OpenJDK and boxes with lots of RAM

[David Holmes]

Hi Jan,

You can use the environment variable _JAVA_OPTIONS to set -Xmx.

The other option is to use your own wrapper script for launching the VM 
that contains whatever flags you need.

David Holmes

On 17/11/2011 11:28 PM, Jan Just Keijser wrote:
> hi all,
>
> I would like to report an issue with OpenJDK 1.6 (and Oracle Java 6u29)
> that we have run into on our grid computing farm:
>
> the latest&greatest worker nodes have 12 cores and 48 GB of RAM ; we
> offer a maximum 12 jobs slots on these worker nodes, in order to
> accomodate small and large jobs (users can requests 1 - 12 cores). To
> ensure that the different jobs don't interfere with each other we also
> set a VMEM limit for each job slot. The current VMEM limit is 48 / 12 =
> 4 GB RAM per job slot. Each single core job that starts has a 'ulimit
> -v' of 4,000,000 .
>
> On these boxes OpenJDK 'java' refuses to start:
>
> $ java -version
> Error occurred during initialization of VM
> Could not reserve enough space for object heap
> Could not create the Java virtual machine.
>
> After some debugging I found that this is caused by the default maximum
> heap size which java allocates: it scans /proc/meminfo to extrac the
> amount of RAM installed and divides it by 4 ; an 'strace' shows that
> indeed 'java' tries to do an 'mmap' call for 12 GB of RAM !
>
> A work around is to always specify '-Xmx2GB' or something similar but
> this does not work for all software that we use , plus , I find it
> annoying that I have to tell this to all my users.
>
> What I would like to see is a system-wide setting for the initial
> maximum heap size, so that
>    java -version
> "just works" . Is this possible?
>
> thanks in advance,
>
> JJK / Jan Just Keijser
>
>