Slab defrag: Add defrag_ratio

Add a defrag ratio and set it to 30% by default.

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

---
 include/linux/slub_def.h |    7 +++++++
 mm/slub.c                |   18 ++++++++++++++++++
 2 files changed, 25 insertions(+)

Index: linux-2.6.23-rc1/include/linux/slub_def.h
===================================================================
--- linux-2.6.23-rc1.orig/include/linux/slub_def.h	2007-07-29 00:33:20.000000000 -0700
+++ linux-2.6.23-rc1/include/linux/slub_def.h	2007-07-29 00:33:22.000000000 -0700
@@ -45,6 +45,13 @@ struct kmem_cache {
 	const struct kmem_cache_ops *ops;
 	int inuse;		/* Offset to metadata */
 	int align;		/* Alignment */
+	int defrag_ratio;	/*
+				 * objects/possible objects limit. If we have
+				 * less that the specified percentage of
+				 * objects allocated then defrag passes
+				 * will start to occur during reclaim.
+				 */
+
 	const char *name;	/* Name (only for display!) */
 	struct list_head list;	/* List of slab caches */
 #ifdef CONFIG_SLUB_DEBUG
Index: linux-2.6.23-rc1/mm/slub.c
===================================================================
--- linux-2.6.23-rc1.orig/mm/slub.c	2007-07-29 00:33:16.000000000 -0700
+++ linux-2.6.23-rc1/mm/slub.c	2007-07-29 00:33:22.000000000 -0700
@@ -2091,6 +2091,7 @@ static int kmem_cache_open(struct kmem_c
 		goto error;
 
 	s->refcount = 1;
+	s->defrag_ratio = 30;
 #ifdef CONFIG_NUMA
 	s->remote_node_defrag_ratio = 100;
 #endif
@@ -3533,6 +3534,22 @@ static ssize_t free_calls_show(struct km
 }
 SLAB_ATTR_RO(free_calls);
 
+static ssize_t defrag_ratio_show(struct kmem_cache *s, char *buf)
+{
+	return sprintf(buf, "%d\n", s->defrag_ratio);
+}
+
+static ssize_t defrag_ratio_store(struct kmem_cache *s,
+				const char *buf, size_t length)
+{
+	int n = simple_strtoul(buf, NULL, 10);
+
+	if (n < 100)
+		s->defrag_ratio = n;
+	return length;
+}
+SLAB_ATTR(defrag_ratio);
+
 #ifdef CONFIG_NUMA
 static ssize_t remote_node_defrag_ratio_show(struct kmem_cache *s, char *buf)
 {
@@ -3575,6 +3592,7 @@ static struct attribute * slab_attrs[] =
 	&shrink_attr.attr,
 	&alloc_calls_attr.attr,
 	&free_calls_attr.attr,
+	&defrag_ratio_attr.attr,
 #ifdef CONFIG_ZONE_DMA
 	&cache_dma_attr.attr,
 #endif