Meant to send this to Shawn. Too early in the morning.
Robin
On Fri, Apr 12, 2013 at 04:31:49AM -0500, Robin Holt wrote:
> On Fri, Apr 12, 2013 at 11:39:51AM +0530, Srivatsa S. Bhat wrote:
> > On 04/12/2013 11:07 AM, Ingo Molnar wrote:
> > >
> > > * Robin Holt <h...@sgi.com> wrote:
> > >
> > >> For the v3.9 release, can we consider my awful patch?
> > >
> > > How about trying what I suggested, to make reboot affine to the boot CPU
> > > explicitly, not by shutting down all the other CPUs, but by
> > > set_cpus_allowed() or
> > > so?
> > >
> >
> > I agree, that sounds like the right thing to do for 3.9. Of course, it
> > would be
> > nice if Shawn could verify that doing that doesn't break his platform due to
> > some unknown corner case.
> >
> > > That should solve the regression, without the ugly special-casing - while
> > > giving
> > > time to address the hot-unplug performance bottleneck.
> > >
> > > Once that is done disable_nonboot_cpus() can be used again for reboot.
> > >
> > > (But no strong feelings either way - both solutions are a workaround in a
> > > sense.)
>
>
> >From 1767003c943325e52ac78cac6fdbaf2ab638888d Mon Sep 17 00:00:00 2001
> From: Robin Holt <h...@sgi.com>
> 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 <h...@sgi.com>
> To: Shawn Guo <shawn....@linaro.org>
> To: Ingo Molnar <mi...@redhat.com>
> To: Russ Anderson <r...@sgi.com>
> Cc: Andrew Morton <a...@linux-foundation.org>
> Cc: "H. Peter Anvin" <h...@zytor.com>
> Cc: Lai Jiangshan <la...@cn.fujitsu.com>
> Cc: Linus Torvalds <torva...@linux-foundation.org>
> Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
> Cc: Michel Lespinasse <wal...@google.com>
> Cc: Oleg Nesterov <o...@redhat.com>
> Cc: "Paul E. McKenney" <paul...@linux.vnet.ibm.com>
> Cc: Paul Mackerras <pau...@samba.org>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Robin Holt <h...@sgi.com>
> Cc: "ru...@rustcorp.com.au" <ru...@rustcorp.com.au>
> Cc: Tejun Heo <t...@kernel.org>
> Cc: the arch/x86 maintainers <x...@kernel.org>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: <sta...@vger.kernel.org>
> ---
> 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));
> +}
> +
> /**
> * kernel_restart - reboot the system
> * @cmd: pointer to buffer containing command to execute for restart
> @@ -368,7 +381,7 @@ EXPORT_SYMBOL(unregister_reboot_notifier);
> void kernel_restart(char *cmd)
> {
> kernel_restart_prepare(cmd);
> - disable_nonboot_cpus();
> + migrate_to_boot_cpu();
> syscore_shutdown();
> if (!cmd)
> printk(KERN_EMERG "Restarting system.\n");
> @@ -414,7 +427,7 @@ void kernel_power_off(void)
> kernel_shutdown_prepare(SYSTEM_POWER_OFF);
> if (pm_power_off_prepare)
> pm_power_off_prepare();
> - disable_nonboot_cpus();
> + migrate_to_boot_cpu();
> syscore_shutdown();
> printk(KERN_EMERG "Power down.\n");
> kmsg_dump(KMSG_DUMP_POWEROFF);
> --
> 1.8.1.2
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
