From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-il1-x12e.google.com (mail-il1-x12e.google.com [IPv6:2607:f8b0:4864:20::12e]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 5F9053B29E for ; Mon, 21 Jun 2021 05:03:29 -0400 (EDT) Received: by mail-il1-x12e.google.com with SMTP id b5so2623584ilc.12 for ; Mon, 21 Jun 2021 02:03:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :content-transfer-encoding; bh=rtDTGTyPMHUkIVwgH1jI6ke08x/PrCQAM4TLDBhbNnM=; b=gIZp4G4YSL9KLsJu4qPNgTpERoyrgrerQcYON76Z+oYfFGZkWpdsVLfkm/AiX/6+WY Pz8k6oDCeIz/Z9x1IFzOIplIt5+6qrECM+ARhfCU7Wv0koUfZXOF3d7mJJdEGwOsK/fF vvOCT4PRSpUDrZ67iC+NjeojgD9c4nShmfKWxw3ytoqJnBw29W6Mrar/csW/DKynlhXs 0MJi9sPV8qkgRdI5WKrWVCo4hYdgOfCAzXH+E5kIrSvInriqjelROabFnijU/dnci12Q 9Ldx+YEIuXOaJZ5LAAY5EAXDRpBA6guRdw3e9fi6q2V4k4YD6F0/B0wA5OyGrvfaDw1+ W0KA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:content-transfer-encoding; bh=rtDTGTyPMHUkIVwgH1jI6ke08x/PrCQAM4TLDBhbNnM=; b=Vv2Hhll2VFrZZfKlpA5981ejWdrmpOLxvRa+uy9AOhszKQ3uj0M63VaRMKG7nhe/kH DcC3LDl5GfDu9m9emL7ZDBIalF6xwjJHboiX4DQCRBbSRD+J3LSe29NH0qLiQdKHk8Gu kJfFLyL3I1IhyoSzyGMxgCWgKSxQBaC54J4hQ2rSr2KPK+90uUwM0yQgxhfqg3Gs1ewF qoOw6tKdzNEG4tyWndXLlRh1e80ZFJ+feHV+l0nqKOPVTK3dAsTvGT6btRGjm4TP/BKB hnW+77YAoadAZmXbSGNs2I9PYXJDBfzMrUkPveYBmzANyGIm8px/fOjieUJltOAcm2EL muZw== X-Gm-Message-State: AOAM532fwX5bgOVj79irNceXLdsz+lo/BGzMU0GCI5VGBWz/Cx22Y1GV DGfCJ+kXQ3zqTEGnnIRsPdBx1VAWYnqRo4Rvywmn3fKD2U0= X-Google-Smtp-Source: ABdhPJxP25qpJBMZTIm1g7mzaZfW2vo5lc3IYYz9eRhO/PXO9B+PLcKh5N9i65pWOIKy4HtB31iN7/yGlCIfGzNP4Cw= X-Received: by 2002:a92:b74b:: with SMTP id c11mr9266399ilm.246.1624266208580; Mon, 21 Jun 2021 02:03:28 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Dave Taht Date: Mon, 21 Jun 2021 02:03:16 -0700 Message-ID: To: starlink@lists.bufferbloat.net Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Subject: Re: [Starlink] on BQL -- Byte Queue Limits X-BeenThere: starlink@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: "Starlink has bufferbloat. Bad." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 21 Jun 2021 09:03:29 -0000 oops: broadcom preso here: http://www.taht.net/~d/broadcom_aug9_2018.pdf On Mon, Jun 21, 2021 at 2:01 AM Dave Taht wrote: > > Have been in the linux kernel since version 3.3, but it requires about > 6 lines of calls within each > device driver to effectively enable. What BQL does is supply one > interrupt's worth of data backpressure > to the overlying queuing discipline (qdisc) to do more magic, where we > had first put latency sensitive > qdiscs like fq_codel. At 100Mbit (without TSO), this is typically 3-8k > of data living on the device tx ring > where prior to the development of BQL and awareness of bufferbloat as > a problem, this had hit numbers as large as 64k*4096... > > Anything that can supply backpressure to the qdisc before it enters the d= evice > driver's ring buffers can be used however - high/low watermarks are > still pretty common - but because > BQL uses byte limits, rather than variably sized (64-64k) packet > limits, and bytes =3D=3D time on most media, BQL is the best thing going > "down there" in the Linux kernel. BSD has no equivalent functionality > as yet. > > Linux AQL - Airtime queue limits - is closely related, but for wifi. > > There is an extension, called XMIT_MORE that helps on batchier > transfers from the qdisc. > > We never wrote BQL up in "bufferbloat and beyond" because it was > already well established when toke > started his MsC thesis, even though it was the breakthrough algorithm > that made all our debloating > work feasible. > > There's a link to a paper and a tutorial about BQL in this old > presentation to broadcom here: > > And a detailed, often ranty but chock full of links to other good old > papers, over here: > https://conferences.sigcomm.org/sigcomm/2014/doc/slides/137.pdf > > IPQ8014 does appear to have a BQL'd ethernet driver, but haven't > looked deeply yet. > > PS Writing this stuff up because this list is largely a new audience > for the bufferbloat related APIs in > the linux kernel > > -- > Latest Podcast: > https://www.linkedin.com/feed/update/urn:li:activity:6791014284936785920/ > > Dave T=C3=A4ht CTO, TekLibre, LLC --=20 Latest Podcast: https://www.linkedin.com/feed/update/urn:li:activity:6791014284936785920/ Dave T=C3=A4ht CTO, TekLibre, LLC