Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755582AbYCKKGA (ORCPT ); Tue, 11 Mar 2008 06:06:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751366AbYCKKFx (ORCPT ); Tue, 11 Mar 2008 06:05:53 -0400 Received: from gate.in-addr.de ([212.8.193.158]:36110 "EHLO mx.in-addr.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750704AbYCKKFw (ORCPT ); Tue, 11 Mar 2008 06:05:52 -0400 X-Greylist: delayed 1478 seconds by postgrey-1.27 at vger.kernel.org; Tue, 11 Mar 2008 06:05:52 EDT Date: Mon, 10 Mar 2008 22:03:52 +0100 From: Lars Marowsky-Bree To: Alan Cox , Daniel Phillips Cc: Grzegorz Kulewski , linux-kernel@vger.kernel.org Subject: Re: [ANNOUNCE] Ramback: faster than a speeding bullet Message-ID: <20080310210352.GJ1581@marowsky-bree.de> References: <200803092346.17556.phillips@phunq.net> <200803100123.51395.phillips@phunq.net> <20080310093737.3c1e938a@core> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20080310093737.3c1e938a@core> X-Ctuhulu: HASTUR User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1404 Lines: 35 On 2008-03-10T09:37:37, Alan Cox wrote: > Why - your chunks simply become a linked list in write barrier order. > Solve your bitmap sweep cost as well. As you are already making a copy > before going to backing store you don't have the internal consistency > problems of further writes during the I/O. You get duplicated blocks though. But yes, I agree - write-backs to the disk must be ordered, other it's going to be too unreliable in practice. An in-memory buffer for a log-structured block device. > Yes you may need to throttle in the specific case of having too many > copies of pages sitting in the queue - but surely that would be the set of > pages that are written but not yet committed from a previous store > barrier ? You could switch from a journal like the above to a bitmap when this overrun occurs. (Typical problem in replication.) SteelEye holds a patent on that though, as far as I know. Regards, Lars -- Teamlead Kernel, SuSE Labs, Research and Development SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG N?rnberg) "Experience is the name everyone gives to their mistakes." -- Oscar Wilde -- 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/