From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jean-Michel Hautbois <jhautbois@gmail.com>
Subject: Re: Difficulties to get 1Gbps on be2net ethernet card
Date: Wed, 30 May 2012 08:51:53 +0200
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To: Eric Dumazet <eric.dumazet@gmail.com>
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2012/5/30 Eric Dumazet <eric.dumazet@gmail.com>:
> On Wed, 2012-05-30 at 08:28 +0200, Jean-Michel Hautbois wrote:
>
>> If this can help, setting tx queue length to 5000 seems to make the
>> problem disappear.
>
> Then you should have drops at Qdisc layer (before your change to 5000)
>
> tc -s -d qdisc
>
>> I didn't specified it : MTU is 4096, UDP packets are 4000 bytes.
>

Yes :
qdisc mq 0: dev eth1 root
 Sent 5710049154383 bytes 1413544639 pkt (dropped 73078, overlimits 0
requeues 281540)
 backlog 0b 0p requeues 281540

Why ? With a 2.6.26 kernel it works well with a tx queue length of 1000.