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<p>Hello Björn-Helge.<br>
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<p>Sigh ... <br>
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<p>First of all, of course, many thanks! This indeed helped a lot!</p>
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<p>Two comments:<br>
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<p>a) Why are Interfaces at Slurm tools changed? I once learned that the Interfaces must be designed to be as stable as possible. Otherwise, users get frustrated and go away.<br>
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<p>b) This only works if I have to specify --mem for a task. Although manageable, I wonder why one needs to be that restrictive. In principle, in the use case outlined, one task could use a bit less memory, and the other may require a bit more the half of the
node's available memory. (So clearly this isn't always predictable.) I only hope that in such cases the second task does not die from OOM ... (I will know soon, I guess.)<br>
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<p>Really, thank you! Was a very helpful hint!</p>
<p>Cheers, Martin<br>
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<div id="x_divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>Von:</b> slurm-users <slurm-users-bounces@lists.schedmd.com> im Auftrag von Bjørn-Helge Mevik <b.h.mevik@usit.uio.no><br>
<b>Gesendet:</b> Mittwoch, 18. Januar 2023 13:49<br>
<b>An:</b> slurm-users@schedmd.com<br>
<b>Betreff:</b> Re: [slurm-users] srun jobfarming hassle question</font>
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<div class="PlainText">"Ohlerich, Martin" <Martin.Ohlerich@lrz.de> writes:<br>
<br>
> Dear Colleagues,<br>
><br>
><br>
> already for quite some years now are we again and again facing issues on our clusters with so-called job-farming (or task-farming) concepts in Slurm jobs using srun. And it bothers me that we can hardly help users with requests in this regard.<br>
><br>
><br>
> From the documentation (<a href="https://slurm.schedmd.com/srun.html#SECTION_EXAMPLES">https://slurm.schedmd.com/srun.html#SECTION_EXAMPLES</a>), it reads like this.<br>
><br>
> -------------------------------------------><br>
><br>
> ...<br>
><br>
> #SBATCH --nodes=??<br>
><br>
> ...<br>
><br>
> srun -N 1 -n 2 ... prog1 &> log.1 &<br>
><br>
> srun -N 1 -n 1 ... prog2 &> log.2 &<br>
<br>
<br>
Unfortunately, that part of the documentation is not quite up-to-date.<br>
The semantics of srun has changed a little the last couple of<br>
years/Slurm versions, so today, you have to use "srun --exact ...". From<br>
"man srun" (version 21.08):<br>
<br>
--exact<br>
Allow a step access to only the resources requested for the<br>
step. By default, all non-GRES resources on each node in<br>
the step allocation will be used. This option only applies<br>
to step allocations.<br>
NOTE: Parallel steps will either be blocked or rejected<br>
until requested step resources are available unless --over‐<br>
lap is specified. Job resources can be held after the com‐<br>
pletion of an srun command while Slurm does job cleanup.<br>
Step epilogs and/or SPANK plugins can further delay the<br>
release of step resources.<br>
<br>
-- <br>
Regards,<br>
Bjørn-Helge Mevik, dr. scient,<br>
Department for Research Computing, University of Oslo<br>
<br>
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