Multiqueue networking [LWN.net]

Multiqueue networking

Posted Jul 10, 2008 3:26 UTC (Thu) by walken (subscriber, #7089)
Parent article: Multiqueue networking

I'm confused, I thought there was already a multiqueue implementation in the kernel ? (see
Documentation/networking/multiqueue.txt in 2.6.25...)

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Multiqueue networking

Posted Jul 10, 2008 5:46 UTC (Thu) by johill (subscriber, #25196) [Link] (3 responses)

Yes, there is indeed already a multiqueue implementation. See davem's blog for an explanation better than I could give.

Multiqueue networking

Posted Jul 10, 2008 8:03 UTC (Thu) by walken (subscriber, #7089) [Link] (2 responses)

Hmmm, thanks for the link :) I'm still very confused though.

Both in his blog and in the patch series initial comment, David mentions duplicating the
qdiscs so that he'd have one per queue rather than one per device. I'm confused about whether
this is supposed to be just an implementation detail to reduce locking somehow, or if this
would be exposed in the traffic shaping user visible interface (in which case I don't
understand how you'd use that :)

Multiqueue networking

Posted Jul 10, 2008 14:05 UTC (Thu) by gdt (subscriber, #6284) [Link]

I don't know about DaveM's work, but real routers offer differing QoS policies per class-of-traffic queue (eg, a limited queue length with tail drop for a class with voice traffic, a long queue with RED drop for classes with TCP traffic). Since Linux implements scheduling and queue policies using qdiscs, a qdisc per queue would make sense.

Multiqueue networking

Posted Jul 21, 2008 10:48 UTC (Mon) by eliezert (subscriber, #35757) [Link]

I think that the main issue was to push the tx lock into the queue.
This was a major shortcoming of the previous implementation.