From owner-freebsd-security@FreeBSD.ORG Sat May 14 02:33:37 2005 Return-Path: Delivered-To: freebsd-security@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 8943D16A4CE for ; Sat, 14 May 2005 02:33:37 +0000 (GMT) Received: from khavrinen.csail.mit.edu (khavrinen.csail.mit.edu [128.30.28.20]) by mx1.FreeBSD.org (Postfix) with ESMTP id E894D43D7E for ; Sat, 14 May 2005 02:33:36 +0000 (GMT) (envelope-from wollman@khavrinen.csail.mit.edu) Received: from khavrinen.csail.mit.edu (localhost.csail.mit.edu [127.0.0.1]) j4E2XV3C018478 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK CN=khavrinen.lcs.mit.edu issuer=SSL+20Client+20CA); Fri, 13 May 2005 22:33:33 -0400 (EDT) (envelope-from wollman@khavrinen.csail.mit.edu) Received: (from wollman@localhost) by khavrinen.csail.mit.edu (8.13.1/8.13.1/Submit) id j4E2XUWX018475; Fri, 13 May 2005 22:33:30 -0400 (EDT) (envelope-from wollman) From: Garrett Wollman MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <17029.25466.587442.577866@khavrinen.csail.mit.edu> Date: Fri, 13 May 2005 22:33:30 -0400 To: "Poul-Henning Kamp" In-Reply-To: <94145.1116037219@critter.freebsd.dk> References: <245f0df105051318564b1ffb6b@mail.gmail.com> <94145.1116037219@critter.freebsd.dk> X-Mailer: VM 7.17 under 21.4 (patch 17) "Jumbo Shrimp" XEmacs Lucid X-Greylist: Sender DNS name whitelisted, not delayed by milter-greylist-1.6 (khavrinen.csail.mit.edu [127.0.0.1]); Fri, 13 May 2005 22:33:33 -0400 (EDT) X-Virus-Scanned: ClamAV 0.84/876/Thu May 12 19:14:29 2005 on khavrinen.csail.mit.edu X-Virus-Status: Clean X-Spam-Status: No, score=0.0 required=5.0 tests=none version=3.0.2 X-Spam-Checker-Version: SpamAssassin 3.0.2 (2004-11-16) on khavrinen.csail.mit.edu X-Mailman-Approved-At: Sat, 14 May 2005 12:46:32 +0000 cc: freebsd-security@FreeBSD.ORG Subject: Re: FreeBSD Security Advisory FreeBSD-SA-05:09.htt [REVISED] X-BeenThere: freebsd-security@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Security issues [members-only posting] List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 14 May 2005 02:33:37 -0000 < said: > The political problem is that if all operating systems do that, > Intel has a pretty dud feature on their hands, and they are not > particularly eager to accept that fact. Intel already had a pretty dud feature on their hands; just ask anyone in the architecture community (probably including those who work for Intel). Pentium 4 CPUs simply don't have enough I/O bandwidth to maintain two simultaneous, independent instruction streams. The value to the feature can't be realized until you have enough cache (in both size and bandwidth) to be able to partition it among logical CPUs in exactly the manner that Colin has suggested. (The fundamental problem in computer architecture for the past several years has been how to deal with the fact that gates are cheap and easy to make, but wires -- particularly external I/O wires -- are expensive and hard.) The only way to get full performance out of an HTT processor today is for both threads to be running out of L1 cache. Multimedia and numerical benchmarks are often parallelizable in this way (assuming the OS provides gang scheduling); general-purpose applications rarely are. -GAWollman