From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-x229.google.com (mail-wm0-x229.google.com [IPv6:2a00:1450:400c:c09::229]) (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 6698B3B2A4 for ; Mon, 27 Nov 2017 10:53:28 -0500 (EST) Received: by mail-wm0-x229.google.com with SMTP id n74so10312651wmi.3 for ; Mon, 27 Nov 2017 07:53:28 -0800 (PST) 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:message-id:references :to; bh=6r3r+jMM/kje87evUF7s8OcfIIB637bv7ElNI14Aea0=; b=AB6vDdQHNiE3RSB//AldXI+BGU+B0K5M76j18tFnDPuP+D4p11pHfzNYsXijAQQBmC JZj3buvL693sSZjc0CJEiqY7VdLk3VwWiBAicAPoetQj+HunySEugGS98L/ipPoUFWoh ME5Unzq424xQaJuG8LryL91JCzvNyt9YnTBZeKDai3ivl28hrpGFgWLwbvoGrmIgqwOz PrQACJwJ3nVgJ4jrXsZhYYJu9uejsEKUaAiG/xdAVuZNxFpdsiwlFpNSp+0Z2416q+Kh R0nHrZfAWTqSyrfwDBb1MYsN0pl8Uqn1ilYX7lpIOKv46d8OH6PDfwVkrXIsihXJod5/ ToKA== 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 :message-id:references:to; bh=6r3r+jMM/kje87evUF7s8OcfIIB637bv7ElNI14Aea0=; b=PivhcfVkvtRUg1dITEdln8hSGI7+8gjXdcp+f7dzkJm39rk60ia1TrxXQgOw1e4cNM 8Ea1eYnryLgNAqREZs0JtnA+0saZuqmNJMOQwMbC3VIoBkvGvIV51Poe5F8NL4Bs/V9L wOzpTS52VMm1dX7mrhx8S3twdKxPxpXoK/Bf/a9j7fYKoQpwqf1cUBzL5C6I0es00FxH yGlMr6aLEkJJQcHmS5uJMePk8Z/+BUqJWlTbE/k5l67ZyGSDgkR5M8g2pFIBI/ylBjvl jHTdqMEAv5WBi/V0ef3sdlI2flsciFrGFWxJF3dxq+z4+/rD6eXDKFqEnFt4odo7GCv/ PGRw== X-Gm-Message-State: AJaThX5r9CYJulCRkwjTZmdjbj/6n0OnbtIyE//YuLWmdvuWjAxlOEFw x9jwQ8FVXjWE7TkFjUDppbA= X-Google-Smtp-Source: AGs4zMZfFGXc7kCvW4yN7RK1AAUlJpG3ZBIiBUOnuw55xxBWTCYZND3gF8wpWOey/JGD9IVhPXzS/g== X-Received: by 10.28.102.6 with SMTP id a6mr16769840wmc.63.1511798007539; Mon, 27 Nov 2017 07:53:27 -0800 (PST) Received: from [10.72.0.130] (h-1169.lbcfree.net. [185.99.119.68]) by smtp.gmail.com with ESMTPSA id z108sm51117780wrb.67.2017.11.27.07.53.26 (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 27 Nov 2017 07:53:26 -0800 (PST) Content-Type: multipart/alternative; boundary="Apple-Mail=_236C557A-B5FA-48E2-9F26-7A2186EE8031" Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) From: Pete Heist In-Reply-To: Date: Mon, 27 Nov 2017 16:53:30 +0100 Cc: =?utf-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= , Cake List Message-Id: References: <85E1A7B2-8AA7-418A-BE43-209A1EC8881A@gmail.com> <87d1447z9w.fsf@toke.dk> <27F95EB1-490B-404C-8F77-98646B6159E7@gmail.com> <1C937A63-CEC1-4173-8812-EA2A85972B73@gmail.com> <20D304DC-494E-4A00-9B39-1E9F4B0F0CB6@gmail.com> <67B1612D-895D-4E3A-8CBD-21580B470696@gmail.com> To: Jonathan Morton X-Mailer: Apple Mail (2.3124) Subject: Re: [Cake] cake flenter results round 1 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: Mon, 27 Nov 2017 15:53:28 -0000 --Apple-Mail=_236C557A-B5FA-48E2-9F26-7A2186EE8031 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=utf-8 > On Nov 27, 2017, at 3:48 PM, Jonathan Morton = wrote: > It's not at all obvious how we'd detect that. Packets are staying in = the queue for less time than the codel target, which is exactly what = you'd get if you weren't saturated at all. >=20 That makes complete sense when you put it that way. Cake has no way of = knowing why the input rate is lower than expected, even if it=E2=80=99s = part of the cause. I don=E2=80=99t think flent can know this either. It can=E2=80=99t = easily know the cause for its total output to be lower than expected. All I know is, this is a common problem in deployments, particularly on = low-end hardware like ER-Xs, that can be tricky for users to figure out. I don=E2=80=99t even think monitoring CPU in general would work. The CPU = could be high because it=E2=80=99s doing other calculations, but = there=E2=80=99s still enough for cake at a low rate, and there=E2=80=99s = no need to warn in that case. I=E2=80=99d be interested in any ideas on = how to know this is happening in the system as a whole. So far, there = are just various clues that one needs to piece together (no or few drops = or marks, less total throughput that expected, high cpu without other = external usage, etc). Then it needs to be proven with a test. Anyway thanks, your clue was what I needed! I need to remember to review = the qdisc stats when something unexpected happens.= --Apple-Mail=_236C557A-B5FA-48E2-9F26-7A2186EE8031 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=utf-8
On Nov 27, 2017, at 3:48 PM, Jonathan Morton <chromatix99@gmail.com> wrote:

It's not at all obvious how we'd detect = that.  Packets are staying in the queue for less time than the = codel target, which is exactly what you'd get if you weren't saturated = at all.

That makes complete = sense when you put it that way. Cake has no way of knowing why the input = rate is lower than expected, even if it=E2=80=99s part of the = cause.

I = don=E2=80=99t think flent can know this either. It can=E2=80=99t easily = know the cause for its total output to be lower than expected.

All I know is, this is a = common problem in deployments, particularly on low-end hardware like = ER-Xs, that can be tricky for users to figure out.

I don=E2=80=99t even = think monitoring CPU in general would work. The CPU could be high = because it=E2=80=99s doing other calculations, but there=E2=80=99s still = enough for cake at a low rate, and there=E2=80=99s no need to warn in = that case. I=E2=80=99d be interested in any ideas on how to know this is = happening in the system as a whole. So far, there are just various clues = that one needs to piece together (no or few drops or marks, less total = throughput that expected, high cpu without other external usage, etc). = Then it needs to be proven with a test.

Anyway thanks, your clue was what I = needed! I need to remember to review the qdisc stats when something = unexpected happens.
= --Apple-Mail=_236C557A-B5FA-48E2-9F26-7A2186EE8031--