Date: Wed, 19 Dec 2001 15:13:42 -0800 (PST) From: Doug White <dwhite@resnet.uoregon.edu> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: <freebsd-current@FreeBSD.ORG> Subject: Re: Seeing a lot of 'microuptime() went backwards' messages during heavy disk I/O Message-ID: <Pine.BSF.4.33.0112191507080.36795-100000@resnet.uoregon.edu> In-Reply-To: <200112192259.fBJMxMF90892@apollo.backplane.com>
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On Wed, 19 Dec 2001, Matthew Dillon wrote: > I'm seeing a lot of this during heavy disk I/O (5 postmark benchmarks > running in parallel): > > microuptime() went backwards (44525.3954411 -> 44524.563978) > microuptime() went backwards (57425.4282241 -> 57424.766121) > microuptime() went backwards (57425.4282241 -> 57424.845844) > microuptime() went backwards (60724.4427887 -> 60724.686232) > microuptime() went backwards (60724.4427887 -> 60724.768808) > microuptime() went backwards (61685.4418845 -> 61685.102724) > microuptime() went backwards (61924.3906516 -> 61924.246151) > microuptime() went backwards (62344.3800035 -> 62344.415407) > > Anyone know what's up? This has been asked on just about every FreeBSD list since the printf was added. Use the archives, man! :) This is when you have a device generating too much interrupt latency -- enough to stall the RTC. Usually the offender is video cards, but in this case it could be your IDE controller. The usual fix is to try changing timecounters; sysctl kern.timecounter.hardware tells you what you're currently using. If you're on CURRENT, it's probably using ACPI. If you want to override it back to TSC, put 'hint.acpi_timer.0.disabled="1"' in your /boot/device.hints. Also try compiling with or without apm since this influences the timecounter as well (although if you're on SMP you might be stuck with the i8254). phk can clarify. :) Doug White | FreeBSD: The Power to Serve dwhite@resnet.uoregon.edu | www.FreeBSD.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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