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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.01.16 at 17:34, <ian.campbell@xxxxxxxxxx> wrote:
> 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
>> > > 
>> > >            If unsure, say Y.
>> > > 
>> > > +# Enable schedulers
>> > > +menu "Schedulers"
>> > > +        visible if EXPERT = "y"
>> > > +
>> > > +config SCHED_CREDIT
>> > > +        bool
>> > > +        default y
>> > > +        ---help---
>> > > +          The 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.

While I can see your point, I dislike useless clutter in .config (also
on Linux, where I every once in a while send some cleanup
patches).

>> > > +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?

The first for which the condition is true.

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

Indeed.

Jan


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