remove __read_mostly?

[Andrew Morton <akpm@osdl.org>]

I'm thinking we should remove __read_mostly.

Because if we use this everywhere where it's supposed to be used, we end up
with .bss and .data 100% populated with write-often variables, packed
closely together.  The cachelines will really flying around.

IOW: __read_mostly optimises read-mostly variables and pessimises
write-often variables.

We want something which optimises both read-mostly and write-often storage.
 We do that by marking the write-often variables with
__cacheline_aligned_in_smp.

OK?

[Problem is, I don't think any of the make-foo-__read_mostly patches
actually identified _which_ write-often variables were affecting `foo', so
we'll be back to square one.]

[Actually, we should do

	#define __write_often __cacheline_aligned_in_smp

and use __write_often

a) for documentation and

b) so the optimisation can be centrally turned off, for space
   optimisation or for performance validation.]
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