Date: Wed, 28 Sep 2011 15:51:56 +0300 From: Alexander Motin <mav@FreeBSD.org> To: =?UTF-8?B?RGFnLUVybGluZyBTbcO4cmdyYXY=?= <des@des.no> Cc: current@freebsd.org Subject: Re: 9 hangs with idletick = 0 Message-ID: <4E83186C.4080707@FreeBSD.org> In-Reply-To: <86bou59gpf.fsf@ds4.des.no> References: <86bou59gpf.fsf@ds4.des.no>
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Dag-Erling Smørgrav wrote: > I have a box running a GENERIC kernel from September 25th that freezes > completely for a few seconds, up to a minute or so, at random intervals. > Sooner or later it freezes permanently (or at least longer than I am > willing to wait for it to unfreeze) and must be power-cycled, as it does > not respond to Ctrl+Alt+Esc. Network activity (such as downloading ISO > images over a 6 Mbps DSL line) seems to aggravate the issue. The > problem goes away if I enable idletick. > > I had the same problems with a slightly customized kernel (basically > GENERIC with unused drivers removed) built from September 10th sources; > I switched to GENERIC to eliminate the possibility that my kernel config > was to blame. > > Prior to that, the machine ran a kernel with the same custom config > built from April 27th sources without any trouble whatsoever, so the > issue must have been introduced sometime between April 27th and > September 10th. > > The machine is an Intel Core 2 Duo E6600 with 4 GB RAM. > > Relevant sysctls: > > kern.eventtimer.choice: HPET(450) HPET1(440) HPET2(440) LAPIC(400) i8254(100) RTC(0) > kern.eventtimer.et.LAPIC.flags: 15 > kern.eventtimer.et.LAPIC.frequency: 0 > kern.eventtimer.et.LAPIC.quality: 400 > kern.eventtimer.et.HPET.flags: 3 > kern.eventtimer.et.HPET.frequency: 14318180 > kern.eventtimer.et.HPET.quality: 450 > kern.eventtimer.et.HPET1.flags: 3 > kern.eventtimer.et.HPET1.frequency: 14318180 > kern.eventtimer.et.HPET1.quality: 440 > kern.eventtimer.et.HPET2.flags: 3 > kern.eventtimer.et.HPET2.frequency: 14318180 > kern.eventtimer.et.HPET2.quality: 440 > kern.eventtimer.et.i8254.flags: 1 > kern.eventtimer.et.i8254.frequency: 1193182 > kern.eventtimer.et.i8254.quality: 100 > kern.eventtimer.et.RTC.flags: 17 > kern.eventtimer.et.RTC.frequency: 32768 > kern.eventtimer.et.RTC.quality: 0 > kern.eventtimer.periodic: 0 > kern.eventtimer.timer: HPET > kern.eventtimer.idletick: 1 > kern.eventtimer.singlemul: 2 > kern.timecounter.tick: 1 > kern.timecounter.choice: TSC-low(1000) i8254(0) HPET(950) ACPI-fast(900) dummy(-1000000) > kern.timecounter.hardware: TSC-low > kern.timecounter.stepwarnings: 0 > kern.timecounter.tc.ACPI-fast.mask: 16777215 > kern.timecounter.tc.ACPI-fast.counter: 6800584 > kern.timecounter.tc.ACPI-fast.frequency: 3579545 > kern.timecounter.tc.ACPI-fast.quality: 900 > kern.timecounter.tc.HPET.mask: 4294967295 > kern.timecounter.tc.HPET.counter: 3991486344 > kern.timecounter.tc.HPET.frequency: 14318180 > kern.timecounter.tc.HPET.quality: 950 > kern.timecounter.tc.i8254.mask: 65535 > kern.timecounter.tc.i8254.counter: 27169 > kern.timecounter.tc.i8254.frequency: 1193182 > kern.timecounter.tc.i8254.quality: 0 > kern.timecounter.tc.TSC-low.mask: 4294967295 > kern.timecounter.tc.TSC-low.counter: 4021161618 > kern.timecounter.tc.TSC-low.frequency: 9375191 > kern.timecounter.tc.TSC-low.quality: 1000 > kern.timecounter.smp_tsc: 1 > kern.timecounter.invariant_tsc: 1 I am surprised that system doesn't react on keyboard. If something happen to the event timer, then system should get time and interactivity problems, but not freeze completely. > Let me know if you need anything else. I can try to bisect, but it will > take time since the freezes are tricky to reproduce. The only change in event timers in last months I remember was in SVN rev 224919. You may try to revert it. But it was supposed to fix rare problem, not create new. I am not sure how can it harm. If short freezes you've descrived happens often enough, you may try to log them down with enabling KTR_SPARE2 ktr event type and disabling logging within few seconds after such freeze happened. -- Alexander Motin
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