From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <pmatilai@redhat.com> Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id A2A7428F3 for <dev@dpdk.org>; Thu, 30 Jun 2016 11:05:23 +0200 (CEST) Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A199185366; Thu, 30 Jun 2016 09:05:22 +0000 (UTC) Received: from sopuli.koti.laiskiainen.org (vpn1-5-182.ams2.redhat.com [10.36.5.182]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u5U95Km5018660; Thu, 30 Jun 2016 05:05:20 -0400 To: Yuanhan Liu <yuanhan.liu@linux.intel.com> References: <1463117111-27050-1-git-send-email-yuanhan.liu@linux.intel.com> <1465271530-27878-1-git-send-email-yuanhan.liu@linux.intel.com> <2add15af-5323-1f0c-b057-e29eeefb94c3@redhat.com> <20160630075700.GH2831@yliu-dev.sh.intel.com> Cc: dev@dpdk.org, huawei.xie@intel.com, Thomas Monjalon <thomas.monjalon@6wind.com>, Rich Lane <rich.lane@bigswitch.com>, Tetsuya Mukawa <mukawa@igel.co.jp> From: Panu Matilainen <pmatilai@redhat.com> Message-ID: <cc0e70aa-70b1-ec40-e1e5-457e80b08e83@redhat.com> Date: Thu, 30 Jun 2016 12:05:19 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 MIME-Version: 1.0 In-Reply-To: <20160630075700.GH2831@yliu-dev.sh.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Thu, 30 Jun 2016 09:05:22 +0000 (UTC) Subject: Re: [dpdk-dev] [PATCH v3 00/20] vhost ABI/API refactoring X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK <dev.dpdk.org> List-Unsubscribe: <http://dpdk.org/ml/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://dpdk.org/ml/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <http://dpdk.org/ml/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> X-List-Received-Date: Thu, 30 Jun 2016 09:05:24 -0000 On 06/30/2016 10:57 AM, Yuanhan Liu wrote: > On Thu, Jun 30, 2016 at 10:39:45AM +0300, Panu Matilainen wrote: >> On 06/07/2016 06:51 AM, Yuanhan Liu wrote: >>> v3: - adapted the new vhost ABI/API changes to tep_term example, to make >>> sure not break build at least. >>> - bumped the ABI version to 3 >>> >>> NOTE: I created a branch at dpdk.org [0] for more conveinient testing: >>> >>> [0]: git://dpdk.org/next/dpdk-next-virtio for-testing >>> >>> >>> Every time we introduce a new feature to vhost, we are likely to break >>> ABI. Moreover, some cleanups (such as the one from Ilya to remove vec_buf >> >from vhost_virtqueue struct) also break ABI. >>> >>> This patch set is meant to resolve above issue ultimately, by hiding >>> virtio_net structure (as well as few others) internaly, and export the >>> virtio_net dev strut to applications by a number, vid, like the way >>> kernel exposes an fd to user space. >>> >>> Back to the patch set, the first part of this set makes some changes to >>> vhost example, vhost-pmd and vhost, bit by bit, to remove the dependence >>> to "virtio_net" struct. And then do the final change to make the current >>> APIs to adapt to using "vid". >>> >>> After that, "vrtio_net_device_ops" is the only left open struct that an >>> application can acces, therefore, it's the only place that might introduce >>> potential ABI breakage in future for extension. Hence, I made few more >>> (5) space reservation, to make sure we will not break ABI for a long time, >>> and hopefuly, forever. >> >> Been intending to say this for a while but seems I never actually got around >> to do so: >> >> This is a really fine example of how to refactor an API against constant ABI >> breakages, thank you Yuanhan! > > Panu, thanks! > >> Exported structs are one of the biggest >> obstacles in keeping a stable ABI while adding new features, and while its >> not always possible to hide everything to this extent, the damage (erm, >> exposure) can usually be considerably limited by careful API design. > > Agreed. > >> Since the first and the foremost objection against doing this in the DPDK >> context is always "but performance!", I'm curious as to what sort of numbers >> you're getting with the new API vs the old one? I'm really hoping other >> libraries would follow suit after seeing that its possible to provide a >> future-proof API/ABI without sacrificing performance :) > > From my (limited) test, nope, I see no performance drop at all, not even a > little. Awesome! With that, hopefully others will see the light and follow its example. If nothing else, they ought to get a bit envious when you can add features left and right without ever having to wait for API/ABI break periods etc ;) - Panu - > > --yliu >