[jboss-user] [Performance Tuning] - Re: VM and GC tuning for JBoss

[PeterJ]

I have never encountered problems setting min and max heap to the same size. Of course, I typically run on systems dedicated to the app server.  If you run a mixed environment (other apps besides the app server) and the load on the app server changes over the course of the day ( example: app server heavily used during day but mostly quiet at night , but at night you have batch jobs running) you might want to set the sizes to different values so that the JVM can release memory space to other apps that might need it.

Setting the eden ratio to 2 is not a good idea.  You will end up with only full collections because when the JVM runs out of eden space, it makes a worst-case assumption that all the objects in eden will end up in the tenured generation, and if there is not enough run on the tenured generation it will do a full collection.  Simplified example: tenured gen is 400MB, young gen is 400MB. Tenured gen has one object of 32 bytes in size. Eden is full, 400MB is greater than 400MB - 32 bytes, so full GC happens.

Yes, turn off explicit gc, and set the client interval (later already set in the jboss bat/shell scripts).

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