From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f41.google.com (mail-wg0-f41.google.com [74.125.82.41]) by dpdk.org (Postfix) with ESMTP id 6DCC68032 for ; Thu, 4 Dec 2014 14:51:02 +0100 (CET) Received: by mail-wg0-f41.google.com with SMTP id y19so22761840wgg.0 for ; Thu, 04 Dec 2014 05:51:02 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:message-id:date:from:user-agent:mime-version:to :cc:subject:references:in-reply-to:content-type :content-transfer-encoding; bh=RSnK4oUtRJScpkH4Rzi9ydZi7yPkKkUigr8L+Jx5scc=; b=LlkX5eU9ue/XfjaGTNaxvFQZYFeyWSdREpPI6aOFGgK9xJZIxrVjkfrIbLiOL5Dl7Z W7waPWhp/dHxzUbRf3eVklSmytxE11tf/xON6Kp31eScMxZ9jZLmiLwV4ZdjCxxBIXqB kojfFHNKQfBuvhpjW5iTNNqLKrTaZgRWiwnISKxLN3YOUCV4it9Oesu+D2i95SRZGG0R 5PbSVWI9QYt+dwG0NBP9VCqQasz/mKP9wBUOyjQnnMY01EKYcEfdgjmhSWKnuk3OIRji mZnhoCK5754vk2XEeHPEh4yQ2Y2Uzv0rTbN9nDOF7T66W96/ZvC0uiozzFXVAVcYuWJ5 Ov1A== X-Gm-Message-State: ALoCoQlF19/UDnpSNossDUpaoau/kYu/LfmoTpG6pcguAWx8oVgofRTPtbxqZqsKdaS8j3HeDuAq X-Received: by 10.180.108.167 with SMTP id hl7mr21375859wib.68.1417701062276; Thu, 04 Dec 2014 05:51:02 -0800 (PST) Received: from [10.16.0.195] (guy78-3-82-239-227-177.fbx.proxad.net. [82.239.227.177]) by mx.google.com with ESMTPSA id f7sm41436894wiz.13.2014.12.04.05.51.01 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 04 Dec 2014 05:51:01 -0800 (PST) Message-ID: <548066C5.4020008@6wind.com> Date: Thu, 04 Dec 2014 14:51:01 +0100 From: Olivier MATZ User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Icedove/24.5.0 MIME-Version: 1.0 To: "Ananyev, Konstantin" , Thomas Monjalon References: <1417532767-1309-1-git-send-email-jijiang.liu@intel.com> <1ED644BD7E0A5F4091CF203DAFB8E4CC01D9FF2B@SHSMSX101.ccr.corp.intel.com> <2601191342CEEE43887BDE71AB977258213BC6F2@IRSMSX105.ger.corp.intel.com> <2324692.x6b6svf072@xps13> <2601191342CEEE43887BDE71AB977258213BC7F9@IRSMSX105.ger.corp.intel.com> In-Reply-To: <2601191342CEEE43887BDE71AB977258213BC7F9@IRSMSX105.ger.corp.intel.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "dev@dpdk.org" Subject: Re: [dpdk-dev] [PATCH v5 2/3] mbuf:add three TX ol_flags and repalce PKT_TX_VXLAN_CKSUM 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: Thu, 04 Dec 2014 13:51:02 -0000 Hi, On 12/04/2014 12:03 PM, Ananyev, Konstantin wrote: >>>>> 1/ (Jijiang's patch) >>>>> PKT_TX_IP_CKSUM /* packet is IPv4, and we want hw cksum */ >>>>> PKT_TX_IPV6 /* packet is IPv6 */ >>>>> PKT_TX_IPV4 /* packet is IPv4, and we don't want hw cksum */ >>>>> >>>>> with PKT_TX_IP_CKSUM and PKT_TX_IPV4 exclusive >>>>> >>>>> and >>>>> >>>>> 2/ >>>>> PKT_TX_IP_CKSUM /* we want hw IP cksum */ >>>>> PKT_TX_IPV6 /* packet is IPv6 */ >>>>> PKT_TX_IPV4 /* packet is IPv4 */ >>>>> >>>>> with PKT_TX_IP_CKSUM implies PKT_TX_IPV4 >>>>> >>>>> >>>>> Solution 2/ looks better from a user point of view. Anyone else has an opinion? >>>> >>>> Let's think about these IPv4/6 flags in terms of checksum and IP version/type, >>>> >>>> 1. For IPv6 >>>> IP checksum is meaningful only for IPv4, so we define 'PKT_TX_IPV6 /* packet is IPv6 */' to tell driver/HW that this is IPV6 >> packet, >>>> here we don't talk about the checksum for IPv6 as it is meaningless. Right? >>>> >>>> PKT_TX_IPV6 /* packet is IPv6 */ ------ IP type: v6; HW checksum: meaningless >>>> >>>> 2. For IPv4, >>>> My patch: >>>> >>>> PKT_TX_IP_CKSUM /* packet is IPv4, and we want hw cksum */--------------------------IP type: v4; HW checksum: Yes >>>> PKT_TX_IPV4 /* packet is IPv4, and we don't want hw cksum */ ----------------------- IP type: v4; HW checksum: No >>>> >>>> You want: >>>> PKT_TX_IP_CKSUM /* we want hw IP cksum */-------------------------- IP type: v4; HW checksum: Yes >>>> PKT_TX_IPV4 /* packet is IPv4*/ ------------------------ IP type: v4; HW checksum: yes or no? >>>> driver/HW don't know, just know this is packet with IPv4 header. >>>> HW checksum: meaningless?? >>> >>> Yep, that's why I also don't like that suggestion: PKT_TX_IPV4 itself doesn't contain all information. >>> PMD will have to check PKT_TX_IP_CKSUM anyway. >> >> I prefer solution 2 because a flag should bring only 1 information. > > Why is that? For example in mbuf we already have a flag that brings 2 things: > PKT_TX_IP_CKSUM /* packet is IPv4, and we want hw cksum */ For the user, it's clearer to have one information in a flag. If you just look at the name of the flag, the natural meaning is 2/, else we would need to rename them in: PKT_TX_IPV4_CKSUM PKT_TX_IPV4_NO_CKSUM > If it would be possible to compress 10 meanings into 1 bit, I would happily do that. > Unfortunately, it is rarely possible :) > >> It's simply saner and could fit to more situations in the future. > > Could you give an example of such situation? > I personally couldn't come up with the case where #2 would have any real advantage. in solution 2/, PKT_TX_IP_CKSUM implies PKT_TX_IPV4 so checking PKT_TX_IP_CKSUM is still enough in drivers. In the driver, it is also simpler. With solution 1/: /* check if we need ipcsum */ if (flags & PKT_TX_IP_CKSUM) /* check if packet is ipv4, may be needed to set a hw field */ if (flags & (PKT_TX_IP_CKSUM|PKT_TX_IPV4)) With solution 2/ /* check if we need ipcsum */ if (flags & PKT_TX_IP_CKSUM) /* check if packet is ipv4, may be needed to set a hw field */ if (flags & PKT_TX_IPV4) I agree it can looks like a detail, but I really think it's important to have the most logical and straightforward api for mbuf, as it's the core of DPDK. Regards, Olivier