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

[Christian König]

Am 07.09.2016 um 17:36 schrieb Ilia Mirkin:
> On Wed, Sep 7, 2016 at 4:08 AM, Michel Dänzer <michel at daenzer.net> wrote:
>> 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.
> Any suggestions that don't involve rewriting nouveau bo handling at
> every level (kernel, ddx, mesa)?

Either just ignore the flag or handle it better, but it's current effect 
of placing buffers into GART is certainly completely wrong and not only 
in this use case.

Regards,
Christian.

>
> Otherwise I'll send a revert for this change.
>
>    -ilia