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 "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
75 public:
76 RemoveSelfForwardPtrObjClosure(G1CollectedHeap* g1, ConcurrentMark* cm,
77 HeapRegion* hr,
78 OopsInHeapRegionClosure* update_rset_cl,
79 bool during_initial_mark,
80 bool during_conc_mark,
81 uint worker_id) :
82 _g1(g1), _cm(cm), _hr(hr), _marked_bytes(0),
83 _update_rset_cl(update_rset_cl),
84 _during_initial_mark(during_initial_mark),
85 _during_conc_mark(during_conc_mark),
86 _worker_id(worker_id) { }
87
88 size_t marked_bytes() { return _marked_bytes; }
89
90 // <original comment>
91 // The original idea here was to coalesce evacuated and dead objects.
92 // However that caused complications with the block offset table (BOT).
93 // In particular if there were two TLABs, one of them partially refined.
94 // |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~|
95 // The BOT entries of the unrefined part of TLAB_2 point to the start
96 // of TLAB_2. If the last object of the TLAB_1 and the first object
97 // of TLAB_2 are coalesced, then the cards of the unrefined part
98 // would point into middle of the filler object.
99 // The current approach is to not coalesce and leave the BOT contents intact.
100 // </original comment>
101 //
102 // We now reset the BOT when we start the object iteration over the
103 // region and refine its entries for every object we come across. So
104 // the above comment is not really relevant and we should be able
105 // to coalesce dead objects if we want to.
106 void do_object(oop obj) {
107 HeapWord* obj_addr = (HeapWord*) obj;
108 assert(_hr->is_in(obj_addr), "sanity");
109 size_t obj_size = obj->size();
110 _hr->update_bot_for_object(obj_addr, obj_size);
111
112 if (obj->is_forwarded() && obj->forwardee() == obj) {
113 // The object failed to move.
114
115 // We consider all objects that we find self-forwarded to be
116 // live. What we'll do is that we'll update the prev marking
117 // info so that they are all under PTAMS and explicitly marked.
118 _cm->markPrev(obj);
119 if (_during_initial_mark) {
120 // For the next marking info we'll only mark the
121 // self-forwarded objects explicitly if we are during
122 // initial-mark (since, normally, we only mark objects pointed
123 // to by roots if we succeed in copying them). By marking all
124 // self-forwarded objects we ensure that we mark any that are
125 // still pointed to be roots. During concurrent marking, and
126 // after initial-mark, we don't need to mark any objects
127 // explicitly and all objects in the CSet are considered
128 // (implicitly) live. So, we won't mark them explicitly and
129 // we'll leave them over NTAMS.
130 _cm->grayRoot(obj, obj_size, _worker_id, _hr);
131 }
132 _marked_bytes += (obj_size * HeapWordSize);
133 obj->set_mark(markOopDesc::prototype());
134
135 // While we were processing RSet buffers during the collection,
136 // we actually didn't scan any cards on the collection set,
137 // since we didn't want to update remembered sets with entries
138 // that point into the collection set, given that live objects
139 // from the collection set are about to move and such entries
140 // will be stale very soon.
141 // This change also dealt with a reliability issue which
142 // involved scanning a card in the collection set and coming
143 // across an array that was being chunked and looking malformed.
144 // The problem is that, if evacuation fails, we might have
145 // remembered set entries missing given that we skipped cards on
146 // the collection set. So, we'll recreate such entries now.
147 obj->oop_iterate(_update_rset_cl);
148 assert(_cm->isPrevMarked(obj), "Should be marked!");
149 } else {
150 // The object has been either evacuated or is dead. Fill it with a
151 // dummy object.
152 MemRegion mr((HeapWord*) obj, obj_size);
153 CollectedHeap::fill_with_object(mr);
154 }
155 }
156 };
157
158 class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {
159 G1CollectedHeap* _g1h;
160 ConcurrentMark* _cm;
161 OopsInHeapRegionClosure *_update_rset_cl;
162 uint _worker_id;
163
164 public:
165 RemoveSelfForwardPtrHRClosure(G1CollectedHeap* g1h,
166 OopsInHeapRegionClosure* update_rset_cl,
167 uint worker_id) :
168 _g1h(g1h), _update_rset_cl(update_rset_cl),
169 _worker_id(worker_id), _cm(_g1h->concurrent_mark()) { }
170
171 bool doHeapRegion(HeapRegion *hr) {
172 bool during_initial_mark = _g1h->g1_policy()->during_initial_mark_pause();
173 bool during_conc_mark = _g1h->mark_in_progress();
174
175 assert(!hr->isHumongous(), "sanity");
176 assert(hr->in_collection_set(), "bad CS");
177
178 if (hr->claimHeapRegion(HeapRegion::ParEvacFailureClaimValue)) {
179 if (hr->evacuation_failed()) {
180 RemoveSelfForwardPtrObjClosure rspc(_g1h, _cm, hr, _update_rset_cl,
181 during_initial_mark,
182 during_conc_mark,
183 _worker_id);
184
185 MemRegion mr(hr->bottom(), hr->end());
186 // We'll recreate the prev marking info so we'll first clear
187 // the prev bitmap range for this region. We never mark any
188 // CSet objects explicitly so the next bitmap range should be
189 // cleared anyway.
190 _cm->clearRangePrevBitmap(mr);
191
192 hr->note_self_forwarding_removal_start(during_initial_mark,
193 during_conc_mark);
194 _g1h->check_bitmaps("Self-Forwarding Ptr Removal", hr);
195
196 // In the common case (i.e. when there is no evacuation
197 // failure) we make sure that the following is done when
198 // the region is freed so that it is "ready-to-go" when it's
199 // re-allocated. However, when evacuation failure happens, a
200 // region will remain in the heap and might ultimately be added
201 // to a CSet in the future. So we have to be careful here and
202 // make sure the region's RSet is ready for parallel iteration
203 // whenever this might be required in the future.
204 hr->rem_set()->reset_for_par_iteration();
205 hr->reset_bot();
206 _update_rset_cl->set_region(hr);
207 hr->object_iterate(&rspc);
208
209 hr->note_self_forwarding_removal_end(during_initial_mark,
210 during_conc_mark,
211 rspc.marked_bytes());
212 }
213 }
214 return false;
215 }
216 };
217
218 class G1ParRemoveSelfForwardPtrsTask: public AbstractGangTask {
219 protected:
220 G1CollectedHeap* _g1h;
221
222 public:
223 G1ParRemoveSelfForwardPtrsTask(G1CollectedHeap* g1h) :
224 AbstractGangTask("G1 Remove Self-forwarding Pointers"),
225 _g1h(g1h) { }
226
227 void work(uint worker_id) {
228 UpdateRSetImmediate immediate_update(_g1h->g1_rem_set());
229 DirtyCardQueue dcq(&_g1h->dirty_card_queue_set());
230 UpdateRSetDeferred deferred_update(_g1h, &dcq);
231
232 OopsInHeapRegionClosure *update_rset_cl = &deferred_update;
233 if (!G1DeferredRSUpdate) {
234 update_rset_cl = &immediate_update;
235 }
236
237 RemoveSelfForwardPtrHRClosure rsfp_cl(_g1h, update_rset_cl, worker_id);
238
239 HeapRegion* hr = _g1h->start_cset_region_for_worker(worker_id);
240 _g1h->collection_set_iterate_from(hr, &rsfp_cl);
241 }
242 };
243
244 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP