On Fri, Nov 30, 2018 at 02:13:54PM -0700, Jens Axboe wrote: > 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 <[email protected]> > Signed-off-by: Jens Axboe <[email protected]> > > --- > > v2: add helper, use it in both spots. also clear ->start_time_ns > so merging doesn't read garbage. > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 7dcef565dc0f..e09d7f500077 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -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; > - 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->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); > -- > Jens Axboe >
