From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id 94F45A3168 for ; Wed, 16 Oct 2019 19:47:27 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id A8BCF1E955; Wed, 16 Oct 2019 19:47:26 +0200 (CEST) Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by dpdk.org (Postfix) with ESMTP id 295851E8B0 for ; Wed, 16 Oct 2019 19:47:24 +0200 (CEST) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Oct 2019 10:47:23 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,304,1566889200"; d="scan'208";a="347495700" Received: from fyigit-mobl.ger.corp.intel.com (HELO [10.237.221.10]) ([10.237.221.10]) by orsmga004.jf.intel.com with ESMTP; 16 Oct 2019 10:47:22 -0700 To: Vamsi Krishna Attunuru , "dev@dpdk.org" Cc: "arybchenko@solarflare.com" , Jerin Jacob Kollanukkaran , "thomas@monjalon.net" References: <20190914055247.3841-2-vattunuru@marvell.com> <20191015095207.13249-1-vattunuru@marvell.com> <20191015095207.13249-2-vattunuru@marvell.com> <36841a25-b5c8-ad4c-9fee-16ad8e0270ff@intel.com> From: Ferruh Yigit Openpgp: preference=signencrypt Autocrypt: addr=ferruh.yigit@intel.com; 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charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Subject: Re: [dpdk-dev] [PATCH v2 1/3] lib/ethdev: add ethdev op to get hash index X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 10/15/2019 6:28 PM, Vamsi Krishna Attunuru wrote: > > >> -----Original Message----- >> From: dev On Behalf Of Ferruh Yigit >> Sent: Tuesday, October 15, 2019 10:17 PM >> To: Vamsi Krishna Attunuru ; dev@dpdk.org >> Cc: arybchenko@solarflare.com; Jerin Jacob Kollanukkaran >> ; thomas@monjalon.net >> Subject: Re: [dpdk-dev] [PATCH v2 1/3] lib/ethdev: add ethdev op to get hash >> index >> >> On 10/15/2019 10:52 AM, vattunuru@marvell.com wrote: >>> From: Vamsi Attunuru >>> >>> Some networking devices may use custom algos for computing hash >>> indices and spread the packets accordingly. >>> >>> Patch adds an eth_dev op to get the hash index correspond to the given >>> hash value received in the initial packet on the given port. >>> >>> Some of the applications compute hash index from the hash value >>> received in the initial packet and than configure the rxq to lcore >>> mapping to make sure the mapped lcore/rxq would receive the upcoming >>> traffic that has similar hash. >>> Such applications may use these API to get the hash index used by the >>> PMD for spreading those traffic. >> >> Hi Vamsi, >> >> Can you please describe this usecase? >> If the application is receiving the packet, it already knows which queue it is >> coming from, what is the benefit of the getting hash index? > > Hi Ferruh, > > I think the commit msg is incomplete and did not explain the use case clearly, my apologies. > Actual usecase is when application precalculates the hash value using some hashlib for a specific type of packet headers with the same hash key that's configured in the HW, application would compute hash_index as hash % reta_size and predict the packets on the computed queue index. But these hash_index computation might be different from PMD/HW computed index(based it's algo design). To fix those disparity, these API been introduced which can be used during configuration time to have > required lcore-rq mapping. Does application tries to predict in which queue a specific flow will land? And configure RETA table OR do the lcore-queue mapping accordingly? Not sure if other PMDs need this too but API seems trivial and it doesn't affect existing code, so no objection from my end for the API. Can you please check the unit test comments? > > >> >> The concern is adding a new API which is specific to a use case and HW and >> won't be used in long term. That will only create technical dept for us. >> >>> >>> Signed-off-by: Vamsi Attunuru >> >> <...> >