# 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 Overclocking (Nvidia and AMD)
* Custom scripts

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

---
## Building and installing [![Build Status](https://travis-ci.org/FeralInteractive/gamemode.svg?branch=master)](https://travis-ci.org/FeralInteractive/gamemode)

*It is preferable to install GameMode with your package manager of choice, if available*. There are Ubuntu (Cosmic), Solus, AUR, Gentoo and Fedora 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`)
```bash
apt install meson libsystemd-dev pkg-config ninja-build git
```
#### Arch
```bash
pacman -S meson systemd git
```
#### Fedora
```bash
dnf install meson systemd-devel pkg-config git
```
#### Gentoo
Gentoo has a bleeding-edge ebuild which builds from sources. It will also pull in all the dependencies so you can work on the source code.
```bash
ACCEPT_KEYWORDS="**" emerge --ask ~games-util/gamemode-9999
```

### Build and Install GameMode
Then clone, build and install a release version of GameMode at 1.2:

```bash
git clone https://github.com/FeralInteractive/gamemode.git
cd gamemode
git checkout 1.2 # omit to build the master branch
./bootstrap.sh
```

To uninstall:
```bash
systemctl --user stop gamemoded.service
cd build/
ninja uninstall
```

---
## Requesting GameMode

After installing `libgamemodeauto.so.0` simply preload it into the game:
```bash
gamemoderun ./game
```
Or edit the steam launch options:
```bash
gamemoderun %command%
```
Please note the backslash here in `\$LIB` is required.

Note: for older versions of GameMode (1.2) use this string in place of `gamemoderun`:
```
LD_PRELOAD="$LD_PRELOAD:/usr/\$LIB/libgamemodeauto.so.0"
```
---
## Configuration

The daemon can currently be configured using a `gamemode.ini` file. [gamemode.ini](https://github.com/FeralInteractive/gamemode/blob/master/example/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:
1. `/usr/share/gamemode/`
2. `/etc/`
3. `$XDG_CONFIG_HOME` or `$HOME/.config/`
4. `$PWD`

The file parsing uses [inih](https://github.com/benhoyt/inih).

---
## Features

### Scheduling
GameMode can leverage support for soft real time mode if the running kernel supports `SCHED_ISO`. This adjusts the scheduling of the game to real time without sacrificing system stability by starving other processes.

GameMode adjusts the nice priority of games to -4 by default to give it a slight IO and CPU priority over other background processes. 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 io priority of games to benefit from reduced lag and latency when a game has to load assets on demand.

### 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 overclocks when activated. AMD overclocking 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.

```C
// 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
```

```C
// 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.

---
## 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](https://github.com/FeralInteractive/gamemode/graphs/contributors) section for an extended list of contributors.

---
## License

Copyright © 2018 Feral Interactive

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