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

Ryan Pugatch rpug at linux.com
Thu Jan 21 16:37:02 UTC 2010

Eric Searcy wrote:
>> The install worked beautifully except that my VM now has an ip assigned
>> of which I'm guessing is in relation to virbr0 which is
>> on the host (and subsequently has no internet
>> connectivity).  Is it possible for me to pass through to my network like
>> before so my VM can have an ip on my local network?
> Unless you specify a bridge in the xen conf file, it uses the first one 
> it finds alphabetically, I believe.  Do you use virbr0 for anything 
> else?  As an easy way of making sure xenbr0 is used, I removed the file 
> /etc/libvirt/qemu/networks/autostart/default.xml which was auto-starting 
> this DHCP (and NATted?) bridge, and I only was using direct access.  But 
> you can also make it explicit on the interface line, one of my HVM VMs 
> has the following:
> vif = [ 'mac=00:16:3e:0a:4c:d2, bridge=xenbr0' ]
> Eric

That worked.. thanks Eric.  However, even with the GPLPV drivers, I am 
seeing a lot of CPU usage when I do anything on the Windows VM.  It 
isn't just the guest that is reporting CPU usage, though.  When I watch 
xm top, the CPU usage jumps on that VM.  Not really sure what else can 
be done to improve performance.

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