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dm cache policy mq: keep track of the number of entries in a multiqueue

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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>
This commit is contained in:
Joe Thornber 2015-02-20 12:58:03 +00:00 committed by Mike Snitzer
parent ac1f9ef211
commit 75da39bf25
1 changed files with 12 additions and 13 deletions
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25
drivers/md/dm-cache-policy-mq.c
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@ -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);
}