org.wildfly.common.cpu.ProcessorInfo Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
package org.wildfly.common.cpu;
/*
* JBoss, Home of Professional Open Source.
* Copyright 2015 Red Hat, Inc., and individual contributors
* as indicated by the @author tags.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Locale;
/**
* Provides general information about the processors on this host.
*
* @author Jason T. Greene
*/
public class ProcessorInfo {
private ProcessorInfo() {
}
private static final String CPUS_ALLOWED = "Cpus_allowed:";
private static final byte[] BITS = new byte[]{0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4};
private static final Charset ASCII = Charset.forName("US-ASCII");
/**
* Returns the number of processors available to this process. On most operating systems this method
* simply delegates to {@link Runtime#availableProcessors()}. However, on Linux, this strategy
* is insufficient, since the JVM does not take into consideration the process' CPU set affinity
* which is employed by cgroups and numactl. Therefore this method will analyze the Linux proc filesystem
* to make the determination. Since the CPU affinity of a process can be change at any time, this method does
* not cache the result. Calls should be limited accordingly.
*
* Note tha on Linux, both SMT units (Hyper-Threading) and CPU cores are counted as a processor.
*
* @return the available processors on this system.
*/
public static int availableProcessors() {
if (System.getSecurityManager() != null) {
return AccessController.doPrivileged((PrivilegedAction) () -> Integer.valueOf(determineProcessors())).intValue();
}
return determineProcessors();
}
private static int determineProcessors() {
int javaProcs = Runtime.getRuntime().availableProcessors();
if (!isLinux()) {
return javaProcs;
}
int maskProcs = 0;
try {
maskProcs = readCPUMask();
} catch (Exception e) {
// yum
}
return maskProcs > 0 ? Math.min(javaProcs, maskProcs) : javaProcs;
}
private static int readCPUMask() throws IOException {
final FileInputStream stream = new FileInputStream("/proc/self/status");
final InputStreamReader inputReader = new InputStreamReader(stream, ASCII);
try (BufferedReader reader = new BufferedReader(inputReader)) {
String line;
while ((line = reader.readLine()) != null) {
if (line.startsWith(CPUS_ALLOWED)) {
int count = 0;
int start = CPUS_ALLOWED.length();
for (int i = start; i < line.length(); i++) {
char ch = line.charAt(i);
if (ch >= '0' && ch <= '9') {
count += BITS[ch - '0'];
} else if (ch >= 'a' && ch <= 'f') {
count += BITS[ch - 'a' + 10];
} else if (ch >= 'A' && ch <= 'F') {
count += BITS[ch - 'A' + 10];
}
}
return count;
}
}
}
return -1;
}
private static boolean isLinux() {
String osArch = System.getProperty("os.name", "unknown").toLowerCase(Locale.US);
return (osArch.contains("linux"));
}
}