linux-kernel - Re: [RFC PATCH 0/5] cgroup/cpuset: A new "isolcpus" paritition

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Message-ID: <cd4c3f92-4a01-e636-7390-8c6a3d0cfe6c@redhat.com>
Date:   Wed, 12 Apr 2023 20:26:03 -0400
From:   Waiman Long <longman@...hat.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Juri Lelli <juri.lelli@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [RFC PATCH 0/5] cgroup/cpuset: A new "isolcpus" paritition


On 4/12/23 20:03, Tejun Heo wrote:
> Hello,
>
> On Wed, Apr 12, 2023 at 04:33:29PM -0400, Waiman Long wrote:
>> I think we can. You mean having a new "cpuset.cpus.isolated" cgroupfs file.
>> So there will be one in the root cgroup that defines all the isolated CPUs
>> one can have. It is then distributed down the hierarchy and can be claimed
>> only if a cgroup becomes an "isolated" partition. There will be a slight
> Yeah, that seems a lot more congruent with the typical pattern.
>
>> change in the semantics of an "isolated" partition, but I doubt there will
>> be much users out there.
> I haven't thought through it too hard but what prevents staying compatible
> with the current behavior?

It is possible to stay compatible with existing behavior. It is just 
that a break from existing behavior will make the solution more clean.

So the new behavior will be:

   If the "cpuset.cpus.isolated" isn't set, the existing rules applies. 
If it is set, the new rule will be used.

Does that look reasonable to you?

Cheers,
Longman