~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/net/ipv4/tcp_bic.c

Version: ~ [ linux-5.5-rc1 ] ~ [ linux-5.4.2 ] ~ [ linux-5.3.15 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.88 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.158 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.206 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.206 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.78 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /*
  2  * Binary Increase Congestion control for TCP
  3  * Home page:
  4  *      http://netsrv.csc.ncsu.edu/twiki/bin/view/Main/BIC
  5  * This is from the implementation of BICTCP in
  6  * Lison-Xu, Kahaled Harfoush, and Injong Rhee.
  7  *  "Binary Increase Congestion Control for Fast, Long Distance
  8  *  Networks" in InfoComm 2004
  9  * Available from:
 10  *  http://netsrv.csc.ncsu.edu/export/bitcp.pdf
 11  *
 12  * Unless BIC is enabled and congestion window is large
 13  * this behaves the same as the original Reno.
 14  */
 15 
 16 #include <linux/mm.h>
 17 #include <linux/module.h>
 18 #include <net/tcp.h>
 19 
 20 
 21 #define BICTCP_BETA_SCALE    1024       /* Scale factor beta calculation
 22                                          * max_cwnd = snd_cwnd * beta
 23                                          */
 24 #define BICTCP_B                4        /*
 25                                           * In binary search,
 26                                           * go to point (max+min)/N
 27                                           */
 28 
 29 static int fast_convergence = 1;
 30 static int max_increment = 16;
 31 static int low_window = 14;
 32 static int beta = 819;          /* = 819/1024 (BICTCP_BETA_SCALE) */
 33 static int initial_ssthresh;
 34 static int smooth_part = 20;
 35 
 36 module_param(fast_convergence, int, 0644);
 37 MODULE_PARM_DESC(fast_convergence, "turn on/off fast convergence");
 38 module_param(max_increment, int, 0644);
 39 MODULE_PARM_DESC(max_increment, "Limit on increment allowed during binary search");
 40 module_param(low_window, int, 0644);
 41 MODULE_PARM_DESC(low_window, "lower bound on congestion window (for TCP friendliness)");
 42 module_param(beta, int, 0644);
 43 MODULE_PARM_DESC(beta, "beta for multiplicative increase");
 44 module_param(initial_ssthresh, int, 0644);
 45 MODULE_PARM_DESC(initial_ssthresh, "initial value of slow start threshold");
 46 module_param(smooth_part, int, 0644);
 47 MODULE_PARM_DESC(smooth_part, "log(B/(B*Smin))/log(B/(B-1))+B, # of RTT from Wmax-B to Wmax");
 48 
 49 
 50 /* BIC TCP Parameters */
 51 struct bictcp {
 52         u32     cnt;            /* increase cwnd by 1 after ACKs */
 53         u32     last_max_cwnd;  /* last maximum snd_cwnd */
 54         u32     loss_cwnd;      /* congestion window at last loss */
 55         u32     last_cwnd;      /* the last snd_cwnd */
 56         u32     last_time;      /* time when updated last_cwnd */
 57         u32     epoch_start;    /* beginning of an epoch */
 58 #define ACK_RATIO_SHIFT 4
 59         u32     delayed_ack;    /* estimate the ratio of Packets/ACKs << 4 */
 60 };
 61 
 62 static inline void bictcp_reset(struct bictcp *ca)
 63 {
 64         ca->cnt = 0;
 65         ca->last_max_cwnd = 0;
 66         ca->last_cwnd = 0;
 67         ca->last_time = 0;
 68         ca->epoch_start = 0;
 69         ca->delayed_ack = 2 << ACK_RATIO_SHIFT;
 70 }
 71 
 72 static void bictcp_init(struct sock *sk)
 73 {
 74         struct bictcp *ca = inet_csk_ca(sk);
 75 
 76         bictcp_reset(ca);
 77         ca->loss_cwnd = 0;
 78 
 79         if (initial_ssthresh)
 80                 tcp_sk(sk)->snd_ssthresh = initial_ssthresh;
 81 }
 82 
 83 /*
 84  * Compute congestion window to use.
 85  */
 86 static inline void bictcp_update(struct bictcp *ca, u32 cwnd)
 87 {
 88         if (ca->last_cwnd == cwnd &&
 89             (s32)(tcp_time_stamp - ca->last_time) <= HZ / 32)
 90                 return;
 91 
 92         ca->last_cwnd = cwnd;
 93         ca->last_time = tcp_time_stamp;
 94 
 95         if (ca->epoch_start == 0) /* record the beginning of an epoch */
 96                 ca->epoch_start = tcp_time_stamp;
 97 
 98         /* start off normal */
 99         if (cwnd <= low_window) {
100                 ca->cnt = cwnd;
101                 return;
102         }
103 
104         /* binary increase */
105         if (cwnd < ca->last_max_cwnd) {
106                 __u32   dist = (ca->last_max_cwnd - cwnd)
107                         / BICTCP_B;
108 
109                 if (dist > max_increment)
110                         /* linear increase */
111                         ca->cnt = cwnd / max_increment;
112                 else if (dist <= 1U)
113                         /* binary search increase */
114                         ca->cnt = (cwnd * smooth_part) / BICTCP_B;
115                 else
116                         /* binary search increase */
117                         ca->cnt = cwnd / dist;
118         } else {
119                 /* slow start AMD linear increase */
120                 if (cwnd < ca->last_max_cwnd + BICTCP_B)
121                         /* slow start */
122                         ca->cnt = (cwnd * smooth_part) / BICTCP_B;
123                 else if (cwnd < ca->last_max_cwnd + max_increment*(BICTCP_B-1))
124                         /* slow start */
125                         ca->cnt = (cwnd * (BICTCP_B-1))
126                                 / (cwnd - ca->last_max_cwnd);
127                 else
128                         /* linear increase */
129                         ca->cnt = cwnd / max_increment;
130         }
131 
132         /* if in slow start or link utilization is very low */
133         if (ca->last_max_cwnd == 0) {
134                 if (ca->cnt > 20) /* increase cwnd 5% per RTT */
135                         ca->cnt = 20;
136         }
137 
138         ca->cnt = (ca->cnt << ACK_RATIO_SHIFT) / ca->delayed_ack;
139         if (ca->cnt == 0)                       /* cannot be zero */
140                 ca->cnt = 1;
141 }
142 
143 static void bictcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
144 {
145         struct tcp_sock *tp = tcp_sk(sk);
146         struct bictcp *ca = inet_csk_ca(sk);
147 
148         if (!tcp_is_cwnd_limited(sk, in_flight))
149                 return;
150 
151         if (tp->snd_cwnd <= tp->snd_ssthresh)
152                 tcp_slow_start(tp);
153         else {
154                 bictcp_update(ca, tp->snd_cwnd);
155                 tcp_cong_avoid_ai(tp, ca->cnt);
156         }
157 
158 }
159 
160 /*
161  *      behave like Reno until low_window is reached,
162  *      then increase congestion window slowly
163  */
164 static u32 bictcp_recalc_ssthresh(struct sock *sk)
165 {
166         const struct tcp_sock *tp = tcp_sk(sk);
167         struct bictcp *ca = inet_csk_ca(sk);
168 
169         ca->epoch_start = 0;    /* end of epoch */
170 
171         /* Wmax and fast convergence */
172         if (tp->snd_cwnd < ca->last_max_cwnd && fast_convergence)
173                 ca->last_max_cwnd = (tp->snd_cwnd * (BICTCP_BETA_SCALE + beta))
174                         / (2 * BICTCP_BETA_SCALE);
175         else
176                 ca->last_max_cwnd = tp->snd_cwnd;
177 
178         ca->loss_cwnd = tp->snd_cwnd;
179 
180 
181         if (tp->snd_cwnd <= low_window)
182                 return max(tp->snd_cwnd >> 1U, 2U);
183         else
184                 return max((tp->snd_cwnd * beta) / BICTCP_BETA_SCALE, 2U);
185 }
186 
187 static u32 bictcp_undo_cwnd(struct sock *sk)
188 {
189         const struct tcp_sock *tp = tcp_sk(sk);
190         const struct bictcp *ca = inet_csk_ca(sk);
191         return max(tp->snd_cwnd, ca->loss_cwnd);
192 }
193 
194 static void bictcp_state(struct sock *sk, u8 new_state)
195 {
196         if (new_state == TCP_CA_Loss)
197                 bictcp_reset(inet_csk_ca(sk));
198 }
199 
200 /* Track delayed acknowledgment ratio using sliding window
201  * ratio = (15*ratio + sample) / 16
202  */
203 static void bictcp_acked(struct sock *sk, u32 cnt, s32 rtt)
204 {
205         const struct inet_connection_sock *icsk = inet_csk(sk);
206 
207         if (icsk->icsk_ca_state == TCP_CA_Open) {
208                 struct bictcp *ca = inet_csk_ca(sk);
209                 cnt -= ca->delayed_ack >> ACK_RATIO_SHIFT;
210                 ca->delayed_ack += cnt;
211         }
212 }
213 
214 
215 static struct tcp_congestion_ops bictcp __read_mostly = {
216         .init           = bictcp_init,
217         .ssthresh       = bictcp_recalc_ssthresh,
218         .cong_avoid     = bictcp_cong_avoid,
219         .set_state      = bictcp_state,
220         .undo_cwnd      = bictcp_undo_cwnd,
221         .pkts_acked     = bictcp_acked,
222         .owner          = THIS_MODULE,
223         .name           = "bic",
224 };
225 
226 static int __init bictcp_register(void)
227 {
228         BUILD_BUG_ON(sizeof(struct bictcp) > ICSK_CA_PRIV_SIZE);
229         return tcp_register_congestion_control(&bictcp);
230 }
231 
232 static void __exit bictcp_unregister(void)
233 {
234         tcp_unregister_congestion_control(&bictcp);
235 }
236 
237 module_init(bictcp_register);
238 module_exit(bictcp_unregister);
239 
240 MODULE_AUTHOR("Stephen Hemminger");
241 MODULE_LICENSE("GPL");
242 MODULE_DESCRIPTION("BIC TCP");
243 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp