johnc@3412: /*
johnc@3412:  * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
johnc@3412:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
johnc@3412:  *
johnc@3412:  * This code is free software; you can redistribute it and/or modify it
johnc@3412:  * under the terms of the GNU General Public License version 2 only, as
johnc@3412:  * published by the Free Software Foundation.
johnc@3412:  *
johnc@3412:  * This code is distributed in the hope that it will be useful, but WITHOUT
johnc@3412:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
johnc@3412:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
johnc@3412:  * version 2 for more details (a copy is included in the LICENSE file that
johnc@3412:  * accompanied this code).
johnc@3412:  *
johnc@3412:  * You should have received a copy of the GNU General Public License version
johnc@3412:  * 2 along with this work; if not, write to the Free Software Foundation,
johnc@3412:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
johnc@3412:  *
johnc@3412:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
johnc@3412:  * or visit www.oracle.com if you need additional information or have any
johnc@3412:  * questions.
johnc@3412:  *
johnc@3412:  */
johnc@3412: 
johnc@3412: #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP
johnc@3412: #define SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP
johnc@3412: 
johnc@3412: #include "gc_implementation/g1/concurrentMark.inline.hpp"
johnc@3412: #include "gc_implementation/g1/dirtyCardQueue.hpp"
johnc@3412: #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
johnc@3412: #include "gc_implementation/g1/g1_globals.hpp"
johnc@3412: #include "gc_implementation/g1/g1OopClosures.inline.hpp"
johnc@3412: #include "gc_implementation/g1/heapRegion.hpp"
johnc@3412: #include "gc_implementation/g1/heapRegionRemSet.hpp"
johnc@3412: #include "utilities/workgroup.hpp"
johnc@3412: 
johnc@3412: // Closures and tasks associated with any self-forwarding pointers
johnc@3412: // installed as a result of an evacuation failure.
johnc@3412: 
johnc@3412: class UpdateRSetDeferred : public OopsInHeapRegionClosure {
johnc@3412: private:
johnc@3412:   G1CollectedHeap* _g1;
johnc@3412:   DirtyCardQueue *_dcq;
johnc@3412:   CardTableModRefBS* _ct_bs;
johnc@3412: 
johnc@3412: public:
johnc@3412:   UpdateRSetDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) :
johnc@3412:     _g1(g1), _ct_bs((CardTableModRefBS*)_g1->barrier_set()), _dcq(dcq) {}
johnc@3412: 
johnc@3412:   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
johnc@3412:   virtual void do_oop(      oop* p) { do_oop_work(p); }
johnc@3412:   template <class T> void do_oop_work(T* p) {
johnc@3412:     assert(_from->is_in_reserved(p), "paranoia");
johnc@3412:     if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) &&
johnc@3412:         !_from->is_survivor()) {
johnc@3412:       size_t card_index = _ct_bs->index_for(p);
johnc@3412:       if (_ct_bs->mark_card_deferred(card_index)) {
johnc@3412:         _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));
johnc@3412:       }
johnc@3412:     }
johnc@3412:   }
johnc@3412: };
johnc@3412: 
johnc@3412: class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
johnc@3412: private:
johnc@3412:   G1CollectedHeap* _g1;
johnc@3412:   ConcurrentMark* _cm;
johnc@3412:   HeapRegion* _hr;
johnc@3412:   size_t _prev_marked_bytes;
johnc@3412:   size_t _next_marked_bytes;
johnc@3412:   OopsInHeapRegionClosure *_update_rset_cl;
johnc@3412: public:
johnc@3412:   RemoveSelfForwardPtrObjClosure(G1CollectedHeap* g1, ConcurrentMark* cm,
johnc@3412:                                  HeapRegion* hr,
johnc@3412:                                  OopsInHeapRegionClosure* update_rset_cl) :
johnc@3412:     _g1(g1), _cm(cm), _hr(hr),
johnc@3412:     _update_rset_cl(update_rset_cl),
johnc@3412:     _prev_marked_bytes(0), _next_marked_bytes(0) {}
johnc@3412: 
johnc@3412:   size_t prev_marked_bytes() { return _prev_marked_bytes; }
johnc@3412:   size_t next_marked_bytes() { return _next_marked_bytes; }
johnc@3412: 
johnc@3412:   // <original comment>
johnc@3412:   // The original idea here was to coalesce evacuated and dead objects.
johnc@3412:   // However that caused complications with the block offset table (BOT).
johnc@3412:   // In particular if there were two TLABs, one of them partially refined.
johnc@3412:   // |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~|
johnc@3412:   // The BOT entries of the unrefined part of TLAB_2 point to the start
johnc@3412:   // of TLAB_2. If the last object of the TLAB_1 and the first object
johnc@3412:   // of TLAB_2 are coalesced, then the cards of the unrefined part
johnc@3412:   // would point into middle of the filler object.
johnc@3412:   // The current approach is to not coalesce and leave the BOT contents intact.
johnc@3412:   // </original comment>
johnc@3412:   //
johnc@3412:   // We now reset the BOT when we start the object iteration over the
johnc@3412:   // region and refine its entries for every object we come across. So
johnc@3412:   // the above comment is not really relevant and we should be able
johnc@3412:   // to coalesce dead objects if we want to.
johnc@3412:   void do_object(oop obj) {
johnc@3412:     HeapWord* obj_addr = (HeapWord*) obj;
johnc@3412:     assert(_hr->is_in(obj_addr), "sanity");
johnc@3412:     size_t obj_size = obj->size();
johnc@3412: 
johnc@3412:     _hr->update_bot_for_object(obj_addr, obj_size);
johnc@3412: 
johnc@3412:     if (obj->is_forwarded() && obj->forwardee() == obj) {
johnc@3412:       // The object failed to move.
johnc@3412:       assert(!_g1->is_obj_dead(obj), "We should not be preserving dead objs.");
johnc@3412:       _cm->markPrev(obj);
johnc@3412:       assert(_cm->isPrevMarked(obj), "Should be marked!");
johnc@3412:       _prev_marked_bytes += (obj_size * HeapWordSize);
johnc@3412:       if (_g1->mark_in_progress() && !_g1->is_obj_ill(obj)) {
johnc@3412:         _cm->markAndGrayObjectIfNecessary(obj);
johnc@3412:       }
johnc@3412:       obj->set_mark(markOopDesc::prototype());
johnc@3412: 
johnc@3412:       // While we were processing RSet buffers during the collection,
johnc@3412:       // we actually didn't scan any cards on the collection set,
johnc@3412:       // since we didn't want to update remembered sets with entries
johnc@3412:       // that point into the collection set, given that live objects
johnc@3412:       // from the collection set are about to move and such entries
johnc@3412:       // will be stale very soon.
johnc@3412:       // This change also dealt with a reliability issue which
johnc@3412:       // involved scanning a card in the collection set and coming
johnc@3412:       // across an array that was being chunked and looking malformed.
johnc@3412:       // The problem is that, if evacuation fails, we might have
johnc@3412:       // remembered set entries missing given that we skipped cards on
johnc@3412:       // the collection set. So, we'll recreate such entries now.
johnc@3412: 
johnc@3412:       obj->oop_iterate(_update_rset_cl);
johnc@3412:       assert(_cm->isPrevMarked(obj), "Should be marked!");
johnc@3412:     } else {
johnc@3412:       // The object has been either evacuated or is dead. Fill it with a
johnc@3412:       // dummy object.
johnc@3412:       MemRegion mr((HeapWord*)obj, obj_size);
johnc@3412:       CollectedHeap::fill_with_object(mr);
johnc@3412:       _cm->clearRangeBothMaps(mr);
johnc@3412:     }
johnc@3412:   }
johnc@3412: };
johnc@3412: 
johnc@3412: class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {
johnc@3412:   G1CollectedHeap* _g1h;
johnc@3412:   ConcurrentMark* _cm;
johnc@3412:   OopsInHeapRegionClosure *_update_rset_cl;
johnc@3412: 
johnc@3412: public:
johnc@3412:   RemoveSelfForwardPtrHRClosure(G1CollectedHeap* g1h,
johnc@3412:                                 OopsInHeapRegionClosure* update_rset_cl) :
johnc@3412:     _g1h(g1h), _update_rset_cl(update_rset_cl),
johnc@3412:     _cm(_g1h->concurrent_mark()) { }
johnc@3412: 
johnc@3412:   bool doHeapRegion(HeapRegion *hr) {
johnc@3412:     assert(!hr->isHumongous(), "sanity");
johnc@3412:     assert(hr->in_collection_set(), "bad CS");
johnc@3412: 
johnc@3412:     if (hr->claimHeapRegion(HeapRegion::ParEvacFailureClaimValue)) {
johnc@3412:       if (hr->evacuation_failed()) {
johnc@3412:         RemoveSelfForwardPtrObjClosure rspc(_g1h, _cm, hr, _update_rset_cl);
johnc@3412: 
johnc@3412:         // In the common case (i.e. when there is no evacuation
johnc@3412:         // failure) we make sure that the following is done when
johnc@3412:         // the region is freed so that it is "ready-to-go" when it's
johnc@3412:         // re-allocated. However, when evacuation failure happens, a
johnc@3412:         // region will remain in the heap and might ultimately be added
johnc@3412:         // to a CSet in the future. So we have to be careful here and
johnc@3412:         // make sure the region's RSet is ready for parallel iteration
johnc@3412:         // whenever this might be required in the future.
johnc@3412:         hr->rem_set()->reset_for_par_iteration();
johnc@3412:         hr->reset_bot();
johnc@3412:         _update_rset_cl->set_region(hr);
johnc@3412:         hr->object_iterate(&rspc);
johnc@3412: 
johnc@3412:         // A number of manipulations to make the TAMS for this region
johnc@3412:         // be the current top, and the marked bytes be the ones observed
johnc@3412:         // in the iteration.
johnc@3412:         if (_cm->at_least_one_mark_complete()) {
johnc@3412:           // The comments below are the postconditions achieved by the
johnc@3412:           // calls.  Note especially the last such condition, which says that
johnc@3412:           // the count of marked bytes has been properly restored.
johnc@3412:           hr->note_start_of_marking(false);
johnc@3412:           // _next_top_at_mark_start == top, _next_marked_bytes == 0
johnc@3412:           hr->add_to_marked_bytes(rspc.prev_marked_bytes());
johnc@3412:           // _next_marked_bytes == prev_marked_bytes.
johnc@3412:           hr->note_end_of_marking();
johnc@3412:           // _prev_top_at_mark_start == top(),
johnc@3412:           // _prev_marked_bytes == prev_marked_bytes
johnc@3412:         }
johnc@3412:         // If there is no mark in progress, we modified the _next variables
johnc@3412:         // above needlessly, but harmlessly.
johnc@3412:         if (_g1h->mark_in_progress()) {
johnc@3412:           hr->note_start_of_marking(false);
johnc@3412:           // _next_top_at_mark_start == top, _next_marked_bytes == 0
johnc@3412:           // _next_marked_bytes == next_marked_bytes.
johnc@3412:         }
johnc@3412:       }
johnc@3412:     }
johnc@3412:     return false;
johnc@3412:   }
johnc@3412: };
johnc@3412: 
johnc@3412: class G1ParRemoveSelfForwardPtrsTask: public AbstractGangTask {
johnc@3412: protected:
johnc@3412:   G1CollectedHeap* _g1h;
johnc@3412: 
johnc@3412: public:
johnc@3412:   G1ParRemoveSelfForwardPtrsTask(G1CollectedHeap* g1h) :
johnc@3412:     AbstractGangTask("G1 Remove Self-forwarding Pointers"),
johnc@3412:     _g1h(g1h) { }
johnc@3412: 
johnc@3412:   void work(uint worker_id) {
johnc@3412:     UpdateRSetImmediate immediate_update(_g1h->g1_rem_set());
johnc@3412:     DirtyCardQueue dcq(&_g1h->dirty_card_queue_set());
johnc@3412:     UpdateRSetDeferred deferred_update(_g1h, &dcq);
johnc@3412: 
johnc@3412:     OopsInHeapRegionClosure *update_rset_cl = &deferred_update;
johnc@3412:     if (!G1DeferredRSUpdate) {
johnc@3412:       update_rset_cl = &immediate_update;
johnc@3412:     }
johnc@3412: 
johnc@3412:     RemoveSelfForwardPtrHRClosure rsfp_cl(_g1h, update_rset_cl);
johnc@3412: 
johnc@3412:     HeapRegion* hr = _g1h->start_cset_region_for_worker(worker_id);
johnc@3412:     _g1h->collection_set_iterate_from(hr, &rsfp_cl);
johnc@3412:   }
johnc@3412: };
johnc@3412: 
johnc@3412: #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP