Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Message-ID: <1538582091.205649.20.camel@acm.org>
Subject: Re: [PATCH] block: BFQ default for single queue devices
From:   Bart Van Assche <bvanassche@acm.org>
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>,
        Artem Bityutskiy <dedekind1@gmail.com>,
        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 08:54:51 -0700
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>
Content-Type: text/plain; charset="UTF-7"
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, 2018-10-03 at 08:29 +-0200, Paolo Valente wrote:
+AD4 +AFs-1+AF0 https://lkml.org/lkml/2017/2/21/791
+AD4 +AFs-2+AF0 http://algo.ing.unimo.it/people/paolo/disk+AF8-sched/results.php
+AD4 +AFs-3+AF0 https://lwn.net/Articles/763603/

From +AFs-2+AF0: +ACI-BFQ loses about 18+ACU with only random readers, because the number
of IOPS becomes so high that the execution time and parallel efficiency of
the schedulers becomes relevant.+ACI Since the number of I/O patterns for which
results are available on +AFs-2+AF0 is limited and since the number of devices for
which test results are available on +AFs-2+AF0 is limited (e.g. RAID is missing),
there might be other cases in which configuring BFQ as the default would
introduce a regression.

I agree with Jens that it's best to leave it to the Linux distributors to
select a default I/O scheduler.

Bart.