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 <net/mac80211.h>
17 #include "rate.h"
18 #include "mesh.h"
19 #include "rc80211_pid.h"
20
21
22 /* This is an implementation of a TX rate control algorithm that uses a PID
23 * controller. Given a target failed frames rate, the controller decides about
24 * TX rate changes to meet the target failed frames rate.
25 *
26 * The controller basically computes the following:
27 *
28 * adj = CP * err + CI * err_avg + CD * (err - last_err) * (1 + sharpening)
29 *
30 * where
31 * adj adjustment value that is used to switch TX rate (see below)
32 * err current error: target vs. current failed frames percentage
33 * last_err last error
34 * err_avg average (i.e. poor man's integral) of recent errors
35 * sharpening non-zero when fast response is needed (i.e. right after
36 * association or no frames sent for a long time), heading
37 * to zero over time
38 * CP Proportional coefficient
39 * CI Integral coefficient
40 * CD Derivative coefficient
41 *
42 * CP, CI, CD are subject to careful tuning.
43 *
44 * The integral component uses a exponential moving average approach instead of
45 * an actual sliding window. The advantage is that we don't need to keep an
46 * array of the last N error values and computation is easier.
47 *
48 * Once we have the adj value, we map it to a rate by means of a learning
49 * algorithm. This algorithm keeps the state of the percentual failed frames
50 * difference between rates. The behaviour of the lowest available rate is kept
51 * as a reference value, and every time we switch between two rates, we compute
52 * the difference between the failed frames each rate exhibited. By doing so,
53 * we compare behaviours which different rates exhibited in adjacent timeslices,
54 * thus the comparison is minimally affected by external conditions. This
55 * difference gets propagated to the whole set of measurements, so that the
56 * reference is always the same. Periodically, we normalize this set so that
57 * recent events weigh the most. By comparing the adj value with this set, we
58 * avoid pejorative switches to lower rates and allow for switches to higher
59 * rates if they behaved well.
60 *
61 * Note that for the computations we use a fixed-point representation to avoid
62 * floating point arithmetic. Hence, all values are shifted left by
63 * RC_PID_ARITH_SHIFT.
64 */
65
66
67 /* Adjust the rate while ensuring that we won't switch to a lower rate if it
68 * exhibited a worse failed frames behaviour and we'll choose the highest rate
69 * whose failed frames behaviour is not worse than the one of the original rate
70 * target. While at it, check that the new rate is valid. */
71 static void rate_control_pid_adjust_rate(struct ieee80211_supported_band *sband,
72 struct ieee80211_sta *sta,
73 struct rc_pid_sta_info *spinfo, int adj,
74 struct rc_pid_rateinfo *rinfo)
75 {
76 int cur_sorted, new_sorted, probe, tmp, n_bitrates, band;
77 int cur = spinfo->txrate_idx;
78
79 band = sband->band;
80 n_bitrates = sband->n_bitrates;
81
82 /* Map passed arguments to sorted values. */
83 cur_sorted = rinfo[cur].rev_index;
84 new_sorted = cur_sorted + adj;
85
86 /* Check limits. */
87 if (new_sorted < 0)
88 new_sorted = rinfo[0].rev_index;
89 else if (new_sorted >= n_bitrates)
90 new_sorted = rinfo[n_bitrates - 1].rev_index;
91
92 tmp = new_sorted;
93
94 if (adj < 0) {
95 /* Ensure that the rate decrease isn't disadvantageous. */
96 for (probe = cur_sorted; probe >= new_sorted; probe--)
97 if (rinfo[probe].diff <= rinfo[cur_sorted].diff &&
98 rate_supported(sta, band, rinfo[probe].index))
99 tmp = probe;
100 } else {
101 /* Look for rate increase with zero (or below) cost. */
102 for (probe = new_sorted + 1; probe < n_bitrates; probe++)
103 if (rinfo[probe].diff <= rinfo[new_sorted].diff &&
104 rate_supported(sta, band, rinfo[probe].index))
105 tmp = probe;
106 }
107
108 /* Fit the rate found to the nearest supported rate. */
109 do {
110 if (rate_supported(sta, band, rinfo[tmp].index)) {
111 spinfo->txrate_idx = rinfo[tmp].index;
112 break;
113 }
114 if (adj < 0)
115 tmp--;
116 else
117 tmp++;
118 } while (tmp < n_bitrates && tmp >= 0);
119
120 #ifdef CONFIG_MAC80211_DEBUGFS
121 rate_control_pid_event_rate_change(&spinfo->events,
122 spinfo->txrate_idx,
123 sband->bitrates[spinfo->txrate_idx].bitrate);
124 #endif
125 }
126
127 /* Normalize the failed frames per-rate differences. */
128 static void rate_control_pid_normalize(struct rc_pid_info *pinfo, int l)
129 {
130 int i, norm_offset = pinfo->norm_offset;
131 struct rc_pid_rateinfo *r = pinfo->rinfo;
132
133 if (r[0].diff > norm_offset)
134 r[0].diff -= norm_offset;
135 else if (r[0].diff < -norm_offset)
136 r[0].diff += norm_offset;
137 for (i = 0; i < l - 1; i++)
138 if (r[i + 1].diff > r[i].diff + norm_offset)
139 r[i + 1].diff -= norm_offset;
140 else if (r[i + 1].diff <= r[i].diff)
141 r[i + 1].diff += norm_offset;
142 }
143
144 static void rate_control_pid_sample(struct rc_pid_info *pinfo,
145 struct ieee80211_supported_band *sband,
146 struct ieee80211_sta *sta,
147 struct rc_pid_sta_info *spinfo)
148 {
149 struct rc_pid_rateinfo *rinfo = pinfo->rinfo;
150 u32 pf;
151 s32 err_avg;
152 u32 err_prop;
153 u32 err_int;
154 u32 err_der;
155 int adj, i, j, tmp;
156 unsigned long period;
157
158 /* In case nothing happened during the previous control interval, turn
159 * the sharpening factor on. */
160 period = (HZ * pinfo->sampling_period + 500) / 1000;
161 if (!period)
162 period = 1;
163 if (jiffies - spinfo->last_sample > 2 * period)
164 spinfo->sharp_cnt = pinfo->sharpen_duration;
165
166 spinfo->last_sample = jiffies;
167
168 /* This should never happen, but in case, we assume the old sample is
169 * still a good measurement and copy it. */
170 if (unlikely(spinfo->tx_num_xmit == 0))
171 pf = spinfo->last_pf;
172 else {
173 /* XXX: BAD HACK!!! */
174 struct sta_info *si = container_of(sta, struct sta_info, sta);
175
176 pf = spinfo->tx_num_failed * 100 / spinfo->tx_num_xmit;
177
178 if (ieee80211_vif_is_mesh(&si->sdata->vif) && pf == 100)
179 mesh_plink_broken(si);
180 pf <<= RC_PID_ARITH_SHIFT;
181 si->fail_avg = ((pf + (spinfo->last_pf << 3)) / 9)
182 >> RC_PID_ARITH_SHIFT;
183 }
184
185 spinfo->tx_num_xmit = 0;
186 spinfo->tx_num_failed = 0;
187
188 /* If we just switched rate, update the rate behaviour info. */
189 if (pinfo->oldrate != spinfo->txrate_idx) {
190
191 i = rinfo[pinfo->oldrate].rev_index;
192 j = rinfo[spinfo->txrate_idx].rev_index;
193
194 tmp = (pf - spinfo->last_pf);
195 tmp = RC_PID_DO_ARITH_RIGHT_SHIFT(tmp, RC_PID_ARITH_SHIFT);
196
197 rinfo[j].diff = rinfo[i].diff + tmp;
198 pinfo->oldrate = spinfo->txrate_idx;
199 }
200 rate_control_pid_normalize(pinfo, sband->n_bitrates);
201
202 /* Compute the proportional, integral and derivative errors. */
203 err_prop = (pinfo->target << RC_PID_ARITH_SHIFT) - pf;
204
205 err_avg = spinfo->err_avg_sc >> pinfo->smoothing_shift;
206 spinfo->err_avg_sc = spinfo->err_avg_sc - err_avg + err_prop;
207 err_int = spinfo->err_avg_sc >> pinfo->smoothing_shift;
208
209 err_der = (pf - spinfo->last_pf) *
210 (1 + pinfo->sharpen_factor * spinfo->sharp_cnt);
211 spinfo->last_pf = pf;
212 if (spinfo->sharp_cnt)
213 spinfo->sharp_cnt--;
214
215 #ifdef CONFIG_MAC80211_DEBUGFS
216 rate_control_pid_event_pf_sample(&spinfo->events, pf, err_prop, err_int,
217 err_der);
218 #endif
219
220 /* Compute the controller output. */
221 adj = (err_prop * pinfo->coeff_p + err_int * pinfo->coeff_i
222 + err_der * pinfo->coeff_d);
223 adj = RC_PID_DO_ARITH_RIGHT_SHIFT(adj, 2 * RC_PID_ARITH_SHIFT);
224
225 /* Change rate. */
226 if (adj)
227 rate_control_pid_adjust_rate(sband, sta, spinfo, adj, rinfo);
228 }
229
230 static void rate_control_pid_tx_status(void *priv, struct ieee80211_supported_band *sband,
231 struct ieee80211_sta *sta, void *priv_sta,
232 struct sk_buff *skb)
233 {
234 struct rc_pid_info *pinfo = priv;
235 struct rc_pid_sta_info *spinfo = priv_sta;
236 unsigned long period;
237 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
238
239 if (!spinfo)
240 return;
241
242 /* Ignore all frames that were sent with a different rate than the rate
243 * we currently advise mac80211 to use. */
244 if (info->status.rates[0].idx != spinfo->txrate_idx)
245 return;
246
247 spinfo->tx_num_xmit++;
248
249 #ifdef CONFIG_MAC80211_DEBUGFS
250 rate_control_pid_event_tx_status(&spinfo->events, info);
251 #endif
252
253 /* We count frames that totally failed to be transmitted as two bad
254 * frames, those that made it out but had some retries as one good and
255 * one bad frame. */
256 if (!(info->flags & IEEE80211_TX_STAT_ACK)) {
257 spinfo->tx_num_failed += 2;
258 spinfo->tx_num_xmit++;
259 } else if (info->status.rates[0].count > 1) {
260 spinfo->tx_num_failed++;
261 spinfo->tx_num_xmit++;
262 }
263
264 /* Update PID controller state. */
265 period = (HZ * pinfo->sampling_period + 500) / 1000;
266 if (!period)
267 period = 1;
268 if (time_after(jiffies, spinfo->last_sample + period))
269 rate_control_pid_sample(pinfo, sband, sta, spinfo);
270 }
271
272 static void
273 rate_control_pid_get_rate(void *priv, struct ieee80211_sta *sta,
274 void *priv_sta,
275 struct ieee80211_tx_rate_control *txrc)
276 {
277 struct sk_buff *skb = txrc->skb;
278 struct ieee80211_supported_band *sband = txrc->sband;
279 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
280 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
281 struct rc_pid_sta_info *spinfo = priv_sta;
282 int rateidx;
283 u16 fc;
284
285 if (txrc->rts)
286 info->control.rates[0].count =
287 txrc->hw->conf.long_frame_max_tx_count;
288 else
289 info->control.rates[0].count =
290 txrc->hw->conf.short_frame_max_tx_count;
291
292 /* Send management frames and NO_ACK data using lowest rate. */
293 fc = le16_to_cpu(hdr->frame_control);
294 if (!sta || !spinfo ||
295 (fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_DATA ||
296 info->flags & IEEE80211_TX_CTL_NO_ACK) {
297 info->control.rates[0].idx = rate_lowest_index(sband, sta);
298 if (info->flags & IEEE80211_TX_CTL_NO_ACK)
299 info->control.rates[0].count = 1;
300
301 return;
302 }
303
304 rateidx = spinfo->txrate_idx;
305
306 if (rateidx >= sband->n_bitrates)
307 rateidx = sband->n_bitrates - 1;
308
309 info->control.rates[0].idx = rateidx;
310
311 #ifdef CONFIG_MAC80211_DEBUGFS
312 rate_control_pid_event_tx_rate(&spinfo->events,
313 rateidx, sband->bitrates[rateidx].bitrate);
314 #endif
315 }
316
317 static void
318 rate_control_pid_rate_init(void *priv, struct ieee80211_supported_band *sband,
319 struct ieee80211_sta *sta, void *priv_sta)
320 {
321 struct rc_pid_sta_info *spinfo = priv_sta;
322 struct rc_pid_info *pinfo = priv;
323 struct rc_pid_rateinfo *rinfo = pinfo->rinfo;
324 struct sta_info *si;
325 int i, j, tmp;
326 bool s;
327
328 /* TODO: This routine should consider using RSSI from previous packets
329 * as we need to have IEEE 802.1X auth succeed immediately after assoc..
330 * Until that method is implemented, we will use the lowest supported
331 * rate as a workaround. */
332
333 /* Sort the rates. This is optimized for the most common case (i.e.
334 * almost-sorted CCK+OFDM rates). Kind of bubble-sort with reversed
335 * mapping too. */
336 for (i = 0; i < sband->n_bitrates; i++) {
337 rinfo[i].index = i;
338 rinfo[i].rev_index = i;
339 if (RC_PID_FAST_START)
340 rinfo[i].diff = 0;
341 else
342 rinfo[i].diff = i * pinfo->norm_offset;
343 }
344 for (i = 1; i < sband->n_bitrates; i++) {
345 s = 0;
346 for (j = 0; j < sband->n_bitrates - i; j++)
347 if (unlikely(sband->bitrates[rinfo[j].index].bitrate >
348 sband->bitrates[rinfo[j + 1].index].bitrate)) {
349 tmp = rinfo[j].index;
350 rinfo[j].index = rinfo[j + 1].index;
351 rinfo[j + 1].index = tmp;
352 rinfo[rinfo[j].index].rev_index = j;
353 rinfo[rinfo[j + 1].index].rev_index = j + 1;
354 s = 1;
355 }
356 if (!s)
357 break;
358 }
359
360 spinfo->txrate_idx = rate_lowest_index(sband, sta);
361 /* HACK */
362 si = container_of(sta, struct sta_info, sta);
363 si->fail_avg = 0;
364 }
365
366 static void *rate_control_pid_alloc(struct ieee80211_hw *hw,
367 struct dentry *debugfsdir)
368 {
369 struct rc_pid_info *pinfo;
370 struct rc_pid_rateinfo *rinfo;
371 struct ieee80211_supported_band *sband;
372 int i, max_rates = 0;
373 #ifdef CONFIG_MAC80211_DEBUGFS
374 struct rc_pid_debugfs_entries *de;
375 #endif
376
377 pinfo = kmalloc(sizeof(*pinfo), GFP_ATOMIC);
378 if (!pinfo)
379 return NULL;
380
381 for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
382 sband = hw->wiphy->bands[i];
383 if (sband && sband->n_bitrates > max_rates)
384 max_rates = sband->n_bitrates;
385 }
386
387 rinfo = kmalloc(sizeof(*rinfo) * max_rates, GFP_ATOMIC);
388 if (!rinfo) {
389 kfree(pinfo);
390 return NULL;
391 }
392
393 pinfo->target = RC_PID_TARGET_PF;
394 pinfo->sampling_period = RC_PID_INTERVAL;
395 pinfo->coeff_p = RC_PID_COEFF_P;
396 pinfo->coeff_i = RC_PID_COEFF_I;
397 pinfo->coeff_d = RC_PID_COEFF_D;
398 pinfo->smoothing_shift = RC_PID_SMOOTHING_SHIFT;
399 pinfo->sharpen_factor = RC_PID_SHARPENING_FACTOR;
400 pinfo->sharpen_duration = RC_PID_SHARPENING_DURATION;
401 pinfo->norm_offset = RC_PID_NORM_OFFSET;
402 pinfo->rinfo = rinfo;
403 pinfo->oldrate = 0;
404
405 #ifdef CONFIG_MAC80211_DEBUGFS
406 de = &pinfo->dentries;
407 de->target = debugfs_create_u32("target_pf", S_IRUSR | S_IWUSR,
408 debugfsdir, &pinfo->target);
409 de->sampling_period = debugfs_create_u32("sampling_period",
410 S_IRUSR | S_IWUSR, debugfsdir,
411 &pinfo->sampling_period);
412 de->coeff_p = debugfs_create_u32("coeff_p", S_IRUSR | S_IWUSR,
413 debugfsdir, (u32 *)&pinfo->coeff_p);
414 de->coeff_i = debugfs_create_u32("coeff_i", S_IRUSR | S_IWUSR,
415 debugfsdir, (u32 *)&pinfo->coeff_i);
416 de->coeff_d = debugfs_create_u32("coeff_d", S_IRUSR | S_IWUSR,
417 debugfsdir, (u32 *)&pinfo->coeff_d);
418 de->smoothing_shift = debugfs_create_u32("smoothing_shift",
419 S_IRUSR | S_IWUSR, debugfsdir,
420 &pinfo->smoothing_shift);
421 de->sharpen_factor = debugfs_create_u32("sharpen_factor",
422 S_IRUSR | S_IWUSR, debugfsdir,
423 &pinfo->sharpen_factor);
424 de->sharpen_duration = debugfs_create_u32("sharpen_duration",
425 S_IRUSR | S_IWUSR, debugfsdir,
426 &pinfo->sharpen_duration);
427 de->norm_offset = debugfs_create_u32("norm_offset",
428 S_IRUSR | S_IWUSR, debugfsdir,
429 &pinfo->norm_offset);
430 #endif
431
432 return pinfo;
433 }
434
435 static void rate_control_pid_free(void *priv)
436 {
437 struct rc_pid_info *pinfo = priv;
438 #ifdef CONFIG_MAC80211_DEBUGFS
439 struct rc_pid_debugfs_entries *de = &pinfo->dentries;
440
441 debugfs_remove(de->norm_offset);
442 debugfs_remove(de->sharpen_duration);
443 debugfs_remove(de->sharpen_factor);
444 debugfs_remove(de->smoothing_shift);
445 debugfs_remove(de->coeff_d);
446 debugfs_remove(de->coeff_i);
447 debugfs_remove(de->coeff_p);
448 debugfs_remove(de->sampling_period);
449 debugfs_remove(de->target);
450 #endif
451
452 kfree(pinfo->rinfo);
453 kfree(pinfo);
454 }
455
456 static void *rate_control_pid_alloc_sta(void *priv, struct ieee80211_sta *sta,
457 gfp_t gfp)
458 {
459 struct rc_pid_sta_info *spinfo;
460
461 spinfo = kzalloc(sizeof(*spinfo), gfp);
462 if (spinfo == NULL)
463 return NULL;
464
465 spinfo->last_sample = jiffies;
466
467 #ifdef CONFIG_MAC80211_DEBUGFS
468 spin_lock_init(&spinfo->events.lock);
469 init_waitqueue_head(&spinfo->events.waitqueue);
470 #endif
471
472 return spinfo;
473 }
474
475 static void rate_control_pid_free_sta(void *priv, struct ieee80211_sta *sta,
476 void *priv_sta)
477 {
478 kfree(priv_sta);
479 }
480
481 static struct rate_control_ops mac80211_rcpid = {
482 .name = "pid",
483 .tx_status = rate_control_pid_tx_status,
484 .get_rate = rate_control_pid_get_rate,
485 .rate_init = rate_control_pid_rate_init,
486 .alloc = rate_control_pid_alloc,
487 .free = rate_control_pid_free,
488 .alloc_sta = rate_control_pid_alloc_sta,
489 .free_sta = rate_control_pid_free_sta,
490 #ifdef CONFIG_MAC80211_DEBUGFS
491 .add_sta_debugfs = rate_control_pid_add_sta_debugfs,
492 .remove_sta_debugfs = rate_control_pid_remove_sta_debugfs,
493 #endif
494 };
495
496 int __init rc80211_pid_init(void)
497 {
498 return ieee80211_rate_control_register(&mac80211_rcpid);
499 }
500
501 void rc80211_pid_exit(void)
502 {
503 ieee80211_rate_control_unregister(&mac80211_rcpid);
504 }
505
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