From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-il1-x12a.google.com (mail-il1-x12a.google.com [IPv6:2607:f8b0:4864:20::12a]) (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 ED51E3B29E for ; Wed, 23 Jun 2021 16:02:50 -0400 (EDT) Received: by mail-il1-x12a.google.com with SMTP id u2so3796687ilk.7 for ; Wed, 23 Jun 2021 13:02:50 -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=nKE0MJYMiK15867pVk/GfU+Hyjcirm8a71q0AndfKHk=; b=m2Y1P+y8z723FvEV3gdmLETbyKL2Zlmyigvvccdv5NdujajVvXQ7GAm+QuAuaFJPe+ 4KCMxhwcnN6OE/B+mbfg+h9veduNk26vzUoS66ZEGZxlBV4NZOD++P09saAson+l1M2y 6feg+SLoV2pL1Ec5JtNnPmMi3QrajDrWK6FErZFOHtOsD6zoq1uq4LhbPj727WCmhw1+ Vnbae/CXZSQb0yMWofXuJkaTwKz/9f/aCVXQxTMER0RNWjD5NgjgCyXMv/8g2Aiyk3Z8 08LPDqKQRDH3INe/BnlLDRZnm3LAauTmm9+V6AZZW96EXxCoFB3QeUSk6mGWzqfCX8G6 +34g== 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=nKE0MJYMiK15867pVk/GfU+Hyjcirm8a71q0AndfKHk=; b=GOB6INls1p/K6vTS/6orwWoh/xVQQgbQHMtWkWuzMVXZKQRMMZE4Lzm8qTiwFph2OW 1UiuTzsA8jgyS4h+WohsjIlM8jjwhLLbmWwjyTx+HsbMx9LZYcOlZirS+APJmXbaReeS E+2mC4eTRmjIYNNO4tDAdRGq30DifvOV4LyMBdVr8Vv9E7S3NyJ/Rqky48Nl7VZKhNfF 4QWZsPoyixMM90rVtM74b6P7mgL3Mf6T4PmYpFt/mSv4Hdy0mYtlL64pgTtmO26r9MqV M73jPeeRJcjLF5ETMTDNE/RDmX+ZCSjd+K6GzTGJWdZkyKznb0qp0DEqmjj67ztl/NjE paZg== X-Gm-Message-State: AOAM532tLAx+T4lrHve0oKDyS0oFF2PdDF4TvhYsR2KvxUik5cwjbnsn X+gcTFTDJmthAQKQMfLlEHWlvtx+4ujt/t6R5seY0NvU X-Google-Smtp-Source: ABdhPJwdeeSYobUJOs0nYSwHFStgjrL39SDEvnBMRMldpzTpUiELhQtwAw55MX1exkn21arthHEL05QKr/VboygybWE= X-Received: by 2002:a05:6e02:1563:: with SMTP id k3mr816259ilu.0.1624478569946; Wed, 23 Jun 2021 13:02:49 -0700 (PDT) MIME-Version: 1.0 References: <0e2c44fc-85ee-8be8-5f6b-1a71141cf07f@kom.tu-darmstadt.de> In-Reply-To: <0e2c44fc-85ee-8be8-5f6b-1a71141cf07f@kom.tu-darmstadt.de> From: Dave Taht Date: Wed, 23 Jun 2021 13:02:38 -0700 Message-ID: To: starlink@lists.bufferbloat.net Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Subject: [Starlink] Fwd: Pie not fully implementable on tofino p4 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: Wed, 23 Jun 2021 20:02:51 -0000 One of the things that has long bugged me about the p4 spec was the lack of an invsqrt which is a single assembly language instruction or about 3k gates, for a newton approximation. Anyway, I wish I had direct comparison data for pie vs codel on p4, two good papers below. ---------- Forwarded message --------- From: Ralf Kundel Date: Wed, Apr 21, 2021 at 9:07 AM Subject: Re: Pie not fully implementable on tofino p4 To: Dave Taht , bloat , Hi, regarding the question: how timestamps come from ingress to egress pipe? Well this depends (on the P4 abstraction) on the P4 version you use. As far as I remember (it is a long time ago) in P4_14 metadata (which can store the timestamp) are handed over implicitly from ingress to egress. In P4_16 you have do do this explicitly in the Deparser of Ingress and Parser of Egress: Simply said you just write the timestamp before the Ethernet header. You can see this here in line 64 to 80: https://github.com/ralfkundel/p4-codel/blob/master/targets/tofino/srcP4/l1s= witchCodel.p4 best, Ralf Am 21.04.21 um 04:42 schrieb Dave Taht: > https://www.comsys.rwth-aachen.de/fileadmin/papers/2021/2021-kunze-aqm-to= fino-p4.pdf > > For a codel comparison, see: > > https://arxiv.org/pdf/2010.04528v1.pdf > > Where the authors show that fq_codel is feasible on the PISA platform... > > but a direct comparison between the two papers is not possible. What I > don't understand about the above paper is how codel timestamps are > passed from ingress to egress. > -- ________________________________________________ Ralf Kundel, M.Sc. Technical University of Darmstadt Dept. of Electrical Engineering and Information Technology Multimedia Communications Lab (KOM) Adaptive Communication Systems Group (ACS) Postal address: TU Darmstadt, FB 18, KOM, Rundeturmstr. 10, 64283 Darmstadt, Germany Location: S3|20 - 216 Tel: +49 6151 16-20855 Email: Ralf.Kundel@kom.tu-darmstadt.de Web: http://www.kom.tu-darmstadt.de ___________________________________________________________ --=20 Latest Podcast: https://www.linkedin.com/feed/update/urn:li:activity:6791014284936785920/ Dave T=C3=A4ht CTO, TekLibre, LLC