---

yaml
---
r: 283404
b: refs/heads/master
c: 3df1ccc
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 543585cc5b07fa99a2dc897159fbf48c1eb73058
+refs/heads/master: 3df1cccdfb3fab6aa9176beb655d802eb384eabc

trunk/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

trunk/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