September 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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Re: How to make TLS and PMIx v4 work together?
by Grigory Shamov 30 Sep '25

30 Sep '25

Forgot to add: the s2n-tls comes from EPEL and is ver 1.5.10. On 2025-09-25, 11:56 AM, "Grigory Shamov via slurm-users" <slurm-users(a)lists.schedmd.com <mailto:slurm-users@lists.schedmd.com>> wrote: Caution! This message was sent from outside the University of Manitoba. Hi All, We have updated SLURM to the current 25.05.x and tried to enable TLS on it. The OS is Alma 8.10, cgroups v1, and PMIx v 4. We see that srun fails for MPI jobs across the nodes, with TLS related errors when using PMIx (the default) but passes with srun --mpi=pmi2 or with mpirun . TLSType = tls/s2n TLSParameters = ca_cert_file= (has all the certs here under /etc/slurm/certs) And the errors when using PMIx are 025-09-25T11:04:43.894] error: con_close_on_poll_error: [n388:6818(fd:15)] socket error encountered while polling: Connection reset by peer [2025-09-25T11:04:50.102] [6451416.0] error: _negotiate: s2n_negotiate() failed S2N_ERR_CERT_UNTRUSTED[335544366]: Certificate is untrusted -> Error encountered in /builddir/build/BUILD/s2n-tls-1.5.10/tls/s2n_x509_validator.c:494 (couple of these) [2025-09-25T11:05:57.878] [6451416.0] error: tls_p_recv: s2n_recv() failed S2N_ERR_CLOSED[134217728]: connection is closed -> Error encountered in /builddir/build/BUILD/s2n-tls-1.5.10/utils/s2n_io.c:37 [2025-09-25T11:05:57.883] [6451416.0] error: tls_p_send: s2n_send() failed S2N_ERR_IO[67108864]: underlying I/O operation failed, check system errno -> Error encountered in /builddir/build/BUILD/s2n-tls-1.5.10/utils/s2n_io.c:28 (couple of these) [2025-09-25T11:05:59.076] error: wrap_on_data: [unix:/var/spool/slurmd/slurmd.socket(fd:17)] on_data returned rc: Unable to proxy slurmstepd message [2025-09-25T11:05:59.076] [6451416.0] error: _stepd_send_recv_msg: slurmd was unable to proxy request message to its final destination [2025-09-25T11:05:59.878] error: _slurmd_send_recv_msg: Failed to send/recv slurmstepd message MESSAGE_TASK_EXIT using proxy_type PROXY_TO_NODE_SEND_RECV 2025-09-25T11:07:36.335] [6451416.0] error: mpi/pmix_v4: pmixp_p2p_send: n388 [0]: pmixp_utils.c:469: send failed, rc=1001, exceeded the retry limit [2025-09-25T11:07:36.335] [6451416.0] error: mpi/pmix_v4: _slurm_send: n388 [0]: pmixp_server.c:1586: Cannot send message to /var/spool/slurmd/stepd.slurm.pmix.6451416.0, size = 27679, hostlist: (null) (and couple more PMIx errors). Looks like PMIx cannot talk to their peers now ? There was no specific configuration for the certgen plugin, because SLURM documentation seems to say it is optional(?). I wonder what do we miss here to have SLURM 25.05 in with TLS enabled and PMIx working? Any advice appreciated! Thanks! -- Grigory Shamov Site Lead / HPC Specialist University of Manitoba and DRI Alliance Canada -- slurm-users mailing list -- slurm-users(a)lists.schedmd.com <mailto:slurm-users@lists.schedmd.com> To unsubscribe send an email to slurm-users-leave(a)lists.schedmd.com <mailto:slurm-users-leave@lists.schedmd.com>

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FUTURE nodes do not return to idle on slurmctld restart
by Steve Kirk 26 Sep '25

26 Sep '25

Hello, We've got a few nodes defined in our slurm.conf in 'FUTURE' state as it's a new hardware type we're working on brining into service. The nodes are currently all allocated to a dedicated partition. The partition is configured as 'state=UP'. As we've built the new nodes and started slurmd+munge, they've appeared in an idle state in the new partition as expected. All good so far. However if the slurmctld is restarted the nodes go back to being in 'FUTURE' state, and do not transition to idle, accept jobs etc. The slurm daemon on the new nodes can clearly still talk to the slurmctld, s* commands on the new nodes work as expected but remain in FUTURE state - until slurmd on each node is restarted. I could have misunderstood something about the FUTURE state but I was expecting them to go back to idle; I understand that slurmctld doesn't communicate out to nodes in FUTURE state but I at least expected them to be picked up when they communicate _in_ to the slurmctld. Is this expected behaviour or perhaps a bug? The reason I've defined the new nodes this way so I don't have to update slurm.conf and restart slurmctld as each is built, but can do that as a single job once everything is finished, however it seems less useful if they can 'disappear' from the cluster as far as users are concerned. Cheers, Steve

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How to make TLS and PMIx v4 work together?
by Grigory Shamov 25 Sep '25

25 Sep '25

Hi All, We have updated SLURM to the current 25.05.x and tried to enable TLS on it. The OS is Alma 8.10, cgroups v1, and PMIx v 4. We see that srun fails for MPI jobs across the nodes, with TLS related errors when using PMIx (the default) but passes with srun --mpi=pmi2 or with mpirun . TLSType = tls/s2n TLSParameters = ca_cert_file= (has all the certs here under /etc/slurm/certs) And the errors when using PMIx are 025-09-25T11:04:43.894] error: con_close_on_poll_error: [n388:6818(fd:15)] socket error encountered while polling: Connection reset by peer [2025-09-25T11:04:50.102] [6451416.0] error: _negotiate: s2n_negotiate() failed S2N_ERR_CERT_UNTRUSTED[335544366]: Certificate is untrusted -> Error encountered in /builddir/build/BUILD/s2n-tls-1.5.10/tls/s2n_x509_validator.c:494 (couple of these) [2025-09-25T11:05:57.878] [6451416.0] error: tls_p_recv: s2n_recv() failed S2N_ERR_CLOSED[134217728]: connection is closed -> Error encountered in /builddir/build/BUILD/s2n-tls-1.5.10/utils/s2n_io.c:37 [2025-09-25T11:05:57.883] [6451416.0] error: tls_p_send: s2n_send() failed S2N_ERR_IO[67108864]: underlying I/O operation failed, check system errno -> Error encountered in /builddir/build/BUILD/s2n-tls-1.5.10/utils/s2n_io.c:28 (couple of these) [2025-09-25T11:05:59.076] error: wrap_on_data: [unix:/var/spool/slurmd/slurmd.socket(fd:17)] on_data returned rc: Unable to proxy slurmstepd message [2025-09-25T11:05:59.076] [6451416.0] error: _stepd_send_recv_msg: slurmd was unable to proxy request message to its final destination [2025-09-25T11:05:59.878] error: _slurmd_send_recv_msg: Failed to send/recv slurmstepd message MESSAGE_TASK_EXIT using proxy_type PROXY_TO_NODE_SEND_RECV 2025-09-25T11:07:36.335] [6451416.0] error: mpi/pmix_v4: pmixp_p2p_send: n388 [0]: pmixp_utils.c:469: send failed, rc=1001, exceeded the retry limit [2025-09-25T11:07:36.335] [6451416.0] error: mpi/pmix_v4: _slurm_send: n388 [0]: pmixp_server.c:1586: Cannot send message to /var/spool/slurmd/stepd.slurm.pmix.6451416.0, size = 27679, hostlist: (null) (and couple more PMIx errors). Looks like PMIx cannot talk to their peers now ? There was no specific configuration for the certgen plugin, because SLURM documentation seems to say it is optional(?). I wonder what do we miss here to have SLURM 25.05 in with TLS enabled and PMIx working? Any advice appreciated! Thanks! -- Grigory Shamov Site Lead / HPC Specialist University of Manitoba and DRI Alliance Canada

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Node switching randomly to down state
by Julien Tailleur 24 Sep '25

24 Sep '25

Dear all, I am maintaining a small computing cluster and I have a weird behavior that I fail at debugging. My cluster comprise one master node and 16 computing servers, organized in two queues, each queue having 8 servers. All servers run up-to-date Debian bullseye. All but 3 servers work flawlessly. From the master node, I can see that 3 servers on one of the queue appear down: jtailleu@kandinsky:~$ sinfo PARTITION AVAIL TIMELIMIT NODES STATE NODELIST Volume* up infinite 8 alloc FX[21-24,31-34] Speed up infinite 3 down* FX[12-14] Speed up infinite 4 alloc FX[41-44] Speed up infinite 1 idle FX11 These servers are reachable by SSH/ping jtailleu@kandinsky:~$ ping -c 1 FX12 PING FX12 (192.168.6.22) 56(84) bytes of data. 64 bytes from FX12 (192.168.6.22): icmp_seq=1 ttl=64 time=0.070 ms --- FX12 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 0.070/0.070/0.070/0.000 ms ##### I can also put these nodes back into idle mode: root@kandinsky:~# scontrol update nodename=FX[12-14] state=idle root@kandinsky:~# sinfo PARTITION AVAIL TIMELIMIT NODES STATE NODELIST Volume* up infinite 8 alloc FX[21-24,31-34] Speed up infinite 3 idle* FX[12-14] Speed up infinite 4 alloc FX[41-44] Speed up infinite 1 idle FX11 But then, they switch back into down mode few minutes later: root@kandinsky:~# sinfo PARTITION AVAIL TIMELIMIT NODES STATE NODELIST Volume* up infinite 8 alloc FX[21-24,31-34] Speed up infinite 3 down* FX[12-14] Speed up infinite 4 alloc FX[41-44] Speed up infinite 1 idle FX11 root@kandinsky:~# sinfo -R REASON USER TIMESTAMP NODELIST Not responding slurm 2025-09-08T15:04:39 FX[12-14] I do not understand where the "not responding" comes from, nor how I can investigate that. Any idea what could trigger this behavior? Best wishes, Julien

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No output and can't job by id
by Dhumal, Dr. Nilesh 22 Sep '25

22 Sep '25

Hello, Recently, we updated Slurm. We are running slrumcld on head node. The slurmdbd is disabled on the head node. The user submits the job and gets the job ID. The squeue is empty, and difficult to track the job progress. The job is not writing any output to a file. How can I resolve this issue? Nilesh Dhumal Associate Professor of Chemistry, http://faculty.fgcu.edu/ndhumal/ Coordinator, FGCU Computational Facility, https://www.fgcu.edu/cas/facultyresources/computationalfacility/ SH-430; Department of Chemistry and Physics Florida Gulf Coast University 10501 FGCU Boulevard South Fort Myers, FL 33965-6565 Phone: (239) 745-4394 Email: ndhumal(a)fgcu.edu

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Node in drain state
by Gestió Servidors 22 Sep '25

22 Sep '25

Hello, I have got a node in "drain" state after finishing a job that was running on it. Log in node reports this information: [...] [2025-09-07T11:09:26.980] task/affinity: task_p_slurmd_batch_request: task_p_slurmd_batch_request: 59238 [2025-09-07T11:09:26.980] task/affinity: batch_bind: job 59238 CPU input mask for node: 0xFFF [2025-09-07T11:09:26.980] task/affinity: batch_bind: job 59238 CPU final HW mask for node: 0xFFF [2025-09-07T11:09:26.980] Launching batch job 59238 for UID 21310 [2025-09-07T11:09:27.006] cred/munge: init: Munge credential signature plugin loaded [2025-09-07T11:09:27.007] [59238.batch] debug: auth/munge: init: loaded [2025-09-07T11:09:27.009] [59238.batch] debug: Reading cgroup.conf file /soft/slurm-23.11.0/etc/cgroup.conf [2025-09-07T11:09:27.025] [59238.batch] debug: cgroup/v1: init: Cgroup v1 plugin loaded [2025-09-07T11:09:27.025] [59238.batch] debug: hash/k12: init: init: KangarooTwelve hash plugin loaded [2025-09-07T11:09:27.026] [59238.batch] debug: task/cgroup: init: core enforcement enabled [2025-09-07T11:09:27.026] [59238.batch] debug: task/cgroup: init: device enforcement enabled [2025-09-07T11:09:27.026] [59238.batch] debug: task/cgroup: init: Tasks containment cgroup plugin loaded [2025-09-07T11:09:27.026] [59238.batch] task/affinity: init: task affinity plugin loaded with CPU mask 0xfff [2025-09-07T11:09:27.027] [59238.batch] debug: jobacct_gather/cgroup: init: Job accounting gather cgroup plugin loaded [2025-09-07T11:09:27.027] [59238.batch] topology/default: init: topology Default plugin loaded [2025-09-07T11:09:27.030] [59238.batch] debug: gpu/generic: init: init: GPU Generic plugin loaded [2025-09-07T11:09:27.031] [59238.batch] debug: laying out the 12 tasks on 1 hosts clus09 dist 2 [2025-09-07T11:09:27.031] [59238.batch] debug: close_slurmd_conn: sending 0: No error [2025-09-07T11:09:27.031] [59238.batch] debug: Message thread started pid = 910040 [2025-09-07T11:09:27.031] [59238.batch] debug: Setting slurmstepd(910040) oom_score_adj to -1000 [2025-09-07T11:09:27.031] [59238.batch] debug: spank: opening plugin stack /soft/slurm-23.11.0/etc/plugstack.conf [2025-09-07T11:09:27.031] [59238.batch] debug: task/cgroup: task_cgroup_cpuset_create: job abstract cores are '0-11' [2025-09-07T11:09:27.031] [59238.batch] debug: task/cgroup: task_cgroup_cpuset_create: step abstract cores are '0-11' [2025-09-07T11:09:27.031] [59238.batch] debug: task/cgroup: task_cgroup_cpuset_create: job physical CPUs are '0-11' [2025-09-07T11:09:27.031] [59238.batch] debug: task/cgroup: task_cgroup_cpuset_create: step physical CPUs are '0-11' [2025-09-07T11:09:27.090] [59238.batch] debug levels are stderr='error', logfile='debug', syslog='fatal' [2025-09-07T11:09:27.090] [59238.batch] starting 1 tasks [2025-09-07T11:09:27.090] [59238.batch] task 0 (910044) started 2025-09-07T11:09:27 [2025-09-07T11:09:27.098] [59238.batch] debug: task/affinity: task_p_pre_launch: affinity StepId=59238.batch, task:0 bind:mask_cpu [2025-09-07T11:09:27.098] [59238.batch] _set_limit: RLIMIT_NPROC : reducing req:255366 to max:159631 [2025-09-07T11:09:27.398] [59238.batch] task 0 (910044) exited with exit code 2. [2025-09-07T11:09:27.399] [59238.batch] debug: task/affinity: task_p_post_term: affinity StepId=59238.batch, task 0 [2025-09-07T11:09:27.399] [59238.batch] debug: signaling condition [2025-09-07T11:09:27.399] [59238.batch] debug: jobacct_gather/cgroup: fini: Job accounting gather cgroup plugin unloaded [2025-09-07T11:09:27.400] [59238.batch] debug: task/cgroup: fini: Tasks containment cgroup plugin unloaded [2025-09-07T11:09:27.400] [59238.batch] job 59238 completed with slurm_rc = 0, job_rc = 512 [2025-09-07T11:09:27.410] [59238.batch] debug: Message thread exited [2025-09-07T11:09:27.410] [59238.batch] stepd_cleanup: done with step (rc[0x200]:Unknown error 512, cleanup_rc[0x0]:No error) [2025-09-07T11:09:27.411] debug: _rpc_terminate_job: uid = 1000 JobId=59238 [2025-09-07T11:09:27.411] debug: credential for job 59238 revoked [...] "sinfo" shows: [root@login-node ~]# sinfo PARTITION TIMELIMIT AVAIL STATE NODELIST CPU_LOAD NODES(A/I) NODES(A/I/O/T) CPUS CPUS(A/I/O/T) REASON node.q* 4:00:00 up drained clus09 0.00 0/0 0/0/1/1 12 0/0/12/12 Kill task faile node.q* 4:00:00 up allocated clus[10-11] 13.82-15.8 2/0 2/0/0/2 12 24/0/0/24 none node.q* 4:00:00 up idle clus[01-06,12] 0.00 0/7 0/7/0/7 12 0/84/0/84 none But it seems there is no error in node... Slurmctld.log in server seems correct, too. Is there any way to reset node to "state=idle" after errors in the same way? Thanks.

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Compute node not responding
by Dhumal, Dr. Nilesh 21 Sep '25

21 Sep '25

Hello, Recently, we installed slum 25 on our cluster. We are not monitoring the user's account. We didn't configure the sql database on the head node. We are running slurmcld on head node and slumd on the compute node. We are getting the following error Head node: compute node not responding. Compute node: 2025-09-19T15:30:23.461] error: Unable to register: Unable to contact slurm controller (connect failure) Do we need to run slumdbd on the head node? I checked the network connection by pinging the compute node from the head node. Do you have any suggestions to resolve this issue? Thanks Nilesh Get Outlook for Android<https://aka.ms/AAb9ysg>

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