1 /*
   2  * Copyright (c) 2012, 2019, 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/g1CollectedHeap.inline.hpp"
  27 #include "gc/g1/g1CollectorState.hpp"
  28 #include "gc/g1/g1ConcurrentMark.inline.hpp"
  29 #include "gc/g1/g1EvacFailure.hpp"
  30 #include "gc/g1/g1HeapVerifier.hpp"
  31 #include "gc/g1/g1OopClosures.inline.hpp"
  32 #include "gc/g1/g1RedirtyCardsQueue.hpp"
  33 #include "gc/g1/heapRegion.hpp"
  34 #include "gc/g1/heapRegionRemSet.hpp"
  35 #include "gc/shared/preservedMarks.inline.hpp"
  36 #include "oops/access.inline.hpp"
  37 #include "oops/compressedOops.inline.hpp"
  38 #include "oops/oop.inline.hpp"
  39 
  40 class UpdateLogBuffersDeferred : public BasicOopIterateClosure {
  41 private:
  42   G1CollectedHeap* _g1h;
  43   G1RedirtyCardsQueue* _rdcq;
  44   G1CardTable*    _ct;
  45 
  46   // Remember the last enqueued card to avoid enqueuing the same card over and over;
  47   // since we only ever handle a card once, this is sufficient.
  48   size_t _last_enqueued_card;
  49 
  50 public:
  51   UpdateLogBuffersDeferred(G1RedirtyCardsQueue* rdcq) :
  52     _g1h(G1CollectedHeap::heap()), _rdcq(rdcq), _ct(_g1h->card_table()), _last_enqueued_card(SIZE_MAX) {}
  53 
  54   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
  55   virtual void do_oop(      oop* p) { do_oop_work(p); }
  56   template <class T> void do_oop_work(T* p) {
  57     assert(_g1h->heap_region_containing(p)->is_in_reserved(p), "paranoia");
  58     assert(!_g1h->heap_region_containing(p)->is_survivor(), "Unexpected evac failure in survivor region");
  59 
  60     T const o = RawAccess<>::oop_load(p);
  61     if (CompressedOops::is_null(o)) {
  62       return;
  63     }
  64 
  65     if (HeapRegion::is_in_same_region(p, CompressedOops::decode(o))) {
  66       return;
  67     }
  68     size_t card_index = _ct->index_for(p);
  69     if (card_index != _last_enqueued_card) {
  70       _rdcq->enqueue(_ct->byte_for_index(card_index));
  71       _last_enqueued_card = card_index;
  72     }
  73   }
  74 };
  75 
  76 class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
  77   G1CollectedHeap* _g1h;
  78   G1ConcurrentMark* _cm;
  79   HeapRegion* _hr;
  80   size_t _marked_bytes;
  81   UpdateLogBuffersDeferred* _log_buffer_cl;
  82   bool _during_initial_mark;
  83   uint _worker_id;
  84   HeapWord* _last_forwarded_object_end;
  85 
  86 public:
  87   RemoveSelfForwardPtrObjClosure(HeapRegion* hr,
  88                                  UpdateLogBuffersDeferred* log_buffer_cl,
  89                                  bool during_initial_mark,
  90                                  uint worker_id) :
  91     _g1h(G1CollectedHeap::heap()),
  92     _cm(_g1h->concurrent_mark()),
  93     _hr(hr),
  94     _marked_bytes(0),
  95     _log_buffer_cl(log_buffer_cl),
  96     _during_initial_mark(during_initial_mark),
  97     _worker_id(worker_id),
  98     _last_forwarded_object_end(hr->bottom()) { }
  99 
 100   size_t marked_bytes() { return _marked_bytes; }
 101 
 102   // Iterate over the live objects in the region to find self-forwarded objects
 103   // that need to be kept live. We need to update the remembered sets of these
 104   // objects. Further update the BOT and marks.
 105   // We can coalesce and overwrite the remaining heap contents with dummy objects
 106   // as they have either been dead or evacuated (which are unreferenced now, i.e.
 107   // dead too) already.
 108   void do_object(oop obj) {
 109     HeapWord* obj_addr = (HeapWord*) obj;
 110     assert(_hr->is_in(obj_addr), "sanity");
 111 
 112     if (obj->is_forwarded() && obj->forwardee() == obj) {
 113       // The object failed to move.
 114 
 115       zap_dead_objects(_last_forwarded_object_end, obj_addr);
 116       // We consider all objects that we find self-forwarded to be
 117       // live. What we'll do is that we'll update the prev marking
 118       // info so that they are all under PTAMS and explicitly marked.
 119       if (!_cm->is_marked_in_prev_bitmap(obj)) {
 120         _cm->mark_in_prev_bitmap(obj);
 121       }
 122       if (_during_initial_mark) {
 123         // For the next marking info we'll only mark the
 124         // self-forwarded objects explicitly if we are during
 125         // initial-mark (since, normally, we only mark objects pointed
 126         // to by roots if we succeed in copying them). By marking all
 127         // self-forwarded objects we ensure that we mark any that are
 128         // still pointed to be roots. During concurrent marking, and
 129         // after initial-mark, we don't need to mark any objects
 130         // explicitly and all objects in the CSet are considered
 131         // (implicitly) live. So, we won't mark them explicitly and
 132         // we'll leave them over NTAMS.
 133         _cm->mark_in_next_bitmap(_worker_id, _hr, obj);
 134       }
 135       size_t obj_size = obj->size();
 136 
 137       _marked_bytes += (obj_size * HeapWordSize);
 138       PreservedMarks::init_forwarded_mark(obj);
 139 
 140       // While we were processing RSet buffers during the collection,
 141       // we actually didn't scan any cards on the collection set,
 142       // since we didn't want to update remembered sets with entries
 143       // that point into the collection set, given that live objects
 144       // from the collection set are about to move and such entries
 145       // will be stale very soon.
 146       // This change also dealt with a reliability issue which
 147       // involved scanning a card in the collection set and coming
 148       // across an array that was being chunked and looking malformed.
 149       // The problem is that, if evacuation fails, we might have
 150       // remembered set entries missing given that we skipped cards on
 151       // the collection set. So, we'll recreate such entries now.
 152       obj->oop_iterate(_log_buffer_cl);
 153 
 154       HeapWord* obj_end = obj_addr + obj_size;
 155       _last_forwarded_object_end = obj_end;
 156       _hr->cross_threshold(obj_addr, obj_end);
 157     }
 158   }
 159 
 160   // Fill the memory area from start to end with filler objects, and update the BOT
 161   // and the mark bitmap accordingly.
 162   void zap_dead_objects(HeapWord* start, HeapWord* end) {
 163     if (start == end) {
 164       return;
 165     }
 166 
 167     size_t gap_size = pointer_delta(end, start);
 168     MemRegion mr(start, gap_size);
 169     if (gap_size >= CollectedHeap::min_fill_size()) {
 170       CollectedHeap::fill_with_objects(start, gap_size);
 171 
 172       HeapWord* end_first_obj = start + ((oop)start)->size();
 173       _hr->cross_threshold(start, end_first_obj);
 174       // Fill_with_objects() may have created multiple (i.e. two)
 175       // objects, as the max_fill_size() is half a region.
 176       // After updating the BOT for the first object, also update the
 177       // BOT for the second object to make the BOT complete.
 178       if (end_first_obj != end) {
 179         _hr->cross_threshold(end_first_obj, end);
 180 #ifdef ASSERT
 181         size_t size_second_obj = ((oop)end_first_obj)->size();
 182         HeapWord* end_of_second_obj = end_first_obj + size_second_obj;
 183         assert(end == end_of_second_obj,
 184                "More than two objects were used to fill the area from " PTR_FORMAT " to " PTR_FORMAT ", "
 185                "second objects size " SIZE_FORMAT " ends at " PTR_FORMAT,
 186                p2i(start), p2i(end), size_second_obj, p2i(end_of_second_obj));
 187 #endif
 188       }
 189     }
 190     _cm->clear_range_in_prev_bitmap(mr);
 191   }
 192 
 193   void zap_remainder() {
 194     zap_dead_objects(_last_forwarded_object_end, _hr->top());
 195   }
 196 };
 197 
 198 class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {
 199   G1CollectedHeap* _g1h;
 200   uint _worker_id;
 201 
 202   G1RedirtyCardsQueue _rdcq;
 203   UpdateLogBuffersDeferred _log_buffer_cl;
 204 
 205 public:
 206   RemoveSelfForwardPtrHRClosure(G1RedirtyCardsQueueSet* rdcqs, uint worker_id) :
 207     _g1h(G1CollectedHeap::heap()),
 208     _worker_id(worker_id),
 209     _rdcq(rdcqs),
 210     _log_buffer_cl(&_rdcq) {
 211   }
 212 
 213   size_t remove_self_forward_ptr_by_walking_hr(HeapRegion* hr,
 214                                                bool during_initial_mark) {
 215     RemoveSelfForwardPtrObjClosure rspc(hr,
 216                                         &_log_buffer_cl,
 217                                         during_initial_mark,
 218                                         _worker_id);
 219     hr->object_iterate(&rspc);
 220     // Need to zap the remainder area of the processed region.
 221     rspc.zap_remainder();
 222 
 223     return rspc.marked_bytes();
 224   }
 225 
 226   bool do_heap_region(HeapRegion *hr) {
 227     assert(!hr->is_pinned(), "Unexpected pinned region at index %u", hr->hrm_index());
 228     assert(hr->in_collection_set(), "bad CS");
 229 
 230     if (hr->evacuation_failed()) {
 231       hr->clear_index_in_opt_cset();
 232 
 233       bool during_initial_mark = _g1h->collector_state()->in_initial_mark_gc();
 234       bool during_conc_mark = _g1h->collector_state()->mark_or_rebuild_in_progress();
 235 
 236       hr->note_self_forwarding_removal_start(during_initial_mark,
 237                                                during_conc_mark);
 238       _g1h->verifier()->check_bitmaps("Self-Forwarding Ptr Removal", hr);
 239 
 240       hr->reset_bot();
 241 
 242       size_t live_bytes = remove_self_forward_ptr_by_walking_hr(hr, during_initial_mark);
 243 
 244       hr->rem_set()->clean_strong_code_roots(hr);
 245       hr->rem_set()->clear_locked(true);
 246 
 247       hr->note_self_forwarding_removal_end(live_bytes);
 248     }
 249     return false;
 250   }
 251 };
 252 
 253 G1ParRemoveSelfForwardPtrsTask::G1ParRemoveSelfForwardPtrsTask(G1RedirtyCardsQueueSet* rdcqs) :
 254   AbstractGangTask("G1 Remove Self-forwarding Pointers"),
 255   _g1h(G1CollectedHeap::heap()),
 256   _rdcqs(rdcqs),
 257   _hrclaimer(_g1h->workers()->active_workers()) { }
 258 
 259 void G1ParRemoveSelfForwardPtrsTask::work(uint worker_id) {
 260   RemoveSelfForwardPtrHRClosure rsfp_cl(_rdcqs, worker_id);
 261 
 262   _g1h->collection_set_iterate_increment_from(&rsfp_cl, &_hrclaimer, worker_id);
 263 }