From 2f3b89a1fe0823fceb544856c9eeb036a75ff091 Mon Sep 17 00:00:00 2001 From: Paolo Valente Date: Tue, 5 Mar 2013 08:04:59 +0000 Subject: [PATCH] pkt_sched: sch_qfq: serve activated aggregates immediately if the scheduler is empty If no aggregate is in service, then the function qfq_dequeue() does not dequeue any packet. For this reason, to guarantee QFQ+ to be work conserving, a just-activated aggregate must be set as in service immediately if it happens to be the only active aggregate. This is done by the function qfq_enqueue(). Unfortunately, the function qfq_add_to_agg(), used to add a class to an aggregate, does not perform this important additional operation. In particular, if: 1) qfq_add_to_agg() is invoked to complete the move of a class from a source aggregate, becoming, for this move, inactive, to a destination aggregate, becoming instead active, and 2) the destination aggregate becomes the only active aggregate, then this aggregate is not however set as in service. QFQ+ remains then in a non-work-conserving state until a new invocation of qfq_enqueue() recovers the situation. This fix solves the problem by moving the logic for setting an aggregate as in service directly into the function qfq_activate_agg(). Hence, from whatever point qfq_activate_aggregate() is invoked, QFQ+ remains work conserving. Since the more-complex logic of this new version of activate_aggregate() is not necessary, in qfq_dequeue(), to reschedule an aggregate that finishes its budget, then the aggregate is now rescheduled by invoking directly the functions needed. Signed-off-by: Paolo Valente Reviewed-by: Fabio Checconi Signed-off-by: David S. Miller --- net/sched/sch_qfq.c | 36 ++++++++++++++++++++++-------------- 1 file changed, 22 insertions(+), 14 deletions(-) diff --git a/net/sched/sch_qfq.c b/net/sched/sch_qfq.c index 39d85cc0db26..8c5172c7f193 100644 --- a/net/sched/sch_qfq.c +++ b/net/sched/sch_qfq.c @@ -1003,6 +1003,12 @@ static inline void charge_actual_service(struct qfq_aggregate *agg) agg->F = agg->S + (u64)service_received * agg->inv_w; } +static inline void qfq_update_agg_ts(struct qfq_sched *q, + struct qfq_aggregate *agg, + enum update_reason reason); + +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); @@ -1030,7 +1036,7 @@ static struct sk_buff *qfq_dequeue(struct Qdisc *sch) in_serv_agg->initial_budget = in_serv_agg->budget = in_serv_agg->budgetmax; - if (!list_empty(&in_serv_agg->active)) + if (!list_empty(&in_serv_agg->active)) { /* * Still active: reschedule for * service. Possible optimization: if no other @@ -1041,8 +1047,9 @@ static struct sk_buff *qfq_dequeue(struct Qdisc *sch) * handle it, we would need to maintain an * extra num_active_aggs field. */ - qfq_activate_agg(q, in_serv_agg, requeue); - else if (sch->q.qlen == 0) { /* no aggregate to serve */ + 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; } @@ -1226,17 +1233,11 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch) cl->deficit = agg->lmax; list_add_tail(&cl->alist, &agg->active); - if (list_first_entry(&agg->active, struct qfq_class, alist) != cl) - return err; /* aggregate was not empty, nothing else to do */ - - /* recharge budget */ - agg->initial_budget = agg->budget = agg->budgetmax; + 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_update_agg_ts(q, agg, enqueue); - if (q->in_serv_agg == NULL) - q->in_serv_agg = agg; - else if (agg != q->in_serv_agg) - qfq_schedule_agg(q, agg); + qfq_activate_agg(q, agg, enqueue); return err; } @@ -1293,8 +1294,15 @@ skip_update: 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); - qfq_schedule_agg(q, agg); + 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, -- 2.20.1