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Date:      Sat, 27 Dec 2008 17:13:58 +1100 (EST)
From:      Ian Smith <smithi@nimnet.asn.au>
To:        Garrett Cooper <yanefbsd@gmail.com>
Cc:        acpi <acpi@freebsd.org>
Subject:   Re: Problem on AMD64
Message-ID:  <20081227160941.I29108@sola.nimnet.asn.au>
In-Reply-To: <7d6fde3d0812261912r1d5abd6cic1513f11cc59f1c5@mail.gmail.com>
References:  <20081221233822.7E92545020@ptavv.es.net> <49500088.2080609@bigfoot.com> <7d6fde3d0812221315s4d03e15dw4b84679b98a6308f@mail.gmail.com> <49534F10.7040305@bigfoot.com> <7d6fde3d0812261912r1d5abd6cic1513f11cc59f1c5@mail.gmail.com>

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On Fri, 26 Dec 2008, Garrett Cooper wrote:
 > On Thu, Dec 25, 2008 at 1:14 AM, David van Kuijk <dynasore@bigfoot.com> wrote:
 [..]
 > >> Look into the following sysctls:
 > >>
 > >> hw.acpi.cpu.cx_lowest
 > >> hw.acpi.cpu.cx_highest
 > >>
 > >
 > > I tried to find out what I can do with those sysctls.
 > > hw.acpi.cpu.cx_highest is not available on my system.

I don't think it exists; C1 state is always available AFAIK.

 > > hw.acpi.cpu.cx_lowest is available and can be set. Are you suggesting I
 > > should set it to C2 or C3???

Give it a try.  Setting it to C3 won't hurt, whether it's used or not.  

First check dev.cpu.%d.cx_supported which shows the supported states.

There's also dev.cpu.%d.cx_lowest (showing the lowest state used) and 
dev.cpu.%d.cx_usage, showing percentage time spent in various states.

If it winds up helping, set performance_cx_lowest=C3 (or C2 or just 
'LOW') in /etc/rc.conf .. see /etc/rc.d/power_profile for how it's used.

 > > A second question;
 > > When I use powerd it switches between clock-frequencies of 1800 and 1000
 > > correctly. Is it possible to set a sysctl so that even lower frequencies are
 > > supported, or are the supported frequencies simply dictated by the
 > > processors in my server (in my case Opteron 1.8 GHz)?

Show us 'sysctl dev.cpu' .. and check dmesg for which if any of acpi 
cpufreq drivers are being used.  Maybe it's powernow for the Opteron?

'sysctl dev | grep settings' may show something about the drivers used.

 > > Cheers,
 > > David
 > 
 > Dog gone it I've been typo'ing that for a long time (see
 > http://lists.freebsd.org/pipermail/cvs-all/2003-November/036370.html).
 > 
 > Try:
 > 
 > hw.acpi.cpu.cx.lowest
 > hw.acpi.cpu.cx.highest
 > 
 > Note that the underscores were in fact periods.

I don't think that suggestion was ever implemented .. there have been 
quite some changes with all this, in fact I'm not sure the acpi(4) man 
is up to date (looking at 7-STABLE manuals online) .. it still talks 
about hw.acpi.cpu.{cx_supported,cx_lowest,cx_usage} where cx_supported 
and cx_usage have moved to dev.cpu.%d .. all a bit confusing.

cheers, Ian



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