linux-kernel - Re: [PATCH v3 0/9] cgroup/cpuset: Add new cpuset partition type & empty effecitve cpus

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Date:   Mon, 9 Aug 2021 21:12:18 -0400
From:   Waiman Long <llong@...hat.com>
To:     Tejun Heo <tj@...nel.org>, Waiman Long <llong@...hat.com>
Cc:     Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <shuah@...nel.org>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>, Phil Auld <pauld@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Michal Koutný <mkoutny@...e.com>
Subject: Re: [PATCH v3 0/9] cgroup/cpuset: Add new cpuset partition type &
 empty effecitve cpus

On 8/9/21 6:46 PM, Tejun Heo wrote:
> Hello, Waiman. Sorry about the delay. Was off for a while.
>
> On Tue, Jul 27, 2021 at 05:14:27PM -0400, Waiman Long wrote:
>> However, if we have a complicated partition setup with multiple child
>> partitions. Invalid cpuset.cpus change in a parent partition will cause all
>> the child partitions to become invalid too. That is the scenario that I
>> don't want to happen inadvertently. Alternatively, we can restrict those
> I don't think there's anything fundamentally wrong with it given the
> requirement that userland has to monitor invalid state transitions.
> The same mass transition can happen through cpu hotplug operations,
> right?
>
>> invalid changes if a child partition exist and let it pass through and make
>> it invalid if it is a standalone partition.
>>
>> Please let me know which approach do you want me to take.
> I think it'd be best if we can stick to some principles rather than
> trying to adjust it for specific scenarios. e.g.:
>
> * If a given state can be reached through cpu hot [un]plug, any
>    configuration attempt which reaches the same state should be allowed
>    with the same end result as cpu hot [un]plug.
>
> * If a given state can't ever be reached in whichever way, the
>    configuration attempting to reach such state should be rejected.

OK, I got it. I will make the necessary changes and submit a new patch 
series.

Thanks,
Longman