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Re: [Xen-devel] [PATCH 08 of 10 v3] libxl: enable automatic placement of guests on NUMA nodes

On Fri, 2012-07-06 at 14:52 +0100, Dario Faggioli wrote:
> On Fri, 2012-07-06 at 14:21 +0100, Ian Campbell wrote: 
> > > Ok, I see. What about something like the below:
> > > 
> > > "However, if the amount of free memory of two candidates is very
> > > similar, we look at how many domains are assigned to each candidate, and
> > > take the one that has fewer of them."
> > 
> > Looks good, thanks.
> > 
> Ok.
> > Is it still "very similar" now that it is a total order or is it
> > actually a strict equality now? (or an equality down to the precision of
> > a float...)
> > 
> It is, at least according to me. In fact, if the normalized difference
> between the amount of free memory of two candidates is 0.1 (i.e.,
> candidates are "very similar") and the difference in number of domains
> is -0.5 (one has half the domains the other does) we get
> 3*0.1-0.5=-0.2 ==> the number of domains is important. OTOH, a
> normalized difference of 0.2 in the amount of free memory (i.e.,
> candidates are no longer "very similar") is enough to prevent the same
> difference in number of domains from subverting the sign of the
> comparison.
> It of course depends on how much details we want to go in in this kind
> of documentation. Given there's no way neither an application developer
> nor an user could change/affect the parameters controlling the
> heuristics, I think what we have there is just fine.
> Did I persuade you? :-P

Yup, wasn't asking for docs just making sure I understood ;-)

> Thanks and Regards,
> Dario

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