net/sched/sch_fq_pie.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Flow Queue PIE discipline
   3  *
   4  * Copyright (C) 2019 Mohit P. Tahiliani <tahiliani@nitk.edu.in>
   5  * Copyright (C) 2019 Sachin D. Patil <sdp.sachin@gmail.com>
   6  * Copyright (C) 2019 V. Saicharan <vsaicharan1998@gmail.com>
   7  * Copyright (C) 2019 Mohit Bhasi <mohitbhasi1998@gmail.com>
   8  * Copyright (C) 2019 Leslie Monis <lesliemonis@gmail.com>
   9  * Copyright (C) 2019 Gautam Ramakrishnan <gautamramk@gmail.com>
  10  */
  11
  12 #include <linux/jhash.h>
  13 #include <linux/sizes.h>
  14 #include <linux/vmalloc.h>
  15 #include <net/pkt_cls.h>
  16 #include <net/pie.h>
  17
  18 /* Flow Queue PIE
  19  *
  20  * Principles:
  21  *   - Packets are classified on flows.
  22  *   - This is a Stochastic model (as we use a hash, several flows might
  23  *                                 be hashed to the same slot)
  24  *   - Each flow has a PIE managed queue.
  25  *   - Flows are linked onto two (Round Robin) lists,
  26  *     so that new flows have priority on old ones.
  27  *   - For a given flow, packets are not reordered.
  28  *   - Drops during enqueue only.
  29  *   - ECN capability is off by default.
  30  *   - ECN threshold (if ECN is enabled) is at 10% by default.
  31  *   - Uses timestamps to calculate queue delay by default.
  32  */
  33
  34 /**
  35  * struct fq_pie_flow - contains data for each flow
  36  * @vars:       pie vars associated with the flow
  37  * @deficit:    number of remaining byte credits
  38  * @backlog:    size of data in the flow
  39  * @qlen:       number of packets in the flow
  40  * @flowchain:  flowchain for the flow
  41  * @head:       first packet in the flow
  42  * @tail:       last packet in the flow
  43  */
  44 struct fq_pie_flow {
  45         struct pie_vars vars;
  46         s32 deficit;
  47         u32 backlog;
  48         u32 qlen;
  49         struct list_head flowchain;
  50         struct sk_buff *head;
  51         struct sk_buff *tail;
  52 };
  53
  54 struct fq_pie_sched_data {
  55         struct tcf_proto __rcu *filter_list; /* optional external classifier */
  56         struct tcf_block *block;
  57         struct fq_pie_flow *flows;
  58         struct Qdisc *sch;
  59         struct list_head old_flows;
  60         struct list_head new_flows;
  61         struct pie_params p_params;
  62         u32 ecn_prob;
  63         u32 flows_cnt;
  64         u32 quantum;
  65         u32 memory_limit;
  66         u32 new_flow_count;
  67         u32 memory_usage;
  68         u32 overmemory;
  69         struct pie_stats stats;
  70         struct timer_list adapt_timer;
  71 };
  72
  73 static unsigned int fq_pie_hash(const struct fq_pie_sched_data *q,
  74                                 struct sk_buff *skb)
  75 {
  76         return reciprocal_scale(skb_get_hash(skb), q->flows_cnt);
  77 }
  78
  79 static unsigned int fq_pie_classify(struct sk_buff *skb, struct Qdisc *sch,
  80                                     int *qerr)
  81 {
  82         struct fq_pie_sched_data *q = qdisc_priv(sch);
  83         struct tcf_proto *filter;
  84         struct tcf_result res;
  85         int result;
  86
  87         if (TC_H_MAJ(skb->priority) == sch->handle &&
  88             TC_H_MIN(skb->priority) > 0 &&
  89             TC_H_MIN(skb->priority) <= q->flows_cnt)
  90                 return TC_H_MIN(skb->priority);
  91
  92         filter = rcu_dereference_bh(q->filter_list);
  93         if (!filter)
  94                 return fq_pie_hash(q, skb) + 1;
  95
  96         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
  97         result = tcf_classify(skb, filter, &res, false);
  98         if (result >= 0) {
  99 #ifdef CONFIG_NET_CLS_ACT
 100                 switch (result) {
 101                 case TC_ACT_STOLEN:
 102                 case TC_ACT_QUEUED:
 103                 case TC_ACT_TRAP:
 104                         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
 105                         /* fall through */
 106                 case TC_ACT_SHOT:
 107                         return 0;
 108                 }
 109 #endif
 110                 if (TC_H_MIN(res.classid) <= q->flows_cnt)
 111                         return TC_H_MIN(res.classid);
 112         }
 113         return 0;
 114 }
 115
 116 /* add skb to flow queue (tail add) */
 117 static inline void flow_queue_add(struct fq_pie_flow *flow,
 118                                   struct sk_buff *skb)
 119 {
 120         if (!flow->head)
 121                 flow->head = skb;
 122         else
 123                 flow->tail->next = skb;
 124         flow->tail = skb;
 125         skb->next = NULL;
 126 }
 127
 128 static int fq_pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 129                                 struct sk_buff **to_free)
 130 {
 131         struct fq_pie_sched_data *q = qdisc_priv(sch);
 132         struct fq_pie_flow *sel_flow;
 133         int uninitialized_var(ret);
 134         u8 memory_limited = false;
 135         u8 enqueue = false;
 136         u32 pkt_len;
 137         u32 idx;
 138
 139         /* Classifies packet into corresponding flow */
 140         idx = fq_pie_classify(skb, sch, &ret);
 141         sel_flow = &q->flows[idx];
 142
 143         /* Checks whether adding a new packet would exceed memory limit */
 144         get_pie_cb(skb)->mem_usage = skb->truesize;
 145         memory_limited = q->memory_usage > q->memory_limit + skb->truesize;
 146
 147         /* Checks if the qdisc is full */
 148         if (unlikely(qdisc_qlen(sch) >= sch->limit)) {
 149                 q->stats.overlimit++;
 150                 goto out;
 151         } else if (unlikely(memory_limited)) {
 152                 q->overmemory++;
 153         }
 154
 155         if (!pie_drop_early(sch, &q->p_params, &sel_flow->vars,
 156                             sel_flow->backlog, skb->len)) {
 157                 enqueue = true;
 158         } else if (q->p_params.ecn &&
 159                    sel_flow->vars.prob <= (MAX_PROB / 100) * q->ecn_prob &&
 160                    INET_ECN_set_ce(skb)) {
 161                 /* If packet is ecn capable, mark it if drop probability
 162                  * is lower than the parameter ecn_prob, else drop it.
 163                  */
 164                 q->stats.ecn_mark++;
 165                 enqueue = true;
 166         }
 167         if (enqueue) {
 168                 /* Set enqueue time only when dq_rate_estimator is disabled. */
 169                 if (!q->p_params.dq_rate_estimator)
 170                         pie_set_enqueue_time(skb);
 171
 172                 pkt_len = qdisc_pkt_len(skb);
 173                 q->stats.packets_in++;
 174                 q->memory_usage += skb->truesize;
 175                 sch->qstats.backlog += pkt_len;
 176                 sch->q.qlen++;
 177                 flow_queue_add(sel_flow, skb);
 178                 if (list_empty(&sel_flow->flowchain)) {
 179                         list_add_tail(&sel_flow->flowchain, &q->new_flows);
 180                         q->new_flow_count++;
 181                         sel_flow->deficit = q->quantum;
 182                         sel_flow->qlen = 0;
 183                         sel_flow->backlog = 0;
 184                 }
 185                 sel_flow->qlen++;
 186                 sel_flow->backlog += pkt_len;
 187                 return NET_XMIT_SUCCESS;
 188         }
 189 out:
 190         q->stats.dropped++;
 191         sel_flow->vars.accu_prob = 0;
 192         sel_flow->vars.accu_prob_overflows = 0;
 193         __qdisc_drop(skb, to_free);
 194         qdisc_qstats_drop(sch);
 195         return NET_XMIT_CN;
 196 }
 197
 198 static const struct nla_policy fq_pie_policy[TCA_FQ_PIE_MAX + 1] = {
 199         [TCA_FQ_PIE_LIMIT]              = {.type = NLA_U32},
 200         [TCA_FQ_PIE_FLOWS]              = {.type = NLA_U32},
 201         [TCA_FQ_PIE_TARGET]             = {.type = NLA_U32},
 202         [TCA_FQ_PIE_TUPDATE]            = {.type = NLA_U32},
 203         [TCA_FQ_PIE_ALPHA]              = {.type = NLA_U32},
 204         [TCA_FQ_PIE_BETA]               = {.type = NLA_U32},
 205         [TCA_FQ_PIE_QUANTUM]            = {.type = NLA_U32},
 206         [TCA_FQ_PIE_MEMORY_LIMIT]       = {.type = NLA_U32},
 207         [TCA_FQ_PIE_ECN_PROB]           = {.type = NLA_U32},
 208         [TCA_FQ_PIE_ECN]                = {.type = NLA_U32},
 209         [TCA_FQ_PIE_BYTEMODE]           = {.type = NLA_U32},
 210         [TCA_FQ_PIE_DQ_RATE_ESTIMATOR]  = {.type = NLA_U32},
 211 };
 212
 213 static inline struct sk_buff *dequeue_head(struct fq_pie_flow *flow)
 214 {
 215         struct sk_buff *skb = flow->head;
 216
 217         flow->head = skb->next;
 218         skb->next = NULL;
 219         return skb;
 220 }
 221
 222 static struct sk_buff *fq_pie_qdisc_dequeue(struct Qdisc *sch)
 223 {
 224         struct fq_pie_sched_data *q = qdisc_priv(sch);
 225         struct sk_buff *skb = NULL;
 226         struct fq_pie_flow *flow;
 227         struct list_head *head;
 228         u32 pkt_len;
 229
 230 begin:
 231         head = &q->new_flows;
 232         if (list_empty(head)) {
 233                 head = &q->old_flows;
 234                 if (list_empty(head))
 235                         return NULL;
 236         }
 237
 238         flow = list_first_entry(head, struct fq_pie_flow, flowchain);
 239         /* Flow has exhausted all its credits */
 240         if (flow->deficit <= 0) {
 241                 flow->deficit += q->quantum;
 242                 list_move_tail(&flow->flowchain, &q->old_flows);
 243                 goto begin;
 244         }
 245
 246         if (flow->head) {
 247                 skb = dequeue_head(flow);
 248                 pkt_len = qdisc_pkt_len(skb);
 249                 sch->qstats.backlog -= pkt_len;
 250                 sch->q.qlen--;
 251                 qdisc_bstats_update(sch, skb);
 252         }
 253
 254         if (!skb) {
 255                 /* force a pass through old_flows to prevent starvation */
 256                 if (head == &q->new_flows && !list_empty(&q->old_flows))
 257                         list_move_tail(&flow->flowchain, &q->old_flows);
 258                 else
 259                         list_del_init(&flow->flowchain);
 260                 goto begin;
 261         }
 262
 263         flow->qlen--;
 264         flow->deficit -= pkt_len;
 265         flow->backlog -= pkt_len;
 266         q->memory_usage -= get_pie_cb(skb)->mem_usage;
 267         pie_process_dequeue(skb, &q->p_params, &flow->vars, flow->backlog);
 268         return skb;
 269 }
 270
 271 static int fq_pie_change(struct Qdisc *sch, struct nlattr *opt,
 272                          struct netlink_ext_ack *extack)
 273 {
 274         struct fq_pie_sched_data *q = qdisc_priv(sch);
 275         struct nlattr *tb[TCA_FQ_PIE_MAX + 1];
 276         unsigned int len_dropped = 0;
 277         unsigned int num_dropped = 0;
 278         int err;
 279
 280         if (!opt)
 281                 return -EINVAL;
 282
 283         err = nla_parse_nested(tb, TCA_FQ_PIE_MAX, opt, fq_pie_policy, extack);
 284         if (err < 0)
 285                 return err;
 286
 287         sch_tree_lock(sch);
 288         if (tb[TCA_FQ_PIE_LIMIT]) {
 289                 u32 limit = nla_get_u32(tb[TCA_FQ_PIE_LIMIT]);
 290
 291                 q->p_params.limit = limit;
 292                 sch->limit = limit;
 293         }
 294         if (tb[TCA_FQ_PIE_FLOWS]) {
 295                 if (q->flows) {
 296                         NL_SET_ERR_MSG_MOD(extack,
 297                                            "Number of flows cannot be changed");
 298                         goto flow_error;
 299                 }
 300                 q->flows_cnt = nla_get_u32(tb[TCA_FQ_PIE_FLOWS]);
 301                 if (!q->flows_cnt || q->flows_cnt > 65536) {
 302                         NL_SET_ERR_MSG_MOD(extack,
 303                                            "Number of flows must be < 65536");
 304                         goto flow_error;
 305                 }
 306         }
 307
 308         /* convert from microseconds to pschedtime */
 309         if (tb[TCA_FQ_PIE_TARGET]) {
 310                 /* target is in us */
 311                 u32 target = nla_get_u32(tb[TCA_FQ_PIE_TARGET]);
 312
 313                 /* convert to pschedtime */
 314                 q->p_params.target =
 315                         PSCHED_NS2TICKS((u64)target * NSEC_PER_USEC);
 316         }
 317
 318         /* tupdate is in jiffies */
 319         if (tb[TCA_FQ_PIE_TUPDATE])
 320                 q->p_params.tupdate =
 321                         usecs_to_jiffies(nla_get_u32(tb[TCA_FQ_PIE_TUPDATE]));
 322
 323         if (tb[TCA_FQ_PIE_ALPHA])
 324                 q->p_params.alpha = nla_get_u32(tb[TCA_FQ_PIE_ALPHA]);
 325
 326         if (tb[TCA_FQ_PIE_BETA])
 327                 q->p_params.beta = nla_get_u32(tb[TCA_FQ_PIE_BETA]);
 328
 329         if (tb[TCA_FQ_PIE_QUANTUM])
 330                 q->quantum = nla_get_u32(tb[TCA_FQ_PIE_QUANTUM]);
 331
 332         if (tb[TCA_FQ_PIE_MEMORY_LIMIT])
 333                 q->memory_limit = nla_get_u32(tb[TCA_FQ_PIE_MEMORY_LIMIT]);
 334
 335         if (tb[TCA_FQ_PIE_ECN_PROB])
 336                 q->ecn_prob = nla_get_u32(tb[TCA_FQ_PIE_ECN_PROB]);
 337
 338         if (tb[TCA_FQ_PIE_ECN])
 339                 q->p_params.ecn = nla_get_u32(tb[TCA_FQ_PIE_ECN]);
 340
 341         if (tb[TCA_FQ_PIE_BYTEMODE])
 342                 q->p_params.bytemode = nla_get_u32(tb[TCA_FQ_PIE_BYTEMODE]);
 343
 344         if (tb[TCA_FQ_PIE_DQ_RATE_ESTIMATOR])
 345                 q->p_params.dq_rate_estimator =
 346                         nla_get_u32(tb[TCA_FQ_PIE_DQ_RATE_ESTIMATOR]);
 347
 348         /* Drop excess packets if new limit is lower */
 349         while (sch->q.qlen > sch->limit) {
 350                 struct sk_buff *skb = fq_pie_qdisc_dequeue(sch);
 351
 352                 kfree_skb(skb);
 353                 len_dropped += qdisc_pkt_len(skb);
 354                 num_dropped += 1;
 355         }
 356         qdisc_tree_reduce_backlog(sch, num_dropped, len_dropped);
 357
 358         sch_tree_unlock(sch);
 359         return 0;
 360
 361 flow_error:
 362         sch_tree_unlock(sch);
 363         return -EINVAL;
 364 }
 365
 366 static void fq_pie_timer(struct timer_list *t)
 367 {
 368         struct fq_pie_sched_data *q = from_timer(q, t, adapt_timer);
 369         struct Qdisc *sch = q->sch;
 370         spinlock_t *root_lock; /* to lock qdisc for probability calculations */
 371         u16 idx;
 372
 373         root_lock = qdisc_lock(qdisc_root_sleeping(sch));
 374         spin_lock(root_lock);
 375
 376         for (idx = 0; idx < q->flows_cnt; idx++)
 377                 pie_calculate_probability(&q->p_params, &q->flows[idx].vars,
 378                                           q->flows[idx].backlog);
 379
 380         /* reset the timer to fire after 'tupdate' jiffies. */
 381         if (q->p_params.tupdate)
 382                 mod_timer(&q->adapt_timer, jiffies + q->p_params.tupdate);
 383
 384         spin_unlock(root_lock);
 385 }
 386
 387 static int fq_pie_init(struct Qdisc *sch, struct nlattr *opt,
 388                        struct netlink_ext_ack *extack)
 389 {
 390         struct fq_pie_sched_data *q = qdisc_priv(sch);
 391         int err;
 392         u16 idx;
 393
 394         pie_params_init(&q->p_params);
 395         sch->limit = 10 * 1024;
 396         q->p_params.limit = sch->limit;
 397         q->quantum = psched_mtu(qdisc_dev(sch));
 398         q->sch = sch;
 399         q->ecn_prob = 10;
 400         q->flows_cnt = 1024;
 401         q->memory_limit = SZ_32M;
 402
 403         INIT_LIST_HEAD(&q->new_flows);
 404         INIT_LIST_HEAD(&q->old_flows);
 405
 406         if (opt) {
 407                 err = fq_pie_change(sch, opt, extack);
 408
 409                 if (err)
 410                         return err;
 411         }
 412
 413         err = tcf_block_get(&q->block, &q->filter_list, sch, extack);
 414         if (err)
 415                 goto init_failure;
 416
 417         q->flows = kvcalloc(q->flows_cnt, sizeof(struct fq_pie_flow),
 418                             GFP_KERNEL);
 419         if (!q->flows) {
 420                 err = -ENOMEM;
 421                 goto init_failure;
 422         }
 423         for (idx = 0; idx < q->flows_cnt; idx++) {
 424                 struct fq_pie_flow *flow = q->flows + idx;
 425
 426                 INIT_LIST_HEAD(&flow->flowchain);
 427                 pie_vars_init(&flow->vars);
 428         }
 429
 430         timer_setup(&q->adapt_timer, fq_pie_timer, 0);
 431         mod_timer(&q->adapt_timer, jiffies + HZ / 2);
 432
 433         return 0;
 434
 435 init_failure:
 436         q->flows_cnt = 0;
 437
 438         return err;
 439 }
 440
 441 static int fq_pie_dump(struct Qdisc *sch, struct sk_buff *skb)
 442 {
 443         struct fq_pie_sched_data *q = qdisc_priv(sch);
 444         struct nlattr *opts;
 445
 446         opts = nla_nest_start(skb, TCA_OPTIONS);
 447         if (!opts)
 448                 return -EMSGSIZE;
 449
 450         /* convert target from pschedtime to us */
 451         if (nla_put_u32(skb, TCA_FQ_PIE_LIMIT, sch->limit) ||
 452             nla_put_u32(skb, TCA_FQ_PIE_FLOWS, q->flows_cnt) ||
 453             nla_put_u32(skb, TCA_FQ_PIE_TARGET,
 454                         ((u32)PSCHED_TICKS2NS(q->p_params.target)) /
 455                         NSEC_PER_USEC) ||
 456             nla_put_u32(skb, TCA_FQ_PIE_TUPDATE,
 457                         jiffies_to_usecs(q->p_params.tupdate)) ||
 458             nla_put_u32(skb, TCA_FQ_PIE_ALPHA, q->p_params.alpha) ||
 459             nla_put_u32(skb, TCA_FQ_PIE_BETA, q->p_params.beta) ||
 460             nla_put_u32(skb, TCA_FQ_PIE_QUANTUM, q->quantum) ||
 461             nla_put_u32(skb, TCA_FQ_PIE_MEMORY_LIMIT, q->memory_limit) ||
 462             nla_put_u32(skb, TCA_FQ_PIE_ECN_PROB, q->ecn_prob) ||
 463             nla_put_u32(skb, TCA_FQ_PIE_ECN, q->p_params.ecn) ||
 464             nla_put_u32(skb, TCA_FQ_PIE_BYTEMODE, q->p_params.bytemode) ||
 465             nla_put_u32(skb, TCA_FQ_PIE_DQ_RATE_ESTIMATOR,
 466                         q->p_params.dq_rate_estimator))
 467                 goto nla_put_failure;
 468
 469         return nla_nest_end(skb, opts);
 470
 471 nla_put_failure:
 472         nla_nest_cancel(skb, opts);
 473         return -EMSGSIZE;
 474 }
 475
 476 static int fq_pie_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
 477 {
 478         struct fq_pie_sched_data *q = qdisc_priv(sch);
 479         struct tc_fq_pie_xstats st = {
 480                 .packets_in     = q->stats.packets_in,
 481                 .overlimit      = q->stats.overlimit,
 482                 .overmemory     = q->overmemory,
 483                 .dropped        = q->stats.dropped,
 484                 .ecn_mark       = q->stats.ecn_mark,
 485                 .new_flow_count = q->new_flow_count,
 486                 .memory_usage   = q->memory_usage,
 487         };
 488         struct list_head *pos;
 489
 490         sch_tree_lock(sch);
 491         list_for_each(pos, &q->new_flows)
 492                 st.new_flows_len++;
 493
 494         list_for_each(pos, &q->old_flows)
 495                 st.old_flows_len++;
 496         sch_tree_unlock(sch);
 497
 498         return gnet_stats_copy_app(d, &st, sizeof(st));
 499 }
 500
 501 static void fq_pie_reset(struct Qdisc *sch)
 502 {
 503         struct fq_pie_sched_data *q = qdisc_priv(sch);
 504         u16 idx;
 505
 506         INIT_LIST_HEAD(&q->new_flows);
 507         INIT_LIST_HEAD(&q->old_flows);
 508         for (idx = 0; idx < q->flows_cnt; idx++) {
 509                 struct fq_pie_flow *flow = q->flows + idx;
 510
 511                 /* Removes all packets from flow */
 512                 rtnl_kfree_skbs(flow->head, flow->tail);
 513                 flow->head = NULL;
 514
 515                 INIT_LIST_HEAD(&flow->flowchain);
 516                 pie_vars_init(&flow->vars);
 517         }
 518
 519         sch->q.qlen = 0;
 520         sch->qstats.backlog = 0;
 521 }
 522
 523 static void fq_pie_destroy(struct Qdisc *sch)
 524 {
 525         struct fq_pie_sched_data *q = qdisc_priv(sch);
 526
 527         tcf_block_put(q->block);
 528         del_timer_sync(&q->adapt_timer);
 529         kvfree(q->flows);
 530 }
 531
 532 static struct Qdisc_ops fq_pie_qdisc_ops __read_mostly = {
 533         .id             = "fq_pie",
 534         .priv_size      = sizeof(struct fq_pie_sched_data),
 535         .enqueue        = fq_pie_qdisc_enqueue,
 536         .dequeue        = fq_pie_qdisc_dequeue,
 537         .peek           = qdisc_peek_dequeued,
 538         .init           = fq_pie_init,
 539         .destroy        = fq_pie_destroy,
 540         .reset          = fq_pie_reset,
 541         .change         = fq_pie_change,
 542         .dump           = fq_pie_dump,
 543         .dump_stats     = fq_pie_dump_stats,
 544         .owner          = THIS_MODULE,
 545 };
 546
 547 static int __init fq_pie_module_init(void)
 548 {
 549         return register_qdisc(&fq_pie_qdisc_ops);
 550 }
 551
 552 static void __exit fq_pie_module_exit(void)
 553 {
 554         unregister_qdisc(&fq_pie_qdisc_ops);
 555 }
 556
 557 module_init(fq_pie_module_init);
 558 module_exit(fq_pie_module_exit);
 559
 560 MODULE_DESCRIPTION("Flow Queue Proportional Integral controller Enhanced (FQ-PIE)");
 561 MODULE_AUTHOR("Mohit P. Tahiliani");
 562 MODULE_LICENSE("GPL");