linux/net/sched/sch_fq_codel.c
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   1/*
   2 * Fair Queue CoDel discipline
   3 *
   4 *      This program is free software; you can redistribute it and/or
   5 *      modify it under the terms of the GNU General Public License
   6 *      as published by the Free Software Foundation; either version
   7 *      2 of the License, or (at your option) any later version.
   8 *
   9 *  Copyright (C) 2012 Eric Dumazet <edumazet@google.com>
  10 */
  11
  12#include <linux/module.h>
  13#include <linux/types.h>
  14#include <linux/kernel.h>
  15#include <linux/jiffies.h>
  16#include <linux/string.h>
  17#include <linux/in.h>
  18#include <linux/errno.h>
  19#include <linux/init.h>
  20#include <linux/skbuff.h>
  21#include <linux/jhash.h>
  22#include <linux/slab.h>
  23#include <linux/vmalloc.h>
  24#include <net/netlink.h>
  25#include <net/pkt_sched.h>
  26#include <net/flow_keys.h>
  27#include <net/codel.h>
  28
  29/*      Fair Queue CoDel.
  30 *
  31 * Principles :
  32 * Packets are classified (internal classifier or external) on flows.
  33 * This is a Stochastic model (as we use a hash, several flows
  34 *                             might be hashed on same slot)
  35 * Each flow has a CoDel managed queue.
  36 * Flows are linked onto two (Round Robin) lists,
  37 * so that new flows have priority on old ones.
  38 *
  39 * For a given flow, packets are not reordered (CoDel uses a FIFO)
  40 * head drops only.
  41 * ECN capability is on by default.
  42 * Low memory footprint (64 bytes per flow)
  43 */
  44
  45struct fq_codel_flow {
  46        struct sk_buff    *head;
  47        struct sk_buff    *tail;
  48        struct list_head  flowchain;
  49        int               deficit;
  50        u32               dropped; /* number of drops (or ECN marks) on this flow */
  51        struct codel_vars cvars;
  52}; /* please try to keep this structure <= 64 bytes */
  53
  54struct fq_codel_sched_data {
  55        struct tcf_proto *filter_list;  /* optional external classifier */
  56        struct fq_codel_flow *flows;    /* Flows table [flows_cnt] */
  57        u32             *backlogs;      /* backlog table [flows_cnt] */
  58        u32             flows_cnt;      /* number of flows */
  59        u32             perturbation;   /* hash perturbation */
  60        u32             quantum;        /* psched_mtu(qdisc_dev(sch)); */
  61        struct codel_params cparams;
  62        struct codel_stats cstats;
  63        u32             drop_overlimit;
  64        u32             new_flow_count;
  65
  66        struct list_head new_flows;     /* list of new flows */
  67        struct list_head old_flows;     /* list of old flows */
  68};
  69
  70static unsigned int fq_codel_hash(const struct fq_codel_sched_data *q,
  71                                  const struct sk_buff *skb)
  72{
  73        struct flow_keys keys;
  74        unsigned int hash;
  75
  76        skb_flow_dissect(skb, &keys);
  77        hash = jhash_3words((__force u32)keys.dst,
  78                            (__force u32)keys.src ^ keys.ip_proto,
  79                            (__force u32)keys.ports, q->perturbation);
  80        return ((u64)hash * q->flows_cnt) >> 32;
  81}
  82
  83static unsigned int fq_codel_classify(struct sk_buff *skb, struct Qdisc *sch,
  84                                      int *qerr)
  85{
  86        struct fq_codel_sched_data *q = qdisc_priv(sch);
  87        struct tcf_result res;
  88        int result;
  89
  90        if (TC_H_MAJ(skb->priority) == sch->handle &&
  91            TC_H_MIN(skb->priority) > 0 &&
  92            TC_H_MIN(skb->priority) <= q->flows_cnt)
  93                return TC_H_MIN(skb->priority);
  94
  95        if (!q->filter_list)
  96                return fq_codel_hash(q, skb) + 1;
  97
  98        *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
  99        result = tc_classify(skb, q->filter_list, &res);
 100        if (result >= 0) {
 101#ifdef CONFIG_NET_CLS_ACT
 102                switch (result) {
 103                case TC_ACT_STOLEN:
 104                case TC_ACT_QUEUED:
 105                        *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
 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/* helper functions : might be changed when/if skb use a standard list_head */
 117
 118/* remove one skb from head of slot queue */
 119static inline struct sk_buff *dequeue_head(struct fq_codel_flow *flow)
 120{
 121        struct sk_buff *skb = flow->head;
 122
 123        flow->head = skb->next;
 124        skb->next = NULL;
 125        return skb;
 126}
 127
 128/* add skb to flow queue (tail add) */
 129static inline void flow_queue_add(struct fq_codel_flow *flow,
 130                                  struct sk_buff *skb)
 131{
 132        if (flow->head == NULL)
 133                flow->head = skb;
 134        else
 135                flow->tail->next = skb;
 136        flow->tail = skb;
 137        skb->next = NULL;
 138}
 139
 140static unsigned int fq_codel_drop(struct Qdisc *sch)
 141{
 142        struct fq_codel_sched_data *q = qdisc_priv(sch);
 143        struct sk_buff *skb;
 144        unsigned int maxbacklog = 0, idx = 0, i, len;
 145        struct fq_codel_flow *flow;
 146
 147        /* Queue is full! Find the fat flow and drop packet from it.
 148         * This might sound expensive, but with 1024 flows, we scan
 149         * 4KB of memory, and we dont need to handle a complex tree
 150         * in fast path (packet queue/enqueue) with many cache misses.
 151         */
 152        for (i = 0; i < q->flows_cnt; i++) {
 153                if (q->backlogs[i] > maxbacklog) {
 154                        maxbacklog = q->backlogs[i];
 155                        idx = i;
 156                }
 157        }
 158        flow = &q->flows[idx];
 159        skb = dequeue_head(flow);
 160        len = qdisc_pkt_len(skb);
 161        q->backlogs[idx] -= len;
 162        kfree_skb(skb);
 163        sch->q.qlen--;
 164        sch->qstats.drops++;
 165        sch->qstats.backlog -= len;
 166        flow->dropped++;
 167        return idx;
 168}
 169
 170static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 171{
 172        struct fq_codel_sched_data *q = qdisc_priv(sch);
 173        unsigned int idx;
 174        struct fq_codel_flow *flow;
 175        int uninitialized_var(ret);
 176
 177        idx = fq_codel_classify(skb, sch, &ret);
 178        if (idx == 0) {
 179                if (ret & __NET_XMIT_BYPASS)
 180                        sch->qstats.drops++;
 181                kfree_skb(skb);
 182                return ret;
 183        }
 184        idx--;
 185
 186        codel_set_enqueue_time(skb);
 187        flow = &q->flows[idx];
 188        flow_queue_add(flow, skb);
 189        q->backlogs[idx] += qdisc_pkt_len(skb);
 190        sch->qstats.backlog += qdisc_pkt_len(skb);
 191
 192        if (list_empty(&flow->flowchain)) {
 193                list_add_tail(&flow->flowchain, &q->new_flows);
 194                q->new_flow_count++;
 195                flow->deficit = q->quantum;
 196                flow->dropped = 0;
 197        }
 198        if (++sch->q.qlen < sch->limit)
 199                return NET_XMIT_SUCCESS;
 200
 201        q->drop_overlimit++;
 202        /* Return Congestion Notification only if we dropped a packet
 203         * from this flow.
 204         */
 205        if (fq_codel_drop(sch) == idx)
 206                return NET_XMIT_CN;
 207
 208        /* As we dropped a packet, better let upper stack know this */
 209        qdisc_tree_decrease_qlen(sch, 1);
 210        return NET_XMIT_SUCCESS;
 211}
 212
 213/* This is the specific function called from codel_dequeue()
 214 * to dequeue a packet from queue. Note: backlog is handled in
 215 * codel, we dont need to reduce it here.
 216 */
 217static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
 218{
 219        struct fq_codel_sched_data *q = qdisc_priv(sch);
 220        struct fq_codel_flow *flow;
 221        struct sk_buff *skb = NULL;
 222
 223        flow = container_of(vars, struct fq_codel_flow, cvars);
 224        if (flow->head) {
 225                skb = dequeue_head(flow);
 226                q->backlogs[flow - q->flows] -= qdisc_pkt_len(skb);
 227                sch->q.qlen--;
 228        }
 229        return skb;
 230}
 231
 232static struct sk_buff *fq_codel_dequeue(struct Qdisc *sch)
 233{
 234        struct fq_codel_sched_data *q = qdisc_priv(sch);
 235        struct sk_buff *skb;
 236        struct fq_codel_flow *flow;
 237        struct list_head *head;
 238        u32 prev_drop_count, prev_ecn_mark;
 239
 240begin:
 241        head = &q->new_flows;
 242        if (list_empty(head)) {
 243                head = &q->old_flows;
 244                if (list_empty(head))
 245                        return NULL;
 246        }
 247        flow = list_first_entry(head, struct fq_codel_flow, flowchain);
 248
 249        if (flow->deficit <= 0) {
 250                flow->deficit += q->quantum;
 251                list_move_tail(&flow->flowchain, &q->old_flows);
 252                goto begin;
 253        }
 254
 255        prev_drop_count = q->cstats.drop_count;
 256        prev_ecn_mark = q->cstats.ecn_mark;
 257
 258        skb = codel_dequeue(sch, &q->cparams, &flow->cvars, &q->cstats,
 259                            dequeue);
 260
 261        flow->dropped += q->cstats.drop_count - prev_drop_count;
 262        flow->dropped += q->cstats.ecn_mark - prev_ecn_mark;
 263
 264        if (!skb) {
 265                /* force a pass through old_flows to prevent starvation */
 266                if ((head == &q->new_flows) && !list_empty(&q->old_flows))
 267                        list_move_tail(&flow->flowchain, &q->old_flows);
 268                else
 269                        list_del_init(&flow->flowchain);
 270                goto begin;
 271        }
 272        qdisc_bstats_update(sch, skb);
 273        flow->deficit -= qdisc_pkt_len(skb);
 274        /* We cant call qdisc_tree_decrease_qlen() if our qlen is 0,
 275         * or HTB crashes. Defer it for next round.
 276         */
 277        if (q->cstats.drop_count && sch->q.qlen) {
 278                qdisc_tree_decrease_qlen(sch, q->cstats.drop_count);
 279                q->cstats.drop_count = 0;
 280        }
 281        return skb;
 282}
 283
 284static void fq_codel_reset(struct Qdisc *sch)
 285{
 286        struct sk_buff *skb;
 287
 288        while ((skb = fq_codel_dequeue(sch)) != NULL)
 289                kfree_skb(skb);
 290}
 291
 292static const struct nla_policy fq_codel_policy[TCA_FQ_CODEL_MAX + 1] = {
 293        [TCA_FQ_CODEL_TARGET]   = { .type = NLA_U32 },
 294        [TCA_FQ_CODEL_LIMIT]    = { .type = NLA_U32 },
 295        [TCA_FQ_CODEL_INTERVAL] = { .type = NLA_U32 },
 296        [TCA_FQ_CODEL_ECN]      = { .type = NLA_U32 },
 297        [TCA_FQ_CODEL_FLOWS]    = { .type = NLA_U32 },
 298        [TCA_FQ_CODEL_QUANTUM]  = { .type = NLA_U32 },
 299};
 300
 301static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt)
 302{
 303        struct fq_codel_sched_data *q = qdisc_priv(sch);
 304        struct nlattr *tb[TCA_FQ_CODEL_MAX + 1];
 305        int err;
 306
 307        if (!opt)
 308                return -EINVAL;
 309
 310        err = nla_parse_nested(tb, TCA_FQ_CODEL_MAX, opt, fq_codel_policy);
 311        if (err < 0)
 312                return err;
 313        if (tb[TCA_FQ_CODEL_FLOWS]) {
 314                if (q->flows)
 315                        return -EINVAL;
 316                q->flows_cnt = nla_get_u32(tb[TCA_FQ_CODEL_FLOWS]);
 317                if (!q->flows_cnt ||
 318                    q->flows_cnt > 65536)
 319                        return -EINVAL;
 320        }
 321        sch_tree_lock(sch);
 322
 323        if (tb[TCA_FQ_CODEL_TARGET]) {
 324                u64 target = nla_get_u32(tb[TCA_FQ_CODEL_TARGET]);
 325
 326                q->cparams.target = (target * NSEC_PER_USEC) >> CODEL_SHIFT;
 327        }
 328
 329        if (tb[TCA_FQ_CODEL_INTERVAL]) {
 330                u64 interval = nla_get_u32(tb[TCA_FQ_CODEL_INTERVAL]);
 331
 332                q->cparams.interval = (interval * NSEC_PER_USEC) >> CODEL_SHIFT;
 333        }
 334
 335        if (tb[TCA_FQ_CODEL_LIMIT])
 336                sch->limit = nla_get_u32(tb[TCA_FQ_CODEL_LIMIT]);
 337
 338        if (tb[TCA_FQ_CODEL_ECN])
 339                q->cparams.ecn = !!nla_get_u32(tb[TCA_FQ_CODEL_ECN]);
 340
 341        if (tb[TCA_FQ_CODEL_QUANTUM])
 342                q->quantum = max(256U, nla_get_u32(tb[TCA_FQ_CODEL_QUANTUM]));
 343
 344        while (sch->q.qlen > sch->limit) {
 345                struct sk_buff *skb = fq_codel_dequeue(sch);
 346
 347                kfree_skb(skb);
 348                q->cstats.drop_count++;
 349        }
 350        qdisc_tree_decrease_qlen(sch, q->cstats.drop_count);
 351        q->cstats.drop_count = 0;
 352
 353        sch_tree_unlock(sch);
 354        return 0;
 355}
 356
 357static void *fq_codel_zalloc(size_t sz)
 358{
 359        void *ptr = kzalloc(sz, GFP_KERNEL | __GFP_NOWARN);
 360
 361        if (!ptr)
 362                ptr = vzalloc(sz);
 363        return ptr;
 364}
 365
 366static void fq_codel_free(void *addr)
 367{
 368        if (addr) {
 369                if (is_vmalloc_addr(addr))
 370                        vfree(addr);
 371                else
 372                        kfree(addr);
 373        }
 374}
 375
 376static void fq_codel_destroy(struct Qdisc *sch)
 377{
 378        struct fq_codel_sched_data *q = qdisc_priv(sch);
 379
 380        tcf_destroy_chain(&q->filter_list);
 381        fq_codel_free(q->backlogs);
 382        fq_codel_free(q->flows);
 383}
 384
 385static int fq_codel_init(struct Qdisc *sch, struct nlattr *opt)
 386{
 387        struct fq_codel_sched_data *q = qdisc_priv(sch);
 388        int i;
 389
 390        sch->limit = 10*1024;
 391        q->flows_cnt = 1024;
 392        q->quantum = psched_mtu(qdisc_dev(sch));
 393        q->perturbation = net_random();
 394        INIT_LIST_HEAD(&q->new_flows);
 395        INIT_LIST_HEAD(&q->old_flows);
 396        codel_params_init(&q->cparams);
 397        codel_stats_init(&q->cstats);
 398        q->cparams.ecn = true;
 399
 400        if (opt) {
 401                int err = fq_codel_change(sch, opt);
 402                if (err)
 403                        return err;
 404        }
 405
 406        if (!q->flows) {
 407                q->flows = fq_codel_zalloc(q->flows_cnt *
 408                                           sizeof(struct fq_codel_flow));
 409                if (!q->flows)
 410                        return -ENOMEM;
 411                q->backlogs = fq_codel_zalloc(q->flows_cnt * sizeof(u32));
 412                if (!q->backlogs) {
 413                        fq_codel_free(q->flows);
 414                        return -ENOMEM;
 415                }
 416                for (i = 0; i < q->flows_cnt; i++) {
 417                        struct fq_codel_flow *flow = q->flows + i;
 418
 419                        INIT_LIST_HEAD(&flow->flowchain);
 420                        codel_vars_init(&flow->cvars);
 421                }
 422        }
 423        if (sch->limit >= 1)
 424                sch->flags |= TCQ_F_CAN_BYPASS;
 425        else
 426                sch->flags &= ~TCQ_F_CAN_BYPASS;
 427        return 0;
 428}
 429
 430static int fq_codel_dump(struct Qdisc *sch, struct sk_buff *skb)
 431{
 432        struct fq_codel_sched_data *q = qdisc_priv(sch);
 433        struct nlattr *opts;
 434
 435        opts = nla_nest_start(skb, TCA_OPTIONS);
 436        if (opts == NULL)
 437                goto nla_put_failure;
 438
 439        if (nla_put_u32(skb, TCA_FQ_CODEL_TARGET,
 440                        codel_time_to_us(q->cparams.target)) ||
 441            nla_put_u32(skb, TCA_FQ_CODEL_LIMIT,
 442                        sch->limit) ||
 443            nla_put_u32(skb, TCA_FQ_CODEL_INTERVAL,
 444                        codel_time_to_us(q->cparams.interval)) ||
 445            nla_put_u32(skb, TCA_FQ_CODEL_ECN,
 446                        q->cparams.ecn) ||
 447            nla_put_u32(skb, TCA_FQ_CODEL_QUANTUM,
 448                        q->quantum) ||
 449            nla_put_u32(skb, TCA_FQ_CODEL_FLOWS,
 450                        q->flows_cnt))
 451                goto nla_put_failure;
 452
 453        nla_nest_end(skb, opts);
 454        return skb->len;
 455
 456nla_put_failure:
 457        return -1;
 458}
 459
 460static int fq_codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
 461{
 462        struct fq_codel_sched_data *q = qdisc_priv(sch);
 463        struct tc_fq_codel_xstats st = {
 464                .type                           = TCA_FQ_CODEL_XSTATS_QDISC,
 465        };
 466        struct list_head *pos;
 467
 468        st.qdisc_stats.maxpacket = q->cstats.maxpacket;
 469        st.qdisc_stats.drop_overlimit = q->drop_overlimit;
 470        st.qdisc_stats.ecn_mark = q->cstats.ecn_mark;
 471        st.qdisc_stats.new_flow_count = q->new_flow_count;
 472
 473        list_for_each(pos, &q->new_flows)
 474                st.qdisc_stats.new_flows_len++;
 475
 476        list_for_each(pos, &q->old_flows)
 477                st.qdisc_stats.old_flows_len++;
 478
 479        return gnet_stats_copy_app(d, &st, sizeof(st));
 480}
 481
 482static struct Qdisc *fq_codel_leaf(struct Qdisc *sch, unsigned long arg)
 483{
 484        return NULL;
 485}
 486
 487static unsigned long fq_codel_get(struct Qdisc *sch, u32 classid)
 488{
 489        return 0;
 490}
 491
 492static unsigned long fq_codel_bind(struct Qdisc *sch, unsigned long parent,
 493                              u32 classid)
 494{
 495        /* we cannot bypass queue discipline anymore */
 496        sch->flags &= ~TCQ_F_CAN_BYPASS;
 497        return 0;
 498}
 499
 500static void fq_codel_put(struct Qdisc *q, unsigned long cl)
 501{
 502}
 503
 504static struct tcf_proto **fq_codel_find_tcf(struct Qdisc *sch, unsigned long cl)
 505{
 506        struct fq_codel_sched_data *q = qdisc_priv(sch);
 507
 508        if (cl)
 509                return NULL;
 510        return &q->filter_list;
 511}
 512
 513static int fq_codel_dump_class(struct Qdisc *sch, unsigned long cl,
 514                          struct sk_buff *skb, struct tcmsg *tcm)
 515{
 516        tcm->tcm_handle |= TC_H_MIN(cl);
 517        return 0;
 518}
 519
 520static int fq_codel_dump_class_stats(struct Qdisc *sch, unsigned long cl,
 521                                     struct gnet_dump *d)
 522{
 523        struct fq_codel_sched_data *q = qdisc_priv(sch);
 524        u32 idx = cl - 1;
 525        struct gnet_stats_queue qs = { 0 };
 526        struct tc_fq_codel_xstats xstats;
 527
 528        if (idx < q->flows_cnt) {
 529                const struct fq_codel_flow *flow = &q->flows[idx];
 530                const struct sk_buff *skb = flow->head;
 531
 532                memset(&xstats, 0, sizeof(xstats));
 533                xstats.type = TCA_FQ_CODEL_XSTATS_CLASS;
 534                xstats.class_stats.deficit = flow->deficit;
 535                xstats.class_stats.ldelay =
 536                        codel_time_to_us(flow->cvars.ldelay);
 537                xstats.class_stats.count = flow->cvars.count;
 538                xstats.class_stats.lastcount = flow->cvars.lastcount;
 539                xstats.class_stats.dropping = flow->cvars.dropping;
 540                if (flow->cvars.dropping) {
 541                        codel_tdiff_t delta = flow->cvars.drop_next -
 542                                              codel_get_time();
 543
 544                        xstats.class_stats.drop_next = (delta >= 0) ?
 545                                codel_time_to_us(delta) :
 546                                -codel_time_to_us(-delta);
 547                }
 548                while (skb) {
 549                        qs.qlen++;
 550                        skb = skb->next;
 551                }
 552                qs.backlog = q->backlogs[idx];
 553                qs.drops = flow->dropped;
 554        }
 555        if (gnet_stats_copy_queue(d, &qs) < 0)
 556                return -1;
 557        if (idx < q->flows_cnt)
 558                return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
 559        return 0;
 560}
 561
 562static void fq_codel_walk(struct Qdisc *sch, struct qdisc_walker *arg)
 563{
 564        struct fq_codel_sched_data *q = qdisc_priv(sch);
 565        unsigned int i;
 566
 567        if (arg->stop)
 568                return;
 569
 570        for (i = 0; i < q->flows_cnt; i++) {
 571                if (list_empty(&q->flows[i].flowchain) ||
 572                    arg->count < arg->skip) {
 573                        arg->count++;
 574                        continue;
 575                }
 576                if (arg->fn(sch, i + 1, arg) < 0) {
 577                        arg->stop = 1;
 578                        break;
 579                }
 580                arg->count++;
 581        }
 582}
 583
 584static const struct Qdisc_class_ops fq_codel_class_ops = {
 585        .leaf           =       fq_codel_leaf,
 586        .get            =       fq_codel_get,
 587        .put            =       fq_codel_put,
 588        .tcf_chain      =       fq_codel_find_tcf,
 589        .bind_tcf       =       fq_codel_bind,
 590        .unbind_tcf     =       fq_codel_put,
 591        .dump           =       fq_codel_dump_class,
 592        .dump_stats     =       fq_codel_dump_class_stats,
 593        .walk           =       fq_codel_walk,
 594};
 595
 596static struct Qdisc_ops fq_codel_qdisc_ops __read_mostly = {
 597        .cl_ops         =       &fq_codel_class_ops,
 598        .id             =       "fq_codel",
 599        .priv_size      =       sizeof(struct fq_codel_sched_data),
 600        .enqueue        =       fq_codel_enqueue,
 601        .dequeue        =       fq_codel_dequeue,
 602        .peek           =       qdisc_peek_dequeued,
 603        .drop           =       fq_codel_drop,
 604        .init           =       fq_codel_init,
 605        .reset          =       fq_codel_reset,
 606        .destroy        =       fq_codel_destroy,
 607        .change         =       fq_codel_change,
 608        .dump           =       fq_codel_dump,
 609        .dump_stats =   fq_codel_dump_stats,
 610        .owner          =       THIS_MODULE,
 611};
 612
 613static int __init fq_codel_module_init(void)
 614{
 615        return register_qdisc(&fq_codel_qdisc_ops);
 616}
 617
 618static void __exit fq_codel_module_exit(void)
 619{
 620        unregister_qdisc(&fq_codel_qdisc_ops);
 621}
 622
 623module_init(fq_codel_module_init)
 624module_exit(fq_codel_module_exit)
 625MODULE_AUTHOR("Eric Dumazet");
 626MODULE_LICENSE("GPL");
 627
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