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

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Message-ID: <57f5803b-11e5-4b91-a4c3-9be191fbf8d3@amd.com>
Date: Wed, 2 Apr 2025 22:53:21 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: <20250402010611.3204674-1-yu.c.chen@...el.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>, "Madadi Vineeth
 Reddy" <vineethr@...ux.ibm.com>
Subject: Re: [PATCH] sched/numa: Add statistics of numa balance task migration
 and swap

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:

$ 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

...

-- 
Thanks and Regards,
Prateek

> 
> Thanks,
> Madadi Vineeth Reddy
> 
>>
>> 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>
>> ---
>> 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.
>> ---
>>   include/linux/sched.h         |  4 ++++
>>   include/linux/vm_event_item.h |  2 ++
>>   kernel/sched/core.c           | 10 ++++++++--
>>   kernel/sched/debug.c          |  4 ++++
>>   mm/memcontrol.c               |  2 ++
>>   mm/vmstat.c                   |  2 ++
>>   6 files changed, 22 insertions(+), 2 deletions(-)
> 
>