linux-kernel - Re: [PATCH] sched/numa: Add statistics of numa balance task migration and swap

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Message-ID: <7710c312-77da-4b8d-bb80-74598433ecd6@amd.com>
Date: Wed, 2 Apr 2025 23:13:03 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Michal Koutný <mkoutny@...e.com>, Chen Yu
	<yu.c.chen@...el.com>
CC: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot
	<vincent.guittot@...aro.org>, Mel Gorman <mgorman@...e.de>, Johannes Weiner
	<hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, Roman Gushchin
	<roman.gushchin@...ux.dev>, Shakeel Butt <shakeel.butt@...ux.dev>, "Muchun
 Song" <muchun.song@...ux.dev>, Andrew Morton <akpm@...ux-foundation.org>,
	"Tim Chen" <tim.c.chen@...el.com>, Aubrey Li <aubrey.li@...el.com>, Rik van
 Riel <riel@...riel.com>, Raghavendra K T <raghavendra.kt@....com>, Baolin
 Wang <baolin.wang@...ux.alibaba.com>, Xunlei Pang <xlpang@...ux.alibaba.com>,
	<linux-kernel@...r.kernel.org>, <cgroups@...r.kernel.org>,
	<linux-mm@...ck.org>, Chen Yu <yu.chen.surf@...mail.com>
Subject: Re: [PATCH] sched/numa: Add statistics of numa balance task migration
 and swap

Hello Michal,

On 4/2/2025 6:54 PM, Michal Koutný wrote:
> Hello Chen.
> 
> On Wed, Apr 02, 2025 at 09:06:11AM +0800, Chen Yu <yu.c.chen@...el.com> wrote:
>> On system with NUMA balancing enabled, it is found that tracking
>> the task activities due to NUMA balancing is helpful.
> ...
>> The following two new fields:
>>
>> numa_task_migrated
>> numa_task_swapped
>>
>> will be displayed in both
>> /sys/fs/cgroup/{GROUP}/memory.stat and /proc/{PID}/sched
> 
> Why is the field /proc/$pid/sched not enough?

The /proc/$pid/sched accounting is only done when schedstats are
enabled. memcg users might want to track it separately without relying
on schedstats which also enables a bunch of other scheduler related
stats collection adding more overheads.

> 
> Also, you may want to update Documentation/admin-guide/cgroup-v2.rst
> too.
> 
> Thanks,
> Michal

-- 
Thanks and Regards,
Prateek