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/align.hpp" 84 #include "utilities/globalDefinitions.hpp" 85 #include "utilities/stack.inline.hpp" 86 87 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 88 89 // INVARIANTS/NOTES 90 // 91 // All allocation activity covered by the G1CollectedHeap interface is 92 // serialized by acquiring the HeapLock. This happens in mem_allocate 93 // and allocate_new_tlab, which are the "entry" points to the 94 // allocation code from the rest of the JVM. (Note that this does not 95 // apply to TLAB allocation, which is not part of this interface: it 96 // is done by clients of this interface.) 97 98 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 99 private: 100 size_t _num_dirtied; 101 G1CollectedHeap* _g1h; 102 G1SATBCardTableLoggingModRefBS* _g1_bs; 103 104 HeapRegion* region_for_card(jbyte* card_ptr) const { 105 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr)); 106 } 107 108 bool will_become_free(HeapRegion* hr) const { 109 // A region will be freed by free_collection_set if the region is in the 110 // collection set and has not had an evacuation failure. 111 return _g1h->is_in_cset(hr) && !hr->evacuation_failed(); 112 } 113 114 public: 115 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(), 116 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { } 117 118 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 119 HeapRegion* hr = region_for_card(card_ptr); 120 121 // Should only dirty cards in regions that won't be freed. 122 if (!will_become_free(hr)) { 123 *card_ptr = CardTableModRefBS::dirty_card_val(); 124 _num_dirtied++; 125 } 126 127 return true; 128 } 129 130 size_t num_dirtied() const { return _num_dirtied; } 131 }; 132 133 134 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 135 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 136 } 137 138 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 139 // The from card cache is not the memory that is actually committed. So we cannot 140 // take advantage of the zero_filled parameter. 141 reset_from_card_cache(start_idx, num_regions); 142 } 143 144 // Returns true if the reference points to an object that 145 // can move in an incremental collection. 146 bool G1CollectedHeap::is_scavengable(const void* p) { 147 HeapRegion* hr = heap_region_containing(p); 148 return !hr->is_pinned(); 149 } 150 151 // Private methods. 152 153 HeapRegion* 154 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 155 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 156 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 157 if (!_secondary_free_list.is_empty()) { 158 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 159 "secondary_free_list has %u entries", 160 _secondary_free_list.length()); 161 // It looks as if there are free regions available on the 162 // secondary_free_list. Let's move them to the free_list and try 163 // again to allocate from it. 164 append_secondary_free_list(); 165 166 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 167 "empty we should have moved at least one entry to the free_list"); 168 HeapRegion* res = _hrm.allocate_free_region(is_old); 169 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 170 "allocated " HR_FORMAT " from secondary_free_list", 171 HR_FORMAT_PARAMS(res)); 172 return res; 173 } 174 175 // Wait here until we get notified either when (a) there are no 176 // more free regions coming or (b) some regions have been moved on 177 // the secondary_free_list. 178 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 179 } 180 181 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 182 "could not allocate from secondary_free_list"); 183 return NULL; 184 } 185 186 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 187 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 188 "the only time we use this to allocate a humongous region is " 189 "when we are allocating a single humongous region"); 190 191 HeapRegion* res; 192 if (G1StressConcRegionFreeing) { 193 if (!_secondary_free_list.is_empty()) { 194 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 195 "forced to look at the secondary_free_list"); 196 res = new_region_try_secondary_free_list(is_old); 197 if (res != NULL) { 198 return res; 199 } 200 } 201 } 202 203 res = _hrm.allocate_free_region(is_old); 204 205 if (res == NULL) { 206 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 207 "res == NULL, trying the secondary_free_list"); 208 res = new_region_try_secondary_free_list(is_old); 209 } 210 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 211 // Currently, only attempts to allocate GC alloc regions set 212 // do_expand to true. So, we should only reach here during a 213 // safepoint. If this assumption changes we might have to 214 // reconsider the use of _expand_heap_after_alloc_failure. 215 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 216 217 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 218 word_size * HeapWordSize); 219 220 if (expand(word_size * HeapWordSize)) { 221 // Given that expand() succeeded in expanding the heap, and we 222 // always expand the heap by an amount aligned to the heap 223 // region size, the free list should in theory not be empty. 224 // In either case allocate_free_region() will check for NULL. 225 res = _hrm.allocate_free_region(is_old); 226 } else { 227 _expand_heap_after_alloc_failure = false; 228 } 229 } 230 return res; 231 } 232 233 HeapWord* 234 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 235 uint num_regions, 236 size_t word_size, 237 AllocationContext_t context) { 238 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 239 assert(is_humongous(word_size), "word_size should be humongous"); 240 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 241 242 // Index of last region in the series. 243 uint last = first + num_regions - 1; 244 245 // We need to initialize the region(s) we just discovered. This is 246 // a bit tricky given that it can happen concurrently with 247 // refinement threads refining cards on these regions and 248 // potentially wanting to refine the BOT as they are scanning 249 // those cards (this can happen shortly after a cleanup; see CR 250 // 6991377). So we have to set up the region(s) carefully and in 251 // a specific order. 252 253 // The word size sum of all the regions we will allocate. 254 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 255 assert(word_size <= word_size_sum, "sanity"); 256 257 // This will be the "starts humongous" region. 258 HeapRegion* first_hr = region_at(first); 259 // The header of the new object will be placed at the bottom of 260 // the first region. 261 HeapWord* new_obj = first_hr->bottom(); 262 // This will be the new top of the new object. 263 HeapWord* obj_top = new_obj + word_size; 264 265 // First, we need to zero the header of the space that we will be 266 // allocating. When we update top further down, some refinement 267 // threads might try to scan the region. By zeroing the header we 268 // ensure that any thread that will try to scan the region will 269 // come across the zero klass word and bail out. 270 // 271 // NOTE: It would not have been correct to have used 272 // CollectedHeap::fill_with_object() and make the space look like 273 // an int array. The thread that is doing the allocation will 274 // later update the object header to a potentially different array 275 // type and, for a very short period of time, the klass and length 276 // fields will be inconsistent. This could cause a refinement 277 // thread to calculate the object size incorrectly. 278 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 279 280 // Next, pad out the unused tail of the last region with filler 281 // objects, for improved usage accounting. 282 // How many words we use for filler objects. 283 size_t word_fill_size = word_size_sum - word_size; 284 285 // How many words memory we "waste" which cannot hold a filler object. 286 size_t words_not_fillable = 0; 287 288 if (word_fill_size >= min_fill_size()) { 289 fill_with_objects(obj_top, word_fill_size); 290 } else if (word_fill_size > 0) { 291 // We have space to fill, but we cannot fit an object there. 292 words_not_fillable = word_fill_size; 293 word_fill_size = 0; 294 } 295 296 // We will set up the first region as "starts humongous". This 297 // will also update the BOT covering all the regions to reflect 298 // that there is a single object that starts at the bottom of the 299 // first region. 300 first_hr->set_starts_humongous(obj_top, word_fill_size); 301 first_hr->set_allocation_context(context); 302 // Then, if there are any, we will set up the "continues 303 // humongous" regions. 304 HeapRegion* hr = NULL; 305 for (uint i = first + 1; i <= last; ++i) { 306 hr = region_at(i); 307 hr->set_continues_humongous(first_hr); 308 hr->set_allocation_context(context); 309 } 310 311 // Up to this point no concurrent thread would have been able to 312 // do any scanning on any region in this series. All the top 313 // fields still point to bottom, so the intersection between 314 // [bottom,top] and [card_start,card_end] will be empty. Before we 315 // update the top fields, we'll do a storestore to make sure that 316 // no thread sees the update to top before the zeroing of the 317 // object header and the BOT initialization. 318 OrderAccess::storestore(); 319 320 // Now, we will update the top fields of the "continues humongous" 321 // regions except the last one. 322 for (uint i = first; i < last; ++i) { 323 hr = region_at(i); 324 hr->set_top(hr->end()); 325 } 326 327 hr = region_at(last); 328 // If we cannot fit a filler object, we must set top to the end 329 // of the humongous object, otherwise we cannot iterate the heap 330 // and the BOT will not be complete. 331 hr->set_top(hr->end() - words_not_fillable); 332 333 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 334 "obj_top should be in last region"); 335 336 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 337 338 assert(words_not_fillable == 0 || 339 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 340 "Miscalculation in humongous allocation"); 341 342 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 343 344 for (uint i = first; i <= last; ++i) { 345 hr = region_at(i); 346 _humongous_set.add(hr); 347 _hr_printer.alloc(hr); 348 } 349 350 return new_obj; 351 } 352 353 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 354 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 355 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 356 } 357 358 // If could fit into free regions w/o expansion, try. 359 // Otherwise, if can expand, do so. 360 // Otherwise, if using ex regions might help, try with ex given back. 361 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 362 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 363 364 _verifier->verify_region_sets_optional(); 365 366 uint first = G1_NO_HRM_INDEX; 367 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 368 369 if (obj_regions == 1) { 370 // Only one region to allocate, try to use a fast path by directly allocating 371 // from the free lists. Do not try to expand here, we will potentially do that 372 // later. 373 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 374 if (hr != NULL) { 375 first = hr->hrm_index(); 376 } 377 } else { 378 // We can't allocate humongous regions spanning more than one region while 379 // cleanupComplete() is running, since some of the regions we find to be 380 // empty might not yet be added to the free list. It is not straightforward 381 // to know in which list they are on so that we can remove them. We only 382 // need to do this if we need to allocate more than one region to satisfy the 383 // current humongous allocation request. If we are only allocating one region 384 // we use the one-region region allocation code (see above), that already 385 // potentially waits for regions from the secondary free list. 386 wait_while_free_regions_coming(); 387 append_secondary_free_list_if_not_empty_with_lock(); 388 389 // Policy: Try only empty regions (i.e. already committed first). Maybe we 390 // are lucky enough to find some. 391 first = _hrm.find_contiguous_only_empty(obj_regions); 392 if (first != G1_NO_HRM_INDEX) { 393 _hrm.allocate_free_regions_starting_at(first, obj_regions); 394 } 395 } 396 397 if (first == G1_NO_HRM_INDEX) { 398 // Policy: We could not find enough regions for the humongous object in the 399 // free list. Look through the heap to find a mix of free and uncommitted regions. 400 // If so, try expansion. 401 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 402 if (first != G1_NO_HRM_INDEX) { 403 // We found something. Make sure these regions are committed, i.e. expand 404 // the heap. Alternatively we could do a defragmentation GC. 405 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 406 word_size * HeapWordSize); 407 408 _hrm.expand_at(first, obj_regions, workers()); 409 g1_policy()->record_new_heap_size(num_regions()); 410 411 #ifdef ASSERT 412 for (uint i = first; i < first + obj_regions; ++i) { 413 HeapRegion* hr = region_at(i); 414 assert(hr->is_free(), "sanity"); 415 assert(hr->is_empty(), "sanity"); 416 assert(is_on_master_free_list(hr), "sanity"); 417 } 418 #endif 419 _hrm.allocate_free_regions_starting_at(first, obj_regions); 420 } else { 421 // Policy: Potentially trigger a defragmentation GC. 422 } 423 } 424 425 HeapWord* result = NULL; 426 if (first != G1_NO_HRM_INDEX) { 427 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 428 word_size, context); 429 assert(result != NULL, "it should always return a valid result"); 430 431 // A successful humongous object allocation changes the used space 432 // information of the old generation so we need to recalculate the 433 // sizes and update the jstat counters here. 434 g1mm()->update_sizes(); 435 } 436 437 _verifier->verify_region_sets_optional(); 438 439 return result; 440 } 441 442 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 443 assert_heap_not_locked_and_not_at_safepoint(); 444 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 445 446 uint dummy_gc_count_before; 447 uint dummy_gclocker_retry_count = 0; 448 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 449 } 450 451 HeapWord* 452 G1CollectedHeap::mem_allocate(size_t word_size, 453 bool* gc_overhead_limit_was_exceeded) { 454 assert_heap_not_locked_and_not_at_safepoint(); 455 456 // Loop until the allocation is satisfied, or unsatisfied after GC. 457 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 458 uint gc_count_before; 459 460 HeapWord* result = NULL; 461 if (!is_humongous(word_size)) { 462 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 463 } else { 464 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 465 } 466 if (result != NULL) { 467 return result; 468 } 469 470 // Create the garbage collection operation... 471 VM_G1CollectForAllocation op(gc_count_before, word_size); 472 op.set_allocation_context(AllocationContext::current()); 473 474 // ...and get the VM thread to execute it. 475 VMThread::execute(&op); 476 477 if (op.prologue_succeeded() && op.pause_succeeded()) { 478 // If the operation was successful we'll return the result even 479 // if it is NULL. If the allocation attempt failed immediately 480 // after a Full GC, it's unlikely we'll be able to allocate now. 481 HeapWord* result = op.result(); 482 if (result != NULL && !is_humongous(word_size)) { 483 // Allocations that take place on VM operations do not do any 484 // card dirtying and we have to do it here. We only have to do 485 // this for non-humongous allocations, though. 486 dirty_young_block(result, word_size); 487 } 488 return result; 489 } else { 490 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 491 return NULL; 492 } 493 assert(op.result() == NULL, 494 "the result should be NULL if the VM op did not succeed"); 495 } 496 497 // Give a warning if we seem to be looping forever. 498 if ((QueuedAllocationWarningCount > 0) && 499 (try_count % QueuedAllocationWarningCount == 0)) { 500 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count); 501 } 502 } 503 504 ShouldNotReachHere(); 505 return NULL; 506 } 507 508 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 509 AllocationContext_t context, 510 uint* gc_count_before_ret, 511 uint* gclocker_retry_count_ret) { 512 // Make sure you read the note in attempt_allocation_humongous(). 513 514 assert_heap_not_locked_and_not_at_safepoint(); 515 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 516 "be called for humongous allocation requests"); 517 518 // We should only get here after the first-level allocation attempt 519 // (attempt_allocation()) failed to allocate. 520 521 // We will loop until a) we manage to successfully perform the 522 // allocation or b) we successfully schedule a collection which 523 // fails to perform the allocation. b) is the only case when we'll 524 // return NULL. 525 HeapWord* result = NULL; 526 for (int try_count = 1; /* we'll return */; try_count += 1) { 527 bool should_try_gc; 528 uint gc_count_before; 529 530 { 531 MutexLockerEx x(Heap_lock); 532 result = _allocator->attempt_allocation_locked(word_size, context); 533 if (result != NULL) { 534 return result; 535 } 536 537 if (GCLocker::is_active_and_needs_gc()) { 538 if (g1_policy()->can_expand_young_list()) { 539 // No need for an ergo verbose message here, 540 // can_expand_young_list() does this when it returns true. 541 result = _allocator->attempt_allocation_force(word_size, context); 542 if (result != NULL) { 543 return result; 544 } 545 } 546 should_try_gc = false; 547 } else { 548 // The GCLocker may not be active but the GCLocker initiated 549 // GC may not yet have been performed (GCLocker::needs_gc() 550 // returns true). In this case we do not try this GC and 551 // wait until the GCLocker initiated GC is performed, and 552 // then retry the allocation. 553 if (GCLocker::needs_gc()) { 554 should_try_gc = false; 555 } else { 556 // Read the GC count while still holding the Heap_lock. 557 gc_count_before = total_collections(); 558 should_try_gc = true; 559 } 560 } 561 } 562 563 if (should_try_gc) { 564 bool succeeded; 565 result = do_collection_pause(word_size, gc_count_before, &succeeded, 566 GCCause::_g1_inc_collection_pause); 567 if (result != NULL) { 568 assert(succeeded, "only way to get back a non-NULL result"); 569 return result; 570 } 571 572 if (succeeded) { 573 // If we get here we successfully scheduled a collection which 574 // failed to allocate. No point in trying to allocate 575 // further. We'll just return NULL. 576 MutexLockerEx x(Heap_lock); 577 *gc_count_before_ret = total_collections(); 578 return NULL; 579 } 580 } else { 581 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 582 MutexLockerEx x(Heap_lock); 583 *gc_count_before_ret = total_collections(); 584 return NULL; 585 } 586 // The GCLocker is either active or the GCLocker initiated 587 // GC has not yet been performed. Stall until it is and 588 // then retry the allocation. 589 GCLocker::stall_until_clear(); 590 (*gclocker_retry_count_ret) += 1; 591 } 592 593 // We can reach here if we were unsuccessful in scheduling a 594 // collection (because another thread beat us to it) or if we were 595 // stalled due to the GC locker. In either can we should retry the 596 // allocation attempt in case another thread successfully 597 // performed a collection and reclaimed enough space. We do the 598 // first attempt (without holding the Heap_lock) here and the 599 // follow-on attempt will be at the start of the next loop 600 // iteration (after taking the Heap_lock). 601 result = _allocator->attempt_allocation(word_size, context); 602 if (result != NULL) { 603 return result; 604 } 605 606 // Give a warning if we seem to be looping forever. 607 if ((QueuedAllocationWarningCount > 0) && 608 (try_count % QueuedAllocationWarningCount == 0)) { 609 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() " 610 "retries %d times", try_count); 611 } 612 } 613 614 ShouldNotReachHere(); 615 return NULL; 616 } 617 618 void G1CollectedHeap::begin_archive_alloc_range(bool open) { 619 assert_at_safepoint(true /* should_be_vm_thread */); 620 if (_archive_allocator == NULL) { 621 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open); 622 } 623 } 624 625 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 626 // Allocations in archive regions cannot be of a size that would be considered 627 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 628 // may be different at archive-restore time. 629 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 630 } 631 632 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 633 assert_at_safepoint(true /* should_be_vm_thread */); 634 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 635 if (is_archive_alloc_too_large(word_size)) { 636 return NULL; 637 } 638 return _archive_allocator->archive_mem_allocate(word_size); 639 } 640 641 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 642 size_t end_alignment_in_bytes) { 643 assert_at_safepoint(true /* should_be_vm_thread */); 644 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 645 646 // Call complete_archive to do the real work, filling in the MemRegion 647 // array with the archive regions. 648 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 649 delete _archive_allocator; 650 _archive_allocator = NULL; 651 } 652 653 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 654 assert(ranges != NULL, "MemRegion array NULL"); 655 assert(count != 0, "No MemRegions provided"); 656 MemRegion reserved = _hrm.reserved(); 657 for (size_t i = 0; i < count; i++) { 658 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 659 return false; 660 } 661 } 662 return true; 663 } 664 665 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, 666 size_t count, 667 bool open) { 668 assert(!is_init_completed(), "Expect to be called at JVM init time"); 669 assert(ranges != NULL, "MemRegion array NULL"); 670 assert(count != 0, "No MemRegions provided"); 671 MutexLockerEx x(Heap_lock); 672 673 MemRegion reserved = _hrm.reserved(); 674 HeapWord* prev_last_addr = NULL; 675 HeapRegion* prev_last_region = NULL; 676 677 // Temporarily disable pretouching of heap pages. This interface is used 678 // when mmap'ing archived heap data in, so pre-touching is wasted. 679 FlagSetting fs(AlwaysPreTouch, false); 680 681 // Enable archive object checking used by G1MarkSweep. We have to let it know 682 // about each archive range, so that objects in those ranges aren't marked. 683 G1ArchiveAllocator::enable_archive_object_check(); 684 685 // For each specified MemRegion range, allocate the corresponding G1 686 // regions and mark them as archive regions. We expect the ranges 687 // in ascending starting address order, without overlap. 688 for (size_t i = 0; i < count; i++) { 689 MemRegion curr_range = ranges[i]; 690 HeapWord* start_address = curr_range.start(); 691 size_t word_size = curr_range.word_size(); 692 HeapWord* last_address = curr_range.last(); 693 size_t commits = 0; 694 695 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 696 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 697 p2i(start_address), p2i(last_address)); 698 guarantee(start_address > prev_last_addr, 699 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 700 p2i(start_address), p2i(prev_last_addr)); 701 prev_last_addr = last_address; 702 703 // Check for ranges that start in the same G1 region in which the previous 704 // range ended, and adjust the start address so we don't try to allocate 705 // the same region again. If the current range is entirely within that 706 // region, skip it, just adjusting the recorded top. 707 HeapRegion* start_region = _hrm.addr_to_region(start_address); 708 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 709 start_address = start_region->end(); 710 if (start_address > last_address) { 711 increase_used(word_size * HeapWordSize); 712 start_region->set_top(last_address + 1); 713 continue; 714 } 715 start_region->set_top(start_address); 716 curr_range = MemRegion(start_address, last_address + 1); 717 start_region = _hrm.addr_to_region(start_address); 718 } 719 720 // Perform the actual region allocation, exiting if it fails. 721 // Then note how much new space we have allocated. 722 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 723 return false; 724 } 725 increase_used(word_size * HeapWordSize); 726 if (commits != 0) { 727 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 728 HeapRegion::GrainWords * HeapWordSize * commits); 729 730 } 731 732 // Mark each G1 region touched by the range as archive, add it to 733 // the old set, and set the allocation context and top. 734 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 735 HeapRegion* last_region = _hrm.addr_to_region(last_address); 736 prev_last_region = last_region; 737 738 while (curr_region != NULL) { 739 assert(curr_region->is_empty() && !curr_region->is_pinned(), 740 "Region already in use (index %u)", curr_region->hrm_index()); 741 curr_region->set_allocation_context(AllocationContext::system()); 742 if (open) { 743 curr_region->set_open_archive(); 744 } else { 745 curr_region->set_closed_archive(); 746 } 747 _hr_printer.alloc(curr_region); 748 _old_set.add(curr_region); 749 HeapWord* top; 750 HeapRegion* next_region; 751 if (curr_region != last_region) { 752 top = curr_region->end(); 753 next_region = _hrm.next_region_in_heap(curr_region); 754 } else { 755 top = last_address + 1; 756 next_region = NULL; 757 } 758 curr_region->set_top(top); 759 curr_region->set_first_dead(top); 760 curr_region->set_end_of_live(top); 761 curr_region = next_region; 762 } 763 764 // Notify mark-sweep of the archive 765 G1ArchiveAllocator::set_range_archive(curr_range, open); 766 } 767 return true; 768 } 769 770 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 771 assert(!is_init_completed(), "Expect to be called at JVM init time"); 772 assert(ranges != NULL, "MemRegion array NULL"); 773 assert(count != 0, "No MemRegions provided"); 774 MemRegion reserved = _hrm.reserved(); 775 HeapWord *prev_last_addr = NULL; 776 HeapRegion* prev_last_region = NULL; 777 778 // For each MemRegion, create filler objects, if needed, in the G1 regions 779 // that contain the address range. The address range actually within the 780 // MemRegion will not be modified. That is assumed to have been initialized 781 // elsewhere, probably via an mmap of archived heap data. 782 MutexLockerEx x(Heap_lock); 783 for (size_t i = 0; i < count; i++) { 784 HeapWord* start_address = ranges[i].start(); 785 HeapWord* last_address = ranges[i].last(); 786 787 assert(reserved.contains(start_address) && reserved.contains(last_address), 788 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 789 p2i(start_address), p2i(last_address)); 790 assert(start_address > prev_last_addr, 791 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 792 p2i(start_address), p2i(prev_last_addr)); 793 794 HeapRegion* start_region = _hrm.addr_to_region(start_address); 795 HeapRegion* last_region = _hrm.addr_to_region(last_address); 796 HeapWord* bottom_address = start_region->bottom(); 797 798 // Check for a range beginning in the same region in which the 799 // previous one ended. 800 if (start_region == prev_last_region) { 801 bottom_address = prev_last_addr + 1; 802 } 803 804 // Verify that the regions were all marked as archive regions by 805 // alloc_archive_regions. 806 HeapRegion* curr_region = start_region; 807 while (curr_region != NULL) { 808 guarantee(curr_region->is_archive(), 809 "Expected archive region at index %u", curr_region->hrm_index()); 810 if (curr_region != last_region) { 811 curr_region = _hrm.next_region_in_heap(curr_region); 812 } else { 813 curr_region = NULL; 814 } 815 } 816 817 prev_last_addr = last_address; 818 prev_last_region = last_region; 819 820 // Fill the memory below the allocated range with dummy object(s), 821 // if the region bottom does not match the range start, or if the previous 822 // range ended within the same G1 region, and there is a gap. 823 if (start_address != bottom_address) { 824 size_t fill_size = pointer_delta(start_address, bottom_address); 825 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 826 increase_used(fill_size * HeapWordSize); 827 } 828 } 829 } 830 831 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 832 uint* gc_count_before_ret, 833 uint* gclocker_retry_count_ret) { 834 assert_heap_not_locked_and_not_at_safepoint(); 835 assert(!is_humongous(word_size), "attempt_allocation() should not " 836 "be called for humongous allocation requests"); 837 838 AllocationContext_t context = AllocationContext::current(); 839 HeapWord* result = _allocator->attempt_allocation(word_size, context); 840 841 if (result == NULL) { 842 result = attempt_allocation_slow(word_size, 843 context, 844 gc_count_before_ret, 845 gclocker_retry_count_ret); 846 } 847 assert_heap_not_locked(); 848 if (result != NULL) { 849 dirty_young_block(result, word_size); 850 } 851 return result; 852 } 853 854 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 855 assert(!is_init_completed(), "Expect to be called at JVM init time"); 856 assert(ranges != NULL, "MemRegion array NULL"); 857 assert(count != 0, "No MemRegions provided"); 858 MemRegion reserved = _hrm.reserved(); 859 HeapWord* prev_last_addr = NULL; 860 HeapRegion* prev_last_region = NULL; 861 size_t size_used = 0; 862 size_t uncommitted_regions = 0; 863 864 // For each Memregion, free the G1 regions that constitute it, and 865 // notify mark-sweep that the range is no longer to be considered 'archive.' 866 MutexLockerEx x(Heap_lock); 867 for (size_t i = 0; i < count; i++) { 868 HeapWord* start_address = ranges[i].start(); 869 HeapWord* last_address = ranges[i].last(); 870 871 assert(reserved.contains(start_address) && reserved.contains(last_address), 872 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 873 p2i(start_address), p2i(last_address)); 874 assert(start_address > prev_last_addr, 875 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 876 p2i(start_address), p2i(prev_last_addr)); 877 size_used += ranges[i].byte_size(); 878 prev_last_addr = last_address; 879 880 HeapRegion* start_region = _hrm.addr_to_region(start_address); 881 HeapRegion* last_region = _hrm.addr_to_region(last_address); 882 883 // Check for ranges that start in the same G1 region in which the previous 884 // range ended, and adjust the start address so we don't try to free 885 // the same region again. If the current range is entirely within that 886 // region, skip it. 887 if (start_region == prev_last_region) { 888 start_address = start_region->end(); 889 if (start_address > last_address) { 890 continue; 891 } 892 start_region = _hrm.addr_to_region(start_address); 893 } 894 prev_last_region = last_region; 895 896 // After verifying that each region was marked as an archive region by 897 // alloc_archive_regions, set it free and empty and uncommit it. 898 HeapRegion* curr_region = start_region; 899 while (curr_region != NULL) { 900 guarantee(curr_region->is_archive(), 901 "Expected archive region at index %u", curr_region->hrm_index()); 902 uint curr_index = curr_region->hrm_index(); 903 _old_set.remove(curr_region); 904 curr_region->set_free(); 905 curr_region->set_top(curr_region->bottom()); 906 if (curr_region != last_region) { 907 curr_region = _hrm.next_region_in_heap(curr_region); 908 } else { 909 curr_region = NULL; 910 } 911 _hrm.shrink_at(curr_index, 1); 912 uncommitted_regions++; 913 } 914 915 // Notify mark-sweep that this is no longer an archive range. 916 G1ArchiveAllocator::set_range_archive(ranges[i], false); 917 } 918 919 if (uncommitted_regions != 0) { 920 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 921 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 922 } 923 decrease_used(size_used); 924 } 925 926 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 927 uint* gc_count_before_ret, 928 uint* gclocker_retry_count_ret) { 929 // The structure of this method has a lot of similarities to 930 // attempt_allocation_slow(). The reason these two were not merged 931 // into a single one is that such a method would require several "if 932 // allocation is not humongous do this, otherwise do that" 933 // conditional paths which would obscure its flow. In fact, an early 934 // version of this code did use a unified method which was harder to 935 // follow and, as a result, it had subtle bugs that were hard to 936 // track down. So keeping these two methods separate allows each to 937 // be more readable. It will be good to keep these two in sync as 938 // much as possible. 939 940 assert_heap_not_locked_and_not_at_safepoint(); 941 assert(is_humongous(word_size), "attempt_allocation_humongous() " 942 "should only be called for humongous allocations"); 943 944 // Humongous objects can exhaust the heap quickly, so we should check if we 945 // need to start a marking cycle at each humongous object allocation. We do 946 // the check before we do the actual allocation. The reason for doing it 947 // before the allocation is that we avoid having to keep track of the newly 948 // allocated memory while we do a GC. 949 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 950 word_size)) { 951 collect(GCCause::_g1_humongous_allocation); 952 } 953 954 // We will loop until a) we manage to successfully perform the 955 // allocation or b) we successfully schedule a collection which 956 // fails to perform the allocation. b) is the only case when we'll 957 // return NULL. 958 HeapWord* result = NULL; 959 for (int try_count = 1; /* we'll return */; try_count += 1) { 960 bool should_try_gc; 961 uint gc_count_before; 962 963 { 964 MutexLockerEx x(Heap_lock); 965 966 // Given that humongous objects are not allocated in young 967 // regions, we'll first try to do the allocation without doing a 968 // collection hoping that there's enough space in the heap. 969 result = humongous_obj_allocate(word_size, AllocationContext::current()); 970 if (result != NULL) { 971 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 972 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 973 return result; 974 } 975 976 if (GCLocker::is_active_and_needs_gc()) { 977 should_try_gc = false; 978 } else { 979 // The GCLocker may not be active but the GCLocker initiated 980 // GC may not yet have been performed (GCLocker::needs_gc() 981 // returns true). In this case we do not try this GC and 982 // wait until the GCLocker initiated GC is performed, and 983 // then retry the allocation. 984 if (GCLocker::needs_gc()) { 985 should_try_gc = false; 986 } else { 987 // Read the GC count while still holding the Heap_lock. 988 gc_count_before = total_collections(); 989 should_try_gc = true; 990 } 991 } 992 } 993 994 if (should_try_gc) { 995 // If we failed to allocate the humongous object, we should try to 996 // do a collection pause (if we're allowed) in case it reclaims 997 // enough space for the allocation to succeed after the pause. 998 999 bool succeeded; 1000 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1001 GCCause::_g1_humongous_allocation); 1002 if (result != NULL) { 1003 assert(succeeded, "only way to get back a non-NULL result"); 1004 return result; 1005 } 1006 1007 if (succeeded) { 1008 // If we get here we successfully scheduled a collection which 1009 // failed to allocate. No point in trying to allocate 1010 // further. We'll just return NULL. 1011 MutexLockerEx x(Heap_lock); 1012 *gc_count_before_ret = total_collections(); 1013 return NULL; 1014 } 1015 } else { 1016 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1017 MutexLockerEx x(Heap_lock); 1018 *gc_count_before_ret = total_collections(); 1019 return NULL; 1020 } 1021 // The GCLocker is either active or the GCLocker initiated 1022 // GC has not yet been performed. Stall until it is and 1023 // then retry the allocation. 1024 GCLocker::stall_until_clear(); 1025 (*gclocker_retry_count_ret) += 1; 1026 } 1027 1028 // We can reach here if we were unsuccessful in scheduling a 1029 // collection (because another thread beat us to it) or if we were 1030 // stalled due to the GC locker. In either can we should retry the 1031 // allocation attempt in case another thread successfully 1032 // performed a collection and reclaimed enough space. Give a 1033 // warning if we seem to be looping forever. 1034 1035 if ((QueuedAllocationWarningCount > 0) && 1036 (try_count % QueuedAllocationWarningCount == 0)) { 1037 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() " 1038 "retries %d times", try_count); 1039 } 1040 } 1041 1042 ShouldNotReachHere(); 1043 return NULL; 1044 } 1045 1046 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1047 AllocationContext_t context, 1048 bool expect_null_mutator_alloc_region) { 1049 assert_at_safepoint(true /* should_be_vm_thread */); 1050 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1051 "the current alloc region was unexpectedly found to be non-NULL"); 1052 1053 if (!is_humongous(word_size)) { 1054 return _allocator->attempt_allocation_locked(word_size, context); 1055 } else { 1056 HeapWord* result = humongous_obj_allocate(word_size, context); 1057 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1058 collector_state()->set_initiate_conc_mark_if_possible(true); 1059 } 1060 return result; 1061 } 1062 1063 ShouldNotReachHere(); 1064 } 1065 1066 class PostCompactionPrinterClosure: public HeapRegionClosure { 1067 private: 1068 G1HRPrinter* _hr_printer; 1069 public: 1070 bool doHeapRegion(HeapRegion* hr) { 1071 assert(!hr->is_young(), "not expecting to find young regions"); 1072 _hr_printer->post_compaction(hr); 1073 return false; 1074 } 1075 1076 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1077 : _hr_printer(hr_printer) { } 1078 }; 1079 1080 void G1CollectedHeap::print_hrm_post_compaction() { 1081 if (_hr_printer.is_active()) { 1082 PostCompactionPrinterClosure cl(hr_printer()); 1083 heap_region_iterate(&cl); 1084 } 1085 1086 } 1087 1088 void G1CollectedHeap::abort_concurrent_cycle() { 1089 // Note: When we have a more flexible GC logging framework that 1090 // allows us to add optional attributes to a GC log record we 1091 // could consider timing and reporting how long we wait in the 1092 // following two methods. 1093 wait_while_free_regions_coming(); 1094 // If we start the compaction before the CM threads finish 1095 // scanning the root regions we might trip them over as we'll 1096 // be moving objects / updating references. So let's wait until 1097 // they are done. By telling them to abort, they should complete 1098 // early. 1099 _cm->root_regions()->abort(); 1100 _cm->root_regions()->wait_until_scan_finished(); 1101 append_secondary_free_list_if_not_empty_with_lock(); 1102 1103 // Disable discovery and empty the discovered lists 1104 // for the CM ref processor. 1105 ref_processor_cm()->disable_discovery(); 1106 ref_processor_cm()->abandon_partial_discovery(); 1107 ref_processor_cm()->verify_no_references_recorded(); 1108 1109 // Abandon current iterations of concurrent marking and concurrent 1110 // refinement, if any are in progress. 1111 concurrent_mark()->abort(); 1112 } 1113 1114 void G1CollectedHeap::prepare_heap_for_full_collection() { 1115 // Make sure we'll choose a new allocation region afterwards. 1116 _allocator->release_mutator_alloc_region(); 1117 _allocator->abandon_gc_alloc_regions(); 1118 g1_rem_set()->cleanupHRRS(); 1119 1120 // We may have added regions to the current incremental collection 1121 // set between the last GC or pause and now. We need to clear the 1122 // incremental collection set and then start rebuilding it afresh 1123 // after this full GC. 1124 abandon_collection_set(collection_set()); 1125 1126 tear_down_region_sets(false /* free_list_only */); 1127 collector_state()->set_gcs_are_young(true); 1128 } 1129 1130 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1131 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1132 assert(used() == recalculate_used(), "Should be equal"); 1133 _verifier->verify_region_sets_optional(); 1134 _verifier->verify_before_gc(); 1135 _verifier->check_bitmaps("Full GC Start"); 1136 } 1137 1138 void G1CollectedHeap::prepare_heap_for_mutators() { 1139 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1140 ClassLoaderDataGraph::purge(); 1141 MetaspaceAux::verify_metrics(); 1142 1143 // Prepare heap for normal collections. 1144 assert(num_free_regions() == 0, "we should not have added any free regions"); 1145 rebuild_region_sets(false /* free_list_only */); 1146 abort_refinement(); 1147 resize_if_necessary_after_full_collection(); 1148 1149 // Rebuild the strong code root lists for each region 1150 rebuild_strong_code_roots(); 1151 1152 // Start a new incremental collection set for the next pause 1153 start_new_collection_set(); 1154 1155 _allocator->init_mutator_alloc_region(); 1156 1157 // Post collection state updates. 1158 MetaspaceGC::compute_new_size(); 1159 } 1160 1161 void G1CollectedHeap::abort_refinement() { 1162 if (_hot_card_cache->use_cache()) { 1163 _hot_card_cache->reset_card_counts(); 1164 _hot_card_cache->reset_hot_cache(); 1165 } 1166 1167 // Discard all remembered set updates. 1168 JavaThread::dirty_card_queue_set().abandon_logs(); 1169 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1170 } 1171 1172 void G1CollectedHeap::verify_after_full_collection() { 1173 check_gc_time_stamps(); 1174 _hrm.verify_optional(); 1175 _verifier->verify_region_sets_optional(); 1176 _verifier->verify_after_gc(); 1177 // Clear the previous marking bitmap, if needed for bitmap verification. 1178 // Note we cannot do this when we clear the next marking bitmap in 1179 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1180 // objects marked during a full GC against the previous bitmap. 1181 // But we need to clear it before calling check_bitmaps below since 1182 // the full GC has compacted objects and updated TAMS but not updated 1183 // the prev bitmap. 1184 if (G1VerifyBitmaps) { 1185 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1186 _cm->clear_prev_bitmap(workers()); 1187 } 1188 _verifier->check_bitmaps("Full GC End"); 1189 1190 // At this point there should be no regions in the 1191 // entire heap tagged as young. 1192 assert(check_young_list_empty(), "young list should be empty at this point"); 1193 1194 // Note: since we've just done a full GC, concurrent 1195 // marking is no longer active. Therefore we need not 1196 // re-enable reference discovery for the CM ref processor. 1197 // That will be done at the start of the next marking cycle. 1198 // We also know that the STW processor should no longer 1199 // discover any new references. 1200 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1201 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1202 ref_processor_stw()->verify_no_references_recorded(); 1203 ref_processor_cm()->verify_no_references_recorded(); 1204 } 1205 1206 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1207 print_hrm_post_compaction(); 1208 heap_transition->print(); 1209 print_heap_after_gc(); 1210 print_heap_regions(); 1211 #ifdef TRACESPINNING 1212 ParallelTaskTerminator::print_termination_counts(); 1213 #endif 1214 } 1215 1216 void G1CollectedHeap::do_full_collection_inner(G1FullGCScope* scope) { 1217 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1218 g1_policy()->record_full_collection_start(); 1219 1220 print_heap_before_gc(); 1221 print_heap_regions(); 1222 1223 abort_concurrent_cycle(); 1224 verify_before_full_collection(scope->is_explicit_gc()); 1225 1226 gc_prologue(true); 1227 prepare_heap_for_full_collection(); 1228 1229 G1SerialFullCollector serial(scope, ref_processor_stw()); 1230 serial.prepare_collection(); 1231 serial.collect(); 1232 serial.complete_collection(); 1233 1234 prepare_heap_for_mutators(); 1235 1236 g1_policy()->record_full_collection_end(); 1237 gc_epilogue(true); 1238 1239 // Post collection verification. 1240 verify_after_full_collection(); 1241 1242 // Post collection logging. 1243 // We should do this after we potentially resize the heap so 1244 // that all the COMMIT / UNCOMMIT events are generated before 1245 // the compaction events. 1246 print_heap_after_full_collection(scope->heap_transition()); 1247 } 1248 1249 bool G1CollectedHeap::do_full_collection(bool explicit_gc, 1250 bool clear_all_soft_refs) { 1251 assert_at_safepoint(true /* should_be_vm_thread */); 1252 1253 if (GCLocker::check_active_before_gc()) { 1254 // Full GC was not completed. 1255 return false; 1256 } 1257 1258 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1259 collector_policy()->should_clear_all_soft_refs(); 1260 1261 G1FullGCScope scope(explicit_gc, do_clear_all_soft_refs); 1262 do_full_collection_inner(&scope); 1263 1264 // Full collection was successfully completed. 1265 return true; 1266 } 1267 1268 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1269 // Currently, there is no facility in the do_full_collection(bool) API to notify 1270 // the caller that the collection did not succeed (e.g., because it was locked 1271 // out by the GC locker). So, right now, we'll ignore the return value. 1272 bool dummy = do_full_collection(true, /* explicit_gc */ 1273 clear_all_soft_refs); 1274 } 1275 1276 void G1CollectedHeap::resize_if_necessary_after_full_collection() { 1277 // Include bytes that will be pre-allocated to support collections, as "used". 1278 const size_t used_after_gc = used(); 1279 const size_t capacity_after_gc = capacity(); 1280 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1281 1282 // This is enforced in arguments.cpp. 1283 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1284 "otherwise the code below doesn't make sense"); 1285 1286 // We don't have floating point command-line arguments 1287 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1288 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1289 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1290 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1291 1292 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1293 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1294 1295 // We have to be careful here as these two calculations can overflow 1296 // 32-bit size_t's. 1297 double used_after_gc_d = (double) used_after_gc; 1298 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1299 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1300 1301 // Let's make sure that they are both under the max heap size, which 1302 // by default will make them fit into a size_t. 1303 double desired_capacity_upper_bound = (double) max_heap_size; 1304 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1305 desired_capacity_upper_bound); 1306 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1307 desired_capacity_upper_bound); 1308 1309 // We can now safely turn them into size_t's. 1310 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1311 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1312 1313 // This assert only makes sense here, before we adjust them 1314 // with respect to the min and max heap size. 1315 assert(minimum_desired_capacity <= maximum_desired_capacity, 1316 "minimum_desired_capacity = " SIZE_FORMAT ", " 1317 "maximum_desired_capacity = " SIZE_FORMAT, 1318 minimum_desired_capacity, maximum_desired_capacity); 1319 1320 // Should not be greater than the heap max size. No need to adjust 1321 // it with respect to the heap min size as it's a lower bound (i.e., 1322 // we'll try to make the capacity larger than it, not smaller). 1323 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1324 // Should not be less than the heap min size. No need to adjust it 1325 // with respect to the heap max size as it's an upper bound (i.e., 1326 // we'll try to make the capacity smaller than it, not greater). 1327 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1328 1329 if (capacity_after_gc < minimum_desired_capacity) { 1330 // Don't expand unless it's significant 1331 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1332 1333 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). " 1334 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1335 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1336 1337 expand(expand_bytes, _workers); 1338 1339 // No expansion, now see if we want to shrink 1340 } else if (capacity_after_gc > maximum_desired_capacity) { 1341 // Capacity too large, compute shrinking size 1342 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1343 1344 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). " 1345 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)", 1346 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio); 1347 1348 shrink(shrink_bytes); 1349 } 1350 } 1351 1352 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1353 AllocationContext_t context, 1354 bool do_gc, 1355 bool clear_all_soft_refs, 1356 bool expect_null_mutator_alloc_region, 1357 bool* gc_succeeded) { 1358 *gc_succeeded = true; 1359 // Let's attempt the allocation first. 1360 HeapWord* result = 1361 attempt_allocation_at_safepoint(word_size, 1362 context, 1363 expect_null_mutator_alloc_region); 1364 if (result != NULL) { 1365 assert(*gc_succeeded, "sanity"); 1366 return result; 1367 } 1368 1369 // In a G1 heap, we're supposed to keep allocation from failing by 1370 // incremental pauses. Therefore, at least for now, we'll favor 1371 // expansion over collection. (This might change in the future if we can 1372 // do something smarter than full collection to satisfy a failed alloc.) 1373 result = expand_and_allocate(word_size, context); 1374 if (result != NULL) { 1375 assert(*gc_succeeded, "sanity"); 1376 return result; 1377 } 1378 1379 if (do_gc) { 1380 // Expansion didn't work, we'll try to do a Full GC. 1381 *gc_succeeded = do_full_collection(false, /* explicit_gc */ 1382 clear_all_soft_refs); 1383 } 1384 1385 return NULL; 1386 } 1387 1388 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1389 AllocationContext_t context, 1390 bool* succeeded) { 1391 assert_at_safepoint(true /* should_be_vm_thread */); 1392 1393 // Attempts to allocate followed by Full GC. 1394 HeapWord* result = 1395 satisfy_failed_allocation_helper(word_size, 1396 context, 1397 true, /* do_gc */ 1398 false, /* clear_all_soft_refs */ 1399 false, /* expect_null_mutator_alloc_region */ 1400 succeeded); 1401 1402 if (result != NULL || !*succeeded) { 1403 return result; 1404 } 1405 1406 // Attempts to allocate followed by Full GC that will collect all soft references. 1407 result = satisfy_failed_allocation_helper(word_size, 1408 context, 1409 true, /* do_gc */ 1410 true, /* clear_all_soft_refs */ 1411 true, /* expect_null_mutator_alloc_region */ 1412 succeeded); 1413 1414 if (result != NULL || !*succeeded) { 1415 return result; 1416 } 1417 1418 // Attempts to allocate, no GC 1419 result = satisfy_failed_allocation_helper(word_size, 1420 context, 1421 false, /* do_gc */ 1422 false, /* clear_all_soft_refs */ 1423 true, /* expect_null_mutator_alloc_region */ 1424 succeeded); 1425 1426 if (result != NULL) { 1427 assert(*succeeded, "sanity"); 1428 return result; 1429 } 1430 1431 assert(!collector_policy()->should_clear_all_soft_refs(), 1432 "Flag should have been handled and cleared prior to this point"); 1433 1434 // What else? We might try synchronous finalization later. If the total 1435 // space available is large enough for the allocation, then a more 1436 // complete compaction phase than we've tried so far might be 1437 // appropriate. 1438 assert(*succeeded, "sanity"); 1439 return NULL; 1440 } 1441 1442 // Attempting to expand the heap sufficiently 1443 // to support an allocation of the given "word_size". If 1444 // successful, perform the allocation and return the address of the 1445 // allocated block, or else "NULL". 1446 1447 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1448 assert_at_safepoint(true /* should_be_vm_thread */); 1449 1450 _verifier->verify_region_sets_optional(); 1451 1452 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1453 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B", 1454 word_size * HeapWordSize); 1455 1456 1457 if (expand(expand_bytes, _workers)) { 1458 _hrm.verify_optional(); 1459 _verifier->verify_region_sets_optional(); 1460 return attempt_allocation_at_safepoint(word_size, 1461 context, 1462 false /* expect_null_mutator_alloc_region */); 1463 } 1464 return NULL; 1465 } 1466 1467 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) { 1468 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1469 aligned_expand_bytes = align_up(aligned_expand_bytes, 1470 HeapRegion::GrainBytes); 1471 1472 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B", 1473 expand_bytes, aligned_expand_bytes); 1474 1475 if (is_maximal_no_gc()) { 1476 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)"); 1477 return false; 1478 } 1479 1480 double expand_heap_start_time_sec = os::elapsedTime(); 1481 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1482 assert(regions_to_expand > 0, "Must expand by at least one region"); 1483 1484 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers); 1485 if (expand_time_ms != NULL) { 1486 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1487 } 1488 1489 if (expanded_by > 0) { 1490 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1491 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1492 g1_policy()->record_new_heap_size(num_regions()); 1493 } else { 1494 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)"); 1495 1496 // The expansion of the virtual storage space was unsuccessful. 1497 // Let's see if it was because we ran out of swap. 1498 if (G1ExitOnExpansionFailure && 1499 _hrm.available() >= regions_to_expand) { 1500 // We had head room... 1501 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1502 } 1503 } 1504 return regions_to_expand > 0; 1505 } 1506 1507 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1508 size_t aligned_shrink_bytes = 1509 ReservedSpace::page_align_size_down(shrink_bytes); 1510 aligned_shrink_bytes = align_down(aligned_shrink_bytes, 1511 HeapRegion::GrainBytes); 1512 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1513 1514 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1515 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1516 1517 1518 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", 1519 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1520 if (num_regions_removed > 0) { 1521 g1_policy()->record_new_heap_size(num_regions()); 1522 } else { 1523 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)"); 1524 } 1525 } 1526 1527 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1528 _verifier->verify_region_sets_optional(); 1529 1530 // We should only reach here at the end of a Full GC which means we 1531 // should not not be holding to any GC alloc regions. The method 1532 // below will make sure of that and do any remaining clean up. 1533 _allocator->abandon_gc_alloc_regions(); 1534 1535 // Instead of tearing down / rebuilding the free lists here, we 1536 // could instead use the remove_all_pending() method on free_list to 1537 // remove only the ones that we need to remove. 1538 tear_down_region_sets(true /* free_list_only */); 1539 shrink_helper(shrink_bytes); 1540 rebuild_region_sets(true /* free_list_only */); 1541 1542 _hrm.verify_optional(); 1543 _verifier->verify_region_sets_optional(); 1544 } 1545 1546 // Public methods. 1547 1548 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) : 1549 CollectedHeap(), 1550 _collector_policy(collector_policy), 1551 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1552 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1553 _g1_policy(create_g1_policy(_gc_timer_stw)), 1554 _collection_set(this, _g1_policy), 1555 _dirty_card_queue_set(false), 1556 _is_alive_closure_cm(this), 1557 _is_alive_closure_stw(this), 1558 _ref_processor_cm(NULL), 1559 _ref_processor_stw(NULL), 1560 _bot(NULL), 1561 _hot_card_cache(NULL), 1562 _g1_rem_set(NULL), 1563 _cg1r(NULL), 1564 _g1mm(NULL), 1565 _preserved_marks_set(true /* in_c_heap */), 1566 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1567 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1568 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1569 _humongous_reclaim_candidates(), 1570 _has_humongous_reclaim_candidates(false), 1571 _archive_allocator(NULL), 1572 _free_regions_coming(false), 1573 _gc_time_stamp(0), 1574 _summary_bytes_used(0), 1575 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1576 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1577 _expand_heap_after_alloc_failure(true), 1578 _old_marking_cycles_started(0), 1579 _old_marking_cycles_completed(0), 1580 _in_cset_fast_test() { 1581 1582 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1583 /* are_GC_task_threads */true, 1584 /* are_ConcurrentGC_threads */false); 1585 _workers->initialize_workers(); 1586 _verifier = new G1HeapVerifier(this); 1587 1588 _allocator = G1Allocator::create_allocator(this); 1589 1590 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics()); 1591 1592 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1593 1594 // Override the default _filler_array_max_size so that no humongous filler 1595 // objects are created. 1596 _filler_array_max_size = _humongous_object_threshold_in_words; 1597 1598 uint n_queues = ParallelGCThreads; 1599 _task_queues = new RefToScanQueueSet(n_queues); 1600 1601 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1602 1603 for (uint i = 0; i < n_queues; i++) { 1604 RefToScanQueue* q = new RefToScanQueue(); 1605 q->initialize(); 1606 _task_queues->register_queue(i, q); 1607 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1608 } 1609 1610 // Initialize the G1EvacuationFailureALot counters and flags. 1611 NOT_PRODUCT(reset_evacuation_should_fail();) 1612 1613 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1614 } 1615 1616 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1617 size_t size, 1618 size_t translation_factor) { 1619 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1620 // Allocate a new reserved space, preferring to use large pages. 1621 ReservedSpace rs(size, preferred_page_size); 1622 G1RegionToSpaceMapper* result = 1623 G1RegionToSpaceMapper::create_mapper(rs, 1624 size, 1625 rs.alignment(), 1626 HeapRegion::GrainBytes, 1627 translation_factor, 1628 mtGC); 1629 1630 os::trace_page_sizes_for_requested_size(description, 1631 size, 1632 preferred_page_size, 1633 rs.alignment(), 1634 rs.base(), 1635 rs.size()); 1636 1637 return result; 1638 } 1639 1640 jint G1CollectedHeap::initialize_concurrent_refinement() { 1641 jint ecode = JNI_OK; 1642 _cg1r = ConcurrentG1Refine::create(&ecode); 1643 return ecode; 1644 } 1645 1646 jint G1CollectedHeap::initialize() { 1647 CollectedHeap::pre_initialize(); 1648 os::enable_vtime(); 1649 1650 // Necessary to satisfy locking discipline assertions. 1651 1652 MutexLocker x(Heap_lock); 1653 1654 // While there are no constraints in the GC code that HeapWordSize 1655 // be any particular value, there are multiple other areas in the 1656 // system which believe this to be true (e.g. oop->object_size in some 1657 // cases incorrectly returns the size in wordSize units rather than 1658 // HeapWordSize). 1659 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1660 1661 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1662 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1663 size_t heap_alignment = collector_policy()->heap_alignment(); 1664 1665 // Ensure that the sizes are properly aligned. 1666 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1667 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1668 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1669 1670 // Reserve the maximum. 1671 1672 // When compressed oops are enabled, the preferred heap base 1673 // is calculated by subtracting the requested size from the 1674 // 32Gb boundary and using the result as the base address for 1675 // heap reservation. If the requested size is not aligned to 1676 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1677 // into the ReservedHeapSpace constructor) then the actual 1678 // base of the reserved heap may end up differing from the 1679 // address that was requested (i.e. the preferred heap base). 1680 // If this happens then we could end up using a non-optimal 1681 // compressed oops mode. 1682 1683 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1684 heap_alignment); 1685 1686 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1687 1688 // Create the barrier set for the entire reserved region. 1689 G1SATBCardTableLoggingModRefBS* bs 1690 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1691 bs->initialize(); 1692 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1693 set_barrier_set(bs); 1694 1695 // Create the hot card cache. 1696 _hot_card_cache = new G1HotCardCache(this); 1697 1698 // Carve out the G1 part of the heap. 1699 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1700 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1701 G1RegionToSpaceMapper* heap_storage = 1702 G1RegionToSpaceMapper::create_mapper(g1_rs, 1703 g1_rs.size(), 1704 page_size, 1705 HeapRegion::GrainBytes, 1706 1, 1707 mtJavaHeap); 1708 os::trace_page_sizes("Heap", 1709 collector_policy()->min_heap_byte_size(), 1710 max_byte_size, 1711 page_size, 1712 heap_rs.base(), 1713 heap_rs.size()); 1714 heap_storage->set_mapping_changed_listener(&_listener); 1715 1716 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1717 G1RegionToSpaceMapper* bot_storage = 1718 create_aux_memory_mapper("Block Offset Table", 1719 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize), 1720 G1BlockOffsetTable::heap_map_factor()); 1721 1722 G1RegionToSpaceMapper* cardtable_storage = 1723 create_aux_memory_mapper("Card Table", 1724 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1725 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1726 1727 G1RegionToSpaceMapper* card_counts_storage = 1728 create_aux_memory_mapper("Card Counts Table", 1729 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1730 G1CardCounts::heap_map_factor()); 1731 1732 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1733 G1RegionToSpaceMapper* prev_bitmap_storage = 1734 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1735 G1RegionToSpaceMapper* next_bitmap_storage = 1736 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1737 1738 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1739 g1_barrier_set()->initialize(cardtable_storage); 1740 // Do later initialization work for concurrent refinement. 1741 _hot_card_cache->initialize(card_counts_storage); 1742 1743 // 6843694 - ensure that the maximum region index can fit 1744 // in the remembered set structures. 1745 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1746 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1747 1748 // Also create a G1 rem set. 1749 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache); 1750 _g1_rem_set->initialize(max_capacity(), max_regions()); 1751 1752 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1753 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1754 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1755 "too many cards per region"); 1756 1757 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1758 1759 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1760 1761 { 1762 HeapWord* start = _hrm.reserved().start(); 1763 HeapWord* end = _hrm.reserved().end(); 1764 size_t granularity = HeapRegion::GrainBytes; 1765 1766 _in_cset_fast_test.initialize(start, end, granularity); 1767 _humongous_reclaim_candidates.initialize(start, end, granularity); 1768 } 1769 1770 // Create the G1ConcurrentMark data structure and thread. 1771 // (Must do this late, so that "max_regions" is defined.) 1772 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1773 if (_cm == NULL || !_cm->completed_initialization()) { 1774 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1775 return JNI_ENOMEM; 1776 } 1777 _cmThread = _cm->cmThread(); 1778 1779 // Now expand into the initial heap size. 1780 if (!expand(init_byte_size, _workers)) { 1781 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1782 return JNI_ENOMEM; 1783 } 1784 1785 // Perform any initialization actions delegated to the policy. 1786 g1_policy()->init(this, &_collection_set); 1787 1788 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1789 SATB_Q_FL_lock, 1790 G1SATBProcessCompletedThreshold, 1791 Shared_SATB_Q_lock); 1792 1793 jint ecode = initialize_concurrent_refinement(); 1794 if (ecode != JNI_OK) { 1795 return ecode; 1796 } 1797 1798 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1799 DirtyCardQ_FL_lock, 1800 (int)concurrent_g1_refine()->yellow_zone(), 1801 (int)concurrent_g1_refine()->red_zone(), 1802 Shared_DirtyCardQ_lock, 1803 NULL, // fl_owner 1804 true); // init_free_ids 1805 1806 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1807 DirtyCardQ_FL_lock, 1808 -1, // never trigger processing 1809 -1, // no limit on length 1810 Shared_DirtyCardQ_lock, 1811 &JavaThread::dirty_card_queue_set()); 1812 1813 // Here we allocate the dummy HeapRegion that is required by the 1814 // G1AllocRegion class. 1815 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1816 1817 // We'll re-use the same region whether the alloc region will 1818 // require BOT updates or not and, if it doesn't, then a non-young 1819 // region will complain that it cannot support allocations without 1820 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1821 dummy_region->set_eden(); 1822 // Make sure it's full. 1823 dummy_region->set_top(dummy_region->end()); 1824 G1AllocRegion::setup(this, dummy_region); 1825 1826 _allocator->init_mutator_alloc_region(); 1827 1828 // Do create of the monitoring and management support so that 1829 // values in the heap have been properly initialized. 1830 _g1mm = new G1MonitoringSupport(this); 1831 1832 G1StringDedup::initialize(); 1833 1834 _preserved_marks_set.init(ParallelGCThreads); 1835 1836 _collection_set.initialize(max_regions()); 1837 1838 return JNI_OK; 1839 } 1840 1841 void G1CollectedHeap::stop() { 1842 // Stop all concurrent threads. We do this to make sure these threads 1843 // do not continue to execute and access resources (e.g. logging) 1844 // that are destroyed during shutdown. 1845 _cg1r->stop(); 1846 _cmThread->stop(); 1847 if (G1StringDedup::is_enabled()) { 1848 G1StringDedup::stop(); 1849 } 1850 } 1851 1852 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1853 return HeapRegion::max_region_size(); 1854 } 1855 1856 void G1CollectedHeap::post_initialize() { 1857 ref_processing_init(); 1858 } 1859 1860 void G1CollectedHeap::ref_processing_init() { 1861 // Reference processing in G1 currently works as follows: 1862 // 1863 // * There are two reference processor instances. One is 1864 // used to record and process discovered references 1865 // during concurrent marking; the other is used to 1866 // record and process references during STW pauses 1867 // (both full and incremental). 1868 // * Both ref processors need to 'span' the entire heap as 1869 // the regions in the collection set may be dotted around. 1870 // 1871 // * For the concurrent marking ref processor: 1872 // * Reference discovery is enabled at initial marking. 1873 // * Reference discovery is disabled and the discovered 1874 // references processed etc during remarking. 1875 // * Reference discovery is MT (see below). 1876 // * Reference discovery requires a barrier (see below). 1877 // * Reference processing may or may not be MT 1878 // (depending on the value of ParallelRefProcEnabled 1879 // and ParallelGCThreads). 1880 // * A full GC disables reference discovery by the CM 1881 // ref processor and abandons any entries on it's 1882 // discovered lists. 1883 // 1884 // * For the STW processor: 1885 // * Non MT discovery is enabled at the start of a full GC. 1886 // * Processing and enqueueing during a full GC is non-MT. 1887 // * During a full GC, references are processed after marking. 1888 // 1889 // * Discovery (may or may not be MT) is enabled at the start 1890 // of an incremental evacuation pause. 1891 // * References are processed near the end of a STW evacuation pause. 1892 // * For both types of GC: 1893 // * Discovery is atomic - i.e. not concurrent. 1894 // * Reference discovery will not need a barrier. 1895 1896 MemRegion mr = reserved_region(); 1897 1898 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1); 1899 1900 // Concurrent Mark ref processor 1901 _ref_processor_cm = 1902 new ReferenceProcessor(mr, // span 1903 mt_processing, 1904 // mt processing 1905 ParallelGCThreads, 1906 // degree of mt processing 1907 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 1908 // mt discovery 1909 MAX2(ParallelGCThreads, ConcGCThreads), 1910 // degree of mt discovery 1911 false, 1912 // Reference discovery is not atomic 1913 &_is_alive_closure_cm); 1914 // is alive closure 1915 // (for efficiency/performance) 1916 1917 // STW ref processor 1918 _ref_processor_stw = 1919 new ReferenceProcessor(mr, // span 1920 mt_processing, 1921 // mt processing 1922 ParallelGCThreads, 1923 // degree of mt processing 1924 (ParallelGCThreads > 1), 1925 // mt discovery 1926 ParallelGCThreads, 1927 // degree of mt discovery 1928 true, 1929 // Reference discovery is atomic 1930 &_is_alive_closure_stw); 1931 // is alive closure 1932 // (for efficiency/performance) 1933 } 1934 1935 CollectorPolicy* G1CollectedHeap::collector_policy() const { 1936 return _collector_policy; 1937 } 1938 1939 size_t G1CollectedHeap::capacity() const { 1940 return _hrm.length() * HeapRegion::GrainBytes; 1941 } 1942 1943 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 1944 hr->reset_gc_time_stamp(); 1945 } 1946 1947 #ifndef PRODUCT 1948 1949 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 1950 private: 1951 unsigned _gc_time_stamp; 1952 bool _failures; 1953 1954 public: 1955 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 1956 _gc_time_stamp(gc_time_stamp), _failures(false) { } 1957 1958 virtual bool doHeapRegion(HeapRegion* hr) { 1959 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 1960 if (_gc_time_stamp != region_gc_time_stamp) { 1961 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 1962 region_gc_time_stamp, _gc_time_stamp); 1963 _failures = true; 1964 } 1965 return false; 1966 } 1967 1968 bool failures() { return _failures; } 1969 }; 1970 1971 void G1CollectedHeap::check_gc_time_stamps() { 1972 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 1973 heap_region_iterate(&cl); 1974 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 1975 } 1976 #endif // PRODUCT 1977 1978 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 1979 _hot_card_cache->drain(cl, worker_i); 1980 } 1981 1982 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 1983 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 1984 size_t n_completed_buffers = 0; 1985 while (dcqs.apply_closure_during_gc(cl, worker_i)) { 1986 n_completed_buffers++; 1987 } 1988 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 1989 dcqs.clear_n_completed_buffers(); 1990 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 1991 } 1992 1993 // Computes the sum of the storage used by the various regions. 1994 size_t G1CollectedHeap::used() const { 1995 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 1996 if (_archive_allocator != NULL) { 1997 result += _archive_allocator->used(); 1998 } 1999 return result; 2000 } 2001 2002 size_t G1CollectedHeap::used_unlocked() const { 2003 return _summary_bytes_used; 2004 } 2005 2006 class SumUsedClosure: public HeapRegionClosure { 2007 size_t _used; 2008 public: 2009 SumUsedClosure() : _used(0) {} 2010 bool doHeapRegion(HeapRegion* r) { 2011 _used += r->used(); 2012 return false; 2013 } 2014 size_t result() { return _used; } 2015 }; 2016 2017 size_t G1CollectedHeap::recalculate_used() const { 2018 double recalculate_used_start = os::elapsedTime(); 2019 2020 SumUsedClosure blk; 2021 heap_region_iterate(&blk); 2022 2023 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2024 return blk.result(); 2025 } 2026 2027 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2028 switch (cause) { 2029 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2030 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2031 case GCCause::_update_allocation_context_stats_inc: return true; 2032 case GCCause::_wb_conc_mark: return true; 2033 default : return false; 2034 } 2035 } 2036 2037 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2038 switch (cause) { 2039 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2040 case GCCause::_g1_humongous_allocation: return true; 2041 default: return is_user_requested_concurrent_full_gc(cause); 2042 } 2043 } 2044 2045 #ifndef PRODUCT 2046 void G1CollectedHeap::allocate_dummy_regions() { 2047 // Let's fill up most of the region 2048 size_t word_size = HeapRegion::GrainWords - 1024; 2049 // And as a result the region we'll allocate will be humongous. 2050 guarantee(is_humongous(word_size), "sanity"); 2051 2052 // _filler_array_max_size is set to humongous object threshold 2053 // but temporarily change it to use CollectedHeap::fill_with_object(). 2054 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2055 2056 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2057 // Let's use the existing mechanism for the allocation 2058 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2059 AllocationContext::system()); 2060 if (dummy_obj != NULL) { 2061 MemRegion mr(dummy_obj, word_size); 2062 CollectedHeap::fill_with_object(mr); 2063 } else { 2064 // If we can't allocate once, we probably cannot allocate 2065 // again. Let's get out of the loop. 2066 break; 2067 } 2068 } 2069 } 2070 #endif // !PRODUCT 2071 2072 void G1CollectedHeap::increment_old_marking_cycles_started() { 2073 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2074 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2075 "Wrong marking cycle count (started: %d, completed: %d)", 2076 _old_marking_cycles_started, _old_marking_cycles_completed); 2077 2078 _old_marking_cycles_started++; 2079 } 2080 2081 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2082 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2083 2084 // We assume that if concurrent == true, then the caller is a 2085 // concurrent thread that was joined the Suspendible Thread 2086 // Set. If there's ever a cheap way to check this, we should add an 2087 // assert here. 2088 2089 // Given that this method is called at the end of a Full GC or of a 2090 // concurrent cycle, and those can be nested (i.e., a Full GC can 2091 // interrupt a concurrent cycle), the number of full collections 2092 // completed should be either one (in the case where there was no 2093 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2094 // behind the number of full collections started. 2095 2096 // This is the case for the inner caller, i.e. a Full GC. 2097 assert(concurrent || 2098 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2099 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2100 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2101 "is inconsistent with _old_marking_cycles_completed = %u", 2102 _old_marking_cycles_started, _old_marking_cycles_completed); 2103 2104 // This is the case for the outer caller, i.e. the concurrent cycle. 2105 assert(!concurrent || 2106 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2107 "for outer caller (concurrent cycle): " 2108 "_old_marking_cycles_started = %u " 2109 "is inconsistent with _old_marking_cycles_completed = %u", 2110 _old_marking_cycles_started, _old_marking_cycles_completed); 2111 2112 _old_marking_cycles_completed += 1; 2113 2114 // We need to clear the "in_progress" flag in the CM thread before 2115 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2116 // is set) so that if a waiter requests another System.gc() it doesn't 2117 // incorrectly see that a marking cycle is still in progress. 2118 if (concurrent) { 2119 _cmThread->set_idle(); 2120 } 2121 2122 // This notify_all() will ensure that a thread that called 2123 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2124 // and it's waiting for a full GC to finish will be woken up. It is 2125 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2126 FullGCCount_lock->notify_all(); 2127 } 2128 2129 void G1CollectedHeap::collect(GCCause::Cause cause) { 2130 assert_heap_not_locked(); 2131 2132 uint gc_count_before; 2133 uint old_marking_count_before; 2134 uint full_gc_count_before; 2135 bool retry_gc; 2136 2137 do { 2138 retry_gc = false; 2139 2140 { 2141 MutexLocker ml(Heap_lock); 2142 2143 // Read the GC count while holding the Heap_lock 2144 gc_count_before = total_collections(); 2145 full_gc_count_before = total_full_collections(); 2146 old_marking_count_before = _old_marking_cycles_started; 2147 } 2148 2149 if (should_do_concurrent_full_gc(cause)) { 2150 // Schedule an initial-mark evacuation pause that will start a 2151 // concurrent cycle. We're setting word_size to 0 which means that 2152 // we are not requesting a post-GC allocation. 2153 VM_G1IncCollectionPause op(gc_count_before, 2154 0, /* word_size */ 2155 true, /* should_initiate_conc_mark */ 2156 g1_policy()->max_pause_time_ms(), 2157 cause); 2158 op.set_allocation_context(AllocationContext::current()); 2159 2160 VMThread::execute(&op); 2161 if (!op.pause_succeeded()) { 2162 if (old_marking_count_before == _old_marking_cycles_started) { 2163 retry_gc = op.should_retry_gc(); 2164 } else { 2165 // A Full GC happened while we were trying to schedule the 2166 // initial-mark GC. No point in starting a new cycle given 2167 // that the whole heap was collected anyway. 2168 } 2169 2170 if (retry_gc) { 2171 if (GCLocker::is_active_and_needs_gc()) { 2172 GCLocker::stall_until_clear(); 2173 } 2174 } 2175 } 2176 } else { 2177 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2178 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2179 2180 // Schedule a standard evacuation pause. We're setting word_size 2181 // to 0 which means that we are not requesting a post-GC allocation. 2182 VM_G1IncCollectionPause op(gc_count_before, 2183 0, /* word_size */ 2184 false, /* should_initiate_conc_mark */ 2185 g1_policy()->max_pause_time_ms(), 2186 cause); 2187 VMThread::execute(&op); 2188 } else { 2189 // Schedule a Full GC. 2190 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2191 VMThread::execute(&op); 2192 } 2193 } 2194 } while (retry_gc); 2195 } 2196 2197 bool G1CollectedHeap::is_in(const void* p) const { 2198 if (_hrm.reserved().contains(p)) { 2199 // Given that we know that p is in the reserved space, 2200 // heap_region_containing() should successfully 2201 // return the containing region. 2202 HeapRegion* hr = heap_region_containing(p); 2203 return hr->is_in(p); 2204 } else { 2205 return false; 2206 } 2207 } 2208 2209 #ifdef ASSERT 2210 bool G1CollectedHeap::is_in_exact(const void* p) const { 2211 bool contains = reserved_region().contains(p); 2212 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2213 if (contains && available) { 2214 return true; 2215 } else { 2216 return false; 2217 } 2218 } 2219 #endif 2220 2221 // Iteration functions. 2222 2223 // Iterates an ObjectClosure over all objects within a HeapRegion. 2224 2225 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2226 ObjectClosure* _cl; 2227 public: 2228 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2229 bool doHeapRegion(HeapRegion* r) { 2230 if (!r->is_continues_humongous()) { 2231 r->object_iterate(_cl); 2232 } 2233 return false; 2234 } 2235 }; 2236 2237 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2238 IterateObjectClosureRegionClosure blk(cl); 2239 heap_region_iterate(&blk); 2240 } 2241 2242 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2243 _hrm.iterate(cl); 2244 } 2245 2246 void G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2247 uint worker_id, 2248 HeapRegionClaimer *hrclaimer) const { 2249 _hrm.par_iterate(cl, worker_id, hrclaimer); 2250 } 2251 2252 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2253 _collection_set.iterate(cl); 2254 } 2255 2256 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2257 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2258 } 2259 2260 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2261 HeapRegion* result = _hrm.next_region_in_heap(from); 2262 while (result != NULL && result->is_pinned()) { 2263 result = _hrm.next_region_in_heap(result); 2264 } 2265 return result; 2266 } 2267 2268 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2269 HeapRegion* hr = heap_region_containing(addr); 2270 return hr->block_start(addr); 2271 } 2272 2273 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2274 HeapRegion* hr = heap_region_containing(addr); 2275 return hr->block_size(addr); 2276 } 2277 2278 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2279 HeapRegion* hr = heap_region_containing(addr); 2280 return hr->block_is_obj(addr); 2281 } 2282 2283 bool G1CollectedHeap::supports_tlab_allocation() const { 2284 return true; 2285 } 2286 2287 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2288 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2289 } 2290 2291 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2292 return _eden.length() * HeapRegion::GrainBytes; 2293 } 2294 2295 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2296 // must be equal to the humongous object limit. 2297 size_t G1CollectedHeap::max_tlab_size() const { 2298 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2299 } 2300 2301 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2302 AllocationContext_t context = AllocationContext::current(); 2303 return _allocator->unsafe_max_tlab_alloc(context); 2304 } 2305 2306 size_t G1CollectedHeap::max_capacity() const { 2307 return _hrm.reserved().byte_size(); 2308 } 2309 2310 jlong G1CollectedHeap::millis_since_last_gc() { 2311 // See the notes in GenCollectedHeap::millis_since_last_gc() 2312 // for more information about the implementation. 2313 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2314 _g1_policy->collection_pause_end_millis(); 2315 if (ret_val < 0) { 2316 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2317 ". returning zero instead.", ret_val); 2318 return 0; 2319 } 2320 return ret_val; 2321 } 2322 2323 void G1CollectedHeap::prepare_for_verify() { 2324 _verifier->prepare_for_verify(); 2325 } 2326 2327 void G1CollectedHeap::verify(VerifyOption vo) { 2328 _verifier->verify(vo); 2329 } 2330 2331 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2332 return true; 2333 } 2334 2335 const char* const* G1CollectedHeap::concurrent_phases() const { 2336 return _cmThread->concurrent_phases(); 2337 } 2338 2339 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2340 return _cmThread->request_concurrent_phase(phase); 2341 } 2342 2343 class PrintRegionClosure: public HeapRegionClosure { 2344 outputStream* _st; 2345 public: 2346 PrintRegionClosure(outputStream* st) : _st(st) {} 2347 bool doHeapRegion(HeapRegion* r) { 2348 r->print_on(_st); 2349 return false; 2350 } 2351 }; 2352 2353 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2354 const HeapRegion* hr, 2355 const VerifyOption vo) const { 2356 switch (vo) { 2357 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2358 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2359 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 2360 default: ShouldNotReachHere(); 2361 } 2362 return false; // keep some compilers happy 2363 } 2364 2365 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2366 const VerifyOption vo) const { 2367 switch (vo) { 2368 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2369 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2370 case VerifyOption_G1UseMarkWord: { 2371 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 2372 return !obj->is_gc_marked() && !hr->is_archive(); 2373 } 2374 default: ShouldNotReachHere(); 2375 } 2376 return false; // keep some compilers happy 2377 } 2378 2379 void G1CollectedHeap::print_heap_regions() const { 2380 LogTarget(Trace, gc, heap, region) lt; 2381 if (lt.is_enabled()) { 2382 LogStream ls(lt); 2383 print_regions_on(&ls); 2384 } 2385 } 2386 2387 void G1CollectedHeap::print_on(outputStream* st) const { 2388 st->print(" %-20s", "garbage-first heap"); 2389 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2390 capacity()/K, used_unlocked()/K); 2391 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 2392 p2i(_hrm.reserved().start()), 2393 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 2394 p2i(_hrm.reserved().end())); 2395 st->cr(); 2396 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2397 uint young_regions = young_regions_count(); 2398 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2399 (size_t) young_regions * HeapRegion::GrainBytes / K); 2400 uint survivor_regions = survivor_regions_count(); 2401 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2402 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2403 st->cr(); 2404 MetaspaceAux::print_on(st); 2405 } 2406 2407 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2408 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2409 "HS=humongous(starts), HC=humongous(continues), " 2410 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2411 "AC=allocation context, " 2412 "TAMS=top-at-mark-start (previous, next)"); 2413 PrintRegionClosure blk(st); 2414 heap_region_iterate(&blk); 2415 } 2416 2417 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2418 print_on(st); 2419 2420 // Print the per-region information. 2421 print_regions_on(st); 2422 } 2423 2424 void G1CollectedHeap::print_on_error(outputStream* st) const { 2425 this->CollectedHeap::print_on_error(st); 2426 2427 if (_cm != NULL) { 2428 st->cr(); 2429 _cm->print_on_error(st); 2430 } 2431 } 2432 2433 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2434 workers()->print_worker_threads_on(st); 2435 _cmThread->print_on(st); 2436 st->cr(); 2437 _cm->print_worker_threads_on(st); 2438 _cg1r->print_worker_threads_on(st); // also prints the sample thread 2439 if (G1StringDedup::is_enabled()) { 2440 G1StringDedup::print_worker_threads_on(st); 2441 } 2442 } 2443 2444 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2445 workers()->threads_do(tc); 2446 tc->do_thread(_cmThread); 2447 _cm->threads_do(tc); 2448 _cg1r->threads_do(tc); // also iterates over the sample thread 2449 if (G1StringDedup::is_enabled()) { 2450 G1StringDedup::threads_do(tc); 2451 } 2452 } 2453 2454 void G1CollectedHeap::print_tracing_info() const { 2455 g1_rem_set()->print_summary_info(); 2456 concurrent_mark()->print_summary_info(); 2457 } 2458 2459 #ifndef PRODUCT 2460 // Helpful for debugging RSet issues. 2461 2462 class PrintRSetsClosure : public HeapRegionClosure { 2463 private: 2464 const char* _msg; 2465 size_t _occupied_sum; 2466 2467 public: 2468 bool doHeapRegion(HeapRegion* r) { 2469 HeapRegionRemSet* hrrs = r->rem_set(); 2470 size_t occupied = hrrs->occupied(); 2471 _occupied_sum += occupied; 2472 2473 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2474 if (occupied == 0) { 2475 tty->print_cr(" RSet is empty"); 2476 } else { 2477 hrrs->print(); 2478 } 2479 tty->print_cr("----------"); 2480 return false; 2481 } 2482 2483 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2484 tty->cr(); 2485 tty->print_cr("========================================"); 2486 tty->print_cr("%s", msg); 2487 tty->cr(); 2488 } 2489 2490 ~PrintRSetsClosure() { 2491 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2492 tty->print_cr("========================================"); 2493 tty->cr(); 2494 } 2495 }; 2496 2497 void G1CollectedHeap::print_cset_rsets() { 2498 PrintRSetsClosure cl("Printing CSet RSets"); 2499 collection_set_iterate(&cl); 2500 } 2501 2502 void G1CollectedHeap::print_all_rsets() { 2503 PrintRSetsClosure cl("Printing All RSets");; 2504 heap_region_iterate(&cl); 2505 } 2506 #endif // PRODUCT 2507 2508 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2509 2510 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2511 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2512 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2513 2514 size_t eden_capacity_bytes = 2515 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2516 2517 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2518 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2519 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2520 } 2521 2522 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2523 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2524 stats->unused(), stats->used(), stats->region_end_waste(), 2525 stats->regions_filled(), stats->direct_allocated(), 2526 stats->failure_used(), stats->failure_waste()); 2527 } 2528 2529 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2530 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2531 gc_tracer->report_gc_heap_summary(when, heap_summary); 2532 2533 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2534 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2535 } 2536 2537 G1CollectedHeap* G1CollectedHeap::heap() { 2538 CollectedHeap* heap = Universe::heap(); 2539 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2540 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2541 return (G1CollectedHeap*)heap; 2542 } 2543 2544 void G1CollectedHeap::gc_prologue(bool full) { 2545 // always_do_update_barrier = false; 2546 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2547 2548 // This summary needs to be printed before incrementing total collections. 2549 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2550 2551 // Update common counters. 2552 increment_total_collections(full /* full gc */); 2553 if (full) { 2554 increment_old_marking_cycles_started(); 2555 reset_gc_time_stamp(); 2556 } else { 2557 increment_gc_time_stamp(); 2558 } 2559 2560 // Fill TLAB's and such 2561 double start = os::elapsedTime(); 2562 accumulate_statistics_all_tlabs(); 2563 ensure_parsability(true); 2564 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2565 } 2566 2567 void G1CollectedHeap::gc_epilogue(bool full) { 2568 // Update common counters. 2569 if (full) { 2570 // Update the number of full collections that have been completed. 2571 increment_old_marking_cycles_completed(false /* concurrent */); 2572 } 2573 2574 // We are at the end of the GC. Total collections has already been increased. 2575 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2576 2577 // FIXME: what is this about? 2578 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2579 // is set. 2580 #if defined(COMPILER2) || INCLUDE_JVMCI 2581 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2582 #endif 2583 // always_do_update_barrier = true; 2584 2585 double start = os::elapsedTime(); 2586 resize_all_tlabs(); 2587 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2588 2589 allocation_context_stats().update(full); 2590 2591 MemoryService::track_memory_usage(); 2592 // We have just completed a GC. Update the soft reference 2593 // policy with the new heap occupancy 2594 Universe::update_heap_info_at_gc(); 2595 } 2596 2597 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2598 uint gc_count_before, 2599 bool* succeeded, 2600 GCCause::Cause gc_cause) { 2601 assert_heap_not_locked_and_not_at_safepoint(); 2602 VM_G1IncCollectionPause op(gc_count_before, 2603 word_size, 2604 false, /* should_initiate_conc_mark */ 2605 g1_policy()->max_pause_time_ms(), 2606 gc_cause); 2607 2608 op.set_allocation_context(AllocationContext::current()); 2609 VMThread::execute(&op); 2610 2611 HeapWord* result = op.result(); 2612 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2613 assert(result == NULL || ret_succeeded, 2614 "the result should be NULL if the VM did not succeed"); 2615 *succeeded = ret_succeeded; 2616 2617 assert_heap_not_locked(); 2618 return result; 2619 } 2620 2621 void 2622 G1CollectedHeap::doConcurrentMark() { 2623 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2624 if (!_cmThread->in_progress()) { 2625 _cmThread->set_started(); 2626 CGC_lock->notify(); 2627 } 2628 } 2629 2630 size_t G1CollectedHeap::pending_card_num() { 2631 size_t extra_cards = 0; 2632 JavaThread *curr = Threads::first(); 2633 while (curr != NULL) { 2634 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2635 extra_cards += dcq.size(); 2636 curr = curr->next(); 2637 } 2638 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2639 size_t buffer_size = dcqs.buffer_size(); 2640 size_t buffer_num = dcqs.completed_buffers_num(); 2641 2642 return buffer_size * buffer_num + extra_cards; 2643 } 2644 2645 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2646 private: 2647 size_t _total_humongous; 2648 size_t _candidate_humongous; 2649 2650 DirtyCardQueue _dcq; 2651 2652 // We don't nominate objects with many remembered set entries, on 2653 // the assumption that such objects are likely still live. 2654 bool is_remset_small(HeapRegion* region) const { 2655 HeapRegionRemSet* const rset = region->rem_set(); 2656 return G1EagerReclaimHumongousObjectsWithStaleRefs 2657 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2658 : rset->is_empty(); 2659 } 2660 2661 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2662 assert(region->is_starts_humongous(), "Must start a humongous object"); 2663 2664 oop obj = oop(region->bottom()); 2665 2666 // Dead objects cannot be eager reclaim candidates. Due to class 2667 // unloading it is unsafe to query their classes so we return early. 2668 if (heap->is_obj_dead(obj, region)) { 2669 return false; 2670 } 2671 2672 // Candidate selection must satisfy the following constraints 2673 // while concurrent marking is in progress: 2674 // 2675 // * In order to maintain SATB invariants, an object must not be 2676 // reclaimed if it was allocated before the start of marking and 2677 // has not had its references scanned. Such an object must have 2678 // its references (including type metadata) scanned to ensure no 2679 // live objects are missed by the marking process. Objects 2680 // allocated after the start of concurrent marking don't need to 2681 // be scanned. 2682 // 2683 // * An object must not be reclaimed if it is on the concurrent 2684 // mark stack. Objects allocated after the start of concurrent 2685 // marking are never pushed on the mark stack. 2686 // 2687 // Nominating only objects allocated after the start of concurrent 2688 // marking is sufficient to meet both constraints. This may miss 2689 // some objects that satisfy the constraints, but the marking data 2690 // structures don't support efficiently performing the needed 2691 // additional tests or scrubbing of the mark stack. 2692 // 2693 // However, we presently only nominate is_typeArray() objects. 2694 // A humongous object containing references induces remembered 2695 // set entries on other regions. In order to reclaim such an 2696 // object, those remembered sets would need to be cleaned up. 2697 // 2698 // We also treat is_typeArray() objects specially, allowing them 2699 // to be reclaimed even if allocated before the start of 2700 // concurrent mark. For this we rely on mark stack insertion to 2701 // exclude is_typeArray() objects, preventing reclaiming an object 2702 // that is in the mark stack. We also rely on the metadata for 2703 // such objects to be built-in and so ensured to be kept live. 2704 // Frequent allocation and drop of large binary blobs is an 2705 // important use case for eager reclaim, and this special handling 2706 // may reduce needed headroom. 2707 2708 return obj->is_typeArray() && is_remset_small(region); 2709 } 2710 2711 public: 2712 RegisterHumongousWithInCSetFastTestClosure() 2713 : _total_humongous(0), 2714 _candidate_humongous(0), 2715 _dcq(&JavaThread::dirty_card_queue_set()) { 2716 } 2717 2718 virtual bool doHeapRegion(HeapRegion* r) { 2719 if (!r->is_starts_humongous()) { 2720 return false; 2721 } 2722 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2723 2724 bool is_candidate = humongous_region_is_candidate(g1h, r); 2725 uint rindex = r->hrm_index(); 2726 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2727 if (is_candidate) { 2728 _candidate_humongous++; 2729 g1h->register_humongous_region_with_cset(rindex); 2730 // Is_candidate already filters out humongous object with large remembered sets. 2731 // If we have a humongous object with a few remembered sets, we simply flush these 2732 // remembered set entries into the DCQS. That will result in automatic 2733 // re-evaluation of their remembered set entries during the following evacuation 2734 // phase. 2735 if (!r->rem_set()->is_empty()) { 2736 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2737 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2738 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 2739 HeapRegionRemSetIterator hrrs(r->rem_set()); 2740 size_t card_index; 2741 while (hrrs.has_next(card_index)) { 2742 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 2743 // The remembered set might contain references to already freed 2744 // regions. Filter out such entries to avoid failing card table 2745 // verification. 2746 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 2747 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 2748 *card_ptr = CardTableModRefBS::dirty_card_val(); 2749 _dcq.enqueue(card_ptr); 2750 } 2751 } 2752 } 2753 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2754 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2755 hrrs.n_yielded(), r->rem_set()->occupied()); 2756 r->rem_set()->clear_locked(); 2757 } 2758 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2759 } 2760 _total_humongous++; 2761 2762 return false; 2763 } 2764 2765 size_t total_humongous() const { return _total_humongous; } 2766 size_t candidate_humongous() const { return _candidate_humongous; } 2767 2768 void flush_rem_set_entries() { _dcq.flush(); } 2769 }; 2770 2771 void G1CollectedHeap::register_humongous_regions_with_cset() { 2772 if (!G1EagerReclaimHumongousObjects) { 2773 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2774 return; 2775 } 2776 double time = os::elapsed_counter(); 2777 2778 // Collect reclaim candidate information and register candidates with cset. 2779 RegisterHumongousWithInCSetFastTestClosure cl; 2780 heap_region_iterate(&cl); 2781 2782 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2783 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2784 cl.total_humongous(), 2785 cl.candidate_humongous()); 2786 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2787 2788 // Finally flush all remembered set entries to re-check into the global DCQS. 2789 cl.flush_rem_set_entries(); 2790 } 2791 2792 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2793 public: 2794 bool doHeapRegion(HeapRegion* hr) { 2795 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2796 hr->verify_rem_set(); 2797 } 2798 return false; 2799 } 2800 }; 2801 2802 uint G1CollectedHeap::num_task_queues() const { 2803 return _task_queues->size(); 2804 } 2805 2806 #if TASKQUEUE_STATS 2807 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2808 st->print_raw_cr("GC Task Stats"); 2809 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2810 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2811 } 2812 2813 void G1CollectedHeap::print_taskqueue_stats() const { 2814 if (!log_is_enabled(Trace, gc, task, stats)) { 2815 return; 2816 } 2817 Log(gc, task, stats) log; 2818 ResourceMark rm; 2819 LogStream ls(log.trace()); 2820 outputStream* st = &ls; 2821 2822 print_taskqueue_stats_hdr(st); 2823 2824 TaskQueueStats totals; 2825 const uint n = num_task_queues(); 2826 for (uint i = 0; i < n; ++i) { 2827 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2828 totals += task_queue(i)->stats; 2829 } 2830 st->print_raw("tot "); totals.print(st); st->cr(); 2831 2832 DEBUG_ONLY(totals.verify()); 2833 } 2834 2835 void G1CollectedHeap::reset_taskqueue_stats() { 2836 const uint n = num_task_queues(); 2837 for (uint i = 0; i < n; ++i) { 2838 task_queue(i)->stats.reset(); 2839 } 2840 } 2841 #endif // TASKQUEUE_STATS 2842 2843 void G1CollectedHeap::wait_for_root_region_scanning() { 2844 double scan_wait_start = os::elapsedTime(); 2845 // We have to wait until the CM threads finish scanning the 2846 // root regions as it's the only way to ensure that all the 2847 // objects on them have been correctly scanned before we start 2848 // moving them during the GC. 2849 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2850 double wait_time_ms = 0.0; 2851 if (waited) { 2852 double scan_wait_end = os::elapsedTime(); 2853 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2854 } 2855 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2856 } 2857 2858 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2859 private: 2860 G1HRPrinter* _hr_printer; 2861 public: 2862 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2863 2864 virtual bool doHeapRegion(HeapRegion* r) { 2865 _hr_printer->cset(r); 2866 return false; 2867 } 2868 }; 2869 2870 void G1CollectedHeap::start_new_collection_set() { 2871 collection_set()->start_incremental_building(); 2872 2873 clear_cset_fast_test(); 2874 2875 guarantee(_eden.length() == 0, "eden should have been cleared"); 2876 g1_policy()->transfer_survivors_to_cset(survivor()); 2877 } 2878 2879 bool 2880 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2881 assert_at_safepoint(true /* should_be_vm_thread */); 2882 guarantee(!is_gc_active(), "collection is not reentrant"); 2883 2884 if (GCLocker::check_active_before_gc()) { 2885 return false; 2886 } 2887 2888 _gc_timer_stw->register_gc_start(); 2889 2890 GCIdMark gc_id_mark; 2891 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2892 2893 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2894 ResourceMark rm; 2895 2896 g1_policy()->note_gc_start(); 2897 2898 wait_for_root_region_scanning(); 2899 2900 print_heap_before_gc(); 2901 print_heap_regions(); 2902 trace_heap_before_gc(_gc_tracer_stw); 2903 2904 _verifier->verify_region_sets_optional(); 2905 _verifier->verify_dirty_young_regions(); 2906 2907 // We should not be doing initial mark unless the conc mark thread is running 2908 if (!_cmThread->should_terminate()) { 2909 // This call will decide whether this pause is an initial-mark 2910 // pause. If it is, during_initial_mark_pause() will return true 2911 // for the duration of this pause. 2912 g1_policy()->decide_on_conc_mark_initiation(); 2913 } 2914 2915 // We do not allow initial-mark to be piggy-backed on a mixed GC. 2916 assert(!collector_state()->during_initial_mark_pause() || 2917 collector_state()->gcs_are_young(), "sanity"); 2918 2919 // We also do not allow mixed GCs during marking. 2920 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 2921 2922 // Record whether this pause is an initial mark. When the current 2923 // thread has completed its logging output and it's safe to signal 2924 // the CM thread, the flag's value in the policy has been reset. 2925 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 2926 2927 // Inner scope for scope based logging, timers, and stats collection 2928 { 2929 EvacuationInfo evacuation_info; 2930 2931 if (collector_state()->during_initial_mark_pause()) { 2932 // We are about to start a marking cycle, so we increment the 2933 // full collection counter. 2934 increment_old_marking_cycles_started(); 2935 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 2936 } 2937 2938 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 2939 2940 GCTraceCPUTime tcpu; 2941 2942 FormatBuffer<> gc_string("Pause "); 2943 if (collector_state()->during_initial_mark_pause()) { 2944 gc_string.append("Initial Mark"); 2945 } else if (collector_state()->gcs_are_young()) { 2946 gc_string.append("Young"); 2947 } else { 2948 gc_string.append("Mixed"); 2949 } 2950 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 2951 2952 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 2953 workers()->active_workers(), 2954 Threads::number_of_non_daemon_threads()); 2955 workers()->update_active_workers(active_workers); 2956 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 2957 2958 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 2959 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 2960 2961 // If the secondary_free_list is not empty, append it to the 2962 // free_list. No need to wait for the cleanup operation to finish; 2963 // the region allocation code will check the secondary_free_list 2964 // and wait if necessary. If the G1StressConcRegionFreeing flag is 2965 // set, skip this step so that the region allocation code has to 2966 // get entries from the secondary_free_list. 2967 if (!G1StressConcRegionFreeing) { 2968 append_secondary_free_list_if_not_empty_with_lock(); 2969 } 2970 2971 G1HeapTransition heap_transition(this); 2972 size_t heap_used_bytes_before_gc = used(); 2973 2974 // Don't dynamically change the number of GC threads this early. A value of 2975 // 0 is used to indicate serial work. When parallel work is done, 2976 // it will be set. 2977 2978 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 2979 IsGCActiveMark x; 2980 2981 gc_prologue(false); 2982 2983 if (VerifyRememberedSets) { 2984 log_info(gc, verify)("[Verifying RemSets before GC]"); 2985 VerifyRegionRemSetClosure v_cl; 2986 heap_region_iterate(&v_cl); 2987 } 2988 2989 _verifier->verify_before_gc(); 2990 2991 _verifier->check_bitmaps("GC Start"); 2992 2993 #if defined(COMPILER2) || INCLUDE_JVMCI 2994 DerivedPointerTable::clear(); 2995 #endif 2996 2997 // Please see comment in g1CollectedHeap.hpp and 2998 // G1CollectedHeap::ref_processing_init() to see how 2999 // reference processing currently works in G1. 3000 3001 // Enable discovery in the STW reference processor 3002 if (g1_policy()->should_process_references()) { 3003 ref_processor_stw()->enable_discovery(); 3004 } else { 3005 ref_processor_stw()->disable_discovery(); 3006 } 3007 3008 { 3009 // We want to temporarily turn off discovery by the 3010 // CM ref processor, if necessary, and turn it back on 3011 // on again later if we do. Using a scoped 3012 // NoRefDiscovery object will do this. 3013 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3014 3015 // Forget the current alloc region (we might even choose it to be part 3016 // of the collection set!). 3017 _allocator->release_mutator_alloc_region(); 3018 3019 // This timing is only used by the ergonomics to handle our pause target. 3020 // It is unclear why this should not include the full pause. We will 3021 // investigate this in CR 7178365. 3022 // 3023 // Preserving the old comment here if that helps the investigation: 3024 // 3025 // The elapsed time induced by the start time below deliberately elides 3026 // the possible verification above. 3027 double sample_start_time_sec = os::elapsedTime(); 3028 3029 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3030 3031 if (collector_state()->during_initial_mark_pause()) { 3032 concurrent_mark()->checkpointRootsInitialPre(); 3033 } 3034 3035 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 3036 3037 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3038 3039 // Make sure the remembered sets are up to date. This needs to be 3040 // done before register_humongous_regions_with_cset(), because the 3041 // remembered sets are used there to choose eager reclaim candidates. 3042 // If the remembered sets are not up to date we might miss some 3043 // entries that need to be handled. 3044 g1_rem_set()->cleanupHRRS(); 3045 3046 register_humongous_regions_with_cset(); 3047 3048 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3049 3050 // We call this after finalize_cset() to 3051 // ensure that the CSet has been finalized. 3052 _cm->verify_no_cset_oops(); 3053 3054 if (_hr_printer.is_active()) { 3055 G1PrintCollectionSetClosure cl(&_hr_printer); 3056 _collection_set.iterate(&cl); 3057 } 3058 3059 // Initialize the GC alloc regions. 3060 _allocator->init_gc_alloc_regions(evacuation_info); 3061 3062 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3063 pre_evacuate_collection_set(); 3064 3065 // Actually do the work... 3066 evacuate_collection_set(evacuation_info, &per_thread_states); 3067 3068 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3069 3070 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3071 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 3072 3073 eagerly_reclaim_humongous_regions(); 3074 3075 record_obj_copy_mem_stats(); 3076 _survivor_evac_stats.adjust_desired_plab_sz(); 3077 _old_evac_stats.adjust_desired_plab_sz(); 3078 3079 double start = os::elapsedTime(); 3080 start_new_collection_set(); 3081 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 3082 3083 if (evacuation_failed()) { 3084 set_used(recalculate_used()); 3085 if (_archive_allocator != NULL) { 3086 _archive_allocator->clear_used(); 3087 } 3088 for (uint i = 0; i < ParallelGCThreads; i++) { 3089 if (_evacuation_failed_info_array[i].has_failed()) { 3090 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3091 } 3092 } 3093 } else { 3094 // The "used" of the the collection set have already been subtracted 3095 // when they were freed. Add in the bytes evacuated. 3096 increase_used(g1_policy()->bytes_copied_during_gc()); 3097 } 3098 3099 if (collector_state()->during_initial_mark_pause()) { 3100 // We have to do this before we notify the CM threads that 3101 // they can start working to make sure that all the 3102 // appropriate initialization is done on the CM object. 3103 concurrent_mark()->checkpointRootsInitialPost(); 3104 collector_state()->set_mark_in_progress(true); 3105 // Note that we don't actually trigger the CM thread at 3106 // this point. We do that later when we're sure that 3107 // the current thread has completed its logging output. 3108 } 3109 3110 allocate_dummy_regions(); 3111 3112 _allocator->init_mutator_alloc_region(); 3113 3114 { 3115 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3116 if (expand_bytes > 0) { 3117 size_t bytes_before = capacity(); 3118 // No need for an ergo logging here, 3119 // expansion_amount() does this when it returns a value > 0. 3120 double expand_ms; 3121 if (!expand(expand_bytes, _workers, &expand_ms)) { 3122 // We failed to expand the heap. Cannot do anything about it. 3123 } 3124 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3125 } 3126 } 3127 3128 // We redo the verification but now wrt to the new CSet which 3129 // has just got initialized after the previous CSet was freed. 3130 _cm->verify_no_cset_oops(); 3131 3132 // This timing is only used by the ergonomics to handle our pause target. 3133 // It is unclear why this should not include the full pause. We will 3134 // investigate this in CR 7178365. 3135 double sample_end_time_sec = os::elapsedTime(); 3136 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3137 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards); 3138 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3139 3140 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3141 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3142 3143 if (VerifyRememberedSets) { 3144 log_info(gc, verify)("[Verifying RemSets after GC]"); 3145 VerifyRegionRemSetClosure v_cl; 3146 heap_region_iterate(&v_cl); 3147 } 3148 3149 _verifier->verify_after_gc(); 3150 _verifier->check_bitmaps("GC End"); 3151 3152 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3153 ref_processor_stw()->verify_no_references_recorded(); 3154 3155 // CM reference discovery will be re-enabled if necessary. 3156 } 3157 3158 #ifdef TRACESPINNING 3159 ParallelTaskTerminator::print_termination_counts(); 3160 #endif 3161 3162 gc_epilogue(false); 3163 } 3164 3165 // Print the remainder of the GC log output. 3166 if (evacuation_failed()) { 3167 log_info(gc)("To-space exhausted"); 3168 } 3169 3170 g1_policy()->print_phases(); 3171 heap_transition.print(); 3172 3173 // It is not yet to safe to tell the concurrent mark to 3174 // start as we have some optional output below. We don't want the 3175 // output from the concurrent mark thread interfering with this 3176 // logging output either. 3177 3178 _hrm.verify_optional(); 3179 _verifier->verify_region_sets_optional(); 3180 3181 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3182 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3183 3184 print_heap_after_gc(); 3185 print_heap_regions(); 3186 trace_heap_after_gc(_gc_tracer_stw); 3187 3188 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3189 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3190 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3191 // before any GC notifications are raised. 3192 g1mm()->update_sizes(); 3193 3194 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3195 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3196 _gc_timer_stw->register_gc_end(); 3197 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3198 } 3199 // It should now be safe to tell the concurrent mark thread to start 3200 // without its logging output interfering with the logging output 3201 // that came from the pause. 3202 3203 if (should_start_conc_mark) { 3204 // CAUTION: after the doConcurrentMark() call below, 3205 // the concurrent marking thread(s) could be running 3206 // concurrently with us. Make sure that anything after 3207 // this point does not assume that we are the only GC thread 3208 // running. Note: of course, the actual marking work will 3209 // not start until the safepoint itself is released in 3210 // SuspendibleThreadSet::desynchronize(). 3211 doConcurrentMark(); 3212 } 3213 3214 return true; 3215 } 3216 3217 void G1CollectedHeap::remove_self_forwarding_pointers() { 3218 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3219 workers()->run_task(&rsfp_task); 3220 } 3221 3222 void G1CollectedHeap::restore_after_evac_failure() { 3223 double remove_self_forwards_start = os::elapsedTime(); 3224 3225 remove_self_forwarding_pointers(); 3226 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3227 _preserved_marks_set.restore(&task_executor); 3228 3229 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3230 } 3231 3232 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3233 if (!_evacuation_failed) { 3234 _evacuation_failed = true; 3235 } 3236 3237 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3238 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3239 } 3240 3241 bool G1ParEvacuateFollowersClosure::offer_termination() { 3242 G1ParScanThreadState* const pss = par_scan_state(); 3243 start_term_time(); 3244 const bool res = terminator()->offer_termination(); 3245 end_term_time(); 3246 return res; 3247 } 3248 3249 void G1ParEvacuateFollowersClosure::do_void() { 3250 G1ParScanThreadState* const pss = par_scan_state(); 3251 pss->trim_queue(); 3252 do { 3253 pss->steal_and_trim_queue(queues()); 3254 } while (!offer_termination()); 3255 } 3256 3257 class G1ParTask : public AbstractGangTask { 3258 protected: 3259 G1CollectedHeap* _g1h; 3260 G1ParScanThreadStateSet* _pss; 3261 RefToScanQueueSet* _queues; 3262 G1RootProcessor* _root_processor; 3263 ParallelTaskTerminator _terminator; 3264 uint _n_workers; 3265 3266 public: 3267 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3268 : AbstractGangTask("G1 collection"), 3269 _g1h(g1h), 3270 _pss(per_thread_states), 3271 _queues(task_queues), 3272 _root_processor(root_processor), 3273 _terminator(n_workers, _queues), 3274 _n_workers(n_workers) 3275 {} 3276 3277 void work(uint worker_id) { 3278 if (worker_id >= _n_workers) return; // no work needed this round 3279 3280 double start_sec = os::elapsedTime(); 3281 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3282 3283 { 3284 ResourceMark rm; 3285 HandleMark hm; 3286 3287 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3288 3289 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3290 pss->set_ref_processor(rp); 3291 3292 double start_strong_roots_sec = os::elapsedTime(); 3293 3294 _root_processor->evacuate_roots(pss->closures(), worker_id); 3295 3296 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3297 // treating the nmethods visited to act as roots for concurrent marking. 3298 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3299 // objects copied by the current evacuation. 3300 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, 3301 pss->closures()->weak_codeblobs(), 3302 worker_id); 3303 3304 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3305 3306 double term_sec = 0.0; 3307 size_t evac_term_attempts = 0; 3308 { 3309 double start = os::elapsedTime(); 3310 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3311 evac.do_void(); 3312 3313 evac_term_attempts = evac.term_attempts(); 3314 term_sec = evac.term_time(); 3315 double elapsed_sec = os::elapsedTime() - start; 3316 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3317 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3318 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3319 } 3320 3321 assert(pss->queue_is_empty(), "should be empty"); 3322 3323 if (log_is_enabled(Debug, gc, task, stats)) { 3324 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3325 size_t lab_waste; 3326 size_t lab_undo_waste; 3327 pss->waste(lab_waste, lab_undo_waste); 3328 _g1h->print_termination_stats(worker_id, 3329 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3330 strong_roots_sec * 1000.0, /* strong roots time */ 3331 term_sec * 1000.0, /* evac term time */ 3332 evac_term_attempts, /* evac term attempts */ 3333 lab_waste, /* alloc buffer waste */ 3334 lab_undo_waste /* undo waste */ 3335 ); 3336 } 3337 3338 // Close the inner scope so that the ResourceMark and HandleMark 3339 // destructors are executed here and are included as part of the 3340 // "GC Worker Time". 3341 } 3342 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3343 } 3344 }; 3345 3346 void G1CollectedHeap::print_termination_stats_hdr() { 3347 log_debug(gc, task, stats)("GC Termination Stats"); 3348 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3349 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3350 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3351 } 3352 3353 void G1CollectedHeap::print_termination_stats(uint worker_id, 3354 double elapsed_ms, 3355 double strong_roots_ms, 3356 double term_ms, 3357 size_t term_attempts, 3358 size_t alloc_buffer_waste, 3359 size_t undo_waste) const { 3360 log_debug(gc, task, stats) 3361 ("%3d %9.2f %9.2f %6.2f " 3362 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3363 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3364 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3365 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3366 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3367 alloc_buffer_waste * HeapWordSize / K, 3368 undo_waste * HeapWordSize / K); 3369 } 3370 3371 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3372 private: 3373 BoolObjectClosure* _is_alive; 3374 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3375 3376 int _initial_string_table_size; 3377 int _initial_symbol_table_size; 3378 3379 bool _process_strings; 3380 int _strings_processed; 3381 int _strings_removed; 3382 3383 bool _process_symbols; 3384 int _symbols_processed; 3385 int _symbols_removed; 3386 3387 bool _process_string_dedup; 3388 3389 public: 3390 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3391 AbstractGangTask("String/Symbol Unlinking"), 3392 _is_alive(is_alive), 3393 _dedup_closure(is_alive, NULL, false), 3394 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3395 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3396 _process_string_dedup(process_string_dedup) { 3397 3398 _initial_string_table_size = StringTable::the_table()->table_size(); 3399 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3400 if (process_strings) { 3401 StringTable::clear_parallel_claimed_index(); 3402 } 3403 if (process_symbols) { 3404 SymbolTable::clear_parallel_claimed_index(); 3405 } 3406 } 3407 3408 ~G1StringAndSymbolCleaningTask() { 3409 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3410 "claim value %d after unlink less than initial string table size %d", 3411 StringTable::parallel_claimed_index(), _initial_string_table_size); 3412 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3413 "claim value %d after unlink less than initial symbol table size %d", 3414 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3415 3416 log_info(gc, stringtable)( 3417 "Cleaned string and symbol table, " 3418 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3419 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3420 strings_processed(), strings_removed(), 3421 symbols_processed(), symbols_removed()); 3422 } 3423 3424 void work(uint worker_id) { 3425 int strings_processed = 0; 3426 int strings_removed = 0; 3427 int symbols_processed = 0; 3428 int symbols_removed = 0; 3429 if (_process_strings) { 3430 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3431 Atomic::add(strings_processed, &_strings_processed); 3432 Atomic::add(strings_removed, &_strings_removed); 3433 } 3434 if (_process_symbols) { 3435 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3436 Atomic::add(symbols_processed, &_symbols_processed); 3437 Atomic::add(symbols_removed, &_symbols_removed); 3438 } 3439 if (_process_string_dedup) { 3440 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3441 } 3442 } 3443 3444 size_t strings_processed() const { return (size_t)_strings_processed; } 3445 size_t strings_removed() const { return (size_t)_strings_removed; } 3446 3447 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3448 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3449 }; 3450 3451 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3452 private: 3453 static Monitor* _lock; 3454 3455 BoolObjectClosure* const _is_alive; 3456 const bool _unloading_occurred; 3457 const uint _num_workers; 3458 3459 // Variables used to claim nmethods. 3460 CompiledMethod* _first_nmethod; 3461 CompiledMethod* volatile _claimed_nmethod; 3462 3463 // The list of nmethods that need to be processed by the second pass. 3464 CompiledMethod* volatile _postponed_list; 3465 volatile uint _num_entered_barrier; 3466 3467 public: 3468 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3469 _is_alive(is_alive), 3470 _unloading_occurred(unloading_occurred), 3471 _num_workers(num_workers), 3472 _first_nmethod(NULL), 3473 _claimed_nmethod(NULL), 3474 _postponed_list(NULL), 3475 _num_entered_barrier(0) 3476 { 3477 CompiledMethod::increase_unloading_clock(); 3478 // Get first alive nmethod 3479 CompiledMethodIterator iter = CompiledMethodIterator(); 3480 if(iter.next_alive()) { 3481 _first_nmethod = iter.method(); 3482 } 3483 _claimed_nmethod = _first_nmethod; 3484 } 3485 3486 ~G1CodeCacheUnloadingTask() { 3487 CodeCache::verify_clean_inline_caches(); 3488 3489 CodeCache::set_needs_cache_clean(false); 3490 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3491 3492 CodeCache::verify_icholder_relocations(); 3493 } 3494 3495 private: 3496 void add_to_postponed_list(CompiledMethod* nm) { 3497 CompiledMethod* old; 3498 do { 3499 old = _postponed_list; 3500 nm->set_unloading_next(old); 3501 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old); 3502 } 3503 3504 void clean_nmethod(CompiledMethod* nm) { 3505 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3506 3507 if (postponed) { 3508 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3509 add_to_postponed_list(nm); 3510 } 3511 3512 // Mark that this thread has been cleaned/unloaded. 3513 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3514 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3515 } 3516 3517 void clean_nmethod_postponed(CompiledMethod* nm) { 3518 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3519 } 3520 3521 static const int MaxClaimNmethods = 16; 3522 3523 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3524 CompiledMethod* first; 3525 CompiledMethodIterator last; 3526 3527 do { 3528 *num_claimed_nmethods = 0; 3529 3530 first = _claimed_nmethod; 3531 last = CompiledMethodIterator(first); 3532 3533 if (first != NULL) { 3534 3535 for (int i = 0; i < MaxClaimNmethods; i++) { 3536 if (!last.next_alive()) { 3537 break; 3538 } 3539 claimed_nmethods[i] = last.method(); 3540 (*num_claimed_nmethods)++; 3541 } 3542 } 3543 3544 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first); 3545 } 3546 3547 CompiledMethod* claim_postponed_nmethod() { 3548 CompiledMethod* claim; 3549 CompiledMethod* next; 3550 3551 do { 3552 claim = _postponed_list; 3553 if (claim == NULL) { 3554 return NULL; 3555 } 3556 3557 next = claim->unloading_next(); 3558 3559 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim); 3560 3561 return claim; 3562 } 3563 3564 public: 3565 // Mark that we're done with the first pass of nmethod cleaning. 3566 void barrier_mark(uint worker_id) { 3567 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3568 _num_entered_barrier++; 3569 if (_num_entered_barrier == _num_workers) { 3570 ml.notify_all(); 3571 } 3572 } 3573 3574 // See if we have to wait for the other workers to 3575 // finish their first-pass nmethod cleaning work. 3576 void barrier_wait(uint worker_id) { 3577 if (_num_entered_barrier < _num_workers) { 3578 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3579 while (_num_entered_barrier < _num_workers) { 3580 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3581 } 3582 } 3583 } 3584 3585 // Cleaning and unloading of nmethods. Some work has to be postponed 3586 // to the second pass, when we know which nmethods survive. 3587 void work_first_pass(uint worker_id) { 3588 // The first nmethods is claimed by the first worker. 3589 if (worker_id == 0 && _first_nmethod != NULL) { 3590 clean_nmethod(_first_nmethod); 3591 _first_nmethod = NULL; 3592 } 3593 3594 int num_claimed_nmethods; 3595 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3596 3597 while (true) { 3598 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3599 3600 if (num_claimed_nmethods == 0) { 3601 break; 3602 } 3603 3604 for (int i = 0; i < num_claimed_nmethods; i++) { 3605 clean_nmethod(claimed_nmethods[i]); 3606 } 3607 } 3608 } 3609 3610 void work_second_pass(uint worker_id) { 3611 CompiledMethod* nm; 3612 // Take care of postponed nmethods. 3613 while ((nm = claim_postponed_nmethod()) != NULL) { 3614 clean_nmethod_postponed(nm); 3615 } 3616 } 3617 }; 3618 3619 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3620 3621 class G1KlassCleaningTask : public StackObj { 3622 BoolObjectClosure* _is_alive; 3623 volatile jint _clean_klass_tree_claimed; 3624 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3625 3626 public: 3627 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3628 _is_alive(is_alive), 3629 _clean_klass_tree_claimed(0), 3630 _klass_iterator() { 3631 } 3632 3633 private: 3634 bool claim_clean_klass_tree_task() { 3635 if (_clean_klass_tree_claimed) { 3636 return false; 3637 } 3638 3639 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 3640 } 3641 3642 InstanceKlass* claim_next_klass() { 3643 Klass* klass; 3644 do { 3645 klass =_klass_iterator.next_klass(); 3646 } while (klass != NULL && !klass->is_instance_klass()); 3647 3648 // this can be null so don't call InstanceKlass::cast 3649 return static_cast<InstanceKlass*>(klass); 3650 } 3651 3652 public: 3653 3654 void clean_klass(InstanceKlass* ik) { 3655 ik->clean_weak_instanceklass_links(_is_alive); 3656 } 3657 3658 void work() { 3659 ResourceMark rm; 3660 3661 // One worker will clean the subklass/sibling klass tree. 3662 if (claim_clean_klass_tree_task()) { 3663 Klass::clean_subklass_tree(_is_alive); 3664 } 3665 3666 // All workers will help cleaning the classes, 3667 InstanceKlass* klass; 3668 while ((klass = claim_next_klass()) != NULL) { 3669 clean_klass(klass); 3670 } 3671 } 3672 }; 3673 3674 class G1ResolvedMethodCleaningTask : public StackObj { 3675 BoolObjectClosure* _is_alive; 3676 volatile jint _resolved_method_task_claimed; 3677 public: 3678 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) : 3679 _is_alive(is_alive), _resolved_method_task_claimed(0) {} 3680 3681 bool claim_resolved_method_task() { 3682 if (_resolved_method_task_claimed) { 3683 return false; 3684 } 3685 return Atomic::cmpxchg(1, (jint*)&_resolved_method_task_claimed, 0) == 0; 3686 } 3687 3688 // These aren't big, one thread can do it all. 3689 void work() { 3690 if (claim_resolved_method_task()) { 3691 ResolvedMethodTable::unlink(_is_alive); 3692 } 3693 } 3694 }; 3695 3696 3697 // To minimize the remark pause times, the tasks below are done in parallel. 3698 class G1ParallelCleaningTask : public AbstractGangTask { 3699 private: 3700 G1StringAndSymbolCleaningTask _string_symbol_task; 3701 G1CodeCacheUnloadingTask _code_cache_task; 3702 G1KlassCleaningTask _klass_cleaning_task; 3703 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task; 3704 3705 public: 3706 // The constructor is run in the VMThread. 3707 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3708 AbstractGangTask("Parallel Cleaning"), 3709 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3710 _code_cache_task(num_workers, is_alive, unloading_occurred), 3711 _klass_cleaning_task(is_alive), 3712 _resolved_method_cleaning_task(is_alive) { 3713 } 3714 3715 // The parallel work done by all worker threads. 3716 void work(uint worker_id) { 3717 // Do first pass of code cache cleaning. 3718 _code_cache_task.work_first_pass(worker_id); 3719 3720 // Let the threads mark that the first pass is done. 3721 _code_cache_task.barrier_mark(worker_id); 3722 3723 // Clean the Strings and Symbols. 3724 _string_symbol_task.work(worker_id); 3725 3726 // Clean unreferenced things in the ResolvedMethodTable 3727 _resolved_method_cleaning_task.work(); 3728 3729 // Wait for all workers to finish the first code cache cleaning pass. 3730 _code_cache_task.barrier_wait(worker_id); 3731 3732 // Do the second code cache cleaning work, which realize on 3733 // the liveness information gathered during the first pass. 3734 _code_cache_task.work_second_pass(worker_id); 3735 3736 // Clean all klasses that were not unloaded. 3737 _klass_cleaning_task.work(); 3738 } 3739 }; 3740 3741 3742 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3743 bool class_unloading_occurred) { 3744 uint n_workers = workers()->active_workers(); 3745 3746 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3747 workers()->run_task(&g1_unlink_task); 3748 } 3749 3750 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3751 bool process_strings, 3752 bool process_symbols, 3753 bool process_string_dedup) { 3754 if (!process_strings && !process_symbols && !process_string_dedup) { 3755 // Nothing to clean. 3756 return; 3757 } 3758 3759 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3760 workers()->run_task(&g1_unlink_task); 3761 3762 } 3763 3764 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3765 private: 3766 DirtyCardQueueSet* _queue; 3767 G1CollectedHeap* _g1h; 3768 public: 3769 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3770 _queue(queue), _g1h(g1h) { } 3771 3772 virtual void work(uint worker_id) { 3773 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3774 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3775 3776 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3777 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3778 3779 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3780 } 3781 }; 3782 3783 void G1CollectedHeap::redirty_logged_cards() { 3784 double redirty_logged_cards_start = os::elapsedTime(); 3785 3786 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3787 dirty_card_queue_set().reset_for_par_iteration(); 3788 workers()->run_task(&redirty_task); 3789 3790 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 3791 dcq.merge_bufferlists(&dirty_card_queue_set()); 3792 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3793 3794 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3795 } 3796 3797 // Weak Reference Processing support 3798 3799 // An always "is_alive" closure that is used to preserve referents. 3800 // If the object is non-null then it's alive. Used in the preservation 3801 // of referent objects that are pointed to by reference objects 3802 // discovered by the CM ref processor. 3803 class G1AlwaysAliveClosure: public BoolObjectClosure { 3804 G1CollectedHeap* _g1; 3805 public: 3806 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3807 bool do_object_b(oop p) { 3808 if (p != NULL) { 3809 return true; 3810 } 3811 return false; 3812 } 3813 }; 3814 3815 bool G1STWIsAliveClosure::do_object_b(oop p) { 3816 // An object is reachable if it is outside the collection set, 3817 // or is inside and copied. 3818 return !_g1->is_in_cset(p) || p->is_forwarded(); 3819 } 3820 3821 // Non Copying Keep Alive closure 3822 class G1KeepAliveClosure: public OopClosure { 3823 G1CollectedHeap* _g1; 3824 public: 3825 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3826 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3827 void do_oop(oop* p) { 3828 oop obj = *p; 3829 assert(obj != NULL, "the caller should have filtered out NULL values"); 3830 3831 const InCSetState cset_state = _g1->in_cset_state(obj); 3832 if (!cset_state.is_in_cset_or_humongous()) { 3833 return; 3834 } 3835 if (cset_state.is_in_cset()) { 3836 assert( obj->is_forwarded(), "invariant" ); 3837 *p = obj->forwardee(); 3838 } else { 3839 assert(!obj->is_forwarded(), "invariant" ); 3840 assert(cset_state.is_humongous(), 3841 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3842 _g1->set_humongous_is_live(obj); 3843 } 3844 } 3845 }; 3846 3847 // Copying Keep Alive closure - can be called from both 3848 // serial and parallel code as long as different worker 3849 // threads utilize different G1ParScanThreadState instances 3850 // and different queues. 3851 3852 class G1CopyingKeepAliveClosure: public OopClosure { 3853 G1CollectedHeap* _g1h; 3854 OopClosure* _copy_non_heap_obj_cl; 3855 G1ParScanThreadState* _par_scan_state; 3856 3857 public: 3858 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3859 OopClosure* non_heap_obj_cl, 3860 G1ParScanThreadState* pss): 3861 _g1h(g1h), 3862 _copy_non_heap_obj_cl(non_heap_obj_cl), 3863 _par_scan_state(pss) 3864 {} 3865 3866 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3867 virtual void do_oop( oop* p) { do_oop_work(p); } 3868 3869 template <class T> void do_oop_work(T* p) { 3870 oop obj = oopDesc::load_decode_heap_oop(p); 3871 3872 if (_g1h->is_in_cset_or_humongous(obj)) { 3873 // If the referent object has been forwarded (either copied 3874 // to a new location or to itself in the event of an 3875 // evacuation failure) then we need to update the reference 3876 // field and, if both reference and referent are in the G1 3877 // heap, update the RSet for the referent. 3878 // 3879 // If the referent has not been forwarded then we have to keep 3880 // it alive by policy. Therefore we have copy the referent. 3881 // 3882 // If the reference field is in the G1 heap then we can push 3883 // on the PSS queue. When the queue is drained (after each 3884 // phase of reference processing) the object and it's followers 3885 // will be copied, the reference field set to point to the 3886 // new location, and the RSet updated. Otherwise we need to 3887 // use the the non-heap or metadata closures directly to copy 3888 // the referent object and update the pointer, while avoiding 3889 // updating the RSet. 3890 3891 if (_g1h->is_in_g1_reserved(p)) { 3892 _par_scan_state->push_on_queue(p); 3893 } else { 3894 assert(!Metaspace::contains((const void*)p), 3895 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 3896 _copy_non_heap_obj_cl->do_oop(p); 3897 } 3898 } 3899 } 3900 }; 3901 3902 // Serial drain queue closure. Called as the 'complete_gc' 3903 // closure for each discovered list in some of the 3904 // reference processing phases. 3905 3906 class G1STWDrainQueueClosure: public VoidClosure { 3907 protected: 3908 G1CollectedHeap* _g1h; 3909 G1ParScanThreadState* _par_scan_state; 3910 3911 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3912 3913 public: 3914 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3915 _g1h(g1h), 3916 _par_scan_state(pss) 3917 { } 3918 3919 void do_void() { 3920 G1ParScanThreadState* const pss = par_scan_state(); 3921 pss->trim_queue(); 3922 } 3923 }; 3924 3925 // Parallel Reference Processing closures 3926 3927 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3928 // processing during G1 evacuation pauses. 3929 3930 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3931 private: 3932 G1CollectedHeap* _g1h; 3933 G1ParScanThreadStateSet* _pss; 3934 RefToScanQueueSet* _queues; 3935 WorkGang* _workers; 3936 uint _active_workers; 3937 3938 public: 3939 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3940 G1ParScanThreadStateSet* per_thread_states, 3941 WorkGang* workers, 3942 RefToScanQueueSet *task_queues, 3943 uint n_workers) : 3944 _g1h(g1h), 3945 _pss(per_thread_states), 3946 _queues(task_queues), 3947 _workers(workers), 3948 _active_workers(n_workers) 3949 { 3950 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 3951 } 3952 3953 // Executes the given task using concurrent marking worker threads. 3954 virtual void execute(ProcessTask& task); 3955 virtual void execute(EnqueueTask& task); 3956 }; 3957 3958 // Gang task for possibly parallel reference processing 3959 3960 class G1STWRefProcTaskProxy: public AbstractGangTask { 3961 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 3962 ProcessTask& _proc_task; 3963 G1CollectedHeap* _g1h; 3964 G1ParScanThreadStateSet* _pss; 3965 RefToScanQueueSet* _task_queues; 3966 ParallelTaskTerminator* _terminator; 3967 3968 public: 3969 G1STWRefProcTaskProxy(ProcessTask& proc_task, 3970 G1CollectedHeap* g1h, 3971 G1ParScanThreadStateSet* per_thread_states, 3972 RefToScanQueueSet *task_queues, 3973 ParallelTaskTerminator* terminator) : 3974 AbstractGangTask("Process reference objects in parallel"), 3975 _proc_task(proc_task), 3976 _g1h(g1h), 3977 _pss(per_thread_states), 3978 _task_queues(task_queues), 3979 _terminator(terminator) 3980 {} 3981 3982 virtual void work(uint worker_id) { 3983 // The reference processing task executed by a single worker. 3984 ResourceMark rm; 3985 HandleMark hm; 3986 3987 G1STWIsAliveClosure is_alive(_g1h); 3988 3989 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3990 pss->set_ref_processor(NULL); 3991 3992 // Keep alive closure. 3993 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 3994 3995 // Complete GC closure 3996 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 3997 3998 // Call the reference processing task's work routine. 3999 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4000 4001 // Note we cannot assert that the refs array is empty here as not all 4002 // of the processing tasks (specifically phase2 - pp2_work) execute 4003 // the complete_gc closure (which ordinarily would drain the queue) so 4004 // the queue may not be empty. 4005 } 4006 }; 4007 4008 // Driver routine for parallel reference processing. 4009 // Creates an instance of the ref processing gang 4010 // task and has the worker threads execute it. 4011 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4012 assert(_workers != NULL, "Need parallel worker threads."); 4013 4014 ParallelTaskTerminator terminator(_active_workers, _queues); 4015 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4016 4017 _workers->run_task(&proc_task_proxy); 4018 } 4019 4020 // Gang task for parallel reference enqueueing. 4021 4022 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4023 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4024 EnqueueTask& _enq_task; 4025 4026 public: 4027 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4028 AbstractGangTask("Enqueue reference objects in parallel"), 4029 _enq_task(enq_task) 4030 { } 4031 4032 virtual void work(uint worker_id) { 4033 _enq_task.work(worker_id); 4034 } 4035 }; 4036 4037 // Driver routine for parallel reference enqueueing. 4038 // Creates an instance of the ref enqueueing gang 4039 // task and has the worker threads execute it. 4040 4041 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4042 assert(_workers != NULL, "Need parallel worker threads."); 4043 4044 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4045 4046 _workers->run_task(&enq_task_proxy); 4047 } 4048 4049 // End of weak reference support closures 4050 4051 // Abstract task used to preserve (i.e. copy) any referent objects 4052 // that are in the collection set and are pointed to by reference 4053 // objects discovered by the CM ref processor. 4054 4055 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4056 protected: 4057 G1CollectedHeap* _g1h; 4058 G1ParScanThreadStateSet* _pss; 4059 RefToScanQueueSet* _queues; 4060 ParallelTaskTerminator _terminator; 4061 uint _n_workers; 4062 4063 public: 4064 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4065 AbstractGangTask("ParPreserveCMReferents"), 4066 _g1h(g1h), 4067 _pss(per_thread_states), 4068 _queues(task_queues), 4069 _terminator(workers, _queues), 4070 _n_workers(workers) 4071 { 4072 g1h->ref_processor_cm()->set_active_mt_degree(workers); 4073 } 4074 4075 void work(uint worker_id) { 4076 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4077 4078 ResourceMark rm; 4079 HandleMark hm; 4080 4081 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4082 pss->set_ref_processor(NULL); 4083 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4084 4085 // Is alive closure 4086 G1AlwaysAliveClosure always_alive(_g1h); 4087 4088 // Copying keep alive closure. Applied to referent objects that need 4089 // to be copied. 4090 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4091 4092 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4093 4094 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4095 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4096 4097 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4098 // So this must be true - but assert just in case someone decides to 4099 // change the worker ids. 4100 assert(worker_id < limit, "sanity"); 4101 assert(!rp->discovery_is_atomic(), "check this code"); 4102 4103 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4104 for (uint idx = worker_id; idx < limit; idx += stride) { 4105 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4106 4107 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4108 while (iter.has_next()) { 4109 // Since discovery is not atomic for the CM ref processor, we 4110 // can see some null referent objects. 4111 iter.load_ptrs(DEBUG_ONLY(true)); 4112 oop ref = iter.obj(); 4113 4114 // This will filter nulls. 4115 if (iter.is_referent_alive()) { 4116 iter.make_referent_alive(); 4117 } 4118 iter.move_to_next(); 4119 } 4120 } 4121 4122 // Drain the queue - which may cause stealing 4123 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4124 drain_queue.do_void(); 4125 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4126 assert(pss->queue_is_empty(), "should be"); 4127 } 4128 }; 4129 4130 void G1CollectedHeap::process_weak_jni_handles() { 4131 double ref_proc_start = os::elapsedTime(); 4132 4133 G1STWIsAliveClosure is_alive(this); 4134 G1KeepAliveClosure keep_alive(this); 4135 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 4136 4137 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4138 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4139 } 4140 4141 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4142 // Any reference objects, in the collection set, that were 'discovered' 4143 // by the CM ref processor should have already been copied (either by 4144 // applying the external root copy closure to the discovered lists, or 4145 // by following an RSet entry). 4146 // 4147 // But some of the referents, that are in the collection set, that these 4148 // reference objects point to may not have been copied: the STW ref 4149 // processor would have seen that the reference object had already 4150 // been 'discovered' and would have skipped discovering the reference, 4151 // but would not have treated the reference object as a regular oop. 4152 // As a result the copy closure would not have been applied to the 4153 // referent object. 4154 // 4155 // We need to explicitly copy these referent objects - the references 4156 // will be processed at the end of remarking. 4157 // 4158 // We also need to do this copying before we process the reference 4159 // objects discovered by the STW ref processor in case one of these 4160 // referents points to another object which is also referenced by an 4161 // object discovered by the STW ref processor. 4162 double preserve_cm_referents_time = 0.0; 4163 4164 // To avoid spawning task when there is no work to do, check that 4165 // a concurrent cycle is active and that some references have been 4166 // discovered. 4167 if (concurrent_mark()->cmThread()->during_cycle() && 4168 ref_processor_cm()->has_discovered_references()) { 4169 double preserve_cm_referents_start = os::elapsedTime(); 4170 uint no_of_gc_workers = workers()->active_workers(); 4171 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4172 per_thread_states, 4173 no_of_gc_workers, 4174 _task_queues); 4175 workers()->run_task(&keep_cm_referents); 4176 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4177 } 4178 4179 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4180 } 4181 4182 // Weak Reference processing during an evacuation pause (part 1). 4183 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4184 double ref_proc_start = os::elapsedTime(); 4185 4186 ReferenceProcessor* rp = _ref_processor_stw; 4187 assert(rp->discovery_enabled(), "should have been enabled"); 4188 4189 // Closure to test whether a referent is alive. 4190 G1STWIsAliveClosure is_alive(this); 4191 4192 // Even when parallel reference processing is enabled, the processing 4193 // of JNI refs is serial and performed serially by the current thread 4194 // rather than by a worker. The following PSS will be used for processing 4195 // JNI refs. 4196 4197 // Use only a single queue for this PSS. 4198 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4199 pss->set_ref_processor(NULL); 4200 assert(pss->queue_is_empty(), "pre-condition"); 4201 4202 // Keep alive closure. 4203 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4204 4205 // Serial Complete GC closure 4206 G1STWDrainQueueClosure drain_queue(this, pss); 4207 4208 // Setup the soft refs policy... 4209 rp->setup_policy(false); 4210 4211 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4212 4213 ReferenceProcessorStats stats; 4214 if (!rp->processing_is_mt()) { 4215 // Serial reference processing... 4216 stats = rp->process_discovered_references(&is_alive, 4217 &keep_alive, 4218 &drain_queue, 4219 NULL, 4220 pt); 4221 } else { 4222 uint no_of_gc_workers = workers()->active_workers(); 4223 4224 // Parallel reference processing 4225 assert(no_of_gc_workers <= rp->max_num_q(), 4226 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4227 no_of_gc_workers, rp->max_num_q()); 4228 4229 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4230 stats = rp->process_discovered_references(&is_alive, 4231 &keep_alive, 4232 &drain_queue, 4233 &par_task_executor, 4234 pt); 4235 } 4236 4237 _gc_tracer_stw->report_gc_reference_stats(stats); 4238 4239 // We have completed copying any necessary live referent objects. 4240 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4241 4242 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4243 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4244 } 4245 4246 // Weak Reference processing during an evacuation pause (part 2). 4247 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4248 double ref_enq_start = os::elapsedTime(); 4249 4250 ReferenceProcessor* rp = _ref_processor_stw; 4251 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4252 4253 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times(); 4254 4255 // Now enqueue any remaining on the discovered lists on to 4256 // the pending list. 4257 if (!rp->processing_is_mt()) { 4258 // Serial reference processing... 4259 rp->enqueue_discovered_references(NULL, pt); 4260 } else { 4261 // Parallel reference enqueueing 4262 4263 uint n_workers = workers()->active_workers(); 4264 4265 assert(n_workers <= rp->max_num_q(), 4266 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4267 n_workers, rp->max_num_q()); 4268 4269 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4270 rp->enqueue_discovered_references(&par_task_executor, pt); 4271 } 4272 4273 rp->verify_no_references_recorded(); 4274 assert(!rp->discovery_enabled(), "should have been disabled"); 4275 4276 // If during an initial mark pause we install a pending list head which is not otherwise reachable 4277 // ensure that it is marked in the bitmap for concurrent marking to discover. 4278 if (collector_state()->during_initial_mark_pause()) { 4279 oop pll_head = Universe::reference_pending_list(); 4280 if (pll_head != NULL) { 4281 _cm->mark_in_next_bitmap(pll_head); 4282 } 4283 } 4284 4285 // FIXME 4286 // CM's reference processing also cleans up the string and symbol tables. 4287 // Should we do that here also? We could, but it is a serial operation 4288 // and could significantly increase the pause time. 4289 4290 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4291 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4292 } 4293 4294 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4295 double merge_pss_time_start = os::elapsedTime(); 4296 per_thread_states->flush(); 4297 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4298 } 4299 4300 void G1CollectedHeap::pre_evacuate_collection_set() { 4301 _expand_heap_after_alloc_failure = true; 4302 _evacuation_failed = false; 4303 4304 // Disable the hot card cache. 4305 _hot_card_cache->reset_hot_cache_claimed_index(); 4306 _hot_card_cache->set_use_cache(false); 4307 4308 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4309 _preserved_marks_set.assert_empty(); 4310 4311 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4312 4313 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4314 if (collector_state()->during_initial_mark_pause()) { 4315 double start_clear_claimed_marks = os::elapsedTime(); 4316 4317 ClassLoaderDataGraph::clear_claimed_marks(); 4318 4319 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4320 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4321 } 4322 } 4323 4324 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4325 // Should G1EvacuationFailureALot be in effect for this GC? 4326 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4327 4328 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4329 4330 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4331 4332 double start_par_time_sec = os::elapsedTime(); 4333 double end_par_time_sec; 4334 4335 { 4336 const uint n_workers = workers()->active_workers(); 4337 G1RootProcessor root_processor(this, n_workers); 4338 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4339 4340 print_termination_stats_hdr(); 4341 4342 workers()->run_task(&g1_par_task); 4343 end_par_time_sec = os::elapsedTime(); 4344 4345 // Closing the inner scope will execute the destructor 4346 // for the G1RootProcessor object. We record the current 4347 // elapsed time before closing the scope so that time 4348 // taken for the destructor is NOT included in the 4349 // reported parallel time. 4350 } 4351 4352 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4353 phase_times->record_par_time(par_time_ms); 4354 4355 double code_root_fixup_time_ms = 4356 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4357 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4358 } 4359 4360 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4361 // Process any discovered reference objects - we have 4362 // to do this _before_ we retire the GC alloc regions 4363 // as we may have to copy some 'reachable' referent 4364 // objects (and their reachable sub-graphs) that were 4365 // not copied during the pause. 4366 if (g1_policy()->should_process_references()) { 4367 preserve_cm_referents(per_thread_states); 4368 process_discovered_references(per_thread_states); 4369 } else { 4370 ref_processor_stw()->verify_no_references_recorded(); 4371 process_weak_jni_handles(); 4372 } 4373 4374 if (G1StringDedup::is_enabled()) { 4375 double fixup_start = os::elapsedTime(); 4376 4377 G1STWIsAliveClosure is_alive(this); 4378 G1KeepAliveClosure keep_alive(this); 4379 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4380 4381 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4382 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4383 } 4384 4385 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4386 4387 if (evacuation_failed()) { 4388 restore_after_evac_failure(); 4389 4390 // Reset the G1EvacuationFailureALot counters and flags 4391 // Note: the values are reset only when an actual 4392 // evacuation failure occurs. 4393 NOT_PRODUCT(reset_evacuation_should_fail();) 4394 } 4395 4396 _preserved_marks_set.assert_empty(); 4397 4398 // Enqueue any remaining references remaining on the STW 4399 // reference processor's discovered lists. We need to do 4400 // this after the card table is cleaned (and verified) as 4401 // the act of enqueueing entries on to the pending list 4402 // will log these updates (and dirty their associated 4403 // cards). We need these updates logged to update any 4404 // RSets. 4405 if (g1_policy()->should_process_references()) { 4406 enqueue_discovered_references(per_thread_states); 4407 } else { 4408 g1_policy()->phase_times()->record_ref_enq_time(0); 4409 } 4410 4411 _allocator->release_gc_alloc_regions(evacuation_info); 4412 4413 merge_per_thread_state_info(per_thread_states); 4414 4415 // Reset and re-enable the hot card cache. 4416 // Note the counts for the cards in the regions in the 4417 // collection set are reset when the collection set is freed. 4418 _hot_card_cache->reset_hot_cache(); 4419 _hot_card_cache->set_use_cache(true); 4420 4421 purge_code_root_memory(); 4422 4423 redirty_logged_cards(); 4424 #if defined(COMPILER2) || INCLUDE_JVMCI 4425 double start = os::elapsedTime(); 4426 DerivedPointerTable::update_pointers(); 4427 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4428 #endif 4429 g1_policy()->print_age_table(); 4430 } 4431 4432 void G1CollectedHeap::record_obj_copy_mem_stats() { 4433 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4434 4435 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4436 create_g1_evac_summary(&_old_evac_stats)); 4437 } 4438 4439 void G1CollectedHeap::free_region(HeapRegion* hr, 4440 FreeRegionList* free_list, 4441 bool skip_remset, 4442 bool skip_hot_card_cache, 4443 bool locked) { 4444 assert(!hr->is_free(), "the region should not be free"); 4445 assert(!hr->is_empty(), "the region should not be empty"); 4446 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4447 assert(free_list != NULL, "pre-condition"); 4448 4449 if (G1VerifyBitmaps) { 4450 MemRegion mr(hr->bottom(), hr->end()); 4451 concurrent_mark()->clearRangePrevBitmap(mr); 4452 } 4453 4454 // Clear the card counts for this region. 4455 // Note: we only need to do this if the region is not young 4456 // (since we don't refine cards in young regions). 4457 if (!skip_hot_card_cache && !hr->is_young()) { 4458 _hot_card_cache->reset_card_counts(hr); 4459 } 4460 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4461 free_list->add_ordered(hr); 4462 } 4463 4464 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4465 FreeRegionList* free_list, 4466 bool skip_remset) { 4467 assert(hr->is_humongous(), "this is only for humongous regions"); 4468 assert(free_list != NULL, "pre-condition"); 4469 hr->clear_humongous(); 4470 free_region(hr, free_list, skip_remset); 4471 } 4472 4473 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4474 const uint humongous_regions_removed) { 4475 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4476 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4477 _old_set.bulk_remove(old_regions_removed); 4478 _humongous_set.bulk_remove(humongous_regions_removed); 4479 } 4480 4481 } 4482 4483 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4484 assert(list != NULL, "list can't be null"); 4485 if (!list->is_empty()) { 4486 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4487 _hrm.insert_list_into_free_list(list); 4488 } 4489 } 4490 4491 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4492 decrease_used(bytes); 4493 } 4494 4495 class G1ParScrubRemSetTask: public AbstractGangTask { 4496 protected: 4497 G1RemSet* _g1rs; 4498 HeapRegionClaimer _hrclaimer; 4499 4500 public: 4501 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) : 4502 AbstractGangTask("G1 ScrubRS"), 4503 _g1rs(g1_rs), 4504 _hrclaimer(num_workers) { 4505 } 4506 4507 void work(uint worker_id) { 4508 _g1rs->scrub(worker_id, &_hrclaimer); 4509 } 4510 }; 4511 4512 void G1CollectedHeap::scrub_rem_set() { 4513 uint num_workers = workers()->active_workers(); 4514 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers); 4515 workers()->run_task(&g1_par_scrub_rs_task); 4516 } 4517 4518 class G1FreeCollectionSetTask : public AbstractGangTask { 4519 private: 4520 4521 // Closure applied to all regions in the collection set to do work that needs to 4522 // be done serially in a single thread. 4523 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4524 private: 4525 EvacuationInfo* _evacuation_info; 4526 const size_t* _surviving_young_words; 4527 4528 // Bytes used in successfully evacuated regions before the evacuation. 4529 size_t _before_used_bytes; 4530 // Bytes used in unsucessfully evacuated regions before the evacuation 4531 size_t _after_used_bytes; 4532 4533 size_t _bytes_allocated_in_old_since_last_gc; 4534 4535 size_t _failure_used_words; 4536 size_t _failure_waste_words; 4537 4538 FreeRegionList _local_free_list; 4539 public: 4540 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4541 HeapRegionClosure(), 4542 _evacuation_info(evacuation_info), 4543 _surviving_young_words(surviving_young_words), 4544 _before_used_bytes(0), 4545 _after_used_bytes(0), 4546 _bytes_allocated_in_old_since_last_gc(0), 4547 _failure_used_words(0), 4548 _failure_waste_words(0), 4549 _local_free_list("Local Region List for CSet Freeing") { 4550 } 4551 4552 virtual bool doHeapRegion(HeapRegion* r) { 4553 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4554 4555 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4556 g1h->clear_in_cset(r); 4557 4558 if (r->is_young()) { 4559 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4560 "Young index %d is wrong for region %u of type %s with %u young regions", 4561 r->young_index_in_cset(), 4562 r->hrm_index(), 4563 r->get_type_str(), 4564 g1h->collection_set()->young_region_length()); 4565 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4566 r->record_surv_words_in_group(words_survived); 4567 } 4568 4569 if (!r->evacuation_failed()) { 4570 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4571 _before_used_bytes += r->used(); 4572 g1h->free_region(r, 4573 &_local_free_list, 4574 true, /* skip_remset */ 4575 true, /* skip_hot_card_cache */ 4576 true /* locked */); 4577 } else { 4578 r->uninstall_surv_rate_group(); 4579 r->set_young_index_in_cset(-1); 4580 r->set_evacuation_failed(false); 4581 // When moving a young gen region to old gen, we "allocate" that whole region 4582 // there. This is in addition to any already evacuated objects. Notify the 4583 // policy about that. 4584 // Old gen regions do not cause an additional allocation: both the objects 4585 // still in the region and the ones already moved are accounted for elsewhere. 4586 if (r->is_young()) { 4587 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4588 } 4589 // The region is now considered to be old. 4590 r->set_old(); 4591 // Do some allocation statistics accounting. Regions that failed evacuation 4592 // are always made old, so there is no need to update anything in the young 4593 // gen statistics, but we need to update old gen statistics. 4594 size_t used_words = r->marked_bytes() / HeapWordSize; 4595 4596 _failure_used_words += used_words; 4597 _failure_waste_words += HeapRegion::GrainWords - used_words; 4598 4599 g1h->old_set_add(r); 4600 _after_used_bytes += r->used(); 4601 } 4602 return false; 4603 } 4604 4605 void complete_work() { 4606 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4607 4608 _evacuation_info->set_regions_freed(_local_free_list.length()); 4609 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4610 4611 g1h->prepend_to_freelist(&_local_free_list); 4612 g1h->decrement_summary_bytes(_before_used_bytes); 4613 4614 G1Policy* policy = g1h->g1_policy(); 4615 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4616 4617 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4618 } 4619 }; 4620 4621 G1CollectionSet* _collection_set; 4622 G1SerialFreeCollectionSetClosure _cl; 4623 const size_t* _surviving_young_words; 4624 4625 size_t _rs_lengths; 4626 4627 volatile jint _serial_work_claim; 4628 4629 struct WorkItem { 4630 uint region_idx; 4631 bool is_young; 4632 bool evacuation_failed; 4633 4634 WorkItem(HeapRegion* r) { 4635 region_idx = r->hrm_index(); 4636 is_young = r->is_young(); 4637 evacuation_failed = r->evacuation_failed(); 4638 } 4639 }; 4640 4641 volatile size_t _parallel_work_claim; 4642 size_t _num_work_items; 4643 WorkItem* _work_items; 4644 4645 void do_serial_work() { 4646 // Need to grab the lock to be allowed to modify the old region list. 4647 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4648 _collection_set->iterate(&_cl); 4649 } 4650 4651 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4652 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4653 4654 HeapRegion* r = g1h->region_at(region_idx); 4655 assert(!g1h->is_on_master_free_list(r), "sanity"); 4656 4657 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4658 4659 if (!is_young) { 4660 g1h->_hot_card_cache->reset_card_counts(r); 4661 } 4662 4663 if (!evacuation_failed) { 4664 r->rem_set()->clear_locked(); 4665 } 4666 } 4667 4668 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4669 private: 4670 size_t _cur_idx; 4671 WorkItem* _work_items; 4672 public: 4673 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4674 4675 virtual bool doHeapRegion(HeapRegion* r) { 4676 _work_items[_cur_idx++] = WorkItem(r); 4677 return false; 4678 } 4679 }; 4680 4681 void prepare_work() { 4682 G1PrepareFreeCollectionSetClosure cl(_work_items); 4683 _collection_set->iterate(&cl); 4684 } 4685 4686 void complete_work() { 4687 _cl.complete_work(); 4688 4689 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4690 policy->record_max_rs_lengths(_rs_lengths); 4691 policy->cset_regions_freed(); 4692 } 4693 public: 4694 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4695 AbstractGangTask("G1 Free Collection Set"), 4696 _cl(evacuation_info, surviving_young_words), 4697 _collection_set(collection_set), 4698 _surviving_young_words(surviving_young_words), 4699 _serial_work_claim(0), 4700 _rs_lengths(0), 4701 _parallel_work_claim(0), 4702 _num_work_items(collection_set->region_length()), 4703 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4704 prepare_work(); 4705 } 4706 4707 ~G1FreeCollectionSetTask() { 4708 complete_work(); 4709 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4710 } 4711 4712 // Chunk size for work distribution. The chosen value has been determined experimentally 4713 // to be a good tradeoff between overhead and achievable parallelism. 4714 static uint chunk_size() { return 32; } 4715 4716 virtual void work(uint worker_id) { 4717 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4718 4719 // Claim serial work. 4720 if (_serial_work_claim == 0) { 4721 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4722 if (value == 0) { 4723 double serial_time = os::elapsedTime(); 4724 do_serial_work(); 4725 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4726 } 4727 } 4728 4729 // Start parallel work. 4730 double young_time = 0.0; 4731 bool has_young_time = false; 4732 double non_young_time = 0.0; 4733 bool has_non_young_time = false; 4734 4735 while (true) { 4736 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4737 size_t cur = end - chunk_size(); 4738 4739 if (cur >= _num_work_items) { 4740 break; 4741 } 4742 4743 double start_time = os::elapsedTime(); 4744 4745 end = MIN2(end, _num_work_items); 4746 4747 for (; cur < end; cur++) { 4748 bool is_young = _work_items[cur].is_young; 4749 4750 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4751 4752 double end_time = os::elapsedTime(); 4753 double time_taken = end_time - start_time; 4754 if (is_young) { 4755 young_time += time_taken; 4756 has_young_time = true; 4757 } else { 4758 non_young_time += time_taken; 4759 has_non_young_time = true; 4760 } 4761 start_time = end_time; 4762 } 4763 } 4764 4765 if (has_young_time) { 4766 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4767 } 4768 if (has_non_young_time) { 4769 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time); 4770 } 4771 } 4772 }; 4773 4774 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4775 _eden.clear(); 4776 4777 double free_cset_start_time = os::elapsedTime(); 4778 4779 { 4780 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4781 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4782 4783 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4784 4785 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4786 cl.name(), 4787 num_workers, 4788 _collection_set.region_length()); 4789 workers()->run_task(&cl, num_workers); 4790 } 4791 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4792 4793 collection_set->clear(); 4794 } 4795 4796 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4797 private: 4798 FreeRegionList* _free_region_list; 4799 HeapRegionSet* _proxy_set; 4800 uint _humongous_objects_reclaimed; 4801 uint _humongous_regions_reclaimed; 4802 size_t _freed_bytes; 4803 public: 4804 4805 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4806 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4807 } 4808 4809 virtual bool doHeapRegion(HeapRegion* r) { 4810 if (!r->is_starts_humongous()) { 4811 return false; 4812 } 4813 4814 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4815 4816 oop obj = (oop)r->bottom(); 4817 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 4818 4819 // The following checks whether the humongous object is live are sufficient. 4820 // The main additional check (in addition to having a reference from the roots 4821 // or the young gen) is whether the humongous object has a remembered set entry. 4822 // 4823 // A humongous object cannot be live if there is no remembered set for it 4824 // because: 4825 // - there can be no references from within humongous starts regions referencing 4826 // the object because we never allocate other objects into them. 4827 // (I.e. there are no intra-region references that may be missed by the 4828 // remembered set) 4829 // - as soon there is a remembered set entry to the humongous starts region 4830 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4831 // until the end of a concurrent mark. 4832 // 4833 // It is not required to check whether the object has been found dead by marking 4834 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4835 // all objects allocated during that time are considered live. 4836 // SATB marking is even more conservative than the remembered set. 4837 // So if at this point in the collection there is no remembered set entry, 4838 // nobody has a reference to it. 4839 // At the start of collection we flush all refinement logs, and remembered sets 4840 // are completely up-to-date wrt to references to the humongous object. 4841 // 4842 // Other implementation considerations: 4843 // - never consider object arrays at this time because they would pose 4844 // considerable effort for cleaning up the the remembered sets. This is 4845 // required because stale remembered sets might reference locations that 4846 // are currently allocated into. 4847 uint region_idx = r->hrm_index(); 4848 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4849 !r->rem_set()->is_empty()) { 4850 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", 4851 region_idx, 4852 (size_t)obj->size() * HeapWordSize, 4853 p2i(r->bottom()), 4854 r->rem_set()->occupied(), 4855 r->rem_set()->strong_code_roots_list_length(), 4856 next_bitmap->is_marked(r->bottom()), 4857 g1h->is_humongous_reclaim_candidate(region_idx), 4858 obj->is_typeArray() 4859 ); 4860 return false; 4861 } 4862 4863 guarantee(obj->is_typeArray(), 4864 "Only eagerly reclaiming type arrays is supported, but the object " 4865 PTR_FORMAT " is not.", p2i(r->bottom())); 4866 4867 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", 4868 region_idx, 4869 (size_t)obj->size() * HeapWordSize, 4870 p2i(r->bottom()), 4871 r->rem_set()->occupied(), 4872 r->rem_set()->strong_code_roots_list_length(), 4873 next_bitmap->is_marked(r->bottom()), 4874 g1h->is_humongous_reclaim_candidate(region_idx), 4875 obj->is_typeArray() 4876 ); 4877 4878 // Need to clear mark bit of the humongous object if already set. 4879 if (next_bitmap->is_marked(r->bottom())) { 4880 next_bitmap->clear(r->bottom()); 4881 } 4882 _humongous_objects_reclaimed++; 4883 do { 4884 HeapRegion* next = g1h->next_region_in_humongous(r); 4885 _freed_bytes += r->used(); 4886 r->set_containing_set(NULL); 4887 _humongous_regions_reclaimed++; 4888 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ ); 4889 r = next; 4890 } while (r != NULL); 4891 4892 return false; 4893 } 4894 4895 uint humongous_objects_reclaimed() { 4896 return _humongous_objects_reclaimed; 4897 } 4898 4899 uint humongous_regions_reclaimed() { 4900 return _humongous_regions_reclaimed; 4901 } 4902 4903 size_t bytes_freed() const { 4904 return _freed_bytes; 4905 } 4906 }; 4907 4908 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4909 assert_at_safepoint(true); 4910 4911 if (!G1EagerReclaimHumongousObjects || 4912 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4913 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4914 return; 4915 } 4916 4917 double start_time = os::elapsedTime(); 4918 4919 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4920 4921 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4922 heap_region_iterate(&cl); 4923 4924 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4925 4926 G1HRPrinter* hrp = hr_printer(); 4927 if (hrp->is_active()) { 4928 FreeRegionListIterator iter(&local_cleanup_list); 4929 while (iter.more_available()) { 4930 HeapRegion* hr = iter.get_next(); 4931 hrp->cleanup(hr); 4932 } 4933 } 4934 4935 prepend_to_freelist(&local_cleanup_list); 4936 decrement_summary_bytes(cl.bytes_freed()); 4937 4938 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4939 cl.humongous_objects_reclaimed()); 4940 } 4941 4942 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4943 public: 4944 virtual bool doHeapRegion(HeapRegion* r) { 4945 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4946 G1CollectedHeap::heap()->clear_in_cset(r); 4947 r->set_young_index_in_cset(-1); 4948 return false; 4949 } 4950 }; 4951 4952 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4953 G1AbandonCollectionSetClosure cl; 4954 collection_set->iterate(&cl); 4955 4956 collection_set->clear(); 4957 collection_set->stop_incremental_building(); 4958 } 4959 4960 void G1CollectedHeap::set_free_regions_coming() { 4961 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 4962 4963 assert(!free_regions_coming(), "pre-condition"); 4964 _free_regions_coming = true; 4965 } 4966 4967 void G1CollectedHeap::reset_free_regions_coming() { 4968 assert(free_regions_coming(), "pre-condition"); 4969 4970 { 4971 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 4972 _free_regions_coming = false; 4973 SecondaryFreeList_lock->notify_all(); 4974 } 4975 4976 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 4977 } 4978 4979 void G1CollectedHeap::wait_while_free_regions_coming() { 4980 // Most of the time we won't have to wait, so let's do a quick test 4981 // first before we take the lock. 4982 if (!free_regions_coming()) { 4983 return; 4984 } 4985 4986 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 4987 4988 { 4989 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 4990 while (free_regions_coming()) { 4991 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 4992 } 4993 } 4994 4995 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 4996 } 4997 4998 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 4999 return _allocator->is_retained_old_region(hr); 5000 } 5001 5002 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5003 _eden.add(hr); 5004 _g1_policy->set_region_eden(hr); 5005 } 5006 5007 #ifdef ASSERT 5008 5009 class NoYoungRegionsClosure: public HeapRegionClosure { 5010 private: 5011 bool _success; 5012 public: 5013 NoYoungRegionsClosure() : _success(true) { } 5014 bool doHeapRegion(HeapRegion* r) { 5015 if (r->is_young()) { 5016 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5017 p2i(r->bottom()), p2i(r->end())); 5018 _success = false; 5019 } 5020 return false; 5021 } 5022 bool success() { return _success; } 5023 }; 5024 5025 bool G1CollectedHeap::check_young_list_empty() { 5026 bool ret = (young_regions_count() == 0); 5027 5028 NoYoungRegionsClosure closure; 5029 heap_region_iterate(&closure); 5030 ret = ret && closure.success(); 5031 5032 return ret; 5033 } 5034 5035 #endif // ASSERT 5036 5037 class TearDownRegionSetsClosure : public HeapRegionClosure { 5038 private: 5039 HeapRegionSet *_old_set; 5040 5041 public: 5042 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5043 5044 bool doHeapRegion(HeapRegion* r) { 5045 if (r->is_old()) { 5046 _old_set->remove(r); 5047 } else if(r->is_young()) { 5048 r->uninstall_surv_rate_group(); 5049 } else { 5050 // We ignore free regions, we'll empty the free list afterwards. 5051 // We ignore humongous regions, we're not tearing down the 5052 // humongous regions set. 5053 assert(r->is_free() || r->is_humongous(), 5054 "it cannot be another type"); 5055 } 5056 return false; 5057 } 5058 5059 ~TearDownRegionSetsClosure() { 5060 assert(_old_set->is_empty(), "post-condition"); 5061 } 5062 }; 5063 5064 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5065 assert_at_safepoint(true /* should_be_vm_thread */); 5066 5067 if (!free_list_only) { 5068 TearDownRegionSetsClosure cl(&_old_set); 5069 heap_region_iterate(&cl); 5070 5071 // Note that emptying the _young_list is postponed and instead done as 5072 // the first step when rebuilding the regions sets again. The reason for 5073 // this is that during a full GC string deduplication needs to know if 5074 // a collected region was young or old when the full GC was initiated. 5075 } 5076 _hrm.remove_all_free_regions(); 5077 } 5078 5079 void G1CollectedHeap::increase_used(size_t bytes) { 5080 _summary_bytes_used += bytes; 5081 } 5082 5083 void G1CollectedHeap::decrease_used(size_t bytes) { 5084 assert(_summary_bytes_used >= bytes, 5085 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5086 _summary_bytes_used, bytes); 5087 _summary_bytes_used -= bytes; 5088 } 5089 5090 void G1CollectedHeap::set_used(size_t bytes) { 5091 _summary_bytes_used = bytes; 5092 } 5093 5094 class RebuildRegionSetsClosure : public HeapRegionClosure { 5095 private: 5096 bool _free_list_only; 5097 HeapRegionSet* _old_set; 5098 HeapRegionManager* _hrm; 5099 size_t _total_used; 5100 5101 public: 5102 RebuildRegionSetsClosure(bool free_list_only, 5103 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5104 _free_list_only(free_list_only), 5105 _old_set(old_set), _hrm(hrm), _total_used(0) { 5106 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5107 if (!free_list_only) { 5108 assert(_old_set->is_empty(), "pre-condition"); 5109 } 5110 } 5111 5112 bool doHeapRegion(HeapRegion* r) { 5113 if (r->is_empty()) { 5114 // Add free regions to the free list 5115 r->set_free(); 5116 r->set_allocation_context(AllocationContext::system()); 5117 _hrm->insert_into_free_list(r); 5118 } else if (!_free_list_only) { 5119 5120 if (r->is_humongous()) { 5121 // We ignore humongous regions. We left the humongous set unchanged. 5122 } else { 5123 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 5124 // We now move all (non-humongous, non-old) regions to old gen, and register them as such. 5125 r->move_to_old(); 5126 _old_set->add(r); 5127 } 5128 _total_used += r->used(); 5129 } 5130 5131 return false; 5132 } 5133 5134 size_t total_used() { 5135 return _total_used; 5136 } 5137 }; 5138 5139 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5140 assert_at_safepoint(true /* should_be_vm_thread */); 5141 5142 if (!free_list_only) { 5143 _eden.clear(); 5144 _survivor.clear(); 5145 } 5146 5147 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5148 heap_region_iterate(&cl); 5149 5150 if (!free_list_only) { 5151 set_used(cl.total_used()); 5152 if (_archive_allocator != NULL) { 5153 _archive_allocator->clear_used(); 5154 } 5155 } 5156 assert(used_unlocked() == recalculate_used(), 5157 "inconsistent used_unlocked(), " 5158 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5159 used_unlocked(), recalculate_used()); 5160 } 5161 5162 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5163 HeapRegion* hr = heap_region_containing(p); 5164 return hr->is_in(p); 5165 } 5166 5167 // Methods for the mutator alloc region 5168 5169 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5170 bool force) { 5171 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5172 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 5173 if (force || should_allocate) { 5174 HeapRegion* new_alloc_region = new_region(word_size, 5175 false /* is_old */, 5176 false /* do_expand */); 5177 if (new_alloc_region != NULL) { 5178 set_region_short_lived_locked(new_alloc_region); 5179 _hr_printer.alloc(new_alloc_region, !should_allocate); 5180 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5181 return new_alloc_region; 5182 } 5183 } 5184 return NULL; 5185 } 5186 5187 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5188 size_t allocated_bytes) { 5189 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5190 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5191 5192 collection_set()->add_eden_region(alloc_region); 5193 increase_used(allocated_bytes); 5194 _hr_printer.retire(alloc_region); 5195 // We update the eden sizes here, when the region is retired, 5196 // instead of when it's allocated, since this is the point that its 5197 // used space has been recored in _summary_bytes_used. 5198 g1mm()->update_eden_size(); 5199 } 5200 5201 // Methods for the GC alloc regions 5202 5203 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 5204 if (dest.is_old()) { 5205 return true; 5206 } else { 5207 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 5208 } 5209 } 5210 5211 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 5212 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5213 5214 if (!has_more_regions(dest)) { 5215 return NULL; 5216 } 5217 5218 const bool is_survivor = dest.is_young(); 5219 5220 HeapRegion* new_alloc_region = new_region(word_size, 5221 !is_survivor, 5222 true /* do_expand */); 5223 if (new_alloc_region != NULL) { 5224 // We really only need to do this for old regions given that we 5225 // should never scan survivors. But it doesn't hurt to do it 5226 // for survivors too. 5227 new_alloc_region->record_timestamp(); 5228 if (is_survivor) { 5229 new_alloc_region->set_survivor(); 5230 _survivor.add(new_alloc_region); 5231 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5232 } else { 5233 new_alloc_region->set_old(); 5234 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5235 } 5236 _hr_printer.alloc(new_alloc_region); 5237 bool during_im = collector_state()->during_initial_mark_pause(); 5238 new_alloc_region->note_start_of_copying(during_im); 5239 return new_alloc_region; 5240 } 5241 return NULL; 5242 } 5243 5244 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5245 size_t allocated_bytes, 5246 InCSetState dest) { 5247 bool during_im = collector_state()->during_initial_mark_pause(); 5248 alloc_region->note_end_of_copying(during_im); 5249 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5250 if (dest.is_old()) { 5251 _old_set.add(alloc_region); 5252 } 5253 _hr_printer.retire(alloc_region); 5254 } 5255 5256 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5257 bool expanded = false; 5258 uint index = _hrm.find_highest_free(&expanded); 5259 5260 if (index != G1_NO_HRM_INDEX) { 5261 if (expanded) { 5262 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5263 HeapRegion::GrainWords * HeapWordSize); 5264 } 5265 _hrm.allocate_free_regions_starting_at(index, 1); 5266 return region_at(index); 5267 } 5268 return NULL; 5269 } 5270 5271 // Optimized nmethod scanning 5272 5273 class RegisterNMethodOopClosure: public OopClosure { 5274 G1CollectedHeap* _g1h; 5275 nmethod* _nm; 5276 5277 template <class T> void do_oop_work(T* p) { 5278 T heap_oop = oopDesc::load_heap_oop(p); 5279 if (!oopDesc::is_null(heap_oop)) { 5280 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5281 HeapRegion* hr = _g1h->heap_region_containing(obj); 5282 assert(!hr->is_continues_humongous(), 5283 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5284 " starting at " HR_FORMAT, 5285 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5286 5287 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5288 hr->add_strong_code_root_locked(_nm); 5289 } 5290 } 5291 5292 public: 5293 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5294 _g1h(g1h), _nm(nm) {} 5295 5296 void do_oop(oop* p) { do_oop_work(p); } 5297 void do_oop(narrowOop* p) { do_oop_work(p); } 5298 }; 5299 5300 class UnregisterNMethodOopClosure: public OopClosure { 5301 G1CollectedHeap* _g1h; 5302 nmethod* _nm; 5303 5304 template <class T> void do_oop_work(T* p) { 5305 T heap_oop = oopDesc::load_heap_oop(p); 5306 if (!oopDesc::is_null(heap_oop)) { 5307 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5308 HeapRegion* hr = _g1h->heap_region_containing(obj); 5309 assert(!hr->is_continues_humongous(), 5310 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5311 " starting at " HR_FORMAT, 5312 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5313 5314 hr->remove_strong_code_root(_nm); 5315 } 5316 } 5317 5318 public: 5319 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5320 _g1h(g1h), _nm(nm) {} 5321 5322 void do_oop(oop* p) { do_oop_work(p); } 5323 void do_oop(narrowOop* p) { do_oop_work(p); } 5324 }; 5325 5326 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5327 CollectedHeap::register_nmethod(nm); 5328 5329 guarantee(nm != NULL, "sanity"); 5330 RegisterNMethodOopClosure reg_cl(this, nm); 5331 nm->oops_do(®_cl); 5332 } 5333 5334 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5335 CollectedHeap::unregister_nmethod(nm); 5336 5337 guarantee(nm != NULL, "sanity"); 5338 UnregisterNMethodOopClosure reg_cl(this, nm); 5339 nm->oops_do(®_cl, true); 5340 } 5341 5342 void G1CollectedHeap::purge_code_root_memory() { 5343 double purge_start = os::elapsedTime(); 5344 G1CodeRootSet::purge(); 5345 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5346 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5347 } 5348 5349 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5350 G1CollectedHeap* _g1h; 5351 5352 public: 5353 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5354 _g1h(g1h) {} 5355 5356 void do_code_blob(CodeBlob* cb) { 5357 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5358 if (nm == NULL) { 5359 return; 5360 } 5361 5362 if (ScavengeRootsInCode) { 5363 _g1h->register_nmethod(nm); 5364 } 5365 } 5366 }; 5367 5368 void G1CollectedHeap::rebuild_strong_code_roots() { 5369 RebuildStrongCodeRootClosure blob_cl(this); 5370 CodeCache::blobs_do(&blob_cl); 5371 }