Topic Title: Poor memory performance on Linux with APUs
Topic Summary: GPU power management hurts CPU performance on Linux with new APU
Created On: 03/19/2014 04:21 PM
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 03/19/2014 04:21 PM
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powerjg
Peon

Posts: 2
Joined: 03/19/2014

Graphics Card / CPU

A10-7850K

 

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

 

Operating System

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

 

Issue Details

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

Gigabyte GA-F2A88XM-D3H

 

Applications and Games

Confirmed with the stream benchmark (http://www.cs.virginia.edu/stream/) and other workloads.

 

Motherboard BIOS Version

Fb6

 

System Memory Type & Amount

Kingston. 1333 MHz 16 GB in 2 DIMMs

 

Additional Details

I ran the same benchmark in Windows and saw about double the performance from Linux.

 

Any suggestions as to how to mitigate this issue?

 03/31/2014 10:37 AM
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powerjg
Peon

Posts: 2
Joined: 03/19/2014

DEAR PEOPLE OF THE FUTURE:

I reflashed an older version of the gigbyte BIOS (F5) and this problem was solved. Just in case someone sees this problem in the future.

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