From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <dev-bounces@dpdk.org> Received: from dpdk.org (dpdk.org [92.243.14.124]) by dpdk.space (Postfix) with ESMTP id 9BAE3A0679 for <public@inbox.dpdk.org>; Mon, 1 Apr 2019 21:23:08 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id A81533576; Mon, 1 Apr 2019 21:23:07 +0200 (CEST) Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by dpdk.org (Postfix) with ESMTP id 92E2934F3 for <dev@dpdk.org>; Mon, 1 Apr 2019 21:23:05 +0200 (CEST) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 01 Apr 2019 12:23:04 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,297,1549958400"; d="scan'208";a="132046668" Received: from fmsmsx103.amr.corp.intel.com ([10.18.124.201]) by orsmga006.jf.intel.com with ESMTP; 01 Apr 2019 12:23:03 -0700 Received: from fmsmsx161.amr.corp.intel.com (10.18.125.9) by FMSMSX103.amr.corp.intel.com (10.18.124.201) with Microsoft SMTP Server (TLS) id 14.3.408.0; Mon, 1 Apr 2019 12:23:03 -0700 Received: from fmsmsx108.amr.corp.intel.com ([169.254.9.216]) by FMSMSX161.amr.corp.intel.com ([169.254.12.31]) with mapi id 14.03.0415.000; Mon, 1 Apr 2019 12:23:03 -0700 From: "Eads, Gage" <gage.eads@intel.com> To: Stephen Hemminger <stephen@networkplumber.org> CC: "dev@dpdk.org" <dev@dpdk.org>, "olivier.matz@6wind.com" <olivier.matz@6wind.com>, "arybchenko@solarflare.com" <arybchenko@solarflare.com>, "Richardson, Bruce" <bruce.richardson@intel.com>, "Ananyev, Konstantin" <konstantin.ananyev@intel.com>, "jerinj@marvell.com" <jerinj@marvell.com>, "mczekaj@marvell.com" <mczekaj@marvell.com>, "nd@arm.com" <nd@arm.com>, "Ola.Liljedahl@arm.com" <Ola.Liljedahl@arm.com> Thread-Topic: [PATCH v7 0/6] Add lock-free ring and mempool handler Thread-Index: AQHU3dM7C6Byp72AjU6cIT29UTs4q6YR7JYAgAGkUICAFAahwA== Date: Mon, 1 Apr 2019 19:23:02 +0000 Message-ID: <9184057F7FC11744A2107296B6B8EB1E5420E60C@FMSMSX108.amr.corp.intel.com> References: <20190306150342.2894-1-gage.eads@intel.com> <20190318213555.17345-1-gage.eads@intel.com> <9184057F7FC11744A2107296B6B8EB1E54207FC7@FMSMSX108.amr.corp.intel.com> <20190319085123.00df99c2@shemminger-XPS-13-9360> In-Reply-To: <20190319085123.00df99c2@shemminger-XPS-13-9360> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-titus-metadata-40: eyJDYXRlZ29yeUxhYmVscyI6IiIsIk1ldGFkYXRhIjp7Im5zIjoiaHR0cDpcL1wvd3d3LnRpdHVzLmNvbVwvbnNcL0ludGVsMyIsImlkIjoiZWE4ZTE5OWYtMDk3YS00Nzc3LTlkYTctNDc5YzA3MGNjNGU2IiwicHJvcHMiOlt7Im4iOiJDVFBDbGFzc2lmaWNhdGlvbiIsInZhbHMiOlt7InZhbHVlIjoiQ1RQX05UIn1dfV19LCJTdWJqZWN0TGFiZWxzIjpbXSwiVE1DVmVyc2lvbiI6IjE3LjEwLjE4MDQuNDkiLCJUcnVzdGVkTGFiZWxIYXNoIjoidkNPWW5FaFpnQWhJdXBnc0VcL0JLSDRsOENEdDRzS2dCYWV2alhSNzEyZm5NdDExMCszU1BjcjZpTktRQjlZaGMifQ== x-ctpclassification: CTP_NT dlp-product: dlpe-windows dlp-version: 11.0.400.15 dlp-reaction: no-action x-originating-ip: [10.1.200.106] Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Subject: Re: [dpdk-dev] [PATCH v7 0/6] Add lock-free ring and mempool handler X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions <dev.dpdk.org> List-Unsubscribe: <https://mails.dpdk.org/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://mails.dpdk.org/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <https://mails.dpdk.org/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> Errors-To: dev-bounces@dpdk.org Sender: "dev" <dev-bounces@dpdk.org> Message-ID: <20190401192302.HIpl2a1K-eb9knv2Ta1pJU1TZJPqO8199n3nC8hIm1k@z> >=20 > On Mon, 18 Mar 2019 21:49:44 +0000 > "Eads, Gage" <gage.eads@intel.com> wrote: >=20 > > Hi all, > > > > Friendly reminder that in order to get this feature into 19.08 (assumin= g > folks also want that :)), the API deprecation notice needs to be merged i= nto > 19.05. > > > > Thanks, > > Gage >=20 > Given the recent API/ABI stability discussion, this is the kind of patch = that > really needs to be examined and justified. Can you point me to the discussion (assuming it was on the ML)? I'm aware o= f Ferruh's changes to the docs, but not the discussion you referenced. The lock-free ring functionality itself is a valuable addition to DPDK, pri= marily because it lacks the standard ring's non-preemptive constraint. The = non-preemptive constraint is important in an application with both high pri= ority, performance-sensitive data-plane components and low-priority control= -plane components. This was important enough to warrant further clarificati= on recently[1], and has been a discussion topic for some time[2][3]. The modified API, rte_ring_get_memsize(), was added to allow users to initi= alize rings in separately allocated memory. This function isn't called in D= PDK's examples/apps/drivers, and a quick google search didn't turn up any o= pen source projects that call the function, so I suspect that a majority of= ring code uses rte_ring_create() instead of rte_ring_get_memsize() + rte_r= ing_init(). So I suspect this interface change will affect a small percenta= ge of DPDK users. As a straw-man counter-proposal, we could instead introduce a lock-free spe= cific function rte_lf_ring_get_memsize() that lock-free ring users would ca= ll instead of rte_ring_get_memsize(). This would avoid the API modification= , but: - It's awkward to have one rte_lf_ring_* function and otherwise access the = lock-free ring through rte_ring_* functions. - It's also easy to envision a user incorrectly calling rte_ring_get_memsiz= e() rather than rte_lf_ring_get_memsize() for a lock-free ring, since other= wise rte_ring_* functions are used. DPDK would have no way to detect that t= he allocated memory is too small, and if such a bug occurs it would manifes= t itself as memory corruption. - Changing rte_ring_get_memsize() to take a flags argument may be the bette= r long-term design, if another flag is introduced that likewise uses a diff= erent ring size. Another approach is to break out the lock-free ring into a fully separate A= PI. One of the goals of my patchset was to allow applications to switch to = lock-free rings with minimal code change; I think the value of the lock-fre= e ring warrants such an approach. (Unfortunately without hard numbers on the cost or benefit of such a change= , these arguments are fairly subjective.) Thanks, Gage [1] https://patches.dpdk.org/patch/43122/ [2] http://mails.dpdk.org/archives/dev/2013-November/000714.html [3] http://mails.dpdk.org/archives/dev/2014-January/001163.html