Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755420Ab3DOKQu (ORCPT ); Mon, 15 Apr 2013 06:16:50 -0400 Received: from mail-ee0-f49.google.com ([74.125.83.49]:59414 "EHLO mail-ee0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753182Ab3DOKQs (ORCPT ); Mon, 15 Apr 2013 06:16:48 -0400 Date: Mon, 15 Apr 2013 12:16:44 +0200 From: Ingo Molnar To: Robin Holt Cc: "Srivatsa S. Bhat" , Paul Mackerras , Linus Torvalds , "H. Peter Anvin" , Andrew Morton , Linux Kernel Mailing List , Russ Anderson , Shawn Guo , Thomas Gleixner , Ingo Molnar , the arch/x86 maintainers , "Paul E. McKenney" , Tejun Heo , Oleg Nesterov , Lai Jiangshan , Michel Lespinasse , "rusty@rustcorp.com.au" , Peter Zijlstra Subject: Re: Bulk CPU Hotplug (Was Re: [PATCH] Do not force shutdown/reboot to boot cpu.) Message-ID: <20130415101644.GC18024@gmail.com> References: <5162EC1A.4050204@zytor.com> <20130408165916.GA3672@sgi.com> <20130410111620.GB29752@gmail.com> <20130411053106.GA9042@drongo> <5166B05E.8010904@linux.vnet.ibm.com> <20130411134837.GE3672@sgi.com> <20130412053718.GC3887@gmail.com> <5167A52F.6020503@linux.vnet.ibm.com> <20130412093149.GT3658@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130412093149.GT3658@sgi.com> 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 Content-Length: 3334 Lines: 85 * Robin Holt wrote: > From 1767003c943325e52ac78cac6fdbaf2ab638888d Mon Sep 17 00:00:00 2001 > From: Robin Holt > Date: Wed, 3 Apr 2013 13:52:00 -0500 > Subject: [PATCH] Migrate shutdown/reboot to boot cpu. > > We recently noticed that reboot of a 1024 cpu machine takes approx 16 > minutes of just stopping the cpus. The slowdown was tracked to commit > f96972f. > > The current implementation does all the work of hot removing the cpus > before halting the system. We are switching to just migrating to the > boot cpu and then calling continuing with shutdown/reboot. > > This also has the effect of not breaking x86's command line parameter for > specifying the reboot cpu. Note, this code was shamelessly copied from > arch/x86/kernel/reboot.c with bits removed pertaining to the reboot_cpu > command line parameter. > > Signed-off-by: Robin Holt > To: Shawn Guo > To: Ingo Molnar > To: Russ Anderson > Cc: Andrew Morton > Cc: "H. Peter Anvin" > Cc: Lai Jiangshan > Cc: Linus Torvalds > Cc: Linux Kernel Mailing List > Cc: Michel Lespinasse > Cc: Oleg Nesterov > Cc: "Paul E. McKenney" > Cc: Paul Mackerras > Cc: Peter Zijlstra > Cc: Robin Holt > Cc: "rusty@rustcorp.com.au" > Cc: Tejun Heo > Cc: the arch/x86 maintainers > Cc: Thomas Gleixner > Cc: > --- > kernel/sys.c | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/kernel/sys.c b/kernel/sys.c > index 0da73cf..4d1047d 100644 > --- a/kernel/sys.c > +++ b/kernel/sys.c > @@ -357,6 +357,19 @@ int unregister_reboot_notifier(struct notifier_block *nb) > } > EXPORT_SYMBOL(unregister_reboot_notifier); > > +void migrate_to_boot_cpu(void) > +{ > + /* The boot cpu is always logical cpu 0 */ > + int reboot_cpu_id = 0; > + > + /* Make certain the cpu I'm about to reboot on is online */ > + if (!cpu_online(reboot_cpu_id)) > + reboot_cpu_id = smp_processor_id(); > + > + /* Make certain I only run on the appropriate processor */ > + set_cpus_allowed_ptr(current, cpumask_of(reboot_cpu_id)); > +} I guess you suspect what I'm going to suggest next? :-) While I think something like this commit would be acceptable as a minimal regression fix, it would be really lovely to add a second patch as well, which removes the same code from arch/x86/kernel/reboot.c:native_machine_shutdown() and merged it with the kernel/sys.c version? That way all platforms gained a reboot_cpu command line, and we'd have less code duplication as well. Win-win. ( While at it, it might make sense to move the reboot/shutdown related bits from kernel/sys.c to a new kernel/shutdown.c or kernel/reboot.c file or so. ) Thanks, Ingo -- 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/