[PATCH v2] x86, mm: Avoid duplicated pxm_to_node() calling.

[Yinghai Lu <yinghai@kernel.org>]

In slit init code, more pxm_to_node() calling are added.

We can store from_node/to_node instead of keep calling pxm_to_node().

After this patch: pxm_to_node() is called n*(1+n)
Before this patch: pxm_to_node() is called n*(1+n*3)

for 8 socket, it will be 72 instead of 200.
for 32 socket, it will be 1056 instead of 3104.

-v2: update title and change log according to Ingo.
     move from_node/to_node in loop and change to const according to
	David Rientjes.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
 
---
 arch/x86/mm/srat.c |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

Index: linux-2.6/arch/x86/mm/srat.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/srat.c
+++ linux-2.6/arch/x86/mm/srat.c
@@ -52,12 +52,18 @@ void __init acpi_numa_slit_init(struct a
 	int i, j;
 
 	for (i = 0; i < slit->locality_count; i++) {
-		if (pxm_to_node(i) == NUMA_NO_NODE)
+		const int from_node = pxm_to_node(i);
+
+		if (from_node == NUMA_NO_NODE)
 			continue;
+
 		for (j = 0; j < slit->locality_count; j++) {
-			if (pxm_to_node(j) == NUMA_NO_NODE)
+			const int to_node = pxm_to_node(j);
+
+			if (to_node == NUMA_NO_NODE)
 				continue;
-			numa_set_distance(pxm_to_node(i), pxm_to_node(j),
+
+			numa_set_distance(from_node, to_node,
 				slit->entry[slit->locality_count * i + j]);
 		}
 	}