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