[PATCH] Avoid excessive sorting of early_node_map[]

find_min_pfn_for_node() and find_min_pfn_with_active_regions() sort
early_node_map[] on every call.  This is an excessive amount of sorting and
that can be avoided.  This patch always searches the whole early_node_map[]
in find_min_pfn_for_node() instead of returning the first value found.  The
map is then only sorted once when required.  Successfully boot tested on a
number of machines.

[akpm@osdl.org: cleanup]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 7 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f12052dc23ff..f26fdc94393e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2877,20 +2877,23 @@ static void __init sort_node_map(void)
                         cmp_node_active_region, NULL);
 }
 
-/* Find the lowest pfn for a node. This depends on a sorted early_node_map */
+/* Find the lowest pfn for a node */
 unsigned long __init find_min_pfn_for_node(unsigned long nid)
 {
         int i;
-
-        /* Regions in the early_node_map can be in any order */
-        sort_node_map();
+        unsigned long min_pfn = ULONG_MAX;
 
         /* Assuming a sorted map, the first range found has the starting pfn */
         for_each_active_range_index_in_nid(i, nid)
-                return early_node_map[i].start_pfn;
+                min_pfn = min(min_pfn, early_node_map[i].start_pfn);
 
-        printk(KERN_WARNING "Could not find start_pfn for node %lu\n", nid);
-        return 0;
+        if (min_pfn == ULONG_MAX) {
+                printk(KERN_WARNING
+                        "Could not find start_pfn for node %lu\n", nid);
+                return 0;
+        }
+
+        return min_pfn;
 }
 
 /**
@@ -2939,6 +2942,9 @@ void __init free_area_init_nodes(unsigned long *max_zone_pfn)
         unsigned long nid;
         enum zone_type i;
 
+        /* Sort early_node_map as initialisation assumes it is sorted */
+        sort_node_map();
+
         /* Record where the zone boundaries are */
         memset(arch_zone_lowest_possible_pfn, 0,
                                 sizeof(arch_zone_lowest_possible_pfn));