From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lorenz Kolb Subject: Re: [PATCH RFC] Simplify the Linux kernel by reducing its state space Date: Sun, 01 Apr 2012 00:19:25 +0200 Message-ID: <4F7782ED.7050407@lkmail.de> References: <20120331163321.GA15809@linux.vnet.ibm.com> <1333227608.2325.4054.camel@edumazet-glaptop> <20120331212149.GI2450@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120331212149.GI2450@linux.vnet.ibm.com> Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: paulmck@linux.vnet.ibm.com Cc: Eric Dumazet , 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, 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 With that patchset in mind, I am working on a really huge patch, which will greatly simplify the Linux kernel for the real problem of having that number of CPUs. That patch will have a lot of changes all over the architectures, so what will be the best way to post it? Should I split it architecture dependend and into one generic part. Currently it is a large blob of millions of changes, but will greatly simplify the Linux kernel. Regards, Lorenz Kolb Am 31.03.2012 23:21, schrieb Paul E. McKenney: > On Sat, Mar 31, 2012 at 11:00:08PM +0200, Eric Dumazet wrote: > >> 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. >> > James Bottomley suggested imaginary numbers of CPUs some time back, > and I suppose there is no reason you cannot have fractional numbers of > CPUs, and perhaps irrational numbers as well. Of course, these last two > would require use of floating-point arithmetic (or something similar) > in the kernel. So I guess we have at several years worth. Over to you > for the negative numbers. ;-) > > Thanx, Paul > > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev >