Re: [PATCH -next 00/11] support concurrent sync io for bfq on a specail occasion

From: Paolo Valente
Date: Tue Apr 26 2022 - 10:25:05 EST

> Il giorno 13 apr 2022, alle ore 13:12, Jan Kara <jack@xxxxxxx> ha scritto:
> On Sat 05-03-22 17:11:54, Yu Kuai wrote:
>> Currently, bfq can't handle sync io concurrently as long as they
>> are not issued from root group. This is because
>> 'bfqd->num_groups_with_pending_reqs > 0' is always true in
>> bfq_asymmetric_scenario().
>> This patchset tries to support concurrent sync io if all the sync ios
>> are issued from the same cgroup:
>> 1) Count root_group into 'num_groups_with_pending_reqs', patch 1-5;
> Seeing the complications and special casing for root_group I wonder: Won't
> we be better off to create fake bfq_sched_data in bfq_data and point
> root_group->sched_data there? AFAICS it would simplify the code
> considerably as root_group would be just another bfq_group, no need to
> special case it in various places, no games with bfqg->my_entity, etc.
> Paolo, do you see any problem with that?

I do see the benefits. My only concern is that then we also need to
check/change the places that rely on the assumption that we would


> Honza
> --
> Jan Kara <jack@xxxxxxxx>
> SUSE Labs, CR