Re: [Xen-devel] Report on Virtualization in Clusters

[Håvard Bjerke <havarbj@xxxxxxxxxxx>]

On Sun, Nov 28, 2004 at 11:17:03AM +0000, Ian Pratt wrote:
> 
> > > It seems from your tests without interrupt coalescing that Xen has a 
> > > higher interrupt-handling overhead than native Linux.  I suppose that 
> > > with the new IO model, Xen needs to flush the TLBs for every interrupt 
> > > that arrives. Do you think this is the reason for the overhead, or are 
> > > the performance problems only due to your hardware being badly supported 
> > > by Xen?
> > 
> > My guess is that it is the former, because we "solved" the problem with the 
> > IOAPIC bug with 'ignorebiostables'. Thus using legacy PIC, everything 
> > seemed to behave normally except when not using IC.
> > 
> > I think it boils down to whether or not using legacy PIC as opposed to (a 
> > supported) IOAPIC has an impact on interrupt handling. If it does, I think 
> > it's the latter reason, otherwise I think it's the former.
> 
> The fact that you had to disable the IOAPIC with ignorebiostables
> is rather concerning. It certainly sounds like Xen is really
> struggling on your platform. What motherboard chipset are the
> machines in your cluster?

They are Intel 875P chipsets

Håvard


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