From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Monjalon Subject: Re: [PATCH v6 1/9] librte_mbuf:the rte_mbuf structure changes Date: Wed, 12 Nov 2014 14:26:17 +0100 Message-ID: <2835075.ZIuhO63ZWU@xps13> References: <1413881168-20239-1-git-send-email-jijiang.liu@intel.com> <1710340.mrZid3JfsP@xps13> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: dev-VfR2kkLFssw@public.gmane.org To: "Liu, Jijiang" Return-path: In-Reply-To: List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org Sender: "dev" Hi guys, We still have some problems with the mbuf changes introduced for VXLAN. I want to raise the packet type issue here. 2014-10-23 02:23, Zhang, Helin: > From: dev [mailto:dev-bounces-VfR2kkLFssw@public.gmane.org] On Behalf Of Thomas Monjalon > > 2014-10-21 14:14, Liu, Jijiang: > > > From: Thomas Monjalon [mailto:thomas.monjalon-pdR9zngts4EAvxtiuMwx3w@public.gmane.org] > > > > 2014-10-21 16:46, Jijiang Liu: > > > > > - uint16_t reserved2; /**< Unused field. Required for padding */ > > > > > + > > > > > + /** > > > > > + * Packet type, which is used to indicate ordinary L2 packet format and > > > > > + * also tunneled packet format such as IP in IP, IP in GRE, MAC in GRE > > > > > + * and MAC in UDP. > > > > > + */ > > > > > + uint16_t packet_type; > > > > > > > > Why not name it "l2_type"? > > 'packet_type' is for storing the hardware identified packet type upon different layers > of protocols (l2, l3, l4, ...). > It is quite useful for user application or middle layer software stacks, it can know > what the packet type is without checking the packet too much by software. > Actually ixgbe already has packet types (less than 10), which is transcoded into 'ol_flags'. > For i40e, the packet type can represent about 256 types of packet, 'ol_flags' does not > have enough bits for it anymore. So put the i40e packet types into mbuf would be better. > Also this field can be used for NON-Intel NICs, I think there must be the similar concepts > of other NICs. And 16 bits 'packet_type' has severl reserved bits for future and NON-Intel NICs. Thanks Helin, that's the best description of packet_type I've seen so far. It's not so clear in the commit log: http://dpdk.org/browse/dpdk/commit/?id=73b7d59cf4f6faf > > > In datasheet, this term is called packet type(s). > > > > That's exactly the point I want you really understand! > > This is a field in generic mbuf structure, so your datasheet has no value here. > > > > > Personally , I think packet type is more clear what meaning of this field is . > > > > You cannot add an API field without knowing what will be its generic meaning. > > Please think about it and describe its scope. I integrated this patch with the VXLAN patchset in the hope that you'll improve the situation afterwards. This is the answer you recently gave to Olivier: http://dpdk.org/ml/archives/dev/2014-November/007599.html " Regarding adding a packet_type in mbuf, we ever had a lot of discussions as follows: http://dpdk.org/ml/archives/dev/2014-October/007027.html http://dpdk.org/ml/archives/dev/2014-September/005240.html http://dpdk.org/ml/archives/dev/2014-September/005241.html http://dpdk.org/ml/archives/dev/2014-September/005274.html " To sum up the situation: - We don't know what are the possible values of packet_type - It's only filled by i40e, while other drivers use ol_flags - There is no special value "unknown" which should be set by drivers not supporting this feature. - Its only usage is to print a decimal value in app/test-pmd/rxonly.c It's now clear that nobody cares about this part of the API. So I'm going to remove packet_type from mbuf. I don't want to keep something that we don't know how to use, that is not consistent across drivers, and that overlap another API part (ol_flags). -- Thomas