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Setting JVM memory options in tomcat?

Is there any drawback setting the -Xms and -Xmx to the same value? And also -XX:MaxPermSize and -XX:PermSize to same value.

It is recommended here.

If there enough physical memory available in server, is it recommended to set bit higher values to both options?

UPDATE:

Environment Java 1.6.0_45 in Solaris 10

java version "1.6.0_45"

Java(TM) SE Runtime Environment (build 1.6.0_45-b06)

Java HotSpot(TM) 64-Bit Server VM (build 20.45-b01, mixed mode)

Solution

  • Setting -xms and -xmx was a good practice in older versions of Java, when adaptive sizing wasn't working good enough. In Java >= 7 it works really nice, so it's no longer needed. If you need more details you have to read about -XX:+UseAdaptiveSizePolicy flag or refer HotSpot documentation

    Another thing you have to remember about is that you have 8GB RAM on your server doesn't mean that you can use it wholly for Java. You have to left some for system buffers

    In Java <= 1.6 setting XMS=XMS and same in case of PermGen is reasonable, but you have to remember about correct tuning of the XMX value, because too much memory will cause cobra effect