From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from EUR01-HE1-obe.outbound.protection.outlook.com (mail-he1eur01on0071.outbound.protection.outlook.com [104.47.0.71]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id A8E073B2A4 for ; Sun, 24 Dec 2017 05:34:17 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=darbyshire-bryant.me.uk; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=+PxVyjGH8F7UcXTMGTSqM5x386qCWYI23AYgnQus5VU=; b=MzYlRp44gpnUT3+W93gnQy2eZYVwIgu0a6Vp6skZLLxKDhe7G0Bdg8KqUdqzWteoLatTSpo9obxPS3beBF2CQxq9MRkTCJNvQWQz0CQv2YWjInx7uGbJGrgMpwF44JWj5M9zO+/v5ToH54MDHXd2Iq3Qd6215eIo64KkKSy4Hmc= Received: from AM0PR0702MB3730.eurprd07.prod.outlook.com (52.133.51.23) by AM0PR0702MB3699.eurprd07.prod.outlook.com (52.133.51.16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P256) id 15.20.366.3; Sun, 24 Dec 2017 10:34:15 +0000 Received: from AM0PR0702MB3730.eurprd07.prod.outlook.com ([fe80::d1fe:f3ea:349d:cb9a]) by AM0PR0702MB3730.eurprd07.prod.outlook.com ([fe80::d1fe:f3ea:349d:cb9a%13]) with mapi id 15.20.0366.003; Sun, 24 Dec 2017 10:34:15 +0000 From: Kevin Darbyshire-Bryant To: Sebastian Moeller CC: Ryan Mounce , Cake List Thread-Topic: [Cake] overheads or rate calculation changed? 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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, 24 Dec 2017 10:34:18 -0000 --Apple-Mail=_C04A3BF7-18D1-4385-99C2-DD7DFD3C40DA Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=utf-8 > On 23 Dec 2017, at 21:03, Sebastian Moeller wrote: >=20 > Hi All, >=20 > just had a look for hard_header_len in the linux kernel: > linux/include/linux/netdevice.h: > * @hard_header_len: Maximum hardware header length. > * @min_header_len: Minimum hardware header length >=20 > this seems to corroborate our observation that hard_header_len is not = a veridical representation of the actual hardware header length, so I = assume the values cake returns are actually true. It also indicates that = except for pure ethernet interfaces hard_header_len is _not_ the right = parameter to evaluate for what cake is evaluating it for... What came as a surprise to me the other day is that whatever = =E2=80=98overhead=E2=80=99 you specify on the command line must = *include* the hard_header_len figure, since the code subtracts =E2=80=98ha= rd header len=E2=80=99 from the passed overhead value. I=E2=80=99ve = probably been doing this wrong for=E2=80=A6 who knows how long. if (tb[TCA_CAKE_OVERHEAD]) { if (tb[TCA_CAKE_ETHERNET]) <<<=E2=80=94 this is = really a synonym for =E2=80=98raw=E2=80=99, in my case it isn=E2=80=99t = passed so else is exec q->rate_overhead =3D = -(nla_get_s32(tb[TCA_CAKE_ETHERNET])); else q->rate_overhead =3D = -(qdisc_dev(sch)->hard_header_len); <<<=E2=80=94note the sneaky = minus! q->rate_overhead +=3D = nla_get_s32(tb[TCA_CAKE_OVERHEAD]); For a while I=E2=80=99ve manually been passing =E2=80=9912=E2=80=99 as a = =E2=80=98bridged-ptm ether-vlan=E2=80=99 equivalent except I should have = been passing =E2=80=9926=E2=80=99. Instead I=E2=80=99ve been reducing = the length of packets by 2 bytes :-) I now just pass the relevant = keywords. Cheers, Kevin D-B Falling into traps so you don=E2=80=99t have to(tm) 012C ACB2 28C6 C53E 9775 9123 B3A2 389B 9DE2 334A --Apple-Mail=_C04A3BF7-18D1-4385-99C2-DD7DFD3C40DA Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="signature.asc" Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Message signed with OpenPGP -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEASyssijGxT6XdZEjs6I4m53iM0oFAlo/gqcACgkQs6I4m53i M0ouBA/+Pj8AO+b1GpoOcM/DYFieBMZoxQEtBlmnHQcR4rWxkdLGBGQPtCKFE88u zX6/koG9CJcoDgmJabT817zABpALwmSKrVH0+TNgVYXw+LWv7vwUboU+LXF4hRLQ TCnHa/D+LQx7xi/bFfGJgd53/piyKPDYrUxpaVNy1DplrAb4obEBr0HrHn8QvMpe MCzhsbqpWG2QaerSjWUXVPzy5xngfGaWjliHdrkRgA8uAV2XesgldhwuqgPh6Snq SeLQDouVkRdtsbDMfuDK4moEa/F++wFMrriZpNO2WDQG36qYNxmJvIZfn3gKddHm 3ng1jUu1JdnkRQz8emOUyOO1uVzwqJ5Lwqrtoo9Iu8UBkgb5duIdshuDa0GmYeEQ pMWUXuA55Zf1CKB3QdK8c+A16zKCnfiPJayshiOFSpjglcaunrzk3YcN9T3vJtG8 WVMvhx+UK2c5/2tnCeUuKfhGWSM+DdCHvGrW/RjQzYPIw9ylNwo8KKGvM5hX9cMq Eii6UiDcO2KPMtUHPlPuCNUe6t05ke+gyd/I3C/K0o6c5rOEBskTbQ4pCp/Yc7XY sf7eGIAdWe3rNXkCwyJbdi1/zgWrndt+4ypxLTlQeX2/SOFWYthrrA5hhF1nODvo 86PQ5gp2mMHaLZYPGcM9zuIfUHLWZ+kqnFsAGAs743s6Gl2WR04= =Ewl4 -----END PGP SIGNATURE----- --Apple-Mail=_C04A3BF7-18D1-4385-99C2-DD7DFD3C40DA--