Is SPARSE_IRQ really needed for all powerpcs ?

The help associated with SPARSE_IRQ says:


   Sparse irq numbering is useful for distro kernels that want
   to define a high CONFIG_NR_CPUS value but still want to have
   low kernel memory footprint on smaller machines.

   ( Sparse irqs can also be beneficial on NUMA boxes, as they spread
     out the interrupt descriptors in a more NUMA-friendly way. )

   If you don't know what to do here, say N.



Is it really usefull/necessary to select it for all powerpc as done by 
arch/powerpc/Kconfig ?

Shouldn't we at least make if conditionnal to SMP ?

Christophe