Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757855Ab2BMUFB (ORCPT ); Mon, 13 Feb 2012 15:05:01 -0500 Received: from mail-iy0-f174.google.com ([209.85.210.174]:33474 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757696Ab2BMUFA convert rfc822-to-8bit (ORCPT ); Mon, 13 Feb 2012 15:05:00 -0500 MIME-Version: 1.0 In-Reply-To: References: <1328055439-9441-1-git-send-email-venki@google.com> <20120201140125.c656df41.akpm@linux-foundation.org> <87d39xj955.fsf@rustcorp.com.au> Date: Mon, 13 Feb 2012 12:04:59 -0800 Message-ID: Subject: Re: [PATCH] Avoid mask based num_possible_cpus and num_online_cpus -v5 From: Venki Pallipadi To: Tony Luck Cc: Rusty Russell , Andrew Morton , KOSAKI Motohiro , KOSAKI Motohiro , Mike Travis , "Srivatsa S. Bhat" , "Paul E. McKenney" , "Rafael J. Wysocki" , Paul Gortmaker , linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1472 Lines: 36 On Mon, Feb 13, 2012 at 11:54 AM, Tony Luck wrote: > On Thu, Feb 2, 2012 at 12:03 PM, Rusty Russell wrote: >> IIRC playing with 3 archs boot code seemed like a recipe for disaster. >> Feel free to try to fix this in -next though, and see what breaks... > > ia64 is what breaks ... well not actually broken ... but some very > weird delays that > show up in different places depending on whether this patch is present. > > First linux-next kernel to be blessed with this patch was > next-20120210. Booting it > I see: > [ ? ?7.164233] Switching to clocksource itc > [ ?146.077315] pnp: PnP ACPI init > > An ugly 138.913 second delay. ?Digging in the code showed that the bad bits > happened inside stop_machine() > > Reverting just this patch makes this big delay disappear: > > [ ? 32.780232] Switching to clocksource itc > [ ? 32.832100] pnp: PnP ACPI init > > but notice that it takes 25 extra seconds to get to this point in the > boot (and while > we expect to save some time by not re-computing num_online_cpus each time we > need it ... this looks to be a lot more than I'd expect!) > > -Tony What is NR_CPUS set to here? And how many actual CPUs are there on this machine? -- 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/