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/g1FullCollector.hpp" 42 #include "gc/g1/g1FullGCScope.hpp" 43 #include "gc/g1/g1GCPhaseTimes.hpp" 44 #include "gc/g1/g1HeapSizingPolicy.hpp" 45 #include "gc/g1/g1HeapTransition.hpp" 46 #include "gc/g1/g1HeapVerifier.hpp" 47 #include "gc/g1/g1HotCardCache.hpp" 48 #include "gc/g1/g1OopClosures.inline.hpp" 49 #include "gc/g1/g1ParScanThreadState.inline.hpp" 50 #include "gc/g1/g1Policy.hpp" 51 #include "gc/g1/g1RegionToSpaceMapper.hpp" 52 #include "gc/g1/g1RemSet.inline.hpp" 53 #include "gc/g1/g1RootClosures.hpp" 54 #include "gc/g1/g1RootProcessor.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 } 150 151 152 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 153 MemRegion mr) { 154 return new HeapRegion(hrs_index, bot(), mr); 155 } 156 157 // Private methods. 158 159 HeapRegion* 160 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 161 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 162 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 163 if (!_secondary_free_list.is_empty()) { 164 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 165 "secondary_free_list has %u entries", 166 _secondary_free_list.length()); 167 // It looks as if there are free regions available on the 168 // secondary_free_list. Let's move them to the free_list and try 169 // again to allocate from it. 170 append_secondary_free_list(); 171 172 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 173 "empty we should have moved at least one entry to the free_list"); 174 HeapRegion* res = _hrm.allocate_free_region(is_old); 175 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 176 "allocated " HR_FORMAT " from secondary_free_list", 177 HR_FORMAT_PARAMS(res)); 178 return res; 179 } 180 181 // Wait here until we get notified either when (a) there are no 182 // more free regions coming or (b) some regions have been moved on 183 // the secondary_free_list. 184 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 185 } 186 187 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 188 "could not allocate from secondary_free_list"); 189 return NULL; 190 } 191 192 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 193 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 194 "the only time we use this to allocate a humongous region is " 195 "when we are allocating a single humongous region"); 196 197 HeapRegion* res; 198 if (G1StressConcRegionFreeing) { 199 if (!_secondary_free_list.is_empty()) { 200 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 201 "forced to look at the secondary_free_list"); 202 res = new_region_try_secondary_free_list(is_old); 203 if (res != NULL) { 204 return res; 205 } 206 } 207 } 208 209 res = _hrm.allocate_free_region(is_old); 210 211 if (res == NULL) { 212 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : " 213 "res == NULL, trying the secondary_free_list"); 214 res = new_region_try_secondary_free_list(is_old); 215 } 216 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 217 // Currently, only attempts to allocate GC alloc regions set 218 // do_expand to true. So, we should only reach here during a 219 // safepoint. If this assumption changes we might have to 220 // reconsider the use of _expand_heap_after_alloc_failure. 221 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 222 223 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B", 224 word_size * HeapWordSize); 225 226 if (expand(word_size * HeapWordSize)) { 227 // Given that expand() succeeded in expanding the heap, and we 228 // always expand the heap by an amount aligned to the heap 229 // region size, the free list should in theory not be empty. 230 // In either case allocate_free_region() will check for NULL. 231 res = _hrm.allocate_free_region(is_old); 232 } else { 233 _expand_heap_after_alloc_failure = false; 234 } 235 } 236 return res; 237 } 238 239 HeapWord* 240 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 241 uint num_regions, 242 size_t word_size, 243 AllocationContext_t context) { 244 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 245 assert(is_humongous(word_size), "word_size should be humongous"); 246 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 247 248 // Index of last region in the series. 249 uint last = first + num_regions - 1; 250 251 // We need to initialize the region(s) we just discovered. This is 252 // a bit tricky given that it can happen concurrently with 253 // refinement threads refining cards on these regions and 254 // potentially wanting to refine the BOT as they are scanning 255 // those cards (this can happen shortly after a cleanup; see CR 256 // 6991377). So we have to set up the region(s) carefully and in 257 // a specific order. 258 259 // The word size sum of all the regions we will allocate. 260 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 261 assert(word_size <= word_size_sum, "sanity"); 262 263 // This will be the "starts humongous" region. 264 HeapRegion* first_hr = region_at(first); 265 // The header of the new object will be placed at the bottom of 266 // the first region. 267 HeapWord* new_obj = first_hr->bottom(); 268 // This will be the new top of the new object. 269 HeapWord* obj_top = new_obj + word_size; 270 271 // First, we need to zero the header of the space that we will be 272 // allocating. When we update top further down, some refinement 273 // threads might try to scan the region. By zeroing the header we 274 // ensure that any thread that will try to scan the region will 275 // come across the zero klass word and bail out. 276 // 277 // NOTE: It would not have been correct to have used 278 // CollectedHeap::fill_with_object() and make the space look like 279 // an int array. The thread that is doing the allocation will 280 // later update the object header to a potentially different array 281 // type and, for a very short period of time, the klass and length 282 // fields will be inconsistent. This could cause a refinement 283 // thread to calculate the object size incorrectly. 284 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 285 286 // Next, pad out the unused tail of the last region with filler 287 // objects, for improved usage accounting. 288 // How many words we use for filler objects. 289 size_t word_fill_size = word_size_sum - word_size; 290 291 // How many words memory we "waste" which cannot hold a filler object. 292 size_t words_not_fillable = 0; 293 294 if (word_fill_size >= min_fill_size()) { 295 fill_with_objects(obj_top, word_fill_size); 296 } else if (word_fill_size > 0) { 297 // We have space to fill, but we cannot fit an object there. 298 words_not_fillable = word_fill_size; 299 word_fill_size = 0; 300 } 301 302 // We will set up the first region as "starts humongous". This 303 // will also update the BOT covering all the regions to reflect 304 // that there is a single object that starts at the bottom of the 305 // first region. 306 first_hr->set_starts_humongous(obj_top, word_fill_size); 307 first_hr->set_allocation_context(context); 308 // Then, if there are any, we will set up the "continues 309 // humongous" regions. 310 HeapRegion* hr = NULL; 311 for (uint i = first + 1; i <= last; ++i) { 312 hr = region_at(i); 313 hr->set_continues_humongous(first_hr); 314 hr->set_allocation_context(context); 315 } 316 317 // Up to this point no concurrent thread would have been able to 318 // do any scanning on any region in this series. All the top 319 // fields still point to bottom, so the intersection between 320 // [bottom,top] and [card_start,card_end] will be empty. Before we 321 // update the top fields, we'll do a storestore to make sure that 322 // no thread sees the update to top before the zeroing of the 323 // object header and the BOT initialization. 324 OrderAccess::storestore(); 325 326 // Now, we will update the top fields of the "continues humongous" 327 // regions except the last one. 328 for (uint i = first; i < last; ++i) { 329 hr = region_at(i); 330 hr->set_top(hr->end()); 331 } 332 333 hr = region_at(last); 334 // If we cannot fit a filler object, we must set top to the end 335 // of the humongous object, otherwise we cannot iterate the heap 336 // and the BOT will not be complete. 337 hr->set_top(hr->end() - words_not_fillable); 338 339 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 340 "obj_top should be in last region"); 341 342 _verifier->check_bitmaps("Humongous Region Allocation", first_hr); 343 344 assert(words_not_fillable == 0 || 345 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(), 346 "Miscalculation in humongous allocation"); 347 348 increase_used((word_size_sum - words_not_fillable) * HeapWordSize); 349 350 for (uint i = first; i <= last; ++i) { 351 hr = region_at(i); 352 _humongous_set.add(hr); 353 _hr_printer.alloc(hr); 354 } 355 356 return new_obj; 357 } 358 359 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) { 360 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size); 361 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 362 } 363 364 // If could fit into free regions w/o expansion, try. 365 // Otherwise, if can expand, do so. 366 // Otherwise, if using ex regions might help, try with ex given back. 367 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 368 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 369 370 _verifier->verify_region_sets_optional(); 371 372 uint first = G1_NO_HRM_INDEX; 373 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size); 374 375 if (obj_regions == 1) { 376 // Only one region to allocate, try to use a fast path by directly allocating 377 // from the free lists. Do not try to expand here, we will potentially do that 378 // later. 379 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 380 if (hr != NULL) { 381 first = hr->hrm_index(); 382 } 383 } else { 384 // We can't allocate humongous regions spanning more than one region while 385 // cleanupComplete() is running, since some of the regions we find to be 386 // empty might not yet be added to the free list. It is not straightforward 387 // to know in which list they are on so that we can remove them. We only 388 // need to do this if we need to allocate more than one region to satisfy the 389 // current humongous allocation request. If we are only allocating one region 390 // we use the one-region region allocation code (see above), that already 391 // potentially waits for regions from the secondary free list. 392 wait_while_free_regions_coming(); 393 append_secondary_free_list_if_not_empty_with_lock(); 394 395 // Policy: Try only empty regions (i.e. already committed first). Maybe we 396 // are lucky enough to find some. 397 first = _hrm.find_contiguous_only_empty(obj_regions); 398 if (first != G1_NO_HRM_INDEX) { 399 _hrm.allocate_free_regions_starting_at(first, obj_regions); 400 } 401 } 402 403 if (first == G1_NO_HRM_INDEX) { 404 // Policy: We could not find enough regions for the humongous object in the 405 // free list. Look through the heap to find a mix of free and uncommitted regions. 406 // If so, try expansion. 407 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 408 if (first != G1_NO_HRM_INDEX) { 409 // We found something. Make sure these regions are committed, i.e. expand 410 // the heap. Alternatively we could do a defragmentation GC. 411 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B", 412 word_size * HeapWordSize); 413 414 _hrm.expand_at(first, obj_regions, workers()); 415 g1_policy()->record_new_heap_size(num_regions()); 416 417 #ifdef ASSERT 418 for (uint i = first; i < first + obj_regions; ++i) { 419 HeapRegion* hr = region_at(i); 420 assert(hr->is_free(), "sanity"); 421 assert(hr->is_empty(), "sanity"); 422 assert(is_on_master_free_list(hr), "sanity"); 423 } 424 #endif 425 _hrm.allocate_free_regions_starting_at(first, obj_regions); 426 } else { 427 // Policy: Potentially trigger a defragmentation GC. 428 } 429 } 430 431 HeapWord* result = NULL; 432 if (first != G1_NO_HRM_INDEX) { 433 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 434 word_size, context); 435 assert(result != NULL, "it should always return a valid result"); 436 437 // A successful humongous object allocation changes the used space 438 // information of the old generation so we need to recalculate the 439 // sizes and update the jstat counters here. 440 g1mm()->update_sizes(); 441 } 442 443 _verifier->verify_region_sets_optional(); 444 445 return result; 446 } 447 448 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 449 assert_heap_not_locked_and_not_at_safepoint(); 450 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 451 452 uint dummy_gc_count_before; 453 uint dummy_gclocker_retry_count = 0; 454 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 455 } 456 457 HeapWord* 458 G1CollectedHeap::mem_allocate(size_t word_size, 459 bool* gc_overhead_limit_was_exceeded) { 460 assert_heap_not_locked_and_not_at_safepoint(); 461 462 // Loop until the allocation is satisfied, or unsatisfied after GC. 463 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 464 uint gc_count_before; 465 466 HeapWord* result = NULL; 467 if (!is_humongous(word_size)) { 468 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 469 } else { 470 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 471 } 472 if (result != NULL) { 473 return result; 474 } 475 476 // Create the garbage collection operation... 477 VM_G1CollectForAllocation op(gc_count_before, word_size); 478 op.set_allocation_context(AllocationContext::current()); 479 480 // ...and get the VM thread to execute it. 481 VMThread::execute(&op); 482 483 if (op.prologue_succeeded() && op.pause_succeeded()) { 484 // If the operation was successful we'll return the result even 485 // if it is NULL. If the allocation attempt failed immediately 486 // after a Full GC, it's unlikely we'll be able to allocate now. 487 HeapWord* result = op.result(); 488 if (result != NULL && !is_humongous(word_size)) { 489 // Allocations that take place on VM operations do not do any 490 // card dirtying and we have to do it here. We only have to do 491 // this for non-humongous allocations, though. 492 dirty_young_block(result, word_size); 493 } 494 return result; 495 } else { 496 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 497 return NULL; 498 } 499 assert(op.result() == NULL, 500 "the result should be NULL if the VM op did not succeed"); 501 } 502 503 // Give a warning if we seem to be looping forever. 504 if ((QueuedAllocationWarningCount > 0) && 505 (try_count % QueuedAllocationWarningCount == 0)) { 506 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count); 507 } 508 } 509 510 ShouldNotReachHere(); 511 return NULL; 512 } 513 514 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 515 AllocationContext_t context, 516 uint* gc_count_before_ret, 517 uint* gclocker_retry_count_ret) { 518 // Make sure you read the note in attempt_allocation_humongous(). 519 520 assert_heap_not_locked_and_not_at_safepoint(); 521 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 522 "be called for humongous allocation requests"); 523 524 // We should only get here after the first-level allocation attempt 525 // (attempt_allocation()) failed to allocate. 526 527 // We will loop until a) we manage to successfully perform the 528 // allocation or b) we successfully schedule a collection which 529 // fails to perform the allocation. b) is the only case when we'll 530 // return NULL. 531 HeapWord* result = NULL; 532 for (int try_count = 1; /* we'll return */; try_count += 1) { 533 bool should_try_gc; 534 uint gc_count_before; 535 536 { 537 MutexLockerEx x(Heap_lock); 538 result = _allocator->attempt_allocation_locked(word_size, context); 539 if (result != NULL) { 540 return result; 541 } 542 543 if (GCLocker::is_active_and_needs_gc()) { 544 if (g1_policy()->can_expand_young_list()) { 545 // No need for an ergo verbose message here, 546 // can_expand_young_list() does this when it returns true. 547 result = _allocator->attempt_allocation_force(word_size, context); 548 if (result != NULL) { 549 return result; 550 } 551 } 552 should_try_gc = false; 553 } else { 554 // The GCLocker may not be active but the GCLocker initiated 555 // GC may not yet have been performed (GCLocker::needs_gc() 556 // returns true). In this case we do not try this GC and 557 // wait until the GCLocker initiated GC is performed, and 558 // then retry the allocation. 559 if (GCLocker::needs_gc()) { 560 should_try_gc = false; 561 } else { 562 // Read the GC count while still holding the Heap_lock. 563 gc_count_before = total_collections(); 564 should_try_gc = true; 565 } 566 } 567 } 568 569 if (should_try_gc) { 570 bool succeeded; 571 result = do_collection_pause(word_size, gc_count_before, &succeeded, 572 GCCause::_g1_inc_collection_pause); 573 if (result != NULL) { 574 assert(succeeded, "only way to get back a non-NULL result"); 575 return result; 576 } 577 578 if (succeeded) { 579 // If we get here we successfully scheduled a collection which 580 // failed to allocate. No point in trying to allocate 581 // further. We'll just return NULL. 582 MutexLockerEx x(Heap_lock); 583 *gc_count_before_ret = total_collections(); 584 return NULL; 585 } 586 } else { 587 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 588 MutexLockerEx x(Heap_lock); 589 *gc_count_before_ret = total_collections(); 590 return NULL; 591 } 592 // The GCLocker is either active or the GCLocker initiated 593 // GC has not yet been performed. Stall until it is and 594 // then retry the allocation. 595 GCLocker::stall_until_clear(); 596 (*gclocker_retry_count_ret) += 1; 597 } 598 599 // We can reach here if we were unsuccessful in scheduling a 600 // collection (because another thread beat us to it) or if we were 601 // stalled due to the GC locker. In either can we should retry the 602 // allocation attempt in case another thread successfully 603 // performed a collection and reclaimed enough space. We do the 604 // first attempt (without holding the Heap_lock) here and the 605 // follow-on attempt will be at the start of the next loop 606 // iteration (after taking the Heap_lock). 607 result = _allocator->attempt_allocation(word_size, context); 608 if (result != NULL) { 609 return result; 610 } 611 612 // Give a warning if we seem to be looping forever. 613 if ((QueuedAllocationWarningCount > 0) && 614 (try_count % QueuedAllocationWarningCount == 0)) { 615 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() " 616 "retries %d times", try_count); 617 } 618 } 619 620 ShouldNotReachHere(); 621 return NULL; 622 } 623 624 void G1CollectedHeap::begin_archive_alloc_range() { 625 assert_at_safepoint(true /* should_be_vm_thread */); 626 if (_archive_allocator == NULL) { 627 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 628 } 629 } 630 631 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 632 // Allocations in archive regions cannot be of a size that would be considered 633 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 634 // may be different at archive-restore time. 635 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 636 } 637 638 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 639 assert_at_safepoint(true /* should_be_vm_thread */); 640 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 641 if (is_archive_alloc_too_large(word_size)) { 642 return NULL; 643 } 644 return _archive_allocator->archive_mem_allocate(word_size); 645 } 646 647 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 648 size_t end_alignment_in_bytes) { 649 assert_at_safepoint(true /* should_be_vm_thread */); 650 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 651 652 // Call complete_archive to do the real work, filling in the MemRegion 653 // array with the archive regions. 654 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 655 delete _archive_allocator; 656 _archive_allocator = NULL; 657 } 658 659 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 660 assert(ranges != NULL, "MemRegion array NULL"); 661 assert(count != 0, "No MemRegions provided"); 662 MemRegion reserved = _hrm.reserved(); 663 for (size_t i = 0; i < count; i++) { 664 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 665 return false; 666 } 667 } 668 return true; 669 } 670 671 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 672 assert(!is_init_completed(), "Expect to be called at JVM init time"); 673 assert(ranges != NULL, "MemRegion array NULL"); 674 assert(count != 0, "No MemRegions provided"); 675 MutexLockerEx x(Heap_lock); 676 677 MemRegion reserved = _hrm.reserved(); 678 HeapWord* prev_last_addr = NULL; 679 HeapRegion* prev_last_region = NULL; 680 681 // Temporarily disable pretouching of heap pages. This interface is used 682 // when mmap'ing archived heap data in, so pre-touching is wasted. 683 FlagSetting fs(AlwaysPreTouch, false); 684 685 // Enable archive object checking used by G1MarkSweep. We have to let it know 686 // about each archive range, so that objects in those ranges aren't marked. 687 G1ArchiveAllocator::enable_archive_object_check(); 688 689 // For each specified MemRegion range, allocate the corresponding G1 690 // regions and mark them as archive regions. We expect the ranges in 691 // ascending starting address order, without overlap. 692 for (size_t i = 0; i < count; i++) { 693 MemRegion curr_range = ranges[i]; 694 HeapWord* start_address = curr_range.start(); 695 size_t word_size = curr_range.word_size(); 696 HeapWord* last_address = curr_range.last(); 697 size_t commits = 0; 698 699 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 700 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 701 p2i(start_address), p2i(last_address)); 702 guarantee(start_address > prev_last_addr, 703 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 704 p2i(start_address), p2i(prev_last_addr)); 705 prev_last_addr = last_address; 706 707 // Check for ranges that start in the same G1 region in which the previous 708 // range ended, and adjust the start address so we don't try to allocate 709 // the same region again. If the current range is entirely within that 710 // region, skip it, just adjusting the recorded top. 711 HeapRegion* start_region = _hrm.addr_to_region(start_address); 712 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 713 start_address = start_region->end(); 714 if (start_address > last_address) { 715 increase_used(word_size * HeapWordSize); 716 start_region->set_top(last_address + 1); 717 continue; 718 } 719 start_region->set_top(start_address); 720 curr_range = MemRegion(start_address, last_address + 1); 721 start_region = _hrm.addr_to_region(start_address); 722 } 723 724 // Perform the actual region allocation, exiting if it fails. 725 // Then note how much new space we have allocated. 726 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) { 727 return false; 728 } 729 increase_used(word_size * HeapWordSize); 730 if (commits != 0) { 731 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B", 732 HeapRegion::GrainWords * HeapWordSize * commits); 733 734 } 735 736 // Mark each G1 region touched by the range as archive, add it to the old set, 737 // and set the allocation context and top. 738 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 739 HeapRegion* last_region = _hrm.addr_to_region(last_address); 740 prev_last_region = last_region; 741 742 while (curr_region != NULL) { 743 assert(curr_region->is_empty() && !curr_region->is_pinned(), 744 "Region already in use (index %u)", curr_region->hrm_index()); 745 curr_region->set_allocation_context(AllocationContext::system()); 746 curr_region->set_archive(); 747 _hr_printer.alloc(curr_region); 748 _old_set.add(curr_region); 749 if (curr_region != last_region) { 750 curr_region->set_top(curr_region->end()); 751 curr_region = _hrm.next_region_in_heap(curr_region); 752 } else { 753 curr_region->set_top(last_address + 1); 754 curr_region = NULL; 755 } 756 } 757 758 // Notify mark-sweep of the archive range. 759 G1ArchiveAllocator::set_range_archive(curr_range, true); 760 } 761 return true; 762 } 763 764 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 765 assert(!is_init_completed(), "Expect to be called at JVM init time"); 766 assert(ranges != NULL, "MemRegion array NULL"); 767 assert(count != 0, "No MemRegions provided"); 768 MemRegion reserved = _hrm.reserved(); 769 HeapWord *prev_last_addr = NULL; 770 HeapRegion* prev_last_region = NULL; 771 772 // For each MemRegion, create filler objects, if needed, in the G1 regions 773 // that contain the address range. The address range actually within the 774 // MemRegion will not be modified. That is assumed to have been initialized 775 // elsewhere, probably via an mmap of archived heap data. 776 MutexLockerEx x(Heap_lock); 777 for (size_t i = 0; i < count; i++) { 778 HeapWord* start_address = ranges[i].start(); 779 HeapWord* last_address = ranges[i].last(); 780 781 assert(reserved.contains(start_address) && reserved.contains(last_address), 782 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 783 p2i(start_address), p2i(last_address)); 784 assert(start_address > prev_last_addr, 785 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 786 p2i(start_address), p2i(prev_last_addr)); 787 788 HeapRegion* start_region = _hrm.addr_to_region(start_address); 789 HeapRegion* last_region = _hrm.addr_to_region(last_address); 790 HeapWord* bottom_address = start_region->bottom(); 791 792 // Check for a range beginning in the same region in which the 793 // previous one ended. 794 if (start_region == prev_last_region) { 795 bottom_address = prev_last_addr + 1; 796 } 797 798 // Verify that the regions were all marked as archive regions by 799 // alloc_archive_regions. 800 HeapRegion* curr_region = start_region; 801 while (curr_region != NULL) { 802 guarantee(curr_region->is_archive(), 803 "Expected archive region at index %u", curr_region->hrm_index()); 804 if (curr_region != last_region) { 805 curr_region = _hrm.next_region_in_heap(curr_region); 806 } else { 807 curr_region = NULL; 808 } 809 } 810 811 prev_last_addr = last_address; 812 prev_last_region = last_region; 813 814 // Fill the memory below the allocated range with dummy object(s), 815 // if the region bottom does not match the range start, or if the previous 816 // range ended within the same G1 region, and there is a gap. 817 if (start_address != bottom_address) { 818 size_t fill_size = pointer_delta(start_address, bottom_address); 819 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 820 increase_used(fill_size * HeapWordSize); 821 } 822 } 823 } 824 825 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 826 uint* gc_count_before_ret, 827 uint* gclocker_retry_count_ret) { 828 assert_heap_not_locked_and_not_at_safepoint(); 829 assert(!is_humongous(word_size), "attempt_allocation() should not " 830 "be called for humongous allocation requests"); 831 832 AllocationContext_t context = AllocationContext::current(); 833 HeapWord* result = _allocator->attempt_allocation(word_size, context); 834 835 if (result == NULL) { 836 result = attempt_allocation_slow(word_size, 837 context, 838 gc_count_before_ret, 839 gclocker_retry_count_ret); 840 } 841 assert_heap_not_locked(); 842 if (result != NULL) { 843 dirty_young_block(result, word_size); 844 } 845 return result; 846 } 847 848 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 849 assert(!is_init_completed(), "Expect to be called at JVM init time"); 850 assert(ranges != NULL, "MemRegion array NULL"); 851 assert(count != 0, "No MemRegions provided"); 852 MemRegion reserved = _hrm.reserved(); 853 HeapWord* prev_last_addr = NULL; 854 HeapRegion* prev_last_region = NULL; 855 size_t size_used = 0; 856 size_t uncommitted_regions = 0; 857 858 // For each Memregion, free the G1 regions that constitute it, and 859 // notify mark-sweep that the range is no longer to be considered 'archive.' 860 MutexLockerEx x(Heap_lock); 861 for (size_t i = 0; i < count; i++) { 862 HeapWord* start_address = ranges[i].start(); 863 HeapWord* last_address = ranges[i].last(); 864 865 assert(reserved.contains(start_address) && reserved.contains(last_address), 866 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 867 p2i(start_address), p2i(last_address)); 868 assert(start_address > prev_last_addr, 869 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 870 p2i(start_address), p2i(prev_last_addr)); 871 size_used += ranges[i].byte_size(); 872 prev_last_addr = last_address; 873 874 HeapRegion* start_region = _hrm.addr_to_region(start_address); 875 HeapRegion* last_region = _hrm.addr_to_region(last_address); 876 877 // Check for ranges that start in the same G1 region in which the previous 878 // range ended, and adjust the start address so we don't try to free 879 // the same region again. If the current range is entirely within that 880 // region, skip it. 881 if (start_region == prev_last_region) { 882 start_address = start_region->end(); 883 if (start_address > last_address) { 884 continue; 885 } 886 start_region = _hrm.addr_to_region(start_address); 887 } 888 prev_last_region = last_region; 889 890 // After verifying that each region was marked as an archive region by 891 // alloc_archive_regions, set it free and empty and uncommit it. 892 HeapRegion* curr_region = start_region; 893 while (curr_region != NULL) { 894 guarantee(curr_region->is_archive(), 895 "Expected archive region at index %u", curr_region->hrm_index()); 896 uint curr_index = curr_region->hrm_index(); 897 _old_set.remove(curr_region); 898 curr_region->set_free(); 899 curr_region->set_top(curr_region->bottom()); 900 if (curr_region != last_region) { 901 curr_region = _hrm.next_region_in_heap(curr_region); 902 } else { 903 curr_region = NULL; 904 } 905 _hrm.shrink_at(curr_index, 1); 906 uncommitted_regions++; 907 } 908 909 // Notify mark-sweep that this is no longer an archive range. 910 G1ArchiveAllocator::set_range_archive(ranges[i], false); 911 } 912 913 if (uncommitted_regions != 0) { 914 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B", 915 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 916 } 917 decrease_used(size_used); 918 } 919 920 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 921 uint* gc_count_before_ret, 922 uint* gclocker_retry_count_ret) { 923 // The structure of this method has a lot of similarities to 924 // attempt_allocation_slow(). The reason these two were not merged 925 // into a single one is that such a method would require several "if 926 // allocation is not humongous do this, otherwise do that" 927 // conditional paths which would obscure its flow. In fact, an early 928 // version of this code did use a unified method which was harder to 929 // follow and, as a result, it had subtle bugs that were hard to 930 // track down. So keeping these two methods separate allows each to 931 // be more readable. It will be good to keep these two in sync as 932 // much as possible. 933 934 assert_heap_not_locked_and_not_at_safepoint(); 935 assert(is_humongous(word_size), "attempt_allocation_humongous() " 936 "should only be called for humongous allocations"); 937 938 // Humongous objects can exhaust the heap quickly, so we should check if we 939 // need to start a marking cycle at each humongous object allocation. We do 940 // the check before we do the actual allocation. The reason for doing it 941 // before the allocation is that we avoid having to keep track of the newly 942 // allocated memory while we do a GC. 943 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 944 word_size)) { 945 collect(GCCause::_g1_humongous_allocation); 946 } 947 948 // We will loop until a) we manage to successfully perform the 949 // allocation or b) we successfully schedule a collection which 950 // fails to perform the allocation. b) is the only case when we'll 951 // return NULL. 952 HeapWord* result = NULL; 953 for (int try_count = 1; /* we'll return */; try_count += 1) { 954 bool should_try_gc; 955 uint gc_count_before; 956 957 { 958 MutexLockerEx x(Heap_lock); 959 960 // Given that humongous objects are not allocated in young 961 // regions, we'll first try to do the allocation without doing a 962 // collection hoping that there's enough space in the heap. 963 result = humongous_obj_allocate(word_size, AllocationContext::current()); 964 if (result != NULL) { 965 size_t size_in_regions = humongous_obj_size_in_regions(word_size); 966 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes); 967 return result; 968 } 969 970 if (GCLocker::is_active_and_needs_gc()) { 971 should_try_gc = false; 972 } else { 973 // The GCLocker may not be active but the GCLocker initiated 974 // GC may not yet have been performed (GCLocker::needs_gc() 975 // returns true). In this case we do not try this GC and 976 // wait until the GCLocker initiated GC is performed, and 977 // then retry the allocation. 978 if (GCLocker::needs_gc()) { 979 should_try_gc = false; 980 } else { 981 // Read the GC count while still holding the Heap_lock. 982 gc_count_before = total_collections(); 983 should_try_gc = true; 984 } 985 } 986 } 987 988 if (should_try_gc) { 989 // If we failed to allocate the humongous object, we should try to 990 // do a collection pause (if we're allowed) in case it reclaims 991 // enough space for the allocation to succeed after the pause. 992 993 bool succeeded; 994 result = do_collection_pause(word_size, gc_count_before, &succeeded, 995 GCCause::_g1_humongous_allocation); 996 if (result != NULL) { 997 assert(succeeded, "only way to get back a non-NULL result"); 998 return result; 999 } 1000 1001 if (succeeded) { 1002 // If we get here we successfully scheduled a collection which 1003 // failed to allocate. No point in trying to allocate 1004 // further. We'll just return NULL. 1005 MutexLockerEx x(Heap_lock); 1006 *gc_count_before_ret = total_collections(); 1007 return NULL; 1008 } 1009 } else { 1010 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1011 MutexLockerEx x(Heap_lock); 1012 *gc_count_before_ret = total_collections(); 1013 return NULL; 1014 } 1015 // The GCLocker is either active or the GCLocker initiated 1016 // GC has not yet been performed. Stall until it is and 1017 // then retry the allocation. 1018 GCLocker::stall_until_clear(); 1019 (*gclocker_retry_count_ret) += 1; 1020 } 1021 1022 // We can reach here if we were unsuccessful in scheduling a 1023 // collection (because another thread beat us to it) or if we were 1024 // stalled due to the GC locker. In either can we should retry the 1025 // allocation attempt in case another thread successfully 1026 // performed a collection and reclaimed enough space. Give a 1027 // warning if we seem to be looping forever. 1028 1029 if ((QueuedAllocationWarningCount > 0) && 1030 (try_count % QueuedAllocationWarningCount == 0)) { 1031 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() " 1032 "retries %d times", try_count); 1033 } 1034 } 1035 1036 ShouldNotReachHere(); 1037 return NULL; 1038 } 1039 1040 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1041 AllocationContext_t context, 1042 bool expect_null_mutator_alloc_region) { 1043 assert_at_safepoint(true /* should_be_vm_thread */); 1044 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1045 "the current alloc region was unexpectedly found to be non-NULL"); 1046 1047 if (!is_humongous(word_size)) { 1048 return _allocator->attempt_allocation_locked(word_size, context); 1049 } else { 1050 HeapWord* result = humongous_obj_allocate(word_size, context); 1051 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1052 collector_state()->set_initiate_conc_mark_if_possible(true); 1053 } 1054 return result; 1055 } 1056 1057 ShouldNotReachHere(); 1058 } 1059 1060 class PostCompactionPrinterClosure: public HeapRegionClosure { 1061 private: 1062 G1HRPrinter* _hr_printer; 1063 public: 1064 bool doHeapRegion(HeapRegion* hr) { 1065 assert(!hr->is_young(), "not expecting to find young regions"); 1066 _hr_printer->post_compaction(hr); 1067 return false; 1068 } 1069 1070 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1071 : _hr_printer(hr_printer) { } 1072 }; 1073 1074 void G1CollectedHeap::print_hrm_post_compaction() { 1075 if (_hr_printer.is_active()) { 1076 PostCompactionPrinterClosure cl(hr_printer()); 1077 heap_region_iterate(&cl); 1078 } 1079 1080 } 1081 1082 void G1CollectedHeap::abort_concurrent_cycle() { 1083 // Note: When we have a more flexible GC logging framework that 1084 // allows us to add optional attributes to a GC log record we 1085 // could consider timing and reporting how long we wait in the 1086 // following two methods. 1087 wait_while_free_regions_coming(); 1088 // If we start the compaction before the CM threads finish 1089 // scanning the root regions we might trip them over as we'll 1090 // be moving objects / updating references. So let's wait until 1091 // they are done. By telling them to abort, they should complete 1092 // early. 1093 _cm->root_regions()->abort(); 1094 _cm->root_regions()->wait_until_scan_finished(); 1095 append_secondary_free_list_if_not_empty_with_lock(); 1096 1097 // Disable discovery and empty the discovered lists 1098 // for the CM ref processor. 1099 ref_processor_cm()->disable_discovery(); 1100 ref_processor_cm()->abandon_partial_discovery(); 1101 ref_processor_cm()->verify_no_references_recorded(); 1102 1103 // Abandon current iterations of concurrent marking and concurrent 1104 // refinement, if any are in progress. 1105 concurrent_mark()->abort(); 1106 } 1107 1108 void G1CollectedHeap::prepare_heap_for_full_collection() { 1109 // Make sure we'll choose a new allocation region afterwards. 1110 _allocator->release_mutator_alloc_region(); 1111 _allocator->abandon_gc_alloc_regions(); 1112 g1_rem_set()->cleanupHRRS(); 1113 1114 // We may have added regions to the current incremental collection 1115 // set between the last GC or pause and now. We need to clear the 1116 // incremental collection set and then start rebuilding it afresh 1117 // after this full GC. 1118 abandon_collection_set(collection_set()); 1119 1120 tear_down_region_sets(false /* free_list_only */); 1121 collector_state()->set_gcs_are_young(true); 1122 } 1123 1124 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) { 1125 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1126 assert(used() == recalculate_used(), "Should be equal"); 1127 _verifier->verify_region_sets_optional(); 1128 _verifier->verify_before_gc(); 1129 _verifier->check_bitmaps("Full GC Start"); 1130 } 1131 1132 void G1CollectedHeap::prepare_heap_for_mutators() { 1133 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1134 ClassLoaderDataGraph::purge(); 1135 MetaspaceAux::verify_metrics(); 1136 1137 // Prepare heap for normal collections. 1138 assert(num_free_regions() == 0, "we should not have added any free regions"); 1139 rebuild_region_sets(false /* free_list_only */); 1140 abort_refinement(); 1141 resize_if_necessary_after_full_collection(); 1142 1143 // Rebuild the strong code root lists for each region 1144 rebuild_strong_code_roots(); 1145 1146 // Start a new incremental collection set for the next pause 1147 start_new_collection_set(); 1148 1149 _allocator->init_mutator_alloc_region(); 1150 1151 // Post collection state updates. 1152 MetaspaceGC::compute_new_size(); 1153 } 1154 1155 void G1CollectedHeap::abort_refinement() { 1156 if (_hot_card_cache->use_cache()) { 1157 _hot_card_cache->reset_card_counts(); 1158 _hot_card_cache->reset_hot_cache(); 1159 } 1160 1161 // Discard all remembered set updates. 1162 JavaThread::dirty_card_queue_set().abandon_logs(); 1163 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1164 } 1165 1166 void G1CollectedHeap::verify_after_full_collection() { 1167 check_gc_time_stamps(); 1168 _hrm.verify_optional(); 1169 _verifier->verify_region_sets_optional(); 1170 _verifier->verify_after_gc(); 1171 // Clear the previous marking bitmap, if needed for bitmap verification. 1172 // Note we cannot do this when we clear the next marking bitmap in 1173 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the 1174 // objects marked during a full GC against the previous bitmap. 1175 // But we need to clear it before calling check_bitmaps below since 1176 // the full GC has compacted objects and updated TAMS but not updated 1177 // the prev bitmap. 1178 if (G1VerifyBitmaps) { 1179 GCTraceTime(Debug, gc)("Clear Bitmap for Verification"); 1180 _cm->clear_prev_bitmap(workers()); 1181 } 1182 _verifier->check_bitmaps("Full GC End"); 1183 1184 // At this point there should be no regions in the 1185 // entire heap tagged as young. 1186 assert(check_young_list_empty(), "young list should be empty at this point"); 1187 1188 // Note: since we've just done a full GC, concurrent 1189 // marking is no longer active. Therefore we need not 1190 // re-enable reference discovery for the CM ref processor. 1191 // That will be done at the start of the next marking cycle. 1192 // We also know that the STW processor should no longer 1193 // discover any new references. 1194 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1195 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1196 ref_processor_stw()->verify_no_references_recorded(); 1197 ref_processor_cm()->verify_no_references_recorded(); 1198 } 1199 1200 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) { 1201 print_hrm_post_compaction(); 1202 heap_transition->print(); 1203 print_heap_after_gc(); 1204 print_heap_regions(); 1205 #ifdef TRACESPINNING 1206 ParallelTaskTerminator::print_termination_counts(); 1207 #endif 1208 } 1209 1210 void G1CollectedHeap::do_full_collection_inner(G1FullGCScope* scope) { 1211 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true); 1212 g1_policy()->record_full_collection_start(); 1213 1214 print_heap_before_gc(); 1215 print_heap_regions(); 1216 1217 abort_concurrent_cycle(); 1218 verify_before_full_collection(scope->is_explicit_gc()); 1219 1220 gc_prologue(true); 1221 prepare_heap_for_full_collection(); 1222 1223 { 1224 G1FullCollector collector(scope, ref_processor_stw(), concurrent_mark()->nextMarkBitMap(), workers()->active_workers()); 1225 // Prepare collection by putting reference processor 1226 // in a correct state. 1227 collector.prepare_collection(); 1228 1229 // Do the actual collection. 1230 collector.collect(); 1231 1232 collector.complete_collection(); 1233 } 1234 1235 prepare_heap_for_mutators(); 1236 1237 g1_policy()->record_full_collection_end(); 1238 gc_epilogue(true); 1239 1240 // Post collection verification. 1241 verify_after_full_collection(); 1242 1243 // Post collection logging. 1244 // We should do this after we potentially resize the heap so 1245 // that all the COMMIT / UNCOMMIT events are generated before 1246 // the compaction events. 1247 print_heap_after_full_collection(scope->heap_transition()); 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 _g1_policy(create_g1_policy()), 1552 _collection_set(this, _g1_policy), 1553 _dirty_card_queue_set(false), 1554 _is_alive_closure_cm(this), 1555 _is_alive_closure_stw(this), 1556 _ref_processor_cm(NULL), 1557 _ref_processor_stw(NULL), 1558 _bot(NULL), 1559 _hot_card_cache(NULL), 1560 _g1_rem_set(NULL), 1561 _cg1r(NULL), 1562 _g1mm(NULL), 1563 _preserved_marks_set(true /* in_c_heap */), 1564 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1565 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1566 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1567 _humongous_reclaim_candidates(), 1568 _has_humongous_reclaim_candidates(false), 1569 _archive_allocator(NULL), 1570 _free_regions_coming(false), 1571 _gc_time_stamp(0), 1572 _summary_bytes_used(0), 1573 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight), 1574 _old_evac_stats("Old", OldPLABSize, PLABWeight), 1575 _expand_heap_after_alloc_failure(true), 1576 _old_marking_cycles_started(0), 1577 _old_marking_cycles_completed(0), 1578 _in_cset_fast_test(), 1579 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1580 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) { 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 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1723 G1RegionToSpaceMapper* cardtable_storage = 1724 create_aux_memory_mapper("Card Table", 1725 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1726 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1727 1728 G1RegionToSpaceMapper* card_counts_storage = 1729 create_aux_memory_mapper("Card Counts Table", 1730 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1731 G1CardCounts::heap_map_factor()); 1732 1733 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size()); 1734 G1RegionToSpaceMapper* prev_bitmap_storage = 1735 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1736 G1RegionToSpaceMapper* next_bitmap_storage = 1737 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor()); 1738 1739 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1740 g1_barrier_set()->initialize(cardtable_storage); 1741 // Do later initialization work for concurrent refinement. 1742 _hot_card_cache->initialize(card_counts_storage); 1743 1744 // 6843694 - ensure that the maximum region index can fit 1745 // in the remembered set structures. 1746 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1747 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1748 1749 // Also create a G1 rem set. 1750 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache); 1751 _g1_rem_set->initialize(max_capacity(), max_regions()); 1752 1753 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1754 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1755 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1756 "too many cards per region"); 1757 1758 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1759 1760 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage); 1761 1762 { 1763 HeapWord* start = _hrm.reserved().start(); 1764 HeapWord* end = _hrm.reserved().end(); 1765 size_t granularity = HeapRegion::GrainBytes; 1766 1767 _in_cset_fast_test.initialize(start, end, granularity); 1768 _humongous_reclaim_candidates.initialize(start, end, granularity); 1769 } 1770 1771 // Create the G1ConcurrentMark data structure and thread. 1772 // (Must do this late, so that "max_regions" is defined.) 1773 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1774 if (_cm == NULL || !_cm->completed_initialization()) { 1775 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark"); 1776 return JNI_ENOMEM; 1777 } 1778 _cmThread = _cm->cmThread(); 1779 1780 // Now expand into the initial heap size. 1781 if (!expand(init_byte_size, _workers)) { 1782 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1783 return JNI_ENOMEM; 1784 } 1785 1786 // Perform any initialization actions delegated to the policy. 1787 g1_policy()->init(this, &_collection_set); 1788 1789 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 1790 SATB_Q_FL_lock, 1791 G1SATBProcessCompletedThreshold, 1792 Shared_SATB_Q_lock); 1793 1794 jint ecode = initialize_concurrent_refinement(); 1795 if (ecode != JNI_OK) { 1796 return ecode; 1797 } 1798 1799 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1800 DirtyCardQ_FL_lock, 1801 (int)concurrent_g1_refine()->yellow_zone(), 1802 (int)concurrent_g1_refine()->red_zone(), 1803 Shared_DirtyCardQ_lock, 1804 NULL, // fl_owner 1805 true); // init_free_ids 1806 1807 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 1808 DirtyCardQ_FL_lock, 1809 -1, // never trigger processing 1810 -1, // no limit on length 1811 Shared_DirtyCardQ_lock, 1812 &JavaThread::dirty_card_queue_set()); 1813 1814 // Here we allocate the dummy HeapRegion that is required by the 1815 // G1AllocRegion class. 1816 HeapRegion* dummy_region = _hrm.get_dummy_region(); 1817 1818 // We'll re-use the same region whether the alloc region will 1819 // require BOT updates or not and, if it doesn't, then a non-young 1820 // region will complain that it cannot support allocations without 1821 // BOT updates. So we'll tag the dummy region as eden to avoid that. 1822 dummy_region->set_eden(); 1823 // Make sure it's full. 1824 dummy_region->set_top(dummy_region->end()); 1825 G1AllocRegion::setup(this, dummy_region); 1826 1827 _allocator->init_mutator_alloc_region(); 1828 1829 // Do create of the monitoring and management support so that 1830 // values in the heap have been properly initialized. 1831 _g1mm = new G1MonitoringSupport(this); 1832 1833 G1StringDedup::initialize(); 1834 1835 _preserved_marks_set.init(ParallelGCThreads); 1836 1837 _collection_set.initialize(max_regions()); 1838 1839 return JNI_OK; 1840 } 1841 1842 void G1CollectedHeap::stop() { 1843 // Stop all concurrent threads. We do this to make sure these threads 1844 // do not continue to execute and access resources (e.g. logging) 1845 // that are destroyed during shutdown. 1846 _cg1r->stop(); 1847 _cmThread->stop(); 1848 if (G1StringDedup::is_enabled()) { 1849 G1StringDedup::stop(); 1850 } 1851 } 1852 1853 size_t G1CollectedHeap::conservative_max_heap_alignment() { 1854 return HeapRegion::max_region_size(); 1855 } 1856 1857 void G1CollectedHeap::post_initialize() { 1858 ref_processing_init(); 1859 } 1860 1861 void G1CollectedHeap::ref_processing_init() { 1862 // Reference processing in G1 currently works as follows: 1863 // 1864 // * There are two reference processor instances. One is 1865 // used to record and process discovered references 1866 // during concurrent marking; the other is used to 1867 // record and process references during STW pauses 1868 // (both full and incremental). 1869 // * Both ref processors need to 'span' the entire heap as 1870 // the regions in the collection set may be dotted around. 1871 // 1872 // * For the concurrent marking ref processor: 1873 // * Reference discovery is enabled at initial marking. 1874 // * Reference discovery is disabled and the discovered 1875 // references processed etc during remarking. 1876 // * Reference discovery is MT (see below). 1877 // * Reference discovery requires a barrier (see below). 1878 // * Reference processing may or may not be MT 1879 // (depending on the value of ParallelRefProcEnabled 1880 // and ParallelGCThreads). 1881 // * A full GC disables reference discovery by the CM 1882 // ref processor and abandons any entries on it's 1883 // discovered lists. 1884 // 1885 // * For the STW processor: 1886 // * Non MT discovery is enabled at the start of a full GC. 1887 // * Processing and enqueueing during a full GC is non-MT. 1888 // * During a full GC, references are processed after marking. 1889 // 1890 // * Discovery (may or may not be MT) is enabled at the start 1891 // of an incremental evacuation pause. 1892 // * References are processed near the end of a STW evacuation pause. 1893 // * For both types of GC: 1894 // * Discovery is atomic - i.e. not concurrent. 1895 // * Reference discovery will not need a barrier. 1896 1897 MemRegion mr = reserved_region(); 1898 1899 // Concurrent Mark ref processor 1900 _ref_processor_cm = 1901 new ReferenceProcessor(mr, // span 1902 ParallelRefProcEnabled && (ParallelGCThreads > 1), 1903 // mt processing 1904 ParallelGCThreads, 1905 // degree of mt processing 1906 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 1907 // mt discovery 1908 MAX2(ParallelGCThreads, ConcGCThreads), 1909 // degree of mt discovery 1910 false, 1911 // Reference discovery is not atomic 1912 &_is_alive_closure_cm); 1913 // is alive closure 1914 // (for efficiency/performance) 1915 1916 // STW ref processor 1917 _ref_processor_stw = 1918 new ReferenceProcessor(mr, // span 1919 ParallelRefProcEnabled && (ParallelGCThreads > 1), 1920 // mt processing 1921 ParallelGCThreads, 1922 // degree of mt processing 1923 (ParallelGCThreads > 1), 1924 // mt discovery 1925 ParallelGCThreads, 1926 // degree of mt discovery 1927 true, 1928 // Reference discovery is atomic 1929 &_is_alive_closure_stw); 1930 // is alive closure 1931 // (for efficiency/performance) 1932 } 1933 1934 CollectorPolicy* G1CollectedHeap::collector_policy() const { 1935 return _collector_policy; 1936 } 1937 1938 size_t G1CollectedHeap::capacity() const { 1939 return _hrm.length() * HeapRegion::GrainBytes; 1940 } 1941 1942 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 1943 hr->reset_gc_time_stamp(); 1944 } 1945 1946 #ifndef PRODUCT 1947 1948 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 1949 private: 1950 unsigned _gc_time_stamp; 1951 bool _failures; 1952 1953 public: 1954 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 1955 _gc_time_stamp(gc_time_stamp), _failures(false) { } 1956 1957 virtual bool doHeapRegion(HeapRegion* hr) { 1958 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 1959 if (_gc_time_stamp != region_gc_time_stamp) { 1960 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr), 1961 region_gc_time_stamp, _gc_time_stamp); 1962 _failures = true; 1963 } 1964 return false; 1965 } 1966 1967 bool failures() { return _failures; } 1968 }; 1969 1970 void G1CollectedHeap::check_gc_time_stamps() { 1971 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 1972 heap_region_iterate(&cl); 1973 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 1974 } 1975 #endif // PRODUCT 1976 1977 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 1978 _hot_card_cache->drain(cl, worker_i); 1979 } 1980 1981 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 1982 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 1983 size_t n_completed_buffers = 0; 1984 while (dcqs.apply_closure_during_gc(cl, worker_i)) { 1985 n_completed_buffers++; 1986 } 1987 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 1988 dcqs.clear_n_completed_buffers(); 1989 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 1990 } 1991 1992 // Computes the sum of the storage used by the various regions. 1993 size_t G1CollectedHeap::used() const { 1994 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 1995 if (_archive_allocator != NULL) { 1996 result += _archive_allocator->used(); 1997 } 1998 return result; 1999 } 2000 2001 size_t G1CollectedHeap::used_unlocked() const { 2002 return _summary_bytes_used; 2003 } 2004 2005 class SumUsedClosure: public HeapRegionClosure { 2006 size_t _used; 2007 public: 2008 SumUsedClosure() : _used(0) {} 2009 bool doHeapRegion(HeapRegion* r) { 2010 _used += r->used(); 2011 return false; 2012 } 2013 size_t result() { return _used; } 2014 }; 2015 2016 size_t G1CollectedHeap::recalculate_used() const { 2017 double recalculate_used_start = os::elapsedTime(); 2018 2019 SumUsedClosure blk; 2020 heap_region_iterate(&blk); 2021 2022 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2023 return blk.result(); 2024 } 2025 2026 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) { 2027 switch (cause) { 2028 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2029 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2030 case GCCause::_update_allocation_context_stats_inc: return true; 2031 case GCCause::_wb_conc_mark: return true; 2032 default : return false; 2033 } 2034 } 2035 2036 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2037 switch (cause) { 2038 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2039 case GCCause::_g1_humongous_allocation: return true; 2040 default: return is_user_requested_concurrent_full_gc(cause); 2041 } 2042 } 2043 2044 #ifndef PRODUCT 2045 void G1CollectedHeap::allocate_dummy_regions() { 2046 // Let's fill up most of the region 2047 size_t word_size = HeapRegion::GrainWords - 1024; 2048 // And as a result the region we'll allocate will be humongous. 2049 guarantee(is_humongous(word_size), "sanity"); 2050 2051 // _filler_array_max_size is set to humongous object threshold 2052 // but temporarily change it to use CollectedHeap::fill_with_object(). 2053 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2054 2055 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2056 // Let's use the existing mechanism for the allocation 2057 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2058 AllocationContext::system()); 2059 if (dummy_obj != NULL) { 2060 MemRegion mr(dummy_obj, word_size); 2061 CollectedHeap::fill_with_object(mr); 2062 } else { 2063 // If we can't allocate once, we probably cannot allocate 2064 // again. Let's get out of the loop. 2065 break; 2066 } 2067 } 2068 } 2069 #endif // !PRODUCT 2070 2071 void G1CollectedHeap::increment_old_marking_cycles_started() { 2072 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2073 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2074 "Wrong marking cycle count (started: %d, completed: %d)", 2075 _old_marking_cycles_started, _old_marking_cycles_completed); 2076 2077 _old_marking_cycles_started++; 2078 } 2079 2080 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2081 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2082 2083 // We assume that if concurrent == true, then the caller is a 2084 // concurrent thread that was joined the Suspendible Thread 2085 // Set. If there's ever a cheap way to check this, we should add an 2086 // assert here. 2087 2088 // Given that this method is called at the end of a Full GC or of a 2089 // concurrent cycle, and those can be nested (i.e., a Full GC can 2090 // interrupt a concurrent cycle), the number of full collections 2091 // completed should be either one (in the case where there was no 2092 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2093 // behind the number of full collections started. 2094 2095 // This is the case for the inner caller, i.e. a Full GC. 2096 assert(concurrent || 2097 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2098 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2099 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2100 "is inconsistent with _old_marking_cycles_completed = %u", 2101 _old_marking_cycles_started, _old_marking_cycles_completed); 2102 2103 // This is the case for the outer caller, i.e. the concurrent cycle. 2104 assert(!concurrent || 2105 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2106 "for outer caller (concurrent cycle): " 2107 "_old_marking_cycles_started = %u " 2108 "is inconsistent with _old_marking_cycles_completed = %u", 2109 _old_marking_cycles_started, _old_marking_cycles_completed); 2110 2111 _old_marking_cycles_completed += 1; 2112 2113 // We need to clear the "in_progress" flag in the CM thread before 2114 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2115 // is set) so that if a waiter requests another System.gc() it doesn't 2116 // incorrectly see that a marking cycle is still in progress. 2117 if (concurrent) { 2118 _cmThread->set_idle(); 2119 } 2120 2121 // This notify_all() will ensure that a thread that called 2122 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2123 // and it's waiting for a full GC to finish will be woken up. It is 2124 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2125 FullGCCount_lock->notify_all(); 2126 } 2127 2128 void G1CollectedHeap::collect(GCCause::Cause cause) { 2129 assert_heap_not_locked(); 2130 2131 uint gc_count_before; 2132 uint old_marking_count_before; 2133 uint full_gc_count_before; 2134 bool retry_gc; 2135 2136 do { 2137 retry_gc = false; 2138 2139 { 2140 MutexLocker ml(Heap_lock); 2141 2142 // Read the GC count while holding the Heap_lock 2143 gc_count_before = total_collections(); 2144 full_gc_count_before = total_full_collections(); 2145 old_marking_count_before = _old_marking_cycles_started; 2146 } 2147 2148 if (should_do_concurrent_full_gc(cause)) { 2149 // Schedule an initial-mark evacuation pause that will start a 2150 // concurrent cycle. We're setting word_size to 0 which means that 2151 // we are not requesting a post-GC allocation. 2152 VM_G1IncCollectionPause op(gc_count_before, 2153 0, /* word_size */ 2154 true, /* should_initiate_conc_mark */ 2155 g1_policy()->max_pause_time_ms(), 2156 cause); 2157 op.set_allocation_context(AllocationContext::current()); 2158 2159 VMThread::execute(&op); 2160 if (!op.pause_succeeded()) { 2161 if (old_marking_count_before == _old_marking_cycles_started) { 2162 retry_gc = op.should_retry_gc(); 2163 } else { 2164 // A Full GC happened while we were trying to schedule the 2165 // initial-mark GC. No point in starting a new cycle given 2166 // that the whole heap was collected anyway. 2167 } 2168 2169 if (retry_gc) { 2170 if (GCLocker::is_active_and_needs_gc()) { 2171 GCLocker::stall_until_clear(); 2172 } 2173 } 2174 } 2175 } else { 2176 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2177 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2178 2179 // Schedule a standard evacuation pause. We're setting word_size 2180 // to 0 which means that we are not requesting a post-GC allocation. 2181 VM_G1IncCollectionPause op(gc_count_before, 2182 0, /* word_size */ 2183 false, /* should_initiate_conc_mark */ 2184 g1_policy()->max_pause_time_ms(), 2185 cause); 2186 VMThread::execute(&op); 2187 } else { 2188 // Schedule a Full GC. 2189 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2190 VMThread::execute(&op); 2191 } 2192 } 2193 } while (retry_gc); 2194 } 2195 2196 bool G1CollectedHeap::is_in(const void* p) const { 2197 if (_hrm.reserved().contains(p)) { 2198 // Given that we know that p is in the reserved space, 2199 // heap_region_containing() should successfully 2200 // return the containing region. 2201 HeapRegion* hr = heap_region_containing(p); 2202 return hr->is_in(p); 2203 } else { 2204 return false; 2205 } 2206 } 2207 2208 #ifdef ASSERT 2209 bool G1CollectedHeap::is_in_exact(const void* p) const { 2210 bool contains = reserved_region().contains(p); 2211 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2212 if (contains && available) { 2213 return true; 2214 } else { 2215 return false; 2216 } 2217 } 2218 #endif 2219 2220 // Iteration functions. 2221 2222 // Iterates an ObjectClosure over all objects within a HeapRegion. 2223 2224 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2225 ObjectClosure* _cl; 2226 public: 2227 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2228 bool doHeapRegion(HeapRegion* r) { 2229 if (!r->is_continues_humongous()) { 2230 r->object_iterate(_cl); 2231 } 2232 return false; 2233 } 2234 }; 2235 2236 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2237 IterateObjectClosureRegionClosure blk(cl); 2238 heap_region_iterate(&blk); 2239 } 2240 2241 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2242 _hrm.iterate(cl); 2243 } 2244 2245 void G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2246 uint worker_id, 2247 HeapRegionClaimerBase *hrclaimer) const { 2248 _hrm.par_iterate(cl, worker_id, hrclaimer); 2249 } 2250 2251 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2252 _collection_set.iterate(cl); 2253 } 2254 2255 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) { 2256 _collection_set.iterate_from(cl, worker_id, workers()->active_workers()); 2257 } 2258 2259 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2260 HeapRegion* hr = heap_region_containing(addr); 2261 return hr->block_start(addr); 2262 } 2263 2264 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2265 HeapRegion* hr = heap_region_containing(addr); 2266 return hr->block_size(addr); 2267 } 2268 2269 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2270 HeapRegion* hr = heap_region_containing(addr); 2271 return hr->block_is_obj(addr); 2272 } 2273 2274 bool G1CollectedHeap::supports_tlab_allocation() const { 2275 return true; 2276 } 2277 2278 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2279 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes; 2280 } 2281 2282 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2283 return _eden.length() * HeapRegion::GrainBytes; 2284 } 2285 2286 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2287 // must be equal to the humongous object limit. 2288 size_t G1CollectedHeap::max_tlab_size() const { 2289 return align_down(_humongous_object_threshold_in_words, MinObjAlignment); 2290 } 2291 2292 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2293 AllocationContext_t context = AllocationContext::current(); 2294 return _allocator->unsafe_max_tlab_alloc(context); 2295 } 2296 2297 size_t G1CollectedHeap::max_capacity() const { 2298 return _hrm.reserved().byte_size(); 2299 } 2300 2301 jlong G1CollectedHeap::millis_since_last_gc() { 2302 // See the notes in GenCollectedHeap::millis_since_last_gc() 2303 // for more information about the implementation. 2304 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) - 2305 _g1_policy->collection_pause_end_millis(); 2306 if (ret_val < 0) { 2307 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT 2308 ". returning zero instead.", ret_val); 2309 return 0; 2310 } 2311 return ret_val; 2312 } 2313 2314 void G1CollectedHeap::prepare_for_verify() { 2315 _verifier->prepare_for_verify(); 2316 } 2317 2318 void G1CollectedHeap::verify(VerifyOption vo) { 2319 _verifier->verify(vo); 2320 } 2321 2322 bool G1CollectedHeap::supports_concurrent_phase_control() const { 2323 return true; 2324 } 2325 2326 const char* const* G1CollectedHeap::concurrent_phases() const { 2327 return _cmThread->concurrent_phases(); 2328 } 2329 2330 bool G1CollectedHeap::request_concurrent_phase(const char* phase) { 2331 return _cmThread->request_concurrent_phase(phase); 2332 } 2333 2334 class PrintRegionClosure: public HeapRegionClosure { 2335 outputStream* _st; 2336 public: 2337 PrintRegionClosure(outputStream* st) : _st(st) {} 2338 bool doHeapRegion(HeapRegion* r) { 2339 r->print_on(_st); 2340 return false; 2341 } 2342 }; 2343 2344 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2345 const HeapRegion* hr, 2346 const VerifyOption vo) const { 2347 switch (vo) { 2348 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 2349 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 2350 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 2351 default: ShouldNotReachHere(); 2352 } 2353 return false; // keep some compilers happy 2354 } 2355 2356 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 2357 const VerifyOption vo) const { 2358 switch (vo) { 2359 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 2360 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 2361 case VerifyOption_G1UseMarkWord: { 2362 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 2363 return !obj->is_gc_marked() && !hr->is_archive(); 2364 } 2365 default: ShouldNotReachHere(); 2366 } 2367 return false; // keep some compilers happy 2368 } 2369 2370 void G1CollectedHeap::print_heap_regions() const { 2371 Log(gc, heap, region) log; 2372 if (log.is_trace()) { 2373 ResourceMark rm; 2374 print_regions_on(log.trace_stream()); 2375 } 2376 } 2377 2378 void G1CollectedHeap::print_on(outputStream* st) const { 2379 st->print(" %-20s", "garbage-first heap"); 2380 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2381 capacity()/K, used_unlocked()/K); 2382 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 2383 p2i(_hrm.reserved().start()), 2384 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 2385 p2i(_hrm.reserved().end())); 2386 st->cr(); 2387 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 2388 uint young_regions = young_regions_count(); 2389 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 2390 (size_t) young_regions * HeapRegion::GrainBytes / K); 2391 uint survivor_regions = survivor_regions_count(); 2392 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 2393 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 2394 st->cr(); 2395 MetaspaceAux::print_on(st); 2396 } 2397 2398 void G1CollectedHeap::print_regions_on(outputStream* st) const { 2399 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, " 2400 "HS=humongous(starts), HC=humongous(continues), " 2401 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 2402 "AC=allocation context, " 2403 "TAMS=top-at-mark-start (previous, next)"); 2404 PrintRegionClosure blk(st); 2405 heap_region_iterate(&blk); 2406 } 2407 2408 void G1CollectedHeap::print_extended_on(outputStream* st) const { 2409 print_on(st); 2410 2411 // Print the per-region information. 2412 print_regions_on(st); 2413 } 2414 2415 void G1CollectedHeap::print_on_error(outputStream* st) const { 2416 this->CollectedHeap::print_on_error(st); 2417 2418 if (_cm != NULL) { 2419 st->cr(); 2420 _cm->print_on_error(st); 2421 } 2422 } 2423 2424 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 2425 workers()->print_worker_threads_on(st); 2426 _cmThread->print_on(st); 2427 st->cr(); 2428 _cm->print_worker_threads_on(st); 2429 _cg1r->print_worker_threads_on(st); // also prints the sample thread 2430 if (G1StringDedup::is_enabled()) { 2431 G1StringDedup::print_worker_threads_on(st); 2432 } 2433 } 2434 2435 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 2436 workers()->threads_do(tc); 2437 tc->do_thread(_cmThread); 2438 _cm->threads_do(tc); 2439 _cg1r->threads_do(tc); // also iterates over the sample thread 2440 if (G1StringDedup::is_enabled()) { 2441 G1StringDedup::threads_do(tc); 2442 } 2443 } 2444 2445 void G1CollectedHeap::print_tracing_info() const { 2446 g1_rem_set()->print_summary_info(); 2447 concurrent_mark()->print_summary_info(); 2448 } 2449 2450 #ifndef PRODUCT 2451 // Helpful for debugging RSet issues. 2452 2453 class PrintRSetsClosure : public HeapRegionClosure { 2454 private: 2455 const char* _msg; 2456 size_t _occupied_sum; 2457 2458 public: 2459 bool doHeapRegion(HeapRegion* r) { 2460 HeapRegionRemSet* hrrs = r->rem_set(); 2461 size_t occupied = hrrs->occupied(); 2462 _occupied_sum += occupied; 2463 2464 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r)); 2465 if (occupied == 0) { 2466 tty->print_cr(" RSet is empty"); 2467 } else { 2468 hrrs->print(); 2469 } 2470 tty->print_cr("----------"); 2471 return false; 2472 } 2473 2474 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 2475 tty->cr(); 2476 tty->print_cr("========================================"); 2477 tty->print_cr("%s", msg); 2478 tty->cr(); 2479 } 2480 2481 ~PrintRSetsClosure() { 2482 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 2483 tty->print_cr("========================================"); 2484 tty->cr(); 2485 } 2486 }; 2487 2488 void G1CollectedHeap::print_cset_rsets() { 2489 PrintRSetsClosure cl("Printing CSet RSets"); 2490 collection_set_iterate(&cl); 2491 } 2492 2493 void G1CollectedHeap::print_all_rsets() { 2494 PrintRSetsClosure cl("Printing All RSets");; 2495 heap_region_iterate(&cl); 2496 } 2497 #endif // PRODUCT 2498 2499 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 2500 2501 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes; 2502 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes; 2503 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked(); 2504 2505 size_t eden_capacity_bytes = 2506 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 2507 2508 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 2509 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, 2510 eden_capacity_bytes, survivor_used_bytes, num_regions()); 2511 } 2512 2513 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 2514 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 2515 stats->unused(), stats->used(), stats->region_end_waste(), 2516 stats->regions_filled(), stats->direct_allocated(), 2517 stats->failure_used(), stats->failure_waste()); 2518 } 2519 2520 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 2521 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 2522 gc_tracer->report_gc_heap_summary(when, heap_summary); 2523 2524 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 2525 gc_tracer->report_metaspace_summary(when, metaspace_summary); 2526 } 2527 2528 G1CollectedHeap* G1CollectedHeap::heap() { 2529 CollectedHeap* heap = Universe::heap(); 2530 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 2531 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 2532 return (G1CollectedHeap*)heap; 2533 } 2534 2535 void G1CollectedHeap::gc_prologue(bool full) { 2536 // always_do_update_barrier = false; 2537 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 2538 2539 // This summary needs to be printed before incrementing total collections. 2540 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections()); 2541 2542 // Update common counters. 2543 increment_total_collections(full /* full gc */); 2544 if (full) { 2545 increment_old_marking_cycles_started(); 2546 reset_gc_time_stamp(); 2547 } else { 2548 increment_gc_time_stamp(); 2549 } 2550 2551 // Fill TLAB's and such 2552 double start = os::elapsedTime(); 2553 accumulate_statistics_all_tlabs(); 2554 ensure_parsability(true); 2555 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2556 } 2557 2558 void G1CollectedHeap::gc_epilogue(bool full) { 2559 // Update common counters. 2560 if (full) { 2561 // Update the number of full collections that have been completed. 2562 increment_old_marking_cycles_completed(false /* concurrent */); 2563 } 2564 2565 // We are at the end of the GC. Total collections has already been increased. 2566 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1); 2567 2568 // FIXME: what is this about? 2569 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 2570 // is set. 2571 #if defined(COMPILER2) || INCLUDE_JVMCI 2572 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 2573 #endif 2574 // always_do_update_barrier = true; 2575 2576 double start = os::elapsedTime(); 2577 resize_all_tlabs(); 2578 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0); 2579 2580 allocation_context_stats().update(full); 2581 2582 MemoryService::track_memory_usage(); 2583 // We have just completed a GC. Update the soft reference 2584 // policy with the new heap occupancy 2585 Universe::update_heap_info_at_gc(); 2586 } 2587 2588 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 2589 uint gc_count_before, 2590 bool* succeeded, 2591 GCCause::Cause gc_cause) { 2592 assert_heap_not_locked_and_not_at_safepoint(); 2593 VM_G1IncCollectionPause op(gc_count_before, 2594 word_size, 2595 false, /* should_initiate_conc_mark */ 2596 g1_policy()->max_pause_time_ms(), 2597 gc_cause); 2598 2599 op.set_allocation_context(AllocationContext::current()); 2600 VMThread::execute(&op); 2601 2602 HeapWord* result = op.result(); 2603 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 2604 assert(result == NULL || ret_succeeded, 2605 "the result should be NULL if the VM did not succeed"); 2606 *succeeded = ret_succeeded; 2607 2608 assert_heap_not_locked(); 2609 return result; 2610 } 2611 2612 void 2613 G1CollectedHeap::doConcurrentMark() { 2614 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 2615 if (!_cmThread->in_progress()) { 2616 _cmThread->set_started(); 2617 CGC_lock->notify(); 2618 } 2619 } 2620 2621 size_t G1CollectedHeap::pending_card_num() { 2622 size_t extra_cards = 0; 2623 JavaThread *curr = Threads::first(); 2624 while (curr != NULL) { 2625 DirtyCardQueue& dcq = curr->dirty_card_queue(); 2626 extra_cards += dcq.size(); 2627 curr = curr->next(); 2628 } 2629 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2630 size_t buffer_size = dcqs.buffer_size(); 2631 size_t buffer_num = dcqs.completed_buffers_num(); 2632 2633 return buffer_size * buffer_num + extra_cards; 2634 } 2635 2636 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 2637 private: 2638 size_t _total_humongous; 2639 size_t _candidate_humongous; 2640 2641 DirtyCardQueue _dcq; 2642 2643 // We don't nominate objects with many remembered set entries, on 2644 // the assumption that such objects are likely still live. 2645 bool is_remset_small(HeapRegion* region) const { 2646 HeapRegionRemSet* const rset = region->rem_set(); 2647 return G1EagerReclaimHumongousObjectsWithStaleRefs 2648 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 2649 : rset->is_empty(); 2650 } 2651 2652 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 2653 assert(region->is_starts_humongous(), "Must start a humongous object"); 2654 2655 oop obj = oop(region->bottom()); 2656 2657 // Dead objects cannot be eager reclaim candidates. Due to class 2658 // unloading it is unsafe to query their classes so we return early. 2659 if (heap->is_obj_dead(obj, region)) { 2660 return false; 2661 } 2662 2663 // Candidate selection must satisfy the following constraints 2664 // while concurrent marking is in progress: 2665 // 2666 // * In order to maintain SATB invariants, an object must not be 2667 // reclaimed if it was allocated before the start of marking and 2668 // has not had its references scanned. Such an object must have 2669 // its references (including type metadata) scanned to ensure no 2670 // live objects are missed by the marking process. Objects 2671 // allocated after the start of concurrent marking don't need to 2672 // be scanned. 2673 // 2674 // * An object must not be reclaimed if it is on the concurrent 2675 // mark stack. Objects allocated after the start of concurrent 2676 // marking are never pushed on the mark stack. 2677 // 2678 // Nominating only objects allocated after the start of concurrent 2679 // marking is sufficient to meet both constraints. This may miss 2680 // some objects that satisfy the constraints, but the marking data 2681 // structures don't support efficiently performing the needed 2682 // additional tests or scrubbing of the mark stack. 2683 // 2684 // However, we presently only nominate is_typeArray() objects. 2685 // A humongous object containing references induces remembered 2686 // set entries on other regions. In order to reclaim such an 2687 // object, those remembered sets would need to be cleaned up. 2688 // 2689 // We also treat is_typeArray() objects specially, allowing them 2690 // to be reclaimed even if allocated before the start of 2691 // concurrent mark. For this we rely on mark stack insertion to 2692 // exclude is_typeArray() objects, preventing reclaiming an object 2693 // that is in the mark stack. We also rely on the metadata for 2694 // such objects to be built-in and so ensured to be kept live. 2695 // Frequent allocation and drop of large binary blobs is an 2696 // important use case for eager reclaim, and this special handling 2697 // may reduce needed headroom. 2698 2699 return obj->is_typeArray() && is_remset_small(region); 2700 } 2701 2702 public: 2703 RegisterHumongousWithInCSetFastTestClosure() 2704 : _total_humongous(0), 2705 _candidate_humongous(0), 2706 _dcq(&JavaThread::dirty_card_queue_set()) { 2707 } 2708 2709 virtual bool doHeapRegion(HeapRegion* r) { 2710 if (!r->is_starts_humongous()) { 2711 return false; 2712 } 2713 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2714 2715 bool is_candidate = humongous_region_is_candidate(g1h, r); 2716 uint rindex = r->hrm_index(); 2717 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 2718 if (is_candidate) { 2719 _candidate_humongous++; 2720 g1h->register_humongous_region_with_cset(rindex); 2721 // Is_candidate already filters out humongous object with large remembered sets. 2722 // If we have a humongous object with a few remembered sets, we simply flush these 2723 // remembered set entries into the DCQS. That will result in automatic 2724 // re-evaluation of their remembered set entries during the following evacuation 2725 // phase. 2726 if (!r->rem_set()->is_empty()) { 2727 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 2728 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 2729 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 2730 HeapRegionRemSetIterator hrrs(r->rem_set()); 2731 size_t card_index; 2732 while (hrrs.has_next(card_index)) { 2733 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 2734 // The remembered set might contain references to already freed 2735 // regions. Filter out such entries to avoid failing card table 2736 // verification. 2737 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 2738 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 2739 *card_ptr = CardTableModRefBS::dirty_card_val(); 2740 _dcq.enqueue(card_ptr); 2741 } 2742 } 2743 } 2744 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 2745 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 2746 hrrs.n_yielded(), r->rem_set()->occupied()); 2747 r->rem_set()->clear_locked(); 2748 } 2749 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 2750 } 2751 _total_humongous++; 2752 2753 return false; 2754 } 2755 2756 size_t total_humongous() const { return _total_humongous; } 2757 size_t candidate_humongous() const { return _candidate_humongous; } 2758 2759 void flush_rem_set_entries() { _dcq.flush(); } 2760 }; 2761 2762 void G1CollectedHeap::register_humongous_regions_with_cset() { 2763 if (!G1EagerReclaimHumongousObjects) { 2764 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 2765 return; 2766 } 2767 double time = os::elapsed_counter(); 2768 2769 // Collect reclaim candidate information and register candidates with cset. 2770 RegisterHumongousWithInCSetFastTestClosure cl; 2771 heap_region_iterate(&cl); 2772 2773 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 2774 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 2775 cl.total_humongous(), 2776 cl.candidate_humongous()); 2777 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 2778 2779 // Finally flush all remembered set entries to re-check into the global DCQS. 2780 cl.flush_rem_set_entries(); 2781 } 2782 2783 class VerifyRegionRemSetClosure : public HeapRegionClosure { 2784 public: 2785 bool doHeapRegion(HeapRegion* hr) { 2786 if (!hr->is_archive() && !hr->is_continues_humongous()) { 2787 hr->verify_rem_set(); 2788 } 2789 return false; 2790 } 2791 }; 2792 2793 uint G1CollectedHeap::num_task_queues() const { 2794 return _task_queues->size(); 2795 } 2796 2797 #if TASKQUEUE_STATS 2798 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 2799 st->print_raw_cr("GC Task Stats"); 2800 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 2801 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 2802 } 2803 2804 void G1CollectedHeap::print_taskqueue_stats() const { 2805 if (!log_is_enabled(Trace, gc, task, stats)) { 2806 return; 2807 } 2808 Log(gc, task, stats) log; 2809 ResourceMark rm; 2810 outputStream* st = log.trace_stream(); 2811 2812 print_taskqueue_stats_hdr(st); 2813 2814 TaskQueueStats totals; 2815 const uint n = num_task_queues(); 2816 for (uint i = 0; i < n; ++i) { 2817 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 2818 totals += task_queue(i)->stats; 2819 } 2820 st->print_raw("tot "); totals.print(st); st->cr(); 2821 2822 DEBUG_ONLY(totals.verify()); 2823 } 2824 2825 void G1CollectedHeap::reset_taskqueue_stats() { 2826 const uint n = num_task_queues(); 2827 for (uint i = 0; i < n; ++i) { 2828 task_queue(i)->stats.reset(); 2829 } 2830 } 2831 #endif // TASKQUEUE_STATS 2832 2833 void G1CollectedHeap::wait_for_root_region_scanning() { 2834 double scan_wait_start = os::elapsedTime(); 2835 // We have to wait until the CM threads finish scanning the 2836 // root regions as it's the only way to ensure that all the 2837 // objects on them have been correctly scanned before we start 2838 // moving them during the GC. 2839 bool waited = _cm->root_regions()->wait_until_scan_finished(); 2840 double wait_time_ms = 0.0; 2841 if (waited) { 2842 double scan_wait_end = os::elapsedTime(); 2843 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 2844 } 2845 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 2846 } 2847 2848 class G1PrintCollectionSetClosure : public HeapRegionClosure { 2849 private: 2850 G1HRPrinter* _hr_printer; 2851 public: 2852 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { } 2853 2854 virtual bool doHeapRegion(HeapRegion* r) { 2855 _hr_printer->cset(r); 2856 return false; 2857 } 2858 }; 2859 2860 void G1CollectedHeap::start_new_collection_set() { 2861 collection_set()->start_incremental_building(); 2862 2863 clear_cset_fast_test(); 2864 2865 guarantee(_eden.length() == 0, "eden should have been cleared"); 2866 g1_policy()->transfer_survivors_to_cset(survivor()); 2867 } 2868 2869 bool 2870 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 2871 assert_at_safepoint(true /* should_be_vm_thread */); 2872 guarantee(!is_gc_active(), "collection is not reentrant"); 2873 2874 if (GCLocker::check_active_before_gc()) { 2875 return false; 2876 } 2877 2878 _gc_timer_stw->register_gc_start(); 2879 2880 GCIdMark gc_id_mark; 2881 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 2882 2883 SvcGCMarker sgcm(SvcGCMarker::MINOR); 2884 ResourceMark rm; 2885 2886 g1_policy()->note_gc_start(); 2887 2888 wait_for_root_region_scanning(); 2889 2890 print_heap_before_gc(); 2891 print_heap_regions(); 2892 trace_heap_before_gc(_gc_tracer_stw); 2893 2894 _verifier->verify_region_sets_optional(); 2895 _verifier->verify_dirty_young_regions(); 2896 2897 // We should not be doing initial mark unless the conc mark thread is running 2898 if (!_cmThread->should_terminate()) { 2899 // This call will decide whether this pause is an initial-mark 2900 // pause. If it is, during_initial_mark_pause() will return true 2901 // for the duration of this pause. 2902 g1_policy()->decide_on_conc_mark_initiation(); 2903 } 2904 2905 // We do not allow initial-mark to be piggy-backed on a mixed GC. 2906 assert(!collector_state()->during_initial_mark_pause() || 2907 collector_state()->gcs_are_young(), "sanity"); 2908 2909 // We also do not allow mixed GCs during marking. 2910 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 2911 2912 // Record whether this pause is an initial mark. When the current 2913 // thread has completed its logging output and it's safe to signal 2914 // the CM thread, the flag's value in the policy has been reset. 2915 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 2916 2917 // Inner scope for scope based logging, timers, and stats collection 2918 { 2919 EvacuationInfo evacuation_info; 2920 2921 if (collector_state()->during_initial_mark_pause()) { 2922 // We are about to start a marking cycle, so we increment the 2923 // full collection counter. 2924 increment_old_marking_cycles_started(); 2925 _cm->gc_tracer_cm()->set_gc_cause(gc_cause()); 2926 } 2927 2928 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 2929 2930 GCTraceCPUTime tcpu; 2931 2932 FormatBuffer<> gc_string("Pause "); 2933 if (collector_state()->during_initial_mark_pause()) { 2934 gc_string.append("Initial Mark"); 2935 } else if (collector_state()->gcs_are_young()) { 2936 gc_string.append("Young"); 2937 } else { 2938 gc_string.append("Mixed"); 2939 } 2940 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true); 2941 2942 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 2943 workers()->active_workers(), 2944 Threads::number_of_non_daemon_threads()); 2945 workers()->update_active_workers(active_workers); 2946 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers()); 2947 2948 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 2949 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 2950 2951 // If the secondary_free_list is not empty, append it to the 2952 // free_list. No need to wait for the cleanup operation to finish; 2953 // the region allocation code will check the secondary_free_list 2954 // and wait if necessary. If the G1StressConcRegionFreeing flag is 2955 // set, skip this step so that the region allocation code has to 2956 // get entries from the secondary_free_list. 2957 if (!G1StressConcRegionFreeing) { 2958 append_secondary_free_list_if_not_empty_with_lock(); 2959 } 2960 2961 G1HeapTransition heap_transition(this); 2962 size_t heap_used_bytes_before_gc = used(); 2963 2964 // Don't dynamically change the number of GC threads this early. A value of 2965 // 0 is used to indicate serial work. When parallel work is done, 2966 // it will be set. 2967 2968 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 2969 IsGCActiveMark x; 2970 2971 gc_prologue(false); 2972 2973 if (VerifyRememberedSets) { 2974 log_info(gc, verify)("[Verifying RemSets before GC]"); 2975 VerifyRegionRemSetClosure v_cl; 2976 heap_region_iterate(&v_cl); 2977 } 2978 2979 _verifier->verify_before_gc(); 2980 2981 _verifier->check_bitmaps("GC Start"); 2982 2983 #if defined(COMPILER2) || INCLUDE_JVMCI 2984 DerivedPointerTable::clear(); 2985 #endif 2986 2987 // Please see comment in g1CollectedHeap.hpp and 2988 // G1CollectedHeap::ref_processing_init() to see how 2989 // reference processing currently works in G1. 2990 2991 // Enable discovery in the STW reference processor 2992 if (g1_policy()->should_process_references()) { 2993 ref_processor_stw()->enable_discovery(); 2994 } else { 2995 ref_processor_stw()->disable_discovery(); 2996 } 2997 2998 { 2999 // We want to temporarily turn off discovery by the 3000 // CM ref processor, if necessary, and turn it back on 3001 // on again later if we do. Using a scoped 3002 // NoRefDiscovery object will do this. 3003 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3004 3005 // Forget the current alloc region (we might even choose it to be part 3006 // of the collection set!). 3007 _allocator->release_mutator_alloc_region(); 3008 3009 // This timing is only used by the ergonomics to handle our pause target. 3010 // It is unclear why this should not include the full pause. We will 3011 // investigate this in CR 7178365. 3012 // 3013 // Preserving the old comment here if that helps the investigation: 3014 // 3015 // The elapsed time induced by the start time below deliberately elides 3016 // the possible verification above. 3017 double sample_start_time_sec = os::elapsedTime(); 3018 3019 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3020 3021 if (collector_state()->during_initial_mark_pause()) { 3022 concurrent_mark()->checkpointRootsInitialPre(); 3023 } 3024 3025 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor); 3026 3027 evacuation_info.set_collectionset_regions(collection_set()->region_length()); 3028 3029 // Make sure the remembered sets are up to date. This needs to be 3030 // done before register_humongous_regions_with_cset(), because the 3031 // remembered sets are used there to choose eager reclaim candidates. 3032 // If the remembered sets are not up to date we might miss some 3033 // entries that need to be handled. 3034 g1_rem_set()->cleanupHRRS(); 3035 3036 register_humongous_regions_with_cset(); 3037 3038 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3039 3040 // We call this after finalize_cset() to 3041 // ensure that the CSet has been finalized. 3042 _cm->verify_no_cset_oops(); 3043 3044 if (_hr_printer.is_active()) { 3045 G1PrintCollectionSetClosure cl(&_hr_printer); 3046 _collection_set.iterate(&cl); 3047 } 3048 3049 // Initialize the GC alloc regions. 3050 _allocator->init_gc_alloc_regions(evacuation_info); 3051 3052 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length()); 3053 pre_evacuate_collection_set(); 3054 3055 // Actually do the work... 3056 evacuate_collection_set(evacuation_info, &per_thread_states); 3057 3058 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3059 3060 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3061 free_collection_set(&_collection_set, evacuation_info, surviving_young_words); 3062 3063 eagerly_reclaim_humongous_regions(); 3064 3065 record_obj_copy_mem_stats(); 3066 _survivor_evac_stats.adjust_desired_plab_sz(); 3067 _old_evac_stats.adjust_desired_plab_sz(); 3068 3069 double start = os::elapsedTime(); 3070 start_new_collection_set(); 3071 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0); 3072 3073 if (evacuation_failed()) { 3074 set_used(recalculate_used()); 3075 if (_archive_allocator != NULL) { 3076 _archive_allocator->clear_used(); 3077 } 3078 for (uint i = 0; i < ParallelGCThreads; i++) { 3079 if (_evacuation_failed_info_array[i].has_failed()) { 3080 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3081 } 3082 } 3083 } else { 3084 // The "used" of the the collection set have already been subtracted 3085 // when they were freed. Add in the bytes evacuated. 3086 increase_used(g1_policy()->bytes_copied_during_gc()); 3087 } 3088 3089 if (collector_state()->during_initial_mark_pause()) { 3090 // We have to do this before we notify the CM threads that 3091 // they can start working to make sure that all the 3092 // appropriate initialization is done on the CM object. 3093 concurrent_mark()->checkpointRootsInitialPost(); 3094 collector_state()->set_mark_in_progress(true); 3095 // Note that we don't actually trigger the CM thread at 3096 // this point. We do that later when we're sure that 3097 // the current thread has completed its logging output. 3098 } 3099 3100 allocate_dummy_regions(); 3101 3102 _allocator->init_mutator_alloc_region(); 3103 3104 { 3105 size_t expand_bytes = _heap_sizing_policy->expansion_amount(); 3106 if (expand_bytes > 0) { 3107 size_t bytes_before = capacity(); 3108 // No need for an ergo logging here, 3109 // expansion_amount() does this when it returns a value > 0. 3110 double expand_ms; 3111 if (!expand(expand_bytes, _workers, &expand_ms)) { 3112 // We failed to expand the heap. Cannot do anything about it. 3113 } 3114 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3115 } 3116 } 3117 3118 // We redo the verification but now wrt to the new CSet which 3119 // has just got initialized after the previous CSet was freed. 3120 _cm->verify_no_cset_oops(); 3121 3122 // This timing is only used by the ergonomics to handle our pause target. 3123 // It is unclear why this should not include the full pause. We will 3124 // investigate this in CR 7178365. 3125 double sample_end_time_sec = os::elapsedTime(); 3126 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3127 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScannedCards); 3128 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); 3129 3130 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before()); 3131 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3132 3133 if (VerifyRememberedSets) { 3134 log_info(gc, verify)("[Verifying RemSets after GC]"); 3135 VerifyRegionRemSetClosure v_cl; 3136 heap_region_iterate(&v_cl); 3137 } 3138 3139 _verifier->verify_after_gc(); 3140 _verifier->check_bitmaps("GC End"); 3141 3142 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3143 ref_processor_stw()->verify_no_references_recorded(); 3144 3145 // CM reference discovery will be re-enabled if necessary. 3146 } 3147 3148 #ifdef TRACESPINNING 3149 ParallelTaskTerminator::print_termination_counts(); 3150 #endif 3151 3152 gc_epilogue(false); 3153 } 3154 3155 // Print the remainder of the GC log output. 3156 if (evacuation_failed()) { 3157 log_info(gc)("To-space exhausted"); 3158 } 3159 3160 g1_policy()->print_phases(); 3161 heap_transition.print(); 3162 3163 // It is not yet to safe to tell the concurrent mark to 3164 // start as we have some optional output below. We don't want the 3165 // output from the concurrent mark thread interfering with this 3166 // logging output either. 3167 3168 _hrm.verify_optional(); 3169 _verifier->verify_region_sets_optional(); 3170 3171 TASKQUEUE_STATS_ONLY(print_taskqueue_stats()); 3172 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3173 3174 print_heap_after_gc(); 3175 print_heap_regions(); 3176 trace_heap_after_gc(_gc_tracer_stw); 3177 3178 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 3179 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 3180 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 3181 // before any GC notifications are raised. 3182 g1mm()->update_sizes(); 3183 3184 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 3185 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 3186 _gc_timer_stw->register_gc_end(); 3187 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 3188 } 3189 // It should now be safe to tell the concurrent mark thread to start 3190 // without its logging output interfering with the logging output 3191 // that came from the pause. 3192 3193 if (should_start_conc_mark) { 3194 // CAUTION: after the doConcurrentMark() call below, 3195 // the concurrent marking thread(s) could be running 3196 // concurrently with us. Make sure that anything after 3197 // this point does not assume that we are the only GC thread 3198 // running. Note: of course, the actual marking work will 3199 // not start until the safepoint itself is released in 3200 // SuspendibleThreadSet::desynchronize(). 3201 doConcurrentMark(); 3202 } 3203 3204 return true; 3205 } 3206 3207 void G1CollectedHeap::remove_self_forwarding_pointers() { 3208 G1ParRemoveSelfForwardPtrsTask rsfp_task; 3209 workers()->run_task(&rsfp_task); 3210 } 3211 3212 void G1CollectedHeap::restore_after_evac_failure() { 3213 double remove_self_forwards_start = os::elapsedTime(); 3214 3215 remove_self_forwarding_pointers(); 3216 SharedRestorePreservedMarksTaskExecutor task_executor(workers()); 3217 _preserved_marks_set.restore(&task_executor); 3218 3219 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 3220 } 3221 3222 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 3223 if (!_evacuation_failed) { 3224 _evacuation_failed = true; 3225 } 3226 3227 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 3228 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m); 3229 } 3230 3231 bool G1ParEvacuateFollowersClosure::offer_termination() { 3232 G1ParScanThreadState* const pss = par_scan_state(); 3233 start_term_time(); 3234 const bool res = terminator()->offer_termination(); 3235 end_term_time(); 3236 return res; 3237 } 3238 3239 void G1ParEvacuateFollowersClosure::do_void() { 3240 G1ParScanThreadState* const pss = par_scan_state(); 3241 pss->trim_queue(); 3242 do { 3243 pss->steal_and_trim_queue(queues()); 3244 } while (!offer_termination()); 3245 } 3246 3247 class G1ParTask : public AbstractGangTask { 3248 protected: 3249 G1CollectedHeap* _g1h; 3250 G1ParScanThreadStateSet* _pss; 3251 RefToScanQueueSet* _queues; 3252 G1RootProcessor* _root_processor; 3253 ParallelTaskTerminator _terminator; 3254 uint _n_workers; 3255 3256 public: 3257 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 3258 : AbstractGangTask("G1 collection"), 3259 _g1h(g1h), 3260 _pss(per_thread_states), 3261 _queues(task_queues), 3262 _root_processor(root_processor), 3263 _terminator(n_workers, _queues), 3264 _n_workers(n_workers) 3265 {} 3266 3267 void work(uint worker_id) { 3268 if (worker_id >= _n_workers) return; // no work needed this round 3269 3270 double start_sec = os::elapsedTime(); 3271 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 3272 3273 { 3274 ResourceMark rm; 3275 HandleMark hm; 3276 3277 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 3278 3279 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3280 pss->set_ref_processor(rp); 3281 3282 double start_strong_roots_sec = os::elapsedTime(); 3283 3284 _root_processor->evacuate_roots(pss->closures(), worker_id); 3285 3286 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 3287 // treating the nmethods visited to act as roots for concurrent marking. 3288 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 3289 // objects copied by the current evacuation. 3290 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, 3291 pss->closures()->weak_codeblobs(), 3292 worker_id); 3293 3294 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 3295 3296 double term_sec = 0.0; 3297 size_t evac_term_attempts = 0; 3298 { 3299 double start = os::elapsedTime(); 3300 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 3301 evac.do_void(); 3302 3303 evac_term_attempts = evac.term_attempts(); 3304 term_sec = evac.term_time(); 3305 double elapsed_sec = os::elapsedTime() - start; 3306 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 3307 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 3308 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 3309 } 3310 3311 assert(pss->queue_is_empty(), "should be empty"); 3312 3313 if (log_is_enabled(Debug, gc, task, stats)) { 3314 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3315 size_t lab_waste; 3316 size_t lab_undo_waste; 3317 pss->waste(lab_waste, lab_undo_waste); 3318 _g1h->print_termination_stats(worker_id, 3319 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 3320 strong_roots_sec * 1000.0, /* strong roots time */ 3321 term_sec * 1000.0, /* evac term time */ 3322 evac_term_attempts, /* evac term attempts */ 3323 lab_waste, /* alloc buffer waste */ 3324 lab_undo_waste /* undo waste */ 3325 ); 3326 } 3327 3328 // Close the inner scope so that the ResourceMark and HandleMark 3329 // destructors are executed here and are included as part of the 3330 // "GC Worker Time". 3331 } 3332 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 3333 } 3334 }; 3335 3336 void G1CollectedHeap::print_termination_stats_hdr() { 3337 log_debug(gc, task, stats)("GC Termination Stats"); 3338 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 3339 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo"); 3340 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 3341 } 3342 3343 void G1CollectedHeap::print_termination_stats(uint worker_id, 3344 double elapsed_ms, 3345 double strong_roots_ms, 3346 double term_ms, 3347 size_t term_attempts, 3348 size_t alloc_buffer_waste, 3349 size_t undo_waste) const { 3350 log_debug(gc, task, stats) 3351 ("%3d %9.2f %9.2f %6.2f " 3352 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 3353 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 3354 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 3355 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 3356 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 3357 alloc_buffer_waste * HeapWordSize / K, 3358 undo_waste * HeapWordSize / K); 3359 } 3360 3361 class G1StringAndSymbolCleaningTask : public AbstractGangTask { 3362 private: 3363 BoolObjectClosure* _is_alive; 3364 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure; 3365 3366 int _initial_string_table_size; 3367 int _initial_symbol_table_size; 3368 3369 bool _process_strings; 3370 int _strings_processed; 3371 int _strings_removed; 3372 3373 bool _process_symbols; 3374 int _symbols_processed; 3375 int _symbols_removed; 3376 3377 bool _process_string_dedup; 3378 3379 public: 3380 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) : 3381 AbstractGangTask("String/Symbol Unlinking"), 3382 _is_alive(is_alive), 3383 _dedup_closure(is_alive, NULL, false), 3384 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 3385 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0), 3386 _process_string_dedup(process_string_dedup) { 3387 3388 _initial_string_table_size = StringTable::the_table()->table_size(); 3389 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 3390 if (process_strings) { 3391 StringTable::clear_parallel_claimed_index(); 3392 } 3393 if (process_symbols) { 3394 SymbolTable::clear_parallel_claimed_index(); 3395 } 3396 } 3397 3398 ~G1StringAndSymbolCleaningTask() { 3399 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 3400 "claim value %d after unlink less than initial string table size %d", 3401 StringTable::parallel_claimed_index(), _initial_string_table_size); 3402 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 3403 "claim value %d after unlink less than initial symbol table size %d", 3404 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 3405 3406 log_info(gc, stringtable)( 3407 "Cleaned string and symbol table, " 3408 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 3409 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 3410 strings_processed(), strings_removed(), 3411 symbols_processed(), symbols_removed()); 3412 } 3413 3414 void work(uint worker_id) { 3415 int strings_processed = 0; 3416 int strings_removed = 0; 3417 int symbols_processed = 0; 3418 int symbols_removed = 0; 3419 if (_process_strings) { 3420 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 3421 Atomic::add(strings_processed, &_strings_processed); 3422 Atomic::add(strings_removed, &_strings_removed); 3423 } 3424 if (_process_symbols) { 3425 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 3426 Atomic::add(symbols_processed, &_symbols_processed); 3427 Atomic::add(symbols_removed, &_symbols_removed); 3428 } 3429 if (_process_string_dedup) { 3430 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id); 3431 } 3432 } 3433 3434 size_t strings_processed() const { return (size_t)_strings_processed; } 3435 size_t strings_removed() const { return (size_t)_strings_removed; } 3436 3437 size_t symbols_processed() const { return (size_t)_symbols_processed; } 3438 size_t symbols_removed() const { return (size_t)_symbols_removed; } 3439 }; 3440 3441 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 3442 private: 3443 static Monitor* _lock; 3444 3445 BoolObjectClosure* const _is_alive; 3446 const bool _unloading_occurred; 3447 const uint _num_workers; 3448 3449 // Variables used to claim nmethods. 3450 CompiledMethod* _first_nmethod; 3451 volatile CompiledMethod* _claimed_nmethod; 3452 3453 // The list of nmethods that need to be processed by the second pass. 3454 volatile CompiledMethod* _postponed_list; 3455 volatile uint _num_entered_barrier; 3456 3457 public: 3458 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 3459 _is_alive(is_alive), 3460 _unloading_occurred(unloading_occurred), 3461 _num_workers(num_workers), 3462 _first_nmethod(NULL), 3463 _claimed_nmethod(NULL), 3464 _postponed_list(NULL), 3465 _num_entered_barrier(0) 3466 { 3467 CompiledMethod::increase_unloading_clock(); 3468 // Get first alive nmethod 3469 CompiledMethodIterator iter = CompiledMethodIterator(); 3470 if(iter.next_alive()) { 3471 _first_nmethod = iter.method(); 3472 } 3473 _claimed_nmethod = (volatile CompiledMethod*)_first_nmethod; 3474 } 3475 3476 ~G1CodeCacheUnloadingTask() { 3477 CodeCache::verify_clean_inline_caches(); 3478 3479 CodeCache::set_needs_cache_clean(false); 3480 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 3481 3482 CodeCache::verify_icholder_relocations(); 3483 } 3484 3485 private: 3486 void add_to_postponed_list(CompiledMethod* nm) { 3487 CompiledMethod* old; 3488 do { 3489 old = (CompiledMethod*)_postponed_list; 3490 nm->set_unloading_next(old); 3491 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 3492 } 3493 3494 void clean_nmethod(CompiledMethod* nm) { 3495 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 3496 3497 if (postponed) { 3498 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 3499 add_to_postponed_list(nm); 3500 } 3501 3502 // Mark that this thread has been cleaned/unloaded. 3503 // After this call, it will be safe to ask if this nmethod was unloaded or not. 3504 nm->set_unloading_clock(CompiledMethod::global_unloading_clock()); 3505 } 3506 3507 void clean_nmethod_postponed(CompiledMethod* nm) { 3508 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 3509 } 3510 3511 static const int MaxClaimNmethods = 16; 3512 3513 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) { 3514 CompiledMethod* first; 3515 CompiledMethodIterator last; 3516 3517 do { 3518 *num_claimed_nmethods = 0; 3519 3520 first = (CompiledMethod*)_claimed_nmethod; 3521 last = CompiledMethodIterator(first); 3522 3523 if (first != NULL) { 3524 3525 for (int i = 0; i < MaxClaimNmethods; i++) { 3526 if (!last.next_alive()) { 3527 break; 3528 } 3529 claimed_nmethods[i] = last.method(); 3530 (*num_claimed_nmethods)++; 3531 } 3532 } 3533 3534 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 3535 } 3536 3537 CompiledMethod* claim_postponed_nmethod() { 3538 CompiledMethod* claim; 3539 CompiledMethod* next; 3540 3541 do { 3542 claim = (CompiledMethod*)_postponed_list; 3543 if (claim == NULL) { 3544 return NULL; 3545 } 3546 3547 next = claim->unloading_next(); 3548 3549 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 3550 3551 return claim; 3552 } 3553 3554 public: 3555 // Mark that we're done with the first pass of nmethod cleaning. 3556 void barrier_mark(uint worker_id) { 3557 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3558 _num_entered_barrier++; 3559 if (_num_entered_barrier == _num_workers) { 3560 ml.notify_all(); 3561 } 3562 } 3563 3564 // See if we have to wait for the other workers to 3565 // finish their first-pass nmethod cleaning work. 3566 void barrier_wait(uint worker_id) { 3567 if (_num_entered_barrier < _num_workers) { 3568 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 3569 while (_num_entered_barrier < _num_workers) { 3570 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 3571 } 3572 } 3573 } 3574 3575 // Cleaning and unloading of nmethods. Some work has to be postponed 3576 // to the second pass, when we know which nmethods survive. 3577 void work_first_pass(uint worker_id) { 3578 // The first nmethods is claimed by the first worker. 3579 if (worker_id == 0 && _first_nmethod != NULL) { 3580 clean_nmethod(_first_nmethod); 3581 _first_nmethod = NULL; 3582 } 3583 3584 int num_claimed_nmethods; 3585 CompiledMethod* claimed_nmethods[MaxClaimNmethods]; 3586 3587 while (true) { 3588 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 3589 3590 if (num_claimed_nmethods == 0) { 3591 break; 3592 } 3593 3594 for (int i = 0; i < num_claimed_nmethods; i++) { 3595 clean_nmethod(claimed_nmethods[i]); 3596 } 3597 } 3598 } 3599 3600 void work_second_pass(uint worker_id) { 3601 CompiledMethod* nm; 3602 // Take care of postponed nmethods. 3603 while ((nm = claim_postponed_nmethod()) != NULL) { 3604 clean_nmethod_postponed(nm); 3605 } 3606 } 3607 }; 3608 3609 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 3610 3611 class G1KlassCleaningTask : public StackObj { 3612 BoolObjectClosure* _is_alive; 3613 volatile jint _clean_klass_tree_claimed; 3614 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 3615 3616 public: 3617 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 3618 _is_alive(is_alive), 3619 _clean_klass_tree_claimed(0), 3620 _klass_iterator() { 3621 } 3622 3623 private: 3624 bool claim_clean_klass_tree_task() { 3625 if (_clean_klass_tree_claimed) { 3626 return false; 3627 } 3628 3629 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 3630 } 3631 3632 InstanceKlass* claim_next_klass() { 3633 Klass* klass; 3634 do { 3635 klass =_klass_iterator.next_klass(); 3636 } while (klass != NULL && !klass->is_instance_klass()); 3637 3638 // this can be null so don't call InstanceKlass::cast 3639 return static_cast<InstanceKlass*>(klass); 3640 } 3641 3642 public: 3643 3644 void clean_klass(InstanceKlass* ik) { 3645 ik->clean_weak_instanceklass_links(_is_alive); 3646 } 3647 3648 void work() { 3649 ResourceMark rm; 3650 3651 // One worker will clean the subklass/sibling klass tree. 3652 if (claim_clean_klass_tree_task()) { 3653 Klass::clean_subklass_tree(_is_alive); 3654 } 3655 3656 // All workers will help cleaning the classes, 3657 InstanceKlass* klass; 3658 while ((klass = claim_next_klass()) != NULL) { 3659 clean_klass(klass); 3660 } 3661 } 3662 }; 3663 3664 class G1ResolvedMethodCleaningTask : public StackObj { 3665 BoolObjectClosure* _is_alive; 3666 volatile jint _resolved_method_task_claimed; 3667 public: 3668 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) : 3669 _is_alive(is_alive), _resolved_method_task_claimed(0) {} 3670 3671 bool claim_resolved_method_task() { 3672 if (_resolved_method_task_claimed) { 3673 return false; 3674 } 3675 return Atomic::cmpxchg(1, (jint*)&_resolved_method_task_claimed, 0) == 0; 3676 } 3677 3678 // These aren't big, one thread can do it all. 3679 void work() { 3680 if (claim_resolved_method_task()) { 3681 ResolvedMethodTable::unlink(_is_alive); 3682 } 3683 } 3684 }; 3685 3686 3687 // To minimize the remark pause times, the tasks below are done in parallel. 3688 class G1ParallelCleaningTask : public AbstractGangTask { 3689 private: 3690 G1StringAndSymbolCleaningTask _string_symbol_task; 3691 G1CodeCacheUnloadingTask _code_cache_task; 3692 G1KlassCleaningTask _klass_cleaning_task; 3693 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task; 3694 3695 public: 3696 // The constructor is run in the VMThread. 3697 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) : 3698 AbstractGangTask("Parallel Cleaning"), 3699 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()), 3700 _code_cache_task(num_workers, is_alive, unloading_occurred), 3701 _klass_cleaning_task(is_alive), 3702 _resolved_method_cleaning_task(is_alive) { 3703 } 3704 3705 // The parallel work done by all worker threads. 3706 void work(uint worker_id) { 3707 // Do first pass of code cache cleaning. 3708 _code_cache_task.work_first_pass(worker_id); 3709 3710 // Let the threads mark that the first pass is done. 3711 _code_cache_task.barrier_mark(worker_id); 3712 3713 // Clean the Strings and Symbols. 3714 _string_symbol_task.work(worker_id); 3715 3716 // Clean unreferenced things in the ResolvedMethodTable 3717 _resolved_method_cleaning_task.work(); 3718 3719 // Wait for all workers to finish the first code cache cleaning pass. 3720 _code_cache_task.barrier_wait(worker_id); 3721 3722 // Do the second code cache cleaning work, which realize on 3723 // the liveness information gathered during the first pass. 3724 _code_cache_task.work_second_pass(worker_id); 3725 3726 // Clean all klasses that were not unloaded. 3727 _klass_cleaning_task.work(); 3728 } 3729 }; 3730 3731 3732 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive, 3733 bool class_unloading_occurred) { 3734 uint n_workers = workers()->active_workers(); 3735 3736 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred); 3737 workers()->run_task(&g1_unlink_task); 3738 } 3739 3740 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive, 3741 bool process_strings, 3742 bool process_symbols, 3743 bool process_string_dedup) { 3744 if (!process_strings && !process_symbols && !process_string_dedup) { 3745 // Nothing to clean. 3746 return; 3747 } 3748 3749 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup); 3750 workers()->run_task(&g1_unlink_task); 3751 3752 } 3753 3754 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 3755 private: 3756 DirtyCardQueueSet* _queue; 3757 G1CollectedHeap* _g1h; 3758 public: 3759 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"), 3760 _queue(queue), _g1h(g1h) { } 3761 3762 virtual void work(uint worker_id) { 3763 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); 3764 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 3765 3766 RedirtyLoggedCardTableEntryClosure cl(_g1h); 3767 _queue->par_apply_closure_to_all_completed_buffers(&cl); 3768 3769 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied()); 3770 } 3771 }; 3772 3773 void G1CollectedHeap::redirty_logged_cards() { 3774 double redirty_logged_cards_start = os::elapsedTime(); 3775 3776 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this); 3777 dirty_card_queue_set().reset_for_par_iteration(); 3778 workers()->run_task(&redirty_task); 3779 3780 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 3781 dcq.merge_bufferlists(&dirty_card_queue_set()); 3782 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 3783 3784 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 3785 } 3786 3787 // Weak Reference Processing support 3788 3789 // An always "is_alive" closure that is used to preserve referents. 3790 // If the object is non-null then it's alive. Used in the preservation 3791 // of referent objects that are pointed to by reference objects 3792 // discovered by the CM ref processor. 3793 class G1AlwaysAliveClosure: public BoolObjectClosure { 3794 G1CollectedHeap* _g1; 3795 public: 3796 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3797 bool do_object_b(oop p) { 3798 if (p != NULL) { 3799 return true; 3800 } 3801 return false; 3802 } 3803 }; 3804 3805 bool G1STWIsAliveClosure::do_object_b(oop p) { 3806 // An object is reachable if it is outside the collection set, 3807 // or is inside and copied. 3808 return !_g1->is_in_cset(p) || p->is_forwarded(); 3809 } 3810 3811 // Non Copying Keep Alive closure 3812 class G1KeepAliveClosure: public OopClosure { 3813 G1CollectedHeap* _g1; 3814 public: 3815 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3816 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3817 void do_oop(oop* p) { 3818 oop obj = *p; 3819 assert(obj != NULL, "the caller should have filtered out NULL values"); 3820 3821 const InCSetState cset_state = _g1->in_cset_state(obj); 3822 if (!cset_state.is_in_cset_or_humongous()) { 3823 return; 3824 } 3825 if (cset_state.is_in_cset()) { 3826 assert( obj->is_forwarded(), "invariant" ); 3827 *p = obj->forwardee(); 3828 } else { 3829 assert(!obj->is_forwarded(), "invariant" ); 3830 assert(cset_state.is_humongous(), 3831 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 3832 _g1->set_humongous_is_live(obj); 3833 } 3834 } 3835 }; 3836 3837 // Copying Keep Alive closure - can be called from both 3838 // serial and parallel code as long as different worker 3839 // threads utilize different G1ParScanThreadState instances 3840 // and different queues. 3841 3842 class G1CopyingKeepAliveClosure: public OopClosure { 3843 G1CollectedHeap* _g1h; 3844 OopClosure* _copy_non_heap_obj_cl; 3845 G1ParScanThreadState* _par_scan_state; 3846 3847 public: 3848 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 3849 OopClosure* non_heap_obj_cl, 3850 G1ParScanThreadState* pss): 3851 _g1h(g1h), 3852 _copy_non_heap_obj_cl(non_heap_obj_cl), 3853 _par_scan_state(pss) 3854 {} 3855 3856 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3857 virtual void do_oop( oop* p) { do_oop_work(p); } 3858 3859 template <class T> void do_oop_work(T* p) { 3860 oop obj = oopDesc::load_decode_heap_oop(p); 3861 3862 if (_g1h->is_in_cset_or_humongous(obj)) { 3863 // If the referent object has been forwarded (either copied 3864 // to a new location or to itself in the event of an 3865 // evacuation failure) then we need to update the reference 3866 // field and, if both reference and referent are in the G1 3867 // heap, update the RSet for the referent. 3868 // 3869 // If the referent has not been forwarded then we have to keep 3870 // it alive by policy. Therefore we have copy the referent. 3871 // 3872 // If the reference field is in the G1 heap then we can push 3873 // on the PSS queue. When the queue is drained (after each 3874 // phase of reference processing) the object and it's followers 3875 // will be copied, the reference field set to point to the 3876 // new location, and the RSet updated. Otherwise we need to 3877 // use the the non-heap or metadata closures directly to copy 3878 // the referent object and update the pointer, while avoiding 3879 // updating the RSet. 3880 3881 if (_g1h->is_in_g1_reserved(p)) { 3882 _par_scan_state->push_on_queue(p); 3883 } else { 3884 assert(!Metaspace::contains((const void*)p), 3885 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 3886 _copy_non_heap_obj_cl->do_oop(p); 3887 } 3888 } 3889 } 3890 }; 3891 3892 // Serial drain queue closure. Called as the 'complete_gc' 3893 // closure for each discovered list in some of the 3894 // reference processing phases. 3895 3896 class G1STWDrainQueueClosure: public VoidClosure { 3897 protected: 3898 G1CollectedHeap* _g1h; 3899 G1ParScanThreadState* _par_scan_state; 3900 3901 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 3902 3903 public: 3904 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 3905 _g1h(g1h), 3906 _par_scan_state(pss) 3907 { } 3908 3909 void do_void() { 3910 G1ParScanThreadState* const pss = par_scan_state(); 3911 pss->trim_queue(); 3912 } 3913 }; 3914 3915 // Parallel Reference Processing closures 3916 3917 // Implementation of AbstractRefProcTaskExecutor for parallel reference 3918 // processing during G1 evacuation pauses. 3919 3920 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 3921 private: 3922 G1CollectedHeap* _g1h; 3923 G1ParScanThreadStateSet* _pss; 3924 RefToScanQueueSet* _queues; 3925 WorkGang* _workers; 3926 uint _active_workers; 3927 3928 public: 3929 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 3930 G1ParScanThreadStateSet* per_thread_states, 3931 WorkGang* workers, 3932 RefToScanQueueSet *task_queues, 3933 uint n_workers) : 3934 _g1h(g1h), 3935 _pss(per_thread_states), 3936 _queues(task_queues), 3937 _workers(workers), 3938 _active_workers(n_workers) 3939 { 3940 g1h->ref_processor_stw()->set_active_mt_degree(n_workers); 3941 } 3942 3943 // Executes the given task using concurrent marking worker threads. 3944 virtual void execute(ProcessTask& task); 3945 virtual void execute(EnqueueTask& task); 3946 }; 3947 3948 // Gang task for possibly parallel reference processing 3949 3950 class G1STWRefProcTaskProxy: public AbstractGangTask { 3951 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 3952 ProcessTask& _proc_task; 3953 G1CollectedHeap* _g1h; 3954 G1ParScanThreadStateSet* _pss; 3955 RefToScanQueueSet* _task_queues; 3956 ParallelTaskTerminator* _terminator; 3957 3958 public: 3959 G1STWRefProcTaskProxy(ProcessTask& proc_task, 3960 G1CollectedHeap* g1h, 3961 G1ParScanThreadStateSet* per_thread_states, 3962 RefToScanQueueSet *task_queues, 3963 ParallelTaskTerminator* terminator) : 3964 AbstractGangTask("Process reference objects in parallel"), 3965 _proc_task(proc_task), 3966 _g1h(g1h), 3967 _pss(per_thread_states), 3968 _task_queues(task_queues), 3969 _terminator(terminator) 3970 {} 3971 3972 virtual void work(uint worker_id) { 3973 // The reference processing task executed by a single worker. 3974 ResourceMark rm; 3975 HandleMark hm; 3976 3977 G1STWIsAliveClosure is_alive(_g1h); 3978 3979 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 3980 pss->set_ref_processor(NULL); 3981 3982 // Keep alive closure. 3983 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 3984 3985 // Complete GC closure 3986 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 3987 3988 // Call the reference processing task's work routine. 3989 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 3990 3991 // Note we cannot assert that the refs array is empty here as not all 3992 // of the processing tasks (specifically phase2 - pp2_work) execute 3993 // the complete_gc closure (which ordinarily would drain the queue) so 3994 // the queue may not be empty. 3995 } 3996 }; 3997 3998 // Driver routine for parallel reference processing. 3999 // Creates an instance of the ref processing gang 4000 // task and has the worker threads execute it. 4001 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4002 assert(_workers != NULL, "Need parallel worker threads."); 4003 4004 ParallelTaskTerminator terminator(_active_workers, _queues); 4005 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4006 4007 _workers->run_task(&proc_task_proxy); 4008 } 4009 4010 // Gang task for parallel reference enqueueing. 4011 4012 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4013 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4014 EnqueueTask& _enq_task; 4015 4016 public: 4017 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4018 AbstractGangTask("Enqueue reference objects in parallel"), 4019 _enq_task(enq_task) 4020 { } 4021 4022 virtual void work(uint worker_id) { 4023 _enq_task.work(worker_id); 4024 } 4025 }; 4026 4027 // Driver routine for parallel reference enqueueing. 4028 // Creates an instance of the ref enqueueing gang 4029 // task and has the worker threads execute it. 4030 4031 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4032 assert(_workers != NULL, "Need parallel worker threads."); 4033 4034 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4035 4036 _workers->run_task(&enq_task_proxy); 4037 } 4038 4039 // End of weak reference support closures 4040 4041 // Abstract task used to preserve (i.e. copy) any referent objects 4042 // that are in the collection set and are pointed to by reference 4043 // objects discovered by the CM ref processor. 4044 4045 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4046 protected: 4047 G1CollectedHeap* _g1h; 4048 G1ParScanThreadStateSet* _pss; 4049 RefToScanQueueSet* _queues; 4050 ParallelTaskTerminator _terminator; 4051 uint _n_workers; 4052 4053 public: 4054 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4055 AbstractGangTask("ParPreserveCMReferents"), 4056 _g1h(g1h), 4057 _pss(per_thread_states), 4058 _queues(task_queues), 4059 _terminator(workers, _queues), 4060 _n_workers(workers) 4061 { 4062 g1h->ref_processor_cm()->set_active_mt_degree(workers); 4063 } 4064 4065 void work(uint worker_id) { 4066 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id); 4067 4068 ResourceMark rm; 4069 HandleMark hm; 4070 4071 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4072 pss->set_ref_processor(NULL); 4073 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4074 4075 // Is alive closure 4076 G1AlwaysAliveClosure always_alive(_g1h); 4077 4078 // Copying keep alive closure. Applied to referent objects that need 4079 // to be copied. 4080 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4081 4082 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4083 4084 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4085 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4086 4087 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4088 // So this must be true - but assert just in case someone decides to 4089 // change the worker ids. 4090 assert(worker_id < limit, "sanity"); 4091 assert(!rp->discovery_is_atomic(), "check this code"); 4092 4093 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4094 for (uint idx = worker_id; idx < limit; idx += stride) { 4095 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4096 4097 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4098 while (iter.has_next()) { 4099 // Since discovery is not atomic for the CM ref processor, we 4100 // can see some null referent objects. 4101 iter.load_ptrs(DEBUG_ONLY(true)); 4102 oop ref = iter.obj(); 4103 4104 // This will filter nulls. 4105 if (iter.is_referent_alive()) { 4106 iter.make_referent_alive(); 4107 } 4108 iter.move_to_next(); 4109 } 4110 } 4111 4112 // Drain the queue - which may cause stealing 4113 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4114 drain_queue.do_void(); 4115 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4116 assert(pss->queue_is_empty(), "should be"); 4117 } 4118 }; 4119 4120 void G1CollectedHeap::process_weak_jni_handles() { 4121 double ref_proc_start = os::elapsedTime(); 4122 4123 G1STWIsAliveClosure is_alive(this); 4124 G1KeepAliveClosure keep_alive(this); 4125 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 4126 4127 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4128 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4129 } 4130 4131 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) { 4132 // Any reference objects, in the collection set, that were 'discovered' 4133 // by the CM ref processor should have already been copied (either by 4134 // applying the external root copy closure to the discovered lists, or 4135 // by following an RSet entry). 4136 // 4137 // But some of the referents, that are in the collection set, that these 4138 // reference objects point to may not have been copied: the STW ref 4139 // processor would have seen that the reference object had already 4140 // been 'discovered' and would have skipped discovering the reference, 4141 // but would not have treated the reference object as a regular oop. 4142 // As a result the copy closure would not have been applied to the 4143 // referent object. 4144 // 4145 // We need to explicitly copy these referent objects - the references 4146 // will be processed at the end of remarking. 4147 // 4148 // We also need to do this copying before we process the reference 4149 // objects discovered by the STW ref processor in case one of these 4150 // referents points to another object which is also referenced by an 4151 // object discovered by the STW ref processor. 4152 double preserve_cm_referents_time = 0.0; 4153 4154 // To avoid spawning task when there is no work to do, check that 4155 // a concurrent cycle is active and that some references have been 4156 // discovered. 4157 if (concurrent_mark()->cmThread()->during_cycle() && 4158 ref_processor_cm()->has_discovered_references()) { 4159 double preserve_cm_referents_start = os::elapsedTime(); 4160 uint no_of_gc_workers = workers()->active_workers(); 4161 G1ParPreserveCMReferentsTask keep_cm_referents(this, 4162 per_thread_states, 4163 no_of_gc_workers, 4164 _task_queues); 4165 workers()->run_task(&keep_cm_referents); 4166 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start; 4167 } 4168 4169 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0); 4170 } 4171 4172 // Weak Reference processing during an evacuation pause (part 1). 4173 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4174 double ref_proc_start = os::elapsedTime(); 4175 4176 ReferenceProcessor* rp = _ref_processor_stw; 4177 assert(rp->discovery_enabled(), "should have been enabled"); 4178 4179 // Closure to test whether a referent is alive. 4180 G1STWIsAliveClosure is_alive(this); 4181 4182 // Even when parallel reference processing is enabled, the processing 4183 // of JNI refs is serial and performed serially by the current thread 4184 // rather than by a worker. The following PSS will be used for processing 4185 // JNI refs. 4186 4187 // Use only a single queue for this PSS. 4188 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 4189 pss->set_ref_processor(NULL); 4190 assert(pss->queue_is_empty(), "pre-condition"); 4191 4192 // Keep alive closure. 4193 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 4194 4195 // Serial Complete GC closure 4196 G1STWDrainQueueClosure drain_queue(this, pss); 4197 4198 // Setup the soft refs policy... 4199 rp->setup_policy(false); 4200 4201 ReferenceProcessorStats stats; 4202 if (!rp->processing_is_mt()) { 4203 // Serial reference processing... 4204 stats = rp->process_discovered_references(&is_alive, 4205 &keep_alive, 4206 &drain_queue, 4207 NULL, 4208 _gc_timer_stw); 4209 } else { 4210 uint no_of_gc_workers = workers()->active_workers(); 4211 4212 // Parallel reference processing 4213 assert(no_of_gc_workers <= rp->max_num_q(), 4214 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4215 no_of_gc_workers, rp->max_num_q()); 4216 4217 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 4218 stats = rp->process_discovered_references(&is_alive, 4219 &keep_alive, 4220 &drain_queue, 4221 &par_task_executor, 4222 _gc_timer_stw); 4223 } 4224 4225 _gc_tracer_stw->report_gc_reference_stats(stats); 4226 4227 // We have completed copying any necessary live referent objects. 4228 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4229 4230 double ref_proc_time = os::elapsedTime() - ref_proc_start; 4231 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 4232 } 4233 4234 // Weak Reference processing during an evacuation pause (part 2). 4235 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 4236 double ref_enq_start = os::elapsedTime(); 4237 4238 ReferenceProcessor* rp = _ref_processor_stw; 4239 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 4240 4241 // Now enqueue any remaining on the discovered lists on to 4242 // the pending list. 4243 if (!rp->processing_is_mt()) { 4244 // Serial reference processing... 4245 rp->enqueue_discovered_references(); 4246 } else { 4247 // Parallel reference enqueueing 4248 4249 uint n_workers = workers()->active_workers(); 4250 4251 assert(n_workers <= rp->max_num_q(), 4252 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u", 4253 n_workers, rp->max_num_q()); 4254 4255 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 4256 rp->enqueue_discovered_references(&par_task_executor); 4257 } 4258 4259 rp->verify_no_references_recorded(); 4260 assert(!rp->discovery_enabled(), "should have been disabled"); 4261 4262 // FIXME 4263 // CM's reference processing also cleans up the string and symbol tables. 4264 // Should we do that here also? We could, but it is a serial operation 4265 // and could significantly increase the pause time. 4266 4267 double ref_enq_time = os::elapsedTime() - ref_enq_start; 4268 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 4269 } 4270 4271 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) { 4272 double merge_pss_time_start = os::elapsedTime(); 4273 per_thread_states->flush(); 4274 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0); 4275 } 4276 4277 void G1CollectedHeap::pre_evacuate_collection_set() { 4278 _expand_heap_after_alloc_failure = true; 4279 _evacuation_failed = false; 4280 4281 // Disable the hot card cache. 4282 _hot_card_cache->reset_hot_cache_claimed_index(); 4283 _hot_card_cache->set_use_cache(false); 4284 4285 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4286 _preserved_marks_set.assert_empty(); 4287 4288 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4289 4290 // InitialMark needs claim bits to keep track of the marked-through CLDs. 4291 if (collector_state()->during_initial_mark_pause()) { 4292 double start_clear_claimed_marks = os::elapsedTime(); 4293 4294 ClassLoaderDataGraph::clear_claimed_marks(); 4295 4296 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0; 4297 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms); 4298 } 4299 } 4300 4301 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4302 // Should G1EvacuationFailureALot be in effect for this GC? 4303 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 4304 4305 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4306 4307 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 4308 4309 double start_par_time_sec = os::elapsedTime(); 4310 double end_par_time_sec; 4311 4312 { 4313 const uint n_workers = workers()->active_workers(); 4314 G1RootProcessor root_processor(this, n_workers); 4315 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 4316 4317 print_termination_stats_hdr(); 4318 4319 workers()->run_task(&g1_par_task); 4320 end_par_time_sec = os::elapsedTime(); 4321 4322 // Closing the inner scope will execute the destructor 4323 // for the G1RootProcessor object. We record the current 4324 // elapsed time before closing the scope so that time 4325 // taken for the destructor is NOT included in the 4326 // reported parallel time. 4327 } 4328 4329 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 4330 phase_times->record_par_time(par_time_ms); 4331 4332 double code_root_fixup_time_ms = 4333 (os::elapsedTime() - end_par_time_sec) * 1000.0; 4334 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 4335 } 4336 4337 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 4338 // Process any discovered reference objects - we have 4339 // to do this _before_ we retire the GC alloc regions 4340 // as we may have to copy some 'reachable' referent 4341 // objects (and their reachable sub-graphs) that were 4342 // not copied during the pause. 4343 if (g1_policy()->should_process_references()) { 4344 preserve_cm_referents(per_thread_states); 4345 process_discovered_references(per_thread_states); 4346 } else { 4347 ref_processor_stw()->verify_no_references_recorded(); 4348 process_weak_jni_handles(); 4349 } 4350 4351 if (G1StringDedup::is_enabled()) { 4352 double fixup_start = os::elapsedTime(); 4353 4354 G1STWIsAliveClosure is_alive(this); 4355 G1KeepAliveClosure keep_alive(this); 4356 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times()); 4357 4358 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 4359 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 4360 } 4361 4362 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4363 4364 if (evacuation_failed()) { 4365 restore_after_evac_failure(); 4366 4367 // Reset the G1EvacuationFailureALot counters and flags 4368 // Note: the values are reset only when an actual 4369 // evacuation failure occurs. 4370 NOT_PRODUCT(reset_evacuation_should_fail();) 4371 } 4372 4373 _preserved_marks_set.assert_empty(); 4374 4375 // Enqueue any remaining references remaining on the STW 4376 // reference processor's discovered lists. We need to do 4377 // this after the card table is cleaned (and verified) as 4378 // the act of enqueueing entries on to the pending list 4379 // will log these updates (and dirty their associated 4380 // cards). We need these updates logged to update any 4381 // RSets. 4382 if (g1_policy()->should_process_references()) { 4383 enqueue_discovered_references(per_thread_states); 4384 } else { 4385 g1_policy()->phase_times()->record_ref_enq_time(0); 4386 } 4387 4388 _allocator->release_gc_alloc_regions(evacuation_info); 4389 4390 merge_per_thread_state_info(per_thread_states); 4391 4392 // Reset and re-enable the hot card cache. 4393 // Note the counts for the cards in the regions in the 4394 // collection set are reset when the collection set is freed. 4395 _hot_card_cache->reset_hot_cache(); 4396 _hot_card_cache->set_use_cache(true); 4397 4398 purge_code_root_memory(); 4399 4400 redirty_logged_cards(); 4401 #if defined(COMPILER2) || INCLUDE_JVMCI 4402 double start = os::elapsedTime(); 4403 DerivedPointerTable::update_pointers(); 4404 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0); 4405 #endif 4406 g1_policy()->print_age_table(); 4407 } 4408 4409 void G1CollectedHeap::record_obj_copy_mem_stats() { 4410 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize); 4411 4412 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 4413 create_g1_evac_summary(&_old_evac_stats)); 4414 } 4415 4416 void G1CollectedHeap::free_region(HeapRegion* hr, 4417 FreeRegionList* free_list, 4418 bool skip_remset, 4419 bool skip_hot_card_cache, 4420 bool locked) { 4421 assert(!hr->is_free(), "the region should not be free"); 4422 assert(!hr->is_empty(), "the region should not be empty"); 4423 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 4424 assert(free_list != NULL, "pre-condition"); 4425 4426 if (G1VerifyBitmaps) { 4427 MemRegion mr(hr->bottom(), hr->end()); 4428 concurrent_mark()->clearRangePrevBitmap(mr); 4429 } 4430 4431 // Clear the card counts for this region. 4432 // Note: we only need to do this if the region is not young 4433 // (since we don't refine cards in young regions). 4434 if (!skip_hot_card_cache && !hr->is_young()) { 4435 _hot_card_cache->reset_card_counts(hr); 4436 } 4437 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */); 4438 free_list->add_ordered(hr); 4439 } 4440 4441 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4442 FreeRegionList* free_list, 4443 bool skip_remset) { 4444 assert(hr->is_humongous(), "this is only for humongous regions"); 4445 assert(free_list != NULL, "pre-condition"); 4446 hr->clear_humongous(); 4447 free_region(hr, free_list, skip_remset); 4448 } 4449 4450 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed, 4451 const uint humongous_regions_removed) { 4452 if (old_regions_removed > 0 || humongous_regions_removed > 0) { 4453 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4454 _old_set.bulk_remove(old_regions_removed); 4455 _humongous_set.bulk_remove(humongous_regions_removed); 4456 } 4457 4458 } 4459 4460 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 4461 assert(list != NULL, "list can't be null"); 4462 if (!list->is_empty()) { 4463 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4464 _hrm.insert_list_into_free_list(list); 4465 } 4466 } 4467 4468 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 4469 decrease_used(bytes); 4470 } 4471 4472 class G1ParScrubRemSetTask: public AbstractGangTask { 4473 protected: 4474 G1RemSet* _g1rs; 4475 HeapRegionClaimer _hrclaimer; 4476 4477 public: 4478 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) : 4479 AbstractGangTask("G1 ScrubRS"), 4480 _g1rs(g1_rs), 4481 _hrclaimer(num_workers) { 4482 } 4483 4484 void work(uint worker_id) { 4485 _g1rs->scrub(worker_id, &_hrclaimer); 4486 } 4487 }; 4488 4489 void G1CollectedHeap::scrub_rem_set() { 4490 uint num_workers = workers()->active_workers(); 4491 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers); 4492 workers()->run_task(&g1_par_scrub_rs_task); 4493 } 4494 4495 class G1FreeCollectionSetTask : public AbstractGangTask { 4496 private: 4497 4498 // Closure applied to all regions in the collection set to do work that needs to 4499 // be done serially in a single thread. 4500 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure { 4501 private: 4502 EvacuationInfo* _evacuation_info; 4503 const size_t* _surviving_young_words; 4504 4505 // Bytes used in successfully evacuated regions before the evacuation. 4506 size_t _before_used_bytes; 4507 // Bytes used in unsucessfully evacuated regions before the evacuation 4508 size_t _after_used_bytes; 4509 4510 size_t _bytes_allocated_in_old_since_last_gc; 4511 4512 size_t _failure_used_words; 4513 size_t _failure_waste_words; 4514 4515 FreeRegionList _local_free_list; 4516 public: 4517 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4518 HeapRegionClosure(), 4519 _evacuation_info(evacuation_info), 4520 _surviving_young_words(surviving_young_words), 4521 _before_used_bytes(0), 4522 _after_used_bytes(0), 4523 _bytes_allocated_in_old_since_last_gc(0), 4524 _failure_used_words(0), 4525 _failure_waste_words(0), 4526 _local_free_list("Local Region List for CSet Freeing") { 4527 } 4528 4529 virtual bool doHeapRegion(HeapRegion* r) { 4530 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4531 4532 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index()); 4533 g1h->clear_in_cset(r); 4534 4535 if (r->is_young()) { 4536 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(), 4537 "Young index %d is wrong for region %u of type %s with %u young regions", 4538 r->young_index_in_cset(), 4539 r->hrm_index(), 4540 r->get_type_str(), 4541 g1h->collection_set()->young_region_length()); 4542 size_t words_survived = _surviving_young_words[r->young_index_in_cset()]; 4543 r->record_surv_words_in_group(words_survived); 4544 } 4545 4546 if (!r->evacuation_failed()) { 4547 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index()); 4548 _before_used_bytes += r->used(); 4549 g1h->free_region(r, 4550 &_local_free_list, 4551 true, /* skip_remset */ 4552 true, /* skip_hot_card_cache */ 4553 true /* locked */); 4554 } else { 4555 r->uninstall_surv_rate_group(); 4556 r->set_young_index_in_cset(-1); 4557 r->set_evacuation_failed(false); 4558 // When moving a young gen region to old gen, we "allocate" that whole region 4559 // there. This is in addition to any already evacuated objects. Notify the 4560 // policy about that. 4561 // Old gen regions do not cause an additional allocation: both the objects 4562 // still in the region and the ones already moved are accounted for elsewhere. 4563 if (r->is_young()) { 4564 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes; 4565 } 4566 // The region is now considered to be old. 4567 r->set_old(); 4568 // Do some allocation statistics accounting. Regions that failed evacuation 4569 // are always made old, so there is no need to update anything in the young 4570 // gen statistics, but we need to update old gen statistics. 4571 size_t used_words = r->marked_bytes() / HeapWordSize; 4572 4573 _failure_used_words += used_words; 4574 _failure_waste_words += HeapRegion::GrainWords - used_words; 4575 4576 g1h->old_set_add(r); 4577 _after_used_bytes += r->used(); 4578 } 4579 return false; 4580 } 4581 4582 void complete_work() { 4583 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4584 4585 _evacuation_info->set_regions_freed(_local_free_list.length()); 4586 _evacuation_info->increment_collectionset_used_after(_after_used_bytes); 4587 4588 g1h->prepend_to_freelist(&_local_free_list); 4589 g1h->decrement_summary_bytes(_before_used_bytes); 4590 4591 G1Policy* policy = g1h->g1_policy(); 4592 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc); 4593 4594 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words); 4595 } 4596 }; 4597 4598 G1CollectionSet* _collection_set; 4599 G1SerialFreeCollectionSetClosure _cl; 4600 const size_t* _surviving_young_words; 4601 4602 size_t _rs_lengths; 4603 4604 volatile jint _serial_work_claim; 4605 4606 struct WorkItem { 4607 uint region_idx; 4608 bool is_young; 4609 bool evacuation_failed; 4610 4611 WorkItem(HeapRegion* r) { 4612 region_idx = r->hrm_index(); 4613 is_young = r->is_young(); 4614 evacuation_failed = r->evacuation_failed(); 4615 } 4616 }; 4617 4618 volatile size_t _parallel_work_claim; 4619 size_t _num_work_items; 4620 WorkItem* _work_items; 4621 4622 void do_serial_work() { 4623 // Need to grab the lock to be allowed to modify the old region list. 4624 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4625 _collection_set->iterate(&_cl); 4626 } 4627 4628 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) { 4629 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4630 4631 HeapRegion* r = g1h->region_at(region_idx); 4632 assert(!g1h->is_on_master_free_list(r), "sanity"); 4633 4634 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths); 4635 4636 if (!is_young) { 4637 g1h->_hot_card_cache->reset_card_counts(r); 4638 } 4639 4640 if (!evacuation_failed) { 4641 r->rem_set()->clear_locked(); 4642 } 4643 } 4644 4645 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure { 4646 private: 4647 size_t _cur_idx; 4648 WorkItem* _work_items; 4649 public: 4650 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { } 4651 4652 virtual bool doHeapRegion(HeapRegion* r) { 4653 _work_items[_cur_idx++] = WorkItem(r); 4654 return false; 4655 } 4656 }; 4657 4658 void prepare_work() { 4659 G1PrepareFreeCollectionSetClosure cl(_work_items); 4660 _collection_set->iterate(&cl); 4661 } 4662 4663 void complete_work() { 4664 _cl.complete_work(); 4665 4666 G1Policy* policy = G1CollectedHeap::heap()->g1_policy(); 4667 policy->record_max_rs_lengths(_rs_lengths); 4668 policy->cset_regions_freed(); 4669 } 4670 public: 4671 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) : 4672 AbstractGangTask("G1 Free Collection Set"), 4673 _cl(evacuation_info, surviving_young_words), 4674 _collection_set(collection_set), 4675 _surviving_young_words(surviving_young_words), 4676 _serial_work_claim(0), 4677 _rs_lengths(0), 4678 _parallel_work_claim(0), 4679 _num_work_items(collection_set->region_length()), 4680 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) { 4681 prepare_work(); 4682 } 4683 4684 ~G1FreeCollectionSetTask() { 4685 complete_work(); 4686 FREE_C_HEAP_ARRAY(WorkItem, _work_items); 4687 } 4688 4689 // Chunk size for work distribution. The chosen value has been determined experimentally 4690 // to be a good tradeoff between overhead and achievable parallelism. 4691 static uint chunk_size() { return 32; } 4692 4693 virtual void work(uint worker_id) { 4694 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4695 4696 // Claim serial work. 4697 if (_serial_work_claim == 0) { 4698 jint value = Atomic::add(1, &_serial_work_claim) - 1; 4699 if (value == 0) { 4700 double serial_time = os::elapsedTime(); 4701 do_serial_work(); 4702 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0); 4703 } 4704 } 4705 4706 // Start parallel work. 4707 double young_time = 0.0; 4708 bool has_young_time = false; 4709 double non_young_time = 0.0; 4710 bool has_non_young_time = false; 4711 4712 while (true) { 4713 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim); 4714 size_t cur = end - chunk_size(); 4715 4716 if (cur >= _num_work_items) { 4717 break; 4718 } 4719 4720 double start_time = os::elapsedTime(); 4721 4722 end = MIN2(end, _num_work_items); 4723 4724 for (; cur < end; cur++) { 4725 bool is_young = _work_items[cur].is_young; 4726 4727 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed); 4728 4729 double end_time = os::elapsedTime(); 4730 double time_taken = end_time - start_time; 4731 if (is_young) { 4732 young_time += time_taken; 4733 has_young_time = true; 4734 } else { 4735 non_young_time += time_taken; 4736 has_non_young_time = true; 4737 } 4738 start_time = end_time; 4739 } 4740 } 4741 4742 if (has_young_time) { 4743 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time); 4744 } 4745 if (has_non_young_time) { 4746 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time); 4747 } 4748 } 4749 }; 4750 4751 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 4752 _eden.clear(); 4753 4754 double free_cset_start_time = os::elapsedTime(); 4755 4756 { 4757 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U); 4758 uint const num_workers = MIN2(workers()->active_workers(), num_chunks); 4759 4760 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words); 4761 4762 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u", 4763 cl.name(), 4764 num_workers, 4765 _collection_set.region_length()); 4766 workers()->run_task(&cl, num_workers); 4767 } 4768 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0); 4769 4770 collection_set->clear(); 4771 } 4772 4773 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 4774 private: 4775 FreeRegionList* _free_region_list; 4776 HeapRegionSet* _proxy_set; 4777 uint _humongous_objects_reclaimed; 4778 uint _humongous_regions_reclaimed; 4779 size_t _freed_bytes; 4780 public: 4781 4782 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 4783 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) { 4784 } 4785 4786 virtual bool doHeapRegion(HeapRegion* r) { 4787 if (!r->is_starts_humongous()) { 4788 return false; 4789 } 4790 4791 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4792 4793 oop obj = (oop)r->bottom(); 4794 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 4795 4796 // The following checks whether the humongous object is live are sufficient. 4797 // The main additional check (in addition to having a reference from the roots 4798 // or the young gen) is whether the humongous object has a remembered set entry. 4799 // 4800 // A humongous object cannot be live if there is no remembered set for it 4801 // because: 4802 // - there can be no references from within humongous starts regions referencing 4803 // the object because we never allocate other objects into them. 4804 // (I.e. there are no intra-region references that may be missed by the 4805 // remembered set) 4806 // - as soon there is a remembered set entry to the humongous starts region 4807 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 4808 // until the end of a concurrent mark. 4809 // 4810 // It is not required to check whether the object has been found dead by marking 4811 // or not, in fact it would prevent reclamation within a concurrent cycle, as 4812 // all objects allocated during that time are considered live. 4813 // SATB marking is even more conservative than the remembered set. 4814 // So if at this point in the collection there is no remembered set entry, 4815 // nobody has a reference to it. 4816 // At the start of collection we flush all refinement logs, and remembered sets 4817 // are completely up-to-date wrt to references to the humongous object. 4818 // 4819 // Other implementation considerations: 4820 // - never consider object arrays at this time because they would pose 4821 // considerable effort for cleaning up the the remembered sets. This is 4822 // required because stale remembered sets might reference locations that 4823 // are currently allocated into. 4824 uint region_idx = r->hrm_index(); 4825 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 4826 !r->rem_set()->is_empty()) { 4827 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", 4828 region_idx, 4829 (size_t)obj->size() * HeapWordSize, 4830 p2i(r->bottom()), 4831 r->rem_set()->occupied(), 4832 r->rem_set()->strong_code_roots_list_length(), 4833 next_bitmap->isMarked(r->bottom()), 4834 g1h->is_humongous_reclaim_candidate(region_idx), 4835 obj->is_typeArray() 4836 ); 4837 return false; 4838 } 4839 4840 guarantee(obj->is_typeArray(), 4841 "Only eagerly reclaiming type arrays is supported, but the object " 4842 PTR_FORMAT " is not.", p2i(r->bottom())); 4843 4844 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", 4845 region_idx, 4846 (size_t)obj->size() * HeapWordSize, 4847 p2i(r->bottom()), 4848 r->rem_set()->occupied(), 4849 r->rem_set()->strong_code_roots_list_length(), 4850 next_bitmap->isMarked(r->bottom()), 4851 g1h->is_humongous_reclaim_candidate(region_idx), 4852 obj->is_typeArray() 4853 ); 4854 4855 // Need to clear mark bit of the humongous object if already set. 4856 if (next_bitmap->isMarked(r->bottom())) { 4857 next_bitmap->clear(r->bottom()); 4858 } 4859 _humongous_objects_reclaimed++; 4860 do { 4861 HeapRegion* next = g1h->next_region_in_humongous(r); 4862 _freed_bytes += r->used(); 4863 r->set_containing_set(NULL); 4864 _humongous_regions_reclaimed++; 4865 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ ); 4866 r = next; 4867 } while (r != NULL); 4868 4869 return false; 4870 } 4871 4872 uint humongous_objects_reclaimed() { 4873 return _humongous_objects_reclaimed; 4874 } 4875 4876 uint humongous_regions_reclaimed() { 4877 return _humongous_regions_reclaimed; 4878 } 4879 4880 size_t bytes_freed() const { 4881 return _freed_bytes; 4882 } 4883 }; 4884 4885 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 4886 assert_at_safepoint(true); 4887 4888 if (!G1EagerReclaimHumongousObjects || 4889 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) { 4890 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 4891 return; 4892 } 4893 4894 double start_time = os::elapsedTime(); 4895 4896 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 4897 4898 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 4899 heap_region_iterate(&cl); 4900 4901 remove_from_old_sets(0, cl.humongous_regions_reclaimed()); 4902 4903 G1HRPrinter* hrp = hr_printer(); 4904 if (hrp->is_active()) { 4905 FreeRegionListIterator iter(&local_cleanup_list); 4906 while (iter.more_available()) { 4907 HeapRegion* hr = iter.get_next(); 4908 hrp->cleanup(hr); 4909 } 4910 } 4911 4912 prepend_to_freelist(&local_cleanup_list); 4913 decrement_summary_bytes(cl.bytes_freed()); 4914 4915 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 4916 cl.humongous_objects_reclaimed()); 4917 } 4918 4919 class G1AbandonCollectionSetClosure : public HeapRegionClosure { 4920 public: 4921 virtual bool doHeapRegion(HeapRegion* r) { 4922 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index()); 4923 G1CollectedHeap::heap()->clear_in_cset(r); 4924 r->set_young_index_in_cset(-1); 4925 return false; 4926 } 4927 }; 4928 4929 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) { 4930 G1AbandonCollectionSetClosure cl; 4931 collection_set->iterate(&cl); 4932 4933 collection_set->clear(); 4934 collection_set->stop_incremental_building(); 4935 } 4936 4937 void G1CollectedHeap::set_free_regions_coming() { 4938 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming"); 4939 4940 assert(!free_regions_coming(), "pre-condition"); 4941 _free_regions_coming = true; 4942 } 4943 4944 void G1CollectedHeap::reset_free_regions_coming() { 4945 assert(free_regions_coming(), "pre-condition"); 4946 4947 { 4948 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 4949 _free_regions_coming = false; 4950 SecondaryFreeList_lock->notify_all(); 4951 } 4952 4953 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming"); 4954 } 4955 4956 void G1CollectedHeap::wait_while_free_regions_coming() { 4957 // Most of the time we won't have to wait, so let's do a quick test 4958 // first before we take the lock. 4959 if (!free_regions_coming()) { 4960 return; 4961 } 4962 4963 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions"); 4964 4965 { 4966 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 4967 while (free_regions_coming()) { 4968 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 4969 } 4970 } 4971 4972 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions"); 4973 } 4974 4975 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 4976 return _allocator->is_retained_old_region(hr); 4977 } 4978 4979 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 4980 _eden.add(hr); 4981 _g1_policy->set_region_eden(hr); 4982 } 4983 4984 #ifdef ASSERT 4985 4986 class NoYoungRegionsClosure: public HeapRegionClosure { 4987 private: 4988 bool _success; 4989 public: 4990 NoYoungRegionsClosure() : _success(true) { } 4991 bool doHeapRegion(HeapRegion* r) { 4992 if (r->is_young()) { 4993 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 4994 p2i(r->bottom()), p2i(r->end())); 4995 _success = false; 4996 } 4997 return false; 4998 } 4999 bool success() { return _success; } 5000 }; 5001 5002 bool G1CollectedHeap::check_young_list_empty() { 5003 bool ret = (young_regions_count() == 0); 5004 5005 NoYoungRegionsClosure closure; 5006 heap_region_iterate(&closure); 5007 ret = ret && closure.success(); 5008 5009 return ret; 5010 } 5011 5012 #endif // ASSERT 5013 5014 class TearDownRegionSetsClosure : public HeapRegionClosure { 5015 private: 5016 HeapRegionSet *_old_set; 5017 5018 public: 5019 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5020 5021 bool doHeapRegion(HeapRegion* r) { 5022 if (r->is_old()) { 5023 _old_set->remove(r); 5024 } else if(r->is_young()) { 5025 r->uninstall_surv_rate_group(); 5026 } else { 5027 // We ignore free regions, we'll empty the free list afterwards. 5028 // We ignore humongous regions, we're not tearing down the 5029 // humongous regions set. 5030 assert(r->is_free() || r->is_humongous(), 5031 "it cannot be another type"); 5032 } 5033 return false; 5034 } 5035 5036 ~TearDownRegionSetsClosure() { 5037 assert(_old_set->is_empty(), "post-condition"); 5038 } 5039 }; 5040 5041 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5042 assert_at_safepoint(true /* should_be_vm_thread */); 5043 5044 if (!free_list_only) { 5045 TearDownRegionSetsClosure cl(&_old_set); 5046 heap_region_iterate(&cl); 5047 5048 // Note that emptying the _young_list is postponed and instead done as 5049 // the first step when rebuilding the regions sets again. The reason for 5050 // this is that during a full GC string deduplication needs to know if 5051 // a collected region was young or old when the full GC was initiated. 5052 } 5053 _hrm.remove_all_free_regions(); 5054 } 5055 5056 void G1CollectedHeap::increase_used(size_t bytes) { 5057 _summary_bytes_used += bytes; 5058 } 5059 5060 void G1CollectedHeap::decrease_used(size_t bytes) { 5061 assert(_summary_bytes_used >= bytes, 5062 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5063 _summary_bytes_used, bytes); 5064 _summary_bytes_used -= bytes; 5065 } 5066 5067 void G1CollectedHeap::set_used(size_t bytes) { 5068 _summary_bytes_used = bytes; 5069 } 5070 5071 class RebuildRegionSetsClosure : public HeapRegionClosure { 5072 private: 5073 bool _free_list_only; 5074 HeapRegionSet* _old_set; 5075 HeapRegionManager* _hrm; 5076 size_t _total_used; 5077 5078 public: 5079 RebuildRegionSetsClosure(bool free_list_only, 5080 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5081 _free_list_only(free_list_only), 5082 _old_set(old_set), _hrm(hrm), _total_used(0) { 5083 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5084 if (!free_list_only) { 5085 assert(_old_set->is_empty(), "pre-condition"); 5086 } 5087 } 5088 5089 bool doHeapRegion(HeapRegion* r) { 5090 if (r->is_empty()) { 5091 // Add free regions to the free list 5092 r->set_free(); 5093 r->set_allocation_context(AllocationContext::system()); 5094 _hrm->insert_into_free_list(r); 5095 } else if (!_free_list_only) { 5096 5097 if (r->is_humongous()) { 5098 // We ignore humongous regions. We left the humongous set unchanged. 5099 } else { 5100 assert(r->is_young() || r->is_free() || r->is_old(), "invariant"); 5101 // We now consider all regions old, so register as such. Leave 5102 // archive regions set that way, however, while still adding 5103 // them to the old set. 5104 if (!r->is_archive()) { 5105 r->set_old(); 5106 } 5107 _old_set->add(r); 5108 } 5109 _total_used += r->used(); 5110 } 5111 5112 return false; 5113 } 5114 5115 size_t total_used() { 5116 return _total_used; 5117 } 5118 }; 5119 5120 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 5121 assert_at_safepoint(true /* should_be_vm_thread */); 5122 5123 if (!free_list_only) { 5124 _eden.clear(); 5125 _survivor.clear(); 5126 } 5127 5128 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 5129 heap_region_iterate(&cl); 5130 5131 if (!free_list_only) { 5132 set_used(cl.total_used()); 5133 if (_archive_allocator != NULL) { 5134 _archive_allocator->clear_used(); 5135 } 5136 } 5137 assert(used_unlocked() == recalculate_used(), 5138 "inconsistent used_unlocked(), " 5139 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 5140 used_unlocked(), recalculate_used()); 5141 } 5142 5143 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5144 HeapRegion* hr = heap_region_containing(p); 5145 return hr->is_in(p); 5146 } 5147 5148 // Methods for the mutator alloc region 5149 5150 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5151 bool force) { 5152 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5153 bool should_allocate = g1_policy()->should_allocate_mutator_region(); 5154 if (force || should_allocate) { 5155 HeapRegion* new_alloc_region = new_region(word_size, 5156 false /* is_old */, 5157 false /* do_expand */); 5158 if (new_alloc_region != NULL) { 5159 set_region_short_lived_locked(new_alloc_region); 5160 _hr_printer.alloc(new_alloc_region, !should_allocate); 5161 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region); 5162 return new_alloc_region; 5163 } 5164 } 5165 return NULL; 5166 } 5167 5168 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5169 size_t allocated_bytes) { 5170 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5171 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 5172 5173 collection_set()->add_eden_region(alloc_region); 5174 increase_used(allocated_bytes); 5175 _hr_printer.retire(alloc_region); 5176 // We update the eden sizes here, when the region is retired, 5177 // instead of when it's allocated, since this is the point that its 5178 // used space has been recored in _summary_bytes_used. 5179 g1mm()->update_eden_size(); 5180 } 5181 5182 // Methods for the GC alloc regions 5183 5184 bool G1CollectedHeap::has_more_regions(InCSetState dest) { 5185 if (dest.is_old()) { 5186 return true; 5187 } else { 5188 return survivor_regions_count() < g1_policy()->max_survivor_regions(); 5189 } 5190 } 5191 5192 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) { 5193 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5194 5195 if (!has_more_regions(dest)) { 5196 return NULL; 5197 } 5198 5199 const bool is_survivor = dest.is_young(); 5200 5201 HeapRegion* new_alloc_region = new_region(word_size, 5202 !is_survivor, 5203 true /* do_expand */); 5204 if (new_alloc_region != NULL) { 5205 // We really only need to do this for old regions given that we 5206 // should never scan survivors. But it doesn't hurt to do it 5207 // for survivors too. 5208 new_alloc_region->record_timestamp(); 5209 if (is_survivor) { 5210 new_alloc_region->set_survivor(); 5211 _survivor.add(new_alloc_region); 5212 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region); 5213 } else { 5214 new_alloc_region->set_old(); 5215 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region); 5216 } 5217 _hr_printer.alloc(new_alloc_region); 5218 bool during_im = collector_state()->during_initial_mark_pause(); 5219 new_alloc_region->note_start_of_copying(during_im); 5220 return new_alloc_region; 5221 } 5222 return NULL; 5223 } 5224 5225 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5226 size_t allocated_bytes, 5227 InCSetState dest) { 5228 bool during_im = collector_state()->during_initial_mark_pause(); 5229 alloc_region->note_end_of_copying(during_im); 5230 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5231 if (dest.is_old()) { 5232 _old_set.add(alloc_region); 5233 } 5234 _hr_printer.retire(alloc_region); 5235 } 5236 5237 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 5238 bool expanded = false; 5239 uint index = _hrm.find_highest_free(&expanded); 5240 5241 if (index != G1_NO_HRM_INDEX) { 5242 if (expanded) { 5243 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B", 5244 HeapRegion::GrainWords * HeapWordSize); 5245 } 5246 _hrm.allocate_free_regions_starting_at(index, 1); 5247 return region_at(index); 5248 } 5249 return NULL; 5250 } 5251 5252 // Optimized nmethod scanning 5253 5254 class RegisterNMethodOopClosure: public OopClosure { 5255 G1CollectedHeap* _g1h; 5256 nmethod* _nm; 5257 5258 template <class T> void do_oop_work(T* p) { 5259 T heap_oop = oopDesc::load_heap_oop(p); 5260 if (!oopDesc::is_null(heap_oop)) { 5261 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5262 HeapRegion* hr = _g1h->heap_region_containing(obj); 5263 assert(!hr->is_continues_humongous(), 5264 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5265 " starting at " HR_FORMAT, 5266 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5267 5268 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 5269 hr->add_strong_code_root_locked(_nm); 5270 } 5271 } 5272 5273 public: 5274 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5275 _g1h(g1h), _nm(nm) {} 5276 5277 void do_oop(oop* p) { do_oop_work(p); } 5278 void do_oop(narrowOop* p) { do_oop_work(p); } 5279 }; 5280 5281 class UnregisterNMethodOopClosure: public OopClosure { 5282 G1CollectedHeap* _g1h; 5283 nmethod* _nm; 5284 5285 template <class T> void do_oop_work(T* p) { 5286 T heap_oop = oopDesc::load_heap_oop(p); 5287 if (!oopDesc::is_null(heap_oop)) { 5288 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 5289 HeapRegion* hr = _g1h->heap_region_containing(obj); 5290 assert(!hr->is_continues_humongous(), 5291 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 5292 " starting at " HR_FORMAT, 5293 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 5294 5295 hr->remove_strong_code_root(_nm); 5296 } 5297 } 5298 5299 public: 5300 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 5301 _g1h(g1h), _nm(nm) {} 5302 5303 void do_oop(oop* p) { do_oop_work(p); } 5304 void do_oop(narrowOop* p) { do_oop_work(p); } 5305 }; 5306 5307 void G1CollectedHeap::register_nmethod(nmethod* nm) { 5308 CollectedHeap::register_nmethod(nm); 5309 5310 guarantee(nm != NULL, "sanity"); 5311 RegisterNMethodOopClosure reg_cl(this, nm); 5312 nm->oops_do(®_cl); 5313 } 5314 5315 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 5316 CollectedHeap::unregister_nmethod(nm); 5317 5318 guarantee(nm != NULL, "sanity"); 5319 UnregisterNMethodOopClosure reg_cl(this, nm); 5320 nm->oops_do(®_cl, true); 5321 } 5322 5323 void G1CollectedHeap::purge_code_root_memory() { 5324 double purge_start = os::elapsedTime(); 5325 G1CodeRootSet::purge(); 5326 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 5327 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 5328 } 5329 5330 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 5331 G1CollectedHeap* _g1h; 5332 5333 public: 5334 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 5335 _g1h(g1h) {} 5336 5337 void do_code_blob(CodeBlob* cb) { 5338 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 5339 if (nm == NULL) { 5340 return; 5341 } 5342 5343 if (ScavengeRootsInCode) { 5344 _g1h->register_nmethod(nm); 5345 } 5346 } 5347 }; 5348 5349 void G1CollectedHeap::rebuild_strong_code_roots() { 5350 RebuildStrongCodeRootClosure blob_cl(this); 5351 CodeCache::blobs_do(&blob_cl); 5352 }