Re: [PATCH v2] sched/debug: Introduce per-CPU debugfs files

[Aaron Tomlin]

On Tue, Jul 28, 2026 at 04:52:38PM -0400, Aaron Tomlin wrote:
> Currently, accessing scheduler debugging details for a specific CPU
> requires reading /sys/kernel/debug/sched/debug, which outputs
> information for all online CPUs. When investigating a latency anomaly or
> scheduling issue isolated to a specific CPU, accessing
> /sys/kernel/debug/sched/cpu/cpu<N>/debug provides an immediate, targeted
> view of that runqueue.
> 
> Add support for per-CPU debug files under:
> /sys/kernel/debug/sched/cpu/cpu<N>/debug. Reading
> /sys/kernel/debug/sched/cpu/cpu<N>/debug calls print_cpu() specifically
> for CPU <N>, exposing CPU-specific runqueue details on demand. If the
> target CPU is currently offline, reading its file returns -ENODEV.
> 
> Signed-off-by: Aaron Tomlin <atomlin@xxxxxxxxxxx>
> ---
> Changes since v1:
> 
>  - Reframed commit message motivation around targeted interactive
>    debugging on large SMP topologies (Peter Zijlstra and Zhan Xusheng)
> 
>  - Gated sched_debug_cpu_show() with a cpu_online(cpu) check
>    returning -ENODEV when target CPU is offline (Zhan Xusheng)
> 
>  - Linked to v1: https://lore.kernel.org/lkml/20260728020309.6169-1-atomlin@xxxxxxxxxxx/
> ---
>  kernel/sched/debug.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 43 insertions(+)

Hi Peter, Ingo, Juri, Vincent,

Sashiko found [1] pre-existing issues, which are not related to this patch.
Would you prefer that I investigate these concerns in this series?
Thank you. 

[1]: https://sashiko.dev/#/patchset/20260728205238.18447-1-atomlin%40atomlin.com

Kind regards,
-- 
Aaron Tomlin