We only need the request fields and the end_io time if we have stats
enabled, or if we have a scheduler attached as those may use it for
completion time stats.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
block/blk-mq.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 7dcef565dc0f..2b458e9da946 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -316,7 +316,8 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
RB_CLEAR_NODE(&rq->rb_node);
rq->rq_disk = NULL;
rq->part = NULL;
- rq->start_time_ns = ktime_get_ns();
+ if (data->q->elevator)
+ rq->start_time_ns = ktime_get_ns();
rq->io_start_time_ns = 0;
rq->nr_phys_segments = 0;
#if defined(CONFIG_BLK_DEV_INTEGRITY)
@@ -522,12 +523,18 @@ EXPORT_SYMBOL_GPL(blk_mq_free_request);
inline void __blk_mq_end_request(struct request *rq, blk_status_t error)
{
- u64 now = ktime_get_ns();
+ u64 now = 0;
+ /*
+ * Only read ktime if we need it, which is if stats are enabled
+ * or we have a scheduler attached that may use it.
+ */
if (rq->rq_flags & RQF_STATS) {
blk_mq_poll_stats_start(rq->q);
+ now = ktime_get_ns();
blk_stat_add(rq, now);
- }
+ } else if (rq->q->elevator)
+ now = ktime_get_ns();
if (rq->internal_tag != -1)
blk_mq_sched_completed_request(rq, now);
--
2.17.1
--
Jens Axboe
