2 * Fair Queue CoDel discipline
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.
9 * Copyright (C) 2012,2015 Eric Dumazet <edumazet@google.com>
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>
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/codel.h>
31 * Packets are classified (internal classifier or external) on flows.
32 * This is a Stochastic model (as we use a hash, several flows
33 * might be hashed on same slot)
34 * Each flow has a CoDel managed queue.
35 * Flows are linked onto two (Round Robin) lists,
36 * so that new flows have priority on old ones.
38 * For a given flow, packets are not reordered (CoDel uses a FIFO)
40 * ECN capability is on by default.
41 * Low memory footprint (64 bytes per flow)
44 struct fq_codel_flow {
47 struct list_head flowchain;
49 u32 dropped; /* number of drops (or ECN marks) on this flow */
50 struct codel_vars cvars;
51 }; /* please try to keep this structure <= 64 bytes */
53 struct fq_codel_sched_data {
54 struct tcf_proto __rcu *filter_list; /* optional external classifier */
55 struct fq_codel_flow *flows; /* Flows table [flows_cnt] */
56 u32 *backlogs; /* backlog table [flows_cnt] */
57 u32 flows_cnt; /* number of flows */
58 u32 perturbation; /* hash perturbation */
59 u32 quantum; /* psched_mtu(qdisc_dev(sch)); */
60 struct codel_params cparams;
61 struct codel_stats cstats;
65 struct list_head new_flows; /* list of new flows */
66 struct list_head old_flows; /* list of old flows */
69 static unsigned int fq_codel_hash(const struct fq_codel_sched_data *q,
72 u32 hash = skb_get_hash_perturb(skb, q->perturbation);
74 return reciprocal_scale(hash, q->flows_cnt);
77 static unsigned int fq_codel_classify(struct sk_buff *skb, struct Qdisc *sch,
80 struct fq_codel_sched_data *q = qdisc_priv(sch);
81 struct tcf_proto *filter;
82 struct tcf_result res;
85 if (TC_H_MAJ(skb->priority) == sch->handle &&
86 TC_H_MIN(skb->priority) > 0 &&
87 TC_H_MIN(skb->priority) <= q->flows_cnt)
88 return TC_H_MIN(skb->priority);
90 filter = rcu_dereference_bh(q->filter_list);
92 return fq_codel_hash(q, skb) + 1;
94 *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
95 result = tc_classify(skb, filter, &res);
97 #ifdef CONFIG_NET_CLS_ACT
101 *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
106 if (TC_H_MIN(res.classid) <= q->flows_cnt)
107 return TC_H_MIN(res.classid);
112 /* helper functions : might be changed when/if skb use a standard list_head */
114 /* remove one skb from head of slot queue */
115 static inline struct sk_buff *dequeue_head(struct fq_codel_flow *flow)
117 struct sk_buff *skb = flow->head;
119 flow->head = skb->next;
124 /* add skb to flow queue (tail add) */
125 static inline void flow_queue_add(struct fq_codel_flow *flow,
128 if (flow->head == NULL)
131 flow->tail->next = skb;
136 static unsigned int fq_codel_drop(struct Qdisc *sch)
138 struct fq_codel_sched_data *q = qdisc_priv(sch);
140 unsigned int maxbacklog = 0, idx = 0, i, len;
141 struct fq_codel_flow *flow;
143 /* Queue is full! Find the fat flow and drop packet from it.
144 * This might sound expensive, but with 1024 flows, we scan
145 * 4KB of memory, and we dont need to handle a complex tree
146 * in fast path (packet queue/enqueue) with many cache misses.
148 for (i = 0; i < q->flows_cnt; i++) {
149 if (q->backlogs[i] > maxbacklog) {
150 maxbacklog = q->backlogs[i];
154 flow = &q->flows[idx];
155 skb = dequeue_head(flow);
156 len = qdisc_pkt_len(skb);
157 q->backlogs[idx] -= len;
160 qdisc_qstats_drop(sch);
161 qdisc_qstats_backlog_dec(sch, skb);
166 static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch)
168 struct fq_codel_sched_data *q = qdisc_priv(sch);
170 struct fq_codel_flow *flow;
171 int uninitialized_var(ret);
173 idx = fq_codel_classify(skb, sch, &ret);
175 if (ret & __NET_XMIT_BYPASS)
176 qdisc_qstats_drop(sch);
182 codel_set_enqueue_time(skb);
183 flow = &q->flows[idx];
184 flow_queue_add(flow, skb);
185 q->backlogs[idx] += qdisc_pkt_len(skb);
186 qdisc_qstats_backlog_inc(sch, skb);
188 if (list_empty(&flow->flowchain)) {
189 list_add_tail(&flow->flowchain, &q->new_flows);
191 flow->deficit = q->quantum;
194 if (++sch->q.qlen <= sch->limit)
195 return NET_XMIT_SUCCESS;
198 /* Return Congestion Notification only if we dropped a packet
201 if (fq_codel_drop(sch) == idx)
204 /* As we dropped a packet, better let upper stack know this */
205 qdisc_tree_decrease_qlen(sch, 1);
206 return NET_XMIT_SUCCESS;
209 /* This is the specific function called from codel_dequeue()
210 * to dequeue a packet from queue. Note: backlog is handled in
211 * codel, we dont need to reduce it here.
213 static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
215 struct fq_codel_sched_data *q = qdisc_priv(sch);
216 struct fq_codel_flow *flow;
217 struct sk_buff *skb = NULL;
219 flow = container_of(vars, struct fq_codel_flow, cvars);
221 skb = dequeue_head(flow);
222 q->backlogs[flow - q->flows] -= qdisc_pkt_len(skb);
228 static struct sk_buff *fq_codel_dequeue(struct Qdisc *sch)
230 struct fq_codel_sched_data *q = qdisc_priv(sch);
232 struct fq_codel_flow *flow;
233 struct list_head *head;
234 u32 prev_drop_count, prev_ecn_mark;
237 head = &q->new_flows;
238 if (list_empty(head)) {
239 head = &q->old_flows;
240 if (list_empty(head))
243 flow = list_first_entry(head, struct fq_codel_flow, flowchain);
245 if (flow->deficit <= 0) {
246 flow->deficit += q->quantum;
247 list_move_tail(&flow->flowchain, &q->old_flows);
251 prev_drop_count = q->cstats.drop_count;
252 prev_ecn_mark = q->cstats.ecn_mark;
254 skb = codel_dequeue(sch, &q->cparams, &flow->cvars, &q->cstats,
257 flow->dropped += q->cstats.drop_count - prev_drop_count;
258 flow->dropped += q->cstats.ecn_mark - prev_ecn_mark;
261 /* force a pass through old_flows to prevent starvation */
262 if ((head == &q->new_flows) && !list_empty(&q->old_flows))
263 list_move_tail(&flow->flowchain, &q->old_flows);
265 list_del_init(&flow->flowchain);
268 qdisc_bstats_update(sch, skb);
269 flow->deficit -= qdisc_pkt_len(skb);
270 /* We cant call qdisc_tree_decrease_qlen() if our qlen is 0,
271 * or HTB crashes. Defer it for next round.
273 if (q->cstats.drop_count && sch->q.qlen) {
274 qdisc_tree_decrease_qlen(sch, q->cstats.drop_count);
275 q->cstats.drop_count = 0;
280 static void fq_codel_reset(struct Qdisc *sch)
284 while ((skb = fq_codel_dequeue(sch)) != NULL)
288 static const struct nla_policy fq_codel_policy[TCA_FQ_CODEL_MAX + 1] = {
289 [TCA_FQ_CODEL_TARGET] = { .type = NLA_U32 },
290 [TCA_FQ_CODEL_LIMIT] = { .type = NLA_U32 },
291 [TCA_FQ_CODEL_INTERVAL] = { .type = NLA_U32 },
292 [TCA_FQ_CODEL_ECN] = { .type = NLA_U32 },
293 [TCA_FQ_CODEL_FLOWS] = { .type = NLA_U32 },
294 [TCA_FQ_CODEL_QUANTUM] = { .type = NLA_U32 },
295 [TCA_FQ_CODEL_CE_THRESHOLD] = { .type = NLA_U32 },
298 static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt)
300 struct fq_codel_sched_data *q = qdisc_priv(sch);
301 struct nlattr *tb[TCA_FQ_CODEL_MAX + 1];
307 err = nla_parse_nested(tb, TCA_FQ_CODEL_MAX, opt, fq_codel_policy);
310 if (tb[TCA_FQ_CODEL_FLOWS]) {
313 q->flows_cnt = nla_get_u32(tb[TCA_FQ_CODEL_FLOWS]);
315 q->flows_cnt > 65536)
320 if (tb[TCA_FQ_CODEL_TARGET]) {
321 u64 target = nla_get_u32(tb[TCA_FQ_CODEL_TARGET]);
323 q->cparams.target = (target * NSEC_PER_USEC) >> CODEL_SHIFT;
326 if (tb[TCA_FQ_CODEL_CE_THRESHOLD]) {
327 u64 val = nla_get_u32(tb[TCA_FQ_CODEL_CE_THRESHOLD]);
329 q->cparams.ce_threshold = (val * NSEC_PER_USEC) >> CODEL_SHIFT;
332 if (tb[TCA_FQ_CODEL_INTERVAL]) {
333 u64 interval = nla_get_u32(tb[TCA_FQ_CODEL_INTERVAL]);
335 q->cparams.interval = (interval * NSEC_PER_USEC) >> CODEL_SHIFT;
338 if (tb[TCA_FQ_CODEL_LIMIT])
339 sch->limit = nla_get_u32(tb[TCA_FQ_CODEL_LIMIT]);
341 if (tb[TCA_FQ_CODEL_ECN])
342 q->cparams.ecn = !!nla_get_u32(tb[TCA_FQ_CODEL_ECN]);
344 if (tb[TCA_FQ_CODEL_QUANTUM])
345 q->quantum = max(256U, nla_get_u32(tb[TCA_FQ_CODEL_QUANTUM]));
347 while (sch->q.qlen > sch->limit) {
348 struct sk_buff *skb = fq_codel_dequeue(sch);
351 q->cstats.drop_count++;
353 qdisc_tree_decrease_qlen(sch, q->cstats.drop_count);
354 q->cstats.drop_count = 0;
356 sch_tree_unlock(sch);
360 static void *fq_codel_zalloc(size_t sz)
362 void *ptr = kzalloc(sz, GFP_KERNEL | __GFP_NOWARN);
369 static void fq_codel_free(void *addr)
374 static void fq_codel_destroy(struct Qdisc *sch)
376 struct fq_codel_sched_data *q = qdisc_priv(sch);
378 tcf_destroy_chain(&q->filter_list);
379 fq_codel_free(q->backlogs);
380 fq_codel_free(q->flows);
383 static int fq_codel_init(struct Qdisc *sch, struct nlattr *opt)
385 struct fq_codel_sched_data *q = qdisc_priv(sch);
388 sch->limit = 10*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, sch);
395 codel_stats_init(&q->cstats);
396 q->cparams.ecn = true;
399 int err = fq_codel_change(sch, opt);
405 q->flows = fq_codel_zalloc(q->flows_cnt *
406 sizeof(struct fq_codel_flow));
409 q->backlogs = fq_codel_zalloc(q->flows_cnt * sizeof(u32));
411 fq_codel_free(q->flows);
414 for (i = 0; i < q->flows_cnt; i++) {
415 struct fq_codel_flow *flow = q->flows + i;
417 INIT_LIST_HEAD(&flow->flowchain);
418 codel_vars_init(&flow->cvars);
422 sch->flags |= TCQ_F_CAN_BYPASS;
424 sch->flags &= ~TCQ_F_CAN_BYPASS;
428 static int fq_codel_dump(struct Qdisc *sch, struct sk_buff *skb)
430 struct fq_codel_sched_data *q = qdisc_priv(sch);
433 opts = nla_nest_start(skb, TCA_OPTIONS);
435 goto nla_put_failure;
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,
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,
445 nla_put_u32(skb, TCA_FQ_CODEL_QUANTUM,
447 nla_put_u32(skb, TCA_FQ_CODEL_FLOWS,
449 goto nla_put_failure;
451 if (q->cparams.ce_threshold != CODEL_DISABLED_THRESHOLD &&
452 nla_put_u32(skb, TCA_FQ_CODEL_CE_THRESHOLD,
453 codel_time_to_us(q->cparams.ce_threshold)))
454 goto nla_put_failure;
456 return nla_nest_end(skb, opts);
462 static int fq_codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
464 struct fq_codel_sched_data *q = qdisc_priv(sch);
465 struct tc_fq_codel_xstats st = {
466 .type = TCA_FQ_CODEL_XSTATS_QDISC,
468 struct list_head *pos;
470 st.qdisc_stats.maxpacket = q->cstats.maxpacket;
471 st.qdisc_stats.drop_overlimit = q->drop_overlimit;
472 st.qdisc_stats.ecn_mark = q->cstats.ecn_mark;
473 st.qdisc_stats.new_flow_count = q->new_flow_count;
474 st.qdisc_stats.ce_mark = q->cstats.ce_mark;
476 list_for_each(pos, &q->new_flows)
477 st.qdisc_stats.new_flows_len++;
479 list_for_each(pos, &q->old_flows)
480 st.qdisc_stats.old_flows_len++;
482 return gnet_stats_copy_app(d, &st, sizeof(st));
485 static struct Qdisc *fq_codel_leaf(struct Qdisc *sch, unsigned long arg)
490 static unsigned long fq_codel_get(struct Qdisc *sch, u32 classid)
495 static unsigned long fq_codel_bind(struct Qdisc *sch, unsigned long parent,
498 /* we cannot bypass queue discipline anymore */
499 sch->flags &= ~TCQ_F_CAN_BYPASS;
503 static void fq_codel_put(struct Qdisc *q, unsigned long cl)
507 static struct tcf_proto __rcu **fq_codel_find_tcf(struct Qdisc *sch,
510 struct fq_codel_sched_data *q = qdisc_priv(sch);
514 return &q->filter_list;
517 static int fq_codel_dump_class(struct Qdisc *sch, unsigned long cl,
518 struct sk_buff *skb, struct tcmsg *tcm)
520 tcm->tcm_handle |= TC_H_MIN(cl);
524 static int fq_codel_dump_class_stats(struct Qdisc *sch, unsigned long cl,
527 struct fq_codel_sched_data *q = qdisc_priv(sch);
529 struct gnet_stats_queue qs = { 0 };
530 struct tc_fq_codel_xstats xstats;
532 if (idx < q->flows_cnt) {
533 const struct fq_codel_flow *flow = &q->flows[idx];
534 const struct sk_buff *skb = flow->head;
536 memset(&xstats, 0, sizeof(xstats));
537 xstats.type = TCA_FQ_CODEL_XSTATS_CLASS;
538 xstats.class_stats.deficit = flow->deficit;
539 xstats.class_stats.ldelay =
540 codel_time_to_us(flow->cvars.ldelay);
541 xstats.class_stats.count = flow->cvars.count;
542 xstats.class_stats.lastcount = flow->cvars.lastcount;
543 xstats.class_stats.dropping = flow->cvars.dropping;
544 if (flow->cvars.dropping) {
545 codel_tdiff_t delta = flow->cvars.drop_next -
548 xstats.class_stats.drop_next = (delta >= 0) ?
549 codel_time_to_us(delta) :
550 -codel_time_to_us(-delta);
556 qs.backlog = q->backlogs[idx];
557 qs.drops = flow->dropped;
559 if (gnet_stats_copy_queue(d, NULL, &qs, 0) < 0)
561 if (idx < q->flows_cnt)
562 return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
566 static void fq_codel_walk(struct Qdisc *sch, struct qdisc_walker *arg)
568 struct fq_codel_sched_data *q = qdisc_priv(sch);
574 for (i = 0; i < q->flows_cnt; i++) {
575 if (list_empty(&q->flows[i].flowchain) ||
576 arg->count < arg->skip) {
580 if (arg->fn(sch, i + 1, arg) < 0) {
588 static const struct Qdisc_class_ops fq_codel_class_ops = {
589 .leaf = fq_codel_leaf,
592 .tcf_chain = fq_codel_find_tcf,
593 .bind_tcf = fq_codel_bind,
594 .unbind_tcf = fq_codel_put,
595 .dump = fq_codel_dump_class,
596 .dump_stats = fq_codel_dump_class_stats,
597 .walk = fq_codel_walk,
600 static struct Qdisc_ops fq_codel_qdisc_ops __read_mostly = {
601 .cl_ops = &fq_codel_class_ops,
603 .priv_size = sizeof(struct fq_codel_sched_data),
604 .enqueue = fq_codel_enqueue,
605 .dequeue = fq_codel_dequeue,
606 .peek = qdisc_peek_dequeued,
607 .drop = fq_codel_drop,
608 .init = fq_codel_init,
609 .reset = fq_codel_reset,
610 .destroy = fq_codel_destroy,
611 .change = fq_codel_change,
612 .dump = fq_codel_dump,
613 .dump_stats = fq_codel_dump_stats,
614 .owner = THIS_MODULE,
617 static int __init fq_codel_module_init(void)
619 return register_qdisc(&fq_codel_qdisc_ops);
622 static void __exit fq_codel_module_exit(void)
624 unregister_qdisc(&fq_codel_qdisc_ops);
627 module_init(fq_codel_module_init)
628 module_exit(fq_codel_module_exit)
629 MODULE_AUTHOR("Eric Dumazet");
630 MODULE_LICENSE("GPL");