[virt-tools-list] Question about CPU % virt-top

[Richard W.M. Jones]

On Thu, Nov 04, 2010 at 01:51:25PM -0400, Hui Kang wrote:
> Hi, Richard
> I have a question about using virt-top to show the physical CPU %. My
> physical machine has 2 physical CPUs.
> I am running 2 VM and both run CPU-bomb programs.
> When I enter the physical cpu mode (virt-top -1), I found that the CPU usage
> shown on the top of the screen is no more than 100%. However, inside both
> VM, I observer a 100% CPU usage by vmstat.
> Since my machine has 2 CPUs, should the number shown in virt-top be 200% (or
> > 100%)? Thanks. 

No because it is scaled to 100% being the total capacity of your host.

This explains how %CPU is calculated:

http://people.redhat.com/~rjones/virt-top/faq.html#calccpu

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://et.redhat.com/~rjones/virt-top