We're already known that Valve Software intends to speak at SIGGRAPH LA 2012 about how they optimized their Linux OpenGL game client -- taking it from just a few frames per second to over 300 FPS. Now on Valve's official Linux blog is a new post this evening about Faster Zombies!.
They talk about how their optimizations came down to modifying the game to work better with the Linux kernel, modifying the game to work better with OpenGL, and optimizing the graphics drivers.
The working better with the Linux kernel came by allowing the Source Engine small block heap code to work under Linux.
As for how they found bottlenecks within their OpenGL renderer to make it more efficient, see Finding Bottlenecks In Your Linux Game, Application.
The Linux driver optimizations come via collaborating with Intel, AMD, and NVIDIA on their respective drivers. Valve has long communicated with AMD and NVIDIA on their binary Linux graphics drivers and then in recent months engaged with the open-source Intel team -- see Valve & Intel Work On Open-Source GPU Drivers.
Using a NVIDIA GeForce GTX 680 graphics card with an Intel Core i7 3930K processor, Windows 7 SP1 was running Left 4 Dead 2 with the Direct3D renderer at 270 FPS while under Linux with OpenGL they are now at 315 FPS! Using the OpenGL renderer on Windows isn't also quite as good with its average frame-rate at around 303 FPS.
That's about it for the Valve Linux news today. Expect more information next week.