[Mesa-dev] [PATCH 1/4] r600g, radeonsi: force VRAM placement for DRI2 buffers

[Michel Dänzer]

On Mon, 2014-02-03 at 18:07 +0100, Marek Olšák wrote:
> Do you mean something like:
> 
> write_domains = VRAM
> read_domains = VRAM | GTT
> 
> I don't think it's perfect.

That's what I meant, and of course it's not perfect. :)


> We should treat rendering by an app and blitting by u_blitter (=
> texture transfers) differently. We don't want u_blitter to mess up our
> idea about which textures are used as a framebuffer, because once
> u_blitter comes into play, everything can be a framebuffer.
> 
> I've got the following idea:
> 
> 1) Set the domain to VRAM | GTT by default for all buffers and textures.
> 2) In set_framebuffer_state, if u_blitter isn't blitting, do this to
> the domains of all renderbuffers: if (domains & VRAM) domains &= ~GTT;

Interesting idea.


> That said, I'm not too excited about this. Allowing more stuff to be
> moved to GTT will have an adverse effect on performance. Being more
> aggressive and trying to put more stuff in VRAM should almost always
> be better if you can avoid buffer ping-ponging.

The above should avoid BO ping pong in some cases, but it may indeed
also cause some BOs to stay in GTT when it would be better for them to
be in VRAM.


> I have been messing with the domains since ever and what we have now
> seems to work best. It's not perfect, but I have already tried all the
> other options and they weren't better.

What metrics did you use to determine that?


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