Java Parameters for Xms and Xmx

[Porteous, Todd]

Hey Guys,

 

I have a system with 32GB of Ram and I’m trying to figure out the best tuning for Java. My Java system locks up at least once a day and have to restart Matterhorn service. I’m currently running 1.5.1 and have the following Java Opts.  Ie 10GB heap Size with process starting off at 6GB.

 

JAVA_OPTS="-Xms6144m -Xmx10240m -XX:MaxPermSize=2048m"

 

What do you all use or recommend?

 

Todd

[Mikey Orr]

Hey Todd-

We use the defaults (-Xms1g -Xmx1g -XX:MaxPermSize=256m) on all of our nodes, except for our player/engage node, which gets "-Xms10g -Xmx10g -XX:MaxPermSize=256m". For some reason, our player node needs a lot of memory. You might want to start with a higher number and then watch the java process with JMX to see how much memory it actually uses. Even with 10g for our player node, it seems to hover around 4 to 6g and periodically flush itself back down to 2g. Here's our monitoring graph over the last 12 days:

You can use the 'jconsole' command to monitor Matterhorn's RAM usage. I think JMX is enabled by default (it seemed to be for me), but check for a "JMX" variable in your /usr/sbin/matterhorn script. Mine looks like this:

JMX="-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=1099 -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false"

Restart matterhorn if JMX wasn't enable. After that, you can type in 'jconsole localhost:1099' on the host to pull up a nice GUI tool to monitor everything. More information about JConsole can be found here: https://docs.oracle.com/javase/8/docs/technotes/guides/management/jconsole.html

Hope that helps! =)

-Mikey

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Mikey Orr

Learning Technologies Mac/Unix Systems Integrator

ITS @ University of California, Santa Cruz