Re: [RFC PATCH v2 08/10] net: sched: pfifo_fast use alf_queue

On 16-07-15 03:09 AM, Jesper Dangaard Brouer wrote:

On Thu, 14 Jul 2016 17:09:43 -0700
John Fastabend [off-list ref] wrote:

quoted

quoted

quoted

 static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc *qdisc,
 			      struct sk_buff **to_free)
 {
-	if (skb_queue_len(&qdisc->q) < qdisc_dev(qdisc)->tx_queue_len) {
-		int band = prio2band[skb->priority & TC_PRIO_MAX];
-		struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
-		struct sk_buff_head *list = band2list(priv, band);
-
-		priv->bitmap |= (1 << band);
-		qdisc->q.qlen++;
-		return __qdisc_enqueue_tail(skb, qdisc, list);
-	}
+	int band = prio2band[skb->priority & TC_PRIO_MAX];
+	struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
+	struct skb_array *q = band2list(priv, band);
+	int err;
 
-	return qdisc_drop(skb, qdisc, to_free);
+	err = skb_array_produce_bh(q, skb);  

Do you need the _bh variant here?  (Doesn't the qdisc run with BH disabled?)

  

Yep its inside rcu_read_lock_bh().

The call rcu_read_lock_bh() already disabled BH (local_bh_disable()).
Thus, you can use the normal variants of skb_array_produce(), it is
(approx 20 cycles) faster than the _bh variant...

hah I was agreeing with you as in yep no need for the _bh variant :)
I must have been low on coffee or something when I wrote that response
because when I read it now it sounds like I really think the _bh is
needed.

At any rate _bh removed thanks!