Re: [patch 2/4] Configure out file locking features

On Thu, Jul 31, 2008 at 06:26:16PM +0200, Thomas Petazzoni wrote:
Le Thu, 31 Jul 2008 18:37:57 +0300,
Adrian Bunk <bunk@xxxxxxxxxx> a écrit :

I'm just not a fan of adding config options for each few kB of code -
we have to maintain them and the more complex the configuration
becomes the more often it breaks.

I'm not a fan of these too, but are there other solutions ?

There are many things that can be done to reduce the kernel size or try
to minimize the growth of the kernel.

E.g. working on --combine -fwhole-program (where David once had
preliminary patches for the per-module approach) might be better.

What became bigger was most likely not related to the patches you
sent.

No, it is not.

Where and why did the kernel become bigger?

It's not up-to-date with 2.6.26 and 2.6.27-rc1, but Bloatwatch
<http://www.selenic.com/bloatwatch/>, by Matt Mackall, is here to
answer these questions. I haven't made the analysis for
2.6.26->2.6.27-rc1.

It can only give some hints where to start searching.

But it tracks a defconfig, and e.g. the nearly doubled size between
2.6.18 and 2.6.19 is both expected and not a problem for embedded
systems.

The real work is to figure out in which areas that are relevant for
embedded systems the kernel became bigger.

Why did CONFIG_FW_LOADER get enabled?
Due to alnoconfig disabling CONFIG_EMBEDDED?

I don't know. Haven't made the analysis for now.

A user will ask:
I'm using $applications with $libraries, can I safely disable this
option?

Hard to tell in the general case.

And e.g. according to a quick grep through the sources uClibc's
updwtmp() seems to cease working without flock().

Correct. But on many embedded systems, we don't care about logging past
user logins. We might even not care about logins at all.

And for embedded systems with which applications is it 100% safe to
disable this option?

And don't answer "doesn't use flock()", I want a real-life example of a
device where you could guarantee a developer that disabling this option
in his product would be safe.

It costs us maintainance of the option and the #ifdef's and gives
users one way more to shoot themselves into the foot in nontrivial to
detect ways.

That's correct, and as I said previously, I fully understand the
maintainance problem of all these new configuration options. I must
admit that I do not really have more objective technical arguments that
would help us deciding whether the code size reduction vs. code
maintainance choice should be made in one direction or the other.

My personal criteron for this patch is still how many real-life systems
can safely disable it.

Sincerly,

Thomas

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

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