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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.1 Subject: Re: [PATCH] block: allow specifying default iosched in config Content-Language: en-US To: Khazhy Kumykov Cc: Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <20220926220134.2633692-1-khazhy@google.com> From: Damien Le Moal Organization: Western Digital Research In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/5/22 03:33, Khazhy Kumykov wrote: > On Mon, Oct 3, 2022 at 11:12 PM Damien Le Moal > wrote: >> >> This will allow a configuration to specify bfq or kyber for all single queue >> devices > That's the idea >> , which include SMR HDDs. Since these can only use mq-deadline (or none >> if the user like living dangerously), this default config-based solution is not >> OK in my opinion. > I don't think this is true - elevator_init_mq will call > elevator_get_by_features, not elevator_get_default for SMR hdds (and > other zoned devices), as it sets required_elevator_features. OK, but my point remains: why not use a udev rule ? Why add a config option to hardcode the default scheduler ? Most average users will have no idea which one to choose... >> >> What is wrong with using a udev rule to set the default disk scheduler ? Most >> distros do that already anyway, so this config may not even be that useful in >> practice. What is the use case here ? >> >> >> -- >> Damien Le Moal >> Western Digital Research >> -- Damien Le Moal Western Digital Research