Loading...
1#ifndef __NET_SCHED_RED_H
2#define __NET_SCHED_RED_H
3
4#include <linux/types.h>
5#include <net/pkt_sched.h>
6#include <net/inet_ecn.h>
7#include <net/dsfield.h>
8
9/* Random Early Detection (RED) algorithm.
10 =======================================
11
12 Source: Sally Floyd and Van Jacobson, "Random Early Detection Gateways
13 for Congestion Avoidance", 1993, IEEE/ACM Transactions on Networking.
14
15 This file codes a "divisionless" version of RED algorithm
16 as written down in Fig.17 of the paper.
17
18 Short description.
19 ------------------
20
21 When a new packet arrives we calculate the average queue length:
22
23 avg = (1-W)*avg + W*current_queue_len,
24
25 W is the filter time constant (chosen as 2^(-Wlog)), it controls
26 the inertia of the algorithm. To allow larger bursts, W should be
27 decreased.
28
29 if (avg > th_max) -> packet marked (dropped).
30 if (avg < th_min) -> packet passes.
31 if (th_min < avg < th_max) we calculate probability:
32
33 Pb = max_P * (avg - th_min)/(th_max-th_min)
34
35 and mark (drop) packet with this probability.
36 Pb changes from 0 (at avg==th_min) to max_P (avg==th_max).
37 max_P should be small (not 1), usually 0.01..0.02 is good value.
38
39 max_P is chosen as a number, so that max_P/(th_max-th_min)
40 is a negative power of two in order arithmetics to contain
41 only shifts.
42
43
44 Parameters, settable by user:
45 -----------------------------
46
47 qth_min - bytes (should be < qth_max/2)
48 qth_max - bytes (should be at least 2*qth_min and less limit)
49 Wlog - bits (<32) log(1/W).
50 Plog - bits (<32)
51
52 Plog is related to max_P by formula:
53
54 max_P = (qth_max-qth_min)/2^Plog;
55
56 F.e. if qth_max=128K and qth_min=32K, then Plog=22
57 corresponds to max_P=0.02
58
59 Scell_log
60 Stab
61
62 Lookup table for log((1-W)^(t/t_ave).
63
64
65 NOTES:
66
67 Upper bound on W.
68 -----------------
69
70 If you want to allow bursts of L packets of size S,
71 you should choose W:
72
73 L + 1 - th_min/S < (1-(1-W)^L)/W
74
75 th_min/S = 32 th_min/S = 4
76
77 log(W) L
78 -1 33
79 -2 35
80 -3 39
81 -4 46
82 -5 57
83 -6 75
84 -7 101
85 -8 135
86 -9 190
87 etc.
88 */
89
90#define RED_STAB_SIZE 256
91#define RED_STAB_MASK (RED_STAB_SIZE - 1)
92
93struct red_stats {
94 u32 prob_drop; /* Early probability drops */
95 u32 prob_mark; /* Early probability marks */
96 u32 forced_drop; /* Forced drops, qavg > max_thresh */
97 u32 forced_mark; /* Forced marks, qavg > max_thresh */
98 u32 pdrop; /* Drops due to queue limits */
99 u32 other; /* Drops due to drop() calls */
100};
101
102struct red_parms {
103 /* Parameters */
104 u32 qth_min; /* Min avg length threshold: A scaled */
105 u32 qth_max; /* Max avg length threshold: A scaled */
106 u32 Scell_max;
107 u32 Rmask; /* Cached random mask, see red_rmask */
108 u8 Scell_log;
109 u8 Wlog; /* log(W) */
110 u8 Plog; /* random number bits */
111 u8 Stab[RED_STAB_SIZE];
112
113 /* Variables */
114 int qcount; /* Number of packets since last random
115 number generation */
116 u32 qR; /* Cached random number */
117
118 unsigned long qavg; /* Average queue length: A scaled */
119 psched_time_t qidlestart; /* Start of current idle period */
120};
121
122static inline u32 red_rmask(u8 Plog)
123{
124 return Plog < 32 ? ((1 << Plog) - 1) : ~0UL;
125}
126
127static inline void red_set_parms(struct red_parms *p,
128 u32 qth_min, u32 qth_max, u8 Wlog, u8 Plog,
129 u8 Scell_log, u8 *stab)
130{
131 /* Reset average queue length, the value is strictly bound
132 * to the parameters below, reseting hurts a bit but leaving
133 * it might result in an unreasonable qavg for a while. --TGR
134 */
135 p->qavg = 0;
136
137 p->qcount = -1;
138 p->qth_min = qth_min << Wlog;
139 p->qth_max = qth_max << Wlog;
140 p->Wlog = Wlog;
141 p->Plog = Plog;
142 p->Rmask = red_rmask(Plog);
143 p->Scell_log = Scell_log;
144 p->Scell_max = (255 << Scell_log);
145
146 memcpy(p->Stab, stab, sizeof(p->Stab));
147}
148
149static inline int red_is_idling(struct red_parms *p)
150{
151 return p->qidlestart != PSCHED_PASTPERFECT;
152}
153
154static inline void red_start_of_idle_period(struct red_parms *p)
155{
156 p->qidlestart = psched_get_time();
157}
158
159static inline void red_end_of_idle_period(struct red_parms *p)
160{
161 p->qidlestart = PSCHED_PASTPERFECT;
162}
163
164static inline void red_restart(struct red_parms *p)
165{
166 red_end_of_idle_period(p);
167 p->qavg = 0;
168 p->qcount = -1;
169}
170
171static inline unsigned long red_calc_qavg_from_idle_time(struct red_parms *p)
172{
173 psched_time_t now;
174 long us_idle;
175 int shift;
176
177 now = psched_get_time();
178 us_idle = psched_tdiff_bounded(now, p->qidlestart, p->Scell_max);
179
180 /*
181 * The problem: ideally, average length queue recalcultion should
182 * be done over constant clock intervals. This is too expensive, so
183 * that the calculation is driven by outgoing packets.
184 * When the queue is idle we have to model this clock by hand.
185 *
186 * SF+VJ proposed to "generate":
187 *
188 * m = idletime / (average_pkt_size / bandwidth)
189 *
190 * dummy packets as a burst after idle time, i.e.
191 *
192 * p->qavg *= (1-W)^m
193 *
194 * This is an apparently overcomplicated solution (f.e. we have to
195 * precompute a table to make this calculation in reasonable time)
196 * I believe that a simpler model may be used here,
197 * but it is field for experiments.
198 */
199
200 shift = p->Stab[(us_idle >> p->Scell_log) & RED_STAB_MASK];
201
202 if (shift)
203 return p->qavg >> shift;
204 else {
205 /* Approximate initial part of exponent with linear function:
206 *
207 * (1-W)^m ~= 1-mW + ...
208 *
209 * Seems, it is the best solution to
210 * problem of too coarse exponent tabulation.
211 */
212 us_idle = (p->qavg * (u64)us_idle) >> p->Scell_log;
213
214 if (us_idle < (p->qavg >> 1))
215 return p->qavg - us_idle;
216 else
217 return p->qavg >> 1;
218 }
219}
220
221static inline unsigned long red_calc_qavg_no_idle_time(struct red_parms *p,
222 unsigned int backlog)
223{
224 /*
225 * NOTE: p->qavg is fixed point number with point at Wlog.
226 * The formula below is equvalent to floating point
227 * version:
228 *
229 * qavg = qavg*(1-W) + backlog*W;
230 *
231 * --ANK (980924)
232 */
233 return p->qavg + (backlog - (p->qavg >> p->Wlog));
234}
235
236static inline unsigned long red_calc_qavg(struct red_parms *p,
237 unsigned int backlog)
238{
239 if (!red_is_idling(p))
240 return red_calc_qavg_no_idle_time(p, backlog);
241 else
242 return red_calc_qavg_from_idle_time(p);
243}
244
245static inline u32 red_random(struct red_parms *p)
246{
247 return net_random() & p->Rmask;
248}
249
250static inline int red_mark_probability(struct red_parms *p, unsigned long qavg)
251{
252 /* The formula used below causes questions.
253
254 OK. qR is random number in the interval 0..Rmask
255 i.e. 0..(2^Plog). If we used floating point
256 arithmetics, it would be: (2^Plog)*rnd_num,
257 where rnd_num is less 1.
258
259 Taking into account, that qavg have fixed
260 point at Wlog, and Plog is related to max_P by
261 max_P = (qth_max-qth_min)/2^Plog; two lines
262 below have the following floating point equivalent:
263
264 max_P*(qavg - qth_min)/(qth_max-qth_min) < rnd/qcount
265
266 Any questions? --ANK (980924)
267 */
268 return !(((qavg - p->qth_min) >> p->Wlog) * p->qcount < p->qR);
269}
270
271enum {
272 RED_BELOW_MIN_THRESH,
273 RED_BETWEEN_TRESH,
274 RED_ABOVE_MAX_TRESH,
275};
276
277static inline int red_cmp_thresh(struct red_parms *p, unsigned long qavg)
278{
279 if (qavg < p->qth_min)
280 return RED_BELOW_MIN_THRESH;
281 else if (qavg >= p->qth_max)
282 return RED_ABOVE_MAX_TRESH;
283 else
284 return RED_BETWEEN_TRESH;
285}
286
287enum {
288 RED_DONT_MARK,
289 RED_PROB_MARK,
290 RED_HARD_MARK,
291};
292
293static inline int red_action(struct red_parms *p, unsigned long qavg)
294{
295 switch (red_cmp_thresh(p, qavg)) {
296 case RED_BELOW_MIN_THRESH:
297 p->qcount = -1;
298 return RED_DONT_MARK;
299
300 case RED_BETWEEN_TRESH:
301 if (++p->qcount) {
302 if (red_mark_probability(p, qavg)) {
303 p->qcount = 0;
304 p->qR = red_random(p);
305 return RED_PROB_MARK;
306 }
307 } else
308 p->qR = red_random(p);
309
310 return RED_DONT_MARK;
311
312 case RED_ABOVE_MAX_TRESH:
313 p->qcount = -1;
314 return RED_HARD_MARK;
315 }
316
317 BUG();
318 return RED_DONT_MARK;
319}
320
321#endif
1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __NET_SCHED_RED_H
3#define __NET_SCHED_RED_H
4
5#include <linux/types.h>
6#include <linux/bug.h>
7#include <net/pkt_sched.h>
8#include <net/inet_ecn.h>
9#include <net/dsfield.h>
10#include <linux/reciprocal_div.h>
11
12/* Random Early Detection (RED) algorithm.
13 =======================================
14
15 Source: Sally Floyd and Van Jacobson, "Random Early Detection Gateways
16 for Congestion Avoidance", 1993, IEEE/ACM Transactions on Networking.
17
18 This file codes a "divisionless" version of RED algorithm
19 as written down in Fig.17 of the paper.
20
21 Short description.
22 ------------------
23
24 When a new packet arrives we calculate the average queue length:
25
26 avg = (1-W)*avg + W*current_queue_len,
27
28 W is the filter time constant (chosen as 2^(-Wlog)), it controls
29 the inertia of the algorithm. To allow larger bursts, W should be
30 decreased.
31
32 if (avg > th_max) -> packet marked (dropped).
33 if (avg < th_min) -> packet passes.
34 if (th_min < avg < th_max) we calculate probability:
35
36 Pb = max_P * (avg - th_min)/(th_max-th_min)
37
38 and mark (drop) packet with this probability.
39 Pb changes from 0 (at avg==th_min) to max_P (avg==th_max).
40 max_P should be small (not 1), usually 0.01..0.02 is good value.
41
42 max_P is chosen as a number, so that max_P/(th_max-th_min)
43 is a negative power of two in order arithmetics to contain
44 only shifts.
45
46
47 Parameters, settable by user:
48 -----------------------------
49
50 qth_min - bytes (should be < qth_max/2)
51 qth_max - bytes (should be at least 2*qth_min and less limit)
52 Wlog - bits (<32) log(1/W).
53 Plog - bits (<32)
54
55 Plog is related to max_P by formula:
56
57 max_P = (qth_max-qth_min)/2^Plog;
58
59 F.e. if qth_max=128K and qth_min=32K, then Plog=22
60 corresponds to max_P=0.02
61
62 Scell_log
63 Stab
64
65 Lookup table for log((1-W)^(t/t_ave).
66
67
68 NOTES:
69
70 Upper bound on W.
71 -----------------
72
73 If you want to allow bursts of L packets of size S,
74 you should choose W:
75
76 L + 1 - th_min/S < (1-(1-W)^L)/W
77
78 th_min/S = 32 th_min/S = 4
79
80 log(W) L
81 -1 33
82 -2 35
83 -3 39
84 -4 46
85 -5 57
86 -6 75
87 -7 101
88 -8 135
89 -9 190
90 etc.
91 */
92
93/*
94 * Adaptative RED : An Algorithm for Increasing the Robustness of RED's AQM
95 * (Sally FLoyd, Ramakrishna Gummadi, and Scott Shenker) August 2001
96 *
97 * Every 500 ms:
98 * if (avg > target and max_p <= 0.5)
99 * increase max_p : max_p += alpha;
100 * else if (avg < target and max_p >= 0.01)
101 * decrease max_p : max_p *= beta;
102 *
103 * target :[qth_min + 0.4*(qth_min - qth_max),
104 * qth_min + 0.6*(qth_min - qth_max)].
105 * alpha : min(0.01, max_p / 4)
106 * beta : 0.9
107 * max_P is a Q0.32 fixed point number (with 32 bits mantissa)
108 * max_P between 0.01 and 0.5 (1% - 50%) [ Its no longer a negative power of two ]
109 */
110#define RED_ONE_PERCENT ((u32)DIV_ROUND_CLOSEST(1ULL<<32, 100))
111
112#define MAX_P_MIN (1 * RED_ONE_PERCENT)
113#define MAX_P_MAX (50 * RED_ONE_PERCENT)
114#define MAX_P_ALPHA(val) min(MAX_P_MIN, val / 4)
115
116#define RED_STAB_SIZE 256
117#define RED_STAB_MASK (RED_STAB_SIZE - 1)
118
119struct red_stats {
120 u32 prob_drop; /* Early probability drops */
121 u32 prob_mark; /* Early probability marks */
122 u32 forced_drop; /* Forced drops, qavg > max_thresh */
123 u32 forced_mark; /* Forced marks, qavg > max_thresh */
124 u32 pdrop; /* Drops due to queue limits */
125 u32 other; /* Drops due to drop() calls */
126};
127
128struct red_parms {
129 /* Parameters */
130 u32 qth_min; /* Min avg length threshold: Wlog scaled */
131 u32 qth_max; /* Max avg length threshold: Wlog scaled */
132 u32 Scell_max;
133 u32 max_P; /* probability, [0 .. 1.0] 32 scaled */
134 /* reciprocal_value(max_P / qth_delta) */
135 struct reciprocal_value max_P_reciprocal;
136 u32 qth_delta; /* max_th - min_th */
137 u32 target_min; /* min_th + 0.4*(max_th - min_th) */
138 u32 target_max; /* min_th + 0.6*(max_th - min_th) */
139 u8 Scell_log;
140 u8 Wlog; /* log(W) */
141 u8 Plog; /* random number bits */
142 u8 Stab[RED_STAB_SIZE];
143};
144
145struct red_vars {
146 /* Variables */
147 int qcount; /* Number of packets since last random
148 number generation */
149 u32 qR; /* Cached random number */
150
151 unsigned long qavg; /* Average queue length: Wlog scaled */
152 ktime_t qidlestart; /* Start of current idle period */
153};
154
155static inline u32 red_maxp(u8 Plog)
156{
157 return Plog < 32 ? (~0U >> Plog) : ~0U;
158}
159
160static inline void red_set_vars(struct red_vars *v)
161{
162 /* Reset average queue length, the value is strictly bound
163 * to the parameters below, reseting hurts a bit but leaving
164 * it might result in an unreasonable qavg for a while. --TGR
165 */
166 v->qavg = 0;
167
168 v->qcount = -1;
169}
170
171static inline bool red_check_params(u32 qth_min, u32 qth_max, u8 Wlog,
172 u8 Scell_log, u8 *stab)
173{
174 if (fls(qth_min) + Wlog >= 32)
175 return false;
176 if (fls(qth_max) + Wlog >= 32)
177 return false;
178 if (Scell_log >= 32)
179 return false;
180 if (qth_max < qth_min)
181 return false;
182 if (stab) {
183 int i;
184
185 for (i = 0; i < RED_STAB_SIZE; i++)
186 if (stab[i] >= 32)
187 return false;
188 }
189 return true;
190}
191
192static inline int red_get_flags(unsigned char qopt_flags,
193 unsigned char historic_mask,
194 struct nlattr *flags_attr,
195 unsigned char supported_mask,
196 struct nla_bitfield32 *p_flags,
197 unsigned char *p_userbits,
198 struct netlink_ext_ack *extack)
199{
200 struct nla_bitfield32 flags;
201
202 if (qopt_flags && flags_attr) {
203 NL_SET_ERR_MSG_MOD(extack, "flags should be passed either through qopt, or through a dedicated attribute");
204 return -EINVAL;
205 }
206
207 if (flags_attr) {
208 flags = nla_get_bitfield32(flags_attr);
209 } else {
210 flags.selector = historic_mask;
211 flags.value = qopt_flags & historic_mask;
212 }
213
214 *p_flags = flags;
215 *p_userbits = qopt_flags & ~historic_mask;
216 return 0;
217}
218
219static inline int red_validate_flags(unsigned char flags,
220 struct netlink_ext_ack *extack)
221{
222 if ((flags & TC_RED_NODROP) && !(flags & TC_RED_ECN)) {
223 NL_SET_ERR_MSG_MOD(extack, "nodrop mode is only meaningful with ECN");
224 return -EINVAL;
225 }
226
227 return 0;
228}
229
230static inline void red_set_parms(struct red_parms *p,
231 u32 qth_min, u32 qth_max, u8 Wlog, u8 Plog,
232 u8 Scell_log, u8 *stab, u32 max_P)
233{
234 int delta = qth_max - qth_min;
235 u32 max_p_delta;
236
237 p->qth_min = qth_min << Wlog;
238 p->qth_max = qth_max << Wlog;
239 p->Wlog = Wlog;
240 p->Plog = Plog;
241 if (delta <= 0)
242 delta = 1;
243 p->qth_delta = delta;
244 if (!max_P) {
245 max_P = red_maxp(Plog);
246 max_P *= delta; /* max_P = (qth_max - qth_min)/2^Plog */
247 }
248 p->max_P = max_P;
249 max_p_delta = max_P / delta;
250 max_p_delta = max(max_p_delta, 1U);
251 p->max_P_reciprocal = reciprocal_value(max_p_delta);
252
253 /* RED Adaptative target :
254 * [min_th + 0.4*(min_th - max_th),
255 * min_th + 0.6*(min_th - max_th)].
256 */
257 delta /= 5;
258 p->target_min = qth_min + 2*delta;
259 p->target_max = qth_min + 3*delta;
260
261 p->Scell_log = Scell_log;
262 p->Scell_max = (255 << Scell_log);
263
264 if (stab)
265 memcpy(p->Stab, stab, sizeof(p->Stab));
266}
267
268static inline int red_is_idling(const struct red_vars *v)
269{
270 return v->qidlestart != 0;
271}
272
273static inline void red_start_of_idle_period(struct red_vars *v)
274{
275 v->qidlestart = ktime_get();
276}
277
278static inline void red_end_of_idle_period(struct red_vars *v)
279{
280 v->qidlestart = 0;
281}
282
283static inline void red_restart(struct red_vars *v)
284{
285 red_end_of_idle_period(v);
286 v->qavg = 0;
287 v->qcount = -1;
288}
289
290static inline unsigned long red_calc_qavg_from_idle_time(const struct red_parms *p,
291 const struct red_vars *v)
292{
293 s64 delta = ktime_us_delta(ktime_get(), v->qidlestart);
294 long us_idle = min_t(s64, delta, p->Scell_max);
295 int shift;
296
297 /*
298 * The problem: ideally, average length queue recalculation should
299 * be done over constant clock intervals. This is too expensive, so
300 * that the calculation is driven by outgoing packets.
301 * When the queue is idle we have to model this clock by hand.
302 *
303 * SF+VJ proposed to "generate":
304 *
305 * m = idletime / (average_pkt_size / bandwidth)
306 *
307 * dummy packets as a burst after idle time, i.e.
308 *
309 * v->qavg *= (1-W)^m
310 *
311 * This is an apparently overcomplicated solution (f.e. we have to
312 * precompute a table to make this calculation in reasonable time)
313 * I believe that a simpler model may be used here,
314 * but it is field for experiments.
315 */
316
317 shift = p->Stab[(us_idle >> p->Scell_log) & RED_STAB_MASK];
318
319 if (shift)
320 return v->qavg >> shift;
321 else {
322 /* Approximate initial part of exponent with linear function:
323 *
324 * (1-W)^m ~= 1-mW + ...
325 *
326 * Seems, it is the best solution to
327 * problem of too coarse exponent tabulation.
328 */
329 us_idle = (v->qavg * (u64)us_idle) >> p->Scell_log;
330
331 if (us_idle < (v->qavg >> 1))
332 return v->qavg - us_idle;
333 else
334 return v->qavg >> 1;
335 }
336}
337
338static inline unsigned long red_calc_qavg_no_idle_time(const struct red_parms *p,
339 const struct red_vars *v,
340 unsigned int backlog)
341{
342 /*
343 * NOTE: v->qavg is fixed point number with point at Wlog.
344 * The formula below is equvalent to floating point
345 * version:
346 *
347 * qavg = qavg*(1-W) + backlog*W;
348 *
349 * --ANK (980924)
350 */
351 return v->qavg + (backlog - (v->qavg >> p->Wlog));
352}
353
354static inline unsigned long red_calc_qavg(const struct red_parms *p,
355 const struct red_vars *v,
356 unsigned int backlog)
357{
358 if (!red_is_idling(v))
359 return red_calc_qavg_no_idle_time(p, v, backlog);
360 else
361 return red_calc_qavg_from_idle_time(p, v);
362}
363
364
365static inline u32 red_random(const struct red_parms *p)
366{
367 return reciprocal_divide(prandom_u32(), p->max_P_reciprocal);
368}
369
370static inline int red_mark_probability(const struct red_parms *p,
371 const struct red_vars *v,
372 unsigned long qavg)
373{
374 /* The formula used below causes questions.
375
376 OK. qR is random number in the interval
377 (0..1/max_P)*(qth_max-qth_min)
378 i.e. 0..(2^Plog). If we used floating point
379 arithmetics, it would be: (2^Plog)*rnd_num,
380 where rnd_num is less 1.
381
382 Taking into account, that qavg have fixed
383 point at Wlog, two lines
384 below have the following floating point equivalent:
385
386 max_P*(qavg - qth_min)/(qth_max-qth_min) < rnd/qcount
387
388 Any questions? --ANK (980924)
389 */
390 return !(((qavg - p->qth_min) >> p->Wlog) * v->qcount < v->qR);
391}
392
393enum {
394 RED_BELOW_MIN_THRESH,
395 RED_BETWEEN_TRESH,
396 RED_ABOVE_MAX_TRESH,
397};
398
399static inline int red_cmp_thresh(const struct red_parms *p, unsigned long qavg)
400{
401 if (qavg < p->qth_min)
402 return RED_BELOW_MIN_THRESH;
403 else if (qavg >= p->qth_max)
404 return RED_ABOVE_MAX_TRESH;
405 else
406 return RED_BETWEEN_TRESH;
407}
408
409enum {
410 RED_DONT_MARK,
411 RED_PROB_MARK,
412 RED_HARD_MARK,
413};
414
415static inline int red_action(const struct red_parms *p,
416 struct red_vars *v,
417 unsigned long qavg)
418{
419 switch (red_cmp_thresh(p, qavg)) {
420 case RED_BELOW_MIN_THRESH:
421 v->qcount = -1;
422 return RED_DONT_MARK;
423
424 case RED_BETWEEN_TRESH:
425 if (++v->qcount) {
426 if (red_mark_probability(p, v, qavg)) {
427 v->qcount = 0;
428 v->qR = red_random(p);
429 return RED_PROB_MARK;
430 }
431 } else
432 v->qR = red_random(p);
433
434 return RED_DONT_MARK;
435
436 case RED_ABOVE_MAX_TRESH:
437 v->qcount = -1;
438 return RED_HARD_MARK;
439 }
440
441 BUG();
442 return RED_DONT_MARK;
443}
444
445static inline void red_adaptative_algo(struct red_parms *p, struct red_vars *v)
446{
447 unsigned long qavg;
448 u32 max_p_delta;
449
450 qavg = v->qavg;
451 if (red_is_idling(v))
452 qavg = red_calc_qavg_from_idle_time(p, v);
453
454 /* v->qavg is fixed point number with point at Wlog */
455 qavg >>= p->Wlog;
456
457 if (qavg > p->target_max && p->max_P <= MAX_P_MAX)
458 p->max_P += MAX_P_ALPHA(p->max_P); /* maxp = maxp + alpha */
459 else if (qavg < p->target_min && p->max_P >= MAX_P_MIN)
460 p->max_P = (p->max_P/10)*9; /* maxp = maxp * Beta */
461
462 max_p_delta = DIV_ROUND_CLOSEST(p->max_P, p->qth_delta);
463 max_p_delta = max(max_p_delta, 1U);
464 p->max_P_reciprocal = reciprocal_value(max_p_delta);
465}
466#endif