From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH RFC] Simplify the Linux kernel by reducing its state space Date: Sat, 31 Mar 2012 09:54:01 -0700 Message-ID: <20120331165401.GD2450@linux.vnet.ibm.com> References: <20120331163321.GA15809@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-hexagon-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="iso-8859-1" To: Geert Uytterhoeven 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, linux-m68k On Sat, Mar 31, 2012 at 06:40:30PM +0200, Geert Uytterhoeven wrote: > Hi Paul, >=20 > On Sat, Mar 31, 2012 at 18:33, Paul E. McKenney > wrote: > > Although there have been numerous complaints about the complexity o= f > > parallel programming (especially over the past 5-10 years), the pla= in > > truth is that the incremental complexity of parallel programming ov= er > > that of sequential programming is not as large as is commonly belie= ved. > > Despite that you might have heard, the mind-numbing complexity of m= odern > > computer systems is not due so much to there being multiple CPUs, b= ut > > rather to there being any CPUs at all. =A0In short, for the ultimat= e in > > computer-system simplicity, the optimal choice is NR_CPUS=3D0. > > > > This commit therefore limits kernel builds to zero CPUs. =A0This ch= ange > > has the beneficial side effect of rendering all kernel bugs harmles= s. > > Furthermore, this commit enables additional beneficial changes, for > > example, the removal of those parts of the kernel that are not need= ed > > when there are zero CPUs. > > > > Signed-off-by: Paul E. McKenney > > Reviewed-by: Thomas Gleixner > > --- > > > > =A0alpha/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 11 += +++++----- > > =A0arm/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0= 6 +++--- > > =A0blackfin/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A03 += +- > > =A0hexagon/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A09 += ++++---- > > =A0ia64/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0= 9 +++++---- > > =A0m32r/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 10= ++++++---- > > =A0mips/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 21= +++++++++++---------- > > =A0mn10300/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A03 += +- > > =A0parisc/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A06= +++--- > > =A0powerpc/platforms/Kconfig.cputype | =A0 =A08 ++++---- > > =A0s390/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 12= +++++++----- > > =A0sh/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 = 11 ++++++----- > > =A0sparc/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A08= ++++---- > > =A0tile/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0= 9 +++++---- > > =A0x86/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 16= +++++++++------- > > =A015 files changed, 78 insertions(+), 64 deletions(-) >=20 > You forgot to fix half of the architectures, a.o. m68k? I must confess that I fixed only the SMP-capable architectures. I of course would welcome additions for UP-only architectures. Thanx, Paul From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Date: Sat, 31 Mar 2012 16:54:01 +0000 Subject: Re: [PATCH RFC] Simplify the Linux kernel by reducing its state space Message-Id: <20120331165401.GD2450@linux.vnet.ibm.com> List-Id: References: <20120331163321.GA15809@linux.vnet.ibm.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: linux-arm-kernel@lists.infradead.org On Sat, Mar 31, 2012 at 06:40:30PM +0200, Geert Uytterhoeven wrote: > Hi Paul, >=20 > On Sat, Mar 31, 2012 at 18:33, 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. =A0In short, for the ultimate in > > computer-system simplicity, the optimal choice is NR_CPUS=3D0. > > > > This commit therefore limits kernel builds to zero CPUs. =A0This 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 > > --- > > > > =A0alpha/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 11 +++++= +----- > > =A0arm/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A06 += ++--- > > =A0blackfin/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A03 ++- > > =A0hexagon/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A09 +++++= ---- > > =A0ia64/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A09 += ++++---- > > =A0m32r/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 10 +++= +++---- > > =A0mips/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 21 +++= ++++++++---------- > > =A0mn10300/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A03 ++- > > =A0parisc/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A06 +++= --- > > =A0powerpc/platforms/Kconfig.cputype | =A0 =A08 ++++---- > > =A0s390/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 12 +++= ++++----- > > =A0sh/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 11 += +++++----- > > =A0sparc/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A08 +++= +---- > > =A0tile/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A09 += ++++---- > > =A0x86/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 16 +++= ++++++------- > > =A015 files changed, 78 insertions(+), 64 deletions(-) >=20 > You forgot to fix half of the architectures, a.o. m68k? I must confess that I fixed only the SMP-capable architectures. I of course would welcome additions for UP-only architectures. Thanx, Paul From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH RFC] Simplify the Linux kernel by reducing its state space Date: Sat, 31 Mar 2012 09:54:01 -0700 Message-ID: <20120331165401.GD2450@linux.vnet.ibm.com> References: <20120331163321.GA15809@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 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, linux-m68k To: Geert Uytterhoeven Return-path: In-Reply-To: List-ID: List-Id: linux-parisc.vger.kernel.org On Sat, Mar 31, 2012 at 06:40:30PM +0200, Geert Uytterhoeven wrote: > Hi Paul, >=20 > On Sat, Mar 31, 2012 at 18:33, Paul E. McKenney > wrote: > > Although there have been numerous complaints about the complexity o= f > > parallel programming (especially over the past 5-10 years), the pla= in > > truth is that the incremental complexity of parallel programming ov= er > > that of sequential programming is not as large as is commonly belie= ved. > > Despite that you might have heard, the mind-numbing complexity of m= odern > > computer systems is not due so much to there being multiple CPUs, b= ut > > rather to there being any CPUs at all. =A0In short, for the ultimat= e in > > computer-system simplicity, the optimal choice is NR_CPUS=3D0. > > > > This commit therefore limits kernel builds to zero CPUs. =A0This ch= ange > > has the beneficial side effect of rendering all kernel bugs harmles= s. > > Furthermore, this commit enables additional beneficial changes, for > > example, the removal of those parts of the kernel that are not need= ed > > when there are zero CPUs. > > > > Signed-off-by: Paul E. McKenney > > Reviewed-by: Thomas Gleixner > > --- > > > > =A0alpha/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 11 += +++++----- > > =A0arm/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0= 6 +++--- > > =A0blackfin/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A03 += +- > > =A0hexagon/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A09 += ++++---- > > =A0ia64/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0= 9 +++++---- > > =A0m32r/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 10= ++++++---- > > =A0mips/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 21= +++++++++++---------- > > =A0mn10300/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A03 += +- > > =A0parisc/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A06= +++--- > > =A0powerpc/platforms/Kconfig.cputype | =A0 =A08 ++++---- > > =A0s390/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 12= +++++++----- > > =A0sh/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 = 11 ++++++----- > > =A0sparc/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A08= ++++---- > > =A0tile/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0= 9 +++++---- > > =A0x86/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 16= +++++++++------- > > =A015 files changed, 78 insertions(+), 64 deletions(-) >=20 > You forgot to fix half of the architectures, a.o. m68k? I must confess that I fixed only the SMP-capable architectures. I of course would welcome additions for UP-only architectures. Thanx, Paul From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e35.co.us.ibm.com (e35.co.us.ibm.com [32.97.110.153]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e35.co.us.ibm.com", Issuer "Equifax" (not verified)) by ozlabs.org (Postfix) with ESMTPS id E1FE4B6F9D for ; Sun, 1 Apr 2012 02:54:21 +1000 (EST) Received: from /spool/local by e35.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sat, 31 Mar 2012 10:54:16 -0600 Received: from d03relay04.boulder.ibm.com (d03relay04.boulder.ibm.com [9.17.195.106]) by d03dlp01.boulder.ibm.com (Postfix) with ESMTP id 564F61FF0048 for ; Sat, 31 Mar 2012 10:54:13 -0600 (MDT) Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by d03relay04.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q2VGsDl7144676 for ; Sat, 31 Mar 2012 10:54:13 -0600 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q2VGsBSO008773 for ; Sat, 31 Mar 2012 10:54:13 -0600 Date: Sat, 31 Mar 2012 09:54:01 -0700 From: "Paul E. McKenney" To: Geert Uytterhoeven Subject: Re: [PATCH RFC] Simplify the Linux kernel by reducing its state space Message-ID: <20120331165401.GD2450@linux.vnet.ibm.com> References: <20120331163321.GA15809@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: Cc: linux-m32r-ja@ml.linux-m32r.org, linux-mips@linux-mips.org, linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, dhowells@redhat.com, sparclinux@vger.kernel.org, linux-s390@vger.kernel.org, linux-am33-list@redhat.com, linux@arm.linux.org.uk, linux-hexagon@vger.kernel.org, x86@kernel.org, jejb@parisc-linux.org, cmetcalf@tilera.com, linux-m68k , uclinux-dist-devel@blackfin.uclinux.org, tglx@linutronix.de, linux-arm-kernel@lists.infradead.org, linux-m32r@ml.linux-m32r.org, linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, linux390@de.ibm.com, linuxppc-dev@lists.ozlabs.org Reply-To: paulmck@linux.vnet.ibm.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Sat, Mar 31, 2012 at 06:40:30PM +0200, Geert Uytterhoeven wrote: > Hi Paul, > > On Sat, Mar 31, 2012 at 18:33, 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 > > --- > > > >  alpha/Kconfig                     |   11 ++++++----- > >  arm/Kconfig                       |    6 +++--- > >  blackfin/Kconfig                  |    3 ++- > >  hexagon/Kconfig                   |    9 +++++---- > >  ia64/Kconfig                      |    9 +++++---- > >  m32r/Kconfig                      |   10 ++++++---- > >  mips/Kconfig                      |   21 +++++++++++---------- > >  mn10300/Kconfig                   |    3 ++- > >  parisc/Kconfig                    |    6 +++--- > >  powerpc/platforms/Kconfig.cputype |    8 ++++---- > >  s390/Kconfig                      |   12 +++++++----- > >  sh/Kconfig                        |   11 ++++++----- > >  sparc/Kconfig                     |    8 ++++---- > >  tile/Kconfig                      |    9 +++++---- > >  x86/Kconfig                       |   16 +++++++++------- > >  15 files changed, 78 insertions(+), 64 deletions(-) > > You forgot to fix half of the architectures, a.o. m68k? I must confess that I fixed only the SMP-capable architectures. I of course would welcome additions for UP-only architectures. Thanx, Paul From mboxrd@z Thu Jan 1 00:00:00 1970 From: paulmck@linux.vnet.ibm.com (Paul E. McKenney) Date: Sat, 31 Mar 2012 09:54:01 -0700 Subject: [PATCH RFC] Simplify the Linux kernel by reducing its state space In-Reply-To: References: <20120331163321.GA15809@linux.vnet.ibm.com> Message-ID: <20120331165401.GD2450@linux.vnet.ibm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Sat, Mar 31, 2012 at 06:40:30PM +0200, Geert Uytterhoeven wrote: > Hi Paul, > > On Sat, Mar 31, 2012 at 18:33, 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 > > --- > > > > ?alpha/Kconfig ? ? ? ? ? ? ? ? ? ? | ? 11 ++++++----- > > ?arm/Kconfig ? ? ? ? ? ? ? ? ? ? ? | ? ?6 +++--- > > ?blackfin/Kconfig ? ? ? ? ? ? ? ? ?| ? ?3 ++- > > ?hexagon/Kconfig ? ? ? ? ? ? ? ? ? | ? ?9 +++++---- > > ?ia64/Kconfig ? ? ? ? ? ? ? ? ? ? ?| ? ?9 +++++---- > > ?m32r/Kconfig ? ? ? ? ? ? ? ? ? ? ?| ? 10 ++++++---- > > ?mips/Kconfig ? ? ? ? ? ? ? ? ? ? ?| ? 21 +++++++++++---------- > > ?mn10300/Kconfig ? ? ? ? ? ? ? ? ? | ? ?3 ++- > > ?parisc/Kconfig ? ? ? ? ? ? ? ? ? ?| ? ?6 +++--- > > ?powerpc/platforms/Kconfig.cputype | ? ?8 ++++---- > > ?s390/Kconfig ? ? ? ? ? ? ? ? ? ? ?| ? 12 +++++++----- > > ?sh/Kconfig ? ? ? ? ? ? ? ? ? ? ? ?| ? 11 ++++++----- > > ?sparc/Kconfig ? ? ? ? ? ? ? ? ? ? | ? ?8 ++++---- > > ?tile/Kconfig ? ? ? ? ? ? ? ? ? ? ?| ? ?9 +++++---- > > ?x86/Kconfig ? ? ? ? ? ? ? ? ? ? ? | ? 16 +++++++++------- > > ?15 files changed, 78 insertions(+), 64 deletions(-) > > You forgot to fix half of the architectures, a.o. m68k? I must confess that I fixed only the SMP-capable architectures. I of course would welcome additions for UP-only architectures. Thanx, Paul From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751300Ab2CaQy5 (ORCPT ); Sat, 31 Mar 2012 12:54:57 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:50295 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750944Ab2CaQy4 (ORCPT ); Sat, 31 Mar 2012 12:54:56 -0400 Date: Sat, 31 Mar 2012 09:54:01 -0700 From: "Paul E. McKenney" To: Geert Uytterhoeven 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, linux-m68k Subject: Re: [PATCH RFC] Simplify the Linux kernel by reducing its state space Message-ID: <20120331165401.GD2450@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20120331163321.GA15809@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12033116-2398-0000-0000-0000057A47C8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Mar 31, 2012 at 06:40:30PM +0200, Geert Uytterhoeven wrote: > Hi Paul, > > On Sat, Mar 31, 2012 at 18:33, 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 > > --- > > > >  alpha/Kconfig                     |   11 ++++++----- > >  arm/Kconfig                       |    6 +++--- > >  blackfin/Kconfig                  |    3 ++- > >  hexagon/Kconfig                   |    9 +++++---- > >  ia64/Kconfig                      |    9 +++++---- > >  m32r/Kconfig                      |   10 ++++++---- > >  mips/Kconfig                      |   21 +++++++++++---------- > >  mn10300/Kconfig                   |    3 ++- > >  parisc/Kconfig                    |    6 +++--- > >  powerpc/platforms/Kconfig.cputype |    8 ++++---- > >  s390/Kconfig                      |   12 +++++++----- > >  sh/Kconfig                        |   11 ++++++----- > >  sparc/Kconfig                     |    8 ++++---- > >  tile/Kconfig                      |    9 +++++---- > >  x86/Kconfig                       |   16 +++++++++------- > >  15 files changed, 78 insertions(+), 64 deletions(-) > > You forgot to fix half of the architectures, a.o. m68k? I must confess that I fixed only the SMP-capable architectures. I of course would welcome additions for UP-only architectures. Thanx, Paul