We have several different types of GPUs in the same 'gpu' partition. The problem we're having occurs when one of those types of GPUs is fully occupied and there are a bunch of queued jobs waiting for those GPUs. If someone requests idle GPUs of a different type, those jobs end up getting stalled, even though there are plenty of GPUs available.
For example, say we have 10 A100 GPUs and 10 H100 GPUs. If there are 10 H100 GPU jobs running and more in queue waiting for them, subsequently submitted A100 jobs will sit in queue even if there are plenty of idle A100 GPUs. The only way we can get the A100 jobs to run is by manually bumping their priority higher than the pending H100 jobs.
Has anyone else encountered this issue? The only way we can think of to potentially solve it is to have separate partitions for each GPU type, but that seems unwieldy.
We are currently running Slurm 24.05.8.
Thanks, Kevin
Yes, we've see the same thing with mosaic/heterogeneous partitions. Our solution is to split based on hardware type.
Having a bunch of partitions may seem unwieldy but the scheduler can handle it. For instance we have 110 partitions and the scheduler handles it fine (most of those are hardware owned by specific groups not public partitions everyone can see). We've taken up the convention of naming our partitions after the hardware type. For instance we have a gpu partition (our A100's) and a gpu_h200 partition. Making it easy for people to identify the hardware. People who can use both will leverage mutltipartition submission ala #SBATCH -p gpu,gpu_h200.
I don't know of a good solution if you want to keep the mosiac partition as it really requires you users to think at a higher level and realize there is vacant hardware that could be used if they just selected a different gpu type. Having a separate partition makes it much easier to see.
-Paul Edmon-
On 9/11/2025 3:23 PM, Kevin M. Hildebrand via slurm-users wrote:
We have several different types of GPUs in the same 'gpu' partition. The problem we're having occurs when one of those types of GPUs is fully occupied and there are a bunch of queued jobs waiting for those GPUs. If someone requests idle GPUs of a different type, those jobs end up getting stalled, even though there are plenty of GPUs available.
For example, say we have 10 A100 GPUs and 10 H100 GPUs. If there are 10 H100 GPU jobs running and more in queue waiting for them, subsequently submitted A100 jobs will sit in queue even if there are plenty of idle A100 GPUs. The only way we can get the A100 jobs to run is by manually bumping their priority higher than the pending H100 jobs.
Has anyone else encountered this issue? The only way we can think of to potentially solve it is to have separate partitions for each GPU type, but that seems unwieldy.
We are currently running Slurm 24.05.8.
Thanks, Kevin
-- Kevin Hildebrand Director of Research Technology and HPC Services Division of IT
Are you saying these are jobs that should be able to run right now but they’re just not getting considered, or there’s something that’s wrong about the way they’re submitted that has to be manually corrected to allow them to run on A100s?
If the former, it sounds like your backfill settings just might be inadequate to allow it to consider jobs far enough down the list.
-- #BlackLivesMatter ____ || \UTGERS, |---------------------------*O*--------------------------- ||_// the State | Ryan Novosielski (he/him) - novosirj@rutgers.edu || \ University | Sr. Technologist - 973/972.0922 (2x0922) ~*~ RBHS Campus || \ of NJ | Office of Advanced Research Computing - MSB A555B, Newark `'
On Sep 11, 2025, at 15:23, Kevin M. Hildebrand via slurm-users slurm-users@lists.schedmd.com wrote:
We have several different types of GPUs in the same 'gpu' partition. The problem we're having occurs when one of those types of GPUs is fully occupied and there are a bunch of queued jobs waiting for those GPUs. If someone requests idle GPUs of a different type, those jobs end up getting stalled, even though there are plenty of GPUs available.
For example, say we have 10 A100 GPUs and 10 H100 GPUs. If there are 10 H100 GPU jobs running and more in queue waiting for them, subsequently submitted A100 jobs will sit in queue even if there are plenty of idle A100 GPUs. The only way we can get the A100 jobs to run is by manually bumping their priority higher than the pending H100 jobs.
Has anyone else encountered this issue? The only way we can think of to potentially solve it is to have separate partitions for each GPU type, but that seems unwieldy.
We are currently running Slurm 24.05.8.
Thanks, Kevin
-- Kevin Hildebrand Director of Research Technology and HPC Services Division of IT
-- slurm-users mailing list -- slurm-users@lists.schedmd.com To unsubscribe send an email to slurm-users-leave@lists.schedmd.com
The former- jobs should run but are not. We currently have these backfill parameters set: bf_continue,bf_max_job_user=10. bf_max_job_test is the default of 500. However sdiag says the number of times bf_max_job_test has been hit is zero, so that's probably not relevant. I can try removing bf_max_job_user, but I don't think that's the issue either, as this problem also seems to affect users with few jobs in queue when a different user has all of one GPU type consumed.
Kevin
On Thu, Sep 11, 2025 at 3:38 PM Ryan Novosielski novosirj@rutgers.edu wrote:
Are you saying these are jobs that should be able to run right now but they’re just not getting considered, or there’s something that’s wrong about the way they’re submitted that has to be manually corrected to allow them to run on A100s?
If the former, it sounds like your backfill settings just might be inadequate to allow it to consider jobs far enough down the list.
-- #BlackLivesMatter ____ || \UTGERS, |---------------------------*O*--------------------------- ||_// the State | Ryan Novosielski (he/him) - novosirj@rutgers.edu || \ University | Sr. Technologist - 973/972.0922 (2x0922) ~*~ RBHS Campus || \ of NJ | Office of Advanced Research Computing - MSB A555B, Newark `'
On Sep 11, 2025, at 15:23, Kevin M. Hildebrand via slurm-users < slurm-users@lists.schedmd.com> wrote:
We have several different types of GPUs in the same 'gpu' partition. The problem we're having occurs when one of those types of GPUs is fully occupied and there are a bunch of queued jobs waiting for those GPUs. If someone requests idle GPUs of a different type, those jobs end up getting stalled, even though there are plenty of GPUs available.
For example, say we have 10 A100 GPUs and 10 H100 GPUs. If there are 10 H100 GPU jobs running and more in queue waiting for them, subsequently submitted A100 jobs will sit in queue even if there are plenty of idle A100 GPUs. The only way we can get the A100 jobs to run is by manually bumping their priority higher than the pending H100 jobs.
Has anyone else encountered this issue? The only way we can think of to potentially solve it is to have separate partitions for each GPU type, but that seems unwieldy.
We are currently running Slurm 24.05.8.
Thanks, Kevin
-- Kevin Hildebrand Director of Research Technology and HPC Services Division of IT
-- slurm-users mailing list -- slurm-users@lists.schedmd.com To unsubscribe send an email to slurm-users-leave@lists.schedmd.com
Kevin M. Hildebrand via slurm-users wrote:
bf_max_job_test is the default of 500. However sdiag says the number of times bf_max_job_test has been hit is zero, so that's probably not relevant.
Du you have weights defined? I've seen the scheduler insisting on waiting for nodes with lower weights when higher weighted ones were idling. An squeue --start will tell.
Gerhard
"Kevin M. Hildebrand via slurm-users" slurm-users@lists.schedmd.com writes:
The former- jobs should run but are not. We currently have these backfill parameters set: bf_continue,bf_max_job_user=10. bf_max_job_test is the default of 500. However sdiag says the number of times bf_max_job_test has been hit is zero, so that's probably not relevant. I can try removing bf_max_job_user, but I don't think that's the issue either, as this problem also seems to affect users with few jobs in queue when a different user has all of one GPU type consumed.
Perhaps you can add more debugging in slurmctld, for instance DebugFlags=Backfill,SelectType (and possibly Gres) and increase SlurmctldDebug to debug2 or debug3. Then you might see *why* it doesn't schedule the jobs.
On 9/12/25 3:09 am, Bjørn-Helge Mevik via slurm-users wrote:
Perhaps you can add more debugging in slurmctld, for instance DebugFlags=Backfill,SelectType (and possibly Gres) and increase SlurmctldDebug to debug2 or debug3.
Both of these can be changed on the fly with scontrol too:
https://slurm.schedmd.com/scontrol.html#OPT_setdebug
https://slurm.schedmd.com/scontrol.html#OPT_setdebugflags
FWIW we run all the time at debug and with debugflags=backfill.
All the best, Chris
-
Bjørn-Helge Mevik -
Christopher Samuel -
Gerhard Strangar -
Kevin M. Hildebrand -
Paul Edmon -
Ryan Novosielski