Freeze due to performance_cx_lowest=LOW

disable apic (hint.apic.0.disabled="1"). I isolated this a little while
ago to the change to enable LAPIC timer. However, there is currently no
easy way to disable the LAPIC timer with APIC enabled so you have to
disable APIC. jhb@ and I have been discussing how to do this better but
no easy answers apparently.

--
Nate

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It must be

#

Right?

Thanks for pointing me out. FWIW, I tried different work-arounds
in my system and got the following results.

Set performance_cx_lowest to as high as C2 in rc.conf -- works.

Add hint.apic.0.disabled="1" to device.hints -- doesn't work, the
system still hangs. I can't see apic mentioned in the dmesg output
irrespective of the setting, but it must be there, given the results
of the next test.

Remove device apic from the kernel completely -- the system won't
halt, but it may suffer data corruption: once syslogd complained
about wrong syntax in its config, which I hadn't touched of course.
(Syslogd starts soon after cx_lowest was set to C3.) At last "cpu0:
too many short sleeps, backing off to C2" appears on the console,
and hw.acpi.cpu.cx_lowest goes up to C2 indeed.

Of course, I shouldn't rule out bugs in my hardware, it is quite
old, a plain vanilla AMD Athlon (Thunderbird) in an Epox EP-8K3AE
motherboard.

Nevertheless, given the problems other people have had, it might
be too early to have performance_cx_lowest=LOW as the _default_
setting. ACPI is a rather special area with some skilled developers
working in it, and encouraging everyone else in this way to fix it
makes little sense IMHO.

--
Yar

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It seems that at least hwpmc(4) depends on APIC for full functionality.

application_pgp-signature_part
1K

This problem has been discussed over on ACPI. It's a problem with the
local APIC timer which does not run in C3 or lower. Nate is looking at a
solution for the problem.

See his message on acpi@ on Sun, 07 May 2006 15:28:29 -0700.

The fixes are to either not use C3 (or C4 if it's available) or to
disable APIC.

For those who are not reading closely, DO NOT confuse APIC with ACPI!
They only look similar.

If the system is UP, there is no really no need for APIC.
--
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: Phone: +1 510 486-8634

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I noticed the same behaviour, but I haven't looked into it yet.


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Quoting Yar Tikhiy <
AOL...

I use performance_cx_lowest=C2 as a workaround.

% sysctl hw.acpi.cpu
hw.acpi.cpu.cx_supported: C1/0 C2/90 C3/900
hw.acpi.cpu.cx_lowest: C2
hw.acpi.cpu.cx_usage: 3.73% 96.26% 0.00%

Bye,
Alexander.

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