linux-kernel - Re: [PATCH -next RFC 0/2] cpuset: Add cpuset.mems.spread

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Message-ID: <doalyrbxmhzm6vvkotoqganga7s375athzlsnbab343wadijb5@winjpuf5m7dd>
Date: Mon, 3 Nov 2025 14:39:43 +0100
From: Michal Koutný <mkoutny@...e.com>
To: Cai Xinchen <caixinchen1@...wei.com>
Cc: llong@...hat.com, tj@...nel.org, hannes@...xchg.org, 
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org, lujialin4@...wei.com
Subject: Re: [PATCH -next RFC 0/2] cpuset: Add cpuset.mems.spread_page to
 cgroup v2

On Mon, Oct 20, 2025 at 02:20:30PM +0800, Cai Xinchen <caixinchen1@...wei.com> wrote:
> The MPOL_INTERLEAVE setting requires restarting the DataNode service.
> In this scenario, the issue can be resolved by restarting the service,

\o/

> but I would prefer not to restart the DataNode service if possible,
> as it would cause a period of service interruption.

AFAICS, the implementation of cpuset's spread page works only for new
allocations (filemap_alloc_folio_noprof/cpuset_do_page_mem_spread) and
there's no migraion in cpuset1_update_task_spread_flags(). So this
simple v1-like spreading would still require restart of the service.

(This challenge of dynamism also a reason why it's not ready for v2,
IMO.)

HTH,
Michal

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