linux-kernel - Re: [PATCH v2] sched/numa: Introduce per cgroup numa balance control

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Message-ID: <ldyynnd3ngxnu3bie7ezuavewshgfepro5kjids6cuxy4imzy5@nt5id7nj5kt7>
Date: Wed, 25 Jun 2025 14:19:35 +0200
From: Michal Koutný <mkoutny@...e.com>
To: Chen Yu <yu.c.chen@...el.com>
Cc: Jonathan Corbet <corbet@....net>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Shakeel Butt <shakeel.butt@...ux.dev>, Juri Lelli <juri.lelli@...hat.com>, 
	Ben Segall <bsegall@...gle.com>, Libo Chen <libo.chen@...cle.com>, Mel Gorman <mgorman@...e.de>, 
	Valentin Schneider <vschneid@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	"Liam R. Howlett" <Liam.Howlett@...cle.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
	Vlastimil Babka <vbabka@...e.cz>, Phil Auld <pauld@...hat.com>, Tejun Heo <tj@...nel.org>, 
	Daniel Jordan <daniel.m.jordan@...cle.com>, Jann Horn <jannh@...gle.com>, Pedro Falcato <pfalcato@...e.de>, 
	Aubrey Li <aubrey.li@...el.com>, Tim Chen <tim.c.chen@...el.com>, 
	"Huang, Ying" <ying.huang@...ux.alibaba.com>, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org
Subject: Re: [PATCH v2] sched/numa: Introduce per cgroup numa balance control

On Wed, Jun 25, 2025 at 06:23:37PM +0800, Chen Yu <yu.c.chen@...el.com> wrote:
> [Problem Statement]
> Currently, NUMA balancing is configured system-wide.
> However, in some production environments, different
> cgroups may have varying requirements for NUMA balancing.
> Some cgroups are CPU-intensive, while others are
> memory-intensive. Some do not benefit from NUMA balancing
> due to the overhead associated with VMA scanning, while
> others prefer NUMA balancing as it helps improve memory
> locality. In this case, system-wide NUMA balancing is
> usually disabled to avoid causing regressions.
> 
> [Proposal]
> Introduce a per-cgroup interface to enable NUMA balancing
> for specific cgroups.

The balancing works with task granularity already and this new attribute
is not much of a resource to control.
Have you considered a per-task attribute? (sched_setattr(), prctl() or
similar) That one could be inherited and respective cgroups would be
seeded with a process with intended values. And cpuset could be
traditionally used to restrict the scope of balancing of such tasks.

WDYT?

> This interface is associated with the CPU subsystem, which
> does not support threaded subtrees, and close to CPU bandwidth
> control.
 (??) does support

> The system administrator needs to set the NUMA balancing mode to
> NUMA_BALANCING_CGROUP=4 to enable this feature. When the system is in
> NUMA_BALANCING_CGROUP mode, NUMA balancing for all cgroups is disabled
> by default. After the administrator enables this feature for a
> specific cgroup, NUMA balancing for that cgroup is enabled.

How much dynamic do you such changes to be? In relation to given
cgroup's/process's lifecycle.

Thanks,
Michal

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