From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id 56B4F4301C; Thu, 10 Aug 2023 13:35:28 +0200 (CEST) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id E178040DFB; Thu, 10 Aug 2023 13:35:27 +0200 (CEST) Received: from dkmailrelay1.smartsharesystems.com (smartserver.smartsharesystems.com [77.243.40.215]) by mails.dpdk.org (Postfix) with ESMTP id 838F240691 for ; Thu, 10 Aug 2023 13:35:26 +0200 (CEST) Received: from smartserver.smartsharesystems.com (smartserver.smartsharesys.local [192.168.4.10]) by dkmailrelay1.smartsharesystems.com (Postfix) with ESMTP id 4864D206BD; Thu, 10 Aug 2023 13:35:26 +0200 (CEST) Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Subject: RE: [RFC PATCH] dmadev: offload to free source buffer Date: Thu, 10 Aug 2023 13:35:23 +0200 X-MimeOLE: Produced By Microsoft Exchange V6.5 Message-ID: <98CBD80474FA8B44BF855DF32C47DC35D87AE1@smartserver.smartshare.dk> In-Reply-To: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [RFC PATCH] dmadev: offload to free source buffer Thread-Index: AQHZyof4Da72IaSPrUSnTi7I079uxa/hrKoAgABV8CCAAAcykIAANhOggAEDhCCAAAeTAIAAF+Zw References: <20230809060835.2030833-1-amitprakashs@marvell.com> <98CBD80474FA8B44BF855DF32C47DC35D87AD9@smartserver.smartshare.dk> A <98CBD80474FA8B44BF855DF32C47DC35D87ADF@smartserver.smartshare.dk> A <98CBD80474FA8B44BF855DF32C47DC35D87AE0@smartserver.smartshare.dk> From: =?iso-8859-1?Q?Morten_Br=F8rup?= To: "Amit Prakash Shukla" , "Chengwen Feng" , "Kevin Laatz" , "Bruce Richardson" Cc: , "Jerin Jacob Kollanukkaran" , , "Vamsi Krishna Attunuru" , , , , , "Nithin Kumar Dabilpuram" , "Anoob Joseph" X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org > From: Amit Prakash Shukla [mailto:amitprakashs@marvell.com] > Sent: Thursday, 10 August 2023 12.28 >=20 > > From: Morten Br=F8rup > > Sent: Thursday, August 10, 2023 3:03 PM > > > > > From: Amit Prakash Shukla [mailto:amitprakashs@marvell.com] > > > Sent: Wednesday, 9 August 2023 20.12 > > > > > > > From: Morten Br=F8rup > > > > Sent: Wednesday, August 9, 2023 8:19 PM > > > > > > > > > From: Amit Prakash Shukla [mailto:amitprakashs@marvell.com] > > > > > Sent: Wednesday, 9 August 2023 16.27 > > > > > > > > > > > From: Morten Br=F8rup > > > > > > Sent: Wednesday, August 9, 2023 2:37 PM > > > > > > > > > > > > > From: Amit Prakash Shukla = [mailto:amitprakashs@marvell.com] > > > > > > > Sent: Wednesday, 9 August 2023 08.09 > > > > > > > > > > > > > > This changeset adds support in DMA library to free source = DMA > > > > > > > buffer by hardware. On a supported hardware, application = can > > > > > > > pass on the mempool information as part of vchan config = when > > > > > > > the DMA transfer direction is configured as > > RTE_DMA_DIR_MEM_TO_DEV. > > > > > > > > > > > > Isn't the DMA source buffer a memory area, and what needs to = be > > > > > > freed > > > > > is > > > > > > the mbuf holding the memory area, i.e. two different = pointers? > > > > > No, it is same pointer. Assume mbuf created via mempool, = mempool > > > > > needs to be given via vchan config and iova passed to > > > > > rte_dma_copy/rte_dma_copy_sg's can be any address in mbuf area = of > > > > > given mempool element. > > > > > For example, mempool element size is S. dequeued buff from > > mempool > > > > > is at X. Any address in (X, X+S) can be given as iova to > rte_dma_copy. > > > > > > > > So the DMA library determines the pointer to the mbuf (in the = given > > > > mempool) by looking at the iova passed to > > > > rte_dma_copy/rte_dma_copy_sg, and then calls rte_mempool_put = with > > that pointer? > > > > > > No. DMA hardware would determine the pointer to the mbuf using = iova > > > address and mempool. Hardware will free the buffer, on completion = of > > data transfer. > > > > OK. If there are any requirements to the mempool, it needs to be > > documented in the source code comments. E.g. does it work with = mempools > > where the mempool driver is an MP_RTS/MC_RTS ring, or a stack? >=20 > I think adding a comment, related to type of supported mempool, in dma > library code might not be needed as it is driver implementation = dependent. > Call to dev->dev_ops->vchan_setup for the driver shall check and = return > error for unsupported type of mempool. Makes sense. But I still think that it needs to be mentioned that = RTE_DMA_CAPA_MEM_TO_DEV_SOURCE_BUFFER_FREE has some limitations, and = doesn't mean that any type of mempool can be used. I suggest you add a note to the description of the new "struct = rte_mempool *mem_to_dev_src_buf_pool" field in the rte_dma_vchan_conf = structure, such as: Note: If the mempool is not supported by the DMA driver, = rte_dma_vchan_setup() will fail. You should also mention it with the description of = RTE_DMA_CAPA_MEM_TO_DEV_SOURCE_BUFFER_FREE flag, such as: Note: Even though the DMA driver has this capability, it may not support = all mempool drivers. If the mempool is not supported by the DMA driver, = rte_dma_vchan_setup() will fail. >=20 > > > > > > > > > > > > > > > > > > > > > > > > > > I like the concept. Something similar might also be useful = for > > > > > > RTE_DMA_DIR_MEM_TO_MEM, e.g. packet capture. Although such a > > use > > > > > > case might require decrementing the mbuf refcount instead of > > > > > > freeing > > > > > the > > > > > > mbuf directly to the mempool. > > > > > This operation is not supported in our hardware. It can be > > > > > implemented in future if any hardware supports it. > > > > > > > > OK, I didn't expect that - just floating the idea. :-) > > > > > > > > > > > > > > > > > > > > > PS: It has been a while since I looked at the DMA library, = so > > > > > > ignore my comments if I got this wrong.