[PATCH] powerpc: Make the NR_CPUS max 8192

[Geert Uytterhoeven]

On Mon, 18 May 2009, Michael Neuling wrote:
> > > We can compile and boot with NR_CPUS=3D8192, so make this the max.  1024
> > > was an arbitrary decision anyway.
> > 
> > Is 8192 still arbitrary? Or does something break above that?
> 
> Yeah, the compile breaks after that with 4K pages.
> 
> In drivers/base/node.c we have:
> 	/* 2008/04/07: buf currently PAGE_SIZE, need 9 chars per 32 bits. */
> 	BUILD_BUG_ON((NR_CPUS/32 * 9) > (PAGE_SIZE-1));
> which causes:
> drivers/base/node.c: In function 'node_read_cpumap':
> drivers/base/node.c:31: error: size of array 'type name' is negative
> 
> I can compile with 16384 CPUs with 64K pages, but it doesn't boot.  
> 
> sfr asked for size info for different builds, so I may as well repost
> them here:
> 
>    text	   data		bss		dec		hex	filename
> 9237767	3225768		4409996		16873531	101783b	vmlinux.1024
> 9247355	4769472		7373708		21390535	14664c7	vmlinux.2048
> 9267239	7857032		13301132	30425403	1d0413b	vmlinux.4096
> 9302623	14035832	25155980	48494435	2e3f763	vmlinux.8192
> 9373283	26389360	48865676	84628319	50b535f	vmlinux.16384

Will distros now start pushing NR_CPUS=8192-kernels on us?

With kind regards,

Geert Uytterhoeven
Software Architect
Techsoft Centre

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