[fedora-virt] virtio block driver performance versus ide

[Dor Laor]

On 10/19/2009 08:39 PM, Pasi Kärkkäinen wrote:
> On Thu, Oct 15, 2009 at 08:45:52PM -0400, Paul Lambert wrote:
>>     I will second this performance observation.  After the latest round of
>>     pathces, I too found that my Windows XP VM was performing much faster than
>>     before and consuming much less cpu time.  I then observed that my Fe-11 VM
>>     was performing considerably slower.  Sure enough, I have checked my hda
>>     for each VM and the Windows was using native IDE and FE-11 was using
>>     virtio.  I have now changed my FE-11 hda to IDE.  Seems to exhibit much
>>     more pep!  So much for paravirtualization.
>>
>
> It sounds like the kvm virtio drivers are not working like they should.
> possible a bug in the drivers..
>
> At least Xen PV drivers are faster than emulated IDE, and use less CPU.

WinXp is an exception for kvm virtio drivers.
More info at http://www.mail-archive.com/kvm@vger.kernel.org/msg22834.html

>
> -- Pasi
>
>>     Paul
>>
>>     On Thu, Oct 15, 2009 at 3:50 PM, Dale Bewley<[1]dlbewley at lib.ucdavis.edu>
>>     wrote:
>>
>>       I assumed the virtio block driver to be faster for a kvm guest than ide,
>>       but I'm seeing quite the opposite. Is this expected?
>>
>>       I normally create guests with a wrapper script around virt-install which
>>       creates guests configured to use IDE disks:
>>
>>       f11-db1.xml-<emulator>/usr/bin/qemu-kvm</emulator>
>>       f11-db1.xml:<disk type='file' device='disk'>
>>       f11-db1.xml-<source file='/var/lib/libvirt/images//f11-db1.img'/>
>>       f11-db1.xml-<target dev='hda' bus='ide'/>
>>       f11-db1.xml:</disk>
>>
>>       I am currently creating a guest with the virt-manager wizard which
>>       apparently uses virtio by default:
>>
>>       f11-archivist.xml-<emulator>/usr/bin/qemu-kvm</emulator>
>>       f11-archivist.xml:<disk type='file' device='disk'>
>>       f11-archivist.xml-<source
>>       file='/var/lib/libvirt/images//f11-archivist.img'/>
>>       f11-archivist.xml-<target dev='vda' bus='virtio'/>
>>       f11-archivist.xml:</disk>
>>
>>       The filesystem formatting and installation are going very very slowly.
>>
>>       Host is 2.6.29.6-213.fc11.x86_64 4x quad core. Guests are also fc11
>>       x86_64.
>>
>>       BTW, I've updated to virt-manager-0.7.0-7, libvirt-0.6.2-18,
>>       qemu-kvm-0.10.6-6, and kernel-2.6.30.8-64 just before creating this
>>       guest but have not restarted libvirtd or rebooted the host.
>>       --
>>       Dale Bewley - Unix Administrator - Shields Library - UC Davis
>>       GPG: 0xB098A0F3 0D5A 9AEB 43F4 F84C 7EFD  1753 064D 2583 B098 A0F3
>>
>>       _______________________________________________
>>       Fedora-virt mailing list
>>       [2]Fedora-virt at redhat.com
>>       [3]https://www.redhat.com/mailman/listinfo/fedora-virt
>>
>> References
>>
>>     Visible links
>>     1. mailto:dlbewley at lib.ucdavis.edu
>>     2. mailto:Fedora-virt at redhat.com
>>     3. https://www.redhat.com/mailman/listinfo/fedora-virt
>
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