Date: Tue, 05 Feb 2002 18:07:34 +0100 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: John Polstra <jdp@polstra.com> Cc: hackers@FreeBSD.ORG, jhb@FreeBSD.ORG Subject: Re: A question about timecounters Message-ID: <90115.1012928854@critter.freebsd.dk> In-Reply-To: Your message of "Tue, 05 Feb 2002 09:06:51 PST." <200202051706.g15H6pp03714@vashon.polstra.com>
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In message <200202051706.g15H6pp03714@vashon.polstra.com>, John Polstra writes: >In article <XFMail.020204234209.jhb@FreeBSD.org>, >John Baldwin <jhb@FreeBSD.ORG> wrote: >> >> > like, "If X is never locked out for longer than Y, this problem >> > cannot happen." I'm looking for definitions of X and Y. X might be >> > hardclock() or softclock() or non-interrupt kernel processing. Y >> > would be some measure of time, probably a function of HZ and/or the >> > timecounter frequency. >> >> X is hardclock I think, since hardclock() calls tc_windup(). > >That makes sense, but on the other hand hardclock seems unlikely to be >delayed by much. The only thing that can block hardclock is another >hardclock, an splclock, or an splhigh. And, maybe, splstatclock. I'm >talking about -stable here, which is where I'm doing my experiments. Try swapping so you use the RTC for hardclock & statclock. Let the i8254 run with 65536 divisor and do only timecounter service. That would be a very interresting experiment. -- 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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