From owner-freebsd-arch@FreeBSD.ORG Tue Mar 16 06:22:52 2004 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id B373D16A4CE for ; Tue, 16 Mar 2004 06:22:52 -0800 (PST) Received: from smtp.distributel.net (cns2.distributel.NET [66.38.181.21]) by mx1.FreeBSD.org (Postfix) with ESMTP id 4E79643D41 for ; Tue, 16 Mar 2004 06:22:52 -0800 (PST) (envelope-from bmilekic@technokratis.com) Received: from godel.mtl.distributel.net (nat.MTL.distributel.NET [66.38.181.24]) by smtp.distributel.net (8.12.6/8.12.6) with ESMTP id i2GEMoM2076810; Tue, 16 Mar 2004 09:22:51 -0500 (EST) Received: from godel.mtl.distributel.net (localhost [127.0.0.1]) i2GELA6p006848; Tue, 16 Mar 2004 09:21:10 -0500 (EST) (envelope-from bmilekic@technokratis.com) Received: (from bmilekic@localhost)i2GELAEG006847; Tue, 16 Mar 2004 09:21:10 -0500 (EST) (envelope-from bmilekic@technokratis.com) X-Authentication-Warning: godel.mtl.distributel.net: bmilekic set sender to bmilekic@technokratis.com using -f Date: Tue, 16 Mar 2004 09:21:10 -0500 From: Bosko Milekic To: Doug Rabson Message-ID: <20040316142110.GA6802@technokratis.com> References: <1077137806.28133.10.camel@herring.nlsystems.com> <1077181355.28133.13.camel@herring.nlsystems.com> <20040316031702.GA3794@technokratis.com> <200403160914.51727.dfr@nlsystems.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200403160914.51727.dfr@nlsystems.com> User-Agent: Mutt/1.4.1i cc: freebsd-arch@FreeBSD.org Subject: Re: Read Copy Update X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 16 Mar 2004 14:22:52 -0000 On Tue, Mar 16, 2004 at 09:14:51AM +0000, Doug Rabson wrote: > On Tuesday 16 March 2004 03:17, Bosko Milekic wrote: > > On Thu, Feb 19, 2004 at 09:02:35AM +0000, Doug Rabson wrote: > > > On Wed, 2004-02-18 at 23:26, Jeff Roberson wrote: > > > > > > > > I think that this is a good path to go down, but I really don't > > > > think we're ready yet. I'd rather see energy spent protecting > > > > code than building more infrastructure. > > > > > > I completely agree. I was just musing about this as a future > > > addition to the locking toolbox. Its certainly not worth trying > > > before enough of the kernel is outside the giant lock to make it > > > worthwhile. > > > > As Jeff said and you agree, it is probably too early for this now. > > Also, I've looked at the paper you quote before SCO's announcement > > (which by the way I had no idea about until now), and I think we'll > > eventually do just as well in the common case without going to the > > RCU model at all. > > Its a pretty neat idea though. I like the sound of being able to e.g. > read from the namecache without needing to take an expensive lock. With > the way 5-CURRENT works, we would probably still need to suppress > context switching which is expensive on intel processors in the current > implementation. I guess that could be fixed using some kind of lazy-cli > scheme. Should be really easy to fix in the common case without having to get really fancy (e.g., just interlock against ourselves on a private per-thread flag) to merely delay cli until the first interrupt. We shouldn't need to mask out per CPU or anything fancy like that. > The main barrier here (apart from the need to push Giant down in more > places and stabilise the existing implementation) is IBM's patent. The > SCO IP claim (bogus as it is) only covers Sequent's original > implementation. Yeah, that sucks. -- Bosko Milekic * bmilekic@technokratis.com * bmilekic@FreeBSD.org TECHNOkRATIS Consulting Services * http://www.technokratis.com/ "It is impossible for anyone to begin to learn what he believes he already knows." -- Epictetus (c.a.d. 55-c135)