1 /*
   2  * Copyright (c) 2012, 2015, 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 #include "precompiled.hpp"
  26 #include "gc/g1/concurrentMark.inline.hpp"
  27 #include "gc/g1/dirtyCardQueue.hpp"
  28 #include "gc/g1/g1CollectedHeap.inline.hpp"
  29 #include "gc/g1/g1CollectorState.hpp"
  30 #include "gc/g1/g1EvacFailure.hpp"
  31 #include "gc/g1/g1OopClosures.inline.hpp"
  32 #include "gc/g1/g1_globals.hpp"
  33 #include "gc/g1/heapRegion.hpp"
  34 #include "gc/g1/heapRegionRemSet.hpp"
  35 
  36 class UpdateRSetDeferred : public OopsInHeapRegionClosure {
  37 private:
  38   G1CollectedHeap* _g1;
  39   DirtyCardQueue *_dcq;
  40   G1SATBCardTableModRefBS* _ct_bs;
  41 
  42 public:
  43   UpdateRSetDeferred(DirtyCardQueue* dcq) :
  44     _g1(G1CollectedHeap::heap()), _ct_bs(_g1->g1_barrier_set()), _dcq(dcq) {}
  45 
  46   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
  47   virtual void do_oop(      oop* p) { do_oop_work(p); }
  48   template <class T> void do_oop_work(T* p) {
  49     assert(_from->is_in_reserved(p), "paranoia");
  50     assert(!_from->is_survivor(), "Unexpected evac failure in survivor region");
  51 
  52     if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p))) {
  53       size_t card_index = _ct_bs->index_for(p);
  54       if (_ct_bs->mark_card_deferred(card_index)) {
  55         _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));
  56       }
  57     }
  58   }
  59 };
  60 
  61 class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
  62 private:
  63   G1CollectedHeap* _g1;
  64   ConcurrentMark* _cm;
  65   HeapRegion* _hr;
  66   size_t _marked_bytes;
  67   OopsInHeapRegionClosure *_update_rset_cl;
  68   bool _during_initial_mark;
  69   uint _worker_id;
  70   HeapWord* _last_forwarded_object_end;
  71 
  72 public:
  73   RemoveSelfForwardPtrObjClosure(HeapRegion* hr,
  74                                  OopsInHeapRegionClosure* update_rset_cl,
  75                                  bool during_initial_mark,
  76                                  uint worker_id) :
  77     _g1(G1CollectedHeap::heap()),
  78     _cm(_g1->concurrent_mark()),
  79     _hr(hr),
  80     _marked_bytes(0),
  81     _update_rset_cl(update_rset_cl),
  82     _during_initial_mark(during_initial_mark),
  83     _worker_id(worker_id),
  84     _last_forwarded_object_end(hr->bottom()) { }
  85 
  86   size_t marked_bytes() { return _marked_bytes; }
  87 
  88   // Iterate over the live objects in the region to find self-forwarded objects
  89   // that need to be kept live. We need to update the remembered sets of these
  90   // objects. Further update the BOT and marks.
  91   // We can coalesce and overwrite the remaining heap contents with dummy objects
  92   // as they have either been dead or evacuated (which are unreferenced now, i.e.
  93   // dead too) already.
  94   void do_object(oop obj) {
  95     HeapWord* obj_addr = (HeapWord*) obj;
  96     assert(_hr->is_in(obj_addr), "sanity");
  97     size_t obj_size = obj->size();
  98     HeapWord* obj_end = obj_addr + obj_size;
  99 
 100     if (obj->is_forwarded() && obj->forwardee() == obj) {
 101       // The object failed to move.
 102 
 103       zap_dead_objects(_last_forwarded_object_end, obj_addr);
 104       // We consider all objects that we find self-forwarded to be
 105       // live. What we'll do is that we'll update the prev marking
 106       // info so that they are all under PTAMS and explicitly marked.
 107       if (!_cm->isPrevMarked(obj)) {
 108         _cm->markPrev(obj);
 109       }
 110       if (_during_initial_mark) {
 111         // For the next marking info we'll only mark the
 112         // self-forwarded objects explicitly if we are during
 113         // initial-mark (since, normally, we only mark objects pointed
 114         // to by roots if we succeed in copying them). By marking all
 115         // self-forwarded objects we ensure that we mark any that are
 116         // still pointed to be roots. During concurrent marking, and
 117         // after initial-mark, we don't need to mark any objects
 118         // explicitly and all objects in the CSet are considered
 119         // (implicitly) live. So, we won't mark them explicitly and
 120         // we'll leave them over NTAMS.
 121         _cm->grayRoot(obj, obj_size, _worker_id, _hr);
 122       }
 123       _marked_bytes += (obj_size * HeapWordSize);
 124       obj->set_mark(markOopDesc::prototype());
 125 
 126       // While we were processing RSet buffers during the collection,
 127       // we actually didn't scan any cards on the collection set,
 128       // since we didn't want to update remembered sets with entries
 129       // that point into the collection set, given that live objects
 130       // from the collection set are about to move and such entries
 131       // will be stale very soon.
 132       // This change also dealt with a reliability issue which
 133       // involved scanning a card in the collection set and coming
 134       // across an array that was being chunked and looking malformed.
 135       // The problem is that, if evacuation fails, we might have
 136       // remembered set entries missing given that we skipped cards on
 137       // the collection set. So, we'll recreate such entries now.
 138       obj->oop_iterate(_update_rset_cl);
 139 
 140       _last_forwarded_object_end = obj_end;
 141       _hr->cross_threshold(obj_addr, obj_end);
 142     }
 143   }
 144 
 145   // Fill the memory area from start to end with filler objects, and update the BOT
 146   // and the mark bitmap accordingly.
 147   void zap_dead_objects(HeapWord* start, HeapWord* end) {
 148     if (start == end) {
 149       return;
 150     }
 151 
 152     size_t gap_size = pointer_delta(end, start);
 153     MemRegion mr(start, gap_size);
 154     if (gap_size >= CollectedHeap::min_fill_size()) {
 155       CollectedHeap::fill_with_objects(start, gap_size);
 156 
 157       HeapWord* end_first_obj = start + ((oop)start)->size();
 158       _hr->cross_threshold(start, end_first_obj);
 159       // Fill_with_objects() may have created multiple (i.e. two)
 160       // objects, as the max_fill_size() is half a region.
 161       // After updating the BOT for the first object, also update the
 162       // BOT for the second object to make the BOT complete.
 163       if (end_first_obj != end) {
 164         _hr->cross_threshold(end_first_obj, end);
 165 #ifdef ASSERT
 166         size_t size_second_obj = ((oop)end_first_obj)->size();
 167         HeapWord* end_of_second_obj = end_first_obj + size_second_obj;
 168         assert(end == end_of_second_obj,
 169                "More than two objects were used to fill the area from " PTR_FORMAT " to " PTR_FORMAT ", "
 170                "second objects size " SIZE_FORMAT " ends at " PTR_FORMAT,
 171                p2i(start), p2i(end), size_second_obj, p2i(end_of_second_obj));
 172 #endif
 173       }
 174     }
 175     _cm->clearRangePrevBitmap(mr);
 176   }
 177 
 178   void zap_remainder() {
 179     zap_dead_objects(_last_forwarded_object_end, _hr->top());
 180   }
 181 };
 182 
 183 class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {
 184   G1CollectedHeap* _g1h;
 185   uint _worker_id;
 186   HeapRegionClaimer* _hrclaimer;
 187 
 188   DirtyCardQueue _dcq;
 189   UpdateRSetDeferred _update_rset_cl;
 190 
 191 public:
 192   RemoveSelfForwardPtrHRClosure(uint worker_id,
 193                                 HeapRegionClaimer* hrclaimer) :
 194     _g1h(G1CollectedHeap::heap()),
 195     _dcq(&_g1h->dirty_card_queue_set()),
 196     _update_rset_cl(&_dcq),
 197     _worker_id(worker_id),
 198     _hrclaimer(hrclaimer) {
 199   }
 200 
 201   size_t remove_self_forward_ptr_by_walking_hr(HeapRegion* hr,
 202                                                bool during_initial_mark) {
 203     RemoveSelfForwardPtrObjClosure rspc(hr,
 204                                         &_update_rset_cl,
 205                                         during_initial_mark,
 206                                         _worker_id);
 207     _update_rset_cl.set_region(hr);
 208     hr->object_iterate(&rspc);
 209     // Need to zap the remainder area of the processed region.
 210     rspc.zap_remainder();
 211 
 212     return rspc.marked_bytes();
 213   }
 214 
 215   bool doHeapRegion(HeapRegion *hr) {
 216     bool during_initial_mark = _g1h->collector_state()->during_initial_mark_pause();
 217     bool during_conc_mark = _g1h->collector_state()->mark_in_progress();
 218 
 219     assert(!hr->is_pinned(), "Unexpected pinned region at index %u", hr->hrm_index());
 220     assert(hr->in_collection_set(), "bad CS");
 221 
 222     if (_hrclaimer->claim_region(hr->hrm_index())) {
 223       if (hr->evacuation_failed()) {
 224         hr->note_self_forwarding_removal_start(during_initial_mark,
 225                                                during_conc_mark);
 226         _g1h->verifier()->check_bitmaps("Self-Forwarding Ptr Removal", hr);
 227 
 228         // In the common case (i.e. when there is no evacuation
 229         // failure) we make sure that the following is done when
 230         // the region is freed so that it is "ready-to-go" when it's
 231         // re-allocated. However, when evacuation failure happens, a
 232         // region will remain in the heap and might ultimately be added
 233         // to a CSet in the future. So we have to be careful here and
 234         // make sure the region's RSet is ready for parallel iteration
 235         // whenever this might be required in the future.
 236         hr->rem_set()->reset_for_par_iteration();
 237         hr->reset_bot();
 238 
 239         size_t live_bytes = remove_self_forward_ptr_by_walking_hr(hr, during_initial_mark);
 240 
 241         hr->rem_set()->clean_strong_code_roots(hr);
 242 
 243         hr->note_self_forwarding_removal_end(during_initial_mark,
 244                                              during_conc_mark,
 245                                              live_bytes);
 246       }
 247     }
 248     return false;
 249   }
 250 };
 251 
 252 G1ParRemoveSelfForwardPtrsTask::G1ParRemoveSelfForwardPtrsTask() :
 253   AbstractGangTask("G1 Remove Self-forwarding Pointers"),
 254   _g1h(G1CollectedHeap::heap()),
 255   _hrclaimer(_g1h->workers()->active_workers()) { }
 256 
 257 void G1ParRemoveSelfForwardPtrsTask::work(uint worker_id) {
 258   RemoveSelfForwardPtrHRClosure rsfp_cl(worker_id, &_hrclaimer);
 259 
 260   HeapRegion* hr = _g1h->start_cset_region_for_worker(worker_id);
 261   _g1h->collection_set_iterate_from(hr, &rsfp_cl);
 262 }
 263 
 264 G1RestorePreservedMarksTask::G1RestorePreservedMarksTask(OopAndMarkOopStack* preserved_objs) :
 265   AbstractGangTask("G1 Restore Preserved Marks"),
 266   _preserved_objs(preserved_objs) {}
 267 
 268 void G1RestorePreservedMarksTask::work(uint worker_id) {
 269   OopAndMarkOopStack& cur = _preserved_objs[worker_id];
 270   while (!cur.is_empty()) {
 271     OopAndMarkOop elem = cur.pop();
 272     elem.set_mark();
 273   }
 274   cur.clear(true);
 275 }
--- EOF ---