netdev - Re: [PATCH 2.6.25 2/4]S2io: Multiqueue network device support

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Date:	Thu, 21 Feb 2008 00:15:13 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	David Miller <davem@...emloft.net>
CC:	Ramkrishna.Vepa@...erion.com, Sreenivasa.Honnur@...erion.com,
	netdev@...r.kernel.org, jeff@...zik.org, support@...erion.com
Subject: Re: [PATCH 2.6.25 2/4]S2io: Multiqueue network device support - FIFO
 selection based on L4 ports

David Miller wrote:
> From: Patrick McHardy <kaber@...sh.net>
> Date: Thu, 21 Feb 2008 00:08:52 +0100
>
>   
>> Ramkrishna Vepa wrote:
>>     
>>>> Sreenivasa Honnur wrote:
>>>>     
>>>>         
>>>>> - Resubmit #2
>>>>> - Transmit fifo selection based on TCP/UDP ports.
>>>>> - Added tx_steering_type loadable parameter for transmit fifo
>>>>>       
>>>>>           
>>> selection.
>>>   
>>>       
>>>>>   0x0 NO_STEERING: Default FIFO is selected.
>>>>>   0x1 TX_PRIORITY_STEERING: FIFO is selected based on skb->priority.
>>>>>   0x2 TX_DEFAULT_STEERING: FIFO is selected based on L4 Ports.
>>>>>
>>>>>       
>>>>>           
>>>> Why duplicate the generic multiqueue classification?
>>>>     
>>>>         
>>> [Ram] Could you be more specific?
>>>   
>>>       
>> The generic multiqueue support classifies packets by setting
>> skb->queue_mapping using qdisc classifiers, which is more
>> flexible and avoids using module parameters.
>>     
>
> But it doesn't do what these multiqueue TX queue hardware devices
> want.  These devices don't want packet scheduler "classification",
> they want load balancing using some key (current cpu number,
> hashing on the packet headers, etc.)  And that's not what our
> packet scheduler classifiers do or should do.
>   

Its what the flow classifier does :)
> We don't want to have to tell people "you have to run 'tc' magic
> foo to use all of the TX queues on your network card."  That's
> completely unreasonable and stupid.
>
> We have to resolve this somehow, and there have been many discussions
> about this a month or so ago.
>   

I see. I missed those discussions, but this has already been
agreed on, fine by me. It would still be preferable to use
queue_mapping instead of priority IMO, even if its activated
by a module parameter, since that leaves the option to use
classifiers.

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