linux/net/mac80211/rc80211_minstrel.c
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   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 <linux/slab.h>
  54#include <net/mac80211.h>
  55#include "rate.h"
  56#include "rc80211_minstrel.h"
  57
  58#define SAMPLE_COLUMNS  10
  59#define SAMPLE_TBL(_mi, _idx, _col) \
  60                _mi->sample_table[(_idx * SAMPLE_COLUMNS) + _col]
  61
  62/* convert mac80211 rate index to local array index */
  63static inline int
  64rix_to_ndx(struct minstrel_sta_info *mi, int rix)
  65{
  66        int i = rix;
  67        for (i = rix; i >= 0; i--)
  68                if (mi->r[i].rix == rix)
  69                        break;
  70        return i;
  71}
  72
  73static void
  74minstrel_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
 152static void
 153minstrel_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
 187static inline unsigned int
 188minstrel_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
 201static int
 202minstrel_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
 216static void
 217minstrel_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
 336static void
 337calc_rate_durations(enum ieee80211_band band,
 338                    struct minstrel_rate *d,
 339                    struct ieee80211_rate *rate)
 340{
 341        int erp = !!(rate->flags & IEEE80211_RATE_ERP_G);
 342
 343        d->perfect_tx_time = ieee80211_frame_duration(band, 1200,
 344                        rate->bitrate, erp, 1);
 345        d->ack_time = ieee80211_frame_duration(band, 10,
 346                        rate->bitrate, erp, 1);
 347}
 348
 349static void
 350init_sample_table(struct minstrel_sta_info *mi)
 351{
 352        unsigned int i, col, new_idx;
 353        unsigned int n_srates = mi->n_rates - 1;
 354        u8 rnd[8];
 355
 356        mi->sample_column = 0;
 357        mi->sample_idx = 0;
 358        memset(mi->sample_table, 0, SAMPLE_COLUMNS * mi->n_rates);
 359
 360        for (col = 0; col < SAMPLE_COLUMNS; col++) {
 361                for (i = 0; i < n_srates; i++) {
 362                        get_random_bytes(rnd, sizeof(rnd));
 363                        new_idx = (i + rnd[i & 7]) % n_srates;
 364
 365                        while (SAMPLE_TBL(mi, new_idx, col) != 0)
 366                                new_idx = (new_idx + 1) % n_srates;
 367
 368                        /* Don't sample the slowest rate (i.e. slowest base
 369                         * rate). We must presume that the slowest rate works
 370                         * fine, or else other management frames will also be
 371                         * failing and the link will break */
 372                        SAMPLE_TBL(mi, new_idx, col) = i + 1;
 373                }
 374        }
 375}
 376
 377static void
 378minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,
 379               struct ieee80211_sta *sta, void *priv_sta)
 380{
 381        struct minstrel_sta_info *mi = priv_sta;
 382        struct minstrel_priv *mp = priv;
 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(sband->band, 10,
 390                                ctl_rate->bitrate,
 391                                !!(ctl_rate->flags & IEEE80211_RATE_ERP_G), 1);
 392
 393        for (i = 0; i < sband->n_bitrates; i++) {
 394                struct minstrel_rate *mr = &mi->r[n];
 395                unsigned int tx_time = 0, tx_time_cts = 0, tx_time_rtscts = 0;
 396                unsigned int tx_time_single;
 397                unsigned int cw = mp->cw_min;
 398
 399                if (!rate_supported(sta, sband->band, i))
 400                        continue;
 401                n++;
 402                memset(mr, 0, sizeof(*mr));
 403
 404                mr->rix = i;
 405                mr->bitrate = sband->bitrates[i].bitrate / 5;
 406                calc_rate_durations(sband->band, mr, &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 * cw) >> 1;
 421                        cw = min((cw << 1) | 1, mp->cw_max);
 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
 448static void *
 449minstrel_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
 479error1:
 480        kfree(mi->r);
 481error:
 482        kfree(mi);
 483        return NULL;
 484}
 485
 486static void
 487minstrel_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
 496static void *
 497minstrel_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#ifdef CONFIG_MAC80211_DEBUGFS
 536        mp->fixed_rate_idx = (u32) -1;
 537        mp->dbg_fixed_rate = debugfs_create_u32("fixed_rate_idx",
 538                        S_IRUGO | S_IWUGO, debugfsdir, &mp->fixed_rate_idx);
 539#endif
 540
 541        return mp;
 542}
 543
 544static void
 545minstrel_free(void *priv)
 546{
 547#ifdef CONFIG_MAC80211_DEBUGFS
 548        debugfs_remove(((struct minstrel_priv *)priv)->dbg_fixed_rate);
 549#endif
 550        kfree(priv);
 551}
 552
 553struct rate_control_ops mac80211_minstrel = {
 554        .name = "minstrel",
 555        .tx_status = minstrel_tx_status,
 556        .get_rate = minstrel_get_rate,
 557        .rate_init = minstrel_rate_init,
 558        .alloc = minstrel_alloc,
 559        .free = minstrel_free,
 560        .alloc_sta = minstrel_alloc_sta,
 561        .free_sta = minstrel_free_sta,
 562#ifdef CONFIG_MAC80211_DEBUGFS
 563        .add_sta_debugfs = minstrel_add_sta_debugfs,
 564        .remove_sta_debugfs = minstrel_remove_sta_debugfs,
 565#endif
 566};
 567
 568int __init
 569rc80211_minstrel_init(void)
 570{
 571        return ieee80211_rate_control_register(&mac80211_minstrel);
 572}
 573
 574void
 575rc80211_minstrel_exit(void)
 576{
 577        ieee80211_rate_control_unregister(&mac80211_minstrel);
 578}
 579
 580
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