Re: [Xen-users] xen server hw

[Andy Smith <andy@xxxxxxxxxxxxxx>]

Hi Casper,

On Sun, Feb 24, 2008 at 04:07:21PM +0200, Casper wrote:
>  I wanted to ask, how to see what hw is most used for DomU virtual 
> machines? I have few DomU running on top of Xen... And I`m interested 
> how match % of CPU and hard disks throughput is used... Can I maybe can 
> stream those data to some database and make charts later?
> Anybody have done it?

You can measure CPU usage of every domU by periodically calling "xm
list --long" and parsing out the cpu_time value (or using libxen to
grab the same data).

This is a counter in seconds, so you can work out a percentage CPU
use based on the difference between two readings.  For example, if
you take readings every 5 minutes (600 seconds) and the difference
between two readings is 120 seconds, then that domain used
120/600=0.2 == 20% of a core in that 5 minute period.  A counter is
also something that RRDTool can graph for you without you having to
do those calculations yourself.

Note that this value may be slightly suspect in that dom0 gets
charged for some of the time a domU spends doing IO.  I do not think
you can get better though without installing software in the domU
(e.g. snmpd).

Measuring disk I/O is harder.  If you use physical devices for domU
filesystems (e.g. LVM volumes) then you can try to parse
/proc/diskstats on dom0.

Network is somewhat easier; just measure the vif in the same way as
you would any other interface.  You'll need to assign static vif
names, and in my experience snmpd doesn't like interfaces that keep
getting removed and added and gets confused quickly.

Hope that gives you some ideas.

Cheers,
Andy

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