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Subject[PATCH] x86: bump default NR_CPUS for 64-bit configuration
Default NR_CPUS==8 is not enough to cover high-end desktop
configuration: Haswell-E has upto 16 threads.

Let's increase default NR_CPUS to 64 on 64-bit configuration. With this
value CPU bitmask will still fit into one unsinged long.

Default for 32-bit configuration is still 8: it's unlikely anybody will
run 32-bit kernel on modern hardware.

As alternative we could bump NR_CPUS to 128 to cover all dual-processor
servers with some margin.

For reference: Debian and Suse build their kernels with NR_CPUS==512,
Fedora -- 1024.

Signed-off-by: Kirill A. Shutemov <>
arch/x86/Kconfig | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 6aaf38ac417d..c3333e5be5d7 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -851,7 +851,8 @@ config NR_CPUS
default "1" if !SMP
default "8192" if MAXSMP
default "32" if SMP && X86_BIGSMP
- default "8" if SMP
+ default "8" if SMP && X86_32
+ default "64" if SMP
This allows you to specify the maximum number of CPUs which this
kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum

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