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-rw-r--r--block/cfq-iosched.c26
1 files changed, 24 insertions, 2 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index fb2141ec205..135b1a48da2 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -237,6 +237,7 @@ struct cfq_data {
struct rb_root prio_trees[CFQ_PRIO_LISTS];
unsigned int busy_queues;
+ unsigned int busy_sync_queues;
int rq_in_driver;
int rq_in_flight[2];
@@ -1344,6 +1345,8 @@ static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
BUG_ON(cfq_cfqq_on_rr(cfqq));
cfq_mark_cfqq_on_rr(cfqq);
cfqd->busy_queues++;
+ if (cfq_cfqq_sync(cfqq))
+ cfqd->busy_sync_queues++;
cfq_resort_rr_list(cfqd, cfqq);
}
@@ -1370,6 +1373,8 @@ static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
cfq_group_service_tree_del(cfqd, cfqq->cfqg);
BUG_ON(!cfqd->busy_queues);
cfqd->busy_queues--;
+ if (cfq_cfqq_sync(cfqq))
+ cfqd->busy_sync_queues--;
}
/*
@@ -2377,6 +2382,7 @@ static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
* Does this cfqq already have too much IO in flight?
*/
if (cfqq->dispatched >= max_dispatch) {
+ bool promote_sync = false;
/*
* idle queue must always only have a single IO in flight
*/
@@ -2384,15 +2390,31 @@ static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
return false;
/*
+ * If there is only one sync queue, and its think time is
+ * small, we can ignore async queue here and give the sync
+ * queue no dispatch limit. The reason is a sync queue can
+ * preempt async queue, limiting the sync queue doesn't make
+ * sense. This is useful for aiostress test.
+ */
+ if (cfq_cfqq_sync(cfqq) && cfqd->busy_sync_queues == 1) {
+ struct cfq_io_context *cic = RQ_CIC(cfqq->next_rq);
+
+ if (sample_valid(cic->ttime_samples) &&
+ cic->ttime_mean < cfqd->cfq_slice_idle)
+ promote_sync = true;
+ }
+
+ /*
* We have other queues, don't allow more IO from this one
*/
- if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq))
+ if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq) &&
+ !promote_sync)
return false;
/*
* Sole queue user, no limit
*/
- if (cfqd->busy_queues == 1)
+ if (cfqd->busy_queues == 1 || promote_sync)
max_dispatch = -1;
else
/*