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List Archive: gentoo-performance
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To: gentoo-performance@g.o
From: Colin Kingsley <ckingsley@...>
Subject: Re: inline considered harmful
Date: Thu, 22 Jul 2004 01:44:36 -0400
true, you could, but it would be much neater to use -O3 and disable
stuff using -fno-whatever. Also, this would have the benefit of
remaining usefull even if a new version of gcc had a diferent set of
optimisations in -O3.

but thats just my oppinion:)



On Wed, 21 Jul 2004 21:16:43 -0400, Douglas Breault Jr.
<genkreton@...> wrote:
> You could just enable -O2 and the following: -frename-registers and -fweb. -O3 is simply -O2 plus those 3 options.
> 
> 
> 
> On Wed, 21 Jul 2004 20:50:01 -0400
> Adam Petaccia <adam@...> wrote:
> 
> > With gcc, is there a way to enable all -O3 options but function
> > inlines?  Would -fno-inline work or something like that?
> >
> > Mario Domenech Goulart wrote:
> >
> > >Hello,
> > >
> > >There's an interesting discussion in the OpenBSD mailing
> > >list about the use of inline.
> > >
> > >Here's the beginning of the thread about this topic:
> > >
> > >,----[ http://www.sigmasoft.com/cgi-bin/wilma_hiliter/openbsd-tech/200407/msg00175.html ]
> > >| inline considered harmful.
> > >|
> > >|     * To: tech@...
> > >|     * Subject: inline considered harmful.
> > >|     * From: Artur Grabowski <art@...>
> > >|     * Date: 21 Jul 2004 03:54:46 +0200
> > >|     * User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2
> > >|
> > >| Today we did a bunch of removal of inline functions in the kernel.
> > >| It all started to make floppies fit, but now it's a quest.
> > >|
> > >| If you think that I'm crazy doing this because it might hurt your
> > >| precious performance, go back to your vax and leave the performance
> > >| tuning to people who have a cache.
> > >|
> > >| Every single inline we removed today (and there are more in the
> > >| pipeline and even more waiting to be fixed) shrunk the code and MADE
> > >| IT FASTER.  Yes, modern cpus have something called "cache". The cache
> > >| prefers the code to be smaller, rather than free from function calls.
> > >| Yes, some cpus have expensive function call overhead. Don't use them.
> > >| i386 has quite expensive function calls, on the other hand it doesn't
> > >| have any relevant amount of registers either. So a function call
> > >| instead of the same function inlined can potentially make the job
> > >| easier for the register allocator in the compiler which could eat the
> > >| overhead. At the same time the instruction cache can run the same code
> > >| in the same place, instead of loading it from main memory 4711 times.
> > >| And guess what? The stack on i386 is in the cache too, so the function
> > >| call overhead isn't that bad anyway.
> > >|
> > >| I'm tired of seeing code where everything is made inline just because
> > >| someone acted on a meme that hasn't been true for over a decade. Bloat,
> > >| bloat and more bloat. Since people can't use inline correctly (it does
> > >| have valid and correct uses), from now on inline in the OpenBSD kernel
> > >| is considered to be a bug until proven otherwise. So. Next time I see
> > >| code that adds to the bloat with inlines, I expect performance figures
> > >| and kernel size comparisons that show that the inline actually
> > >| contributes anything. Otherwise the code does not go in.
> > >|
> > >| There's still a lot of work to be done in the kernel (yes, macros can
> > >| be evil too, just see nfs), so send diffs. And there's a whole
> > >| unexplored field in userland too.
> > >|
> > >| //art
> > >`----
> > >
> > >Mario
> > >
> > >
> > >--
> > >gentoo-performance@g.o mailing list
> > >
> > >
> > >
> > >
> >
> > --
> > gentoo-performance@g.o mailing list
> >
> 
> 
>

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gentoo-performance@g.o mailing list

Replies:
Re: inline considered harmful
-- Douglas Breault Jr.
Re: inline considered harmful
-- Colin Kingsley
References:
inline considered harmful
-- Mario Domenech Goulart
Re: inline considered harmful
-- Adam Petaccia
Re: inline considered harmful
-- Douglas Breault Jr.
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Updated Jun 17, 2009

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