1 // SPDX-License-Identifier: GPL-2.0-only << 2 /* 1 /* 3 * Binary Increase Congestion control for TCP 2 * Binary Increase Congestion control for TCP 4 * Home page: 3 * Home page: 5 * http://netsrv.csc.ncsu.edu/twiki/bin/v 4 * http://netsrv.csc.ncsu.edu/twiki/bin/view/Main/BIC 6 * This is from the implementation of BICTCP i 5 * This is from the implementation of BICTCP in 7 * Lison-Xu, Kahaled Harfoush, and Injong Rhee 6 * Lison-Xu, Kahaled Harfoush, and Injong Rhee. 8 * "Binary Increase Congestion Control for Fa 7 * "Binary Increase Congestion Control for Fast, Long Distance 9 * Networks" in InfoComm 2004 8 * Networks" in InfoComm 2004 10 * Available from: 9 * Available from: 11 * http://netsrv.csc.ncsu.edu/export/bitcp.pd 10 * http://netsrv.csc.ncsu.edu/export/bitcp.pdf 12 * 11 * 13 * Unless BIC is enabled and congestion window 12 * Unless BIC is enabled and congestion window is large 14 * this behaves the same as the original Reno. 13 * this behaves the same as the original Reno. 15 */ 14 */ 16 15 17 #include <linux/mm.h> 16 #include <linux/mm.h> 18 #include <linux/module.h> 17 #include <linux/module.h> 19 #include <net/tcp.h> 18 #include <net/tcp.h> 20 19 21 #define BICTCP_BETA_SCALE 1024 /* Sca 20 #define BICTCP_BETA_SCALE 1024 /* Scale factor beta calculation 22 * max 21 * max_cwnd = snd_cwnd * beta 23 */ 22 */ 24 #define BICTCP_B 4 /* 23 #define BICTCP_B 4 /* 25 * In 24 * In binary search, 26 * go 25 * go to point (max+min)/N 27 */ 26 */ 28 27 29 static int fast_convergence = 1; 28 static int fast_convergence = 1; 30 static int max_increment = 16; 29 static int max_increment = 16; 31 static int low_window = 14; 30 static int low_window = 14; 32 static int beta = 819; /* = 819/1024 31 static int beta = 819; /* = 819/1024 (BICTCP_BETA_SCALE) */ 33 static int initial_ssthresh; 32 static int initial_ssthresh; 34 static int smooth_part = 20; 33 static int smooth_part = 20; 35 34 36 module_param(fast_convergence, int, 0644); 35 module_param(fast_convergence, int, 0644); 37 MODULE_PARM_DESC(fast_convergence, "turn on/of 36 MODULE_PARM_DESC(fast_convergence, "turn on/off fast convergence"); 38 module_param(max_increment, int, 0644); 37 module_param(max_increment, int, 0644); 39 MODULE_PARM_DESC(max_increment, "Limit on incr 38 MODULE_PARM_DESC(max_increment, "Limit on increment allowed during binary search"); 40 module_param(low_window, int, 0644); 39 module_param(low_window, int, 0644); 41 MODULE_PARM_DESC(low_window, "lower bound on c 40 MODULE_PARM_DESC(low_window, "lower bound on congestion window (for TCP friendliness)"); 42 module_param(beta, int, 0644); 41 module_param(beta, int, 0644); 43 MODULE_PARM_DESC(beta, "beta for multiplicativ 42 MODULE_PARM_DESC(beta, "beta for multiplicative increase"); 44 module_param(initial_ssthresh, int, 0644); 43 module_param(initial_ssthresh, int, 0644); 45 MODULE_PARM_DESC(initial_ssthresh, "initial va 44 MODULE_PARM_DESC(initial_ssthresh, "initial value of slow start threshold"); 46 module_param(smooth_part, int, 0644); 45 module_param(smooth_part, int, 0644); 47 MODULE_PARM_DESC(smooth_part, "log(B/(B*Smin)) 46 MODULE_PARM_DESC(smooth_part, "log(B/(B*Smin))/log(B/(B-1))+B, # of RTT from Wmax-B to Wmax"); 48 47 49 /* BIC TCP Parameters */ 48 /* BIC TCP Parameters */ 50 struct bictcp { 49 struct bictcp { 51 u32 cnt; /* increase cw 50 u32 cnt; /* increase cwnd by 1 after ACKs */ 52 u32 last_max_cwnd; /* last maximu 51 u32 last_max_cwnd; /* last maximum snd_cwnd */ 53 u32 last_cwnd; /* the last sn 52 u32 last_cwnd; /* the last snd_cwnd */ 54 u32 last_time; /* time when u 53 u32 last_time; /* time when updated last_cwnd */ 55 u32 epoch_start; /* beginning o 54 u32 epoch_start; /* beginning of an epoch */ 56 #define ACK_RATIO_SHIFT 4 55 #define ACK_RATIO_SHIFT 4 57 u32 delayed_ack; /* estimate th 56 u32 delayed_ack; /* estimate the ratio of Packets/ACKs << 4 */ 58 }; 57 }; 59 58 60 static inline void bictcp_reset(struct bictcp 59 static inline void bictcp_reset(struct bictcp *ca) 61 { 60 { 62 ca->cnt = 0; 61 ca->cnt = 0; 63 ca->last_max_cwnd = 0; 62 ca->last_max_cwnd = 0; 64 ca->last_cwnd = 0; 63 ca->last_cwnd = 0; 65 ca->last_time = 0; 64 ca->last_time = 0; 66 ca->epoch_start = 0; 65 ca->epoch_start = 0; 67 ca->delayed_ack = 2 << ACK_RATIO_SHIFT 66 ca->delayed_ack = 2 << ACK_RATIO_SHIFT; 68 } 67 } 69 68 70 static void bictcp_init(struct sock *sk) 69 static void bictcp_init(struct sock *sk) 71 { 70 { 72 struct bictcp *ca = inet_csk_ca(sk); 71 struct bictcp *ca = inet_csk_ca(sk); 73 72 74 bictcp_reset(ca); 73 bictcp_reset(ca); 75 74 76 if (initial_ssthresh) 75 if (initial_ssthresh) 77 tcp_sk(sk)->snd_ssthresh = ini 76 tcp_sk(sk)->snd_ssthresh = initial_ssthresh; 78 } 77 } 79 78 80 /* 79 /* 81 * Compute congestion window to use. 80 * Compute congestion window to use. 82 */ 81 */ 83 static inline void bictcp_update(struct bictcp 82 static inline void bictcp_update(struct bictcp *ca, u32 cwnd) 84 { 83 { 85 if (ca->last_cwnd == cwnd && 84 if (ca->last_cwnd == cwnd && 86 (s32)(tcp_jiffies32 - ca->last_tim 85 (s32)(tcp_jiffies32 - ca->last_time) <= HZ / 32) 87 return; 86 return; 88 87 89 ca->last_cwnd = cwnd; 88 ca->last_cwnd = cwnd; 90 ca->last_time = tcp_jiffies32; 89 ca->last_time = tcp_jiffies32; 91 90 92 if (ca->epoch_start == 0) /* record th 91 if (ca->epoch_start == 0) /* record the beginning of an epoch */ 93 ca->epoch_start = tcp_jiffies3 92 ca->epoch_start = tcp_jiffies32; 94 93 95 /* start off normal */ 94 /* start off normal */ 96 if (cwnd <= low_window) { 95 if (cwnd <= low_window) { 97 ca->cnt = cwnd; 96 ca->cnt = cwnd; 98 return; 97 return; 99 } 98 } 100 99 101 /* binary increase */ 100 /* binary increase */ 102 if (cwnd < ca->last_max_cwnd) { 101 if (cwnd < ca->last_max_cwnd) { 103 __u32 dist = (ca->last_max_c 102 __u32 dist = (ca->last_max_cwnd - cwnd) 104 / BICTCP_B; 103 / BICTCP_B; 105 104 106 if (dist > max_increment) 105 if (dist > max_increment) 107 /* linear increase */ 106 /* linear increase */ 108 ca->cnt = cwnd / max_i 107 ca->cnt = cwnd / max_increment; 109 else if (dist <= 1U) 108 else if (dist <= 1U) 110 /* binary search incre 109 /* binary search increase */ 111 ca->cnt = (cwnd * smoo 110 ca->cnt = (cwnd * smooth_part) / BICTCP_B; 112 else 111 else 113 /* binary search incre 112 /* binary search increase */ 114 ca->cnt = cwnd / dist; 113 ca->cnt = cwnd / dist; 115 } else { 114 } else { 116 /* slow start AMD linear incre 115 /* slow start AMD linear increase */ 117 if (cwnd < ca->last_max_cwnd + 116 if (cwnd < ca->last_max_cwnd + BICTCP_B) 118 /* slow start */ 117 /* slow start */ 119 ca->cnt = (cwnd * smoo 118 ca->cnt = (cwnd * smooth_part) / BICTCP_B; 120 else if (cwnd < ca->last_max_c 119 else if (cwnd < ca->last_max_cwnd + max_increment*(BICTCP_B-1)) 121 /* slow start */ 120 /* slow start */ 122 ca->cnt = (cwnd * (BIC 121 ca->cnt = (cwnd * (BICTCP_B-1)) 123 / (cwnd - ca-> 122 / (cwnd - ca->last_max_cwnd); 124 else 123 else 125 /* linear increase */ 124 /* linear increase */ 126 ca->cnt = cwnd / max_i 125 ca->cnt = cwnd / max_increment; 127 } 126 } 128 127 129 /* if in slow start or link utilizatio 128 /* if in slow start or link utilization is very low */ 130 if (ca->last_max_cwnd == 0) { 129 if (ca->last_max_cwnd == 0) { 131 if (ca->cnt > 20) /* increase 130 if (ca->cnt > 20) /* increase cwnd 5% per RTT */ 132 ca->cnt = 20; 131 ca->cnt = 20; 133 } 132 } 134 133 135 ca->cnt = (ca->cnt << ACK_RATIO_SHIFT) 134 ca->cnt = (ca->cnt << ACK_RATIO_SHIFT) / ca->delayed_ack; 136 if (ca->cnt == 0) 135 if (ca->cnt == 0) /* cannot be zero */ 137 ca->cnt = 1; 136 ca->cnt = 1; 138 } 137 } 139 138 140 static void bictcp_cong_avoid(struct sock *sk, 139 static void bictcp_cong_avoid(struct sock *sk, u32 ack, u32 acked) 141 { 140 { 142 struct tcp_sock *tp = tcp_sk(sk); 141 struct tcp_sock *tp = tcp_sk(sk); 143 struct bictcp *ca = inet_csk_ca(sk); 142 struct bictcp *ca = inet_csk_ca(sk); 144 143 145 if (!tcp_is_cwnd_limited(sk)) 144 if (!tcp_is_cwnd_limited(sk)) 146 return; 145 return; 147 146 148 if (tcp_in_slow_start(tp)) { !! 147 if (tcp_in_slow_start(tp)) 149 acked = tcp_slow_start(tp, ack !! 148 tcp_slow_start(tp, acked); 150 if (!acked) !! 149 else { 151 return; !! 150 bictcp_update(ca, tp->snd_cwnd); >> 151 tcp_cong_avoid_ai(tp, ca->cnt, 1); 152 } 152 } 153 bictcp_update(ca, tcp_snd_cwnd(tp)); << 154 tcp_cong_avoid_ai(tp, ca->cnt, acked); << 155 } 153 } 156 154 157 /* 155 /* 158 * behave like Reno until low_window is r 156 * behave like Reno until low_window is reached, 159 * then increase congestion window slowly 157 * then increase congestion window slowly 160 */ 158 */ 161 static u32 bictcp_recalc_ssthresh(struct sock 159 static u32 bictcp_recalc_ssthresh(struct sock *sk) 162 { 160 { 163 const struct tcp_sock *tp = tcp_sk(sk) 161 const struct tcp_sock *tp = tcp_sk(sk); 164 struct bictcp *ca = inet_csk_ca(sk); 162 struct bictcp *ca = inet_csk_ca(sk); 165 163 166 ca->epoch_start = 0; /* end of epoc 164 ca->epoch_start = 0; /* end of epoch */ 167 165 168 /* Wmax and fast convergence */ 166 /* Wmax and fast convergence */ 169 if (tcp_snd_cwnd(tp) < ca->last_max_cw !! 167 if (tp->snd_cwnd < ca->last_max_cwnd && fast_convergence) 170 ca->last_max_cwnd = (tcp_snd_c !! 168 ca->last_max_cwnd = (tp->snd_cwnd * (BICTCP_BETA_SCALE + beta)) 171 / (2 * BICTCP_BETA_SCA 169 / (2 * BICTCP_BETA_SCALE); 172 else 170 else 173 ca->last_max_cwnd = tcp_snd_cw !! 171 ca->last_max_cwnd = tp->snd_cwnd; 174 172 175 if (tcp_snd_cwnd(tp) <= low_window) !! 173 if (tp->snd_cwnd <= low_window) 176 return max(tcp_snd_cwnd(tp) >> !! 174 return max(tp->snd_cwnd >> 1U, 2U); 177 else 175 else 178 return max((tcp_snd_cwnd(tp) * !! 176 return max((tp->snd_cwnd * beta) / BICTCP_BETA_SCALE, 2U); 179 } 177 } 180 178 181 static void bictcp_state(struct sock *sk, u8 n 179 static void bictcp_state(struct sock *sk, u8 new_state) 182 { 180 { 183 if (new_state == TCP_CA_Loss) 181 if (new_state == TCP_CA_Loss) 184 bictcp_reset(inet_csk_ca(sk)); 182 bictcp_reset(inet_csk_ca(sk)); 185 } 183 } 186 184 187 /* Track delayed acknowledgment ratio using sl 185 /* Track delayed acknowledgment ratio using sliding window 188 * ratio = (15*ratio + sample) / 16 186 * ratio = (15*ratio + sample) / 16 189 */ 187 */ 190 static void bictcp_acked(struct sock *sk, cons 188 static void bictcp_acked(struct sock *sk, const struct ack_sample *sample) 191 { 189 { 192 const struct inet_connection_sock *ics 190 const struct inet_connection_sock *icsk = inet_csk(sk); 193 191 194 if (icsk->icsk_ca_state == TCP_CA_Open 192 if (icsk->icsk_ca_state == TCP_CA_Open) { 195 struct bictcp *ca = inet_csk_c 193 struct bictcp *ca = inet_csk_ca(sk); 196 194 197 ca->delayed_ack += sample->pkt 195 ca->delayed_ack += sample->pkts_acked - 198 (ca->delayed_ack >> AC 196 (ca->delayed_ack >> ACK_RATIO_SHIFT); 199 } 197 } 200 } 198 } 201 199 202 static struct tcp_congestion_ops bictcp __read 200 static struct tcp_congestion_ops bictcp __read_mostly = { 203 .init = bictcp_init, 201 .init = bictcp_init, 204 .ssthresh = bictcp_recalc_ssthre 202 .ssthresh = bictcp_recalc_ssthresh, 205 .cong_avoid = bictcp_cong_avoid, 203 .cong_avoid = bictcp_cong_avoid, 206 .set_state = bictcp_state, 204 .set_state = bictcp_state, 207 .undo_cwnd = tcp_reno_undo_cwnd, 205 .undo_cwnd = tcp_reno_undo_cwnd, 208 .pkts_acked = bictcp_acked, 206 .pkts_acked = bictcp_acked, 209 .owner = THIS_MODULE, 207 .owner = THIS_MODULE, 210 .name = "bic", 208 .name = "bic", 211 }; 209 }; 212 210 213 static int __init bictcp_register(void) 211 static int __init bictcp_register(void) 214 { 212 { 215 BUILD_BUG_ON(sizeof(struct bictcp) > I 213 BUILD_BUG_ON(sizeof(struct bictcp) > ICSK_CA_PRIV_SIZE); 216 return tcp_register_congestion_control 214 return tcp_register_congestion_control(&bictcp); 217 } 215 } 218 216 219 static void __exit bictcp_unregister(void) 217 static void __exit bictcp_unregister(void) 220 { 218 { 221 tcp_unregister_congestion_control(&bic 219 tcp_unregister_congestion_control(&bictcp); 222 } 220 } 223 221 224 module_init(bictcp_register); 222 module_init(bictcp_register); 225 module_exit(bictcp_unregister); 223 module_exit(bictcp_unregister); 226 224 227 MODULE_AUTHOR("Stephen Hemminger"); 225 MODULE_AUTHOR("Stephen Hemminger"); 228 MODULE_LICENSE("GPL"); 226 MODULE_LICENSE("GPL"); 229 MODULE_DESCRIPTION("BIC TCP"); 227 MODULE_DESCRIPTION("BIC TCP"); 230 228
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