim_clean_klass_tree_task() { 3686 if (_clean_klass_tree_claimed) { 3687 return false; 3688 } 3689 3690 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 3691 } 3692 3693 InstanceKlass* claim_next_klass() { 3694 Klass* klass; 3695 do { 3696 klass =_klass_iterator.next_klass(); 3697 } while (klass != NULL && !klass->is_instance_klass()); 3698 3699 // this can be null so don't call InstanceKlass::cast 3700 return static_cast<InstanceKlass*>(klass); 3701 } 3702 3703 public: 3704 3705 void clean_klass(InstanceKlass* ik) { 3706 ik->clean_weak_instanceklass_links(_is_alive); 3707 } 3708 3709 void work() { 3710 ResourceMark rm; 3711 3712 // One worker will clean the subklass/sibling klass tree. 3713 if (claim_clean_klass_tree_task()) { 3714 Klass::clean_subklass_tree(_is_alive); 3715 } 3716 3717 // All workers will help cleaning the classes, 3718 InstanceKlass* klass; 3719 while ((klass = claim_next_klass()) != NULL) { 3720 clean_klass(klass); 3721 } 3722 } 3723 }; 3724 3725 class G1ResolvedMethodCleaningTask : public StackObj { 3726 BoolObjectClosure* _is_alive; 3727 volatile jint _resolved_method_task_claimed; 3728 public: 3729 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) : 3730 _is_alive(is_alive), _resolved_method_task_claimed(0) {} 3731 3732 bool claim_resolved_method_task() { 3733 if (_resolved_method_task_claimed) { 3734 return false; 3735 } 3736 return Atomic::cmpxchg(1, (jint*)&_resolved_method_task_claimed, 0) == 0; 3737 } 3738 3739 // These aren't big, one thread can do it all. 3740 void work() { 3741 if (claim_resolved_method_task()) { 3742 ResolvedMethodTable::unlink(_is_alive); 3743 } 3744 } 3745 }; 3746 3747 3748 // To minimize the remark pause times, the tasks below are done in parallel. 3749 class G1ParallelCleaningTask : public AbstractGangTask { 3750 private: 3751 G1StringAndSymbolCleaningTask _string_symbol_task; 3752 G1CodeCacheUnloadingTask _code_cache_task; 3753 G1KlassCleaningTask _klass_cleaning_task; 3754 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task; 3755 3756 public: 3757 // The constructor is run in the VMThread. 3758 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3759 AbstractGangTask("Parallel Cleaning"), 3760 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3761 _code_cache_task(num_workers, is_alive, unloading_occurred), 3762 _klass_cleaning_task(is_alive), 3763 _resolved_method_cleaning_task(is_alive) { 3764 } 3765 3766 // The parallel work done by all worker threads. 3767 void work(uint worker_id) { 3768 // Do first pass of code cache cleaning. 3769 _code_cache_task.work_first_pass(worker_id); 3770 3771 // Let the threads mark that the first pass is done. 3772 _code_cache_task.barrier_mark(worker_id); 3773 3774 // Clean the Strings and Symbols. 3775 _string_symbol_task.work(worker_id); 3776 3777 // Clean unreferenced things in the ResolvedMethodTable 3778 _resolved_method_cleaning_task.work(); 3779 3780 // Wait for all workers to finish the first code cache cleaning pass. 3781 _code_cache_task.barrier_wait(worker_id); 3782 3783 // Do the second code cache cleaning work, which realize on 3784 // the liveness information gathered during the first pass. 3785 _code_cache_task.work_second_pass(worker_id); 3786 3787 // Clean all klasses that were not unloaded. 3788 _klass_cleaning_task.work(); 3789 } 3790 }; 3791 3792 3793 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3794 bool class_unloading_occurred) { 3795 uint n_workers = workers()->active_workers(); 3796 3797 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3798 workers()->run_task(&g1_unlink_task); 3799 } 3800 3801 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3802 bool process_strings, 3803 bool process_symbols, 3804 bool process_string_dedup) { 3805 if (!process_strings && !process_symbols && !process_string_dedup) { 3806 // Nothing to clean. 3807 return; 3808 } 3809 3810 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3811 workers()->run_task(&g1_unlink_task); 3812 3813 } 3814 3815 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3816 private: 3817 DirtyCardQueueSet* _queue; 3818 G1CollectedHeap* _g1h; 3819 public: 3820 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3821 _queue(queue), _g1h(g1h) { } 3822 3823 virtual void work(uint worker_id) { 3824 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3825 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3826 3827 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3828 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3829 3830 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3831 } 3832 }; 3833 3834 void G1CollectedHeap::redirty_logged_cards() { 3835 double redirty_logged_cards_start = os::elapsedTime(); 3836 3837 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3838 dirty_card_queue_set().reset_for_par_iteration(); 3839 workers()->run_task(&redirty_task); 3840 3841 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 3842 dcq.merge_bufferlists(&dirty_card_queue_set()); 3843 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3844 3845 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3846 } 3847 3848 // Weak Reference Processing support 3849 3850 // An always "is_alive" closure that is used to preserve referents. 3851 // If the object is non-null then it's alive. Used in the preservation 3852 // of referent objects that are pointed to by reference objects 3853 // discovered by the CM ref processor. 3854 class G1AlwaysAliveClosure: public BoolObjectClosure { 3855 G1CollectedHeap* _g1; 3856 public: 3857 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3858 bool do_object_b(oop p) { 3859 if (p != NULL) { 3860 return true; 3861 } 3862 return false; 3863 } 3864 }; 3865 3866 bool G1STWIsAliveClosure::do_object_b(oop p) { 3867 // An object is reachable if it is outside the collection set, 3868 // or is inside and copied. 3869 return !_g1->is_in_cset(p) || p->is_forwarded(); 3870 } 3871 3872 // Non Copying Keep Alive closure 3873 class G1KeepAliveClosure: public OopClosure { 3874 G1CollectedHeap* _g1; 3875 public: 3876 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3877 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3878 void do_oop(oop* p) { 3879 oop obj = *p; 3880 assert(obj != NULL, "the caller should have filtered out NULL values"); 3881 3882 const InCSetState cset_state = _g1->in_cset_state(obj); 3883 if (!cset_state.is_in_cset_or_humongous()) { 3884 return; 3885 } 3886 if (cset_state.is_in_cset()) { 3887 assert( obj->is_forwarded(), "invariant" ); 3888 *p = obj->forwardee(); 3889 } else { 3890 assert(!obj->is_forwarded(), "invariant" ); 3891 assert(cset_state.is_humongous(), 3892 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3893 _g1->set_humongous_is_live(obj); 3894 } 3895 } 3896 }; 3897 3898 // Copying Keep Alive closure - can be called from both 3899 // serial and parallel code as long as different worker 3900 // threads utilize different G1ParScanThreadState instances 3901 // and different queues. 3902 3903 class G1CopyingKeepAliveClosure: public OopClosure { 3904 G1CollectedHeap* _g1h; 3905 OopClosure* _copy_non_heap_obj_cl; 3906 G1ParScanThreadState* _par_scan_state; 3907 3908 public: 3909 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3910 OopClosure* non_heap_obj_cl, 3911 G1ParScanThreadState* pss): 3912 _g1h(g1h), 3913 _copy_non_heap_obj_cl(non_heap_obj_cl), 3914 _par_scan_state(pss) 3915 {} 3916 3917 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3918 virtual void do_oop( oop* p) { do_oop_work(p); } 3919 3920 template <class T> void do_oop_work(T* p) { 3921 oop obj = oopDesc::load_decode_heap_oop(p); 3922 3923 if (_g1h->is_in_cset_or_humongous(obj)) { 3924 // If the referent object has been forwarded (either copied 3925 // to a new location or to itself in the event of an 3926 // evacuation failure) then we need to update the reference 3927 // field and, if both reference and referent are in the G1 3928 // heap, update the RSet for the referent. 3929 // 3930 // If the referent has not been forwarded then we have to keep 3931 // it alive by policy. Therefore we have copy the referent. 3932 // 3933 // If the reference field is in the G1 heap then we can push 3934 // on the PSS queue. When the queue is drained (after each 3935 // phase of reference processing) the object and it's followers 3936 // will be copied, the reference field set to point to the 3937 // new location, and the RSet updated. Otherwise we need to 3938 // use the the non-heap or metadata closures directly to copy 3939 // the referent object and update the pointer, while avoiding 3940 // updating the RSet. 3941 3942 if (_g1h->is_in_g1_reserved(p)) { 3943 _par_scan_state->push_on_queue(p); 3944 } else { 3945 assert(!Metaspace::contains((const void*)p), 3946 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 3947 _copy_non_heap_obj_cl->do_oop(p); 3948 } 3949 } 3950 } 3951 }; 3952 3953 // Serial drain queue closure. Called as the 'complete_gc' 3954 // closure for each discovered list in some of the 3955 // reference processing phases. 3956 3957 class G1STWDrainQueueClosure: public VoidClosure { 3958 protected: 3959 G1CollectedHeap* _g1h; 3960 G1ParScanThreadState* _par_scan_state; 3961 3962 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3963 3964 public: 3965 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3966 _g1h(g1h), 3967 _par_scan_state(pss) 3968 { } 3969 3970 void do_void() { 3971 G1ParScanThreadState* const pss = par_scan_state(); 3972 pss->trim_queue(); 3973 } 3974 }; 3975 3976 // Parallel Reference Processing closures 3977 3978 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3979 // processing during G1 evacuation pauses. 3980 3981 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3982 private: 3983 G1CollectedHeap* _g1h; 3984 G1ParScanThreadStateSet* _pss; 3985 RefToScanQueueSet* _queues; 3986 WorkGang* _workers; 3987 uint _active_workers; 3988 3989 public: 3990 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3991 G1ParScanThreadStateSet* per_thread_states, 3992 WorkGang* workers, 3993 RefToScanQueueSet *task_queues, 3994 uint n_workers) : 3995 _g1h(g1h), 3996 _pss(per_thread_states), 3997 _queues(task_queues), 3998 _workers(workers), 3999 _active_workers(n_workers) 4000 { 4001 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 4002 } 4003 4004 // Executes the given task using concurrent marking worker threads. 4005 virtual void execute(ProcessTask& task); 4006 virtual void execute(EnqueueTask& task); 4007 }; 4008 4009 // Gang task for possibly parallel reference processing 4010 4011 class G1STWRefProcTaskProxy: public AbstractGangTask { 4012 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4013 ProcessTask& _proc_task; 4014 G1CollectedHeap* _g1h; 4015 G1ParScanThreadStateSet* _pss; 4016 RefToScanQueueSet* _task_queues; 4017 ParallelTaskTerminator* _terminator; 4018 4019 public: 4020 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4021 G1CollectedHeap* g1h, 4022 G1ParScanThreadStateSet* per_thread_states, 4023 RefToScanQueueSet *task_queues, 4024 ParallelTaskTerminator* terminator) : 4025 AbstractGangTask("Process reference objects in parallel"), 4026 _proc_task(proc_task), 4027 _g1h(g1h), 4028 _pss(per_thread_states), 4029 _task_queues(task_queues), 4030 _terminator(terminator) 4031 {} 4032 4033 virtual void work(uint worker_id) { 4034 // The reference processing task executed by a single worker. 4035 ResourceMark rm; 4036 HandleMark hm; 4037 4038 G1STWIsAliveClosure is_alive(_g1h); 4039 4040 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4041 pss->set_ref_processor(NULL); 4042 4043 // Keep alive closure. 4044 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4045 4046 // Complete GC closure 4047 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4048 4049 // Call the reference processing task's work routine. 4050 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4051 4052 // Note we cannot assert that the refs array is empty here as not all 4053 // of the processing tasks (specifically phase2 - pp2_work) execute 4054 // the complete_gc closure (which ordinarily would drain the queue) so 4055 // the queue may not be empty. 4056 } 4057 }; 4058 4059 // Driver routine for parallel reference processing. 4060 // Creates an instance of the ref processing gang 4061 // task and has the worker threads execute it. 4062 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4063 assert(_workers != NULL, "Need parallel worker threads."); 4064 4065 ParallelTaskTerminator terminator(_active_workers, _queues); 4066 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4067 4068 _workers->run_task(&proc_task_proxy); 4069 } 4070 4071 // Gang task for parallel reference enqueueing. 4072 4073 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4074 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4075 EnqueueTask& _enq_task; 4076 4077 public: 4078 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4079 AbstractGangTask("Enqueue reference objects in parallel"), 4080 _enq_task(enq_task) 4081 { } 4082 4083 virtual void work(uint worker_id) { 4084 _enq_task.work(worker_id); 4085 } 4086 }; 4087 4088 // Driver routine for parallel reference enqueueing. 4089 // Creates an instance of the ref enqueueing gang 4090 // task and has the worker threads execute it. 4091 4092 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4093 assert(_workers != NULL, "Need parallel worker threads."); 4094 4095 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4096 4097 _workers->run_task(&enq_task_proxy); 4098 } 4099 4100 // End of weak reference support closures 4101 4102 // Abstract task used to preserve (i.e. copy) any referent objects 4103 // that are in the collection set and are pointed to by reference 4104 // objects discovered by the CM ref processor. 4105 4106 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4107 protected: 4108 G1CollectedHeap* _g1h; 4109 G1ParScanThreadStateSet* _pss; 4110 RefToScanQueueSet* _queues; 4111 ParallelTaskTerminator _terminator; 4112 uint _n_workers; 4113 4114 public: 4115 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4116 AbstractGangTask("ParPreserveCMReferents"), 4117 _g1h(g1h), 4118 _pss(per_thread_states), 4119 _queues(task_queues), 4120 _terminator(workers, _queues), 4121 _n_workers(workers) 4122 { 4123 g1h->ref_processor_cm()->set_active_mt_degree(workers); 4124 } 4125 4126 void work(uint worker_id) { 4127 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4128 4129 ResourceMark rm; 4130 HandleMark hm; 4131 4132 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4133 pss->set_ref_processor(NULL); 4134 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4135 4136 // Is alive closure 4137 G1AlwaysAliveClosure always_alive(_g1h); 4138 4139 // Copying keep alive closure. Applied to referent objects that need 4140 // to be copied. 4141 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4142 4143 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4144 4145 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4146 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4147 4148 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4149 // So this must be true - but assert just in case someone decides to 4150 // change the worker ids. 4151 assert(worker_id < limit, "sanity"); 4152 assert(!rp->discovery_is_atomic(), "check this code"); 4153 4154 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4155 for (uint idx = worker_id; idx < limit; idx += stride) { 4156 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4157 4158 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4159 while (iter.has_next()) { 4160 // Since discovery is not atomic for the CM ref processor, we 4161 // can see some null referent objects. 4162 iter.load_ptrs(DEBUG_ONLY(true)); 4163 oop ref = iter.obj(); 4164 4165 // This will filter nulls. 4166 if (iter.is_referent_alive()) { 4167 iter.make_referent_alive(); 4168 } 4169 iter.move_to_next(); 4170 } 4171 } 4172 4173 // Drain the queue - which may cause stealing 4174 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4175 drain_queue.do_void(); 4176 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4177 assert(pss->queue_is_empty(), "should be"); 4178 } 4179 }; 4180 4181 void G1CollectedHeap::process_weak_jni_handles() { 4182 double ref_proc_start = os::elapsedTime(); 4183 4184 G1STWIsAliveClosure is_alive(this); 4185 G1KeepAliveClosure keep_alive(this); 4186 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 4187 4188 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4189 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4190 } 4191 4192 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4193 // Any reference objects, in the collection set, that were 'discovered' 4194 // by the CM ref processor should have already been copied (either by 4195 // applying the external root copy closure to the discovered lists, or 4196 // by following an RSet entry). 4197 // 4198 // But some of the referents, that are in the collection set, that these 4199 // reference objects point to may not have been copied: the STW ref 4200 // processor would have seen that the reference object had already 4201 // been 'discovered' and would have skipped discovering the reference, 4202 // but would not have treated the reference object as a regular oop. 4203 // As a result the copy closure would not have been applied to the 4204 // referent object. 4205 // 4206 // We need to explicitly copy these referent objects - the references 4207 // will be processed at the end of remarking. 4208 // 4209 // We also need to do this copying before we process the reference 4210 // objects discovered by the STW ref processor in case one of these 4211 // referents points to another object which is also referenced by an 4212 // object discovered by the STW ref processor. 4213 double preserve_cm_referents_time = 0.0; 4214 4215 // To avoid spawning task when there is no work to do, check that 4216 // a concurrent cycle is active and that some references have been 4217 // discovered. 4218 if (concurrent_mark()->cmThread()->during_cycle() && 4219 ref_processor_cm()->has_discovered_references()) { 4220 double preserve_cm_referents_start = os::elapsedTime(); 4221 uint no_of_gc_workers = workers()->active_workers(); 4222 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4223 per_thread_states, 4224 no_of_gc_workers, 4225 _task_queues); 4226 workers()->run_task(&keep_cm_referents); 4227 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4228 } 4229 4230 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4231 } 4232 4233 // Weak Reference processing during an evacuation pause (part 1). 4234 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4235 double ref_proc_start = os::elapsedTime(); 4236 4237 ReferenceProcessor* rp = _ref_processor_stw; 4238 assert(rp->discovery_enabled(), "should have been enabled"); 4239 4240 // Closure to test whether a referent is alive. 4241 G1STWIsAliveClosure is_alive(this); 4242 4243 // Even when parallel reference processing is enabled, the processing 4244 // of JNI refs is serial and performed serially by the current thread 4245 // rather than by a worker. The following PSS will be used for processing 4246 // JNI refs. 4247 4248 // Use only a single queue for this PSS. 4249 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4250 pss->set_ref_processor(NULL); 4251 assert(pss->queue_is_empty(), "pre-condition"); 4252 4253 // Keep alive closure. 4254 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4255 4256 // Serial Complete GC closure 4257 G1STWDrainQueueClosure drain_queue(this, pss); 4258 4259 // Setup the soft refs policy... 4260 rp->setup_policy(false); 4261 4262 ReferenceProcessorStats stats; 4263 if (!rp->processing_is_mt()) { 4264 // Serial reference processing... 4265 stats = rp->process_discovered_references(&is_alive, 4266 &keep_alive, 4267 &drain_queue, 4268 NULL, 4269 _gc_timer_stw); 4270 } else { 4271 uint no_of_gc_workers = workers()->active_workers(); 4272 4273 // Parallel reference processing 4274 assert(no_of_gc_workers <= rp->max_num_q(), 4275 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4276 no_of_gc_workers, rp->max_num_q()); 4277 4278 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4279 stats = rp->process_discovered_references(&is_alive, 4280 &keep_alive, 4281 &drain_queue, 4282 &par_task_executor, 4283 _gc_timer_stw); 4284 } 4285 4286 _gc_tracer_stw->report_gc_reference_stats(stats); 4287 4288 // We have completed copying any necessary live referent objects. 4289 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4290 4291 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4292 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4293 } 4294 4295 // Weak Reference processing during an evacuation pause (part 2). 4296 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4297 double ref_enq_start = os::elapsedTime(); 4298 4299 ReferenceProcessor* rp = _ref_processor_stw; 4300 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4301 4302 // Now enqueue any remaining on the discovered lists on to 4303 // the pending list. 4304 if (!rp->processing_is_mt()) { 4305 // Serial reference processing... 4306 rp->enqueue_discovered_references(); 4307 } else { 4308 // Parallel reference enqueueing 4309 4310 uint n_workers = workers()->active_workers(); 4311 4312 assert(n_workers <= rp->max_num_q(), 4313 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4314 n_workers, rp->max_num_q()); 4315 4316 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4317 rp->enqueue_discovered_references(&par_task_executor); 4318 } 4319 4320 rp->verify_no_references_recorded(); 4321 assert(!rp->discovery_enabled(), "should have been disabled"); 4322 4323 // FIXME 4324 // CM's reference processing also cleans up the string and symbol tables. 4325 // Should we do that here also? We could, but it is a serial operation 4326 // and could significantly increase the pause time. 4327 4328 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4329 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4330 } 4331 4332 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4333 double merge_pss_time_start = os::elapsedTime(); 4334 per_thread_states->flush(); 4335 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4336 } 4337 4338 void G1CollectedHeap::pre_evacuate_collection_set() { 4339 _expand_heap_after_alloc_failure = true; 4340 _evacuation_failed = false; 4341 4342 // Disable the hot card cache. 4343 _hot_card_cache->reset_hot_cache_claimed_index(); 4344 _hot_card_cache->set_use_cache(false); 4345 4346 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4347 _preserved_marks_set.assert_empty(); 4348 4349 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4350 4351 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4352 if (collector_state()->during_initial_mark_pause()) { 4353 double start_clear_claimed_marks = os::elapsedTime(); 4354 4355 ClassLoaderDataGraph::clear_claimed_marks(); 4356 4357 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4358 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4359 } 4360 } 4361 4362 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4363 // Should G1EvacuationFailureALot be in effect for this GC? 4364 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4365 4366 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4367 4368 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4369 4370 double start_par_time_sec = os::elapsedTime(); 4371 double end_par_time_sec; 4372 4373 { 4374 const uint n_workers = workers()->active_workers(); 4375 G1RootProcessor root_processor(this, n_workers); 4376 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4377 4378 print_termination_stats_hdr(); 4379 4380 workers()->run_task(&g1_par_task); 4381 end_par_time_sec = os::elapsedTime(); 4382 4383 // Closing the inner scope will execute the destructor 4384 // for the G1RootProcessor object. We record the current 4385 // elapsed time before closing the scope so that time 4386 // taken for the destructor is NOT included in the 4387 // reported parallel time. 4388 } 4389 4390 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4391 phase_times->record_par_time(par_time_ms); 4392 4393 double code_root_fixup_time_ms = 4394 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4395 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4396 } 4397 4398 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4399 // Process any discovered reference objects - we have 4400 // to do this _before_ we retire the GC alloc regions 4401 // as we may have to copy some 'reachable' referent 4402 // objects (and their reachable sub-graphs) that were 4403 // not copied during the pause. 4404 if (g1_policy()->should_process_references()) { 4405 preserve_cm_referents(per_thread_states); 4406 process_discovered_references(per_thread_states); 4407 } else { 4408 ref_processor_stw()->verify_no_references_recorded(); 4409 process_weak_jni_handles(); 4410 } 4411 4412 if (G1StringDedup::is_enabled()) { 4413 double fixup_start = os::elapsedTime(); 4414 4415 G1STWIsAliveClosure is_alive(this); 4416 G1KeepAliveClosure keep_alive(this); 4417 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4418 4419 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4420 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4421 } 4422 4423 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4424 4425 if (evacuation_failed()) { 4426 restore_after_evac_failure(); 4427 4428 // Reset the G1EvacuationFailureALot counters and flags 4429 // Note: the values are reset only when an actual 4430 // evacuation failure occurs. 4431 NOT_PRODUCT(reset_evacuation_should_fail();) 4432 } 4433 4434 _preserved_marks_set.assert_empty(); 4435 4436 // Enqueue any remaining references remaining on the STW 4437 // reference processor's discovered lists. We need to do 4438 // this after the card table is cleaned (and verified) as 4439 // the act of enqueueing entries on to the pending list 4440 // will log these updates (and dirty their associated 4441 // cards). We need these updates logged to update any 4442 // RSets. 4443 if (g1_policy()->should_process_references()) { 4444 enqueue_discovered_references(per_thread_states); 4445 } else { 4446 g1_policy()->phase_times()->record_ref_enq_time(0); 4447 } 4448 4449 _allocator->release_gc_alloc_regions(evacuation_info); 4450 4451 merge_per_thread_state_info(per_thread_states); 4452 4453 // Reset and re-enable the hot card cache. 4454 // Note the counts for the cards in the regions in the 4455 // collection set are reset when the collection set is freed. 4456 _hot_card_cache->reset_hot_cache(); 4457 _hot_card_cache->set_use_cache(true); 4458 4459 purge_code_root_memory(); 4460 4461 redirty_logged_cards(); 4462 #if defined(COMPILER2) || INCLUDE_JVMCI 4463 double start = os::elapsedTime(); 4464 DerivedPointerTable::update_pointers(); 4465 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4466 #endif 4467 g1_policy()->print_age_table(); 4468 } 4469 4470 void G1CollectedHeap::record_obj_copy_mem_stats() { 4471 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4472 4473 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4474 create_g1_evac_summary(&_old_evac_stats)); 4475 } 4476 4477 void G1CollectedHeap::free_region(HeapRegion* hr, 4478 FreeRegionList* free_list, 4479 bool skip_remset, 4480 bool skip_hot_card_cache, 4481 bool locked) { 4482 assert(!hr->is_free(), "the region should not be free"); 4483 assert(!hr->is_empty(), "the region should not be empty"); 4484 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4485 assert(free_list != NULL, "pre-condition"); 4486 4487 if (G1VerifyBitmaps) { 4488 MemRegion mr(hr->bottom(), hr->end()); 4489 concurrent_mark()->clearRangePrevBitmap(mr); 4490 } 4491 4492 // Clear the card counts for this region. 4493 // Note: we only need to do this if the region is not young 4494 // (since we don't refine cards in young regions). 4495 if (!skip_hot_card_cache && !hr->is_young()) { 4496 _hot_card_cache->reset_card_counts(hr); 4497 } 4498 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4499 free_list->add_ordered(hr); 4500 } 4501 4502 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4503 FreeRegionList* free_list, 4504 bool skip_remset) { 4505 assert(hr->is_humongous(), "this is only for humongous regions"); 4506 assert(free_list != NULL, "pre-condition"); 4507 hr->clear_humongous(); 4508 free_region(hr, free_list, skip_remset); 4509 } 4510 4511 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4512 const uint humongous_regions_removed) { 4513 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4514 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4515 _old_set.bulk_remove(old_regions_removed); 4516 _humongous_set.bulk_remove(humongous_regions_removed); 4517 } 4518 4519 } 4520 4521 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4522 assert(list != NULL, "list can't be null"); 4523 if (!list->is_empty()) { 4524 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4525 _hrm.insert_list_into_free_list(list); 4526 } 4527 } 4528 4529 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4530 decrease_used(bytes); 4531 } 4532 4533 class G1ParScrubRemSetTask: public AbstractGangTask { 4534 protected: 4535 G1RemSet* _g1rs; 4536 HeapRegionClaimer _hrclaimer; 4537 4538 public: 4539 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) : 4540 AbstractGangTask("G1 ScrubRS"), 4541 _g1rs(g1_rs), 4542 _hrclaimer(num_workers) { 4543 } 4544 4545 void work(uint worker_id) { 4546 _g1rs->scrub(worker_id, &_hrclaimer); 4547 } 4548 }; 4549 4550 void G1CollectedHeap::scrub_rem_set() { 4551 uint num_workers = workers()->active_workers(); 4552 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers); 4553 workers()->run_task(&g1_par_scrub_rs_task); 4554 } 4555 4556 class G1FreeCollectionSetTask : public AbstractGangTask { 4557 private: 4558 4559 // Closure applied to all regions in the collection set to do work that needs to 4560 // be done serially in a single thread. 4561 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4562 private: 4563 EvacuationInfo* _evacuation_info; 4564 const size_t* _surviving_young_words; 4565 4566 // Bytes used in successfully evacuated regions before the evacuation. 4567 size_t _before_used_bytes; 4568 // Bytes used in unsucessfully evacuated regions before the evacuation 4569 size_t _after_used_bytes; 4570 4571 size_t _bytes_allocated_in_old_since_last_gc; 4572 4573 size_t _failure_used_words; 4574 size_t _failure_waste_words; 4575 4576 FreeRegionList _local_free_list; 4577 public: 4578 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4579 HeapRegionClosure(), 4580 _evacuation_info(evacuation_info), 4581 _surviving_young_words(surviving_young_words), 4582 _before_used_bytes(0), 4583 _after_used_bytes(0), 4584 _bytes_allocated_in_old_since_last_gc(0), 4585 _failure_used_words(0), 4586 _failure_waste_words(0), 4587 _local_free_list("Local Region List for CSet Freeing") { 4588 } 4589 4590 virtual bool doHeapRegion(HeapRegion* r) { 4591 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4592 4593 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4594 g1h->clear_in_cset(r); 4595 4596 if (r->is_young()) { 4597 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4598 "Young index %d is wrong for region %u of type %s with %u young regions", 4599 r->young_index_in_cset(), 4600 r->hrm_index(), 4601 r->get_type_str(), 4602 g1h->collection_set()->young_region_length()); 4603 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4604 r->record_surv_words_in_group(words_survived); 4605 } 4606 4607 if (!r->evacuation_failed()) { 4608 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4609 _before_used_bytes += r->used(); 4610 g1h->free_region(r, 4611 &_local_free_list, 4612 true, /* skip_remset */ 4613 true, /* skip_hot_card_cache */ 4614 true /* locked */); 4615 } else { 4616 r->uninstall_surv_rate_group(); 4617 r->set_young_index_in_cset(-1); 4618 r->set_evacuation_failed(false); 4619 // When moving a young gen region to old gen, we "allocate" that whole region 4620 // there. This is in addition to any already evacuated objects. Notify the 4621 // policy about that. 4622 // Old gen regions do not cause an additional allocation: both the objects 4623 // still in the region and the ones already moved are accounted for elsewhere. 4624 if (r->is_young()) { 4625 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4626 } 4627 // The region is now considered to be old. 4628 r->set_old(); 4629 // Do some allocation statistics accounting. Regions that failed evacuation 4630 // are always made old, so there is no need to update anything in the young 4631 // gen statistics, but we need to update old gen statistics. 4632 size_t used_words = r->marked_bytes() / HeapWordSize; 4633 4634 _failure_used_words += used_words; 4635 _failure_waste_words += HeapRegion::GrainWords - used_words; 4636 4637 g1h->old_set_add(r); 4638 _after_used_bytes += r->used(); 4639 } 4640 return false; 4641 } 4642 4643 void complete_work() { 4644 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4645 4646 _evacuation_info->set_regions_freed(_local_free_list.length()); 4647 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4648 4649 g1h->prepend_to_freelist(&_local_free_list); 4650 g1h->decrement_summary_bytes(_before_used_bytes); 4651 4652 G1Policy* policy = g1h->g1_policy(); 4653 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4654 4655 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4656 } 4657 }; 4658 4659 G1CollectionSet* _collection_set; 4660 G1SerialFreeCollectionSetClosure _cl; 4661 const size_t* _surviving_young_words; 4662 4663 size_t _rs_lengths; 4664 4665 volatile jint _serial_work_claim; 4666 4667 struct WorkItem { 4668 uint region_idx; 4669 bool is_young; 4670 bool evacuation_failed; 4671 4672 WorkItem(HeapRegion* r) { 4673 region_idx = r->hrm_index(); 4674 is_young = r->is_young(); 4675 evacuation_failed = r->evacuation_failed(); 4676 } 4677 }; 4678 4679 volatile size_t _parallel_work_claim; 4680 size_t _num_work_items; 4681 WorkItem* _work_items; 4682 4683 void do_serial_work() { 4684 // Need to grab the lock to be allowed to modify the old region list. 4685 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4686 _collection_set->iterate(&_cl); 4687 } 4688 4689 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4690 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4691 4692 HeapRegion* r = g1h->region_at(region_idx); 4693 assert(!g1h->is_on_master_free_list(r), "sanity"); 4694 4695 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4696 4697 if (!is_young) { 4698 g1h->_hot_card_cache->reset_card_counts(r); 4699 } 4700 4701 if (!evacuation_failed) { 4702 r->rem_set()->clear_locked(); 4703 } 4704 } 4705 4706 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4707 private: 4708 size_t _cur_idx; 4709 WorkItem* _work_items; 4710 public: 4711 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4712 4713 virtual bool doHeapRegion(HeapRegion* r) { 4714 _work_items[_cur_idx++] = WorkItem(r); 4715 return false; 4716 } 4717 }; 4718 4719 void prepare_work() { 4720 G1PrepareFreeCollectionSetClosure cl(_work_items); 4721 _collection_set->iterate(&cl); 4722 } 4723 4724 void complete_work() { 4725 _cl.complete_work(); 4726 4727 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4728 policy->record_max_rs_lengths(_rs_lengths); 4729 policy->cset_regions_freed(); 4730 } 4731 public: 4732 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4733 AbstractGangTask("G1 Free Collection Set"), 4734 _cl(evacuation_info, surviving_young_words), 4735 _collection_set(collection_set), 4736 _surviving_young_words(surviving_young_words), 4737 _serial_work_claim(0), 4738 _rs_lengths(0), 4739 _parallel_work_claim(0), 4740 _num_work_items(collection_set->region_length()), 4741 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4742 prepare_work(); 4743 } 4744 4745 ~G1FreeCollectionSetTask() { 4746 complete_work(); 4747 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4748 } 4749 4750 // Chunk size for work distribution. The chosen value has been determined experimentally 4751 // to be a good tradeoff between overhead and achievable parallelism. 4752 static uint chunk_size() { return 32; } 4753 4754 virtual void work(uint worker_id) { 4755 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4756 4757 // Claim serial work. 4758 if (_serial_work_claim == 0) { 4759 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4760 if (value == 0) { 4761 double serial_time = os::elapsedTime(); 4762 do_serial_work(); 4763 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4764 } 4765 } 4766 4767 // Start parallel work. 4768 double young_time = 0.0; 4769 bool has_young_time = false; 4770 double non_young_time = 0.0; 4771 bool has_non_young_time = false; 4772 4773 while (true) { 4774 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4775 size_t cur = end - chunk_size(); 4776 4777 if (cur >= _num_work_items) { 4778 break; 4779 } 4780 4781 double start_time = os::elapsedTime(); 4782 4783 end = MIN2(end, _num_work_items); 4784 4785 for (; cur < end; cur++) { 4786 bool is_young = _work_items[cur].is_young; 4787 4788 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4789 4790 double end_time = os::elapsedTime(); 4791 double time_taken = end_time - start_time; 4792 if (is_young) { 4793 young_time += time_taken; 4794 has_young_time = true; 4795 } else { 4796 non_young_time += time_taken; 4797 has_non_young_time = true; 4798 } 4799 start_time = end_time; 4800 } 4801 } 4802 4803 if (has_young_time) { 4804 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4805 } 4806 if (has_non_young_time) { 4807 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time); 4808 } 4809 } 4810 }; 4811 4812 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4813 _eden.clear(); 4814 4815 double free_cset_start_time = os::elapsedTime(); 4816 4817 { 4818 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4819 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4820 4821 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4822 4823 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4824 cl.name(), 4825 num_workers, 4826 _collection_set.region_length()); 4827 workers()->run_task(&cl, num_workers); 4828 } 4829 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4830 4831 collection_set->clear(); 4832 } 4833 4834 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4835 private: 4836 FreeRegionList* _free_region_list; 4837 HeapRegionSet* _proxy_set; 4838 uint _humongous_objects_reclaimed; 4839 uint _humongous_regions_reclaimed; 4840 size_t _freed_bytes; 4841 public: 4842 4843 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4844 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4845 } 4846 4847 virtual bool doHeapRegion(HeapRegion* r) { 4848 if (!r->is_starts_humongous()) { 4849 return false; 4850 } 4851 4852 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4853 4854 oop obj = (oop)r->bottom(); 4855 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 4856 4857 // The following checks whether the humongous object is live are sufficient. 4858 // The main additional check (in addition to having a reference from the roots 4859 // or the young gen) is whether the humongous object has a remembered set entry. 4860 // 4861 // A humongous object cannot be live if there is no remembered set for it 4862 // because: 4863 // - there can be no references from within humongous starts regions referencing 4864 // the object because we never allocate other objects into them. 4865 // (I.e. there are no intra-region references that may be missed by the 4866 // remembered set) 4867 // - as soon there is a remembered set entry to the humongous starts region 4868 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4869 // until the end of a concurrent mark. 4870 // 4871 // It is not required to check whether the object has been found dead by marking 4872 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4873 // all objects allocated during that time are considered live. 4874 // SATB marking is even more conservative than the remembered set. 4875 // So if at this point in the collection there is no remembered set entry, 4876 // nobody has a reference to it. 4877 // At the start of collection we flush all refinement logs, and remembered sets 4878 // are completely up-to-date wrt to references to the humongous object. 4879 // 4880 // Other implementation considerations: 4881 // - never consider object arrays at this time because they would pose 4882 // considerable effort for cleaning up the the remembered sets. This is 4883 // required because stale remembered sets might reference locations that 4884 // are currently allocated into. 4885 uint region_idx = r->hrm_index(); 4886 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4887 !r->rem_set()->is_empty()) { 4888 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", 4889 region_idx, 4890 (size_t)obj->size() * HeapWordSize, 4891 p2i(r->bottom()), 4892 r->rem_set()->occupied(), 4893 r->rem_set()->strong_code_roots_list_length(), 4894 next_bitmap->isMarked(r->bottom()), 4895 g1h->is_humongous_reclaim_candidate(region_idx), 4896 obj->is_typeArray() 4897 ); 4898 return false; 4899 } 4900 4901 guarantee(obj->is_typeArray(), 4902 "Only eagerly reclaiming type arrays is supported, but the object " 4903 PTR_FORMAT " is not.", p2i(r->bottom())); 4904 4905 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", 4906 region_idx, 4907 (size_t)obj->size() * HeapWordSize, 4908 p2i(r->bottom()), 4909 r->rem_set()->occupied(), 4910 r->rem_set()->strong_code_roots_list_length(), 4911 next_bitmap->isMarked(r->bottom()), 4912 g1h->is_humongous_reclaim_candidate(region_idx), 4913 obj->is_typeArray() 4914 ); 4915 4916 // Need to clear mark bit of the humongous object if already set. 4917 if (next_bitmap->isMarked(r->bottom())) { 4918 next_bitmap->clear(r->bottom()); 4919 } 4920 _humongous_objects_reclaimed++; 4921 do { 4922 HeapRegion* next = g1h->next_region_in_humongous(r); 4923 _freed_bytes += r->used(); 4924 r->set_containing_set(NULL); 4925 _humongous_regions_reclaimed++; 4926 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ ); 4927 r = next; 4928 } while (r != NULL); 4929 4930 return false; 4931 } 4932 4933 uint humongous_objects_reclaimed() { 4934 return _humongous_objects_reclaimed; 4935 } 4936 4937 uint humongous_regions_reclaimed() { 4938 return _humongous_regions_reclaimed; 4939 } 4940 4941 size_t bytes_freed() const { 4942 return _freed_bytes; 4943 } 4944 }; 4945 4946 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4947 assert_at_safepoint(true); 4948 4949 if (!G1EagerReclaimHumongousObjects || 4950 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4951 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4952 return; 4953 } 4954 4955 double start_time = os::elapsedTime(); 4956 4957 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4958 4959 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4960 heap_region_iterate(&cl); 4961 4962 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4963 4964 G1HRPrinter* hrp = hr_printer(); 4965 if (hrp->is_active()) { 4966 FreeRegionListIterator iter(&local_cleanup_list); 4967 while (iter.more_available()) { 4968 HeapRegion* hr = iter.get_next(); 4969 hrp->cleanup(hr); 4970 } 4971 } 4972 4973 prepend_to_freelist(&local_cleanup_list); 4974 decrement_summary_bytes(cl.bytes_freed()); 4975 4976 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4977 cl.humongous_objects_reclaimed()); 4978 } 4979 4980 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4981 public: 4982 virtual bool doHeapRegion(HeapRegion* r) { 4983 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4984 G1CollectedHeap::heap()->clear_in_cset(r); 4985 r->set_young_index_in_cset(-1); 4986 return false; 4987 } 4988 }; 4989 4990 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4991 G1AbandonCollectionSetClosure cl; 4992 collection_set->iterate(&cl); 4993 4994 collection_set->clear(); 4995 collection_set->stop_incremental_building(); 4996 } 4997 4998 void G1CollectedHeap::set_free_regions_coming() { 4999 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 5000 5001 assert(!free_regions_coming(), "pre-condition"); 5002 _free_regions_coming = true; 5003 } 5004 5005 void G1CollectedHeap::reset_free_regions_coming() { 5006 assert(free_regions_coming(), "pre-condition"); 5007 5008 { 5009 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5010 _free_regions_coming = false; 5011 SecondaryFreeList_lock->notify_all(); 5012 } 5013 5014 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 5015 } 5016 5017 void G1CollectedHeap::wait_while_free_regions_coming() { 5018 // Most of the time we won't have to wait, so let's do a quick test 5019 // first before we take the lock. 5020 if (!free_regions_coming()) { 5021 return; 5022 } 5023 5024 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 5025 5026 { 5027 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5028 while (free_regions_coming()) { 5029 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5030 } 5031 } 5032 5033 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 5034 } 5035 5036 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5037 return _allocator->is_retained_old_region(hr); 5038 } 5039 5040 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5041 _eden.add(hr); 5042 _g1_policy->set_region_eden(hr); 5043 } 5044 5045 #ifdef ASSERT 5046 5047 class NoYoungRegionsClosure: public HeapRegionClosure { 5048 private: 5049 bool _success; 5050 public: 5051 NoYoungRegionsClosure() : _success(true) { } 5052 bool doHeapRegion(HeapRegion* r) { 5053 if (r->is_young()) { 5054 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5055 p2i(r->bottom()), p2i(r->end())); 5056 _success = false; 5057 } 5058 return false; 5059 } 5060 bool success() { return _success; } 5061 }; 5062 5063 bool G1CollectedHeap::check_young_list_empty() { 5064 bool ret = (young_regions_count() == 0); 5065 5066 NoYoungRegionsClosure closure; 5067 heap_region_iterate(&closure); 5068 ret = ret && closure.success(); 5069 5070 return ret; 5071 } 5072 5073 #endif // ASSERT 5074 5075 class TearDownRegionSetsClosure : public HeapRegionClosure { 5076 private: 5077 HeapRegionSet *_old_set; 5078 5079 public: 5080 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5081 5082 bool doHeapRegion(HeapRegion* r) { 5083 if (r->is_old()) { 5084 _old_set->remove(r); 5085 } else if(r->is_young()) { 5086 r->uninstall_surv_rate_group(); 5087 } else { 5088 // We ignore free regions, we'll empty the free list afterwards. 5089 // We ignore humongous regions, we're not tearing down the 5090 // humongous regions set. 5091 assert(r->is_free() || r->is_humongous(), 5092 "it cannot be another type"); 5093 } 5094 return false; 5095 } 5096 5097 ~TearDownRegionSetsClosure() { 5098 assert(_old_set->is_empty(), "post-condition"); 5099 } 5100 }; 5101 5102 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5103 assert_at_safepoint(true /* should_be_vm_thread */); 5104 5105 if (!free_list_only) { 5106 TearDownRegionSetsClosure cl(&_old_set); 5107 heap_region_iterate(&cl); 5108 5109 // Note that emptying the _young_list is postponed and instead done as 5110 // the first step when rebuilding the regions sets again. The reason for 5111 // this is that during a full GC string deduplication needs to know if 5112 // a collected region was young or old when the full GC was initiated. 5113 } 5114 _hrm.remove_all_free_regions(); 5115 } 5116 5117 void G1CollectedHeap::increase_used(size_t bytes) { 5118 _summary_bytes_used += bytes; 5119 } 5120 5121 void G1CollectedHeap::decrease_used(size_t bytes) { 5122 assert(_summary_bytes_used >= bytes, 5123 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5124 _summary_bytes_used, bytes); 5125 _summary_bytes_used -= bytes; 5126 } 5127 5128 void G1CollectedHeap::set_used(size_t bytes) { 5129 _summary_bytes_used = bytes; 5130 } 5131 5132 class RebuildRegionSetsClosure : public HeapRegionClosure { 5133 private: 5134 bool _free_list_only; 5135 HeapRegionSet* _old_set; 5136 HeapRegionManager* _hrm; 5137 size_t _total_used; 5138 5139 public: 5140 RebuildRegionSetsClosure(bool free_list_only, 5141 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5142 _free_list_only(free_list_only), 5143 _old_set(old_set), _hrm(hrm), _total_used(0) { 5144 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5145 if (!free_list_only) { 5146 assert(_old_set->is_empty(), "pre-condition"); 5147 } 5148 } 5149 5150 bool doHeapRegion(HeapRegion* r) { 5151 if (r->is_empty()) { 5152 // Add free regions to the free list 5153 r->set_free(); 5154 r->set_allocation_context(AllocationContext::system()); 5155 _hrm->insert_into_free_list(r); 5156 } else if (!_free_list_only) { 5157 5158 if (r->is_humongous()) { 5159 // We ignore humongous regions. We left the humongous set unchanged. 5160 } else { 5161 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 5162 // We now consider all regions old, so register as such. Leave 5163 // archive regions set that way, however, while still adding 5164 // them to the old set. 5165 if (!r->is_archive()) { 5166 r->set_old(); 5167 } 5168 _old_set->add(r); 5169 } 5170 _total_used += r->used(); 5171 } 5172 5173 return false; 5174 } 5175 5176 size_t total_used() { 5177 return _total_used; 5178 } 5179 }; 5180 5181 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5182 assert_at_safepoint(true /* should_be_vm_thread */); 5183 5184 if (!free_list_only) { 5185 _eden.clear(); 5186 _survivor.clear(); 5187 } 5188 5189 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5190 heap_region_iterate(&cl); 5191 5192 if (!free_list_only) { 5193 set_used(cl.total_used()); 5194 if (_archive_allocator != NULL) { 5195 _archive_allocator->clear_used(); 5196 } 5197 } 5198 assert(used_unlocked() == recalculate_used(), 5199 "inconsistent used_unlocked(), " 5200 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5201 used_unlocked(), recalculate_used()); 5202 } 5203 5204 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 5205 _refine_cte_cl->set_concurrent(concurrent); 5206 } 5207 5208 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5209 HeapRegion* hr = heap_region_containing(p); 5210 return hr->is_in(p); 5211 } 5212 5213 // Methods for the mutator alloc region 5214 5215 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5216 bool force) { 5217 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5218 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 5219 if (force || should_allocate) { 5220 HeapRegion* new_alloc_region = new_region(word_size, 5221 false /* is_old */, 5222 false /* do_expand */); 5223 if (new_alloc_region != NULL) { 5224 set_region_short_lived_locked(new_alloc_region); 5225 _hr_printer.alloc(new_alloc_region, !should_allocate); 5226 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5227 return new_alloc_region; 5228 } 5229 } 5230 return NULL; 5231 } 5232 5233 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5234 size_t allocated_bytes) { 5235 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5236 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5237 5238 collection_set()->add_eden_region(alloc_region); 5239 increase_used(allocated_bytes); 5240 _hr_printer.retire(alloc_region); 5241 // We update the eden sizes here, when the region is retired, 5242 // instead of when it's allocated, since this is the point that its 5243 // used space has been recored in _summary_bytes_used. 5244 g1mm()->update_eden_size(); 5245 } 5246 5247 // Methods for the GC alloc regions 5248 5249 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 5250 if (dest.is_old()) { 5251 return true; 5252 } else { 5253 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 5254 } 5255 } 5256 5257 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 5258 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5259 5260 if (!has_more_regions(dest)) { 5261 return NULL; 5262 } 5263 5264 const bool is_survivor = dest.is_young(); 5265 5266 HeapRegion* new_alloc_region = new_region(word_size, 5267 !is_survivor, 5268 true /* do_expand */); 5269 if (new_alloc_region != NULL) { 5270 // We really only need to do this for old regions given that we 5271 // should never scan survivors. But it doesn't hurt to do it 5272 // for survivors too. 5273 new_alloc_region->record_timestamp(); 5274 if (is_survivor) { 5275 new_alloc_region->set_survivor(); 5276 _survivor.add(new_alloc_region); 5277 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5278 } else { 5279 new_alloc_region->set_old(); 5280 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5281 } 5282 _hr_printer.alloc(new_alloc_region); 5283 bool during_im = collector_state()->during_initial_mark_pause(); 5284 new_alloc_region->note_start_of_copying(during_im); 5285 return new_alloc_region; 5286 } 5287 return NULL; 5288 } 5289 5290 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5291 size_t allocated_bytes, 5292 InCSetState dest) { 5293 bool during_im = collector_state()->during_initial_mark_pause(); 5294 alloc_region->note_end_of_copying(during_im); 5295 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5296 if (dest.is_old()) { 5297 _old_set.add(alloc_region); 5298 } 5299 _hr_printer.retire(alloc_region); 5300 } 5301 5302 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5303 bool expanded = false; 5304 uint index = _hrm.find_highest_free(&expanded); 5305 5306 if (index != G1_NO_HRM_INDEX) { 5307 if (expanded) { 5308 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5309 HeapRegion::GrainWords * HeapWordSize); 5310 } 5311 _hrm.allocate_free_regions_starting_at(index, 1); 5312 return region_at(index); 5313 } 5314 return NULL; 5315 } 5316 5317 // Optimized nmethod scanning 5318 5319 class RegisterNMethodOopClosure: public OopClosure { 5320 G1CollectedHeap* _g1h; 5321 nmethod* _nm; 5322 5323 template <class T> void do_oop_work(T* p) { 5324 T heap_oop = oopDesc::load_heap_oop(p); 5325 if (!oopDesc::is_null(heap_oop)) { 5326 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5327 HeapRegion* hr = _g1h->heap_region_containing(obj); 5328 assert(!hr->is_continues_humongous(), 5329 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5330 " starting at " HR_FORMAT, 5331 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5332 5333 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5334 hr->add_strong_code_root_locked(_nm); 5335 } 5336 } 5337 5338 public: 5339 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5340 _g1h(g1h), _nm(nm) {} 5341 5342 void do_oop(oop* p) { do_oop_work(p); } 5343 void do_oop(narrowOop* p) { do_oop_work(p); } 5344 }; 5345 5346 class UnregisterNMethodOopClosure: public OopClosure { 5347 G1CollectedHeap* _g1h; 5348 nmethod* _nm; 5349 5350 template <class T> void do_oop_work(T* p) { 5351 T heap_oop = oopDesc::load_heap_oop(p); 5352 if (!oopDesc::is_null(heap_oop)) { 5353 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5354 HeapRegion* hr = _g1h->heap_region_containing(obj); 5355 assert(!hr->is_continues_humongous(), 5356 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5357 " starting at " HR_FORMAT, 5358 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5359 5360 hr->remove_strong_code_root(_nm); 5361 } 5362 } 5363 5364 public: 5365 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5366 _g1h(g1h), _nm(nm) {} 5367 5368 void do_oop(oop* p) { do_oop_work(p); } 5369 void do_oop(narrowOop* p) { do_oop_work(p); } 5370 }; 5371 5372 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5373 CollectedHeap::register_nmethod(nm); 5374 5375 guarantee(nm != NULL, "sanity"); 5376 RegisterNMethodOopClosure reg_cl(this, nm); 5377 nm->oops_do(®_cl); 5378 } 5379 5380 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5381 CollectedHeap::unregister_nmethod(nm); 5382 5383 guarantee(nm != NULL, "sanity"); 5384 UnregisterNMethodOopClosure reg_cl(this, nm); 5385 nm->oops_do(®_cl, true); 5386 } 5387 5388 void G1CollectedHeap::purge_code_root_memory() { 5389 double purge_start = os::elapsedTime(); 5390 G1CodeRootSet::purge(); 5391 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5392 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5393 } 5394 5395 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5396 G1CollectedHeap* _g1h; 5397 5398 public: 5399 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5400 _g1h(g1h) {} 5401 5402 void do_code_blob(CodeBlob* cb) { 5403 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5404 if (nm == NULL) { 5405 return; 5406 } 5407 5408 if (ScavengeRootsInCode) { 5409 _g1h->register_nmethod(nm); 5410 } 5411 } 5412 }; 5413 5414 void G1CollectedHeap::rebuild_strong_code_roots() { 5415 RebuildStrongCodeRootClosure blob_cl(this); 5416 CodeCache::blobs_do(&blob_cl); 5417 }