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 void G1StringDedup::stop() {
48 assert(is_enabled(), "String deduplication not enabled");
49 G1StringDedupThread::stop();
50 }
51
52 bool G1StringDedup::is_candidate_from_mark(oop obj) {
53 if (java_lang_String::is_instance(obj)) {
54 bool from_young = G1CollectedHeap::heap()->heap_region_containing_raw(obj)->is_young();
55 if (from_young && obj->age() < StringDeduplicationAgeThreshold) {
56 // Candidate found. String is being evacuated from young to old but has not
57 // reached the deduplication age threshold, i.e. has not previously been a
58 // candidate during its life in the young generation.
59 return true;
60 }
61 }
62
63 // Not a candidate
64 return false;
65 }
66
67 void G1StringDedup::enqueue_from_mark(oop java_string) {
68 assert(is_enabled(), "String deduplication not enabled");
69 if (is_candidate_from_mark(java_string)) {
70 G1StringDedupQueue::push(0 /* worker_id */, java_string);
71 }
72 }
73
74 bool G1StringDedup::is_candidate_from_evacuation(bool from_young, bool to_young, oop obj) {
75 if (from_young && java_lang_String::is_instance(obj)) {
76 if (to_young && obj->age() == StringDeduplicationAgeThreshold) {
77 // Candidate found. String is being evacuated from young to young and just
78 // reached the deduplication age threshold.
79 return true;
80 }
81 if (!to_young && obj->age() < StringDeduplicationAgeThreshold) {
82 // Candidate found. String is being evacuated from young to old but has not
83 // reached the deduplication age threshold, i.e. has not previously been a
84 // candidate during its life in the young generation.
85 return true;
86 }
87 }
88
89 // Not a candidate
90 return false;
91 }
92
93 void G1StringDedup::enqueue_from_evacuation(bool from_young, bool to_young, uint worker_id, oop java_string) {
94 assert(is_enabled(), "String deduplication not enabled");
95 if (is_candidate_from_evacuation(from_young, to_young, java_string)) {
96 G1StringDedupQueue::push(worker_id, java_string);
97 }
98 }
99
100 void G1StringDedup::deduplicate(oop java_string) {
101 assert(is_enabled(), "String deduplication not enabled");
102 G1StringDedupStat dummy; // Statistics from this path is never used
103 G1StringDedupTable::deduplicate(java_string, dummy);
104 }
105
106 void G1StringDedup::oops_do(OopClosure* keep_alive) {
107 assert(is_enabled(), "String deduplication not enabled");
108 unlink_or_oops_do(NULL, keep_alive);
109 }
110
111 void G1StringDedup::unlink(BoolObjectClosure* is_alive) {
112 assert(is_enabled(), "String deduplication not enabled");
113 // Don't allow a potential resize or rehash during unlink, as the unlink
114 // operation itself might remove enough entries to invalidate such a decision.
115 unlink_or_oops_do(is_alive, NULL, false /* allow_resize_and_rehash */);
116 }
117
118 //
119 // Task for parallel unlink_or_oops_do() operation on the deduplication queue
120 // and table.
121 //
122 class G1StringDedupUnlinkOrOopsDoTask : public AbstractGangTask {
123 private:
124 G1StringDedupUnlinkOrOopsDoClosure _cl;
125
126 public:
127 G1StringDedupUnlinkOrOopsDoTask(BoolObjectClosure* is_alive,
128 OopClosure* keep_alive,
129 bool allow_resize_and_rehash) :
130 AbstractGangTask("G1StringDedupUnlinkOrOopsDoTask"),
131 _cl(is_alive, keep_alive, allow_resize_and_rehash) {
132 }
133
134 virtual void work(uint worker_id) {
135 double queue_fixup_start = os::elapsedTime();
136 G1StringDedupQueue::unlink_or_oops_do(&_cl);
137
138 double table_fixup_start = os::elapsedTime();
139 G1StringDedupTable::unlink_or_oops_do(&_cl, worker_id);
140
141 double queue_fixup_time_ms = (table_fixup_start - queue_fixup_start) * 1000.0;
142 double table_fixup_time_ms = (os::elapsedTime() - table_fixup_start) * 1000.0;
143 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
144 g1p->phase_times()->record_string_dedup_queue_fixup_worker_time(worker_id, queue_fixup_time_ms);
145 g1p->phase_times()->record_string_dedup_table_fixup_worker_time(worker_id, table_fixup_time_ms);
146 }
147 };
148
149 void G1StringDedup::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* keep_alive, bool allow_resize_and_rehash) {
150 assert(is_enabled(), "String deduplication not enabled");
151 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
152 g1p->phase_times()->note_string_dedup_fixup_start();
153 double fixup_start = os::elapsedTime();
154
155 G1StringDedupUnlinkOrOopsDoTask task(is_alive, keep_alive, allow_resize_and_rehash);
156 if (G1CollectedHeap::use_parallel_gc_threads()) {
157 G1CollectedHeap* g1h = G1CollectedHeap::heap();
158 g1h->set_par_threads();
159 g1h->workers()->run_task(&task);
160 g1h->set_par_threads(0);
161 } else {
162 task.work(0);
163 }
164
165 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
166 g1p->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
167 g1p->phase_times()->note_string_dedup_fixup_end();
168 }
169
170 void G1StringDedup::threads_do(ThreadClosure* tc) {
171 assert(is_enabled(), "String deduplication not enabled");
172 tc->do_thread(G1StringDedupThread::thread());
173 }
174
175 void G1StringDedup::print_worker_threads_on(outputStream* st) {
176 assert(is_enabled(), "String deduplication not enabled");
177 G1StringDedupThread::thread()->print_on(st);
178 st->cr();
179 }
180
181 void G1StringDedup::verify() {
182 assert(is_enabled(), "String deduplication not enabled");
183 G1StringDedupQueue::verify();
184 G1StringDedupTable::verify();
185 }
186
187 G1StringDedupUnlinkOrOopsDoClosure::G1StringDedupUnlinkOrOopsDoClosure(BoolObjectClosure* is_alive,
188 OopClosure* keep_alive,
189 bool allow_resize_and_rehash) :
190 _is_alive(is_alive),
191 _keep_alive(keep_alive),
192 _resized_table(NULL),
193 _rehashed_table(NULL),
194 _next_queue(0),
195 _next_bucket(0) {
196 if (allow_resize_and_rehash) {
197 // If both resize and rehash is needed, only do resize. Rehash of
198 // the table will eventually happen if the situation persists.
199 _resized_table = G1StringDedupTable::prepare_resize();
200 if (!is_resizing()) {
201 _rehashed_table = G1StringDedupTable::prepare_rehash();
202 }
203 }
204 }
205
206 G1StringDedupUnlinkOrOopsDoClosure::~G1StringDedupUnlinkOrOopsDoClosure() {
207 assert(!is_resizing() || !is_rehashing(), "Can not both resize and rehash");
208 if (is_resizing()) {
209 G1StringDedupTable::finish_resize(_resized_table);
210 } else if (is_rehashing()) {
211 G1StringDedupTable::finish_rehash(_rehashed_table);
212 }
213 }