2 * net/sched/sch_sfb.c Stochastic Fair Blue
4 * Copyright (c) 2008-2011 Juliusz Chroboczek <jch@pps.jussieu.fr>
5 * Copyright (c) 2011 Eric Dumazet <eric.dumazet@gmail.com>
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * version 2 as published by the Free Software Foundation.
11 * W. Feng, D. Kandlur, D. Saha, K. Shin. Blue:
12 * A New Class of Active Queue Management Algorithms.
13 * U. Michigan CSE-TR-387-99, April 1999.
15 * http://www.thefengs.com/wuchang/blue/CSE-TR-387-99.pdf
19 #include <linux/module.h>
20 #include <linux/types.h>
21 #include <linux/kernel.h>
22 #include <linux/errno.h>
23 #include <linux/skbuff.h>
24 #include <linux/random.h>
25 #include <linux/siphash.h>
27 #include <net/pkt_sched.h>
28 #include <net/pkt_cls.h>
29 #include <net/inet_ecn.h>
32 * SFB uses two B[l][n] : L x N arrays of bins (L levels, N bins per level)
33 * This implementation uses L = 8 and N = 16
34 * This permits us to split one 32bit hash (provided per packet by rxhash or
35 * external classifier) into 8 subhashes of 4 bits.
37 #define SFB_BUCKET_SHIFT 4
38 #define SFB_NUMBUCKETS (1 << SFB_BUCKET_SHIFT) /* N bins per Level */
39 #define SFB_BUCKET_MASK (SFB_NUMBUCKETS - 1)
40 #define SFB_LEVELS (32 / SFB_BUCKET_SHIFT) /* L */
42 /* SFB algo uses a virtual queue, named "bin" */
44 u16 qlen; /* length of virtual queue */
45 u16 p_mark; /* marking probability */
48 /* We use a double buffering right before hash change
49 * (Section 4.4 of SFB reference : moving hash functions)
52 siphash_key_t perturbation; /* siphash key */
53 struct sfb_bucket bins[SFB_LEVELS][SFB_NUMBUCKETS];
56 struct sfb_sched_data {
58 struct tcf_proto __rcu *filter_list;
59 struct tcf_block *block;
60 unsigned long rehash_interval;
61 unsigned long warmup_time; /* double buffering warmup time in jiffies */
63 u32 bin_size; /* maximum queue length per bin */
64 u32 increment; /* d1 */
65 u32 decrement; /* d2 */
66 u32 limit; /* HARD maximal queue length */
70 unsigned long rehash_time;
71 unsigned long token_time;
73 u8 slot; /* current active bins (0 or 1) */
74 bool double_buffering;
75 struct sfb_bins bins[2];
82 u32 childdrop; /* drops in child qdisc */
83 u32 marked; /* ECN mark */
88 * Each queued skb might be hashed on one or two bins
89 * We store in skb_cb the two hash values.
90 * (A zero value means double buffering was not used)
96 static inline struct sfb_skb_cb *sfb_skb_cb(const struct sk_buff *skb)
98 qdisc_cb_private_validate(skb, sizeof(struct sfb_skb_cb));
99 return (struct sfb_skb_cb *)qdisc_skb_cb(skb)->data;
103 * If using 'internal' SFB flow classifier, hash comes from skb rxhash
104 * If using external classifier, hash comes from the classid.
106 static u32 sfb_hash(const struct sk_buff *skb, u32 slot)
108 return sfb_skb_cb(skb)->hashes[slot];
111 /* Probabilities are coded as Q0.16 fixed-point values,
112 * with 0xFFFF representing 65535/65536 (almost 1.0)
113 * Addition and subtraction are saturating in [0, 65535]
115 static u32 prob_plus(u32 p1, u32 p2)
119 return min_t(u32, res, SFB_MAX_PROB);
122 static u32 prob_minus(u32 p1, u32 p2)
124 return p1 > p2 ? p1 - p2 : 0;
127 static void increment_one_qlen(u32 sfbhash, u32 slot, struct sfb_sched_data *q)
130 struct sfb_bucket *b = &q->bins[slot].bins[0][0];
132 for (i = 0; i < SFB_LEVELS; i++) {
133 u32 hash = sfbhash & SFB_BUCKET_MASK;
135 sfbhash >>= SFB_BUCKET_SHIFT;
136 if (b[hash].qlen < 0xFFFF)
138 b += SFB_NUMBUCKETS; /* next level */
142 static void increment_qlen(const struct sfb_skb_cb *cb, struct sfb_sched_data *q)
146 sfbhash = cb->hashes[0];
148 increment_one_qlen(sfbhash, 0, q);
150 sfbhash = cb->hashes[1];
152 increment_one_qlen(sfbhash, 1, q);
155 static void decrement_one_qlen(u32 sfbhash, u32 slot,
156 struct sfb_sched_data *q)
159 struct sfb_bucket *b = &q->bins[slot].bins[0][0];
161 for (i = 0; i < SFB_LEVELS; i++) {
162 u32 hash = sfbhash & SFB_BUCKET_MASK;
164 sfbhash >>= SFB_BUCKET_SHIFT;
165 if (b[hash].qlen > 0)
167 b += SFB_NUMBUCKETS; /* next level */
171 static void decrement_qlen(const struct sk_buff *skb, struct sfb_sched_data *q)
175 sfbhash = sfb_hash(skb, 0);
177 decrement_one_qlen(sfbhash, 0, q);
179 sfbhash = sfb_hash(skb, 1);
181 decrement_one_qlen(sfbhash, 1, q);
184 static void decrement_prob(struct sfb_bucket *b, struct sfb_sched_data *q)
186 b->p_mark = prob_minus(b->p_mark, q->decrement);
189 static void increment_prob(struct sfb_bucket *b, struct sfb_sched_data *q)
191 b->p_mark = prob_plus(b->p_mark, q->increment);
194 static void sfb_zero_all_buckets(struct sfb_sched_data *q)
196 memset(&q->bins, 0, sizeof(q->bins));
200 * compute max qlen, max p_mark, and avg p_mark
202 static u32 sfb_compute_qlen(u32 *prob_r, u32 *avgpm_r, const struct sfb_sched_data *q)
205 u32 qlen = 0, prob = 0, totalpm = 0;
206 const struct sfb_bucket *b = &q->bins[q->slot].bins[0][0];
208 for (i = 0; i < SFB_LEVELS * SFB_NUMBUCKETS; i++) {
211 totalpm += b->p_mark;
212 if (prob < b->p_mark)
217 *avgpm_r = totalpm / (SFB_LEVELS * SFB_NUMBUCKETS);
222 static void sfb_init_perturbation(u32 slot, struct sfb_sched_data *q)
224 get_random_bytes(&q->bins[slot].perturbation,
225 sizeof(q->bins[slot].perturbation));
228 static void sfb_swap_slot(struct sfb_sched_data *q)
230 sfb_init_perturbation(q->slot, q);
232 q->double_buffering = false;
235 /* Non elastic flows are allowed to use part of the bandwidth, expressed
236 * in "penalty_rate" packets per second, with "penalty_burst" burst
238 static bool sfb_rate_limit(struct sk_buff *skb, struct sfb_sched_data *q)
240 if (q->penalty_rate == 0 || q->penalty_burst == 0)
243 if (q->tokens_avail < 1) {
244 unsigned long age = min(10UL * HZ, jiffies - q->token_time);
246 q->tokens_avail = (age * q->penalty_rate) / HZ;
247 if (q->tokens_avail > q->penalty_burst)
248 q->tokens_avail = q->penalty_burst;
249 q->token_time = jiffies;
250 if (q->tokens_avail < 1)
258 static bool sfb_classify(struct sk_buff *skb, struct tcf_proto *fl,
259 int *qerr, u32 *salt)
261 struct tcf_result res;
264 result = tcf_classify(skb, fl, &res, false);
266 #ifdef CONFIG_NET_CLS_ACT
271 *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
277 *salt = TC_H_MIN(res.classid);
283 static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
284 struct sk_buff **to_free)
287 struct sfb_sched_data *q = qdisc_priv(sch);
288 unsigned int len = qdisc_pkt_len(skb);
289 struct Qdisc *child = q->qdisc;
290 struct tcf_proto *fl;
291 struct sfb_skb_cb cb;
297 int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
299 if (unlikely(sch->q.qlen >= q->limit)) {
300 qdisc_qstats_overlimit(sch);
301 q->stats.queuedrop++;
305 if (q->rehash_interval > 0) {
306 unsigned long limit = q->rehash_time + q->rehash_interval;
308 if (unlikely(time_after(jiffies, limit))) {
310 q->rehash_time = jiffies;
311 } else if (unlikely(!q->double_buffering && q->warmup_time > 0 &&
312 time_after(jiffies, limit - q->warmup_time))) {
313 q->double_buffering = true;
317 fl = rcu_dereference_bh(q->filter_list);
321 /* If using external classifiers, get result and record it. */
322 if (!sfb_classify(skb, fl, &ret, &salt))
324 sfbhash = siphash_1u32(salt, &q->bins[slot].perturbation);
326 sfbhash = skb_get_hash_perturb(skb, &q->bins[slot].perturbation);
332 sfb_skb_cb(skb)->hashes[slot] = sfbhash;
334 for (i = 0; i < SFB_LEVELS; i++) {
335 u32 hash = sfbhash & SFB_BUCKET_MASK;
336 struct sfb_bucket *b = &q->bins[slot].bins[i][hash];
338 sfbhash >>= SFB_BUCKET_SHIFT;
340 decrement_prob(b, q);
341 else if (b->qlen >= q->bin_size)
342 increment_prob(b, q);
343 if (minqlen > b->qlen)
345 if (p_min > b->p_mark)
350 sfb_skb_cb(skb)->hashes[slot] = 0;
352 if (unlikely(minqlen >= q->max)) {
353 qdisc_qstats_overlimit(sch);
354 q->stats.bucketdrop++;
358 if (unlikely(p_min >= SFB_MAX_PROB)) {
360 if (q->double_buffering) {
361 sfbhash = skb_get_hash_perturb(skb,
362 &q->bins[slot].perturbation);
365 sfb_skb_cb(skb)->hashes[slot] = sfbhash;
367 for (i = 0; i < SFB_LEVELS; i++) {
368 u32 hash = sfbhash & SFB_BUCKET_MASK;
369 struct sfb_bucket *b = &q->bins[slot].bins[i][hash];
371 sfbhash >>= SFB_BUCKET_SHIFT;
373 decrement_prob(b, q);
374 else if (b->qlen >= q->bin_size)
375 increment_prob(b, q);
378 if (sfb_rate_limit(skb, q)) {
379 qdisc_qstats_overlimit(sch);
380 q->stats.penaltydrop++;
386 r = prandom_u32() & SFB_MAX_PROB;
388 if (unlikely(r < p_min)) {
389 if (unlikely(p_min > SFB_MAX_PROB / 2)) {
390 /* If we're marking that many packets, then either
391 * this flow is unresponsive, or we're badly congested.
392 * In either case, we want to start dropping packets.
394 if (r < (p_min - SFB_MAX_PROB / 2) * 2) {
395 q->stats.earlydrop++;
399 if (INET_ECN_set_ce(skb)) {
402 q->stats.earlydrop++;
408 memcpy(&cb, sfb_skb_cb(skb), sizeof(cb));
409 ret = qdisc_enqueue(skb, child, to_free);
410 if (likely(ret == NET_XMIT_SUCCESS)) {
411 sch->qstats.backlog += len;
413 increment_qlen(&cb, q);
414 } else if (net_xmit_drop_count(ret)) {
415 q->stats.childdrop++;
416 qdisc_qstats_drop(sch);
421 qdisc_drop(skb, sch, to_free);
424 if (ret & __NET_XMIT_BYPASS)
425 qdisc_qstats_drop(sch);
430 static struct sk_buff *sfb_dequeue(struct Qdisc *sch)
432 struct sfb_sched_data *q = qdisc_priv(sch);
433 struct Qdisc *child = q->qdisc;
436 skb = child->dequeue(q->qdisc);
439 qdisc_bstats_update(sch, skb);
440 qdisc_qstats_backlog_dec(sch, skb);
442 decrement_qlen(skb, q);
448 static struct sk_buff *sfb_peek(struct Qdisc *sch)
450 struct sfb_sched_data *q = qdisc_priv(sch);
451 struct Qdisc *child = q->qdisc;
453 return child->ops->peek(child);
456 /* No sfb_drop -- impossible since the child doesn't return the dropped skb. */
458 static void sfb_reset(struct Qdisc *sch)
460 struct sfb_sched_data *q = qdisc_priv(sch);
462 qdisc_reset(q->qdisc);
463 sch->qstats.backlog = 0;
466 q->double_buffering = false;
467 sfb_zero_all_buckets(q);
468 sfb_init_perturbation(0, q);
471 static void sfb_destroy(struct Qdisc *sch)
473 struct sfb_sched_data *q = qdisc_priv(sch);
475 tcf_block_put(q->block);
479 static const struct nla_policy sfb_policy[TCA_SFB_MAX + 1] = {
480 [TCA_SFB_PARMS] = { .len = sizeof(struct tc_sfb_qopt) },
483 static const struct tc_sfb_qopt sfb_default_ops = {
484 .rehash_interval = 600 * MSEC_PER_SEC,
485 .warmup_time = 60 * MSEC_PER_SEC,
489 .increment = (SFB_MAX_PROB + 500) / 1000, /* 0.1 % */
490 .decrement = (SFB_MAX_PROB + 3000) / 6000,
495 static int sfb_change(struct Qdisc *sch, struct nlattr *opt,
496 struct netlink_ext_ack *extack)
498 struct sfb_sched_data *q = qdisc_priv(sch);
500 struct nlattr *tb[TCA_SFB_MAX + 1];
501 const struct tc_sfb_qopt *ctl = &sfb_default_ops;
506 err = nla_parse_nested(tb, TCA_SFB_MAX, opt, sfb_policy, NULL);
510 if (tb[TCA_SFB_PARMS] == NULL)
513 ctl = nla_data(tb[TCA_SFB_PARMS]);
518 limit = qdisc_dev(sch)->tx_queue_len;
520 child = fifo_create_dflt(sch, &pfifo_qdisc_ops, limit, extack);
522 return PTR_ERR(child);
524 if (child != &noop_qdisc)
525 qdisc_hash_add(child, true);
528 qdisc_tree_reduce_backlog(q->qdisc, q->qdisc->q.qlen,
529 q->qdisc->qstats.backlog);
533 q->rehash_interval = msecs_to_jiffies(ctl->rehash_interval);
534 q->warmup_time = msecs_to_jiffies(ctl->warmup_time);
535 q->rehash_time = jiffies;
537 q->increment = ctl->increment;
538 q->decrement = ctl->decrement;
540 q->bin_size = ctl->bin_size;
541 q->penalty_rate = ctl->penalty_rate;
542 q->penalty_burst = ctl->penalty_burst;
543 q->tokens_avail = ctl->penalty_burst;
544 q->token_time = jiffies;
547 q->double_buffering = false;
548 sfb_zero_all_buckets(q);
549 sfb_init_perturbation(0, q);
550 sfb_init_perturbation(1, q);
552 sch_tree_unlock(sch);
557 static int sfb_init(struct Qdisc *sch, struct nlattr *opt,
558 struct netlink_ext_ack *extack)
560 struct sfb_sched_data *q = qdisc_priv(sch);
563 err = tcf_block_get(&q->block, &q->filter_list, sch, extack);
567 q->qdisc = &noop_qdisc;
568 return sfb_change(sch, opt, extack);
571 static int sfb_dump(struct Qdisc *sch, struct sk_buff *skb)
573 struct sfb_sched_data *q = qdisc_priv(sch);
575 struct tc_sfb_qopt opt = {
576 .rehash_interval = jiffies_to_msecs(q->rehash_interval),
577 .warmup_time = jiffies_to_msecs(q->warmup_time),
580 .bin_size = q->bin_size,
581 .increment = q->increment,
582 .decrement = q->decrement,
583 .penalty_rate = q->penalty_rate,
584 .penalty_burst = q->penalty_burst,
587 sch->qstats.backlog = q->qdisc->qstats.backlog;
588 opts = nla_nest_start(skb, TCA_OPTIONS);
590 goto nla_put_failure;
591 if (nla_put(skb, TCA_SFB_PARMS, sizeof(opt), &opt))
592 goto nla_put_failure;
593 return nla_nest_end(skb, opts);
596 nla_nest_cancel(skb, opts);
600 static int sfb_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
602 struct sfb_sched_data *q = qdisc_priv(sch);
603 struct tc_sfb_xstats st = {
604 .earlydrop = q->stats.earlydrop,
605 .penaltydrop = q->stats.penaltydrop,
606 .bucketdrop = q->stats.bucketdrop,
607 .queuedrop = q->stats.queuedrop,
608 .childdrop = q->stats.childdrop,
609 .marked = q->stats.marked,
612 st.maxqlen = sfb_compute_qlen(&st.maxprob, &st.avgprob, q);
614 return gnet_stats_copy_app(d, &st, sizeof(st));
617 static int sfb_dump_class(struct Qdisc *sch, unsigned long cl,
618 struct sk_buff *skb, struct tcmsg *tcm)
623 static int sfb_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
624 struct Qdisc **old, struct netlink_ext_ack *extack)
626 struct sfb_sched_data *q = qdisc_priv(sch);
631 *old = qdisc_replace(sch, new, &q->qdisc);
635 static struct Qdisc *sfb_leaf(struct Qdisc *sch, unsigned long arg)
637 struct sfb_sched_data *q = qdisc_priv(sch);
642 static unsigned long sfb_find(struct Qdisc *sch, u32 classid)
647 static void sfb_unbind(struct Qdisc *sch, unsigned long arg)
651 static int sfb_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
652 struct nlattr **tca, unsigned long *arg,
653 struct netlink_ext_ack *extack)
658 static int sfb_delete(struct Qdisc *sch, unsigned long cl)
663 static void sfb_walk(struct Qdisc *sch, struct qdisc_walker *walker)
666 if (walker->count >= walker->skip)
667 if (walker->fn(sch, 1, walker) < 0) {
675 static struct tcf_block *sfb_tcf_block(struct Qdisc *sch, unsigned long cl,
676 struct netlink_ext_ack *extack)
678 struct sfb_sched_data *q = qdisc_priv(sch);
685 static unsigned long sfb_bind(struct Qdisc *sch, unsigned long parent,
692 static const struct Qdisc_class_ops sfb_class_ops = {
696 .change = sfb_change_class,
697 .delete = sfb_delete,
699 .tcf_block = sfb_tcf_block,
700 .bind_tcf = sfb_bind,
701 .unbind_tcf = sfb_unbind,
702 .dump = sfb_dump_class,
705 static struct Qdisc_ops sfb_qdisc_ops __read_mostly = {
707 .priv_size = sizeof(struct sfb_sched_data),
708 .cl_ops = &sfb_class_ops,
709 .enqueue = sfb_enqueue,
710 .dequeue = sfb_dequeue,
714 .destroy = sfb_destroy,
715 .change = sfb_change,
717 .dump_stats = sfb_dump_stats,
718 .owner = THIS_MODULE,
721 static int __init sfb_module_init(void)
723 return register_qdisc(&sfb_qdisc_ops);
726 static void __exit sfb_module_exit(void)
728 unregister_qdisc(&sfb_qdisc_ops);
731 module_init(sfb_module_init)
732 module_exit(sfb_module_exit)
734 MODULE_DESCRIPTION("Stochastic Fair Blue queue discipline");
735 MODULE_AUTHOR("Juliusz Chroboczek");
736 MODULE_AUTHOR("Eric Dumazet");
737 MODULE_LICENSE("GPL");