For performance reasons its best to use memory node local memory for
per-cpu buffers.

This logic comes from a much larger patch proposed by Stephane.
Suggested-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Stephane Eranian <eranian@google.com>
LKML-Reference: <20101019134808.514465326@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>