[libvirt-users] Sluggish performance with virtio and Win10

[Dominique Ramaekers]

Qemu can work with vmdk but some features of vmdk aren’t used. So I can understand vmdk is slow.

Best practice:

1.       Use LVM is you can (harder to transfer/copy images)

2.       Alternative raw-file for speed (but you lose functionalities)

3.       Qcow for functionality in a file image (snapshots, compression,…)

I think other formats are supported for compatibility reasons in testing and migration scenarios, not for production environments.




Van: libvirt-users-bounces at redhat.com [mailto:libvirt-users-bounces at redhat.com] Namens John Obaterspok
Verzonden: vrijdag 19 februari 2016 7:16
Aan: Martin Kletzander
CC: libvirt-users at redhat.com
Onderwerp: Re: [libvirt-users] Sluggish performance with virtio and Win10



2016-02-18 15:15 GMT+01:00 Martin Kletzander <mkletzan at redhat.com<mailto:mkletzan at redhat.com>>:
On Thu, Feb 18, 2016 at 12:59:52PM +0100, John Obaterspok wrote:
2016-02-18 11:25 GMT+01:00 Martin Kletzander <mkletzan at redhat.com<mailto:mkletzan at redhat.com>>:
On Thu, Feb 18, 2016 at 10:41:42AM +0100, John Obaterspok wrote:
2016-02-18 10:13 GMT+01:00 Martin Kletzander <mkletzan at redhat.com<mailto:mkletzan at redhat.com>>:

On Thu, Feb 18, 2016 at 08:49:38AM +0100, John Obaterspok wrote:

Hello,

I'm using virt-manager on my F23 box to run a Windows 10 image but the
performance is so bad it's killing me.

I have "vmx" flag in /proc/cpuinfo

# lsmod |grep kvm
kvm_intel             167936  6
kvm                   503808  1 kvm_intel

virtio-win-0.1.112-1.noarch

But no virtio modules loaded. Should they be loaded nowadays?

Not on the host AFAIK.

The disk format used is vmdk with no caching and native mode.
The io is 100% in windows task manager performing less than 1MB/s

Any clues?


What are the figures from the host?  What is qemu doing and what are the
other processes and devices doing?


What is the best way to find this out?

{,a,h}top should do for the initial runs, just to see if the block layer
is busy or the CPU is busy or something else is blocking it

atop seems to indicate that sdd is busy?

DSK |          sdd |  busy     96% |              |  read    1455 | write
1319 |  KiB/r      5 | KiB/w      9 |               | MBr/s   0.74 | MBw/s
 1.26  | avq     1.01 |               | avio 3.43 ms |

# mount | grep sdd
/dev/sdd2 on /vm type ext4 (rw,relatime,seclabel,data=ordered)

And it doesn't do that in any other process on the host?  It looks like
it's not related to virtualisation...


Hi,

I changed from vmdk to raw and the Write performance went from 1.6 MB/s to ~100 MB/s
Is vmdk write performance so bad?

Result:
http://postimg.org/image/gcqe5affn/

-- john
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