netdev - Re: [RFC patch net-next-2.6] net: allow multiple rx

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Date:	Fri, 1 Jul 2011 17:00:41 +0200
From:	Jiri Pirko <jpirko@...hat.com>
To:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
Cc:	Michał Mirosław <mirqus@...il.com>,
	Stephen Hemminger <shemminger@...tta.com>,
	netdev@...r.kernel.org, davem@...emloft.net, kaber@...sh.net,
	fubar@...ibm.com, eric.dumazet@...il.com, andy@...yhouse.net
Subject: Re: [RFC patch net-next-2.6] net: allow multiple rx_handler
 registration

Fri, Jul 01, 2011 at 04:57:07PM CEST, nicolas.2p.debian@...il.com wrote:
>Le 01/07/2011 08:36, Michał Mirosław a écrit :
>>2011/6/30 Jiri Pirko<jpirko@...hat.com>:
>>>Thu, Jun 30, 2011 at 06:27:12PM CEST, shemminger@...tta.com wrote:
>>>>On Thu, 30 Jun 2011 17:16:49 +0200
>>>>Jiri Pirko<jpirko@...hat.com>  wrote:
>>>>
>>>>>For some net topos it is necessary to have multiple "soft-net-devices"
>>>>>hooked on one netdev. For example very common is to have
>>>>>eth<->(br+vlan). Vlan is not using rh_handler (yet) but also for example
>>>>>macvlan would be useful to have hooked on same netdev as br.
>>>>>
>>>>>This patch introduces rx_handler list. size struct net_device stays
>>>>>intact. Measured performance regression on eth-br topo is ~1% (on received
>>>>>pkts generated by pktgen) and on eth-bond topo it is ~0.25%
>>>>>
>>>>>On br I think that the performance can be brought back maybe by using per-cpu
>>>>>variables to store port in rx_path (I must check this)
>>>>>
>>>>>Please comment.
>>>>>
>>>>>Signed-off-by: Jiri Pirko<jpirko@...hat.com>
>>>>
>>>>I am ok with the infrastructure, but why should Vlan use rh_handle.
>>>
>>>Well why it shoudln't. It would fit into what rx_handler is here for - the
>>>code would be more unified. Also net_device struct would lose struct
>>>vlan_group __rcu *vlgrp pointer (and reducing net_device size is always
>>>good thing).
>>>
>>>>It is wrong to allow macvlan and bridge to share same device.
>>>>Right now the code blocks users from doing lots of stupid things.
>>>
>>>Right, this is since rx_handler was introduced. Before that all these
>>>stupid configs were allowed. It's possible easily to forbid unwanted
>>>configs by checking priv flags.
>>
>>We could introduce a catch-all macvlan/vlan device that would take
>>addresses/VLANs which are not covered by other configured
>>macvlans/vlans. This would allow clearer configuration and would make
>>the evaluation order explicit. As a bonus, this will give another
>>device to put tcpdump on. ;-)
>
>'Sounds like what I had in mind in http://marc.info/?l=linux-netdev&m=130622112921245&w=2 .

Looks useful. I'm goint to look at how to implement this.

Thanks.

>
>	Nicolas.
>
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