Re: [PATCH UPDATED] percpu: use dynamic percpu allocator as thedefault percpu allocator

[Ingo Molnar]

* Matthew Wilcox <matthew@xxxxxx> wrote:

> On Wed, Apr 01, 2009 at 12:39:46PM -0700, Linus Torvalds wrote:
>
> > The thing is, things like "read_mostly" or "access_rarely" may 
> > talk about how we access those individual variables, but you're 
> > missing a _huge_ chunk of the puzzle if you ignore the 
> > _correlations_ of those accesses with accesses to other 
> > variables.
> > 
> > The thign is, if you have variables 'a' and 'b', and they are 
> > always accessed together, then it's probably worth it to put 
> > them in the same cacheline.
> 
> If you've got two global variables that are generally accessed 
> together, they should probably be `annotated' as such by putting 
> them in a struct.

It is certainly done so in a number of cases (say the RCU core and 
the scheduler), but i dont think it should be forced or preferred in 
any way.

IMHO it's equally good and clean code to have the global variables 
separately at the top of a .c file. Sometimes it's cleaner.

	Ingo
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