[slurm-users] Use gres to handle permissions of /dev/dri/card* and /dev/dri/renderD*?

Martin Pecka peci1 at seznam.cz
Thu Jan 6 17:20:49 UTC 2022

Hello, I'm reviving a bit of old thread, but I just noticed I don't see 
my January 2021 message in the archives, so I'm sending it again now 
that the issue again got live on our side.

To quickly recap, we want to add permissions not only to /dev/nvidia* 
devices based on the requested gres, but also to the corresponding 
/dev/dri/card* and /dev/dri/renderD* devices - they are all connected to 
the same GPU, but the additional two allow using the card for rendering 
instead of CUDA computations etc. I had some idea how to achieve that 
without changing SLURM codebase, and I got something that could almost 
work. It probably just needs some polishing. Could anybody please 
comment whether the proposed solution is a good idea?

The 15 Jan 2021 message:

So I started thinking if this could not be somehow handled by a prologue 
script and direct cgroup manipulation? I'm no expert in either, so 
please check my lines of thoughts.

|#!/bin/bash PATH=/usr/bin/:/bin 
run inside the cgroup? cgroup=$(cat /proc/self/cgroup | grep devices | 
cut -d: -f3) # or something else? # blacklist all DRM devices (major 
226) cgset -r devices.deny="a 226:* rwm" devices:${cgroup} for 
NVIDIA_SMI_ID in |||${gpus//,/ }|; do # find on which PCI path does this device sit 
pci_id=$(nvidia-smi -i $NVIDIA_SMI_ID --query-gpu=pci.bus_id 
--format=noheader,csv | tail -c+5 | tr '[:upper:]' '[:lower:]') # find 
the DRM devices sitting on the same PCI bus card=$(ls 
/sys/bus/pci/devices/${pci_id}/drm/ | grep card | xargs basename) 
render=$(ls /sys/bus/pci/devices/${pci_id}/drm/ | grep renderD | xargs 
basename) # allow access to the DRM devices [ -n "${card}" ] && |||cgset -r devices.allow="c $(cat /sys/class/drm/${card}/dev) rw" 
devices:${cgroup} && echo "Allowed /dev/dri/${card} DRI device access"| |||[ -n "${render}" ] && |||cgset -r devices.allow="c $(cat 
/sys/class/drm/${render}/dev) rw" devices:${cgroup}||||||&& echo "Allowed /dev/dri/${render} render node access"|| done |

Now I wonder whether this should be Prolog=, TaskProlog= or something 
else (that would also change whether I look at CUDA_VISIBLE_DEVICES or 
SLURM_STEP_GPUS, and how I figure out the cgroup name). I guess that 
were this script run as the invoking user, then nothing would prevent 
him from gaining access to all devices again. So I'd incline to treat it 
as a Prolog= script run by root. How would I get the cgroup ID then? 
Compose it from parts as mentioned in the slurm cgroups docs? 
(/cgroup/cpuset/slurm/uid_100/job_123/step_0/task_2) Or is there a more 
reliable way?

A related but offtopic idea popped up in my head when thinking about 
GPUs. Most of them are actually a consolidation of more devices like 
stream processors, encoders, decoders, raytraces, shaders, memory etc. 
Could it be possible (in future) to actually offer each of these pieces 
as a different gres? The problem is most of them do not have any special 
file which the user could lock to tell the others he's playing there 
now. So it'd probably require support at the level of cgroup 
implemetation, which, in turn, would require changing all GPU drivers. 
And it would require being able to request just chunks of GPU memory 
(not sure if that's possible right now, but I think I saw some pull 
request about that).

Thank you for hints!


Dne 21.10.2020 v 19:09 Martin Pecka napsal(a):

> Or maybe could this be "emulated" by a set of 3 GRES per card that are 
> "linked" together? I.e. rules like "if the user requests GRES 
> /dev/dri/card0, he will also automatically need to claim 
> /dev/dri/renderD128 and /dev/nvidia0"?
> Dne 21.10.2020 v 18:52 Daniel Letai napsal(a):
>> Take a look at https://github.com/SchedMD/slurm/search?q=dri%2F
>> If the ROCM-SMI API is present, using AutoDetect=rsmi in gres.conf 
>> might be enough, if I'm reading this right.
>> Of course, this assumes the cards in question are AMD and not NVIDIA.
>> On 20/10/2020 23:58, Mgr. Martin Pecka wrote:
>>> Pinging this topic again. Nobody has an idea how to define multiple 
>>> files to be treated as a single gres?
>>> Thank you for help,
>>> Martin Pecka
>>> Dne 4.9.2020 v 21:29 Martin Pecka napsal(a):
>>>> Hello, we want to use EGL backend for accessing OpenGL without the 
>>>> need for Xorg. This approach requires access to devices 
>>>> /dev/dri/card* and /dev/dri/renderD* . Is there a way to give 
>>>> access to these devices along with /dev/nvidia* which we use for 
>>>> CUDA? Ideally as a single generic resource that would give 
>>>> permissions to all three files at once.
>>>> Thank you for any tips.

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