OpenJDK and boxes with lots of RAM

[Jan Just Keijser]

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