JVM性能分析工具jstack介紹

JDK本身提供了很多方便的JVM性能調優監控工具，除了集成式的VisualVM和jConsole外， 還有jps、jstack、jmap、jhat、jstat、hprof等小巧的工具，每一種工具都有其自身的特點， 用戶可以根據你需要檢測的應用或者程序片段的狀況，適當的選擇相應的工具進行檢測， 先通過一個表格形式簡要介紹下這幾個命令的作用和使用方法。本文重點介紹jstack的使用方法。

命令	作用
jps	基礎工具
jstack	查看某個Java進程內的線程堆棧信息
jmap	jmap導出堆內存，然后使用jhat來進行分析
jhat	jmap導出堆內存，然后使用jhat來進行分析
jstat	JVM統計監測工具
hprof	hprof能夠展現CPU使用率，統計堆內存使用情況

jps使用

可以列出本機所有java進程的pid

選項

• -q 僅輸出VM標識符，不包括class name,jar name,arguments in main method
• -m 輸出main method的參數
• -l 輸出完全的包名，應用主類名，jar的完全路徑名
• -v 輸出jvm參數
• -V 輸出通過flag文件傳遞到JVM中的參數(.hotspotrc文件或-XX:Flags=所指定的文件
• -Joption 傳遞參數到vm,例如:-J-Xms48m

示例：

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[root@CZT-FS1 board-api]# jps -lvm 67136 board-api-1.0.0-SNAPSHOT.jar --spring.config.location=application.yml -Xms1024m -Xmx1024m 100547 board-web-1.0.0-SNAPSHOT.jar --spring.config.location=application.yml -Xms512m 8819 app-manage-api-1.0.0-SNAPSHOT.jar --spring.config.location=application.yml -Xms512m 120226 adm-web-1.0.0-SNAPSHOT.jar --spring.config.location=file:./application.yml -Xms512m 105268 wechat-api-1.0.0-SNAPSHOT.jar --spring.config.location=application.yml -Xms512m 89172 sun.tools.jps.Jps -lvm -Denv.class.path=.:/usr/local/jdk/lib/dt.jar:/usr/local/jdk/lib/tools.jar:/usr/local/jdk/jre/lib -Dapplication.home=/usr/local/jdk -Xms8m 44921 app-manage-1.0.0-SNAPSHOT.jar --spring.config.location=file:./application.yml -Xms512m -Xmx1024m

我們選取PID=67136的Java進程作為后續研究對象。

top使用

除了常用的打印所有進程使用資源外，還可以對單獨的進程，打印線程資源排行榜，按T鍵可對TIME倒序排列， 也就是CPU運行時間。TIME列就是各個Java線程耗費的CPU時間，我們線程pid為67163的線程作為后續線程研究對象

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[root@CZT-FS1 board-api]# top -Hp 67136 top - 11:22:26 up 166 days, 17:06, 1 user, load average: 0.07, 0.02, 0.00 Tasks: 140 total, 0 running, 140 sleeping, 0 stopped, 0 zombie Cpu(s): 0.1%us, 0.0%sy, 0.0%ni, 99.9%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 16309360k total, 16120904k used, 188456k free, 174440k buffers Swap: 8175612k total, 461868k used, 7713744k free, 7831512k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 67163 root 20 0 6825m 867m 14m S 2.0 5.4 16:22.87 java 67136 root 20 0 6825m 867m 14m S 0.0 5.4 0:00.00 java 67137 root 20 0 6825m 867m 14m S 0.0 5.4 0:10.82 java 67138 root 20 0 6825m 867m 14m S 0.0 5.4 0:00.32 java 67139 root 20 0 6825m 867m 14m S 0.0 5.4 0:00.32 java 67140 root 20 0 6825m 867m 14m S 0.0 5.4 0:00.31 java 67141 root 20 0 6825m 867m 14m S 0.0 5.4 0:00.35 java 67142 root 20 0 6825m 867m 14m S 0.0 5.4 0:00.35 java 67143 root 20 0 6825m 867m 14m S 0.0 5.4 0:00.36 java 67144 root 20 0 6825m 867m 14m S 0.0 5.4 0:00.33 java 67145 root 20 0 6825m 867m 14m S 0.0 5.4 0:00.31 java 67146 root 20 0 6825m 867m 14m S 0.0 5.4 0:08.29 java 67147 root 20 0 6825m 867m 14m S 0.0 5.4 0:00.02 java 67148 root 20 0 6825m 867m 14m S 0.0 5.4 0:00.35 java 67149 root 20 0 6825m 867m 14m S 0.0 5.4 0:00.00 java 67150 root 20 0 6825m 867m 14m S 0.0 5.4 0:25.08 java

jstack使用

jstack主要用來查看某個Java進程內的線程堆棧信息。語法格式如下：

1	jstack [option] pid

參數如下：

1. -l long listings，會打印出額外的鎖信息，在發生死鎖時可以用jstack -l pid來觀察鎖持有情況
2. -m mixed mode，不僅會輸出Java堆棧信息，還會輸出C/C++堆棧信息（比如Native方法）

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[root@CZT-FS1 board-api]# jstack -l 67136 | more Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.161-b12 mixed mode): "Thread-12126" #12389 daemon prio=6 os_prio=0 tid=0x00007f3190075800 nid=0x15d08 runnable [0x00007f31f43c4000] java.lang.Thread.State: RUNNABLE at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.socketRead(SocketInputStream.java:116) at java.net.SocketInputStream.read(SocketInputStream.java:171) at java.net.SocketInputStream.read(SocketInputStream.java:141) at java.io.BufferedInputStream.read1(BufferedInputStream.java:284) at java.io.BufferedInputStream.read(BufferedInputStream.java:345) - locked <0x00000000f49e3158> (a java.io.BufferedInputStream) at java.io.BufferedInputStream.fill(BufferedInputStream.java:246) at java.io.BufferedInputStream.read(BufferedInputStream.java:265) - locked <0x00000000f49e51a8> (a org.apache.commons.net.telnet.TelnetInputStream) at org.apache.commons.net.telnet.TelnetInputStream.__read(TelnetInputStream.java:132) at org.apache.commons.net.telnet.TelnetInputStream.run(TelnetInputStream.java:603) at java.lang.Thread.run(Thread.java:748) Locked ownable synchronizers: - None "Thread-12125" #12388 daemon prio=6 os_prio=0 tid=0x00007f31c4602000 nid=0x15cf2 runnable [0x00007f31f4bcc000] java.lang.Thread.State: RUNNABLE at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.socketRead(SocketInputStream.java:116) at java.net.SocketInputStream.read(SocketInputStream.java:171)

使用printf "%x\n"，獲得線程ID=的十六進制值。

1 2	[root@CZT-FS1 board-api]# printf "%x\n" 67163 1065b

查看該線程的堆棧：

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[root@CZT-FS1 board-api]# jstack -l 67136 | grep 1065b -A20 "System Clock" #17 daemon prio=5 os_prio=0 tid=0x00007f322d089000 nid=0x1065b runnable [0x00007f320487c000] java.lang.Thread.State: TIMED_WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x00000000c19c8d18> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078) at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1093) at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) Locked ownable synchronizers: - None "Druid-ConnectionPool-Destroy-1390913202" #16 daemon prio=5 os_prio=0 tid=0x00007f322ea27800 nid=0x1065a waiting on condition [0x00007f320497d000] java.lang.Thread.State: TIMED_WAITING (sleeping) at java.lang.Thread.sleep(Native Method) at com.alibaba.druid.pool.DruidDataSource$DestroyConnectionThread.run(DruidDataSource.java:2538)