[jboss-user] [Installation, Configuration & DEPLOYMENT] - Re: startup jvm memory config suggestions

PeterJ do-not-reply at jboss.com
Mon Mar 10 17:52:46 EDT 2008

Your max perm gen setting is 128m, but only 16m has been allocated and only 8m is in use. Do you redeploy applications often? That is what usually causes the need for a larger perm gen. If so, leave it at 256m, it is good insurance.

Looking at the heap usage, ignore the first gc - it is one that jbossas forces during startup. Actually, about the first dozen gcs can be ignored because they are all startup related. Looking at the last gc, almost all of the objects in the young generation were collected (less that 1mb of the objects survived the collection). I suspect that the young generation, currently set at 179m, is too big. And the overall heap size of 2.6gb is way too big - you are using all of 200mb of it.

Replace the -Xms and -Xmx with these settings:

-Xms600m -Xmx600m -XX:MaxNewSize=100m -XX:NewSize=100m

If that causes the old generation to fill up too quickly, increase everything:

-Xms800m -Xmx800m -XX:MaxNewSize=150m -XX:NewSize=150m

Also, gather the gc data using only -verbose:gc and plot the data. Looking at the plot of the graph will give you a better idea of how to adjust the heap settings.

See also http://www.jboss.com/index.html?module=bb&op=viewtopic&t=130504

By the way, are you running 64-bit Red Hat with a 64-bit JVM?

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