From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751163AbWERXM6 (ORCPT ); Thu, 18 May 2006 19:12:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751167AbWERXM6 (ORCPT ); Thu, 18 May 2006 19:12:58 -0400 Received: from wx-out-0102.google.com ([66.249.82.203]:8871 "EHLO wx-out-0102.google.com") by vger.kernel.org with ESMTP id S1751163AbWERXM5 (ORCPT ); Thu, 18 May 2006 19:12:57 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:user-agent:mime-version:to:cc:subject:references:in-reply-to:content-type:content-transfer-encoding; b=j2FV2Ot429hSLRIpqAirgI4OvYdK0RNeW/nMQoYBnzdcP1KJADZyfGEF3r8fowrV1cVTK/3+LnqiBfHbjC3EcTEJLB33lO7p/pFe0pZ13oAwgehtuQAndz2iBVrIh+xGJctOZssJXnHVNBdfou8MynpscJ9dcIe5NO/WltvvUqk= Message-ID: <446CFF77.9050008@gmail.com> Date: Fri, 19 May 2006 08:12:55 +0900 From: Tejun Heo User-Agent: Thunderbird 1.5.0.2 (X11/20060501) MIME-Version: 1.0 To: Jeff Garzik 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> <446C9492.2040704@garzik.org> In-Reply-To: <446C9492.2040704@garzik.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Jeff Garzik wrote: > 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. Yeap, to achieve high streaming rate, it would be best to have preallocated ring buffer and ring pointers. If this high-bw streaming thing becomes common, we can add it to sg, I guess. -- tejun