[Bug 59895] New: Weird clocking issue with atom laptop with gen3 intel graphics

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=59895

          Priority: medium
            Bug ID: 59895
          Assignee: chris at chris-wilson.co.uk
           Summary: Weird clocking issue with atom laptop with gen3 intel
                    graphics
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
          Severity: enhancement
    Classification: Unclassified
                OS: Linux (All)
          Reporter: sergio.callegari at gmail.com
          Hardware: x86 (IA32)
            Status: NEW
           Version: git
         Component: Driver/intel
           Product: xorg

Hi,

this is a minor thing, an 'enhancement'.

On this rather underpowered machine, if you run something that is intensive
only for the GPU, but not for the CPU the opengl rendering speed becomes
orrible. And you have a weird situation where loading the machine improves the
graphical performance rather than reducing it.

Sample case using glxgears. I know that it is not a benchmark, but here I am
using it precisely because it loads the GPU and only very modestly the CPU.

Due to vsync, glxgears should give approximately 60 fps.

If I start glxgears, with nothing else running, I see 60fps for the first 5
seconds, then 20-30 fps. At this point, if I launch something else that makes
the cpu work, glxgears rises back to 60fps, if I stop the extra CPU load
glxgears goes back to 30fps.

I suspect that when the cpu is not loaded enough the CPU clock drops down also
bringing down the GPU clock or the memory clock with it and this degrades the
GPU performance a lot. Should the GPU driver be able to tell the kernel 'I'm
making the GPU work hard, do not drop down the clock speed?'

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