Hi,
On Wed, 22 Dec 2010, Tony Lindgren wrote:
* Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx> [101221 14:00]:
On Tue, 21 Dec 2010 11:27:35 -0800
Tony Lindgren <tony@xxxxxxxxxxx> 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..
I also think the idea is good, and this should be maybe posted to wider
audience than just linux-omap.
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.
I took a quick look at omap2plus_defconfig kernel, and non-init text/data
for 29 boards takes 85K. If we would page align those memory consumption
would increase during init to 29*8=232K, but after other boards are
freed we would eventually save 85-8=77K.
Under mach-omap2, another big consumer is clock data which takes also
around 80 K, while e.g. on 2420 only 14 K is needed.
A.
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