Commit 75da39bf authored by Joe Thornber's avatar Joe Thornber Committed by Mike Snitzer
Browse files

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: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent ac1f9ef2

drivers/md/dm-cache-policy-mq.c

+12 −13
Original line number Diff line number Diff line
@@ -126,6 +126,7 @@ static void iot_examine_bio(struct io_tracker *t, struct bio *bio) 
#define NR_QUEUE_LEVELS 16u



struct queue {

	unsigned nr_elts;

	struct list_head qs[NR_QUEUE_LEVELS];

};
@@ -133,23 +134,14 @@ static void queue_init(struct queue *q) 
{

	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 bool queue_empty(struct queue *q) 
 */

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 @@ static struct list_head *queue_pop(struct queue *q) 
	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 push(struct mq_policy *mq, struct entry *e) 
 */

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);

}