1 /*
2 * Copyright (c) 2012, 2018, 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 #include "oops/oop.inline.hpp"
38
39 class UpdateRSetDeferred : public ExtendedOopClosure {
40 private:
41 G1CollectedHeap* _g1;
42 DirtyCardQueue* _dcq;
43 G1CardTable* _ct;
44
45 public:
46 UpdateRSetDeferred(DirtyCardQueue* dcq) :
47 _g1(G1CollectedHeap::heap()), _ct(_g1->card_table()), _dcq(dcq) {}
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(_g1->heap_region_containing(p)->is_in_reserved(p), "paranoia");
53 assert(!_g1->heap_region_containing(p)->is_survivor(), "Unexpected evac failure in survivor region");
54
55 T const o = oopDesc::load_heap_oop(p);
56 if (oopDesc::is_null(o)) {
57 return;
58 }
59
60 if (HeapRegion::is_in_same_region(p, oopDesc::decode_heap_oop(o))) {
61 return;
62 }
63 size_t card_index = _ct->index_for(p);
64 if (_ct->mark_card_deferred(card_index)) {
65 _dcq->enqueue((jbyte*)_ct->byte_for_index(card_index));
66 }
67 }
68 };
69
70 class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
71 private:
72 G1CollectedHeap* _g1;
73 G1ConcurrentMark* _cm;
74 HeapRegion* _hr;
75 size_t _marked_bytes;
76 UpdateRSetDeferred* _update_rset_cl;
77 bool _during_initial_mark;
78 uint _worker_id;
79 HeapWord* _last_forwarded_object_end;
80
81 public:
82 RemoveSelfForwardPtrObjClosure(HeapRegion* hr,
83 UpdateRSetDeferred* update_rset_cl,
84 bool during_initial_mark,
85 uint worker_id) :
86 _g1(G1CollectedHeap::heap()),
87 _cm(_g1->concurrent_mark()),
88 _hr(hr),
89 _marked_bytes(0),
90 _update_rset_cl(update_rset_cl),
91 _during_initial_mark(during_initial_mark),
92 _worker_id(worker_id),
93 _last_forwarded_object_end(hr->bottom()) { }
94
95 size_t marked_bytes() { return _marked_bytes; }
96
97 // Iterate over the live objects in the region to find self-forwarded objects
98 // that need to be kept live. We need to update the remembered sets of these
99 // objects. Further update the BOT and marks.
100 // We can coalesce and overwrite the remaining heap contents with dummy objects
101 // as they have either been dead or evacuated (which are unreferenced now, i.e.
102 // dead too) already.
103 void do_object(oop obj) {
104 HeapWord* obj_addr = (HeapWord*) obj;
105 assert(_hr->is_in(obj_addr), "sanity");
106
107 if (obj->is_forwarded() && obj->forwardee() == obj) {
108 // The object failed to move.
109
110 zap_dead_objects(_last_forwarded_object_end, obj_addr);
111 // We consider all objects that we find self-forwarded to be
112 // live. What we'll do is that we'll update the prev marking
113 // info so that they are all under PTAMS and explicitly marked.
114 if (!_cm->is_marked_in_prev_bitmap(obj)) {
115 _cm->mark_in_prev_bitmap(obj);
116 }
117 if (_during_initial_mark) {
118 // For the next marking info we'll only mark the
119 // self-forwarded objects explicitly if we are during
120 // initial-mark (since, normally, we only mark objects pointed
121 // to by roots if we succeed in copying them). By marking all
122 // self-forwarded objects we ensure that we mark any that are
123 // still pointed to be roots. During concurrent marking, and
124 // after initial-mark, we don't need to mark any objects
125 // explicitly and all objects in the CSet are considered
126 // (implicitly) live. So, we won't mark them explicitly and
127 // we'll leave them over NTAMS.
128 _cm->mark_in_next_bitmap(_hr, obj);
129 }
130 size_t obj_size = obj->size();
131
132 _marked_bytes += (obj_size * HeapWordSize);
133 PreservedMarks::init_forwarded_mark(obj);
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
149 HeapWord* obj_end = obj_addr + obj_size;
150 _last_forwarded_object_end = obj_end;
151 _hr->cross_threshold(obj_addr, obj_end);
152 }
153 }
154
155 // Fill the memory area from start to end with filler objects, and update the BOT
156 // and the mark bitmap accordingly.
157 void zap_dead_objects(HeapWord* start, HeapWord* end) {
158 if (start == end) {
159 return;
160 }
161
162 size_t gap_size = pointer_delta(end, start);
163 MemRegion mr(start, gap_size);
164 if (gap_size >= CollectedHeap::min_fill_size()) {
165 CollectedHeap::fill_with_objects(start, gap_size);
166
167 HeapWord* end_first_obj = start + ((oop)start)->size();
168 _hr->cross_threshold(start, end_first_obj);
169 // Fill_with_objects() may have created multiple (i.e. two)
170 // objects, as the max_fill_size() is half a region.
171 // After updating the BOT for the first object, also update the
172 // BOT for the second object to make the BOT complete.
173 if (end_first_obj != end) {
174 _hr->cross_threshold(end_first_obj, end);
175 #ifdef ASSERT
176 size_t size_second_obj = ((oop)end_first_obj)->size();
177 HeapWord* end_of_second_obj = end_first_obj + size_second_obj;
178 assert(end == end_of_second_obj,
179 "More than two objects were used to fill the area from " PTR_FORMAT " to " PTR_FORMAT ", "
180 "second objects size " SIZE_FORMAT " ends at " PTR_FORMAT,
181 p2i(start), p2i(end), size_second_obj, p2i(end_of_second_obj));
182 #endif
183 }
184 }
185 _cm->clear_range_in_prev_bitmap(mr);
186 }
187
188 void zap_remainder() {
189 zap_dead_objects(_last_forwarded_object_end, _hr->top());
190 }
191 };
192
193 class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {
194 G1CollectedHeap* _g1h;
195 uint _worker_id;
196 HeapRegionClaimer* _hrclaimer;
197
198 DirtyCardQueue _dcq;
199 UpdateRSetDeferred _update_rset_cl;
200
201 public:
202 RemoveSelfForwardPtrHRClosure(uint worker_id,
203 HeapRegionClaimer* hrclaimer) :
204 _g1h(G1CollectedHeap::heap()),
205 _dcq(&_g1h->dirty_card_queue_set()),
206 _update_rset_cl(&_dcq),
207 _worker_id(worker_id),
208 _hrclaimer(hrclaimer) {
209 }
210
211 size_t remove_self_forward_ptr_by_walking_hr(HeapRegion* hr,
212 bool during_initial_mark) {
213 RemoveSelfForwardPtrObjClosure rspc(hr,
214 &_update_rset_cl,
215 during_initial_mark,
216 _worker_id);
217 hr->object_iterate(&rspc);
218 // Need to zap the remainder area of the processed region.
219 rspc.zap_remainder();
220
221 return rspc.marked_bytes();
222 }
223
224 bool do_heap_region(HeapRegion *hr) {
225 assert(!hr->is_pinned(), "Unexpected pinned region at index %u", hr->hrm_index());
226 assert(hr->in_collection_set(), "bad CS");
227
228 if (_hrclaimer->claim_region(hr->hrm_index())) {
229 if (hr->evacuation_failed()) {
230 bool during_initial_mark = _g1h->collector_state()->during_initial_mark_pause();
231 bool during_conc_mark = _g1h->collector_state()->mark_in_progress();
232
233 hr->note_self_forwarding_removal_start(during_initial_mark,
234 during_conc_mark);
235 _g1h->verifier()->check_bitmaps("Self-Forwarding Ptr Removal", hr);
236
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(live_bytes);
244 }
245 }
246 return false;
247 }
248 };
249
250 G1ParRemoveSelfForwardPtrsTask::G1ParRemoveSelfForwardPtrsTask() :
251 AbstractGangTask("G1 Remove Self-forwarding Pointers"),
252 _g1h(G1CollectedHeap::heap()),
253 _hrclaimer(_g1h->workers()->active_workers()) { }
254
255 void G1ParRemoveSelfForwardPtrsTask::work(uint worker_id) {
256 RemoveSelfForwardPtrHRClosure rsfp_cl(worker_id, &_hrclaimer);
257
258 _g1h->collection_set_iterate_from(&rsfp_cl, worker_id);
259 }