RE: [Xen-devel] CPU Utilization

Dave Thompson \(davetho\)
Mon, 12 Dec 2005 19:41:50 -0000

> -----Original Message-----
> From: Rob Gardner [mailto:rob.gardner@hp.com]
> Sent: Monday, December 12, 2005 1:23 PM
> To: Dave Thompson (davetho)
> Cc: xen-devel@lists.xensource.com
> Subject: Re: [Xen-devel] CPU Utilization
>
> Dave Thompson (davetho) wrote:
>
> >I have a question concerning the CPU utilization number provided by
> >the ''xm top'' command in xen 3.0.  I''ve
noticed that if I run a TCP
> >performance tool on domain 0 which simply receives and echos back
> >a TCP stream, the output of ''xm top'' during the test
does not match
> >up with the output of ''top'' on domain 0 in terms of
CPU utilization
> >(nor with the CPU utilization computed by the test program).
> >
> >...
> >
> >Any idea why these displays disagree?
> >
> >
>
> Top shows cpu usage for user processes in dom0, while xm top
> shows cpu usage for the domain, which includes cpu time spent
> in the dom0 kernel.

Doesn''t top''s CPU summary line show both?  I thought us=user
space,
sy=system, ni=nice, id=idle, hi=hwintr, si=softintr.  So in my
example 1% in user space, 7.3% in system level, 3.3% in h/w intr,
and 15% in soft intr.  Total of 26.6% utilized of which 25.6% is
in kernel.

> Perhaps the thing you''re running incurs lots of kernel cpu
> time, but not
> user time?
>
> Rob