Re: [Xen-devel] CPU Utilization

[Anthony Liguori <aliguori@xxxxxxxxxx>]

top isn't smart enough to realize that for a portion of the running 
time, a domain has been pre-empted out and is not running.
top will then charge whatever was running at pre-emption time for the 
time that other domain running.
Regards,

Anthony Liguori

Dave Thompson (davetho) wrote:

>  
>
> > -----Original Message-----
> > From: Rob Gardner [mailto:rob.gardner@xxxxxx] 
> > Sent: Monday, December 12, 2005 1:23 PM
> > To: Dave Thompson (davetho)
> > Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> > 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
> >
> >    
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>
>  

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