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

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Message-ID: <7cbbbd8f-a4b4-491d-bb60-97defff6007c@intel.com>
Date: Thu, 3 Apr 2025 10:47:44 +0800
From: "Chen, Yu C" <yu.c.chen@...el.com>
To: Michal Koutný <mkoutny@...e.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>, K Prateek
 Nayak <kprateek.nayak@....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

Hi Michal,

thanks for taking a look at this,

On 4/2/2025 9:24 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?
> 

In the context of NUMA balancing, it would be helpful to not only 
monitor on the activities of individual task/thread but also the 
resource usage and task migrations at the group level - which helps us 
quickly evaluate the performance and resource usage of the container - 
like per memcg numa_pages_migrated, numa_pte_updates introduced in
commit f77f0c751478 ("mm,memcg: provide per-cgroup counters for NUMA 
balancing operations"). Yes, we can iterate the /proc/$pid/sched to
find the accumulated NUMA stat, and the introduction of per - cgroup 
numa stat can help users more conveniently track the overall data of the 
workload.

Besides, I'm considering evaluating the per - cgroup NUMA balance 
control[1] to help users do fine - grain control per workload. This per 
- cgroup NUMA balance stat could be used to evaluate the efficiency of 
per - cgroup NUMA balance.

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

Got it, will do in next version.

[1] 
https://lore.kernel.org/lkml/b3f1f6c478127a38b9091a8341374ba160d25c5a.1740483690.git.yu.c.chen@intel.com/

thanks,
Chenyu

> 
> Thanks,
> Michal