dm cache policy mq: keep track of the number of entries in a multiqueue
Small optimisation, now queue_empty() doesn't need to walk all levels of
the multiqueue.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm-cache-policy-mq.c b/drivers/md/dm-cache-policy-mq.c
index 13f547a..ca05d69 100644
--- a/drivers/md/dm-cache-policy-mq.c
+++ b/drivers/md/dm-cache-policy-mq.c
@@ -126,6 +126,7 @@
#define NR_QUEUE_LEVELS 16u
struct queue {
+ unsigned nr_elts;
struct list_head qs[NR_QUEUE_LEVELS];
};
@@ -133,23 +134,14 @@
{
unsigned i;
+ q->nr_elts = 0;
for (i = 0; i < NR_QUEUE_LEVELS; i++)
INIT_LIST_HEAD(q->qs + i);
}
-/*
- * Checks to see if the queue is empty.
- * FIXME: reduce cpu usage.
- */
static bool queue_empty(struct queue *q)
{
- unsigned i;
-
- for (i = 0; i < NR_QUEUE_LEVELS; i++)
- if (!list_empty(q->qs + i))
- return false;
-
- return true;
+ return q->nr_elts == 0;
}
/*
@@ -157,11 +149,13 @@
*/
static void queue_push(struct queue *q, unsigned level, struct list_head *elt)
{
+ q->nr_elts++;
list_add_tail(elt, q->qs + level);
}
-static void queue_remove(struct list_head *elt)
+static void queue_remove(struct queue *q, struct list_head *elt)
{
+ q->nr_elts--;
list_del(elt);
}
@@ -197,6 +191,7 @@
struct list_head *r = queue_peek(q);
if (r) {
+ q->nr_elts--;
list_del(r);
/* have we just emptied the bottom level? */
@@ -496,7 +491,11 @@
*/
static void del(struct mq_policy *mq, struct entry *e)
{
- queue_remove(&e->list);
+ if (in_cache(mq, e))
+ queue_remove(e->dirty ? &mq->cache_dirty : &mq->cache_clean, &e->list);
+ else
+ queue_remove(&mq->pre_cache, &e->list);
+
hash_remove(e);
}