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1 | /* | |
2 | * Copyright 2002-2005, Instant802 Networks, Inc. | |
3 | * Copyright 2005, Devicescape Software, Inc. | |
4 | * Copyright 2007, Mattias Nissler <mattias.nissler@gmx.de> | |
5 | * Copyright 2007-2008, Stefano Brivio <stefano.brivio@polimi.it> | |
6 | * | |
7 | * This program is free software; you can redistribute it and/or modify | |
8 | * it under the terms of the GNU General Public License version 2 as | |
9 | * published by the Free Software Foundation. | |
10 | */ | |
11 | ||
12 | #include <linux/netdevice.h> | |
13 | #include <linux/types.h> | |
14 | #include <linux/skbuff.h> | |
15 | #include <linux/debugfs.h> | |
16 | #include <linux/slab.h> | |
17 | #include <net/mac80211.h> | |
18 | #include "rate.h" | |
19 | #include "mesh.h" | |
20 | #include "rc80211_pid.h" | |
21 | ||
22 | ||
23 | /* This is an implementation of a TX rate control algorithm that uses a PID | |
24 | * controller. Given a target failed frames rate, the controller decides about | |
25 | * TX rate changes to meet the target failed frames rate. | |
26 | * | |
27 | * The controller basically computes the following: | |
28 | * | |
29 | * adj = CP * err + CI * err_avg + CD * (err - last_err) * (1 + sharpening) | |
30 | * | |
31 | * where | |
32 | * adj adjustment value that is used to switch TX rate (see below) | |
33 | * err current error: target vs. current failed frames percentage | |
34 | * last_err last error | |
35 | * err_avg average (i.e. poor man's integral) of recent errors | |
36 | * sharpening non-zero when fast response is needed (i.e. right after | |
37 | * association or no frames sent for a long time), heading | |
38 | * to zero over time | |
39 | * CP Proportional coefficient | |
40 | * CI Integral coefficient | |
41 | * CD Derivative coefficient | |
42 | * | |
43 | * CP, CI, CD are subject to careful tuning. | |
44 | * | |
45 | * The integral component uses a exponential moving average approach instead of | |
46 | * an actual sliding window. The advantage is that we don't need to keep an | |
47 | * array of the last N error values and computation is easier. | |
48 | * | |
49 | * Once we have the adj value, we map it to a rate by means of a learning | |
50 | * algorithm. This algorithm keeps the state of the percentual failed frames | |
51 | * difference between rates. The behaviour of the lowest available rate is kept | |
52 | * as a reference value, and every time we switch between two rates, we compute | |
53 | * the difference between the failed frames each rate exhibited. By doing so, | |
54 | * we compare behaviours which different rates exhibited in adjacent timeslices, | |
55 | * thus the comparison is minimally affected by external conditions. This | |
56 | * difference gets propagated to the whole set of measurements, so that the | |
57 | * reference is always the same. Periodically, we normalize this set so that | |
58 | * recent events weigh the most. By comparing the adj value with this set, we | |
59 | * avoid pejorative switches to lower rates and allow for switches to higher | |
60 | * rates if they behaved well. | |
61 | * | |
62 | * Note that for the computations we use a fixed-point representation to avoid | |
63 | * floating point arithmetic. Hence, all values are shifted left by | |
64 | * RC_PID_ARITH_SHIFT. | |
65 | */ | |
66 | ||
67 | ||
68 | /* Adjust the rate while ensuring that we won't switch to a lower rate if it | |
69 | * exhibited a worse failed frames behaviour and we'll choose the highest rate | |
70 | * whose failed frames behaviour is not worse than the one of the original rate | |
71 | * target. While at it, check that the new rate is valid. */ | |
72 | static void rate_control_pid_adjust_rate(struct ieee80211_supported_band *sband, | |
73 | struct ieee80211_sta *sta, | |
74 | struct rc_pid_sta_info *spinfo, int adj, | |
75 | struct rc_pid_rateinfo *rinfo) | |
76 | { | |
77 | int cur_sorted, new_sorted, probe, tmp, n_bitrates, band; | |
78 | int cur = spinfo->txrate_idx; | |
79 | ||
80 | band = sband->band; | |
81 | n_bitrates = sband->n_bitrates; | |
82 | ||
83 | /* Map passed arguments to sorted values. */ | |
84 | cur_sorted = rinfo[cur].rev_index; | |
85 | new_sorted = cur_sorted + adj; | |
86 | ||
87 | /* Check limits. */ | |
88 | if (new_sorted < 0) | |
89 | new_sorted = rinfo[0].rev_index; | |
90 | else if (new_sorted >= n_bitrates) | |
91 | new_sorted = rinfo[n_bitrates - 1].rev_index; | |
92 | ||
93 | tmp = new_sorted; | |
94 | ||
95 | if (adj < 0) { | |
96 | /* Ensure that the rate decrease isn't disadvantageous. */ | |
97 | for (probe = cur_sorted; probe >= new_sorted; probe--) | |
98 | if (rinfo[probe].diff <= rinfo[cur_sorted].diff && | |
99 | rate_supported(sta, band, rinfo[probe].index)) | |
100 | tmp = probe; | |
101 | } else { | |
102 | /* Look for rate increase with zero (or below) cost. */ | |
103 | for (probe = new_sorted + 1; probe < n_bitrates; probe++) | |
104 | if (rinfo[probe].diff <= rinfo[new_sorted].diff && | |
105 | rate_supported(sta, band, rinfo[probe].index)) | |
106 | tmp = probe; | |
107 | } | |
108 | ||
109 | /* Fit the rate found to the nearest supported rate. */ | |
110 | do { | |
111 | if (rate_supported(sta, band, rinfo[tmp].index)) { | |
112 | spinfo->txrate_idx = rinfo[tmp].index; | |
113 | break; | |
114 | } | |
115 | if (adj < 0) | |
116 | tmp--; | |
117 | else | |
118 | tmp++; | |
119 | } while (tmp < n_bitrates && tmp >= 0); | |
120 | ||
121 | #ifdef CONFIG_MAC80211_DEBUGFS | |
122 | rate_control_pid_event_rate_change(&spinfo->events, | |
123 | spinfo->txrate_idx, | |
124 | sband->bitrates[spinfo->txrate_idx].bitrate); | |
125 | #endif | |
126 | } | |
127 | ||
128 | /* Normalize the failed frames per-rate differences. */ | |
129 | static void rate_control_pid_normalize(struct rc_pid_info *pinfo, int l) | |
130 | { | |
131 | int i, norm_offset = pinfo->norm_offset; | |
132 | struct rc_pid_rateinfo *r = pinfo->rinfo; | |
133 | ||
134 | if (r[0].diff > norm_offset) | |
135 | r[0].diff -= norm_offset; | |
136 | else if (r[0].diff < -norm_offset) | |
137 | r[0].diff += norm_offset; | |
138 | for (i = 0; i < l - 1; i++) | |
139 | if (r[i + 1].diff > r[i].diff + norm_offset) | |
140 | r[i + 1].diff -= norm_offset; | |
141 | else if (r[i + 1].diff <= r[i].diff) | |
142 | r[i + 1].diff += norm_offset; | |
143 | } | |
144 | ||
145 | static void rate_control_pid_sample(struct rc_pid_info *pinfo, | |
146 | struct ieee80211_supported_band *sband, | |
147 | struct ieee80211_sta *sta, | |
148 | struct rc_pid_sta_info *spinfo) | |
149 | { | |
150 | struct rc_pid_rateinfo *rinfo = pinfo->rinfo; | |
151 | u32 pf; | |
152 | s32 err_avg; | |
153 | u32 err_prop; | |
154 | u32 err_int; | |
155 | u32 err_der; | |
156 | int adj, i, j, tmp; | |
157 | unsigned long period; | |
158 | ||
159 | /* In case nothing happened during the previous control interval, turn | |
160 | * the sharpening factor on. */ | |
161 | period = msecs_to_jiffies(pinfo->sampling_period); | |
162 | if (jiffies - spinfo->last_sample > 2 * period) | |
163 | spinfo->sharp_cnt = pinfo->sharpen_duration; | |
164 | ||
165 | spinfo->last_sample = jiffies; | |
166 | ||
167 | /* This should never happen, but in case, we assume the old sample is | |
168 | * still a good measurement and copy it. */ | |
169 | if (unlikely(spinfo->tx_num_xmit == 0)) | |
170 | pf = spinfo->last_pf; | |
171 | else | |
172 | pf = spinfo->tx_num_failed * 100 / spinfo->tx_num_xmit; | |
173 | ||
174 | spinfo->tx_num_xmit = 0; | |
175 | spinfo->tx_num_failed = 0; | |
176 | ||
177 | /* If we just switched rate, update the rate behaviour info. */ | |
178 | if (pinfo->oldrate != spinfo->txrate_idx) { | |
179 | ||
180 | i = rinfo[pinfo->oldrate].rev_index; | |
181 | j = rinfo[spinfo->txrate_idx].rev_index; | |
182 | ||
183 | tmp = (pf - spinfo->last_pf); | |
184 | tmp = RC_PID_DO_ARITH_RIGHT_SHIFT(tmp, RC_PID_ARITH_SHIFT); | |
185 | ||
186 | rinfo[j].diff = rinfo[i].diff + tmp; | |
187 | pinfo->oldrate = spinfo->txrate_idx; | |
188 | } | |
189 | rate_control_pid_normalize(pinfo, sband->n_bitrates); | |
190 | ||
191 | /* Compute the proportional, integral and derivative errors. */ | |
192 | err_prop = (pinfo->target - pf) << RC_PID_ARITH_SHIFT; | |
193 | ||
194 | err_avg = spinfo->err_avg_sc >> pinfo->smoothing_shift; | |
195 | spinfo->err_avg_sc = spinfo->err_avg_sc - err_avg + err_prop; | |
196 | err_int = spinfo->err_avg_sc >> pinfo->smoothing_shift; | |
197 | ||
198 | err_der = (pf - spinfo->last_pf) * | |
199 | (1 + pinfo->sharpen_factor * spinfo->sharp_cnt); | |
200 | spinfo->last_pf = pf; | |
201 | if (spinfo->sharp_cnt) | |
202 | spinfo->sharp_cnt--; | |
203 | ||
204 | #ifdef CONFIG_MAC80211_DEBUGFS | |
205 | rate_control_pid_event_pf_sample(&spinfo->events, pf, err_prop, err_int, | |
206 | err_der); | |
207 | #endif | |
208 | ||
209 | /* Compute the controller output. */ | |
210 | adj = (err_prop * pinfo->coeff_p + err_int * pinfo->coeff_i | |
211 | + err_der * pinfo->coeff_d); | |
212 | adj = RC_PID_DO_ARITH_RIGHT_SHIFT(adj, 2 * RC_PID_ARITH_SHIFT); | |
213 | ||
214 | /* Change rate. */ | |
215 | if (adj) | |
216 | rate_control_pid_adjust_rate(sband, sta, spinfo, adj, rinfo); | |
217 | } | |
218 | ||
219 | static void rate_control_pid_tx_status(void *priv, struct ieee80211_supported_band *sband, | |
220 | struct ieee80211_sta *sta, void *priv_sta, | |
221 | struct sk_buff *skb) | |
222 | { | |
223 | struct rc_pid_info *pinfo = priv; | |
224 | struct rc_pid_sta_info *spinfo = priv_sta; | |
225 | unsigned long period; | |
226 | struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); | |
227 | ||
228 | if (!spinfo) | |
229 | return; | |
230 | ||
231 | /* Ignore all frames that were sent with a different rate than the rate | |
232 | * we currently advise mac80211 to use. */ | |
233 | if (info->status.rates[0].idx != spinfo->txrate_idx) | |
234 | return; | |
235 | ||
236 | spinfo->tx_num_xmit++; | |
237 | ||
238 | #ifdef CONFIG_MAC80211_DEBUGFS | |
239 | rate_control_pid_event_tx_status(&spinfo->events, info); | |
240 | #endif | |
241 | ||
242 | /* We count frames that totally failed to be transmitted as two bad | |
243 | * frames, those that made it out but had some retries as one good and | |
244 | * one bad frame. */ | |
245 | if (!(info->flags & IEEE80211_TX_STAT_ACK)) { | |
246 | spinfo->tx_num_failed += 2; | |
247 | spinfo->tx_num_xmit++; | |
248 | } else if (info->status.rates[0].count > 1) { | |
249 | spinfo->tx_num_failed++; | |
250 | spinfo->tx_num_xmit++; | |
251 | } | |
252 | ||
253 | /* Update PID controller state. */ | |
254 | period = msecs_to_jiffies(pinfo->sampling_period); | |
255 | if (time_after(jiffies, spinfo->last_sample + period)) | |
256 | rate_control_pid_sample(pinfo, sband, sta, spinfo); | |
257 | } | |
258 | ||
259 | static void | |
260 | rate_control_pid_get_rate(void *priv, struct ieee80211_sta *sta, | |
261 | void *priv_sta, | |
262 | struct ieee80211_tx_rate_control *txrc) | |
263 | { | |
264 | struct sk_buff *skb = txrc->skb; | |
265 | struct ieee80211_supported_band *sband = txrc->sband; | |
266 | struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); | |
267 | struct rc_pid_sta_info *spinfo = priv_sta; | |
268 | int rateidx; | |
269 | ||
270 | if (txrc->rts) | |
271 | info->control.rates[0].count = | |
272 | txrc->hw->conf.long_frame_max_tx_count; | |
273 | else | |
274 | info->control.rates[0].count = | |
275 | txrc->hw->conf.short_frame_max_tx_count; | |
276 | ||
277 | /* Send management frames and NO_ACK data using lowest rate. */ | |
278 | if (rate_control_send_low(sta, priv_sta, txrc)) | |
279 | return; | |
280 | ||
281 | rateidx = spinfo->txrate_idx; | |
282 | ||
283 | if (rateidx >= sband->n_bitrates) | |
284 | rateidx = sband->n_bitrates - 1; | |
285 | ||
286 | info->control.rates[0].idx = rateidx; | |
287 | ||
288 | #ifdef CONFIG_MAC80211_DEBUGFS | |
289 | rate_control_pid_event_tx_rate(&spinfo->events, | |
290 | rateidx, sband->bitrates[rateidx].bitrate); | |
291 | #endif | |
292 | } | |
293 | ||
294 | static void | |
295 | rate_control_pid_rate_init(void *priv, struct ieee80211_supported_band *sband, | |
296 | struct cfg80211_chan_def *chandef, | |
297 | struct ieee80211_sta *sta, void *priv_sta) | |
298 | { | |
299 | struct rc_pid_sta_info *spinfo = priv_sta; | |
300 | struct rc_pid_info *pinfo = priv; | |
301 | struct rc_pid_rateinfo *rinfo = pinfo->rinfo; | |
302 | int i, j, tmp; | |
303 | bool s; | |
304 | ||
305 | /* TODO: This routine should consider using RSSI from previous packets | |
306 | * as we need to have IEEE 802.1X auth succeed immediately after assoc.. | |
307 | * Until that method is implemented, we will use the lowest supported | |
308 | * rate as a workaround. */ | |
309 | ||
310 | /* Sort the rates. This is optimized for the most common case (i.e. | |
311 | * almost-sorted CCK+OFDM rates). Kind of bubble-sort with reversed | |
312 | * mapping too. */ | |
313 | for (i = 0; i < sband->n_bitrates; i++) { | |
314 | rinfo[i].index = i; | |
315 | rinfo[i].rev_index = i; | |
316 | if (RC_PID_FAST_START) | |
317 | rinfo[i].diff = 0; | |
318 | else | |
319 | rinfo[i].diff = i * pinfo->norm_offset; | |
320 | } | |
321 | for (i = 1; i < sband->n_bitrates; i++) { | |
322 | s = false; | |
323 | for (j = 0; j < sband->n_bitrates - i; j++) | |
324 | if (unlikely(sband->bitrates[rinfo[j].index].bitrate > | |
325 | sband->bitrates[rinfo[j + 1].index].bitrate)) { | |
326 | tmp = rinfo[j].index; | |
327 | rinfo[j].index = rinfo[j + 1].index; | |
328 | rinfo[j + 1].index = tmp; | |
329 | rinfo[rinfo[j].index].rev_index = j; | |
330 | rinfo[rinfo[j + 1].index].rev_index = j + 1; | |
331 | s = true; | |
332 | } | |
333 | if (!s) | |
334 | break; | |
335 | } | |
336 | ||
337 | spinfo->txrate_idx = rate_lowest_index(sband, sta); | |
338 | } | |
339 | ||
340 | static void *rate_control_pid_alloc(struct ieee80211_hw *hw, | |
341 | struct dentry *debugfsdir) | |
342 | { | |
343 | struct rc_pid_info *pinfo; | |
344 | struct rc_pid_rateinfo *rinfo; | |
345 | struct ieee80211_supported_band *sband; | |
346 | int i, max_rates = 0; | |
347 | #ifdef CONFIG_MAC80211_DEBUGFS | |
348 | struct rc_pid_debugfs_entries *de; | |
349 | #endif | |
350 | ||
351 | pinfo = kmalloc(sizeof(*pinfo), GFP_ATOMIC); | |
352 | if (!pinfo) | |
353 | return NULL; | |
354 | ||
355 | for (i = 0; i < IEEE80211_NUM_BANDS; i++) { | |
356 | sband = hw->wiphy->bands[i]; | |
357 | if (sband && sband->n_bitrates > max_rates) | |
358 | max_rates = sband->n_bitrates; | |
359 | } | |
360 | ||
361 | rinfo = kmalloc(sizeof(*rinfo) * max_rates, GFP_ATOMIC); | |
362 | if (!rinfo) { | |
363 | kfree(pinfo); | |
364 | return NULL; | |
365 | } | |
366 | ||
367 | pinfo->target = RC_PID_TARGET_PF; | |
368 | pinfo->sampling_period = RC_PID_INTERVAL; | |
369 | pinfo->coeff_p = RC_PID_COEFF_P; | |
370 | pinfo->coeff_i = RC_PID_COEFF_I; | |
371 | pinfo->coeff_d = RC_PID_COEFF_D; | |
372 | pinfo->smoothing_shift = RC_PID_SMOOTHING_SHIFT; | |
373 | pinfo->sharpen_factor = RC_PID_SHARPENING_FACTOR; | |
374 | pinfo->sharpen_duration = RC_PID_SHARPENING_DURATION; | |
375 | pinfo->norm_offset = RC_PID_NORM_OFFSET; | |
376 | pinfo->rinfo = rinfo; | |
377 | pinfo->oldrate = 0; | |
378 | ||
379 | #ifdef CONFIG_MAC80211_DEBUGFS | |
380 | de = &pinfo->dentries; | |
381 | de->target = debugfs_create_u32("target_pf", S_IRUSR | S_IWUSR, | |
382 | debugfsdir, &pinfo->target); | |
383 | de->sampling_period = debugfs_create_u32("sampling_period", | |
384 | S_IRUSR | S_IWUSR, debugfsdir, | |
385 | &pinfo->sampling_period); | |
386 | de->coeff_p = debugfs_create_u32("coeff_p", S_IRUSR | S_IWUSR, | |
387 | debugfsdir, (u32 *)&pinfo->coeff_p); | |
388 | de->coeff_i = debugfs_create_u32("coeff_i", S_IRUSR | S_IWUSR, | |
389 | debugfsdir, (u32 *)&pinfo->coeff_i); | |
390 | de->coeff_d = debugfs_create_u32("coeff_d", S_IRUSR | S_IWUSR, | |
391 | debugfsdir, (u32 *)&pinfo->coeff_d); | |
392 | de->smoothing_shift = debugfs_create_u32("smoothing_shift", | |
393 | S_IRUSR | S_IWUSR, debugfsdir, | |
394 | &pinfo->smoothing_shift); | |
395 | de->sharpen_factor = debugfs_create_u32("sharpen_factor", | |
396 | S_IRUSR | S_IWUSR, debugfsdir, | |
397 | &pinfo->sharpen_factor); | |
398 | de->sharpen_duration = debugfs_create_u32("sharpen_duration", | |
399 | S_IRUSR | S_IWUSR, debugfsdir, | |
400 | &pinfo->sharpen_duration); | |
401 | de->norm_offset = debugfs_create_u32("norm_offset", | |
402 | S_IRUSR | S_IWUSR, debugfsdir, | |
403 | &pinfo->norm_offset); | |
404 | #endif | |
405 | ||
406 | return pinfo; | |
407 | } | |
408 | ||
409 | static void rate_control_pid_free(void *priv) | |
410 | { | |
411 | struct rc_pid_info *pinfo = priv; | |
412 | #ifdef CONFIG_MAC80211_DEBUGFS | |
413 | struct rc_pid_debugfs_entries *de = &pinfo->dentries; | |
414 | ||
415 | debugfs_remove(de->norm_offset); | |
416 | debugfs_remove(de->sharpen_duration); | |
417 | debugfs_remove(de->sharpen_factor); | |
418 | debugfs_remove(de->smoothing_shift); | |
419 | debugfs_remove(de->coeff_d); | |
420 | debugfs_remove(de->coeff_i); | |
421 | debugfs_remove(de->coeff_p); | |
422 | debugfs_remove(de->sampling_period); | |
423 | debugfs_remove(de->target); | |
424 | #endif | |
425 | ||
426 | kfree(pinfo->rinfo); | |
427 | kfree(pinfo); | |
428 | } | |
429 | ||
430 | static void *rate_control_pid_alloc_sta(void *priv, struct ieee80211_sta *sta, | |
431 | gfp_t gfp) | |
432 | { | |
433 | struct rc_pid_sta_info *spinfo; | |
434 | ||
435 | spinfo = kzalloc(sizeof(*spinfo), gfp); | |
436 | if (spinfo == NULL) | |
437 | return NULL; | |
438 | ||
439 | spinfo->last_sample = jiffies; | |
440 | ||
441 | #ifdef CONFIG_MAC80211_DEBUGFS | |
442 | spin_lock_init(&spinfo->events.lock); | |
443 | init_waitqueue_head(&spinfo->events.waitqueue); | |
444 | #endif | |
445 | ||
446 | return spinfo; | |
447 | } | |
448 | ||
449 | static void rate_control_pid_free_sta(void *priv, struct ieee80211_sta *sta, | |
450 | void *priv_sta) | |
451 | { | |
452 | kfree(priv_sta); | |
453 | } | |
454 | ||
455 | static const struct rate_control_ops mac80211_rcpid = { | |
456 | .name = "pid", | |
457 | .tx_status = rate_control_pid_tx_status, | |
458 | .get_rate = rate_control_pid_get_rate, | |
459 | .rate_init = rate_control_pid_rate_init, | |
460 | .alloc = rate_control_pid_alloc, | |
461 | .free = rate_control_pid_free, | |
462 | .alloc_sta = rate_control_pid_alloc_sta, | |
463 | .free_sta = rate_control_pid_free_sta, | |
464 | #ifdef CONFIG_MAC80211_DEBUGFS | |
465 | .add_sta_debugfs = rate_control_pid_add_sta_debugfs, | |
466 | .remove_sta_debugfs = rate_control_pid_remove_sta_debugfs, | |
467 | #endif | |
468 | }; | |
469 | ||
470 | int __init rc80211_pid_init(void) | |
471 | { | |
472 | return ieee80211_rate_control_register(&mac80211_rcpid); | |
473 | } | |
474 | ||
475 | void rc80211_pid_exit(void) | |
476 | { | |
477 | ieee80211_rate_control_unregister(&mac80211_rcpid); | |
478 | } |