From: Adrian Bunk <bunk@stusta.de>
To: Ingo Molnar <mingo@elte.hu>
Cc: Arjan van de Ven <arjan@infradead.org>,
Tim Schmielau <tim@physik3.uni-rostock.de>,
Linus Torvalds <torvalds@osdl.org>, Dave Jones <davej@redhat.com>,
Andrew Morton <akpm@osdl.org>,
lkml <linux-kernel@vger.kernel.org>,
mpm@selenic.com
Subject: Re: [patch 00/2] improve .text size on gcc 4.0 and newer compilers
Date: Mon, 2 Jan 2006 16:01:58 +0100 [thread overview]
Message-ID: <20060102150158.GE17398@stusta.de> (raw)
In-Reply-To: <20060102140511.GA2968@elte.hu>
On Mon, Jan 02, 2006 at 03:05:11PM +0100, Ingo Molnar wrote:
>
> * Adrian Bunk <bunk@stusta.de> wrote:
>
> > > > > Your uninline patch might be simple, but the safe way would be Arjan's
> > > > > approach to start removing all the buggy inline's from .c files.
> > > >
> > > > sure, that's another thing to do, but it's also clear that there's no
> > > > reason to force inlines in the -Os case.
> > > >
> > > > There are 22,000+ inline functions in the kernel right now (inlined
> > > > about a 100,000 times), and we'd have to change _thousands_ of them.
> > > > They are causing an unjustified code bloat of somewhere around 20-30%.
> > > > (some of them are very much justified, especially in core kernel code)
> > >
> > > my patch attacks the top bloaters, and gains about 30k to 40k (depending
> > > on compiler). Gaining the other 300k is going to be a LOT of churn, not
> > > just in amount of work... so to some degree my patch shows that it's a
> > > bit of a hopeless battle.
> >
> > A quick grep shows at about 10.000 inline's in .c files, and nearly
> > all of them should be removed.
> >
> > Yes this is a serious amount of work, but it's an ideal janitorial
> > task.
>
> oh, it is certainly an insane amount of janitorial work - which is also
> precisely why this well-known and seemingly trivial problem has
> escallated so much!
>
> the nontrivial thing is that the moment trivial things get widespread,
> _the mechanism_ needs a change. I.e. the 'widespread inlines' arent the
> big problem, the big problem is that the widespread inlines _got
> widespread_. I'm not sure whether i'm being clear enough: think of the
> 22,000 inlines as a symptom of a deeper problem, not as the problem
> itself. That is i am trying to get through (to you and to others).
My point goes more into the following direction:
- 10,000 inline's are in .c files
- 12,000 inline's are in .h files
The interesting one's are the latter:
- if they are too big, the smallest solution is to move them to .c files
- it might cause a size _increase_ if some version if gcc will not
inline all of them
The latter gives warnings with -Winline, and adding this flag to the
gloval CFLAGS and analyzing all the warnings (especially with -Os) could
make my point void.
>...
> what is the 'deeper problem'? I believe it is a combination of two
> (well-known) things:
>
> 1) people add 'inline' too easily
> 2) we default to 'always inline'
>
> problem #1 is very hard to influence, because it's a basic psychology
> issue. Pretty much the only approach to fix this is to educate people.
> But it is hard to change the ways people code, and it's a long-term
> thing with no reasonable expectation of success. So while we can and
> should improve education of this issue (this thread will certainly raise
> awareness of it), we cannot rely on it alone.
>
> i think the only realistic approach is to attack component #2: do not
> default to 'always inline' but default to 'inline if the compiler agrees
> too'. I do think we should default to 'compiler decides' (when using a
> gcc4 compiler), as this also has some obvious advantages:
>
> - different inlining when compiler optimizes for size not for speed
>
> changing this also means we need to map a few trivial cases where kernel
> code relies on inlining (or relies on non-inlining), but those are
> fortunately easy and mostly well-known.
>...
> so all in one, unless we attack #1 or #2 _with a bigger effective effort
> than we spend on attacking the symptoms_, we will only achieve a
> temporary, short-term reprieve.
#1 should definitely be done.
And you do slightly manage to convince me that #2 is a good (additional)
approach (if -Winline gets added to the global CFLAGS).
> Ingo
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
next prev parent reply other threads:[~2006-01-02 15:01 UTC|newest]
Thread overview: 210+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-12-28 11:46 [patch 00/2] improve .text size on gcc 4.0 and newer compilers Ingo Molnar
2005-12-28 19:17 ` Linus Torvalds
2005-12-28 19:34 ` Arjan van de Ven
2005-12-28 21:02 ` Linus Torvalds
2005-12-28 21:17 ` Arjan van de Ven
2005-12-28 21:23 ` Ingo Molnar
2005-12-28 21:48 ` Ingo Molnar
2005-12-28 23:56 ` Krzysztof Halasa
2005-12-29 7:41 ` Ingo Molnar
2005-12-29 8:02 ` Dave Jones
2005-12-29 19:44 ` Krzysztof Halasa
2005-12-29 4:11 ` Andrew Morton
2005-12-29 7:32 ` Ingo Molnar
2005-12-29 14:58 ` Horst von Brand
2005-12-29 15:40 ` Adrian Bunk
2005-12-29 17:41 ` Linus Torvalds
2005-12-29 18:42 ` Arjan van de Ven
2005-12-29 18:45 ` Arjan van de Ven
2005-12-29 20:19 ` Ingo Molnar
2005-12-29 22:20 ` Matt Mackall
2005-12-29 20:28 ` Dave Jones
2005-12-29 20:49 ` Linus Torvalds
2005-12-29 21:25 ` Linus Torvalds
[not found] ` <20051229224839.GA12247@elte.hu>
2005-12-29 22:58 ` Arjan van de Ven
2005-12-30 2:03 ` Tim Schmielau
2005-12-30 2:15 ` Tim Schmielau
2005-12-30 7:49 ` Ingo Molnar
2005-12-31 14:38 ` Adrian Bunk
2005-12-31 14:45 ` Ingo Molnar
2005-12-31 15:08 ` Adrian Bunk
2006-01-02 10:37 ` Ingo Molnar
2006-01-02 10:48 ` Arjan van de Ven
2006-01-02 13:43 ` Adrian Bunk
2006-01-02 14:05 ` Ingo Molnar
2006-01-02 15:01 ` Adrian Bunk [this message]
2006-01-02 18:44 ` Krzysztof Halasa
2006-01-02 18:51 ` Arjan van de Ven
2006-01-02 19:49 ` Krzysztof Halasa
2006-01-02 19:54 ` Arjan van de Ven
2006-01-02 20:05 ` Krzysztof Halasa
2006-01-02 20:18 ` Jörn Engel
2006-01-02 22:23 ` Russell King
2006-01-02 23:55 ` Alan Cox
2006-01-03 3:59 ` Daniel Jacobowitz
2006-01-03 8:53 ` Russell King
2006-01-03 8:56 ` Arjan van de Ven
2006-01-03 9:00 ` Russell King
2006-01-03 9:10 ` Arjan van de Ven
2006-01-03 9:14 ` Vitaly Wool
2006-01-02 19:03 ` Andrew Morton
2006-01-02 19:17 ` Jakub Jelinek
2006-01-02 19:30 ` Andrew Morton
2006-01-02 19:41 ` Linus Torvalds
2006-01-02 19:53 ` Ingo Molnar
2006-01-02 20:28 ` Jakub Jelinek
2006-01-02 20:09 ` Ingo Molnar
2006-01-02 20:24 ` Andrew Morton
2006-01-02 20:40 ` Ingo Molnar
2006-01-02 20:30 ` Ingo Molnar
2006-01-02 19:12 ` Linus Torvalds
2006-01-02 19:59 ` Krzysztof Halasa
2006-01-02 20:13 ` Ingo Molnar
2006-01-02 21:00 ` Jan Engelhardt
2006-01-02 22:43 ` Linus Torvalds
2006-01-02 13:42 ` Adrian Bunk
2006-01-02 18:28 ` Andrew Morton
2006-01-02 18:49 ` Arjan van de Ven
2006-01-02 19:26 ` Jörn Engel
2006-01-02 21:51 ` Grant Coady
2006-01-02 22:03 ` Antonio Vargas
2006-01-02 22:56 ` Arjan van de Ven
2006-01-02 23:10 ` Grant Coady
2006-01-02 23:57 ` Alan Cox
2006-01-02 23:58 ` Grant Coady
2006-01-03 5:31 ` Nick Piggin
2006-01-03 23:40 ` Martin J. Bligh
2006-01-04 4:28 ` Matt Mackall
2006-01-04 5:51 ` Martin J. Bligh
2006-01-04 17:10 ` Matt Mackall
2006-01-04 22:37 ` Linus Torvalds
2006-01-05 0:55 ` Martin Bligh
2006-01-04 17:36 ` Zwane Mwaikambo
2005-12-31 3:51 ` Kurt Wall
2005-12-30 3:31 ` Nicolas Pitre
2005-12-29 22:41 ` userspace breakage Dave Jones
2005-12-29 21:23 ` Jeff V. Merkey
2005-12-29 23:42 ` Linus Torvalds
2005-12-29 22:17 ` Jeff V. Merkey
2005-12-30 0:10 ` Linus Torvalds
2005-12-29 23:54 ` Jeff V. Merkey
2005-12-30 0:32 ` Linus Torvalds
2005-12-30 14:45 ` Jeff V. Merkey
2005-12-30 16:17 ` Rik van Riel
2005-12-30 15:01 ` Jeff V. Merkey
2005-12-30 11:17 ` Bernd Petrovitsch
2005-12-30 14:59 ` Jeff V. Merkey
2005-12-30 20:22 ` Steven Rostedt
2005-12-30 21:26 ` Linus Torvalds
2005-12-30 23:49 ` Andrew Morton
2005-12-31 8:33 ` Arjan van de Ven
2005-12-31 15:30 ` Steven Rostedt
2005-12-31 16:40 ` Francois Romieu
2005-12-30 11:19 ` Bernd Petrovitsch
2005-12-30 14:53 ` Jeff V. Merkey
2005-12-30 17:17 ` Bernd Petrovitsch
2005-12-29 22:47 ` Ismail Donmez
2005-12-29 22:56 ` Linus Torvalds
2005-12-29 23:03 ` Dave Jones
2006-01-03 20:28 ` Greg KH
2006-01-03 20:37 ` Dave Jones
2006-01-04 23:00 ` Paolo Ciarrocchi
2006-01-05 4:42 ` Greg KH
2005-12-29 23:25 ` Adrian Bunk
2005-12-29 23:52 ` Linus Torvalds
2005-12-30 8:09 ` Arjan van de Ven
2006-01-03 20:28 ` Greg KH
2005-12-29 23:07 ` Dmitry Torokhov
2005-12-30 0:38 ` Ryan Anderson
2005-12-30 0:46 ` Dave Jones
2005-12-30 1:05 ` Linus Torvalds
2005-12-30 1:19 ` Dave Airlie
2005-12-30 1:21 ` Dave Jones
2005-12-30 2:10 ` Jiri Slaby
2005-12-30 2:14 ` Dave Jones
2005-12-30 2:35 ` Jiri Slaby
2005-12-30 5:14 ` Theodore Ts'o
2005-12-30 0:49 ` Linus Torvalds
2005-12-30 3:47 ` [patch 00/2] improve .text size on gcc 4.0 and newer compilers Mark Lord
2005-12-30 3:56 ` Dave Jones
2005-12-30 3:57 ` Mark Lord
2005-12-30 4:02 ` Dave Jones
2005-12-30 4:11 ` Mark Lord
2005-12-30 4:14 ` Mark Lord
2005-12-30 4:20 ` Mark Lord
2005-12-30 5:04 ` Dave Jones
2005-12-29 23:16 ` Willy Tarreau
2005-12-30 8:05 ` Arjan van de Ven
2005-12-30 8:15 ` Willy Tarreau
2005-12-30 8:24 ` Arjan van de Ven
2005-12-30 9:20 ` Willy Tarreau
2005-12-30 13:38 ` Adrian Bunk
2005-12-30 8:33 ` Jesper Juhl
2005-12-30 9:28 ` Willy Tarreau
2005-12-30 9:37 ` Jesper Juhl
2005-12-30 9:38 ` Willy Tarreau
2005-12-30 19:53 ` Alistair John Strachan
2005-12-29 7:49 ` Arjan van de Ven
2005-12-29 15:01 ` Horst von Brand
2005-12-30 15:28 ` Alan Cox
2005-12-30 20:59 ` Adrian Bunk
2005-12-30 22:12 ` Matt Mackall
2005-12-30 23:54 ` Adrian Bunk
2005-12-31 9:20 ` Arjan van de Ven
2005-12-29 14:38 ` Christoph Hellwig
2005-12-29 14:54 ` Arjan van de Ven
2005-12-29 15:35 ` Adrian Bunk
2005-12-29 15:38 ` Arjan van de Ven
2005-12-29 15:42 ` Jakub Jelinek
2005-12-29 19:14 ` Adrian Bunk
2005-12-30 9:28 ` Andi Kleen
2005-12-30 9:40 ` Ingo Molnar
2005-12-30 10:14 ` Ingo Molnar
2005-12-30 13:31 ` Adrian Bunk
2005-12-30 14:08 ` Christian Trefzer
2005-12-30 10:25 ` Andi Kleen
2005-12-29 0:37 ` Rogério Brito
2006-01-03 3:36 ` Daniel Jacobowitz
2005-12-29 4:38 ` Adrian Bunk
2005-12-29 7:59 ` Ingo Molnar
2005-12-29 13:52 ` Adrian Bunk
2005-12-29 19:57 ` Horst von Brand
2005-12-29 20:25 ` Ingo Molnar
2005-12-31 15:22 ` Adrian Bunk
2006-01-05 0:55 Chuck Ebbert
2006-01-05 1:07 ` Martin Bligh
2006-01-05 12:19 ` Arjan van de Ven
2006-01-05 14:30 ` Jakub Jelinek
2006-01-05 16:55 ` Linus Torvalds
2006-01-05 18:42 ` Daniel Jacobowitz
2006-01-05 17:02 ` Matt Mackall
2006-01-05 17:59 ` Martin Bligh
2006-01-05 18:09 ` Arjan van de Ven
2006-01-05 18:43 ` Daniel Jacobowitz
2006-01-05 19:17 ` Linus Torvalds
2006-01-05 19:40 ` Linus Torvalds
2006-01-05 19:49 ` Martin Bligh
2006-01-05 20:13 ` Linus Torvalds
2006-01-05 20:15 ` Linus Torvalds
2006-01-05 23:30 ` Ingo Molnar
2006-01-05 23:54 ` Linus Torvalds
2006-01-06 0:15 ` Ingo Molnar
2006-01-06 0:27 ` Linus Torvalds
2006-01-06 0:54 ` Ingo Molnar
2006-01-06 0:02 ` Martin Bligh
2006-01-06 0:40 ` Ingo Molnar
2006-01-06 0:55 ` Martin Bligh
2006-01-06 1:48 ` Mitchell Blank Jr
2006-01-06 0:50 ` Mitchell Blank Jr
2006-01-06 0:58 ` Ingo Molnar
2006-01-06 1:22 ` Mitchell Blank Jr
2006-01-05 21:34 ` Matt Mackall
2006-01-05 22:08 ` Linus Torvalds
2006-01-05 22:36 ` Matt Mackall
2006-01-05 22:49 ` Martin Bligh
2006-01-05 23:02 ` Matt Mackall
2006-01-05 22:55 ` Ingo Molnar
2006-01-05 23:11 ` Matt Mackall
2006-01-05 23:27 ` Jesse Barnes
2006-01-05 23:58 ` Ingo Molnar
2006-01-05 21:32 ` Grzegorz Kulewski
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