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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 472EBC433DF for ; Tue, 19 May 2020 17:49:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1FD1420708 for ; Tue, 19 May 2020 17:49:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729423AbgESRtU (ORCPT ); Tue, 19 May 2020 13:49:20 -0400 Received: from mga01.intel.com ([192.55.52.88]:44933 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726059AbgESRtT (ORCPT ); Tue, 19 May 2020 13:49:19 -0400 IronPort-SDR: mHE+khGHz4PSIQ7vDLaSQ5z0KT5oaTPzKfMifC1FMP4x8sEGJCY7DWObytRrKIkDff+XfU8KrQ wjNEMa6KkKmQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 May 2020 10:49:05 -0700 IronPort-SDR: MYW1UuulTzlhBMvTgl1szX1qyh5J9CHwu/jTPJeIQLCFA3iFS92wri7b23GBe48OFv0XFwY6xG nUT8iY49OnXQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,410,1583222400"; d="scan'208";a="466218150" Received: from stputhen-mobl1.amr.corp.intel.com (HELO ellie) ([10.209.5.127]) by fmsmga006.fm.intel.com with ESMTP; 19 May 2020 10:49:05 -0700 From: Vinicius Costa Gomes To: Murali Karicheri , Jakub Kicinski Cc: David Miller , olteanv@gmail.com, intel-wired-lan@lists.osuosl.org, jeffrey.t.kirsher@intel.com, netdev@vger.kernel.org, vladimir.oltean@nxp.com, po.liu@nxp.com, Jose.Abreu@synopsys.com Subject: Re: [next-queue RFC 0/4] ethtool: Add support for frame preemption In-Reply-To: <29959a1a-fc45-6870-fa11-311866b51aa0@ti.com> 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> <29959a1a-fc45-6870-fa11-311866b51aa0@ti.com> Date: Tue, 19 May 2020 10:49:04 -0700 Message-ID: <87ftbvolwv.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Murali Karicheri writes: >> 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. The way I see, the issue that Jakub is pointing here is more of usability/understandability. By having the express/preemptible queue mapping in TC, we have the configuration near where the "priority to queue" mapping happens. That improves the ease of configuration, makes it easier to spot mistakes, that kind of thing, all of which are a big plus. Right now, I am seeing this hybrid approach as a good compromise, we have the queue settings near to where the kinds of traffic are mapped to queues, and we have the rest of the hardware configuration in ethtool. Cheers, -- Vinicius