From 48da34b7a74201f15315cb1fc40bb9a7bd2b4940 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Sun, 18 Sep 2016 00:57:34 +0200 Subject: [PATCH] sched: add and use qdisc_skb_head helpers This change replaces sk_buff_head struct in Qdiscs with new qdisc_skb_head. Its similar to the skb_buff_head api, but does not use skb->prev pointers. Qdiscs will commonly enqueue at the tail of a list and dequeue at head. While skb_buff_head works fine for this, enqueue/dequeue needs to also adjust the prev pointer of next element. The ->prev pointer is not required for qdiscs so we can just leave it undefined and avoid one cacheline write access for en/dequeue. Suggested-by: Eric Dumazet Signed-off-by: Florian Westphal Signed-off-by: David S. Miller --- include/net/sch_generic.h | 63 +++++++++++++++++++++++++++++++-------- net/sched/sch_generic.c | 21 ++++++------- net/sched/sch_htb.c | 24 ++++++++++++--- net/sched/sch_netem.c | 14 +++++++-- 4 files changed, 94 insertions(+), 28 deletions(-) diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index 0741ed41575b..e6aa0a249672 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -36,6 +36,14 @@ struct qdisc_size_table { u16 data[]; }; +/* similar to sk_buff_head, but skb->prev pointer is undefined. */ +struct qdisc_skb_head { + struct sk_buff *head; + struct sk_buff *tail; + __u32 qlen; + spinlock_t lock; +}; + struct Qdisc { int (*enqueue)(struct sk_buff *skb, struct Qdisc *sch, @@ -76,7 +84,7 @@ struct Qdisc { * For performance sake on SMP, we put highly modified fields at the end */ struct sk_buff *gso_skb ____cacheline_aligned_in_smp; - struct sk_buff_head q; + struct qdisc_skb_head q; struct gnet_stats_basic_packed bstats; seqcount_t running; struct gnet_stats_queue qstats; @@ -600,10 +608,27 @@ static inline void qdisc_qstats_overlimit(struct Qdisc *sch) sch->qstats.overlimits++; } +static inline void qdisc_skb_head_init(struct qdisc_skb_head *qh) +{ + qh->head = NULL; + qh->tail = NULL; + qh->qlen = 0; +} + static inline int __qdisc_enqueue_tail(struct sk_buff *skb, struct Qdisc *sch, - struct sk_buff_head *list) + struct qdisc_skb_head *qh) { - __skb_queue_tail(list, skb); + struct sk_buff *last = qh->tail; + + if (last) { + skb->next = NULL; + last->next = skb; + qh->tail = skb; + } else { + qh->tail = skb; + qh->head = skb; + } + qh->qlen++; qdisc_qstats_backlog_inc(sch, skb); return NET_XMIT_SUCCESS; @@ -614,9 +639,17 @@ static inline int qdisc_enqueue_tail(struct sk_buff *skb, struct Qdisc *sch) return __qdisc_enqueue_tail(skb, sch, &sch->q); } -static inline struct sk_buff *__qdisc_dequeue_head(struct sk_buff_head *list) +static inline struct sk_buff *__qdisc_dequeue_head(struct qdisc_skb_head *qh) { - struct sk_buff *skb = __skb_dequeue(list); + struct sk_buff *skb = qh->head; + + if (likely(skb != NULL)) { + qh->head = skb->next; + qh->qlen--; + if (qh->head == NULL) + qh->tail = NULL; + skb->next = NULL; + } return skb; } @@ -643,10 +676,10 @@ static inline void __qdisc_drop(struct sk_buff *skb, struct sk_buff **to_free) } static inline unsigned int __qdisc_queue_drop_head(struct Qdisc *sch, - struct sk_buff_head *list, + struct qdisc_skb_head *qh, struct sk_buff **to_free) { - struct sk_buff *skb = __skb_dequeue(list); + struct sk_buff *skb = __qdisc_dequeue_head(qh); if (likely(skb != NULL)) { unsigned int len = qdisc_pkt_len(skb); @@ -667,7 +700,9 @@ static inline unsigned int qdisc_queue_drop_head(struct Qdisc *sch, static inline struct sk_buff *qdisc_peek_head(struct Qdisc *sch) { - return skb_peek(&sch->q); + const struct qdisc_skb_head *qh = &sch->q; + + return qh->head; } /* generic pseudo peek method for non-work-conserving qdisc */ @@ -702,15 +737,19 @@ static inline struct sk_buff *qdisc_dequeue_peeked(struct Qdisc *sch) return skb; } -static inline void __qdisc_reset_queue(struct sk_buff_head *list) +static inline void __qdisc_reset_queue(struct qdisc_skb_head *qh) { /* * We do not know the backlog in bytes of this list, it * is up to the caller to correct it */ - if (!skb_queue_empty(list)) { - rtnl_kfree_skbs(list->next, list->prev); - __skb_queue_head_init(list); + ASSERT_RTNL(); + if (qh->qlen) { + rtnl_kfree_skbs(qh->head, qh->tail); + + qh->head = NULL; + qh->tail = NULL; + qh->qlen = 0; } } diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index 73877d9c2bcb..6cfb6e9038c2 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -466,7 +466,7 @@ static const u8 prio2band[TC_PRIO_MAX + 1] = { */ struct pfifo_fast_priv { u32 bitmap; - struct sk_buff_head q[PFIFO_FAST_BANDS]; + struct qdisc_skb_head q[PFIFO_FAST_BANDS]; }; /* @@ -477,7 +477,7 @@ struct pfifo_fast_priv { */ static const int bitmap2band[] = {-1, 0, 1, 0, 2, 0, 1, 0}; -static inline struct sk_buff_head *band2list(struct pfifo_fast_priv *priv, +static inline struct qdisc_skb_head *band2list(struct pfifo_fast_priv *priv, int band) { return priv->q + band; @@ -489,7 +489,7 @@ static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc *qdisc, if (qdisc->q.qlen < qdisc_dev(qdisc)->tx_queue_len) { int band = prio2band[skb->priority & TC_PRIO_MAX]; struct pfifo_fast_priv *priv = qdisc_priv(qdisc); - struct sk_buff_head *list = band2list(priv, band); + struct qdisc_skb_head *list = band2list(priv, band); priv->bitmap |= (1 << band); qdisc->q.qlen++; @@ -505,8 +505,8 @@ static struct sk_buff *pfifo_fast_dequeue(struct Qdisc *qdisc) int band = bitmap2band[priv->bitmap]; if (likely(band >= 0)) { - struct sk_buff_head *list = band2list(priv, band); - struct sk_buff *skb = __qdisc_dequeue_head(list); + struct qdisc_skb_head *qh = band2list(priv, band); + struct sk_buff *skb = __qdisc_dequeue_head(qh); if (likely(skb != NULL)) { qdisc_qstats_backlog_dec(qdisc, skb); @@ -514,7 +514,7 @@ static struct sk_buff *pfifo_fast_dequeue(struct Qdisc *qdisc) } qdisc->q.qlen--; - if (skb_queue_empty(list)) + if (qh->qlen == 0) priv->bitmap &= ~(1 << band); return skb; @@ -529,9 +529,9 @@ static struct sk_buff *pfifo_fast_peek(struct Qdisc *qdisc) int band = bitmap2band[priv->bitmap]; if (band >= 0) { - struct sk_buff_head *list = band2list(priv, band); + struct qdisc_skb_head *qh = band2list(priv, band); - return skb_peek(list); + return qh->head; } return NULL; @@ -569,7 +569,7 @@ static int pfifo_fast_init(struct Qdisc *qdisc, struct nlattr *opt) struct pfifo_fast_priv *priv = qdisc_priv(qdisc); for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) - __skb_queue_head_init(band2list(priv, prio)); + qdisc_skb_head_init(band2list(priv, prio)); /* Can by-pass the queue discipline */ qdisc->flags |= TCQ_F_CAN_BYPASS; @@ -617,7 +617,8 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue, sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p); sch->padded = (char *) sch - (char *) p; } - skb_queue_head_init(&sch->q); + qdisc_skb_head_init(&sch->q); + spin_lock_init(&sch->q.lock); spin_lock_init(&sch->busylock); lockdep_set_class(&sch->busylock, diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c index 53dbfa187870..c798d0de8a9d 100644 --- a/net/sched/sch_htb.c +++ b/net/sched/sch_htb.c @@ -162,7 +162,7 @@ struct htb_sched { struct work_struct work; /* non shaped skbs; let them go directly thru */ - struct sk_buff_head direct_queue; + struct qdisc_skb_head direct_queue; long direct_pkts; struct qdisc_watchdog watchdog; @@ -570,6 +570,22 @@ static inline void htb_deactivate(struct htb_sched *q, struct htb_class *cl) list_del_init(&cl->un.leaf.drop_list); } +static void htb_enqueue_tail(struct sk_buff *skb, struct Qdisc *sch, + struct qdisc_skb_head *qh) +{ + struct sk_buff *last = qh->tail; + + if (last) { + skb->next = NULL; + last->next = skb; + qh->tail = skb; + } else { + qh->tail = skb; + qh->head = skb; + } + qh->qlen++; +} + static int htb_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free) { @@ -580,7 +596,7 @@ static int htb_enqueue(struct sk_buff *skb, struct Qdisc *sch, if (cl == HTB_DIRECT) { /* enqueue to helper queue */ if (q->direct_queue.qlen < q->direct_qlen) { - __skb_queue_tail(&q->direct_queue, skb); + htb_enqueue_tail(skb, sch, &q->direct_queue); q->direct_pkts++; } else { return qdisc_drop(skb, sch, to_free); @@ -888,7 +904,7 @@ static struct sk_buff *htb_dequeue(struct Qdisc *sch) unsigned long start_at; /* try to dequeue direct packets as high prio (!) to minimize cpu work */ - skb = __skb_dequeue(&q->direct_queue); + skb = __qdisc_dequeue_head(&q->direct_queue); if (skb != NULL) { ok: qdisc_bstats_update(sch, skb); @@ -1019,7 +1035,7 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt) qdisc_watchdog_init(&q->watchdog, sch); INIT_WORK(&q->work, htb_work_func); - __skb_queue_head_init(&q->direct_queue); + qdisc_skb_head_init(&q->direct_queue); if (tb[TCA_HTB_DIRECT_QLEN]) q->direct_qlen = nla_get_u32(tb[TCA_HTB_DIRECT_QLEN]); diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index 0a964b35f8c7..9f7b380cf0a3 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -413,6 +413,16 @@ static struct sk_buff *netem_segment(struct sk_buff *skb, struct Qdisc *sch, return segs; } +static void netem_enqueue_skb_head(struct qdisc_skb_head *qh, struct sk_buff *skb) +{ + skb->next = qh->head; + + if (!qh->head) + qh->tail = skb; + qh->head = skb; + qh->qlen++; +} + /* * Insert one skb into qdisc. * Note: parent depends on return value to account for queue length. @@ -523,7 +533,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff *last; if (sch->q.qlen) - last = skb_peek_tail(&sch->q); + last = sch->q.tail; else last = netem_rb_to_skb(rb_last(&q->t_root)); if (last) { @@ -552,7 +562,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, cb->time_to_send = psched_get_time(); q->counter = 0; - __skb_queue_head(&sch->q, skb); + netem_enqueue_skb_head(&sch->q, skb); sch->qstats.requeues++; } -- 2.39.5