[Bug 90112] [BSW bisected] Lightsmark/CS/ Portal/ Half Life 2 games performance decreased by 15%-45%

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=90112

--- Comment #20 from Eero Tamminen <eero.t.tamminen at intel.com> ---
kernel Pstate driver "powersave" governor can currently do funky stuff (switch
tasks from high freq core to low freq core for no apparent reason) on BSW for
workloads that are both CPU & GPU bound and TDP limited, like I think the
indicated Source engine games are.  And CPU running at low speed can cause also
GPU to run at low speed.

Unless one is tracking both GPU & CPU frequencies and task migration in tests,
it might be better to check these kind of optimizations first with:
- test being fixed on single core with "taskset" command, and/or
- both CPU & GPU being fixed to (non-turbo) speed (in BSW C0 case, one could
try e.g. 1.5Ghz for CPU and 500Mhz for GPU)

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