sys/netinet/cc/cc_cdg.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
   3  *
   4  * Copyright (c) 2009-2013
   5  *      Swinburne University of Technology, Melbourne, Australia
   6  * All rights reserved.
   7  *
   8  * This software was developed at the Centre for Advanced Internet
   9  * Architectures, Swinburne University of Technology, by David Hayes, made
  10  * possible in part by a gift from The Cisco University Research Program Fund,
  11  * a corporate advised fund of Silicon Valley Community Foundation. Development
  12  * and testing were further assisted by a grant from the FreeBSD Foundation.
  13  *
  14  * Redistribution and use in source and binary forms, with or without
  15  * modification, are permitted provided that the following conditions
  16  * are met:
  17  * 1. Redistributions of source code must retain the above copyright
  18  *    notice, this list of conditions and the following disclaimer.
  19  * 2. Redistributions in binary form must reproduce the above copyright
  20  *    notice, this list of conditions and the following disclaimer in the
  21  *    documentation and/or other materials provided with the distribution.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  */
  35
  36 /*
  37  * CAIA Delay-Gradient (CDG) congestion control algorithm
  38  *
  39  * An implemention of the delay-gradient congestion control algorithm proposed
  40  * in the following paper:
  41  *
  42  * D. A. Hayes and G. Armitage, "Revisiting TCP Congestion Control using Delay
  43  * Gradients", in IFIP Networking, Valencia, Spain, 9-13 May 2011.
  44  *
  45  * Developed as part of the NewTCP research project at Swinburne University of
  46  * Technology's Centre for Advanced Internet Architectures, Melbourne,
  47  * Australia. More details are available at:
  48  *   http://caia.swin.edu.au/urp/newtcp/
  49  */
  50
  51 #include <sys/cdefs.h>
  52 __FBSDID("$FreeBSD$");
  53
  54 #include <sys/param.h>
  55 #include <sys/hhook.h>
  56 #include <sys/kernel.h>
  57 #include <sys/khelp.h>
  58 #include <sys/limits.h>
  59 #include <sys/lock.h>
  60 #include <sys/malloc.h>
  61 #include <sys/module.h>
  62 #include <sys/queue.h>
  63 #include <sys/socket.h>
  64 #include <sys/socketvar.h>
  65 #include <sys/sysctl.h>
  66 #include <sys/systm.h>
  67
  68 #include <net/vnet.h>
  69
  70 #include <netinet/tcp.h>
  71 #include <netinet/tcp_seq.h>
  72 #include <netinet/tcp_timer.h>
  73 #include <netinet/tcp_var.h>
  74 #include <netinet/cc/cc.h>
  75 #include <netinet/cc/cc_module.h>
  76
  77 #include <netinet/khelp/h_ertt.h>
  78
  79 #include <vm/uma.h>
  80
  81 #define CDG_VERSION "0.1"
  82
  83 #define CAST_PTR_INT(X) (*((int*)(X)))
  84
  85 /* Private delay-gradient induced congestion control signal. */
  86 #define CC_CDG_DELAY 0x01000000
  87
  88 /* NewReno window deflation factor on loss (as a percentage). */
  89 #define RENO_BETA 50
  90
  91 /* Queue states. */
  92 #define CDG_Q_EMPTY     1
  93 #define CDG_Q_RISING    2
  94 #define CDG_Q_FALLING   3
  95 #define CDG_Q_FULL      4
  96 #define CDG_Q_UNKNOWN   9999
  97
  98 /* Number of bit shifts used in probexp lookup table. */
  99 #define EXP_PREC 15
 100
 101 /* Largest gradient represented in probexp lookup table. */
 102 #define MAXGRAD 5
 103
 104 /*
 105  * Delay Precision Enhance - number of bit shifts used for qtrend related
 106  * integer arithmetic precision.
 107  */
 108 #define D_P_E 7
 109
 110 struct qdiff_sample {
 111         long qdiff;
 112         STAILQ_ENTRY(qdiff_sample) qdiff_lnk;
 113 };
 114
 115 struct cdg {
 116         long max_qtrend;
 117         long min_qtrend;
 118         STAILQ_HEAD(minrtts_head, qdiff_sample) qdiffmin_q;
 119         STAILQ_HEAD(maxrtts_head, qdiff_sample) qdiffmax_q;
 120         long window_incr;
 121         /* rttcount for window increase when in congestion avoidance */
 122         long rtt_count;
 123         /* maximum measured rtt within an rtt period */
 124         int maxrtt_in_rtt;
 125         /* maximum measured rtt within prev rtt period */
 126         int maxrtt_in_prevrtt;
 127         /* minimum measured rtt within an rtt period */
 128         int minrtt_in_rtt;
 129         /* minimum measured rtt within prev rtt period */
 130         int minrtt_in_prevrtt;
 131         /* consecutive congestion episode counter */
 132         uint32_t consec_cong_cnt;
 133         /* when tracking a new reno type loss window */
 134         uint32_t shadow_w;
 135         /* maximum number of samples in the moving average queue */
 136         int sample_q_size;
 137         /* number of samples in the moving average queue */
 138         int num_samples;
 139         /* estimate of the queue state of the path */
 140         int queue_state;
 141 };
 142
 143 /*
 144  * Lookup table for:
 145  *   (1 - exp(-x)) << EXP_PREC, where x = [0,MAXGRAD] in 2^-7 increments
 146  *
 147  * Note: probexp[0] is set to 10 (not 0) as a safety for very low increase
 148  * gradients.
 149  */
 150 static const int probexp[641] = {
 151    10,255,508,759,1008,1255,1501,1744,1985,2225,2463,2698,2932,3165,3395,3624,
 152    3850,4075,4299,4520,4740,4958,5175,5389,5602,5814,6024,6232,6438,6643,6846,
 153    7048,7248,7447,7644,7839,8033,8226,8417,8606,8794,8981,9166,9350,9532,9713,
 154    9892,10070,10247,10422,10596,10769,10940,11110,11278,11445,11611,11776,11939,
 155    12101,12262,12422,12580,12737,12893,13048,13201,13354,13505,13655,13803,13951,
 156    14097,14243,14387,14530,14672,14813,14952,15091,15229,15365,15500,15635,15768,
 157    15900,16032,16162,16291,16419,16547,16673,16798,16922,17046,17168,17289,17410,
 158    17529,17648,17766,17882,17998,18113,18227,18340,18453,18564,18675,18784,18893,
 159    19001,19108,19215,19320,19425,19529,19632,19734,19835,19936,20036,20135,20233,
 160    20331,20427,20523,20619,20713,20807,20900,20993,21084,21175,21265,21355,21444,
 161    21532,21619,21706,21792,21878,21962,22046,22130,22213,22295,22376,22457,22537,
 162    22617,22696,22774,22852,22929,23006,23082,23157,23232,23306,23380,23453,23525,
 163    23597,23669,23739,23810,23879,23949,24017,24085,24153,24220,24286,24352,24418,
 164    24483,24547,24611,24675,24738,24800,24862,24924,24985,25045,25106,25165,25224,
 165    25283,25341,25399,25456,25513,25570,25626,25681,25737,25791,25846,25899,25953,
 166    26006,26059,26111,26163,26214,26265,26316,26366,26416,26465,26514,26563,26611,
 167    26659,26707,26754,26801,26847,26893,26939,26984,27029,27074,27118,27162,27206,
 168    27249,27292,27335,27377,27419,27460,27502,27543,27583,27624,27664,27703,27743,
 169    27782,27821,27859,27897,27935,27973,28010,28047,28084,28121,28157,28193,28228,
 170    28263,28299,28333,28368,28402,28436,28470,28503,28536,28569,28602,28634,28667,
 171    28699,28730,28762,28793,28824,28854,28885,28915,28945,28975,29004,29034,29063,
 172    29092,29120,29149,29177,29205,29232,29260,29287,29314,29341,29368,29394,29421,
 173    29447,29472,29498,29524,29549,29574,29599,29623,29648,29672,29696,29720,29744,
 174    29767,29791,29814,29837,29860,29882,29905,29927,29949,29971,29993,30014,30036,
 175    30057,30078,30099,30120,30141,30161,30181,30201,30221,30241,30261,30280,30300,
 176    30319,30338,30357,30376,30394,30413,30431,30449,30467,30485,30503,30521,30538,
 177    30555,30573,30590,30607,30624,30640,30657,30673,30690,30706,30722,30738,30753,
 178    30769,30785,30800,30815,30831,30846,30861,30876,30890,30905,30919,30934,30948,
 179    30962,30976,30990,31004,31018,31031,31045,31058,31072,31085,31098,31111,31124,
 180    31137,31149,31162,31174,31187,31199,31211,31223,31235,31247,31259,31271,31283,
 181    31294,31306,31317,31328,31339,31351,31362,31373,31383,31394,31405,31416,31426,
 182    31436,31447,31457,31467,31477,31487,31497,31507,31517,31527,31537,31546,31556,
 183    31565,31574,31584,31593,31602,31611,31620,31629,31638,31647,31655,31664,31673,
 184    31681,31690,31698,31706,31715,31723,31731,31739,31747,31755,31763,31771,31778,
 185    31786,31794,31801,31809,31816,31824,31831,31838,31846,31853,31860,31867,31874,
 186    31881,31888,31895,31902,31908,31915,31922,31928,31935,31941,31948,31954,31960,
 187    31967,31973,31979,31985,31991,31997,32003,32009,32015,32021,32027,32033,32038,
 188    32044,32050,32055,32061,32066,32072,32077,32083,32088,32093,32098,32104,32109,
 189    32114,32119,32124,32129,32134,32139,32144,32149,32154,32158,32163,32168,32173,
 190    32177,32182,32186,32191,32195,32200,32204,32209,32213,32217,32222,32226,32230,
 191    32234,32238,32242,32247,32251,32255,32259,32263,32267,32270,32274,32278,32282,
 192    32286,32290,32293,32297,32301,32304,32308,32311,32315,32318,32322,32325,32329,
 193    32332,32336,32339,32342,32346,32349,32352,32356,32359,32362,32365,32368,32371,
 194    32374,32377,32381,32384,32387,32389,32392,32395,32398,32401,32404,32407,32410,
 195    32412,32415,32418,32421,32423,32426,32429,32431,32434,32437,32439,32442,32444,
 196    32447,32449,32452,32454,32457,32459,32461,32464,32466,32469,32471,32473,32476,
 197    32478,32480,32482,32485,32487,32489,32491,32493,32495,32497,32500,32502,32504,
 198    32506,32508,32510,32512,32514,32516,32518,32520,32522,32524,32526,32527,32529,
 199    32531,32533,32535,32537,32538,32540,32542,32544,32545,32547};
 200
 201 static uma_zone_t qdiffsample_zone;
 202
 203 static MALLOC_DEFINE(M_CDG, "cdg data",
 204   "Per connection data required for the CDG congestion control algorithm");
 205
 206 static int ertt_id;
 207
 208 VNET_DEFINE_STATIC(uint32_t, cdg_alpha_inc);
 209 VNET_DEFINE_STATIC(uint32_t, cdg_beta_delay);
 210 VNET_DEFINE_STATIC(uint32_t, cdg_beta_loss);
 211 VNET_DEFINE_STATIC(uint32_t, cdg_smoothing_factor);
 212 VNET_DEFINE_STATIC(uint32_t, cdg_exp_backoff_scale);
 213 VNET_DEFINE_STATIC(uint32_t, cdg_consec_cong);
 214 VNET_DEFINE_STATIC(uint32_t, cdg_hold_backoff);
 215 #define V_cdg_alpha_inc         VNET(cdg_alpha_inc)
 216 #define V_cdg_beta_delay        VNET(cdg_beta_delay)
 217 #define V_cdg_beta_loss         VNET(cdg_beta_loss)
 218 #define V_cdg_smoothing_factor  VNET(cdg_smoothing_factor)
 219 #define V_cdg_exp_backoff_scale VNET(cdg_exp_backoff_scale)
 220 #define V_cdg_consec_cong       VNET(cdg_consec_cong)
 221 #define V_cdg_hold_backoff      VNET(cdg_hold_backoff)
 222
 223 /* Function prototypes. */
 224 static int cdg_mod_init(void);
 225 static int cdg_mod_destroy(void);
 226 static void cdg_conn_init(struct cc_var *ccv);
 227 static int cdg_cb_init(struct cc_var *ccv);
 228 static void cdg_cb_destroy(struct cc_var *ccv);
 229 static void cdg_cong_signal(struct cc_var *ccv, uint32_t signal_type);
 230 static void cdg_ack_received(struct cc_var *ccv, uint16_t ack_type);
 231
 232 struct cc_algo cdg_cc_algo = {
 233         .name = "cdg",
 234         .mod_init = cdg_mod_init,
 235         .ack_received = cdg_ack_received,
 236         .cb_destroy = cdg_cb_destroy,
 237         .cb_init = cdg_cb_init,
 238         .conn_init = cdg_conn_init,
 239         .cong_signal = cdg_cong_signal,
 240         .mod_destroy = cdg_mod_destroy
 241 };
 242
 243 /* Vnet created and being initialised. */
 244 static void
 245 cdg_init_vnet(const void *unused __unused)
 246 {
 247
 248         V_cdg_alpha_inc = 0;
 249         V_cdg_beta_delay = 70;
 250         V_cdg_beta_loss = 50;
 251         V_cdg_smoothing_factor = 8;
 252         V_cdg_exp_backoff_scale = 3;
 253         V_cdg_consec_cong = 5;
 254         V_cdg_hold_backoff = 5;
 255 }
 256
 257 static int
 258 cdg_mod_init(void)
 259 {
 260         VNET_ITERATOR_DECL(v);
 261
 262         ertt_id = khelp_get_id("ertt");
 263         if (ertt_id <= 0)
 264                 return (EINVAL);
 265
 266         qdiffsample_zone = uma_zcreate("cdg_qdiffsample",
 267             sizeof(struct qdiff_sample), NULL, NULL, NULL, NULL, 0, 0);
 268
 269         VNET_LIST_RLOCK();
 270         VNET_FOREACH(v) {
 271                 CURVNET_SET(v);
 272                 cdg_init_vnet(NULL);
 273                 CURVNET_RESTORE();
 274         }
 275         VNET_LIST_RUNLOCK();
 276
 277         cdg_cc_algo.post_recovery = newreno_cc_algo.post_recovery;
 278         cdg_cc_algo.after_idle = newreno_cc_algo.after_idle;
 279
 280         return (0);
 281 }
 282
 283 static int
 284 cdg_mod_destroy(void)
 285 {
 286
 287         uma_zdestroy(qdiffsample_zone);
 288         return (0);
 289 }
 290
 291 static int
 292 cdg_cb_init(struct cc_var *ccv)
 293 {
 294         struct cdg *cdg_data;
 295
 296         cdg_data = malloc(sizeof(struct cdg), M_CDG, M_NOWAIT);
 297         if (cdg_data == NULL)
 298                 return (ENOMEM);
 299
 300         cdg_data->shadow_w = 0;
 301         cdg_data->max_qtrend = 0;
 302         cdg_data->min_qtrend = 0;
 303         cdg_data->queue_state = CDG_Q_UNKNOWN;
 304         cdg_data->maxrtt_in_rtt = 0;
 305         cdg_data->maxrtt_in_prevrtt = 0;
 306         cdg_data->minrtt_in_rtt = INT_MAX;
 307         cdg_data->minrtt_in_prevrtt = 0;
 308         cdg_data->window_incr = 0;
 309         cdg_data->rtt_count = 0;
 310         cdg_data->consec_cong_cnt = 0;
 311         cdg_data->sample_q_size = V_cdg_smoothing_factor;
 312         cdg_data->num_samples = 0;
 313         STAILQ_INIT(&cdg_data->qdiffmin_q);
 314         STAILQ_INIT(&cdg_data->qdiffmax_q);
 315
 316         ccv->cc_data = cdg_data;
 317
 318         return (0);
 319 }
 320
 321 static void
 322 cdg_conn_init(struct cc_var *ccv)
 323 {
 324         struct cdg *cdg_data = ccv->cc_data;
 325
 326         /*
 327          * Initialise the shadow_cwnd in case we are competing with loss based
 328          * flows from the start
 329          */
 330         cdg_data->shadow_w = CCV(ccv, snd_cwnd);
 331 }
 332
 333 static void
 334 cdg_cb_destroy(struct cc_var *ccv)
 335 {
 336         struct cdg *cdg_data;
 337         struct qdiff_sample *qds, *qds_n;
 338
 339         cdg_data = ccv->cc_data;
 340
 341         qds = STAILQ_FIRST(&cdg_data->qdiffmin_q);
 342         while (qds != NULL) {
 343                 qds_n = STAILQ_NEXT(qds, qdiff_lnk);
 344                 uma_zfree(qdiffsample_zone,qds);
 345                 qds = qds_n;
 346         }
 347
 348         qds = STAILQ_FIRST(&cdg_data->qdiffmax_q);
 349         while (qds != NULL) {
 350                 qds_n = STAILQ_NEXT(qds, qdiff_lnk);
 351                 uma_zfree(qdiffsample_zone,qds);
 352                 qds = qds_n;
 353         }
 354
 355         free(ccv->cc_data, M_CDG);
 356 }
 357
 358 static int
 359 cdg_beta_handler(SYSCTL_HANDLER_ARGS)
 360 {
 361
 362         if (req->newptr != NULL &&
 363             (CAST_PTR_INT(req->newptr) == 0 || CAST_PTR_INT(req->newptr) > 100))
 364                 return (EINVAL);
 365
 366         return (sysctl_handle_int(oidp, arg1, arg2, req));
 367 }
 368
 369 static int
 370 cdg_exp_backoff_scale_handler(SYSCTL_HANDLER_ARGS)
 371 {
 372
 373         if (req->newptr != NULL && CAST_PTR_INT(req->newptr) < 1)
 374                 return (EINVAL);
 375
 376         return (sysctl_handle_int(oidp, arg1, arg2, req));
 377 }
 378
 379 static inline uint32_t
 380 cdg_window_decrease(struct cc_var *ccv, unsigned long owin, unsigned int beta)
 381 {
 382
 383         return ((ulmin(CCV(ccv, snd_wnd), owin) * beta) / 100);
 384 }
 385
 386 /*
 387  * Window increase function
 388  * This window increase function is independent of the initial window size
 389  * to ensure small window flows are not discriminated against (i.e. fairness).
 390  * It increases at 1pkt/rtt like Reno for alpha_inc rtts, and then 2pkts/rtt for
 391  * the next alpha_inc rtts, etc.
 392  */
 393 static void
 394 cdg_window_increase(struct cc_var *ccv, int new_measurement)
 395 {
 396         struct cdg *cdg_data;
 397         int incr, s_w_incr;
 398
 399         cdg_data = ccv->cc_data;
 400         incr = s_w_incr = 0;
 401
 402         if (CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh)) {
 403                 /* Slow start. */
 404                 incr = CCV(ccv, t_maxseg);
 405                 s_w_incr = incr;
 406                 cdg_data->window_incr = cdg_data->rtt_count = 0;
 407         } else {
 408                 /* Congestion avoidance. */
 409                 if (new_measurement) {
 410                         s_w_incr = CCV(ccv, t_maxseg);
 411                         if (V_cdg_alpha_inc == 0) {
 412                                 incr = CCV(ccv, t_maxseg);
 413                         } else {
 414                                 if (++cdg_data->rtt_count >= V_cdg_alpha_inc) {
 415                                         cdg_data->window_incr++;
 416                                         cdg_data->rtt_count = 0;
 417                                 }
 418                                 incr = CCV(ccv, t_maxseg) *
 419                                     cdg_data->window_incr;
 420                         }
 421                 }
 422         }
 423
 424         if (cdg_data->shadow_w > 0)
 425                 cdg_data->shadow_w = ulmin(cdg_data->shadow_w + s_w_incr,
 426                     TCP_MAXWIN << CCV(ccv, snd_scale));
 427
 428         CCV(ccv, snd_cwnd) = ulmin(CCV(ccv, snd_cwnd) + incr,
 429             TCP_MAXWIN << CCV(ccv, snd_scale));
 430 }
 431
 432 static void
 433 cdg_cong_signal(struct cc_var *ccv, uint32_t signal_type)
 434 {
 435         struct cdg *cdg_data = ccv->cc_data;
 436
 437         switch(signal_type) {
 438         case CC_CDG_DELAY:
 439                 CCV(ccv, snd_ssthresh) = cdg_window_decrease(ccv,
 440                     CCV(ccv, snd_cwnd), V_cdg_beta_delay);
 441                 CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
 442                 CCV(ccv, snd_recover) = CCV(ccv, snd_max);
 443                 cdg_data->window_incr = cdg_data->rtt_count = 0;
 444                 ENTER_CONGRECOVERY(CCV(ccv, t_flags));
 445                 break;
 446         case CC_NDUPACK:
 447                 /*
 448                  * If already responding to congestion OR we have guessed no
 449                  * queue in the path is full.
 450                  */
 451                 if (IN_CONGRECOVERY(CCV(ccv, t_flags)) ||
 452                     cdg_data->queue_state < CDG_Q_FULL) {
 453                         CCV(ccv, snd_ssthresh) = CCV(ccv, snd_cwnd);
 454                         CCV(ccv, snd_recover) = CCV(ccv, snd_max);
 455                 } else {
 456                         /*
 457                          * Loss is likely to be congestion related. We have
 458                          * inferred a queue full state, so have shadow window
 459                          * react to loss as NewReno would.
 460                          */
 461                         if (cdg_data->shadow_w > 0)
 462                                 cdg_data->shadow_w = cdg_window_decrease(ccv,
 463                                     cdg_data->shadow_w, RENO_BETA);
 464
 465                         CCV(ccv, snd_ssthresh) = max(cdg_data->shadow_w,
 466                             cdg_window_decrease(ccv, CCV(ccv, snd_cwnd),
 467                             V_cdg_beta_loss));
 468
 469                         cdg_data->window_incr = cdg_data->rtt_count = 0;
 470                 }
 471                 ENTER_RECOVERY(CCV(ccv, t_flags));
 472                 break;
 473         default:
 474                 newreno_cc_algo.cong_signal(ccv, signal_type);
 475                 break;
 476         }
 477 }
 478
 479 /*
 480  * Using a negative exponential probabilistic backoff so that sources with
 481  * varying RTTs which share the same link will, on average, have the same
 482  * probability of backoff over time.
 483  *
 484  * Prob_backoff = 1 - exp(-qtrend / V_cdg_exp_backoff_scale), where
 485  * V_cdg_exp_backoff_scale is the average qtrend for the exponential backoff.
 486  */
 487 static inline int
 488 prob_backoff(long qtrend)
 489 {
 490         int backoff, idx, p;
 491
 492         backoff = (qtrend > ((MAXGRAD * V_cdg_exp_backoff_scale) << D_P_E));
 493
 494         if (!backoff) {
 495                 if (V_cdg_exp_backoff_scale > 1)
 496                         idx = (qtrend + V_cdg_exp_backoff_scale / 2) /
 497                             V_cdg_exp_backoff_scale;
 498                 else
 499                         idx = qtrend;
 500
 501                 /* Backoff probability proportional to rate of queue growth. */
 502                 p = (INT_MAX / (1 << EXP_PREC)) * probexp[idx];
 503                 backoff = (random() < p);
 504         }
 505
 506         return (backoff);
 507 }
 508
 509 static inline void
 510 calc_moving_average(struct cdg *cdg_data, long qdiff_max, long qdiff_min)
 511 {
 512         struct qdiff_sample *qds;
 513
 514         ++cdg_data->num_samples;
 515         if (cdg_data->num_samples > cdg_data->sample_q_size) {
 516                 /* Minimum RTT. */
 517                 qds = STAILQ_FIRST(&cdg_data->qdiffmin_q);
 518                 cdg_data->min_qtrend =  cdg_data->min_qtrend +
 519                     (qdiff_min - qds->qdiff) / cdg_data->sample_q_size;
 520                 STAILQ_REMOVE_HEAD(&cdg_data->qdiffmin_q, qdiff_lnk);
 521                 qds->qdiff = qdiff_min;
 522                 STAILQ_INSERT_TAIL(&cdg_data->qdiffmin_q, qds, qdiff_lnk);
 523
 524                 /* Maximum RTT. */
 525                 qds = STAILQ_FIRST(&cdg_data->qdiffmax_q);
 526                 cdg_data->max_qtrend =  cdg_data->max_qtrend +
 527                     (qdiff_max - qds->qdiff) / cdg_data->sample_q_size;
 528                 STAILQ_REMOVE_HEAD(&cdg_data->qdiffmax_q, qdiff_lnk);
 529                 qds->qdiff = qdiff_max;
 530                 STAILQ_INSERT_TAIL(&cdg_data->qdiffmax_q, qds, qdiff_lnk);
 531                 --cdg_data->num_samples;
 532         } else {
 533                 qds = uma_zalloc(qdiffsample_zone, M_NOWAIT);
 534                 if (qds != NULL) {
 535                         cdg_data->min_qtrend = cdg_data->min_qtrend +
 536                             qdiff_min / cdg_data->sample_q_size;
 537                         qds->qdiff = qdiff_min;
 538                         STAILQ_INSERT_TAIL(&cdg_data->qdiffmin_q, qds,
 539                             qdiff_lnk);
 540                 }
 541
 542                 qds = uma_zalloc(qdiffsample_zone, M_NOWAIT);
 543                 if (qds) {
 544                         cdg_data->max_qtrend = cdg_data->max_qtrend +
 545                             qdiff_max / cdg_data->sample_q_size;
 546                         qds->qdiff = qdiff_max;
 547                         STAILQ_INSERT_TAIL(&cdg_data->qdiffmax_q, qds,
 548                             qdiff_lnk);
 549                 }
 550         }
 551 }
 552
 553 static void
 554 cdg_ack_received(struct cc_var *ccv, uint16_t ack_type)
 555 {
 556         struct cdg *cdg_data;
 557         struct ertt *e_t;
 558         long qdiff_max, qdiff_min;
 559         int congestion, new_measurement, slowstart;
 560
 561         cdg_data = ccv->cc_data;
 562         e_t = (struct ertt *)khelp_get_osd(CCV(ccv, osd), ertt_id);
 563         new_measurement = e_t->flags & ERTT_NEW_MEASUREMENT;
 564         congestion = 0;
 565         cdg_data->maxrtt_in_rtt = imax(e_t->rtt, cdg_data->maxrtt_in_rtt);
 566         cdg_data->minrtt_in_rtt = imin(e_t->rtt, cdg_data->minrtt_in_rtt);
 567
 568         if (new_measurement) {
 569                 slowstart = (CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh));
 570                 /*
 571                  * Update smoothed gradient measurements. Since we are only
 572                  * using one measurement per RTT, use max or min rtt_in_rtt.
 573                  * This is also less noisy than a sample RTT measurement. Max
 574                  * RTT measurements can have trouble due to OS issues.
 575                  */
 576                 if (cdg_data->maxrtt_in_prevrtt) {
 577                         qdiff_max = ((long)(cdg_data->maxrtt_in_rtt -
 578                             cdg_data->maxrtt_in_prevrtt) << D_P_E );
 579                         qdiff_min = ((long)(cdg_data->minrtt_in_rtt -
 580                             cdg_data->minrtt_in_prevrtt) << D_P_E );
 581
 582                         calc_moving_average(cdg_data, qdiff_max, qdiff_min);
 583
 584                         /* Probabilistic backoff with respect to gradient. */
 585                         if (slowstart && qdiff_min > 0)
 586                                 congestion = prob_backoff(qdiff_min);
 587                         else if (cdg_data->min_qtrend > 0)
 588                                 congestion = prob_backoff(cdg_data->min_qtrend);
 589                         else if (slowstart && qdiff_max > 0)
 590                                 congestion = prob_backoff(qdiff_max);
 591                         else if (cdg_data->max_qtrend > 0)
 592                                 congestion = prob_backoff(cdg_data->max_qtrend);
 593
 594                         /* Update estimate of queue state. */
 595                         if (cdg_data->min_qtrend > 0 &&
 596                             cdg_data->max_qtrend <= 0) {
 597                                 cdg_data->queue_state = CDG_Q_FULL;
 598                         } else if (cdg_data->min_qtrend >= 0 &&
 599                             cdg_data->max_qtrend < 0) {
 600                                 cdg_data->queue_state = CDG_Q_EMPTY;
 601                                 cdg_data->shadow_w = 0;
 602                         } else if (cdg_data->min_qtrend > 0 &&
 603                             cdg_data->max_qtrend > 0) {
 604                                 cdg_data->queue_state = CDG_Q_RISING;
 605                         } else if (cdg_data->min_qtrend < 0 &&
 606                             cdg_data->max_qtrend < 0) {
 607                                 cdg_data->queue_state = CDG_Q_FALLING;
 608                         }
 609
 610                         if (cdg_data->min_qtrend < 0 ||
 611                             cdg_data->max_qtrend < 0)
 612                                 cdg_data->consec_cong_cnt = 0;
 613                 }
 614
 615                 cdg_data->minrtt_in_prevrtt = cdg_data->minrtt_in_rtt;
 616                 cdg_data->minrtt_in_rtt = INT_MAX;
 617                 cdg_data->maxrtt_in_prevrtt = cdg_data->maxrtt_in_rtt;
 618                 cdg_data->maxrtt_in_rtt = 0;
 619                 e_t->flags &= ~ERTT_NEW_MEASUREMENT;
 620         }
 621
 622         if (congestion) {
 623                 cdg_data->consec_cong_cnt++;
 624                 if (!IN_RECOVERY(CCV(ccv, t_flags))) {
 625                         if (cdg_data->consec_cong_cnt <= V_cdg_consec_cong)
 626                                 cdg_cong_signal(ccv, CC_CDG_DELAY);
 627                         else
 628                                 /*
 629                                  * We have been backing off but the queue is not
 630                                  * falling. Assume we are competing with
 631                                  * loss-based flows and don't back off for the
 632                                  * next V_cdg_hold_backoff RTT periods.
 633                                  */
 634                                 if (cdg_data->consec_cong_cnt >=
 635                                     V_cdg_consec_cong + V_cdg_hold_backoff)
 636                                         cdg_data->consec_cong_cnt = 0;
 637
 638                         /* Won't see effect until 2nd RTT. */
 639                         cdg_data->maxrtt_in_prevrtt = 0;
 640                         /*
 641                          * Resync shadow window in case we are competing with a
 642                          * loss based flow
 643                          */
 644                         cdg_data->shadow_w = ulmax(CCV(ccv, snd_cwnd),
 645                             cdg_data->shadow_w);
 646                 }
 647         } else if (ack_type == CC_ACK)
 648                 cdg_window_increase(ccv, new_measurement);
 649 }
 650
 651 /* When a vnet is created and being initialised, init the per-stack CDG vars. */
 652 VNET_SYSINIT(cdg_init_vnet, SI_SUB_PROTO_BEGIN, SI_ORDER_FIRST,
 653     cdg_init_vnet, NULL);
 654
 655 SYSCTL_DECL(_net_inet_tcp_cc_cdg);
 656 SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, cdg, CTLFLAG_RW, NULL,
 657     "CAIA delay-gradient congestion control related settings");
 658
 659 SYSCTL_STRING(_net_inet_tcp_cc_cdg, OID_AUTO, version,
 660     CTLFLAG_RD, CDG_VERSION, sizeof(CDG_VERSION) - 1,
 661     "Current algorithm/implementation version number");
 662
 663 SYSCTL_UINT(_net_inet_tcp_cc_cdg, OID_AUTO, alpha_inc,
 664     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(cdg_alpha_inc), 0,
 665     "Increment the window increase factor alpha by 1 MSS segment every "
 666     "alpha_inc RTTs during congestion avoidance mode.");
 667
 668 SYSCTL_PROC(_net_inet_tcp_cc_cdg, OID_AUTO, beta_delay,
 669     CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW, &VNET_NAME(cdg_beta_delay), 70,
 670     &cdg_beta_handler, "IU",
 671     "Delay-based window decrease factor as a percentage "
 672     "(on delay-based backoff, w = w * beta_delay / 100)");
 673
 674 SYSCTL_PROC(_net_inet_tcp_cc_cdg, OID_AUTO, beta_loss,
 675     CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW, &VNET_NAME(cdg_beta_loss), 50,
 676     &cdg_beta_handler, "IU",
 677     "Loss-based window decrease factor as a percentage "
 678     "(on loss-based backoff, w = w * beta_loss / 100)");
 679
 680 SYSCTL_PROC(_net_inet_tcp_cc_cdg, OID_AUTO, exp_backoff_scale,
 681     CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW,
 682     &VNET_NAME(cdg_exp_backoff_scale), 2, &cdg_exp_backoff_scale_handler, "IU",
 683     "Scaling parameter for the probabilistic exponential backoff");
 684
 685 SYSCTL_UINT(_net_inet_tcp_cc_cdg,  OID_AUTO, smoothing_factor,
 686     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(cdg_smoothing_factor), 8,
 687     "Number of samples used for moving average smoothing (0 = no smoothing)");
 688
 689 SYSCTL_UINT(_net_inet_tcp_cc_cdg, OID_AUTO, loss_compete_consec_cong,
 690     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(cdg_consec_cong), 5,
 691     "Number of consecutive delay-gradient based congestion episodes which will "
 692     "trigger loss based CC compatibility");
 693
 694 SYSCTL_UINT(_net_inet_tcp_cc_cdg, OID_AUTO, loss_compete_hold_backoff,
 695     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(cdg_hold_backoff), 5,
 696     "Number of consecutive delay-gradient based congestion episodes to hold "
 697     "the window backoff for loss based CC compatibility");
 698
 699 DECLARE_CC_MODULE(cdg, &cdg_cc_algo);
 700
 701 MODULE_DEPEND(cdg, ertt, 1, 1, 1);