block: revert 4f1e963 ("blk-throtl: optimize IOPS throttle for large IO scenarios")

Revert commit 4f1e963 ("blk-throtl: optimize IOPS throttle for large
IO scenarios") since we have another easier way to address this issue and
get better iops throttling result.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220216044514.2903784-9-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Ming Lei

block/blk-throttle.c

@@ -640,8 +640,6 @@ static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
 	tg->bytes_disp[rw] = 0;
 	tg->io_disp[rw] = 0;
 
-	atomic_set(&tg->io_split_cnt[rw], 0);
-
 	/*
 	 * Previous slice has expired. We must have trimmed it after last
 	 * bio dispatch. That means since start of last slice, we never used
@@ -665,8 +663,6 @@ static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw)
 	tg->slice_start[rw] = jiffies;
 	tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
 
-	atomic_set(&tg->io_split_cnt[rw], 0);
-
 	throtl_log(&tg->service_queue,
 		   "[%c] new slice start=%lu end=%lu jiffies=%lu",
 		   rw == READ ? 'R' : 'W', tg->slice_start[rw],
@@ -900,9 +896,6 @@ static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
 				jiffies + tg->td->throtl_slice);
 	}
 
-	if (iops_limit != UINT_MAX)
-		tg->io_disp[rw] += atomic_xchg(&tg->io_split_cnt[rw], 0);
-
 	if (tg_with_in_bps_limit(tg, bio, bps_limit, &bps_wait) &&
 	    tg_with_in_iops_limit(tg, bio, iops_limit, &iops_wait)) {
 		if (wait)
@@ -1927,14 +1920,12 @@ static void throtl_downgrade_check(struct throtl_grp *tg)
 	}
 
 	if (tg->iops[READ][LIMIT_LOW]) {
-		tg->last_io_disp[READ] += atomic_xchg(&tg->last_io_split_cnt[READ], 0);
 		iops = tg->last_io_disp[READ] * HZ / elapsed_time;
 		if (iops >= tg->iops[READ][LIMIT_LOW])
 			tg->last_low_overflow_time[READ] = now;
 	}
 
 	if (tg->iops[WRITE][LIMIT_LOW]) {
-		tg->last_io_disp[WRITE] += atomic_xchg(&tg->last_io_split_cnt[WRITE], 0);
 		iops = tg->last_io_disp[WRITE] * HZ / elapsed_time;
 		if (iops >= tg->iops[WRITE][LIMIT_LOW])
 			tg->last_low_overflow_time[WRITE] = now;
@@ -2053,25 +2044,6 @@ static inline void throtl_update_latency_buckets(struct throtl_data *td)
 }
 #endif
 
-void blk_throtl_charge_bio_split(struct bio *bio)
-{
-	struct blkcg_gq *blkg = bio->bi_blkg;
-	struct throtl_grp *parent = blkg_to_tg(blkg);
-	struct throtl_service_queue *parent_sq;
-	bool rw = bio_data_dir(bio);
-
-	do {
-		if (!parent->has_rules[rw])
-			break;
-
-		atomic_inc(&parent->io_split_cnt[rw]);
-		atomic_inc(&parent->last_io_split_cnt[rw]);
-
-		parent_sq = parent->service_queue.parent_sq;
-		parent = sq_to_tg(parent_sq);
-	} while (parent);
-}
-
 bool __blk_throtl_bio(struct bio *bio)
 {
 	struct request_queue *q = bdev_get_queue(bio->bi_bdev);

block/blk-throttle.h

@@ -138,9 +138,6 @@ struct throtl_grp {
 	unsigned int bad_bio_cnt; /* bios exceeding latency threshold */
 	unsigned long bio_cnt_reset_time;
 
-	atomic_t io_split_cnt[2];
-	atomic_t last_io_split_cnt[2];
-
 	struct blkg_rwstat stat_bytes;
 	struct blkg_rwstat stat_ios;
 };
@@ -164,13 +161,11 @@ static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
 static inline int blk_throtl_init(struct request_queue *q) { return 0; }
 static inline void blk_throtl_exit(struct request_queue *q) { }
 static inline void blk_throtl_register_queue(struct request_queue *q) { }
-static inline void blk_throtl_charge_bio_split(struct bio *bio) { }
 static inline bool blk_throtl_bio(struct bio *bio) { return false; }
 #else /* CONFIG_BLK_DEV_THROTTLING */
 int blk_throtl_init(struct request_queue *q);
 void blk_throtl_exit(struct request_queue *q);
 void blk_throtl_register_queue(struct request_queue *q);
-void blk_throtl_charge_bio_split(struct bio *bio);
 bool __blk_throtl_bio(struct bio *bio);
 static inline bool blk_throtl_bio(struct bio *bio)
 {