From owner-freebsd-current@FreeBSD.ORG  Sat Jan 24 19:45:24 2004
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
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 224D316A4CE
	for <current@freebsd.org>; Sat, 24 Jan 2004 19:45:24 -0800 (PST)
Received: from harmony.village.org (rover.bsdimp.com [204.144.255.66])
	by mx1.FreeBSD.org (Postfix) with ESMTP id DF09F43D31
	for <current@freebsd.org>; Sat, 24 Jan 2004 19:45:22 -0800 (PST)
	(envelope-from imp@bsdimp.com)
Received: from localhost (warner@rover2.village.org [10.0.0.1])
	by harmony.village.org (8.12.10/8.12.9) with ESMTP id i0P3jIET047473;
	Sat, 24 Jan 2004 20:45:18 -0700 (MST)
	(envelope-from imp@bsdimp.com)
Date: Sat, 24 Jan 2004 20:45:14 -0700 (MST)
Message-Id: <20040124.204514.109171577.imp@bsdimp.com>
To: dillon@apollo.backplane.com
From: "M. Warner Losh" <imp@bsdimp.com>
In-Reply-To: <200401242031.i0OKVD8A037265@apollo.backplane.com>
References: <44827.1074974041@critter.freebsd.dk>
	<200401242031.i0OKVD8A037265@apollo.backplane.com>
X-Mailer: Mew version 3.3 on Emacs 21.3 / Mule 5.0 (SAKAKI)
Mime-Version: 1.0
Content-Type: Text/Plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
cc: phk@phk.freebsd.dk
cc: wmoran@potentialtech.com
cc: current@freebsd.org
Subject: Re: DragonflyBSD kernel clock improvements 
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 25 Jan 2004 03:45:24 -0000

In message: <200401242031.i0OKVD8A037265@apollo.backplane.com>
            Matthew Dillon <dillon@apollo.backplane.com> writes:
:     No apic timer.  No acpi timer.  No TSC garbage.  none of that.

We've found at work that while the 8254's timer tends to be the best
universally available time keeping device, it is only as good as the
quarts oscillator driving it.  Other time keeping can be more precise.
We've found that systems with APM disabled have a more stable NTP
server when they are running on CPUs with TSC using the TSC
timecounter, but about a factor of 5, mostly due to a reduced jitter
in timestamping the PPS interrupts that we generate.  Of course, we
don't care one whit about SMP support for these systems.

Maybe there are better ways to obtain these results.  While not
directly releated to the nanosleep work, but just another point of
view.

Warner