1 files changed, 35 insertions, 10 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index f2f6c59c5b05..9d7645f24b05 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -42,6 +42,25 @@ static LIST_HEAD(all_q_list);
 static void blk_mq_poll_stats_start(struct request_queue *q);
 static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb);
 
+/* Must be consisitent with function below */
+#define BLK_MQ_POLL_STATS_BKTS 16
+static int blk_mq_poll_stats_bkt(const struct request *rq)
+{
+	int ddir, bytes, bucket;
+
+	ddir = blk_stat_rq_ddir(rq);
+	bytes = blk_rq_bytes(rq);
+
+	bucket = ddir + 2*(ilog2(bytes) - 9);
+
+	if (bucket < 0)
+		return -1;
+	else if (bucket >= BLK_MQ_POLL_STATS_BKTS)
+		return ddir + BLK_MQ_POLL_STATS_BKTS - 2;
+
+	return bucket;
+}
+
 /*
  * Check if any of the ctx's have pending work in this hardware queue
  */
@@ -2257,7 +2276,8 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
 	q->mq_ops = set->ops;
 
 	q->poll_cb = blk_stat_alloc_callback(blk_mq_poll_stats_fn,
-					     blk_stat_rq_ddir, 2, q);
+					     blk_mq_poll_stats_bkt,
+					     BLK_MQ_POLL_STATS_BKTS, q);
 	if (!q->poll_cb)
 		goto err_exit;
 
@@ -2683,11 +2703,12 @@ static void blk_mq_poll_stats_start(struct request_queue *q)
 static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb)
 {
 	struct request_queue *q = cb->data;
+	int bucket;
 
-	if (cb->stat[READ].nr_samples)
-		q->poll_stat[READ] = cb->stat[READ];
-	if (cb->stat[WRITE].nr_samples)
-		q->poll_stat[WRITE] = cb->stat[WRITE];
+	for (bucket = 0; bucket < BLK_MQ_POLL_STATS_BKTS; bucket++) {
+		if (cb->stat[bucket].nr_samples)
+			q->poll_stat[bucket] = cb->stat[bucket];
+	}
 }
 
 static unsigned long blk_mq_poll_nsecs(struct request_queue *q,
@@ -2695,6 +2716,7 @@ static unsigned long blk_mq_poll_nsecs(struct request_queue *q,
 				       struct request *rq)
 {
 	unsigned long ret = 0;
+	int bucket;
 
 	/*
 	 * If stats collection isn't on, don't sleep but turn it on for
@@ -2709,12 +2731,15 @@ static unsigned long blk_mq_poll_nsecs(struct request_queue *q,
 	 * For instance, if the completion latencies are tight, we can
 	 * get closer than just half the mean. This is especially
 	 * important on devices where the completion latencies are longer
-	 * than ~10 usec.
+	 * than ~10 usec. We do use the stats for the relevant IO size
+	 * if available which does lead to better estimates.
 	 */
-	if (req_op(rq) == REQ_OP_READ && q->poll_stat[READ].nr_samples)
-		ret = (q->poll_stat[READ].mean + 1) / 2;
-	else if (req_op(rq) == REQ_OP_WRITE && q->poll_stat[WRITE].nr_samples)
-		ret = (q->poll_stat[WRITE].mean + 1) / 2;
+	bucket = blk_mq_poll_stats_bkt(rq);
+	if (bucket < 0)
+		return ret;
+
+	if (q->poll_stat[bucket].nr_samples)
+		ret = (q->poll_stat[bucket].mean + 1) / 2;
 
 	return ret;
 }