Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754961AbZCYVeR (ORCPT ); Wed, 25 Mar 2009 17:34:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753148AbZCYVeB (ORCPT ); Wed, 25 Mar 2009 17:34:01 -0400 Received: from srv5.dvmed.net ([207.36.208.214]:60457 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752685AbZCYVeA (ORCPT ); Wed, 25 Mar 2009 17:34:00 -0400 Message-ID: <49CAA31B.7080107@garzik.org> Date: Wed, 25 Mar 2009 17:33:15 -0400 From: Jeff Garzik User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Linus Torvalds CC: Theodore Tso , Ingo Molnar , Alan Cox , Arjan van de Ven , Andrew Morton , Peter Zijlstra , Nick Piggin , David Rees , Jesper Krogh , Linux Kernel Mailing List Subject: Re: Linux 2.6.29 References: <20090324093245.GA22483@elte.hu> <20090324101011.6555a0b9@lxorguk.ukuu.org.uk> <20090324103111.GA26691@elte.hu> <20090324132032.GK5814@mit.edu> <20090324184549.GE32307@mit.edu> <49C93AB0.6070300@garzik.org> <20090325093913.GJ27476@kernel.dk> <49CA86BD.6060205@garzik.org> <20090325194341.GB27476@kernel.dk> <49CA9346.6040108@garzik.org> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -4.4 (----) X-Spam-Report: SpamAssassin version 3.2.5 on srv5.dvmed.net summary: Content analysis details: (-4.4 points, 5.0 required) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1026 Lines: 25 Linus Torvalds wrote: > OS X, for example, doesn't do the disk barrier. It requires you to do a > separate FULL_FSYNC (or something similar) ioctl to get that. Apparently > exactly because users don't expect quite _that_ big of a performance hit. I can understand that, more from an admin standpoint than anything... ATA disks' FLUSH CACHE is horribly coarse-grained, all-or-nothing. SCSI's SYNCHRONIZE CACHE at least gives us an optional (LBA, length) pair that can be used to avoid to flushing everything in the cache. Microsoft has publicly proposed a WRITE BARRIER command for ATA, to try and improve the situation: http://www.t13.org/Documents/UploadedDocuments/docs2007/e07174r0-Write_Barrier_Command_Proposal.doc but that isn't in the field yet (if ever?) Jeff -- 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/