netdev - Re: net_sched: gred: red_calc_qavg() called with current qavg for backlog?

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Message-ID: <20120424123730.GI27640@canuck.infradead.org>
Date:	Tue, 24 Apr 2012 08:37:30 -0400
From:	Thomas Graf <tgraf@...radead.org>
To:	David Miller <davem@...emloft.net>
Cc:	david.ward@...mit.edu, tgraf@...g.ch, eric.dumazet@...il.com,
	netdev@...r.kernel.org
Subject: Re: net_sched: gred: red_calc_qavg() called with current qavg for
 backlog?

On Sat, Apr 21, 2012 at 04:10:32PM -0400, David Miller wrote:
> From: "Ward, David - 0663 - MITLL" <david.ward@...mit.edu>
> Date: Sat, 21 Apr 2012 14:46:31 -0400
> 
> > In net/sched/sch_gred.c:
> > 
> > static int gred_dump(struct Qdisc *sch, struct sk_buff *skb)
> > {
> >      struct gred_sched *table = qdisc_priv(sch);
> > ...
> >      for (i = 0; i < MAX_DPs; i++) {
> >          struct gred_sched_data *q = table->tab[i];
> >          struct tc_gred_qopt opt;
> > ...
> >          opt.qave = red_calc_qavg(&q->parms, &q->vars, q->vars.qavg);
> > 
> > 
> > I can't tell if red_calc_qavg is intentionally being passed the current 
> > qavg as the backlog (which effectively causes qavg to only be 
> > re-calculated if we are idling)?  Or should this be:
> > 
> >          opt.qave = red_calc_qavg(&q->parms,
> >                                   &q->vars,
> >                                   gred_backlog(table, q, sch));
> 
> Looking at commit 22b33429ab93155895854e9518a253680a920493
> ("[PKT_SCHED]: GRED: Use new generic red interface") it appears
> that this line is intentional so that the dump reports the same
> qave as it would have before Thomas's changes.

When doing the convert, I simply preserved behaviour. I am not sure on
what basis the original behaviour has been written.
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