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

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Date:	Fri, 1 Jul 2011 17:01:47 +0200
From:	Michał Mirosław <mirqus@...il.com>
To:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
Cc:	Jiri Pirko <jpirko@...hat.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

W dniu 1 lipca 2011 16:57 użytkownik Nicolas de Pesloüan
<nicolas.2p.debian@...il.com> napisał:
> 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 .

Almost. My idea assumes that eth0.any won't strip VLAN headers (so its
just looks like a filtered eth0).

Best Regards,
Michał Mirosław
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