]> git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blob - include/net/red.h
netlink: pass extended ACK struct to parsing functions
[mirror_ubuntu-bionic-kernel.git] / include / net / red.h
1 #ifndef __NET_SCHED_RED_H
2 #define __NET_SCHED_RED_H
3
4 #include <linux/types.h>
5 #include <linux/bug.h>
6 #include <net/pkt_sched.h>
7 #include <net/inet_ecn.h>
8 #include <net/dsfield.h>
9 #include <linux/reciprocal_div.h>
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 + W*current_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
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
115 #define RED_STAB_SIZE 256
116 #define RED_STAB_MASK (RED_STAB_SIZE - 1)
117
118 struct red_stats {
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 */
125 };
126
127 struct red_parms {
128 /* Parameters */
129 u32 qth_min; /* Min avg length threshold: Wlog scaled */
130 u32 qth_max; /* Max avg length threshold: Wlog scaled */
131 u32 Scell_max;
132 u32 max_P; /* probability, [0 .. 1.0] 32 scaled */
133 /* reciprocal_value(max_P / qth_delta) */
134 struct reciprocal_value max_P_reciprocal;
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) */
138 u8 Scell_log;
139 u8 Wlog; /* log(W) */
140 u8 Plog; /* random number bits */
141 u8 Stab[RED_STAB_SIZE];
142 };
143
144 struct red_vars {
145 /* Variables */
146 int qcount; /* Number of packets since last random
147 number generation */
148 u32 qR; /* Cached random number */
149
150 unsigned long qavg; /* Average queue length: Wlog scaled */
151 ktime_t qidlestart; /* Start of current idle period */
152 };
153
154 static inline u32 red_maxp(u8 Plog)
155 {
156 return Plog < 32 ? (~0U >> Plog) : ~0U;
157 }
158
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 }
169
170 static inline void red_set_parms(struct red_parms *p,
171 u32 qth_min, u32 qth_max, u8 Wlog, u8 Plog,
172 u8 Scell_log, u8 *stab, u32 max_P)
173 {
174 int delta = qth_max - qth_min;
175 u32 max_p_delta;
176
177 p->qth_min = qth_min << Wlog;
178 p->qth_max = qth_max << Wlog;
179 p->Wlog = Wlog;
180 p->Plog = Plog;
181 if (delta < 0)
182 delta = 1;
183 p->qth_delta = delta;
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);
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
201 p->Scell_log = Scell_log;
202 p->Scell_max = (255 << Scell_log);
203
204 if (stab)
205 memcpy(p->Stab, stab, sizeof(p->Stab));
206 }
207
208 static inline int red_is_idling(const struct red_vars *v)
209 {
210 return v->qidlestart != 0;
211 }
212
213 static inline void red_start_of_idle_period(struct red_vars *v)
214 {
215 v->qidlestart = ktime_get();
216 }
217
218 static inline void red_end_of_idle_period(struct red_vars *v)
219 {
220 v->qidlestart = 0;
221 }
222
223 static inline void red_restart(struct red_vars *v)
224 {
225 red_end_of_idle_period(v);
226 v->qavg = 0;
227 v->qcount = -1;
228 }
229
230 static inline unsigned long red_calc_qavg_from_idle_time(const struct red_parms *p,
231 const struct red_vars *v)
232 {
233 s64 delta = ktime_us_delta(ktime_get(), v->qidlestart);
234 long us_idle = min_t(s64, delta, p->Scell_max);
235 int shift;
236
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 *
249 * v->qavg *= (1-W)^m
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)
260 return v->qavg >> shift;
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 */
269 us_idle = (v->qavg * (u64)us_idle) >> p->Scell_log;
270
271 if (us_idle < (v->qavg >> 1))
272 return v->qavg - us_idle;
273 else
274 return v->qavg >> 1;
275 }
276 }
277
278 static inline unsigned long red_calc_qavg_no_idle_time(const struct red_parms *p,
279 const struct red_vars *v,
280 unsigned int backlog)
281 {
282 /*
283 * NOTE: v->qavg is fixed point number with point at Wlog.
284 * The formula below is equvalent to floating point
285 * version:
286 *
287 * qavg = qavg*(1-W) + backlog*W;
288 *
289 * --ANK (980924)
290 */
291 return v->qavg + (backlog - (v->qavg >> p->Wlog));
292 }
293
294 static inline unsigned long red_calc_qavg(const struct red_parms *p,
295 const struct red_vars *v,
296 unsigned int backlog)
297 {
298 if (!red_is_idling(v))
299 return red_calc_qavg_no_idle_time(p, v, backlog);
300 else
301 return red_calc_qavg_from_idle_time(p, v);
302 }
303
304
305 static inline u32 red_random(const struct red_parms *p)
306 {
307 return reciprocal_divide(prandom_u32(), p->max_P_reciprocal);
308 }
309
310 static inline int red_mark_probability(const struct red_parms *p,
311 const struct red_vars *v,
312 unsigned long qavg)
313 {
314 /* The formula used below causes questions.
315
316 OK. qR is random number in the interval
317 (0..1/max_P)*(qth_max-qth_min)
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
323 point at Wlog, two lines
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 */
330 return !(((qavg - p->qth_min) >> p->Wlog) * v->qcount < v->qR);
331 }
332
333 enum {
334 RED_BELOW_MIN_THRESH,
335 RED_BETWEEN_TRESH,
336 RED_ABOVE_MAX_TRESH,
337 };
338
339 static inline int red_cmp_thresh(const struct red_parms *p, unsigned long qavg)
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
355 static inline int red_action(const struct red_parms *p,
356 struct red_vars *v,
357 unsigned long qavg)
358 {
359 switch (red_cmp_thresh(p, qavg)) {
360 case RED_BELOW_MIN_THRESH:
361 v->qcount = -1;
362 return RED_DONT_MARK;
363
364 case RED_BETWEEN_TRESH:
365 if (++v->qcount) {
366 if (red_mark_probability(p, v, qavg)) {
367 v->qcount = 0;
368 v->qR = red_random(p);
369 return RED_PROB_MARK;
370 }
371 } else
372 v->qR = red_random(p);
373
374 return RED_DONT_MARK;
375
376 case RED_ABOVE_MAX_TRESH:
377 v->qcount = -1;
378 return RED_HARD_MARK;
379 }
380
381 BUG();
382 return RED_DONT_MARK;
383 }
384
385 static inline void red_adaptative_algo(struct red_parms *p, struct red_vars *v)
386 {
387 unsigned long qavg;
388 u32 max_p_delta;
389
390 qavg = v->qavg;
391 if (red_is_idling(v))
392 qavg = red_calc_qavg_from_idle_time(p, v);
393
394 /* v->qavg is fixed point number with point at Wlog */
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);
403 max_p_delta = max(max_p_delta, 1U);
404 p->max_P_reciprocal = reciprocal_value(max_p_delta);
405 }
406 #endif