Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755248Ab1DAUKV (ORCPT ); Fri, 1 Apr 2011 16:10:21 -0400 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:40427 "EHLO www.etchedpixels.co.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753974Ab1DAUKU (ORCPT ); Fri, 1 Apr 2011 16:10:20 -0400 Date: Fri, 1 Apr 2011 21:10:49 +0100 From: Alan Cox To: Charles Samuels Cc: "linux-kernel@vger.kernel.org" Subject: Re: Queuing of disk writes Message-ID: <20110401211049.6c183cfc@lxorguk.ukuu.org.uk> In-Reply-To: <201104011259.53936.charles@cariden.com> References: <201104011259.53936.charles@cariden.com> X-Mailer: Claws Mail 3.7.8 (GTK+ 2.22.0; x86_64-redhat-linux-gnu) Face: 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 Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 961 Lines: 24 > the kernel's write cache, and then consequently the disk drive's DMA queue. As > a result of that, the harddrive can pick the correct order to do these writes, > significantly reducing seek times. Well that depends a lot on the data, if its very scattered and random it may not help much. > And yes, I *know* fsync is a poor method to determine if data is actually > committed to something non-volatile. :) fsync/fdatasync should at least make sure it hit the disk. If barriers are enabled the rest too. What file system are you using - some of the file systems have serious limits in this are around fsync and ordering and you may be hitting those. The ultima answer is probably an SSD of course 8) Alan -- 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/