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Angelo P. Castellani5ef81472007-02-22 00:23:05 -08001/*
2 *
3 * YeAH TCP
4 *
5 * For further details look at:
Weilong Chen49564e52013-12-23 14:37:32 +08006 * https://web.archive.org/web/20080316215752/http://wil.cs.caltech.edu/pfldnet2007/paper/YeAH_TCP.pdf
Angelo P. Castellani5ef81472007-02-22 00:23:05 -08007 *
8 */
Stephen Hemminger77522372007-04-23 22:28:23 -07009#include <linux/mm.h>
10#include <linux/module.h>
11#include <linux/skbuff.h>
12#include <linux/inet_diag.h>
Angelo P. Castellani5ef81472007-02-22 00:23:05 -080013
Stephen Hemminger77522372007-04-23 22:28:23 -070014#include <net/tcp.h>
Angelo P. Castellani5ef81472007-02-22 00:23:05 -080015
Stephen Hemminger77522372007-04-23 22:28:23 -070016#include "tcp_vegas.h"
Angelo P. Castellani5ef81472007-02-22 00:23:05 -080017
Weilong Chen49564e52013-12-23 14:37:32 +080018#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 */
Angelo P. Castellani5ef81472007-02-22 00:23:05 -080025
26#define TCP_SCALABLE_AI_CNT 100U
27
28/* YeAH variables */
29struct yeah {
Stephen Hemminger77522372007-04-23 22:28:23 -070030 struct vegas vegas; /* must be first */
Angelo P. Castellani5ef81472007-02-22 00:23:05 -080031
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
42static 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);
Angelo P. Castellani5ef81472007-02-22 00:23:05 -080057}
58
Stephen Hemminger30cfd0b2007-07-25 23:49:34 -070059static void tcp_yeah_pkts_acked(struct sock *sk, u32 pkts_acked, s32 rtt_us)
Angelo P. Castellani5ef81472007-02-22 00:23:05 -080060{
61 const struct inet_connection_sock *icsk = inet_csk(sk);
62 struct yeah *yeah = inet_csk_ca(sk);
63
64 if (icsk->icsk_ca_state == TCP_CA_Open)
65 yeah->pkts_acked = pkts_acked;
Stephen Hemminger164891a2007-04-23 22:26:16 -070066
Stephen Hemminger30cfd0b2007-07-25 23:49:34 -070067 tcp_vegas_pkts_acked(sk, pkts_acked, rtt_us);
Angelo P. Castellani5ef81472007-02-22 00:23:05 -080068}
69
Eric Dumazet24901552014-05-02 21:18:05 -070070static void tcp_yeah_cong_avoid(struct sock *sk, u32 ack, u32 acked)
Angelo P. Castellani5ef81472007-02-22 00:23:05 -080071{
72 struct tcp_sock *tp = tcp_sk(sk);
73 struct yeah *yeah = inet_csk_ca(sk);
74
Eric Dumazet24901552014-05-02 21:18:05 -070075 if (!tcp_is_cwnd_limited(sk))
Angelo P. Castellani5ef81472007-02-22 00:23:05 -080076 return;
77
Stephen Hemminger77522372007-04-23 22:28:23 -070078 if (tp->snd_cwnd <= tp->snd_ssthresh)
Yuchung Cheng9f9843a72013-10-31 11:07:31 -070079 tcp_slow_start(tp, acked);
Stephen Hemminger77522372007-04-23 22:28:23 -070080
81 else if (!yeah->doing_reno_now) {
Angelo P. Castellani5ef81472007-02-22 00:23:05 -080082 /* Scalable */
83
Jianjun Kong5a5f3a82008-11-03 00:24:34 -080084 tp->snd_cwnd_cnt += yeah->pkts_acked;
stephen hemminger688d1942014-08-29 23:32:05 -070085 if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)) {
Angelo P. Castellani5ef81472007-02-22 00:23:05 -080086 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
87 tp->snd_cwnd++;
88 tp->snd_cwnd_cnt = 0;
89 }
90
91 yeah->pkts_acked = 1;
92
93 } else {
94 /* Reno */
Neal Cardwelle73ebb02015-01-28 20:01:35 -050095 tcp_cong_avoid_ai(tp, tp->snd_cwnd, 1);
Angelo P. Castellani5ef81472007-02-22 00:23:05 -080096 }
97
Stephen Hemminger77522372007-04-23 22:28:23 -070098 /* The key players are v_vegas.beg_snd_una and v_beg_snd_nxt.
Angelo P. Castellani5ef81472007-02-22 00:23:05 -080099 *
100 * These are so named because they represent the approximate values
101 * of snd_una and snd_nxt at the beginning of the current RTT. More
102 * precisely, they represent the amount of data sent during the RTT.
103 * At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
Stephen Hemminger77522372007-04-23 22:28:23 -0700104 * we will calculate that (v_beg_snd_nxt - v_vegas.beg_snd_una) outstanding
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800105 * bytes of data have been ACKed during the course of the RTT, giving
106 * an "actual" rate of:
107 *
Stephen Hemminger77522372007-04-23 22:28:23 -0700108 * (v_beg_snd_nxt - v_vegas.beg_snd_una) / (rtt duration)
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800109 *
Stephen Hemminger77522372007-04-23 22:28:23 -0700110 * Unfortunately, v_vegas.beg_snd_una is not exactly equal to snd_una,
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800111 * because delayed ACKs can cover more than one segment, so they
112 * don't line up yeahly with the boundaries of RTTs.
113 *
114 * Another unfortunate fact of life is that delayed ACKs delay the
115 * advance of the left edge of our send window, so that the number
116 * of bytes we send in an RTT is often less than our cwnd will allow.
117 * So we keep track of our cwnd separately, in v_beg_snd_cwnd.
118 */
119
Stephen Hemminger77522372007-04-23 22:28:23 -0700120 if (after(ack, yeah->vegas.beg_snd_nxt)) {
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800121 /* We do the Vegas calculations only if we got enough RTT
122 * samples that we can be reasonably sure that we got
123 * at least one RTT sample that wasn't from a delayed ACK.
124 * If we only had 2 samples total,
125 * then that means we're getting only 1 ACK per RTT, which
126 * means they're almost certainly delayed ACKs.
127 * If we have 3 samples, we should be OK.
128 */
129
Stephen Hemminger77522372007-04-23 22:28:23 -0700130 if (yeah->vegas.cntRTT > 2) {
Stephen Hemminger43e68392007-03-06 20:21:20 -0800131 u32 rtt, queue;
132 u64 bw;
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800133
134 /* We have enough RTT samples, so, using the Vegas
135 * algorithm, we determine if we should increase or
136 * decrease cwnd, and by how much.
137 */
138
139 /* Pluck out the RTT we are using for the Vegas
140 * calculations. This is the min RTT seen during the
141 * last RTT. Taking the min filters out the effects
142 * of delayed ACKs, at the cost of noticing congestion
143 * a bit later.
144 */
Stephen Hemminger77522372007-04-23 22:28:23 -0700145 rtt = yeah->vegas.minRTT;
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800146
Stephen Hemminger43e68392007-03-06 20:21:20 -0800147 /* Compute excess number of packets above bandwidth
148 * Avoid doing full 64 bit divide.
149 */
150 bw = tp->snd_cwnd;
Stephen Hemminger77522372007-04-23 22:28:23 -0700151 bw *= rtt - yeah->vegas.baseRTT;
Stephen Hemminger43e68392007-03-06 20:21:20 -0800152 do_div(bw, rtt);
153 queue = bw;
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800154
Stephen Hemminger43e68392007-03-06 20:21:20 -0800155 if (queue > TCP_YEAH_ALPHA ||
Stephen Hemminger77522372007-04-23 22:28:23 -0700156 rtt - yeah->vegas.baseRTT > (yeah->vegas.baseRTT / TCP_YEAH_PHY)) {
Joe Perches9d4fb272009-11-23 10:41:23 -0800157 if (queue > TCP_YEAH_ALPHA &&
158 tp->snd_cwnd > yeah->reno_count) {
Stephen Hemminger43e68392007-03-06 20:21:20 -0800159 u32 reduction = min(queue / TCP_YEAH_GAMMA ,
160 tp->snd_cwnd >> TCP_YEAH_EPSILON);
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800161
162 tp->snd_cwnd -= reduction;
163
Stephen Hemminger43e68392007-03-06 20:21:20 -0800164 tp->snd_cwnd = max(tp->snd_cwnd,
165 yeah->reno_count);
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800166
167 tp->snd_ssthresh = tp->snd_cwnd;
Stephen Hemminger43e68392007-03-06 20:21:20 -0800168 }
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800169
170 if (yeah->reno_count <= 2)
Stephen Hemminger43e68392007-03-06 20:21:20 -0800171 yeah->reno_count = max(tp->snd_cwnd>>1, 2U);
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800172 else
173 yeah->reno_count++;
174
Stephen Hemminger43e68392007-03-06 20:21:20 -0800175 yeah->doing_reno_now = min(yeah->doing_reno_now + 1,
176 0xffffffU);
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800177 } else {
178 yeah->fast_count++;
179
180 if (yeah->fast_count > TCP_YEAH_ZETA) {
181 yeah->reno_count = 2;
182 yeah->fast_count = 0;
183 }
184
185 yeah->doing_reno_now = 0;
186 }
187
188 yeah->lastQ = queue;
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800189 }
190
191 /* Save the extent of the current window so we can use this
192 * at the end of the next RTT.
193 */
Stephen Hemminger77522372007-04-23 22:28:23 -0700194 yeah->vegas.beg_snd_una = yeah->vegas.beg_snd_nxt;
195 yeah->vegas.beg_snd_nxt = tp->snd_nxt;
196 yeah->vegas.beg_snd_cwnd = tp->snd_cwnd;
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800197
198 /* Wipe the slate clean for the next RTT. */
Stephen Hemminger77522372007-04-23 22:28:23 -0700199 yeah->vegas.cntRTT = 0;
200 yeah->vegas.minRTT = 0x7fffffff;
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800201 }
202}
203
stephen hemminger688d1942014-08-29 23:32:05 -0700204static u32 tcp_yeah_ssthresh(struct sock *sk)
205{
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800206 const struct tcp_sock *tp = tcp_sk(sk);
207 struct yeah *yeah = inet_csk_ca(sk);
208 u32 reduction;
209
210 if (yeah->doing_reno_now < TCP_YEAH_RHO) {
211 reduction = yeah->lastQ;
212
Weilong Chen0c9a67d2013-12-23 14:37:27 +0800213 reduction = min(reduction, max(tp->snd_cwnd>>1, 2U));
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800214
Weilong Chen0c9a67d2013-12-23 14:37:27 +0800215 reduction = max(reduction, tp->snd_cwnd >> TCP_YEAH_DELTA);
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800216 } else
Jianjun Kong5a5f3a82008-11-03 00:24:34 -0800217 reduction = max(tp->snd_cwnd>>1, 2U);
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800218
219 yeah->fast_count = 0;
220 yeah->reno_count = max(yeah->reno_count>>1, 2U);
221
Neal Cardwell83d15e72016-01-11 13:42:43 -0500222 return max_t(int, tp->snd_cwnd - reduction, 2);
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800223}
224
Stephen Hemmingera252beb2011-03-10 00:40:17 -0800225static struct tcp_congestion_ops tcp_yeah __read_mostly = {
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800226 .init = tcp_yeah_init,
227 .ssthresh = tcp_yeah_ssthresh,
228 .cong_avoid = tcp_yeah_cong_avoid,
Angelo P. Castellani5ef81472007-02-22 00:23:05 -0800229 .set_state = tcp_vegas_state,
230 .cwnd_event = tcp_vegas_cwnd_event,
231 .get_info = tcp_vegas_get_info,
232 .pkts_acked = tcp_yeah_pkts_acked,
233
234 .owner = THIS_MODULE,
235 .name = "yeah",
236};
237
238static int __init tcp_yeah_register(void)
239{
240 BUG_ON(sizeof(struct yeah) > ICSK_CA_PRIV_SIZE);
241 tcp_register_congestion_control(&tcp_yeah);
242 return 0;
243}
244
245static void __exit tcp_yeah_unregister(void)
246{
247 tcp_unregister_congestion_control(&tcp_yeah);
248}
249
250module_init(tcp_yeah_register);
251module_exit(tcp_yeah_unregister);
252
253MODULE_AUTHOR("Angelo P. Castellani");
254MODULE_LICENSE("GPL");
255MODULE_DESCRIPTION("YeAH TCP");