From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753292AbbDGDhv (ORCPT ); Mon, 6 Apr 2015 23:37:51 -0400 Received: from mail-wg0-f48.google.com ([74.125.82.48]:34542 "EHLO mail-wg0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753139AbbDGDhs (ORCPT ); Mon, 6 Apr 2015 23:37:48 -0400 MIME-Version: 1.0 From: Pengfei Yuan <0xcoolypf@gmail.com> Date: Tue, 7 Apr 2015 11:37:27 +0800 Message-ID: Subject: Why not build kernel with -O3 To: linux-kernel@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Why not add an option to build kernel with -O3? Regards, YUAN, Pengfei