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    SubjectRe: [PATCH] x86: Allow NR_CPUS=1024


    On 11/03/2013 05:18 AM, Ingo Molnar wrote:
    >
    > * Josh Boyer <jwboyer@redhat.com> wrote:
    >
    >> The current range for SMP configs is 2 - 512, or a full 4096 in the case
    >> of MAXSMP. There are machines that have 1024 CPUs in them today and
    >> configuring a kernel for that means you are forced to set MAXSMP. This
    >> adds additional unnecessary overhead. While that overhead might be
    >> considered tiny for large machines, it isn't necessarily so if you are
    >> building a kernel that runs across a wide variety of machines. We
    >> increase the range to 1024 to help with this.
    >>
    >> Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
    >> ---
    >> arch/x86/Kconfig | 2 +-
    >> 1 file changed, 1 insertion(+), 1 deletion(-)
    >>
    >> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
    >> index f67e839..d726b2d 100644
    >> --- a/arch/x86/Kconfig
    >> +++ b/arch/x86/Kconfig
    >> @@ -825,7 +825,7 @@ config MAXSMP
    >> config NR_CPUS
    >> int "Maximum number of CPUs" if SMP && !MAXSMP
    >> range 2 8 if SMP && X86_32 && !X86_BIGSMP
    >> - range 2 512 if SMP && !MAXSMP
    >> + range 2 1024 if SMP && !MAXSMP
    >> default "1" if !SMP
    >> default "4096" if MAXSMP
    >> default "32" if SMP && (X86_NUMAQ || X86_SUMMIT || X86_BIGSMP || X86_ES7000)
    >
    > Any reason not to allow it to go up to 4096? The original concern was that
    > CPUS=4096 wasn't working very well and you had to select MAXSMP
    > deliberately and keep all the pieces.
    >
    > But today it's all pretty robust so I see no reason why not to allow up to
    > 4096 CPUs.

    Adding Russ from SGI as they are one of the consumers of a large CPU count.

    I have no objections to raising this to 4096 FWIW. I think it is a good idea,
    and it is long overdue.

    P.

    >
    > Thanks,
    >
    > Ingo


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