Re: [Xen-devel] Fwd: Question about the status of vNUMA in Xen

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Tue, 2015-09-08 at 10:50 +0100, Wei Liu wrote:
> On Tue, Sep 08, 2015 at 01:21:04AM +0000, çæç wrote:

> > > So far, I have read the Xen NUMA Roadmap page and watched the
> > > video about vNUMA in Xen on Youtube. I have known that some work
> > > has been done for vNUMA in Xen. Since my benchmark result show a
> > > great improvement in Xen-4.5.1 when compared with Xen-4.0.1. I'm
> > > puzzled if vNUMA has contributed to that improvement.
> > 
> > No. That's mostly due to other improvements.
> > 
> > Wei.

> > Iâm sorry that I didnât express clearly in the last mail. What I want to
> > know is
> > 
> > that how much the NUMA optimizations (including NUMA-aware VM placement,
> > 
> > NUMA-aware scheduling and vNUMA)  contribute to the improvement
> > 
> 
Going from 4.0 to 4.5, you get automatic placement and NUMA aware
scheduling, not to mention that many other improvements happened in
between those two release, even if they may not look NUMA-related at a
first glance, may well be leading to better performance.

The NUMA roadmap page is slightly outdated, and I commit to update it
ASAP.

Anyway, if you want to isolate the contribution of each single feature,
you can configure things in such a way that you 'temporarily disable'
them. For instance, you can use vcpu pinning di tweak/disable automatic
placement, and check how the numbers change. For tweaking/disabling NUMA
aware scheduling, you should play with hard and soft affinity (i.e.,
some more refined ways of doing pinning, check what `xl vcpu-pin' does
these days).

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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