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-rw-r--r--block/cfq-iosched.c166
1 files changed, 90 insertions, 76 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 9e809345f71..a0102a507da 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -160,6 +160,7 @@ struct cfq_queue {
unsigned long slice_end;
long slice_resid;
+ unsigned int slice_dispatch;
/* pending metadata requests */
int meta_pending;
@@ -774,10 +775,16 @@ static void __cfq_set_active_queue(struct cfq_data *cfqd,
if (cfqq) {
cfq_log_cfqq(cfqd, cfqq, "set_active");
cfqq->slice_end = 0;
+ cfqq->slice_dispatch = 0;
+
+ cfq_clear_cfqq_must_dispatch(cfqq);
+ cfq_clear_cfqq_wait_request(cfqq);
cfq_clear_cfqq_must_alloc_slice(cfqq);
cfq_clear_cfqq_fifo_expire(cfqq);
cfq_mark_cfqq_slice_new(cfqq);
cfq_clear_cfqq_queue_new(cfqq);
+
+ del_timer(&cfqd->idle_slice_timer);
}
cfqd->active_queue = cfqq;
@@ -1053,66 +1060,6 @@ keep_queue:
return cfqq;
}
-/*
- * Dispatch some requests from cfqq, moving them to the request queue
- * dispatch list.
- */
-static int
-__cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
- int max_dispatch)
-{
- int dispatched = 0;
-
- BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
-
- do {
- struct request *rq;
-
- /*
- * follow expired path, else get first next available
- */
- rq = cfq_check_fifo(cfqq);
- if (rq == NULL)
- rq = cfqq->next_rq;
-
- /*
- * finally, insert request into driver dispatch list
- */
- cfq_dispatch_insert(cfqd->queue, rq);
-
- dispatched++;
-
- if (!cfqd->active_cic) {
- atomic_inc(&RQ_CIC(rq)->ioc->refcount);
- cfqd->active_cic = RQ_CIC(rq);
- }
-
- if (RB_EMPTY_ROOT(&cfqq->sort_list))
- break;
-
- /*
- * If there is a non-empty RT cfqq waiting for current
- * cfqq's timeslice to complete, pre-empt this cfqq
- */
- if (!cfq_class_rt(cfqq) && cfqd->busy_rt_queues)
- break;
-
- } while (dispatched < max_dispatch);
-
- /*
- * expire an async queue immediately if it has used up its slice. idle
- * queue always expire after 1 dispatch round.
- */
- if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
- dispatched >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
- cfq_class_idle(cfqq))) {
- cfqq->slice_end = jiffies + 1;
- cfq_slice_expired(cfqd, 0);
- }
-
- return dispatched;
-}
-
static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
{
int dispatched = 0;
@@ -1146,11 +1093,45 @@ 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)
+{
+ 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_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;
- int dispatched;
+ unsigned int max_dispatch;
if (!cfqd->busy_queues)
return 0;
@@ -1158,29 +1139,62 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
if (unlikely(force))
return cfq_forced_dispatch(cfqd);
- dispatched = 0;
- while ((cfqq = cfq_select_queue(cfqd)) != NULL) {
- int max_dispatch;
+ cfqq = cfq_select_queue(cfqd);
+ if (!cfqq)
+ return 0;
+
+ /*
+ * 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;
- max_dispatch = cfqd->cfq_quantum;
+ max_dispatch = cfqd->cfq_quantum;
+ if (cfq_class_idle(cfqq))
+ max_dispatch = 1;
+
+ /*
+ * Does this cfqq already have too much IO in flight?
+ */
+ if (cfqq->dispatched >= max_dispatch) {
+ /*
+ * idle queue must always only have a single IO in flight
+ */
if (cfq_class_idle(cfqq))
- max_dispatch = 1;
+ return 0;
- if (cfqq->dispatched >= max_dispatch && cfqd->busy_queues > 1)
- break;
+ /*
+ * We have other queues, don't allow more IO from this one
+ */
+ if (cfqd->busy_queues > 1)
+ return 0;
- if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
- break;
+ /*
+ * we are the only queue, allow up to 4 times of 'quantum'
+ */
+ if (cfqq->dispatched >= 4 * max_dispatch)
+ return 0;
+ }
- cfq_clear_cfqq_must_dispatch(cfqq);
- cfq_clear_cfqq_wait_request(cfqq);
- del_timer(&cfqd->idle_slice_timer);
+ /*
+ * Dispatch a request from this cfqq
+ */
+ cfq_dispatch_request(cfqd, cfqq);
+ cfqq->slice_dispatch++;
- dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
+ /*
+ * expire an async queue immediately if it has used up its slice. idle
+ * queue always expire after 1 dispatch round.
+ */
+ if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
+ cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
+ cfq_class_idle(cfqq))) {
+ cfqq->slice_end = jiffies + 1;
+ cfq_slice_expired(cfqd, 0);
}
- cfq_log(cfqd, "dispatched=%d", dispatched);
- return dispatched;
+ cfq_log(cfqd, "dispatched a request");
+ return 1;
}
/*