[Beowulf] Controlling java's hunger for RAM

Christopher Samuel samuel at unimelb.edu.au
Mon Feb 20 22:39:37 EST 2012


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Hi folks,

A perennial issue on our x86 clusters is Java and its
unpredictableness for wanting RAM.  It seems it defaults to trying to
mmap() a quarter of system RAM (12GB on our 48GB nodes for instance)
unless overridden by the -Xmx parameter.

Now we'd like a way to be able to set a default for -Xmx for all Java
processes, but cannot use $_JAVA_OPTIONS as that overrides the command
line options rather than the other way around (which would have been
the sensible way to do it).

The reason why is that Torque sets RLIMIT_RSS to enforce memory
requests on jobs, and malloc() now usually calls mmap() to allocate
rather than sbrk() so RLIMIT_DATA is useless (not enforced).

Any ideas??

cheers!
Chris
- -- 
    Christopher Samuel - Senior Systems Administrator
 VLSCI - Victorian Life Sciences Computation Initiative
 Email: samuel at unimelb.edu.au Phone: +61 (0)3 903 55545
         http://www.vlsci.unimelb.edu.au/

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