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From: Eric Dumazet <eric.dumazet@gmail.com>
To: Nandita Dukkipati <nanditad@google.com>
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Date: Fri, 29 Jun 2012 06:18:59 +0200
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Cc: netdev <netdev@vger.kernel.org>, Yuchung Cheng <ycheng@google.com>,
	codel@lists.bufferbloat.net, Matt Mathis <mattmathis@google.com>,
	Neal Cardwell <ncardwell@google.com>, David Miller <davem@davemloft.net>
Subject: Re: [Codel] [PATCH net-next] fq_codel: report congestion
 notification at enqueue time
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On Thu, 2012-06-28 at 16:52 -0700, Nandita Dukkipati wrote:
> As you know I really like this idea. My main concern is that the same
> packet could cause TCP to reduce cwnd twice within an RTT - first on
> enqueue and then if this packet is ECN marked on dequeue. I don't
> think this is the desired behavior. Can we avoid it?

I'll work on this.

In my experiences, I found that no drops (or ECN marks) were done at
dequeue time once one NET_XMIT_CN was returned, but its certainly
possible if other flows compete with this one.

Strangely, SFQ has the same behavior and nobody complained yet ;)

Thanks