linux-kernel - Re: [PATCH V3 0/4] genirq/affinity: irq vector spread among online CPUs as far as possible

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Date:   Thu, 08 Mar 2018 15:18:33 +0200
From:   Artem Bityutskiy <dedekind1@...il.com>
To:     Ming Lei <ming.lei@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Christoph Hellwig <hch@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org
Cc:     linux-block@...r.kernel.org, Laurence Oberman <loberman@...hat.com>
Subject: Re: [PATCH V3 0/4] genirq/affinity: irq vector spread among online
 CPUs as far as possible

On Thu, 2018-03-08 at 18:53 +0800, Ming Lei wrote:
> Hi,
> 
> This patchset tries to spread among online CPUs as far as possible, so
> that we can avoid to allocate too less irq vectors with online CPUs
> mapped.
> 
> For example, in a 8cores system, 4 cpu cores(4~7) are offline/non present,
> on a device with 4 queues:
> 
> 1) before this patchset
> 	irq 39, cpu list 0-2
> 	irq 40, cpu list 3-4,6
> 	irq 41, cpu list 5
> 	irq 42, cpu list 7
> 
> 2) after this patchset
> 	irq 39, cpu list 0,4
> 	irq 40, cpu list 1,6
> 	irq 41, cpu list 2,5
> 	irq 42, cpu list 3,7
> 
> Without this patchset, only two vectors(39, 40) can be active, but there
> can be 4 active irq vectors after applying this patchset.

Tested-by: Artem Bityutskiy <artem.bityutskiy@...el.com>
Link: https://lkml.kernel.org/r/1519311270.2535.53.camel@intel.com

Ming,

this patchset fixes the v4.16-rcX regression that I reported few weeks
ago. I applied it and verified that Dell R640 server that I mentioned
in the bug report boots up and the disk works.

So this is not just an improvement, it also includes a bugfix. 

Thanks!