The defrag_ratio is used to set the threshold at which defragmentation
should be attempted on a slab page.
The allocation ratio is measured by the percentage of the available slots
allocated.
Add a defrag ratio field and set it to 30% by default. A limit of 30% specified
that less than 3 out of 10 available slots for objects are in use before
slab defragmeentation runs.
Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Christoph Lameter <clameter@xxxxxxx>
Signed-off-by: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
---
include/linux/slub_def.h | 7 +++++++
mm/slub.c | 23 +++++++++++++++++++++++
2 files changed, 30 insertions(+)
Index: linux-2.6/include/linux/slub_def.h
===================================================================
--- linux-2.6.orig/include/linux/slub_def.h 2008-05-05 18:27:21.212659137 -0700
+++ linux-2.6/include/linux/slub_def.h 2008-05-05 18:48:42.745160406 -0700
@@ -88,6 +88,13 @@ struct kmem_cache {
void (*ctor)(struct kmem_cache *, void *);
int inuse; /* Offset to metadata */
int align; /* Alignment */
+ int defrag_ratio; /*
+ * Ratio used to check the percentage of
+ * objects allocate in a slab page.
+ * If less than this ratio is allocated
+ * then reclaim attempts are made.
+ */
+
const char *name; /* Name (only for display!) */
struct list_head list; /* List of slab caches */
#ifdef CONFIG_SLUB_DEBUG
Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c 2008-05-05 18:47:18.872659344 -0700
+++ linux-2.6/mm/slub.c 2008-05-05 18:48:42.745160406 -0700
@@ -2337,6 +2337,7 @@ 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
@@ -4060,6 +4061,27 @@ 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)
+{
+ unsigned long ratio;
+ int err;
+
+ err = strict_strtoul(buf, 10, &ratio);
+ if (err)
+ return err;
+
+ if (ratio < 100)
+ s->defrag_ratio = ratio;
+ return length;
+}
+SLAB_ATTR(defrag_ratio);
+
#ifdef CONFIG_NUMA
static ssize_t remote_node_defrag_ratio_show(struct kmem_cache *s, char *buf)
{
@@ -4167,6 +4189,7 @@ 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
--
--
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