0 Replies Latest reply on Jan 13, 2005 2:28 PM by Gerald Shifrin

    JVM Heap Settings

    Gerald Shifrin Newbie

      I see a lot of discussion here on setting the JVM heap size, but I haven't seen any guidelines on what are some reasonable values for various types of applications. Since I've started running into some Java OutOfMemoryError's lately, I've increased my heap sizes and perm generation size to:

      -Xms128m -Xmx128m -XX:MaxPermSize=96m

      This is with JBoss 3.2.5, Solaris 8, and Oracle 10g.

      I've seen recommendations to make your min and max heap size the same (though I can't say why). The default min and max are 2m and 64m, but lots of places say that's not enough.

      I see also that with Java 1.4.2 there are a number of other heap and GC parameter settings (see http://java.sun.com/docs/hotspot/gc1.4.2/).

      I see that the web-console shows some information about the current state:

      JVM Environment
      Free Memory: 82 MB
      Max Memory: 126 MB
      Total Memory: 126 MB
      #Threads: 84

      Question is whether there is any other useful information to be found in jmx-console or elsewhere and what experiences have other folks had with various JVM and other tuning parameters.

      I know there are some rather dated tuning docs around. It'd be nice if we could get those updated for JVM 1.4 and JBoss 3.2.x/4.x.