Re: [Xen-devel] How to reduce high latency on PV-on-HVM?

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 5 Jan 2011, Pasi KÃrkkÃinen wrote:
> On Wed, Jan 05, 2011 at 01:47:01PM +0000, Stefano Stabellini wrote:
> > On Tue, 4 Jan 2011, shen.qilong wrote:
> > > AboutÂpingÂlatencyÂinÂPV-on-HVM
> > > IÂhadÂtriedÂa test toÂpingÂbetweenÂtwoÂVM(PV-on-HVM)ÂinÂtheÂsameÂhost 
> > > server with bridge model.
> > > Â
> > > I think there would be slightly latency mostly(less than 1ms).
> > > But IÂfoundÂthatÂthere are too muchÂhighÂlatency package (moreÂthanÂ1ms) 
> > > inÂPV-on-HVMÂ+ÂbridgeÂenvironment.
> > > Â
> > > Â
> > > The following is the test environment and the test result:
> > > Â
> > > ServerÂusesÂxen-4.0.0,Âdomain-0ÂisÂkernel-2.6.32.13ÂandÂPV-on-HVMÂisÂ
> > > kernel-2.6.x.Â
> > > TheÂserverÂandÂclientÂareÂconnectedÂthroughÂaÂsameÂnetworkÂbridge.Â
> > > Â
> > > Can someone help me, or tell me something?
> > 
> > If you boot your guest kernel with loglevel=9, can you see the following 
> > line
> > among the boot messages?
> > 
> > Xen HVM callback vector for event delivery is enabled
> 
> Hmm.. is this message message for the optimization available in Xen 4.1 ? 
> 
 
Nope, it is for the basic optimization that is in the xen-4.0-testing
tree too.
Looking more closely, it should be present in 4.0.1 but not in 4.0.0, so
it is unlikely you have it.
It would be interesting to do the same test on a more recent 4.0.x
hypervisor.

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