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[Xen-users] Managing Dom0 load?

To: xen-users <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-users] Managing Dom0 load?
From: Berni Elbourn <berni@xxxxxxxxxxxxxxxxxxxx>
Date: Wed, 03 Jun 2009 09:27:30 +0100
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I am using Debian lenny in Dom0. Disk is a two disk md raid1. DomUs have physical lvm.

It seems no matter how I assign the affinity in the DomUs:- top on Dom0 shows cpu0 is "clogged up" with typically 0%id 80%wa yet cores 1-3 are 99.7%id. eg:

top - 09:20:07 up 11 days, 10:05,  2 users,  load average: 0.28, 0.07, 0.06
Tasks: 117 total,   1 running, 116 sleeping,   0 stopped,   0 zombie
Cpu0 : 0.3%us, 7.0%sy, 0.0%ni, 6.7%id, 86.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu1 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu2 : 0.0%us, 0.3%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu3 : 0.0%us, 0.0%sy, 0.0%ni, 98.0%id, 2.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem:   3442688k total,  2419176k used,  1023512k free,   837112k buffers
Swap: 39061944k total,      152k used, 39061792k free,  1189380k cached

Here is the configuration:

Name ID VCPU CPU State Time(s) CPU Affinity
Domain-0                             0     0     1   -b-   11836.7 any cpu
Domain-0                             0     1     3   -b-    1326.2 any cpu
Domain-0                             0     2     2   r--    2943.1 any cpu
Domain-0                             0     3     0   -b-    3384.9 any cpu
debian                              20     0     2   -b-      34.7 1-3
edubuntu                            18     0     3   -b-      19.6 1-3
gos                                 17     0     3   -b-      19.6 1-3
ltsp                                15     0     2   -b-      14.4 1-3

Is it possible to spread the load (particularly io) in Dom0 over the 4 cores?



PS: As an aside I have used tasksel to move the backup job in Dom0 onto core 3 - that does seem to load up cpu0 and 3 more evenly.

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