NR_CPUS configuration option wrong
in [Kernel]
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From: Frank A. Kingswood on 20 May 2010 13:40 Hi! The configuration MAXSMP help text indicates it is used to enable configuration of number of CPUs. However, NR_CPUS depends on !MAXSMP. arch/x86/Kconfig: 758 config NR_CPUS 759 int "Maximum number of CPUs" if SMP && !MAXSMP Frank -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Randy Dunlap on 20 May 2010 13:50 On Thu, 20 May 2010 18:34:32 +0100 Frank A. Kingswood wrote: > Hi! > > The configuration MAXSMP help text indicates it is used to enable > configuration of number of CPUs. However, NR_CPUS depends on !MAXSMP. > > arch/x86/Kconfig: > 758 config NR_CPUS > 759 int "Maximum number of CPUs" if SMP && !MAXSMP That line depends on !MAXSMP. Then below there, we find: default "4096" if MAXSMP OK? --- ~Randy *** Remember to use Documentation/SubmitChecklist when testing your code *** -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Frank A. Kingswood on 20 May 2010 14:40 Randy Dunlap wrote: > On Thu, 20 May 2010 18:34:32 +0100 Frank A. Kingswood wrote: > >> Hi! >> >> The configuration MAXSMP help text indicates it is used to enable >> configuration of number of CPUs. However, NR_CPUS depends on !MAXSMP. >> >> arch/x86/Kconfig: >> 758 config NR_CPUS >> 759 int "Maximum number of CPUs" if SMP && !MAXSMP > > That line depends on !MAXSMP. Then below there, we find: > > default "4096" if MAXSMP Hah, weird. I can see now it is possible to parse the MAXSMP help this way, but it was not obvious. In menuconfig you see two questions: [ ] Configure Maximum number of SMP Processors and NUMA Nodes [8] Maximum number of CPUs and setting the first one YES makes the second one go away. Perhaps restating the help as "Set number of SMP processors and NUMA nodes to the maximum that the kernel supports" might help. Thanks, Frank -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Randy Dunlap on 20 May 2010 14:40 On 05/20/10 11:32, Frank A. Kingswood wrote: > Randy Dunlap wrote: >> On Thu, 20 May 2010 18:34:32 +0100 Frank A. Kingswood wrote: >> >>> Hi! >>> >>> The configuration MAXSMP help text indicates it is used to enable >>> configuration of number of CPUs. However, NR_CPUS depends on !MAXSMP. >>> >>> arch/x86/Kconfig: >>> 758 config NR_CPUS >>> 759 int "Maximum number of CPUs" if SMP && !MAXSMP >> >> That line depends on !MAXSMP. Then below there, we find: >> >> default "4096" if MAXSMP > > Hah, weird. > I can see now it is possible to parse the MAXSMP help this way, but it > was not obvious. Ambiguity is fairly easy. :( > In menuconfig you see two questions: > > [ ] Configure Maximum number of SMP Processors and NUMA Nodes > [8] Maximum number of CPUs > > and setting the first one YES makes the second one go away. > > Perhaps restating the help as "Set number of SMP processors and NUMA > nodes to the maximum that the kernel supports" might help. Yes, that sounds better. Want to submit a patch for that? -- ~Randy *** Remember to use Documentation/SubmitChecklist when testing your code *** -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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