page-allocator: limit the number of MIGRATE_RESERVE pageblocks per zone

[deliverable/linux.git] / mm / page_alloc.c

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4c847cc57cafdcac5d56a808a13c796d31cc1e51..33b1a4762a7bb07a22b65ccda65ef4bd738dccac 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2836,7 +2836,8 @@ static void setup_zone_migrate_reserve(struct zone *zone)
 {
        unsigned long start_pfn, pfn, end_pfn;
        struct page *page;
-       unsigned long reserve, block_migratetype;
+       unsigned long block_migratetype;
+       int reserve;
 
        /* Get the start pfn, end pfn and the number of blocks to reserve */
        start_pfn = zone->zone_start_pfn;
@@ -2844,6 +2845,15 @@ static void setup_zone_migrate_reserve(struct zone *zone)
        reserve = roundup(min_wmark_pages(zone), pageblock_nr_pages) >>
                                                        pageblock_order;
 
+       /*
+        * Reserve blocks are generally in place to help high-order atomic
+        * allocations that are short-lived. A min_free_kbytes value that
+        * would result in more than 2 reserve blocks for atomic allocations
+        * is assumed to be in place to help anti-fragmentation for the
+        * future allocation of hugepages at runtime.
+        */
+       reserve = min(2, reserve);
+
        for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
                if (!pfn_valid(pfn))
                        continue;