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block cfq: don't use atomic_t for cfq_group 

cfq_group->ref is used with queue_lock hold, the only exception is
cfq_set_request, which looks like a bug to me, so ref doesn't need
to be an atomic and atomic operation is slower.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Shaohua Li 2011-01-07 08:48:28 +01:00 committed by Jens Axboe
parent 30d7b9448f
commit 329a67815b
1 changed files with 12 additions and 11 deletions
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23
block/cfq-iosched.c
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@ -207,7 +207,7 @@ struct cfq_group {
struct blkio_group blkg; struct blkio_group blkg;
#ifdef CONFIG_CFQ_GROUP_IOSCHED #ifdef CONFIG_CFQ_GROUP_IOSCHED
struct hlist_node cfqd_node; struct hlist_node cfqd_node;
atomic_t ref; int ref;
#endif #endif
/* number of requests that are on the dispatch list or inside driver */ /* number of requests that are on the dispatch list or inside driver */
int dispatched; int dispatched;
@ -1014,7 +1014,7 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
* elevator which will be dropped by either elevator exit * elevator which will be dropped by either elevator exit
* or cgroup deletion path depending on who is exiting first. * or cgroup deletion path depending on who is exiting first.
*/ */
atomic_set(&cfqg->ref, 1); cfqg->ref = 1;
/* /*
* Add group onto cgroup list. It might happen that bdi->dev is * Add group onto cgroup list. It might happen that bdi->dev is
@ -1059,7 +1059,7 @@ static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg) static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
{ {
atomic_inc(&cfqg->ref); cfqg->ref++;
return cfqg; return cfqg;
} }
@ -1071,7 +1071,7 @@ static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
cfqq->cfqg = cfqg; cfqq->cfqg = cfqg;
/* cfqq reference on cfqg */ /* cfqq reference on cfqg */
atomic_inc(&cfqq->cfqg->ref); cfqq->cfqg->ref++;
} }
static void cfq_put_cfqg(struct cfq_group *cfqg) static void cfq_put_cfqg(struct cfq_group *cfqg)
@ -1079,8 +1079,9 @@ static void cfq_put_cfqg(struct cfq_group *cfqg)
struct cfq_rb_root *st; struct cfq_rb_root *st;
int i, j; int i, j;
BUG_ON(atomic_read(&cfqg->ref) <= 0); BUG_ON(cfqg->ref <= 0);
if (!atomic_dec_and_test(&cfqg->ref)) cfqg->ref--;
if (cfqg->ref)
return; return;
for_each_cfqg_st(cfqg, i, j, st) for_each_cfqg_st(cfqg, i, j, st)
BUG_ON(!RB_EMPTY_ROOT(&st->rb)); BUG_ON(!RB_EMPTY_ROOT(&st->rb));
@ -1188,7 +1189,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
cfq_group_service_tree_del(cfqd, cfqq->cfqg); cfq_group_service_tree_del(cfqd, cfqq->cfqg);
cfqq->orig_cfqg = cfqq->cfqg; cfqq->orig_cfqg = cfqq->cfqg;
cfqq->cfqg = &cfqd->root_group; cfqq->cfqg = &cfqd->root_group;
atomic_inc(&cfqd->root_group.ref); cfqd->root_group.ref++;
group_changed = 1; group_changed = 1;
} else if (!cfqd->cfq_group_isolation } else if (!cfqd->cfq_group_isolation
&& cfqq_type(cfqq) == SYNC_WORKLOAD && cfqq->orig_cfqg) { && cfqq_type(cfqq) == SYNC_WORKLOAD && cfqq->orig_cfqg) {
@ -3681,12 +3682,12 @@ new_queue:
cfqq->allocated[rw]++; cfqq->allocated[rw]++;
cfqq->ref++; cfqq->ref++;
spin_unlock_irqrestore(q->queue_lock, flags);
rq->elevator_private = cic; rq->elevator_private = cic;
rq->elevator_private2 = cfqq; rq->elevator_private2 = cfqq;
rq->elevator_private3 = cfq_ref_get_cfqg(cfqq->cfqg); rq->elevator_private3 = cfq_ref_get_cfqg(cfqq->cfqg);
spin_unlock_irqrestore(q->queue_lock, flags);
return 0; return 0;
queue_fail: queue_fail:
@ -3884,7 +3885,7 @@ static void *cfq_init_queue(struct request_queue *q)
* Take a reference to root group which we never drop. This is just * Take a reference to root group which we never drop. This is just
* to make sure that cfq_put_cfqg() does not try to kfree root group * to make sure that cfq_put_cfqg() does not try to kfree root group
*/ */
atomic_set(&cfqg->ref, 1); cfqg->ref = 1;
rcu_read_lock(); rcu_read_lock();
cfq_blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, cfq_blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg,
(void *)cfqd, 0); (void *)cfqd, 0);