linux-kernel - Re: [External] Re: [PATCH] cpuset: introduce non-blocking cpuset.mems setting option

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Message-ID: <x7wdhodqgp2qcwnwutuuedhe6iuzj2dqzhazallamsyzdxsf7k@n2tcicd4ai3u>
Date: Tue, 17 Jun 2025 14:40:02 +0200
From: Michal Koutný <mkoutny@...e.com>
To: Zhongkun He <hezhongkun.hzk@...edance.com>
Cc: Tejun Heo <tj@...nel.org>, Waiman Long <llong@...hat.com>, 
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org, muchun.song@...ux.dev
Subject: Re: [External] Re: [PATCH] cpuset: introduce non-blocking
 cpuset.mems setting option

Hello.

On Sat, May 24, 2025 at 09:10:21AM +0800, Zhongkun He <hezhongkun.hzk@...edance.com> wrote:
> This is a story about optimizing CPU and memory bandwidth utilization.
> In our production environment, the application exhibits distinct peak
> and off-peak cycles and the cpuset.mems interface is modified
> several times within a day.
> 
> During off-peak periods, tasks are evenly distributed across all NUMA nodes.
> When peak periods arrive, we collectively migrate tasks to a designated node,
> freeing up another node to accommodate new resource-intensive tasks.
> 
> We move the task by modifying the cpuset.cpus and cpuset.mems and
> the memory migration is an option with cpuset.memory_migrate
> interface in V1. After we relocate the threads, the memory will be
> migrated by syscall move_pages in userspace slowly, within a few
> minutes.

Why do you need cpuset.mems at all?
IIUC, you could configure cpuset.mems to a union of possible nodes for
the pod and then you leave up the adjustments of affinity upon the
userspace.

Thanks,
Michal

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