From owner-freebsd-current@FreeBSD.ORG Fri Nov 28 21:59:02 2003 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 8B75C16A4CE for ; Fri, 28 Nov 2003 21:59:02 -0800 (PST) Received: from hak.cnd.mcgill.ca (hak.cnd.mcgill.ca [132.216.11.133]) by mx1.FreeBSD.org (Postfix) with ESMTP id 0A2E743FA3 for ; Fri, 28 Nov 2003 21:59:01 -0800 (PST) (envelope-from mat@hak.cnd.mcgill.ca) Received: from hak.cnd.mcgill.ca (localhost [127.0.0.1]) by hak.cnd.mcgill.ca (8.12.9/8.12.8) with ESMTP id hAT5uM15035495; Sat, 29 Nov 2003 00:56:22 -0500 (EST) (envelope-from mat@hak.cnd.mcgill.ca) Received: (from mat@localhost) by hak.cnd.mcgill.ca (8.12.9/8.12.8/Submit) id hAT5uL0Y035494; Sat, 29 Nov 2003 00:56:21 -0500 (EST) Date: Sat, 29 Nov 2003 00:56:21 -0500 From: Mathew Kanner To: "Marc G. Fournier" Message-ID: <20031129055621.GC26657@cnd.mcgill.ca> References: <20031128212342.G99096@ganymede.hub.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20031128212342.G99096@ganymede.hub.org> User-Agent: Mutt/1.4.1i Organization: I speak for myself, operating in Montreal, CANADA X-Spam-Status: No, hits=0.0 required=5.0 tests=none autolearn=no version=2.60 X-Spam-Checker-Version: SpamAssassin 2.60 (1.212-2003-09-23-exp) on hak.cnd.mcgill.ca cc: freebsd-current@freebsd.org Subject: Re: Time jumping on both 4.x and 5.x ... X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 29 Nov 2003 05:59:02 -0000 On Nov 28, Marc G. Fournier wrote: > > In trying to isolate an issue where the PostgreSQL 'explain analyze' is > showing "odd results" (namely, negative time estimates on queries), Tom > Lane wrote a quick C program to test gettimeofday() (program attached) ... > the results on a 4.9-PRERELEASE kernel of Sep 20 14:16:48 ADT 2003 shows: > > neptune# time ./timetest > out of order tv_sec: 1070068479 99040, prev 1070069174 725235 > out of order tv_usec: 1070068479 99040, prev 1070069174 725235 > out of order tv_sec: 1070069175 19687, prev 1070068479 99040 > out of order tv_usec: 1070069175 19687, prev 1070068479 99040 > out of order tv_sec: 1070068499 99377, prev 1070069194 625573 > out of order tv_usec: 1070068499 99377, prev 1070069194 625573 > out of order tv_sec: 1070069194 808542, prev 1070068499 99377 > ^C1.171u 23.461s 0:24.68 99.7% 5+169k 1+0io 0pf+0w > > One person on the list has tried the same script on a 5.2 kernel, and > reports seeing similar results, but after a longer period of time (~30min) > ... > > In most (all?) cases, the offset appears to be ~+/-695 secs ... Linux ppl > on the list, running the same problem, seem to be able to reproduce the > issue, except they are only finding differences of 1 microsecond, and then > only on older kernels (2.2.x, apparently) ... those running newer Linux > kernels are reporting a clean run ... FreeBSD 5.2 (up, no acpia): I get the errors only when I force heavy load and swapping. - kern.timecounter.hardware: TSC - FreeBSD tube.xx.xx5.2-BETA FreeBSD 5.2-BETA #6: Fri Nov 28 14:20:25 EST 2003 xx@xx i386 FreeBSD 4.8 (up): Didn't see the error on a nominally loaded server, I tested for about ten minutes. - kern.timecounter.hardware: i8254 - FreeBSD yy.yy.yy.yy4.8-STABLE FreeBSD 4.8-STABLE #0: Wed Jul 30 13:51:04 EDT 2003 xx@xx i386 --Mat -- sig machine boken