From: Christoph Lameter <clameter@sgi.com>
Subject: slub: Make the order configurable for each slab cache

Makes /sys/kernel/slab/<slabname>/order writable. The allocation
order can then be changed dynamically during runtime.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
 mm/slub.c |   32 ++++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c	2008-02-15 14:55:50.668027902 -0800
+++ linux-2.6/mm/slub.c	2008-02-15 14:57:57.256909543 -0800
@@ -2263,7 +2263,7 @@ static int init_kmem_cache_nodes(struct 
  * calculate_sizes() determines the order and the distribution of data within
  * a slab object.
  */
-static int calculate_sizes(struct kmem_cache *s)
+static int calculate_sizes(struct kmem_cache *s, int forced_order)
 {
 	unsigned long flags = s->flags;
 	unsigned long size = s->objsize;
@@ -2351,7 +2351,11 @@ static int calculate_sizes(struct kmem_c
 	size = ALIGN(size, align);
 	s->size = size;
 
-	s->order = calculate_order(size);
+	if (forced_order >= 0)
+		s->order = forced_order;
+	else
+		s->order = calculate_order(size);
+
 	if (s->order < 0)
 		return 0;
 
@@ -2368,7 +2372,7 @@ static int calculate_sizes(struct kmem_c
 	/*
 	 * Determine the number of objects per slab
 	 */
-	s->objects = (PAGE_SIZE << s->order) / size;
+	s->objects = max_t(unsigned long, s->objects, (PAGE_SIZE << s->order) / size);
 	s->objects0 = PAGE_SIZE / size;
 
 	return !!s->objects;
@@ -2387,7 +2391,7 @@ static int kmem_cache_open(struct kmem_c
 	s->align = align;
 	s->flags = kmem_cache_flags(size, flags, name, ctor);
 
-	if (!calculate_sizes(s))
+	if (!calculate_sizes(s, -1))
 		goto error;
 
 	s->refcount = 1;
@@ -3839,11 +3843,23 @@ static ssize_t objs_per_slab_show(struct
 }
 SLAB_ATTR_RO(objs_per_slab);
 
+static ssize_t order_store(struct kmem_cache *s,
+				const char *buf, size_t length)
+{
+	int order = simple_strtoul(buf, NULL, 10);
+
+	if (order > slub_max_order)
+		return -EINVAL;
+
+	calculate_sizes(s, order);
+	return length;
+}
+
 static ssize_t order_show(struct kmem_cache *s, char *buf)
 {
 	return sprintf(buf, "%d\n", s->order);
 }
-SLAB_ATTR_RO(order);
+SLAB_ATTR(order);
 
 static ssize_t ctor_show(struct kmem_cache *s, char *buf)
 {
@@ -3971,7 +3987,7 @@ static ssize_t red_zone_store(struct kme
 	s->flags &= ~SLAB_RED_ZONE;
 	if (buf[0] == '1')
 		s->flags |= SLAB_RED_ZONE;
-	calculate_sizes(s);
+	calculate_sizes(s, -1);
 	return length;
 }
 SLAB_ATTR(red_zone);
@@ -3990,7 +4006,7 @@ static ssize_t poison_store(struct kmem_
 	s->flags &= ~SLAB_POISON;
 	if (buf[0] == '1')
 		s->flags |= SLAB_POISON;
-	calculate_sizes(s);
+	calculate_sizes(s, -1);
 	return length;
 }
 SLAB_ATTR(poison);
@@ -4009,7 +4025,7 @@ static ssize_t store_user_store(struct k
 	s->flags &= ~SLAB_STORE_USER;
 	if (buf[0] == '1')
 		s->flags |= SLAB_STORE_USER;
-	calculate_sizes(s);
+	calculate_sizes(s, -1);
 	return length;
 }
 SLAB_ATTR(store_user);