[Codel] [Bloat] [PATCH v12] codel: Controlled Delay AQM

Josh Hunt joshua.hunt at berkeley.edu
Wed May 9 12:32:33 EDT 2012


On Wed, May 9, 2012 at 8:50 AM, Eric Dumazet <eric.dumazet at gmail.com> wrote:
> From: Eric Dumazet <edumazet at google.com>
>
> An implementation of CoDel AQM, from Kathleen Nichols and Van Jacobson.
>
>  http://queue.acm.org/detail.cfm?id=2209336
>
> Based on initial work from Dave Taht.
>
> Refactored to help future codel inclusion as plugin for other linux
> qdisc (SFQ), like done with RED plugin.
>
> Tested up to 10Gb speeds with no particular problems.
>
> Signed-off-by: Eric Dumazet <edumazet at google.com>
> Signed-off-by: Dave Taht <dave.taht at bufferbloat.net>
> Cc: Kathleen Nichols <nichols at pollere.com>
> Cc: Van Jacobson <van at pollere.net>
> ---
> v12: algo changes after Kathleen & Van last updates
>   - introduction of lastcount.
>   - minbytes renamed to maxpacket.
>   - maxpacket automatically learns biggest packet size.
>   - ldelay record sojourn time of last dequeued packet.
>   - various changes, better comments...
>
> I hope this is the last version before upstream submission (netdev)
> I'll send the iproute2 patch as well.
>
>  include/linux/pkt_sched.h |   28 +++
>  include/net/codel.h       |  325 ++++++++++++++++++++++++++++++++++++
>  net/sched/Kconfig         |   11 +
>  net/sched/Makefile        |    1
>  net/sched/sch_codel.c     |  272 ++++++++++++++++++++++++++++++
>  5 files changed, 637 insertions(+)
>
> diff --git a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
> index ffe975c..453dd2c 100644
> --- a/include/linux/pkt_sched.h
> +++ b/include/linux/pkt_sched.h
> @@ -655,4 +655,32 @@ struct tc_qfq_stats {
>        __u32 lmax;
>  };
>
> +/* CODEL */
> +
> +enum {
> +       TCA_CODEL_UNSPEC,
> +       TCA_CODEL_TARGET,
> +       TCA_CODEL_LIMIT,
> +       TCA_CODEL_INTERVAL,
> +       TCA_CODEL_ECN,
> +       __TCA_CODEL_MAX
> +};
> +
> +#define TCA_CODEL_MAX  (__TCA_CODEL_MAX - 1)
> +
> +struct tc_codel_xstats {
> +       __u32   maxpacket; /* largest packet we've seen so far */
> +       __u32   count;
> +       __u32   lastcount;
> +       __u32   ldelay; /* in-queue delay seen by most recently dequeued packet */
> +       __u32   drop_next;
> +       __u32   drop_overlimit;
> +       __u32   ecn_mark;
> +       __u32   dropping;
> +       __u32   state1;
> +       __u32   state2;
> +       __u32   state3;
> +       __u32   states;
> +};
> +
>  #endif
> diff --git a/include/net/codel.h b/include/net/codel.h
> new file mode 100644
> index 0000000..565c1fe
> --- /dev/null
> +++ b/include/net/codel.h
> @@ -0,0 +1,325 @@
> +#ifndef __NET_SCHED_CODEL_H
> +#define __NET_SCHED_CODEL_H
> +
> +/*
> + * Codel - The Controlled-Delay Active Queue Management algorithm
> + *
> + *  Copyright (C) 2011-2012 Kathleen Nichols <nichols at pollere.com>
> + *  Copyright (C) 2011-2012 Van Jacobson <van at pollere.net>
> + *  Copyright (C) 2012 Michael D. Taht <dave.taht at bufferbloat.net>
> + *  Copyright (C) 2012 Eric Dumazet <edumazet at google.com>
> + *
> + * Redistribution and use in source and binary forms, with or without
> + * modification, are permitted provided that the following conditions
> + * are met:
> + * 1. Redistributions of source code must retain the above copyright
> + *    notice, this list of conditions, and the following disclaimer,
> + *    without modification.
> + * 2. Redistributions in binary form must reproduce the above copyright
> + *    notice, this list of conditions and the following disclaimer in the
> + *    documentation and/or other materials provided with the distribution.
> + * 3. The names of the authors may not be used to endorse or promote products
> + *    derived from this software without specific prior written permission.
> + *
> + * Alternatively, provided that this notice is retained in full, this
> + * software may be distributed under the terms of the GNU General
> + * Public License ("GPL") version 2, in which case the provisions of the
> + * GPL apply INSTEAD OF those given above.
> + *
> + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
> + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
> + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
> + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
> + * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
> + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
> + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
> + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
> + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
> + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
> + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
> + * DAMAGE.
> + *
> + */
> +
> +#include <linux/types.h>
> +#include <linux/bug.h>
> +#include <linux/ktime.h>
> +#include <net/inet_ecn.h>
> +
> +/* Controlling Queue Delay (CoDel) algorithm
> + * =========================================
> + * Source : Kathleen Nichols and Van Jacobson
> + * http://queue.acm.org/detail.cfm?id=2209396

This link is dead. Looks like it's a typo and should be:
http://queue.acm.org/detail.cfm?id=2209336

Josh

> + *
> + * Implemented on linux by Dave Taht and Eric Dumazet
> + */
> +
> +
> +/*
> + * CoDel uses a 1024 nsec clock, encoded in u32
> + * This gives a range of 2199 seconds, because of signed compares
> + */
> +typedef u32 codel_time_t;
> +#define CODEL_SHIFT 10
> +#define MS2TIME(a) ((a * NSEC_PER_MSEC) >> CODEL_SHIFT)
> +
> +static inline codel_time_t codel_get_time(void)
> +{
> +       u64 ns = ktime_to_ns(ktime_get());
> +
> +       return ns >> CODEL_SHIFT;
> +}
> +
> +#define codel_time_after(a, b)         ((s32)(a) - (s32)(b) > 0)
> +#define codel_time_after_eq(a, b)      ((s32)(a) - (s32)(b) >= 0)
> +#define codel_time_before(a, b)                ((s32)(a) - (s32)(b) < 0)
> +#define codel_time_before_eq(a, b)     ((s32)(a) - (s32)(b) <= 0)
> +
> +struct codel_skb_cb {
> +       codel_time_t enqueue_time;
> +};
> +
> +static struct codel_skb_cb *get_codel_cb(const struct sk_buff *skb)
> +{
> +       qdisc_cb_private_validate(skb, sizeof(struct codel_skb_cb));
> +       return (struct codel_skb_cb *)qdisc_skb_cb(skb)->data;
> +}
> +
> +static codel_time_t codel_get_enqueue_time(const struct sk_buff *skb)
> +{
> +       return get_codel_cb(skb)->enqueue_time;
> +}
> +
> +static void codel_set_enqueue_time(struct sk_buff *skb)
> +{
> +       get_codel_cb(skb)->enqueue_time = codel_get_time();
> +}
> +
> +static inline u32 codel_time_to_us(codel_time_t val)
> +{
> +       u64 valns = ((u64)val << CODEL_SHIFT);
> +
> +       do_div(valns, NSEC_PER_USEC);
> +       return (u32)valns;
> +}
> +
> +struct codel_params {
> +       u32             maxpacket; /* largest packet we've seen so far */
> +       codel_time_t    target;   /* target queue size (in time units) */
> +       codel_time_t    interval; /* width of moving time window */
> +       bool            ecn;      /* is ECN enabled */
> +};
> +
> +struct codel_vars {
> +       u32             count;  /* how many drops we've done since the last time
> +                                * we entered dropping state
> +                                */
> +       u32             lastcount;      /* count at entry to dropping state */
> +       bool            dropping;       /* set to true id in dropping state */
> +
> +       codel_time_t    first_above_time; /* when we went (or will go) continuously
> +                                          * above target for interval
> +                                          */
> +       codel_time_t    drop_next;      /* time to drop next packet, or when we dropped last */
> +       codel_time_t    ldelay; /* sojourn time of last dequeued packet */
> +};
> +
> +/* contains stats and some shared info */
> +struct codel_stats {
> +       struct Qdisc    *sch;
> +       u32             drop_count; /* temp count of dropped packets in dequeue() */
> +
> +       u32             ecn_mark; /* number of packets we ECN marked instead of dropping */
> +       u32             states; /* number of codel_dequeue() calls */
> +       u32             state1; /* number of times ok_to_drop was set to true */
> +       u32             state2;
> +       u32             state3;
> +};
> +
> +static void codel_params_init(struct codel_params *params,
> +                             const struct Qdisc *sch)
> +{
> +       params->maxpacket = 256;
> +       params->interval = MS2TIME(100);
> +       params->target = MS2TIME(5);
> +       params->ecn = false;
> +}
> +
> +static void codel_vars_init(struct codel_vars *vars)
> +{
> +       vars->drop_next = 0;
> +       vars->first_above_time = 0;
> +       vars->dropping = false; /* exit dropping state */
> +       vars->count = 0;
> +       vars->lastcount = 0;
> +}
> +
> +static void codel_stats_init(struct codel_stats *stats,
> +                            struct Qdisc *sch)
> +{
> +       stats->sch = sch; /* back pointer for qdisc_drop() calls */
> +}
> +
> +/* return interval/sqrt(x) with good precision */
> +static u32 codel_inv_sqrt(u32 _interval, u32 _x)
> +{
> +       u64 interval = _interval;
> +       unsigned long x = _x;
> +
> +       /* Scale operands for max precision */
> +
> +#if BITS_PER_LONG == 64
> +       x <<= 32; /* On 64bit arches, we can prescale x by 32bits */
> +       interval <<= 16;
> +#endif
> +
> +       while (x < (1UL << (BITS_PER_LONG - 2))) {
> +               x <<= 2;
> +               interval <<= 1;
> +       }
> +       do_div(interval, int_sqrt(x));
> +       return (u32)interval;
> +}
> +
> +static codel_time_t codel_control_law(codel_time_t t,
> +                                     codel_time_t interval,
> +                                     u32 count)
> +{
> +       return t + codel_inv_sqrt(interval, count);
> +}
> +
> +
> +static bool codel_should_drop(struct sk_buff *skb,
> +                             unsigned int *backlog,
> +                             struct codel_vars *vars,
> +                             struct codel_params *params,
> +                             struct codel_stats *stats,
> +                             codel_time_t now)
> +{
> +       bool ok_to_drop;
> +
> +       if (!skb) {
> +               vars->first_above_time = 0;
> +               return false;
> +       }
> +
> +       vars->ldelay = now - codel_get_enqueue_time(skb);
> +       *backlog -= qdisc_pkt_len(skb);
> +
> +       if (unlikely(qdisc_pkt_len(skb) > params->maxpacket))
> +               params->maxpacket = qdisc_pkt_len(skb);
> +
> +       if (codel_time_before(vars->ldelay, params->target) ||
> +           *backlog <= params->maxpacket) {
> +               /* went below - stay below for at least interval */
> +               vars->first_above_time = 0;
> +               return false;
> +       }
> +       ok_to_drop = false;
> +       if (vars->first_above_time == 0) {
> +               /* just went above from below. If we stay above
> +                * for at least interval we'll say it's ok to drop
> +                */
> +               vars->first_above_time = now + params->interval;
> +       } else if (codel_time_after(now, vars->first_above_time)) {
> +               ok_to_drop = true;
> +               stats->state1++;
> +       }
> +       return ok_to_drop;
> +}
> +
> +typedef struct sk_buff * (*codel_skb_dequeue_t)(struct codel_vars *vars,
> +                                               struct Qdisc *sch);
> +
> +static struct sk_buff *codel_dequeue(struct codel_params *params,
> +                                    struct codel_vars *vars,
> +                                    struct codel_stats *stats,
> +                                    codel_skb_dequeue_t dequeue_func,
> +                                    u32 *backlog)
> +{
> +       struct sk_buff *skb = dequeue_func(vars, stats->sch);
> +       codel_time_t now;
> +       bool drop;
> +
> +       stats->states++;
> +       if (!skb) {
> +               vars->dropping = false;
> +               return skb;
> +       }
> +       now = codel_get_time();
> +       drop = codel_should_drop(skb, backlog,
> +                               vars, params, stats,
> +                               now);
> +       if (vars->dropping) {
> +               if (!drop) {
> +                       /* sojourn time below target - leave dropping state */
> +                       vars->dropping = false;
> +               } else if (codel_time_after_eq(now, vars->drop_next)) {
> +                       stats->state2++;
> +                       /* It's time for the next drop. Drop the current
> +                        * packet and dequeue the next. The dequeue might
> +                        * take us out of dropping state.
> +                        * If not, schedule the next drop.
> +                        * A large backlog might result in drop rates so high
> +                        * that the next drop should happen now,
> +                        * hence the while loop.
> +                        */
> +                       while (vars->dropping &&
> +                              codel_time_after_eq(now, vars->drop_next)) {
> +                               vars->count++;
> +                               if (params->ecn && INET_ECN_set_ce(skb)) {
> +                                       stats->ecn_mark++;
> +                                       vars->drop_next =
> +                                               codel_control_law(vars->drop_next,
> +                                                                 params->interval,
> +                                                                 vars->count);
> +                                       goto end;
> +                               }
> +                               qdisc_drop(skb, stats->sch);
> +                               stats->drop_count++;
> +                               skb = dequeue_func(vars, stats->sch);
> +                               if (!codel_should_drop(skb, backlog,
> +                                                      vars, params, stats, now)) {
> +                                       /* leave dropping state */
> +                                       vars->dropping = false;
> +                               } else {
> +                                       /* and schedule the next drop */
> +                                       vars->drop_next =
> +                                               codel_control_law(vars->drop_next,
> +                                                                 params->interval,
> +                                                                 vars->count);
> +                               }
> +                       }
> +               }
> +       } else if (drop) {
> +               if (params->ecn && INET_ECN_set_ce(skb)) {
> +                       stats->ecn_mark++;
> +               } else {
> +                       qdisc_drop(skb, stats->sch);
> +                       stats->drop_count++;
> +
> +                       skb = dequeue_func(vars, stats->sch);
> +                       drop = codel_should_drop(skb, backlog, vars, params,
> +                                                stats, now);
> +               }
> +               vars->dropping = true;
> +               stats->state3++;
> +               /*
> +                * if min went above target close to when we last went below it
> +                * assume that the drop rate that controlled the queue on the
> +                * last cycle is a good starting point to control it now.
> +                */
> +               if (codel_time_before(now - vars->drop_next,
> +                                     16 * params->interval)) {
> +                       vars->count = vars->count - vars->lastcount + 1;
> +               } else {
> +                       vars->count = 1;
> +               }
> +               vars->lastcount = vars->count;
> +               vars->drop_next = codel_control_law(now, params->interval,
> +                                                   vars->count);
> +       }
> +end:
> +       return skb;
> +}
> +#endif
> diff --git a/net/sched/Kconfig b/net/sched/Kconfig
> index 75b58f8..fadd252 100644
> --- a/net/sched/Kconfig
> +++ b/net/sched/Kconfig
> @@ -250,6 +250,17 @@ config NET_SCH_QFQ
>
>          If unsure, say N.
>
> +config NET_SCH_CODEL
> +       tristate "Controlled Delay AQM (CODEL)"
> +       help
> +         Say Y here if you want to use the Controlled Delay (CODEL)
> +         packet scheduling algorithm.
> +
> +         To compile this driver as a module, choose M here: the module
> +         will be called sch_codel.
> +
> +         If unsure, say N.
> +
>  config NET_SCH_INGRESS
>        tristate "Ingress Qdisc"
>        depends on NET_CLS_ACT
> diff --git a/net/sched/Makefile b/net/sched/Makefile
> index 8cdf4e2..30fab03 100644
> --- a/net/sched/Makefile
> +++ b/net/sched/Makefile
> @@ -37,6 +37,7 @@ obj-$(CONFIG_NET_SCH_PLUG)    += sch_plug.o
>  obj-$(CONFIG_NET_SCH_MQPRIO)   += sch_mqprio.o
>  obj-$(CONFIG_NET_SCH_CHOKE)    += sch_choke.o
>  obj-$(CONFIG_NET_SCH_QFQ)      += sch_qfq.o
> +obj-$(CONFIG_NET_SCH_CODEL)    += sch_codel.o
>
>  obj-$(CONFIG_NET_CLS_U32)      += cls_u32.o
>  obj-$(CONFIG_NET_CLS_ROUTE4)   += cls_route.o
> diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c
> new file mode 100644
> index 0000000..3112afa
> --- /dev/null
> +++ b/net/sched/sch_codel.c
> @@ -0,0 +1,272 @@
> +/*
> + * Codel - The Controlled-Delay Active Queue Management algorithm
> + *
> + *  Copyright (C) 2011-2012 Kathleen Nichols <nichols at pollere.com>
> + *  Copyright (C) 2011-2012 Van Jacobson <van at pollere.net>
> + *
> + *  Implemented on linux by :
> + *  Copyright (C) 2012 Michael D. Taht <dave.taht at bufferbloat.net>
> + *  Copyright (C) 2012 Eric Dumazet <edumazet at google.com>
> + *
> + * Redistribution and use in source and binary forms, with or without
> + * modification, are permitted provided that the following conditions
> + * are met:
> + * 1. Redistributions of source code must retain the above copyright
> + *    notice, this list of conditions, and the following disclaimer,
> + *    without modification.
> + * 2. Redistributions in binary form must reproduce the above copyright
> + *    notice, this list of conditions and the following disclaimer in the
> + *    documentation and/or other materials provided with the distribution.
> + * 3. The names of the authors may not be used to endorse or promote products
> + *    derived from this software without specific prior written permission.
> + *
> + * Alternatively, provided that this notice is retained in full, this
> + * software may be distributed under the terms of the GNU General
> + * Public License ("GPL") version 2, in which case the provisions of the
> + * GPL apply INSTEAD OF those given above.
> + *
> + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
> + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
> + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
> + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
> + * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
> + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
> + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
> + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
> + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
> + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
> + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
> + * DAMAGE.
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/types.h>
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <linux/skbuff.h>
> +#include <net/pkt_sched.h>
> +#include <net/codel.h>
> +
> +
> +#define DEFAULT_CODEL_LIMIT 1000
> +
> +struct codel_sched_data {
> +       struct codel_params     params;
> +       struct codel_vars       vars;
> +       struct codel_stats      stats;
> +       u32                     drop_overlimit;
> +};
> +
> +/* This is the specific function called from codel_dequeue()
> + * to dequeue a packet from queue. Note: backlog is handled in
> + * codel, we dont need to reduce it here.
> + */
> +static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
> +{
> +       struct sk_buff *skb = __skb_dequeue(&sch->q);
> +
> +       prefetch(&skb->end); /* we'll need skb_shinfo() */
> +       return skb;
> +}
> +
> +static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch)
> +{
> +       struct codel_sched_data *q = qdisc_priv(sch);
> +       struct sk_buff *skb;
> +
> +       skb = codel_dequeue(&q->params, &q->vars, &q->stats,
> +                           dequeue, &sch->qstats.backlog);
> +       /* We cant call qdisc_tree_decrease_qlen() if our qlen is 0,
> +        * or HTB crashes. Defer it for next round.
> +        */
> +       if (q->stats.drop_count && sch->q.qlen) {
> +               qdisc_tree_decrease_qlen(sch, q->stats.drop_count);
> +               q->stats.drop_count = 0;
> +       }
> +       if (skb)
> +               qdisc_bstats_update(sch, skb);
> +       return skb;
> +}
> +
> +static int codel_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch)
> +{
> +       struct codel_sched_data *q;
> +
> +       if (likely(qdisc_qlen(sch) < sch->limit)) {
> +               codel_set_enqueue_time(skb);
> +               return qdisc_enqueue_tail(skb, sch);
> +       }
> +       q = qdisc_priv(sch);
> +       q->drop_overlimit++;
> +       return qdisc_drop(skb, sch);
> +}
> +
> +static const struct nla_policy codel_policy[TCA_CODEL_MAX + 1] = {
> +       [TCA_CODEL_TARGET]      = { .type = NLA_U32 },
> +       [TCA_CODEL_LIMIT]       = { .type = NLA_U32 },
> +       [TCA_CODEL_INTERVAL]    = { .type = NLA_U32 },
> +       [TCA_CODEL_ECN]         = { .type = NLA_U32 },
> +};
> +
> +static int codel_change(struct Qdisc *sch, struct nlattr *opt)
> +{
> +       struct codel_sched_data *q = qdisc_priv(sch);
> +       struct nlattr *tb[TCA_CODEL_MAX + 1];
> +       unsigned int qlen;
> +       int err;
> +
> +       if (!opt)
> +               return -EINVAL;
> +
> +       err = nla_parse_nested(tb, TCA_CODEL_MAX, opt, codel_policy);
> +       if (err < 0)
> +               return err;
> +
> +       sch_tree_lock(sch);
> +       if (tb[TCA_CODEL_TARGET]) {
> +               u32 target = nla_get_u32(tb[TCA_CODEL_TARGET]);
> +
> +               q->params.target = ((u64)target * NSEC_PER_USEC) >> CODEL_SHIFT;
> +       }
> +       if (tb[TCA_CODEL_INTERVAL]) {
> +               u32 interval = nla_get_u32(tb[TCA_CODEL_INTERVAL]);
> +
> +               q->params.interval = ((u64)interval * NSEC_PER_USEC) >> CODEL_SHIFT;
> +       }
> +       if (tb[TCA_CODEL_LIMIT])
> +               sch->limit = nla_get_u32(tb[TCA_CODEL_LIMIT]);
> +
> +       if (tb[TCA_CODEL_ECN])
> +               q->params.ecn = !!nla_get_u32(tb[TCA_CODEL_ECN]);
> +
> +       qlen = sch->q.qlen;
> +       while (sch->q.qlen > sch->limit) {
> +               struct sk_buff *skb = __skb_dequeue(&sch->q);
> +
> +               sch->qstats.backlog -= qdisc_pkt_len(skb);
> +               qdisc_drop(skb, sch);
> +       }
> +       qdisc_tree_decrease_qlen(sch, qlen - sch->q.qlen);
> +
> +       sch_tree_unlock(sch);
> +       return 0;
> +}
> +
> +static int codel_init(struct Qdisc *sch, struct nlattr *opt)
> +{
> +       struct codel_sched_data *q = qdisc_priv(sch);
> +
> +       /* It should be possible to run with no limit,
> +        * with infinite memory :)
> +        */
> +       sch->limit = DEFAULT_CODEL_LIMIT;
> +
> +       codel_params_init(&q->params, sch);
> +       codel_vars_init(&q->vars);
> +       codel_stats_init(&q->stats, sch);
> +
> +       if (opt) {
> +               int err = codel_change(sch, opt);
> +
> +               if (err)
> +                       return err;
> +       }
> +
> +       if (sch->limit >= 1)
> +               sch->flags |= TCQ_F_CAN_BYPASS;
> +       else
> +               sch->flags &= ~TCQ_F_CAN_BYPASS;
> +
> +       return 0;
> +}
> +
> +static int codel_dump(struct Qdisc *sch, struct sk_buff *skb)
> +{
> +       struct codel_sched_data *q = qdisc_priv(sch);
> +       struct nlattr *opts;
> +
> +       opts = nla_nest_start(skb, TCA_OPTIONS);
> +       if (opts == NULL)
> +               goto nla_put_failure;
> +
> +       if (nla_put_u32(skb, TCA_CODEL_TARGET,
> +                       codel_time_to_us(q->params.target)) ||
> +           nla_put_u32(skb, TCA_CODEL_LIMIT,
> +                       sch->limit) ||
> +           nla_put_u32(skb, TCA_CODEL_INTERVAL,
> +                       codel_time_to_us(q->params.interval)) ||
> +           nla_put_u32(skb, TCA_CODEL_ECN,
> +                       q->params.ecn))
> +               goto nla_put_failure;
> +
> +       return nla_nest_end(skb, opts);
> +
> +nla_put_failure:
> +       nla_nest_cancel(skb, opts);
> +       return -1;
> +}
> +
> +static int codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
> +{
> +       const struct codel_sched_data *q = qdisc_priv(sch);
> +       struct tc_codel_xstats st = {
> +               .maxpacket = q->params.maxpacket,
> +               .count  = q->vars.count,
> +               .lastcount = q->vars.lastcount,
> +               .states = q->stats.states,
> +               .state1 = q->stats.state1,
> +               .state2 = q->stats.state2,
> +               .state3 = q->stats.state3,
> +               .drop_overlimit = q->drop_overlimit,
> +               .ldelay = codel_time_to_us(q->vars.ldelay),
> +               .dropping = q->vars.dropping,
> +               .ecn_mark = q->stats.ecn_mark,
> +       };
> +
> +       if (q->vars.dropping && q->vars.drop_next)
> +               st.drop_next = codel_time_to_us(q->vars.drop_next -
> +                                               codel_get_time());
> +
> +       return gnet_stats_copy_app(d, &st, sizeof(st));
> +}
> +
> +static void codel_reset(struct Qdisc *sch)
> +{
> +       struct codel_sched_data *q = qdisc_priv(sch);
> +
> +       qdisc_reset_queue(sch);
> +       codel_vars_init(&q->vars);
> +}
> +
> +static struct Qdisc_ops codel_qdisc_ops __read_mostly = {
> +       .id             =       "codel",
> +       .priv_size      =       sizeof(struct codel_sched_data),
> +
> +       .enqueue        =       codel_qdisc_enqueue,
> +       .dequeue        =       codel_qdisc_dequeue,
> +       .peek           =       qdisc_peek_dequeued,
> +       .init           =       codel_init,
> +       .reset          =       codel_reset,
> +       .change         =       codel_change,
> +       .dump           =       codel_dump,
> +       .dump_stats     =       codel_dump_stats,
> +       .owner          =       THIS_MODULE,
> +};
> +
> +static int __init codel_module_init(void)
> +{
> +       return register_qdisc(&codel_qdisc_ops);
> +}
> +static void __exit codel_module_exit(void)
> +{
> +       unregister_qdisc(&codel_qdisc_ops);
> +}
> +module_init(codel_module_init)
> +module_exit(codel_module_exit)
> +
> +MODULE_DESCRIPTION("Controlled Delay queue discipline");
> +MODULE_AUTHOR("Dave Taht");
> +MODULE_AUTHOR("Eric Dumazet");
> +MODULE_LICENSE("Dual BSD/GPL");
>
>
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