netdev - Re: [PATCH take 2] pkt_sched: Fix qdisc_watchdog() vs. dev

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Date:	Wed, 24 Sep 2008 16:04:27 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	kaber@...sh.net, alexander.h.duyck@...el.com
Subject: Re: [PATCH take 2] pkt_sched: Fix qdisc_watchdog() vs.
	dev_deactivate() race

On Wed, Sep 24, 2008 at 07:15:21AM +0000, Jarek Poplawski wrote:
>
> > Then each qdisc can decide which child to recursively dequeue
> > based on that token (or ignore it for non-prio qdiscs such as
> > HTB).
> 
> I don't think HTB could be considered as a non-prio qdisc.

It is non-prio in the sense that it has other criteria for deciding
which child qdisc to enqueue into.

> As matter of fact I can't figure out this idea of a prio at the root
> or leaf either. Could you explain in which point do you expect the
> gain? If it's about the locks, what kind of synchronization would be
> used to assure packets from lower prio queues (or qdiscs?)  aren't
> sent to free tx queues, while higher prio wait on stopped ones?

It's very simple really.  For a non-leaf prio you determine which
child qdisc to enqueue into using the priority.  For a leaf prio
you determine which software queue to enqueue into based on the
priority.

To put it another way, what I'm saying is that instead of duplicating
the qdiscs as we do now for pfifo_fast, we should make the leaf
qdiscs duplicate its software queues to match the hardware queues
it's feeding into.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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