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.