From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265817AbUHaAjL (ORCPT ); Mon, 30 Aug 2004 20:39:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265847AbUHaAjL (ORCPT ); Mon, 30 Aug 2004 20:39:11 -0400 Received: from rwcrmhc12.comcast.net ([216.148.227.85]:19450 "EHLO rwcrmhc12.comcast.net") by vger.kernel.org with ESMTP id S265817AbUHaAjE (ORCPT ); Mon, 30 Aug 2004 20:39:04 -0400 Subject: Re: [PATCH] Re: boot time, process start time, and NOW time From: Albert Cahalan To: john stultz Cc: Tim Schmielau , george anzinger , Andrew Morton OSDL , 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: <1093909116.14662.105.camel@cog.beaverton.ibm.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> <1093909116.14662.105.camel@cog.beaverton.ibm.com> Content-Type: text/plain Organization: Message-Id: <1093912654.434.7022.camel@cube> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.2.4 Date: 30 Aug 2004 20:37:34 -0400 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2004-08-30 at 19:38, john stultz wrote: > This isn't going to happen instantly by any means. I'm trying to > get the time of day rework finished as soon as I can, but I've > got the day job to do as well. In the mean time, we can staple gun > any user visible exported HZ/jiffies values so they are accurate > (using ACTHZ or gettimeofday), and also look into changing HZ to a > less error-ful value. HZ=1001 has been suggested and looks quite > promising (although /net/schec/estimator.c wants a power of 4). Well, pick something else. Here's a list of choices with error under 0.0025%, in the 240..1300 range, that can be evenly divided by four. Dropping back a bit would be good, to better tolerate systems with firmware that steals enough time to cause lost clock ticks. I like 400, 488, and 556. 864 and 1112 are decent too. It might be useful having 400 as a multiple of 100. I don't think /net/sched/estimator.c needs such great accuracy. If that were sacrificed, one could do much better with HZ at 363, 519, or 627. %error HZerror PIT# HZ actual -0.00217900 -0.007234 3594 332 331.992766 -0.00217900 -0.014469 1797 664 663.985531 -0.00217900 -0.021703 1198 996 995.978297 -0.00184378 -0.014676 1499 796 795.985324 -0.00150855 -0.004586 3925 304 303.995414 -0.00150855 -0.005732 3140 380 379.994268 -0.00150855 -0.006034 2983 400 399.993966 -0.00150855 -0.009474 1900 628 627.990526 -0.00150855 -0.011465 1570 760 759.988535 -0.00150855 -0.018947 950 1256 1255.981053 -0.00083809 -0.002581 3874 308 307.997419 -0.00083809 -0.003051 3278 364 363.996949 -0.00083809 -0.004794 2086 572 571.995206 -0.00083809 -0.004995 2002 596 595.995005 -0.00083809 -0.005163 1937 616 615.994837 -0.00083809 -0.006101 1639 728 727.993899 -0.00083809 -0.009588 1043 1144 1143.990412 -0.00083809 -0.009990 1001 1192 1191.990010 -0.00050285 -0.006376 941 1268 1267.993624 -0.00016762 -0.000483 4143 288 287.999517 -0.00016762 -0.000724 2762 432 431.999276 -0.00016762 -0.001448 1381 864 863.998552 +0.00050286 +0.001488 4031 296 296.001488 +0.00050286 +0.002796 2146 556 556.002796 +0.00050286 +0.005592 1073 1112 1112.005592 +0.00150859 +0.018163 991 1204 1204.018163 +0.00184384 +0.004499 4890 244 244.004499 +0.00184384 +0.008998 2445 488 488.008998 +0.00184384 +0.012022 1830 652 652.012022 +0.00184384 +0.013497 1630 732 732.013497 +0.00184384 +0.022495 978 1220 1220.022495 +0.00217909 +0.027282 953 1252 1252.027282