sched: CHOKe flow scheduler

CHOKe ("CHOose and Kill" or "CHOose and Keep") is an alternative
packet scheduler based on the Random Exponential Drop (RED) algorithm.

The core idea is:
  For every packet arrival:
  	Calculate Qave
	if (Qave < minth)
	     Queue the new packet
	else
	     Select randomly a packet from the queue
	     if (both packets from same flow)
	     then Drop both the packets
	     else if (Qave > maxth)
	          Drop packet
	     else
	       	  Admit packet with proability p (same as RED)

See also:
  Rong Pan, Balaji Prabhakar, Konstantinos Psounis, "CHOKe: a stateless active
   queue management scheme for approximating fair bandwidth allocation",
  Proceeding of INFOCOM'2000, March 2000.

Help from:
     Eric Dumazet <eric.dumazet@gmail.com>
     Patrick McHardy <kaber@trash.net>

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
stephen hemminger 2011-02-02 15:21:10 +00:00 committed by David S. Miller
parent 119b3d3869
commit 45e144339a
4 changed files with 718 additions and 0 deletions

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@ -247,6 +247,35 @@ struct tc_gred_sopt {
__u16 pad1; __u16 pad1;
}; };
/* CHOKe section */
enum {
TCA_CHOKE_UNSPEC,
TCA_CHOKE_PARMS,
TCA_CHOKE_STAB,
__TCA_CHOKE_MAX,
};
#define TCA_CHOKE_MAX (__TCA_CHOKE_MAX - 1)
struct tc_choke_qopt {
__u32 limit; /* Hard queue length (packets) */
__u32 qth_min; /* Min average threshold (packets) */
__u32 qth_max; /* Max average threshold (packets) */
unsigned char Wlog; /* log(W) */
unsigned char Plog; /* log(P_max/(qth_max-qth_min)) */
unsigned char Scell_log; /* cell size for idle damping */
unsigned char flags; /* see RED flags */
};
struct tc_choke_xstats {
__u32 early; /* Early drops */
__u32 pdrop; /* Drops due to queue limits */
__u32 other; /* Drops due to drop() calls */
__u32 marked; /* Marked packets */
__u32 matched; /* Drops due to flow match */
};
/* HTB section */ /* HTB section */
#define TC_HTB_NUMPRIO 8 #define TC_HTB_NUMPRIO 8
#define TC_HTB_MAXDEPTH 8 #define TC_HTB_MAXDEPTH 8

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@ -217,6 +217,17 @@ config NET_SCH_MQPRIO
If unsure, say N. If unsure, say N.
config NET_SCH_CHOKE
tristate "CHOose and Keep responsive flow scheduler (CHOKE)"
help
Say Y here if you want to use the CHOKe packet scheduler (CHOose
and Keep for responsive flows, CHOose and Kill for unresponsive
flows). This is a variation of RED which trys to penalize flows
that monopolize the queue.
To compile this code as a module, choose M here: the
module will be called sch_choke.
config NET_SCH_INGRESS config NET_SCH_INGRESS
tristate "Ingress Qdisc" tristate "Ingress Qdisc"
depends on NET_CLS_ACT depends on NET_CLS_ACT

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@ -33,6 +33,8 @@ obj-$(CONFIG_NET_SCH_ATM) += sch_atm.o
obj-$(CONFIG_NET_SCH_NETEM) += sch_netem.o obj-$(CONFIG_NET_SCH_NETEM) += sch_netem.o
obj-$(CONFIG_NET_SCH_DRR) += sch_drr.o obj-$(CONFIG_NET_SCH_DRR) += sch_drr.o
obj-$(CONFIG_NET_SCH_MQPRIO) += sch_mqprio.o obj-$(CONFIG_NET_SCH_MQPRIO) += sch_mqprio.o
obj-$(CONFIG_NET_SCH_CHOKE) += sch_choke.o
obj-$(CONFIG_NET_CLS_U32) += cls_u32.o obj-$(CONFIG_NET_CLS_U32) += cls_u32.o
obj-$(CONFIG_NET_CLS_ROUTE4) += cls_route.o obj-$(CONFIG_NET_CLS_ROUTE4) += cls_route.o
obj-$(CONFIG_NET_CLS_FW) += cls_fw.o obj-$(CONFIG_NET_CLS_FW) += cls_fw.o

676
net/sched/sch_choke.c Normal file
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@ -0,0 +1,676 @@
/*
* net/sched/sch_choke.c CHOKE scheduler
*
* Copyright (c) 2011 Stephen Hemminger <shemminger@vyatta.com>
* 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.
*
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/reciprocal_div.h>
#include <net/pkt_sched.h>
#include <net/inet_ecn.h>
#include <net/red.h>
#include <linux/ip.h>
#include <net/ip.h>
#include <linux/ipv6.h>
#include <net/ipv6.h>
/*
CHOKe stateless AQM for fair bandwidth allocation
=================================================
CHOKe (CHOose and Keep for responsive flows, CHOose and Kill for
unresponsive flows) is a variant of RED that penalizes misbehaving flows but
maintains no flow state. The difference from RED is an additional step
during the enqueuing process. If average queue size is over the
low threshold (qmin), a packet is chosen at random from the queue.
If both the new and chosen packet are from the same flow, both
are dropped. Unlike RED, CHOKe is not really a "classful" qdisc because it
needs to access packets in queue randomly. It has a minimal class
interface to allow overriding the builtin flow classifier with
filters.
Source:
R. Pan, B. Prabhakar, and K. Psounis, "CHOKe, A Stateless
Active Queue Management Scheme for Approximating Fair Bandwidth Allocation",
IEEE INFOCOM, 2000.
A. Tang, J. Wang, S. Low, "Understanding CHOKe: Throughput and Spatial
Characteristics", IEEE/ACM Transactions on Networking, 2004
*/
/* Upper bound on size of sk_buff table (packets) */
#define CHOKE_MAX_QUEUE (128*1024 - 1)
struct choke_sched_data {
/* Parameters */
u32 limit;
unsigned char flags;
struct red_parms parms;
/* Variables */
struct tcf_proto *filter_list;
struct {
u32 prob_drop; /* Early probability drops */
u32 prob_mark; /* Early probability marks */
u32 forced_drop; /* Forced drops, qavg > max_thresh */
u32 forced_mark; /* Forced marks, qavg > max_thresh */
u32 pdrop; /* Drops due to queue limits */
u32 other; /* Drops due to drop() calls */
u32 matched; /* Drops to flow match */
} stats;
unsigned int head;
unsigned int tail;
unsigned int tab_mask; /* size - 1 */
struct sk_buff **tab;
};
/* deliver a random number between 0 and N - 1 */
static u32 random_N(unsigned int N)
{
return reciprocal_divide(random32(), N);
}
/* number of elements in queue including holes */
static unsigned int choke_len(const struct choke_sched_data *q)
{
return (q->tail - q->head) & q->tab_mask;
}
/* Is ECN parameter configured */
static int use_ecn(const struct choke_sched_data *q)
{
return q->flags & TC_RED_ECN;
}
/* Should packets over max just be dropped (versus marked) */
static int use_harddrop(const struct choke_sched_data *q)
{
return q->flags & TC_RED_HARDDROP;
}
/* Move head pointer forward to skip over holes */
static void choke_zap_head_holes(struct choke_sched_data *q)
{
do {
q->head = (q->head + 1) & q->tab_mask;
if (q->head == q->tail)
break;
} while (q->tab[q->head] == NULL);
}
/* Move tail pointer backwards to reuse holes */
static void choke_zap_tail_holes(struct choke_sched_data *q)
{
do {
q->tail = (q->tail - 1) & q->tab_mask;
if (q->head == q->tail)
break;
} while (q->tab[q->tail] == NULL);
}
/* Drop packet from queue array by creating a "hole" */
static void choke_drop_by_idx(struct Qdisc *sch, unsigned int idx)
{
struct choke_sched_data *q = qdisc_priv(sch);
struct sk_buff *skb = q->tab[idx];
q->tab[idx] = NULL;
if (idx == q->head)
choke_zap_head_holes(q);
if (idx == q->tail)
choke_zap_tail_holes(q);
sch->qstats.backlog -= qdisc_pkt_len(skb);
qdisc_drop(skb, sch);
qdisc_tree_decrease_qlen(sch, 1);
--sch->q.qlen;
}
/*
* Compare flow of two packets
* Returns true only if source and destination address and port match.
* false for special cases
*/
static bool choke_match_flow(struct sk_buff *skb1,
struct sk_buff *skb2)
{
int off1, off2, poff;
const u32 *ports1, *ports2;
u8 ip_proto;
__u32 hash1;
if (skb1->protocol != skb2->protocol)
return false;
/* Use hash value as quick check
* Assumes that __skb_get_rxhash makes IP header and ports linear
*/
hash1 = skb_get_rxhash(skb1);
if (!hash1 || hash1 != skb_get_rxhash(skb2))
return false;
/* Probably match, but be sure to avoid hash collisions */
off1 = skb_network_offset(skb1);
off2 = skb_network_offset(skb2);
switch (skb1->protocol) {
case __constant_htons(ETH_P_IP): {
const struct iphdr *ip1, *ip2;
ip1 = (const struct iphdr *) (skb1->data + off1);
ip2 = (const struct iphdr *) (skb2->data + off2);
ip_proto = ip1->protocol;
if (ip_proto != ip2->protocol ||
ip1->saddr != ip2->saddr || ip1->daddr != ip2->daddr)
return false;
if ((ip1->frag_off | ip2->frag_off) & htons(IP_MF | IP_OFFSET))
ip_proto = 0;
off1 += ip1->ihl * 4;
off2 += ip2->ihl * 4;
break;
}
case __constant_htons(ETH_P_IPV6): {
const struct ipv6hdr *ip1, *ip2;
ip1 = (const struct ipv6hdr *) (skb1->data + off1);
ip2 = (const struct ipv6hdr *) (skb2->data + off2);
ip_proto = ip1->nexthdr;
if (ip_proto != ip2->nexthdr ||
ipv6_addr_cmp(&ip1->saddr, &ip2->saddr) ||
ipv6_addr_cmp(&ip1->daddr, &ip2->daddr))
return false;
off1 += 40;
off2 += 40;
}
default: /* Maybe compare MAC header here? */
return false;
}
poff = proto_ports_offset(ip_proto);
if (poff < 0)
return true;
off1 += poff;
off2 += poff;
ports1 = (__force u32 *)(skb1->data + off1);
ports2 = (__force u32 *)(skb2->data + off2);
return *ports1 == *ports2;
}
static inline void choke_set_classid(struct sk_buff *skb, u16 classid)
{
*(unsigned int *)(qdisc_skb_cb(skb)->data) = classid;
}
static u16 choke_get_classid(const struct sk_buff *skb)
{
return *(unsigned int *)(qdisc_skb_cb(skb)->data);
}
/*
* Classify flow using either:
* 1. pre-existing classification result in skb
* 2. fast internal classification
* 3. use TC filter based classification
*/
static bool choke_classify(struct sk_buff *skb,
struct Qdisc *sch, int *qerr)
{
struct choke_sched_data *q = qdisc_priv(sch);
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
choke_set_classid(skb, TC_H_MIN(res.classid));
return true;
}
return false;
}
/*
* Select a packet at random from queue
* HACK: since queue can have holes from previous deletion; retry several
* times to find a random skb but then just give up and return the head
* Will return NULL if queue is empty (q->head == q->tail)
*/
static struct sk_buff *choke_peek_random(const struct choke_sched_data *q,
unsigned int *pidx)
{
struct sk_buff *skb;
int retrys = 3;
do {
*pidx = (q->head + random_N(choke_len(q))) & q->tab_mask;
skb = q->tab[*pidx];
if (skb)
return skb;
} while (--retrys > 0);
return q->tab[*pidx = q->head];
}
/*
* Compare new packet with random packet in queue
* returns true if matched and sets *pidx
*/
static bool choke_match_random(const struct choke_sched_data *q,
struct sk_buff *nskb,
unsigned int *pidx)
{
struct sk_buff *oskb;
if (q->head == q->tail)
return false;
oskb = choke_peek_random(q, pidx);
if (q->filter_list)
return choke_get_classid(nskb) == choke_get_classid(oskb);
return choke_match_flow(oskb, nskb);
}
static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch)
{
struct choke_sched_data *q = qdisc_priv(sch);
struct red_parms *p = &q->parms;
int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
if (q->filter_list) {
/* If using external classifiers, get result and record it. */
if (!choke_classify(skb, sch, &ret))
goto other_drop; /* Packet was eaten by filter */
}
/* Compute average queue usage (see RED) */
p->qavg = red_calc_qavg(p, sch->q.qlen);
if (red_is_idling(p))
red_end_of_idle_period(p);
/* Is queue small? */
if (p->qavg <= p->qth_min)
p->qcount = -1;
else {
unsigned int idx;
/* Draw a packet at random from queue and compare flow */
if (choke_match_random(q, skb, &idx)) {
q->stats.matched++;
choke_drop_by_idx(sch, idx);
goto congestion_drop;
}
/* Queue is large, always mark/drop */
if (p->qavg > p->qth_max) {
p->qcount = -1;
sch->qstats.overlimits++;
if (use_harddrop(q) || !use_ecn(q) ||
!INET_ECN_set_ce(skb)) {
q->stats.forced_drop++;
goto congestion_drop;
}
q->stats.forced_mark++;
} else if (++p->qcount) {
if (red_mark_probability(p, p->qavg)) {
p->qcount = 0;
p->qR = red_random(p);
sch->qstats.overlimits++;
if (!use_ecn(q) || !INET_ECN_set_ce(skb)) {
q->stats.prob_drop++;
goto congestion_drop;
}
q->stats.prob_mark++;
}
} else
p->qR = red_random(p);
}
/* Admit new packet */
if (sch->q.qlen < q->limit) {
q->tab[q->tail] = skb;
q->tail = (q->tail + 1) & q->tab_mask;
++sch->q.qlen;
sch->qstats.backlog += qdisc_pkt_len(skb);
return NET_XMIT_SUCCESS;
}
q->stats.pdrop++;
sch->qstats.drops++;
kfree_skb(skb);
return NET_XMIT_DROP;
congestion_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 *choke_dequeue(struct Qdisc *sch)
{
struct choke_sched_data *q = qdisc_priv(sch);
struct sk_buff *skb;
if (q->head == q->tail) {
if (!red_is_idling(&q->parms))
red_start_of_idle_period(&q->parms);
return NULL;
}
skb = q->tab[q->head];
q->tab[q->head] = NULL;
choke_zap_head_holes(q);
--sch->q.qlen;
sch->qstats.backlog -= qdisc_pkt_len(skb);
qdisc_bstats_update(sch, skb);
return skb;
}
static unsigned int choke_drop(struct Qdisc *sch)
{
struct choke_sched_data *q = qdisc_priv(sch);
unsigned int len;
len = qdisc_queue_drop(sch);
if (len > 0)
q->stats.other++;
else {
if (!red_is_idling(&q->parms))
red_start_of_idle_period(&q->parms);
}
return len;
}
static void choke_reset(struct Qdisc *sch)
{
struct choke_sched_data *q = qdisc_priv(sch);
red_restart(&q->parms);
}
static const struct nla_policy choke_policy[TCA_CHOKE_MAX + 1] = {
[TCA_CHOKE_PARMS] = { .len = sizeof(struct tc_red_qopt) },
[TCA_CHOKE_STAB] = { .len = RED_STAB_SIZE },
};
static void choke_free(void *addr)
{
if (addr) {
if (is_vmalloc_addr(addr))
vfree(addr);
else
kfree(addr);
}
}
static int choke_change(struct Qdisc *sch, struct nlattr *opt)
{
struct choke_sched_data *q = qdisc_priv(sch);
struct nlattr *tb[TCA_CHOKE_MAX + 1];
const struct tc_red_qopt *ctl;
int err;
struct sk_buff **old = NULL;
unsigned int mask;
if (opt == NULL)
return -EINVAL;
err = nla_parse_nested(tb, TCA_CHOKE_MAX, opt, choke_policy);
if (err < 0)
return err;
if (tb[TCA_CHOKE_PARMS] == NULL ||
tb[TCA_CHOKE_STAB] == NULL)
return -EINVAL;
ctl = nla_data(tb[TCA_CHOKE_PARMS]);
if (ctl->limit > CHOKE_MAX_QUEUE)
return -EINVAL;
mask = roundup_pow_of_two(ctl->limit + 1) - 1;
if (mask != q->tab_mask) {
struct sk_buff **ntab;
ntab = kcalloc(mask + 1, sizeof(struct sk_buff *), GFP_KERNEL);
if (!ntab)
ntab = vzalloc((mask + 1) * sizeof(struct sk_buff *));
if (!ntab)
return -ENOMEM;
sch_tree_lock(sch);
old = q->tab;
if (old) {
unsigned int oqlen = sch->q.qlen, tail = 0;
while (q->head != q->tail) {
struct sk_buff *skb = q->tab[q->head];
q->head = (q->head + 1) & q->tab_mask;
if (!skb)
continue;
if (tail < mask) {
ntab[tail++] = skb;
continue;
}
sch->qstats.backlog -= qdisc_pkt_len(skb);
--sch->q.qlen;
qdisc_drop(skb, sch);
}
qdisc_tree_decrease_qlen(sch, oqlen - sch->q.qlen);
q->head = 0;
q->tail = tail;
}
q->tab_mask = mask;
q->tab = ntab;
} else
sch_tree_lock(sch);
q->flags = ctl->flags;
q->limit = ctl->limit;
red_set_parms(&q->parms, ctl->qth_min, ctl->qth_max, ctl->Wlog,
ctl->Plog, ctl->Scell_log,
nla_data(tb[TCA_CHOKE_STAB]));
if (q->head == q->tail)
red_end_of_idle_period(&q->parms);
sch_tree_unlock(sch);
choke_free(old);
return 0;
}
static int choke_init(struct Qdisc *sch, struct nlattr *opt)
{
return choke_change(sch, opt);
}
static int choke_dump(struct Qdisc *sch, struct sk_buff *skb)
{
struct choke_sched_data *q = qdisc_priv(sch);
struct nlattr *opts = NULL;
struct tc_red_qopt opt = {
.limit = q->limit,
.flags = q->flags,
.qth_min = q->parms.qth_min >> q->parms.Wlog,
.qth_max = q->parms.qth_max >> q->parms.Wlog,
.Wlog = q->parms.Wlog,
.Plog = q->parms.Plog,
.Scell_log = q->parms.Scell_log,
};
opts = nla_nest_start(skb, TCA_OPTIONS);
if (opts == NULL)
goto nla_put_failure;
NLA_PUT(skb, TCA_CHOKE_PARMS, sizeof(opt), &opt);
return nla_nest_end(skb, opts);
nla_put_failure:
nla_nest_cancel(skb, opts);
return -EMSGSIZE;
}
static int choke_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
{
struct choke_sched_data *q = qdisc_priv(sch);
struct tc_choke_xstats st = {
.early = q->stats.prob_drop + q->stats.forced_drop,
.marked = q->stats.prob_mark + q->stats.forced_mark,
.pdrop = q->stats.pdrop,
.other = q->stats.other,
.matched = q->stats.matched,
};
return gnet_stats_copy_app(d, &st, sizeof(st));
}
static void choke_destroy(struct Qdisc *sch)
{
struct choke_sched_data *q = qdisc_priv(sch);
tcf_destroy_chain(&q->filter_list);
choke_free(q->tab);
}
static struct Qdisc *choke_leaf(struct Qdisc *sch, unsigned long arg)
{
return NULL;
}
static unsigned long choke_get(struct Qdisc *sch, u32 classid)
{
return 0;
}
static void choke_put(struct Qdisc *q, unsigned long cl)
{
}
static unsigned long choke_bind(struct Qdisc *sch, unsigned long parent,
u32 classid)
{
return 0;
}
static struct tcf_proto **choke_find_tcf(struct Qdisc *sch, unsigned long cl)
{
struct choke_sched_data *q = qdisc_priv(sch);
if (cl)
return NULL;
return &q->filter_list;
}
static int choke_dump_class(struct Qdisc *sch, unsigned long cl,
struct sk_buff *skb, struct tcmsg *tcm)
{
tcm->tcm_handle |= TC_H_MIN(cl);
return 0;
}
static void choke_walk(struct Qdisc *sch, struct qdisc_walker *arg)
{
if (!arg->stop) {
if (arg->fn(sch, 1, arg) < 0) {
arg->stop = 1;
return;
}
arg->count++;
}
}
static const struct Qdisc_class_ops choke_class_ops = {
.leaf = choke_leaf,
.get = choke_get,
.put = choke_put,
.tcf_chain = choke_find_tcf,
.bind_tcf = choke_bind,
.unbind_tcf = choke_put,
.dump = choke_dump_class,
.walk = choke_walk,
};
static struct sk_buff *choke_peek_head(struct Qdisc *sch)
{
struct choke_sched_data *q = qdisc_priv(sch);
return (q->head != q->tail) ? q->tab[q->head] : NULL;
}
static struct Qdisc_ops choke_qdisc_ops __read_mostly = {
.id = "choke",
.priv_size = sizeof(struct choke_sched_data),
.enqueue = choke_enqueue,
.dequeue = choke_dequeue,
.peek = choke_peek_head,
.drop = choke_drop,
.init = choke_init,
.destroy = choke_destroy,
.reset = choke_reset,
.change = choke_change,
.dump = choke_dump,
.dump_stats = choke_dump_stats,
.owner = THIS_MODULE,
};
static int __init choke_module_init(void)
{
return register_qdisc(&choke_qdisc_ops);
}
static void __exit choke_module_exit(void)
{
unregister_qdisc(&choke_qdisc_ops);
}
module_init(choke_module_init)
module_exit(choke_module_exit)
MODULE_LICENSE("GPL");