block: avoid duplicate calls to get_part() in disk stat code

get_part() is fairly expensive, as it O(N) loops over partitions
to find the right one. In lots of normal IO paths we end up looking
up the partition twice, to make matters even worse. Change the
stat add code to accept a passed in partition instead.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 10 insertions, 8 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 1b7dddf..2987fe4 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -54,15 +54,16 @@ static DEFINE_PER_CPU(struct list_head, blk_cpu_done);
 
 static void drive_stat_acct(struct request *rq, int new_io)
 {
+	struct hd_struct *part;
 	int rw = rq_data_dir(rq);
 
 	if (!blk_fs_request(rq) || !rq->rq_disk)
 		return;
 
-	if (!new_io) {
-		__all_stat_inc(rq->rq_disk, merges[rw], rq->sector);
-	} else {
-		struct hd_struct *part = get_part(rq->rq_disk, rq->sector);
+	part = get_part(rq->rq_disk, rq->sector);
+	if (!new_io)
+		__all_stat_inc(rq->rq_disk, part, merges[rw], rq->sector);
+	else {
 		disk_round_stats(rq->rq_disk);
 		rq->rq_disk->in_flight++;
 		if (part) {
@@ -1538,10 +1539,11 @@ static int __end_that_request_first(struct request *req, int error,
 	}
 
 	if (blk_fs_request(req) && req->rq_disk) {
+		struct hd_struct *part = get_part(req->rq_disk, req->sector);
 		const int rw = rq_data_dir(req);
 
-		all_stat_add(req->rq_disk, sectors[rw],
-			     nr_bytes >> 9, req->sector);
+		all_stat_add(req->rq_disk, part, sectors[rw],
+				nr_bytes >> 9, req->sector);
 	}
 
 	total_bytes = bio_nbytes = 0;
@@ -1727,8 +1729,8 @@ static void end_that_request_last(struct request *req, int error)
 		const int rw = rq_data_dir(req);
 		struct hd_struct *part = get_part(disk, req->sector);
 
-		__all_stat_inc(disk, ios[rw], req->sector);
-		__all_stat_add(disk, ticks[rw], duration, req->sector);
+		__all_stat_inc(disk, part, ios[rw], req->sector);
+		__all_stat_add(disk, part, ticks[rw], duration, req->sector);
 		disk_round_stats(disk);
 		disk->in_flight--;
 		if (part) {