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

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Message-ID: <fff4f53b-eec6-409a-840a-0e8be64fe1a2@amd.com>
Date: Wed, 2 Apr 2025 23:05:16 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Chen Yu <yu.c.chen@...el.com>, 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>
CC: 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 Chenyu,

On 4/2/2025 6:36 AM, Chen Yu wrote:
> On system with NUMA balancing enabled, it is found that tracking
> the task activities due to NUMA balancing is helpful. NUMA balancing
> has two mechanisms for task migration: one is to migrate the task to
> an idle CPU in its preferred node, the other is to swap tasks on
> different nodes if they are on each other's preferred node.
> 
> The kernel already has NUMA page migration statistics in
> /sys/fs/cgroup/mytest/memory.stat and /proc/{PID}/sched.
> but does not have statistics for task migration/swap.
> Add the task migration and swap count accordingly.
> 
> 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

Running sched-messaging with schedstats enabled, I could see both
"numa_task_migrated" and "numa_task_swapped" being populated for the
sched-messaging threads:

$ for i in $(ls /proc/4030/task/); do grep "numa_task_migrated" /proc/$i/sched; done | tr -s ' ' | cut -d ' ' -f3 | sort | uniq -c
     400 0
     231 1
      10 2

$ for i in $(ls /proc/4030/task/); do grep "numa_task_swapped" /proc/$i/sched; done | tr -s ' ' | cut -d ' ' -f3 | sort | uniq -c
     389 0
     193 1
      47 2
      11 3
       1 4

> 
> Previous RFC version can be found here:
> https://lore.kernel.org/lkml/1847c5ef828ad4835a35e3a54b88d2e13bce0eea.1740483690.git.yu.c.chen@intel.com/
> 
> Signed-off-by: Chen Yu <yu.c.chen@...el.com>

Feel free to add:

Tested-by: K Prateek Nayak <kprateek.nayak@....com>

-- 
Thanks and Regards,
Prateek

> ---
> RFC->v1: Rename the nr_numa_task_migrated to
>           numa_task_migrated, and nr_numa_task_swapped
>           numa_task_swapped in /proc/{PID}/sched,
>           so both cgroup's memory.stat and task's
>           sched have the same field name.
>

[..snip..]