Re: [PATCH v3 1/5] wbt: don't show valid wbt_lat_usec in sysfs while wbt is disabled

[Yu Kuai]

Hi, Jan

在 2022/09/26 19:47, Jan Kara 写道:
> On Mon 26-09-22 18:25:18, Yu Kuai wrote:
> > Hi, Jan
> >
> > 在 2022/09/26 17:44, Jan Kara 写道:
> > > On Thu 22-09-22 19:35:54, Yu Kuai wrote:
> > > > Currently, if wbt is initialized and then disabled by
> > > > wbt_disable_default(), sysfs will still show valid wbt_lat_usec, which
> > > > will confuse users that wbt is still enabled.
> > > >
> > > > This patch shows wbt_lat_usec as zero and forbid to set it while wbt
> > > > is disabled.
> > >
> > > So I agree we should show 0 in wbt_lat_usec if wbt is disabled by
> > > wbt_disable_default(). But why do you forbid setting of wbt_lat_usec?
> > > IMHO if wbt_lat_usec is set, admin wants to turn on wbt so we should just
> > > update rwb->enable_state to WBT_STATE_ON_MANUAL.
> >
> > I was thinking that don't enable wbt if elevator is bfq. Since we know
> > that performance is bad, thus it doesn't make sense to me to do that,
> > and user might doesn't aware of the problem.
>
> Yeah, I don't think it is a good idea (that is the reason why it is
> disabled by default) but in priciple I don't see a reason why we should
> block admin from enabling it.

I'll enable it in next version.

Thanks,
Kuai