netdev - Re: [net-next-2.6 PATCH v4 2/2] net_sched: implement a root container qdisc sch

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Date:	Tue, 04 Jan 2011 07:46:43 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	John Fastabend <john.r.fastabend@...el.com>
Cc:	davem@...emloft.net, jarkao2@...il.com, hadi@...erus.ca,
	shemminger@...tta.com, tgraf@...radead.org,
	bhutchings@...arflare.com, nhorman@...driver.com,
	netdev@...r.kernel.org
Subject: Re: [net-next-2.6 PATCH v4 2/2] net_sched: implement a root
 container qdisc sch_mclass

Le lundi 03 janvier 2011 à 19:05 -0800, John Fastabend a écrit :
> This implements a mqprio queueing discipline that by default creates
> a pfifo_fast qdisc per tx queue and provides the needed configuration
> interface.


> +static int mqprio_dump(struct Qdisc *sch, struct sk_buff *skb)
> +{
> +	struct net_device *dev = qdisc_dev(sch);
> +	struct mqprio_sched *priv = qdisc_priv(sch);
> +	unsigned char *b = skb_tail_pointer(skb);
> +	struct tc_mqprio_qopt opt;
> +	struct Qdisc *qdisc;
> +	unsigned int i;
> +
> +	sch->q.qlen = 0;
> +	memset(&sch->bstats, 0, sizeof(sch->bstats));
> +	memset(&sch->qstats, 0, sizeof(sch->qstats));
> +
> +	for (i = 0; i < dev->num_tx_queues; i++) {
> +		qdisc = netdev_get_tx_queue(dev, i)->qdisc;
> +		spin_lock_bh(qdisc_lock(qdisc));
> +		sch->q.qlen		+= qdisc->q.qlen;
> +		sch->bstats.bytes	+= qdisc->bstats.bytes;
> +		sch->bstats.packets	+= qdisc->bstats.packets;
> +		sch->qstats.qlen	+= qdisc->qstats.qlen;
> +		sch->qstats.backlog	+= qdisc->qstats.backlog;
> +		sch->qstats.drops	+= qdisc->qstats.drops;
> +		sch->qstats.requeues	+= qdisc->qstats.requeues;
> +		sch->qstats.overlimits	+= qdisc->qstats.overlimits;
> +		spin_unlock_bh(qdisc_lock(qdisc));
> +	}
> +

I understand this code already exists in mq, I just want to note that
some qdiscs update their stats in their dump() subroutine, because their
enqueue()/dequeue() doesnt update all fields.

We might add a gather_stats() method, eventually, to get rid of all
oddities we currently have with 0 backlogs (or qlen) here and here ;)

For example, I am not even sure qdisc->qstats.qlen should not be
replaced by to qdisc->qstats.qlen in your loop, as done in
mqprio_dump_class_stats()

Reviewed-by: Eric Dumazet <eric.dumazet@...il.com>


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