Linux環境cpu過高，定位問題步驟（附實例）

原創

2020-05-25 19:38

一、問題描述

生產環境cpu過高問題，排查雖然不易，但是是有一定的套路，可以加快問題定位從而排查的。

二、步驟

1.查看cpu佔用高的進程

top

2. ps -ef或者jps進一步定位，得知是一個怎麼樣的一個後臺程序

3.查看對應進程下，每個線程的運行情況

ps -mp pid -o THREAD,tid,time
例如
ps -mp 29556 -o THREAD,tid,time
ps -mp 11823 -o THREAD,tid,time

4.將佔用資源奪得線程threadpid：進制轉換，2HEX

printf "%x\n" threadpid

5.查看對應線程存在的問題

jstack 進程ID | grep tid(16進制線程ID小寫英文） -A60

三、編寫cpu高消耗代碼並且部署服務器

1.java代碼

package com.ray.cpu;

public class cpuOccupy {


    public void cpuCircle() {

        int num = 0;
        long start = System.currentTimeMillis() / 1000;
        while (true) {
            num = num + 1;

            if (num == Integer.MAX_VALUE) {
                System.out.println("reset");
                num = 0;
            }

            if ((System.currentTimeMillis() / 1000) - start > 1000) {
                return;
            }
        }
    }


    public static void main(String[] args) {
        new cpuOccupy().cpuCircle();
    }
}

2.配置maven相關配置:打jar包並且指定運行主類

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.ray.cpu</groupId>
    <artifactId>occupied</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
 
    </dependencies>
    <build>
        <!--<pluginManagement>&lt;!&ndash; lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) &ndash;&gt;-->
        <plugins>

            <plugin>
                <!--<groupId>org.apache.maven.plugins</groupId>-->
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.3.2</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>

            <plugin>
                <artifactId>maven-assembly-plugin </artifactId>
                <configuration>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                    <archive>
                        <manifest>
                            <mainClass>com.ray.cpu.cpuOccupy</mainClass>
                        </manifest>
                    </archive>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>


        </plugins>
        <!--</pluginManagement>-->
    </build>

</project>

關鍵點：打包jar包插件，以及指定主類

3.打包

4.上傳linux服務器並且運行

 
# java -jar occupied-1.0-SNAPSHOT-jar-with-dependencies.jar

四、排查問題

1. top查看佔用cpu資源較多的程序PID：13645

2. 查看對應進程下，每個線程的運行情況

[root@cloudera ~]# ps -mp 13645 -o THREAD,tid,time
USER     %CPU PRI SCNT WCHAN  USER SYSTEM   TID     TIME
root     98.7   -    - -         -      -     - 00:00:36
root      0.0  19    - futex_    -      - 13645 00:00:00
root     98.6  19    - -         -      - 13648 00:00:36
root      0.0  19    - futex_    -      - 13650 00:00:00
root      0.0  19    - futex_    -      - 13651 00:00:00
root      0.0  19    - futex_    -      - 13653 00:00:00
root      0.0  19    - futex_    -      - 13655 00:00:00
root      0.0  19    - futex_    -      - 13658 00:00:00
root      0.0  19    - futex_    -      - 13664 00:00:00
root      0.0  19    - futex_    -      - 13665 00:00:00
root      0.0  19    - futex_    -      - 13666 00:00:00
root      0.0  19    - futex_    -      - 13669 00:00:00
root      0.0  19    - futex_    -      - 13670 00:00:00
root      0.0  19    - futex_    -      - 13673 00:00:00
root      0.0  19    - futex_    -      - 13674 00:00:00
root      0.0  19    - futex_    -      - 13678 00:00:00
root      0.0  19    - futex_    -      - 13679 00:00:00
root      0.0  19    - futex_    -      - 13680 00:00:00
root      0.0  19    - futex_    -      - 13685 00:00:00
root      0.0  19    - futex_    -      - 13687 00:00:00
root      0.0  19    - futex_    -      - 13688 00:00:00

3. 將佔用資源奪得線程threadpid：進制轉換16進制，2HEX

[root@cloudera ~]# printf "%x\n" 13648
3550

4.定位線程問題

jstack 13645 | grep 3550 -A60

5.定位java程序位置（非常詳細）

五、參考

1. Java CPU 佔用高模擬及排查

https://blog.csdn.net/jiankunking/article/details/79749836

2.排查Java的CPU性能問題

https://blog.csdn.net/jiankunking/article/details/80297136

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