Re: [PATCH 1/5] s390/tick: Remove CIF_NOHZ_DELAY flag

[Mete Durlu]

On 6/9/26 11:52, Christian Loehle wrote:
> On 6/9/26 10:40, Mete Durlu wrote:
> > On 6/9/26 10:10, Christian Loehle wrote:
> > > On 6/9/26 08:52, Mete Durlu wrote:
> > > > Remove obsolete tick delay heuristic [1]. The upcoming cpuidle driver
> > > > handles frequent sleep/wakeup cycles more effectively.
> > > >
> > > > [1] https://lore.kernel.org/all/20090929122533.402715150@xxxxxxxxxx/
> > > >
> > > > Suggested-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
> > > > Signed-off-by: Mete Durlu <meted@xxxxxxxxxxxxx>
> > > > ---
> > > For bisectibility does it make sense to move this and 2/5 to the end?
> >
> > I am unable to see how that would help. Could you elaborate?
>
> CIF_NOHZ_DELAY is only obsolete because of the new s390 cpuidle driver
> handles NOHZ better overall right?
> So my suggestion was to only obsolete it once everything is in place?

CIF_NOHZ_DELAY could modify the idle driver's decisions when it comes to
disabling the scheduling tick. It could be hard to bisect a problem with
the driver if we move the removal of the flag after the drivers
introduction. Because then the commit that enables the driver can have
a significantly different behavior.

Plus,having the flag obsolete without any other mechanism doing a
similar job would make the effect and related behavior more visible and
easier to debug.

At least this is my opinion but I am not an expert in kernel bisecting
tbh.