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From artnaseef <...@artnaseef.com>
Subject Re: Hung ActiveMQ broker and processes are blocking
Date Tue, 07 Jan 2014 17:17:38 GMT
I need to research the "used heap size" to understand what are the right
numbers that way.  Using jconsole or visualvm, the total heap size is
displayed and graphed in an easy-to-use format, and the total never
exceeds the max (when it hits, GC kicks in).

BTW, another great tool for looking at JVM stats from the command-line is
jstat:

    jstat -gccapacity <pid>

Here's a page that lists all of the output formats:
http://docs.oracle.com/javase/1.5.0/docs/tooldocs/share/jstat.html.

Here is the option that enables GC for permgen:

    -XX:+CMSPermGenSweepingEnabled

We also use this one:

    -XX:+CMSClassUnloadingEnabled

The JVM puts out this warning with the former, so these may be equivalent:

    Please use CMSClassUnloadingEnabled in place of
CMSPermGenSweepingEnabled in the future

Note that, if your JVM is running out of Heap, and not permgen, then it
will be necessary to determine what's causing the broker JVM to run out of
memory.  One common cause is slow consumers without PFC, or using a
configuration for which PFC does not work.

A good heap dump and analysis tool are the best bet in that case.





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