Commit 2f9babc0 authored by Eric Dumazet's avatar Eric Dumazet Committed by Paolo Abeni
Browse files

net_sched: sch_fq: prefetch one skb ahead in dequeue() 



prefetch the skb that we are likely to dequeue at the next dequeue().

Also call fq_dequeue_skb() a bit sooner in fq_dequeue().

This reduces the window between read of q.qlen and
changes of fields in the cache line that could be dirtied
by another cpu trying to queue a packet.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20251121083256.674562-10-edumazet@google.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 3c1100f0

net/sched/sch_fq.c

+5 −2
Original line number Diff line number Diff line
@@ -480,7 +480,10 @@ static void fq_erase_head(struct Qdisc *sch, struct fq_flow *flow, 
			  struct sk_buff *skb)

{

	if (skb == flow->head) {

		flow->head = skb->next;

		struct sk_buff *next = skb->next;



		prefetch(next);

		flow->head = next;

	} else {

		rb_erase(&skb->rbnode, &flow->t_root);

		skb->dev = qdisc_dev(sch);
@@ -712,6 +715,7 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch) 
			goto begin;

		}

		prefetch(&skb->end);

		fq_dequeue_skb(sch, f, skb);

		if ((s64)(now - time_next_packet - q->ce_threshold) > 0) {

			INET_ECN_set_ce(skb);

			q->stat_ce_mark++;
@@ -719,7 +723,6 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch) 
		if (--f->qlen == 0)

			q->inactive_flows++;

		q->band_pkt_count[fq_skb_cb(skb)->band]--;

		fq_dequeue_skb(sch, f, skb);

	} else {

		head->first = f->next;

		/* force a pass through old_flows to prevent starvation */