From owner-freebsd-current@FreeBSD.ORG  Sun Apr  6 11:54:10 2003
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 CD8F437B401
	for <current@freebsd.org>; Sun,  6 Apr 2003 11:54:10 -0700 (PDT)
Received: from critter.freebsd.dk (critter.freebsd.dk [212.242.86.163])
	by mx1.FreeBSD.org (Postfix) with ESMTP id A9D7043FBF
	for <current@freebsd.org>; Sun,  6 Apr 2003 11:54:09 -0700 (PDT)
	(envelope-from phk@phk.freebsd.dk)
Received: from critter.freebsd.dk (localhost [127.0.0.1])
	by critter.freebsd.dk (8.12.9/8.12.9) with ESMTP id h36Is8Ld028860;
	Sun, 6 Apr 2003 20:54:08 +0200 (CEST)
	(envelope-from phk@phk.freebsd.dk)
To: des@ofug.org (Dag-Erling =?iso-8859-1?q?Sm=F8rgrav?=)
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: Your message of "Sun, 06 Apr 2003 20:40:24 +0200."
             <xzp4r5bmpuv.fsf@flood.ping.uio.no> 
Date: Sun, 06 Apr 2003 20:54:08 +0200
Message-ID: <28859.1049655248@critter.freebsd.dk>
cc: current@freebsd.org
Subject: Re: weird fxp / timecounter interaction in top-of-tree 
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, 06 Apr 2003 18:54:11 -0000

In message <xzp4r5bmpuv.fsf@flood.ping.uio.no>, Dag-Erling =?iso-8859-1?q?Sm=F8
rgrav?= writes:
>"Poul-Henning Kamp" <phk@phk.freebsd.dk> writes:
>> > and tc_init() to use the *first* timecounter it runs across (on i386,
>> > this is generally the i8254), leaving the admin to pick another one if
>> > the default does not suit her.  See the attached patch.
>> This is wrong.  Please do not commit it.
>
>OK.  Any suggestion as to how we could rank timecounters so we can
>switch to a better one when it becomes available?  Is this something
>we can determine statically (with a compiled-in preference list), or
>do we have to determine it at run time?

Defining "best" is at best hard, so I have resorted to the simple
technique we use now:  Don't call tc_init on a timecounter unless
you want to use it.

Provided people set it sensibly, we could add a "priority" field
to the timecounter structure and have tc_init() respect that.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.