Wong Hoi Sing Edison | 7c106d7 | 2006-06-05 17:27:58 -0700 | [diff] [blame] | 1 | /* |
| 2 | * TCP Low Priority (TCP-LP) |
| 3 | * |
| 4 | * TCP Low Priority is a distributed algorithm whose goal is to utilize only |
| 5 | * the excess network bandwidth as compared to the ``fair share`` of |
| 6 | * bandwidth as targeted by TCP. Available from: |
| 7 | * http://www.ece.rice.edu/~akuzma/Doc/akuzma/TCP-LP.pdf |
| 8 | * |
| 9 | * Original Author: |
| 10 | * Aleksandar Kuzmanovic <akuzma@northwestern.edu> |
| 11 | * |
| 12 | * See http://www-ece.rice.edu/networks/TCP-LP/ for their implementation. |
| 13 | * As of 2.6.13, Linux supports pluggable congestion control algorithms. |
| 14 | * Due to the limitation of the API, we take the following changes from |
| 15 | * the original TCP-LP implementation: |
| 16 | * o We use newReno in most core CA handling. Only add some checking |
| 17 | * within cong_avoid. |
| 18 | * o Error correcting in remote HZ, therefore remote HZ will be keeped |
| 19 | * on checking and updating. |
| 20 | * o Handling calculation of One-Way-Delay (OWD) within rtt_sample, sicne |
| 21 | * OWD have a similar meaning as RTT. Also correct the buggy formular. |
| 22 | * o Handle reaction for Early Congestion Indication (ECI) within |
| 23 | * pkts_acked, as mentioned within pseudo code. |
| 24 | * o OWD is handled in relative format, where local time stamp will in |
| 25 | * tcp_time_stamp format. |
| 26 | * |
| 27 | * Port from 2.4.19 to 2.6.16 as module by: |
| 28 | * Wong Hoi Sing Edison <hswong3i@gmail.com> |
| 29 | * Hung Hing Lun <hlhung3i@gmail.com> |
| 30 | * |
| 31 | * Version: $Id: tcp_lp.c,v 1.22 2006-05-02 18:18:19 hswong3i Exp $ |
| 32 | */ |
| 33 | |
| 34 | #include <linux/config.h> |
| 35 | #include <linux/module.h> |
| 36 | #include <net/tcp.h> |
| 37 | |
| 38 | /* resolution of owd */ |
| 39 | #define LP_RESOL 1000 |
| 40 | |
| 41 | /** |
| 42 | * enum tcp_lp_state |
| 43 | * @LP_VALID_RHZ: is remote HZ valid? |
| 44 | * @LP_VALID_OWD: is OWD valid? |
| 45 | * @LP_WITHIN_THR: are we within threshold? |
| 46 | * @LP_WITHIN_INF: are we within inference? |
| 47 | * |
| 48 | * TCP-LP's state flags. |
| 49 | * We create this set of state flag mainly for debugging. |
| 50 | */ |
| 51 | enum tcp_lp_state { |
| 52 | LP_VALID_RHZ = (1 << 0), |
| 53 | LP_VALID_OWD = (1 << 1), |
| 54 | LP_WITHIN_THR = (1 << 3), |
| 55 | LP_WITHIN_INF = (1 << 4), |
| 56 | }; |
| 57 | |
| 58 | /** |
| 59 | * struct lp |
| 60 | * @flag: TCP-LP state flag |
| 61 | * @sowd: smoothed OWD << 3 |
| 62 | * @owd_min: min OWD |
| 63 | * @owd_max: max OWD |
| 64 | * @owd_max_rsv: resrved max owd |
| 65 | * @remote_hz: estimated remote HZ |
| 66 | * @remote_ref_time: remote reference time |
| 67 | * @local_ref_time: local reference time |
| 68 | * @last_drop: time for last active drop |
| 69 | * @inference: current inference |
| 70 | * |
| 71 | * TCP-LP's private struct. |
| 72 | * We get the idea from original TCP-LP implementation where only left those we |
| 73 | * found are really useful. |
| 74 | */ |
| 75 | struct lp { |
| 76 | u32 flag; |
| 77 | u32 sowd; |
| 78 | u32 owd_min; |
| 79 | u32 owd_max; |
| 80 | u32 owd_max_rsv; |
| 81 | u32 remote_hz; |
| 82 | u32 remote_ref_time; |
| 83 | u32 local_ref_time; |
| 84 | u32 last_drop; |
| 85 | u32 inference; |
| 86 | }; |
| 87 | |
| 88 | /** |
| 89 | * tcp_lp_init |
| 90 | * |
| 91 | * Init all required variables. |
| 92 | * Clone the handling from Vegas module implementation. |
| 93 | */ |
| 94 | static void tcp_lp_init(struct sock *sk) |
| 95 | { |
| 96 | struct lp *lp = inet_csk_ca(sk); |
| 97 | |
| 98 | lp->flag = 0; |
| 99 | lp->sowd = 0; |
| 100 | lp->owd_min = 0xffffffff; |
| 101 | lp->owd_max = 0; |
| 102 | lp->owd_max_rsv = 0; |
| 103 | lp->remote_hz = 0; |
| 104 | lp->remote_ref_time = 0; |
| 105 | lp->local_ref_time = 0; |
| 106 | lp->last_drop = 0; |
| 107 | lp->inference = 0; |
| 108 | } |
| 109 | |
| 110 | /** |
| 111 | * tcp_lp_cong_avoid |
| 112 | * |
| 113 | * Implementation of cong_avoid. |
| 114 | * Will only call newReno CA when away from inference. |
| 115 | * From TCP-LP's paper, this will be handled in additive increasement. |
| 116 | */ |
| 117 | static void tcp_lp_cong_avoid(struct sock *sk, u32 ack, u32 rtt, u32 in_flight, |
| 118 | int flag) |
| 119 | { |
| 120 | struct lp *lp = inet_csk_ca(sk); |
| 121 | |
| 122 | if (!(lp->flag & LP_WITHIN_INF)) |
| 123 | tcp_reno_cong_avoid(sk, ack, rtt, in_flight, flag); |
| 124 | } |
| 125 | |
| 126 | /** |
| 127 | * tcp_lp_remote_hz_estimator |
| 128 | * |
| 129 | * Estimate remote HZ. |
| 130 | * We keep on updating the estimated value, where original TCP-LP |
| 131 | * implementation only guest it for once and use forever. |
| 132 | */ |
| 133 | static u32 tcp_lp_remote_hz_estimator(struct sock *sk) |
| 134 | { |
| 135 | struct tcp_sock *tp = tcp_sk(sk); |
| 136 | struct lp *lp = inet_csk_ca(sk); |
| 137 | s64 rhz = lp->remote_hz << 6; /* remote HZ << 6 */ |
| 138 | s64 m = 0; |
| 139 | |
| 140 | /* not yet record reference time |
| 141 | * go away!! record it before come back!! */ |
| 142 | if (lp->remote_ref_time == 0 || lp->local_ref_time == 0) |
| 143 | goto out; |
| 144 | |
| 145 | /* we can't calc remote HZ with no different!! */ |
| 146 | if (tp->rx_opt.rcv_tsval == lp->remote_ref_time |
| 147 | || tp->rx_opt.rcv_tsecr == lp->local_ref_time) |
| 148 | goto out; |
| 149 | |
| 150 | m = HZ * (tp->rx_opt.rcv_tsval - |
| 151 | lp->remote_ref_time) / (tp->rx_opt.rcv_tsecr - |
| 152 | lp->local_ref_time); |
| 153 | if (m < 0) |
| 154 | m = -m; |
| 155 | |
| 156 | if (rhz != 0) { |
| 157 | m -= rhz >> 6; /* m is now error in remote HZ est */ |
| 158 | rhz += m; /* 63/64 old + 1/64 new */ |
| 159 | } else |
| 160 | rhz = m << 6; |
| 161 | |
| 162 | /* record time for successful remote HZ calc */ |
| 163 | lp->flag |= LP_VALID_RHZ; |
| 164 | |
| 165 | out: |
| 166 | /* record reference time stamp */ |
| 167 | lp->remote_ref_time = tp->rx_opt.rcv_tsval; |
| 168 | lp->local_ref_time = tp->rx_opt.rcv_tsecr; |
| 169 | |
| 170 | return rhz >> 6; |
| 171 | } |
| 172 | |
| 173 | /** |
| 174 | * tcp_lp_owd_calculator |
| 175 | * |
| 176 | * Calculate one way delay (in relative format). |
| 177 | * Original implement OWD as minus of remote time difference to local time |
| 178 | * difference directly. As this time difference just simply equal to RTT, when |
| 179 | * the network status is stable, remote RTT will equal to local RTT, and result |
| 180 | * OWD into zero. |
| 181 | * It seems to be a bug and so we fixed it. |
| 182 | */ |
| 183 | static u32 tcp_lp_owd_calculator(struct sock *sk) |
| 184 | { |
| 185 | struct tcp_sock *tp = tcp_sk(sk); |
| 186 | struct lp *lp = inet_csk_ca(sk); |
| 187 | s64 owd = 0; |
| 188 | |
| 189 | lp->remote_hz = tcp_lp_remote_hz_estimator(sk); |
| 190 | |
| 191 | if (lp->flag & LP_VALID_RHZ) { |
| 192 | owd = |
| 193 | tp->rx_opt.rcv_tsval * (LP_RESOL / lp->remote_hz) - |
| 194 | tp->rx_opt.rcv_tsecr * (LP_RESOL / HZ); |
| 195 | if (owd < 0) |
| 196 | owd = -owd; |
| 197 | } |
| 198 | |
| 199 | if (owd > 0) |
| 200 | lp->flag |= LP_VALID_OWD; |
| 201 | else |
| 202 | lp->flag &= ~LP_VALID_OWD; |
| 203 | |
| 204 | return owd; |
| 205 | } |
| 206 | |
| 207 | /** |
| 208 | * tcp_lp_rtt_sample |
| 209 | * |
| 210 | * Implementation or rtt_sample. |
| 211 | * Will take the following action, |
| 212 | * 1. calc OWD, |
| 213 | * 2. record the min/max OWD, |
| 214 | * 3. calc smoothed OWD (SOWD). |
| 215 | * Most ideas come from the original TCP-LP implementation. |
| 216 | */ |
| 217 | static void tcp_lp_rtt_sample(struct sock *sk, u32 usrtt) |
| 218 | { |
| 219 | struct lp *lp = inet_csk_ca(sk); |
| 220 | s64 mowd = tcp_lp_owd_calculator(sk); |
| 221 | |
| 222 | /* sorry that we don't have valid data */ |
| 223 | if (!(lp->flag & LP_VALID_RHZ) || !(lp->flag & LP_VALID_OWD)) |
| 224 | return; |
| 225 | |
| 226 | /* record the next min owd */ |
| 227 | if (mowd < lp->owd_min) |
| 228 | lp->owd_min = mowd; |
| 229 | |
| 230 | /* always forget the max of the max |
| 231 | * we just set owd_max as one below it */ |
| 232 | if (mowd > lp->owd_max) { |
| 233 | if (mowd > lp->owd_max_rsv) { |
| 234 | if (lp->owd_max_rsv == 0) |
| 235 | lp->owd_max = mowd; |
| 236 | else |
| 237 | lp->owd_max = lp->owd_max_rsv; |
| 238 | lp->owd_max_rsv = mowd; |
| 239 | } else |
| 240 | lp->owd_max = mowd; |
| 241 | } |
| 242 | |
| 243 | /* calc for smoothed owd */ |
| 244 | if (lp->sowd != 0) { |
| 245 | mowd -= lp->sowd >> 3; /* m is now error in owd est */ |
| 246 | lp->sowd += mowd; /* owd = 7/8 owd + 1/8 new */ |
| 247 | } else |
| 248 | lp->sowd = mowd << 3; /* take the measured time be owd */ |
| 249 | } |
| 250 | |
| 251 | /** |
| 252 | * tcp_lp_pkts_acked |
| 253 | * |
| 254 | * Implementation of pkts_acked. |
| 255 | * Deal with active drop under Early Congestion Indication. |
| 256 | * Only drop to half and 1 will be handle, because we hope to use back |
| 257 | * newReno in increase case. |
| 258 | * We work it out by following the idea from TCP-LP's paper directly |
| 259 | */ |
| 260 | static void tcp_lp_pkts_acked(struct sock *sk, u32 num_acked) |
| 261 | { |
| 262 | struct tcp_sock *tp = tcp_sk(sk); |
| 263 | struct lp *lp = inet_csk_ca(sk); |
| 264 | |
| 265 | /* calc inference */ |
| 266 | if (tcp_time_stamp > tp->rx_opt.rcv_tsecr) |
| 267 | lp->inference = 3 * (tcp_time_stamp - tp->rx_opt.rcv_tsecr); |
| 268 | |
| 269 | /* test if within inference */ |
| 270 | if (lp->last_drop && (tcp_time_stamp - lp->last_drop < lp->inference)) |
| 271 | lp->flag |= LP_WITHIN_INF; |
| 272 | else |
| 273 | lp->flag &= ~LP_WITHIN_INF; |
| 274 | |
| 275 | /* test if within threshold */ |
| 276 | if (lp->sowd >> 3 < |
| 277 | lp->owd_min + 15 * (lp->owd_max - lp->owd_min) / 100) |
| 278 | lp->flag |= LP_WITHIN_THR; |
| 279 | else |
| 280 | lp->flag &= ~LP_WITHIN_THR; |
| 281 | |
| 282 | pr_debug("TCP-LP: %05o|%5u|%5u|%15u|%15u|%15u\n", lp->flag, |
| 283 | tp->snd_cwnd, lp->remote_hz, lp->owd_min, lp->owd_max, |
| 284 | lp->sowd >> 3); |
| 285 | |
| 286 | if (lp->flag & LP_WITHIN_THR) |
| 287 | return; |
| 288 | |
| 289 | /* FIXME: try to reset owd_min and owd_max here |
| 290 | * so decrease the chance the min/max is no longer suitable |
| 291 | * and will usually within threshold when whithin inference */ |
| 292 | lp->owd_min = lp->sowd >> 3; |
| 293 | lp->owd_max = lp->sowd >> 2; |
| 294 | lp->owd_max_rsv = lp->sowd >> 2; |
| 295 | |
| 296 | /* happened within inference |
| 297 | * drop snd_cwnd into 1 */ |
| 298 | if (lp->flag & LP_WITHIN_INF) |
| 299 | tp->snd_cwnd = 1U; |
| 300 | |
| 301 | /* happened after inference |
| 302 | * cut snd_cwnd into half */ |
| 303 | else |
| 304 | tp->snd_cwnd = max(tp->snd_cwnd >> 1U, 1U); |
| 305 | |
| 306 | /* record this drop time */ |
| 307 | lp->last_drop = tcp_time_stamp; |
| 308 | } |
| 309 | |
| 310 | static struct tcp_congestion_ops tcp_lp = { |
| 311 | .init = tcp_lp_init, |
| 312 | .ssthresh = tcp_reno_ssthresh, |
| 313 | .cong_avoid = tcp_lp_cong_avoid, |
| 314 | .min_cwnd = tcp_reno_min_cwnd, |
| 315 | .rtt_sample = tcp_lp_rtt_sample, |
| 316 | .pkts_acked = tcp_lp_pkts_acked, |
| 317 | |
| 318 | .owner = THIS_MODULE, |
| 319 | .name = "lp" |
| 320 | }; |
| 321 | |
| 322 | static int __init tcp_lp_register(void) |
| 323 | { |
| 324 | BUG_ON(sizeof(struct lp) > ICSK_CA_PRIV_SIZE); |
| 325 | return tcp_register_congestion_control(&tcp_lp); |
| 326 | } |
| 327 | |
| 328 | static void __exit tcp_lp_unregister(void) |
| 329 | { |
| 330 | tcp_unregister_congestion_control(&tcp_lp); |
| 331 | } |
| 332 | |
| 333 | module_init(tcp_lp_register); |
| 334 | module_exit(tcp_lp_unregister); |
| 335 | |
| 336 | MODULE_AUTHOR("Wong Hoi Sing Edison, Hung Hing Lun"); |
| 337 | MODULE_LICENSE("GPL"); |
| 338 | MODULE_DESCRIPTION("TCP Low Priority"); |