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Fri, 17 Apr 2020 04:40:24 -0400 X-MC-Unique: rkgAPLslMnmg37plxAw2VQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 12269800D53; Fri, 17 Apr 2020 08:40:20 +0000 (UTC) Received: from [10.36.110.44] (unknown [10.36.110.44]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5E2E5196AE; Fri, 17 Apr 2020 08:40:17 +0000 (UTC) To: "Fu, Patrick" , Jerin Jacob Cc: "dev@dpdk.org" , "Ye, Xiaolong" , "Hu, Jiayu" , "Wang, Zhihong" , "Liang, Cunming" References: <89B17B9B05A1964E8D40D6090018F28151277ADF@SHSMSX107.ccr.corp.intel.com> <89B17B9B05A1964E8D40D6090018F28151277C5C@SHSMSX107.ccr.corp.intel.com> From: Maxime Coquelin Autocrypt: addr=maxime.coquelin@redhat.com; keydata= mQINBFOEQQIBEADjNLYZZqghYuWv1nlLisptPJp+TSxE/KuP7x47e1Gr5/oMDJ1OKNG8rlNg kLgBQUki3voWhUbMb69ybqdMUHOl21DGCj0BTU3lXwapYXOAnsh8q6RRM+deUpasyT+Jvf3a gU35dgZcomRh5HPmKMU4KfeA38cVUebsFec1HuJAWzOb/UdtQkYyZR4rbzw8SbsOemtMtwOx YdXodneQD7KuRU9IhJKiEfipwqk2pufm2VSGl570l5ANyWMA/XADNhcEXhpkZ1Iwj3TWO7XR uH4xfvPl8nBsLo/EbEI7fbuUULcAnHfowQslPUm6/yaGv6cT5160SPXT1t8U9QDO6aTSo59N jH519JS8oeKZB1n1eLDslCfBpIpWkW8ZElGkOGWAN0vmpLfdyiqBNNyS3eGAfMkJ6b1A24un /TKc6j2QxM0QK4yZGfAxDxtvDv9LFXec8ENJYsbiR6WHRHq7wXl/n8guyh5AuBNQ3LIK44x0 KjGXP1FJkUhUuruGyZsMrDLBRHYi+hhDAgRjqHgoXi5XGETA1PAiNBNnQwMf5aubt+mE2Q5r qLNTgwSo2dpTU3+mJ3y3KlsIfoaxYI7XNsPRXGnZi4hbxmeb2NSXgdCXhX3nELUNYm4ArKBP LugOIT/zRwk0H0+RVwL2zHdMO1Tht1UOFGfOZpvuBF60jhMzbQARAQABtCxNYXhpbWUgQ29x dWVsaW4gPG1heGltZS5jb3F1ZWxpbkByZWRoYXQuY29tPokCOAQTAQIAIgUCV3u/5QIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQyjiNKEaHD4ma2g/+P+Hg9WkONPaY1J4AR7Uf kBneosS4NO3CRy0x4WYmUSLYMLx1I3VH6SVjqZ6uBoYy6Fs6TbF6SHNc7QbB6Qjo3neqnQR1 71Ua1MFvIob8vUEl3jAR/+oaE1UJKrxjWztpppQTukIk4oJOmXbL0nj3d8dA2QgHdTyttZ1H xzZJWWz6vqxCrUqHU7RSH9iWg9R2iuTzii4/vk1oi4Qz7y/q8ONOq6ffOy/t5xSZOMtZCspu Mll2Szzpc/trFO0pLH4LZZfz/nXh2uuUbk8qRIJBIjZH3ZQfACffgfNefLe2PxMqJZ8mFJXc RQO0ONZvwoOoHL6CcnFZp2i0P5ddduzwPdGsPq1bnIXnZqJSl3dUfh3xG5ArkliZ/++zGF1O wvpGvpIuOgLqjyCNNRoR7cP7y8F24gWE/HqJBXs1qzdj/5Hr68NVPV1Tu/l2D1KMOcL5sOrz 2jLXauqDWn1Okk9hkXAP7+0Cmi6QwAPuBT3i6t2e8UdtMtCE4sLesWS/XohnSFFscZR6Vaf3 gKdWiJ/fW64L6b9gjkWtHd4jAJBAIAx1JM6xcA1xMbAFsD8gA2oDBWogHGYcScY/4riDNKXi lw92d6IEHnSf6y7KJCKq8F+Jrj2BwRJiFKTJ6ChbOpyyR6nGTckzsLgday2KxBIyuh4w+hMq TGDSp2rmWGJjASq5Ag0EVPSbkwEQAMkaNc084Qvql+XW+wcUIY+Dn9A2D1gMr2BVwdSfVDN7 0ZYxo9PvSkzh6eQmnZNQtl8WSHl3VG3IEDQzsMQ2ftZn2sxjcCadexrQQv3Lu60Tgj7YVYRM H+fLYt9W5YuWduJ+FPLbjIKynBf6JCRMWr75QAOhhhaI0tsie3eDsKQBA0w7WCuPiZiheJaL 4MDe9hcH4rM3ybnRW7K2dLszWNhHVoYSFlZGYh+MGpuODeQKDS035+4H2rEWgg+iaOwqD7bg CQXwTZ1kSrm8NxIRVD3MBtzp9SZdUHLfmBl/tLVwDSZvHZhhvJHC6Lj6VL4jPXF5K2+Nn/Su CQmEBisOmwnXZhhu8ulAZ7S2tcl94DCo60ReheDoPBU8PR2TLg8rS5f9w6mLYarvQWL7cDtT d2eX3Z6TggfNINr/RTFrrAd7NHl5h3OnlXj7PQ1f0kfufduOeCQddJN4gsQfxo/qvWVB7PaE 1WTIggPmWS+Xxijk7xG6x9McTdmGhYaPZBpAxewK8ypl5+yubVsE9yOOhKMVo9DoVCjh5To5 aph7CQWfQsV7cd9PfSJjI2lXI0dhEXhQ7lRCFpf3V3mD6CyrhpcJpV6XVGjxJvGUale7+IOp sQIbPKUHpB2F+ZUPWds9yyVxGwDxD8WLqKKy0WLIjkkSsOb9UBNzgRyzrEC9lgQ/ABEBAAGJ Ah8EGAECAAkFAlT0m5MCGwwACgkQyjiNKEaHD4nU8hAAtt0xFJAy0sOWqSmyxTc7FUcX+pbD KVyPlpl6urKKMk1XtVMUPuae/+UwvIt0urk1mXi6DnrAN50TmQqvdjcPTQ6uoZ8zjgGeASZg jj0/bJGhgUr9U7oG7Hh2F8vzpOqZrdd65MRkxmc7bWj1k81tOU2woR/Gy8xLzi0k0KUa8ueB iYOcZcIGTcs9CssVwQjYaXRoeT65LJnTxYZif2pfNxfINFzCGw42s3EtZFteczClKcVSJ1+L +QUY/J24x0/ocQX/M1PwtZbB4c/2Pg/t5FS+s6UB1Ce08xsJDcwyOPIH6O3tccZuriHgvqKP yKz/Ble76+NFlTK1mpUlfM7PVhD5XzrDUEHWRTeTJSvJ8TIPL4uyfzhjHhlkCU0mw7Pscyxn DE8G0UYMEaNgaZap8dcGMYH/96EfE5s/nTX0M6MXV0yots7U2BDb4soLCxLOJz4tAFDtNFtA wLBhXRSvWhdBJZiig/9CG3dXmKfi2H+wdUCSvEFHRpgo7GK8/Kh3vGhgKmnnxhl8ACBaGy9n fxjSxjSO6rj4/MeenmlJw1yebzkX8ZmaSi8BHe+n6jTGEFNrbiOdWpJgc5yHIZZnwXaW54QT UhhSjDL1rV2B4F28w30jYmlRmm2RdN7iCZfbyP3dvFQTzQ4ySquuPkIGcOOHrvZzxbRjzMx1 Mwqu3GQ= Message-ID: <8e4691c5-3e58-fb5d-f1f5-6b9c994c3949@redhat.com> Date: Fri, 17 Apr 2020 10:40:15 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <89B17B9B05A1964E8D40D6090018F28151277C5C@SHSMSX107.ccr.corp.intel.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 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 4/17/20 10:29 AM, Fu, Patrick wrote: > Hi Jerin, > >> -----Original Message----- >> From: Jerin Jacob >> Sent: Friday, April 17, 2020 4:02 PM >> To: Fu, Patrick >> Cc: dev@dpdk.org; Maxime Coquelin ; 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 12:56 PM Fu, Patrick wrote: >>> >>> Background >>> ==================================== >>> DPDK vhost library implements a user-space VirtIO net backend allowing >> host applications to directly communicate with VirtIO front-end in VMs and >> containers. However, every vhost enqueue/dequeue operation requires to >> copy packet buffers between guest and host memory. The overhead of >> copying large bulk of data makes the vhost backend become the I/O >> bottleneck. DMA engines, including un-core DMA accelerator, like Crystal >> Beach DMA (CBDMA) and Data Streaming Accelerator (DSA), and discrete >> card general purpose DMA, are extremely efficient in data movement within >> system memory. Therefore, we propose a set of asynchronous DMA data >> movement API in vhost library for DMA acceleration. With offloading packet >> copies in vhost data-path from the CPU to the DMA engine, which can not >> only accelerate data transfers, but also save precious CPU core resources. >>> >>> New API Overview >>> ==================================== >>> The proposed APIs in the vhost library support various DMA engines to >> accelerate data transfers in the data-path. For the higher performance, DMA >> engines work in an asynchronous manner, where DMA data transfers and >> CPU computations are executed in parallel. The proposed API consists of >> control path API and data path API. The control path API includes >> Registration API and DMA operation callback, and the data path API includes >> asynchronous API. To remove the dependency of vendor specific DMA >> engines, the DMA operation callback provides generic DMA data transfer >> abstractions. To support asynchronous DMA data movement, the new async >> API provides asynchronous ring operation semantic in data-path. To >> enable/disable DMA acceleration for virtqueues, users need to use >> registration API is to register/unregister DMA callback implementations to >> the vhost library and bind DMA channels to virtqueues. The DMA channels >> used by virtqueues are provided by DPDK applications, which is backed by >> virtual or physical DMA devices. >>> The proposed APIs are consisted of 3 sub-sets: >>> 1. DMA Registration APIs >>> 2. DMA Operation Callbacks >>> 3. Async Data APIs >>> >>> DMA Registration APIs >>> ==================================== >>> DMA acceleration is per queue basis. DPDK applications need to explicitly >> decide whether a virtqueue needs DMA acceleration and which DMA channel >> to use. In addition, a DMA channel is dedicated to a virtqueue and a DMA >> channel cannot be bound to multiple virtqueues at the same time. To enable >> DMA acceleration for a virtqueue, DPDK applications need to implement >> DMA operation callbacks for a specific DMA type (e.g. CBDMA) first, then >> register the callbacks to the vhost library and bind a DMA channel to a >> virtqueue, and finally use the new async API to perform data-path operations >> on the virtqueue. >>> The definitions of registration API are shown below: >>> int rte_vhost_async_channel_register(int vid, uint16_t queue_id, >>> struct rte_vdma_device_ops >>> *ops); >>> >>> int rte_vhost_async_channel_unregister(int vid, uint16_t queue_id); >> >> We already have multiple DMA implementation over raw dev. >> Why not make a new dmadev class for DMA acceleration and use it by virtio >> and any other clients? > > 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? Thanks, Maxime > Thanks, > > Patrick >