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->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 }