From owner-freebsd-net Fri Aug 2 16:13:34 2002 Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id DF32237B400 for ; Fri, 2 Aug 2002 16:13:31 -0700 (PDT) Received: from iguana.icir.org (iguana.icir.org [192.150.187.36]) by mx1.FreeBSD.org (Postfix) with ESMTP id 9AA4B43E70 for ; Fri, 2 Aug 2002 16:13:31 -0700 (PDT) (envelope-from rizzo@iguana.icir.org) Received: (from rizzo@localhost) by iguana.icir.org (8.11.6/8.11.3) id g72NCCW90816; Fri, 2 Aug 2002 16:12:12 -0700 (PDT) (envelope-from rizzo) Date: Fri, 2 Aug 2002 16:12:12 -0700 From: Luigi Rizzo To: Martin Karsten Cc: freebsd-net@FreeBSD.ORG Subject: Re: device polling breaks ntp? Message-ID: <20020802161212.F90290@iguana.icir.org> References: <200208021516.g72FG4M18743@KOM.tu-darmstadt.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <200208021516.g72FG4M18743@KOM.tu-darmstadt.de>; from Martin.Karsten@KOM.tu-darmstadt.de on Fri, Aug 02, 2002 at 05:16:03PM +0200 Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org DEVICE_POLLING can basically introduce a variance of up to 1/HZ on the delivery of network packets. Then i have no idea on how ntpd is affected by variance in the samples. cheers luigi On Fri, Aug 02, 2002 at 05:16:03PM +0200, Martin Karsten wrote: > I have reasons to believe that network device polling breaks the > functionality of ntpd. I'm using FreeBSD 4.5 and ntp-4.1.71. > > When device polling is enabled *before* ntpd is started (particularly, when > device polling is enabled at boot time), ntpd seems to be unable to properly > synchronize with a reference clock. While I understand that the increased > packet delay variance introduced by network device polling might affect > ntpd's algorithms to estimate the network delay, it also seems to break > clock synchronization with a locally attached GPS-receiver. > > When network device polling is enabled *after* ntpd is started, it does not > cause immediate problems and I have not further investigated what exactly > happens in this case. > > In any case, disabling sysctl kern.polling.enable and restarting ntpd > results in proper operation of ntpd. > > Is this behaviour known and is there a workaround? > > Thanks, > Martin > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-net" in the body of the message To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message