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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2011-01-05 at 13:59 +0000, Stefano Stabellini wrote:
> 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:
> > > > About ping latency in PV-on-HVM
> > > > I had tried a test to ping between two VM(PV-on-HVM) in the same host 
> > > > server with bridge model.
> > > >  
> > > > I think there would be slightly latency mostly(less than 1ms).
> > > > But I found that there are too much high latency package (more than 
> > > > 1ms) in PV-on-HVM + bridge environment.
> > > >  
> > > >  
> > > > The following is the test environment and the test result:
> > > >  
> > > > Server uses xen-4.0.0, domain-0 is kernel-2.6.32.13 and PV-on-HVM is 
> > > > kernel-2.6.x. 
> > > > The server and client are connected through a same network bridge. 
> > > >  
> > > > 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.

It also depends on precisely which "kernel-2.6.x" is being used in the
guest, doesn't it?

Ian.


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