Java Optimization on Linux

[nix45]

We're about to set up an active/passive cluster on two Red Hat Enterprise Linux ES 3.0 servers. The servers will host a Java app that is very resource intensive. The servers are Compaq ProLiant DL380's with dual P4's and 4GBs of RAM each.

I don't know anything about Java, I just do the system administration here. Are there any Java performance tuning tweaks that can be done to the servers to improve the performance of the servers?

Thanks,
Chris

 

[stefanwagner]

You may start the java with:

java -server -Xms ... -Xmx ... ...

which is well known, but if you don't know java at all, it might be hard to find.

java -X

will give you a brief description of the -X... flags,

java

the for normal flags.

Basic documentation may be found at

file:///$JAVA_HOME/docs/guide/vm/index.html

or online from the sun-web-page.

 

[nix45]

FYI, someone from Sun said this...



Here are some general suggestions I was able to track down.

Size the java heap accordingly. There is a 2GB contiguous memory limit
on linux, so try sizing the heap at 1.6gb.
For the hotspot JVM the flags are:
java -server -Xms1600m -Xmx1600m

more advanced options are available if GC is a bottleneck.
First, try AggressiveHeap.
-server -Xms1600m -Xmx1600m -XX:+AggressiveHeap

AggressiveHeap turns on ParallelGC, TLABs and sizes the young
generation, along with a few other platform and competitive benchmarking
specific flags. The important flags to try are:

-Xmn400m (size young gen. to 1/4 overall heap size to start)

-XX:+UseParallelGC

-XX:+UseTLAB