diff mbox series

[1/2] block: add blk_time_get_ns() helper

Message ID 20240115215840.54432-2-axboe@kernel.dk (mailing list archive)
State New, archived
Headers show
Series Cache issue side time querying | expand

Commit Message

Jens Axboe Jan. 15, 2024, 9:53 p.m. UTC 
No functional changes intended, this patch just wraps ktime_get_ns()
with a block helper.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 block/blk-cgroup.c     |  2 +-
 block/blk-flush.c      |  2 +-
 block/blk-iocost.c     |  6 +++---
 block/blk-mq.c         | 16 ++++++++--------
 block/blk-throttle.c   |  6 +++---
 block/blk-wbt.c        |  5 ++---
 include/linux/blkdev.h |  5 +++++
 7 files changed, 23 insertions(+), 19 deletions(-)

Comments

Yu Kuai Jan. 16, 2024, 6:42 a.m. UTC | #1 
Hi,

在 2024/01/16 5:53, Jens Axboe 写道:
>   
> @@ -2810,7 +2810,7 @@ static void ioc_rqos_done(struct rq_qos *rqos, struct request *rq)
>   		return;
>   	}
>   
> -	on_q_ns = ktime_get_ns() - rq->alloc_time_ns;
> +	on_q_ns = blk_time_get_ns() - rq->alloc_time_ns;

Just notice that this is from io completion path, and the same as
blk_account_io_done(), where plug does not exist. Hence ktime_get_ns()
will still be called multiple times after patch 2.

Do you think will this worth to be optimized? For example, add a new
field in request so that each rq completion will only call
ktime_get_ns() once. Furthermore, we can optimize io_tices precision
from jiffies to ns.

Thanks,
Kuai
Jens Axboe Jan. 16, 2024, 2:41 p.m. UTC | #2 
On 1/15/24 11:42 PM, Yu Kuai wrote:
> Hi,
> 
> ? 2024/01/16 5:53, Jens Axboe ??:
>>   @@ -2810,7 +2810,7 @@ static void ioc_rqos_done(struct rq_qos *rqos, struct request *rq)
>>           return;
>>       }
>>   -    on_q_ns = ktime_get_ns() - rq->alloc_time_ns;
>> +    on_q_ns = blk_time_get_ns() - rq->alloc_time_ns;
> 
> Just notice that this is from io completion path, and the same as
> blk_account_io_done(), where plug does not exist. Hence ktime_get_ns()
> will still be called multiple times after patch 2.
> 
> Do you think will this worth to be optimized? For example, add a new
> field in request so that each rq completion will only call
> ktime_get_ns() once. Furthermore, we can optimize io_tices precision
> from jiffies to ns.

Right, as mentioned this is just an issue side optimization, my intent
is/was to convert all callers of ktime_get_ns() to use the internal one.
The completion side will just not get any amortization of the frequency
of time calls for now, but then it's prepared for that later on. That,
to me, was nicer than doing selective conversions as then it's not clear
if the two time sources could be compared.

It isn't complete yet, I just did the main components.

Putting it in the request is one way, ideally we'd have completion
batching via struct io_comp_batch for the completion side. At least that
was my plan.
diff mbox series

Patch

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index ff93c385ba5a..bdbb557feb5a 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1846,7 +1846,7 @@  static void blkcg_maybe_throttle_blkg(struct blkcg_gq *blkg, bool use_memdelay)
 {
 	unsigned long pflags;
 	bool clamp;
-	u64 now = ktime_to_ns(ktime_get());
+	u64 now = blk_time_get_ns();
 	u64 exp;
 	u64 delay_nsec = 0;
 	int tok;
diff --git a/block/blk-flush.c b/block/blk-flush.c
index 3f4d41952ef2..b0f314f4bc14 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -143,7 +143,7 @@  static void blk_account_io_flush(struct request *rq)
 	part_stat_lock();
 	part_stat_inc(part, ios[STAT_FLUSH]);
 	part_stat_add(part, nsecs[STAT_FLUSH],
-		      ktime_get_ns() - rq->start_time_ns);
+		      blk_time_get_ns() - rq->start_time_ns);
 	part_stat_unlock();
 }
 
diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index c8beec6d7df0..e54b17261d96 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -829,7 +829,7 @@  static int ioc_autop_idx(struct ioc *ioc, struct gendisk *disk)
 
 	/* step up/down based on the vrate */
 	vrate_pct = div64_u64(ioc->vtime_base_rate * 100, VTIME_PER_USEC);
-	now_ns = ktime_get_ns();
+	now_ns = blk_time_get_ns();
 
 	if (p->too_fast_vrate_pct && p->too_fast_vrate_pct <= vrate_pct) {
 		if (!ioc->autop_too_fast_at)
@@ -1044,7 +1044,7 @@  static void ioc_now(struct ioc *ioc, struct ioc_now *now)
 	unsigned seq;
 	u64 vrate;
 
-	now->now_ns = ktime_get();
+	now->now_ns = blk_time_get_ns();
 	now->now = ktime_to_us(now->now_ns);
 	vrate = atomic64_read(&ioc->vtime_rate);
 
@@ -2810,7 +2810,7 @@  static void ioc_rqos_done(struct rq_qos *rqos, struct request *rq)
 		return;
 	}
 
-	on_q_ns = ktime_get_ns() - rq->alloc_time_ns;
+	on_q_ns = blk_time_get_ns() - rq->alloc_time_ns;
 	rq_wait_ns = rq->start_time_ns - rq->alloc_time_ns;
 	size_nsec = div64_u64(calc_size_vtime_cost(rq, ioc), VTIME_PER_NSEC);
 
diff --git a/block/blk-mq.c b/block/blk-mq.c
index aa87fcfda1ec..aff9e9492f59 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -323,7 +323,7 @@  void blk_rq_init(struct request_queue *q, struct request *rq)
 	RB_CLEAR_NODE(&rq->rb_node);
 	rq->tag = BLK_MQ_NO_TAG;
 	rq->internal_tag = BLK_MQ_NO_TAG;
-	rq->start_time_ns = ktime_get_ns();
+	rq->start_time_ns = blk_time_get_ns();
 	rq->part = NULL;
 	blk_crypto_rq_set_defaults(rq);
 }
@@ -333,7 +333,7 @@  EXPORT_SYMBOL(blk_rq_init);
 static inline void blk_mq_rq_time_init(struct request *rq, u64 alloc_time_ns)
 {
 	if (blk_mq_need_time_stamp(rq))
-		rq->start_time_ns = ktime_get_ns();
+		rq->start_time_ns = blk_time_get_ns();
 	else
 		rq->start_time_ns = 0;
 
@@ -444,7 +444,7 @@  static struct request *__blk_mq_alloc_requests(struct blk_mq_alloc_data *data)
 
 	/* alloc_time includes depth and tag waits */
 	if (blk_queue_rq_alloc_time(q))
-		alloc_time_ns = ktime_get_ns();
+		alloc_time_ns = blk_time_get_ns();
 
 	if (data->cmd_flags & REQ_NOWAIT)
 		data->flags |= BLK_MQ_REQ_NOWAIT;
@@ -629,7 +629,7 @@  struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
 
 	/* alloc_time includes depth and tag waits */
 	if (blk_queue_rq_alloc_time(q))
-		alloc_time_ns = ktime_get_ns();
+		alloc_time_ns = blk_time_get_ns();
 
 	/*
 	 * If the tag allocator sleeps we could get an allocation for a
@@ -1042,7 +1042,7 @@  static inline void __blk_mq_end_request_acct(struct request *rq, u64 now)
 inline void __blk_mq_end_request(struct request *rq, blk_status_t error)
 {
 	if (blk_mq_need_time_stamp(rq))
-		__blk_mq_end_request_acct(rq, ktime_get_ns());
+		__blk_mq_end_request_acct(rq, blk_time_get_ns());
 
 	blk_mq_finish_request(rq);
 
@@ -1085,7 +1085,7 @@  void blk_mq_end_request_batch(struct io_comp_batch *iob)
 	u64 now = 0;
 
 	if (iob->need_ts)
-		now = ktime_get_ns();
+		now = blk_time_get_ns();
 
 	while ((rq = rq_list_pop(&iob->req_list)) != NULL) {
 		prefetch(rq->bio);
@@ -1255,7 +1255,7 @@  void blk_mq_start_request(struct request *rq)
 
 	if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags) &&
 	    !blk_rq_is_passthrough(rq)) {
-		rq->io_start_time_ns = ktime_get_ns();
+		rq->io_start_time_ns = blk_time_get_ns();
 		rq->stats_sectors = blk_rq_sectors(rq);
 		rq->rq_flags |= RQF_STATS;
 		rq_qos_issue(q, rq);
@@ -3107,7 +3107,7 @@  blk_status_t blk_insert_cloned_request(struct request *rq)
 	blk_mq_run_dispatch_ops(q,
 			ret = blk_mq_request_issue_directly(rq, true));
 	if (ret)
-		blk_account_io_done(rq, ktime_get_ns());
+		blk_account_io_done(rq, blk_time_get_ns());
 	return ret;
 }
 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 16f5766620a4..da9dc1f793c3 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1815,7 +1815,7 @@  static bool throtl_tg_is_idle(struct throtl_grp *tg)
 	time = min_t(unsigned long, MAX_IDLE_TIME, 4 * tg->idletime_threshold);
 	ret = tg->latency_target == DFL_LATENCY_TARGET ||
 	      tg->idletime_threshold == DFL_IDLE_THRESHOLD ||
-	      (ktime_get_ns() >> 10) - tg->last_finish_time > time ||
+	      (blk_time_get_ns() >> 10) - tg->last_finish_time > time ||
 	      tg->avg_idletime > tg->idletime_threshold ||
 	      (tg->latency_target && tg->bio_cnt &&
 		tg->bad_bio_cnt * 5 < tg->bio_cnt);
@@ -2060,7 +2060,7 @@  static void blk_throtl_update_idletime(struct throtl_grp *tg)
 	if (last_finish_time == 0)
 		return;
 
-	now = ktime_get_ns() >> 10;
+	now = blk_time_get_ns() >> 10;
 	if (now <= last_finish_time ||
 	    last_finish_time == tg->checked_last_finish_time)
 		return;
@@ -2327,7 +2327,7 @@  void blk_throtl_bio_endio(struct bio *bio)
 	if (!tg->td->limit_valid[LIMIT_LOW])
 		return;
 
-	finish_time_ns = ktime_get_ns();
+	finish_time_ns = blk_time_get_ns();
 	tg->last_finish_time = finish_time_ns >> 10;
 
 	start_time = bio_issue_time(&bio->bi_issue) >> 10;
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 5ba3cd574eac..d5dcf44ef0de 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -274,13 +274,12 @@  static inline bool stat_sample_valid(struct blk_rq_stat *stat)
 
 static u64 rwb_sync_issue_lat(struct rq_wb *rwb)
 {
-	u64 now, issue = READ_ONCE(rwb->sync_issue);
+	u64 issue = READ_ONCE(rwb->sync_issue);
 
 	if (!issue || !rwb->sync_cookie)
 		return 0;
 
-	now = ktime_to_ns(ktime_get());
-	return now - issue;
+	return blk_time_to_ns() - issue;
 }
 
 static inline unsigned int wbt_inflight(struct rq_wb *rwb)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 99e4f5e72213..2f9ceea0e23b 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -974,6 +974,11 @@  static inline void blk_flush_plug(struct blk_plug *plug, bool async)
 
 int blkdev_issue_flush(struct block_device *bdev);
 long nr_blockdev_pages(void);
+
+static inline u64 blk_time_get_ns(void)
+{
+	return ktime_get_ns();
+}
 #else /* CONFIG_BLOCK */
 struct blk_plug {
 };