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

[Li, Samuel]

Ø  But we still have to support cases where we have 1GB stolen VRAM, and wasting those 1GB would suck a bit.
Not really, since we only move display buffer here.

Regards,
Samuel Li

From: Koenig, Christian
Sent: Wednesday, March 21, 2018 10:07 AM
To: Marek Olšák <maraeo at gmail.com>
Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Alex Deucher <alexdeucher at gmail.com>; Michel Dänzer <michel at daenzer.net>; amd-gfx list <amd-gfx at lists.freedesktop.org>; Li, Samuel <Samuel.Li at amd.com>
Subject: Re: [PATCH 1/2] drm/amdgpu: Enable scatter gather display support

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

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