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
38 class UpdateRSetDeferred : public ExtendedOopClosure {
39 private:
40 G1CollectedHeap* _g1;
41 DirtyCardQueue *_dcq;
42 G1SATBCardTableModRefBS* _ct_bs;
43 HeapRegion* _from;
44
45 public:
46 UpdateRSetDeferred(DirtyCardQueue* dcq) :
47 _g1(G1CollectedHeap::heap()), _ct_bs(_g1->g1_barrier_set()), _dcq(dcq), _from(NULL) {}
48
49 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
50 virtual void do_oop( oop* p) { do_oop_work(p); }
51 template <class T> void do_oop_work(T* p) {
52 assert(_from->is_in_reserved(p), "paranoia");
53 assert(!_from->is_survivor(), "Unexpected evac failure in survivor region");
54
55 if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p))) {
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 void set_region(HeapRegion* from) { _from = from; }
64 };
65
66 class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
67 private:
68 G1CollectedHeap* _g1;
69 G1ConcurrentMark* _cm;
70 HeapRegion* _hr;
71 size_t _marked_bytes;
72 UpdateRSetDeferred* _update_rset_cl;
73 bool _during_initial_mark;
74 uint _worker_id;
75 HeapWord* _last_forwarded_object_end;
76
77 public:
78 RemoveSelfForwardPtrObjClosure(HeapRegion* hr,
79 UpdateRSetDeferred* update_rset_cl,
80 bool during_initial_mark,
81 uint worker_id) :
82 _g1(G1CollectedHeap::heap()),
83 _cm(_g1->concurrent_mark()),
84 _hr(hr),
85 _marked_bytes(0),
86 _update_rset_cl(update_rset_cl),
87 _during_initial_mark(during_initial_mark),
88 _worker_id(worker_id),
89 _last_forwarded_object_end(hr->bottom()) { }
90
91 size_t marked_bytes() { return _marked_bytes; }
92
93 // Iterate over the live objects in the region to find self-forwarded objects
94 // that need to be kept live. We need to update the remembered sets of these
95 // objects. Further update the BOT and marks.
96 // We can coalesce and overwrite the remaining heap contents with dummy objects
97 // as they have either been dead or evacuated (which are unreferenced now, i.e.
98 // dead too) already.
99 void do_object(oop obj) {
100 HeapWord* obj_addr = (HeapWord*) obj;
101 assert(_hr->is_in(obj_addr), "sanity");
102
103 if (obj->is_forwarded() && obj->forwardee() == obj) {
104 // The object failed to move.
105
106 zap_dead_objects(_last_forwarded_object_end, obj_addr);
107 // We consider all objects that we find self-forwarded to be
108 // live. What we'll do is that we'll update the prev marking
109 // info so that they are all under PTAMS and explicitly marked.
110 if (!_cm->isPrevMarked(obj)) {
111 _cm->markPrev(obj);
112 }
113 if (_during_initial_mark) {
114 // For the next marking info we'll only mark the
115 // self-forwarded objects explicitly if we are during
116 // initial-mark (since, normally, we only mark objects pointed
117 // to by roots if we succeed in copying them). By marking all
118 // self-forwarded objects we ensure that we mark any that are
119 // still pointed to be roots. During concurrent marking, and
120 // after initial-mark, we don't need to mark any objects
121 // explicitly and all objects in the CSet are considered
122 // (implicitly) live. So, we won't mark them explicitly and
123 // we'll leave them over NTAMS.
124 _cm->grayRoot(obj, _hr);
125 }
126 size_t obj_size = obj->size();
127
128 _marked_bytes += (obj_size * HeapWordSize);
129 PreservedMarks::init_forwarded_mark(obj);
130
131 // While we were processing RSet buffers during the collection,
132 // we actually didn't scan any cards on the collection set,
133 // since we didn't want to update remembered sets with entries
134 // that point into the collection set, given that live objects
135 // from the collection set are about to move and such entries
136 // will be stale very soon.
137 // This change also dealt with a reliability issue which
138 // involved scanning a card in the collection set and coming
139 // across an array that was being chunked and looking malformed.
140 // The problem is that, if evacuation fails, we might have
141 // remembered set entries missing given that we skipped cards on
142 // the collection set. So, we'll recreate such entries now.
143 obj->oop_iterate(_update_rset_cl);
144
145 HeapWord* obj_end = obj_addr + obj_size;
146 _last_forwarded_object_end = obj_end;
147 _hr->cross_threshold(obj_addr, obj_end);
148 }
149 }
150
151 // Fill the memory area from start to end with filler objects, and update the BOT
152 // and the mark bitmap accordingly.
153 void zap_dead_objects(HeapWord* start, HeapWord* end) {
154 if (start == end) {
155 return;
156 }
157
158 size_t gap_size = pointer_delta(end, start);
159 MemRegion mr(start, gap_size);
160 if (gap_size >= CollectedHeap::min_fill_size()) {
161 CollectedHeap::fill_with_objects(start, gap_size);
162
163 HeapWord* end_first_obj = start + ((oop)start)->size();
164 _hr->cross_threshold(start, end_first_obj);
165 // Fill_with_objects() may have created multiple (i.e. two)
166 // objects, as the max_fill_size() is half a region.
167 // After updating the BOT for the first object, also update the
168 // BOT for the second object to make the BOT complete.
169 if (end_first_obj != end) {
170 _hr->cross_threshold(end_first_obj, end);
171 #ifdef ASSERT
172 size_t size_second_obj = ((oop)end_first_obj)->size();
173 HeapWord* end_of_second_obj = end_first_obj + size_second_obj;
174 assert(end == end_of_second_obj,
175 "More than two objects were used to fill the area from " PTR_FORMAT " to " PTR_FORMAT ", "
176 "second objects size " SIZE_FORMAT " ends at " PTR_FORMAT,
177 p2i(start), p2i(end), size_second_obj, p2i(end_of_second_obj));
178 #endif
179 }
180 }
181 _cm->clearRangePrevBitmap(mr);
182 }
183
184 void zap_remainder() {
185 zap_dead_objects(_last_forwarded_object_end, _hr->top());
186 }
187 };
188
189 class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {
190 G1CollectedHeap* _g1h;
191 uint _worker_id;
192 HeapRegionClaimer* _hrclaimer;
193
194 DirtyCardQueue _dcq;
195 UpdateRSetDeferred _update_rset_cl;
196
197 public:
198 RemoveSelfForwardPtrHRClosure(uint worker_id,
199 HeapRegionClaimer* hrclaimer) :
200 _g1h(G1CollectedHeap::heap()),
201 _dcq(&_g1h->dirty_card_queue_set()),
202 _update_rset_cl(&_dcq),
203 _worker_id(worker_id),
204 _hrclaimer(hrclaimer) {
205 }
206
207 size_t remove_self_forward_ptr_by_walking_hr(HeapRegion* hr,
208 bool during_initial_mark) {
209 RemoveSelfForwardPtrObjClosure rspc(hr,
210 &_update_rset_cl,
211 during_initial_mark,
212 _worker_id);
213 _update_rset_cl.set_region(hr);
214 hr->object_iterate(&rspc);
215 // Need to zap the remainder area of the processed region.
216 rspc.zap_remainder();
217
218 return rspc.marked_bytes();
219 }
220
221 bool doHeapRegion(HeapRegion *hr) {
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 bool during_initial_mark = _g1h->collector_state()->during_initial_mark_pause();
228 bool during_conc_mark = _g1h->collector_state()->mark_in_progress();
229
230 hr->note_self_forwarding_removal_start(during_initial_mark,
231 during_conc_mark);
232 _g1h->verifier()->check_bitmaps("Self-Forwarding Ptr Removal", hr);
233
234 hr->reset_bot();
235
236 size_t live_bytes = remove_self_forward_ptr_by_walking_hr(hr, during_initial_mark);
237
238 hr->rem_set()->clean_strong_code_roots(hr);
239
240 hr->note_self_forwarding_removal_end(live_bytes);
241 }
242 }
243 return false;
244 }
245 };
246
247 G1ParRemoveSelfForwardPtrsTask::G1ParRemoveSelfForwardPtrsTask() :
248 AbstractGangTask("G1 Remove Self-forwarding Pointers"),
249 _g1h(G1CollectedHeap::heap()),
250 _hrclaimer(_g1h->workers()->active_workers()) { }
251
252 void G1ParRemoveSelfForwardPtrsTask::work(uint worker_id) {
253 RemoveSelfForwardPtrHRClosure rsfp_cl(worker_id, &_hrclaimer);
254
255 _g1h->collection_set_iterate_from(&rsfp_cl, worker_id);
256 }