From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754299AbbDHNQd (ORCPT ); Wed, 8 Apr 2015 09:16:33 -0400 Received: from mail-wi0-f171.google.com ([209.85.212.171]:37222 "EHLO mail-wi0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754276AbbDHNQb (ORCPT ); Wed, 8 Apr 2015 09:16:31 -0400 MIME-Version: 1.0 In-Reply-To: References: <1428388995.3152.10.camel@gmail.com> <1428401356.3152.38.camel@gmail.com> <55241C51.8040107@gmail.com> From: Pengfei Yuan <0xcoolypf@gmail.com> Date: Wed, 8 Apr 2015 21:16:10 +0800 Message-ID: Subject: Re: Why not build kernel with -O3 To: Richard Weinberger Cc: Austin S Hemmelgarn , Mike Galbraith , LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2015-04-08 20:19 GMT+08:00 Richard Weinberger : > On Wed, Apr 8, 2015 at 3:00 AM, Pengfei Yuan <0xcoolypf@gmail.com> wrote: >> Could you please provide some examples that I can investigate? >> Thanks! > > It would be awesome if you could find out which gcc optimizations > cause the speed up. > "gcc -c -Q -O3 --help=optimizers" will help you. > This is really helpful. But I can only find very short description for each option from https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html > Please also double check your results. > You need do to multiple runs, etc... > Especially the redis speed up looks odd. Does redis really spend that much time > in the kernel? Redis is special among the six applications because it is single-threaded. Yuan