Re: [PATCH v5 2/2] sched/numa: add statistics of numa balance task

[Michal Koutný]

On Tue, Jun 03, 2025 at 10:46:06PM +0800, "Chen, Yu C" <yu.c.chen@xxxxxxxxx> wrote:
> My understanding is that the "misplaced" container is not strictly tied
> to set_mempolicy or cpuset configuration, but is mainly caused by the
> scheduler's generic load balancer.

You are convincing me with this that, cpu.stat fits the concept better.
Doesn't that sound like that to you?

> Regarding the threaded subtrees mode, I was previously unfamiliar with
> it and have been trying to understand it better.

No problem.

> If I understand correctly, if threads within a single process are
> placed in different cgroups via cpuset, we might need to scan
> /proc/<PID>/sched to collect NUMA task migration/swap statistics.

The premise of your series was that you didn't want to do that :-)

> I agree with your prior point that NUMA balancing task activity is not
> directly
> associated with either the Memory controller or the CPU controller. Although
> showing this data in cpu.stat might seem more appropriate, we expose it in
> memory.stat due to the following trade-offs(or as an exception for
> NUMA balancing):
> 
> 1.It aligns with existing NUMA-related metrics already present in
> memory.stat.

That one I'd buy into. OTOH, I'd hope this could be overcome with
documentation.

> 2.It simplifies code implementation.

I'd say that only applies when accepting memory.stat as the better
place. I think the appropriately matching API should be picked first and
implementation is only secondary to that.
From your reasoning above, I think that the concept is closer to be in
cpu.stat ¯\_(ツ)_/¯

Michal

Attachment: signature.asc
Description: PGP signature