Commit f0bf84a5 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

blk-iocost: add three debug stat - cost.wait, indebt and indelay 



These are really cheap to collect and can be useful in debugging iocost
behavior. Add them as debug stats for now.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 04603755

block/blk-iocost.c

+72 −5
Original line number Diff line number Diff line
@@ -452,6 +452,9 @@ struct iocg_pcpu_stat { 


struct iocg_stat {

	u64				usage_us;

	u64				wait_us;

	u64				indebt_us;

	u64				indelay_us;

};



/* per device-cgroup pair */
@@ -538,6 +541,9 @@ struct ioc_gq { 
	struct iocg_stat		last_stat;

	u64				last_stat_abs_vusage;

	u64				usage_delta_us;

	u64				wait_since;

	u64				indebt_since;

	u64				indelay_since;



	/* this iocg's depth in the hierarchy and ancestors including self */

	int				level;
@@ -1303,9 +1309,15 @@ static bool iocg_kick_delay(struct ioc_gq *iocg, struct ioc_now *now) 
	}



	if (delay >= MIN_DELAY) {

		if (!iocg->indelay_since)

			iocg->indelay_since = now->now;

		blkcg_set_delay(blkg, delay * NSEC_PER_USEC);

		return true;

	} else {

		if (iocg->indelay_since) {

			iocg->local_stat.indelay_us += now->now - iocg->indelay_since;

			iocg->indelay_since = 0;

		}

		iocg->delay = 0;

		blkcg_clear_delay(blkg);

		return false;
@@ -1325,8 +1337,10 @@ static void iocg_incur_debt(struct ioc_gq *iocg, u64 abs_cost, 
	 * Once in debt, debt handling owns inuse. @iocg stays at the minimum

	 * inuse donating all of it share to others until its debt is paid off.

	 */

	if (!iocg->abs_vdebt && abs_cost)

	if (!iocg->abs_vdebt && abs_cost) {

		iocg->indebt_since = now->now;

		propagate_weights(iocg, iocg->active, 0, false, now);

	}



	iocg->abs_vdebt += abs_cost;
@@ -1348,10 +1362,14 @@ static void iocg_pay_debt(struct ioc_gq *iocg, u64 abs_vpay, 
	iocg->abs_vdebt -= min(abs_vpay, iocg->abs_vdebt);



	/* if debt is paid in full, restore inuse */

	if (!iocg->abs_vdebt)

	if (!iocg->abs_vdebt) {

		iocg->local_stat.indebt_us += now->now - iocg->indebt_since;

		iocg->indebt_since = 0;



		propagate_weights(iocg, iocg->active, iocg->last_inuse,

				  false, now);

	}

}



static int iocg_wake_fn(struct wait_queue_entry *wq_entry, unsigned mode,

			int flags, void *key)
@@ -1436,8 +1454,17 @@ static void iocg_kick_waitq(struct ioc_gq *iocg, bool pay_debt, 


	__wake_up_locked_key(&iocg->waitq, TASK_NORMAL, &ctx);



	if (!waitqueue_active(&iocg->waitq))

	if (!waitqueue_active(&iocg->waitq)) {

		if (iocg->wait_since) {

			iocg->local_stat.wait_us += now->now - iocg->wait_since;

			iocg->wait_since = 0;

		}

		return;

	}



	if (!iocg->wait_since)

		iocg->wait_since = now->now;



	if (WARN_ON_ONCE(ctx.vbudget >= 0))

		return;
@@ -1579,8 +1606,15 @@ static void iocg_flush_stat_one(struct ioc_gq *iocg, struct ioc_now *now) 
	iocg->usage_delta_us = div64_u64(vusage_delta, ioc->vtime_base_rate);

	iocg->local_stat.usage_us += iocg->usage_delta_us;



	/* propagate upwards */

	new_stat.usage_us =

		iocg->local_stat.usage_us + iocg->desc_stat.usage_us;

	new_stat.wait_us =

		iocg->local_stat.wait_us + iocg->desc_stat.wait_us;

	new_stat.indebt_us =

		iocg->local_stat.indebt_us + iocg->desc_stat.indebt_us;

	new_stat.indelay_us =

		iocg->local_stat.indelay_us + iocg->desc_stat.indelay_us;



	/* propagate the deltas to the parent */

	if (iocg->level > 0) {
@@ -1589,6 +1623,12 @@ static void iocg_flush_stat_one(struct ioc_gq *iocg, struct ioc_now *now) 


		parent_stat->usage_us +=

			new_stat.usage_us - iocg->last_stat.usage_us;

		parent_stat->wait_us +=

			new_stat.wait_us - iocg->last_stat.wait_us;

		parent_stat->indebt_us +=

			new_stat.indebt_us - iocg->last_stat.indebt_us;

		parent_stat->indelay_us +=

			new_stat.indelay_us - iocg->last_stat.indelay_us;

	}



	iocg->last_stat = new_stat;
@@ -1961,8 +2001,6 @@ static void ioc_timer_fn(struct timer_list *timer) 
		return;

	}



	iocg_flush_stat(&ioc->active_iocgs, &now);



	/*

	 * Waiters determine the sleep durations based on the vrate they

	 * saw at the time of sleep.  If vrate has increased, some waiters
@@ -1976,6 +2014,22 @@ static void ioc_timer_fn(struct timer_list *timer) 


		spin_lock(&iocg->waitq.lock);



		/* flush wait and indebt stat deltas */

		if (iocg->wait_since) {

			iocg->local_stat.wait_us += now.now - iocg->wait_since;

			iocg->wait_since = now.now;

		}

		if (iocg->indebt_since) {

			iocg->local_stat.indebt_us +=

				now.now - iocg->indebt_since;

			iocg->indebt_since = now.now;

		}

		if (iocg->indelay_since) {

			iocg->local_stat.indelay_us +=

				now.now - iocg->indelay_since;

			iocg->indelay_since = now.now;

		}



		if (waitqueue_active(&iocg->waitq) || iocg->abs_vdebt ||

		    iocg->delay) {

			/* might be oversleeping vtime / hweight changes, kick */
@@ -2010,6 +2064,12 @@ static void ioc_timer_fn(struct timer_list *timer) 
	}

	commit_weights(ioc);



	/*

	 * Wait and indebt stat are flushed above and the donation calculation

	 * below needs updated usage stat. Let's bring stat up-to-date.

	 */

	iocg_flush_stat(&ioc->active_iocgs, &now);



	/* calc usage and see whether some weights need to be moved around */

	list_for_each_entry(iocg, &ioc->active_iocgs, active_list) {

		u64 vdone, vtime, usage_us, usage_dur;
@@ -2835,6 +2895,13 @@ static size_t ioc_pd_stat(struct blkg_policy_data *pd, char *buf, size_t size) 
	pos += scnprintf(buf + pos, size - pos, " cost.usage=%llu",

			 iocg->last_stat.usage_us);



	if (blkcg_debug_stats)

		pos += scnprintf(buf + pos, size - pos,

				 " cost.wait=%llu cost.indebt=%llu cost.indelay=%llu",

				 iocg->last_stat.wait_us,

				 iocg->last_stat.indebt_us,

				 iocg->last_stat.indelay_us);



	return pos;

}