linux-kernel - [tip:x86/build] x86/kconfig: Bump default NR_CPUS from 8 to 64 for 64-bit configuration

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Date:	Fri, 8 May 2015 06:29:27 -0700
From:	"tip-bot for Kirill A. Shutemov" <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	hpa@...or.com, mingo@...nel.org, peterz@...radead.org,
	tglx@...utronix.de, torvalds@...ux-foundation.org,
	kirill.shutemov@...ux.intel.com, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org
Subject: [tip:x86/build] x86/kconfig:
  Bump default NR_CPUS from 8 to 64 for 64-bit configuration

Commit-ID:  c5c19941ad1bb18f010ae47f1db333c00b276d55
Gitweb:     http://git.kernel.org/tip/c5c19941ad1bb18f010ae47f1db333c00b276d55
Author:     Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
AuthorDate: Fri, 8 May 2015 13:25:45 +0300
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 8 May 2015 12:58:56 +0200

x86/kconfig: Bump default NR_CPUS from 8 to 64 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 unsigned long.

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

As an 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 <kirill.shutemov@...ux.intel.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1431080745-19792-1-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/Kconfig | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 226d569..83cd1c7 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
 	---help---
 	  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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