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Date:      Fri, 28 Dec 2018 09:22:15 +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@https.bugs.freebsd.org/bugzilla/>

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

            Bug ID: 234455
           Summary: CPU frequency scaling fails for multiple cores
           Product: Base System
           Version: 12.0-RELEASE
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: bugs@FreeBSD.org
          Reporter: dfrg@xsmail.com

An intel i5-8400 processor has 6 cores. On both FreeBSD 11.2 and 12.0-RELEA=
SE
frequency scaling via both powerd or explicit sysctl is broken unless all b=
ut
one core is disabled via BIOS.

# sysctl dev.cpu.0.freq_levels
dev.cpu.0.freq_levels: 2801/65000 2800/65000 2700/61690 2500/55888 2400/527=
59
2200/47301 2100/44946 1900/39204 1800/37000 1700/34277 1500/29546 1400/27531
1200/22557 1100/20688 900/16549 800/14296

# sysctl dev.cpu.0.freq=3D2800
dev.cpu.0.freq: 800 -> 800

It appears cf_set_method() returns EPERM at sys/kern_cpu.c:287 and commenti=
ng
out that conditional restores frequency scaling when multiple cores are
enabled.

Whilst this ugly local patch suffices its obviously not correct and I'm not
sure how to proceed from here.

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