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.Executor;
28 import java.util.concurrent.ForkJoinPool;
29 import javax.management.ObjectName;
30 import jdk.management.VirtualThreadSchedulerMXBean;
31 import jdk.internal.access.JavaLangAccess;
32 import jdk.internal.access.SharedSecrets;
33 import jdk.internal.vm.ContinuationSupport;
34 import sun.management.Util;
35
36 /**
37 * Provides the implementation of the management interface for the JDK's default virtual
38 * thread scheduler.
39 */
40 public class VirtualThreadSchedulerImpls {
41 private VirtualThreadSchedulerImpls() {
42 }
43
44 public static VirtualThreadSchedulerMXBean create() {
45 if (ContinuationSupport.isSupported()) {
46 return new VirtualThreadSchedulerImpl();
47 } else {
48 return new BoundVirtualThreadSchedulerImpl();
49 }
50 }
51
52 /**
53 * Base implementation of VirtualThreadSchedulerMXBean.
54 */
55 private abstract static class BaseVirtualThreadSchedulerImpl
56 implements VirtualThreadSchedulerMXBean {
57
58 @Override
59 public final ObjectName getObjectName() {
60 return Util.newObjectName("jdk.management:type=VirtualThreadScheduler");
61 }
62
63 @Override
64 public String toString() {
65 var sb = new StringBuilder("[parallelism=");
66 sb.append(getParallelism());
67 append(sb, "size", getPoolSize());
68 append(sb, "mounted", getMountedVirtualThreadCount());
69 append(sb, "queued", getQueuedVirtualThreadCount());
70 sb.append(']');
71 return sb.toString();
72 }
73
74 private void append(StringBuilder sb, String name, long value) {
75 sb.append(", ").append(name).append('=');
76 if (value >= 0) {
77 sb.append(value);
78 } else {
79 sb.append("<unavailable>");
80 }
81 }
82 }
83
84 /**
85 * Implementation of VirtualThreadSchedulerMXBean when virtual threads are
86 * implemented with continuations + scheduler.
87 */
88 private static final class VirtualThreadSchedulerImpl extends BaseVirtualThreadSchedulerImpl {
89 /**
90 * Holder class for scheduler.
91 */
92 private static class Scheduler {
93 private static final Executor scheduler =
94 SharedSecrets.getJavaLangAccess().virtualThreadDefaultScheduler();
95 static Executor instance() {
96 return scheduler;
97 }
98 }
99
100 @Override
101 public int getParallelism() {
102 if (Scheduler.instance() instanceof ForkJoinPool pool) {
103 return pool.getParallelism();
104 }
105 throw new InternalError(); // should not get here
106 }
107
108 @Override
109 public void setParallelism(int size) {
110 if (Scheduler.instance() instanceof ForkJoinPool pool) {
111 pool.setParallelism(size);
112 if (pool.getPoolSize() < size) {
113 // FJ worker thread creation is on-demand
114 Thread.startVirtualThread(() -> { });
115 }
116
117 return;
118 }
119 throw new UnsupportedOperationException(); // should not get here
120 }
121
122 @Override
123 public int getPoolSize() {
124 if (Scheduler.instance() instanceof ForkJoinPool pool) {
125 return pool.getPoolSize();
126 }
127 return -1; // should not get here
128 }
129
130 @Override
131 public int getMountedVirtualThreadCount() {
132 if (Scheduler.instance() instanceof ForkJoinPool pool) {
133 return pool.getActiveThreadCount();
134 }
135 return -1; // should not get here
136 }
137
138 @Override
139 public long getQueuedVirtualThreadCount() {
140 if (Scheduler.instance() instanceof ForkJoinPool pool) {
141 return pool.getQueuedTaskCount() + pool.getQueuedSubmissionCount();
142 }
143 return -1L; // should not get here
144 }
145 }
146
147 /**
148 * Implementation of VirtualThreadSchedulerMXBean when virtual threads are backed
149 * by platform threads.
150 */
151 private static final class BoundVirtualThreadSchedulerImpl extends BaseVirtualThreadSchedulerImpl {
152 @Override
153 public int getParallelism() {
154 return Integer.MAX_VALUE;
155 }
156
157 @Override
158 public void setParallelism(int size) {
159 throw new UnsupportedOperationException();
160 }
161
162 @Override
163 public int getPoolSize() {
164 return -1;
165 }
166
167 @Override
168 public int getMountedVirtualThreadCount() {
169 return -1;
170 }
171
172 @Override
173 public long getQueuedVirtualThreadCount() {
174 return -1L;
175 }
176 }
177 }
178