Commit f6f8ef9a authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'pie-minor-improvements' 



Leslie Monis says:

====================
pie: minor improvements

This patch series includes the following minor changes with
respect to the PIE/FQ-PIE qdiscs:

 - Patch 1 removes some ambiguity by using the term "backlog"
           instead of "qlen" when referring to the queue length
           in bytes.
 - Patch 2 removes redundant type casting on two expressions.
 - Patch 3 removes the pie_vars->accu_prob_overflows variable
           without affecting the precision in calculations and
           makes the size of the pie_vars structure exactly 64
           bytes.
 - Patch 4 realigns a comment affected by a change in patch 3.

Changes from v1 to v2:
 - Kept 8 as the argument to prandom_bytes() instead of changing it
   to 7 as suggested by David Miller.
====================

Reviewed-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents ef710370 5c5840e4

include/net/pie.h

+14 −17
Original line number Diff line number Diff line
@@ -8,7 +8,7 @@ 
#include <net/inet_ecn.h>

#include <net/pkt_sched.h>



#define MAX_PROB	U64_MAX

#define MAX_PROB	(U64_MAX >> BITS_PER_BYTE)

#define DTIME_INVALID	U64_MAX

#define QUEUE_THRESHOLD	16384

#define DQCOUNT_INVALID	-1
@@ -46,8 +46,7 @@ struct pie_params { 
 * @accu_prob:		accumulated drop probability

 * @dq_count:		number of bytes dequeued in a measurement cycle

 * @avg_dq_rate:	calculated average dq rate

 * @qlen_old:			queue length during previous qdelay calculation

 * @accu_prob_overflows:	number of times accu_prob overflows

 * @backlog_old:	queue backlog during previous qdelay calculation

 */

struct pie_vars {

	psched_time_t qdelay;
@@ -58,8 +57,7 @@ struct pie_vars { 
	u64 accu_prob;

	u64 dq_count;

	u32 avg_dq_rate;

	u32 qlen_old;

	u8 accu_prob_overflows;

	u32 backlog_old;

};



/**
@@ -107,7 +105,6 @@ static inline void pie_vars_init(struct pie_vars *vars) 
	vars->accu_prob = 0;

	vars->dq_count = DQCOUNT_INVALID;

	vars->avg_dq_rate = 0;

	vars->accu_prob_overflows = 0;

}



static inline struct pie_skb_cb *get_pie_cb(const struct sk_buff *skb)
@@ -127,12 +124,12 @@ static inline void pie_set_enqueue_time(struct sk_buff *skb) 
}



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

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

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



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

			 struct pie_vars *vars, u32 qlen);

			 struct pie_vars *vars, u32 backlog);



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

			       u32 qlen);

			       u32 backlog);



#endif

net/sched/sch_fq_pie.c

+0 −1
Original line number Diff line number Diff line
@@ -189,7 +189,6 @@ static int fq_pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch, 
out:

	q->stats.dropped++;

	sel_flow->vars.accu_prob = 0;

	sel_flow->vars.accu_prob_overflows = 0;

	__qdisc_drop(skb, to_free);

	qdisc_qstats_drop(sch);

	return NET_XMIT_CN;

net/sched/sch_pie.c

+19 −28
Original line number Diff line number Diff line
@@ -31,7 +31,7 @@ struct pie_sched_data { 
};



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

		    struct pie_vars *vars, u32 qlen, u32 packet_size)

		    struct pie_vars *vars, u32 backlog, u32 packet_size)

{

	u64 rnd;

	u64 local_prob = vars->prob;
@@ -51,7 +51,7 @@ bool pie_drop_early(struct Qdisc *sch, struct pie_params *params, 
	/* If we have fewer than 2 mtu-sized packets, disable pie_drop_early,

	 * similar to min_th in RED

	 */

	if (qlen < 2 * mtu)

	if (backlog < 2 * mtu)

		return false;



	/* If bytemode is turned on, use packet size to compute new
@@ -62,27 +62,19 @@ bool pie_drop_early(struct Qdisc *sch, struct pie_params *params, 
	else

		local_prob = vars->prob;



	if (local_prob == 0) {

	if (local_prob == 0)

		vars->accu_prob = 0;

		vars->accu_prob_overflows = 0;

	}



	if (local_prob > MAX_PROB - vars->accu_prob)

		vars->accu_prob_overflows++;



	else

		vars->accu_prob += local_prob;



	if (vars->accu_prob_overflows == 0 &&

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

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

		return false;

	if (vars->accu_prob_overflows == 8 &&

	    vars->accu_prob >= MAX_PROB / 2)

	if (vars->accu_prob >= (MAX_PROB / 2) * 17)

		return true;



	prandom_bytes(&rnd, 8);

	if (rnd < local_prob) {

	if ((rnd >> BITS_PER_BYTE) < local_prob) {

		vars->accu_prob = 0;

		vars->accu_prob_overflows = 0;

		return true;

	}
@@ -129,7 +121,6 @@ static int pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch, 
out:

	q->stats.dropped++;

	q->vars.accu_prob = 0;

	q->vars.accu_prob_overflows = 0;

	return qdisc_drop(skb, sch, to_free);

}
@@ -215,7 +206,7 @@ static int pie_change(struct Qdisc *sch, struct nlattr *opt, 
}



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

			 struct pie_vars *vars, u32 qlen)

			 struct pie_vars *vars, u32 backlog)

{

	psched_time_t now = psched_get_time();

	u32 dtime = 0;
@@ -231,7 +222,7 @@ void pie_process_dequeue(struct sk_buff *skb, struct pie_params *params, 


		vars->dq_tstamp = now;



		if (qlen == 0)

		if (backlog == 0)

			vars->qdelay = 0;



		if (dtime == 0)
@@ -244,7 +235,7 @@ void pie_process_dequeue(struct sk_buff *skb, struct pie_params *params, 
	 * we have enough packets to calculate the drain rate. Save

	 * current time as dq_tstamp and start measurement cycle.

	 */

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

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

		vars->dq_tstamp = psched_get_time();

		vars->dq_count = 0;

	}
@@ -283,7 +274,7 @@ void pie_process_dequeue(struct sk_buff *skb, struct pie_params *params, 
			 * dq_count to 0 to re-enter the if block when the next

			 * packet is dequeued

			 */

			if (qlen < QUEUE_THRESHOLD) {

			if (backlog < QUEUE_THRESHOLD) {

				vars->dq_count = DQCOUNT_INVALID;

			} else {

				vars->dq_count = 0;
@@ -307,7 +298,7 @@ burst_allowance_reduction: 
EXPORT_SYMBOL_GPL(pie_process_dequeue);



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

			       u32 qlen)

			       u32 backlog)

{

	psched_time_t qdelay = 0;	/* in pschedtime */

	psched_time_t qdelay_old = 0;	/* in pschedtime */
@@ -322,7 +313,7 @@ void pie_calculate_probability(struct pie_params *params, struct pie_vars *vars, 
		vars->qdelay_old = vars->qdelay;



		if (vars->avg_dq_rate > 0)

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

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

		else

			qdelay = 0;

	} else {
@@ -330,10 +321,10 @@ void pie_calculate_probability(struct pie_params *params, struct pie_vars *vars, 
		qdelay_old = vars->qdelay_old;

	}



	/* If qdelay is zero and qlen is not, it means qlen is very small,

	/* If qdelay is zero and backlog is not, it means backlog is very small,

	 * so we do not update probabilty in this round.

	 */

	if (qdelay == 0 && qlen != 0)

	if (qdelay == 0 && backlog != 0)

		update_prob = false;



	/* In the algorithm, alpha and beta are between 0 and 2 with typical
@@ -363,8 +354,8 @@ void pie_calculate_probability(struct pie_params *params, struct pie_vars *vars, 
	}



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

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

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

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

	delta += beta * (qdelay - qdelay_old);



	oldprob = vars->prob;
@@ -409,7 +400,7 @@ void pie_calculate_probability(struct pie_params *params, struct pie_vars *vars, 
		vars->prob -= vars->prob / 64;



	vars->qdelay = qdelay;

	vars->qlen_old = qlen;

	vars->backlog_old = backlog;



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

	 * 1. If the delay has been low for 2 consecutive Tupdate periods

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