cfq-iosched: fix async queue behaviour
With the cfq_queue hash removal, we inadvertently got rid of the
async queue sharing. This was not intentional, in fact CFQ purposely
shares the async queue per priority level to get good merging for
async writes.
So put some logic in cfq_get_queue() to track the shared queues.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index baef5fc7..e0aa4da 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -92,6 +92,8 @@
struct cfq_queue *active_queue;
struct cfq_io_context *active_cic;
+ struct cfq_queue *async_cfqq[IOPRIO_BE_NR];
+
struct timer_list idle_class_timer;
sector_t last_position;
@@ -1351,8 +1353,8 @@
}
static struct cfq_queue *
-cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
- gfp_t gfp_mask)
+cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
+ struct task_struct *tsk, gfp_t gfp_mask)
{
struct cfq_queue *cfqq, *new_cfqq = NULL;
struct cfq_io_context *cic;
@@ -1405,12 +1407,35 @@
if (new_cfqq)
kmem_cache_free(cfq_pool, new_cfqq);
- atomic_inc(&cfqq->ref);
out:
WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
return cfqq;
}
+static struct cfq_queue *
+cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
+ gfp_t gfp_mask)
+{
+ const int ioprio = task_ioprio(tsk);
+ struct cfq_queue *cfqq = NULL;
+
+ if (!is_sync)
+ cfqq = cfqd->async_cfqq[ioprio];
+ if (!cfqq)
+ cfqq = cfq_find_alloc_queue(cfqd, is_sync, tsk, gfp_mask);
+
+ /*
+ * pin the queue now that it's allocated, scheduler exit will prune it
+ */
+ if (!is_sync && !cfqd->async_cfqq[ioprio]) {
+ atomic_inc(&cfqq->ref);
+ cfqd->async_cfqq[ioprio] = cfqq;
+ }
+
+ atomic_inc(&cfqq->ref);
+ return cfqq;
+}
+
/*
* We drop cfq io contexts lazily, so we may find a dead one.
*/
@@ -2019,6 +2044,7 @@
{
struct cfq_data *cfqd = e->elevator_data;
request_queue_t *q = cfqd->queue;
+ int i;
cfq_shutdown_timer_wq(cfqd);
@@ -2035,6 +2061,13 @@
__cfq_exit_single_io_context(cfqd, cic);
}
+ /*
+ * Put the async queues
+ */
+ for (i = 0; i < IOPRIO_BE_NR; i++)
+ if (cfqd->async_cfqq[i])
+ cfq_put_queue(cfqd->async_cfqq[i]);
+
spin_unlock_irq(q->queue_lock);
cfq_shutdown_timer_wq(cfqd);
