[Intel-gfx] [PATCH] Xv: free tearing on textured video

Keith Packard keithp at keithp.com
Wed Feb 25 18:24:47 CET 2009


On Wed, 2009-02-25 at 12:05 -0500, Kristian Høgsberg wrote:

> I'll have to try it out - I'm not sure what the exact effect of
> syncing everything to vblank might be.  For all I know it may not be
> noticable at all, except for cases where you do a lot of individual
> read backs per frame... time for me to stop waving the hands and try
> it.

We block the chip until vblank, once the command to blt the video is
queued. So, any other rendering will back-up behind the video blt. If
anything needs to wait for the GPU (for a fallback, or ring full,
or...), you'll block the CPU as well.

Tests made long ago made it clear that you wanted to avoid this, but
perhaps now that we've got better GPU usage things won't be nearly as
bad.

-- 
keith.packard at intel.com
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