From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladislav Bolkhovitin Subject: Re: [PATCH 2.6.25.1] Add scsi_execute_async_fifo() Date: Fri, 02 May 2008 22:09:51 +0400 Message-ID: <481B58EF.2030707@vlnb.net> References: <200805021638.42972.bart.vanassche@gmail.com> <20080502153306.GB7376@infradead.org> <20080502155525.GA16353@infradead.org> <1209745084.3121.39.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=KOI8-R; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-relay-01.mailcluster.net ([77.221.130.213]:34347 "EHLO mail-relay-01.mailcluster.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755822AbYEBSio (ORCPT ); Fri, 2 May 2008 14:38:44 -0400 In-Reply-To: <1209745084.3121.39.camel@localhost.localdomain> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: Bart Van Assche , Christoph Hellwig , linux-scsi@vger.kernel.org, scst-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org James Bottomley wrote: > On Fri, 2008-05-02 at 18:06 +0200, Bart Van Assche wrote: >> On Fri, May 2, 2008 at 5:55 PM, Christoph Hellwig wrote: >>> On Fri, May 02, 2008 at 05:53:22PM +0200, Bart Van Assche wrote: >>>> Regarding out-of-tree modules: this is just a preparatory step before >>>> submitting SCST for inclusion in the mainstream kernel. >>> And what crackpipe did you smoke to thing we'd put duplicated target >>> framework in? >> Why are you so aggressive ? I didn't insult you in any way. >> >> Regarding inclusion of SCSI target code in the mainline, this subject >> has already been discussed extensively in the past >> (http://lkml.org/lkml/2008/1/23/134). The conclusion was clear: SCST >> is faster than any other existing iSCSI target for Linux (IET, STGT, >> LIO), stable, well maintained and the most standards compliant target. >> Why do you want to reopen this discussion ? > > That's an interesting rewrite of history. The evidence you presented > showed fairly identical results apart from on one contrived IB benchmark > that couldn't directly compare the two. > > I'm also on record in the thread saying that was insufficient proof for > me to justify throwing STGT out and replacing it with SCST. James, why do you keep ignoring important points, written by me in that e-mail: http://lkml.org/lkml/2008/1/30/178? Namely: 1. Solid architecture of SCST is inherently more simple than distributed user/kernel space processing, when kernel behaves under control of user space, used in STGT, and allows to get better results with less effort. Better in all aspects: simplicity (hence, maintainability), reliability and performance. Linux once made step away from microkernel based design and that was for really good reasons. 2. Zero-copy operations with page cache will halve processing latency on high speed links, like InfiniBand, and it is impossible to implement that in a sane way with STGT approach, while for SCST it can be implemented simply and naturally. Vlad