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

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

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.)


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