[Bug 234455] CPU frequency scaling fails for multiple cores

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=234455

--- Comment #5 from Conrad Meyer <cem at freebsd.org> ---
@Dave, did you try debug.acpi.disabled="thermal"?  It seems bizarre that the
default dev.cpu.0.freq is 800.  Is that the case at boot, or was your initial
description after running, say, powerd?  It might be that Coffeelake does not
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/D18028

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

I do not recommend powerd and would suggest disabling it.  In fact, we should
probably remove it from FreeBSD.  It is extremely legacy and only really works
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 — P-state throttling doesn't
get you much anymore.

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