Graphics Card / CPU
AMD Catalyst Driver Version, and Driver History
Reproduced on 13.35 (14.3 beta 1.0 released 3/12/14), 13.30_rc3 (released 1/13/14), and 13.251
Linux. OpenSuse 13.1
Linux simcoe 3.11.10-7-desktop #1 SMP PREEMPT Mon Feb 3 09:41:24 UTC 2014 (750023e) x86_64 x86_64 x86_64 GNU/Linux
The memory system performance with Kaveri under Linux is very poor. Running the stream benchmark (linked below) I only see about 5 GB/s bandwidth. This should be 10-12 on a normal DDR3 system.
With further investigation, it seems that the power management features of the graphics driver are affecting the CPU performance. When I run aticonfig --odgc I see that the GPU DRAM frequency is set to 333 MHz (out of max 667).
However, if I run something compute intensive on the GPU (like ConstantBandwidth from the AMD APPSDK examples), the GPU memory frequency increases to 667. When I run the stream benchmark while the GPU is in high-performance mode I see the expected throughput (~10 GB/s).
Unfortunately, when I try to manually set the GPU memory frequency with aticonfig it tells me that my adapter is unsupported. "ERROR - ATI Overdrive(TM) is not supported on Adapter 0 - AMD Radeon(TM) R7 Graphics
Additionally, I did not see this problem with in Windows.
Motherboard or System Make & Model
Applications and Games
Confirmed with the stream benchmark (http://www.cs.virginia.edu/stream/) and other workloads.
Motherboard BIOS Version
System Memory Type & Amount
Kingston. 1333 MHz 16 GB in 2 DIMMs
I ran the same benchmark in Windows and saw about double the performance from Linux.
Any suggestions as to how to mitigate this issue?