1/*
2 * Copyright (c) 2014, 2019, 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.hpp"
28#include "gc/g1/g1StringDedup.hpp"
29#include "gc/g1/g1StringDedupQueue.hpp"
30#include "logging/log.hpp"
31#include "oops/oop.inline.hpp"
32#include "runtime/atomic.hpp"
33#include "runtime/mutexLocker.hpp"
34#include "runtime/safepointVerifiers.hpp"
35#include "utilities/stack.inline.hpp"
36
37const size_t G1StringDedupQueue::_max_size = 1000000; // Max number of elements per queue
38const size_t G1StringDedupQueue::_max_cache_size = 0; // Max cache size per queue
39
40G1StringDedupQueue::G1StringDedupQueue() :
41 _cursor(0),
42 _cancel(false),
43 _empty(true),
44 _dropped(0) {
45 _nqueues = ParallelGCThreads;
46 _queues = NEW_C_HEAP_ARRAY(G1StringDedupWorkerQueue, _nqueues, mtGC);
47 for (size_t i = 0; i < _nqueues; i++) {
48 new (_queues + i) G1StringDedupWorkerQueue(G1StringDedupWorkerQueue::default_segment_size(), _max_cache_size, _max_size);
49 }
50}
51
52G1StringDedupQueue::~G1StringDedupQueue() {
53 ShouldNotReachHere();
54}
55
56void G1StringDedupQueue::wait_impl() {
57 MonitorLocker ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);
58 while (_empty && !_cancel) {
59 ml.wait();
60 }
61}
62
63void G1StringDedupQueue::cancel_wait_impl() {
64 MonitorLocker ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);
65 _cancel = true;
66 ml.notify();
67}
68
69void G1StringDedupQueue::push_impl(uint worker_id, oop java_string) {
70 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint");
71 assert(worker_id < _nqueues, "Invalid queue");
72
73 // Push and notify waiter
74 G1StringDedupWorkerQueue& worker_queue = _queues[worker_id];
75 if (!worker_queue.is_full()) {
76 worker_queue.push(java_string);
77 if (_empty) {
78 MonitorLocker ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);
79 if (_empty) {
80 // Mark non-empty and notify waiter
81 _empty = false;
82 ml.notify();
83 }
84 }
85 } else {
86 // Queue is full, drop the string and update the statistics
87 Atomic::inc(&_dropped);
88 }
89}
90
91oop G1StringDedupQueue::pop_impl() {
92 assert(!SafepointSynchronize::is_at_safepoint(), "Must not be at safepoint");
93 NoSafepointVerifier nsv;
94
95 // Try all queues before giving up
96 for (size_t tries = 0; tries < _nqueues; tries++) {
97 // The cursor indicates where we left of last time
98 G1StringDedupWorkerQueue* queue = &_queues[_cursor];
99 while (!queue->is_empty()) {
100 oop obj = queue->pop();
101 // The oop we pop can be NULL if it was marked
102 // dead. Just ignore those and pop the next oop.
103 if (obj != NULL) {
104 return obj;
105 }
106 }
107
108 // Try next queue
109 _cursor = (_cursor + 1) % _nqueues;
110 }
111
112 // Mark empty
113 _empty = true;
114
115 return NULL;
116}
117
118void G1StringDedupQueue::unlink_or_oops_do_impl(StringDedupUnlinkOrOopsDoClosure* cl, size_t queue) {
119 assert(queue < _nqueues, "Invalid queue");
120 StackIterator<oop, mtGC> iter(_queues[queue]);
121 while (!iter.is_empty()) {
122 oop* p = iter.next_addr();
123 if (*p != NULL) {
124 if (cl->is_alive(*p)) {
125 cl->keep_alive(p);
126 } else {
127 // Clear dead reference
128 *p = NULL;
129 }
130 }
131 }
132}
133
134void G1StringDedupQueue::print_statistics_impl() {
135 log_debug(gc, stringdedup)(" Queue");
136 log_debug(gc, stringdedup)(" Dropped: " UINTX_FORMAT, _dropped);
137}
138
139void G1StringDedupQueue::verify_impl() {
140 for (size_t i = 0; i < _nqueues; i++) {
141 StackIterator<oop, mtGC> iter(_queues[i]);
142 while (!iter.is_empty()) {
143 oop obj = iter.next();
144 if (obj != NULL) {
145 guarantee(G1CollectedHeap::heap()->is_in_reserved(obj), "Object must be on the heap");
146 guarantee(!obj->is_forwarded(), "Object must not be forwarded");
147 guarantee(java_lang_String::is_instance(obj), "Object must be a String");
148 }
149 }
150 }
151}
152