DLL is thought to adjust the system hardware resource allocation logic for games. It looks like a 'Game Mode' is coming to Windows 10 in an update in the not-too-distant future. Evidence pointing to this dedicated Windows gaming mode comes from a Twitter user called Walking Cat, who has pawed over the 14997 build of Windows 10 on the prowl for interesting changes. The Walking Cat (AKA @h0x0d) discovered a new OS library file called 'gamemode.dll'.