Feral Interactive don't just port a lot of games to Linux, they also work on some open source bits here and there. One of their projects is GameMode, which just got a new release.
GameMode is a "daemon/lib combo for Linux that allows games to request a set of optimisations be temporarily applied to the host OS and/or a game process". In simple terms, it can help ensure your Linux PC is giving the game all it can to run smoothly. Looks like someone new is handling the project too, with Alex Smith having left Feral Interactive.
Today, GameMode 1.5 went up with some features worked on by Intel's Jason Ekstrand and Red Hat's Christian Kellner. Features added include the ability to dynamically switch the CPU governor used on Intel integrated GPUs, as using "performance" was causing issues when the GPU is under load so it can switch over to "powersave" now when needed which will "save power on the CPU side which lets the GPU clock up higher". A very interesting issue, you can read more about here.
You can find GameMode and read more about it on GitHub.
What else do Feral have that's open source? Their launch scripts are open too, developers doing Linux builds might find that quite useful too.