* Thomas Petazzoni <[email protected]> [101221 14:00]:
> On Tue, 21 Dec 2010 11:27:35 -0800
> Tony Lindgren <[email protected]> wrote:
>
> > > Therefore, we introduce an infrastructure that allows to put code
> > > and data into specific sections, called "conditional sections". All
> > > those sections are compiled into the final kernel image, but at
> > > runtime, by calling a function, we can get rid of the unused
> > > sections.
> >
> > Great, something is certainly needed to free the unused memory.
>
> Nice to see that the idea is welcome. Did you had a look at the
> implementation in patch 1/6 ?
No not yet, will take a look after we're done with this upcoming
merge window..
> > > For example, on OMAP, you can declare data as being omap2 specific
> > > this way:
> > >
> > > static int __omap2_data foobar;
> > >
> > > Then, in the board code of an OMAP3 or OMAP4 platform, you can call:
> > >
> > > free_unused_cond_section("omap2");
> >
> > Sounds like this could be done after the cpu detection automatically?
>
> Yes, it definitely should.
>
> > I don't know what the section limitations are, but it would be nice
> > to have a separate section for each machine.. Then we could just
> > "free_unused_machines()" during the init.. :)
>
> I don't think there are any specific limitations, so we can just create
> as many section as we want.
>
> However, in order to be able to free each section independently from
> another, I have to page align all those conditional sections. This
> means that having one section for only a tiny amount of data is going
> to waste space instead of saving space. So the conditional section
> should gather a sufficiently large amount of data (> 4 KB) to actually
> be valuable.
Yeah I don't know how much non-init data we have for each board-*.c
file. Maybe there is not much for each machine.
Ideally the new sections would be arch/arm generic sections and not
omap specific. I could see ARMv6 and ARMv7 sections being one way
to group them, but that does not help to drop omap3 specific data
on omap4.
Regards,
Tony
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