Re: [Xen-users] vcpus and the virtual machine manager

[Mike Sievers <saturngeist@xxxxxxxxxxxxxx>]

Hi Diego,

I wrote in my config: vcpus=4
and I thought that the domU has the performance of 4 cpus.

1nd)
xm vcpu-list | grep vm7
vm7                              35     0     5   -b-     235.8 1,3,5,7
vm7                              35     1     5   -b-     167.9 1,3,5,7
vm7                              35     2     7   -b-      88.1 1,3,5,7
vm7                              35     3     5   -b-      92.7 1,3,5,7

2nd)
with cpus="4-7"

xm vcpu-list | grep vm7
vm7                              36     0     4   -b-       8.6 4-7

More performance with the 2nd version?

Best,
Mike

2011/8/25 Diego Dave <diego.dave.s@xxxxxxxxx>

Hi Mike,

"vcpus" option set the virtual cpus, not the physical cpus to use.

If your server have 8 cpus, they are numbered from 0 to 7.

If you want to assign the last 4 physical cpus, you must add to the
DomU cfg file the option "cpus = '4-7'. Then you can see the assigning
using "xm vcpu-list" in command line.

Is very good practice to manage the cpu assigning, it increases the
performance of VMs, and avoid problems when sharing cpus, like
freezing because of I/O events.

Regards,

Diego

2011/8/25 Mike Sievers <saturngeist@xxxxxxxxxxxxxx>:

> Hi List,
>
> with vcpus=4 I can choose the number of cpus.
>
> My virtual machine manager GUI shows:
> Maximum allocation: 2
> Host CPUs: 8
>
> How do I increase the maximum allocations?
>
> Best,
> Mike
>

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