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Mon, 20 Apr 2020 08:10:32 -0400 X-MC-Unique: OjkQQ4LxOv2uHP-YnEwAlg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A06A7107ACCA; Mon, 20 Apr 2020 12:10:30 +0000 (UTC) Received: from [10.36.110.18] (unknown [10.36.110.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D8FCEA105F; Mon, 20 Apr 2020 12:10:28 +0000 (UTC) To: Jerin Jacob Cc: "Liang, Cunming" , "Fu, Patrick" , "dev@dpdk.org" , "Ye, Xiaolong" , "Hu, Jiayu" , "Wang, Zhihong" References: <89B17B9B05A1964E8D40D6090018F28151277ADF@SHSMSX107.ccr.corp.intel.com> <89B17B9B05A1964E8D40D6090018F28151277C5C@SHSMSX107.ccr.corp.intel.com> <8e4691c5-3e58-fb5d-f1f5-6b9c994c3949@redhat.com> <89B17B9B05A1964E8D40D6090018F28151277D4F@SHSMSX107.ccr.corp.intel.com> <0aaa4b51-f705-1dc4-db60-00e9084db2ea@redhat.com> From: Maxime Coquelin Autocrypt: addr=maxime.coquelin@redhat.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [dpdk-dev] [RFC] Accelerating Data Movement for DPDK vHost with DMA Engines 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" On 4/20/20 2:08 PM, Jerin Jacob wrote: > On Mon, Apr 20, 2020 at 5:14 PM Maxime Coquelin > wrote: >> >> >> >> On 4/20/20 1:13 PM, Jerin Jacob wrote: >>> On Mon, Apr 20, 2020 at 1:29 PM Liang, Cunming wrote: >>>> >>>> >>>> >>>>> -----Original Message----- >>>>> From: Jerin Jacob >>>>> Sent: Friday, April 17, 2020 5:55 PM >>>>> To: Fu, Patrick >>>>> Cc: Maxime Coquelin ; dev@dpdk.org; Ye, >>>>> Xiaolong ; Hu, Jiayu ; Wang, >>>>> Zhihong ; Liang, Cunming >>>>> Subject: Re: [dpdk-dev] [RFC] Accelerating Data Movement for DPDK vHost with >>>>> DMA Engines >>>>> >>>>> On Fri, Apr 17, 2020 at 2:56 PM Fu, Patrick wrote: >>>>>> >>>>>> >>>> [...] >>>>>>>> >>>>>>>> I believe it doesn't conflict. The purpose of this RFC is to >>>>>>>> create an async >>>>>>> data path in vhost-user and provide a way for applications to work >>>>>>> with this new path. dmadev is another topic which could be discussed >>>>>>> separately. If we do have the dmadev available in the future, this >>>>>>> vhost async data path could certainly be backed by the new dma >>>>>>> abstraction without major interface change. >>>>>>> >>>>>>> Maybe that one advantage of a dmadev class is that it would be >>>>>>> easier and more transparent for the application to consume. >>>>>>> >>>>>>> The application would register some DMA devices, pass them to the >>>>>>> Vhost library, and then rte_vhost_submit_enqueue_burst and >>>>>>> rte_vhost_poll_enqueue_completed would call the dmadev callbacks directly. >>>>>>> >>>>>>> Do you think that could work? >>>>>>> >>>>>> Yes, this is a workable model. As I said in previous reply, I have no objection to >>>>> make the dmadev. However, what we currently want to do is creating the async >>>>> data path for vhost, and we actually have no preference to the underlying DMA >>>>> device model. I believe our current design of the API proto type /data structures >>>>> are quite common for various DMA acceleration solutions and there is no blocker >>>>> for any new DMA device to adapt to these APIs or extend to a new one. >>>>> >>>>> IMO, as a driver writer, we should not be writing TWO DMA driver. One for vhost >>>>> and other one for rawdev. >>>> It's the most simplest case if statically 1:1 mapping driver (e.g. {port, queue}) to a vhost session {vid, qid}. However, it's not enough scalable to integrate device model with vhost library. There're a few intentions belong to app logic rather than driver, e.g. 1:N load balancing, various device type usages (e.g. vhost zcopy via ethdev) and etc. >>> >>> >>> Before moving to reply to comments, Which DMA engine you are planning >>> to integrate with vHOST? >>> Is is ioat? if not ioat(drivers/raw/ioat/), How do you think, how we >>> can integrate this IOAT DMA engine to vHOST as a use case? >>> >> >> I guess it could be done in the vhost example. > > > Could not see any reference to DMA in examples/vhost* > That's because we are discussing the API to introduce DMA support in this exact mail thread, nothing has been merged yet. Maxime