From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladislav Bolkhovitin Subject: Re: Open-FCoE on linux-scsi Date: Tue, 08 Jan 2008 20:38:29 +0300 Message-ID: <4783B515.1030001@vlnb.net> References: <10A7D0016239E24092DEF05CCC582E4302BB68C8@fmsmsx411.amr.corp.intel.com> <200801031035.m03AZYcJ012171@mbox.iij4u.or.jp> <477FCD8C.2040404@vlnb.net> <20080106103138Q.tomof@acm.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-relay-02.mailcluster.net ([77.221.130.214]:34470 "EHLO mail-relay-01.mailcluster.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751210AbYAHRiK (ORCPT ); Tue, 8 Jan 2008 12:38:10 -0500 In-Reply-To: <20080106103138Q.tomof@acm.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: FUJITA Tomonori Cc: robert.w.love@intel.com, yi.zou@intel.com, christopher.leech@intel.com, vasu.dev@intel.com, linux-scsi@vger.kernel.org, fujita.tomonori@lab.ntt.co.jp FUJITA Tomonori wrote: >>Thus, I believe, that partial user space, partial kernel space approach >>for building SCSI targets is the move in the wrong direction, because it >>brings practically nothing, but costs a lot. > > We have not discussed such topic. FCoE target can be implemented fully > in user space if I understand correctly. Really? FCoE target doesn't need an FC hardware target? And FCoE isn't sensitive to the packets forwarding latency? For fully in-kernel approach it is possible to make the packets forwarding zero-copy in both directions FC<->Ethernet, which is practically impossible with user space. Modern memory has few GB/s throughput, so guess how much latency data copying will add on 10Gbps speed. Thus, I believe, if performance matters, FCoE should be in kernel, at least hot processing path, when management possibly done in user space as for open-iscsi. But user space/kernel separation should only be done if the additional user space/kernel interface won't complicate things too much. Vlad