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From: Eric Dumazet <eric.dumazet@gmail.com>
To: Dave Taht <dave.taht@gmail.com>
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Date: Mon, 18 Jun 2012 04:58:26 +0200
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	Dave =?ISO-8859-1?Q?T=E4ht?= <dave.taht@bufferbloat.net>
Subject: Re: [Codel] [RFC PATCH] Codel: Enable packet drop with ECN-marked
 packets on a threshold
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On Sun, 2012-06-17 at 22:40 -0400, Dave Taht wrote:
> On Sun, Jun 17, 2012 at 10:17 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:

> > if (A && B && C)
> >
> > Even if (C) is false, but A is true, B is evaluated.
> 
> A is always true (or always false)
> B in this case is usually false except on the kinds of ECN-heavy
> workloads that exposed this issue
> and C is probably higher overhead than A or B
> 
> So a better conditional is possible...

Not only better, but _correct_ ;)

To have a chance to be correct, your patch should have been :


if (params->ecn &&
    vars->ldelay <= 2 * params->target &&
    INET_ECN_set_ce(skb))

Because INET_ECN_set_ce(skb) is _doing_ ecn marking, and returns true is
ECN was successfully applied to the packet.