From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754178AbbLFEYb (ORCPT ); Sat, 5 Dec 2015 23:24:31 -0500 Received: from smtp.codeaurora.org ([198.145.29.96]:37321 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753395AbbLFEY3 (ORCPT ); Sat, 5 Dec 2015 23:24:29 -0500 Subject: Re: [RFC] User space to kernel space copy optimization To: Vinod Koul References: <564A5057.9080203@codeaurora.org> <20151205081030.GM1854@localhost> Cc: dmaengine@vger.kernel.org, linux-arm-kernel@lists.infradead.org, "linux-kernel@vger.kernel.org" From: Sinan Kaya Message-ID: <5663B87D.6010808@codeaurora.org> Date: Sat, 5 Dec 2015 23:24:29 -0500 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 In-Reply-To: <20151205081030.GM1854@localhost> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/5/2015 3:10 AM, Vinod Koul wrote: > On Mon, Nov 16, 2015 at 04:53:27PM -0500, Sinan Kaya wrote: >> One of the things I'm interested in is to use a memcpy capable DMA >> engine HW to optimize user space and kernel space parameter copying. >> >> Of course, this will not be viable for all parameter sizes but I can see >> this being useful. The goal is to save power in the cost of little >> performance. >> >> Before I go and invent my own mechanism, I'd like to have ideas on what >> an acceptable solution would look like. Especially, I'm looking for a >> generic implementation that could plug into any DMA engine HW. > > Do you have a proposal on how this generic solution should look like, broad > contours of the design to start off with and we can start from that point > No, not yet. AFAIK, some of these optimization ideas have been tried by the Intel IO/AT in the past (kernel 2.6) and were rejected by the upstream. I wanted to see if anybody had better ideas these days that is upstream friendly. -- Sinan Kaya Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project