Subject: Re: 2.6: QoS scheduling not working with IP-over-IP

From: "David S. Miller" <[email-masked]>
Date: Fri, 13 Feb 2004 21:36:06 -0800

On Fri, 13 Feb 2004 23:51:02 +0100
Patrick McHardy <[email-masked]> wrote:

> while looking for other devices that may be affected I noticed
> this fix changes behaviour in dev_activate. dev_activate creates
> pfifo_fast queues for devices with tx_queue_len != 0 and noqueue
> qdiscs otherwise.

Thanks for spotting this.

> Although it is uncomfortable for some users, I don't know if there
> is anything to fix at all. Work-conserving qdiscs are useless for
> virtual devices, as you say there is maximum one packet queued at
> any time. For non-work-conserving qdiscs with default pfifo qdiscs
> as leaves, I'd say it is simply a configuration error not to increase
> tx_queue_len. Even with a length of 1 (or a off-by-one), you won't get
> good results, except when the traffic is already well-formed. All that
> is changed is that nonsensical configurations stop working.

Another way to view this is that configurations that, while nonsensical,
used to send packets properly no longer do.

However, I do agree with you, and we should not promote this kind of crap.
I'm going to revert the changeset that set tx_queue_len to 1 in the tunnels.

Thanks again Patrick.