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Re: [Xen-devel] Xen 4.5 development update (July update)

On Mon, Jul 28, 2014 at 07:35:22PM +0200, Dario Faggioli wrote:
> On mar, 2014-07-22 at 20:28 -0400, konrad.wilk@xxxxxxxxxx wrote:
> > == x86 == 
> > *  HT enabled, virtualization overhead is high (Xen 4.4) (none)
> >    kernbench demonstrated it
> >    looking and tracing it
> >   -  Dario Faggioli
> > 
> There is a (sub-)thread sill ongoing here:
> http://www.gossamer-threads.com/lists/xen/devel/339409
> However, there have been found counterexamples, i.e., numbers showing
> that virt overhead is similar with and without HT, so I think this
> bullet can go away (not sure with what tracking status...)

The 'This confirms, for me, that it's an SMT balancing issue that we're seen. '
is not an issue anymore? As in we can get bad and good results depending
on the workload?

Now here is another question - did you run the guests with 'xen_nopvspin'
to see if this was an PV ticketlock (or the lack of it) issue?

Also what did the " I'll try more runs, e.g. with number of VCPUs equal
less than nr_corse/2 and see what happens." come out to be?

Thank you!
> 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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