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[Xen-users] Limiting number of CPU for Dom0.

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Limiting number of CPU for Dom0.
From: Marcin <migor@xxxxx>
Date: Mon, 12 Dec 2005 21:44:23 +0100
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1. Is is possible to limit the number of CPU available to Domain0?
I've got Tyan 8221 motherboard, two dual core Opteron 280,
with xen-3.0 32bit installed and four domains.
I'd like to make the following CPU assignment:
Dom0: cpu=0-2
Dom1: cpu=3
Dom2: cpu=3
Dom3: cpu=3.

I tried to use:
        xm vcpu-set Domain-0 3
command, but with no luck.
Is there something like boot param for number of CPU?

2. I tried to walk around #1 problem with vcpu-pin command:
xm vcpu-pin Domain-0 0 0
xm vcpu-pin Domain-0 1 1
xm vcpu-pin Domain-0 2 2
xm vcpu-pin Domain-0 3 0-2
#(now, the last CPU should be unassigned, so lets pin it to DomUs)
xm vcpu-pin Dom1 0 3
xm vcpu-pin Dom2 0 3
xm vcpu-pin Dom3 0 3

but I've experienced a major slowdown, a very high CPU system
utilization (40-50%) in Dom0, and the following entries in kernel.log
near every hour:
Dec 12 12:45:21 host [177113.460002] Timer ISR/3: Time went backwards:
delta=-2658 cpu_delta=-2658 shadow=177112460744268 off=999253612
processed=177113460000000 cpu_processed=177113460000000
Dec 12 12:45:21 host [177113.460010]  0: 177113460000000
Dec 12 12:45:21 host [177113.460013]  1: 177113430000000
Dec 12 12:45:21 host [177113.460015]  2: 177113450000000
Dec 12 12:45:21 host [177113.460017]  3: 177113460000000

Thanks for reply,

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