Re: [Xen-devel] [PATCH] xl: fix sedf parameters checking

[Dario Faggioli <raistlin@xxxxxxxx>]

On Thu, 2012-06-21 at 11:40 +0100, Ian Campbell wrote:
> > Also, I can't just set period to zero, as the call will fail also if I
> > try to set weight=0, besides setting it internally in the scheduler code
> > (and that's why it is that that is returned when you ask for
> > actual/default scheduling parameters). :-O
> > 
> > However, if you set extratime=1 (with period=0 and slice=0), whatever
> > weight you provide, will be zeroed by the hypervisor, even if you can't
> > pass weight=0 yourself.
> 
> Ah, ok, so the key thing, which I think needs to be in the comment, is
> that weight must be non-zero in this case but that the specific value is
> irrelevant since it will be zeroed.
> 
Exactly!

> I think it might be worth also mentioning in the comment what best
> effort means in practice.I think it means a domain which can use extra
> time but which has no actual period/slice/weight of its own (despite the
> wrinkle about how you must supply weight).
> 
Ok.
 
> > Tricky eh?
> 
> Tricky isn't the half of it ;-)
>
:-)

> > Both when I did this in the first place and now, I tried to look at what
> > main_sched_sedf() does and replicate that logic as much as I can, to
> > make things easier to understand. The point here is we're being called
> > by a different context/situation, but I maybe can give it another shot
> > and see if I can quickly come up with something less mind blowing! :-P
> 
> I think actually with your explanations the current way seems to make
> sense to me, some more detail in the comments should be sufficient I
> think. Rewriting it again into something (even if it were less mind
> blowing) would likely still mean another round of this sort of
> conversation I expect  ;-)
> 
Me too. I'll add those bits and resend then.

Thanks and Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://retis.sssup.it/people/faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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