From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752092Ab3AZPUW (ORCPT ); Sat, 26 Jan 2013 10:20:22 -0500 Received: from terminus.zytor.com ([198.137.202.10]:52820 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751066Ab3AZPUT (ORCPT ); Sat, 26 Jan 2013 10:20:19 -0500 User-Agent: K-9 Mail for Android In-Reply-To: <20130126125208.GC21395@pd.tnic> References: <1359123061-6139-1-git-send-email-ling.ma@alipay.com> <20130126125208.GC21395@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: Re: [tip:x86/asm] x86/defconfig: Turn on CONFIG_CC_OPTIMIZE_FOR_SIZE= y in the 64-bit defconfig From: "H. Peter Anvin" Date: Sat, 26 Jan 2013 07:18:26 -0800 To: Borislav Petkov , mingo@kernel.org, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, arjan@linux.intel.com, jbeulich@suse.com, ling.ml@alipay.com, rostedt@goodmis.org, akpm@linux-foundation.org, tglx@linutronix.de CC: linux-tip-commits@vger.kernel.org Message-ID: <8b0dfc4a-6f9c-498a-9844-4d99deb3052f@email.android.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On the CPUs Ling is testing on the downsides of -Os probably matter less, in particular since rep movsb works well. It is questionable as a generic default, though. The whole -Ok discussion came from that. Borislav Petkov wrote: >On Sat, Jan 26, 2013 at 04:25:57AM -0800, tip-bot for Ma Ling wrote: >> During the same time (269.410275674 seconds) IPC from Os is >> 0.37, O2 is 0.36, Os improved performance 2.7%. >> >> Signed-off-by: Ma Ling >> Cc: Linus Torvalds >> Cc: Arjan van de Ven >> Cc: Andrew Morton >> Cc: Jan Beulich >> Cc: Steven Rostedt >> Link: >http://lkml.kernel.org/r/1359123061-6139-1-git-send-email-ling.ma@alipay.com >> [ So, this is a bit symbolic as most people don't use the defconfig, >> but the measurements are useful nevertheless so let's commit this >> if there are no objections. ] > >What about > >commit 3a55fb0d9fe8e2f4594329edd58c5fd6f35a99dd >Author: Kirill Smelkov >Date: Fri Nov 2 15:41:01 2012 +0400 > > Tell the world we gave up on pushing CC_OPTIMIZE_FOR_SIZE > >? > >Reportedly, -Os generates suboptimal code in certain cases and we >advise >against it with this patch. -- Sent from my mobile phone. Please excuse brevity and lack of formatting.