Re: [PATCH v4 21/21] xl: vNUMA support

[Dario Faggioli <dario.faggioli@citrix.com>]

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On Thu, 2015-01-29 at 17:46 +0000, Wei Liu wrote:
> On Thu, Jan 29, 2015 at 11:10:39AM +0000, Ian Campbell wrote:
> > On Wed, 2015-01-28 at 22:52 +0000, Wei Liu wrote:

Hey,

While reviewing v5, I realized I always wanted to, but never replied to
this email! :-(

Very quickly...

> > > > > +For example, for a guest with 2 virtual nodes, user can specify:
> > > > > +
> > > > > +  vnuma_vdistance = [ [10, 20], [20, 10] ]
> > > > 
> > > > Any guidance on how a user should choose these numbers?
> > > > 
> > > 
> > > I think using the number from numactl is good enough.
> > 
> > Worth mentioning in the docs I think.
> > 
> > > > Do we support a mode where something figures this out based on the
> > > > underlying distances between the pnode to which a vnode is assigned?
> > > > 
> > > 
> > > Dario is working on that.
> > 
> > I thought he was working on automatic numa placement (i.e. figuring out
> > the best set of pnodes to map the vnodes to), whereas what I was
> > suggesting was that given the user has specified a vnode->pnode mapping
> > it should be possible to construct a distances table pretty trivially
> > from that. Is Dario working on that too?
> > 
> 
> Right. That's trivial inside libxl.
> 
> What I meant was Dario was about to touch all these automation stuffs it
> might be trivial for him to just do it all in one go. Of course if he
> has not done that I can add the logic myself.
>
Yes, Ian, that is a valid way of coming up with a default set of
distance values.

And as Wei says, our agreement is that he would make things work when
all the parameters are explicitly specified. Then, I'll take care of the
automation required to deal with situations where some parameters are
missing.

That include triggering automatic placement, in a way that it properly
accounts for vNUMA, and other things, among which default values for
distances, if nothing is specified.

Regards,
Dario

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