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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: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2018-11-28 10:50:07 -07:00
parent 2149da0748
commit fe1f452640
1 changed files with 17 additions and 2 deletions
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19
block/blk-mq.c
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@ -281,6 +281,15 @@ bool blk_mq_can_queue(struct blk_mq_hw_ctx *hctx)
} }
EXPORT_SYMBOL(blk_mq_can_queue); 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, static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
unsigned int tag, unsigned int op) 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); RB_CLEAR_NODE(&rq->rb_node);
rq->rq_disk = NULL; rq->rq_disk = NULL;
rq->part = NULL; rq->part = NULL;
rq->start_time_ns = ktime_get_ns(); 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->io_start_time_ns = 0;
rq->nr_phys_segments = 0; rq->nr_phys_segments = 0;
#if defined(CONFIG_BLK_DEV_INTEGRITY) #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) 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) { if (rq->rq_flags & RQF_STATS) {
blk_mq_poll_stats_start(rq->q); blk_mq_poll_stats_start(rq->q);