1 /*
   2  * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/g1/concurrentG1Refine.hpp"
  27 #include "gc/g1/concurrentG1RefineThread.hpp"
  28 #include "gc/g1/g1BlockOffsetTable.inline.hpp"
  29 #include "gc/g1/g1CodeBlobClosure.hpp"
  30 #include "gc/g1/g1CollectedHeap.inline.hpp"
  31 #include "gc/g1/g1CollectorPolicy.hpp"
  32 #include "gc/g1/g1GCPhaseTimes.hpp"
  33 #include "gc/g1/g1HotCardCache.hpp"
  34 #include "gc/g1/g1OopClosures.inline.hpp"
  35 #include "gc/g1/g1RemSet.inline.hpp"
  36 #include "gc/g1/heapRegionManager.inline.hpp"
  37 #include "gc/g1/heapRegionRemSet.hpp"
  38 #include "memory/iterator.hpp"
  39 #include "oops/oop.inline.hpp"
  40 #include "utilities/globalDefinitions.hpp"
  41 #include "utilities/intHisto.hpp"
  42 #include "utilities/stack.inline.hpp"
  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     _prev_period_summary()
  80 {
  81   _cset_rs_update_cl = NEW_C_HEAP_ARRAY(G1ParPushHeapRSClosure*, n_workers(), mtGC);
  82   for (uint i = 0; i < n_workers(); i++) {
  83     _cset_rs_update_cl[i] = NULL;
  84   }
  85   if (G1SummarizeRSetStats) {
  86     _prev_period_summary.initialize(this);
  87   }
  88 }
  89 
  90 G1RemSet::~G1RemSet() {
  91   for (uint i = 0; i < n_workers(); i++) {
  92     assert(_cset_rs_update_cl[i] == NULL, "it should be");
  93   }
  94   FREE_C_HEAP_ARRAY(G1ParPushHeapRSClosure*, _cset_rs_update_cl);
  95 }
  96 
  97 class ScanRSClosure : public HeapRegionClosure {
  98   size_t _cards_done, _cards;
  99   G1CollectedHeap* _g1h;
 100 
 101   G1ParPushHeapRSClosure* _oc;
 102   CodeBlobClosure* _code_root_cl;
 103 
 104   G1BlockOffsetSharedArray* _bot_shared;
 105   G1SATBCardTableModRefBS *_ct_bs;
 106 
 107   double _strong_code_root_scan_time_sec;
 108   uint   _worker_i;
 109   size_t _block_size;
 110   bool   _try_claimed;
 111 
 112 public:
 113   ScanRSClosure(G1ParPushHeapRSClosure* oc,
 114                 CodeBlobClosure* code_root_cl,
 115                 uint worker_i) :
 116     _oc(oc),
 117     _code_root_cl(code_root_cl),
 118     _strong_code_root_scan_time_sec(0.0),
 119     _cards(0),
 120     _cards_done(0),
 121     _worker_i(worker_i),
 122     _try_claimed(false)
 123   {
 124     _g1h = G1CollectedHeap::heap();
 125     _bot_shared = _g1h->bot_shared();
 126     _ct_bs = _g1h->g1_barrier_set();
 127     _block_size = MAX2<size_t>(G1RSetScanBlockSize, 1);
 128   }
 129 
 130   void set_try_claimed() { _try_claimed = true; }
 131 
 132   void scanCard(size_t index, HeapRegion *r) {
 133     // Stack allocate the DirtyCardToOopClosure instance
 134     HeapRegionDCTOC cl(_g1h, r, _oc,
 135                        CardTableModRefBS::Precise);
 136 
 137     // Set the "from" region in the closure.
 138     _oc->set_region(r);
 139     MemRegion card_region(_bot_shared->address_for_index(index), G1BlockOffsetSharedArray::N_words);
 140     MemRegion pre_gc_allocated(r->bottom(), r->scan_top());
 141     MemRegion mr = pre_gc_allocated.intersection(card_region);
 142     if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
 143       // We make the card as "claimed" lazily (so races are possible
 144       // but they're benign), which reduces the number of duplicate
 145       // scans (the rsets of the regions in the cset can intersect).
 146       _ct_bs->set_card_claimed(index);
 147       _cards_done++;
 148       cl.do_MemRegion(mr);
 149     }
 150   }
 151 
 152   void printCard(HeapRegion* card_region, size_t card_index,
 153                  HeapWord* card_start) {
 154     gclog_or_tty->print_cr("T %u Region [" PTR_FORMAT ", " PTR_FORMAT ") "
 155                            "RS names card " SIZE_FORMAT_HEX ": "
 156                            "[" PTR_FORMAT ", " PTR_FORMAT ")",
 157                            _worker_i,
 158                            p2i(card_region->bottom()), p2i(card_region->end()),
 159                            card_index,
 160                            p2i(card_start), p2i(card_start + G1BlockOffsetSharedArray::N_words));
 161   }
 162 
 163   void scan_strong_code_roots(HeapRegion* r) {
 164     double scan_start = os::elapsedTime();
 165     r->strong_code_roots_do(_code_root_cl);
 166     _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
 167   }
 168 
 169   bool doHeapRegion(HeapRegion* r) {
 170     assert(r->in_collection_set(), "should only be called on elements of CS.");
 171     HeapRegionRemSet* hrrs = r->rem_set();
 172     if (hrrs->iter_is_complete()) return false; // All done.
 173     if (!_try_claimed && !hrrs->claim_iter()) return false;
 174     // If we ever free the collection set concurrently, we should also
 175     // clear the card table concurrently therefore we won't need to
 176     // add regions of the collection set to the dirty cards region.
 177     _g1h->push_dirty_cards_region(r);
 178     // If we didn't return above, then
 179     //   _try_claimed || r->claim_iter()
 180     // is true: either we're supposed to work on claimed-but-not-complete
 181     // regions, or we successfully claimed the region.
 182 
 183     HeapRegionRemSetIterator iter(hrrs);
 184     size_t card_index;
 185 
 186     // We claim cards in block so as to reduce the contention. The block size is determined by
 187     // the G1RSetScanBlockSize parameter.
 188     size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
 189     for (size_t current_card = 0; iter.has_next(card_index); current_card++) {
 190       if (current_card >= jump_to_card + _block_size) {
 191         jump_to_card = hrrs->iter_claimed_next(_block_size);
 192       }
 193       if (current_card < jump_to_card) continue;
 194       HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
 195 #if 0
 196       gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
 197                           card_start, card_start + CardTableModRefBS::card_size_in_words);
 198 #endif
 199 
 200       HeapRegion* card_region = _g1h->heap_region_containing(card_start);
 201       _cards++;
 202 
 203       if (!card_region->is_on_dirty_cards_region_list()) {
 204         _g1h->push_dirty_cards_region(card_region);
 205       }
 206 
 207       // If the card is dirty, then we will scan it during updateRS.
 208       if (!card_region->in_collection_set() &&
 209           !_ct_bs->is_card_dirty(card_index)) {
 210         scanCard(card_index, card_region);
 211       }
 212     }
 213     if (!_try_claimed) {
 214       // Scan the strong code root list attached to the current region
 215       scan_strong_code_roots(r);
 216 
 217       hrrs->set_iter_complete();
 218     }
 219     return false;
 220   }
 221 
 222   double strong_code_root_scan_time_sec() {
 223     return _strong_code_root_scan_time_sec;
 224   }
 225 
 226   size_t cards_done() { return _cards_done;}
 227   size_t cards_looked_up() { return _cards;}
 228 };
 229 
 230 size_t G1RemSet::scanRS(G1ParPushHeapRSClosure* oc,
 231                         OopClosure* non_heap_roots,
 232                         uint worker_i) {
 233   double rs_time_start = os::elapsedTime();
 234 
 235   G1CodeBlobClosure code_root_cl(non_heap_roots);
 236 
 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   _g1p->phase_times()->record_time_secs(G1GCPhaseTimes::ScanRS, worker_i, scan_rs_time_sec);
 249   _g1p->phase_times()->record_time_secs(G1GCPhaseTimes::CodeRoots, worker_i, scanRScl.strong_code_root_scan_time_sec());
 250 
 251   return scanRScl.cards_done();
 252 }
 253 
 254 // Closure used for updating RSets and recording references that
 255 // point into the collection set. Only called during an
 256 // evacuation pause.
 257 
 258 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
 259   G1RemSet* _g1rs;
 260   DirtyCardQueue* _into_cset_dcq;
 261 public:
 262   RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
 263                                               DirtyCardQueue* into_cset_dcq) :
 264     _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
 265   {}
 266   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 267     // The only time we care about recording cards that
 268     // contain references that point into the collection set
 269     // is during RSet updating within an evacuation pause.
 270     // In this case worker_i should be the id of a GC worker thread.
 271     assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
 272     assert(worker_i < ParallelGCThreads, "should be a GC worker");
 273 
 274     if (_g1rs->refine_card(card_ptr, worker_i, true)) {
 275       // 'card_ptr' contains references that point into the collection
 276       // set. We need to record the card in the DCQS
 277       // (G1CollectedHeap::into_cset_dirty_card_queue_set())
 278       // that's used for that purpose.
 279       //
 280       // Enqueue the card
 281       _into_cset_dcq->enqueue(card_ptr);
 282     }
 283     return true;
 284   }
 285 };
 286 
 287 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, uint worker_i) {
 288   G1GCParPhaseTimesTracker x(_g1p->phase_times(), G1GCPhaseTimes::UpdateRS, worker_i);
 289   // Apply the given closure to all remaining log entries.
 290   RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
 291 
 292   _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
 293 }
 294 
 295 void G1RemSet::cleanupHRRS() {
 296   HeapRegionRemSet::cleanup();
 297 }
 298 
 299 size_t G1RemSet::oops_into_collection_set_do(G1ParPushHeapRSClosure* oc,
 300                                              OopClosure* non_heap_roots,
 301                                              uint worker_i) {
 302 #if CARD_REPEAT_HISTO
 303   ct_freq_update_histo_and_reset();
 304 #endif
 305 
 306   // We cache the value of 'oc' closure into the appropriate slot in the
 307   // _cset_rs_update_cl for this worker
 308   assert(worker_i < n_workers(), "sanity");
 309   _cset_rs_update_cl[worker_i] = oc;
 310 
 311   // A DirtyCardQueue that is used to hold cards containing references
 312   // that point into the collection set. This DCQ is associated with a
 313   // special DirtyCardQueueSet (see g1CollectedHeap.hpp).  Under normal
 314   // circumstances (i.e. the pause successfully completes), these cards
 315   // are just discarded (there's no need to update the RSets of regions
 316   // that were in the collection set - after the pause these regions
 317   // are wholly 'free' of live objects. In the event of an evacuation
 318   // failure the cards/buffers in this queue set are passed to the
 319   // DirtyCardQueueSet that is used to manage RSet updates
 320   DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
 321 
 322   updateRS(&into_cset_dcq, worker_i);
 323   size_t cards_scanned = scanRS(oc, non_heap_roots, worker_i);
 324 
 325   // We now clear the cached values of _cset_rs_update_cl for this worker
 326   _cset_rs_update_cl[worker_i] = NULL;
 327   return cards_scanned;
 328 }
 329 
 330 void G1RemSet::prepare_for_oops_into_collection_set_do() {
 331   cleanupHRRS();
 332   _g1->set_refine_cte_cl_concurrency(false);
 333   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 334   dcqs.concatenate_logs();
 335 }
 336 
 337 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
 338   // Cleanup after copy
 339   _g1->set_refine_cte_cl_concurrency(true);
 340   // Set all cards back to clean.
 341   _g1->cleanUpCardTable();
 342 
 343   DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
 344   int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
 345 
 346   if (_g1->evacuation_failed()) {
 347     double restore_remembered_set_start = os::elapsedTime();
 348 
 349     // Restore remembered sets for the regions pointing into the collection set.
 350     // We just need to transfer the completed buffers from the DirtyCardQueueSet
 351     // used to hold cards that contain references that point into the collection set
 352     // to the DCQS used to hold the deferred RS updates.
 353     _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
 354     _g1->g1_policy()->phase_times()->record_evac_fail_restore_remsets((os::elapsedTime() - restore_remembered_set_start) * 1000.0);
 355   }
 356 
 357   // Free any completed buffers in the DirtyCardQueueSet used to hold cards
 358   // which contain references that point into the collection.
 359   _g1->into_cset_dirty_card_queue_set().clear();
 360   assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
 361          "all buffers should be freed");
 362   _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
 363 }
 364 
 365 class ScrubRSClosure: public HeapRegionClosure {
 366   G1CollectedHeap* _g1h;
 367   BitMap* _region_bm;
 368   BitMap* _card_bm;
 369   CardTableModRefBS* _ctbs;
 370 public:
 371   ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
 372     _g1h(G1CollectedHeap::heap()),
 373     _region_bm(region_bm), _card_bm(card_bm),
 374     _ctbs(_g1h->g1_barrier_set()) {}
 375 
 376   bool doHeapRegion(HeapRegion* r) {
 377     if (!r->is_continues_humongous()) {
 378       r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
 379     }
 380     return false;
 381   }
 382 };
 383 
 384 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm, uint worker_num, HeapRegionClaimer *hrclaimer) {
 385   ScrubRSClosure scrub_cl(region_bm, card_bm);
 386   _g1->heap_region_par_iterate(&scrub_cl, worker_num, hrclaimer);
 387 }
 388 
 389 G1TriggerClosure::G1TriggerClosure() :
 390   _triggered(false) { }
 391 
 392 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
 393                                                              OopClosure* oop_cl)  :
 394   _trigger_cl(t_cl), _oop_cl(oop_cl) { }
 395 
 396 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
 397   _c1(c1), _c2(c2) { }
 398 
 399 G1UpdateRSOrPushRefOopClosure::
 400 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
 401                               G1RemSet* rs,
 402                               G1ParPushHeapRSClosure* push_ref_cl,
 403                               bool record_refs_into_cset,
 404                               uint worker_i) :
 405   _g1(g1h), _g1_rem_set(rs), _from(NULL),
 406   _record_refs_into_cset(record_refs_into_cset),
 407   _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
 408 
 409 // Returns true if the given card contains references that point
 410 // into the collection set, if we're checking for such references;
 411 // false otherwise.
 412 
 413 bool G1RemSet::refine_card(jbyte* card_ptr, uint worker_i,
 414                            bool check_for_refs_into_cset) {
 415   assert(_g1->is_in_exact(_ct_bs->addr_for(card_ptr)),
 416          err_msg("Card at " PTR_FORMAT " index " SIZE_FORMAT " representing heap at " PTR_FORMAT " (%u) must be in committed heap",
 417                  p2i(card_ptr),
 418                  _ct_bs->index_for(_ct_bs->addr_for(card_ptr)),
 419                  p2i(_ct_bs->addr_for(card_ptr)),
 420                  _g1->addr_to_region(_ct_bs->addr_for(card_ptr))));
 421 
 422   // If the card is no longer dirty, nothing to do.
 423   if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
 424     // No need to return that this card contains refs that point
 425     // into the collection set.
 426     return false;
 427   }
 428 
 429   // Construct the region representing the card.
 430   HeapWord* start = _ct_bs->addr_for(card_ptr);
 431   // And find the region containing it.
 432   HeapRegion* r = _g1->heap_region_containing(start);
 433 
 434   // Why do we have to check here whether a card is on a young region,
 435   // given that we dirty young regions and, as a result, the
 436   // post-barrier is supposed to filter them out and never to enqueue
 437   // them? When we allocate a new region as the "allocation region" we
 438   // actually dirty its cards after we release the lock, since card
 439   // dirtying while holding the lock was a performance bottleneck. So,
 440   // as a result, it is possible for other threads to actually
 441   // allocate objects in the region (after the acquire the lock)
 442   // before all the cards on the region are dirtied. This is unlikely,
 443   // and it doesn't happen often, but it can happen. So, the extra
 444   // check below filters out those cards.
 445   if (r->is_young()) {
 446     return false;
 447   }
 448 
 449   // While we are processing RSet buffers during the collection, we
 450   // actually don't want to scan any cards on the collection set,
 451   // since we don't want to update remembered sets with entries that
 452   // point into the collection set, given that live objects from the
 453   // collection set are about to move and such entries will be stale
 454   // very soon. This change also deals with a reliability issue which
 455   // involves scanning a card in the collection set and coming across
 456   // an array that was being chunked and looking malformed. Note,
 457   // however, that if evacuation fails, we have to scan any objects
 458   // that were not moved and create any missing entries.
 459   if (r->in_collection_set()) {
 460     return false;
 461   }
 462 
 463   // The result from the hot card cache insert call is either:
 464   //   * pointer to the current card
 465   //     (implying that the current card is not 'hot'),
 466   //   * null
 467   //     (meaning we had inserted the card ptr into the "hot" card cache,
 468   //     which had some headroom),
 469   //   * a pointer to a "hot" card that was evicted from the "hot" cache.
 470   //
 471 
 472   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
 473   if (hot_card_cache->use_cache()) {
 474     assert(!check_for_refs_into_cset, "sanity");
 475     assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
 476 
 477     card_ptr = hot_card_cache->insert(card_ptr);
 478     if (card_ptr == NULL) {
 479       // There was no eviction. Nothing to do.
 480       return false;
 481     }
 482 
 483     start = _ct_bs->addr_for(card_ptr);
 484     r = _g1->heap_region_containing(start);
 485 
 486     // Checking whether the region we got back from the cache
 487     // is young here is inappropriate. The region could have been
 488     // freed, reallocated and tagged as young while in the cache.
 489     // Hence we could see its young type change at any time.
 490   }
 491 
 492   // Don't use addr_for(card_ptr + 1) which can ask for
 493   // a card beyond the heap.  This is not safe without a perm
 494   // gen at the upper end of the heap.
 495   HeapWord* end   = start + CardTableModRefBS::card_size_in_words;
 496   MemRegion dirtyRegion(start, end);
 497 
 498 #if CARD_REPEAT_HISTO
 499   init_ct_freq_table(_g1->max_capacity());
 500   ct_freq_note_card(_ct_bs->index_for(start));
 501 #endif
 502 
 503   G1ParPushHeapRSClosure* oops_in_heap_closure = NULL;
 504   if (check_for_refs_into_cset) {
 505     // ConcurrentG1RefineThreads have worker numbers larger than what
 506     // _cset_rs_update_cl[] is set up to handle. But those threads should
 507     // only be active outside of a collection which means that when they
 508     // reach here they should have check_for_refs_into_cset == false.
 509     assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
 510     oops_in_heap_closure = _cset_rs_update_cl[worker_i];
 511   }
 512   G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
 513                                                  _g1->g1_rem_set(),
 514                                                  oops_in_heap_closure,
 515                                                  check_for_refs_into_cset,
 516                                                  worker_i);
 517   update_rs_oop_cl.set_from(r);
 518 
 519   G1TriggerClosure trigger_cl;
 520   FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
 521   G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
 522   G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
 523 
 524   FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
 525                         (check_for_refs_into_cset ?
 526                                 (OopClosure*)&mux :
 527                                 (OopClosure*)&update_rs_oop_cl));
 528 
 529   // The region for the current card may be a young region. The
 530   // current card may have been a card that was evicted from the
 531   // card cache. When the card was inserted into the cache, we had
 532   // determined that its region was non-young. While in the cache,
 533   // the region may have been freed during a cleanup pause, reallocated
 534   // and tagged as young.
 535   //
 536   // We wish to filter out cards for such a region but the current
 537   // thread, if we're running concurrently, may "see" the young type
 538   // change at any time (so an earlier "is_young" check may pass or
 539   // fail arbitrarily). We tell the iteration code to perform this
 540   // filtering when it has been determined that there has been an actual
 541   // allocation in this region and making it safe to check the young type.
 542   bool filter_young = true;
 543 
 544   HeapWord* stop_point =
 545     r->oops_on_card_seq_iterate_careful(dirtyRegion,
 546                                         &filter_then_update_rs_oop_cl,
 547                                         filter_young,
 548                                         card_ptr);
 549 
 550   // If stop_point is non-null, then we encountered an unallocated region
 551   // (perhaps the unfilled portion of a TLAB.)  For now, we'll dirty the
 552   // card and re-enqueue: if we put off the card until a GC pause, then the
 553   // unallocated portion will be filled in.  Alternatively, we might try
 554   // the full complexity of the technique used in "regular" precleaning.
 555   if (stop_point != NULL) {
 556     // The card might have gotten re-dirtied and re-enqueued while we
 557     // worked.  (In fact, it's pretty likely.)
 558     if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
 559       *card_ptr = CardTableModRefBS::dirty_card_val();
 560       MutexLockerEx x(Shared_DirtyCardQ_lock,
 561                       Mutex::_no_safepoint_check_flag);
 562       DirtyCardQueue* sdcq =
 563         JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
 564       sdcq->enqueue(card_ptr);
 565     }
 566   } else {
 567     _conc_refine_cards++;
 568   }
 569 
 570   // This gets set to true if the card being refined has
 571   // references that point into the collection set.
 572   bool has_refs_into_cset = trigger_cl.triggered();
 573 
 574   // We should only be detecting that the card contains references
 575   // that point into the collection set if the current thread is
 576   // a GC worker thread.
 577   assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
 578            "invalid result at non safepoint");
 579 
 580   return has_refs_into_cset;
 581 }
 582 
 583 void G1RemSet::print_periodic_summary_info(const char* header) {
 584   G1RemSetSummary current;
 585   current.initialize(this);
 586 
 587   _prev_period_summary.subtract_from(&current);
 588   print_summary_info(&_prev_period_summary, header);
 589 
 590   _prev_period_summary.set(&current);
 591 }
 592 
 593 void G1RemSet::print_summary_info() {
 594   G1RemSetSummary current;
 595   current.initialize(this);
 596 
 597   print_summary_info(&current, " Cumulative RS summary");
 598 }
 599 
 600 void G1RemSet::print_summary_info(G1RemSetSummary * summary, const char * header) {
 601   assert(summary != NULL, "just checking");
 602 
 603   if (header != NULL) {
 604     gclog_or_tty->print_cr("%s", header);
 605   }
 606 
 607 #if CARD_REPEAT_HISTO
 608   gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
 609   gclog_or_tty->print_cr("  # of repeats --> # of cards with that number.");
 610   card_repeat_count.print_on(gclog_or_tty);
 611 #endif
 612 
 613   summary->print_on(gclog_or_tty);
 614 }
 615 
 616 void G1RemSet::prepare_for_verify() {
 617   if (G1HRRSFlushLogBuffersOnVerify &&
 618       (VerifyBeforeGC || VerifyAfterGC)
 619       &&  (!_g1->collector_state()->full_collection() || G1VerifyRSetsDuringFullGC)) {
 620     cleanupHRRS();
 621     _g1->set_refine_cte_cl_concurrency(false);
 622     if (SafepointSynchronize::is_at_safepoint()) {
 623       DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 624       dcqs.concatenate_logs();
 625     }
 626 
 627     G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
 628     bool use_hot_card_cache = hot_card_cache->use_cache();
 629     hot_card_cache->set_use_cache(false);
 630 
 631     DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
 632     updateRS(&into_cset_dcq, 0);
 633     _g1->into_cset_dirty_card_queue_set().clear();
 634 
 635     hot_card_cache->set_use_cache(use_hot_card_cache);
 636     assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
 637   }
 638 }
--- EOF ---