netdev - Re: netem and hierarchical ingress traffic shaping

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Date:	Fri, 23 Dec 2011 18:33:59 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	"John A. Sullivan III" <jsullivan@...nsourcedevel.com>,
	netdev@...r.kernel.org
Subject: Re: netem and hierarchical ingress traffic shaping

Le dimanche 18 décembre 2011 à 11:55 -0800, Stephen Hemminger a écrit :
> On Sun, 18 Dec 2011 00:12:12 -0500
> "John A. Sullivan III" <jsullivan@...nsourcedevel.com> wrote:
> 
> > Since netem appears to be classless, we realized we would need to
> > replace the SFQ on each leaf with netem which we really didn't want to
> > do - not only to not lose SFQ but because we didn't want to maintain the
> > netem parameters on each leaf.  So, we activated our ifb1 interface,
> > placed netem on it and redirected all the egress traffic to ifb1.  Taht
> > worked fine.
> 
> Current versions of netem can take one class.
> --

Hmm, I can see that (commit 10f6dfcfde884441) 

But it wont work very well, it assumes qdisc uses a single queue if
netem reordering is requested :

(__skb_queue_head(&q->qdisc->q, skb))

We should allow reordering if netem queue is changed from tfifo, only if
new qdisc is compatible with __skb_queue_head(&q->qdisc->q, skb)

(maybe providing a new ->queue_at_head() new ops)





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