From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752934AbbDGGnS (ORCPT ); Tue, 7 Apr 2015 02:43:18 -0400 Received: from mail-wg0-f50.google.com ([74.125.82.50]:35363 "EHLO mail-wg0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750878AbbDGGnR (ORCPT ); Tue, 7 Apr 2015 02:43:17 -0400 Message-ID: <1428388995.3152.10.camel@gmail.com> Subject: Re: Why not build kernel with -O3 From: Mike Galbraith To: Pengfei Yuan <0xcoolypf@gmail.com> Cc: linux-kernel@vger.kernel.org Date: Tue, 07 Apr 2015 08:43:15 +0200 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.16.0 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 ;-) -Mike