Version:  2.0.40 2.2.26 2.4.37 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18

Linux/net/sched/sch_fq_codel.c

  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 
 45 struct 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 
 54 struct fq_codel_sched_data {
 55         struct tcf_proto __rcu *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 
 70 static 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 
 81         return reciprocal_scale(hash, q->flows_cnt);
 82 }
 83 
 84 static unsigned int fq_codel_classify(struct sk_buff *skb, struct Qdisc *sch,
 85                                       int *qerr)
 86 {
 87         struct fq_codel_sched_data *q = qdisc_priv(sch);
 88         struct tcf_proto *filter;
 89         struct tcf_result res;
 90         int result;
 91 
 92         if (TC_H_MAJ(skb->priority) == sch->handle &&
 93             TC_H_MIN(skb->priority) > 0 &&
 94             TC_H_MIN(skb->priority) <= q->flows_cnt)
 95                 return TC_H_MIN(skb->priority);
 96 
 97         filter = rcu_dereference(q->filter_list);
 98         if (!filter)
 99                 return fq_codel_hash(q, skb) + 1;
100 
101         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
102         result = tc_classify(skb, filter, &res);
103         if (result >= 0) {
104 #ifdef CONFIG_NET_CLS_ACT
105                 switch (result) {
106                 case TC_ACT_STOLEN:
107                 case TC_ACT_QUEUED:
108                         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
109                 case TC_ACT_SHOT:
110                         return 0;
111                 }
112 #endif
113                 if (TC_H_MIN(res.classid) <= q->flows_cnt)
114                         return TC_H_MIN(res.classid);
115         }
116         return 0;
117 }
118 
119 /* helper functions : might be changed when/if skb use a standard list_head */
120 
121 /* remove one skb from head of slot queue */
122 static inline struct sk_buff *dequeue_head(struct fq_codel_flow *flow)
123 {
124         struct sk_buff *skb = flow->head;
125 
126         flow->head = skb->next;
127         skb->next = NULL;
128         return skb;
129 }
130 
131 /* add skb to flow queue (tail add) */
132 static inline void flow_queue_add(struct fq_codel_flow *flow,
133                                   struct sk_buff *skb)
134 {
135         if (flow->head == NULL)
136                 flow->head = skb;
137         else
138                 flow->tail->next = skb;
139         flow->tail = skb;
140         skb->next = NULL;
141 }
142 
143 static unsigned int fq_codel_drop(struct Qdisc *sch)
144 {
145         struct fq_codel_sched_data *q = qdisc_priv(sch);
146         struct sk_buff *skb;
147         unsigned int maxbacklog = 0, idx = 0, i, len;
148         struct fq_codel_flow *flow;
149 
150         /* Queue is full! Find the fat flow and drop packet from it.
151          * This might sound expensive, but with 1024 flows, we scan
152          * 4KB of memory, and we dont need to handle a complex tree
153          * in fast path (packet queue/enqueue) with many cache misses.
154          */
155         for (i = 0; i < q->flows_cnt; i++) {
156                 if (q->backlogs[i] > maxbacklog) {
157                         maxbacklog = q->backlogs[i];
158                         idx = i;
159                 }
160         }
161         flow = &q->flows[idx];
162         skb = dequeue_head(flow);
163         len = qdisc_pkt_len(skb);
164         q->backlogs[idx] -= len;
165         kfree_skb(skb);
166         sch->q.qlen--;
167         qdisc_qstats_drop(sch);
168         qdisc_qstats_backlog_dec(sch, skb);
169         flow->dropped++;
170         return idx;
171 }
172 
173 static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch)
174 {
175         struct fq_codel_sched_data *q = qdisc_priv(sch);
176         unsigned int idx;
177         struct fq_codel_flow *flow;
178         int uninitialized_var(ret);
179 
180         idx = fq_codel_classify(skb, sch, &ret);
181         if (idx == 0) {
182                 if (ret & __NET_XMIT_BYPASS)
183                         qdisc_qstats_drop(sch);
184                 kfree_skb(skb);
185                 return ret;
186         }
187         idx--;
188 
189         codel_set_enqueue_time(skb);
190         flow = &q->flows[idx];
191         flow_queue_add(flow, skb);
192         q->backlogs[idx] += qdisc_pkt_len(skb);
193         qdisc_qstats_backlog_inc(sch, skb);
194 
195         if (list_empty(&flow->flowchain)) {
196                 list_add_tail(&flow->flowchain, &q->new_flows);
197                 q->new_flow_count++;
198                 flow->deficit = q->quantum;
199                 flow->dropped = 0;
200         }
201         if (++sch->q.qlen <= sch->limit)
202                 return NET_XMIT_SUCCESS;
203 
204         q->drop_overlimit++;
205         /* Return Congestion Notification only if we dropped a packet
206          * from this flow.
207          */
208         if (fq_codel_drop(sch) == idx)
209                 return NET_XMIT_CN;
210 
211         /* As we dropped a packet, better let upper stack know this */
212         qdisc_tree_decrease_qlen(sch, 1);
213         return NET_XMIT_SUCCESS;
214 }
215 
216 /* This is the specific function called from codel_dequeue()
217  * to dequeue a packet from queue. Note: backlog is handled in
218  * codel, we dont need to reduce it here.
219  */
220 static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
221 {
222         struct fq_codel_sched_data *q = qdisc_priv(sch);
223         struct fq_codel_flow *flow;
224         struct sk_buff *skb = NULL;
225 
226         flow = container_of(vars, struct fq_codel_flow, cvars);
227         if (flow->head) {
228                 skb = dequeue_head(flow);
229                 q->backlogs[flow - q->flows] -= qdisc_pkt_len(skb);
230                 sch->q.qlen--;
231         }
232         return skb;
233 }
234 
235 static struct sk_buff *fq_codel_dequeue(struct Qdisc *sch)
236 {
237         struct fq_codel_sched_data *q = qdisc_priv(sch);
238         struct sk_buff *skb;
239         struct fq_codel_flow *flow;
240         struct list_head *head;
241         u32 prev_drop_count, prev_ecn_mark;
242 
243 begin:
244         head = &q->new_flows;
245         if (list_empty(head)) {
246                 head = &q->old_flows;
247                 if (list_empty(head))
248                         return NULL;
249         }
250         flow = list_first_entry(head, struct fq_codel_flow, flowchain);
251 
252         if (flow->deficit <= 0) {
253                 flow->deficit += q->quantum;
254                 list_move_tail(&flow->flowchain, &q->old_flows);
255                 goto begin;
256         }
257 
258         prev_drop_count = q->cstats.drop_count;
259         prev_ecn_mark = q->cstats.ecn_mark;
260 
261         skb = codel_dequeue(sch, &q->cparams, &flow->cvars, &q->cstats,
262                             dequeue);
263 
264         flow->dropped += q->cstats.drop_count - prev_drop_count;
265         flow->dropped += q->cstats.ecn_mark - prev_ecn_mark;
266 
267         if (!skb) {
268                 /* force a pass through old_flows to prevent starvation */
269                 if ((head == &q->new_flows) && !list_empty(&q->old_flows))
270                         list_move_tail(&flow->flowchain, &q->old_flows);
271                 else
272                         list_del_init(&flow->flowchain);
273                 goto begin;
274         }
275         qdisc_bstats_update(sch, skb);
276         flow->deficit -= qdisc_pkt_len(skb);
277         /* We cant call qdisc_tree_decrease_qlen() if our qlen is 0,
278          * or HTB crashes. Defer it for next round.
279          */
280         if (q->cstats.drop_count && sch->q.qlen) {
281                 qdisc_tree_decrease_qlen(sch, q->cstats.drop_count);
282                 q->cstats.drop_count = 0;
283         }
284         return skb;
285 }
286 
287 static void fq_codel_reset(struct Qdisc *sch)
288 {
289         struct sk_buff *skb;
290 
291         while ((skb = fq_codel_dequeue(sch)) != NULL)
292                 kfree_skb(skb);
293 }
294 
295 static const struct nla_policy fq_codel_policy[TCA_FQ_CODEL_MAX + 1] = {
296         [TCA_FQ_CODEL_TARGET]   = { .type = NLA_U32 },
297         [TCA_FQ_CODEL_LIMIT]    = { .type = NLA_U32 },
298         [TCA_FQ_CODEL_INTERVAL] = { .type = NLA_U32 },
299         [TCA_FQ_CODEL_ECN]      = { .type = NLA_U32 },
300         [TCA_FQ_CODEL_FLOWS]    = { .type = NLA_U32 },
301         [TCA_FQ_CODEL_QUANTUM]  = { .type = NLA_U32 },
302 };
303 
304 static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt)
305 {
306         struct fq_codel_sched_data *q = qdisc_priv(sch);
307         struct nlattr *tb[TCA_FQ_CODEL_MAX + 1];
308         int err;
309 
310         if (!opt)
311                 return -EINVAL;
312 
313         err = nla_parse_nested(tb, TCA_FQ_CODEL_MAX, opt, fq_codel_policy);
314         if (err < 0)
315                 return err;
316         if (tb[TCA_FQ_CODEL_FLOWS]) {
317                 if (q->flows)
318                         return -EINVAL;
319                 q->flows_cnt = nla_get_u32(tb[TCA_FQ_CODEL_FLOWS]);
320                 if (!q->flows_cnt ||
321                     q->flows_cnt > 65536)
322                         return -EINVAL;
323         }
324         sch_tree_lock(sch);
325 
326         if (tb[TCA_FQ_CODEL_TARGET]) {
327                 u64 target = nla_get_u32(tb[TCA_FQ_CODEL_TARGET]);
328 
329                 q->cparams.target = (target * NSEC_PER_USEC) >> CODEL_SHIFT;
330         }
331 
332         if (tb[TCA_FQ_CODEL_INTERVAL]) {
333                 u64 interval = nla_get_u32(tb[TCA_FQ_CODEL_INTERVAL]);
334 
335                 q->cparams.interval = (interval * NSEC_PER_USEC) >> CODEL_SHIFT;
336         }
337 
338         if (tb[TCA_FQ_CODEL_LIMIT])
339                 sch->limit = nla_get_u32(tb[TCA_FQ_CODEL_LIMIT]);
340 
341         if (tb[TCA_FQ_CODEL_ECN])
342                 q->cparams.ecn = !!nla_get_u32(tb[TCA_FQ_CODEL_ECN]);
343 
344         if (tb[TCA_FQ_CODEL_QUANTUM])
345                 q->quantum = max(256U, nla_get_u32(tb[TCA_FQ_CODEL_QUANTUM]));
346 
347         while (sch->q.qlen > sch->limit) {
348                 struct sk_buff *skb = fq_codel_dequeue(sch);
349 
350                 kfree_skb(skb);
351                 q->cstats.drop_count++;
352         }
353         qdisc_tree_decrease_qlen(sch, q->cstats.drop_count);
354         q->cstats.drop_count = 0;
355 
356         sch_tree_unlock(sch);
357         return 0;
358 }
359 
360 static void *fq_codel_zalloc(size_t sz)
361 {
362         void *ptr = kzalloc(sz, GFP_KERNEL | __GFP_NOWARN);
363 
364         if (!ptr)
365                 ptr = vzalloc(sz);
366         return ptr;
367 }
368 
369 static void fq_codel_free(void *addr)
370 {
371         kvfree(addr);
372 }
373 
374 static void fq_codel_destroy(struct Qdisc *sch)
375 {
376         struct fq_codel_sched_data *q = qdisc_priv(sch);
377 
378         tcf_destroy_chain(&q->filter_list);
379         fq_codel_free(q->backlogs);
380         fq_codel_free(q->flows);
381 }
382 
383 static int fq_codel_init(struct Qdisc *sch, struct nlattr *opt)
384 {
385         struct fq_codel_sched_data *q = qdisc_priv(sch);
386         int i;
387 
388         sch->limit = 10*1024;
389         q->flows_cnt = 1024;
390         q->quantum = psched_mtu(qdisc_dev(sch));
391         q->perturbation = prandom_u32();
392         INIT_LIST_HEAD(&q->new_flows);
393         INIT_LIST_HEAD(&q->old_flows);
394         codel_params_init(&q->cparams);
395         codel_stats_init(&q->cstats);
396         q->cparams.ecn = true;
397 
398         if (opt) {
399                 int err = fq_codel_change(sch, opt);
400                 if (err)
401                         return err;
402         }
403 
404         if (!q->flows) {
405                 q->flows = fq_codel_zalloc(q->flows_cnt *
406                                            sizeof(struct fq_codel_flow));
407                 if (!q->flows)
408                         return -ENOMEM;
409                 q->backlogs = fq_codel_zalloc(q->flows_cnt * sizeof(u32));
410                 if (!q->backlogs) {
411                         fq_codel_free(q->flows);
412                         return -ENOMEM;
413                 }
414                 for (i = 0; i < q->flows_cnt; i++) {
415                         struct fq_codel_flow *flow = q->flows + i;
416 
417                         INIT_LIST_HEAD(&flow->flowchain);
418                         codel_vars_init(&flow->cvars);
419                 }
420         }
421         if (sch->limit >= 1)
422                 sch->flags |= TCQ_F_CAN_BYPASS;
423         else
424                 sch->flags &= ~TCQ_F_CAN_BYPASS;
425         return 0;
426 }
427 
428 static int fq_codel_dump(struct Qdisc *sch, struct sk_buff *skb)
429 {
430         struct fq_codel_sched_data *q = qdisc_priv(sch);
431         struct nlattr *opts;
432 
433         opts = nla_nest_start(skb, TCA_OPTIONS);
434         if (opts == NULL)
435                 goto nla_put_failure;
436 
437         if (nla_put_u32(skb, TCA_FQ_CODEL_TARGET,
438                         codel_time_to_us(q->cparams.target)) ||
439             nla_put_u32(skb, TCA_FQ_CODEL_LIMIT,
440                         sch->limit) ||
441             nla_put_u32(skb, TCA_FQ_CODEL_INTERVAL,
442                         codel_time_to_us(q->cparams.interval)) ||
443             nla_put_u32(skb, TCA_FQ_CODEL_ECN,
444                         q->cparams.ecn) ||
445             nla_put_u32(skb, TCA_FQ_CODEL_QUANTUM,
446                         q->quantum) ||
447             nla_put_u32(skb, TCA_FQ_CODEL_FLOWS,
448                         q->flows_cnt))
449                 goto nla_put_failure;
450 
451         return nla_nest_end(skb, opts);
452 
453 nla_put_failure:
454         return -1;
455 }
456 
457 static int fq_codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
458 {
459         struct fq_codel_sched_data *q = qdisc_priv(sch);
460         struct tc_fq_codel_xstats st = {
461                 .type                           = TCA_FQ_CODEL_XSTATS_QDISC,
462         };
463         struct list_head *pos;
464 
465         st.qdisc_stats.maxpacket = q->cstats.maxpacket;
466         st.qdisc_stats.drop_overlimit = q->drop_overlimit;
467         st.qdisc_stats.ecn_mark = q->cstats.ecn_mark;
468         st.qdisc_stats.new_flow_count = q->new_flow_count;
469 
470         list_for_each(pos, &q->new_flows)
471                 st.qdisc_stats.new_flows_len++;
472 
473         list_for_each(pos, &q->old_flows)
474                 st.qdisc_stats.old_flows_len++;
475 
476         return gnet_stats_copy_app(d, &st, sizeof(st));
477 }
478 
479 static struct Qdisc *fq_codel_leaf(struct Qdisc *sch, unsigned long arg)
480 {
481         return NULL;
482 }
483 
484 static unsigned long fq_codel_get(struct Qdisc *sch, u32 classid)
485 {
486         return 0;
487 }
488 
489 static unsigned long fq_codel_bind(struct Qdisc *sch, unsigned long parent,
490                               u32 classid)
491 {
492         /* we cannot bypass queue discipline anymore */
493         sch->flags &= ~TCQ_F_CAN_BYPASS;
494         return 0;
495 }
496 
497 static void fq_codel_put(struct Qdisc *q, unsigned long cl)
498 {
499 }
500 
501 static struct tcf_proto __rcu **fq_codel_find_tcf(struct Qdisc *sch,
502                                                   unsigned long cl)
503 {
504         struct fq_codel_sched_data *q = qdisc_priv(sch);
505 
506         if (cl)
507                 return NULL;
508         return &q->filter_list;
509 }
510 
511 static int fq_codel_dump_class(struct Qdisc *sch, unsigned long cl,
512                           struct sk_buff *skb, struct tcmsg *tcm)
513 {
514         tcm->tcm_handle |= TC_H_MIN(cl);
515         return 0;
516 }
517 
518 static int fq_codel_dump_class_stats(struct Qdisc *sch, unsigned long cl,
519                                      struct gnet_dump *d)
520 {
521         struct fq_codel_sched_data *q = qdisc_priv(sch);
522         u32 idx = cl - 1;
523         struct gnet_stats_queue qs = { 0 };
524         struct tc_fq_codel_xstats xstats;
525 
526         if (idx < q->flows_cnt) {
527                 const struct fq_codel_flow *flow = &q->flows[idx];
528                 const struct sk_buff *skb = flow->head;
529 
530                 memset(&xstats, 0, sizeof(xstats));
531                 xstats.type = TCA_FQ_CODEL_XSTATS_CLASS;
532                 xstats.class_stats.deficit = flow->deficit;
533                 xstats.class_stats.ldelay =
534                         codel_time_to_us(flow->cvars.ldelay);
535                 xstats.class_stats.count = flow->cvars.count;
536                 xstats.class_stats.lastcount = flow->cvars.lastcount;
537                 xstats.class_stats.dropping = flow->cvars.dropping;
538                 if (flow->cvars.dropping) {
539                         codel_tdiff_t delta = flow->cvars.drop_next -
540                                               codel_get_time();
541 
542                         xstats.class_stats.drop_next = (delta >= 0) ?
543                                 codel_time_to_us(delta) :
544                                 -codel_time_to_us(-delta);
545                 }
546                 while (skb) {
547                         qs.qlen++;
548                         skb = skb->next;
549                 }
550                 qs.backlog = q->backlogs[idx];
551                 qs.drops = flow->dropped;
552         }
553         if (gnet_stats_copy_queue(d, NULL, &qs, 0) < 0)
554                 return -1;
555         if (idx < q->flows_cnt)
556                 return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
557         return 0;
558 }
559 
560 static void fq_codel_walk(struct Qdisc *sch, struct qdisc_walker *arg)
561 {
562         struct fq_codel_sched_data *q = qdisc_priv(sch);
563         unsigned int i;
564 
565         if (arg->stop)
566                 return;
567 
568         for (i = 0; i < q->flows_cnt; i++) {
569                 if (list_empty(&q->flows[i].flowchain) ||
570                     arg->count < arg->skip) {
571                         arg->count++;
572                         continue;
573                 }
574                 if (arg->fn(sch, i + 1, arg) < 0) {
575                         arg->stop = 1;
576                         break;
577                 }
578                 arg->count++;
579         }
580 }
581 
582 static const struct Qdisc_class_ops fq_codel_class_ops = {
583         .leaf           =       fq_codel_leaf,
584         .get            =       fq_codel_get,
585         .put            =       fq_codel_put,
586         .tcf_chain      =       fq_codel_find_tcf,
587         .bind_tcf       =       fq_codel_bind,
588         .unbind_tcf     =       fq_codel_put,
589         .dump           =       fq_codel_dump_class,
590         .dump_stats     =       fq_codel_dump_class_stats,
591         .walk           =       fq_codel_walk,
592 };
593 
594 static struct Qdisc_ops fq_codel_qdisc_ops __read_mostly = {
595         .cl_ops         =       &fq_codel_class_ops,
596         .id             =       "fq_codel",
597         .priv_size      =       sizeof(struct fq_codel_sched_data),
598         .enqueue        =       fq_codel_enqueue,
599         .dequeue        =       fq_codel_dequeue,
600         .peek           =       qdisc_peek_dequeued,
601         .drop           =       fq_codel_drop,
602         .init           =       fq_codel_init,
603         .reset          =       fq_codel_reset,
604         .destroy        =       fq_codel_destroy,
605         .change         =       fq_codel_change,
606         .dump           =       fq_codel_dump,
607         .dump_stats =   fq_codel_dump_stats,
608         .owner          =       THIS_MODULE,
609 };
610 
611 static int __init fq_codel_module_init(void)
612 {
613         return register_qdisc(&fq_codel_qdisc_ops);
614 }
615 
616 static void __exit fq_codel_module_exit(void)
617 {
618         unregister_qdisc(&fq_codel_qdisc_ops);
619 }
620 
621 module_init(fq_codel_module_init)
622 module_exit(fq_codel_module_exit)
623 MODULE_AUTHOR("Eric Dumazet");
624 MODULE_LICENSE("GPL");
625 

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