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Re: [fedora-virt] virtio block driver performance versus ide



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 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

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      [2]Fedora-virt redhat com
      [3]https://www.redhat.com/mailman/listinfo/fedora-virt

References

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