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