From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752940Ab3KGJQF (ORCPT ); Thu, 7 Nov 2013 04:16:05 -0500 Received: from mail-ee0-f52.google.com ([74.125.83.52]:57459 "EHLO mail-ee0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750802Ab3KGJP7 (ORCPT ); Thu, 7 Nov 2013 04:15:59 -0500 Date: Thu, 7 Nov 2013 10:15:55 +0100 From: Ingo Molnar To: Josh Boyer Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , prarit@redhat.com, x86@kernel.org, linux-kernel@vger.kernel.org, Russ Anderson Subject: Re: [PATCH v3] x86/cpu: Allow higher NR_CPUS values Message-ID: <20131107091555.GA2671@gmail.com> References: <20131101141148.GH8652@hansolo.jdub.homelinux.org> <20131105143728.GJ9944@hansolo.jdub.homelinux.org> <20131106071540.GA3053@gmail.com> <20131106152113.GQ9944@hansolo.jdub.homelinux.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131106152113.GQ9944@hansolo.jdub.homelinux.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Josh Boyer wrote: > The current range for SMP configs is 2 - 512 CPUs, 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. > > To cover the range of more common machines today, we allow NR_CPUS to be > up to 4096 when CPUMASK_OFFSTACK is enabled. Relatedly, we no longer make > that option depend on DEBUG_PER_CPU_MASKS. > index b3c8be0..50b47cd 100644 > --- a/lib/Kconfig > +++ b/lib/Kconfig > @@ -342,7 +342,8 @@ config CHECK_SIGNATURE > bool > > config CPUMASK_OFFSTACK > - bool "Force CPU masks off stack" if DEBUG_PER_CPU_MAPS > + bool "Force CPU masks off stack" > + depends on SMP > help > Use dynamic allocation for cpumask_var_t, instead of putting > them on the stack. This is a bit more expensive, but avoids So this chunk really doesn't belong into the patch - it should be a separate patch. Also, because I already applied the patch (sans the unrelated chunk) please only send this single change against tip:master. Thanks, Ingo