Bug 34377

Summary: Radeon driver PCIe throughput not up to PCIe2.0 levels
Product: Mesa Reporter: luc <lucvermoesen>
Component: Drivers/DRI/R600Assignee: Default DRI bug account <dri-devel>
Status: RESOLVED WONTFIX QA Contact:
Severity: normal    
Priority: medium    
Version: git   
Hardware: x86 (IA32)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:
Attachments: test data and test program for PCIe gen2 issue

Description luc 2011-02-17 01:12:43 UTC 
Created attachment 43476 [details]
test data and test program for PCIe gen2 issue

On an HD5450 card, when I load the latest gallium3D driver with kernel 2.6.38-rc4 and firmware I got from http://people.freedesktop.org/~agd5f/radeon_ucode/ , this together with the latest git checkouts for X and modules (and thus also xf86-video-ati) and latest mesa git checkout that has been built with –enable-gallium-r600

installing the radeon kernel module with 
modprobe radeon modeset=1 pcie_gen2=1
 

Then I get 0.5GB/s CPU->GPU 
From GPU -> CPU, I get about the same 0.5GB/s.

When I load the fglrx ati proprietary driver (11.1) for the 5450 card, then I get throughputs of about 2GB/s in both directions. 

Running the same test in same environment on the HD5970 
with the gallium drivers and kernel mode setting and pcie_gen2 activation, i get about the same figures as above.
With fglrx for 5970, then 5970 only performs well in CPU->GPU with about 2GB/s and only 0.5GB/s in GPU->CPU direction 

I have included the test and configuration output for both cases (fglrx and radeon) and also code for the testprogram might you want to reproduce this case.
Comment 1 Andreas Boll 2012-11-02 16:37:56 UTC 
Note: classic r600 driver has been abandoned.
Please use r600g (gallium driver) instead.

Is this still an issue with a newer driver/kernel?
Comment 2 commiethebeastie 2013-05-12 07:38:52 UTC 
It`s all OK, you video card is very limited by GPU perfomance.
Comment 3 commiethebeastie 2013-05-12 07:42:24 UTC 
2011-02-17 01:12:43 UTC 

Ohhh~
Comment 4 Alex Deucher 2013-05-12 14:03:32 UTC 
pcie 2 mode has been enabled by default for a while now.  Also, most recent motherboards bring up the card in pcie 2 mode by default. HD5450 cards tend to have slower ddr3 vram rather than the faster gddr5 as higher end cards do.  Is this still an issue with a more recent kernel and mesa?
Comment 5 Andreas Boll 2014-07-07 16:04:23 UTC 
The classic r600 driver has been abandoned long ago.
It was replaced by the Gallium driver r600g.

If you have issues with r600g please file a new bug report with component Drivers/Gallium/r600

Thanks.

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