[Mesa-dev] [PATCH 0/6] Enable Pixman for Mesa

Jason Ekstrand jason at jlekstrand.net
Mon Jun 30 08:26:53 PDT 2014

On Mon, Jun 30, 2014 at 3:18 AM, Juha-Pekka Heikkila <
juhapekka.heikkila at gmail.com> wrote:

> On 25.06.2014 23:47, Matt Turner wrote:
> > On Wed, Jun 25, 2014 at 5:38 AM, Juha-Pekka Heikkila
> > <juhapekka.heikkila at gmail.com> wrote:
> >> This is my old set which enable using Pixman on Mesa for some texture
> >> conversion fast paths. As is this passes Piglit quick set on my IVB.
> >
> > Pixman doesn't actually have fast paths for swizzling, like we're
> > using in this series. I imagine improvements we're seeing here are
> > simply because Mesa's code is slow.
> >
> > I never pursued this idea for a couple of reasons. One is that we
> > should probably use the GPU to do the conversions in the ideal case.
> > Also, pixman doesn't support floating-point formats. Some work has
> > been done in the last year or so to make this much easier to implement
> > though.
> >
> > The first reason above shouldn't block other improvements, and the
> > second reason is fixable with some contributions to pixman. And pixman
> > is really a trivial dependency, so that shouldn't be a problem.
> >
> > Soren thinks this is worth doing and I trust him.
> >
> > I think a worthwhile goal would be to add support to pixman for doing
> > a bunch of the conversions Mesa requires and then dropping the code in
> > Mesa. Are you interested in doing that? I know Jason (Cc'd) is working
> > on cleaning up a bunch of this code.
> >
> > Are you planning to contribute swizzling fast paths to pixman? The
> > power-of-two-sized-component formats should be really easy to optimize
> > using the SSE shuffle instructions.
> >
> Hi Matt, Jason,
> Which parts of texture conversion are you Jason touching, does your
> changes overlap with the patches I put here?

Sorry, I haven't had much of a chance to look at your patchs.  My stuff is
probably going to touch all of the texture upload code and (hopefully) give
us some speed improvements all-around.  In particular, I'm hoping to reduce
conversion to/from floating point and add generalized fast-paths whenever
possible.  That said, going directly to pixman may still be better in some
certain cases.  As Ken said, I'm not sure if pixman has actual fast-paths,
so it would be worth looking into what Mesa is doing different from Pixman.

> As for doing (more) Pixmanization for Mesa on this part I think I can do
> it and start to look into making patches for Pixman to support Mesa
> better. I hope to be away from keyboards for few weeks so it'll be
> August when I start anything on this.

Actually, that will work out fairly well.  I'm going to be hitting the
texture upload code pretty hard the next week or two and should have
results by the time you have a chance to start back up.  That way we won't
be stepping on each other too badly.

Also, what was your set-up for doing power comparisons?  As I dive into
this, I'd like to see how my results compare.

--Jason Ekstrand
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