1 /*
2 * Copyright (c) 2012, 2019, 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/g1CollectedHeap.inline.hpp"
27 #include "gc/g1/g1CollectorState.hpp"
28 #include "gc/g1/g1ConcurrentMark.inline.hpp"
29 #include "gc/g1/g1EvacFailure.hpp"
30 #include "gc/g1/g1HeapVerifier.hpp"
31 #include "gc/g1/g1OopClosures.inline.hpp"
32 #include "gc/g1/g1RedirtyCardsQueue.hpp"
33 #include "gc/g1/heapRegion.hpp"
34 #include "gc/g1/heapRegionRemSet.hpp"
35 #include "gc/shared/preservedMarks.inline.hpp"
36 #include "oops/access.inline.hpp"
37 #include "oops/compressedOops.inline.hpp"
38 #include "oops/oop.inline.hpp"
39
40 class UpdateLogBuffersDeferred : public BasicOopIterateClosure {
41 private:
42 G1CollectedHeap* _g1h;
43 G1RedirtyCardsQueue* _rdcq;
44 G1CardTable* _ct;
45
46 // Remember the last enqueued card to avoid enqueuing the same card over and over;
47 // since we only ever handle a card once, this is sufficient.
48 size_t _last_enqueued_card;
49
50 public:
51 UpdateLogBuffersDeferred(G1RedirtyCardsQueue* rdcq) :
52 _g1h(G1CollectedHeap::heap()), _rdcq(rdcq), _ct(_g1h->card_table()), _last_enqueued_card(SIZE_MAX) {}
53
54 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
55 virtual void do_oop( oop* p) { do_oop_work(p); }
56 template <class T> void do_oop_work(T* p) {
57 assert(_g1h->heap_region_containing(p)->is_in_reserved(p), "paranoia");
58 assert(!_g1h->heap_region_containing(p)->is_survivor(), "Unexpected evac failure in survivor region");
59
60 T const o = RawAccess<>::oop_load(p);
61 if (CompressedOops::is_null(o)) {
62 return;
63 }
64
65 if (HeapRegion::is_in_same_region(p, CompressedOops::decode(o))) {
66 return;
67 }
68 size_t card_index = _ct->index_for(p);
69 if (card_index != _last_enqueued_card) {
70 _rdcq->enqueue(_ct->byte_for_index(card_index));
71 _last_enqueued_card = card_index;
72 }
73 }
74 };
75
76 class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
77 G1CollectedHeap* _g1h;
78 G1ConcurrentMark* _cm;
79 HeapRegion* _hr;
80 size_t _marked_bytes;
81 UpdateLogBuffersDeferred* _log_buffer_cl;
82 bool _during_initial_mark;
83 uint _worker_id;
84 HeapWord* _last_forwarded_object_end;
85
86 public:
87 RemoveSelfForwardPtrObjClosure(HeapRegion* hr,
88 UpdateLogBuffersDeferred* log_buffer_cl,
89 bool during_initial_mark,
90 uint worker_id) :
91 _g1h(G1CollectedHeap::heap()),
92 _cm(_g1h->concurrent_mark()),
93 _hr(hr),
94 _marked_bytes(0),
95 _log_buffer_cl(log_buffer_cl),
96 _during_initial_mark(during_initial_mark),
97 _worker_id(worker_id),
98 _last_forwarded_object_end(hr->bottom()) { }
99
100 size_t marked_bytes() { return _marked_bytes; }
101
102 // Iterate over the live objects in the region to find self-forwarded objects
103 // that need to be kept live. We need to update the remembered sets of these
104 // objects. Further update the BOT and marks.
105 // We can coalesce and overwrite the remaining heap contents with dummy objects
106 // as they have either been dead or evacuated (which are unreferenced now, i.e.
107 // dead too) already.
108 void do_object(oop obj) {
109 HeapWord* obj_addr = cast_from_oop<HeapWord*>(obj);
110 assert(_hr->is_in(obj_addr), "sanity");
111
112 if (obj->is_forwarded() && obj->forwardee() == obj) {
113 // The object failed to move.
114
115 zap_dead_objects(_last_forwarded_object_end, obj_addr);
116 // We consider all objects that we find self-forwarded to be
117 // live. What we'll do is that we'll update the prev marking
118 // info so that they are all under PTAMS and explicitly marked.
119 if (!_cm->is_marked_in_prev_bitmap(obj)) {
120 _cm->mark_in_prev_bitmap(obj);
121 }
122 if (_during_initial_mark) {
123 // For the next marking info we'll only mark the
124 // self-forwarded objects explicitly if we are during
125 // initial-mark (since, normally, we only mark objects pointed
126 // to by roots if we succeed in copying them). By marking all
127 // self-forwarded objects we ensure that we mark any that are
128 // still pointed to be roots. During concurrent marking, and
129 // after initial-mark, we don't need to mark any objects
130 // explicitly and all objects in the CSet are considered
131 // (implicitly) live. So, we won't mark them explicitly and
132 // we'll leave them over NTAMS.
133 _cm->mark_in_next_bitmap(_worker_id, _hr, obj);
134 }
135 size_t obj_size = obj->size();
136
137 _marked_bytes += (obj_size * HeapWordSize);
138 PreservedMarks::init_forwarded_mark(obj);
139
140 // While we were processing RSet buffers during the collection,
141 // we actually didn't scan any cards on the collection set,
142 // since we didn't want to update remembered sets with entries
143 // that point into the collection set, given that live objects
144 // from the collection set are about to move and such entries
145 // will be stale very soon.
146 // This change also dealt with a reliability issue which
147 // involved scanning a card in the collection set and coming
148 // across an array that was being chunked and looking malformed.
149 // The problem is that, if evacuation fails, we might have
150 // remembered set entries missing given that we skipped cards on
151 // the collection set. So, we'll recreate such entries now.
152 obj->oop_iterate(_log_buffer_cl);
153
154 HeapWord* obj_end = obj_addr + obj_size;
155 _last_forwarded_object_end = obj_end;
156 _hr->cross_threshold(obj_addr, obj_end);
157 }
158 }
159
160 // Fill the memory area from start to end with filler objects, and update the BOT
161 // and the mark bitmap accordingly.
162 void zap_dead_objects(HeapWord* start, HeapWord* end) {
163 if (start == end) {
164 return;
165 }
166
167 size_t gap_size = pointer_delta(end, start);
168 MemRegion mr(start, gap_size);
169 if (gap_size >= CollectedHeap::min_fill_size()) {
170 CollectedHeap::fill_with_objects(start, gap_size);
171
172 HeapWord* end_first_obj = start + ((oop)start)->size();
173 _hr->cross_threshold(start, end_first_obj);
174 // Fill_with_objects() may have created multiple (i.e. two)
175 // objects, as the max_fill_size() is half a region.
176 // After updating the BOT for the first object, also update the
177 // BOT for the second object to make the BOT complete.
178 if (end_first_obj != end) {
179 _hr->cross_threshold(end_first_obj, end);
180 #ifdef ASSERT
181 size_t size_second_obj = ((oop)end_first_obj)->size();
182 HeapWord* end_of_second_obj = end_first_obj + size_second_obj;
183 assert(end == end_of_second_obj,
184 "More than two objects were used to fill the area from " PTR_FORMAT " to " PTR_FORMAT ", "
185 "second objects size " SIZE_FORMAT " ends at " PTR_FORMAT,
186 p2i(start), p2i(end), size_second_obj, p2i(end_of_second_obj));
187 #endif
188 }
189 }
190 _cm->clear_range_in_prev_bitmap(mr);
191 }
192
193 void zap_remainder() {
194 zap_dead_objects(_last_forwarded_object_end, _hr->top());
195 }
196 };
197
198 class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {
199 G1CollectedHeap* _g1h;
200 uint _worker_id;
201
202 G1RedirtyCardsQueue _rdcq;
203 UpdateLogBuffersDeferred _log_buffer_cl;
204
205 public:
206 RemoveSelfForwardPtrHRClosure(G1RedirtyCardsQueueSet* rdcqs, uint worker_id) :
207 _g1h(G1CollectedHeap::heap()),
208 _worker_id(worker_id),
209 _rdcq(rdcqs),
210 _log_buffer_cl(&_rdcq) {
211 }
212
213 size_t remove_self_forward_ptr_by_walking_hr(HeapRegion* hr,
214 bool during_initial_mark) {
215 RemoveSelfForwardPtrObjClosure rspc(hr,
216 &_log_buffer_cl,
217 during_initial_mark,
218 _worker_id);
219 hr->object_iterate(&rspc);
220 // Need to zap the remainder area of the processed region.
221 rspc.zap_remainder();
222
223 return rspc.marked_bytes();
224 }
225
226 bool do_heap_region(HeapRegion *hr) {
227 assert(!hr->is_pinned(), "Unexpected pinned region at index %u", hr->hrm_index());
228 assert(hr->in_collection_set(), "bad CS");
229
230 if (hr->evacuation_failed()) {
231 hr->clear_index_in_opt_cset();
232
233 bool during_initial_mark = _g1h->collector_state()->in_initial_mark_gc();
234 bool during_conc_mark = _g1h->collector_state()->mark_or_rebuild_in_progress();
235
236 hr->note_self_forwarding_removal_start(during_initial_mark,
237 during_conc_mark);
238 _g1h->verifier()->check_bitmaps("Self-Forwarding Ptr Removal", hr);
239
240 hr->reset_bot();
241
242 size_t live_bytes = remove_self_forward_ptr_by_walking_hr(hr, during_initial_mark);
243
244 hr->rem_set()->clean_strong_code_roots(hr);
245 hr->rem_set()->clear_locked(true);
246
247 hr->note_self_forwarding_removal_end(live_bytes);
248 }
249 return false;
250 }
251 };
252
253 G1ParRemoveSelfForwardPtrsTask::G1ParRemoveSelfForwardPtrsTask(G1RedirtyCardsQueueSet* rdcqs) :
254 AbstractGangTask("G1 Remove Self-forwarding Pointers"),
255 _g1h(G1CollectedHeap::heap()),
256 _rdcqs(rdcqs),
257 _hrclaimer(_g1h->workers()->active_workers()) { }
258
259 void G1ParRemoveSelfForwardPtrsTask::work(uint worker_id) {
260 RemoveSelfForwardPtrHRClosure rsfp_cl(_rdcqs, worker_id);
261
262 _g1h->collection_set_iterate_increment_from(&rsfp_cl, &_hrclaimer, worker_id);
263 }