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.
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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 "oops/markOop.inline.hpp"
36 #include "utilities/workgroup.hpp"
37
38 // Closures and tasks associated with any self-forwarding pointers
39 // installed as a result of an evacuation failure.
40
41 class UpdateRSetDeferred : public OopsInHeapRegionClosure {
42 private:
43 G1CollectedHeap* _g1;
44 DirtyCardQueue *_dcq;
45 G1SATBCardTableModRefBS* _ct_bs;
46
47 public:
48 UpdateRSetDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) :
49 _g1(g1), _ct_bs(_g1->g1_barrier_set()), _dcq(dcq) {}
50
51 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
52 virtual void do_oop( oop* p) { do_oop_work(p); }
53 template <class T> void do_oop_work(T* p) {
54 assert(_from->is_in_reserved(p), "paranoia");
55 if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) &&
56 !_from->is_survivor()) {
57 size_t card_index = _ct_bs->index_for(p);
58 if (_ct_bs->mark_card_deferred(card_index)) {
59 _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));
60 }
61 }
62 }
63 };
64
65 class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
66 private:
67 G1CollectedHeap* _g1;
68 ConcurrentMark* _cm;
69 HeapRegion* _hr;
70 size_t _marked_bytes;
71 OopsInHeapRegionClosure *_update_rset_cl;
72 bool _during_initial_mark;
73 bool _during_conc_mark;
74 uint _worker_id;
75 HeapWord* _end_of_last_gap;
76 HeapWord* _last_gap_threshold;
77 HeapWord* _last_obj_threshold;
78
79 public:
80 RemoveSelfForwardPtrObjClosure(G1CollectedHeap* g1, ConcurrentMark* cm,
81 HeapRegion* hr,
82 OopsInHeapRegionClosure* update_rset_cl,
83 bool during_initial_mark,
84 bool during_conc_mark,
85 uint worker_id) :
86 _g1(g1), _cm(cm), _hr(hr), _marked_bytes(0),
87 _update_rset_cl(update_rset_cl),
88 _during_initial_mark(during_initial_mark),
89 _during_conc_mark(during_conc_mark),
90 _worker_id(worker_id),
91 _end_of_last_gap(hr->bottom()),
92 _last_gap_threshold(hr->bottom()),
93 _last_obj_threshold(hr->bottom()) { }
94
95 size_t marked_bytes() { return _marked_bytes; }
96
97 // <original comment>
98 // The original idea here was to coalesce evacuated and dead objects.
99 // However that caused complications with the block offset table (BOT).
100 // In particular if there were two TLABs, one of them partially refined.
101 // |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~|
102 // The BOT entries of the unrefined part of TLAB_2 point to the start
103 // of TLAB_2. If the last object of the TLAB_1 and the first object
104 // of TLAB_2 are coalesced, then the cards of the unrefined part
105 // would point into middle of the filler object.
106 // The current approach is to not coalesce and leave the BOT contents intact.
107 // </original comment>
108 //
109 // We now reset the BOT when we start the object iteration over the
110 // region and refine its entries for every object we come across. So
111 // the above comment is not really relevant and we should be able
112 // to coalesce dead objects if we want to.
113 void do_object(oop obj) {
114 HeapWord* obj_addr = (HeapWord*) obj;
115 assert(_hr->is_in(obj_addr), "sanity");
116 size_t obj_size = obj->size();
117 HeapWord* obj_end = obj_addr + obj_size;
118
119 if (_end_of_last_gap != obj_addr) {
120 // there was a gap before obj_addr
121 _last_gap_threshold = _hr->cross_threshold(_end_of_last_gap, obj_addr);
122 }
123
124 markOop m = obj->mark();
125 if (m->is_marked() && ((oop)m->decode_pointer() == obj)) {
126
127 // The object failed to move.
128
129 // We consider all objects that we find self-forwarded to be
130 // live. What we'll do is that we'll update the prev marking
131 // info so that they are all under PTAMS and explicitly marked.
132 if (!_cm->isPrevMarked(obj)) {
133 _cm->markPrev(obj);
134 }
135 if (_during_initial_mark) {
136 // For the next marking info we'll only mark the
137 // self-forwarded objects explicitly if we are during
138 // initial-mark (since, normally, we only mark objects pointed
139 // to by roots if we succeed in copying them). By marking all
140 // self-forwarded objects we ensure that we mark any that are
141 // still pointed to be roots. During concurrent marking, and
142 // after initial-mark, we don't need to mark any objects
143 // explicitly and all objects in the CSet are considered
144 // (implicitly) live. So, we won't mark them explicitly and
145 // we'll leave them over NTAMS.
146 _cm->grayRoot(obj, obj_size, _worker_id, _hr);
147 }
148 _marked_bytes += (obj_size * HeapWordSize);
149 obj->set_mark(markOopDesc::prototype());
150
151 // While we were processing RSet buffers during the collection,
152 // we actually didn't scan any cards on the collection set,
153 // since we didn't want to update remembered sets with entries
154 // that point into the collection set, given that live objects
155 // from the collection set are about to move and such entries
156 // will be stale very soon.
157 // This change also dealt with a reliability issue which
158 // involved scanning a card in the collection set and coming
159 // across an array that was being chunked and looking malformed.
160 // The problem is that, if evacuation fails, we might have
161 // remembered set entries missing given that we skipped cards on
162 // the collection set. So, we'll recreate such entries now.
163 obj->oop_iterate(_update_rset_cl);
164 } else {
165
166 // The object has been either evacuated or is dead. Fill it with a
167 // dummy object.
168 MemRegion mr(obj_addr, obj_size);
169 CollectedHeap::fill_with_object(mr);
170
171 // must nuke all dead objects which we skipped when iterating over the region
172 _cm->clearRangePrevBitmap(MemRegion(_end_of_last_gap, obj_end));
173 }
174 _end_of_last_gap = obj_end;
175 _last_obj_threshold = _hr->cross_threshold(obj_addr, obj_end);
176 }
177 };
178
179 class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {
180 G1CollectedHeap* _g1h;
181 ConcurrentMark* _cm;
182 uint _worker_id;
183 HeapRegionClaimer* _hrclaimer;
184
185 DirtyCardQueue _dcq;
186 UpdateRSetDeferred _update_rset_cl;
187
188 public:
189 RemoveSelfForwardPtrHRClosure(G1CollectedHeap* g1h,
190 uint worker_id,
191 HeapRegionClaimer* hrclaimer) :
192 _g1h(g1h), _dcq(&g1h->dirty_card_queue_set()), _update_rset_cl(g1h, &_dcq),
193 _worker_id(worker_id), _cm(_g1h->concurrent_mark()), _hrclaimer(hrclaimer) {
194 }
195
196 bool doHeapRegion(HeapRegion *hr) {
197 bool during_initial_mark = _g1h->g1_policy()->during_initial_mark_pause();
198 bool during_conc_mark = _g1h->mark_in_progress();
199
200 assert(!hr->is_humongous(), "sanity");
201 assert(hr->in_collection_set(), "bad CS");
202
203 if (_hrclaimer->claim_region(hr->hrm_index())) {
204 if (hr->evacuation_failed()) {
205 RemoveSelfForwardPtrObjClosure rspc(_g1h, _cm, hr, &_update_rset_cl,
206 during_initial_mark,
207 during_conc_mark,
208 _worker_id);
209
210 hr->note_self_forwarding_removal_start(during_initial_mark,
211 during_conc_mark);
212 _g1h->check_bitmaps("Self-Forwarding Ptr Removal", hr);
213
214 // In the common case (i.e. when there is no evacuation
215 // failure) we make sure that the following is done when
216 // the region is freed so that it is "ready-to-go" when it's
217 // re-allocated. However, when evacuation failure happens, a
218 // region will remain in the heap and might ultimately be added
219 // to a CSet in the future. So we have to be careful here and
220 // make sure the region's RSet is ready for parallel iteration
221 // whenever this might be required in the future.
222 hr->rem_set()->reset_for_par_iteration();
223 hr->reset_bot();
224 _update_rset_cl.set_region(hr);
225 hr->object_iterate(&rspc);
226
227 hr->rem_set()->clean_strong_code_roots(hr);
228
229 hr->note_self_forwarding_removal_end(during_initial_mark,
230 during_conc_mark,
231 rspc.marked_bytes());
232 }
233 }
234 return false;
235 }
236 };
237
238 class G1ParRemoveSelfForwardPtrsTask: public AbstractGangTask {
239 protected:
240 G1CollectedHeap* _g1h;
241 HeapRegionClaimer _hrclaimer;
242
243 public:
244 G1ParRemoveSelfForwardPtrsTask(G1CollectedHeap* g1h) :
245 AbstractGangTask("G1 Remove Self-forwarding Pointers"), _g1h(g1h),
246 _hrclaimer(g1h->workers()->active_workers()) {}
247
248 void work(uint worker_id) {
249 RemoveSelfForwardPtrHRClosure rsfp_cl(_g1h, worker_id, &_hrclaimer);
250
251 HeapRegion* hr = _g1h->start_cset_region_for_worker(worker_id);
252 _g1h->collection_set_iterate_from(hr, &rsfp_cl);
253 }
254 };
255
256 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP