Date: Fri, 17 Feb 2012 11:39:21 -0500 From: Jung-uk Kim <jkim@FreeBSD.org> To: freebsd-stable@FreeBSD.org Cc: Alexander Kabaev <kan@freebsd.org>, "threads@freebsd.org" <threads@freebsd.org>, Julian Elischer <julian@freebsd.org>, David Xu <davidxu@freebsd.org>, Andriy Gapon <avg@freebsd.org> Subject: Re: pthread_cond_timedwait() broken in 9-stable? [possible answer] Message-ID: <201202171139.23610.jkim@FreeBSD.org> In-Reply-To: <4F3DB3AE.5000109@freebsd.org> References: <4F3C2671.3090808__7697.00510795719$1329343207$gmane$org@freebsd.org> <4F3DA27A.3090903@freebsd.org> <4F3DB3AE.5000109@freebsd.org>
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On Thursday 16 February 2012 08:55 pm, Julian Elischer wrote: > kern.timecounter.tick: 1 > kern.timecounter.choice: TSC-low(1000) i8254(0) HPET(950) > ACPI-fast(900) dummy(-1000000) > kern.timecounter.hardware: ACPI-fast > kern.timecounter.stepwarnings: 0 > > switching the machine from TSC_low to ACPI-fast fixes the problem. > > in 8.x it used to default to ACPI > but I used to switch it to "TSC" to get better performance. > > I wonder why TSC-low is now bad to use.. > maybe the TSCs are not as well sychronised as they were in 8.x? Can you please show us verbose dmesg output? FYI, TSC and TSC-low are not very different. TSC-low is just lower resolution version of TSC for SMP. Only difference is, we have automated your timecounter choice, i.e., if TSCs seem reasonably well-synchronized, select it by default but give lower resolution. In other words, if your TSC timecounter was never going backwards previously, TSC-low timecounter won't, guaranteed. So, the root cause should be somewhere else. Jung-uk Kim
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