Commit e00946fe authored Mar 25, 2006 by Christoph Lameter Committed by Linus Torvalds Mar 25, 2006

[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>

parent 3ded175a

mm/slab.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -971,6 +971,13 @@ static void __drain_alien_cache(struct kmem_cache *cachep,

		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 @@ static void reap_alien(struct kmem_cache cachep, struct kmem_list3 l3)

		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);
		}