On Thu, Jul 31, 2008 at 04:20:07PM +0200, Thomas Petazzoni wrote:
> Le Thu, 31 Jul 2008 16:53:19 +0300,
> Adrian Bunk <bunk@xxxxxxxxxx> a écrit :
>
> > As I've already said in the past I'm personally not a huge fan of
> > these patches, but if it brings advantages in real-life situations
> > it's hard to argue against it.
>
> Yes, I've seen your points about that kind of patches on
> linux-embedded, and I understand them. I agree that adding dozens and
> dozens of configuration items for small features doesn't look like
> something sustainable on the long run. However, the kernel keeps
> growing and this isn't sustainable either on the long run for *some*
> embedded users. So, what should we do ? (That's a real question)
I'm not against making the kernel smaller.
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.
> Some numbers about a bootable x86 allnoconfig kernel with ELF, ext2 and
> IDE support :
>
> text data bss dec hex filename
> 1110389 119468 217088 1446945 161421 vmlinux.2.6.26
> 1134606 118840 212992 1466438 166046 vmlinux.2.6.27-rc1
> 24217 -628 -4096 19493 4C25 +/-
What became bigger was most likely not related to the patches you sent.
Where and why did the kernel become bigger?
> (The only configuration change between the two kernels is
> CONFIG_FW_LOADER n->y, which pulls drivers/base/firmware_class.o, 3k).
Why did CONFIG_FW_LOADER get enabled?
Due to alnoconfig disabling CONFIG_EMBEDDED?
> > In which use cases can users safely disable this option, and on what
> > devices have you verified that CONFIG_FILE_LOCKING=n kernels actually
> > work in practice?
>
> As long as they don't use NFS (realistic in many production
> environments) and that the applications do not rely on advisory locking
> (flock() and fnctl() F_GETLK and F_SETLK), file locking can be
> disabled.
But what does that mean in practice?
A user will ask:
I'm using $applications with $libraries, can I safely disable this option?
And e.g. according to a quick grep through the sources uClibc's
updwtmp() seems to cease working without flock().
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.
> In practice, I only tested a CONFIG_FILE_LOCKING=n kernel
> with a basic Busybox under Qemu.
>
> 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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