Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright 2001-2009 Sun Microsystems, Inc.  All Rights Reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

  * CA 95054 USA or visit www.sun.com if you need additional information or

  * have any questions.

  *

  */

 #include "incls/_precompiled.incl"

 #include "incls/_g1RemSet.cpp.incl"

 #define CARD_REPEAT_HISTO 0

 #if CARD_REPEAT_HISTO

 static size_t ct_freq_sz;

 static jbyte* ct_freq = NULL;

 void init_ct_freq_table(size_t heap_sz_bytes) {

   if (ct_freq == NULL) {

     ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size;

     ct_freq = new jbyte[ct_freq_sz];

     for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0;

   }

 }

 void ct_freq_note_card(size_t index) {

   assert(0 <= index && index < ct_freq_sz, "Bounds error.");

   if (ct_freq[index] < 100) { ct_freq[index]++; }

 }

 static IntHistogram card_repeat_count(10, 10);

 void ct_freq_update_histo_and_reset() {

   for (size_t j = 0; j < ct_freq_sz; j++) {

     card_repeat_count.add_entry(ct_freq[j]);

     ct_freq[j] = 0;

   }

 }

 #endif

 class IntoCSOopClosure: public OopsInHeapRegionClosure {

   OopsInHeapRegionClosure* _blk;

   G1CollectedHeap* _g1;

 public:

   IntoCSOopClosure(G1CollectedHeap* g1, OopsInHeapRegionClosure* blk) :

     _g1(g1), _blk(blk) {}

   void set_region(HeapRegion* from) {

     _blk->set_region(from);

   }

   virtual void do_oop(narrowOop* p) { do_oop_work(p); }

   virtual void do_oop(      oop* p) { do_oop_work(p); }

   template <class T> void do_oop_work(T* p) {

     oop obj = oopDesc::load_decode_heap_oop(p);

     if (_g1->obj_in_cs(obj)) _blk->do_oop(p);

   }

   bool apply_to_weak_ref_discovered_field() { return true; }

   bool idempotent() { return true; }

 };

 class IntoCSRegionClosure: public HeapRegionClosure {

   IntoCSOopClosure _blk;

   G1CollectedHeap* _g1;

 public:

   IntoCSRegionClosure(G1CollectedHeap* g1, OopsInHeapRegionClosure* blk) :

     _g1(g1), _blk(g1, blk) {}

   bool doHeapRegion(HeapRegion* r) {

     if (!r->in_collection_set()) {

       _blk.set_region(r);

       if (r->isHumongous()) {

         if (r->startsHumongous()) {

           oop obj = oop(r->bottom());

           obj->oop_iterate(&_blk);

         }

       } else {

         r->oop_before_save_marks_iterate(&_blk);

       }

     }

     return false;

   }

 };

 void

 StupidG1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,

                                             int worker_i) {

   IntoCSRegionClosure rc(_g1, oc);

   _g1->heap_region_iterate(&rc);

 }

 class VerifyRSCleanCardOopClosure: public OopClosure {

   G1CollectedHeap* _g1;

 public:

   VerifyRSCleanCardOopClosure(G1CollectedHeap* g1) : _g1(g1) {}

   virtual void do_oop(narrowOop* p) { do_oop_work(p); }

   virtual void do_oop(      oop* p) { do_oop_work(p); }

   template <class T> void do_oop_work(T* p) {

     oop obj = oopDesc::load_decode_heap_oop(p);

     HeapRegion* to = _g1->heap_region_containing(obj);

     guarantee(to == NULL || !to->in_collection_set(),

               "Missed a rem set member.");

   }

 };

 HRInto_G1RemSet::HRInto_G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs)

   : G1RemSet(g1), _ct_bs(ct_bs), _g1p(_g1->g1_policy()),

     _cg1r(g1->concurrent_g1_refine()),

     _par_traversal_in_progress(false), _new_refs(NULL),

     _cards_scanned(NULL), _total_cards_scanned(0)

 {

   _seq_task = new SubTasksDone(NumSeqTasks);

   guarantee(n_workers() > 0, "There should be some workers");

   _new_refs = NEW_C_HEAP_ARRAY(GrowableArray<OopOrNarrowOopStar>*, n_workers());

   for (uint i = 0; i < n_workers(); i++) {

     _new_refs[i] = new (ResourceObj::C_HEAP) GrowableArray<OopOrNarrowOopStar>(8192,true);

   }

 }

 HRInto_G1RemSet::~HRInto_G1RemSet() {

   delete _seq_task;

   for (uint i = 0; i < n_workers(); i++) {

     delete _new_refs[i];

   }

   FREE_C_HEAP_ARRAY(GrowableArray<OopOrNarrowOopStar>*, _new_refs);

 }

 void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) {

   if (_g1->is_in_g1_reserved(mr.start())) {

     _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size));

     if (_start_first == NULL) _start_first = mr.start();

   }

 }

 class ScanRSClosure : public HeapRegionClosure {

   size_t _cards_done, _cards;

   G1CollectedHeap* _g1h;

   OopsInHeapRegionClosure* _oc;

   G1BlockOffsetSharedArray* _bot_shared;

   CardTableModRefBS *_ct_bs;

   int _worker_i;

   bool _try_claimed;

   size_t _min_skip_distance, _max_skip_distance;

 public:

   ScanRSClosure(OopsInHeapRegionClosure* oc, int worker_i) :

     _oc(oc),

     _cards(0),

     _cards_done(0),

     _worker_i(worker_i),

     _try_claimed(false)

   {

     _g1h = G1CollectedHeap::heap();

     _bot_shared = _g1h->bot_shared();

     _ct_bs = (CardTableModRefBS*) (_g1h->barrier_set());

     _min_skip_distance = 16;

     _max_skip_distance = 2 * _g1h->n_par_threads() * _min_skip_distance;

   }

   void set_try_claimed() { _try_claimed = true; }

   void scanCard(size_t index, HeapRegion *r) {

     _cards_done++;

     DirtyCardToOopClosure* cl =

       r->new_dcto_closure(_oc,

                          CardTableModRefBS::Precise,

                          HeapRegionDCTOC::IntoCSFilterKind);

     // Set the "from" region in the closure.

     _oc->set_region(r);

     HeapWord* card_start = _bot_shared->address_for_index(index);

     HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words;

     Space *sp = SharedHeap::heap()->space_containing(card_start);

     MemRegion sm_region;

     if (ParallelGCThreads > 0) {

       // first find the used area

       sm_region = sp->used_region_at_save_marks();

     } else {

       // The closure is not idempotent.  We shouldn't look at objects

       // allocated during the GC.

       sm_region = sp->used_region_at_save_marks();

     }

     MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end));

     if (!mr.is_empty()) {

       cl->do_MemRegion(mr);

     }

   }

   void printCard(HeapRegion* card_region, size_t card_index,

                  HeapWord* card_start) {

     gclog_or_tty->print_cr("T %d Region [" PTR_FORMAT ", " PTR_FORMAT ") "

                            "RS names card %p: "

                            "[" PTR_FORMAT ", " PTR_FORMAT ")",

                            _worker_i,

                            card_region->bottom(), card_region->end(),

                            card_index,

                            card_start, card_start + G1BlockOffsetSharedArray::N_words);

   }

   bool doHeapRegion(HeapRegion* r) {

     assert(r->in_collection_set(), "should only be called on elements of CS.");

     HeapRegionRemSet* hrrs = r->rem_set();

     if (hrrs->iter_is_complete()) return false; // All done.

     if (!_try_claimed && !hrrs->claim_iter()) return false;

     _g1h->push_dirty_cards_region(r);

     // If we didn't return above, then

     //   _try_claimed || r->claim_iter()

     // is true: either we're supposed to work on claimed-but-not-complete

     // regions, or we successfully claimed the region.

     HeapRegionRemSetIterator* iter = _g1h->rem_set_iterator(_worker_i);

     hrrs->init_iterator(iter);

     size_t card_index;

     size_t skip_distance = 0, current_card = 0, jump_to_card = 0;

     while (iter->has_next(card_index)) {

       if (current_card < jump_to_card) {

         ++current_card;

         continue;

       }

       HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);

 #if 0

       gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",

                           card_start, card_start + CardTableModRefBS::card_size_in_words);

 #endif

       HeapRegion* card_region = _g1h->heap_region_containing(card_start);

       assert(card_region != NULL, "Yielding cards not in the heap?");

       _cards++;

       if (!card_region->is_on_dirty_cards_region_list()) {

         _g1h->push_dirty_cards_region(card_region);

       }

        // If the card is dirty, then we will scan it during updateRS.

       if (!card_region->in_collection_set() && !_ct_bs->is_card_dirty(card_index)) {

           if (!_ct_bs->is_card_claimed(card_index) && _ct_bs->claim_card(card_index)) {

             scanCard(card_index, card_region);

           } else if (_try_claimed) {

             if (jump_to_card == 0 || jump_to_card != current_card) {

               // We did some useful work in the previous iteration.

               // Decrease the distance.

               skip_distance = MAX2(skip_distance >> 1, _min_skip_distance);

             } else {

               // Previous iteration resulted in a claim failure.

               // Increase the distance.

               skip_distance = MIN2(skip_distance << 1, _max_skip_distance);

             }

             jump_to_card = current_card + skip_distance;

           }

       }

       ++current_card;

     }

     if (!_try_claimed) {

       hrrs->set_iter_complete();

     }

     return false;

   }

   // Set all cards back to clean.

   void cleanup() {_g1h->cleanUpCardTable();}

   size_t cards_done() { return _cards_done;}

   size_t cards_looked_up() { return _cards;}

 };

 // We want the parallel threads to start their scanning at

 // different collection set regions to avoid contention.

 // If we have:

 //          n collection set regions

 //          p threads

 // Then thread t will start at region t * floor (n/p)

 HeapRegion* HRInto_G1RemSet::calculateStartRegion(int worker_i) {

   HeapRegion* result = _g1p->collection_set();

   if (ParallelGCThreads > 0) {

     size_t cs_size = _g1p->collection_set_size();

     int n_workers = _g1->workers()->total_workers();

     size_t cs_spans = cs_size / n_workers;

     size_t ind      = cs_spans * worker_i;

     for (size_t i = 0; i < ind; i++)

       result = result->next_in_collection_set();

   }

   return result;

 }

 void HRInto_G1RemSet::scanRS(OopsInHeapRegionClosure* oc, int worker_i) {

   double rs_time_start = os::elapsedTime();

   HeapRegion *startRegion = calculateStartRegion(worker_i);

   BufferingOopsInHeapRegionClosure boc(oc);

   ScanRSClosure scanRScl(&boc, worker_i);

   _g1->collection_set_iterate_from(startRegion, &scanRScl);

   scanRScl.set_try_claimed();

   _g1->collection_set_iterate_from(startRegion, &scanRScl);

   boc.done();

   double closure_app_time_sec = boc.closure_app_seconds();

   double scan_rs_time_sec = (os::elapsedTime() - rs_time_start) -

     closure_app_time_sec;

   double closure_app_time_ms = closure_app_time_sec * 1000.0;

   assert( _cards_scanned != NULL, "invariant" );

   _cards_scanned[worker_i] = scanRScl.cards_done();

   _g1p->record_scan_rs_start_time(worker_i, rs_time_start * 1000.0);

   _g1p->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);

   double scan_new_refs_time_ms = _g1p->get_scan_new_refs_time(worker_i);

   if (scan_new_refs_time_ms > 0.0) {

     closure_app_time_ms += scan_new_refs_time_ms;

   }

   _g1p->record_obj_copy_time(worker_i, closure_app_time_ms);

 }

 void HRInto_G1RemSet::updateRS(int worker_i) {

   ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();

   double start = os::elapsedTime();

   _g1p->record_update_rs_start_time(worker_i, start * 1000.0);

   // Apply the appropriate closure to all remaining log entries.

   _g1->iterate_dirty_card_closure(false, worker_i);

   // Now there should be no dirty cards.

   if (G1RSLogCheckCardTable) {

     CountNonCleanMemRegionClosure cl(_g1);

     _ct_bs->mod_card_iterate(&cl);

     // XXX This isn't true any more: keeping cards of young regions

     // marked dirty broke it.  Need some reasonable fix.

     guarantee(cl.n() == 0, "Card table should be clean.");

   }

   _g1p->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);

 }

 #ifndef PRODUCT

 class PrintRSClosure : public HeapRegionClosure {

   int _count;

 public:

   PrintRSClosure() : _count(0) {}

   bool doHeapRegion(HeapRegion* r) {

     HeapRegionRemSet* hrrs = r->rem_set();

     _count += (int) hrrs->occupied();

     if (hrrs->occupied() == 0) {

       gclog_or_tty->print("Heap Region [" PTR_FORMAT ", " PTR_FORMAT ") "

                           "has no remset entries\n",

                           r->bottom(), r->end());

     } else {

       gclog_or_tty->print("Printing rem set for heap region [" PTR_FORMAT ", " PTR_FORMAT ")\n",

                           r->bottom(), r->end());

       r->print();

       hrrs->print();

       gclog_or_tty->print("\nDone printing rem set\n");

     }

     return false;

   }

   int occupied() {return _count;}

 };

 #endif

 class CountRSSizeClosure: public HeapRegionClosure {

   size_t _n;

   size_t _tot;

   size_t _max;

   HeapRegion* _max_r;

   enum {

     N = 20,

     MIN = 6

   };

   int _histo[N];

 public:

   CountRSSizeClosure() : _n(0), _tot(0), _max(0), _max_r(NULL) {

     for (int i = 0; i < N; i++) _histo[i] = 0;

   }

   bool doHeapRegion(HeapRegion* r) {

     if (!r->continuesHumongous()) {

       size_t occ = r->rem_set()->occupied();

       _n++;

       _tot += occ;

       if (occ > _max) {

         _max = occ;

         _max_r = r;

       }

       // Fit it into a histo bin.

       int s = 1 << MIN;

       int i = 0;

       while (occ > (size_t) s && i < (N-1)) {

         s = s << 1;

         i++;

       }

       _histo[i]++;

     }

     return false;

   }

   size_t n() { return _n; }

   size_t tot() { return _tot; }

   size_t mx() { return _max; }

   HeapRegion* mxr() { return _max_r; }

   void print_histo() {

     int mx = N;

     while (mx >= 0) {

       if (_histo[mx-1] > 0) break;

       mx--;

     }

     gclog_or_tty->print_cr("Number of regions with given RS sizes:");

     gclog_or_tty->print_cr("           <= %8d   %8d", 1 << MIN, _histo[0]);

     for (int i = 1; i < mx-1; i++) {

       gclog_or_tty->print_cr("  %8d  - %8d   %8d",

                     (1 << (MIN + i - 1)) + 1,

                     1 << (MIN + i),

                     _histo[i]);

     }

     gclog_or_tty->print_cr("            > %8d   %8d", (1 << (MIN+mx-2))+1, _histo[mx-1]);

   }

 };

 template <class T> void

 HRInto_G1RemSet::scanNewRefsRS_work(OopsInHeapRegionClosure* oc,

                                     int worker_i) {

   double scan_new_refs_start_sec = os::elapsedTime();

   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   CardTableModRefBS* ct_bs = (CardTableModRefBS*) (g1h->barrier_set());

   for (int i = 0; i < _new_refs[worker_i]->length(); i++) {

     T* p = (T*) _new_refs[worker_i]->at(i);

     oop obj = oopDesc::load_decode_heap_oop(p);

     // *p was in the collection set when p was pushed on "_new_refs", but

     // another thread may have processed this location from an RS, so it

     // might not point into the CS any longer.  If so, it's obviously been

     // processed, and we don't need to do anything further.

     if (g1h->obj_in_cs(obj)) {

       HeapRegion* r = g1h->heap_region_containing(p);

       DEBUG_ONLY(HeapRegion* to = g1h->heap_region_containing(obj));

       oc->set_region(r);

       // If "p" has already been processed concurrently, this is

       // idempotent.

       oc->do_oop(p);

     }

   }

   _g1p->record_scan_new_refs_time(worker_i,

                                   (os::elapsedTime() - scan_new_refs_start_sec)

                                   * 1000.0);

 }

 void HRInto_G1RemSet::cleanupHRRS() {

   HeapRegionRemSet::cleanup();

 }

 void

 HRInto_G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,

                                              int worker_i) {

 #if CARD_REPEAT_HISTO

   ct_freq_update_histo_and_reset();

 #endif

   if (worker_i == 0) {

     _cg1r->clear_and_record_card_counts();

   }

   // Make this into a command-line flag...

   if (G1RSCountHisto && (ParallelGCThreads == 0 || worker_i == 0)) {

     CountRSSizeClosure count_cl;

     _g1->heap_region_iterate(&count_cl);

     gclog_or_tty->print_cr("Avg of %d RS counts is %f, max is %d, "

                   "max region is " PTR_FORMAT,

                   count_cl.n(), (float)count_cl.tot()/(float)count_cl.n(),

                   count_cl.mx(), count_cl.mxr());

     count_cl.print_histo();

   }

   if (ParallelGCThreads > 0) {

     // The two flags below were introduced temporarily to serialize

     // the updating and scanning of remembered sets. There are some

     // race conditions when these two operations are done in parallel

     // and they are causing failures. When we resolve said race

     // conditions, we'll revert back to parallel remembered set

     // updating and scanning. See CRs 6677707 and 6677708.

     if (G1ParallelRSetUpdatingEnabled || (worker_i == 0)) {

       updateRS(worker_i);

       scanNewRefsRS(oc, worker_i);

     } else {

       _g1p->record_update_rs_start_time(worker_i, os::elapsedTime() * 1000.0);

       _g1p->record_update_rs_processed_buffers(worker_i, 0.0);

       _g1p->record_update_rs_time(worker_i, 0.0);

       _g1p->record_scan_new_refs_time(worker_i, 0.0);

     }

     if (G1ParallelRSetScanningEnabled || (worker_i == 0)) {

       scanRS(oc, worker_i);

     } else {

       _g1p->record_scan_rs_start_time(worker_i, os::elapsedTime() * 1000.0);

       _g1p->record_scan_rs_time(worker_i, 0.0);

     }

   } else {

     assert(worker_i == 0, "invariant");

     updateRS(0);

     scanNewRefsRS(oc, 0);

     scanRS(oc, 0);

   }

 }

 void HRInto_G1RemSet::

 prepare_for_oops_into_collection_set_do() {

 #if G1_REM_SET_LOGGING

   PrintRSClosure cl;

   _g1->collection_set_iterate(&cl);

 #endif

   cleanupHRRS();

   ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();

   _g1->set_refine_cte_cl_concurrency(false);

   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();

   dcqs.concatenate_logs();

   assert(!_par_traversal_in_progress, "Invariant between iterations.");

   if (ParallelGCThreads > 0) {

     set_par_traversal(true);

     _seq_task->set_par_threads((int)n_workers());

   }

   guarantee( _cards_scanned == NULL, "invariant" );

   _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers());

   for (uint i = 0; i < n_workers(); ++i) {

     _cards_scanned[i] = 0;

   }

   _total_cards_scanned = 0;

 }

 class cleanUpIteratorsClosure : public HeapRegionClosure {

   bool doHeapRegion(HeapRegion *r) {

     HeapRegionRemSet* hrrs = r->rem_set();

     hrrs->init_for_par_iteration();

     return false;

   }

 };

 class UpdateRSetOopsIntoCSImmediate : public OopClosure {

   G1CollectedHeap* _g1;

 public:

   UpdateRSetOopsIntoCSImmediate(G1CollectedHeap* g1) : _g1(g1) { }

   virtual void do_oop(narrowOop* p) { do_oop_work(p); }

   virtual void do_oop(      oop* p) { do_oop_work(p); }

   template <class T> void do_oop_work(T* p) {

     HeapRegion* to = _g1->heap_region_containing(oopDesc::load_decode_heap_oop(p));

     if (to->in_collection_set()) {

       to->rem_set()->add_reference(p, 0);

     }

   }

 };

 class UpdateRSetOopsIntoCSDeferred : public OopClosure {

   G1CollectedHeap* _g1;

   CardTableModRefBS* _ct_bs;

   DirtyCardQueue* _dcq;

 public:

   UpdateRSetOopsIntoCSDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) :

     _g1(g1), _ct_bs((CardTableModRefBS*)_g1->barrier_set()), _dcq(dcq) { }

   virtual void do_oop(narrowOop* p) { do_oop_work(p); }

   virtual void do_oop(      oop* p) { do_oop_work(p); }

   template <class T> void do_oop_work(T* p) {

     oop obj = oopDesc::load_decode_heap_oop(p);

     if (_g1->obj_in_cs(obj)) {

       size_t card_index = _ct_bs->index_for(p);

       if (_ct_bs->mark_card_deferred(card_index)) {

         _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));

       }

     }

   }

 };

 template <class T> void HRInto_G1RemSet::new_refs_iterate_work(OopClosure* cl) {

   for (size_t i = 0; i < n_workers(); i++) {

     for (int j = 0; j < _new_refs[i]->length(); j++) {

       T* p = (T*) _new_refs[i]->at(j);

       cl->do_oop(p);

     }

   }

 }

 void HRInto_G1RemSet::cleanup_after_oops_into_collection_set_do() {

   guarantee( _cards_scanned != NULL, "invariant" );

   _total_cards_scanned = 0;

   for (uint i = 0; i < n_workers(); ++i)

     _total_cards_scanned += _cards_scanned[i];

   FREE_C_HEAP_ARRAY(size_t, _cards_scanned);

   _cards_scanned = NULL;

   // Cleanup after copy

 #if G1_REM_SET_LOGGING

   PrintRSClosure cl;

   _g1->heap_region_iterate(&cl);

 #endif

   _g1->set_refine_cte_cl_concurrency(true);

   cleanUpIteratorsClosure iterClosure;

   _g1->collection_set_iterate(&iterClosure);

   // Set all cards back to clean.

   _g1->cleanUpCardTable();

   if (ParallelGCThreads > 0) {

     set_par_traversal(false);

   }

   if (_g1->evacuation_failed()) {

     // Restore remembered sets for the regions pointing into

     // the collection set.

     if (G1DeferredRSUpdate) {

       DirtyCardQueue dcq(&_g1->dirty_card_queue_set());

       UpdateRSetOopsIntoCSDeferred deferred_update(_g1, &dcq);

       new_refs_iterate(&deferred_update);

     } else {

       UpdateRSetOopsIntoCSImmediate immediate_update(_g1);

       new_refs_iterate(&immediate_update);

     }

   }

   for (uint i = 0; i < n_workers(); i++) {

     _new_refs[i]->clear();

   }

   assert(!_par_traversal_in_progress, "Invariant between iterations.");

 }

 class UpdateRSObjectClosure: public ObjectClosure {

   UpdateRSOopClosure* _update_rs_oop_cl;

 public:

   UpdateRSObjectClosure(UpdateRSOopClosure* update_rs_oop_cl) :

     _update_rs_oop_cl(update_rs_oop_cl) {}

   void do_object(oop obj) {

     obj->oop_iterate(_update_rs_oop_cl);

   }

 };

 class ScrubRSClosure: public HeapRegionClosure {

   G1CollectedHeap* _g1h;

   BitMap* _region_bm;

   BitMap* _card_bm;

   CardTableModRefBS* _ctbs;

 public:

   ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :

     _g1h(G1CollectedHeap::heap()),

     _region_bm(region_bm), _card_bm(card_bm),

     _ctbs(NULL)

   {

     ModRefBarrierSet* bs = _g1h->mr_bs();

     guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition");

     _ctbs = (CardTableModRefBS*)bs;

   }

   bool doHeapRegion(HeapRegion* r) {

     if (!r->continuesHumongous()) {

       r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);

     }

     return false;

   }

 };

 void HRInto_G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) {

   ScrubRSClosure scrub_cl(region_bm, card_bm);

   _g1->heap_region_iterate(&scrub_cl);

 }

 void HRInto_G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm,

                                 int worker_num, int claim_val) {

   ScrubRSClosure scrub_cl(region_bm, card_bm);

   _g1->heap_region_par_iterate_chunked(&scrub_cl, worker_num, claim_val);

 }

 static IntHistogram out_of_histo(50, 50);

 void HRInto_G1RemSet::concurrentRefineOneCard(jbyte* card_ptr, int worker_i) {

   // If the card is no longer dirty, nothing to do.

   if (*card_ptr != CardTableModRefBS::dirty_card_val()) return;

   // Construct the region representing the card.

   HeapWord* start = _ct_bs->addr_for(card_ptr);

   // And find the region containing it.

   HeapRegion* r = _g1->heap_region_containing(start);

   if (r == NULL) {

     guarantee(_g1->is_in_permanent(start), "Or else where?");

     return;  // Not in the G1 heap (might be in perm, for example.)

   }

   // Why do we have to check here whether a card is on a young region,

   // given that we dirty young regions and, as a result, the

   // post-barrier is supposed to filter them out and never to enqueue

   // them? When we allocate a new region as the "allocation region" we

   // actually dirty its cards after we release the lock, since card

   // dirtying while holding the lock was a performance bottleneck. So,

   // as a result, it is possible for other threads to actually

   // allocate objects in the region (after the acquire the lock)

   // before all the cards on the region are dirtied. This is unlikely,

   // and it doesn't happen often, but it can happen. So, the extra

   // check below filters out those cards.

   if (r->is_young()) {

     return;

   }

   // While we are processing RSet buffers during the collection, we

   // actually don't want to scan any cards on the collection set,

   // since we don't want to update remebered sets with entries that

   // point into the collection set, given that live objects from the

   // collection set are about to move and such entries will be stale

   // very soon. This change also deals with a reliability issue which

   // involves scanning a card in the collection set and coming across

   // an array that was being chunked and looking malformed. Note,

   // however, that if evacuation fails, we have to scan any objects

   // that were not moved and create any missing entries.

   if (r->in_collection_set()) {

     return;

   }

   // Should we defer it?

   if (_cg1r->use_cache()) {

     card_ptr = _cg1r->cache_insert(card_ptr);

     // If it was not an eviction, nothing to do.

     if (card_ptr == NULL) return;

     // OK, we have to reset the card start, region, etc.

     start = _ct_bs->addr_for(card_ptr);

     r = _g1->heap_region_containing(start);

     if (r == NULL) {

       guarantee(_g1->is_in_permanent(start), "Or else where?");

       return;  // Not in the G1 heap (might be in perm, for example.)

     }

     guarantee(!r->is_young(), "It was evicted in the current minor cycle.");

   }

   HeapWord* end   = _ct_bs->addr_for(card_ptr + 1);

   MemRegion dirtyRegion(start, end);

 #if CARD_REPEAT_HISTO

   init_ct_freq_table(_g1->g1_reserved_obj_bytes());

   ct_freq_note_card(_ct_bs->index_for(start));

 #endif

   UpdateRSOopClosure update_rs_oop_cl(this, worker_i);

   update_rs_oop_cl.set_from(r);

   FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r, &update_rs_oop_cl);

   // Undirty the card.

   *card_ptr = CardTableModRefBS::clean_card_val();

   // We must complete this write before we do any of the reads below.

   OrderAccess::storeload();

   // And process it, being careful of unallocated portions of TLAB's.

   HeapWord* stop_point =

     r->oops_on_card_seq_iterate_careful(dirtyRegion,

                                         &filter_then_update_rs_oop_cl);

   // If stop_point is non-null, then we encountered an unallocated region

   // (perhaps the unfilled portion of a TLAB.)  For now, we'll dirty the

   // card and re-enqueue: if we put off the card until a GC pause, then the

   // unallocated portion will be filled in.  Alternatively, we might try

   // the full complexity of the technique used in "regular" precleaning.

   if (stop_point != NULL) {

     // The card might have gotten re-dirtied and re-enqueued while we

     // worked.  (In fact, it's pretty likely.)

     if (*card_ptr != CardTableModRefBS::dirty_card_val()) {

       *card_ptr = CardTableModRefBS::dirty_card_val();

       MutexLockerEx x(Shared_DirtyCardQ_lock,

                       Mutex::_no_safepoint_check_flag);

       DirtyCardQueue* sdcq =

         JavaThread::dirty_card_queue_set().shared_dirty_card_queue();

       sdcq->enqueue(card_ptr);

     }

   } else {

     out_of_histo.add_entry(filter_then_update_rs_oop_cl.out_of_region());

     _conc_refine_cards++;

   }

 }

 class HRRSStatsIter: public HeapRegionClosure {

   size_t _occupied;

   size_t _total_mem_sz;

   size_t _max_mem_sz;

   HeapRegion* _max_mem_sz_region;

 public:

   HRRSStatsIter() :

     _occupied(0),

     _total_mem_sz(0),

     _max_mem_sz(0),

     _max_mem_sz_region(NULL)

   {}

   bool doHeapRegion(HeapRegion* r) {

     if (r->continuesHumongous()) return false;

     size_t mem_sz = r->rem_set()->mem_size();

     if (mem_sz > _max_mem_sz) {

       _max_mem_sz = mem_sz;

       _max_mem_sz_region = r;

     }

     _total_mem_sz += mem_sz;

     size_t occ = r->rem_set()->occupied();

     _occupied += occ;

     return false;

   }

   size_t total_mem_sz() { return _total_mem_sz; }

   size_t max_mem_sz() { return _max_mem_sz; }

   size_t occupied() { return _occupied; }

   HeapRegion* max_mem_sz_region() { return _max_mem_sz_region; }

 };

 class PrintRSThreadVTimeClosure : public ThreadClosure {

 public:

   virtual void do_thread(Thread *t) {

     ConcurrentG1RefineThread* crt = (ConcurrentG1RefineThread*) t;

     gclog_or_tty->print("    %5.2f", crt->vtime_accum());

   }

 };

 void HRInto_G1RemSet::print_summary_info() {

   G1CollectedHeap* g1 = G1CollectedHeap::heap();

 #if CARD_REPEAT_HISTO

   gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");

   gclog_or_tty->print_cr("  # of repeats --> # of cards with that number.");

   card_repeat_count.print_on(gclog_or_tty);

 #endif

   if (FILTEROUTOFREGIONCLOSURE_DOHISTOGRAMCOUNT) {

     gclog_or_tty->print_cr("\nG1 rem-set out-of-region histogram: ");

     gclog_or_tty->print_cr("  # of CS ptrs --> # of cards with that number.");

     out_of_histo.print_on(gclog_or_tty);

   }

   gclog_or_tty->print_cr("\n Concurrent RS processed %d cards",

                          _conc_refine_cards);

   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();

   jint tot_processed_buffers =

     dcqs.processed_buffers_mut() + dcqs.processed_buffers_rs_thread();

   gclog_or_tty->print_cr("  Of %d completed buffers:", tot_processed_buffers);

   gclog_or_tty->print_cr("     %8d (%5.1f%%) by conc RS threads.",

                 dcqs.processed_buffers_rs_thread(),

                 100.0*(float)dcqs.processed_buffers_rs_thread()/

                 (float)tot_processed_buffers);

   gclog_or_tty->print_cr("     %8d (%5.1f%%) by mutator threads.",

                 dcqs.processed_buffers_mut(),

                 100.0*(float)dcqs.processed_buffers_mut()/

                 (float)tot_processed_buffers);

   gclog_or_tty->print_cr("  Conc RS threads times(s)");

   PrintRSThreadVTimeClosure p;

   gclog_or_tty->print("     ");

   g1->concurrent_g1_refine()->threads_do(&p);

   gclog_or_tty->print_cr("");

   if (G1UseHRIntoRS) {

     HRRSStatsIter blk;

     g1->heap_region_iterate(&blk);

     gclog_or_tty->print_cr("  Total heap region rem set sizes = " SIZE_FORMAT "K."

                            "  Max = " SIZE_FORMAT "K.",

                            blk.total_mem_sz()/K, blk.max_mem_sz()/K);

     gclog_or_tty->print_cr("  Static structures = " SIZE_FORMAT "K,"

                            " free_lists = " SIZE_FORMAT "K.",

                            HeapRegionRemSet::static_mem_size()/K,

                            HeapRegionRemSet::fl_mem_size()/K);

     gclog_or_tty->print_cr("    %d occupied cards represented.",

                            blk.occupied());

     gclog_or_tty->print_cr("    Max sz region = [" PTR_FORMAT ", " PTR_FORMAT " )"

                            ", cap = " SIZE_FORMAT "K, occ = " SIZE_FORMAT "K.",

                            blk.max_mem_sz_region()->bottom(), blk.max_mem_sz_region()->end(),

                            (blk.max_mem_sz_region()->rem_set()->mem_size() + K - 1)/K,

                            (blk.max_mem_sz_region()->rem_set()->occupied() + K - 1)/K);

     gclog_or_tty->print_cr("    Did %d coarsenings.",

                   HeapRegionRemSet::n_coarsenings());

   }

 }

 void HRInto_G1RemSet::prepare_for_verify() {

   if (G1HRRSFlushLogBuffersOnVerify &&

       (VerifyBeforeGC || VerifyAfterGC)

       &&  !_g1->full_collection()) {

     cleanupHRRS();

     _g1->set_refine_cte_cl_concurrency(false);

     if (SafepointSynchronize::is_at_safepoint()) {

       DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();

       dcqs.concatenate_logs();

     }

     bool cg1r_use_cache = _cg1r->use_cache();

     _cg1r->set_use_cache(false);

     updateRS(0);

     _cg1r->set_use_cache(cg1r_use_cache);

     assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");

   }

 }