高CPU Java应用分析

模拟CPU 40%左右

import java.util.concurrent.CountDownLatch;

public class Main extends Thread {
    private CountDownLatch c;

    public Main(String name, CountDownLatch c) {
        super(name);
        this.c = c;
    }

    @Override
    public void run() {
        for (int i = 0; i < 500000000; i++) {
            System.out.print(i);
        }
        c.countDown();
    }

    public static void main(String[] args) throws InterruptedException {
        CountDownLatch c = new CountDownLatch(1);
        Main thread1 = new Main("thread1", c);
        thread1.start();

        c.await();
    }
}

后台运行jar包

java -jar maven_test.jar &

安装jstack

yum install java-1.8.0-openjdk-devel.x86_64 -y

找到占用CPU最高的进程是Java进程59635

top

找到占用CPU最高的线程59647

top -H -p 59635

输出线程PID 59647对应的16进制数是e8ff

printf "%x\n" 59647

jstack查看Java进程中线程信息，过滤e8ff相关的线程信息

jstack 59635 | grep e8ff -A 20

根据jstack的输出，主流程也是一个线程

参考资料
java 线上应用排查CPU过高（模拟场景）