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/heapRegionSeq.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   guarantee(n_workers() > 0, "There should be some workers");
  84   _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers(), mtGC);
  85   for (uint i = 0; i < n_workers(); i++) {
  86     _cset_rs_update_cl[i] = NULL;
  87   }
  88   if (G1SummarizeRSetStats) {
  89     _prev_period_summary.initialize(this);
  90   }
  91 }
  92 
  93 G1RemSet::~G1RemSet() {
  94   delete _seq_task;
  95   for (uint i = 0; i < n_workers(); i++) {
  96     assert(_cset_rs_update_cl[i] == NULL, "it should be");
  97   }
  98   FREE_C_HEAP_ARRAY(OopsInHeapRegionClosure*, _cset_rs_update_cl, mtGC);
  99 }
 100 
 101 void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) {
 102   if (_g1->is_in_g1_reserved(mr.start())) {
 103     _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size));
 104     if (_start_first == NULL) _start_first = mr.start();
 105   }
 106 }
 107 
 108 class ScanRSClosure : public HeapRegionClosure {
 109   size_t _cards_done, _cards;
 110   G1CollectedHeap* _g1h;
 111 
 112   OopsInHeapRegionClosure* _oc;
 113   CodeBlobToOopClosure* _code_root_cl;
 114 
 115   G1BlockOffsetSharedArray* _bot_shared;
 116   G1SATBCardTableModRefBS *_ct_bs;
 117 
 118   double _strong_code_root_scan_time_sec;
 119   uint   _worker_i;
 120   int    _block_size;
 121   bool   _try_claimed;
 122 
 123 public:
 124   ScanRSClosure(OopsInHeapRegionClosure* oc,
 125                 CodeBlobToOopClosure* code_root_cl,
 126                 uint worker_i) :
 127     _oc(oc),
 128     _code_root_cl(code_root_cl),
 129     _strong_code_root_scan_time_sec(0.0),
 130     _cards(0),
 131     _cards_done(0),
 132     _worker_i(worker_i),
 133     _try_claimed(false)
 134   {
 135     _g1h = G1CollectedHeap::heap();
 136     _bot_shared = _g1h->bot_shared();
 137     _ct_bs = _g1h->g1_barrier_set();
 138     _block_size = MAX2<int>(G1RSetScanBlockSize, 1);
 139   }
 140 
 141   void set_try_claimed() { _try_claimed = true; }
 142 
 143   void scanCard(size_t index, HeapRegion *r) {
 144     // Stack allocate the DirtyCardToOopClosure instance
 145     HeapRegionDCTOC cl(_g1h, r, _oc,
 146                        CardTableModRefBS::Precise,
 147                        HeapRegionDCTOC::IntoCSFilterKind);
 148 
 149     // Set the "from" region in the closure.
 150     _oc->set_region(r);
 151     HeapWord* card_start = _bot_shared->address_for_index(index);
 152     HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words;
 153     Space *sp = SharedHeap::heap()->space_containing(card_start);
 154     MemRegion sm_region = sp->used_region_at_save_marks();
 155     MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end));
 156     if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
 157       // We make the card as "claimed" lazily (so races are possible
 158       // but they're benign), which reduces the number of duplicate
 159       // scans (the rsets of the regions in the cset can intersect).
 160       _ct_bs->set_card_claimed(index);
 161       _cards_done++;
 162       cl.do_MemRegion(mr);
 163     }
 164   }
 165 
 166   void printCard(HeapRegion* card_region, size_t card_index,
 167                  HeapWord* card_start) {
 168     gclog_or_tty->print_cr("T %u Region [" PTR_FORMAT ", " PTR_FORMAT ") "
 169                            "RS names card " SIZE_FORMAT_HEX ": "
 170                            "[" PTR_FORMAT ", " PTR_FORMAT ")",
 171                            _worker_i,
 172                            card_region->bottom(), card_region->end(),
 173                            card_index,
 174                            card_start, card_start + G1BlockOffsetSharedArray::N_words);
 175   }
 176 
 177   void scan_strong_code_roots(HeapRegion* r) {
 178     double scan_start = os::elapsedTime();
 179     r->strong_code_roots_do(_code_root_cl);
 180     _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
 181   }
 182 
 183   bool doHeapRegion(HeapRegion* r) {
 184     assert(r->in_collection_set(), "should only be called on elements of CS.");
 185     HeapRegionRemSet* hrrs = r->rem_set();
 186     if (hrrs->iter_is_complete()) return false; // All done.
 187     if (!_try_claimed && !hrrs->claim_iter()) return false;
 188     // If we ever free the collection set concurrently, we should also
 189     // clear the card table concurrently therefore we won't need to
 190     // add regions of the collection set to the dirty cards region.
 191     _g1h->push_dirty_cards_region(r);
 192     // If we didn't return above, then
 193     //   _try_claimed || r->claim_iter()
 194     // is true: either we're supposed to work on claimed-but-not-complete
 195     // regions, or we successfully claimed the region.
 196 
 197     HeapRegionRemSetIterator iter(hrrs);
 198     size_t card_index;
 199 
 200     // We claim cards in block so as to reduce the contention. The block size is determined by
 201     // the G1RSetScanBlockSize parameter.
 202     size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
 203     for (size_t current_card = 0; iter.has_next(card_index); current_card++) {
 204       if (current_card >= jump_to_card + _block_size) {
 205         jump_to_card = hrrs->iter_claimed_next(_block_size);
 206       }
 207       if (current_card < jump_to_card) continue;
 208       HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
 209 #if 0
 210       gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
 211                           card_start, card_start + CardTableModRefBS::card_size_in_words);
 212 #endif
 213 
 214       HeapRegion* card_region = _g1h->heap_region_containing(card_start);
 215       _cards++;
 216 
 217       if (!card_region->is_on_dirty_cards_region_list()) {
 218         _g1h->push_dirty_cards_region(card_region);
 219       }
 220 
 221       // If the card is dirty, then we will scan it during updateRS.
 222       if (!card_region->in_collection_set() &&
 223           !_ct_bs->is_card_dirty(card_index)) {
 224         scanCard(card_index, card_region);
 225       }
 226     }
 227     if (!_try_claimed) {
 228       // Scan the strong code root list attached to the current region
 229       scan_strong_code_roots(r);
 230 
 231       hrrs->set_iter_complete();
 232     }
 233     return false;
 234   }
 235 
 236   double strong_code_root_scan_time_sec() {
 237     return _strong_code_root_scan_time_sec;
 238   }
 239 
 240   size_t cards_done() { return _cards_done;}
 241   size_t cards_looked_up() { return _cards;}
 242 };
 243 
 244 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc,
 245                       CodeBlobToOopClosure* code_root_cl,
 246                       uint worker_i) {
 247   double rs_time_start = os::elapsedTime();
 248   HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);
 249 
 250   ScanRSClosure scanRScl(oc, code_root_cl, worker_i);
 251 
 252   _g1->collection_set_iterate_from(startRegion, &scanRScl);
 253   scanRScl.set_try_claimed();
 254   _g1->collection_set_iterate_from(startRegion, &scanRScl);
 255 
 256   double scan_rs_time_sec = (os::elapsedTime() - rs_time_start)
 257                             - scanRScl.strong_code_root_scan_time_sec();
 258 
 259   assert(_cards_scanned != NULL, "invariant");
 260   _cards_scanned[worker_i] = scanRScl.cards_done();
 261 
 262   _g1p->phase_times()->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
 263   _g1p->phase_times()->record_strong_code_root_scan_time(worker_i,
 264                                                          scanRScl.strong_code_root_scan_time_sec() * 1000.0);
 265 }
 266 
 267 // Closure used for updating RSets and recording references that
 268 // point into the collection set. Only called during an
 269 // evacuation pause.
 270 
 271 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
 272   G1RemSet* _g1rs;
 273   DirtyCardQueue* _into_cset_dcq;
 274 public:
 275   RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
 276                                               DirtyCardQueue* into_cset_dcq) :
 277     _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
 278   {}
 279   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 280     // The only time we care about recording cards that
 281     // contain references that point into the collection set
 282     // is during RSet updating within an evacuation pause.
 283     // In this case worker_i should be the id of a GC worker thread.
 284     assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
 285     assert(worker_i < (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "should be a GC worker");
 286 
 287     if (_g1rs->refine_card(card_ptr, worker_i, true)) {
 288       // 'card_ptr' contains references that point into the collection
 289       // set. We need to record the card in the DCQS
 290       // (G1CollectedHeap::into_cset_dirty_card_queue_set())
 291       // that's used for that purpose.
 292       //
 293       // Enqueue the card
 294       _into_cset_dcq->enqueue(card_ptr);
 295     }
 296     return true;
 297   }
 298 };
 299 
 300 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, uint worker_i) {
 301   double start = os::elapsedTime();
 302   // Apply the given closure to all remaining log entries.
 303   RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
 304 
 305   _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
 306 
 307   // Now there should be no dirty cards.
 308   if (G1RSLogCheckCardTable) {
 309     CountNonCleanMemRegionClosure cl(_g1);
 310     _ct_bs->mod_card_iterate(&cl);
 311     // XXX This isn't true any more: keeping cards of young regions
 312     // marked dirty broke it.  Need some reasonable fix.
 313     guarantee(cl.n() == 0, "Card table should be clean.");
 314   }
 315 
 316   _g1p->phase_times()->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
 317 }
 318 
 319 void G1RemSet::cleanupHRRS() {
 320   HeapRegionRemSet::cleanup();
 321 }
 322 
 323 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
 324                                            CodeBlobToOopClosure* code_root_cl,
 325                                            uint worker_i) {
 326 #if CARD_REPEAT_HISTO
 327   ct_freq_update_histo_and_reset();
 328 #endif
 329 
 330   // We cache the value of 'oc' closure into the appropriate slot in the
 331   // _cset_rs_update_cl for this worker
 332   assert(worker_i < n_workers(), "sanity");
 333   _cset_rs_update_cl[worker_i] = oc;
 334 
 335   // A DirtyCardQueue that is used to hold cards containing references
 336   // that point into the collection set. This DCQ is associated with a
 337   // special DirtyCardQueueSet (see g1CollectedHeap.hpp).  Under normal
 338   // circumstances (i.e. the pause successfully completes), these cards
 339   // are just discarded (there's no need to update the RSets of regions
 340   // that were in the collection set - after the pause these regions
 341   // are wholly 'free' of live objects. In the event of an evacuation
 342   // failure the cards/buffers in this queue set are:
 343   // * passed to the DirtyCardQueueSet that is used to manage deferred
 344   //   RSet updates, or
 345   // * scanned for references that point into the collection set
 346   //   and the RSet of the corresponding region in the collection set
 347   //   is updated immediately.
 348   DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
 349 
 350   assert((ParallelGCThreads > 0) || worker_i == 0, "invariant");
 351 
 352   updateRS(&into_cset_dcq, worker_i);
 353   scanRS(oc, code_root_cl, worker_i);
 354 
 355   // We now clear the cached values of _cset_rs_update_cl for this worker
 356   _cset_rs_update_cl[worker_i] = NULL;
 357 }
 358 
 359 void G1RemSet::prepare_for_oops_into_collection_set_do() {
 360   cleanupHRRS();
 361   ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();
 362   _g1->set_refine_cte_cl_concurrency(false);
 363   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 364   dcqs.concatenate_logs();
 365 
 366   guarantee( _cards_scanned == NULL, "invariant" );
 367   _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC);
 368   for (uint i = 0; i < n_workers(); ++i) {
 369     _cards_scanned[i] = 0;
 370   }
 371   _total_cards_scanned = 0;
 372 }
 373 
 374 
 375 // This closure, applied to a DirtyCardQueueSet, is used to immediately
 376 // update the RSets for the regions in the CSet. For each card it iterates
 377 // through the oops which coincide with that card. It scans the reference
 378 // fields in each oop; when it finds an oop that points into the collection
 379 // set, the RSet for the region containing the referenced object is updated.
 380 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure {
 381   G1CollectedHeap* _g1;
 382   CardTableModRefBS* _ct_bs;
 383 public:
 384   UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1,
 385                                           CardTableModRefBS* bs):
 386     _g1(g1), _ct_bs(bs)
 387   { }
 388 
 389   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 390     // Construct the region representing the card.
 391     HeapWord* start = _ct_bs->addr_for(card_ptr);
 392     // And find the region containing it.
 393     HeapRegion* r = _g1->heap_region_containing(start);
 394 
 395     // Scan oops in the card looking for references into the collection set
 396     // Don't use addr_for(card_ptr + 1) which can ask for
 397     // a card beyond the heap.  This is not safe without a perm
 398     // gen.
 399     HeapWord* end   = start + CardTableModRefBS::card_size_in_words;
 400     MemRegion scanRegion(start, end);
 401 
 402     UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set());
 403     FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl);
 404     FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl);
 405 
 406     // We can pass false as the "filter_young" parameter here as:
 407     // * we should be in a STW pause,
 408     // * the DCQS to which this closure is applied is used to hold
 409     //   references that point into the collection set from the prior
 410     //   RSet updating,
 411     // * the post-write barrier shouldn't be logging updates to young
 412     //   regions (but there is a situation where this can happen - see
 413     //   the comment in G1RemSet::refine_card() below -
 414     //   that should not be applicable here), and
 415     // * during actual RSet updating, the filtering of cards in young
 416     //   regions in HeapRegion::oops_on_card_seq_iterate_careful is
 417     //   employed.
 418     // As a result, when this closure is applied to "refs into cset"
 419     // DCQS, we shouldn't see any cards in young regions.
 420     update_rs_cl.set_region(r);
 421     HeapWord* stop_point =
 422       r->oops_on_card_seq_iterate_careful(scanRegion,
 423                                           &filter_then_update_rs_cset_oop_cl,
 424                                           false /* filter_young */,
 425                                           NULL  /* card_ptr */);
 426 
 427     // Since this is performed in the event of an evacuation failure, we
 428     // we shouldn't see a non-null stop point
 429     assert(stop_point == NULL, "saw an unallocated region");
 430     return true;
 431   }
 432 };
 433 
 434 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
 435   guarantee( _cards_scanned != NULL, "invariant" );
 436   _total_cards_scanned = 0;
 437   for (uint i = 0; i < n_workers(); ++i) {
 438     _total_cards_scanned += _cards_scanned[i];
 439   }
 440   FREE_C_HEAP_ARRAY(size_t, _cards_scanned, mtGC);
 441   _cards_scanned = NULL;
 442   // Cleanup after copy
 443   _g1->set_refine_cte_cl_concurrency(true);
 444   // Set all cards back to clean.
 445   _g1->cleanUpCardTable();
 446 
 447   DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
 448   int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
 449 
 450   if (_g1->evacuation_failed()) {
 451     double restore_remembered_set_start = os::elapsedTime();
 452 
 453     // Restore remembered sets for the regions pointing into the collection set.
 454     if (G1DeferredRSUpdate) {
 455       // If deferred RS updates are enabled then we just need to transfer
 456       // the completed buffers from (a) the DirtyCardQueueSet used to hold
 457       // cards that contain references that point into the collection set
 458       // to (b) the DCQS used to hold the deferred RS updates
 459       _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
 460     } else {
 461 
 462       CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set();
 463       UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs);
 464 
 465       int n_completed_buffers = 0;
 466       while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate,
 467                                                     0, 0, true)) {
 468         n_completed_buffers++;
 469       }
 470       assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers");
 471     }
 472 
 473     _g1->g1_policy()->phase_times()->record_evac_fail_restore_remsets((os::elapsedTime() - restore_remembered_set_start) * 1000.0);
 474   }
 475 
 476   // Free any completed buffers in the DirtyCardQueueSet used to hold cards
 477   // which contain references that point into the collection.
 478   _g1->into_cset_dirty_card_queue_set().clear();
 479   assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
 480          "all buffers should be freed");
 481   _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
 482 }
 483 
 484 class ScrubRSClosure: public HeapRegionClosure {
 485   G1CollectedHeap* _g1h;
 486   BitMap* _region_bm;
 487   BitMap* _card_bm;
 488   CardTableModRefBS* _ctbs;
 489 public:
 490   ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
 491     _g1h(G1CollectedHeap::heap()),
 492     _region_bm(region_bm), _card_bm(card_bm),
 493     _ctbs(_g1h->g1_barrier_set()) {}
 494 
 495   bool doHeapRegion(HeapRegion* r) {
 496     if (!r->continuesHumongous()) {
 497       r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
 498     }
 499     return false;
 500   }
 501 };
 502 
 503 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) {
 504   ScrubRSClosure scrub_cl(region_bm, card_bm);
 505   _g1->heap_region_iterate(&scrub_cl);
 506 }
 507 
 508 void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm,
 509                                 uint worker_num, int claim_val) {
 510   ScrubRSClosure scrub_cl(region_bm, card_bm);
 511   _g1->heap_region_par_iterate_chunked(&scrub_cl,
 512                                        worker_num,
 513                                        n_workers(),
 514                                        claim_val);
 515 }
 516 
 517 G1TriggerClosure::G1TriggerClosure() :
 518   _triggered(false) { }
 519 
 520 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
 521                                                              OopClosure* oop_cl)  :
 522   _trigger_cl(t_cl), _oop_cl(oop_cl) { }
 523 
 524 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
 525   _c1(c1), _c2(c2) { }
 526 
 527 G1UpdateRSOrPushRefOopClosure::
 528 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
 529                               G1RemSet* rs,
 530                               OopsInHeapRegionClosure* push_ref_cl,
 531                               bool record_refs_into_cset,
 532                               uint worker_i) :
 533   _g1(g1h), _g1_rem_set(rs), _from(NULL),
 534   _record_refs_into_cset(record_refs_into_cset),
 535   _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
 536 
 537 // Returns true if the given card contains references that point
 538 // into the collection set, if we're checking for such references;
 539 // false otherwise.
 540 
 541 bool G1RemSet::refine_card(jbyte* card_ptr, uint worker_i,
 542                            bool check_for_refs_into_cset) {
 543   assert(_g1->is_in_exact(_ct_bs->addr_for(card_ptr)),
 544          err_msg("Card at "PTR_FORMAT" index "SIZE_FORMAT" representing heap at "PTR_FORMAT" (%u) must be in committed heap",
 545                  p2i(card_ptr),
 546                  _ct_bs->index_for(_ct_bs->addr_for(card_ptr)),
 547                  _ct_bs->addr_for(card_ptr),
 548                  _g1->addr_to_region(_ct_bs->addr_for(card_ptr))));
 549 
 550   // If the card is no longer dirty, nothing to do.
 551   if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
 552     // No need to return that this card contains refs that point
 553     // into the collection set.
 554     return false;
 555   }
 556 
 557   // Construct the region representing the card.
 558   HeapWord* start = _ct_bs->addr_for(card_ptr);
 559   // And find the region containing it.
 560   HeapRegion* r = _g1->heap_region_containing(start);
 561 
 562   // Why do we have to check here whether a card is on a young region,
 563   // given that we dirty young regions and, as a result, the
 564   // post-barrier is supposed to filter them out and never to enqueue
 565   // them? When we allocate a new region as the "allocation region" we
 566   // actually dirty its cards after we release the lock, since card
 567   // dirtying while holding the lock was a performance bottleneck. So,
 568   // as a result, it is possible for other threads to actually
 569   // allocate objects in the region (after the acquire the lock)
 570   // before all the cards on the region are dirtied. This is unlikely,
 571   // and it doesn't happen often, but it can happen. So, the extra
 572   // check below filters out those cards.
 573   if (r->is_young()) {
 574     return false;
 575   }
 576 
 577   // While we are processing RSet buffers during the collection, we
 578   // actually don't want to scan any cards on the collection set,
 579   // since we don't want to update remembered sets with entries that
 580   // point into the collection set, given that live objects from the
 581   // collection set are about to move and such entries will be stale
 582   // very soon. This change also deals with a reliability issue which
 583   // involves scanning a card in the collection set and coming across
 584   // an array that was being chunked and looking malformed. Note,
 585   // however, that if evacuation fails, we have to scan any objects
 586   // that were not moved and create any missing entries.
 587   if (r->in_collection_set()) {
 588     return false;
 589   }
 590 
 591   // The result from the hot card cache insert call is either:
 592   //   * pointer to the current card
 593   //     (implying that the current card is not 'hot'),
 594   //   * null
 595   //     (meaning we had inserted the card ptr into the "hot" card cache,
 596   //     which had some headroom),
 597   //   * a pointer to a "hot" card that was evicted from the "hot" cache.
 598   //
 599 
 600   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
 601   if (hot_card_cache->use_cache()) {
 602     assert(!check_for_refs_into_cset, "sanity");
 603     assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
 604 
 605     card_ptr = hot_card_cache->insert(card_ptr);
 606     if (card_ptr == NULL) {
 607       // There was no eviction. Nothing to do.
 608       return false;
 609     }
 610 
 611     start = _ct_bs->addr_for(card_ptr);
 612     r = _g1->heap_region_containing(start);
 613 
 614     // Checking whether the region we got back from the cache
 615     // is young here is inappropriate. The region could have been
 616     // freed, reallocated and tagged as young while in the cache.
 617     // Hence we could see its young type change at any time.
 618   }
 619 
 620   // Don't use addr_for(card_ptr + 1) which can ask for
 621   // a card beyond the heap.  This is not safe without a perm
 622   // gen at the upper end of the heap.
 623   HeapWord* end   = start + CardTableModRefBS::card_size_in_words;
 624   MemRegion dirtyRegion(start, end);
 625 
 626 #if CARD_REPEAT_HISTO
 627   init_ct_freq_table(_g1->max_capacity());
 628   ct_freq_note_card(_ct_bs->index_for(start));
 629 #endif
 630 
 631   OopsInHeapRegionClosure* oops_in_heap_closure = NULL;
 632   if (check_for_refs_into_cset) {
 633     // ConcurrentG1RefineThreads have worker numbers larger than what
 634     // _cset_rs_update_cl[] is set up to handle. But those threads should
 635     // only be active outside of a collection which means that when they
 636     // reach here they should have check_for_refs_into_cset == false.
 637     assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
 638     oops_in_heap_closure = _cset_rs_update_cl[worker_i];
 639   }
 640   G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
 641                                                  _g1->g1_rem_set(),
 642                                                  oops_in_heap_closure,
 643                                                  check_for_refs_into_cset,
 644                                                  worker_i);
 645   update_rs_oop_cl.set_from(r);
 646 
 647   G1TriggerClosure trigger_cl;
 648   FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
 649   G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
 650   G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
 651 
 652   FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
 653                         (check_for_refs_into_cset ?
 654                                 (OopClosure*)&mux :
 655                                 (OopClosure*)&update_rs_oop_cl));
 656 
 657   // The region for the current card may be a young region. The
 658   // current card may have been a card that was evicted from the
 659   // card cache. When the card was inserted into the cache, we had
 660   // determined that its region was non-young. While in the cache,
 661   // the region may have been freed during a cleanup pause, reallocated
 662   // and tagged as young.
 663   //
 664   // We wish to filter out cards for such a region but the current
 665   // thread, if we're running concurrently, may "see" the young type
 666   // change at any time (so an earlier "is_young" check may pass or
 667   // fail arbitrarily). We tell the iteration code to perform this
 668   // filtering when it has been determined that there has been an actual
 669   // allocation in this region and making it safe to check the young type.
 670   bool filter_young = true;
 671 
 672   HeapWord* stop_point =
 673     r->oops_on_card_seq_iterate_careful(dirtyRegion,
 674                                         &filter_then_update_rs_oop_cl,
 675                                         filter_young,
 676                                         card_ptr);
 677 
 678   // If stop_point is non-null, then we encountered an unallocated region
 679   // (perhaps the unfilled portion of a TLAB.)  For now, we'll dirty the
 680   // card and re-enqueue: if we put off the card until a GC pause, then the
 681   // unallocated portion will be filled in.  Alternatively, we might try
 682   // the full complexity of the technique used in "regular" precleaning.
 683   if (stop_point != NULL) {
 684     // The card might have gotten re-dirtied and re-enqueued while we
 685     // worked.  (In fact, it's pretty likely.)
 686     if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
 687       *card_ptr = CardTableModRefBS::dirty_card_val();
 688       MutexLockerEx x(Shared_DirtyCardQ_lock,
 689                       Mutex::_no_safepoint_check_flag);
 690       DirtyCardQueue* sdcq =
 691         JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
 692       sdcq->enqueue(card_ptr);
 693     }
 694   } else {
 695     _conc_refine_cards++;
 696   }
 697 
 698   // This gets set to true if the card being refined has
 699   // references that point into the collection set.
 700   bool has_refs_into_cset = trigger_cl.triggered();
 701 
 702   // We should only be detecting that the card contains references
 703   // that point into the collection set if the current thread is
 704   // a GC worker thread.
 705   assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
 706            "invalid result at non safepoint");
 707 
 708   return has_refs_into_cset;
 709 }
 710 
 711 void G1RemSet::print_periodic_summary_info(const char* header) {
 712   G1RemSetSummary current;
 713   current.initialize(this);
 714 
 715   _prev_period_summary.subtract_from(&current);
 716   print_summary_info(&_prev_period_summary, header);
 717 
 718   _prev_period_summary.set(&current);
 719 }
 720 
 721 void G1RemSet::print_summary_info() {
 722   G1RemSetSummary current;
 723   current.initialize(this);
 724 
 725   print_summary_info(&current, " Cumulative RS summary");
 726 }
 727 
 728 void G1RemSet::print_summary_info(G1RemSetSummary * summary, const char * header) {
 729   assert(summary != NULL, "just checking");
 730 
 731   if (header != NULL) {
 732     gclog_or_tty->print_cr("%s", header);
 733   }
 734 
 735 #if CARD_REPEAT_HISTO
 736   gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
 737   gclog_or_tty->print_cr("  # of repeats --> # of cards with that number.");
 738   card_repeat_count.print_on(gclog_or_tty);
 739 #endif
 740 
 741   summary->print_on(gclog_or_tty);
 742 }
 743 
 744 void G1RemSet::prepare_for_verify() {
 745   if (G1HRRSFlushLogBuffersOnVerify &&
 746       (VerifyBeforeGC || VerifyAfterGC)
 747       &&  (!_g1->full_collection() || G1VerifyRSetsDuringFullGC)) {
 748     cleanupHRRS();
 749     _g1->set_refine_cte_cl_concurrency(false);
 750     if (SafepointSynchronize::is_at_safepoint()) {
 751       DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 752       dcqs.concatenate_logs();
 753     }
 754 
 755     G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
 756     bool use_hot_card_cache = hot_card_cache->use_cache();
 757     hot_card_cache->set_use_cache(false);
 758 
 759     DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
 760     updateRS(&into_cset_dcq, 0);
 761     _g1->into_cset_dirty_card_queue_set().clear();
 762 
 763     hot_card_cache->set_use_cache(use_hot_card_cache);
 764     assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
 765   }
 766 }