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Date:      Tue, 21 Jan 2020 20:16:22 +0000
From:      bugzilla-noreply@freebsd.org
To:        bugs@FreeBSD.org
Subject:   [Bug 234455] CPU frequency scaling fails for multiple cores
Message-ID:  <bug-234455-227-a9IX2Kf1Cg@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-234455-227@https.bugs.freebsd.org/bugzilla/>
References:  <bug-234455-227@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D234455

--- Comment #5 from Conrad Meyer <cem@freebsd.org> ---
@Dave, did you try debug.acpi.disabled=3D"thermal"?  It seems bizarre that =
the
default dev.cpu.0.freq is 800.  Is that the case at boot, or was your initi=
al
description after running, say, powerd?  It might be that Coffeelake does n=
ot
really support est and needs Intel Speed Shift instead.  That is not yet in
tree but there is a work-in-progress patch: https://reviews.freebsd.org/D18=
028

@Erich, I suspect these are unrelated issues in that a different cpufreq dr=
iver
is used on Zen (hwpstate) and Intel (est).  But maybe there is some relatio=
n.

I do not recommend powerd and would suggest disabling it.  In fact, we shou=
ld
probably remove it from FreeBSD.  It is extremely legacy and only really wo=
rks
correctly on ancient single core devices.

I also don't recommend manual p-state setting via sysctl.  Modern CPUs do a
fantastic job of power saving with C states alone =E2=80=94 P-state throttl=
ing doesn't
get you much anymore.

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