PRIME render offload is the ability to have an X screen rendered by one GPU, but choose certain applications within that X screen to be rendered on a different GPU. This is particularly useful in combination with dynamic power management to leave an NVIDIA GPU powered off except when it is needed to render select performance-sensitive applications.
The GPU rendering the majority of the X screen is known as the "sink", and the GPU to which certain application rendering is "offloaded" is known as the "source". The render offload source produces content that is presented on the render offload sink. The NVIDIA driver can function as a PRIME render offload source, to offload rendering of GLX+OpenGL or Vulkan, presenting to an X screen driven by the xf86-video-modesetting X driver.
NVIDIA's PRIME render offload support requires X.Org xserver version 1.20.7 or newer.
On systems with both an integrated GPU and an NVIDIA discrete GPU, the X.Org X server version 1.20.7 and newer will automatically use NVIDIA's PRIME render offload support if the system BIOS is configured to boot on the iGPU and no other explicit configuration files are present. Note that some Linux distributions (such as Ubuntu) may configure the X server differently. Please refer to your distribution's documentation for details.
If GPU screen creation was successful, the log file
/var/log/Xorg.0.log should contain lines with
"NVIDIA(G0)", and querying the RandR providers with
xrandr --listproviders should display a
provider named "NVIDIA-G0" (for "NVIDIA GPU screen 0"). For
Providers: number : 2 Provider 0: id: 0x221 cap: 0x9, Source Output, Sink Offload crtcs: 3 outputs: 6 associated providers: 0 name:modesetting Provider 1: id: 0x1f8 cap: 0x0 crtcs: 0 outputs: 0 associated providers: 0 name:NVIDIA-G0
To configure a graphics application to be offloaded to the
NVIDIA GPU screen, set the environment variable
1. If the graphics application uses Vulkan
or EGL, that should be all that is needed. If the graphics
application uses GLX, then also set the environment variable
nvidia, so that GLVND loads the
NVIDIA GLX driver.
__NV_PRIME_RENDER_OFFLOAD=1 vkcube __NV_PRIME_RENDER_OFFLOAD=1 __GLX_VENDOR_LIBRARY_NAME=nvidia glxinfo | grep vendor
variable causes the special Vulkan layer
VK_LAYER_NV_optimus to be loaded. Vulkan
applications use the Vulkan API to enumerate the GPUs in the system
and select which GPU to use; most Vulkan applications will use the
first GPU reported by Vulkan. The
VK_LAYER_NV_optimus layer causes the GPUs
to be sorted such that the NVIDIA GPUs are enumerated first. For
finer-grained control, the
VK_LAYER_NV_optimus layer looks at the
environment variable. The value
VK_LAYER_NV_optimus to only report NVIDIA
GPUs to the Vulkan application. The value
VK_LAYER_NV_optimus to only report
non-NVIDIA GPUs to the Vulkan application.
__NV_PRIME_RENDER_OFFLOAD=1 __VK_LAYER_NV_optimus=NVIDIA_only vkcube __NV_PRIME_RENDER_OFFLOAD=1 __VK_LAYER_NV_optimus=non_NVIDIA_only vkcube
For OpenGL with either GLX or EGL, the environment variable
finer-grained control. While
__NV_PRIME_RENDER_OFFLOAD=1 tells GLX or
EGL to use the first NVIDIA GPU screen,
__NV_PRIME_RENDER_OFFLOAD_PROVIDER can use
an RandR provider name to pick a specific NVIDIA GPU screen, using
the NVIDIA GPU screen names reported by
__NV_PRIME_RENDER_OFFLOAD=1 __GLX_VENDOR_LIBRARY_NAME=nvidia glxgears __NV_PRIME_RENDER_OFFLOAD_PROVIDER=NVIDIA-G0 __GLX_VENDOR_LIBRARY_NAME=nvidia glxgears __NV_PRIME_RENDER_OFFLOAD=1 eglinfo __NV_PRIME_RENDER_OFFLOAD_PROVIDER=NVIDIA-G0 eglinfo
After starting the X server, verify that the
xf86-video-modesetting X driver is using "glamoregl". The log file
/var/log/Xorg.0.log should contain
something like this:
[1272173.618] (II) Loading sub module "glamoregl" [1272173.618] (II) LoadModule: "glamoregl" [1272173.618] (II) Loading /usr/lib/xorg/modules/libglamoregl.so [1272173.622] (II) Module glamoregl: vendor="X.Org Foundation" [1272173.622] compiled for 1.20.4, module version = 1.0.1 [1272173.622] ABI class: X.Org ANSI C Emulation, version 0.4 [1272173.638] (II) modeset(0): glamor X acceleration enabled on Mesa DRI Intel(R) HD Graphics 630 (Kaby Lake GT2) [1272173.638] (II) modeset(0): glamor initialized
If glamoregl could not be loaded, the X log may report something like:
[1271802.673] (II) Loading sub module "glamoregl" [1271802.673] (II) LoadModule: "glamoregl" [1271802.673] (WW) Warning, couldn't open module glamoregl [1271802.673] (EE) modeset: Failed to load module "glamoregl" (module does not exist, 0) [1271802.673] (EE) modeset(0): Failed to load glamor module.
in which case, consult your distribution's documentation for how to (re-)install the package containing glamoregl.
If the server didn't create a GPU screen automatically, ensure
that the nvidia_drm kernel module is loaded. This should normally
happen by default, but you can confirm by running
lsmod | grep nvidia_drm to see if the
kernel module is loaded. Run
nvidia_drm to load it.
If automatic configuration does not work, it may be necessary to explicitly configure the iGPU and dGPU devices in xorg.conf:
Section "ServerLayout" Identifier "layout" Screen 0 "iGPU" EndSection Section "Device" Identifier "iGPU" Driver "modesetting" EndSection Section "Screen" Identifier "iGPU" Device "iGPU" EndSection Section "Device" Identifier "dGPU" Driver "nvidia" EndSection