Commit | Line | Data |
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5ef81475 AC |
1 | /* |
2 | * | |
3 | * YeAH TCP | |
4 | * | |
5 | * For further details look at: | |
49564e55 | 6 | * https://web.archive.org/web/20080316215752/http://wil.cs.caltech.edu/pfldnet2007/paper/YeAH_TCP.pdf |
5ef81475 AC |
7 | * |
8 | */ | |
7752237e SH |
9 | #include <linux/mm.h> |
10 | #include <linux/module.h> | |
11 | #include <linux/skbuff.h> | |
12 | #include <linux/inet_diag.h> | |
5ef81475 | 13 | |
7752237e | 14 | #include <net/tcp.h> |
5ef81475 | 15 | |
7752237e | 16 | #include "tcp_vegas.h" |
5ef81475 | 17 | |
49564e55 WC |
18 | #define TCP_YEAH_ALPHA 80 /* number of packets queued at the bottleneck */ |
19 | #define TCP_YEAH_GAMMA 1 /* fraction of queue to be removed per rtt */ | |
20 | #define TCP_YEAH_DELTA 3 /* log minimum fraction of cwnd to be removed on loss */ | |
21 | #define TCP_YEAH_EPSILON 1 /* log maximum fraction to be removed on early decongestion */ | |
22 | #define TCP_YEAH_PHY 8 /* maximum delta from base */ | |
23 | #define TCP_YEAH_RHO 16 /* minimum number of consecutive rtt to consider competition on loss */ | |
24 | #define TCP_YEAH_ZETA 50 /* minimum number of state switches to reset reno_count */ | |
5ef81475 AC |
25 | |
26 | #define TCP_SCALABLE_AI_CNT 100U | |
27 | ||
28 | /* YeAH variables */ | |
29 | struct yeah { | |
7752237e | 30 | struct vegas vegas; /* must be first */ |
5ef81475 AC |
31 | |
32 | /* YeAH */ | |
33 | u32 lastQ; | |
34 | u32 doing_reno_now; | |
35 | ||
36 | u32 reno_count; | |
37 | u32 fast_count; | |
38 | ||
39 | u32 pkts_acked; | |
40 | }; | |
41 | ||
42 | static void tcp_yeah_init(struct sock *sk) | |
43 | { | |
44 | struct tcp_sock *tp = tcp_sk(sk); | |
45 | struct yeah *yeah = inet_csk_ca(sk); | |
46 | ||
47 | tcp_vegas_init(sk); | |
48 | ||
49 | yeah->doing_reno_now = 0; | |
50 | yeah->lastQ = 0; | |
51 | ||
52 | yeah->reno_count = 2; | |
53 | ||
54 | /* Ensure the MD arithmetic works. This is somewhat pedantic, | |
55 | * since I don't think we will see a cwnd this large. :) */ | |
56 | tp->snd_cwnd_clamp = min_t(u32, tp->snd_cwnd_clamp, 0xffffffff/128); | |
57 | ||
58 | } | |
59 | ||
60 | ||
30cfd0ba | 61 | static void tcp_yeah_pkts_acked(struct sock *sk, u32 pkts_acked, s32 rtt_us) |
5ef81475 AC |
62 | { |
63 | const struct inet_connection_sock *icsk = inet_csk(sk); | |
64 | struct yeah *yeah = inet_csk_ca(sk); | |
65 | ||
66 | if (icsk->icsk_ca_state == TCP_CA_Open) | |
67 | yeah->pkts_acked = pkts_acked; | |
164891aa | 68 | |
30cfd0ba | 69 | tcp_vegas_pkts_acked(sk, pkts_acked, rtt_us); |
5ef81475 AC |
70 | } |
71 | ||
9f9843a7 YC |
72 | static void tcp_yeah_cong_avoid(struct sock *sk, u32 ack, u32 acked, |
73 | u32 in_flight) | |
5ef81475 AC |
74 | { |
75 | struct tcp_sock *tp = tcp_sk(sk); | |
76 | struct yeah *yeah = inet_csk_ca(sk); | |
77 | ||
78 | if (!tcp_is_cwnd_limited(sk, in_flight)) | |
79 | return; | |
80 | ||
7752237e | 81 | if (tp->snd_cwnd <= tp->snd_ssthresh) |
9f9843a7 | 82 | tcp_slow_start(tp, acked); |
7752237e SH |
83 | |
84 | else if (!yeah->doing_reno_now) { | |
5ef81475 AC |
85 | /* Scalable */ |
86 | ||
5a5f3a8d | 87 | tp->snd_cwnd_cnt += yeah->pkts_acked; |
5ef81475 AC |
88 | if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){ |
89 | if (tp->snd_cwnd < tp->snd_cwnd_clamp) | |
90 | tp->snd_cwnd++; | |
91 | tp->snd_cwnd_cnt = 0; | |
92 | } | |
93 | ||
94 | yeah->pkts_acked = 1; | |
95 | ||
96 | } else { | |
97 | /* Reno */ | |
758ce5c8 | 98 | tcp_cong_avoid_ai(tp, tp->snd_cwnd); |
5ef81475 AC |
99 | } |
100 | ||
7752237e | 101 | /* The key players are v_vegas.beg_snd_una and v_beg_snd_nxt. |
5ef81475 AC |
102 | * |
103 | * These are so named because they represent the approximate values | |
104 | * of snd_una and snd_nxt at the beginning of the current RTT. More | |
105 | * precisely, they represent the amount of data sent during the RTT. | |
106 | * At the end of the RTT, when we receive an ACK for v_beg_snd_nxt, | |
7752237e | 107 | * we will calculate that (v_beg_snd_nxt - v_vegas.beg_snd_una) outstanding |
5ef81475 AC |
108 | * bytes of data have been ACKed during the course of the RTT, giving |
109 | * an "actual" rate of: | |
110 | * | |
7752237e | 111 | * (v_beg_snd_nxt - v_vegas.beg_snd_una) / (rtt duration) |
5ef81475 | 112 | * |
7752237e | 113 | * Unfortunately, v_vegas.beg_snd_una is not exactly equal to snd_una, |
5ef81475 AC |
114 | * because delayed ACKs can cover more than one segment, so they |
115 | * don't line up yeahly with the boundaries of RTTs. | |
116 | * | |
117 | * Another unfortunate fact of life is that delayed ACKs delay the | |
118 | * advance of the left edge of our send window, so that the number | |
119 | * of bytes we send in an RTT is often less than our cwnd will allow. | |
120 | * So we keep track of our cwnd separately, in v_beg_snd_cwnd. | |
121 | */ | |
122 | ||
7752237e | 123 | if (after(ack, yeah->vegas.beg_snd_nxt)) { |
5ef81475 AC |
124 | |
125 | /* We do the Vegas calculations only if we got enough RTT | |
126 | * samples that we can be reasonably sure that we got | |
127 | * at least one RTT sample that wasn't from a delayed ACK. | |
128 | * If we only had 2 samples total, | |
129 | * then that means we're getting only 1 ACK per RTT, which | |
130 | * means they're almost certainly delayed ACKs. | |
131 | * If we have 3 samples, we should be OK. | |
132 | */ | |
133 | ||
7752237e | 134 | if (yeah->vegas.cntRTT > 2) { |
43e68392 SH |
135 | u32 rtt, queue; |
136 | u64 bw; | |
5ef81475 AC |
137 | |
138 | /* We have enough RTT samples, so, using the Vegas | |
139 | * algorithm, we determine if we should increase or | |
140 | * decrease cwnd, and by how much. | |
141 | */ | |
142 | ||
143 | /* Pluck out the RTT we are using for the Vegas | |
144 | * calculations. This is the min RTT seen during the | |
145 | * last RTT. Taking the min filters out the effects | |
146 | * of delayed ACKs, at the cost of noticing congestion | |
147 | * a bit later. | |
148 | */ | |
7752237e | 149 | rtt = yeah->vegas.minRTT; |
5ef81475 | 150 | |
43e68392 SH |
151 | /* Compute excess number of packets above bandwidth |
152 | * Avoid doing full 64 bit divide. | |
153 | */ | |
154 | bw = tp->snd_cwnd; | |
7752237e | 155 | bw *= rtt - yeah->vegas.baseRTT; |
43e68392 SH |
156 | do_div(bw, rtt); |
157 | queue = bw; | |
158 | ||
159 | if (queue > TCP_YEAH_ALPHA || | |
7752237e | 160 | rtt - yeah->vegas.baseRTT > (yeah->vegas.baseRTT / TCP_YEAH_PHY)) { |
9d4fb27d JP |
161 | if (queue > TCP_YEAH_ALPHA && |
162 | tp->snd_cwnd > yeah->reno_count) { | |
43e68392 SH |
163 | u32 reduction = min(queue / TCP_YEAH_GAMMA , |
164 | tp->snd_cwnd >> TCP_YEAH_EPSILON); | |
5ef81475 AC |
165 | |
166 | tp->snd_cwnd -= reduction; | |
167 | ||
43e68392 SH |
168 | tp->snd_cwnd = max(tp->snd_cwnd, |
169 | yeah->reno_count); | |
5ef81475 AC |
170 | |
171 | tp->snd_ssthresh = tp->snd_cwnd; | |
43e68392 | 172 | } |
5ef81475 AC |
173 | |
174 | if (yeah->reno_count <= 2) | |
43e68392 | 175 | yeah->reno_count = max(tp->snd_cwnd>>1, 2U); |
5ef81475 AC |
176 | else |
177 | yeah->reno_count++; | |
178 | ||
43e68392 SH |
179 | yeah->doing_reno_now = min(yeah->doing_reno_now + 1, |
180 | 0xffffffU); | |
5ef81475 AC |
181 | } else { |
182 | yeah->fast_count++; | |
183 | ||
184 | if (yeah->fast_count > TCP_YEAH_ZETA) { | |
185 | yeah->reno_count = 2; | |
186 | yeah->fast_count = 0; | |
187 | } | |
188 | ||
189 | yeah->doing_reno_now = 0; | |
190 | } | |
191 | ||
192 | yeah->lastQ = queue; | |
193 | ||
194 | } | |
195 | ||
196 | /* Save the extent of the current window so we can use this | |
197 | * at the end of the next RTT. | |
198 | */ | |
7752237e SH |
199 | yeah->vegas.beg_snd_una = yeah->vegas.beg_snd_nxt; |
200 | yeah->vegas.beg_snd_nxt = tp->snd_nxt; | |
201 | yeah->vegas.beg_snd_cwnd = tp->snd_cwnd; | |
5ef81475 AC |
202 | |
203 | /* Wipe the slate clean for the next RTT. */ | |
7752237e SH |
204 | yeah->vegas.cntRTT = 0; |
205 | yeah->vegas.minRTT = 0x7fffffff; | |
5ef81475 AC |
206 | } |
207 | } | |
208 | ||
209 | static u32 tcp_yeah_ssthresh(struct sock *sk) { | |
210 | const struct tcp_sock *tp = tcp_sk(sk); | |
211 | struct yeah *yeah = inet_csk_ca(sk); | |
212 | u32 reduction; | |
213 | ||
214 | if (yeah->doing_reno_now < TCP_YEAH_RHO) { | |
215 | reduction = yeah->lastQ; | |
216 | ||
0c9a67d2 | 217 | reduction = min(reduction, max(tp->snd_cwnd>>1, 2U)); |
5ef81475 | 218 | |
0c9a67d2 | 219 | reduction = max(reduction, tp->snd_cwnd >> TCP_YEAH_DELTA); |
5ef81475 | 220 | } else |
5a5f3a8d | 221 | reduction = max(tp->snd_cwnd>>1, 2U); |
5ef81475 AC |
222 | |
223 | yeah->fast_count = 0; | |
224 | yeah->reno_count = max(yeah->reno_count>>1, 2U); | |
225 | ||
226 | return tp->snd_cwnd - reduction; | |
227 | } | |
228 | ||
a252bebe | 229 | static struct tcp_congestion_ops tcp_yeah __read_mostly = { |
164891aa | 230 | .flags = TCP_CONG_RTT_STAMP, |
5ef81475 AC |
231 | .init = tcp_yeah_init, |
232 | .ssthresh = tcp_yeah_ssthresh, | |
233 | .cong_avoid = tcp_yeah_cong_avoid, | |
234 | .min_cwnd = tcp_reno_min_cwnd, | |
5ef81475 AC |
235 | .set_state = tcp_vegas_state, |
236 | .cwnd_event = tcp_vegas_cwnd_event, | |
237 | .get_info = tcp_vegas_get_info, | |
238 | .pkts_acked = tcp_yeah_pkts_acked, | |
239 | ||
240 | .owner = THIS_MODULE, | |
241 | .name = "yeah", | |
242 | }; | |
243 | ||
244 | static int __init tcp_yeah_register(void) | |
245 | { | |
246 | BUG_ON(sizeof(struct yeah) > ICSK_CA_PRIV_SIZE); | |
247 | tcp_register_congestion_control(&tcp_yeah); | |
248 | return 0; | |
249 | } | |
250 | ||
251 | static void __exit tcp_yeah_unregister(void) | |
252 | { | |
253 | tcp_unregister_congestion_control(&tcp_yeah); | |
254 | } | |
255 | ||
256 | module_init(tcp_yeah_register); | |
257 | module_exit(tcp_yeah_unregister); | |
258 | ||
259 | MODULE_AUTHOR("Angelo P. Castellani"); | |
260 | MODULE_LICENSE("GPL"); | |
261 | MODULE_DESCRIPTION("YeAH TCP"); |