From owner-freebsd-stable@FreeBSD.ORG Mon Jun 5 17:36:03 2006 Return-Path: X-Original-To: stable@freebsd.org Delivered-To: freebsd-stable@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 2482C16AD03 for ; Mon, 5 Jun 2006 17:36:03 +0000 (UTC) (envelope-from lists@jnielsen.net) Received: from ns1.jnielsen.net (ns1.jnielsen.net [69.55.238.237]) by mx1.FreeBSD.org (Postfix) with ESMTP id AF8F243D46 for ; Mon, 5 Jun 2006 17:36:02 +0000 (GMT) (envelope-from lists@jnielsen.net) Received: from localhost (jn@ns1 [69.55.238.237]) (authenticated bits=0) by ns1.jnielsen.net (8.12.9p2/8.12.9) with ESMTP id k55Ha1lM065781 for ; Mon, 5 Jun 2006 10:36:01 -0700 (PDT) (envelope-from lists@jnielsen.net) From: John Nielsen To: stable@freebsd.org Date: Mon, 5 Jun 2006 13:35:32 -0400 User-Agent: KMail/1.9.1 X-Face: #X5#Y*q>F:]zT!DegL3z5Xo'^MN[$8k\[4^3rN~wm=s=Uw(sW}R?3b^*f1Wu*. X-Virus-Scanned: ClamAV version 0.88, clamav-milter version 0.87 on ns1.jnielsen.net X-Virus-Status: Clean Cc: Subject: MySQL, ntpd, and kern.timecounter 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: Mon, 05 Jun 2006 17:36:08 -0000 I have a FreeBSD 6.1 machine set up as a web and MySQL database server. Since the application is a bit database-intensive, I followed several of the MySQL tuning recommendations from this page: http://wikitest.freebsd.org/MySQL One of those was to change kern.timecounter.choice from ACPI-fast to TSC. That was fine for MySQL, but the real-world timekeeping on this hardware with TSC is so bad that it broke ntpd and the clock started drifting several seconds every hour. Timekeeping with ACPI-fast was quite reliable. I'm looking for recommendations in general, but I'll pose a few specific questions below as well. Should I change the timecounter back? How big an impact does the choice of timecounter have on performance with MySQL 4.1.19 and FreeBSD 6.1? Is there a conservative way I can answer this question myself for a server that's already in production? Can ntpd be coaxed into working with such bad timekeeping (as long as it's consistently bad)? Would Bad Things happen if I ran ntpdate or ntpd -q once or twice a day? Would this be considered an abuse of the ntp server(s)? Would I run a risk of confusing / breaking cron or sendmail or syslogd or anything else with the time jumps? All input appreciated. Thanks! JN