net/mac80211/rc80211_pid.h

   1 /*
   2  * Copyright 2007, Mattias Nissler <mattias.nissler@gmx.de>
   3  * Copyright 2007, Stefano Brivio <stefano.brivio@polimi.it>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  */
   9
  10 #ifndef RC80211_PID_H
  11 #define RC80211_PID_H
  12
  13 /* Sampling period for measuring percentage of failed frames in ms. */
  14 #define RC_PID_INTERVAL                 125
  15
  16 /* Exponential averaging smoothness (used for I part of PID controller) */
  17 #define RC_PID_SMOOTHING_SHIFT          3
  18 #define RC_PID_SMOOTHING                (1 << RC_PID_SMOOTHING_SHIFT)
  19
  20 /* Sharpening factor (used for D part of PID controller) */
  21 #define RC_PID_SHARPENING_FACTOR        0
  22 #define RC_PID_SHARPENING_DURATION      0
  23
  24 /* Fixed point arithmetic shifting amount. */
  25 #define RC_PID_ARITH_SHIFT              8
  26
  27 /* Proportional PID component coefficient. */
  28 #define RC_PID_COEFF_P                  15
  29 /* Integral PID component coefficient. */
  30 #define RC_PID_COEFF_I                  9
  31 /* Derivative PID component coefficient. */
  32 #define RC_PID_COEFF_D                  15
  33
  34 /* Target failed frames rate for the PID controller. NB: This effectively gives
  35  * maximum failed frames percentage we're willing to accept. If the wireless
  36  * link quality is good, the controller will fail to adjust failed frames
  37  * percentage to the target. This is intentional.
  38  */
  39 #define RC_PID_TARGET_PF                14
  40
  41 /* Rate behaviour normalization quantity over time. */
  42 #define RC_PID_NORM_OFFSET              3
  43
  44 /* Push high rates right after loading. */
  45 #define RC_PID_FAST_START               0
  46
  47 /* Arithmetic right shift for positive and negative values for ISO C. */
  48 #define RC_PID_DO_ARITH_RIGHT_SHIFT(x, y) \
  49         ((x) < 0 ? -((-(x)) >> (y)) : (x) >> (y))
  50
  51 enum rc_pid_event_type {
  52         RC_PID_EVENT_TYPE_TX_STATUS,
  53         RC_PID_EVENT_TYPE_RATE_CHANGE,
  54         RC_PID_EVENT_TYPE_TX_RATE,
  55         RC_PID_EVENT_TYPE_PF_SAMPLE,
  56 };
  57
  58 union rc_pid_event_data {
  59         /* RC_PID_EVENT_TX_STATUS */
  60         struct {
  61                 u32 flags;
  62                 struct ieee80211_tx_info tx_status;
  63         };
  64         /* RC_PID_EVENT_TYPE_RATE_CHANGE */
  65         /* RC_PID_EVENT_TYPE_TX_RATE */
  66         struct {
  67                 int index;
  68                 int rate;
  69         };
  70         /* RC_PID_EVENT_TYPE_PF_SAMPLE */
  71         struct {
  72                 s32 pf_sample;
  73                 s32 prop_err;
  74                 s32 int_err;
  75                 s32 der_err;
  76         };
  77 };
  78
  79 struct rc_pid_event {
  80         /* The time when the event occurred */
  81         unsigned long timestamp;
  82
  83         /* Event ID number */
  84         unsigned int id;
  85
  86         /* Type of event */
  87         enum rc_pid_event_type type;
  88
  89         /* type specific data */
  90         union rc_pid_event_data data;
  91 };
  92
  93 /* Size of the event ring buffer. */
  94 #define RC_PID_EVENT_RING_SIZE 32
  95
  96 struct rc_pid_event_buffer {
  97         /* Counter that generates event IDs */
  98         unsigned int ev_count;
  99
 100         /* Ring buffer of events */
 101         struct rc_pid_event ring[RC_PID_EVENT_RING_SIZE];
 102
 103         /* Index to the entry in events_buf to be reused */
 104         unsigned int next_entry;
 105
 106         /* Lock that guards against concurrent access to this buffer struct */
 107         spinlock_t lock;
 108
 109         /* Wait queue for poll/select and blocking I/O */
 110         wait_queue_head_t waitqueue;
 111 };
 112
 113 struct rc_pid_events_file_info {
 114         /* The event buffer we read */
 115         struct rc_pid_event_buffer *events;
 116
 117         /* The entry we have should read next */
 118         unsigned int next_entry;
 119 };
 120
 121 /**
 122  * struct rc_pid_debugfs_entries - tunable parameters
 123  *
 124  * Algorithm parameters, tunable via debugfs.
 125  * @target: target percentage for failed frames
 126  * @sampling_period: error sampling interval in milliseconds
 127  * @coeff_p: absolute value of the proportional coefficient
 128  * @coeff_i: absolute value of the integral coefficient
 129  * @coeff_d: absolute value of the derivative coefficient
 130  * @smoothing_shift: absolute value of the integral smoothing factor (i.e.
 131  *      amount of smoothing introduced by the exponential moving average)
 132  * @sharpen_factor: absolute value of the derivative sharpening factor (i.e.
 133  *      amount of emphasis given to the derivative term after low activity
 134  *      events)
 135  * @sharpen_duration: duration of the sharpening effect after the detected low
 136  *      activity event, relative to sampling_period
 137  * @norm_offset: amount of normalization periodically performed on the learnt
 138  *      rate behaviour values (lower means we should trust more what we learnt
 139  *      about behaviour of rates, higher means we should trust more the natural
 140  *      ordering of rates)
 141  */
 142 struct rc_pid_debugfs_entries {
 143         struct dentry *target;
 144         struct dentry *sampling_period;
 145         struct dentry *coeff_p;
 146         struct dentry *coeff_i;
 147         struct dentry *coeff_d;
 148         struct dentry *smoothing_shift;
 149         struct dentry *sharpen_factor;
 150         struct dentry *sharpen_duration;
 151         struct dentry *norm_offset;
 152 };
 153
 154 void rate_control_pid_event_tx_status(struct rc_pid_event_buffer *buf,
 155                                       struct ieee80211_tx_info *stat);
 156
 157 void rate_control_pid_event_rate_change(struct rc_pid_event_buffer *buf,
 158                                                int index, int rate);
 159
 160 void rate_control_pid_event_tx_rate(struct rc_pid_event_buffer *buf,
 161                                            int index, int rate);
 162
 163 void rate_control_pid_event_pf_sample(struct rc_pid_event_buffer *buf,
 164                                              s32 pf_sample, s32 prop_err,
 165                                              s32 int_err, s32 der_err);
 166
 167 void rate_control_pid_add_sta_debugfs(void *priv, void *priv_sta,
 168                                              struct dentry *dir);
 169
 170 void rate_control_pid_remove_sta_debugfs(void *priv, void *priv_sta);
 171
 172 struct rc_pid_sta_info {
 173         unsigned long last_change;
 174         unsigned long last_sample;
 175
 176         u32 tx_num_failed;
 177         u32 tx_num_xmit;
 178
 179         int txrate_idx;
 180
 181         /* Average failed frames percentage error (i.e. actual vs. target
 182          * percentage), scaled by RC_PID_SMOOTHING. This value is computed
 183          * using using an exponential weighted average technique:
 184          *
 185          *           (RC_PID_SMOOTHING - 1) * err_avg_old + err
 186          * err_avg = ------------------------------------------
 187          *                       RC_PID_SMOOTHING
 188          *
 189          * where err_avg is the new approximation, err_avg_old the previous one
 190          * and err is the error w.r.t. to the current failed frames percentage
 191          * sample. Note that the bigger RC_PID_SMOOTHING the more weight is
 192          * given to the previous estimate, resulting in smoother behavior (i.e.
 193          * corresponding to a longer integration window).
 194          *
 195          * For computation, we actually don't use the above formula, but this
 196          * one:
 197          *
 198          * err_avg_scaled = err_avg_old_scaled - err_avg_old + err
 199          *
 200          * where:
 201          *      err_avg_scaled = err * RC_PID_SMOOTHING
 202          *      err_avg_old_scaled = err_avg_old * RC_PID_SMOOTHING
 203          *
 204          * This avoids floating point numbers and the per_failed_old value can
 205          * easily be obtained by shifting per_failed_old_scaled right by
 206          * RC_PID_SMOOTHING_SHIFT.
 207          */
 208         s32 err_avg_sc;
 209
 210         /* Last framed failes percentage sample. */
 211         u32 last_pf;
 212
 213         /* Sharpening needed. */
 214         u8 sharp_cnt;
 215
 216 #ifdef CONFIG_MAC80211_DEBUGFS
 217         /* Event buffer */
 218         struct rc_pid_event_buffer events;
 219
 220         /* Events debugfs file entry */
 221         struct dentry *events_entry;
 222 #endif
 223 };
 224
 225 /* Algorithm parameters. We keep them on a per-algorithm approach, so they can
 226  * be tuned individually for each interface.
 227  */
 228 struct rc_pid_rateinfo {
 229
 230         /* Map sorted rates to rates in ieee80211_hw_mode. */
 231         int index;
 232
 233         /* Map rates in ieee80211_hw_mode to sorted rates. */
 234         int rev_index;
 235
 236         /* Did we do any measurement on this rate? */
 237         bool valid;
 238
 239         /* Comparison with the lowest rate. */
 240         int diff;
 241 };
 242
 243 struct rc_pid_info {
 244
 245         /* The failed frames percentage target. */
 246         unsigned int target;
 247
 248         /* Rate at which failed frames percentage is sampled in 0.001s. */
 249         unsigned int sampling_period;
 250
 251         /* P, I and D coefficients. */
 252         int coeff_p;
 253         int coeff_i;
 254         int coeff_d;
 255
 256         /* Exponential averaging shift. */
 257         unsigned int smoothing_shift;
 258
 259         /* Sharpening factor and duration. */
 260         unsigned int sharpen_factor;
 261         unsigned int sharpen_duration;
 262
 263         /* Normalization offset. */
 264         unsigned int norm_offset;
 265
 266         /* Rates information. */
 267         struct rc_pid_rateinfo *rinfo;
 268
 269         /* Index of the last used rate. */
 270         int oldrate;
 271
 272 #ifdef CONFIG_MAC80211_DEBUGFS
 273         /* Debugfs entries created for the parameters above. */
 274         struct rc_pid_debugfs_entries dentries;
 275 #endif
 276 };
 277
 278 #endif /* RC80211_PID_H */