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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 C61ABC433E0 for ; Tue, 19 May 2020 16:34:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 90C0D207D3 for ; Tue, 19 May 2020 16:34:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ti.com header.i=@ti.com header.b="oS7HJU0w" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729260AbgESQes (ORCPT ); Tue, 19 May 2020 12:34:48 -0400 Received: from lelv0142.ext.ti.com ([198.47.23.249]:58766 "EHLO lelv0142.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728775AbgESQes (ORCPT ); Tue, 19 May 2020 12:34:48 -0400 Received: from fllv0034.itg.ti.com ([10.64.40.246]) by lelv0142.ext.ti.com (8.15.2/8.15.2) with ESMTP id 04JGYVRH038062; Tue, 19 May 2020 11:34:31 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1589906071; bh=/vOqGrqZKFEISSBDGaUAsu38PgJE2S0bQf4x+D43qGc=; h=Subject:To:CC:References:From:Date:In-Reply-To; b=oS7HJU0w57Y720J+uVw+hhQwcf/pxqv8iCO/mP9lSKjM36MRjDOetWPjdDb3g/hdu 06kGAQurGlp1gRWxO57EWDghp+AY0YFHPH/YpXAdOSBcXElnrnmAYTGPuUaKMwbWRO 0MsSt57DwYXSIFSRibut8/AH29BH2AeD83ikwlfk= Received: from DLEE104.ent.ti.com (dlee104.ent.ti.com [157.170.170.34]) by fllv0034.itg.ti.com (8.15.2/8.15.2) with ESMTPS id 04JGYVK3122996 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 19 May 2020 11:34:31 -0500 Received: from DLEE103.ent.ti.com (157.170.170.33) by DLEE104.ent.ti.com (157.170.170.34) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1979.3; Tue, 19 May 2020 11:34:31 -0500 Received: from lelv0327.itg.ti.com (10.180.67.183) by DLEE103.ent.ti.com (157.170.170.33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1979.3 via Frontend Transport; Tue, 19 May 2020 11:34:31 -0500 Received: from [10.250.74.234] (ileax41-snat.itg.ti.com [10.172.224.153]) by lelv0327.itg.ti.com (8.15.2/8.15.2) with ESMTP id 04JGYUrS115717; Tue, 19 May 2020 11:34:30 -0500 Subject: Re: [next-queue RFC 0/4] ethtool: Add support for frame preemption To: Vinicius Costa Gomes , Jakub Kicinski CC: David Miller , , , , , , , References: <20200516012948.3173993-1-vinicius.gomes@intel.com> <20200516.133739.285740119627243211.davem@davemloft.net> <20200516.151932.575795129235955389.davem@davemloft.net> <87wo59oyhr.fsf@intel.com> <20200518135613.379f6a63@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <87h7wcq4nx.fsf@intel.com> From: Murali Karicheri Message-ID: <29959a1a-fc45-6870-fa11-311866b51aa0@ti.com> Date: Tue, 19 May 2020 12:34:30 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <87h7wcq4nx.fsf@intel.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 5/18/20 6:06 PM, Vinicius Costa Gomes wrote: > Hi, > > Jakub Kicinski writes: >> >> Please take a look at the example from the cover letter: >> >> $ ethtool $ sudo ./ethtool --show-frame-preemption >> enp3s0 Frame preemption settings for enp3s0: >> support: supported >> active: active >> supported queues: 0xf >> supported queues: 0xe >> minimum fragment size: 68 >> >> Reading this I have no idea what 0xe is. I have to go and query TC API >> to see what priorities and queues that will be. Which IMHO is a strong >> argument that this information belongs there in the first place. > > That was the (only?) strong argument in favor of having frame preemption > in the TC side when this was last discussed. > > We can have a hybrid solution, we can move the express/preemptible per > queue map to mqprio/taprio/whatever. And have the more specific > configuration knobs, minimum fragment size, etc, in ethtool. Isn't this a pure h/w feature? FPE is implemented at L2 and involves fragments that are only seen by h/w and never at Linux network core unlike IP fragments and is transparent to network stack. However it enhances priority handling at h/w to the next level by pre-empting existing lower priority traffic to give way to express queue traffic and improve latency. So everything happens in h/w. So ethtool makes perfect sense here as it is a queue configuration. I agree with Vinicius and Vladmir to support this in ethtool instead of TC. Murali > > What do you think? > > > Cheers, > -- Murali Karicheri Texas Instruments