From: Bart Van Assche <Bart.VanAssche@sandisk.com>
To: "paolo.valente@linaro.org" <paolo.valente@linaro.org>,
        "linus.walleij@linaro.org" <linus.walleij@linaro.org>
CC: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        "fchecconi@gmail.com" <fchecconi@gmail.com>,
        "axboe@kernel.dk" <axboe@kernel.dk>,
        "broonie@kernel.org" <broonie@kernel.org>,
        "avanzini.arianna@gmail.com" <avanzini.arianna@gmail.com>,
        "tj@kernel.org" <tj@kernel.org>,
        "ulf.hansson@linaro.org" <ulf.hansson@linaro.org>
Subject: Re: [PATCH RFC 00/14] Add the BFQ I/O Scheduler to blk-mq
Thread-Topic: [PATCH RFC 00/14] Add the BFQ I/O Scheduler to blk-mq
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Date: Sat, 18 Mar 2017 17:46:47 +0000
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On Sat, 2017-03-18 at 18:09 +0100, Linus Walleij wrote:
> On Sat, Mar 18, 2017 at 11:52 AM, Paolo Valente
> <paolo.valente@linaro.org> wrote:
> > > Il giorno 14 mar 2017, alle ore 16:32, Bart Van Assche <bart.vanassche@sandisk.com> ha scritto:
> > > (...) what should
> > > a developer do who only has access to a small subset of all the storage
> > > devices that are supported by the Linux kernel and hence who can not run the
> > > benchmark against every supported storage device?
> 
> Don't we use the community for that? We are dependent on people
> downloading and testing our code eventually, I mean sure it's good if
> we make some reasonable effort to test changes we do, but we are
> only humans, and we get corrected by the experience of other humans.

Hello Linus,

Do you mean relying on the community to test other storage devices before
or after a patch is upstream? Relying on the community to file bug reports
after a patch is upstream would be wrong. The Linux kernel should not be
used for experiments. As you know patches that are sent upstream should
not introduce regressions.

My primary concern about BFQ is that it is a very complicated I/O scheduler
and also that the concepts used internally in that I/O scheduler are far
away from the concepts we are used to when reasoning about I/O devices. I'm
concerned that this will make the BFQ I/O scheduler hard to maintain.

Bart.