Re: [PATCH 2/2] sched/isolation: Add cpu_is_isolated() API

[Waiman Long <longman@redhat.com>]

On 2/6/23 10:47, Michal Koutný wrote:
> Hello.
>
> On Fri, Feb 03, 2023 at 10:53:46PM -0500, Waiman Long <longman@redhat.com> wrote:
>> CPUs in an isolated cpuset partition is similar to HK_TYPE_DOMAIN CPUs as
>> load balancing is disabled. I can add an API to access the cpumask and add
>> to this API. However, that list is dynamic as it can be changed at run time.
>> Will that be a problem?
> I can see a problem already -- as a CPU can be dynamically switched to
> "isolated" mode so should all dependent operations support that (switch)
> too, i.e. the CPUs local PCP caches would have to be drained when the
> CPU enters isolation.
I see the long term goal is to have more isolation capability to be done 
dynamically. However, we are not there yet. There is still a lot of work 
to do to achieve that.
>
>> Or should that be used separately?
> It'd be nice to have both (cpuset and cmdline flags) eventually unified.
>
> Alas, it only leads me conservatively to:
>
> #ifndef CONFIG_CPUSETS
> // the proposed implementaion
> else
> static inline bool cpu_is_isolated(int cpu) {
> 	return true;
> }
> #endif

That is too conservative from my point of view. We can have further 
discussion when a patch is ready.

Cheers,
Longman