Date: Mon, 29 Jun 1998 08:56:26 +0200 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: John Hay <jhay@mikom.csir.co.za> Cc: freebsd-smp@FreeBSD.ORG Subject: Re: time problem? Message-ID: <9570.899103386@critter.freebsd.dk> In-Reply-To: Your message of "Sat, 28 Jun 1998 20:14:48 %2B0200." <199806281814.UAA09849@zibbi.mikom.csir.co.za>
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In message <199806281814.UAA09849@zibbi.mikom.csir.co.za>, John Hay writes: >I have an 1 pps signal connected to DCD of my serial port. What source do you use for this ? >---------------- >A: 899000790.981073054 #29011 D: 1.000004191 >A: 899000792.826104370 #29012 D: 1.845031316 >A: 899016109.813482765 #44329 D: 0.999940488 >A: 899016111.668519664 #44330 D: 1.855036899 >---------- > >So on sequence numbers 29012 and 44330, I have gained .85 seconds >in the space of a second. For the 15000 seconds between 29012 and >44329 there were no glitches or jumps. Now, one source of this could be interrupts diasabled for too long, since your timestamps depend on the sio interrupt that would be my primary suspect. Is there anything that makes it happen more often ? >Is this function, i8254_get_timecount(), used by something that can >have a permanent effect on time? I thought it was only used by >nanotime() and microtime() to get the offset from the previous tick, >but that it wasn't used to calculate the next tick? It shouldn't be, apart from "tco_forward()" which bumps the timecounters reference time once each hardclock() (kern/kern_clock.c) -- Poul-Henning Kamp FreeBSD coreteam member phk@FreeBSD.ORG "Real hackers run -current on their laptop." "ttyv0" -- What UNIX calls a $20K state-of-the-art, 3D, hi-res color terminal To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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