Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753116AbYJAXVH (ORCPT ); Wed, 1 Oct 2008 19:21:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752007AbYJAXUz (ORCPT ); Wed, 1 Oct 2008 19:20:55 -0400 Received: from mx2.redhat.com ([66.187.237.31]:51595 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751731AbYJAXUy (ORCPT ); Wed, 1 Oct 2008 19:20:54 -0400 Date: Wed, 1 Oct 2008 19:19:45 -0400 From: Chuck Ebbert To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, Arjan van de Ven Subject: [patch x86/core] x86: allow number of additional hotplug CPUs to be set at compile time Message-ID: <20081001191945.4182d0be@redhat.com> Organization: Red Hat, Inc. Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3219 Lines: 93 From: Chuck Ebbert x86: allow number of additional hotplug CPUs to be set at compile time The default number of additional CPU IDs for hotplugging is determined by asking ACPI or mptables how many "disabled" CPUs there are in the system, but many systems get this wrong so that e.g. a uniprocessor machine gets an extra CPU allocated and never switches to single CPU mode. And sometimes CPU hotplugging is enabled only for suspend/hibernate anyway, so the additional CPU IDs are not wanted. Allow the number to be set to zero at compile time. Also, force the number of extra CPUs to zero if hotplugging is disabled which allows removing some conditional code. Tested on uniprocessor x86_64 that ACPI claims has a disabled processor, with CPU hotplugging configured. ("After" has the number of additional CPUs set to 0) Before: NR_CPUS: 512, nr_cpu_ids: 2, nr_node_ids 1 After: NR_CPUS: 512, nr_cpu_ids: 1, nr_node_ids 1 Signed-off-by: Chuck Ebbert --- Index: linux-2.6.26.noarch/arch/x86/Kconfig =================================================================== --- linux-2.6.26.noarch.orig/arch/x86/Kconfig +++ linux-2.6.26.noarch/arch/x86/Kconfig @@ -1366,6 +1366,24 @@ config HOTPLUG_CPU Say N if you want to disable CPU hotplug and don't need to suspend. +config HOTPLUG_DEFAULT_ADDITIONAL_CPUS + def_bool y + prompt "Allocate extra CPUs for hotplugging after boot" if HOTPLUG_CPU + ---help--- + Say yes here to use the default, which allows as many CPUs as are marked + "disabled" by ACPI or MPTABLES to be hotplugged after bootup. + + Say no if you do not want to allow CPUs to be added after booting, for + example if you only need CPU hotplugging enabled for suspend/resume. + + This value may be overridden at boot time with the "additional_cpus" + kernel parameter, if CPU_HOTPLUG is enabled. + +config HOTPLUG_ADDITIONAL_CPUS + int + default 0 if !HOTPLUG_CPU || !HOTPLUG_DEFAULT_ADDITIONAL_CPUS + default -1 + config COMPAT_VDSO def_bool y prompt "Compat VDSO support" Index: linux-2.6.26.noarch/arch/x86/kernel/smpboot.c =================================================================== --- linux-2.6.26.noarch.orig/arch/x86/kernel/smpboot.c +++ linux-2.6.26.noarch/arch/x86/kernel/smpboot.c @@ -1254,7 +1254,7 @@ void __init native_smp_cpus_done(unsigne check_nmi_watchdog(); } -static int additional_cpus __initdata = -1; +static int additional_cpus __initdata = CONFIG_HOTPLUG_ADDITIONAL_CPUS; /* * cpu_possible_map should be static, it cannot change as cpu's @@ -1282,16 +1282,13 @@ __init void prefill_possible_map(void) if (!num_processors) num_processors = 1; -#ifdef CONFIG_HOTPLUG_CPU if (additional_cpus == -1) { if (disabled_cpus > 0) additional_cpus = disabled_cpus; else additional_cpus = 0; } -#else - additional_cpus = 0; -#endif + possible = num_processors + additional_cpus; if (possible > NR_CPUS) possible = NR_CPUS; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/