From owner-svn-src-head@FreeBSD.ORG  Tue Dec 14 20:30:49 2010
Return-Path: <owner-svn-src-head@FreeBSD.ORG>
Delivered-To: svn-src-head@freebsd.org
Received: from [127.0.0.1] (freefall.freebsd.org [IPv6:2001:4f8:fff6::28])
	by hub.freebsd.org (Postfix) with ESMTP id EA73C106566B;
	Tue, 14 Dec 2010 20:30:48 +0000 (UTC)
	(envelope-from jkim@FreeBSD.org)
From: Jung-uk Kim <jkim@FreeBSD.org>
To: src-committers@FreeBSD.org
Date: Tue, 14 Dec 2010 15:30:33 -0500
User-Agent: KMail/1.6.2
References: <201012142007.oBEK7pLd028994@svn.freebsd.org>
In-Reply-To: <201012142007.oBEK7pLd028994@svn.freebsd.org>
MIME-Version: 1.0
Content-Disposition: inline
Content-Type: text/plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Message-Id: <201012141530.40603.jkim@FreeBSD.org>
Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org
Subject: Re: svn commit: r216443 - in head/sys: amd64/amd64 dev/acpica
	i386/i386
X-BeenThere: svn-src-head@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: SVN commit messages for the src tree for head/-current
	<svn-src-head.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-head>,
	<mailto:svn-src-head-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/svn-src-head>
List-Post: <mailto:svn-src-head@freebsd.org>
List-Help: <mailto:svn-src-head-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-head>,
	<mailto:svn-src-head-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 14 Dec 2010 20:30:49 -0000

On Tuesday 14 December 2010 03:07 pm, Jung-uk Kim wrote:
> Author: jkim
> Date: Tue Dec 14 20:07:51 2010
> New Revision: 216443
> URL: http://svn.freebsd.org/changeset/base/216443
>
> Log:
>   Stop lying about supporting cpu_est_clockrate() when TSC is
> invariant.  This function always returned the nominal frequency
> instead of current frequency because we use RDTSC instruction to
> calculate difference in CPU ticks, which is supposedly constant for
> the case.  Now we support cpu_get_nominal_mhz() for the case,
> instead.  Note it should be just enough for most usage cases
> because cpu_est_clockrate() is often times abused to find maximum
> frequency of the processor.

Actually, I wanted to support cpu_est_clockrate() as well and the 
following was my naive attempt:

http://people.freebsd.org/~jkim/tsc.diff

Unfortunately, it only worked for AMD64 Family 0Fh and below where we 
don't need this hack at all.  I tried everything I could (e.g., 
fooling around with branch prediction) but it constantly gave me 
better MHz for under-clocked cases. :-/

Jung-uk Kim