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 "gc_implementation/g1/concurrentG1Refine.hpp"
  27 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
  28 #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp"
  29 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  30 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  31 #include "gc_implementation/g1/g1HotCardCache.hpp"
  32 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  33 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  34 #include "gc_implementation/g1/g1RemSet.inline.hpp"
  35 #include "gc_implementation/g1/heapRegionManager.inline.hpp"
  36 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  37 #include "memory/iterator.hpp"
  38 #include "oops/oop.inline.hpp"
  39 #include "utilities/globalDefinitions.hpp"
  40 #include "utilities/intHisto.hpp"
  41 
  42 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  43 
  44 #define CARD_REPEAT_HISTO 0
  45 
  46 #if CARD_REPEAT_HISTO
  47 static size_t ct_freq_sz;
  48 static jbyte* ct_freq = NULL;
  49 
  50 void init_ct_freq_table(size_t heap_sz_bytes) {
  51   if (ct_freq == NULL) {
  52     ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size;
  53     ct_freq = new jbyte[ct_freq_sz];
  54     for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0;
  55   }
  56 }
  57 
  58 void ct_freq_note_card(size_t index) {
  59   assert(0 <= index && index < ct_freq_sz, "Bounds error.");
  60   if (ct_freq[index] < 100) { ct_freq[index]++; }
  61 }
  62 
  63 static IntHistogram card_repeat_count(10, 10);
  64 
  65 void ct_freq_update_histo_and_reset() {
  66   for (size_t j = 0; j < ct_freq_sz; j++) {
  67     card_repeat_count.add_entry(ct_freq[j]);
  68     ct_freq[j] = 0;
  69   }
  70 
  71 }
  72 #endif
  73 
  74 G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs)
  75   : _g1(g1), _conc_refine_cards(0),
  76     _ct_bs(ct_bs), _g1p(_g1->g1_policy()),
  77     _cg1r(g1->concurrent_g1_refine()),
  78     _cset_rs_update_cl(NULL),
  79     _cards_scanned(NULL), _total_cards_scanned(0),
  80     _prev_period_summary()
  81 {
  82   _seq_task = new SubTasksDone(NumSeqTasks);
  83   _cset_rs_update_cl = NEW_C_HEAP_ARRAY(G1ParPushHeapRSClosure*, n_workers(), mtGC);
  84   for (uint i = 0; i < n_workers(); i++) {
  85     _cset_rs_update_cl[i] = NULL;
  86   }
  87   if (G1SummarizeRSetStats) {
  88     _prev_period_summary.initialize(this);
  89   }
  90 }
  91 
  92 G1RemSet::~G1RemSet() {
  93   delete _seq_task;
  94   for (uint i = 0; i < n_workers(); i++) {
  95     assert(_cset_rs_update_cl[i] == NULL, "it should be");
  96   }
  97   FREE_C_HEAP_ARRAY(G1ParPushHeapRSClosure*, _cset_rs_update_cl);
  98 }
  99 
 100 class ScanRSClosure : public HeapRegionClosure {
 101   size_t _cards_done, _cards;
 102   G1CollectedHeap* _g1h;
 103 
 104   G1ParPushHeapRSClosure* _oc;
 105   CodeBlobClosure* _code_root_cl;
 106 
 107   G1BlockOffsetSharedArray* _bot_shared;
 108   G1SATBCardTableModRefBS *_ct_bs;
 109 
 110   double _strong_code_root_scan_time_sec;
 111   uint   _worker_i;
 112   int    _block_size;
 113   bool   _try_claimed;
 114 
 115 public:
 116   ScanRSClosure(G1ParPushHeapRSClosure* oc,
 117                 CodeBlobClosure* code_root_cl,
 118                 uint worker_i) :
 119     _oc(oc),
 120     _code_root_cl(code_root_cl),
 121     _strong_code_root_scan_time_sec(0.0),
 122     _cards(0),
 123     _cards_done(0),
 124     _worker_i(worker_i),
 125     _try_claimed(false)
 126   {
 127     _g1h = G1CollectedHeap::heap();
 128     _bot_shared = _g1h->bot_shared();
 129     _ct_bs = _g1h->g1_barrier_set();
 130     _block_size = MAX2<int>(G1RSetScanBlockSize, 1);
 131   }
 132 
 133   void set_try_claimed() { _try_claimed = true; }
 134 
 135   void scanCard(size_t index, HeapRegion *r) {
 136     // Stack allocate the DirtyCardToOopClosure instance
 137     HeapRegionDCTOC cl(_g1h, r, _oc,
 138                        CardTableModRefBS::Precise);
 139 
 140     // Set the "from" region in the closure.
 141     _oc->set_region(r);
 142     MemRegion card_region(_bot_shared->address_for_index(index), G1BlockOffsetSharedArray::N_words);
 143     MemRegion pre_gc_allocated(r->bottom(), r->scan_top());
 144     MemRegion mr = pre_gc_allocated.intersection(card_region);
 145     if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
 146       // We make the card as "claimed" lazily (so races are possible
 147       // but they're benign), which reduces the number of duplicate
 148       // scans (the rsets of the regions in the cset can intersect).
 149       _ct_bs->set_card_claimed(index);
 150       _cards_done++;
 151       cl.do_MemRegion(mr);
 152     }
 153   }
 154 
 155   void printCard(HeapRegion* card_region, size_t card_index,
 156                  HeapWord* card_start) {
 157     gclog_or_tty->print_cr("T %u Region [" PTR_FORMAT ", " PTR_FORMAT ") "
 158                            "RS names card " SIZE_FORMAT_HEX ": "
 159                            "[" PTR_FORMAT ", " PTR_FORMAT ")",
 160                            _worker_i,
 161                            card_region->bottom(), card_region->end(),
 162                            card_index,
 163                            card_start, card_start + G1BlockOffsetSharedArray::N_words);
 164   }
 165 
 166   void scan_strong_code_roots(HeapRegion* r) {
 167     double scan_start = os::elapsedTime();
 168     r->strong_code_roots_do(_code_root_cl);
 169     _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
 170   }
 171 
 172   bool doHeapRegion(HeapRegion* r) {
 173     assert(r->in_collection_set(), "should only be called on elements of CS.");
 174     HeapRegionRemSet* hrrs = r->rem_set();
 175     if (hrrs->iter_is_complete()) return false; // All done.
 176     if (!_try_claimed && !hrrs->claim_iter()) return false;
 177     // If we ever free the collection set concurrently, we should also
 178     // clear the card table concurrently therefore we won't need to
 179     // add regions of the collection set to the dirty cards region.
 180     _g1h->push_dirty_cards_region(r);
 181     // If we didn't return above, then
 182     //   _try_claimed || r->claim_iter()
 183     // is true: either we're supposed to work on claimed-but-not-complete
 184     // regions, or we successfully claimed the region.
 185 
 186     HeapRegionRemSetIterator iter(hrrs);
 187     size_t card_index;
 188 
 189     // We claim cards in block so as to reduce the contention. The block size is determined by
 190     // the G1RSetScanBlockSize parameter.
 191     size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
 192     for (size_t current_card = 0; iter.has_next(card_index); current_card++) {
 193       if (current_card >= jump_to_card + _block_size) {
 194         jump_to_card = hrrs->iter_claimed_next(_block_size);
 195       }
 196       if (current_card < jump_to_card) continue;
 197       HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
 198 #if 0
 199       gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
 200                           card_start, card_start + CardTableModRefBS::card_size_in_words);
 201 #endif
 202 
 203       HeapRegion* card_region = _g1h->heap_region_containing(card_start);
 204       _cards++;
 205 
 206       if (!card_region->is_on_dirty_cards_region_list()) {
 207         _g1h->push_dirty_cards_region(card_region);
 208       }
 209 
 210       // If the card is dirty, then we will scan it during updateRS.
 211       if (!card_region->in_collection_set() &&
 212           !_ct_bs->is_card_dirty(card_index)) {
 213         scanCard(card_index, card_region);
 214       }
 215     }
 216     if (!_try_claimed) {
 217       // Scan the strong code root list attached to the current region
 218       scan_strong_code_roots(r);
 219 
 220       hrrs->set_iter_complete();
 221     }
 222     return false;
 223   }
 224 
 225   double strong_code_root_scan_time_sec() {
 226     return _strong_code_root_scan_time_sec;
 227   }
 228 
 229   size_t cards_done() { return _cards_done;}
 230   size_t cards_looked_up() { return _cards;}
 231 };
 232 
 233 void G1RemSet::scanRS(G1ParPushHeapRSClosure* oc,
 234                       CodeBlobClosure* code_root_cl,
 235                       uint worker_i) {
 236   double rs_time_start = os::elapsedTime();
 237   HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);
 238 
 239   ScanRSClosure scanRScl(oc, code_root_cl, worker_i);
 240 
 241   _g1->collection_set_iterate_from(startRegion, &scanRScl);
 242   scanRScl.set_try_claimed();
 243   _g1->collection_set_iterate_from(startRegion, &scanRScl);
 244 
 245   double scan_rs_time_sec = (os::elapsedTime() - rs_time_start)
 246                             - scanRScl.strong_code_root_scan_time_sec();
 247 
 248   assert(_cards_scanned != NULL, "invariant");
 249   _cards_scanned[worker_i] = scanRScl.cards_done();
 250 
 251   _g1p->phase_times()->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
 252   _g1p->phase_times()->record_strong_code_root_scan_time(worker_i,
 253                                                          scanRScl.strong_code_root_scan_time_sec() * 1000.0);
 254 }
 255 
 256 // Closure used for updating RSets and recording references that
 257 // point into the collection set. Only called during an
 258 // evacuation pause.
 259 
 260 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
 261   G1RemSet* _g1rs;
 262   DirtyCardQueue* _into_cset_dcq;
 263 public:
 264   RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
 265                                               DirtyCardQueue* into_cset_dcq) :
 266     _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
 267   {}
 268   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 269     // The only time we care about recording cards that
 270     // contain references that point into the collection set
 271     // is during RSet updating within an evacuation pause.
 272     // In this case worker_i should be the id of a GC worker thread.
 273     assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
 274     assert(worker_i < ParallelGCThreads, "should be a GC worker");
 275 
 276     if (_g1rs->refine_card(card_ptr, worker_i, true)) {
 277       // 'card_ptr' contains references that point into the collection
 278       // set. We need to record the card in the DCQS
 279       // (G1CollectedHeap::into_cset_dirty_card_queue_set())
 280       // that's used for that purpose.
 281       //
 282       // Enqueue the card
 283       _into_cset_dcq->enqueue(card_ptr);
 284     }
 285     return true;
 286   }
 287 };
 288 
 289 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, uint worker_i) {
 290   double start = os::elapsedTime();
 291   // Apply the given closure to all remaining log entries.
 292   RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
 293 
 294   _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
 295 
 296   _g1p->phase_times()->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
 297 }
 298 
 299 void G1RemSet::cleanupHRRS() {
 300   HeapRegionRemSet::cleanup();
 301 }
 302 
 303 void G1RemSet::oops_into_collection_set_do(G1ParPushHeapRSClosure* oc,
 304                                            CodeBlobClosure* code_root_cl,
 305                                            uint worker_i) {
 306 #if CARD_REPEAT_HISTO
 307   ct_freq_update_histo_and_reset();
 308 #endif
 309 
 310   // We cache the value of 'oc' closure into the appropriate slot in the
 311   // _cset_rs_update_cl for this worker
 312   assert(worker_i < n_workers(), "sanity");
 313   _cset_rs_update_cl[worker_i] = oc;
 314 
 315   // A DirtyCardQueue that is used to hold cards containing references
 316   // that point into the collection set. This DCQ is associated with a
 317   // special DirtyCardQueueSet (see g1CollectedHeap.hpp).  Under normal
 318   // circumstances (i.e. the pause successfully completes), these cards
 319   // are just discarded (there's no need to update the RSets of regions
 320   // that were in the collection set - after the pause these regions
 321   // are wholly 'free' of live objects. In the event of an evacuation
 322   // failure the cards/buffers in this queue set are passed to the
 323   // DirtyCardQueueSet that is used to manage RSet updates
 324   DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
 325 
 326   updateRS(&into_cset_dcq, worker_i);
 327   scanRS(oc, code_root_cl, worker_i);
 328 
 329   // We now clear the cached values of _cset_rs_update_cl for this worker
 330   _cset_rs_update_cl[worker_i] = NULL;
 331 }
 332 
 333 void G1RemSet::prepare_for_oops_into_collection_set_do() {
 334   cleanupHRRS();
 335   _g1->set_refine_cte_cl_concurrency(false);
 336   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 337   dcqs.concatenate_logs();
 338 
 339   guarantee( _cards_scanned == NULL, "invariant" );
 340   _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC);
 341   for (uint i = 0; i < n_workers(); ++i) {
 342     _cards_scanned[i] = 0;
 343   }
 344   _total_cards_scanned = 0;
 345 }
 346 
 347 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
 348   guarantee( _cards_scanned != NULL, "invariant" );
 349   _total_cards_scanned = 0;
 350   for (uint i = 0; i < n_workers(); ++i) {
 351     _total_cards_scanned += _cards_scanned[i];
 352   }
 353   FREE_C_HEAP_ARRAY(size_t, _cards_scanned);
 354   _cards_scanned = NULL;
 355   // Cleanup after copy
 356   _g1->set_refine_cte_cl_concurrency(true);
 357   // Set all cards back to clean.
 358   _g1->cleanUpCardTable();
 359 
 360   DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
 361   int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
 362 
 363   if (_g1->evacuation_failed()) {
 364     double restore_remembered_set_start = os::elapsedTime();
 365 
 366     // Restore remembered sets for the regions pointing into the collection set.
 367     // We just need to transfer the completed buffers from the DirtyCardQueueSet
 368     // used to hold cards that contain references that point into the collection set
 369     // to the DCQS used to hold the deferred RS updates.
 370     _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
 371     _g1->g1_policy()->phase_times()->record_evac_fail_restore_remsets((os::elapsedTime() - restore_remembered_set_start) * 1000.0);
 372   }
 373 
 374   // Free any completed buffers in the DirtyCardQueueSet used to hold cards
 375   // which contain references that point into the collection.
 376   _g1->into_cset_dirty_card_queue_set().clear();
 377   assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
 378          "all buffers should be freed");
 379   _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
 380 }
 381 
 382 class ScrubRSClosure: public HeapRegionClosure {
 383   G1CollectedHeap* _g1h;
 384   BitMap* _region_bm;
 385   BitMap* _card_bm;
 386   CardTableModRefBS* _ctbs;
 387 public:
 388   ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
 389     _g1h(G1CollectedHeap::heap()),
 390     _region_bm(region_bm), _card_bm(card_bm),
 391     _ctbs(_g1h->g1_barrier_set()) {}
 392 
 393   bool doHeapRegion(HeapRegion* r) {
 394     if (!r->is_continues_humongous()) {
 395       r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
 396     }
 397     return false;
 398   }
 399 };
 400 
 401 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm, uint worker_num, HeapRegionClaimer *hrclaimer) {
 402   ScrubRSClosure scrub_cl(region_bm, card_bm);
 403   _g1->heap_region_par_iterate(&scrub_cl, worker_num, hrclaimer);
 404 }
 405 
 406 G1TriggerClosure::G1TriggerClosure() :
 407   _triggered(false) { }
 408 
 409 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
 410                                                              OopClosure* oop_cl)  :
 411   _trigger_cl(t_cl), _oop_cl(oop_cl) { }
 412 
 413 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
 414   _c1(c1), _c2(c2) { }
 415 
 416 G1UpdateRSOrPushRefOopClosure::
 417 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
 418                               G1RemSet* rs,
 419                               G1ParPushHeapRSClosure* push_ref_cl,
 420                               bool record_refs_into_cset,
 421                               uint worker_i) :
 422   _g1(g1h), _g1_rem_set(rs), _from(NULL),
 423   _record_refs_into_cset(record_refs_into_cset),
 424   _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
 425 
 426 // Returns true if the given card contains references that point
 427 // into the collection set, if we're checking for such references;
 428 // false otherwise.
 429 
 430 bool G1RemSet::refine_card(jbyte* card_ptr, uint worker_i,
 431                            bool check_for_refs_into_cset) {
 432   assert(_g1->is_in_exact(_ct_bs->addr_for(card_ptr)),
 433          err_msg("Card at "PTR_FORMAT" index "SIZE_FORMAT" representing heap at "PTR_FORMAT" (%u) must be in committed heap",
 434                  p2i(card_ptr),
 435                  _ct_bs->index_for(_ct_bs->addr_for(card_ptr)),
 436                  _ct_bs->addr_for(card_ptr),
 437                  _g1->addr_to_region(_ct_bs->addr_for(card_ptr))));
 438 
 439   // If the card is no longer dirty, nothing to do.
 440   if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
 441     // No need to return that this card contains refs that point
 442     // into the collection set.
 443     return false;
 444   }
 445 
 446   // Construct the region representing the card.
 447   HeapWord* start = _ct_bs->addr_for(card_ptr);
 448   // And find the region containing it.
 449   HeapRegion* r = _g1->heap_region_containing(start);
 450 
 451   // Why do we have to check here whether a card is on a young region,
 452   // given that we dirty young regions and, as a result, the
 453   // post-barrier is supposed to filter them out and never to enqueue
 454   // them? When we allocate a new region as the "allocation region" we
 455   // actually dirty its cards after we release the lock, since card
 456   // dirtying while holding the lock was a performance bottleneck. So,
 457   // as a result, it is possible for other threads to actually
 458   // allocate objects in the region (after the acquire the lock)
 459   // before all the cards on the region are dirtied. This is unlikely,
 460   // and it doesn't happen often, but it can happen. So, the extra
 461   // check below filters out those cards.
 462   if (r->is_young()) {
 463     return false;
 464   }
 465 
 466   // While we are processing RSet buffers during the collection, we
 467   // actually don't want to scan any cards on the collection set,
 468   // since we don't want to update remembered sets with entries that
 469   // point into the collection set, given that live objects from the
 470   // collection set are about to move and such entries will be stale
 471   // very soon. This change also deals with a reliability issue which
 472   // involves scanning a card in the collection set and coming across
 473   // an array that was being chunked and looking malformed. Note,
 474   // however, that if evacuation fails, we have to scan any objects
 475   // that were not moved and create any missing entries.
 476   if (r->in_collection_set()) {
 477     return false;
 478   }
 479 
 480   // The result from the hot card cache insert call is either:
 481   //   * pointer to the current card
 482   //     (implying that the current card is not 'hot'),
 483   //   * null
 484   //     (meaning we had inserted the card ptr into the "hot" card cache,
 485   //     which had some headroom),
 486   //   * a pointer to a "hot" card that was evicted from the "hot" cache.
 487   //
 488 
 489   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
 490   if (hot_card_cache->use_cache()) {
 491     assert(!check_for_refs_into_cset, "sanity");
 492     assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
 493 
 494     card_ptr = hot_card_cache->insert(card_ptr);
 495     if (card_ptr == NULL) {
 496       // There was no eviction. Nothing to do.
 497       return false;
 498     }
 499 
 500     start = _ct_bs->addr_for(card_ptr);
 501     r = _g1->heap_region_containing(start);
 502 
 503     // Checking whether the region we got back from the cache
 504     // is young here is inappropriate. The region could have been
 505     // freed, reallocated and tagged as young while in the cache.
 506     // Hence we could see its young type change at any time.
 507   }
 508 
 509   // Don't use addr_for(card_ptr + 1) which can ask for
 510   // a card beyond the heap.  This is not safe without a perm
 511   // gen at the upper end of the heap.
 512   HeapWord* end   = start + CardTableModRefBS::card_size_in_words;
 513   MemRegion dirtyRegion(start, end);
 514 
 515 #if CARD_REPEAT_HISTO
 516   init_ct_freq_table(_g1->max_capacity());
 517   ct_freq_note_card(_ct_bs->index_for(start));
 518 #endif
 519 
 520   G1ParPushHeapRSClosure* oops_in_heap_closure = NULL;
 521   if (check_for_refs_into_cset) {
 522     // ConcurrentG1RefineThreads have worker numbers larger than what
 523     // _cset_rs_update_cl[] is set up to handle. But those threads should
 524     // only be active outside of a collection which means that when they
 525     // reach here they should have check_for_refs_into_cset == false.
 526     assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
 527     oops_in_heap_closure = _cset_rs_update_cl[worker_i];
 528   }
 529   G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
 530                                                  _g1->g1_rem_set(),
 531                                                  oops_in_heap_closure,
 532                                                  check_for_refs_into_cset,
 533                                                  worker_i);
 534   update_rs_oop_cl.set_from(r);
 535 
 536   G1TriggerClosure trigger_cl;
 537   FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
 538   G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
 539   G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
 540 
 541   FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
 542                         (check_for_refs_into_cset ?
 543                                 (OopClosure*)&mux :
 544                                 (OopClosure*)&update_rs_oop_cl));
 545 
 546   // The region for the current card may be a young region. The
 547   // current card may have been a card that was evicted from the
 548   // card cache. When the card was inserted into the cache, we had
 549   // determined that its region was non-young. While in the cache,
 550   // the region may have been freed during a cleanup pause, reallocated
 551   // and tagged as young.
 552   //
 553   // We wish to filter out cards for such a region but the current
 554   // thread, if we're running concurrently, may "see" the young type
 555   // change at any time (so an earlier "is_young" check may pass or
 556   // fail arbitrarily). We tell the iteration code to perform this
 557   // filtering when it has been determined that there has been an actual
 558   // allocation in this region and making it safe to check the young type.
 559   bool filter_young = true;
 560 
 561   HeapWord* stop_point =
 562     r->oops_on_card_seq_iterate_careful(dirtyRegion,
 563                                         &filter_then_update_rs_oop_cl,
 564                                         filter_young,
 565                                         card_ptr);
 566 
 567   // If stop_point is non-null, then we encountered an unallocated region
 568   // (perhaps the unfilled portion of a TLAB.)  For now, we'll dirty the
 569   // card and re-enqueue: if we put off the card until a GC pause, then the
 570   // unallocated portion will be filled in.  Alternatively, we might try
 571   // the full complexity of the technique used in "regular" precleaning.
 572   if (stop_point != NULL) {
 573     // The card might have gotten re-dirtied and re-enqueued while we
 574     // worked.  (In fact, it's pretty likely.)
 575     if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
 576       *card_ptr = CardTableModRefBS::dirty_card_val();
 577       MutexLockerEx x(Shared_DirtyCardQ_lock,
 578                       Mutex::_no_safepoint_check_flag);
 579       DirtyCardQueue* sdcq =
 580         JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
 581       sdcq->enqueue(card_ptr);
 582     }
 583   } else {
 584     _conc_refine_cards++;
 585   }
 586 
 587   // This gets set to true if the card being refined has
 588   // references that point into the collection set.
 589   bool has_refs_into_cset = trigger_cl.triggered();
 590 
 591   // We should only be detecting that the card contains references
 592   // that point into the collection set if the current thread is
 593   // a GC worker thread.
 594   assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
 595            "invalid result at non safepoint");
 596 
 597   return has_refs_into_cset;
 598 }
 599 
 600 void G1RemSet::print_periodic_summary_info(const char* header) {
 601   G1RemSetSummary current;
 602   current.initialize(this);
 603 
 604   _prev_period_summary.subtract_from(&current);
 605   print_summary_info(&_prev_period_summary, header);
 606 
 607   _prev_period_summary.set(&current);
 608 }
 609 
 610 void G1RemSet::print_summary_info() {
 611   G1RemSetSummary current;
 612   current.initialize(this);
 613 
 614   print_summary_info(&current, " Cumulative RS summary");
 615 }
 616 
 617 void G1RemSet::print_summary_info(G1RemSetSummary * summary, const char * header) {
 618   assert(summary != NULL, "just checking");
 619 
 620   if (header != NULL) {
 621     gclog_or_tty->print_cr("%s", header);
 622   }
 623 
 624 #if CARD_REPEAT_HISTO
 625   gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
 626   gclog_or_tty->print_cr("  # of repeats --> # of cards with that number.");
 627   card_repeat_count.print_on(gclog_or_tty);
 628 #endif
 629 
 630   summary->print_on(gclog_or_tty);
 631 }
 632 
 633 void G1RemSet::prepare_for_verify() {
 634   if (G1HRRSFlushLogBuffersOnVerify &&
 635       (VerifyBeforeGC || VerifyAfterGC)
 636       &&  (!_g1->full_collection() || G1VerifyRSetsDuringFullGC)) {
 637     cleanupHRRS();
 638     _g1->set_refine_cte_cl_concurrency(false);
 639     if (SafepointSynchronize::is_at_safepoint()) {
 640       DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 641       dcqs.concatenate_logs();
 642     }
 643 
 644     G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
 645     bool use_hot_card_cache = hot_card_cache->use_cache();
 646     hot_card_cache->set_use_cache(false);
 647 
 648     DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
 649     updateRS(&into_cset_dcq, 0);
 650     _g1->into_cset_dirty_card_queue_set().clear();
 651 
 652     hot_card_cache->set_use_cache(use_hot_card_cache);
 653     assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
 654   }
 655 }
--- EOF ---