]>
Commit | Line | Data |
---|---|---|
09c434b8 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
df3271f3 | 2 | /* |
ae27e98a | 3 | * TCP CUBIC: Binary Increase Congestion control for TCP v2.3 |
6b3d6263 SH |
4 | * Home page: |
5 | * http://netsrv.csc.ncsu.edu/twiki/bin/view/Main/BIC | |
df3271f3 | 6 | * This is from the implementation of CUBIC TCP in |
ae27e98a SH |
7 | * Sangtae Ha, Injong Rhee and Lisong Xu, |
8 | * "CUBIC: A New TCP-Friendly High-Speed TCP Variant" | |
9 | * in ACM SIGOPS Operating System Review, July 2008. | |
df3271f3 | 10 | * Available from: |
ae27e98a SH |
11 | * http://netsrv.csc.ncsu.edu/export/cubic_a_new_tcp_2008.pdf |
12 | * | |
13 | * CUBIC integrates a new slow start algorithm, called HyStart. | |
14 | * The details of HyStart are presented in | |
15 | * Sangtae Ha and Injong Rhee, | |
16 | * "Taming the Elephants: New TCP Slow Start", NCSU TechReport 2008. | |
17 | * Available from: | |
18 | * http://netsrv.csc.ncsu.edu/export/hystart_techreport_2008.pdf | |
19 | * | |
20 | * All testing results are available from: | |
21 | * http://netsrv.csc.ncsu.edu/wiki/index.php/TCP_Testing | |
df3271f3 SH |
22 | * |
23 | * Unless CUBIC is enabled and congestion window is large | |
24 | * this behaves the same as the original Reno. | |
25 | */ | |
26 | ||
df3271f3 SH |
27 | #include <linux/mm.h> |
28 | #include <linux/module.h> | |
6f6d6a1a | 29 | #include <linux/math64.h> |
df3271f3 | 30 | #include <net/tcp.h> |
df3271f3 SH |
31 | |
32 | #define BICTCP_BETA_SCALE 1024 /* Scale factor beta calculation | |
33 | * max_cwnd = snd_cwnd * beta | |
34 | */ | |
df3271f3 SH |
35 | #define BICTCP_HZ 10 /* BIC HZ 2^10 = 1024 */ |
36 | ||
ae27e98a SH |
37 | /* Two methods of hybrid slow start */ |
38 | #define HYSTART_ACK_TRAIN 0x1 | |
39 | #define HYSTART_DELAY 0x2 | |
40 | ||
41 | /* Number of delay samples for detecting the increase of delay */ | |
42 | #define HYSTART_MIN_SAMPLES 8 | |
cff04e2d ED |
43 | #define HYSTART_DELAY_MIN (4000U) /* 4 ms */ |
44 | #define HYSTART_DELAY_MAX (16000U) /* 16 ms */ | |
ae27e98a SH |
45 | #define HYSTART_DELAY_THRESH(x) clamp(x, HYSTART_DELAY_MIN, HYSTART_DELAY_MAX) |
46 | ||
59758f44 | 47 | static int fast_convergence __read_mostly = 1; |
6b3d6263 | 48 | static int beta __read_mostly = 717; /* = 717/1024 (BICTCP_BETA_SCALE) */ |
66e1e3b2 | 49 | static int initial_ssthresh __read_mostly; |
59758f44 SH |
50 | static int bic_scale __read_mostly = 41; |
51 | static int tcp_friendliness __read_mostly = 1; | |
df3271f3 | 52 | |
ae27e98a SH |
53 | static int hystart __read_mostly = 1; |
54 | static int hystart_detect __read_mostly = HYSTART_ACK_TRAIN | HYSTART_DELAY; | |
55 | static int hystart_low_window __read_mostly = 16; | |
cff04e2d | 56 | static int hystart_ack_delta_us __read_mostly = 2000; |
ae27e98a | 57 | |
59758f44 SH |
58 | static u32 cube_rtt_scale __read_mostly; |
59 | static u32 beta_scale __read_mostly; | |
60 | static u64 cube_factor __read_mostly; | |
89b3d9aa SH |
61 | |
62 | /* Note parameters that are used for precomputing scale factors are read-only */ | |
df3271f3 SH |
63 | module_param(fast_convergence, int, 0644); |
64 | MODULE_PARM_DESC(fast_convergence, "turn on/off fast convergence"); | |
6b3d6263 | 65 | module_param(beta, int, 0644); |
df3271f3 SH |
66 | MODULE_PARM_DESC(beta, "beta for multiplicative increase"); |
67 | module_param(initial_ssthresh, int, 0644); | |
68 | MODULE_PARM_DESC(initial_ssthresh, "initial value of slow start threshold"); | |
89b3d9aa | 69 | module_param(bic_scale, int, 0444); |
df3271f3 SH |
70 | MODULE_PARM_DESC(bic_scale, "scale (scaled by 1024) value for bic function (bic_scale/1024)"); |
71 | module_param(tcp_friendliness, int, 0644); | |
72 | MODULE_PARM_DESC(tcp_friendliness, "turn on/off tcp friendliness"); | |
ae27e98a SH |
73 | module_param(hystart, int, 0644); |
74 | MODULE_PARM_DESC(hystart, "turn on/off hybrid slow start algorithm"); | |
75 | module_param(hystart_detect, int, 0644); | |
d6ecf328 | 76 | MODULE_PARM_DESC(hystart_detect, "hybrid slow start detection mechanisms" |
ae27e98a SH |
77 | " 1: packet-train 2: delay 3: both packet-train and delay"); |
78 | module_param(hystart_low_window, int, 0644); | |
79 | MODULE_PARM_DESC(hystart_low_window, "lower bound cwnd for hybrid slow start"); | |
cff04e2d ED |
80 | module_param(hystart_ack_delta_us, int, 0644); |
81 | MODULE_PARM_DESC(hystart_ack_delta_us, "spacing between ack's indicating train (usecs)"); | |
df3271f3 | 82 | |
df3271f3 SH |
83 | /* BIC TCP Parameters */ |
84 | struct bictcp { | |
85 | u32 cnt; /* increase cwnd by 1 after ACKs */ | |
688d1945 | 86 | u32 last_max_cwnd; /* last maximum snd_cwnd */ |
df3271f3 SH |
87 | u32 last_cwnd; /* the last snd_cwnd */ |
88 | u32 last_time; /* time when updated last_cwnd */ | |
89 | u32 bic_origin_point;/* origin point of bic function */ | |
688d1945 | 90 | u32 bic_K; /* time to origin point |
91 | from the beginning of the current epoch */ | |
cff04e2d | 92 | u32 delay_min; /* min delay (usec) */ |
df3271f3 SH |
93 | u32 epoch_start; /* beginning of an epoch */ |
94 | u32 ack_cnt; /* number of acks */ | |
95 | u32 tcp_cwnd; /* estimated tcp cwnd */ | |
9cd981dc | 96 | u16 unused; |
ae27e98a SH |
97 | u8 sample_cnt; /* number of samples to decide curr_rtt */ |
98 | u8 found; /* the exit point is found? */ | |
99 | u32 round_start; /* beginning of each round */ | |
100 | u32 end_seq; /* end_seq of the round */ | |
17a6e9f1 | 101 | u32 last_ack; /* last time when the ACK spacing is close */ |
ae27e98a | 102 | u32 curr_rtt; /* the minimum rtt of current round */ |
df3271f3 SH |
103 | }; |
104 | ||
105 | static inline void bictcp_reset(struct bictcp *ca) | |
106 | { | |
f4d133d8 | 107 | memset(ca, 0, offsetof(struct bictcp, unused)); |
ae27e98a SH |
108 | ca->found = 0; |
109 | } | |
110 | ||
cff04e2d | 111 | static inline u32 bictcp_clock_us(const struct sock *sk) |
17a6e9f1 | 112 | { |
cff04e2d | 113 | return tcp_sk(sk)->tcp_mstamp; |
17a6e9f1 | 114 | } |
115 | ||
ae27e98a SH |
116 | static inline void bictcp_hystart_reset(struct sock *sk) |
117 | { | |
118 | struct tcp_sock *tp = tcp_sk(sk); | |
119 | struct bictcp *ca = inet_csk_ca(sk); | |
120 | ||
cff04e2d | 121 | ca->round_start = ca->last_ack = bictcp_clock_us(sk); |
ae27e98a | 122 | ca->end_seq = tp->snd_nxt; |
35821fc2 | 123 | ca->curr_rtt = ~0U; |
ae27e98a | 124 | ca->sample_cnt = 0; |
df3271f3 SH |
125 | } |
126 | ||
d22f6ad1 | 127 | static void cubictcp_init(struct sock *sk) |
df3271f3 | 128 | { |
5a45f008 NC |
129 | struct bictcp *ca = inet_csk_ca(sk); |
130 | ||
131 | bictcp_reset(ca); | |
ae27e98a SH |
132 | |
133 | if (hystart) | |
134 | bictcp_hystart_reset(sk); | |
135 | ||
136 | if (!hystart && initial_ssthresh) | |
df3271f3 SH |
137 | tcp_sk(sk)->snd_ssthresh = initial_ssthresh; |
138 | } | |
139 | ||
d22f6ad1 | 140 | static void cubictcp_cwnd_event(struct sock *sk, enum tcp_ca_event event) |
30927520 ED |
141 | { |
142 | if (event == CA_EVENT_TX_START) { | |
30927520 | 143 | struct bictcp *ca = inet_csk_ca(sk); |
d635fbe2 | 144 | u32 now = tcp_jiffies32; |
c2e7204d ED |
145 | s32 delta; |
146 | ||
147 | delta = now - tcp_sk(sk)->lsndtime; | |
30927520 ED |
148 | |
149 | /* We were application limited (idle) for a while. | |
150 | * Shift epoch_start to keep cwnd growth to cubic curve. | |
151 | */ | |
c2e7204d | 152 | if (ca->epoch_start && delta > 0) { |
30927520 | 153 | ca->epoch_start += delta; |
c2e7204d ED |
154 | if (after(ca->epoch_start, now)) |
155 | ca->epoch_start = now; | |
156 | } | |
30927520 ED |
157 | return; |
158 | } | |
159 | } | |
160 | ||
7e58886b SH |
161 | /* calculate the cubic root of x using a table lookup followed by one |
162 | * Newton-Raphson iteration. | |
163 | * Avg err ~= 0.195% | |
df3271f3 | 164 | */ |
9eb2d627 | 165 | static u32 cubic_root(u64 a) |
df3271f3 | 166 | { |
7e58886b SH |
167 | u32 x, b, shift; |
168 | /* | |
169 | * cbrt(x) MSB values for x MSB values in [0..63]. | |
170 | * Precomputed then refined by hand - Willy Tarreau | |
171 | * | |
172 | * For x in [0..63], | |
173 | * v = cbrt(x << 18) - 1 | |
174 | * cbrt(x) = (v[x] + 10) >> 6 | |
9eb2d627 | 175 | */ |
7e58886b SH |
176 | static const u8 v[] = { |
177 | /* 0x00 */ 0, 54, 54, 54, 118, 118, 118, 118, | |
178 | /* 0x08 */ 123, 129, 134, 138, 143, 147, 151, 156, | |
179 | /* 0x10 */ 157, 161, 164, 168, 170, 173, 176, 179, | |
180 | /* 0x18 */ 181, 185, 187, 190, 192, 194, 197, 199, | |
181 | /* 0x20 */ 200, 202, 204, 206, 209, 211, 213, 215, | |
182 | /* 0x28 */ 217, 219, 221, 222, 224, 225, 227, 229, | |
183 | /* 0x30 */ 231, 232, 234, 236, 237, 239, 240, 242, | |
184 | /* 0x38 */ 244, 245, 246, 248, 250, 251, 252, 254, | |
185 | }; | |
186 | ||
187 | b = fls64(a); | |
188 | if (b < 7) { | |
189 | /* a in [0..63] */ | |
190 | return ((u32)v[(u32)a] + 35) >> 6; | |
191 | } | |
192 | ||
193 | b = ((b * 84) >> 8) - 1; | |
194 | shift = (a >> (b * 3)); | |
195 | ||
196 | x = ((u32)(((u32)v[shift] + 10) << b)) >> 6; | |
197 | ||
198 | /* | |
199 | * Newton-Raphson iteration | |
200 | * 2 | |
201 | * x = ( 2 * x + a / x ) / 3 | |
202 | * k+1 k k | |
203 | */ | |
6f6d6a1a | 204 | x = (2 * x + (u32)div64_u64(a, (u64)x * (u64)(x - 1))); |
7e58886b | 205 | x = ((x * 341) >> 10); |
9eb2d627 | 206 | return x; |
df3271f3 SH |
207 | } |
208 | ||
df3271f3 SH |
209 | /* |
210 | * Compute congestion window to use. | |
211 | */ | |
9cd981dc | 212 | static inline void bictcp_update(struct bictcp *ca, u32 cwnd, u32 acked) |
df3271f3 | 213 | { |
2ed0edf9 ED |
214 | u32 delta, bic_target, max_cnt; |
215 | u64 offs, t; | |
df3271f3 | 216 | |
9cd981dc | 217 | ca->ack_cnt += acked; /* count the number of ACKed packets */ |
df3271f3 SH |
218 | |
219 | if (ca->last_cwnd == cwnd && | |
ac35f562 | 220 | (s32)(tcp_jiffies32 - ca->last_time) <= HZ / 32) |
df3271f3 SH |
221 | return; |
222 | ||
d6b1a8a9 NC |
223 | /* The CUBIC function can update ca->cnt at most once per jiffy. |
224 | * On all cwnd reduction events, ca->epoch_start is set to 0, | |
225 | * which will force a recalculation of ca->cnt. | |
226 | */ | |
ac35f562 | 227 | if (ca->epoch_start && tcp_jiffies32 == ca->last_time) |
d6b1a8a9 NC |
228 | goto tcp_friendliness; |
229 | ||
df3271f3 | 230 | ca->last_cwnd = cwnd; |
ac35f562 | 231 | ca->last_time = tcp_jiffies32; |
df3271f3 | 232 | |
df3271f3 | 233 | if (ca->epoch_start == 0) { |
ac35f562 | 234 | ca->epoch_start = tcp_jiffies32; /* record beginning */ |
9cd981dc | 235 | ca->ack_cnt = acked; /* start counting */ |
df3271f3 SH |
236 | ca->tcp_cwnd = cwnd; /* syn with cubic */ |
237 | ||
238 | if (ca->last_max_cwnd <= cwnd) { | |
239 | ca->bic_K = 0; | |
240 | ca->bic_origin_point = cwnd; | |
241 | } else { | |
89b3d9aa SH |
242 | /* Compute new K based on |
243 | * (wmax-cwnd) * (srtt>>3 / HZ) / c * 2^(3*bictcp_HZ) | |
244 | */ | |
245 | ca->bic_K = cubic_root(cube_factor | |
246 | * (ca->last_max_cwnd - cwnd)); | |
df3271f3 SH |
247 | ca->bic_origin_point = ca->last_max_cwnd; |
248 | } | |
249 | } | |
250 | ||
e905a9ed YH |
251 | /* cubic function - calc*/ |
252 | /* calculate c * time^3 / rtt, | |
253 | * while considering overflow in calculation of time^3 | |
89b3d9aa | 254 | * (so time^3 is done by using 64 bit) |
df3271f3 | 255 | * and without the support of division of 64bit numbers |
89b3d9aa | 256 | * (so all divisions are done by using 32 bit) |
e905a9ed YH |
257 | * also NOTE the unit of those veriables |
258 | * time = (t - K) / 2^bictcp_HZ | |
259 | * c = bic_scale >> 10 | |
df3271f3 SH |
260 | * rtt = (srtt >> 3) / HZ |
261 | * !!! The following code does not have overflow problems, | |
262 | * if the cwnd < 1 million packets !!! | |
e905a9ed | 263 | */ |
df3271f3 | 264 | |
ac35f562 | 265 | t = (s32)(tcp_jiffies32 - ca->epoch_start); |
cff04e2d | 266 | t += usecs_to_jiffies(ca->delay_min); |
df3271f3 | 267 | /* change the unit from HZ to bictcp_HZ */ |
2ed0edf9 ED |
268 | t <<= BICTCP_HZ; |
269 | do_div(t, HZ); | |
df3271f3 | 270 | |
e905a9ed | 271 | if (t < ca->bic_K) /* t - K */ |
89b3d9aa | 272 | offs = ca->bic_K - t; |
e905a9ed YH |
273 | else |
274 | offs = t - ca->bic_K; | |
df3271f3 | 275 | |
89b3d9aa SH |
276 | /* c/rtt * (t-K)^3 */ |
277 | delta = (cube_rtt_scale * offs * offs * offs) >> (10+3*BICTCP_HZ); | |
688d1945 | 278 | if (t < ca->bic_K) /* below origin*/ |
e905a9ed | 279 | bic_target = ca->bic_origin_point - delta; |
688d1945 | 280 | else /* above origin*/ |
e905a9ed | 281 | bic_target = ca->bic_origin_point + delta; |
df3271f3 | 282 | |
e905a9ed YH |
283 | /* cubic function - calc bictcp_cnt*/ |
284 | if (bic_target > cwnd) { | |
df3271f3 | 285 | ca->cnt = cwnd / (bic_target - cwnd); |
e905a9ed YH |
286 | } else { |
287 | ca->cnt = 100 * cwnd; /* very small increment*/ | |
288 | } | |
df3271f3 | 289 | |
b5ccd073 SH |
290 | /* |
291 | * The initial growth of cubic function may be too conservative | |
292 | * when the available bandwidth is still unknown. | |
293 | */ | |
5a45f008 | 294 | if (ca->last_max_cwnd == 0 && ca->cnt > 20) |
b5ccd073 SH |
295 | ca->cnt = 20; /* increase cwnd 5% per RTT */ |
296 | ||
d6b1a8a9 | 297 | tcp_friendliness: |
df3271f3 SH |
298 | /* TCP Friendly */ |
299 | if (tcp_friendliness) { | |
89b3d9aa | 300 | u32 scale = beta_scale; |
688d1945 | 301 | |
89b3d9aa | 302 | delta = (cwnd * scale) >> 3; |
e905a9ed YH |
303 | while (ca->ack_cnt > delta) { /* update tcp cwnd */ |
304 | ca->ack_cnt -= delta; | |
305 | ca->tcp_cwnd++; | |
df3271f3 SH |
306 | } |
307 | ||
688d1945 | 308 | if (ca->tcp_cwnd > cwnd) { /* if bic is slower than tcp */ |
89b3d9aa SH |
309 | delta = ca->tcp_cwnd - cwnd; |
310 | max_cnt = cwnd / delta; | |
df3271f3 SH |
311 | if (ca->cnt > max_cnt) |
312 | ca->cnt = max_cnt; | |
313 | } | |
e905a9ed | 314 | } |
df3271f3 | 315 | |
d578e18c NC |
316 | /* The maximum rate of cwnd increase CUBIC allows is 1 packet per |
317 | * 2 packets ACKed, meaning cwnd grows at 1.5x per RTT. | |
318 | */ | |
319 | ca->cnt = max(ca->cnt, 2U); | |
df3271f3 SH |
320 | } |
321 | ||
d22f6ad1 | 322 | static void cubictcp_cong_avoid(struct sock *sk, u32 ack, u32 acked) |
df3271f3 SH |
323 | { |
324 | struct tcp_sock *tp = tcp_sk(sk); | |
325 | struct bictcp *ca = inet_csk_ca(sk); | |
326 | ||
24901551 | 327 | if (!tcp_is_cwnd_limited(sk)) |
df3271f3 SH |
328 | return; |
329 | ||
071d5080 | 330 | if (tcp_in_slow_start(tp)) { |
9cd981dc NC |
331 | acked = tcp_slow_start(tp, acked); |
332 | if (!acked) | |
333 | return; | |
df3271f3 | 334 | } |
0d24ea1d | 335 | bictcp_update(ca, tcp_snd_cwnd(tp), acked); |
9cd981dc | 336 | tcp_cong_avoid_ai(tp, ca->cnt, acked); |
df3271f3 SH |
337 | } |
338 | ||
d22f6ad1 | 339 | static u32 cubictcp_recalc_ssthresh(struct sock *sk) |
df3271f3 SH |
340 | { |
341 | const struct tcp_sock *tp = tcp_sk(sk); | |
342 | struct bictcp *ca = inet_csk_ca(sk); | |
343 | ||
344 | ca->epoch_start = 0; /* end of epoch */ | |
345 | ||
346 | /* Wmax and fast convergence */ | |
0d24ea1d ED |
347 | if (tcp_snd_cwnd(tp) < ca->last_max_cwnd && fast_convergence) |
348 | ca->last_max_cwnd = (tcp_snd_cwnd(tp) * (BICTCP_BETA_SCALE + beta)) | |
df3271f3 SH |
349 | / (2 * BICTCP_BETA_SCALE); |
350 | else | |
0d24ea1d | 351 | ca->last_max_cwnd = tcp_snd_cwnd(tp); |
df3271f3 | 352 | |
0d24ea1d | 353 | return max((tcp_snd_cwnd(tp) * beta) / BICTCP_BETA_SCALE, 2U); |
df3271f3 SH |
354 | } |
355 | ||
d22f6ad1 | 356 | static void cubictcp_state(struct sock *sk, u8 new_state) |
df3271f3 | 357 | { |
ae27e98a | 358 | if (new_state == TCP_CA_Loss) { |
df3271f3 | 359 | bictcp_reset(inet_csk_ca(sk)); |
ae27e98a SH |
360 | bictcp_hystart_reset(sk); |
361 | } | |
362 | } | |
363 | ||
f278b99c ED |
364 | /* Account for TSO/GRO delays. |
365 | * Otherwise short RTT flows could get too small ssthresh, since during | |
366 | * slow start we begin with small TSO packets and ca->delay_min would | |
367 | * not account for long aggregation delay when TSO packets get bigger. | |
368 | * Ideally even with a very small RTT we would like to have at least one | |
369 | * TSO packet being sent and received by GRO, and another one in qdisc layer. | |
370 | * We apply another 100% factor because @rate is doubled at this point. | |
371 | * We cap the cushion to 1ms. | |
372 | */ | |
373 | static u32 hystart_ack_delay(struct sock *sk) | |
374 | { | |
375 | unsigned long rate; | |
376 | ||
377 | rate = READ_ONCE(sk->sk_pacing_rate); | |
378 | if (!rate) | |
379 | return 0; | |
380 | return min_t(u64, USEC_PER_MSEC, | |
381 | div64_ul((u64)GSO_MAX_SIZE * 4 * USEC_PER_SEC, rate)); | |
382 | } | |
383 | ||
ae27e98a SH |
384 | static void hystart_update(struct sock *sk, u32 delay) |
385 | { | |
386 | struct tcp_sock *tp = tcp_sk(sk); | |
387 | struct bictcp *ca = inet_csk_ca(sk); | |
ede656e8 | 388 | u32 threshold; |
ae27e98a | 389 | |
7e0083f3 ED |
390 | if (after(tp->snd_una, ca->end_seq)) |
391 | bictcp_hystart_reset(sk); | |
392 | ||
6e3a8a93 | 393 | if (hystart_detect & HYSTART_ACK_TRAIN) { |
cff04e2d | 394 | u32 now = bictcp_clock_us(sk); |
ae27e98a SH |
395 | |
396 | /* first detection parameter - ack-train detection */ | |
cff04e2d | 397 | if ((s32)(now - ca->last_ack) <= hystart_ack_delta_us) { |
17a6e9f1 | 398 | ca->last_ack = now; |
ede656e8 | 399 | |
f278b99c ED |
400 | threshold = ca->delay_min + hystart_ack_delay(sk); |
401 | ||
ede656e8 ED |
402 | /* Hystart ack train triggers if we get ack past |
403 | * ca->delay_min/2. | |
404 | * Pacing might have delayed packets up to RTT/2 | |
405 | * during slow start. | |
406 | */ | |
407 | if (sk->sk_pacing_status == SK_PACING_NONE) | |
408 | threshold >>= 1; | |
409 | ||
410 | if ((s32)(now - ca->round_start) > threshold) { | |
473900a5 | 411 | ca->found = 1; |
f278b99c ED |
412 | pr_debug("hystart_ack_train (%u > %u) delay_min %u (+ ack_delay %u) cwnd %u\n", |
413 | now - ca->round_start, threshold, | |
0d24ea1d | 414 | ca->delay_min, hystart_ack_delay(sk), tcp_snd_cwnd(tp)); |
c10d9310 ED |
415 | NET_INC_STATS(sock_net(sk), |
416 | LINUX_MIB_TCPHYSTARTTRAINDETECT); | |
417 | NET_ADD_STATS(sock_net(sk), | |
418 | LINUX_MIB_TCPHYSTARTTRAINCWND, | |
0d24ea1d ED |
419 | tcp_snd_cwnd(tp)); |
420 | tp->snd_ssthresh = tcp_snd_cwnd(tp); | |
6e3a8a93 | 421 | } |
ae27e98a | 422 | } |
6e3a8a93 | 423 | } |
ae27e98a | 424 | |
6e3a8a93 | 425 | if (hystart_detect & HYSTART_DELAY) { |
ae27e98a | 426 | /* obtain the minimum delay of more than sampling packets */ |
b344579c NC |
427 | if (ca->curr_rtt > delay) |
428 | ca->curr_rtt = delay; | |
ae27e98a | 429 | if (ca->sample_cnt < HYSTART_MIN_SAMPLES) { |
ae27e98a SH |
430 | ca->sample_cnt++; |
431 | } else { | |
432 | if (ca->curr_rtt > ca->delay_min + | |
42eef7a0 | 433 | HYSTART_DELAY_THRESH(ca->delay_min >> 3)) { |
473900a5 | 434 | ca->found = 1; |
c10d9310 ED |
435 | NET_INC_STATS(sock_net(sk), |
436 | LINUX_MIB_TCPHYSTARTDELAYDETECT); | |
437 | NET_ADD_STATS(sock_net(sk), | |
438 | LINUX_MIB_TCPHYSTARTDELAYCWND, | |
0d24ea1d ED |
439 | tcp_snd_cwnd(tp)); |
440 | tp->snd_ssthresh = tcp_snd_cwnd(tp); | |
6e3a8a93 | 441 | } |
ae27e98a | 442 | } |
ae27e98a | 443 | } |
df3271f3 SH |
444 | } |
445 | ||
d22f6ad1 | 446 | static void cubictcp_acked(struct sock *sk, const struct ack_sample *sample) |
df3271f3 | 447 | { |
ae27e98a | 448 | const struct tcp_sock *tp = tcp_sk(sk); |
e7d0c885 SH |
449 | struct bictcp *ca = inet_csk_ca(sk); |
450 | u32 delay; | |
df3271f3 | 451 | |
e7d0c885 | 452 | /* Some calls are for duplicates without timetamps */ |
756ee172 | 453 | if (sample->rtt_us < 0) |
e7d0c885 SH |
454 | return; |
455 | ||
456 | /* Discard delay samples right after fast recovery */ | |
ac35f562 | 457 | if (ca->epoch_start && (s32)(tcp_jiffies32 - ca->epoch_start) < HZ) |
e7d0c885 SH |
458 | return; |
459 | ||
cff04e2d | 460 | delay = sample->rtt_us; |
e7d0c885 SH |
461 | if (delay == 0) |
462 | delay = 1; | |
463 | ||
464 | /* first time call or link delay decreases */ | |
f278b99c ED |
465 | if (ca->delay_min == 0 || ca->delay_min > delay) |
466 | ca->delay_min = delay; | |
ae27e98a SH |
467 | |
468 | /* hystart triggers when cwnd is larger than some threshold */ | |
f278b99c | 469 | if (!ca->found && tcp_in_slow_start(tp) && hystart && |
0d24ea1d | 470 | tcp_snd_cwnd(tp) >= hystart_low_window) |
ae27e98a | 471 | hystart_update(sk, delay); |
e7d0c885 | 472 | } |
df3271f3 | 473 | |
a252bebe | 474 | static struct tcp_congestion_ops cubictcp __read_mostly = { |
d22f6ad1 MKL |
475 | .init = cubictcp_init, |
476 | .ssthresh = cubictcp_recalc_ssthresh, | |
477 | .cong_avoid = cubictcp_cong_avoid, | |
478 | .set_state = cubictcp_state, | |
f1722a1b | 479 | .undo_cwnd = tcp_reno_undo_cwnd, |
d22f6ad1 MKL |
480 | .cwnd_event = cubictcp_cwnd_event, |
481 | .pkts_acked = cubictcp_acked, | |
df3271f3 SH |
482 | .owner = THIS_MODULE, |
483 | .name = "cubic", | |
484 | }; | |
485 | ||
486 | static int __init cubictcp_register(void) | |
487 | { | |
74975d40 | 488 | BUILD_BUG_ON(sizeof(struct bictcp) > ICSK_CA_PRIV_SIZE); |
89b3d9aa SH |
489 | |
490 | /* Precompute a bunch of the scaling factors that are used per-packet | |
491 | * based on SRTT of 100ms | |
492 | */ | |
493 | ||
688d1945 | 494 | beta_scale = 8*(BICTCP_BETA_SCALE+beta) / 3 |
495 | / (BICTCP_BETA_SCALE - beta); | |
89b3d9aa | 496 | |
22119240 | 497 | cube_rtt_scale = (bic_scale * 10); /* 1024*c/rtt */ |
89b3d9aa SH |
498 | |
499 | /* calculate the "K" for (wmax-cwnd) = c/rtt * K^3 | |
500 | * so K = cubic_root( (wmax-cwnd)*rtt/c ) | |
501 | * the unit of K is bictcp_HZ=2^10, not HZ | |
502 | * | |
503 | * c = bic_scale >> 10 | |
504 | * rtt = 100ms | |
505 | * | |
506 | * the following code has been designed and tested for | |
507 | * cwnd < 1 million packets | |
508 | * RTT < 100 seconds | |
509 | * HZ < 1,000,00 (corresponding to 10 nano-second) | |
510 | */ | |
511 | ||
512 | /* 1/c * 2^2*bictcp_HZ * srtt */ | |
513 | cube_factor = 1ull << (10+3*BICTCP_HZ); /* 2^40 */ | |
514 | ||
515 | /* divide by bic_scale and by constant Srtt (100ms) */ | |
516 | do_div(cube_factor, bic_scale * 10); | |
517 | ||
df3271f3 SH |
518 | return tcp_register_congestion_control(&cubictcp); |
519 | } | |
520 | ||
521 | static void __exit cubictcp_unregister(void) | |
522 | { | |
523 | tcp_unregister_congestion_control(&cubictcp); | |
524 | } | |
525 | ||
526 | module_init(cubictcp_register); | |
527 | module_exit(cubictcp_unregister); | |
528 | ||
529 | MODULE_AUTHOR("Sangtae Ha, Stephen Hemminger"); | |
530 | MODULE_LICENSE("GPL"); | |
531 | MODULE_DESCRIPTION("CUBIC TCP"); | |
ae27e98a | 532 | MODULE_VERSION("2.3"); |