Subject: Re: [PATCH v3 09/14] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1

From: Quentin Perret <[email-masked]>
Date: Thu, 19 Nov 2020 09:29:22 +0000

On Friday 13 Nov 2020 at 09:37:14 (+0000), Will Deacon wrote:
> If the scheduler cannot find an allowed CPU for a task,
> cpuset_cpus_allowed_fallback() will widen the affinity to cpu_possible_mask
> if cgroup v1 is in use.
> 
> In preparation for allowing architectures to provide their own fallback
> mask, just return early if we're not using cgroup v2 and allow
> select_fallback_rq() to figure out the mask by itself.
> 
> Cc: Li Zefan <[email-masked]>
> Cc: Tejun Heo <[email-masked]>
> Cc: Johannes Weiner <[email-masked]>
> Signed-off-by: Will Deacon <[email-masked]>

That makes select_fallback_rq() slightly more expensive if you're using
cgroup v1, but I don't expect that be really measurable in real-world
workloads, so:

Reviewed-by: Quentin Perret <[email-masked]>

Thanks,
Quentin

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