From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: Re: [PATCH 0/6] SRP initiator related bug fixes Date: Mon, 7 Dec 2015 09:15:37 -0800 Message-ID: <5665BEB9.5030501@sandisk.com> References: <565DE3EC.2070002@sandisk.com> <56621CDF.3070604@sandisk.com> <20151205111715.GA31393@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20151205111715.GA31393-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Christoph Hellwig Cc: Doug Ledford , Sagi Grimberg , Sebastian Parschauer , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-rdma@vger.kernel.org On 12/05/2015 03:17 AM, Christoph Hellwig wrote: > Hi Bart, > > On Fri, Dec 04, 2015 at 03:08:15PM -0800, Bart Van Assche wrote: >> While preparing this patch series I noticed that none of the SCSI RDMA >> initiator drivers syncs RDMA buffers before performing RDMA. Does >> anyone know why something like the code below is not present in these >> drivers and why no dma_sync_sg operations are present in struct >> ib_dma_mapping_ops ? > > dma_map*/dma_unmap* have to do implicit syncs, so no explicit call > is required. That's probably the reason why we don't need them in > the weird RDMA shadows of these functions (for which I still don't > understand the reason, while we're at it..). Hello Christoph, struct ib_dma_mapping_ops was added through commit "IB: Add DMA mapping functions to allow device drivers to interpose" (https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=9b513090a3c5e4964f9ac09016c1586988abb3d5). I'm not sure that these functions are still needed by the qib or ipath drivers since the .dma_address and .dma_len members have been removed some time ago from that structure (see also http://thread.gmane.org/gmane.linux.drivers.rdma/19730). It would be useful to have data available that shows the performance difference with and without struct ib_dma_mapping_ops for the qib and ipath drivers but I do not know whether such data is available publicly. Bart. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html