Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751828AbWCMUGp (ORCPT ); Mon, 13 Mar 2006 15:06:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751857AbWCMUGp (ORCPT ); Mon, 13 Mar 2006 15:06:45 -0500 Received: from fmr20.intel.com ([134.134.136.19]:53906 "EHLO orsfmr005.jf.intel.com") by vger.kernel.org with ESMTP id S1751828AbWCMUGo (ORCPT ); Mon, 13 Mar 2006 15:06:44 -0500 Date: Mon, 13 Mar 2006 12:05:52 -0800 From: Ashok Raj To: Andrew Morton Cc: Ashok Raj , olel@ans.pl, venkatesh.pallipadi@intel.com, linux-kernel@vger.kernel.org, suresh.b.siddha@intel.com, rajesh.shah@intel.com, ak@muc.de Subject: Re: More than 8 CPUs detected and CONFIG_X86_PC cannot handle it on 2.6.16-rc6 Message-ID: <20060313120552.A25020@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> <20060313113615.A24797@unix-os.sc.intel.com> <20060313115155.24dfb6f3.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: <20060313115155.24dfb6f3.akpm@osdl.org>; from akpm@osdl.org on Mon, Mar 13, 2006 at 11:51:55AM -0800 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2235 Lines: 58 On Mon, Mar 13, 2006 at 11:51:55AM -0800, Andrew Morton wrote: > > One of the main reasons for turning on CONFIG_HOTPLUG_CPU on x86 is > actually for suspend-to-disk on SMP. I don't think it's desirable to force > all those little machines to use X86_GENERICARCH || X86_BIGSMP. And it'd > be good to make that warning go away for 2.6.16. But we cant use X86_PC since it uses logical flat mode for IPI's that could cause hangup's if we deliver IPI's using IPI broadcast shortcut. In i386 we do have an alternate that would use mask value to deliver IPI's but Andi's recommendataion was to use flat physical mode just like what we do for X86_64. Other than the IPI mode, are there any other things that hurt small systems by choosing bigsmp mode? Venki suggested we could make it !X86_PC instead of listing GENERICARCH or BIGSMP separately. -- 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_PC ---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/