linux-kernel - Re: [RFC PATCH 1/2] block: strict rq

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Date:	Sat, 23 Jul 2011 20:38:20 +0200
From:	Jens Axboe <jaxboe@...ionio.com>
To:	Christoph Hellwig <hch@...radead.org>
CC:	Dan Williams <dan.j.williams@...el.com>,
	Roland Dreier <roland@...estorage.com>,
	Dave Jiang <dave.jiang@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>
Subject: Re: [RFC PATCH 1/2] block: strict rq_affinity

On 2011-07-23 03:46, Christoph Hellwig wrote:
> On Fri, Jul 22, 2011 at 01:59:39PM -0700, Dan Williams wrote:
>> Some storage controllers benefit from completions always being steered
>> to the strict requester cpu rather than the looser "per-socket" steering
>> that blk_cpu_to_group() attempts by default.
> 
> Isn't this actually dependent on the cpu, and not the storage
> controller?

It is, it's completely indendent of the controller used. Perhaps some
drivers could have a very heavy end io completion handling causing the
problem to become larger, but in general it's an artifact of the CPU and
not the controller.

-- 
Jens Axboe

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