linux-kernel - Re: [RFC PATCH v2 1/1] scsi: mpi3mr: Introduce smp_affinity

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Message-ID: <ntxbqgnwvjdxggl5hno7eqae6ccpzwoyule3gwo4pnb53h4jiy@qfvkb3ocdeef>
Date: Thu, 19 Jun 2025 15:35:14 -0400
From: Aaron Tomlin <atomlin@...mlin.com>
To: John Garry <john.g.garry@...cle.com>
Cc: "Sean A." <sean@...e.io>, 
	"James.Bottomley@...senpartnership.com" <James.Bottomley@...senpartnership.com>, "kashyap.desai@...adcom.com" <kashyap.desai@...adcom.com>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>, 
	"martin.petersen@...cle.com" <martin.petersen@...cle.com>, 
	"mpi3mr-linuxdrv.pdl@...adcom.com" <mpi3mr-linuxdrv.pdl@...adcom.com>, "sreekanth.reddy@...adcom.com" <sreekanth.reddy@...adcom.com>, 
	"sumit.saxena@...adcom.com" <sumit.saxena@...adcom.com>
Subject: Re: [RFC PATCH v2 1/1] scsi: mpi3mr: Introduce smp_affinity_enable
 module parameter

On Wed, Jun 18, 2025 at 07:49:16AM +0100, John Garry wrote:
> BTW, if you use taskset to set the affinity of a process and ensure that
> /sys/block/xxx/queue/rq_affinity is set so that we complete on same CPU as
> submitted, then I thought that this would ensure that interrupts are not
> bothering other CPUs.

Hi John,

I'm trying to understand this better. If I'm not mistaken, modifying
/sys/block/[device]/queue/rq_affinity impacts where requests are processed.
Could you clarify how this would prevent an IRQ from being delivered to an
isolated CPU?

-- 
Aaron Tomlin