From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH net-next] tcp: introduce TCPSpuriousRtxHostQueues SNMP
 counter
Date: Thu, 18 Apr 2013 11:06:21 -0700
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	 <20130418104510.3624457a@nehalam.linuxnetplumber.net>
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Cc: David Miller <davem@davemloft.net>,
	netdev <netdev@vger.kernel.org>,
	Yuchung Cheng <ycheng@google.com>,
	Neal Cardwell <ncardwell@google.com>,
	Tom Herbert <therbert@google.com>,
	Willem de Bruijn <willemb@google.com>
To: Stephen Hemminger <stephen@networkplumber.org>
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On Thu, 2013-04-18 at 10:45 -0700, Stephen Hemminger wrote:
> On Thu, 18 Apr 2013 09:52:51 -0700
> Eric Dumazet <eric.dumazet@gmail.com> wrote:
> 
> > From: Eric Dumazet <edumazet@google.com>
> > 
> > Host queues (Qdisc + NIC) can hold packets so long that TCP can
> > eventually retransmit a packet before the first transmit even left
> > the host.
> 
> I though you were use fq_codel ;-) and that wouldn't happen.

Remind that fq_codel drops packets at dequeue time only ;)

So TCP stack could retransmit while prior packet is still in fq_codel
queue.