From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268987AbUHaVGU (ORCPT ); Tue, 31 Aug 2004 17:06:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269162AbUHaVCW (ORCPT ); Tue, 31 Aug 2004 17:02:22 -0400 Received: from e1.ny.us.ibm.com ([32.97.182.101]:58821 "EHLO e1.ny.us.ibm.com") by vger.kernel.org with ESMTP id S267705AbUHaU7T (ORCPT ); Tue, 31 Aug 2004 16:59:19 -0400 Subject: Re: [PATCH] Re: boot time, process start time, and NOW time From: john stultz To: george anzinger Cc: Tim Schmielau , Andrew Morton , Petri Kaukasoina , albert@users.sourceforge.net, hirofumi@mail.parknet.co.jp, lkml , voland@dmz.com.pl, nicolas.george@ens.fr, david+powerix@blue-labs.org In-Reply-To: <4134D11B.7050800@mvista.com> References: <87smcf5zx7.fsf@devron.myhome.or.jp> <20040816124136.27646d14.akpm@osdl.org> <412285A5.9080003@mvista.com> <1092782243.2429.254.camel@cog.beaverton.ibm.com> <1092787863.2429.311.camel@cog.beaverton.ibm.com> <1092781172.2301.1654.camel@cube> <1092791363.2429.319.camel@cog.beaverton.ibm.com> <20040819191537.GA24060@elektroni.ee.tut.fi> <20040826040436.360f05f7.akpm@osdl.org> <1093916047.14662.144.camel@cog.beaverton.ibm.com> <4134D11B.7050800@mvista.com> Content-Type: text/plain Message-Id: <1093985817.14662.155.camel@cog.beaverton.ibm.com> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.5 (1.4.5-7) Date: Tue, 31 Aug 2004 13:56:58 -0700 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2004-08-31 at 12:27, George Anzinger wrote: > Tim Schmielau wrote: > > On Mon, 30 Aug 2004, john stultz wrote: > >>On Mon, 2004-08-30 at 16:00, Tim Schmielau wrote: > >> > >>>George, please excuse my lack of understanding. What again where the > >>>precise reasons to have an ntp-corrected uptime? > >> > >>Ah, here's the thread with the first mention of it that I could find. > >> > >>http://www.uwsg.iu.edu/hypermail/linux/kernel/0306.1/1471.html > > As I recall the problem was that jiffies since boot was being converted to get > uptime base on 1/HZ = 1 jiffie. Since it is really not quite that, there was an > error. Using clock_monotonic seemed like the right answer as it eliminated the > error AND made the result consistant with get_clock(CLOCK_MONOTONIC,..). > > The alternate answer is, of course, to directly convert the elapsed jiffies. > The main problem with this is that this can be a BIG number and, therefor, the > math needs to be carefully. And, of course, it is inconsistant with > get_clock(), but that is a new interface... Hmmm. Well, I may be starting to lean in Tim's direction of pulling the clock_monotonic based uptime and going back to the jiffies based uptime. Atleast until we can make all the /proc/ output consistent. I just worry that it actually fixed a problem for someone, and backing it out would just reopen that. Thoughts? -john