The defrag_ratio is used to set the threshold when a slabcache should be
defragmented.
The allocation ratio is measured in a percentage of the available slots.
The percentage will be lower for slabs that are more fragmented.
Add a defrag ratio field and set it to 30% by default. A limit of 30%
that less than 3 out of 10 available slots for objects are in use.
Signed-off-by: Christoph Lameter <clameter@xxxxxxx>
---
include/linux/slub_def.h | 7 +++++++
mm/slub.c | 18 ++++++++++++++++++
2 files changed, 25 insertions(+), 0 deletions(-)
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 5912b58..291881d 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -52,6 +52,13 @@ struct kmem_cache {
void (*ctor)(void *, struct kmem_cache *, unsigned long);
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
diff --git a/mm/slub.c b/mm/slub.c
index e63aba5..f95a760 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2200,6 +2200,7 @@ static int kmem_cache_open(struct kmem_cache *s, gfp_t gfpflags,
goto error;
s->refcount = 1;
+ s->defrag_ratio = 30;
#ifdef CONFIG_NUMA
s->remote_node_defrag_ratio = 100;
#endif
@@ -3717,6 +3718,22 @@ static ssize_t free_calls_show(struct kmem_cache *s, char *buf)
}
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)
{
@@ -3759,6 +3776,7 @@ 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
--
1.5.2.4
--
-
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