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

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Message-ID: <1276090953.2442.140.camel@edumazet-laptop>
Date:	Wed, 09 Jun 2010 15:42:33 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	tim.gardner@...onical.com
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: 2.6.35-rc2, CONFIG_RPS is filling the dmesg log

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)



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