From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lj1-x235.google.com (mail-lj1-x235.google.com [IPv6:2a00:1450:4864:20::235]) (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 650433B29E; Sat, 21 Jul 2018 10:38:25 -0400 (EDT) Received: by mail-lj1-x235.google.com with SMTP id y17-v6so13396326ljy.8; Sat, 21 Jul 2018 07:38:25 -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=b68YTG5GDHphSHf3LK53OjBIbURf484kMDuxfW77Km0=; b=ZZfPNppEutk76kxzpX1yG1aKTtP15w/fZplTSgzDSMzs29AK4V7IawloquVg+3qay6 hPEB0R/Lparwj4tazfO/JFldVQHmHgjPo8E7T2k2C26J9FypwhoekZOoKd0wDdOUmOTo 7QrnL+YDsiUtk6Bh2BRiEnujZkDD71n+tHLX5epzkLeGYup4ZxhKon6K1SKVwi79zYz/ NuRRkLPPsebT9X3pJ8O4CARBl8zgz6zmjTw7utrxT+WA290kP9ys8FJQYefUt5LY/9P6 V3GMIEL1UlnggA0WRdPBtaJjGgvooazzCy8t8ye9uA8sdfmWwYYVdgH97dmNkhwGkOea Lu0Q== 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=b68YTG5GDHphSHf3LK53OjBIbURf484kMDuxfW77Km0=; b=IaEw6pqTwCZZXpTCARQn+3CnDnrRkAPuNMor8XA/WUdO+oTZE+G4b5a0WQjfkhM+iZ Ayz2A2dkjZbyynbudmTF0c0PrmFr4q6jQCeBkC9cPItfVe9HgP5YlpFj7reD6YnIUbjk BkWR+ldHsEGDne6krI1JNiW5ydwPu5zYYCgVyigA3iHiAt0EA2Su5Z4xnvKDXG8oFS4Y mnfbjeU76jmiFTyRX3jfqzq8bomKeWMSyVr1XlUm7s7peRmz45/t8Qc/ebg98FHjeCqq TY4yiBLZiBj8vmYhV4UcjXVdxytsN8PZpXotO+Yp69PW/pEhCmHJArpJ3yL9X/g5npUv e+sA== X-Gm-Message-State: AOUpUlHsDV0Uhw32i5Lh3752Qcc0wRhQMbJwCqtbvmYhlr4OrEn8v2vH o/+/Aqv6H305DpoMO5+qrLw= X-Google-Smtp-Source: AAOMgpe6JRJJJskNQGVmk2E8UlFNBU7U7c6ugDdqKYLOB17qJEht18lCRm8GOWgAZQFQVayde9XaJw== X-Received: by 2002:a2e:990b:: with SMTP id v11-v6mr3010100lji.87.1532183904386; Sat, 21 Jul 2018 07:38:24 -0700 (PDT) Received: from [192.168.239.216] (83-245-233-124-nat-p.elisa-mobile.fi. [83.245.233.124]) by smtp.gmail.com with ESMTPSA id o27-v6sm696312lfb.78.2018.07.21.07.38.23 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 21 Jul 2018 07:38:23 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 11.5 \(3445.9.1\)) From: Jonathan Morton In-Reply-To: Date: Sat, 21 Jul 2018 17:38:22 +0300 Cc: Dave Taht , Cake List , make-wifi-fast@lists.bufferbloat.net, bloat Content-Transfer-Encoding: quoted-printable Message-Id: <1A06B0BB-4B2F-4E94-B947-EF41BCC3F18C@gmail.com> References: To: Luca Muscariello X-Mailer: Apple Mail (2.3445.9.1) Subject: Re: [Make-wifi-fast] Van Jacobson's slides on timing wheels at netdevconf 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: Sat, 21 Jul 2018 14:38:25 -0000 > On 20 Jul, 2018, at 5:47 pm, Luca Muscariello = wrote: >=20 > and C) you can implement any packet scheduler using a timing wheel = using virtual times. To do this perfectly, you have to assume that no packets will arrive = within your scheduling horizon which should be scheduled within that = horizon. An example of such a situation would be sparse flows in DRR++, which is = a key part of fq_codel and Cake. So to implement DRR++ using timing = wheels, you have to choose your scheduling horizon carefully so as to = minimise the delay to sparse packets. Given that task scheduling latency in Linux is on the order of 1ms, a = horizon of this magnitude could be acceptable. But dedicated hardware = could do better still. - Jonathan Morton