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Subject[PATCH 14/15] cfq-iosched: improve sync vs async workloads
Date
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
block/cfq-iosched.c | 31 ++++++++++++++++++-------------
1 files changed, 18 insertions(+), 13 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index f920527..772df89 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -96,6 +96,7 @@ struct cfq_data {
struct hlist_head *cfq_hash;

int rq_in_driver;
+ int sync_flight;
int hw_tag;

/*
@@ -905,11 +906,15 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
*/
static void cfq_dispatch_insert(request_queue_t *q, struct request *rq)
{
+ struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_queue *cfqq = RQ_CFQQ(rq);

cfq_remove_request(rq);
cfqq->dispatched++;
elv_dispatch_sort(q, rq);
+
+ if (cfq_cfqq_sync(cfqq))
+ cfqd->sync_flight++;
}

/*
@@ -1094,27 +1099,24 @@ static int cfq_dispatch_requests(request_queue_t *q, int force)
while ((cfqq = cfq_select_queue(cfqd)) != NULL) {
int max_dispatch;

- if (cfqd->busy_queues > 1) {
- /*
- * So we have dispatched before in this round, if the
- * next queue has idling enabled (must be sync), don't
- * allow it service until the previous have completed.
- */
- if (cfqd->rq_in_driver && cfq_cfqq_idle_window(cfqq) &&
- dispatched)
+ max_dispatch = cfqd->cfq_quantum;
+ if (cfq_class_idle(cfqq))
+ max_dispatch = 1;
+
+ if (cfqq->dispatched >= max_dispatch) {
+ if (cfqd->busy_queues > 1)
break;
- if (cfqq->dispatched >= cfqd->cfq_quantum)
+ if (cfqq->dispatched >= 4 * max_dispatch)
break;
}

+ if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
+ break;
+
cfq_clear_cfqq_must_dispatch(cfqq);
cfq_clear_cfqq_wait_request(cfqq);
del_timer(&cfqd->idle_slice_timer);

- max_dispatch = cfqd->cfq_quantum;
- if (cfq_class_idle(cfqq))
- max_dispatch = 1;
-
dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
}

@@ -1767,6 +1769,9 @@ static void cfq_completed_request(request_queue_t *q, struct request *rq)
cfqd->rq_in_driver--;
cfqq->dispatched--;

+ if (cfq_cfqq_sync(cfqq))
+ cfqd->sync_flight--;
+
if (!cfq_class_idle(cfqq))
cfqd->last_end_request = now;

--
1.5.1.1.190.g74474
-
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