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android-kvm / linux / bbdbfa25d4955fb8a22ce47d45add0fa6359d7ed / . / net / sched / sch_qfq.c
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// SPDX-License-Identifier: GPL-2.0-only
/*
* net/sched/sch_qfq.c Quick Fair Queueing Plus Scheduler.
*
* Copyright (c) 2009 Fabio Checconi, Luigi Rizzo, and Paolo Valente.
* Copyright (c) 2012 Paolo Valente.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/bitops.h>
#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/pkt_sched.h>
#include <net/sch_generic.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>
/* Quick Fair Queueing Plus
========================
Sources:
[1] Paolo Valente,
"Reducing the Execution Time of Fair-Queueing Schedulers."
http://algo.ing.unimo.it/people/paolo/agg-sched/agg-sched.pdf
Sources for QFQ:
[2] Fabio Checconi, Luigi Rizzo, and Paolo Valente: "QFQ: Efficient
Packet Scheduling with Tight Bandwidth Distribution Guarantees."
See also:
http://retis.sssup.it/~fabio/linux/qfq/
*/
/*
QFQ+ divides classes into aggregates of at most MAX_AGG_CLASSES
classes. Each aggregate is timestamped with a virtual start time S
and a virtual finish time F, and scheduled according to its
timestamps. S and F are computed as a function of a system virtual
time function V. The classes within each aggregate are instead
scheduled with DRR.
To speed up operations, QFQ+ divides also aggregates into a limited
number of groups. Which group a class belongs to depends on the
ratio between the maximum packet length for the class and the weight
of the class. Groups have their own S and F. In the end, QFQ+
schedules groups, then aggregates within groups, then classes within
aggregates. See [1] and [2] for a full description.
Virtual time computations.
S, F and V are all computed in fixed point arithmetic with
FRAC_BITS decimal bits.
QFQ_MAX_INDEX is the maximum index allowed for a group. We need
one bit per index.
QFQ_MAX_WSHIFT is the maximum power of two supported as a weight.
The layout of the bits is as below:
[ MTU_SHIFT ][ FRAC_BITS ]
[ MAX_INDEX ][ MIN_SLOT_SHIFT ]
^.__grp->index = 0
*.__grp->slot_shift
where MIN_SLOT_SHIFT is derived by difference from the others.
The max group index corresponds to Lmax/w_min, where
Lmax=1<<MTU_SHIFT, w_min = 1 .
From this, and knowing how many groups (MAX_INDEX) we want,
we can derive the shift corresponding to each group.
Because we often need to compute
F = S + len/w_i and V = V + len/wsum
instead of storing w_i store the value
inv_w = (1<<FRAC_BITS)/w_i
so we can do F = S + len * inv_w * wsum.
We use W_TOT in the formulas so we can easily move between
static and adaptive weight sum.
The per-scheduler-instance data contain all the data structures
for the scheduler: bitmaps and bucket lists.
*/
/*
* Maximum number of consecutive slots occupied by backlogged classes
* inside a group.
*/
#define QFQ_MAX_SLOTS 32
/*
* Shifts used for aggregate<->group mapping. We allow class weights that are
* in the range [1, 2^MAX_WSHIFT], and we try to map each aggregate i to the
* group with the smallest index that can support the L_i / r_i configured
* for the classes in the aggregate.
*
* grp->index is the index of the group; and grp->slot_shift
* is the shift for the corresponding (scaled) sigma_i.
*/
#define QFQ_MAX_INDEX 24
#define QFQ_MAX_WSHIFT 10
#define QFQ_MAX_WEIGHT (1<<QFQ_MAX_WSHIFT) /* see qfq_slot_insert */
#define QFQ_MAX_WSUM (64*QFQ_MAX_WEIGHT)
#define FRAC_BITS 30 /* fixed point arithmetic */
#define ONE_FP (1UL << FRAC_BITS)
#define QFQ_MTU_SHIFT 16 /* to support TSO/GSO */
#define QFQ_MIN_LMAX 512 /* see qfq_slot_insert */
#define QFQ_MAX_AGG_CLASSES 8 /* max num classes per aggregate allowed */
/*
* Possible group states. These values are used as indexes for the bitmaps
* array of struct qfq_queue.
*/
enum qfq_state { ER, IR, EB, IB, QFQ_MAX_STATE };
struct qfq_group;
struct qfq_aggregate;
struct qfq_class {
struct Qdisc_class_common common;
unsigned int filter_cnt;
struct gnet_stats_basic_packed bstats;
struct gnet_stats_queue qstats;
struct net_rate_estimator __rcu *rate_est;
struct Qdisc *qdisc;
struct list_head alist; /* Link for active-classes list. */
struct qfq_aggregate *agg; /* Parent aggregate. */
int deficit; /* DRR deficit counter. */
};
struct qfq_aggregate {
struct hlist_node next; /* Link for the slot list. */
u64 S, F; /* flow timestamps (exact) */
/* group we belong to. In principle we would need the index,
* which is log_2(lmax/weight), but we never reference it
* directly, only the group.
*/
struct qfq_group *grp;
/* these are copied from the flowset. */
u32 class_weight; /* Weight of each class in this aggregate. */
/* Max pkt size for the classes in this aggregate, DRR quantum. */
int lmax;
u32 inv_w; /* ONE_FP/(sum of weights of classes in aggr.). */
u32 budgetmax; /* Max budget for this aggregate. */
u32 initial_budget, budget; /* Initial and current budget. */
int num_classes; /* Number of classes in this aggr. */
struct list_head active; /* DRR queue of active classes. */
struct hlist_node nonfull_next; /* See nonfull_aggs in qfq_sched. */
};
struct qfq_group {
u64 S, F; /* group timestamps (approx). */
unsigned int slot_shift; /* Slot shift. */
unsigned int index; /* Group index. */
unsigned int front; /* Index of the front slot. */
unsigned long full_slots; /* non-empty slots */
/* Array of RR lists of active aggregates. */
struct hlist_head slots[QFQ_MAX_SLOTS];
};
struct qfq_sched {
struct tcf_proto __rcu *filter_list;
struct tcf_block *block;
struct Qdisc_class_hash clhash;
u64 oldV, V; /* Precise virtual times. */
struct qfq_aggregate *in_serv_agg; /* Aggregate being served. */
u32 wsum; /* weight sum */
u32 iwsum; /* inverse weight sum */
unsigned long bitmaps[QFQ_MAX_STATE]; /* Group bitmaps. */
struct qfq_group groups[QFQ_MAX_INDEX + 1]; /* The groups. */
u32 min_slot_shift; /* Index of the group-0 bit in the bitmaps. */
u32 max_agg_classes; /* Max number of classes per aggr. */
struct hlist_head nonfull_aggs; /* Aggs with room for more classes. */
};
/*
* Possible reasons why the timestamps of an aggregate are updated
* enqueue: the aggregate switches from idle to active and must scheduled
* for service
* requeue: the aggregate finishes its budget, so it stops being served and
* must be rescheduled for service
*/
enum update_reason {enqueue, requeue};
static struct qfq_class *qfq_find_class(struct Qdisc *sch, u32 classid)
{
struct qfq_sched *q = qdisc_priv(sch);
struct Qdisc_class_common *clc;
clc = qdisc_class_find(&q->clhash, classid);
if (clc == NULL)
return NULL;
return container_of(clc, struct qfq_class, common);
}
static const struct nla_policy qfq_policy[TCA_QFQ_MAX + 1] = {
[TCA_QFQ_WEIGHT] = { .type = NLA_U32 },
[TCA_QFQ_LMAX] = { .type = NLA_U32 },
};
/*
* Calculate a flow index, given its weight and maximum packet length.
* index = log_2(maxlen/weight) but we need to apply the scaling.
* This is used only once at flow creation.
*/
static int qfq_calc_index(u32 inv_w, unsigned int maxlen, u32 min_slot_shift)
{
u64 slot_size = (u64)maxlen * inv_w;
unsigned long size_map;
int index = 0;
size_map = slot_size >> min_slot_shift;
if (!size_map)
goto out;
index = __fls(size_map) + 1; /* basically a log_2 */
index -= !(slot_size - (1ULL << (index + min_slot_shift - 1)));
if (index < 0)
index = 0;
out:
pr_debug("qfq calc_index: W = %lu, L = %u, I = %d\n",
(unsigned long) ONE_FP/inv_w, maxlen, index);
return index;
}
static void qfq_deactivate_agg(struct qfq_sched *, struct qfq_aggregate *);
static void qfq_activate_agg(struct qfq_sched *, struct qfq_aggregate *,
enum update_reason);
static void qfq_init_agg(struct qfq_sched *q, struct qfq_aggregate *agg,
u32 lmax, u32 weight)
{
INIT_LIST_HEAD(&agg->active);
hlist_add_head(&agg->nonfull_next, &q->nonfull_aggs);
agg->lmax = lmax;
agg->class_weight = weight;
}
static struct qfq_aggregate *qfq_find_agg(struct qfq_sched *q,
u32 lmax, u32 weight)
{
struct qfq_aggregate *agg;
hlist_for_each_entry(agg, &q->nonfull_aggs, nonfull_next)
if (agg->lmax == lmax && agg->class_weight == weight)
return agg;
return NULL;
}
/* Update aggregate as a function of the new number of classes. */
static void qfq_update_agg(struct qfq_sched *q, struct qfq_aggregate *agg,
int new_num_classes)
{
u32 new_agg_weight;
if (new_num_classes == q->max_agg_classes)
hlist_del_init(&agg->nonfull_next);
if (agg->num_classes > new_num_classes &&
new_num_classes == q->max_agg_classes - 1) /* agg no more full */
hlist_add_head(&agg->nonfull_next, &q->nonfull_aggs);
/* The next assignment may let
* agg->initial_budget > agg->budgetmax
* hold, we will take it into account in charge_actual_service().
*/
agg->budgetmax = new_num_classes * agg->lmax;
new_agg_weight = agg->class_weight * new_num_classes;
agg->inv_w = ONE_FP/new_agg_weight;
if (agg->grp == NULL) {
int i = qfq_calc_index(agg->inv_w, agg->budgetmax,
q->min_slot_shift);
agg->grp = &q->groups[i];
}
q->wsum +=
(int) agg->class_weight * (new_num_classes - agg->num_classes);
q->iwsum = ONE_FP / q->wsum;
agg->num_classes = new_num_classes;
}
/* Add class to aggregate. */
static void qfq_add_to_agg(struct qfq_sched *q,
struct qfq_aggregate *agg,
struct qfq_class *cl)
{
cl->agg = agg;
qfq_update_agg(q, agg, agg->num_classes+1);
if (cl->qdisc->q.qlen > 0) { /* adding an active class */
list_add_tail(&cl->alist, &agg->active);
if (list_first_entry(&agg->active, struct qfq_class, alist) ==
cl && q->in_serv_agg != agg) /* agg was inactive */
qfq_activate_agg(q, agg, enqueue); /* schedule agg */
}
}
static struct qfq_aggregate *qfq_choose_next_agg(struct qfq_sched *);
static void qfq_destroy_agg(struct qfq_sched *q, struct qfq_aggregate *agg)
{
hlist_del_init(&agg->nonfull_next);
q->wsum -= agg->class_weight;
if (q->wsum != 0)
q->iwsum = ONE_FP / q->wsum;
if (q->in_serv_agg == agg)
q->in_serv_agg = qfq_choose_next_agg(q);
kfree(agg);
}
/* Deschedule class from within its parent aggregate. */
static void qfq_deactivate_class(struct qfq_sched *q, struct qfq_class *cl)
{
struct qfq_aggregate *agg = cl->agg;
list_del(&cl->alist); /* remove from RR queue of the aggregate */
if (list_empty(&agg->active)) /* agg is now inactive */
qfq_deactivate_agg(q, agg);
}
/* Remove class from its parent aggregate. */
static void qfq_rm_from_agg(struct qfq_sched *q, struct qfq_class *cl)
{
struct qfq_aggregate *agg = cl->agg;
cl->agg = NULL;
if (agg->num_classes == 1) { /* agg being emptied, destroy it */
qfq_destroy_agg(q, agg);
return;
}
qfq_update_agg(q, agg, agg->num_classes-1);
}
/* Deschedule class and remove it from its parent aggregate. */
static void qfq_deact_rm_from_agg(struct qfq_sched *q, struct qfq_class *cl)
{
if (cl->qdisc->q.qlen > 0) /* class is active */
qfq_deactivate_class(q, cl);
qfq_rm_from_agg(q, cl);
}
/* Move class to a new aggregate, matching the new class weight and/or lmax */
static int qfq_change_agg(struct Qdisc *sch, struct qfq_class *cl, u32 weight,
u32 lmax)
{
struct qfq_sched *q = qdisc_priv(sch);
struct qfq_aggregate *new_agg = qfq_find_agg(q, lmax, weight);
if (new_agg == NULL) { /* create new aggregate */
new_agg = kzalloc(sizeof(*new_agg), GFP_ATOMIC);
if (new_agg == NULL)
return -ENOBUFS;
qfq_init_agg(q, new_agg, lmax, weight);
}
qfq_deact_rm_from_agg(q, cl);
qfq_add_to_agg(q, new_agg, cl);
return 0;
}
static int qfq_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
struct nlattr **tca, unsigned long *arg,
struct netlink_ext_ack *extack)
{
struct qfq_sched *q = qdisc_priv(sch);
struct qfq_class *cl = (struct qfq_class *)*arg;
bool existing = false;
struct nlattr *tb[TCA_QFQ_MAX + 1];
struct qfq_aggregate *new_agg = NULL;
u32 weight, lmax, inv_w;
int err;
int delta_w;
if (tca[TCA_OPTIONS] == NULL) {
pr_notice("qfq: no options\n");
return -EINVAL;
}
err = nla_parse_nested_deprecated(tb, TCA_QFQ_MAX, tca[TCA_OPTIONS],
qfq_policy, NULL);
if (err < 0)
return err;
if (tb[TCA_QFQ_WEIGHT]) {
weight = nla_get_u32(tb[TCA_QFQ_WEIGHT]);
if (!weight || weight > (1UL << QFQ_MAX_WSHIFT)) {
pr_notice("qfq: invalid weight %u\n", weight);
return -EINVAL;
}
} else
weight = 1;
if (tb[TCA_QFQ_LMAX]) {
lmax = nla_get_u32(tb[TCA_QFQ_LMAX]);
if (lmax < QFQ_MIN_LMAX || lmax > (1UL << QFQ_MTU_SHIFT)) {
pr_notice("qfq: invalid max length %u\n", lmax);
return -EINVAL;
}
} else
lmax = psched_mtu(qdisc_dev(sch));
inv_w = ONE_FP / weight;
weight = ONE_FP / inv_w;
if (cl != NULL &&
lmax == cl->agg->lmax &&
weight == cl->agg->class_weight)
return 0; /* nothing to change */
delta_w = weight - (cl ? cl->agg->class_weight : 0);
if (q->wsum + delta_w > QFQ_MAX_WSUM) {
pr_notice("qfq: total weight out of range (%d + %u)\n",
delta_w, q->wsum);
return -EINVAL;
}
if (cl != NULL) { /* modify existing class */
if (tca[TCA_RATE]) {
err = gen_replace_estimator(&cl->bstats, NULL,
&cl->rate_est,
NULL,
qdisc_root_sleeping_running(sch),
tca[TCA_RATE]);
if (err)
return err;
}
existing = true;
goto set_change_agg;
}
/* create and init new class */
cl = kzalloc(sizeof(struct qfq_class), GFP_KERNEL);
if (cl == NULL)
return -ENOBUFS;
cl->common.classid = classid;
cl->deficit = lmax;
cl->qdisc = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
classid, NULL);
if (cl->qdisc == NULL)
cl->qdisc = &noop_qdisc;
if (tca[TCA_RATE]) {
err = gen_new_estimator(&cl->bstats, NULL,
&cl->rate_est,
NULL,
qdisc_root_sleeping_running(sch),
tca[TCA_RATE]);
if (err)
goto destroy_class;
}
if (cl->qdisc != &noop_qdisc)
qdisc_hash_add(cl->qdisc, true);
set_change_agg:
sch_tree_lock(sch);
new_agg = qfq_find_agg(q, lmax, weight);
if (new_agg == NULL) { /* create new aggregate */
sch_tree_unlock(sch);
new_agg = kzalloc(sizeof(*new_agg), GFP_KERNEL);
if (new_agg == NULL) {
err = -ENOBUFS;
gen_kill_estimator(&cl->rate_est);
goto destroy_class;
}
sch_tree_lock(sch);
qfq_init_agg(q, new_agg, lmax, weight);
}
if (existing)
qfq_deact_rm_from_agg(q, cl);
else
qdisc_class_hash_insert(&q->clhash, &cl->common);
qfq_add_to_agg(q, new_agg, cl);
sch_tree_unlock(sch);
qdisc_class_hash_grow(sch, &q->clhash);
*arg = (unsigned long)cl;
return 0;
destroy_class:
qdisc_put(cl->qdisc);
kfree(cl);
return err;
}
static void qfq_destroy_class(struct Qdisc *sch, struct qfq_class *cl)
{
struct qfq_sched *q = qdisc_priv(sch);
qfq_rm_from_agg(q, cl);
gen_kill_estimator(&cl->rate_est);
qdisc_put(cl->qdisc);
kfree(cl);
}
static int qfq_delete_class(struct Qdisc *sch, unsigned long arg,
struct netlink_ext_ack *extack)
{
struct qfq_sched *q = qdisc_priv(sch);
struct qfq_class *cl = (struct qfq_class *)arg;
if (cl->filter_cnt > 0)
return -EBUSY;
sch_tree_lock(sch);
qdisc_purge_queue(cl->qdisc);
qdisc_class_hash_remove(&q->clhash, &cl->common);
sch_tree_unlock(sch);
qfq_destroy_class(sch, cl);
return 0;
}
static unsigned long qfq_search_class(struct Qdisc *sch, u32 classid)
{
return (unsigned long)qfq_find_class(sch, classid);
}
static struct tcf_block *qfq_tcf_block(struct Qdisc *sch, unsigned long cl,
struct netlink_ext_ack *extack)
{
struct qfq_sched *q = qdisc_priv(sch);
if (cl)
return NULL;
return q->block;
}
static unsigned long qfq_bind_tcf(struct Qdisc *sch, unsigned long parent,
u32 classid)
{
struct qfq_class *cl = qfq_find_class(sch, classid);
if (cl != NULL)
cl->filter_cnt++;
return (unsigned long)cl;
}
static void qfq_unbind_tcf(struct Qdisc *sch, unsigned long arg)
{
struct qfq_class *cl = (struct qfq_class *)arg;
cl->filter_cnt--;
}
static int qfq_graft_class(struct Qdisc *sch, unsigned long arg,
struct Qdisc *new, struct Qdisc **old,
struct netlink_ext_ack *extack)
{
struct qfq_class *cl = (struct qfq_class *)arg;
if (new == NULL) {
new = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
cl->common.classid, NULL);
if (new == NULL)
new = &noop_qdisc;
}
*old = qdisc_replace(sch, new, &cl->qdisc);
return 0;
}
static struct Qdisc *qfq_class_leaf(struct Qdisc *sch, unsigned long arg)
{
struct qfq_class *cl = (struct qfq_class *)arg;
return cl->qdisc;
}
static int qfq_dump_class(struct Qdisc *sch, unsigned long arg,
struct sk_buff *skb, struct tcmsg *tcm)
{
struct qfq_class *cl = (struct qfq_class *)arg;
struct nlattr *nest;
tcm->tcm_parent = TC_H_ROOT;
tcm->tcm_handle = cl->common.classid;
tcm->tcm_info = cl->qdisc->handle;
nest = nla_nest_start_noflag(skb, TCA_OPTIONS);
if (nest == NULL)
goto nla_put_failure;
if (nla_put_u32(skb, TCA_QFQ_WEIGHT, cl->agg->class_weight) ||
nla_put_u32(skb, TCA_QFQ_LMAX, cl->agg->lmax))
goto nla_put_failure;
return nla_nest_end(skb, nest);
nla_put_failure:
nla_nest_cancel(skb, nest);
return -EMSGSIZE;
}
static int qfq_dump_class_stats(struct Qdisc *sch, unsigned long arg,
struct gnet_dump *d)
{
struct qfq_class *cl = (struct qfq_class *)arg;
struct tc_qfq_stats xstats;
memset(&xstats, 0, sizeof(xstats));
xstats.weight = cl->agg->class_weight;
xstats.lmax = cl->agg->lmax;
if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
d, NULL, &cl->bstats) < 0 ||
gnet_stats_copy_rate_est(d, &cl->rate_est) < 0 ||
qdisc_qstats_copy(d, cl->qdisc) < 0)
return -1;
return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
}
static void qfq_walk(struct Qdisc *sch, struct qdisc_walker *arg)
{
struct qfq_sched *q = qdisc_priv(sch);
struct qfq_class *cl;
unsigned int i;
if (arg->stop)
return;
for (i = 0; i < q->clhash.hashsize; i++) {
hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
if (arg->count < arg->skip) {
arg->count++;
continue;
}
if (arg->fn(sch, (unsigned long)cl, arg) < 0) {
arg->stop = 1;
return;
}
arg->count++;
}
}
}
static struct qfq_class *qfq_classify(struct sk_buff *skb, struct Qdisc *sch,
int *qerr)
{
struct qfq_sched *q = qdisc_priv(sch);
struct qfq_class *cl;
struct tcf_result res;
struct tcf_proto *fl;
int result;
if (TC_H_MAJ(skb->priority ^ sch->handle) == 0) {
pr_debug("qfq_classify: found %d\n", skb->priority);
cl = qfq_find_class(sch, skb->priority);
if (cl != NULL)
return cl;
}
*qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
fl = rcu_dereference_bh(q->filter_list);
result = tcf_classify(skb, NULL, fl, &res, false);
if (result >= 0) {
#ifdef CONFIG_NET_CLS_ACT
switch (result) {
case TC_ACT_QUEUED:
case TC_ACT_STOLEN:
case TC_ACT_TRAP:
*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
fallthrough;
case TC_ACT_SHOT:
return NULL;
}
#endif
cl = (struct qfq_class *)res.class;
if (cl == NULL)
cl = qfq_find_class(sch, res.classid);
return cl;
}
return NULL;
}
/* Generic comparison function, handling wraparound. */
static inline int qfq_gt(u64 a, u64 b)
{
return (s64)(a - b) > 0;
}
/* Round a precise timestamp to its slotted value. */
static inline u64 qfq_round_down(u64 ts, unsigned int shift)
{
return ts & ~((1ULL << shift) - 1);
}
/* return the pointer to the group with lowest index in the bitmap */
static inline struct qfq_group *qfq_ffs(struct qfq_sched *q,
unsigned long bitmap)
{
int index = __ffs(bitmap);
return &q->groups[index];
}
/* Calculate a mask to mimic what would be ffs_from(). */
static inline unsigned long mask_from(unsigned long bitmap, int from)
{
return bitmap & ~((1UL << from) - 1);
}
/*
* The state computation relies on ER=0, IR=1, EB=2, IB=3
* First compute eligibility comparing grp->S, q->V,
* then check if someone is blocking us and possibly add EB
*/
static int qfq_calc_state(struct qfq_sched *q, const struct qfq_group *grp)
{
/* if S > V we are not eligible */
unsigned int state = qfq_gt(grp->S, q->V);
unsigned long mask = mask_from(q->bitmaps[ER], grp->index);
struct qfq_group *next;
if (mask) {
next = qfq_ffs(q, mask);
if (qfq_gt(grp->F, next->F))
state |= EB;
}
return state;
}
/*
* In principle
* q->bitmaps[dst] |= q->bitmaps[src] & mask;
* q->bitmaps[src] &= ~mask;
* but we should make sure that src != dst
*/
static inline void qfq_move_groups(struct qfq_sched *q, unsigned long mask,
int src, int dst)
{
q->bitmaps[dst] |= q->bitmaps[src] & mask;
q->bitmaps[src] &= ~mask;
}
static void qfq_unblock_groups(struct qfq_sched *q, int index, u64 old_F)
{
unsigned long mask = mask_from(q->bitmaps[ER], index + 1);
struct qfq_group *next;
if (mask) {
next = qfq_ffs(q, mask);
if (!qfq_gt(next->F, old_F))
return;
}
mask = (1UL << index) - 1;
qfq_move_groups(q, mask, EB, ER);
qfq_move_groups(q, mask, IB, IR);
}
/*
* perhaps
*
old_V ^= q->V;
old_V >>= q->min_slot_shift;
if (old_V) {
...
}
*
*/
static void qfq_make_eligible(struct qfq_sched *q)
{
unsigned long vslot = q->V >> q->min_slot_shift;
unsigned long old_vslot = q->oldV >> q->min_slot_shift;
if (vslot != old_vslot) {
unsigned long mask;
int last_flip_pos = fls(vslot ^ old_vslot);
if (last_flip_pos > 31) /* higher than the number of groups */
mask = ~0UL; /* make all groups eligible */
else
mask = (1UL << last_flip_pos) - 1;
qfq_move_groups(q, mask, IR, ER);
qfq_move_groups(q, mask, IB, EB);
}
}
/*
* The index of the slot in which the input aggregate agg is to be
* inserted must not be higher than QFQ_MAX_SLOTS-2. There is a '-2'
* and not a '-1' because the start time of the group may be moved
* backward by one slot after the aggregate has been inserted, and
* this would cause non-empty slots to be right-shifted by one
* position.
*
* QFQ+ fully satisfies this bound to the slot index if the parameters
* of the classes are not changed dynamically, and if QFQ+ never
* happens to postpone the service of agg unjustly, i.e., it never
* happens that the aggregate becomes backlogged and eligible, or just
* eligible, while an aggregate with a higher approximated finish time
* is being served. In particular, in this case QFQ+ guarantees that
* the timestamps of agg are low enough that the slot index is never
* higher than 2. Unfortunately, QFQ+ cannot provide the same
* guarantee if it happens to unjustly postpone the service of agg, or
* if the parameters of some class are changed.
*
* As for the first event, i.e., an out-of-order service, the
* upper bound to the slot index guaranteed by QFQ+ grows to
* 2 +
* QFQ_MAX_AGG_CLASSES * ((1<<QFQ_MTU_SHIFT)/QFQ_MIN_LMAX) *
* (current_max_weight/current_wsum) <= 2 + 8 * 128 * 1.
*
* The following function deals with this problem by backward-shifting
* the timestamps of agg, if needed, so as to guarantee that the slot
* index is never higher than QFQ_MAX_SLOTS-2. This backward-shift may
* cause the service of other aggregates to be postponed, yet the
* worst-case guarantees of these aggregates are not violated. In
* fact, in case of no out-of-order service, the timestamps of agg
* would have been even lower than they are after the backward shift,
* because QFQ+ would have guaranteed a maximum value equal to 2 for
* the slot index, and 2 < QFQ_MAX_SLOTS-2. Hence the aggregates whose
* service is postponed because of the backward-shift would have
* however waited for the service of agg before being served.
*
* The other event that may cause the slot index to be higher than 2
* for agg is a recent change of the parameters of some class. If the
* weight of a class is increased or the lmax (max_pkt_size) of the
* class is decreased, then a new aggregate with smaller slot size
* than the original parent aggregate of the class may happen to be
* activated. The activation of this aggregate should be properly
* delayed to when the service of the class has finished in the ideal
* system tracked by QFQ+. If the activation of the aggregate is not
* delayed to this reference time instant, then this aggregate may be
* unjustly served before other aggregates waiting for service. This
* may cause the above bound to the slot index to be violated for some
* of these unlucky aggregates.
*
* Instead of delaying the activation of the new aggregate, which is
* quite complex, the above-discussed capping of the slot index is
* used to handle also the consequences of a change of the parameters
* of a class.
*/
static void qfq_slot_insert(struct qfq_group *grp, struct qfq_aggregate *agg,
u64 roundedS)
{
u64 slot = (roundedS - grp->S) >> grp->slot_shift;
unsigned int i; /* slot index in the bucket list */
if (unlikely(slot > QFQ_MAX_SLOTS - 2)) {
u64 deltaS = roundedS - grp->S -
((u64)(QFQ_MAX_SLOTS - 2)<<grp->slot_shift);
agg->S -= deltaS;
agg->F -= deltaS;
slot = QFQ_MAX_SLOTS - 2;
}
i = (grp->front + slot) % QFQ_MAX_SLOTS;
hlist_add_head(&agg->next, &grp->slots[i]);
__set_bit(slot, &grp->full_slots);
}
/* Maybe introduce hlist_first_entry?? */
static struct qfq_aggregate *qfq_slot_head(struct qfq_group *grp)
{
return hlist_entry(grp->slots[grp->front].first,
struct qfq_aggregate, next);
}
/*
* remove the entry from the slot
*/
static void qfq_front_slot_remove(struct qfq_group *grp)
{
struct qfq_aggregate *agg = qfq_slot_head(grp);
BUG_ON(!agg);
hlist_del(&agg->next);
if (hlist_empty(&grp->slots[grp->front]))
__clear_bit(0, &grp->full_slots);
}
/*
* Returns the first aggregate in the first non-empty bucket of the
* group. As a side effect, adjusts the bucket list so the first
* non-empty bucket is at position 0 in full_slots.
*/
static struct qfq_aggregate *qfq_slot_scan(struct qfq_group *grp)
{
unsigned int i;
pr_debug("qfq slot_scan: grp %u full %#lx\n",
grp->index, grp->full_slots);
if (grp->full_slots == 0)
return NULL;
i = __ffs(grp->full_slots); /* zero based */
if (i > 0) {
grp->front = (grp->front + i) % QFQ_MAX_SLOTS;
grp->full_slots >>= i;
}
return qfq_slot_head(grp);
}
/*
* adjust the bucket list. When the start time of a group decreases,
* we move the index down (modulo QFQ_MAX_SLOTS) so we don't need to
* move the objects. The mask of occupied slots must be shifted
* because we use ffs() to find the first non-empty slot.
* This covers decreases in the group's start time, but what about
* increases of the start time ?
* Here too we should make sure that i is less than 32
*/
static void qfq_slot_rotate(struct qfq_group *grp, u64 roundedS)
{
unsigned int i = (grp->S - roundedS) >> grp->slot_shift;
grp->full_slots <<= i;
grp->front = (grp->front - i) % QFQ_MAX_SLOTS;
}
static void qfq_update_eligible(struct qfq_sched *q)
{
struct qfq_group *grp;
unsigned long ineligible;
ineligible = q->bitmaps[IR] | q->bitmaps[IB];
if (ineligible) {
if (!q->bitmaps[ER]) {
grp = qfq_ffs(q, ineligible);
if (qfq_gt(grp->S, q->V))
q->V = grp->S;
}
qfq_make_eligible(q);
}
}
/* Dequeue head packet of the head class in the DRR queue of the aggregate. */
static void agg_dequeue(struct qfq_aggregate *agg,
struct qfq_class *cl, unsigned int len)
{
qdisc_dequeue_peeked(cl->qdisc);
cl->deficit -= (int) len;
if (cl->qdisc->q.qlen == 0) /* no more packets, remove from list */
list_del(&cl->alist);
else if (cl->deficit < qdisc_pkt_len(cl->qdisc->ops->peek(cl->qdisc))) {
cl->deficit += agg->lmax;
list_move_tail(&cl->alist, &agg->active);
}
}
static inline struct sk_buff *qfq_peek_skb(struct qfq_aggregate *agg,
struct qfq_class **cl,
unsigned int *len)
{
struct sk_buff *skb;
*cl = list_first_entry(&agg->active, struct qfq_class, alist);
skb = (*cl)->qdisc->ops->peek((*cl)->qdisc);
if (skb == NULL)
WARN_ONCE(1, "qfq_dequeue: non-workconserving leaf\n");
else
*len = qdisc_pkt_len(skb);
return skb;
}
/* Update F according to the actual service received by the aggregate. */
static inline void charge_actual_service(struct qfq_aggregate *agg)
{
/* Compute the service received by the aggregate, taking into
* account that, after decreasing the number of classes in
* agg, it may happen that
* agg->initial_budget - agg->budget > agg->bugdetmax
*/
u32 service_received = min(agg->budgetmax,
agg->initial_budget - agg->budget);
agg->F = agg->S + (u64)service_received * agg->inv_w;
}
/* Assign a reasonable start time for a new aggregate in group i.
* Admissible values for \hat(F) are multiples of \sigma_i
* no greater than V+\sigma_i . Larger values mean that
* we had a wraparound so we consider the timestamp to be stale.
*
* If F is not stale and F >= V then we set S = F.
* Otherwise we should assign S = V, but this may violate
* the ordering in EB (see [2]). So, if we have groups in ER,
* set S to the F_j of the first group j which would be blocking us.
* We are guaranteed not to move S backward because
* otherwise our group i would still be blocked.
*/
static void qfq_update_start(struct qfq_sched *q, struct qfq_aggregate *agg)
{
unsigned long mask;
u64 limit, roundedF;
int slot_shift = agg->grp->slot_shift;
roundedF = qfq_round_down(agg->F, slot_shift);
limit = qfq_round_down(q->V, slot_shift) + (1ULL << slot_shift);
if (!qfq_gt(agg->F, q->V) || qfq_gt(roundedF, limit)) {
/* timestamp was stale */
mask = mask_from(q->bitmaps[ER], agg->grp->index);
if (mask) {
struct qfq_group *next = qfq_ffs(q, mask);
if (qfq_gt(roundedF, next->F)) {
if (qfq_gt(limit, next->F))
agg->S = next->F;
else /* preserve timestamp correctness */
agg->S = limit;
return;
}
}
agg->S = q->V;
} else /* timestamp is not stale */
agg->S = agg->F;
}
/* Update the timestamps of agg before scheduling/rescheduling it for
* service. In particular, assign to agg->F its maximum possible
* value, i.e., the virtual finish time with which the aggregate
* should be labeled if it used all its budget once in service.
*/
static inline void
qfq_update_agg_ts(struct qfq_sched *q,
struct qfq_aggregate *agg, enum update_reason reason)
{
if (reason != requeue)
qfq_update_start(q, agg);
else /* just charge agg for the service received */
agg->S = agg->F;
agg->F = agg->S + (u64)agg->budgetmax * agg->inv_w;
}
static void qfq_schedule_agg(struct qfq_sched *q, struct qfq_aggregate *agg);
static struct sk_buff *qfq_dequeue(struct Qdisc *sch)
{
struct qfq_sched *q = qdisc_priv(sch);
struct qfq_aggregate *in_serv_agg = q->in_serv_agg;
struct qfq_class *cl;
struct sk_buff *skb = NULL;
/* next-packet len, 0 means no more active classes in in-service agg */
unsigned int len = 0;
if (in_serv_agg == NULL)
return NULL;
if (!list_empty(&in_serv_agg->active))
skb = qfq_peek_skb(in_serv_agg, &cl, &len);
/*
* If there are no active classes in the in-service aggregate,
* or if the aggregate has not enough budget to serve its next
* class, then choose the next aggregate to serve.
*/
if (len == 0 || in_serv_agg->budget < len) {
charge_actual_service(in_serv_agg);
/* recharge the budget of the aggregate */
in_serv_agg->initial_budget = in_serv_agg->budget =
in_serv_agg->budgetmax;
if (!list_empty(&in_serv_agg->active)) {
/*
* Still active: reschedule for
* service. Possible optimization: if no other
* aggregate is active, then there is no point
* in rescheduling this aggregate, and we can
* just keep it as the in-service one. This
* should be however a corner case, and to
* handle it, we would need to maintain an
* extra num_active_aggs field.
*/
qfq_update_agg_ts(q, in_serv_agg, requeue);
qfq_schedule_agg(q, in_serv_agg);
} else if (sch->q.qlen == 0) { /* no aggregate to serve */
q->in_serv_agg = NULL;
return NULL;
}
/*
* If we get here, there are other aggregates queued:
* choose the new aggregate to serve.
*/
in_serv_agg = q->in_serv_agg = qfq_choose_next_agg(q);
skb = qfq_peek_skb(in_serv_agg, &cl, &len);
}
if (!skb)
return NULL;
qdisc_qstats_backlog_dec(sch, skb);
sch->q.qlen--;
qdisc_bstats_update(sch, skb);
agg_dequeue(in_serv_agg, cl, len);
/* If lmax is lowered, through qfq_change_class, for a class
* owning pending packets with larger size than the new value
* of lmax, then the following condition may hold.
*/
if (unlikely(in_serv_agg->budget < len))
in_serv_agg->budget = 0;
else
in_serv_agg->budget -= len;
q->V += (u64)len * q->iwsum;
pr_debug("qfq dequeue: len %u F %lld now %lld\n",
len, (unsigned long long) in_serv_agg->F,
(unsigned long long) q->V);
return skb;
}
static struct qfq_aggregate *qfq_choose_next_agg(struct qfq_sched *q)
{
struct qfq_group *grp;
struct qfq_aggregate *agg, *new_front_agg;
u64 old_F;
qfq_update_eligible(q);
q->oldV = q->V;
if (!q->bitmaps[ER])
return NULL;
grp = qfq_ffs(q, q->bitmaps[ER]);
old_F = grp->F;
agg = qfq_slot_head(grp);
/* agg starts to be served, remove it from schedule */
qfq_front_slot_remove(grp);
new_front_agg = qfq_slot_scan(grp);
if (new_front_agg == NULL) /* group is now inactive, remove from ER */
__clear_bit(grp->index, &q->bitmaps[ER]);
else {
u64 roundedS = qfq_round_down(new_front_agg->S,
grp->slot_shift);
unsigned int s;
if (grp->S == roundedS)
return agg;
grp->S = roundedS;
grp->F = roundedS + (2ULL << grp->slot_shift);
__clear_bit(grp->index, &q->bitmaps[ER]);
s = qfq_calc_state(q, grp);
__set_bit(grp->index, &q->bitmaps[s]);
}
qfq_unblock_groups(q, grp->index, old_F);
return agg;
}
static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
struct sk_buff **to_free)
{
unsigned int len = qdisc_pkt_len(skb), gso_segs;
struct qfq_sched *q = qdisc_priv(sch);
struct qfq_class *cl;
struct qfq_aggregate *agg;
int err = 0;
bool first;
cl = qfq_classify(skb, sch, &err);
if (cl == NULL) {
if (err & __NET_XMIT_BYPASS)
qdisc_qstats_drop(sch);
__qdisc_drop(skb, to_free);
return err;
}
pr_debug("qfq_enqueue: cl = %x\n", cl->common.classid);
if (unlikely(cl->agg->lmax < len)) {
pr_debug("qfq: increasing maxpkt from %u to %u for class %u",
cl->agg->lmax, len, cl->common.classid);
err = qfq_change_agg(sch, cl, cl->agg->class_weight, len);
if (err) {
cl->qstats.drops++;
return qdisc_drop(skb, sch, to_free);
}
}
gso_segs = skb_is_gso(skb) ? skb_shinfo(skb)->gso_segs : 1;
first = !cl->qdisc->q.qlen;
err = qdisc_enqueue(skb, cl->qdisc, to_free);
if (unlikely(err != NET_XMIT_SUCCESS)) {
pr_debug("qfq_enqueue: enqueue failed %d\n", err);
if (net_xmit_drop_count(err)) {
cl->qstats.drops++;
qdisc_qstats_drop(sch);
}
return err;
}
cl->bstats.bytes += len;
cl->bstats.packets += gso_segs;
sch->qstats.backlog += len;
++sch->q.qlen;
agg = cl->agg;
/* if the queue was not empty, then done here */
if (!first) {
if (unlikely(skb == cl->qdisc->ops->peek(cl->qdisc)) &&
list_first_entry(&agg->active, struct qfq_class, alist)
== cl && cl->deficit < len)
list_move_tail(&cl->alist, &agg->active);
return err;
}
/* schedule class for service within the aggregate */
cl->deficit = agg->lmax;
list_add_tail(&cl->alist, &agg->active);
if (list_first_entry(&agg->active, struct qfq_class, alist) != cl ||
q->in_serv_agg == agg)
return err; /* non-empty or in service, nothing else to do */
qfq_activate_agg(q, agg, enqueue);
return err;
}
/*
* Schedule aggregate according to its timestamps.
*/
static void qfq_schedule_agg(struct qfq_sched *q, struct qfq_aggregate *agg)
{
struct qfq_group *grp = agg->grp;
u64 roundedS;
int s;
roundedS = qfq_round_down(agg->S, grp->slot_shift);
/*
* Insert agg in the correct bucket.
* If agg->S >= grp->S we don't need to adjust the
* bucket list and simply go to the insertion phase.
* Otherwise grp->S is decreasing, we must make room
* in the bucket list, and also recompute the group state.
* Finally, if there were no flows in this group and nobody
* was in ER make sure to adjust V.
*/
if (grp->full_slots) {
if (!qfq_gt(grp->S, agg->S))
goto skip_update;
/* create a slot for this agg->S */
qfq_slot_rotate(grp, roundedS);
/* group was surely ineligible, remove */
__clear_bit(grp->index, &q->bitmaps[IR]);
__clear_bit(grp->index, &q->bitmaps[IB]);
} else if (!q->bitmaps[ER] && qfq_gt(roundedS, q->V) &&
q->in_serv_agg == NULL)
q->V = roundedS;
grp->S = roundedS;
grp->F = roundedS + (2ULL << grp->slot_shift);
s = qfq_calc_state(q, grp);
__set_bit(grp->index, &q->bitmaps[s]);
pr_debug("qfq enqueue: new state %d %#lx S %lld F %lld V %lld\n",
s, q->bitmaps[s],
(unsigned long long) agg->S,
(unsigned long long) agg->F,
(unsigned long long) q->V);
skip_update:
qfq_slot_insert(grp, agg, roundedS);
}
/* Update agg ts and schedule agg for service */
static void qfq_activate_agg(struct qfq_sched *q, struct qfq_aggregate *agg,
enum update_reason reason)
{
agg->initial_budget = agg->budget = agg->budgetmax; /* recharge budg. */
qfq_update_agg_ts(q, agg, reason);
if (q->in_serv_agg == NULL) { /* no aggr. in service or scheduled */
q->in_serv_agg = agg; /* start serving this aggregate */
/* update V: to be in service, agg must be eligible */
q->oldV = q->V = agg->S;
} else if (agg != q->in_serv_agg)
qfq_schedule_agg(q, agg);
}
static void qfq_slot_remove(struct qfq_sched *q, struct qfq_group *grp,
struct qfq_aggregate *agg)
{
unsigned int i, offset;
u64 roundedS;
roundedS = qfq_round_down(agg->S, grp->slot_shift);
offset = (roundedS - grp->S) >> grp->slot_shift;
i = (grp->front + offset) % QFQ_MAX_SLOTS;
hlist_del(&agg->next);
if (hlist_empty(&grp->slots[i]))
__clear_bit(offset, &grp->full_slots);
}
/*
* Called to forcibly deschedule an aggregate. If the aggregate is
* not in the front bucket, or if the latter has other aggregates in
* the front bucket, we can simply remove the aggregate with no other
* side effects.
* Otherwise we must propagate the event up.
*/
static void qfq_deactivate_agg(struct qfq_sched *q, struct qfq_aggregate *agg)
{
struct qfq_group *grp = agg->grp;
unsigned long mask;
u64 roundedS;
int s;
if (agg == q->in_serv_agg) {
charge_actual_service(agg);
q->in_serv_agg = qfq_choose_next_agg(q);
return;
}
agg->F = agg->S;
qfq_slot_remove(q, grp, agg);
if (!grp->full_slots) {
__clear_bit(grp->index, &q->bitmaps[IR]);
__clear_bit(grp->index, &q->bitmaps[EB]);
__clear_bit(grp->index, &q->bitmaps[IB]);
if (test_bit(grp->index, &q->bitmaps[ER]) &&
!(q->bitmaps[ER] & ~((1UL << grp->index) - 1))) {
mask = q->bitmaps[ER] & ((1UL << grp->index) - 1);
if (mask)
mask = ~((1UL << __fls(mask)) - 1);
else
mask = ~0UL;
qfq_move_groups(q, mask, EB, ER);
qfq_move_groups(q, mask, IB, IR);
}
__clear_bit(grp->index, &q->bitmaps[ER]);
} else if (hlist_empty(&grp->slots[grp->front])) {
agg = qfq_slot_scan(grp);
roundedS = qfq_round_down(agg->S, grp->slot_shift);
if (grp->S != roundedS) {
__clear_bit(grp->index, &q->bitmaps[ER]);
__clear_bit(grp->index, &q->bitmaps[IR]);
__clear_bit(grp->index, &q->bitmaps[EB]);
__clear_bit(grp->index, &q->bitmaps[IB]);
grp->S = roundedS;
grp->F = roundedS + (2ULL << grp->slot_shift);
s = qfq_calc_state(q, grp);
__set_bit(grp->index, &q->bitmaps[s]);
}
}
}
static void qfq_qlen_notify(struct Qdisc *sch, unsigned long arg)
{
struct qfq_sched *q = qdisc_priv(sch);
struct qfq_class *cl = (struct qfq_class *)arg;
qfq_deactivate_class(q, cl);
}
static int qfq_init_qdisc(struct Qdisc *sch, struct nlattr *opt,
struct netlink_ext_ack *extack)
{
struct qfq_sched *q = qdisc_priv(sch);
struct qfq_group *grp;
int i, j, err;
u32 max_cl_shift, maxbudg_shift, max_classes;
err = tcf_block_get(&q->block, &q->filter_list, sch, extack);
if (err)
return err;
err = qdisc_class_hash_init(&q->clhash);
if (err < 0)
return err;
if (qdisc_dev(sch)->tx_queue_len + 1 > QFQ_MAX_AGG_CLASSES)
max_classes = QFQ_MAX_AGG_CLASSES;
else
max_classes = qdisc_dev(sch)->tx_queue_len + 1;
/* max_cl_shift = floor(log_2(max_classes)) */
max_cl_shift = __fls(max_classes);
q->max_agg_classes = 1<<max_cl_shift;
/* maxbudg_shift = log2(max_len * max_classes_per_agg) */
maxbudg_shift = QFQ_MTU_SHIFT + max_cl_shift;
q->min_slot_shift = FRAC_BITS + maxbudg_shift - QFQ_MAX_INDEX;
for (i = 0; i <= QFQ_MAX_INDEX; i++) {
grp = &q->groups[i];
grp->index = i;
grp->slot_shift = q->min_slot_shift + i;
for (j = 0; j < QFQ_MAX_SLOTS; j++)
INIT_HLIST_HEAD(&grp->slots[j]);
}
INIT_HLIST_HEAD(&q->nonfull_aggs);
return 0;
}
static void qfq_reset_qdisc(struct Qdisc *sch)
{
struct qfq_sched *q = qdisc_priv(sch);
struct qfq_class *cl;
unsigned int i;
for (i = 0; i < q->clhash.hashsize; i++) {
hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
if (cl->qdisc->q.qlen > 0)
qfq_deactivate_class(q, cl);
qdisc_reset(cl->qdisc);
}
}
sch->qstats.backlog = 0;
sch->q.qlen = 0;
}
static void qfq_destroy_qdisc(struct Qdisc *sch)
{
struct qfq_sched *q = qdisc_priv(sch);
struct qfq_class *cl;
struct hlist_node *next;
unsigned int i;
tcf_block_put(q->block);
for (i = 0; i < q->clhash.hashsize; i++) {
hlist_for_each_entry_safe(cl, next, &q->clhash.hash[i],
common.hnode) {
qfq_destroy_class(sch, cl);
}
}
qdisc_class_hash_destroy(&q->clhash);
}
static const struct Qdisc_class_ops qfq_class_ops = {
.change = qfq_change_class,
.delete = qfq_delete_class,
.find = qfq_search_class,
.tcf_block = qfq_tcf_block,
.bind_tcf = qfq_bind_tcf,
.unbind_tcf = qfq_unbind_tcf,
.graft = qfq_graft_class,
.leaf = qfq_class_leaf,
.qlen_notify = qfq_qlen_notify,
.dump = qfq_dump_class,
.dump_stats = qfq_dump_class_stats,
.walk = qfq_walk,
};
static struct Qdisc_ops qfq_qdisc_ops __read_mostly = {
.cl_ops = &qfq_class_ops,
.id = "qfq",
.priv_size = sizeof(struct qfq_sched),
.enqueue = qfq_enqueue,
.dequeue = qfq_dequeue,
.peek = qdisc_peek_dequeued,
.init = qfq_init_qdisc,
.reset = qfq_reset_qdisc,
.destroy = qfq_destroy_qdisc,
.owner = THIS_MODULE,
};
static int __init qfq_init(void)
{
return register_qdisc(&qfq_qdisc_ops);
}
static void __exit qfq_exit(void)
{
unregister_qdisc(&qfq_qdisc_ops);
}
module_init(qfq_init);
module_exit(qfq_exit);
MODULE_LICENSE("GPL");