Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761535AbXFTEYt (ORCPT ); Wed, 20 Jun 2007 00:24:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755434AbXFTEYl (ORCPT ); Wed, 20 Jun 2007 00:24:41 -0400 Received: from mx1.redhat.com ([66.187.233.31]:33159 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753200AbXFTEYl (ORCPT ); Wed, 20 Jun 2007 00:24:41 -0400 Date: Wed, 20 Jun 2007 00:24:34 -0400 From: Dave Jones To: Andrew Morton Cc: tim.c.chen@linux.intel.com, linux-kernel@vger.kernel.org, Linus Torvalds Subject: Re: Change in default vm_dirty_ratio Message-ID: <20070620042434.GC12096@redhat.com> Mail-Followup-To: Dave Jones , Andrew Morton , tim.c.chen@linux.intel.com, linux-kernel@vger.kernel.org, Linus Torvalds References: <1182201271.4883.22.camel@localhost.localdomain> <20070618164711.9de1c38e.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070618164711.9de1c38e.akpm@linux-foundation.org> User-Agent: Mutt/1.5.14 (2007-02-12) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1993 Lines: 45 On Mon, Jun 18, 2007 at 04:47:11PM -0700, Andrew Morton wrote: > Frankly, I find it very depressing that the kernel defaults matter. These > things are trivially tunable and you'd think that after all these years, > distro initscripts would be establishing the settings, based upon expected > workload, amount of memory, number and bandwidth of attached devices, etc. "This is hard, lets make it someone else's problem" shouldn't ever be the answer, especially if the end result is that we become even more dependant on bits of userspace running before the system becomes useful. > Heck, there should even be userspace daemons which observe ongoing system > behaviour and which adaptively tune these things to the most appropriate > level. > > But nope, nothing. See the 'libtune' crack that people have been trying to get distros to adopt for a long time. If we need some form of adaptive behaviour, the kernel needs to be doing this monitoring/adapting, not some userspace daemon that may not get scheduled before its too late. If the kernel can't get the defaults right, what makes you think userspace can do better ? Just as the kernel can't get "one size fits all" right, there's no silver bullet just by clicking "this is a database server" button to have it configure random sysctls etc. These things require thought and planning that daemons will never get right in every case. And when they get it wrong, the results can be worse than the stock defaults. libtune is the latest in a series of attempts to do this dynamic runtime adjustment (hell, I even started such a project myself back circa 2000 which thankfully never really took off). It's a bad idea that just won't die. Dave -- http://www.codemonkey.org.uk - 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/