From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964984AbdAKD2A (ORCPT ); Tue, 10 Jan 2017 22:28:00 -0500 Received: from userp1050.oracle.com ([156.151.31.82]:39915 "EHLO userp1050.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964945AbdAKD17 (ORCPT ); Tue, 10 Jan 2017 22:27:59 -0500 Subject: Re: [PATCH 0/9] IB: Optimize DMA mapping To: Bart Van Assche , Doug Ledford References: <20170111005648.14988-1-bart.vanassche@sandisk.com> Cc: linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org From: "santosh.shilimkar@oracle.com" Organization: Oracle Corporation Message-ID: <320aa1cd-8110-2724-a43d-514efc386127@oracle.com> Date: Tue, 10 Jan 2017 17:28:14 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:45.0) Gecko/20100101 Thunderbird/45.6.0 MIME-Version: 1.0 In-Reply-To: <20170111005648.14988-1-bart.vanassche@sandisk.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: userp1040.oracle.com [156.151.31.81] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/10/17 4:56 PM, Bart Van Assche wrote: > Hello Doug, > > As you know there are two sets of DMA mapping operations in the Linux > kernel: > - One set of DMA mapping operations that is used by most drivers. > - Another set of DMA mapping operations that is only used by the RDMA > drivers. > Having two sets of DMA mapping operations is not only a source of > confusion but also a source of unnecessary overhead. The DMA mapping > operations are in the hot path so it is important that the overhead > of these operations is as low as possible. Hence this patch series > that converts the RDMA code to the standard DMA mapping API and > thereby eliminates the if (dev->dma_ops) test from the hot path. An > additional benefit is that the size of HW and SW drivers that do not > use DMA is reduced by switching to dma_virt_ops. > This is really good series. I was always wondering why the extra indirection was added first place on streaming APIs. Regards, Santosh