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 /* find & sort topmost throughput rates */
74 minstrel_sort_best_tp_rates(struct minstrel_sta_info *mi, int i, u8 *tp_list)
76 int j = MAX_THR_RATES;
78 while (j > 0 && mi->r[i].stats.cur_tp > mi->r[tp_list[j - 1]].stats.cur_tp)
80 if (j < MAX_THR_RATES - 1)
81 memmove(&tp_list[j + 1], &tp_list[j], MAX_THR_RATES - (j + 1));
82 if (j < MAX_THR_RATES)
87 minstrel_set_rate(struct minstrel_sta_info *mi, struct ieee80211_sta_rates *ratetbl,
90 struct minstrel_rate *r = &mi->r[idx];
92 ratetbl->rate[offset].idx = r->rix;
93 ratetbl->rate[offset].count = r->adjusted_retry_count;
94 ratetbl->rate[offset].count_cts = r->retry_count_cts;
95 ratetbl->rate[offset].count_rts = r->stats.retry_count_rtscts;
99 minstrel_update_rates(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
101 struct ieee80211_sta_rates *ratetbl;
104 ratetbl = kzalloc(sizeof(*ratetbl), GFP_ATOMIC);
108 /* Start with max_tp_rate */
109 minstrel_set_rate(mi, ratetbl, i++, mi->max_tp_rate[0]);
111 if (mp->hw->max_rates >= 3) {
112 /* At least 3 tx rates supported, use max_tp_rate2 next */
113 minstrel_set_rate(mi, ratetbl, i++, mi->max_tp_rate[1]);
116 if (mp->hw->max_rates >= 2) {
117 /* At least 2 tx rates supported, use max_prob_rate next */
118 minstrel_set_rate(mi, ratetbl, i++, mi->max_prob_rate);
121 /* Use lowest rate last */
122 ratetbl->rate[i].idx = mi->lowest_rix;
123 ratetbl->rate[i].count = mp->max_retry;
124 ratetbl->rate[i].count_cts = mp->max_retry;
125 ratetbl->rate[i].count_rts = mp->max_retry;
127 rate_control_set_rates(mp->hw, mi->sta, ratetbl);
131 * Recalculate success probabilities and counters for a given rate using EWMA
134 minstrel_calc_rate_stats(struct minstrel_rate_stats *mrs)
136 if (unlikely(mrs->attempts > 0)) {
137 mrs->sample_skipped = 0;
138 mrs->cur_prob = MINSTREL_FRAC(mrs->success, mrs->attempts);
139 if (unlikely(!mrs->att_hist))
140 mrs->prob_ewma = mrs->cur_prob;
142 mrs->prob_ewma = minstrel_ewma(mrs->prob_ewma,
143 mrs->cur_prob, EWMA_LEVEL);
144 mrs->att_hist += mrs->attempts;
145 mrs->succ_hist += mrs->success;
147 mrs->sample_skipped++;
150 mrs->last_success = mrs->success;
151 mrs->last_attempts = mrs->attempts;
157 minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
159 u8 tmp_tp_rate[MAX_THR_RATES];
160 u8 tmp_prob_rate = 0;
164 for (i = 0; i < MAX_THR_RATES; i++)
167 for (i = 0; i < mi->n_rates; i++) {
168 struct minstrel_rate *mr = &mi->r[i];
169 struct minstrel_rate_stats *mrs = &mi->r[i].stats;
171 usecs = mr->perfect_tx_time;
175 /* Update success probabilities per rate */
176 minstrel_calc_rate_stats(mrs);
178 /* Update throughput per rate, reset thr. below 10% success */
179 if (mrs->prob_ewma < MINSTREL_FRAC(10, 100))
182 mrs->cur_tp = mrs->prob_ewma * (1000000 / usecs);
184 /* Sample less often below the 10% chance of success.
185 * Sample less often above the 95% chance of success. */
186 if (mrs->prob_ewma > MINSTREL_FRAC(95, 100) ||
187 mrs->prob_ewma < MINSTREL_FRAC(10, 100)) {
188 mr->adjusted_retry_count = mrs->retry_count >> 1;
189 if (mr->adjusted_retry_count > 2)
190 mr->adjusted_retry_count = 2;
191 mr->sample_limit = 4;
193 mr->sample_limit = -1;
194 mr->adjusted_retry_count = mrs->retry_count;
196 if (!mr->adjusted_retry_count)
197 mr->adjusted_retry_count = 2;
199 minstrel_sort_best_tp_rates(mi, i, tmp_tp_rate);
201 /* To determine the most robust rate (max_prob_rate) used at
202 * 3rd mmr stage we distinct between two cases:
203 * (1) if any success probabilitiy >= 95%, out of those rates
204 * choose the maximum throughput rate as max_prob_rate
205 * (2) if all success probabilities < 95%, the rate with
206 * highest success probability is chosen as max_prob_rate */
207 if (mrs->prob_ewma >= MINSTREL_FRAC(95, 100)) {
208 if (mrs->cur_tp >= mi->r[tmp_prob_rate].stats.cur_tp)
211 if (mrs->prob_ewma >= mi->r[tmp_prob_rate].stats.prob_ewma)
216 /* Assign the new rate set */
217 memcpy(mi->max_tp_rate, tmp_tp_rate, sizeof(mi->max_tp_rate));
218 mi->max_prob_rate = tmp_prob_rate;
220 #ifdef CONFIG_MAC80211_DEBUGFS
221 /* use fixed index if set */
222 if (mp->fixed_rate_idx != -1) {
223 mi->max_tp_rate[0] = mp->fixed_rate_idx;
224 mi->max_tp_rate[1] = mp->fixed_rate_idx;
225 mi->max_prob_rate = mp->fixed_rate_idx;
229 /* Reset update timer */
230 mi->last_stats_update = jiffies;
232 minstrel_update_rates(mp, mi);
236 minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
237 struct ieee80211_sta *sta, void *priv_sta,
238 struct ieee80211_tx_info *info)
240 struct minstrel_priv *mp = priv;
241 struct minstrel_sta_info *mi = priv_sta;
242 struct ieee80211_tx_rate *ar = info->status.rates;
246 success = !!(info->flags & IEEE80211_TX_STAT_ACK);
248 for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
252 ndx = rix_to_ndx(mi, ar[i].idx);
256 mi->r[ndx].stats.attempts += ar[i].count;
258 if ((i != IEEE80211_TX_MAX_RATES - 1) && (ar[i + 1].idx < 0))
259 mi->r[ndx].stats.success += success;
262 if ((info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE) && (i >= 0))
263 mi->sample_packets++;
265 if (mi->sample_deferred > 0)
266 mi->sample_deferred--;
268 if (time_after(jiffies, mi->last_stats_update +
269 (mp->update_interval * HZ) / 1000))
270 minstrel_update_stats(mp, mi);
274 static inline unsigned int
275 minstrel_get_retry_count(struct minstrel_rate *mr,
276 struct ieee80211_tx_info *info)
278 u8 retry = mr->adjusted_retry_count;
280 if (info->control.use_rts)
281 retry = max_t(u8, 2, min(mr->stats.retry_count_rtscts, retry));
282 else if (info->control.use_cts_prot)
283 retry = max_t(u8, 2, min(mr->retry_count_cts, retry));
289 minstrel_get_next_sample(struct minstrel_sta_info *mi)
291 unsigned int sample_ndx;
292 sample_ndx = SAMPLE_TBL(mi, mi->sample_row, mi->sample_column);
294 if ((int) mi->sample_row >= mi->n_rates) {
297 if (mi->sample_column >= SAMPLE_COLUMNS)
298 mi->sample_column = 0;
304 minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
305 void *priv_sta, struct ieee80211_tx_rate_control *txrc)
307 struct sk_buff *skb = txrc->skb;
308 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
309 struct minstrel_sta_info *mi = priv_sta;
310 struct minstrel_priv *mp = priv;
311 struct ieee80211_tx_rate *rate = &info->control.rates[0];
312 struct minstrel_rate *msr, *mr;
319 /* management/no-ack frames do not use rate control */
320 if (rate_control_send_low(sta, priv_sta, txrc))
323 /* check multi-rate-retry capabilities & adjust lookaround_rate */
324 mrr_capable = mp->has_mrr &&
326 !txrc->bss_conf->use_cts_prot;
328 sampling_ratio = mp->lookaround_rate_mrr;
330 sampling_ratio = mp->lookaround_rate;
332 /* increase sum packet counter */
335 #ifdef CONFIG_MAC80211_DEBUGFS
336 if (mp->fixed_rate_idx != -1)
340 delta = (mi->total_packets * sampling_ratio / 100) -
341 (mi->sample_packets + mi->sample_deferred / 2);
343 /* delta < 0: no sampling required */
344 prev_sample = mi->prev_sample;
345 mi->prev_sample = false;
346 if (delta < 0 || (!mrr_capable && prev_sample))
349 if (mi->total_packets >= 10000) {
350 mi->sample_deferred = 0;
351 mi->sample_packets = 0;
352 mi->total_packets = 0;
353 } else if (delta > mi->n_rates * 2) {
354 /* With multi-rate retry, not every planned sample
355 * attempt actually gets used, due to the way the retry
356 * chain is set up - [max_tp,sample,prob,lowest] for
357 * sample_rate < max_tp.
359 * If there's too much sampling backlog and the link
360 * starts getting worse, minstrel would start bursting
361 * out lots of sampling frames, which would result
362 * in a large throughput loss. */
363 mi->sample_packets += (delta - mi->n_rates * 2);
366 /* get next random rate sample */
367 ndx = minstrel_get_next_sample(mi);
369 mr = &mi->r[mi->max_tp_rate[0]];
371 /* Decide if direct ( 1st mrr stage) or indirect (2nd mrr stage)
372 * rate sampling method should be used.
373 * Respect such rates that are not sampled for 20 interations.
376 msr->perfect_tx_time > mr->perfect_tx_time &&
377 msr->stats.sample_skipped < 20) {
378 /* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
379 * packets that have the sampling rate deferred to the
380 * second MRR stage. Increase the sample counter only
381 * if the deferred sample rate was actually used.
382 * Use the sample_deferred counter to make sure that
383 * the sampling is not done in large bursts */
384 info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
386 mi->sample_deferred++;
388 if (!msr->sample_limit)
391 mi->sample_packets++;
392 if (msr->sample_limit > 0)
396 /* If we're not using MRR and the sampling rate already
397 * has a probability of >95%, we shouldn't be attempting
398 * to use it, as this only wastes precious airtime */
400 (mi->r[ndx].stats.prob_ewma > MINSTREL_FRAC(95, 100)))
403 mi->prev_sample = true;
405 rate->idx = mi->r[ndx].rix;
406 rate->count = minstrel_get_retry_count(&mi->r[ndx], info);
411 calc_rate_durations(enum ieee80211_band band,
412 struct minstrel_rate *d,
413 struct ieee80211_rate *rate,
414 struct cfg80211_chan_def *chandef)
416 int erp = !!(rate->flags & IEEE80211_RATE_ERP_G);
417 int shift = ieee80211_chandef_get_shift(chandef);
419 d->perfect_tx_time = ieee80211_frame_duration(band, 1200,
420 DIV_ROUND_UP(rate->bitrate, 1 << shift), erp, 1,
422 d->ack_time = ieee80211_frame_duration(band, 10,
423 DIV_ROUND_UP(rate->bitrate, 1 << shift), erp, 1,
428 init_sample_table(struct minstrel_sta_info *mi)
430 unsigned int i, col, new_idx;
433 mi->sample_column = 0;
435 memset(mi->sample_table, 0xff, SAMPLE_COLUMNS * mi->n_rates);
437 for (col = 0; col < SAMPLE_COLUMNS; col++) {
438 prandom_bytes(rnd, sizeof(rnd));
439 for (i = 0; i < mi->n_rates; i++) {
440 new_idx = (i + rnd[i & 7]) % mi->n_rates;
441 while (SAMPLE_TBL(mi, new_idx, col) != 0xff)
442 new_idx = (new_idx + 1) % mi->n_rates;
444 SAMPLE_TBL(mi, new_idx, col) = i;
450 minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,
451 struct cfg80211_chan_def *chandef,
452 struct ieee80211_sta *sta, void *priv_sta)
454 struct minstrel_sta_info *mi = priv_sta;
455 struct minstrel_priv *mp = priv;
456 struct ieee80211_rate *ctl_rate;
457 unsigned int i, n = 0;
458 unsigned int t_slot = 9; /* FIXME: get real slot time */
462 mi->lowest_rix = rate_lowest_index(sband, sta);
463 ctl_rate = &sband->bitrates[mi->lowest_rix];
464 mi->sp_ack_dur = ieee80211_frame_duration(sband->band, 10,
466 !!(ctl_rate->flags & IEEE80211_RATE_ERP_G), 1,
467 ieee80211_chandef_get_shift(chandef));
469 rate_flags = ieee80211_chandef_rate_flags(&mp->hw->conf.chandef);
470 memset(mi->max_tp_rate, 0, sizeof(mi->max_tp_rate));
471 mi->max_prob_rate = 0;
473 for (i = 0; i < sband->n_bitrates; i++) {
474 struct minstrel_rate *mr = &mi->r[n];
475 struct minstrel_rate_stats *mrs = &mi->r[n].stats;
476 unsigned int tx_time = 0, tx_time_cts = 0, tx_time_rtscts = 0;
477 unsigned int tx_time_single;
478 unsigned int cw = mp->cw_min;
481 if (!rate_supported(sta, sband->band, i))
483 if ((rate_flags & sband->bitrates[i].flags) != rate_flags)
487 memset(mr, 0, sizeof(*mr));
488 memset(mrs, 0, sizeof(*mrs));
491 shift = ieee80211_chandef_get_shift(chandef);
492 mr->bitrate = DIV_ROUND_UP(sband->bitrates[i].bitrate,
494 calc_rate_durations(sband->band, mr, &sband->bitrates[i],
497 /* calculate maximum number of retransmissions before
498 * fallback (based on maximum segment size) */
499 mr->sample_limit = -1;
500 mrs->retry_count = 1;
501 mr->retry_count_cts = 1;
502 mrs->retry_count_rtscts = 1;
503 tx_time = mr->perfect_tx_time + mi->sp_ack_dur;
505 /* add one retransmission */
506 tx_time_single = mr->ack_time + mr->perfect_tx_time;
508 /* contention window */
509 tx_time_single += (t_slot * cw) >> 1;
510 cw = min((cw << 1) | 1, mp->cw_max);
512 tx_time += tx_time_single;
513 tx_time_cts += tx_time_single + mi->sp_ack_dur;
514 tx_time_rtscts += tx_time_single + 2 * mi->sp_ack_dur;
515 if ((tx_time_cts < mp->segment_size) &&
516 (mr->retry_count_cts < mp->max_retry))
517 mr->retry_count_cts++;
518 if ((tx_time_rtscts < mp->segment_size) &&
519 (mrs->retry_count_rtscts < mp->max_retry))
520 mrs->retry_count_rtscts++;
521 } while ((tx_time < mp->segment_size) &&
522 (++mr->stats.retry_count < mp->max_retry));
523 mr->adjusted_retry_count = mrs->retry_count;
524 if (!(sband->bitrates[i].flags & IEEE80211_RATE_ERP_G))
525 mr->retry_count_cts = mrs->retry_count;
528 for (i = n; i < sband->n_bitrates; i++) {
529 struct minstrel_rate *mr = &mi->r[i];
534 mi->last_stats_update = jiffies;
536 init_sample_table(mi);
537 minstrel_update_rates(mp, mi);
541 minstrel_alloc_sta(void *priv, struct ieee80211_sta *sta, gfp_t gfp)
543 struct ieee80211_supported_band *sband;
544 struct minstrel_sta_info *mi;
545 struct minstrel_priv *mp = priv;
546 struct ieee80211_hw *hw = mp->hw;
550 mi = kzalloc(sizeof(struct minstrel_sta_info), gfp);
554 for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
555 sband = hw->wiphy->bands[i];
556 if (sband && sband->n_bitrates > max_rates)
557 max_rates = sband->n_bitrates;
560 mi->r = kzalloc(sizeof(struct minstrel_rate) * max_rates, gfp);
564 mi->sample_table = kmalloc(SAMPLE_COLUMNS * max_rates, gfp);
565 if (!mi->sample_table)
568 mi->last_stats_update = jiffies;
579 minstrel_free_sta(void *priv, struct ieee80211_sta *sta, void *priv_sta)
581 struct minstrel_sta_info *mi = priv_sta;
583 kfree(mi->sample_table);
589 minstrel_init_cck_rates(struct minstrel_priv *mp)
591 static const int bitrates[4] = { 10, 20, 55, 110 };
592 struct ieee80211_supported_band *sband;
593 u32 rate_flags = ieee80211_chandef_rate_flags(&mp->hw->conf.chandef);
596 sband = mp->hw->wiphy->bands[IEEE80211_BAND_2GHZ];
600 for (i = 0, j = 0; i < sband->n_bitrates; i++) {
601 struct ieee80211_rate *rate = &sband->bitrates[i];
603 if (rate->flags & IEEE80211_RATE_ERP_G)
606 if ((rate_flags & sband->bitrates[i].flags) != rate_flags)
609 for (j = 0; j < ARRAY_SIZE(bitrates); j++) {
610 if (rate->bitrate != bitrates[j])
613 mp->cck_rates[j] = i;
620 minstrel_alloc(struct ieee80211_hw *hw, struct dentry *debugfsdir)
622 struct minstrel_priv *mp;
624 mp = kzalloc(sizeof(struct minstrel_priv), GFP_ATOMIC);
628 /* contention window settings
629 * Just an approximation. Using the per-queue values would complicate
630 * the calculations and is probably unnecessary */
634 /* number of packets (in %) to use for sampling other rates
635 * sample less often for non-mrr packets, because the overhead
636 * is much higher than with mrr */
637 mp->lookaround_rate = 5;
638 mp->lookaround_rate_mrr = 10;
640 /* maximum time that the hw is allowed to stay in one MRR segment */
641 mp->segment_size = 6000;
643 if (hw->max_rate_tries > 0)
644 mp->max_retry = hw->max_rate_tries;
646 /* safe default, does not necessarily have to match hw properties */
649 if (hw->max_rates >= 4)
653 mp->update_interval = 100;
655 #ifdef CONFIG_MAC80211_DEBUGFS
656 mp->fixed_rate_idx = (u32) -1;
657 mp->dbg_fixed_rate = debugfs_create_u32("fixed_rate_idx",
658 S_IRUGO | S_IWUGO, debugfsdir, &mp->fixed_rate_idx);
661 minstrel_init_cck_rates(mp);
667 minstrel_free(void *priv)
669 #ifdef CONFIG_MAC80211_DEBUGFS
670 debugfs_remove(((struct minstrel_priv *)priv)->dbg_fixed_rate);
675 static u32 minstrel_get_expected_throughput(void *priv_sta)
677 struct minstrel_sta_info *mi = priv_sta;
678 int idx = mi->max_tp_rate[0];
680 /* convert pkt per sec in kbps (1200 is the average pkt size used for
683 return MINSTREL_TRUNC(mi->r[idx].stats.cur_tp) * 1200 * 8 / 1024;
686 const struct rate_control_ops mac80211_minstrel = {
688 .tx_status_noskb = minstrel_tx_status,
689 .get_rate = minstrel_get_rate,
690 .rate_init = minstrel_rate_init,
691 .alloc = minstrel_alloc,
692 .free = minstrel_free,
693 .alloc_sta = minstrel_alloc_sta,
694 .free_sta = minstrel_free_sta,
695 #ifdef CONFIG_MAC80211_DEBUGFS
696 .add_sta_debugfs = minstrel_add_sta_debugfs,
697 .remove_sta_debugfs = minstrel_remove_sta_debugfs,
699 .get_expected_throughput = minstrel_get_expected_throughput,
703 rc80211_minstrel_init(void)
705 return ieee80211_rate_control_register(&mac80211_minstrel);
709 rc80211_minstrel_exit(void)
711 ieee80211_rate_control_unregister(&mac80211_minstrel);