[torquedev] [PATCH] Change pbs_mom to set RLIMIT_AS instead of RLIMIT_DATA for mem/pmem limits.

Chris Samuel csamuel at vpac.org
Sat Jan 10 06:39:39 MST 2009

Hi folks,

Responses will be sporadic for a while as we're still chasing
annoyingly random hardware issues.. :-(

----- "Åke Sandgren" <ake.sandgren at hpc2n.umu.se> wrote:

> I think this is a bad idea.
> vmem and pvmem can be mapped to RLIMIT_AS but mem and pmem can't.

If you want glibc to do what it used to then they are necessary.

> If you set RLIMIT_AS for (p)mem then there is no way to use (p)vmem
> any longer.

I don't think that's true, pbs_mom already tests to ensure
that (p)vmem > (p)mem and fixes it if it is not.

> pmem is the memory usage, pvmem is the virtual memory usage.

That's what Torque thinks, but..

> RLIMIT_AS is virtual memory limit.

..this is no longer the case with the way that glibc has
changed how it allocates memory, and like it or not RLIMIT_AS
now does what RLIMIT_DATA used to to! :-(

> (p)mem limits must (currently) be enforced, if at all,  by pbs_mom
> through checking of actual usage.

I'd prefer to do both, if possible.

> Hopefully the kernel developers will someday make it possible to use
> RLIMIT_RSS which is a much better mapping of (p)mem.

Agreed, but I'm not sure if those distinctions are that
clear in the kernel these days.   Need to dive further
into the vm subsystem to tell..

> But at the moment RLIMIT_RSS is not used in the linux kernel.

Hmm, that could be a nice little project for someone!

Christopher Samuel - (03) 9925 4751 - Systems Manager
 The Victorian Partnership for Advanced Computing
 P.O. Box 201, Carlton South, VIC 3053, Australia
VPAC is a not-for-profit Registered Research Agency

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