1 /*
2 * Copyright (c) 2014, 2017, 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.inline.hpp"
27 #include "gc/g1/g1CollectedHeap.inline.hpp"
28 #include "gc/g1/g1GCPhaseTimes.hpp"
29 #include "gc/g1/g1StringDedup.hpp"
30 #include "gc/g1/g1StringDedupQueue.hpp"
31 #include "gc/g1/g1StringDedupStat.hpp"
32 #include "gc/g1/g1StringDedupTable.hpp"
33 #include "gc/g1/g1StringDedupThread.hpp"
34 #include "runtime/atomic.hpp"
35
36 bool G1StringDedup::_enabled = false;
37
38 void G1StringDedup::initialize() {
39 assert(UseG1GC, "String deduplication only available with G1");
40 if (UseStringDeduplication) {
41 _enabled = true;
42 G1StringDedupQueue::create();
43 G1StringDedupTable::create();
44 G1StringDedupThread::create();
45 }
46 }
47
48 void G1StringDedup::stop() {
49 assert(is_enabled(), "String deduplication not enabled");
50 G1StringDedupThread::thread()->stop();
51 }
52
53 bool G1StringDedup::is_candidate_from_mark(oop obj) {
54 if (java_lang_String::is_instance_inlined(obj)) {
55 bool from_young = G1CollectedHeap::heap()->heap_region_containing(obj)->is_young();
56 if (from_young && obj->age() < StringDeduplicationAgeThreshold) {
57 // Candidate found. String is being evacuated from young to old but has not
58 // reached the deduplication age threshold, i.e. has not previously been a
59 // candidate during its life in the young generation.
60 return true;
61 }
62 }
63
64 // Not a candidate
65 return false;
66 }
67
68 void G1StringDedup::enqueue_from_mark(oop java_string) {
69 assert(is_enabled(), "String deduplication not enabled");
70 if (is_candidate_from_mark(java_string)) {
71 G1StringDedupQueue::push(0 /* worker_id */, java_string);
72 }
73 }
74
75 bool G1StringDedup::is_candidate_from_evacuation(bool from_young, bool to_young, oop obj) {
76 if (from_young && java_lang_String::is_instance_inlined(obj)) {
77 if (to_young && obj->age() == StringDeduplicationAgeThreshold) {
78 // Candidate found. String is being evacuated from young to young and just
79 // reached the deduplication age threshold.
80 return true;
81 }
82 if (!to_young && obj->age() < StringDeduplicationAgeThreshold) {
83 // Candidate found. String is being evacuated from young to old but has not
84 // reached the deduplication age threshold, i.e. has not previously been a
85 // candidate during its life in the young generation.
86 return true;
87 }
88 }
89
90 // Not a candidate
91 return false;
92 }
93
94 void G1StringDedup::enqueue_from_evacuation(bool from_young, bool to_young, uint worker_id, oop java_string) {
95 assert(is_enabled(), "String deduplication not enabled");
96 if (is_candidate_from_evacuation(from_young, to_young, java_string)) {
97 G1StringDedupQueue::push(worker_id, java_string);
98 }
99 }
100
101 void G1StringDedup::deduplicate(oop java_string) {
102 assert(is_enabled(), "String deduplication not enabled");
103 G1StringDedupStat dummy; // Statistics from this path is never used
104 G1StringDedupTable::deduplicate(java_string, dummy);
105 }
106
107 void G1StringDedup::oops_do(OopClosure* keep_alive) {
108 assert(is_enabled(), "String deduplication not enabled");
109 unlink_or_oops_do(NULL, keep_alive, true /* allow_resize_and_rehash */);
110 }
111
112 void G1StringDedup::parallel_unlink(G1StringDedupUnlinkOrOopsDoClosure* unlink, uint worker_id) {
113 assert(is_enabled(), "String deduplication not enabled");
114 G1StringDedupQueue::unlink_or_oops_do(unlink);
115 G1StringDedupTable::unlink_or_oops_do(unlink, worker_id);
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 G1GCPhaseTimes* _phase_times;
126
127 public:
128 G1StringDedupUnlinkOrOopsDoTask(BoolObjectClosure* is_alive,
129 OopClosure* keep_alive,
130 bool allow_resize_and_rehash,
131 G1GCPhaseTimes* phase_times) :
132 AbstractGangTask("G1StringDedupUnlinkOrOopsDoTask"),
133 _cl(is_alive, keep_alive, allow_resize_and_rehash), _phase_times(phase_times) { }
134
135 virtual void work(uint worker_id) {
136 {
137 G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id);
138 G1StringDedupQueue::unlink_or_oops_do(&_cl);
139 }
140 {
141 G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id);
142 G1StringDedupTable::unlink_or_oops_do(&_cl, worker_id);
143 }
144 }
145 };
146
147 void G1StringDedup::unlink_or_oops_do(BoolObjectClosure* is_alive,
148 OopClosure* keep_alive,
149 bool allow_resize_and_rehash,
150 G1GCPhaseTimes* phase_times) {
151 assert(is_enabled(), "String deduplication not enabled");
152
153 G1StringDedupUnlinkOrOopsDoTask task(is_alive, keep_alive, allow_resize_and_rehash, phase_times);
154 G1CollectedHeap* g1h = G1CollectedHeap::heap();
155 g1h->workers()->run_task(&task);
156 }
157
158 void G1StringDedup::threads_do(ThreadClosure* tc) {
159 assert(is_enabled(), "String deduplication not enabled");
160 tc->do_thread(G1StringDedupThread::thread());
161 }
162
163 void G1StringDedup::print_worker_threads_on(outputStream* st) {
164 assert(is_enabled(), "String deduplication not enabled");
165 G1StringDedupThread::thread()->print_on(st);
166 st->cr();
167 }
168
169 void G1StringDedup::verify() {
170 assert(is_enabled(), "String deduplication not enabled");
171 G1StringDedupQueue::verify();
172 G1StringDedupTable::verify();
173 }
174
175 G1StringDedupUnlinkOrOopsDoClosure::G1StringDedupUnlinkOrOopsDoClosure(BoolObjectClosure* is_alive,
176 OopClosure* keep_alive,
177 bool allow_resize_and_rehash) :
178 _is_alive(is_alive),
179 _keep_alive(keep_alive),
180 _resized_table(NULL),
181 _rehashed_table(NULL),
182 _next_queue(0),
183 _next_bucket(0) {
184 if (allow_resize_and_rehash) {
185 // If both resize and rehash is needed, only do resize. Rehash of
186 // the table will eventually happen if the situation persists.
187 _resized_table = G1StringDedupTable::prepare_resize();
188 if (!is_resizing()) {
189 _rehashed_table = G1StringDedupTable::prepare_rehash();
190 }
191 }
192 }
193
194 G1StringDedupUnlinkOrOopsDoClosure::~G1StringDedupUnlinkOrOopsDoClosure() {
195 assert(!is_resizing() || !is_rehashing(), "Can not both resize and rehash");
196 if (is_resizing()) {
197 G1StringDedupTable::finish_resize(_resized_table);
198 } else if (is_rehashing()) {
199 G1StringDedupTable::finish_rehash(_rehashed_table);
200 }
201 }
202
203 // Atomically claims the next available queue for exclusive access by
204 // the current thread. Returns the queue number of the claimed queue.
205 size_t G1StringDedupUnlinkOrOopsDoClosure::claim_queue() {
206 return Atomic::add((size_t)1, &_next_queue) - 1;
207 }
208
209 // Atomically claims the next available table partition for exclusive
210 // access by the current thread. Returns the table bucket number where
211 // the claimed partition starts.
212 size_t G1StringDedupUnlinkOrOopsDoClosure::claim_table_partition(size_t partition_size) {
213 return Atomic::add(partition_size, &_next_bucket) - partition_size;
214 }