[Intel-gfx] intel_prepare_render(intel); unhelpful?

[Peter Clifton]

On Mon, 2010-11-01 at 14:41 -0700, Eric Anholt wrote:
> > I'm going to look at the case I "think" I hit an improvement for and
> > dissect _why_, then get back to you.

I'll check this again shortly.. (I recall I was testing this with the
display lists anyway)..
 
> > I'm chasing my code right now to see why it is emitting lots of batches
> > when not using display lists for benchmarking purposes. I got my figures
> > muddled up before.. I'm seeing 5 batches / frame when using Display
> > lists, and nearer 40 when not. (I previously reported the other way
> > around).
> 
> I'd love to know too.  INTEL_DEBUG=state (in the midst of much other
> spam) dumps out a report of how many times various state changes got
> flagged, which may highlight a change between the two modes.

The large number of batches was due to a dumb dumb thing I was doing
with VBOs.. rather than just discarding the memory after rendering some
primitives, I was mapping the same VBO and re-uploading, causing
synchronisation.

Actually, I had two VBOs and was alternating between them, but was still
of course causing synchronisation at the map stage. Fixed now, so my non
display-list code is much faster again.

I guess it kind of begs the question why the compiled display list needs
4 or 5 batches to do what my own code manages in 1.

-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
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