From:
greent10--- via slurm-users <slurm-users@lists.schedmd.com>
Date: Monday, 20 May 2024 at 12:10
To: Emyr James <emyr.james@crg.eu>, Davide DelVento <davide.quantum@gmail.com>
Cc: slurm-users@lists.schedmd.com <slurm-users@lists.schedmd.com>
Subject: [slurm-users] Re: memory high water mark reporting
Hi,
We have had similar questions from users regarding how best to find out the high memory peak of a job since they may run a job and get a not very useful value for variables in sacct such as the MaxRSS since
Slurm didn’t poll during the use of its maximum memory usage.
With Cgroupv1 looking online it looks like memory.max_usage_in_bytes takes into account caches so can vary on how much I/O is used whilst total_rss in memory.stats looks more useful maybe. Maybe memory.peak
is clearer?
Its not clear in the documentation how a user should in the sacct values to infer the actual usage of jobs to correct their behaviour in future submissions.
I would be keen to see improvements in high water mark reporting. I noticed that the jobacctgather plugin documentation was deleted back in Slurm 21.08 – Spank plugin does possibly look like the way to go.
Also it seems a common problem across technologies e.g.
https://github.com/google/cadvisor/issues/3286
Tom
From:
Emyr James via slurm-users <slurm-users@lists.schedmd.com>
Date: Monday, 20 May 2024 at 10:50
To: Davide DelVento <davide.quantum@gmail.com>, Emyr James <emyr.james@crg.eu>
Cc: slurm-users@lists.schedmd.com <slurm-users@lists.schedmd.com>
Subject: [slurm-users] Re: memory high water mark reporting
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It looks like it's possible to hook something in at the right place using the slurm_spank_task_exit or slurm_spank_exit plugins. Does anyone have any experience or examples of doing this ? Is there any more documentation
available on this functionality ?
Emyr James
Head of Scientific IT
CRG - Centre for Genomic Regulation
From: Emyr James via slurm-users <slurm-users@lists.schedmd.com>
Sent: 17 May 2024 01:15
To: Davide DelVento <davide.quantum@gmail.com>
Cc: slurm-users@lists.schedmd.com <slurm-users@lists.schedmd.com>
Subject: [slurm-users] Re: memory high water mark reporting
I have got a very simple LD_PRELOAD that can do this. Maybe I should see if I can force slurmstepd to be run with that LD_PRELOAD and then see if that does it.
Ultimately am trying to get all the useful accounting metrics into a clickhouse database. If the LD_PRELOAD on slurmstepd seems to work then I can expand it to insert the relevant row into the clickhouse DB in
the C code of the preload library.
But still...this seems like a very basic thing to do and am very suprised that it seems so difficult to do this with the standard accounting recording out of the box.
Emyr James
Head of Scientific IT
CRG - Centre for Genomic Regulation
From: Davide DelVento <davide.quantum@gmail.com>
Sent: 17 May 2024 01:02
To: Emyr James <emyr.james@crg.eu>
Cc: slurm-users@lists.schedmd.com <slurm-users@lists.schedmd.com>
Subject: Re: [slurm-users] memory high water mark reporting
Not exactly the answer to your question (which I don't know) but if you can get to prefix whatever is executed with this https://github.com/NCAR/peak_memusage
(which also uses getrusage) or a variant you will be able to do that.
We are trying out slurm having been running grid engine for a long while.
In grid engine, the cgroups peak memory and max_rss are generated at the end of a job and recorded. It logs the information from the cgroup hierarchy as well as doing a getrusage call right at the end on the parent
pid of the whole job "container" before cleaning up.
With slurm it seems that the only way memory is recorded is by the acct gather polling. I am trying to add something in an epilog script to get the memory.peak but It looks like the cgroup hierarchy has been destroyed
by the time the epilog is run.
Where in the code is the cgroup hierarchy cleared up ? Is there no way to add something in so that the accounting is updated during the job cleanup process so that peak memory usage can be accurately logged ?
I can reduce the polling interval from 30s to 5s but don't know if this causes a lot of overhead and in any case this seems to not be a sensible way to get values that should just be determined right at the end
by an event rather than using polling.
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