Re: [PATCH] lib/group_cpus: make group CPU cluster aware

[Andrew Morton]

On Fri, 24 Oct 2025 10:30:38 +0800 Wangyang Guo <wangyang.guo@xxxxxxxxx> wrote:

> As CPU core counts increase, the number of NVMe IRQs may be smaller than
> the total number of CPUs. This forces multiple CPUs to share the same
> IRQ. If the IRQ affinity and the CPU’s cluster do not align, a
> performance penalty can be observed on some platforms.

It would be helpful to quantify "performance penalty".  At least give
readers some approximate understanding of how serious this issue is,
please.

> This patch improves IRQ affinity by grouping CPUs by cluster within each
> NUMA domain, ensuring better locality between CPUs and their assigned
> NVMe IRQs.
>
> Reviewed-by: Tianyou Li <tianyou.li@xxxxxxxxx>
> Reviewed-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
> Tested-by: Dan Liang <dan.liang@xxxxxxxxx>
> Signed-off-by: Wangyang Guo <wangyang.guo@xxxxxxxxx>

Patch hasn't attracted additional review so I'll queue this version for
some testing in mm.git's mm-nonmm-unstable branch.  I'll add a
note-to-self that a changelog addition is desirable.

Thanks.