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 <[email protected]> --- 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
