October 2025 - slurm-users - lists.schedmd.com

Optimizing CPU allocation in Slurm with hyperthreading enabled
by Guillaume COCHARD 02 Mar '26

02 Mar '26

Hello, The Slurm documentation states that "The default allocation method within a node is cyclic allocation (allocate available CPUs in a round-robin fashion across the sockets within a node)." In our case, we are using hyperthreading, which means that if two jobs requesting one CPU each arrive at the same time on an empty node, they will be assigned to the two threads of the same physical core. To improve performance, we would like Slurm to allocate CPUs (in our case, threads) in a way that prioritizes using one thread per physical core first, and only once all cores are occupied, assign the second thread of each core. This would be similar to the Least Loaded Node (LLN) approach, but instead of distributing jobs across nodes, it would distribute them across physical cores (Least Loaded Core). We do not want to disable hyperthreading; we simply want to optimize core usage when a machine is not fully loaded. We also want this to be a cluster-wide setting, and not a user and/or job setting. Our current slurm.conf contains: ConstrainCores = no SelectType = select/cons_tres SelectTypeParameters = CR_CPU_MEMORY And our cgroup.conf contains: ConstrainDevices=yes ConstrainCores=yes Does anyone know how to achieve this? Thanks, Guillaume

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slurmctld hourly: Unexpected missing socket error
by Jason Ellul 13 Jan '26

13 Jan '26

Hi all, I am hoping someone can help with our problem. Every hour after restarting slurmctld the controller becomes unresponsive to commands for 1 sec, reporting errors such as: [2024-07-15T11:45:48.509] error: slurm_send_node_msg: [socket:[934767]] slurm_bufs_sendto(msg_type=RESPONSE_JOB_INFO) failed: Unexpected missing socket error [2024-07-15T11:45:48.509] error: slurm_send_node_msg: [socket:[934760]] slurm_bufs_sendto(msg_type=RESPONSE_SLURM_RC) failed: Unexpected missing socket error [2024-07-15T11:45:48.509] error: slurm_send_node_msg: [socket:[934875]] slurm_bufs_sendto(msg_type=RESPONSE_JOB_INFO) failed: Unexpected missing socket error [2024-07-15T11:45:48.509] error: slurm_send_node_msg: [socket:[934906]] slurm_bufs_sendto(msg_type=RESPONSE_JOB_INFO) failed: Unexpected missing socket error [2024-07-15T11:45:48.509] error: slurm_send_node_msg: [socket:[939016]] slurm_bufs_sendto(msg_type=RESPONSE_JOB_INFO) failed: Unexpected missing socket error It occurs consistently at around the hour mark, but generally not at other times, unless we run a reconfigure or restart the controller. We don’t see any issues in the slurmdbd.log and the errors are also always msg type RESPONSE. We have tried building a new server on different infrastructure, but the problem has persisted. Yesterday we even tried updating slurm to v24.05.1 in the hope that may provide a fix. During our troubleshooting we have: Set: * SchedulerParameters = max_rpc_cnt=400,sched_min_interval=50000,sched_max_job_start=300,batch_sched_delay=20,bf_resolution=600,bf_min_prio_reserve=2000,bf_min_age_reserve=600 * SlurmctldPort = 6808-6817 But although the stats in sdiag have improved we still see the errors. On our monitoring software we also see a drop in network and disk activity during this 1 second, always at approx. 1 hour after restarting the controller. Many Thanks in advance Jason Jason Ellul Head - Research Computing Facility Office of Cancer Research Peter MacCallum Cancer Centre

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Slurm release candidate version 25.11.0rc1 is available for testing
by Tim Wickberg 28 Oct '25

28 Oct '25

We are pleased to announce the availability of Slurm release candidate 25.11.0rc1. To highlight some new features coming in 25.11: * Added new "Expedited Requeue" mode for batch jobs. Batch jobs with --requeue=expedite will automatically requeue on node failure, or if the batch script returns a non-zero exit code and one or more Epilog scripts fail. Expedited requeue jobs are eligible to restart immediately, are treated as the highest priority job in the system, and their previously allocated set of nodes will be prevented from launching other work. * Added a new "Mode 3" of operation to Hierarchical Resources. This mode complements the existing Mode 1 and Mode 2 by summing usage from lower levels automatically. This can be used, e.g., to implement a power-capping mode modeling power distribution between the datacenter, local distribution, and individual racks. * Added direct support for exporting OpenMetrics (Prometheus) telemetry from slurmctld. This is accessible on SlurmctldPort on SlurmctldHost by default, or can be disabled if desired. * Added an experimental asynchronous-reply mode to slurmctld. If enabled with "SlurmctldParameters=enable_async_reply", RPC responses are offloaded to the kernel for further processing, freeing individual worker threads for new traffic. This is the first release candidate of the upcoming 25.11 release series, and represents the end of development for this release, and a finalization of the RPC and state file formats. If any issues are identified with this release candidate, please report them through https://bugs.schedmd.com against the 25.11.x version and we will address them before the first production 25.11.0 release is made. Please note that the release candidates are not intended for production use. A preview of the updated documentation can be found at https://slurm.schedmd.com/archive/slurm-master/ . Slurm can be downloaded from https://www.schedmd.com/download-slurm/. The changelog for 25.11 can be found here: https://github.com/SchedMD/slurm/blob/master/CHANGELOG/slurm-25.11.md -- Tim Wickberg Chief Technology Officer, SchedMD LLC Commercial Slurm Development and Support

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AuthInfo broken in 25.05.1 ?
by michael＠mayer.cx 27 Oct '25

27 Oct '25

I am using the AuthInfo in both slurm.conf and slurmdbd.conf to point to a different location for the munge socket. This works as expected in slurmdbd, but it does not work for slurmctld. In slurmctld it seems to ignore this setting and try to locate the munge socket at the default location and then fail. When using the same approach in 23.11.11, for example, AuthInfo is working as expected for both slurmctld and slurmdbd. Sample config from slurm.conf and slurmdbd.conf AuthType=auth/munge AuthInfo=socket=/my/non-default/location/of/munge.socket I'd be grateful for any pointer whether this is a genuine bug/regression or not. Many thanks, Michael.

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Possible to require jobs to use NVLink-ed pairs of GPUs?
by Marcus Lauer 27 Oct '25

27 Oct '25

One of our researchers asked whether it was possible to require a job to use NVLink-ed pairs of GPUs. I see that there is a support ticket on the SchedMD site which covers this (https://support.schedmd.com/show_bug.cgi?id=15995) That ticket is a few years old though. Does anyone happen to know whether support for this has been added in newer releases of SLURM? The cluster in question does use "AutoDetect=nvml" in its gres.conf and the output of "slurmd -G" shows that SLURM is aware of the NVLink pairs. I assume the scheduler is trying to use that information. What I want to know is whether there is some way for an end-user to add a constraint (for example) to a job such that it only runs on an NVLink-ed pair of GPUs. I do know that there are other ways to implement this such as requiring jobs to run with even numbers of GPUs, perhaps just on some nodes to allow single GPU jobs to run on the remaining nodes. I'm specifically asking about a flag or setting a user could apply to their jobs. If there is such a thing maybe someone here knows about it. If so I'd love to hear about it. Thanks! -- *Mr. Marcus Lauer* Systems Administrator Penn Engineering University of Pennsylvania https://www.seas.upenn.edu/

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Limit number of allocated GPUs
by Gestió Servidors 23 Oct '25

23 Oct '25

Hello, I have three nodes, serving each one 2 GPUs. I would like to limit (qos??) that a user could user only one GPU from earch server, but user could user simultaneously three GPUs if each GPU belongs to different servers. With this QoS "sacctmgr add qos test-limit-GPUs MaxJobsPerUser=3 MaxTRESPerUser=gres/gpu=1" I can limit to one GPU, but then user can't run other job in a GPU from other server. How must I configure QoS (or other method) to allow more than one job requesting GPUs but never in the same server? Thanks.

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Job remains "PENDING" with reason "QOSMaxGRESPerUser"
by Gestió Servidors 23 Oct '25

23 Oct '25

Hello, I have added a new "qos" with these parameters: sacctmgr add qos test-GPUs MaxJobsPerUser=6 MaxTRESPerUser=gres/gpu=1 MaxSubmitJobsPerUser=25. With it, I only allow 6 running jobs per user, a total of 25 pending+running job per user and only 1 GPU. I have applied this qos directly to a partition in slurm.conf. When a user submits to that partition requesting 2 or more GPUs, job remains "PD" (pending) and notifies "QOSMaxGRESPerUser" in NODELIST column, but I would like to know if it would be possible to direcly reject job and avoid that job remains at queue? For example, if I submit 50 jobs, after number 25 I get message "sbatch: error: Batch job submission failed: Job violates accounting/QOS policy (job submit limit, user's size and/or time limits) sbatch: error: QOSMaxSubmitJobPerUserLimit" 25 times) Thanks.

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dynamic node slurm node list order
by Assmann, Greta Marie 23 Oct '25

23 Oct '25

Hello, we would like to understand how the internal SLURM node list order works. More detailed info: Our setup: We have a Slurm cluster with N dynamic nodes (heterogeneous node types) in a partition and we observe that if all resources are free, jobs always get submitted to one specific node first. This node is also the node that turns up at the top of the list when doing an $ scontrol show nodes . As we do not have a defined node list in slurm.conf as it is done for non-dynamic nodes, we were wondering how the order is set up. Interestingly, when deleting (and unregistering) this node from the cluster and re-registering it again, the node is still at the same position when doing scontrol show nodes. Is there some internal node list order caching or similar? How is the node list order defined ? Thanks , Greta Dr. Greta Assmann Data Analysis and Research Infrastructure OBBA 230 Forschungsstrasse 111 5232 Villigen-PSI email: greta.assmann(a)psi.ch

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Slurm and Slinky events this fall, update events page
by Tim Wickberg 14 Oct '25

14 Oct '25

We'll have a bit more details as conference season quickly approaches this November, but SchedMD staff are presenting at KubeCon NA on Slinky [1]. We'll be manning the Slurm Booth at SC25 [2], as well as hosting the annual Slurm Community Birds-of-a-Feather session [3]. I'll also send a link out to the survey questions for the BoF to the slurm-users list ahead of the conference, and we'll be going into a bit more depth on the answers during the BoF this year. The events page on the SchedMD website has more detail on future events as well: https://www.schedmd.com/events/ A few folks had asked, and apparently we never mentioned this more publicly, but: SchedMD does not plan to hold an in-person SLUG in 2025 or 2026. We are working to bring some of the same content to our YouTube channel [4] as a way to more broadly disseminate some of that same content, starting with the Slurm 25.11 release overview in December. - Tim [1] https://kccncna2025.sched.com/event/27FW5/ [2] The Slurm Booth is #1641. [3] https://sc25.conference-program.com/presentation/?id=bof101&sess=sess471 [4] https://www.youtube.com/SchedMDSlurm -- Tim Wickberg Chief Technology Officer, SchedMD LLC Commercial Slurm Development and Support

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Slurm version 25.05.4 is now available
by Marshall Garey 14 Oct '25

14 Oct '25

We are pleased to announce the availability of Slurm version 25.05.4. This version increases the default number of maximum connections to slurmctld from 50 to 512, fixes a regression added in 25.05.2 that broke compatibility with PMIx v2.x through v3.1.0rc1, and fixes other minor to moderate bugs. The full list of changes are available in the CHANGELOG: https://github.com/SchedMD/slurm/blob/slurm-25.05/CHANGELOG/slurm-25.05.md Slurm can be downloaded from: https://www.schedmd.com/download-slurm/ -- Marshall Garey Release Management, Support, and Development SchedMD LLC - Commercial Slurm Development and Support

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Preemption Scheduler Tuning Knobs
by Reed Dier 13 Oct '25

13 Oct '25

Hoping someone may be able to help demystify some questions around the scheduler and preemption decisions. I'm trying to help better predict the scheduler behavior as it pertains to preemption to create more predictable scheduling. Version is 24.11.5, OS U22.04 I have a fairly simple lo/hi partition which the same set of nodes are assigned > PartitionName=partition-lo Nodes=foo[00..NN] Default=YES MaxTime=INFINITE OverSubscribe=FORCE:1 State=UP > PartitionName=partition-hi Nodes=foo[00..NN] Default=YES MaxTime=INFINITE OverSubscribe=NO State=UP PreemptMode=OFF And then I have 2 QOSs per partition > Name Priority GraceTime Preempt PreemptMode UsageFactor MaxJobsPU MaxTRESPA MaxJobsPA > ---------------- ---------- ---------- ---------------------- ----------- ----------- --------- ------------- --------- > qos-stateless-lo 1 00:00:00 requeue 1.000000 > qos-stateful-lo 1 00:00:00 suspend 1.000000 NN cpu=NNN NNN > qos-stateful-hi 5 00:00:00 qos-state[ful,less]-lo cluster 1.000000 cpu=NNN > qos-stateless-hi 5 00:00:00 qos-state[ful,less]-lo cluster 1.000000 And the general way that it works out is that stateful jobs will typically spawn stateless jobs. Stateful jobs will get suspended, while stateless jobs will get requeued. And then there are some general guard rails around stateful jobs clogging the queue and preventing stateless jobs from scheduling and creating a deadlock, but thats not the specific issue here. > SchedulerType=sched/backfill > SelectType=select/cons_tres > SelectTypeParameters=CR_CPU_Memory > SchedulerParameters=max_rpc_cnt=500,\ > sched_min_interval=50000,\ > sched_max_job_start=300,\ > batch_sched_delay=6 > PriorityType=priority/multifactor > PreemptType=preempt/qos > PreemptMode=SUSPEND,GANG Workload is rather "high throughput", so a few settings were influenced by that <https://slurm.schedmd.com/high_throughput.html> guide. What I end up seeing is that it can take sometimes, but not always, take a while for lo jobs to be preempted by hi jobs, an example below, but if the mailing list eats images, a link to it here: https://imgur.com/a/7xVFC8a This is a rather low resolution view, as it is just a scraper running on 5 minute increments, but the blue filled area are "hi" jobs running, where the yellow are "lo" jobs running. Second image (dashed lines) are pending jobs for the same partitions. Oddly, this specific instance did not show any preemption events in the slurmctld logs, but users/admins were a bit perplexed as to why this drug on for so long, and without preemption kicking in. I was considering looking deeper into to try to better understand and predict preemption decisions: default_queue_depth partition_job_depth sched_interval sched_min_interval defer Hopefully someone can point me to some nuggets of information around this? Appreciate any pointers, Reed

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About tpology.conf
by ysaiki18＠gmail.com 12 Oct '25

12 Oct '25

Must topology.conf, like slurm.conf, be accessible to all nodes?

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Prolog error causing node to drain
by Ratnasamy, Fritz 11 Oct '25

11 Oct '25

Hi, We have a running slurm cluster and users have been submitting jobs for the past 3 months without any issues. Recently, some nodes jobs are getting drained randomly due to the reason "prolog error" Our slurm.conf has these 2 lines regarding prolog: PrologFlags=Contain,Alloc,X11 Prolog=/slurm_stuff/bin/prolog.d/prolog* Inside the prolog.d folder, there are 2 scripts which run with no errors as far as I can see but is there a way to debug why the nodes are going in draining mode once in a while because of "prolog error"? That seems to happen at random times and on random nodes. From the log file, I can see only this: Oct 06 00:57:43 pgpu008.chicagobooth.edu slurmd[3709622]: slurmd: error: prolog failed: rc:230 output:Successfully started proces> Oct 06 00:57:43 pgpu008.chicagobooth.edu slurmd[3709622]: slurmd: error: [job 20398] prolog failed status=230:0 Oct 06 00:57:43 pgpu008 slurmd[3709622]: slurmd: Job 20398 already killed, do not launch batch job Oct 06 13:06:23 pgpu008 systemd[1]: Stopping Slurm node daemon... Oct 06 13:06:23 pgpu008 slurmd[3709622]: slurmd: Caught SIGTERM. Shutting down. Oct 06 13:06:23 pgpu008 slurmd[3709622]: slurmd: Slurmd shutdown completing Currently, now the job 20398 that is getting killed in the picture above is in the state "Launch failed requeue held" after I resume the node. *Fritz Ratnasamy*Data Scientist Information Technology

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Testing Slurm on FreeBSD – Offering Feedback and Collaboration
by Rikka Göring 08 Oct '25

08 Oct '25

Hello everyone, I’d like to briefly introduce myself and share some good news. I maintain the FreeBSD port of Slurm (sysutils/slurm-wlm) and have just completed the upgrade to the latest release. Alongside this, several FreeBSD-related fixes I had been maintaining locally have now been merged upstream by SchedMD engineers, which is an encouraging step for portability. With the updated port now running reliably on FreeBSD, I can offer: - Regular build and runtime testing of Slurm on FreeBSD, - Feedback on portability patches and non-Linux code paths, - Collaboration with anyone interested in running or experimenting with Slurm on BSD systems. My goal is to help ensure that Slurm remains portable and usable on FreeBSD, and to contribute back testing and fixes where possible. If you’re working on anything that may affect portability, feel free to reach out — I’d be glad to test and provide results from the FreeBSD side. Best regards, Rikka Göring

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Unexpected missing socket error
by Ozeryan, Vladimir 07 Oct '25

07 Oct '25

Hello everyone, Not sure if you guys have heard this tune already but did anyone come across a solution for "Unexpected missing socket error". There is nothing useful in the logs but the message appears on compute nodes and slurm controller node. Thank you, Vlad Ozeryan AMDS - AB1 Linux-Support Vladimir.Ozeryan(a)jhuapl.edu Ext. 23966

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Setting GrpTRES for specific Account only for specific Partition(s)
by Paul Raines 06 Oct '25

06 Oct '25

I am trying to figure out how one can limit resources like with GrpTRES for specific accounts only for specific partitions in the cluster Lets say I have a cluster with 3 partitions Part1, Part2, and Part3 and 3 accounts Acct1, Acct2, and Acct3 I want Acct1 to be limited to 10 cpus on Part1, Acct2 to be limited to 5 cpus on Part1, and Acct3 to be limited to 8 cpus on Part1. No limits for any account on the other two partitions at present. I have tried # sacctmgr modify account Acct1 where partition=Part1 set GrpTRES=cpu=10 Modified account associations... Nothing modified I have tried creating a QOS to assign # sacctmgr add qos cpus10 # sacctmgr modify qos cpus10 set GrpTRES=cpu=10 # sacctmgr modify account Acct1 where partition=Part1 set qos=cpus10 Modified account associations... Nothing modified I cannot set a Partition QOS since that would apply to all accounts on the partition giving them the same limit I cannot just set a general Account limit (or QOS) since that would apply to all Partitions. I really don't want to have to have different Accounts for each partition so I can set Account wide limits. That would make users have to remember which Account to use with which Partiton. It looks like the following works but requires having to repeat for all users in every Account sacctmgr -i add user User1 account=Acct1 partition=Part1 \ fairshare=parent qos=cpus10 # limits on the Acct1 partition sacctmgr -i add user User1 account=Acct1 \ fairshare=parent # no limits on any other partition But in essense is not much better than having different Accounts for each partition as I now have to maintain multiple user entries per Account: one for partitios with no-limits and and additional one for each partition that needs limits. I guess at least users don't have to remember what account to use when submitting to a partition. Its seems there should be some simpler way to do this. A way to say "this is the limit for this Account on this Partion for all current users and any future users added to the Account" Am I missing something? The information in this e-mail is intended only for the person to whom it is addressed. If you believe this e-mail was sent to you in error and the e-mail contains patient information, please contact the Mass General Brigham Compliance HelpLine at https://www.massgeneralbrigham.org/complianceline <https://www.massgeneralbrigham.org/complianceline> . Please note that this e-mail is not secure (encrypted). If you do not wish to continue communication over unencrypted e-mail, please notify the sender of this message immediately. Continuing to send or respond to e-mail after receiving this message means you understand and accept this risk and wish to continue to communicate over unencrypted e-mail.

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cloud compute limits/budget
by Tom Sparks 03 Oct '25

03 Oct '25

I am setting up a single user slurm I have limited budget for cloud gpu compute ($40) I am wondering if slurm has ability to stop me from going over my budget? I have read the slurm's powersaving / configureless nodes guides Are they other guides I should look at?

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SRUN and SBATCH network issues on configless login node.
by Bruno Bruzzo 01 Oct '25

01 Oct '25

Hi all, first of all, sorry for my English, it's not my native language. We are currently experiencing an issue with srun and salloc on our login nodes, while sbatch works properly. slurm version 23.11.4. slurmctld runs on management node mmgt01. srun and salloc fail intermittently on login node, that means we can successfully use srun on login node from time to time, but it stops working for a while without us changing any configuration. login nodes reports the following to the user: $ srun -N 1 -n 64 --partition=gpunode --pty /bin/bash srun: job 4872 queued and waiting for resources srun: error: Security violation, slurm message from uid 202 srun: error: Security violation, slurm message from uid 202 srun: error: Security violation, slurm message from uid 202 srun: error: Task launch for StepId=4872.0 failed on node cn065: Invalid job credential srun: error: Application launch failed: Invalid job credential srun: Job step aborted uid 202 is the slurm user. On the server side, slurmctld logs show: sched: _slurm_rpc_allocate_resources JobId=4872 NodeList=(null) usec=228 sched: Allocate JobId=4872 NodeList=cn065 #CPUs=64 Partition=gpunode error: slurm_receive_msgs: [[snmgt01]:38727] failed: Zero Bytes were transmitted or received Killing interactive JobId=4872: Communication connection failure _job_complete: JobId=4872 WEXITSTATUS 1 _job_complete: JobId=4872 done step_partial_comp: JobId=4872 StepID=0 invalid; this step may have already completed _slurm_rpc_complete_job_allocation: JobId=4872 error Job/step already completing or completed We suspect it is a network issue regarding the Zero Bytes were transmitted or received. The configless system is working properly. Slurmd on login node can read changes made at slurm.conf after a scontrol reconfig. srun runs successfully from management nodes and from compute nodes. The issue is from the login node. scontrol ping always shows DOWN from login node, even when we can successfully run srun or salloc. $ scontrol ping Slurmctld(primary) at mmgt01 is DOWN We checked as well for munge consistency. mmgt and login nodes have the hostnames of their respective others on /etc/hosts. They can communicate. We would really appreciate some tips on what we could be missing. Best regards, Bruno Bruzzo System Administrator - Clementina XXI

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