From 57dbb2d83d100ea601c54fe129bfde0678db5dee Mon Sep 17 00:00:00 2001 From: Hagen Paul Pfeifer Date: Sun, 24 Jan 2010 12:30:59 +0000 Subject: [PATCH] sched: add head drop fifo queue This adds an additional queuing strategy, called pfifo_head_drop, to remove the oldest skb in the case of an overflow within the queue - the head element - instead of the last skb (tail). To remove the oldest skb in congested situations is useful for sensor network environments where newer packets reflect the superior information. Reviewed-by: Florian Westphal Acked-by: Patrick McHardy Signed-off-by: Hagen Paul Pfeifer Signed-off-by: David S. Miller --- include/net/pkt_sched.h | 1 + include/net/sch_generic.h | 19 +++++++++++++++++++ net/sched/sch_api.c | 1 + net/sched/sch_fifo.c | 34 ++++++++++++++++++++++++++++++++++ 4 files changed, 55 insertions(+) diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h index 2d567265363e..b6cdc33b39c1 100644 --- a/include/net/pkt_sched.h +++ b/include/net/pkt_sched.h @@ -71,6 +71,7 @@ extern void qdisc_watchdog_cancel(struct qdisc_watchdog *wd); extern struct Qdisc_ops pfifo_qdisc_ops; extern struct Qdisc_ops bfifo_qdisc_ops; +extern struct Qdisc_ops pfifo_head_drop_qdisc_ops; extern int fifo_set_limit(struct Qdisc *q, unsigned int limit); extern struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops, diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index dad558bc06fa..67dc08eaaa45 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -427,6 +427,25 @@ static inline struct sk_buff *qdisc_dequeue_head(struct Qdisc *sch) return __qdisc_dequeue_head(sch, &sch->q); } +static inline unsigned int __qdisc_queue_drop_head(struct Qdisc *sch, + struct sk_buff_head *list) +{ + struct sk_buff *skb = __qdisc_dequeue_head(sch, list); + + if (likely(skb != NULL)) { + unsigned int len = qdisc_pkt_len(skb); + kfree_skb(skb); + return len; + } + + return 0; +} + +static inline unsigned int qdisc_queue_drop_head(struct Qdisc *sch) +{ + return __qdisc_queue_drop_head(sch, &sch->q); +} + static inline struct sk_buff *__qdisc_dequeue_tail(struct Qdisc *sch, struct sk_buff_head *list) { diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c index 75fd1c672c61..6cd491013b50 100644 --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -1707,6 +1707,7 @@ static int __init pktsched_init(void) { register_qdisc(&pfifo_qdisc_ops); register_qdisc(&bfifo_qdisc_ops); + register_qdisc(&pfifo_head_drop_qdisc_ops); register_qdisc(&mq_qdisc_ops); proc_net_fops_create(&init_net, "psched", 0, &psched_fops); diff --git a/net/sched/sch_fifo.c b/net/sched/sch_fifo.c index 69188e8358b4..4b0a6cc44c77 100644 --- a/net/sched/sch_fifo.c +++ b/net/sched/sch_fifo.c @@ -43,6 +43,26 @@ static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc* sch) return qdisc_reshape_fail(skb, sch); } +static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc* sch) +{ + struct sk_buff *skb_head; + struct fifo_sched_data *q = qdisc_priv(sch); + + if (likely(skb_queue_len(&sch->q) < q->limit)) + return qdisc_enqueue_tail(skb, sch); + + /* queue full, remove one skb to fulfill the limit */ + skb_head = qdisc_dequeue_head(sch); + sch->bstats.bytes -= qdisc_pkt_len(skb_head); + sch->bstats.packets--; + sch->qstats.drops++; + kfree_skb(skb_head); + + qdisc_enqueue_tail(skb, sch); + + return NET_XMIT_CN; +} + static int fifo_init(struct Qdisc *sch, struct nlattr *opt) { struct fifo_sched_data *q = qdisc_priv(sch); @@ -108,6 +128,20 @@ struct Qdisc_ops bfifo_qdisc_ops __read_mostly = { }; EXPORT_SYMBOL(bfifo_qdisc_ops); +struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = { + .id = "pfifo_head_drop", + .priv_size = sizeof(struct fifo_sched_data), + .enqueue = pfifo_tail_enqueue, + .dequeue = qdisc_dequeue_head, + .peek = qdisc_peek_head, + .drop = qdisc_queue_drop_head, + .init = fifo_init, + .reset = qdisc_reset_queue, + .change = fifo_init, + .dump = fifo_dump, + .owner = THIS_MODULE, +}; + /* Pass size change message down to embedded FIFO */ int fifo_set_limit(struct Qdisc *q, unsigned int limit) { -- 2.20.1