Any clue what is causing this problem? My job is failing on all compute nodes with this message: ib_iface.c:1060 UCX ERROR ibv_create_cq(cqe=4096) failed: Cannot allocate memory : Please set max locked memory (ulimit -l) to 'unlimited' (current: 64 kbytes) It doesn't make sense because on all nodes except for the head node, the memory locking limit is "unlimited": $ ssh n004 $ ulimit -Hl -Sl max locked memory (kbytes, -l) unlimited max locked memory (kbytes, -l) unlimited On the head node, the limit is still set at 64 kb, but I thought that it wouldn't matter since the processes run on the compute nodes. I configured MPICH with ch4 and UCX 1.15.0: $ ../mpich-4.1.2/configure --prefix=/opt/mpich --with-device=ch4:ucx --with-ucx=/home/kmccall/ucx-1.15.0/install --with-slurm -enable-debuginfo --enable-g=debug 2>&1 | tee c.txt and my launch command is unremarkable: mpiexec \ -print-all-exitcodes \ -wdir ${work_dir} \ -np ${num_proc} \ -ppn 1 \ application... The cluster is running Red Hat Enterprise Linux release 8.6, slurm 20.11.8, and the compiler version is g++ 8.5.0. Just for reference, here is the compete error message sequenct from slurm.out SLURM_JOB_NODELIST = n[004-008] [1697913222.014184] [n004:39165:0] ib_iface.c:1060 UCX ERROR ibv_create_cq(cqe=4096) failed: Cannot allocate memory : Please set max locked memory (ulimit -l) to 'unlimited' (current: 64 kbytes) [1697913222.014288] [n006:38767:0] ib_iface.c:1060 UCX ERROR ibv_create_cq(cqe=4096) failed: Cannot allocate memory : Please set max locked memory (ulimit -l) to 'unlimited' (current: 64 kbytes) [1697913222.014374] [n005:39166:0] ib_iface.c:1060 UCX ERROR ibv_create_cq(cqe=4096) failed: Cannot allocate memory : Please set max locked memory (ulimit -l) to 'unlimited' (current: 64 kbytes) [1697913222.014851] [n008:38524:0] ib_iface.c:1060 UCX ERROR ibv_create_cq(cqe=4096) failed: Cannot allocate memory : Please set max locked memory (ulimit -l) to 'unlimited' (current: 64 kbytes) [1697913222.014807] [n007:38753:0] ib_iface.c:1060 UCX ERROR ibv_create_cq(cqe=4096) failed: Cannot allocate memory : Please set max locked memory (ulimit -l) to 'unlimited' (current: 64 kbytes) Abort(607769871) on node 0 (rank 0 in comm 0): Fatal error in internal_Init: Other MPI error, error stack: internal_Init(66).............: MPI_Init(argc=0x7ffe9e2b475c, argv=0x7ffe9e2b4750) failed MPII_Init_thread(257).........: MPIR_init_comm_world(34)......: MPIR_Comm_commit(770).........: MPIR_Comm_commit_internal(558): MPID_Comm_commit_pre_hook(158): MPIDI_UCX_init_world(252).....: init_worker(38)...............: ucx function returned with failed status(ucx_init.c 38 init_worker Input/output error) Abort(339334415) on node 2 (rank 2 in comm 0): Fatal error in internal_Init: Other MPI error, error stack: internal_Init(66).............: MPI_Init(argc=0x7ffd5fd79e5c, argv=0x7ffd5fd79e50) failed MPII_Init_thread(257).........: MPIR_init_comm_world(34)......: MPIR_Comm_commit(770).........: MPIR_Comm_commit_internal(558): MPID_Comm_commit_pre_hook(158): MPIDI_UCX_init_world(252).....: init_worker(38)...............: ucx function returned with failed status(ucx_init.c 38 init_worker Input/output error)