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Commit ea0ea2bc authored by Shaohua Li's avatar Shaohua Li Committed by Jens Axboe
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blk-throttle: cap discard request size 



discard request usually is very big and easily use all bandwidth budget
of a cgroup. discard request size doesn't really mean the size of data
written, so it doesn't make sense to account it into bandwidth budget.
Jens pointed out treating the size 0 doesn't make sense too, because
discard request does have cost. But it's not easy to find the actual
cost. This patch simply makes the size one sector.

Signed-off-by: default avatarShaohua Li <shli@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 6470812e

block/blk-throttle.c

+14 −4
Original line number Diff line number Diff line
@@ -382,6 +382,14 @@ static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw) 
	}								\

} while (0)



static inline unsigned int throtl_bio_data_size(struct bio *bio)

{

	/* assume it's one sector */

	if (unlikely(bio_op(bio) == REQ_OP_DISCARD))

		return 512;

	return bio->bi_iter.bi_size;

}



static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)

{

	INIT_LIST_HEAD(&qn->node);
@@ -934,6 +942,7 @@ static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio, 
	bool rw = bio_data_dir(bio);

	u64 bytes_allowed, extra_bytes, tmp;

	unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;

	unsigned int bio_size = throtl_bio_data_size(bio);



	jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
@@ -947,14 +956,14 @@ static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio, 
	do_div(tmp, HZ);

	bytes_allowed = tmp;



	if (tg->bytes_disp[rw] + bio->bi_iter.bi_size <= bytes_allowed) {

	if (tg->bytes_disp[rw] + bio_size <= bytes_allowed) {

		if (wait)

			*wait = 0;

		return true;

	}



	/* Calc approx time to dispatch */

	extra_bytes = tg->bytes_disp[rw] + bio->bi_iter.bi_size - bytes_allowed;

	extra_bytes = tg->bytes_disp[rw] + bio_size - bytes_allowed;

	jiffy_wait = div64_u64(extra_bytes * HZ, tg_bps_limit(tg, rw));



	if (!jiffy_wait)
@@ -1034,11 +1043,12 @@ static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio, 
static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)

{

	bool rw = bio_data_dir(bio);

	unsigned int bio_size = throtl_bio_data_size(bio);



	/* Charge the bio to the group */

	tg->bytes_disp[rw] += bio->bi_iter.bi_size;

	tg->bytes_disp[rw] += bio_size;

	tg->io_disp[rw]++;

	tg->last_bytes_disp[rw] += bio->bi_iter.bi_size;

	tg->last_bytes_disp[rw] += bio_size;

	tg->last_io_disp[rw]++;



	/*