CentOS virt - Jan 2010 - Windows Xen VM's have high guest CPU usage and poor performance

Hello all,

I have a PowerEdge 2950 that I am using to host Windows XP VM's under 
CentOS.  I am experiencing poor performance in the Xen VM's.  Any time I 
try to do something, the CPU usage (as reported by the Windows task 
manager) hits 100% for a few and then drops back down.  This is causing 
the VM's to run sluggish and be quite annoying to use.  Example.. I 
click IE.. cpu hits 100% and IE takes a bit to open.  I go to a 
website.. 100%.. I click a link.. 100%. This is the case even if I only 
have one VM running.

I now have 32 VM's running on the machine and dom0's cpu usage as 
reported by xm top is 622%.  It seems like Xen is just performing poorly 
while handling these Windows VMs.  Any suggestions?  I have Windows VM's 
on other hardware (typically PowerEdge R905s and R710s and they seem ok).

This 2950 is a decent machine.. 32G RAM, 2x Xeon E5405 (quad core) at 
2ghz.  And I'm only allocating 1 CPU and 768MB RAM for each VM.

Sample config:

name = "win01n"
maxmem = 768
memory = 768
vcpus = 1
builder = "hvm"
kernel = "/usr/lib/xen/boot/hvmloader"
boot = "c"
pae = 1
acpi = 1
apic = 0
localtime = 1
on_poweroff = "destroy"
on_reboot = "restart"
on_crash = "restart"
device_model = "/usr/lib64/xen/bin/qemu-dm"
usbdevice = "tablet"
sdl = 0
vnc = 1
vncunused = 0
vncdisplay = "1"
disk = [ 'file:/var/xen/running/win01n,ioemu:hda,w' ]
vif = [ "bridge=xenbr0" ]
serial = "pty"



Thanks in advance for any insight!


	- Ryan

On 01/21/2010 05:18 AM, Ryan Pugatch wrote:
> Hello all,
>
> I have a PowerEdge 2950 that I am using to host Windows XP VM's under 
> CentOS.  I am experiencing poor performance in the Xen VM's.  Any time
I
> try to do something, the CPU usage (as reported by the Windows task 
> manager) hits 100% for a few and then drops back down.  This is causing 
> the VM's to run sluggish and be quite annoying to use.  Example.. I 
> click IE.. cpu hits 100% and IE takes a bit to open.  I go to a 
> website.. 100%.. I click a link.. 100%. This is the case even if I only 
> have one VM running.
>
> I now have 32 VM's running on the machine and dom0's cpu usage as 
> reported by xm top is 622%.  It seems like Xen is just performing poorly 
> while handling these Windows VMs.  Any suggestions?  I have Windows
VM's
> on other hardware (typically PowerEdge R905s and R710s and they seem ok).
>
> This 2950 is a decent machine.. 32G RAM, 2x Xeon E5405 (quad core) at 
> 2ghz.  And I'm only allocating 1 CPU and 768MB RAM for each VM.
>
> Sample config:
>
> name = "win01n"
> maxmem = 768
> memory = 768
> vcpus = 1
> builder = "hvm"
> kernel = "/usr/lib/xen/boot/hvmloader"
> boot = "c"
> pae = 1
> acpi = 1
> apic = 0
> localtime = 1
> on_poweroff = "destroy"
> on_reboot = "restart"
> on_crash = "restart"
> device_model = "/usr/lib64/xen/bin/qemu-dm"
> usbdevice = "tablet"
> sdl = 0
> vnc = 1
> vncunused = 0
> vncdisplay = "1"
> disk = [ 'file:/var/xen/running/win01n,ioemu:hda,w' ]
> vif = [ "bridge=xenbr0" ]
> serial = "pty"
>
>
>
> Thanks in advance for any insight!
>
>   
Check Pasi's advices from 
http://lists.centos.org/pipermail/centos-virt/2009-August/001121.html , 
maybe they apply to you too

On Wed, Jan 20, 2010 at 10:18:06PM -0500, Ryan Pugatch
wrote:
> Hello all,
> 
> I have a PowerEdge 2950 that I am using to host Windows XP VM's under 
> CentOS.  I am experiencing poor performance in the Xen VM's.  Any time
I
> try to do something, the CPU usage (as reported by the Windows task 
> manager) hits 100% for a few and then drops back down.  This is causing 
> the VM's to run sluggish and be quite annoying to use.  Example.. I 
> click IE.. cpu hits 100% and IE takes a bit to open.  I go to a 
> website.. 100%.. I click a link.. 100%. This is the case even if I only 
> have one VM running.
> 
> I now have 32 VM's running on the machine and dom0's cpu usage as 
> reported by xm top is 622%.  It seems like Xen is just performing poorly 
> while handling these Windows VMs.  Any suggestions?  I have Windows
VM's
> on other hardware (typically PowerEdge R905s and R710s and they seem ok).
> 
> This 2950 is a decent machine.. 32G RAM, 2x Xeon E5405 (quad core) at 
> 2ghz.  And I'm only allocating 1 CPU and 768MB RAM for each VM.
> 
> Sample config:
> 
> name = "win01n"
> maxmem = 768
> memory = 768
> vcpus = 1
> builder = "hvm"
> kernel = "/usr/lib/xen/boot/hvmloader"
> boot = "c"
> pae = 1
> acpi = 1
> apic = 0
> localtime = 1
> on_poweroff = "destroy"
> on_reboot = "restart"
> on_crash = "restart"
> device_model = "/usr/lib64/xen/bin/qemu-dm"
> usbdevice = "tablet"
> sdl = 0
> vnc = 1
> vncunused = 0
> vncdisplay = "1"
> disk = [ 'file:/var/xen/running/win01n,ioemu:hda,w' ]
> vif = [ "bridge=xenbr0" ]
> serial = "pty"
> 
> 
> 
> Thanks in advance for any insight!
> 
So I take it you're not using PV-on-HVM drivers in Windows.. 
ie. windows is using the emulated NIC and IDE disk?

That will be slow.

You need to use PV drivers. See GPLPV drivers:
http://wiki.xensource.com/xenwiki/XenWindowsGplPv/
http://www.meadowcourt.org/downloads/

0.11.0.188 is the latest binary release.

-- Pasi