[linux.git] / include / net / red.h

#ifndef __NET_SCHED_RED_H
#define __NET_SCHED_RED_H

#include <linux/types.h>
#include <net/pkt_sched.h>
#include <net/inet_ecn.h>
#include <net/dsfield.h>
#include <linux/reciprocal_div.h>

/*	Random Early Detection (RED) algorithm.
	=======================================

	Source: Sally Floyd and Van Jacobson, "Random Early Detection Gateways
	for Congestion Avoidance", 1993, IEEE/ACM Transactions on Networking.

	This file codes a "divisionless" version of RED algorithm
	as written down in Fig.17 of the paper.

	Short description.
	------------------

	When a new packet arrives we calculate the average queue length:

	avg = (1-W)*avg + W*current_queue_len,

	W is the filter time constant (chosen as 2^(-Wlog)), it controls
	the inertia of the algorithm. To allow larger bursts, W should be
	decreased.

	if (avg > th_max) -> packet marked (dropped).
	if (avg < th_min) -> packet passes.
	if (th_min < avg < th_max) we calculate probability:

	Pb = max_P * (avg - th_min)/(th_max-th_min)

	and mark (drop) packet with this probability.
	Pb changes from 0 (at avg==th_min) to max_P (avg==th_max).
	max_P should be small (not 1), usually 0.01..0.02 is good value.

	max_P is chosen as a number, so that max_P/(th_max-th_min)
	is a negative power of two in order arithmetics to contain
	only shifts.


	Parameters, settable by user:
	-----------------------------

	qth_min		- bytes (should be < qth_max/2)
	qth_max		- bytes (should be at least 2*qth_min and less limit)
	Wlog	       	- bits (<32) log(1/W).
	Plog	       	- bits (<32)

	Plog is related to max_P by formula:

	max_P = (qth_max-qth_min)/2^Plog;

	F.e. if qth_max=128K and qth_min=32K, then Plog=22
	corresponds to max_P=0.02

	Scell_log
	Stab

	Lookup table for log((1-W)^(t/t_ave).


	NOTES:

	Upper bound on W.
	-----------------

	If you want to allow bursts of L packets of size S,
	you should choose W:

	L + 1 - th_min/S < (1-(1-W)^L)/W

	th_min/S = 32         th_min/S = 4

	log(W)	L
	-1	33
	-2	35
	-3	39
	-4	46
	-5	57
	-6	75
	-7	101
	-8	135
	-9	190
	etc.
 */

/*
 * Adaptative RED : An Algorithm for Increasing the Robustness of RED's AQM
 * (Sally FLoyd, Ramakrishna Gummadi, and Scott Shenker) August 2001
 *
 * Every 500 ms:
 *  if (avg > target and max_p <= 0.5)
 *   increase max_p : max_p += alpha;
 *  else if (avg < target and max_p >= 0.01)
 *   decrease max_p : max_p *= beta;
 *
 * target :[qth_min + 0.4*(qth_min - qth_max),
 *          qth_min + 0.6*(qth_min - qth_max)].
 * alpha : min(0.01, max_p / 4)
 * beta : 0.9
 * max_P is a Q0.32 fixed point number (with 32 bits mantissa)
 * max_P between 0.01 and 0.5 (1% - 50%) [ Its no longer a negative power of two ]
 */
#define RED_ONE_PERCENT ((u32)DIV_ROUND_CLOSEST(1ULL<<32, 100))

#define MAX_P_MIN (1 * RED_ONE_PERCENT)
#define MAX_P_MAX (50 * RED_ONE_PERCENT)
#define MAX_P_ALPHA(val) min(MAX_P_MIN, val / 4)

#define RED_STAB_SIZE	256
#define RED_STAB_MASK	(RED_STAB_SIZE - 1)

struct red_stats {
	u32		prob_drop;	/* Early probability drops */
	u32		prob_mark;	/* Early probability marks */
	u32		forced_drop;	/* Forced drops, qavg > max_thresh */
	u32		forced_mark;	/* Forced marks, qavg > max_thresh */
	u32		pdrop;          /* Drops due to queue limits */
	u32		other;          /* Drops due to drop() calls */
};

struct red_parms {
	/* Parameters */
	u32		qth_min;	/* Min avg length threshold: Wlog scaled */
	u32		qth_max;	/* Max avg length threshold: Wlog scaled */
	u32		Scell_max;
	u32		max_P;		/* probability, [0 .. 1.0] 32 scaled */
	u32		max_P_reciprocal; /* reciprocal_value(max_P / qth_delta) */
	u32		qth_delta;	/* max_th - min_th */
	u32		target_min;	/* min_th + 0.4*(max_th - min_th) */
	u32		target_max;	/* min_th + 0.6*(max_th - min_th) */
	u8		Scell_log;
	u8		Wlog;		/* log(W)		*/
	u8		Plog;		/* random number bits	*/
	u8		Stab[RED_STAB_SIZE];
};

struct red_vars {
	/* Variables */
	int		qcount;		/* Number of packets since last random
					   number generation */
	u32		qR;		/* Cached random number */

	unsigned long	qavg;		/* Average queue length: Wlog scaled */
	ktime_t		qidlestart;	/* Start of current idle period */
};

static inline u32 red_maxp(u8 Plog)
{
	return Plog < 32 ? (~0U >> Plog) : ~0U;
}

static inline void red_set_vars(struct red_vars *v)
{
	/* Reset average queue length, the value is strictly bound
	 * to the parameters below, reseting hurts a bit but leaving
	 * it might result in an unreasonable qavg for a while. --TGR
	 */
	v->qavg		= 0;

	v->qcount	= -1;
}

static inline void red_set_parms(struct red_parms *p,
				 u32 qth_min, u32 qth_max, u8 Wlog, u8 Plog,
				 u8 Scell_log, u8 *stab, u32 max_P)
{
	int delta = qth_max - qth_min;
	u32 max_p_delta;

	p->qth_min	= qth_min << Wlog;
	p->qth_max	= qth_max << Wlog;
	p->Wlog		= Wlog;
	p->Plog		= Plog;
	if (delta < 0)
		delta = 1;
	p->qth_delta	= delta;
	if (!max_P) {
		max_P = red_maxp(Plog);
		max_P *= delta; /* max_P = (qth_max - qth_min)/2^Plog */
	}
	p->max_P = max_P;
	max_p_delta = max_P / delta;
	max_p_delta = max(max_p_delta, 1U);
	p->max_P_reciprocal  = reciprocal_value(max_p_delta);

	/* RED Adaptative target :
	 * [min_th + 0.4*(min_th - max_th),
	 *  min_th + 0.6*(min_th - max_th)].
	 */
	delta /= 5;
	p->target_min = qth_min + 2*delta;
	p->target_max = qth_min + 3*delta;

	p->Scell_log	= Scell_log;
	p->Scell_max	= (255 << Scell_log);

	memcpy(p->Stab, stab, sizeof(p->Stab));
}

static inline int red_is_idling(const struct red_vars *v)
{
	return v->qidlestart.tv64 != 0;
}

static inline void red_start_of_idle_period(struct red_vars *v)
{
	v->qidlestart = ktime_get();
}

static inline void red_end_of_idle_period(struct red_vars *v)
{
	v->qidlestart.tv64 = 0;
}

static inline void red_restart(struct red_vars *v)
{
	red_end_of_idle_period(v);
	v->qavg = 0;
	v->qcount = -1;
}

static inline unsigned long red_calc_qavg_from_idle_time(const struct red_parms *p,
							 const struct red_vars *v)
{
	s64 delta = ktime_us_delta(ktime_get(), v->qidlestart);
	long us_idle = min_t(s64, delta, p->Scell_max);
	int  shift;

	/*
	 * The problem: ideally, average length queue recalcultion should
	 * be done over constant clock intervals. This is too expensive, so
	 * that the calculation is driven by outgoing packets.
	 * When the queue is idle we have to model this clock by hand.
	 *
	 * SF+VJ proposed to "generate":
	 *
	 *	m = idletime / (average_pkt_size / bandwidth)
	 *
	 * dummy packets as a burst after idle time, i.e.
	 *
	 * 	p->qavg *= (1-W)^m
	 *
	 * This is an apparently overcomplicated solution (f.e. we have to
	 * precompute a table to make this calculation in reasonable time)
	 * I believe that a simpler model may be used here,
	 * but it is field for experiments.
	 */

	shift = p->Stab[(us_idle >> p->Scell_log) & RED_STAB_MASK];

	if (shift)
		return v->qavg >> shift;
	else {
		/* Approximate initial part of exponent with linear function:
		 *
		 * 	(1-W)^m ~= 1-mW + ...
		 *
		 * Seems, it is the best solution to
		 * problem of too coarse exponent tabulation.
		 */
		us_idle = (v->qavg * (u64)us_idle) >> p->Scell_log;

		if (us_idle < (v->qavg >> 1))
			return v->qavg - us_idle;
		else
			return v->qavg >> 1;
	}
}

static inline unsigned long red_calc_qavg_no_idle_time(const struct red_parms *p,
						       const struct red_vars *v,
						       unsigned int backlog)
{
	/*
	 * NOTE: p->qavg is fixed point number with point at Wlog.
	 * The formula below is equvalent to floating point
	 * version:
	 *
	 * 	qavg = qavg*(1-W) + backlog*W;
	 *
	 * --ANK (980924)
	 */
	return v->qavg + (backlog - (v->qavg >> p->Wlog));
}

static inline unsigned long red_calc_qavg(const struct red_parms *p,
					  const struct red_vars *v,
					  unsigned int backlog)
{
	if (!red_is_idling(v))
		return red_calc_qavg_no_idle_time(p, v, backlog);
	else
		return red_calc_qavg_from_idle_time(p, v);
}


static inline u32 red_random(const struct red_parms *p)
{
	return reciprocal_divide(net_random(), p->max_P_reciprocal);
}

static inline int red_mark_probability(const struct red_parms *p,
				       const struct red_vars *v,
				       unsigned long qavg)
{
	/* The formula used below causes questions.

	   OK. qR is random number in the interval
		(0..1/max_P)*(qth_max-qth_min)
	   i.e. 0..(2^Plog). If we used floating point
	   arithmetics, it would be: (2^Plog)*rnd_num,
	   where rnd_num is less 1.

	   Taking into account, that qavg have fixed
	   point at Wlog, two lines
	   below have the following floating point equivalent:

	   max_P*(qavg - qth_min)/(qth_max-qth_min) < rnd/qcount

	   Any questions? --ANK (980924)
	 */
	return !(((qavg - p->qth_min) >> p->Wlog) * v->qcount < v->qR);
}

enum {
	RED_BELOW_MIN_THRESH,
	RED_BETWEEN_TRESH,
	RED_ABOVE_MAX_TRESH,
};

static inline int red_cmp_thresh(const struct red_parms *p, unsigned long qavg)
{
	if (qavg < p->qth_min)
		return RED_BELOW_MIN_THRESH;
	else if (qavg >= p->qth_max)
		return RED_ABOVE_MAX_TRESH;
	else
		return RED_BETWEEN_TRESH;
}

enum {
	RED_DONT_MARK,
	RED_PROB_MARK,
	RED_HARD_MARK,
};

static inline int red_action(const struct red_parms *p,
			     struct red_vars *v,
			     unsigned long qavg)
{
	switch (red_cmp_thresh(p, qavg)) {
		case RED_BELOW_MIN_THRESH:
			v->qcount = -1;
			return RED_DONT_MARK;

		case RED_BETWEEN_TRESH:
			if (++v->qcount) {
				if (red_mark_probability(p, v, qavg)) {
					v->qcount = 0;
					v->qR = red_random(p);
					return RED_PROB_MARK;
				}
			} else
				v->qR = red_random(p);

			return RED_DONT_MARK;

		case RED_ABOVE_MAX_TRESH:
			v->qcount = -1;
			return RED_HARD_MARK;
	}

	BUG();
	return RED_DONT_MARK;
}

static inline void red_adaptative_algo(struct red_parms *p, struct red_vars *v)
{
	unsigned long qavg;
	u32 max_p_delta;

	qavg = v->qavg;
	if (red_is_idling(v))
		qavg = red_calc_qavg_from_idle_time(p, v);

	/* p->qavg is fixed point number with point at Wlog */
	qavg >>= p->Wlog;

	if (qavg > p->target_max && p->max_P <= MAX_P_MAX)
		p->max_P += MAX_P_ALPHA(p->max_P); /* maxp = maxp + alpha */
	else if (qavg < p->target_min && p->max_P >= MAX_P_MIN)
		p->max_P = (p->max_P/10)*9; /* maxp = maxp * Beta */

	max_p_delta = DIV_ROUND_CLOSEST(p->max_P, p->qth_delta);
	max_p_delta = max(max_p_delta, 1U);
	p->max_P_reciprocal = reciprocal_value(max_p_delta);
}
#endif
Commit	Line	Data
a7834745 TG	1	#ifndef __NET_SCHED_RED_H
	2	#define __NET_SCHED_RED_H
	3
a7834745 TG	4	#include <linux/types.h>
	5	#include <net/pkt_sched.h>
	6	#include <net/inet_ecn.h>
	7	#include <net/dsfield.h>
8af2a218	8	#include <linux/reciprocal_div.h>
a7834745 TG	9
	10	/* Random Early Detection (RED) algorithm.
	11	=======================================
	12
	13	Source: Sally Floyd and Van Jacobson, "Random Early Detection Gateways
	14	for Congestion Avoidance", 1993, IEEE/ACM Transactions on Networking.
	15
	16	This file codes a "divisionless" version of RED algorithm
	17	as written down in Fig.17 of the paper.
	18
	19	Short description.
	20	------------------
	21
	22	When a new packet arrives we calculate the average queue length:
	23
	24	avg = (1-W)avg + Wcurrent_queue_len,
	25
	26	W is the filter time constant (chosen as 2^(-Wlog)), it controls
	27	the inertia of the algorithm. To allow larger bursts, W should be
	28	decreased.
	29
	30	if (avg > th_max) -> packet marked (dropped).
	31	if (avg < th_min) -> packet passes.
	32	if (th_min < avg < th_max) we calculate probability:
	33
	34	Pb = max_P * (avg - th_min)/(th_max-th_min)
	35
	36	and mark (drop) packet with this probability.
	37	Pb changes from 0 (at avg==th_min) to max_P (avg==th_max).
	38	max_P should be small (not 1), usually 0.01..0.02 is good value.
	39
	40	max_P is chosen as a number, so that max_P/(th_max-th_min)
	41	is a negative power of two in order arithmetics to contain
	42	only shifts.
	43
	44
	45	Parameters, settable by user:
	46	-----------------------------
	47
	48	qth_min - bytes (should be < qth_max/2)
	49	qth_max - bytes (should be at least 2*qth_min and less limit)
	50	Wlog - bits (<32) log(1/W).
	51	Plog - bits (<32)
	52
	53	Plog is related to max_P by formula:
	54
	55	max_P = (qth_max-qth_min)/2^Plog;
	56
	57	F.e. if qth_max=128K and qth_min=32K, then Plog=22
	58	corresponds to max_P=0.02
	59
	60	Scell_log
	61	Stab
	62
	63	Lookup table for log((1-W)^(t/t_ave).
	64
	65
	66	NOTES:
	67
	68	Upper bound on W.
	69	-----------------
	70
	71	If you want to allow bursts of L packets of size S,
	72	you should choose W:
73
74	L + 1 - th_min/S < (1-(1-W)^L)/W
75
76	th_min/S = 32 th_min/S = 4
77
78	log(W) L
79	-1 33
80	-2 35
81	-3 39
82	-4 46
83	-5 57
84	-6 75
85	-7 101
86	-8 135
87	-9 190
88	etc.
89	*/
90
8af2a218 ED	91	/*
	92	* Adaptative RED : An Algorithm for Increasing the Robustness of RED's AQM
	93	* (Sally FLoyd, Ramakrishna Gummadi, and Scott Shenker) August 2001
	94	*
	95	* Every 500 ms:
	96	* if (avg > target and max_p <= 0.5)
	97	* increase max_p : max_p += alpha;
	98	* else if (avg < target and max_p >= 0.01)
	99	* decrease max_p : max_p *= beta;
	100	*
	101	* target :[qth_min + 0.4*(qth_min - qth_max),
	102	* qth_min + 0.6*(qth_min - qth_max)].
	103	* alpha : min(0.01, max_p / 4)
	104	* beta : 0.9
	105	* max_P is a Q0.32 fixed point number (with 32 bits mantissa)
	106	* max_P between 0.01 and 0.5 (1% - 50%) [ Its no longer a negative power of two ]
	107	*/
	108	#define RED_ONE_PERCENT ((u32)DIV_ROUND_CLOSEST(1ULL<<32, 100))
	109
	110	#define MAX_P_MIN (1 * RED_ONE_PERCENT)
	111	#define MAX_P_MAX (50 * RED_ONE_PERCENT)
	112	#define MAX_P_ALPHA(val) min(MAX_P_MIN, val / 4)
	113
a7834745 TG	114	#define RED_STAB_SIZE 256
	115	#define RED_STAB_MASK (RED_STAB_SIZE - 1)
	116
fd2c3ef7	117	struct red_stats {
a7834745 TG	118	u32 prob_drop; /* Early probability drops */
	119	u32 prob_mark; /* Early probability marks */
	120	u32 forced_drop; /* Forced drops, qavg > max_thresh */
	121	u32 forced_mark; /* Forced marks, qavg > max_thresh */
	122	u32 pdrop; /* Drops due to queue limits */
	123	u32 other; /* Drops due to drop() calls */
a7834745 TG	124	};
a7834745 TG	125
fd2c3ef7	126	struct red_parms {
a7834745	127	/* Parameters */
8af2a218 ED	128	u32 qth_min; /* Min avg length threshold: Wlog scaled */
8af2a218 ED	129	u32 qth_max; /* Max avg length threshold: Wlog scaled */
a7834745	130	u32 Scell_max;
8af2a218 ED	131	u32 max_P; /* probability, [0 .. 1.0] 32 scaled */
	132	u32 max_P_reciprocal; /* reciprocal_value(max_P / qth_delta) */
	133	u32 qth_delta; /* max_th - min_th */
	134	u32 target_min; /* min_th + 0.4(max_th - min_th) /
	135	u32 target_max; /* min_th + 0.6(max_th - min_th) /
a7834745 TG	136	u8 Scell_log;
	137	u8 Wlog; /* log(W) */
	138	u8 Plog; /* random number bits */
	139	u8 Stab[RED_STAB_SIZE];
eeca6688	140	};
a7834745	141
eeca6688	142	struct red_vars {
a7834745 TG	143	/* Variables */
	144	int qcount; /* Number of packets since last random
	145	number generation */
	146	u32 qR; /* Cached random number */
	147
8af2a218	148	unsigned long qavg; /* Average queue length: Wlog scaled */
ea6a5d3b	149	ktime_t qidlestart; /* Start of current idle period */
a7834745 TG	150	};
a7834745 TG	151
8af2a218	152	static inline u32 red_maxp(u8 Plog)
a7834745	153	{
8af2a218	154	return Plog < 32 ? (~0U >> Plog) : ~0U;
a7834745 TG	155	}
a7834745 TG	156
eeca6688 ED	157	static inline void red_set_vars(struct red_vars *v)
	158	{
	159	/* Reset average queue length, the value is strictly bound
	160	* to the parameters below, reseting hurts a bit but leaving
	161	* it might result in an unreasonable qavg for a while. --TGR
	162	*/
	163	v->qavg = 0;
	164
	165	v->qcount = -1;
	166	}
8af2a218	167
a7834745 TG	168	static inline void red_set_parms(struct red_parms *p,
a7834745 TG	169	u32 qth_min, u32 qth_max, u8 Wlog, u8 Plog,
a73ed26b	170	u8 Scell_log, u8 *stab, u32 max_P)
a7834745	171	{
8af2a218	172	int delta = qth_max - qth_min;
a73ed26b	173	u32 max_p_delta;
8af2a218	174
a7834745 TG	175	p->qth_min = qth_min << Wlog;
	176	p->qth_max = qth_max << Wlog;
	177	p->Wlog = Wlog;
	178	p->Plog = Plog;
8af2a218 ED	179	if (delta < 0)
	180	delta = 1;
	181	p->qth_delta = delta;
a73ed26b ED	182	if (!max_P) {
	183	max_P = red_maxp(Plog);
	184	max_P = delta; / max_P = (qth_max - qth_min)/2^Plog */
	185	}
	186	p->max_P = max_P;
	187	max_p_delta = max_P / delta;
	188	max_p_delta = max(max_p_delta, 1U);
	189	p->max_P_reciprocal = reciprocal_value(max_p_delta);
8af2a218 ED	190
	191	/* RED Adaptative target :
	192	* [min_th + 0.4*(min_th - max_th),
	193	* min_th + 0.6*(min_th - max_th)].
	194	*/
	195	delta /= 5;
	196	p->target_min = qth_min + 2*delta;
	197	p->target_max = qth_min + 3*delta;
	198
a7834745 TG	199	p->Scell_log = Scell_log;
	200	p->Scell_max = (255 << Scell_log);
	201
	202	memcpy(p->Stab, stab, sizeof(p->Stab));
	203	}
	204
eeca6688	205	static inline int red_is_idling(const struct red_vars *v)
a7834745	206	{
eeca6688	207	return v->qidlestart.tv64 != 0;
a7834745 TG	208	}
a7834745 TG	209
eeca6688	210	static inline void red_start_of_idle_period(struct red_vars *v)
a7834745	211	{
eeca6688	212	v->qidlestart = ktime_get();
a7834745 TG	213	}
a7834745 TG	214
eeca6688	215	static inline void red_end_of_idle_period(struct red_vars *v)
a7834745	216	{
eeca6688	217	v->qidlestart.tv64 = 0;
a7834745 TG	218	}
a7834745 TG	219
eeca6688	220	static inline void red_restart(struct red_vars *v)
a7834745	221	{
eeca6688 ED	222	red_end_of_idle_period(v);
	223	v->qavg = 0;
	224	v->qcount = -1;
a7834745 TG	225	}
a7834745 TG	226
eeca6688 ED	227	static inline unsigned long red_calc_qavg_from_idle_time(const struct red_parms *p,
eeca6688 ED	228	const struct red_vars *v)
a7834745	229	{
eeca6688	230	s64 delta = ktime_us_delta(ktime_get(), v->qidlestart);
ea6a5d3b	231	long us_idle = min_t(s64, delta, p->Scell_max);
a7834745 TG	232	int shift;
a7834745 TG	233
a7834745 TG	234	/*
	235	* The problem: ideally, average length queue recalcultion should
	236	* be done over constant clock intervals. This is too expensive, so
	237	* that the calculation is driven by outgoing packets.
	238	* When the queue is idle we have to model this clock by hand.
	239	*
	240	* SF+VJ proposed to "generate":
	241	*
	242	* m = idletime / (average_pkt_size / bandwidth)
	243	*
	244	* dummy packets as a burst after idle time, i.e.
	245	*
	246	* p->qavg *= (1-W)^m
	247	*
	248	* This is an apparently overcomplicated solution (f.e. we have to
	249	* precompute a table to make this calculation in reasonable time)
	250	* I believe that a simpler model may be used here,
	251	* but it is field for experiments.
	252	*/
	253
	254	shift = p->Stab[(us_idle >> p->Scell_log) & RED_STAB_MASK];
	255
	256	if (shift)
eeca6688	257	return v->qavg >> shift;
a7834745 TG	258	else {
	259	/* Approximate initial part of exponent with linear function:
	260	*
	261	* (1-W)^m ~= 1-mW + ...
	262	*
	263	* Seems, it is the best solution to
	264	* problem of too coarse exponent tabulation.
	265	*/
eeca6688	266	us_idle = (v->qavg * (u64)us_idle) >> p->Scell_log;
a7834745	267
eeca6688 ED	268	if (us_idle < (v->qavg >> 1))
eeca6688 ED	269	return v->qavg - us_idle;
a7834745	270	else
eeca6688	271	return v->qavg >> 1;
a7834745 TG	272	}
	273	}
	274
8af2a218	275	static inline unsigned long red_calc_qavg_no_idle_time(const struct red_parms *p,
eeca6688	276	const struct red_vars *v,
a7834745 TG	277	unsigned int backlog)
	278	{
	279	/*
	280	* NOTE: p->qavg is fixed point number with point at Wlog.
	281	* The formula below is equvalent to floating point
	282	* version:
	283	*
	284	* qavg = qavg(1-W) + backlogW;
	285	*
	286	* --ANK (980924)
	287	*/
eeca6688	288	return v->qavg + (backlog - (v->qavg >> p->Wlog));
a7834745 TG	289	}
a7834745 TG	290
8af2a218	291	static inline unsigned long red_calc_qavg(const struct red_parms *p,
eeca6688	292	const struct red_vars *v,
a7834745 TG	293	unsigned int backlog)
a7834745 TG	294	{
eeca6688 ED	295	if (!red_is_idling(v))
eeca6688 ED	296	return red_calc_qavg_no_idle_time(p, v, backlog);
a7834745	297	else
eeca6688	298	return red_calc_qavg_from_idle_time(p, v);
a7834745 TG	299	}
a7834745 TG	300
8af2a218 ED	301
8af2a218 ED	302	static inline u32 red_random(const struct red_parms *p)
a7834745	303	{
8af2a218	304	return reciprocal_divide(net_random(), p->max_P_reciprocal);
a7834745 TG	305	}
a7834745 TG	306
eeca6688 ED	307	static inline int red_mark_probability(const struct red_parms *p,
	308	const struct red_vars *v,
	309	unsigned long qavg)
a7834745 TG	310	{
	311	/* The formula used below causes questions.
	312
8af2a218 ED	313	OK. qR is random number in the interval
8af2a218 ED	314	(0..1/max_P)*(qth_max-qth_min)
a7834745 TG	315	i.e. 0..(2^Plog). If we used floating point
	316	arithmetics, it would be: (2^Plog)*rnd_num,
	317	where rnd_num is less 1.
	318
	319	Taking into account, that qavg have fixed
8af2a218	320	point at Wlog, two lines
a7834745 TG	321	below have the following floating point equivalent:
	322
	323	max_P*(qavg - qth_min)/(qth_max-qth_min) < rnd/qcount
	324
	325	Any questions? --ANK (980924)
	326	*/
eeca6688	327	return !(((qavg - p->qth_min) >> p->Wlog) * v->qcount < v->qR);
a7834745 TG	328	}
	329
	330	enum {
	331	RED_BELOW_MIN_THRESH,
	332	RED_BETWEEN_TRESH,
	333	RED_ABOVE_MAX_TRESH,
	334	};
	335
eeca6688	336	static inline int red_cmp_thresh(const struct red_parms *p, unsigned long qavg)
a7834745 TG	337	{
	338	if (qavg < p->qth_min)
	339	return RED_BELOW_MIN_THRESH;
	340	else if (qavg >= p->qth_max)
	341	return RED_ABOVE_MAX_TRESH;
	342	else
	343	return RED_BETWEEN_TRESH;
	344	}
	345
	346	enum {
	347	RED_DONT_MARK,
	348	RED_PROB_MARK,
	349	RED_HARD_MARK,
	350	};
	351
eeca6688 ED	352	static inline int red_action(const struct red_parms *p,
	353	struct red_vars *v,
	354	unsigned long qavg)
a7834745 TG	355	{
	356	switch (red_cmp_thresh(p, qavg)) {
	357	case RED_BELOW_MIN_THRESH:
eeca6688	358	v->qcount = -1;
a7834745 TG	359	return RED_DONT_MARK;
	360
	361	case RED_BETWEEN_TRESH:
eeca6688 ED	362	if (++v->qcount) {
	363	if (red_mark_probability(p, v, qavg)) {
	364	v->qcount = 0;
	365	v->qR = red_random(p);
a7834745 TG	366	return RED_PROB_MARK;
	367	}
	368	} else
eeca6688	369	v->qR = red_random(p);
a7834745 TG	370
	371	return RED_DONT_MARK;
	372
	373	case RED_ABOVE_MAX_TRESH:
eeca6688	374	v->qcount = -1;
a7834745 TG	375	return RED_HARD_MARK;
	376	}
	377
	378	BUG();
	379	return RED_DONT_MARK;
	380	}
	381
eeca6688	382	static inline void red_adaptative_algo(struct red_parms p, struct red_vars v)
8af2a218 ED	383	{
	384	unsigned long qavg;
	385	u32 max_p_delta;
	386
eeca6688 ED	387	qavg = v->qavg;
	388	if (red_is_idling(v))
	389	qavg = red_calc_qavg_from_idle_time(p, v);
8af2a218 ED	390
	391	/* p->qavg is fixed point number with point at Wlog */
	392	qavg >>= p->Wlog;
	393
	394	if (qavg > p->target_max && p->max_P <= MAX_P_MAX)
	395	p->max_P += MAX_P_ALPHA(p->max_P); /* maxp = maxp + alpha */
	396	else if (qavg < p->target_min && p->max_P >= MAX_P_MIN)
	397	p->max_P = (p->max_P/10)9; / maxp = maxp * Beta */
	398
	399	max_p_delta = DIV_ROUND_CLOSEST(p->max_P, p->qth_delta);
a73ed26b	400	max_p_delta = max(max_p_delta, 1U);
8af2a218 ED	401	p->max_P_reciprocal = reciprocal_value(max_p_delta);
8af2a218 ED	402	}
a7834745	403	#endif