Re: [PATCH v2 4/4] block, bfq: consider request size in bfq_asymmetric_scenario()

[yukuai (C)]

On 2021/09/15 15:36, Paolo Valente wrote:
> > Il giorno 7 set 2021, alle ore 13:29, yukuai (C) <yukuai3@xxxxxxxxxx> ha scritto:
> >
> > On 2021/08/27 1:00, Paolo Valente wrote:
> > > > Il giorno 6 ago 2021, alle ore 04:08, Yu Kuai <yukuai3@xxxxxxxxxx> ha scritto:
> > > >
> > > > There is a special case when bfq do not need to idle when more than
> > > > one groups is active:
> > > Unfortunately, there is a misunderstanding here.  If more than one
> > > group is active, then idling is not needed only if a lot of symmetry
> > > conditions also hold:
> > > - all active groups have the same weight
> > > - all active groups contain the same number of active queues
> >
> > Hi, Paolo
> >
> > I didn't think of this contition.
> >
> > It's seems that if we want to idle when more than one group is active,
> > there are two additional conditions:
> >
> > - all dispatched requests have the same size
> > - all active groups contain the same number of active queues
>
> Also the weights and the I/O priorities of the queues inside the
> groups needs to be controlled, unfortunately.
>
> > Thus we still need to track how many queues are active in each group.
> > The conditions seems to be too much, do you think is it worth it to
> > add support to idle when more than one group is active?
>
> I think I see your point.  The problem is that these states are
> dynamic.  So, if we suspend tracking all the above information while
> more than one group is active, then we are with no state in case only
> one group remains active.

Hi, Paolo

In this case, I'll drop the last two patches in the next iteration.

Thanks,
Kuai