From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-x232.google.com (mail-lf0-x232.google.com [IPv6:2a00:1450:4010:c07::232]) (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 944B73BA8E for ; Wed, 18 Apr 2018 10:12:52 -0400 (EDT) Received: by mail-lf0-x232.google.com with SMTP id m202-v6so2880578lfe.8 for ; Wed, 18 Apr 2018 07:12:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=xSbXfd5krLRq4BqasvT/3rFqcMR3uHe4T9JEwHwNGas=; b=e40yJCCvErHkUwk+kltEpwAi7usYe5zNcydWAwovgwFMDClBTbtXO5pwiCL7rsio9d 1PerJk2Ek7tf1tJt65+3smJPlMbDvLHr9qBUKUeji1q/ssMpGD7tsGnQHVKQXbJR/cCM fWFu9QC4QQaYjh2h/z1hnhY+8J61E+YUbjwQktKOsc9IlpgnJYPtTYUIxeb9GOwAxiEr 5EhNdbvgLP48l46gv7BlXGZT9yVLdP6En5tvYbPJPi1O/tJGiS3vxp5LqngoWFnyOy83 uShx5Ia81YaNoVbhsJm3vlQSE+O8tIQRjmJma5e/aEz81YkISO34NVo8jrvHT6jQ9gGW jrvQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=xSbXfd5krLRq4BqasvT/3rFqcMR3uHe4T9JEwHwNGas=; b=mtTKAOr2M+y9yyUAVTfV8dyI36uyO4tvhD9RSej13OR/EWXe3Zz2zCOMlPZHeI0oc5 Z6uwqPoxs2slZUKyMaRkC1S5zfr3QFj9yzBwsiHiU1r2iIR75gn5l9i07VEg50cRBJXd o9wf0NdBscv1ilrgZdLhvHdVfC6cc1nN+cx2715356dV4RtyuHn6ahdxdmDhzVEnq9zU IY9Ol2Ni4XM1XkW9DtZKBumK4mkwHcumwSL0THyo+MqK9SsDmCPspifzXJTN/E0qP7T2 nf4Oo+wkd5i9EN5CdOA2eEcTVWboOcXm+Z0bRUJJeDIjWqEpZsjUM2UJmlgJ5/TOG4Qo VGAQ== X-Gm-Message-State: ALQs6tCT8c9mqept9kuts7/ENd9O1qjJnnxAFAMZ5bpQ9D0OUYt4tmqf 4uDgsAAZdCmQmncM3FAFLaA= X-Google-Smtp-Source: AIpwx4/1fjKfMk0UTT/bv+RxL46jZNnguNc+jSAaJGO8yAnc2CssBawMlr9o7fEQytupz0vaAje94Q== X-Received: by 10.46.129.7 with SMTP id d7mr1712161ljg.148.1524060771357; Wed, 18 Apr 2018 07:12:51 -0700 (PDT) Received: from [192.168.239.216] (83-245-234-255-nat-p.elisa-mobile.fi. [83.245.234.255]) by smtp.gmail.com with ESMTPSA id v64sm222103lje.56.2018.04.18.07.12.49 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 18 Apr 2018 07:12:50 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 11.3 \(3445.6.18\)) From: Jonathan Morton In-Reply-To: <87604o3get.fsf@toke.dk> Date: Wed, 18 Apr 2018 17:12:40 +0300 Cc: cake@lists.bufferbloat.net Content-Transfer-Encoding: quoted-printable Message-Id: <578552B2-5127-451A-AFE8-93AE9BB07368@gmail.com> References: <87vacq419h.fsf@toke.dk> <874lk9533l.fsf@toke.dk> <87604o3get.fsf@toke.dk> To: =?utf-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= X-Mailer: Apple Mail (2.3445.6.18) Subject: Re: [Cake] A few puzzling Cake results X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 18 Apr 2018 14:12:52 -0000 > On 18 Apr, 2018, at 2:25 pm, Toke H=C3=B8iland-J=C3=B8rgensen = wrote: >=20 > So if there is one active bulk flow, we allow each flow to queue four > packets. But if there are ten active bulk flows, we allow *each* flow = to > queue *40* packets. No - because the drain rate per flow scales inversely with the number of = flows, we have to wait for 40 MTUs' serialisation delay to get 4 packets = out of *each* flow. Without that, we can end up with very high drop rates which, in ingress = mode, don't actually improve congestion on the bottleneck link because = TCP can't reduce its window below 4 MTUs, and it's having to retransmit = all the lost packets as well. That loses us a lot of goodput for no = good reason. So I do accept the increase in intra-flow latency when the flow count = grows beyond the link's capacity to cope. It helps us keep the = inter-flow induced latency low while maintaining bulk goodput, which is = more important. - Jonathan Morton