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 jdk.internal.vm;
26
27 import java.nio.charset.StandardCharsets;
28 import java.util.Iterator;
29 import java.util.List;
30 import java.util.Map;
31 import java.util.stream.Collectors;
32 import java.util.stream.IntStream;
33 import jdk.internal.access.JavaLangAccess;
34 import jdk.internal.access.SharedSecrets;
35 import jdk.internal.misc.Unsafe;
36 import sun.nio.ch.Poller;
37
38 /**
39 * The implementation for the jcmd Thread.vthread_summary diagnostic command.
40 */
41 public class VThreadSummary {
42 private static final Unsafe U = Unsafe.getUnsafe();
43 private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();
44
45 // maximum number of thread containers to print
46 private static final int MAX_THREAD_CONTAINERS = 256;
47
48 private VThreadSummary() { }
49
50 /**
51 * Invoked by the VM to print virtual thread summary information.
52 * @return the UTF-8 encoded information to print
53 */
54 private static byte[] print() {
55 StringBuilder sb = new StringBuilder();
56
57 // print virtual thread scheduler
58 printSchedulers(sb);
59 sb.append(System.lineSeparator());
60
61 // print I/O pollers if initialized
62 if (!U.shouldBeInitialized(Poller.class)) {
63 printPollers(sb);
64 sb.append(System.lineSeparator());
65 }
66
67 // print thread groupings/containers
68 printThreadContainers(sb);
69 sb.append(System.lineSeparator());
70
71 return sb.toString().getBytes(StandardCharsets.UTF_8);
72 }
73
74 /**
75 * Print information on the virtual thread schedulers to given string builder.
76 */
77 private static void printSchedulers(StringBuilder sb) {
78 sb.append("Virtual thread scheduler:")
79 .append(System.lineSeparator());
80 sb.append(JLA.virtualThreadDefaultScheduler())
81 .append(System.lineSeparator());
82
83 sb.append(System.lineSeparator());
84
85 sb.append("Timeout schedulers:")
86 .append(System.lineSeparator());
87 var schedulers = JLA.virtualThreadDelayedTaskSchedulers().toList();
88 for (int i = 0; i < schedulers.size(); i++) {
89 sb.append('[')
90 .append(i)
91 .append("] ")
92 .append(schedulers.get(i))
93 .append(System.lineSeparator());
94 }
95 }
96
97 /**
98 * Print information on threads registered for I/O to the given string builder.
99 */
100 private static void printPollers(StringBuilder sb) {
101 Poller masterPoller = Poller.masterPoller();
102 List<Poller> readPollers = Poller.readPollers();
103 List<Poller> writePollers = Poller.writePollers();
104
105 if (masterPoller != null) {
106 sb.append("Master I/O poller:")
107 .append(System.lineSeparator())
108 .append(masterPoller)
109 .append(System.lineSeparator());
110 sb.append(System.lineSeparator());
111 }
112
113 sb.append("Read I/O pollers:");
114 sb.append(System.lineSeparator());
115 IntStream.range(0, readPollers.size())
116 .forEach(i -> sb.append('[')
117 .append(i)
118 .append("] ")
119 .append(readPollers.get(i))
120 .append(System.lineSeparator()));
121 sb.append(System.lineSeparator());
122
123 sb.append("Write I/O pollers:");
124 sb.append(System.lineSeparator());
125 IntStream.range(0, writePollers.size())
126 .forEach(i -> sb.append('[')
127 .append(i)
128 .append("] ")
129 .append(writePollers.get(i))
130 .append(System.lineSeparator()));
131 }
132
133 /**
134 * Print the thread containers that don't have an owner to the given string builder.
135 * The output will include the root container and all thread pools.
136 *
137 * In the future, this could be extended to support structured concurrency so that
138 * it prints a tree of owned thread containers.
139 */
140 private static void printThreadContainers(StringBuilder sb) {
141 sb.append("Thread groupings:")
142 .append(System.lineSeparator());
143
144 ThreadContainer root = ThreadContainers.root();
145 printThreadContainer(root, sb);
146
147 int printed = 1;
148 Iterator<ThreadContainer> iterator = root.children().iterator();
149 while (iterator.hasNext() && printed < MAX_THREAD_CONTAINERS) {
150 ThreadContainer container = iterator.next();
151 if (container.owner() == null) {
152 printThreadContainer(container, sb);
153 printed++;
154 }
155 }
156 if (iterator.hasNext()) {
157 sb.append("<truncated ...>")
158 .append(System.lineSeparator());
159 }
160 }
161
162 /**
163 * Print a thread container to the given string builder.
164 */
165 private static void printThreadContainer(ThreadContainer container, StringBuilder sb) {
166 Map<Boolean, Long> threadCounts = container.threads()
167 .collect(Collectors.partitioningBy(Thread::isVirtual, Collectors.counting()));
168 long platformThreadCount = threadCounts.get(Boolean.FALSE);
169 long virtualThreadCount = threadCounts.get(Boolean.TRUE);
170 sb.append(container)
171 .append(" [platform threads = ")
172 .append(platformThreadCount)
173 .append(", virtual threads = ")
174 .append(virtualThreadCount)
175 .append("]")
176 .append(System.lineSeparator());
177 }
178 }