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sched: add head drop fifo queue

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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 <fw@strlen.de>
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Hagen Paul Pfeifer
2010-01-24 12:30:59 +00:00
committed by David S. Miller
parent d74340d31b
commit 57dbb2d83d
4 changed files with 55 additions and 0 deletions
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34
net/sched/sch_fifo.c
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@@ -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)
{