From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758359AbYDTMsh (ORCPT ); Sun, 20 Apr 2008 08:48:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754860AbYDTMs1 (ORCPT ); Sun, 20 Apr 2008 08:48:27 -0400 Received: from 1wt.eu ([62.212.114.60]:3215 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753106AbYDTMs1 (ORCPT ); Sun, 20 Apr 2008 08:48:27 -0400 Date: Sun, 20 Apr 2008 14:47:17 +0200 From: Willy Tarreau To: Andi Kleen Cc: Adrian Bunk , Alan Cox , Shawn Bohrer , Ingo Molnar , Andrew Morton , Linux Kernel Mailing List , Arjan van de Ven , Thomas Gleixner Subject: Re: x86: 4kstacks default Message-ID: <20080420124717.GH8474@1wt.eu> References: <200804181737.m3IHbabI010051@hera.kernel.org> <20080418142934.38ce6bf4.akpm@linux-foundation.org> <20080419142329.GA5339@elte.hu> <20080419145948.GA4528@lintop> <20080420080901.GF1595@cs181133002.pp.htv.fi> <20080420090623.7b173ef1@the-village.bc.nu> <20080420085104.GG1595@cs181133002.pp.htv.fi> <20080420103611.2c0d3519@the-village.bc.nu> <20080420104444.GI1595@cs181133002.pp.htv.fi> <87y778aezh.fsf@basil.nowhere.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87y778aezh.fsf@basil.nowhere.org> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Apr 20, 2008 at 02:27:14PM +0200, Andi Kleen wrote: > Adrian Bunk writes: > > > > 6k is known to work, and there aren't many problems known with 4k. > > > > And from a QA point of view the only way of getting 4k thoroughly tested > > But you have to first ask why do you want 4k tested? Does it serve > any useful purpose in itself? I don't think so. Or you're saying > it's important to support 50k kernel threads on 32bit kernels? Clearly if I have the choice between a kernel which can run 50k threads and a kernel which does not crash under me during an I/O error, I choose the later! I don't even imagine what purpose 50k kernel threads may serve. I certainly can understand that reducing memory footprint is useful, but if we want wider testing of 4k stacks, considering they may fail in error path in complex I/O environment, it's not likely during -rc kernels that we'll detect problems, and if we push them down the throat of users in a stable release, of course they will thank us very much for crashing their NFS servers in production during peak hours. I have nothing against changing the default setting to 4k provided that it is easy to get back to the save setting (ie changing a config option, or better, a cmdline parameter). I just don't agree with the idea of forcing users to swim in the sh*t, it only brings bad reputation to Linux. What would really help would be to have 8k stacks with the lower page causing a fault and print a stack trace upon first access. That way, the safe setting would still report us useful information without putting users into trouble. Willy