[PATCH] slab: Bypass free lists for __drain_alien_cache()
__drain_alien_cache() currently drains objects by freeing them to the
(remote) freelists of the original node. However, each node also has a
shared list containing objects to be used on any processor of that node.
We can avoid a number of remote node accesses by copying the pointers to
the free objects directly into the remote shared array.
And while we are at it: Skip alien draining if the alien cache spinlock is
already taken.
Kiran reported that this is a performance benefit.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/slab.c b/mm/slab.c
index dee857a..351aa6c 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -971,6 +971,13 @@
if (ac->avail) {
spin_lock(&rl3->list_lock);
+ /*
+ * Stuff objects into the remote nodes shared array first.
+ * That way we could avoid the overhead of putting the objects
+ * into the free lists and getting them back later.
+ */
+ transfer_objects(rl3->shared, ac, ac->limit);
+
free_block(cachep, ac->entry, ac->avail, node);
ac->avail = 0;
spin_unlock(&rl3->list_lock);
@@ -986,8 +993,8 @@
if (l3->alien) {
struct array_cache *ac = l3->alien[node];
- if (ac && ac->avail) {
- spin_lock_irq(&ac->lock);
+
+ if (ac && ac->avail && spin_trylock_irq(&ac->lock)) {
__drain_alien_cache(cachep, ac, node);
spin_unlock_irq(&ac->lock);
}
