From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vk0-x231.google.com (mail-vk0-x231.google.com [IPv6:2607:f8b0:400c:c05::231]) (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 74E3F3B25E; Tue, 3 May 2016 09:35:34 -0400 (EDT) Received: by mail-vk0-x231.google.com with SMTP id m188so23335252vka.1; Tue, 03 May 2016 06:35:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:subject:from:to:cc:date:in-reply-to:references :mime-version:content-transfer-encoding; bh=pMnyOqa/AhK38AbXugJQShxIKJW13MHF4EehesyCnKs=; b=V8afMmFN8hoTGK3d+vVqXxInUHfd7tXPPeqWbJHrlYI9DTtptAoL0x7LD3X9XcOSxT QFpOEKV/9wl9T/hnioP5JWMozaALi/7hvIEdw27utQm2TuRu3cztn/Sb6VKtJyDMasJd 9Vr5FBKk9bCJZl4u3rL/MPUEs3Z76lJmMeOZ5pP79p2Kp4rODzarSf365g5f5FJyUbGS 5B3/1xKURj04QVgk6cOxWdhk6Ep3ZCIDwIi1D7+uE5mBQKxZk4jcjbG6MdddJD/9ag+N 00y3eZMduc5LbW2SFc8okmsIiDJM8e28Lqu5JBii6k62yekYkyvO46w8CMuOVfcsa0dd EpSw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:mime-version:content-transfer-encoding; bh=pMnyOqa/AhK38AbXugJQShxIKJW13MHF4EehesyCnKs=; b=PgrX37YkYyKfki/L3T90BOmPAarNZgrCV+p7+giATSKzR8u0TavwXpWIprirzzvf54 EB/NW0EoIBmWhf3/C96BqnmTouig52Tv8VWPdEAKK1h+uFSKQQ0j4CrNhAfOdquresko T1Yqf+yUREaHYwK0kOn35VSMIPzEP8gfLeQbbkrFuU73W56QjWXtEOWWZkp+Ty5BEtnA 3981NRaFSjD/DUSSgw88G3YECP5uQUVXhKZ+6yuu/3mUPsq//+Ii8CxP7BYeMpxXPM6I HgYvA1gxiwK/MD4pLtPgMVt5HPblhHsr22c19FJn6wlhwGigy/9qrQ3DSsZmYnUiGgrp 5Tlg== X-Gm-Message-State: AOPr4FUY84RtGXTQVKO4/+xxeBJTSyck/u3tWGUk77bh82pEXxqnn5nrTH+NDcCA4Ygmhg== X-Received: by 10.159.35.15 with SMTP id 15mr1033150uae.109.1462282534056; Tue, 03 May 2016 06:35:34 -0700 (PDT) Received: from [100.96.105.11] ([100.96.105.11]) by smtp.googlemail.com with ESMTPSA id 35sm556831uax.16.2016.05.03.06.35.32 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 03 May 2016 06:35:33 -0700 (PDT) Message-ID: <1462282531.5535.307.camel@edumazet-glaptop3.roam.corp.google.com> From: Eric Dumazet To: "Agarwal, Anil" Cc: Dave Taht , Jonathan Morton , "make-wifi-fast@lists.bufferbloat.net" , "codel@lists.bufferbloat.net" , ath10k Date: Tue, 03 May 2016 06:35:31 -0700 In-Reply-To: <7A2801D5E40DD64A85E38DF22117852CD09A1873@wdc1exchmbxp01.hq.corp.viasat.com> References: <1462125592.5535.194.camel@edumazet-glaptop3.roam.corp.google.com> <865DA393-262D-40B6-A9D3-1B978CD5F6C6@gmail.com> <7A2801D5E40DD64A85E38DF22117852CD09A181F@wdc1exchmbxp01.hq.corp.viasat.com> <7A2801D5E40DD64A85E38DF22117852CD09A1873@wdc1exchmbxp01.hq.corp.viasat.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: Re: [Make-wifi-fast] [Codel] fq_codel_drop vs a udp flood X-BeenThere: make-wifi-fast@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 03 May 2016 13:35:34 -0000 On Tue, 2016-05-03 at 12:50 +0000, Agarwal, Anil wrote: > I should be more precise about the statement about the inaccuracy of the algorithm. > Given that we dequeue packets in round robin manner, the maxqidx value may, on occasions, point to a queue > which is smaller than the largest queue by up to one MTU. That is not true. Linux qdiscs (fq_codel being one of them) can carry big packets, up to 64KB in size. You can not assume GRO/GSO are disabled. We absolutely want them for high performance. There is no way fq_codel will track in real time the biggest flow 'just in case we have to drop packets at enqueue()' This is a conscious choice I made years ago. This patch will fix the performance issue and keep the normal operations fast. https://patchwork.ozlabs.org/patch/617307/