Date: Tue, 05 Feb 2002 19:58:35 +0100 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: John Polstra <jdp@polstra.com> Cc: hackers@freebsd.org Subject: Re: A question about timecounters Message-ID: <91801.1012935515@critter.freebsd.dk> In-Reply-To: Your message of "Tue, 05 Feb 2002 10:51:37 PST." <200202051851.g15IpbU04184@vashon.polstra.com>
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In message <200202051851.g15IpbU04184@vashon.polstra.com>, John Polstra writes: >In article <91477.1012934678@critter.freebsd.dk>, >Poul-Henning Kamp <phk@critter.freebsd.dk> wrote: >> In message <200202051830.g15IUq004143@vashon.polstra.com>, John Polstra writes: >> >In article <200202051826.g15IQDt04095@vashon.polstra.com>, >> >John Polstra <jdp@polstra.com> wrote: >> > >> >Another interesting thing is that the jumps are always 7.7x seconds >> >back -- usually 7.79 seconds. This is even true with more data points >> >from two different machines. >> >> Yes, I noticed, but didn't dare draw conclusions based on two data points. > >It's pretty consistent -- always 7.7somthing. > >> This points to an arithmetic overflow (ie: point 3 in my previous email) > >Yes, I think you're onto something now. It's a 550 MHz. machine, so >the TSC increments every 1.82 nsec. And 1.82 nsec * 2^32 is 7.81 >seconds. :-) In that case I'm almost willing to put an AnchorSteam on microuptime() being interrupted for more than good is in which case the splhigh() should cure it. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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