diff options
author | Florian Westphal <fw@strlen.de> | 2016-09-18 00:57:34 +0200 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2016-09-19 01:47:18 -0400 |
commit | 48da34b7a74201f15315cb1fc40bb9a7bd2b4940 (patch) | |
tree | 123595224534ee49f1175b6ef8371728b6d31538 /include/net/sch_generic.h | |
parent | ed760cb8aae7c2b84c193d4a7637b0c9e752f07e (diff) | |
download | linux-stable-48da34b7a74201f15315cb1fc40bb9a7bd2b4940.tar.gz linux-stable-48da34b7a74201f15315cb1fc40bb9a7bd2b4940.tar.bz2 linux-stable-48da34b7a74201f15315cb1fc40bb9a7bd2b4940.zip |
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 <edumazet@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/sch_generic.h')
-rw-r--r-- | include/net/sch_generic.h | 63 |
1 files changed, 51 insertions, 12 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; } } |