linux-kernel - Re: [GIT PULL, v2] perf changes

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Date:	Fri, 28 May 2010 09:00:26 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Paul Mackerras <paulus@...ba.org>, linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Fr?d?ric Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL, v2] perf changes

* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Tue, 25 May 2010, Ingo Molnar wrote:
> >
> >  75 files changed, 1847 insertions(+), 3147 deletions(-)
> 
> I was excited by this ("A code _reduction_! Will wonders never cease?"), but 
> it turns out that all of the reduction was due to removing some unused 
> utility functions from the user-level tools.

Simple things first and maybe it turns into a habit!

> The actual kernel still grew:
>
>  32 files changed, 1327 insertions(+), 964 deletions(-)
>
> oh well. Merged anyway.

Hey, while i have to admit to being a member of the infinitely large group of 
kernel developers working hard to ensure that the kernel's size follows 
Moore's Law - this time i beg to differ, as we _did_ manage to shrink the 
kernel! ;-)

Here's the before/after vmlinux comparison:

 (x86 defconfig, 64-bit): vmlinux: 

                       text      data      bss       dec      hex  filename
                    .......................................................
 cad719d (before):  8441843   1281100   983876  10706819   a35f83   vmlinux
 c5617b2 ( after):  8417488   1277724   983876  10679088   a2f330   vmlinux
                    .......................................................
                    -24.35K    -3.37K
                     -0.28%    -0.26%

Ob'Suggestion: we could help debloating efforts by officially declaring to 
take provably-debloating patches up to -rc4? (with a vmlinux comparison 
mandated in the changelog or such)

Debloating patches tend to reduce complexity, and hence are more 
regression-resistent. (They are also rare, so it's not like we would be 
risking a flood of patches.)

That would be a clever way to redirect the creative energies of kernel 
developers who are otherwise bored by -rc1's legendary stability and always 
try to sneak further features upstream post -rc1.

Such a policy would mean that while the merge window for bloating patches is a 
strict ~1.5 weeks, the merge window for debloating patches would be a generous 
~1.5 months.

Maybe such a mild hint would help propagate the idea some more.

Dunno - just an idea,

	Ingo
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