Re: [Xen-devel] [PATCH v5 2/5] build: Hook the schedulers into Kconfig

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Thu, 2016-01-14 at 10:23 -0600, Jonathan Creekmore wrote:
> Jan Beulich writes:
> 
> > > > > On 14.01.16 at 15:49, <jonathan.creekmore@xxxxxxxxx> wrote:
> > > --- a/xen/common/Kconfig
> > > +++ b/xen/common/Kconfig
> > > @@ -51,4 +51,63 @@ config KEXEC
> > > 
> > > Â ÂÂIf unsure, say Y.
> > > 
> > > +# Enable schedulers
> > > +menu "Schedulers"
> > > + visible if EXPERT = "y"
> > > +
> > > +config SCHED_CREDIT
> > > + bool
> > > + default y
> > > + ---help---
> > > + ÂÂThe traditional credit scheduler is a general purpose
> > > scheduler.
> > 
> > So is this option now useful for anything?
> 
> It keeps the code between all of the schedulers consistent (all of them
> have a #define if they are compiled it)

FWIW I think this (consistency) is a reasonable argument for having this
option even if it doesn't actually do anything.

>  and helps keep my downstream
> patch smaller.
> 
> > 
> > > +choice
> > > + prompt "Default Scheduler?"
> > > + default SCHED_CREDIT_DEFAULT if SCHED_CREDIT
> > > + default SCHED_CREDIT2_DEFAULT if SCHED_CREDIT2
> > > + default SCHED_RTDS_DEFAULT if SCHED_RTDS
> > > + default SCHED_ARINC653_DEFAULT if SCHED_ARINC653
> > 
> > And certainly all these defaults are now pointless, considering
> > that the condition of the first one is "if y".
> 
> Yes, I could rip all of those out now since credit is always the
> default. I left it in there for the ideal case that credit didn't have
> to be special cased but, at this point, I will rip it out if you want.

What is the behaviour of the above set of "default"s if more than one of
the SCHED_* is enabled? Does it pick the first, last, one at random?

If credit is now always the default I think that would be better expressed
with a single "default SCHED_CREDIT_DEFAULT".


Ian.

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