From owner-freebsd-current@FreeBSD.ORG  Sun Jul 23 18:58:05 2006
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
X-Original-To: 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 3E92F16A556
	for <freebsd-current@freebsd.org>; Sun, 23 Jul 2006 18:58:05 +0000 (UTC)
	(envelope-from sthaug@nethelp.no)
Received: from bizet.nethelp.no (bizet.nethelp.no [195.1.209.33])
	by mx1.FreeBSD.org (Postfix) with SMTP id 8768243D49
	for <freebsd-current@freebsd.org>; Sun, 23 Jul 2006 18:58:01 +0000 (GMT)
	(envelope-from sthaug@nethelp.no)
Received: (qmail 49137 invoked from network); 23 Jul 2006 18:57:59 -0000
Received: from bizet.nethelp.no (HELO localhost) (195.1.209.33)
	by bizet.nethelp.no with SMTP; 23 Jul 2006 18:57:59 -0000
Date: Sun, 23 Jul 2006 20:57:59 +0200 (CEST)
Message-Id: <20060723.205759.74723866.sthaug@nethelp.no>
To: lists@wm-access.no
From: sthaug@nethelp.no
In-Reply-To: <44C3B674.3040804@wm-access.no>
References: <200607191315.k6JDFpvM048354@lurza.secnetix.de>
	<20060720.093457.1661914908.imp@bsdimp.com>
	<44C3B674.3040804@wm-access.no>
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: freebsd-current@freebsd.org, imp@bsdimp.com
Subject: Re: vmstat's entries type
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
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, 23 Jul 2006 18:58:05 -0000

> > One approach that we could use for 64-bit counters would be to just
> > use 32-bits one, and poll them for overflow and bump an overflow
> > count.  This assumes that the 32-bit counters overflow much less often
> > than the polling interval, and easily triples the amount of storage
> > for each of them...  It is ugly :-(
> > 
> 
> What's wrong with the add+adc (asm) approach found on any i386?

Presumably the fact that add + adc isn't an atomic operation. So if
you want to guarantee 64 bit consistency, you need locking or similar.

Steinar Haug, Nethelp consulting, sthaug@nethelp.no