Re: [HTCondor-users] How to tie slots to cpus ?

[luis.fernandez.alvarez@xxxxxxx]

Hello Valerio,

I am in the process of setting up a configuration similar to what you are looking for.

Just to confirm we're talking about the same scenario, this is what I plan to deploy:

• One partitionable slot per NUMA node ( in our machines with 2 NUMA nodes, I will set resources to 50%).
• Each partitionable slot can define its own base cgroup, so I will define htcondor_numa0, htcondor_numa1 and assign it to each slot.

Then, how to handle the numa nodes? In my case I am running CentOS 7, and they encourage using systemd. It doesn't offer all the options so it's going to be a bit hacky:

• Create a couple of root systemd slices (htcondor_numa0, htcondor_numa1).
• Create a companion service bound to the slice (htcondor_numa0-config.service).
• This service is in charge of setting the cpusets & mems to the cgroup.
• Finally, I add an extra dependency in systemd to ensure that the slices are enabled and run before htcondor service.

Once I have this in place (I am planning to test this week), I can provide and shared the final config define in our cluster.

Cheers,
Luis

On 11/10/2021 09:26, valerio@xxxxxxxxxx wrote:

This is an example of how to use cpusets with shell:

mount -t cgroup -ocpuset cpuset /sys/fs/cgroup/cpuset
cd /sys/fs/cgroup/cpuset
mkdir Charlie
cd Charlie
/bin/echo 2-3 > cpuset.cpus
/bin/echo 1 > cpuset.mems
/bin/echo $$ > tasks
sh
# The subshell 'sh' is now running in cpuset Charlie
# The next line should display '/Charlie'
cat /proc/self/cpuset

I need an example of how to use cpusets for HTCondor slots.

Thanks.

Valerio

On Sun, 2021-10-10 at 08:00 -0500, tpdownes@xxxxxxxxx wrote:

Greg almost certainly wrote the thing. I must have seen (and searches for) the old ENFORCE_CPU_AFFINITY and SLOT settings Iâve used in past.

That said, I only see that ASSIGN_CPU_AFFINITY claims to pin jobs to cores, not that it will do so in a NUMA-aware way.

Tom

On Sat, Oct 9, 2021 at 9:17 PM <valerio@xxxxxxxxxx> wrote:

On Fri, 2021-09-03 at 11:07 -0500, tpdownes@xxxxxxxxx wrote:

I think it's worth adding to Greg's response that I don't believeÂASSIGN_CPU_AFFINITY will, all on its own, map jobs to NUMA nodes. I believe your best bet here is to create N partitionable slots, with N equal to the number of physical CPUs you have. Then combine ASSIGN_CPU_AFFINITY andÂSLOT<N>_CPU_AFFINITY so that each slot is mapped to NUMA nodes.

If you want to polish the doorknob, you should also look into setting cgroup cpusets on HTCondor so that it has "exclusive" access where it can and that the other top-level cgroups (e.g. system.slice) do not have access to very many cores. There obviously has to be some overlap unless you're willing to reduce the # of cores available to HTCondor.

https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/cpusets.html

PS: you should consider reducing the "cpuquota" available to HTCondor in its cgroup. It's always good to have 0.25 core available for ssh!

https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/cpuacct.html

Tom

The 9.2.0 manual says that ASSIGN_CPU_AFFINITY replaces both ENFORCE_CPU_AFFINITY and SLOT<N>_CPU_AFFINITY.

Is SLOT<N>_CPU_AFFINITY still a valid configuration variable?

https://htcondor.readthedocs.io/en/latest/admin-manual/configuration-macros.html#ASSIGN_CPU_AFFINITY

Thanks,

Valerio

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