From 63b45bdb7c40e7c717fbeac78c39cb8bf67188f5 Mon Sep 17 00:00:00 2001
From: Christoph Lameter <clameter@sgi.com>
Date: Fri, 15 Feb 2008 15:22:23 -0800
Subject: [PATCH] slub: Make the order configurable for each slab cache

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

Signed-off-by: Christoph Lameter <clameter@sgi.com>
---
 mm/slub.c |   36 ++++++++++++++++++++++++++----------
 1 file changed, 26 insertions(+), 10 deletions(-)

Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c	2008-02-29 11:37:55.683150755 -0800
+++ linux-2.6/mm/slub.c	2008-02-29 11:39:07.335520086 -0800
@@ -2136,7 +2136,7 @@ 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;
@@ -2225,7 +2225,11 @@ 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;
 
@@ -2242,9 +2246,9 @@ static int calculate_sizes(struct kmem_c
 	/*
 	 * Determine the number of objects per slab
 	 */
-	s->max_objects = (PAGE_SIZE << s->order) / size;
-	s->min_objects = (PAGE_SIZE << get_order(size)) / size;
-
+	s->max_objects = max_t(unsigned long, s->max_objects,
+					(PAGE_SIZE << s->order) / size);
+	s->min_objects = (PAGE_SIZE << get_order(size)) / size;
 	return !!s->max_objects;
 
 }
@@ -2261,7 +2265,7 @@ 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;
@@ -3716,11 +3720,23 @@ 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 || order < slub_min_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)
 {
@@ -3848,7 +3864,7 @@ 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);
@@ -3867,7 +3883,7 @@ 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);
@@ -3886,7 +3902,7 @@ 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);