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Subject: Re: [PATCH RFC 09/22] block, cfq: replace CFQ with the BFQ-v0 I/O scheduler
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From: Paolo Valente <paolo.valente@linaro.org>
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Date: Wed, 9 Mar 2016 07:55:28 +0100
Cc: Linus Walleij <linus.walleij@linaro.org>, Tejun Heo <tj@kernel.org>,
        Jens Axboe <axboe@kernel.dk>, Fabio Checconi <fchecconi@gmail.com>,
        Arianna Avanzini <avanzini.arianna@gmail.com>,
        linux-block@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Ulf Hansson <ulf.hansson@linaro.org>, Mark Brown <broonie@kernel.org>
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To: Christoph Hellwig <hch@infradead.org>
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Il giorno 04/mar/2016, alle ore 18:39, Christoph Hellwig <hch@infradead.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