[tip:x86/mm] x86/mm: Avoid duplicated pxm_to_node() calls

[tip-bot for Yinghai Lu <tipbot@zytor.com>]

Commit-ID:  ba6a328f7dfc95b20df5e0eb33c698187e997190
Gitweb:     http://git.kernel.org/tip/ba6a328f7dfc95b20df5e0eb33c698187e997190
Author:     Yinghai Lu <yinghai@kernel.org>
AuthorDate: Sun, 26 Jan 2014 13:01:42 -0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Sun, 9 Feb 2014 15:32:31 +0100

x86/mm: Avoid duplicated pxm_to_node() calls

In slit init code, too many pxm_to_node() function calls are done.

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

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

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

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: David Rientjes <rientjes@google.com>
Link: http://lkml.kernel.org/r/1390770102-4007-1-git-send-email-yinghai@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/mm/srat.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/x86/mm/srat.c b/arch/x86/mm/srat.c
index 1953e9c..66338a6 100644
--- a/arch/x86/mm/srat.c
+++ b/arch/x86/mm/srat.c
@@ -52,12 +52,18 @@ void __init acpi_numa_slit_init(struct acpi_table_slit *slit)
 	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]);
 		}
 	}