/* * net/sched/sch_sfb.c Stochastic Fair Blue * * Copyright (c) 2008-2011 Juliusz Chroboczek <jch@pps.jussieu.fr> * Copyright (c) 2011 Eric Dumazet <eric.dumazet@gmail.com> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * version 2 as published by the Free Software Foundation. * * W. Feng, D. Kandlur, D. Saha, K. Shin. Blue: * A New Class of Active Queue Management Algorithms. * U. Michigan CSE-TR-387-99, April 1999. * * http://www.thefengs.com/wuchang/blue/CSE-TR-387-99.pdf * */ #include <linux/module.h> #include <linux/types.h> #include <linux/kernel.h> #include <linux/errno.h> #include <linux/skbuff.h> #include <linux/random.h> #include <linux/jhash.h> #include <net/ip.h> #include <net/pkt_sched.h> #include <net/inet_ecn.h> /* * SFB uses two B[l][n] : L x N arrays of bins (L levels, N bins per level) * This implementation uses L = 8 and N = 16 * This permits us to split one 32bit hash (provided per packet by rxhash or * external classifier) into 8 subhashes of 4 bits. */ #define SFB_BUCKET_SHIFT 4 #define SFB_NUMBUCKETS (1 << SFB_BUCKET_SHIFT) /* N bins per Level */ #define SFB_BUCKET_MASK (SFB_NUMBUCKETS - 1) #define SFB_LEVELS (32 / SFB_BUCKET_SHIFT) /* L */ /* SFB algo uses a virtual queue, named "bin" */ struct sfb_bucket { u16 qlen; /* length of virtual queue */ u16 p_mark; /* marking probability */ }; /* We use a double buffering right before hash change * (Section 4.4 of SFB reference : moving hash functions) */ struct sfb_bins { u32 perturbation; /* jhash perturbation */ struct sfb_bucket bins[SFB_LEVELS][SFB_NUMBUCKETS]; }; struct sfb_sched_data { struct Qdisc *qdisc; struct tcf_proto __rcu *filter_list; unsigned long rehash_interval; unsigned long warmup_time; /* double buffering warmup time in jiffies */ u32 max; u32 bin_size; /* maximum queue length per bin */ u32 increment; /* d1 */ u32 decrement; /* d2 */ u32 limit; /* HARD maximal queue length */ u32 penalty_rate; u32 penalty_burst; u32 tokens_avail; unsigned long rehash_time; unsigned long token_time; u8 slot; /* current active bins (0 or 1) */ bool double_buffering; struct sfb_bins bins[2]; struct { u32 earlydrop; u32 penaltydrop; u32 bucketdrop; u32 queuedrop; u32 childdrop; /* drops in child qdisc */ u32 marked; /* ECN mark */ } stats; }; /* * Each queued skb might be hashed on one or two bins * We store in skb_cb the two hash values. * (A zero value means double buffering was not used) */ struct sfb_skb_cb { u32 hashes[2]; }; static inline struct sfb_skb_cb *sfb_skb_cb(const struct sk_buff *skb) { qdisc_cb_private_validate(skb, sizeof(struct sfb_skb_cb)); return (struct sfb_skb_cb *)qdisc_skb_cb(skb)->data; } /* * If using 'internal' SFB flow classifier, hash comes from skb rxhash * If using external classifier, hash comes from the classid. */ static u32 sfb_hash(const struct sk_buff *skb, u32 slot) { return sfb_skb_cb(skb)->hashes[slot]; } /* Probabilities are coded as Q0.16 fixed-point values, * with 0xFFFF representing 65535/65536 (almost 1.0) * Addition and subtraction are saturating in [0, 65535] */ static u32 prob_plus(u32 p1, u32 p2) { u32 res = p1 + p2; return min_t(u32, res, SFB_MAX_PROB); } static u32 prob_minus(u32 p1, u32 p2) { return p1 > p2 ? p1 - p2 : 0; } static void increment_one_qlen(u32 sfbhash, u32 slot, struct sfb_sched_data *q) { int i; struct sfb_bucket *b = &q->bins[slot].bins[0][0]; for (i = 0; i < SFB_LEVELS; i++) { u32 hash = sfbhash & SFB_BUCKET_MASK; sfbhash >>= SFB_BUCKET_SHIFT; if (b[hash].qlen < 0xFFFF) b[hash].qlen++; b += SFB_NUMBUCKETS; /* next level */ } } static void increment_qlen(const struct sk_buff *skb, struct sfb_sched_data *q) { u32 sfbhash; sfbhash = sfb_hash(skb, 0); if (sfbhash) increment_one_qlen(sfbhash, 0, q); sfbhash = sfb_hash(skb, 1); if (sfbhash) increment_one_qlen(sfbhash, 1, q); } static void decrement_one_qlen(u32 sfbhash, u32 slot, struct sfb_sched_data *q) { int i; struct sfb_bucket *b = &q->bins[slot].bins[0][0]; for (i = 0; i < SFB_LEVELS; i++) { u32 hash = sfbhash & SFB_BUCKET_MASK; sfbhash >>= SFB_BUCKET_SHIFT; if (b[hash].qlen > 0) b[hash].qlen--; b += SFB_NUMBUCKETS; /* next level */ } } static void decrement_qlen(const struct sk_buff *skb, struct sfb_sched_data *q) { u32 sfbhash; sfbhash = sfb_hash(skb, 0); if (sfbhash) decrement_one_qlen(sfbhash, 0, q); sfbhash = sfb_hash(skb, 1); if (sfbhash) decrement_one_qlen(sfbhash, 1, q); } static void decrement_prob(struct sfb_bucket *b, struct sfb_sched_data *q) { b->p_mark = prob_minus(b->p_mark, q->decrement); } static void increment_prob(struct sfb_bucket *b, struct sfb_sched_data *q) { b->p_mark = prob_plus(b->p_mark, q->increment); } static void sfb_zero_all_buckets(struct sfb_sched_data *q) { memset(&q->bins, 0, sizeof(q->bins)); } /* * compute max qlen, max p_mark, and avg p_mark */ static u32 sfb_compute_qlen(u32 *prob_r, u32 *avgpm_r, const struct sfb_sched_data *q) { int i; u32 qlen = 0, prob = 0, totalpm = 0; const struct sfb_bucket *b = &q->bins[q->slot].bins[0][0]; for (i = 0; i < SFB_LEVELS * SFB_NUMBUCKETS; i++) { if (qlen < b->qlen) qlen = b->qlen; totalpm += b->p_mark; if (prob < b->p_mark) prob = b->p_mark; b++; } *prob_r = prob; *avgpm_r = totalpm / (SFB_LEVELS * SFB_NUMBUCKETS); return qlen; } static void sfb_init_perturbation(u32 slot, struct sfb_sched_data *q) { q->bins[slot].perturbation = prandom_u32(); } static void sfb_swap_slot(struct sfb_sched_data *q) { sfb_init_perturbation(q->slot, q); q->slot ^= 1; q->double_buffering = false; } /* Non elastic flows are allowed to use part of the bandwidth, expressed * in "penalty_rate" packets per second, with "penalty_burst" burst */ static bool sfb_rate_limit(struct sk_buff *skb, struct sfb_sched_data *q) { if (q->penalty_rate == 0 || q->penalty_burst == 0) return true; if (q->tokens_avail < 1) { unsigned long age = min(10UL * HZ, jiffies - q->token_time); q->tokens_avail = (age * q->penalty_rate) / HZ; if (q->tokens_avail > q->penalty_burst) q->tokens_avail = q->penalty_burst; q->token_time = jiffies; if (q->tokens_avail < 1) return true; } q->tokens_avail--; return false; } static bool sfb_classify(struct sk_buff *skb, struct tcf_proto *fl, int *qerr, u32 *salt) { struct tcf_result res; int result; result = tc_classify(skb, fl, &res, false); if (result >= 0) { #ifdef CONFIG_NET_CLS_ACT switch (result) { case TC_ACT_STOLEN: case TC_ACT_QUEUED: *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN; case TC_ACT_SHOT: return false; } #endif *salt = TC_H_MIN(res.classid); return true; } return false; } static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free) { struct sfb_sched_data *q = qdisc_priv(sch); struct Qdisc *child = q->qdisc; struct tcf_proto *fl; int i; u32 p_min = ~0; u32 minqlen = ~0; u32 r, sfbhash; u32 slot = q->slot; int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS; if (unlikely(sch->q.qlen >= q->limit)) { qdisc_qstats_overlimit(sch); q->stats.queuedrop++; goto drop; } if (q->rehash_interval > 0) { unsigned long limit = q->rehash_time + q->rehash_interval; if (unlikely(time_after(jiffies, limit))) { sfb_swap_slot(q); q->rehash_time = jiffies; } else if (unlikely(!q->double_buffering && q->warmup_time > 0 && time_after(jiffies, limit - q->warmup_time))) { q->double_buffering = true; } } fl = rcu_dereference_bh(q->filter_list); if (fl) { u32 salt; /* If using external classifiers, get result and record it. */ if (!sfb_classify(skb, fl, &ret, &salt)) goto other_drop; sfbhash = jhash_1word(salt, q->bins[slot].perturbation); } else { sfbhash = skb_get_hash_perturb(skb, q->bins[slot].perturbation); } if (!sfbhash) sfbhash = 1; sfb_skb_cb(skb)->hashes[slot] = sfbhash; for (i = 0; i < SFB_LEVELS; i++) { u32 hash = sfbhash & SFB_BUCKET_MASK; struct sfb_bucket *b = &q->bins[slot].bins[i][hash]; sfbhash >>= SFB_BUCKET_SHIFT; if (b->qlen == 0) decrement_prob(b, q); else if (b->qlen >= q->bin_size) increment_prob(b, q); if (minqlen > b->qlen) minqlen = b->qlen; if (p_min > b->p_mark) p_min = b->p_mark; } slot ^= 1; sfb_skb_cb(skb)->hashes[slot] = 0; if (unlikely(minqlen >= q->max)) { qdisc_qstats_overlimit(sch); q->stats.bucketdrop++; goto drop; } if (unlikely(p_min >= SFB_MAX_PROB)) { /* Inelastic flow */ if (q->double_buffering) { sfbhash = skb_get_hash_perturb(skb, q->bins[slot].perturbation); if (!sfbhash) sfbhash = 1; sfb_skb_cb(skb)->hashes[slot] = sfbhash; for (i = 0; i < SFB_LEVELS; i++) { u32 hash = sfbhash & SFB_BUCKET_MASK; struct sfb_bucket *b = &q->bins[slot].bins[i][hash]; sfbhash >>= SFB_BUCKET_SHIFT; if (b->qlen == 0) decrement_prob(b, q); else if (b->qlen >= q->bin_size) increment_prob(b, q); } } if (sfb_rate_limit(skb, q)) { qdisc_qstats_overlimit(sch); q->stats.penaltydrop++; goto drop; } goto enqueue; } r = prandom_u32() & SFB_MAX_PROB; if (unlikely(r < p_min)) { if (unlikely(p_min > SFB_MAX_PROB / 2)) { /* If we're marking that many packets, then either * this flow is unresponsive, or we're badly congested. * In either case, we want to start dropping packets. */ if (r < (p_min - SFB_MAX_PROB / 2) * 2) { q->stats.earlydrop++; goto drop; } } if (INET_ECN_set_ce(skb)) { q->stats.marked++; } else { q->stats.earlydrop++; goto drop; } } enqueue: ret = qdisc_enqueue(skb, child, to_free); if (likely(ret == NET_XMIT_SUCCESS)) { qdisc_qstats_backlog_inc(sch, skb); sch->q.qlen++; increment_qlen(skb, q); } else if (net_xmit_drop_count(ret)) { q->stats.childdrop++; qdisc_qstats_drop(sch); } return ret; drop: qdisc_drop(skb, sch, to_free); return NET_XMIT_CN; other_drop: if (ret & __NET_XMIT_BYPASS) qdisc_qstats_drop(sch); kfree_skb(skb); return ret; } static struct sk_buff *sfb_dequeue(struct Qdisc *sch) { struct sfb_sched_data *q = qdisc_priv(sch); struct Qdisc *child = q->qdisc; struct sk_buff *skb; skb = child->dequeue(q->qdisc); if (skb) { qdisc_bstats_update(sch, skb); qdisc_qstats_backlog_dec(sch, skb); sch->q.qlen--; decrement_qlen(skb, q); } return skb; } static struct sk_buff *sfb_peek(struct Qdisc *sch) { struct sfb_sched_data *q = qdisc_priv(sch); struct Qdisc *child = q->qdisc; return child->ops->peek(child); } /* No sfb_drop -- impossible since the child doesn't return the dropped skb. */ static void sfb_reset(struct Qdisc *sch) { struct sfb_sched_data *q = qdisc_priv(sch); qdisc_reset(q->qdisc); sch->qstats.backlog = 0; sch->q.qlen = 0; q->slot = 0; q->double_buffering = false; sfb_zero_all_buckets(q); sfb_init_perturbation(0, q); } static void sfb_destroy(struct Qdisc *sch) { struct sfb_sched_data *q = qdisc_priv(sch); tcf_destroy_chain(&q->filter_list); qdisc_destroy(q->qdisc); } static const struct nla_policy sfb_policy[TCA_SFB_MAX + 1] = { [TCA_SFB_PARMS] = { .len = sizeof(struct tc_sfb_qopt) }, }; static const struct tc_sfb_qopt sfb_default_ops = { .rehash_interval = 600 * MSEC_PER_SEC, .warmup_time = 60 * MSEC_PER_SEC, .limit = 0, .max = 25, .bin_size = 20, .increment = (SFB_MAX_PROB + 500) / 1000, /* 0.1 % */ .decrement = (SFB_MAX_PROB + 3000) / 6000, .penalty_rate = 10, .penalty_burst = 20, }; static int sfb_change(struct Qdisc *sch, struct nlattr *opt) { struct sfb_sched_data *q = qdisc_priv(sch); struct Qdisc *child; struct nlattr *tb[TCA_SFB_MAX + 1]; const struct tc_sfb_qopt *ctl = &sfb_default_ops; u32 limit; int err; if (opt) { err = nla_parse_nested(tb, TCA_SFB_MAX, opt, sfb_policy); if (err < 0) return -EINVAL; if (tb[TCA_SFB_PARMS] == NULL) return -EINVAL; ctl = nla_data(tb[TCA_SFB_PARMS]); } limit = ctl->limit; if (limit == 0) limit = qdisc_dev(sch)->tx_queue_len; child = fifo_create_dflt(sch, &pfifo_qdisc_ops, limit); if (IS_ERR(child)) return PTR_ERR(child); sch_tree_lock(sch); qdisc_tree_reduce_backlog(q->qdisc, q->qdisc->q.qlen, q->qdisc->qstats.backlog); qdisc_destroy(q->qdisc); q->qdisc = child; q->rehash_interval = msecs_to_jiffies(ctl->rehash_interval); q->warmup_time = msecs_to_jiffies(ctl->warmup_time); q->rehash_time = jiffies; q->limit = limit; q->increment = ctl->increment; q->decrement = ctl->decrement; q->max = ctl->max; q->bin_size = ctl->bin_size; q->penalty_rate = ctl->penalty_rate; q->penalty_burst = ctl->penalty_burst; q->tokens_avail = ctl->penalty_burst; q->token_time = jiffies; q->slot = 0; q->double_buffering = false; sfb_zero_all_buckets(q); sfb_init_perturbation(0, q); sfb_init_perturbation(1, q); sch_tree_unlock(sch); return 0; } static int sfb_init(struct Qdisc *sch, struct nlattr *opt) { struct sfb_sched_data *q = qdisc_priv(sch); q->qdisc = &noop_qdisc; return sfb_change(sch, opt); } static int sfb_dump(struct Qdisc *sch, struct sk_buff *skb) { struct sfb_sched_data *q = qdisc_priv(sch); struct nlattr *opts; struct tc_sfb_qopt opt = { .rehash_interval = jiffies_to_msecs(q->rehash_interval), .warmup_time = jiffies_to_msecs(q->warmup_time), .limit = q->limit, .max = q->max, .bin_size = q->bin_size, .increment = q->increment, .decrement = q->decrement, .penalty_rate = q->penalty_rate, .penalty_burst = q->penalty_burst, }; sch->qstats.backlog = q->qdisc->qstats.backlog; opts = nla_nest_start(skb, TCA_OPTIONS); if (opts == NULL) goto nla_put_failure; if (nla_put(skb, TCA_SFB_PARMS, sizeof(opt), &opt)) goto nla_put_failure; return nla_nest_end(skb, opts); nla_put_failure: nla_nest_cancel(skb, opts); return -EMSGSIZE; } static int sfb_dump_stats(struct Qdisc *sch, struct gnet_dump *d) { struct sfb_sched_data *q = qdisc_priv(sch); struct tc_sfb_xstats st = { .earlydrop = q->stats.earlydrop, .penaltydrop = q->stats.penaltydrop, .bucketdrop = q->stats.bucketdrop, .queuedrop = q->stats.queuedrop, .childdrop = q->stats.childdrop, .marked = q->stats.marked, }; st.maxqlen = sfb_compute_qlen(&st.maxprob, &st.avgprob, q); return gnet_stats_copy_app(d, &st, sizeof(st)); } static int sfb_dump_class(struct Qdisc *sch, unsigned long cl, struct sk_buff *skb, struct tcmsg *tcm) { return -ENOSYS; } static int sfb_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new, struct Qdisc **old) { struct sfb_sched_data *q = qdisc_priv(sch); if (new == NULL) new = &noop_qdisc; *old = qdisc_replace(sch, new, &q->qdisc); return 0; } static struct Qdisc *sfb_leaf(struct Qdisc *sch, unsigned long arg) { struct sfb_sched_data *q = qdisc_priv(sch); return q->qdisc; } static unsigned long sfb_get(struct Qdisc *sch, u32 classid) { return 1; } static void sfb_put(struct Qdisc *sch, unsigned long arg) { } static int sfb_change_class(struct Qdisc *sch, u32 classid, u32 parentid, struct nlattr **tca, unsigned long *arg) { return -ENOSYS; } static int sfb_delete(struct Qdisc *sch, unsigned long cl) { return -ENOSYS; } static void sfb_walk(struct Qdisc *sch, struct qdisc_walker *walker) { if (!walker->stop) { if (walker->count >= walker->skip) if (walker->fn(sch, 1, walker) < 0) { walker->stop = 1; return; } walker->count++; } } static struct tcf_proto __rcu **sfb_find_tcf(struct Qdisc *sch, unsigned long cl) { struct sfb_sched_data *q = qdisc_priv(sch); if (cl) return NULL; return &q->filter_list; } static unsigned long sfb_bind(struct Qdisc *sch, unsigned long parent, u32 classid) { return 0; } static const struct Qdisc_class_ops sfb_class_ops = { .graft = sfb_graft, .leaf = sfb_leaf, .get = sfb_get, .put = sfb_put, .change = sfb_change_class, .delete = sfb_delete, .walk = sfb_walk, .tcf_chain = sfb_find_tcf, .bind_tcf = sfb_bind, .unbind_tcf = sfb_put, .dump = sfb_dump_class, }; static struct Qdisc_ops sfb_qdisc_ops __read_mostly = { .id = "sfb", .priv_size = sizeof(struct sfb_sched_data), .cl_ops = &sfb_class_ops, .enqueue = sfb_enqueue, .dequeue = sfb_dequeue, .peek = sfb_peek, .init = sfb_init, .reset = sfb_reset, .destroy = sfb_destroy, .change = sfb_change, .dump = sfb_dump, .dump_stats = sfb_dump_stats, .owner = THIS_MODULE, }; static int __init sfb_module_init(void) { return register_qdisc(&sfb_qdisc_ops); } static void __exit sfb_module_exit(void) { unregister_qdisc(&sfb_qdisc_ops); } module_init(sfb_module_init) module_exit(sfb_module_exit) MODULE_DESCRIPTION("Stochastic Fair Blue queue discipline"); MODULE_AUTHOR("Juliusz Chroboczek"); MODULE_AUTHOR("Eric Dumazet"); MODULE_LICENSE("GPL");