From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by dpdk.space (Postfix) with ESMTP id CD22BA00E6 for ; Thu, 21 Mar 2019 20:37:39 +0100 (CET) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 8F13D1B676; Thu, 21 Mar 2019 20:37:38 +0100 (CET) Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by dpdk.org (Postfix) with ESMTP id D3F261B658 for ; Thu, 21 Mar 2019 20:37:36 +0100 (CET) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Mar 2019 12:37:35 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,253,1549958400"; d="scan'208";a="309240439" Received: from fyigit-mobl.ger.corp.intel.com (HELO [10.237.221.46]) ([10.237.221.46]) by orsmga005.jf.intel.com with ESMTP; 21 Mar 2019 12:37:32 -0700 To: Tom Barbette Cc: Andrew Rybchenko , Thomas Monjalon , dev@dpdk.org, Shahaf Shuler , "bruce.richardson@intel.com" , "john.mcnamara@intel.com" , Yongseok Koh , Alejandro Lucero , Konstantin Ananyev References: <3811860b2a7b4bd2be2e9d3fd7de23c0@exdb05.ug.kth.se> <1546947039501.61612@kth.se> <688f9052-b861-0446-5eda-44952bb39f1e@linux.intel.com> <3407362.WhE9PAp8Q4@xps> From: Ferruh Yigit Openpgp: preference=signencrypt Autocrypt: addr=ferruh.yigit@intel.com; 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WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [dpdk-dev] [PATCH 1/3] rte_ethdev: Add API function to read dev clock 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" Message-ID: <20190321193731.5BJ2-LuV82CqAaxdh_aQTi9zW5COMP56SRTJzH6IaqM@z> On 3/20/2019 3:57 PM, Andrew Rybchenko wrote: > On 3/20/19 5:48 PM, Thomas Monjalon wrote: >> 19/03/2019 14:32, Yigit, Ferruh: >>> On 1/8/2019 11:30 AM, Tom Barbette wrote: >>>> Ferruh Yigit wrote: >>>>> Why timestamp offloading become useless? When timestamp offloading enabled, >>>>> device fills 'mbuf.timestamp' and you can use it. >>>> But the frequency is unknown, and the reference time neither. So it can be used only to know that "some time passed" between packets. >>>> >>>>> For your case this timestamp for mlx is device clock and you are adding this API >>>>> to be able to convert device clock to real time, this is not something enables >>>>> the timestamp offload. >>>> I get your point, but a keyboard is highly required to use a computer. It's pretty much useless without it. Without this API, the timestamp offload makes no sense. It's a random number generator at best... >>>> >>>>> Technically driver can set the 'mbuf.timestamp' with the real clock right, if it >>>>> is required? Or this can be defined by a devarg? >>>> I don't think so. Device have no sense of system time. And doing it in the driver is tricky because it depends on the user needs. Catch-up with NTP updates would need a timer and various parameters... Hence we prefer to give a simple working code, and users may do this if they want. >>>> >>>> >>>> For the other comments it's not my call... I would just underline that timestamp offload is not usable in the current state, and there is a lot of use case for monitoring latency-sensitive applications. >>> Hi Thomas, Andrew, >>> >>> CAn you please comment on patch, it adds a new 'rte_eth_read_clock()' API to >>> read device clock to read timestamp value, later to use this value to map to the >>> actual time. >>> So that can convert timestamp information from each packet into real time. >> The approach is smart in my opinion. >> It is requesting the time generator (at its source) and allowing >> the app to do any kind of time handling strategy. >> >>> My question was if this is common requirement or specific to single device? >> It will work with any device providing some timestamps. >> There is nothing specific here in my opinion. >> >>> And if can be handles in driver level. >> Yes, it may be handled differently. >> But this approach looks to be the most flexible and reliable. >> >> Acked-by: Thomas Monjalon > > Taking into account that timestamp in mbuf is not normalized (neither > unit nor reference) and the API helps to normalize units, it makes sense. > I recall discussion about timestamp if should be normalized or > not, the decision was to keep it undefined. > > Acked-by: Andrew Rybchenko > Hi Tom, mlx patch doesn't apply cleanly, can you please send a new version on top of latest head? Thanks, ferruh