From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Sat, 31 Mar 2012 23:00:32 +0200 (CEST) Received: from mail-wg0-f43.google.com ([74.125.82.43]:45081 "EHLO mail-wg0-f43.google.com" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S1903631Ab2CaVAS (ORCPT ); Sat, 31 Mar 2012 23:00:18 +0200 Received: by wgbdr12 with SMTP id dr12so1367604wgb.24 for ; Sat, 31 Mar 2012 14:00:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer:content-transfer-encoding; bh=cvvbGMem4llGGSx7vHAzopZWFJXuOPwRRXOuYBt14BA=; b=Eh/BPLX58xPJw2TTpkmhXwMk53mByIXhcxI4BhB7l68ZBbnmnqR1hyNdlVOwZRiRFW AHYcKDHrfHcL/C0JW3Lj3Cqj+IRZNbF5lB/mROhbfoSQnmWixAzEQGHYfmeaHeeYRS8P Qq/12wGVWCIo+9NBu4oXc/gc8ObJ41DdevBIe1onk9UL+KU+cAJiXo9C+53uJvRLsWjb lNYPwXHPwqkTY+YogostbbUYYinjv8PP3tajMo62Ul9kRr1u176AYyIF1KKwZHeSiK2k D/gTPitONv60mxfncwAsosrryDORmQ9yeGUYkl+D1w/98WZkTmgzAeljz5POVmcjbAej s1ww== Received: by 10.180.88.199 with SMTP id bi7mr9309940wib.12.1333227613215; Sat, 31 Mar 2012 14:00:13 -0700 (PDT) Received: from [192.168.179.45] ([74.125.122.49]) by mx.google.com with ESMTPS id j3sm30752149wiw.1.2012.03.31.14.00.09 (version=SSLv3 cipher=OTHER); Sat, 31 Mar 2012 14:00:12 -0700 (PDT) Subject: Re: [PATCH RFC] Simplify the Linux kernel by reducing its state space From: Eric Dumazet To: paulmck@linux.vnet.ibm.com Cc: linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, uclinux-dist-devel@blackfin.uclinux.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m32r@ml.linux-m32r.org, linux-m32r-ja@ml.linux-m32r.org, linux-mips@linux-mips.org, linux-am33-list@redhat.com, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, tglx@linutronix.de, linux@arm.linux.org.uk, dhowells@redhat.com, jejb@parisc-linux.org, linux390@de.ibm.com, x86@kernel.org, cmetcalf@tilera.com In-Reply-To: <20120331163321.GA15809@linux.vnet.ibm.com> References: <20120331163321.GA15809@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Date: Sat, 31 Mar 2012 23:00:08 +0200 Message-ID: <1333227608.2325.4054.camel@edumazet-glaptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit X-archive-position: 32844 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: eric.dumazet@gmail.com Precedence: bulk X-list: linux-mips Return-Path: On Sun, 2012-04-01 at 00:33 +0800, Paul E. McKenney wrote: > Although there have been numerous complaints about the complexity of > parallel programming (especially over the past 5-10 years), the plain > truth is that the incremental complexity of parallel programming over > that of sequential programming is not as large as is commonly believed. > Despite that you might have heard, the mind-numbing complexity of modern > computer systems is not due so much to there being multiple CPUs, but > rather to there being any CPUs at all. In short, for the ultimate in > computer-system simplicity, the optimal choice is NR_CPUS=0. > > This commit therefore limits kernel builds to zero CPUs. This change > has the beneficial side effect of rendering all kernel bugs harmless. > Furthermore, this commit enables additional beneficial changes, for > example, the removal of those parts of the kernel that are not needed > when there are zero CPUs. > > Signed-off-by: Paul E. McKenney > Reviewed-by: Thomas Gleixner > --- Hmm... I believe you could go one step forward and allow negative values as well. Antimatter was proven to exist after all. Hint : nr_cpu_ids is an "int", not an "unsigned int" Bonus: Existing bugs become "must have" features. Of course there is no hurry and this can wait 365 days.