linux-kernel - Re: [PATCH RFC 09/22] block, cfq: replace CFQ with the BFQ-v0 I/O scheduler

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Message-ID: <56E2AAE8.8000203@kyup.com>
Date:	Fri, 11 Mar 2016 13:24:24 +0200
From:	Nikolay Borisov <kernel@...p.com>
To:	Christoph Hellwig <hch@...radead.org>,
	Linus Walleij <linus.walleij@...aro.org>
Cc:	Ulf Hansson <ulf.hansson@...aro.org>, Tejun Heo <tj@...nel.org>,
	Paolo Valente <paolo.valente@...aro.org>,
	Jens Axboe <axboe@...nel.dk>,
	Fabio Checconi <fchecconi@...il.com>,
	Arianna Avanzini <avanzini.arianna@...il.com>,
	linux-block@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH RFC 09/22] block, cfq: replace CFQ with the BFQ-v0 I/O
 scheduler



On 03/11/2016 01:17 PM, Christoph Hellwig wrote:
> On Sat, Mar 05, 2016 at 07:18:30PM +0700, Linus Walleij wrote:
>> Depends on what time horizon and target I'd say. Paolo was in contact with
>> the MMC/SD subsystem maintainer Ulf Hansson. (e)MMC/SD are both
>> synchronous command-response-based protocols, and as of today
>> single-channel. So everone's smartphone and tablet etc are today
>> single-channel. I don't know if there is even a protocol change coming
>> to augment this, the only duct-tapeish solution I've heard about is
>> command queueing which is basically a kind of pipelining of requests.
> 
> We use blkj-mq for single queue devices as well, in fact most consumers
> are single queue.  MMC is a prime candidate that hould move over soon.

Out of curiosity - would it make sense to have something like BFQ/CFQ
for single-queue blk-mq users?