[Bug 107410] [SKL] Up to 20% performance regression in GpuTest Triangle, due to 2x higher CPU power usage

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=107410

--- Comment #8 from Eero Tamminen <eero.t.tamminen at intel.com> ---
(In reply to Srinivas Pandruvada from comment #6)
> First check if you have
> /sys/devices/system/cpu/intel_pstate/hwp_dynamic_boost == 1
> Unfortunately some Xeon E3 reused DESKTOP CPU ID.

It's "1" on the regressing SKL machines, and "0" on the "U" one that didn't
regress.


> If yes, as Chris suggested, try
> #echo 0 >  /sys/devices/system/cpu/intel_pstate/hwp_dynamic_boost
> 
> If this fixes

At least the largest GpuTest Triangle regression disappears.


> try the attached patch.

I'm running the full set of benchmarks with this, so it takes a while.  I'll
report  results tomorrow.


> After this patch should be 
> /sys/devices/system/cpu/intel_pstate/hwp_dynamic_boost == 0 if your platform
> is not a E3.

With the patch it's "0".


(In reply to Srinivas Pandruvada from comment #7)
> Also do test on clear Linux, which always runs in performance mode?

Why?  I assume this is not just to test performance governor [1]...


1. We're tracking upstream Git versions, not older distro versions of SW, so we
build our own git versions of (drm-tip) kernel and rest of the 3D stack, and
use those also on Clear Linux (currently we use Clear only on BXT).

2. You need to define what you mean by "Clear Linux".

It updates frequently and at least I haven't yet found a way to determine what
its packages have actually been built from/with.  Its package management
doesn't seem to provide the basic information of:
- which exact sources
- what patches
- compile options
Are used to build a package.


[1] We switched to powersave governor a while because it gives slightly better
performance in (3D) benchmarks than Clear Linux default "performance" governor,
and didn't regress in any of our (3D) benchmarks. Besides, with Francisco's
P-state improvements applied on top of it, (3D / IGP) perf improves very
noticeably (only) with powersave.

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