Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753395Ab3IJQYZ (ORCPT ); Tue, 10 Sep 2013 12:24:25 -0400 Received: from mail-ee0-f52.google.com ([74.125.83.52]:37464 "EHLO mail-ee0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752463Ab3IJQYX (ORCPT ); Tue, 10 Sep 2013 12:24:23 -0400 MIME-Version: 1.0 In-Reply-To: <522F3ACC.9000701@linux.intel.com> References: <20130910130811.507933095@infradead.org> <20130910135152.GD7537@gmail.com> <20130910135636.GA8268@gmail.com> <522F3ACC.9000701@linux.intel.com> Date: Tue, 10 Sep 2013 09:24:21 -0700 X-Google-Sender-Auth: koa1p7l-7y13DsfLoycT_eP1RrQ Message-ID: Subject: Re: [PATCH 0/7] preempt_count rework -v2 From: Linus Torvalds To: Arjan van de Ven Cc: Ingo Molnar , Peter Zijlstra , Andi Kleen , Peter Anvin , Mike Galbraith , Thomas Gleixner , Frederic Weisbecker , Linux Kernel Mailing List , "linux-arch@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 917 Lines: 24 On Tue, Sep 10, 2013 at 8:29 AM, Arjan van de Ven wrote: >> > also.. yuck on using "dec" > "dec" sucks, please use "sub foo ,1" instead That's a bigger instruction, largely due to the constant. > (dec sucks because of its broken flags behavior; it creates basically a > bubble in the pipeline) Intel could (and should) just fix that. It's "easy" enough - you just need to rename the carry flag as a separate register (and make sure that the conditional instructions that don't use it don't think they need it). In fact I thought Intel already did that on their large cores. Are you sure they still have trouble with inc/dec? Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/