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[Xen-users] XEN schedulers and domU cpu starving

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Subject: [Xen-users] XEN schedulers and domU cpu starving
From: Sergey Lukashevich <lukash33@xxxxxxx>
Date: Fri, 07 Nov 2008 18:55:56 +0300
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Reply-to: Sergey Lukashevich <lukash33@xxxxxxx>
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I use XEN for several years in Linux PVM environment. Huge multiprocessor 
servers are attractive goals as XEN hosts. But performance issues could confuse 
me. For instance, I need a method:

What is the preferred method of determining the fact a domU is CPU starving?

Performance control may be a complicated task in a multiprocessor XEN host.
Administrators need clear monitoring and performance isolation tools.
Some runtime informatin could show them 'xm top' on dom0, some - 'top' on domUs.
What happens when there is lack of CPU resources on XEN host?
It depends on the scheduler, I think.
Complicated XEN schedulers CAN use extra CPU cycles when physical CPUs are idle.
How to rule the situation of CPU starving?
What is the best method of determining the moment to add some VCPUs?
And when to add some REAL CPUs?
This is the most interesting issues for the admin.
Can someone guide me to master XEN CPU performance or anyone needs rely on his 
own experience only?
I found no clear documentation on the Net so far.

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