[patch 2/2] slub: add min_partial sysfs tunable

[David Rientjes]

Now that a cache's min_partial has been moved to struct kmem_cache, it's
possible to easily tune it from userspace by adding a sysfs attribute.

It may not be desirable to keep a large number of partial slabs around if
a cache is used infrequently and memory, especially when constrained by a
cgroup, is scarce.  It's better to allow userspace to set the minimum
policy per cache instead of relying explicitly on kmem_cache_shrink().

Cc: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
 mm/slub.c |   21 +++++++++++++++++++++
 1 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3839,6 +3839,26 @@ static ssize_t order_show(struct kmem_cache *s, char *buf)
 }
 SLAB_ATTR(order);
 
+static ssize_t min_partial_show(struct kmem_cache *s, char *buf)
+{
+	return sprintf(buf, "%lu\n", s->min_partial);
+}
+
+static ssize_t min_partial_store(struct kmem_cache *s, const char *buf,
+				 size_t length)
+{
+	unsigned long min;
+	int err;
+
+	err = strict_strtoul(buf, 10, &min);
+	if (err)
+		return err;
+
+	calculate_min_partial(s, min);
+	return length;
+}
+SLAB_ATTR(min_partial);
+
 static ssize_t ctor_show(struct kmem_cache *s, char *buf)
 {
 	if (s->ctor) {
@@ -4154,6 +4174,7 @@ static struct attribute *slab_attrs[] = {
 	&object_size_attr.attr,
 	&objs_per_slab_attr.attr,
 	&order_attr.attr,
+	&min_partial_attr.attr,
 	&objects_attr.attr,
 	&objects_partial_attr.attr,
 	&total_objects_attr.attr,
--
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