Re: [Xen-devel] [PATCH v2 16/16] libxl: automatic NUMA placement affects soft affinity

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 11/14/2013 04:48 PM, Dario Faggioli wrote:
> On gio, 2013-11-14 at 16:03 +0000, George Dunlap wrote:
> > On 13/11/13 19:13, Dario Faggioli wrote:
> > > vCPU soft affinity and NUMA-aware scheduling does not have
> > > to be related. However, soft affinity is how NUMA-aware
> > > scheduling is actually implemented, and therefore, by default,
> > > the results of automatic NUMA placement (at VM creation time)
> > > are also used to set the soft affinity of all the vCPUs of
> > > the domain.
> > >
> > > Of course, this only happens if automatic NUMA placement is
> > > enabled and actually takes place (for instance, if the user
> > > does not specify any hard and soft affiniy in the xl config
> > > file).
> > >
> > > This also takes care of the vice-versa, i.e., don't trigger
> > > automatic placement if the config file specifies either an
> > > hard (the check for which was already there) or a soft (the
> > > check for which is introduced by this commit) affinity.
> > It looks like with this patch you set *both* hard and soft affinities
> > when doing auto-numa placement.  Would it make more sense to change it
> > to setting only the soft affinity, and leaving the hard affinity to "any"?
> Nope, it indeed sets only soft affinity after automatic placement, hard
> affinity is left untouched.
Oh, right -- dur, I had it in my head that you were setting hard 
affinities before this patch (and since I didn't see them removed I 
assumed they were still there.)  But that's what we did sometime in 
ancient history, before the scheduler paid attention to the domain numa 
affinity. :-)
That being the case,

Acked-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>

(If I have time I may come by and do a closer review later.)

 -George


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