From: "H. Peter Anvin" Subject: Re: [PATCH 1/1] x86: fix text_poke Date: Fri, 25 Apr 2008 08:57:20 -0700 Message-ID: <4811FF60.6040905@zytor.com> References: <20080425.021301.193689806.davem@davemloft.net> <1209343883-7991-1-git-send-email-jirislaby@gmail.com> <20080425151931.GA25510@elte.hu> <20080425152650.GA894@elte.hu> <20080425155000.GA4438@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Linus Torvalds , Jiri Slaby , David Miller , zdenek.kabelac@gmail.com, rjw@sisk.pl, paulmck@linux.vnet.ibm.com, akpm@linux-foundation.org, linux-ext4@vger.kernel.org, herbert@gondor.apana.org.au, penberg@cs.helsinki.fi, clameter@sgi.com, linux-kernel@vger.kernel.org, Mathieu Desnoyers , Andi Kleen , pageexec@freemail.hu, Jeremy Fitzhardinge To: Ingo Molnar Return-path: Received: from terminus.zytor.com ([198.137.202.10]:43223 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756882AbYDYQFW (ORCPT ); Fri, 25 Apr 2008 12:05:22 -0400 In-Reply-To: <20080425155000.GA4438@elte.hu> Sender: linux-ext4-owner@vger.kernel.org List-ID: Ingo Molnar wrote: > > text_poke() itself only applies/unapplies the LOCK prefix - a single > byte. We shouldnt be doing that at all: the cost of LOCK is > insignificant (a few cycles) and most systems are SMP anyway. > Alas, on older CPUs the cost of LOCK can be massive. The question is how much we really care - the embedded people (who would definitely be affected) will simply build UP kernels, and this only affects booting SMP kernels on UP. -hpa