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authorJens Axboe <jens.axboe@oracle.com>2009-10-06 20:49:37 +0200
committerJens Axboe <jens.axboe@oracle.com>2009-10-06 20:49:37 +0200
commit0b182d617eb50762b483658dd6dd9a9fbcb25758 (patch)
tree28c7084cb5566cb26e5c6f96b3c055304afcbbbf /block
parent1b59dd511b9a36d4be3c01d7c7024aeec36dc651 (diff)
cfq-iosched: abstract out the 'may this cfqq dispatch' logic
Makes the whole thing easier to read, cfq_dispatch_requests() was a bit messy before. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block')
-rw-r--r--block/cfq-iosched.c121
1 files changed, 67 insertions, 54 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 690ebd96dc4..5c3cee93329 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1247,67 +1247,21 @@ static int cfq_forced_dispatch(struct cfq_data *cfqd)
return dispatched;
}
-/*
- * Dispatch a request from cfqq, moving them to the request queue
- * dispatch list.
- */
-static void cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
- struct request *rq;
-
- BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
-
- /*
- * follow expired path, else get first next available
- */
- rq = cfq_check_fifo(cfqq);
- if (!rq)
- rq = cfqq->next_rq;
-
- /*
- * insert request into driver dispatch list
- */
- cfq_dispatch_insert(cfqd->queue, rq);
-
- if (!cfqd->active_cic) {
- struct cfq_io_context *cic = RQ_CIC(rq);
-
- atomic_long_inc(&cic->ioc->refcount);
- cfqd->active_cic = cic;
- }
-}
-
-/*
- * Find the cfqq that we need to service and move a request from that to the
- * dispatch list
- */
-static int cfq_dispatch_requests(struct request_queue *q, int force)
-{
- struct cfq_data *cfqd = q->elevator->elevator_data;
- struct cfq_queue *cfqq;
unsigned int max_dispatch;
- if (!cfqd->busy_queues)
- return 0;
-
- if (unlikely(force))
- return cfq_forced_dispatch(cfqd);
-
- cfqq = cfq_select_queue(cfqd);
- if (!cfqq)
- return 0;
-
/*
* Drain async requests before we start sync IO
*/
if (cfq_cfqq_idle_window(cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
- return 0;
+ return false;
/*
* If this is an async queue and we have sync IO in flight, let it wait
*/
if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
- return 0;
+ return false;
max_dispatch = cfqd->cfq_quantum;
if (cfq_class_idle(cfqq))
@@ -1321,13 +1275,13 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
* idle queue must always only have a single IO in flight
*/
if (cfq_class_idle(cfqq))
- return 0;
+ return false;
/*
* We have other queues, don't allow more IO from this one
*/
if (cfqd->busy_queues > 1)
- return 0;
+ return false;
/*
* Sole queue user, allow bigger slice
@@ -1351,13 +1305,72 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
max_dispatch = depth;
}
- if (cfqq->dispatched >= max_dispatch)
+ /*
+ * If we're below the current max, allow a dispatch
+ */
+ return cfqq->dispatched < max_dispatch;
+}
+
+/*
+ * Dispatch a request from cfqq, moving them to the request queue
+ * dispatch list.
+ */
+static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+ struct request *rq;
+
+ BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
+
+ if (!cfq_may_dispatch(cfqd, cfqq))
+ return false;
+
+ /*
+ * follow expired path, else get first next available
+ */
+ rq = cfq_check_fifo(cfqq);
+ if (!rq)
+ rq = cfqq->next_rq;
+
+ /*
+ * insert request into driver dispatch list
+ */
+ cfq_dispatch_insert(cfqd->queue, rq);
+
+ if (!cfqd->active_cic) {
+ struct cfq_io_context *cic = RQ_CIC(rq);
+
+ atomic_long_inc(&cic->ioc->refcount);
+ cfqd->active_cic = cic;
+ }
+
+ return true;
+}
+
+/*
+ * Find the cfqq that we need to service and move a request from that to the
+ * dispatch list
+ */
+static int cfq_dispatch_requests(struct request_queue *q, int force)
+{
+ struct cfq_data *cfqd = q->elevator->elevator_data;
+ struct cfq_queue *cfqq;
+
+ if (!cfqd->busy_queues)
+ return 0;
+
+ if (unlikely(force))
+ return cfq_forced_dispatch(cfqd);
+
+ cfqq = cfq_select_queue(cfqd);
+ if (!cfqq)
return 0;
/*
- * Dispatch a request from this cfqq
+ * Dispatch a request from this cfqq, if it is allowed
*/
- cfq_dispatch_request(cfqd, cfqq);
+ if (!cfq_dispatch_request(cfqd, cfqq))
+ return 0;
+
cfqq->slice_dispatch++;
cfq_clear_cfqq_must_dispatch(cfqq);