This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


[Xen-users] Dom0 CPU?

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 
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?



Xen-users mailing list