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

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Message-ID: <31aa40f3-ca75-4e44-a1d0-e2ab3ce17fdd@linux.ibm.com>
Date: Wed, 2 Apr 2025 23:38:53 +0530
From: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
To: K Prateek Nayak <kprateek.nayak@....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>, Chen Yu <yu.c.chen@...el.com>,
        Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
Subject: Re: [PATCH] sched/numa: Add statistics of numa balance task migration
 and swap

On 02/04/25 22:53, K Prateek Nayak wrote:
> On 4/2/2025 7:03 PM, Madadi Vineeth Reddy wrote:
>> Hi Chen Yu,
>>
>> On 02/04/25 06:36, 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
>>
>> I applied this patch, but I still don't see the two new fields
>> in /proc/{PID}/sched.
>>
>> Am I missing any additional steps?
> 
> You also need to enable schedstats:
> 
> echo 1 > /proc/sys/kernel/sched_schedstats
> 
> After that it should be visible:

Thanks, Prateek! I had missed enabling schedstats. Now that it's enabled,
I can see the fields.

Thanks,
Madadi Vineeth Reddy 

> 
> $ cat /proc/4030/sched
> sched-messaging (4030, #threads: 641)
> -------------------------------------------------------------------
> se.exec_start                                :        283818.948537
> 
> ...
> 
> nr_forced_migrations                         :                    0
> numa_task_migrated                           :                    0
> numa_task_swapped                            :                    0
> nr_wakeups                                   :                    0
> 
> ...
>