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

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Message-Id: <970CEAFA-1214-451B-9691-A3AEAD179D82@linaro.org>
Date:	Wed, 9 Mar 2016 07:55:28 +0100
From:	Paolo Valente <paolo.valente@...aro.org>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Tejun Heo <tj@...nel.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>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH RFC 09/22] block, cfq: replace CFQ with the BFQ-v0 I/O scheduler


Il giorno 04/mar/2016, alle ore 18:39, Christoph Hellwig <hch@...radead.org> ha scritto:

> On Sat, Mar 05, 2016 at 12:29:39AM +0700, Linus Walleij wrote:
>> Hi Tejun,
>> 
>> I'm doing a summary of this discussion as a part of presenting
>> Linaro's involvement in Paolo's work. So I try to understand things.
> 
> Btw, can someone explain why you guys waste so much time hacking and
> arguing about a legacy codebase (old request code and I/O schedulers)
> that everyone would really like to see disappear.  Why don't you
> spend your time on blk-mq where you have an entirely clean slate
> for scheduling?

I do agree that it would very important to deal with blk-mq. And much more difficult. IMHO, a clean way to proceed is to first try to improve bandwidth and latency guarantees in the simplest, single-queue case. Then to face the multi-queue case, leveraging the lessons learned in the single-queue case.

Thanks,
Paolo