Re: Recommendation for activating a deferred module init in the kernel

[Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>]

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On Wed, 18 Jun 2008, Adrian Bunk wrote:
> On Wed, Jun 18, 2008 at 10:59:50AM +0100, David Woodhouse wrote:
> > On Wed, 2008-06-18 at 10:57 +0200, Geert Uytterhoeven wrote:
> > > On Wed, 18 Jun 2008, Adrian Bunk wrote:
> > > > You miss the size increase imposed by CONFIG_MODULES=y.
> > > > 
> > > > E.g. setting CONFIG_MODULES=y in the arm collie_defconfig will
> > > > increase the size of vmlinux by 14% (sic).
> > > > 
> > > > I haven't investigated why it takes that much space, but stuff like 
> > > > kernel/module.o taking 23kB and each EXPORT_SYMBOL requiring a few
> > > > bytes simply cannot be completely eliminated.
> > > 
> > > Sounds like we need a tool that strips out the unneeded symbols, given a list
> > > of modules?
> > 
> > And do the --gc-sections step again after that... :)
> 
> But even after all optimizations CONFIG_MODULES=y will still cause a 
> significant additional cost [1] when thinking in the dimensions of 
> Tim's "the 30 or so Linux-tiny patches that I use get me about 110k of 
> reductions.  For me, this is about 5% of my kernel size" statement in 
> another thread.
> 
> [1] as I said, kernel/module.o alone takes 23kB

Which could be freed after the last module has been loaded?

With kind regards,

Geert Uytterhoeven
Software Architect

Sony Techsoft Centre
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