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authorFlorian Westphal <fw@strlen.de>2016-09-18 00:57:34 +0200
committerDavid S. Miller <davem@davemloft.net>2016-09-19 01:47:18 -0400
commit48da34b7a74201f15315cb1fc40bb9a7bd2b4940 (patch)
tree123595224534ee49f1175b6ef8371728b6d31538 /include
parented760cb8aae7c2b84c193d4a7637b0c9e752f07e (diff)
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')
-rw-r--r--include/net/sch_generic.h63
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;
}
}