Messages in this thread Patch in this message | | | Date | Wed, 26 Mar 2008 18:09:24 +0200 | From | Adrian Bunk <> | Subject | Re: [PATCH 2/2] x86: Modify Kconfig to allow up to 4096 cpus |
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On Tue, Mar 25, 2008 at 06:41:39PM -0700, Mike Travis wrote: > Increase the limit of NR_CPUS to 4096 and introduce a boolean > called "MAXSMP" which when set (e.g. "allyesconfig"), will set > NR_CPUS = 4096 and NODES_SHIFT = 9 (512).
I'm not really getting the point of MAXSMP - people should simply pick their values, and when they want the maximum "(2-4096)" and "(1-15)" already provide this information (except that your patch hides the latter information from the user).
And with your patch, even with MAXSMP=y people could still set NR_CPUS=7 and NODES_SHIFT=15 or whatever else they want...
More interesting would be why you want it to set NODES_SHIFT to something less than the maximum value of 15. I'm getting the fact that 2^15 > 4096 and that 15 might be nonsensical high, but this sounds more like requiring a patch to limit the range to 9?
>... > --- linux.trees.git.orig/arch/x86/Kconfig > +++ linux.trees.git/arch/x86/Kconfig > @@ -522,16 +522,24 @@ config SWIOTLB > access 32-bits of memory can be used on systems with more than > 3 GB of memory. If unsure, say Y. > > +config MAXSMP > + bool "Configure Maximum number of SMP Processors" > + depends on X86_64 && SMP > + default n > + help > + Configure maximum number of CPUS for this architecture. > + If unsure, say N. > > config NR_CPUS > - int "Maximum number of CPUs (2-255)" > - range 2 255 > + int "Maximum number of CPUs (2-4096)" > + range 2 4096 > depends on SMP > + default "4096" if MAXSMP > default "32" if X86_NUMAQ || X86_SUMMIT || X86_BIGSMP || X86_ES7000 > default "8" > help > This allows you to specify the maximum number of CPUs which this > - kernel will support. The maximum supported value is 255 and the > + kernel will support. The maximum supported value is 4096 and the > minimum value which makes sense is 2. > > This is purely to save memory - each supported CPU adds > @@ -918,12 +926,16 @@ config NUMA_EMU > number of nodes. This is only useful for debugging. > > config NODES_SHIFT > - int "Max num nodes shift(1-15)" > + int "Maximum NUMA Nodes (as a power of 2)" > range 1 15 if X86_64 > + default "9" if MAXSMP > default "6" if X86_64 > default "4" if X86_NUMAQ > default "3" > depends on NEED_MULTIPLE_NODES > + help > + Specify the maximum number of NUMA Nodes available on the target > + system. Increases memory reserved to accomodate various tables. > > config HAVE_ARCH_BOOTMEM_NODE > def_bool y >
cu Adrian
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"Is there not promise of rain?" Ling Tan asked suddenly out of the darkness. There had been need of rain for many days. "Only a promise," Lao Er said. Pearl S. Buck - Dragon Seed
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