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

[Venkat Rao Bagalkote]

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@xxxxxxxxx/
> v2:
> https://lore.kernel.org/lkml/20250408101444.192519-1-yu.c.chen@xxxxxxxxx/
> v1:
> https://lore.kernel.org/lkml/20250402010611.3204674-1-yu.c.chen@xxxxxxxxx/
>
> 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@xxxxxxxxxxxxx>



Regards,

Venkat.