From owner-freebsd-hackers Fri Sep 15 2: 2:16 2000 Delivered-To: freebsd-hackers@freebsd.org Received: from mail-04-real.cdsnet.net (mail-04-real.cdsnet.net [63.163.68.109]) by hub.freebsd.org (Postfix) with SMTP id 6FA1A37B423 for ; Fri, 15 Sep 2000 02:02:11 -0700 (PDT) Received: (qmail 45612 invoked from network); 15 Sep 2000 09:02:03 -0000 Received: from apocalypse.cdsnet.net (63.163.68.5) by mail-04-real.cdsnet.net with SMTP; 15 Sep 2000 09:02:03 -0000 Date: Fri, 15 Sep 2000 02:02:03 -0700 (PDT) From: Jaye Mathisen X-Sender: mrcpu@apocalypse.cdsnet.net To: Poul-Henning Kamp Cc: current@FreeBSD.ORG, hackers@FreeBSD.ORG Subject: Re: looking for "microuptime went backwards" victims... In-Reply-To: <53059.968085674@critter> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG I get it on my newsserver pretty much every night when expire runs. 12 IDE drives on 3 Promise controllers. I was just actually about to replace the MB, thinking it was just something freaky or unstable. I will try the patch. On Mon, 4 Sep 2000, Poul-Henning Kamp wrote: > > I'm looking for the remaining victims of the dreaded "microuptime > went backwards" message. > > If you can reliably reproduce the problem, please contact me, so > we can arrange for some very detailed tracing to try to find out > what exactly is going on. I have not been able to trigger the > problem in my lab in a long time. > > If you see the message only occationally, please try the attached > patch and let me know if this changes the picture. The patch is > not meant as a fix, but it might reduce the impact of this condition > considerably when it happens. Basically by reducing the width of > the timecounter the magnitude of the hit we take if the timecounter > goes backwards is reduced from about an hour to approx 110msec. > > Reducing the width to less than 17 bits starts to run the risk of > ambiguity due to clock rollover. > > This patch may not be safe with PCAUDIO. > > Poul-Henning > > Index: clock.c > =================================================================== > RCS file: /home/ncvs/src/sys/i386/isa/clock.c,v > retrieving revision 1.155 > diff -u -r1.155 clock.c > --- clock.c 2000/07/30 21:05:22 1.155 > +++ clock.c 2000/09/04 16:34:16 > @@ -194,7 +194,7 @@ > static struct timecounter i8254_timecounter = { > i8254_get_timecount, /* get_timecount */ > 0, /* no poll_pps */ > - ~0u, /* counter_mask */ > + 0x1ffff, /* counter_mask */ > 0, /* frequency */ > "i8254" /* name */ > }; > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > phk@FreeBSD.ORG | TCP/IP since RFC 956 > FreeBSD coreteam member | 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-current" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message