Commit ab3f555f authored by mperes's avatar mperes Committed by nouveau
Browse files

Initial contribution to the power management section

parent 3a5a5a8b
......@@ -52,6 +52,36 @@ the "regular" GPU, set DRI_PRIME to 0 or omit it. The behaviour can be seen in t
$ DRI_PRIME=1 glxinfo | grep "OpenGL vendor string"
OpenGL vendor string: nouveau
### Power management
When an application is using 'PRIME GPU offloading', both the discrete and the integrated GPUs are active and aside from optimizations at the driver level, nothing else can be done. However, when no application is making use of the discrete GPU, the default behaviour should be for the card to automatically power down entirely after 5 seconds.
This dynamic power management feature has been added in Linux 3.12 but requires Linux 3.13 to work properly with Nouveau. If you cannot make use of this feature and do not mind not using your NVIDIA GPU, it is recommended to blacklist the 'nouveau' module and to use bbswitch to turn off the NVIDIA GPU. Look onto your distribution's wiki for more information.
#### Checking the current power state
You can query the current power state and policy by running as root:
# cat /sys/kernel/debug/vgaswitcheroo/switch
0:DIS: :DynOff:0000:01:00.0
2:DIS-Audio: :Off:0000:01:00.1
Each line of the output is of the following format:
* A number: not important
* A string:
* DIS: Discrete GPU (your AMD or NVIDIA GPU)
* IGD: Integrated Graphics (your Intel card?)
* DIS-Audio: The audio device exported by your discrete GPU for HDMI sound playback
* A power state:
* OFF: The device is powered off
* ON: The device is powered on
* DynOff: The device will be powered on when needed and powered off when unused for some time
* The PCI-ID of the device
#### U
### Known issues
#### Everything seems to work but the output is black
......@@ -60,12 +90,6 @@ Try using a re-parenting compositor. Those compositors usually provide 3D effect
*WARNING*: Currently, Kwin only works when using the desktop effects. In the case where the window would be pure black, please try minimizing/maximizing or redimensioning the window. This bug is being investigated.
#### Increased power consumption
When using prime, the NVIDIA GPU cannot be put offline which means it drains power even if it is not in use. This problem is being addressed but it isn't entirely trivial to fix this issue. This issue will disapear step-by-step when we add support for power management.
If you do not plan on using your NVIDIA GPU, it is recomended to blacklist the Nouveau module and to use bbswitch to turn off the Nouveau card. Look onto your distribution's wiki for more information.
#### Poor performance when using the Nouveau card
Right now, Nouveau does not support reclocking and other power management feature. This cripples the performance of the GPU a lot along with increasing the power consumption compared to the proprietary driver.
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