Date: Mon, 30 Jun 2008 10:38:26 -0400 From: "Bob Johnson" <fbsdlists@gmail.com> To: "David Allen" <the.real.david.allen@gmail.com> Cc: freebsd-questions@freebsd.org Subject: Re: calcru: runtime went backwards errors Message-ID: <54db43990806300738n33d10fe7te27b9c9f3c295a4@mail.gmail.com> In-Reply-To: <2daa8b4e0806300627s39d49347r9e0e5675e4c25088@mail.gmail.com> References: <2daa8b4e0806300627s39d49347r9e0e5675e4c25088@mail.gmail.com>
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On 6/30/08, David Allen <the.real.david.allen@gmail.com> wrote: > I've been seeing errors like the following appearing: > > Jun 30 03:13:57 ford kernel: calcru: runtime went backwards from 261 > usec to 258 usec for pid 516 (devd) [...] > Jun 30 03:13:57 ford kernel: calcru: runtime went backwards from 486 > usec to 481 usec for pid 0 (swapper) > > and narrowed down the cause to openntpd. > > Do these errors fall into the Mostly Harmless category? It's probably just an annoyance, unless it is happening so often it causes other problems. The FreeBSD FAQ used to have a nice explanation of this, but it has been replaced by a discussion that simply assumes the problem is caused by the Intel SpeedStep implementation on your motherboard: http://www.freebsd.org/doc/en_US.ISO8859-1/books/faq/troubleshoot.html#Q5.24. But in general, this error can be caused by several things, including a device that is slow to respond to interrupts. One thing that often helps on SMP systems is to make sure your timecounter isn't using TSC: $ sysctl kern.timecounter kern.timecounter.tick: 1 kern.timecounter.choice: TSC(-100) HPET(900) ACPI-fast(1000) i8254(0) dummy(-1000000) kern.timecounter.hardware: ACPI-fast [...] - Bob
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