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Commit 57dbb2d8 authored by Hagen Paul Pfeifer's avatar Hagen Paul Pfeifer Committed by David S. Miller
Browse files

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: default avatarFlorian Westphal <fw@strlen.de>
Acked-by: default avatarPatrick McHardy <kaber@trash.net>
Signed-off-by: default avatarHagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent d74340d3

include/net/pkt_sched.h

+1 −0
Original line number Diff line number Diff line
@@ -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,

include/net/sch_generic.h

+19 −0
Original line number Diff line number Diff line
@@ -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)

{

net/sched/sch_api.c

+1 −0
Original line number Diff line number Diff line
@@ -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);

net/sched/sch_fifo.c

+34 −0
Original line number Diff line number Diff line
@@ -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)

{