From owner-freebsd-security@FreeBSD.ORG Sat May 14 13:08:31 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 6C19E16A4CE; Sat, 14 May 2005 13:08:31 +0000 (GMT) Received: from osl1smout1.broadpark.no (osl1smout1.broadpark.no [80.202.4.58]) by mx1.FreeBSD.org (Postfix) with ESMTP id E373F43D48; Sat, 14 May 2005 13:08:30 +0000 (GMT) (envelope-from des@des.no) Received: from osl1sminn1.broadpark.no ([80.202.4.59]) by osl1smout1.broadpark.no (Sun Java System Messaging Server 6.1 HotFix 0.05 (built Oct 21 2004)) with ESMTP id <0IGH0029BJP41GD0@osl1smout1.broadpark.no>; Sat, 14 May 2005 17:15:04 +0200 (CEST) Received: from dsa.des.no ([80.203.228.37]) by osl1sminn1.broadpark.no (Sun Java System Messaging Server 6.1 HotFix 0.05 (built Oct 21 2004)) with ESMTP id <0IGH00LHEE0H6QA0@osl1sminn1.broadpark.no>; Sat, 14 May 2005 15:12:17 +0200 (CEST) Received: by dsa.des.no (Pony Express, from userid 666) id 3A4CC45165; Sat, 14 May 2005 15:08:29 +0200 (CEST) Received: from xps.des.no (xps.des.no [10.0.0.12]) by dsa.des.no (Pony Express) with ESMTP id 83F2945131; Sat, 14 May 2005 15:08:25 +0200 (CEST) Received: by xps.des.no (Postfix, from userid 1001) id 761B933C3B; Sat, 14 May 2005 15:08:25 +0200 (CEST) Date: Sat, 14 May 2005 15:08:25 +0200 From: des@des.no (=?iso-8859-1?q?Dag-Erling_Sm=F8rgrav?=) In-reply-to: <94145.1116037219@critter.freebsd.dk> To: Poul-Henning Kamp Message-id: <86fywqdkfq.fsf@xps.des.no> MIME-version: 1.0 Content-type: text/plain; charset=iso-8859-1 Content-transfer-encoding: quoted-printable X-Spam-Checker-Version: SpamAssassin 3.0.2 (2004-11-16) on dsa.des.no References: <94145.1116037219@critter.freebsd.dk> User-Agent: Gnus/5.110002 (No Gnus v0.2) Emacs/21.3 (berkeley-unix) X-Spam-Status: No, score=-2.8 required=5.0 tests=ALL_TRUSTED,AWL autolearn=disabled version=3.0.2 X-Spam-Level: cc: freebsd-security@freebsd.org cc: das@freebsd.org cc: "Drew B. \[Security Expertise/Freelance Security research\]." 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 13:08:31 -0000 "Poul-Henning Kamp" writes: > The correct (technical) workaround (IMO) is to restrict HTT to be > used only for threads from the same process. > > 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. No. Intel themselves recommend only scheduling threads from the same address space on the same physical core, simply because it improves cache efficiency. Scheduling threads from separate processes on the same physical core can actually *reduce* performance due to cache churn. Fixing our scheduler to avoid scheduling threads from different processes on the same physical core is likely to increase performance across the board, because heavily multithreaded software will get a bigger boost and single-threaded software will be penalized less than it is today. DES --=20 Dag-Erling Sm=F8rgrav - des@des.no