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linux/net/mac80211/rc80211_minstrel.c

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/*
* Copyright (C) 2008 Felix Fietkau <nbd@openwrt.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Based on minstrel.c:
* Copyright (C) 2005-2007 Derek Smithies <derek@indranet.co.nz>
* Sponsored by Indranet Technologies Ltd
*
* Based on sample.c:
* Copyright (c) 2005 John Bicket
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer,
* without modification.
* 2. Redistributions in binary form must reproduce at minimum a disclaimer
* similar to the "NO WARRANTY" disclaimer below ("Disclaimer") and any
* redistribution must be conditioned upon including a substantially
* similar Disclaimer requirement for further binary redistribution.
* 3. Neither the names of the above-listed copyright holders nor the names
* of any contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* Alternatively, this software may be distributed under the terms of the
* GNU General Public License ("GPL") version 2 as published by the Free
* Software Foundation.
*
* NO WARRANTY
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF NONINFRINGEMENT, MERCHANTIBILITY
* AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
* THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY,
* OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
* IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGES.
*/
#include <linux/netdevice.h>
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/debugfs.h>
#include <linux/random.h>
#include <linux/ieee80211.h>
#include <linux/slab.h>
#include <net/mac80211.h>
#include "rate.h"
#include "rc80211_minstrel.h"
#define SAMPLE_TBL(_mi, _idx, _col) \
_mi->sample_table[(_idx * SAMPLE_COLUMNS) + _col]
/* convert mac80211 rate index to local array index */
static inline int
rix_to_ndx(struct minstrel_sta_info *mi, int rix)
{
int i = rix;
for (i = rix; i >= 0; i--)
if (mi->r[i].rix == rix)
break;
return i;
}
/* return current EMWA throughput */
int minstrel_get_tp_avg(struct minstrel_rate *mr, int prob_ewma)
{
int usecs;
usecs = mr->perfect_tx_time;
if (!usecs)
usecs = 1000000;
/* reset thr. below 10% success */
if (mr->stats.prob_ewma < MINSTREL_FRAC(10, 100))
return 0;
if (prob_ewma > MINSTREL_FRAC(90, 100))
return MINSTREL_TRUNC(100000 * (MINSTREL_FRAC(90, 100) / usecs));
else
return MINSTREL_TRUNC(100000 * (prob_ewma / usecs));
}
/* find & sort topmost throughput rates */
static inline void
minstrel_sort_best_tp_rates(struct minstrel_sta_info *mi, int i, u8 *tp_list)
{
int j;
struct minstrel_rate_stats *tmp_mrs;
struct minstrel_rate_stats *cur_mrs = &mi->r[i].stats;
for (j = MAX_THR_RATES; j > 0; --j) {
tmp_mrs = &mi->r[tp_list[j - 1]].stats;
if (minstrel_get_tp_avg(&mi->r[i], cur_mrs->prob_ewma) <=
minstrel_get_tp_avg(&mi->r[tp_list[j - 1]], tmp_mrs->prob_ewma))
break;
}
if (j < MAX_THR_RATES - 1)
memmove(&tp_list[j + 1], &tp_list[j], MAX_THR_RATES - (j + 1));
if (j < MAX_THR_RATES)
tp_list[j] = i;
}
static void
minstrel_set_rate(struct minstrel_sta_info *mi, struct ieee80211_sta_rates *ratetbl,
int offset, int idx)
{
struct minstrel_rate *r = &mi->r[idx];
ratetbl->rate[offset].idx = r->rix;
ratetbl->rate[offset].count = r->adjusted_retry_count;
ratetbl->rate[offset].count_cts = r->retry_count_cts;
ratetbl->rate[offset].count_rts = r->stats.retry_count_rtscts;
}
static void
minstrel_update_rates(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
{
struct ieee80211_sta_rates *ratetbl;
int i = 0;
ratetbl = kzalloc(sizeof(*ratetbl), GFP_ATOMIC);
if (!ratetbl)
return;
/* Start with max_tp_rate */
minstrel_set_rate(mi, ratetbl, i++, mi->max_tp_rate[0]);
if (mp->hw->max_rates >= 3) {
/* At least 3 tx rates supported, use max_tp_rate2 next */
minstrel_set_rate(mi, ratetbl, i++, mi->max_tp_rate[1]);
}
if (mp->hw->max_rates >= 2) {
/* At least 2 tx rates supported, use max_prob_rate next */
minstrel_set_rate(mi, ratetbl, i++, mi->max_prob_rate);
}
/* Use lowest rate last */
ratetbl->rate[i].idx = mi->lowest_rix;
ratetbl->rate[i].count = mp->max_retry;
ratetbl->rate[i].count_cts = mp->max_retry;
ratetbl->rate[i].count_rts = mp->max_retry;
rate_control_set_rates(mp->hw, mi->sta, ratetbl);
}
/*
* Recalculate statistics and counters of a given rate
*/
void
minstrel_calc_rate_stats(struct minstrel_rate_stats *mrs)
{
unsigned int cur_prob;
if (unlikely(mrs->attempts > 0)) {
mrs->sample_skipped = 0;
cur_prob = MINSTREL_FRAC(mrs->success, mrs->attempts);
if (unlikely(!mrs->att_hist)) {
mrs->prob_ewma = cur_prob;
} else {
/*update exponential weighted moving avarage */
mrs->prob_ewma = minstrel_ewma(mrs->prob_ewma,
cur_prob,
EWMA_LEVEL);
}
mrs->att_hist += mrs->attempts;
mrs->succ_hist += mrs->success;
} else {
mrs->sample_skipped++;
}
mrs->last_success = mrs->success;
mrs->last_attempts = mrs->attempts;
mrs->success = 0;
mrs->attempts = 0;
}
static void
minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
{
u8 tmp_tp_rate[MAX_THR_RATES];
u8 tmp_prob_rate = 0;
int i, tmp_cur_tp, tmp_prob_tp;
for (i = 0; i < MAX_THR_RATES; i++)
tmp_tp_rate[i] = 0;
for (i = 0; i < mi->n_rates; i++) {
struct minstrel_rate *mr = &mi->r[i];
struct minstrel_rate_stats *mrs = &mi->r[i].stats;
struct minstrel_rate_stats *tmp_mrs = &mi->r[tmp_prob_rate].stats;
/* Update statistics of success probability per rate */
minstrel_calc_rate_stats(mrs);
/* Sample less often below the 10% chance of success.
* Sample less often above the 95% chance of success. */
if (mrs->prob_ewma > MINSTREL_FRAC(95, 100) ||
mrs->prob_ewma < MINSTREL_FRAC(10, 100)) {
mr->adjusted_retry_count = mrs->retry_count >> 1;
if (mr->adjusted_retry_count > 2)
mr->adjusted_retry_count = 2;
mr->sample_limit = 4;
} else {
mr->sample_limit = -1;
mr->adjusted_retry_count = mrs->retry_count;
}
if (!mr->adjusted_retry_count)
mr->adjusted_retry_count = 2;
minstrel_sort_best_tp_rates(mi, i, tmp_tp_rate);
/* To determine the most robust rate (max_prob_rate) used at
* 3rd mmr stage we distinct between two cases:
* (1) if any success probabilitiy >= 95%, out of those rates
* choose the maximum throughput rate as max_prob_rate
* (2) if all success probabilities < 95%, the rate with
* highest success probability is chosen as max_prob_rate */
if (mrs->prob_ewma >= MINSTREL_FRAC(95, 100)) {
tmp_cur_tp = minstrel_get_tp_avg(mr, mrs->prob_ewma);
tmp_prob_tp = minstrel_get_tp_avg(&mi->r[tmp_prob_rate],
tmp_mrs->prob_ewma);
if (tmp_cur_tp >= tmp_prob_tp)
tmp_prob_rate = i;
} else {
if (mrs->prob_ewma >= tmp_mrs->prob_ewma)
tmp_prob_rate = i;
}
}
/* Assign the new rate set */
memcpy(mi->max_tp_rate, tmp_tp_rate, sizeof(mi->max_tp_rate));
mi->max_prob_rate = tmp_prob_rate;
#ifdef CONFIG_MAC80211_DEBUGFS
/* use fixed index if set */
if (mp->fixed_rate_idx != -1) {
mi->max_tp_rate[0] = mp->fixed_rate_idx;
mi->max_tp_rate[1] = mp->fixed_rate_idx;
mi->max_prob_rate = mp->fixed_rate_idx;
}
#endif
/* Reset update timer */
mi->last_stats_update = jiffies;
minstrel_update_rates(mp, mi);
}
static void
minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
void *priv_sta, struct ieee80211_tx_status *st)
{
struct ieee80211_tx_info *info = st->info;
struct minstrel_priv *mp = priv;
struct minstrel_sta_info *mi = priv_sta;
struct ieee80211_tx_rate *ar = info->status.rates;
int i, ndx;
int success;
success = !!(info->flags & IEEE80211_TX_STAT_ACK);
for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
if (ar[i].idx < 0)
break;
ndx = rix_to_ndx(mi, ar[i].idx);
if (ndx < 0)
continue;
mi->r[ndx].stats.attempts += ar[i].count;
if ((i != IEEE80211_TX_MAX_RATES - 1) && (ar[i + 1].idx < 0))
mi->r[ndx].stats.success += success;
}
if ((info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE) && (i >= 0))
mi->sample_packets++;
if (mi->sample_deferred > 0)
mi->sample_deferred--;
if (time_after(jiffies, mi->last_stats_update +
(mp->update_interval * HZ) / 1000))
minstrel_update_stats(mp, mi);
}
static inline unsigned int
minstrel_get_retry_count(struct minstrel_rate *mr,
struct ieee80211_tx_info *info)
{
u8 retry = mr->adjusted_retry_count;
if (info->control.use_rts)
retry = max_t(u8, 2, min(mr->stats.retry_count_rtscts, retry));
else if (info->control.use_cts_prot)
retry = max_t(u8, 2, min(mr->retry_count_cts, retry));
return retry;
}
static int
minstrel_get_next_sample(struct minstrel_sta_info *mi)
{
unsigned int sample_ndx;
sample_ndx = SAMPLE_TBL(mi, mi->sample_row, mi->sample_column);
mi->sample_row++;
if ((int) mi->sample_row >= mi->n_rates) {
mi->sample_row = 0;
mi->sample_column++;
if (mi->sample_column >= SAMPLE_COLUMNS)
mi->sample_column = 0;
}
return sample_ndx;
}
static void
minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
void *priv_sta, struct ieee80211_tx_rate_control *txrc)
{
struct sk_buff *skb = txrc->skb;
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
struct minstrel_sta_info *mi = priv_sta;
struct minstrel_priv *mp = priv;
struct ieee80211_tx_rate *rate = &info->control.rates[0];
struct minstrel_rate *msr, *mr;
unsigned int ndx;
bool mrr_capable;
bool prev_sample;
int delta;
int sampling_ratio;
/* management/no-ack frames do not use rate control */
if (rate_control_send_low(sta, priv_sta, txrc))
return;
/* check multi-rate-retry capabilities & adjust lookaround_rate */
mrr_capable = mp->has_mrr &&
!txrc->rts &&
!txrc->bss_conf->use_cts_prot;
if (mrr_capable)
sampling_ratio = mp->lookaround_rate_mrr;
else
sampling_ratio = mp->lookaround_rate;
/* increase sum packet counter */
mi->total_packets++;
#ifdef CONFIG_MAC80211_DEBUGFS
if (mp->fixed_rate_idx != -1)
return;
#endif
/* Don't use EAPOL frames for sampling on non-mrr hw */
if (mp->hw->max_rates == 1 &&
(info->control.flags & IEEE80211_TX_CTRL_PORT_CTRL_PROTO))
return;
delta = (mi->total_packets * sampling_ratio / 100) -
(mi->sample_packets + mi->sample_deferred / 2);
/* delta < 0: no sampling required */
prev_sample = mi->prev_sample;
mi->prev_sample = false;
if (delta < 0 || (!mrr_capable && prev_sample))
return;
if (mi->total_packets >= 10000) {
mi->sample_deferred = 0;
mi->sample_packets = 0;
mi->total_packets = 0;
} else if (delta > mi->n_rates * 2) {
/* With multi-rate retry, not every planned sample
* attempt actually gets used, due to the way the retry
* chain is set up - [max_tp,sample,prob,lowest] for
* sample_rate < max_tp.
*
* If there's too much sampling backlog and the link
* starts getting worse, minstrel would start bursting
* out lots of sampling frames, which would result
* in a large throughput loss. */
mi->sample_packets += (delta - mi->n_rates * 2);
}
/* get next random rate sample */
ndx = minstrel_get_next_sample(mi);
msr = &mi->r[ndx];
mr = &mi->r[mi->max_tp_rate[0]];
/* Decide if direct ( 1st mrr stage) or indirect (2nd mrr stage)
* rate sampling method should be used.
* Respect such rates that are not sampled for 20 interations.
*/
if (mrr_capable &&
msr->perfect_tx_time > mr->perfect_tx_time &&
msr->stats.sample_skipped < 20) {
/* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
* packets that have the sampling rate deferred to the
* second MRR stage. Increase the sample counter only
* if the deferred sample rate was actually used.
* Use the sample_deferred counter to make sure that
* the sampling is not done in large bursts */
info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
rate++;
mi->sample_deferred++;
} else {
if (!msr->sample_limit)
return;
mi->sample_packets++;
if (msr->sample_limit > 0)
msr->sample_limit--;
}
/* If we're not using MRR and the sampling rate already
* has a probability of >95%, we shouldn't be attempting
* to use it, as this only wastes precious airtime */
if (!mrr_capable &&
(mi->r[ndx].stats.prob_ewma > MINSTREL_FRAC(95, 100)))
return;
mi->prev_sample = true;
rate->idx = mi->r[ndx].rix;
rate->count = minstrel_get_retry_count(&mi->r[ndx], info);
}
static void
calc_rate_durations(enum nl80211_band band,
struct minstrel_rate *d,
struct ieee80211_rate *rate,
struct cfg80211_chan_def *chandef)
{
int erp = !!(rate->flags & IEEE80211_RATE_ERP_G);
int shift = ieee80211_chandef_get_shift(chandef);
d->perfect_tx_time = ieee80211_frame_duration(band, 1200,
DIV_ROUND_UP(rate->bitrate, 1 << shift), erp, 1,
shift);
d->ack_time = ieee80211_frame_duration(band, 10,
DIV_ROUND_UP(rate->bitrate, 1 << shift), erp, 1,
shift);
}
static void
init_sample_table(struct minstrel_sta_info *mi)
{
unsigned int i, col, new_idx;
u8 rnd[8];
mi->sample_column = 0;
mi->sample_row = 0;
memset(mi->sample_table, 0xff, SAMPLE_COLUMNS * mi->n_rates);
for (col = 0; col < SAMPLE_COLUMNS; col++) {
prandom_bytes(rnd, sizeof(rnd));
for (i = 0; i < mi->n_rates; i++) {
new_idx = (i + rnd[i & 7]) % mi->n_rates;
while (SAMPLE_TBL(mi, new_idx, col) != 0xff)
new_idx = (new_idx + 1) % mi->n_rates;
SAMPLE_TBL(mi, new_idx, col) = i;
}
}
}
static void
minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,
struct cfg80211_chan_def *chandef,
struct ieee80211_sta *sta, void *priv_sta)
{
struct minstrel_sta_info *mi = priv_sta;
struct minstrel_priv *mp = priv;
struct ieee80211_rate *ctl_rate;
unsigned int i, n = 0;
unsigned int t_slot = 9; /* FIXME: get real slot time */
u32 rate_flags;
mi->sta = sta;
mi->lowest_rix = rate_lowest_index(sband, sta);
ctl_rate = &sband->bitrates[mi->lowest_rix];
mi->sp_ack_dur = ieee80211_frame_duration(sband->band, 10,
ctl_rate->bitrate,
!!(ctl_rate->flags & IEEE80211_RATE_ERP_G), 1,
ieee80211_chandef_get_shift(chandef));
rate_flags = ieee80211_chandef_rate_flags(&mp->hw->conf.chandef);
memset(mi->max_tp_rate, 0, sizeof(mi->max_tp_rate));
mi->max_prob_rate = 0;
for (i = 0; i < sband->n_bitrates; i++) {
struct minstrel_rate *mr = &mi->r[n];
struct minstrel_rate_stats *mrs = &mi->r[n].stats;
unsigned int tx_time = 0, tx_time_cts = 0, tx_time_rtscts = 0;
unsigned int tx_time_single;
unsigned int cw = mp->cw_min;
int shift;
if (!rate_supported(sta, sband->band, i))
continue;
if ((rate_flags & sband->bitrates[i].flags) != rate_flags)
continue;
n++;
memset(mr, 0, sizeof(*mr));
memset(mrs, 0, sizeof(*mrs));
mr->rix = i;
shift = ieee80211_chandef_get_shift(chandef);
mr->bitrate = DIV_ROUND_UP(sband->bitrates[i].bitrate,
(1 << shift) * 5);
calc_rate_durations(sband->band, mr, &sband->bitrates[i],
chandef);
/* calculate maximum number of retransmissions before
* fallback (based on maximum segment size) */
mr->sample_limit = -1;
mrs->retry_count = 1;
mr->retry_count_cts = 1;
mrs->retry_count_rtscts = 1;
tx_time = mr->perfect_tx_time + mi->sp_ack_dur;
do {
/* add one retransmission */
tx_time_single = mr->ack_time + mr->perfect_tx_time;
/* contention window */
tx_time_single += (t_slot * cw) >> 1;
cw = min((cw << 1) | 1, mp->cw_max);
tx_time += tx_time_single;
tx_time_cts += tx_time_single + mi->sp_ack_dur;
tx_time_rtscts += tx_time_single + 2 * mi->sp_ack_dur;
if ((tx_time_cts < mp->segment_size) &&
(mr->retry_count_cts < mp->max_retry))
mr->retry_count_cts++;
if ((tx_time_rtscts < mp->segment_size) &&
(mrs->retry_count_rtscts < mp->max_retry))
mrs->retry_count_rtscts++;
} while ((tx_time < mp->segment_size) &&
(++mr->stats.retry_count < mp->max_retry));
mr->adjusted_retry_count = mrs->retry_count;
if (!(sband->bitrates[i].flags & IEEE80211_RATE_ERP_G))
mr->retry_count_cts = mrs->retry_count;
}
for (i = n; i < sband->n_bitrates; i++) {
struct minstrel_rate *mr = &mi->r[i];
mr->rix = -1;
}
mi->n_rates = n;
mi->last_stats_update = jiffies;
init_sample_table(mi);
minstrel_update_rates(mp, mi);
}
static u32 minstrel_get_expected_throughput(void *priv_sta)
{
struct minstrel_sta_info *mi = priv_sta;
struct minstrel_rate_stats *tmp_mrs;
int idx = mi->max_tp_rate[0];
int tmp_cur_tp;
/* convert pkt per sec in kbps (1200 is the average pkt size used for
* computing cur_tp
*/
tmp_mrs = &mi->r[idx].stats;
tmp_cur_tp = minstrel_get_tp_avg(&mi->r[idx], tmp_mrs->prob_ewma) * 10;
tmp_cur_tp = tmp_cur_tp * 1200 * 8 / 1024;
return tmp_cur_tp;
}
const struct rate_control_ops mac80211_minstrel = {
.tx_status_ext = minstrel_tx_status,
.get_rate = minstrel_get_rate,
.rate_init = minstrel_rate_init,
.get_expected_throughput = minstrel_get_expected_throughput,
};
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