Summary
Game Mode is turned on automatically by putting a recognised game into Full Screen mode; there’s no alternative method. A game is taken out of Game Mode automatically by returning it from Full Screen mode, or (possibly) manually in its menu in the menu bar. Game Mode is controlled by gamepolicyd. Game Mode results in RunningBoard making some services, including gameconsole, critical, and suppressing other background servics. These could improve the game’s access to CPU cores, but this seems unlikely to have much effect on performance. Game Mode appears to increase GPU load by the game, although it’s not clear whether this is significantly greater than would be achieved by Full Screen mode alone. Game Mode puts Bluetooth into Low Latency mode, reducing input latency from game controllers, and audio latency to output devices.