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

[Chen, Yu C]

Hi Michal,

thanks for taking a look at this,

On 4/2/2025 9:24 PM, Michal Koutný wrote:
> Hello Chen.
>
> On Wed, Apr 02, 2025 at 09:06:11AM +0800, Chen Yu <yu.c.chen@xxxxxxxxx> wrote:
> > On system with NUMA balancing enabled, it is found that tracking
> > the task activities due to NUMA balancing is helpful.
> ...
> > 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
>
> Why is the field /proc/$pid/sched not enough?

In the context of NUMA balancing, it would be helpful to not only 
monitor on the activities of individual task/thread but also the 
resource usage and task migrations at the group level - which helps us 
quickly evaluate the performance and resource usage of the container - 
like per memcg numa_pages_migrated, numa_pte_updates introduced in
commit f77f0c751478 ("mm,memcg: provide per-cgroup counters for NUMA 
balancing operations"). Yes, we can iterate the /proc/$pid/sched to
find the accumulated NUMA stat, and the introduction of per - cgroup 
numa stat can help users more conveniently track the overall data of the 
workload.

Besides, I'm considering evaluating the per - cgroup NUMA balance 
control[1] to help users do fine - grain control per workload. This per 
- cgroup NUMA balance stat could be used to evaluate the efficiency of 
per - cgroup NUMA balance.

> Also, you may want to update Documentation/admin-guide/cgroup-v2.rst
> too.

Got it, will do in next version.

[1] 
https://lore.kernel.org/lkml/b3f1f6c478127a38b9091a8341374ba160d25c5a.1740483690.git.yu.c.chen@xxxxxxxxx/

thanks,
Chenyu

> Thanks,
> Michal