[GE users] vf, h_vmem or both?

icaci hristo at mc.phys.uni-sofia.bg
Wed Jun 10 10:40:02 BST 2009


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Hi,

We use h_vmem for scheduling in our cluster installation. We've also set h_vmem into each execution node's complex_values attribute, gave it a default value of 2G in SGE's complexes table and made it a consumable. It works fine and SGE kills jobs that run over the user specified h_vmem value but there are some gotchas:

- h_vmem limits the virtual memory consumption and in certain tasks that could be way more than the physical memory used. Thus users have to specify more memory than really needed (especially for OpenMPI jobs that use shared memory segments for IPC) and so we've set the h_vmem on each exec host to 150% of its real RAM quantity. Since our nodes do not have swap partitions the infamous Linux OOM killer kicks in from time to time...

- some jobs allocate large amounts of RAM in the beginning and then release it. Since h_vmem is a consumable resource it happens that some nodes have free RAM and CPU slots but no jobs can run there since h_vmem does not increase automatically when RAM is freed but only when jobs are finished.

Hope that helps,

Hristo

On 09.06.2009, at 13:43, futuritymmx wrote:

Hi Everyone,

We have a consumable complex called ?virtual_free? / ?vf? which we use to make sure that jobs don?t use more memory than a machine has available.  The users specify the maximum amount of memory they feel that their jobs will use.

However, some users underestimate the amount on memory they use and others have jobs with memory leaks.  We?d like to start using ?h_vmem? to kill jobs that consume more memory that expected.

I was wondering if ?h_vmem? is automatically used by the grid engine and scheduler to work out where jobs should be run, preventing too many jobs running on a machine that require a lot of memory?  If not, will our users still need to specify the ?vf? complex as well as the ?h_vmem? complex?

Thanks for any help you can give.

Neil




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