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Re: [Xen-users] Performance monitoring for Xen

> Hi Mark Thanks
> Still i have few queries left ..


> 1. Can i specify the number of CPU to the clients also. For e.g two CPU to
> WindowXP and one to Fedora in Xen Server.

You can choose how many virtual CPUs a guest is allowed in the guest's config 
file.  This determines how many physical CPUs the domain can be running on 
simultaneously *at most*.  E.g. if you set a domain to have only one vCPU it 
will think that it's uniprocessor, and it'll only ever be allowed to use on 
pCPU (physical CPU) at any given time.

If you set a domain to have several vCPUs then any subset of those vCPUs might 
be run at any time on available pCPUs.

You can also specify the percentage of CPU bandwidth a domain will get in 
terms of percentage of one pCPU.  Let me give examples:

A domain with one vCPU and 80% bandwidth would run for on any available pCPUs, 
one at a time, for time equivalent to 80% of the capacity of a single pCPU.

A domain with two vCPUs and 80% bandwidth would run any available pCPUs, up to 
two at a time, for time equivalent to 80% capacity of a single pCPU, /in 
total/.  i.e. each vCPU might get 40% of a time slice whilst running on 
different pCPUs simultaneously.

A domain with two vCPUs and 180% bandwidth should run on two pCPUs with each 
vCPU getting around 90% of the capacity of each pCPU.

Exactly how the time is broken up between the vCPUs will vary depending on 
which pCPUs are available at the time.  Also, you can pin vCPUs onto pCPUs so 
that (if you want) you can dedicate entire pCPUs to a domain, or you can 
restrict a domain to only run on some of the available pCPUs in the system.  
So you could partition your 4 pCPU system to act like 2 x 2-way SMP, or like 
4x Uniprocessor, or just share all the CPUs flexibly.

> 2. What parameter i should look for while i m doing performance monitoring
> . For instance i m looking into CPU utilization and response time.

xm li returns information on CPU utilization, in terms of the total time used 
so far.  xm top shows a live readout of CPU utilization as well as some other 
info.  Various friendly interfaces to Xen (including virt-manager) also give 
CPU usage readouts.

For response time, I'm not so sure what the best way to get stats is...  
There's some performance monitoring stuff in the Xen distribution.  You also 
used to be able to get some statistics out of the Xen scheduler, but I'm not 
sure how supported that is now; it required special compilation options in 
any case.

Hope that helps some!


Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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