From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: =?utf-8?B?44CQUXVlc3Rpb27jgJFXaGV0aGVy?= =?utf-8?Q?_it's_legal_to_enabl?= =?utf-8?Q?e?= same physical DMA memory mapped for different NIC device? Date: Tue, 3 Jan 2012 15:33:57 -0500 Message-ID: <20120103203357.GD17472@phenom.dumpdata.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-pci-owner@vger.kernel.org To: "ustc.mail" Cc: linux-pci@vger.kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-arch.vger.kernel.org On Wed, Dec 07, 2011 at 10:16:40PM +0800, ustc.mail wrote: > Dear all, > > In NIC driver, to eliminate the overhead of dma_map_single() for DMA > packet data, we have statically allocated huge DMA memory buffer ring > at once instead of calling dma_map_single() per packet. Considering > to further reduce the copy overhead between different NIC(port) ring > while forwarding, one packet from a input NIC(port) will be > transferred to output NIC(port) with no any copy action. > > To satisfy this requirement, the packet memory should be mapped into > input port and unmapped when leaving input port, then mapped into > output port and unmapped later. > > Whether it's legal to map the same DMA memory into input and output > port simultaneously? If it's not, then the zero-copy for packet > forwarding is not feasible? > Did you ever a get a response about this? Is the output/input port on a seperate device function? Or is it just a specific MMIO BAR in your PCI device? > Hope PCI expert to post your suggestion. > > Thanks! > > --Yanfei > > -- > To unsubscribe from this list: send the line "unsubscribe linux-pci" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from acsinet15.oracle.com ([141.146.126.227]:47356 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751189Ab2ACUfp (ORCPT ); Tue, 3 Jan 2012 15:35:45 -0500 Date: Tue, 3 Jan 2012 15:33:57 -0500 From: Konrad Rzeszutek Wilk Subject: Re: =?utf-8?B?44CQUXVlc3Rpb27jgJFXaGV0aGVy?= =?utf-8?Q?_it's_legal_to_enabl?= =?utf-8?Q?e?= same physical DMA memory mapped for different NIC device? Message-ID: <20120103203357.GD17472@phenom.dumpdata.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: "ustc.mail" Cc: linux-pci@vger.kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: <20120103203357.aFCOTdG_nx283nsz9ptDFLLqpywCqRk2jDi_gBiGuvQ@z> On Wed, Dec 07, 2011 at 10:16:40PM +0800, ustc.mail wrote: > Dear all, > > In NIC driver, to eliminate the overhead of dma_map_single() for DMA > packet data, we have statically allocated huge DMA memory buffer ring > at once instead of calling dma_map_single() per packet. Considering > to further reduce the copy overhead between different NIC(port) ring > while forwarding, one packet from a input NIC(port) will be > transferred to output NIC(port) with no any copy action. > > To satisfy this requirement, the packet memory should be mapped into > input port and unmapped when leaving input port, then mapped into > output port and unmapped later. > > Whether it's legal to map the same DMA memory into input and output > port simultaneously? If it's not, then the zero-copy for packet > forwarding is not feasible? > Did you ever a get a response about this? Is the output/input port on a seperate device function? Or is it just a specific MMIO BAR in your PCI device? > Hope PCI expert to post your suggestion. > > Thanks! > > --Yanfei > > -- > To unsubscribe from this list: send the line "unsubscribe linux-pci" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html