[Xen-users] Re: Pin CPU of dom0

[weiming <zephyr.zhao@xxxxxxxxx>]

I found a post http://lists.xensource.com/archives/html/xen-users/2006-02/msg00874.html

Following the post, after I moved "maxcpus=4" from the kernel line to the module line in the grub file, still no success.

sudo xm vcpu-list
Name                                ID  VCPU   CPU State   Time(s) CPU Affinity
Domain-0                             0     0     0   r--      11.8 any cpu
Domain-0                             0     1     4   -b-       6.2 any cpu
Domain-0                             0     2     7   -b-       1.4 any cpu
Domain-0                             0     3     7   -b-       1.8 any cpu
Domain-0                             0     4     -   --p       0.0 any cpu
Domain-0                             0     5     -   --p       0.0 any cpu
Domain-0                             0     6     -   --p       0.0 any cpu
Domain-0                             0     7     -   --p       0.0 any cpu
dom1                                 1     0     4   -b-      26.0 4
dom2                                 2     0     6   r--      17.3 6


Sometime, Dom0 and guests still runs on same physical cpu. Somethime, they runs on separate cpus.
Is there any way to pin dom0 to specific CPUs?

Thanks,
Weiming

On Fri, Feb 15, 2008 at 11:57 AM, weiming <zephyr.zhao@xxxxxxxxx> wrote:

Hello,

I searched the mail list, but can't find a solution.

I have a machine with 8 cores. I want to set the CPU affinity for dom0. For example, let Dom0 use processor 0-3, let guests use 4-7

For guest domains, I can do this by setting the "cpus"
For dom0. there's no such option. The only one I know is in /etc/xen-config.sxp, which has "dom0-cpus" setting. Someone suggests that "

by setting (com0-cpus n), where n is the 
> number of CPU's


> > you want to use. It picks from the low to high numbers, so 
> you if you
> > set it to 1, it will pick CPU0, if you set it to 3, it will 
> pick CPU0,
> > CPU1, CPU2, and so on.



However, it seems not working for me. I set (dom0-cpus 4), pin cpu 4 to dom1, cpu 6 to dom2: 
sudo xm vcpu-list
Name                                ID  VCPU   CPU State   Time(s) CPU Affinity
Domain-0                             0     0     1   r--      10.3 any cpu


Domain-0                             0     1     5   -b-       2.6 any cpu
Domain-0                             0     2     2   -b-       1.1 any cpu
Domain-0                             0     3     4   -b-       1.6 any cpu


Domain-0                             0     4     -   --p       0.6 any cpu
Domain-0                             0     5     -   --p       0.6 any cpu
Domain-0                             0     6     -   --p       0.4 any cpu


Domain-0                             0     7     -   --p       0.6 any cpu
dom1                                 1     0     4   -b-       7.7 4
dom2                                 2     0     6   -b-       7.6 6



So, dom0 is actually using CPU 1,2,4,5 instead of 0,1,2,3

Then I added "maxcpus=4" in the grub file
  kernel /boot/xen.gz console=vga maxcpus=4

After reboot, 
sudo xm vcpu-list
Name                                ID  VCPU   CPU State   Time(s) CPU Affinity


Domain-0                             0     0     0   r--       8.0 any cpu
Domain-0                             0     1     3   -b-       2.3 any cpu
Domain-0                             0     2     1   -b-       1.4 any cpu


Domain-0                             0     3     2   -b-       1.1 any cpu

It looks good. but when I tried to startup the guests, I got error:
sudo xm create xm1
Using config file "./xm1".
Error: (22, 'Invalid argument')



Any ideas?

Thanks,
Weiming

 

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