Re: [PATCH 3/5] cgroup/cpuset: Find another usable CPU if none found in current cpuset

[Waiman Long]

On 3/24/23 14:19, Michal Koutný wrote:
> On Fri, Mar 24, 2023 at 02:32:50PM +0000, Will Deacon <will@xxxxxxxxxx> wrote:
> > So approaches such as killing tasks or rejecting system calls tend not
> > to work as well, since you inevitably get divergent behaviour leading
> > to functional breakage rather than e.g. performance anomalies.
> What about temporary performance drop from 100% to 0% aka freezing the
> tasks for the duration of the mismatching affinity config?

That can be a lot of extra work to freeze it. I will prefer something 
simpler.

Without this patch, I believe it will lead to a cpumask of 0 which will 
cause the scheduler to pick a fallback cpu. It looks like the fallback 
code may be able to pick up the right cpu or it may panic the system 
(less likely).

Cheers,
Longman
> > Having said that, the behaviour we currently have in mainline seems to
> > be alright, so please don't go out of your way to accomodate these SoCs.
> I see. (Just wondering what you think about the fourth option above.)
>
> Thanks,
> Michal