From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753576AbZBGOCh (ORCPT ); Sat, 7 Feb 2009 09:02:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751529AbZBGOC2 (ORCPT ); Sat, 7 Feb 2009 09:02:28 -0500 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:48595 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750920AbZBGOC2 (ORCPT ); Sat, 7 Feb 2009 09:02:28 -0500 Date: Sat, 7 Feb 2009 14:02:45 +0000 From: Alan Cox To: "Pallipadi, Venkatesh" Cc: H Peter Anvin , Ingo Molnar , thomas@linux-os.sc.intel.com, linux-kernel Subject: Re: [PATCH] x86: Add clflush before monitor for Intel 7400 series - v2 Message-ID: <20090207140245.1e91a88f@lxorguk.ukuu.org.uk> In-Reply-To: <20090207004728.GA17586@linux-os.sc.intel.com> References: <20090207004728.GA17586@linux-os.sc.intel.com> X-Mailer: Claws Mail 3.5.0 (GTK+ 2.12.12; x86_64-redhat-linux-gnu) Organization: Red Hat UK Cyf., Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, Y Deyrnas Gyfunol. Cofrestrwyd yng Nghymru a Lloegr o'r rhif cofrestru 3798903 Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 6 Feb 2009 16:47:29 -0800 "Pallipadi, Venkatesh" wrote: > > > For Intel 7400 series CPUs, the recommendation is to use a clflush on the > monitored address just before monitor and mwait pair [1]. This clflush makes > sure that there are no false wakeups from mwait when the monitored address > was recently written to. Given our mwait usages will very quickly go back to sleep in such a case and it would almost certainly be one sleep only is this really worth the effort ?