Date: Mon, 29 May 2006 12:57:23 +0400 From: Yar Tikhiy <yar@comp.chem.msu.su> To: Kevin Oberman <oberman@es.net> Cc: njl@freebsd.org, freebsd-current@freebsd.org Subject: Re: Freeze due to performance_cx_lowest=LOW Message-ID: <20060529085723.GA98288@comp.chem.msu.su> In-Reply-To: <20060528221154.7351845043@ptavv.es.net> References: <20060528142039.GA80613@comp.chem.msu.su> <20060528221154.7351845043@ptavv.es.net>
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On Sun, May 28, 2006 at 03:11:54PM -0700, Kevin Oberman wrote: > > > > A while ago I installed CURRENT on my new home PC and noticed that > > the system would hang hard at the boot time soon after setting > > cx_lowest to C3 according to the LOW setting in /etc/defaults/rc.conf. > > The last message on the console was each time: Mounting NFS file > > systems:. Setting performance_cx_lowest to HIGH made the problem > > go away. > > > > Now I've just tried again to return performance_cx_lowest to its > > modern default setting in a fresh CURRENT and found that the bug > > is still there. Is it due to my ACPI HW being broken? I'll be > > glad to show relevant debug output from my ACPI if told how to get > > it. Thanks. > > 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. It must be http://lists.freebsd.org/pipermail/freebsd-acpi/2006-May/002742.html Right? > 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. 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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