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Commit fe1f4526 authored by Jens Axboe's avatar Jens Axboe
Browse files

blk-mq: don't call ktime_get_ns() if we don't need it 



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.

Reviewed-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 2149da07

block/blk-mq.c

+17 −2
Original line number Diff line number Diff line
@@ -281,6 +281,15 @@ bool blk_mq_can_queue(struct blk_mq_hw_ctx *hctx) 
}

EXPORT_SYMBOL(blk_mq_can_queue);



/*

 * Only need start/end time stamping if we have stats enabled, or using

 * an IO scheduler.

 */

static inline bool blk_mq_need_time_stamp(struct request *rq)

{

	return (rq->rq_flags & RQF_IO_STAT) || rq->q->elevator;

}



static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,

		unsigned int tag, unsigned int op)

{
@@ -316,7 +325,10 @@ 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;

	if (blk_mq_need_time_stamp(rq))

		rq->start_time_ns = ktime_get_ns();

	else

		rq->start_time_ns = 0;

	rq->io_start_time_ns = 0;

	rq->nr_phys_segments = 0;

#if defined(CONFIG_BLK_DEV_INTEGRITY)
@@ -522,7 +534,10 @@ 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;



	if (blk_mq_need_time_stamp(rq))

		now = ktime_get_ns();



	if (rq->rq_flags & RQF_STATS) {

		blk_mq_poll_stats_start(rq->q);