From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750737AbWERPg5 (ORCPT ); Thu, 18 May 2006 11:36:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750933AbWERPg5 (ORCPT ); Thu, 18 May 2006 11:36:57 -0400 Received: from srv5.dvmed.net ([207.36.208.214]:12675 "EHLO mail.dvmed.net") by vger.kernel.org with ESMTP id S1750737AbWERPg4 (ORCPT ); Thu, 18 May 2006 11:36:56 -0400 Message-ID: <446C9492.2040704@garzik.org> Date: Thu, 18 May 2006 11:36:50 -0400 From: Jeff Garzik User-Agent: Thunderbird 1.5.0.2 (X11/20060501) MIME-Version: 1.0 To: Tejun Heo CC: Jan Wagner , linux-kernel@vger.kernel.org Subject: Re: support for sata7 Streaming Feature Set? References: <4466D6FB.1040603@gmail.com> <446BD8F2.10509@gmail.com> In-Reply-To: <446BD8F2.10509@gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -4.1 (----) X-Spam-Report: SpamAssassin version 3.1.1 on srv5.dvmed.net summary: Content analysis details: (-4.1 points, 5.0 required) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Tejun Heo wrote: > One thing to think about before supporting streaming from/to harddisks > from userland is how to make data flow efficiently from userland to > kernel and back. But, no matter what, kernel <-> userland usually > involves one data copy, so I don't think making sg similarly efficient > would be too difficult (it might be already). Actually, the kernel usually maps userland pages, eliminating the need for a copy. write(2) may have copied data into that page originally, but mmap(2) need not have. Jeff