Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 28 Feb 2002 15:14:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 28 Feb 2002 15:13:04 -0500 Received: from atrey.karlin.mff.cuni.cz ([195.113.31.123]:21779 "EHLO atrey.karlin.mff.cuni.cz") by vger.kernel.org with ESMTP id ; Thu, 28 Feb 2002 15:12:53 -0500 Date: Thu, 28 Feb 2002 21:12:48 +0100 From: Pavel Machek To: Andrew Morton Cc: kernel list Subject: Re: Sync over loop devices takes ages? [2.4.17] Message-ID: <20020228201248.GA20466@atrey.karlin.mff.cuni.cz> In-Reply-To: <20020228095955.GH774@elf.ucw.cz> <3C7E716E.9DC59B12@zip.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3C7E716E.9DC59B12@zip.com.au> User-Agent: Mutt/1.3.24i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > I have a script (attached). At one point it tries to do sync... That > > sync take a long time, with disk mostly unused. > > When doing (say) ext2-on-loop-on-ext2 you should always ensure > that the blocksize for the topmost filesystem is the same as > the one underneath. So probably you wanted `mkfs.ext2 -b 4096'. > > If you have a 1k blocksize filesystem loop-mounted on a 4k blocksize > filesystem, every write of a 1k block requires a read of the underlying > 4k block. Which is excrutiatingly slow. Oh, but I *want* to do 1k filesystem test! Performance seems okay in 2.4.19-pre?aa?.... And even 2.4.18 is slightly faster. [BTW it is fully cached (100MB test on 256MB machine) so 4k reads should not be such a big problem.] Pavel -- Casualities in World Trade Center: ~3k dead inside the building, cryptography in U.S.A. and free speech in Czech Republic. - 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/