/*
* Copyright 2002-2005, Instant802 Networks, Inc.
* Copyright 2005, Devicescape Software, Inc.
* Copyright 2007, Mattias Nissler <mattias.nissler@gmx.de>
* Copyright 2007-2008, Stefano Brivio <stefano.brivio@polimi.it>
*
* 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.
*/
#include <linux/netdevice.h>
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/debugfs.h>
#include <net/mac80211.h>
#include "rate.h"
#include "mesh.h"
#include "rc80211_pid.h"
/* This is an implementation of a TX rate control algorithm that uses a PID
* controller. Given a target failed frames rate, the controller decides about
* TX rate changes to meet the target failed frames rate.
*
* The controller basically computes the following:
*
* adj = CP * err + CI * err_avg + CD * (err - last_err) * (1 + sharpening)
*
* where
* adj adjustment value that is used to switch TX rate (see below)
* err current error: target vs. current failed frames percentage
* last_err last error
* err_avg average (i.e. poor man's integral) of recent errors
* sharpening non-zero when fast response is needed (i.e. right after
* association or no frames sent for a long time), heading
* to zero over time
* CP Proportional coefficient
* CI Integral coefficient
* CD Derivative coefficient
*
* CP, CI, CD are subject to careful tuning.
*
* The integral component uses a exponential moving average approach instead of
* an actual sliding window. The advantage is that we don't need to keep an
* array of the last N error values and computation is easier.
*
* Once we have the adj value, we map it to a rate by means of a learning
* algorithm. This algorithm keeps the state of the percentual failed frames
* difference between rates. The behaviour of the lowest available rate is kept
* as a reference value, and every time we switch between two rates, we compute
* the difference between the failed frames each rate exhibited. By doing so,
* we compare behaviours which different rates exhibited in adjacent timeslices,
* thus the comparison is minimally affected by external conditions. This
* difference gets propagated to the whole set of measurements, so that the
* reference is always the same. Periodically, we normalize this set so that
* recent events weigh the most. By comparing the adj value with this set, we
* avoid pejorative switches to lower rates and allow for switches to higher
* rates if they behaved well.
*
* Note that for the computations we use a fixed-point representation to avoid
* floating point arithmetic. Hence, all values are shifted left by
* RC_PID_ARITH_SHIFT.
*/
/* Adjust the rate while ensuring that we won't switch to a lower rate if it
* exhibited a worse failed frames behaviour and we'll choose the highest rate
* whose failed frames behaviour is not worse than the one of the original rate
* target. While at it, check that the new rate is valid. */
static void rate_control_pid_adjust_rate(struct ieee80211_supported_band *sband,
struct ieee80211_sta *sta,
struct rc_pid_sta_info *spinfo, int adj,
struct rc_pid_rateinfo *rinfo)
{
int cur_sorted, new_sorted, probe, tmp, n_bitrates, band;
int cur = spinfo->txrate_idx;
band = sband->band;
n_bitrates = sband->n_bitrates;
/* Map passed arguments to sorted values. */
cur_sorted = rinfo[cur].rev_index;
new_sorted = cur_sorted + adj;
/* Check limits. */
if (new_sorted < 0)
new_sorted = rinfo[0].rev_index;
else if (new_sorted >= n_bitrates)
new_sorted = rinfo[n_bitrates - 1].rev_index;
tmp = new_sorted;
if (adj < 0) {
/* Ensure that the rate decrease isn't disadvantageous. */
for (probe = cur_sorted; probe >= new_sorted; probe--)
if (rinfo[probe].diff <= rinfo[cur_sorted].diff &&
rate_supported(sta, band, rinfo[probe].index))
tmp = probe;
} else {
/* Look for rate increase with zero (or below) cost. */
for (probe = new_sorted + 1; probe < n_bitrates; probe++)
if (rinfo[probe].diff <= rinfo[new_sorted].diff &&
rate_supported(sta, band, rinfo[probe].index))
tmp = probe;
}
/* Fit the rate found to the nearest supported rate. */
do {
if (rate_supported(sta, band, rinfo[tmp].index)) {
spinfo->txrate_idx = rinfo[tmp].index;
break;
}
if (adj < 0)
tmp--;
else
tmp++;
} while (tmp < n_bitrates && tmp >= 0);
#ifdef CONFIG_MAC80211_DEBUGFS
rate_control_pid_event_rate_change(&spinfo->events,
spinfo->txrate_idx,
sband->bitrates[spinfo->txrate_idx].bitrate);
#endif
}
/* Normalize the failed frames per-rate differences. */
static void rate_control_pid_normalize(struct rc_pid_info *pinfo, int l)
{
int i, norm_offset = pinfo->norm_offset;
struct rc_pid_rateinfo *r = pinfo->rinfo;
if (r[0].diff > norm_offset)
r[0].diff -= norm_offset;
else if (r[0].diff < -norm_offset)
r[0].diff += norm_offset;
for (i = 0; i < l - 1; i++)
if (r[i + 1].diff > r[i].diff + norm_offset)
r[i + 1].diff -= norm_offset;
else if (r[i + 1].diff <= r[i].diff)
r[i + 1].diff += norm_offset;
}
static void rate_control_pid_sample(struct rc_pid_info *pinfo,
struct ieee80211_supported_band *sband,
struct ieee80211_sta *sta,
struct rc_pid_sta_info *spinfo)
{
struct rc_pid_rateinfo *rinfo = pinfo->rinfo;
u32 pf;
s32 err_avg;
u32 err_prop;
u32 err_int;
u32 err_der;
int adj, i, j, tmp;
unsigned long period;
/* In case nothing happened during the previous control interval, turn
* the sharpening factor on. */
period = msecs_to_jiffies(pinfo->sampling_period);
if (jiffies - spinfo->last_sample > 2 * period)
spinfo->sharp_cnt = pinfo->sharpen_duration;
spinfo->last_sample = jiffies;
/* This should never happen, but in case, we assume the old sample is
* still a good measurement and copy it. */
if (unlikely(spinfo->tx_num_xmit == 0))
pf = spinfo->last_pf;
else
pf = spinfo->tx_num_failed * 100 / spinfo->tx_num_xmit;
spinfo->tx_num_xmit = 0;
spinfo->tx_num_failed = 0;
/* If we just switched rate, update the rate behaviour info. */
if (pinfo->oldrate != spinfo->txrate_idx) {
i = rinfo[pinfo->oldrate].rev_index;
j = rinfo[spinfo->txrate_idx].rev_index;
tmp = (pf - spinfo->last_pf);
tmp = RC_PID_DO_ARITH_RIGHT_SHIFT(tmp, RC_PID_ARITH_SHIFT);
rinfo[j].diff = rinfo[i].diff + tmp;
pinfo->oldrate = spinfo->txrate_idx;
}
rate_control_pid_normalize(pinfo, sband->n_bitrates);
/* Compute the proportional, integral and derivative errors. */
err_prop = (pinfo->target - pf) << RC_PID_ARITH_SHIFT;
err_avg = spinfo->err_avg_sc >> pinfo->smoothing_shift;
spinfo->err_avg_sc = spinfo->err_avg_sc - err_avg + err_prop;
err_int = spinfo->err_avg_sc >> pinfo->smoothing_shift;
err_der = (pf - spinfo->last_pf) *
(1 + pinfo->sharpen_factor * spinfo->sharp_cnt);
spinfo->last_pf = pf;
if (spinfo->sharp_cnt)
spinfo->sharp_cnt--;
#ifdef CONFIG_MAC80211_DEBUGFS
rate_control_pid_event_pf_sample(&spinfo->events, pf, err_prop, err_int,
err_der);
#endif
/* Compute the controller output. */
adj = (err_prop * pinfo->coeff_p + err_int * pinfo->coeff_i
+ err_der * pinfo->coeff_d);
adj = RC_PID_DO_ARITH_RIGHT_SHIFT(adj, 2 * RC_PID_ARITH_SHIFT);
/* Change rate. */
if (adj)
rate_control_pid_adjust_rate(sband, sta, spinfo, adj, rinfo);
}
static void rate_control_pid_tx_status(void *priv, struct ieee80211_supported_band *sband,
struct ieee80211_sta *sta, void *priv_sta,
struct sk_buff *skb)
{
struct rc_pid_info *pinfo = priv;
struct rc_pid_sta_info *spinfo = priv_sta;
unsigned long period;
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
if (!spinfo)
return;
/* Ignore all frames that were sent with a different rate than the rate
* we currently advise mac80211 to use. */
if (info->status.rates[0].idx != spinfo->txrate_idx)
return;
spinfo->tx_num_xmit++;
#ifdef CONFIG_MAC80211_DEBUGFS
rate_control_pid_event_tx_status(&spinfo->events, info);
#endif
/* We count frames that totally failed to be transmitted as two bad
* frames, those that made it out but had some retries as one good and
* one bad frame. */
if (!(info->flags & IEEE80211_TX_STAT_ACK)) {
spinfo->tx_num_failed += 2;
spinfo->tx_num_xmit++;
} else if (info->status.rates[0].count > 1) {
spinfo->tx_num_failed++;
spinfo->tx_num_xmit++;
}
/* Update PID controller state. */
period = msecs_to_jiffies(pinfo->sampling_period);
if (time_after(jiffies, spinfo->last_sample + period))
rate_control_pid_sample(pinfo, sband, sta, spinfo);
}
static void
rate_control_pid_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_supported_band *sband = txrc->sband;
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
struct rc_pid_sta_info *spinfo = priv_sta;
int rateidx;
if (txrc->rts)
info->control.rates[0].count =
txrc->hw->conf.long_frame_max_tx_count;
else
info->control.rates[0].count =
txrc->hw->conf.short_frame_max_tx_count;
/* Send management frames and NO_ACK data using lowest rate. */
if (rate_control_send_low(sta, priv_sta, txrc))
return;
rateidx = spinfo->txrate_idx;
if (rateidx >= sband->n_bitrates)
rateidx = sband->n_bitrates - 1;
info->control.rates[0].idx = rateidx;
#ifdef CONFIG_MAC80211_DEBUGFS
rate_control_pid_event_tx_rate(&spinfo->events,
rateidx, sband->bitrates[rateidx].bitrate);
#endif
}
static void
rate_control_pid_rate_init(void *priv, struct ieee80211_supported_band *sband,
struct ieee80211_sta *sta, void *priv_sta)
{
struct rc_pid_sta_info *spinfo = priv_sta;
struct rc_pid_info *pinfo = priv;
struct rc_pid_rateinfo *rinfo = pinfo->rinfo;
int i, j, tmp;
bool s;
/* TODO: This routine should consider using RSSI from previous packets
* as we need to have IEEE 802.1X auth succeed immediately after assoc..
* Until that method is implemented, we will use the lowest supported
* rate as a workaround. */
/* Sort the rates. This is optimized for the most common case (i.e.
* almost-sorted CCK+OFDM rates). Kind of bubble-sort with reversed
* mapping too. */
for (i = 0; i < sband->n_bitrates; i++) {
rinfo[i].index = i;
rinfo[i].rev_index = i;
if (RC_PID_FAST_START)
rinfo[i].diff = 0;
else
rinfo[i].diff = i * pinfo->norm_offset;
}
for (i = 1; i < sband->n_bitrates; i++) {
s = 0;
for (j = 0; j < sband->n_bitrates - i; j++)
if (unlikely(sband->bitrates[rinfo[j].index].bitrate >
sband->bitrates[rinfo[j + 1].index].bitrate)) {
tmp = rinfo[j].index;
rinfo[j].index = rinfo[j + 1].index;
rinfo[j + 1].index = tmp;
rinfo[rinfo[j].index].rev_index = j;
rinfo[rinfo[j + 1].index].rev_index = j + 1;
s = 1;
}
if (!s)
break;
}
spinfo->txrate_idx = rate_lowest_index(sband, sta);
}
static void *rate_control_pid_alloc(struct ieee80211_hw *hw,
struct dentry *debugfsdir)
{
struct rc_pid_info *pinfo;
struct rc_pid_rateinfo *rinfo;
struct ieee80211_supported_band *sband;
int i, max_rates = 0;
#ifdef CONFIG_MAC80211_DEBUGFS
struct rc_pid_debugfs_entries *de;
#endif
pinfo = kmalloc(sizeof(*pinfo), GFP_ATOMIC);
if (!pinfo)
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;
}
rinfo = kmalloc(sizeof(*rinfo) * max_rates, GFP_ATOMIC);
if (!rinfo) {
kfree(pinfo);
return NULL;
}
pinfo->target = RC_PID_TARGET_PF;
pinfo->sampling_period = RC_PID_INTERVAL;
pinfo->coeff_p = RC_PID_COEFF_P;
pinfo->coeff_i = RC_PID_COEFF_I;
pinfo->coeff_d = RC_PID_COEFF_D;
pinfo->smoothing_shift = RC_PID_SMOOTHING_SHIFT;
pinfo->sharpen_factor = RC_PID_SHARPENING_FACTOR;
pinfo->sharpen_duration = RC_PID_SHARPENING_DURATION;
pinfo->norm_offset = RC_PID_NORM_OFFSET;
pinfo->rinfo = rinfo;
pinfo->oldrate = 0;
#ifdef CONFIG_MAC80211_DEBUGFS
de = &pinfo->dentries;
de->target = debugfs_create_u32("target_pf", S_IRUSR | S_IWUSR,
debugfsdir, &pinfo->target);
de->sampling_period = debugfs_create_u32("sampling_period",
S_IRUSR | S_IWUSR, debugfsdir,
&pinfo->sampling_period);
de->coeff_p = debugfs_create_u32("coeff_p", S_IRUSR | S_IWUSR,
debugfsdir, (u32 *)&pinfo->coeff_p);
de->coeff_i = debugfs_create_u32("coeff_i", S_IRUSR | S_IWUSR,
debugfsdir, (u32 *)&pinfo->coeff_i);
de->coeff_d = debugfs_create_u32("coeff_d", S_IRUSR | S_IWUSR,
debugfsdir, (u32 *)&pinfo->coeff_d);
de->smoothing_shift = debugfs_create_u32("smoothing_shift",
S_IRUSR | S_IWUSR, debugfsdir,
&pinfo->smoothing_shift);
de->sharpen_factor = debugfs_create_u32("sharpen_factor",
S_IRUSR | S_IWUSR, debugfsdir,
&pinfo->sharpen_factor);
de->sharpen_duration = debugfs_create_u32("sharpen_duration",
S_IRUSR | S_IWUSR, debugfsdir,
&pinfo->sharpen_duration);
de->norm_offset = debugfs_create_u32("norm_offset",
S_IRUSR | S_IWUSR, debugfsdir,
&pinfo->norm_offset);
#endif
return pinfo;
}
static void rate_control_pid_free(void *priv)
{
struct rc_pid_info *pinfo = priv;
#ifdef CONFIG_MAC80211_DEBUGFS
struct rc_pid_debugfs_entries *de = &pinfo->dentries;
debugfs_remove(de->norm_offset);
debugfs_remove(de->sharpen_duration);
debugfs_remove(de->sharpen_factor);
debugfs_remove(de->smoothing_shift);
debugfs_remove(de->coeff_d);
debugfs_remove(de->coeff_i);
debugfs_remove(de->coeff_p);
debugfs_remove(de->sampling_period);
debugfs_remove(de->target);
#endif
kfree(pinfo->rinfo);
kfree(pinfo);
}
static void *rate_control_pid_alloc_sta(void *priv, struct ieee80211_sta *sta,
gfp_t gfp)
{
struct rc_pid_sta_info *spinfo;
spinfo = kzalloc(sizeof(*spinfo), gfp);
if (spinfo == NULL)
return NULL;
spinfo->last_sample = jiffies;
#ifdef CONFIG_MAC80211_DEBUGFS
spin_lock_init(&spinfo->events.lock);
init_waitqueue_head(&spinfo->events.waitqueue);
#endif
return spinfo;
}
static void rate_control_pid_free_sta(void *priv, struct ieee80211_sta *sta,
void *priv_sta)
{
kfree(priv_sta);
}
static struct rate_control_ops mac80211_rcpid = {
.name = "pid",
.tx_status = rate_control_pid_tx_status,
.get_rate = rate_control_pid_get_rate,
.rate_init = rate_control_pid_rate_init,
.alloc = rate_control_pid_alloc,
.free = rate_control_pid_free,
.alloc_sta = rate_control_pid_alloc_sta,
.free_sta = rate_control_pid_free_sta,
#ifdef CONFIG_MAC80211_DEBUGFS
.add_sta_debugfs = rate_control_pid_add_sta_debugfs,
.remove_sta_debugfs = rate_control_pid_remove_sta_debugfs,
#endif
};
int __init rc80211_pid_init(void)
{
return ieee80211_rate_control_register(&mac80211_rcpid);
}
void rc80211_pid_exit(void)
{
ieee80211_rate_control_unregister(&mac80211_rcpid);
}
