netdev - Re: AW: AW: RFC: replace packets already in queue

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Message-ID: <4FF20557.4090501@gmail.com>
Date:	Mon, 02 Jul 2012 22:32:23 +0200
From:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
To:	"Erdt, Ralph" <ralph.erdt@...e.fraunhofer.de>
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	Rick Jones <rick.jones2@...com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: AW: AW: RFC: replace packets already in queue

Le 02/07/2012 10:38, Erdt, Ralph a écrit :
>>> Even if the wireless queue is a problem (because of our setup, this
>> is
>>> not a problem), the network stack queue (*) is the biggest queue, and
>>> a good point to optimize.
>>
>> Hmm, I am not convinced you have no queues on wireless.
>>
>> Please describe how you managed this.
>>
>> In fact this is the biggest problem with wireless : mac82011 framework
>> aggressively pull packets from Linux packet qdisc in order to perform
>> packet aggregation.
>
> I did not talking about W-LAN (802.11). I'm talking about an property technology which is able to
> send over KILOMETERs (WLAN<  100m) but with VERY low bandwidth: 9600 bit (no Mega, Giga or Kilo!)
> (W-LAN: slowest: 1Mbit). The devices is loosely connected to our boxes: No linux driver but a
> program which create an virtual network device. This just sends one packet to the devices and
> then waits for the acknowledgement that the packet was sent. THEN the next packet will be send.
> There is no further queue, because the wireless is so lame, that there is no need for that! (BTW:
> the qdisc and the connector are distinct problems/programs. There is no dependency.)

If I were you, I would use a tun/tap interface and manage a private packet queue in userspace. This 
way, you wouldn't have to manage the overhead of porting your kernel code to every new kernel versions.

	Nicolas.
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