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