From owner-cvs-all@FreeBSD.ORG  Mon Jun 14 19:40:29 2004
Return-Path: <owner-cvs-all@FreeBSD.ORG>
Delivered-To: cvs-all@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id 6E88216A4CE; Mon, 14 Jun 2004 19:40:29 +0000 (GMT)
Received: from elvis.mu.org (elvis.mu.org [192.203.228.196])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id 5660343D54; Mon, 14 Jun 2004 19:40:29 +0000 (GMT)
	(envelope-from mux@freebsd.org)
Received: by elvis.mu.org (Postfix, from userid 1920)
	id 56DF65C83D; Mon, 14 Jun 2004 12:39:42 -0700 (PDT)
Date: Mon, 14 Jun 2004 21:39:42 +0200
From: Maxime Henrion <mux@freebsd.org>
To: Alfred Perlstein <alfred@freebsd.org>
Message-ID: <20040614193942.GD9228@elvis.mu.org>
References: <Pine.NEB.3.96L.1040614141907.34947B-100000@fledge.watson.org>
	<200406141458.02468.jhb@FreeBSD.org> <20040614192422.GH61448@elvis.mu.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20040614192422.GH61448@elvis.mu.org>
User-Agent: Mutt/1.4.2.1i
cc: src-committers@FreeBSD.org
cc: John Baldwin <jhb@FreeBSD.org>
cc: cvs-src@FreeBSD.org
cc: cvs-all@FreeBSD.org
cc: Robert Watson <rwatson@FreeBSD.org>
cc: "David E. O'Brien" <obrien@FreeBSD.org>
Subject: Re: cvs commit: src/sys/amd64/conf GENERIC
X-BeenThere: cvs-all@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: CVS commit messages for the entire tree <cvs-all.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-all>,
	<mailto:cvs-all-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/cvs-all>
List-Post: <mailto:cvs-all@freebsd.org>
List-Help: <mailto:cvs-all-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-all>,
	<mailto:cvs-all-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 14 Jun 2004 19:40:29 -0000

Alfred Perlstein wrote:
> * John Baldwin <jhb@FreeBSD.org> [040614 11:57] wrote:
> > 
> > I'm betting it is just triggering a race.  When I first did the adaptive 
> > mutexes I stress tested it (-j <bignum> buildworld loops) on an ultra60, an 
> > alpha ds20, and a quad pii-xeon w/o any lockups.
> 
> Just a side note, I think it's the Berkeley DB's recent code that
> will spin a number of times based on the number of CPUs present in
> the system.  Meaning, it might make sense to spin more on a quad
> than on a dual proc machine.  It might be worth checking this out.

What do you mean by spinning more?  As far as I know, with adaptive
mutexes, if some thread tries to lock a blocking mutex that is already
held by another thread currently running on another CPU, then it spins
instead of blocking, assuming the other thread will soon release the
mutex.  Obviously, this has more chances to happen if there are more
CPUs in the system but I don't get what you mean here.

Cheers,
Maxime