[Mesa-dev] [PATCH 07/12] intel: Make the fake packed depth/stencil mappings use a cached temporary.

[Chad Versace]

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On 12/05/2011 11:42 AM, Eric Anholt wrote:
> Before, we had an uncached read of S8 to untile, then a RMW (so
> uncached penalty) of the packed S8Z24 to store the value, then the
> consumer would uncached read that once per pixel.  If data was written
> to the map, we would then have to uncached read the written data back
> out and do the scatter to the tiled S8 buffer (also uncached access
> penalties, since WC couldn't actually combine).  So 3 or 5 uncached
> accesses per pixel in the ROI (and we we were ignoring the ROI, so it
> was the whole image).
> 
> Now we get an uncached read of S8 to untile, and an uncached read of
> Z.  The consumer gets to do cached accesses.  Then if data was
> written, we do streaming Z writes (WC success), and scattered S8
> tiling writes (uncached penalty).  So 2 or 3 uncached accesses per
> pixel in the ROI.
> 
> This should be a performance win, to the extent that anybody is doing
> software accesses of packed depth/stencil buffers.
> ---
>  src/mesa/drivers/dri/intel/intel_mipmap_tree.c |  243 +++++++++++++-----------
>  src/mesa/drivers/dri/intel/intel_tex.h         |    6 -
>  2 files changed, 128 insertions(+), 121 deletions(-)


I like this improvement.

Reviewed-by: Chad Versace <chad.versace at linux.intel.com>

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