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

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Date:	Thu, 30 Jun 2011 19:32:58 +0200
From:	Jiri Pirko <jpirko@...hat.com>
To:	Ben Greear <greearb@...delatech.com>
Cc:	Stephen Hemminger <shemminger@...tta.com>, netdev@...r.kernel.org,
	davem@...emloft.net, kaber@...sh.net, fubar@...ibm.com,
	eric.dumazet@...il.com, nicolas.2p.debian@...il.com,
	andy@...yhouse.net
Subject: Re: [RFC patch net-next-2.6] net: allow multiple rx_handler
 registration

Thu, Jun 30, 2011 at 07:29:16PM CEST, greearb@...delatech.com wrote:
>On 06/30/2011 10:22 AM, Jiri Pirko wrote:
>>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.
>
>What sorts of stupid things?  I didn't look at your patch, but does it handle
>ordering?  In other words, is a bridge logic always handled before VLAN logic?
>
>The old hard-coded stuff in dev.c inherently determined ordering.  For dynamic
>handlers, we may need to enforce ordering to give the user any chance of doing
>things right (it would be very confusing to have the behaviour change completely
>if you added bridge module before vlan module v/s vlan before bridge).

You should read the patch first :) Ordering is handled there.

>
>Thanks,
>Ben
>>
>>>
>>--
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>
>
>-- 
>Ben Greear <greearb@...delatech.com>
>Candela Technologies Inc  http://www.candelatech.com
>
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