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 <net/mac80211.h>
55 #include "rc80211_minstrel.h"
57 #define SAMPLE_COLUMNS 10
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)
74 use_low_rate(struct sk_buff *skb)
76 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
77 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
80 fc = le16_to_cpu(hdr->frame_control);
82 return ((info->flags & IEEE80211_TX_CTL_NO_ACK) ||
83 (fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_DATA);
88 minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
90 u32 max_tp = 0, index_max_tp = 0, index_max_tp2 = 0;
91 u32 max_prob = 0, index_max_prob = 0;
96 mi->stats_update = jiffies;
97 for (i = 0; i < mi->n_rates; i++) {
98 struct minstrel_rate *mr = &mi->r[i];
100 usecs = mr->perfect_tx_time;
104 /* To avoid rounding issues, probabilities scale from 0 (0%)
107 p = (mr->success * 18000) / mr->attempts;
108 mr->succ_hist += mr->success;
109 mr->att_hist += mr->attempts;
111 p = ((p * (100 - mp->ewma_level)) + (mr->probability *
112 mp->ewma_level)) / 100;
114 mr->cur_tp = p * (1000000 / usecs);
117 mr->last_success = mr->success;
118 mr->last_attempts = mr->attempts;
122 /* Sample less often below the 10% chance of success.
123 * Sample less often above the 95% chance of success. */
124 if ((mr->probability > 17100) || (mr->probability < 1800)) {
125 mr->adjusted_retry_count = mr->retry_count >> 1;
126 if (mr->adjusted_retry_count > 2)
127 mr->adjusted_retry_count = 2;
128 mr->sample_limit = 4;
130 mr->sample_limit = -1;
131 mr->adjusted_retry_count = mr->retry_count;
133 if (!mr->adjusted_retry_count)
134 mr->adjusted_retry_count = 2;
137 for (i = 0; i < mi->n_rates; i++) {
138 struct minstrel_rate *mr = &mi->r[i];
139 if (max_tp < mr->cur_tp) {
143 if (max_prob < mr->probability) {
145 max_prob = mr->probability;
150 for (i = 0; i < mi->n_rates; i++) {
151 struct minstrel_rate *mr = &mi->r[i];
153 if (i == index_max_tp)
156 if (max_tp < mr->cur_tp) {
161 mi->max_tp_rate = index_max_tp;
162 mi->max_tp_rate2 = index_max_tp2;
163 mi->max_prob_rate = index_max_prob;
167 minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
168 struct ieee80211_sta *sta, void *priv_sta,
171 struct minstrel_sta_info *mi = priv_sta;
172 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
173 struct ieee80211_tx_rate *ar = info->status.rates;
177 success = !!(info->flags & IEEE80211_TX_STAT_ACK);
179 for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
183 ndx = rix_to_ndx(mi, ar[i].idx);
187 mi->r[ndx].attempts += ar[i].count;
189 if ((i != IEEE80211_TX_MAX_RATES - 1) && (ar[i + 1].idx < 0))
190 mi->r[ndx].success += success;
193 if ((info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE) && (i >= 0))
196 if (mi->sample_deferred > 0)
197 mi->sample_deferred--;
201 static inline unsigned int
202 minstrel_get_retry_count(struct minstrel_rate *mr,
203 struct ieee80211_tx_info *info)
205 unsigned int retry = mr->adjusted_retry_count;
207 if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_RTS_CTS)
208 retry = max(2U, min(mr->retry_count_rtscts, retry));
209 else if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_CTS_PROTECT)
210 retry = max(2U, min(mr->retry_count_cts, retry));
216 minstrel_get_next_sample(struct minstrel_sta_info *mi)
218 unsigned int sample_ndx;
219 sample_ndx = SAMPLE_TBL(mi, mi->sample_idx, mi->sample_column);
221 if ((int) mi->sample_idx > (mi->n_rates - 2)) {
224 if (mi->sample_column >= SAMPLE_COLUMNS)
225 mi->sample_column = 0;
231 minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
232 void *priv_sta, struct ieee80211_tx_rate_control *txrc)
234 struct sk_buff *skb = txrc->skb;
235 struct ieee80211_supported_band *sband = txrc->sband;
236 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
237 struct minstrel_sta_info *mi = priv_sta;
238 struct minstrel_priv *mp = priv;
239 struct ieee80211_tx_rate *ar = info->control.rates;
240 unsigned int ndx, sample_ndx = 0;
242 bool sample_slower = false;
248 if (!sta || !mi || use_low_rate(skb)) {
249 ar[0].idx = rate_lowest_index(sband, sta);
250 if (info->flags & IEEE80211_TX_CTL_NO_ACK)
253 ar[0].count = mp->max_retry;
257 mrr = mp->has_mrr && !txrc->rts && !txrc->bss_conf->use_cts_prot;
259 if (time_after(jiffies, mi->stats_update + (mp->update_interval *
261 minstrel_update_stats(mp, mi);
263 ndx = mi->max_tp_rate;
266 sample_rate = mp->lookaround_rate_mrr;
268 sample_rate = mp->lookaround_rate;
271 delta = (mi->packet_count * sample_rate / 100) -
272 (mi->sample_count + mi->sample_deferred / 2);
274 /* delta > 0: sampling required */
275 if ((delta > 0) && (mrr || !mi->prev_sample)) {
276 struct minstrel_rate *msr;
277 if (mi->packet_count >= 10000) {
278 mi->sample_deferred = 0;
279 mi->sample_count = 0;
280 mi->packet_count = 0;
281 } else if (delta > mi->n_rates * 2) {
282 /* With multi-rate retry, not every planned sample
283 * attempt actually gets used, due to the way the retry
284 * chain is set up - [max_tp,sample,prob,lowest] for
285 * sample_rate < max_tp.
287 * If there's too much sampling backlog and the link
288 * starts getting worse, minstrel would start bursting
289 * out lots of sampling frames, which would result
290 * in a large throughput loss. */
291 mi->sample_count += (delta - mi->n_rates * 2);
294 sample_ndx = minstrel_get_next_sample(mi);
295 msr = &mi->r[sample_ndx];
297 sample_slower = mrr && (msr->perfect_tx_time >
298 mi->r[ndx].perfect_tx_time);
300 if (!sample_slower) {
301 if (msr->sample_limit != 0) {
304 if (msr->sample_limit > 0)
310 /* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
311 * packets that have the sampling rate deferred to the
312 * second MRR stage. Increase the sample counter only
313 * if the deferred sample rate was actually used.
314 * Use the sample_deferred counter to make sure that
315 * the sampling is not done in large bursts */
316 info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
317 mi->sample_deferred++;
320 mi->prev_sample = sample;
322 /* If we're not using MRR and the sampling rate already
323 * has a probability of >95%, we shouldn't be attempting
324 * to use it, as this only wastes precious airtime */
325 if (!mrr && sample && (mi->r[ndx].probability > 17100))
326 ndx = mi->max_tp_rate;
328 ar[0].idx = mi->r[ndx].rix;
329 ar[0].count = minstrel_get_retry_count(&mi->r[ndx], info);
333 ar[0].count = mp->max_retry;
334 ar[1].idx = mi->lowest_rix;
335 ar[1].count = mp->max_retry;
342 mrr_ndx[0] = sample_ndx;
344 mrr_ndx[0] = mi->max_tp_rate;
346 mrr_ndx[0] = mi->max_tp_rate2;
348 mrr_ndx[1] = mi->max_prob_rate;
350 for (i = 1; i < 4; i++) {
351 ar[i].idx = mi->r[mrr_ndx[i - 1]].rix;
352 ar[i].count = mi->r[mrr_ndx[i - 1]].adjusted_retry_count;
358 calc_rate_durations(struct minstrel_sta_info *mi, struct ieee80211_local *local,
359 struct minstrel_rate *d, struct ieee80211_rate *rate)
361 int erp = !!(rate->flags & IEEE80211_RATE_ERP_G);
363 d->perfect_tx_time = ieee80211_frame_duration(local, 1200,
364 rate->bitrate, erp, 1);
365 d->ack_time = ieee80211_frame_duration(local, 10,
366 rate->bitrate, erp, 1);
370 init_sample_table(struct minstrel_sta_info *mi)
372 unsigned int i, col, new_idx;
373 unsigned int n_srates = mi->n_rates - 1;
376 mi->sample_column = 0;
378 memset(mi->sample_table, 0, SAMPLE_COLUMNS * mi->n_rates);
380 for (col = 0; col < SAMPLE_COLUMNS; col++) {
381 for (i = 0; i < n_srates; i++) {
382 get_random_bytes(rnd, sizeof(rnd));
383 new_idx = (i + rnd[i & 7]) % n_srates;
385 while (SAMPLE_TBL(mi, new_idx, col) != 0)
386 new_idx = (new_idx + 1) % n_srates;
388 /* Don't sample the slowest rate (i.e. slowest base
389 * rate). We must presume that the slowest rate works
390 * fine, or else other management frames will also be
391 * failing and the link will break */
392 SAMPLE_TBL(mi, new_idx, col) = i + 1;
398 minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,
399 struct ieee80211_sta *sta, void *priv_sta)
401 struct minstrel_sta_info *mi = priv_sta;
402 struct minstrel_priv *mp = priv;
403 struct ieee80211_local *local = hw_to_local(mp->hw);
404 struct ieee80211_rate *ctl_rate;
405 unsigned int i, n = 0;
406 unsigned int t_slot = 9; /* FIXME: get real slot time */
408 mi->lowest_rix = rate_lowest_index(sband, sta);
409 ctl_rate = &sband->bitrates[mi->lowest_rix];
410 mi->sp_ack_dur = ieee80211_frame_duration(local, 10, ctl_rate->bitrate,
411 !!(ctl_rate->flags & IEEE80211_RATE_ERP_G), 1);
413 for (i = 0; i < sband->n_bitrates; i++) {
414 struct minstrel_rate *mr = &mi->r[n];
415 unsigned int tx_time = 0, tx_time_cts = 0, tx_time_rtscts = 0;
416 unsigned int tx_time_single;
417 unsigned int cw = mp->cw_min;
419 if (!rate_supported(sta, sband->band, i))
422 memset(mr, 0, sizeof(*mr));
425 mr->bitrate = sband->bitrates[i].bitrate / 5;
426 calc_rate_durations(mi, local, mr,
427 &sband->bitrates[i]);
429 /* calculate maximum number of retransmissions before
430 * fallback (based on maximum segment size) */
431 mr->sample_limit = -1;
433 mr->retry_count_cts = 1;
434 mr->retry_count_rtscts = 1;
435 tx_time = mr->perfect_tx_time + mi->sp_ack_dur;
437 /* add one retransmission */
438 tx_time_single = mr->ack_time + mr->perfect_tx_time;
440 /* contention window */
441 tx_time_single += t_slot + min(cw, mp->cw_max);
444 tx_time += tx_time_single;
445 tx_time_cts += tx_time_single + mi->sp_ack_dur;
446 tx_time_rtscts += tx_time_single + 2 * mi->sp_ack_dur;
447 if ((tx_time_cts < mp->segment_size) &&
448 (mr->retry_count_cts < mp->max_retry))
449 mr->retry_count_cts++;
450 if ((tx_time_rtscts < mp->segment_size) &&
451 (mr->retry_count_rtscts < mp->max_retry))
452 mr->retry_count_rtscts++;
453 } while ((tx_time < mp->segment_size) &&
454 (++mr->retry_count < mp->max_retry));
455 mr->adjusted_retry_count = mr->retry_count;
458 for (i = n; i < sband->n_bitrates; i++) {
459 struct minstrel_rate *mr = &mi->r[i];
464 mi->stats_update = jiffies;
466 init_sample_table(mi);
470 minstrel_alloc_sta(void *priv, struct ieee80211_sta *sta, gfp_t gfp)
472 struct ieee80211_supported_band *sband;
473 struct minstrel_sta_info *mi;
474 struct minstrel_priv *mp = priv;
475 struct ieee80211_hw *hw = mp->hw;
479 mi = kzalloc(sizeof(struct minstrel_sta_info), gfp);
483 for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
484 sband = hw->wiphy->bands[i];
485 if (sband && sband->n_bitrates > max_rates)
486 max_rates = sband->n_bitrates;
489 mi->r = kzalloc(sizeof(struct minstrel_rate) * max_rates, gfp);
493 mi->sample_table = kmalloc(SAMPLE_COLUMNS * max_rates, gfp);
494 if (!mi->sample_table)
497 mi->stats_update = jiffies;
508 minstrel_free_sta(void *priv, struct ieee80211_sta *sta, void *priv_sta)
510 struct minstrel_sta_info *mi = priv_sta;
512 kfree(mi->sample_table);
518 minstrel_alloc(struct ieee80211_hw *hw, struct dentry *debugfsdir)
520 struct minstrel_priv *mp;
522 mp = kzalloc(sizeof(struct minstrel_priv), GFP_ATOMIC);
526 /* contention window settings
527 * Just an approximation. Using the per-queue values would complicate
528 * the calculations and is probably unnecessary */
532 /* number of packets (in %) to use for sampling other rates
533 * sample less often for non-mrr packets, because the overhead
534 * is much higher than with mrr */
535 mp->lookaround_rate = 5;
536 mp->lookaround_rate_mrr = 10;
538 /* moving average weight for EWMA */
541 /* maximum time that the hw is allowed to stay in one MRR segment */
542 mp->segment_size = 6000;
544 if (hw->max_rate_tries > 0)
545 mp->max_retry = hw->max_rate_tries;
547 /* safe default, does not necessarily have to match hw properties */
550 if (hw->max_rates >= 4)
554 mp->update_interval = 100;
560 minstrel_free(void *priv)
565 static struct rate_control_ops mac80211_minstrel = {
567 .tx_status = minstrel_tx_status,
568 .get_rate = minstrel_get_rate,
569 .rate_init = minstrel_rate_init,
570 .alloc = minstrel_alloc,
571 .free = minstrel_free,
572 .alloc_sta = minstrel_alloc_sta,
573 .free_sta = minstrel_free_sta,
574 #ifdef CONFIG_MAC80211_DEBUGFS
575 .add_sta_debugfs = minstrel_add_sta_debugfs,
576 .remove_sta_debugfs = minstrel_remove_sta_debugfs,
581 rc80211_minstrel_init(void)
583 return ieee80211_rate_control_register(&mac80211_minstrel);
587 rc80211_minstrel_exit(void)
589 ieee80211_rate_control_unregister(&mac80211_minstrel);