From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 24 Aug 2001 20:53:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 24 Aug 2001 20:53:28 -0400 Received: from humbolt.nl.linux.org ([131.211.28.48]:5644 "EHLO humbolt.nl.linux.org") by vger.kernel.org with ESMTP id ; Fri, 24 Aug 2001 20:53:18 -0400 Content-Type: text/plain; charset=US-ASCII From: Daniel Phillips To: otto.wyss@bluewin.ch, "linux-kernel@vger.kernel.org" Subject: Re: Why don't have bits the same rights as humans! (flushing to disk waiting time) Date: Sat, 25 Aug 2001 03:00:07 +0200 X-Mailer: KMail [version 1.3.1] In-Reply-To: <3B802B68.ADA545DB@bluewin.ch> In-Reply-To: <3B802B68.ADA545DB@bluewin.ch> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Message-Id: <20010825005328Z16138-32383+1259@humbolt.nl.linux.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On August 19, 2001 11:11 pm, Otto Wyss wrote: > I recently wrote some small files to the floppy disk and noticed almost nothing > happened immediately but after a certain time the floppy actually started > writing. So this action took more than 30 seconds instead just a few. This > remembered me of the elevator problem in the kernel. To transfer this example > into real live: A person who wants to take the elevator has to wait 8 hours > before the elevator even starts. While probably everyone agrees this is > ridiculous in real live astonishingly nobody complains about it in case of a disk. My early flush patch, posted a month or so ago, takes care of this nicely. I'm just waiting for 2.5 to roll around to do some more work on it. > [...] > Could anybody produce any real figures to prove/disprove my theory? Could > anybody benchmark the disk access for the 3 waiting times (0, 200ms 30sec) with > different loads? Your theory is correct. I implemented the idea, took measurements, and found dramatic performance improvements under some loads, while getting worse on none. You can search lwn.net for a nice writeup by Jonathan Corbett. -- Daniel