Kenneth Graunke
ff0253a5ed
There's no point in performing depth writes when the depth test comparison function is set to GL_EQUAL - it would just write out the same value that's already there (if it is written at all). While this is harmless from a functional perspective, it hurts performance. Obviously, writing to memory is not free, but there's another more subtle impact as well: it can prevent early depth optimizations. Depth writes aren't supposed to happen for pixels that are killed by fragment shader discard statements or the alpha test. So, with depth writes enabled and either of those, the pixel shader must be invoked to determine whether or not to perform the write. This is fairly stupid in the EQUAL case - we're running a shader to decide whether to replace the existing depth value with itself. By disabling these pointless writes, we allow early depth even with discards and alpha testing, allowing the hardware to skip the pixel shader altogether if the depth test fails. Improves performance of Unigine Valley: - Skylake GT2: +17.8% - Broadwell GT3e: +11.5% - Cherrytrail: +19.4% Huge thanks to Mark Janes for building frameretrace [1], the performance analysis tool that helped us find this issue, and to Robert Bragg for providing us performance metrics on Linux. Mark also spent the time to analyze Valley performance on Windows vs. Linux and discovered a discrepancy in early depth test metrics. Once he had isolated a draw call and drawn attention to the problem, fixing it was pretty simple. [1] https://github.com/janesma/apitrace/wiki/frameretrace-branch Signed-off-by: Kenneth Graunke <kenneth@whitecape.org> Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com> Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
File: docs/README.WIN32 Last updated: 21 June 2013 Quick Start ----- ----- Windows drivers are build with SCons. Makefiles or Visual Studio projects are no longer shipped or supported. Run scons libgl-gdi to build gallium based GDI driver. This will work both with MSVS or Mingw. Windows Drivers ------- ------- At this time, only the gallium GDI driver is known to work. Source code also exists in the tree for other drivers in src/mesa/drivers/windows, but the status of this code is unknown. Recipe ------ Building on windows requires several open-source packages. These are steps that work as of this writing. - install python 2.7 - install scons (latest) - install mingw, flex, and bison - install pywin32 from here: http://www.lfd.uci.edu/~gohlke/pythonlibs get pywin32-218.4.win-amd64-py2.7.exe - install git - download mesa from git see http://www.mesa3d.org/repository.html - run scons General ------- After building, you can copy the above DLL files to a place in your PATH such as $SystemRoot/SYSTEM32. If you don't like putting things in a system directory, place them in the same directory as the executable(s). Be careful about accidentially overwriting files of the same name in the SYSTEM32 directory. The DLL files are built so that the external entry points use the stdcall calling convention. Static LIB files are not built. The LIB files that are built with are the linker import files associated with the DLL files. The si-glu sources are used to build the GLU libs. This was done mainly to get the better tessellator code. If you have a Windows-related build problem or question, please post to the mesa-dev or mesa-users list.