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

Rusty Russell
2008-06-13T00:38:38Z

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.