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Message-ID: <1538550325.14984.108.camel@gmail.com>
Subject: Re: [PATCH] block: BFQ default for single queue devices
From:   Artem Bityutskiy <dedekind1@gmail.com>
Reply-To: dedekind1@gmail.com
To:     Paolo Valente <paolo.valente@linaro.org>,
        Jens Axboe <axboe@kernel.dk>
Cc:     Linus Walleij <linus.walleij@linaro.org>,
        linux-block <linux-block@vger.kernel.org>,
        linux-mmc <linux-mmc@vger.kernel.org>,
        linux-mtd@lists.infradead.org, Pavel Machek <pavel@ucw.cz>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Richard Weinberger <richard@nod.at>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Jan Kara <jack@suse.cz>, Andreas Herrmann <aherrmann@suse.com>,
        Mel Gorman <mgorman@suse.com>,
        Chunyan Zhang <zhang.chunyan@linaro.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        'Paolo Valente' via bfq-iosched 
        <bfq-iosched@googlegroups.com>,
        Oleksandr Natalenko <oleksandr@natalenko.name>,
        Mark Brown <broonie@kernel.org>
Date:   Wed, 03 Oct 2018 10:05:25 +0300
In-Reply-To: <B5321A64-8A1A-42FF-A337-F4524BDA179B@linaro.org>
References: <20181002124329.21248-1-linus.walleij@linaro.org>
         <05fdbe23-ec01-895f-e67e-abff85c1ece2@kernel.dk>
         <B5321A64-8A1A-42FF-A337-F4524BDA179B@linaro.org>
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On Wed, 2018-10-03 at 08:29 +0200, Paolo Valente wrote:
> So, I do understand your need for conservativeness, but, after so much
> evidence on single-queue devices, and so many years! :), what's the
> point in keeping Linux worse for virtually everybody, by default?

Sounds like what we just need a mechanism for the device (ubi block in
this case) to select the I/O scheduler. I doubt enhancing the default
scheduler selection logic in 'elevator.c' is the right answer. Just
give the driver authority to override the defaults.