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

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Message-Id: <20251221111047.597248db9868d278c7786f6b@linux-foundation.org>
Date: Sun, 21 Dec 2025 11:10:47 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Wangyang Guo <wangyang.guo@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
 Tianyou Li <tianyou.li@...el.com>, Tim Chen <tim.c.chen@...ux.intel.com>,
 Dan Liang <dan.liang@...el.com>
Subject: Re: [PATCH] lib/group_cpus: make group CPU cluster aware

On Fri, 24 Oct 2025 10:30:38 +0800 Wangyang Guo <wangyang.guo@...el.com> 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@...el.com>
> Reviewed-by: Tim Chen <tim.c.chen@...ux.intel.com>
> Tested-by: Dan Liang <dan.liang@...el.com>
> Signed-off-by: Wangyang Guo <wangyang.guo@...el.com>

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.