Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932365AbWCMTgi (ORCPT ); Mon, 13 Mar 2006 14:36:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932368AbWCMTgi (ORCPT ); Mon, 13 Mar 2006 14:36:38 -0500 Received: from fmr22.intel.com ([143.183.121.14]:59557 "EHLO scsfmr002.sc.intel.com") by vger.kernel.org with ESMTP id S932365AbWCMTgh (ORCPT ); Mon, 13 Mar 2006 14:36:37 -0500 Date: Mon, 13 Mar 2006 11:36:15 -0800 From: Ashok Raj To: Andrew Morton Cc: Krzysztof Oledzki , venkatesh.pallipadi@intel.com, linux-kernel@vger.kernel.org, ashok.raj@intel.com, suresh.b.siddha@intel.com, rajesh.shah@intel.com Subject: Re: More than 8 CPUs detected and CONFIG_X86_PC cannot handle it on 2.6.16-rc6 Message-ID: <20060313113615.A24797@unix-os.sc.intel.com> References: <20060311210353.7eccb6ed.akpm@osdl.org> <20060312032523.109361c1.akpm@osdl.org> <20060312073524.A9213@unix-os.sc.intel.com> <20060312143053.530ef6c9.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <20060312143053.530ef6c9.akpm@osdl.org>; from akpm@osdl.org on Sun, Mar 12, 2006 at 02:30:53PM -0800 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2043 Lines: 55 On Sun, Mar 12, 2006 at 02:30:53PM -0800, Andrew Morton wrote: > > Maybe we should have: > > if (num_possible_cpus() <= 8) > dont_do_any_of_that_stuff(); > > That's assuming that hotplug-cpu-capable platforms are correctly setting > cpu_possible_map. Do they? That wont work, since we use HOTPLUG_CPU to suspend/resume as well. We switched to using bigsmp (that uses physflat for IPI's) just to avoid sending IPI's to offline CPUs. When we use logical flat we use shortcuts that have ill effects on CPUs that are offline. Think making CONFIG_HOTPLUG_CPU depend on X86_GENERICARCH, or X86_BIGSMP seems like a better choice. -- Cheers, Ashok Raj - Open Source Technology Center When CONFIG_HOTPLUG_CPU is turned on we always use physflat mode (bigsmp) even when #of CPUs are less than 8 to avoid sending IPI to offline processors. Without having BIGSMP on it spits out a warning during boot on systems that seems misleading, since it complains even on systems that have less than 8 cpus. Signed-off-by: Ashok Raj --------------------------------------------------------- arch/i386/Kconfig | 2 +- 1 files changed, 1 insertion(+), 1 deletion(-) Index: linux-2.6.16-rc6-mm1/arch/i386/Kconfig =================================================================== --- linux-2.6.16-rc6-mm1.orig/arch/i386/Kconfig +++ linux-2.6.16-rc6-mm1/arch/i386/Kconfig @@ -760,7 +760,7 @@ config PHYSICAL_START config HOTPLUG_CPU bool "Support for hot-pluggable CPUs (EXPERIMENTAL)" - depends on SMP && HOTPLUG && EXPERIMENTAL && !X86_VOYAGER + depends on SMP && HOTPLUG && EXPERIMENTAL && !X86_VOYAGER && (X86_GENERICARCH || X86_BIGSMP) ---help--- Say Y here to experiment with turning CPUs off and on. CPUs can be controlled through /sys/devices/system/cpu. - 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/