2 * Copyright (C) 2008 Felix Fietkau <nbd@openwrt.org>
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
9 * Copyright (C) 2005-2007 Derek Smithies <derek@indranet.co.nz>
10 * Sponsored by Indranet Technologies Ltd
13 * Copyright (c) 2005 John Bicket
14 * All rights reserved.
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions
19 * 1. Redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer,
21 * without modification.
22 * 2. Redistributions in binary form must reproduce at minimum a disclaimer
23 * similar to the "NO WARRANTY" disclaimer below ("Disclaimer") and any
24 * redistribution must be conditioned upon including a substantially
25 * similar Disclaimer requirement for further binary redistribution.
26 * 3. Neither the names of the above-listed copyright holders nor the names
27 * of any contributors may be used to endorse or promote products derived
28 * from this software without specific prior written permission.
30 * Alternatively, this software may be distributed under the terms of the
31 * GNU General Public License ("GPL") version 2 as published by the Free
32 * Software Foundation.
35 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
36 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
37 * LIMITED TO, THE IMPLIED WARRANTIES OF NONINFRINGEMENT, MERCHANTIBILITY
38 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
39 * THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY,
40 * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
41 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
42 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
43 * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
44 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
45 * THE POSSIBILITY OF SUCH DAMAGES.
47 #include <linux/netdevice.h>
48 #include <linux/types.h>
49 #include <linux/skbuff.h>
50 #include <linux/debugfs.h>
51 #include <linux/random.h>
52 #include <linux/ieee80211.h>
53 #include <linux/slab.h>
54 #include <net/mac80211.h>
56 #include "rc80211_minstrel.h"
58 #define SAMPLE_TBL(_mi, _idx, _col) \
59 _mi->sample_table[(_idx * SAMPLE_COLUMNS) + _col]
61 /* convert mac80211 rate index to local array index */
63 rix_to_ndx(struct minstrel_sta_info *mi, int rix)
66 for (i = rix; i >= 0; i--)
67 if (mi->r[i].rix == rix)
72 /* return current EMWA throughput */
73 int minstrel_get_tp_avg(struct minstrel_rate *mr, int prob_ewma)
77 usecs = mr->perfect_tx_time;
81 /* reset thr. below 10% success */
82 if (mr->stats.prob_ewma < MINSTREL_FRAC(10, 100))
85 if (prob_ewma > MINSTREL_FRAC(90, 100))
86 return MINSTREL_TRUNC(100000 * (MINSTREL_FRAC(90, 100) / usecs));
88 return MINSTREL_TRUNC(100000 * (prob_ewma / usecs));
91 /* find & sort topmost throughput rates */
93 minstrel_sort_best_tp_rates(struct minstrel_sta_info *mi, int i, u8 *tp_list)
96 struct minstrel_rate_stats *tmp_mrs;
97 struct minstrel_rate_stats *cur_mrs = &mi->r[i].stats;
99 for (j = MAX_THR_RATES; j > 0; --j) {
100 tmp_mrs = &mi->r[tp_list[j - 1]].stats;
101 if (minstrel_get_tp_avg(&mi->r[i], cur_mrs->prob_ewma) <=
102 minstrel_get_tp_avg(&mi->r[tp_list[j - 1]], tmp_mrs->prob_ewma))
106 if (j < MAX_THR_RATES - 1)
107 memmove(&tp_list[j + 1], &tp_list[j], MAX_THR_RATES - (j + 1));
108 if (j < MAX_THR_RATES)
113 minstrel_set_rate(struct minstrel_sta_info *mi, struct ieee80211_sta_rates *ratetbl,
116 struct minstrel_rate *r = &mi->r[idx];
118 ratetbl->rate[offset].idx = r->rix;
119 ratetbl->rate[offset].count = r->adjusted_retry_count;
120 ratetbl->rate[offset].count_cts = r->retry_count_cts;
121 ratetbl->rate[offset].count_rts = r->stats.retry_count_rtscts;
125 minstrel_update_rates(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
127 struct ieee80211_sta_rates *ratetbl;
130 ratetbl = kzalloc(sizeof(*ratetbl), GFP_ATOMIC);
134 /* Start with max_tp_rate */
135 minstrel_set_rate(mi, ratetbl, i++, mi->max_tp_rate[0]);
137 if (mp->hw->max_rates >= 3) {
138 /* At least 3 tx rates supported, use max_tp_rate2 next */
139 minstrel_set_rate(mi, ratetbl, i++, mi->max_tp_rate[1]);
142 if (mp->hw->max_rates >= 2) {
143 /* At least 2 tx rates supported, use max_prob_rate next */
144 minstrel_set_rate(mi, ratetbl, i++, mi->max_prob_rate);
147 /* Use lowest rate last */
148 ratetbl->rate[i].idx = mi->lowest_rix;
149 ratetbl->rate[i].count = mp->max_retry;
150 ratetbl->rate[i].count_cts = mp->max_retry;
151 ratetbl->rate[i].count_rts = mp->max_retry;
153 rate_control_set_rates(mp->hw, mi->sta, ratetbl);
157 * Recalculate statistics and counters of a given rate
160 minstrel_calc_rate_stats(struct minstrel_rate_stats *mrs)
162 unsigned int cur_prob;
164 if (unlikely(mrs->attempts > 0)) {
165 mrs->sample_skipped = 0;
166 cur_prob = MINSTREL_FRAC(mrs->success, mrs->attempts);
167 if (unlikely(!mrs->att_hist)) {
168 mrs->prob_ewma = cur_prob;
170 /*update exponential weighted moving avarage */
171 mrs->prob_ewma = minstrel_ewma(mrs->prob_ewma,
175 mrs->att_hist += mrs->attempts;
176 mrs->succ_hist += mrs->success;
178 mrs->sample_skipped++;
181 mrs->last_success = mrs->success;
182 mrs->last_attempts = mrs->attempts;
188 minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
190 u8 tmp_tp_rate[MAX_THR_RATES];
191 u8 tmp_prob_rate = 0;
192 int i, tmp_cur_tp, tmp_prob_tp;
194 for (i = 0; i < MAX_THR_RATES; i++)
197 for (i = 0; i < mi->n_rates; i++) {
198 struct minstrel_rate *mr = &mi->r[i];
199 struct minstrel_rate_stats *mrs = &mi->r[i].stats;
200 struct minstrel_rate_stats *tmp_mrs = &mi->r[tmp_prob_rate].stats;
202 /* Update statistics of success probability per rate */
203 minstrel_calc_rate_stats(mrs);
205 /* Sample less often below the 10% chance of success.
206 * Sample less often above the 95% chance of success. */
207 if (mrs->prob_ewma > MINSTREL_FRAC(95, 100) ||
208 mrs->prob_ewma < MINSTREL_FRAC(10, 100)) {
209 mr->adjusted_retry_count = mrs->retry_count >> 1;
210 if (mr->adjusted_retry_count > 2)
211 mr->adjusted_retry_count = 2;
212 mr->sample_limit = 4;
214 mr->sample_limit = -1;
215 mr->adjusted_retry_count = mrs->retry_count;
217 if (!mr->adjusted_retry_count)
218 mr->adjusted_retry_count = 2;
220 minstrel_sort_best_tp_rates(mi, i, tmp_tp_rate);
222 /* To determine the most robust rate (max_prob_rate) used at
223 * 3rd mmr stage we distinct between two cases:
224 * (1) if any success probabilitiy >= 95%, out of those rates
225 * choose the maximum throughput rate as max_prob_rate
226 * (2) if all success probabilities < 95%, the rate with
227 * highest success probability is chosen as max_prob_rate */
228 if (mrs->prob_ewma >= MINSTREL_FRAC(95, 100)) {
229 tmp_cur_tp = minstrel_get_tp_avg(mr, mrs->prob_ewma);
230 tmp_prob_tp = minstrel_get_tp_avg(&mi->r[tmp_prob_rate],
232 if (tmp_cur_tp >= tmp_prob_tp)
235 if (mrs->prob_ewma >= tmp_mrs->prob_ewma)
240 /* Assign the new rate set */
241 memcpy(mi->max_tp_rate, tmp_tp_rate, sizeof(mi->max_tp_rate));
242 mi->max_prob_rate = tmp_prob_rate;
244 #ifdef CONFIG_MAC80211_DEBUGFS
245 /* use fixed index if set */
246 if (mp->fixed_rate_idx != -1) {
247 mi->max_tp_rate[0] = mp->fixed_rate_idx;
248 mi->max_tp_rate[1] = mp->fixed_rate_idx;
249 mi->max_prob_rate = mp->fixed_rate_idx;
253 /* Reset update timer */
254 mi->last_stats_update = jiffies;
256 minstrel_update_rates(mp, mi);
260 minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
261 void *priv_sta, struct ieee80211_tx_status *st)
263 struct ieee80211_tx_info *info = st->info;
264 struct minstrel_priv *mp = priv;
265 struct minstrel_sta_info *mi = priv_sta;
266 struct ieee80211_tx_rate *ar = info->status.rates;
270 success = !!(info->flags & IEEE80211_TX_STAT_ACK);
272 for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
273 if (ar[i].idx < 0 || !ar[i].count)
276 ndx = rix_to_ndx(mi, ar[i].idx);
280 mi->r[ndx].stats.attempts += ar[i].count;
282 if ((i != IEEE80211_TX_MAX_RATES - 1) && (ar[i + 1].idx < 0))
283 mi->r[ndx].stats.success += success;
286 if (time_after(jiffies, mi->last_stats_update +
287 (mp->update_interval * HZ) / 1000))
288 minstrel_update_stats(mp, mi);
292 static inline unsigned int
293 minstrel_get_retry_count(struct minstrel_rate *mr,
294 struct ieee80211_tx_info *info)
296 u8 retry = mr->adjusted_retry_count;
298 if (info->control.use_rts)
299 retry = max_t(u8, 2, min(mr->stats.retry_count_rtscts, retry));
300 else if (info->control.use_cts_prot)
301 retry = max_t(u8, 2, min(mr->retry_count_cts, retry));
307 minstrel_get_next_sample(struct minstrel_sta_info *mi)
309 unsigned int sample_ndx;
310 sample_ndx = SAMPLE_TBL(mi, mi->sample_row, mi->sample_column);
312 if ((int) mi->sample_row >= mi->n_rates) {
315 if (mi->sample_column >= SAMPLE_COLUMNS)
316 mi->sample_column = 0;
322 minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
323 void *priv_sta, struct ieee80211_tx_rate_control *txrc)
325 struct sk_buff *skb = txrc->skb;
326 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
327 struct minstrel_sta_info *mi = priv_sta;
328 struct minstrel_priv *mp = priv;
329 struct ieee80211_tx_rate *rate = &info->control.rates[0];
330 struct minstrel_rate *msr, *mr;
337 /* check multi-rate-retry capabilities & adjust lookaround_rate */
338 mrr_capable = mp->has_mrr &&
340 !txrc->bss_conf->use_cts_prot;
342 sampling_ratio = mp->lookaround_rate_mrr;
344 sampling_ratio = mp->lookaround_rate;
346 /* increase sum packet counter */
349 #ifdef CONFIG_MAC80211_DEBUGFS
350 if (mp->fixed_rate_idx != -1)
354 /* Don't use EAPOL frames for sampling on non-mrr hw */
355 if (mp->hw->max_rates == 1 &&
356 (info->control.flags & IEEE80211_TX_CTRL_PORT_CTRL_PROTO))
359 delta = (mi->total_packets * sampling_ratio / 100) -
362 /* delta < 0: no sampling required */
363 prev_sample = mi->prev_sample;
364 mi->prev_sample = false;
365 if (delta < 0 || (!mrr_capable && prev_sample))
368 if (mi->total_packets >= 10000) {
369 mi->sample_packets = 0;
370 mi->total_packets = 0;
371 } else if (delta > mi->n_rates * 2) {
372 /* With multi-rate retry, not every planned sample
373 * attempt actually gets used, due to the way the retry
374 * chain is set up - [max_tp,sample,prob,lowest] for
375 * sample_rate < max_tp.
377 * If there's too much sampling backlog and the link
378 * starts getting worse, minstrel would start bursting
379 * out lots of sampling frames, which would result
380 * in a large throughput loss. */
381 mi->sample_packets += (delta - mi->n_rates * 2);
384 /* get next random rate sample */
385 ndx = minstrel_get_next_sample(mi);
387 mr = &mi->r[mi->max_tp_rate[0]];
389 /* Decide if direct ( 1st mrr stage) or indirect (2nd mrr stage)
390 * rate sampling method should be used.
391 * Respect such rates that are not sampled for 20 interations.
393 if (msr->perfect_tx_time < mr->perfect_tx_time ||
394 msr->stats.sample_skipped >= 20) {
395 if (!msr->sample_limit)
398 mi->sample_packets++;
399 if (msr->sample_limit > 0)
403 /* If we're not using MRR and the sampling rate already
404 * has a probability of >95%, we shouldn't be attempting
405 * to use it, as this only wastes precious airtime */
407 (mi->r[ndx].stats.prob_ewma > MINSTREL_FRAC(95, 100)))
410 mi->prev_sample = true;
412 rate->idx = mi->r[ndx].rix;
413 rate->count = minstrel_get_retry_count(&mi->r[ndx], info);
414 info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
419 calc_rate_durations(enum nl80211_band band,
420 struct minstrel_rate *d,
421 struct ieee80211_rate *rate,
422 struct cfg80211_chan_def *chandef)
424 int erp = !!(rate->flags & IEEE80211_RATE_ERP_G);
425 int shift = ieee80211_chandef_get_shift(chandef);
427 d->perfect_tx_time = ieee80211_frame_duration(band, 1200,
428 DIV_ROUND_UP(rate->bitrate, 1 << shift), erp, 1,
430 d->ack_time = ieee80211_frame_duration(band, 10,
431 DIV_ROUND_UP(rate->bitrate, 1 << shift), erp, 1,
436 init_sample_table(struct minstrel_sta_info *mi)
438 unsigned int i, col, new_idx;
441 mi->sample_column = 0;
443 memset(mi->sample_table, 0xff, SAMPLE_COLUMNS * mi->n_rates);
445 for (col = 0; col < SAMPLE_COLUMNS; col++) {
446 prandom_bytes(rnd, sizeof(rnd));
447 for (i = 0; i < mi->n_rates; i++) {
448 new_idx = (i + rnd[i & 7]) % mi->n_rates;
449 while (SAMPLE_TBL(mi, new_idx, col) != 0xff)
450 new_idx = (new_idx + 1) % mi->n_rates;
452 SAMPLE_TBL(mi, new_idx, col) = i;
458 minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,
459 struct cfg80211_chan_def *chandef,
460 struct ieee80211_sta *sta, void *priv_sta)
462 struct minstrel_sta_info *mi = priv_sta;
463 struct minstrel_priv *mp = priv;
464 struct ieee80211_rate *ctl_rate;
465 unsigned int i, n = 0;
466 unsigned int t_slot = 9; /* FIXME: get real slot time */
470 mi->lowest_rix = rate_lowest_index(sband, sta);
471 ctl_rate = &sband->bitrates[mi->lowest_rix];
472 mi->sp_ack_dur = ieee80211_frame_duration(sband->band, 10,
474 !!(ctl_rate->flags & IEEE80211_RATE_ERP_G), 1,
475 ieee80211_chandef_get_shift(chandef));
477 rate_flags = ieee80211_chandef_rate_flags(&mp->hw->conf.chandef);
478 memset(mi->max_tp_rate, 0, sizeof(mi->max_tp_rate));
479 mi->max_prob_rate = 0;
481 for (i = 0; i < sband->n_bitrates; i++) {
482 struct minstrel_rate *mr = &mi->r[n];
483 struct minstrel_rate_stats *mrs = &mi->r[n].stats;
484 unsigned int tx_time = 0, tx_time_cts = 0, tx_time_rtscts = 0;
485 unsigned int tx_time_single;
486 unsigned int cw = mp->cw_min;
489 if (!rate_supported(sta, sband->band, i))
491 if ((rate_flags & sband->bitrates[i].flags) != rate_flags)
495 memset(mr, 0, sizeof(*mr));
496 memset(mrs, 0, sizeof(*mrs));
499 shift = ieee80211_chandef_get_shift(chandef);
500 mr->bitrate = DIV_ROUND_UP(sband->bitrates[i].bitrate,
502 calc_rate_durations(sband->band, mr, &sband->bitrates[i],
505 /* calculate maximum number of retransmissions before
506 * fallback (based on maximum segment size) */
507 mr->sample_limit = -1;
508 mrs->retry_count = 1;
509 mr->retry_count_cts = 1;
510 mrs->retry_count_rtscts = 1;
511 tx_time = mr->perfect_tx_time + mi->sp_ack_dur;
513 /* add one retransmission */
514 tx_time_single = mr->ack_time + mr->perfect_tx_time;
516 /* contention window */
517 tx_time_single += (t_slot * cw) >> 1;
518 cw = min((cw << 1) | 1, mp->cw_max);
520 tx_time += tx_time_single;
521 tx_time_cts += tx_time_single + mi->sp_ack_dur;
522 tx_time_rtscts += tx_time_single + 2 * mi->sp_ack_dur;
523 if ((tx_time_cts < mp->segment_size) &&
524 (mr->retry_count_cts < mp->max_retry))
525 mr->retry_count_cts++;
526 if ((tx_time_rtscts < mp->segment_size) &&
527 (mrs->retry_count_rtscts < mp->max_retry))
528 mrs->retry_count_rtscts++;
529 } while ((tx_time < mp->segment_size) &&
530 (++mr->stats.retry_count < mp->max_retry));
531 mr->adjusted_retry_count = mrs->retry_count;
532 if (!(sband->bitrates[i].flags & IEEE80211_RATE_ERP_G))
533 mr->retry_count_cts = mrs->retry_count;
536 for (i = n; i < sband->n_bitrates; i++) {
537 struct minstrel_rate *mr = &mi->r[i];
542 mi->last_stats_update = jiffies;
544 init_sample_table(mi);
545 minstrel_update_rates(mp, mi);
548 static u32 minstrel_get_expected_throughput(void *priv_sta)
550 struct minstrel_sta_info *mi = priv_sta;
551 struct minstrel_rate_stats *tmp_mrs;
552 int idx = mi->max_tp_rate[0];
555 /* convert pkt per sec in kbps (1200 is the average pkt size used for
558 tmp_mrs = &mi->r[idx].stats;
559 tmp_cur_tp = minstrel_get_tp_avg(&mi->r[idx], tmp_mrs->prob_ewma) * 10;
560 tmp_cur_tp = tmp_cur_tp * 1200 * 8 / 1024;
565 const struct rate_control_ops mac80211_minstrel = {
566 .tx_status_ext = minstrel_tx_status,
567 .get_rate = minstrel_get_rate,
568 .rate_init = minstrel_rate_init,
569 .get_expected_throughput = minstrel_get_expected_throughput,