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 <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 */
  62static inline int
  63rix_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
  73static inline bool
  74use_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
  88static void
  89minstrel_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
 167static void
 168minstrel_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
 199static inline unsigned int
 200minstrel_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
 213static int
 214minstrel_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 ((int) 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
 228static void
 229minstrel_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
 352static void
 353calc_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
 364static void
 365init_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
 392static void
 393minstrel_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
 464static void *
 465minstrel_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[i];
 480                if (sband && 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
 495error1:
 496        kfree(mi->r);
 497error:
 498        kfree(mi);
 499        return NULL;
 500}
 501
 502static void
 503minstrel_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
 512static void *
 513minstrel_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
 554static void
 555minstrel_free(void *priv)
 556{
 557        kfree(priv);
 558}
 559
 560static 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
 575int __init
 576rc80211_minstrel_init(void)
 577{
 578        return ieee80211_rate_control_register(&mac80211_minstrel);
 579}
 580
 581void
 582rc80211_minstrel_exit(void)
 583{
 584        ieee80211_rate_control_unregister(&mac80211_minstrel);
 585}
 586
 587