From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net (mout.gmx.net [212.227.17.21]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "mout.gmx.net", Issuer "TeleSec ServerPass DE-1" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 0461621F404 for ; Sun, 1 Nov 2015 10:07:10 -0800 (PST) Received: from hms-beagle.home.lan ([217.237.68.126]) by mail.gmx.com (mrgmx101) with ESMTPSA (Nemesis) id 0LlYrb-1aQuTM3Zrz-00bHch for ; Sun, 01 Nov 2015 19:07:07 +0100 From: Sebastian Moeller Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable Message-Id: Date: Sun, 1 Nov 2015 19:07:44 +0100 To: cake@lists.bufferbloat.net Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) X-Mailer: Apple Mail (2.1878.6) X-Provags-ID: V03:K0:tRLpd1anOJXxuUjAlzz1mx3RlPeDcTnUEHeugjU+75edqc7R4Re ipAcUYgrcRtCIJTI3Yd015JLFBC2m0XYftwmHKypPn5Q7iNnYM1yffTu0zXRZgWlP35H4O9 nx8cNlC5WlRETvUpny/kcRn+7hKFwyHq+ORH9B2GDo6UfpGZWnwXtT+i8C4SukOCwsGhyyr y7KR9ziD+Q9gKuHinUe3Q== X-UI-Out-Filterresults: notjunk:1;V01:K0:yxh9zXrt5ag=:G0oiCrjKOxTKMxFtnf2gLz +P8zO79U21wZZWvNIGUtx/e68F8n1rUqUcSx3IvhClfxMwWz63tFx13jBxUnjcGkGD3NPuKql LCMqZ1/rUVuGiWfWxuICZyO6v3GZBLlaid66HoQc7t5sU9N9TEcDKrLIkGvAnO0yTyo50TcSD VwQdcjimw8oGh5MvHmmw75DEDgmjLmZyqJ4BtE4v4lK6QyPhev7n6JK3HHz3Q2B9gqW1FUTKx GkRsuuRPVXSnw+lGS/KGcr+iG60nGzZNl4iiUmo0QGvYSRAdOqAjfhrlFi+kju/mP9A9khCgv 9Ff/HNxj3QMD7ol/fxhT7Zzzu22jY97k1d6mx82KW6LCwjgZPH6a2Y9vexpKjcwcgS9vStGo7 xhjGV0nbjvkhvk4kxqQqT4VOdctutu2r9u7mIuVZonkcqnjKzObhdPu8k1zZ4H/2BJmuQaPDj zaGBkqrQUpqpChTqMKlAZLbCt1Y0bd3pn2FnsmjDdcNo6MxOWrg1AYBgZ2B2PDGj49LBeNlaV mIJ0mFt4B/plmWvnfLjYl92mFoUgAjhp7W5qjMXJSYWCzKyJMZ3IL4SGVFMSDkWtYfDt1D5DH KKvuM5emI5MCFs+oPZXIiS2BxE354PzGnqVAGxDiaJiU1jAGmw2wIOjW2FCimv5kfBNQvwLfK dDqpljWH5xzGzV8TRsNOsN7ByalUEpy4e2yV6VkBMCDhFJWotCahJZDqH405etHPabEtkH65B BnaGNJSDHYHY/5n4aQjKMzYmBoK17NHE6wfiqhZn6JJwlM/R+guPYgXnU9ZOp+rLmNve16MwA 7jpbzzS Subject: [Cake] cake target corner cases? X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.13 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, 01 Nov 2015 18:07:33 -0000 Dear cake committee, I just played around with the most recent sch_cake and noticed: user@computer:~/CODE/tc-adv/tc> sudo tc-adv qdisc del dev eth0 root user@computer:~/CODE/tc-adv/tc> sudo tc-adv qdisc replace dev eth0 root = cake bandwidth 1Mbit ; sudo tc-adv -s qdisc qdisc cake 8005: dev eth0 root refcnt 6 bandwidth 1Mbit diffserv4 flows = rtt 100.0ms raw=20 Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)=20 backlog 0b 0p requeues 0=20 capacity estimate: 1Mbit Tin 0 Tin 1 Tin 2 Tin 3 =20 thresh 1Mbit 937504bit 750Kbit 250Kbit target 18.2ms 19.4ms 24.2ms 72.7ms interval 145.3ms 155.0ms 193.8ms 581.4ms Pk-delay 0us 0us 0us 0us Av-delay 0us 0us 0us 0us Sp-delay 0us 0us 0us 0us pkts 0 0 0 0 bytes 0 0 0 0 way-inds 0 0 0 0 way-miss 0 0 0 0 way-cols 0 0 0 0 drops 0 0 0 0 marks 0 0 0 0 Sp-flows 0 0 0 0 Bk-flows 0 0 0 0 last-len 0 0 0 0 max-len 0 0 0 0 Here target is always 12.5% of interval instead of the expected 6.25% 1/16 =3D 0.0625 72.7/581.4 =3D 0.125042999656 24.2/193.8 =3D 0.124871001032 19.4/155.0 =3D 0.125161290323 18.2/145.3 =3D 0.125258086717 But the bandwidth is really low, so pushing target closer to the = bandwidth conserving side of the codel rationale might be fine, since = latency is bad to begin with and bandwidth also pretty scarce. But it = might be interesting to do a few more measurements at low bandwidths to = confirm that the 12.5% of interval logic holds water; one could also = argue that people with such links (a lot of DSL lines have even less = upload, so this certainly is not extreme) might think that any added ms = of delay matters (more than bandwidth); currently we leave the user no = remedy... user@computer:~/CODE/tc-adv/tc> sudo tc-adv qdisc del dev eth0 root user@computer:~/CODE/tc-adv/tc> sudo tc-adv qdisc replace dev eth0 root = cake bandwidth 10Mbit ; sudo tc-adv -s qdisc qdisc cake 8006: dev eth0 root refcnt 6 bandwidth 10Mbit diffserv4 flows = rtt 100.0ms raw=20 Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)=20 backlog 0b 0p requeues 0=20 capacity estimate: 10Mbit Tin 0 Tin 1 Tin 2 Tin 3 =20 thresh 10Mbit 9375Kbit 7500Kbit 2500Kbit target 6.2ms 6.2ms 6.2ms 7.3ms interval 100.0ms 100.0ms 100.0ms 101.0ms Pk-delay 0us 0us 0us 0us Av-delay 0us 0us 0us 0us Sp-delay 0us 0us 0us 0us pkts 0 0 0 0 bytes 0 0 0 0 way-inds 0 0 0 0 way-miss 0 0 0 0 way-cols 0 0 0 0 drops 0 0 0 0 marks 0 0 0 0 Sp-flows 0 0 0 0 Bk-flows 0 0 0 0 last-len 0 0 0 0 max-len 0 0 0 0 This looks okay, except Tin3 has target at 7.3/101.0 =3D 0.0722772277228 = 7% of interval. Both observations might actually be on purpose, but if so we should = document that behavior as expected, for example in the man page=85 Best Regards Sebastian