Re: [PATCH 1 of 4 v6/leftover] libxl: enable automatic placement of guests on NUMA nodes

[Ian Jackson <Ian.Jackson@eu.citrix.com>]

Dario Faggioli writes ("Re: [PATCH 1 of 4 v6/leftover] libxl: enable automatic placement of guests on NUMA nodes"):
> On Mon, 2012-07-23 at 12:38 +0100, Ian Jackson wrote:
> > This probably deserves a log message.
> 
> It's there: it's being printed by libxl__get_numa_candidate(). It's like
> that to avoid printing more of them, which would be confusing, e.g.,
> something like this:
> 
>  libxl: ERROR Too many nodes
>  libxl: ERROR No placement found
> 
> Is that acceptable?

Two messages is better than one vague one.  One message would be
better but then you have to make sure of course that every path
prints exactly one message.

...
> > Isn't this an argument that the limit should be 16 ?  (Also 65535
> > steps since placement on 0 nodes is typically not an option.)
> 
> Well, it is for me, but as we agreed on 8, I went for that. What I
> wanted was just make sure we (or whoever else) know/remember that 16
> cold work too, in case that turns out to be useful in future. That being
> said, if you agree on raising the cap to 16 right now, I'll be glad to
> do that. :-D

I don't have a particular opinion on exactly what the cap should be.
It should be sufficiently tight to prevent runaways.  A 2^16 worst
case computation on domain start is certainly arguably acceptable.

Thanks,
Ian.