Commit 5205ea00 authored by Mohit P. Tahiliani's avatar Mohit P. Tahiliani Committed by David S. Miller
Browse files

net: sched: pie: export symbols to be reused by FQ-PIE 



This patch makes the drop_early(), calculate_probability() and
pie_process_dequeue() functions generic enough to be used by
both PIE and FQ-PIE (to be added in a future commit). The major
change here is in the way the functions take in arguments. This
patch exports these functions and makes FQ-PIE dependent on
sch_pie.

Signed-off-by: default avatarMohit P. Tahiliani <tahiliani@nitk.edu.in>
Signed-off-by: default avatarLeslie Monis <lesliemonis@gmail.com>
Signed-off-by: default avatarGautam Ramakrishnan <gautamramk@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 00ea2fb7

include/net/pie.h

+9 −0
Original line number Diff line number Diff line
@@ -124,4 +124,13 @@ static inline void pie_set_enqueue_time(struct sk_buff *skb) 
	get_pie_cb(skb)->enqueue_time = psched_get_time();

}



bool pie_drop_early(struct Qdisc *sch, struct pie_params *params,

		    struct pie_vars *vars, u32 qlen, u32 packet_size);



void pie_process_dequeue(struct sk_buff *skb, struct pie_params *params,

			 struct pie_vars *vars, u32 qlen);



void pie_calculate_probability(struct pie_params *params, struct pie_vars *vars,

			       u32 qlen);



#endif

net/sched/sch_pie.c

+88 −85
Original line number Diff line number Diff line
@@ -30,64 +30,65 @@ struct pie_sched_data { 
	struct Qdisc *sch;

};



static bool drop_early(struct Qdisc *sch, u32 packet_size)

bool pie_drop_early(struct Qdisc *sch, struct pie_params *params,

		    struct pie_vars *vars, u32 qlen, u32 packet_size)

{

	struct pie_sched_data *q = qdisc_priv(sch);

	u64 rnd;

	u64 local_prob = q->vars.prob;

	u64 local_prob = vars->prob;

	u32 mtu = psched_mtu(qdisc_dev(sch));



	/* If there is still burst allowance left skip random early drop */

	if (q->vars.burst_time > 0)

	if (vars->burst_time > 0)

		return false;



	/* If current delay is less than half of target, and

	 * if drop prob is low already, disable early_drop

	 */

	if ((q->vars.qdelay < q->params.target / 2) &&

	    (q->vars.prob < MAX_PROB / 5))

	if ((vars->qdelay < params->target / 2) &&

	    (vars->prob < MAX_PROB / 5))

		return false;



	/* If we have fewer than 2 mtu-sized packets, disable drop_early,

	/* If we have fewer than 2 mtu-sized packets, disable pie_drop_early,

	 * similar to min_th in RED

	 */

	if (sch->qstats.backlog < 2 * mtu)

	if (qlen < 2 * mtu)

		return false;



	/* If bytemode is turned on, use packet size to compute new

	 * probablity. Smaller packets will have lower drop prob in this case

	 */

	if (q->params.bytemode && packet_size <= mtu)

	if (params->bytemode && packet_size <= mtu)

		local_prob = (u64)packet_size * div_u64(local_prob, mtu);

	else

		local_prob = q->vars.prob;

		local_prob = vars->prob;



	if (local_prob == 0) {

		q->vars.accu_prob = 0;

		q->vars.accu_prob_overflows = 0;

		vars->accu_prob = 0;

		vars->accu_prob_overflows = 0;

	}



	if (local_prob > MAX_PROB - q->vars.accu_prob)

		q->vars.accu_prob_overflows++;

	if (local_prob > MAX_PROB - vars->accu_prob)

		vars->accu_prob_overflows++;



	q->vars.accu_prob += local_prob;

	vars->accu_prob += local_prob;



	if (q->vars.accu_prob_overflows == 0 &&

	    q->vars.accu_prob < (MAX_PROB / 100) * 85)

	if (vars->accu_prob_overflows == 0 &&

	    vars->accu_prob < (MAX_PROB / 100) * 85)

		return false;

	if (q->vars.accu_prob_overflows == 8 &&

	    q->vars.accu_prob >= MAX_PROB / 2)

	if (vars->accu_prob_overflows == 8 &&

	    vars->accu_prob >= MAX_PROB / 2)

		return true;



	prandom_bytes(&rnd, 8);

	if (rnd < local_prob) {

		q->vars.accu_prob = 0;

		q->vars.accu_prob_overflows = 0;

		vars->accu_prob = 0;

		vars->accu_prob_overflows = 0;

		return true;

	}



	return false;

}

EXPORT_SYMBOL_GPL(pie_drop_early);



static int pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,

			     struct sk_buff **to_free)
@@ -100,7 +101,8 @@ static int pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch, 
		goto out;

	}



	if (!drop_early(sch, skb->len)) {

	if (!pie_drop_early(sch, &q->params, &q->vars, sch->qstats.backlog,

			    skb->len)) {

		enqueue = true;

	} else if (q->params.ecn && (q->vars.prob <= MAX_PROB / 10) &&

		   INET_ECN_set_ce(skb)) {
@@ -212,26 +214,25 @@ static int pie_change(struct Qdisc *sch, struct nlattr *opt, 
	return 0;

}



static void pie_process_dequeue(struct Qdisc *sch, struct sk_buff *skb)

void pie_process_dequeue(struct sk_buff *skb, struct pie_params *params,

			 struct pie_vars *vars, u32 qlen)

{

	struct pie_sched_data *q = qdisc_priv(sch);

	int qlen = sch->qstats.backlog;	/* current queue size in bytes */

	psched_time_t now = psched_get_time();

	u32 dtime = 0;



	/* If dq_rate_estimator is disabled, calculate qdelay using the

	 * packet timestamp.

	 */

	if (!q->params.dq_rate_estimator) {

		q->vars.qdelay = now - pie_get_enqueue_time(skb);

	if (!params->dq_rate_estimator) {

		vars->qdelay = now - pie_get_enqueue_time(skb);



		if (q->vars.dq_tstamp != DTIME_INVALID)

			dtime = now - q->vars.dq_tstamp;

		if (vars->dq_tstamp != DTIME_INVALID)

			dtime = now - vars->dq_tstamp;



		q->vars.dq_tstamp = now;

		vars->dq_tstamp = now;



		if (qlen == 0)

			q->vars.qdelay = 0;

			vars->qdelay = 0;



		if (dtime == 0)

			return;
@@ -243,9 +244,9 @@ static void pie_process_dequeue(struct Qdisc *sch, struct sk_buff *skb) 
	 * we have enough packets to calculate the drain rate. Save

	 * current time as dq_tstamp and start measurement cycle.

	 */

	if (qlen >= QUEUE_THRESHOLD && q->vars.dq_count == DQCOUNT_INVALID) {

		q->vars.dq_tstamp = psched_get_time();

		q->vars.dq_count = 0;

	if (qlen >= QUEUE_THRESHOLD && vars->dq_count == DQCOUNT_INVALID) {

		vars->dq_tstamp = psched_get_time();

		vars->dq_count = 0;

	}



	/* Calculate the average drain rate from this value. If queue length
@@ -257,25 +258,25 @@ static void pie_process_dequeue(struct Qdisc *sch, struct sk_buff *skb) 
	 * in bytes, time difference in psched_time, hence rate is in

	 * bytes/psched_time.

	 */

	if (q->vars.dq_count != DQCOUNT_INVALID) {

		q->vars.dq_count += skb->len;

	if (vars->dq_count != DQCOUNT_INVALID) {

		vars->dq_count += skb->len;



		if (q->vars.dq_count >= QUEUE_THRESHOLD) {

			u32 count = q->vars.dq_count << PIE_SCALE;

		if (vars->dq_count >= QUEUE_THRESHOLD) {

			u32 count = vars->dq_count << PIE_SCALE;



			dtime = now - q->vars.dq_tstamp;

			dtime = now - vars->dq_tstamp;



			if (dtime == 0)

				return;



			count = count / dtime;



			if (q->vars.avg_dq_rate == 0)

				q->vars.avg_dq_rate = count;

			if (vars->avg_dq_rate == 0)

				vars->avg_dq_rate = count;

			else

				q->vars.avg_dq_rate =

				    (q->vars.avg_dq_rate -

				     (q->vars.avg_dq_rate >> 3)) + (count >> 3);

				vars->avg_dq_rate =

				    (vars->avg_dq_rate -

				     (vars->avg_dq_rate >> 3)) + (count >> 3);



			/* If the queue has receded below the threshold, we hold

			 * on to the last drain rate calculated, else we reset
@@ -283,10 +284,10 @@ static void pie_process_dequeue(struct Qdisc *sch, struct sk_buff *skb) 
			 * packet is dequeued

			 */

			if (qlen < QUEUE_THRESHOLD) {

				q->vars.dq_count = DQCOUNT_INVALID;

				vars->dq_count = DQCOUNT_INVALID;

			} else {

				q->vars.dq_count = 0;

				q->vars.dq_tstamp = psched_get_time();

				vars->dq_count = 0;

				vars->dq_tstamp = psched_get_time();

			}



			goto burst_allowance_reduction;
@@ -296,18 +297,18 @@ static void pie_process_dequeue(struct Qdisc *sch, struct sk_buff *skb) 
	return;



burst_allowance_reduction:

	if (q->vars.burst_time > 0) {

		if (q->vars.burst_time > dtime)

			q->vars.burst_time -= dtime;

	if (vars->burst_time > 0) {

		if (vars->burst_time > dtime)

			vars->burst_time -= dtime;

		else

			q->vars.burst_time = 0;

			vars->burst_time = 0;

	}

}

EXPORT_SYMBOL_GPL(pie_process_dequeue);



static void calculate_probability(struct Qdisc *sch)

void pie_calculate_probability(struct pie_params *params, struct pie_vars *vars,

			       u32 qlen)

{

	struct pie_sched_data *q = qdisc_priv(sch);

	u32 qlen = sch->qstats.backlog;	/* queue size in bytes */

	psched_time_t qdelay = 0;	/* in pschedtime */

	psched_time_t qdelay_old = 0;	/* in pschedtime */

	s64 delta = 0;		/* determines the change in probability */
@@ -316,17 +317,17 @@ static void calculate_probability(struct Qdisc *sch) 
	u32 power;

	bool update_prob = true;



	if (q->params.dq_rate_estimator) {

		qdelay_old = q->vars.qdelay;

		q->vars.qdelay_old = q->vars.qdelay;

	if (params->dq_rate_estimator) {

		qdelay_old = vars->qdelay;

		vars->qdelay_old = vars->qdelay;



		if (q->vars.avg_dq_rate > 0)

			qdelay = (qlen << PIE_SCALE) / q->vars.avg_dq_rate;

		if (vars->avg_dq_rate > 0)

			qdelay = (qlen << PIE_SCALE) / vars->avg_dq_rate;

		else

			qdelay = 0;

	} else {

		qdelay = q->vars.qdelay;

		qdelay_old = q->vars.qdelay_old;

		qdelay = vars->qdelay;

		qdelay_old = vars->qdelay_old;

	}



	/* If qdelay is zero and qlen is not, it means qlen is very small,
@@ -342,18 +343,18 @@ static void calculate_probability(struct Qdisc *sch) 
	 * probability. alpha/beta are updated locally below by scaling down

	 * by 16 to come to 0-2 range.

	 */

	alpha = ((u64)q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;

	beta = ((u64)q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;

	alpha = ((u64)params->alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;

	beta = ((u64)params->beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;



	/* We scale alpha and beta differently depending on how heavy the

	 * congestion is. Please see RFC 8033 for details.

	 */

	if (q->vars.prob < MAX_PROB / 10) {

	if (vars->prob < MAX_PROB / 10) {

		alpha >>= 1;

		beta >>= 1;



		power = 100;

		while (q->vars.prob < div_u64(MAX_PROB, power) &&

		while (vars->prob < div_u64(MAX_PROB, power) &&

		       power <= 1000000) {

			alpha >>= 2;

			beta >>= 2;
@@ -362,14 +363,14 @@ static void calculate_probability(struct Qdisc *sch) 
	}



	/* alpha and beta should be between 0 and 32, in multiples of 1/16 */

	delta += alpha * (u64)(qdelay - q->params.target);

	delta += alpha * (u64)(qdelay - params->target);

	delta += beta * (u64)(qdelay - qdelay_old);



	oldprob = q->vars.prob;

	oldprob = vars->prob;



	/* to ensure we increase probability in steps of no more than 2% */

	if (delta > (s64)(MAX_PROB / (100 / 2)) &&

	    q->vars.prob >= MAX_PROB / 10)

	    vars->prob >= MAX_PROB / 10)

		delta = (MAX_PROB / 100) * 2;



	/* Non-linear drop:
@@ -380,12 +381,12 @@ static void calculate_probability(struct Qdisc *sch) 
	if (qdelay > (PSCHED_NS2TICKS(250 * NSEC_PER_MSEC)))

		delta += MAX_PROB / (100 / 2);



	q->vars.prob += delta;

	vars->prob += delta;



	if (delta > 0) {

		/* prevent overflow */

		if (q->vars.prob < oldprob) {

			q->vars.prob = MAX_PROB;

		if (vars->prob < oldprob) {

			vars->prob = MAX_PROB;

			/* Prevent normalization error. If probability is at

			 * maximum value already, we normalize it here, and

			 * skip the check to do a non-linear drop in the next
@@ -395,8 +396,8 @@ static void calculate_probability(struct Qdisc *sch) 
		}

	} else {

		/* prevent underflow */

		if (q->vars.prob > oldprob)

			q->vars.prob = 0;

		if (vars->prob > oldprob)

			vars->prob = 0;

	}



	/* Non-linear drop in probability: Reduce drop probability quickly if
@@ -405,10 +406,10 @@ static void calculate_probability(struct Qdisc *sch) 


	if (qdelay == 0 && qdelay_old == 0 && update_prob)

		/* Reduce drop probability to 98.4% */

		q->vars.prob -= q->vars.prob / 64u;

		vars->prob -= vars->prob / 64;



	q->vars.qdelay = qdelay;

	q->vars.qlen_old = qlen;

	vars->qdelay = qdelay;

	vars->qlen_old = qlen;



	/* We restart the measurement cycle if the following conditions are met

	 * 1. If the delay has been low for 2 consecutive Tupdate periods
@@ -416,16 +417,17 @@ static void calculate_probability(struct Qdisc *sch) 
	 * 3. If average dq_rate_estimator is enabled, we have atleast one

	 *    estimate for the avg_dq_rate ie., is a non-zero value

	 */

	if ((q->vars.qdelay < q->params.target / 2) &&

	    (q->vars.qdelay_old < q->params.target / 2) &&

	    q->vars.prob == 0 &&

	    (!q->params.dq_rate_estimator || q->vars.avg_dq_rate > 0)) {

		pie_vars_init(&q->vars);

	if ((vars->qdelay < params->target / 2) &&

	    (vars->qdelay_old < params->target / 2) &&

	    vars->prob == 0 &&

	    (!params->dq_rate_estimator || vars->avg_dq_rate > 0)) {

		pie_vars_init(vars);

	}



	if (!q->params.dq_rate_estimator)

		q->vars.qdelay_old = qdelay;

	if (!params->dq_rate_estimator)

		vars->qdelay_old = qdelay;

}

EXPORT_SYMBOL_GPL(pie_calculate_probability);



static void pie_timer(struct timer_list *t)

{
@@ -434,7 +436,7 @@ static void pie_timer(struct timer_list *t) 
	spinlock_t *root_lock = qdisc_lock(qdisc_root_sleeping(sch));



	spin_lock(root_lock);

	calculate_probability(sch);

	pie_calculate_probability(&q->params, &q->vars, sch->qstats.backlog);



	/* reset the timer to fire after 'tupdate'. tupdate is in jiffies. */

	if (q->params.tupdate)
@@ -523,12 +525,13 @@ static int pie_dump_stats(struct Qdisc *sch, struct gnet_dump *d) 


static struct sk_buff *pie_qdisc_dequeue(struct Qdisc *sch)

{

	struct pie_sched_data *q = qdisc_priv(sch);

	struct sk_buff *skb = qdisc_dequeue_head(sch);



	if (!skb)

		return NULL;



	pie_process_dequeue(sch, skb);

	pie_process_dequeue(skb, &q->params, &q->vars, sch->qstats.backlog);

	return skb;

}

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