From owner-freebsd-stable@FreeBSD.ORG Mon Mar 15 18:02:59 2004 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id D986516A4CE for ; Mon, 15 Mar 2004 18:02:59 -0800 (PST) Received: from mail.menalto.com (www.menalto.com [209.237.226.157]) by mx1.FreeBSD.org (Postfix) with ESMTP id ADA6D43D2F for ; Mon, 15 Mar 2004 18:02:59 -0800 (PST) (envelope-from bharat@menalto.com) Received: from bmedirattatg (nat-hdqt.vasoftware.com [198.186.202.17]) by mail.menalto.com (8.12.11/8.12.11) with SMTP id i2G22uDG005241 for ; Mon, 15 Mar 2004 18:02:56 -0800 (PST) (envelope-from bharat@menalto.com) Message-ID: <0d0d01c40afa$ccac1d30$c90c030a@bmedirattatg> From: "Bharat Mediratta" To: References: <20040315152550.M213@Daath.hq.communityconnect.com> <20040315204827.GQ30555@therub.org> Date: Mon, 15 Mar 2004 18:02:50 -0800 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1158 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 Subject: Re: HyperThreading CPU's X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 16 Mar 2004 02:03:00 -0000 From: "Dan Rue" ... > 20031022: > Support for HyperThread logical CPUs has now been enabled by > default. As a result, the HTT kernel option no longer exists. > Instead, the logical CPUs are always started so that they can > handle interrupts. However, the extra logical CPUs are prevented > from executing user processes by default. To enable the logical > CPUs, change the value of the machdep.hlt_logical_cpus from 1 to > 0. This value can also be set from the loader as a tunable of > the same name. Does 4.9 actually make effective use of HTT? I read recently (can't remember where, but I can probably find it if pressed) that in 4.8 enabling HTT was probably going to cause performance degradatation due to locking issues in the kernel. I've been itching to upgrade to 5.x to get more value out of my MP+HTT box, but don't want to upgrade until it's production release quality. If the 4.9 kernel really takes advantage of HTT, that would be worth upgrading for, IMO. -Bharat