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Commit 8e89d13f authored by Vivek Goyal's avatar Vivek Goyal Committed by Jens Axboe
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blkio: Implementation of IOPS limit logic 



o core logic of implementing IOPS throttling.

Signed-off-by: default avatarVivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 7702e8f4

block/blk-throttle.c

+127 −37
Original line number Diff line number Diff line
@@ -59,8 +59,13 @@ struct throtl_grp { 
	/* bytes per second rate limits */

	uint64_t bps[2];



	/* IOPS limits */

	unsigned int iops[2];



	/* Number of bytes disptached in current slice */

	uint64_t bytes_disp[2];

	/* Number of bio's dispatched in current slice */

	unsigned int io_disp[2];



	/* When did we start a new slice */

	unsigned long slice_start[2];
@@ -194,6 +199,8 @@ static struct throtl_grp * throtl_find_alloc_tg(struct throtl_data *td, 


	tg->bps[READ] = blkcg_get_read_bps(blkcg, tg->blkg.dev);

	tg->bps[WRITE] = blkcg_get_write_bps(blkcg, tg->blkg.dev);

	tg->iops[READ] = blkcg_get_read_iops(blkcg, tg->blkg.dev);

	tg->iops[WRITE] = blkcg_get_write_iops(blkcg, tg->blkg.dev);



	hlist_add_head(&tg->tg_node, &td->tg_list);

	td->nr_undestroyed_grps++;
@@ -335,6 +342,7 @@ static inline void 
throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)

{

	tg->bytes_disp[rw] = 0;

	tg->io_disp[rw] = 0;

	tg->slice_start[rw] = jiffies;

	tg->slice_end[rw] = jiffies + throtl_slice;

	throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu",
@@ -365,7 +373,7 @@ throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw) 
static inline void

throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)

{

	unsigned long nr_slices, bytes_trim, time_elapsed;

	unsigned long nr_slices, bytes_trim, time_elapsed, io_trim;



	BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
@@ -385,8 +393,9 @@ throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw) 
		return;



	bytes_trim = (tg->bps[rw] * throtl_slice * nr_slices)/HZ;

	io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;



	if (!bytes_trim)

	if (!bytes_trim && !io_trim)

		return;



	if (tg->bytes_disp[rw] >= bytes_trim)
@@ -394,52 +403,63 @@ throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw) 
	else

		tg->bytes_disp[rw] = 0;



	if (tg->io_disp[rw] >= io_trim)

		tg->io_disp[rw] -= io_trim;

	else

		tg->io_disp[rw] = 0;



	tg->slice_start[rw] += nr_slices * throtl_slice;



	throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%lu"

	throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%lu io=%lu"

			" start=%lu end=%lu jiffies=%lu",

			rw == READ ? 'R' : 'W', nr_slices, bytes_trim,

			rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,

			tg->slice_start[rw], tg->slice_end[rw], jiffies);

}



/*

 * Returns whether one can dispatch a bio or not. Also returns approx number

 * of jiffies to wait before this bio is with-in IO rate and can be dispatched

 */

static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,

static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg,

		struct bio *bio, unsigned long *wait)

{

	bool rw = bio_data_dir(bio);

	u64 bytes_allowed, extra_bytes;

	unsigned int io_allowed;

	unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;



	/*

	 * Currently whole state machine of group depends on first bio

	 * queued in the group bio list. So one should not be calling

	 * this function with a different bio if there are other bios

	 * queued.

	 */

	BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));

	jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];



	/* If tg->bps = -1, then BW is unlimited */

	if (tg->bps[rw] == -1) {

	/* Slice has just started. Consider one slice interval */

	if (!jiffy_elapsed)

		jiffy_elapsed_rnd = throtl_slice;



	jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);



	io_allowed = (tg->iops[rw] * jiffies_to_msecs(jiffy_elapsed_rnd))

				/ MSEC_PER_SEC;



	if (tg->io_disp[rw] + 1 <= io_allowed) {

		if (wait)

			*wait = 0;

		return 1;

	}



	/*

	 * If previous slice expired, start a new one otherwise renew/extend

	 * existing slice to make sure it is at least throtl_slice interval

	 * long since now.

	 */

	if (throtl_slice_used(td, tg, rw))

		throtl_start_new_slice(td, tg, rw);

	else {

		if (time_before(tg->slice_end[rw], jiffies + throtl_slice))

			throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);

	/* Calc approx time to dispatch */

	jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;



	if (jiffy_wait > jiffy_elapsed)

		jiffy_wait = jiffy_wait - jiffy_elapsed;

	else

		jiffy_wait = 1;



	if (wait)

		*wait = jiffy_wait;

	return 0;

}



static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg,

		struct bio *bio, unsigned long *wait)

{

	bool rw = bio_data_dir(bio);

	u64 bytes_allowed, extra_bytes;

	unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;



	jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];



	/* Slice has just started. Consider one slice interval */
@@ -469,12 +489,62 @@ static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg, 
	 * up we did. Add that time also.

	 */

	jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);



	if (wait)

		*wait = jiffy_wait;

	return 0;

}



/*

 * Returns whether one can dispatch a bio or not. Also returns approx number

 * of jiffies to wait before this bio is with-in IO rate and can be dispatched

 */

static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,

				struct bio *bio, unsigned long *wait)

{

	bool rw = bio_data_dir(bio);

	unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;



	/*

 	 * Currently whole state machine of group depends on first bio

	 * queued in the group bio list. So one should not be calling

	 * this function with a different bio if there are other bios

	 * queued.

	 */

	BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));



	if (time_before(tg->slice_end[rw], jiffies + jiffy_wait))

		throtl_extend_slice(td, tg, rw, jiffies + jiffy_wait);

	/* If tg->bps = -1, then BW is unlimited */

	if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {

		if (wait)

			*wait = 0;

		return 1;

	}



	/*

	 * If previous slice expired, start a new one otherwise renew/extend

	 * existing slice to make sure it is at least throtl_slice interval

	 * long since now.

	 */

	if (throtl_slice_used(td, tg, rw))

		throtl_start_new_slice(td, tg, rw);

	else {

		if (time_before(tg->slice_end[rw], jiffies + throtl_slice))

			throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);

	}



	if (tg_with_in_bps_limit(td, tg, bio, &bps_wait)

	    && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) {

		if (wait)

			*wait = 0;

		return 1;

	}



	max_wait = max(bps_wait, iops_wait);



	if (wait)

		*wait = max_wait;



	if (time_before(tg->slice_end[rw], jiffies + max_wait))

		throtl_extend_slice(td, tg, rw, jiffies + max_wait);



	return 0;

}
@@ -486,13 +556,13 @@ static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio) 


	/* Charge the bio to the group */

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

	tg->io_disp[rw]++;



	/*

	 * TODO: This will take blkg->stats_lock. Figure out a way

	 * to avoid this cost.

	 */

	blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, rw, sync);



}



static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg,
@@ -763,6 +833,18 @@ static void throtl_update_blkio_group_write_bps (struct blkio_group *blkg, 
	tg_of_blkg(blkg)->bps[WRITE] = write_bps;

}



static void throtl_update_blkio_group_read_iops (struct blkio_group *blkg,

			unsigned int read_iops)

{

	tg_of_blkg(blkg)->iops[READ] = read_iops;

}



static void throtl_update_blkio_group_write_iops (struct blkio_group *blkg,

			unsigned int write_iops)

{

	tg_of_blkg(blkg)->iops[WRITE] = write_iops;

}



void throtl_shutdown_timer_wq(struct request_queue *q)

{

	struct throtl_data *td = q->td;
@@ -777,7 +859,12 @@ static struct blkio_policy_type blkio_policy_throtl = { 
					throtl_update_blkio_group_read_bps,

		.blkio_update_group_write_bps_fn =

					throtl_update_blkio_group_write_bps,

		.blkio_update_group_read_iops_fn =

					throtl_update_blkio_group_read_iops,

		.blkio_update_group_write_iops_fn =

					throtl_update_blkio_group_write_iops,

	},

	.plid = BLKIO_POLICY_THROTL,

};



int blk_throtl_bio(struct request_queue *q, struct bio **biop)
@@ -811,9 +898,11 @@ int blk_throtl_bio(struct request_queue *q, struct bio **biop) 
	}



queue_bio:

	throtl_log_tg(td, tg, "[%c] bio. disp=%u sz=%u bps=%llu"

			" queued=%d/%d", rw == READ ? 'R' : 'W',

	throtl_log_tg(td, tg, "[%c] bio. bdisp=%u sz=%u bps=%llu"

			" iodisp=%u iops=%u queued=%d/%d",

			rw == READ ? 'R' : 'W',

			tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],

			tg->io_disp[rw], tg->iops[rw],

			tg->nr_queued[READ], tg->nr_queued[WRITE]);



	throtl_add_bio_tg(q->td, tg, bio);
@@ -850,6 +939,7 @@ int blk_throtl_init(struct request_queue *q) 


	/* Practically unlimited BW */

	tg->bps[0] = tg->bps[1] = -1;

	tg->iops[0] = tg->iops[1] = -1;

	atomic_set(&tg->ref, 1);



	INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work);