Re: [PATCH] block: allow specifying default iosched in config

From: Khazhy Kumykov
Date: Tue Oct 04 2022 - 14:34:26 EST

On Mon, Oct 3, 2022 at 11:12 PM Damien Le Moal
<damien.lemoal@xxxxxxxxxxxxxxxxxx> 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