From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vc0-x229.google.com (mail-vc0-x229.google.com [IPv6:2607:f8b0:400c:c03::229]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id BB39A21F129 for ; Sun, 6 Oct 2013 09:36:33 -0700 (PDT) Received: by mail-vc0-f169.google.com with SMTP id ib11so2567172vcb.14 for ; Sun, 06 Oct 2013 09:36:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=GwJWDhY5wbtlB37CszhN/+gZdeRTIsO9X6SiuVBwyGA=; b=g+5YH+CFrbyUKg92zlx7eUs6s3OFLsQGDZkIT//1rlC8STWZqraRP0oN6mxOw3S3aK bzuDWrjvLGSgU45Cga5wc2iIvatbd0qZ6Ln1BK/mzXIXzYzM/XbIBHEvo80aFfxn9VuS WaLFBbWGHh6W9tZMYr9DqD935oSBGVF2VATXM86rq3GAAvPcHjvLDcbcHdOhLcdAiqOJ JjQt54lNEOav0f7EhJd9uFprSLZUVXiyl1zkJsQGtRp93VE4MKq4G9Mb8QtHZRUTk4De bXsGa9KKCT9fMkcSwy71asttcWagycxgbJOSfvePcYhHrWjViINKi1/fjYgFEsgobcu+ uQ0Q== MIME-Version: 1.0 X-Received: by 10.221.64.17 with SMTP id xg17mr22178730vcb.5.1381077392763; Sun, 06 Oct 2013 09:36:32 -0700 (PDT) Received: by 10.52.74.137 with HTTP; Sun, 6 Oct 2013 09:36:32 -0700 (PDT) In-Reply-To: <52517B63.1060705@superduper.net> References: <5250DB8F.4060004@superduper.net> <52517B63.1060705@superduper.net> Date: Sun, 6 Oct 2013 12:36:32 -0400 Message-ID: Subject: Re: Enabling Byte Queue Limits in the ath5k wireless driver From: Anirudh Sivaraman To: Simon Barber Content-Type: text/plain; charset=UTF-8 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 16:36:34 -0000 On Sun, Oct 6, 2013 at 11:01 AM, Simon Barber wrote: > 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. > I thought, based on http://lwn.net/Articles/454390/, that the queue length is dynamically adjusted by DQL/BQL/TQL. This is the device driver control loop I was referring to. This queue length in turn dictates when the dequeue function is called at the qdisc layer, where CoDel is running. Please correct me if I am wrong here. Anirudh > 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 > >