1 /*
2 * Copyright (c) 2024, 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25 package com.sun.management.internal;
26
27 import java.util.concurrent.ForkJoinPool;
28 import javax.management.ObjectName;
29 import jdk.management.VirtualThreadSchedulerMXBean;
30 import jdk.internal.access.JavaLangAccess;
31 import jdk.internal.access.SharedSecrets;
32 import jdk.internal.vm.ContinuationSupport;
33 import sun.management.Util;
34
35 /**
36 * Provides the implementation of the management interface for the JDK's virtual thread scheduler.
37 */
38 public class VirtualThreadSchedulerImpls {
39 private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();
40
41 private VirtualThreadSchedulerImpls() {
42 }
43
44 /**
45 * Creates the VirtualThreadSchedulerMXBean.
46 */
47 public static VirtualThreadSchedulerMXBean create() {
48 // -XX:-VMContinuations
49 if (!ContinuationSupport.isSupported()) {
50 return new BoundVirtualThreadSchedulerImpl();
51 }
52
53 // built-in ForkJoinPool scheduler
54 if (System.getProperty("jdk.virtualThreadScheduler.implClass") == null) {
55 return new BuiltinVirtualThreadSchedulerImpl();
56 }
57
58 // custom scheduler implements VirtualThreadSchedulerMXBean
59 if (JLA.defaultVirtualThreadScheduler() instanceof VirtualThreadSchedulerMXBean bean) {
60 return bean;
61 }
62
63 // custom scheduler does not implement VirtualThreadSchedulerMXBean
64 return new CustomVirtualThreadSchedulerImpl();
65 }
66
67 /**
68 * Base implementation of VirtualThreadSchedulerMXBean.
69 */
70 private abstract static class BaseVirtualThreadSchedulerImpl
71 implements VirtualThreadSchedulerMXBean {
72
73 @Override
74 public final ObjectName getObjectName() {
75 return Util.newObjectName("jdk.management:type=VirtualThreadScheduler");
76 }
77
78 @Override
79 public String toString() {
80 var sb = new StringBuilder("[parallelism=");
81 sb.append(getParallelism());
82 append(sb, "size", getPoolSize());
83 append(sb, "mounted", getMountedVirtualThreadCount());
84 append(sb, "queued", getQueuedVirtualThreadCount());
85 sb.append(']');
86 return sb.toString();
87 }
88
89 private void append(StringBuilder sb, String name, long value) {
90 sb.append(", ").append(name).append('=');
91 if (value >= 0) {
92 sb.append(value);
93 } else {
94 sb.append("<unavailable>");
95 }
96 }
97 }
98
99 /**
100 * Implementation of VirtualThreadSchedulerMXBean when virtual threads are
101 * implemented with continuations and the built-in ForkJoinPool scheduler.
102 */
103 private static final class BuiltinVirtualThreadSchedulerImpl
104 extends BaseVirtualThreadSchedulerImpl {
105
106 private ForkJoinPool forkJoinPool() {
107 return (ForkJoinPool) JLA.builtinVirtualThreadScheduler();
108 }
109
110 @Override
111 public int getParallelism() {
112 return forkJoinPool().getParallelism();
113 }
114
115 @Override
116 public void setParallelism(int size) {
117 forkJoinPool().setParallelism(size);
118 }
119
120 @Override
121 public int getPoolSize() {
122 return forkJoinPool().getPoolSize();
123 }
124
125 @Override
126 public int getMountedVirtualThreadCount() {
127 return forkJoinPool().getActiveThreadCount();
128 }
129
130 @Override
131 public long getQueuedVirtualThreadCount() {
132 ForkJoinPool p = forkJoinPool();
133 return p.getQueuedTaskCount() + p.getQueuedSubmissionCount();
134 }
135 }
136
137 /**
138 * Implementation of VirtualThreadSchedulerMXBean when virtual threads are backed
139 * by platform threads.
140 */
141 private static final class BoundVirtualThreadSchedulerImpl
142 extends BaseVirtualThreadSchedulerImpl {
143 @Override
144 public int getParallelism() {
145 return Integer.MAX_VALUE;
146 }
147
148 @Override
149 public void setParallelism(int size) {
150 throw new UnsupportedOperationException();
151 }
152
153 @Override
154 public int getPoolSize() {
155 return -1;
156 }
157
158 @Override
159 public int getMountedVirtualThreadCount() {
160 return -1;
161 }
162
163 @Override
164 public long getQueuedVirtualThreadCount() {
165 return -1L;
166 }
167 }
168
169 /**
170 * Implementation of VirtualThreadSchedulerMXBean when using a custom virtual
171 * thread scheduler that does not implement VirtualThreadSchedulerMXBean.
172 */
173 private static final class CustomVirtualThreadSchedulerImpl
174 extends BaseVirtualThreadSchedulerImpl {
175
176 @Override
177 public int getParallelism() {
178 return 1;
179 }
180
181 @Override
182 public void setParallelism(int size) {
183 throw new UnsupportedOperationException();
184 }
185
186 @Override
187 public int getPoolSize() {
188 return -1;
189 }
190
191 @Override
192 public int getMountedVirtualThreadCount() {
193 return -1;
194 }
195
196 @Override
197 public long getQueuedVirtualThreadCount() {
198 return -1L;
199 }
200 }
201 }
202