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[Xen-devel] Setting dom0-cpus to 0 doesn't use all cpus as documented

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Subject: [Xen-devel] Setting dom0-cpus to 0 doesn't use all cpus as documented
From: "Carb, Brian A" <Brian.Carb@xxxxxxxxxx>
Date: Tue, 9 May 2006 10:56:40 -0400
Cc: "Subrahmanian, Raj" <raj.subrahmanian@xxxxxxxxxx>, "Krysan, Susan" <KRYSANS@xxxxxxxxxx>, "Vessey, Bruce A" <Bruce.Vessey@xxxxxxxxxx>, "Puthiyaparambil, Aravindh" <aravindh.puthiyaparambil@xxxxxxxxxx>, "Carb, Brian A" <Brian.Carb@xxxxxxxxxx>
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Thread-topic: Setting dom0-cpus to 0 doesn't use all cpus as documented

The comments for dom0-cpus in the xend-config.sxp file indicate that
setting this value to 0 in an SMP system will cause dom0 to use all the
available CPUs. However, it appears as if setting this value to 0 does
not change the number of CPUs at all.

I'm running SLES10 Beta 11 and xen-unstable changeset 9960 on a Unisys
ES7000 with 32 CPUs and 32GB memory. In xend-config.sxp, dom0-cpus is
set to 0. When xen dom0 boots, it is using all 32 procs (as reported by
'grep processor /proc/cpuinfo | wc -l').

If I edit the xend-config.sxp file, change the value of dom0-cpus to 1,
and restart xend, dom0 correctly uses 1 CPUs. If I then change dom0-cpus
to 0 and restart xend, dom0 still uses 1 cpu. The only way to have dom0
use 32 cpus again is to either set the value of dom0-cpus to 32, or
reboot xen.

Has anyone else seen this behavior?

brian carb
unisys cmp technology lab
malvern, pa

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