From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753954Ab3KCOmb (ORCPT ); Sun, 3 Nov 2013 09:42:31 -0500 Received: from relay3.sgi.com ([192.48.152.1]:51078 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753841Ab3KCOm3 (ORCPT ); Sun, 3 Nov 2013 09:42:29 -0500 Date: Sun, 3 Nov 2013 08:42:27 -0600 From: Russ Anderson To: Prarit Bhargava Cc: Ingo Molnar , Josh Boyer , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86: Allow NR_CPUS=1024 Message-ID: <20131103144227.GB6926@sgi.com> Reply-To: Russ Anderson References: <20131101141148.GH8652@hansolo.jdub.homelinux.org> <20131103101825.GA6605@gmail.com> <52765DBC.1090208@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52765DBC.1090208@redhat.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Nov 03, 2013 at 09:29:16AM -0500, Prarit Bhargava wrote: > On 11/03/2013 05:18 AM, Ingo Molnar wrote: > > > > * Josh Boyer 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 > >> --- > >> 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. I obviously agree with increasing to 4096. The bigger the better. -- Russ Anderson, OS RAS/Partitioning Project Lead SGI - Silicon Graphics Inc rja@sgi.com