From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752826AbaCGMmw (ORCPT ); Fri, 7 Mar 2014 07:42:52 -0500 Received: from b.ns.miles-group.at ([95.130.255.144]:1660 "EHLO radon.swed.at" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751581AbaCGMmu (ORCPT ); Fri, 7 Mar 2014 07:42:50 -0500 Message-ID: <5319BEC0.4050006@nod.at> Date: Fri, 07 Mar 2014 13:42:40 +0100 From: Richard Weinberger User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: Austin S Hemmelgarn , Borislav Petkov , Jon Ringle CC: Greg KH , "Ringle, Jonathan" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] Add option to build with -O3 References: <1393977709-9809-1-git-send-email-jringle@gridpoint.com> <20140305050927.GA8534@kroah.com> <5319BE19.5000607@gmail.com> In-Reply-To: <5319BE19.5000607@gmail.com> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 07.03.2014 13:39, schrieb Austin S Hemmelgarn: > On 2014-03-06 08:28, Richard Weinberger wrote: >> On Wed, Mar 5, 2014 at 6:37 AM, Jon Ringle >> wrote: >>> >>> >>> On Wed, 5 Mar 2014, Greg KH wrote: >>> >>>> On Tue, Mar 04, 2014 at 07:01:49PM -0500, Jon Ringle wrote: >>>>> +config CC_OPTIMIZE_FOR_SPEED + bool "Optimze for speed >>>>> (-O3)" + help + Enabling this option will pass "-O3" >>>>> to gcc + resulting in a larger kernel (but possibly >>>>> faster) >>>> >>>> Are you sure about that? Have you measured it? >>> >>> I do know that there is an improvement performance-wise for my >>> particular use-case. >>> >>> My target is an ARM board being built with gcc-4.8.2. My board >>> has on it a sc16is740 that is used as an RS-485 port. The >>> sc16is740 is on the i2c bus, so when an interrupt comes in to >>> indicate that there is data available to be read, I need to get >>> the data over the i2c bus. I do this on a kthread to do this >>> work. The i2c transactions (using i2c-davinci driver) are also >>> interrupt driven. I was seeing a lot of lost packets when >>> receiving data at only 19200. Adding the -O3 compile option >>> helped in this regard in that I am now rarely seeing packet >>> loss. >> >> Please also see: >> http://www.gossamer-threads.com/lists/linux/kernel/1835761?do=post_view_threaded#1835761 >> >> > Ironically, combining these might achieve a significant performance > improvement over CONFIG_GENERIC_CPU and -O2. *might* We still need a sane proof. Thanks, //richard