From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262202AbVAEBJY (ORCPT ); Tue, 4 Jan 2005 20:09:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262203AbVAEBJY (ORCPT ); Tue, 4 Jan 2005 20:09:24 -0500 Received: from clock-tower.bc.nu ([81.2.110.250]:15031 "EHLO localhost.localdomain") by vger.kernel.org with ESMTP id S262176AbVAEBGV (ORCPT ); Tue, 4 Jan 2005 20:06:21 -0500 Subject: Re: Very high load on P4 machines with 2.4.28 From: Alan Cox To: Nicholas Berry Cc: grendel@caudium.net, willy@w.ods.org, Linux Kernel Mailing List In-Reply-To: References: Content-Type: text/plain Content-Transfer-Encoding: 7bit Message-Id: <1104879448.17176.72.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 (1.4.6-2) Date: Wed, 05 Jan 2005 00:02:08 +0000 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Maw, 2005-01-04 at 22:41, Nicholas Berry wrote: > Indeed. AIX (sorry) 5.3 on POWER5 explicitly disables SMT (IBM > hyperthreading) if the load doesn't warrant it. > > (Now how about that for Linux?) :) It would be very nice to do but AFAIK no current processor with hypedthreading lets you do dynamic disabling. We do try and land tasks on the real processors before other SMT threads and to leave the other threads idle. I'm not sure we could do much more unless flipping the cache control bits on packages when idle is a win (which I doubt)