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 <paulmck@xxxxxxxxxxxxxxxxxx> > > Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > --- > > 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
