[PATCH 1/2] drm/amdgpu: Enable scatter gather display support

[Christian König]

Am 21.03.2018 um 14:57 schrieb Marek Olšák:
> On Wed, Mar 21, 2018 at 4:13 AM, Christian König 
> <ckoenig.leichtzumerken at gmail.com 
> <mailto:ckoenig.leichtzumerken at gmail.com>> wrote:
>
>     Am 21.03.2018 um 06:08 schrieb Marek Olšák:
>>     On Tue, Mar 20, 2018 at 4:16 PM, Christian König
>>     <christian.koenig at amd.com <mailto:christian.koenig at amd.com>> wrote:
>>
>>         That's what I meant with use up the otherwise unused VRAM. I
>>         don't see any disadvantage of always setting GTT as second
>>         domain on APUs.
>>
>>         My assumption was that we dropped this in userspace for
>>         displayable surfaces, but Marek proved that wrong.
>>
>>         So what we should do is actually to add GTT as fallback to
>>         all BOs on APUs in Mesa and only make sure that the kernel is
>>         capable of handling GTT with optimal performance (e.g. have
>>         user huge pages etc..).
>>
>>
>>     VRAM|GTT is practically as good as GTT. VRAM with BO priorities
>>     and eviction throttling is the true "VRAM|GTT".
>>
>>     I don't know how else to make use of VRAM intelligently.
>
>     Well why not set VRAM|GTT as default on APUs? That should still
>     save quite a bunch of moves even with throttling.
>
>
> I explained why: VRAM|GTT is practically as good as GTT.
>
>
>     I mean there really shouldn't be any advantage to use VRAM any
>     more except that we want to use it up as long as it is available.
>
>
> Why are you suggesting to use VRAM|GTT then? Let's just only use GTT 
> on all APUs.

Then we don't use the memory stolen for VRAM.

See we want to get to a point where we have any ~16MB of stolen VRAM on 
APUs and everything else in GTT.

But we still have to support cases where we have 1GB stolen VRAM, and 
wasting those 1GB would suck a bit.

Christian.

>
> Marek

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/amd-gfx/attachments/20180321/d458d1bb/attachment-0001.html>