From owner-freebsd-smp@FreeBSD.ORG Mon Apr 17 18:13:00 2006 Return-Path: X-Original-To: smp@freebsd.org Delivered-To: freebsd-smp@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 049A316A402 for ; Mon, 17 Apr 2006 18:13:00 +0000 (UTC) (envelope-from surerlistmail@gmail.com) Received: from nproxy.gmail.com (nproxy.gmail.com [64.233.182.189]) by mx1.FreeBSD.org (Postfix) with ESMTP id 5DF0D43D53 for ; Mon, 17 Apr 2006 18:12:59 +0000 (GMT) (envelope-from surerlistmail@gmail.com) Received: by nproxy.gmail.com with SMTP id m18so536584nfc for ; Mon, 17 Apr 2006 11:12:57 -0700 (PDT) DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=iiPbSqKcuWJqD2SKR8u5sOSQhKWCsz533sY6WiJejKlOmMKBFrR0rZeK+mokcIgGMUUHzTy1HsDB3JQmGjRanR5h3nUpVUcD6g6ksDmKtuMpFg6T/GISEfzz0hLPzHUXF9tjEoQfjSdanzIckKsg2f3j6WMjZgp64U2ri0kkfuo= Received: by 10.48.31.4 with SMTP id e4mr724892nfe; Mon, 17 Apr 2006 11:12:57 -0700 (PDT) Received: by 10.49.61.12 with HTTP; Mon, 17 Apr 2006 11:12:57 -0700 (PDT) Message-ID: Date: Mon, 17 Apr 2006 14:12:57 -0400 From: "Surer Dink" To: "Kris Kennaway" , smp@freebsd.org, current@freebsd.org In-Reply-To: <20060417162216.GA90886@xor.obsecurity.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline References: <20060417162216.GA90886@xor.obsecurity.org> Cc: Subject: Re: Anomalous performance increase from mutex profiling X-BeenThere: freebsd-smp@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: FreeBSD SMP implementation group List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 17 Apr 2006 18:13:00 -0000 On 4/17/06, Kris Kennaway wrote: > On Mon, Apr 17, 2006 at 03:54:07AM -0400, Surer Dink wrote: > > Please excuse if this is a stupid question - but might using MCS or > > QOLB locks in this situation be useful? > > What are they? Mellor-Crummy Scott: http://www.cs.rochester.edu/u/scott/papers/1991_ASPLOS_sync.pdf An overview comparing various possible optimizations for a few lock types, including MCS and QOLB: ftp://ftp.cs.utexas.edu/pub/dburger/papers/ISCA97_qolb.pdf I believe the QOLB proposal only suggested hardware modificaition for performance improvement, but could be implemented entirely in software - the overheads are high, but offer substantial performance benefit in high contention situations. MCS is based on QOSB, however fully implemented in software. There is also a proposal for changing lock to MCS dynamically, however I have not read it: ftp://ftp.cag.lcs.mit.edu/pub/papers/pdf/reactive.pdf