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
37 class UpdateRSetDeferred : public OopsInHeapRegionClosure {
38 private:
39 G1CollectedHeap* _g1;
40 DirtyCardQueue *_dcq;
41 G1SATBCardTableModRefBS* _ct_bs;
42
43 public:
44 UpdateRSetDeferred(DirtyCardQueue* dcq) :
45 _g1(G1CollectedHeap::heap()), _ct_bs(_g1->g1_barrier_set()), _dcq(dcq) {}
46
47 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
48 virtual void do_oop( oop* p) { do_oop_work(p); }
49 template <class T> void do_oop_work(T* p) {
50 assert(_from->is_in_reserved(p), "paranoia");
51 assert(!_from->is_survivor(), "Unexpected evac failure in survivor region");
52
53 if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p))) {
54 size_t card_index = _ct_bs->index_for(p);
55 if (_ct_bs->mark_card_deferred(card_index)) {
56 _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));
57 }
58 }
59 }
60 };
61
62 class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
63 private:
64 G1CollectedHeap* _g1;
65 G1ConcurrentMark* _cm;
66 HeapRegion* _hr;
67 size_t _marked_bytes;
68 OopsInHeapRegionClosure *_update_rset_cl;
69 bool _during_initial_mark;
70 uint _worker_id;
71 HeapWord* _last_forwarded_object_end;
72
73 public:
74 RemoveSelfForwardPtrObjClosure(HeapRegion* hr,
75 OopsInHeapRegionClosure* update_rset_cl,
76 bool during_initial_mark,
77 uint worker_id) :
78 _g1(G1CollectedHeap::heap()),
79 _cm(_g1->concurrent_mark()),
80 _hr(hr),
81 _marked_bytes(0),
82 _update_rset_cl(update_rset_cl),
83 _during_initial_mark(during_initial_mark),
84 _worker_id(worker_id),
85 _last_forwarded_object_end(hr->bottom()) { }
86
87 size_t marked_bytes() { return _marked_bytes; }
88
89 // Iterate over the live objects in the region to find self-forwarded objects
90 // that need to be kept live. We need to update the remembered sets of these
91 // objects. Further update the BOT and marks.
92 // We can coalesce and overwrite the remaining heap contents with dummy objects
93 // as they have either been dead or evacuated (which are unreferenced now, i.e.
94 // dead too) already.
95 void do_object(oop obj) {
96 HeapWord* obj_addr = (HeapWord*) obj;
97 assert(_hr->is_in(obj_addr), "sanity");
98
99 if (obj->is_forwarded() && obj->forwardee() == obj) {
100 // The object failed to move.
101
102 zap_dead_objects(_last_forwarded_object_end, obj_addr);
103 // We consider all objects that we find self-forwarded to be
104 // live. What we'll do is that we'll update the prev marking
105 // info so that they are all under PTAMS and explicitly marked.
106 if (!_cm->isPrevMarked(obj)) {
107 _cm->markPrev(obj);
108 }
109 if (_during_initial_mark) {
110 // For the next marking info we'll only mark the
111 // self-forwarded objects explicitly if we are during
112 // initial-mark (since, normally, we only mark objects pointed
113 // to by roots if we succeed in copying them). By marking all
114 // self-forwarded objects we ensure that we mark any that are
115 // still pointed to be roots. During concurrent marking, and
116 // after initial-mark, we don't need to mark any objects
117 // explicitly and all objects in the CSet are considered
118 // (implicitly) live. So, we won't mark them explicitly and
119 // we'll leave them over NTAMS.
120 _cm->grayRoot(obj, _hr);
121 }
122 size_t obj_size = obj->size();
123
124 _marked_bytes += (obj_size * HeapWordSize);
125 obj->set_mark(markOopDesc::prototype());
126
127 // While we were processing RSet buffers during the collection,
128 // we actually didn't scan any cards on the collection set,
129 // since we didn't want to update remembered sets with entries
130 // that point into the collection set, given that live objects
131 // from the collection set are about to move and such entries
132 // will be stale very soon.
133 // This change also dealt with a reliability issue which
134 // involved scanning a card in the collection set and coming
135 // across an array that was being chunked and looking malformed.
136 // The problem is that, if evacuation fails, we might have
137 // remembered set entries missing given that we skipped cards on
138 // the collection set. So, we'll recreate such entries now.
139 obj->oop_iterate(_update_rset_cl);
140
141 HeapWord* obj_end = obj_addr + obj_size;
142 _last_forwarded_object_end = obj_end;
143 _hr->cross_threshold(obj_addr, obj_end);
144 }
145 }
146
147 // Fill the memory area from start to end with filler objects, and update the BOT
148 // and the mark bitmap accordingly.
149 void zap_dead_objects(HeapWord* start, HeapWord* end) {
150 if (start == end) {
151 return;
152 }
153
154 size_t gap_size = pointer_delta(end, start);
155 MemRegion mr(start, gap_size);
156 if (gap_size >= CollectedHeap::min_fill_size()) {
157 CollectedHeap::fill_with_objects(start, gap_size);
158
159 HeapWord* end_first_obj = start + ((oop)start)->size();
160 _hr->cross_threshold(start, end_first_obj);
161 // Fill_with_objects() may have created multiple (i.e. two)
162 // objects, as the max_fill_size() is half a region.
163 // After updating the BOT for the first object, also update the
164 // BOT for the second object to make the BOT complete.
165 if (end_first_obj != end) {
166 _hr->cross_threshold(end_first_obj, end);
167 #ifdef ASSERT
168 size_t size_second_obj = ((oop)end_first_obj)->size();
169 HeapWord* end_of_second_obj = end_first_obj + size_second_obj;
170 assert(end == end_of_second_obj,
171 "More than two objects were used to fill the area from " PTR_FORMAT " to " PTR_FORMAT ", "
172 "second objects size " SIZE_FORMAT " ends at " PTR_FORMAT,
173 p2i(start), p2i(end), size_second_obj, p2i(end_of_second_obj));
174 #endif
175 }
176 }
177 _cm->clearRangePrevBitmap(mr);
178 }
179
180 void zap_remainder() {
181 zap_dead_objects(_last_forwarded_object_end, _hr->top());
182 }
183 };
184
185 class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {
186 G1CollectedHeap* _g1h;
187 uint _worker_id;
188 HeapRegionClaimer* _hrclaimer;
189
190 DirtyCardQueue _dcq;
191 UpdateRSetDeferred _update_rset_cl;
192
193 public:
194 RemoveSelfForwardPtrHRClosure(uint worker_id,
195 HeapRegionClaimer* hrclaimer) :
196 _g1h(G1CollectedHeap::heap()),
197 _dcq(&_g1h->dirty_card_queue_set()),
198 _update_rset_cl(&_dcq),
199 _worker_id(worker_id),
200 _hrclaimer(hrclaimer) {
201 }
202
203 size_t remove_self_forward_ptr_by_walking_hr(HeapRegion* hr,
204 bool during_initial_mark) {
205 RemoveSelfForwardPtrObjClosure rspc(hr,
206 &_update_rset_cl,
207 during_initial_mark,
208 _worker_id);
209 _update_rset_cl.set_region(hr);
210 hr->object_iterate(&rspc);
211 // Need to zap the remainder area of the processed region.
212 rspc.zap_remainder();
213
214 return rspc.marked_bytes();
215 }
216
217 bool doHeapRegion(HeapRegion *hr) {
218 bool during_initial_mark = _g1h->collector_state()->during_initial_mark_pause();
219 bool during_conc_mark = _g1h->collector_state()->mark_in_progress();
220
221 assert(!hr->is_pinned(), "Unexpected pinned region at index %u", hr->hrm_index());
222 assert(hr->in_collection_set(), "bad CS");
223
224 if (_hrclaimer->claim_region(hr->hrm_index())) {
225 if (hr->evacuation_failed()) {
226 hr->note_self_forwarding_removal_start(during_initial_mark,
227 during_conc_mark);
228 _g1h->verifier()->check_bitmaps("Self-Forwarding Ptr Removal", hr);
229
230 // In the common case (i.e. when there is no evacuation
231 // failure) we make sure that the following is done when
232 // the region is freed so that it is "ready-to-go" when it's
233 // re-allocated. However, when evacuation failure happens, a
234 // region will remain in the heap and might ultimately be added
235 // to a CSet in the future. So we have to be careful here and
236 // make sure the region's RSet is ready for parallel iteration
237 // whenever this might be required in the future.
238 hr->rem_set()->reset_for_par_iteration();
239 hr->reset_bot();
240
241 size_t live_bytes = remove_self_forward_ptr_by_walking_hr(hr, during_initial_mark);
242
243 hr->rem_set()->clean_strong_code_roots(hr);
244
245 hr->note_self_forwarding_removal_end(during_initial_mark,
246 during_conc_mark,
247 live_bytes);
248 }
249 }
250 return false;
251 }
252 };
253
254 G1ParRemoveSelfForwardPtrsTask::G1ParRemoveSelfForwardPtrsTask() :
255 AbstractGangTask("G1 Remove Self-forwarding Pointers"),
256 _g1h(G1CollectedHeap::heap()),
257 _hrclaimer(_g1h->workers()->active_workers()) { }
258
259 void G1ParRemoveSelfForwardPtrsTask::work(uint worker_id) {
260 RemoveSelfForwardPtrHRClosure rsfp_cl(worker_id, &_hrclaimer);
261
262 HeapRegion* hr = _g1h->start_cset_region_for_worker(worker_id);
263 _g1h->collection_set_iterate_from(hr, &rsfp_cl);
264 }
265
266 G1RestorePreservedMarksTask::G1RestorePreservedMarksTask(OopAndMarkOopStack* preserved_objs) :
267 AbstractGangTask("G1 Restore Preserved Marks"),
268 _preserved_objs(preserved_objs) {}
269
270 void G1RestorePreservedMarksTask::work(uint worker_id) {
271 OopAndMarkOopStack& cur = _preserved_objs[worker_id];
272 while (!cur.is_empty()) {
273 OopAndMarkOop elem = cur.pop();
274 elem.set_mark();
275 }
276 cur.clear(true);
277 }