From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761638AbZBEBIo (ORCPT ); Wed, 4 Feb 2009 20:08:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760379AbZBEBI1 (ORCPT ); Wed, 4 Feb 2009 20:08:27 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:36137 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761042AbZBEBI0 (ORCPT ); Wed, 4 Feb 2009 20:08:26 -0500 Date: Thu, 5 Feb 2009 02:08:11 +0100 From: Ingo Molnar To: Bron Gondwana , Davide Libenzi Cc: Linus Torvalds , Norbert Preining , "Rafael J. Wysocki" , Linux Kernel Mailing List , Jens Axboe , Hiroshi Shimamoto Subject: Re: 2.6.29-rc3-git6: Reported regressions from 2.6.28 Message-ID: <20090205010811.GA5152@elte.hu> References: <20090204181109.GR21085@gamma.logic.tuwien.ac.at> <20090204185606.GA12991@elte.hu> <20090204222256.GA6954@brong.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090204222256.GA6954@brong.net> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (Cc:-ed Davide) * Bron Gondwana wrote: > On Wed, Feb 04, 2009 at 07:56:06PM +0100, Ingo Molnar wrote: > > [...] it is a natural reaction: > > they only see the small trivial annoyance they intruduce themselves - > > which is in a code area and usecase they are prominently familiar with, > > so they cannot personally relate to the trouble that users go through if > > they hit such issues. > > Amen. Preach it. I spent quite a while just a week ago arguing that > every semi-loaded machine out there using epoll should not require the > admin to discover that their previously happy software stack was suddenly > hitting an artificially tiny per-user instances count. > > Luckily I was able to find multiple blog posts and mailing list archives > with people who had literally spent _days_ tracking down why things had > broken for them when they upgraded to a new -stable kernel. > > You really do have to assume that your users don't have time for this > shit. Anything that really can't DTRT automatically needs to be covered > with plenty of easy to follow instructions on how to fix the problem - > because for someone unfamiliar with that area of the system it really does > take enormous effort to track down what's changed. do you know which commit that was (or which exact tunable default value it is about) and whether we could restore the old default safely, and whether there's some reasonable minium must-have value that still works well in practice? With Moore's law still alive and kicking there's normally no reason to narrow defaults - if then they get increased or get changed to some auto-size-to-hw-capabilities dynamic method. Upstream defaults usually get narrowed only for really good reasons and often the reason is DoS and security and a specific testcase that kills a default box with a too large default. Sometimes they get narrowed spuriously and then we can fix things reasonably. Ingo