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 }
  85
  86
  87 static void
  88 minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
  89 {
  90         u32 max_tp = 0, index_max_tp = 0, index_max_tp2 = 0;
  91         u32 max_prob = 0, index_max_prob = 0;
  92         u32 usecs;
  93         u32 p;
  94         int i;
  95
  96         mi->stats_update = jiffies;
  97         for (i = 0; i < mi->n_rates; i++) {
  98                 struct minstrel_rate *mr = &mi->r[i];
  99
 100                 usecs = mr->perfect_tx_time;
 101                 if (!usecs)
 102                         usecs = 1000000;
 103
 104                 /* To avoid rounding issues, probabilities scale from 0 (0%)
 105                  * to 18000 (100%) */
 106                 if (mr->attempts) {
 107                         p = (mr->success * 18000) / mr->attempts;
 108                         mr->succ_hist += mr->success;
 109                         mr->att_hist += mr->attempts;
 110                         mr->cur_prob = p;
 111                         p = ((p * (100 - mp->ewma_level)) + (mr->probability *
 112                                 mp->ewma_level)) / 100;
 113                         mr->probability = p;
 114                         mr->cur_tp = p * (1000000 / usecs);
 115                 }
 116
 117                 mr->last_success = mr->success;
 118                 mr->last_attempts = mr->attempts;
 119                 mr->success = 0;
 120                 mr->attempts = 0;
 121
 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;
 129                 } else {
 130                         mr->sample_limit = -1;
 131                         mr->adjusted_retry_count = mr->retry_count;
 132                 }
 133                 if (!mr->adjusted_retry_count)
 134                         mr->adjusted_retry_count = 2;
 135         }
 136
 137         for (i = 0; i < mi->n_rates; i++) {
 138                 struct minstrel_rate *mr = &mi->r[i];
 139                 if (max_tp < mr->cur_tp) {
 140                         index_max_tp = i;
 141                         max_tp = mr->cur_tp;
 142                 }
 143                 if (max_prob < mr->probability) {
 144                         index_max_prob = i;
 145                         max_prob = mr->probability;
 146                 }
 147         }
 148
 149         max_tp = 0;
 150         for (i = 0; i < mi->n_rates; i++) {
 151                 struct minstrel_rate *mr = &mi->r[i];
 152
 153                 if (i == index_max_tp)
 154                         continue;
 155
 156                 if (max_tp < mr->cur_tp) {
 157                         index_max_tp2 = i;
 158                         max_tp = mr->cur_tp;
 159                 }
 160         }
 161         mi->max_tp_rate = index_max_tp;
 162         mi->max_tp_rate2 = index_max_tp2;
 163         mi->max_prob_rate = index_max_prob;
 164 }
 165
 166 static void
 167 minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
 168                    struct ieee80211_sta *sta, void *priv_sta,
 169                    struct sk_buff *skb)
 170 {
 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;
 174         int i, ndx;
 175         int success;
 176
 177         success = !!(info->flags & IEEE80211_TX_STAT_ACK);
 178
 179         for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
 180                 if (ar[i].idx < 0)
 181                         break;
 182
 183                 ndx = rix_to_ndx(mi, ar[i].idx);
 184                 mi->r[ndx].attempts += ar[i].count;
 185
 186                 if ((i != IEEE80211_TX_MAX_RATES - 1) && (ar[i + 1].idx < 0))
 187                         mi->r[ndx].success += success;
 188         }
 189
 190         if ((info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE) && (i >= 0))
 191                 mi->sample_count++;
 192
 193         if (mi->sample_deferred > 0)
 194                 mi->sample_deferred--;
 195 }
 196
 197
 198 static inline unsigned int
 199 minstrel_get_retry_count(struct minstrel_rate *mr,
 200                          struct ieee80211_tx_info *info)
 201 {
 202         unsigned int retry = mr->adjusted_retry_count;
 203
 204         if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_RTS_CTS)
 205                 retry = max(2U, min(mr->retry_count_rtscts, retry));
 206         else if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_CTS_PROTECT)
 207                 retry = max(2U, min(mr->retry_count_cts, retry));
 208         return retry;
 209 }
 210
 211
 212 static int
 213 minstrel_get_next_sample(struct minstrel_sta_info *mi)
 214 {
 215         unsigned int sample_ndx;
 216         sample_ndx = SAMPLE_TBL(mi, mi->sample_idx, mi->sample_column);
 217         mi->sample_idx++;
 218         if ((int) mi->sample_idx > (mi->n_rates - 2)) {
 219                 mi->sample_idx = 0;
 220                 mi->sample_column++;
 221                 if (mi->sample_column >= SAMPLE_COLUMNS)
 222                         mi->sample_column = 0;
 223         }
 224         return sample_ndx;
 225 }
 226
 227 static void
 228 minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
 229                   void *priv_sta, struct ieee80211_tx_rate_control *txrc)
 230 {
 231         struct sk_buff *skb = txrc->skb;
 232         struct ieee80211_supported_band *sband = txrc->sband;
 233         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 234         struct minstrel_sta_info *mi = priv_sta;
 235         struct minstrel_priv *mp = priv;
 236         struct ieee80211_tx_rate *ar = info->control.rates;
 237         unsigned int ndx, sample_ndx = 0;
 238         bool mrr;
 239         bool sample_slower = false;
 240         bool sample = false;
 241         int i, delta;
 242         int mrr_ndx[3];
 243         int sample_rate;
 244
 245         if (!sta || !mi || use_low_rate(skb)) {
 246                 ar[0].idx = rate_lowest_index(sband, sta);
 247                 if (info->flags & IEEE80211_TX_CTL_NO_ACK)
 248                         ar[0].count = 1;
 249                 else
 250                         ar[0].count = mp->max_retry;
 251                 return;
 252         }
 253
 254         mrr = mp->has_mrr && !txrc->rts && !txrc->bss_conf->use_cts_prot;
 255
 256         if (time_after(jiffies, mi->stats_update + (mp->update_interval *
 257                         HZ) / 1000))
 258                 minstrel_update_stats(mp, mi);
 259
 260         ndx = mi->max_tp_rate;
 261
 262         if (mrr)
 263                 sample_rate = mp->lookaround_rate_mrr;
 264         else
 265                 sample_rate = mp->lookaround_rate;
 266
 267         mi->packet_count++;
 268         delta = (mi->packet_count * sample_rate / 100) -
 269                         (mi->sample_count + mi->sample_deferred / 2);
 270
 271         /* delta > 0: sampling required */
 272         if ((delta > 0) && (mrr || !mi->prev_sample)) {
 273                 struct minstrel_rate *msr;
 274                 if (mi->packet_count >= 10000) {
 275                         mi->sample_deferred = 0;
 276                         mi->sample_count = 0;
 277                         mi->packet_count = 0;
 278                 } else if (delta > mi->n_rates * 2) {
 279                         /* With multi-rate retry, not every planned sample
 280                          * attempt actually gets used, due to the way the retry
 281                          * chain is set up - [max_tp,sample,prob,lowest] for
 282                          * sample_rate < max_tp.
 283                          *
 284                          * If there's too much sampling backlog and the link
 285                          * starts getting worse, minstrel would start bursting
 286                          * out lots of sampling frames, which would result
 287                          * in a large throughput loss. */
 288                         mi->sample_count += (delta - mi->n_rates * 2);
 289                 }
 290
 291                 sample_ndx = minstrel_get_next_sample(mi);
 292                 msr = &mi->r[sample_ndx];
 293                 sample = true;
 294                 sample_slower = mrr && (msr->perfect_tx_time >
 295                         mi->r[ndx].perfect_tx_time);
 296
 297                 if (!sample_slower) {
 298                         if (msr->sample_limit != 0) {
 299                                 ndx = sample_ndx;
 300                                 mi->sample_count++;
 301                                 if (msr->sample_limit > 0)
 302                                         msr->sample_limit--;
 303                         } else {
 304                                 sample = false;
 305                         }
 306                 } else {
 307                         /* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
 308                          * packets that have the sampling rate deferred to the
 309                          * second MRR stage. Increase the sample counter only
 310                          * if the deferred sample rate was actually used.
 311                          * Use the sample_deferred counter to make sure that
 312                          * the sampling is not done in large bursts */
 313                         info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
 314                         mi->sample_deferred++;
 315                 }
 316         }
 317         mi->prev_sample = sample;
 318
 319         /* If we're not using MRR and the sampling rate already
 320          * has a probability of >95%, we shouldn't be attempting
 321          * to use it, as this only wastes precious airtime */
 322         if (!mrr && sample && (mi->r[ndx].probability > 17100))
 323                 ndx = mi->max_tp_rate;
 324
 325         ar[0].idx = mi->r[ndx].rix;
 326         ar[0].count = minstrel_get_retry_count(&mi->r[ndx], info);
 327
 328         if (!mrr) {
 329                 if (!sample)
 330                         ar[0].count = mp->max_retry;
 331                 ar[1].idx = mi->lowest_rix;
 332                 ar[1].count = mp->max_retry;
 333                 return;
 334         }
 335
 336         /* MRR setup */
 337         if (sample) {
 338                 if (sample_slower)
 339                         mrr_ndx[0] = sample_ndx;
 340                 else
 341                         mrr_ndx[0] = mi->max_tp_rate;
 342         } else {
 343                 mrr_ndx[0] = mi->max_tp_rate2;
 344         }
 345         mrr_ndx[1] = mi->max_prob_rate;
 346         mrr_ndx[2] = 0;
 347         for (i = 1; i < 4; i++) {
 348                 ar[i].idx = mi->r[mrr_ndx[i - 1]].rix;
 349                 ar[i].count = mi->r[mrr_ndx[i - 1]].adjusted_retry_count;
 350         }
 351 }
 352
 353
 354 static void
 355 calc_rate_durations(struct minstrel_sta_info *mi, struct ieee80211_local *local,
 356                     struct minstrel_rate *d, struct ieee80211_rate *rate)
 357 {
 358         int erp = !!(rate->flags & IEEE80211_RATE_ERP_G);
 359
 360         d->perfect_tx_time = ieee80211_frame_duration(local, 1200,
 361                         rate->bitrate, erp, 1);
 362         d->ack_time = ieee80211_frame_duration(local, 10,
 363                         rate->bitrate, erp, 1);
 364 }
 365
 366 static void
 367 init_sample_table(struct minstrel_sta_info *mi)
 368 {
 369         unsigned int i, col, new_idx;
 370         unsigned int n_srates = mi->n_rates - 1;
 371         u8 rnd[8];
 372
 373         mi->sample_column = 0;
 374         mi->sample_idx = 0;
 375         memset(mi->sample_table, 0, SAMPLE_COLUMNS * mi->n_rates);
 376
 377         for (col = 0; col < SAMPLE_COLUMNS; col++) {
 378                 for (i = 0; i < n_srates; i++) {
 379                         get_random_bytes(rnd, sizeof(rnd));
 380                         new_idx = (i + rnd[i & 7]) % n_srates;
 381
 382                         while (SAMPLE_TBL(mi, new_idx, col) != 0)
 383                                 new_idx = (new_idx + 1) % n_srates;
 384
 385                         /* Don't sample the slowest rate (i.e. slowest base
 386                          * rate). We must presume that the slowest rate works
 387                          * fine, or else other management frames will also be
 388                          * failing and the link will break */
 389                         SAMPLE_TBL(mi, new_idx, col) = i + 1;
 390                 }
 391         }
 392 }
 393
 394 static void
 395 minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,
 396                struct ieee80211_sta *sta, void *priv_sta)
 397 {
 398         struct minstrel_sta_info *mi = priv_sta;
 399         struct minstrel_priv *mp = priv;
 400         struct ieee80211_local *local = hw_to_local(mp->hw);
 401         struct ieee80211_rate *ctl_rate;
 402         unsigned int i, n = 0;
 403         unsigned int t_slot = 9; /* FIXME: get real slot time */
 404
 405         mi->lowest_rix = rate_lowest_index(sband, sta);
 406         ctl_rate = &sband->bitrates[mi->lowest_rix];
 407         mi->sp_ack_dur = ieee80211_frame_duration(local, 10, ctl_rate->bitrate,
 408                                 !!(ctl_rate->flags & IEEE80211_RATE_ERP_G), 1);
 409
 410         for (i = 0; i < sband->n_bitrates; i++) {
 411                 struct minstrel_rate *mr = &mi->r[n];
 412                 unsigned int tx_time = 0, tx_time_cts = 0, tx_time_rtscts = 0;
 413                 unsigned int tx_time_single;
 414                 unsigned int cw = mp->cw_min;
 415
 416                 if (!rate_supported(sta, sband->band, i))
 417                         continue;
 418                 n++;
 419                 memset(mr, 0, sizeof(*mr));
 420
 421                 mr->rix = i;
 422                 mr->bitrate = sband->bitrates[i].bitrate / 5;
 423                 calc_rate_durations(mi, local, mr,
 424                                 &sband->bitrates[i]);
 425
 426                 /* calculate maximum number of retransmissions before
 427                  * fallback (based on maximum segment size) */
 428                 mr->sample_limit = -1;
 429                 mr->retry_count = 1;
 430                 mr->retry_count_cts = 1;
 431                 mr->retry_count_rtscts = 1;
 432                 tx_time = mr->perfect_tx_time + mi->sp_ack_dur;
 433                 do {
 434                         /* add one retransmission */
 435                         tx_time_single = mr->ack_time + mr->perfect_tx_time;
 436
 437                         /* contention window */
 438                         tx_time_single += t_slot + min(cw, mp->cw_max);
 439                         cw = (cw + 1) << 1;
 440
 441                         tx_time += tx_time_single;
 442                         tx_time_cts += tx_time_single + mi->sp_ack_dur;
 443                         tx_time_rtscts += tx_time_single + 2 * mi->sp_ack_dur;
 444                         if ((tx_time_cts < mp->segment_size) &&
 445                                 (mr->retry_count_cts < mp->max_retry))
 446                                 mr->retry_count_cts++;
 447                         if ((tx_time_rtscts < mp->segment_size) &&
 448                                 (mr->retry_count_rtscts < mp->max_retry))
 449                                 mr->retry_count_rtscts++;
 450                 } while ((tx_time < mp->segment_size) &&
 451                                 (++mr->retry_count < mp->max_retry));
 452                 mr->adjusted_retry_count = mr->retry_count;
 453         }
 454
 455         for (i = n; i < sband->n_bitrates; i++) {
 456                 struct minstrel_rate *mr = &mi->r[i];
 457                 mr->rix = -1;
 458         }
 459
 460         mi->n_rates = n;
 461         mi->stats_update = jiffies;
 462
 463         init_sample_table(mi);
 464 }
 465
 466 static void *
 467 minstrel_alloc_sta(void *priv, struct ieee80211_sta *sta, gfp_t gfp)
 468 {
 469         struct ieee80211_supported_band *sband;
 470         struct minstrel_sta_info *mi;
 471         struct minstrel_priv *mp = priv;
 472         struct ieee80211_hw *hw = mp->hw;
 473         int max_rates = 0;
 474         int i;
 475
 476         mi = kzalloc(sizeof(struct minstrel_sta_info), gfp);
 477         if (!mi)
 478                 return NULL;
 479
 480         for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
 481                 sband = hw->wiphy->bands[i];
 482                 if (sband && sband->n_bitrates > max_rates)
 483                         max_rates = sband->n_bitrates;
 484         }
 485
 486         mi->r = kzalloc(sizeof(struct minstrel_rate) * max_rates, gfp);
 487         if (!mi->r)
 488                 goto error;
 489
 490         mi->sample_table = kmalloc(SAMPLE_COLUMNS * max_rates, gfp);
 491         if (!mi->sample_table)
 492                 goto error1;
 493
 494         mi->stats_update = jiffies;
 495         return mi;
 496
 497 error1:
 498         kfree(mi->r);
 499 error:
 500         kfree(mi);
 501         return NULL;
 502 }
 503
 504 static void
 505 minstrel_free_sta(void *priv, struct ieee80211_sta *sta, void *priv_sta)
 506 {
 507         struct minstrel_sta_info *mi = priv_sta;
 508
 509         kfree(mi->sample_table);
 510         kfree(mi->r);
 511         kfree(mi);
 512 }
 513
 514 static void *
 515 minstrel_alloc(struct ieee80211_hw *hw, struct dentry *debugfsdir)
 516 {
 517         struct minstrel_priv *mp;
 518
 519         mp = kzalloc(sizeof(struct minstrel_priv), GFP_ATOMIC);
 520         if (!mp)
 521                 return NULL;
 522
 523         /* contention window settings
 524          * Just an approximation. Using the per-queue values would complicate
 525          * the calculations and is probably unnecessary */
 526         mp->cw_min = 15;
 527         mp->cw_max = 1023;
 528
 529         /* number of packets (in %) to use for sampling other rates
 530          * sample less often for non-mrr packets, because the overhead
 531          * is much higher than with mrr */
 532         mp->lookaround_rate = 5;
 533         mp->lookaround_rate_mrr = 10;
 534
 535         /* moving average weight for EWMA */
 536         mp->ewma_level = 75;
 537
 538         /* maximum time that the hw is allowed to stay in one MRR segment */
 539         mp->segment_size = 6000;
 540
 541         if (hw->max_rate_tries > 0)
 542                 mp->max_retry = hw->max_rate_tries;
 543         else
 544                 /* safe default, does not necessarily have to match hw properties */
 545                 mp->max_retry = 7;
 546
 547         if (hw->max_rates >= 4)
 548                 mp->has_mrr = true;
 549
 550         mp->hw = hw;
 551         mp->update_interval = 100;
 552
 553         return mp;
 554 }
 555
 556 static void
 557 minstrel_free(void *priv)
 558 {
 559         kfree(priv);
 560 }
 561
 562 static struct rate_control_ops mac80211_minstrel = {
 563         .name = "minstrel",
 564         .tx_status = minstrel_tx_status,
 565         .get_rate = minstrel_get_rate,
 566         .rate_init = minstrel_rate_init,
 567         .alloc = minstrel_alloc,
 568         .free = minstrel_free,
 569         .alloc_sta = minstrel_alloc_sta,
 570         .free_sta = minstrel_free_sta,
 571 #ifdef CONFIG_MAC80211_DEBUGFS
 572         .add_sta_debugfs = minstrel_add_sta_debugfs,
 573         .remove_sta_debugfs = minstrel_remove_sta_debugfs,
 574 #endif
 575 };
 576
 577 int __init
 578 rc80211_minstrel_init(void)
 579 {
 580         return ieee80211_rate_control_register(&mac80211_minstrel);
 581 }
 582
 583 void
 584 rc80211_minstrel_exit(void)
 585 {
 586         ieee80211_rate_control_unregister(&mac80211_minstrel);
 587 }
 588