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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 822B8CA9EA0 for ; Tue, 22 Oct 2019 18:33:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D91AA2184C for ; Tue, 22 Oct 2019 18:33:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=hartkopp.net header.i=@hartkopp.net header.b="alWThASu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732622AbfJVSdQ (ORCPT ); Tue, 22 Oct 2019 14:33:16 -0400 Received: from mo4-p01-ob.smtp.rzone.de ([81.169.146.166]:11772 "EHLO mo4-p01-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727851AbfJVSdQ (ORCPT ); Tue, 22 Oct 2019 14:33:16 -0400 X-Greylist: delayed 716 seconds by postgrey-1.27 at vger.kernel.org; Tue, 22 Oct 2019 14:33:15 EDT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; t=1571769195; s=strato-dkim-0002; d=hartkopp.net; h=In-Reply-To:Date:Message-ID:From:References:Cc:To:Subject: X-RZG-CLASS-ID:X-RZG-AUTH:From:Subject:Sender; bh=SUO95hzSSetluapukGk/6rTRVcsFbnMspEM+35/uuT4=; b=alWThASuhCMAIG3VYFJW3cr7HXEFou07OHqbHkWKg/TZNXnBsE14KIvZLT4dsLtC4e Xn362WNpG+Oogx0jul2w7hedZHLJfDzh3JVkctB/hehg0rKGMZTZ8N0DzoQU6Hob6oFl dhVf9fmDy+OKwG/97YHgY/G0jNEQBwmyFMa7UR2GFOPWzjz4rAebFQmqZvOraBEgsNL5 9jCNnYXUUz6FpozyTR/iv1bURM1R5/rHiIXLckWHvNlvKI2Jp/vw6OhdSt18pUEKG7Uc KPYfnNHJfZDd5qaH3RsGKE10JHLlA9B84mv6j3vhQHGUMDdKDvVTFSw24rMWx8cFB+iL svuA== X-RZG-AUTH: ":P2MHfkW8eP4Mre39l357AZT/I7AY/7nT2yrDxb8mjG14FZxedJy6qgO1o3PMaViOoLMJVsh5kk59" X-RZG-CLASS-ID: mo00 Received: from [192.168.40.177] by smtp.strato.de (RZmta 44.28.1 DYNA|AUTH) with ESMTPSA id 20981av9MILER1D (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (curve secp521r1 with 521 ECDH bits, eq. 15360 bits RSA)) (Client did not present a certificate); Tue, 22 Oct 2019 20:21:14 +0200 (CEST) Subject: Re: [PATCH v2] net: sch_generic: Use pfifo_fast as fallback scheduler for CAN hardware To: Eric Dumazet , Stephen Hemminger , Marc Kleine-Budde Cc: Vincent Prince , jiri@resnulli.us, jhs@mojatatu.com, netdev@vger.kernel.org, dave.taht@gmail.com, linux-can@vger.kernel.org, kernel@pengutronix.de, xiyou.wangcong@gmail.com, davem@davemloft.net References: <20190327165632.10711-1-mkl@pengutronix.de> <1571750597-14030-1-git-send-email-vincent.prince.fr@gmail.com> <84b8ce24-fe5d-ead0-0d1d-03ea24b36f71@pengutronix.de> <20191022094254.489fd6a4@hermes.lan> From: Oliver Hartkopp Message-ID: <894a5426-b649-fd51-9aad-e66543374b9e@hartkopp.net> Date: Tue, 22 Oct 2019 20:21:08 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 22/10/2019 19.28, Eric Dumazet wrote > On 10/22/19 9:42 AM, Stephen Hemminger wrote: > >> Why not fix fq_codel to return the same errors as other qdisc? >> > > I believe the same problem would happen with any qdisc not doing tail drops. > > Do we really want to enforce all qdisc to have a common drop strategy ? CAN has no drop strategy. There is no transport protocol at this point which can handle and compensate drops. CAN is just about PDUs that are sent on a special medium. And that's what this patch was about. > > For example, FQ could implement a strategy dropping the oldest packet in the queue, > which is absolutely not related to the enqueue order. > We have a CAN ID related ematch rule in em_canid.c to be able to configure HTBs, delays or drops. But this is for testing and special use-cases. Silently dropped frames are not expected. Regards, Oliver