Re: 2.5 and lowmemory boxens

[Andrew Morton <akpm@digeo.com>]

Andi Kleen wrote:
> 
> "Samium Gromoff" <_deepfire@mail.ru> writes:
> 
> >    first: i`ve successfully ran 2.5.43 on a 386sx20/4M ram notebook.
> >
> >  the one problem was the ppp over serial not working, but i suspect
> >  that it just needs to be recompiled with 2.5 headers (am i right?).
> >
> >  the other was, well, the fact that ultra-stripped 2.5.43
> >  still used 200k more memory than 2.4.19, and thats despite it was
> >  compiled with -Os instead of -O2.
> >  actually it was 2000k free with 2.4 vs 1800k  free with 2.5
> >
> >  i know Rik had plans of some ultra bloody embedded/lowmem
> >  changes for such cases. i`d like to hear about things in the area :)
> 
> I would start with clamping down all the hash tables.

Well here's some low-hanging fruit:

mnm:/usr/src/25> size kernel/pid.o
   text    data     bss     dec     hex filename
   1677    1088  131104  133869   20aed kernel/pid.o

(I have a trollpatch to fix this)

And the radix_tree_node mempool is 140k; I plan to do away with
that altogether.

timer.c and sched.c have significant NR_CPUS bloat problems on SMP.
Working on that.