linux-kernel - Re: [PATCH RFC] cpuset: Make cpusets get restored on hotplug

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Date:   Thu, 26 Mar 2020 17:47:36 -0400
From:   Waiman Long <longman@...hat.com>
To:     Sonny Rao <sonnyrao@...gle.com>
Cc:     Joel Fernandes <joel@...lfernandes.org>, Tejun Heo <tj@...nel.org>,
        linux-kernel@...r.kernel.org, Dmitry Shmidt <dimitrysh@...gle.com>,
        Amit Pundir <amit.pundir@...aro.org>, kernel-team@...roid.com,
        Jesse Barnes <jsbarnes@...gle.com>, vpillai@...italocean.com,
        Peter Zijlstra <peterz@...radead.org>,
        Guenter Roeck <groeck@...omium.org>,
        Greg Kerr <kerrnel@...gle.com>, cgroups@...r.kernel.org,
        Johannes Weiner <hannes@...xchg.org>,
        Li Zefan <lizefan@...wei.com>
Subject: Re: [PATCH RFC] cpuset: Make cpusets get restored on hotplug

On 3/26/20 4:05 PM, Sonny Rao wrote:
>> I think Tejun is concerned about a change in the default behavior of
>> cpuset v1.
>>
>> There is a special v2 mode for cpuset that is enabled by the mount
>> option "cpuset_v2_mode". This causes the cpuset v1 to adopt some of the
>> v2 behavior. I introduced this v2 mode a while back to address, I think,
>> a similar concern. Could you try that to see if it is able to address
>> your problem? If not, you can make some code adjustment within the
>> framework of the v2 mode. As long as it is an opt-in, I think we are
>> open to further change.
> I am surprised if anyone actually wants this behavior, we (Chrome OS)
> found out about it accidentally, and then found that Android had been
> carrying a patch to fix it.  And if it were a desirable behavior then
> why isn't it an option in v2?
>
I am a bit confused. The v2 mode make cpuset v1 behaves more like cpuset
v2. The original v1 behavior has some obvious issue that was fixed in
v2. So what v2 option are you talking about?

Regards,
Longman