GameMode

GameMode is a daemon/lib combo for Linux that allows games to request a set of optimisations be temporarily applied to the host OS.

GameMode was designed primarily as a stop-gap solution to problems with the Intel and AMD CPU powersave or ondemand governors, but is now host to a range of optimisation features and configurations.

Currently GameMode includes support for optimisations including:

CPU governor
I/O priority
Kernel scheduler (SCHED_ISO)
Screensaver inhibiting
GPU performance mode (NVIDIA and AMD), GPU overclocking (NVIDIA)
Custom scripts

Issues with GameMode should be reported here in the issues section, and not reported to Feral directly.

Building and installing

It is preferable to install GameMode with your package manager of choice, if available. There are Ubuntu (Cosmic), Debian, Solus, AUR, Gentoo, Fedora and openSUSE packages available at the time of writing.

Install Dependencies

GameMode depends on meson for building and systemd for internal communication. This repo contains a bootstrap.sh script to allow for quick install to the user bus, but check meson_options.txt for custom settings.

Ubuntu/Debian (you may also need `dbus-user-session`)

apt install meson libsystemd-dev pkg-config ninja-build git

Arch

pacman -S meson systemd git

Fedora

dnf install meson systemd-devel pkg-config git

Gentoo

Gentoo has an ebuild which builds a stable release from sources. It will also pull in all the dependencies so you can work on the source code.

emerge --ask games-util/gamemode

You can also install using the latest sources from git:

ACCEPT_KEYWORDS="**" emerge --ask ~games-util/gamemode-9999

Build and Install GameMode

Then clone, build and install a release version of GameMode at 1.3.1:

git clone https://github.com/FeralInteractive/gamemode.git
cd gamemode
git checkout 1.3.1 # omit to build the master branch
./bootstrap.sh

To uninstall:

systemctl --user stop gamemoded.service
cd build/
ninja uninstall

Requesting GameMode

After installing libgamemodeauto.so.0 simply preload it into the game:

gamemoderun ./game

Or edit the Steam launch options:

gamemoderun %command%

Note: for older versions of GameMode (before 1.3) use this string in place of gamemoderun:

LD_PRELOAD="$LD_PRELOAD:/usr/\$LIB/libgamemodeauto.so.0"

Please note the backslash here in \$LIB is required.

Configuration

The daemon can currently be configured using a gamemode.ini file. gamemode.ini is an example of what this file would look like, with explanations for all the variables.

Config files are loaded and merged from the following directories, in order:

/usr/share/gamemode/
/etc/
$XDG_CONFIG_HOME or $HOME/.config/
$PWD

The file parsing uses inih.

Features

Scheduling

GameMode can leverage support for soft real time mode if the running kernel supports SCHED_ISO (not currently supported in upstream kernels), controlled by the softrealtime option. This adjusts the scheduling of the game to real time without sacrificing system stability by starving other processes.

GameMode can adjust the nice priority of games to give them a slight IO and CPU priority over other background processes, controlled by the renice option. This only works if your user is permitted to adjust priorities within the limits configured by PAM. GameMode can be configured to take care of it by passing with-pam-group=group to the build options where group is a group your user needs to be part of. For more information, see /etc/security/limits.conf.

Please take note that some games may actually run seemingly slower with SCHED_ISO if the game makes use of busy looping while interacting with the graphic driver. The same may happen if you apply too strong nice values. This effect is called priority inversion: Due to the high priority given to busy loops, there may be too few resources left for the graphics driver. Thus, sane defaults were chosen to not expose this effect on most systems. Part of this default is a heuristic which automatically turns off SCHED_ISO if GameMode detects three or less CPU cores. Your experience may change based on using GL threaded optimizations, CPU core binding (taskset), the graphic driver, or different CPU architectures. If you experience bad input latency or inconsistent FPS, try switching these configurations on or off first and report back. SCHED_ISO comes with a protection against this effect by falling back to normal scheduling as soon as the SCHED_ISO process uses more than 70% avarage across all CPU cores. This default value can be adjusted outside of the scope of GameMode (it's in /proc/sys/kernel/iso_cpu). This value also protects against compromising system stability, do not set it to 100% as this would turn the game into a full real time process, thus potentially starving all other OS components from CPU resources.

IO priority

GameMode can adjust the I/O priority of games to benefit from reduced lag and latency when a game has to load assets on demand. This is done by default.

For those with overclocked CPUs

If you have an AMD CPU and have disabled Cool'n'Quiet, or you have an Intel CPU and have disabled SpeedStep, then GameMode's governor settings will not work, as your CPU is not running with a governor. You are already getting maximum performance.

If you are unsure, bootstrap.sh will warn you if your system lacks CPU governor control.

Scripts and other features will still work.

GPU optimisations

GameMode is able to automatically apply GPU performance mode changes on AMD and NVIDIA, and overclocking on NVIDIA, when activated. AMD support currently requires the amdgpu kernel module, and NVIDIA requires the coolbits extension to be enabled in the NVIDIA settings.

It is very much encouraged for users to find out their own overclocking limits manually before venturing into configuring them in GameMode, and activating this feature in GameMode assumes you take responsibility for the effects of said overclocks.

More information can be found in the example/gamemode.ini file.

Note that both NVIDIA (GPUBoost) and AMD (Overdrive) devices and drivers already attempt to internally overclock if possible, but it is still common for enthusiasts to want to manually push the upper threshold.

Developers

The design of GameMode has a clear-cut abstraction between the host daemon and library (gamemoded and libgamemode), and the client loaders (libgamemodeauto and gamemode_client.h) that allows for safe use without worrying about whether the daemon is installed or running. This design also means that while the host library currently relies on systemd for exchanging messages with the daemon, it's entirely possible to implement other internals that still work with the same clients.

Components

gamemoded runs in the background, activates game mode on request, refcounts and also checks caller PID lifetime. Run man gamemoded for command line options.

libgamemode is an internal library used to dispatch requests to the daemon. Note: libgamemode should never be linked with directly.

libgamemodeauto is a simple dynamic library that automatically requests game mode when loaded. Useful to LD_PRELOAD into any game as needed.

gamemode_client.h is as single header lib that lets a game request game mode and handle errors.

Integration

Developers can integrate the request directly into an app. Note that none of these client methods force your users to have the daemon installed or running - they will safely no-op if the host is missing.

// Manually with error checking
#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 can clean up after game exits

// Automatically on program start and finish
#define GAMEMODE_AUTO
#include "gamemode_client.h"

Or, distribute libgamemodeauto.so and either add -lgamemodeauto to your linker arguments, or add it to an LD_PRELOAD in a launch script.

Supervisor support

Developers can also create apps that manage GameMode on the system, for other processes:

#include "gamemode_client.h"

	gamemode_request_start_for(gamePID);
	gamemode_request_end_for(gamePID);

This functionality can also be controlled in the config file in the supervisor section.

Contributions

Pull Requests

Pull requests must match with the coding style found in the .clang-format file, please run this before committing:

clang-format -i $(find . -name '*.[ch]' -not -path "*subprojects/*")

Planned Features

Additional mode-switch plugins
Improved client state tracking (PID is unreliable)

Maintained by

Feral Interactive

See the contributors section for an extended list of contributors.

License

GameMode is available under the terms of the BSD 3-Clause License (Revised)

Cipherbunker/gamemode