- 根目录:
- net
- sched
- sch_sfb.c
/*
* 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 *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)
{
BUILD_BUG_ON(sizeof(skb->cb) <
sizeof(struct qdisc_skb_cb) + 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 = net_random();
}
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 sfb_sched_data *q,
int *qerr, u32 *salt)
{
struct tcf_result res;
int result;
result = tc_classify(skb, q->filter_list, &res);
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 sfb_sched_data *q = qdisc_priv(sch);
struct Qdisc *child = q->qdisc;
int i;
u32 p_min = ~0;
u32 minqlen = ~0;
u32 r, slot, salt, sfbhash;
int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
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;
}
}
if (q->filter_list) {
/* If using external classifiers, get result and record it. */
if (!sfb_classify(skb, q, &ret, &salt))
goto other_drop;
} else {
salt = skb_get_rxhash(skb);
}
slot = q->slot;
sfbhash = jhash_1word(salt, 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 || sch->q.qlen >= q->limit)) {
sch->qstats.overlimits++;
if (minqlen >= q->max)
q->stats.bucketdrop++;
else
q->stats.queuedrop++;
goto drop;
}
if (unlikely(p_min >= SFB_MAX_PROB)) {
/* Inelastic flow */
if (q->double_buffering) {
sfbhash = jhash_1word(salt, 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)) {
sch->qstats.overlimits++;
q->stats.penaltydrop++;
goto drop;
}
goto enqueue;
}
r = net_random() & 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);
if (likely(ret == NET_XMIT_SUCCESS)) {
sch->q.qlen++;
increment_qlen(skb, q);
} else if (net_xmit_drop_count(ret)) {
q->stats.childdrop++;
sch->qstats.drops++;
}
return ret;
drop:
qdisc_drop(skb, sch);
return NET_XMIT_CN;
other_drop:
if (ret & __NET_XMIT_BYPASS)
sch->qstats.drops++;
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);
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->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 = max_t(u32, qdisc_dev(sch)->tx_queue_len, 1);
child = fifo_create_dflt(sch, &pfifo_qdisc_ops, limit);
if (IS_ERR(child))
return PTR_ERR(child);
sch_tree_lock(sch);
qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen);
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);
NLA_PUT(skb, TCA_SFB_PARMS, sizeof(opt), &opt);
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;
sch_tree_lock(sch);
*old = q->qdisc;
q->qdisc = new;
qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
qdisc_reset(*old);
sch_tree_unlock(sch);
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 **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");