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

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Message-ID: <dadfc308-bf2b-4c54-9518-0d5f6355cf23@intel.com>
Date: Mon, 22 Dec 2025 11:03:05 +0800
From: "Guo, Wangyang" <wangyang.guo@...el.com>
To: Andrew Morton <akpm@...ux-foundation.org>
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 12/22/2025 3:10 AM, Andrew Morton wrote:
> 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.
> 
Thanks for your reminder, will update changelog in next version. We see 
15%+ performance difference in FIO libaio/randread/bs=8k.

>> 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 a lot for your time and support! Please let me know if you have 
any further comments or guidance. Any feedback would be appreciated.


BR
Wangyang