Why The R9 290 & Other Select Radeon GPUs Are Performing Miserably On Linux 4.7

Written by Michael Larabel in Radeon on 20 June 2016 at 09:47 AM EDT. 22 Comments
With this weekend's 5-Way Mesa 12.1-dev + Linux 4.7 Git Radeon Comparison and other tests I've done on Linux 4.7 Git with Radeon hardware, the R9 290 has regressed to the point of performing noticeably worse than other AMD GCN GPUs... Many other Phoronix readers with different Rx 200/300 graphics cards have also confirmed their graphics cards performing poorly on Linux 4.7.

It's a regression introduced by Linux 4.7. I thought I already did a post explaining the apparent cause, but it seems to have never left my queue. Anyhow, on the same system with a Radeon R9 290 "Hawaii", here's the performance difference between Linux 4.6 and 4.7:
Linux 4.7 R9 290 Regression

Linux 4.7 R9 290 Regression

Linux 4.7 R9 290 Regression

While some have speculated that this is some Ubuntu issue, a bug relating to a problem with the Nine state tracker (even though I never use it...), etc, in reality this appears to be just a DPM (Dynamic Power Management) regression with at least Hawaii GPUs on Linux 4.7. When looking at the dmesg between Linux 4.6 and 4.7 Git, there is now a DPM error at boot time. [drm:ci_dpm_set_power_state [radeon]] *ERROR* ci_upload_dpm_level_enable_mask failed. So presumably, the GPU is stuck in a lower-power state rather than its highest performance state / frequency.

So if your system too has been slowed down by Linux 4.7, I'd suggest taking a look at your dmesg to see if it too mentions any DPM errors. Hopefully the regression is addressed prior to Linux 4.7 final and at least isn't some Ubuntu issue or any of the number of other theories I've seen voiced in the forums and elsewhere in recent days.
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Michael Larabel

Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via MichaelLarabel.com.

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