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From: "matt c" <matt@legalizefreedom.org>
To: "gentoo-dev ML" <gentoo-dev@gentoo.org>
Subject: Re: [gentoo-dev] "Distro Day (Measuring the benefits of the Gentooapproach)"
Date: Thu, 14 Aug 2003 10:38:47 -0700	[thread overview]
Message-ID: <011501c3628a$ea89e3a0$1401a8c0@punx> (raw)
In-Reply-To: 1060880359.28694.346.camel@rattus.Localdomain

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" <billk@iinet.net.au>
Subject: Re: [gentoo-dev] "Distro Day (Measuring the benefits of the
Gentooapproach)"
<snip>
> 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


  reply	other threads:[~2003-08-14 17:38 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-08-13 13:38 [gentoo-dev] "Distro Day (Measuring the benefits of the Gentoo approach)" Philippe Lafoucrière
2003-08-13 14:07 ` brett holcomb
2003-08-13 15:03   ` Sven Vermeulen
2003-08-13 16:15     ` Alan
2003-08-13 20:30       ` Chris Gianelloni
2003-08-13 14:08 ` Chris Gianelloni
2003-08-13 14:12   ` Brad Laue
2003-08-13 14:20   ` Philippe Lafoucrière
2003-08-13 14:25     ` Philippe Lafoucrière
2003-08-13 14:32     ` Chris Gianelloni
2003-08-13 16:17       ` Alan
2003-08-13 16:22         ` Patrick Kursawe
2003-08-13 20:35           ` Chris Gianelloni
2003-08-13 20:32         ` Chris Gianelloni
2003-08-14 10:02           ` Paul de Vrieze
2003-08-13 21:15     ` FRLinux
2003-08-13 22:49       ` William Kenworthy
2003-08-14  2:04         ` Brian Jackson
2003-08-14 10:10         ` Paul de Vrieze
2003-08-14 12:30         ` Chris Gianelloni
2003-08-14 16:59           ` William Kenworthy
2003-08-14 17:38             ` matt c [this message]
2003-08-14 19:22         ` FRLinux
2003-08-14 23:01           ` William Kenworthy
2003-08-13 14:24 ` David Holm
2003-08-13 14:28   ` Philippe Lafoucrière
2003-08-13 16:16     ` Eric Olinger
2003-08-13 19:00   ` Jon Portnoy
2003-08-13 20:02     ` Mike Frysinger
2003-08-14  1:07       ` [gentoo-dev] 'Distro Day (Measuring the benefits of the Gentoo approach)' donnie berkholz
2003-08-14  1:13         ` Jon Portnoy
2003-08-14 11:01         ` Chris Gianelloni
2003-08-13 14:34 ` [gentoo-dev] "Distro Day (Measuring the benefits of the Gentoo approach)" Stuart Herbert
2003-08-13 14:34 ` Svyatogor
2003-08-13 17:46 ` Adam Porich

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