GameMode

A preliminary implementation of a daemon/lib combo to allow games to request a performance mode from the host OS on Linux. It was designed primarily as a stop-gap solution to problems with the Intel and AMD CPU powersave or ondemand governors, but is intended to be expanded beyond just CPU power states as needed.

Currently using sd-bus on the user bus internally for messaging

Components

Host

gamemoded

Runs in the background, waits for requests, refcounts and also checks caller PID lifetime.

Accepts -d (daemonize) and -l (log to syslog)

libgamemode

Dynamic library to dispatch requests to the daemon

Note: Behaviour of gamemoded may change, so libgamemode should never be linked with directly.

cpugovctl

Small program used to to control the cpu governor.

Accepts get (gets current governor) and set <GOVERNOR> (sets the current governor).

Clients

libgamemodeauto

Simple dynamic library that automatically requests game mode when loaded. Minimal dependencies.

Useful to LD_PRELOAD into any game as needed.

gamemode_client.h

Very small header only lib that lets a game request game mode and handle errors. Minimal dependencies.

Can also be included with GAMEMODE_AUTO defined to behave automatically.

Build and install

Daemon and host library

Dependencies

meson

systemd

# Ubuntu
apt install meson libsystemd-dev pkg-config
# Arch
pacman -S meson systemd

git clone <git repo>
cd gamemode
./bootstrap.sh

Using with any game or program

After installing libgamemodeauto.so simple preload it into the program. Examples:

LD_PRELOAD=/usr/\$LIB/libgamemodeauto.so ./game

Or steam launch options

LD_PRELOAD=/usr/\$LIB/libgamemodeauto.so %command%

Building into a game or program

You may want to build in functionality directly into an app, this stops the need for users to have to manually set anything up.

gamemode_client.h and libgamemodeauto are safe to use regardless of whether libgamemode and gamemoded are installed on the system. They also do not require systemd.

Using directly

#include "gamemode_client.h"

	if( gamemode_request_start() < 0 )
		fprintf( stderr, "gamemode request failed: %s\n", gamemode_error_string() );

	/* run game... */

	gamemode_request_end(); // Not required, gamemoded will clean up after game exists anyway

Using automatically

Option 1: Include in code

#define GAMEMODE_AUTO
#include "gamemode_client.h"

Option 2: Link and distribute

Add -lgamemodeauto to linker arguments and distribute libgamemodeauto.so with the game

Option 3: Distribute and script

Distribute libgamemodeauto.so with the game and add to LD_PRELOAD in a launch script

Configuration

The daemon can currently be configured using a gamemode.ini file in /usr/share/gamemode/. It will load the file when starting up.

An example of what the file could look like is found in the example directory.

The file parsing uses inih.

Pull Requests

Pull requests must match with the coding style found in the .clang-format file

clang-format -i $(find . -name '*.[ch]')

Planned Features

Additional mode-switch plugins
User confuguration with whitelist/blacklist for programs
User configuration for custom mode-switch plugins
Additional state tracking not based solely on PID

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