1 /*
   2  * Copyright (c) 2012, 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 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP
  27 
  28 #include "gc_implementation/g1/concurrentMark.inline.hpp"
  29 #include "gc_implementation/g1/dirtyCardQueue.hpp"
  30 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  31 #include "gc_implementation/g1/g1_globals.hpp"
  32 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  33 #include "gc_implementation/g1/heapRegion.hpp"
  34 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  35 #include "utilities/workgroup.hpp"
  36 
  37 // Closures and tasks associated with any self-forwarding pointers
  38 // installed as a result of an evacuation failure.
  39 
  40 class UpdateRSetDeferred : public OopsInHeapRegionClosure {
  41 private:
  42   G1CollectedHeap* _g1;
  43   DirtyCardQueue *_dcq;
  44   G1SATBCardTableModRefBS* _ct_bs;
  45 
  46 public:
  47   UpdateRSetDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) :
  48     _g1(g1), _ct_bs(_g1->g1_barrier_set()), _dcq(dcq) {}
  49 
  50   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
  51   virtual void do_oop(      oop* p) { do_oop_work(p); }
  52   template <class T> void do_oop_work(T* p) {
  53     assert(_from->is_in_reserved(p), "paranoia");
  54     if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) &&
  55         !_from->is_survivor()) {
  56       size_t card_index = _ct_bs->index_for(p);
  57       if (_ct_bs->mark_card_deferred(card_index)) {
  58         _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));
  59       }
  60     }
  61   }
  62 };
  63 
  64 class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
  65 private:
  66   G1CollectedHeap* _g1;
  67   ConcurrentMark* _cm;
  68   HeapRegion* _hr;
  69   size_t _marked_bytes;
  70   OopsInHeapRegionClosure *_update_rset_cl;
  71   bool _during_initial_mark;
  72   bool _during_conc_mark;
  73   uint _worker_id;
  74   HeapWord* _end_of_last_gap;
  75   HeapWord* _last_gap_threshold;
  76   HeapWord* _last_obj_threshold;
  77 
  78 public:
  79   RemoveSelfForwardPtrObjClosure(G1CollectedHeap* g1, ConcurrentMark* cm,
  80                                  HeapRegion* hr,
  81                                  OopsInHeapRegionClosure* update_rset_cl,
  82                                  bool during_initial_mark,
  83                                  bool during_conc_mark,
  84                                  uint worker_id) :
  85     _g1(g1), _cm(cm), _hr(hr), _marked_bytes(0),
  86     _update_rset_cl(update_rset_cl),
  87     _during_initial_mark(during_initial_mark),
  88     _during_conc_mark(during_conc_mark),
  89     _worker_id(worker_id),
  90     _end_of_last_gap(hr->bottom()),
  91     _last_gap_threshold(hr->bottom()),
  92     _last_obj_threshold(hr->bottom()) { }
  93 
  94   size_t marked_bytes() { return _marked_bytes; }
  95 
  96   // <original comment>
  97   // The original idea here was to coalesce evacuated and dead objects.
  98   // However that caused complications with the block offset table (BOT).
  99   // In particular if there were two TLABs, one of them partially refined.
 100   // |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~|
 101   // The BOT entries of the unrefined part of TLAB_2 point to the start
 102   // of TLAB_2. If the last object of the TLAB_1 and the first object
 103   // of TLAB_2 are coalesced, then the cards of the unrefined part
 104   // would point into middle of the filler object.
 105   // The current approach is to not coalesce and leave the BOT contents intact.
 106   // </original comment>
 107   //
 108   // We now reset the BOT when we start the object iteration over the
 109   // region and refine its entries for every object we come across. So
 110   // the above comment is not really relevant and we should be able
 111   // to coalesce dead objects if we want to.
 112   void do_object(oop obj) {
 113     HeapWord* obj_addr = (HeapWord*) obj;
 114     assert(_hr->is_in(obj_addr), "sanity");
 115     size_t obj_size = obj->size();
 116     HeapWord* obj_end = obj_addr + obj_size;
 117 
 118     if (_end_of_last_gap != obj_addr) {
 119       // there was a gap before obj_addr
 120       _last_gap_threshold = _hr->cross_threshold(_end_of_last_gap, obj_addr);
 121     }
 122 
 123     if (obj->is_forwarded() && obj->forwardee() == obj) {
 124       // The object failed to move.
 125 
 126       // We consider all objects that we find self-forwarded to be
 127       // live. What we'll do is that we'll update the prev marking
 128       // info so that they are all under PTAMS and explicitly marked.
 129       if (!_cm->isPrevMarked(obj)) {
 130         _cm->markPrev(obj);
 131       }
 132       if (_during_initial_mark) {
 133         // For the next marking info we'll only mark the
 134         // self-forwarded objects explicitly if we are during
 135         // initial-mark (since, normally, we only mark objects pointed
 136         // to by roots if we succeed in copying them). By marking all
 137         // self-forwarded objects we ensure that we mark any that are
 138         // still pointed to be roots. During concurrent marking, and
 139         // after initial-mark, we don't need to mark any objects
 140         // explicitly and all objects in the CSet are considered
 141         // (implicitly) live. So, we won't mark them explicitly and
 142         // we'll leave them over NTAMS.
 143         _cm->grayRoot(obj, obj_size, _worker_id, _hr);
 144       }
 145       _marked_bytes += (obj_size * HeapWordSize);
 146       obj->set_mark(markOopDesc::prototype());
 147 
 148       // While we were processing RSet buffers during the collection,
 149       // we actually didn't scan any cards on the collection set,
 150       // since we didn't want to update remembered sets with entries
 151       // that point into the collection set, given that live objects
 152       // from the collection set are about to move and such entries
 153       // will be stale very soon.
 154       // This change also dealt with a reliability issue which
 155       // involved scanning a card in the collection set and coming
 156       // across an array that was being chunked and looking malformed.
 157       // The problem is that, if evacuation fails, we might have
 158       // remembered set entries missing given that we skipped cards on
 159       // the collection set. So, we'll recreate such entries now.
 160       obj->oop_iterate(_update_rset_cl);
 161     } else {
 162 
 163       // The object has been either evacuated or is dead. Fill it with a
 164       // dummy object.
 165       MemRegion mr(obj_addr, obj_size);
 166       CollectedHeap::fill_with_object(mr);
 167 
 168       // must nuke all dead objects which we skipped when iterating over the region
 169       _cm->clearRangePrevBitmap(MemRegion(_end_of_last_gap, obj_end));
 170     }
 171     _end_of_last_gap = obj_end;
 172     _last_obj_threshold = _hr->cross_threshold(obj_addr, obj_end);
 173   }
 174 };
 175 
 176 class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {
 177   G1CollectedHeap* _g1h;
 178   ConcurrentMark* _cm;
 179   uint _worker_id;
 180   HeapRegionClaimer* _hrclaimer;
 181 
 182   DirtyCardQueue _dcq;
 183   UpdateRSetDeferred _update_rset_cl;
 184 
 185 public:
 186   RemoveSelfForwardPtrHRClosure(G1CollectedHeap* g1h,
 187                                 uint worker_id,
 188                                 HeapRegionClaimer* hrclaimer) :
 189       _g1h(g1h), _dcq(&g1h->dirty_card_queue_set()), _update_rset_cl(g1h, &_dcq),
 190       _worker_id(worker_id), _cm(_g1h->concurrent_mark()), _hrclaimer(hrclaimer) {
 191   }
 192 
 193   bool doHeapRegion(HeapRegion *hr) {
 194     bool during_initial_mark = _g1h->g1_policy()->during_initial_mark_pause();
 195     bool during_conc_mark = _g1h->mark_in_progress();
 196 
 197     assert(!hr->is_humongous(), "sanity");
 198     assert(hr->in_collection_set(), "bad CS");
 199 
 200     if (_hrclaimer->claim_region(hr->hrm_index())) {
 201       if (hr->evacuation_failed()) {
 202         RemoveSelfForwardPtrObjClosure rspc(_g1h, _cm, hr, &_update_rset_cl,
 203                                             during_initial_mark,
 204                                             during_conc_mark,
 205                                             _worker_id);
 206 
 207         hr->note_self_forwarding_removal_start(during_initial_mark,
 208                                                during_conc_mark);
 209         _g1h->check_bitmaps("Self-Forwarding Ptr Removal", hr);
 210 
 211         // In the common case (i.e. when there is no evacuation
 212         // failure) we make sure that the following is done when
 213         // the region is freed so that it is "ready-to-go" when it's
 214         // re-allocated. However, when evacuation failure happens, a
 215         // region will remain in the heap and might ultimately be added
 216         // to a CSet in the future. So we have to be careful here and
 217         // make sure the region's RSet is ready for parallel iteration
 218         // whenever this might be required in the future.
 219         hr->rem_set()->reset_for_par_iteration();
 220         hr->reset_bot();
 221         _update_rset_cl.set_region(hr);
 222         hr->object_iterate(&rspc);
 223 
 224         hr->rem_set()->clean_strong_code_roots(hr);
 225 
 226         hr->note_self_forwarding_removal_end(during_initial_mark,
 227                                              during_conc_mark,
 228                                              rspc.marked_bytes());
 229       }
 230     }
 231     return false;
 232   }
 233 };
 234 
 235 class G1ParRemoveSelfForwardPtrsTask: public AbstractGangTask {
 236 protected:
 237   G1CollectedHeap* _g1h;
 238   HeapRegionClaimer _hrclaimer;
 239 
 240 public:
 241   G1ParRemoveSelfForwardPtrsTask(G1CollectedHeap* g1h) :
 242       AbstractGangTask("G1 Remove Self-forwarding Pointers"), _g1h(g1h),
 243       _hrclaimer(g1h->workers()->active_workers()) {}
 244 
 245   void work(uint worker_id) {
 246     RemoveSelfForwardPtrHRClosure rsfp_cl(_g1h, worker_id, &_hrclaimer);
 247 
 248     HeapRegion* hr = _g1h->start_cset_region_for_worker(worker_id);
 249     _g1h->collection_set_iterate_from(hr, &rsfp_cl);
 250   }
 251 };
 252 
 253 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP