| Message ID | 73f58a60-cfa8-5736-d42a-9297601a1f71@kernel.dk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] blk-mq: don't call ktime_get_ns() if we don't need it | expand |
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 <osandov@fb.com> > Signed-off-by: Jens Axboe <axboe@kernel.dk> > > --- > > 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 >
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);
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@kernel.dk> --- v2: add helper, use it in both spots. also clear ->start_time_ns so merging doesn't read garbage.