From owner-svn-src-head@FreeBSD.ORG  Tue Jun 21 15:57:26 2011
Return-Path: <owner-svn-src-head@FreeBSD.ORG>
Delivered-To: svn-src-head@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 854551065672;
	Tue, 21 Jun 2011 15:57:26 +0000 (UTC) (envelope-from jhb@freebsd.org)
Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42])
	by mx1.freebsd.org (Postfix) with ESMTP id 59A9F8FC17;
	Tue, 21 Jun 2011 15:57:26 +0000 (UTC)
Received: from bigwig.baldwin.cx (66.111.2.69.static.nyinternet.net
	[66.111.2.69])
	by cyrus.watson.org (Postfix) with ESMTPSA id 076E946B03;
	Tue, 21 Jun 2011 11:57:26 -0400 (EDT)
Received: from jhbbsd.localnet (unknown [209.249.190.124])
	by bigwig.baldwin.cx (Postfix) with ESMTPSA id 87E218A01F;
	Tue, 21 Jun 2011 11:57:25 -0400 (EDT)
From: John Baldwin <jhb@freebsd.org>
To: "Jung-uk Kim" <jkim@freebsd.org>
Date: Tue, 21 Jun 2011 11:56:38 -0400
User-Agent: KMail/1.13.5 (FreeBSD/8.2-CBSD-20110325; KDE/4.5.5; amd64; ; )
References: <201106081938.p58JcWuB044252@svn.freebsd.org>
	<201106210910.25697.jhb@freebsd.org>
	<201106211149.02280.jkim@FreeBSD.org>
In-Reply-To: <201106211149.02280.jkim@FreeBSD.org>
MIME-Version: 1.0
Content-Type: Text/Plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Message-Id: <201106211156.38396.jhb@freebsd.org>
X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.6
	(bigwig.baldwin.cx); Tue, 21 Jun 2011 11:57:25 -0400 (EDT)
Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org,
	src-committers@freebsd.org, Bruce Evans <brde@optusnet.com.au>
Subject: Re: svn commit: r222866 - head/sys/x86/x86
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, 21 Jun 2011 15:57:26 -0000

On Tuesday, June 21, 2011 11:48:55 am Jung-uk Kim wrote:
> On Tuesday 21 June 2011 09:10 am, John Baldwin wrote:
> > On Monday, June 20, 2011 7:41:00 pm Jung-uk Kim wrote:
> > > My questions to you:
> > >
> > > a) Why do we care TSC timecounter when it is not invariant where
> > > we *know* it is unusable and set to negative quality?
> >
> > What if the user knows they will not enable CPU throttling so for
> > them the TSC is safe?  In that case, TSC is a more efficient
> > timecounter and if the user constrains the system to make the TSC
> > safe we should let them use it.
> 
> In that case, it must be a UP system, the quality is still 800, and 
> TSC value won't be shifted.
> 
> My question was specific to SMP cases.  Sorry, I didn't make that 
> clear.

What if the user has an SMP system where the TSCs are in sync but it's
older so it doesn't set the TSC invariant bit set in cpuid.  Are we
now forbidding that user from using the TSC?

-- 
John Baldwin