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>
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.
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>
19 #include "rc80211_pid.h"
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.
26 * The controller basically computes the following:
28 * adj = CP * err + CI * err_avg + CD * (err - last_err) * (1 + sharpening)
31 * adj adjustment value that is used to switch TX rate (see below)
32 * err current error: target vs. current failed frames percentage
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
38 * CP Proportional coefficient
39 * CI Integral coefficient
40 * CD Derivative coefficient
42 * CP, CI, CD are subject to careful tuning.
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.
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.
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
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_local *local,
72 struct sta_info *sta, int adj,
73 struct rc_pid_rateinfo *rinfo)
75 struct ieee80211_sub_if_data *sdata;
76 struct ieee80211_supported_band *sband;
77 int cur_sorted, new_sorted, probe, tmp, n_bitrates, band;
78 struct rc_pid_sta_info *spinfo = (void *)sta->rate_ctrl_priv;
79 int cur = spinfo->txrate_idx;
82 sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
84 n_bitrates = sband->n_bitrates;
86 /* Map passed arguments to sorted values. */
87 cur_sorted = rinfo[cur].rev_index;
88 new_sorted = cur_sorted + adj;
92 new_sorted = rinfo[0].rev_index;
93 else if (new_sorted >= n_bitrates)
94 new_sorted = rinfo[n_bitrates - 1].rev_index;
99 /* Ensure that the rate decrease isn't disadvantageous. */
100 for (probe = cur_sorted; probe >= new_sorted; probe--)
101 if (rinfo[probe].diff <= rinfo[cur_sorted].diff &&
102 rate_supported(sta, band, rinfo[probe].index))
105 /* Look for rate increase with zero (or below) cost. */
106 for (probe = new_sorted + 1; probe < n_bitrates; probe++)
107 if (rinfo[probe].diff <= rinfo[new_sorted].diff &&
108 rate_supported(sta, band, rinfo[probe].index))
112 /* Fit the rate found to the nearest supported rate. */
114 if (rate_supported(sta, band, rinfo[tmp].index)) {
115 spinfo->txrate_idx = rinfo[tmp].index;
122 } while (tmp < n_bitrates && tmp >= 0);
124 #ifdef CONFIG_MAC80211_DEBUGFS
125 rate_control_pid_event_rate_change(&spinfo->events,
127 sband->bitrates[spinfo->txrate_idx].bitrate);
131 /* Normalize the failed frames per-rate differences. */
132 static void rate_control_pid_normalize(struct rc_pid_info *pinfo, int l)
134 int i, norm_offset = pinfo->norm_offset;
135 struct rc_pid_rateinfo *r = pinfo->rinfo;
137 if (r[0].diff > norm_offset)
138 r[0].diff -= norm_offset;
139 else if (r[0].diff < -norm_offset)
140 r[0].diff += norm_offset;
141 for (i = 0; i < l - 1; i++)
142 if (r[i + 1].diff > r[i].diff + norm_offset)
143 r[i + 1].diff -= norm_offset;
144 else if (r[i + 1].diff <= r[i].diff)
145 r[i + 1].diff += norm_offset;
148 static void rate_control_pid_sample(struct rc_pid_info *pinfo,
149 struct ieee80211_local *local,
150 struct sta_info *sta)
152 struct ieee80211_sub_if_data *sdata = sta->sdata;
153 struct rc_pid_sta_info *spinfo = sta->rate_ctrl_priv;
154 struct rc_pid_rateinfo *rinfo = pinfo->rinfo;
155 struct ieee80211_supported_band *sband;
162 unsigned long period;
164 sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
165 spinfo = sta->rate_ctrl_priv;
167 /* In case nothing happened during the previous control interval, turn
168 * the sharpening factor on. */
169 period = (HZ * pinfo->sampling_period + 500) / 1000;
172 if (jiffies - spinfo->last_sample > 2 * period)
173 spinfo->sharp_cnt = pinfo->sharpen_duration;
175 spinfo->last_sample = jiffies;
177 /* This should never happen, but in case, we assume the old sample is
178 * still a good measurement and copy it. */
179 if (unlikely(spinfo->tx_num_xmit == 0))
180 pf = spinfo->last_pf;
182 pf = spinfo->tx_num_failed * 100 / spinfo->tx_num_xmit;
183 if (ieee80211_vif_is_mesh(&sdata->vif) && pf == 100)
184 mesh_plink_broken(sta);
185 pf <<= RC_PID_ARITH_SHIFT;
186 sta->fail_avg = ((pf + (spinfo->last_pf << 3)) / 9)
187 >> RC_PID_ARITH_SHIFT;
190 spinfo->tx_num_xmit = 0;
191 spinfo->tx_num_failed = 0;
193 /* If we just switched rate, update the rate behaviour info. */
194 if (pinfo->oldrate != spinfo->txrate_idx) {
196 i = rinfo[pinfo->oldrate].rev_index;
197 j = rinfo[spinfo->txrate_idx].rev_index;
199 tmp = (pf - spinfo->last_pf);
200 tmp = RC_PID_DO_ARITH_RIGHT_SHIFT(tmp, RC_PID_ARITH_SHIFT);
202 rinfo[j].diff = rinfo[i].diff + tmp;
203 pinfo->oldrate = spinfo->txrate_idx;
205 rate_control_pid_normalize(pinfo, sband->n_bitrates);
207 /* Compute the proportional, integral and derivative errors. */
208 err_prop = (pinfo->target << RC_PID_ARITH_SHIFT) - pf;
210 err_avg = spinfo->err_avg_sc >> pinfo->smoothing_shift;
211 spinfo->err_avg_sc = spinfo->err_avg_sc - err_avg + err_prop;
212 err_int = spinfo->err_avg_sc >> pinfo->smoothing_shift;
214 err_der = (pf - spinfo->last_pf) *
215 (1 + pinfo->sharpen_factor * spinfo->sharp_cnt);
216 spinfo->last_pf = pf;
217 if (spinfo->sharp_cnt)
220 #ifdef CONFIG_MAC80211_DEBUGFS
221 rate_control_pid_event_pf_sample(&spinfo->events, pf, err_prop, err_int,
225 /* Compute the controller output. */
226 adj = (err_prop * pinfo->coeff_p + err_int * pinfo->coeff_i
227 + err_der * pinfo->coeff_d);
228 adj = RC_PID_DO_ARITH_RIGHT_SHIFT(adj, 2 * RC_PID_ARITH_SHIFT);
232 rate_control_pid_adjust_rate(local, sta, adj, rinfo);
235 static void rate_control_pid_tx_status(void *priv, struct net_device *dev,
238 struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
239 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
240 struct ieee80211_sub_if_data *sdata;
241 struct rc_pid_info *pinfo = priv;
242 struct sta_info *sta;
243 struct rc_pid_sta_info *spinfo;
244 unsigned long period;
245 struct ieee80211_supported_band *sband;
246 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
250 sta = sta_info_get(local, hdr->addr1);
251 sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
256 spinfo = sta->rate_ctrl_priv;
258 /* Don't update the state if we're not controlling the rate. */
260 if (sdata->force_unicast_rateidx > -1) {
261 spinfo->txrate_idx = sdata->max_ratectrl_rateidx;
265 /* Ignore all frames that were sent with a different rate than the rate
266 * we currently advise mac80211 to use. */
267 if (info->tx_rate_idx != spinfo->txrate_idx)
270 spinfo->tx_num_xmit++;
272 #ifdef CONFIG_MAC80211_DEBUGFS
273 rate_control_pid_event_tx_status(&spinfo->events, info);
276 /* We count frames that totally failed to be transmitted as two bad
277 * frames, those that made it out but had some retries as one good and
279 if (info->status.excessive_retries) {
280 spinfo->tx_num_failed += 2;
281 spinfo->tx_num_xmit++;
282 } else if (info->status.retry_count) {
283 spinfo->tx_num_failed++;
284 spinfo->tx_num_xmit++;
287 /* Update PID controller state. */
288 period = (HZ * pinfo->sampling_period + 500) / 1000;
291 if (time_after(jiffies, spinfo->last_sample + period))
292 rate_control_pid_sample(pinfo, local, sta);
298 static void rate_control_pid_get_rate(void *priv, struct net_device *dev,
299 struct ieee80211_supported_band *sband,
301 struct rate_selection *sel)
303 struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
304 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
305 struct ieee80211_sub_if_data *sdata;
306 struct rc_pid_sta_info *spinfo;
307 struct sta_info *sta;
313 sta = sta_info_get(local, hdr->addr1);
315 /* Send management frames and broadcast/multicast data using lowest
317 fc = le16_to_cpu(hdr->frame_control);
318 if ((fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_DATA ||
319 is_multicast_ether_addr(hdr->addr1) || !sta) {
320 sel->rate_idx = rate_lowest_index(local, sband, sta);
325 /* If a forced rate is in effect, select it. */
326 sdata = IEEE80211_DEV_TO_SUB_IF(dev);
327 spinfo = (struct rc_pid_sta_info *)sta->rate_ctrl_priv;
328 if (sdata->force_unicast_rateidx > -1)
329 spinfo->txrate_idx = sdata->force_unicast_rateidx;
331 rateidx = spinfo->txrate_idx;
333 if (rateidx >= sband->n_bitrates)
334 rateidx = sband->n_bitrates - 1;
338 sel->rate_idx = rateidx;
340 #ifdef CONFIG_MAC80211_DEBUGFS
341 rate_control_pid_event_tx_rate(
342 &((struct rc_pid_sta_info *) sta->rate_ctrl_priv)->events,
343 rateidx, sband->bitrates[rateidx].bitrate);
347 static void rate_control_pid_rate_init(void *priv, void *priv_sta,
348 struct ieee80211_local *local,
349 struct sta_info *sta)
351 /* TODO: This routine should consider using RSSI from previous packets
352 * as we need to have IEEE 802.1X auth succeed immediately after assoc..
353 * Until that method is implemented, we will use the lowest supported
354 * rate as a workaround. */
355 struct ieee80211_supported_band *sband;
356 struct rc_pid_sta_info *spinfo = (void *)sta->rate_ctrl_priv;
358 sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
359 spinfo->txrate_idx = rate_lowest_index(local, sband, sta);
363 static void *rate_control_pid_alloc(struct ieee80211_local *local)
365 struct rc_pid_info *pinfo;
366 struct rc_pid_rateinfo *rinfo;
367 struct ieee80211_supported_band *sband;
370 #ifdef CONFIG_MAC80211_DEBUGFS
371 struct rc_pid_debugfs_entries *de;
374 sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
376 pinfo = kmalloc(sizeof(*pinfo), GFP_ATOMIC);
380 /* We can safely assume that sband won't change unless we get
382 rinfo = kmalloc(sizeof(*rinfo) * sband->n_bitrates, GFP_ATOMIC);
388 pinfo->target = RC_PID_TARGET_PF;
389 pinfo->sampling_period = RC_PID_INTERVAL;
390 pinfo->coeff_p = RC_PID_COEFF_P;
391 pinfo->coeff_i = RC_PID_COEFF_I;
392 pinfo->coeff_d = RC_PID_COEFF_D;
393 pinfo->smoothing_shift = RC_PID_SMOOTHING_SHIFT;
394 pinfo->sharpen_factor = RC_PID_SHARPENING_FACTOR;
395 pinfo->sharpen_duration = RC_PID_SHARPENING_DURATION;
396 pinfo->norm_offset = RC_PID_NORM_OFFSET;
397 pinfo->rinfo = rinfo;
400 /* Sort the rates. This is optimized for the most common case (i.e.
401 * almost-sorted CCK+OFDM rates). Kind of bubble-sort with reversed
403 for (i = 0; i < sband->n_bitrates; i++) {
405 rinfo[i].rev_index = i;
406 if (RC_PID_FAST_START)
409 rinfo[i].diff = i * pinfo->norm_offset;
411 for (i = 1; i < sband->n_bitrates; i++) {
413 for (j = 0; j < sband->n_bitrates - i; j++)
414 if (unlikely(sband->bitrates[rinfo[j].index].bitrate >
415 sband->bitrates[rinfo[j + 1].index].bitrate)) {
416 tmp = rinfo[j].index;
417 rinfo[j].index = rinfo[j + 1].index;
418 rinfo[j + 1].index = tmp;
419 rinfo[rinfo[j].index].rev_index = j;
420 rinfo[rinfo[j + 1].index].rev_index = j + 1;
427 #ifdef CONFIG_MAC80211_DEBUGFS
428 de = &pinfo->dentries;
429 de->dir = debugfs_create_dir("rc80211_pid",
430 local->hw.wiphy->debugfsdir);
431 de->target = debugfs_create_u32("target_pf", S_IRUSR | S_IWUSR,
432 de->dir, &pinfo->target);
433 de->sampling_period = debugfs_create_u32("sampling_period",
434 S_IRUSR | S_IWUSR, de->dir,
435 &pinfo->sampling_period);
436 de->coeff_p = debugfs_create_u32("coeff_p", S_IRUSR | S_IWUSR,
437 de->dir, &pinfo->coeff_p);
438 de->coeff_i = debugfs_create_u32("coeff_i", S_IRUSR | S_IWUSR,
439 de->dir, &pinfo->coeff_i);
440 de->coeff_d = debugfs_create_u32("coeff_d", S_IRUSR | S_IWUSR,
441 de->dir, &pinfo->coeff_d);
442 de->smoothing_shift = debugfs_create_u32("smoothing_shift",
443 S_IRUSR | S_IWUSR, de->dir,
444 &pinfo->smoothing_shift);
445 de->sharpen_factor = debugfs_create_u32("sharpen_factor",
446 S_IRUSR | S_IWUSR, de->dir,
447 &pinfo->sharpen_factor);
448 de->sharpen_duration = debugfs_create_u32("sharpen_duration",
449 S_IRUSR | S_IWUSR, de->dir,
450 &pinfo->sharpen_duration);
451 de->norm_offset = debugfs_create_u32("norm_offset",
452 S_IRUSR | S_IWUSR, de->dir,
453 &pinfo->norm_offset);
459 static void rate_control_pid_free(void *priv)
461 struct rc_pid_info *pinfo = priv;
462 #ifdef CONFIG_MAC80211_DEBUGFS
463 struct rc_pid_debugfs_entries *de = &pinfo->dentries;
465 debugfs_remove(de->norm_offset);
466 debugfs_remove(de->sharpen_duration);
467 debugfs_remove(de->sharpen_factor);
468 debugfs_remove(de->smoothing_shift);
469 debugfs_remove(de->coeff_d);
470 debugfs_remove(de->coeff_i);
471 debugfs_remove(de->coeff_p);
472 debugfs_remove(de->sampling_period);
473 debugfs_remove(de->target);
474 debugfs_remove(de->dir);
481 static void rate_control_pid_clear(void *priv)
485 static void *rate_control_pid_alloc_sta(void *priv, gfp_t gfp)
487 struct rc_pid_sta_info *spinfo;
489 spinfo = kzalloc(sizeof(*spinfo), gfp);
493 spinfo->last_sample = jiffies;
495 #ifdef CONFIG_MAC80211_DEBUGFS
496 spin_lock_init(&spinfo->events.lock);
497 init_waitqueue_head(&spinfo->events.waitqueue);
503 static void rate_control_pid_free_sta(void *priv, void *priv_sta)
505 struct rc_pid_sta_info *spinfo = priv_sta;
509 static struct rate_control_ops mac80211_rcpid = {
511 .tx_status = rate_control_pid_tx_status,
512 .get_rate = rate_control_pid_get_rate,
513 .rate_init = rate_control_pid_rate_init,
514 .clear = rate_control_pid_clear,
515 .alloc = rate_control_pid_alloc,
516 .free = rate_control_pid_free,
517 .alloc_sta = rate_control_pid_alloc_sta,
518 .free_sta = rate_control_pid_free_sta,
519 #ifdef CONFIG_MAC80211_DEBUGFS
520 .add_sta_debugfs = rate_control_pid_add_sta_debugfs,
521 .remove_sta_debugfs = rate_control_pid_remove_sta_debugfs,
525 int __init rc80211_pid_init(void)
527 return ieee80211_rate_control_register(&mac80211_rcpid);
530 void rc80211_pid_exit(void)
532 ieee80211_rate_control_unregister(&mac80211_rcpid);