linux-kernel - Re: [PATCH v4 0/2] sched/numa: add statistics of numa balance task migration

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Message-ID: <42d27ed9-79a1-4bf9-863f-c5b37b11d788@linux.ibm.com>
Date: Thu, 8 May 2025 15:53:09 +0530
From: Venkat Rao Bagalkote <venkat88@...ux.ibm.com>
To: Chen Yu <yu.c.chen@...el.com>, Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc: mkoutny@...e.com, Ingo Molnar <mingo@...hat.com>,
        Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>, Mel Gorman <mgorman@...e.de>,
        Michal Hocko <mhocko@...nel.org>, Muchun Song <muchun.song@...ux.dev>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Shakeel Butt <shakeel.butt@...ux.dev>,
        "Chen, Tim C" <tim.c.chen@...el.com>, Aubrey Li <aubrey.li@...el.com>,
        Libo Chen <libo.chen@...cle.com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Madadi Vineeth Reddy <vineethr@...ux.ibm.com>,
        "Jain, Ayush"
 <ayushjai@....com>, cgroups@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Chen Yu <yu.chen.surf@...mail.com>
Subject: Re: [PATCH v4 0/2] sched/numa: add statistics of numa balance task
 migration


On 07/05/25 4:44 pm, Chen Yu wrote:
> Introducing the task migration and swap statistics in the following places:
> /sys/fs/cgroup/{GROUP}/memory.stat
> /proc/{PID}/sched
> /proc/vmstat
>
> These statistics facilitate a rapid evaluation of the performance and resource
> utilization of the target workload.
>
> Patch 1 is a fix from Libo to avoid task swapping for kernel threads,
> because Numa balance only cares about the user pages via VMA.
>
> Patch 2 is the major change to expose the statistics of task migration and
> swapping in corresponding files.
>
> The reason to fold patch 1 and patch 2 into 1 patch set is that patch 1 is
> necessary for patch 2 to avoid accessing a NULL mm_struct from a kernel
> thread, which causes NULL pointer exception.
>
> The Tested-by and Acked-by tags are preserved, because these tags are provided
> in version 1 which has the p->mm check.
>
> Previous version:
> v3:
> https://lore.kernel.org/lkml/20250430103623.3349842-1-yu.c.chen@intel.com/
> v2:
> https://lore.kernel.org/lkml/20250408101444.192519-1-yu.c.chen@intel.com/
> v1:
> https://lore.kernel.org/lkml/20250402010611.3204674-1-yu.c.chen@intel.com/
>
> Chen Yu (1):
>    sched/numa: add statistics of numa balance task migration
>
> Libo Chen (1):
>    sched/numa: fix task swap by skipping kernel threads
>
>   Documentation/admin-guide/cgroup-v2.rst | 6 ++++++
>   include/linux/sched.h                   | 4 ++++
>   include/linux/vm_event_item.h           | 2 ++
>   kernel/sched/core.c                     | 9 +++++++--
>   kernel/sched/debug.c                    | 4 ++++
>   kernel/sched/fair.c                     | 3 ++-
>   mm/memcontrol.c                         | 2 ++
>   mm/vmstat.c                             | 2 ++
>   8 files changed, 29 insertions(+), 3 deletions(-)
>

Hello Chenyu,


Tested this patch by applying on top of next-20250507, and it fixes the 
NULL pointer exception error on IBM Power9 system. Hence,


Tested-by: Venkat Rao Bagalkote <venkat88@...ux.ibm.com>



Regards,

Venkat.