From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <anatoly.burakov@intel.com> Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by dpdk.org (Postfix) with ESMTP id 2430B1B1E6 for <dev@dpdk.org>; Thu, 14 Feb 2019 11:19:06 +0100 (CET) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 14 Feb 2019 02:19:06 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,368,1544515200"; d="scan'208";a="144202565" Received: from aburakov-mobl1.ger.corp.intel.com (HELO [10.252.18.208]) ([10.252.18.208]) by fmsmga004.fm.intel.com with ESMTP; 14 Feb 2019 02:19:02 -0800 To: Shahaf Shuler <shahafs@mellanox.com>, Alejandro Lucero <alejandro.lucero@netronome.com> Cc: Yongseok Koh <yskoh@mellanox.com>, Thomas Monjalon <thomas@monjalon.net>, Ferruh Yigit <ferruh.yigit@intel.com>, "nhorman@tuxdriver.com" <nhorman@tuxdriver.com>, Gaetan Rivet <gaetan.rivet@6wind.com>, dev <dev@dpdk.org> References: <cover.1550048187.git.shahafs@mellanox.com> <CAD+H9922gjrmwbRr5Qo7cVqvE5DBJj27hvq-+_16GAPjYWbBcg@mail.gmail.com> <AM0PR0502MB3795448496DA4721C809ECE6C3660@AM0PR0502MB3795.eurprd05.prod.outlook.com> From: "Burakov, Anatoly" <anatoly.burakov@intel.com> Message-ID: <81f4bbef-8d6a-d845-eb07-966bbccf4849@intel.com> Date: Thu, 14 Feb 2019 10:19:03 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: <AM0PR0502MB3795448496DA4721C809ECE6C3660@AM0PR0502MB3795.eurprd05.prod.outlook.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Subject: Re: [dpdk-dev] [PATCH 0/6] introduce DMA memory mapping for external memory 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> X-List-Received-Date: Thu, 14 Feb 2019 10:19:07 -0000 On 13-Feb-19 7:24 PM, Shahaf Shuler wrote: > Wednesday, February 13, 2019 1:43 PM, Alejandro Lucero: >> Subject: Re: [dpdk-dev] [PATCH 0/6] introduce DMA memory mapping for >> external memory >> >> On Wed, Feb 13, 2019 at 9:11 AM Shahaf Shuler <shahafs@mellanox.com> >> wrote: >> >>> This series is in continue to RFC[1]. >>> >>> The DPDK APIs expose 3 different modes to work with memory used for >> DMA: >>> >>> 1. Use the DPDK owned memory (backed by the DPDK provided >> hugepages). >>> This memory is allocated by the DPDK libraries, included in the DPDK >>> memory system (memseg lists) and automatically DMA mapped by the >> DPDK >>> layers. >>> >>> 2. Use memory allocated by the user and register to the DPDK memory >>> systems. This is also referred as external memory. Upon registration >>> of the external memory, the DPDK layers will DMA map it to all needed >>> devices. >>> >>> 3. Use memory allocated by the user and not registered to the DPDK >>> memory system. This is for users who wants to have tight control on >>> this memory. The user will need to explicitly call DMA map function in >>> order to register such memory to the different devices. >>> >>> The scope of the patch focus on #3 above. >>> >>> >> Why can not we have case 2 covering case 3? > > Because it is not our choice rather the DPDK application. > We could not allow it, and force the application to register their external memory to the DPDK memory management system. However IMO it will be wrong. > The use case exists - some application wants to manage their memory by themselves. w/o the extra overhead of rte_malloc, without creating a special socket to populate the memory and without redundant API calls to rte_extmem_*. > > Simply allocate chunk of memory, DMA map it to device and that’s it. Just a small note: while this sounds good on paper, i should point out that at least *registering* the memory with DPDK is a necessity. You may see rte_extmem_* calls as redundant (and i agree, to an extent), but we don't advertise our PMD's capabilities in a way that makes it easy to determine whether a particular PMD will or will not work without registering external memory within DPDK (i.e. does it use rte_virt2memseg() internally, for example). So, extmem register calls are a necessary evil in such case, and IMO should be called out as required for such external memory usage scenario. -- Thanks, Anatoly