linux-kernel - Re: [PATCH v5] cpuset: Avoid invalidating sibling partitions on cpuset.cpus conflict.

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Message-ID: <in2stxqa2swky4zwzlrm4h5vuz627ruedhq6zqr22xqwv5di7c@vcwc3z2sczx4>
Date: Thu, 11 Dec 2025 11:59:27 +0100
From: Michal Koutný <mkoutny@...e.com>
To: Sun Shaojie <sunshaojie@...inos.cn>
Cc: cgroups@...r.kernel.org, chenridong@...weicloud.com, 
	hannes@...xchg.org, linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	llong@...hat.com, shuah@...nel.org, tj@...nel.org
Subject: Re: [PATCH v5] cpuset: Avoid invalidating sibling partitions on
 cpuset.cpus conflict.

On Wed, Dec 10, 2025 at 06:11:08PM +0800, Sun Shaojie <sunshaojie@...inos.cn> wrote:
> Regardless of whether A1 through A5 belong to the same user or different
> users, arbitration conflicts between sibling nodes can still occur (e.g.,
> due to user misconfiguration). The key question is: when such a conflict
> arises, should all sibling nodes be invalidated, or only the node that
> triggered the conflict?

Any serious [1] affinity users should watch for cpuset.cpus.partition
already (since it can be invalidated by hotplug or IMO more probable
ancestor re-configuration). Do you agree?

Then I'd say it's reasonable to invalidate all (same reasoning -- it
doesn't matter on the order in which siblings are configured, I consider
local partitions). What would you see as the upsides of invalidating
only the last offender (under the assumption above about watching)?

Thanks,
Michal

[1] The others may make use of the proposed cpu.max.concurrency [2]
[2] https://lpc.events/event/18/contributions/1978/


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