From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Barbette Subject: Re: [PATCH 1/3] rte_ethdev: Add API function to read dev clock Date: Tue, 8 Jan 2019 11:30:39 +0000 Message-ID: <1546947039501.61612@kth.se> References: <3811860b2a7b4bd2be2e9d3fd7de23c0@exdb05.ug.kth.se> , Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Cc: "bruce.richardson@intel.com" , "john.mcnamara@intel.com" , Thomas Monjalon , Andrew Rybchenko , Yongseok Koh , Alejandro Lucero , Konstantin Ananyev To: Ferruh Yigit , Shahaf Shuler , "dev@dpdk.org" Return-path: Received: from smtp-4.sys.kth.se (smtp-4.sys.kth.se [130.237.48.193]) by dpdk.org (Postfix) with ESMTP id 8CF291B537 for ; Tue, 8 Jan 2019 12:30:46 +0100 (CET) In-Reply-To: Content-Language: fr-FR List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Ferruh Yigit wrote:=0A= > Why timestamp offloading become useless? When timestamp offloading enable= d,=0A= > device fills 'mbuf.timestamp' and you can use it.=0A= But the frequency is unknown, and the reference time neither. So it can be = used only to know that "some time passed" between packets.=0A= =0A= > For your case this timestamp for mlx is device clock and you are adding t= his API=0A= > to be able to convert device clock to real time, this is not something en= ables=0A= > the timestamp offload.=0A= 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 ma= kes no sense. It's a random number generator at best...=0A= =0A= > Technically driver can set the 'mbuf.timestamp' with the real clock right= , if it=0A= > is required? Or this can be defined by a devarg?=0A= 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 up= dates would need a timer and various parameters... Hence we prefer to give = a simple working code, and users may do this if they want.=0A= =0A= =0A= For the other comments it's not my call... I would just underline that time= stamp offload is not usable in the current state, and there is a lot of use= case for monitoring latency-sensitive applications.=0A= =0A= Tom=