From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 16924 invoked by uid 1002); 14 Aug 2003 17:38:45 -0000 Mailing-List: contact gentoo-dev-help@gentoo.org; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-dev@gentoo.org Received: (qmail 26831 invoked from network); 14 Aug 2003 17:38:45 -0000 Message-ID: <011501c3628a$ea89e3a0$1401a8c0@punx> From: "matt c" To: "gentoo-dev ML" References: <1060781901.7508.17.camel@biproc> <1060783729.4133.42.camel@vertigo> <1060784410.7503.29.camel@biproc> <1060809305.3784.2.camel@localhost> <1060814942.27241.148.camel@rattus.Localdomain> <1060864255.19236.147.camel@vertigo> <1060880359.28694.346.camel@rattus.Localdomain> Date: Thu, 14 Aug 2003 10:38:47 -0700 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1158 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 Subject: Re: [gentoo-dev] "Distro Day (Measuring the benefits of the Gentooapproach)" X-Archives-Salt: 19ba9323-3459-4308-b4cf-6e49d57963c2 X-Archives-Hash: b07da4a66a61077027746cb7d6912838 Sorry for butchering your email, I only wanted to ask the list about one point I saw that you made. ----- Original Message ----- From: "William Kenworthy" Subject: Re: [gentoo-dev] "Distro Day (Measuring the benefits of the Gentooapproach)" > Wish more would do as you have done - I dont think too many follow this > approach. Most seem to just do the reccomended, or go for the max. I > did a few key apps, made my choices and have stayed with them. If a > really useful cflags project gets up, it would be nice to run it > regularly and perhaps find that the new gcc just emerged gives a > measured 5% speed up if you use the new -supercharger flag! I think that this is where the confusion with many "experts" on optimization lies. What is a good program to use as a benchmark for optimizations and compiler flags? How does one measure the performance gain? Is the performance gain just in load time, or in processor usage throughout the program? Do the benefits of using a particular optimization translate from one program to the next? Some programs are snappier with -O2, some perform twice as quick with -O3. Who is to say? How does one know for certain? I have found that, for the most part, -O2 compiled apps runs much faster on my system. I don't have any hard numbers, but I do know I decided to rebuild my system recently with just -O2 ,-pipe, and -fomit-frame-pointer only - Everything I do seems to be a bit more responsive. >>From what I've been hearing, I think the general consensus is that -O2 seems to be a better optimization than -O3 *in general, for the most people*, yes? Right now the "Decent examples" in make.conf include (in both examples) -O3 as the optimization level to use. If -O2 is that much better, would it not be the sane thing to recommend to users who read make.conf to use -O2? I don't know - do -finline-functions and -frename-registers really make that much of a difference? I am no expert at compiler internals. I only know what has been my experience and what others say. Just a thought. Matt -- gentoo-dev@gentoo.org mailing list