[vfio-users] Slow performance on VM win7 install

Laszlo Ersek lersek at redhat.com
Mon Apr 11 15:37:33 UTC 2016

On 04/05/16 04:26, Mark wrote:
> Hello, I've had this problem consistently in both ubuntu server and arch
> (fresh installs this week).  When booting a brand new VM and the win7
> iso attached to cdrom, I am getting extremely poor performance.  The
> first 'Windows is loading files...' screen takes about 3 full seconds to
> fill the progress bar, then starts the bar over and loads VERY slowly. 
> iotop shows the qemu process moving at 1100-1300K/s.
> Prior to this week, windows installs would load through the second
> progress bar part in a matter of seconds. It is now taking almost 4
> minutes.  I wanted to see if this was a windows iso specific issue (I
> highly doubt it) and loaded and arch iso.  Again, on choosing to load
> arch install environment iotop reported no higher than 1133K/s,
> averaging about 1100K/s during the loading. Once in the install shell, I
> was able to issue a quick speed test (dd if=/dev/cdrom of=/dev/zero
> bs=1M count=1024) which resulted in about 128M/s.


>     <disk type='file' device='cdrom'>
>       <driver name='qemu' type='raw'/>
>       <source file='/stor/Downloads/archlinux-2016.03.01-dual.iso'/>
>       <target dev='hda' bus='ide'/>
>       <readonly/>
>       <address type='drive' controller='0' bus='0' target='0' unit='0'/>
>     </disk>

This has been fixed in

Thank you for the report and subsequent testing.


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