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 int cur = sta->txrate_idx;
81 sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
83 n_bitrates = sband->n_bitrates;
85 /* Map passed arguments to sorted values. */
86 cur_sorted = rinfo[cur].rev_index;
87 new_sorted = cur_sorted + adj;
91 new_sorted = rinfo[0].rev_index;
92 else if (new_sorted >= n_bitrates)
93 new_sorted = rinfo[n_bitrates - 1].rev_index;
98 /* Ensure that the rate decrease isn't disadvantageous. */
99 for (probe = cur_sorted; probe >= new_sorted; probe--)
100 if (rinfo[probe].diff <= rinfo[cur_sorted].diff &&
101 rate_supported(sta, band, rinfo[probe].index))
104 /* Look for rate increase with zero (or below) cost. */
105 for (probe = new_sorted + 1; probe < n_bitrates; probe++)
106 if (rinfo[probe].diff <= rinfo[new_sorted].diff &&
107 rate_supported(sta, band, rinfo[probe].index))
111 /* Fit the rate found to the nearest supported rate. */
113 if (rate_supported(sta, band, rinfo[tmp].index)) {
114 sta->txrate_idx = rinfo[tmp].index;
121 } while (tmp < n_bitrates && tmp >= 0);
123 #ifdef CONFIG_MAC80211_DEBUGFS
124 rate_control_pid_event_rate_change(
125 &((struct rc_pid_sta_info *)sta->rate_ctrl_priv)->events,
126 sta->txrate_idx, sband->bitrates[sta->txrate_idx].bitrate);
130 /* Normalize the failed frames per-rate differences. */
131 static void rate_control_pid_normalize(struct rc_pid_info *pinfo, int l)
133 int i, norm_offset = pinfo->norm_offset;
134 struct rc_pid_rateinfo *r = pinfo->rinfo;
136 if (r[0].diff > norm_offset)
137 r[0].diff -= norm_offset;
138 else if (r[0].diff < -norm_offset)
139 r[0].diff += norm_offset;
140 for (i = 0; i < l - 1; i++)
141 if (r[i + 1].diff > r[i].diff + norm_offset)
142 r[i + 1].diff -= norm_offset;
143 else if (r[i + 1].diff <= r[i].diff)
144 r[i + 1].diff += norm_offset;
147 static void rate_control_pid_sample(struct rc_pid_info *pinfo,
148 struct ieee80211_local *local,
149 struct sta_info *sta)
151 #ifdef CONFIG_MAC80211_MESH
152 struct ieee80211_sub_if_data *sdata = sta->sdata;
154 struct rc_pid_sta_info *spinfo = sta->rate_ctrl_priv;
155 struct rc_pid_rateinfo *rinfo = pinfo->rinfo;
156 struct ieee80211_supported_band *sband;
163 unsigned long period;
165 sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
166 spinfo = sta->rate_ctrl_priv;
168 /* In case nothing happened during the previous control interval, turn
169 * the sharpening factor on. */
170 period = (HZ * pinfo->sampling_period + 500) / 1000;
173 if (jiffies - spinfo->last_sample > 2 * period)
174 spinfo->sharp_cnt = pinfo->sharpen_duration;
176 spinfo->last_sample = jiffies;
178 /* This should never happen, but in case, we assume the old sample is
179 * still a good measurement and copy it. */
180 if (unlikely(spinfo->tx_num_xmit == 0))
181 pf = spinfo->last_pf;
183 pf = spinfo->tx_num_failed * 100 / spinfo->tx_num_xmit;
184 #ifdef CONFIG_MAC80211_MESH
186 sdata->vif.type == IEEE80211_IF_TYPE_MESH_POINT)
187 mesh_plink_broken(sta);
189 pf <<= RC_PID_ARITH_SHIFT;
190 sta->fail_avg = ((pf + (spinfo->last_pf << 3)) / 9)
191 >> RC_PID_ARITH_SHIFT;
194 spinfo->tx_num_xmit = 0;
195 spinfo->tx_num_failed = 0;
197 /* If we just switched rate, update the rate behaviour info. */
198 if (pinfo->oldrate != sta->txrate_idx) {
200 i = rinfo[pinfo->oldrate].rev_index;
201 j = rinfo[sta->txrate_idx].rev_index;
203 tmp = (pf - spinfo->last_pf);
204 tmp = RC_PID_DO_ARITH_RIGHT_SHIFT(tmp, RC_PID_ARITH_SHIFT);
206 rinfo[j].diff = rinfo[i].diff + tmp;
207 pinfo->oldrate = sta->txrate_idx;
209 rate_control_pid_normalize(pinfo, sband->n_bitrates);
211 /* Compute the proportional, integral and derivative errors. */
212 err_prop = (pinfo->target << RC_PID_ARITH_SHIFT) - pf;
214 err_avg = spinfo->err_avg_sc >> pinfo->smoothing_shift;
215 spinfo->err_avg_sc = spinfo->err_avg_sc - err_avg + err_prop;
216 err_int = spinfo->err_avg_sc >> pinfo->smoothing_shift;
218 err_der = (pf - spinfo->last_pf) *
219 (1 + pinfo->sharpen_factor * spinfo->sharp_cnt);
220 spinfo->last_pf = pf;
221 if (spinfo->sharp_cnt)
224 #ifdef CONFIG_MAC80211_DEBUGFS
225 rate_control_pid_event_pf_sample(&spinfo->events, pf, err_prop, err_int,
229 /* Compute the controller output. */
230 adj = (err_prop * pinfo->coeff_p + err_int * pinfo->coeff_i
231 + err_der * pinfo->coeff_d);
232 adj = RC_PID_DO_ARITH_RIGHT_SHIFT(adj, 2 * RC_PID_ARITH_SHIFT);
236 rate_control_pid_adjust_rate(local, sta, adj, rinfo);
239 static void rate_control_pid_tx_status(void *priv, struct net_device *dev,
242 struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
243 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
244 struct ieee80211_sub_if_data *sdata;
245 struct rc_pid_info *pinfo = priv;
246 struct sta_info *sta;
247 struct rc_pid_sta_info *spinfo;
248 unsigned long period;
249 struct ieee80211_supported_band *sband;
250 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
254 sta = sta_info_get(local, hdr->addr1);
255 sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
260 /* Don't update the state if we're not controlling the rate. */
262 if (sdata->force_unicast_rateidx > -1) {
263 sta->txrate_idx = sdata->max_ratectrl_rateidx;
267 /* Ignore all frames that were sent with a different rate than the rate
268 * we currently advise mac80211 to use. */
269 if (info->tx_rate_idx != sta->txrate_idx)
272 spinfo = sta->rate_ctrl_priv;
273 spinfo->tx_num_xmit++;
275 #ifdef CONFIG_MAC80211_DEBUGFS
276 rate_control_pid_event_tx_status(&spinfo->events, info);
279 /* We count frames that totally failed to be transmitted as two bad
280 * frames, those that made it out but had some retries as one good and
282 if (info->status.excessive_retries) {
283 spinfo->tx_num_failed += 2;
284 spinfo->tx_num_xmit++;
285 } else if (info->status.retry_count) {
286 spinfo->tx_num_failed++;
287 spinfo->tx_num_xmit++;
290 if (info->status.excessive_retries) {
291 sta->tx_retry_failed++;
292 sta->tx_num_consecutive_failures++;
293 sta->tx_num_mpdu_fail++;
295 sta->tx_num_consecutive_failures = 0;
296 sta->tx_num_mpdu_ok++;
298 sta->tx_retry_count += info->status.retry_count;
299 sta->tx_num_mpdu_fail += info->status.retry_count;
301 /* Update PID controller state. */
302 period = (HZ * pinfo->sampling_period + 500) / 1000;
305 if (time_after(jiffies, spinfo->last_sample + period))
306 rate_control_pid_sample(pinfo, local, sta);
312 static void rate_control_pid_get_rate(void *priv, struct net_device *dev,
313 struct ieee80211_supported_band *sband,
315 struct rate_selection *sel)
317 struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
318 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
319 struct ieee80211_sub_if_data *sdata;
320 struct sta_info *sta;
326 sta = sta_info_get(local, hdr->addr1);
328 /* Send management frames and broadcast/multicast data using lowest
330 fc = le16_to_cpu(hdr->frame_control);
331 if ((fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_DATA ||
332 is_multicast_ether_addr(hdr->addr1) || !sta) {
333 sel->rate_idx = rate_lowest_index(local, sband, sta);
338 /* If a forced rate is in effect, select it. */
339 sdata = IEEE80211_DEV_TO_SUB_IF(dev);
340 if (sdata->force_unicast_rateidx > -1)
341 sta->txrate_idx = sdata->force_unicast_rateidx;
343 rateidx = sta->txrate_idx;
345 if (rateidx >= sband->n_bitrates)
346 rateidx = sband->n_bitrates - 1;
348 sta->last_txrate_idx = rateidx;
352 sel->rate_idx = rateidx;
354 #ifdef CONFIG_MAC80211_DEBUGFS
355 rate_control_pid_event_tx_rate(
356 &((struct rc_pid_sta_info *) sta->rate_ctrl_priv)->events,
357 rateidx, sband->bitrates[rateidx].bitrate);
361 static void rate_control_pid_rate_init(void *priv, void *priv_sta,
362 struct ieee80211_local *local,
363 struct sta_info *sta)
365 /* TODO: This routine should consider using RSSI from previous packets
366 * as we need to have IEEE 802.1X auth succeed immediately after assoc..
367 * Until that method is implemented, we will use the lowest supported
368 * rate as a workaround. */
369 struct ieee80211_supported_band *sband;
371 sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
372 sta->txrate_idx = rate_lowest_index(local, sband, sta);
376 static void *rate_control_pid_alloc(struct ieee80211_local *local)
378 struct rc_pid_info *pinfo;
379 struct rc_pid_rateinfo *rinfo;
380 struct ieee80211_supported_band *sband;
383 #ifdef CONFIG_MAC80211_DEBUGFS
384 struct rc_pid_debugfs_entries *de;
387 sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
389 pinfo = kmalloc(sizeof(*pinfo), GFP_ATOMIC);
393 /* We can safely assume that sband won't change unless we get
395 rinfo = kmalloc(sizeof(*rinfo) * sband->n_bitrates, GFP_ATOMIC);
401 pinfo->target = RC_PID_TARGET_PF;
402 pinfo->sampling_period = RC_PID_INTERVAL;
403 pinfo->coeff_p = RC_PID_COEFF_P;
404 pinfo->coeff_i = RC_PID_COEFF_I;
405 pinfo->coeff_d = RC_PID_COEFF_D;
406 pinfo->smoothing_shift = RC_PID_SMOOTHING_SHIFT;
407 pinfo->sharpen_factor = RC_PID_SHARPENING_FACTOR;
408 pinfo->sharpen_duration = RC_PID_SHARPENING_DURATION;
409 pinfo->norm_offset = RC_PID_NORM_OFFSET;
410 pinfo->rinfo = rinfo;
413 /* Sort the rates. This is optimized for the most common case (i.e.
414 * almost-sorted CCK+OFDM rates). Kind of bubble-sort with reversed
416 for (i = 0; i < sband->n_bitrates; i++) {
418 rinfo[i].rev_index = i;
419 if (RC_PID_FAST_START)
422 rinfo[i].diff = i * pinfo->norm_offset;
424 for (i = 1; i < sband->n_bitrates; i++) {
426 for (j = 0; j < sband->n_bitrates - i; j++)
427 if (unlikely(sband->bitrates[rinfo[j].index].bitrate >
428 sband->bitrates[rinfo[j + 1].index].bitrate)) {
429 tmp = rinfo[j].index;
430 rinfo[j].index = rinfo[j + 1].index;
431 rinfo[j + 1].index = tmp;
432 rinfo[rinfo[j].index].rev_index = j;
433 rinfo[rinfo[j + 1].index].rev_index = j + 1;
440 #ifdef CONFIG_MAC80211_DEBUGFS
441 de = &pinfo->dentries;
442 de->dir = debugfs_create_dir("rc80211_pid",
443 local->hw.wiphy->debugfsdir);
444 de->target = debugfs_create_u32("target_pf", S_IRUSR | S_IWUSR,
445 de->dir, &pinfo->target);
446 de->sampling_period = debugfs_create_u32("sampling_period",
447 S_IRUSR | S_IWUSR, de->dir,
448 &pinfo->sampling_period);
449 de->coeff_p = debugfs_create_u32("coeff_p", S_IRUSR | S_IWUSR,
450 de->dir, &pinfo->coeff_p);
451 de->coeff_i = debugfs_create_u32("coeff_i", S_IRUSR | S_IWUSR,
452 de->dir, &pinfo->coeff_i);
453 de->coeff_d = debugfs_create_u32("coeff_d", S_IRUSR | S_IWUSR,
454 de->dir, &pinfo->coeff_d);
455 de->smoothing_shift = debugfs_create_u32("smoothing_shift",
456 S_IRUSR | S_IWUSR, de->dir,
457 &pinfo->smoothing_shift);
458 de->sharpen_factor = debugfs_create_u32("sharpen_factor",
459 S_IRUSR | S_IWUSR, de->dir,
460 &pinfo->sharpen_factor);
461 de->sharpen_duration = debugfs_create_u32("sharpen_duration",
462 S_IRUSR | S_IWUSR, de->dir,
463 &pinfo->sharpen_duration);
464 de->norm_offset = debugfs_create_u32("norm_offset",
465 S_IRUSR | S_IWUSR, de->dir,
466 &pinfo->norm_offset);
472 static void rate_control_pid_free(void *priv)
474 struct rc_pid_info *pinfo = priv;
475 #ifdef CONFIG_MAC80211_DEBUGFS
476 struct rc_pid_debugfs_entries *de = &pinfo->dentries;
478 debugfs_remove(de->norm_offset);
479 debugfs_remove(de->sharpen_duration);
480 debugfs_remove(de->sharpen_factor);
481 debugfs_remove(de->smoothing_shift);
482 debugfs_remove(de->coeff_d);
483 debugfs_remove(de->coeff_i);
484 debugfs_remove(de->coeff_p);
485 debugfs_remove(de->sampling_period);
486 debugfs_remove(de->target);
487 debugfs_remove(de->dir);
494 static void rate_control_pid_clear(void *priv)
498 static void *rate_control_pid_alloc_sta(void *priv, gfp_t gfp)
500 struct rc_pid_sta_info *spinfo;
502 spinfo = kzalloc(sizeof(*spinfo), gfp);
506 spinfo->last_sample = jiffies;
508 #ifdef CONFIG_MAC80211_DEBUGFS
509 spin_lock_init(&spinfo->events.lock);
510 init_waitqueue_head(&spinfo->events.waitqueue);
516 static void rate_control_pid_free_sta(void *priv, void *priv_sta)
518 struct rc_pid_sta_info *spinfo = priv_sta;
522 static struct rate_control_ops mac80211_rcpid = {
524 .tx_status = rate_control_pid_tx_status,
525 .get_rate = rate_control_pid_get_rate,
526 .rate_init = rate_control_pid_rate_init,
527 .clear = rate_control_pid_clear,
528 .alloc = rate_control_pid_alloc,
529 .free = rate_control_pid_free,
530 .alloc_sta = rate_control_pid_alloc_sta,
531 .free_sta = rate_control_pid_free_sta,
532 #ifdef CONFIG_MAC80211_DEBUGFS
533 .add_sta_debugfs = rate_control_pid_add_sta_debugfs,
534 .remove_sta_debugfs = rate_control_pid_remove_sta_debugfs,
538 int __init rc80211_pid_init(void)
540 return ieee80211_rate_control_register(&mac80211_rcpid);
543 void rc80211_pid_exit(void)
545 ieee80211_rate_control_unregister(&mac80211_rcpid);