/* * 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. * * 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/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 refcnt; 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 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 void qfq_purge_queue(struct qfq_class *cl) { unsigned int len = cl->qdisc->q.qlen; unsigned int backlog = cl->qdisc->qstats.backlog; qdisc_reset(cl->qdisc); qdisc_tree_reduce_backlog(cl->qdisc, len, backlog); } 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 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(tb, TCA_QFQ_MAX, tca[TCA_OPTIONS], qfq_policy); 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->refcnt = 1; cl->common.classid = classid; cl->deficit = lmax; cl->qdisc = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops, classid); 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; } sch_tree_lock(sch); qdisc_class_hash_insert(&q->clhash, &cl->common); sch_tree_unlock(sch); qdisc_class_hash_grow(sch, &q->clhash); 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); qfq_add_to_agg(q, new_agg, cl); sch_tree_unlock(sch); *arg = (unsigned long)cl; return 0; destroy_class: qdisc_destroy(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_destroy(cl->qdisc); kfree(cl); } static int qfq_delete_class(struct Qdisc *sch, unsigned long arg) { 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); qfq_purge_queue(cl); qdisc_class_hash_remove(&q->clhash, &cl->common); BUG_ON(--cl->refcnt == 0); /* * This shouldn't happen: we "hold" one cops->get() when called * from tc_ctl_tclass; the destroy method is done from cops->put(). */ sch_tree_unlock(sch); return 0; } static unsigned long qfq_get_class(struct Qdisc *sch, u32 classid) { struct qfq_class *cl = qfq_find_class(sch, classid); if (cl != NULL) cl->refcnt++; return (unsigned long)cl; } static void qfq_put_class(struct Qdisc *sch, unsigned long arg) { struct qfq_class *cl = (struct qfq_class *)arg; if (--cl->refcnt == 0) qfq_destroy_class(sch, cl); } static struct tcf_proto __rcu **qfq_tcf_chain(struct Qdisc *sch, unsigned long cl) { struct qfq_sched *q = qdisc_priv(sch); if (cl) return NULL; return &q->filter_list; } 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 qfq_class *cl = (struct qfq_class *)arg; if (new == NULL) { new = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops, cl->common.classid); 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(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 || gnet_stats_copy_queue(d, NULL, &cl->qdisc->qstats, cl->qdisc->q.qlen) < 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 = tc_classify(skb, fl, &res, false); if (result >= 0) { #ifdef CONFIG_NET_CLS_ACT switch (result) { case TC_ACT_QUEUED: case TC_ACT_STOLEN: *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN; 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) { struct qfq_sched *q = qdisc_priv(sch); struct qfq_class *cl; struct qfq_aggregate *agg; int err = 0; cl = qfq_classify(skb, sch, &err); if (cl == NULL) { if (err & __NET_XMIT_BYPASS) qdisc_qstats_drop(sch); kfree_skb(skb); return err; } pr_debug("qfq_enqueue: cl = %x\n", cl->common.classid); if (unlikely(cl->agg->lmax < qdisc_pkt_len(skb))) { pr_debug("qfq: increasing maxpkt from %u to %u for class %u", cl->agg->lmax, qdisc_pkt_len(skb), cl->common.classid); err = qfq_change_agg(sch, cl, cl->agg->class_weight, qdisc_pkt_len(skb)); if (err) { cl->qstats.drops++; return qdisc_drop(skb, sch, to_free); } } 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; } bstats_update(&cl->bstats, skb); qdisc_qstats_backlog_inc(sch, skb); ++sch->q.qlen; agg = cl->agg; /* if the queue was not empty, then done here */ if (cl->qdisc->q.qlen != 1) { if (unlikely(skb == cl->qdisc->ops->peek(cl->qdisc)) && list_first_entry(&agg->active, struct qfq_class, alist) == cl && cl->deficit < qdisc_pkt_len(skb)) 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; if (cl->qdisc->q.qlen == 0) qfq_deactivate_class(q, cl); } static int qfq_init_qdisc(struct Qdisc *sch, struct nlattr *opt) { struct qfq_sched *q = qdisc_priv(sch); struct qfq_group *grp; int i, j, err; u32 max_cl_shift, maxbudg_shift, max_classes; 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_destroy_chain(&q->filter_list); 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, .get = qfq_get_class, .put = qfq_put_class, .tcf_chain = qfq_tcf_chain, .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");