1 /*
2 * Copyright (c) 2017, 2020, Red Hat, Inc. 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
27 #include "gc/shared/stringdedup/stringDedup.inline.hpp"
28 #include "gc/shared/workgroup.hpp"
29 #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
30 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
31 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
32 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
33 #include "gc/shenandoah/shenandoahStringDedup.hpp"
34 #include "gc/shenandoah/shenandoahStrDedupQueue.hpp"
35 #include "gc/shenandoah/shenandoahUtils.hpp"
36 #include "runtime/thread.hpp"
37
initialize()38 void ShenandoahStringDedup::initialize() {
39 assert(UseShenandoahGC, "String deduplication available with Shenandoah GC");
40 StringDedup::initialize_impl<ShenandoahStrDedupQueue, StringDedupStat>();
41 }
42
43 /* Enqueue candidates for deduplication.
44 * The method should only be called by GC worker threads during marking phases.
45 */
enqueue_candidate(oop java_string)46 void ShenandoahStringDedup::enqueue_candidate(oop java_string) {
47 assert(Thread::current()->is_Worker_thread(),
48 "Only from a GC worker thread");
49
50 if (java_string->age() <= StringDeduplicationAgeThreshold) {
51 const markWord mark = java_string->mark();
52
53 // Having/had displaced header, too risk to deal with them, skip
54 if (mark == markWord::INFLATING() || mark.has_displaced_mark_helper()) {
55 return;
56 }
57
58 // Increase string age and enqueue it when it rearches age threshold
59 markWord new_mark = mark.incr_age();
60 if (mark == java_string->cas_set_mark(new_mark, mark)) {
61 if (mark.age() == StringDeduplicationAgeThreshold) {
62 StringDedupQueue::push(ShenandoahWorkerSession::worker_id(), java_string);
63 }
64 }
65 }
66 }
67
68 // Deduplicate a string, return true if it is deduplicated.
deduplicate(oop java_string)69 void ShenandoahStringDedup::deduplicate(oop java_string) {
70 assert(is_enabled(), "String deduplication not enabled");
71 StringDedupStat dummy; // Statistics from this path is never used
72 StringDedupTable::deduplicate(java_string, &dummy);
73 }
74
parallel_oops_do(ShenandoahPhaseTimings::Phase phase,BoolObjectClosure * is_alive,OopClosure * cl,uint worker_id)75 void ShenandoahStringDedup::parallel_oops_do(ShenandoahPhaseTimings::Phase phase,
76 BoolObjectClosure* is_alive, OopClosure* cl, uint worker_id) {
77 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
78 assert(is_enabled(), "String deduplication not enabled");
79
80 StringDedupUnlinkOrOopsDoClosure sd_cl(is_alive, cl);
81 {
82 ShenandoahWorkerTimingsTracker x(phase, ShenandoahPhaseTimings::StringDedupQueueRoots, worker_id);
83 StringDedupQueue::unlink_or_oops_do(&sd_cl);
84 }
85
86 {
87 ShenandoahWorkerTimingsTracker x(phase, ShenandoahPhaseTimings::StringDedupTableRoots, worker_id);
88 StringDedupTable::unlink_or_oops_do(&sd_cl, worker_id);
89 }
90 }
91
oops_do_slow(OopClosure * cl)92 void ShenandoahStringDedup::oops_do_slow(OopClosure* cl) {
93 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
94 assert(is_enabled(), "String deduplication not enabled");
95 AlwaysTrueClosure always_true;
96 StringDedupUnlinkOrOopsDoClosure sd_cl(&always_true, cl);
97 StringDedupQueue::unlink_or_oops_do(&sd_cl);
98 StringDedupTable::unlink_or_oops_do(&sd_cl, 0);
99 }
100
101 //
102 // Task for parallel unlink_or_oops_do() operation on the deduplication queue
103 // and table.
104 //
105 class ShenandoahStringDedupUnlinkOrOopsDoTask : public AbstractGangTask {
106 private:
107 StringDedupUnlinkOrOopsDoClosure _cl;
108
109 public:
ShenandoahStringDedupUnlinkOrOopsDoTask(BoolObjectClosure * is_alive,OopClosure * keep_alive,bool allow_resize_and_rehash)110 ShenandoahStringDedupUnlinkOrOopsDoTask(BoolObjectClosure* is_alive,
111 OopClosure* keep_alive,
112 bool allow_resize_and_rehash) :
113 AbstractGangTask("StringDedupUnlinkOrOopsDoTask"),
114 _cl(is_alive, keep_alive) {
115 StringDedup::gc_prologue(allow_resize_and_rehash);
116 }
117
~ShenandoahStringDedupUnlinkOrOopsDoTask()118 ~ShenandoahStringDedupUnlinkOrOopsDoTask() {
119 StringDedup::gc_epilogue();
120 }
121
work(uint worker_id)122 virtual void work(uint worker_id) {
123 StringDedupQueue::unlink_or_oops_do(&_cl);
124 StringDedupTable::unlink_or_oops_do(&_cl, worker_id);
125 }
126 };
127
unlink_or_oops_do(BoolObjectClosure * is_alive,OopClosure * keep_alive,bool allow_resize_and_rehash)128 void ShenandoahStringDedup::unlink_or_oops_do(BoolObjectClosure* is_alive,
129 OopClosure* keep_alive,
130 bool allow_resize_and_rehash) {
131 assert(is_enabled(), "String deduplication not enabled");
132
133 ShenandoahStringDedupUnlinkOrOopsDoTask task(is_alive, keep_alive, allow_resize_and_rehash);
134 ShenandoahHeap* heap = ShenandoahHeap::heap();
135 heap->workers()->run_task(&task);
136 }
137