block: consolidate struct request timestamp fields

Currently, struct request has four timestamp fields:

- A start time, set at get_request time, in jiffies, used for iostats
- An I/O start time, set at start_request time, in ktime nanoseconds,
  used for blk-stats (i.e., wbt, kyber, hybrid polling)
- Another start time and another I/O start time, used for cfq and bfq

These can all be consolidated into one start time and one I/O start
time, both in ktime nanoseconds, shaving off up to 16 bytes from struct
request depending on the kernel config.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 2 insertions, 3 deletions

diff --git a/block/blk-stat.c b/block/blk-stat.c
index 725a881723b0..175c143ac5b9 100644
--- a/block/blk-stat.c
+++ b/block/blk-stat.c
@@ -47,15 +47,14 @@ static void __blk_stat_add(struct blk_rq_stat *stat, u64 value)
 	stat->nr_samples++;
 }
 
-void blk_stat_add(struct request *rq)
+void blk_stat_add(struct request *rq, u64 now)
 {
 	struct request_queue *q = rq->q;
 	struct blk_stat_callback *cb;
 	struct blk_rq_stat *stat;
 	int bucket;
-	u64 now, value;
+	u64 value;
 
-	now = ktime_get_ns();
 	value = (now >= rq->io_start_time_ns) ? now - rq->io_start_time_ns : 0;
 
 	blk_throtl_stat_add(rq, value);