aboutsummaryrefslogtreecommitdiff
path: root/net/mac80211/rc80211_pid.h
blob: 6510f8ee738eca7303ff77c8583e7659dbfe4040 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
/*
 * 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
 * published by the Free Software Foundation.
 */

#ifndef RC80211_PID_H
#define RC80211_PID_H

/* Sampling period for measuring percentage of failed frames in ms. */
#define RC_PID_INTERVAL			125

/* Exponential averaging smoothness (used for I part of PID controller) */
#define RC_PID_SMOOTHING_SHIFT		3
#define RC_PID_SMOOTHING		(1 << RC_PID_SMOOTHING_SHIFT)

/* Sharpening factor (used for D part of PID controller) */
#define RC_PID_SHARPENING_FACTOR	0
#define RC_PID_SHARPENING_DURATION	0

/* Fixed point arithmetic shifting amount. */
#define RC_PID_ARITH_SHIFT		8

/* Proportional PID component coefficient. */
#define RC_PID_COEFF_P			15
/* Integral PID component coefficient. */
#define RC_PID_COEFF_I			9
/* Derivative PID component coefficient. */
#define RC_PID_COEFF_D			15

/* Target failed frames rate for the PID controller. NB: This effectively gives
 * maximum failed frames percentage we're willing to accept. If the wireless
 * link quality is good, the controller will fail to adjust failed frames
 * percentage to the target. This is intentional.
 */
#define RC_PID_TARGET_PF		14

/* 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))

enum rc_pid_event_type {
	RC_PID_EVENT_TYPE_TX_STATUS,
	RC_PID_EVENT_TYPE_RATE_CHANGE,
	RC_PID_EVENT_TYPE_TX_RATE,
	RC_PID_EVENT_TYPE_PF_SAMPLE,
};

union rc_pid_event_data {
	/* RC_PID_EVENT_TX_STATUS */
	struct {
		u32 flags;
		struct ieee80211_tx_info tx_status;
	};
	/* RC_PID_EVENT_TYPE_RATE_CHANGE */
	/* RC_PID_EVENT_TYPE_TX_RATE */
	struct {
		int index;
		int rate;
	};
	/* RC_PID_EVENT_TYPE_PF_SAMPLE */
	struct {
		s32 pf_sample;
		s32 prop_err;
		s32 int_err;
		s32 der_err;
	};
};

struct rc_pid_event {
	/* The time when the event occured */
	unsigned long timestamp;

	/* Event ID number */
	unsigned int id;

	/* Type of event */
	enum rc_pid_event_type type;

	/* type specific data */
	union rc_pid_event_data data;
};

/* Size of the event ring buffer. */
#define RC_PID_EVENT_RING_SIZE 32

struct rc_pid_event_buffer {
	/* Counter that generates event IDs */
	unsigned int ev_count;

	/* Ring buffer of events */
	struct rc_pid_event ring[RC_PID_EVENT_RING_SIZE];

	/* Index to the entry in events_buf to be reused */
	unsigned int next_entry;

	/* Lock that guards against concurrent access to this buffer struct */
	spinlock_t lock;

	/* Wait queue for poll/select and blocking I/O */
	wait_queue_head_t waitqueue;
};

struct rc_pid_events_file_info {
	/* The event buffer we read */
	struct rc_pid_event_buffer *events;

	/* The entry we have should read next */
	unsigned int next_entry;
};

/**
 * struct rc_pid_debugfs_entries - tunable parameters
 *
 * Algorithm parameters, tunable via debugfs.
 * @target: target percentage for failed frames
 * @sampling_period: error sampling interval in milliseconds
 * @coeff_p: absolute value of the proportional coefficient
 * @coeff_i: absolute value of the integral coefficient
 * @coeff_d: absolute value of the derivative coefficient
 * @smoothing_shift: absolute value of the integral smoothing factor (i.e.
 *	amount of smoothing introduced by the exponential moving average)
 * @sharpen_factor: absolute value of the derivative sharpening factor (i.e.
 *	amount of emphasis given to the derivative term after low activity
 *	events)
 * @sharpen_duration: duration of the sharpening effect after the detected low
 *	activity event, relative to sampling_period
 * @norm_offset: amount of normalization periodically performed on the learnt
 *	rate behaviour values (lower means we should trust more what we learnt
 *	about behaviour of rates, higher means we should trust more the natural
 *	ordering of rates)
 */
struct rc_pid_debugfs_entries {
	struct dentry *target;
	struct dentry *sampling_period;
	struct dentry *coeff_p;
	struct dentry *coeff_i;
	struct dentry *coeff_d;
	struct dentry *smoothing_shift;
	struct dentry *sharpen_factor;
	struct dentry *sharpen_duration;
	struct dentry *norm_offset;
};

void rate_control_pid_event_tx_status(struct rc_pid_event_buffer *buf,
				      struct ieee80211_tx_info *stat);

void rate_control_pid_event_rate_change(struct rc_pid_event_buffer *buf,
					       int index, int rate);

void rate_control_pid_event_tx_rate(struct rc_pid_event_buffer *buf,
					   int index, int rate);

void rate_control_pid_event_pf_sample(struct rc_pid_event_buffer *buf,
					     s32 pf_sample, s32 prop_err,
					     s32 int_err, s32 der_err);

void rate_control_pid_add_sta_debugfs(void *priv, void *priv_sta,
					     struct dentry *dir);

void rate_control_pid_remove_sta_debugfs(void *priv, void *priv_sta);

struct rc_pid_sta_info {
	unsigned long last_change;
	unsigned long last_sample;

	u32 tx_num_failed;
	u32 tx_num_xmit;

	int txrate_idx;

	/* Average failed frames percentage error (i.e. actual vs. target
	 * percentage), scaled by RC_PID_SMOOTHING. This value is computed
	 * using using an exponential weighted average technique:
	 *
	 *           (RC_PID_SMOOTHING - 1) * err_avg_old + err
	 * err_avg = ------------------------------------------
	 *                       RC_PID_SMOOTHING
	 *
	 * where err_avg is the new approximation, err_avg_old the previous one
	 * and err is the error w.r.t. to the current failed frames percentage
	 * sample. Note that the bigger RC_PID_SMOOTHING the more weight is
	 * given to the previous estimate, resulting in smoother behavior (i.e.
	 * corresponding to a longer integration window).
	 *
	 * For computation, we actually don't use the above formula, but this
	 * one:
	 *
	 * err_avg_scaled = err_avg_old_scaled - err_avg_old + err
	 *
	 * where:
	 * 	err_avg_scaled = err * RC_PID_SMOOTHING
	 * 	err_avg_old_scaled = err_avg_old * RC_PID_SMOOTHING
	 *
	 * This avoids floating point numbers and the per_failed_old value can
	 * easily be obtained by shifting per_failed_old_scaled right by
	 * RC_PID_SMOOTHING_SHIFT.
	 */
	s32 err_avg_sc;

	/* Last framed failes percentage sample. */
	u32 last_pf;

	/* Sharpening needed. */
	u8 sharp_cnt;

#ifdef CONFIG_MAC80211_DEBUGFS
	/* Event buffer */
	struct rc_pid_event_buffer events;

	/* Events debugfs file entry */
	struct dentry *events_entry;
#endif
};

/* 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;

	/* Did we do any measurement on this rate? */
	bool valid;

	/* Comparison with the lowest rate. */
	int diff;
};

struct rc_pid_info {

	/* The failed frames percentage target. */
	unsigned int target;

	/* Rate at which failed frames percentage is sampled in 0.001s. */
	unsigned int sampling_period;

	/* P, I and D coefficients. */
	int coeff_p;
	int coeff_i;
	int coeff_d;

	/* Exponential averaging shift. */
	unsigned int smoothing_shift;

	/* Sharpening factor and duration. */
	unsigned int sharpen_factor;
	unsigned int sharpen_duration;

	/* Normalization offset. */
	unsigned int norm_offset;

	/* Rates information. */
	struct rc_pid_rateinfo *rinfo;

	/* Index of the last used rate. */
	int oldrate;

#ifdef CONFIG_MAC80211_DEBUGFS
	/* Debugfs entries created for the parameters above. */
	struct rc_pid_debugfs_entries dentries;
#endif
};

#endif /* RC80211_PID_H */