1 /*
2 * Copyright (c) 2014, 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
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23 */
24
25 #ifndef SHARE_VM_GC_G1_G1PARSCANTHREADSTATE_INLINE_HPP
26 #define SHARE_VM_GC_G1_G1PARSCANTHREADSTATE_INLINE_HPP
27
28 #include "gc/g1/g1CollectedHeap.inline.hpp"
29 #include "gc/g1/g1ParScanThreadState.hpp"
30 #include "gc/g1/g1RemSet.hpp"
31 #include "oops/access.inline.hpp"
32 #include "oops/oop.inline.hpp"
33
34 template <class T> void G1ParScanThreadState::do_oop_evac(T* p) {
35 // Reference should not be NULL here as such are never pushed to the task queue.
36 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
37
38 // Although we never intentionally push references outside of the collection
39 // set, due to (benign) races in the claim mechanism during RSet scanning more
40 // than one thread might claim the same card. So the same card may be
41 // processed multiple times, and so we might get references into old gen here.
42 // So we need to redo this check.
43 const InCSetState in_cset_state = _g1h->in_cset_state(obj);
44 // References pushed onto the work stack should never point to a humongous region
45 // as they are not added to the collection set due to above precondition.
46 assert(!in_cset_state.is_humongous(),
47 "Obj " PTR_FORMAT " should not refer to humongous region %u from " PTR_FORMAT,
48 p2i(obj), _g1h->addr_to_region((HeapWord*)obj), p2i(p));
49
50 if (!in_cset_state.is_in_cset()) {
51 // In this case somebody else already did all the work.
52 return;
53 }
54
55 markOop m = obj->mark_raw();
56 if (m->is_marked()) {
57 obj = (oop) m->decode_pointer();
58 } else {
59 obj = copy_to_survivor_space(in_cset_state, obj, m);
60 }
61 RawAccess<IS_NOT_NULL>::oop_store(p, obj);
62
63 assert(obj != NULL, "Must be");
64 if (!HeapRegion::is_in_same_region(p, obj)) {
65 HeapRegion* from = _g1h->heap_region_containing(p);
66 update_rs(from, p, obj);
67 }
68 }
69
70 template <class T> inline void G1ParScanThreadState::push_on_queue(T* ref) {
71 assert(verify_ref(ref), "sanity");
72 _refs->push(ref);
73 }
74
75 inline void G1ParScanThreadState::do_oop_partial_array(oop* p) {
76 assert(has_partial_array_mask(p), "invariant");
77 oop from_obj = clear_partial_array_mask(p);
78
79 assert(_g1h->is_in_reserved(from_obj), "must be in heap.");
80 assert(from_obj->is_objArray(), "must be obj array");
81 objArrayOop from_obj_array = objArrayOop(from_obj);
82 // The from-space object contains the real length.
83 int length = from_obj_array->length();
84
85 assert(from_obj->is_forwarded(), "must be forwarded");
86 oop to_obj = from_obj->forwardee();
87 assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
88 objArrayOop to_obj_array = objArrayOop(to_obj);
89 // We keep track of the next start index in the length field of the
90 // to-space object.
91 int next_index = to_obj_array->length();
92 assert(0 <= next_index && next_index < length,
93 "invariant, next index: %d, length: %d", next_index, length);
94
95 int start = next_index;
96 int end = length;
97 int remainder = end - start;
98 // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
99 if (remainder > 2 * ParGCArrayScanChunk) {
100 end = start + ParGCArrayScanChunk;
101 to_obj_array->set_length(end);
102 // Push the remainder before we process the range in case another
103 // worker has run out of things to do and can steal it.
104 oop* from_obj_p = set_partial_array_mask(from_obj);
105 push_on_queue(from_obj_p);
106 } else {
107 assert(length == end, "sanity");
108 // We'll process the final range for this object. Restore the length
109 // so that the heap remains parsable in case of evacuation failure.
110 to_obj_array->set_length(end);
111 }
112 _scanner.set_region(_g1h->heap_region_containing(to_obj));
113 // Process indexes [start,end). It will also process the header
114 // along with the first chunk (i.e., the chunk with start == 0).
115 // Note that at this point the length field of to_obj_array is not
116 // correct given that we are using it to keep track of the next
117 // start index. oop_iterate_range() (thankfully!) ignores the length
118 // field and only relies on the start / end parameters. It does
119 // however return the size of the object which will be incorrect. So
120 // we have to ignore it even if we wanted to use it.
121 to_obj_array->oop_iterate_range(&_scanner, start, end);
122 }
123
124 inline void G1ParScanThreadState::deal_with_reference(oop* ref_to_scan) {
125 if (!has_partial_array_mask(ref_to_scan)) {
126 do_oop_evac(ref_to_scan);
127 } else {
128 do_oop_partial_array(ref_to_scan);
129 }
130 }
131
132 inline void G1ParScanThreadState::deal_with_reference(narrowOop* ref_to_scan) {
133 assert(!has_partial_array_mask(ref_to_scan), "NarrowOop* elements should never be partial arrays.");
134 do_oop_evac(ref_to_scan);
135 }
136
137 inline void G1ParScanThreadState::dispatch_reference(StarTask ref) {
138 assert(verify_task(ref), "sanity");
139 if (ref.is_narrow()) {
140 deal_with_reference((narrowOop*)ref);
141 } else {
142 deal_with_reference((oop*)ref);
143 }
144 }
145
146 void G1ParScanThreadState::steal_and_trim_queue(RefToScanQueueSet *task_queues) {
147 StarTask stolen_task;
148 while (task_queues->steal(_worker_id, stolen_task)) {
149 assert(verify_task(stolen_task), "sanity");
150 dispatch_reference(stolen_task);
151
152 // We've just processed a reference and we might have made
153 // available new entries on the queues. So we have to make sure
154 // we drain the queues as necessary.
155 trim_queue();
156 }
157 }
158
159 inline bool G1ParScanThreadState::needs_partial_trimming() const {
160 return !_refs->overflow_empty() || _refs->size() > _stack_trim_upper_threshold;
161 }
162
163 inline bool G1ParScanThreadState::is_partially_trimmed() const {
164 return _refs->overflow_empty() && _refs->size() <= _stack_trim_lower_threshold;
165 }
166
167 inline void G1ParScanThreadState::trim_queue_to_threshold(uint threshold) {
168 StarTask ref;
169 // Drain the overflow stack first, so other threads can potentially steal.
170 while (_refs->pop_overflow(ref)) {
171 if (!_refs->try_push_to_taskqueue(ref)) {
172 dispatch_reference(ref);
173 }
174 }
175
176 while (_refs->pop_local(ref, threshold)) {
177 dispatch_reference(ref);
178 }
179 }
180
181 inline void G1ParScanThreadState::trim_queue_partially() {
182 if (!needs_partial_trimming()) {
183 return;
184 }
185
186 const Ticks start = Ticks::now();
187 do {
188 trim_queue_to_threshold(_stack_trim_lower_threshold);
189 } while (!is_partially_trimmed());
190 _trim_ticks += Ticks::now() - start;
191 }
192
193 inline Tickspan G1ParScanThreadState::trim_ticks() const {
194 return _trim_ticks;
195 }
196
197 inline void G1ParScanThreadState::reset_trim_ticks() {
198 _trim_ticks = Tickspan();
199 }
200
201 #endif // SHARE_VM_GC_G1_G1PARSCANTHREADSTATE_INLINE_HPP