Valve recently announced that it was working to get Left 4 Dead 2 up and running on a native Linux Ubuntu OS. That mission is still in progress, but this week Valve announced that the game now runs faster on Linux than it does on Windows 7.
In the newest post on the Valve Linux Development blog, Valve said that when they started working on the Linux port of Left 4 Dead 2, they were only able to get six frames per second out of the game with a PC that has an Intel Core i7 3930k processor, a NVIDIA GeForce GTX 680 graphics card and 32 GB of RAM. The Windows 7 version of Left 4 Dead 2 went up to 270.6 frames per second on Direct3D drivers.
The Linux team has made a ton of progress and now they report that, running on a 32-bit version of Linux and OpenGL drivers, they were able to get Left 4 Dead 2 running at 315 frames per second. How is this possible? The blog states:
It appears that it’s not related to multitasking overhead. We have been doing some fairly close analysis and it comes down to a few additional microseconds overhead per batch in Direct3D which does not affect OpenGL on Windows. Now that we know the hardware is capable of more performance, we will go back and figure out how to mitigate this effect under Direct3D.
There's still no word on when the Linux version of Left 4 Dead 2 will be released.
Source: Valve Linux blog