March 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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Assistance with Node Restrictions and Priority for Users in Floating Partition
by Manisha Yadav 28 Aug '25

28 Aug '25

Dear Team, I have a scenario where I need to provide priority access to multiple users from different projects for only 3 nodes. This means that, at any given time, only 3 nodes can be used in that partition, and if one user is utilizing all 3 nodes, no other user should be able to submit jobs to that partition, or their jobs should remain in the queue. To achieve this, I attempted to use QoS by creating a floating partition with some of the nodes and configuring a QoS with priority. I also set a limit with GrpTRES=gres/gpu=24, given that each node has 8 GPUs, and there are 3 nodes in total. I then attached the QoS to the partition and assigned it to the users who need access. I Also tried MaxTRES=gres/gpu=24 While this setup works as expected in the testing environment for CPUs, it is not functioning as intended in production, and it is not effectively restricting node usage in the partition. Could anyone provide suggestions or guidance on how to properly implement node restrictions along with priority? Thank you for your assistance. Best regards, Manisha Yadav ------------------------------------------------------------------------------------------------------------ [ C-DAC is on Social-Media too. Kindly follow us at: Facebook: https://www.facebook.com/CDACINDIA & Twitter: @cdacindia ] This e-mail is for the sole use of the intended recipient(s) and may contain confidential and privileged information. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies and the original message. Any unauthorized review, use, disclosure, dissemination, forwarding, printing or copying of this email is strictly prohibited and appropriate legal action will be taken. ------------------------------------------------------------------------------------------------------------

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Minimum cpu cores per node partition level configuration
by Jeherul Islam 10 Apr '25

10 Apr '25

Dear All, I need to configure the slurm so the user must take a certain minimum number of CPU cores for a particular partition(not system-wide). Otherwise, the job must not run. Any suggestions will be highly appreciated. With Thanks and Regards -- Jeherul Islam

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cpus and gpus partitions and how to optimize the resource usage
by Massimo Sgaravatto 31 Mar '25

31 Mar '25

Dear all We have just installed a small SLURM cluster composed of 12 nodes: - 6 CPU only nodes: 2 Sockets=2, 96 CoresPerSocket 2, ThreadsPerCore=2, 1.5 TB of RAM - 6 nodes with also GPUS: same conf of the CPU-only node + 4 H100 per node We started with a setup with 2 partitions: - a 'onlycpus' partition which sees all the cpu-only nodes - a 'gpus' partition which sees the nodes with gpus and asked users to use the 'gpus' partition only for jobs that need gpus (for the time being we are not technically enforced that). The problem is that a job requiring a GPU usually needs only a few cores and only a few GB of RAM, which means wasting a lot of CPU cores. And having all nodes in the same partition would mean that there is the risk that a job requiring a GPU can't start if all CPU cores and/or all memory is used by CPU only jobs I went through the mailing list archive and I think that "splitting" a GPU node into two logical nodes (one to be used in the 'gpus' partition and one to be used in the 'onlycpus' partition) as discussed in [*] would help. Since that proposed solution is considered by his author a "bit of a kludge" and since I read that splitting a node into multiple logical nodes is in a general a bad idea, I'd like to understand if you could suggest other/best options. I also found this [**] thread, but I don't like too much that approach (i.e. relying on MaxCPUsPerNode) because it would mean having 3 partition (if I have got it right): two partitions for cpu only jobs and 1 partition for gpu jobs Many thanks, Massimo [*] https://groups.google.com/g/slurm-users/c/IUd7jLKME3M [**] https://groups.google.com/g/slurm-users/c/o7AiYAQ1YJ0

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Preemption question
by Kamil Wilczek 31 Mar '25

31 Mar '25

Dear All, I would like to be able to preempt (SUSPEND) a single QoS of a user that blocks the queue for several days. Currently I have about 100 users on the cluster and it seems that setting the "Preempt" option to each QoS (we have personal QoSes) is not optimal. https://slurm.schedmd.com/sacctmgr.html#OPT_Preempt Is there a way to to set an option to this single problematic QoS, saying that the QoS can be preempted by any other QoS? It would be much more administrator-friendly solution ;) Kind regards -- Kamil Wilczek [https://keys.openpgp.org/] [D415917E84B8DA5A60E853B6E676ED061316B69B]

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Slurm 24.05 and OpenMPI
by Matthias Leopold 28 Mar '25

28 Mar '25

Hi, I built a small Slurm 21.08 cluster with NVIDIA GPU hardware and NVIDIA deepops framework a couple of years ago. It is based on Ubuntu 20.04 and makes use of the NVIDIA pyxis/enroot container solution. For operational validation I used the nccl-tests application in a container. nccl-tests is compiled with MPI support (OpenMPI 4.1.6 or 4.1.7) and I used it also for validation of MPI jobs. Slurm jobs use "pmix" and tasks are launched via srun (not mpirun). Some of the GPUs can talk to each other via Infiniband, but MPI is rarely used at our site and I'm fully aware that my MPI knowledge is very limited. Still it worked with Slurm 21.08. Now I built a Slurm 24.05 cluster based on Ubuntu 24.04 and started to move hardware there. When I run my nccl-tests container (also with newer software) I see error messages like this: [node1:21437] OPAL ERROR: Unreachable in file ext3x_client.c at line 111 -------------------------------------------------------------------------- The application appears to have been direct launched using "srun", but OMPI was not built with SLURM's PMI support and therefore cannot execute. There are several options for building PMI support under SLURM, depending upon the SLURM version you are using: version 16.05 or later: you can use SLURM's PMIx support. This requires that you configure and build SLURM --with-pmix. Versions earlier than 16.05: you must use either SLURM's PMI-1 or PMI-2 support. SLURM builds PMI-1 by default, or you can manually install PMI-2. You must then build Open MPI using --with-pmi pointing to the SLURM PMI library location. Please configure as appropriate and try again. -------------------------------------------------------------------------- *** An error occurred in MPI_Init *** on a NULL communicator *** MPI_ERRORS_ARE_FATAL (processes in this communicator will now abort, *** and potentially your MPI job) [node1:21437] Local abort before MPI_INIT completed completed successfully, but am not able to aggregate error messages, and not able to guarantee that all other processes were killed! One simple question: Is this related to https://github.com/open-mpi/ompi/issues/12471? If so: is there some workaround? I'm very grateful for any comments. I know that a lot of detail information is missing, but maybe someone can still already give me a hint where to look. Thanks a lot Matthias

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Doubt with SelectTypeParameters in slurm.conf
by Gestió Servidors 28 Mar '25

28 Mar '25

Hello, I'm running some tests in a very small testing environment (before applying in the real scenario). My environment is only a computer with a old Intel i4 with this "lscpu" configuration: Architecture: x86_64 CPU(s): 8 On-line CPU(s) list: 0-7 Thread(s) per core: 2 Core(s) per socket: 4 Socket(s): 1 NUMA node(s): 1 Vendor ID: GenuineIntel BIOS Vendor ID: Intel(R) Corporation CPU family: 6 Model: 26 Model name: Intel(R) Core(TM) i7 CPU 950 @ 3.07GHz "slurmd -C" returns: "CPUs=8 Boards=1 SocketsPerBoard=1 CoresPerSocket=4 ThreadsPerCore=2". My slurm.conf is configured with: SelectType=select/cons_tres SelectTypeParameters=CR_Core AccountingStorageTRES=cpu,mem,node,billing,fs/disk,vmem,pages After running a simple "helloworld" test, I have noticed that if SelectTypeParameters=CR_Core, system always reserves me an even number of CPUs (during "pending" time, I can see the real number I have requested, but when job starts "running", that number is increased to the next even number). Howerver, if I reconfigure slurm with SelectTypeParameters=CR_CPU, system reserves me the correct number of CPUs (during "pending" time and, also, during "running" time). I suppose that my system must be configured with CR_CPU, according https://slurm.schedmd.com/cons_tres.html, but could someone confirm that? Thanks.

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bit_cache_init failure on the second time backup controller tries to take control
by Safdar Iqbal 28 Mar '25

28 Mar '25

Hi, We're running into an issue where slurmctld core-dumps with the following error. This happens on the backup controller, if it needs to take over from the primary, _for a second time_. slurmctld: fatal: bit_cache_init: cannot change size once set Has anyone seen this error before? Also if there are any existing discussions and/or tickets related to this, please let me know. Our slurm version is 24.11.1. ________________ Steps to reproduce: 1. On a healthy cluster, we make the primary controller unavailable. Since we're running our cluster on cloud VMs, we cause this by stopping the primary controller VM. 2. From the logs we can see the backup controller take over, and log the message "Running as primary controller" 3. We then start the primary again, making sure the IP addresses and hostnames stay consistent. Once slurmctld on the primary has started and taken back control, we can see the log "Running as primary controller" on that VM. 4. We then stop the primary controller VM again, causing the backup to try taking the control a second time. This time however the slurmctld on the backup coredumps, with following log entries from journalctl -u slurmctld: slurmctld: fatal: bit_cache_init: cannot change size once set slurmctld.service: Main process exited, code=dumped, status=6/ABRT slurmctld.service: Failed with result 'core-dump'. Thanks! - Safdar

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How limit CPUs per node in a partition
by Gestió Servidors 27 Mar '25

27 Mar '25

Hello, I have a testing partition with only a node. That server has 12 CPUs (it's a very old server) (2 sockets, 6 cores per socket, 1 thread per core). That partition, called "test.q" only has that node, so by default, partition test.q has 12 CPUs (all from testing node). However, now I would like to decrease that CPU number from 12 to 4, for example. "slurmd -C" returns "CPUs=12 Boards=1 SocketsPerBoard=2 CoresPerSocket=6 ThreadsPerCore=1" as I have said to you before and if in slurm.conf I configure partition in this way "PartitionName=test.q Nodes=test-node MaxTime=10:00 State=UP AllocNodes=clus-login MaxCPUsPerNode=4", partition continues accepting jobs with 12 CPUs. Is it any wrong in my configuration? How could I get my purpose? Thanks. -- [cid:image001.jpg@01DB9F0E.FDD9A7A0]<http://www.uab.cat/> Daniel Ruiz Molina Tècnic Mitjà Informàtic Arquitectura de Computadors i Sistemes Operatius Escola d'Enginyeria Edifici Q - Despatx QC/3052 - Carrer de les Sitges Campus de la UAB · 08193 Bellaterra (Cerdanyola del Vallès) · Barcelona · Spain +34 93 581 35 44 www.uab.cat<http://www.uab.cat/> Daniel Ruiz at UAB<https://tinyurl.com/yd95zb8j> [cid:image002.jpg@01DB9F0E.FDD9A7A0]<www.linkedin.com/in/daniel-ruiz-molina-50a83b27> Aquest missatge s'adreça exclusivament a la persona destinatària i pot contenir informació privada o confidencial. Si l'heu rebut per error, comuniqueu-nos-ho i destruïu-lo, i tingueu present que no teniu autorització per fer-ne cap ús. Abans d'imprimir aquest missatge penseu en el medi ambient.

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