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

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Message-ID: <7e3a521e-acf7-c3a8-a29b-c51874862344@opensource.wdc.com>
Date:   Wed, 5 Oct 2022 07:40:26 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Khazhy Kumykov <khazhy@...omium.org>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: allow specifying default iosched in config

On 10/5/22 03:33, Khazhy Kumykov wrote:
> On Mon, Oct 3, 2022 at 11:12 PM Damien Le Moal
> <damien.lemoal@...nsource.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.

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