netdev - Re: UDP ordering when using multiple rx queue

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Message-ID: <CAL8zT=jMPCv_Lc7gJYGHRhHZop9aWJfp2w1o_cD0Z8SRdtck7Q@mail.gmail.com>
Date:	Wed, 11 Jul 2012 13:13:21 +0200
From:	Jean-Michel Hautbois <jhautbois@...il.com>
To:	Merav Sicron <meravs@...adcom.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: UDP ordering when using multiple rx queue

2012/7/11 Merav Sicron <meravs@...adcom.com>:
> On Wed, 2012-07-11 at 00:53 -0700, Jean-Michel Hautbois wrote:
>
>> Several tests lead to a simple conclusion : when the NIC has only one
>> RX queue, everything is ok (like be2net for instance), but when it has
>> more than one RX queue, then I can have "lost packets".
>> This is the case for bnx2x or mlx4 for instance.
> >From what you describe I assume that you use different source IP /
> destination IP in each packet - is this something that you can control?
> Because with the same IP addresses the traffic will be steered to the
> same queue.

OK, sorry for not having explained that : the packets are multicast
with a port for each stream. Sending one stream multicast on a bnx2x
based NIC can lead to several queues used (two, for what I can see)
and then, to the problem reported.

>> Here are my questions :
>> - Is it possible to force a driver to use only one rx queue, even if
>> it can use more without reloading the driver (and this is feasible
>> only when a parameter exists for that !) ?
> You can reduce the number of queues using "ethtool -L ethX combined 1".
> Note however that it will cause automatic driver unload/load.

OK, thanks for this tip :).

JM
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