August 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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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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slurmrestd unable to find plugin rest_auth/jwt
by Jon Marshall 28 Aug '25

28 Aug '25

Hi, I feel like I must have missed something obvious here, so hopefully someone can spot it! We recently updated to Slurm 24.11.6 on our cluster and I made sure to compile --with slurmrestd and --with jwt, as there are a few things I've been meaning to try out with the REST API. From the rpmbuild config.log I get: $ ./configure --build=x86_64-redhat-linux-gnu --host=x86_64-redhat-linux-gnu --program-prefix= --disable-dependency-tracking --prefix=/usr --exec-prefix=/usr --bindir=/usr/bin --sbindir=/usr/sbin --sysconfdir=/etc/slurm --datadir=/usr/share --includedir=/usr/include --libdir=/usr/lib64 --libexecdir=/usr/libexec --localstatedir=/var --sharedstatedir=/var/lib --mandir=/usr/share/man --infodir=/usr/share/info --with-systemdsystemunitdir=/usr/lib/systemd/system --enable-pkgconfig --with-jwt -- configure:21020: checking for jwt.h configure:21020: gcc -c -DNUMA_VERSION1_COMPATIBILITY -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -Wl,-z,lazy -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -fno-omit-frame-pointer conftest.c >&5 configure:21020: $? = 0 configure:21020: result: yes configure:21028: checking for jwt_add_header in -ljwt configure:21051: gcc -o conftest -DNUMA_VERSION1_COMPATIBILITY -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -Wl,-z,lazy -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -fno-omit-frame-pointer -Wl,-z,relro -Wl,-z,lazy conftest.c -ljwt -ldl -lrt -lm -lresolv >&5 configure:21051: $? = 0 configure:21061: result: yes -- config.status:1746: creating src/plugins/auth/jwt/Makefile -- config.status:1746: creating src/slurmrestd/plugins/auth/jwt/Makefile -- ac_cv_header_jwt_h=yes -- ac_cv_lib_jwt_jwt_add_header=yes -- JWT_LDFLAGS='-ljwt' And: configure:26873: checking whether to compile slurmrestd configure:26904: result: yes -- configure:26915: checking for slurmrestd default port configure:26933: result: 6820 And indeed I get a slurmrestd package out of it, which I've successfully installed with no errors. I've created a JWT key and rolled it out to the controller node, but when I go to check auth types I get: slurmrestd -a rest_auth/jwt slurmrestd: fatal: Unable to find plugin: rest_auth/jwt Running an strace on this process shows that it does in fact stat the .so that does in fact exist: stat("/usr/lib64/slurm/auth_jwt.so", {st_mode=S_IFREG|0755, st_size=283728, ...}) = 0 And I'm kind of stumped now. I've checked through all the resolved bug tickets to see if I can spot what is wrong but I'm getting nothing, and I can't find anything in the mailing lists either, other than things I've checked. Has anyone else had similar issues, or can someone see the blindingly obvious thing I'm missing? Cheers Jon Jon Marshall High Performance Computing Specialist IT and Scientific Computing Team Cancer Research UK Cambridge Institute Li Ka Shing Centre | Robinson Way | Cambridge | CB2 0RE Web<http://www.cruk.cam.ac.uk/> | Facebook<http://www.facebook.com/cancerresearchuk> | Twitter<http://twitter.com/CR_UK> [Description: CRI Logo]<http://www.cruk.cam.ac.uk/>

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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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Node Health Check Program
by Paul Edmon 27 Aug '25

27 Aug '25

We've been using NHC (https://github.com/mej/nhc) for years with much success. However that project hasn't had a release in 2 years and the various Issues filed indicate that there might be problems with Rocky 9 (which we are looking to upgrade to). Do people that are at EL9 use NHC? Is there a fork? Is there a different code that people use for doing node health checks? -Paul Edmon-

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Slurm 25.05: Retrieving jobs GPU Indices on Heterogeneous Cluster
by David Gauchard 27 Aug '25

27 Aug '25

Hello, I'm running Slurm 25.05 on a heterogeneous cluster (several kind of GPU in the same node) with AutoDetect=nvml and shared mode. When submitting a job with `#SBATCH --gres=gpu:1`, CUDA_VISIBLE_DEVICES is correctly set to a single and valid free GPU index but `scontrol show jobid` does not report any detail about GPU allocation. How can I retrieve the GPU indices assigned to running jobs (reflecting CUDA_VISIBLE_DEVICES) in shared mode? Is there a Slurm command or configuration to enable tracking of these indices on a heterogeneous cluster? The goal is to help automatic choice of the free and appropriate gpu according to the job's needs in order to save bigger gpus for bigger jobs at the time of submitting. Thanks

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Issues with dynamic configless nodes and pam_slurm_adopt
by Leonardo Sala 26 Aug '25

26 Aug '25

Hallo everyone we have recently noticed that when running nodes in configless and dynamic mode, pam_slurm_adopt does not work properly, denying ssh access when the user has a running job. We traced down the issue to the fact that the dynamic nodes are registered with FQDN (e.g. c01.psi.ch), while pam_slurm_adopt uses this routine (https://github.com/SchedMD/slurm/blob/master/src/common/stepd_api.c#L181) to guess the stepd hostname, using the host short name (so, c01). If we use gethostname instead of gethostname_short then it works again. Has anybody experience with this, and is there a way to have dynamic configless nodes registering with the short hostname? Thanks! cheers leo -- Paul Scherrer Institut Dr. Leonardo Sala Group Leader Data Analysis and Research Infrastructure Group Leader Data Curation a.i. Deputy Department Head Science IT Infrastructure and Services department Science IT Infrastructure and Services department (AWI) OBBA/230 Forschungstrasse 111 5232 Villigen PSI Switzerland Phone: +41 56 310 3369 leonardo.sala(a)psi.ch www.psi.ch

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Tips or experiences with Burst Buffers?
by Bjørn-Helge Mevik 21 Aug '25

21 Aug '25

Dear all! We are currently considering setting up the (Lua) Burst Buffer plugin to stage in and out files. Those of you who have done this (or at least tried): do you have any experiences or tips to share? -- Regards, Bjørn-Helge Mevik

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GPFS nvme limit storage per job
by Ratnasamy, Fritz 19 Aug '25

19 Aug '25

We have our new dedicated GPFS storage and were wondering how to accommodate all the users on the local nvme. Is there a way for slurm to enforce a per-job quota for every user so we make sure they don't take all the space? Thanks, *Fritz Ratnasamy*Data Scientist Information Technology

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