Re: [Xen-devel] Xen & I/O in clusters - Single Vs. Dual CPU issue

[Ian Pratt <Ian.Pratt@xxxxxxxxxxxx>]

> The native systems can have either XT-PIC or IOAPIC, and it seems that both 
> have equal performance. In Xen0, however, by looking through dmesg, there 
> doesn't seem to be any IOAPIC. Is it possible to enable (or disable) IOAPIC 
> in Xen0?

If you boot with 'ignorebiostables' on the Xen command line Xen
will ignore the IOAPIC and use the PIC.

I could believe there might be a lurking performance problem with
PIC support as it probably hasn't had the same level of
performance testing as IOAPIC.

Ian
 -=- MIME -=- 
On Fri, Oct 29, 2004 at 06:24:35PM +0100, Ian Pratt wrote:
>=20
> > But, in a dual CPU cluster, Intel Xenon CPU 2.40 GHz  Ethernet=20
> > controller: Intel Corp. 82547GI Gigabit Ethernet Controller, we get=20
> > only 1%
> > (from 114 000 KB/s -> 110 000 KB/s) performance loss.)
>=20
> Good, that's the result we expect.
>=20
> > Hi, we have validated the single CPU results in another single CPU=20
> > cluster, and we still get an performance loss about 30%
> > (ca. 85 000 KB/s between two dom0 nodes (and NOT 114 000 KB/s),
> > Specs:
> > Ethernet controller: Intel Corp. 82547GI Gigabit Ethernet Controller
> > CPU: Intel(R) Pentium(R) 4 CPU 3.40GHz single CPU
> > RAM: 1 GB)
>=20
> Hmm, have your systems got an IOAPIC, or is Xen using the legacy
> PIC code? The latter probably hasn't been thoroughly performance
> tested...
>=20

The native systems can have either XT-PIC or IOAPIC, and it seems that bo=
th have equal performance. In Xen0, however, by looking through dmesg, th=
ere doesn't seem to be any IOAPIC. Is it possible to enable (or disable) =
IOAPIC in Xen0?

H=E5vard



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