Jps Jmap Jstack Jsta 是什么及如何用

 

命令	jps	jstack	jmap	jstat
jdk自带	都是jdk自带的,可能没设置环境变量 需要到{#JAVA_HOME}}/bin/ 下面去使用
作用	同 ps-ef|grep java	查看线程	查看内存	性能分析
使用	不能	检测死锁 查找cpu占用高的线程	得到运行java程序的内存分配的详细情况。例如实例个数，大小等	这是一个比较实用的一个命令，可以观察到classloader，compiler，gc相关信息。可以时时监控资源和性能

 

 

 

 

• 检测死锁

................ JNI global references: 15 #输出中每一个java.lang.Thread.State都是一个线程,正常情况文件输出到此结束,如果有异常则会继续提示,如下是一个死锁提示 Found one Java-level deadlock: ============================= "mythread2": waiting for ownable synchronizer 0x00000007958bc0a8, (a java.util.concurrent.locks.ReentrantLock$NonfairSync), which is held by "mythread1" "mythread1": waiting for ownable synchronizer 0x00000007958bc0d8, (a java.util.concurrent.locks.ReentrantLock$NonfairSync), which is held by "mythread2" Java stack information for the threads listed above: =================================================== "mythread2": at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x00000007958bc0a8> (a java.util.concurrent.locks.ReentrantLock$NonfairSync) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836) at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870) at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199) at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209) at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285) at com.spring.cloud.test.sort.DeathLock$2.run(DeathLock.java:35) "mythread1": at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x00000007958bc0d8> (a java.util.concurrent.locks.ReentrantLock$NonfairSync) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836) at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870) at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199) at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209) at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285) at com.spring.cloud.test.sort.DeathLock$1.run(DeathLock.java:23) Found 1 deadlock.

 

• 找耗费资源最多线程 在mac可能不好使

top# cpu使用 进程排序 top -H -p 17850 #查看进程下的所有线程 printf "%x\n" 17880 #转换线程为16进制 jstack 17850|grep 45d8 -A 30 #查找此线程