From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 583FEC433E0 for ; Fri, 24 Jul 2020 00:57:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 26B72208A9 for ; Fri, 24 Jul 2020 00:57:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595552227; bh=r5WxFrMiDdKHTC3n7Eg5/S6BdCaIflcHYZos9cjnVOI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=lW7kr2ouPzTzpKuBowBUNjGI/YXmRWJmF9y/jE7EQQRXobXCdTN24q5cyu60+w1G1 8SvlITM2JzNkQVbk5I1Uvozr0/PenJOjLFWnO6ZBXUAwR1yvkYmqAorY9bDxL2sOg2 mTMH5Sm4E5kPSxkVI0h8EZ/h1kVO9ywHq/KQEfzI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728362AbgGXA5G (ORCPT ); Thu, 23 Jul 2020 20:57:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:33630 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727783AbgGXA5F (ORCPT ); Thu, 23 Jul 2020 20:57:05 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DF6B12086A; Fri, 24 Jul 2020 00:57:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595552225; bh=r5WxFrMiDdKHTC3n7Eg5/S6BdCaIflcHYZos9cjnVOI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=A6VgWN4htxp/7jHEyuT/i8Rz/5PrRRJcbIlv5FoYcEQGIwgzxxxNP8mvELD6OpEmo fQFEb2RN093Ag/ZOmX8rPgE4StK8ZyCK18P3YSyEmevfo1QAufGZaeiOiltVe1G5l6 /sbTQfMJ7T0UtIEnmBt9bfFSv6bfZqNc0jfKe8AU= Date: Thu, 23 Jul 2020 17:57:04 -0700 From: Andrew Morton To: Feng Tang Cc: Masahiro Yamada , Michal Marek , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds , andi.kleen@intel.com, ying.huang@intel.com, andriy.shevchenko@intel.com Subject: Re: [RFC PATCH] makefile: add debug option to enable function aligned on 32 bytes Message-Id: <20200723175704.44c4b890e76dc6dc68bf3674@linux-foundation.org> In-Reply-To: <20200723062933.GA65362@shbuild999.sh.intel.com> References: <1595475001-90945-1-git-send-email-feng.tang@intel.com> <20200722203919.8b7c9b35ff51d66550c3846c@linux-foundation.org> <20200723062933.GA65362@shbuild999.sh.intel.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 23 Jul 2020 14:29:33 +0800 Feng Tang wrote: > > > gcc has an option '-falign-functions=n' to force text aligned, and with > > > that option enabled, some of those performance changes will be gone, > > > like [1][2][3]. > > > > > > Add this option so that developers and 0day can easily find performance > > > bump caused by text alignment change, > > > > Would they use it this way, or would they simply always enable the > > option to reduce the variability? > > I may mis-understood it in my last reply. If you are asking about how > will developers and 0day use this option, for 0day, I've talked with > 0day folks, they may just enable it by default, as 0day cares more about > the performance delta caused by a commit (Adding Philip and Rong from > 0day). OK, thanks, I suspected as much. The patch is so simple and probably-will-work, I guess we toss it in there and see. However it would be good if the 0day people could use it for a while and then provide some feedback on whether it is actually proving useful. If not, we get to remove some stuff.