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 4EFDFA05D3 for ; Wed, 24 Apr 2019 13:08:51 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 41E534CA6; Wed, 24 Apr 2019 13:08:50 +0200 (CEST) Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by dpdk.org (Postfix) with ESMTP id D27061DBC for ; Wed, 24 Apr 2019 13:08:48 +0200 (CEST) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 24 Apr 2019 04:08:47 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,389,1549958400"; d="scan'208";a="143202307" Received: from aburakov-mobl1.ger.corp.intel.com (HELO [10.237.220.108]) ([10.237.220.108]) by fmsmga008.fm.intel.com with ESMTP; 24 Apr 2019 04:08:46 -0700 To: Ray Kinsella , Bruce Richardson , Honnappa Nagarahalli Cc: "dev@dpdk.org" , Stephen Hemminger , "Ananyev, Konstantin" , "thomas@monjalon.net" , nd References: <20190417083637.GB1890@bricha3-MOBL.ger.corp.intel.com> <20190418102811.GB1817@bricha3-MOBL.ger.corp.intel.com> <2ec4da50-d874-865a-6bcc-916ac676be39@ashroe.eu> From: "Burakov, Anatoly" Message-ID: <43980ebb-ef8a-6e6d-c152-cf6160ace892@intel.com> Date: Wed, 24 Apr 2019 12:08:45 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <2ec4da50-d874-865a-6bcc-916ac676be39@ashroe.eu> Content-Type: text/plain; charset="UTF-8"; format="flowed" Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [dpdk-dev] ABI and inline functions 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: <20190424110845.SnnzyF87jAV7T43uak7sF3nMJ-9iCbItoe16GFFVbJI@z> On 23-Apr-19 3:12 PM, Ray Kinsella wrote: > > > On 18/04/2019 11:28, Bruce Richardson wrote: >> On Thu, Apr 18, 2019 at 04:34:53AM +0000, Honnappa Nagarahalli wrote: >>>> >>>> On Wed, Apr 17, 2019 at 05:12:43AM +0000, Honnappa Nagarahalli wrote: >>>>> Hello, >>>>> There was a conversation [1] in the context of RCU library. I thought >>>>> it needs participation from broader audience. Summary for the context >>>>> (please look at [1] for full details) >>>>> >>>> >>>> Thanks for kicking off this discussion >>>> >>>>> 1) How do we provide ABI compatibility when the code base contains >>>> inline functions? Unless we freeze development in these inline functions and >>>> corresponding structures, it might not be possible to claim ABI compatibility. >>>> Application has to be recompiled. >>>> >>>> I agree that in some cases the application "might" need to be recompiled, >>>> but on the other hand I also think that there are many cases where ABI >>>> function versioning can still be used to mitigate things. For example, if we >>>> think of a couple of various scenarios: >>>> >>>> 1. If everything is inline and variables are allocated by app, e.g. >>>> spinlock on stack, then there is no issue as everything is application >>>> contained. >>> If there is a bug fix which requires the structure to change, the application would need to recompile. I guess you are talking about a scenario when nothing changed in the inline function/variables. >>> >> >> If the application wants the bugfix, then yes. However, if the app is >> unaffected by the bug, then it should have the option of updating DPDK >> without a recompile. > > I would also imagine that should be an extremely rare case, that a > bugfix would require a structure change ... perhaps for an alignment issues? Multiprocess threading issues is one case i've had to do that more than once. > > The reality is that most other system libraries provide strong > guarantees ... to date we have provided very little. > To our credit, the libraries you're likely referring to aren't trying to reimplement the Linux kernel :) I don't think we do these API/ABI breaks just because we like doing them - DPDK is complex, and getting everything right the first time *and* allowing for future evolution is not a trivial undertaking. To me, part of the problem is that DPDK is an "everything and the kitchen sink" kind of library where there is a bunch of drivers, a whole quasi-OS layer of dealing with hardware in a cross-platform manner, a separate memory management system, a bunch of libraries such as hash/lpm tables, plus there's QOS, IP Pipeline, flow stuff, etc. - normally, "a library" would concentrate on doing one thing well. DPDK, on the other hand, tries to do *everything* well. The sheer breadth of DPDK's scope is, i think, contributing to the breakages. If you keep 99% of your libraries stable between version, but there's a small ABI tweak in an LPM library, the entire DPDK stability gets invalidated. Perhaps limiting DPDK's scope would help with this as well. > >> >> Regards, >> /Bruce >> > -- Thanks, Anatoly