max Java memory + TOMCAT + server with 144GB RAM

Question

I did my homework and i could not find an answer for my problem.

I have a server with 144GB ram (147456MB) I do have java JDK 1.6.0_24-b07 I also have tomcat 7.0.10.0

I would like to assign as much memory as possible.

I would like to have something like Xmx=130000M (or even Xmx=135000M). I want to have as much JVM memory as possible.

Curently i can not jump over 111000M it says Out of Heap Space

JAVA_OPTS="$JAVA_OPTS "-Xms111000M
JAVA_OPTS="$JAVA_OPTS "-Xmx111000M
JAVA_OPTS="$JAVA_OPTS "-XX:PermSize=64M
JAVA_OPTS="$JAVA_OPTS "-XX:MaxPermSize=256M
JAVA_OPTS="$JAVA_OPTS "-d64
JAVA_OPTS="$JAVA_OPTS "-XX:+UseParallelOldGC 

And i really have to have Xms=Xmx I tried a lot of options and I could not jump over. Is it possible to have "bit" extra memory?

Regards Bob

Answer 1

First of all, Java needs a bit of memory to manage the heap. So if you allocate 1GB heap, it will allocate 1.5GB (heap + permgen + code space + ....). So you need to check how much memory Java really allocates from the OS when you say -Xms111000M -Xmx111000M. Note that you need -Xms or Java will slowly allocate the memory and it will be hard to test the OOM condition.

Also make sure that you actually have that much memory available in a single chunk. So maybe some other process needs a lot of RAM or your RAM is split into two smaller chunks (should not happen with a MMU since all pages for a process will always appear to be continuous but maybe you've found a bug).