net/mac80211/rc80211_minstrel.c

   1 /*
   2  * Copyright (C) 2008 Felix Fietkau <nbd@openwrt.org>
   3  *
   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.
   7  *
   8  * Based on minstrel.c:
   9  *   Copyright (C) 2005-2007 Derek Smithies <derek@indranet.co.nz>
  10  *   Sponsored by Indranet Technologies Ltd
  11  *
  12  * Based on sample.c:
  13  *   Copyright (c) 2005 John Bicket
  14  *   All rights reserved.
  15  *
  16  *   Redistribution and use in source and binary forms, with or without
  17  *   modification, are permitted provided that the following conditions
  18  *   are met:
  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.
  29  *
  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.
  33  *
  34  *   NO WARRANTY
  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.
  46  */
  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>
  54 #include "rate.h"
  55 #include "rc80211_minstrel.h"
  56
  57 #define SAMPLE_COLUMNS  10
  58 #define SAMPLE_TBL(_mi, _idx, _col) \
  59                 _mi->sample_table[(_idx * SAMPLE_COLUMNS) + _col]
  60
  61 /* convert mac80211 rate index to local array index */
  62 static inline int
  63 rix_to_ndx(struct minstrel_sta_info *mi, int rix)
  64 {
  65         int i = rix;
  66         for (i = rix; i >= 0; i--)
  67                 if (mi->r[i].rix == rix)
  68                         break;
  69         WARN_ON(mi->r[i].rix != rix);
  70         return i;
  71 }
  72
  73 static inline bool
  74 use_low_rate(struct sk_buff *skb)
  75 {
  76         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
  77         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
  78         u16 fc;
  79
  80         fc = le16_to_cpu(hdr->frame_control);
  81
  82         return ((info->flags & IEEE80211_TX_CTL_NO_ACK) ||
  83                 (fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_DATA ||
  84                 is_multicast_ether_addr(hdr->addr1));
  85 }
  86
  87
  88 static void
  89 minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
  90 {
  91         u32 max_tp = 0, index_max_tp = 0, index_max_tp2 = 0;
  92         u32 max_prob = 0, index_max_prob = 0;
  93         u32 usecs;
  94         u32 p;
  95         int i;
  96
  97         mi->stats_update = jiffies;
  98         for (i = 0; i < mi->n_rates; i++) {
  99                 struct minstrel_rate *mr = &mi->r[i];
 100
 101                 usecs = mr->perfect_tx_time;
 102                 if (!usecs)
 103                         usecs = 1000000;
 104
 105                 /* To avoid rounding issues, probabilities scale from 0 (0%)
 106                  * to 18000 (100%) */
 107                 if (mr->attempts) {
 108                         p = (mr->success * 18000) / mr->attempts;
 109                         mr->succ_hist += mr->success;
 110                         mr->att_hist += mr->attempts;
 111                         mr->cur_prob = p;
 112                         p = ((p * (100 - mp->ewma_level)) + (mr->probability *
 113                                 mp->ewma_level)) / 100;
 114                         mr->probability = p;
 115                         mr->cur_tp = p * (1000000 / usecs);
 116                 }
 117
 118                 mr->last_success = mr->success;
 119                 mr->last_attempts = mr->attempts;
 120                 mr->success = 0;
 121                 mr->attempts = 0;
 122
 123                 /* Sample less often below the 10% chance of success.
 124                  * Sample less often above the 95% chance of success. */
 125                 if ((mr->probability > 17100) || (mr->probability < 1800)) {
 126                         mr->adjusted_retry_count = mr->retry_count >> 1;
 127                         if (mr->adjusted_retry_count > 2)
 128                                 mr->adjusted_retry_count = 2;
 129                         mr->sample_limit = 4;
 130                 } else {
 131                         mr->sample_limit = -1;
 132                         mr->adjusted_retry_count = mr->retry_count;
 133                 }
 134                 if (!mr->adjusted_retry_count)
 135                         mr->adjusted_retry_count = 2;
 136         }
 137
 138         for (i = 0; i < mi->n_rates; i++) {
 139                 struct minstrel_rate *mr = &mi->r[i];
 140                 if (max_tp < mr->cur_tp) {
 141                         index_max_tp = i;
 142                         max_tp = mr->cur_tp;
 143                 }
 144                 if (max_prob < mr->probability) {
 145                         index_max_prob = i;
 146                         max_prob = mr->probability;
 147                 }
 148         }
 149
 150         max_tp = 0;
 151         for (i = 0; i < mi->n_rates; i++) {
 152                 struct minstrel_rate *mr = &mi->r[i];
 153
 154                 if (i == index_max_tp)
 155                         continue;
 156
 157                 if (max_tp < mr->cur_tp) {
 158                         index_max_tp2 = i;
 159                         max_tp = mr->cur_tp;
 160                 }
 161         }
 162         mi->max_tp_rate = index_max_tp;
 163         mi->max_tp_rate2 = index_max_tp2;
 164         mi->max_prob_rate = index_max_prob;
 165 }
 166
 167 static void
 168 minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
 169                    struct ieee80211_sta *sta, void *priv_sta,
 170                    struct sk_buff *skb)
 171 {
 172         struct minstrel_sta_info *mi = priv_sta;
 173         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 174         struct ieee80211_tx_rate *ar = info->status.rates;
 175         int i, ndx;
 176         int success;
 177
 178         success = !!(info->flags & IEEE80211_TX_STAT_ACK);
 179
 180         for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
 181                 if (ar[i].idx < 0)
 182                         break;
 183
 184                 ndx = rix_to_ndx(mi, ar[i].idx);
 185                 mi->r[ndx].attempts += ar[i].count;
 186
 187                 if ((i != IEEE80211_TX_MAX_RATES - 1) && (ar[i + 1].idx < 0))
 188                         mi->r[ndx].success += success;
 189         }
 190
 191         if ((info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE) && (i >= 0))
 192                 mi->sample_count++;
 193
 194         if (mi->sample_deferred > 0)
 195                 mi->sample_deferred--;
 196 }
 197
 198
 199 static inline unsigned int
 200 minstrel_get_retry_count(struct minstrel_rate *mr,
 201                          struct ieee80211_tx_info *info)
 202 {
 203         unsigned int retry = mr->adjusted_retry_count;
 204
 205         if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_RTS_CTS)
 206                 retry = max(2U, min(mr->retry_count_rtscts, retry));
 207         else if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_CTS_PROTECT)
 208                 retry = max(2U, min(mr->retry_count_cts, retry));
 209         return retry;
 210 }
 211
 212
 213 static int
 214 minstrel_get_next_sample(struct minstrel_sta_info *mi)
 215 {
 216         unsigned int sample_ndx;
 217         sample_ndx = SAMPLE_TBL(mi, mi->sample_idx, mi->sample_column);
 218         mi->sample_idx++;
 219         if (mi->sample_idx > (mi->n_rates - 2)) {
 220                 mi->sample_idx = 0;
 221                 mi->sample_column++;
 222                 if (mi->sample_column >= SAMPLE_COLUMNS)
 223                         mi->sample_column = 0;
 224         }
 225         return sample_ndx;
 226 }
 227
 228 static void
 229 minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
 230                   void *priv_sta, struct ieee80211_tx_rate_control *txrc)
 231 {
 232         struct sk_buff *skb = txrc->skb;
 233         struct ieee80211_supported_band *sband = txrc->sband;
 234         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 235         struct minstrel_sta_info *mi = priv_sta;
 236         struct minstrel_priv *mp = priv;
 237         struct ieee80211_tx_rate *ar = info->control.rates;
 238         unsigned int ndx, sample_ndx = 0;
 239         bool mrr;
 240         bool sample_slower = false;
 241         bool sample = false;
 242         int i, delta;
 243         int mrr_ndx[3];
 244         int sample_rate;
 245
 246         if (!sta || !mi || use_low_rate(skb)) {
 247                 ar[0].idx = rate_lowest_index(sband, sta);
 248                 ar[0].count = mp->max_retry;
 249                 return;
 250         }
 251
 252         mrr = mp->has_mrr && !txrc->rts && !txrc->bss_conf->use_cts_prot;
 253
 254         if (time_after(jiffies, mi->stats_update + (mp->update_interval *
 255                         HZ) / 1000))
 256                 minstrel_update_stats(mp, mi);
 257
 258         ndx = mi->max_tp_rate;
 259
 260         if (mrr)
 261                 sample_rate = mp->lookaround_rate_mrr;
 262         else
 263                 sample_rate = mp->lookaround_rate;
 264
 265         mi->packet_count++;
 266         delta = (mi->packet_count * sample_rate / 100) -
 267                         (mi->sample_count + mi->sample_deferred / 2);
 268
 269         /* delta > 0: sampling required */
 270         if ((delta > 0) && (mrr || !mi->prev_sample)) {
 271                 struct minstrel_rate *msr;
 272                 if (mi->packet_count >= 10000) {
 273                         mi->sample_deferred = 0;
 274                         mi->sample_count = 0;
 275                         mi->packet_count = 0;
 276                 } else if (delta > mi->n_rates * 2) {
 277                         /* With multi-rate retry, not every planned sample
 278                          * attempt actually gets used, due to the way the retry
 279                          * chain is set up - [max_tp,sample,prob,lowest] for
 280                          * sample_rate < max_tp.
 281                          *
 282                          * If there's too much sampling backlog and the link
 283                          * starts getting worse, minstrel would start bursting
 284                          * out lots of sampling frames, which would result
 285                          * in a large throughput loss. */
 286                         mi->sample_count += (delta - mi->n_rates * 2);
 287                 }
 288
 289                 sample_ndx = minstrel_get_next_sample(mi);
 290                 msr = &mi->r[sample_ndx];
 291                 sample = true;
 292                 sample_slower = mrr && (msr->perfect_tx_time >
 293                         mi->r[ndx].perfect_tx_time);
 294
 295                 if (!sample_slower) {
 296                         if (msr->sample_limit != 0) {
 297                                 ndx = sample_ndx;
 298                                 mi->sample_count++;
 299                                 if (msr->sample_limit > 0)
 300                                         msr->sample_limit--;
 301                         } else {
 302                                 sample = false;
 303                         }
 304                 } else {
 305                         /* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
 306                          * packets that have the sampling rate deferred to the
 307                          * second MRR stage. Increase the sample counter only
 308                          * if the deferred sample rate was actually used.
 309                          * Use the sample_deferred counter to make sure that
 310                          * the sampling is not done in large bursts */
 311                         info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
 312                         mi->sample_deferred++;
 313                 }
 314         }
 315         mi->prev_sample = sample;
 316
 317         /* If we're not using MRR and the sampling rate already
 318          * has a probability of >95%, we shouldn't be attempting
 319          * to use it, as this only wastes precious airtime */
 320         if (!mrr && sample && (mi->r[ndx].probability > 17100))
 321                 ndx = mi->max_tp_rate;
 322
 323         ar[0].idx = mi->r[ndx].rix;
 324         ar[0].count = minstrel_get_retry_count(&mi->r[ndx], info);
 325
 326         if (!mrr) {
 327                 if (!sample)
 328                         ar[0].count = mp->max_retry;
 329                 ar[1].idx = mi->lowest_rix;
 330                 ar[1].count = mp->max_retry;
 331                 return;
 332         }
 333
 334         /* MRR setup */
 335         if (sample) {
 336                 if (sample_slower)
 337                         mrr_ndx[0] = sample_ndx;
 338                 else
 339                         mrr_ndx[0] = mi->max_tp_rate;
 340         } else {
 341                 mrr_ndx[0] = mi->max_tp_rate2;
 342         }
 343         mrr_ndx[1] = mi->max_prob_rate;
 344         mrr_ndx[2] = 0;
 345         for (i = 1; i < 4; i++) {
 346                 ar[i].idx = mi->r[mrr_ndx[i - 1]].rix;
 347                 ar[i].count = mi->r[mrr_ndx[i - 1]].adjusted_retry_count;
 348         }
 349 }
 350
 351
 352 static void
 353 calc_rate_durations(struct minstrel_sta_info *mi, struct ieee80211_local *local,
 354                     struct minstrel_rate *d, struct ieee80211_rate *rate)
 355 {
 356         int erp = !!(rate->flags & IEEE80211_RATE_ERP_G);
 357
 358         d->perfect_tx_time = ieee80211_frame_duration(local, 1200,
 359                         rate->bitrate, erp, 1);
 360         d->ack_time = ieee80211_frame_duration(local, 10,
 361                         rate->bitrate, erp, 1);
 362 }
 363
 364 static void
 365 init_sample_table(struct minstrel_sta_info *mi)
 366 {
 367         unsigned int i, col, new_idx;
 368         unsigned int n_srates = mi->n_rates - 1;
 369         u8 rnd[8];
 370
 371         mi->sample_column = 0;
 372         mi->sample_idx = 0;
 373         memset(mi->sample_table, 0, SAMPLE_COLUMNS * mi->n_rates);
 374
 375         for (col = 0; col < SAMPLE_COLUMNS; col++) {
 376                 for (i = 0; i < n_srates; i++) {
 377                         get_random_bytes(rnd, sizeof(rnd));
 378                         new_idx = (i + rnd[i & 7]) % n_srates;
 379
 380                         while (SAMPLE_TBL(mi, new_idx, col) != 0)
 381                                 new_idx = (new_idx + 1) % n_srates;
 382
 383                         /* Don't sample the slowest rate (i.e. slowest base
 384                          * rate). We must presume that the slowest rate works
 385                          * fine, or else other management frames will also be
 386                          * failing and the link will break */
 387                         SAMPLE_TBL(mi, new_idx, col) = i + 1;
 388                 }
 389         }
 390 }
 391
 392 static void
 393 minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,
 394                struct ieee80211_sta *sta, void *priv_sta)
 395 {
 396         struct minstrel_sta_info *mi = priv_sta;
 397         struct minstrel_priv *mp = priv;
 398         struct ieee80211_local *local = hw_to_local(mp->hw);
 399         struct ieee80211_rate *ctl_rate;
 400         unsigned int i, n = 0;
 401         unsigned int t_slot = 9; /* FIXME: get real slot time */
 402
 403         mi->lowest_rix = rate_lowest_index(sband, sta);
 404         ctl_rate = &sband->bitrates[mi->lowest_rix];
 405         mi->sp_ack_dur = ieee80211_frame_duration(local, 10, ctl_rate->bitrate,
 406                                 !!(ctl_rate->flags & IEEE80211_RATE_ERP_G), 1);
 407
 408         for (i = 0; i < sband->n_bitrates; i++) {
 409                 struct minstrel_rate *mr = &mi->r[n];
 410                 unsigned int tx_time = 0, tx_time_cts = 0, tx_time_rtscts = 0;
 411                 unsigned int tx_time_single;
 412                 unsigned int cw = mp->cw_min;
 413
 414                 if (!rate_supported(sta, sband->band, i))
 415                         continue;
 416                 n++;
 417                 memset(mr, 0, sizeof(*mr));
 418
 419                 mr->rix = i;
 420                 mr->bitrate = sband->bitrates[i].bitrate / 5;
 421                 calc_rate_durations(mi, local, mr,
 422                                 &sband->bitrates[i]);
 423
 424                 /* calculate maximum number of retransmissions before
 425                  * fallback (based on maximum segment size) */
 426                 mr->sample_limit = -1;
 427                 mr->retry_count = 1;
 428                 mr->retry_count_cts = 1;
 429                 mr->retry_count_rtscts = 1;
 430                 tx_time = mr->perfect_tx_time + mi->sp_ack_dur;
 431                 do {
 432                         /* add one retransmission */
 433                         tx_time_single = mr->ack_time + mr->perfect_tx_time;
 434
 435                         /* contention window */
 436                         tx_time_single += t_slot + min(cw, mp->cw_max);
 437                         cw = (cw + 1) << 1;
 438
 439                         tx_time += tx_time_single;
 440                         tx_time_cts += tx_time_single + mi->sp_ack_dur;
 441                         tx_time_rtscts += tx_time_single + 2 * mi->sp_ack_dur;
 442                         if ((tx_time_cts < mp->segment_size) &&
 443                                 (mr->retry_count_cts < mp->max_retry))
 444                                 mr->retry_count_cts++;
 445                         if ((tx_time_rtscts < mp->segment_size) &&
 446                                 (mr->retry_count_rtscts < mp->max_retry))
 447                                 mr->retry_count_rtscts++;
 448                 } while ((tx_time < mp->segment_size) &&
 449                                 (++mr->retry_count < mp->max_retry));
 450                 mr->adjusted_retry_count = mr->retry_count;
 451         }
 452
 453         for (i = n; i < sband->n_bitrates; i++) {
 454                 struct minstrel_rate *mr = &mi->r[i];
 455                 mr->rix = -1;
 456         }
 457
 458         mi->n_rates = n;
 459         mi->stats_update = jiffies;
 460
 461         init_sample_table(mi);
 462 }
 463
 464 static void *
 465 minstrel_alloc_sta(void *priv, struct ieee80211_sta *sta, gfp_t gfp)
 466 {
 467         struct ieee80211_supported_band *sband;
 468         struct minstrel_sta_info *mi;
 469         struct minstrel_priv *mp = priv;
 470         struct ieee80211_hw *hw = mp->hw;
 471         int max_rates = 0;
 472         int i;
 473
 474         mi = kzalloc(sizeof(struct minstrel_sta_info), gfp);
 475         if (!mi)
 476                 return NULL;
 477
 478         for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
 479                 sband = hw->wiphy->bands[hw->conf.channel->band];
 480                 if (sband->n_bitrates > max_rates)
 481                         max_rates = sband->n_bitrates;
 482         }
 483
 484         mi->r = kzalloc(sizeof(struct minstrel_rate) * max_rates, gfp);
 485         if (!mi->r)
 486                 goto error;
 487
 488         mi->sample_table = kmalloc(SAMPLE_COLUMNS * max_rates, gfp);
 489         if (!mi->sample_table)
 490                 goto error1;
 491
 492         mi->stats_update = jiffies;
 493         return mi;
 494
 495 error1:
 496         kfree(mi->r);
 497 error:
 498         kfree(mi);
 499         return NULL;
 500 }
 501
 502 static void
 503 minstrel_free_sta(void *priv, struct ieee80211_sta *sta, void *priv_sta)
 504 {
 505         struct minstrel_sta_info *mi = priv_sta;
 506
 507         kfree(mi->sample_table);
 508         kfree(mi->r);
 509         kfree(mi);
 510 }
 511
 512 static void *
 513 minstrel_alloc(struct ieee80211_hw *hw, struct dentry *debugfsdir)
 514 {
 515         struct minstrel_priv *mp;
 516
 517         mp = kzalloc(sizeof(struct minstrel_priv), GFP_ATOMIC);
 518         if (!mp)
 519                 return NULL;
 520
 521         /* contention window settings
 522          * Just an approximation. Using the per-queue values would complicate
 523          * the calculations and is probably unnecessary */
 524         mp->cw_min = 15;
 525         mp->cw_max = 1023;
 526
 527         /* number of packets (in %) to use for sampling other rates
 528          * sample less often for non-mrr packets, because the overhead
 529          * is much higher than with mrr */
 530         mp->lookaround_rate = 5;
 531         mp->lookaround_rate_mrr = 10;
 532
 533         /* moving average weight for EWMA */
 534         mp->ewma_level = 75;
 535
 536         /* maximum time that the hw is allowed to stay in one MRR segment */
 537         mp->segment_size = 6000;
 538
 539         if (hw->max_rate_tries > 0)
 540                 mp->max_retry = hw->max_rate_tries;
 541         else
 542                 /* safe default, does not necessarily have to match hw properties */
 543                 mp->max_retry = 7;
 544
 545         if (hw->max_rates >= 4)
 546                 mp->has_mrr = true;
 547
 548         mp->hw = hw;
 549         mp->update_interval = 100;
 550
 551         return mp;
 552 }
 553
 554 static void
 555 minstrel_free(void *priv)
 556 {
 557         kfree(priv);
 558 }
 559
 560 static struct rate_control_ops mac80211_minstrel = {
 561         .name = "minstrel",
 562         .tx_status = minstrel_tx_status,
 563         .get_rate = minstrel_get_rate,
 564         .rate_init = minstrel_rate_init,
 565         .alloc = minstrel_alloc,
 566         .free = minstrel_free,
 567         .alloc_sta = minstrel_alloc_sta,
 568         .free_sta = minstrel_free_sta,
 569 #ifdef CONFIG_MAC80211_DEBUGFS
 570         .add_sta_debugfs = minstrel_add_sta_debugfs,
 571         .remove_sta_debugfs = minstrel_remove_sta_debugfs,
 572 #endif
 573 };
 574
 575 int __init
 576 rc80211_minstrel_init(void)
 577 {
 578         return ieee80211_rate_control_register(&mac80211_minstrel);
 579 }
 580
 581 void
 582 rc80211_minstrel_exit(void)
 583 {
 584         ieee80211_rate_control_unregister(&mac80211_minstrel);
 585 }
 586