From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lj1-x244.google.com (mail-lj1-x244.google.com [IPv6:2a00:1450:4864:20::244]) (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 BFE3F3B2A4 for ; Sat, 7 Sep 2019 20:59:06 -0400 (EDT) Received: by mail-lj1-x244.google.com with SMTP id y23so9345509lje.9 for ; Sat, 07 Sep 2019 17:59:06 -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=rdlnFjDss5TOEvfCwzQ5JXa2/a60yGZL/m5hZAGI5a4=; b=tHTaq7UOgm4zNbLtHJvTv3HmysSgN0SujHJ7XSwl5IXjcsXX4J06aaZHagYD5i+So2 WIwkGEDtqlXnL9eKU63KJFO94vu3aCkVUY9NFT0AQQOXTrbZRHYvEGm0ZKzWsTpouDjb 3U9iuzTVDKSZ5hl+VfwPB0ZE+V83q8HeuxVVmbLES/sFPW0xsjIpAhuwnWV3B5ntfaxV u3aj7zPitMhHwVOrUwtqShnXHykdn3U92vQdORCziFY6FLctzogfqxDFQLNGVTDmA32b QmJNAWSazNrAt3N6Q+TY2Uw6pXyQlegzeFQJwPYKsQ9kr3gLRNaof3oNppY9WZYq9hmv +n3Q== 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=rdlnFjDss5TOEvfCwzQ5JXa2/a60yGZL/m5hZAGI5a4=; b=WMZKfEUtTspD6jJ5GkrhDg4x4k4SGntCSPrhhF+0e/g/wWFqdnO5TUNEtLV1u88tZn /+L6Ql7tEysEQLUudzaYguW2PyyqBCHOKc7t9aP3r4FVGoQRlKXjhO/xvnr8NZEpXxh8 2uMleC9Z7fesIsvm7LMyjYokwJjjyTD+ryqjgywSZmFaO7hOySS/PBxkIg0Zux6cQUla 6y72/xDv37fHZ2Z2rrNZh0vQjHTs00HDI5W+2mdFL+KxjIZUmX5WMvx/qJ5qpMxBK5KL yBcNctp0RVIRHqF74b7Nyih/aLCIxiA4wEDOCUB620jYHDGzsnSBrEUBLYajIOOQM+Q+ epNw== X-Gm-Message-State: APjAAAX7PA1zgNv1Mr52ceBMBbfjTf9vxBAwjJnKVkT8BP4cjfRRILNJ 3H5yq44ZK7nB1tc/dMcAlB+Hv5oIFv0= X-Google-Smtp-Source: APXvYqy2916oV4Rmj2ko20tvThg287i84bQEv12YYd4CN8Pph/UegCkpoH+W+Xqg+9TsP2uLUqYlhA== X-Received: by 2002:a2e:8814:: with SMTP id x20mr10939532ljh.221.1567904345733; Sat, 07 Sep 2019 17:59:05 -0700 (PDT) Received: from jonathartonsmbp.lan (83-245-237-193-nat-p.elisa-mobile.fi. [83.245.237.193]) by smtp.gmail.com with ESMTPSA id a3sm1937853ljb.36.2019.09.07.17.59.04 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 07 Sep 2019 17:59:04 -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: <9a90111b-2389-4dc6-8409-18c40f895540@www.fastmail.com> Date: Sun, 8 Sep 2019 03:59:03 +0300 Cc: cake@lists.bufferbloat.net Content-Transfer-Encoding: quoted-printable Message-Id: <43F02160-E691-4393-A0C0-8AB4AD962700@gmail.com> References: <2825CE14-2109-4580-A086-9701F4D3ADF0@gmail.com> <18b1c174-b88d-4664-9aa8-9c42925fc14c@www.fastmail.com> <9a90111b-2389-4dc6-8409-18c40f895540@www.fastmail.com> To: Justin Kilpatrick X-Mailer: Apple Mail (2.3445.9.1) Subject: Re: [Cake] Fighting bloat in the face of uncertinty 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: Sun, 08 Sep 2019 00:59:07 -0000 > On 8 Sep, 2019, at 3:03 am, Justin Kilpatrick = wrote: >=20 > So you believe that setting the target RTT closer to the path latency = was not the main contributor to reducing bloat? Is there a configuration = I could use to demonstrate that one way or the other?=20 The second-order effect I mentioned is related to the 'target' = parameter. Checking the code, I am reminded that while Cake itself can = have 'target' set from userspace, there actually isn't a parameter to = the tc module which allows setting it independently of 'rtt'. But there = *is* a table in q_cake.c (in tc) which you can temporarily extend with = the following entries for experimentation: static struct cake_preset presets[] =3D { {"datacentre", 5, 100}, {"lan", 50, 1000}, {"metro", 500, 10000}, {"regional", 1500, 30000}, {"internet", 5000, 100000}, {"oceanic", 15000, 300000}, {"satellite", 50000, 1000000}, {"interplanetary", 50000000, 1000000000}, + + {"metro-loose", 5000, 10000}, + {"internet-tight", 500, 100000}, }; If the effect is genuinely due to marking rate, then 'metro-loose' = should behave like 'metro' and 'internet-tight' should behave like = 'internet', to a first-order approximation. If, on the other hand, it's = due to the second-order interaction with CPU scheduling latency, the = reverse may be true. The latter is not something you should be counting = on, as it will insert random AQM marking even when the link is not = actually saturated. You could also set it back to 'internet' and progressively reduce the = bandwidth parameter, making the Cake shaper into the actual bottleneck. = This is the correct fix for the problem, and you should notice an = instant improvement as soon as the bandwidth parameter is correct. - Jonathan Morton=