Re: [Xen-devel] NUMA TODO-list for xen-devel

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

> >>>>> The question is whether this is really useful beyond the (I would
> >>>>> suppose) relatively small set of cases where migration isn't
> >>>>> needed.
> >>>>>
> >>>> Mmm... Not sure I'm getting what you're saying here, sorry. Are you
> >>>> suggesting that exposing a virtual topology is not a good idea as it
> >>>> poses constraints/prevents live migration?
> >
> > Honestly, what would be the problems with migration? NUMA awareness is
> > actually a software optimization, so we will not really break something
> > if the advertised topology isn't the real one.
> 
> Sure, nothing would break, but the purpose of the whole feature
> is improving performance, and that might get entirely lost (or
> even worse) after a migration to a different topology host.

+1

In the end, customers who care about getting 99.9% of native performance
should use physical hardware.  Live migration means that someone/something
is trying to do resource optimization and so performance optimization is
secondary.  But claiming great performance before migration and getting
sucky performance after migration, is IMHO a disaster, especially when
future "cloud users" won't have a clue whether their environment has
migrated or not.

Just my two cents...


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