From owner-cvs-src@FreeBSD.ORG  Tue Nov  9 21:09:15 2004
Return-Path: <owner-cvs-src@FreeBSD.ORG>
Delivered-To: cvs-src@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id E0D6816A4CE; Tue,  9 Nov 2004 21:09:15 +0000 (GMT)
Received: from fledge.watson.org (fledge.watson.org [204.156.12.50])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id 8D75843D45; Tue,  9 Nov 2004 21:09:15 +0000 (GMT)
	(envelope-from robert@fledge.watson.org)
Received: from fledge.watson.org (localhost [127.0.0.1])
	by fledge.watson.org (8.13.1/8.13.1) with ESMTP id iA9L85V9061043;
	Tue, 9 Nov 2004 16:08:05 -0500 (EST)
	(envelope-from robert@fledge.watson.org)
Received: from localhost (robert@localhost)iA9L85bp061040;
	Tue, 9 Nov 2004 21:08:05 GMT	(envelope-from robert@fledge.watson.org)
Date: Tue, 9 Nov 2004 21:08:05 +0000 (GMT)
From: Robert Watson <rwatson@FreeBSD.org>
X-Sender: robert@fledge.watson.org
To: Julian Elischer <julian@elischer.org>
In-Reply-To: <419109EB.8010809@elischer.org>
Message-ID: <Pine.NEB.3.96L.1041109210654.60848A-100000@fledge.watson.org>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
cc: src-committers@FreeBSD.org
cc: John Baldwin <jhb@FreeBSD.org>
cc: Alan Cox <alc@FreeBSD.org>
cc: cvs-src@FreeBSD.org
cc: Mike Silbersack <silby@silby.com>
cc: cvs-all@FreeBSD.org
cc: Stephan Uphoff <ups@tree.com>
Subject: Re: cvs commit: src/sys/i386/i386 pmap.c
X-BeenThere: cvs-src@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: CVS commit messages for the src tree <cvs-src.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-src>,
	<mailto:cvs-src-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/cvs-src>
List-Post: <mailto:cvs-src@freebsd.org>
List-Help: <mailto:cvs-src-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-src>,
	<mailto:cvs-src-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 09 Nov 2004 21:09:16 -0000


On Tue, 9 Nov 2004, Julian Elischer wrote:

> Is this with HTT? 
> 
> We've dicoverred that HTT makes better code run slower, remember? 

Nope, the issue here is a minor tweak in the spin lock code that causes
moving away from an atomic operation to make it run slower rather than
faster.  I think John has a theory that the lack of using an atomic
operation slows the rate at which the change is visible on other
processors by virtue of being non-atomic, so locks contend longer.

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert@fledge.watson.org      Principal Research Scientist, McAfee Research