Commit | Line | Data |
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c462238d SH |
1 | /* |
2 | * TCP Illinois congestion control. | |
3 | * Home page: | |
4 | * http://www.ews.uiuc.edu/~shaoliu/tcpillinois/index.html | |
5 | * | |
6 | * The algorithm is described in: | |
7 | * "TCP-Illinois: A Loss and Delay-Based Congestion Control Algorithm | |
8 | * for High-Speed Networks" | |
9 | * http://www.ews.uiuc.edu/~shaoliu/papersandslides/liubassri06perf.pdf | |
10 | * | |
11 | * Implemented from description in paper and ns-2 simulation. | |
12 | * Copyright (C) 2007 Stephen Hemminger <shemminger@linux-foundation.org> | |
13 | */ | |
14 | ||
15 | #include <linux/module.h> | |
16 | #include <linux/skbuff.h> | |
17 | #include <linux/inet_diag.h> | |
18 | #include <asm/div64.h> | |
19 | #include <net/tcp.h> | |
20 | ||
21 | #define ALPHA_SHIFT 7 | |
22 | #define ALPHA_SCALE (1u<<ALPHA_SHIFT) | |
23 | #define ALPHA_MIN ((3*ALPHA_SCALE)/10) /* ~0.3 */ | |
24 | #define ALPHA_MAX (10*ALPHA_SCALE) /* 10.0 */ | |
25 | #define ALPHA_BASE ALPHA_SCALE /* 1.0 */ | |
65d1b4a7 SH |
26 | #define U32_MAX ((u32)~0U) |
27 | #define RTT_MAX (U32_MAX / ALPHA_MAX) /* 3.3 secs */ | |
c462238d SH |
28 | |
29 | #define BETA_SHIFT 6 | |
30 | #define BETA_SCALE (1u<<BETA_SHIFT) | |
65d1b4a7 SH |
31 | #define BETA_MIN (BETA_SCALE/8) /* 0.125 */ |
32 | #define BETA_MAX (BETA_SCALE/2) /* 0.5 */ | |
33 | #define BETA_BASE BETA_MAX | |
c462238d SH |
34 | |
35 | static int win_thresh __read_mostly = 15; | |
65d1b4a7 | 36 | module_param(win_thresh, int, 0); |
c462238d SH |
37 | MODULE_PARM_DESC(win_thresh, "Window threshold for starting adaptive sizing"); |
38 | ||
65d1b4a7 SH |
39 | static int theta __read_mostly = 5; |
40 | module_param(theta, int, 0); | |
41 | MODULE_PARM_DESC(theta, "# of fast RTT's before full growth"); | |
c462238d SH |
42 | |
43 | /* TCP Illinois Parameters */ | |
65d1b4a7 SH |
44 | struct illinois { |
45 | u64 sum_rtt; /* sum of rtt's measured within last rtt */ | |
46 | u16 cnt_rtt; /* # of rtts measured within last rtt */ | |
47 | u32 base_rtt; /* min of all rtt in usec */ | |
48 | u32 max_rtt; /* max of all rtt in usec */ | |
49 | u32 end_seq; /* right edge of current RTT */ | |
50 | u32 alpha; /* Additive increase */ | |
51 | u32 beta; /* Muliplicative decrease */ | |
52 | u16 acked; /* # packets acked by current ACK */ | |
53 | u8 rtt_above; /* average rtt has gone above threshold */ | |
54 | u8 rtt_low; /* # of rtts measurements below threshold */ | |
c462238d SH |
55 | }; |
56 | ||
65d1b4a7 SH |
57 | static void rtt_reset(struct sock *sk) |
58 | { | |
59 | struct tcp_sock *tp = tcp_sk(sk); | |
60 | struct illinois *ca = inet_csk_ca(sk); | |
61 | ||
62 | ca->end_seq = tp->snd_nxt; | |
63 | ca->cnt_rtt = 0; | |
64 | ca->sum_rtt = 0; | |
65 | ||
66 | /* TODO: age max_rtt? */ | |
67 | } | |
68 | ||
c462238d SH |
69 | static void tcp_illinois_init(struct sock *sk) |
70 | { | |
65d1b4a7 SH |
71 | struct illinois *ca = inet_csk_ca(sk); |
72 | ||
73 | ca->alpha = ALPHA_MAX; | |
74 | ca->beta = BETA_BASE; | |
75 | ca->base_rtt = 0x7fffffff; | |
76 | ca->max_rtt = 0; | |
77 | ||
78 | ca->acked = 0; | |
79 | ca->rtt_low = 0; | |
80 | ca->rtt_above = 0; | |
c462238d | 81 | |
65d1b4a7 | 82 | rtt_reset(sk); |
c462238d SH |
83 | } |
84 | ||
65d1b4a7 | 85 | /* Measure RTT for each ack. */ |
164891aa | 86 | static void tcp_illinois_acked(struct sock *sk, u32 pkts_acked, ktime_t last) |
c462238d | 87 | { |
65d1b4a7 | 88 | struct illinois *ca = inet_csk_ca(sk); |
164891aa SH |
89 | u32 rtt; |
90 | ||
91 | ca->acked = pkts_acked; | |
92 | ||
b9ce204f IJ |
93 | if (ktime_equal(last, net_invalid_timestamp())) |
94 | return; | |
95 | ||
84299b3b | 96 | rtt = ktime_to_us(net_timedelta(last)); |
65d1b4a7 SH |
97 | |
98 | /* ignore bogus values, this prevents wraparound in alpha math */ | |
99 | if (rtt > RTT_MAX) | |
100 | rtt = RTT_MAX; | |
c462238d | 101 | |
65d1b4a7 SH |
102 | /* keep track of minimum RTT seen so far */ |
103 | if (ca->base_rtt > rtt) | |
104 | ca->base_rtt = rtt; | |
105 | ||
106 | /* and max */ | |
107 | if (ca->max_rtt < rtt) | |
c462238d SH |
108 | ca->max_rtt = rtt; |
109 | ||
65d1b4a7 SH |
110 | ++ca->cnt_rtt; |
111 | ca->sum_rtt += rtt; | |
c462238d SH |
112 | } |
113 | ||
65d1b4a7 SH |
114 | /* Maximum queuing delay */ |
115 | static inline u32 max_delay(const struct illinois *ca) | |
c462238d | 116 | { |
65d1b4a7 SH |
117 | return ca->max_rtt - ca->base_rtt; |
118 | } | |
c462238d | 119 | |
65d1b4a7 SH |
120 | /* Average queuing delay */ |
121 | static inline u32 avg_delay(const struct illinois *ca) | |
122 | { | |
123 | u64 t = ca->sum_rtt; | |
c462238d | 124 | |
65d1b4a7 SH |
125 | do_div(t, ca->cnt_rtt); |
126 | return t - ca->base_rtt; | |
c462238d SH |
127 | } |
128 | ||
129 | /* | |
130 | * Compute value of alpha used for additive increase. | |
131 | * If small window then use 1.0, equivalent to Reno. | |
132 | * | |
133 | * For larger windows, adjust based on average delay. | |
134 | * A. If average delay is at minimum (we are uncongested), | |
135 | * then use large alpha (10.0) to increase faster. | |
136 | * B. If average delay is at maximum (getting congested) | |
65d1b4a7 | 137 | * then use small alpha (0.3) |
c462238d SH |
138 | * |
139 | * The result is a convex window growth curve. | |
140 | */ | |
65d1b4a7 | 141 | static u32 alpha(struct illinois *ca, u32 da, u32 dm) |
c462238d | 142 | { |
65d1b4a7 | 143 | u32 d1 = dm / 100; /* Low threshold */ |
c462238d | 144 | |
c462238d | 145 | if (da <= d1) { |
65d1b4a7 SH |
146 | /* If never got out of low delay zone, then use max */ |
147 | if (!ca->rtt_above) | |
c462238d | 148 | return ALPHA_MAX; |
65d1b4a7 SH |
149 | |
150 | /* Wait for 5 good RTT's before allowing alpha to go alpha max. | |
151 | * This prevents one good RTT from causing sudden window increase. | |
152 | */ | |
153 | if (++ca->rtt_low < theta) | |
154 | return ca->alpha; | |
155 | ||
156 | ca->rtt_low = 0; | |
157 | ca->rtt_above = 0; | |
158 | return ALPHA_MAX; | |
c462238d SH |
159 | } |
160 | ||
65d1b4a7 | 161 | ca->rtt_above = 1; |
c462238d SH |
162 | |
163 | /* | |
164 | * Based on: | |
165 | * | |
166 | * (dm - d1) amin amax | |
167 | * k1 = ------------------- | |
168 | * amax - amin | |
169 | * | |
170 | * (dm - d1) amin | |
171 | * k2 = ---------------- - d1 | |
172 | * amax - amin | |
173 | * | |
174 | * k1 | |
175 | * alpha = ---------- | |
176 | * k2 + da | |
177 | */ | |
178 | ||
179 | dm -= d1; | |
180 | da -= d1; | |
65d1b4a7 SH |
181 | return (dm * ALPHA_MAX) / |
182 | (dm + (da * (ALPHA_MAX - ALPHA_MIN)) / ALPHA_MIN); | |
c462238d SH |
183 | } |
184 | ||
185 | /* | |
186 | * Beta used for multiplicative decrease. | |
187 | * For small window sizes returns same value as Reno (0.5) | |
188 | * | |
189 | * If delay is small (10% of max) then beta = 1/8 | |
190 | * If delay is up to 80% of max then beta = 1/2 | |
191 | * In between is a linear function | |
192 | */ | |
65d1b4a7 | 193 | static u32 beta(u32 da, u32 dm) |
c462238d | 194 | { |
c462238d SH |
195 | u32 d2, d3; |
196 | ||
c462238d SH |
197 | d2 = dm / 10; |
198 | if (da <= d2) | |
199 | return BETA_MIN; | |
65d1b4a7 | 200 | |
c462238d SH |
201 | d3 = (8 * dm) / 10; |
202 | if (da >= d3 || d3 <= d2) | |
203 | return BETA_MAX; | |
204 | ||
205 | /* | |
206 | * Based on: | |
207 | * | |
208 | * bmin d3 - bmax d2 | |
209 | * k3 = ------------------- | |
210 | * d3 - d2 | |
211 | * | |
212 | * bmax - bmin | |
213 | * k4 = ------------- | |
214 | * d3 - d2 | |
215 | * | |
216 | * b = k3 + k4 da | |
217 | */ | |
218 | return (BETA_MIN * d3 - BETA_MAX * d2 + (BETA_MAX - BETA_MIN) * da) | |
219 | / (d3 - d2); | |
220 | } | |
221 | ||
65d1b4a7 SH |
222 | /* Update alpha and beta values once per RTT */ |
223 | static void update_params(struct sock *sk) | |
224 | { | |
225 | struct tcp_sock *tp = tcp_sk(sk); | |
226 | struct illinois *ca = inet_csk_ca(sk); | |
227 | ||
228 | if (tp->snd_cwnd < win_thresh) { | |
229 | ca->alpha = ALPHA_BASE; | |
230 | ca->beta = BETA_BASE; | |
231 | } else if (ca->cnt_rtt > 0) { | |
232 | u32 dm = max_delay(ca); | |
233 | u32 da = avg_delay(ca); | |
234 | ||
235 | ca->alpha = alpha(ca, da, dm); | |
236 | ca->beta = beta(da, dm); | |
237 | } | |
238 | ||
239 | rtt_reset(sk); | |
240 | } | |
241 | ||
242 | /* | |
243 | * In case of loss, reset to default values | |
244 | */ | |
245 | static void tcp_illinois_state(struct sock *sk, u8 new_state) | |
246 | { | |
247 | struct illinois *ca = inet_csk_ca(sk); | |
248 | ||
249 | if (new_state == TCP_CA_Loss) { | |
250 | ca->alpha = ALPHA_BASE; | |
251 | ca->beta = BETA_BASE; | |
252 | ca->rtt_low = 0; | |
253 | ca->rtt_above = 0; | |
254 | rtt_reset(sk); | |
255 | } | |
256 | } | |
257 | ||
258 | /* | |
259 | * Increase window in response to successful acknowledgment. | |
260 | */ | |
16751347 | 261 | static void tcp_illinois_cong_avoid(struct sock *sk, u32 ack, |
65d1b4a7 SH |
262 | u32 in_flight, int flag) |
263 | { | |
264 | struct tcp_sock *tp = tcp_sk(sk); | |
265 | struct illinois *ca = inet_csk_ca(sk); | |
266 | ||
267 | if (after(ack, ca->end_seq)) | |
268 | update_params(sk); | |
269 | ||
270 | /* RFC2861 only increase cwnd if fully utilized */ | |
271 | if (!tcp_is_cwnd_limited(sk, in_flight)) | |
272 | return; | |
273 | ||
274 | /* In slow start */ | |
275 | if (tp->snd_cwnd <= tp->snd_ssthresh) | |
276 | tcp_slow_start(tp); | |
277 | ||
278 | else { | |
279 | u32 delta; | |
280 | ||
281 | /* snd_cwnd_cnt is # of packets since last cwnd increment */ | |
282 | tp->snd_cwnd_cnt += ca->acked; | |
283 | ca->acked = 1; | |
284 | ||
285 | /* This is close approximation of: | |
286 | * tp->snd_cwnd += alpha/tp->snd_cwnd | |
287 | */ | |
288 | delta = (tp->snd_cwnd_cnt * ca->alpha) >> ALPHA_SHIFT; | |
289 | if (delta >= tp->snd_cwnd) { | |
290 | tp->snd_cwnd = min(tp->snd_cwnd + delta / tp->snd_cwnd, | |
291 | (u32) tp->snd_cwnd_clamp); | |
292 | tp->snd_cwnd_cnt = 0; | |
293 | } | |
294 | } | |
295 | } | |
296 | ||
c462238d SH |
297 | static u32 tcp_illinois_ssthresh(struct sock *sk) |
298 | { | |
299 | struct tcp_sock *tp = tcp_sk(sk); | |
65d1b4a7 | 300 | struct illinois *ca = inet_csk_ca(sk); |
c462238d SH |
301 | |
302 | /* Multiplicative decrease */ | |
65d1b4a7 | 303 | return max((tp->snd_cwnd * ca->beta) >> BETA_SHIFT, 2U); |
c462238d SH |
304 | } |
305 | ||
65d1b4a7 SH |
306 | |
307 | /* Extract info for Tcp socket info provided via netlink. */ | |
308 | static void tcp_illinois_info(struct sock *sk, u32 ext, | |
309 | struct sk_buff *skb) | |
c462238d | 310 | { |
65d1b4a7 | 311 | const struct illinois *ca = inet_csk_ca(sk); |
c462238d SH |
312 | |
313 | if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) { | |
314 | struct tcpvegas_info info = { | |
315 | .tcpv_enabled = 1, | |
65d1b4a7 SH |
316 | .tcpv_rttcnt = ca->cnt_rtt, |
317 | .tcpv_minrtt = ca->base_rtt, | |
c462238d | 318 | }; |
65d1b4a7 SH |
319 | u64 t = ca->sum_rtt; |
320 | ||
321 | do_div(t, ca->cnt_rtt); | |
322 | info.tcpv_rtt = t; | |
c462238d SH |
323 | |
324 | nla_put(skb, INET_DIAG_VEGASINFO, sizeof(info), &info); | |
325 | } | |
326 | } | |
327 | ||
328 | static struct tcp_congestion_ops tcp_illinois = { | |
164891aa | 329 | .flags = TCP_CONG_RTT_STAMP, |
c462238d SH |
330 | .init = tcp_illinois_init, |
331 | .ssthresh = tcp_illinois_ssthresh, | |
332 | .min_cwnd = tcp_reno_min_cwnd, | |
333 | .cong_avoid = tcp_illinois_cong_avoid, | |
65d1b4a7 | 334 | .set_state = tcp_illinois_state, |
65d1b4a7 SH |
335 | .get_info = tcp_illinois_info, |
336 | .pkts_acked = tcp_illinois_acked, | |
c462238d SH |
337 | |
338 | .owner = THIS_MODULE, | |
339 | .name = "illinois", | |
340 | }; | |
341 | ||
342 | static int __init tcp_illinois_register(void) | |
343 | { | |
65d1b4a7 | 344 | BUILD_BUG_ON(sizeof(struct illinois) > ICSK_CA_PRIV_SIZE); |
c462238d SH |
345 | return tcp_register_congestion_control(&tcp_illinois); |
346 | } | |
347 | ||
348 | static void __exit tcp_illinois_unregister(void) | |
349 | { | |
350 | tcp_unregister_congestion_control(&tcp_illinois); | |
351 | } | |
352 | ||
353 | module_init(tcp_illinois_register); | |
354 | module_exit(tcp_illinois_unregister); | |
355 | ||
356 | MODULE_AUTHOR("Stephen Hemminger, Shao Liu"); | |
357 | MODULE_LICENSE("GPL"); | |
358 | MODULE_DESCRIPTION("TCP Illinois"); | |
65d1b4a7 | 359 | MODULE_VERSION("1.0"); |