netdev - Re: [RFC] [PATCH] Don't run __qdisc

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Date:	Tue, 28 Jul 2009 08:37:13 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	David Miller <davem@...emloft.net>, krkumar2@...ibm.com,
	netdev@...r.kernel.org
Subject: Re: [RFC] [PATCH] Don't run __qdisc_run() on a stopped TX queue

On Tue, Jul 28, 2009 at 04:03:54PM +0800, Herbert Xu wrote:
> On Tue, Jul 28, 2009 at 06:43:19AM +0000, Jarek Poplawski wrote:
> >
> > I guess the main sacrifice of Herbert's idea is sch_multiq, and we
> > could probably consider some compromise like doing qdisc_run (with
> > qdisc_restart) a callback or only adding a "if default qdisc" check,
> > depending on costs/gains.
> 
> Indeed, getting rid of multiple queues for all non-default qdiscs
> is overly drastic.  Here's a different plan.  We add the proposed
> check only for the default qdisc (we still need to fix act_skbedit)
> though) while all non-default qdiscs continue to behave as they
> currently do.
> 
> This can be done by setting dev_queue for non-default qdiscs to
> NULL and checking that before we do qdisc_run:
> 
> 	if (!dev_queue || !queue_stopped(dev_queue))
> 		qdisc_run
> 
> This makes sense as non-default qdiscs do not map bijectively onto
> dev queues so they shouldn't really have a pointer to a dev queue.
> 
> Of course we'll need to fix those places that use dev_queue for
> other purposes such as getting back to the device.  If that is
> too much work we could just add a new field that is identical
> to dev_queue for the default qdisc but is NULL for non-default
> qdiscs.

Hmm.. would something IMHO_more_readable/less_fixing like:
(qdisc->flags & TCQ_F_DEFAULT) be too much? (Btw, IIRC there was an
idea long time ago to treat all queues equally.)

Cheers,
Jarek P.
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