From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by dpdk.org (Postfix) with ESMTP id 04C0058E8 for ; Fri, 28 Nov 2014 12:16:17 +0100 (CET) Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga101.jf.intel.com with ESMTP; 28 Nov 2014 03:16:16 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.07,476,1413270000"; d="scan'208";a="644975343" Received: from irsmsx109.ger.corp.intel.com ([163.33.3.23]) by orsmga002.jf.intel.com with ESMTP; 28 Nov 2014 03:16:16 -0800 Received: from irsmsx105.ger.corp.intel.com ([169.254.7.144]) by IRSMSX109.ger.corp.intel.com ([169.254.13.244]) with mapi id 14.03.0195.001; Fri, 28 Nov 2014 11:16:15 +0000 From: "Ananyev, Konstantin" To: Olivier MATZ , "Liu, Jijiang" Thread-Topic: [dpdk-dev] [PATCH 1/3] mbuf:add two TX offload flags and change three fields Thread-Index: AQHQCikb8nVQX/4wQEWUH1iPbQ9du5x0gSyAgAABBFCAAC/e0IABKpkAgAAA+aA= Date: Fri, 28 Nov 2014 11:16:14 +0000 Message-ID: <2601191342CEEE43887BDE71AB977258213BB274@IRSMSX105.ger.corp.intel.com> References: <1417076319-629-1-git-send-email-jijiang.liu@intel.com> <1417076319-629-2-git-send-email-jijiang.liu@intel.com> <5476F626.2020708@6wind.com> <1ED644BD7E0A5F4091CF203DAFB8E4CC01D9EEA0@SHSMSX101.ccr.corp.intel.com> <2601191342CEEE43887BDE71AB977258213BADB8@IRSMSX105.ger.corp.intel.com> <2601191342CEEE43887BDE71AB977258213BAE90@IRSMSX105.ger.corp.intel.com> <54785264.1020208@6wind.com> In-Reply-To: <54785264.1020208@6wind.com> Accept-Language: en-IE, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [163.33.239.182] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Cc: "dev@dpdk.org" Subject: Re: [dpdk-dev] [PATCH 1/3] mbuf:add two TX offload flags and change three fields X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 28 Nov 2014 11:16:19 -0000 Hi Olver, > -----Original Message----- > From: Olivier MATZ [mailto:olivier.matz@6wind.com] > Sent: Friday, November 28, 2014 10:46 AM > To: Ananyev, Konstantin; Liu, Jijiang > Cc: dev@dpdk.org > Subject: Re: [dpdk-dev] [PATCH 1/3] mbuf:add two TX offload flags and cha= nge three fields >=20 > Hi Konstantin, >=20 > On 11/27/2014 06:01 PM, Ananyev, Konstantin wrote: > >> Yes, I think it could be done that way too. > >> Though I still prefer to keep l4tun_len - it makes things a bit cleane= r (at least to me). > >> After all we do have space for it in mbuf's tx_offload. > > > > As one more thing in favour of separate l4tun_len field: > > l2_len is 7 bit long, so in theory it might be not enough, as for FVL: > > 12:18 L4TUNLEN L4 Tunneling Length (Teredo / GRE header / VXLAN header)= defined in Words. >=20 > The l2_len field is 7 bits long because it was mapped to ixgbe hardware. Yes. > If it's not enough (although I'm not sure it's possible to have a header > larger than 128 bytes in this case), it's probably because we should > not have been doing that. I also can't imagine the L2 header being that long. >>From other side - I just don't like an idea of PMD stripping off HW capabil= ities. > Maybe these generic fields should be generic :) > If it's not enough, what about changing l2_len to 8 bits? Yes, was thinking about the same thing. Maybe instead of introducing l4tun_len, we should increase l2_len and outer= _l2_len sizes to 8bits each?=20 Though that would break the pair: l2_len : 7 l3_len :9=20 Which is quite useful, as it fits into 2B, and maps exactly to ixgbe TCD la= yout. Wonder if we change it, would be there any performance penalty for ixgbe, a= nd if yes how big. >=20 > Often in the recent discussions, I see as an argument "fortville needs > this so we need to add it in the mbuf". I agree that currently > fortville is the only hardware supported for the new features, so it > can make sense to act like this, but we have to accept to come back > to this API in the future if it makes less sense with other drivers. Yes, it is sometime hard to keep a balance. >>From one side people would like to have a clean and generic API, from othe= r side people would like to have ab ability to use all features that HW supports.= =20 >=20 > Also, application developers can be annoyed to see that the mbuf flags > and meta data are just duplicating information that is already present > in the packet. >=20 > About the l4tun_len, it's another field the application has to fill, > but it's maybe cleaner. I just wanted to clarify why I'm discussing > these points. >=20 > Regards, > Olivier