From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from masada.superduper.net (masada.superduper.net [85.133.44.198]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by huchra.bufferbloat.net (Postfix) with ESMTPS id D1183200875 for ; Mon, 1 Aug 2011 11:58:53 -0700 (PDT) Received: from snappy-wlan.parc.xerox.com ([13.1.108.21]) by masada.superduper.net with esmtpsa (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.72) (envelope-from ) id 1QnyPt-0004KK-7U for bloat@lists.bufferbloat.net; Mon, 01 Aug 2011 20:44:48 +0100 Message-ID: <4E37022A.2070705@superduper.net> Date: Mon, 01 Aug 2011 12:44:42 -0700 From: Simon Barber User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.18) Gecko/20110617 Lightning/1.0b2 Thunderbird/3.1.11 MIME-Version: 1.0 To: bloat@lists.bufferbloat.net References: <20110801133044.GA28112@tuxdriver.com> In-Reply-To: <20110801133044.GA28112@tuxdriver.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -2.9 (--) Subject: Re: [Bloat] bufferbloat bug 216 could use some eyeballs badly X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 01 Aug 2011 18:58:55 -0000 I did the original implementation of wireless queuing in mac80211. The original implementation installed a special wireless root qdisc on the interface in order to model the hardware queues correctly, and allow leaf qdiscs to be installed. Ideally the MAC queues would also have been moved into this qdisc. The wireless root qdisc sat on an interface that represented the physical radio and had an 802.11 frame type. There were one or more 802.3 format virtual interfaces that represented wireless client or APs. The wireless qdisc on the native 802.11 interface saw frames in 802.11 format, and hence could calculate how much airtime would be taken transmitting the frame - this would allow development of qdiscs to do things like share airtime rather than bandwidth. The wireless root qdisc exposed the native hardware queues that exist in 802.11 chip sets and bypassed the normal single queue netdev interface. This allowed the hardware queues to be fed independently. Unfortunately the native 802.11 interface was deemed confusing to users, and this code got pulled out of the kernel, thus preventing the qdisc system from ever properly working when more than one virtual Ethernet interface is used with a wireless card - such as when you run multiple virtual APs on a wireless card, or simultaneous AP and client modes. This concept of a special wireless root qdisc is necessary to model the hardware queues and the MAC queues in 802.11 correctly - you're not queuing lots of frames in the driver, rather extending the queuing system to implement parts of the MAC. Simon On 08/01/2011 06:30 AM, John W. Linville wrote: > On Mon, Aug 01, 2011 at 06:06:43AM -0600, Dave Taht wrote: >> If anyone can spare some eyeballs for the discussion of wireless-n AMPDUs >> and their interaction with bufferbloat, and groks TCP's behavior and/or >> wireless's behavior, I'd appreciate some comment on: >> >> http://www.bufferbloat.net/issues/216 >> >> Losing SOME appropriate packets, somewhere in the wireless stack, is >> necessary. > > It seems appropriate to Cc: linux-wireless@vger.kernel.org for this... >