__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.
Depends on the earlier patch that introduces the transfer_objects() function.
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 <[email protected]>
Index: linux-2.6.16-rc6-mm2/mm/slab.c
===================================================================
--- linux-2.6.16-rc6-mm2.orig/mm/slab.c 2006-03-21 14:53:40.000000000 -0800
+++ linux-2.6.16-rc6-mm2/mm/slab.c 2006-03-21 14:55:09.000000000 -0800
@@ -974,6 +974,13 @@ static void __drain_alien_cache(struct k
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);
@@ -989,8 +996,8 @@ static void reap_alien(struct kmem_cache
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);
}
-
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