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Adept I

clGgetDeviceIDs suddenly very slow

We are currently developing an OpenCL application on Windows 10 (Visual Studio 2017) but have noticed that the OpenCL performance has recently degraded, with the call to clGetDeviceIDs now taking around 10 seconds. Subsequent calls take 2-3 seconds (until we restart our application).

This has only started recently, but we can't figure out what has changed to cause this. It doesn't seem to be an issue in our code as we've tried a version from a couple of weeks ago that was known to work, and this is exhibiting the same delay.

I'm assuming something has changed on the PC but we don't know what. It isn't the graphics drivers, as these haven't changed for several months. Ditto for Windows updates.

The only other change made recently was the installation of Visual Studio 2013 (to work on some unrelated legacy stuff). Is it possible this could have messed up runtimes required by OpenCL? Looking for any suggestions as to where to look or how to diagnose the issue further.

The graphics card is a Radeon Pro WX7100 by the way.

1 Reply
Big Boss

From the above description, it's difficult to point out anything for this slowdown. As you mentioned that the driver hasn't been changed for long, so I guess it's not a driver issue here. Anyway, here are my suggestions:

  1. Try the latest driver and then observe the performance.
  2. Use some profiling tools to get more detailed timing information about the OpenCL APIs. For example, CodeXL's API timeline trace can be used for this. If you see any unexpected time gap in the API timeline trace, please share the profiling data with us. 
  3. As you said that installation of VS 2013 could be a possible reason for the slowdown, please uninstall it and then try. It would help to confirm your point.