From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net (mout.gmx.net [212.227.15.15]) (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 648B521F806 for ; Sat, 7 Nov 2015 07:08:20 -0800 (PST) Received: from hms-beagle.home.lan ([217.237.68.126]) by mail.gmx.com (mrgmx001) with ESMTPSA (Nemesis) id 0MLvGW-1ZnNSN0nDo-007lCA; Sat, 07 Nov 2015 16:08:15 +0100 Content-Type: text/plain; charset=windows-1252 Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) From: Sebastian Moeller In-Reply-To: Date: Sat, 7 Nov 2015 16:08:29 +0100 Content-Transfer-Encoding: quoted-printable Message-Id: References: <87pozspckj.fsf@toke.dk> <6A2609D9-7747-487B-9484-ECC69C50DE96@gmx.de> <874mh3pai9.fsf@toke.dk> <50C2A7B7-1B81-41E1-B534-CA449296FE77@gmail.com> <87ziysldij.fsf@toke.dk> <87vb9fl7ec.fsf@toke.dk> <87611fkyd7.fsf@toke.dk> <340E3F23-2F9C-449F-ACA7-86031FBE3B31@gmail.com> <87y4eambyd.fsf@alrua-karlstad.karlstad.toke.dk> To: Jonathan Morton X-Mailer: Apple Mail (2.1878.6) X-Provags-ID: V03:K0:q34uuMPPSBGtNRG3+S1WaJsLdVthJ/5fhYK8/mjGU2dQBzuHpZ6 REhcjdk6jc2i3Zh+LLK+qv4LYmSiGTqbM3LU4dS8Ilp7VGcIk0gLMkLvpAZsFF7H0PkXg7g jwZcbZeAwNOY/1abF2ladBaTn8hIKM+yK0IEUvxxB0K/xH5pCR1u+k1ZgiDWf0SuWyFhXeU MXuihUWfgQtoQgNCgPOYA== X-UI-Out-Filterresults: notjunk:1;V01:K0:z7ALf818I9A=:/6a9ovx7remJKDxOAiegRE 3TCJ3MVwttxX+QdQx6FwdJnGtoZiqx1qpdXERQaWQXItgypzYjUZ8OuVyk4ehNMemffEiGvRJ fSHGw0n5FapO0BnXqhLDuFYttDQXgwjYFJTCiml5WQHdt9BxRzQbp8MQSHcfEABoQ4SMnXEGQ YZo9G4tay6X6IQelgM8/PGW0YY65JQCcNYBozn3MNKgqpst1+VN6AW6wSBU/uWV6zC3t1wj91 uLLSjc3WhkBV10VihG5yPrNDvTkN7nq6ONLWx45hlFDmOHHZ3A8Rn+JezDA2O+EdFJZj8XpWK QQopd6UF+9ZPlqmnZRZ5KVlBG3s0HzdLofbwWHztNjZLoEQhnhLMAwLjp1RCEJQj5J4K4/MAw g91gXsPAHZy6AyV5eWOlvfm8NVrKqJOU1vfvR+dvXMNKdTTlNxC6pK+sercpcOsB/1ZLaN75o WawAIBQHtRRHYd/rSHbFz13PLTdOQ8ZOdopdL9F3oIj7byxEcO8EPsXsZjTlXSAP0JB6CwvrV hNC6ASlZYT+sRa9CWIWGJAZrbXyC7pqFdwk99lpKPKj9db7ejaxT7DGw07b4zQsoeTRElQpXl xS3blUqa1wg5fCfPp7+N9LJmzyxC0JQK/xsZhK9qw4wjv3vP7IOdIvcTeEgCakBF8DXKvdhC+ kWGOpX/IQlOi3O19GFrvGYDixyDV+YpxDt43Rkj12WPnWH/f7Jh/aqyT40YXtMApzGzLbm4Iw 3Yzd/tIugTl+yCV+pqCPE4+H4OU4SNhZhpRmsaXSN0/TgnjR/TQwpCHlcwwVKWtBFFiGBpuFQ 6Y0ZXzK Cc: cake@lists.bufferbloat.net Subject: Re: [Cake] Long-RTT broken again 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: Sat, 07 Nov 2015 15:08:44 -0000 Hi Jonathan, pretty cool, ans subtle ;) On Nov 7, 2015, at 11:51 , Jonathan Morton = wrote: > Okay, I=92ve tracked down the problem. Turns out to be one of C=92s = more subtle misfeatures. >=20 > I calculate the desired buffer size as rate * interval * 4. Since = interval is in =B5s, rate * interval is a 64-bit temporary. However, I = forgot to cast either of these operands to the new width first, so the = upper half of the product was never calculated. After dividing by = 250000, the resulting buffer size was 8918 bytes - which was clamped up = to 64KB by a sanity check immediately afterwards. >=20 > It=92s thus remarkable that we got as much throughput as we did. >=20 > While fixing this, I=92m also adding configurability of the buffer = limit and statistics of how much of the buffer was actually ever used. = Additionally, I=92m choosing a saner default for =93unlimited=94 mode. Oh, shiny ;) I take it the parameter is limiting the queue = memory as measured by skb->truesize ; just checked, it wants the size in = KB. I just committed a change to report that in the usage help tc will = display=85 Best Regards Sebastian >=20 > - Jonathan Morton >=20