1/*
2 * Copyright (c) 2012, 2016, 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/dirtyCardQueue.hpp"
27#include "gc/g1/g1CollectedHeap.inline.hpp"
28#include "gc/g1/g1CollectorState.hpp"
29#include "gc/g1/g1ConcurrentMark.inline.hpp"
30#include "gc/g1/g1EvacFailure.hpp"
31#include "gc/g1/g1HeapVerifier.hpp"
32#include "gc/g1/g1OopClosures.inline.hpp"
33#include "gc/g1/g1_globals.hpp"
34#include "gc/g1/heapRegion.hpp"
35#include "gc/g1/heapRegionRemSet.hpp"
36#include "gc/shared/preservedMarks.inline.hpp"
37
38class UpdateRSetDeferred : public OopsInHeapRegionClosure {
39private:
40  G1CollectedHeap* _g1;
41  DirtyCardQueue *_dcq;
42  G1SATBCardTableModRefBS* _ct_bs;
43
44public:
45  UpdateRSetDeferred(DirtyCardQueue* dcq) :
46    _g1(G1CollectedHeap::heap()), _ct_bs(_g1->g1_barrier_set()), _dcq(dcq) {}
47
48  virtual void do_oop(narrowOop* p) { do_oop_work(p); }
49  virtual void do_oop(      oop* p) { do_oop_work(p); }
50  template <class T> void do_oop_work(T* p) {
51    assert(_from->is_in_reserved(p), "paranoia");
52    assert(!_from->is_survivor(), "Unexpected evac failure in survivor region");
53
54    if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p))) {
55      size_t card_index = _ct_bs->index_for(p);
56      if (_ct_bs->mark_card_deferred(card_index)) {
57        _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));
58      }
59    }
60  }
61};
62
63class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
64private:
65  G1CollectedHeap* _g1;
66  G1ConcurrentMark* _cm;
67  HeapRegion* _hr;
68  size_t _marked_bytes;
69  OopsInHeapRegionClosure *_update_rset_cl;
70  bool _during_initial_mark;
71  uint _worker_id;
72  HeapWord* _last_forwarded_object_end;
73
74public:
75  RemoveSelfForwardPtrObjClosure(HeapRegion* hr,
76                                 OopsInHeapRegionClosure* update_rset_cl,
77                                 bool during_initial_mark,
78                                 uint worker_id) :
79    _g1(G1CollectedHeap::heap()),
80    _cm(_g1->concurrent_mark()),
81    _hr(hr),
82    _marked_bytes(0),
83    _update_rset_cl(update_rset_cl),
84    _during_initial_mark(during_initial_mark),
85    _worker_id(worker_id),
86    _last_forwarded_object_end(hr->bottom()) { }
87
88  size_t marked_bytes() { return _marked_bytes; }
89
90  // Iterate over the live objects in the region to find self-forwarded objects
91  // that need to be kept live. We need to update the remembered sets of these
92  // objects. Further update the BOT and marks.
93  // We can coalesce and overwrite the remaining heap contents with dummy objects
94  // as they have either been dead or evacuated (which are unreferenced now, i.e.
95  // dead too) already.
96  void do_object(oop obj) {
97    HeapWord* obj_addr = (HeapWord*) obj;
98    assert(_hr->is_in(obj_addr), "sanity");
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, _hr);
122      }
123      size_t obj_size = obj->size();
124
125      _marked_bytes += (obj_size * HeapWordSize);
126      PreservedMarks::init_forwarded_mark(obj);
127
128      // While we were processing RSet buffers during the collection,
129      // we actually didn't scan any cards on the collection set,
130      // since we didn't want to update remembered sets with entries
131      // that point into the collection set, given that live objects
132      // from the collection set are about to move and such entries
133      // will be stale very soon.
134      // This change also dealt with a reliability issue which
135      // involved scanning a card in the collection set and coming
136      // across an array that was being chunked and looking malformed.
137      // The problem is that, if evacuation fails, we might have
138      // remembered set entries missing given that we skipped cards on
139      // the collection set. So, we'll recreate such entries now.
140      obj->oop_iterate(_update_rset_cl);
141
142      HeapWord* obj_end = obj_addr + obj_size;
143      _last_forwarded_object_end = obj_end;
144      _hr->cross_threshold(obj_addr, obj_end);
145    }
146  }
147
148  // Fill the memory area from start to end with filler objects, and update the BOT
149  // and the mark bitmap accordingly.
150  void zap_dead_objects(HeapWord* start, HeapWord* end) {
151    if (start == end) {
152      return;
153    }
154
155    size_t gap_size = pointer_delta(end, start);
156    MemRegion mr(start, gap_size);
157    if (gap_size >= CollectedHeap::min_fill_size()) {
158      CollectedHeap::fill_with_objects(start, gap_size);
159
160      HeapWord* end_first_obj = start + ((oop)start)->size();
161      _hr->cross_threshold(start, end_first_obj);
162      // Fill_with_objects() may have created multiple (i.e. two)
163      // objects, as the max_fill_size() is half a region.
164      // After updating the BOT for the first object, also update the
165      // BOT for the second object to make the BOT complete.
166      if (end_first_obj != end) {
167        _hr->cross_threshold(end_first_obj, end);
168#ifdef ASSERT
169        size_t size_second_obj = ((oop)end_first_obj)->size();
170        HeapWord* end_of_second_obj = end_first_obj + size_second_obj;
171        assert(end == end_of_second_obj,
172               "More than two objects were used to fill the area from " PTR_FORMAT " to " PTR_FORMAT ", "
173               "second objects size " SIZE_FORMAT " ends at " PTR_FORMAT,
174               p2i(start), p2i(end), size_second_obj, p2i(end_of_second_obj));
175#endif
176      }
177    }
178    _cm->clearRangePrevBitmap(mr);
179  }
180
181  void zap_remainder() {
182    zap_dead_objects(_last_forwarded_object_end, _hr->top());
183  }
184};
185
186class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {
187  G1CollectedHeap* _g1h;
188  uint _worker_id;
189  HeapRegionClaimer* _hrclaimer;
190
191  DirtyCardQueue _dcq;
192  UpdateRSetDeferred _update_rset_cl;
193
194public:
195  RemoveSelfForwardPtrHRClosure(uint worker_id,
196                                HeapRegionClaimer* hrclaimer) :
197    _g1h(G1CollectedHeap::heap()),
198    _dcq(&_g1h->dirty_card_queue_set()),
199    _update_rset_cl(&_dcq),
200    _worker_id(worker_id),
201    _hrclaimer(hrclaimer) {
202  }
203
204  size_t remove_self_forward_ptr_by_walking_hr(HeapRegion* hr,
205                                               bool during_initial_mark) {
206    RemoveSelfForwardPtrObjClosure rspc(hr,
207                                        &_update_rset_cl,
208                                        during_initial_mark,
209                                        _worker_id);
210    _update_rset_cl.set_region(hr);
211    hr->object_iterate(&rspc);
212    // Need to zap the remainder area of the processed region.
213    rspc.zap_remainder();
214
215    return rspc.marked_bytes();
216  }
217
218  bool doHeapRegion(HeapRegion *hr) {
219    bool during_initial_mark = _g1h->collector_state()->during_initial_mark_pause();
220    bool during_conc_mark = _g1h->collector_state()->mark_in_progress();
221
222    assert(!hr->is_pinned(), "Unexpected pinned region at index %u", hr->hrm_index());
223    assert(hr->in_collection_set(), "bad CS");
224
225    if (_hrclaimer->claim_region(hr->hrm_index())) {
226      if (hr->evacuation_failed()) {
227        hr->note_self_forwarding_removal_start(during_initial_mark,
228                                               during_conc_mark);
229        _g1h->verifier()->check_bitmaps("Self-Forwarding Ptr Removal", hr);
230
231        hr->reset_bot();
232
233        size_t live_bytes = remove_self_forward_ptr_by_walking_hr(hr, during_initial_mark);
234
235        hr->rem_set()->clean_strong_code_roots(hr);
236
237        hr->note_self_forwarding_removal_end(during_initial_mark,
238                                             during_conc_mark,
239                                             live_bytes);
240      }
241    }
242    return false;
243  }
244};
245
246G1ParRemoveSelfForwardPtrsTask::G1ParRemoveSelfForwardPtrsTask() :
247  AbstractGangTask("G1 Remove Self-forwarding Pointers"),
248  _g1h(G1CollectedHeap::heap()),
249  _hrclaimer(_g1h->workers()->active_workers()) { }
250
251void G1ParRemoveSelfForwardPtrsTask::work(uint worker_id) {
252  RemoveSelfForwardPtrHRClosure rsfp_cl(worker_id, &_hrclaimer);
253
254  _g1h->collection_set_iterate_from(&rsfp_cl, worker_id);
255}
256