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/symbolTable.hpp" 28 #include "code/codeCache.hpp" 29 #include "gc/g1/concurrentMark.inline.hpp" 30 #include "gc/g1/concurrentMarkThread.inline.hpp" 31 #include "gc/g1/g1CollectedHeap.inline.hpp" 32 #include "gc/g1/g1CollectorPolicy.hpp" 33 #include "gc/g1/g1ErgoVerbose.hpp" 34 #include "gc/g1/g1Log.hpp" 35 #include "gc/g1/g1OopClosures.inline.hpp" 36 #include "gc/g1/g1RemSet.hpp" 37 #include "gc/g1/g1StringDedup.hpp" 38 #include "gc/g1/heapRegion.inline.hpp" 39 #include "gc/g1/heapRegionManager.inline.hpp" 40 #include "gc/g1/heapRegionRemSet.hpp" 41 #include "gc/g1/heapRegionSet.inline.hpp" 42 #include "gc/g1/suspendibleThreadSet.hpp" 43 #include "gc/shared/gcTimer.hpp" 44 #include "gc/shared/gcTrace.hpp" 45 #include "gc/shared/gcTraceTime.hpp" 46 #include "gc/shared/genOopClosures.inline.hpp" 47 #include "gc/shared/referencePolicy.hpp" 48 #include "gc/shared/strongRootsScope.hpp" 49 #include "gc/shared/taskqueue.inline.hpp" 50 #include "gc/shared/vmGCOperations.hpp" 51 #include "memory/allocation.hpp" 52 #include "memory/resourceArea.hpp" 53 #include "oops/oop.inline.hpp" 54 #include "runtime/atomic.inline.hpp" 55 #include "runtime/handles.inline.hpp" 56 #include "runtime/java.hpp" 57 #include "runtime/prefetch.inline.hpp" 58 #include "services/memTracker.hpp" 59 60 // Concurrent marking bit map wrapper 61 62 CMBitMapRO::CMBitMapRO(int shifter) : 63 _bm(), 64 _shifter(shifter) { 65 _bmStartWord = 0; 66 _bmWordSize = 0; 67 } 68 69 HeapWord* CMBitMapRO::getNextMarkedWordAddress(const HeapWord* addr, 70 const HeapWord* limit) const { 71 // First we must round addr *up* to a possible object boundary. 72 addr = (HeapWord*)align_size_up((intptr_t)addr, 73 HeapWordSize << _shifter); 74 size_t addrOffset = heapWordToOffset(addr); 75 if (limit == NULL) { 76 limit = _bmStartWord + _bmWordSize; 77 } 78 size_t limitOffset = heapWordToOffset(limit); 79 size_t nextOffset = _bm.get_next_one_offset(addrOffset, limitOffset); 80 HeapWord* nextAddr = offsetToHeapWord(nextOffset); 81 assert(nextAddr >= addr, "get_next_one postcondition"); 82 assert(nextAddr == limit || isMarked(nextAddr), 83 "get_next_one postcondition"); 84 return nextAddr; 85 } 86 87 HeapWord* CMBitMapRO::getNextUnmarkedWordAddress(const HeapWord* addr, 88 const HeapWord* limit) const { 89 size_t addrOffset = heapWordToOffset(addr); 90 if (limit == NULL) { 91 limit = _bmStartWord + _bmWordSize; 92 } 93 size_t limitOffset = heapWordToOffset(limit); 94 size_t nextOffset = _bm.get_next_zero_offset(addrOffset, limitOffset); 95 HeapWord* nextAddr = offsetToHeapWord(nextOffset); 96 assert(nextAddr >= addr, "get_next_one postcondition"); 97 assert(nextAddr == limit || !isMarked(nextAddr), 98 "get_next_one postcondition"); 99 return nextAddr; 100 } 101 102 int CMBitMapRO::heapWordDiffToOffsetDiff(size_t diff) const { 103 assert((diff & ((1 << _shifter) - 1)) == 0, "argument check"); 104 return (int) (diff >> _shifter); 105 } 106 107 #ifndef PRODUCT 108 bool CMBitMapRO::covers(MemRegion heap_rs) const { 109 // assert(_bm.map() == _virtual_space.low(), "map inconsistency"); 110 assert(((size_t)_bm.size() * ((size_t)1 << _shifter)) == _bmWordSize, 111 "size inconsistency"); 112 return _bmStartWord == (HeapWord*)(heap_rs.start()) && 113 _bmWordSize == heap_rs.word_size(); 114 } 115 #endif 116 117 void CMBitMapRO::print_on_error(outputStream* st, const char* prefix) const { 118 _bm.print_on_error(st, prefix); 119 } 120 121 size_t CMBitMap::compute_size(size_t heap_size) { 122 return ReservedSpace::allocation_align_size_up(heap_size / mark_distance()); 123 } 124 125 size_t CMBitMap::mark_distance() { 126 return MinObjAlignmentInBytes * BitsPerByte; 127 } 128 129 void CMBitMap::initialize(MemRegion heap, G1RegionToSpaceMapper* storage) { 130 _bmStartWord = heap.start(); 131 _bmWordSize = heap.word_size(); 132 133 _bm.set_map((BitMap::bm_word_t*) storage->reserved().start()); 134 _bm.set_size(_bmWordSize >> _shifter); 135 136 storage->set_mapping_changed_listener(&_listener); 137 } 138 139 void CMBitMapMappingChangedListener::on_commit(uint start_region, size_t num_regions, bool zero_filled) { 140 if (zero_filled) { 141 return; 142 } 143 // We need to clear the bitmap on commit, removing any existing information. 144 MemRegion mr(G1CollectedHeap::heap()->bottom_addr_for_region(start_region), num_regions * HeapRegion::GrainWords); 145 _bm->clearRange(mr); 146 } 147 148 // Closure used for clearing the given mark bitmap. 149 class ClearBitmapHRClosure : public HeapRegionClosure { 150 private: 151 ConcurrentMark* _cm; 152 CMBitMap* _bitmap; 153 bool _may_yield; // The closure may yield during iteration. If yielded, abort the iteration. 154 public: 155 ClearBitmapHRClosure(ConcurrentMark* cm, CMBitMap* bitmap, bool may_yield) : HeapRegionClosure(), _cm(cm), _bitmap(bitmap), _may_yield(may_yield) { 156 assert(!may_yield || cm != NULL, "CM must be non-NULL if this closure is expected to yield."); 157 } 158 159 virtual bool doHeapRegion(HeapRegion* r) { 160 size_t const chunk_size_in_words = M / HeapWordSize; 161 162 HeapWord* cur = r->bottom(); 163 HeapWord* const end = r->end(); 164 165 while (cur < end) { 166 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end)); 167 _bitmap->clearRange(mr); 168 169 cur += chunk_size_in_words; 170 171 // Abort iteration if after yielding the marking has been aborted. 172 if (_may_yield && _cm->do_yield_check() && _cm->has_aborted()) { 173 return true; 174 } 175 // Repeat the asserts from before the start of the closure. We will do them 176 // as asserts here to minimize their overhead on the product. However, we 177 // will have them as guarantees at the beginning / end of the bitmap 178 // clearing to get some checking in the product. 179 assert(!_may_yield || _cm->cmThread()->during_cycle(), "invariant"); 180 assert(!_may_yield || !G1CollectedHeap::heap()->mark_in_progress(), "invariant"); 181 } 182 183 return false; 184 } 185 }; 186 187 class ParClearNextMarkBitmapTask : public AbstractGangTask { 188 ClearBitmapHRClosure* _cl; 189 HeapRegionClaimer _hrclaimer; 190 bool _suspendible; // If the task is suspendible, workers must join the STS. 191 192 public: 193 ParClearNextMarkBitmapTask(ClearBitmapHRClosure *cl, uint n_workers, bool suspendible) : 194 _cl(cl), _suspendible(suspendible), AbstractGangTask("Parallel Clear Bitmap Task"), _hrclaimer(n_workers) {} 195 196 void work(uint worker_id) { 197 SuspendibleThreadSetJoiner sts_join(_suspendible); 198 G1CollectedHeap::heap()->heap_region_par_iterate(_cl, worker_id, &_hrclaimer, true); 199 } 200 }; 201 202 void CMBitMap::clearAll() { 203 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 204 ClearBitmapHRClosure cl(NULL, this, false /* may_yield */); 205 uint n_workers = g1h->workers()->active_workers(); 206 ParClearNextMarkBitmapTask task(&cl, n_workers, false); 207 g1h->workers()->run_task(&task); 208 guarantee(cl.complete(), "Must have completed iteration."); 209 return; 210 } 211 212 void CMBitMap::markRange(MemRegion mr) { 213 mr.intersection(MemRegion(_bmStartWord, _bmWordSize)); 214 assert(!mr.is_empty(), "unexpected empty region"); 215 assert((offsetToHeapWord(heapWordToOffset(mr.end())) == 216 ((HeapWord *) mr.end())), 217 "markRange memory region end is not card aligned"); 218 // convert address range into offset range 219 _bm.at_put_range(heapWordToOffset(mr.start()), 220 heapWordToOffset(mr.end()), true); 221 } 222 223 void CMBitMap::clearRange(MemRegion mr) { 224 mr.intersection(MemRegion(_bmStartWord, _bmWordSize)); 225 assert(!mr.is_empty(), "unexpected empty region"); 226 // convert address range into offset range 227 _bm.at_put_range(heapWordToOffset(mr.start()), 228 heapWordToOffset(mr.end()), false); 229 } 230 231 MemRegion CMBitMap::getAndClearMarkedRegion(HeapWord* addr, 232 HeapWord* end_addr) { 233 HeapWord* start = getNextMarkedWordAddress(addr); 234 start = MIN2(start, end_addr); 235 HeapWord* end = getNextUnmarkedWordAddress(start); 236 end = MIN2(end, end_addr); 237 assert(start <= end, "Consistency check"); 238 MemRegion mr(start, end); 239 if (!mr.is_empty()) { 240 clearRange(mr); 241 } 242 return mr; 243 } 244 245 CMMarkStack::CMMarkStack(ConcurrentMark* cm) : 246 _base(NULL), _cm(cm) 247 #ifdef ASSERT 248 , _drain_in_progress(false) 249 , _drain_in_progress_yields(false) 250 #endif 251 {} 252 253 bool CMMarkStack::allocate(size_t capacity) { 254 // allocate a stack of the requisite depth 255 ReservedSpace rs(ReservedSpace::allocation_align_size_up(capacity * sizeof(oop))); 256 if (!rs.is_reserved()) { 257 warning("ConcurrentMark MarkStack allocation failure"); 258 return false; 259 } 260 MemTracker::record_virtual_memory_type((address)rs.base(), mtGC); 261 if (!_virtual_space.initialize(rs, rs.size())) { 262 warning("ConcurrentMark MarkStack backing store failure"); 263 // Release the virtual memory reserved for the marking stack 264 rs.release(); 265 return false; 266 } 267 assert(_virtual_space.committed_size() == rs.size(), 268 "Didn't reserve backing store for all of ConcurrentMark stack?"); 269 _base = (oop*) _virtual_space.low(); 270 setEmpty(); 271 _capacity = (jint) capacity; 272 _saved_index = -1; 273 _should_expand = false; 274 return true; 275 } 276 277 void CMMarkStack::expand() { 278 // Called, during remark, if we've overflown the marking stack during marking. 279 assert(isEmpty(), "stack should been emptied while handling overflow"); 280 assert(_capacity <= (jint) MarkStackSizeMax, "stack bigger than permitted"); 281 // Clear expansion flag 282 _should_expand = false; 283 if (_capacity == (jint) MarkStackSizeMax) { 284 if (PrintGCDetails && Verbose) { 285 gclog_or_tty->print_cr(" (benign) Can't expand marking stack capacity, at max size limit"); 286 } 287 return; 288 } 289 // Double capacity if possible 290 jint new_capacity = MIN2(_capacity*2, (jint) MarkStackSizeMax); 291 // Do not give up existing stack until we have managed to 292 // get the double capacity that we desired. 293 ReservedSpace rs(ReservedSpace::allocation_align_size_up(new_capacity * 294 sizeof(oop))); 295 if (rs.is_reserved()) { 296 // Release the backing store associated with old stack 297 _virtual_space.release(); 298 // Reinitialize virtual space for new stack 299 if (!_virtual_space.initialize(rs, rs.size())) { 300 fatal("Not enough swap for expanded marking stack capacity"); 301 } 302 _base = (oop*)(_virtual_space.low()); 303 _index = 0; 304 _capacity = new_capacity; 305 } else { 306 if (PrintGCDetails && Verbose) { 307 // Failed to double capacity, continue; 308 gclog_or_tty->print(" (benign) Failed to expand marking stack capacity from " 309 SIZE_FORMAT"K to " SIZE_FORMAT"K", 310 _capacity / K, new_capacity / K); 311 } 312 } 313 } 314 315 void CMMarkStack::set_should_expand() { 316 // If we're resetting the marking state because of an 317 // marking stack overflow, record that we should, if 318 // possible, expand the stack. 319 _should_expand = _cm->has_overflown(); 320 } 321 322 CMMarkStack::~CMMarkStack() { 323 if (_base != NULL) { 324 _base = NULL; 325 _virtual_space.release(); 326 } 327 } 328 329 void CMMarkStack::par_push_arr(oop* ptr_arr, int n) { 330 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 331 jint start = _index; 332 jint next_index = start + n; 333 if (next_index > _capacity) { 334 _overflow = true; 335 return; 336 } 337 // Otherwise. 338 _index = next_index; 339 for (int i = 0; i < n; i++) { 340 int ind = start + i; 341 assert(ind < _capacity, "By overflow test above."); 342 _base[ind] = ptr_arr[i]; 343 } 344 } 345 346 bool CMMarkStack::par_pop_arr(oop* ptr_arr, int max, int* n) { 347 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 348 jint index = _index; 349 if (index == 0) { 350 *n = 0; 351 return false; 352 } else { 353 int k = MIN2(max, index); 354 jint new_ind = index - k; 355 for (int j = 0; j < k; j++) { 356 ptr_arr[j] = _base[new_ind + j]; 357 } 358 _index = new_ind; 359 *n = k; 360 return true; 361 } 362 } 363 364 template<class OopClosureClass> 365 bool CMMarkStack::drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after) { 366 assert(!_drain_in_progress || !_drain_in_progress_yields || yield_after 367 || SafepointSynchronize::is_at_safepoint(), 368 "Drain recursion must be yield-safe."); 369 bool res = true; 370 debug_only(_drain_in_progress = true); 371 debug_only(_drain_in_progress_yields = yield_after); 372 while (!isEmpty()) { 373 oop newOop = pop(); 374 assert(G1CollectedHeap::heap()->is_in_reserved(newOop), "Bad pop"); 375 assert(newOop->is_oop(), "Expected an oop"); 376 assert(bm == NULL || bm->isMarked((HeapWord*)newOop), 377 "only grey objects on this stack"); 378 newOop->oop_iterate(cl); 379 if (yield_after && _cm->do_yield_check()) { 380 res = false; 381 break; 382 } 383 } 384 debug_only(_drain_in_progress = false); 385 return res; 386 } 387 388 void CMMarkStack::note_start_of_gc() { 389 assert(_saved_index == -1, 390 "note_start_of_gc()/end_of_gc() bracketed incorrectly"); 391 _saved_index = _index; 392 } 393 394 void CMMarkStack::note_end_of_gc() { 395 // This is intentionally a guarantee, instead of an assert. If we 396 // accidentally add something to the mark stack during GC, it 397 // will be a correctness issue so it's better if we crash. we'll 398 // only check this once per GC anyway, so it won't be a performance 399 // issue in any way. 400 guarantee(_saved_index == _index, 401 err_msg("saved index: %d index: %d", _saved_index, _index)); 402 _saved_index = -1; 403 } 404 405 void CMMarkStack::oops_do(OopClosure* f) { 406 assert(_saved_index == _index, 407 err_msg("saved index: %d index: %d", _saved_index, _index)); 408 for (int i = 0; i < _index; i += 1) { 409 f->do_oop(&_base[i]); 410 } 411 } 412 413 CMRootRegions::CMRootRegions() : 414 _young_list(NULL), _cm(NULL), _scan_in_progress(false), 415 _should_abort(false), _next_survivor(NULL) { } 416 417 void CMRootRegions::init(G1CollectedHeap* g1h, ConcurrentMark* cm) { 418 _young_list = g1h->young_list(); 419 _cm = cm; 420 } 421 422 void CMRootRegions::prepare_for_scan() { 423 assert(!scan_in_progress(), "pre-condition"); 424 425 // Currently, only survivors can be root regions. 426 assert(_next_survivor == NULL, "pre-condition"); 427 _next_survivor = _young_list->first_survivor_region(); 428 _scan_in_progress = (_next_survivor != NULL); 429 _should_abort = false; 430 } 431 432 HeapRegion* CMRootRegions::claim_next() { 433 if (_should_abort) { 434 // If someone has set the should_abort flag, we return NULL to 435 // force the caller to bail out of their loop. 436 return NULL; 437 } 438 439 // Currently, only survivors can be root regions. 440 HeapRegion* res = _next_survivor; 441 if (res != NULL) { 442 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 443 // Read it again in case it changed while we were waiting for the lock. 444 res = _next_survivor; 445 if (res != NULL) { 446 if (res == _young_list->last_survivor_region()) { 447 // We just claimed the last survivor so store NULL to indicate 448 // that we're done. 449 _next_survivor = NULL; 450 } else { 451 _next_survivor = res->get_next_young_region(); 452 } 453 } else { 454 // Someone else claimed the last survivor while we were trying 455 // to take the lock so nothing else to do. 456 } 457 } 458 assert(res == NULL || res->is_survivor(), "post-condition"); 459 460 return res; 461 } 462 463 void CMRootRegions::scan_finished() { 464 assert(scan_in_progress(), "pre-condition"); 465 466 // Currently, only survivors can be root regions. 467 if (!_should_abort) { 468 assert(_next_survivor == NULL, "we should have claimed all survivors"); 469 } 470 _next_survivor = NULL; 471 472 { 473 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 474 _scan_in_progress = false; 475 RootRegionScan_lock->notify_all(); 476 } 477 } 478 479 bool CMRootRegions::wait_until_scan_finished() { 480 if (!scan_in_progress()) return false; 481 482 { 483 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 484 while (scan_in_progress()) { 485 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag); 486 } 487 } 488 return true; 489 } 490 491 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 492 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 493 #endif // _MSC_VER 494 495 uint ConcurrentMark::scale_parallel_threads(uint n_par_threads) { 496 return MAX2((n_par_threads + 2) / 4, 1U); 497 } 498 499 ConcurrentMark::ConcurrentMark(G1CollectedHeap* g1h, G1RegionToSpaceMapper* prev_bitmap_storage, G1RegionToSpaceMapper* next_bitmap_storage) : 500 _g1h(g1h), 501 _markBitMap1(), 502 _markBitMap2(), 503 _parallel_marking_threads(0), 504 _max_parallel_marking_threads(0), 505 _sleep_factor(0.0), 506 _marking_task_overhead(1.0), 507 _cleanup_sleep_factor(0.0), 508 _cleanup_task_overhead(1.0), 509 _cleanup_list("Cleanup List"), 510 _region_bm((BitMap::idx_t)(g1h->max_regions()), false /* in_resource_area*/), 511 _card_bm((g1h->reserved_region().byte_size() + CardTableModRefBS::card_size - 1) >> 512 CardTableModRefBS::card_shift, 513 false /* in_resource_area*/), 514 515 _prevMarkBitMap(&_markBitMap1), 516 _nextMarkBitMap(&_markBitMap2), 517 518 _markStack(this), 519 // _finger set in set_non_marking_state 520 521 _max_worker_id((uint)ParallelGCThreads), 522 // _active_tasks set in set_non_marking_state 523 // _tasks set inside the constructor 524 _task_queues(new CMTaskQueueSet((int) _max_worker_id)), 525 _terminator(ParallelTaskTerminator((int) _max_worker_id, _task_queues)), 526 527 _has_overflown(false), 528 _concurrent(false), 529 _has_aborted(false), 530 _aborted_gc_id(GCId::undefined()), 531 _restart_for_overflow(false), 532 _concurrent_marking_in_progress(false), 533 534 // _verbose_level set below 535 536 _init_times(), 537 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(), 538 _cleanup_times(), 539 _total_counting_time(0.0), 540 _total_rs_scrub_time(0.0), 541 542 _parallel_workers(NULL), 543 544 _count_card_bitmaps(NULL), 545 _count_marked_bytes(NULL), 546 _completed_initialization(false) { 547 CMVerboseLevel verbose_level = (CMVerboseLevel) G1MarkingVerboseLevel; 548 if (verbose_level < no_verbose) { 549 verbose_level = no_verbose; 550 } 551 if (verbose_level > high_verbose) { 552 verbose_level = high_verbose; 553 } 554 _verbose_level = verbose_level; 555 556 if (verbose_low()) { 557 gclog_or_tty->print_cr("[global] init, heap start = "PTR_FORMAT", " 558 "heap end = " PTR_FORMAT, p2i(_heap_start), p2i(_heap_end)); 559 } 560 561 _markBitMap1.initialize(g1h->reserved_region(), prev_bitmap_storage); 562 _markBitMap2.initialize(g1h->reserved_region(), next_bitmap_storage); 563 564 // Create & start a ConcurrentMark thread. 565 _cmThread = new ConcurrentMarkThread(this); 566 assert(cmThread() != NULL, "CM Thread should have been created"); 567 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm"); 568 if (_cmThread->osthread() == NULL) { 569 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread"); 570 } 571 572 assert(CGC_lock != NULL, "Where's the CGC_lock?"); 573 assert(_markBitMap1.covers(g1h->reserved_region()), "_markBitMap1 inconsistency"); 574 assert(_markBitMap2.covers(g1h->reserved_region()), "_markBitMap2 inconsistency"); 575 576 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set(); 577 satb_qs.set_buffer_size(G1SATBBufferSize); 578 579 _root_regions.init(_g1h, this); 580 581 if (ConcGCThreads > ParallelGCThreads) { 582 warning("Can't have more ConcGCThreads (" UINTX_FORMAT ") " 583 "than ParallelGCThreads (" UINTX_FORMAT ").", 584 ConcGCThreads, ParallelGCThreads); 585 return; 586 } 587 if (!FLAG_IS_DEFAULT(ConcGCThreads) && ConcGCThreads > 0) { 588 // Note: ConcGCThreads has precedence over G1MarkingOverheadPercent 589 // if both are set 590 _sleep_factor = 0.0; 591 _marking_task_overhead = 1.0; 592 } else if (G1MarkingOverheadPercent > 0) { 593 // We will calculate the number of parallel marking threads based 594 // on a target overhead with respect to the soft real-time goal 595 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0; 596 double overall_cm_overhead = 597 (double) MaxGCPauseMillis * marking_overhead / 598 (double) GCPauseIntervalMillis; 599 double cpu_ratio = 1.0 / (double) os::processor_count(); 600 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio); 601 double marking_task_overhead = 602 overall_cm_overhead / marking_thread_num * 603 (double) os::processor_count(); 604 double sleep_factor = 605 (1.0 - marking_task_overhead) / marking_task_overhead; 606 607 FLAG_SET_ERGO(uintx, ConcGCThreads, (uint) marking_thread_num); 608 _sleep_factor = sleep_factor; 609 _marking_task_overhead = marking_task_overhead; 610 } else { 611 // Calculate the number of parallel marking threads by scaling 612 // the number of parallel GC threads. 613 uint marking_thread_num = scale_parallel_threads((uint) ParallelGCThreads); 614 FLAG_SET_ERGO(uintx, ConcGCThreads, marking_thread_num); 615 _sleep_factor = 0.0; 616 _marking_task_overhead = 1.0; 617 } 618 619 assert(ConcGCThreads > 0, "Should have been set"); 620 _parallel_marking_threads = (uint) ConcGCThreads; 621 _max_parallel_marking_threads = _parallel_marking_threads; 622 623 if (parallel_marking_threads() > 1) { 624 _cleanup_task_overhead = 1.0; 625 } else { 626 _cleanup_task_overhead = marking_task_overhead(); 627 } 628 _cleanup_sleep_factor = 629 (1.0 - cleanup_task_overhead()) / cleanup_task_overhead(); 630 631 #if 0 632 gclog_or_tty->print_cr("Marking Threads %d", parallel_marking_threads()); 633 gclog_or_tty->print_cr("CM Marking Task Overhead %1.4lf", marking_task_overhead()); 634 gclog_or_tty->print_cr("CM Sleep Factor %1.4lf", sleep_factor()); 635 gclog_or_tty->print_cr("CL Marking Task Overhead %1.4lf", cleanup_task_overhead()); 636 gclog_or_tty->print_cr("CL Sleep Factor %1.4lf", cleanup_sleep_factor()); 637 #endif 638 639 _parallel_workers = new FlexibleWorkGang("G1 Marker", 640 _max_parallel_marking_threads, false, true); 641 if (_parallel_workers == NULL) { 642 vm_exit_during_initialization("Failed necessary allocation."); 643 } else { 644 _parallel_workers->initialize_workers(); 645 } 646 647 if (FLAG_IS_DEFAULT(MarkStackSize)) { 648 size_t mark_stack_size = 649 MIN2(MarkStackSizeMax, 650 MAX2(MarkStackSize, (size_t) (parallel_marking_threads() * TASKQUEUE_SIZE))); 651 // Verify that the calculated value for MarkStackSize is in range. 652 // It would be nice to use the private utility routine from Arguments. 653 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) { 654 warning("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): " 655 "must be between 1 and " SIZE_FORMAT, 656 mark_stack_size, MarkStackSizeMax); 657 return; 658 } 659 FLAG_SET_ERGO(size_t, MarkStackSize, mark_stack_size); 660 } else { 661 // Verify MarkStackSize is in range. 662 if (FLAG_IS_CMDLINE(MarkStackSize)) { 663 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) { 664 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) { 665 warning("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): " 666 "must be between 1 and " SIZE_FORMAT, 667 MarkStackSize, MarkStackSizeMax); 668 return; 669 } 670 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) { 671 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) { 672 warning("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")" 673 " or for MarkStackSizeMax (" SIZE_FORMAT ")", 674 MarkStackSize, MarkStackSizeMax); 675 return; 676 } 677 } 678 } 679 } 680 681 if (!_markStack.allocate(MarkStackSize)) { 682 warning("Failed to allocate CM marking stack"); 683 return; 684 } 685 686 _tasks = NEW_C_HEAP_ARRAY(CMTask*, _max_worker_id, mtGC); 687 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_worker_id, mtGC); 688 689 _count_card_bitmaps = NEW_C_HEAP_ARRAY(BitMap, _max_worker_id, mtGC); 690 _count_marked_bytes = NEW_C_HEAP_ARRAY(size_t*, _max_worker_id, mtGC); 691 692 BitMap::idx_t card_bm_size = _card_bm.size(); 693 694 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail 695 _active_tasks = _max_worker_id; 696 697 uint max_regions = _g1h->max_regions(); 698 for (uint i = 0; i < _max_worker_id; ++i) { 699 CMTaskQueue* task_queue = new CMTaskQueue(); 700 task_queue->initialize(); 701 _task_queues->register_queue(i, task_queue); 702 703 _count_card_bitmaps[i] = BitMap(card_bm_size, false); 704 _count_marked_bytes[i] = NEW_C_HEAP_ARRAY(size_t, max_regions, mtGC); 705 706 _tasks[i] = new CMTask(i, this, 707 _count_marked_bytes[i], 708 &_count_card_bitmaps[i], 709 task_queue, _task_queues); 710 711 _accum_task_vtime[i] = 0.0; 712 } 713 714 // Calculate the card number for the bottom of the heap. Used 715 // in biasing indexes into the accounting card bitmaps. 716 _heap_bottom_card_num = 717 intptr_t(uintptr_t(_g1h->reserved_region().start()) >> 718 CardTableModRefBS::card_shift); 719 720 // Clear all the liveness counting data 721 clear_all_count_data(); 722 723 // so that the call below can read a sensible value 724 _heap_start = g1h->reserved_region().start(); 725 set_non_marking_state(); 726 _completed_initialization = true; 727 } 728 729 void ConcurrentMark::reset() { 730 // Starting values for these two. This should be called in a STW 731 // phase. 732 MemRegion reserved = _g1h->g1_reserved(); 733 _heap_start = reserved.start(); 734 _heap_end = reserved.end(); 735 736 // Separated the asserts so that we know which one fires. 737 assert(_heap_start != NULL, "heap bounds should look ok"); 738 assert(_heap_end != NULL, "heap bounds should look ok"); 739 assert(_heap_start < _heap_end, "heap bounds should look ok"); 740 741 // Reset all the marking data structures and any necessary flags 742 reset_marking_state(); 743 744 if (verbose_low()) { 745 gclog_or_tty->print_cr("[global] resetting"); 746 } 747 748 // We do reset all of them, since different phases will use 749 // different number of active threads. So, it's easiest to have all 750 // of them ready. 751 for (uint i = 0; i < _max_worker_id; ++i) { 752 _tasks[i]->reset(_nextMarkBitMap); 753 } 754 755 // we need this to make sure that the flag is on during the evac 756 // pause with initial mark piggy-backed 757 set_concurrent_marking_in_progress(); 758 } 759 760 761 void ConcurrentMark::reset_marking_state(bool clear_overflow) { 762 _markStack.set_should_expand(); 763 _markStack.setEmpty(); // Also clears the _markStack overflow flag 764 if (clear_overflow) { 765 clear_has_overflown(); 766 } else { 767 assert(has_overflown(), "pre-condition"); 768 } 769 _finger = _heap_start; 770 771 for (uint i = 0; i < _max_worker_id; ++i) { 772 CMTaskQueue* queue = _task_queues->queue(i); 773 queue->set_empty(); 774 } 775 } 776 777 void ConcurrentMark::set_concurrency(uint active_tasks) { 778 assert(active_tasks <= _max_worker_id, "we should not have more"); 779 780 _active_tasks = active_tasks; 781 // Need to update the three data structures below according to the 782 // number of active threads for this phase. 783 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues); 784 _first_overflow_barrier_sync.set_n_workers((int) active_tasks); 785 _second_overflow_barrier_sync.set_n_workers((int) active_tasks); 786 } 787 788 void ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) { 789 set_concurrency(active_tasks); 790 791 _concurrent = concurrent; 792 // We propagate this to all tasks, not just the active ones. 793 for (uint i = 0; i < _max_worker_id; ++i) 794 _tasks[i]->set_concurrent(concurrent); 795 796 if (concurrent) { 797 set_concurrent_marking_in_progress(); 798 } else { 799 // We currently assume that the concurrent flag has been set to 800 // false before we start remark. At this point we should also be 801 // in a STW phase. 802 assert(!concurrent_marking_in_progress(), "invariant"); 803 assert(out_of_regions(), 804 err_msg("only way to get here: _finger: "PTR_FORMAT", _heap_end: "PTR_FORMAT, 805 p2i(_finger), p2i(_heap_end))); 806 } 807 } 808 809 void ConcurrentMark::set_non_marking_state() { 810 // We set the global marking state to some default values when we're 811 // not doing marking. 812 reset_marking_state(); 813 _active_tasks = 0; 814 clear_concurrent_marking_in_progress(); 815 } 816 817 ConcurrentMark::~ConcurrentMark() { 818 // The ConcurrentMark instance is never freed. 819 ShouldNotReachHere(); 820 } 821 822 void ConcurrentMark::clearNextBitmap() { 823 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 824 825 // Make sure that the concurrent mark thread looks to still be in 826 // the current cycle. 827 guarantee(cmThread()->during_cycle(), "invariant"); 828 829 // We are finishing up the current cycle by clearing the next 830 // marking bitmap and getting it ready for the next cycle. During 831 // this time no other cycle can start. So, let's make sure that this 832 // is the case. 833 guarantee(!g1h->mark_in_progress(), "invariant"); 834 835 ClearBitmapHRClosure cl(this, _nextMarkBitMap, true /* may_yield */); 836 ParClearNextMarkBitmapTask task(&cl, parallel_marking_threads(), true); 837 _parallel_workers->run_task(&task); 838 839 // Clear the liveness counting data. If the marking has been aborted, the abort() 840 // call already did that. 841 if (cl.complete()) { 842 clear_all_count_data(); 843 } 844 845 // Repeat the asserts from above. 846 guarantee(cmThread()->during_cycle(), "invariant"); 847 guarantee(!g1h->mark_in_progress(), "invariant"); 848 } 849 850 class CheckBitmapClearHRClosure : public HeapRegionClosure { 851 CMBitMap* _bitmap; 852 bool _error; 853 public: 854 CheckBitmapClearHRClosure(CMBitMap* bitmap) : _bitmap(bitmap) { 855 } 856 857 virtual bool doHeapRegion(HeapRegion* r) { 858 // This closure can be called concurrently to the mutator, so we must make sure 859 // that the result of the getNextMarkedWordAddress() call is compared to the 860 // value passed to it as limit to detect any found bits. 861 // We can use the region's orig_end() for the limit and the comparison value 862 // as it always contains the "real" end of the region that never changes and 863 // has no side effects. 864 // Due to the latter, there can also be no problem with the compiler generating 865 // reloads of the orig_end() call. 866 HeapWord* end = r->orig_end(); 867 return _bitmap->getNextMarkedWordAddress(r->bottom(), end) != end; 868 } 869 }; 870 871 bool ConcurrentMark::nextMarkBitmapIsClear() { 872 CheckBitmapClearHRClosure cl(_nextMarkBitMap); 873 _g1h->heap_region_iterate(&cl); 874 return cl.complete(); 875 } 876 877 class NoteStartOfMarkHRClosure: public HeapRegionClosure { 878 public: 879 bool doHeapRegion(HeapRegion* r) { 880 if (!r->is_continues_humongous()) { 881 r->note_start_of_marking(); 882 } 883 return false; 884 } 885 }; 886 887 void ConcurrentMark::checkpointRootsInitialPre() { 888 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 889 G1CollectorPolicy* g1p = g1h->g1_policy(); 890 891 _has_aborted = false; 892 893 // Initialize marking structures. This has to be done in a STW phase. 894 reset(); 895 896 // For each region note start of marking. 897 NoteStartOfMarkHRClosure startcl; 898 g1h->heap_region_iterate(&startcl); 899 } 900 901 902 void ConcurrentMark::checkpointRootsInitialPost() { 903 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 904 905 // If we force an overflow during remark, the remark operation will 906 // actually abort and we'll restart concurrent marking. If we always 907 // force an overflow during remark we'll never actually complete the 908 // marking phase. So, we initialize this here, at the start of the 909 // cycle, so that at the remaining overflow number will decrease at 910 // every remark and we'll eventually not need to cause one. 911 force_overflow_stw()->init(); 912 913 // Start Concurrent Marking weak-reference discovery. 914 ReferenceProcessor* rp = g1h->ref_processor_cm(); 915 // enable ("weak") refs discovery 916 rp->enable_discovery(); 917 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle 918 919 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 920 // This is the start of the marking cycle, we're expected all 921 // threads to have SATB queues with active set to false. 922 satb_mq_set.set_active_all_threads(true, /* new active value */ 923 false /* expected_active */); 924 925 _root_regions.prepare_for_scan(); 926 927 // update_g1_committed() will be called at the end of an evac pause 928 // when marking is on. So, it's also called at the end of the 929 // initial-mark pause to update the heap end, if the heap expands 930 // during it. No need to call it here. 931 } 932 933 /* 934 * Notice that in the next two methods, we actually leave the STS 935 * during the barrier sync and join it immediately afterwards. If we 936 * do not do this, the following deadlock can occur: one thread could 937 * be in the barrier sync code, waiting for the other thread to also 938 * sync up, whereas another one could be trying to yield, while also 939 * waiting for the other threads to sync up too. 940 * 941 * Note, however, that this code is also used during remark and in 942 * this case we should not attempt to leave / enter the STS, otherwise 943 * we'll either hit an assert (debug / fastdebug) or deadlock 944 * (product). So we should only leave / enter the STS if we are 945 * operating concurrently. 946 * 947 * Because the thread that does the sync barrier has left the STS, it 948 * is possible to be suspended for a Full GC or an evacuation pause 949 * could occur. This is actually safe, since the entering the sync 950 * barrier is one of the last things do_marking_step() does, and it 951 * doesn't manipulate any data structures afterwards. 952 */ 953 954 void ConcurrentMark::enter_first_sync_barrier(uint worker_id) { 955 bool barrier_aborted; 956 957 if (verbose_low()) { 958 gclog_or_tty->print_cr("[%u] entering first barrier", worker_id); 959 } 960 961 { 962 SuspendibleThreadSetLeaver sts_leave(concurrent()); 963 barrier_aborted = !_first_overflow_barrier_sync.enter(); 964 } 965 966 // at this point everyone should have synced up and not be doing any 967 // more work 968 969 if (verbose_low()) { 970 if (barrier_aborted) { 971 gclog_or_tty->print_cr("[%u] aborted first barrier", worker_id); 972 } else { 973 gclog_or_tty->print_cr("[%u] leaving first barrier", worker_id); 974 } 975 } 976 977 if (barrier_aborted) { 978 // If the barrier aborted we ignore the overflow condition and 979 // just abort the whole marking phase as quickly as possible. 980 return; 981 } 982 983 // If we're executing the concurrent phase of marking, reset the marking 984 // state; otherwise the marking state is reset after reference processing, 985 // during the remark pause. 986 // If we reset here as a result of an overflow during the remark we will 987 // see assertion failures from any subsequent set_concurrency_and_phase() 988 // calls. 989 if (concurrent()) { 990 // let the task associated with with worker 0 do this 991 if (worker_id == 0) { 992 // task 0 is responsible for clearing the global data structures 993 // We should be here because of an overflow. During STW we should 994 // not clear the overflow flag since we rely on it being true when 995 // we exit this method to abort the pause and restart concurrent 996 // marking. 997 reset_marking_state(true /* clear_overflow */); 998 force_overflow()->update(); 999 1000 if (G1Log::fine()) { 1001 gclog_or_tty->gclog_stamp(concurrent_gc_id()); 1002 gclog_or_tty->print_cr("[GC concurrent-mark-reset-for-overflow]"); 1003 } 1004 } 1005 } 1006 1007 // after this, each task should reset its own data structures then 1008 // then go into the second barrier 1009 } 1010 1011 void ConcurrentMark::enter_second_sync_barrier(uint worker_id) { 1012 bool barrier_aborted; 1013 1014 if (verbose_low()) { 1015 gclog_or_tty->print_cr("[%u] entering second barrier", worker_id); 1016 } 1017 1018 { 1019 SuspendibleThreadSetLeaver sts_leave(concurrent()); 1020 barrier_aborted = !_second_overflow_barrier_sync.enter(); 1021 } 1022 1023 // at this point everything should be re-initialized and ready to go 1024 1025 if (verbose_low()) { 1026 if (barrier_aborted) { 1027 gclog_or_tty->print_cr("[%u] aborted second barrier", worker_id); 1028 } else { 1029 gclog_or_tty->print_cr("[%u] leaving second barrier", worker_id); 1030 } 1031 } 1032 } 1033 1034 #ifndef PRODUCT 1035 void ForceOverflowSettings::init() { 1036 _num_remaining = G1ConcMarkForceOverflow; 1037 _force = false; 1038 update(); 1039 } 1040 1041 void ForceOverflowSettings::update() { 1042 if (_num_remaining > 0) { 1043 _num_remaining -= 1; 1044 _force = true; 1045 } else { 1046 _force = false; 1047 } 1048 } 1049 1050 bool ForceOverflowSettings::should_force() { 1051 if (_force) { 1052 _force = false; 1053 return true; 1054 } else { 1055 return false; 1056 } 1057 } 1058 #endif // !PRODUCT 1059 1060 class CMConcurrentMarkingTask: public AbstractGangTask { 1061 private: 1062 ConcurrentMark* _cm; 1063 ConcurrentMarkThread* _cmt; 1064 1065 public: 1066 void work(uint worker_id) { 1067 assert(Thread::current()->is_ConcurrentGC_thread(), 1068 "this should only be done by a conc GC thread"); 1069 ResourceMark rm; 1070 1071 double start_vtime = os::elapsedVTime(); 1072 1073 { 1074 SuspendibleThreadSetJoiner sts_join; 1075 1076 assert(worker_id < _cm->active_tasks(), "invariant"); 1077 CMTask* the_task = _cm->task(worker_id); 1078 the_task->record_start_time(); 1079 if (!_cm->has_aborted()) { 1080 do { 1081 double start_vtime_sec = os::elapsedVTime(); 1082 double mark_step_duration_ms = G1ConcMarkStepDurationMillis; 1083 1084 the_task->do_marking_step(mark_step_duration_ms, 1085 true /* do_termination */, 1086 false /* is_serial*/); 1087 1088 double end_vtime_sec = os::elapsedVTime(); 1089 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec; 1090 _cm->clear_has_overflown(); 1091 1092 _cm->do_yield_check(worker_id); 1093 1094 jlong sleep_time_ms; 1095 if (!_cm->has_aborted() && the_task->has_aborted()) { 1096 sleep_time_ms = 1097 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0); 1098 { 1099 SuspendibleThreadSetLeaver sts_leave; 1100 os::sleep(Thread::current(), sleep_time_ms, false); 1101 } 1102 } 1103 } while (!_cm->has_aborted() && the_task->has_aborted()); 1104 } 1105 the_task->record_end_time(); 1106 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant"); 1107 } 1108 1109 double end_vtime = os::elapsedVTime(); 1110 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime); 1111 } 1112 1113 CMConcurrentMarkingTask(ConcurrentMark* cm, 1114 ConcurrentMarkThread* cmt) : 1115 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { } 1116 1117 ~CMConcurrentMarkingTask() { } 1118 }; 1119 1120 // Calculates the number of active workers for a concurrent 1121 // phase. 1122 uint ConcurrentMark::calc_parallel_marking_threads() { 1123 uint n_conc_workers = 0; 1124 if (!UseDynamicNumberOfGCThreads || 1125 (!FLAG_IS_DEFAULT(ConcGCThreads) && 1126 !ForceDynamicNumberOfGCThreads)) { 1127 n_conc_workers = max_parallel_marking_threads(); 1128 } else { 1129 n_conc_workers = 1130 AdaptiveSizePolicy::calc_default_active_workers( 1131 max_parallel_marking_threads(), 1132 1, /* Minimum workers */ 1133 parallel_marking_threads(), 1134 Threads::number_of_non_daemon_threads()); 1135 // Don't scale down "n_conc_workers" by scale_parallel_threads() because 1136 // that scaling has already gone into "_max_parallel_marking_threads". 1137 } 1138 assert(n_conc_workers > 0, "Always need at least 1"); 1139 return n_conc_workers; 1140 } 1141 1142 void ConcurrentMark::scanRootRegion(HeapRegion* hr, uint worker_id) { 1143 // Currently, only survivors can be root regions. 1144 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant"); 1145 G1RootRegionScanClosure cl(_g1h, this, worker_id); 1146 1147 const uintx interval = PrefetchScanIntervalInBytes; 1148 HeapWord* curr = hr->bottom(); 1149 const HeapWord* end = hr->top(); 1150 while (curr < end) { 1151 Prefetch::read(curr, interval); 1152 oop obj = oop(curr); 1153 int size = obj->oop_iterate(&cl); 1154 assert(size == obj->size(), "sanity"); 1155 curr += size; 1156 } 1157 } 1158 1159 class CMRootRegionScanTask : public AbstractGangTask { 1160 private: 1161 ConcurrentMark* _cm; 1162 1163 public: 1164 CMRootRegionScanTask(ConcurrentMark* cm) : 1165 AbstractGangTask("Root Region Scan"), _cm(cm) { } 1166 1167 void work(uint worker_id) { 1168 assert(Thread::current()->is_ConcurrentGC_thread(), 1169 "this should only be done by a conc GC thread"); 1170 1171 CMRootRegions* root_regions = _cm->root_regions(); 1172 HeapRegion* hr = root_regions->claim_next(); 1173 while (hr != NULL) { 1174 _cm->scanRootRegion(hr, worker_id); 1175 hr = root_regions->claim_next(); 1176 } 1177 } 1178 }; 1179 1180 void ConcurrentMark::scanRootRegions() { 1181 // Start of concurrent marking. 1182 ClassLoaderDataGraph::clear_claimed_marks(); 1183 1184 // scan_in_progress() will have been set to true only if there was 1185 // at least one root region to scan. So, if it's false, we 1186 // should not attempt to do any further work. 1187 if (root_regions()->scan_in_progress()) { 1188 _parallel_marking_threads = calc_parallel_marking_threads(); 1189 assert(parallel_marking_threads() <= max_parallel_marking_threads(), 1190 "Maximum number of marking threads exceeded"); 1191 uint active_workers = MAX2(1U, parallel_marking_threads()); 1192 1193 CMRootRegionScanTask task(this); 1194 _parallel_workers->set_active_workers(active_workers); 1195 _parallel_workers->run_task(&task); 1196 1197 // It's possible that has_aborted() is true here without actually 1198 // aborting the survivor scan earlier. This is OK as it's 1199 // mainly used for sanity checking. 1200 root_regions()->scan_finished(); 1201 } 1202 } 1203 1204 void ConcurrentMark::markFromRoots() { 1205 // we might be tempted to assert that: 1206 // assert(asynch == !SafepointSynchronize::is_at_safepoint(), 1207 // "inconsistent argument?"); 1208 // However that wouldn't be right, because it's possible that 1209 // a safepoint is indeed in progress as a younger generation 1210 // stop-the-world GC happens even as we mark in this generation. 1211 1212 _restart_for_overflow = false; 1213 force_overflow_conc()->init(); 1214 1215 // _g1h has _n_par_threads 1216 _parallel_marking_threads = calc_parallel_marking_threads(); 1217 assert(parallel_marking_threads() <= max_parallel_marking_threads(), 1218 "Maximum number of marking threads exceeded"); 1219 1220 uint active_workers = MAX2(1U, parallel_marking_threads()); 1221 assert(active_workers > 0, "Should have been set"); 1222 1223 // Parallel task terminator is set in "set_concurrency_and_phase()" 1224 set_concurrency_and_phase(active_workers, true /* concurrent */); 1225 1226 CMConcurrentMarkingTask markingTask(this, cmThread()); 1227 _parallel_workers->set_active_workers(active_workers); 1228 _parallel_workers->run_task(&markingTask); 1229 print_stats(); 1230 } 1231 1232 // Helper class to get rid of some boilerplate code. 1233 class G1CMTraceTime : public GCTraceTime { 1234 static bool doit_and_prepend(bool doit) { 1235 if (doit) { 1236 gclog_or_tty->put(' '); 1237 } 1238 return doit; 1239 } 1240 1241 public: 1242 G1CMTraceTime(const char* title, bool doit) 1243 : GCTraceTime(title, doit_and_prepend(doit), false, G1CollectedHeap::heap()->gc_timer_cm(), 1244 G1CollectedHeap::heap()->concurrent_mark()->concurrent_gc_id()) { 1245 } 1246 }; 1247 1248 void ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) { 1249 // world is stopped at this checkpoint 1250 assert(SafepointSynchronize::is_at_safepoint(), 1251 "world should be stopped"); 1252 1253 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1254 1255 // If a full collection has happened, we shouldn't do this. 1256 if (has_aborted()) { 1257 g1h->set_marking_complete(); // So bitmap clearing isn't confused 1258 return; 1259 } 1260 1261 SvcGCMarker sgcm(SvcGCMarker::OTHER); 1262 1263 if (VerifyDuringGC) { 1264 HandleMark hm; // handle scope 1265 g1h->prepare_for_verify(); 1266 Universe::verify(VerifyOption_G1UsePrevMarking, 1267 " VerifyDuringGC:(before)"); 1268 } 1269 g1h->check_bitmaps("Remark Start"); 1270 1271 G1CollectorPolicy* g1p = g1h->g1_policy(); 1272 g1p->record_concurrent_mark_remark_start(); 1273 1274 double start = os::elapsedTime(); 1275 1276 checkpointRootsFinalWork(); 1277 1278 double mark_work_end = os::elapsedTime(); 1279 1280 weakRefsWork(clear_all_soft_refs); 1281 1282 if (has_overflown()) { 1283 // Oops. We overflowed. Restart concurrent marking. 1284 _restart_for_overflow = true; 1285 if (G1TraceMarkStackOverflow) { 1286 gclog_or_tty->print_cr("\nRemark led to restart for overflow."); 1287 } 1288 1289 // Verify the heap w.r.t. the previous marking bitmap. 1290 if (VerifyDuringGC) { 1291 HandleMark hm; // handle scope 1292 g1h->prepare_for_verify(); 1293 Universe::verify(VerifyOption_G1UsePrevMarking, 1294 " VerifyDuringGC:(overflow)"); 1295 } 1296 1297 // Clear the marking state because we will be restarting 1298 // marking due to overflowing the global mark stack. 1299 reset_marking_state(); 1300 } else { 1301 { 1302 G1CMTraceTime trace("GC aggregate-data", G1Log::finer()); 1303 1304 // Aggregate the per-task counting data that we have accumulated 1305 // while marking. 1306 aggregate_count_data(); 1307 } 1308 1309 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 1310 // We're done with marking. 1311 // This is the end of the marking cycle, we're expected all 1312 // threads to have SATB queues with active set to true. 1313 satb_mq_set.set_active_all_threads(false, /* new active value */ 1314 true /* expected_active */); 1315 1316 if (VerifyDuringGC) { 1317 HandleMark hm; // handle scope 1318 g1h->prepare_for_verify(); 1319 Universe::verify(VerifyOption_G1UseNextMarking, 1320 " VerifyDuringGC:(after)"); 1321 } 1322 g1h->check_bitmaps("Remark End"); 1323 assert(!restart_for_overflow(), "sanity"); 1324 // Completely reset the marking state since marking completed 1325 set_non_marking_state(); 1326 } 1327 1328 // Expand the marking stack, if we have to and if we can. 1329 if (_markStack.should_expand()) { 1330 _markStack.expand(); 1331 } 1332 1333 // Statistics 1334 double now = os::elapsedTime(); 1335 _remark_mark_times.add((mark_work_end - start) * 1000.0); 1336 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0); 1337 _remark_times.add((now - start) * 1000.0); 1338 1339 g1p->record_concurrent_mark_remark_end(); 1340 1341 G1CMIsAliveClosure is_alive(g1h); 1342 g1h->gc_tracer_cm()->report_object_count_after_gc(&is_alive); 1343 } 1344 1345 // Base class of the closures that finalize and verify the 1346 // liveness counting data. 1347 class CMCountDataClosureBase: public HeapRegionClosure { 1348 protected: 1349 G1CollectedHeap* _g1h; 1350 ConcurrentMark* _cm; 1351 CardTableModRefBS* _ct_bs; 1352 1353 BitMap* _region_bm; 1354 BitMap* _card_bm; 1355 1356 // Takes a region that's not empty (i.e., it has at least one 1357 // live object in it and sets its corresponding bit on the region 1358 // bitmap to 1. If the region is "starts humongous" it will also set 1359 // to 1 the bits on the region bitmap that correspond to its 1360 // associated "continues humongous" regions. 1361 void set_bit_for_region(HeapRegion* hr) { 1362 assert(!hr->is_continues_humongous(), "should have filtered those out"); 1363 1364 BitMap::idx_t index = (BitMap::idx_t) hr->hrm_index(); 1365 if (!hr->is_starts_humongous()) { 1366 // Normal (non-humongous) case: just set the bit. 1367 _region_bm->par_at_put(index, true); 1368 } else { 1369 // Starts humongous case: calculate how many regions are part of 1370 // this humongous region and then set the bit range. 1371 BitMap::idx_t end_index = (BitMap::idx_t) hr->last_hc_index(); 1372 _region_bm->par_at_put_range(index, end_index, true); 1373 } 1374 } 1375 1376 public: 1377 CMCountDataClosureBase(G1CollectedHeap* g1h, 1378 BitMap* region_bm, BitMap* card_bm): 1379 _g1h(g1h), _cm(g1h->concurrent_mark()), 1380 _ct_bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())), 1381 _region_bm(region_bm), _card_bm(card_bm) { } 1382 }; 1383 1384 // Closure that calculates the # live objects per region. Used 1385 // for verification purposes during the cleanup pause. 1386 class CalcLiveObjectsClosure: public CMCountDataClosureBase { 1387 CMBitMapRO* _bm; 1388 size_t _region_marked_bytes; 1389 1390 public: 1391 CalcLiveObjectsClosure(CMBitMapRO *bm, G1CollectedHeap* g1h, 1392 BitMap* region_bm, BitMap* card_bm) : 1393 CMCountDataClosureBase(g1h, region_bm, card_bm), 1394 _bm(bm), _region_marked_bytes(0) { } 1395 1396 bool doHeapRegion(HeapRegion* hr) { 1397 1398 if (hr->is_continues_humongous()) { 1399 // We will ignore these here and process them when their 1400 // associated "starts humongous" region is processed (see 1401 // set_bit_for_heap_region()). Note that we cannot rely on their 1402 // associated "starts humongous" region to have their bit set to 1403 // 1 since, due to the region chunking in the parallel region 1404 // iteration, a "continues humongous" region might be visited 1405 // before its associated "starts humongous". 1406 return false; 1407 } 1408 1409 HeapWord* ntams = hr->next_top_at_mark_start(); 1410 HeapWord* start = hr->bottom(); 1411 1412 assert(start <= hr->end() && start <= ntams && ntams <= hr->end(), 1413 err_msg("Preconditions not met - " 1414 "start: "PTR_FORMAT", ntams: "PTR_FORMAT", end: "PTR_FORMAT, 1415 p2i(start), p2i(ntams), p2i(hr->end()))); 1416 1417 // Find the first marked object at or after "start". 1418 start = _bm->getNextMarkedWordAddress(start, ntams); 1419 1420 size_t marked_bytes = 0; 1421 1422 while (start < ntams) { 1423 oop obj = oop(start); 1424 int obj_sz = obj->size(); 1425 HeapWord* obj_end = start + obj_sz; 1426 1427 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start); 1428 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(obj_end); 1429 1430 // Note: if we're looking at the last region in heap - obj_end 1431 // could be actually just beyond the end of the heap; end_idx 1432 // will then correspond to a (non-existent) card that is also 1433 // just beyond the heap. 1434 if (_g1h->is_in_g1_reserved(obj_end) && !_ct_bs->is_card_aligned(obj_end)) { 1435 // end of object is not card aligned - increment to cover 1436 // all the cards spanned by the object 1437 end_idx += 1; 1438 } 1439 1440 // Set the bits in the card BM for the cards spanned by this object. 1441 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */); 1442 1443 // Add the size of this object to the number of marked bytes. 1444 marked_bytes += (size_t)obj_sz * HeapWordSize; 1445 1446 // Find the next marked object after this one. 1447 start = _bm->getNextMarkedWordAddress(obj_end, ntams); 1448 } 1449 1450 // Mark the allocated-since-marking portion... 1451 HeapWord* top = hr->top(); 1452 if (ntams < top) { 1453 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams); 1454 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top); 1455 1456 // Note: if we're looking at the last region in heap - top 1457 // could be actually just beyond the end of the heap; end_idx 1458 // will then correspond to a (non-existent) card that is also 1459 // just beyond the heap. 1460 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) { 1461 // end of object is not card aligned - increment to cover 1462 // all the cards spanned by the object 1463 end_idx += 1; 1464 } 1465 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */); 1466 1467 // This definitely means the region has live objects. 1468 set_bit_for_region(hr); 1469 } 1470 1471 // Update the live region bitmap. 1472 if (marked_bytes > 0) { 1473 set_bit_for_region(hr); 1474 } 1475 1476 // Set the marked bytes for the current region so that 1477 // it can be queried by a calling verification routine 1478 _region_marked_bytes = marked_bytes; 1479 1480 return false; 1481 } 1482 1483 size_t region_marked_bytes() const { return _region_marked_bytes; } 1484 }; 1485 1486 // Heap region closure used for verifying the counting data 1487 // that was accumulated concurrently and aggregated during 1488 // the remark pause. This closure is applied to the heap 1489 // regions during the STW cleanup pause. 1490 1491 class VerifyLiveObjectDataHRClosure: public HeapRegionClosure { 1492 G1CollectedHeap* _g1h; 1493 ConcurrentMark* _cm; 1494 CalcLiveObjectsClosure _calc_cl; 1495 BitMap* _region_bm; // Region BM to be verified 1496 BitMap* _card_bm; // Card BM to be verified 1497 bool _verbose; // verbose output? 1498 1499 BitMap* _exp_region_bm; // Expected Region BM values 1500 BitMap* _exp_card_bm; // Expected card BM values 1501 1502 int _failures; 1503 1504 public: 1505 VerifyLiveObjectDataHRClosure(G1CollectedHeap* g1h, 1506 BitMap* region_bm, 1507 BitMap* card_bm, 1508 BitMap* exp_region_bm, 1509 BitMap* exp_card_bm, 1510 bool verbose) : 1511 _g1h(g1h), _cm(g1h->concurrent_mark()), 1512 _calc_cl(_cm->nextMarkBitMap(), g1h, exp_region_bm, exp_card_bm), 1513 _region_bm(region_bm), _card_bm(card_bm), _verbose(verbose), 1514 _exp_region_bm(exp_region_bm), _exp_card_bm(exp_card_bm), 1515 _failures(0) { } 1516 1517 int failures() const { return _failures; } 1518 1519 bool doHeapRegion(HeapRegion* hr) { 1520 if (hr->is_continues_humongous()) { 1521 // We will ignore these here and process them when their 1522 // associated "starts humongous" region is processed (see 1523 // set_bit_for_heap_region()). Note that we cannot rely on their 1524 // associated "starts humongous" region to have their bit set to 1525 // 1 since, due to the region chunking in the parallel region 1526 // iteration, a "continues humongous" region might be visited 1527 // before its associated "starts humongous". 1528 return false; 1529 } 1530 1531 int failures = 0; 1532 1533 // Call the CalcLiveObjectsClosure to walk the marking bitmap for 1534 // this region and set the corresponding bits in the expected region 1535 // and card bitmaps. 1536 bool res = _calc_cl.doHeapRegion(hr); 1537 assert(res == false, "should be continuing"); 1538 1539 MutexLockerEx x((_verbose ? ParGCRareEvent_lock : NULL), 1540 Mutex::_no_safepoint_check_flag); 1541 1542 // Verify the marked bytes for this region. 1543 size_t exp_marked_bytes = _calc_cl.region_marked_bytes(); 1544 size_t act_marked_bytes = hr->next_marked_bytes(); 1545 1546 // We're not OK if expected marked bytes > actual marked bytes. It means 1547 // we have missed accounting some objects during the actual marking. 1548 if (exp_marked_bytes > act_marked_bytes) { 1549 if (_verbose) { 1550 gclog_or_tty->print_cr("Region %u: marked bytes mismatch: " 1551 "expected: " SIZE_FORMAT ", actual: " SIZE_FORMAT, 1552 hr->hrm_index(), exp_marked_bytes, act_marked_bytes); 1553 } 1554 failures += 1; 1555 } 1556 1557 // Verify the bit, for this region, in the actual and expected 1558 // (which was just calculated) region bit maps. 1559 // We're not OK if the bit in the calculated expected region 1560 // bitmap is set and the bit in the actual region bitmap is not. 1561 BitMap::idx_t index = (BitMap::idx_t) hr->hrm_index(); 1562 1563 bool expected = _exp_region_bm->at(index); 1564 bool actual = _region_bm->at(index); 1565 if (expected && !actual) { 1566 if (_verbose) { 1567 gclog_or_tty->print_cr("Region %u: region bitmap mismatch: " 1568 "expected: %s, actual: %s", 1569 hr->hrm_index(), 1570 BOOL_TO_STR(expected), BOOL_TO_STR(actual)); 1571 } 1572 failures += 1; 1573 } 1574 1575 // Verify that the card bit maps for the cards spanned by the current 1576 // region match. We have an error if we have a set bit in the expected 1577 // bit map and the corresponding bit in the actual bitmap is not set. 1578 1579 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(hr->bottom()); 1580 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(hr->top()); 1581 1582 for (BitMap::idx_t i = start_idx; i < end_idx; i+=1) { 1583 expected = _exp_card_bm->at(i); 1584 actual = _card_bm->at(i); 1585 1586 if (expected && !actual) { 1587 if (_verbose) { 1588 gclog_or_tty->print_cr("Region %u: card bitmap mismatch at " SIZE_FORMAT ": " 1589 "expected: %s, actual: %s", 1590 hr->hrm_index(), i, 1591 BOOL_TO_STR(expected), BOOL_TO_STR(actual)); 1592 } 1593 failures += 1; 1594 } 1595 } 1596 1597 if (failures > 0 && _verbose) { 1598 gclog_or_tty->print_cr("Region " HR_FORMAT ", ntams: " PTR_FORMAT ", " 1599 "marked_bytes: calc/actual " SIZE_FORMAT "/" SIZE_FORMAT, 1600 HR_FORMAT_PARAMS(hr), p2i(hr->next_top_at_mark_start()), 1601 _calc_cl.region_marked_bytes(), hr->next_marked_bytes()); 1602 } 1603 1604 _failures += failures; 1605 1606 // We could stop iteration over the heap when we 1607 // find the first violating region by returning true. 1608 return false; 1609 } 1610 }; 1611 1612 class G1ParVerifyFinalCountTask: public AbstractGangTask { 1613 protected: 1614 G1CollectedHeap* _g1h; 1615 ConcurrentMark* _cm; 1616 BitMap* _actual_region_bm; 1617 BitMap* _actual_card_bm; 1618 1619 uint _n_workers; 1620 1621 BitMap* _expected_region_bm; 1622 BitMap* _expected_card_bm; 1623 1624 int _failures; 1625 bool _verbose; 1626 1627 HeapRegionClaimer _hrclaimer; 1628 1629 public: 1630 G1ParVerifyFinalCountTask(G1CollectedHeap* g1h, 1631 BitMap* region_bm, BitMap* card_bm, 1632 BitMap* expected_region_bm, BitMap* expected_card_bm) 1633 : AbstractGangTask("G1 verify final counting"), 1634 _g1h(g1h), _cm(_g1h->concurrent_mark()), 1635 _actual_region_bm(region_bm), _actual_card_bm(card_bm), 1636 _expected_region_bm(expected_region_bm), _expected_card_bm(expected_card_bm), 1637 _failures(0), _verbose(false), 1638 _n_workers(_g1h->workers()->active_workers()), _hrclaimer(_n_workers) { 1639 assert(VerifyDuringGC, "don't call this otherwise"); 1640 assert(_expected_card_bm->size() == _actual_card_bm->size(), "sanity"); 1641 assert(_expected_region_bm->size() == _actual_region_bm->size(), "sanity"); 1642 1643 _verbose = _cm->verbose_medium(); 1644 } 1645 1646 void work(uint worker_id) { 1647 assert(worker_id < _n_workers, "invariant"); 1648 1649 VerifyLiveObjectDataHRClosure verify_cl(_g1h, 1650 _actual_region_bm, _actual_card_bm, 1651 _expected_region_bm, 1652 _expected_card_bm, 1653 _verbose); 1654 1655 _g1h->heap_region_par_iterate(&verify_cl, worker_id, &_hrclaimer); 1656 1657 Atomic::add(verify_cl.failures(), &_failures); 1658 } 1659 1660 int failures() const { return _failures; } 1661 }; 1662 1663 // Closure that finalizes the liveness counting data. 1664 // Used during the cleanup pause. 1665 // Sets the bits corresponding to the interval [NTAMS, top] 1666 // (which contains the implicitly live objects) in the 1667 // card liveness bitmap. Also sets the bit for each region, 1668 // containing live data, in the region liveness bitmap. 1669 1670 class FinalCountDataUpdateClosure: public CMCountDataClosureBase { 1671 public: 1672 FinalCountDataUpdateClosure(G1CollectedHeap* g1h, 1673 BitMap* region_bm, 1674 BitMap* card_bm) : 1675 CMCountDataClosureBase(g1h, region_bm, card_bm) { } 1676 1677 bool doHeapRegion(HeapRegion* hr) { 1678 1679 if (hr->is_continues_humongous()) { 1680 // We will ignore these here and process them when their 1681 // associated "starts humongous" region is processed (see 1682 // set_bit_for_heap_region()). Note that we cannot rely on their 1683 // associated "starts humongous" region to have their bit set to 1684 // 1 since, due to the region chunking in the parallel region 1685 // iteration, a "continues humongous" region might be visited 1686 // before its associated "starts humongous". 1687 return false; 1688 } 1689 1690 HeapWord* ntams = hr->next_top_at_mark_start(); 1691 HeapWord* top = hr->top(); 1692 1693 assert(hr->bottom() <= ntams && ntams <= hr->end(), "Preconditions."); 1694 1695 // Mark the allocated-since-marking portion... 1696 if (ntams < top) { 1697 // This definitely means the region has live objects. 1698 set_bit_for_region(hr); 1699 1700 // Now set the bits in the card bitmap for [ntams, top) 1701 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams); 1702 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top); 1703 1704 // Note: if we're looking at the last region in heap - top 1705 // could be actually just beyond the end of the heap; end_idx 1706 // will then correspond to a (non-existent) card that is also 1707 // just beyond the heap. 1708 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) { 1709 // end of object is not card aligned - increment to cover 1710 // all the cards spanned by the object 1711 end_idx += 1; 1712 } 1713 1714 assert(end_idx <= _card_bm->size(), 1715 err_msg("oob: end_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT, 1716 end_idx, _card_bm->size())); 1717 assert(start_idx < _card_bm->size(), 1718 err_msg("oob: start_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT, 1719 start_idx, _card_bm->size())); 1720 1721 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */); 1722 } 1723 1724 // Set the bit for the region if it contains live data 1725 if (hr->next_marked_bytes() > 0) { 1726 set_bit_for_region(hr); 1727 } 1728 1729 return false; 1730 } 1731 }; 1732 1733 class G1ParFinalCountTask: public AbstractGangTask { 1734 protected: 1735 G1CollectedHeap* _g1h; 1736 ConcurrentMark* _cm; 1737 BitMap* _actual_region_bm; 1738 BitMap* _actual_card_bm; 1739 1740 uint _n_workers; 1741 HeapRegionClaimer _hrclaimer; 1742 1743 public: 1744 G1ParFinalCountTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm) 1745 : AbstractGangTask("G1 final counting"), 1746 _g1h(g1h), _cm(_g1h->concurrent_mark()), 1747 _actual_region_bm(region_bm), _actual_card_bm(card_bm), 1748 _n_workers(_g1h->workers()->active_workers()), _hrclaimer(_n_workers) { 1749 } 1750 1751 void work(uint worker_id) { 1752 assert(worker_id < _n_workers, "invariant"); 1753 1754 FinalCountDataUpdateClosure final_update_cl(_g1h, 1755 _actual_region_bm, 1756 _actual_card_bm); 1757 1758 _g1h->heap_region_par_iterate(&final_update_cl, worker_id, &_hrclaimer); 1759 } 1760 }; 1761 1762 class G1ParNoteEndTask; 1763 1764 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure { 1765 G1CollectedHeap* _g1; 1766 size_t _max_live_bytes; 1767 uint _regions_claimed; 1768 size_t _freed_bytes; 1769 FreeRegionList* _local_cleanup_list; 1770 HeapRegionSetCount _old_regions_removed; 1771 HeapRegionSetCount _humongous_regions_removed; 1772 HRRSCleanupTask* _hrrs_cleanup_task; 1773 double _claimed_region_time; 1774 double _max_region_time; 1775 1776 public: 1777 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1, 1778 FreeRegionList* local_cleanup_list, 1779 HRRSCleanupTask* hrrs_cleanup_task) : 1780 _g1(g1), 1781 _max_live_bytes(0), _regions_claimed(0), 1782 _freed_bytes(0), 1783 _claimed_region_time(0.0), _max_region_time(0.0), 1784 _local_cleanup_list(local_cleanup_list), 1785 _old_regions_removed(), 1786 _humongous_regions_removed(), 1787 _hrrs_cleanup_task(hrrs_cleanup_task) { } 1788 1789 size_t freed_bytes() { return _freed_bytes; } 1790 const HeapRegionSetCount& old_regions_removed() { return _old_regions_removed; } 1791 const HeapRegionSetCount& humongous_regions_removed() { return _humongous_regions_removed; } 1792 1793 bool doHeapRegion(HeapRegion *hr) { 1794 if (hr->is_continues_humongous()) { 1795 return false; 1796 } 1797 // We use a claim value of zero here because all regions 1798 // were claimed with value 1 in the FinalCount task. 1799 _g1->reset_gc_time_stamps(hr); 1800 double start = os::elapsedTime(); 1801 _regions_claimed++; 1802 hr->note_end_of_marking(); 1803 _max_live_bytes += hr->max_live_bytes(); 1804 1805 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) { 1806 _freed_bytes += hr->used(); 1807 hr->set_containing_set(NULL); 1808 if (hr->is_humongous()) { 1809 assert(hr->is_starts_humongous(), "we should only see starts humongous"); 1810 _humongous_regions_removed.increment(1u, hr->capacity()); 1811 _g1->free_humongous_region(hr, _local_cleanup_list, true); 1812 } else { 1813 _old_regions_removed.increment(1u, hr->capacity()); 1814 _g1->free_region(hr, _local_cleanup_list, true); 1815 } 1816 } else { 1817 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task); 1818 } 1819 1820 double region_time = (os::elapsedTime() - start); 1821 _claimed_region_time += region_time; 1822 if (region_time > _max_region_time) { 1823 _max_region_time = region_time; 1824 } 1825 return false; 1826 } 1827 1828 size_t max_live_bytes() { return _max_live_bytes; } 1829 uint regions_claimed() { return _regions_claimed; } 1830 double claimed_region_time_sec() { return _claimed_region_time; } 1831 double max_region_time_sec() { return _max_region_time; } 1832 }; 1833 1834 class G1ParNoteEndTask: public AbstractGangTask { 1835 friend class G1NoteEndOfConcMarkClosure; 1836 1837 protected: 1838 G1CollectedHeap* _g1h; 1839 size_t _max_live_bytes; 1840 size_t _freed_bytes; 1841 FreeRegionList* _cleanup_list; 1842 HeapRegionClaimer _hrclaimer; 1843 1844 public: 1845 G1ParNoteEndTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) : 1846 AbstractGangTask("G1 note end"), _g1h(g1h), _max_live_bytes(0), _freed_bytes(0), _cleanup_list(cleanup_list), _hrclaimer(n_workers) { 1847 } 1848 1849 void work(uint worker_id) { 1850 FreeRegionList local_cleanup_list("Local Cleanup List"); 1851 HRRSCleanupTask hrrs_cleanup_task; 1852 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, &local_cleanup_list, 1853 &hrrs_cleanup_task); 1854 _g1h->heap_region_par_iterate(&g1_note_end, worker_id, &_hrclaimer); 1855 assert(g1_note_end.complete(), "Shouldn't have yielded!"); 1856 1857 // Now update the lists 1858 _g1h->remove_from_old_sets(g1_note_end.old_regions_removed(), g1_note_end.humongous_regions_removed()); 1859 { 1860 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 1861 _g1h->decrement_summary_bytes(g1_note_end.freed_bytes()); 1862 _max_live_bytes += g1_note_end.max_live_bytes(); 1863 _freed_bytes += g1_note_end.freed_bytes(); 1864 1865 // If we iterate over the global cleanup list at the end of 1866 // cleanup to do this printing we will not guarantee to only 1867 // generate output for the newly-reclaimed regions (the list 1868 // might not be empty at the beginning of cleanup; we might 1869 // still be working on its previous contents). So we do the 1870 // printing here, before we append the new regions to the global 1871 // cleanup list. 1872 1873 G1HRPrinter* hr_printer = _g1h->hr_printer(); 1874 if (hr_printer->is_active()) { 1875 FreeRegionListIterator iter(&local_cleanup_list); 1876 while (iter.more_available()) { 1877 HeapRegion* hr = iter.get_next(); 1878 hr_printer->cleanup(hr); 1879 } 1880 } 1881 1882 _cleanup_list->add_ordered(&local_cleanup_list); 1883 assert(local_cleanup_list.is_empty(), "post-condition"); 1884 1885 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task); 1886 } 1887 } 1888 size_t max_live_bytes() { return _max_live_bytes; } 1889 size_t freed_bytes() { return _freed_bytes; } 1890 }; 1891 1892 class G1ParScrubRemSetTask: public AbstractGangTask { 1893 protected: 1894 G1RemSet* _g1rs; 1895 BitMap* _region_bm; 1896 BitMap* _card_bm; 1897 HeapRegionClaimer _hrclaimer; 1898 1899 public: 1900 G1ParScrubRemSetTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm, uint n_workers) : 1901 AbstractGangTask("G1 ScrubRS"), _g1rs(g1h->g1_rem_set()), _region_bm(region_bm), _card_bm(card_bm), _hrclaimer(n_workers) { 1902 } 1903 1904 void work(uint worker_id) { 1905 _g1rs->scrub(_region_bm, _card_bm, worker_id, &_hrclaimer); 1906 } 1907 1908 }; 1909 1910 void ConcurrentMark::cleanup() { 1911 // world is stopped at this checkpoint 1912 assert(SafepointSynchronize::is_at_safepoint(), 1913 "world should be stopped"); 1914 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1915 1916 // If a full collection has happened, we shouldn't do this. 1917 if (has_aborted()) { 1918 g1h->set_marking_complete(); // So bitmap clearing isn't confused 1919 return; 1920 } 1921 1922 g1h->verify_region_sets_optional(); 1923 1924 if (VerifyDuringGC) { 1925 HandleMark hm; // handle scope 1926 g1h->prepare_for_verify(); 1927 Universe::verify(VerifyOption_G1UsePrevMarking, 1928 " VerifyDuringGC:(before)"); 1929 } 1930 g1h->check_bitmaps("Cleanup Start"); 1931 1932 G1CollectorPolicy* g1p = g1h->g1_policy(); 1933 g1p->record_concurrent_mark_cleanup_start(); 1934 1935 double start = os::elapsedTime(); 1936 1937 HeapRegionRemSet::reset_for_cleanup_tasks(); 1938 1939 // Do counting once more with the world stopped for good measure. 1940 G1ParFinalCountTask g1_par_count_task(g1h, &_region_bm, &_card_bm); 1941 1942 g1h->workers()->run_task(&g1_par_count_task); 1943 1944 if (VerifyDuringGC) { 1945 // Verify that the counting data accumulated during marking matches 1946 // that calculated by walking the marking bitmap. 1947 1948 // Bitmaps to hold expected values 1949 BitMap expected_region_bm(_region_bm.size(), true); 1950 BitMap expected_card_bm(_card_bm.size(), true); 1951 1952 G1ParVerifyFinalCountTask g1_par_verify_task(g1h, 1953 &_region_bm, 1954 &_card_bm, 1955 &expected_region_bm, 1956 &expected_card_bm); 1957 1958 g1h->workers()->run_task(&g1_par_verify_task); 1959 1960 guarantee(g1_par_verify_task.failures() == 0, "Unexpected accounting failures"); 1961 } 1962 1963 size_t start_used_bytes = g1h->used(); 1964 g1h->set_marking_complete(); 1965 1966 double count_end = os::elapsedTime(); 1967 double this_final_counting_time = (count_end - start); 1968 _total_counting_time += this_final_counting_time; 1969 1970 if (G1PrintRegionLivenessInfo) { 1971 G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Marking"); 1972 _g1h->heap_region_iterate(&cl); 1973 } 1974 1975 // Install newly created mark bitMap as "prev". 1976 swapMarkBitMaps(); 1977 1978 g1h->reset_gc_time_stamp(); 1979 1980 uint n_workers = _g1h->workers()->active_workers(); 1981 1982 // Note end of marking in all heap regions. 1983 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list, n_workers); 1984 g1h->workers()->run_task(&g1_par_note_end_task); 1985 g1h->check_gc_time_stamps(); 1986 1987 if (!cleanup_list_is_empty()) { 1988 // The cleanup list is not empty, so we'll have to process it 1989 // concurrently. Notify anyone else that might be wanting free 1990 // regions that there will be more free regions coming soon. 1991 g1h->set_free_regions_coming(); 1992 } 1993 1994 // call below, since it affects the metric by which we sort the heap 1995 // regions. 1996 if (G1ScrubRemSets) { 1997 double rs_scrub_start = os::elapsedTime(); 1998 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1h, &_region_bm, &_card_bm, n_workers); 1999 g1h->workers()->run_task(&g1_par_scrub_rs_task); 2000 2001 double rs_scrub_end = os::elapsedTime(); 2002 double this_rs_scrub_time = (rs_scrub_end - rs_scrub_start); 2003 _total_rs_scrub_time += this_rs_scrub_time; 2004 } 2005 2006 // this will also free any regions totally full of garbage objects, 2007 // and sort the regions. 2008 g1h->g1_policy()->record_concurrent_mark_cleanup_end(); 2009 2010 // Statistics. 2011 double end = os::elapsedTime(); 2012 _cleanup_times.add((end - start) * 1000.0); 2013 2014 if (G1Log::fine()) { 2015 g1h->g1_policy()->print_heap_transition(start_used_bytes); 2016 } 2017 2018 // Clean up will have freed any regions completely full of garbage. 2019 // Update the soft reference policy with the new heap occupancy. 2020 Universe::update_heap_info_at_gc(); 2021 2022 if (VerifyDuringGC) { 2023 HandleMark hm; // handle scope 2024 g1h->prepare_for_verify(); 2025 Universe::verify(VerifyOption_G1UsePrevMarking, 2026 " VerifyDuringGC:(after)"); 2027 } 2028 2029 g1h->check_bitmaps("Cleanup End"); 2030 2031 g1h->verify_region_sets_optional(); 2032 2033 // We need to make this be a "collection" so any collection pause that 2034 // races with it goes around and waits for completeCleanup to finish. 2035 g1h->increment_total_collections(); 2036 2037 // Clean out dead classes and update Metaspace sizes. 2038 if (ClassUnloadingWithConcurrentMark) { 2039 ClassLoaderDataGraph::purge(); 2040 } 2041 MetaspaceGC::compute_new_size(); 2042 2043 // We reclaimed old regions so we should calculate the sizes to make 2044 // sure we update the old gen/space data. 2045 g1h->g1mm()->update_sizes(); 2046 g1h->allocation_context_stats().update_after_mark(); 2047 2048 g1h->trace_heap_after_concurrent_cycle(); 2049 } 2050 2051 void ConcurrentMark::completeCleanup() { 2052 if (has_aborted()) return; 2053 2054 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2055 2056 _cleanup_list.verify_optional(); 2057 FreeRegionList tmp_free_list("Tmp Free List"); 2058 2059 if (G1ConcRegionFreeingVerbose) { 2060 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : " 2061 "cleanup list has %u entries", 2062 _cleanup_list.length()); 2063 } 2064 2065 // No one else should be accessing the _cleanup_list at this point, 2066 // so it is not necessary to take any locks 2067 while (!_cleanup_list.is_empty()) { 2068 HeapRegion* hr = _cleanup_list.remove_region(true /* from_head */); 2069 assert(hr != NULL, "Got NULL from a non-empty list"); 2070 hr->par_clear(); 2071 tmp_free_list.add_ordered(hr); 2072 2073 // Instead of adding one region at a time to the secondary_free_list, 2074 // we accumulate them in the local list and move them a few at a 2075 // time. This also cuts down on the number of notify_all() calls 2076 // we do during this process. We'll also append the local list when 2077 // _cleanup_list is empty (which means we just removed the last 2078 // region from the _cleanup_list). 2079 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) || 2080 _cleanup_list.is_empty()) { 2081 if (G1ConcRegionFreeingVerbose) { 2082 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : " 2083 "appending %u entries to the secondary_free_list, " 2084 "cleanup list still has %u entries", 2085 tmp_free_list.length(), 2086 _cleanup_list.length()); 2087 } 2088 2089 { 2090 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 2091 g1h->secondary_free_list_add(&tmp_free_list); 2092 SecondaryFreeList_lock->notify_all(); 2093 } 2094 #ifndef PRODUCT 2095 if (G1StressConcRegionFreeing) { 2096 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) { 2097 os::sleep(Thread::current(), (jlong) 1, false); 2098 } 2099 } 2100 #endif 2101 } 2102 } 2103 assert(tmp_free_list.is_empty(), "post-condition"); 2104 } 2105 2106 // Supporting Object and Oop closures for reference discovery 2107 // and processing in during marking 2108 2109 bool G1CMIsAliveClosure::do_object_b(oop obj) { 2110 HeapWord* addr = (HeapWord*)obj; 2111 return addr != NULL && 2112 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj)); 2113 } 2114 2115 // 'Keep Alive' oop closure used by both serial parallel reference processing. 2116 // Uses the CMTask associated with a worker thread (for serial reference 2117 // processing the CMTask for worker 0 is used) to preserve (mark) and 2118 // trace referent objects. 2119 // 2120 // Using the CMTask and embedded local queues avoids having the worker 2121 // threads operating on the global mark stack. This reduces the risk 2122 // of overflowing the stack - which we would rather avoid at this late 2123 // state. Also using the tasks' local queues removes the potential 2124 // of the workers interfering with each other that could occur if 2125 // operating on the global stack. 2126 2127 class G1CMKeepAliveAndDrainClosure: public OopClosure { 2128 ConcurrentMark* _cm; 2129 CMTask* _task; 2130 int _ref_counter_limit; 2131 int _ref_counter; 2132 bool _is_serial; 2133 public: 2134 G1CMKeepAliveAndDrainClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) : 2135 _cm(cm), _task(task), _is_serial(is_serial), 2136 _ref_counter_limit(G1RefProcDrainInterval) { 2137 assert(_ref_counter_limit > 0, "sanity"); 2138 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code"); 2139 _ref_counter = _ref_counter_limit; 2140 } 2141 2142 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 2143 virtual void do_oop( oop* p) { do_oop_work(p); } 2144 2145 template <class T> void do_oop_work(T* p) { 2146 if (!_cm->has_overflown()) { 2147 oop obj = oopDesc::load_decode_heap_oop(p); 2148 if (_cm->verbose_high()) { 2149 gclog_or_tty->print_cr("\t[%u] we're looking at location " 2150 "*"PTR_FORMAT" = "PTR_FORMAT, 2151 _task->worker_id(), p2i(p), p2i((void*) obj)); 2152 } 2153 2154 _task->deal_with_reference(obj); 2155 _ref_counter--; 2156 2157 if (_ref_counter == 0) { 2158 // We have dealt with _ref_counter_limit references, pushing them 2159 // and objects reachable from them on to the local stack (and 2160 // possibly the global stack). Call CMTask::do_marking_step() to 2161 // process these entries. 2162 // 2163 // We call CMTask::do_marking_step() in a loop, which we'll exit if 2164 // there's nothing more to do (i.e. we're done with the entries that 2165 // were pushed as a result of the CMTask::deal_with_reference() calls 2166 // above) or we overflow. 2167 // 2168 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted() 2169 // flag while there may still be some work to do. (See the comment at 2170 // the beginning of CMTask::do_marking_step() for those conditions - 2171 // one of which is reaching the specified time target.) It is only 2172 // when CMTask::do_marking_step() returns without setting the 2173 // has_aborted() flag that the marking step has completed. 2174 do { 2175 double mark_step_duration_ms = G1ConcMarkStepDurationMillis; 2176 _task->do_marking_step(mark_step_duration_ms, 2177 false /* do_termination */, 2178 _is_serial); 2179 } while (_task->has_aborted() && !_cm->has_overflown()); 2180 _ref_counter = _ref_counter_limit; 2181 } 2182 } else { 2183 if (_cm->verbose_high()) { 2184 gclog_or_tty->print_cr("\t[%u] CM Overflow", _task->worker_id()); 2185 } 2186 } 2187 } 2188 }; 2189 2190 // 'Drain' oop closure used by both serial and parallel reference processing. 2191 // Uses the CMTask associated with a given worker thread (for serial 2192 // reference processing the CMtask for worker 0 is used). Calls the 2193 // do_marking_step routine, with an unbelievably large timeout value, 2194 // to drain the marking data structures of the remaining entries 2195 // added by the 'keep alive' oop closure above. 2196 2197 class G1CMDrainMarkingStackClosure: public VoidClosure { 2198 ConcurrentMark* _cm; 2199 CMTask* _task; 2200 bool _is_serial; 2201 public: 2202 G1CMDrainMarkingStackClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) : 2203 _cm(cm), _task(task), _is_serial(is_serial) { 2204 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code"); 2205 } 2206 2207 void do_void() { 2208 do { 2209 if (_cm->verbose_high()) { 2210 gclog_or_tty->print_cr("\t[%u] Drain: Calling do_marking_step - serial: %s", 2211 _task->worker_id(), BOOL_TO_STR(_is_serial)); 2212 } 2213 2214 // We call CMTask::do_marking_step() to completely drain the local 2215 // and global marking stacks of entries pushed by the 'keep alive' 2216 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above). 2217 // 2218 // CMTask::do_marking_step() is called in a loop, which we'll exit 2219 // if there's nothing more to do (i.e. we've completely drained the 2220 // entries that were pushed as a a result of applying the 'keep alive' 2221 // closure to the entries on the discovered ref lists) or we overflow 2222 // the global marking stack. 2223 // 2224 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted() 2225 // flag while there may still be some work to do. (See the comment at 2226 // the beginning of CMTask::do_marking_step() for those conditions - 2227 // one of which is reaching the specified time target.) It is only 2228 // when CMTask::do_marking_step() returns without setting the 2229 // has_aborted() flag that the marking step has completed. 2230 2231 _task->do_marking_step(1000000000.0 /* something very large */, 2232 true /* do_termination */, 2233 _is_serial); 2234 } while (_task->has_aborted() && !_cm->has_overflown()); 2235 } 2236 }; 2237 2238 // Implementation of AbstractRefProcTaskExecutor for parallel 2239 // reference processing at the end of G1 concurrent marking 2240 2241 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 2242 private: 2243 G1CollectedHeap* _g1h; 2244 ConcurrentMark* _cm; 2245 WorkGang* _workers; 2246 uint _active_workers; 2247 2248 public: 2249 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h, 2250 ConcurrentMark* cm, 2251 WorkGang* workers, 2252 uint n_workers) : 2253 _g1h(g1h), _cm(cm), 2254 _workers(workers), _active_workers(n_workers) { } 2255 2256 // Executes the given task using concurrent marking worker threads. 2257 virtual void execute(ProcessTask& task); 2258 virtual void execute(EnqueueTask& task); 2259 }; 2260 2261 class G1CMRefProcTaskProxy: public AbstractGangTask { 2262 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 2263 ProcessTask& _proc_task; 2264 G1CollectedHeap* _g1h; 2265 ConcurrentMark* _cm; 2266 2267 public: 2268 G1CMRefProcTaskProxy(ProcessTask& proc_task, 2269 G1CollectedHeap* g1h, 2270 ConcurrentMark* cm) : 2271 AbstractGangTask("Process reference objects in parallel"), 2272 _proc_task(proc_task), _g1h(g1h), _cm(cm) { 2273 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 2274 assert(rp->processing_is_mt(), "shouldn't be here otherwise"); 2275 } 2276 2277 virtual void work(uint worker_id) { 2278 ResourceMark rm; 2279 HandleMark hm; 2280 CMTask* task = _cm->task(worker_id); 2281 G1CMIsAliveClosure g1_is_alive(_g1h); 2282 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */); 2283 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */); 2284 2285 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain); 2286 } 2287 }; 2288 2289 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) { 2290 assert(_workers != NULL, "Need parallel worker threads."); 2291 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT"); 2292 2293 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm); 2294 2295 // We need to reset the concurrency level before each 2296 // proxy task execution, so that the termination protocol 2297 // and overflow handling in CMTask::do_marking_step() knows 2298 // how many workers to wait for. 2299 _cm->set_concurrency(_active_workers); 2300 _workers->run_task(&proc_task_proxy); 2301 } 2302 2303 class G1CMRefEnqueueTaskProxy: public AbstractGangTask { 2304 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 2305 EnqueueTask& _enq_task; 2306 2307 public: 2308 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) : 2309 AbstractGangTask("Enqueue reference objects in parallel"), 2310 _enq_task(enq_task) { } 2311 2312 virtual void work(uint worker_id) { 2313 _enq_task.work(worker_id); 2314 } 2315 }; 2316 2317 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 2318 assert(_workers != NULL, "Need parallel worker threads."); 2319 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT"); 2320 2321 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task); 2322 2323 // Not strictly necessary but... 2324 // 2325 // We need to reset the concurrency level before each 2326 // proxy task execution, so that the termination protocol 2327 // and overflow handling in CMTask::do_marking_step() knows 2328 // how many workers to wait for. 2329 _cm->set_concurrency(_active_workers); 2330 _workers->run_task(&enq_task_proxy); 2331 } 2332 2333 void ConcurrentMark::weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes) { 2334 G1CollectedHeap::heap()->parallel_cleaning(is_alive, true, true, purged_classes); 2335 } 2336 2337 void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) { 2338 if (has_overflown()) { 2339 // Skip processing the discovered references if we have 2340 // overflown the global marking stack. Reference objects 2341 // only get discovered once so it is OK to not 2342 // de-populate the discovered reference lists. We could have, 2343 // but the only benefit would be that, when marking restarts, 2344 // less reference objects are discovered. 2345 return; 2346 } 2347 2348 ResourceMark rm; 2349 HandleMark hm; 2350 2351 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2352 2353 // Is alive closure. 2354 G1CMIsAliveClosure g1_is_alive(g1h); 2355 2356 // Inner scope to exclude the cleaning of the string and symbol 2357 // tables from the displayed time. 2358 { 2359 G1CMTraceTime t("GC ref-proc", G1Log::finer()); 2360 2361 ReferenceProcessor* rp = g1h->ref_processor_cm(); 2362 2363 // See the comment in G1CollectedHeap::ref_processing_init() 2364 // about how reference processing currently works in G1. 2365 2366 // Set the soft reference policy 2367 rp->setup_policy(clear_all_soft_refs); 2368 assert(_markStack.isEmpty(), "mark stack should be empty"); 2369 2370 // Instances of the 'Keep Alive' and 'Complete GC' closures used 2371 // in serial reference processing. Note these closures are also 2372 // used for serially processing (by the the current thread) the 2373 // JNI references during parallel reference processing. 2374 // 2375 // These closures do not need to synchronize with the worker 2376 // threads involved in parallel reference processing as these 2377 // instances are executed serially by the current thread (e.g. 2378 // reference processing is not multi-threaded and is thus 2379 // performed by the current thread instead of a gang worker). 2380 // 2381 // The gang tasks involved in parallel reference processing create 2382 // their own instances of these closures, which do their own 2383 // synchronization among themselves. 2384 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */); 2385 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */); 2386 2387 // We need at least one active thread. If reference processing 2388 // is not multi-threaded we use the current (VMThread) thread, 2389 // otherwise we use the work gang from the G1CollectedHeap and 2390 // we utilize all the worker threads we can. 2391 bool processing_is_mt = rp->processing_is_mt(); 2392 uint active_workers = (processing_is_mt ? g1h->workers()->active_workers() : 1U); 2393 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U); 2394 2395 // Parallel processing task executor. 2396 G1CMRefProcTaskExecutor par_task_executor(g1h, this, 2397 g1h->workers(), active_workers); 2398 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL); 2399 2400 // Set the concurrency level. The phase was already set prior to 2401 // executing the remark task. 2402 set_concurrency(active_workers); 2403 2404 // Set the degree of MT processing here. If the discovery was done MT, 2405 // the number of threads involved during discovery could differ from 2406 // the number of active workers. This is OK as long as the discovered 2407 // Reference lists are balanced (see balance_all_queues() and balance_queues()). 2408 rp->set_active_mt_degree(active_workers); 2409 2410 // Process the weak references. 2411 const ReferenceProcessorStats& stats = 2412 rp->process_discovered_references(&g1_is_alive, 2413 &g1_keep_alive, 2414 &g1_drain_mark_stack, 2415 executor, 2416 g1h->gc_timer_cm(), 2417 concurrent_gc_id()); 2418 g1h->gc_tracer_cm()->report_gc_reference_stats(stats); 2419 2420 // The do_oop work routines of the keep_alive and drain_marking_stack 2421 // oop closures will set the has_overflown flag if we overflow the 2422 // global marking stack. 2423 2424 assert(_markStack.overflow() || _markStack.isEmpty(), 2425 "mark stack should be empty (unless it overflowed)"); 2426 2427 if (_markStack.overflow()) { 2428 // This should have been done already when we tried to push an 2429 // entry on to the global mark stack. But let's do it again. 2430 set_has_overflown(); 2431 } 2432 2433 assert(rp->num_q() == active_workers, "why not"); 2434 2435 rp->enqueue_discovered_references(executor); 2436 2437 rp->verify_no_references_recorded(); 2438 assert(!rp->discovery_enabled(), "Post condition"); 2439 } 2440 2441 if (has_overflown()) { 2442 // We can not trust g1_is_alive if the marking stack overflowed 2443 return; 2444 } 2445 2446 assert(_markStack.isEmpty(), "Marking should have completed"); 2447 2448 // Unload Klasses, String, Symbols, Code Cache, etc. 2449 { 2450 G1CMTraceTime trace("Unloading", G1Log::finer()); 2451 2452 if (ClassUnloadingWithConcurrentMark) { 2453 bool purged_classes; 2454 2455 { 2456 G1CMTraceTime trace("System Dictionary Unloading", G1Log::finest()); 2457 purged_classes = SystemDictionary::do_unloading(&g1_is_alive, false /* Defer klass cleaning */); 2458 } 2459 2460 { 2461 G1CMTraceTime trace("Parallel Unloading", G1Log::finest()); 2462 weakRefsWorkParallelPart(&g1_is_alive, purged_classes); 2463 } 2464 } 2465 2466 if (G1StringDedup::is_enabled()) { 2467 G1CMTraceTime trace("String Deduplication Unlink", G1Log::finest()); 2468 G1StringDedup::unlink(&g1_is_alive); 2469 } 2470 } 2471 } 2472 2473 void ConcurrentMark::swapMarkBitMaps() { 2474 CMBitMapRO* temp = _prevMarkBitMap; 2475 _prevMarkBitMap = (CMBitMapRO*)_nextMarkBitMap; 2476 _nextMarkBitMap = (CMBitMap*) temp; 2477 } 2478 2479 // Closure for marking entries in SATB buffers. 2480 class CMSATBBufferClosure : public SATBBufferClosure { 2481 private: 2482 CMTask* _task; 2483 G1CollectedHeap* _g1h; 2484 2485 // This is very similar to CMTask::deal_with_reference, but with 2486 // more relaxed requirements for the argument, so this must be more 2487 // circumspect about treating the argument as an object. 2488 void do_entry(void* entry) const { 2489 _task->increment_refs_reached(); 2490 HeapRegion* hr = _g1h->heap_region_containing_raw(entry); 2491 if (entry < hr->next_top_at_mark_start()) { 2492 // Until we get here, we don't know whether entry refers to a valid 2493 // object; it could instead have been a stale reference. 2494 oop obj = static_cast<oop>(entry); 2495 assert(obj->is_oop(true /* ignore mark word */), 2496 err_msg("Invalid oop in SATB buffer: " PTR_FORMAT, p2i(obj))); 2497 _task->make_reference_grey(obj, hr); 2498 } 2499 } 2500 2501 public: 2502 CMSATBBufferClosure(CMTask* task, G1CollectedHeap* g1h) 2503 : _task(task), _g1h(g1h) { } 2504 2505 virtual void do_buffer(void** buffer, size_t size) { 2506 for (size_t i = 0; i < size; ++i) { 2507 do_entry(buffer[i]); 2508 } 2509 } 2510 }; 2511 2512 class G1RemarkThreadsClosure : public ThreadClosure { 2513 CMSATBBufferClosure _cm_satb_cl; 2514 G1CMOopClosure _cm_cl; 2515 MarkingCodeBlobClosure _code_cl; 2516 int _thread_parity; 2517 2518 public: 2519 G1RemarkThreadsClosure(G1CollectedHeap* g1h, CMTask* task) : 2520 _cm_satb_cl(task, g1h), 2521 _cm_cl(g1h, g1h->concurrent_mark(), task), 2522 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations), 2523 _thread_parity(Threads::thread_claim_parity()) {} 2524 2525 void do_thread(Thread* thread) { 2526 if (thread->is_Java_thread()) { 2527 if (thread->claim_oops_do(true, _thread_parity)) { 2528 JavaThread* jt = (JavaThread*)thread; 2529 2530 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking 2531 // however the liveness of oops reachable from nmethods have very complex lifecycles: 2532 // * Alive if on the stack of an executing method 2533 // * Weakly reachable otherwise 2534 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be 2535 // live by the SATB invariant but other oops recorded in nmethods may behave differently. 2536 jt->nmethods_do(&_code_cl); 2537 2538 jt->satb_mark_queue().apply_closure_and_empty(&_cm_satb_cl); 2539 } 2540 } else if (thread->is_VM_thread()) { 2541 if (thread->claim_oops_do(true, _thread_parity)) { 2542 JavaThread::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(&_cm_satb_cl); 2543 } 2544 } 2545 } 2546 }; 2547 2548 class CMRemarkTask: public AbstractGangTask { 2549 private: 2550 ConcurrentMark* _cm; 2551 public: 2552 void work(uint worker_id) { 2553 // Since all available tasks are actually started, we should 2554 // only proceed if we're supposed to be active. 2555 if (worker_id < _cm->active_tasks()) { 2556 CMTask* task = _cm->task(worker_id); 2557 task->record_start_time(); 2558 { 2559 ResourceMark rm; 2560 HandleMark hm; 2561 2562 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task); 2563 Threads::threads_do(&threads_f); 2564 } 2565 2566 do { 2567 task->do_marking_step(1000000000.0 /* something very large */, 2568 true /* do_termination */, 2569 false /* is_serial */); 2570 } while (task->has_aborted() && !_cm->has_overflown()); 2571 // If we overflow, then we do not want to restart. We instead 2572 // want to abort remark and do concurrent marking again. 2573 task->record_end_time(); 2574 } 2575 } 2576 2577 CMRemarkTask(ConcurrentMark* cm, uint active_workers) : 2578 AbstractGangTask("Par Remark"), _cm(cm) { 2579 _cm->terminator()->reset_for_reuse(active_workers); 2580 } 2581 }; 2582 2583 void ConcurrentMark::checkpointRootsFinalWork() { 2584 ResourceMark rm; 2585 HandleMark hm; 2586 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2587 2588 G1CMTraceTime trace("Finalize Marking", G1Log::finer()); 2589 2590 g1h->ensure_parsability(false); 2591 2592 // this is remark, so we'll use up all active threads 2593 uint active_workers = g1h->workers()->active_workers(); 2594 set_concurrency_and_phase(active_workers, false /* concurrent */); 2595 // Leave _parallel_marking_threads at it's 2596 // value originally calculated in the ConcurrentMark 2597 // constructor and pass values of the active workers 2598 // through the gang in the task. 2599 2600 { 2601 StrongRootsScope srs(active_workers); 2602 2603 CMRemarkTask remarkTask(this, active_workers); 2604 // We will start all available threads, even if we decide that the 2605 // active_workers will be fewer. The extra ones will just bail out 2606 // immediately. 2607 g1h->workers()->run_task(&remarkTask); 2608 } 2609 2610 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 2611 guarantee(has_overflown() || 2612 satb_mq_set.completed_buffers_num() == 0, 2613 err_msg("Invariant: has_overflown = %s, num buffers = %d", 2614 BOOL_TO_STR(has_overflown()), 2615 satb_mq_set.completed_buffers_num())); 2616 2617 print_stats(); 2618 } 2619 2620 void ConcurrentMark::clearRangePrevBitmap(MemRegion mr) { 2621 // Note we are overriding the read-only view of the prev map here, via 2622 // the cast. 2623 ((CMBitMap*)_prevMarkBitMap)->clearRange(mr); 2624 } 2625 2626 void ConcurrentMark::clearRangeNextBitmap(MemRegion mr) { 2627 _nextMarkBitMap->clearRange(mr); 2628 } 2629 2630 HeapRegion* 2631 ConcurrentMark::claim_region(uint worker_id) { 2632 // "checkpoint" the finger 2633 HeapWord* finger = _finger; 2634 2635 // _heap_end will not change underneath our feet; it only changes at 2636 // yield points. 2637 while (finger < _heap_end) { 2638 assert(_g1h->is_in_g1_reserved(finger), "invariant"); 2639 2640 // Note on how this code handles humongous regions. In the 2641 // normal case the finger will reach the start of a "starts 2642 // humongous" (SH) region. Its end will either be the end of the 2643 // last "continues humongous" (CH) region in the sequence, or the 2644 // standard end of the SH region (if the SH is the only region in 2645 // the sequence). That way claim_region() will skip over the CH 2646 // regions. However, there is a subtle race between a CM thread 2647 // executing this method and a mutator thread doing a humongous 2648 // object allocation. The two are not mutually exclusive as the CM 2649 // thread does not need to hold the Heap_lock when it gets 2650 // here. So there is a chance that claim_region() will come across 2651 // a free region that's in the progress of becoming a SH or a CH 2652 // region. In the former case, it will either 2653 // a) Miss the update to the region's end, in which case it will 2654 // visit every subsequent CH region, will find their bitmaps 2655 // empty, and do nothing, or 2656 // b) Will observe the update of the region's end (in which case 2657 // it will skip the subsequent CH regions). 2658 // If it comes across a region that suddenly becomes CH, the 2659 // scenario will be similar to b). So, the race between 2660 // claim_region() and a humongous object allocation might force us 2661 // to do a bit of unnecessary work (due to some unnecessary bitmap 2662 // iterations) but it should not introduce and correctness issues. 2663 HeapRegion* curr_region = _g1h->heap_region_containing_raw(finger); 2664 2665 // Above heap_region_containing_raw may return NULL as we always scan claim 2666 // until the end of the heap. In this case, just jump to the next region. 2667 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords; 2668 2669 // Is the gap between reading the finger and doing the CAS too long? 2670 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger); 2671 if (res == finger && curr_region != NULL) { 2672 // we succeeded 2673 HeapWord* bottom = curr_region->bottom(); 2674 HeapWord* limit = curr_region->next_top_at_mark_start(); 2675 2676 if (verbose_low()) { 2677 gclog_or_tty->print_cr("[%u] curr_region = "PTR_FORMAT" " 2678 "["PTR_FORMAT", "PTR_FORMAT"), " 2679 "limit = "PTR_FORMAT, 2680 worker_id, p2i(curr_region), p2i(bottom), p2i(end), p2i(limit)); 2681 } 2682 2683 // notice that _finger == end cannot be guaranteed here since, 2684 // someone else might have moved the finger even further 2685 assert(_finger >= end, "the finger should have moved forward"); 2686 2687 if (verbose_low()) { 2688 gclog_or_tty->print_cr("[%u] we were successful with region = " 2689 PTR_FORMAT, worker_id, p2i(curr_region)); 2690 } 2691 2692 if (limit > bottom) { 2693 if (verbose_low()) { 2694 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is not empty, " 2695 "returning it ", worker_id, p2i(curr_region)); 2696 } 2697 return curr_region; 2698 } else { 2699 assert(limit == bottom, 2700 "the region limit should be at bottom"); 2701 if (verbose_low()) { 2702 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is empty, " 2703 "returning NULL", worker_id, p2i(curr_region)); 2704 } 2705 // we return NULL and the caller should try calling 2706 // claim_region() again. 2707 return NULL; 2708 } 2709 } else { 2710 assert(_finger > finger, "the finger should have moved forward"); 2711 if (verbose_low()) { 2712 if (curr_region == NULL) { 2713 gclog_or_tty->print_cr("[%u] found uncommitted region, moving finger, " 2714 "global finger = "PTR_FORMAT", " 2715 "our finger = "PTR_FORMAT, 2716 worker_id, p2i(_finger), p2i(finger)); 2717 } else { 2718 gclog_or_tty->print_cr("[%u] somebody else moved the finger, " 2719 "global finger = "PTR_FORMAT", " 2720 "our finger = "PTR_FORMAT, 2721 worker_id, p2i(_finger), p2i(finger)); 2722 } 2723 } 2724 2725 // read it again 2726 finger = _finger; 2727 } 2728 } 2729 2730 return NULL; 2731 } 2732 2733 #ifndef PRODUCT 2734 enum VerifyNoCSetOopsPhase { 2735 VerifyNoCSetOopsStack, 2736 VerifyNoCSetOopsQueues 2737 }; 2738 2739 class VerifyNoCSetOopsClosure : public OopClosure, public ObjectClosure { 2740 private: 2741 G1CollectedHeap* _g1h; 2742 VerifyNoCSetOopsPhase _phase; 2743 int _info; 2744 2745 const char* phase_str() { 2746 switch (_phase) { 2747 case VerifyNoCSetOopsStack: return "Stack"; 2748 case VerifyNoCSetOopsQueues: return "Queue"; 2749 default: ShouldNotReachHere(); 2750 } 2751 return NULL; 2752 } 2753 2754 void do_object_work(oop obj) { 2755 guarantee(!_g1h->obj_in_cs(obj), 2756 err_msg("obj: "PTR_FORMAT" in CSet, phase: %s, info: %d", 2757 p2i((void*) obj), phase_str(), _info)); 2758 } 2759 2760 public: 2761 VerifyNoCSetOopsClosure() : _g1h(G1CollectedHeap::heap()) { } 2762 2763 void set_phase(VerifyNoCSetOopsPhase phase, int info = -1) { 2764 _phase = phase; 2765 _info = info; 2766 } 2767 2768 virtual void do_oop(oop* p) { 2769 oop obj = oopDesc::load_decode_heap_oop(p); 2770 do_object_work(obj); 2771 } 2772 2773 virtual void do_oop(narrowOop* p) { 2774 // We should not come across narrow oops while scanning marking 2775 // stacks 2776 ShouldNotReachHere(); 2777 } 2778 2779 virtual void do_object(oop obj) { 2780 do_object_work(obj); 2781 } 2782 }; 2783 2784 void ConcurrentMark::verify_no_cset_oops() { 2785 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint"); 2786 if (!G1CollectedHeap::heap()->mark_in_progress()) { 2787 return; 2788 } 2789 2790 VerifyNoCSetOopsClosure cl; 2791 2792 // Verify entries on the global mark stack 2793 cl.set_phase(VerifyNoCSetOopsStack); 2794 _markStack.oops_do(&cl); 2795 2796 // Verify entries on the task queues 2797 for (uint i = 0; i < _max_worker_id; i += 1) { 2798 cl.set_phase(VerifyNoCSetOopsQueues, i); 2799 CMTaskQueue* queue = _task_queues->queue(i); 2800 queue->oops_do(&cl); 2801 } 2802 2803 // Verify the global finger 2804 HeapWord* global_finger = finger(); 2805 if (global_finger != NULL && global_finger < _heap_end) { 2806 // The global finger always points to a heap region boundary. We 2807 // use heap_region_containing_raw() to get the containing region 2808 // given that the global finger could be pointing to a free region 2809 // which subsequently becomes continues humongous. If that 2810 // happens, heap_region_containing() will return the bottom of the 2811 // corresponding starts humongous region and the check below will 2812 // not hold any more. 2813 // Since we always iterate over all regions, we might get a NULL HeapRegion 2814 // here. 2815 HeapRegion* global_hr = _g1h->heap_region_containing_raw(global_finger); 2816 guarantee(global_hr == NULL || global_finger == global_hr->bottom(), 2817 err_msg("global finger: "PTR_FORMAT" region: "HR_FORMAT, 2818 p2i(global_finger), HR_FORMAT_PARAMS(global_hr))); 2819 } 2820 2821 // Verify the task fingers 2822 assert(parallel_marking_threads() <= _max_worker_id, "sanity"); 2823 for (int i = 0; i < (int) parallel_marking_threads(); i += 1) { 2824 CMTask* task = _tasks[i]; 2825 HeapWord* task_finger = task->finger(); 2826 if (task_finger != NULL && task_finger < _heap_end) { 2827 // See above note on the global finger verification. 2828 HeapRegion* task_hr = _g1h->heap_region_containing_raw(task_finger); 2829 guarantee(task_hr == NULL || task_finger == task_hr->bottom() || 2830 !task_hr->in_collection_set(), 2831 err_msg("task finger: "PTR_FORMAT" region: "HR_FORMAT, 2832 p2i(task_finger), HR_FORMAT_PARAMS(task_hr))); 2833 } 2834 } 2835 } 2836 #endif // PRODUCT 2837 2838 // Aggregate the counting data that was constructed concurrently 2839 // with marking. 2840 class AggregateCountDataHRClosure: public HeapRegionClosure { 2841 G1CollectedHeap* _g1h; 2842 ConcurrentMark* _cm; 2843 CardTableModRefBS* _ct_bs; 2844 BitMap* _cm_card_bm; 2845 uint _max_worker_id; 2846 2847 public: 2848 AggregateCountDataHRClosure(G1CollectedHeap* g1h, 2849 BitMap* cm_card_bm, 2850 uint max_worker_id) : 2851 _g1h(g1h), _cm(g1h->concurrent_mark()), 2852 _ct_bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())), 2853 _cm_card_bm(cm_card_bm), _max_worker_id(max_worker_id) { } 2854 2855 bool doHeapRegion(HeapRegion* hr) { 2856 if (hr->is_continues_humongous()) { 2857 // We will ignore these here and process them when their 2858 // associated "starts humongous" region is processed. 2859 // Note that we cannot rely on their associated 2860 // "starts humongous" region to have their bit set to 1 2861 // since, due to the region chunking in the parallel region 2862 // iteration, a "continues humongous" region might be visited 2863 // before its associated "starts humongous". 2864 return false; 2865 } 2866 2867 HeapWord* start = hr->bottom(); 2868 HeapWord* limit = hr->next_top_at_mark_start(); 2869 HeapWord* end = hr->end(); 2870 2871 assert(start <= limit && limit <= hr->top() && hr->top() <= hr->end(), 2872 err_msg("Preconditions not met - " 2873 "start: "PTR_FORMAT", limit: "PTR_FORMAT", " 2874 "top: "PTR_FORMAT", end: "PTR_FORMAT, 2875 p2i(start), p2i(limit), p2i(hr->top()), p2i(hr->end()))); 2876 2877 assert(hr->next_marked_bytes() == 0, "Precondition"); 2878 2879 if (start == limit) { 2880 // NTAMS of this region has not been set so nothing to do. 2881 return false; 2882 } 2883 2884 // 'start' should be in the heap. 2885 assert(_g1h->is_in_g1_reserved(start) && _ct_bs->is_card_aligned(start), "sanity"); 2886 // 'end' *may* be just beyond the end of the heap (if hr is the last region) 2887 assert(!_g1h->is_in_g1_reserved(end) || _ct_bs->is_card_aligned(end), "sanity"); 2888 2889 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start); 2890 BitMap::idx_t limit_idx = _cm->card_bitmap_index_for(limit); 2891 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(end); 2892 2893 // If ntams is not card aligned then we bump card bitmap index 2894 // for limit so that we get the all the cards spanned by 2895 // the object ending at ntams. 2896 // Note: if this is the last region in the heap then ntams 2897 // could be actually just beyond the end of the the heap; 2898 // limit_idx will then correspond to a (non-existent) card 2899 // that is also outside the heap. 2900 if (_g1h->is_in_g1_reserved(limit) && !_ct_bs->is_card_aligned(limit)) { 2901 limit_idx += 1; 2902 } 2903 2904 assert(limit_idx <= end_idx, "or else use atomics"); 2905 2906 // Aggregate the "stripe" in the count data associated with hr. 2907 uint hrm_index = hr->hrm_index(); 2908 size_t marked_bytes = 0; 2909 2910 for (uint i = 0; i < _max_worker_id; i += 1) { 2911 size_t* marked_bytes_array = _cm->count_marked_bytes_array_for(i); 2912 BitMap* task_card_bm = _cm->count_card_bitmap_for(i); 2913 2914 // Fetch the marked_bytes in this region for task i and 2915 // add it to the running total for this region. 2916 marked_bytes += marked_bytes_array[hrm_index]; 2917 2918 // Now union the bitmaps[0,max_worker_id)[start_idx..limit_idx) 2919 // into the global card bitmap. 2920 BitMap::idx_t scan_idx = task_card_bm->get_next_one_offset(start_idx, limit_idx); 2921 2922 while (scan_idx < limit_idx) { 2923 assert(task_card_bm->at(scan_idx) == true, "should be"); 2924 _cm_card_bm->set_bit(scan_idx); 2925 assert(_cm_card_bm->at(scan_idx) == true, "should be"); 2926 2927 // BitMap::get_next_one_offset() can handle the case when 2928 // its left_offset parameter is greater than its right_offset 2929 // parameter. It does, however, have an early exit if 2930 // left_offset == right_offset. So let's limit the value 2931 // passed in for left offset here. 2932 BitMap::idx_t next_idx = MIN2(scan_idx + 1, limit_idx); 2933 scan_idx = task_card_bm->get_next_one_offset(next_idx, limit_idx); 2934 } 2935 } 2936 2937 // Update the marked bytes for this region. 2938 hr->add_to_marked_bytes(marked_bytes); 2939 2940 // Next heap region 2941 return false; 2942 } 2943 }; 2944 2945 class G1AggregateCountDataTask: public AbstractGangTask { 2946 protected: 2947 G1CollectedHeap* _g1h; 2948 ConcurrentMark* _cm; 2949 BitMap* _cm_card_bm; 2950 uint _max_worker_id; 2951 uint _active_workers; 2952 HeapRegionClaimer _hrclaimer; 2953 2954 public: 2955 G1AggregateCountDataTask(G1CollectedHeap* g1h, 2956 ConcurrentMark* cm, 2957 BitMap* cm_card_bm, 2958 uint max_worker_id, 2959 uint n_workers) : 2960 AbstractGangTask("Count Aggregation"), 2961 _g1h(g1h), _cm(cm), _cm_card_bm(cm_card_bm), 2962 _max_worker_id(max_worker_id), 2963 _active_workers(n_workers), 2964 _hrclaimer(_active_workers) { 2965 } 2966 2967 void work(uint worker_id) { 2968 AggregateCountDataHRClosure cl(_g1h, _cm_card_bm, _max_worker_id); 2969 2970 _g1h->heap_region_par_iterate(&cl, worker_id, &_hrclaimer); 2971 } 2972 }; 2973 2974 2975 void ConcurrentMark::aggregate_count_data() { 2976 uint n_workers = _g1h->workers()->active_workers(); 2977 2978 G1AggregateCountDataTask g1_par_agg_task(_g1h, this, &_card_bm, 2979 _max_worker_id, n_workers); 2980 2981 _g1h->workers()->run_task(&g1_par_agg_task); 2982 } 2983 2984 // Clear the per-worker arrays used to store the per-region counting data 2985 void ConcurrentMark::clear_all_count_data() { 2986 // Clear the global card bitmap - it will be filled during 2987 // liveness count aggregation (during remark) and the 2988 // final counting task. 2989 _card_bm.clear(); 2990 2991 // Clear the global region bitmap - it will be filled as part 2992 // of the final counting task. 2993 _region_bm.clear(); 2994 2995 uint max_regions = _g1h->max_regions(); 2996 assert(_max_worker_id > 0, "uninitialized"); 2997 2998 for (uint i = 0; i < _max_worker_id; i += 1) { 2999 BitMap* task_card_bm = count_card_bitmap_for(i); 3000 size_t* marked_bytes_array = count_marked_bytes_array_for(i); 3001 3002 assert(task_card_bm->size() == _card_bm.size(), "size mismatch"); 3003 assert(marked_bytes_array != NULL, "uninitialized"); 3004 3005 memset(marked_bytes_array, 0, (size_t) max_regions * sizeof(size_t)); 3006 task_card_bm->clear(); 3007 } 3008 } 3009 3010 void ConcurrentMark::print_stats() { 3011 if (verbose_stats()) { 3012 gclog_or_tty->print_cr("---------------------------------------------------------------------"); 3013 for (size_t i = 0; i < _active_tasks; ++i) { 3014 _tasks[i]->print_stats(); 3015 gclog_or_tty->print_cr("---------------------------------------------------------------------"); 3016 } 3017 } 3018 } 3019 3020 // abandon current marking iteration due to a Full GC 3021 void ConcurrentMark::abort() { 3022 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next 3023 // concurrent bitmap clearing. 3024 _nextMarkBitMap->clearAll(); 3025 3026 // Note we cannot clear the previous marking bitmap here 3027 // since VerifyDuringGC verifies the objects marked during 3028 // a full GC against the previous bitmap. 3029 3030 // Clear the liveness counting data 3031 clear_all_count_data(); 3032 // Empty mark stack 3033 reset_marking_state(); 3034 for (uint i = 0; i < _max_worker_id; ++i) { 3035 _tasks[i]->clear_region_fields(); 3036 } 3037 _first_overflow_barrier_sync.abort(); 3038 _second_overflow_barrier_sync.abort(); 3039 const GCId& gc_id = _g1h->gc_tracer_cm()->gc_id(); 3040 if (!gc_id.is_undefined()) { 3041 // We can do multiple full GCs before ConcurrentMarkThread::run() gets a chance 3042 // to detect that it was aborted. Only keep track of the first GC id that we aborted. 3043 _aborted_gc_id = gc_id; 3044 } 3045 _has_aborted = true; 3046 3047 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 3048 satb_mq_set.abandon_partial_marking(); 3049 // This can be called either during or outside marking, we'll read 3050 // the expected_active value from the SATB queue set. 3051 satb_mq_set.set_active_all_threads( 3052 false, /* new active value */ 3053 satb_mq_set.is_active() /* expected_active */); 3054 3055 _g1h->trace_heap_after_concurrent_cycle(); 3056 _g1h->register_concurrent_cycle_end(); 3057 } 3058 3059 const GCId& ConcurrentMark::concurrent_gc_id() { 3060 if (has_aborted()) { 3061 return _aborted_gc_id; 3062 } 3063 return _g1h->gc_tracer_cm()->gc_id(); 3064 } 3065 3066 static void print_ms_time_info(const char* prefix, const char* name, 3067 NumberSeq& ns) { 3068 gclog_or_tty->print_cr("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).", 3069 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg()); 3070 if (ns.num() > 0) { 3071 gclog_or_tty->print_cr("%s [std. dev = %8.2f ms, max = %8.2f ms]", 3072 prefix, ns.sd(), ns.maximum()); 3073 } 3074 } 3075 3076 void ConcurrentMark::print_summary_info() { 3077 gclog_or_tty->print_cr(" Concurrent marking:"); 3078 print_ms_time_info(" ", "init marks", _init_times); 3079 print_ms_time_info(" ", "remarks", _remark_times); 3080 { 3081 print_ms_time_info(" ", "final marks", _remark_mark_times); 3082 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times); 3083 3084 } 3085 print_ms_time_info(" ", "cleanups", _cleanup_times); 3086 gclog_or_tty->print_cr(" Final counting total time = %8.2f s (avg = %8.2f ms).", 3087 _total_counting_time, 3088 (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 / 3089 (double)_cleanup_times.num() 3090 : 0.0)); 3091 if (G1ScrubRemSets) { 3092 gclog_or_tty->print_cr(" RS scrub total time = %8.2f s (avg = %8.2f ms).", 3093 _total_rs_scrub_time, 3094 (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 / 3095 (double)_cleanup_times.num() 3096 : 0.0)); 3097 } 3098 gclog_or_tty->print_cr(" Total stop_world time = %8.2f s.", 3099 (_init_times.sum() + _remark_times.sum() + 3100 _cleanup_times.sum())/1000.0); 3101 gclog_or_tty->print_cr(" Total concurrent time = %8.2f s " 3102 "(%8.2f s marking).", 3103 cmThread()->vtime_accum(), 3104 cmThread()->vtime_mark_accum()); 3105 } 3106 3107 void ConcurrentMark::print_worker_threads_on(outputStream* st) const { 3108 _parallel_workers->print_worker_threads_on(st); 3109 } 3110 3111 void ConcurrentMark::print_on_error(outputStream* st) const { 3112 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT, 3113 p2i(_prevMarkBitMap), p2i(_nextMarkBitMap)); 3114 _prevMarkBitMap->print_on_error(st, " Prev Bits: "); 3115 _nextMarkBitMap->print_on_error(st, " Next Bits: "); 3116 } 3117 3118 // We take a break if someone is trying to stop the world. 3119 bool ConcurrentMark::do_yield_check(uint worker_id) { 3120 if (SuspendibleThreadSet::should_yield()) { 3121 if (worker_id == 0) { 3122 _g1h->g1_policy()->record_concurrent_pause(); 3123 } 3124 SuspendibleThreadSet::yield(); 3125 return true; 3126 } else { 3127 return false; 3128 } 3129 } 3130 3131 #ifndef PRODUCT 3132 // for debugging purposes 3133 void ConcurrentMark::print_finger() { 3134 gclog_or_tty->print_cr("heap ["PTR_FORMAT", "PTR_FORMAT"), global finger = "PTR_FORMAT, 3135 p2i(_heap_start), p2i(_heap_end), p2i(_finger)); 3136 for (uint i = 0; i < _max_worker_id; ++i) { 3137 gclog_or_tty->print(" %u: " PTR_FORMAT, i, p2i(_tasks[i]->finger())); 3138 } 3139 gclog_or_tty->cr(); 3140 } 3141 #endif 3142 3143 template<bool scan> 3144 inline void CMTask::process_grey_object(oop obj) { 3145 assert(scan || obj->is_typeArray(), "Skipping scan of grey non-typeArray"); 3146 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), "invariant"); 3147 3148 if (_cm->verbose_high()) { 3149 gclog_or_tty->print_cr("[%u] processing grey object " PTR_FORMAT, 3150 _worker_id, p2i((void*) obj)); 3151 } 3152 3153 size_t obj_size = obj->size(); 3154 _words_scanned += obj_size; 3155 3156 if (scan) { 3157 obj->oop_iterate(_cm_oop_closure); 3158 } 3159 statsOnly( ++_objs_scanned ); 3160 check_limits(); 3161 } 3162 3163 template void CMTask::process_grey_object<true>(oop); 3164 template void CMTask::process_grey_object<false>(oop); 3165 3166 // Closure for iteration over bitmaps 3167 class CMBitMapClosure : public BitMapClosure { 3168 private: 3169 // the bitmap that is being iterated over 3170 CMBitMap* _nextMarkBitMap; 3171 ConcurrentMark* _cm; 3172 CMTask* _task; 3173 3174 public: 3175 CMBitMapClosure(CMTask *task, ConcurrentMark* cm, CMBitMap* nextMarkBitMap) : 3176 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { } 3177 3178 bool do_bit(size_t offset) { 3179 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset); 3180 assert(_nextMarkBitMap->isMarked(addr), "invariant"); 3181 assert( addr < _cm->finger(), "invariant"); 3182 3183 statsOnly( _task->increase_objs_found_on_bitmap() ); 3184 assert(addr >= _task->finger(), "invariant"); 3185 3186 // We move that task's local finger along. 3187 _task->move_finger_to(addr); 3188 3189 _task->scan_object(oop(addr)); 3190 // we only partially drain the local queue and global stack 3191 _task->drain_local_queue(true); 3192 _task->drain_global_stack(true); 3193 3194 // if the has_aborted flag has been raised, we need to bail out of 3195 // the iteration 3196 return !_task->has_aborted(); 3197 } 3198 }; 3199 3200 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h, 3201 ConcurrentMark* cm, 3202 CMTask* task) 3203 : _g1h(g1h), _cm(cm), _task(task) { 3204 assert(_ref_processor == NULL, "should be initialized to NULL"); 3205 3206 if (G1UseConcMarkReferenceProcessing) { 3207 _ref_processor = g1h->ref_processor_cm(); 3208 assert(_ref_processor != NULL, "should not be NULL"); 3209 } 3210 } 3211 3212 void CMTask::setup_for_region(HeapRegion* hr) { 3213 assert(hr != NULL, 3214 "claim_region() should have filtered out NULL regions"); 3215 assert(!hr->is_continues_humongous(), 3216 "claim_region() should have filtered out continues humongous regions"); 3217 3218 if (_cm->verbose_low()) { 3219 gclog_or_tty->print_cr("[%u] setting up for region "PTR_FORMAT, 3220 _worker_id, p2i(hr)); 3221 } 3222 3223 _curr_region = hr; 3224 _finger = hr->bottom(); 3225 update_region_limit(); 3226 } 3227 3228 void CMTask::update_region_limit() { 3229 HeapRegion* hr = _curr_region; 3230 HeapWord* bottom = hr->bottom(); 3231 HeapWord* limit = hr->next_top_at_mark_start(); 3232 3233 if (limit == bottom) { 3234 if (_cm->verbose_low()) { 3235 gclog_or_tty->print_cr("[%u] found an empty region " 3236 "["PTR_FORMAT", "PTR_FORMAT")", 3237 _worker_id, p2i(bottom), p2i(limit)); 3238 } 3239 // The region was collected underneath our feet. 3240 // We set the finger to bottom to ensure that the bitmap 3241 // iteration that will follow this will not do anything. 3242 // (this is not a condition that holds when we set the region up, 3243 // as the region is not supposed to be empty in the first place) 3244 _finger = bottom; 3245 } else if (limit >= _region_limit) { 3246 assert(limit >= _finger, "peace of mind"); 3247 } else { 3248 assert(limit < _region_limit, "only way to get here"); 3249 // This can happen under some pretty unusual circumstances. An 3250 // evacuation pause empties the region underneath our feet (NTAMS 3251 // at bottom). We then do some allocation in the region (NTAMS 3252 // stays at bottom), followed by the region being used as a GC 3253 // alloc region (NTAMS will move to top() and the objects 3254 // originally below it will be grayed). All objects now marked in 3255 // the region are explicitly grayed, if below the global finger, 3256 // and we do not need in fact to scan anything else. So, we simply 3257 // set _finger to be limit to ensure that the bitmap iteration 3258 // doesn't do anything. 3259 _finger = limit; 3260 } 3261 3262 _region_limit = limit; 3263 } 3264 3265 void CMTask::giveup_current_region() { 3266 assert(_curr_region != NULL, "invariant"); 3267 if (_cm->verbose_low()) { 3268 gclog_or_tty->print_cr("[%u] giving up region "PTR_FORMAT, 3269 _worker_id, p2i(_curr_region)); 3270 } 3271 clear_region_fields(); 3272 } 3273 3274 void CMTask::clear_region_fields() { 3275 // Values for these three fields that indicate that we're not 3276 // holding on to a region. 3277 _curr_region = NULL; 3278 _finger = NULL; 3279 _region_limit = NULL; 3280 } 3281 3282 void CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) { 3283 if (cm_oop_closure == NULL) { 3284 assert(_cm_oop_closure != NULL, "invariant"); 3285 } else { 3286 assert(_cm_oop_closure == NULL, "invariant"); 3287 } 3288 _cm_oop_closure = cm_oop_closure; 3289 } 3290 3291 void CMTask::reset(CMBitMap* nextMarkBitMap) { 3292 guarantee(nextMarkBitMap != NULL, "invariant"); 3293 3294 if (_cm->verbose_low()) { 3295 gclog_or_tty->print_cr("[%u] resetting", _worker_id); 3296 } 3297 3298 _nextMarkBitMap = nextMarkBitMap; 3299 clear_region_fields(); 3300 3301 _calls = 0; 3302 _elapsed_time_ms = 0.0; 3303 _termination_time_ms = 0.0; 3304 _termination_start_time_ms = 0.0; 3305 3306 #if _MARKING_STATS_ 3307 _aborted = 0; 3308 _aborted_overflow = 0; 3309 _aborted_cm_aborted = 0; 3310 _aborted_yield = 0; 3311 _aborted_timed_out = 0; 3312 _aborted_satb = 0; 3313 _aborted_termination = 0; 3314 _steal_attempts = 0; 3315 _steals = 0; 3316 _local_pushes = 0; 3317 _local_pops = 0; 3318 _local_max_size = 0; 3319 _objs_scanned = 0; 3320 _global_pushes = 0; 3321 _global_pops = 0; 3322 _global_max_size = 0; 3323 _global_transfers_to = 0; 3324 _global_transfers_from = 0; 3325 _regions_claimed = 0; 3326 _objs_found_on_bitmap = 0; 3327 _satb_buffers_processed = 0; 3328 #endif // _MARKING_STATS_ 3329 } 3330 3331 bool CMTask::should_exit_termination() { 3332 regular_clock_call(); 3333 // This is called when we are in the termination protocol. We should 3334 // quit if, for some reason, this task wants to abort or the global 3335 // stack is not empty (this means that we can get work from it). 3336 return !_cm->mark_stack_empty() || has_aborted(); 3337 } 3338 3339 void CMTask::reached_limit() { 3340 assert(_words_scanned >= _words_scanned_limit || 3341 _refs_reached >= _refs_reached_limit , 3342 "shouldn't have been called otherwise"); 3343 regular_clock_call(); 3344 } 3345 3346 void CMTask::regular_clock_call() { 3347 if (has_aborted()) return; 3348 3349 // First, we need to recalculate the words scanned and refs reached 3350 // limits for the next clock call. 3351 recalculate_limits(); 3352 3353 // During the regular clock call we do the following 3354 3355 // (1) If an overflow has been flagged, then we abort. 3356 if (_cm->has_overflown()) { 3357 set_has_aborted(); 3358 return; 3359 } 3360 3361 // If we are not concurrent (i.e. we're doing remark) we don't need 3362 // to check anything else. The other steps are only needed during 3363 // the concurrent marking phase. 3364 if (!concurrent()) return; 3365 3366 // (2) If marking has been aborted for Full GC, then we also abort. 3367 if (_cm->has_aborted()) { 3368 set_has_aborted(); 3369 statsOnly( ++_aborted_cm_aborted ); 3370 return; 3371 } 3372 3373 double curr_time_ms = os::elapsedVTime() * 1000.0; 3374 3375 // (3) If marking stats are enabled, then we update the step history. 3376 #if _MARKING_STATS_ 3377 if (_words_scanned >= _words_scanned_limit) { 3378 ++_clock_due_to_scanning; 3379 } 3380 if (_refs_reached >= _refs_reached_limit) { 3381 ++_clock_due_to_marking; 3382 } 3383 3384 double last_interval_ms = curr_time_ms - _interval_start_time_ms; 3385 _interval_start_time_ms = curr_time_ms; 3386 _all_clock_intervals_ms.add(last_interval_ms); 3387 3388 if (_cm->verbose_medium()) { 3389 gclog_or_tty->print_cr("[%u] regular clock, interval = %1.2lfms, " 3390 "scanned = "SIZE_FORMAT"%s, refs reached = "SIZE_FORMAT"%s", 3391 _worker_id, last_interval_ms, 3392 _words_scanned, 3393 (_words_scanned >= _words_scanned_limit) ? " (*)" : "", 3394 _refs_reached, 3395 (_refs_reached >= _refs_reached_limit) ? " (*)" : ""); 3396 } 3397 #endif // _MARKING_STATS_ 3398 3399 // (4) We check whether we should yield. If we have to, then we abort. 3400 if (SuspendibleThreadSet::should_yield()) { 3401 // We should yield. To do this we abort the task. The caller is 3402 // responsible for yielding. 3403 set_has_aborted(); 3404 statsOnly( ++_aborted_yield ); 3405 return; 3406 } 3407 3408 // (5) We check whether we've reached our time quota. If we have, 3409 // then we abort. 3410 double elapsed_time_ms = curr_time_ms - _start_time_ms; 3411 if (elapsed_time_ms > _time_target_ms) { 3412 set_has_aborted(); 3413 _has_timed_out = true; 3414 statsOnly( ++_aborted_timed_out ); 3415 return; 3416 } 3417 3418 // (6) Finally, we check whether there are enough completed STAB 3419 // buffers available for processing. If there are, we abort. 3420 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 3421 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) { 3422 if (_cm->verbose_low()) { 3423 gclog_or_tty->print_cr("[%u] aborting to deal with pending SATB buffers", 3424 _worker_id); 3425 } 3426 // we do need to process SATB buffers, we'll abort and restart 3427 // the marking task to do so 3428 set_has_aborted(); 3429 statsOnly( ++_aborted_satb ); 3430 return; 3431 } 3432 } 3433 3434 void CMTask::recalculate_limits() { 3435 _real_words_scanned_limit = _words_scanned + words_scanned_period; 3436 _words_scanned_limit = _real_words_scanned_limit; 3437 3438 _real_refs_reached_limit = _refs_reached + refs_reached_period; 3439 _refs_reached_limit = _real_refs_reached_limit; 3440 } 3441 3442 void CMTask::decrease_limits() { 3443 // This is called when we believe that we're going to do an infrequent 3444 // operation which will increase the per byte scanned cost (i.e. move 3445 // entries to/from the global stack). It basically tries to decrease the 3446 // scanning limit so that the clock is called earlier. 3447 3448 if (_cm->verbose_medium()) { 3449 gclog_or_tty->print_cr("[%u] decreasing limits", _worker_id); 3450 } 3451 3452 _words_scanned_limit = _real_words_scanned_limit - 3453 3 * words_scanned_period / 4; 3454 _refs_reached_limit = _real_refs_reached_limit - 3455 3 * refs_reached_period / 4; 3456 } 3457 3458 void CMTask::move_entries_to_global_stack() { 3459 // local array where we'll store the entries that will be popped 3460 // from the local queue 3461 oop buffer[global_stack_transfer_size]; 3462 3463 int n = 0; 3464 oop obj; 3465 while (n < global_stack_transfer_size && _task_queue->pop_local(obj)) { 3466 buffer[n] = obj; 3467 ++n; 3468 } 3469 3470 if (n > 0) { 3471 // we popped at least one entry from the local queue 3472 3473 statsOnly( ++_global_transfers_to; _local_pops += n ); 3474 3475 if (!_cm->mark_stack_push(buffer, n)) { 3476 if (_cm->verbose_low()) { 3477 gclog_or_tty->print_cr("[%u] aborting due to global stack overflow", 3478 _worker_id); 3479 } 3480 set_has_aborted(); 3481 } else { 3482 // the transfer was successful 3483 3484 if (_cm->verbose_medium()) { 3485 gclog_or_tty->print_cr("[%u] pushed %d entries to the global stack", 3486 _worker_id, n); 3487 } 3488 statsOnly( size_t tmp_size = _cm->mark_stack_size(); 3489 if (tmp_size > _global_max_size) { 3490 _global_max_size = tmp_size; 3491 } 3492 _global_pushes += n ); 3493 } 3494 } 3495 3496 // this operation was quite expensive, so decrease the limits 3497 decrease_limits(); 3498 } 3499 3500 void CMTask::get_entries_from_global_stack() { 3501 // local array where we'll store the entries that will be popped 3502 // from the global stack. 3503 oop buffer[global_stack_transfer_size]; 3504 int n; 3505 _cm->mark_stack_pop(buffer, global_stack_transfer_size, &n); 3506 assert(n <= global_stack_transfer_size, 3507 "we should not pop more than the given limit"); 3508 if (n > 0) { 3509 // yes, we did actually pop at least one entry 3510 3511 statsOnly( ++_global_transfers_from; _global_pops += n ); 3512 if (_cm->verbose_medium()) { 3513 gclog_or_tty->print_cr("[%u] popped %d entries from the global stack", 3514 _worker_id, n); 3515 } 3516 for (int i = 0; i < n; ++i) { 3517 bool success = _task_queue->push(buffer[i]); 3518 // We only call this when the local queue is empty or under a 3519 // given target limit. So, we do not expect this push to fail. 3520 assert(success, "invariant"); 3521 } 3522 3523 statsOnly( size_t tmp_size = (size_t)_task_queue->size(); 3524 if (tmp_size > _local_max_size) { 3525 _local_max_size = tmp_size; 3526 } 3527 _local_pushes += n ); 3528 } 3529 3530 // this operation was quite expensive, so decrease the limits 3531 decrease_limits(); 3532 } 3533 3534 void CMTask::drain_local_queue(bool partially) { 3535 if (has_aborted()) return; 3536 3537 // Decide what the target size is, depending whether we're going to 3538 // drain it partially (so that other tasks can steal if they run out 3539 // of things to do) or totally (at the very end). 3540 size_t target_size; 3541 if (partially) { 3542 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize); 3543 } else { 3544 target_size = 0; 3545 } 3546 3547 if (_task_queue->size() > target_size) { 3548 if (_cm->verbose_high()) { 3549 gclog_or_tty->print_cr("[%u] draining local queue, target size = " SIZE_FORMAT, 3550 _worker_id, target_size); 3551 } 3552 3553 oop obj; 3554 bool ret = _task_queue->pop_local(obj); 3555 while (ret) { 3556 statsOnly( ++_local_pops ); 3557 3558 if (_cm->verbose_high()) { 3559 gclog_or_tty->print_cr("[%u] popped "PTR_FORMAT, _worker_id, 3560 p2i((void*) obj)); 3561 } 3562 3563 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" ); 3564 assert(!_g1h->is_on_master_free_list( 3565 _g1h->heap_region_containing((HeapWord*) obj)), "invariant"); 3566 3567 scan_object(obj); 3568 3569 if (_task_queue->size() <= target_size || has_aborted()) { 3570 ret = false; 3571 } else { 3572 ret = _task_queue->pop_local(obj); 3573 } 3574 } 3575 3576 if (_cm->verbose_high()) { 3577 gclog_or_tty->print_cr("[%u] drained local queue, size = %u", 3578 _worker_id, _task_queue->size()); 3579 } 3580 } 3581 } 3582 3583 void CMTask::drain_global_stack(bool partially) { 3584 if (has_aborted()) return; 3585 3586 // We have a policy to drain the local queue before we attempt to 3587 // drain the global stack. 3588 assert(partially || _task_queue->size() == 0, "invariant"); 3589 3590 // Decide what the target size is, depending whether we're going to 3591 // drain it partially (so that other tasks can steal if they run out 3592 // of things to do) or totally (at the very end). Notice that, 3593 // because we move entries from the global stack in chunks or 3594 // because another task might be doing the same, we might in fact 3595 // drop below the target. But, this is not a problem. 3596 size_t target_size; 3597 if (partially) { 3598 target_size = _cm->partial_mark_stack_size_target(); 3599 } else { 3600 target_size = 0; 3601 } 3602 3603 if (_cm->mark_stack_size() > target_size) { 3604 if (_cm->verbose_low()) { 3605 gclog_or_tty->print_cr("[%u] draining global_stack, target size " SIZE_FORMAT, 3606 _worker_id, target_size); 3607 } 3608 3609 while (!has_aborted() && _cm->mark_stack_size() > target_size) { 3610 get_entries_from_global_stack(); 3611 drain_local_queue(partially); 3612 } 3613 3614 if (_cm->verbose_low()) { 3615 gclog_or_tty->print_cr("[%u] drained global stack, size = " SIZE_FORMAT, 3616 _worker_id, _cm->mark_stack_size()); 3617 } 3618 } 3619 } 3620 3621 // SATB Queue has several assumptions on whether to call the par or 3622 // non-par versions of the methods. this is why some of the code is 3623 // replicated. We should really get rid of the single-threaded version 3624 // of the code to simplify things. 3625 void CMTask::drain_satb_buffers() { 3626 if (has_aborted()) return; 3627 3628 // We set this so that the regular clock knows that we're in the 3629 // middle of draining buffers and doesn't set the abort flag when it 3630 // notices that SATB buffers are available for draining. It'd be 3631 // very counter productive if it did that. :-) 3632 _draining_satb_buffers = true; 3633 3634 CMSATBBufferClosure satb_cl(this, _g1h); 3635 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 3636 3637 // This keeps claiming and applying the closure to completed buffers 3638 // until we run out of buffers or we need to abort. 3639 while (!has_aborted() && 3640 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) { 3641 if (_cm->verbose_medium()) { 3642 gclog_or_tty->print_cr("[%u] processed an SATB buffer", _worker_id); 3643 } 3644 statsOnly( ++_satb_buffers_processed ); 3645 regular_clock_call(); 3646 } 3647 3648 _draining_satb_buffers = false; 3649 3650 assert(has_aborted() || 3651 concurrent() || 3652 satb_mq_set.completed_buffers_num() == 0, "invariant"); 3653 3654 // again, this was a potentially expensive operation, decrease the 3655 // limits to get the regular clock call early 3656 decrease_limits(); 3657 } 3658 3659 void CMTask::print_stats() { 3660 gclog_or_tty->print_cr("Marking Stats, task = %u, calls = %d", 3661 _worker_id, _calls); 3662 gclog_or_tty->print_cr(" Elapsed time = %1.2lfms, Termination time = %1.2lfms", 3663 _elapsed_time_ms, _termination_time_ms); 3664 gclog_or_tty->print_cr(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms", 3665 _step_times_ms.num(), _step_times_ms.avg(), 3666 _step_times_ms.sd()); 3667 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms", 3668 _step_times_ms.maximum(), _step_times_ms.sum()); 3669 3670 #if _MARKING_STATS_ 3671 gclog_or_tty->print_cr(" Clock Intervals (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms", 3672 _all_clock_intervals_ms.num(), _all_clock_intervals_ms.avg(), 3673 _all_clock_intervals_ms.sd()); 3674 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms", 3675 _all_clock_intervals_ms.maximum(), 3676 _all_clock_intervals_ms.sum()); 3677 gclog_or_tty->print_cr(" Clock Causes (cum): scanning = " SIZE_FORMAT ", marking = " SIZE_FORMAT, 3678 _clock_due_to_scanning, _clock_due_to_marking); 3679 gclog_or_tty->print_cr(" Objects: scanned = " SIZE_FORMAT ", found on the bitmap = " SIZE_FORMAT, 3680 _objs_scanned, _objs_found_on_bitmap); 3681 gclog_or_tty->print_cr(" Local Queue: pushes = " SIZE_FORMAT ", pops = " SIZE_FORMAT ", max size = " SIZE_FORMAT, 3682 _local_pushes, _local_pops, _local_max_size); 3683 gclog_or_tty->print_cr(" Global Stack: pushes = " SIZE_FORMAT ", pops = " SIZE_FORMAT ", max size = " SIZE_FORMAT, 3684 _global_pushes, _global_pops, _global_max_size); 3685 gclog_or_tty->print_cr(" transfers to = " SIZE_FORMAT ", transfers from = " SIZE_FORMAT, 3686 _global_transfers_to,_global_transfers_from); 3687 gclog_or_tty->print_cr(" Regions: claimed = " SIZE_FORMAT, _regions_claimed); 3688 gclog_or_tty->print_cr(" SATB buffers: processed = " SIZE_FORMAT, _satb_buffers_processed); 3689 gclog_or_tty->print_cr(" Steals: attempts = " SIZE_FORMAT ", successes = " SIZE_FORMAT, 3690 _steal_attempts, _steals); 3691 gclog_or_tty->print_cr(" Aborted: " SIZE_FORMAT ", due to", _aborted); 3692 gclog_or_tty->print_cr(" overflow: " SIZE_FORMAT ", global abort: " SIZE_FORMAT ", yield: " SIZE_FORMAT, 3693 _aborted_overflow, _aborted_cm_aborted, _aborted_yield); 3694 gclog_or_tty->print_cr(" time out: " SIZE_FORMAT ", SATB: " SIZE_FORMAT ", termination: " SIZE_FORMAT, 3695 _aborted_timed_out, _aborted_satb, _aborted_termination); 3696 #endif // _MARKING_STATS_ 3697 } 3698 3699 bool ConcurrentMark::try_stealing(uint worker_id, int* hash_seed, oop& obj) { 3700 return _task_queues->steal(worker_id, hash_seed, obj); 3701 } 3702 3703 /***************************************************************************** 3704 3705 The do_marking_step(time_target_ms, ...) method is the building 3706 block of the parallel marking framework. It can be called in parallel 3707 with other invocations of do_marking_step() on different tasks 3708 (but only one per task, obviously) and concurrently with the 3709 mutator threads, or during remark, hence it eliminates the need 3710 for two versions of the code. When called during remark, it will 3711 pick up from where the task left off during the concurrent marking 3712 phase. Interestingly, tasks are also claimable during evacuation 3713 pauses too, since do_marking_step() ensures that it aborts before 3714 it needs to yield. 3715 3716 The data structures that it uses to do marking work are the 3717 following: 3718 3719 (1) Marking Bitmap. If there are gray objects that appear only 3720 on the bitmap (this happens either when dealing with an overflow 3721 or when the initial marking phase has simply marked the roots 3722 and didn't push them on the stack), then tasks claim heap 3723 regions whose bitmap they then scan to find gray objects. A 3724 global finger indicates where the end of the last claimed region 3725 is. A local finger indicates how far into the region a task has 3726 scanned. The two fingers are used to determine how to gray an 3727 object (i.e. whether simply marking it is OK, as it will be 3728 visited by a task in the future, or whether it needs to be also 3729 pushed on a stack). 3730 3731 (2) Local Queue. The local queue of the task which is accessed 3732 reasonably efficiently by the task. Other tasks can steal from 3733 it when they run out of work. Throughout the marking phase, a 3734 task attempts to keep its local queue short but not totally 3735 empty, so that entries are available for stealing by other 3736 tasks. Only when there is no more work, a task will totally 3737 drain its local queue. 3738 3739 (3) Global Mark Stack. This handles local queue overflow. During 3740 marking only sets of entries are moved between it and the local 3741 queues, as access to it requires a mutex and more fine-grain 3742 interaction with it which might cause contention. If it 3743 overflows, then the marking phase should restart and iterate 3744 over the bitmap to identify gray objects. Throughout the marking 3745 phase, tasks attempt to keep the global mark stack at a small 3746 length but not totally empty, so that entries are available for 3747 popping by other tasks. Only when there is no more work, tasks 3748 will totally drain the global mark stack. 3749 3750 (4) SATB Buffer Queue. This is where completed SATB buffers are 3751 made available. Buffers are regularly removed from this queue 3752 and scanned for roots, so that the queue doesn't get too 3753 long. During remark, all completed buffers are processed, as 3754 well as the filled in parts of any uncompleted buffers. 3755 3756 The do_marking_step() method tries to abort when the time target 3757 has been reached. There are a few other cases when the 3758 do_marking_step() method also aborts: 3759 3760 (1) When the marking phase has been aborted (after a Full GC). 3761 3762 (2) When a global overflow (on the global stack) has been 3763 triggered. Before the task aborts, it will actually sync up with 3764 the other tasks to ensure that all the marking data structures 3765 (local queues, stacks, fingers etc.) are re-initialized so that 3766 when do_marking_step() completes, the marking phase can 3767 immediately restart. 3768 3769 (3) When enough completed SATB buffers are available. The 3770 do_marking_step() method only tries to drain SATB buffers right 3771 at the beginning. So, if enough buffers are available, the 3772 marking step aborts and the SATB buffers are processed at 3773 the beginning of the next invocation. 3774 3775 (4) To yield. when we have to yield then we abort and yield 3776 right at the end of do_marking_step(). This saves us from a lot 3777 of hassle as, by yielding we might allow a Full GC. If this 3778 happens then objects will be compacted underneath our feet, the 3779 heap might shrink, etc. We save checking for this by just 3780 aborting and doing the yield right at the end. 3781 3782 From the above it follows that the do_marking_step() method should 3783 be called in a loop (or, otherwise, regularly) until it completes. 3784 3785 If a marking step completes without its has_aborted() flag being 3786 true, it means it has completed the current marking phase (and 3787 also all other marking tasks have done so and have all synced up). 3788 3789 A method called regular_clock_call() is invoked "regularly" (in 3790 sub ms intervals) throughout marking. It is this clock method that 3791 checks all the abort conditions which were mentioned above and 3792 decides when the task should abort. A work-based scheme is used to 3793 trigger this clock method: when the number of object words the 3794 marking phase has scanned or the number of references the marking 3795 phase has visited reach a given limit. Additional invocations to 3796 the method clock have been planted in a few other strategic places 3797 too. The initial reason for the clock method was to avoid calling 3798 vtime too regularly, as it is quite expensive. So, once it was in 3799 place, it was natural to piggy-back all the other conditions on it 3800 too and not constantly check them throughout the code. 3801 3802 If do_termination is true then do_marking_step will enter its 3803 termination protocol. 3804 3805 The value of is_serial must be true when do_marking_step is being 3806 called serially (i.e. by the VMThread) and do_marking_step should 3807 skip any synchronization in the termination and overflow code. 3808 Examples include the serial remark code and the serial reference 3809 processing closures. 3810 3811 The value of is_serial must be false when do_marking_step is 3812 being called by any of the worker threads in a work gang. 3813 Examples include the concurrent marking code (CMMarkingTask), 3814 the MT remark code, and the MT reference processing closures. 3815 3816 *****************************************************************************/ 3817 3818 void CMTask::do_marking_step(double time_target_ms, 3819 bool do_termination, 3820 bool is_serial) { 3821 assert(time_target_ms >= 1.0, "minimum granularity is 1ms"); 3822 assert(concurrent() == _cm->concurrent(), "they should be the same"); 3823 3824 G1CollectorPolicy* g1_policy = _g1h->g1_policy(); 3825 assert(_task_queues != NULL, "invariant"); 3826 assert(_task_queue != NULL, "invariant"); 3827 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant"); 3828 3829 assert(!_claimed, 3830 "only one thread should claim this task at any one time"); 3831 3832 // OK, this doesn't safeguard again all possible scenarios, as it is 3833 // possible for two threads to set the _claimed flag at the same 3834 // time. But it is only for debugging purposes anyway and it will 3835 // catch most problems. 3836 _claimed = true; 3837 3838 _start_time_ms = os::elapsedVTime() * 1000.0; 3839 statsOnly( _interval_start_time_ms = _start_time_ms ); 3840 3841 // If do_stealing is true then do_marking_step will attempt to 3842 // steal work from the other CMTasks. It only makes sense to 3843 // enable stealing when the termination protocol is enabled 3844 // and do_marking_step() is not being called serially. 3845 bool do_stealing = do_termination && !is_serial; 3846 3847 double diff_prediction_ms = 3848 g1_policy->get_new_prediction(&_marking_step_diffs_ms); 3849 _time_target_ms = time_target_ms - diff_prediction_ms; 3850 3851 // set up the variables that are used in the work-based scheme to 3852 // call the regular clock method 3853 _words_scanned = 0; 3854 _refs_reached = 0; 3855 recalculate_limits(); 3856 3857 // clear all flags 3858 clear_has_aborted(); 3859 _has_timed_out = false; 3860 _draining_satb_buffers = false; 3861 3862 ++_calls; 3863 3864 if (_cm->verbose_low()) { 3865 gclog_or_tty->print_cr("[%u] >>>>>>>>>> START, call = %d, " 3866 "target = %1.2lfms >>>>>>>>>>", 3867 _worker_id, _calls, _time_target_ms); 3868 } 3869 3870 // Set up the bitmap and oop closures. Anything that uses them is 3871 // eventually called from this method, so it is OK to allocate these 3872 // statically. 3873 CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap); 3874 G1CMOopClosure cm_oop_closure(_g1h, _cm, this); 3875 set_cm_oop_closure(&cm_oop_closure); 3876 3877 if (_cm->has_overflown()) { 3878 // This can happen if the mark stack overflows during a GC pause 3879 // and this task, after a yield point, restarts. We have to abort 3880 // as we need to get into the overflow protocol which happens 3881 // right at the end of this task. 3882 set_has_aborted(); 3883 } 3884 3885 // First drain any available SATB buffers. After this, we will not 3886 // look at SATB buffers before the next invocation of this method. 3887 // If enough completed SATB buffers are queued up, the regular clock 3888 // will abort this task so that it restarts. 3889 drain_satb_buffers(); 3890 // ...then partially drain the local queue and the global stack 3891 drain_local_queue(true); 3892 drain_global_stack(true); 3893 3894 do { 3895 if (!has_aborted() && _curr_region != NULL) { 3896 // This means that we're already holding on to a region. 3897 assert(_finger != NULL, "if region is not NULL, then the finger " 3898 "should not be NULL either"); 3899 3900 // We might have restarted this task after an evacuation pause 3901 // which might have evacuated the region we're holding on to 3902 // underneath our feet. Let's read its limit again to make sure 3903 // that we do not iterate over a region of the heap that 3904 // contains garbage (update_region_limit() will also move 3905 // _finger to the start of the region if it is found empty). 3906 update_region_limit(); 3907 // We will start from _finger not from the start of the region, 3908 // as we might be restarting this task after aborting half-way 3909 // through scanning this region. In this case, _finger points to 3910 // the address where we last found a marked object. If this is a 3911 // fresh region, _finger points to start(). 3912 MemRegion mr = MemRegion(_finger, _region_limit); 3913 3914 if (_cm->verbose_low()) { 3915 gclog_or_tty->print_cr("[%u] we're scanning part " 3916 "["PTR_FORMAT", "PTR_FORMAT") " 3917 "of region "HR_FORMAT, 3918 _worker_id, p2i(_finger), p2i(_region_limit), 3919 HR_FORMAT_PARAMS(_curr_region)); 3920 } 3921 3922 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(), 3923 "humongous regions should go around loop once only"); 3924 3925 // Some special cases: 3926 // If the memory region is empty, we can just give up the region. 3927 // If the current region is humongous then we only need to check 3928 // the bitmap for the bit associated with the start of the object, 3929 // scan the object if it's live, and give up the region. 3930 // Otherwise, let's iterate over the bitmap of the part of the region 3931 // that is left. 3932 // If the iteration is successful, give up the region. 3933 if (mr.is_empty()) { 3934 giveup_current_region(); 3935 regular_clock_call(); 3936 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) { 3937 if (_nextMarkBitMap->isMarked(mr.start())) { 3938 // The object is marked - apply the closure 3939 BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start()); 3940 bitmap_closure.do_bit(offset); 3941 } 3942 // Even if this task aborted while scanning the humongous object 3943 // we can (and should) give up the current region. 3944 giveup_current_region(); 3945 regular_clock_call(); 3946 } else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) { 3947 giveup_current_region(); 3948 regular_clock_call(); 3949 } else { 3950 assert(has_aborted(), "currently the only way to do so"); 3951 // The only way to abort the bitmap iteration is to return 3952 // false from the do_bit() method. However, inside the 3953 // do_bit() method we move the _finger to point to the 3954 // object currently being looked at. So, if we bail out, we 3955 // have definitely set _finger to something non-null. 3956 assert(_finger != NULL, "invariant"); 3957 3958 // Region iteration was actually aborted. So now _finger 3959 // points to the address of the object we last scanned. If we 3960 // leave it there, when we restart this task, we will rescan 3961 // the object. It is easy to avoid this. We move the finger by 3962 // enough to point to the next possible object header (the 3963 // bitmap knows by how much we need to move it as it knows its 3964 // granularity). 3965 assert(_finger < _region_limit, "invariant"); 3966 HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger); 3967 // Check if bitmap iteration was aborted while scanning the last object 3968 if (new_finger >= _region_limit) { 3969 giveup_current_region(); 3970 } else { 3971 move_finger_to(new_finger); 3972 } 3973 } 3974 } 3975 // At this point we have either completed iterating over the 3976 // region we were holding on to, or we have aborted. 3977 3978 // We then partially drain the local queue and the global stack. 3979 // (Do we really need this?) 3980 drain_local_queue(true); 3981 drain_global_stack(true); 3982 3983 // Read the note on the claim_region() method on why it might 3984 // return NULL with potentially more regions available for 3985 // claiming and why we have to check out_of_regions() to determine 3986 // whether we're done or not. 3987 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) { 3988 // We are going to try to claim a new region. We should have 3989 // given up on the previous one. 3990 // Separated the asserts so that we know which one fires. 3991 assert(_curr_region == NULL, "invariant"); 3992 assert(_finger == NULL, "invariant"); 3993 assert(_region_limit == NULL, "invariant"); 3994 if (_cm->verbose_low()) { 3995 gclog_or_tty->print_cr("[%u] trying to claim a new region", _worker_id); 3996 } 3997 HeapRegion* claimed_region = _cm->claim_region(_worker_id); 3998 if (claimed_region != NULL) { 3999 // Yes, we managed to claim one 4000 statsOnly( ++_regions_claimed ); 4001 4002 if (_cm->verbose_low()) { 4003 gclog_or_tty->print_cr("[%u] we successfully claimed " 4004 "region "PTR_FORMAT, 4005 _worker_id, p2i(claimed_region)); 4006 } 4007 4008 setup_for_region(claimed_region); 4009 assert(_curr_region == claimed_region, "invariant"); 4010 } 4011 // It is important to call the regular clock here. It might take 4012 // a while to claim a region if, for example, we hit a large 4013 // block of empty regions. So we need to call the regular clock 4014 // method once round the loop to make sure it's called 4015 // frequently enough. 4016 regular_clock_call(); 4017 } 4018 4019 if (!has_aborted() && _curr_region == NULL) { 4020 assert(_cm->out_of_regions(), 4021 "at this point we should be out of regions"); 4022 } 4023 } while ( _curr_region != NULL && !has_aborted()); 4024 4025 if (!has_aborted()) { 4026 // We cannot check whether the global stack is empty, since other 4027 // tasks might be pushing objects to it concurrently. 4028 assert(_cm->out_of_regions(), 4029 "at this point we should be out of regions"); 4030 4031 if (_cm->verbose_low()) { 4032 gclog_or_tty->print_cr("[%u] all regions claimed", _worker_id); 4033 } 4034 4035 // Try to reduce the number of available SATB buffers so that 4036 // remark has less work to do. 4037 drain_satb_buffers(); 4038 } 4039 4040 // Since we've done everything else, we can now totally drain the 4041 // local queue and global stack. 4042 drain_local_queue(false); 4043 drain_global_stack(false); 4044 4045 // Attempt at work stealing from other task's queues. 4046 if (do_stealing && !has_aborted()) { 4047 // We have not aborted. This means that we have finished all that 4048 // we could. Let's try to do some stealing... 4049 4050 // We cannot check whether the global stack is empty, since other 4051 // tasks might be pushing objects to it concurrently. 4052 assert(_cm->out_of_regions() && _task_queue->size() == 0, 4053 "only way to reach here"); 4054 4055 if (_cm->verbose_low()) { 4056 gclog_or_tty->print_cr("[%u] starting to steal", _worker_id); 4057 } 4058 4059 while (!has_aborted()) { 4060 oop obj; 4061 statsOnly( ++_steal_attempts ); 4062 4063 if (_cm->try_stealing(_worker_id, &_hash_seed, obj)) { 4064 if (_cm->verbose_medium()) { 4065 gclog_or_tty->print_cr("[%u] stolen "PTR_FORMAT" successfully", 4066 _worker_id, p2i((void*) obj)); 4067 } 4068 4069 statsOnly( ++_steals ); 4070 4071 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), 4072 "any stolen object should be marked"); 4073 scan_object(obj); 4074 4075 // And since we're towards the end, let's totally drain the 4076 // local queue and global stack. 4077 drain_local_queue(false); 4078 drain_global_stack(false); 4079 } else { 4080 break; 4081 } 4082 } 4083 } 4084 4085 // If we are about to wrap up and go into termination, check if we 4086 // should raise the overflow flag. 4087 if (do_termination && !has_aborted()) { 4088 if (_cm->force_overflow()->should_force()) { 4089 _cm->set_has_overflown(); 4090 regular_clock_call(); 4091 } 4092 } 4093 4094 // We still haven't aborted. Now, let's try to get into the 4095 // termination protocol. 4096 if (do_termination && !has_aborted()) { 4097 // We cannot check whether the global stack is empty, since other 4098 // tasks might be concurrently pushing objects on it. 4099 // Separated the asserts so that we know which one fires. 4100 assert(_cm->out_of_regions(), "only way to reach here"); 4101 assert(_task_queue->size() == 0, "only way to reach here"); 4102 4103 if (_cm->verbose_low()) { 4104 gclog_or_tty->print_cr("[%u] starting termination protocol", _worker_id); 4105 } 4106 4107 _termination_start_time_ms = os::elapsedVTime() * 1000.0; 4108 4109 // The CMTask class also extends the TerminatorTerminator class, 4110 // hence its should_exit_termination() method will also decide 4111 // whether to exit the termination protocol or not. 4112 bool finished = (is_serial || 4113 _cm->terminator()->offer_termination(this)); 4114 double termination_end_time_ms = os::elapsedVTime() * 1000.0; 4115 _termination_time_ms += 4116 termination_end_time_ms - _termination_start_time_ms; 4117 4118 if (finished) { 4119 // We're all done. 4120 4121 if (_worker_id == 0) { 4122 // let's allow task 0 to do this 4123 if (concurrent()) { 4124 assert(_cm->concurrent_marking_in_progress(), "invariant"); 4125 // we need to set this to false before the next 4126 // safepoint. This way we ensure that the marking phase 4127 // doesn't observe any more heap expansions. 4128 _cm->clear_concurrent_marking_in_progress(); 4129 } 4130 } 4131 4132 // We can now guarantee that the global stack is empty, since 4133 // all other tasks have finished. We separated the guarantees so 4134 // that, if a condition is false, we can immediately find out 4135 // which one. 4136 guarantee(_cm->out_of_regions(), "only way to reach here"); 4137 guarantee(_cm->mark_stack_empty(), "only way to reach here"); 4138 guarantee(_task_queue->size() == 0, "only way to reach here"); 4139 guarantee(!_cm->has_overflown(), "only way to reach here"); 4140 guarantee(!_cm->mark_stack_overflow(), "only way to reach here"); 4141 4142 if (_cm->verbose_low()) { 4143 gclog_or_tty->print_cr("[%u] all tasks terminated", _worker_id); 4144 } 4145 } else { 4146 // Apparently there's more work to do. Let's abort this task. It 4147 // will restart it and we can hopefully find more things to do. 4148 4149 if (_cm->verbose_low()) { 4150 gclog_or_tty->print_cr("[%u] apparently there is more work to do", 4151 _worker_id); 4152 } 4153 4154 set_has_aborted(); 4155 statsOnly( ++_aborted_termination ); 4156 } 4157 } 4158 4159 // Mainly for debugging purposes to make sure that a pointer to the 4160 // closure which was statically allocated in this frame doesn't 4161 // escape it by accident. 4162 set_cm_oop_closure(NULL); 4163 double end_time_ms = os::elapsedVTime() * 1000.0; 4164 double elapsed_time_ms = end_time_ms - _start_time_ms; 4165 // Update the step history. 4166 _step_times_ms.add(elapsed_time_ms); 4167 4168 if (has_aborted()) { 4169 // The task was aborted for some reason. 4170 4171 statsOnly( ++_aborted ); 4172 4173 if (_has_timed_out) { 4174 double diff_ms = elapsed_time_ms - _time_target_ms; 4175 // Keep statistics of how well we did with respect to hitting 4176 // our target only if we actually timed out (if we aborted for 4177 // other reasons, then the results might get skewed). 4178 _marking_step_diffs_ms.add(diff_ms); 4179 } 4180 4181 if (_cm->has_overflown()) { 4182 // This is the interesting one. We aborted because a global 4183 // overflow was raised. This means we have to restart the 4184 // marking phase and start iterating over regions. However, in 4185 // order to do this we have to make sure that all tasks stop 4186 // what they are doing and re-initialize in a safe manner. We 4187 // will achieve this with the use of two barrier sync points. 4188 4189 if (_cm->verbose_low()) { 4190 gclog_or_tty->print_cr("[%u] detected overflow", _worker_id); 4191 } 4192 4193 if (!is_serial) { 4194 // We only need to enter the sync barrier if being called 4195 // from a parallel context 4196 _cm->enter_first_sync_barrier(_worker_id); 4197 4198 // When we exit this sync barrier we know that all tasks have 4199 // stopped doing marking work. So, it's now safe to 4200 // re-initialize our data structures. At the end of this method, 4201 // task 0 will clear the global data structures. 4202 } 4203 4204 statsOnly( ++_aborted_overflow ); 4205 4206 // We clear the local state of this task... 4207 clear_region_fields(); 4208 4209 if (!is_serial) { 4210 // ...and enter the second barrier. 4211 _cm->enter_second_sync_barrier(_worker_id); 4212 } 4213 // At this point, if we're during the concurrent phase of 4214 // marking, everything has been re-initialized and we're 4215 // ready to restart. 4216 } 4217 4218 if (_cm->verbose_low()) { 4219 gclog_or_tty->print_cr("[%u] <<<<<<<<<< ABORTING, target = %1.2lfms, " 4220 "elapsed = %1.2lfms <<<<<<<<<<", 4221 _worker_id, _time_target_ms, elapsed_time_ms); 4222 if (_cm->has_aborted()) { 4223 gclog_or_tty->print_cr("[%u] ========== MARKING ABORTED ==========", 4224 _worker_id); 4225 } 4226 } 4227 } else { 4228 if (_cm->verbose_low()) { 4229 gclog_or_tty->print_cr("[%u] <<<<<<<<<< FINISHED, target = %1.2lfms, " 4230 "elapsed = %1.2lfms <<<<<<<<<<", 4231 _worker_id, _time_target_ms, elapsed_time_ms); 4232 } 4233 } 4234 4235 _claimed = false; 4236 } 4237 4238 CMTask::CMTask(uint worker_id, 4239 ConcurrentMark* cm, 4240 size_t* marked_bytes, 4241 BitMap* card_bm, 4242 CMTaskQueue* task_queue, 4243 CMTaskQueueSet* task_queues) 4244 : _g1h(G1CollectedHeap::heap()), 4245 _worker_id(worker_id), _cm(cm), 4246 _claimed(false), 4247 _nextMarkBitMap(NULL), _hash_seed(17), 4248 _task_queue(task_queue), 4249 _task_queues(task_queues), 4250 _cm_oop_closure(NULL), 4251 _marked_bytes_array(marked_bytes), 4252 _card_bm(card_bm) { 4253 guarantee(task_queue != NULL, "invariant"); 4254 guarantee(task_queues != NULL, "invariant"); 4255 4256 statsOnly( _clock_due_to_scanning = 0; 4257 _clock_due_to_marking = 0 ); 4258 4259 _marking_step_diffs_ms.add(0.5); 4260 } 4261 4262 // These are formatting macros that are used below to ensure 4263 // consistent formatting. The *_H_* versions are used to format the 4264 // header for a particular value and they should be kept consistent 4265 // with the corresponding macro. Also note that most of the macros add 4266 // the necessary white space (as a prefix) which makes them a bit 4267 // easier to compose. 4268 4269 // All the output lines are prefixed with this string to be able to 4270 // identify them easily in a large log file. 4271 #define G1PPRL_LINE_PREFIX "###" 4272 4273 #define G1PPRL_ADDR_BASE_FORMAT " "PTR_FORMAT"-"PTR_FORMAT 4274 #ifdef _LP64 4275 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s" 4276 #else // _LP64 4277 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s" 4278 #endif // _LP64 4279 4280 // For per-region info 4281 #define G1PPRL_TYPE_FORMAT " %-4s" 4282 #define G1PPRL_TYPE_H_FORMAT " %4s" 4283 #define G1PPRL_BYTE_FORMAT " "SIZE_FORMAT_W(9) 4284 #define G1PPRL_BYTE_H_FORMAT " %9s" 4285 #define G1PPRL_DOUBLE_FORMAT " %14.1f" 4286 #define G1PPRL_DOUBLE_H_FORMAT " %14s" 4287 4288 // For summary info 4289 #define G1PPRL_SUM_ADDR_FORMAT(tag) " "tag":"G1PPRL_ADDR_BASE_FORMAT 4290 #define G1PPRL_SUM_BYTE_FORMAT(tag) " "tag": "SIZE_FORMAT 4291 #define G1PPRL_SUM_MB_FORMAT(tag) " "tag": %1.2f MB" 4292 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag)" / %1.2f %%" 4293 4294 G1PrintRegionLivenessInfoClosure:: 4295 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name) 4296 : _out(out), 4297 _total_used_bytes(0), _total_capacity_bytes(0), 4298 _total_prev_live_bytes(0), _total_next_live_bytes(0), 4299 _hum_used_bytes(0), _hum_capacity_bytes(0), 4300 _hum_prev_live_bytes(0), _hum_next_live_bytes(0), 4301 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) { 4302 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4303 MemRegion g1_reserved = g1h->g1_reserved(); 4304 double now = os::elapsedTime(); 4305 4306 // Print the header of the output. 4307 _out->cr(); 4308 _out->print_cr(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now); 4309 _out->print_cr(G1PPRL_LINE_PREFIX" HEAP" 4310 G1PPRL_SUM_ADDR_FORMAT("reserved") 4311 G1PPRL_SUM_BYTE_FORMAT("region-size"), 4312 p2i(g1_reserved.start()), p2i(g1_reserved.end()), 4313 HeapRegion::GrainBytes); 4314 _out->print_cr(G1PPRL_LINE_PREFIX); 4315 _out->print_cr(G1PPRL_LINE_PREFIX 4316 G1PPRL_TYPE_H_FORMAT 4317 G1PPRL_ADDR_BASE_H_FORMAT 4318 G1PPRL_BYTE_H_FORMAT 4319 G1PPRL_BYTE_H_FORMAT 4320 G1PPRL_BYTE_H_FORMAT 4321 G1PPRL_DOUBLE_H_FORMAT 4322 G1PPRL_BYTE_H_FORMAT 4323 G1PPRL_BYTE_H_FORMAT, 4324 "type", "address-range", 4325 "used", "prev-live", "next-live", "gc-eff", 4326 "remset", "code-roots"); 4327 _out->print_cr(G1PPRL_LINE_PREFIX 4328 G1PPRL_TYPE_H_FORMAT 4329 G1PPRL_ADDR_BASE_H_FORMAT 4330 G1PPRL_BYTE_H_FORMAT 4331 G1PPRL_BYTE_H_FORMAT 4332 G1PPRL_BYTE_H_FORMAT 4333 G1PPRL_DOUBLE_H_FORMAT 4334 G1PPRL_BYTE_H_FORMAT 4335 G1PPRL_BYTE_H_FORMAT, 4336 "", "", 4337 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)", 4338 "(bytes)", "(bytes)"); 4339 } 4340 4341 // It takes as a parameter a reference to one of the _hum_* fields, it 4342 // deduces the corresponding value for a region in a humongous region 4343 // series (either the region size, or what's left if the _hum_* field 4344 // is < the region size), and updates the _hum_* field accordingly. 4345 size_t G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* hum_bytes) { 4346 size_t bytes = 0; 4347 // The > 0 check is to deal with the prev and next live bytes which 4348 // could be 0. 4349 if (*hum_bytes > 0) { 4350 bytes = MIN2(HeapRegion::GrainBytes, *hum_bytes); 4351 *hum_bytes -= bytes; 4352 } 4353 return bytes; 4354 } 4355 4356 // It deduces the values for a region in a humongous region series 4357 // from the _hum_* fields and updates those accordingly. It assumes 4358 // that that _hum_* fields have already been set up from the "starts 4359 // humongous" region and we visit the regions in address order. 4360 void G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* used_bytes, 4361 size_t* capacity_bytes, 4362 size_t* prev_live_bytes, 4363 size_t* next_live_bytes) { 4364 assert(_hum_used_bytes > 0 && _hum_capacity_bytes > 0, "pre-condition"); 4365 *used_bytes = get_hum_bytes(&_hum_used_bytes); 4366 *capacity_bytes = get_hum_bytes(&_hum_capacity_bytes); 4367 *prev_live_bytes = get_hum_bytes(&_hum_prev_live_bytes); 4368 *next_live_bytes = get_hum_bytes(&_hum_next_live_bytes); 4369 } 4370 4371 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) { 4372 const char* type = r->get_type_str(); 4373 HeapWord* bottom = r->bottom(); 4374 HeapWord* end = r->end(); 4375 size_t capacity_bytes = r->capacity(); 4376 size_t used_bytes = r->used(); 4377 size_t prev_live_bytes = r->live_bytes(); 4378 size_t next_live_bytes = r->next_live_bytes(); 4379 double gc_eff = r->gc_efficiency(); 4380 size_t remset_bytes = r->rem_set()->mem_size(); 4381 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size(); 4382 4383 if (r->is_starts_humongous()) { 4384 assert(_hum_used_bytes == 0 && _hum_capacity_bytes == 0 && 4385 _hum_prev_live_bytes == 0 && _hum_next_live_bytes == 0, 4386 "they should have been zeroed after the last time we used them"); 4387 // Set up the _hum_* fields. 4388 _hum_capacity_bytes = capacity_bytes; 4389 _hum_used_bytes = used_bytes; 4390 _hum_prev_live_bytes = prev_live_bytes; 4391 _hum_next_live_bytes = next_live_bytes; 4392 get_hum_bytes(&used_bytes, &capacity_bytes, 4393 &prev_live_bytes, &next_live_bytes); 4394 end = bottom + HeapRegion::GrainWords; 4395 } else if (r->is_continues_humongous()) { 4396 get_hum_bytes(&used_bytes, &capacity_bytes, 4397 &prev_live_bytes, &next_live_bytes); 4398 assert(end == bottom + HeapRegion::GrainWords, "invariant"); 4399 } 4400 4401 _total_used_bytes += used_bytes; 4402 _total_capacity_bytes += capacity_bytes; 4403 _total_prev_live_bytes += prev_live_bytes; 4404 _total_next_live_bytes += next_live_bytes; 4405 _total_remset_bytes += remset_bytes; 4406 _total_strong_code_roots_bytes += strong_code_roots_bytes; 4407 4408 // Print a line for this particular region. 4409 _out->print_cr(G1PPRL_LINE_PREFIX 4410 G1PPRL_TYPE_FORMAT 4411 G1PPRL_ADDR_BASE_FORMAT 4412 G1PPRL_BYTE_FORMAT 4413 G1PPRL_BYTE_FORMAT 4414 G1PPRL_BYTE_FORMAT 4415 G1PPRL_DOUBLE_FORMAT 4416 G1PPRL_BYTE_FORMAT 4417 G1PPRL_BYTE_FORMAT, 4418 type, p2i(bottom), p2i(end), 4419 used_bytes, prev_live_bytes, next_live_bytes, gc_eff, 4420 remset_bytes, strong_code_roots_bytes); 4421 4422 return false; 4423 } 4424 4425 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() { 4426 // add static memory usages to remembered set sizes 4427 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size(); 4428 // Print the footer of the output. 4429 _out->print_cr(G1PPRL_LINE_PREFIX); 4430 _out->print_cr(G1PPRL_LINE_PREFIX 4431 " SUMMARY" 4432 G1PPRL_SUM_MB_FORMAT("capacity") 4433 G1PPRL_SUM_MB_PERC_FORMAT("used") 4434 G1PPRL_SUM_MB_PERC_FORMAT("prev-live") 4435 G1PPRL_SUM_MB_PERC_FORMAT("next-live") 4436 G1PPRL_SUM_MB_FORMAT("remset") 4437 G1PPRL_SUM_MB_FORMAT("code-roots"), 4438 bytes_to_mb(_total_capacity_bytes), 4439 bytes_to_mb(_total_used_bytes), 4440 perc(_total_used_bytes, _total_capacity_bytes), 4441 bytes_to_mb(_total_prev_live_bytes), 4442 perc(_total_prev_live_bytes, _total_capacity_bytes), 4443 bytes_to_mb(_total_next_live_bytes), 4444 perc(_total_next_live_bytes, _total_capacity_bytes), 4445 bytes_to_mb(_total_remset_bytes), 4446 bytes_to_mb(_total_strong_code_roots_bytes)); 4447 _out->cr(); 4448 }