1 /*
   2  * Copyright (c) 2001, 2013, 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/bufferingOopClosure.hpp"
  27 #include "gc_implementation/g1/concurrentG1Refine.hpp"
  28 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
  29 #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp"
  30 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  31 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  32 #include "gc_implementation/g1/g1HotCardCache.hpp"
  33 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  34 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  35 #include "gc_implementation/g1/g1RemSet.inline.hpp"
  36 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
  37 #include "memory/iterator.hpp"
  38 #include "oops/oop.inline.hpp"
  39 #include "utilities/intHisto.hpp"
  40 
  41 #define CARD_REPEAT_HISTO 0
  42 
  43 #if CARD_REPEAT_HISTO
  44 static size_t ct_freq_sz;
  45 static jbyte* ct_freq = NULL;
  46 
  47 void init_ct_freq_table(size_t heap_sz_bytes) {
  48   if (ct_freq == NULL) {
  49     ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size;
  50     ct_freq = new jbyte[ct_freq_sz];
  51     for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0;
  52   }
  53 }
  54 
  55 void ct_freq_note_card(size_t index) {
  56   assert(0 <= index && index < ct_freq_sz, "Bounds error.");
  57   if (ct_freq[index] < 100) { ct_freq[index]++; }
  58 }
  59 
  60 static IntHistogram card_repeat_count(10, 10);
  61 
  62 void ct_freq_update_histo_and_reset() {
  63   for (size_t j = 0; j < ct_freq_sz; j++) {
  64     card_repeat_count.add_entry(ct_freq[j]);
  65     ct_freq[j] = 0;
  66   }
  67 
  68 }
  69 #endif
  70 
  71 G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs)
  72   : _g1(g1), _conc_refine_cards(0),
  73     _ct_bs(ct_bs), _g1p(_g1->g1_policy()),
  74     _cg1r(g1->concurrent_g1_refine()),
  75     _cset_rs_update_cl(NULL),
  76     _cards_scanned(NULL), _total_cards_scanned(0)
  77 {
  78   _seq_task = new SubTasksDone(NumSeqTasks);
  79   guarantee(n_workers() > 0, "There should be some workers");
  80   _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers(), mtGC);
  81   for (uint i = 0; i < n_workers(); i++) {
  82     _cset_rs_update_cl[i] = NULL;
  83   }
  84 }
  85 
  86 G1RemSet::~G1RemSet() {
  87   delete _seq_task;
  88   for (uint i = 0; i < n_workers(); i++) {
  89     assert(_cset_rs_update_cl[i] == NULL, "it should be");
  90   }
  91   FREE_C_HEAP_ARRAY(OopsInHeapRegionClosure*, _cset_rs_update_cl, mtGC);
  92 }
  93 
  94 void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) {
  95   if (_g1->is_in_g1_reserved(mr.start())) {
  96     _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size));
  97     if (_start_first == NULL) _start_first = mr.start();
  98   }
  99 }
 100 
 101 class ScanRSClosure : public HeapRegionClosure {
 102   size_t _cards_done, _cards;
 103   G1CollectedHeap* _g1h;
 104   OopsInHeapRegionClosure* _oc;
 105   G1BlockOffsetSharedArray* _bot_shared;
 106   CardTableModRefBS *_ct_bs;
 107   int _worker_i;
 108   int _block_size;
 109   bool _try_claimed;
 110 public:
 111   ScanRSClosure(OopsInHeapRegionClosure* oc, int worker_i) :
 112     _oc(oc),
 113     _cards(0),
 114     _cards_done(0),
 115     _worker_i(worker_i),
 116     _try_claimed(false)
 117   {
 118     _g1h = G1CollectedHeap::heap();
 119     _bot_shared = _g1h->bot_shared();
 120     _ct_bs = (CardTableModRefBS*) (_g1h->barrier_set());
 121     _block_size = MAX2<int>(G1RSetScanBlockSize, 1);
 122   }
 123 
 124   void set_try_claimed() { _try_claimed = true; }
 125 
 126   void scanCard(size_t index, HeapRegion *r) {
 127     // Stack allocate the DirtyCardToOopClosure instance
 128     HeapRegionDCTOC cl(_g1h, r, _oc,
 129                        CardTableModRefBS::Precise,
 130                        HeapRegionDCTOC::IntoCSFilterKind);
 131 
 132     // Set the "from" region in the closure.
 133     _oc->set_region(r);
 134     HeapWord* card_start = _bot_shared->address_for_index(index);
 135     HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words;
 136     Space *sp = SharedHeap::heap()->space_containing(card_start);
 137     MemRegion sm_region = sp->used_region_at_save_marks();
 138     MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end));
 139     if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
 140       // We make the card as "claimed" lazily (so races are possible
 141       // but they're benign), which reduces the number of duplicate
 142       // scans (the rsets of the regions in the cset can intersect).
 143       _ct_bs->set_card_claimed(index);
 144       _cards_done++;
 145       cl.do_MemRegion(mr);
 146     }
 147   }
 148 
 149   void printCard(HeapRegion* card_region, size_t card_index,
 150                  HeapWord* card_start) {
 151     gclog_or_tty->print_cr("T %d Region [" PTR_FORMAT ", " PTR_FORMAT ") "
 152                            "RS names card %p: "
 153                            "[" PTR_FORMAT ", " PTR_FORMAT ")",
 154                            _worker_i,
 155                            card_region->bottom(), card_region->end(),
 156                            card_index,
 157                            card_start, card_start + G1BlockOffsetSharedArray::N_words);
 158   }
 159 
 160   bool doHeapRegion(HeapRegion* r) {
 161     assert(r->in_collection_set(), "should only be called on elements of CS.");
 162     HeapRegionRemSet* hrrs = r->rem_set();
 163     if (hrrs->iter_is_complete()) return false; // All done.
 164     if (!_try_claimed && !hrrs->claim_iter()) return false;
 165     // If we ever free the collection set concurrently, we should also
 166     // clear the card table concurrently therefore we won't need to
 167     // add regions of the collection set to the dirty cards region.
 168     _g1h->push_dirty_cards_region(r);
 169     // If we didn't return above, then
 170     //   _try_claimed || r->claim_iter()
 171     // is true: either we're supposed to work on claimed-but-not-complete
 172     // regions, or we successfully claimed the region.
 173     HeapRegionRemSetIterator* iter = _g1h->rem_set_iterator(_worker_i);
 174     hrrs->init_iterator(iter);
 175     size_t card_index;
 176 
 177     // We claim cards in block so as to recude the contention. The block size is determined by
 178     // the G1RSetScanBlockSize parameter.
 179     size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
 180     for (size_t current_card = 0; iter->has_next(card_index); current_card++) {
 181       if (current_card >= jump_to_card + _block_size) {
 182         jump_to_card = hrrs->iter_claimed_next(_block_size);
 183       }
 184       if (current_card < jump_to_card) continue;
 185       HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
 186 #if 0
 187       gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
 188                           card_start, card_start + CardTableModRefBS::card_size_in_words);
 189 #endif
 190 
 191       HeapRegion* card_region = _g1h->heap_region_containing(card_start);
 192       assert(card_region != NULL, "Yielding cards not in the heap?");
 193       _cards++;
 194 
 195       if (!card_region->is_on_dirty_cards_region_list()) {
 196         _g1h->push_dirty_cards_region(card_region);
 197       }
 198 
 199       // If the card is dirty, then we will scan it during updateRS.
 200       if (!card_region->in_collection_set() &&
 201           !_ct_bs->is_card_dirty(card_index)) {
 202         scanCard(card_index, card_region);
 203       }
 204     }
 205     if (!_try_claimed) {
 206       hrrs->set_iter_complete();
 207     }
 208     return false;
 209   }
 210   size_t cards_done() { return _cards_done;}
 211   size_t cards_looked_up() { return _cards;}
 212 };
 213 
 214 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc, int worker_i) {
 215   double rs_time_start = os::elapsedTime();
 216   HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);
 217 
 218   ScanRSClosure scanRScl(oc, worker_i);
 219 
 220   _g1->collection_set_iterate_from(startRegion, &scanRScl);
 221   scanRScl.set_try_claimed();
 222   _g1->collection_set_iterate_from(startRegion, &scanRScl);
 223 
 224   double scan_rs_time_sec = os::elapsedTime() - rs_time_start;
 225 
 226   assert( _cards_scanned != NULL, "invariant" );
 227   _cards_scanned[worker_i] = scanRScl.cards_done();
 228 
 229   _g1p->phase_times()->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
 230 }
 231 
 232 // Closure used for updating RSets and recording references that
 233 // point into the collection set. Only called during an
 234 // evacuation pause.
 235 
 236 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
 237   G1RemSet* _g1rs;
 238   DirtyCardQueue* _into_cset_dcq;
 239 public:
 240   RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
 241                                               DirtyCardQueue* into_cset_dcq) :
 242     _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
 243   {}
 244   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 245     // The only time we care about recording cards that
 246     // contain references that point into the collection set
 247     // is during RSet updating within an evacuation pause.
 248     // In this case worker_i should be the id of a GC worker thread.
 249     assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
 250     assert(worker_i < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "should be a GC worker");
 251 
 252     if (_g1rs->refine_card(card_ptr, worker_i, true)) {
 253       // 'card_ptr' contains references that point into the collection
 254       // set. We need to record the card in the DCQS
 255       // (G1CollectedHeap::into_cset_dirty_card_queue_set())
 256       // that's used for that purpose.
 257       //
 258       // Enqueue the card
 259       _into_cset_dcq->enqueue(card_ptr);
 260     }
 261     return true;
 262   }
 263 };
 264 
 265 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, int worker_i) {
 266   double start = os::elapsedTime();
 267   // Apply the given closure to all remaining log entries.
 268   RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
 269 
 270   _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
 271 
 272   // Now there should be no dirty cards.
 273   if (G1RSLogCheckCardTable) {
 274     CountNonCleanMemRegionClosure cl(_g1);
 275     _ct_bs->mod_card_iterate(&cl);
 276     // XXX This isn't true any more: keeping cards of young regions
 277     // marked dirty broke it.  Need some reasonable fix.
 278     guarantee(cl.n() == 0, "Card table should be clean.");
 279   }
 280 
 281   _g1p->phase_times()->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
 282 }
 283 
 284 void G1RemSet::cleanupHRRS() {
 285   HeapRegionRemSet::cleanup();
 286 }
 287 
 288 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
 289                                              int worker_i) {
 290 #if CARD_REPEAT_HISTO
 291   ct_freq_update_histo_and_reset();
 292 #endif
 293 
 294   // We cache the value of 'oc' closure into the appropriate slot in the
 295   // _cset_rs_update_cl for this worker
 296   assert(worker_i < (int)n_workers(), "sanity");
 297   _cset_rs_update_cl[worker_i] = oc;
 298 
 299   // A DirtyCardQueue that is used to hold cards containing references
 300   // that point into the collection set. This DCQ is associated with a
 301   // special DirtyCardQueueSet (see g1CollectedHeap.hpp).  Under normal
 302   // circumstances (i.e. the pause successfully completes), these cards
 303   // are just discarded (there's no need to update the RSets of regions
 304   // that were in the collection set - after the pause these regions
 305   // are wholly 'free' of live objects. In the event of an evacuation
 306   // failure the cards/buffers in this queue set are:
 307   // * passed to the DirtyCardQueueSet that is used to manage deferred
 308   //   RSet updates, or
 309   // * scanned for references that point into the collection set
 310   //   and the RSet of the corresponding region in the collection set
 311   //   is updated immediately.
 312   DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
 313 
 314   assert((ParallelGCThreads > 0) || worker_i == 0, "invariant");
 315 
 316   // The two flags below were introduced temporarily to serialize
 317   // the updating and scanning of remembered sets. There are some
 318   // race conditions when these two operations are done in parallel
 319   // and they are causing failures. When we resolve said race
 320   // conditions, we'll revert back to parallel remembered set
 321   // updating and scanning. See CRs 6677707 and 6677708.
 322   if (G1UseParallelRSetUpdating || (worker_i == 0)) {
 323     updateRS(&into_cset_dcq, worker_i);
 324   } else {
 325     _g1p->phase_times()->record_update_rs_processed_buffers(worker_i, 0);
 326     _g1p->phase_times()->record_update_rs_time(worker_i, 0.0);
 327   }
 328   if (G1UseParallelRSetScanning || (worker_i == 0)) {
 329     scanRS(oc, worker_i);
 330   } else {
 331     _g1p->phase_times()->record_scan_rs_time(worker_i, 0.0);
 332   }
 333 
 334   // We now clear the cached values of _cset_rs_update_cl for this worker
 335   _cset_rs_update_cl[worker_i] = NULL;
 336 }
 337 
 338 void G1RemSet::prepare_for_oops_into_collection_set_do() {
 339   cleanupHRRS();
 340   ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();
 341   _g1->set_refine_cte_cl_concurrency(false);
 342   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 343   dcqs.concatenate_logs();
 344 
 345   if (G1CollectedHeap::use_parallel_gc_threads()) {
 346     // Don't set the number of workers here.  It will be set
 347     // when the task is run
 348     // _seq_task->set_n_termination((int)n_workers());
 349   }
 350   guarantee( _cards_scanned == NULL, "invariant" );
 351   _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC);
 352   for (uint i = 0; i < n_workers(); ++i) {
 353     _cards_scanned[i] = 0;
 354   }
 355   _total_cards_scanned = 0;
 356 }
 357 
 358 
 359 // This closure, applied to a DirtyCardQueueSet, is used to immediately
 360 // update the RSets for the regions in the CSet. For each card it iterates
 361 // through the oops which coincide with that card. It scans the reference
 362 // fields in each oop; when it finds an oop that points into the collection
 363 // set, the RSet for the region containing the referenced object is updated.
 364 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure {
 365   G1CollectedHeap* _g1;
 366   CardTableModRefBS* _ct_bs;
 367 public:
 368   UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1,
 369                                           CardTableModRefBS* bs):
 370     _g1(g1), _ct_bs(bs)
 371   { }
 372 
 373   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 374     // Construct the region representing the card.
 375     HeapWord* start = _ct_bs->addr_for(card_ptr);
 376     // And find the region containing it.
 377     HeapRegion* r = _g1->heap_region_containing(start);
 378     assert(r != NULL, "unexpected null");
 379 
 380     // Scan oops in the card looking for references into the collection set
 381     // Don't use addr_for(card_ptr + 1) which can ask for
 382     // a card beyond the heap.  This is not safe without a perm
 383     // gen.
 384     HeapWord* end   = start + CardTableModRefBS::card_size_in_words;
 385     MemRegion scanRegion(start, end);
 386 
 387     UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set());
 388     FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl);
 389     FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl);
 390 
 391     // We can pass false as the "filter_young" parameter here as:
 392     // * we should be in a STW pause,
 393     // * the DCQS to which this closure is applied is used to hold
 394     //   references that point into the collection set from the prior
 395     //   RSet updating,
 396     // * the post-write barrier shouldn't be logging updates to young
 397     //   regions (but there is a situation where this can happen - see
 398     //   the comment in G1RemSet::refine_card() below -
 399     //   that should not be applicable here), and
 400     // * during actual RSet updating, the filtering of cards in young
 401     //   regions in HeapRegion::oops_on_card_seq_iterate_careful is
 402     //   employed.
 403     // As a result, when this closure is applied to "refs into cset"
 404     // DCQS, we shouldn't see any cards in young regions.
 405     update_rs_cl.set_region(r);
 406     HeapWord* stop_point =
 407       r->oops_on_card_seq_iterate_careful(scanRegion,
 408                                           &filter_then_update_rs_cset_oop_cl,
 409                                           false /* filter_young */,
 410                                           NULL  /* card_ptr */);
 411 
 412     // Since this is performed in the event of an evacuation failure, we
 413     // we shouldn't see a non-null stop point
 414     assert(stop_point == NULL, "saw an unallocated region");
 415     return true;
 416   }
 417 };
 418 
 419 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
 420   guarantee( _cards_scanned != NULL, "invariant" );
 421   _total_cards_scanned = 0;
 422   for (uint i = 0; i < n_workers(); ++i) {
 423     _total_cards_scanned += _cards_scanned[i];
 424   }
 425   FREE_C_HEAP_ARRAY(size_t, _cards_scanned, mtGC);
 426   _cards_scanned = NULL;
 427   // Cleanup after copy
 428   _g1->set_refine_cte_cl_concurrency(true);
 429   // Set all cards back to clean.
 430   _g1->cleanUpCardTable();
 431 
 432   DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
 433   int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
 434 
 435   if (_g1->evacuation_failed()) {
 436     // Restore remembered sets for the regions pointing into the collection set.
 437 
 438     if (G1DeferredRSUpdate) {
 439       // If deferred RS updates are enabled then we just need to transfer
 440       // the completed buffers from (a) the DirtyCardQueueSet used to hold
 441       // cards that contain references that point into the collection set
 442       // to (b) the DCQS used to hold the deferred RS updates
 443       _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
 444     } else {
 445 
 446       CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set();
 447       UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs);
 448 
 449       int n_completed_buffers = 0;
 450       while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate,
 451                                                     0, 0, true)) {
 452         n_completed_buffers++;
 453       }
 454       assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers");
 455     }
 456   }
 457 
 458   // Free any completed buffers in the DirtyCardQueueSet used to hold cards
 459   // which contain references that point into the collection.
 460   _g1->into_cset_dirty_card_queue_set().clear();
 461   assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
 462          "all buffers should be freed");
 463   _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
 464 }
 465 
 466 class ScrubRSClosure: public HeapRegionClosure {
 467   G1CollectedHeap* _g1h;
 468   BitMap* _region_bm;
 469   BitMap* _card_bm;
 470   CardTableModRefBS* _ctbs;
 471 public:
 472   ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
 473     _g1h(G1CollectedHeap::heap()),
 474     _region_bm(region_bm), _card_bm(card_bm),
 475     _ctbs(NULL)
 476   {
 477     ModRefBarrierSet* bs = _g1h->mr_bs();
 478     guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition");
 479     _ctbs = (CardTableModRefBS*)bs;
 480   }
 481 
 482   bool doHeapRegion(HeapRegion* r) {
 483     if (!r->continuesHumongous()) {
 484       r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
 485     }
 486     return false;
 487   }
 488 };
 489 
 490 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) {
 491   ScrubRSClosure scrub_cl(region_bm, card_bm);
 492   _g1->heap_region_iterate(&scrub_cl);
 493 }
 494 
 495 void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm,
 496                                 uint worker_num, int claim_val) {
 497   ScrubRSClosure scrub_cl(region_bm, card_bm);
 498   _g1->heap_region_par_iterate_chunked(&scrub_cl,
 499                                        worker_num,
 500                                        n_workers(),
 501                                        claim_val);
 502 }
 503 
 504 G1TriggerClosure::G1TriggerClosure() :
 505   _triggered(false) { }
 506 
 507 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
 508                                                              OopClosure* oop_cl)  :
 509   _trigger_cl(t_cl), _oop_cl(oop_cl) { }
 510 
 511 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
 512   _c1(c1), _c2(c2) { }
 513 
 514 G1UpdateRSOrPushRefOopClosure::
 515 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
 516                               G1RemSet* rs,
 517                               OopsInHeapRegionClosure* push_ref_cl,
 518                               bool record_refs_into_cset,
 519                               int worker_i) :
 520   _g1(g1h), _g1_rem_set(rs), _from(NULL),
 521   _record_refs_into_cset(record_refs_into_cset),
 522   _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
 523 
 524 
 525 bool G1RemSet::refine_card_helper(jbyte* card_ptr, int worker_i,
 526                                   bool check_for_refs_into_cset) {
 527   // Returns true if the given card contains references that point
 528   // into the collection set, if we're checking for such references;
 529   // false otherwise.
 530 
 531   // Construct the region representing the card.
 532   HeapWord* start = _ct_bs->addr_for(card_ptr);
 533   // And find the region containing it.
 534   HeapRegion* r = _g1->heap_region_containing(start);
 535   assert(r != NULL, "unexpected null");
 536 
 537   // Don't use addr_for(card_ptr + 1) which can ask for
 538   // a card beyond the heap.  This is not safe without a perm
 539   // gen at the upper end of the heap.
 540   HeapWord* end   = start + CardTableModRefBS::card_size_in_words;
 541   MemRegion dirtyRegion(start, end);
 542 
 543 #if CARD_REPEAT_HISTO
 544   init_ct_freq_table(_g1->max_capacity());
 545   ct_freq_note_card(_ct_bs->index_for(start));
 546 #endif
 547 
 548   OopsInHeapRegionClosure* oops_in_heap_closure = NULL;
 549   if (check_for_refs_into_cset) {
 550     // ConcurrentG1RefineThreads have worker numbers larger than what
 551     // _cset_rs_update_cl[] is set up to handle. But those threads should
 552     // only be active outside of a collection which means that when they
 553     // reach here they should have check_for_refs_into_cset == false.
 554     assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
 555     oops_in_heap_closure = _cset_rs_update_cl[worker_i];
 556   }
 557   G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
 558                                                  _g1->g1_rem_set(),
 559                                                  oops_in_heap_closure,
 560                                                  check_for_refs_into_cset,
 561                                                  worker_i);
 562   update_rs_oop_cl.set_from(r);
 563 
 564   G1TriggerClosure trigger_cl;
 565   FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
 566   G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
 567   G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
 568 
 569   FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
 570                         (check_for_refs_into_cset ?
 571                                 (OopClosure*)&mux :
 572                                 (OopClosure*)&update_rs_oop_cl));
 573 
 574   // The region for the current card may be a young region. The
 575   // current card may have been a card that was evicted from the
 576   // card cache. When the card was inserted into the cache, we had
 577   // determined that its region was non-young. While in the cache,
 578   // the region may have been freed during a cleanup pause, reallocated
 579   // and tagged as young.
 580   //
 581   // We wish to filter out cards for such a region but the current
 582   // thread, if we're running concurrently, may "see" the young type
 583   // change at any time (so an earlier "is_young" check may pass or
 584   // fail arbitrarily). We tell the iteration code to perform this
 585   // filtering when it has been determined that there has been an actual
 586   // allocation in this region and making it safe to check the young type.
 587   bool filter_young = true;
 588 
 589   HeapWord* stop_point =
 590     r->oops_on_card_seq_iterate_careful(dirtyRegion,
 591                                         &filter_then_update_rs_oop_cl,
 592                                         filter_young,
 593                                         card_ptr);
 594 
 595   // If stop_point is non-null, then we encountered an unallocated region
 596   // (perhaps the unfilled portion of a TLAB.)  For now, we'll dirty the
 597   // card and re-enqueue: if we put off the card until a GC pause, then the
 598   // unallocated portion will be filled in.  Alternatively, we might try
 599   // the full complexity of the technique used in "regular" precleaning.
 600   if (stop_point != NULL) {
 601     // The card might have gotten re-dirtied and re-enqueued while we
 602     // worked.  (In fact, it's pretty likely.)
 603     if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
 604       *card_ptr = CardTableModRefBS::dirty_card_val();
 605       MutexLockerEx x(Shared_DirtyCardQ_lock,
 606                       Mutex::_no_safepoint_check_flag);
 607       DirtyCardQueue* sdcq =
 608         JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
 609       sdcq->enqueue(card_ptr);
 610     }
 611   } else {
 612     _conc_refine_cards++;
 613   }
 614 
 615   return trigger_cl.triggered();
 616 }
 617 
 618 bool G1RemSet::refine_card(jbyte* card_ptr, int worker_i,
 619                            bool check_for_refs_into_cset) {
 620 
 621   // If the card is no longer dirty, nothing to do.
 622   if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
 623     // No need to return that this card contains refs that point
 624     // into the collection set.
 625     return false;
 626   }
 627 
 628   // Construct the region representing the card.
 629   HeapWord* start = _ct_bs->addr_for(card_ptr);
 630   // And find the region containing it.
 631   HeapRegion* r = _g1->heap_region_containing(start);
 632   if (r == NULL) {
 633     // Again no need to return that this card contains refs that
 634     // point into the collection set.
 635     return false;  // Not in the G1 heap (might be in perm, for example.)
 636   }
 637 
 638   // Why do we have to check here whether a card is on a young region,
 639   // given that we dirty young regions and, as a result, the
 640   // post-barrier is supposed to filter them out and never to enqueue
 641   // them? When we allocate a new region as the "allocation region" we
 642   // actually dirty its cards after we release the lock, since card
 643   // dirtying while holding the lock was a performance bottleneck. So,
 644   // as a result, it is possible for other threads to actually
 645   // allocate objects in the region (after the acquire the lock)
 646   // before all the cards on the region are dirtied. This is unlikely,
 647   // and it doesn't happen often, but it can happen. So, the extra
 648   // check below filters out those cards.
 649   if (r->is_young()) {
 650     return false;
 651   }
 652 
 653   // While we are processing RSet buffers during the collection, we
 654   // actually don't want to scan any cards on the collection set,
 655   // since we don't want to update remebered sets with entries that
 656   // point into the collection set, given that live objects from the
 657   // collection set are about to move and such entries will be stale
 658   // very soon. This change also deals with a reliability issue which
 659   // involves scanning a card in the collection set and coming across
 660   // an array that was being chunked and looking malformed. Note,
 661   // however, that if evacuation fails, we have to scan any objects
 662   // that were not moved and create any missing entries.
 663   if (r->in_collection_set()) {
 664     return false;
 665   }
 666 
 667   // The result from the hot card cache insert call is either:
 668   //   * pointer to the current card
 669   //     (implying that the current card is not 'hot'),
 670   //   * null
 671   //     (meaning we had inserted the card ptr into the "hot" card cache,
 672   //     which had some headroom),
 673   //   * a pointer to a "hot" card that was evicted from the "hot" cache.
 674   //
 675 
 676   // This gets set to true if the card being refined has
 677   // references that point into the collection set.
 678   bool has_refs_into_cset = false;
 679 
 680   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
 681   if (hot_card_cache->use_cache()) {
 682     assert(!check_for_refs_into_cset, "sanity");
 683     assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
 684 
 685     card_ptr = hot_card_cache->insert(card_ptr);
 686     if (card_ptr == NULL) {
 687       // There was no eviction. Nothing to do.
 688       return has_refs_into_cset;
 689     }
 690 
 691     start = _ct_bs->addr_for(card_ptr);
 692     r = _g1->heap_region_containing(start);
 693     if (r == NULL) {
 694       // Not in the G1 heap
 695       return has_refs_into_cset;
 696     }
 697 
 698     // Checking whether the region we got back from the cache
 699     // is young here is inappropriate. The region could have been
 700     // freed, reallocated and tagged as young while in the cache.
 701     // Hence we could see its young type change at any time.
 702   }
 703 
 704   has_refs_into_cset = refine_card_helper(card_ptr, worker_i,
 705                                           check_for_refs_into_cset);
 706   // We should only be detecting that the card contains references
 707   // that point into the collection set if the current thread is
 708   // a GC worker thread.
 709   assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
 710            "invalid result at non safepoint");
 711 
 712   return has_refs_into_cset;
 713 }
 714 
 715 class HRRSStatsIter: public HeapRegionClosure {
 716   size_t _occupied;
 717   size_t _total_mem_sz;
 718   size_t _max_mem_sz;
 719   HeapRegion* _max_mem_sz_region;
 720 public:
 721   HRRSStatsIter() :
 722     _occupied(0),
 723     _total_mem_sz(0),
 724     _max_mem_sz(0),
 725     _max_mem_sz_region(NULL)
 726   {}
 727 
 728   bool doHeapRegion(HeapRegion* r) {
 729     if (r->continuesHumongous()) return false;
 730     size_t mem_sz = r->rem_set()->mem_size();
 731     if (mem_sz > _max_mem_sz) {
 732       _max_mem_sz = mem_sz;
 733       _max_mem_sz_region = r;
 734     }
 735     _total_mem_sz += mem_sz;
 736     size_t occ = r->rem_set()->occupied();
 737     _occupied += occ;
 738     return false;
 739   }
 740   size_t total_mem_sz() { return _total_mem_sz; }
 741   size_t max_mem_sz() { return _max_mem_sz; }
 742   size_t occupied() { return _occupied; }
 743   HeapRegion* max_mem_sz_region() { return _max_mem_sz_region; }
 744 };
 745 
 746 class PrintRSThreadVTimeClosure : public ThreadClosure {
 747 public:
 748   virtual void do_thread(Thread *t) {
 749     ConcurrentG1RefineThread* crt = (ConcurrentG1RefineThread*) t;
 750     gclog_or_tty->print("    %5.2f", crt->vtime_accum());
 751   }
 752 };
 753 
 754 void G1RemSet::print_summary_info() {
 755   G1CollectedHeap* g1 = G1CollectedHeap::heap();
 756 
 757 #if CARD_REPEAT_HISTO
 758   gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
 759   gclog_or_tty->print_cr("  # of repeats --> # of cards with that number.");
 760   card_repeat_count.print_on(gclog_or_tty);
 761 #endif
 762 
 763   gclog_or_tty->print_cr("\n Concurrent RS processed %d cards",
 764                          _conc_refine_cards);
 765   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 766   jint tot_processed_buffers =
 767     dcqs.processed_buffers_mut() + dcqs.processed_buffers_rs_thread();
 768   gclog_or_tty->print_cr("  Of %d completed buffers:", tot_processed_buffers);
 769   gclog_or_tty->print_cr("     %8d (%5.1f%%) by conc RS threads.",
 770                 dcqs.processed_buffers_rs_thread(),
 771                 100.0*(float)dcqs.processed_buffers_rs_thread()/
 772                 (float)tot_processed_buffers);
 773   gclog_or_tty->print_cr("     %8d (%5.1f%%) by mutator threads.",
 774                 dcqs.processed_buffers_mut(),
 775                 100.0*(float)dcqs.processed_buffers_mut()/
 776                 (float)tot_processed_buffers);
 777   gclog_or_tty->print_cr("  Conc RS threads times(s)");
 778   PrintRSThreadVTimeClosure p;
 779   gclog_or_tty->print("     ");
 780   g1->concurrent_g1_refine()->threads_do(&p);
 781   gclog_or_tty->print_cr("");
 782 
 783   HRRSStatsIter blk;
 784   g1->heap_region_iterate(&blk);
 785   gclog_or_tty->print_cr("  Total heap region rem set sizes = "SIZE_FORMAT"K."
 786                          "  Max = "SIZE_FORMAT"K.",
 787                          blk.total_mem_sz()/K, blk.max_mem_sz()/K);
 788   gclog_or_tty->print_cr("  Static structures = "SIZE_FORMAT"K,"
 789                          " free_lists = "SIZE_FORMAT"K.",
 790                          HeapRegionRemSet::static_mem_size() / K,
 791                          HeapRegionRemSet::fl_mem_size() / K);
 792   gclog_or_tty->print_cr("    "SIZE_FORMAT" occupied cards represented.",
 793                          blk.occupied());
 794   HeapRegion* max_mem_sz_region = blk.max_mem_sz_region();
 795   HeapRegionRemSet* rem_set = max_mem_sz_region->rem_set();
 796   gclog_or_tty->print_cr("    Max size region = "HR_FORMAT", "
 797                          "size = "SIZE_FORMAT "K, occupied = "SIZE_FORMAT"K.",
 798                          HR_FORMAT_PARAMS(max_mem_sz_region),
 799                          (rem_set->mem_size() + K - 1)/K,
 800                          (rem_set->occupied() + K - 1)/K);
 801   gclog_or_tty->print_cr("    Did %d coarsenings.",
 802                          HeapRegionRemSet::n_coarsenings());
 803 }
 804 
 805 void G1RemSet::prepare_for_verify() {
 806   if (G1HRRSFlushLogBuffersOnVerify &&
 807       (VerifyBeforeGC || VerifyAfterGC)
 808       &&  !_g1->full_collection()) {
 809     cleanupHRRS();
 810     _g1->set_refine_cte_cl_concurrency(false);
 811     if (SafepointSynchronize::is_at_safepoint()) {
 812       DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 813       dcqs.concatenate_logs();
 814     }
 815 
 816     G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
 817     bool use_hot_card_cache = hot_card_cache->use_cache();
 818     hot_card_cache->set_use_cache(false);
 819 
 820     DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
 821     updateRS(&into_cset_dcq, 0);
 822     _g1->into_cset_dirty_card_queue_set().clear();
 823 
 824     hot_card_cache->set_use_cache(use_hot_card_cache);
 825     assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
 826   }
 827 }