https://bugs.freedesktop.org/show_bug.cgi?id=101182

Bug ID: 101182 Summary: Reading amdgpu_pm_info causes stutter with Linux 4.12-rc Product: DRI Version: DRI git Hardware: Other OS: All Status: NEW Severity: normal Priority: medium Component: DRM/AMDgpu Assignee: dri-devel@lists.freedesktop.org Reporter: haagch@frickel.club

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/e097b91a85c85718576589402e... 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.