Valve Planning To Carry Mesa GL Thread Feature On SteamOS, Per-Game Features
The discussion around OpenGL threaded dispatch for Mesa hasn't ended. There is opposition to landing this code in mainline Mesa if there are Piglit regressions, the potential for game/application crashes, and other issues, even if the feature were to be enabled by default.
It's not clear if this feature will land in the near-future in Mesa given these problems, but according to AMD's Marek Olšák it's looking like Valve may carry the code in their own Mesa packages for SteamOS.
Marek wrote a few minutes ago on the Mesa list, "Pierre-Loup from Valve said on IRC yesterday that they are probably gonna ship glthread and make their own whitelist, regardless of the outcome of this discussion. It would be preferable to have that whitelist in master too, but that may be difficult if we can't merge it. If distributions and vendors start shipping glthread, we might as well merge it, because at that point there is no advantage in keeping this out of tree if it forces users to use out of tree builds. We'll get bug reports regardless."
Also interesting is that besides carrying the glthread work, they are moving toward application/game-specific profiles for Mesa. This too has been a contentious issue now and in the past with Mesa not preferring to ship workarounds or game-specific optimizations based upon the game that's detected running. While it's common place for NVIDIA and AMD drivers to apply specific features/workarounds/optimizations based upon the detected game running, the upstream Mesa developers generally have been opposed to such approach, but now it's looking like Valve may take it into their own hands by starting with a white-list of games where OpenGL threading should automatically be enabled.
Stay tuned and we'll see what happens.