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 /*

  * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.

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

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  * 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP

 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP

 #include "gc_implementation/g1/concurrentMark.inline.hpp"

 #include "gc_implementation/g1/dirtyCardQueue.hpp"

 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"

 #include "gc_implementation/g1/g1_globals.hpp"

 #include "gc_implementation/g1/g1OopClosures.inline.hpp"

 #include "gc_implementation/g1/heapRegion.hpp"

 #include "gc_implementation/g1/heapRegionRemSet.hpp"

 #include "utilities/workgroup.hpp"

 // Closures and tasks associated with any self-forwarding pointers

 // installed as a result of an evacuation failure.

 class UpdateRSetDeferred : public OopsInHeapRegionClosure {

 private:

   G1CollectedHeap* _g1;

   DirtyCardQueue *_dcq;

   G1SATBCardTableModRefBS* _ct_bs;

 public:

   UpdateRSetDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) :

     _g1(g1), _ct_bs(_g1->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) {

     assert(_from->is_in_reserved(p), "paranoia");

     if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) &&

         !_from->is_survivor()) {

       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));

       }

     }

   }

 };

 class RemoveSelfForwardPtrObjClosure: public ObjectClosure {

 private:

   G1CollectedHeap* _g1;

   ConcurrentMark* _cm;

   HeapRegion* _hr;

   size_t _marked_bytes;

   OopsInHeapRegionClosure *_update_rset_cl;

   bool _during_initial_mark;

   bool _during_conc_mark;

   uint _worker_id;

   HeapWord* _end_of_last_gap;

   HeapWord* _last_gap_threshold;

   HeapWord* _last_obj_threshold;

 public:

   RemoveSelfForwardPtrObjClosure(G1CollectedHeap* g1, ConcurrentMark* cm,

                                  HeapRegion* hr,

                                  OopsInHeapRegionClosure* update_rset_cl,

                                  bool during_initial_mark,

                                  bool during_conc_mark,

                                  uint worker_id) :

     _g1(g1), _cm(cm), _hr(hr), _marked_bytes(0),

     _update_rset_cl(update_rset_cl),

     _during_initial_mark(during_initial_mark),

     _during_conc_mark(during_conc_mark),

     _worker_id(worker_id),

     _end_of_last_gap(hr->bottom()),

     _last_gap_threshold(hr->bottom()),

     _last_obj_threshold(hr->bottom()) { }

   size_t marked_bytes() { return _marked_bytes; }

   // <original comment>

   // The original idea here was to coalesce evacuated and dead objects.

   // However that caused complications with the block offset table (BOT).

   // In particular if there were two TLABs, one of them partially refined.

   // |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~|

   // The BOT entries of the unrefined part of TLAB_2 point to the start

   // of TLAB_2. If the last object of the TLAB_1 and the first object

   // of TLAB_2 are coalesced, then the cards of the unrefined part

   // would point into middle of the filler object.

   // The current approach is to not coalesce and leave the BOT contents intact.

   // </original comment>

   //

   // We now reset the BOT when we start the object iteration over the

   // region and refine its entries for every object we come across. So

   // the above comment is not really relevant and we should be able

   // to coalesce dead objects if we want to.

   void do_object(oop obj) {

     HeapWord* obj_addr = (HeapWord*) obj;

     assert(_hr->is_in(obj_addr), "sanity");

     size_t obj_size = obj->size();

     HeapWord* obj_end = obj_addr + obj_size;

     if (_end_of_last_gap != obj_addr) {

       // there was a gap before obj_addr

       _last_gap_threshold = _hr->cross_threshold(_end_of_last_gap, obj_addr);

     }

     if (obj->is_forwarded() && obj->forwardee() == obj) {

       // The object failed to move.

       // We consider all objects that we find self-forwarded to be

       // live. What we'll do is that we'll update the prev marking

       // info so that they are all under PTAMS and explicitly marked.

       if (!_cm->isPrevMarked(obj)) {

         _cm->markPrev(obj);

       }

       if (_during_initial_mark) {

         // For the next marking info we'll only mark the

         // self-forwarded objects explicitly if we are during

         // initial-mark (since, normally, we only mark objects pointed

         // to by roots if we succeed in copying them). By marking all

         // self-forwarded objects we ensure that we mark any that are

         // still pointed to be roots. During concurrent marking, and

         // after initial-mark, we don't need to mark any objects

         // explicitly and all objects in the CSet are considered

         // (implicitly) live. So, we won't mark them explicitly and

         // we'll leave them over NTAMS.

         _cm->grayRoot(obj, obj_size, _worker_id, _hr);

       }

       _marked_bytes += (obj_size * HeapWordSize);

       obj->set_mark(markOopDesc::prototype());

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

       // we actually didn't scan any cards on the collection set,

       // since we didn't want to update remembered 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 dealt with a reliability issue which

       // involved scanning a card in the collection set and coming

       // across an array that was being chunked and looking malformed.

       // The problem is that, if evacuation fails, we might have

       // remembered set entries missing given that we skipped cards on

       // the collection set. So, we'll recreate such entries now.

       obj->oop_iterate(_update_rset_cl);

     } else {

       // The object has been either evacuated or is dead. Fill it with a

       // dummy object.

       MemRegion mr(obj_addr, obj_size);

       CollectedHeap::fill_with_object(mr);

       // must nuke all dead objects which we skipped when iterating over the region

       _cm->clearRangePrevBitmap(MemRegion(_end_of_last_gap, obj_end));

     }

     _end_of_last_gap = obj_end;

     _last_obj_threshold = _hr->cross_threshold(obj_addr, obj_end);

   }

 };

 class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {

   G1CollectedHeap* _g1h;

   ConcurrentMark* _cm;

   OopsInHeapRegionClosure *_update_rset_cl;

   uint _worker_id;

 public:

   RemoveSelfForwardPtrHRClosure(G1CollectedHeap* g1h,

                                 OopsInHeapRegionClosure* update_rset_cl,

                                 uint worker_id) :

     _g1h(g1h), _update_rset_cl(update_rset_cl),

     _worker_id(worker_id), _cm(_g1h->concurrent_mark()) { }

   bool doHeapRegion(HeapRegion *hr) {

     bool during_initial_mark = _g1h->g1_policy()->during_initial_mark_pause();

     bool during_conc_mark = _g1h->mark_in_progress();

     assert(!hr->isHumongous(), "sanity");

     assert(hr->in_collection_set(), "bad CS");

     if (hr->claimHeapRegion(HeapRegion::ParEvacFailureClaimValue)) {

       if (hr->evacuation_failed()) {

         RemoveSelfForwardPtrObjClosure rspc(_g1h, _cm, hr, _update_rset_cl,

                                             during_initial_mark,

                                             during_conc_mark,

                                             _worker_id);

         hr->note_self_forwarding_removal_start(during_initial_mark,

                                                during_conc_mark);

         // In the common case (i.e. when there is no evacuation

         // failure) we make sure that the following is done when

         // the region is freed so that it is "ready-to-go" when it's

         // re-allocated. However, when evacuation failure happens, a

         // region will remain in the heap and might ultimately be added

         // to a CSet in the future. So we have to be careful here and

         // make sure the region's RSet is ready for parallel iteration

         // whenever this might be required in the future.

         hr->rem_set()->reset_for_par_iteration();

         hr->reset_bot();

         _update_rset_cl->set_region(hr);

         hr->object_iterate(&rspc);

         hr->note_self_forwarding_removal_end(during_initial_mark,

                                              during_conc_mark,

                                              rspc.marked_bytes());

       }

     }

     return false;

   }

 };

 class G1ParRemoveSelfForwardPtrsTask: public AbstractGangTask {

 protected:

   G1CollectedHeap* _g1h;

 public:

   G1ParRemoveSelfForwardPtrsTask(G1CollectedHeap* g1h) :

     AbstractGangTask("G1 Remove Self-forwarding Pointers"),

     _g1h(g1h) { }

   void work(uint worker_id) {

     UpdateRSetImmediate immediate_update(_g1h->g1_rem_set());

     DirtyCardQueue dcq(&_g1h->dirty_card_queue_set());

     UpdateRSetDeferred deferred_update(_g1h, &dcq);

     OopsInHeapRegionClosure *update_rset_cl = &deferred_update;

     if (!G1DeferredRSUpdate) {

       update_rset_cl = &immediate_update;

     }

     RemoveSelfForwardPtrHRClosure rsfp_cl(_g1h, update_rset_cl, worker_id);

     HeapRegion* hr = _g1h->start_cset_region_for_worker(worker_id);

     _g1h->collection_set_iterate_from(hr, &rsfp_cl);

   }

 };

 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP