[Bug 110750] New: Hangouts in ChromeOS pegs the GPU at max frequency

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=110750

            Bug ID: 110750
           Summary: Hangouts in ChromeOS pegs the GPU at max frequency
           Product: DRI
           Version: DRI git
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: major
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: nathan.d.ciobanu at linux.intel.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Running Hangouts on ChromeOS pegs the GPU at max frequency while the camera is
enabled. 

A quicker way to reproduce this issue is to access this URL in the Chrome
browser: https://appr.tc/?debug=loopback&vsc=vp8&vrc=vp8

A bisect of the ChromeOS kernel releases has pointed to this patch as the point
when this issue started occurring:
"7b92c1bd0540 - drm/i915: Avoid keeping waitboost active for signaling threads"
which has been backported to chromeos-4.4 and later kernels. 

It is quite evident what the patch and the subsequent work intended to do but a
user space client like Hangouts seems to increase power consumption with no
benefit from the increased performance - IIUC. The GPU utilization is between
30 to 40% while the frequency is max at 1050MHz (on my i7 KBL-Y Pixelbook).

As an experiment we capped the max GT frequency to 500MHz and saw a drop of
about 2W with no hit to performance. 

Question is: how can we improve the power consumption given the above patch in
the Hangouts case? 

Note;
On Ubuntu running Hangouts in the Chrome browser we see more GPU frequency
scaling but power consumption is still really high. 

Since this is more of a question I haven't included logs yet but let me know if
you want to see something and I will upload.

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