[PATCH] Locking optimization for cache_reap

Dimitri Sivanich
2004-07-23T19:05:55Z

Here is another cache_reap optimization that reduces latency when
applied after the 'Move cache_reap out of timer context' patch I
submitted on 7/14 (for inclusion in -mm next week).

This applies to 2.6.8-rc2 + the above mentioned patch.

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>

Index: linux/mm/slab.c
===================================================================
--- linux.orig/mm/slab.c
+++ linux/mm/slab.c
@@ -2619,27 +2619,6 @@ static void enable_cpucache (kmem_cache_
cachep->name, -err);
}

-static void drain_array(kmem_cache_t *cachep, struct array_cache *ac)
-{
- int tofree;
-
- check_irq_off();
- if (ac->touched) {
- ac->touched = 0;
- } else if (ac->avail) {
- tofree = (ac->limit+4)/5;
- if (tofree > ac->avail) {
- tofree = (ac->avail+1)/2;
- }
- spin_lock(&cachep->spinlock);
- free_block(cachep, ac_entry(ac), tofree);
- spin_unlock(&cachep->spinlock);
- ac->avail -= tofree;
- memmove(&ac_entry(ac)[0], &ac_entry(ac)[tofree],
- sizeof(void*)*ac->avail);
- }
-}
-
static void drain_array_locked(kmem_cache_t *cachep,
struct array_cache *ac, int force)
{
@@ -2697,16 +2676,14 @@ static void cache_reap (void *unused)
goto next;

check_irq_on();
- local_irq_disable();
- drain_array(searchp, ac_data(searchp));

- if(time_after(searchp->lists.next_reap, jiffies))
- goto next_irqon;
+ spin_lock_irq(&searchp->spinlock);
+
+ drain_array_locked(searchp, ac_data(searchp), 0);

- spin_lock(&searchp->spinlock);
- if(time_after(searchp->lists.next_reap, jiffies)) {
+ if(time_after(searchp->lists.next_reap, jiffies))
goto next_unlock;
- }
+
searchp->lists.next_reap = jiffies + REAPTIMEOUT_LIST3;

if (searchp->lists.shared)
@@ -2739,9 +2716,7 @@ static void cache_reap (void *unused)
spin_lock_irq(&searchp->spinlock);
} while(--tofree > 0);
next_unlock:
- spin_unlock(&searchp->spinlock);
-next_irqon:
- local_irq_enable();
+ spin_unlock_irq(&searchp->spinlock);
next:
;
}