commit 008830bc321c0fc22c0db8d5b0b56f854ed90a5c
author Eric Dumazet <edumazet@google.com> Tue Jun 21 23:16:50 2016 -0700
committer David S. Miller <davem@davemloft.net> Sat Jun 25 12:19:35 2016 -0400
tree 99d4bfa6d32a42e48b598223a5443eb3443ca532
parent 520ac30f45519b0a82dd92117c181d1d6144677b

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: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_fq_codel.c

diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c
index f715195..a5ea0e9 100644
--- a/net/sched/sch_fq_codel.c
+++ b/net/sched/sch_fq_codel.c
@@ -172,7 +172,7 @@
 	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 @@
 		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 @@
 	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);
 	}