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RE: [Xen-users] xen cpu affinity, ie; pinning cpus

To: "Brian Krusic" <brian@xxxxxxxxxx>, "Xen Users" <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-users] xen cpu affinity, ie; pinning cpus
From: "Robert Dunkley" <Robert@xxxxxxxxx>
Date: Wed, 21 Oct 2009 20:03:31 +0100
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Thread-topic: [Xen-users] xen cpu affinity, ie; pinning cpus
Hi Brian,
 
You need to set this in your kernel config as well as xend-config.sxp, eg. add the following to your kernel line in grub.conf:
dom0_max_vcpus=2
 
Set d cpu affinity, ie; pinning cpus

Hi all,

I've read a few posts about this and have pinned my domUs.

I've a dual quad core Opteron.

I've also set dom0-cpus 1 in my xend-config file.

xm vcpu-list shows

Name                                ID  VCPU   CPU State   Time(s) CPU 
Affinity
Domain-0                             0     0     0   r--   59582.6 any 
cpu
Domain-0                             0     1     -   --p   13227.9 any 
cpu
Domain-0                             0     2     -   --p   13527.5 any 
cpu
Domain-0                             0     3     -   --p   12448.3 any 
cpu
Domain-0                             0     4     -   --p   13520.6 any 
cpu
Domain-0                             0     5     -   --p   17223.0 any 
cpu
Domain-0                             0     6     -   --p   12614.1 any 
cpu
Domain-0                             0     7     -   --p   13570.9 any 
cpu
bugs                                24     0     2   -b-     598.5 2
logantools                          26     0     3   -b-     147.8 3
nello                               27     0     5   -b-     246.7 5
zmail                               25     0     6   -b-    8064.4 6
zmail                               25     1     7   r--    7681.2 7

Every few seconds, the first occurrence of Domain-0 changes to 4, then 
back to 0.

Why?

If I change dom0-cpus 2 so that it uses 2 cpus, xend won't restart and 
errors;

[2009-10-21 10:36:54 26309] INFO (XendDomainInfo:157) Recreating 
domain 0, UUID 00000000-0000-0000-0000-000000000000. at /local/domain/0
[2009-10-21 10:36:54 26309] DEBUG (XendDomain:452) Adding Domain: 0
[2009-10-21 10:36:54 26309] DEBUG (XendDomain:386) number of vcpus to 
use is 2
[2009-10-21 10:36:54 26309] ERROR (SrvDaemon:349) Exception starting 
xend (Cannot set vcpus greater than max vcpus on running domain)
Traceback (most recent call last):

So it appears I don't understand cpu pinning when it comes to dom0.

- Brian


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