netdev - Re: [net-next PATCH v2 3/3] net: sched: fall back to noqueue when removing root qdisc

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Date:	Wed, 26 Aug 2015 11:48:26 +0200
From:	Phil Sutter <phil@....cc>
To:	Jesper Dangaard Brouer <brouer@...hat.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, eric.dumazet@...il.com
Subject: Re: [net-next PATCH v2 3/3] net: sched: fall back to noqueue when
 removing root qdisc

Hi Jesper,

On Sun, Aug 23, 2015 at 08:53:57PM +0200, Jesper Dangaard Brouer wrote:
> On Sun, 23 Aug 2015 20:44:42 +0200
> Jesper Dangaard Brouer <brouer@...hat.com> wrote:
> 
> > On Sat, 22 Aug 2015 02:20:56 +0200
> > Phil Sutter <phil@....cc> wrote:
> > 
> > > When removing the root qdisc, the interface should fall back to noqueue
> > > as the 'real' minimal qdisc instead of the default one. 
> > 
> > I worry this behavior could break existing scripts.
> 
> You would break OpenWRT package "qos-scripts", specifically:
>  https://github.com/openwrt-mirror/openwrt/blob/master/package/network/config/qos-scripts/files/usr/bin/qos-stop

Thanks for pointing this out!

> Which cleans-up/clear the qdisc setup by removing the root qdisc,
> assuming and depending on the default qdisc is re-assigned.

OK. Since the premise of the whole thing is to not break existing
scripts, this sadly tears down my approach.

> > I prefer the idea of allowing tc command to assign noqueue (to any
> > device).  This makes the action explicit for the user, instead of being
> > a side-effect of removing a qdisc. (and does not break backward compat)

I will give this another go. What I didn't like was that after attaching
noqueue, tc would output nothing when asked to show the attached qdisc -
which is of debatable correctness at least. But maybe that's just a user
space problem I could address separately.

Cheers, Phil
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