From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F0FA5C4360F for ; Wed, 27 Mar 2019 19:24:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BD6A3206C0 for ; Wed, 27 Mar 2019 19:24:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387985AbfC0TYd (ORCPT ); Wed, 27 Mar 2019 15:24:33 -0400 Received: from metis.ext.pengutronix.de ([85.220.165.71]:39697 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731515AbfC0TYc (ORCPT ); Wed, 27 Mar 2019 15:24:32 -0400 Received: from gallifrey.ext.pengutronix.de ([2001:67c:670:201:5054:ff:fe8d:eefb] helo=bjornoya.blackshift.org) by metis.ext.pengutronix.de with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1h9EA0-0008TG-PG; Wed, 27 Mar 2019 20:24:28 +0100 Received: from [IPv6:2a03:f580:87bc:d400:845f:6e2c:f24d:6770] (unknown [IPv6:2a03:f580:87bc:d400:845f:6e2c:f24d:6770]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mkl@blackshift.org", Issuer "StartCom Class 1 Client CA" (not verified)) (Authenticated sender: mkl@blackshift.org) by smtp.blackshift.org (Postfix) with ESMTPSA id ACCCF3EF2E5; Wed, 27 Mar 2019 19:24:25 +0000 (UTC) To: Stephen Hemminger Cc: Jiri Pirko , netdev@vger.kernel.org, Dave Taht , Jamal Hadi Salim , kernel@pengutronix.de, Cong Wang , linux-can@vger.kernel.org, davem@davemloft.net References: <20190327165632.10711-1-mkl@pengutronix.de> <20190327113059.6b1224ab@shemminger-XPS-13-9360> From: Marc Kleine-Budde Openpgp: preference=signencrypt Autocrypt: addr=mkl@pengutronix.de; prefer-encrypt=mutual; keydata= mQINBFFVq30BEACtnSvtXHoeHJxG6nRULcvlkW6RuNwHKmrqoksispp43X8+nwqIFYgb8UaX zu8T6kZP2wEIpM9RjEL3jdBjZNCsjSS6x1qzpc2+2ivjdiJsqeaagIgvy2JWy7vUa4/PyGfx QyUeXOxdj59DvLwAx8I6hOgeHx2X/ntKAMUxwawYfPZpP3gwTNKc27dJWSomOLgp+gbmOmgc 6U5KwhAxPTEb3CsT5RicsC+uQQFumdl5I6XS+pbeXZndXwnj5t84M+HEj7RN6bUfV2WZO/AB Xt5+qFkC/AVUcj/dcHvZwQJlGeZxoi4veCoOT2MYqfR0ax1MmN+LVRvKm29oSyD4Ts/97cbs XsZDRxnEG3z/7Winiv0ZanclA7v7CQwrzsbpCv+oj+zokGuKasofzKdpywkjAfSE1zTyF+8K nxBAmzwEqeQ3iKqBc3AcCseqSPX53mPqmwvNVS2GqBpnOfY7Mxr1AEmxdEcRYbhG6Xdn+ACq Dq0Db3A++3PhMSaOu125uIAIwMXRJIzCXYSqXo8NIeo9tobk0C/9w3fUfMTrBDtSviLHqlp8 eQEP8+TDSmRP/CwmFHv36jd+XGmBHzW5I7qw0OORRwNFYBeEuiOIgxAfjjbLGHh9SRwEqXAL kw+WVTwh0MN1k7I9/CDVlGvc3yIKS0sA+wudYiselXzgLuP5cQARAQABtCZNYXJjIEtsZWlu ZS1CdWRkZSA8bWtsQHBlbmd1dHJvbml4LmRlPokCVAQTAQoAPgIbAwIeAQIXgAULCQgHAwUV CgkICwUWAgMBABYhBMFAC6CzmJ5vvH1bXCte4hHFiupUBQJcUsSbBQkM366zAAoJECte4hHF iupUgkAP/2RdxKPZ3GMqag33jKwKAbn/fRqAFWqUH9TCsRH3h6+/uEPnZdzhkL4a9p/6OeJn Z6NXqgsyRAOTZsSFcwlfxLNHVxBWm8pMwrBecdt4lzrjSt/3ws2GqxPsmza1Gs61lEdYvLST Ix2vPbB4FAfE0kizKAjRZzlwOyuHOr2ilujDsKTpFtd8lV1nBNNn6HBIBR5ShvJnwyUdzuby tOsSt7qJEvF1x3y49bHCy3uy+MmYuoEyG6zo9udUzhVsKe3hHYC2kfB16ZOBjFC3lH2U5An+ yQYIIPZrSWXUeKjeMaKGvbg6W9Oi4XEtrwpzUGhbewxCZZCIrzAH2hz0dUhacxB201Y/faY6 BdTS75SPs+zjTYo8yE9Y9eG7x/lB60nQjJiZVNvZ88QDfVuLl/heuIq+fyNajBbqbtBT5CWf mOP4Dh4xjm3Vwlz8imWW/drEVJZJrPYqv0HdPbY8jVMpqoe5jDloyVn3prfLdXSbKPexlJaW 5tnPd4lj8rqOFShRnLFCibpeHWIumqrIqIkiRA9kFW3XMgtU6JkIrQzhJb6Tc6mZg2wuYW0d Wo2qvdziMgPkMFiWJpsxM9xPk9BBVwR+uojNq5LzdCsXQ2seG0dhaOTaaIDWVS8U/V8Nqjrl 6bGG2quo5YzJuXKjtKjZ4R6k762pHJ3tnzI/jnlc1sXzuQENBFxSzJYBCAC58uHRFEjVVE3J 31eyEQT6H1zSFCccTMPO/ewwAnotQWo98Bc67ecmprcnjRjSUKTbyY/eFxS21JnC4ZB0pJKx MNwK6zq71wLmpseXOgjufuG3kvCgwHLGf/nkBHXmSINHvW00eFK/kJBakwHEbddq8Dr4ewmr G7yr8d6A3CSn/qhOYWhIxNORK3SVo4Io7ExNX/ljbisGsgRzsWvY1JlN4sabSNEr7a8YaqTd 2CfFe/5fPcQRGsfhAbH2pVGigr7JddONJPXGE7XzOrx5KTwEv19H6xNe+D/W3FwjZdO4TKIo vcZveSDrFWOi4o2Te4O5OB/2zZbNWPEON8MaXi9zABEBAAGJA3IEGAEKACYWIQTBQAugs5ie b7x9W1wrXuIRxYrqVAUCXFLMlgIbAgUJAeKNmgFACRArXuIRxYrqVMB0IAQZAQoAHRYhBJrx JF84Dn3PPNRrhVrGIaOR5J0gBQJcUsyWAAoJEFrGIaOR5J0grw4H/itil/yryJCvzi6iuZHS suSHHOiEf+UQHib1MLP96LM7FmDabjVSmJDpH4TsMu17A0HTG+bPMAdeia0+q9FWSvSHYW8D wNhfkb8zojpa37qBpVpiNy7r6BKGSRSoFOv6m/iIoRJuJ041AEKao6djj/FdQF8OV1EtWKRO +nE2bNuDCcwHkhHP+FHExdzhKSmnIsMjGpGwIQKN6DxlJ7fN4W7UZFIQdSO21ei+akinBo4K O0uNCnVmePU1UzrwXKG2sS2f97A+sZE89vkc59NtfPHhofI3JkmYexIF6uqLA3PumTqLQ2Lu bywPAC3YNphlhmBrG589p+sdtwDQlpoH9O7NeBAAg/lyGOUUIONrheii/l/zR0xxr2TDE6tq 6HZWdtjWoqcaky6MSyJQIeJ20AjzdV/PxMkd8zOijRVTnlK44bcfidqFM6yuT1bvXAO6NOPy pvBRnfP66L/xECnZe7s07rXpNFy72XGNZwhj89xfpK4a9E8HQcOD0mNtCJaz7TTugqBOsQx2 45VPHosmhdtBQ6/gjlf2WY9FXb5RyceeSuK4lVrz9uZB+fUHBge/giOSsrqFo/9fWAZsE67k 6Mkdbpc7ZQwxelcpP/giB9N+XAfBsffQ8q6kIyuFV4ILsIECCIA4nt1rYmzphv6t5J6PmlTq TzW9jNzbYANoOFAGnjzNRyc9i8UiLvjhTzaKPBOkQfhStEJaZrdSWuR/7Tt2wZBBoNTsgNAw A+cEu+SWCvdX7vNpsCHMiHtcEmVt5R0Tex1Ky87EfXdnGR2mDi6Iyxi3MQcHez3C61Ga3Baf P8UtXR6zrrrlX22xXtpNJf4I4Z6RaLpB/avIXTFXPbJ8CUUbVD2R2mZ/jyzaTzgiABDZspbS gw17QQUrKqUog0nHXuaGGA1uvreHTnyBWx5P8FP7rhtvYKhw6XdJ06ns+2SFcQv0Bv6PcSDK aRXmnW+OsDthn84x1YkfGIRJEPvvmiOKQsFEiB4OUtTX2pheYmZcZc81KFfJMmE8Z9+LT6Ry uSS5AQ0EXFLNDgEIAL14qAzTMCE1PwRrYJRI/RSQGAGF3HLdYvjbQd9Ozzg02K3mNCF2Phb1 cjsbMk/V6WMxYoZCEtCh4X2GjQG2GDDW4KC9HOa8cTmr9Vcno+f+pUle09TMzWDgtnH92WKx d0FIQev1zDbxU7lk1dIqyOjjpyhmR8Put6vgunvuIjGJ/GapHL/O0yjVlpumtmow6eME2muc TeJjpapPWBGcy/8VU4LM8xMeMWv8DtQML5ogyJxZ0Smt+AntIzcF9miV2SeYXA3OFiojQstF vScN7owL1XiQ3UjJotCp6pUcSVgVv0SgJXbDo5Nv87M2itn68VPfTu2uBBxRYqXQovsR++kA EQEAAYkCPAQYAQoAJhYhBMFAC6CzmJ5vvH1bXCte4hHFiupUBQJcUs0OAhsMBQkB4o0iAAoJ ECte4hHFiupUbioQAJ40bEJmMOF28vFcGvQrpI+lfHJGk9zSrh4F4SlJyOVWV1yWyUAINr8w v1aamg2nAppZ16z4nAnGU/47tWZ4P8blLVG8x4SWzz3D7MCy1FsQBTrWGLqWldPhkBAGp2VH xDOK4rLhuQWx3H5zd3kPXaIgvHI3EliWaQN+u2xmTQSJN75I/V47QsaPvkm4TVe3JlB7l1Fg OmSvYx31YC+3slh89ayjPWt8hFaTLnB9NaW9bLhs3E2ESF9Dei0FRXIt3qnFV/hnETsx3X4h KEnXxhSRDVeURP7V6P/z3+WIfddVKZk5ZLHi39fJpxvsg9YLSfStMJ/cJfiPXk1vKdoa+FjN 7nGAZyF6NHTNhsI7aHnvZMDavmAD3lK6CY+UBGtGQA3QhrUc2cedp1V53lXwor/D/D3Wo9wY iSXKOl4fFCh2Peo7qYmFUaDdyiCxvFm+YcIeMZ8wO5udzkjDtP4lWKAn4tUcdcwMOT5d0I3q WATP4wFI8QktNBqF3VY47HFwF9PtNuOZIqeAquKezywUc5KqKdqEWCPx9pfLxBAh3GW2Zfjp lP6A5upKs2ktDZOC2HZXP4IJ1GTk8hnfS4ade8s9FNcwu9m3JlxcGKLPq5DnIbPVQI1UUR4F QyAqTtIdSpeFYbvH8D7pO4lxLSz2ZyBMk+aKKs6GL5MqEci8OcFW Subject: Re: [RFC] net: sch_generic: fq_codel vs pfifo_fast Message-ID: <0edf15df-b607-70f7-5fe8-2860eb663a53@pengutronix.de> Date: Wed, 27 Mar 2019 20:24:13 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190327113059.6b1224ab@shemminger-XPS-13-9360> Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="B08wmT3aOsbSbdXvTtADrwYlMLJ2ufiSo" X-SA-Exim-Connect-IP: 2001:67c:670:201:5054:ff:fe8d:eefb X-SA-Exim-Mail-From: mkl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: netdev@vger.kernel.org Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --B08wmT3aOsbSbdXvTtADrwYlMLJ2ufiSo Content-Type: multipart/mixed; boundary="holF2ua9ouqkCCnran9GCZoatAI6XTVfX"; protected-headers="v1" From: Marc Kleine-Budde To: Stephen Hemminger Cc: Jiri Pirko , netdev@vger.kernel.org, Dave Taht , Jamal Hadi Salim , kernel@pengutronix.de, Cong Wang , linux-can@vger.kernel.org, davem@davemloft.net Message-ID: <0edf15df-b607-70f7-5fe8-2860eb663a53@pengutronix.de> Subject: Re: [RFC] net: sch_generic: fq_codel vs pfifo_fast References: <20190327165632.10711-1-mkl@pengutronix.de> <20190327113059.6b1224ab@shemminger-XPS-13-9360> In-Reply-To: <20190327113059.6b1224ab@shemminger-XPS-13-9360> --holF2ua9ouqkCCnran9GCZoatAI6XTVfX Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: quoted-printable On 3/27/19 7:30 PM, Stephen Hemminger wrote: >> on CAN networking hardware we (the CAN community) experience a lot sil= ent, >> unwanted frame drops inside the kernel. (See first patch for details.)= So >> here's a patch series to keep pfifo_fast as default scheduler for CAN = hardware >> by default. >=20 > Why do you set fq_codel as default qdisc if you know it doesn't work ri= ght for your > environment. Is this a distro's want one value problem? This is a many fold problem. - Consider a random Linux developer attaching one of the mainline supported USB-CAN adapters to his/her development laptop and doing some random CAN test. As far a I heard all modern Linux distributions (but not debian) enable fq_codel per kernel .config or via systemd. The user will experiences dropped CAN frames on the first 1000 packages. This is not a good user experience. - From the user space point of view the sysctl net.core.default_qdisc behaves a bit strange. Why can I enable a queuing discipline by default that's known not to work on CAN devices. You might think the kernel (should) know that CAN devices best work with pfifo_fast (or not NET_SCHED at all). - Addressing your question directly: Mixed environment. fq_codel works great on Ethernet, but terrible on CAN. Of course I an use "tc" to configure the way I want to. But from my point of view it would be nice, if the kernel uses sane default...and handles the net.core.default_qdisc default in a sane way. Marc --=20 Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de | --holF2ua9ouqkCCnran9GCZoatAI6XTVfX-- --B08wmT3aOsbSbdXvTtADrwYlMLJ2ufiSo Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEmvEkXzgOfc881GuFWsYho5HknSAFAlybzd0ACgkQWsYho5Hk nSDXvwgAi+AoBehM1mWjzA8ehC4n01JWxl0eL0gycRenUTMsK6CLHcbuVLVewGxl KuxTUEFTUjKj9KYcgAaFn71JBr5VKwdHfePhjAEL5O46zxfOf1lSv4WjDBSj1WOj IyboBZuqoahvBtwTkEBEA5eZ6fLNsTth1jr+6ZEzaPkEWeLo9N6Gr/AKaYRfUfTa HoWizlAj56Tn0ak6eHEZc+S1ZM3xJakHf/zXzI1TGojlb+tsWGmDWkitPXJ12eSh dscI4Tcyo6KGSqdIfp5BrQ5CLsRVTMg8nIz4k8jMPQCXvqKLKTXZ+kUEAfW+UFBb cPj1qzgR70Q1NOwxJnbDj2hNjvXeOw== =szgw -----END PGP SIGNATURE----- --B08wmT3aOsbSbdXvTtADrwYlMLJ2ufiSo--