"Fixes" for page flipping under PRIME on AMD & nouveau

[Michel Dänzer]

On 27/08/16 05:07 AM, Mario Kleiner wrote:
> On 08/18/2016 04:32 AM, Michel Dänzer wrote:
>> On 18/08/16 08:51 AM, Mario Kleiner wrote:
>>>
>>> and the offload gpu imports those and renders into them. That saves
>>> one extra copy, so should be somewhat more efficient.
>>
>> Using two shared buffers actually isn't as efficient as possible wrt
>> inter-GPU bandwidth.
> 
> Out of interest, why? You'd have only one detiling copy VRAM -> RAM?

Yeah, that's basically it. With a single shared buffer, only the parts
which have changed since last time need to be copied between the GPUs;
the slave GPU can copy the other changed parts from its other local
scanout pixmap (with TearFree enabled; note that this isn't quite
implemented yet in our drivers for slave output, but I'm planning to do
it soon). With two shared pixmaps, some changed parts have to be copied
between GPUs several times.


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