Re: Report on Virtualization in Clusters

[Håvard Bjerke <havarbj@idi.ntnu.no>]

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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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