[CentOS-virt] Windows Xen VM's have high guest CPU usage and poor performance

Pasi Kärkkäinen pasik at iki.fi
Fri Jan 22 09:20:10 UTC 2010

On Thu, Jan 21, 2010 at 04:39:31PM -0500, Ryan Pugatch wrote:
> Pasi Kärkkäinen wrote:
>> Oh, one more thing.. is it only the guest VM taking cpu time when you 
>> monitor with "xm top"?
>> Do you have the latest service packs installed in the guest? 
>> Have you tried monitoring the performance from inside the guest, to 
>> figure out what takes cpu time there? 
>> -- Pasi
> The guest is running XP w/ SP3.  It is not just the guest VM taking cpu  
> time.  Basically, whatever process I am doing hits 100% cpu usage in  
> Windows.  If I open IE, it will use 100% cpu for a bit while it opens.  
> If I try to click on a website, it will do it again.  Thus, it is  
> causing a very sluggish session as it keeps pausing.  It isn't just IE,  
> it's any program I try to use.  This CPU usage is reflected in xm top as  
> both the guest's CPU% will hit 100% as will Dom-0.

Did you verify from Windows Task Manager you're actually using the GPLPV 
PV drivers/devices?

How do you use the WinXP guest? Through the VNC console, or by using RDP
over the network? RDP is recommended, since it's much faster.

Does WinXP have high IOwait? 

> I have done pretty much everything specified in the Xen Best Practices.  
> In fact, I have dedicated 4GB to Dom-0.

Dom0 only needs 512 MB - 1024 MB (imho) on a common machine.

-- Pasi

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