A stutter once wouldn't be so bad, but apps like radeon-profile repeatedly read this file, so rendering stutters constantly. You will have a hard time spotting it in the average fps graph, but with my (still very inaccurate) low-fps patch at https://github.com/ChristophHaag/mesa-mesa/commit/e097b91a85c85718576589402e075e7f5668e68c it's very visible that there is at least one frame that's delayed a lot each time amdgpu_pm_info is read. The GPU load does give an independent hint that something is wrong though. To reproduce: run glxgears run sudo watch --interval=.3 cat /sys/kernel/debug/dri/0/amdgpu_pm_info observe stuttering in glxgears. RX 480, Linux 4.12-rc2. I haven't tested 4.11 to confirm, but if I remember correctly, this happens in mainline since 4.12.
Created attachment 131501 [details] screenshot showing the stuttering in the HUD
amdgpu_pm_info exposes power statistics now which causes a small delay to sample the power usage. If you want to poll the current clocks, there is an ioctl interface to query this information.
Can this be done asynchronously in the driver so it doesn't impact the rendering of 3D applications?
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