2 files changed, 23 insertions, 3 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index a0c5c5f4fce..b21093eabef 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2362,6 +2362,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
         slram=          [HW,MTD]
 
+        slab_max_order= [MM, SLAB]
+                        Determines the maximum allowed order for slabs.
+                        A high setting may cause OOMs due to memory
+                        fragmentation.  Defaults to 1 for systems with
+                        more than 32MB of RAM, 0 otherwise.
+
         slub_debug[=options[,slabs]]    [MM, SLUB]
                         Enabling slub_debug allows one to determine the
                         culprit if slab objects become corrupted. Enabling
diff --git a/mm/slab.c b/mm/slab.c
index 1a482e8402c..b0414d12fd0 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -479,11 +479,13 @@ EXPORT_SYMBOL(slab_buffer_size);
 #endif
 
 /*
- * Do not go above this order unless 0 objects fit into the slab.
+ * Do not go above this order unless 0 objects fit into the slab or
+ * overridden on the command line.
  */
 #define SLAB_MAX_ORDER_HI       1
 #define SLAB_MAX_ORDER_LO       0
 static int slab_max_order = SLAB_MAX_ORDER_LO;
+static bool slab_max_order_set __initdata;
 
 /*
  * Functions for storing/retrieving the cachep and or slab from the page
@@ -851,6 +853,17 @@ static int __init noaliencache_setup(char *s)
 }
 __setup("noaliencache", noaliencache_setup);
 
+static int __init slab_max_order_setup(char *str)
+{
+        get_option(&str, &slab_max_order);
+        slab_max_order = slab_max_order < 0 ? 0 :
+                                min(slab_max_order, MAX_ORDER - 1);
+        slab_max_order_set = true;
+
+        return 1;
+}
+__setup("slab_max_order=", slab_max_order_setup);
+
 #ifdef CONFIG_NUMA
 /*
  * Special reaping functions for NUMA systems called from cache_reap().
@@ -1499,9 +1512,10 @@ void __init kmem_cache_init(void)
 
         /*
          * Fragmentation resistance on low memory - only use bigger
-         * page orders on machines with more than 32MB of memory.
+         * page orders on machines with more than 32MB of memory if
+         * not overridden on the command line.
          */
-        if (totalram_pages > (32 << 20) >> PAGE_SHIFT)
+        if (!slab_max_order_set && totalram_pages > (32 << 20) >> PAGE_SHIFT)
                 slab_max_order = SLAB_MAX_ORDER_HI;
 
         /* Bootstrap is tricky, because several objects are allocated