powerpc: Enable sparse irq_descs on powerpc
Defining CONFIG_SPARSE_IRQ enables generic code that gets rid of the
static irq_desc array, and replaces it with an array of pointers to
irq_descs.
It also allows node local allocation of irq_descs, however we
currently don't have the information available to do that, so we just
allocate them on all on node 0.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 3aa79f8..61abde1 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -377,6 +377,19 @@
CPU. Generally saying Y is safe, although some problems have been
reported with SMP Power Macintoshes with this option enabled.
+config SPARSE_IRQ
+ bool "Support sparse irq numbering"
+ default y
+ help
+ This enables support for sparse irqs. This 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 irq_desc[] array in a more NUMA-friendly way. )
+
+ If you don't know what to do here, say Y.
+
config NUMA
bool "NUMA support"
depends on PPC64