[Qemu-devel] Threaded VNC server status - time to enable by default ?

[Qemu-devel] Threaded VNC server status - time to enable by default ?

[Daniel P. Berrange]

We recently had a request in Fedora to enable the VNC server thread
support in our builds of QEMU. There have been periodic messages on
this list that suggest the threaded VNC server has better performance
and less latency.

My view though, is that there must be some good reason why QEMU does
not enable it by default already. Can anyone say why QEMU has not
enabled the VNC server threads by default ?

If there is no such reason, can we just kill the configure options
--{disable,enable}-vnc-thread, and have everyone use the VNC server
thread support forever more. I struggle to see the point in maintaining
these two separate codepaths for the VNC server. Whichever one is
not the default is, IMHO, destined to bitrot through lack of widespread
testing and so we're better off getting everyone to use & test the
same codepath.

Regards,
Daniel
-- 
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Re: [Qemu-devel] Threaded VNC server status - time to enable by default ?

[Anthony Liguori]

On 06/20/2012 04:15 AM, Daniel P. Berrange wrote:
> We recently had a request in Fedora to enable the VNC server thread
> support in our builds of QEMU. There have been periodic messages on
> this list that suggest the threaded VNC server has better performance
> and less latency.
>
> My view though, is that there must be some good reason why QEMU does
> not enable it by default already. Can anyone say why QEMU has not
> enabled the VNC server threads by default ?
>
> If there is no such reason, can we just kill the configure options
> --{disable,enable}-vnc-thread, and have everyone use the VNC server
> thread support forever more. I struggle to see the point in maintaining
> these two separate codepaths for the VNC server. Whichever one is
> not the default is, IMHO, destined to bitrot through lack of widespread
> testing and so we're better off getting everyone to use&  test the
> same codepath.

At the time it was introduced, QEMU still has no hard requirement on having 
pthreads as a dependency (the I/O thread was still optional).

We're past that point now so there's no harm in unconditionally enabling the VNC 
thread pool.

Regards,

Anthony Liguori

>
> Regards,
> Daniel

Re: [Qemu-devel] Threaded VNC server status - time to enable by default ?

[Daniel P. Berrange]

On Wed, Jun 20, 2012 at 07:58:53AM -0500, Anthony Liguori wrote:
> On 06/20/2012 04:15 AM, Daniel P. Berrange wrote:
> >We recently had a request in Fedora to enable the VNC server thread
> >support in our builds of QEMU. There have been periodic messages on
> >this list that suggest the threaded VNC server has better performance
> >and less latency.
> >
> >My view though, is that there must be some good reason why QEMU does
> >not enable it by default already. Can anyone say why QEMU has not
> >enabled the VNC server threads by default ?
> >
> >If there is no such reason, can we just kill the configure options
> >--{disable,enable}-vnc-thread, and have everyone use the VNC server
> >thread support forever more. I struggle to see the point in maintaining
> >these two separate codepaths for the VNC server. Whichever one is
> >not the default is, IMHO, destined to bitrot through lack of widespread
> >testing and so we're better off getting everyone to use&  test the
> >same codepath.
> 
> At the time it was introduced, QEMU still has no hard requirement on
> having pthreads as a dependency (the I/O thread was still optional).
> 
> We're past that point now so there's no harm in unconditionally
> enabling the VNC thread pool.

Ok, I'll post a patch to that effect.

Regards,
Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|