From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751636AbZHSJXp (ORCPT ); Wed, 19 Aug 2009 05:23:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751494AbZHSJXo (ORCPT ); Wed, 19 Aug 2009 05:23:44 -0400 Received: from vpn.id2.novell.com ([195.33.99.129]:19551 "EHLO vpn.id2.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751617AbZHSJXn convert rfc822-to-8bit (ORCPT ); Wed, 19 Aug 2009 05:23:43 -0400 Message-Id: <4A8BE0BE0200007800010890@vpn.id2.novell.com> X-Mailer: Novell GroupWise Internet Agent 8.0.0 Date: Wed, 19 Aug 2009 10:23:42 +0100 From: "Jan Beulich" To: "Thomas Gleixner" Cc: , "Peter Zijlstra" , , Subject: Re: [PATCH] x86: make use of inc/dec conditional References: <4A8BCA850200007800010836@vpn.id2.novell.com> <1250668860.7583.327.camel@twins> <4A8BDB51020000780001086E@vpn.id2.novell.com> In-Reply-To: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>> Thomas Gleixner 19.08.09 11:06 >>> >You still do not tell on which machines the INC/DEC instructions >should be avoided and why. GCC avoiding it is not a convincing >argument. On Pentium4 (Prescott/Nocona) inc/dec not modifying the carry flag cause an extra instruction dependency on EFLAGS, and hence extra latency in when the instruction can be scheduled for execution. Jan