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xen-devel
Re: [Xen-devel] CPU Utilization
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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