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[204.195.33.123]) by smtp.gmail.com with ESMTPSA id u6sm6335035pgr.3.2021.10.01.08.07.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 01 Oct 2021 08:08:00 -0700 (PDT) Date: Fri, 1 Oct 2021 08:07:55 -0700 From: Stephen Hemminger <stephen@networkplumber.org> To: Ferruh Yigit <ferruh.yigit@intel.com> Cc: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>, Thomas Monjalon <thomas@monjalon.net>, Jerin Jacob <jerinj@marvell.com>, Xiaoyun Li <xiaoyun.li@intel.com>, Chas Williams <chas3@att.com>, "Min Hu (Connor)" <humin29@huawei.com>, Hemant Agrawal <hemant.agrawal@nxp.com>, Sachin Saxena <sachin.saxena@oss.nxp.com>, Qi Zhang <qi.z.zhang@intel.com>, Xiao Wang <xiao.w.wang@intel.com>, Matan Azrad <matan@nvidia.com>, Viacheslav Ovsiienko <viacheslavo@nvidia.com>, Harman Kalra <hkalra@marvell.com>, Maciej Czekaj <mczekaj@marvell.com>, Ray Kinsella <mdr@ashroe.eu>, Bernard Iremonger <bernard.iremonger@intel.com>, Konstantin Ananyev <konstantin.ananyev@intel.com>, Kiran Kumar K <kirankumark@marvell.com>, Nithin Dabilpuram <ndabilpuram@marvell.com>, David Hunt <david.hunt@intel.com>, John McNamara <john.mcnamara@intel.com>, Bruce Richardson <bruce.richardson@intel.com>, Igor Russkikh <irusskikh@marvell.com>, Steven Webster <steven.webster@windriver.com>, Matt Peters <matt.peters@windriver.com>, Somalapuram Amaranath <asomalap@amd.com>, Rasesh Mody <rmody@marvell.com>, Shahed Shaikh <shshaikh@marvell.com>, Ajit Khaparde <ajit.khaparde@broadcom.com>, Somnath Kotur <somnath.kotur@broadcom.com>, Sunil Kumar Kori <skori@marvell.com>, Satha Rao <skoteshwar@marvell.com>, Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>, Haiyue Wang <haiyue.wang@intel.com>, Marcin Wojtas <mw@semihalf.com>, Michal Krawczyk <mk@semihalf.com>, Shai Brandes <shaibran@amazon.com>, Evgeny Schemeilin <evgenys@amazon.com>, Igor Chauskin <igorch@amazon.com>, Gagandeep Singh <g.singh@nxp.com>, John Daley <johndale@cisco.com>, Hyong Youb Kim <hyonkim@cisco.com>, Ziyang Xuan <xuanziyang2@huawei.com>, Xiaoyun Wang <cloud.wangxiaoyun@huawei.com>, Guoyang Zhou <zhouguoyang@huawei.com>, Yisen Zhuang <yisen.zhuang@huawei.com>, Lijun Ou <oulijun@huawei.com>, Beilei Xing <beilei.xing@intel.com>, Jingjing Wu <jingjing.wu@intel.com>, Qiming Yang <qiming.yang@intel.com>, Andrew Boyer <aboyer@pensando.io>, Rosen Xu <rosen.xu@intel.com>, Shijith Thotton <sthotton@marvell.com>, Srisivasubramanian Srinivasan <srinivasan@marvell.com>, Zyta Szpak <zr@semihalf.com>, Liron Himi <lironh@marvell.com>, Heinrich Kuhn <heinrich.kuhn@corigine.com>, Devendra Singh Rawat <dsinghrawat@marvell.com>, Keith Wiles <keith.wiles@intel.com>, Jiawen Wu <jiawenwu@trustnetic.com>, Jian Wang <jianwang@trustnetic.com>, Maxime Coquelin <maxime.coquelin@redhat.com>, Chenbo Xia <chenbo.xia@intel.com>, Nicolas Chautru <nicolas.chautru@intel.com>, Harry van Haaren <harry.van.haaren@intel.com>, Cristian Dumitrescu <cristian.dumitrescu@intel.com>, Radu Nicolau <radu.nicolau@intel.com>, Akhil Goyal <gakhil@marvell.com>, Tomasz Kantecki <tomasz.kantecki@intel.com>, Declan Doherty <declan.doherty@intel.com>, Pavan Nikhilesh <pbhagavatula@marvell.com>, Kirill Rybalchenko <kirill.rybalchenko@intel.com>, Jasvinder Singh <jasvinder.singh@intel.com>, dev@dpdk.org Message-ID: <20211001080755.21647298@hermes.local> In-Reply-To: <20211001143624.3744505-1-ferruh.yigit@intel.com> References: <20210722172113.3236450-1-ferruh.yigit@intel.com> <20211001143624.3744505-1-ferruh.yigit@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [dpdk-dev] [PATCH v3 1/6] ethdev: fix max Rx packet length X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions <dev.dpdk.org> List-Unsubscribe: <https://mails.dpdk.org/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://mails.dpdk.org/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <https://mails.dpdk.org/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> Errors-To: dev-bounces@dpdk.org Sender: "dev" <dev-bounces@dpdk.org> On Fri, 1 Oct 2021 15:36:18 +0100 Ferruh Yigit <ferruh.yigit@intel.com> wrote: > Other issues causing confusion is: > * maximum transmission unit (MTU) is payload of the Ethernet frame. And > 'max_rx_pkt_len' is the size of the Ethernet frame. Difference is > Ethernet frame overhead, and this overhead may be different from > device to device based on what device supports, like VLAN and QinQ. > * 'max_rx_pkt_len' is only valid when application requested jumbo frame, > which adds additional confusion and some APIs and PMDs already > discards this documented behavior. > * For the jumbo frame enabled case, 'max_rx_pkt_len' is an mandatory > field, this adds configuration complexity for application. One other issue which DPDK inherits from Linux and BSD is that MTU (Maximum Transmission Unit) is overloaded to mean MRU (Maximum Receive Unit). On Linux, network devices are allowed to receive packets of any size they want. MTU is used as a hint about "you need to accept at least MTU size packets on receive". So MRU >= MTU. In practice, and documentation, MRU and MTU are used synonymously.