1 /* 2 * Copyright (c) 2001, 2015, 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 "code/codeCache.hpp" 29 #include "code/icBuffer.hpp" 30 #include "gc/g1/bufferingOopClosure.hpp" 31 #include "gc/g1/concurrentG1Refine.hpp" 32 #include "gc/g1/concurrentG1RefineThread.hpp" 33 #include "gc/g1/concurrentMarkThread.inline.hpp" 34 #include "gc/g1/g1Allocator.inline.hpp" 35 #include "gc/g1/g1CollectedHeap.inline.hpp" 36 #include "gc/g1/g1CollectorPolicy.hpp" 37 #include "gc/g1/g1CollectorState.hpp" 38 #include "gc/g1/g1ErgoVerbose.hpp" 39 #include "gc/g1/g1EvacFailure.hpp" 40 #include "gc/g1/g1EvacStats.inline.hpp" 41 #include "gc/g1/g1GCPhaseTimes.hpp" 42 #include "gc/g1/g1Log.hpp" 43 #include "gc/g1/g1MarkSweep.hpp" 44 #include "gc/g1/g1OopClosures.inline.hpp" 45 #include "gc/g1/g1ParScanThreadState.inline.hpp" 46 #include "gc/g1/g1RegionToSpaceMapper.hpp" 47 #include "gc/g1/g1RemSet.inline.hpp" 48 #include "gc/g1/g1RootClosures.hpp" 49 #include "gc/g1/g1RootProcessor.hpp" 50 #include "gc/g1/g1StringDedup.hpp" 51 #include "gc/g1/g1YCTypes.hpp" 52 #include "gc/g1/heapRegion.inline.hpp" 53 #include "gc/g1/heapRegionRemSet.hpp" 54 #include "gc/g1/heapRegionSet.inline.hpp" 55 #include "gc/g1/suspendibleThreadSet.hpp" 56 #include "gc/g1/vm_operations_g1.hpp" 57 #include "gc/shared/gcHeapSummary.hpp" 58 #include "gc/shared/gcId.hpp" 59 #include "gc/shared/gcLocker.inline.hpp" 60 #include "gc/shared/gcTimer.hpp" 61 #include "gc/shared/gcTrace.hpp" 62 #include "gc/shared/gcTraceTime.hpp" 63 #include "gc/shared/generationSpec.hpp" 64 #include "gc/shared/isGCActiveMark.hpp" 65 #include "gc/shared/referenceProcessor.hpp" 66 #include "gc/shared/taskqueue.inline.hpp" 67 #include "memory/allocation.hpp" 68 #include "memory/iterator.hpp" 69 #include "oops/oop.inline.hpp" 70 #include "runtime/atomic.inline.hpp" 71 #include "runtime/init.hpp" 72 #include "runtime/orderAccess.inline.hpp" 73 #include "runtime/vmThread.hpp" 74 #include "utilities/globalDefinitions.hpp" 75 #include "utilities/stack.inline.hpp" 76 77 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 78 79 // INVARIANTS/NOTES 80 // 81 // All allocation activity covered by the G1CollectedHeap interface is 82 // serialized by acquiring the HeapLock. This happens in mem_allocate 83 // and allocate_new_tlab, which are the "entry" points to the 84 // allocation code from the rest of the JVM. (Note that this does not 85 // apply to TLAB allocation, which is not part of this interface: it 86 // is done by clients of this interface.) 87 88 // Local to this file. 89 90 class RefineCardTableEntryClosure: public CardTableEntryClosure { 91 bool _concurrent; 92 public: 93 RefineCardTableEntryClosure() : _concurrent(true) { } 94 95 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 96 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false); 97 // This path is executed by the concurrent refine or mutator threads, 98 // concurrently, and so we do not care if card_ptr contains references 99 // that point into the collection set. 100 assert(!oops_into_cset, "should be"); 101 102 if (_concurrent && SuspendibleThreadSet::should_yield()) { 103 // Caller will actually yield. 104 return false; 105 } 106 // Otherwise, we finished successfully; return true. 107 return true; 108 } 109 110 void set_concurrent(bool b) { _concurrent = b; } 111 }; 112 113 114 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 115 private: 116 size_t _num_processed; 117 118 public: 119 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { } 120 121 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 122 *card_ptr = CardTableModRefBS::dirty_card_val(); 123 _num_processed++; 124 return true; 125 } 126 127 size_t num_processed() const { return _num_processed; } 128 }; 129 130 131 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 132 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions); 133 } 134 135 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 136 // The from card cache is not the memory that is actually committed. So we cannot 137 // take advantage of the zero_filled parameter. 138 reset_from_card_cache(start_idx, num_regions); 139 } 140 141 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 142 { 143 // Claim the right to put the region on the dirty cards region list 144 // by installing a self pointer. 145 HeapRegion* next = hr->get_next_dirty_cards_region(); 146 if (next == NULL) { 147 HeapRegion* res = (HeapRegion*) 148 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 149 NULL); 150 if (res == NULL) { 151 HeapRegion* head; 152 do { 153 // Put the region to the dirty cards region list. 154 head = _dirty_cards_region_list; 155 next = (HeapRegion*) 156 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 157 if (next == head) { 158 assert(hr->get_next_dirty_cards_region() == hr, 159 "hr->get_next_dirty_cards_region() != hr"); 160 if (next == NULL) { 161 // The last region in the list points to itself. 162 hr->set_next_dirty_cards_region(hr); 163 } else { 164 hr->set_next_dirty_cards_region(next); 165 } 166 } 167 } while (next != head); 168 } 169 } 170 } 171 172 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 173 { 174 HeapRegion* head; 175 HeapRegion* hr; 176 do { 177 head = _dirty_cards_region_list; 178 if (head == NULL) { 179 return NULL; 180 } 181 HeapRegion* new_head = head->get_next_dirty_cards_region(); 182 if (head == new_head) { 183 // The last region. 184 new_head = NULL; 185 } 186 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 187 head); 188 } while (hr != head); 189 assert(hr != NULL, "invariant"); 190 hr->set_next_dirty_cards_region(NULL); 191 return hr; 192 } 193 194 // Returns true if the reference points to an object that 195 // can move in an incremental collection. 196 bool G1CollectedHeap::is_scavengable(const void* p) { 197 HeapRegion* hr = heap_region_containing(p); 198 return !hr->is_pinned(); 199 } 200 201 // Private methods. 202 203 HeapRegion* 204 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 205 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 206 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 207 if (!_secondary_free_list.is_empty()) { 208 if (G1ConcRegionFreeingVerbose) { 209 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 210 "secondary_free_list has %u entries", 211 _secondary_free_list.length()); 212 } 213 // It looks as if there are free regions available on the 214 // secondary_free_list. Let's move them to the free_list and try 215 // again to allocate from it. 216 append_secondary_free_list(); 217 218 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 219 "empty we should have moved at least one entry to the free_list"); 220 HeapRegion* res = _hrm.allocate_free_region(is_old); 221 if (G1ConcRegionFreeingVerbose) { 222 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 223 "allocated " HR_FORMAT " from secondary_free_list", 224 HR_FORMAT_PARAMS(res)); 225 } 226 return res; 227 } 228 229 // Wait here until we get notified either when (a) there are no 230 // more free regions coming or (b) some regions have been moved on 231 // the secondary_free_list. 232 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 233 } 234 235 if (G1ConcRegionFreeingVerbose) { 236 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 237 "could not allocate from secondary_free_list"); 238 } 239 return NULL; 240 } 241 242 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 243 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 244 "the only time we use this to allocate a humongous region is " 245 "when we are allocating a single humongous region"); 246 247 HeapRegion* res; 248 if (G1StressConcRegionFreeing) { 249 if (!_secondary_free_list.is_empty()) { 250 if (G1ConcRegionFreeingVerbose) { 251 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 252 "forced to look at the secondary_free_list"); 253 } 254 res = new_region_try_secondary_free_list(is_old); 255 if (res != NULL) { 256 return res; 257 } 258 } 259 } 260 261 res = _hrm.allocate_free_region(is_old); 262 263 if (res == NULL) { 264 if (G1ConcRegionFreeingVerbose) { 265 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 266 "res == NULL, trying the secondary_free_list"); 267 } 268 res = new_region_try_secondary_free_list(is_old); 269 } 270 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 271 // Currently, only attempts to allocate GC alloc regions set 272 // do_expand to true. So, we should only reach here during a 273 // safepoint. If this assumption changes we might have to 274 // reconsider the use of _expand_heap_after_alloc_failure. 275 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 276 277 ergo_verbose1(ErgoHeapSizing, 278 "attempt heap expansion", 279 ergo_format_reason("region allocation request failed") 280 ergo_format_byte("allocation request"), 281 word_size * HeapWordSize); 282 if (expand(word_size * HeapWordSize)) { 283 // Given that expand() succeeded in expanding the heap, and we 284 // always expand the heap by an amount aligned to the heap 285 // region size, the free list should in theory not be empty. 286 // In either case allocate_free_region() will check for NULL. 287 res = _hrm.allocate_free_region(is_old); 288 } else { 289 _expand_heap_after_alloc_failure = false; 290 } 291 } 292 return res; 293 } 294 295 HeapWord* 296 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 297 uint num_regions, 298 size_t word_size, 299 AllocationContext_t context) { 300 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 301 assert(is_humongous(word_size), "word_size should be humongous"); 302 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 303 304 // Index of last region in the series + 1. 305 uint last = first + num_regions; 306 307 // We need to initialize the region(s) we just discovered. This is 308 // a bit tricky given that it can happen concurrently with 309 // refinement threads refining cards on these regions and 310 // potentially wanting to refine the BOT as they are scanning 311 // those cards (this can happen shortly after a cleanup; see CR 312 // 6991377). So we have to set up the region(s) carefully and in 313 // a specific order. 314 315 // The word size sum of all the regions we will allocate. 316 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 317 assert(word_size <= word_size_sum, "sanity"); 318 319 // This will be the "starts humongous" region. 320 HeapRegion* first_hr = region_at(first); 321 // The header of the new object will be placed at the bottom of 322 // the first region. 323 HeapWord* new_obj = first_hr->bottom(); 324 // This will be the new top of the new object. 325 HeapWord* obj_top = new_obj + word_size; 326 327 // First, we need to zero the header of the space that we will be 328 // allocating. When we update top further down, some refinement 329 // threads might try to scan the region. By zeroing the header we 330 // ensure that any thread that will try to scan the region will 331 // come across the zero klass word and bail out. 332 // 333 // NOTE: It would not have been correct to have used 334 // CollectedHeap::fill_with_object() and make the space look like 335 // an int array. The thread that is doing the allocation will 336 // later update the object header to a potentially different array 337 // type and, for a very short period of time, the klass and length 338 // fields will be inconsistent. This could cause a refinement 339 // thread to calculate the object size incorrectly. 340 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 341 342 // We will set up the first region as "starts humongous". This 343 // will also update the BOT covering all the regions to reflect 344 // that there is a single object that starts at the bottom of the 345 // first region. 346 first_hr->set_starts_humongous(obj_top); 347 first_hr->set_allocation_context(context); 348 // Then, if there are any, we will set up the "continues 349 // humongous" regions. 350 HeapRegion* hr = NULL; 351 for (uint i = first + 1; i < last; ++i) { 352 hr = region_at(i); 353 hr->set_continues_humongous(first_hr); 354 hr->set_allocation_context(context); 355 } 356 357 // Up to this point no concurrent thread would have been able to 358 // do any scanning on any region in this series. All the top 359 // fields still point to bottom, so the intersection between 360 // [bottom,top] and [card_start,card_end] will be empty. Before we 361 // update the top fields, we'll do a storestore to make sure that 362 // no thread sees the update to top before the zeroing of the 363 // object header and the BOT initialization. 364 OrderAccess::storestore(); 365 366 // Now that the BOT and the object header have been initialized, 367 // we can update top of the "starts humongous" region. 368 first_hr->set_top(MIN2(first_hr->end(), obj_top)); 369 if (_hr_printer.is_active()) { 370 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, first_hr->top()); 371 } 372 373 // Now, we will update the top fields of the "continues humongous" 374 // regions. 375 hr = NULL; 376 for (uint i = first + 1; i < last; ++i) { 377 hr = region_at(i); 378 if ((i + 1) == last) { 379 // last continues humongous region 380 assert(hr->bottom() < obj_top && obj_top <= hr->end(), 381 "new_top should fall on this region"); 382 hr->set_top(obj_top); 383 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, obj_top); 384 } else { 385 // not last one 386 assert(obj_top > hr->end(), "obj_top should be above this region"); 387 hr->set_top(hr->end()); 388 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 389 } 390 } 391 // If we have continues humongous regions (hr != NULL), its top should 392 // match obj_top. 393 assert(hr == NULL || (hr->top() == obj_top), "sanity"); 394 check_bitmaps("Humongous Region Allocation", first_hr); 395 396 increase_used(word_size * HeapWordSize); 397 398 for (uint i = first; i < last; ++i) { 399 _humongous_set.add(region_at(i)); 400 } 401 402 return new_obj; 403 } 404 405 // If could fit into free regions w/o expansion, try. 406 // Otherwise, if can expand, do so. 407 // Otherwise, if using ex regions might help, try with ex given back. 408 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 409 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 410 411 verify_region_sets_optional(); 412 413 uint first = G1_NO_HRM_INDEX; 414 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords); 415 416 if (obj_regions == 1) { 417 // Only one region to allocate, try to use a fast path by directly allocating 418 // from the free lists. Do not try to expand here, we will potentially do that 419 // later. 420 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 421 if (hr != NULL) { 422 first = hr->hrm_index(); 423 } 424 } else { 425 // We can't allocate humongous regions spanning more than one region while 426 // cleanupComplete() is running, since some of the regions we find to be 427 // empty might not yet be added to the free list. It is not straightforward 428 // to know in which list they are on so that we can remove them. We only 429 // need to do this if we need to allocate more than one region to satisfy the 430 // current humongous allocation request. If we are only allocating one region 431 // we use the one-region region allocation code (see above), that already 432 // potentially waits for regions from the secondary free list. 433 wait_while_free_regions_coming(); 434 append_secondary_free_list_if_not_empty_with_lock(); 435 436 // Policy: Try only empty regions (i.e. already committed first). Maybe we 437 // are lucky enough to find some. 438 first = _hrm.find_contiguous_only_empty(obj_regions); 439 if (first != G1_NO_HRM_INDEX) { 440 _hrm.allocate_free_regions_starting_at(first, obj_regions); 441 } 442 } 443 444 if (first == G1_NO_HRM_INDEX) { 445 // Policy: We could not find enough regions for the humongous object in the 446 // free list. Look through the heap to find a mix of free and uncommitted regions. 447 // If so, try expansion. 448 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 449 if (first != G1_NO_HRM_INDEX) { 450 // We found something. Make sure these regions are committed, i.e. expand 451 // the heap. Alternatively we could do a defragmentation GC. 452 ergo_verbose1(ErgoHeapSizing, 453 "attempt heap expansion", 454 ergo_format_reason("humongous allocation request failed") 455 ergo_format_byte("allocation request"), 456 word_size * HeapWordSize); 457 458 _hrm.expand_at(first, obj_regions); 459 g1_policy()->record_new_heap_size(num_regions()); 460 461 #ifdef ASSERT 462 for (uint i = first; i < first + obj_regions; ++i) { 463 HeapRegion* hr = region_at(i); 464 assert(hr->is_free(), "sanity"); 465 assert(hr->is_empty(), "sanity"); 466 assert(is_on_master_free_list(hr), "sanity"); 467 } 468 #endif 469 _hrm.allocate_free_regions_starting_at(first, obj_regions); 470 } else { 471 // Policy: Potentially trigger a defragmentation GC. 472 } 473 } 474 475 HeapWord* result = NULL; 476 if (first != G1_NO_HRM_INDEX) { 477 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 478 word_size, context); 479 assert(result != NULL, "it should always return a valid result"); 480 481 // A successful humongous object allocation changes the used space 482 // information of the old generation so we need to recalculate the 483 // sizes and update the jstat counters here. 484 g1mm()->update_sizes(); 485 } 486 487 verify_region_sets_optional(); 488 489 return result; 490 } 491 492 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 493 assert_heap_not_locked_and_not_at_safepoint(); 494 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 495 496 uint dummy_gc_count_before; 497 uint dummy_gclocker_retry_count = 0; 498 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 499 } 500 501 HeapWord* 502 G1CollectedHeap::mem_allocate(size_t word_size, 503 bool* gc_overhead_limit_was_exceeded) { 504 assert_heap_not_locked_and_not_at_safepoint(); 505 506 // Loop until the allocation is satisfied, or unsatisfied after GC. 507 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 508 uint gc_count_before; 509 510 HeapWord* result = NULL; 511 if (!is_humongous(word_size)) { 512 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 513 } else { 514 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 515 } 516 if (result != NULL) { 517 return result; 518 } 519 520 // Create the garbage collection operation... 521 VM_G1CollectForAllocation op(gc_count_before, word_size); 522 op.set_allocation_context(AllocationContext::current()); 523 524 // ...and get the VM thread to execute it. 525 VMThread::execute(&op); 526 527 if (op.prologue_succeeded() && op.pause_succeeded()) { 528 // If the operation was successful we'll return the result even 529 // if it is NULL. If the allocation attempt failed immediately 530 // after a Full GC, it's unlikely we'll be able to allocate now. 531 HeapWord* result = op.result(); 532 if (result != NULL && !is_humongous(word_size)) { 533 // Allocations that take place on VM operations do not do any 534 // card dirtying and we have to do it here. We only have to do 535 // this for non-humongous allocations, though. 536 dirty_young_block(result, word_size); 537 } 538 return result; 539 } else { 540 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 541 return NULL; 542 } 543 assert(op.result() == NULL, 544 "the result should be NULL if the VM op did not succeed"); 545 } 546 547 // Give a warning if we seem to be looping forever. 548 if ((QueuedAllocationWarningCount > 0) && 549 (try_count % QueuedAllocationWarningCount == 0)) { 550 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 551 } 552 } 553 554 ShouldNotReachHere(); 555 return NULL; 556 } 557 558 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 559 AllocationContext_t context, 560 uint* gc_count_before_ret, 561 uint* gclocker_retry_count_ret) { 562 // Make sure you read the note in attempt_allocation_humongous(). 563 564 assert_heap_not_locked_and_not_at_safepoint(); 565 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 566 "be called for humongous allocation requests"); 567 568 // We should only get here after the first-level allocation attempt 569 // (attempt_allocation()) failed to allocate. 570 571 // We will loop until a) we manage to successfully perform the 572 // allocation or b) we successfully schedule a collection which 573 // fails to perform the allocation. b) is the only case when we'll 574 // return NULL. 575 HeapWord* result = NULL; 576 for (int try_count = 1; /* we'll return */; try_count += 1) { 577 bool should_try_gc; 578 uint gc_count_before; 579 580 { 581 MutexLockerEx x(Heap_lock); 582 result = _allocator->attempt_allocation_locked(word_size, context); 583 if (result != NULL) { 584 return result; 585 } 586 587 if (GC_locker::is_active_and_needs_gc()) { 588 if (g1_policy()->can_expand_young_list()) { 589 // No need for an ergo verbose message here, 590 // can_expand_young_list() does this when it returns true. 591 result = _allocator->attempt_allocation_force(word_size, context); 592 if (result != NULL) { 593 return result; 594 } 595 } 596 should_try_gc = false; 597 } else { 598 // The GCLocker may not be active but the GCLocker initiated 599 // GC may not yet have been performed (GCLocker::needs_gc() 600 // returns true). In this case we do not try this GC and 601 // wait until the GCLocker initiated GC is performed, and 602 // then retry the allocation. 603 if (GC_locker::needs_gc()) { 604 should_try_gc = false; 605 } else { 606 // Read the GC count while still holding the Heap_lock. 607 gc_count_before = total_collections(); 608 should_try_gc = true; 609 } 610 } 611 } 612 613 if (should_try_gc) { 614 bool succeeded; 615 result = do_collection_pause(word_size, gc_count_before, &succeeded, 616 GCCause::_g1_inc_collection_pause); 617 if (result != NULL) { 618 assert(succeeded, "only way to get back a non-NULL result"); 619 return result; 620 } 621 622 if (succeeded) { 623 // If we get here we successfully scheduled a collection which 624 // failed to allocate. No point in trying to allocate 625 // further. We'll just return NULL. 626 MutexLockerEx x(Heap_lock); 627 *gc_count_before_ret = total_collections(); 628 return NULL; 629 } 630 } else { 631 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 632 MutexLockerEx x(Heap_lock); 633 *gc_count_before_ret = total_collections(); 634 return NULL; 635 } 636 // The GCLocker is either active or the GCLocker initiated 637 // GC has not yet been performed. Stall until it is and 638 // then retry the allocation. 639 GC_locker::stall_until_clear(); 640 (*gclocker_retry_count_ret) += 1; 641 } 642 643 // We can reach here if we were unsuccessful in scheduling a 644 // collection (because another thread beat us to it) or if we were 645 // stalled due to the GC locker. In either can we should retry the 646 // allocation attempt in case another thread successfully 647 // performed a collection and reclaimed enough space. We do the 648 // first attempt (without holding the Heap_lock) here and the 649 // follow-on attempt will be at the start of the next loop 650 // iteration (after taking the Heap_lock). 651 result = _allocator->attempt_allocation(word_size, context); 652 if (result != NULL) { 653 return result; 654 } 655 656 // Give a warning if we seem to be looping forever. 657 if ((QueuedAllocationWarningCount > 0) && 658 (try_count % QueuedAllocationWarningCount == 0)) { 659 warning("G1CollectedHeap::attempt_allocation_slow() " 660 "retries %d times", try_count); 661 } 662 } 663 664 ShouldNotReachHere(); 665 return NULL; 666 } 667 668 void G1CollectedHeap::begin_archive_alloc_range() { 669 assert_at_safepoint(true /* should_be_vm_thread */); 670 if (_archive_allocator == NULL) { 671 _archive_allocator = G1ArchiveAllocator::create_allocator(this); 672 } 673 } 674 675 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) { 676 // Allocations in archive regions cannot be of a size that would be considered 677 // humongous even for a minimum-sized region, because G1 region sizes/boundaries 678 // may be different at archive-restore time. 679 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words()); 680 } 681 682 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) { 683 assert_at_safepoint(true /* should_be_vm_thread */); 684 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 685 if (is_archive_alloc_too_large(word_size)) { 686 return NULL; 687 } 688 return _archive_allocator->archive_mem_allocate(word_size); 689 } 690 691 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 692 size_t end_alignment_in_bytes) { 693 assert_at_safepoint(true /* should_be_vm_thread */); 694 assert(_archive_allocator != NULL, "_archive_allocator not initialized"); 695 696 // Call complete_archive to do the real work, filling in the MemRegion 697 // array with the archive regions. 698 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes); 699 delete _archive_allocator; 700 _archive_allocator = NULL; 701 } 702 703 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) { 704 assert(ranges != NULL, "MemRegion array NULL"); 705 assert(count != 0, "No MemRegions provided"); 706 MemRegion reserved = _hrm.reserved(); 707 for (size_t i = 0; i < count; i++) { 708 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) { 709 return false; 710 } 711 } 712 return true; 713 } 714 715 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) { 716 assert(!is_init_completed(), "Expect to be called at JVM init time"); 717 assert(ranges != NULL, "MemRegion array NULL"); 718 assert(count != 0, "No MemRegions provided"); 719 MutexLockerEx x(Heap_lock); 720 721 MemRegion reserved = _hrm.reserved(); 722 HeapWord* prev_last_addr = NULL; 723 HeapRegion* prev_last_region = NULL; 724 725 // Temporarily disable pretouching of heap pages. This interface is used 726 // when mmap'ing archived heap data in, so pre-touching is wasted. 727 FlagSetting fs(AlwaysPreTouch, false); 728 729 // Enable archive object checking in G1MarkSweep. We have to let it know 730 // about each archive range, so that objects in those ranges aren't marked. 731 G1MarkSweep::enable_archive_object_check(); 732 733 // For each specified MemRegion range, allocate the corresponding G1 734 // regions and mark them as archive regions. We expect the ranges in 735 // ascending starting address order, without overlap. 736 for (size_t i = 0; i < count; i++) { 737 MemRegion curr_range = ranges[i]; 738 HeapWord* start_address = curr_range.start(); 739 size_t word_size = curr_range.word_size(); 740 HeapWord* last_address = curr_range.last(); 741 size_t commits = 0; 742 743 guarantee(reserved.contains(start_address) && reserved.contains(last_address), 744 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 745 p2i(start_address), p2i(last_address)); 746 guarantee(start_address > prev_last_addr, 747 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 748 p2i(start_address), p2i(prev_last_addr)); 749 prev_last_addr = last_address; 750 751 // Check for ranges that start in the same G1 region in which the previous 752 // range ended, and adjust the start address so we don't try to allocate 753 // the same region again. If the current range is entirely within that 754 // region, skip it, just adjusting the recorded top. 755 HeapRegion* start_region = _hrm.addr_to_region(start_address); 756 if ((prev_last_region != NULL) && (start_region == prev_last_region)) { 757 start_address = start_region->end(); 758 if (start_address > last_address) { 759 increase_used(word_size * HeapWordSize); 760 start_region->set_top(last_address + 1); 761 continue; 762 } 763 start_region->set_top(start_address); 764 curr_range = MemRegion(start_address, last_address + 1); 765 start_region = _hrm.addr_to_region(start_address); 766 } 767 768 // Perform the actual region allocation, exiting if it fails. 769 // Then note how much new space we have allocated. 770 if (!_hrm.allocate_containing_regions(curr_range, &commits)) { 771 return false; 772 } 773 increase_used(word_size * HeapWordSize); 774 if (commits != 0) { 775 ergo_verbose1(ErgoHeapSizing, 776 "attempt heap expansion", 777 ergo_format_reason("allocate archive regions") 778 ergo_format_byte("total size"), 779 HeapRegion::GrainWords * HeapWordSize * commits); 780 } 781 782 // Mark each G1 region touched by the range as archive, add it to the old set, 783 // and set the allocation context and top. 784 HeapRegion* curr_region = _hrm.addr_to_region(start_address); 785 HeapRegion* last_region = _hrm.addr_to_region(last_address); 786 prev_last_region = last_region; 787 788 while (curr_region != NULL) { 789 assert(curr_region->is_empty() && !curr_region->is_pinned(), 790 "Region already in use (index %u)", curr_region->hrm_index()); 791 _hr_printer.alloc(curr_region, G1HRPrinter::Archive); 792 curr_region->set_allocation_context(AllocationContext::system()); 793 curr_region->set_archive(); 794 _old_set.add(curr_region); 795 if (curr_region != last_region) { 796 curr_region->set_top(curr_region->end()); 797 curr_region = _hrm.next_region_in_heap(curr_region); 798 } else { 799 curr_region->set_top(last_address + 1); 800 curr_region = NULL; 801 } 802 } 803 804 // Notify mark-sweep of the archive range. 805 G1MarkSweep::set_range_archive(curr_range, true); 806 } 807 return true; 808 } 809 810 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) { 811 assert(!is_init_completed(), "Expect to be called at JVM init time"); 812 assert(ranges != NULL, "MemRegion array NULL"); 813 assert(count != 0, "No MemRegions provided"); 814 MemRegion reserved = _hrm.reserved(); 815 HeapWord *prev_last_addr = NULL; 816 HeapRegion* prev_last_region = NULL; 817 818 // For each MemRegion, create filler objects, if needed, in the G1 regions 819 // that contain the address range. The address range actually within the 820 // MemRegion will not be modified. That is assumed to have been initialized 821 // elsewhere, probably via an mmap of archived heap data. 822 MutexLockerEx x(Heap_lock); 823 for (size_t i = 0; i < count; i++) { 824 HeapWord* start_address = ranges[i].start(); 825 HeapWord* last_address = ranges[i].last(); 826 827 assert(reserved.contains(start_address) && reserved.contains(last_address), 828 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 829 p2i(start_address), p2i(last_address)); 830 assert(start_address > prev_last_addr, 831 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 832 p2i(start_address), p2i(prev_last_addr)); 833 834 HeapRegion* start_region = _hrm.addr_to_region(start_address); 835 HeapRegion* last_region = _hrm.addr_to_region(last_address); 836 HeapWord* bottom_address = start_region->bottom(); 837 838 // Check for a range beginning in the same region in which the 839 // previous one ended. 840 if (start_region == prev_last_region) { 841 bottom_address = prev_last_addr + 1; 842 } 843 844 // Verify that the regions were all marked as archive regions by 845 // alloc_archive_regions. 846 HeapRegion* curr_region = start_region; 847 while (curr_region != NULL) { 848 guarantee(curr_region->is_archive(), 849 "Expected archive region at index %u", curr_region->hrm_index()); 850 if (curr_region != last_region) { 851 curr_region = _hrm.next_region_in_heap(curr_region); 852 } else { 853 curr_region = NULL; 854 } 855 } 856 857 prev_last_addr = last_address; 858 prev_last_region = last_region; 859 860 // Fill the memory below the allocated range with dummy object(s), 861 // if the region bottom does not match the range start, or if the previous 862 // range ended within the same G1 region, and there is a gap. 863 if (start_address != bottom_address) { 864 size_t fill_size = pointer_delta(start_address, bottom_address); 865 G1CollectedHeap::fill_with_objects(bottom_address, fill_size); 866 increase_used(fill_size * HeapWordSize); 867 } 868 } 869 } 870 871 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size, 872 uint* gc_count_before_ret, 873 uint* gclocker_retry_count_ret) { 874 assert_heap_not_locked_and_not_at_safepoint(); 875 assert(!is_humongous(word_size), "attempt_allocation() should not " 876 "be called for humongous allocation requests"); 877 878 AllocationContext_t context = AllocationContext::current(); 879 HeapWord* result = _allocator->attempt_allocation(word_size, context); 880 881 if (result == NULL) { 882 result = attempt_allocation_slow(word_size, 883 context, 884 gc_count_before_ret, 885 gclocker_retry_count_ret); 886 } 887 assert_heap_not_locked(); 888 if (result != NULL) { 889 dirty_young_block(result, word_size); 890 } 891 return result; 892 } 893 894 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) { 895 assert(!is_init_completed(), "Expect to be called at JVM init time"); 896 assert(ranges != NULL, "MemRegion array NULL"); 897 assert(count != 0, "No MemRegions provided"); 898 MemRegion reserved = _hrm.reserved(); 899 HeapWord* prev_last_addr = NULL; 900 HeapRegion* prev_last_region = NULL; 901 size_t size_used = 0; 902 size_t uncommitted_regions = 0; 903 904 // For each Memregion, free the G1 regions that constitute it, and 905 // notify mark-sweep that the range is no longer to be considered 'archive.' 906 MutexLockerEx x(Heap_lock); 907 for (size_t i = 0; i < count; i++) { 908 HeapWord* start_address = ranges[i].start(); 909 HeapWord* last_address = ranges[i].last(); 910 911 assert(reserved.contains(start_address) && reserved.contains(last_address), 912 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]", 913 p2i(start_address), p2i(last_address)); 914 assert(start_address > prev_last_addr, 915 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT , 916 p2i(start_address), p2i(prev_last_addr)); 917 size_used += ranges[i].byte_size(); 918 prev_last_addr = last_address; 919 920 HeapRegion* start_region = _hrm.addr_to_region(start_address); 921 HeapRegion* last_region = _hrm.addr_to_region(last_address); 922 923 // Check for ranges that start in the same G1 region in which the previous 924 // range ended, and adjust the start address so we don't try to free 925 // the same region again. If the current range is entirely within that 926 // region, skip it. 927 if (start_region == prev_last_region) { 928 start_address = start_region->end(); 929 if (start_address > last_address) { 930 continue; 931 } 932 start_region = _hrm.addr_to_region(start_address); 933 } 934 prev_last_region = last_region; 935 936 // After verifying that each region was marked as an archive region by 937 // alloc_archive_regions, set it free and empty and uncommit it. 938 HeapRegion* curr_region = start_region; 939 while (curr_region != NULL) { 940 guarantee(curr_region->is_archive(), 941 "Expected archive region at index %u", curr_region->hrm_index()); 942 uint curr_index = curr_region->hrm_index(); 943 _old_set.remove(curr_region); 944 curr_region->set_free(); 945 curr_region->set_top(curr_region->bottom()); 946 if (curr_region != last_region) { 947 curr_region = _hrm.next_region_in_heap(curr_region); 948 } else { 949 curr_region = NULL; 950 } 951 _hrm.shrink_at(curr_index, 1); 952 uncommitted_regions++; 953 } 954 955 // Notify mark-sweep that this is no longer an archive range. 956 G1MarkSweep::set_range_archive(ranges[i], false); 957 } 958 959 if (uncommitted_regions != 0) { 960 ergo_verbose1(ErgoHeapSizing, 961 "attempt heap shrinking", 962 ergo_format_reason("uncommitted archive regions") 963 ergo_format_byte("total size"), 964 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions); 965 } 966 decrease_used(size_used); 967 } 968 969 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 970 uint* gc_count_before_ret, 971 uint* gclocker_retry_count_ret) { 972 // The structure of this method has a lot of similarities to 973 // attempt_allocation_slow(). The reason these two were not merged 974 // into a single one is that such a method would require several "if 975 // allocation is not humongous do this, otherwise do that" 976 // conditional paths which would obscure its flow. In fact, an early 977 // version of this code did use a unified method which was harder to 978 // follow and, as a result, it had subtle bugs that were hard to 979 // track down. So keeping these two methods separate allows each to 980 // be more readable. It will be good to keep these two in sync as 981 // much as possible. 982 983 assert_heap_not_locked_and_not_at_safepoint(); 984 assert(is_humongous(word_size), "attempt_allocation_humongous() " 985 "should only be called for humongous allocations"); 986 987 // Humongous objects can exhaust the heap quickly, so we should check if we 988 // need to start a marking cycle at each humongous object allocation. We do 989 // the check before we do the actual allocation. The reason for doing it 990 // before the allocation is that we avoid having to keep track of the newly 991 // allocated memory while we do a GC. 992 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 993 word_size)) { 994 collect(GCCause::_g1_humongous_allocation); 995 } 996 997 // We will loop until a) we manage to successfully perform the 998 // allocation or b) we successfully schedule a collection which 999 // fails to perform the allocation. b) is the only case when we'll 1000 // return NULL. 1001 HeapWord* result = NULL; 1002 for (int try_count = 1; /* we'll return */; try_count += 1) { 1003 bool should_try_gc; 1004 uint gc_count_before; 1005 1006 { 1007 MutexLockerEx x(Heap_lock); 1008 1009 // Given that humongous objects are not allocated in young 1010 // regions, we'll first try to do the allocation without doing a 1011 // collection hoping that there's enough space in the heap. 1012 result = humongous_obj_allocate(word_size, AllocationContext::current()); 1013 if (result != NULL) { 1014 return result; 1015 } 1016 1017 if (GC_locker::is_active_and_needs_gc()) { 1018 should_try_gc = false; 1019 } else { 1020 // The GCLocker may not be active but the GCLocker initiated 1021 // GC may not yet have been performed (GCLocker::needs_gc() 1022 // returns true). In this case we do not try this GC and 1023 // wait until the GCLocker initiated GC is performed, and 1024 // then retry the allocation. 1025 if (GC_locker::needs_gc()) { 1026 should_try_gc = false; 1027 } else { 1028 // Read the GC count while still holding the Heap_lock. 1029 gc_count_before = total_collections(); 1030 should_try_gc = true; 1031 } 1032 } 1033 } 1034 1035 if (should_try_gc) { 1036 // If we failed to allocate the humongous object, we should try to 1037 // do a collection pause (if we're allowed) in case it reclaims 1038 // enough space for the allocation to succeed after the pause. 1039 1040 bool succeeded; 1041 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1042 GCCause::_g1_humongous_allocation); 1043 if (result != NULL) { 1044 assert(succeeded, "only way to get back a non-NULL result"); 1045 return result; 1046 } 1047 1048 if (succeeded) { 1049 // If we get here we successfully scheduled a collection which 1050 // failed to allocate. No point in trying to allocate 1051 // further. We'll just return NULL. 1052 MutexLockerEx x(Heap_lock); 1053 *gc_count_before_ret = total_collections(); 1054 return NULL; 1055 } 1056 } else { 1057 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1058 MutexLockerEx x(Heap_lock); 1059 *gc_count_before_ret = total_collections(); 1060 return NULL; 1061 } 1062 // The GCLocker is either active or the GCLocker initiated 1063 // GC has not yet been performed. Stall until it is and 1064 // then retry the allocation. 1065 GC_locker::stall_until_clear(); 1066 (*gclocker_retry_count_ret) += 1; 1067 } 1068 1069 // We can reach here if we were unsuccessful in scheduling a 1070 // collection (because another thread beat us to it) or if we were 1071 // stalled due to the GC locker. In either can we should retry the 1072 // allocation attempt in case another thread successfully 1073 // performed a collection and reclaimed enough space. Give a 1074 // warning if we seem to be looping forever. 1075 1076 if ((QueuedAllocationWarningCount > 0) && 1077 (try_count % QueuedAllocationWarningCount == 0)) { 1078 warning("G1CollectedHeap::attempt_allocation_humongous() " 1079 "retries %d times", try_count); 1080 } 1081 } 1082 1083 ShouldNotReachHere(); 1084 return NULL; 1085 } 1086 1087 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1088 AllocationContext_t context, 1089 bool expect_null_mutator_alloc_region) { 1090 assert_at_safepoint(true /* should_be_vm_thread */); 1091 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region, 1092 "the current alloc region was unexpectedly found to be non-NULL"); 1093 1094 if (!is_humongous(word_size)) { 1095 return _allocator->attempt_allocation_locked(word_size, context); 1096 } else { 1097 HeapWord* result = humongous_obj_allocate(word_size, context); 1098 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1099 collector_state()->set_initiate_conc_mark_if_possible(true); 1100 } 1101 return result; 1102 } 1103 1104 ShouldNotReachHere(); 1105 } 1106 1107 class PostMCRemSetClearClosure: public HeapRegionClosure { 1108 G1CollectedHeap* _g1h; 1109 ModRefBarrierSet* _mr_bs; 1110 public: 1111 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1112 _g1h(g1h), _mr_bs(mr_bs) {} 1113 1114 bool doHeapRegion(HeapRegion* r) { 1115 HeapRegionRemSet* hrrs = r->rem_set(); 1116 1117 _g1h->reset_gc_time_stamps(r); 1118 1119 if (r->is_continues_humongous()) { 1120 // We'll assert that the strong code root list and RSet is empty 1121 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1122 assert(hrrs->occupied() == 0, "RSet should be empty"); 1123 } else { 1124 hrrs->clear(); 1125 } 1126 // You might think here that we could clear just the cards 1127 // corresponding to the used region. But no: if we leave a dirty card 1128 // in a region we might allocate into, then it would prevent that card 1129 // from being enqueued, and cause it to be missed. 1130 // Re: the performance cost: we shouldn't be doing full GC anyway! 1131 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1132 1133 return false; 1134 } 1135 }; 1136 1137 void G1CollectedHeap::clear_rsets_post_compaction() { 1138 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1139 heap_region_iterate(&rs_clear); 1140 } 1141 1142 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1143 G1CollectedHeap* _g1h; 1144 UpdateRSOopClosure _cl; 1145 public: 1146 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) : 1147 _cl(g1->g1_rem_set(), worker_i), 1148 _g1h(g1) 1149 { } 1150 1151 bool doHeapRegion(HeapRegion* r) { 1152 if (!r->is_continues_humongous()) { 1153 _cl.set_from(r); 1154 r->oop_iterate(&_cl); 1155 } 1156 return false; 1157 } 1158 }; 1159 1160 class ParRebuildRSTask: public AbstractGangTask { 1161 G1CollectedHeap* _g1; 1162 HeapRegionClaimer _hrclaimer; 1163 1164 public: 1165 ParRebuildRSTask(G1CollectedHeap* g1) : 1166 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1167 1168 void work(uint worker_id) { 1169 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1170 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1171 } 1172 }; 1173 1174 class PostCompactionPrinterClosure: public HeapRegionClosure { 1175 private: 1176 G1HRPrinter* _hr_printer; 1177 public: 1178 bool doHeapRegion(HeapRegion* hr) { 1179 assert(!hr->is_young(), "not expecting to find young regions"); 1180 if (hr->is_free()) { 1181 // We only generate output for non-empty regions. 1182 } else if (hr->is_starts_humongous()) { 1183 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1184 } else if (hr->is_continues_humongous()) { 1185 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1186 } else if (hr->is_archive()) { 1187 _hr_printer->post_compaction(hr, G1HRPrinter::Archive); 1188 } else if (hr->is_old()) { 1189 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1190 } else { 1191 ShouldNotReachHere(); 1192 } 1193 return false; 1194 } 1195 1196 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1197 : _hr_printer(hr_printer) { } 1198 }; 1199 1200 void G1CollectedHeap::print_hrm_post_compaction() { 1201 PostCompactionPrinterClosure cl(hr_printer()); 1202 heap_region_iterate(&cl); 1203 } 1204 1205 bool G1CollectedHeap::do_collection(bool explicit_gc, 1206 bool clear_all_soft_refs, 1207 size_t word_size) { 1208 assert_at_safepoint(true /* should_be_vm_thread */); 1209 1210 if (GC_locker::check_active_before_gc()) { 1211 return false; 1212 } 1213 1214 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1215 gc_timer->register_gc_start(); 1216 1217 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1218 GCIdMark gc_id_mark; 1219 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1220 1221 SvcGCMarker sgcm(SvcGCMarker::FULL); 1222 ResourceMark rm; 1223 1224 G1Log::update_level(); 1225 print_heap_before_gc(); 1226 trace_heap_before_gc(gc_tracer); 1227 1228 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1229 1230 verify_region_sets_optional(); 1231 1232 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1233 collector_policy()->should_clear_all_soft_refs(); 1234 1235 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1236 1237 { 1238 IsGCActiveMark x; 1239 1240 // Timing 1241 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant"); 1242 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 1243 1244 { 1245 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL); 1246 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1247 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1248 1249 g1_policy()->record_full_collection_start(); 1250 1251 // Note: When we have a more flexible GC logging framework that 1252 // allows us to add optional attributes to a GC log record we 1253 // could consider timing and reporting how long we wait in the 1254 // following two methods. 1255 wait_while_free_regions_coming(); 1256 // If we start the compaction before the CM threads finish 1257 // scanning the root regions we might trip them over as we'll 1258 // be moving objects / updating references. So let's wait until 1259 // they are done. By telling them to abort, they should complete 1260 // early. 1261 _cm->root_regions()->abort(); 1262 _cm->root_regions()->wait_until_scan_finished(); 1263 append_secondary_free_list_if_not_empty_with_lock(); 1264 1265 gc_prologue(true); 1266 increment_total_collections(true /* full gc */); 1267 increment_old_marking_cycles_started(); 1268 1269 assert(used() == recalculate_used(), "Should be equal"); 1270 1271 verify_before_gc(); 1272 1273 check_bitmaps("Full GC Start"); 1274 pre_full_gc_dump(gc_timer); 1275 1276 #if defined(COMPILER2) || INCLUDE_JVMCI 1277 DerivedPointerTable::clear(); 1278 #endif 1279 1280 // Disable discovery and empty the discovered lists 1281 // for the CM ref processor. 1282 ref_processor_cm()->disable_discovery(); 1283 ref_processor_cm()->abandon_partial_discovery(); 1284 ref_processor_cm()->verify_no_references_recorded(); 1285 1286 // Abandon current iterations of concurrent marking and concurrent 1287 // refinement, if any are in progress. We have to do this before 1288 // wait_until_scan_finished() below. 1289 concurrent_mark()->abort(); 1290 1291 // Make sure we'll choose a new allocation region afterwards. 1292 _allocator->release_mutator_alloc_region(); 1293 _allocator->abandon_gc_alloc_regions(); 1294 g1_rem_set()->cleanupHRRS(); 1295 1296 // We should call this after we retire any currently active alloc 1297 // regions so that all the ALLOC / RETIRE events are generated 1298 // before the start GC event. 1299 _hr_printer.start_gc(true /* full */, (size_t) total_collections()); 1300 1301 // We may have added regions to the current incremental collection 1302 // set between the last GC or pause and now. We need to clear the 1303 // incremental collection set and then start rebuilding it afresh 1304 // after this full GC. 1305 abandon_collection_set(g1_policy()->inc_cset_head()); 1306 g1_policy()->clear_incremental_cset(); 1307 g1_policy()->stop_incremental_cset_building(); 1308 1309 tear_down_region_sets(false /* free_list_only */); 1310 collector_state()->set_gcs_are_young(true); 1311 1312 // See the comments in g1CollectedHeap.hpp and 1313 // G1CollectedHeap::ref_processing_init() about 1314 // how reference processing currently works in G1. 1315 1316 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1317 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1318 1319 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1320 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1321 1322 ref_processor_stw()->enable_discovery(); 1323 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1324 1325 // Do collection work 1326 { 1327 HandleMark hm; // Discard invalid handles created during gc 1328 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1329 } 1330 1331 assert(num_free_regions() == 0, "we should not have added any free regions"); 1332 rebuild_region_sets(false /* free_list_only */); 1333 1334 // Enqueue any discovered reference objects that have 1335 // not been removed from the discovered lists. 1336 ref_processor_stw()->enqueue_discovered_references(); 1337 1338 #if defined(COMPILER2) || INCLUDE_JVMCI 1339 DerivedPointerTable::update_pointers(); 1340 #endif 1341 1342 MemoryService::track_memory_usage(); 1343 1344 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1345 ref_processor_stw()->verify_no_references_recorded(); 1346 1347 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1348 ClassLoaderDataGraph::purge(); 1349 MetaspaceAux::verify_metrics(); 1350 1351 // Note: since we've just done a full GC, concurrent 1352 // marking is no longer active. Therefore we need not 1353 // re-enable reference discovery for the CM ref processor. 1354 // That will be done at the start of the next marking cycle. 1355 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1356 ref_processor_cm()->verify_no_references_recorded(); 1357 1358 reset_gc_time_stamp(); 1359 // Since everything potentially moved, we will clear all remembered 1360 // sets, and clear all cards. Later we will rebuild remembered 1361 // sets. We will also reset the GC time stamps of the regions. 1362 clear_rsets_post_compaction(); 1363 check_gc_time_stamps(); 1364 1365 // Resize the heap if necessary. 1366 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); 1367 1368 if (_hr_printer.is_active()) { 1369 // We should do this after we potentially resize the heap so 1370 // that all the COMMIT / UNCOMMIT events are generated before 1371 // the end GC event. 1372 1373 print_hrm_post_compaction(); 1374 _hr_printer.end_gc(true /* full */, (size_t) total_collections()); 1375 } 1376 1377 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1378 if (hot_card_cache->use_cache()) { 1379 hot_card_cache->reset_card_counts(); 1380 hot_card_cache->reset_hot_cache(); 1381 } 1382 1383 // Rebuild remembered sets of all regions. 1384 uint n_workers = 1385 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1386 workers()->active_workers(), 1387 Threads::number_of_non_daemon_threads()); 1388 workers()->set_active_workers(n_workers); 1389 1390 ParRebuildRSTask rebuild_rs_task(this); 1391 workers()->run_task(&rebuild_rs_task); 1392 1393 // Rebuild the strong code root lists for each region 1394 rebuild_strong_code_roots(); 1395 1396 if (true) { // FIXME 1397 MetaspaceGC::compute_new_size(); 1398 } 1399 1400 #ifdef TRACESPINNING 1401 ParallelTaskTerminator::print_termination_counts(); 1402 #endif 1403 1404 // Discard all rset updates 1405 JavaThread::dirty_card_queue_set().abandon_logs(); 1406 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1407 1408 _young_list->reset_sampled_info(); 1409 // At this point there should be no regions in the 1410 // entire heap tagged as young. 1411 assert(check_young_list_empty(true /* check_heap */), 1412 "young list should be empty at this point"); 1413 1414 // Update the number of full collections that have been completed. 1415 increment_old_marking_cycles_completed(false /* concurrent */); 1416 1417 _hrm.verify_optional(); 1418 verify_region_sets_optional(); 1419 1420 verify_after_gc(); 1421 1422 // Clear the previous marking bitmap, if needed for bitmap verification. 1423 // Note we cannot do this when we clear the next marking bitmap in 1424 // ConcurrentMark::abort() above since VerifyDuringGC verifies the 1425 // objects marked during a full GC against the previous bitmap. 1426 // But we need to clear it before calling check_bitmaps below since 1427 // the full GC has compacted objects and updated TAMS but not updated 1428 // the prev bitmap. 1429 if (G1VerifyBitmaps) { 1430 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll(); 1431 } 1432 check_bitmaps("Full GC End"); 1433 1434 // Start a new incremental collection set for the next pause 1435 assert(g1_policy()->collection_set() == NULL, "must be"); 1436 g1_policy()->start_incremental_cset_building(); 1437 1438 clear_cset_fast_test(); 1439 1440 _allocator->init_mutator_alloc_region(); 1441 1442 g1_policy()->record_full_collection_end(); 1443 1444 if (G1Log::fine()) { 1445 g1_policy()->print_heap_transition(); 1446 } 1447 1448 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1449 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1450 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1451 // before any GC notifications are raised. 1452 g1mm()->update_sizes(); 1453 1454 gc_epilogue(true); 1455 } 1456 1457 if (G1Log::finer()) { 1458 g1_policy()->print_detailed_heap_transition(true /* full */); 1459 } 1460 1461 print_heap_after_gc(); 1462 trace_heap_after_gc(gc_tracer); 1463 1464 post_full_gc_dump(gc_timer); 1465 1466 gc_timer->register_gc_end(); 1467 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1468 } 1469 1470 return true; 1471 } 1472 1473 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1474 // do_collection() will return whether it succeeded in performing 1475 // the GC. Currently, there is no facility on the 1476 // do_full_collection() API to notify the caller than the collection 1477 // did not succeed (e.g., because it was locked out by the GC 1478 // locker). So, right now, we'll ignore the return value. 1479 bool dummy = do_collection(true, /* explicit_gc */ 1480 clear_all_soft_refs, 1481 0 /* word_size */); 1482 } 1483 1484 // This code is mostly copied from TenuredGeneration. 1485 void 1486 G1CollectedHeap:: 1487 resize_if_necessary_after_full_collection(size_t word_size) { 1488 // Include the current allocation, if any, and bytes that will be 1489 // pre-allocated to support collections, as "used". 1490 const size_t used_after_gc = used(); 1491 const size_t capacity_after_gc = capacity(); 1492 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1493 1494 // This is enforced in arguments.cpp. 1495 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1496 "otherwise the code below doesn't make sense"); 1497 1498 // We don't have floating point command-line arguments 1499 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1500 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1501 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1502 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1503 1504 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1505 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1506 1507 // We have to be careful here as these two calculations can overflow 1508 // 32-bit size_t's. 1509 double used_after_gc_d = (double) used_after_gc; 1510 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1511 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1512 1513 // Let's make sure that they are both under the max heap size, which 1514 // by default will make them fit into a size_t. 1515 double desired_capacity_upper_bound = (double) max_heap_size; 1516 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1517 desired_capacity_upper_bound); 1518 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1519 desired_capacity_upper_bound); 1520 1521 // We can now safely turn them into size_t's. 1522 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1523 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1524 1525 // This assert only makes sense here, before we adjust them 1526 // with respect to the min and max heap size. 1527 assert(minimum_desired_capacity <= maximum_desired_capacity, 1528 "minimum_desired_capacity = " SIZE_FORMAT ", " 1529 "maximum_desired_capacity = " SIZE_FORMAT, 1530 minimum_desired_capacity, maximum_desired_capacity); 1531 1532 // Should not be greater than the heap max size. No need to adjust 1533 // it with respect to the heap min size as it's a lower bound (i.e., 1534 // we'll try to make the capacity larger than it, not smaller). 1535 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1536 // Should not be less than the heap min size. No need to adjust it 1537 // with respect to the heap max size as it's an upper bound (i.e., 1538 // we'll try to make the capacity smaller than it, not greater). 1539 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1540 1541 if (capacity_after_gc < minimum_desired_capacity) { 1542 // Don't expand unless it's significant 1543 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1544 ergo_verbose4(ErgoHeapSizing, 1545 "attempt heap expansion", 1546 ergo_format_reason("capacity lower than " 1547 "min desired capacity after Full GC") 1548 ergo_format_byte("capacity") 1549 ergo_format_byte("occupancy") 1550 ergo_format_byte_perc("min desired capacity"), 1551 capacity_after_gc, used_after_gc, 1552 minimum_desired_capacity, (double) MinHeapFreeRatio); 1553 expand(expand_bytes); 1554 1555 // No expansion, now see if we want to shrink 1556 } else if (capacity_after_gc > maximum_desired_capacity) { 1557 // Capacity too large, compute shrinking size 1558 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1559 ergo_verbose4(ErgoHeapSizing, 1560 "attempt heap shrinking", 1561 ergo_format_reason("capacity higher than " 1562 "max desired capacity after Full GC") 1563 ergo_format_byte("capacity") 1564 ergo_format_byte("occupancy") 1565 ergo_format_byte_perc("max desired capacity"), 1566 capacity_after_gc, used_after_gc, 1567 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1568 shrink(shrink_bytes); 1569 } 1570 } 1571 1572 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size, 1573 AllocationContext_t context, 1574 bool do_gc, 1575 bool clear_all_soft_refs, 1576 bool expect_null_mutator_alloc_region, 1577 bool* gc_succeeded) { 1578 *gc_succeeded = true; 1579 // Let's attempt the allocation first. 1580 HeapWord* result = 1581 attempt_allocation_at_safepoint(word_size, 1582 context, 1583 expect_null_mutator_alloc_region); 1584 if (result != NULL) { 1585 assert(*gc_succeeded, "sanity"); 1586 return result; 1587 } 1588 1589 // In a G1 heap, we're supposed to keep allocation from failing by 1590 // incremental pauses. Therefore, at least for now, we'll favor 1591 // expansion over collection. (This might change in the future if we can 1592 // do something smarter than full collection to satisfy a failed alloc.) 1593 result = expand_and_allocate(word_size, context); 1594 if (result != NULL) { 1595 assert(*gc_succeeded, "sanity"); 1596 return result; 1597 } 1598 1599 if (do_gc) { 1600 // Expansion didn't work, we'll try to do a Full GC. 1601 *gc_succeeded = do_collection(false, /* explicit_gc */ 1602 clear_all_soft_refs, 1603 word_size); 1604 } 1605 1606 return NULL; 1607 } 1608 1609 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1610 AllocationContext_t context, 1611 bool* succeeded) { 1612 assert_at_safepoint(true /* should_be_vm_thread */); 1613 1614 // Attempts to allocate followed by Full GC. 1615 HeapWord* result = 1616 satisfy_failed_allocation_helper(word_size, 1617 context, 1618 true, /* do_gc */ 1619 false, /* clear_all_soft_refs */ 1620 false, /* expect_null_mutator_alloc_region */ 1621 succeeded); 1622 1623 if (result != NULL || !*succeeded) { 1624 return result; 1625 } 1626 1627 // Attempts to allocate followed by Full GC that will collect all soft references. 1628 result = satisfy_failed_allocation_helper(word_size, 1629 context, 1630 true, /* do_gc */ 1631 true, /* clear_all_soft_refs */ 1632 true, /* expect_null_mutator_alloc_region */ 1633 succeeded); 1634 1635 if (result != NULL || !*succeeded) { 1636 return result; 1637 } 1638 1639 // Attempts to allocate, no GC 1640 result = satisfy_failed_allocation_helper(word_size, 1641 context, 1642 false, /* do_gc */ 1643 false, /* clear_all_soft_refs */ 1644 true, /* expect_null_mutator_alloc_region */ 1645 succeeded); 1646 1647 if (result != NULL) { 1648 assert(*succeeded, "sanity"); 1649 return result; 1650 } 1651 1652 assert(!collector_policy()->should_clear_all_soft_refs(), 1653 "Flag should have been handled and cleared prior to this point"); 1654 1655 // What else? We might try synchronous finalization later. If the total 1656 // space available is large enough for the allocation, then a more 1657 // complete compaction phase than we've tried so far might be 1658 // appropriate. 1659 assert(*succeeded, "sanity"); 1660 return NULL; 1661 } 1662 1663 // Attempting to expand the heap sufficiently 1664 // to support an allocation of the given "word_size". If 1665 // successful, perform the allocation and return the address of the 1666 // allocated block, or else "NULL". 1667 1668 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1669 assert_at_safepoint(true /* should_be_vm_thread */); 1670 1671 verify_region_sets_optional(); 1672 1673 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1674 ergo_verbose1(ErgoHeapSizing, 1675 "attempt heap expansion", 1676 ergo_format_reason("allocation request failed") 1677 ergo_format_byte("allocation request"), 1678 word_size * HeapWordSize); 1679 if (expand(expand_bytes)) { 1680 _hrm.verify_optional(); 1681 verify_region_sets_optional(); 1682 return attempt_allocation_at_safepoint(word_size, 1683 context, 1684 false /* expect_null_mutator_alloc_region */); 1685 } 1686 return NULL; 1687 } 1688 1689 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) { 1690 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1691 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1692 HeapRegion::GrainBytes); 1693 ergo_verbose2(ErgoHeapSizing, 1694 "expand the heap", 1695 ergo_format_byte("requested expansion amount") 1696 ergo_format_byte("attempted expansion amount"), 1697 expand_bytes, aligned_expand_bytes); 1698 1699 if (is_maximal_no_gc()) { 1700 ergo_verbose0(ErgoHeapSizing, 1701 "did not expand the heap", 1702 ergo_format_reason("heap already fully expanded")); 1703 return false; 1704 } 1705 1706 double expand_heap_start_time_sec = os::elapsedTime(); 1707 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1708 assert(regions_to_expand > 0, "Must expand by at least one region"); 1709 1710 uint expanded_by = _hrm.expand_by(regions_to_expand); 1711 if (expand_time_ms != NULL) { 1712 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS; 1713 } 1714 1715 if (expanded_by > 0) { 1716 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1717 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1718 g1_policy()->record_new_heap_size(num_regions()); 1719 } else { 1720 ergo_verbose0(ErgoHeapSizing, 1721 "did not expand the heap", 1722 ergo_format_reason("heap expansion operation failed")); 1723 // The expansion of the virtual storage space was unsuccessful. 1724 // Let's see if it was because we ran out of swap. 1725 if (G1ExitOnExpansionFailure && 1726 _hrm.available() >= regions_to_expand) { 1727 // We had head room... 1728 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1729 } 1730 } 1731 return regions_to_expand > 0; 1732 } 1733 1734 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1735 size_t aligned_shrink_bytes = 1736 ReservedSpace::page_align_size_down(shrink_bytes); 1737 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1738 HeapRegion::GrainBytes); 1739 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1740 1741 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1742 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1743 1744 ergo_verbose3(ErgoHeapSizing, 1745 "shrink the heap", 1746 ergo_format_byte("requested shrinking amount") 1747 ergo_format_byte("aligned shrinking amount") 1748 ergo_format_byte("attempted shrinking amount"), 1749 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1750 if (num_regions_removed > 0) { 1751 g1_policy()->record_new_heap_size(num_regions()); 1752 } else { 1753 ergo_verbose0(ErgoHeapSizing, 1754 "did not shrink the heap", 1755 ergo_format_reason("heap shrinking operation failed")); 1756 } 1757 } 1758 1759 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1760 verify_region_sets_optional(); 1761 1762 // We should only reach here at the end of a Full GC which means we 1763 // should not not be holding to any GC alloc regions. The method 1764 // below will make sure of that and do any remaining clean up. 1765 _allocator->abandon_gc_alloc_regions(); 1766 1767 // Instead of tearing down / rebuilding the free lists here, we 1768 // could instead use the remove_all_pending() method on free_list to 1769 // remove only the ones that we need to remove. 1770 tear_down_region_sets(true /* free_list_only */); 1771 shrink_helper(shrink_bytes); 1772 rebuild_region_sets(true /* free_list_only */); 1773 1774 _hrm.verify_optional(); 1775 verify_region_sets_optional(); 1776 } 1777 1778 // Public methods. 1779 1780 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1781 CollectedHeap(), 1782 _g1_policy(policy_), 1783 _dirty_card_queue_set(false), 1784 _is_alive_closure_cm(this), 1785 _is_alive_closure_stw(this), 1786 _ref_processor_cm(NULL), 1787 _ref_processor_stw(NULL), 1788 _bot_shared(NULL), 1789 _cg1r(NULL), 1790 _g1mm(NULL), 1791 _refine_cte_cl(NULL), 1792 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1793 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1794 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1795 _humongous_reclaim_candidates(), 1796 _has_humongous_reclaim_candidates(false), 1797 _archive_allocator(NULL), 1798 _free_regions_coming(false), 1799 _young_list(new YoungList(this)), 1800 _gc_time_stamp(0), 1801 _summary_bytes_used(0), 1802 _survivor_evac_stats(YoungPLABSize, PLABWeight), 1803 _old_evac_stats(OldPLABSize, PLABWeight), 1804 _expand_heap_after_alloc_failure(true), 1805 _old_marking_cycles_started(0), 1806 _old_marking_cycles_completed(0), 1807 _heap_summary_sent(false), 1808 _in_cset_fast_test(), 1809 _dirty_cards_region_list(NULL), 1810 _worker_cset_start_region(NULL), 1811 _worker_cset_start_region_time_stamp(NULL), 1812 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1813 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1814 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1815 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1816 1817 _workers = new WorkGang("GC Thread", ParallelGCThreads, 1818 /* are_GC_task_threads */true, 1819 /* are_ConcurrentGC_threads */false); 1820 _workers->initialize_workers(); 1821 1822 _allocator = G1Allocator::create_allocator(this); 1823 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords); 1824 1825 // Override the default _filler_array_max_size so that no humongous filler 1826 // objects are created. 1827 _filler_array_max_size = _humongous_object_threshold_in_words; 1828 1829 uint n_queues = ParallelGCThreads; 1830 _task_queues = new RefToScanQueueSet(n_queues); 1831 1832 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1833 assert(n_rem_sets > 0, "Invariant."); 1834 1835 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1836 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC); 1837 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1838 1839 for (uint i = 0; i < n_queues; i++) { 1840 RefToScanQueue* q = new RefToScanQueue(); 1841 q->initialize(); 1842 _task_queues->register_queue(i, q); 1843 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1844 } 1845 clear_cset_start_regions(); 1846 1847 // Initialize the G1EvacuationFailureALot counters and flags. 1848 NOT_PRODUCT(reset_evacuation_should_fail();) 1849 1850 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1851 } 1852 1853 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1854 size_t size, 1855 size_t translation_factor) { 1856 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1857 // Allocate a new reserved space, preferring to use large pages. 1858 ReservedSpace rs(size, preferred_page_size); 1859 G1RegionToSpaceMapper* result = 1860 G1RegionToSpaceMapper::create_mapper(rs, 1861 size, 1862 rs.alignment(), 1863 HeapRegion::GrainBytes, 1864 translation_factor, 1865 mtGC); 1866 if (TracePageSizes) { 1867 gclog_or_tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT, 1868 description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size); 1869 } 1870 return result; 1871 } 1872 1873 jint G1CollectedHeap::initialize() { 1874 CollectedHeap::pre_initialize(); 1875 os::enable_vtime(); 1876 1877 G1Log::init(); 1878 1879 // Necessary to satisfy locking discipline assertions. 1880 1881 MutexLocker x(Heap_lock); 1882 1883 // We have to initialize the printer before committing the heap, as 1884 // it will be used then. 1885 _hr_printer.set_active(G1PrintHeapRegions); 1886 1887 // While there are no constraints in the GC code that HeapWordSize 1888 // be any particular value, there are multiple other areas in the 1889 // system which believe this to be true (e.g. oop->object_size in some 1890 // cases incorrectly returns the size in wordSize units rather than 1891 // HeapWordSize). 1892 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1893 1894 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1895 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1896 size_t heap_alignment = collector_policy()->heap_alignment(); 1897 1898 // Ensure that the sizes are properly aligned. 1899 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1900 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1901 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1902 1903 _refine_cte_cl = new RefineCardTableEntryClosure(); 1904 1905 jint ecode = JNI_OK; 1906 _cg1r = ConcurrentG1Refine::create(this, _refine_cte_cl, &ecode); 1907 if (_cg1r == NULL) { 1908 return ecode; 1909 } 1910 1911 // Reserve the maximum. 1912 1913 // When compressed oops are enabled, the preferred heap base 1914 // is calculated by subtracting the requested size from the 1915 // 32Gb boundary and using the result as the base address for 1916 // heap reservation. If the requested size is not aligned to 1917 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1918 // into the ReservedHeapSpace constructor) then the actual 1919 // base of the reserved heap may end up differing from the 1920 // address that was requested (i.e. the preferred heap base). 1921 // If this happens then we could end up using a non-optimal 1922 // compressed oops mode. 1923 1924 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1925 heap_alignment); 1926 1927 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1928 1929 // Create the barrier set for the entire reserved region. 1930 G1SATBCardTableLoggingModRefBS* bs 1931 = new G1SATBCardTableLoggingModRefBS(reserved_region()); 1932 bs->initialize(); 1933 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity"); 1934 set_barrier_set(bs); 1935 1936 // Also create a G1 rem set. 1937 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 1938 1939 // Carve out the G1 part of the heap. 1940 1941 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1942 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 1943 G1RegionToSpaceMapper* heap_storage = 1944 G1RegionToSpaceMapper::create_mapper(g1_rs, 1945 g1_rs.size(), 1946 page_size, 1947 HeapRegion::GrainBytes, 1948 1, 1949 mtJavaHeap); 1950 os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(), 1951 max_byte_size, page_size, 1952 heap_rs.base(), 1953 heap_rs.size()); 1954 heap_storage->set_mapping_changed_listener(&_listener); 1955 1956 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 1957 G1RegionToSpaceMapper* bot_storage = 1958 create_aux_memory_mapper("Block offset table", 1959 G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize), 1960 G1BlockOffsetSharedArray::heap_map_factor()); 1961 1962 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1963 G1RegionToSpaceMapper* cardtable_storage = 1964 create_aux_memory_mapper("Card table", 1965 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 1966 G1SATBCardTableLoggingModRefBS::heap_map_factor()); 1967 1968 G1RegionToSpaceMapper* card_counts_storage = 1969 create_aux_memory_mapper("Card counts table", 1970 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize), 1971 G1CardCounts::heap_map_factor()); 1972 1973 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size()); 1974 G1RegionToSpaceMapper* prev_bitmap_storage = 1975 create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1976 G1RegionToSpaceMapper* next_bitmap_storage = 1977 create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::heap_map_factor()); 1978 1979 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1980 g1_barrier_set()->initialize(cardtable_storage); 1981 // Do later initialization work for concurrent refinement. 1982 _cg1r->init(card_counts_storage); 1983 1984 // 6843694 - ensure that the maximum region index can fit 1985 // in the remembered set structures. 1986 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1987 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1988 1989 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1990 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1991 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 1992 "too many cards per region"); 1993 1994 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1995 1996 _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage); 1997 1998 { 1999 HeapWord* start = _hrm.reserved().start(); 2000 HeapWord* end = _hrm.reserved().end(); 2001 size_t granularity = HeapRegion::GrainBytes; 2002 2003 _in_cset_fast_test.initialize(start, end, granularity); 2004 _humongous_reclaim_candidates.initialize(start, end, granularity); 2005 } 2006 2007 // Create the ConcurrentMark data structure and thread. 2008 // (Must do this late, so that "max_regions" is defined.) 2009 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 2010 if (_cm == NULL || !_cm->completed_initialization()) { 2011 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 2012 return JNI_ENOMEM; 2013 } 2014 _cmThread = _cm->cmThread(); 2015 2016 // Initialize the from_card cache structure of HeapRegionRemSet. 2017 HeapRegionRemSet::init_heap(max_regions()); 2018 2019 // Now expand into the initial heap size. 2020 if (!expand(init_byte_size)) { 2021 vm_shutdown_during_initialization("Failed to allocate initial heap."); 2022 return JNI_ENOMEM; 2023 } 2024 2025 // Perform any initialization actions delegated to the policy. 2026 g1_policy()->init(); 2027 2028 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2029 SATB_Q_FL_lock, 2030 G1SATBProcessCompletedThreshold, 2031 Shared_SATB_Q_lock); 2032 2033 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 2034 DirtyCardQ_CBL_mon, 2035 DirtyCardQ_FL_lock, 2036 concurrent_g1_refine()->yellow_zone(), 2037 concurrent_g1_refine()->red_zone(), 2038 Shared_DirtyCardQ_lock); 2039 2040 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 2041 DirtyCardQ_CBL_mon, 2042 DirtyCardQ_FL_lock, 2043 -1, // never trigger processing 2044 -1, // no limit on length 2045 Shared_DirtyCardQ_lock, 2046 &JavaThread::dirty_card_queue_set()); 2047 2048 // Here we allocate the dummy HeapRegion that is required by the 2049 // G1AllocRegion class. 2050 HeapRegion* dummy_region = _hrm.get_dummy_region(); 2051 2052 // We'll re-use the same region whether the alloc region will 2053 // require BOT updates or not and, if it doesn't, then a non-young 2054 // region will complain that it cannot support allocations without 2055 // BOT updates. So we'll tag the dummy region as eden to avoid that. 2056 dummy_region->set_eden(); 2057 // Make sure it's full. 2058 dummy_region->set_top(dummy_region->end()); 2059 G1AllocRegion::setup(this, dummy_region); 2060 2061 _allocator->init_mutator_alloc_region(); 2062 2063 // Do create of the monitoring and management support so that 2064 // values in the heap have been properly initialized. 2065 _g1mm = new G1MonitoringSupport(this); 2066 2067 G1StringDedup::initialize(); 2068 2069 _preserved_objs = NEW_C_HEAP_ARRAY(OopAndMarkOopStack, ParallelGCThreads, mtGC); 2070 for (uint i = 0; i < ParallelGCThreads; i++) { 2071 new (&_preserved_objs[i]) OopAndMarkOopStack(); 2072 } 2073 2074 return JNI_OK; 2075 } 2076 2077 void G1CollectedHeap::stop() { 2078 // Stop all concurrent threads. We do this to make sure these threads 2079 // do not continue to execute and access resources (e.g. gclog_or_tty) 2080 // that are destroyed during shutdown. 2081 _cg1r->stop(); 2082 _cmThread->stop(); 2083 if (G1StringDedup::is_enabled()) { 2084 G1StringDedup::stop(); 2085 } 2086 } 2087 2088 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2089 return HeapRegion::max_region_size(); 2090 } 2091 2092 void G1CollectedHeap::post_initialize() { 2093 CollectedHeap::post_initialize(); 2094 ref_processing_init(); 2095 } 2096 2097 void G1CollectedHeap::ref_processing_init() { 2098 // Reference processing in G1 currently works as follows: 2099 // 2100 // * There are two reference processor instances. One is 2101 // used to record and process discovered references 2102 // during concurrent marking; the other is used to 2103 // record and process references during STW pauses 2104 // (both full and incremental). 2105 // * Both ref processors need to 'span' the entire heap as 2106 // the regions in the collection set may be dotted around. 2107 // 2108 // * For the concurrent marking ref processor: 2109 // * Reference discovery is enabled at initial marking. 2110 // * Reference discovery is disabled and the discovered 2111 // references processed etc during remarking. 2112 // * Reference discovery is MT (see below). 2113 // * Reference discovery requires a barrier (see below). 2114 // * Reference processing may or may not be MT 2115 // (depending on the value of ParallelRefProcEnabled 2116 // and ParallelGCThreads). 2117 // * A full GC disables reference discovery by the CM 2118 // ref processor and abandons any entries on it's 2119 // discovered lists. 2120 // 2121 // * For the STW processor: 2122 // * Non MT discovery is enabled at the start of a full GC. 2123 // * Processing and enqueueing during a full GC is non-MT. 2124 // * During a full GC, references are processed after marking. 2125 // 2126 // * Discovery (may or may not be MT) is enabled at the start 2127 // of an incremental evacuation pause. 2128 // * References are processed near the end of a STW evacuation pause. 2129 // * For both types of GC: 2130 // * Discovery is atomic - i.e. not concurrent. 2131 // * Reference discovery will not need a barrier. 2132 2133 MemRegion mr = reserved_region(); 2134 2135 // Concurrent Mark ref processor 2136 _ref_processor_cm = 2137 new ReferenceProcessor(mr, // span 2138 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2139 // mt processing 2140 ParallelGCThreads, 2141 // degree of mt processing 2142 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2143 // mt discovery 2144 MAX2(ParallelGCThreads, ConcGCThreads), 2145 // degree of mt discovery 2146 false, 2147 // Reference discovery is not atomic 2148 &_is_alive_closure_cm); 2149 // is alive closure 2150 // (for efficiency/performance) 2151 2152 // STW ref processor 2153 _ref_processor_stw = 2154 new ReferenceProcessor(mr, // span 2155 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2156 // mt processing 2157 ParallelGCThreads, 2158 // degree of mt processing 2159 (ParallelGCThreads > 1), 2160 // mt discovery 2161 ParallelGCThreads, 2162 // degree of mt discovery 2163 true, 2164 // Reference discovery is atomic 2165 &_is_alive_closure_stw); 2166 // is alive closure 2167 // (for efficiency/performance) 2168 } 2169 2170 CollectorPolicy* G1CollectedHeap::collector_policy() const { 2171 return g1_policy(); 2172 } 2173 2174 size_t G1CollectedHeap::capacity() const { 2175 return _hrm.length() * HeapRegion::GrainBytes; 2176 } 2177 2178 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2179 hr->reset_gc_time_stamp(); 2180 } 2181 2182 #ifndef PRODUCT 2183 2184 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2185 private: 2186 unsigned _gc_time_stamp; 2187 bool _failures; 2188 2189 public: 2190 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2191 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2192 2193 virtual bool doHeapRegion(HeapRegion* hr) { 2194 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2195 if (_gc_time_stamp != region_gc_time_stamp) { 2196 gclog_or_tty->print_cr("Region " HR_FORMAT " has GC time stamp = %d, " 2197 "expected %d", HR_FORMAT_PARAMS(hr), 2198 region_gc_time_stamp, _gc_time_stamp); 2199 _failures = true; 2200 } 2201 return false; 2202 } 2203 2204 bool failures() { return _failures; } 2205 }; 2206 2207 void G1CollectedHeap::check_gc_time_stamps() { 2208 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2209 heap_region_iterate(&cl); 2210 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2211 } 2212 #endif // PRODUCT 2213 2214 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) { 2215 _cg1r->hot_card_cache()->drain(cl, worker_i); 2216 } 2217 2218 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) { 2219 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2220 size_t n_completed_buffers = 0; 2221 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2222 n_completed_buffers++; 2223 } 2224 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2225 dcqs.clear_n_completed_buffers(); 2226 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2227 } 2228 2229 // Computes the sum of the storage used by the various regions. 2230 size_t G1CollectedHeap::used() const { 2231 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions(); 2232 if (_archive_allocator != NULL) { 2233 result += _archive_allocator->used(); 2234 } 2235 return result; 2236 } 2237 2238 size_t G1CollectedHeap::used_unlocked() const { 2239 return _summary_bytes_used; 2240 } 2241 2242 class SumUsedClosure: public HeapRegionClosure { 2243 size_t _used; 2244 public: 2245 SumUsedClosure() : _used(0) {} 2246 bool doHeapRegion(HeapRegion* r) { 2247 _used += r->used(); 2248 return false; 2249 } 2250 size_t result() { return _used; } 2251 }; 2252 2253 size_t G1CollectedHeap::recalculate_used() const { 2254 double recalculate_used_start = os::elapsedTime(); 2255 2256 SumUsedClosure blk; 2257 heap_region_iterate(&blk); 2258 2259 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2260 return blk.result(); 2261 } 2262 2263 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2264 switch (cause) { 2265 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2266 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2267 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent; 2268 case GCCause::_g1_humongous_allocation: return true; 2269 case GCCause::_update_allocation_context_stats_inc: return true; 2270 case GCCause::_wb_conc_mark: return true; 2271 default: return false; 2272 } 2273 } 2274 2275 #ifndef PRODUCT 2276 void G1CollectedHeap::allocate_dummy_regions() { 2277 // Let's fill up most of the region 2278 size_t word_size = HeapRegion::GrainWords - 1024; 2279 // And as a result the region we'll allocate will be humongous. 2280 guarantee(is_humongous(word_size), "sanity"); 2281 2282 // _filler_array_max_size is set to humongous object threshold 2283 // but temporarily change it to use CollectedHeap::fill_with_object(). 2284 SizeTFlagSetting fs(_filler_array_max_size, word_size); 2285 2286 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2287 // Let's use the existing mechanism for the allocation 2288 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2289 AllocationContext::system()); 2290 if (dummy_obj != NULL) { 2291 MemRegion mr(dummy_obj, word_size); 2292 CollectedHeap::fill_with_object(mr); 2293 } else { 2294 // If we can't allocate once, we probably cannot allocate 2295 // again. Let's get out of the loop. 2296 break; 2297 } 2298 } 2299 } 2300 #endif // !PRODUCT 2301 2302 void G1CollectedHeap::increment_old_marking_cycles_started() { 2303 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2304 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2305 "Wrong marking cycle count (started: %d, completed: %d)", 2306 _old_marking_cycles_started, _old_marking_cycles_completed); 2307 2308 _old_marking_cycles_started++; 2309 } 2310 2311 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2312 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2313 2314 // We assume that if concurrent == true, then the caller is a 2315 // concurrent thread that was joined the Suspendible Thread 2316 // Set. If there's ever a cheap way to check this, we should add an 2317 // assert here. 2318 2319 // Given that this method is called at the end of a Full GC or of a 2320 // concurrent cycle, and those can be nested (i.e., a Full GC can 2321 // interrupt a concurrent cycle), the number of full collections 2322 // completed should be either one (in the case where there was no 2323 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2324 // behind the number of full collections started. 2325 2326 // This is the case for the inner caller, i.e. a Full GC. 2327 assert(concurrent || 2328 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2329 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2330 "for inner caller (Full GC): _old_marking_cycles_started = %u " 2331 "is inconsistent with _old_marking_cycles_completed = %u", 2332 _old_marking_cycles_started, _old_marking_cycles_completed); 2333 2334 // This is the case for the outer caller, i.e. the concurrent cycle. 2335 assert(!concurrent || 2336 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2337 "for outer caller (concurrent cycle): " 2338 "_old_marking_cycles_started = %u " 2339 "is inconsistent with _old_marking_cycles_completed = %u", 2340 _old_marking_cycles_started, _old_marking_cycles_completed); 2341 2342 _old_marking_cycles_completed += 1; 2343 2344 // We need to clear the "in_progress" flag in the CM thread before 2345 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2346 // is set) so that if a waiter requests another System.gc() it doesn't 2347 // incorrectly see that a marking cycle is still in progress. 2348 if (concurrent) { 2349 _cmThread->set_idle(); 2350 } 2351 2352 // This notify_all() will ensure that a thread that called 2353 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2354 // and it's waiting for a full GC to finish will be woken up. It is 2355 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2356 FullGCCount_lock->notify_all(); 2357 } 2358 2359 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2360 GCIdMarkAndRestore conc_gc_id_mark; 2361 collector_state()->set_concurrent_cycle_started(true); 2362 _gc_timer_cm->register_gc_start(start_time); 2363 2364 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2365 trace_heap_before_gc(_gc_tracer_cm); 2366 _cmThread->set_gc_id(GCId::current()); 2367 } 2368 2369 void G1CollectedHeap::register_concurrent_cycle_end() { 2370 if (collector_state()->concurrent_cycle_started()) { 2371 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2372 if (_cm->has_aborted()) { 2373 _gc_tracer_cm->report_concurrent_mode_failure(); 2374 } 2375 2376 _gc_timer_cm->register_gc_end(); 2377 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2378 2379 // Clear state variables to prepare for the next concurrent cycle. 2380 collector_state()->set_concurrent_cycle_started(false); 2381 _heap_summary_sent = false; 2382 } 2383 } 2384 2385 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2386 if (collector_state()->concurrent_cycle_started()) { 2387 // This function can be called when: 2388 // the cleanup pause is run 2389 // the concurrent cycle is aborted before the cleanup pause. 2390 // the concurrent cycle is aborted after the cleanup pause, 2391 // but before the concurrent cycle end has been registered. 2392 // Make sure that we only send the heap information once. 2393 if (!_heap_summary_sent) { 2394 GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id()); 2395 trace_heap_after_gc(_gc_tracer_cm); 2396 _heap_summary_sent = true; 2397 } 2398 } 2399 } 2400 2401 void G1CollectedHeap::collect(GCCause::Cause cause) { 2402 assert_heap_not_locked(); 2403 2404 uint gc_count_before; 2405 uint old_marking_count_before; 2406 uint full_gc_count_before; 2407 bool retry_gc; 2408 2409 do { 2410 retry_gc = false; 2411 2412 { 2413 MutexLocker ml(Heap_lock); 2414 2415 // Read the GC count while holding the Heap_lock 2416 gc_count_before = total_collections(); 2417 full_gc_count_before = total_full_collections(); 2418 old_marking_count_before = _old_marking_cycles_started; 2419 } 2420 2421 if (should_do_concurrent_full_gc(cause)) { 2422 // Schedule an initial-mark evacuation pause that will start a 2423 // concurrent cycle. We're setting word_size to 0 which means that 2424 // we are not requesting a post-GC allocation. 2425 VM_G1IncCollectionPause op(gc_count_before, 2426 0, /* word_size */ 2427 true, /* should_initiate_conc_mark */ 2428 g1_policy()->max_pause_time_ms(), 2429 cause); 2430 op.set_allocation_context(AllocationContext::current()); 2431 2432 VMThread::execute(&op); 2433 if (!op.pause_succeeded()) { 2434 if (old_marking_count_before == _old_marking_cycles_started) { 2435 retry_gc = op.should_retry_gc(); 2436 } else { 2437 // A Full GC happened while we were trying to schedule the 2438 // initial-mark GC. No point in starting a new cycle given 2439 // that the whole heap was collected anyway. 2440 } 2441 2442 if (retry_gc) { 2443 if (GC_locker::is_active_and_needs_gc()) { 2444 GC_locker::stall_until_clear(); 2445 } 2446 } 2447 } 2448 } else { 2449 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2450 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2451 2452 // Schedule a standard evacuation pause. We're setting word_size 2453 // to 0 which means that we are not requesting a post-GC allocation. 2454 VM_G1IncCollectionPause op(gc_count_before, 2455 0, /* word_size */ 2456 false, /* should_initiate_conc_mark */ 2457 g1_policy()->max_pause_time_ms(), 2458 cause); 2459 VMThread::execute(&op); 2460 } else { 2461 // Schedule a Full GC. 2462 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2463 VMThread::execute(&op); 2464 } 2465 } 2466 } while (retry_gc); 2467 } 2468 2469 bool G1CollectedHeap::is_in(const void* p) const { 2470 if (_hrm.reserved().contains(p)) { 2471 // Given that we know that p is in the reserved space, 2472 // heap_region_containing() should successfully 2473 // return the containing region. 2474 HeapRegion* hr = heap_region_containing(p); 2475 return hr->is_in(p); 2476 } else { 2477 return false; 2478 } 2479 } 2480 2481 #ifdef ASSERT 2482 bool G1CollectedHeap::is_in_exact(const void* p) const { 2483 bool contains = reserved_region().contains(p); 2484 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2485 if (contains && available) { 2486 return true; 2487 } else { 2488 return false; 2489 } 2490 } 2491 #endif 2492 2493 bool G1CollectedHeap::obj_in_cs(oop obj) { 2494 HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj); 2495 return r != NULL && r->in_collection_set(); 2496 } 2497 2498 // Iteration functions. 2499 2500 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2501 2502 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2503 ExtendedOopClosure* _cl; 2504 public: 2505 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2506 bool doHeapRegion(HeapRegion* r) { 2507 if (!r->is_continues_humongous()) { 2508 r->oop_iterate(_cl); 2509 } 2510 return false; 2511 } 2512 }; 2513 2514 // Iterates an ObjectClosure over all objects within a HeapRegion. 2515 2516 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2517 ObjectClosure* _cl; 2518 public: 2519 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2520 bool doHeapRegion(HeapRegion* r) { 2521 if (!r->is_continues_humongous()) { 2522 r->object_iterate(_cl); 2523 } 2524 return false; 2525 } 2526 }; 2527 2528 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2529 IterateObjectClosureRegionClosure blk(cl); 2530 heap_region_iterate(&blk); 2531 } 2532 2533 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2534 _hrm.iterate(cl); 2535 } 2536 2537 void 2538 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2539 uint worker_id, 2540 HeapRegionClaimer *hrclaimer, 2541 bool concurrent) const { 2542 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2543 } 2544 2545 // Clear the cached CSet starting regions and (more importantly) 2546 // the time stamps. Called when we reset the GC time stamp. 2547 void G1CollectedHeap::clear_cset_start_regions() { 2548 assert(_worker_cset_start_region != NULL, "sanity"); 2549 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2550 2551 for (uint i = 0; i < ParallelGCThreads; i++) { 2552 _worker_cset_start_region[i] = NULL; 2553 _worker_cset_start_region_time_stamp[i] = 0; 2554 } 2555 } 2556 2557 // Given the id of a worker, obtain or calculate a suitable 2558 // starting region for iterating over the current collection set. 2559 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2560 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2561 2562 HeapRegion* result = NULL; 2563 unsigned gc_time_stamp = get_gc_time_stamp(); 2564 2565 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2566 // Cached starting region for current worker was set 2567 // during the current pause - so it's valid. 2568 // Note: the cached starting heap region may be NULL 2569 // (when the collection set is empty). 2570 result = _worker_cset_start_region[worker_i]; 2571 assert(result == NULL || result->in_collection_set(), "sanity"); 2572 return result; 2573 } 2574 2575 // The cached entry was not valid so let's calculate 2576 // a suitable starting heap region for this worker. 2577 2578 // We want the parallel threads to start their collection 2579 // set iteration at different collection set regions to 2580 // avoid contention. 2581 // If we have: 2582 // n collection set regions 2583 // p threads 2584 // Then thread t will start at region floor ((t * n) / p) 2585 2586 result = g1_policy()->collection_set(); 2587 uint cs_size = g1_policy()->cset_region_length(); 2588 uint active_workers = workers()->active_workers(); 2589 2590 uint end_ind = (cs_size * worker_i) / active_workers; 2591 uint start_ind = 0; 2592 2593 if (worker_i > 0 && 2594 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2595 // Previous workers starting region is valid 2596 // so let's iterate from there 2597 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2598 result = _worker_cset_start_region[worker_i - 1]; 2599 } 2600 2601 for (uint i = start_ind; i < end_ind; i++) { 2602 result = result->next_in_collection_set(); 2603 } 2604 2605 // Note: the calculated starting heap region may be NULL 2606 // (when the collection set is empty). 2607 assert(result == NULL || result->in_collection_set(), "sanity"); 2608 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2609 "should be updated only once per pause"); 2610 _worker_cset_start_region[worker_i] = result; 2611 OrderAccess::storestore(); 2612 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2613 return result; 2614 } 2615 2616 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2617 HeapRegion* r = g1_policy()->collection_set(); 2618 while (r != NULL) { 2619 HeapRegion* next = r->next_in_collection_set(); 2620 if (cl->doHeapRegion(r)) { 2621 cl->incomplete(); 2622 return; 2623 } 2624 r = next; 2625 } 2626 } 2627 2628 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2629 HeapRegionClosure *cl) { 2630 if (r == NULL) { 2631 // The CSet is empty so there's nothing to do. 2632 return; 2633 } 2634 2635 assert(r->in_collection_set(), 2636 "Start region must be a member of the collection set."); 2637 HeapRegion* cur = r; 2638 while (cur != NULL) { 2639 HeapRegion* next = cur->next_in_collection_set(); 2640 if (cl->doHeapRegion(cur) && false) { 2641 cl->incomplete(); 2642 return; 2643 } 2644 cur = next; 2645 } 2646 cur = g1_policy()->collection_set(); 2647 while (cur != r) { 2648 HeapRegion* next = cur->next_in_collection_set(); 2649 if (cl->doHeapRegion(cur) && false) { 2650 cl->incomplete(); 2651 return; 2652 } 2653 cur = next; 2654 } 2655 } 2656 2657 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2658 HeapRegion* result = _hrm.next_region_in_heap(from); 2659 while (result != NULL && result->is_pinned()) { 2660 result = _hrm.next_region_in_heap(result); 2661 } 2662 return result; 2663 } 2664 2665 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2666 HeapRegion* hr = heap_region_containing(addr); 2667 return hr->block_start(addr); 2668 } 2669 2670 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2671 HeapRegion* hr = heap_region_containing(addr); 2672 return hr->block_size(addr); 2673 } 2674 2675 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2676 HeapRegion* hr = heap_region_containing(addr); 2677 return hr->block_is_obj(addr); 2678 } 2679 2680 bool G1CollectedHeap::supports_tlab_allocation() const { 2681 return true; 2682 } 2683 2684 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2685 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2686 } 2687 2688 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2689 return young_list()->eden_used_bytes(); 2690 } 2691 2692 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2693 // must be equal to the humongous object limit. 2694 size_t G1CollectedHeap::max_tlab_size() const { 2695 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment); 2696 } 2697 2698 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2699 AllocationContext_t context = AllocationContext::current(); 2700 return _allocator->unsafe_max_tlab_alloc(context); 2701 } 2702 2703 size_t G1CollectedHeap::max_capacity() const { 2704 return _hrm.reserved().byte_size(); 2705 } 2706 2707 jlong G1CollectedHeap::millis_since_last_gc() { 2708 // assert(false, "NYI"); 2709 return 0; 2710 } 2711 2712 void G1CollectedHeap::prepare_for_verify() { 2713 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2714 ensure_parsability(false); 2715 } 2716 g1_rem_set()->prepare_for_verify(); 2717 } 2718 2719 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 2720 VerifyOption vo) { 2721 switch (vo) { 2722 case VerifyOption_G1UsePrevMarking: 2723 return hr->obj_allocated_since_prev_marking(obj); 2724 case VerifyOption_G1UseNextMarking: 2725 return hr->obj_allocated_since_next_marking(obj); 2726 case VerifyOption_G1UseMarkWord: 2727 return false; 2728 default: 2729 ShouldNotReachHere(); 2730 } 2731 return false; // keep some compilers happy 2732 } 2733 2734 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 2735 switch (vo) { 2736 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 2737 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 2738 case VerifyOption_G1UseMarkWord: return NULL; 2739 default: ShouldNotReachHere(); 2740 } 2741 return NULL; // keep some compilers happy 2742 } 2743 2744 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 2745 switch (vo) { 2746 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 2747 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 2748 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 2749 default: ShouldNotReachHere(); 2750 } 2751 return false; // keep some compilers happy 2752 } 2753 2754 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 2755 switch (vo) { 2756 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 2757 case VerifyOption_G1UseNextMarking: return "NTAMS"; 2758 case VerifyOption_G1UseMarkWord: return "NONE"; 2759 default: ShouldNotReachHere(); 2760 } 2761 return NULL; // keep some compilers happy 2762 } 2763 2764 class VerifyRootsClosure: public OopClosure { 2765 private: 2766 G1CollectedHeap* _g1h; 2767 VerifyOption _vo; 2768 bool _failures; 2769 public: 2770 // _vo == UsePrevMarking -> use "prev" marking information, 2771 // _vo == UseNextMarking -> use "next" marking information, 2772 // _vo == UseMarkWord -> use mark word from object header. 2773 VerifyRootsClosure(VerifyOption vo) : 2774 _g1h(G1CollectedHeap::heap()), 2775 _vo(vo), 2776 _failures(false) { } 2777 2778 bool failures() { return _failures; } 2779 2780 template <class T> void do_oop_nv(T* p) { 2781 T heap_oop = oopDesc::load_heap_oop(p); 2782 if (!oopDesc::is_null(heap_oop)) { 2783 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2784 if (_g1h->is_obj_dead_cond(obj, _vo)) { 2785 gclog_or_tty->print_cr("Root location " PTR_FORMAT " " 2786 "points to dead obj " PTR_FORMAT, p2i(p), p2i(obj)); 2787 if (_vo == VerifyOption_G1UseMarkWord) { 2788 gclog_or_tty->print_cr(" Mark word: " INTPTR_FORMAT, (intptr_t)obj->mark()); 2789 } 2790 obj->print_on(gclog_or_tty); 2791 _failures = true; 2792 } 2793 } 2794 } 2795 2796 void do_oop(oop* p) { do_oop_nv(p); } 2797 void do_oop(narrowOop* p) { do_oop_nv(p); } 2798 }; 2799 2800 class G1VerifyCodeRootOopClosure: public OopClosure { 2801 G1CollectedHeap* _g1h; 2802 OopClosure* _root_cl; 2803 nmethod* _nm; 2804 VerifyOption _vo; 2805 bool _failures; 2806 2807 template <class T> void do_oop_work(T* p) { 2808 // First verify that this root is live 2809 _root_cl->do_oop(p); 2810 2811 if (!G1VerifyHeapRegionCodeRoots) { 2812 // We're not verifying the code roots attached to heap region. 2813 return; 2814 } 2815 2816 // Don't check the code roots during marking verification in a full GC 2817 if (_vo == VerifyOption_G1UseMarkWord) { 2818 return; 2819 } 2820 2821 // Now verify that the current nmethod (which contains p) is 2822 // in the code root list of the heap region containing the 2823 // object referenced by p. 2824 2825 T heap_oop = oopDesc::load_heap_oop(p); 2826 if (!oopDesc::is_null(heap_oop)) { 2827 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2828 2829 // Now fetch the region containing the object 2830 HeapRegion* hr = _g1h->heap_region_containing(obj); 2831 HeapRegionRemSet* hrrs = hr->rem_set(); 2832 // Verify that the strong code root list for this region 2833 // contains the nmethod 2834 if (!hrrs->strong_code_roots_list_contains(_nm)) { 2835 gclog_or_tty->print_cr("Code root location " PTR_FORMAT " " 2836 "from nmethod " PTR_FORMAT " not in strong " 2837 "code roots for region [" PTR_FORMAT "," PTR_FORMAT ")", 2838 p2i(p), p2i(_nm), p2i(hr->bottom()), p2i(hr->end())); 2839 _failures = true; 2840 } 2841 } 2842 } 2843 2844 public: 2845 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo): 2846 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {} 2847 2848 void do_oop(oop* p) { do_oop_work(p); } 2849 void do_oop(narrowOop* p) { do_oop_work(p); } 2850 2851 void set_nmethod(nmethod* nm) { _nm = nm; } 2852 bool failures() { return _failures; } 2853 }; 2854 2855 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure { 2856 G1VerifyCodeRootOopClosure* _oop_cl; 2857 2858 public: 2859 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl): 2860 _oop_cl(oop_cl) {} 2861 2862 void do_code_blob(CodeBlob* cb) { 2863 nmethod* nm = cb->as_nmethod_or_null(); 2864 if (nm != NULL) { 2865 _oop_cl->set_nmethod(nm); 2866 nm->oops_do(_oop_cl); 2867 } 2868 } 2869 }; 2870 2871 class YoungRefCounterClosure : public OopClosure { 2872 G1CollectedHeap* _g1h; 2873 int _count; 2874 public: 2875 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 2876 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 2877 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 2878 2879 int count() { return _count; } 2880 void reset_count() { _count = 0; }; 2881 }; 2882 2883 class VerifyKlassClosure: public KlassClosure { 2884 YoungRefCounterClosure _young_ref_counter_closure; 2885 OopClosure *_oop_closure; 2886 public: 2887 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 2888 void do_klass(Klass* k) { 2889 k->oops_do(_oop_closure); 2890 2891 _young_ref_counter_closure.reset_count(); 2892 k->oops_do(&_young_ref_counter_closure); 2893 if (_young_ref_counter_closure.count() > 0) { 2894 guarantee(k->has_modified_oops(), "Klass " PTR_FORMAT ", has young refs but is not dirty.", p2i(k)); 2895 } 2896 } 2897 }; 2898 2899 class VerifyLivenessOopClosure: public OopClosure { 2900 G1CollectedHeap* _g1h; 2901 VerifyOption _vo; 2902 public: 2903 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 2904 _g1h(g1h), _vo(vo) 2905 { } 2906 void do_oop(narrowOop *p) { do_oop_work(p); } 2907 void do_oop( oop *p) { do_oop_work(p); } 2908 2909 template <class T> void do_oop_work(T *p) { 2910 oop obj = oopDesc::load_decode_heap_oop(p); 2911 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 2912 "Dead object referenced by a not dead object"); 2913 } 2914 }; 2915 2916 class VerifyObjsInRegionClosure: public ObjectClosure { 2917 private: 2918 G1CollectedHeap* _g1h; 2919 size_t _live_bytes; 2920 HeapRegion *_hr; 2921 VerifyOption _vo; 2922 public: 2923 // _vo == UsePrevMarking -> use "prev" marking information, 2924 // _vo == UseNextMarking -> use "next" marking information, 2925 // _vo == UseMarkWord -> use mark word from object header. 2926 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 2927 : _live_bytes(0), _hr(hr), _vo(vo) { 2928 _g1h = G1CollectedHeap::heap(); 2929 } 2930 void do_object(oop o) { 2931 VerifyLivenessOopClosure isLive(_g1h, _vo); 2932 assert(o != NULL, "Huh?"); 2933 if (!_g1h->is_obj_dead_cond(o, _vo)) { 2934 // If the object is alive according to the mark word, 2935 // then verify that the marking information agrees. 2936 // Note we can't verify the contra-positive of the 2937 // above: if the object is dead (according to the mark 2938 // word), it may not be marked, or may have been marked 2939 // but has since became dead, or may have been allocated 2940 // since the last marking. 2941 if (_vo == VerifyOption_G1UseMarkWord) { 2942 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 2943 } 2944 2945 o->oop_iterate_no_header(&isLive); 2946 if (!_hr->obj_allocated_since_prev_marking(o)) { 2947 size_t obj_size = o->size(); // Make sure we don't overflow 2948 _live_bytes += (obj_size * HeapWordSize); 2949 } 2950 } 2951 } 2952 size_t live_bytes() { return _live_bytes; } 2953 }; 2954 2955 class VerifyArchiveOopClosure: public OopClosure { 2956 public: 2957 VerifyArchiveOopClosure(HeapRegion *hr) { } 2958 void do_oop(narrowOop *p) { do_oop_work(p); } 2959 void do_oop( oop *p) { do_oop_work(p); } 2960 2961 template <class T> void do_oop_work(T *p) { 2962 oop obj = oopDesc::load_decode_heap_oop(p); 2963 guarantee(obj == NULL || G1MarkSweep::in_archive_range(obj), 2964 "Archive object at " PTR_FORMAT " references a non-archive object at " PTR_FORMAT, 2965 p2i(p), p2i(obj)); 2966 } 2967 }; 2968 2969 class VerifyArchiveRegionClosure: public ObjectClosure { 2970 public: 2971 VerifyArchiveRegionClosure(HeapRegion *hr) { } 2972 // Verify that all object pointers are to archive regions. 2973 void do_object(oop o) { 2974 VerifyArchiveOopClosure checkOop(NULL); 2975 assert(o != NULL, "Should not be here for NULL oops"); 2976 o->oop_iterate_no_header(&checkOop); 2977 } 2978 }; 2979 2980 class VerifyRegionClosure: public HeapRegionClosure { 2981 private: 2982 bool _par; 2983 VerifyOption _vo; 2984 bool _failures; 2985 public: 2986 // _vo == UsePrevMarking -> use "prev" marking information, 2987 // _vo == UseNextMarking -> use "next" marking information, 2988 // _vo == UseMarkWord -> use mark word from object header. 2989 VerifyRegionClosure(bool par, VerifyOption vo) 2990 : _par(par), 2991 _vo(vo), 2992 _failures(false) {} 2993 2994 bool failures() { 2995 return _failures; 2996 } 2997 2998 bool doHeapRegion(HeapRegion* r) { 2999 // For archive regions, verify there are no heap pointers to 3000 // non-pinned regions. For all others, verify liveness info. 3001 if (r->is_archive()) { 3002 VerifyArchiveRegionClosure verify_oop_pointers(r); 3003 r->object_iterate(&verify_oop_pointers); 3004 return true; 3005 } 3006 if (!r->is_continues_humongous()) { 3007 bool failures = false; 3008 r->verify(_vo, &failures); 3009 if (failures) { 3010 _failures = true; 3011 } else if (!r->is_starts_humongous()) { 3012 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 3013 r->object_iterate(¬_dead_yet_cl); 3014 if (_vo != VerifyOption_G1UseNextMarking) { 3015 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 3016 gclog_or_tty->print_cr("[" PTR_FORMAT "," PTR_FORMAT "] " 3017 "max_live_bytes " SIZE_FORMAT " " 3018 "< calculated " SIZE_FORMAT, 3019 p2i(r->bottom()), p2i(r->end()), 3020 r->max_live_bytes(), 3021 not_dead_yet_cl.live_bytes()); 3022 _failures = true; 3023 } 3024 } else { 3025 // When vo == UseNextMarking we cannot currently do a sanity 3026 // check on the live bytes as the calculation has not been 3027 // finalized yet. 3028 } 3029 } 3030 } 3031 return false; // stop the region iteration if we hit a failure 3032 } 3033 }; 3034 3035 // This is the task used for parallel verification of the heap regions 3036 3037 class G1ParVerifyTask: public AbstractGangTask { 3038 private: 3039 G1CollectedHeap* _g1h; 3040 VerifyOption _vo; 3041 bool _failures; 3042 HeapRegionClaimer _hrclaimer; 3043 3044 public: 3045 // _vo == UsePrevMarking -> use "prev" marking information, 3046 // _vo == UseNextMarking -> use "next" marking information, 3047 // _vo == UseMarkWord -> use mark word from object header. 3048 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3049 AbstractGangTask("Parallel verify task"), 3050 _g1h(g1h), 3051 _vo(vo), 3052 _failures(false), 3053 _hrclaimer(g1h->workers()->active_workers()) {} 3054 3055 bool failures() { 3056 return _failures; 3057 } 3058 3059 void work(uint worker_id) { 3060 HandleMark hm; 3061 VerifyRegionClosure blk(true, _vo); 3062 _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer); 3063 if (blk.failures()) { 3064 _failures = true; 3065 } 3066 } 3067 }; 3068 3069 void G1CollectedHeap::verify(bool silent, VerifyOption vo) { 3070 if (SafepointSynchronize::is_at_safepoint()) { 3071 assert(Thread::current()->is_VM_thread(), 3072 "Expected to be executed serially by the VM thread at this point"); 3073 3074 if (!silent) { gclog_or_tty->print("Roots "); } 3075 VerifyRootsClosure rootsCl(vo); 3076 VerifyKlassClosure klassCl(this, &rootsCl); 3077 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false); 3078 3079 // We apply the relevant closures to all the oops in the 3080 // system dictionary, class loader data graph, the string table 3081 // and the nmethods in the code cache. 3082 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo); 3083 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl); 3084 3085 { 3086 G1RootProcessor root_processor(this, 1); 3087 root_processor.process_all_roots(&rootsCl, 3088 &cldCl, 3089 &blobsCl); 3090 } 3091 3092 bool failures = rootsCl.failures() || codeRootsCl.failures(); 3093 3094 if (vo != VerifyOption_G1UseMarkWord) { 3095 // If we're verifying during a full GC then the region sets 3096 // will have been torn down at the start of the GC. Therefore 3097 // verifying the region sets will fail. So we only verify 3098 // the region sets when not in a full GC. 3099 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3100 verify_region_sets(); 3101 } 3102 3103 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3104 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3105 3106 G1ParVerifyTask task(this, vo); 3107 workers()->run_task(&task); 3108 if (task.failures()) { 3109 failures = true; 3110 } 3111 3112 } else { 3113 VerifyRegionClosure blk(false, vo); 3114 heap_region_iterate(&blk); 3115 if (blk.failures()) { 3116 failures = true; 3117 } 3118 } 3119 3120 if (G1StringDedup::is_enabled()) { 3121 if (!silent) gclog_or_tty->print("StrDedup "); 3122 G1StringDedup::verify(); 3123 } 3124 3125 if (failures) { 3126 gclog_or_tty->print_cr("Heap:"); 3127 // It helps to have the per-region information in the output to 3128 // help us track down what went wrong. This is why we call 3129 // print_extended_on() instead of print_on(). 3130 print_extended_on(gclog_or_tty); 3131 gclog_or_tty->cr(); 3132 gclog_or_tty->flush(); 3133 } 3134 guarantee(!failures, "there should not have been any failures"); 3135 } else { 3136 if (!silent) { 3137 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet"); 3138 if (G1StringDedup::is_enabled()) { 3139 gclog_or_tty->print(", StrDedup"); 3140 } 3141 gclog_or_tty->print(") "); 3142 } 3143 } 3144 } 3145 3146 void G1CollectedHeap::verify(bool silent) { 3147 verify(silent, VerifyOption_G1UsePrevMarking); 3148 } 3149 3150 double G1CollectedHeap::verify(bool guard, const char* msg) { 3151 double verify_time_ms = 0.0; 3152 3153 if (guard && total_collections() >= VerifyGCStartAt) { 3154 double verify_start = os::elapsedTime(); 3155 HandleMark hm; // Discard invalid handles created during verification 3156 prepare_for_verify(); 3157 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 3158 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 3159 } 3160 3161 return verify_time_ms; 3162 } 3163 3164 void G1CollectedHeap::verify_before_gc() { 3165 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:"); 3166 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 3167 } 3168 3169 void G1CollectedHeap::verify_after_gc() { 3170 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:"); 3171 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 3172 } 3173 3174 class PrintRegionClosure: public HeapRegionClosure { 3175 outputStream* _st; 3176 public: 3177 PrintRegionClosure(outputStream* st) : _st(st) {} 3178 bool doHeapRegion(HeapRegion* r) { 3179 r->print_on(_st); 3180 return false; 3181 } 3182 }; 3183 3184 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3185 const HeapRegion* hr, 3186 const VerifyOption vo) const { 3187 switch (vo) { 3188 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 3189 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 3190 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive(); 3191 default: ShouldNotReachHere(); 3192 } 3193 return false; // keep some compilers happy 3194 } 3195 3196 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3197 const VerifyOption vo) const { 3198 switch (vo) { 3199 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 3200 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 3201 case VerifyOption_G1UseMarkWord: { 3202 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj); 3203 return !obj->is_gc_marked() && !hr->is_archive(); 3204 } 3205 default: ShouldNotReachHere(); 3206 } 3207 return false; // keep some compilers happy 3208 } 3209 3210 void G1CollectedHeap::print_on(outputStream* st) const { 3211 st->print(" %-20s", "garbage-first heap"); 3212 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3213 capacity()/K, used_unlocked()/K); 3214 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")", 3215 p2i(_hrm.reserved().start()), 3216 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords), 3217 p2i(_hrm.reserved().end())); 3218 st->cr(); 3219 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3220 uint young_regions = _young_list->length(); 3221 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3222 (size_t) young_regions * HeapRegion::GrainBytes / K); 3223 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3224 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3225 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3226 st->cr(); 3227 MetaspaceAux::print_on(st); 3228 } 3229 3230 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3231 print_on(st); 3232 3233 // Print the per-region information. 3234 st->cr(); 3235 st->print_cr("Heap Regions: (E=young(eden), S=young(survivor), O=old, " 3236 "HS=humongous(starts), HC=humongous(continues), " 3237 "CS=collection set, F=free, A=archive, TS=gc time stamp, " 3238 "PTAMS=previous top-at-mark-start, " 3239 "NTAMS=next top-at-mark-start)"); 3240 PrintRegionClosure blk(st); 3241 heap_region_iterate(&blk); 3242 } 3243 3244 void G1CollectedHeap::print_on_error(outputStream* st) const { 3245 this->CollectedHeap::print_on_error(st); 3246 3247 if (_cm != NULL) { 3248 st->cr(); 3249 _cm->print_on_error(st); 3250 } 3251 } 3252 3253 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3254 workers()->print_worker_threads_on(st); 3255 _cmThread->print_on(st); 3256 st->cr(); 3257 _cm->print_worker_threads_on(st); 3258 _cg1r->print_worker_threads_on(st); 3259 if (G1StringDedup::is_enabled()) { 3260 G1StringDedup::print_worker_threads_on(st); 3261 } 3262 } 3263 3264 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3265 workers()->threads_do(tc); 3266 tc->do_thread(_cmThread); 3267 _cg1r->threads_do(tc); 3268 if (G1StringDedup::is_enabled()) { 3269 G1StringDedup::threads_do(tc); 3270 } 3271 } 3272 3273 void G1CollectedHeap::print_tracing_info() const { 3274 // We'll overload this to mean "trace GC pause statistics." 3275 if (TraceYoungGenTime || TraceOldGenTime) { 3276 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3277 // to that. 3278 g1_policy()->print_tracing_info(); 3279 } 3280 if (G1SummarizeRSetStats) { 3281 g1_rem_set()->print_summary_info(); 3282 } 3283 if (G1SummarizeConcMark) { 3284 concurrent_mark()->print_summary_info(); 3285 } 3286 g1_policy()->print_yg_surv_rate_info(); 3287 } 3288 3289 #ifndef PRODUCT 3290 // Helpful for debugging RSet issues. 3291 3292 class PrintRSetsClosure : public HeapRegionClosure { 3293 private: 3294 const char* _msg; 3295 size_t _occupied_sum; 3296 3297 public: 3298 bool doHeapRegion(HeapRegion* r) { 3299 HeapRegionRemSet* hrrs = r->rem_set(); 3300 size_t occupied = hrrs->occupied(); 3301 _occupied_sum += occupied; 3302 3303 gclog_or_tty->print_cr("Printing RSet for region " HR_FORMAT, 3304 HR_FORMAT_PARAMS(r)); 3305 if (occupied == 0) { 3306 gclog_or_tty->print_cr(" RSet is empty"); 3307 } else { 3308 hrrs->print(); 3309 } 3310 gclog_or_tty->print_cr("----------"); 3311 return false; 3312 } 3313 3314 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3315 gclog_or_tty->cr(); 3316 gclog_or_tty->print_cr("========================================"); 3317 gclog_or_tty->print_cr("%s", msg); 3318 gclog_or_tty->cr(); 3319 } 3320 3321 ~PrintRSetsClosure() { 3322 gclog_or_tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 3323 gclog_or_tty->print_cr("========================================"); 3324 gclog_or_tty->cr(); 3325 } 3326 }; 3327 3328 void G1CollectedHeap::print_cset_rsets() { 3329 PrintRSetsClosure cl("Printing CSet RSets"); 3330 collection_set_iterate(&cl); 3331 } 3332 3333 void G1CollectedHeap::print_all_rsets() { 3334 PrintRSetsClosure cl("Printing All RSets");; 3335 heap_region_iterate(&cl); 3336 } 3337 #endif // PRODUCT 3338 3339 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() { 3340 YoungList* young_list = heap()->young_list(); 3341 3342 size_t eden_used_bytes = young_list->eden_used_bytes(); 3343 size_t survivor_used_bytes = young_list->survivor_used_bytes(); 3344 3345 size_t eden_capacity_bytes = 3346 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes; 3347 3348 VirtualSpaceSummary heap_summary = create_heap_space_summary(); 3349 return G1HeapSummary(heap_summary, used(), eden_used_bytes, eden_capacity_bytes, survivor_used_bytes); 3350 } 3351 3352 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) { 3353 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(), 3354 stats->unused(), stats->used(), stats->region_end_waste(), 3355 stats->regions_filled(), stats->direct_allocated(), 3356 stats->failure_used(), stats->failure_waste()); 3357 } 3358 3359 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) { 3360 const G1HeapSummary& heap_summary = create_g1_heap_summary(); 3361 gc_tracer->report_gc_heap_summary(when, heap_summary); 3362 3363 const MetaspaceSummary& metaspace_summary = create_metaspace_summary(); 3364 gc_tracer->report_metaspace_summary(when, metaspace_summary); 3365 } 3366 3367 3368 G1CollectedHeap* G1CollectedHeap::heap() { 3369 CollectedHeap* heap = Universe::heap(); 3370 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()"); 3371 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap"); 3372 return (G1CollectedHeap*)heap; 3373 } 3374 3375 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3376 // always_do_update_barrier = false; 3377 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3378 // Fill TLAB's and such 3379 accumulate_statistics_all_tlabs(); 3380 ensure_parsability(true); 3381 3382 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) && 3383 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 3384 g1_rem_set()->print_periodic_summary_info("Before GC RS summary"); 3385 } 3386 } 3387 3388 void G1CollectedHeap::gc_epilogue(bool full) { 3389 3390 if (G1SummarizeRSetStats && 3391 (G1SummarizeRSetStatsPeriod > 0) && 3392 // we are at the end of the GC. Total collections has already been increased. 3393 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) { 3394 g1_rem_set()->print_periodic_summary_info("After GC RS summary"); 3395 } 3396 3397 // FIXME: what is this about? 3398 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3399 // is set. 3400 #if defined(COMPILER2) || INCLUDE_JVMCI 3401 assert(DerivedPointerTable::is_empty(), "derived pointer present"); 3402 #endif 3403 // always_do_update_barrier = true; 3404 3405 resize_all_tlabs(); 3406 allocation_context_stats().update(full); 3407 3408 // We have just completed a GC. Update the soft reference 3409 // policy with the new heap occupancy 3410 Universe::update_heap_info_at_gc(); 3411 } 3412 3413 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3414 uint gc_count_before, 3415 bool* succeeded, 3416 GCCause::Cause gc_cause) { 3417 assert_heap_not_locked_and_not_at_safepoint(); 3418 g1_policy()->record_stop_world_start(); 3419 VM_G1IncCollectionPause op(gc_count_before, 3420 word_size, 3421 false, /* should_initiate_conc_mark */ 3422 g1_policy()->max_pause_time_ms(), 3423 gc_cause); 3424 3425 op.set_allocation_context(AllocationContext::current()); 3426 VMThread::execute(&op); 3427 3428 HeapWord* result = op.result(); 3429 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3430 assert(result == NULL || ret_succeeded, 3431 "the result should be NULL if the VM did not succeed"); 3432 *succeeded = ret_succeeded; 3433 3434 assert_heap_not_locked(); 3435 return result; 3436 } 3437 3438 void 3439 G1CollectedHeap::doConcurrentMark() { 3440 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3441 if (!_cmThread->in_progress()) { 3442 _cmThread->set_started(); 3443 CGC_lock->notify(); 3444 } 3445 } 3446 3447 size_t G1CollectedHeap::pending_card_num() { 3448 size_t extra_cards = 0; 3449 JavaThread *curr = Threads::first(); 3450 while (curr != NULL) { 3451 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3452 extra_cards += dcq.size(); 3453 curr = curr->next(); 3454 } 3455 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3456 size_t buffer_size = dcqs.buffer_size(); 3457 size_t buffer_num = dcqs.completed_buffers_num(); 3458 3459 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3460 // in bytes - not the number of 'entries'. We need to convert 3461 // into a number of cards. 3462 return (buffer_size * buffer_num + extra_cards) / oopSize; 3463 } 3464 3465 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 3466 private: 3467 size_t _total_humongous; 3468 size_t _candidate_humongous; 3469 3470 DirtyCardQueue _dcq; 3471 3472 // We don't nominate objects with many remembered set entries, on 3473 // the assumption that such objects are likely still live. 3474 bool is_remset_small(HeapRegion* region) const { 3475 HeapRegionRemSet* const rset = region->rem_set(); 3476 return G1EagerReclaimHumongousObjectsWithStaleRefs 3477 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 3478 : rset->is_empty(); 3479 } 3480 3481 bool is_typeArray_region(HeapRegion* region) const { 3482 return oop(region->bottom())->is_typeArray(); 3483 } 3484 3485 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 3486 assert(region->is_starts_humongous(), "Must start a humongous object"); 3487 3488 // Candidate selection must satisfy the following constraints 3489 // while concurrent marking is in progress: 3490 // 3491 // * In order to maintain SATB invariants, an object must not be 3492 // reclaimed if it was allocated before the start of marking and 3493 // has not had its references scanned. Such an object must have 3494 // its references (including type metadata) scanned to ensure no 3495 // live objects are missed by the marking process. Objects 3496 // allocated after the start of concurrent marking don't need to 3497 // be scanned. 3498 // 3499 // * An object must not be reclaimed if it is on the concurrent 3500 // mark stack. Objects allocated after the start of concurrent 3501 // marking are never pushed on the mark stack. 3502 // 3503 // Nominating only objects allocated after the start of concurrent 3504 // marking is sufficient to meet both constraints. This may miss 3505 // some objects that satisfy the constraints, but the marking data 3506 // structures don't support efficiently performing the needed 3507 // additional tests or scrubbing of the mark stack. 3508 // 3509 // However, we presently only nominate is_typeArray() objects. 3510 // A humongous object containing references induces remembered 3511 // set entries on other regions. In order to reclaim such an 3512 // object, those remembered sets would need to be cleaned up. 3513 // 3514 // We also treat is_typeArray() objects specially, allowing them 3515 // to be reclaimed even if allocated before the start of 3516 // concurrent mark. For this we rely on mark stack insertion to 3517 // exclude is_typeArray() objects, preventing reclaiming an object 3518 // that is in the mark stack. We also rely on the metadata for 3519 // such objects to be built-in and so ensured to be kept live. 3520 // Frequent allocation and drop of large binary blobs is an 3521 // important use case for eager reclaim, and this special handling 3522 // may reduce needed headroom. 3523 3524 return is_typeArray_region(region) && is_remset_small(region); 3525 } 3526 3527 public: 3528 RegisterHumongousWithInCSetFastTestClosure() 3529 : _total_humongous(0), 3530 _candidate_humongous(0), 3531 _dcq(&JavaThread::dirty_card_queue_set()) { 3532 } 3533 3534 virtual bool doHeapRegion(HeapRegion* r) { 3535 if (!r->is_starts_humongous()) { 3536 return false; 3537 } 3538 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3539 3540 bool is_candidate = humongous_region_is_candidate(g1h, r); 3541 uint rindex = r->hrm_index(); 3542 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 3543 if (is_candidate) { 3544 _candidate_humongous++; 3545 g1h->register_humongous_region_with_cset(rindex); 3546 // Is_candidate already filters out humongous object with large remembered sets. 3547 // If we have a humongous object with a few remembered sets, we simply flush these 3548 // remembered set entries into the DCQS. That will result in automatic 3549 // re-evaluation of their remembered set entries during the following evacuation 3550 // phase. 3551 if (!r->rem_set()->is_empty()) { 3552 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 3553 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 3554 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 3555 HeapRegionRemSetIterator hrrs(r->rem_set()); 3556 size_t card_index; 3557 while (hrrs.has_next(card_index)) { 3558 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 3559 // The remembered set might contain references to already freed 3560 // regions. Filter out such entries to avoid failing card table 3561 // verification. 3562 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) { 3563 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 3564 *card_ptr = CardTableModRefBS::dirty_card_val(); 3565 _dcq.enqueue(card_ptr); 3566 } 3567 } 3568 } 3569 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 3570 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 3571 hrrs.n_yielded(), r->rem_set()->occupied()); 3572 r->rem_set()->clear_locked(); 3573 } 3574 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 3575 } 3576 _total_humongous++; 3577 3578 return false; 3579 } 3580 3581 size_t total_humongous() const { return _total_humongous; } 3582 size_t candidate_humongous() const { return _candidate_humongous; } 3583 3584 void flush_rem_set_entries() { _dcq.flush(); } 3585 }; 3586 3587 void G1CollectedHeap::register_humongous_regions_with_cset() { 3588 if (!G1EagerReclaimHumongousObjects) { 3589 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 3590 return; 3591 } 3592 double time = os::elapsed_counter(); 3593 3594 // Collect reclaim candidate information and register candidates with cset. 3595 RegisterHumongousWithInCSetFastTestClosure cl; 3596 heap_region_iterate(&cl); 3597 3598 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 3599 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 3600 cl.total_humongous(), 3601 cl.candidate_humongous()); 3602 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3603 3604 // Finally flush all remembered set entries to re-check into the global DCQS. 3605 cl.flush_rem_set_entries(); 3606 } 3607 3608 #ifdef ASSERT 3609 class VerifyCSetClosure: public HeapRegionClosure { 3610 public: 3611 bool doHeapRegion(HeapRegion* hr) { 3612 // Here we check that the CSet region's RSet is ready for parallel 3613 // iteration. The fields that we'll verify are only manipulated 3614 // when the region is part of a CSet and is collected. Afterwards, 3615 // we reset these fields when we clear the region's RSet (when the 3616 // region is freed) so they are ready when the region is 3617 // re-allocated. The only exception to this is if there's an 3618 // evacuation failure and instead of freeing the region we leave 3619 // it in the heap. In that case, we reset these fields during 3620 // evacuation failure handling. 3621 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3622 3623 // Here's a good place to add any other checks we'd like to 3624 // perform on CSet regions. 3625 return false; 3626 } 3627 }; 3628 #endif // ASSERT 3629 3630 uint G1CollectedHeap::num_task_queues() const { 3631 return _task_queues->size(); 3632 } 3633 3634 #if TASKQUEUE_STATS 3635 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3636 st->print_raw_cr("GC Task Stats"); 3637 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3638 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3639 } 3640 3641 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3642 print_taskqueue_stats_hdr(st); 3643 3644 TaskQueueStats totals; 3645 const uint n = num_task_queues(); 3646 for (uint i = 0; i < n; ++i) { 3647 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr(); 3648 totals += task_queue(i)->stats; 3649 } 3650 st->print_raw("tot "); totals.print(st); st->cr(); 3651 3652 DEBUG_ONLY(totals.verify()); 3653 } 3654 3655 void G1CollectedHeap::reset_taskqueue_stats() { 3656 const uint n = num_task_queues(); 3657 for (uint i = 0; i < n; ++i) { 3658 task_queue(i)->stats.reset(); 3659 } 3660 } 3661 #endif // TASKQUEUE_STATS 3662 3663 void G1CollectedHeap::log_gc_header() { 3664 if (!G1Log::fine()) { 3665 return; 3666 } 3667 3668 gclog_or_tty->gclog_stamp(); 3669 3670 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) 3671 .append(collector_state()->gcs_are_young() ? "(young)" : "(mixed)") 3672 .append(collector_state()->during_initial_mark_pause() ? " (initial-mark)" : ""); 3673 3674 gclog_or_tty->print("[%s", (const char*)gc_cause_str); 3675 } 3676 3677 void G1CollectedHeap::log_gc_footer(double pause_time_sec) { 3678 if (!G1Log::fine()) { 3679 return; 3680 } 3681 3682 if (G1Log::finer()) { 3683 if (evacuation_failed()) { 3684 gclog_or_tty->print(" (to-space exhausted)"); 3685 } 3686 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3687 g1_policy()->print_phases(pause_time_sec); 3688 g1_policy()->print_detailed_heap_transition(); 3689 } else { 3690 if (evacuation_failed()) { 3691 gclog_or_tty->print("--"); 3692 } 3693 g1_policy()->print_heap_transition(); 3694 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3695 } 3696 gclog_or_tty->flush(); 3697 } 3698 3699 void G1CollectedHeap::wait_for_root_region_scanning() { 3700 double scan_wait_start = os::elapsedTime(); 3701 // We have to wait until the CM threads finish scanning the 3702 // root regions as it's the only way to ensure that all the 3703 // objects on them have been correctly scanned before we start 3704 // moving them during the GC. 3705 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3706 double wait_time_ms = 0.0; 3707 if (waited) { 3708 double scan_wait_end = os::elapsedTime(); 3709 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3710 } 3711 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3712 } 3713 3714 bool 3715 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3716 assert_at_safepoint(true /* should_be_vm_thread */); 3717 guarantee(!is_gc_active(), "collection is not reentrant"); 3718 3719 if (GC_locker::check_active_before_gc()) { 3720 return false; 3721 } 3722 3723 _gc_timer_stw->register_gc_start(); 3724 3725 GCIdMark gc_id_mark; 3726 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3727 3728 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3729 ResourceMark rm; 3730 3731 wait_for_root_region_scanning(); 3732 3733 G1Log::update_level(); 3734 print_heap_before_gc(); 3735 trace_heap_before_gc(_gc_tracer_stw); 3736 3737 verify_region_sets_optional(); 3738 verify_dirty_young_regions(); 3739 3740 // This call will decide whether this pause is an initial-mark 3741 // pause. If it is, during_initial_mark_pause() will return true 3742 // for the duration of this pause. 3743 g1_policy()->decide_on_conc_mark_initiation(); 3744 3745 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3746 assert(!collector_state()->during_initial_mark_pause() || 3747 collector_state()->gcs_are_young(), "sanity"); 3748 3749 // We also do not allow mixed GCs during marking. 3750 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity"); 3751 3752 // Record whether this pause is an initial mark. When the current 3753 // thread has completed its logging output and it's safe to signal 3754 // the CM thread, the flag's value in the policy has been reset. 3755 bool should_start_conc_mark = collector_state()->during_initial_mark_pause(); 3756 3757 // Inner scope for scope based logging, timers, and stats collection 3758 { 3759 EvacuationInfo evacuation_info; 3760 3761 if (collector_state()->during_initial_mark_pause()) { 3762 // We are about to start a marking cycle, so we increment the 3763 // full collection counter. 3764 increment_old_marking_cycles_started(); 3765 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3766 } 3767 3768 _gc_tracer_stw->report_yc_type(collector_state()->yc_type()); 3769 3770 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 3771 3772 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3773 workers()->active_workers(), 3774 Threads::number_of_non_daemon_threads()); 3775 workers()->set_active_workers(active_workers); 3776 3777 double pause_start_sec = os::elapsedTime(); 3778 g1_policy()->note_gc_start(active_workers); 3779 log_gc_header(); 3780 3781 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3782 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3783 3784 // If the secondary_free_list is not empty, append it to the 3785 // free_list. No need to wait for the cleanup operation to finish; 3786 // the region allocation code will check the secondary_free_list 3787 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3788 // set, skip this step so that the region allocation code has to 3789 // get entries from the secondary_free_list. 3790 if (!G1StressConcRegionFreeing) { 3791 append_secondary_free_list_if_not_empty_with_lock(); 3792 } 3793 3794 assert(check_young_list_well_formed(), "young list should be well formed"); 3795 3796 // Don't dynamically change the number of GC threads this early. A value of 3797 // 0 is used to indicate serial work. When parallel work is done, 3798 // it will be set. 3799 3800 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3801 IsGCActiveMark x; 3802 3803 gc_prologue(false); 3804 increment_total_collections(false /* full gc */); 3805 increment_gc_time_stamp(); 3806 3807 verify_before_gc(); 3808 3809 check_bitmaps("GC Start"); 3810 3811 #if defined(COMPILER2) || INCLUDE_JVMCI 3812 DerivedPointerTable::clear(); 3813 #endif 3814 3815 // Please see comment in g1CollectedHeap.hpp and 3816 // G1CollectedHeap::ref_processing_init() to see how 3817 // reference processing currently works in G1. 3818 3819 // Enable discovery in the STW reference processor 3820 ref_processor_stw()->enable_discovery(); 3821 3822 { 3823 // We want to temporarily turn off discovery by the 3824 // CM ref processor, if necessary, and turn it back on 3825 // on again later if we do. Using a scoped 3826 // NoRefDiscovery object will do this. 3827 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3828 3829 // Forget the current alloc region (we might even choose it to be part 3830 // of the collection set!). 3831 _allocator->release_mutator_alloc_region(); 3832 3833 // We should call this after we retire the mutator alloc 3834 // region(s) so that all the ALLOC / RETIRE events are generated 3835 // before the start GC event. 3836 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 3837 3838 // This timing is only used by the ergonomics to handle our pause target. 3839 // It is unclear why this should not include the full pause. We will 3840 // investigate this in CR 7178365. 3841 // 3842 // Preserving the old comment here if that helps the investigation: 3843 // 3844 // The elapsed time induced by the start time below deliberately elides 3845 // the possible verification above. 3846 double sample_start_time_sec = os::elapsedTime(); 3847 3848 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3849 3850 if (collector_state()->during_initial_mark_pause()) { 3851 concurrent_mark()->checkpointRootsInitialPre(); 3852 } 3853 3854 double time_remaining_ms = g1_policy()->finalize_young_cset_part(target_pause_time_ms); 3855 g1_policy()->finalize_old_cset_part(time_remaining_ms); 3856 3857 evacuation_info.set_collectionset_regions(g1_policy()->cset_region_length()); 3858 3859 // Make sure the remembered sets are up to date. This needs to be 3860 // done before register_humongous_regions_with_cset(), because the 3861 // remembered sets are used there to choose eager reclaim candidates. 3862 // If the remembered sets are not up to date we might miss some 3863 // entries that need to be handled. 3864 g1_rem_set()->cleanupHRRS(); 3865 3866 register_humongous_regions_with_cset(); 3867 3868 assert(check_cset_fast_test(), "Inconsistency in the InCSetState table."); 3869 3870 _cm->note_start_of_gc(); 3871 // We call this after finalize_cset() to 3872 // ensure that the CSet has been finalized. 3873 _cm->verify_no_cset_oops(); 3874 3875 if (_hr_printer.is_active()) { 3876 HeapRegion* hr = g1_policy()->collection_set(); 3877 while (hr != NULL) { 3878 _hr_printer.cset(hr); 3879 hr = hr->next_in_collection_set(); 3880 } 3881 } 3882 3883 #ifdef ASSERT 3884 VerifyCSetClosure cl; 3885 collection_set_iterate(&cl); 3886 #endif // ASSERT 3887 3888 // Initialize the GC alloc regions. 3889 _allocator->init_gc_alloc_regions(evacuation_info); 3890 3891 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), g1_policy()->young_cset_region_length()); 3892 pre_evacuate_collection_set(); 3893 3894 // Actually do the work... 3895 evacuate_collection_set(evacuation_info, &per_thread_states); 3896 3897 post_evacuate_collection_set(evacuation_info, &per_thread_states); 3898 3899 const size_t* surviving_young_words = per_thread_states.surviving_young_words(); 3900 free_collection_set(g1_policy()->collection_set(), evacuation_info, surviving_young_words); 3901 3902 eagerly_reclaim_humongous_regions(); 3903 3904 g1_policy()->clear_collection_set(); 3905 3906 // Start a new incremental collection set for the next pause. 3907 g1_policy()->start_incremental_cset_building(); 3908 3909 clear_cset_fast_test(); 3910 3911 _young_list->reset_sampled_info(); 3912 3913 // Don't check the whole heap at this point as the 3914 // GC alloc regions from this pause have been tagged 3915 // as survivors and moved on to the survivor list. 3916 // Survivor regions will fail the !is_young() check. 3917 assert(check_young_list_empty(false /* check_heap */), 3918 "young list should be empty"); 3919 3920 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3921 _young_list->first_survivor_region(), 3922 _young_list->last_survivor_region()); 3923 3924 _young_list->reset_auxilary_lists(); 3925 3926 if (evacuation_failed()) { 3927 set_used(recalculate_used()); 3928 if (_archive_allocator != NULL) { 3929 _archive_allocator->clear_used(); 3930 } 3931 for (uint i = 0; i < ParallelGCThreads; i++) { 3932 if (_evacuation_failed_info_array[i].has_failed()) { 3933 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3934 } 3935 } 3936 } else { 3937 // The "used" of the the collection set have already been subtracted 3938 // when they were freed. Add in the bytes evacuated. 3939 increase_used(g1_policy()->bytes_copied_during_gc()); 3940 } 3941 3942 if (collector_state()->during_initial_mark_pause()) { 3943 // We have to do this before we notify the CM threads that 3944 // they can start working to make sure that all the 3945 // appropriate initialization is done on the CM object. 3946 concurrent_mark()->checkpointRootsInitialPost(); 3947 collector_state()->set_mark_in_progress(true); 3948 // Note that we don't actually trigger the CM thread at 3949 // this point. We do that later when we're sure that 3950 // the current thread has completed its logging output. 3951 } 3952 3953 allocate_dummy_regions(); 3954 3955 _allocator->init_mutator_alloc_region(); 3956 3957 { 3958 size_t expand_bytes = g1_policy()->expansion_amount(); 3959 if (expand_bytes > 0) { 3960 size_t bytes_before = capacity(); 3961 // No need for an ergo verbose message here, 3962 // expansion_amount() does this when it returns a value > 0. 3963 double expand_ms; 3964 if (!expand(expand_bytes, &expand_ms)) { 3965 // We failed to expand the heap. Cannot do anything about it. 3966 } 3967 g1_policy()->phase_times()->record_expand_heap_time(expand_ms); 3968 } 3969 } 3970 3971 // We redo the verification but now wrt to the new CSet which 3972 // has just got initialized after the previous CSet was freed. 3973 _cm->verify_no_cset_oops(); 3974 _cm->note_end_of_gc(); 3975 3976 // This timing is only used by the ergonomics to handle our pause target. 3977 // It is unclear why this should not include the full pause. We will 3978 // investigate this in CR 7178365. 3979 double sample_end_time_sec = os::elapsedTime(); 3980 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3981 size_t total_cards_scanned = per_thread_states.total_cards_scanned(); 3982 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned); 3983 3984 evacuation_info.set_collectionset_used_before(g1_policy()->collection_set_bytes_used_before()); 3985 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc()); 3986 3987 MemoryService::track_memory_usage(); 3988 3989 // In prepare_for_verify() below we'll need to scan the deferred 3990 // update buffers to bring the RSets up-to-date if 3991 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3992 // the update buffers we'll probably need to scan cards on the 3993 // regions we just allocated to (i.e., the GC alloc 3994 // regions). However, during the last GC we called 3995 // set_saved_mark() on all the GC alloc regions, so card 3996 // scanning might skip the [saved_mark_word()...top()] area of 3997 // those regions (i.e., the area we allocated objects into 3998 // during the last GC). But it shouldn't. Given that 3999 // saved_mark_word() is conditional on whether the GC time stamp 4000 // on the region is current or not, by incrementing the GC time 4001 // stamp here we invalidate all the GC time stamps on all the 4002 // regions and saved_mark_word() will simply return top() for 4003 // all the regions. This is a nicer way of ensuring this rather 4004 // than iterating over the regions and fixing them. In fact, the 4005 // GC time stamp increment here also ensures that 4006 // saved_mark_word() will return top() between pauses, i.e., 4007 // during concurrent refinement. So we don't need the 4008 // is_gc_active() check to decided which top to use when 4009 // scanning cards (see CR 7039627). 4010 increment_gc_time_stamp(); 4011 4012 verify_after_gc(); 4013 check_bitmaps("GC End"); 4014 4015 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 4016 ref_processor_stw()->verify_no_references_recorded(); 4017 4018 // CM reference discovery will be re-enabled if necessary. 4019 } 4020 4021 // We should do this after we potentially expand the heap so 4022 // that all the COMMIT events are generated before the end GC 4023 // event, and after we retire the GC alloc regions so that all 4024 // RETIRE events are generated before the end GC event. 4025 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 4026 4027 #ifdef TRACESPINNING 4028 ParallelTaskTerminator::print_termination_counts(); 4029 #endif 4030 4031 gc_epilogue(false); 4032 } 4033 4034 // Print the remainder of the GC log output. 4035 log_gc_footer(os::elapsedTime() - pause_start_sec); 4036 4037 // It is not yet to safe to tell the concurrent mark to 4038 // start as we have some optional output below. We don't want the 4039 // output from the concurrent mark thread interfering with this 4040 // logging output either. 4041 4042 _hrm.verify_optional(); 4043 verify_region_sets_optional(); 4044 4045 TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats()); 4046 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 4047 4048 print_heap_after_gc(); 4049 trace_heap_after_gc(_gc_tracer_stw); 4050 4051 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 4052 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 4053 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 4054 // before any GC notifications are raised. 4055 g1mm()->update_sizes(); 4056 4057 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 4058 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 4059 _gc_timer_stw->register_gc_end(); 4060 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 4061 } 4062 // It should now be safe to tell the concurrent mark thread to start 4063 // without its logging output interfering with the logging output 4064 // that came from the pause. 4065 4066 if (should_start_conc_mark) { 4067 // CAUTION: after the doConcurrentMark() call below, 4068 // the concurrent marking thread(s) could be running 4069 // concurrently with us. Make sure that anything after 4070 // this point does not assume that we are the only GC thread 4071 // running. Note: of course, the actual marking work will 4072 // not start until the safepoint itself is released in 4073 // SuspendibleThreadSet::desynchronize(). 4074 doConcurrentMark(); 4075 } 4076 4077 return true; 4078 } 4079 4080 void G1CollectedHeap::remove_self_forwarding_pointers() { 4081 double remove_self_forwards_start = os::elapsedTime(); 4082 4083 G1ParRemoveSelfForwardPtrsTask rsfp_task; 4084 workers()->run_task(&rsfp_task); 4085 4086 // Now restore saved marks, if any. 4087 for (uint i = 0; i < ParallelGCThreads; i++) { 4088 OopAndMarkOopStack& cur = _preserved_objs[i]; 4089 while (!cur.is_empty()) { 4090 OopAndMarkOop elem = cur.pop(); 4091 elem.set_mark(); 4092 } 4093 cur.clear(true); 4094 } 4095 4096 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 4097 } 4098 4099 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) { 4100 if (!_evacuation_failed) { 4101 _evacuation_failed = true; 4102 } 4103 4104 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size()); 4105 4106 // We want to call the "for_promotion_failure" version only in the 4107 // case of a promotion failure. 4108 if (m->must_be_preserved_for_promotion_failure(obj)) { 4109 OopAndMarkOop elem(obj, m); 4110 _preserved_objs[worker_id].push(elem); 4111 } 4112 } 4113 4114 class G1ParEvacuateFollowersClosure : public VoidClosure { 4115 private: 4116 double _start_term; 4117 double _term_time; 4118 size_t _term_attempts; 4119 4120 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); } 4121 void end_term_time() { _term_time += os::elapsedTime() - _start_term; } 4122 protected: 4123 G1CollectedHeap* _g1h; 4124 G1ParScanThreadState* _par_scan_state; 4125 RefToScanQueueSet* _queues; 4126 ParallelTaskTerminator* _terminator; 4127 4128 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4129 RefToScanQueueSet* queues() { return _queues; } 4130 ParallelTaskTerminator* terminator() { return _terminator; } 4131 4132 public: 4133 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4134 G1ParScanThreadState* par_scan_state, 4135 RefToScanQueueSet* queues, 4136 ParallelTaskTerminator* terminator) 4137 : _g1h(g1h), _par_scan_state(par_scan_state), 4138 _queues(queues), _terminator(terminator), 4139 _start_term(0.0), _term_time(0.0), _term_attempts(0) {} 4140 4141 void do_void(); 4142 4143 double term_time() const { return _term_time; } 4144 size_t term_attempts() const { return _term_attempts; } 4145 4146 private: 4147 inline bool offer_termination(); 4148 }; 4149 4150 bool G1ParEvacuateFollowersClosure::offer_termination() { 4151 G1ParScanThreadState* const pss = par_scan_state(); 4152 start_term_time(); 4153 const bool res = terminator()->offer_termination(); 4154 end_term_time(); 4155 return res; 4156 } 4157 4158 void G1ParEvacuateFollowersClosure::do_void() { 4159 G1ParScanThreadState* const pss = par_scan_state(); 4160 pss->trim_queue(); 4161 do { 4162 pss->steal_and_trim_queue(queues()); 4163 } while (!offer_termination()); 4164 } 4165 4166 class G1ParTask : public AbstractGangTask { 4167 protected: 4168 G1CollectedHeap* _g1h; 4169 G1ParScanThreadStateSet* _pss; 4170 RefToScanQueueSet* _queues; 4171 G1RootProcessor* _root_processor; 4172 ParallelTaskTerminator _terminator; 4173 uint _n_workers; 4174 4175 public: 4176 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers) 4177 : AbstractGangTask("G1 collection"), 4178 _g1h(g1h), 4179 _pss(per_thread_states), 4180 _queues(task_queues), 4181 _root_processor(root_processor), 4182 _terminator(n_workers, _queues), 4183 _n_workers(n_workers) 4184 {} 4185 4186 void work(uint worker_id) { 4187 if (worker_id >= _n_workers) return; // no work needed this round 4188 4189 double start_sec = os::elapsedTime(); 4190 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec); 4191 4192 { 4193 ResourceMark rm; 4194 HandleMark hm; 4195 4196 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4197 4198 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4199 pss->set_ref_processor(rp); 4200 4201 double start_strong_roots_sec = os::elapsedTime(); 4202 4203 _root_processor->evacuate_roots(pss->closures(), worker_id); 4204 4205 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss); 4206 4207 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid 4208 // treating the nmethods visited to act as roots for concurrent marking. 4209 // We only want to make sure that the oops in the nmethods are adjusted with regard to the 4210 // objects copied by the current evacuation. 4211 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl, 4212 pss->closures()->weak_codeblobs(), 4213 worker_id); 4214 4215 _pss->add_cards_scanned(worker_id, cards_scanned); 4216 4217 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec; 4218 4219 double term_sec = 0.0; 4220 size_t evac_term_attempts = 0; 4221 { 4222 double start = os::elapsedTime(); 4223 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator); 4224 evac.do_void(); 4225 4226 evac_term_attempts = evac.term_attempts(); 4227 term_sec = evac.term_time(); 4228 double elapsed_sec = os::elapsedTime() - start; 4229 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 4230 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 4231 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts); 4232 } 4233 4234 assert(pss->queue_is_empty(), "should be empty"); 4235 4236 if (PrintTerminationStats) { 4237 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 4238 size_t lab_waste; 4239 size_t lab_undo_waste; 4240 pss->waste(lab_waste, lab_undo_waste); 4241 _g1h->print_termination_stats(gclog_or_tty, 4242 worker_id, 4243 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */ 4244 strong_roots_sec * 1000.0, /* strong roots time */ 4245 term_sec * 1000.0, /* evac term time */ 4246 evac_term_attempts, /* evac term attempts */ 4247 lab_waste, /* alloc buffer waste */ 4248 lab_undo_waste /* undo waste */ 4249 ); 4250 } 4251 4252 // Close the inner scope so that the ResourceMark and HandleMark 4253 // destructors are executed here and are included as part of the 4254 // "GC Worker Time". 4255 } 4256 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 4257 } 4258 }; 4259 4260 void G1CollectedHeap::print_termination_stats_hdr(outputStream* const st) { 4261 st->print_raw_cr("GC Termination Stats"); 4262 st->print_raw_cr(" elapsed --strong roots-- -------termination------- ------waste (KiB)------"); 4263 st->print_raw_cr("thr ms ms % ms % attempts total alloc undo"); 4264 st->print_raw_cr("--- --------- --------- ------ --------- ------ -------- ------- ------- -------"); 4265 } 4266 4267 void G1CollectedHeap::print_termination_stats(outputStream* const st, 4268 uint worker_id, 4269 double elapsed_ms, 4270 double strong_roots_ms, 4271 double term_ms, 4272 size_t term_attempts, 4273 size_t alloc_buffer_waste, 4274 size_t undo_waste) const { 4275 st->print_cr("%3d %9.2f %9.2f %6.2f " 4276 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 4277 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 4278 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms, 4279 term_ms, term_ms * 100 / elapsed_ms, term_attempts, 4280 (alloc_buffer_waste + undo_waste) * HeapWordSize / K, 4281 alloc_buffer_waste * HeapWordSize / K, 4282 undo_waste * HeapWordSize / K); 4283 } 4284 4285 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 4286 private: 4287 BoolObjectClosure* _is_alive; 4288 int _initial_string_table_size; 4289 int _initial_symbol_table_size; 4290 4291 bool _process_strings; 4292 int _strings_processed; 4293 int _strings_removed; 4294 4295 bool _process_symbols; 4296 int _symbols_processed; 4297 int _symbols_removed; 4298 4299 public: 4300 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 4301 AbstractGangTask("String/Symbol Unlinking"), 4302 _is_alive(is_alive), 4303 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 4304 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 4305 4306 _initial_string_table_size = StringTable::the_table()->table_size(); 4307 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 4308 if (process_strings) { 4309 StringTable::clear_parallel_claimed_index(); 4310 } 4311 if (process_symbols) { 4312 SymbolTable::clear_parallel_claimed_index(); 4313 } 4314 } 4315 4316 ~G1StringSymbolTableUnlinkTask() { 4317 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 4318 "claim value %d after unlink less than initial string table size %d", 4319 StringTable::parallel_claimed_index(), _initial_string_table_size); 4320 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 4321 "claim value %d after unlink less than initial symbol table size %d", 4322 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size); 4323 4324 if (G1TraceStringSymbolTableScrubbing) { 4325 gclog_or_tty->print_cr("Cleaned string and symbol table, " 4326 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 4327 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 4328 strings_processed(), strings_removed(), 4329 symbols_processed(), symbols_removed()); 4330 } 4331 } 4332 4333 void work(uint worker_id) { 4334 int strings_processed = 0; 4335 int strings_removed = 0; 4336 int symbols_processed = 0; 4337 int symbols_removed = 0; 4338 if (_process_strings) { 4339 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 4340 Atomic::add(strings_processed, &_strings_processed); 4341 Atomic::add(strings_removed, &_strings_removed); 4342 } 4343 if (_process_symbols) { 4344 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 4345 Atomic::add(symbols_processed, &_symbols_processed); 4346 Atomic::add(symbols_removed, &_symbols_removed); 4347 } 4348 } 4349 4350 size_t strings_processed() const { return (size_t)_strings_processed; } 4351 size_t strings_removed() const { return (size_t)_strings_removed; } 4352 4353 size_t symbols_processed() const { return (size_t)_symbols_processed; } 4354 size_t symbols_removed() const { return (size_t)_symbols_removed; } 4355 }; 4356 4357 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 4358 private: 4359 static Monitor* _lock; 4360 4361 BoolObjectClosure* const _is_alive; 4362 const bool _unloading_occurred; 4363 const uint _num_workers; 4364 4365 // Variables used to claim nmethods. 4366 nmethod* _first_nmethod; 4367 volatile nmethod* _claimed_nmethod; 4368 4369 // The list of nmethods that need to be processed by the second pass. 4370 volatile nmethod* _postponed_list; 4371 volatile uint _num_entered_barrier; 4372 4373 public: 4374 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 4375 _is_alive(is_alive), 4376 _unloading_occurred(unloading_occurred), 4377 _num_workers(num_workers), 4378 _first_nmethod(NULL), 4379 _claimed_nmethod(NULL), 4380 _postponed_list(NULL), 4381 _num_entered_barrier(0) 4382 { 4383 nmethod::increase_unloading_clock(); 4384 // Get first alive nmethod 4385 NMethodIterator iter = NMethodIterator(); 4386 if(iter.next_alive()) { 4387 _first_nmethod = iter.method(); 4388 } 4389 _claimed_nmethod = (volatile nmethod*)_first_nmethod; 4390 } 4391 4392 ~G1CodeCacheUnloadingTask() { 4393 CodeCache::verify_clean_inline_caches(); 4394 4395 CodeCache::set_needs_cache_clean(false); 4396 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 4397 4398 CodeCache::verify_icholder_relocations(); 4399 } 4400 4401 private: 4402 void add_to_postponed_list(nmethod* nm) { 4403 nmethod* old; 4404 do { 4405 old = (nmethod*)_postponed_list; 4406 nm->set_unloading_next(old); 4407 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 4408 } 4409 4410 void clean_nmethod(nmethod* nm) { 4411 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 4412 4413 if (postponed) { 4414 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 4415 add_to_postponed_list(nm); 4416 } 4417 4418 // Mark that this thread has been cleaned/unloaded. 4419 // After this call, it will be safe to ask if this nmethod was unloaded or not. 4420 nm->set_unloading_clock(nmethod::global_unloading_clock()); 4421 } 4422 4423 void clean_nmethod_postponed(nmethod* nm) { 4424 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 4425 } 4426 4427 static const int MaxClaimNmethods = 16; 4428 4429 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) { 4430 nmethod* first; 4431 NMethodIterator last; 4432 4433 do { 4434 *num_claimed_nmethods = 0; 4435 4436 first = (nmethod*)_claimed_nmethod; 4437 last = NMethodIterator(first); 4438 4439 if (first != NULL) { 4440 4441 for (int i = 0; i < MaxClaimNmethods; i++) { 4442 if (!last.next_alive()) { 4443 break; 4444 } 4445 claimed_nmethods[i] = last.method(); 4446 (*num_claimed_nmethods)++; 4447 } 4448 } 4449 4450 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 4451 } 4452 4453 nmethod* claim_postponed_nmethod() { 4454 nmethod* claim; 4455 nmethod* next; 4456 4457 do { 4458 claim = (nmethod*)_postponed_list; 4459 if (claim == NULL) { 4460 return NULL; 4461 } 4462 4463 next = claim->unloading_next(); 4464 4465 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 4466 4467 return claim; 4468 } 4469 4470 public: 4471 // Mark that we're done with the first pass of nmethod cleaning. 4472 void barrier_mark(uint worker_id) { 4473 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4474 _num_entered_barrier++; 4475 if (_num_entered_barrier == _num_workers) { 4476 ml.notify_all(); 4477 } 4478 } 4479 4480 // See if we have to wait for the other workers to 4481 // finish their first-pass nmethod cleaning work. 4482 void barrier_wait(uint worker_id) { 4483 if (_num_entered_barrier < _num_workers) { 4484 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4485 while (_num_entered_barrier < _num_workers) { 4486 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 4487 } 4488 } 4489 } 4490 4491 // Cleaning and unloading of nmethods. Some work has to be postponed 4492 // to the second pass, when we know which nmethods survive. 4493 void work_first_pass(uint worker_id) { 4494 // The first nmethods is claimed by the first worker. 4495 if (worker_id == 0 && _first_nmethod != NULL) { 4496 clean_nmethod(_first_nmethod); 4497 _first_nmethod = NULL; 4498 } 4499 4500 int num_claimed_nmethods; 4501 nmethod* claimed_nmethods[MaxClaimNmethods]; 4502 4503 while (true) { 4504 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 4505 4506 if (num_claimed_nmethods == 0) { 4507 break; 4508 } 4509 4510 for (int i = 0; i < num_claimed_nmethods; i++) { 4511 clean_nmethod(claimed_nmethods[i]); 4512 } 4513 } 4514 } 4515 4516 void work_second_pass(uint worker_id) { 4517 nmethod* nm; 4518 // Take care of postponed nmethods. 4519 while ((nm = claim_postponed_nmethod()) != NULL) { 4520 clean_nmethod_postponed(nm); 4521 } 4522 } 4523 }; 4524 4525 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never); 4526 4527 class G1KlassCleaningTask : public StackObj { 4528 BoolObjectClosure* _is_alive; 4529 volatile jint _clean_klass_tree_claimed; 4530 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 4531 4532 public: 4533 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 4534 _is_alive(is_alive), 4535 _clean_klass_tree_claimed(0), 4536 _klass_iterator() { 4537 } 4538 4539 private: 4540 bool claim_clean_klass_tree_task() { 4541 if (_clean_klass_tree_claimed) { 4542 return false; 4543 } 4544 4545 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 4546 } 4547 4548 InstanceKlass* claim_next_klass() { 4549 Klass* klass; 4550 do { 4551 klass =_klass_iterator.next_klass(); 4552 } while (klass != NULL && !klass->is_instance_klass()); 4553 4554 // this can be null so don't call InstanceKlass::cast 4555 return static_cast<InstanceKlass*>(klass); 4556 } 4557 4558 public: 4559 4560 void clean_klass(InstanceKlass* ik) { 4561 ik->clean_weak_instanceklass_links(_is_alive); 4562 } 4563 4564 void work() { 4565 ResourceMark rm; 4566 4567 // One worker will clean the subklass/sibling klass tree. 4568 if (claim_clean_klass_tree_task()) { 4569 Klass::clean_subklass_tree(_is_alive); 4570 } 4571 4572 // All workers will help cleaning the classes, 4573 InstanceKlass* klass; 4574 while ((klass = claim_next_klass()) != NULL) { 4575 clean_klass(klass); 4576 } 4577 } 4578 }; 4579 4580 // To minimize the remark pause times, the tasks below are done in parallel. 4581 class G1ParallelCleaningTask : public AbstractGangTask { 4582 private: 4583 G1StringSymbolTableUnlinkTask _string_symbol_task; 4584 G1CodeCacheUnloadingTask _code_cache_task; 4585 G1KlassCleaningTask _klass_cleaning_task; 4586 4587 public: 4588 // The constructor is run in the VMThread. 4589 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 4590 AbstractGangTask("Parallel Cleaning"), 4591 _string_symbol_task(is_alive, process_strings, process_symbols), 4592 _code_cache_task(num_workers, is_alive, unloading_occurred), 4593 _klass_cleaning_task(is_alive) { 4594 } 4595 4596 // The parallel work done by all worker threads. 4597 void work(uint worker_id) { 4598 // Do first pass of code cache cleaning. 4599 _code_cache_task.work_first_pass(worker_id); 4600 4601 // Let the threads mark that the first pass is done. 4602 _code_cache_task.barrier_mark(worker_id); 4603 4604 // Clean the Strings and Symbols. 4605 _string_symbol_task.work(worker_id); 4606 4607 // Wait for all workers to finish the first code cache cleaning pass. 4608 _code_cache_task.barrier_wait(worker_id); 4609 4610 // Do the second code cache cleaning work, which realize on 4611 // the liveness information gathered during the first pass. 4612 _code_cache_task.work_second_pass(worker_id); 4613 4614 // Clean all klasses that were not unloaded. 4615 _klass_cleaning_task.work(); 4616 } 4617 }; 4618 4619 4620 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 4621 bool process_strings, 4622 bool process_symbols, 4623 bool class_unloading_occurred) { 4624 uint n_workers = workers()->active_workers(); 4625 4626 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 4627 n_workers, class_unloading_occurred); 4628 workers()->run_task(&g1_unlink_task); 4629 } 4630 4631 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 4632 bool process_strings, bool process_symbols) { 4633 { 4634 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 4635 workers()->run_task(&g1_unlink_task); 4636 } 4637 4638 if (G1StringDedup::is_enabled()) { 4639 G1StringDedup::unlink(is_alive); 4640 } 4641 } 4642 4643 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 4644 private: 4645 DirtyCardQueueSet* _queue; 4646 public: 4647 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { } 4648 4649 virtual void work(uint worker_id) { 4650 G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times(); 4651 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 4652 4653 RedirtyLoggedCardTableEntryClosure cl; 4654 _queue->par_apply_closure_to_all_completed_buffers(&cl); 4655 4656 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed()); 4657 } 4658 }; 4659 4660 void G1CollectedHeap::redirty_logged_cards() { 4661 double redirty_logged_cards_start = os::elapsedTime(); 4662 4663 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set()); 4664 dirty_card_queue_set().reset_for_par_iteration(); 4665 workers()->run_task(&redirty_task); 4666 4667 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 4668 dcq.merge_bufferlists(&dirty_card_queue_set()); 4669 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 4670 4671 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 4672 } 4673 4674 // Weak Reference Processing support 4675 4676 // An always "is_alive" closure that is used to preserve referents. 4677 // If the object is non-null then it's alive. Used in the preservation 4678 // of referent objects that are pointed to by reference objects 4679 // discovered by the CM ref processor. 4680 class G1AlwaysAliveClosure: public BoolObjectClosure { 4681 G1CollectedHeap* _g1; 4682 public: 4683 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4684 bool do_object_b(oop p) { 4685 if (p != NULL) { 4686 return true; 4687 } 4688 return false; 4689 } 4690 }; 4691 4692 bool G1STWIsAliveClosure::do_object_b(oop p) { 4693 // An object is reachable if it is outside the collection set, 4694 // or is inside and copied. 4695 return !_g1->is_in_cset(p) || p->is_forwarded(); 4696 } 4697 4698 // Non Copying Keep Alive closure 4699 class G1KeepAliveClosure: public OopClosure { 4700 G1CollectedHeap* _g1; 4701 public: 4702 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4703 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 4704 void do_oop(oop* p) { 4705 oop obj = *p; 4706 assert(obj != NULL, "the caller should have filtered out NULL values"); 4707 4708 const InCSetState cset_state = _g1->in_cset_state(obj); 4709 if (!cset_state.is_in_cset_or_humongous()) { 4710 return; 4711 } 4712 if (cset_state.is_in_cset()) { 4713 assert( obj->is_forwarded(), "invariant" ); 4714 *p = obj->forwardee(); 4715 } else { 4716 assert(!obj->is_forwarded(), "invariant" ); 4717 assert(cset_state.is_humongous(), 4718 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()); 4719 _g1->set_humongous_is_live(obj); 4720 } 4721 } 4722 }; 4723 4724 // Copying Keep Alive closure - can be called from both 4725 // serial and parallel code as long as different worker 4726 // threads utilize different G1ParScanThreadState instances 4727 // and different queues. 4728 4729 class G1CopyingKeepAliveClosure: public OopClosure { 4730 G1CollectedHeap* _g1h; 4731 OopClosure* _copy_non_heap_obj_cl; 4732 G1ParScanThreadState* _par_scan_state; 4733 4734 public: 4735 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4736 OopClosure* non_heap_obj_cl, 4737 G1ParScanThreadState* pss): 4738 _g1h(g1h), 4739 _copy_non_heap_obj_cl(non_heap_obj_cl), 4740 _par_scan_state(pss) 4741 {} 4742 4743 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4744 virtual void do_oop( oop* p) { do_oop_work(p); } 4745 4746 template <class T> void do_oop_work(T* p) { 4747 oop obj = oopDesc::load_decode_heap_oop(p); 4748 4749 if (_g1h->is_in_cset_or_humongous(obj)) { 4750 // If the referent object has been forwarded (either copied 4751 // to a new location or to itself in the event of an 4752 // evacuation failure) then we need to update the reference 4753 // field and, if both reference and referent are in the G1 4754 // heap, update the RSet for the referent. 4755 // 4756 // If the referent has not been forwarded then we have to keep 4757 // it alive by policy. Therefore we have copy the referent. 4758 // 4759 // If the reference field is in the G1 heap then we can push 4760 // on the PSS queue. When the queue is drained (after each 4761 // phase of reference processing) the object and it's followers 4762 // will be copied, the reference field set to point to the 4763 // new location, and the RSet updated. Otherwise we need to 4764 // use the the non-heap or metadata closures directly to copy 4765 // the referent object and update the pointer, while avoiding 4766 // updating the RSet. 4767 4768 if (_g1h->is_in_g1_reserved(p)) { 4769 _par_scan_state->push_on_queue(p); 4770 } else { 4771 assert(!Metaspace::contains((const void*)p), 4772 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)); 4773 _copy_non_heap_obj_cl->do_oop(p); 4774 } 4775 } 4776 } 4777 }; 4778 4779 // Serial drain queue closure. Called as the 'complete_gc' 4780 // closure for each discovered list in some of the 4781 // reference processing phases. 4782 4783 class G1STWDrainQueueClosure: public VoidClosure { 4784 protected: 4785 G1CollectedHeap* _g1h; 4786 G1ParScanThreadState* _par_scan_state; 4787 4788 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4789 4790 public: 4791 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 4792 _g1h(g1h), 4793 _par_scan_state(pss) 4794 { } 4795 4796 void do_void() { 4797 G1ParScanThreadState* const pss = par_scan_state(); 4798 pss->trim_queue(); 4799 } 4800 }; 4801 4802 // Parallel Reference Processing closures 4803 4804 // Implementation of AbstractRefProcTaskExecutor for parallel reference 4805 // processing during G1 evacuation pauses. 4806 4807 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 4808 private: 4809 G1CollectedHeap* _g1h; 4810 G1ParScanThreadStateSet* _pss; 4811 RefToScanQueueSet* _queues; 4812 WorkGang* _workers; 4813 uint _active_workers; 4814 4815 public: 4816 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 4817 G1ParScanThreadStateSet* per_thread_states, 4818 WorkGang* workers, 4819 RefToScanQueueSet *task_queues, 4820 uint n_workers) : 4821 _g1h(g1h), 4822 _pss(per_thread_states), 4823 _queues(task_queues), 4824 _workers(workers), 4825 _active_workers(n_workers) 4826 { 4827 assert(n_workers > 0, "shouldn't call this otherwise"); 4828 } 4829 4830 // Executes the given task using concurrent marking worker threads. 4831 virtual void execute(ProcessTask& task); 4832 virtual void execute(EnqueueTask& task); 4833 }; 4834 4835 // Gang task for possibly parallel reference processing 4836 4837 class G1STWRefProcTaskProxy: public AbstractGangTask { 4838 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 4839 ProcessTask& _proc_task; 4840 G1CollectedHeap* _g1h; 4841 G1ParScanThreadStateSet* _pss; 4842 RefToScanQueueSet* _task_queues; 4843 ParallelTaskTerminator* _terminator; 4844 4845 public: 4846 G1STWRefProcTaskProxy(ProcessTask& proc_task, 4847 G1CollectedHeap* g1h, 4848 G1ParScanThreadStateSet* per_thread_states, 4849 RefToScanQueueSet *task_queues, 4850 ParallelTaskTerminator* terminator) : 4851 AbstractGangTask("Process reference objects in parallel"), 4852 _proc_task(proc_task), 4853 _g1h(g1h), 4854 _pss(per_thread_states), 4855 _task_queues(task_queues), 4856 _terminator(terminator) 4857 {} 4858 4859 virtual void work(uint worker_id) { 4860 // The reference processing task executed by a single worker. 4861 ResourceMark rm; 4862 HandleMark hm; 4863 4864 G1STWIsAliveClosure is_alive(_g1h); 4865 4866 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4867 pss->set_ref_processor(NULL); 4868 4869 // Keep alive closure. 4870 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4871 4872 // Complete GC closure 4873 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator); 4874 4875 // Call the reference processing task's work routine. 4876 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 4877 4878 // Note we cannot assert that the refs array is empty here as not all 4879 // of the processing tasks (specifically phase2 - pp2_work) execute 4880 // the complete_gc closure (which ordinarily would drain the queue) so 4881 // the queue may not be empty. 4882 } 4883 }; 4884 4885 // Driver routine for parallel reference processing. 4886 // Creates an instance of the ref processing gang 4887 // task and has the worker threads execute it. 4888 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 4889 assert(_workers != NULL, "Need parallel worker threads."); 4890 4891 ParallelTaskTerminator terminator(_active_workers, _queues); 4892 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator); 4893 4894 _workers->run_task(&proc_task_proxy); 4895 } 4896 4897 // Gang task for parallel reference enqueueing. 4898 4899 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 4900 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 4901 EnqueueTask& _enq_task; 4902 4903 public: 4904 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 4905 AbstractGangTask("Enqueue reference objects in parallel"), 4906 _enq_task(enq_task) 4907 { } 4908 4909 virtual void work(uint worker_id) { 4910 _enq_task.work(worker_id); 4911 } 4912 }; 4913 4914 // Driver routine for parallel reference enqueueing. 4915 // Creates an instance of the ref enqueueing gang 4916 // task and has the worker threads execute it. 4917 4918 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 4919 assert(_workers != NULL, "Need parallel worker threads."); 4920 4921 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 4922 4923 _workers->run_task(&enq_task_proxy); 4924 } 4925 4926 // End of weak reference support closures 4927 4928 // Abstract task used to preserve (i.e. copy) any referent objects 4929 // that are in the collection set and are pointed to by reference 4930 // objects discovered by the CM ref processor. 4931 4932 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 4933 protected: 4934 G1CollectedHeap* _g1h; 4935 G1ParScanThreadStateSet* _pss; 4936 RefToScanQueueSet* _queues; 4937 ParallelTaskTerminator _terminator; 4938 uint _n_workers; 4939 4940 public: 4941 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) : 4942 AbstractGangTask("ParPreserveCMReferents"), 4943 _g1h(g1h), 4944 _pss(per_thread_states), 4945 _queues(task_queues), 4946 _terminator(workers, _queues), 4947 _n_workers(workers) 4948 { } 4949 4950 void work(uint worker_id) { 4951 ResourceMark rm; 4952 HandleMark hm; 4953 4954 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id); 4955 pss->set_ref_processor(NULL); 4956 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 4957 4958 // Is alive closure 4959 G1AlwaysAliveClosure always_alive(_g1h); 4960 4961 // Copying keep alive closure. Applied to referent objects that need 4962 // to be copied. 4963 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss); 4964 4965 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 4966 4967 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 4968 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 4969 4970 // limit is set using max_num_q() - which was set using ParallelGCThreads. 4971 // So this must be true - but assert just in case someone decides to 4972 // change the worker ids. 4973 assert(worker_id < limit, "sanity"); 4974 assert(!rp->discovery_is_atomic(), "check this code"); 4975 4976 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 4977 for (uint idx = worker_id; idx < limit; idx += stride) { 4978 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 4979 4980 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 4981 while (iter.has_next()) { 4982 // Since discovery is not atomic for the CM ref processor, we 4983 // can see some null referent objects. 4984 iter.load_ptrs(DEBUG_ONLY(true)); 4985 oop ref = iter.obj(); 4986 4987 // This will filter nulls. 4988 if (iter.is_referent_alive()) { 4989 iter.make_referent_alive(); 4990 } 4991 iter.move_to_next(); 4992 } 4993 } 4994 4995 // Drain the queue - which may cause stealing 4996 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator); 4997 drain_queue.do_void(); 4998 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 4999 assert(pss->queue_is_empty(), "should be"); 5000 } 5001 }; 5002 5003 // Weak Reference processing during an evacuation pause (part 1). 5004 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 5005 double ref_proc_start = os::elapsedTime(); 5006 5007 ReferenceProcessor* rp = _ref_processor_stw; 5008 assert(rp->discovery_enabled(), "should have been enabled"); 5009 5010 // Any reference objects, in the collection set, that were 'discovered' 5011 // by the CM ref processor should have already been copied (either by 5012 // applying the external root copy closure to the discovered lists, or 5013 // by following an RSet entry). 5014 // 5015 // But some of the referents, that are in the collection set, that these 5016 // reference objects point to may not have been copied: the STW ref 5017 // processor would have seen that the reference object had already 5018 // been 'discovered' and would have skipped discovering the reference, 5019 // but would not have treated the reference object as a regular oop. 5020 // As a result the copy closure would not have been applied to the 5021 // referent object. 5022 // 5023 // We need to explicitly copy these referent objects - the references 5024 // will be processed at the end of remarking. 5025 // 5026 // We also need to do this copying before we process the reference 5027 // objects discovered by the STW ref processor in case one of these 5028 // referents points to another object which is also referenced by an 5029 // object discovered by the STW ref processor. 5030 5031 uint no_of_gc_workers = workers()->active_workers(); 5032 5033 G1ParPreserveCMReferentsTask keep_cm_referents(this, 5034 per_thread_states, 5035 no_of_gc_workers, 5036 _task_queues); 5037 5038 workers()->run_task(&keep_cm_referents); 5039 5040 // Closure to test whether a referent is alive. 5041 G1STWIsAliveClosure is_alive(this); 5042 5043 // Even when parallel reference processing is enabled, the processing 5044 // of JNI refs is serial and performed serially by the current thread 5045 // rather than by a worker. The following PSS will be used for processing 5046 // JNI refs. 5047 5048 // Use only a single queue for this PSS. 5049 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0); 5050 pss->set_ref_processor(NULL); 5051 assert(pss->queue_is_empty(), "pre-condition"); 5052 5053 // Keep alive closure. 5054 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss); 5055 5056 // Serial Complete GC closure 5057 G1STWDrainQueueClosure drain_queue(this, pss); 5058 5059 // Setup the soft refs policy... 5060 rp->setup_policy(false); 5061 5062 ReferenceProcessorStats stats; 5063 if (!rp->processing_is_mt()) { 5064 // Serial reference processing... 5065 stats = rp->process_discovered_references(&is_alive, 5066 &keep_alive, 5067 &drain_queue, 5068 NULL, 5069 _gc_timer_stw); 5070 } else { 5071 // Parallel reference processing 5072 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5073 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5074 5075 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers); 5076 stats = rp->process_discovered_references(&is_alive, 5077 &keep_alive, 5078 &drain_queue, 5079 &par_task_executor, 5080 _gc_timer_stw); 5081 } 5082 5083 _gc_tracer_stw->report_gc_reference_stats(stats); 5084 5085 // We have completed copying any necessary live referent objects. 5086 assert(pss->queue_is_empty(), "both queue and overflow should be empty"); 5087 5088 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5089 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 5090 } 5091 5092 // Weak Reference processing during an evacuation pause (part 2). 5093 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) { 5094 double ref_enq_start = os::elapsedTime(); 5095 5096 ReferenceProcessor* rp = _ref_processor_stw; 5097 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5098 5099 // Now enqueue any remaining on the discovered lists on to 5100 // the pending list. 5101 if (!rp->processing_is_mt()) { 5102 // Serial reference processing... 5103 rp->enqueue_discovered_references(); 5104 } else { 5105 // Parallel reference enqueueing 5106 5107 uint n_workers = workers()->active_workers(); 5108 5109 assert(rp->num_q() == n_workers, "sanity"); 5110 assert(n_workers <= rp->max_num_q(), "sanity"); 5111 5112 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers); 5113 rp->enqueue_discovered_references(&par_task_executor); 5114 } 5115 5116 rp->verify_no_references_recorded(); 5117 assert(!rp->discovery_enabled(), "should have been disabled"); 5118 5119 // FIXME 5120 // CM's reference processing also cleans up the string and symbol tables. 5121 // Should we do that here also? We could, but it is a serial operation 5122 // and could significantly increase the pause time. 5123 5124 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5125 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5126 } 5127 5128 void G1CollectedHeap::pre_evacuate_collection_set() { 5129 _expand_heap_after_alloc_failure = true; 5130 _evacuation_failed = false; 5131 5132 // Disable the hot card cache. 5133 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5134 hot_card_cache->reset_hot_cache_claimed_index(); 5135 hot_card_cache->set_use_cache(false); 5136 5137 } 5138 5139 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 5140 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5141 5142 // Should G1EvacuationFailureALot be in effect for this GC? 5143 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5144 5145 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5146 double start_par_time_sec = os::elapsedTime(); 5147 double end_par_time_sec; 5148 5149 { 5150 const uint n_workers = workers()->active_workers(); 5151 G1RootProcessor root_processor(this, n_workers); 5152 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers); 5153 // InitialMark needs claim bits to keep track of the marked-through CLDs. 5154 if (collector_state()->during_initial_mark_pause()) { 5155 ClassLoaderDataGraph::clear_claimed_marks(); 5156 } 5157 5158 // The individual threads will set their evac-failure closures. 5159 if (PrintTerminationStats) { 5160 print_termination_stats_hdr(gclog_or_tty); 5161 } 5162 5163 workers()->run_task(&g1_par_task); 5164 end_par_time_sec = os::elapsedTime(); 5165 5166 // Closing the inner scope will execute the destructor 5167 // for the G1RootProcessor object. We record the current 5168 // elapsed time before closing the scope so that time 5169 // taken for the destructor is NOT included in the 5170 // reported parallel time. 5171 } 5172 5173 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 5174 5175 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5176 phase_times->record_par_time(par_time_ms); 5177 5178 double code_root_fixup_time_ms = 5179 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5180 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 5181 5182 // Process any discovered reference objects - we have 5183 // to do this _before_ we retire the GC alloc regions 5184 // as we may have to copy some 'reachable' referent 5185 // objects (and their reachable sub-graphs) that were 5186 // not copied during the pause. 5187 process_discovered_references(per_thread_states); 5188 5189 if (G1StringDedup::is_enabled()) { 5190 double fixup_start = os::elapsedTime(); 5191 5192 G1STWIsAliveClosure is_alive(this); 5193 G1KeepAliveClosure keep_alive(this); 5194 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times); 5195 5196 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 5197 phase_times->record_string_dedup_fixup_time(fixup_time_ms); 5198 } 5199 5200 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5201 5202 if (evacuation_failed()) { 5203 remove_self_forwarding_pointers(); 5204 5205 // Reset the G1EvacuationFailureALot counters and flags 5206 // Note: the values are reset only when an actual 5207 // evacuation failure occurs. 5208 NOT_PRODUCT(reset_evacuation_should_fail();) 5209 } 5210 5211 // Enqueue any remaining references remaining on the STW 5212 // reference processor's discovered lists. We need to do 5213 // this after the card table is cleaned (and verified) as 5214 // the act of enqueueing entries on to the pending list 5215 // will log these updates (and dirty their associated 5216 // cards). We need these updates logged to update any 5217 // RSets. 5218 enqueue_discovered_references(per_thread_states); 5219 } 5220 5221 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) { 5222 _allocator->release_gc_alloc_regions(evacuation_info); 5223 5224 per_thread_states->flush(); 5225 5226 record_obj_copy_mem_stats(); 5227 5228 _survivor_evac_stats.adjust_desired_plab_sz(); 5229 _old_evac_stats.adjust_desired_plab_sz(); 5230 5231 // Reset and re-enable the hot card cache. 5232 // Note the counts for the cards in the regions in the 5233 // collection set are reset when the collection set is freed. 5234 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5235 hot_card_cache->reset_hot_cache(); 5236 hot_card_cache->set_use_cache(true); 5237 5238 purge_code_root_memory(); 5239 5240 redirty_logged_cards(); 5241 #if defined(COMPILER2) || INCLUDE_JVMCI 5242 DerivedPointerTable::update_pointers(); 5243 #endif 5244 } 5245 5246 void G1CollectedHeap::record_obj_copy_mem_stats() { 5247 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats), 5248 create_g1_evac_summary(&_old_evac_stats)); 5249 } 5250 5251 void G1CollectedHeap::free_region(HeapRegion* hr, 5252 FreeRegionList* free_list, 5253 bool par, 5254 bool locked) { 5255 assert(!hr->is_free(), "the region should not be free"); 5256 assert(!hr->is_empty(), "the region should not be empty"); 5257 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 5258 assert(free_list != NULL, "pre-condition"); 5259 5260 if (G1VerifyBitmaps) { 5261 MemRegion mr(hr->bottom(), hr->end()); 5262 concurrent_mark()->clearRangePrevBitmap(mr); 5263 } 5264 5265 // Clear the card counts for this region. 5266 // Note: we only need to do this if the region is not young 5267 // (since we don't refine cards in young regions). 5268 if (!hr->is_young()) { 5269 _cg1r->hot_card_cache()->reset_card_counts(hr); 5270 } 5271 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 5272 free_list->add_ordered(hr); 5273 } 5274 5275 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5276 FreeRegionList* free_list, 5277 bool par) { 5278 assert(hr->is_humongous(), "this is only for humongous regions"); 5279 assert(free_list != NULL, "pre-condition"); 5280 hr->clear_humongous(); 5281 free_region(hr, free_list, par); 5282 } 5283 5284 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, 5285 const HeapRegionSetCount& humongous_regions_removed) { 5286 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) { 5287 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5288 _old_set.bulk_remove(old_regions_removed); 5289 _humongous_set.bulk_remove(humongous_regions_removed); 5290 } 5291 5292 } 5293 5294 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 5295 assert(list != NULL, "list can't be null"); 5296 if (!list->is_empty()) { 5297 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 5298 _hrm.insert_list_into_free_list(list); 5299 } 5300 } 5301 5302 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 5303 decrease_used(bytes); 5304 } 5305 5306 class G1ParCleanupCTTask : public AbstractGangTask { 5307 G1SATBCardTableModRefBS* _ct_bs; 5308 G1CollectedHeap* _g1h; 5309 HeapRegion* volatile _su_head; 5310 public: 5311 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 5312 G1CollectedHeap* g1h) : 5313 AbstractGangTask("G1 Par Cleanup CT Task"), 5314 _ct_bs(ct_bs), _g1h(g1h) { } 5315 5316 void work(uint worker_id) { 5317 HeapRegion* r; 5318 while (r = _g1h->pop_dirty_cards_region()) { 5319 clear_cards(r); 5320 } 5321 } 5322 5323 void clear_cards(HeapRegion* r) { 5324 // Cards of the survivors should have already been dirtied. 5325 if (!r->is_survivor()) { 5326 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 5327 } 5328 } 5329 }; 5330 5331 #ifndef PRODUCT 5332 class G1VerifyCardTableCleanup: public HeapRegionClosure { 5333 G1CollectedHeap* _g1h; 5334 G1SATBCardTableModRefBS* _ct_bs; 5335 public: 5336 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs) 5337 : _g1h(g1h), _ct_bs(ct_bs) { } 5338 virtual bool doHeapRegion(HeapRegion* r) { 5339 if (r->is_survivor()) { 5340 _g1h->verify_dirty_region(r); 5341 } else { 5342 _g1h->verify_not_dirty_region(r); 5343 } 5344 return false; 5345 } 5346 }; 5347 5348 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 5349 // All of the region should be clean. 5350 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5351 MemRegion mr(hr->bottom(), hr->end()); 5352 ct_bs->verify_not_dirty_region(mr); 5353 } 5354 5355 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 5356 // We cannot guarantee that [bottom(),end()] is dirty. Threads 5357 // dirty allocated blocks as they allocate them. The thread that 5358 // retires each region and replaces it with a new one will do a 5359 // maximal allocation to fill in [pre_dummy_top(),end()] but will 5360 // not dirty that area (one less thing to have to do while holding 5361 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 5362 // is dirty. 5363 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5364 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 5365 if (hr->is_young()) { 5366 ct_bs->verify_g1_young_region(mr); 5367 } else { 5368 ct_bs->verify_dirty_region(mr); 5369 } 5370 } 5371 5372 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 5373 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5374 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 5375 verify_dirty_region(hr); 5376 } 5377 } 5378 5379 void G1CollectedHeap::verify_dirty_young_regions() { 5380 verify_dirty_young_list(_young_list->first_region()); 5381 } 5382 5383 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 5384 HeapWord* tams, HeapWord* end) { 5385 guarantee(tams <= end, 5386 "tams: " PTR_FORMAT " end: " PTR_FORMAT, p2i(tams), p2i(end)); 5387 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end); 5388 if (result < end) { 5389 gclog_or_tty->cr(); 5390 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: " PTR_FORMAT, 5391 bitmap_name, p2i(result)); 5392 gclog_or_tty->print_cr("## %s tams: " PTR_FORMAT " end: " PTR_FORMAT, 5393 bitmap_name, p2i(tams), p2i(end)); 5394 return false; 5395 } 5396 return true; 5397 } 5398 5399 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) { 5400 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap(); 5401 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap(); 5402 5403 HeapWord* bottom = hr->bottom(); 5404 HeapWord* ptams = hr->prev_top_at_mark_start(); 5405 HeapWord* ntams = hr->next_top_at_mark_start(); 5406 HeapWord* end = hr->end(); 5407 5408 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end); 5409 5410 bool res_n = true; 5411 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window 5412 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap 5413 // if we happen to be in that state. 5414 if (collector_state()->mark_in_progress() || !_cmThread->in_progress()) { 5415 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end); 5416 } 5417 if (!res_p || !res_n) { 5418 gclog_or_tty->print_cr("#### Bitmap verification failed for " HR_FORMAT, 5419 HR_FORMAT_PARAMS(hr)); 5420 gclog_or_tty->print_cr("#### Caller: %s", caller); 5421 return false; 5422 } 5423 return true; 5424 } 5425 5426 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) { 5427 if (!G1VerifyBitmaps) return; 5428 5429 guarantee(verify_bitmaps(caller, hr), "bitmap verification"); 5430 } 5431 5432 class G1VerifyBitmapClosure : public HeapRegionClosure { 5433 private: 5434 const char* _caller; 5435 G1CollectedHeap* _g1h; 5436 bool _failures; 5437 5438 public: 5439 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) : 5440 _caller(caller), _g1h(g1h), _failures(false) { } 5441 5442 bool failures() { return _failures; } 5443 5444 virtual bool doHeapRegion(HeapRegion* hr) { 5445 bool result = _g1h->verify_bitmaps(_caller, hr); 5446 if (!result) { 5447 _failures = true; 5448 } 5449 return false; 5450 } 5451 }; 5452 5453 void G1CollectedHeap::check_bitmaps(const char* caller) { 5454 if (!G1VerifyBitmaps) return; 5455 5456 G1VerifyBitmapClosure cl(caller, this); 5457 heap_region_iterate(&cl); 5458 guarantee(!cl.failures(), "bitmap verification"); 5459 } 5460 5461 class G1CheckCSetFastTableClosure : public HeapRegionClosure { 5462 private: 5463 bool _failures; 5464 public: 5465 G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { } 5466 5467 virtual bool doHeapRegion(HeapRegion* hr) { 5468 uint i = hr->hrm_index(); 5469 InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i); 5470 if (hr->is_humongous()) { 5471 if (hr->in_collection_set()) { 5472 gclog_or_tty->print_cr("\n## humongous region %u in CSet", i); 5473 _failures = true; 5474 return true; 5475 } 5476 if (cset_state.is_in_cset()) { 5477 gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i); 5478 _failures = true; 5479 return true; 5480 } 5481 if (hr->is_continues_humongous() && cset_state.is_humongous()) { 5482 gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i); 5483 _failures = true; 5484 return true; 5485 } 5486 } else { 5487 if (cset_state.is_humongous()) { 5488 gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i); 5489 _failures = true; 5490 return true; 5491 } 5492 if (hr->in_collection_set() != cset_state.is_in_cset()) { 5493 gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u", 5494 hr->in_collection_set(), cset_state.value(), i); 5495 _failures = true; 5496 return true; 5497 } 5498 if (cset_state.is_in_cset()) { 5499 if (hr->is_young() != (cset_state.is_young())) { 5500 gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u", 5501 hr->is_young(), cset_state.value(), i); 5502 _failures = true; 5503 return true; 5504 } 5505 if (hr->is_old() != (cset_state.is_old())) { 5506 gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u", 5507 hr->is_old(), cset_state.value(), i); 5508 _failures = true; 5509 return true; 5510 } 5511 } 5512 } 5513 return false; 5514 } 5515 5516 bool failures() const { return _failures; } 5517 }; 5518 5519 bool G1CollectedHeap::check_cset_fast_test() { 5520 G1CheckCSetFastTableClosure cl; 5521 _hrm.iterate(&cl); 5522 return !cl.failures(); 5523 } 5524 #endif // PRODUCT 5525 5526 void G1CollectedHeap::cleanUpCardTable() { 5527 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5528 double start = os::elapsedTime(); 5529 5530 { 5531 // Iterate over the dirty cards region list. 5532 G1ParCleanupCTTask cleanup_task(ct_bs, this); 5533 5534 workers()->run_task(&cleanup_task); 5535 #ifndef PRODUCT 5536 if (G1VerifyCTCleanup || VerifyAfterGC) { 5537 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 5538 heap_region_iterate(&cleanup_verifier); 5539 } 5540 #endif 5541 } 5542 5543 double elapsed = os::elapsedTime() - start; 5544 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 5545 } 5546 5547 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) { 5548 size_t pre_used = 0; 5549 FreeRegionList local_free_list("Local List for CSet Freeing"); 5550 5551 double young_time_ms = 0.0; 5552 double non_young_time_ms = 0.0; 5553 5554 // Since the collection set is a superset of the the young list, 5555 // all we need to do to clear the young list is clear its 5556 // head and length, and unlink any young regions in the code below 5557 _young_list->clear(); 5558 5559 G1CollectorPolicy* policy = g1_policy(); 5560 5561 double start_sec = os::elapsedTime(); 5562 bool non_young = true; 5563 5564 HeapRegion* cur = cs_head; 5565 int age_bound = -1; 5566 size_t rs_lengths = 0; 5567 5568 while (cur != NULL) { 5569 assert(!is_on_master_free_list(cur), "sanity"); 5570 if (non_young) { 5571 if (cur->is_young()) { 5572 double end_sec = os::elapsedTime(); 5573 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5574 non_young_time_ms += elapsed_ms; 5575 5576 start_sec = os::elapsedTime(); 5577 non_young = false; 5578 } 5579 } else { 5580 if (!cur->is_young()) { 5581 double end_sec = os::elapsedTime(); 5582 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5583 young_time_ms += elapsed_ms; 5584 5585 start_sec = os::elapsedTime(); 5586 non_young = true; 5587 } 5588 } 5589 5590 rs_lengths += cur->rem_set()->occupied_locked(); 5591 5592 HeapRegion* next = cur->next_in_collection_set(); 5593 assert(cur->in_collection_set(), "bad CS"); 5594 cur->set_next_in_collection_set(NULL); 5595 clear_in_cset(cur); 5596 5597 if (cur->is_young()) { 5598 int index = cur->young_index_in_cset(); 5599 assert(index != -1, "invariant"); 5600 assert((uint) index < policy->young_cset_region_length(), "invariant"); 5601 size_t words_survived = surviving_young_words[index]; 5602 cur->record_surv_words_in_group(words_survived); 5603 5604 // At this point the we have 'popped' cur from the collection set 5605 // (linked via next_in_collection_set()) but it is still in the 5606 // young list (linked via next_young_region()). Clear the 5607 // _next_young_region field. 5608 cur->set_next_young_region(NULL); 5609 } else { 5610 int index = cur->young_index_in_cset(); 5611 assert(index == -1, "invariant"); 5612 } 5613 5614 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 5615 (!cur->is_young() && cur->young_index_in_cset() == -1), 5616 "invariant" ); 5617 5618 if (!cur->evacuation_failed()) { 5619 MemRegion used_mr = cur->used_region(); 5620 5621 // And the region is empty. 5622 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 5623 pre_used += cur->used(); 5624 free_region(cur, &local_free_list, false /* par */, true /* locked */); 5625 } else { 5626 cur->uninstall_surv_rate_group(); 5627 if (cur->is_young()) { 5628 cur->set_young_index_in_cset(-1); 5629 } 5630 cur->set_evacuation_failed(false); 5631 // The region is now considered to be old. 5632 cur->set_old(); 5633 // Do some allocation statistics accounting. Regions that failed evacuation 5634 // are always made old, so there is no need to update anything in the young 5635 // gen statistics, but we need to update old gen statistics. 5636 size_t used_words = cur->marked_bytes() / HeapWordSize; 5637 _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words); 5638 _old_set.add(cur); 5639 evacuation_info.increment_collectionset_used_after(cur->used()); 5640 } 5641 cur = next; 5642 } 5643 5644 evacuation_info.set_regions_freed(local_free_list.length()); 5645 policy->record_max_rs_lengths(rs_lengths); 5646 policy->cset_regions_freed(); 5647 5648 double end_sec = os::elapsedTime(); 5649 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5650 5651 if (non_young) { 5652 non_young_time_ms += elapsed_ms; 5653 } else { 5654 young_time_ms += elapsed_ms; 5655 } 5656 5657 prepend_to_freelist(&local_free_list); 5658 decrement_summary_bytes(pre_used); 5659 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 5660 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 5661 } 5662 5663 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 5664 private: 5665 FreeRegionList* _free_region_list; 5666 HeapRegionSet* _proxy_set; 5667 HeapRegionSetCount _humongous_regions_removed; 5668 size_t _freed_bytes; 5669 public: 5670 5671 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 5672 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) { 5673 } 5674 5675 virtual bool doHeapRegion(HeapRegion* r) { 5676 if (!r->is_starts_humongous()) { 5677 return false; 5678 } 5679 5680 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 5681 5682 oop obj = (oop)r->bottom(); 5683 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 5684 5685 // The following checks whether the humongous object is live are sufficient. 5686 // The main additional check (in addition to having a reference from the roots 5687 // or the young gen) is whether the humongous object has a remembered set entry. 5688 // 5689 // A humongous object cannot be live if there is no remembered set for it 5690 // because: 5691 // - there can be no references from within humongous starts regions referencing 5692 // the object because we never allocate other objects into them. 5693 // (I.e. there are no intra-region references that may be missed by the 5694 // remembered set) 5695 // - as soon there is a remembered set entry to the humongous starts region 5696 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 5697 // until the end of a concurrent mark. 5698 // 5699 // It is not required to check whether the object has been found dead by marking 5700 // or not, in fact it would prevent reclamation within a concurrent cycle, as 5701 // all objects allocated during that time are considered live. 5702 // SATB marking is even more conservative than the remembered set. 5703 // So if at this point in the collection there is no remembered set entry, 5704 // nobody has a reference to it. 5705 // At the start of collection we flush all refinement logs, and remembered sets 5706 // are completely up-to-date wrt to references to the humongous object. 5707 // 5708 // Other implementation considerations: 5709 // - never consider object arrays at this time because they would pose 5710 // considerable effort for cleaning up the the remembered sets. This is 5711 // required because stale remembered sets might reference locations that 5712 // are currently allocated into. 5713 uint region_idx = r->hrm_index(); 5714 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 5715 !r->rem_set()->is_empty()) { 5716 5717 if (G1TraceEagerReclaimHumongousObjects) { 5718 gclog_or_tty->print_cr("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", 5719 region_idx, 5720 (size_t)obj->size() * HeapWordSize, 5721 p2i(r->bottom()), 5722 r->rem_set()->occupied(), 5723 r->rem_set()->strong_code_roots_list_length(), 5724 next_bitmap->isMarked(r->bottom()), 5725 g1h->is_humongous_reclaim_candidate(region_idx), 5726 obj->is_typeArray() 5727 ); 5728 } 5729 5730 return false; 5731 } 5732 5733 guarantee(obj->is_typeArray(), 5734 "Only eagerly reclaiming type arrays is supported, but the object " 5735 PTR_FORMAT " is not.", p2i(r->bottom())); 5736 5737 if (G1TraceEagerReclaimHumongousObjects) { 5738 gclog_or_tty->print_cr("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", 5739 region_idx, 5740 (size_t)obj->size() * HeapWordSize, 5741 p2i(r->bottom()), 5742 r->rem_set()->occupied(), 5743 r->rem_set()->strong_code_roots_list_length(), 5744 next_bitmap->isMarked(r->bottom()), 5745 g1h->is_humongous_reclaim_candidate(region_idx), 5746 obj->is_typeArray() 5747 ); 5748 } 5749 // Need to clear mark bit of the humongous object if already set. 5750 if (next_bitmap->isMarked(r->bottom())) { 5751 next_bitmap->clear(r->bottom()); 5752 } 5753 do { 5754 HeapRegion* next = g1h->next_region_in_humongous(r); 5755 _freed_bytes += r->used(); 5756 r->set_containing_set(NULL); 5757 _humongous_regions_removed.increment(1u, r->capacity()); 5758 g1h->free_humongous_region(r, _free_region_list, false); 5759 r = next; 5760 } while (r != NULL); 5761 5762 return false; 5763 } 5764 5765 HeapRegionSetCount& humongous_free_count() { 5766 return _humongous_regions_removed; 5767 } 5768 5769 size_t bytes_freed() const { 5770 return _freed_bytes; 5771 } 5772 5773 size_t humongous_reclaimed() const { 5774 return _humongous_regions_removed.length(); 5775 } 5776 }; 5777 5778 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 5779 assert_at_safepoint(true); 5780 5781 if (!G1EagerReclaimHumongousObjects || 5782 (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) { 5783 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 5784 return; 5785 } 5786 5787 double start_time = os::elapsedTime(); 5788 5789 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 5790 5791 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 5792 heap_region_iterate(&cl); 5793 5794 HeapRegionSetCount empty_set; 5795 remove_from_old_sets(empty_set, cl.humongous_free_count()); 5796 5797 G1HRPrinter* hrp = hr_printer(); 5798 if (hrp->is_active()) { 5799 FreeRegionListIterator iter(&local_cleanup_list); 5800 while (iter.more_available()) { 5801 HeapRegion* hr = iter.get_next(); 5802 hrp->cleanup(hr); 5803 } 5804 } 5805 5806 prepend_to_freelist(&local_cleanup_list); 5807 decrement_summary_bytes(cl.bytes_freed()); 5808 5809 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 5810 cl.humongous_reclaimed()); 5811 } 5812 5813 // This routine is similar to the above but does not record 5814 // any policy statistics or update free lists; we are abandoning 5815 // the current incremental collection set in preparation of a 5816 // full collection. After the full GC we will start to build up 5817 // the incremental collection set again. 5818 // This is only called when we're doing a full collection 5819 // and is immediately followed by the tearing down of the young list. 5820 5821 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 5822 HeapRegion* cur = cs_head; 5823 5824 while (cur != NULL) { 5825 HeapRegion* next = cur->next_in_collection_set(); 5826 assert(cur->in_collection_set(), "bad CS"); 5827 cur->set_next_in_collection_set(NULL); 5828 clear_in_cset(cur); 5829 cur->set_young_index_in_cset(-1); 5830 cur = next; 5831 } 5832 } 5833 5834 void G1CollectedHeap::set_free_regions_coming() { 5835 if (G1ConcRegionFreeingVerbose) { 5836 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 5837 "setting free regions coming"); 5838 } 5839 5840 assert(!free_regions_coming(), "pre-condition"); 5841 _free_regions_coming = true; 5842 } 5843 5844 void G1CollectedHeap::reset_free_regions_coming() { 5845 assert(free_regions_coming(), "pre-condition"); 5846 5847 { 5848 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5849 _free_regions_coming = false; 5850 SecondaryFreeList_lock->notify_all(); 5851 } 5852 5853 if (G1ConcRegionFreeingVerbose) { 5854 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 5855 "reset free regions coming"); 5856 } 5857 } 5858 5859 void G1CollectedHeap::wait_while_free_regions_coming() { 5860 // Most of the time we won't have to wait, so let's do a quick test 5861 // first before we take the lock. 5862 if (!free_regions_coming()) { 5863 return; 5864 } 5865 5866 if (G1ConcRegionFreeingVerbose) { 5867 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 5868 "waiting for free regions"); 5869 } 5870 5871 { 5872 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5873 while (free_regions_coming()) { 5874 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5875 } 5876 } 5877 5878 if (G1ConcRegionFreeingVerbose) { 5879 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 5880 "done waiting for free regions"); 5881 } 5882 } 5883 5884 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) { 5885 return _allocator->is_retained_old_region(hr); 5886 } 5887 5888 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5889 _young_list->push_region(hr); 5890 } 5891 5892 class NoYoungRegionsClosure: public HeapRegionClosure { 5893 private: 5894 bool _success; 5895 public: 5896 NoYoungRegionsClosure() : _success(true) { } 5897 bool doHeapRegion(HeapRegion* r) { 5898 if (r->is_young()) { 5899 gclog_or_tty->print_cr("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 5900 p2i(r->bottom()), p2i(r->end())); 5901 _success = false; 5902 } 5903 return false; 5904 } 5905 bool success() { return _success; } 5906 }; 5907 5908 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 5909 bool ret = _young_list->check_list_empty(check_sample); 5910 5911 if (check_heap) { 5912 NoYoungRegionsClosure closure; 5913 heap_region_iterate(&closure); 5914 ret = ret && closure.success(); 5915 } 5916 5917 return ret; 5918 } 5919 5920 class TearDownRegionSetsClosure : public HeapRegionClosure { 5921 private: 5922 HeapRegionSet *_old_set; 5923 5924 public: 5925 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 5926 5927 bool doHeapRegion(HeapRegion* r) { 5928 if (r->is_old()) { 5929 _old_set->remove(r); 5930 } else { 5931 // We ignore free regions, we'll empty the free list afterwards. 5932 // We ignore young regions, we'll empty the young list afterwards. 5933 // We ignore humongous regions, we're not tearing down the 5934 // humongous regions set. 5935 assert(r->is_free() || r->is_young() || r->is_humongous(), 5936 "it cannot be another type"); 5937 } 5938 return false; 5939 } 5940 5941 ~TearDownRegionSetsClosure() { 5942 assert(_old_set->is_empty(), "post-condition"); 5943 } 5944 }; 5945 5946 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 5947 assert_at_safepoint(true /* should_be_vm_thread */); 5948 5949 if (!free_list_only) { 5950 TearDownRegionSetsClosure cl(&_old_set); 5951 heap_region_iterate(&cl); 5952 5953 // Note that emptying the _young_list is postponed and instead done as 5954 // the first step when rebuilding the regions sets again. The reason for 5955 // this is that during a full GC string deduplication needs to know if 5956 // a collected region was young or old when the full GC was initiated. 5957 } 5958 _hrm.remove_all_free_regions(); 5959 } 5960 5961 void G1CollectedHeap::increase_used(size_t bytes) { 5962 _summary_bytes_used += bytes; 5963 } 5964 5965 void G1CollectedHeap::decrease_used(size_t bytes) { 5966 assert(_summary_bytes_used >= bytes, 5967 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT, 5968 _summary_bytes_used, bytes); 5969 _summary_bytes_used -= bytes; 5970 } 5971 5972 void G1CollectedHeap::set_used(size_t bytes) { 5973 _summary_bytes_used = bytes; 5974 } 5975 5976 class RebuildRegionSetsClosure : public HeapRegionClosure { 5977 private: 5978 bool _free_list_only; 5979 HeapRegionSet* _old_set; 5980 HeapRegionManager* _hrm; 5981 size_t _total_used; 5982 5983 public: 5984 RebuildRegionSetsClosure(bool free_list_only, 5985 HeapRegionSet* old_set, HeapRegionManager* hrm) : 5986 _free_list_only(free_list_only), 5987 _old_set(old_set), _hrm(hrm), _total_used(0) { 5988 assert(_hrm->num_free_regions() == 0, "pre-condition"); 5989 if (!free_list_only) { 5990 assert(_old_set->is_empty(), "pre-condition"); 5991 } 5992 } 5993 5994 bool doHeapRegion(HeapRegion* r) { 5995 if (r->is_empty()) { 5996 // Add free regions to the free list 5997 r->set_free(); 5998 r->set_allocation_context(AllocationContext::system()); 5999 _hrm->insert_into_free_list(r); 6000 } else if (!_free_list_only) { 6001 assert(!r->is_young(), "we should not come across young regions"); 6002 6003 if (r->is_humongous()) { 6004 // We ignore humongous regions. We left the humongous set unchanged. 6005 } else { 6006 // Objects that were compacted would have ended up on regions 6007 // that were previously old or free. Archive regions (which are 6008 // old) will not have been touched. 6009 assert(r->is_free() || r->is_old(), "invariant"); 6010 // We now consider them old, so register as such. Leave 6011 // archive regions set that way, however, while still adding 6012 // them to the old set. 6013 if (!r->is_archive()) { 6014 r->set_old(); 6015 } 6016 _old_set->add(r); 6017 } 6018 _total_used += r->used(); 6019 } 6020 6021 return false; 6022 } 6023 6024 size_t total_used() { 6025 return _total_used; 6026 } 6027 }; 6028 6029 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6030 assert_at_safepoint(true /* should_be_vm_thread */); 6031 6032 if (!free_list_only) { 6033 _young_list->empty_list(); 6034 } 6035 6036 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 6037 heap_region_iterate(&cl); 6038 6039 if (!free_list_only) { 6040 set_used(cl.total_used()); 6041 if (_archive_allocator != NULL) { 6042 _archive_allocator->clear_used(); 6043 } 6044 } 6045 assert(used_unlocked() == recalculate_used(), 6046 "inconsistent used_unlocked(), " 6047 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 6048 used_unlocked(), recalculate_used()); 6049 } 6050 6051 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6052 _refine_cte_cl->set_concurrent(concurrent); 6053 } 6054 6055 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6056 HeapRegion* hr = heap_region_containing(p); 6057 return hr->is_in(p); 6058 } 6059 6060 // Methods for the mutator alloc region 6061 6062 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6063 bool force) { 6064 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6065 assert(!force || g1_policy()->can_expand_young_list(), 6066 "if force is true we should be able to expand the young list"); 6067 bool young_list_full = g1_policy()->is_young_list_full(); 6068 if (force || !young_list_full) { 6069 HeapRegion* new_alloc_region = new_region(word_size, 6070 false /* is_old */, 6071 false /* do_expand */); 6072 if (new_alloc_region != NULL) { 6073 set_region_short_lived_locked(new_alloc_region); 6074 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6075 check_bitmaps("Mutator Region Allocation", new_alloc_region); 6076 return new_alloc_region; 6077 } 6078 } 6079 return NULL; 6080 } 6081 6082 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6083 size_t allocated_bytes) { 6084 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6085 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 6086 6087 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6088 increase_used(allocated_bytes); 6089 _hr_printer.retire(alloc_region); 6090 // We update the eden sizes here, when the region is retired, 6091 // instead of when it's allocated, since this is the point that its 6092 // used space has been recored in _summary_bytes_used. 6093 g1mm()->update_eden_size(); 6094 } 6095 6096 // Methods for the GC alloc regions 6097 6098 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6099 uint count, 6100 InCSetState dest) { 6101 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6102 6103 if (count < g1_policy()->max_regions(dest)) { 6104 const bool is_survivor = (dest.is_young()); 6105 HeapRegion* new_alloc_region = new_region(word_size, 6106 !is_survivor, 6107 true /* do_expand */); 6108 if (new_alloc_region != NULL) { 6109 // We really only need to do this for old regions given that we 6110 // should never scan survivors. But it doesn't hurt to do it 6111 // for survivors too. 6112 new_alloc_region->record_timestamp(); 6113 if (is_survivor) { 6114 new_alloc_region->set_survivor(); 6115 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6116 check_bitmaps("Survivor Region Allocation", new_alloc_region); 6117 } else { 6118 new_alloc_region->set_old(); 6119 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6120 check_bitmaps("Old Region Allocation", new_alloc_region); 6121 } 6122 bool during_im = collector_state()->during_initial_mark_pause(); 6123 new_alloc_region->note_start_of_copying(during_im); 6124 return new_alloc_region; 6125 } 6126 } 6127 return NULL; 6128 } 6129 6130 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6131 size_t allocated_bytes, 6132 InCSetState dest) { 6133 bool during_im = collector_state()->during_initial_mark_pause(); 6134 alloc_region->note_end_of_copying(during_im); 6135 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6136 if (dest.is_young()) { 6137 young_list()->add_survivor_region(alloc_region); 6138 } else { 6139 _old_set.add(alloc_region); 6140 } 6141 _hr_printer.retire(alloc_region); 6142 } 6143 6144 HeapRegion* G1CollectedHeap::alloc_highest_free_region() { 6145 bool expanded = false; 6146 uint index = _hrm.find_highest_free(&expanded); 6147 6148 if (index != G1_NO_HRM_INDEX) { 6149 if (expanded) { 6150 ergo_verbose1(ErgoHeapSizing, 6151 "attempt heap expansion", 6152 ergo_format_reason("requested address range outside heap bounds") 6153 ergo_format_byte("region size"), 6154 HeapRegion::GrainWords * HeapWordSize); 6155 } 6156 _hrm.allocate_free_regions_starting_at(index, 1); 6157 return region_at(index); 6158 } 6159 return NULL; 6160 } 6161 6162 // Heap region set verification 6163 6164 class VerifyRegionListsClosure : public HeapRegionClosure { 6165 private: 6166 HeapRegionSet* _old_set; 6167 HeapRegionSet* _humongous_set; 6168 HeapRegionManager* _hrm; 6169 6170 public: 6171 HeapRegionSetCount _old_count; 6172 HeapRegionSetCount _humongous_count; 6173 HeapRegionSetCount _free_count; 6174 6175 VerifyRegionListsClosure(HeapRegionSet* old_set, 6176 HeapRegionSet* humongous_set, 6177 HeapRegionManager* hrm) : 6178 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm), 6179 _old_count(), _humongous_count(), _free_count(){ } 6180 6181 bool doHeapRegion(HeapRegion* hr) { 6182 if (hr->is_young()) { 6183 // TODO 6184 } else if (hr->is_humongous()) { 6185 assert(hr->containing_set() == _humongous_set, "Heap region %u is humongous but not in humongous set.", hr->hrm_index()); 6186 _humongous_count.increment(1u, hr->capacity()); 6187 } else if (hr->is_empty()) { 6188 assert(_hrm->is_free(hr), "Heap region %u is empty but not on the free list.", hr->hrm_index()); 6189 _free_count.increment(1u, hr->capacity()); 6190 } else if (hr->is_old()) { 6191 assert(hr->containing_set() == _old_set, "Heap region %u is old but not in the old set.", hr->hrm_index()); 6192 _old_count.increment(1u, hr->capacity()); 6193 } else { 6194 // There are no other valid region types. Check for one invalid 6195 // one we can identify: pinned without old or humongous set. 6196 assert(!hr->is_pinned(), "Heap region %u is pinned but not old (archive) or humongous.", hr->hrm_index()); 6197 ShouldNotReachHere(); 6198 } 6199 return false; 6200 } 6201 6202 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) { 6203 guarantee(old_set->length() == _old_count.length(), "Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()); 6204 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), "Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6205 old_set->total_capacity_bytes(), _old_count.capacity()); 6206 6207 guarantee(humongous_set->length() == _humongous_count.length(), "Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()); 6208 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), "Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6209 humongous_set->total_capacity_bytes(), _humongous_count.capacity()); 6210 6211 guarantee(free_list->num_free_regions() == _free_count.length(), "Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count.length()); 6212 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), "Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6213 free_list->total_capacity_bytes(), _free_count.capacity()); 6214 } 6215 }; 6216 6217 void G1CollectedHeap::verify_region_sets() { 6218 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6219 6220 // First, check the explicit lists. 6221 _hrm.verify(); 6222 { 6223 // Given that a concurrent operation might be adding regions to 6224 // the secondary free list we have to take the lock before 6225 // verifying it. 6226 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6227 _secondary_free_list.verify_list(); 6228 } 6229 6230 // If a concurrent region freeing operation is in progress it will 6231 // be difficult to correctly attributed any free regions we come 6232 // across to the correct free list given that they might belong to 6233 // one of several (free_list, secondary_free_list, any local lists, 6234 // etc.). So, if that's the case we will skip the rest of the 6235 // verification operation. Alternatively, waiting for the concurrent 6236 // operation to complete will have a non-trivial effect on the GC's 6237 // operation (no concurrent operation will last longer than the 6238 // interval between two calls to verification) and it might hide 6239 // any issues that we would like to catch during testing. 6240 if (free_regions_coming()) { 6241 return; 6242 } 6243 6244 // Make sure we append the secondary_free_list on the free_list so 6245 // that all free regions we will come across can be safely 6246 // attributed to the free_list. 6247 append_secondary_free_list_if_not_empty_with_lock(); 6248 6249 // Finally, make sure that the region accounting in the lists is 6250 // consistent with what we see in the heap. 6251 6252 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm); 6253 heap_region_iterate(&cl); 6254 cl.verify_counts(&_old_set, &_humongous_set, &_hrm); 6255 } 6256 6257 // Optimized nmethod scanning 6258 6259 class RegisterNMethodOopClosure: public OopClosure { 6260 G1CollectedHeap* _g1h; 6261 nmethod* _nm; 6262 6263 template <class T> void do_oop_work(T* p) { 6264 T heap_oop = oopDesc::load_heap_oop(p); 6265 if (!oopDesc::is_null(heap_oop)) { 6266 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6267 HeapRegion* hr = _g1h->heap_region_containing(obj); 6268 assert(!hr->is_continues_humongous(), 6269 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6270 " starting at " HR_FORMAT, 6271 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 6272 6273 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 6274 hr->add_strong_code_root_locked(_nm); 6275 } 6276 } 6277 6278 public: 6279 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6280 _g1h(g1h), _nm(nm) {} 6281 6282 void do_oop(oop* p) { do_oop_work(p); } 6283 void do_oop(narrowOop* p) { do_oop_work(p); } 6284 }; 6285 6286 class UnregisterNMethodOopClosure: public OopClosure { 6287 G1CollectedHeap* _g1h; 6288 nmethod* _nm; 6289 6290 template <class T> void do_oop_work(T* p) { 6291 T heap_oop = oopDesc::load_heap_oop(p); 6292 if (!oopDesc::is_null(heap_oop)) { 6293 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6294 HeapRegion* hr = _g1h->heap_region_containing(obj); 6295 assert(!hr->is_continues_humongous(), 6296 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6297 " starting at " HR_FORMAT, 6298 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())); 6299 6300 hr->remove_strong_code_root(_nm); 6301 } 6302 } 6303 6304 public: 6305 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6306 _g1h(g1h), _nm(nm) {} 6307 6308 void do_oop(oop* p) { do_oop_work(p); } 6309 void do_oop(narrowOop* p) { do_oop_work(p); } 6310 }; 6311 6312 void G1CollectedHeap::register_nmethod(nmethod* nm) { 6313 CollectedHeap::register_nmethod(nm); 6314 6315 guarantee(nm != NULL, "sanity"); 6316 RegisterNMethodOopClosure reg_cl(this, nm); 6317 nm->oops_do(®_cl); 6318 } 6319 6320 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 6321 CollectedHeap::unregister_nmethod(nm); 6322 6323 guarantee(nm != NULL, "sanity"); 6324 UnregisterNMethodOopClosure reg_cl(this, nm); 6325 nm->oops_do(®_cl, true); 6326 } 6327 6328 void G1CollectedHeap::purge_code_root_memory() { 6329 double purge_start = os::elapsedTime(); 6330 G1CodeRootSet::purge(); 6331 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 6332 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 6333 } 6334 6335 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 6336 G1CollectedHeap* _g1h; 6337 6338 public: 6339 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 6340 _g1h(g1h) {} 6341 6342 void do_code_blob(CodeBlob* cb) { 6343 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 6344 if (nm == NULL) { 6345 return; 6346 } 6347 6348 if (ScavengeRootsInCode) { 6349 _g1h->register_nmethod(nm); 6350 } 6351 } 6352 }; 6353 6354 void G1CollectedHeap::rebuild_strong_code_roots() { 6355 RebuildStrongCodeRootClosure blob_cl(this); 6356 CodeCache::blobs_do(&blob_cl); 6357 }