rc80211_minstrel.c
Go to the documentation of this file.
00001 /*
00002  * Copyright (C) 2008 Felix Fietkau <nbd@openwrt.org>
00003  *
00004  * This program is free software; you can redistribute it and/or modify
00005  * it under the terms of the GNU General Public License version 2 as
00006  * published by the Free Software Foundation.
00007  *
00008  * Based on minstrel.c:
00009  *   Copyright (C) 2005-2007 Derek Smithies <derek@indranet.co.nz>
00010  *   Sponsored by Indranet Technologies Ltd
00011  *
00012  * Based on sample.c:
00013  *   Copyright (c) 2005 John Bicket
00014  *   All rights reserved.
00015  *
00016  *   Redistribution and use in source and binary forms, with or without
00017  *   modification, are permitted provided that the following conditions
00018  *   are met:
00019  *   1. Redistributions of source code must retain the above copyright
00020  *      notice, this list of conditions and the following disclaimer,
00021  *      without modification.
00022  *   2. Redistributions in binary form must reproduce at minimum a disclaimer
00023  *      similar to the "NO WARRANTY" disclaimer below ("Disclaimer") and any
00024  *      redistribution must be conditioned upon including a substantially
00025  *      similar Disclaimer requirement for further binary redistribution.
00026  *   3. Neither the names of the above-listed copyright holders nor the names
00027  *      of any contributors may be used to endorse or promote products derived
00028  *      from this software without specific prior written permission.
00029  *
00030  *   Alternatively, this software may be distributed under the terms of the
00031  *   GNU General Public License ("GPL") version 2 as published by the Free
00032  *   Software Foundation.
00033  *
00034  *   NO WARRANTY
00035  *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
00036  *   ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00037  *   LIMITED TO, THE IMPLIED WARRANTIES OF NONINFRINGEMENT, MERCHANTIBILITY
00038  *   AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
00039  *   THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY,
00040  *   OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
00041  *   SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
00042  *   INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
00043  *   IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
00044  *   ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
00045  *   THE POSSIBILITY OF SUCH DAMAGES.
00046  */
00047 #include <linux/netdevice.h>
00048 #include <linux/types.h>
00049 #include <linux/skbuff.h>
00050 #include <linux/debugfs.h>
00051 #include <linux/random.h>
00052 #include <linux/ieee80211.h>
00053 #include <linux/slab.h>
00054 #include <net/mac80211.h>
00055 #include "rate.h"
00056 #include "rc80211_minstrel.h"
00057 
00058 #define SAMPLE_COLUMNS  10
00059 #define SAMPLE_TBL(_mi, _idx, _col) \
00060                 _mi->sample_table[(_idx * SAMPLE_COLUMNS) + _col]
00061 
00062 /* convert mac80211 rate index to local array index */
00063 static inline int
00064 rix_to_ndx(struct minstrel_sta_info *mi, int rix)
00065 {
00066         int i = rix;
00067         for (i = rix; i >= 0; i--)
00068                 if (mi->r[i].rix == rix)
00069                         break;
00070         return i;
00071 }
00072 
00073 static void
00074 minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
00075 {
00076         u32 max_tp = 0, index_max_tp = 0, index_max_tp2 = 0;
00077         u32 max_prob = 0, index_max_prob = 0;
00078         u32 usecs;
00079         u32 p;
00080         int i;
00081 
00082         mi->stats_update = jiffies;
00083         for (i = 0; i < mi->n_rates; i++) {
00084                 struct minstrel_rate *mr = &mi->r[i];
00085 
00086                 usecs = mr->perfect_tx_time;
00087                 if (!usecs)
00088                         usecs = 1000000;
00089 
00090                 /* To avoid rounding issues, probabilities scale from 0 (0%)
00091                  * to 18000 (100%) */
00092                 if (mr->attempts) {
00093                         p = (mr->success * 18000) / mr->attempts;
00094                         mr->succ_hist += mr->success;
00095                         mr->att_hist += mr->attempts;
00096                         mr->cur_prob = p;
00097                         p = ((p * (100 - mp->ewma_level)) + (mr->probability *
00098                                 mp->ewma_level)) / 100;
00099                         mr->probability = p;
00100                         mr->cur_tp = p * (1000000 / usecs);
00101                 }
00102 
00103                 mr->last_success = mr->success;
00104                 mr->last_attempts = mr->attempts;
00105                 mr->success = 0;
00106                 mr->attempts = 0;
00107 
00108                 /* Sample less often below the 10% chance of success.
00109                  * Sample less often above the 95% chance of success. */
00110                 if ((mr->probability > 17100) || (mr->probability < 1800)) {
00111                         mr->adjusted_retry_count = mr->retry_count >> 1;
00112                         if (mr->adjusted_retry_count > 2)
00113                                 mr->adjusted_retry_count = 2;
00114                         mr->sample_limit = 4;
00115                 } else {
00116                         mr->sample_limit = -1;
00117                         mr->adjusted_retry_count = mr->retry_count;
00118                 }
00119                 if (!mr->adjusted_retry_count)
00120                         mr->adjusted_retry_count = 2;
00121         }
00122 
00123         for (i = 0; i < mi->n_rates; i++) {
00124                 struct minstrel_rate *mr = &mi->r[i];
00125                 if (max_tp < mr->cur_tp) {
00126                         index_max_tp = i;
00127                         max_tp = mr->cur_tp;
00128                 }
00129                 if (max_prob < mr->probability) {
00130                         index_max_prob = i;
00131                         max_prob = mr->probability;
00132                 }
00133         }
00134 
00135         max_tp = 0;
00136         for (i = 0; i < mi->n_rates; i++) {
00137                 struct minstrel_rate *mr = &mi->r[i];
00138 
00139                 if (i == index_max_tp)
00140                         continue;
00141 
00142                 if (max_tp < mr->cur_tp) {
00143                         index_max_tp2 = i;
00144                         max_tp = mr->cur_tp;
00145                 }
00146         }
00147         mi->max_tp_rate = index_max_tp;
00148         mi->max_tp_rate2 = index_max_tp2;
00149         mi->max_prob_rate = index_max_prob;
00150 }
00151 
00152 static void
00153 minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
00154                    struct ieee80211_sta *sta, void *priv_sta,
00155                    struct sk_buff *skb)
00156 {
00157         struct minstrel_sta_info *mi = priv_sta;
00158         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
00159         struct ieee80211_tx_rate *ar = info->status.rates;
00160         int i, ndx;
00161         int success;
00162 
00163         success = !!(info->flags & IEEE80211_TX_STAT_ACK);
00164 
00165         for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
00166                 if (ar[i].idx < 0)
00167                         break;
00168 
00169                 ndx = rix_to_ndx(mi, ar[i].idx);
00170                 if (ndx < 0)
00171                         continue;
00172 
00173                 mi->r[ndx].attempts += ar[i].count;
00174 
00175                 if ((i != IEEE80211_TX_MAX_RATES - 1) && (ar[i + 1].idx < 0))
00176                         mi->r[ndx].success += success;
00177         }
00178 
00179         if ((info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE) && (i >= 0))
00180                 mi->sample_count++;
00181 
00182         if (mi->sample_deferred > 0)
00183                 mi->sample_deferred--;
00184 }
00185 
00186 
00187 static inline unsigned int
00188 minstrel_get_retry_count(struct minstrel_rate *mr,
00189                          struct ieee80211_tx_info *info)
00190 {
00191         unsigned int retry = mr->adjusted_retry_count;
00192 
00193         if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_RTS_CTS)
00194                 retry = max(2U, min(mr->retry_count_rtscts, retry));
00195         else if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_CTS_PROTECT)
00196                 retry = max(2U, min(mr->retry_count_cts, retry));
00197         return retry;
00198 }
00199 
00200 
00201 static int
00202 minstrel_get_next_sample(struct minstrel_sta_info *mi)
00203 {
00204         unsigned int sample_ndx;
00205         sample_ndx = SAMPLE_TBL(mi, mi->sample_idx, mi->sample_column);
00206         mi->sample_idx++;
00207         if ((int) mi->sample_idx > (mi->n_rates - 2)) {
00208                 mi->sample_idx = 0;
00209                 mi->sample_column++;
00210                 if (mi->sample_column >= SAMPLE_COLUMNS)
00211                         mi->sample_column = 0;
00212         }
00213         return sample_ndx;
00214 }
00215 
00216 static void
00217 minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
00218                   void *priv_sta, struct ieee80211_tx_rate_control *txrc)
00219 {
00220         struct sk_buff *skb = txrc->skb;
00221         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
00222         struct minstrel_sta_info *mi = priv_sta;
00223         struct minstrel_priv *mp = priv;
00224         struct ieee80211_tx_rate *ar = info->control.rates;
00225         unsigned int ndx, sample_ndx = 0;
00226         bool mrr;
00227         bool sample_slower = false;
00228         bool sample = false;
00229         int i, delta;
00230         int mrr_ndx[3];
00231         int sample_rate;
00232 
00233         if (rate_control_send_low(sta, priv_sta, txrc))
00234                 return;
00235 
00236         mrr = mp->has_mrr && !txrc->rts && !txrc->bss_conf->use_cts_prot;
00237 
00238         if (time_after(jiffies, mi->stats_update + (mp->update_interval *
00239                         HZ) / 1000))
00240                 minstrel_update_stats(mp, mi);
00241 
00242         ndx = mi->max_tp_rate;
00243 
00244         if (mrr)
00245                 sample_rate = mp->lookaround_rate_mrr;
00246         else
00247                 sample_rate = mp->lookaround_rate;
00248 
00249         mi->packet_count++;
00250         delta = (mi->packet_count * sample_rate / 100) -
00251                         (mi->sample_count + mi->sample_deferred / 2);
00252 
00253         /* delta > 0: sampling required */
00254         if ((delta > 0) && (mrr || !mi->prev_sample)) {
00255                 struct minstrel_rate *msr;
00256                 if (mi->packet_count >= 10000) {
00257                         mi->sample_deferred = 0;
00258                         mi->sample_count = 0;
00259                         mi->packet_count = 0;
00260                 } else if (delta > mi->n_rates * 2) {
00261                         /* With multi-rate retry, not every planned sample
00262                          * attempt actually gets used, due to the way the retry
00263                          * chain is set up - [max_tp,sample,prob,lowest] for
00264                          * sample_rate < max_tp.
00265                          *
00266                          * If there's too much sampling backlog and the link
00267                          * starts getting worse, minstrel would start bursting
00268                          * out lots of sampling frames, which would result
00269                          * in a large throughput loss. */
00270                         mi->sample_count += (delta - mi->n_rates * 2);
00271                 }
00272 
00273                 sample_ndx = minstrel_get_next_sample(mi);
00274                 msr = &mi->r[sample_ndx];
00275                 sample = true;
00276                 sample_slower = mrr && (msr->perfect_tx_time >
00277                         mi->r[ndx].perfect_tx_time);
00278 
00279                 if (!sample_slower) {
00280                         if (msr->sample_limit != 0) {
00281                                 ndx = sample_ndx;
00282                                 mi->sample_count++;
00283                                 if (msr->sample_limit > 0)
00284                                         msr->sample_limit--;
00285                         } else {
00286                                 sample = false;
00287                         }
00288                 } else {
00289                         /* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
00290                          * packets that have the sampling rate deferred to the
00291                          * second MRR stage. Increase the sample counter only
00292                          * if the deferred sample rate was actually used.
00293                          * Use the sample_deferred counter to make sure that
00294                          * the sampling is not done in large bursts */
00295                         info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
00296                         mi->sample_deferred++;
00297                 }
00298         }
00299         mi->prev_sample = sample;
00300 
00301         /* If we're not using MRR and the sampling rate already
00302          * has a probability of >95%, we shouldn't be attempting
00303          * to use it, as this only wastes precious airtime */
00304         if (!mrr && sample && (mi->r[ndx].probability > 17100))
00305                 ndx = mi->max_tp_rate;
00306 
00307         ar[0].idx = mi->r[ndx].rix;
00308         ar[0].count = minstrel_get_retry_count(&mi->r[ndx], info);
00309 
00310         if (!mrr) {
00311                 if (!sample)
00312                         ar[0].count = mp->max_retry;
00313                 ar[1].idx = mi->lowest_rix;
00314                 ar[1].count = mp->max_retry;
00315                 return;
00316         }
00317 
00318         /* MRR setup */
00319         if (sample) {
00320                 if (sample_slower)
00321                         mrr_ndx[0] = sample_ndx;
00322                 else
00323                         mrr_ndx[0] = mi->max_tp_rate;
00324         } else {
00325                 mrr_ndx[0] = mi->max_tp_rate2;
00326         }
00327         mrr_ndx[1] = mi->max_prob_rate;
00328         mrr_ndx[2] = 0;
00329         for (i = 1; i < 4; i++) {
00330                 ar[i].idx = mi->r[mrr_ndx[i - 1]].rix;
00331                 ar[i].count = mi->r[mrr_ndx[i - 1]].adjusted_retry_count;
00332         }
00333 }
00334 
00335 
00336 static void
00337 calc_rate_durations(enum ieee80211_band band,
00338                     struct minstrel_rate *d,
00339                     struct ieee80211_rate *rate)
00340 {
00341         int erp = !!(rate->flags & IEEE80211_RATE_ERP_G);
00342 
00343         d->perfect_tx_time = ieee80211_frame_duration(band, 1200,
00344                         rate->bitrate, erp, 1);
00345         d->ack_time = ieee80211_frame_duration(band, 10,
00346                         rate->bitrate, erp, 1);
00347 }
00348 
00349 static void
00350 init_sample_table(struct minstrel_sta_info *mi)
00351 {
00352         unsigned int i, col, new_idx;
00353         unsigned int n_srates = mi->n_rates - 1;
00354         u8 rnd[8];
00355 
00356         mi->sample_column = 0;
00357         mi->sample_idx = 0;
00358         memset(mi->sample_table, 0, SAMPLE_COLUMNS * mi->n_rates);
00359 
00360         for (col = 0; col < SAMPLE_COLUMNS; col++) {
00361                 for (i = 0; i < n_srates; i++) {
00362                         get_random_bytes(rnd, sizeof(rnd));
00363                         new_idx = (i + rnd[i & 7]) % n_srates;
00364 
00365                         while (SAMPLE_TBL(mi, new_idx, col) != 0)
00366                                 new_idx = (new_idx + 1) % n_srates;
00367 
00368                         /* Don't sample the slowest rate (i.e. slowest base
00369                          * rate). We must presume that the slowest rate works
00370                          * fine, or else other management frames will also be
00371                          * failing and the link will break */
00372                         SAMPLE_TBL(mi, new_idx, col) = i + 1;
00373                 }
00374         }
00375 }
00376 
00377 static void
00378 minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,
00379                struct ieee80211_sta *sta, void *priv_sta)
00380 {
00381         struct minstrel_sta_info *mi = priv_sta;
00382         struct minstrel_priv *mp = priv;
00383         struct ieee80211_rate *ctl_rate;
00384         unsigned int i, n = 0;
00385         unsigned int t_slot = 9; /* FIXME: get real slot time */
00386 
00387         mi->lowest_rix = rate_lowest_index(sband, sta);
00388         ctl_rate = &sband->bitrates[mi->lowest_rix];
00389         mi->sp_ack_dur = ieee80211_frame_duration(sband->band, 10,
00390                                 ctl_rate->bitrate,
00391                                 !!(ctl_rate->flags & IEEE80211_RATE_ERP_G), 1);
00392 
00393         for (i = 0; i < sband->n_bitrates; i++) {
00394                 struct minstrel_rate *mr = &mi->r[n];
00395                 unsigned int tx_time = 0, tx_time_cts = 0, tx_time_rtscts = 0;
00396                 unsigned int tx_time_single;
00397                 unsigned int cw = mp->cw_min;
00398 
00399                 if (!rate_supported(sta, sband->band, i))
00400                         continue;
00401                 n++;
00402                 memset(mr, 0, sizeof(*mr));
00403 
00404                 mr->rix = i;
00405                 mr->bitrate = sband->bitrates[i].bitrate / 5;
00406                 calc_rate_durations(sband->band, mr, &sband->bitrates[i]);
00407 
00408                 /* calculate maximum number of retransmissions before
00409                  * fallback (based on maximum segment size) */
00410                 mr->sample_limit = -1;
00411                 mr->retry_count = 1;
00412                 mr->retry_count_cts = 1;
00413                 mr->retry_count_rtscts = 1;
00414                 tx_time = mr->perfect_tx_time + mi->sp_ack_dur;
00415                 do {
00416                         /* add one retransmission */
00417                         tx_time_single = mr->ack_time + mr->perfect_tx_time;
00418 
00419                         /* contention window */
00420                         tx_time_single += (t_slot * cw) >> 1;
00421                         cw = min((cw << 1) | 1, mp->cw_max);
00422 
00423                         tx_time += tx_time_single;
00424                         tx_time_cts += tx_time_single + mi->sp_ack_dur;
00425                         tx_time_rtscts += tx_time_single + 2 * mi->sp_ack_dur;
00426                         if ((tx_time_cts < mp->segment_size) &&
00427                                 (mr->retry_count_cts < mp->max_retry))
00428                                 mr->retry_count_cts++;
00429                         if ((tx_time_rtscts < mp->segment_size) &&
00430                                 (mr->retry_count_rtscts < mp->max_retry))
00431                                 mr->retry_count_rtscts++;
00432                 } while ((tx_time < mp->segment_size) &&
00433                                 (++mr->retry_count < mp->max_retry));
00434                 mr->adjusted_retry_count = mr->retry_count;
00435         }
00436 
00437         for (i = n; i < sband->n_bitrates; i++) {
00438                 struct minstrel_rate *mr = &mi->r[i];
00439                 mr->rix = -1;
00440         }
00441 
00442         mi->n_rates = n;
00443         mi->stats_update = jiffies;
00444 
00445         init_sample_table(mi);
00446 }
00447 
00448 static void *
00449 minstrel_alloc_sta(void *priv, struct ieee80211_sta *sta, gfp_t gfp)
00450 {
00451         struct ieee80211_supported_band *sband;
00452         struct minstrel_sta_info *mi;
00453         struct minstrel_priv *mp = priv;
00454         struct ieee80211_hw *hw = mp->hw;
00455         int max_rates = 0;
00456         int i;
00457 
00458         mi = kzalloc(sizeof(struct minstrel_sta_info), gfp);
00459         if (!mi)
00460                 return NULL;
00461 
00462         for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
00463                 sband = hw->wiphy->bands[i];
00464                 if (sband && sband->n_bitrates > max_rates)
00465                         max_rates = sband->n_bitrates;
00466         }
00467 
00468         mi->r = kzalloc(sizeof(struct minstrel_rate) * max_rates, gfp);
00469         if (!mi->r)
00470                 goto error;
00471 
00472         mi->sample_table = kmalloc(SAMPLE_COLUMNS * max_rates, gfp);
00473         if (!mi->sample_table)
00474                 goto error1;
00475 
00476         mi->stats_update = jiffies;
00477         return mi;
00478 
00479 error1:
00480         kfree(mi->r);
00481 error:
00482         kfree(mi);
00483         return NULL;
00484 }
00485 
00486 static void
00487 minstrel_free_sta(void *priv, struct ieee80211_sta *sta, void *priv_sta)
00488 {
00489         struct minstrel_sta_info *mi = priv_sta;
00490 
00491         kfree(mi->sample_table);
00492         kfree(mi->r);
00493         kfree(mi);
00494 }
00495 
00496 static void *
00497 minstrel_alloc(struct ieee80211_hw *hw, struct dentry *debugfsdir)
00498 {
00499         struct minstrel_priv *mp;
00500 
00501         mp = kzalloc(sizeof(struct minstrel_priv), GFP_ATOMIC);
00502         if (!mp)
00503                 return NULL;
00504 
00505         /* contention window settings
00506          * Just an approximation. Using the per-queue values would complicate
00507          * the calculations and is probably unnecessary */
00508         mp->cw_min = 15;
00509         mp->cw_max = 1023;
00510 
00511         /* number of packets (in %) to use for sampling other rates
00512          * sample less often for non-mrr packets, because the overhead
00513          * is much higher than with mrr */
00514         mp->lookaround_rate = 5;
00515         mp->lookaround_rate_mrr = 10;
00516 
00517         /* moving average weight for EWMA */
00518         mp->ewma_level = 75;
00519 
00520         /* maximum time that the hw is allowed to stay in one MRR segment */
00521         mp->segment_size = 6000;
00522 
00523         if (hw->max_rate_tries > 0)
00524                 mp->max_retry = hw->max_rate_tries;
00525         else
00526                 /* safe default, does not necessarily have to match hw properties */
00527                 mp->max_retry = 7;
00528 
00529         if (hw->max_rates >= 4)
00530                 mp->has_mrr = true;
00531 
00532         mp->hw = hw;
00533         mp->update_interval = 100;
00534 
00535 #ifdef CONFIG_MAC80211_DEBUGFS
00536         mp->fixed_rate_idx = (u32) -1;
00537         mp->dbg_fixed_rate = debugfs_create_u32("fixed_rate_idx",
00538                         S_IRUGO | S_IWUGO, debugfsdir, &mp->fixed_rate_idx);
00539 #endif
00540 
00541         return mp;
00542 }
00543 
00544 static void
00545 minstrel_free(void *priv)
00546 {
00547 #ifdef CONFIG_MAC80211_DEBUGFS
00548         debugfs_remove(((struct minstrel_priv *)priv)->dbg_fixed_rate);
00549 #endif
00550         kfree(priv);
00551 }
00552 
00553 struct rate_control_ops mac80211_minstrel = {
00554         .name = "minstrel",
00555         .tx_status = minstrel_tx_status,
00556         .get_rate = minstrel_get_rate,
00557         .rate_init = minstrel_rate_init,
00558         .alloc = minstrel_alloc,
00559         .free = minstrel_free,
00560         .alloc_sta = minstrel_alloc_sta,
00561         .free_sta = minstrel_free_sta,
00562 #ifdef CONFIG_MAC80211_DEBUGFS
00563         .add_sta_debugfs = minstrel_add_sta_debugfs,
00564         .remove_sta_debugfs = minstrel_remove_sta_debugfs,
00565 #endif
00566 };
00567 
00568 int __init
00569 rc80211_minstrel_init(void)
00570 {
00571         return ieee80211_rate_control_register(&mac80211_minstrel);
00572 }
00573 
00574 void
00575 rc80211_minstrel_exit(void)
00576 {
00577         ieee80211_rate_control_unregister(&mac80211_minstrel);
00578 }
00579 


ros_rt_wmp
Author(s): Danilo Tardioli, dantard@unizar.es
autogenerated on Mon Oct 6 2014 08:27:10