From owner-freebsd-performance@FreeBSD.ORG  Tue Mar 17 15:49:26 2009
Return-Path: <owner-freebsd-performance@FreeBSD.ORG>
Delivered-To: freebsd-performance@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 5B265106571F
	for <freebsd-performance@freebsd.org>;
	Tue, 17 Mar 2009 15:49:26 +0000 (UTC)
	(envelope-from mkotlov@gmail.com)
Received: from yw-out-2324.google.com (yw-out-2324.google.com [74.125.46.28])
	by mx1.freebsd.org (Postfix) with ESMTP id 1681B8FC13
	for <freebsd-performance@freebsd.org>;
	Tue, 17 Mar 2009 15:49:25 +0000 (UTC)
	(envelope-from mkotlov@gmail.com)
Received: by yw-out-2324.google.com with SMTP id 5so30744ywh.13
	for <freebsd-performance@freebsd.org>;
	Tue, 17 Mar 2009 08:49:25 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma;
	h=domainkey-signature:mime-version:received:date:message-id:subject
	:from:to:content-type:content-transfer-encoding;
	bh=AoUVEeQPK0u3JSDlYlNdVGUyrgEUHSRd0tWoBTnIXkQ=;
	b=ouboiPv60AR7MTMb+I2U7HTnXFeZXuPDLg4/ORf7lChkW7/zH44AzNYhGpmv1xU97I
	5O/R2xIbF3VIS1VgSU5wgT36v2HRaXJEctgL0nt+VyFx2z//aLDE17bm+bQytOLK73Dv
	TYu7hFCKaSWWLF5S6lFiBSXtuJ4B16h//fxYQ=
DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma;
	h=mime-version:date:message-id:subject:from:to:content-type
	:content-transfer-encoding;
	b=dXQ5y5QQVN+63mRso8SuxtC8p9daHlUgIwtKIjTsvJk8nU8eOJNKP1BO6sDVVK3IRf
	ao3EHyLdnxwn0Hup4FhYS/Wj/nSMViymNONIIYBJl3aiAKoeIzgzYDkSUZAb7wKQTxv+
	aegUE/KtEqADQb0ADOtej2yrE9+kl1glRYAF4=
MIME-Version: 1.0
Received: by 10.231.16.129 with SMTP id o1mr62052iba.9.1237303075117; Tue, 17 
	Mar 2009 08:17:55 -0700 (PDT)
Date: Tue, 17 Mar 2009 11:17:55 -0400
Message-ID: <3edc36610903170817t7ab70c16tdeed1cb3a99e9a52@mail.gmail.com>
From: Mari Kotlov <mkotlov@gmail.com>
To: freebsd-performance@freebsd.org
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Subject: sysctl with KERN_BOOTTIME option vs. gettimeofday()
X-BeenThere: freebsd-performance@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Performance/tuning <freebsd-performance.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-performance>,
	<mailto:freebsd-performance-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-performance>
List-Post: <mailto:freebsd-performance@freebsd.org>
List-Help: <mailto:freebsd-performance-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-performance>,
	<mailto:freebsd-performance-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 17 Mar 2009 15:49:27 -0000

Hi everyone,
I am doing a port of C++ code from Windows to FreeBSD and need to
replace function GetTickCount(), which is used mostly for the purposes
of obtaining elapsed time (e.g. as a millisecond timer). As I
understand it, there are two ways to do that: 1) via sysctl() function
with CTL_KERN&KERN_BOOTTIME options and 2) via gettimeofday(). In both
case, struct timeval is returned, so I can compute the difference
between the two times and get the elapsed time.

I am wondering if anyone could tell me performance implications of
using sysctl() function call to obtain system boot time vs.
gettimeofday(). Is one better than the other? More efficient? Are
there advantages or disadvantages to using either of these two
methods? Any insight would be appreciated.

Thanks very much in advance,
Mari.