1 /* 2 * Copyright (c) 2001, 2014, 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_implementation/g1/concurrentMark.inline.hpp" 30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp" 31 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp" 32 #include "gc_implementation/g1/g1CollectorPolicy.hpp" 33 #include "gc_implementation/g1/g1ErgoVerbose.hpp" 34 #include "gc_implementation/g1/g1Log.hpp" 35 #include "gc_implementation/g1/g1OopClosures.inline.hpp" 36 #include "gc_implementation/g1/g1RemSet.hpp" 37 #include "gc_implementation/g1/heapRegion.inline.hpp" 38 #include "gc_implementation/g1/heapRegionManager.inline.hpp" 39 #include "gc_implementation/g1/heapRegionRemSet.hpp" 40 #include "gc_implementation/g1/heapRegionSet.inline.hpp" 41 #include "gc_implementation/shared/vmGCOperations.hpp" 42 #include "gc_implementation/shared/gcTimer.hpp" 43 #include "gc_implementation/shared/gcTrace.hpp" 44 #include "gc_implementation/shared/gcTraceTime.hpp" 45 #include "memory/allocation.hpp" 46 #include "memory/genOopClosures.inline.hpp" 47 #include "memory/referencePolicy.hpp" 48 #include "memory/resourceArea.hpp" 49 #include "oops/oop.inline.hpp" 50 #include "runtime/handles.inline.hpp" 51 #include "runtime/java.hpp" 52 #include "runtime/prefetch.inline.hpp" 53 #include "services/memTracker.hpp" 54 55 // Concurrent marking bit map wrapper 56 57 CMBitMapRO::CMBitMapRO(int shifter) : 58 _bm(), 59 _shifter(shifter) { 60 _bmStartWord = 0; 61 _bmWordSize = 0; 62 } 63 64 HeapWord* CMBitMapRO::getNextMarkedWordAddress(const HeapWord* addr, 65 const HeapWord* limit) const { 66 // First we must round addr *up* to a possible object boundary. 67 addr = (HeapWord*)align_size_up((intptr_t)addr, 68 HeapWordSize << _shifter); 69 size_t addrOffset = heapWordToOffset(addr); 70 if (limit == NULL) { 71 limit = _bmStartWord + _bmWordSize; 72 } 73 size_t limitOffset = heapWordToOffset(limit); 74 size_t nextOffset = _bm.get_next_one_offset(addrOffset, limitOffset); 75 HeapWord* nextAddr = offsetToHeapWord(nextOffset); 76 assert(nextAddr >= addr, "get_next_one postcondition"); 77 assert(nextAddr == limit || isMarked(nextAddr), 78 "get_next_one postcondition"); 79 return nextAddr; 80 } 81 82 HeapWord* CMBitMapRO::getNextUnmarkedWordAddress(const HeapWord* addr, 83 const HeapWord* limit) const { 84 size_t addrOffset = heapWordToOffset(addr); 85 if (limit == NULL) { 86 limit = _bmStartWord + _bmWordSize; 87 } 88 size_t limitOffset = heapWordToOffset(limit); 89 size_t nextOffset = _bm.get_next_zero_offset(addrOffset, limitOffset); 90 HeapWord* nextAddr = offsetToHeapWord(nextOffset); 91 assert(nextAddr >= addr, "get_next_one postcondition"); 92 assert(nextAddr == limit || !isMarked(nextAddr), 93 "get_next_one postcondition"); 94 return nextAddr; 95 } 96 97 int CMBitMapRO::heapWordDiffToOffsetDiff(size_t diff) const { 98 assert((diff & ((1 << _shifter) - 1)) == 0, "argument check"); 99 return (int) (diff >> _shifter); 100 } 101 102 #ifndef PRODUCT 103 bool CMBitMapRO::covers(MemRegion heap_rs) const { 104 // assert(_bm.map() == _virtual_space.low(), "map inconsistency"); 105 assert(((size_t)_bm.size() * ((size_t)1 << _shifter)) == _bmWordSize, 106 "size inconsistency"); 107 return _bmStartWord == (HeapWord*)(heap_rs.start()) && 108 _bmWordSize == heap_rs.word_size(); 109 } 110 #endif 111 112 void CMBitMapRO::print_on_error(outputStream* st, const char* prefix) const { 113 _bm.print_on_error(st, prefix); 114 } 115 116 size_t CMBitMap::compute_size(size_t heap_size) { 117 return ReservedSpace::allocation_align_size_up(heap_size / mark_distance()); 118 } 119 120 size_t CMBitMap::mark_distance() { 121 return MinObjAlignmentInBytes * BitsPerByte; 122 } 123 124 void CMBitMap::initialize(MemRegion heap, G1RegionToSpaceMapper* storage) { 125 _bmStartWord = heap.start(); 126 _bmWordSize = heap.word_size(); 127 128 _bm.set_map((BitMap::bm_word_t*) storage->reserved().start()); 129 _bm.set_size(_bmWordSize >> _shifter); 130 131 storage->set_mapping_changed_listener(&_listener); 132 } 133 134 void CMBitMapMappingChangedListener::on_commit(uint start_region, size_t num_regions, bool zero_filled) { 135 if (zero_filled) { 136 return; 137 } 138 // We need to clear the bitmap on commit, removing any existing information. 139 MemRegion mr(G1CollectedHeap::heap()->bottom_addr_for_region(start_region), num_regions * HeapRegion::GrainWords); 140 _bm->clearRange(mr); 141 } 142 143 // Closure used for clearing the given mark bitmap. 144 class ClearBitmapHRClosure : public HeapRegionClosure { 145 private: 146 ConcurrentMark* _cm; 147 CMBitMap* _bitmap; 148 bool _may_yield; // The closure may yield during iteration. If yielded, abort the iteration. 149 public: 150 ClearBitmapHRClosure(ConcurrentMark* cm, CMBitMap* bitmap, bool may_yield) : HeapRegionClosure(), _cm(cm), _bitmap(bitmap), _may_yield(may_yield) { 151 assert(!may_yield || cm != NULL, "CM must be non-NULL if this closure is expected to yield."); 152 } 153 154 virtual bool doHeapRegion(HeapRegion* r) { 155 size_t const chunk_size_in_words = M / HeapWordSize; 156 157 HeapWord* cur = r->bottom(); 158 HeapWord* const end = r->end(); 159 160 while (cur < end) { 161 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end)); 162 _bitmap->clearRange(mr); 163 164 cur += chunk_size_in_words; 165 166 // Abort iteration if after yielding the marking has been aborted. 167 if (_may_yield && _cm->do_yield_check() && _cm->has_aborted()) { 168 return true; 169 } 170 // Repeat the asserts from before the start of the closure. We will do them 171 // as asserts here to minimize their overhead on the product. However, we 172 // will have them as guarantees at the beginning / end of the bitmap 173 // clearing to get some checking in the product. 174 assert(!_may_yield || _cm->cmThread()->during_cycle(), "invariant"); 175 assert(!_may_yield || !G1CollectedHeap::heap()->mark_in_progress(), "invariant"); 176 } 177 178 return false; 179 } 180 }; 181 182 void CMBitMap::clearAll() { 183 ClearBitmapHRClosure cl(NULL, this, false /* may_yield */); 184 G1CollectedHeap::heap()->heap_region_iterate(&cl); 185 guarantee(cl.complete(), "Must have completed iteration."); 186 return; 187 } 188 189 void CMBitMap::markRange(MemRegion mr) { 190 mr.intersection(MemRegion(_bmStartWord, _bmWordSize)); 191 assert(!mr.is_empty(), "unexpected empty region"); 192 assert((offsetToHeapWord(heapWordToOffset(mr.end())) == 193 ((HeapWord *) mr.end())), 194 "markRange memory region end is not card aligned"); 195 // convert address range into offset range 196 _bm.at_put_range(heapWordToOffset(mr.start()), 197 heapWordToOffset(mr.end()), true); 198 } 199 200 void CMBitMap::clearRange(MemRegion mr) { 201 mr.intersection(MemRegion(_bmStartWord, _bmWordSize)); 202 assert(!mr.is_empty(), "unexpected empty region"); 203 // convert address range into offset range 204 _bm.at_put_range(heapWordToOffset(mr.start()), 205 heapWordToOffset(mr.end()), false); 206 } 207 208 MemRegion CMBitMap::getAndClearMarkedRegion(HeapWord* addr, 209 HeapWord* end_addr) { 210 HeapWord* start = getNextMarkedWordAddress(addr); 211 start = MIN2(start, end_addr); 212 HeapWord* end = getNextUnmarkedWordAddress(start); 213 end = MIN2(end, end_addr); 214 assert(start <= end, "Consistency check"); 215 MemRegion mr(start, end); 216 if (!mr.is_empty()) { 217 clearRange(mr); 218 } 219 return mr; 220 } 221 222 CMMarkStack::CMMarkStack(ConcurrentMark* cm) : 223 _base(NULL), _cm(cm) 224 #ifdef ASSERT 225 , _drain_in_progress(false) 226 , _drain_in_progress_yields(false) 227 #endif 228 {} 229 230 bool CMMarkStack::allocate(size_t capacity) { 231 // allocate a stack of the requisite depth 232 ReservedSpace rs(ReservedSpace::allocation_align_size_up(capacity * sizeof(oop))); 233 if (!rs.is_reserved()) { 234 warning("ConcurrentMark MarkStack allocation failure"); 235 return false; 236 } 237 MemTracker::record_virtual_memory_type((address)rs.base(), mtGC); 238 if (!_virtual_space.initialize(rs, rs.size())) { 239 warning("ConcurrentMark MarkStack backing store failure"); 240 // Release the virtual memory reserved for the marking stack 241 rs.release(); 242 return false; 243 } 244 assert(_virtual_space.committed_size() == rs.size(), 245 "Didn't reserve backing store for all of ConcurrentMark stack?"); 246 _base = (oop*) _virtual_space.low(); 247 setEmpty(); 248 _capacity = (jint) capacity; 249 _saved_index = -1; 250 _should_expand = false; 251 NOT_PRODUCT(_max_depth = 0); 252 return true; 253 } 254 255 void CMMarkStack::expand() { 256 // Called, during remark, if we've overflown the marking stack during marking. 257 assert(isEmpty(), "stack should been emptied while handling overflow"); 258 assert(_capacity <= (jint) MarkStackSizeMax, "stack bigger than permitted"); 259 // Clear expansion flag 260 _should_expand = false; 261 if (_capacity == (jint) MarkStackSizeMax) { 262 if (PrintGCDetails && Verbose) { 263 gclog_or_tty->print_cr(" (benign) Can't expand marking stack capacity, at max size limit"); 264 } 265 return; 266 } 267 // Double capacity if possible 268 jint new_capacity = MIN2(_capacity*2, (jint) MarkStackSizeMax); 269 // Do not give up existing stack until we have managed to 270 // get the double capacity that we desired. 271 ReservedSpace rs(ReservedSpace::allocation_align_size_up(new_capacity * 272 sizeof(oop))); 273 if (rs.is_reserved()) { 274 // Release the backing store associated with old stack 275 _virtual_space.release(); 276 // Reinitialize virtual space for new stack 277 if (!_virtual_space.initialize(rs, rs.size())) { 278 fatal("Not enough swap for expanded marking stack capacity"); 279 } 280 _base = (oop*)(_virtual_space.low()); 281 _index = 0; 282 _capacity = new_capacity; 283 } else { 284 if (PrintGCDetails && Verbose) { 285 // Failed to double capacity, continue; 286 gclog_or_tty->print(" (benign) Failed to expand marking stack capacity from " 287 SIZE_FORMAT"K to " SIZE_FORMAT"K", 288 _capacity / K, new_capacity / K); 289 } 290 } 291 } 292 293 void CMMarkStack::set_should_expand() { 294 // If we're resetting the marking state because of an 295 // marking stack overflow, record that we should, if 296 // possible, expand the stack. 297 _should_expand = _cm->has_overflown(); 298 } 299 300 CMMarkStack::~CMMarkStack() { 301 if (_base != NULL) { 302 _base = NULL; 303 _virtual_space.release(); 304 } 305 } 306 307 void CMMarkStack::par_push(oop ptr) { 308 while (true) { 309 if (isFull()) { 310 _overflow = true; 311 return; 312 } 313 // Otherwise... 314 jint index = _index; 315 jint next_index = index+1; 316 jint res = Atomic::cmpxchg(next_index, &_index, index); 317 if (res == index) { 318 _base[index] = ptr; 319 // Note that we don't maintain this atomically. We could, but it 320 // doesn't seem necessary. 321 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index)); 322 return; 323 } 324 // Otherwise, we need to try again. 325 } 326 } 327 328 void CMMarkStack::par_adjoin_arr(oop* ptr_arr, int n) { 329 while (true) { 330 if (isFull()) { 331 _overflow = true; 332 return; 333 } 334 // Otherwise... 335 jint index = _index; 336 jint next_index = index + n; 337 if (next_index > _capacity) { 338 _overflow = true; 339 return; 340 } 341 jint res = Atomic::cmpxchg(next_index, &_index, index); 342 if (res == index) { 343 for (int i = 0; i < n; i++) { 344 int ind = index + i; 345 assert(ind < _capacity, "By overflow test above."); 346 _base[ind] = ptr_arr[i]; 347 } 348 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index)); 349 return; 350 } 351 // Otherwise, we need to try again. 352 } 353 } 354 355 void CMMarkStack::par_push_arr(oop* ptr_arr, int n) { 356 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 357 jint start = _index; 358 jint next_index = start + n; 359 if (next_index > _capacity) { 360 _overflow = true; 361 return; 362 } 363 // Otherwise. 364 _index = next_index; 365 for (int i = 0; i < n; i++) { 366 int ind = start + i; 367 assert(ind < _capacity, "By overflow test above."); 368 _base[ind] = ptr_arr[i]; 369 } 370 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index)); 371 } 372 373 bool CMMarkStack::par_pop_arr(oop* ptr_arr, int max, int* n) { 374 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 375 jint index = _index; 376 if (index == 0) { 377 *n = 0; 378 return false; 379 } else { 380 int k = MIN2(max, index); 381 jint new_ind = index - k; 382 for (int j = 0; j < k; j++) { 383 ptr_arr[j] = _base[new_ind + j]; 384 } 385 _index = new_ind; 386 *n = k; 387 return true; 388 } 389 } 390 391 template<class OopClosureClass> 392 bool CMMarkStack::drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after) { 393 assert(!_drain_in_progress || !_drain_in_progress_yields || yield_after 394 || SafepointSynchronize::is_at_safepoint(), 395 "Drain recursion must be yield-safe."); 396 bool res = true; 397 debug_only(_drain_in_progress = true); 398 debug_only(_drain_in_progress_yields = yield_after); 399 while (!isEmpty()) { 400 oop newOop = pop(); 401 assert(G1CollectedHeap::heap()->is_in_reserved(newOop), "Bad pop"); 402 assert(newOop->is_oop(), "Expected an oop"); 403 assert(bm == NULL || bm->isMarked((HeapWord*)newOop), 404 "only grey objects on this stack"); 405 newOop->oop_iterate(cl); 406 if (yield_after && _cm->do_yield_check()) { 407 res = false; 408 break; 409 } 410 } 411 debug_only(_drain_in_progress = false); 412 return res; 413 } 414 415 void CMMarkStack::note_start_of_gc() { 416 assert(_saved_index == -1, 417 "note_start_of_gc()/end_of_gc() bracketed incorrectly"); 418 _saved_index = _index; 419 } 420 421 void CMMarkStack::note_end_of_gc() { 422 // This is intentionally a guarantee, instead of an assert. If we 423 // accidentally add something to the mark stack during GC, it 424 // will be a correctness issue so it's better if we crash. we'll 425 // only check this once per GC anyway, so it won't be a performance 426 // issue in any way. 427 guarantee(_saved_index == _index, 428 err_msg("saved index: %d index: %d", _saved_index, _index)); 429 _saved_index = -1; 430 } 431 432 void CMMarkStack::oops_do(OopClosure* f) { 433 assert(_saved_index == _index, 434 err_msg("saved index: %d index: %d", _saved_index, _index)); 435 for (int i = 0; i < _index; i += 1) { 436 f->do_oop(&_base[i]); 437 } 438 } 439 440 CMRootRegions::CMRootRegions() : 441 _young_list(NULL), _cm(NULL), _scan_in_progress(false), 442 _should_abort(false), _next_survivor(NULL) { } 443 444 void CMRootRegions::init(G1CollectedHeap* g1h, ConcurrentMark* cm) { 445 _young_list = g1h->young_list(); 446 _cm = cm; 447 } 448 449 void CMRootRegions::prepare_for_scan() { 450 assert(!scan_in_progress(), "pre-condition"); 451 452 // Currently, only survivors can be root regions. 453 assert(_next_survivor == NULL, "pre-condition"); 454 _next_survivor = _young_list->first_survivor_region(); 455 _scan_in_progress = (_next_survivor != NULL); 456 _should_abort = false; 457 } 458 459 HeapRegion* CMRootRegions::claim_next() { 460 if (_should_abort) { 461 // If someone has set the should_abort flag, we return NULL to 462 // force the caller to bail out of their loop. 463 return NULL; 464 } 465 466 // Currently, only survivors can be root regions. 467 HeapRegion* res = _next_survivor; 468 if (res != NULL) { 469 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 470 // Read it again in case it changed while we were waiting for the lock. 471 res = _next_survivor; 472 if (res != NULL) { 473 if (res == _young_list->last_survivor_region()) { 474 // We just claimed the last survivor so store NULL to indicate 475 // that we're done. 476 _next_survivor = NULL; 477 } else { 478 _next_survivor = res->get_next_young_region(); 479 } 480 } else { 481 // Someone else claimed the last survivor while we were trying 482 // to take the lock so nothing else to do. 483 } 484 } 485 assert(res == NULL || res->is_survivor(), "post-condition"); 486 487 return res; 488 } 489 490 void CMRootRegions::scan_finished() { 491 assert(scan_in_progress(), "pre-condition"); 492 493 // Currently, only survivors can be root regions. 494 if (!_should_abort) { 495 assert(_next_survivor == NULL, "we should have claimed all survivors"); 496 } 497 _next_survivor = NULL; 498 499 { 500 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 501 _scan_in_progress = false; 502 RootRegionScan_lock->notify_all(); 503 } 504 } 505 506 bool CMRootRegions::wait_until_scan_finished() { 507 if (!scan_in_progress()) return false; 508 509 { 510 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 511 while (scan_in_progress()) { 512 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag); 513 } 514 } 515 return true; 516 } 517 518 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 519 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 520 #endif // _MSC_VER 521 522 uint ConcurrentMark::scale_parallel_threads(uint n_par_threads) { 523 return MAX2((n_par_threads + 2) / 4, 1U); 524 } 525 526 ConcurrentMark::ConcurrentMark(G1CollectedHeap* g1h, G1RegionToSpaceMapper* prev_bitmap_storage, G1RegionToSpaceMapper* next_bitmap_storage) : 527 _g1h(g1h), 528 _markBitMap1(), 529 _markBitMap2(), 530 _parallel_marking_threads(0), 531 _max_parallel_marking_threads(0), 532 _sleep_factor(0.0), 533 _marking_task_overhead(1.0), 534 _cleanup_sleep_factor(0.0), 535 _cleanup_task_overhead(1.0), 536 _cleanup_list("Cleanup List"), 537 _region_bm((BitMap::idx_t)(g1h->max_regions()), false /* in_resource_area*/), 538 _card_bm((g1h->reserved_region().byte_size() + CardTableModRefBS::card_size - 1) >> 539 CardTableModRefBS::card_shift, 540 false /* in_resource_area*/), 541 542 _prevMarkBitMap(&_markBitMap1), 543 _nextMarkBitMap(&_markBitMap2), 544 545 _markStack(this), 546 // _finger set in set_non_marking_state 547 548 _max_worker_id(MAX2((uint)ParallelGCThreads, 1U)), 549 // _active_tasks set in set_non_marking_state 550 // _tasks set inside the constructor 551 _task_queues(new CMTaskQueueSet((int) _max_worker_id)), 552 _terminator(ParallelTaskTerminator((int) _max_worker_id, _task_queues)), 553 554 _has_overflown(false), 555 _concurrent(false), 556 _has_aborted(false), 557 _aborted_gc_id(GCId::undefined()), 558 _restart_for_overflow(false), 559 _concurrent_marking_in_progress(false), 560 561 // _verbose_level set below 562 563 _init_times(), 564 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(), 565 _cleanup_times(), 566 _total_counting_time(0.0), 567 _total_rs_scrub_time(0.0), 568 569 _parallel_workers(NULL), 570 571 _count_card_bitmaps(NULL), 572 _count_marked_bytes(NULL), 573 _completed_initialization(false) { 574 CMVerboseLevel verbose_level = (CMVerboseLevel) G1MarkingVerboseLevel; 575 if (verbose_level < no_verbose) { 576 verbose_level = no_verbose; 577 } 578 if (verbose_level > high_verbose) { 579 verbose_level = high_verbose; 580 } 581 _verbose_level = verbose_level; 582 583 if (verbose_low()) { 584 gclog_or_tty->print_cr("[global] init, heap start = "PTR_FORMAT", " 585 "heap end = " INTPTR_FORMAT, p2i(_heap_start), p2i(_heap_end)); 586 } 587 588 _markBitMap1.initialize(g1h->reserved_region(), prev_bitmap_storage); 589 _markBitMap2.initialize(g1h->reserved_region(), next_bitmap_storage); 590 591 // Create & start a ConcurrentMark thread. 592 _cmThread = new ConcurrentMarkThread(this); 593 assert(cmThread() != NULL, "CM Thread should have been created"); 594 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm"); 595 if (_cmThread->osthread() == NULL) { 596 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread"); 597 } 598 599 assert(CGC_lock != NULL, "Where's the CGC_lock?"); 600 assert(_markBitMap1.covers(g1h->reserved_region()), "_markBitMap1 inconsistency"); 601 assert(_markBitMap2.covers(g1h->reserved_region()), "_markBitMap2 inconsistency"); 602 603 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set(); 604 satb_qs.set_buffer_size(G1SATBBufferSize); 605 606 _root_regions.init(_g1h, this); 607 608 if (ConcGCThreads > ParallelGCThreads) { 609 warning("Can't have more ConcGCThreads (" UINTX_FORMAT ") " 610 "than ParallelGCThreads (" UINTX_FORMAT ").", 611 ConcGCThreads, ParallelGCThreads); 612 return; 613 } 614 if (ParallelGCThreads == 0) { 615 // if we are not running with any parallel GC threads we will not 616 // spawn any marking threads either 617 _parallel_marking_threads = 0; 618 _max_parallel_marking_threads = 0; 619 _sleep_factor = 0.0; 620 _marking_task_overhead = 1.0; 621 } else { 622 if (!FLAG_IS_DEFAULT(ConcGCThreads) && ConcGCThreads > 0) { 623 // Note: ConcGCThreads has precedence over G1MarkingOverheadPercent 624 // if both are set 625 _sleep_factor = 0.0; 626 _marking_task_overhead = 1.0; 627 } else if (G1MarkingOverheadPercent > 0) { 628 // We will calculate the number of parallel marking threads based 629 // on a target overhead with respect to the soft real-time goal 630 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0; 631 double overall_cm_overhead = 632 (double) MaxGCPauseMillis * marking_overhead / 633 (double) GCPauseIntervalMillis; 634 double cpu_ratio = 1.0 / (double) os::processor_count(); 635 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio); 636 double marking_task_overhead = 637 overall_cm_overhead / marking_thread_num * 638 (double) os::processor_count(); 639 double sleep_factor = 640 (1.0 - marking_task_overhead) / marking_task_overhead; 641 642 FLAG_SET_ERGO(uintx, ConcGCThreads, (uint) marking_thread_num); 643 _sleep_factor = sleep_factor; 644 _marking_task_overhead = marking_task_overhead; 645 } else { 646 // Calculate the number of parallel marking threads by scaling 647 // the number of parallel GC threads. 648 uint marking_thread_num = scale_parallel_threads((uint) ParallelGCThreads); 649 FLAG_SET_ERGO(uintx, ConcGCThreads, marking_thread_num); 650 _sleep_factor = 0.0; 651 _marking_task_overhead = 1.0; 652 } 653 654 assert(ConcGCThreads > 0, "Should have been set"); 655 _parallel_marking_threads = (uint) ConcGCThreads; 656 _max_parallel_marking_threads = _parallel_marking_threads; 657 658 if (parallel_marking_threads() > 1) { 659 _cleanup_task_overhead = 1.0; 660 } else { 661 _cleanup_task_overhead = marking_task_overhead(); 662 } 663 _cleanup_sleep_factor = 664 (1.0 - cleanup_task_overhead()) / cleanup_task_overhead(); 665 666 #if 0 667 gclog_or_tty->print_cr("Marking Threads %d", parallel_marking_threads()); 668 gclog_or_tty->print_cr("CM Marking Task Overhead %1.4lf", marking_task_overhead()); 669 gclog_or_tty->print_cr("CM Sleep Factor %1.4lf", sleep_factor()); 670 gclog_or_tty->print_cr("CL Marking Task Overhead %1.4lf", cleanup_task_overhead()); 671 gclog_or_tty->print_cr("CL Sleep Factor %1.4lf", cleanup_sleep_factor()); 672 #endif 673 674 guarantee(parallel_marking_threads() > 0, "peace of mind"); 675 _parallel_workers = new FlexibleWorkGang("G1 Parallel Marking Threads", 676 _max_parallel_marking_threads, false, true); 677 if (_parallel_workers == NULL) { 678 vm_exit_during_initialization("Failed necessary allocation."); 679 } else { 680 _parallel_workers->initialize_workers(); 681 } 682 } 683 684 if (FLAG_IS_DEFAULT(MarkStackSize)) { 685 uintx mark_stack_size = 686 MIN2(MarkStackSizeMax, 687 MAX2(MarkStackSize, (uintx) (parallel_marking_threads() * TASKQUEUE_SIZE))); 688 // Verify that the calculated value for MarkStackSize is in range. 689 // It would be nice to use the private utility routine from Arguments. 690 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) { 691 warning("Invalid value calculated for MarkStackSize (" UINTX_FORMAT "): " 692 "must be between " UINTX_FORMAT " and " UINTX_FORMAT, 693 mark_stack_size, (uintx) 1, MarkStackSizeMax); 694 return; 695 } 696 FLAG_SET_ERGO(uintx, MarkStackSize, mark_stack_size); 697 } else { 698 // Verify MarkStackSize is in range. 699 if (FLAG_IS_CMDLINE(MarkStackSize)) { 700 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) { 701 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) { 702 warning("Invalid value specified for MarkStackSize (" UINTX_FORMAT "): " 703 "must be between " UINTX_FORMAT " and " UINTX_FORMAT, 704 MarkStackSize, (uintx) 1, MarkStackSizeMax); 705 return; 706 } 707 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) { 708 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) { 709 warning("Invalid value specified for MarkStackSize (" UINTX_FORMAT ")" 710 " or for MarkStackSizeMax (" UINTX_FORMAT ")", 711 MarkStackSize, MarkStackSizeMax); 712 return; 713 } 714 } 715 } 716 } 717 718 if (!_markStack.allocate(MarkStackSize)) { 719 warning("Failed to allocate CM marking stack"); 720 return; 721 } 722 723 _tasks = NEW_C_HEAP_ARRAY(CMTask*, _max_worker_id, mtGC); 724 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_worker_id, mtGC); 725 726 _count_card_bitmaps = NEW_C_HEAP_ARRAY(BitMap, _max_worker_id, mtGC); 727 _count_marked_bytes = NEW_C_HEAP_ARRAY(size_t*, _max_worker_id, mtGC); 728 729 BitMap::idx_t card_bm_size = _card_bm.size(); 730 731 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail 732 _active_tasks = _max_worker_id; 733 734 size_t max_regions = (size_t) _g1h->max_regions(); 735 for (uint i = 0; i < _max_worker_id; ++i) { 736 CMTaskQueue* task_queue = new CMTaskQueue(); 737 task_queue->initialize(); 738 _task_queues->register_queue(i, task_queue); 739 740 _count_card_bitmaps[i] = BitMap(card_bm_size, false); 741 _count_marked_bytes[i] = NEW_C_HEAP_ARRAY(size_t, max_regions, mtGC); 742 743 _tasks[i] = new CMTask(i, this, 744 _count_marked_bytes[i], 745 &_count_card_bitmaps[i], 746 task_queue, _task_queues); 747 748 _accum_task_vtime[i] = 0.0; 749 } 750 751 // Calculate the card number for the bottom of the heap. Used 752 // in biasing indexes into the accounting card bitmaps. 753 _heap_bottom_card_num = 754 intptr_t(uintptr_t(_g1h->reserved_region().start()) >> 755 CardTableModRefBS::card_shift); 756 757 // Clear all the liveness counting data 758 clear_all_count_data(); 759 760 // so that the call below can read a sensible value 761 _heap_start = g1h->reserved_region().start(); 762 set_non_marking_state(); 763 _completed_initialization = true; 764 } 765 766 void ConcurrentMark::reset() { 767 // Starting values for these two. This should be called in a STW 768 // phase. 769 MemRegion reserved = _g1h->g1_reserved(); 770 _heap_start = reserved.start(); 771 _heap_end = reserved.end(); 772 773 // Separated the asserts so that we know which one fires. 774 assert(_heap_start != NULL, "heap bounds should look ok"); 775 assert(_heap_end != NULL, "heap bounds should look ok"); 776 assert(_heap_start < _heap_end, "heap bounds should look ok"); 777 778 // Reset all the marking data structures and any necessary flags 779 reset_marking_state(); 780 781 if (verbose_low()) { 782 gclog_or_tty->print_cr("[global] resetting"); 783 } 784 785 // We do reset all of them, since different phases will use 786 // different number of active threads. So, it's easiest to have all 787 // of them ready. 788 for (uint i = 0; i < _max_worker_id; ++i) { 789 _tasks[i]->reset(_nextMarkBitMap); 790 } 791 792 // we need this to make sure that the flag is on during the evac 793 // pause with initial mark piggy-backed 794 set_concurrent_marking_in_progress(); 795 } 796 797 798 void ConcurrentMark::reset_marking_state(bool clear_overflow) { 799 _markStack.set_should_expand(); 800 _markStack.setEmpty(); // Also clears the _markStack overflow flag 801 if (clear_overflow) { 802 clear_has_overflown(); 803 } else { 804 assert(has_overflown(), "pre-condition"); 805 } 806 _finger = _heap_start; 807 808 for (uint i = 0; i < _max_worker_id; ++i) { 809 CMTaskQueue* queue = _task_queues->queue(i); 810 queue->set_empty(); 811 } 812 } 813 814 void ConcurrentMark::set_concurrency(uint active_tasks) { 815 assert(active_tasks <= _max_worker_id, "we should not have more"); 816 817 _active_tasks = active_tasks; 818 // Need to update the three data structures below according to the 819 // number of active threads for this phase. 820 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues); 821 _first_overflow_barrier_sync.set_n_workers((int) active_tasks); 822 _second_overflow_barrier_sync.set_n_workers((int) active_tasks); 823 } 824 825 void ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) { 826 set_concurrency(active_tasks); 827 828 _concurrent = concurrent; 829 // We propagate this to all tasks, not just the active ones. 830 for (uint i = 0; i < _max_worker_id; ++i) 831 _tasks[i]->set_concurrent(concurrent); 832 833 if (concurrent) { 834 set_concurrent_marking_in_progress(); 835 } else { 836 // We currently assume that the concurrent flag has been set to 837 // false before we start remark. At this point we should also be 838 // in a STW phase. 839 assert(!concurrent_marking_in_progress(), "invariant"); 840 assert(out_of_regions(), 841 err_msg("only way to get here: _finger: "PTR_FORMAT", _heap_end: "PTR_FORMAT, 842 p2i(_finger), p2i(_heap_end))); 843 } 844 } 845 846 void ConcurrentMark::set_non_marking_state() { 847 // We set the global marking state to some default values when we're 848 // not doing marking. 849 reset_marking_state(); 850 _active_tasks = 0; 851 clear_concurrent_marking_in_progress(); 852 } 853 854 ConcurrentMark::~ConcurrentMark() { 855 // The ConcurrentMark instance is never freed. 856 ShouldNotReachHere(); 857 } 858 859 void ConcurrentMark::clearNextBitmap() { 860 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 861 862 // Make sure that the concurrent mark thread looks to still be in 863 // the current cycle. 864 guarantee(cmThread()->during_cycle(), "invariant"); 865 866 // We are finishing up the current cycle by clearing the next 867 // marking bitmap and getting it ready for the next cycle. During 868 // this time no other cycle can start. So, let's make sure that this 869 // is the case. 870 guarantee(!g1h->mark_in_progress(), "invariant"); 871 872 ClearBitmapHRClosure cl(this, _nextMarkBitMap, true /* may_yield */); 873 g1h->heap_region_iterate(&cl); 874 875 // Clear the liveness counting data. If the marking has been aborted, the abort() 876 // call already did that. 877 if (cl.complete()) { 878 clear_all_count_data(); 879 } 880 881 // Repeat the asserts from above. 882 guarantee(cmThread()->during_cycle(), "invariant"); 883 guarantee(!g1h->mark_in_progress(), "invariant"); 884 } 885 886 class CheckBitmapClearHRClosure : public HeapRegionClosure { 887 CMBitMap* _bitmap; 888 bool _error; 889 public: 890 CheckBitmapClearHRClosure(CMBitMap* bitmap) : _bitmap(bitmap) { 891 } 892 893 virtual bool doHeapRegion(HeapRegion* r) { 894 // This closure can be called concurrently to the mutator, so we must make sure 895 // that the result of the getNextMarkedWordAddress() call is compared to the 896 // value passed to it as limit to detect any found bits. 897 // We can use the region's orig_end() for the limit and the comparison value 898 // as it always contains the "real" end of the region that never changes and 899 // has no side effects. 900 // Due to the latter, there can also be no problem with the compiler generating 901 // reloads of the orig_end() call. 902 HeapWord* end = r->orig_end(); 903 return _bitmap->getNextMarkedWordAddress(r->bottom(), end) != end; 904 } 905 }; 906 907 bool ConcurrentMark::nextMarkBitmapIsClear() { 908 CheckBitmapClearHRClosure cl(_nextMarkBitMap); 909 _g1h->heap_region_iterate(&cl); 910 return cl.complete(); 911 } 912 913 class NoteStartOfMarkHRClosure: public HeapRegionClosure { 914 public: 915 bool doHeapRegion(HeapRegion* r) { 916 if (!r->continuesHumongous()) { 917 r->note_start_of_marking(); 918 } 919 return false; 920 } 921 }; 922 923 void ConcurrentMark::checkpointRootsInitialPre() { 924 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 925 G1CollectorPolicy* g1p = g1h->g1_policy(); 926 927 _has_aborted = false; 928 929 #ifndef PRODUCT 930 if (G1PrintReachableAtInitialMark) { 931 print_reachable("at-cycle-start", 932 VerifyOption_G1UsePrevMarking, true /* all */); 933 } 934 #endif 935 936 // Initialise marking structures. This has to be done in a STW phase. 937 reset(); 938 939 // For each region note start of marking. 940 NoteStartOfMarkHRClosure startcl; 941 g1h->heap_region_iterate(&startcl); 942 } 943 944 945 void ConcurrentMark::checkpointRootsInitialPost() { 946 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 947 948 // If we force an overflow during remark, the remark operation will 949 // actually abort and we'll restart concurrent marking. If we always 950 // force an oveflow during remark we'll never actually complete the 951 // marking phase. So, we initilize this here, at the start of the 952 // cycle, so that at the remaining overflow number will decrease at 953 // every remark and we'll eventually not need to cause one. 954 force_overflow_stw()->init(); 955 956 // Start Concurrent Marking weak-reference discovery. 957 ReferenceProcessor* rp = g1h->ref_processor_cm(); 958 // enable ("weak") refs discovery 959 rp->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); 960 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle 961 962 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 963 // This is the start of the marking cycle, we're expected all 964 // threads to have SATB queues with active set to false. 965 satb_mq_set.set_active_all_threads(true, /* new active value */ 966 false /* expected_active */); 967 968 _root_regions.prepare_for_scan(); 969 970 // update_g1_committed() will be called at the end of an evac pause 971 // when marking is on. So, it's also called at the end of the 972 // initial-mark pause to update the heap end, if the heap expands 973 // during it. No need to call it here. 974 } 975 976 /* 977 * Notice that in the next two methods, we actually leave the STS 978 * during the barrier sync and join it immediately afterwards. If we 979 * do not do this, the following deadlock can occur: one thread could 980 * be in the barrier sync code, waiting for the other thread to also 981 * sync up, whereas another one could be trying to yield, while also 982 * waiting for the other threads to sync up too. 983 * 984 * Note, however, that this code is also used during remark and in 985 * this case we should not attempt to leave / enter the STS, otherwise 986 * we'll either hit an asseert (debug / fastdebug) or deadlock 987 * (product). So we should only leave / enter the STS if we are 988 * operating concurrently. 989 * 990 * Because the thread that does the sync barrier has left the STS, it 991 * is possible to be suspended for a Full GC or an evacuation pause 992 * could occur. This is actually safe, since the entering the sync 993 * barrier is one of the last things do_marking_step() does, and it 994 * doesn't manipulate any data structures afterwards. 995 */ 996 997 void ConcurrentMark::enter_first_sync_barrier(uint worker_id) { 998 if (verbose_low()) { 999 gclog_or_tty->print_cr("[%u] entering first barrier", worker_id); 1000 } 1001 1002 if (concurrent()) { 1003 SuspendibleThreadSet::leave(); 1004 } 1005 1006 bool barrier_aborted = !_first_overflow_barrier_sync.enter(); 1007 1008 if (concurrent()) { 1009 SuspendibleThreadSet::join(); 1010 } 1011 // at this point everyone should have synced up and not be doing any 1012 // more work 1013 1014 if (verbose_low()) { 1015 if (barrier_aborted) { 1016 gclog_or_tty->print_cr("[%u] aborted first barrier", worker_id); 1017 } else { 1018 gclog_or_tty->print_cr("[%u] leaving first barrier", worker_id); 1019 } 1020 } 1021 1022 if (barrier_aborted) { 1023 // If the barrier aborted we ignore the overflow condition and 1024 // just abort the whole marking phase as quickly as possible. 1025 return; 1026 } 1027 1028 // If we're executing the concurrent phase of marking, reset the marking 1029 // state; otherwise the marking state is reset after reference processing, 1030 // during the remark pause. 1031 // If we reset here as a result of an overflow during the remark we will 1032 // see assertion failures from any subsequent set_concurrency_and_phase() 1033 // calls. 1034 if (concurrent()) { 1035 // let the task associated with with worker 0 do this 1036 if (worker_id == 0) { 1037 // task 0 is responsible for clearing the global data structures 1038 // We should be here because of an overflow. During STW we should 1039 // not clear the overflow flag since we rely on it being true when 1040 // we exit this method to abort the pause and restart concurent 1041 // marking. 1042 reset_marking_state(true /* clear_overflow */); 1043 force_overflow()->update(); 1044 1045 if (G1Log::fine()) { 1046 gclog_or_tty->gclog_stamp(concurrent_gc_id()); 1047 gclog_or_tty->print_cr("[GC concurrent-mark-reset-for-overflow]"); 1048 } 1049 } 1050 } 1051 1052 // after this, each task should reset its own data structures then 1053 // then go into the second barrier 1054 } 1055 1056 void ConcurrentMark::enter_second_sync_barrier(uint worker_id) { 1057 if (verbose_low()) { 1058 gclog_or_tty->print_cr("[%u] entering second barrier", worker_id); 1059 } 1060 1061 if (concurrent()) { 1062 SuspendibleThreadSet::leave(); 1063 } 1064 1065 bool barrier_aborted = !_second_overflow_barrier_sync.enter(); 1066 1067 if (concurrent()) { 1068 SuspendibleThreadSet::join(); 1069 } 1070 // at this point everything should be re-initialized and ready to go 1071 1072 if (verbose_low()) { 1073 if (barrier_aborted) { 1074 gclog_or_tty->print_cr("[%u] aborted second barrier", worker_id); 1075 } else { 1076 gclog_or_tty->print_cr("[%u] leaving second barrier", worker_id); 1077 } 1078 } 1079 } 1080 1081 #ifndef PRODUCT 1082 void ForceOverflowSettings::init() { 1083 _num_remaining = G1ConcMarkForceOverflow; 1084 _force = false; 1085 update(); 1086 } 1087 1088 void ForceOverflowSettings::update() { 1089 if (_num_remaining > 0) { 1090 _num_remaining -= 1; 1091 _force = true; 1092 } else { 1093 _force = false; 1094 } 1095 } 1096 1097 bool ForceOverflowSettings::should_force() { 1098 if (_force) { 1099 _force = false; 1100 return true; 1101 } else { 1102 return false; 1103 } 1104 } 1105 #endif // !PRODUCT 1106 1107 class CMConcurrentMarkingTask: public AbstractGangTask { 1108 private: 1109 ConcurrentMark* _cm; 1110 ConcurrentMarkThread* _cmt; 1111 1112 public: 1113 void work(uint worker_id) { 1114 assert(Thread::current()->is_ConcurrentGC_thread(), 1115 "this should only be done by a conc GC thread"); 1116 ResourceMark rm; 1117 1118 double start_vtime = os::elapsedVTime(); 1119 1120 SuspendibleThreadSet::join(); 1121 1122 assert(worker_id < _cm->active_tasks(), "invariant"); 1123 CMTask* the_task = _cm->task(worker_id); 1124 the_task->record_start_time(); 1125 if (!_cm->has_aborted()) { 1126 do { 1127 double start_vtime_sec = os::elapsedVTime(); 1128 double mark_step_duration_ms = G1ConcMarkStepDurationMillis; 1129 1130 the_task->do_marking_step(mark_step_duration_ms, 1131 true /* do_termination */, 1132 false /* is_serial*/); 1133 1134 double end_vtime_sec = os::elapsedVTime(); 1135 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec; 1136 _cm->clear_has_overflown(); 1137 1138 _cm->do_yield_check(worker_id); 1139 1140 jlong sleep_time_ms; 1141 if (!_cm->has_aborted() && the_task->has_aborted()) { 1142 sleep_time_ms = 1143 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0); 1144 SuspendibleThreadSet::leave(); 1145 os::sleep(Thread::current(), sleep_time_ms, false); 1146 SuspendibleThreadSet::join(); 1147 } 1148 } while (!_cm->has_aborted() && the_task->has_aborted()); 1149 } 1150 the_task->record_end_time(); 1151 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant"); 1152 1153 SuspendibleThreadSet::leave(); 1154 1155 double end_vtime = os::elapsedVTime(); 1156 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime); 1157 } 1158 1159 CMConcurrentMarkingTask(ConcurrentMark* cm, 1160 ConcurrentMarkThread* cmt) : 1161 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { } 1162 1163 ~CMConcurrentMarkingTask() { } 1164 }; 1165 1166 // Calculates the number of active workers for a concurrent 1167 // phase. 1168 uint ConcurrentMark::calc_parallel_marking_threads() { 1169 if (G1CollectedHeap::use_parallel_gc_threads()) { 1170 uint n_conc_workers = 0; 1171 if (!UseDynamicNumberOfGCThreads || 1172 (!FLAG_IS_DEFAULT(ConcGCThreads) && 1173 !ForceDynamicNumberOfGCThreads)) { 1174 n_conc_workers = max_parallel_marking_threads(); 1175 } else { 1176 n_conc_workers = 1177 AdaptiveSizePolicy::calc_default_active_workers( 1178 max_parallel_marking_threads(), 1179 1, /* Minimum workers */ 1180 parallel_marking_threads(), 1181 Threads::number_of_non_daemon_threads()); 1182 // Don't scale down "n_conc_workers" by scale_parallel_threads() because 1183 // that scaling has already gone into "_max_parallel_marking_threads". 1184 } 1185 assert(n_conc_workers > 0, "Always need at least 1"); 1186 return n_conc_workers; 1187 } 1188 // If we are not running with any parallel GC threads we will not 1189 // have spawned any marking threads either. Hence the number of 1190 // concurrent workers should be 0. 1191 return 0; 1192 } 1193 1194 void ConcurrentMark::scanRootRegion(HeapRegion* hr, uint worker_id) { 1195 // Currently, only survivors can be root regions. 1196 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant"); 1197 G1RootRegionScanClosure cl(_g1h, this, worker_id); 1198 1199 const uintx interval = PrefetchScanIntervalInBytes; 1200 HeapWord* curr = hr->bottom(); 1201 const HeapWord* end = hr->top(); 1202 while (curr < end) { 1203 Prefetch::read(curr, interval); 1204 oop obj = oop(curr); 1205 int size = obj->oop_iterate(&cl); 1206 assert(size == obj->size(), "sanity"); 1207 curr += size; 1208 } 1209 } 1210 1211 class CMRootRegionScanTask : public AbstractGangTask { 1212 private: 1213 ConcurrentMark* _cm; 1214 1215 public: 1216 CMRootRegionScanTask(ConcurrentMark* cm) : 1217 AbstractGangTask("Root Region Scan"), _cm(cm) { } 1218 1219 void work(uint worker_id) { 1220 assert(Thread::current()->is_ConcurrentGC_thread(), 1221 "this should only be done by a conc GC thread"); 1222 1223 CMRootRegions* root_regions = _cm->root_regions(); 1224 HeapRegion* hr = root_regions->claim_next(); 1225 while (hr != NULL) { 1226 _cm->scanRootRegion(hr, worker_id); 1227 hr = root_regions->claim_next(); 1228 } 1229 } 1230 }; 1231 1232 void ConcurrentMark::scanRootRegions() { 1233 // Start of concurrent marking. 1234 ClassLoaderDataGraph::clear_claimed_marks(); 1235 1236 // scan_in_progress() will have been set to true only if there was 1237 // at least one root region to scan. So, if it's false, we 1238 // should not attempt to do any further work. 1239 if (root_regions()->scan_in_progress()) { 1240 _parallel_marking_threads = calc_parallel_marking_threads(); 1241 assert(parallel_marking_threads() <= max_parallel_marking_threads(), 1242 "Maximum number of marking threads exceeded"); 1243 uint active_workers = MAX2(1U, parallel_marking_threads()); 1244 1245 CMRootRegionScanTask task(this); 1246 if (use_parallel_marking_threads()) { 1247 _parallel_workers->set_active_workers((int) active_workers); 1248 _parallel_workers->run_task(&task); 1249 } else { 1250 task.work(0); 1251 } 1252 1253 // It's possible that has_aborted() is true here without actually 1254 // aborting the survivor scan earlier. This is OK as it's 1255 // mainly used for sanity checking. 1256 root_regions()->scan_finished(); 1257 } 1258 } 1259 1260 void ConcurrentMark::markFromRoots() { 1261 // we might be tempted to assert that: 1262 // assert(asynch == !SafepointSynchronize::is_at_safepoint(), 1263 // "inconsistent argument?"); 1264 // However that wouldn't be right, because it's possible that 1265 // a safepoint is indeed in progress as a younger generation 1266 // stop-the-world GC happens even as we mark in this generation. 1267 1268 _restart_for_overflow = false; 1269 force_overflow_conc()->init(); 1270 1271 // _g1h has _n_par_threads 1272 _parallel_marking_threads = calc_parallel_marking_threads(); 1273 assert(parallel_marking_threads() <= max_parallel_marking_threads(), 1274 "Maximum number of marking threads exceeded"); 1275 1276 uint active_workers = MAX2(1U, parallel_marking_threads()); 1277 1278 // Parallel task terminator is set in "set_concurrency_and_phase()" 1279 set_concurrency_and_phase(active_workers, true /* concurrent */); 1280 1281 CMConcurrentMarkingTask markingTask(this, cmThread()); 1282 if (use_parallel_marking_threads()) { 1283 _parallel_workers->set_active_workers((int)active_workers); 1284 // Don't set _n_par_threads because it affects MT in process_roots() 1285 // and the decisions on that MT processing is made elsewhere. 1286 assert(_parallel_workers->active_workers() > 0, "Should have been set"); 1287 _parallel_workers->run_task(&markingTask); 1288 } else { 1289 markingTask.work(0); 1290 } 1291 print_stats(); 1292 } 1293 1294 void ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) { 1295 // world is stopped at this checkpoint 1296 assert(SafepointSynchronize::is_at_safepoint(), 1297 "world should be stopped"); 1298 1299 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1300 1301 // If a full collection has happened, we shouldn't do this. 1302 if (has_aborted()) { 1303 g1h->set_marking_complete(); // So bitmap clearing isn't confused 1304 return; 1305 } 1306 1307 SvcGCMarker sgcm(SvcGCMarker::OTHER); 1308 1309 if (VerifyDuringGC) { 1310 HandleMark hm; // handle scope 1311 Universe::heap()->prepare_for_verify(); 1312 Universe::verify(VerifyOption_G1UsePrevMarking, 1313 " VerifyDuringGC:(before)"); 1314 } 1315 g1h->check_bitmaps("Remark Start"); 1316 1317 G1CollectorPolicy* g1p = g1h->g1_policy(); 1318 g1p->record_concurrent_mark_remark_start(); 1319 1320 double start = os::elapsedTime(); 1321 1322 checkpointRootsFinalWork(); 1323 1324 double mark_work_end = os::elapsedTime(); 1325 1326 weakRefsWork(clear_all_soft_refs); 1327 1328 if (has_overflown()) { 1329 // Oops. We overflowed. Restart concurrent marking. 1330 _restart_for_overflow = true; 1331 if (G1TraceMarkStackOverflow) { 1332 gclog_or_tty->print_cr("\nRemark led to restart for overflow."); 1333 } 1334 1335 // Verify the heap w.r.t. the previous marking bitmap. 1336 if (VerifyDuringGC) { 1337 HandleMark hm; // handle scope 1338 Universe::heap()->prepare_for_verify(); 1339 Universe::verify(VerifyOption_G1UsePrevMarking, 1340 " VerifyDuringGC:(overflow)"); 1341 } 1342 1343 // Clear the marking state because we will be restarting 1344 // marking due to overflowing the global mark stack. 1345 reset_marking_state(); 1346 } else { 1347 // Aggregate the per-task counting data that we have accumulated 1348 // while marking. 1349 aggregate_count_data(); 1350 1351 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 1352 // We're done with marking. 1353 // This is the end of the marking cycle, we're expected all 1354 // threads to have SATB queues with active set to true. 1355 satb_mq_set.set_active_all_threads(false, /* new active value */ 1356 true /* expected_active */); 1357 1358 if (VerifyDuringGC) { 1359 HandleMark hm; // handle scope 1360 Universe::heap()->prepare_for_verify(); 1361 Universe::verify(VerifyOption_G1UseNextMarking, 1362 " VerifyDuringGC:(after)"); 1363 } 1364 g1h->check_bitmaps("Remark End"); 1365 assert(!restart_for_overflow(), "sanity"); 1366 // Completely reset the marking state since marking completed 1367 set_non_marking_state(); 1368 } 1369 1370 // Expand the marking stack, if we have to and if we can. 1371 if (_markStack.should_expand()) { 1372 _markStack.expand(); 1373 } 1374 1375 // Statistics 1376 double now = os::elapsedTime(); 1377 _remark_mark_times.add((mark_work_end - start) * 1000.0); 1378 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0); 1379 _remark_times.add((now - start) * 1000.0); 1380 1381 g1p->record_concurrent_mark_remark_end(); 1382 1383 G1CMIsAliveClosure is_alive(g1h); 1384 g1h->gc_tracer_cm()->report_object_count_after_gc(&is_alive); 1385 } 1386 1387 // Base class of the closures that finalize and verify the 1388 // liveness counting data. 1389 class CMCountDataClosureBase: public HeapRegionClosure { 1390 protected: 1391 G1CollectedHeap* _g1h; 1392 ConcurrentMark* _cm; 1393 CardTableModRefBS* _ct_bs; 1394 1395 BitMap* _region_bm; 1396 BitMap* _card_bm; 1397 1398 // Takes a region that's not empty (i.e., it has at least one 1399 // live object in it and sets its corresponding bit on the region 1400 // bitmap to 1. If the region is "starts humongous" it will also set 1401 // to 1 the bits on the region bitmap that correspond to its 1402 // associated "continues humongous" regions. 1403 void set_bit_for_region(HeapRegion* hr) { 1404 assert(!hr->continuesHumongous(), "should have filtered those out"); 1405 1406 BitMap::idx_t index = (BitMap::idx_t) hr->hrm_index(); 1407 if (!hr->startsHumongous()) { 1408 // Normal (non-humongous) case: just set the bit. 1409 _region_bm->par_at_put(index, true); 1410 } else { 1411 // Starts humongous case: calculate how many regions are part of 1412 // this humongous region and then set the bit range. 1413 BitMap::idx_t end_index = (BitMap::idx_t) hr->last_hc_index(); 1414 _region_bm->par_at_put_range(index, end_index, true); 1415 } 1416 } 1417 1418 public: 1419 CMCountDataClosureBase(G1CollectedHeap* g1h, 1420 BitMap* region_bm, BitMap* card_bm): 1421 _g1h(g1h), _cm(g1h->concurrent_mark()), 1422 _ct_bs((CardTableModRefBS*) (g1h->barrier_set())), 1423 _region_bm(region_bm), _card_bm(card_bm) { } 1424 }; 1425 1426 // Closure that calculates the # live objects per region. Used 1427 // for verification purposes during the cleanup pause. 1428 class CalcLiveObjectsClosure: public CMCountDataClosureBase { 1429 CMBitMapRO* _bm; 1430 size_t _region_marked_bytes; 1431 1432 public: 1433 CalcLiveObjectsClosure(CMBitMapRO *bm, G1CollectedHeap* g1h, 1434 BitMap* region_bm, BitMap* card_bm) : 1435 CMCountDataClosureBase(g1h, region_bm, card_bm), 1436 _bm(bm), _region_marked_bytes(0) { } 1437 1438 bool doHeapRegion(HeapRegion* hr) { 1439 1440 if (hr->continuesHumongous()) { 1441 // We will ignore these here and process them when their 1442 // associated "starts humongous" region is processed (see 1443 // set_bit_for_heap_region()). Note that we cannot rely on their 1444 // associated "starts humongous" region to have their bit set to 1445 // 1 since, due to the region chunking in the parallel region 1446 // iteration, a "continues humongous" region might be visited 1447 // before its associated "starts humongous". 1448 return false; 1449 } 1450 1451 HeapWord* ntams = hr->next_top_at_mark_start(); 1452 HeapWord* start = hr->bottom(); 1453 1454 assert(start <= hr->end() && start <= ntams && ntams <= hr->end(), 1455 err_msg("Preconditions not met - " 1456 "start: "PTR_FORMAT", ntams: "PTR_FORMAT", end: "PTR_FORMAT, 1457 p2i(start), p2i(ntams), p2i(hr->end()))); 1458 1459 // Find the first marked object at or after "start". 1460 start = _bm->getNextMarkedWordAddress(start, ntams); 1461 1462 size_t marked_bytes = 0; 1463 1464 while (start < ntams) { 1465 oop obj = oop(start); 1466 int obj_sz = obj->size(); 1467 HeapWord* obj_end = start + obj_sz; 1468 1469 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start); 1470 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(obj_end); 1471 1472 // Note: if we're looking at the last region in heap - obj_end 1473 // could be actually just beyond the end of the heap; end_idx 1474 // will then correspond to a (non-existent) card that is also 1475 // just beyond the heap. 1476 if (_g1h->is_in_g1_reserved(obj_end) && !_ct_bs->is_card_aligned(obj_end)) { 1477 // end of object is not card aligned - increment to cover 1478 // all the cards spanned by the object 1479 end_idx += 1; 1480 } 1481 1482 // Set the bits in the card BM for the cards spanned by this object. 1483 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */); 1484 1485 // Add the size of this object to the number of marked bytes. 1486 marked_bytes += (size_t)obj_sz * HeapWordSize; 1487 1488 // Find the next marked object after this one. 1489 start = _bm->getNextMarkedWordAddress(obj_end, ntams); 1490 } 1491 1492 // Mark the allocated-since-marking portion... 1493 HeapWord* top = hr->top(); 1494 if (ntams < top) { 1495 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams); 1496 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top); 1497 1498 // Note: if we're looking at the last region in heap - top 1499 // could be actually just beyond the end of the heap; end_idx 1500 // will then correspond to a (non-existent) card that is also 1501 // just beyond the heap. 1502 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) { 1503 // end of object is not card aligned - increment to cover 1504 // all the cards spanned by the object 1505 end_idx += 1; 1506 } 1507 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */); 1508 1509 // This definitely means the region has live objects. 1510 set_bit_for_region(hr); 1511 } 1512 1513 // Update the live region bitmap. 1514 if (marked_bytes > 0) { 1515 set_bit_for_region(hr); 1516 } 1517 1518 // Set the marked bytes for the current region so that 1519 // it can be queried by a calling verificiation routine 1520 _region_marked_bytes = marked_bytes; 1521 1522 return false; 1523 } 1524 1525 size_t region_marked_bytes() const { return _region_marked_bytes; } 1526 }; 1527 1528 // Heap region closure used for verifying the counting data 1529 // that was accumulated concurrently and aggregated during 1530 // the remark pause. This closure is applied to the heap 1531 // regions during the STW cleanup pause. 1532 1533 class VerifyLiveObjectDataHRClosure: public HeapRegionClosure { 1534 G1CollectedHeap* _g1h; 1535 ConcurrentMark* _cm; 1536 CalcLiveObjectsClosure _calc_cl; 1537 BitMap* _region_bm; // Region BM to be verified 1538 BitMap* _card_bm; // Card BM to be verified 1539 bool _verbose; // verbose output? 1540 1541 BitMap* _exp_region_bm; // Expected Region BM values 1542 BitMap* _exp_card_bm; // Expected card BM values 1543 1544 int _failures; 1545 1546 public: 1547 VerifyLiveObjectDataHRClosure(G1CollectedHeap* g1h, 1548 BitMap* region_bm, 1549 BitMap* card_bm, 1550 BitMap* exp_region_bm, 1551 BitMap* exp_card_bm, 1552 bool verbose) : 1553 _g1h(g1h), _cm(g1h->concurrent_mark()), 1554 _calc_cl(_cm->nextMarkBitMap(), g1h, exp_region_bm, exp_card_bm), 1555 _region_bm(region_bm), _card_bm(card_bm), _verbose(verbose), 1556 _exp_region_bm(exp_region_bm), _exp_card_bm(exp_card_bm), 1557 _failures(0) { } 1558 1559 int failures() const { return _failures; } 1560 1561 bool doHeapRegion(HeapRegion* hr) { 1562 if (hr->continuesHumongous()) { 1563 // We will ignore these here and process them when their 1564 // associated "starts humongous" region is processed (see 1565 // set_bit_for_heap_region()). Note that we cannot rely on their 1566 // associated "starts humongous" region to have their bit set to 1567 // 1 since, due to the region chunking in the parallel region 1568 // iteration, a "continues humongous" region might be visited 1569 // before its associated "starts humongous". 1570 return false; 1571 } 1572 1573 int failures = 0; 1574 1575 // Call the CalcLiveObjectsClosure to walk the marking bitmap for 1576 // this region and set the corresponding bits in the expected region 1577 // and card bitmaps. 1578 bool res = _calc_cl.doHeapRegion(hr); 1579 assert(res == false, "should be continuing"); 1580 1581 MutexLockerEx x((_verbose ? ParGCRareEvent_lock : NULL), 1582 Mutex::_no_safepoint_check_flag); 1583 1584 // Verify the marked bytes for this region. 1585 size_t exp_marked_bytes = _calc_cl.region_marked_bytes(); 1586 size_t act_marked_bytes = hr->next_marked_bytes(); 1587 1588 // We're not OK if expected marked bytes > actual marked bytes. It means 1589 // we have missed accounting some objects during the actual marking. 1590 if (exp_marked_bytes > act_marked_bytes) { 1591 if (_verbose) { 1592 gclog_or_tty->print_cr("Region %u: marked bytes mismatch: " 1593 "expected: " SIZE_FORMAT ", actual: " SIZE_FORMAT, 1594 hr->hrm_index(), exp_marked_bytes, act_marked_bytes); 1595 } 1596 failures += 1; 1597 } 1598 1599 // Verify the bit, for this region, in the actual and expected 1600 // (which was just calculated) region bit maps. 1601 // We're not OK if the bit in the calculated expected region 1602 // bitmap is set and the bit in the actual region bitmap is not. 1603 BitMap::idx_t index = (BitMap::idx_t) hr->hrm_index(); 1604 1605 bool expected = _exp_region_bm->at(index); 1606 bool actual = _region_bm->at(index); 1607 if (expected && !actual) { 1608 if (_verbose) { 1609 gclog_or_tty->print_cr("Region %u: region bitmap mismatch: " 1610 "expected: %s, actual: %s", 1611 hr->hrm_index(), 1612 BOOL_TO_STR(expected), BOOL_TO_STR(actual)); 1613 } 1614 failures += 1; 1615 } 1616 1617 // Verify that the card bit maps for the cards spanned by the current 1618 // region match. We have an error if we have a set bit in the expected 1619 // bit map and the corresponding bit in the actual bitmap is not set. 1620 1621 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(hr->bottom()); 1622 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(hr->top()); 1623 1624 for (BitMap::idx_t i = start_idx; i < end_idx; i+=1) { 1625 expected = _exp_card_bm->at(i); 1626 actual = _card_bm->at(i); 1627 1628 if (expected && !actual) { 1629 if (_verbose) { 1630 gclog_or_tty->print_cr("Region %u: card bitmap mismatch at " SIZE_FORMAT ": " 1631 "expected: %s, actual: %s", 1632 hr->hrm_index(), i, 1633 BOOL_TO_STR(expected), BOOL_TO_STR(actual)); 1634 } 1635 failures += 1; 1636 } 1637 } 1638 1639 if (failures > 0 && _verbose) { 1640 gclog_or_tty->print_cr("Region " HR_FORMAT ", ntams: " PTR_FORMAT ", " 1641 "marked_bytes: calc/actual " SIZE_FORMAT "/" SIZE_FORMAT, 1642 HR_FORMAT_PARAMS(hr), p2i(hr->next_top_at_mark_start()), 1643 _calc_cl.region_marked_bytes(), hr->next_marked_bytes()); 1644 } 1645 1646 _failures += failures; 1647 1648 // We could stop iteration over the heap when we 1649 // find the first violating region by returning true. 1650 return false; 1651 } 1652 }; 1653 1654 class G1ParVerifyFinalCountTask: public AbstractGangTask { 1655 protected: 1656 G1CollectedHeap* _g1h; 1657 ConcurrentMark* _cm; 1658 BitMap* _actual_region_bm; 1659 BitMap* _actual_card_bm; 1660 1661 uint _n_workers; 1662 1663 BitMap* _expected_region_bm; 1664 BitMap* _expected_card_bm; 1665 1666 int _failures; 1667 bool _verbose; 1668 1669 public: 1670 G1ParVerifyFinalCountTask(G1CollectedHeap* g1h, 1671 BitMap* region_bm, BitMap* card_bm, 1672 BitMap* expected_region_bm, BitMap* expected_card_bm) 1673 : AbstractGangTask("G1 verify final counting"), 1674 _g1h(g1h), _cm(_g1h->concurrent_mark()), 1675 _actual_region_bm(region_bm), _actual_card_bm(card_bm), 1676 _expected_region_bm(expected_region_bm), _expected_card_bm(expected_card_bm), 1677 _failures(0), _verbose(false), 1678 _n_workers(0) { 1679 assert(VerifyDuringGC, "don't call this otherwise"); 1680 1681 // Use the value already set as the number of active threads 1682 // in the call to run_task(). 1683 if (G1CollectedHeap::use_parallel_gc_threads()) { 1684 assert( _g1h->workers()->active_workers() > 0, 1685 "Should have been previously set"); 1686 _n_workers = _g1h->workers()->active_workers(); 1687 } else { 1688 _n_workers = 1; 1689 } 1690 1691 assert(_expected_card_bm->size() == _actual_card_bm->size(), "sanity"); 1692 assert(_expected_region_bm->size() == _actual_region_bm->size(), "sanity"); 1693 1694 _verbose = _cm->verbose_medium(); 1695 } 1696 1697 void work(uint worker_id) { 1698 assert(worker_id < _n_workers, "invariant"); 1699 1700 VerifyLiveObjectDataHRClosure verify_cl(_g1h, 1701 _actual_region_bm, _actual_card_bm, 1702 _expected_region_bm, 1703 _expected_card_bm, 1704 _verbose); 1705 1706 if (G1CollectedHeap::use_parallel_gc_threads()) { 1707 _g1h->heap_region_par_iterate_chunked(&verify_cl, 1708 worker_id, 1709 _n_workers, 1710 HeapRegion::VerifyCountClaimValue); 1711 } else { 1712 _g1h->heap_region_iterate(&verify_cl); 1713 } 1714 1715 Atomic::add(verify_cl.failures(), &_failures); 1716 } 1717 1718 int failures() const { return _failures; } 1719 }; 1720 1721 // Closure that finalizes the liveness counting data. 1722 // Used during the cleanup pause. 1723 // Sets the bits corresponding to the interval [NTAMS, top] 1724 // (which contains the implicitly live objects) in the 1725 // card liveness bitmap. Also sets the bit for each region, 1726 // containing live data, in the region liveness bitmap. 1727 1728 class FinalCountDataUpdateClosure: public CMCountDataClosureBase { 1729 public: 1730 FinalCountDataUpdateClosure(G1CollectedHeap* g1h, 1731 BitMap* region_bm, 1732 BitMap* card_bm) : 1733 CMCountDataClosureBase(g1h, region_bm, card_bm) { } 1734 1735 bool doHeapRegion(HeapRegion* hr) { 1736 1737 if (hr->continuesHumongous()) { 1738 // We will ignore these here and process them when their 1739 // associated "starts humongous" region is processed (see 1740 // set_bit_for_heap_region()). Note that we cannot rely on their 1741 // associated "starts humongous" region to have their bit set to 1742 // 1 since, due to the region chunking in the parallel region 1743 // iteration, a "continues humongous" region might be visited 1744 // before its associated "starts humongous". 1745 return false; 1746 } 1747 1748 HeapWord* ntams = hr->next_top_at_mark_start(); 1749 HeapWord* top = hr->top(); 1750 1751 assert(hr->bottom() <= ntams && ntams <= hr->end(), "Preconditions."); 1752 1753 // Mark the allocated-since-marking portion... 1754 if (ntams < top) { 1755 // This definitely means the region has live objects. 1756 set_bit_for_region(hr); 1757 1758 // Now set the bits in the card bitmap for [ntams, top) 1759 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams); 1760 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top); 1761 1762 // Note: if we're looking at the last region in heap - top 1763 // could be actually just beyond the end of the heap; end_idx 1764 // will then correspond to a (non-existent) card that is also 1765 // just beyond the heap. 1766 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) { 1767 // end of object is not card aligned - increment to cover 1768 // all the cards spanned by the object 1769 end_idx += 1; 1770 } 1771 1772 assert(end_idx <= _card_bm->size(), 1773 err_msg("oob: end_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT, 1774 end_idx, _card_bm->size())); 1775 assert(start_idx < _card_bm->size(), 1776 err_msg("oob: start_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT, 1777 start_idx, _card_bm->size())); 1778 1779 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */); 1780 } 1781 1782 // Set the bit for the region if it contains live data 1783 if (hr->next_marked_bytes() > 0) { 1784 set_bit_for_region(hr); 1785 } 1786 1787 return false; 1788 } 1789 }; 1790 1791 class G1ParFinalCountTask: public AbstractGangTask { 1792 protected: 1793 G1CollectedHeap* _g1h; 1794 ConcurrentMark* _cm; 1795 BitMap* _actual_region_bm; 1796 BitMap* _actual_card_bm; 1797 1798 uint _n_workers; 1799 1800 public: 1801 G1ParFinalCountTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm) 1802 : AbstractGangTask("G1 final counting"), 1803 _g1h(g1h), _cm(_g1h->concurrent_mark()), 1804 _actual_region_bm(region_bm), _actual_card_bm(card_bm), 1805 _n_workers(0) { 1806 // Use the value already set as the number of active threads 1807 // in the call to run_task(). 1808 if (G1CollectedHeap::use_parallel_gc_threads()) { 1809 assert( _g1h->workers()->active_workers() > 0, 1810 "Should have been previously set"); 1811 _n_workers = _g1h->workers()->active_workers(); 1812 } else { 1813 _n_workers = 1; 1814 } 1815 } 1816 1817 void work(uint worker_id) { 1818 assert(worker_id < _n_workers, "invariant"); 1819 1820 FinalCountDataUpdateClosure final_update_cl(_g1h, 1821 _actual_region_bm, 1822 _actual_card_bm); 1823 1824 if (G1CollectedHeap::use_parallel_gc_threads()) { 1825 _g1h->heap_region_par_iterate_chunked(&final_update_cl, 1826 worker_id, 1827 _n_workers, 1828 HeapRegion::FinalCountClaimValue); 1829 } else { 1830 _g1h->heap_region_iterate(&final_update_cl); 1831 } 1832 } 1833 }; 1834 1835 class G1ParNoteEndTask; 1836 1837 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure { 1838 G1CollectedHeap* _g1; 1839 size_t _max_live_bytes; 1840 uint _regions_claimed; 1841 size_t _freed_bytes; 1842 FreeRegionList* _local_cleanup_list; 1843 HeapRegionSetCount _old_regions_removed; 1844 HeapRegionSetCount _humongous_regions_removed; 1845 HRRSCleanupTask* _hrrs_cleanup_task; 1846 double _claimed_region_time; 1847 double _max_region_time; 1848 1849 public: 1850 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1, 1851 FreeRegionList* local_cleanup_list, 1852 HRRSCleanupTask* hrrs_cleanup_task) : 1853 _g1(g1), 1854 _max_live_bytes(0), _regions_claimed(0), 1855 _freed_bytes(0), 1856 _claimed_region_time(0.0), _max_region_time(0.0), 1857 _local_cleanup_list(local_cleanup_list), 1858 _old_regions_removed(), 1859 _humongous_regions_removed(), 1860 _hrrs_cleanup_task(hrrs_cleanup_task) { } 1861 1862 size_t freed_bytes() { return _freed_bytes; } 1863 const HeapRegionSetCount& old_regions_removed() { return _old_regions_removed; } 1864 const HeapRegionSetCount& humongous_regions_removed() { return _humongous_regions_removed; } 1865 1866 bool doHeapRegion(HeapRegion *hr) { 1867 if (hr->continuesHumongous()) { 1868 return false; 1869 } 1870 // We use a claim value of zero here because all regions 1871 // were claimed with value 1 in the FinalCount task. 1872 _g1->reset_gc_time_stamps(hr); 1873 double start = os::elapsedTime(); 1874 _regions_claimed++; 1875 hr->note_end_of_marking(); 1876 _max_live_bytes += hr->max_live_bytes(); 1877 1878 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) { 1879 _freed_bytes += hr->used(); 1880 hr->set_containing_set(NULL); 1881 if (hr->isHumongous()) { 1882 assert(hr->startsHumongous(), "we should only see starts humongous"); 1883 _humongous_regions_removed.increment(1u, hr->capacity()); 1884 _g1->free_humongous_region(hr, _local_cleanup_list, true); 1885 } else { 1886 _old_regions_removed.increment(1u, hr->capacity()); 1887 _g1->free_region(hr, _local_cleanup_list, true); 1888 } 1889 } else { 1890 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task); 1891 } 1892 1893 double region_time = (os::elapsedTime() - start); 1894 _claimed_region_time += region_time; 1895 if (region_time > _max_region_time) { 1896 _max_region_time = region_time; 1897 } 1898 return false; 1899 } 1900 1901 size_t max_live_bytes() { return _max_live_bytes; } 1902 uint regions_claimed() { return _regions_claimed; } 1903 double claimed_region_time_sec() { return _claimed_region_time; } 1904 double max_region_time_sec() { return _max_region_time; } 1905 }; 1906 1907 class G1ParNoteEndTask: public AbstractGangTask { 1908 friend class G1NoteEndOfConcMarkClosure; 1909 1910 protected: 1911 G1CollectedHeap* _g1h; 1912 size_t _max_live_bytes; 1913 size_t _freed_bytes; 1914 FreeRegionList* _cleanup_list; 1915 1916 public: 1917 G1ParNoteEndTask(G1CollectedHeap* g1h, 1918 FreeRegionList* cleanup_list) : 1919 AbstractGangTask("G1 note end"), _g1h(g1h), 1920 _max_live_bytes(0), _freed_bytes(0), _cleanup_list(cleanup_list) { } 1921 1922 void work(uint worker_id) { 1923 double start = os::elapsedTime(); 1924 FreeRegionList local_cleanup_list("Local Cleanup List"); 1925 HRRSCleanupTask hrrs_cleanup_task; 1926 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, &local_cleanup_list, 1927 &hrrs_cleanup_task); 1928 if (G1CollectedHeap::use_parallel_gc_threads()) { 1929 _g1h->heap_region_par_iterate_chunked(&g1_note_end, worker_id, 1930 _g1h->workers()->active_workers(), 1931 HeapRegion::NoteEndClaimValue); 1932 } else { 1933 _g1h->heap_region_iterate(&g1_note_end); 1934 } 1935 assert(g1_note_end.complete(), "Shouldn't have yielded!"); 1936 1937 // Now update the lists 1938 _g1h->remove_from_old_sets(g1_note_end.old_regions_removed(), g1_note_end.humongous_regions_removed()); 1939 { 1940 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 1941 _g1h->decrement_summary_bytes(g1_note_end.freed_bytes()); 1942 _max_live_bytes += g1_note_end.max_live_bytes(); 1943 _freed_bytes += g1_note_end.freed_bytes(); 1944 1945 // If we iterate over the global cleanup list at the end of 1946 // cleanup to do this printing we will not guarantee to only 1947 // generate output for the newly-reclaimed regions (the list 1948 // might not be empty at the beginning of cleanup; we might 1949 // still be working on its previous contents). So we do the 1950 // printing here, before we append the new regions to the global 1951 // cleanup list. 1952 1953 G1HRPrinter* hr_printer = _g1h->hr_printer(); 1954 if (hr_printer->is_active()) { 1955 FreeRegionListIterator iter(&local_cleanup_list); 1956 while (iter.more_available()) { 1957 HeapRegion* hr = iter.get_next(); 1958 hr_printer->cleanup(hr); 1959 } 1960 } 1961 1962 _cleanup_list->add_ordered(&local_cleanup_list); 1963 assert(local_cleanup_list.is_empty(), "post-condition"); 1964 1965 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task); 1966 } 1967 } 1968 size_t max_live_bytes() { return _max_live_bytes; } 1969 size_t freed_bytes() { return _freed_bytes; } 1970 }; 1971 1972 class G1ParScrubRemSetTask: public AbstractGangTask { 1973 protected: 1974 G1RemSet* _g1rs; 1975 BitMap* _region_bm; 1976 BitMap* _card_bm; 1977 public: 1978 G1ParScrubRemSetTask(G1CollectedHeap* g1h, 1979 BitMap* region_bm, BitMap* card_bm) : 1980 AbstractGangTask("G1 ScrubRS"), _g1rs(g1h->g1_rem_set()), 1981 _region_bm(region_bm), _card_bm(card_bm) { } 1982 1983 void work(uint worker_id) { 1984 if (G1CollectedHeap::use_parallel_gc_threads()) { 1985 _g1rs->scrub_par(_region_bm, _card_bm, worker_id, 1986 HeapRegion::ScrubRemSetClaimValue); 1987 } else { 1988 _g1rs->scrub(_region_bm, _card_bm); 1989 } 1990 } 1991 1992 }; 1993 1994 void ConcurrentMark::cleanup() { 1995 // world is stopped at this checkpoint 1996 assert(SafepointSynchronize::is_at_safepoint(), 1997 "world should be stopped"); 1998 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1999 2000 // If a full collection has happened, we shouldn't do this. 2001 if (has_aborted()) { 2002 g1h->set_marking_complete(); // So bitmap clearing isn't confused 2003 return; 2004 } 2005 2006 g1h->verify_region_sets_optional(); 2007 2008 if (VerifyDuringGC) { 2009 HandleMark hm; // handle scope 2010 Universe::heap()->prepare_for_verify(); 2011 Universe::verify(VerifyOption_G1UsePrevMarking, 2012 " VerifyDuringGC:(before)"); 2013 } 2014 g1h->check_bitmaps("Cleanup Start"); 2015 2016 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy(); 2017 g1p->record_concurrent_mark_cleanup_start(); 2018 2019 double start = os::elapsedTime(); 2020 2021 HeapRegionRemSet::reset_for_cleanup_tasks(); 2022 2023 uint n_workers; 2024 2025 // Do counting once more with the world stopped for good measure. 2026 G1ParFinalCountTask g1_par_count_task(g1h, &_region_bm, &_card_bm); 2027 2028 if (G1CollectedHeap::use_parallel_gc_threads()) { 2029 assert(g1h->check_heap_region_claim_values(HeapRegion::InitialClaimValue), 2030 "sanity check"); 2031 2032 g1h->set_par_threads(); 2033 n_workers = g1h->n_par_threads(); 2034 assert(g1h->n_par_threads() == n_workers, 2035 "Should not have been reset"); 2036 g1h->workers()->run_task(&g1_par_count_task); 2037 // Done with the parallel phase so reset to 0. 2038 g1h->set_par_threads(0); 2039 2040 assert(g1h->check_heap_region_claim_values(HeapRegion::FinalCountClaimValue), 2041 "sanity check"); 2042 } else { 2043 n_workers = 1; 2044 g1_par_count_task.work(0); 2045 } 2046 2047 if (VerifyDuringGC) { 2048 // Verify that the counting data accumulated during marking matches 2049 // that calculated by walking the marking bitmap. 2050 2051 // Bitmaps to hold expected values 2052 BitMap expected_region_bm(_region_bm.size(), true); 2053 BitMap expected_card_bm(_card_bm.size(), true); 2054 2055 G1ParVerifyFinalCountTask g1_par_verify_task(g1h, 2056 &_region_bm, 2057 &_card_bm, 2058 &expected_region_bm, 2059 &expected_card_bm); 2060 2061 if (G1CollectedHeap::use_parallel_gc_threads()) { 2062 g1h->set_par_threads((int)n_workers); 2063 g1h->workers()->run_task(&g1_par_verify_task); 2064 // Done with the parallel phase so reset to 0. 2065 g1h->set_par_threads(0); 2066 2067 assert(g1h->check_heap_region_claim_values(HeapRegion::VerifyCountClaimValue), 2068 "sanity check"); 2069 } else { 2070 g1_par_verify_task.work(0); 2071 } 2072 2073 guarantee(g1_par_verify_task.failures() == 0, "Unexpected accounting failures"); 2074 } 2075 2076 size_t start_used_bytes = g1h->used(); 2077 g1h->set_marking_complete(); 2078 2079 double count_end = os::elapsedTime(); 2080 double this_final_counting_time = (count_end - start); 2081 _total_counting_time += this_final_counting_time; 2082 2083 if (G1PrintRegionLivenessInfo) { 2084 G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Marking"); 2085 _g1h->heap_region_iterate(&cl); 2086 } 2087 2088 // Install newly created mark bitMap as "prev". 2089 swapMarkBitMaps(); 2090 2091 g1h->reset_gc_time_stamp(); 2092 2093 // Note end of marking in all heap regions. 2094 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list); 2095 if (G1CollectedHeap::use_parallel_gc_threads()) { 2096 g1h->set_par_threads((int)n_workers); 2097 g1h->workers()->run_task(&g1_par_note_end_task); 2098 g1h->set_par_threads(0); 2099 2100 assert(g1h->check_heap_region_claim_values(HeapRegion::NoteEndClaimValue), 2101 "sanity check"); 2102 } else { 2103 g1_par_note_end_task.work(0); 2104 } 2105 g1h->check_gc_time_stamps(); 2106 2107 if (!cleanup_list_is_empty()) { 2108 // The cleanup list is not empty, so we'll have to process it 2109 // concurrently. Notify anyone else that might be wanting free 2110 // regions that there will be more free regions coming soon. 2111 g1h->set_free_regions_coming(); 2112 } 2113 2114 // call below, since it affects the metric by which we sort the heap 2115 // regions. 2116 if (G1ScrubRemSets) { 2117 double rs_scrub_start = os::elapsedTime(); 2118 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1h, &_region_bm, &_card_bm); 2119 if (G1CollectedHeap::use_parallel_gc_threads()) { 2120 g1h->set_par_threads((int)n_workers); 2121 g1h->workers()->run_task(&g1_par_scrub_rs_task); 2122 g1h->set_par_threads(0); 2123 2124 assert(g1h->check_heap_region_claim_values( 2125 HeapRegion::ScrubRemSetClaimValue), 2126 "sanity check"); 2127 } else { 2128 g1_par_scrub_rs_task.work(0); 2129 } 2130 2131 double rs_scrub_end = os::elapsedTime(); 2132 double this_rs_scrub_time = (rs_scrub_end - rs_scrub_start); 2133 _total_rs_scrub_time += this_rs_scrub_time; 2134 } 2135 2136 // this will also free any regions totally full of garbage objects, 2137 // and sort the regions. 2138 g1h->g1_policy()->record_concurrent_mark_cleanup_end((int)n_workers); 2139 2140 // Statistics. 2141 double end = os::elapsedTime(); 2142 _cleanup_times.add((end - start) * 1000.0); 2143 2144 if (G1Log::fine()) { 2145 g1h->print_size_transition(gclog_or_tty, 2146 start_used_bytes, 2147 g1h->used(), 2148 g1h->capacity()); 2149 } 2150 2151 // Clean up will have freed any regions completely full of garbage. 2152 // Update the soft reference policy with the new heap occupancy. 2153 Universe::update_heap_info_at_gc(); 2154 2155 if (VerifyDuringGC) { 2156 HandleMark hm; // handle scope 2157 Universe::heap()->prepare_for_verify(); 2158 Universe::verify(VerifyOption_G1UsePrevMarking, 2159 " VerifyDuringGC:(after)"); 2160 } 2161 g1h->check_bitmaps("Cleanup End"); 2162 2163 g1h->verify_region_sets_optional(); 2164 2165 // We need to make this be a "collection" so any collection pause that 2166 // races with it goes around and waits for completeCleanup to finish. 2167 g1h->increment_total_collections(); 2168 2169 // Clean out dead classes and update Metaspace sizes. 2170 if (ClassUnloadingWithConcurrentMark) { 2171 ClassLoaderDataGraph::purge(); 2172 } 2173 MetaspaceGC::compute_new_size(); 2174 2175 // We reclaimed old regions so we should calculate the sizes to make 2176 // sure we update the old gen/space data. 2177 g1h->g1mm()->update_sizes(); 2178 g1h->allocation_context_stats().update_after_mark(); 2179 2180 g1h->trace_heap_after_concurrent_cycle(); 2181 } 2182 2183 void ConcurrentMark::completeCleanup() { 2184 if (has_aborted()) return; 2185 2186 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2187 2188 _cleanup_list.verify_optional(); 2189 FreeRegionList tmp_free_list("Tmp Free List"); 2190 2191 if (G1ConcRegionFreeingVerbose) { 2192 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : " 2193 "cleanup list has %u entries", 2194 _cleanup_list.length()); 2195 } 2196 2197 // No one else should be accessing the _cleanup_list at this point, 2198 // so it is not necessary to take any locks 2199 while (!_cleanup_list.is_empty()) { 2200 HeapRegion* hr = _cleanup_list.remove_region(true /* from_head */); 2201 assert(hr != NULL, "Got NULL from a non-empty list"); 2202 hr->par_clear(); 2203 tmp_free_list.add_ordered(hr); 2204 2205 // Instead of adding one region at a time to the secondary_free_list, 2206 // we accumulate them in the local list and move them a few at a 2207 // time. This also cuts down on the number of notify_all() calls 2208 // we do during this process. We'll also append the local list when 2209 // _cleanup_list is empty (which means we just removed the last 2210 // region from the _cleanup_list). 2211 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) || 2212 _cleanup_list.is_empty()) { 2213 if (G1ConcRegionFreeingVerbose) { 2214 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : " 2215 "appending %u entries to the secondary_free_list, " 2216 "cleanup list still has %u entries", 2217 tmp_free_list.length(), 2218 _cleanup_list.length()); 2219 } 2220 2221 { 2222 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 2223 g1h->secondary_free_list_add(&tmp_free_list); 2224 SecondaryFreeList_lock->notify_all(); 2225 } 2226 2227 if (G1StressConcRegionFreeing) { 2228 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) { 2229 os::sleep(Thread::current(), (jlong) 1, false); 2230 } 2231 } 2232 } 2233 } 2234 assert(tmp_free_list.is_empty(), "post-condition"); 2235 } 2236 2237 // Supporting Object and Oop closures for reference discovery 2238 // and processing in during marking 2239 2240 bool G1CMIsAliveClosure::do_object_b(oop obj) { 2241 HeapWord* addr = (HeapWord*)obj; 2242 return addr != NULL && 2243 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj)); 2244 } 2245 2246 // 'Keep Alive' oop closure used by both serial parallel reference processing. 2247 // Uses the CMTask associated with a worker thread (for serial reference 2248 // processing the CMTask for worker 0 is used) to preserve (mark) and 2249 // trace referent objects. 2250 // 2251 // Using the CMTask and embedded local queues avoids having the worker 2252 // threads operating on the global mark stack. This reduces the risk 2253 // of overflowing the stack - which we would rather avoid at this late 2254 // state. Also using the tasks' local queues removes the potential 2255 // of the workers interfering with each other that could occur if 2256 // operating on the global stack. 2257 2258 class G1CMKeepAliveAndDrainClosure: public OopClosure { 2259 ConcurrentMark* _cm; 2260 CMTask* _task; 2261 int _ref_counter_limit; 2262 int _ref_counter; 2263 bool _is_serial; 2264 public: 2265 G1CMKeepAliveAndDrainClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) : 2266 _cm(cm), _task(task), _is_serial(is_serial), 2267 _ref_counter_limit(G1RefProcDrainInterval) { 2268 assert(_ref_counter_limit > 0, "sanity"); 2269 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code"); 2270 _ref_counter = _ref_counter_limit; 2271 } 2272 2273 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 2274 virtual void do_oop( oop* p) { do_oop_work(p); } 2275 2276 template <class T> void do_oop_work(T* p) { 2277 if (!_cm->has_overflown()) { 2278 oop obj = oopDesc::load_decode_heap_oop(p); 2279 if (_cm->verbose_high()) { 2280 gclog_or_tty->print_cr("\t[%u] we're looking at location " 2281 "*"PTR_FORMAT" = "PTR_FORMAT, 2282 _task->worker_id(), p2i(p), p2i((void*) obj)); 2283 } 2284 2285 _task->deal_with_reference(obj); 2286 _ref_counter--; 2287 2288 if (_ref_counter == 0) { 2289 // We have dealt with _ref_counter_limit references, pushing them 2290 // and objects reachable from them on to the local stack (and 2291 // possibly the global stack). Call CMTask::do_marking_step() to 2292 // process these entries. 2293 // 2294 // We call CMTask::do_marking_step() in a loop, which we'll exit if 2295 // there's nothing more to do (i.e. we're done with the entries that 2296 // were pushed as a result of the CMTask::deal_with_reference() calls 2297 // above) or we overflow. 2298 // 2299 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted() 2300 // flag while there may still be some work to do. (See the comment at 2301 // the beginning of CMTask::do_marking_step() for those conditions - 2302 // one of which is reaching the specified time target.) It is only 2303 // when CMTask::do_marking_step() returns without setting the 2304 // has_aborted() flag that the marking step has completed. 2305 do { 2306 double mark_step_duration_ms = G1ConcMarkStepDurationMillis; 2307 _task->do_marking_step(mark_step_duration_ms, 2308 false /* do_termination */, 2309 _is_serial); 2310 } while (_task->has_aborted() && !_cm->has_overflown()); 2311 _ref_counter = _ref_counter_limit; 2312 } 2313 } else { 2314 if (_cm->verbose_high()) { 2315 gclog_or_tty->print_cr("\t[%u] CM Overflow", _task->worker_id()); 2316 } 2317 } 2318 } 2319 }; 2320 2321 // 'Drain' oop closure used by both serial and parallel reference processing. 2322 // Uses the CMTask associated with a given worker thread (for serial 2323 // reference processing the CMtask for worker 0 is used). Calls the 2324 // do_marking_step routine, with an unbelievably large timeout value, 2325 // to drain the marking data structures of the remaining entries 2326 // added by the 'keep alive' oop closure above. 2327 2328 class G1CMDrainMarkingStackClosure: public VoidClosure { 2329 ConcurrentMark* _cm; 2330 CMTask* _task; 2331 bool _is_serial; 2332 public: 2333 G1CMDrainMarkingStackClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) : 2334 _cm(cm), _task(task), _is_serial(is_serial) { 2335 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code"); 2336 } 2337 2338 void do_void() { 2339 do { 2340 if (_cm->verbose_high()) { 2341 gclog_or_tty->print_cr("\t[%u] Drain: Calling do_marking_step - serial: %s", 2342 _task->worker_id(), BOOL_TO_STR(_is_serial)); 2343 } 2344 2345 // We call CMTask::do_marking_step() to completely drain the local 2346 // and global marking stacks of entries pushed by the 'keep alive' 2347 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above). 2348 // 2349 // CMTask::do_marking_step() is called in a loop, which we'll exit 2350 // if there's nothing more to do (i.e. we'completely drained the 2351 // entries that were pushed as a a result of applying the 'keep alive' 2352 // closure to the entries on the discovered ref lists) or we overflow 2353 // the global marking stack. 2354 // 2355 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted() 2356 // flag while there may still be some work to do. (See the comment at 2357 // the beginning of CMTask::do_marking_step() for those conditions - 2358 // one of which is reaching the specified time target.) It is only 2359 // when CMTask::do_marking_step() returns without setting the 2360 // has_aborted() flag that the marking step has completed. 2361 2362 _task->do_marking_step(1000000000.0 /* something very large */, 2363 true /* do_termination */, 2364 _is_serial); 2365 } while (_task->has_aborted() && !_cm->has_overflown()); 2366 } 2367 }; 2368 2369 // Implementation of AbstractRefProcTaskExecutor for parallel 2370 // reference processing at the end of G1 concurrent marking 2371 2372 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 2373 private: 2374 G1CollectedHeap* _g1h; 2375 ConcurrentMark* _cm; 2376 WorkGang* _workers; 2377 int _active_workers; 2378 2379 public: 2380 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h, 2381 ConcurrentMark* cm, 2382 WorkGang* workers, 2383 int n_workers) : 2384 _g1h(g1h), _cm(cm), 2385 _workers(workers), _active_workers(n_workers) { } 2386 2387 // Executes the given task using concurrent marking worker threads. 2388 virtual void execute(ProcessTask& task); 2389 virtual void execute(EnqueueTask& task); 2390 }; 2391 2392 class G1CMRefProcTaskProxy: public AbstractGangTask { 2393 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 2394 ProcessTask& _proc_task; 2395 G1CollectedHeap* _g1h; 2396 ConcurrentMark* _cm; 2397 2398 public: 2399 G1CMRefProcTaskProxy(ProcessTask& proc_task, 2400 G1CollectedHeap* g1h, 2401 ConcurrentMark* cm) : 2402 AbstractGangTask("Process reference objects in parallel"), 2403 _proc_task(proc_task), _g1h(g1h), _cm(cm) { 2404 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 2405 assert(rp->processing_is_mt(), "shouldn't be here otherwise"); 2406 } 2407 2408 virtual void work(uint worker_id) { 2409 ResourceMark rm; 2410 HandleMark hm; 2411 CMTask* task = _cm->task(worker_id); 2412 G1CMIsAliveClosure g1_is_alive(_g1h); 2413 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */); 2414 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */); 2415 2416 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain); 2417 } 2418 }; 2419 2420 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) { 2421 assert(_workers != NULL, "Need parallel worker threads."); 2422 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT"); 2423 2424 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm); 2425 2426 // We need to reset the concurrency level before each 2427 // proxy task execution, so that the termination protocol 2428 // and overflow handling in CMTask::do_marking_step() knows 2429 // how many workers to wait for. 2430 _cm->set_concurrency(_active_workers); 2431 _g1h->set_par_threads(_active_workers); 2432 _workers->run_task(&proc_task_proxy); 2433 _g1h->set_par_threads(0); 2434 } 2435 2436 class G1CMRefEnqueueTaskProxy: public AbstractGangTask { 2437 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 2438 EnqueueTask& _enq_task; 2439 2440 public: 2441 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) : 2442 AbstractGangTask("Enqueue reference objects in parallel"), 2443 _enq_task(enq_task) { } 2444 2445 virtual void work(uint worker_id) { 2446 _enq_task.work(worker_id); 2447 } 2448 }; 2449 2450 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 2451 assert(_workers != NULL, "Need parallel worker threads."); 2452 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT"); 2453 2454 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task); 2455 2456 // Not strictly necessary but... 2457 // 2458 // We need to reset the concurrency level before each 2459 // proxy task execution, so that the termination protocol 2460 // and overflow handling in CMTask::do_marking_step() knows 2461 // how many workers to wait for. 2462 _cm->set_concurrency(_active_workers); 2463 _g1h->set_par_threads(_active_workers); 2464 _workers->run_task(&enq_task_proxy); 2465 _g1h->set_par_threads(0); 2466 } 2467 2468 void ConcurrentMark::weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes) { 2469 G1CollectedHeap::heap()->parallel_cleaning(is_alive, true, true, purged_classes); 2470 } 2471 2472 // Helper class to get rid of some boilerplate code. 2473 class G1RemarkGCTraceTime : public GCTraceTime { 2474 static bool doit_and_prepend(bool doit) { 2475 if (doit) { 2476 gclog_or_tty->put(' '); 2477 } 2478 return doit; 2479 } 2480 2481 public: 2482 G1RemarkGCTraceTime(const char* title, bool doit) 2483 : GCTraceTime(title, doit_and_prepend(doit), false, G1CollectedHeap::heap()->gc_timer_cm(), 2484 G1CollectedHeap::heap()->concurrent_mark()->concurrent_gc_id()) { 2485 } 2486 }; 2487 2488 void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) { 2489 if (has_overflown()) { 2490 // Skip processing the discovered references if we have 2491 // overflown the global marking stack. Reference objects 2492 // only get discovered once so it is OK to not 2493 // de-populate the discovered reference lists. We could have, 2494 // but the only benefit would be that, when marking restarts, 2495 // less reference objects are discovered. 2496 return; 2497 } 2498 2499 ResourceMark rm; 2500 HandleMark hm; 2501 2502 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2503 2504 // Is alive closure. 2505 G1CMIsAliveClosure g1_is_alive(g1h); 2506 2507 // Inner scope to exclude the cleaning of the string and symbol 2508 // tables from the displayed time. 2509 { 2510 if (G1Log::finer()) { 2511 gclog_or_tty->put(' '); 2512 } 2513 GCTraceTime t("GC ref-proc", G1Log::finer(), false, g1h->gc_timer_cm(), concurrent_gc_id()); 2514 2515 ReferenceProcessor* rp = g1h->ref_processor_cm(); 2516 2517 // See the comment in G1CollectedHeap::ref_processing_init() 2518 // about how reference processing currently works in G1. 2519 2520 // Set the soft reference policy 2521 rp->setup_policy(clear_all_soft_refs); 2522 assert(_markStack.isEmpty(), "mark stack should be empty"); 2523 2524 // Instances of the 'Keep Alive' and 'Complete GC' closures used 2525 // in serial reference processing. Note these closures are also 2526 // used for serially processing (by the the current thread) the 2527 // JNI references during parallel reference processing. 2528 // 2529 // These closures do not need to synchronize with the worker 2530 // threads involved in parallel reference processing as these 2531 // instances are executed serially by the current thread (e.g. 2532 // reference processing is not multi-threaded and is thus 2533 // performed by the current thread instead of a gang worker). 2534 // 2535 // The gang tasks involved in parallel reference procssing create 2536 // their own instances of these closures, which do their own 2537 // synchronization among themselves. 2538 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */); 2539 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */); 2540 2541 // We need at least one active thread. If reference processing 2542 // is not multi-threaded we use the current (VMThread) thread, 2543 // otherwise we use the work gang from the G1CollectedHeap and 2544 // we utilize all the worker threads we can. 2545 bool processing_is_mt = rp->processing_is_mt() && g1h->workers() != NULL; 2546 uint active_workers = (processing_is_mt ? g1h->workers()->active_workers() : 1U); 2547 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U); 2548 2549 // Parallel processing task executor. 2550 G1CMRefProcTaskExecutor par_task_executor(g1h, this, 2551 g1h->workers(), active_workers); 2552 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL); 2553 2554 // Set the concurrency level. The phase was already set prior to 2555 // executing the remark task. 2556 set_concurrency(active_workers); 2557 2558 // Set the degree of MT processing here. If the discovery was done MT, 2559 // the number of threads involved during discovery could differ from 2560 // the number of active workers. This is OK as long as the discovered 2561 // Reference lists are balanced (see balance_all_queues() and balance_queues()). 2562 rp->set_active_mt_degree(active_workers); 2563 2564 // Process the weak references. 2565 const ReferenceProcessorStats& stats = 2566 rp->process_discovered_references(&g1_is_alive, 2567 &g1_keep_alive, 2568 &g1_drain_mark_stack, 2569 executor, 2570 g1h->gc_timer_cm(), 2571 concurrent_gc_id()); 2572 g1h->gc_tracer_cm()->report_gc_reference_stats(stats); 2573 2574 // The do_oop work routines of the keep_alive and drain_marking_stack 2575 // oop closures will set the has_overflown flag if we overflow the 2576 // global marking stack. 2577 2578 assert(_markStack.overflow() || _markStack.isEmpty(), 2579 "mark stack should be empty (unless it overflowed)"); 2580 2581 if (_markStack.overflow()) { 2582 // This should have been done already when we tried to push an 2583 // entry on to the global mark stack. But let's do it again. 2584 set_has_overflown(); 2585 } 2586 2587 assert(rp->num_q() == active_workers, "why not"); 2588 2589 rp->enqueue_discovered_references(executor); 2590 2591 rp->verify_no_references_recorded(); 2592 assert(!rp->discovery_enabled(), "Post condition"); 2593 } 2594 2595 if (has_overflown()) { 2596 // We can not trust g1_is_alive if the marking stack overflowed 2597 return; 2598 } 2599 2600 assert(_markStack.isEmpty(), "Marking should have completed"); 2601 2602 // Unload Klasses, String, Symbols, Code Cache, etc. 2603 { 2604 G1RemarkGCTraceTime trace("Unloading", G1Log::finer()); 2605 2606 if (ClassUnloadingWithConcurrentMark) { 2607 // Cleaning of klasses depends on correct information from MetadataMarkOnStack. The CodeCache::mark_on_stack 2608 // part is too slow to be done serially, so it is handled during the weakRefsWorkParallelPart phase. 2609 // Defer the cleaning until we have complete on_stack data. 2610 MetadataOnStackMark md_on_stack(false /* Don't visit the code cache at this point */); 2611 2612 bool purged_classes; 2613 2614 { 2615 G1RemarkGCTraceTime trace("System Dictionary Unloading", G1Log::finest()); 2616 purged_classes = SystemDictionary::do_unloading(&g1_is_alive, false /* Defer klass cleaning */); 2617 } 2618 2619 { 2620 G1RemarkGCTraceTime trace("Parallel Unloading", G1Log::finest()); 2621 weakRefsWorkParallelPart(&g1_is_alive, purged_classes); 2622 } 2623 2624 { 2625 G1RemarkGCTraceTime trace("Deallocate Metadata", G1Log::finest()); 2626 ClassLoaderDataGraph::free_deallocate_lists(); 2627 } 2628 } 2629 2630 if (G1StringDedup::is_enabled()) { 2631 G1RemarkGCTraceTime trace("String Deduplication Unlink", G1Log::finest()); 2632 G1StringDedup::unlink(&g1_is_alive); 2633 } 2634 } 2635 } 2636 2637 void ConcurrentMark::swapMarkBitMaps() { 2638 CMBitMapRO* temp = _prevMarkBitMap; 2639 _prevMarkBitMap = (CMBitMapRO*)_nextMarkBitMap; 2640 _nextMarkBitMap = (CMBitMap*) temp; 2641 } 2642 2643 // Closure for marking entries in SATB buffers. 2644 class CMSATBBufferClosure : public SATBBufferClosure { 2645 private: 2646 CMTask* _task; 2647 G1CollectedHeap* _g1h; 2648 2649 // This is very similar to CMTask::deal_with_reference, but with 2650 // more relaxed requirements for the argument, so this must be more 2651 // circumspect about treating the argument as an object. 2652 void do_entry(void* entry) const { 2653 _task->increment_refs_reached(); 2654 HeapRegion* hr = _g1h->heap_region_containing_raw(entry); 2655 if (entry < hr->next_top_at_mark_start()) { 2656 // Until we get here, we don't know whether entry refers to a valid 2657 // object; it could instead have been a stale reference. 2658 oop obj = static_cast<oop>(entry); 2659 assert(obj->is_oop(true /* ignore mark word */), 2660 err_msg("Invalid oop in SATB buffer: " PTR_FORMAT, p2i(obj))); 2661 _task->make_reference_grey(obj, hr); 2662 } 2663 } 2664 2665 public: 2666 CMSATBBufferClosure(CMTask* task, G1CollectedHeap* g1h) 2667 : _task(task), _g1h(g1h) { } 2668 2669 virtual void do_buffer(void** buffer, size_t size) { 2670 for (size_t i = 0; i < size; ++i) { 2671 do_entry(buffer[i]); 2672 } 2673 } 2674 }; 2675 2676 class G1RemarkThreadsClosure : public ThreadClosure { 2677 CMSATBBufferClosure _cm_satb_cl; 2678 G1CMOopClosure _cm_cl; 2679 MarkingCodeBlobClosure _code_cl; 2680 int _thread_parity; 2681 bool _is_par; 2682 2683 public: 2684 G1RemarkThreadsClosure(G1CollectedHeap* g1h, CMTask* task, bool is_par) : 2685 _cm_satb_cl(task, g1h), 2686 _cm_cl(g1h, g1h->concurrent_mark(), task), 2687 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations), 2688 _thread_parity(SharedHeap::heap()->strong_roots_parity()), _is_par(is_par) {} 2689 2690 void do_thread(Thread* thread) { 2691 if (thread->is_Java_thread()) { 2692 if (thread->claim_oops_do(_is_par, _thread_parity)) { 2693 JavaThread* jt = (JavaThread*)thread; 2694 2695 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking 2696 // however the liveness of oops reachable from nmethods have very complex lifecycles: 2697 // * Alive if on the stack of an executing method 2698 // * Weakly reachable otherwise 2699 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be 2700 // live by the SATB invariant but other oops recorded in nmethods may behave differently. 2701 jt->nmethods_do(&_code_cl); 2702 2703 jt->satb_mark_queue().apply_closure_and_empty(&_cm_satb_cl); 2704 } 2705 } else if (thread->is_VM_thread()) { 2706 if (thread->claim_oops_do(_is_par, _thread_parity)) { 2707 JavaThread::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(&_cm_satb_cl); 2708 } 2709 } 2710 } 2711 }; 2712 2713 class CMRemarkTask: public AbstractGangTask { 2714 private: 2715 ConcurrentMark* _cm; 2716 bool _is_serial; 2717 public: 2718 void work(uint worker_id) { 2719 // Since all available tasks are actually started, we should 2720 // only proceed if we're supposed to be actived. 2721 if (worker_id < _cm->active_tasks()) { 2722 CMTask* task = _cm->task(worker_id); 2723 task->record_start_time(); 2724 { 2725 ResourceMark rm; 2726 HandleMark hm; 2727 2728 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task, !_is_serial); 2729 Threads::threads_do(&threads_f); 2730 } 2731 2732 do { 2733 task->do_marking_step(1000000000.0 /* something very large */, 2734 true /* do_termination */, 2735 _is_serial); 2736 } while (task->has_aborted() && !_cm->has_overflown()); 2737 // If we overflow, then we do not want to restart. We instead 2738 // want to abort remark and do concurrent marking again. 2739 task->record_end_time(); 2740 } 2741 } 2742 2743 CMRemarkTask(ConcurrentMark* cm, int active_workers, bool is_serial) : 2744 AbstractGangTask("Par Remark"), _cm(cm), _is_serial(is_serial) { 2745 _cm->terminator()->reset_for_reuse(active_workers); 2746 } 2747 }; 2748 2749 void ConcurrentMark::checkpointRootsFinalWork() { 2750 ResourceMark rm; 2751 HandleMark hm; 2752 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2753 2754 G1RemarkGCTraceTime trace("Finalize Marking", G1Log::finer()); 2755 2756 g1h->ensure_parsability(false); 2757 2758 if (G1CollectedHeap::use_parallel_gc_threads()) { 2759 G1CollectedHeap::StrongRootsScope srs(g1h); 2760 // this is remark, so we'll use up all active threads 2761 uint active_workers = g1h->workers()->active_workers(); 2762 if (active_workers == 0) { 2763 assert(active_workers > 0, "Should have been set earlier"); 2764 active_workers = (uint) ParallelGCThreads; 2765 g1h->workers()->set_active_workers(active_workers); 2766 } 2767 set_concurrency_and_phase(active_workers, false /* concurrent */); 2768 // Leave _parallel_marking_threads at it's 2769 // value originally calculated in the ConcurrentMark 2770 // constructor and pass values of the active workers 2771 // through the gang in the task. 2772 2773 CMRemarkTask remarkTask(this, active_workers, false /* is_serial */); 2774 // We will start all available threads, even if we decide that the 2775 // active_workers will be fewer. The extra ones will just bail out 2776 // immediately. 2777 g1h->set_par_threads(active_workers); 2778 g1h->workers()->run_task(&remarkTask); 2779 g1h->set_par_threads(0); 2780 } else { 2781 G1CollectedHeap::StrongRootsScope srs(g1h); 2782 uint active_workers = 1; 2783 set_concurrency_and_phase(active_workers, false /* concurrent */); 2784 2785 // Note - if there's no work gang then the VMThread will be 2786 // the thread to execute the remark - serially. We have 2787 // to pass true for the is_serial parameter so that 2788 // CMTask::do_marking_step() doesn't enter the sync 2789 // barriers in the event of an overflow. Doing so will 2790 // cause an assert that the current thread is not a 2791 // concurrent GC thread. 2792 CMRemarkTask remarkTask(this, active_workers, true /* is_serial*/); 2793 remarkTask.work(0); 2794 } 2795 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 2796 guarantee(has_overflown() || 2797 satb_mq_set.completed_buffers_num() == 0, 2798 err_msg("Invariant: has_overflown = %s, num buffers = %d", 2799 BOOL_TO_STR(has_overflown()), 2800 satb_mq_set.completed_buffers_num())); 2801 2802 print_stats(); 2803 } 2804 2805 #ifndef PRODUCT 2806 2807 class PrintReachableOopClosure: public OopClosure { 2808 private: 2809 G1CollectedHeap* _g1h; 2810 outputStream* _out; 2811 VerifyOption _vo; 2812 bool _all; 2813 2814 public: 2815 PrintReachableOopClosure(outputStream* out, 2816 VerifyOption vo, 2817 bool all) : 2818 _g1h(G1CollectedHeap::heap()), 2819 _out(out), _vo(vo), _all(all) { } 2820 2821 void do_oop(narrowOop* p) { do_oop_work(p); } 2822 void do_oop( oop* p) { do_oop_work(p); } 2823 2824 template <class T> void do_oop_work(T* p) { 2825 oop obj = oopDesc::load_decode_heap_oop(p); 2826 const char* str = NULL; 2827 const char* str2 = ""; 2828 2829 if (obj == NULL) { 2830 str = ""; 2831 } else if (!_g1h->is_in_g1_reserved(obj)) { 2832 str = " O"; 2833 } else { 2834 HeapRegion* hr = _g1h->heap_region_containing(obj); 2835 bool over_tams = _g1h->allocated_since_marking(obj, hr, _vo); 2836 bool marked = _g1h->is_marked(obj, _vo); 2837 2838 if (over_tams) { 2839 str = " >"; 2840 if (marked) { 2841 str2 = " AND MARKED"; 2842 } 2843 } else if (marked) { 2844 str = " M"; 2845 } else { 2846 str = " NOT"; 2847 } 2848 } 2849 2850 _out->print_cr(" "PTR_FORMAT": "PTR_FORMAT"%s%s", 2851 p2i(p), p2i((void*) obj), str, str2); 2852 } 2853 }; 2854 2855 class PrintReachableObjectClosure : public ObjectClosure { 2856 private: 2857 G1CollectedHeap* _g1h; 2858 outputStream* _out; 2859 VerifyOption _vo; 2860 bool _all; 2861 HeapRegion* _hr; 2862 2863 public: 2864 PrintReachableObjectClosure(outputStream* out, 2865 VerifyOption vo, 2866 bool all, 2867 HeapRegion* hr) : 2868 _g1h(G1CollectedHeap::heap()), 2869 _out(out), _vo(vo), _all(all), _hr(hr) { } 2870 2871 void do_object(oop o) { 2872 bool over_tams = _g1h->allocated_since_marking(o, _hr, _vo); 2873 bool marked = _g1h->is_marked(o, _vo); 2874 bool print_it = _all || over_tams || marked; 2875 2876 if (print_it) { 2877 _out->print_cr(" "PTR_FORMAT"%s", 2878 p2i((void *)o), (over_tams) ? " >" : (marked) ? " M" : ""); 2879 PrintReachableOopClosure oopCl(_out, _vo, _all); 2880 o->oop_iterate_no_header(&oopCl); 2881 } 2882 } 2883 }; 2884 2885 class PrintReachableRegionClosure : public HeapRegionClosure { 2886 private: 2887 G1CollectedHeap* _g1h; 2888 outputStream* _out; 2889 VerifyOption _vo; 2890 bool _all; 2891 2892 public: 2893 bool doHeapRegion(HeapRegion* hr) { 2894 HeapWord* b = hr->bottom(); 2895 HeapWord* e = hr->end(); 2896 HeapWord* t = hr->top(); 2897 HeapWord* p = _g1h->top_at_mark_start(hr, _vo); 2898 _out->print_cr("** ["PTR_FORMAT", "PTR_FORMAT"] top: "PTR_FORMAT" " 2899 "TAMS: " PTR_FORMAT, p2i(b), p2i(e), p2i(t), p2i(p)); 2900 _out->cr(); 2901 2902 HeapWord* from = b; 2903 HeapWord* to = t; 2904 2905 if (to > from) { 2906 _out->print_cr("Objects in [" PTR_FORMAT ", " PTR_FORMAT "]", p2i(from), p2i(to)); 2907 _out->cr(); 2908 PrintReachableObjectClosure ocl(_out, _vo, _all, hr); 2909 hr->object_iterate_mem_careful(MemRegion(from, to), &ocl); 2910 _out->cr(); 2911 } 2912 2913 return false; 2914 } 2915 2916 PrintReachableRegionClosure(outputStream* out, 2917 VerifyOption vo, 2918 bool all) : 2919 _g1h(G1CollectedHeap::heap()), _out(out), _vo(vo), _all(all) { } 2920 }; 2921 2922 void ConcurrentMark::print_reachable(const char* str, 2923 VerifyOption vo, 2924 bool all) { 2925 gclog_or_tty->cr(); 2926 gclog_or_tty->print_cr("== Doing heap dump... "); 2927 2928 if (G1PrintReachableBaseFile == NULL) { 2929 gclog_or_tty->print_cr(" #### error: no base file defined"); 2930 return; 2931 } 2932 2933 if (strlen(G1PrintReachableBaseFile) + 1 + strlen(str) > 2934 (JVM_MAXPATHLEN - 1)) { 2935 gclog_or_tty->print_cr(" #### error: file name too long"); 2936 return; 2937 } 2938 2939 char file_name[JVM_MAXPATHLEN]; 2940 sprintf(file_name, "%s.%s", G1PrintReachableBaseFile, str); 2941 gclog_or_tty->print_cr(" dumping to file %s", file_name); 2942 2943 fileStream fout(file_name); 2944 if (!fout.is_open()) { 2945 gclog_or_tty->print_cr(" #### error: could not open file"); 2946 return; 2947 } 2948 2949 outputStream* out = &fout; 2950 out->print_cr("-- USING %s", _g1h->top_at_mark_start_str(vo)); 2951 out->cr(); 2952 2953 out->print_cr("--- ITERATING OVER REGIONS"); 2954 out->cr(); 2955 PrintReachableRegionClosure rcl(out, vo, all); 2956 _g1h->heap_region_iterate(&rcl); 2957 out->cr(); 2958 2959 gclog_or_tty->print_cr(" done"); 2960 gclog_or_tty->flush(); 2961 } 2962 2963 #endif // PRODUCT 2964 2965 void ConcurrentMark::clearRangePrevBitmap(MemRegion mr) { 2966 // Note we are overriding the read-only view of the prev map here, via 2967 // the cast. 2968 ((CMBitMap*)_prevMarkBitMap)->clearRange(mr); 2969 } 2970 2971 void ConcurrentMark::clearRangeNextBitmap(MemRegion mr) { 2972 _nextMarkBitMap->clearRange(mr); 2973 } 2974 2975 HeapRegion* 2976 ConcurrentMark::claim_region(uint worker_id) { 2977 // "checkpoint" the finger 2978 HeapWord* finger = _finger; 2979 2980 // _heap_end will not change underneath our feet; it only changes at 2981 // yield points. 2982 while (finger < _heap_end) { 2983 assert(_g1h->is_in_g1_reserved(finger), "invariant"); 2984 2985 // Note on how this code handles humongous regions. In the 2986 // normal case the finger will reach the start of a "starts 2987 // humongous" (SH) region. Its end will either be the end of the 2988 // last "continues humongous" (CH) region in the sequence, or the 2989 // standard end of the SH region (if the SH is the only region in 2990 // the sequence). That way claim_region() will skip over the CH 2991 // regions. However, there is a subtle race between a CM thread 2992 // executing this method and a mutator thread doing a humongous 2993 // object allocation. The two are not mutually exclusive as the CM 2994 // thread does not need to hold the Heap_lock when it gets 2995 // here. So there is a chance that claim_region() will come across 2996 // a free region that's in the progress of becoming a SH or a CH 2997 // region. In the former case, it will either 2998 // a) Miss the update to the region's end, in which case it will 2999 // visit every subsequent CH region, will find their bitmaps 3000 // empty, and do nothing, or 3001 // b) Will observe the update of the region's end (in which case 3002 // it will skip the subsequent CH regions). 3003 // If it comes across a region that suddenly becomes CH, the 3004 // scenario will be similar to b). So, the race between 3005 // claim_region() and a humongous object allocation might force us 3006 // to do a bit of unnecessary work (due to some unnecessary bitmap 3007 // iterations) but it should not introduce and correctness issues. 3008 HeapRegion* curr_region = _g1h->heap_region_containing_raw(finger); 3009 3010 // Above heap_region_containing_raw may return NULL as we always scan claim 3011 // until the end of the heap. In this case, just jump to the next region. 3012 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords; 3013 3014 // Is the gap between reading the finger and doing the CAS too long? 3015 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger); 3016 if (res == finger && curr_region != NULL) { 3017 // we succeeded 3018 HeapWord* bottom = curr_region->bottom(); 3019 HeapWord* limit = curr_region->next_top_at_mark_start(); 3020 3021 if (verbose_low()) { 3022 gclog_or_tty->print_cr("[%u] curr_region = "PTR_FORMAT" " 3023 "["PTR_FORMAT", "PTR_FORMAT"), " 3024 "limit = "PTR_FORMAT, 3025 worker_id, p2i(curr_region), p2i(bottom), p2i(end), p2i(limit)); 3026 } 3027 3028 // notice that _finger == end cannot be guaranteed here since, 3029 // someone else might have moved the finger even further 3030 assert(_finger >= end, "the finger should have moved forward"); 3031 3032 if (verbose_low()) { 3033 gclog_or_tty->print_cr("[%u] we were successful with region = " 3034 PTR_FORMAT, worker_id, p2i(curr_region)); 3035 } 3036 3037 if (limit > bottom) { 3038 if (verbose_low()) { 3039 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is not empty, " 3040 "returning it ", worker_id, p2i(curr_region)); 3041 } 3042 return curr_region; 3043 } else { 3044 assert(limit == bottom, 3045 "the region limit should be at bottom"); 3046 if (verbose_low()) { 3047 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is empty, " 3048 "returning NULL", worker_id, p2i(curr_region)); 3049 } 3050 // we return NULL and the caller should try calling 3051 // claim_region() again. 3052 return NULL; 3053 } 3054 } else { 3055 assert(_finger > finger, "the finger should have moved forward"); 3056 if (verbose_low()) { 3057 if (curr_region == NULL) { 3058 gclog_or_tty->print_cr("[%u] found uncommitted region, moving finger, " 3059 "global finger = "PTR_FORMAT", " 3060 "our finger = "PTR_FORMAT, 3061 worker_id, p2i(_finger), p2i(finger)); 3062 } else { 3063 gclog_or_tty->print_cr("[%u] somebody else moved the finger, " 3064 "global finger = "PTR_FORMAT", " 3065 "our finger = "PTR_FORMAT, 3066 worker_id, p2i(_finger), p2i(finger)); 3067 } 3068 } 3069 3070 // read it again 3071 finger = _finger; 3072 } 3073 } 3074 3075 return NULL; 3076 } 3077 3078 #ifndef PRODUCT 3079 enum VerifyNoCSetOopsPhase { 3080 VerifyNoCSetOopsStack, 3081 VerifyNoCSetOopsQueues 3082 }; 3083 3084 class VerifyNoCSetOopsClosure : public OopClosure, public ObjectClosure { 3085 private: 3086 G1CollectedHeap* _g1h; 3087 VerifyNoCSetOopsPhase _phase; 3088 int _info; 3089 3090 const char* phase_str() { 3091 switch (_phase) { 3092 case VerifyNoCSetOopsStack: return "Stack"; 3093 case VerifyNoCSetOopsQueues: return "Queue"; 3094 default: ShouldNotReachHere(); 3095 } 3096 return NULL; 3097 } 3098 3099 void do_object_work(oop obj) { 3100 guarantee(!_g1h->obj_in_cs(obj), 3101 err_msg("obj: "PTR_FORMAT" in CSet, phase: %s, info: %d", 3102 p2i((void*) obj), phase_str(), _info)); 3103 } 3104 3105 public: 3106 VerifyNoCSetOopsClosure() : _g1h(G1CollectedHeap::heap()) { } 3107 3108 void set_phase(VerifyNoCSetOopsPhase phase, int info = -1) { 3109 _phase = phase; 3110 _info = info; 3111 } 3112 3113 virtual void do_oop(oop* p) { 3114 oop obj = oopDesc::load_decode_heap_oop(p); 3115 do_object_work(obj); 3116 } 3117 3118 virtual void do_oop(narrowOop* p) { 3119 // We should not come across narrow oops while scanning marking 3120 // stacks 3121 ShouldNotReachHere(); 3122 } 3123 3124 virtual void do_object(oop obj) { 3125 do_object_work(obj); 3126 } 3127 }; 3128 3129 void ConcurrentMark::verify_no_cset_oops() { 3130 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint"); 3131 if (!G1CollectedHeap::heap()->mark_in_progress()) { 3132 return; 3133 } 3134 3135 VerifyNoCSetOopsClosure cl; 3136 3137 // Verify entries on the global mark stack 3138 cl.set_phase(VerifyNoCSetOopsStack); 3139 _markStack.oops_do(&cl); 3140 3141 // Verify entries on the task queues 3142 for (uint i = 0; i < _max_worker_id; i += 1) { 3143 cl.set_phase(VerifyNoCSetOopsQueues, i); 3144 CMTaskQueue* queue = _task_queues->queue(i); 3145 queue->oops_do(&cl); 3146 } 3147 3148 // Verify the global finger 3149 HeapWord* global_finger = finger(); 3150 if (global_finger != NULL && global_finger < _heap_end) { 3151 // The global finger always points to a heap region boundary. We 3152 // use heap_region_containing_raw() to get the containing region 3153 // given that the global finger could be pointing to a free region 3154 // which subsequently becomes continues humongous. If that 3155 // happens, heap_region_containing() will return the bottom of the 3156 // corresponding starts humongous region and the check below will 3157 // not hold any more. 3158 // Since we always iterate over all regions, we might get a NULL HeapRegion 3159 // here. 3160 HeapRegion* global_hr = _g1h->heap_region_containing_raw(global_finger); 3161 guarantee(global_hr == NULL || global_finger == global_hr->bottom(), 3162 err_msg("global finger: "PTR_FORMAT" region: "HR_FORMAT, 3163 p2i(global_finger), HR_FORMAT_PARAMS(global_hr))); 3164 } 3165 3166 // Verify the task fingers 3167 assert(parallel_marking_threads() <= _max_worker_id, "sanity"); 3168 for (int i = 0; i < (int) parallel_marking_threads(); i += 1) { 3169 CMTask* task = _tasks[i]; 3170 HeapWord* task_finger = task->finger(); 3171 if (task_finger != NULL && task_finger < _heap_end) { 3172 // See above note on the global finger verification. 3173 HeapRegion* task_hr = _g1h->heap_region_containing_raw(task_finger); 3174 guarantee(task_hr == NULL || task_finger == task_hr->bottom() || 3175 !task_hr->in_collection_set(), 3176 err_msg("task finger: "PTR_FORMAT" region: "HR_FORMAT, 3177 p2i(task_finger), HR_FORMAT_PARAMS(task_hr))); 3178 } 3179 } 3180 } 3181 #endif // PRODUCT 3182 3183 // Aggregate the counting data that was constructed concurrently 3184 // with marking. 3185 class AggregateCountDataHRClosure: public HeapRegionClosure { 3186 G1CollectedHeap* _g1h; 3187 ConcurrentMark* _cm; 3188 CardTableModRefBS* _ct_bs; 3189 BitMap* _cm_card_bm; 3190 uint _max_worker_id; 3191 3192 public: 3193 AggregateCountDataHRClosure(G1CollectedHeap* g1h, 3194 BitMap* cm_card_bm, 3195 uint max_worker_id) : 3196 _g1h(g1h), _cm(g1h->concurrent_mark()), 3197 _ct_bs((CardTableModRefBS*) (g1h->barrier_set())), 3198 _cm_card_bm(cm_card_bm), _max_worker_id(max_worker_id) { } 3199 3200 bool doHeapRegion(HeapRegion* hr) { 3201 if (hr->continuesHumongous()) { 3202 // We will ignore these here and process them when their 3203 // associated "starts humongous" region is processed. 3204 // Note that we cannot rely on their associated 3205 // "starts humongous" region to have their bit set to 1 3206 // since, due to the region chunking in the parallel region 3207 // iteration, a "continues humongous" region might be visited 3208 // before its associated "starts humongous". 3209 return false; 3210 } 3211 3212 HeapWord* start = hr->bottom(); 3213 HeapWord* limit = hr->next_top_at_mark_start(); 3214 HeapWord* end = hr->end(); 3215 3216 assert(start <= limit && limit <= hr->top() && hr->top() <= hr->end(), 3217 err_msg("Preconditions not met - " 3218 "start: "PTR_FORMAT", limit: "PTR_FORMAT", " 3219 "top: "PTR_FORMAT", end: "PTR_FORMAT, 3220 p2i(start), p2i(limit), p2i(hr->top()), p2i(hr->end()))); 3221 3222 assert(hr->next_marked_bytes() == 0, "Precondition"); 3223 3224 if (start == limit) { 3225 // NTAMS of this region has not been set so nothing to do. 3226 return false; 3227 } 3228 3229 // 'start' should be in the heap. 3230 assert(_g1h->is_in_g1_reserved(start) && _ct_bs->is_card_aligned(start), "sanity"); 3231 // 'end' *may* be just beyone the end of the heap (if hr is the last region) 3232 assert(!_g1h->is_in_g1_reserved(end) || _ct_bs->is_card_aligned(end), "sanity"); 3233 3234 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start); 3235 BitMap::idx_t limit_idx = _cm->card_bitmap_index_for(limit); 3236 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(end); 3237 3238 // If ntams is not card aligned then we bump card bitmap index 3239 // for limit so that we get the all the cards spanned by 3240 // the object ending at ntams. 3241 // Note: if this is the last region in the heap then ntams 3242 // could be actually just beyond the end of the the heap; 3243 // limit_idx will then correspond to a (non-existent) card 3244 // that is also outside the heap. 3245 if (_g1h->is_in_g1_reserved(limit) && !_ct_bs->is_card_aligned(limit)) { 3246 limit_idx += 1; 3247 } 3248 3249 assert(limit_idx <= end_idx, "or else use atomics"); 3250 3251 // Aggregate the "stripe" in the count data associated with hr. 3252 uint hrm_index = hr->hrm_index(); 3253 size_t marked_bytes = 0; 3254 3255 for (uint i = 0; i < _max_worker_id; i += 1) { 3256 size_t* marked_bytes_array = _cm->count_marked_bytes_array_for(i); 3257 BitMap* task_card_bm = _cm->count_card_bitmap_for(i); 3258 3259 // Fetch the marked_bytes in this region for task i and 3260 // add it to the running total for this region. 3261 marked_bytes += marked_bytes_array[hrm_index]; 3262 3263 // Now union the bitmaps[0,max_worker_id)[start_idx..limit_idx) 3264 // into the global card bitmap. 3265 BitMap::idx_t scan_idx = task_card_bm->get_next_one_offset(start_idx, limit_idx); 3266 3267 while (scan_idx < limit_idx) { 3268 assert(task_card_bm->at(scan_idx) == true, "should be"); 3269 _cm_card_bm->set_bit(scan_idx); 3270 assert(_cm_card_bm->at(scan_idx) == true, "should be"); 3271 3272 // BitMap::get_next_one_offset() can handle the case when 3273 // its left_offset parameter is greater than its right_offset 3274 // parameter. It does, however, have an early exit if 3275 // left_offset == right_offset. So let's limit the value 3276 // passed in for left offset here. 3277 BitMap::idx_t next_idx = MIN2(scan_idx + 1, limit_idx); 3278 scan_idx = task_card_bm->get_next_one_offset(next_idx, limit_idx); 3279 } 3280 } 3281 3282 // Update the marked bytes for this region. 3283 hr->add_to_marked_bytes(marked_bytes); 3284 3285 // Next heap region 3286 return false; 3287 } 3288 }; 3289 3290 class G1AggregateCountDataTask: public AbstractGangTask { 3291 protected: 3292 G1CollectedHeap* _g1h; 3293 ConcurrentMark* _cm; 3294 BitMap* _cm_card_bm; 3295 uint _max_worker_id; 3296 int _active_workers; 3297 3298 public: 3299 G1AggregateCountDataTask(G1CollectedHeap* g1h, 3300 ConcurrentMark* cm, 3301 BitMap* cm_card_bm, 3302 uint max_worker_id, 3303 int n_workers) : 3304 AbstractGangTask("Count Aggregation"), 3305 _g1h(g1h), _cm(cm), _cm_card_bm(cm_card_bm), 3306 _max_worker_id(max_worker_id), 3307 _active_workers(n_workers) { } 3308 3309 void work(uint worker_id) { 3310 AggregateCountDataHRClosure cl(_g1h, _cm_card_bm, _max_worker_id); 3311 3312 if (G1CollectedHeap::use_parallel_gc_threads()) { 3313 _g1h->heap_region_par_iterate_chunked(&cl, worker_id, 3314 _active_workers, 3315 HeapRegion::AggregateCountClaimValue); 3316 } else { 3317 _g1h->heap_region_iterate(&cl); 3318 } 3319 } 3320 }; 3321 3322 3323 void ConcurrentMark::aggregate_count_data() { 3324 int n_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 3325 _g1h->workers()->active_workers() : 3326 1); 3327 3328 G1AggregateCountDataTask g1_par_agg_task(_g1h, this, &_card_bm, 3329 _max_worker_id, n_workers); 3330 3331 if (G1CollectedHeap::use_parallel_gc_threads()) { 3332 assert(_g1h->check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3333 "sanity check"); 3334 _g1h->set_par_threads(n_workers); 3335 _g1h->workers()->run_task(&g1_par_agg_task); 3336 _g1h->set_par_threads(0); 3337 3338 assert(_g1h->check_heap_region_claim_values(HeapRegion::AggregateCountClaimValue), 3339 "sanity check"); 3340 _g1h->reset_heap_region_claim_values(); 3341 } else { 3342 g1_par_agg_task.work(0); 3343 } 3344 } 3345 3346 // Clear the per-worker arrays used to store the per-region counting data 3347 void ConcurrentMark::clear_all_count_data() { 3348 // Clear the global card bitmap - it will be filled during 3349 // liveness count aggregation (during remark) and the 3350 // final counting task. 3351 _card_bm.clear(); 3352 3353 // Clear the global region bitmap - it will be filled as part 3354 // of the final counting task. 3355 _region_bm.clear(); 3356 3357 uint max_regions = _g1h->max_regions(); 3358 assert(_max_worker_id > 0, "uninitialized"); 3359 3360 for (uint i = 0; i < _max_worker_id; i += 1) { 3361 BitMap* task_card_bm = count_card_bitmap_for(i); 3362 size_t* marked_bytes_array = count_marked_bytes_array_for(i); 3363 3364 assert(task_card_bm->size() == _card_bm.size(), "size mismatch"); 3365 assert(marked_bytes_array != NULL, "uninitialized"); 3366 3367 memset(marked_bytes_array, 0, (size_t) max_regions * sizeof(size_t)); 3368 task_card_bm->clear(); 3369 } 3370 } 3371 3372 void ConcurrentMark::print_stats() { 3373 if (verbose_stats()) { 3374 gclog_or_tty->print_cr("---------------------------------------------------------------------"); 3375 for (size_t i = 0; i < _active_tasks; ++i) { 3376 _tasks[i]->print_stats(); 3377 gclog_or_tty->print_cr("---------------------------------------------------------------------"); 3378 } 3379 } 3380 } 3381 3382 // abandon current marking iteration due to a Full GC 3383 void ConcurrentMark::abort() { 3384 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next 3385 // concurrent bitmap clearing. 3386 _nextMarkBitMap->clearAll(); 3387 3388 // Note we cannot clear the previous marking bitmap here 3389 // since VerifyDuringGC verifies the objects marked during 3390 // a full GC against the previous bitmap. 3391 3392 // Clear the liveness counting data 3393 clear_all_count_data(); 3394 // Empty mark stack 3395 reset_marking_state(); 3396 for (uint i = 0; i < _max_worker_id; ++i) { 3397 _tasks[i]->clear_region_fields(); 3398 } 3399 _first_overflow_barrier_sync.abort(); 3400 _second_overflow_barrier_sync.abort(); 3401 const GCId& gc_id = _g1h->gc_tracer_cm()->gc_id(); 3402 if (!gc_id.is_undefined()) { 3403 // We can do multiple full GCs before ConcurrentMarkThread::run() gets a chance 3404 // to detect that it was aborted. Only keep track of the first GC id that we aborted. 3405 _aborted_gc_id = gc_id; 3406 } 3407 _has_aborted = true; 3408 3409 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 3410 satb_mq_set.abandon_partial_marking(); 3411 // This can be called either during or outside marking, we'll read 3412 // the expected_active value from the SATB queue set. 3413 satb_mq_set.set_active_all_threads( 3414 false, /* new active value */ 3415 satb_mq_set.is_active() /* expected_active */); 3416 3417 _g1h->trace_heap_after_concurrent_cycle(); 3418 _g1h->register_concurrent_cycle_end(); 3419 } 3420 3421 const GCId& ConcurrentMark::concurrent_gc_id() { 3422 if (has_aborted()) { 3423 return _aborted_gc_id; 3424 } 3425 return _g1h->gc_tracer_cm()->gc_id(); 3426 } 3427 3428 static void print_ms_time_info(const char* prefix, const char* name, 3429 NumberSeq& ns) { 3430 gclog_or_tty->print_cr("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).", 3431 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg()); 3432 if (ns.num() > 0) { 3433 gclog_or_tty->print_cr("%s [std. dev = %8.2f ms, max = %8.2f ms]", 3434 prefix, ns.sd(), ns.maximum()); 3435 } 3436 } 3437 3438 void ConcurrentMark::print_summary_info() { 3439 gclog_or_tty->print_cr(" Concurrent marking:"); 3440 print_ms_time_info(" ", "init marks", _init_times); 3441 print_ms_time_info(" ", "remarks", _remark_times); 3442 { 3443 print_ms_time_info(" ", "final marks", _remark_mark_times); 3444 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times); 3445 3446 } 3447 print_ms_time_info(" ", "cleanups", _cleanup_times); 3448 gclog_or_tty->print_cr(" Final counting total time = %8.2f s (avg = %8.2f ms).", 3449 _total_counting_time, 3450 (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 / 3451 (double)_cleanup_times.num() 3452 : 0.0)); 3453 if (G1ScrubRemSets) { 3454 gclog_or_tty->print_cr(" RS scrub total time = %8.2f s (avg = %8.2f ms).", 3455 _total_rs_scrub_time, 3456 (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 / 3457 (double)_cleanup_times.num() 3458 : 0.0)); 3459 } 3460 gclog_or_tty->print_cr(" Total stop_world time = %8.2f s.", 3461 (_init_times.sum() + _remark_times.sum() + 3462 _cleanup_times.sum())/1000.0); 3463 gclog_or_tty->print_cr(" Total concurrent time = %8.2f s " 3464 "(%8.2f s marking).", 3465 cmThread()->vtime_accum(), 3466 cmThread()->vtime_mark_accum()); 3467 } 3468 3469 void ConcurrentMark::print_worker_threads_on(outputStream* st) const { 3470 if (use_parallel_marking_threads()) { 3471 _parallel_workers->print_worker_threads_on(st); 3472 } 3473 } 3474 3475 void ConcurrentMark::print_on_error(outputStream* st) const { 3476 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT, 3477 p2i(_prevMarkBitMap), p2i(_nextMarkBitMap)); 3478 _prevMarkBitMap->print_on_error(st, " Prev Bits: "); 3479 _nextMarkBitMap->print_on_error(st, " Next Bits: "); 3480 } 3481 3482 // We take a break if someone is trying to stop the world. 3483 bool ConcurrentMark::do_yield_check(uint worker_id) { 3484 if (SuspendibleThreadSet::should_yield()) { 3485 if (worker_id == 0) { 3486 _g1h->g1_policy()->record_concurrent_pause(); 3487 } 3488 SuspendibleThreadSet::yield(); 3489 return true; 3490 } else { 3491 return false; 3492 } 3493 } 3494 3495 #ifndef PRODUCT 3496 // for debugging purposes 3497 void ConcurrentMark::print_finger() { 3498 gclog_or_tty->print_cr("heap ["PTR_FORMAT", "PTR_FORMAT"), global finger = "PTR_FORMAT, 3499 p2i(_heap_start), p2i(_heap_end), p2i(_finger)); 3500 for (uint i = 0; i < _max_worker_id; ++i) { 3501 gclog_or_tty->print(" %u: " PTR_FORMAT, i, p2i(_tasks[i]->finger())); 3502 } 3503 gclog_or_tty->cr(); 3504 } 3505 #endif 3506 3507 template<bool scan> 3508 inline void CMTask::process_grey_object(oop obj) { 3509 assert(scan || obj->is_typeArray(), "Skipping scan of grey non-typeArray"); 3510 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), "invariant"); 3511 3512 if (_cm->verbose_high()) { 3513 gclog_or_tty->print_cr("[%u] processing grey object " PTR_FORMAT, 3514 _worker_id, p2i((void*) obj)); 3515 } 3516 3517 size_t obj_size = obj->size(); 3518 _words_scanned += obj_size; 3519 3520 if (scan) { 3521 obj->oop_iterate(_cm_oop_closure); 3522 } 3523 statsOnly( ++_objs_scanned ); 3524 check_limits(); 3525 } 3526 3527 template void CMTask::process_grey_object<true>(oop); 3528 template void CMTask::process_grey_object<false>(oop); 3529 3530 // Closure for iteration over bitmaps 3531 class CMBitMapClosure : public BitMapClosure { 3532 private: 3533 // the bitmap that is being iterated over 3534 CMBitMap* _nextMarkBitMap; 3535 ConcurrentMark* _cm; 3536 CMTask* _task; 3537 3538 public: 3539 CMBitMapClosure(CMTask *task, ConcurrentMark* cm, CMBitMap* nextMarkBitMap) : 3540 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { } 3541 3542 bool do_bit(size_t offset) { 3543 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset); 3544 assert(_nextMarkBitMap->isMarked(addr), "invariant"); 3545 assert( addr < _cm->finger(), "invariant"); 3546 3547 statsOnly( _task->increase_objs_found_on_bitmap() ); 3548 assert(addr >= _task->finger(), "invariant"); 3549 3550 // We move that task's local finger along. 3551 _task->move_finger_to(addr); 3552 3553 _task->scan_object(oop(addr)); 3554 // we only partially drain the local queue and global stack 3555 _task->drain_local_queue(true); 3556 _task->drain_global_stack(true); 3557 3558 // if the has_aborted flag has been raised, we need to bail out of 3559 // the iteration 3560 return !_task->has_aborted(); 3561 } 3562 }; 3563 3564 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h, 3565 ConcurrentMark* cm, 3566 CMTask* task) 3567 : _g1h(g1h), _cm(cm), _task(task) { 3568 assert(_ref_processor == NULL, "should be initialized to NULL"); 3569 3570 if (G1UseConcMarkReferenceProcessing) { 3571 _ref_processor = g1h->ref_processor_cm(); 3572 assert(_ref_processor != NULL, "should not be NULL"); 3573 } 3574 } 3575 3576 void CMTask::setup_for_region(HeapRegion* hr) { 3577 assert(hr != NULL, 3578 "claim_region() should have filtered out NULL regions"); 3579 assert(!hr->continuesHumongous(), 3580 "claim_region() should have filtered out continues humongous regions"); 3581 3582 if (_cm->verbose_low()) { 3583 gclog_or_tty->print_cr("[%u] setting up for region "PTR_FORMAT, 3584 _worker_id, p2i(hr)); 3585 } 3586 3587 _curr_region = hr; 3588 _finger = hr->bottom(); 3589 update_region_limit(); 3590 } 3591 3592 void CMTask::update_region_limit() { 3593 HeapRegion* hr = _curr_region; 3594 HeapWord* bottom = hr->bottom(); 3595 HeapWord* limit = hr->next_top_at_mark_start(); 3596 3597 if (limit == bottom) { 3598 if (_cm->verbose_low()) { 3599 gclog_or_tty->print_cr("[%u] found an empty region " 3600 "["PTR_FORMAT", "PTR_FORMAT")", 3601 _worker_id, p2i(bottom), p2i(limit)); 3602 } 3603 // The region was collected underneath our feet. 3604 // We set the finger to bottom to ensure that the bitmap 3605 // iteration that will follow this will not do anything. 3606 // (this is not a condition that holds when we set the region up, 3607 // as the region is not supposed to be empty in the first place) 3608 _finger = bottom; 3609 } else if (limit >= _region_limit) { 3610 assert(limit >= _finger, "peace of mind"); 3611 } else { 3612 assert(limit < _region_limit, "only way to get here"); 3613 // This can happen under some pretty unusual circumstances. An 3614 // evacuation pause empties the region underneath our feet (NTAMS 3615 // at bottom). We then do some allocation in the region (NTAMS 3616 // stays at bottom), followed by the region being used as a GC 3617 // alloc region (NTAMS will move to top() and the objects 3618 // originally below it will be grayed). All objects now marked in 3619 // the region are explicitly grayed, if below the global finger, 3620 // and we do not need in fact to scan anything else. So, we simply 3621 // set _finger to be limit to ensure that the bitmap iteration 3622 // doesn't do anything. 3623 _finger = limit; 3624 } 3625 3626 _region_limit = limit; 3627 } 3628 3629 void CMTask::giveup_current_region() { 3630 assert(_curr_region != NULL, "invariant"); 3631 if (_cm->verbose_low()) { 3632 gclog_or_tty->print_cr("[%u] giving up region "PTR_FORMAT, 3633 _worker_id, p2i(_curr_region)); 3634 } 3635 clear_region_fields(); 3636 } 3637 3638 void CMTask::clear_region_fields() { 3639 // Values for these three fields that indicate that we're not 3640 // holding on to a region. 3641 _curr_region = NULL; 3642 _finger = NULL; 3643 _region_limit = NULL; 3644 } 3645 3646 void CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) { 3647 if (cm_oop_closure == NULL) { 3648 assert(_cm_oop_closure != NULL, "invariant"); 3649 } else { 3650 assert(_cm_oop_closure == NULL, "invariant"); 3651 } 3652 _cm_oop_closure = cm_oop_closure; 3653 } 3654 3655 void CMTask::reset(CMBitMap* nextMarkBitMap) { 3656 guarantee(nextMarkBitMap != NULL, "invariant"); 3657 3658 if (_cm->verbose_low()) { 3659 gclog_or_tty->print_cr("[%u] resetting", _worker_id); 3660 } 3661 3662 _nextMarkBitMap = nextMarkBitMap; 3663 clear_region_fields(); 3664 3665 _calls = 0; 3666 _elapsed_time_ms = 0.0; 3667 _termination_time_ms = 0.0; 3668 _termination_start_time_ms = 0.0; 3669 3670 #if _MARKING_STATS_ 3671 _local_pushes = 0; 3672 _local_pops = 0; 3673 _local_max_size = 0; 3674 _objs_scanned = 0; 3675 _global_pushes = 0; 3676 _global_pops = 0; 3677 _global_max_size = 0; 3678 _global_transfers_to = 0; 3679 _global_transfers_from = 0; 3680 _regions_claimed = 0; 3681 _objs_found_on_bitmap = 0; 3682 _satb_buffers_processed = 0; 3683 _steal_attempts = 0; 3684 _steals = 0; 3685 _aborted = 0; 3686 _aborted_overflow = 0; 3687 _aborted_cm_aborted = 0; 3688 _aborted_yield = 0; 3689 _aborted_timed_out = 0; 3690 _aborted_satb = 0; 3691 _aborted_termination = 0; 3692 #endif // _MARKING_STATS_ 3693 } 3694 3695 bool CMTask::should_exit_termination() { 3696 regular_clock_call(); 3697 // This is called when we are in the termination protocol. We should 3698 // quit if, for some reason, this task wants to abort or the global 3699 // stack is not empty (this means that we can get work from it). 3700 return !_cm->mark_stack_empty() || has_aborted(); 3701 } 3702 3703 void CMTask::reached_limit() { 3704 assert(_words_scanned >= _words_scanned_limit || 3705 _refs_reached >= _refs_reached_limit , 3706 "shouldn't have been called otherwise"); 3707 regular_clock_call(); 3708 } 3709 3710 void CMTask::regular_clock_call() { 3711 if (has_aborted()) return; 3712 3713 // First, we need to recalculate the words scanned and refs reached 3714 // limits for the next clock call. 3715 recalculate_limits(); 3716 3717 // During the regular clock call we do the following 3718 3719 // (1) If an overflow has been flagged, then we abort. 3720 if (_cm->has_overflown()) { 3721 set_has_aborted(); 3722 return; 3723 } 3724 3725 // If we are not concurrent (i.e. we're doing remark) we don't need 3726 // to check anything else. The other steps are only needed during 3727 // the concurrent marking phase. 3728 if (!concurrent()) return; 3729 3730 // (2) If marking has been aborted for Full GC, then we also abort. 3731 if (_cm->has_aborted()) { 3732 set_has_aborted(); 3733 statsOnly( ++_aborted_cm_aborted ); 3734 return; 3735 } 3736 3737 double curr_time_ms = os::elapsedVTime() * 1000.0; 3738 3739 // (3) If marking stats are enabled, then we update the step history. 3740 #if _MARKING_STATS_ 3741 if (_words_scanned >= _words_scanned_limit) { 3742 ++_clock_due_to_scanning; 3743 } 3744 if (_refs_reached >= _refs_reached_limit) { 3745 ++_clock_due_to_marking; 3746 } 3747 3748 double last_interval_ms = curr_time_ms - _interval_start_time_ms; 3749 _interval_start_time_ms = curr_time_ms; 3750 _all_clock_intervals_ms.add(last_interval_ms); 3751 3752 if (_cm->verbose_medium()) { 3753 gclog_or_tty->print_cr("[%u] regular clock, interval = %1.2lfms, " 3754 "scanned = "SIZE_FORMAT"%s, refs reached = "SIZE_FORMAT"%s", 3755 _worker_id, last_interval_ms, 3756 _words_scanned, 3757 (_words_scanned >= _words_scanned_limit) ? " (*)" : "", 3758 _refs_reached, 3759 (_refs_reached >= _refs_reached_limit) ? " (*)" : ""); 3760 } 3761 #endif // _MARKING_STATS_ 3762 3763 // (4) We check whether we should yield. If we have to, then we abort. 3764 if (SuspendibleThreadSet::should_yield()) { 3765 // We should yield. To do this we abort the task. The caller is 3766 // responsible for yielding. 3767 set_has_aborted(); 3768 statsOnly( ++_aborted_yield ); 3769 return; 3770 } 3771 3772 // (5) We check whether we've reached our time quota. If we have, 3773 // then we abort. 3774 double elapsed_time_ms = curr_time_ms - _start_time_ms; 3775 if (elapsed_time_ms > _time_target_ms) { 3776 set_has_aborted(); 3777 _has_timed_out = true; 3778 statsOnly( ++_aborted_timed_out ); 3779 return; 3780 } 3781 3782 // (6) Finally, we check whether there are enough completed STAB 3783 // buffers available for processing. If there are, we abort. 3784 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 3785 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) { 3786 if (_cm->verbose_low()) { 3787 gclog_or_tty->print_cr("[%u] aborting to deal with pending SATB buffers", 3788 _worker_id); 3789 } 3790 // we do need to process SATB buffers, we'll abort and restart 3791 // the marking task to do so 3792 set_has_aborted(); 3793 statsOnly( ++_aborted_satb ); 3794 return; 3795 } 3796 } 3797 3798 void CMTask::recalculate_limits() { 3799 _real_words_scanned_limit = _words_scanned + words_scanned_period; 3800 _words_scanned_limit = _real_words_scanned_limit; 3801 3802 _real_refs_reached_limit = _refs_reached + refs_reached_period; 3803 _refs_reached_limit = _real_refs_reached_limit; 3804 } 3805 3806 void CMTask::decrease_limits() { 3807 // This is called when we believe that we're going to do an infrequent 3808 // operation which will increase the per byte scanned cost (i.e. move 3809 // entries to/from the global stack). It basically tries to decrease the 3810 // scanning limit so that the clock is called earlier. 3811 3812 if (_cm->verbose_medium()) { 3813 gclog_or_tty->print_cr("[%u] decreasing limits", _worker_id); 3814 } 3815 3816 _words_scanned_limit = _real_words_scanned_limit - 3817 3 * words_scanned_period / 4; 3818 _refs_reached_limit = _real_refs_reached_limit - 3819 3 * refs_reached_period / 4; 3820 } 3821 3822 void CMTask::move_entries_to_global_stack() { 3823 // local array where we'll store the entries that will be popped 3824 // from the local queue 3825 oop buffer[global_stack_transfer_size]; 3826 3827 int n = 0; 3828 oop obj; 3829 while (n < global_stack_transfer_size && _task_queue->pop_local(obj)) { 3830 buffer[n] = obj; 3831 ++n; 3832 } 3833 3834 if (n > 0) { 3835 // we popped at least one entry from the local queue 3836 3837 statsOnly( ++_global_transfers_to; _local_pops += n ); 3838 3839 if (!_cm->mark_stack_push(buffer, n)) { 3840 if (_cm->verbose_low()) { 3841 gclog_or_tty->print_cr("[%u] aborting due to global stack overflow", 3842 _worker_id); 3843 } 3844 set_has_aborted(); 3845 } else { 3846 // the transfer was successful 3847 3848 if (_cm->verbose_medium()) { 3849 gclog_or_tty->print_cr("[%u] pushed %d entries to the global stack", 3850 _worker_id, n); 3851 } 3852 statsOnly( int tmp_size = _cm->mark_stack_size(); 3853 if (tmp_size > _global_max_size) { 3854 _global_max_size = tmp_size; 3855 } 3856 _global_pushes += n ); 3857 } 3858 } 3859 3860 // this operation was quite expensive, so decrease the limits 3861 decrease_limits(); 3862 } 3863 3864 void CMTask::get_entries_from_global_stack() { 3865 // local array where we'll store the entries that will be popped 3866 // from the global stack. 3867 oop buffer[global_stack_transfer_size]; 3868 int n; 3869 _cm->mark_stack_pop(buffer, global_stack_transfer_size, &n); 3870 assert(n <= global_stack_transfer_size, 3871 "we should not pop more than the given limit"); 3872 if (n > 0) { 3873 // yes, we did actually pop at least one entry 3874 3875 statsOnly( ++_global_transfers_from; _global_pops += n ); 3876 if (_cm->verbose_medium()) { 3877 gclog_or_tty->print_cr("[%u] popped %d entries from the global stack", 3878 _worker_id, n); 3879 } 3880 for (int i = 0; i < n; ++i) { 3881 bool success = _task_queue->push(buffer[i]); 3882 // We only call this when the local queue is empty or under a 3883 // given target limit. So, we do not expect this push to fail. 3884 assert(success, "invariant"); 3885 } 3886 3887 statsOnly( int tmp_size = _task_queue->size(); 3888 if (tmp_size > _local_max_size) { 3889 _local_max_size = tmp_size; 3890 } 3891 _local_pushes += n ); 3892 } 3893 3894 // this operation was quite expensive, so decrease the limits 3895 decrease_limits(); 3896 } 3897 3898 void CMTask::drain_local_queue(bool partially) { 3899 if (has_aborted()) return; 3900 3901 // Decide what the target size is, depending whether we're going to 3902 // drain it partially (so that other tasks can steal if they run out 3903 // of things to do) or totally (at the very end). 3904 size_t target_size; 3905 if (partially) { 3906 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize); 3907 } else { 3908 target_size = 0; 3909 } 3910 3911 if (_task_queue->size() > target_size) { 3912 if (_cm->verbose_high()) { 3913 gclog_or_tty->print_cr("[%u] draining local queue, target size = " SIZE_FORMAT, 3914 _worker_id, target_size); 3915 } 3916 3917 oop obj; 3918 bool ret = _task_queue->pop_local(obj); 3919 while (ret) { 3920 statsOnly( ++_local_pops ); 3921 3922 if (_cm->verbose_high()) { 3923 gclog_or_tty->print_cr("[%u] popped "PTR_FORMAT, _worker_id, 3924 p2i((void*) obj)); 3925 } 3926 3927 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" ); 3928 assert(!_g1h->is_on_master_free_list( 3929 _g1h->heap_region_containing((HeapWord*) obj)), "invariant"); 3930 3931 scan_object(obj); 3932 3933 if (_task_queue->size() <= target_size || has_aborted()) { 3934 ret = false; 3935 } else { 3936 ret = _task_queue->pop_local(obj); 3937 } 3938 } 3939 3940 if (_cm->verbose_high()) { 3941 gclog_or_tty->print_cr("[%u] drained local queue, size = %d", 3942 _worker_id, _task_queue->size()); 3943 } 3944 } 3945 } 3946 3947 void CMTask::drain_global_stack(bool partially) { 3948 if (has_aborted()) return; 3949 3950 // We have a policy to drain the local queue before we attempt to 3951 // drain the global stack. 3952 assert(partially || _task_queue->size() == 0, "invariant"); 3953 3954 // Decide what the target size is, depending whether we're going to 3955 // drain it partially (so that other tasks can steal if they run out 3956 // of things to do) or totally (at the very end). Notice that, 3957 // because we move entries from the global stack in chunks or 3958 // because another task might be doing the same, we might in fact 3959 // drop below the target. But, this is not a problem. 3960 size_t target_size; 3961 if (partially) { 3962 target_size = _cm->partial_mark_stack_size_target(); 3963 } else { 3964 target_size = 0; 3965 } 3966 3967 if (_cm->mark_stack_size() > target_size) { 3968 if (_cm->verbose_low()) { 3969 gclog_or_tty->print_cr("[%u] draining global_stack, target size " SIZE_FORMAT, 3970 _worker_id, target_size); 3971 } 3972 3973 while (!has_aborted() && _cm->mark_stack_size() > target_size) { 3974 get_entries_from_global_stack(); 3975 drain_local_queue(partially); 3976 } 3977 3978 if (_cm->verbose_low()) { 3979 gclog_or_tty->print_cr("[%u] drained global stack, size = " SIZE_FORMAT, 3980 _worker_id, _cm->mark_stack_size()); 3981 } 3982 } 3983 } 3984 3985 // SATB Queue has several assumptions on whether to call the par or 3986 // non-par versions of the methods. this is why some of the code is 3987 // replicated. We should really get rid of the single-threaded version 3988 // of the code to simplify things. 3989 void CMTask::drain_satb_buffers() { 3990 if (has_aborted()) return; 3991 3992 // We set this so that the regular clock knows that we're in the 3993 // middle of draining buffers and doesn't set the abort flag when it 3994 // notices that SATB buffers are available for draining. It'd be 3995 // very counter productive if it did that. :-) 3996 _draining_satb_buffers = true; 3997 3998 CMSATBBufferClosure satb_cl(this, _g1h); 3999 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 4000 4001 // This keeps claiming and applying the closure to completed buffers 4002 // until we run out of buffers or we need to abort. 4003 while (!has_aborted() && 4004 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) { 4005 if (_cm->verbose_medium()) { 4006 gclog_or_tty->print_cr("[%u] processed an SATB buffer", _worker_id); 4007 } 4008 statsOnly( ++_satb_buffers_processed ); 4009 regular_clock_call(); 4010 } 4011 4012 _draining_satb_buffers = false; 4013 4014 assert(has_aborted() || 4015 concurrent() || 4016 satb_mq_set.completed_buffers_num() == 0, "invariant"); 4017 4018 // again, this was a potentially expensive operation, decrease the 4019 // limits to get the regular clock call early 4020 decrease_limits(); 4021 } 4022 4023 void CMTask::print_stats() { 4024 gclog_or_tty->print_cr("Marking Stats, task = %u, calls = %d", 4025 _worker_id, _calls); 4026 gclog_or_tty->print_cr(" Elapsed time = %1.2lfms, Termination time = %1.2lfms", 4027 _elapsed_time_ms, _termination_time_ms); 4028 gclog_or_tty->print_cr(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms", 4029 _step_times_ms.num(), _step_times_ms.avg(), 4030 _step_times_ms.sd()); 4031 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms", 4032 _step_times_ms.maximum(), _step_times_ms.sum()); 4033 4034 #if _MARKING_STATS_ 4035 gclog_or_tty->print_cr(" Clock Intervals (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms", 4036 _all_clock_intervals_ms.num(), _all_clock_intervals_ms.avg(), 4037 _all_clock_intervals_ms.sd()); 4038 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms", 4039 _all_clock_intervals_ms.maximum(), 4040 _all_clock_intervals_ms.sum()); 4041 gclog_or_tty->print_cr(" Clock Causes (cum): scanning = %d, marking = %d", 4042 _clock_due_to_scanning, _clock_due_to_marking); 4043 gclog_or_tty->print_cr(" Objects: scanned = %d, found on the bitmap = %d", 4044 _objs_scanned, _objs_found_on_bitmap); 4045 gclog_or_tty->print_cr(" Local Queue: pushes = %d, pops = %d, max size = %d", 4046 _local_pushes, _local_pops, _local_max_size); 4047 gclog_or_tty->print_cr(" Global Stack: pushes = %d, pops = %d, max size = %d", 4048 _global_pushes, _global_pops, _global_max_size); 4049 gclog_or_tty->print_cr(" transfers to = %d, transfers from = %d", 4050 _global_transfers_to,_global_transfers_from); 4051 gclog_or_tty->print_cr(" Regions: claimed = %d", _regions_claimed); 4052 gclog_or_tty->print_cr(" SATB buffers: processed = %d", _satb_buffers_processed); 4053 gclog_or_tty->print_cr(" Steals: attempts = %d, successes = %d", 4054 _steal_attempts, _steals); 4055 gclog_or_tty->print_cr(" Aborted: %d, due to", _aborted); 4056 gclog_or_tty->print_cr(" overflow: %d, global abort: %d, yield: %d", 4057 _aborted_overflow, _aborted_cm_aborted, _aborted_yield); 4058 gclog_or_tty->print_cr(" time out: %d, SATB: %d, termination: %d", 4059 _aborted_timed_out, _aborted_satb, _aborted_termination); 4060 #endif // _MARKING_STATS_ 4061 } 4062 4063 /***************************************************************************** 4064 4065 The do_marking_step(time_target_ms, ...) method is the building 4066 block of the parallel marking framework. It can be called in parallel 4067 with other invocations of do_marking_step() on different tasks 4068 (but only one per task, obviously) and concurrently with the 4069 mutator threads, or during remark, hence it eliminates the need 4070 for two versions of the code. When called during remark, it will 4071 pick up from where the task left off during the concurrent marking 4072 phase. Interestingly, tasks are also claimable during evacuation 4073 pauses too, since do_marking_step() ensures that it aborts before 4074 it needs to yield. 4075 4076 The data structures that it uses to do marking work are the 4077 following: 4078 4079 (1) Marking Bitmap. If there are gray objects that appear only 4080 on the bitmap (this happens either when dealing with an overflow 4081 or when the initial marking phase has simply marked the roots 4082 and didn't push them on the stack), then tasks claim heap 4083 regions whose bitmap they then scan to find gray objects. A 4084 global finger indicates where the end of the last claimed region 4085 is. A local finger indicates how far into the region a task has 4086 scanned. The two fingers are used to determine how to gray an 4087 object (i.e. whether simply marking it is OK, as it will be 4088 visited by a task in the future, or whether it needs to be also 4089 pushed on a stack). 4090 4091 (2) Local Queue. The local queue of the task which is accessed 4092 reasonably efficiently by the task. Other tasks can steal from 4093 it when they run out of work. Throughout the marking phase, a 4094 task attempts to keep its local queue short but not totally 4095 empty, so that entries are available for stealing by other 4096 tasks. Only when there is no more work, a task will totally 4097 drain its local queue. 4098 4099 (3) Global Mark Stack. This handles local queue overflow. During 4100 marking only sets of entries are moved between it and the local 4101 queues, as access to it requires a mutex and more fine-grain 4102 interaction with it which might cause contention. If it 4103 overflows, then the marking phase should restart and iterate 4104 over the bitmap to identify gray objects. Throughout the marking 4105 phase, tasks attempt to keep the global mark stack at a small 4106 length but not totally empty, so that entries are available for 4107 popping by other tasks. Only when there is no more work, tasks 4108 will totally drain the global mark stack. 4109 4110 (4) SATB Buffer Queue. This is where completed SATB buffers are 4111 made available. Buffers are regularly removed from this queue 4112 and scanned for roots, so that the queue doesn't get too 4113 long. During remark, all completed buffers are processed, as 4114 well as the filled in parts of any uncompleted buffers. 4115 4116 The do_marking_step() method tries to abort when the time target 4117 has been reached. There are a few other cases when the 4118 do_marking_step() method also aborts: 4119 4120 (1) When the marking phase has been aborted (after a Full GC). 4121 4122 (2) When a global overflow (on the global stack) has been 4123 triggered. Before the task aborts, it will actually sync up with 4124 the other tasks to ensure that all the marking data structures 4125 (local queues, stacks, fingers etc.) are re-initialized so that 4126 when do_marking_step() completes, the marking phase can 4127 immediately restart. 4128 4129 (3) When enough completed SATB buffers are available. The 4130 do_marking_step() method only tries to drain SATB buffers right 4131 at the beginning. So, if enough buffers are available, the 4132 marking step aborts and the SATB buffers are processed at 4133 the beginning of the next invocation. 4134 4135 (4) To yield. when we have to yield then we abort and yield 4136 right at the end of do_marking_step(). This saves us from a lot 4137 of hassle as, by yielding we might allow a Full GC. If this 4138 happens then objects will be compacted underneath our feet, the 4139 heap might shrink, etc. We save checking for this by just 4140 aborting and doing the yield right at the end. 4141 4142 From the above it follows that the do_marking_step() method should 4143 be called in a loop (or, otherwise, regularly) until it completes. 4144 4145 If a marking step completes without its has_aborted() flag being 4146 true, it means it has completed the current marking phase (and 4147 also all other marking tasks have done so and have all synced up). 4148 4149 A method called regular_clock_call() is invoked "regularly" (in 4150 sub ms intervals) throughout marking. It is this clock method that 4151 checks all the abort conditions which were mentioned above and 4152 decides when the task should abort. A work-based scheme is used to 4153 trigger this clock method: when the number of object words the 4154 marking phase has scanned or the number of references the marking 4155 phase has visited reach a given limit. Additional invocations to 4156 the method clock have been planted in a few other strategic places 4157 too. The initial reason for the clock method was to avoid calling 4158 vtime too regularly, as it is quite expensive. So, once it was in 4159 place, it was natural to piggy-back all the other conditions on it 4160 too and not constantly check them throughout the code. 4161 4162 If do_termination is true then do_marking_step will enter its 4163 termination protocol. 4164 4165 The value of is_serial must be true when do_marking_step is being 4166 called serially (i.e. by the VMThread) and do_marking_step should 4167 skip any synchronization in the termination and overflow code. 4168 Examples include the serial remark code and the serial reference 4169 processing closures. 4170 4171 The value of is_serial must be false when do_marking_step is 4172 being called by any of the worker threads in a work gang. 4173 Examples include the concurrent marking code (CMMarkingTask), 4174 the MT remark code, and the MT reference processing closures. 4175 4176 *****************************************************************************/ 4177 4178 void CMTask::do_marking_step(double time_target_ms, 4179 bool do_termination, 4180 bool is_serial) { 4181 assert(time_target_ms >= 1.0, "minimum granularity is 1ms"); 4182 assert(concurrent() == _cm->concurrent(), "they should be the same"); 4183 4184 G1CollectorPolicy* g1_policy = _g1h->g1_policy(); 4185 assert(_task_queues != NULL, "invariant"); 4186 assert(_task_queue != NULL, "invariant"); 4187 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant"); 4188 4189 assert(!_claimed, 4190 "only one thread should claim this task at any one time"); 4191 4192 // OK, this doesn't safeguard again all possible scenarios, as it is 4193 // possible for two threads to set the _claimed flag at the same 4194 // time. But it is only for debugging purposes anyway and it will 4195 // catch most problems. 4196 _claimed = true; 4197 4198 _start_time_ms = os::elapsedVTime() * 1000.0; 4199 statsOnly( _interval_start_time_ms = _start_time_ms ); 4200 4201 // If do_stealing is true then do_marking_step will attempt to 4202 // steal work from the other CMTasks. It only makes sense to 4203 // enable stealing when the termination protocol is enabled 4204 // and do_marking_step() is not being called serially. 4205 bool do_stealing = do_termination && !is_serial; 4206 4207 double diff_prediction_ms = 4208 g1_policy->get_new_prediction(&_marking_step_diffs_ms); 4209 _time_target_ms = time_target_ms - diff_prediction_ms; 4210 4211 // set up the variables that are used in the work-based scheme to 4212 // call the regular clock method 4213 _words_scanned = 0; 4214 _refs_reached = 0; 4215 recalculate_limits(); 4216 4217 // clear all flags 4218 clear_has_aborted(); 4219 _has_timed_out = false; 4220 _draining_satb_buffers = false; 4221 4222 ++_calls; 4223 4224 if (_cm->verbose_low()) { 4225 gclog_or_tty->print_cr("[%u] >>>>>>>>>> START, call = %d, " 4226 "target = %1.2lfms >>>>>>>>>>", 4227 _worker_id, _calls, _time_target_ms); 4228 } 4229 4230 // Set up the bitmap and oop closures. Anything that uses them is 4231 // eventually called from this method, so it is OK to allocate these 4232 // statically. 4233 CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap); 4234 G1CMOopClosure cm_oop_closure(_g1h, _cm, this); 4235 set_cm_oop_closure(&cm_oop_closure); 4236 4237 if (_cm->has_overflown()) { 4238 // This can happen if the mark stack overflows during a GC pause 4239 // and this task, after a yield point, restarts. We have to abort 4240 // as we need to get into the overflow protocol which happens 4241 // right at the end of this task. 4242 set_has_aborted(); 4243 } 4244 4245 // First drain any available SATB buffers. After this, we will not 4246 // look at SATB buffers before the next invocation of this method. 4247 // If enough completed SATB buffers are queued up, the regular clock 4248 // will abort this task so that it restarts. 4249 drain_satb_buffers(); 4250 // ...then partially drain the local queue and the global stack 4251 drain_local_queue(true); 4252 drain_global_stack(true); 4253 4254 do { 4255 if (!has_aborted() && _curr_region != NULL) { 4256 // This means that we're already holding on to a region. 4257 assert(_finger != NULL, "if region is not NULL, then the finger " 4258 "should not be NULL either"); 4259 4260 // We might have restarted this task after an evacuation pause 4261 // which might have evacuated the region we're holding on to 4262 // underneath our feet. Let's read its limit again to make sure 4263 // that we do not iterate over a region of the heap that 4264 // contains garbage (update_region_limit() will also move 4265 // _finger to the start of the region if it is found empty). 4266 update_region_limit(); 4267 // We will start from _finger not from the start of the region, 4268 // as we might be restarting this task after aborting half-way 4269 // through scanning this region. In this case, _finger points to 4270 // the address where we last found a marked object. If this is a 4271 // fresh region, _finger points to start(). 4272 MemRegion mr = MemRegion(_finger, _region_limit); 4273 4274 if (_cm->verbose_low()) { 4275 gclog_or_tty->print_cr("[%u] we're scanning part " 4276 "["PTR_FORMAT", "PTR_FORMAT") " 4277 "of region "HR_FORMAT, 4278 _worker_id, p2i(_finger), p2i(_region_limit), 4279 HR_FORMAT_PARAMS(_curr_region)); 4280 } 4281 4282 assert(!_curr_region->isHumongous() || mr.start() == _curr_region->bottom(), 4283 "humongous regions should go around loop once only"); 4284 4285 // Some special cases: 4286 // If the memory region is empty, we can just give up the region. 4287 // If the current region is humongous then we only need to check 4288 // the bitmap for the bit associated with the start of the object, 4289 // scan the object if it's live, and give up the region. 4290 // Otherwise, let's iterate over the bitmap of the part of the region 4291 // that is left. 4292 // If the iteration is successful, give up the region. 4293 if (mr.is_empty()) { 4294 giveup_current_region(); 4295 regular_clock_call(); 4296 } else if (_curr_region->isHumongous() && mr.start() == _curr_region->bottom()) { 4297 if (_nextMarkBitMap->isMarked(mr.start())) { 4298 // The object is marked - apply the closure 4299 BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start()); 4300 bitmap_closure.do_bit(offset); 4301 } 4302 // Even if this task aborted while scanning the humongous object 4303 // we can (and should) give up the current region. 4304 giveup_current_region(); 4305 regular_clock_call(); 4306 } else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) { 4307 giveup_current_region(); 4308 regular_clock_call(); 4309 } else { 4310 assert(has_aborted(), "currently the only way to do so"); 4311 // The only way to abort the bitmap iteration is to return 4312 // false from the do_bit() method. However, inside the 4313 // do_bit() method we move the _finger to point to the 4314 // object currently being looked at. So, if we bail out, we 4315 // have definitely set _finger to something non-null. 4316 assert(_finger != NULL, "invariant"); 4317 4318 // Region iteration was actually aborted. So now _finger 4319 // points to the address of the object we last scanned. If we 4320 // leave it there, when we restart this task, we will rescan 4321 // the object. It is easy to avoid this. We move the finger by 4322 // enough to point to the next possible object header (the 4323 // bitmap knows by how much we need to move it as it knows its 4324 // granularity). 4325 assert(_finger < _region_limit, "invariant"); 4326 HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger); 4327 // Check if bitmap iteration was aborted while scanning the last object 4328 if (new_finger >= _region_limit) { 4329 giveup_current_region(); 4330 } else { 4331 move_finger_to(new_finger); 4332 } 4333 } 4334 } 4335 // At this point we have either completed iterating over the 4336 // region we were holding on to, or we have aborted. 4337 4338 // We then partially drain the local queue and the global stack. 4339 // (Do we really need this?) 4340 drain_local_queue(true); 4341 drain_global_stack(true); 4342 4343 // Read the note on the claim_region() method on why it might 4344 // return NULL with potentially more regions available for 4345 // claiming and why we have to check out_of_regions() to determine 4346 // whether we're done or not. 4347 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) { 4348 // We are going to try to claim a new region. We should have 4349 // given up on the previous one. 4350 // Separated the asserts so that we know which one fires. 4351 assert(_curr_region == NULL, "invariant"); 4352 assert(_finger == NULL, "invariant"); 4353 assert(_region_limit == NULL, "invariant"); 4354 if (_cm->verbose_low()) { 4355 gclog_or_tty->print_cr("[%u] trying to claim a new region", _worker_id); 4356 } 4357 HeapRegion* claimed_region = _cm->claim_region(_worker_id); 4358 if (claimed_region != NULL) { 4359 // Yes, we managed to claim one 4360 statsOnly( ++_regions_claimed ); 4361 4362 if (_cm->verbose_low()) { 4363 gclog_or_tty->print_cr("[%u] we successfully claimed " 4364 "region "PTR_FORMAT, 4365 _worker_id, p2i(claimed_region)); 4366 } 4367 4368 setup_for_region(claimed_region); 4369 assert(_curr_region == claimed_region, "invariant"); 4370 } 4371 // It is important to call the regular clock here. It might take 4372 // a while to claim a region if, for example, we hit a large 4373 // block of empty regions. So we need to call the regular clock 4374 // method once round the loop to make sure it's called 4375 // frequently enough. 4376 regular_clock_call(); 4377 } 4378 4379 if (!has_aborted() && _curr_region == NULL) { 4380 assert(_cm->out_of_regions(), 4381 "at this point we should be out of regions"); 4382 } 4383 } while ( _curr_region != NULL && !has_aborted()); 4384 4385 if (!has_aborted()) { 4386 // We cannot check whether the global stack is empty, since other 4387 // tasks might be pushing objects to it concurrently. 4388 assert(_cm->out_of_regions(), 4389 "at this point we should be out of regions"); 4390 4391 if (_cm->verbose_low()) { 4392 gclog_or_tty->print_cr("[%u] all regions claimed", _worker_id); 4393 } 4394 4395 // Try to reduce the number of available SATB buffers so that 4396 // remark has less work to do. 4397 drain_satb_buffers(); 4398 } 4399 4400 // Since we've done everything else, we can now totally drain the 4401 // local queue and global stack. 4402 drain_local_queue(false); 4403 drain_global_stack(false); 4404 4405 // Attempt at work stealing from other task's queues. 4406 if (do_stealing && !has_aborted()) { 4407 // We have not aborted. This means that we have finished all that 4408 // we could. Let's try to do some stealing... 4409 4410 // We cannot check whether the global stack is empty, since other 4411 // tasks might be pushing objects to it concurrently. 4412 assert(_cm->out_of_regions() && _task_queue->size() == 0, 4413 "only way to reach here"); 4414 4415 if (_cm->verbose_low()) { 4416 gclog_or_tty->print_cr("[%u] starting to steal", _worker_id); 4417 } 4418 4419 while (!has_aborted()) { 4420 oop obj; 4421 statsOnly( ++_steal_attempts ); 4422 4423 if (_cm->try_stealing(_worker_id, &_hash_seed, obj)) { 4424 if (_cm->verbose_medium()) { 4425 gclog_or_tty->print_cr("[%u] stolen "PTR_FORMAT" successfully", 4426 _worker_id, p2i((void*) obj)); 4427 } 4428 4429 statsOnly( ++_steals ); 4430 4431 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), 4432 "any stolen object should be marked"); 4433 scan_object(obj); 4434 4435 // And since we're towards the end, let's totally drain the 4436 // local queue and global stack. 4437 drain_local_queue(false); 4438 drain_global_stack(false); 4439 } else { 4440 break; 4441 } 4442 } 4443 } 4444 4445 // If we are about to wrap up and go into termination, check if we 4446 // should raise the overflow flag. 4447 if (do_termination && !has_aborted()) { 4448 if (_cm->force_overflow()->should_force()) { 4449 _cm->set_has_overflown(); 4450 regular_clock_call(); 4451 } 4452 } 4453 4454 // We still haven't aborted. Now, let's try to get into the 4455 // termination protocol. 4456 if (do_termination && !has_aborted()) { 4457 // We cannot check whether the global stack is empty, since other 4458 // tasks might be concurrently pushing objects on it. 4459 // Separated the asserts so that we know which one fires. 4460 assert(_cm->out_of_regions(), "only way to reach here"); 4461 assert(_task_queue->size() == 0, "only way to reach here"); 4462 4463 if (_cm->verbose_low()) { 4464 gclog_or_tty->print_cr("[%u] starting termination protocol", _worker_id); 4465 } 4466 4467 _termination_start_time_ms = os::elapsedVTime() * 1000.0; 4468 4469 // The CMTask class also extends the TerminatorTerminator class, 4470 // hence its should_exit_termination() method will also decide 4471 // whether to exit the termination protocol or not. 4472 bool finished = (is_serial || 4473 _cm->terminator()->offer_termination(this)); 4474 double termination_end_time_ms = os::elapsedVTime() * 1000.0; 4475 _termination_time_ms += 4476 termination_end_time_ms - _termination_start_time_ms; 4477 4478 if (finished) { 4479 // We're all done. 4480 4481 if (_worker_id == 0) { 4482 // let's allow task 0 to do this 4483 if (concurrent()) { 4484 assert(_cm->concurrent_marking_in_progress(), "invariant"); 4485 // we need to set this to false before the next 4486 // safepoint. This way we ensure that the marking phase 4487 // doesn't observe any more heap expansions. 4488 _cm->clear_concurrent_marking_in_progress(); 4489 } 4490 } 4491 4492 // We can now guarantee that the global stack is empty, since 4493 // all other tasks have finished. We separated the guarantees so 4494 // that, if a condition is false, we can immediately find out 4495 // which one. 4496 guarantee(_cm->out_of_regions(), "only way to reach here"); 4497 guarantee(_cm->mark_stack_empty(), "only way to reach here"); 4498 guarantee(_task_queue->size() == 0, "only way to reach here"); 4499 guarantee(!_cm->has_overflown(), "only way to reach here"); 4500 guarantee(!_cm->mark_stack_overflow(), "only way to reach here"); 4501 4502 if (_cm->verbose_low()) { 4503 gclog_or_tty->print_cr("[%u] all tasks terminated", _worker_id); 4504 } 4505 } else { 4506 // Apparently there's more work to do. Let's abort this task. It 4507 // will restart it and we can hopefully find more things to do. 4508 4509 if (_cm->verbose_low()) { 4510 gclog_or_tty->print_cr("[%u] apparently there is more work to do", 4511 _worker_id); 4512 } 4513 4514 set_has_aborted(); 4515 statsOnly( ++_aborted_termination ); 4516 } 4517 } 4518 4519 // Mainly for debugging purposes to make sure that a pointer to the 4520 // closure which was statically allocated in this frame doesn't 4521 // escape it by accident. 4522 set_cm_oop_closure(NULL); 4523 double end_time_ms = os::elapsedVTime() * 1000.0; 4524 double elapsed_time_ms = end_time_ms - _start_time_ms; 4525 // Update the step history. 4526 _step_times_ms.add(elapsed_time_ms); 4527 4528 if (has_aborted()) { 4529 // The task was aborted for some reason. 4530 4531 statsOnly( ++_aborted ); 4532 4533 if (_has_timed_out) { 4534 double diff_ms = elapsed_time_ms - _time_target_ms; 4535 // Keep statistics of how well we did with respect to hitting 4536 // our target only if we actually timed out (if we aborted for 4537 // other reasons, then the results might get skewed). 4538 _marking_step_diffs_ms.add(diff_ms); 4539 } 4540 4541 if (_cm->has_overflown()) { 4542 // This is the interesting one. We aborted because a global 4543 // overflow was raised. This means we have to restart the 4544 // marking phase and start iterating over regions. However, in 4545 // order to do this we have to make sure that all tasks stop 4546 // what they are doing and re-initialise in a safe manner. We 4547 // will achieve this with the use of two barrier sync points. 4548 4549 if (_cm->verbose_low()) { 4550 gclog_or_tty->print_cr("[%u] detected overflow", _worker_id); 4551 } 4552 4553 if (!is_serial) { 4554 // We only need to enter the sync barrier if being called 4555 // from a parallel context 4556 _cm->enter_first_sync_barrier(_worker_id); 4557 4558 // When we exit this sync barrier we know that all tasks have 4559 // stopped doing marking work. So, it's now safe to 4560 // re-initialise our data structures. At the end of this method, 4561 // task 0 will clear the global data structures. 4562 } 4563 4564 statsOnly( ++_aborted_overflow ); 4565 4566 // We clear the local state of this task... 4567 clear_region_fields(); 4568 4569 if (!is_serial) { 4570 // ...and enter the second barrier. 4571 _cm->enter_second_sync_barrier(_worker_id); 4572 } 4573 // At this point, if we're during the concurrent phase of 4574 // marking, everything has been re-initialized and we're 4575 // ready to restart. 4576 } 4577 4578 if (_cm->verbose_low()) { 4579 gclog_or_tty->print_cr("[%u] <<<<<<<<<< ABORTING, target = %1.2lfms, " 4580 "elapsed = %1.2lfms <<<<<<<<<<", 4581 _worker_id, _time_target_ms, elapsed_time_ms); 4582 if (_cm->has_aborted()) { 4583 gclog_or_tty->print_cr("[%u] ========== MARKING ABORTED ==========", 4584 _worker_id); 4585 } 4586 } 4587 } else { 4588 if (_cm->verbose_low()) { 4589 gclog_or_tty->print_cr("[%u] <<<<<<<<<< FINISHED, target = %1.2lfms, " 4590 "elapsed = %1.2lfms <<<<<<<<<<", 4591 _worker_id, _time_target_ms, elapsed_time_ms); 4592 } 4593 } 4594 4595 _claimed = false; 4596 } 4597 4598 CMTask::CMTask(uint worker_id, 4599 ConcurrentMark* cm, 4600 size_t* marked_bytes, 4601 BitMap* card_bm, 4602 CMTaskQueue* task_queue, 4603 CMTaskQueueSet* task_queues) 4604 : _g1h(G1CollectedHeap::heap()), 4605 _worker_id(worker_id), _cm(cm), 4606 _claimed(false), 4607 _nextMarkBitMap(NULL), _hash_seed(17), 4608 _task_queue(task_queue), 4609 _task_queues(task_queues), 4610 _cm_oop_closure(NULL), 4611 _marked_bytes_array(marked_bytes), 4612 _card_bm(card_bm) { 4613 guarantee(task_queue != NULL, "invariant"); 4614 guarantee(task_queues != NULL, "invariant"); 4615 4616 statsOnly( _clock_due_to_scanning = 0; 4617 _clock_due_to_marking = 0 ); 4618 4619 _marking_step_diffs_ms.add(0.5); 4620 } 4621 4622 // These are formatting macros that are used below to ensure 4623 // consistent formatting. The *_H_* versions are used to format the 4624 // header for a particular value and they should be kept consistent 4625 // with the corresponding macro. Also note that most of the macros add 4626 // the necessary white space (as a prefix) which makes them a bit 4627 // easier to compose. 4628 4629 // All the output lines are prefixed with this string to be able to 4630 // identify them easily in a large log file. 4631 #define G1PPRL_LINE_PREFIX "###" 4632 4633 #define G1PPRL_ADDR_BASE_FORMAT " "PTR_FORMAT"-"PTR_FORMAT 4634 #ifdef _LP64 4635 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s" 4636 #else // _LP64 4637 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s" 4638 #endif // _LP64 4639 4640 // For per-region info 4641 #define G1PPRL_TYPE_FORMAT " %-4s" 4642 #define G1PPRL_TYPE_H_FORMAT " %4s" 4643 #define G1PPRL_BYTE_FORMAT " "SIZE_FORMAT_W(9) 4644 #define G1PPRL_BYTE_H_FORMAT " %9s" 4645 #define G1PPRL_DOUBLE_FORMAT " %14.1f" 4646 #define G1PPRL_DOUBLE_H_FORMAT " %14s" 4647 4648 // For summary info 4649 #define G1PPRL_SUM_ADDR_FORMAT(tag) " "tag":"G1PPRL_ADDR_BASE_FORMAT 4650 #define G1PPRL_SUM_BYTE_FORMAT(tag) " "tag": "SIZE_FORMAT 4651 #define G1PPRL_SUM_MB_FORMAT(tag) " "tag": %1.2f MB" 4652 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag)" / %1.2f %%" 4653 4654 G1PrintRegionLivenessInfoClosure:: 4655 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name) 4656 : _out(out), 4657 _total_used_bytes(0), _total_capacity_bytes(0), 4658 _total_prev_live_bytes(0), _total_next_live_bytes(0), 4659 _hum_used_bytes(0), _hum_capacity_bytes(0), 4660 _hum_prev_live_bytes(0), _hum_next_live_bytes(0), 4661 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) { 4662 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 4663 MemRegion g1_reserved = g1h->g1_reserved(); 4664 double now = os::elapsedTime(); 4665 4666 // Print the header of the output. 4667 _out->cr(); 4668 _out->print_cr(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now); 4669 _out->print_cr(G1PPRL_LINE_PREFIX" HEAP" 4670 G1PPRL_SUM_ADDR_FORMAT("reserved") 4671 G1PPRL_SUM_BYTE_FORMAT("region-size"), 4672 p2i(g1_reserved.start()), p2i(g1_reserved.end()), 4673 HeapRegion::GrainBytes); 4674 _out->print_cr(G1PPRL_LINE_PREFIX); 4675 _out->print_cr(G1PPRL_LINE_PREFIX 4676 G1PPRL_TYPE_H_FORMAT 4677 G1PPRL_ADDR_BASE_H_FORMAT 4678 G1PPRL_BYTE_H_FORMAT 4679 G1PPRL_BYTE_H_FORMAT 4680 G1PPRL_BYTE_H_FORMAT 4681 G1PPRL_DOUBLE_H_FORMAT 4682 G1PPRL_BYTE_H_FORMAT 4683 G1PPRL_BYTE_H_FORMAT, 4684 "type", "address-range", 4685 "used", "prev-live", "next-live", "gc-eff", 4686 "remset", "code-roots"); 4687 _out->print_cr(G1PPRL_LINE_PREFIX 4688 G1PPRL_TYPE_H_FORMAT 4689 G1PPRL_ADDR_BASE_H_FORMAT 4690 G1PPRL_BYTE_H_FORMAT 4691 G1PPRL_BYTE_H_FORMAT 4692 G1PPRL_BYTE_H_FORMAT 4693 G1PPRL_DOUBLE_H_FORMAT 4694 G1PPRL_BYTE_H_FORMAT 4695 G1PPRL_BYTE_H_FORMAT, 4696 "", "", 4697 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)", 4698 "(bytes)", "(bytes)"); 4699 } 4700 4701 // It takes as a parameter a reference to one of the _hum_* fields, it 4702 // deduces the corresponding value for a region in a humongous region 4703 // series (either the region size, or what's left if the _hum_* field 4704 // is < the region size), and updates the _hum_* field accordingly. 4705 size_t G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* hum_bytes) { 4706 size_t bytes = 0; 4707 // The > 0 check is to deal with the prev and next live bytes which 4708 // could be 0. 4709 if (*hum_bytes > 0) { 4710 bytes = MIN2(HeapRegion::GrainBytes, *hum_bytes); 4711 *hum_bytes -= bytes; 4712 } 4713 return bytes; 4714 } 4715 4716 // It deduces the values for a region in a humongous region series 4717 // from the _hum_* fields and updates those accordingly. It assumes 4718 // that that _hum_* fields have already been set up from the "starts 4719 // humongous" region and we visit the regions in address order. 4720 void G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* used_bytes, 4721 size_t* capacity_bytes, 4722 size_t* prev_live_bytes, 4723 size_t* next_live_bytes) { 4724 assert(_hum_used_bytes > 0 && _hum_capacity_bytes > 0, "pre-condition"); 4725 *used_bytes = get_hum_bytes(&_hum_used_bytes); 4726 *capacity_bytes = get_hum_bytes(&_hum_capacity_bytes); 4727 *prev_live_bytes = get_hum_bytes(&_hum_prev_live_bytes); 4728 *next_live_bytes = get_hum_bytes(&_hum_next_live_bytes); 4729 } 4730 4731 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) { 4732 const char* type = r->get_type_str(); 4733 HeapWord* bottom = r->bottom(); 4734 HeapWord* end = r->end(); 4735 size_t capacity_bytes = r->capacity(); 4736 size_t used_bytes = r->used(); 4737 size_t prev_live_bytes = r->live_bytes(); 4738 size_t next_live_bytes = r->next_live_bytes(); 4739 double gc_eff = r->gc_efficiency(); 4740 size_t remset_bytes = r->rem_set()->mem_size(); 4741 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size(); 4742 4743 if (r->startsHumongous()) { 4744 assert(_hum_used_bytes == 0 && _hum_capacity_bytes == 0 && 4745 _hum_prev_live_bytes == 0 && _hum_next_live_bytes == 0, 4746 "they should have been zeroed after the last time we used them"); 4747 // Set up the _hum_* fields. 4748 _hum_capacity_bytes = capacity_bytes; 4749 _hum_used_bytes = used_bytes; 4750 _hum_prev_live_bytes = prev_live_bytes; 4751 _hum_next_live_bytes = next_live_bytes; 4752 get_hum_bytes(&used_bytes, &capacity_bytes, 4753 &prev_live_bytes, &next_live_bytes); 4754 end = bottom + HeapRegion::GrainWords; 4755 } else if (r->continuesHumongous()) { 4756 get_hum_bytes(&used_bytes, &capacity_bytes, 4757 &prev_live_bytes, &next_live_bytes); 4758 assert(end == bottom + HeapRegion::GrainWords, "invariant"); 4759 } 4760 4761 _total_used_bytes += used_bytes; 4762 _total_capacity_bytes += capacity_bytes; 4763 _total_prev_live_bytes += prev_live_bytes; 4764 _total_next_live_bytes += next_live_bytes; 4765 _total_remset_bytes += remset_bytes; 4766 _total_strong_code_roots_bytes += strong_code_roots_bytes; 4767 4768 // Print a line for this particular region. 4769 _out->print_cr(G1PPRL_LINE_PREFIX 4770 G1PPRL_TYPE_FORMAT 4771 G1PPRL_ADDR_BASE_FORMAT 4772 G1PPRL_BYTE_FORMAT 4773 G1PPRL_BYTE_FORMAT 4774 G1PPRL_BYTE_FORMAT 4775 G1PPRL_DOUBLE_FORMAT 4776 G1PPRL_BYTE_FORMAT 4777 G1PPRL_BYTE_FORMAT, 4778 type, p2i(bottom), p2i(end), 4779 used_bytes, prev_live_bytes, next_live_bytes, gc_eff, 4780 remset_bytes, strong_code_roots_bytes); 4781 4782 return false; 4783 } 4784 4785 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() { 4786 // add static memory usages to remembered set sizes 4787 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size(); 4788 // Print the footer of the output. 4789 _out->print_cr(G1PPRL_LINE_PREFIX); 4790 _out->print_cr(G1PPRL_LINE_PREFIX 4791 " SUMMARY" 4792 G1PPRL_SUM_MB_FORMAT("capacity") 4793 G1PPRL_SUM_MB_PERC_FORMAT("used") 4794 G1PPRL_SUM_MB_PERC_FORMAT("prev-live") 4795 G1PPRL_SUM_MB_PERC_FORMAT("next-live") 4796 G1PPRL_SUM_MB_FORMAT("remset") 4797 G1PPRL_SUM_MB_FORMAT("code-roots"), 4798 bytes_to_mb(_total_capacity_bytes), 4799 bytes_to_mb(_total_used_bytes), 4800 perc(_total_used_bytes, _total_capacity_bytes), 4801 bytes_to_mb(_total_prev_live_bytes), 4802 perc(_total_prev_live_bytes, _total_capacity_bytes), 4803 bytes_to_mb(_total_next_live_bytes), 4804 perc(_total_next_live_bytes, _total_capacity_bytes), 4805 bytes_to_mb(_total_remset_bytes), 4806 bytes_to_mb(_total_strong_code_roots_bytes)); 4807 _out->cr(); 4808 }