[linux-2.6-block.git] / include / net / red.h

#ifndef __NET_SCHED_RED_H
#define __NET_SCHED_RED_H

#include <linux/types.h>
#include <linux/bug.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 */
	/* reciprocal_value(max_P / qth_delta) */
	struct reciprocal_value	max_P_reciprocal;
	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);

	if (stab)
		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.
	 *
	 * 	v->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: v->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(prandom_u32(), 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);

	/* v->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	4	#include <linux/types.h>
187f1882	5	#include <linux/bug.h>
a7834745 TG	6	#include <net/pkt_sched.h>
	7	#include <net/inet_ecn.h>
	8	#include <net/dsfield.h>
8af2a218	9	#include <linux/reciprocal_div.h>
a7834745 TG	10
	11	/* Random Early Detection (RED) algorithm.
	12	=======================================
	13
	14	Source: Sally Floyd and Van Jacobson, "Random Early Detection Gateways
	15	for Congestion Avoidance", 1993, IEEE/ACM Transactions on Networking.
	16
	17	This file codes a "divisionless" version of RED algorithm
	18	as written down in Fig.17 of the paper.
	19
	20	Short description.
	21	------------------
	22
	23	When a new packet arrives we calculate the average queue length:
	24
	25	avg = (1-W)avg + Wcurrent_queue_len,
	26
	27	W is the filter time constant (chosen as 2^(-Wlog)), it controls
	28	the inertia of the algorithm. To allow larger bursts, W should be
	29	decreased.
	30
	31	if (avg > th_max) -> packet marked (dropped).
	32	if (avg < th_min) -> packet passes.
	33	if (th_min < avg < th_max) we calculate probability:
	34
	35	Pb = max_P * (avg - th_min)/(th_max-th_min)
	36
	37	and mark (drop) packet with this probability.
	38	Pb changes from 0 (at avg==th_min) to max_P (avg==th_max).
	39	max_P should be small (not 1), usually 0.01..0.02 is good value.
	40
	41	max_P is chosen as a number, so that max_P/(th_max-th_min)
	42	is a negative power of two in order arithmetics to contain
	43	only shifts.
	44
	45
	46	Parameters, settable by user:
	47	-----------------------------
	48
	49	qth_min - bytes (should be < qth_max/2)
	50	qth_max - bytes (should be at least 2*qth_min and less limit)
	51	Wlog - bits (<32) log(1/W).
	52	Plog - bits (<32)
	53
	54	Plog is related to max_P by formula:
	55
	56	max_P = (qth_max-qth_min)/2^Plog;
	57
	58	F.e. if qth_max=128K and qth_min=32K, then Plog=22
	59	corresponds to max_P=0.02
	60
	61	Scell_log
	62	Stab
	63
	64	Lookup table for log((1-W)^(t/t_ave).
	65
	66
	67	NOTES:
	68
	69	Upper bound on W.
	70	-----------------
	71
	72	If you want to allow bursts of L packets of size S,
	73	you should choose W:
74
75	L + 1 - th_min/S < (1-(1-W)^L)/W
76
77	th_min/S = 32 th_min/S = 4
78
79	log(W) L
80	-1 33
81	-2 35
82	-3 39
83	-4 46
84	-5 57
85	-6 75
86	-7 101
87	-8 135
88	-9 190
89	etc.
90	*/
91
8af2a218 ED	92	/*
	93	* Adaptative RED : An Algorithm for Increasing the Robustness of RED's AQM
	94	* (Sally FLoyd, Ramakrishna Gummadi, and Scott Shenker) August 2001
	95	*
	96	* Every 500 ms:
	97	* if (avg > target and max_p <= 0.5)
	98	* increase max_p : max_p += alpha;
	99	* else if (avg < target and max_p >= 0.01)
	100	* decrease max_p : max_p *= beta;
	101	*
	102	* target :[qth_min + 0.4*(qth_min - qth_max),
	103	* qth_min + 0.6*(qth_min - qth_max)].
	104	* alpha : min(0.01, max_p / 4)
	105	* beta : 0.9
	106	* max_P is a Q0.32 fixed point number (with 32 bits mantissa)
	107	* max_P between 0.01 and 0.5 (1% - 50%) [ Its no longer a negative power of two ]
	108	*/
	109	#define RED_ONE_PERCENT ((u32)DIV_ROUND_CLOSEST(1ULL<<32, 100))
	110
	111	#define MAX_P_MIN (1 * RED_ONE_PERCENT)
	112	#define MAX_P_MAX (50 * RED_ONE_PERCENT)
	113	#define MAX_P_ALPHA(val) min(MAX_P_MIN, val / 4)
	114
a7834745 TG	115	#define RED_STAB_SIZE 256
	116	#define RED_STAB_MASK (RED_STAB_SIZE - 1)
	117
fd2c3ef7	118	struct red_stats {
a7834745 TG	119	u32 prob_drop; /* Early probability drops */
	120	u32 prob_mark; /* Early probability marks */
	121	u32 forced_drop; /* Forced drops, qavg > max_thresh */
	122	u32 forced_mark; /* Forced marks, qavg > max_thresh */
	123	u32 pdrop; /* Drops due to queue limits */
	124	u32 other; /* Drops due to drop() calls */
a7834745 TG	125	};
a7834745 TG	126
fd2c3ef7	127	struct red_parms {
a7834745	128	/* Parameters */
8af2a218 ED	129	u32 qth_min; /* Min avg length threshold: Wlog scaled */
8af2a218 ED	130	u32 qth_max; /* Max avg length threshold: Wlog scaled */
a7834745	131	u32 Scell_max;
8af2a218	132	u32 max_P; /* probability, [0 .. 1.0] 32 scaled */
809fa972 HFS	133	/* reciprocal_value(max_P / qth_delta) */
809fa972 HFS	134	struct reciprocal_value max_P_reciprocal;
8af2a218 ED	135	u32 qth_delta; /* max_th - min_th */
	136	u32 target_min; /* min_th + 0.4(max_th - min_th) /
	137	u32 target_max; /* min_th + 0.6(max_th - min_th) /
a7834745 TG	138	u8 Scell_log;
	139	u8 Wlog; /* log(W) */
	140	u8 Plog; /* random number bits */
	141	u8 Stab[RED_STAB_SIZE];
eeca6688	142	};
a7834745	143
eeca6688	144	struct red_vars {
a7834745 TG	145	/* Variables */
	146	int qcount; /* Number of packets since last random
	147	number generation */
	148	u32 qR; /* Cached random number */
	149
8af2a218	150	unsigned long qavg; /* Average queue length: Wlog scaled */
ea6a5d3b	151	ktime_t qidlestart; /* Start of current idle period */
a7834745 TG	152	};
a7834745 TG	153
8af2a218	154	static inline u32 red_maxp(u8 Plog)
a7834745	155	{
8af2a218	156	return Plog < 32 ? (~0U >> Plog) : ~0U;
a7834745 TG	157	}
a7834745 TG	158
eeca6688 ED	159	static inline void red_set_vars(struct red_vars *v)
	160	{
	161	/* Reset average queue length, the value is strictly bound
	162	* to the parameters below, reseting hurts a bit but leaving
	163	* it might result in an unreasonable qavg for a while. --TGR
	164	*/
	165	v->qavg = 0;
	166
	167	v->qcount = -1;
	168	}
8af2a218	169
a7834745 TG	170	static inline void red_set_parms(struct red_parms *p,
a7834745 TG	171	u32 qth_min, u32 qth_max, u8 Wlog, u8 Plog,
a73ed26b	172	u8 Scell_log, u8 *stab, u32 max_P)
a7834745	173	{
8af2a218	174	int delta = qth_max - qth_min;
a73ed26b	175	u32 max_p_delta;
8af2a218	176
a7834745 TG	177	p->qth_min = qth_min << Wlog;
	178	p->qth_max = qth_max << Wlog;
	179	p->Wlog = Wlog;
	180	p->Plog = Plog;
8af2a218 ED	181	if (delta < 0)
	182	delta = 1;
	183	p->qth_delta = delta;
a73ed26b ED	184	if (!max_P) {
	185	max_P = red_maxp(Plog);
	186	max_P = delta; / max_P = (qth_max - qth_min)/2^Plog */
	187	}
	188	p->max_P = max_P;
	189	max_p_delta = max_P / delta;
	190	max_p_delta = max(max_p_delta, 1U);
	191	p->max_P_reciprocal = reciprocal_value(max_p_delta);
8af2a218 ED	192
	193	/* RED Adaptative target :
	194	* [min_th + 0.4*(min_th - max_th),
	195	* min_th + 0.6*(min_th - max_th)].
	196	*/
	197	delta /= 5;
	198	p->target_min = qth_min + 2*delta;
	199	p->target_max = qth_min + 3*delta;
	200
a7834745 TG	201	p->Scell_log = Scell_log;
	202	p->Scell_max = (255 << Scell_log);
	203
ddecf0f4 ED	204	if (stab)
ddecf0f4 ED	205	memcpy(p->Stab, stab, sizeof(p->Stab));
a7834745 TG	206	}
a7834745 TG	207
eeca6688	208	static inline int red_is_idling(const struct red_vars *v)
a7834745	209	{
eeca6688	210	return v->qidlestart.tv64 != 0;
a7834745 TG	211	}
a7834745 TG	212
eeca6688	213	static inline void red_start_of_idle_period(struct red_vars *v)
a7834745	214	{
eeca6688	215	v->qidlestart = ktime_get();
a7834745 TG	216	}
a7834745 TG	217
eeca6688	218	static inline void red_end_of_idle_period(struct red_vars *v)
a7834745	219	{
eeca6688	220	v->qidlestart.tv64 = 0;
a7834745 TG	221	}
a7834745 TG	222
eeca6688	223	static inline void red_restart(struct red_vars *v)
a7834745	224	{
eeca6688 ED	225	red_end_of_idle_period(v);
	226	v->qavg = 0;
	227	v->qcount = -1;
a7834745 TG	228	}
a7834745 TG	229
eeca6688 ED	230	static inline unsigned long red_calc_qavg_from_idle_time(const struct red_parms *p,
eeca6688 ED	231	const struct red_vars *v)
a7834745	232	{
eeca6688	233	s64 delta = ktime_us_delta(ktime_get(), v->qidlestart);
ea6a5d3b	234	long us_idle = min_t(s64, delta, p->Scell_max);
a7834745 TG	235	int shift;
a7834745 TG	236
a7834745 TG	237	/*
	238	* The problem: ideally, average length queue recalcultion should
	239	* be done over constant clock intervals. This is too expensive, so
	240	* that the calculation is driven by outgoing packets.
	241	* When the queue is idle we have to model this clock by hand.
	242	*
	243	* SF+VJ proposed to "generate":
	244	*
	245	* m = idletime / (average_pkt_size / bandwidth)
	246	*
	247	* dummy packets as a burst after idle time, i.e.
	248	*
4362aaf6	249	* v->qavg *= (1-W)^m
a7834745 TG	250	*
	251	* This is an apparently overcomplicated solution (f.e. we have to
	252	* precompute a table to make this calculation in reasonable time)
	253	* I believe that a simpler model may be used here,
	254	* but it is field for experiments.
	255	*/
	256
	257	shift = p->Stab[(us_idle >> p->Scell_log) & RED_STAB_MASK];
	258
	259	if (shift)
eeca6688	260	return v->qavg >> shift;
a7834745 TG	261	else {
	262	/* Approximate initial part of exponent with linear function:
	263	*
	264	* (1-W)^m ~= 1-mW + ...
	265	*
	266	* Seems, it is the best solution to
	267	* problem of too coarse exponent tabulation.
	268	*/
eeca6688	269	us_idle = (v->qavg * (u64)us_idle) >> p->Scell_log;
a7834745	270
eeca6688 ED	271	if (us_idle < (v->qavg >> 1))
eeca6688 ED	272	return v->qavg - us_idle;
a7834745	273	else
eeca6688	274	return v->qavg >> 1;
a7834745 TG	275	}
	276	}
	277
8af2a218	278	static inline unsigned long red_calc_qavg_no_idle_time(const struct red_parms *p,
eeca6688	279	const struct red_vars *v,
a7834745 TG	280	unsigned int backlog)
	281	{
	282	/*
4362aaf6	283	* NOTE: v->qavg is fixed point number with point at Wlog.
a7834745 TG	284	* The formula below is equvalent to floating point
	285	* version:
	286	*
	287	* qavg = qavg(1-W) + backlogW;
	288	*
	289	* --ANK (980924)
	290	*/
eeca6688	291	return v->qavg + (backlog - (v->qavg >> p->Wlog));
a7834745 TG	292	}
a7834745 TG	293
8af2a218	294	static inline unsigned long red_calc_qavg(const struct red_parms *p,
eeca6688	295	const struct red_vars *v,
a7834745 TG	296	unsigned int backlog)
a7834745 TG	297	{
eeca6688 ED	298	if (!red_is_idling(v))
eeca6688 ED	299	return red_calc_qavg_no_idle_time(p, v, backlog);
a7834745	300	else
eeca6688	301	return red_calc_qavg_from_idle_time(p, v);
a7834745 TG	302	}
a7834745 TG	303
8af2a218 ED	304
8af2a218 ED	305	static inline u32 red_random(const struct red_parms *p)
a7834745	306	{
63862b5b	307	return reciprocal_divide(prandom_u32(), p->max_P_reciprocal);
a7834745 TG	308	}
a7834745 TG	309
eeca6688 ED	310	static inline int red_mark_probability(const struct red_parms *p,
	311	const struct red_vars *v,
	312	unsigned long qavg)
a7834745 TG	313	{
	314	/* The formula used below causes questions.
	315
8af2a218 ED	316	OK. qR is random number in the interval
8af2a218 ED	317	(0..1/max_P)*(qth_max-qth_min)
a7834745 TG	318	i.e. 0..(2^Plog). If we used floating point
	319	arithmetics, it would be: (2^Plog)*rnd_num,
	320	where rnd_num is less 1.
	321
	322	Taking into account, that qavg have fixed
8af2a218	323	point at Wlog, two lines
a7834745 TG	324	below have the following floating point equivalent:
	325
	326	max_P*(qavg - qth_min)/(qth_max-qth_min) < rnd/qcount
	327
	328	Any questions? --ANK (980924)
	329	*/
eeca6688	330	return !(((qavg - p->qth_min) >> p->Wlog) * v->qcount < v->qR);
a7834745 TG	331	}
	332
	333	enum {
	334	RED_BELOW_MIN_THRESH,
	335	RED_BETWEEN_TRESH,
	336	RED_ABOVE_MAX_TRESH,
	337	};
	338
eeca6688	339	static inline int red_cmp_thresh(const struct red_parms *p, unsigned long qavg)
a7834745 TG	340	{
	341	if (qavg < p->qth_min)
	342	return RED_BELOW_MIN_THRESH;
	343	else if (qavg >= p->qth_max)
	344	return RED_ABOVE_MAX_TRESH;
	345	else
	346	return RED_BETWEEN_TRESH;
	347	}
	348
	349	enum {
	350	RED_DONT_MARK,
	351	RED_PROB_MARK,
	352	RED_HARD_MARK,
	353	};
	354
eeca6688 ED	355	static inline int red_action(const struct red_parms *p,
	356	struct red_vars *v,
	357	unsigned long qavg)
a7834745 TG	358	{
	359	switch (red_cmp_thresh(p, qavg)) {
	360	case RED_BELOW_MIN_THRESH:
eeca6688	361	v->qcount = -1;
a7834745 TG	362	return RED_DONT_MARK;
	363
	364	case RED_BETWEEN_TRESH:
eeca6688 ED	365	if (++v->qcount) {
	366	if (red_mark_probability(p, v, qavg)) {
	367	v->qcount = 0;
	368	v->qR = red_random(p);
a7834745 TG	369	return RED_PROB_MARK;
	370	}
	371	} else
eeca6688	372	v->qR = red_random(p);
a7834745 TG	373
	374	return RED_DONT_MARK;
	375
	376	case RED_ABOVE_MAX_TRESH:
eeca6688	377	v->qcount = -1;
a7834745 TG	378	return RED_HARD_MARK;
	379	}
	380
	381	BUG();
	382	return RED_DONT_MARK;
	383	}
	384
eeca6688	385	static inline void red_adaptative_algo(struct red_parms p, struct red_vars v)
8af2a218 ED	386	{
	387	unsigned long qavg;
	388	u32 max_p_delta;
	389
eeca6688 ED	390	qavg = v->qavg;
	391	if (red_is_idling(v))
	392	qavg = red_calc_qavg_from_idle_time(p, v);
8af2a218	393
4362aaf6	394	/* v->qavg is fixed point number with point at Wlog */
8af2a218 ED	395	qavg >>= p->Wlog;
	396
	397	if (qavg > p->target_max && p->max_P <= MAX_P_MAX)
	398	p->max_P += MAX_P_ALPHA(p->max_P); /* maxp = maxp + alpha */
	399	else if (qavg < p->target_min && p->max_P >= MAX_P_MIN)
	400	p->max_P = (p->max_P/10)9; / maxp = maxp * Beta */
	401
	402	max_p_delta = DIV_ROUND_CLOSEST(p->max_P, p->qth_delta);
a73ed26b	403	max_p_delta = max(max_p_delta, 1U);
8af2a218 ED	404	p->max_P_reciprocal = reciprocal_value(max_p_delta);
8af2a218 ED	405	}
a7834745	406	#endif