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 sun.nio.ch.Poller;
36
37 /**
38 * The implementation for the jcmd Thread.vthread_summary diagnostic command.
39 */
40 public class VThreadSummary {
41 private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();
42
43 // maximum number of thread containers to print
44 private static final int MAX_THREAD_CONTAINERS = 256;
45
46 // set to true if I/O poller in use
47 private static volatile boolean pollerInitialized;
48
49 private VThreadSummary() { }
50
51 /**
52 * Invoked by the poller I/O mechanism when it initializes.
53 */
54 public static void pollerInitialized() {
55 pollerInitialized = true;
56 }
57
58 /**
59 * Invoked by the VM to print virtual thread summary information.
60 * @return the UTF-8 encoded information to print
61 */
62 private static byte[] print() {
63 StringBuilder sb = new StringBuilder();
64
65 // print thread containers (thread groupings)
66 new ThreadContainersPrinter(sb, MAX_THREAD_CONTAINERS).run();
67 sb.append(System.lineSeparator());
68
69 // print virtual thread scheduler
70 printSchedulerInfo(sb);
71 sb.append(System.lineSeparator());
72
73 // print I/O pollers if initialized
74 if (pollerInitialized) {
75 printPollerInfo(sb);
76 }
77
78 return sb.toString().getBytes(StandardCharsets.UTF_8);
79 }
80
81 /**
82 * Prints the tree of thread containers starting from the root container.
83 */
84 private static class ThreadContainersPrinter {
85 private final StringBuilder sb;
86 private final int max;
87 private int count;
88
89 ThreadContainersPrinter(StringBuilder sb, int max) {
90 this.sb = sb;
91 this.max = max;
92 }
93
94 void run() {
95 printThreadContainers(ThreadContainers.root(), 0);
96 }
97
98 /**
99 * Prints the given thread container and its children.
100 * @return true if the thread container and all its children were printed,
101 * false if the output was truncated because the max was reached
102 */
103 private boolean printThreadContainers(ThreadContainer container, int depth) {
104 if (!printThreadContainer(container, depth)) {
105 return false;
106 }
107 boolean truncated = container.children()
108 .map(c -> printThreadContainers(c, depth + 1))
109 .anyMatch(b -> b == false);
110 return !truncated;
111 }
112
113 /**
114 * Prints the given thread container or a "truncated" message if the maximum
115 * number of thread containers has already been printed.
116 * @param container the thread container
117 * @param depth the depth in the tree, for indentation purposes
118 * @return true if the thread container was printed, false if beyond max
119 */
120 private boolean printThreadContainer(ThreadContainer container, int depth) {
121 count++;
122 if (count > max) {
123 sb.append("<truncated ...>")
124 .append(System.lineSeparator());
125 return false;
126 }
127
128 Map<Boolean, Long> threadCounts = container.threads()
129 .collect(Collectors.partitioningBy(Thread::isVirtual, Collectors.counting()));
130 long platformThreadCount = threadCounts.get(Boolean.FALSE);
131 long virtualThreadCount = threadCounts.get(Boolean.TRUE);
132 if (depth > 0) {
133 int indent = depth * 4;
134 sb.append(" ".repeat(indent)).append("+-- ");
135 }
136 sb.append(container)
137 .append(" [platform threads = ")
138 .append(platformThreadCount)
139 .append(", virtual threads = ")
140 .append(virtualThreadCount)
141 .append("]")
142 .append(System.lineSeparator());
143
144 return true;
145 }
146 }
147
148 /**
149 * Print information on the virtual thread schedulers to given string buffer.
150 */
151 static void printSchedulerInfo(StringBuilder sb) {
152 sb.append("Default virtual thread scheduler:")
153 .append(System.lineSeparator());
154 sb.append(JLA.virtualThreadDefaultScheduler())
155 .append(System.lineSeparator());
156
157 sb.append(System.lineSeparator());
158
159 sb.append("Timeout schedulers:")
160 .append(System.lineSeparator());
161 var schedulers = JLA.virtualThreadDelayedTaskSchedulers().toList();
162 for (int i = 0; i < schedulers.size(); i++) {
163 sb.append('[')
164 .append(i)
165 .append("] ")
166 .append(schedulers.get(i))
167 .append(System.lineSeparator());
168 }
169 }
170
171 /**
172 * Print information on threads registered for I/O to the given string buffer.
173 */
174 private static void printPollerInfo(StringBuilder sb) {
175 Poller masterPoller = Poller.masterPoller();
176 List<Poller> readPollers = Poller.readPollers();
177 List<Poller> writePollers = Poller.writePollers();
178
179 if (masterPoller != null) {
180 sb.append("Master I/O poller:")
181 .append(System.lineSeparator())
182 .append(masterPoller)
183 .append(System.lineSeparator());
184
185 sb.append(System.lineSeparator());
186 }
187
188 sb.append("Read I/O pollers:");
189 sb.append(System.lineSeparator());
190 IntStream.range(0, readPollers.size())
191 .forEach(i -> sb.append('[')
192 .append(i)
193 .append("] ")
194 .append(readPollers.get(i))
195 .append(System.lineSeparator()));
196
197 sb.append(System.lineSeparator());
198
199 sb.append("Write I/O pollers:");
200 sb.append(System.lineSeparator());
201 IntStream.range(0, writePollers.size())
202 .forEach(i -> sb.append('[')
203 .append(i)
204 .append("] ")
205 .append(writePollers.get(i))
206 .append(System.lineSeparator()));
207 }
208 }