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From:   Khazhy Kumykov <khazhy@chromium.org>
Date:   Tue, 4 Oct 2022 11:33:54 -0700
Message-ID: <CACGdZYKh4TXSaAAzJa13xsMH=tFzb4dYrPzOS3HHLLU8K-362g@mail.gmail.com>
Subject: Re: [PATCH] block: allow specifying default iosched in config
To:     Damien Le Moal <damien.lemoal@opensource.wdc.com>
Cc:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org
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On Mon, Oct 3, 2022 at 11:12 PM Damien Le Moal
<damien.lemoal@opensource.wdc.com> 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.
>
> 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
>