Commit d47a0ac7 authored Jan 01, 2012 by Eric Dumazet Committed by David S. Miller Jan 03, 2012

sch_sfq: dont put new flow at the end of flows



SFQ enqueue algo puts a new flow _behind_ all pre-existing flows in the
circular list. In fact this is probably an old SFQ implementation bug.

100 Mbits = ~8333 full frames per second, or ~8 frames per ms.

With 50 flows, it means your "new flow" will have to wait 50 packets
being sent before its own packet. Thats the ~6ms.

We certainly can change SFQ to give a priority advantage to new flows,
so that next dequeued packet is taken from a new flow, not an old one.

Reported-by: Dave Taht <dave.taht@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 1c015b3b

net/sched/sch_sfq.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -366,11 +366,11 @@ sfq_enqueue(struct sk_buff skb, struct Qdisc sch)
		if (slot->qlen == 1) { /* The flow is new */
		if (q->tail == NULL) { /* It is the first flow */
		slot->next = x;
		q->tail = slot;
		} else {
		slot->next = q->tail->next;
		q->tail->next = x;
		}
		q->tail = slot;
		slot->allot = q->scaled_quantum;
		}
		if (++sch->q.qlen <= q->limit)

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