Re: [patch 04/41] cpu ops: Core piece for generic atomic per cpu operations

[Rusty Russell]

On Friday 13 June 2008 03:19:51 Christoph Lameter wrote:
> Populating the per cpu areas on demand is a good thing especially for
> configurations with a large number of processors. If we really go to 
> support 4k processor by default then we need to allocate the smallest
> amount of per cpu structures necessary.  Maybe ACPI or so can tell us how 
> many processors are possible and we only allocate those. But it would be
> best if the percpu structures are only allocated for actually active
> processors.

cpu_possible_map should definitely be minimal, but your point is well made: 
dynamic percpu could actually cut memory allocation.  If we go for a hybrid 
scheme where static percpu is always allocated from the initial chunk, 
however, we still need the current pessimistic overallocation.

Mike's a clever guy, I'm sure he'll think of something :)
Rusty.
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