linux/net/mac80211/rc80211_minstrel.c
Felix Fietkau eae44756d6 minstrel: make the rate control ops reusable from another rc implementation
This patch makes it possible to reuse the minstrel rate control ops
from another rate control module. This is useful in preparing for the
new 802.11n implementation of minstrel, which will reuse the old code
for legacy stations.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
2010-03-10 17:44:23 -05:00

570 lines
16 KiB
C

/*
* 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 <net/mac80211.h>
#include "rate.h"
#include "rc80211_minstrel.h"
#define SAMPLE_COLUMNS 10
#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;
WARN_ON(i < 0);
return i;
}
static void
minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
{
u32 max_tp = 0, index_max_tp = 0, index_max_tp2 = 0;
u32 max_prob = 0, index_max_prob = 0;
u32 usecs;
u32 p;
int i;
mi->stats_update = jiffies;
for (i = 0; i < mi->n_rates; i++) {
struct minstrel_rate *mr = &mi->r[i];
usecs = mr->perfect_tx_time;
if (!usecs)
usecs = 1000000;
/* To avoid rounding issues, probabilities scale from 0 (0%)
* to 18000 (100%) */
if (mr->attempts) {
p = (mr->success * 18000) / mr->attempts;
mr->succ_hist += mr->success;
mr->att_hist += mr->attempts;
mr->cur_prob = p;
p = ((p * (100 - mp->ewma_level)) + (mr->probability *
mp->ewma_level)) / 100;
mr->probability = p;
mr->cur_tp = p * (1000000 / usecs);
}
mr->last_success = mr->success;
mr->last_attempts = mr->attempts;
mr->success = 0;
mr->attempts = 0;
/* Sample less often below the 10% chance of success.
* Sample less often above the 95% chance of success. */
if ((mr->probability > 17100) || (mr->probability < 1800)) {
mr->adjusted_retry_count = mr->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 = mr->retry_count;
}
if (!mr->adjusted_retry_count)
mr->adjusted_retry_count = 2;
}
for (i = 0; i < mi->n_rates; i++) {
struct minstrel_rate *mr = &mi->r[i];
if (max_tp < mr->cur_tp) {
index_max_tp = i;
max_tp = mr->cur_tp;
}
if (max_prob < mr->probability) {
index_max_prob = i;
max_prob = mr->probability;
}
}
max_tp = 0;
for (i = 0; i < mi->n_rates; i++) {
struct minstrel_rate *mr = &mi->r[i];
if (i == index_max_tp)
continue;
if (max_tp < mr->cur_tp) {
index_max_tp2 = i;
max_tp = mr->cur_tp;
}
}
mi->max_tp_rate = index_max_tp;
mi->max_tp_rate2 = index_max_tp2;
mi->max_prob_rate = index_max_prob;
}
static void
minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
struct ieee80211_sta *sta, void *priv_sta,
struct sk_buff *skb)
{
struct minstrel_sta_info *mi = priv_sta;
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
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].attempts += ar[i].count;
if ((i != IEEE80211_TX_MAX_RATES - 1) && (ar[i + 1].idx < 0))
mi->r[ndx].success += success;
}
if ((info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE) && (i >= 0))
mi->sample_count++;
if (mi->sample_deferred > 0)
mi->sample_deferred--;
}
static inline unsigned int
minstrel_get_retry_count(struct minstrel_rate *mr,
struct ieee80211_tx_info *info)
{
unsigned int retry = mr->adjusted_retry_count;
if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_RTS_CTS)
retry = max(2U, min(mr->retry_count_rtscts, retry));
else if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_CTS_PROTECT)
retry = max(2U, 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_idx, mi->sample_column);
mi->sample_idx++;
if ((int) mi->sample_idx > (mi->n_rates - 2)) {
mi->sample_idx = 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 *ar = info->control.rates;
unsigned int ndx, sample_ndx = 0;
bool mrr;
bool sample_slower = false;
bool sample = false;
int i, delta;
int mrr_ndx[3];
int sample_rate;
if (rate_control_send_low(sta, priv_sta, txrc))
return;
mrr = mp->has_mrr && !txrc->rts && !txrc->bss_conf->use_cts_prot;
if (time_after(jiffies, mi->stats_update + (mp->update_interval *
HZ) / 1000))
minstrel_update_stats(mp, mi);
ndx = mi->max_tp_rate;
if (mrr)
sample_rate = mp->lookaround_rate_mrr;
else
sample_rate = mp->lookaround_rate;
mi->packet_count++;
delta = (mi->packet_count * sample_rate / 100) -
(mi->sample_count + mi->sample_deferred / 2);
/* delta > 0: sampling required */
if ((delta > 0) && (mrr || !mi->prev_sample)) {
struct minstrel_rate *msr;
if (mi->packet_count >= 10000) {
mi->sample_deferred = 0;
mi->sample_count = 0;
mi->packet_count = 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_count += (delta - mi->n_rates * 2);
}
sample_ndx = minstrel_get_next_sample(mi);
msr = &mi->r[sample_ndx];
sample = true;
sample_slower = mrr && (msr->perfect_tx_time >
mi->r[ndx].perfect_tx_time);
if (!sample_slower) {
if (msr->sample_limit != 0) {
ndx = sample_ndx;
mi->sample_count++;
if (msr->sample_limit > 0)
msr->sample_limit--;
} else {
sample = false;
}
} else {
/* 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;
mi->sample_deferred++;
}
}
mi->prev_sample = sample;
/* 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 && sample && (mi->r[ndx].probability > 17100))
ndx = mi->max_tp_rate;
ar[0].idx = mi->r[ndx].rix;
ar[0].count = minstrel_get_retry_count(&mi->r[ndx], info);
if (!mrr) {
if (!sample)
ar[0].count = mp->max_retry;
ar[1].idx = mi->lowest_rix;
ar[1].count = mp->max_retry;
return;
}
/* MRR setup */
if (sample) {
if (sample_slower)
mrr_ndx[0] = sample_ndx;
else
mrr_ndx[0] = mi->max_tp_rate;
} else {
mrr_ndx[0] = mi->max_tp_rate2;
}
mrr_ndx[1] = mi->max_prob_rate;
mrr_ndx[2] = 0;
for (i = 1; i < 4; i++) {
ar[i].idx = mi->r[mrr_ndx[i - 1]].rix;
ar[i].count = mi->r[mrr_ndx[i - 1]].adjusted_retry_count;
}
}
static void
calc_rate_durations(struct minstrel_sta_info *mi, struct ieee80211_local *local,
struct minstrel_rate *d, struct ieee80211_rate *rate)
{
int erp = !!(rate->flags & IEEE80211_RATE_ERP_G);
d->perfect_tx_time = ieee80211_frame_duration(local, 1200,
rate->bitrate, erp, 1);
d->ack_time = ieee80211_frame_duration(local, 10,
rate->bitrate, erp, 1);
}
static void
init_sample_table(struct minstrel_sta_info *mi)
{
unsigned int i, col, new_idx;
unsigned int n_srates = mi->n_rates - 1;
u8 rnd[8];
mi->sample_column = 0;
mi->sample_idx = 0;
memset(mi->sample_table, 0, SAMPLE_COLUMNS * mi->n_rates);
for (col = 0; col < SAMPLE_COLUMNS; col++) {
for (i = 0; i < n_srates; i++) {
get_random_bytes(rnd, sizeof(rnd));
new_idx = (i + rnd[i & 7]) % n_srates;
while (SAMPLE_TBL(mi, new_idx, col) != 0)
new_idx = (new_idx + 1) % n_srates;
/* Don't sample the slowest rate (i.e. slowest base
* rate). We must presume that the slowest rate works
* fine, or else other management frames will also be
* failing and the link will break */
SAMPLE_TBL(mi, new_idx, col) = i + 1;
}
}
}
static void
minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,
struct ieee80211_sta *sta, void *priv_sta)
{
struct minstrel_sta_info *mi = priv_sta;
struct minstrel_priv *mp = priv;
struct ieee80211_local *local = hw_to_local(mp->hw);
struct ieee80211_rate *ctl_rate;
unsigned int i, n = 0;
unsigned int t_slot = 9; /* FIXME: get real slot time */
mi->lowest_rix = rate_lowest_index(sband, sta);
ctl_rate = &sband->bitrates[mi->lowest_rix];
mi->sp_ack_dur = ieee80211_frame_duration(local, 10, ctl_rate->bitrate,
!!(ctl_rate->flags & IEEE80211_RATE_ERP_G), 1);
for (i = 0; i < sband->n_bitrates; i++) {
struct minstrel_rate *mr = &mi->r[n];
unsigned int tx_time = 0, tx_time_cts = 0, tx_time_rtscts = 0;
unsigned int tx_time_single;
unsigned int cw = mp->cw_min;
if (!rate_supported(sta, sband->band, i))
continue;
n++;
memset(mr, 0, sizeof(*mr));
mr->rix = i;
mr->bitrate = sband->bitrates[i].bitrate / 5;
calc_rate_durations(mi, local, mr,
&sband->bitrates[i]);
/* calculate maximum number of retransmissions before
* fallback (based on maximum segment size) */
mr->sample_limit = -1;
mr->retry_count = 1;
mr->retry_count_cts = 1;
mr->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 + min(cw, mp->cw_max);
cw = (cw << 1) | 1;
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) &&
(mr->retry_count_rtscts < mp->max_retry))
mr->retry_count_rtscts++;
} while ((tx_time < mp->segment_size) &&
(++mr->retry_count < mp->max_retry));
mr->adjusted_retry_count = mr->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->stats_update = jiffies;
init_sample_table(mi);
}
static void *
minstrel_alloc_sta(void *priv, struct ieee80211_sta *sta, gfp_t gfp)
{
struct ieee80211_supported_band *sband;
struct minstrel_sta_info *mi;
struct minstrel_priv *mp = priv;
struct ieee80211_hw *hw = mp->hw;
int max_rates = 0;
int i;
mi = kzalloc(sizeof(struct minstrel_sta_info), gfp);
if (!mi)
return NULL;
for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
sband = hw->wiphy->bands[i];
if (sband && sband->n_bitrates > max_rates)
max_rates = sband->n_bitrates;
}
mi->r = kzalloc(sizeof(struct minstrel_rate) * max_rates, gfp);
if (!mi->r)
goto error;
mi->sample_table = kmalloc(SAMPLE_COLUMNS * max_rates, gfp);
if (!mi->sample_table)
goto error1;
mi->stats_update = jiffies;
return mi;
error1:
kfree(mi->r);
error:
kfree(mi);
return NULL;
}
static void
minstrel_free_sta(void *priv, struct ieee80211_sta *sta, void *priv_sta)
{
struct minstrel_sta_info *mi = priv_sta;
kfree(mi->sample_table);
kfree(mi->r);
kfree(mi);
}
static void *
minstrel_alloc(struct ieee80211_hw *hw, struct dentry *debugfsdir)
{
struct minstrel_priv *mp;
mp = kzalloc(sizeof(struct minstrel_priv), GFP_ATOMIC);
if (!mp)
return NULL;
/* contention window settings
* Just an approximation. Using the per-queue values would complicate
* the calculations and is probably unnecessary */
mp->cw_min = 15;
mp->cw_max = 1023;
/* number of packets (in %) to use for sampling other rates
* sample less often for non-mrr packets, because the overhead
* is much higher than with mrr */
mp->lookaround_rate = 5;
mp->lookaround_rate_mrr = 10;
/* moving average weight for EWMA */
mp->ewma_level = 75;
/* maximum time that the hw is allowed to stay in one MRR segment */
mp->segment_size = 6000;
if (hw->max_rate_tries > 0)
mp->max_retry = hw->max_rate_tries;
else
/* safe default, does not necessarily have to match hw properties */
mp->max_retry = 7;
if (hw->max_rates >= 4)
mp->has_mrr = true;
mp->hw = hw;
mp->update_interval = 100;
return mp;
}
static void
minstrel_free(void *priv)
{
kfree(priv);
}
struct rate_control_ops mac80211_minstrel = {
.name = "minstrel",
.tx_status = minstrel_tx_status,
.get_rate = minstrel_get_rate,
.rate_init = minstrel_rate_init,
.alloc = minstrel_alloc,
.free = minstrel_free,
.alloc_sta = minstrel_alloc_sta,
.free_sta = minstrel_free_sta,
#ifdef CONFIG_MAC80211_DEBUGFS
.add_sta_debugfs = minstrel_add_sta_debugfs,
.remove_sta_debugfs = minstrel_remove_sta_debugfs,
#endif
};
int __init
rc80211_minstrel_init(void)
{
return ieee80211_rate_control_register(&mac80211_minstrel);
}
void
rc80211_minstrel_exit(void)
{
ieee80211_rate_control_unregister(&mac80211_minstrel);
}