From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from masada.superduper.net (unknown [IPv6:2001:ba8:1f1:f263::2]) (using TLSv1 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (Client did not present a certificate) by huchra.bufferbloat.net (Postfix) with ESMTPS id C014C200875 for ; Sun, 6 Oct 2013 08:02:19 -0700 (PDT) Received: from [209.104.70.126] (helo=[172.16.1.193]) by masada.superduper.net with esmtpsa (TLS1.0:DHE_RSA_CAMELLIA_256_CBC_SHA1:256) (Exim 4.80) (envelope-from ) id 1VSpqZ-0003NY-6V; Sun, 06 Oct 2013 16:02:17 +0100 Message-ID: <52517B63.1060705@superduper.net> Date: Sun, 06 Oct 2013 08:01:55 -0700 From: Simon Barber User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.0 MIME-Version: 1.0 To: Anirudh Sivaraman Subject: Re: Enabling Byte Queue Limits in the ath5k wireless driver References: <5250DB8F.4060004@superduper.net> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -2.9 (--) Cc: bloat-devel@lists.bufferbloat.net X-BeenThere: bloat-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: "Developers working on AQM, device drivers, and networking stacks" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 06 Oct 2013 15:02:20 -0000 BQL or TQL are open-loop - there is no feedback. The amount of bytes or total packet transmission time in the queue is counted when packets enter and leave the queue, and a hard limit of total bytes or total time in queue is set. When I say time - I mean that on a packet entering the queue the total time the packet will take to transmit is calculated, and that time is added to a count to the total time currently in queue. When a packet has been transmitted the time is subtracted from the total time in queue. There would be no interference with CODEL running in front of this. Simon On 10/6/2013 6:31 AM, Anirudh Sivaraman wrote: > On Sat, Oct 5, 2013 at 11:39 PM, Simon Barber wrote: >> BQL does make sense, but TQL would be even better - 'Time Queue Limits'. >> Which would work based on an estimate of how much time each packet will take >> to send, and limiting the hardware queue to contain a total mount of 'time'. >> The purpose of the hardware queue is to mask interrupt and other latencies >> involved in refilling an empty queue - a time based phenomenon. Hence time >> is the best metric to control it - with fixed speed interfaced like ethernet >> bytes=time, but not so on wireless. >> > Thank you for your reply. TQL does make more sense for wireless at > least. However, assuming that someone implement a qdisc like CoDel and > attaches it to the wireless interface, doesn't TQL (or for that matter > BQL) lead to two possibly competing control loops (one at the qdisc, > and one at the device driver)? > > Anirudh >> Simon >> >> >> On 10/3/2013 11:49 AM, Anirudh Sivaraman wrote: >>> Hi, >>> >>> I am looking into enabling BQL for the ath5k driver, and was wondering >>> if anyone here knows of any prior efforts in this direction. In >>> particular, is BQL even a sensible strategy for wireless drivers? >>> Thank you in advance for any advice you may have in this regard. >>> >>> Anirudh >>> _______________________________________________ >>> Bloat-devel mailing list >>> Bloat-devel@lists.bufferbloat.net >>> https://lists.bufferbloat.net/listinfo/bloat-devel >> >> _______________________________________________ >> Bloat-devel mailing list >> Bloat-devel@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/bloat-devel