VirtualGL
Why VirtualGL
To display a 3D application running remotely on a cluster, you could use X11 forwarding to display the application on your local machine. This is usually very slow and often unusable.
An alternative approach is to use VNC - also called Remote Desktop - to run GUI applications remotely on the cluster.
This approach only works well with applications that only need moderate 3D rendering where software rendering is good enough.
For applications that need to render large complicated models, hardware accelerated 3D rendering must be used.
However, VNC cannot directly utilize the graphic devices on the cluster for rendering. VirtualGL, in conjunction with VNC, provides a commonly used solution for remote 3D rendering with hardware acceleration.
How to use VirtualGL
VirtualGL 3.0+ supports the traditional GLX back end and the new EGL back end for 3D rendering.
The EGL back end uses a DRI (Direct Rendering Infrastructure) device to access a graphics device, while the GLX back end uses an X server to access a graphics device. The EGL back end allows simultaneous jobs on the same node, each using their own dedicated GPU device for rendering. Although it can render many applications properly, the EGL back end may fail to render some applications. The GLX back end supports a wider range of OpenGL applications than the EGL back end, however, only one X server can work properly with the graphics devices on the node. This means only one job can use the GLX back end on any GPU node, no matter how many GPU devices the node has.
We suggest you use the EGL back end first. If it does not render your application properly, then switch to the GLX back end.
We have provided a wrapper script ycrc_vglrun to make it easy for you to
choose which back end to use for 3D rendering. In the following examples, we will use ParaView
(unless mentioned otherwise) to demonstrate how to use ycrc_vglrun.
Note
If you need to run a hardware accelerated GUI application, you should first start a Remote Desktop on a GPU node, and then run the application from the shell in the Remote Desktop as shown below. We have not incorporated VirtualGL into the standalone interactive Apps on OOD that could benefit from VirtualGL. However, this could change in the future.
Use VirtualGL with the EGL back end
EGL is the default back end which ycrc_vglrun will choose to use if no option is provided. You can also add the -e
option to choose the EGL back end explicitly.
module load ParaView
ycrc_vglrun paraview
module load ParaView
ycrc_vglrun -e paraview
Use VirtualGL with the GLX back end
If your application cannot be rendered properly with the EGL back end, your next step is to try the GLX back end.
You should choose it explicitly with the -g option.
module load ParaView
ycrc_vglrun -g paraview
Run MATLAB with hardware OpenGL rendering
By default, MATLAB will use software OpenGL rendering. To run MATLAB with hardware OpenGL rendering,
add -nosoftwareopengl.
module load MATLAB
ycrc_vglrun matlab -nosoftwareopengl
Troubleshoot
nvidia-smi or vglrun cannot be found
You must submit your job to a GPU node. If you are using the Remote Desktop from OOD,
make sure you have specified gpu as 1 and partition as gpu or any other partition
with GPU nodes.
GLX back end is used by another application
If you get the following message when running your application with the GLX back end,
you need to add --exclude=nodename to Advanced options in the Remote Desktop OOD user interface
and resubmit Remote Desktop. Replace nodename with the actual node name from the message.
VirtualGL with the GLX back end is currently used by another application.
Please resubmit your job with
--exclude=c22n01