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    SubjectRe: [PATCH RFC] Simplify the Linux kernel by reducing its state space
    On Sun, Apr 01, 2012 at 12:19:25AM +0200, Lorenz Kolb wrote:
    > 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.

    Perhaps a branch on a public git tree? If you are doing what I suspect
    you are, you will end up with a very large patch set. ;-)

    Thanx, Paul

    > 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<paulmck@linux.vnet.ibm.com>
    > >>>Reviewed-by: Thomas Gleixner<tglx@linutronix.de>
    > >>>---
    > >>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
    >



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