Re: [PATCH 20/35] Use a pre-calculated value for num_online_nodes()

[Christoph Lameter <cl@linux-foundation.org>]

Trying to the same in the style of nr_node_ids etc.


Subject: Provide nr_online_nodes and nr_possible_nodes

It seems that its beneficial to have a less expensive way to check for the
number of currently active and possible nodes in a NUMA system. This will
simplify further kernel optimizations for the cases in which only a single
node is online or possible.

Signed-off-by: Christoph Lameter <cl@linux-foundation.org>

Index: linux-2.6/include/linux/nodemask.h
===================================================================
--- linux-2.6.orig/include/linux/nodemask.h	2009-03-19 15:04:28.000000000 -0500
+++ linux-2.6/include/linux/nodemask.h	2009-03-19 15:33:18.000000000 -0500
@@ -408,6 +408,20 @@
 #define next_online_node(nid)	next_node((nid), node_states[N_ONLINE])

 extern int nr_node_ids;
+extern int nr_online_nodes;
+extern int nr_possible_nodes;
+
+static inline void node_set_online(int nid)
+{
+	node_set_state(nid, N_ONLINE);
+	nr_online_nodes = num_node_state(N_ONLINE);
+}
+
+static inline void node_set_offline(int nid)
+{
+	node_clear_state(nid, N_ONLINE);
+	nr_online_nodes = num_node_state(N_ONLINE);
+}
 #else

 static inline int node_state(int node, enum node_states state)
@@ -434,7 +448,8 @@
 #define first_online_node	0
 #define next_online_node(nid)	(MAX_NUMNODES)
 #define nr_node_ids		1
-
+#define nr_online_nodes		1
+#define nr_possible_nodes	1
 #endif

 #define node_online_map 	node_states[N_ONLINE]
@@ -454,8 +469,7 @@
 #define node_online(node)	node_state((node), N_ONLINE)
 #define node_possible(node)	node_state((node), N_POSSIBLE)

-#define node_set_online(node)	   node_set_state((node), N_ONLINE)
-#define node_set_offline(node)	   node_clear_state((node), N_ONLINE)
+

 #define for_each_node(node)	   for_each_node_state(node, N_POSSIBLE)
 #define for_each_online_node(node) for_each_node_state(node, N_ONLINE)
Index: linux-2.6/mm/hugetlb.c
===================================================================
--- linux-2.6.orig/mm/hugetlb.c	2009-03-19 15:11:49.000000000 -0500
+++ linux-2.6/mm/hugetlb.c	2009-03-19 15:12:13.000000000 -0500
@@ -875,7 +875,7 @@
 	 * can no longer free unreserved surplus pages. This occurs when
 	 * the nodes with surplus pages have no free pages.
 	 */
-	unsigned long remaining_iterations = num_online_nodes();
+	unsigned long remaining_iterations = nr_online_nodes;

 	/* Uncommit the reservation */
 	h->resv_huge_pages -= unused_resv_pages;
@@ -904,7 +904,7 @@
 			h->surplus_huge_pages--;
 			h->surplus_huge_pages_node[nid]--;
 			nr_pages--;
-			remaining_iterations = num_online_nodes();
+			remaining_iterations = nr_online_nodes;
 		}
 	}
 }
Index: linux-2.6/mm/page_alloc.c
===================================================================
--- linux-2.6.orig/mm/page_alloc.c	2009-03-19 15:12:19.000000000 -0500
+++ linux-2.6/mm/page_alloc.c	2009-03-19 15:30:21.000000000 -0500
@@ -168,6 +168,10 @@
 #if MAX_NUMNODES > 1
 int nr_node_ids __read_mostly = MAX_NUMNODES;
 EXPORT_SYMBOL(nr_node_ids);
+int nr_online_nodes __read_mostly = 1;
+EXPORT_SYMBOL(nr_online_nodes);
+int nr_possible_nodes __read_mostly = MAX_NUMNODES;
+EXPORT_SYMBOL(nr_possible_nodes);
 #endif

 int page_group_by_mobility_disabled __read_mostly;
@@ -2115,7 +2119,7 @@
 }


-#define MAX_NODE_LOAD (num_online_nodes())
+#define MAX_NODE_LOAD nr_online_nodes
 static int node_load[MAX_NUMNODES];

 /**
Index: linux-2.6/mm/slab.c
===================================================================
--- linux-2.6.orig/mm/slab.c	2009-03-19 15:13:45.000000000 -0500
+++ linux-2.6/mm/slab.c	2009-03-19 15:15:28.000000000 -0500
@@ -881,7 +881,6 @@
   */

 static int use_alien_caches __read_mostly = 1;
-static int numa_platform __read_mostly = 1;
 static int __init noaliencache_setup(char *s)
 {
 	use_alien_caches = 0;
@@ -1434,9 +1433,8 @@
 	int order;
 	int node;

-	if (num_possible_nodes() == 1) {
+	if (nr_possible_nodes == 1) {
 		use_alien_caches = 0;
-		numa_platform = 0;
 	}

 	for (i = 0; i < NUM_INIT_LISTS; i++) {
@@ -3526,7 +3524,7 @@
 	 * variable to skip the call, which is mostly likely to be present in
 	 * the cache.
 	 */
-	if (numa_platform && cache_free_alien(cachep, objp))
+	if (nr_possible_nodes > 1 && cache_free_alien(cachep, objp))
 		return;

 	if (likely(ac->avail < ac->limit)) {
Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c	2009-03-19 15:13:15.000000000 -0500
+++ linux-2.6/mm/slub.c	2009-03-19 15:13:38.000000000 -0500
@@ -3648,7 +3648,7 @@
 						 to_cpumask(l->cpus));
 		}

-		if (num_online_nodes() > 1 && !nodes_empty(l->nodes) &&
+		if (nr_online_nodes > 1 && !nodes_empty(l->nodes) &&
 				len < PAGE_SIZE - 60) {
 			len += sprintf(buf + len, " nodes=");
 			len += nodelist_scnprintf(buf + len, PAGE_SIZE - len - 50,
Index: linux-2.6/net/sunrpc/svc.c
===================================================================
--- linux-2.6.orig/net/sunrpc/svc.c	2009-03-19 15:16:21.000000000 -0500
+++ linux-2.6/net/sunrpc/svc.c	2009-03-19 15:16:51.000000000 -0500
@@ -124,7 +124,7 @@
 {
 	unsigned int node;

-	if (num_online_nodes() > 1) {
+	if (nr_online_nodes > 1) {
 		/*
 		 * Actually have multiple NUMA nodes,
 		 * so split pools on NUMA node boundaries

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