From: Martin Bligh <mbligh@mbligh.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Linus Torvalds <torvalds@osdl.org>,
Matt Mackall <mpm@selenic.com>,
Arjan van de Ven <arjan@infradead.org>,
Chuck Ebbert <76306.1226@compuserve.com>,
Adrian Bunk <bunk@stusta.de>, Andrew Morton <akpm@osdl.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Dave Jones <davej@redhat.com>,
Tim Schmielau <tim@physik3.uni-rostock.de>
Subject: Re: [patch 00/2] improve .text size on gcc 4.0 and newer compilers
Date: Thu, 05 Jan 2006 16:02:09 -0800 [thread overview]
Message-ID: <43BDB381.6020701@mbligh.org> (raw)
In-Reply-To: <20060105233049.GA3441@elte.hu>
> I think the only sane solution [that would be endorsed by distributions]
> is to allow users to reorder function sections runtime (per boot). That
> is alot faster and more robust (from a production POV) than a full
> recompilation of the kernel. Recompilation is always risky, it needs too
> much context, and has too many tool dependencies - and is thus currently
> untestable.
<smhuch> - the sound of my eyeballs popping out and splatting against
the opposite wall.
So ... recompilation is not testable, but boot time reordering of the
code somehow is? ;-) Yes, I understand the distro toolchain issues, but
it's still a scary solution ...
Personally, I'd think the sane thing is not to try to optimise by
workload, but get 80% of the benefit by just reordering on a more
generalized workload. Doing boot-time reordering for this on non-custom
kernels just seems terrifying .. it's not that huge a benefit, surely?
> one problem are modules though - they could only be reordered within
> themselves. On an average system which has ~100 modules loaded, the
> average icache fragmentation is +100*128/2 == 6.4K [with 128 byte L1
> cachelines], which can be significant (depending on the workload). OTOH,
> modules do have strong internal cohesion - they contain functions that
> belong together conceptually. So by reordering functions within modules
> we'll likely be able to realize most of the icache savings possible. The
> only exception would be workloads that utilize many modules at a high
> frequency. Such workloads will likely trash the icache anyway.
I was thinking about that with modules earlier, and whether modular
kernels would actually be faster because of that than a statically
compiled one. But don't you get similar effects from the .o groupings by
file we get? or does the linker not preserve those groupings?
M.
next prev parent reply other threads:[~2006-01-06 0:07 UTC|newest]
Thread overview: 167+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-05 0:55 [patch 00/2] improve .text size on gcc 4.0 and newer compilers 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 [this message]
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
-- strict thread matches above, loose matches on Subject: below --
2005-12-28 11:46 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
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
2005-12-30 3:47 ` 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
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