netdev - Re: 2.6.35-rc2, CONFIG_RPS is filling the dmesg log

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Message-ID: <4C0FB1D3.60901@canonical.com>
Date:	Wed, 09 Jun 2010 09:22:59 -0600
From:	Tim Gardner <tim.gardner@...onical.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	netdev <netdev@...r.kernel.org>
Subject: Re: 2.6.35-rc2, CONFIG_RPS is filling the dmesg log

On 06/09/2010 07:42 AM, Eric Dumazet wrote:
> Le mercredi 09 juin 2010 à 07:27 -0600, Tim Gardner a écrit :
>> On 06/08/2010 02:55 PM, Tim Gardner wrote:
>>> With 2.6.35-rc2 my dmesg log is being flooded with messages like this:
>>>
>>> br0 received packet on queue 4, but number of RX queues is 1
>>>
>>> This machine is bridged for KVM and has 2 igb network adapters.
>>>
>>> The root cause appears to be CONFIG_RPS=y and the fact that none of the
>>> drivers that call skb_record_rx_queue() perform their net device
>>> allocation using alloc_netdev_mq(), thereby initializing num_rx_queues
>>> to a maximum of 1.
>>>
>>> Given that this is early RPS days, is the warning in get_rps_cpu()
>>> really necessary? It would appear that _all_ of the multi-receive queue
>>> devices that call skb_record_rx_queue() will cause this log noise.
>>>
>>> By the way, how do you turn off CONFIG_RPS? The only way I could get it
>>> disabled was to change the default in net/Kconfig to 'n'.
>>>
>>> rtg
>>
>> This is the route that I'm taking with Ubuntu in the short term. I'll
>> have lots of server testers complaining pretty soon if I don't take care
>> of this now. It does keep my server logs from filling.
>>
>> rtg
>>
>
> Probably fine, but your commit message is not exact :
>
>    So far no users of skb_record_rx_queue() use alloc_netdev_mq() for
>    network device initialization, so don't print a warning about num_rx_queues
>    imbalances in get_rps_cpu() unless they have actually been allocated.
>
> In fact, drivers that use skb_record_rx_queue() did use alloc_netdev_mq().
>
> Problem is : packets going thru bridge/bonding that are not yet
> multiqueue enabled. If R[PF]S enabled for these "virtual devices",
> we trigger the get_rps_cpu() warning.
>
> Also, in a bonding setup, we still have a problem
> because all tx packets will go thru tx queue 0 (dev_pick_tx() job)
>
> (That might be good to know that for Ubuntu server testers)
>

How about this?

-- 
Tim Gardner tim.gardner@...onical.com

View attachment "0001-UBUNTU-SAUCE-net-Print-num_rx_queues-imbalance-warni.patch" of type "text/x-patch" (1444 bytes)