[Mesa-dev] [PATCH 09/10] st/vdpau: implement the new DMA-buf based interop

[Michel Dänzer]

On 07/09/16 04:19 AM, Christian König wrote:
> Am 06.09.2016 um 21:05 schrieb Ilia Mirkin:
>> On Tue, Sep 6, 2016 at 2:22 PM, Christian König
>> <deathsimple at vodafone.de> wrote:
>>> Am 06.09.2016 um 16:23 schrieb Ilia Mirkin:
>>>> On Mon, Sep 5, 2016 at 2:48 AM, Michel Dänzer <michel at daenzer.net>
>>>> wrote:
>>>>> On 05/09/16 04:37 AM, Ilia Mirkin wrote:
>>>>>> On Tue, Mar 8, 2016 at 7:21 AM, Christian König
>>>>>> <deathsimple at vodafone.de> wrote:
>>>>>>> @@ -80,7 +82,7 @@ vlVdpOutputSurfaceCreate(VdpDevice device,
>>>>>>>       res_tmpl.depth0 = 1;
>>>>>>>       res_tmpl.array_size = 1;
>>>>>>>       res_tmpl.bind = PIPE_BIND_SAMPLER_VIEW |
>>>>>>> PIPE_BIND_RENDER_TARGET |
>>>>>>> -                   PIPE_BIND_LINEAR;
>>>>>>> +                   PIPE_BIND_LINEAR | PIPE_BIND_SHARED;
>>>>>> Hi Christian,
>>>>>>
>>>>>> This change appears to have semi-broken vdpau on nouveau. Whenever I
>>>>>> flip on the OSD in mplayer, the rendering becomes *extremely* slow.
>>>>>> However regular up-scaling without the OSD is plenty fast. This
>>>>>> effectively is forcing the output surfaces to live in GART instead of
>>>>>> VRAM.
>>>>> Strictly speaking, they'd only need to be forced to GART while they're
>>>>> actually being shared between different GPUs. That's how it works with
>>>>> the amdgpu and radeon kernel drivers.
>>>> Any suggestions on how to handle this? Perhaps reallocate + copy the
>>>> surface in st/vdpau when actual dmabuf sharing is requested?
>>>>
>>>> To be clear - with this change, vdpau with nouveau is unusable in the
>>>> presence of an OSD in mplayer. The OSD comes up whenever you seek
>>>> around in the video, so in effect, it's unusable. Used to work great.
>>>
>>> Well I think you should clearly figure out why adding
>>> PIPE_BIND_SHARED has
>>> such dramatic effect.
>> Because the buffer goes into GART. And then you try to blend on it,
>> which involves readback from GART (that's how the functions OSD is
>> based on work, I believe). We normally don't allocate renderable
>> surfaces or textures in GART.
>>
>>> We not only need this for DMA-buf based interop, but also for the
>>> DRI3 based
>>> sharing of buffers with X.
>>>
>>> So that clearly sounds like a bug in nouveau to me.
>> OK, so SHARED != GART? With nouveau, buffers are placed statically in
>> either VRAM or GART, so I think that if it's shared it has to end up
>> in GART, no?
> 
> As far as I understand it no. Shared just means that we can share it
> between applications, doesn't it? Or does it mean the buffer should be
> shareable between GPUs?
> 
> Could be that my understanding was wrong and so if it's the later feel
> free to provide a patch to just remove the flag.
> 
>> I'm pretty weak on all these concepts, as well as how the DRI3 stuff
>> works, unfortunately.
> 
> I have to confess I'm not so deeply into this stuff either. Marek,
> Michel what exactly is the meaning of the flag?

According to src/gallium/docs/source/screen.rst:

* ``PIPE_BIND_SHARED``: A sharable buffer that can be given to another
  process.

It's also used e.g. for buffers shared via DRI3. So I'm afraid this is
something nouveau has to deal with better.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer