Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754739AbZCZDDT (ORCPT ); Wed, 25 Mar 2009 23:03:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750822AbZCZDDJ (ORCPT ); Wed, 25 Mar 2009 23:03:09 -0400 Received: from an-out-0708.google.com ([209.85.132.240]:12943 "EHLO an-out-0708.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750738AbZCZDDH convert rfc822-to-8bit (ORCPT ); Wed, 25 Mar 2009 23:03:07 -0400 MIME-Version: 1.0 In-Reply-To: <49CAEDA7.1080902@garzik.org> References: <20090324093245.GA22483@elte.hu> <20090325150041.GM32307@mit.edu> <20090325185824.GO32307@mit.edu> <20090325194851.GA1617@infradead.org> <20090325215016.GP32307@mit.edu> <20090326021034.GA26559@srcf.ucam.org> <49CAEDA7.1080902@garzik.org> Date: Wed, 25 Mar 2009 23:03:03 -0400 Message-ID: Subject: Re: Linux 2.6.29 From: Kyle Moffett To: Jeff Garzik Cc: Matthew Garrett , Theodore Tso , Christoph Hellwig , Linus Torvalds , Jan Kara , Andrew Morton , Ingo Molnar , Alan Cox , Arjan van de Ven , Peter Zijlstra , Nick Piggin , Jens Axboe , David Rees , Jesper Krogh , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1175 Lines: 26 On Wed, Mar 25, 2009 at 10:51 PM, Jeff Garzik wrote: > Then you have just reinvented the transactional userspace API that people > often want to replace POSIX API with.  Maybe one day they will succeed. > > But "POSIX API replacement" is an area never short of proposals... :) Well, I think the goal is not to *replace* the POSIX API or even provide "transactional" guarantees. The performance penalty for atomic transactions is pretty high, and most programs (like GIT) don't really give a damn, as they provide that on a higher level. It's like the difference between a modern SMP system that supports memory barriers and write snooping and one of the theoretical "transactional memory" designs that have never caught on. To be honest I think we could provide much better data consistency guarantees and remove a lot of fsync() calls with just a basic per-filesystem barrier() call. Cheers, Kyle Moffett -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/