Re: [Xen-devel] [PATCH RFC V4 0/5] kvm : Paravirt-spinlock support for KVM guests

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Jan 25, 2012 at 11:15:36PM +0530, Raghavendra K T wrote:
> On 01/25/2012 10:05 PM, Konrad Rzeszutek Wilk wrote:
> >>So it seems we have worst case overhead of around 8%. But we see
> >>improvement of at-least 15% once when little more time is spent in
> >>critical section.
> >
> >Is this with collecting the histogram information about spinlocks? We found
> >that if you enable that for production runs it makes them quite slower.
> >
> 
> Ok. Are you referring to CONFIG_KVM_DEBUG_FS/CONFIG_XEN_DEBUG_FS?. Not

Those were the ones.

> it was not enabled. But then may be I was not precise. This test was
> only on native. So it should have not affected IMO.

Yup.
> 
> It is nice to know that histogram affects, since I was always under the
> impression that it does not affect much on guest too. My experiments
> had almost always enabled that.
> 
> Let me know if you referred to something else..

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