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

[K Prateek Nayak]

Hello Chenyu,

On 4/2/2025 6:36 AM, 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

Running sched-messaging with schedstats enabled, I could see both
"numa_task_migrated" and "numa_task_swapped" being populated for the
sched-messaging threads:

$ for i in $(ls /proc/4030/task/); do grep "numa_task_migrated" /proc/$i/sched; done | tr -s ' ' | cut -d ' ' -f3 | sort | uniq -c
    400 0
    231 1
     10 2

$ for i in $(ls /proc/4030/task/); do grep "numa_task_swapped" /proc/$i/sched; done | tr -s ' ' | cut -d ' ' -f3 | sort | uniq -c
    389 0
    193 1
     47 2
     11 3
      1 4

> Previous RFC version can be found here:
> https://lore.kernel.org/lkml/1847c5ef828ad4835a35e3a54b88d2e13bce0eea.1740483690.git.yu.c.chen@xxxxxxxxx/
>
> Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>

Feel free to add:

Tested-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>

--
Thanks and Regards,
Prateek

> ---
> 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.

[..snip..]