Re: [Qemu-devel] RFC: running the user interface in a thread ...

[Dave Airlie]

On 21 January 2016 at 19:05, Paolo Bonzini <address@hidden> wrote:
>
>
> On 21/01/2016 09:44, Dave Airlie wrote:
>> I've hacked on this before, but only with SDL and it was pretty dirty,
>> and it gave a fairly decent
>> speed up.
>>
>> My thoughts are to use dataplane like design to process the queue in a
>> separate thread,
>> and then have some sort of channel between the UI and virtio-gpu
>> thread to handle things like
>> screen resize etc.
>>
>> http://cgit.freedesktop.org/~airlied/qemu/commit/?h=dave3d&id=fe22a0955255afef12b947c4a91efa57e7a7c429
>> is my previous horror patch.
>
> Instead of having a full-blown thread, are there things (such as the
> TGSI->GLSL conversion) that could be simply offloaded to a userspace
> thread pool, either in QEMU or in virglrenderer?

Not really, the TGSI->GLSL overhead is quite minor, the problem is the
produced GLSL then gets passed to
OpenGL to compile, and depending on the quality of the original
program and my conversion code, the
GLSL compiler can get quite upset.

In theory Mesa could help here, but GL isn't thread friendly at all,
so it probably won't help in the virgl
case even if it did. Since most GL apps compile a shader and block on
using it straight away doing it
in a thread won't help unblock things.

So I think it would be best to have all the virgl vq processing happen
in it's own thread with some API
to the UI to do UI resizes (the most difficult) and dirty regions etc.

Dave.