netdev - Re: [RFC] sched: CHOKe packet scheduler (v0.2)

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Date:	Wed, 05 Jan 2011 21:06:07 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [RFC] sched: CHOKe packet scheduler (v0.2)

Le mercredi 05 janvier 2011 à 11:21 -0800, Stephen Hemminger a écrit :
> This implements the CHOKe packet scheduler based on the existing
> Linux RED scheduler based on the algorithm described in the paper.
> 

> +
> +static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch)
> +{
> +	struct choke_sched_data *q = qdisc_priv(sch);
> +	struct red_parms *p = &q->parms;
> +
> +	p->qavg = red_calc_qavg(p, skb_queue_len(&sch->q));
> +	if (red_is_idling(p))
> +		red_end_of_idle_period(p);
> +
> +	if (p->qavg <= p->qth_min)
> +		p->qcount = -1;
> +	else {
> +		struct sk_buff *oskb;
> +
> +		/* Draw a packet at random from queue */
> +		oskb = skb_peek_random(&sch->q);
> +
> +		/* Both packets from same flow?
> +		 * Assumes skb_get_rxhash already set hash on oskb->rxhash
> +		 * prior to queuing

but this is not true... if at that time, p->qavg was <= p->qth_min.
Packet was directly enqueued.

Just use :

if (skb_get_rxhash(oskb) == skb_get_rxhash(skb))

Since skb_get_rxhash(skb) doesnt recompute rxhash if already set.

Hmm... I am now wondering if this actually works on egress at all
(can we use rxhash here I mean)



> +		 */
> +		if (oskb->rxhash == skb_get_rxhash(skb)) {
> +			/* Drop both packets */
> +			__skb_unlink(oskb, &sch->q);
> +			qdisc_drop(oskb, sch);
> +			goto congestion_drop;
> +		}


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