1 /*
2 * Copyright (c) 2014, 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 "classfile/javaClasses.hpp"
27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
28 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
29 #include "gc_implementation/g1/g1StringDedup.hpp"
30 #include "gc_implementation/g1/g1StringDedupQueue.hpp"
31 #include "gc_implementation/g1/g1StringDedupStat.hpp"
32 #include "gc_implementation/g1/g1StringDedupTable.hpp"
33 #include "gc_implementation/g1/g1StringDedupThread.hpp"
34
35 bool G1StringDedup::_enabled = false;
36
37 void G1StringDedup::initialize() {
38 assert(UseG1GC, "String deduplication only available with G1");
39 if (UseStringDeduplication) {
40 _enabled = true;
41 G1StringDedupQueue::create();
42 G1StringDedupTable::create();
43 G1StringDedupThread::create();
44 }
45 }
46
47 bool G1StringDedup::is_candidate_from_mark(oop obj) {
48 if (java_lang_String::is_instance(obj)) {
49 bool from_young = G1CollectedHeap::heap()->heap_region_containing_raw(obj)->is_young();
50 if (from_young && obj->age() < StringDeduplicationAgeThreshold) {
51 // Candidate found. String is being evacuated from young to old but has not
52 // reached the deduplication age threshold, i.e. has not previously been a
53 // candidate during its life in the young generation.
54 return true;
55 }
56 }
57
58 // Not a candidate
59 return false;
60 }
61
62 void G1StringDedup::enqueue_from_mark(oop java_string) {
63 assert(is_enabled(), "String deduplication not enabled");
64 if (is_candidate_from_mark(java_string)) {
65 G1StringDedupQueue::push(0 /* worker_id */, java_string);
66 }
67 }
68
69 bool G1StringDedup::is_candidate_from_evacuation(bool from_young, bool to_young, oop obj) {
70 if (from_young && java_lang_String::is_instance(obj)) {
71 if (to_young && obj->age() == StringDeduplicationAgeThreshold) {
72 // Candidate found. String is being evacuated from young to young and just
73 // reached the deduplication age threshold.
74 return true;
75 }
76 if (!to_young && obj->age() < StringDeduplicationAgeThreshold) {
77 // Candidate found. String is being evacuated from young to old but has not
78 // reached the deduplication age threshold, i.e. has not previously been a
79 // candidate during its life in the young generation.
80 return true;
81 }
82 }
83
84 // Not a candidate
85 return false;
86 }
87
88 void G1StringDedup::enqueue_from_evacuation(bool from_young, bool to_young, uint worker_id, oop java_string) {
89 assert(is_enabled(), "String deduplication not enabled");
90 if (is_candidate_from_evacuation(from_young, to_young, java_string)) {
91 G1StringDedupQueue::push(worker_id, java_string);
92 }
93 }
94
95 void G1StringDedup::deduplicate(oop java_string) {
96 assert(is_enabled(), "String deduplication not enabled");
97 G1StringDedupStat dummy; // Statistics from this path is never used
98 G1StringDedupTable::deduplicate(java_string, dummy);
99 }
100
101 void G1StringDedup::oops_do(OopClosure* keep_alive) {
102 assert(is_enabled(), "String deduplication not enabled");
103 unlink_or_oops_do(NULL, keep_alive);
104 }
105
106 void G1StringDedup::unlink(BoolObjectClosure* is_alive) {
107 assert(is_enabled(), "String deduplication not enabled");
108 // Don't allow a potential resize or rehash during unlink, as the unlink
109 // operation itself might remove enough entries to invalidate such a decision.
110 unlink_or_oops_do(is_alive, NULL, false /* allow_resize_and_rehash */);
111 }
112
113 //
114 // Task for parallel unlink_or_oops_do() operation on the deduplication queue
115 // and table.
116 //
117 class G1StringDedupUnlinkOrOopsDoTask : public AbstractGangTask {
118 private:
119 G1StringDedupUnlinkOrOopsDoClosure _cl;
120
121 public:
122 G1StringDedupUnlinkOrOopsDoTask(BoolObjectClosure* is_alive,
123 OopClosure* keep_alive,
124 bool allow_resize_and_rehash) :
125 AbstractGangTask("G1StringDedupUnlinkOrOopsDoTask"),
126 _cl(is_alive, keep_alive, allow_resize_and_rehash) {
127 }
128
129 virtual void work(uint worker_id) {
130 double queue_fixup_start = os::elapsedTime();
131 G1StringDedupQueue::unlink_or_oops_do(&_cl);
132
133 double table_fixup_start = os::elapsedTime();
134 G1StringDedupTable::unlink_or_oops_do(&_cl, worker_id);
135
136 double queue_fixup_time_ms = (table_fixup_start - queue_fixup_start) * 1000.0;
137 double table_fixup_time_ms = (os::elapsedTime() - table_fixup_start) * 1000.0;
138 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
139 g1p->phase_times()->record_string_dedup_queue_fixup_worker_time(worker_id, queue_fixup_time_ms);
140 g1p->phase_times()->record_string_dedup_table_fixup_worker_time(worker_id, table_fixup_time_ms);
141 }
142 };
143
144 void G1StringDedup::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* keep_alive, bool allow_resize_and_rehash) {
145 assert(is_enabled(), "String deduplication not enabled");
146 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
147 g1p->phase_times()->note_string_dedup_fixup_start();
148 double fixup_start = os::elapsedTime();
149
150 G1StringDedupUnlinkOrOopsDoTask task(is_alive, keep_alive, allow_resize_and_rehash);
151 if (G1CollectedHeap::use_parallel_gc_threads()) {
152 G1CollectedHeap* g1h = G1CollectedHeap::heap();
153 g1h->set_par_threads();
154 g1h->workers()->run_task(&task);
155 g1h->set_par_threads(0);
156 } else {
157 task.work(0);
158 }
159
160 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
161 g1p->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
162 g1p->phase_times()->note_string_dedup_fixup_end();
163 }
164
165 void G1StringDedup::threads_do(ThreadClosure* tc) {
166 assert(is_enabled(), "String deduplication not enabled");
167 tc->do_thread(G1StringDedupThread::thread());
168 }
169
170 void G1StringDedup::print_worker_threads_on(outputStream* st) {
171 assert(is_enabled(), "String deduplication not enabled");
172 G1StringDedupThread::thread()->print_on(st);
173 st->cr();
174 }
175
176 void G1StringDedup::verify() {
177 assert(is_enabled(), "String deduplication not enabled");
178 G1StringDedupQueue::verify();
179 G1StringDedupTable::verify();
180 }
181
182 G1StringDedupUnlinkOrOopsDoClosure::G1StringDedupUnlinkOrOopsDoClosure(BoolObjectClosure* is_alive,
183 OopClosure* keep_alive,
184 bool allow_resize_and_rehash) :
185 _is_alive(is_alive),
186 _keep_alive(keep_alive),
187 _resized_table(NULL),
188 _rehashed_table(NULL),
189 _next_queue(0),
190 _next_bucket(0) {
191 if (allow_resize_and_rehash) {
192 // If both resize and rehash is needed, only do resize. Rehash of
193 // the table will eventually happen if the situation persists.
194 _resized_table = G1StringDedupTable::prepare_resize();
195 if (!is_resizing()) {
196 _rehashed_table = G1StringDedupTable::prepare_rehash();
197 }
198 }
199 }
200
201 G1StringDedupUnlinkOrOopsDoClosure::~G1StringDedupUnlinkOrOopsDoClosure() {
202 assert(!is_resizing() || !is_rehashing(), "Can not both resize and rehash");
203 if (is_resizing()) {
204 G1StringDedupTable::finish_resize(_resized_table);
205 } else if (is_rehashing()) {
206 G1StringDedupTable::finish_rehash(_rehashed_table);
207 }
208 }