Wednesday, January 8, 2014

freedreno update: new year edition

Time for another freedreno update.  hw binning support, and fun with gallium HUD.


The big news is that hw binning pass support (for a3xx) is working.   This is a pre-pass for all the draws which generates a visibility stream (ie. basically which vertices apply to which tiles) used to speed up the tile rendering step by filtering out non visible vertices for a given tile.

tl;dr: games or anything with a healthy vertex loading (ie. not window managers) are showing 35-45% fps boost.

Currently it is not enabled by default.  I'd like some time for it to get more testing before it is enabled by default.  For now, use the FD_MESA_DEBUG environment variable to enable it, ie:

  FD_MESA_DEBUG=binning supertuxkart

Also, since I was looking for a way to correlate fps with various other statistics (in particular batches per second vs frames per second), I started playing with the gallium performance monitor HUD (heads-up-display).  With the addition of a few driver custom queries, I had what I needed:

The driver custom queries:
  • draw-calls
  • batches - number of batches per second, sum of batches-sysmem plus batches-gmem
  • batches-gmem - a set of tiles in GMEM rendered, for each tile (optionally) system mem -> gmem (restore), plus N draws, plus gmem -> system mem (resolve); value in batches per second
  • batches-sysmem - draws to system memory (GMEM bypass) per second
  • restores - number of GMEM batches that required restore per second
So above screenshot was generated with:

 export GALLIUM_HUD=cpu0+cpu1+cpu2+cpu3,fps+batches-sysmem+batches-gmem+restores,draw-calls
 export FD_MESA_DEBUG=binning
 supertuxkart -s 1280x720 --demo-mode 1

The binning and query support are on mesa master.