[Xen-users] Dom0 CPU?

["Shaun" <mailinglists@xxxxxxxxxxxxxxxx>]

The manual states the following

`If you are running IO intensive tasks, its typically better to dedicate 
either a hyperthread or whole core to running domain 0, and hence pin other 
domains so that they can't use CPU 0`

Right now I have a host that has 4 procs (dual xeon, with HT) and dom0 us 
showing all 4 procs.  Since IO is whats thrashed first on these things (at 
least with in my env) i would like to dedicated 1 logical proc to dom0 and 
have the guests use the other 3.  First question is how can i tell dom0 to 
not use all 4 procs?  I have tryed vcpu-set 0 0 but that didnt change 
anything.  I could vcpu-pin cpu 0-3 to cpu0 but that seams like a bad idea 
because now dom0 thinks it has 4 cpu's but actually it's 1.

[root@localhost bin]# xm vcpu-list
Name                              ID  VCPU  CPU  State  Time(s)  CPU 
Affinity
Domain-0                           0     0    0   -b-    2771.4  any cpu
Domain-0                           0     1    1   -b-    2837.8  any cpu
Domain-0                           0     2    2   -b-    2159.9  any cpu
Domain-0                           0     3    3   r--    2283.8  any cpu

So first question is, how can i get dom0 to stop using all 4 procs and to 
only use 1?  Second whats the best way to have guests use the rest of the 
cpu?  Do i need to write a script that runs through each guest settting it 
manually to 1, 2, or 3?

Another question, i started up 20 guests and all guests uses cpu 1 or 3, 
none of them used 0 or 2.  Why?

Thanks

Shaun 




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