March 24, 2014 by huionn
Sometimes a buggy java program may consume a lot of CPU. In order to troubleshoot it, you need to identify which threads in the java program are taking up so much cpu time.
There are two ways to find the problematic threads:
1) use jconsole plugin such as “top thread” plugin (http://lsd.luminis.nl/top-threads-plugin-for-jconsole/) or jtop plugin (demo plugin for jconsole). The plugin gathers the thread info through JMX.
2) use linux top command and stack trace
To check which in the Java process that has high CPU usage:
top –p <PID> –H
By default, the threads are sorted by cpu usage. pid can be obtained from either ps or jps.
Then use jstack to dump the stack traces of threads.
jstack –l [-m] <PID> > /tmp/stackdump
Depending on the format of jstack output, you may match the Thread ID from top directly to jstack output, or you may need to convert the Thread ID to hex to match nid (native thread id) in jstack output.
for example, if the thread id (in PID column of ‘top’) is 4096, the nid is 0x1000.