From owner-freebsd-stable@FreeBSD.ORG Thu Jan 19 20:04:38 2012 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id EB280106567D for ; Thu, 19 Jan 2012 20:04:38 +0000 (UTC) (envelope-from lists@rewt.org.uk) Received: from abby.lhr1.as41113.net (abby.lhr1.as41113.net [91.208.177.20]) by mx1.freebsd.org (Postfix) with ESMTP id ACE048FC20 for ; Thu, 19 Jan 2012 20:04:38 +0000 (UTC) Received: from jasmine.internethq (unknown [91.208.177.192]) by abby.lhr1.as41113.net (Postfix) with ESMTP id C8B5B22849 for ; Thu, 19 Jan 2012 20:04:36 +0000 (UTC) Received: from [172.16.11.44] (jwh-laptop.internethq [172.16.11.44]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by jasmine.internethq (Postfix) with ESMTPS id 073D1106A2142; Thu, 19 Jan 2012 20:04:50 +0000 (GMT) Message-ID: <4F187752.80409@rewt.org.uk> Date: Thu, 19 Jan 2012 20:04:34 +0000 From: Joe Holden User-Agent: Thunderbird 2.0.0.24 (Windows/20100228) MIME-Version: 1.0 To: Ian Lepore References: <4F15D643.8000907@rewt.org.uk> <1326913229.1669.281.camel@revolution.hippie.lan> In-Reply-To: <1326913229.1669.281.camel@revolution.hippie.lan> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: FreeBSD Stable Mailing List Subject: Re: Timekeeping in stable/9 X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 19 Jan 2012 20:04:39 -0000 Looks like this is down to the dynamic/tickless changes in 9 (that aren't even noted in the release notes), the machines have now been switched to linux as the lack of responses/care given to my recent postings has been noted and it was deemed that using linux would be less hassle in the long run. Unfortunate decision but I am inclined to agree. Thanks, J Ian Lepore wrote: > On Tue, 2012-01-17 at 20:12 +0000, Joe Holden wrote: >> Hi guys, >> >> Has anyone else noticed the tendency for 9.0-R to be unable to >> accurately keep time? I've got a couple of machines that have been >> upgraded from 8.2 that are struggling, in particular a Virtual box guest >> that was fine on 8.2, but now that's its been upgraded to 9.0 counts at >> anything from 2 to 20 seconds per 5 second sample, the result is similar >> with HPET, ACPI-fast and TSC. >> >> I also have physical boxes which new seem to drift quite substantially, >> ntpd cannot keep up and as these boxes need to be able to report the >> time relatively accurately, it is causing problems with log times and >> such... >> >> Any suggestions most welcome! >> >> Thanks, >> J > > I finally got a 9.0 generic build done today and I've been watching the > timekeeping on 3 systems and they're all doing just fine. Two of the > systems are performing pretty much identically to how they did on 8.2; > the clock frequency correction calculated by ntpd differs by less than > 1ppm. On the other system the kernel timekeeping routines are now > choosing to use a different clock so I don't get a direct comparison of > the old vs new drift rate, but the drift is still reasonable (100ppm > now, used to be around 88, on an old 300mhz MediaGx-based system). > > I haven't had time yet to learn about the new eventtimer stuff in 9.0, > but I know you can get some info on the choices it made via sysctl > kern.eventtimer. Before 9.0 I'd check sysctl kern.clockrate and vmstat > -i and make sure the chosen clock is interrupting at the right rate, but > now with the eventtimer stuff there's not an obvious correlation between > hz and profhz and stathz and any particular device's interrupt rate, at > least for some clock choices (on the old MediaGx system without ACPI or > HPET it seems to work more like it used to). > > -- Ian > >