Use OpenCL on AMD APU but use discrete GPU for the X server

Question

Is it possible to enable OpenCL on an A10-7800 without using it for the X server? I have a Linux box that I use for GPGPU programming. A discrete GEForce 740 card is used for both the X server and running OpenCL & Cuda programs I develop. I would also like the option of running OpenCL code on the APU's integrated GPU cores.

Everything I've read so far implies that if I want to use the APU for OpenCL, I have to install Catalyst and, AFAIK, that means using it for the X server. Is this true? Would there be an advantage to using the APU for my X server and using the GEForce solely for GPGPU code?

Gambeson

If x server is 64 bit, you could try 32 bit driver for APU so it is not seen by x-server? – Fourlegged

Answer 1

I had a similar goal, so I've built a system with AMD APU (4 regular cores + 6 GPUs) and Nvidia discrete graphics board. Sorry to say it wasn't easy to make it work, so I asked a question on the Ask Ubuntu forum, didn't get any answers, experimented a lot with hardware and software setup, and finally have posted my own answer to my question.

I'll describe my setup again here - who knows, what might happen with my auto-answered question on the Ask Ubuntu?

At first, I had to enable the integrated graphics hardware via a BIOS flag. This flag is called IGFX Multi-Monitor on my motherboard (ASUS A88X-PRO).

The second step was to find a right mix of a low-level graphics driver and high-level OpenCL implementation. The low-level driver for AMD processors is called AMD Catalyst and has a file name fglrx. I didn't install this driver from the Ubuntu software center - instead I used a version 15.302, directly downloaded from the AMD site. I had to install a significant number of prerequisites for this driver. The most important finding was that I had to skip running the aticonfig command after the fglrx installation - this command actually configures the X server to use this driver for graphics output, and I didn't want that.

Then I've installed the AMD SDK Ver 3.0 (release 130.136, earlier releases didn't work with my fglrx) - it's the OpenCL implementation from AMD. The clinfo command reports both CPUs and GPUs with correct number of cores now.

So, I have a hybrid AMD processor, supported by the OpenCL, with all the graphics output, supported by a discrete graphics card with Nvidia processor.

Good luck!

Red

Thanks for the answer. Your situation closely mirrors mine and the information you provided will certainly get me further down the road when I try it out. Or else get me in deeper over my head! :) – Gambeson

Finally got around to trying HEKTO's advice and got close. Very close. When I boot, I can run clinfo and it reports that there are two platforms available - the NVidia card and the APU. But subsequent attempts to run clinfo or oclDeviceQuery result in a segfault. Searching the web shows that this may be a known issue. I'm sure it isn't helped that I'm running Linux Mint, which isn't really a supported platform for what I want to do but the fact that I'm close gives me hope. – Gambeson

Answer 2

I maintain a Linux server (OpenSUSE, but the distribution shouldn't matter) containing both NVIDIA and (a discrete) AMD GPU. It's headless, so technically I do not know whether the X server will create additional problems, but I don't think so. You can always configure xorg.conf to use exactly the driver you want. Or for that matter: install Catalyst, but delete the X server driver file itself, which is not the same thing that you need for OpenCL.

There is one problem with a mixed-vendor system that I noticed, however: AMDs OpenCL driver (ICD) will go spelunking for a libGL.so library, I guess in order to do OpenCL/OpenGL-interop. If it finds any of the NVIDIA-supplied libGL.so's, it will get confused and hang - at least on my machine. I "solved" this by deleting all libGL.so's (I do not need it on a headless compute server), but that might not be an acceptable solution for you. Maybe you can arrange things such that the AMD-supplied libGL.so's take precedence, possibly by installing the AMD driver last.

Guerrilla