/* * Copyright (c) 2012, 2013, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #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 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; } // // 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. // // // 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; uint _worker_id; DirtyCardQueue _dcq; UpdateRSetDeferred _update_rset_cl; public: RemoveSelfForwardPtrHRClosure(G1CollectedHeap* g1h, uint worker_id) : _g1h(g1h), _dcq(&g1h->dirty_card_queue_set()), _update_rset_cl(g1h, &_dcq), _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); _g1h->check_bitmaps("Self-Forwarding Ptr Removal", hr); // 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->rem_set()->clean_strong_code_roots(hr); 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) { RemoveSelfForwardPtrHRClosure rsfp_cl(_g1h, 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