Some days ago I installed both CS:GO and Garry's Mod later on a new OS (Linux Mint 17.2 Cinnamon) and after trying to play, FPS is suddenly decreasing and decreasing especially while I play on a server or offline and as for the menu of those games, I don't experience input lags whatsoever...
In Windows it worked fine without problems but on Linux Mint I dunno what exactly cause this issue, either is the OS or something. Other games like Terraria, GoldSrc games and POSTAL 2 work like a charm without lags, except CS:GO and Garry's Mod are those who I get shit tons of FPS drops. I tried also on CS:GO to change the settings to very low but still same results.
Oh, and another thing is that my GPU is Intel HD Graphics (yea a shitty one, I know). Maybe Linux Mint does not fully recognize this GPU or what?