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