Date: Tue, 5 Feb 2002 11:51:58 -0700 From: Nate Williams <nate@yogotech.com> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: John Polstra <jdp@polstra.com>, hackers@FreeBSD.ORG Subject: Re: A question about timecounters Message-ID: <15456.10702.319710.952387@caddis.yogotech.com> In-Reply-To: <91325.1012934584@critter.freebsd.dk> References: <200202051826.g15IQDt04095@vashon.polstra.com> <91325.1012934584@critter.freebsd.dk>
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> >> Can you try to MFC rev 1.111 and see if that changes anything ? > > > >That produced some interesting results. I am still testing under > >very heavy network interrupt load. With the change from 1.111, I > >still get the microuptime messages about as often. But look how > >much larger the reported backwards jumps are: > > > > microuptime() went backwards (896.225603 -> 888.463636) > > microuptime() went backwards (896.225603 -> 888.494440) > > microuptime() went backwards (896.225603 -> 888.500875) > > microuptime() went backwards (1184.392277 -> 1176.603001) > > microuptime() went backwards (1184.392277 -> 1176.603749) > > (Ok, I'll MFC 1.111) Huh? It appears that 1.111 makes things worse, not better (larger jumps). Can you explain why you think this is a good things, since it seems to be a bad thing to me. > Sanity-check: this is NOT a multi-CPU system, right ? As stated before, both are > 1Ghz single-CPU systems running -stable, although I'm sure John is capable of a answering this on his own. :) > We now have three options left: > hardclock interrupt starvation This is Bruce's hypothesis, right? > scheduling related anomaly wrt to the use of microuptime(). > arithmetic overflow because the call to microuptime() gets > interrupted for too long. 'Interrupted for too long'. Do you mean 'not interrupted enough', aka a long interrupt blockage? (I'm trying to understand here.) Nate To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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