PRIME is a technology used to manage hybrid graphics found on recent laptops (Optimus for NVIDIA, AMD Dynamic Switchable Graphics for ATI).
The following drivers support it:
First, check the list of video cards attached to your display :
$ xrandr --listproviders Providers: number : 2 Provider 0: id: 0x7d cap: 0xb, Source Output, Sink Output, Sink Offload crtcs: 3 outputs: 4 associated providers: 1 name:Intel Provider 1: id: 0x56 cap: 0xf, Source Output, Sink Output, Source Offload, Sink Offload crtcs: 6 outputs: 1 associated providers: 1 name:radeon
We can see that there are two graphic cards : Intel, the integrated card (id 0x7d) and radeon, the discrete card (id 0x56), which should be used for GPU-intensive applications. We can see that, by default, Intel is always used :
$ glxinfo | grep "OpenGL renderer" OpenGL renderer string: Mesa DRI Intel(R) Ivybridge Mobile
To use your discrete card (in this case, radeon), you must first define it as an offload provider for the integrated one, since it’s the integrated one that is connected to your display.
$ xrandr --setprovideroffloadsink 0x56 0x7d
Now, you can use your discrete card for the applications who need it the most (for example games, 3D modelers…):
$ DRI_PRIME=1 glxinfo | grep "OpenGL renderer" OpenGL renderer string: Gallium 0.4 on AMD TURKS
Other applications will still use the less power-hungry integrated card. The xrandr --setprovideroffloadsink 0x56 0x7d must be run at each X server restart ; you may want to make a script and auto-run it at the startup of desktop environment (or you may put it in /etc/X11/xinit/xinitrc.d/)
When an application is rendered with the discrete card, it only renders a black screen
In some cases PRIME needs a composition manager to properly work. If your window manager doesn’t do compositing, you can use xcompmgr on top of it.
Black screen with GL-based compositors
Currently there are issues with GL-based compositors and PRIME offloading. While Xrender-based compositors (xcompmgr, xfwm, compton's default backend, cairo-compmgr, and a few others) will work without issue, GL-based compositors (Mutter/muffin, Compiz, compton with GLX backend, Kwin's OpenGL backend, etc) will initially show a black screen, as if there was no compositor running. While you can force an image to appear by resizing the offloaded window, this is not a practical solution as it will not work for things such as full screen Wine applications. This means that desktop environments such as GNOME3 and Cinnamon have issues with using PRIME offloading.
Additionally if you are using an Intel IGP you might be able to fix the GL Compositing issue by running the IGP as UXA instead of SNA, however this may cause issues with the offloading process (ie, xrandr --listproviders may not list the discrete GPU).