Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933187AbZC0AbG (ORCPT ); Thu, 26 Mar 2009 20:31:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933118AbZC0Aan (ORCPT ); Thu, 26 Mar 2009 20:30:43 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:44719 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933115AbZC0Aam (ORCPT ); Thu, 26 Mar 2009 20:30:42 -0400 Date: Thu, 26 Mar 2009 17:27:43 -0700 (PDT) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: Andrew Morton cc: Theodore Tso , David Rees , Jesper Krogh , Linux Kernel Mailing List Subject: Re: Linux 2.6.29 In-Reply-To: <20090326171148.9bf8f1ec.akpm@linux-foundation.org> Message-ID: References: <49C87B87.4020108@krogh.cc> <72dbd3150903232346g5af126d7sb5ad4949a7b5041f@mail.gmail.com> <49C88C80.5010803@krogh.cc> <72dbd3150903241200v38720ca0x392c381f295bdea@mail.gmail.com> <20090325183011.GN32307@mit.edu> <20090325220530.GR32307@mit.edu> <20090326171148.9bf8f1ec.akpm@linux-foundation.org> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1504 Lines: 43 On Thu, 26 Mar 2009, Andrew Morton wrote: > > userspace can do it quite easily. Run a self-tuning script after > installation and when the disk hardware changes significantly. Uhhuh. "user space can do it". That's the global cop-out. The fact is, user-space isn't doing it, and never has done anything even _remotely_ like it. In fact, I claim that it's impossible to do. If you give me a number for the throughput of your harddisk, I will laugh in your face and call you a moron. Why? Because no such number exists. It depends on the access patterns. If you write one large file, the number will be very different (and not just by a few percent) from the numbers of you writing thousands of small files, or re-writing a large database in random order. So no. User space CAN NOT DO IT, and the fact that you even claim something like that shows a distinct lack of thought. > Maybe we should set the tunables to 99.9% to make it suck enough to > motivate someone. The only times tunables have worked for us is when they auto-tune. IOW, we don't have "use 35% of memory for buffer cache" tunables, we just dynamically auto-tune memory use. And no, we don't expect user space to run some "tuning program for their load" either. Linus -- 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/