From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f53.google.com (mail-wg0-f53.google.com [74.125.82.53]) by dpdk.org (Postfix) with ESMTP id A05D9C808 for ; Fri, 19 Jun 2015 15:17:56 +0200 (CEST) Received: by wguu7 with SMTP id u7so17306500wgu.3 for ; Fri, 19 Jun 2015 06:17:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:organization :user-agent:in-reply-to:references:mime-version :content-transfer-encoding:content-type; bh=ms3A+5Q7KMx82Z+IKoorRJMP3yiuGM5KVXHzcs8MHB0=; b=OWoenav6QCqIsujJENaUUhSN6rYW9w3LyP8MBAJMApdSsxIoMeb5cqzrXMANdwWiS2 JV0BQykwc3kedv9Vdu3dNPf//VEUPpOu71nIzeDM1Y4xBndkO4vh5I/i/Rm0b0+1mH4f QjlLzbgelss97M2y1n0mdFDfvGkaluanxVXvOFqRv70umsYrwachfUz8anKUrgw/nf5N APnv39kFEcrplkhxsCiPlr2Kw0qc0knmcIqLgvedDhtazR+kfGV87uERiOCkx6+3vkRU ftbssk+mVPNMgRwlczZNkrgP3TiEdd9kt/XQmGWTnLxvrLKCmBeRQBU6LZ0Kb2Aqa3Xz H/MA== X-Gm-Message-State: ALoCoQnvGrRoQ+siuexSsp/s3tr5uQyyshedKYWmlj7TF9mUfcM2LQM1Bq7SofNgqmW+GqgMjLTW X-Received: by 10.194.174.194 with SMTP id bu2mr26167949wjc.76.1434719876476; Fri, 19 Jun 2015 06:17:56 -0700 (PDT) Received: from xps13.localnet (136-92-190-109.dsl.ovh.fr. [109.190.92.136]) by mx.google.com with ESMTPSA id ma15sm3699183wic.20.2015.06.19.06.17.54 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 19 Jun 2015 06:17:55 -0700 (PDT) From: Thomas Monjalon To: Neil Horman Date: Fri, 19 Jun 2015 15:16:53 +0200 Message-ID: <1784476.c2eg9hZKIA@xps13> Organization: 6WIND User-Agent: KMail/4.14.8 (Linux/4.0.4-2-ARCH; KDE/4.14.8; x86_64; ; ) In-Reply-To: <20150619130255.GA4619@hmsreliant.think-freely.org> References: <9092314.MoyqUJ5VU2@xps13> <2237584.tmRa3ku4eh@xps13> <20150619130255.GA4619@hmsreliant.think-freely.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Cc: dev@dpdk.org Subject: Re: [dpdk-dev] [dpdk-announce] important design choices - statistics - ABI X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 19 Jun 2015 13:17:56 -0000 2015-06-19 09:02, Neil Horman: > On Fri, Jun 19, 2015 at 02:32:33PM +0200, Thomas Monjalon wrote: > > 2015-06-19 06:26, Neil Horman: > > > On Thu, Jun 18, 2015 at 04:55:45PM +0000, O'Driscoll, Tim wrote: > > > > For the 2.1 release, I think we should agree to make patches that change > > > > the ABI controllable via a compile-time option. I like Olivier's proposal > > > > on using a single option (CONFIG_RTE_NEXT_ABI) to control all of these > > > > changes instead of a separate option per patch set (see > > > > http://dpdk.org/ml/archives/dev/2015-June/019147.html), so I think we > > > > should rework the affected patch sets to use that approach for 2.1. > > > > > > This is a bad idea. Making ABI dependent on compile time options isn't a > > > maintainable solution. It breaks the notion of how LIBABIVER is supposed to > > > work (that is to say you make it impossible to really tell what ABI version you > > > are building). > > > > The idea was to make LIBABIVER increment dependent of CONFIG_RTE_NEXT_ABI. > > So one ABI version number refers always to the same ABI. > > > > > If you have two compile time options that modify the ABI, you > > > have to burn through 4 possible LIBABIVER version values to accomodate all > > > possible combinations, and then you need to remember that when you make them > > > statically applicable. > > > > The idea is to have only 1 compile-time option: CONFIG_RTE_NEXT_ABI. > > > > Your intent when introducing ABI policy was to allow smooth porting of > > applications from a DPDK version to another. Right? > > The adopted solution was to provide backward compatibility during 1 release. > > But there are cases where it's not possible. So the policy was to notice > > the future change and wait one release cycle to break the ABI (failing > > compatibility goals). > > The compile-time option may provide an alternative DPDK packaging when the > > ABI backward compatibility cannot be provided (case of mbuf changes). > > In such case, it's still possible to upgrade DPDK by providing 2 versions of > > DPDK libs. So the existing apps continue to link with the previous ABI and > > have the possibility of migrating to the new one. > > Another advantage of this approach is that we don't have to wait 1 release > > to integrate the changes. > > The last advantage is to benefit early of these changes with static libraries. > > Hm, ok, thats a bit more reasonable, but it still seems shaky to me. > Implementing an ABI preview option like this implies the notion that, after a > release, you have to remove all the ifdefs that you inserted to create the new > ABI. That seems like an easy task, but it becomes a pain when the ABI delta is > large, and is predicated on the centralization of work effort (that is to say > you need to identify someone to submit the 'remove the NEXT_ABI config ifdefs > from the build' patch every release. It won't be so huge if we reserve the NEXT_ABI solution to changes which cannot have easy backward compatibility with the compat macros you introduced. I feel I can do the job of removing the ifdefs NEXT_ABI after each release. At the same time, the deprecated API, using the compat macros, will be removed. > What might be better would be a dpdk-next branch (or even a dpdk-next tree, of > the sort that Thomas Herbert proposed a few weeks ago). This tree was created after Thomas' request: http://dpdk.org/browse/next/dpdk-next/ > Patches that aren't ABI stable can be put on the next-branch/tree in thier > final format. You can delcare the branch unstable (thereby reserving your > right to rebase it). People can use that to preview the next ABI version > (complete with the update LIBABIVER bump), and when you release dpdk-X, > the new ABI for dpdk-X+1 is achieved by simply merging. Having this tree living would be a nice improvement but it won't provide any stable (and enough validated) releases to rely on.