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

From: Damien Le Moal
Date: Tue Oct 04 2022 - 18:40:46 EST

On 10/5/22 03:33, Khazhy Kumykov wrote:
> 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.

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