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.
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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/g1DirtyCardQueue.hpp"
30#include "gc/g1/g1EvacFailure.hpp"
31#include "gc/g1/g1HeapVerifier.hpp"
32#include "gc/g1/g1OopClosures.inline.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
40class UpdateRSetDeferred : public BasicOopIterateClosure {
41private:
42 G1CollectedHeap* _g1h;
43 G1DirtyCardQueue* _dcq;
44 G1CardTable* _ct;
45
46public:
47 UpdateRSetDeferred(G1DirtyCardQueue* dcq) :
48 _g1h(G1CollectedHeap::heap()), _dcq(dcq), _ct(_g1h->card_table()) {}
49
50 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
51 virtual void do_oop( oop* p) { do_oop_work(p); }
52 template <class T> void do_oop_work(T* p) {
53 assert(_g1h->heap_region_containing(p)->is_in_reserved(p), "paranoia");
54 assert(!_g1h->heap_region_containing(p)->is_survivor(), "Unexpected evac failure in survivor region");
55
56 T const o = RawAccess<>::oop_load(p);
57 if (CompressedOops::is_null(o)) {
58 return;
59 }
60
61 if (HeapRegion::is_in_same_region(p, CompressedOops::decode(o))) {
62 return;
63 }
64 size_t card_index = _ct->index_for(p);
65 if (_ct->mark_card_deferred(card_index)) {
66 _dcq->enqueue(_ct->byte_for_index(card_index));
67 }
68 }
69};
70
71class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
72 G1CollectedHeap* _g1h;
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
81public:
82 RemoveSelfForwardPtrObjClosure(HeapRegion* hr,
83 UpdateRSetDeferred* update_rset_cl,
84 bool during_initial_mark,
85 uint worker_id) :
86 _g1h(G1CollectedHeap::heap()),
87 _cm(_g1h->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(_worker_id, _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
193class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {
194 G1CollectedHeap* _g1h;
195 uint _worker_id;
196 HeapRegionClaimer* _hrclaimer;
197
198 G1DirtyCardQueue _dcq;
199 UpdateRSetDeferred _update_rset_cl;
200
201public:
202 RemoveSelfForwardPtrHRClosure(uint worker_id,
203 HeapRegionClaimer* hrclaimer) :
204 _g1h(G1CollectedHeap::heap()),
205 _worker_id(worker_id),
206 _hrclaimer(hrclaimer),
207 _dcq(&_g1h->dirty_card_queue_set()),
208 _update_rset_cl(&_dcq){
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 hr->clear_index_in_opt_cset();
231
232 bool during_initial_mark = _g1h->collector_state()->in_initial_mark_gc();
233 bool during_conc_mark = _g1h->collector_state()->mark_or_rebuild_in_progress();
234
235 hr->note_self_forwarding_removal_start(during_initial_mark,
236 during_conc_mark);
237 _g1h->verifier()->check_bitmaps("Self-Forwarding Ptr Removal", hr);
238
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 hr->rem_set()->clear_locked(true);
245
246 hr->note_self_forwarding_removal_end(live_bytes);
247 }
248 }
249 return false;
250 }
251};
252
253G1ParRemoveSelfForwardPtrsTask::G1ParRemoveSelfForwardPtrsTask() :
254 AbstractGangTask("G1 Remove Self-forwarding Pointers"),
255 _g1h(G1CollectedHeap::heap()),
256 _hrclaimer(_g1h->workers()->active_workers()) { }
257
258void G1ParRemoveSelfForwardPtrsTask::work(uint worker_id) {
259 RemoveSelfForwardPtrHRClosure rsfp_cl(worker_id, &_hrclaimer);
260
261 _g1h->collection_set_iterate_increment_from(&rsfp_cl, worker_id);
262}
263