[slubllv4 14/16] slub: fast release on full slab

[Christoph Lameter <cl@linux.com>]

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Make deactivation occur implicitly while checking out the current freelist.

This avoids one cmpxchg operation on a slab that is now fully in use.

Signed-off-by: Christoph Lameter <cl@linux.com>

---
 mm/slub.c |   18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c	2011-05-06 12:56:13.000000000 -0500
+++ linux-2.6/mm/slub.c	2011-05-06 12:56:38.000000000 -0500
@@ -1943,9 +1943,21 @@ static void *__slab_alloc(struct kmem_ca
 			object = page->freelist;
 			counters = page->counters;
 			new.counters = counters;
-			new.inuse = page->objects;
 			VM_BUG_ON(!new.frozen);
 
+			/*
+			 * If there is no object left then we use this loop to
+			 * deactivate the slab which is simple since no objects
+			 * are left in the slab and therefore we do not need to
+			 * put the page back onto the partial list.
+			 *
+			 * If there are objects left then we retrieve them
+			 * and use them to refill the per cpu queue.
+			*/
+
+			new.inuse = page->objects;
+			new.frozen = object != NULL;
+
 		} while (!cmpxchg_double_slab(s, page,
 				object, counters,
 				NULL, new.counters,
@@ -1955,8 +1967,10 @@ static void *__slab_alloc(struct kmem_ca
 load_freelist:
 	VM_BUG_ON(!page->frozen);
 
-	if (unlikely(!object))
+	if (unlikely(!object)) {
+		c->page = NULL;
 		goto new_slab;
+	}
 
 	c->freelist = get_freepointer(s, object);
 	c->tid = next_tid(c->tid);