From owner-freebsd-current@FreeBSD.ORG Thu May 6 11:55:33 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id B3DCF16A4CF for ; Thu, 6 May 2004 11:55:33 -0700 (PDT) Received: from mail1.speakeasy.net (mail1.speakeasy.net [216.254.0.201]) by mx1.FreeBSD.org (Postfix) with ESMTP id 6108243D49 for ; Thu, 6 May 2004 11:55:33 -0700 (PDT) (envelope-from jhb@FreeBSD.org) Received: (qmail 26001 invoked from network); 6 May 2004 18:55:32 -0000 Received: from dsl027-160-063.atl1.dsl.speakeasy.net (HELO server.baldwin.cx) ([216.27.160.63]) (envelope-sender ) encrypted SMTP for ; 6 May 2004 18:55:32 -0000 Received: from 10.50.40.205 (gw1.twc.weather.com [216.133.140.1]) by server.baldwin.cx (8.12.11/8.12.11) with ESMTP id i46ItLt2007898; Thu, 6 May 2004 14:55:29 -0400 (EDT) (envelope-from jhb@FreeBSD.org) From: John Baldwin To: freebsd-current@FreeBSD.org Date: Thu, 6 May 2004 14:47:14 -0400 User-Agent: KMail/1.6 References: <200405061411.27216.jhb@FreeBSD.org> <16538.33610.967480.120194@grasshopper.cs.duke.edu> In-Reply-To: <16538.33610.967480.120194@grasshopper.cs.duke.edu> MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200405061447.14406.jhb@FreeBSD.org> X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on server.baldwin.cx cc: Andrew Gallatin cc: current@FreeBSD.org Subject: Re: 4.7 vs 5.2.1 SMP/UP bridging performance X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 06 May 2004 18:55:33 -0000 On Thursday 06 May 2004 02:26 pm, Andrew Gallatin wrote: > John Baldwin writes: > > and lfence is only on PIV+. I don't recall when mfence first appeared.. > > perhaps PII? If the lock is really expensive, then perhaps we could > > make atomic_cmpset() be actual functions (ugh) rather than inlines that > > did a branch to use foofence for PIV rather than the default. The > > branches would suck, but it might be faster than the lock. Of course, > > this would greatly pessimize non-PIV. > > According to http://www.sandpile.org/ia32/coherent.htm, > both mfence and lfence require SSE2, so sfence has the broadest > coverage. > > But since only P4 needs it, and since lfence is ~25% cheaper, maybe > there should be a separate config option for it, and it should be a > straight conditional compile option for those of us cursed w/P4s. That could work I guess. Just can't stick it in GENERIC. options INTEL_MADE_MY_PIV_A_TORTOISE or some such. :) -- John Baldwin <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org