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Commit 008830bc authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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net_sched: fq_codel: cache skb->truesize into skb->cb 



Now we defer skb drops, it makes sense to keep a copy
of skb->truesize in struct codel_skb_cb to avoid one
cache line miss per dropped skb in fq_codel_drop(),
to reduce latencies a bit further.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 520ac30f

include/net/codel_qdisc.h

+1 −0
Original line number Diff line number Diff line
@@ -52,6 +52,7 @@ 
/* Qdiscs using codel plugin must use codel_skb_cb in their own cb[] */

struct codel_skb_cb {

	codel_time_t enqueue_time;

	unsigned int mem_usage;

};



static struct codel_skb_cb *get_codel_cb(const struct sk_buff *skb)

net/sched/sch_fq_codel.c

+4 −3
Original line number Diff line number Diff line
@@ -172,7 +172,7 @@ static unsigned int fq_codel_drop(struct Qdisc *sch, unsigned int max_packets, 
	do {

		skb = dequeue_head(flow);

		len += qdisc_pkt_len(skb);

		mem += skb->truesize;

		mem += get_codel_cb(skb)->mem_usage;

		__qdisc_drop(skb, to_free);

	} while (++i < max_packets && len < threshold);
@@ -216,7 +216,8 @@ static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch, 
		flow->deficit = q->quantum;

		flow->dropped = 0;

	}

	q->memory_usage += skb->truesize;

	get_codel_cb(skb)->mem_usage = skb->truesize;

	q->memory_usage += get_codel_cb(skb)->mem_usage;

	memory_limited = q->memory_usage > q->memory_limit;

	if (++sch->q.qlen <= sch->limit && !memory_limited)

		return NET_XMIT_SUCCESS;
@@ -267,7 +268,7 @@ static struct sk_buff *dequeue_func(struct codel_vars *vars, void *ctx) 
	if (flow->head) {

		skb = dequeue_head(flow);

		q->backlogs[flow - q->flows] -= qdisc_pkt_len(skb);

		q->memory_usage -= skb->truesize;

		q->memory_usage -= get_codel_cb(skb)->mem_usage;

		sch->q.qlen--;

		sch->qstats.backlog -= qdisc_pkt_len(skb);

	}