linux-kernel - Re: [PATCH RFC] Simplify the Linux kernel by reducing its state space

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Date:	Sun, 01 Apr 2012 00:19:25 +0200
From:	Lorenz Kolb <linuxppcemb@...ail.de>
To:	paulmck@...ux.vnet.ibm.com
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	linux-m32r-ja@...linux-m32r.org, linux-mips@...ux-mips.org,
	linux-ia64@...r.kernel.org, linux-sh@...r.kernel.org,
	dhowells@...hat.com, sparclinux@...r.kernel.org,
	linux-s390@...r.kernel.org, linux-am33-list@...hat.com,
	linux@....linux.org.uk, linux-hexagon@...r.kernel.org,
	x86@...nel.org, jejb@...isc-linux.org, cmetcalf@...era.com,
	uclinux-dist-devel@...ckfin.uclinux.org, tglx@...utronix.de,
	linux-arm-kernel@...ts.infradead.org, linux-m32r@...linux-m32r.org,
	linux-parisc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-alpha@...r.kernel.org, linux390@...ibm.com,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH RFC] Simplify the Linux kernel by reducing its state space

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<paulmck@...ux.vnet.ibm.com>
>>> Reviewed-by: Thomas Gleixner<tglx@...utronix.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@...ts.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
>    

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