From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753227AbbDGHHU (ORCPT ); Tue, 7 Apr 2015 03:07:20 -0400 Received: from mail-wi0-f177.google.com ([209.85.212.177]:34187 "EHLO mail-wi0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751222AbbDGHHQ (ORCPT ); Tue, 7 Apr 2015 03:07:16 -0400 Message-ID: <55238221.9070905@plexistor.com> Date: Tue, 07 Apr 2015 10:07:13 +0300 From: Boaz Harrosh User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Mike Galbraith , Pengfei Yuan <0xcoolypf@gmail.com> CC: linux-kernel@vger.kernel.org Subject: Re: Why not build kernel with -O3 References: <1428388995.3152.10.camel@gmail.com> In-Reply-To: <1428388995.3152.10.camel@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/07/2015 09:43 AM, Mike Galbraith wrote: > On Tue, 2015-04-07 at 11:37 +0800, Pengfei Yuan wrote: >> Hi, >> >> I have conducted some experiments to compare kernels built with -O2 >> and -O3. Here are the results: >> >> Application Performance O2 Performance O3 Improvement >> Apache 127814.14 req/s 130321.24 req/s 1.96% >> Nginx 537589.08 req/s 556723.32 req/s 3.56% >> MySQL 70661.38 tx/s 71008.47 tx/s 0.49% >> PostgreSQL 79763.39 tx/s 79535.59 tx/s -0.29% >> Redis 352547.47 op/s 405417.24 op/s 15.0% >> Memcached 844439.14 op/s 845321.79 op/s 0.10% >> >> Geomean: +3.34% >> >> Experiment environment: Linux 3.19.3, GCC 4.9.3 prerelease, Core-i7 >> 4770, 32G RAM, 10GbE >> >> LMbench microbenchmark also shows reduction in various latencies, as >> well as increase of throughputs. > > Please show multiple run data for all permutations of supported gcc > version/arch ;-) > He did say optional. So I'd imagine it would be a Kconfig of its own. So the default can be as today, but people that want to experiment need not hack the source code. Cheers Boaz > -Mike