diff options
| -rw-r--r-- | net/mac80211/rc80211_pid.c | 181 |
1 files changed, 161 insertions, 20 deletions
diff --git a/net/mac80211/rc80211_pid.c b/net/mac80211/rc80211_pid.c index b358824b5ac..1116dc67ddd 100644 --- a/net/mac80211/rc80211_pid.c +++ b/net/mac80211/rc80211_pid.c @@ -2,6 +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> * * 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 @@ -39,12 +40,18 @@ * 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 need to map it to a TX rate to be selected. - * For now, we depend on the rates to be ordered in a way such that more robust - * rates (i.e. such that exhibit a lower framed failed percentage) come first. - * E.g. for the 802.11b/g case, we first have the b rates in ascending order, - * then the g rates. The adj simply decides the index of the TX rate in the list - * to switch to (relative to the current TX rate entry). + * 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 @@ -78,6 +85,16 @@ */ #define RC_PID_TARGET_PF (11 << RC_PID_ARITH_SHIFT) +/* Rate behaviour normalization quantity over time. */ +#define RC_PID_NORM_OFFSET 3 + +/* Push high rates right after loading. */ +#define RC_PID_FAST_START 0 + +/* Arithmetic right shift for positive and negative values for ISO C. */ +#define RC_PID_DO_ARITH_RIGHT_SHIFT(x, y) \ + (x) < 0 ? -((-(x)) >> (y)) : (x) >> (y) + struct rc_pid_sta_info { unsigned long last_change; unsigned long last_sample; @@ -121,6 +138,18 @@ struct rc_pid_sta_info { /* Algorithm parameters. We keep them on a per-algorithm approach, so they can * be tuned individually for each interface. */ +struct rc_pid_rateinfo { + + /* Map sorted rates to rates in ieee80211_hw_mode. */ + int index; + + /* Map rates in ieee80211_hw_mode to sorted rates. */ + int rev_index; + + /* Comparison with the lowest rate. */ + int diff; +}; + struct rc_pid_info { /* The failed frames percentage target. */ @@ -130,15 +159,56 @@ struct rc_pid_info { s32 coeff_p; s32 coeff_i; s32 coeff_d; + + /* Rates information. */ + struct rc_pid_rateinfo *rinfo; + + /* Index of the last used rate. */ + int oldrate; }; +/* 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; + + if (cur + adj < 0) + return 0; + if (cur + adj >= l) + return l - 1; + + i = r[cur + adj].rev_index; + + j = r[cur].rev_index; + + if (adj < 0) { + tmp = i; + for (k = j; k >= i; k--) + if (r[k].diff <= r[j].diff) + tmp = k; + return r[tmp].index; + } else if (adj > 0) { + tmp = i; + for (k = i + 1; k + i < l; k++) + if (r[k].diff <= r[i].diff) + tmp = k; + return r[tmp].index; + } + return cur + adj; +} static void rate_control_pid_adjust_rate(struct ieee80211_local *local, - struct sta_info *sta, int adj) + struct sta_info *sta, int adj, + struct rc_pid_rateinfo *rinfo) { struct ieee80211_sub_if_data *sdata; struct ieee80211_hw_mode *mode; - int newidx = sta->txrate + adj; + int newidx; int maxrate; int back = (adj > 0) ? 1 : -1; @@ -151,10 +221,8 @@ static void rate_control_pid_adjust_rate(struct ieee80211_local *local, mode = local->oper_hw_mode; maxrate = sdata->bss ? sdata->bss->max_ratectrl_rateidx : -1; - if (newidx < 0) - newidx = 0; - else if (newidx >= mode->num_rates) - newidx = mode->num_rates - 1; + newidx = rate_control_pid_shift_adjust(rinfo, adj, sta->txrate, + mode->num_rates); while (newidx != sta->txrate) { if (rate_supported(sta, mode, newidx) && @@ -167,18 +235,37 @@ static void rate_control_pid_adjust_rate(struct ieee80211_local *local, } } +/* Normalize the failed frames per-rate differences. */ +static void rate_control_pid_normalize(struct rc_pid_rateinfo *r, int l) +{ + int i; + + if (r[0].diff > RC_PID_NORM_OFFSET) + r[0].diff -= RC_PID_NORM_OFFSET; + else if (r[0].diff < -RC_PID_NORM_OFFSET) + r[0].diff += RC_PID_NORM_OFFSET; + for (i = 0; i < l - 1; i++) + if (r[i + 1].diff > r[i].diff + RC_PID_NORM_OFFSET) + r[i + 1].diff -= RC_PID_NORM_OFFSET; + else if (r[i + 1].diff <= r[i].diff) + r[i + 1].diff += RC_PID_NORM_OFFSET; +} + static void rate_control_pid_sample(struct rc_pid_info *pinfo, struct ieee80211_local *local, struct sta_info *sta) { struct rc_pid_sta_info *spinfo = sta->rate_ctrl_priv; + struct rc_pid_rateinfo *rinfo = pinfo->rinfo; + struct ieee80211_hw_mode *mode; u32 pf; s32 err_avg; s32 err_prop; s32 err_int; s32 err_der; - int adj; + int adj, i, j, tmp; + mode = local->oper_hw_mode; spinfo = sta->rate_ctrl_priv; spinfo->last_sample = jiffies; @@ -194,6 +281,20 @@ static void rate_control_pid_sample(struct rc_pid_info *pinfo, spinfo->tx_num_failed = 0; } + /* If we just switched rate, update the rate behaviour info. */ + if (pinfo->oldrate != sta->txrate) { + + i = rinfo[pinfo->oldrate].rev_index; + j = rinfo[sta->txrate].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 = sta->txrate; + } + rate_control_pid_normalize(rinfo, mode->num_rates); + /* Compute the proportional, integral and derivative errors. */ err_prop = RC_PID_TARGET_PF - pf; @@ -207,16 +308,11 @@ static void rate_control_pid_sample(struct rc_pid_info *pinfo, /* Compute the controller output. */ adj = (err_prop * pinfo->coeff_p + err_int * pinfo->coeff_i + err_der * pinfo->coeff_d); - - /* We need to do an arithmetic right shift. ISO C says this is - * implementation defined for negative left operands. Hence, be - * careful to get it right, also for negative values. */ - adj = (adj < 0) ? -((-adj) >> (2 * RC_PID_ARITH_SHIFT)) : - adj >> (2 * RC_PID_ARITH_SHIFT); + adj = RC_PID_DO_ARITH_RIGHT_SHIFT(adj, 2 * RC_PID_ARITH_SHIFT); /* Change rate. */ if (adj) - rate_control_pid_adjust_rate(local, sta, adj); + rate_control_pid_adjust_rate(local, sta, adj, rinfo); } static void rate_control_pid_tx_status(void *priv, struct net_device *dev, @@ -316,13 +412,57 @@ static void rate_control_pid_rate_init(void *priv, void *priv_sta, static void *rate_control_pid_alloc(struct ieee80211_local *local) { struct rc_pid_info *pinfo; + struct rc_pid_rateinfo *rinfo; + struct ieee80211_hw_mode *mode; + int i, j, tmp; + bool s; pinfo = kmalloc(sizeof(*pinfo), GFP_ATOMIC); + if (!pinfo) + return NULL; + + /* We can safely assume that oper_hw_mode won't change unless we get + * reinitialized. */ + mode = local->oper_hw_mode; + rinfo = kmalloc(sizeof(*rinfo) * mode->num_rates, GFP_ATOMIC); + if (!rinfo) { + kfree(pinfo); + return NULL; + } + + /* 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 < mode->num_rates; i++) { + rinfo[i].index = i; + rinfo[i].rev_index = i; + if (RC_PID_FAST_START) + rinfo[i].diff = 0; + else + rinfo[i].diff = i * RC_PID_NORM_OFFSET; + } + for (i = 1; i < mode->num_rates; i++) { + s = 0; + for (j = 0; j < mode->num_rates - i; j++) + if (unlikely(mode->rates[rinfo[j].index].rate > + mode->rates[rinfo[j + 1].index].rate)) { + 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; + } pinfo->target = RC_PID_TARGET_PF; pinfo->coeff_p = RC_PID_COEFF_P; pinfo->coeff_i = RC_PID_COEFF_I; pinfo->coeff_d = RC_PID_COEFF_D; + pinfo->rinfo = rinfo; + pinfo->oldrate = 0; return pinfo; } @@ -330,6 +470,7 @@ static void *rate_control_pid_alloc(struct ieee80211_local *local) static void rate_control_pid_free(void *priv) { struct rc_pid_info *pinfo = priv; + kfree(pinfo->rinfo); kfree(pinfo); } |