4% performance drop in GLB 2.7 Egypt from "Use a 565 format for GL_RGB and GL_UNSIGNED_SHORT_5_6_5 textures"
Submitted by Eero Tamminen
Assigned to Intel 3D Bugs Mailing List
Link to original bug (#103939)
Description
Following commit was bisected (on SKL GT2) to be cause for a performance drop in GLB 2.7 Egypt onscreen and offscreen tests:
commit 18bdf735 Author: Kenneth Graunke kenneth@whitecape.org AuthorDate: Wed Oct 4 01:08:37 2017 -0700 Commit: Kenneth Graunke kenneth@whitecape.org CommitDate: Thu Oct 5 14:30:47 2017 -0700
mesa: Use a 565 format for GL_RGB and GL_UNSIGNED_SHORT_5_6_5 textures.
Found while trying to optimize an application.
Not observed to help performance on i965, but should at least reduce
the memory usage of such textures a bit.
Reviewed-by: Eric Anholt <eric@anholt.net>
Tested-by: Eero Tamminen <eero.t.tamminen@intel.com>Egypt performance drop is clearly visible on following platforms:
- 4% on BSW N3050 & SKL GT2 & KBL GT2
- 2% on BXT J4205 & HSW GT2 & SKL GT4e
- 2% on BYT N2820 (only offscreen version)
(BSW & BYT have 1-channel memory, others 2-channel.)
On some other platforms the performance also increases, as was expected:
- 3% on BDW GT3
- 1% on BDW GT2 & SNB GT2 (only offscreen version)
(Sorry for filing this so late. I had been waiting to see whether blorp rework / texture RBC would affect this, but forgot it. That didn't affect Egypt.)
Version: git