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rc80211-pid: fix rate adjustment

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Merge rate_control_pid_shift_adjust() to rate_control_pid_adjust_rate()
in order to make the learning algorithm aware of constraints on rates. Also
add some comments and rename variables.

This fixes a bug which prevented 802.11b/g non-AP STAs from working with
802.11b only AP STAs.

This patch was originally destined for 2.6.26, and is being backported
to fix a user reported problem in post-2.6.24 kernels.

Signed-off-by: Stefano Brivio <stefano.brivio@polimi.it>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Stefano Brivio 2008-03-02 11:33:10 +01:00 committed by John W. Linville
parent ec9b6add7d
commit 1d60ab0574
1 changed files with 43 additions and 49 deletions
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92
net/mac80211/rc80211_pid_algo.c
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@ -2,7 +2,7 @@
* Copyright 2002-2005, Instant802 Networks, Inc.
* Copyright 2005, Devicescape Software, Inc.
* Copyright 2007, Mattias Nissler <mattias.nissler@gmx.de>
* Copyright 2007, Stefano Brivio <stefano.brivio@polimi.it>
* 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
@ -63,72 +63,66 @@
* RC_PID_ARITH_SHIFT.
*/
/* Shift the adjustment so 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 adjustment is within the ranges. Then,
* provide the new rate index. */
static int rate_control_pid_shift_adjust(struct rc_pid_rateinfo *r,
int adj, int cur, int l)
{
int i, j, k, tmp;
j = r[cur].rev_index;
i = j + adj;
if (i < 0)
return r[0].index;
if (i >= l - 1)
return r[l - 1].index;
tmp = i;
if (adj < 0) {
for (k = j; k >= i; k--)
if (r[k].diff <= r[j].diff)
tmp = k;
} else {
for (k = i + 1; k + i < l; k++)
if (r[k].diff <= r[i].diff)
tmp = k;
}
return r[tmp].index;
}
/* 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_local *local,
struct sta_info *sta, int adj,
struct rc_pid_rateinfo *rinfo)
{
struct ieee80211_sub_if_data *sdata;
struct ieee80211_hw_mode *mode;
int newidx;
int maxrate;
int back = (adj > 0) ? 1 : -1;
int cur_sorted, new_sorted, probe, tmp, n_bitrates;
int cur = sta->txrate;
sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
mode = local->oper_hw_mode;
maxrate = sdata->bss ? sdata->bss->max_ratectrl_rateidx : -1;
n_bitrates = mode->num_rates;
newidx = rate_control_pid_shift_adjust(rinfo, adj, sta->txrate,
mode->num_rates);
/* Map passed arguments to sorted values. */
cur_sorted = rinfo[cur].rev_index;
new_sorted = cur_sorted + adj;
while (newidx != sta->txrate) {
if (rate_supported(sta, mode, newidx) &&
(maxrate < 0 || newidx <= maxrate)) {
sta->txrate = newidx;
/* 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, mode, 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, mode, rinfo[probe].index))
tmp = probe;
}
/* Fit the rate found to the nearest supported rate. */
do {
if (rate_supported(sta, mode, rinfo[tmp].index)) {
sta->txrate = rinfo[tmp].index;
break;
}
newidx += back;
}
if (adj < 0)
tmp--;
else
tmp++;
} while (tmp < n_bitrates && tmp >= 0);
#ifdef CONFIG_MAC80211_DEBUGFS
rate_control_pid_event_rate_change(
&((struct rc_pid_sta_info *)sta->rate_ctrl_priv)->events,
newidx, mode->rates[newidx].rate);
cur, mode->rates[cur].rate);
#endif
}