目錄
- 一、命令介紹
- 二、使用實例
- 實例一：jstack查看輸出
- 實例二：jstack統計線程數
- 實例三：jstack檢測死鎖
- 實例四：jstack檢測CPU高
一、命令介紹
Usage:jstack [-l] <pid>(to connect to running process) //連接活動線程jstack -F [-m] [-l] <pid>(to connect to a hung process) //連接阻塞線程jstack [-m] [-l] <executable> <core>(to connect to a core file) //連接dump的文件jstack [-m] [-l] [server_id@]<remote server IP or hostname>(to connect to a remote debug server) //連接遠程服務器Options:-F to force a thread dump. Use when jstack <pid> does not respond (process is hung)-m to print both java and native frames (mixed mode)-l long listing. Prints additional information about locks-h or -help to print this help message
二、使用實例
要使用jstack命令，首先我們要先找到要查看的進程ID，命令如下：
$ ps -ef | grep --color "com.javaagent.Main"
結果如下：
紅框中即為進程ID。
實例一：jstack查看輸出
命令如下：
$ jstack -l 69239
輸出結果：
$ jstack -l 692392020-03-03 15:16:07
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.121-b13 mixed mode):"Attach Listener" #13 daemon prio=9 os_prio=31 tid=0x00007f9242141000 nid=0x5707 waiting on condition [0x0000000000000000]java.lang.Thread.State: RUNNABLELocked ownable synchronizers:- None"ThreadTest" #11 prio=5 os_prio=31 tid=0x00007f9242140800 nid=0x5503 waiting on condition [0x00007000013d2000]java.lang.Thread.State: TIMED_WAITING (sleeping)at java.lang.Thread.sleep(Native Method)at com.javaagent.Main$2.run(Main.java:64)at java.lang.Thread.run(Thread.java:745)Locked ownable synchronizers:- None..."ThreadTest_2" #10 prio=5 os_prio=31 tid=0x00007f9242100000 nid=0x5303 in Object.wait() [0x00007000012cf000]java.lang.Thread.State: WAITING (on object monitor)at java.lang.Object.wait(Native Method)- waiting on <0x0000000795856e18> (a java.lang.Object)at java.lang.Object.wait(Object.java:502)at com.javaagent.Main$1.run(Main.java:41)- locked <0x0000000795856e18> (a java.lang.Object)at java.lang.Thread.run(Thread.java:745)Locked ownable synchronizers:- None"Finalizer" #3 daemon prio=8 os_prio=31 tid=0x00007f9242004000 nid=0x3003 in Object.wait() [0x000070000092e000]java.lang.Thread.State: WAITING (on object monitor)at java.lang.Object.wait(Native Method)- waiting on <0x0000000795588ec8> (a java.lang.ref.ReferenceQueue$Lock)at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)- locked <0x0000000795588ec8> (a java.lang.ref.ReferenceQueue$Lock)at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)Locked ownable synchronizers:- None"VM Thread" os_prio=31 tid=0x00007f9243841800 nid=0x2c03 runnable "GC task thread#0 (ParallelGC)" os_prio=31 tid=0x00007f9243810800 nid=0x2403 runnable "GC task thread#1 (ParallelGC)" os_prio=31 tid=0x00007f9243811000 nid=0x2603 runnable "GC task thread#2 (ParallelGC)" os_prio=31 tid=0x00007f9243811800 nid=0x2803 runnable "GC task thread#3 (ParallelGC)" os_prio=31 tid=0x00007f9243812800 nid=0x2a03 runnable "VM Periodic Task Thread" os_prio=31 tid=0x00007f9243805000 nid=0x4d03 waiting on condition JNI global references: 25
實例二：jstack統計線程數
命令如下：
$ jstack -l 69239 | grep 'java.lang.Thread.State' | wc -l
輸出結果：
12
實例三：jstack檢測死鎖
死鎖代碼：
package com.javaagent.thread;public class DieThread implements Runnable {public static Object obj1=new Object();public static Object obj2=new Object();private boolean flag;public DieThread(boolean bl){flag = bl;}@Overridepublic void run() {if(flag) {while(true) {synchronized(obj1) {System.out.println(Thread.currentThread().getName()+"....if...obj1...");synchronized(obj2) {System.out.println(Thread.currentThread().getName()+".....if.....obj2.....");}}}}else {while(true){synchronized(obj2) {System.out.println(Thread.currentThread().getName()+"....else...obj2...");synchronized(obj1) {System.out.println(Thread.currentThread().getName()+".....else.....obj1.....");}}}}}
}public class Main {public static void main(String[] args){DieThread d1=new DieThread(true);DieThread d2=new DieThread(false);final Thread t1 = new Thread(d1);final Thread t2 = new Thread(d2);t1.setName("DieThread_1");t2.setName("DieThread_2");t1.start();t2.start();}
}
命令如下：
$ jstack -l 69239
死鎖日志：
"DieThread_2" #11 prio=5 os_prio=31 tid=0x00007fc761896000 nid=0x5503 waiting for monitor entry [0x000070000134f000]java.lang.Thread.State: BLOCKED (on object monitor)at com.javaagent.thread.DieThread.run(DieThread.java:32)- waiting to lock <0x000000079586a768> (a java.lang.Object)- locked <0x000000079586a778> (a java.lang.Object)at java.lang.Thread.run(Thread.java:745)Locked ownable synchronizers:- None"DieThread_1" #10 prio=5 os_prio=31 tid=0x00007fc7610dd800 nid=0x5307 waiting for monitor entry [0x000070000124c000]java.lang.Thread.State: BLOCKED (on object monitor)at com.javaagent.thread.DieThread.run(DieThread.java:21)- waiting to lock <0x000000079586a778> (a java.lang.Object)- locked <0x000000079586a768> (a java.lang.Object)at java.lang.Thread.run(Thread.java:745)Locked ownable synchronizers:- NoneFound one Java-level deadlock:
=============================
"DieThread_2":waiting to lock monitor 0x00007fc7620421f8 (object 0x000000079586a768, a java.lang.Object),which is held by "DieThread_1"
"DieThread_1":waiting to lock monitor 0x00007fc762042358 (object 0x000000079586a778, a java.lang.Object),which is held by "DieThread_2"Java stack information for the threads listed above:
===================================================
"DieThread_2":at com.javaagent.thread.DieThread.run(DieThread.java:32)- waiting to lock <0x000000079586a768> (a java.lang.Object)- locked <0x000000079586a778> (a java.lang.Object)at java.lang.Thread.run(Thread.java:745)
"DieThread_1":at com.javaagent.thread.DieThread.run(DieThread.java:21)- waiting to lock <0x000000079586a778> (a java.lang.Object)- locked <0x000000079586a768> (a java.lang.Object)at java.lang.Thread.run(Thread.java:745)Found 1 deadlock.
實例四：jstack檢測CPU高
步驟一：查看cpu占用高進程
輸入命令：
$ top
輸出結果：
top - 07:50:58 up 53 days, 23:38, 2 users, load average: 0.00, 0.00, 0.00
Tasks: 113 total, 1 running, 112 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.2%us, 0.2%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 7771904k total, 1770024k used, 6001880k free, 160496k buffers
Swap: 1048572k total, 0k used, 1048572k free, 844572k cachedPID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 9075 root 20 0 19468 1540 1116 R 0.7 0.0 0:00.02 top 1177 root 20 0 240m 4252 1688 S 0.3 0.1 176:47.24 oneagentwatchdo 1546 zabbix 20 0 81212 1616 728 S 0.3 0.0 28:12.55 zabbix_agentd 4433 root 20 0 4495m 566m 14m S 0.3 7.5 61:48.80 java 1 root 20 0 23804 1772 1364 S 0.0 0.0 0:00.82 init 2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd 3 root RT 0 0 0 0 S 0.0 0.0 0:03.89 migration/0 4 root 20 0 0 0 0 S 0.0 0.0 0:16.97 ksoftirqd/0
步驟二：查看cpu占用高線程
輸入命令：
$ top -H -p 4433
輸出結果：
top - 07:52:22 up 53 days, 23:40, 2 users, load average: 0.08, 0.02, 0.01
Tasks: 62 total, 0 running, 62 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.1%us, 0.1%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 7771904k total, 1770296k used, 6001608k free, 160496k buffers
Swap: 1048572k total, 0k used, 1048572k free, 844576k cachedPID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 4433 root 20 0 4495m 566m 14m S 0.0 7.5 0:00.00 java 4434 root 20 0 4495m 566m 14m S 0.0 7.5 0:09.75 java 4435 root 20 0 4495m 566m 14m S 0.0 7.5 0:00.99 java 4436 root 20 0 4495m 566m 14m S 0.0 7.5 0:01.00 java 4437 root 20 0 4495m 566m 14m S 0.0 7.5 2:10.19 java 4438 root 20 0 4495m 566m 14m S 0.0 7.5 0:00.08 java 4439 root 20 0 4495m 566m 14m S 0.0 7.5 0:00.07 java 4440 root 20 0 4495m 566m 14m S 0.0 7.5 0:00.00 java 4441 root 20 0 4495m 566m 14m S 0.0 7.5 0:06.90 java 4446 root 20 0 4495m 566m 14m S 0.0 7.5 1:10.37 java 4447 root 20 0 4495m 566m 14m S 0.0 7.5 0:04.77 java 4448 root 20 0 4495m 566m 14m S 0.0 7.5 0:56.77 java
步驟三：轉換線程ID
printf "%x\n" 4434 //轉換成16進制
輸出結果：
1152 //16進制
步驟四：定位cpu占用線程
輸入命令：
$ jstack 4433 | grep 1152 -A 30
說明：
- 4433：進程ID；
- 1152：線程16進制ID；
輸出結果：
"main" #1 prio=5 os_prio=0 tid=0x00007f3b5c00b800 nid=0x1152 runnable [0x00007f3b61c8d000]java.lang.Thread.State: RUNNABLEat java.net.PlainSocketImpl.socketAccept(Native Method)at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:409)at java.net.ServerSocket.implAccept(ServerSocket.java:545)at java.net.ServerSocket.accept(ServerSocket.java:513)at org.apache.catalina.core.StandardServer.await(StandardServer.java:470)at org.apache.catalina.startup.Catalina.await(Catalina.java:793)at org.apache.catalina.startup.Catalina.start(Catalina.java:739)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:498)at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:294)at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:428)"VM Thread" os_prio=0 tid=0x00007f3b5c0fc000 nid=0x1155 runnable "GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00007f3b5c020800 nid=0x1153 runnable "GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00007f3b5c022800 nid=0x1154 runnable "VM Periodic Task Thread" os_prio=0 tid=0x00007f3b5cad6000 nid=0x117d waiting on condition JNI global references: 262
