Re: creating netdev queues on the fly?

Le jeudi 10 novembre 2011 à 17:26 +0100, Johannes Berg a écrit :

On Thu, 2011-11-10 at 15:35 +0100, Eric Dumazet wrote:

quoted

quoted

So to get to my question: What if we could create netdev queues on the
fly?

quoted

In term of qdisc management I believe its a bit complex if we start to
dynamically add netdev queues :)

Yeah I was thinking that would be the problematic part.

quoted

My first idea would be to extend Qdisc management so that a device can
callback qdisc when a frame is finaly delivered / consumed / discarded.

We currently only have qdisc->enqueue() and qdisc->dequeue(), we could
add qdisc->deliver_callback(skb)

You keep devices as they are, with a netdevqueue per hardware queue.

Then, using a Qdisc like existing ones, but with a limit of
outstanding(given to device but not yet consumed) packets per class.

external tc classifier would deliver a hash/index depending on remote
station.

So basically you'd have a class for each station? Or a class for each
station/AC? That's a lot of classes rather than queues, are they
pre-allocated, or does it not matter? Overall that sounds like a good
approach.

They could be statically allocated in a stochastic fashion (Sorry, SFQ
is one of my favorite qdisc, very light in memory/cpu and yet powerful)

net/sched/sch_sfq.c

Of course, HFSC / DRR are considered more flexible, but eat _much_ more
memory.

http://people.netfilter.org/kaber/shaping

You declare a hash divisor of 1024 to map one station to one class
(Might have hash collision of course...)

Each active slot contains a local queue to one remote station.
Each queue can be pfifo or whatever smart qdisc (sfq, or a more flexible
qdisc)

Then you use a filter to select the appropriate class :

tc filter add dev ${dev} protocol all pref 1 parent $handle handle 1 \
	flow hash keys remote_station divisor 1024



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