Hello,

We are running into an issue with the resource request for CPU resources when also requesting GPU resources. Specifically with the use of --cpus-per-gpu

For context, we are running a 8 GPU node with shared access. The configuration is 
(not showing nodes for brevity). 
   AllowGroups=ALL AllowAccounts=ALL AllowQos=ALL
   AllocNodes=ALL Default=NO QoS=N/A
   DefaultTime=01:00:00 DisableRootJobs=NO ExclusiveUser=NO GraceTime=0 Hidden=NO
   MaxNodes=UNLIMITED MaxTime=1-00:00:00 MinNodes=0 LLN=NO MaxCPUsPerNode=UNLIMITED
   PriorityJobFactor=0 PriorityTier=0 RootOnly=NO ReqResv=NO OverSubscribe=NO
   OverTimeLimit=NONE PreemptMode=OFF
   State=UP TotalCPUs=17152 TotalNodes=134 SelectTypeParameters=CR_SOCKET_MEMORY
   JobDefaults=(null)
   DefMemPerCPU=1840 MaxMemPerCPU=3680
   TRES=cpu=17152,mem=32830000M,node=134,billing=137216,gres/gpu=1072
   TRESBillingWeights=CPU=2,Mem=0.24G,gres/GPU=128

So we allocate memory based on the number of cores requested (whether through tasks or slurm 'cpus'). The desired behaviour for non-exclusive gpu partition allocations is that we have 8 cores allocated for each gpu allocated on the node. Testing shows that we do get a minimum of 8 cores in an allocation, but depending on --cpus-per-task or --cpus-per-gpu options in the request, we otherwise get only 8 cores, or else all 64 cores.

Ultimately, we think the optimal desired behaviour will be achieved through the use of a Slurm CLI filter so that number of cores and allocated memory be solely dependent upon the number of allocated GPUs on the node, possibly through enforcing --cpus-per-gpu and --mem-per-gpu settings. 

The test runs below use the following script to report allocated cores and GPUs; each allocation is for a single node (and a single task), --cpu-bind=none and --gpu-bind=none are used in the srun invocation to disable any binding to a subset of the allocated resources.

#!/usr/bin/env bash
mask=$(hwloc-bind --get)
echo "cores $(hwloc-calc -I core $mask)"
echo "NUMA domains $(hwloc-calc -I NUMAnode $mask)"
/opt/rocm/bin/rocm-smi --showbus | grep '^GPU'
We see the same behaviour on both the gpu and gpu-dev partitions. Except where relevant, salloc and srun output has been omitted.

## Tests without specifying -c/--cpus-per-task or --cpus-per-gpu

Here we get eight cores no matter what. A zero GPU allocation succeeds (it'd be best if it did not) and is granted eight cores.

+ salloc -n 1 -N 1 -p gpu-dev -A pawsey0001-gpu --gpus=0 srun -n 1 -N 1 --cpu-bind=none --gpu-bind=none ./report
cores 0,1,2,3,4,5,6,7
NUMA domains 0
WARNING: No AMD GPUs specified

+ salloc -n 1 -N 1 -p gpu-dev -A pawsey0001-gpu --gpus=1 srun -n 1 -N 1 --cpu-bind=none --gpu-bind=none ./report
cores 0,1,2,3,4,5,6,7
NUMA domains 0
GPU[0]          : PCI Bus: 0000:D1:00.0

+ salloc -n 1 -N 1 -p gpu-dev -A pawsey0001-gpu --gpus=2 srun -n 1 -N 1 --cpu-bind=none --gpu-bind=none ./report
cores 0,1,2,3,4,5,6,7
NUMA domains 0
GPU[0]          : PCI Bus: 0000:D1:00.0
GPU[1]          : PCI Bus: 0000:D6:00.0

+ salloc -n 1 -N 1 -p gpu-dev -A pawsey0001-gpu --gpus=4 srun -n 1 -N 1 --cpu-bind=none --gpu-bind=none ./report
cores 0,1,2,3,4,5,6,7
NUMA domains 0
GPU[0]          : PCI Bus: 0000:C9:00.0
GPU[1]          : PCI Bus: 0000:CE:00.0
GPU[2]          : PCI Bus: 0000:D1:00.0
GPU[3]          : PCI Bus: 0000:D6:00.0

## Tests with --cpus-per-gpu=8

This gives the desired result for one GPU (that is --ntasks=1 --gpus-per-task=1 --cpus-per-task=8 is fine) but is otherwise weird:

A request for 2 or 6 GPUs fails with an unavailable node configuration error.
A request for 3 or 4 GPUs allocates 33 cores comprising the first two NUMA domains (4 CCXs) and the first core of the next.
+ salloc -n 1 -N 1 -p gpu-dev -A pawsey0001-gpu --cpus-per-gpu=8 --gpus=1 srun -n 1 -N 1 --cpu-bind=none --gpu-bind=none ./report
cores 0,1,2,3,4,5,6,7
NUMA domains 0
GPU[0]          : PCI Bus: 0000:D1:00.0

+ salloc -n 1 -N 1 -p gpu-dev -A pawsey0001-gpu --cpus-per-gpu=8 --gpus=2 srun -n 1 -N 1 --cpu-bind=none --gpu-bind=none ./report
salloc: error: Job submit/allocate failed: Requested node configuration is not available

+ salloc -n 1 -N 1 -p gpu-dev -A pawsey0001-gpu --cpus-per-gpu=8 --gpus=3 srun -n 1 -N 1 --cpu-bind=none --gpu-bind=none ./report
cores 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32
NUMA domains 0,2,3
GPU[0]		: PCI Bus: 0000:D1:00.0
GPU[1]		: PCI Bus: 0000:D9:00.0
GPU[2]		: PCI Bus: 0000:DE:00.0

+ salloc -n 1 -N 1 -p gpu-dev -A pawsey0001-gpu --cpus-per-gpu=8 --gpus=4 srun -n 1 -N 1 --cpu-bind=none --gpu-bind=none ./report
cores 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32
NUMA domains 0,2,3
GPU[0]          : PCI Bus: 0000:C1:00.0
GPU[1]          : PCI Bus: 0000:D1:00.0
GPU[2]          : PCI Bus: 0000:D9:00.0
GPU[3]          : PCI Bus: 0000:DE:00.0

+ salloc -n 1 -N 1 -p gpu-dev -A pawsey0001-gpu --cpus-per-gpu=8 --gpus=6 srun -n 1 -N 1 --cpu-bind=none --gpu-bind=none ./report
salloc: error: Job submit/allocate failed: Requested node configuration is not available

The key issue here is failed resource requests which should definitely be satisfied. 

## Tests with --cpus-per-task
Here the tests are run with an explicit request for eight times as many cores as GPUs. A request for 1 GPU and eight cores grants eight cores; requests for 2 GPUs and 16 cores or 4 GPUs and 32 cores grant all 64 cores.

+ salloc -n 1 -N 1 -p gpu-dev -A pawsey0001-gpu --cpus-per-task=8 --gpus=1 srun -n 1 -N 1 --cpu-bind=none --gpu-bind=none ./report
cores 0,1,2,3,4,5,6,7
NUMA domains 0
GPU[0]          : PCI Bus: 0000:D1:00.0

+ salloc -n 1 -N 1 -p gpu-dev -A pawsey0001-gpu --cpus-per-task=16 --gpus=2 srun -n 1 -N 1 --cpu-bind=none --gpu-bind=none ./report
cores 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,↳53,54,55,56,57,58,59,60,61,62,63
NUMA domains 0,1,2,3
GPU[0]          : PCI Bus: 0000:D1:00.0
GPU[1]          : PCI Bus: 0000:D6:00.0

+ salloc -n 1 -N 1 -p gpu-dev -A pawsey0001-gpu --cpus-per-task=32 --gpus=4 srun -n 1 -N 1 --cpu-bind=none --gpu-bind=none ./report
cores 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,↳53,54,55,56,57,58,59,60,61,62,63
NUMA domains 0,1,2,3
GPU[0]          : PCI Bus: 0000:C9:00.0
GPU[1]          : PCI Bus: 0000:CE:00.0
GPU[2]          : PCI Bus: 0000:D1:00.0
GPU[3]          : PCI Bus: 0000:D6:00.0


It is not obvious why slurm behaves so oddly with --cpus-per-gpu and why with --cpus-per-task sometimes we are getting more cpus than requested.